Publications reported by three months

1.Zieliński T.G., Venegas R., Perrot C., Červenka M., Chevillotte F., Attenborough K., Benchmarks for microstructure-based modelling of sound absorbing rigid-frame porous media, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2020.115441, Vol.483, pp.115441-1-38, 2020
Zieliński T.G., Venegas R., Perrot C., Červenka M., Chevillotte F., Attenborough K., Benchmarks for microstructure-based modelling of sound absorbing rigid-frame porous media, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2020.115441, Vol.483, pp.115441-1-38, 2020

Abstract:
This work presents benchmark examples related to the modelling of sound absorbing porous media with rigid frame based on the periodic geometry of their microstructures. To this end, rigorous mathematical derivations are recalled to provide all necessary equations, useful relations, and formulae for the so-called direct multi-scale computations, as well as for the hybrid multi-scale calculations based on the numerically determined transport parameters of porous materials. The results of such direct and hybrid multi-scale calculations are not only cross verified, but also confirmed by direct numerical simulations based on the linearised Navier-Stokes-Fourier equations. In addition, relevant theoretical and numerical issues are discussed, and some practical hints are given.

Keywords:
porous media, periodic microstructure, wave propagation, sound absorption

2.Wasilewski M., Pisarski D., Adaptive semi-active control of a beam structure subjected to a moving load traversing with time-varying velocity, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2020.115404, Vol.481, pp.115404-1-20, 2020
Wasilewski M., Pisarski D., Adaptive semi-active control of a beam structure subjected to a moving load traversing with time-varying velocity, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2020.115404, Vol.481, pp.115404-1-20, 2020

Abstract:
A novel method for adaptive semi-active vibration control of structures subjected to a movingload is studied. The velocity of the load is assumed to be time-varying. The controller consistsof an internal model of the moving load, which is being frequently updated to accommodatechanges in the load's velocity. The control method relies on a near-optimal switching con-trol law that is based on the solution to the algebraic Lyapunov equation. The infinite-horizonformulation of the control problem enables us to use efficient numerical algorithms for adap-tive recomputing of the control signal. The asymptotic stability of the closed-loop system andperformance improvement in comparison to the passive method are analysed and formallyproven. The controller is tested by means of numerical experiments involving a flexible beamequipped with a set of semi-active viscous dampers. We investigate three distinct simulationscenarios, which correspond to highly non-uniform motions of the load that consist of accel-eration, deceleration and temporary halt phases. The results of the simulations are comparedto passive and optimal open-loop strategies.

Keywords:
vibration control, adaptive control, semi-active control, moving load, stabilisation

3.Richter Ł., Żuk P.J., Szymczak P., Paczesny J., Bąk K.M., Szymborski T., Garstecki P., Stone H.A., Hołyst R., Drummond C., Ions in an AC electric field: strong long-range repulsion between oppositely charged surfaces, PHYSICAL REVIEW LETTERS, ISSN: 0031-9007, DOI: 10.1103/PhysRevLett.125.056001, Vol.125, No.5, pp.056001-1-5, 2020
Richter Ł., Żuk P.J., Szymczak P., Paczesny J., Bąk K.M., Szymborski T., Garstecki P., Stone H.A., Hołyst R., Drummond C., Ions in an AC electric field: strong long-range repulsion between oppositely charged surfaces, PHYSICAL REVIEW LETTERS, ISSN: 0031-9007, DOI: 10.1103/PhysRevLett.125.056001, Vol.125, No.5, pp.056001-1-5, 2020

Abstract:
Two oppositely charged surfaces separated by a dielectric medium attract each other. In contrast we observe a strong repulsion between two plates of a capacitor that is filled with an aqueous electrolyte upon application of an alternating potential difference between the plates. This long-range force increases with the ratio of diffusion coefficients of the ions in the medium and reaches a steady state after a few minutes, which is much larger than the millisecond timescale of diffusion across the narrow gap. The repulsive force, an order of magnitude stronger than the electrostatic attraction observed in the same setup in air, results from the increase in osmotic pressure as a consequence of the field-induced excess of cations and anions due to lateral transport from adjacent reservoirs.

4.Han A., Byra M., Heba E., Andre M.P., Erdman J.W.Jr., Loomba R., Sirlin C.B., O'Brien W.D.Jr., Noninvasive diagnosis of nonalcoholic fatty liver disease and quantification of liver fat with radiofrequency ultrasound data using one-dimensional convolutional neural networks, Radiology, ISSN: 0033-8419, DOI: 10.1148/radiol.2020191160, Vol.295, No.2, pp.342-350, 2020
Han A., Byra M., Heba E., Andre M.P., Erdman J.W.Jr., Loomba R., Sirlin C.B., O'Brien W.D.Jr., Noninvasive diagnosis of nonalcoholic fatty liver disease and quantification of liver fat with radiofrequency ultrasound data using one-dimensional convolutional neural networks, Radiology, ISSN: 0033-8419, DOI: 10.1148/radiol.2020191160, Vol.295, No.2, pp.342-350, 2020

Abstract:
Background: Radiofrequency ultrasound data from the liver contain rich information about liver microstructure and composition. Deep learning might exploit such information to assess nonalcoholic fatty liver disease (NAFLD). Purpose: To develop and evaluate deep learning algorithms that use radiofrequency data for NAFLD assessment, with MRI-derived proton density fat fraction (PDFF) as the reference. Materials and Methods: A HIPAA-compliant secondary analysis of a single-center prospective study was performed for adult participants with NAFLD and control participants without liver disease. Participants in the parent study were recruited between February 2012 and March 2014 and underwent same-day US and MRI of the liver. Participants were randomly divided into an equal number of training and test groups. The training group was used to develop two algorithms via cross-validation: a classifier to diagnose NAFLD (MRI PDFF ≥ 5%) and a fat fraction estimator to predict MRI PDFF. Both algorithms used one-dimensional convolutional neural networks. The test group was used to evaluate the classifier for sensitivity, specificity, positive predictive value, negative predictive value, and accuracy and to evaluate the estimator for correlation, bias, limits of agreements, and linearity between predicted fat fraction and MRI PDFF. Results: A total of 204 participants were analyzed, 140 had NAFLD (mean age, 52 years ± 14 [standard deviation]; 82 women) and 64 were control participants (mean age, 46 years ± 21; 42 women). In the test group, the classifier provided 96% (95% confidence interval [CI]: 90%, 99%) (98 of 102) accuracy for NAFLD diagnosis (sensitivity, 97% [95% CI: 90%, 100%], 68 of 70; specificity, 94% [95% CI: 79%, 99%], 30 of 32; positive predictive value, 97% [95% CI: 90%, 99%], 68 of 70; negative predictive value, 94% [95% CI: 79%, 98%], 30 of 32). The estimator-predicted fat fraction correlated with MRI PDFF (Pearson r = 0.85). The mean bias was 0.8% (P = .08), and 95% limits of agreement were -7.6% to 9.1%. The predicted fat fraction was linear with an MRI PDFF of 18% or less (r = 0.89, slope = 1.1, intercept = 1.3) and nonlinear with an MRI PDFF greater than 18%. Conclusion: Deep learning algorithms using radiofrequency ultrasound data are accurate for diagnosis of nonalcoholic fatty liver disease and hepatic fat fraction quantification when other causes of steatosis are excluded.

5.Grzywacz H., Milczarek M., Jenczyk P., Dera W., Michałowski M., Jarząbek D.M., Quantitative measurement of nanofriction between PMMA thin films and various AFM probes, MEASUREMENT, ISSN: 0263-2241, DOI: 10.1016/j.measurement.2020.108267, Vol.168, pp.108267-1-13, 2020
Grzywacz H., Milczarek M., Jenczyk P., Dera W., Michałowski M., Jarząbek D.M., Quantitative measurement of nanofriction between PMMA thin films and various AFM probes, MEASUREMENT, ISSN: 0263-2241, DOI: 10.1016/j.measurement.2020.108267, Vol.168, pp.108267-1-13, 2020

Abstract:
This study reports the quantitative, precise and accurate results of nanoscale friction measurements with the use of an Atomic Force Microscope calibrated with a precise nanoforce sensor. For this purpose, three samples of spin-coated thin Polymethylmethacrylate (PMMA) films were prepared with the following thicknesses: 235, 343, and 513 nm. Three different AFM probes were used for the friction measurements: with diamond-like carbon (DLC) tip with a small (15 nm) or big (2 µm) tip radius, and a reference silicon tip with a small (8 nm) radius. The results show that in all of the studied cases, the coefficient of friction strongly depends on the applied load, being much higher for a lower load. Furthermore, a strong relation of the friction force on the cantilever's geometry, the scanning velocity, and the film thickness was observed.

Keywords:
lateral force microscopy, friction, thin PMMA films, atomic force microscope, DLC coatings, adhesion

6.Yang H., Akinoglu E.M., Guo L., Jin M., Zhou G., Giersig M., Shui L., Mulvaney P., A PTFE helical capillary microreactor for the high throughput synthesis of monodisperse silica particles, Chemical Engineering Journal, ISSN: 1385-8947, DOI: 10.1016/j.cej.2020.126063, Vol.401, pp.126063-1-29, 2020
Yang H., Akinoglu E.M., Guo L., Jin M., Zhou G., Giersig M., Shui L., Mulvaney P., A PTFE helical capillary microreactor for the high throughput synthesis of monodisperse silica particles, Chemical Engineering Journal, ISSN: 1385-8947, DOI: 10.1016/j.cej.2020.126063, Vol.401, pp.126063-1-29, 2020

Abstract:
We propose a simple and inexpensive SiO2 submicron particle synthesis method based on a PTFE helical capillary microreactor. The device is based on Dean flow mediated, ultrafast mixing of two liquid phases in a microfluidic spiral pipe. Excellent control of particle size between 100 nm and 600 nm and narrow polydispersity can be achieved by controlling the device and process parameters. Numerical simulations are performed to determine the optimal device dimensions. In the mother liquor the silica particles exhibit zeta potentials < -60 mV, rendering them very stable even at high particle volume fractions. The current device typically produces around 0.234 g/h of the silica particles.

Keywords:
SiO2 particle synthesis, continuous flow synthesis, helical capillary microreactor

7.Gupta A., Żuk P.J., Stone H.A., Charging dynamics of overlapping double layers in a cylindrical nanopore, PHYSICAL REVIEW LETTERS, ISSN: 0031-9007, DOI: 10.1103/PhysRevLett.125.076001, Vol.125, No.7, pp.076001-1-6, 2020
Gupta A., Żuk P.J., Stone H.A., Charging dynamics of overlapping double layers in a cylindrical nanopore, PHYSICAL REVIEW LETTERS, ISSN: 0031-9007, DOI: 10.1103/PhysRevLett.125.076001, Vol.125, No.7, pp.076001-1-6, 2020

Abstract:
The charging of electrical double layers inside a cylindrical pore has applications to supercapacitors, batteries, desalination and biosensors. The charging dynamics in the limit of thin double layers, i.e., when the double layer thickness is much smaller than the pore radius, is commonly described using an effective RC transmission line circuit. Here, we perform direct numerical simulations (DNS) of the Poisson-Nernst-Planck equations to study the double layer charging for the scenario of overlapping double layers, i.e., when the double layer thickness is comparable to the pore radius. We develop an analytical model that accurately predicts the results of DNS. Also, we construct a modified effective circuit for the overlapping double layer limit, and find that the modified circuit is identical to the RC transmission line but with different values and physical interpretation of the capacitive and resistive elements. In particular, the effective surface potential is reduced, the capacitor represents a volumetric current source, and the charging timescale is weakly dependent on the ratio of the pore radius and the double layer thickness.

8.Darban H., Luciano R., Caporale A., Fabbrocino F., Higher modes of buckling in shear deformable nanobeams, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2020.103338, Vol.154, pp.103338-1-18, 2020
Darban H., Luciano R., Caporale A., Fabbrocino F., Higher modes of buckling in shear deformable nanobeams, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2020.103338, Vol.154, pp.103338-1-18, 2020

Abstract:
The size-dependent buckling instability of shear deformable nanobeams rested on a two-parameter elastic foundation is studied through the stress-driven nonlocal theory of elasticity and the kinematic assumptions of the Timoshenko beam theory. The small-scale size effects are taken into account by nonlocal constitutive relationships, which define the strains at each point as integral convolutions in terms of the stresses in all the points and a kernel. In this manner, the nonlocal elasticity formulation is well-posed and does not include inconsistencies usually arising using other nonlocal models. The size-dependent governing differential equations in terms of the transverse displacement and the cross-sectional rotation are decoupled, and closed form solutions are presented for the displacement functions. Proper boundary conditions are imposed and the buckling problem is reduced to finding roots of a determinant of a matrix, whose elements are given explicitly for different classical edge conditions. The closed form treatment of the problem avoids the numerical instabilities usually occurring within numerical techniques, and allows to find also higher buckling loads and shape modes. Several nanobeams rested on the Winkler or Pasternak elastic foundations and characterized by different boundary conditions, shear deformability, and nonlocality are considered and the critical loads and shape modes are presented, including those for the higher modes of buckling. Excellent agreements are found with the available approximate numerical results in the literature and novel insightful findings are presented and discussed, which are in accordance with experimental observations.

Keywords:
nanobeam, buckling, elastic foundation, closed form solution, nonlocal elasticity, size effect

9.Zieliński T.G., Opiela K.C., Pawłowski P., Dauchez N., Boutin T., Kennedy J., Trimble D., Rice H., Van Damme B., Hannema G., Wróbel R., Kim S., Ghaffari Mosanenzadeh S., Fang N.X., Yang J., Briere de La Hosseraye B., Hornikx M.C.J., Salze E., Galland M.-A., Boonen R., Carvalho de Sousa A., Deckers E., Gaborit M., Groby J.-P., Reproducibility of sound-absorbing periodic porous materials using additive manufacturing technologies: round robin study, Additive Manufacturing, ISSN: 2214-8604, DOI: 10.1016/j.addma.2020.101564, Vol.36, pp.101564-1-24, 2020
Zieliński T.G., Opiela K.C., Pawłowski P., Dauchez N., Boutin T., Kennedy J., Trimble D., Rice H., Van Damme B., Hannema G., Wróbel R., Kim S., Ghaffari Mosanenzadeh S., Fang N.X., Yang J., Briere de La Hosseraye B., Hornikx M.C.J., Salze E., Galland M.-A., Boonen R., Carvalho de Sousa A., Deckers E., Gaborit M., Groby J.-P., Reproducibility of sound-absorbing periodic porous materials using additive manufacturing technologies: round robin study, Additive Manufacturing, ISSN: 2214-8604, DOI: 10.1016/j.addma.2020.101564, Vol.36, pp.101564-1-24, 2020

Abstract:
The purpose of this work is to check if additive manufacturing technologies are suitable for reproducing porous samples designed for sound absorption. The work is an inter-laboratory test, in which the production of samples and their acoustic measurements are carried out independently by different laboratories, sharing only the same geometry codes describing agreed periodic cellular designs. Different additive manufacturing technologies and equipment are used to make samples. Although most of the results obtained from measurements performed on samples with the same cellular design are very close, it is shown that some discrepancies are due to shape and surface imperfections, or microporosity, induced by the manufacturing process. The proposed periodic cellular designs can be easily reproduced and are suitable for further benchmarking of additive manufacturing techniques for rapid prototyping of acoustic materials and metamaterials.

Keywords:
porous materials, designed periodicity, additive manufacturing, sound absorption

10.Darban H., Fabbrocino F., Luciano R., Size-dependent linear elastic fracture of nanobeams, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2020.103381, Vol.157, pp.103381-1-13, 2020
Darban H., Fabbrocino F., Luciano R., Size-dependent linear elastic fracture of nanobeams, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2020.103381, Vol.157, pp.103381-1-13, 2020

Abstract:
A nonlocal linear elastic fracture formulation is presented based on a discrete layer approach and an interface model to study cracked nanobeams. The formulation uses the stress-driven nonlocal theory of elasticity to account for the size-dependency in the constitutive equations, and the Bernoulli-Euler beam theory to define the kinematic field. Two fundamental mode I and mode II fracture nanospecimens with applications in Engineering Science are studied to reveal principal characteristics of the linear elastic fracture of beams at nanoscale. The domains are discretized both through the transverse and longitudinal directions and the field variables are derived by solving systems of the nonlocal equilibrium equations subjected to the variationally consistent and constitutive boundary and continuity conditions. The energy release rates of the fracture nanospecimens are calculated both from the global energy consideration and from the localized fields at the tip of the crack, i.e. the cohesive forces and the displacement jumps. The results are shown to be the same, proving the capability of the interface model to predict localized fields at the crack tip which are important for the cohesive fracture problems. It is found that the nanospecimens with higher nonlocality have higher fracture resistance and load bearing capacity due to higher energy absorptions and lower energy release rates. The crack propagation in the nanospecimens are also studied and load-displacement curves are presented. The nonlocality considerably increases the stiffness of the initial linear response of the nanospecimens. The fracture model is also able to capture the non-linear post-peak response and the unstable crack propagation, the snap-back instability, which is more intense for nanospecimens with higher nonlocality.

Keywords:
cracked nanobeams, nonlocal fracture, energy release rate, cohesive, crack propagation

11.Marszałek A., Burczyński T., Ordered fuzzy random variable: definition and the concept of normality, INFORMATION SCIENCES, ISSN: 0020-0255, DOI: 10.1016/j.ins.2020.08.120, pp.1-12, 2020
Marszałek A., Burczyński T., Ordered fuzzy random variable: definition and the concept of normality, INFORMATION SCIENCES, ISSN: 0020-0255, DOI: 10.1016/j.ins.2020.08.120, pp.1-12, 2020

Abstract:
The concept of fuzzy random variable combines two sources of uncertainty: randomness and fuzziness, whereas the model of ordered fuzzy numbers provides a representation of inaccurate quantitative data, and is an alternative to the standard fuzzy numbers model proposed by Zadeh. This paper develops the model of ordered fuzzy numbers by defining the concept of fuzzy random variables for these numbers, called further ordered fuzzy random variables. Thanks to the well-defined arithmetic of ordered fuzzy numbers (existence of neutral and opposite elements) and the introduced ordered fuzzy random variables; it becomes possible to construct fully fuzzy stochastic time series models such as e.g., the autoregressive model or the GARCH model in the form of classical equations, which can be estimated using the least-squares or the maximum likelihood method. Furthermore, the concept of normality of ordered fuzzy random variables and the method to generate pseudo-random ordered fuzzy variables with normal distribution are introduced.

Keywords:
ordered fuzzy numbers, fuzzy random variables, ordered fuzzy random variables, normal ordered fuzzy random variable

12.Kowalczyk-Gajewska K., Maździarz M., Elastic properties of nanocrystalline materials of hexagonal symmetry: the core-shell model and atomistic estimates, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2020.103393, Vol.157, pp.103393-1-21, 2020
Kowalczyk-Gajewska K., Maździarz M., Elastic properties of nanocrystalline materials of hexagonal symmetry: the core-shell model and atomistic estimates, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2020.103393, Vol.157, pp.103393-1-21, 2020

Abstract:
Anisotropic core-shell model of a nano-grained polycrystal is extended to estimate the effective elastic stiffness of several metals of hexagonal crystal lattice symmetry. In the approach the bulk nanocrystalline material is described as a two-phase medium with different properties for a grain boundary zone and a grain core. While the grain core is anisotropic, the boundary zone is isotropic and has a thickness defined by the cutoff radius of a corresponding atomistic potential for the considered metal. The predictions of the proposed mean-field model are verified with respect to simulations performed with the use of the Large-scale Atomic/Molecular Massively Parallel Simulator, the Embedded Atom Model, and the molecular statics method. The effect of the grain size on the overall elastic moduli of nanocrystalline material with random distribution of orientations is analyzed.

Keywords:
molecular statics, elasticity, polycrystal, effective medium, hexagonal symmetry

13.Lengiewicz J., Souza M., Lahmar M.A., Courbon C., Dalmas D., Stupkiewicz S., Scheibert J., Finite deformations govern the anisotropic shear-induced area reduction of soft elastic contacts, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, ISSN: 0022-5096, DOI: 10.1016/j.jmps.2020.104056, Vol.143, pp.104056-1-19, 2020
Lengiewicz J., Souza M., Lahmar M.A., Courbon C., Dalmas D., Stupkiewicz S., Scheibert J., Finite deformations govern the anisotropic shear-induced area reduction of soft elastic contacts, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, ISSN: 0022-5096, DOI: 10.1016/j.jmps.2020.104056, Vol.143, pp.104056-1-19, 2020

Abstract:
Solid contacts involving soft materials are important in mechanical engineering or biomechanics. Experimentally, such contacts have been shown to shrink significantly under shear, an effect which is usually explained using adhesion models. Here we show that quantitative agreement with recent high-load experiments can be obtained, with no adjustable parameter, using a non-adhesive model, provided that finite deformations are taken into account. Analysis of the model uncovers the basic mechanisms underlying anisotropic shear-induced area reduction, local contact lifting being the dominant one. We confirm experimentally the relevance of all those mechanisms, by tracking the shear-induced evolution of tracers inserted close to the surface of a smooth elastomer sphere in contact with a smooth glass plate. Our results suggest that finite deformations are an alternative to adhesion, when interpreting a variety of sheared contact experiments involving soft materials.

Keywords:
contact mechanics, friction, contact area, elastomer, full-field measurement

14.Maździarz M., Mościcki T., New zirconium diboride polymorphs—first-principles calculations, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13133022, Vol.13, No.13, pp.3022-1-13, 2020
Maździarz M., Mościcki T., New zirconium diboride polymorphs—first-principles calculations, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13133022, Vol.13, No.13, pp.3022-1-13, 2020

Abstract:
Two new hypothetical zirconium diboride (ZrB 2) polymorphs: (hP6-P6 3 /mmc-space group, no. 194) and (oP6-Pmmn-space group, no. 59), were thoroughly studied under the first-principles density functional theory calculations from the structural, mechanical and thermodynamic properties point of view. The proposed phases are thermodynamically stable (negative formation enthalpy). Studies of mechanical properties indicate that new polymorphs are less hard than the known phase (hP3-P6/mmm-space group, no. 191) and are not brittle. Analysis of phonon band structure and density of states (DOS) also show that the phonon modes have positive frequencies everywhere and the new ZrB 2 phases are not only mechanically but also dynamically stable. The estimated acoustic Debye temperature, ΘD, for the two new proposed ZrB 2 phases is about 760 K. The thermodynamic properties such as internal energy, free energy, entropy and constant-volume specific heat are also presented.

Keywords:
zirconium diboride, ab initio calculations, mechanical properties, elastic properties, phonons

15.Wang K., Kopeć M., Chang S., Qu B., Liu J., Politis D.J., Wang L., Liu G., Enhanced formability and forming efficiency for two-phase titanium alloys by fast light alloys stamping technology (FAST), Materials & Design, ISSN: 0264-1275, DOI: 10.1016/j.matdes.2020.108948, pp.1-25, 2020
Wang K., Kopeć M., Chang S., Qu B., Liu J., Politis D.J., Wang L., Liu G., Enhanced formability and forming efficiency for two-phase titanium alloys by fast light alloys stamping technology (FAST), Materials & Design, ISSN: 0264-1275, DOI: 10.1016/j.matdes.2020.108948, pp.1-25, 2020

Abstract:
During hot stamping of titanium alloys, insufficient forming temperatures result in limited material formability, whereas temperatures approaching the β phase transus also result in reduced formability due to phase transformation, grain coarsening and oxidation during the long-time heating. To solve this problem, Fast light Alloys Stamping Technology (FAST) is proposed in this paper, where fast heating is employed. Effects of heating parameters on the formability and post-form strength were studied by tensile tests. Forming of a wing stiffener was performed to validate this new process. Results show that microstructure of TC4 alloy after fast heating was in nonequilibrium state, which could enhance ductility significantly compared with the equilibrium state. When TC4 alloy was first heated to 950 °C with heating rate of 100 °C/s and then cooled to 700 °C, the elongation at 700 °C was more than 3 times that of a slow heating rate with soaking. Nano-scaled martensite with high dislocation density transformed from β phase was observed under fast heating condition. A complex shaped wing stiffener was successfully formed from TC4 titanium alloy in less than 70 s including heating, transfer and forming, and the post-form strength was almost the same with the initial blank.

Keywords:
titanium alloys, fast heating, hot stamping, formability, post-form strength

16.Moreira R., Chwastyk M., Baker J.L., Vargas Guzman H.A., Poma A., Quantitative determination of mechanical stability in the novel coronavirus spike protein, NANOSCALE, ISSN: 2040-3364, DOI: 10.1039/D0NR03969A, pp.1-6, 2020
Moreira R., Chwastyk M., Baker J.L., Vargas Guzman H.A., Poma A., Quantitative determination of mechanical stability in the novel coronavirus spike protein, NANOSCALE, ISSN: 2040-3364, DOI: 10.1039/D0NR03969A, pp.1-6, 2020

Abstract:
We report on the novel observation about the gain in mechanical stability of the SARS-CoV-2 (CoV2) spike (S) protein in comparison with SARS-CoV from 2002 (CoV1). Our findings have several biological implications in the subfamily of coronaviruses, as they suggest that the receptor binding domain (RBD) (~200 amino acids) plays a fundamental role as a damping element of the massive viral particle's motion prior to cell-recognition, while also facilitating viral attachment, fusion and entry. The mechanical stability via pulling of the RBD is 250 pN and 200 pN for CoV2 and CoV1 respectively, and the additional stability observed for CoV2 (~50 pN) might play a role in the increasing spread of COVID-19.

17.Jóźwiak-Niedźwiedzka D., Antolik A., Dziedzic K., Gméling K., Bogusz K., Laboratory investigations on fine aggregates used for concrete pavements due to the risk of ASR, Road Materials and Pavement Design, ISSN: 1468-0629, DOI: 10.1080/14680629.2020.1796767, pp.1-13, 2020
Jóźwiak-Niedźwiedzka D., Antolik A., Dziedzic K., Gméling K., Bogusz K., Laboratory investigations on fine aggregates used for concrete pavements due to the risk of ASR, Road Materials and Pavement Design, ISSN: 1468-0629, DOI: 10.1080/14680629.2020.1796767, pp.1-13, 2020

Abstract:
The assessment of the aggregate suitability for concrete pavements applies mainly to coarse aggregate. However, even fine aggregate can significantly affect the long-term durability of concrete when it is susceptible to alkali-silica reaction (ASR). The sustainable use of available fine aggregates for the production of concrete, while reducing the effects of ASR, requires special preventive measures. The paper proposed different procedures to determine the chemical composition of aggregate and the related ASR risk. The study covers various properties of natural fine aggregates from glacial deposits. The experiments included determination of chemical composition by prompt gamma activation analysis (PGAA), quantitative mineralogical characterisation on thin sections using digital image procedure (DIP) and expansion measurements in mortar bar test (MBT). The strong correlation of sand origin and its susceptibility to ASR was observed. Content of micro- and cryptocrystalline quartz in siliceous sand was found to have a crucial effect on its performance in AMBT.

Keywords:
fine aggregate, alkali-silica reaction, mineral composition, prompt gamma activation analysis, digital image procedure, glacial deposit

18.Gabriele V.R., Shvonski A., Hoffman C.S., Giersig M., Herczynski A., Naughton M.J., Kempa K., Towards spectrally selective catastrophic response, PHYSICAL REVIEW E, ISSN: 2470-0045, DOI: 10.1103/PhysRevE.101.062415, Vol.101, pp.062415-1-6, 2020
Gabriele V.R., Shvonski A., Hoffman C.S., Giersig M., Herczynski A., Naughton M.J., Kempa K., Towards spectrally selective catastrophic response, PHYSICAL REVIEW E, ISSN: 2470-0045, DOI: 10.1103/PhysRevE.101.062415, Vol.101, pp.062415-1-6, 2020

Abstract:
We study the large-amplitude response of classical molecules to electromagnetic radiation, showing the universality of the transition from linear to nonlinear response and breakup at sufficiently large amplitudes. We demonstrate that a range of models, from the simple harmonic oscillator to the successful Peyrard-Bishop-Dauxois type models of DNA, which include realistic effects of the environment (including damping and dephasing due to thermal fluctuations), lead to characteristic universal behavior: formation of domains of dissociation in driving force amplitude-frequency space, characterized by the presence of local boundary minima. We demonstrate that by simply following the progression of the resonance maxima in this space, while gradually increasing intensity of the radiation, one must necessarily arrive at one of these minima, i.e., a point where the ultrahigh spectral selectivity is retained. We show that this universal property, applicable to other oscillatory systems, is a consequence of the fact that these models belong to the fold catastrophe universality class of Thom's catastrophe theory. This in turn implies that for most biostructures, including DNA, high spectral sensitivity near the onset of the denaturation processes can be expected. Such spectrally selective molecular denaturation could find important applications in biology and medicine.

19.Mieloch A.A., Żurawek M., Giersig M., Rozwadowska N., Rybka J.D., Bioevaluation of superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with dihexadecyl phosphate (DHP), Scientific Reports, ISSN: 2045-2322, DOI: 10.1038/s41598-020-59478-2, Vol.10, pp.2725-1-11, 2020
Mieloch A.A., Żurawek M., Giersig M., Rozwadowska N., Rybka J.D., Bioevaluation of superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with dihexadecyl phosphate (DHP), Scientific Reports, ISSN: 2045-2322, DOI: 10.1038/s41598-020-59478-2, Vol.10, pp.2725-1-11, 2020

Abstract:
Superparamagnetic iron oxide nanoparticles (SPIONs) have been investigated for wide variety of applications. Their unique properties render them highly applicable as MRI contrast agents, in magnetic hyperthermia or targeted drug delivery. SPIONs surface properties affect a whole array of parameters such as: solubility, toxicity, stability, biodistribution etc. Therefore, progress in the field of SPIONs surface functionalization is crucial for further development of therapeutic or diagnostic agents. In this study, SPIONs were synthesized by thermal decomposition of iron (III) acetylacetonate Fe(acac)3 and functionalized with dihexadecyl phosphate (DHP) via phase transfer. Bioactivity of the SPION-DHP was assessed on SW1353 and TCam-2 cancer derived cell lines. The following test were conducted: cytotoxicity and proliferation assay, reactive oxygen species (ROS) assay, SPIONs uptake (via Iron Staining and ICP-MS), expression analysis of the following genes: alkaline phosphatase (ALPL); ferritin light chain (FTL); serine/threonine protein phosphatase 2A (PP2A); protein tyrosine phosphatase non-receptor type 11 (PTPN11); transferrin receptor 1 (TFRC) via RT-qPCR. SPION-DHP nanoparticles were successfully obtained and did not reveal significant cytotoxicity in the range of tested concentrations. ROS generation was elevated, however not correlated with the concentrations. Gene expression profile was slightly altered only in SW1353 cells.

20.Byra M., Jarosik P., Szubert A., Galperine M., Ojeda-Fournier H., Olson L., O'Boyle M., Comstock Ch., Andre M., Breast mass segmentation in ultrasound with selective kernel U-Net convolutional neural network, Biomedical Signal Processing and Control, ISSN: 1746-8094, DOI: 10.1016/j.bspc.2020.102027, Vol.61, pp.102027-1-10, 2020
Byra M., Jarosik P., Szubert A., Galperine M., Ojeda-Fournier H., Olson L., O'Boyle M., Comstock Ch., Andre M., Breast mass segmentation in ultrasound with selective kernel U-Net convolutional neural network, Biomedical Signal Processing and Control, ISSN: 1746-8094, DOI: 10.1016/j.bspc.2020.102027, Vol.61, pp.102027-1-10, 2020

Abstract:
In this work, we propose a deep learning method for breast mass segmentation in ultrasound (US). Variations in breast mass size and image characteristics make the automatic segmentation difficult. To addressthis issue, we developed a selective kernel (SK) U-Net convolutional neural network. The aim of the SKswas to adjust network's receptive fields via an attention mechanism, and fuse feature maps extractedwith dilated and conventional convolutions. The proposed method was developed and evaluated usingUS images collected from 882 breast masses. Moreover, we used three datasets of US images collectedat different medical centers for testing (893 US images). On our test set of 150 US images, the SK-U-Netachieved mean Dice score of 0.826, and outperformed regular U-Net, Dice score of 0.778. When evaluatedon three separate datasets, the proposed method yielded mean Dice scores ranging from 0.646 to 0.780. Additional fine-tuning of our better-performing model with data collected at different centers improvedmean Dice scores by ~6%. SK-U-Net utilized both dilated and regular convolutions to process US images. We found strong correlation, Spearman's rank coefficient of 0.7, between the utilization of dilated convo-lutions and breast mass size in the case of network's expansion path. Our study shows the usefulness ofdeep learning methods for breast mass segmentation. SK-U-Net implementation and pre-trained weightscan be found at github.com/mbyr/bus_seg.

Keywords:
attention mechanism, breast mass segmentation, convolutional neural networks, deep learning, receptive field, ultrasound imaging

21.Byra M., Dobruch-Sobczak K., Klimonda Z., Piotrzkowska-Wróblewska H., Litniewski J., Early prediction of response to neoadjuvant chemotherapy in breast cancer sonography using Siamese convolutional neural networks, IEEE Journal of Biomedical and Health Informatics, ISSN: 2168-2208, DOI: 10.1109/JBHI.2020.3008040, pp.1-8, 2020
Byra M., Dobruch-Sobczak K., Klimonda Z., Piotrzkowska-Wróblewska H., Litniewski J., Early prediction of response to neoadjuvant chemotherapy in breast cancer sonography using Siamese convolutional neural networks, IEEE Journal of Biomedical and Health Informatics, ISSN: 2168-2208, DOI: 10.1109/JBHI.2020.3008040, pp.1-8, 2020

Abstract:
Early prediction of response to neoadjuvant chemotherapy (NAC) in breast cancer is crucial for guiding therapy decisions. In this work, we propose a deep learning based approach for the early NAC response prediction in ultrasound (US) imaging. We used transfer learning with deep convolutional neural networks (CNNs) to develop the response prediction models. The usefulness of two transfer learning techniques was examined. First, a CNN pre-trained on the ImageNet dataset was utilized. Second, we applied double transfer learning, the CNN pre-trained on the ImageNet dataset was additionally fine-tuned with breast mass US images to differentiate malignant and benign lesions. Two prediction tasks were investigated. First, a L1 regularized logistic regression prediction model was developed based on generic neural features extracted from US images collected before the chemotherapy (a priori prediction). Second, Siamese CNNs were used to quantify differences between US images collected before the treatment and after the first and second course of NAC. The proposed methods were evaluated using US data collected from 39 tumors. The better performing deep learning models achieved areas under the receiver operating characteristic curve of 0.797 and 0.847 in the case of the a priori prediction and the Siamese model, respectively. The proposed approach was compared with a
method based on handcrafted morphological features. Our study presents the feasibility of using transfer learning with CNNs for the NAC response prediction in US imaging.

Keywords:
breast cancer, deep learning, neoadjuvant chemotherapy, Siamese convolutional neural networks, ultrasound imaging

22.Ghalya N., Sellier A., Ekiel-Jeżewska M.L., Feuillebois F., Effective viscosity of a dilute homogeneous suspension of spheres in Poiseuille flow between parallel slip walls, JOURNAL OF FLUID MECHANICS, ISSN: 0022-1120, DOI: 10.1017/jfm.2020.429, Vol.899, pp.A13-1-36, 2020
Ghalya N., Sellier A., Ekiel-Jeżewska M.L., Feuillebois F., Effective viscosity of a dilute homogeneous suspension of spheres in Poiseuille flow between parallel slip walls, JOURNAL OF FLUID MECHANICS, ISSN: 0022-1120, DOI: 10.1017/jfm.2020.429, Vol.899, pp.A13-1-36, 2020

Abstract:
For flows in microchannels, a slip on the walls may be efficient in reducing viscous dissipation. A related issue, addressed in this article, is to decrease the effective viscosity of a dilute monodisperse suspension of spheres in Poiseuille flow by using two parallel slip walls. Extending the approach developed for no-slip walls in Feuillebois et al. (J. Fluid Mech., vol. 800, 2016, pp. 111–139), a formal expression is obtained for the suspension intrinsic viscosity [μ] solely in terms of a stresslet component and a quadrupole component exerted on a single freely suspended sphere. In the calculation of [μ], the hydrodynamic interactions between a sphere and the slip walls are approximated using either the nearest wall model or the wall-superposition model. Both the stresslet and quadrupole are derived and accurately calculated using bipolar coordinates. Results are presented for [μ] in terms of H/(2a) and ˜λ = λ/a ≤ 1, where H is the gap between walls, a is the sphere radius and λ is the wall slip length using the Navier slip boundary condition. As compared with the no-slip case, the intrinsic viscosity strongly depends on ˜λ for given H/(2a), especially for small H/(2a). For example, in the very confined case H/(2a) = 2 (a lower bound found for practical validity of single-wall models) and for ˜λ = 1, the intrinsic viscosity is three times smaller than for a suspension bounded by no-slip walls and five times smaller than for an unbounded suspension (Einstein, Ann. Phys., vol. 19, 1906, pp. 289–306). We also provide a handy formula fitting our results for [μ] in the entire range 2 ≤ H/(2a) ≤ 100 and ˜λ ≤ 1.

Keywords:
complex fluids, low-Reynolds-number flows

23.Hat B., Jaruszewicz-Błońska J., Lipniacki T., Model-based optimization of combination protocols for irradiation-insensitive cancers, Scientific Reports, ISSN: 2045-2322, DOI: 10.1038/s41598-020-69380-6, Vol.10, pp.12652-1-14, 2020
Hat B., Jaruszewicz-Błońska J., Lipniacki T., Model-based optimization of combination protocols for irradiation-insensitive cancers, Scientific Reports, ISSN: 2045-2322, DOI: 10.1038/s41598-020-69380-6, Vol.10, pp.12652-1-14, 2020

Abstract:
Alternations in the p53 regulatory network may render cancer cells resistant to the radiation-induced apoptosis. In this theoretical study we search for the best protocols combining targeted therapy with radiation to treat cancers with wild-type p53, but having downregulated expression of PTEN or overexpression of Wip1 resulting in resistance to radiation monotherapy. Instead of using the maximum tolerated dose paradigm, we exploit stochastic computational model of the p53 regulatory network to calculate apoptotic fractions for both normal and cancer cells. We consider combination protocols, with irradiations repeated every 12, 18, 24, or 36 h to find that timing between Mdm2 inhibitor delivery and irradiation significantly influences the apoptotic cell fractions. We assume that uptake of the inhibitor is higher by cancer than by normal cells and that cancer cells receive higher irradiation doses from intersecting beams. These two assumptions were found necessary for the existence of protocols inducing massive apoptosis in cancer cells without killing large fraction of normal cells neighboring tumor. The best found protocols have irradiations repeated every 24 or 36 h with two inhibitor doses per irradiation cycle, and allow to induce apoptosis in more than 95% of cancer cells, killing less than 10% of normal cells.

24.Jóźwiak-Niedźwiedzka D., Fantilli A.P., Wool-reinforced cement based composites, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13163590, Vol.13, No.16, pp.3590-1-13, 2020
Jóźwiak-Niedźwiedzka D., Fantilli A.P., Wool-reinforced cement based composites, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13163590, Vol.13, No.16, pp.3590-1-13, 2020

Abstract:
In this paper, an overview of the latest research activities in the field of cement-based composites incorporating sheep wool reinforcement is presented. First, the characteristics of this type of natural fibre are described. Then, the current use of sheep wool fibres in cement-based composites is discussed. The research problems regarding the properties of cement matrix composites reinforced with sheep wool are divided into four groups: thermal and acoustic properties, mechanical behavior, durability issues, and microstructure aspects. The latter two groups are analysed separately, because both durability and microstructure are of particular importance for future applications of wool reinforcement. Finally, the main directions of future researches are presented.

Keywords:
natural fibres, sheep wool fibres, mechanical properties, durability, microstructure

25.Lewandowski-Szewczyk M.J., Stupkiewicz S., Non-standard contact conditions in generalized continua: microblock contact model for a Cosserat body, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2020.07.001, Vol.202, pp.881-894, 2020
Lewandowski-Szewczyk M.J., Stupkiewicz S., Non-standard contact conditions in generalized continua: microblock contact model for a Cosserat body, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2020.07.001, Vol.202, pp.881-894, 2020

Abstract:
Generalized continuum theories involve non-standard boundary conditions that are associated with the additional kinematic variables introduced in those theories, e.g., higher gradients of the displacement field or additional kinematic degrees of freedom. Accordingly, formulation of a contact problem for such a continuum necessarily requires that adequate contact conditions are formulated for the additional kinematic variables and/or for the respective generalized tractions. In this paper, we address several related open problems, namely, how to enhance the classic contact conditions to include the effects of the additional kinematic variables, how to link the enhanced contact model to the underlying microstructure of the solid, and how to do it in a consistent manner. As a first step towards a new class of contact models for generalized continua, a microblock contact model is derived for a Cosserat solid based on simple micromechanical considerations. To illustrate the non-trivial effects introduced by the non-standard boundary conditions, the problem of compression of an infinite strip with nonaligned microblocks is considered, and the analytical solution is derived for the corresponding boundary layers. A Hertz-like contact problem is also solved numerically with the focus on non-standard features of the solution and on the related size effects.

Keywords:
microstructure, contact problems, size effects, boundary layers, Cosserat continuum

26.Ceroni F., Darban H., Luciano R., Analysis of bond behavior of injected anchors in masonry elements by means of finite element modeling, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2020.112099, Vol.241, pp.112099-1-18, 2020
Ceroni F., Darban H., Luciano R., Analysis of bond behavior of injected anchors in masonry elements by means of finite element modeling, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2020.112099, Vol.241, pp.112099-1-18, 2020

Abstract:
Injected anchors made of steel bars embedded in masonry elements by means of cement-based grout represented in the past a wide solution for avoiding out-of-plane mechanisms. Corrosion phenomena in steel bars reduced the effectiveness of such type of intervention over time. Innovative materials, as the Fiber Reinforced Plastic ones, can represent a suitable alternative to increase durability and performance of injected anchors. Since the effectiveness of injected anchors is strictly related to bond behaviour along both the bar-grout and the grout-masonry interfaces, a detailed analysis by means of a Finite Element model was developed for different types of bars embedded in masonry elements. The numerical model was firstly calibrated on some experimental results of pull-out tests available in literature and, then, is used for investigating the effects of several parameters on both local and global behaviour. Load-displacement curves and local distributions of shear stresses are examined in detail. The numerical analyses evidenced that the maximum tensile force in the anchor mainly depends on the shear strength of the bar-grout and the grout-masonry interfaces and on the embedded length, but for very long embedded length, it can be limited by the tensile failure in the anchor or in the masonry.

Keywords:
masonry, FRP bars, injected anchors, bond, pull-out test, FE model

27.Pisarski D., Szmidt T., Konowrocki R., Decentralized semi‐active structural vibration control based on optimal system modelling, STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2624, pp.e2624-1-20, 2020
Pisarski D., Szmidt T., Konowrocki R., Decentralized semi‐active structural vibration control based on optimal system modelling, STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2624, pp.e2624-1-20, 2020

Abstract:
The problem of decentralized semi‐active stabilization of vibration of a beam structure is studied. The decentralized controller's architecture is attained by means of optimal system modelling. In this approach, based on a specially designed and optimized set of basis functions, the solution to the continuous Euler-Bernoulli beam equation is approximated by a discrete system, where the mass and stiffness matrices ensure that the assumed stabilizing control law can be operated by using solely the local state information. The performance of the method is examined through numerical experiments for a series of free‐vibration scenarios with comparison to competitive decentralized and centralized control strategies. The performance impact of the selection of the parameters of the optimal system model is also studied. The designed method allows practical modular arrangements of the control system and is applicable to large‐scale structures.

Keywords:
bilinear system, decentralized control, polynomial basis, semi-active control, stabilization

28.Zawidzki M., Szklarski J., Multi-objective optimization of the floor plan of a single story family house considering position and orientation, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2019.102766, Vol.141, pp.1-16, 2020
Zawidzki M., Szklarski J., Multi-objective optimization of the floor plan of a single story family house considering position and orientation, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2019.102766, Vol.141, pp.1-16, 2020

Abstract:
Improving the architectural layout for diverse objectives using rigorous mathematical optimization methods gradually receives more attention by the researchers. Such optimization however, is usually reduced to a much simpler and relatively well-defined problem such as: facility layout optimization, quadratic assignment problem, rectangle partitioning. Nonetheless, architects are usually skeptical about such approaches since they produce solutions which lack certain architectural qualities. This paper proposes a framework where architectural functional layout (FL) is optimized for the following objectives: functionality (defined by users), insolation (calculated according to geographical conditions), outside view attractiveness (assessed on-site) and external noise (measured on-site). Incorporating the latter two and simultaneous optimization of FLs for objectives related specifically to the site: position and orientation are the novel contributions of this paper. Firstly, a set of candidate FLs is generated, next they are evaluated for optimal location and orientation on a given site. Optimality is conceived here as maximization of real-valued objective function combining: user's satisfaction level of the outside views, shielding from external noise, and insolation
preference. The importance of these factors for each type of room is assessed by the user (as weights). A case study on an existing site is presented. The view quality was arbitrarily assessed and the noise map was assessed by A-weighted equivalent sound level measurements. A general gradient-based method for finding optimal and near-optimal solutions was applied. The output of this optimization is a set of room configurations with their locations and orientations on the site returned to the user for final selection.

Keywords:
architectural optimization, subjective evaluation, functional layout, acoustic comfort, coarse grid

29.Jóźwiak-Niedźwiedzka D., Dąbrowski M., Bogusz K., Glinicki M.A., Influence of slag cement on the permeability of concrete for biological shielding structures, Energies, ISSN: 1996-1073, DOI: 10.3390/en13174582, Vol.13, No.17, pp.4582-1-16, 2020
Jóźwiak-Niedźwiedzka D., Dąbrowski M., Bogusz K., Glinicki M.A., Influence of slag cement on the permeability of concrete for biological shielding structures, Energies, ISSN: 1996-1073, DOI: 10.3390/en13174582, Vol.13, No.17, pp.4582-1-16, 2020

Abstract:
Durability of concrete designed for radiation shielding structures is an important issue in nuclear power plant safety. An investigation of the permeability of concrete containing heavyweight aggregates and water-bearing aggregates was performed with respect to gaseous and liquid media. Mix design was developed using Portland and slag cement, crushed magnetite and serpentine aggregate. The use of slag cement in concrete containing magnetite and serpentine aggregates resulted in the substantial improvement of the compressive strength in comparison with Portland cement concrete. The application of slag cement was found to reduce the chloride ingress, regardless of the special aggregate use. The coefficient of chloride migration was within the range 5 ÷ 8 × 10^−12 m^2/s and 17 ÷ 25 × 10^−12 m^2/s for slag cement concrete and Portland cement concrete, respectively. At the same time, the carbonation depth was increased twice for slag cement concrete in comparison to Portland cement concrete. However, the maximum carbonation depth after one year of exposure to 1% CO2 was only 14 mm for slag cement concrete, and 7 mm for reference concrete. The total pore volume evaluated using mercury intrusion porosimetry was influenced by the type of special aggregate used. It was shown that concrete with various contents of magnetite aggregate and slag cement achieved the smallest total pore volume. While serpentine coarse aggregate caused an increase in total pore volume in comparison to concrete with magnetite aggregate.

Keywords:
chloride permeability, carbonation, slag cement, radiation shielding concrete, microstructure, MIP, mix design, Portland cement, magnetite

30.Nosewicz S., Rojek J., Chmielewski M., Discrete element framework for determination of sintering and postsintering residual stresses of particle reinforced composites, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13184015, Vol.13, No.18, pp.4015-1- 20, 2020
Nosewicz S., Rojek J., Chmielewski M., Discrete element framework for determination of sintering and postsintering residual stresses of particle reinforced composites, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13184015, Vol.13, No.18, pp.4015-1- 20, 2020

Abstract:
In this paper, the discrete element method framework is employed to determine and analyze the stresses induced during and after the powder metallurgy process of particle-reinforced composite. Applied mechanical loading and the differences in the thermal expansion coefficients of metal/intermetallic matrix and ceramic reinforcing particles during cooling produce the complex state of stresses in and between the particles, leading to the occurrence of material defects, such as cracks, and in consequence the composite degradation. Therefore, the viscoelastic model of pressure-assisted sintering of a two-phase powder mixture is applied in order to study the stress field of particle assembly of intermetallic-ceramic composite NiAl/Al2O3. The stress evaluation is performed at two levels: macroscopic and microscopic. Macroscopic averaged stress is determined using the homogenization method using the representative volume element. Microscopic stresses are calculated both in the body of particles and in the contact interface (necks) between particles. Obtained results are in line with the cooling mechanism of the two-phase materials.

Keywords:
sintering, discrete element method, residual stress, particle-reinforced composites

31.Kukla D., Kopeć M., Kowalewski Z.L., Politis D.J., Jóźwiak S., Senderowski C., Thermal barrier stability and wear behavior of CVD deposited aluminide coatings for MAR 247 nickel superalloy, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13173863, Vol.13, No.17, pp.3863-1-11, 2020
Kukla D., Kopeć M., Kowalewski Z.L., Politis D.J., Jóźwiak S., Senderowski C., Thermal barrier stability and wear behavior of CVD deposited aluminide coatings for MAR 247 nickel superalloy, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13173863, Vol.13, No.17, pp.3863-1-11, 2020

Abstract:
In this paper, aluminide coatings of various thicknesses and microstructural uniformity obtained using chemical vapor deposition (CVD) were studied in detail. The optimized CVD process parameters of 1040 °C for 12 h in a protective hydrogen atmosphere enabled the production of high density and porosity-free aluminide coatings. These coatings were characterized by beneficial mechanical features including thermal stability, wear resistance and good adhesion strength to MAR 247 nickel superalloy substrate. The microstructure of the coating was characterized through scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Mechanical properties and wear resistance of aluminide coatings were examined using microhardness, scratch test and standardized wear tests, respectively. Intermetallic phases from the Ni-Al system at specific thicknesses (20-30 µm), and the chemical and phase composition were successfully evaluated at optimized CVD process parameters. The optimization of the CVD process was verified to offer high performance coating properties including improved heat, adhesion and abrasion resistance.

Keywords:
chemical vapor deposition, nickel alloys, coatings, X-ray analysis

32.Akhter M.J., Kuś W., Mrozek A., Burczyński T., Mechanical properties of monolayer MoS2 with randomly distributed defects, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13061307, Vol.13, No.6, pp.1307-1-14, 2020
Akhter M.J., Kuś W., Mrozek A., Burczyński T., Mechanical properties of monolayer MoS2 with randomly distributed defects, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13061307, Vol.13, No.6, pp.1307-1-14, 2020

Abstract:
The variation of elastic constants stiffness coefficients with respect to different percentage ratios of defects in monolayer molybdenum disulfide (MLMoS2) is reported for a particular set of atomistic nanostructural characteristics. The common method suggested is to use conventional defects such as single vacancy or di vacancy, and the recent studies use stone-walled multiple defects for highlighting the differences in the mechanical and electronic properties of 2D materials. Modeling the size influence of monolayer MoS2 by generating defects which are randomly distributed for a different percentage from 0% to 25% is considered in the paper. In this work, the geometry of the monolayer MoS2 defects modeled as randomized over the domain are taken into account. For simulation, the molecular static method is adopted and study the effect of elastic stiffness parameters of the 2D MoS2 material. Our findings reveals that the expansion of defects concentration leads to a decrease in the elastic properties, the sheer decrease in the elastic properties is found at 25%. We also study the diffusion of Molybdenum (Mo) in Sulphur (S) layers of atoms within MoS2 with Mo antisite defects. The elastic constants dwindle in the case of antisite defects too, but when compared to pure defects, the reduction was to a smaller extent in monolayer MoS2. Nevertheless, the Mo diffusion in sulfur gets to be more and more isotropic with the increase in the defect concentrations and elastic stiffness decreases with antisite defects concentration up to 25%. The distribution of antisite defects plays a vital role in modulating Mo diffusion in sulfur. These results will be helpful and give insights in the design of 2D materials.

Keywords:
mono-layer MoS2, mechanical properties, molecular statics/dynamics, defects, random distributed defects

33.Ura D.P., Rosell-Llompart J., Zaszczyńska A., Vasilyev G., Gradys A., Szewczyk P.K., Knapczyk-Korczak J., Avrahami R., Šišková A.O., Arinstein A., Sajkiewicz P., Zussman E., Stachewicz U., The role of electrical polarity in electrospinning and on the mechanical and structural properties of as-spun fibers, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13184169, Vol.13, No.18, pp.4169-1-18, 2020
Ura D.P., Rosell-Llompart J., Zaszczyńska A., Vasilyev G., Gradys A., Szewczyk P.K., Knapczyk-Korczak J., Avrahami R., Šišková A.O., Arinstein A., Sajkiewicz P., Zussman E., Stachewicz U., The role of electrical polarity in electrospinning and on the mechanical and structural properties of as-spun fibers, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13184169, Vol.13, No.18, pp.4169-1-18, 2020

Abstract:
Electric field strength and polarity in electrospinning processes and their effect on process dynamics and the physical properties of as-spun fibers is studied. Using a solution of the neutral polymer such as poly(methyl methacrylate) (PMMA) we explored the electrospun jet motion issued from a Taylor cone. We focused on the straight jet section up to the incipient stage of the bending instability and on the radius of the disk of the fibers deposited on the collecting electrode. A new correlation formula using dimensionless parameters was found, characterizing the effect of the electric field on the length of the straight jet, L˜E~E˜0.55. This correlation was found to be valid when the spinneret was either negatively or positively charged and the electrode grounded. The fiber deposition radius was found to be independent of the electric field strength and polarity. When the spinneret was negatively charged, L˜E was longer, the as-spun fibers were wider. The positively charged setup resulted in fibers with enhanced mechanical properties and higher crystallinity. This work demonstrates that often-overlooked electrical polarity and field strength parameters influence the dynamics of fiber electrospinning, which is crucial for designing polymer fiber properties and optimizing their collection.

Keywords:
fibers, electrical polarity, charges, electrospinning, PMMA, mechanical properties

34.Kovalchuk V., Mladenov I.M., Classical motions of infinitesimal rotators on mylar balloons, MATHEMATICAL METHODS IN THE APPLIED SCIENCES, ISSN: 0170-4214, DOI: 10.1002/mma.6660, pp.1-14, 2020
Kovalchuk V., Mladenov I.M., Classical motions of infinitesimal rotators on mylar balloons, MATHEMATICAL METHODS IN THE APPLIED SCIENCES, ISSN: 0170-4214, DOI: 10.1002/mma.6660, pp.1-14, 2020

Abstract:
This paper starts with the derivation of the most general equations of motion for the infinitesimal rotators moving on arbitrary two‐dimensional surfaces of revolution. Both geodesic and geodetic (i.e., without any external potential) equations of motion on surfaces with nontrivial curvatures that are embedded into the three dimensional Euclidean space are discussed. The Mylar balloon as a concrete example for the application of the scheme was chosen. A new parameterization of this surface is presented, and the corresponding equations of motion for geodesics and geodetics are expressed in an analytical form through the elliptic functions and elliptic integrals. The so‐obtained results are also compared with those for the two‐dimensional sphere embedded into the three‐dimensional Euclidean space for which it can be shown that the geodesics and geodetics are plane curves realized as the great and small circles on the sphere, respectively.

Keywords:
elliptic integrals and elliptic functions, geodesics and geodetics, infinitesimal rotators, mylar balloons, non-Euclidean spaces, surfaces of revolution

35.Zaszczyńska A., Sajkiewicz P.Ł., Gradys A., Tymkiewicz R., Urbanek O., Kołbuk D., Influence of process-material conditions on the structure and biological properties of electrospun polyvinylidene fluoride fibers, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2020.133368, Vol.68, No.3, pp.627-633, 2020
Zaszczyńska A., Sajkiewicz P.Ł., Gradys A., Tymkiewicz R., Urbanek O., Kołbuk D., Influence of process-material conditions on the structure and biological properties of electrospun polyvinylidene fluoride fibers, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2020.133368, Vol.68, No.3, pp.627-633, 2020

Abstract:
Polyvinylidene fluoride (PVDF) is one of the most important piezoelectric polymers. Piezoelectricity in PVDF appears in polar β and ɣ phases. Piezoelectric fibers obtained by means of electrospinning may be used in tissue engineering (TE) as a smart analogue of the natural extracellular matrix (ECM). We present results showing the effect of rotational speed of the collecting drum on morphology, phase content and in vitro biological properties of PVDF nonwovens. Morphology and phase composition were analyzed using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR), respectively. It was shown that increasing rotational speed of the collector leads to an increase in fiber orientation, reduction in fiber diameter and considerable increase of polar phase content, both b and g. In vitro cell culture experiments, carried out with the use of ultrasounds in order to generate electrical potential via piezoelectricity, indicate a positive effect of polar phases on fibroblasts. Our preliminary results demonstrate that piezoelectric PVDF scaffolds are promising materials for tissue engineering applications, particularly for neural tissue regeneration, where the electric potential is crucial.

Keywords:
scaffolds, electrospinning, polyvinylidene fluoride, tissue engineering

36.Jarosik P., Klimonda Z., Lewandowski M., Byra M., Breast lesion classification based on ultrasonic radio-frequency signals using convolutional neural networks, Biocybernetics and Biomedical Engineering, ISSN: 0208-5216, DOI: 10.1016/j.bbe.2020.04.002, Vol.40, No.3, pp.977-986, 2020
Jarosik P., Klimonda Z., Lewandowski M., Byra M., Breast lesion classification based on ultrasonic radio-frequency signals using convolutional neural networks, Biocybernetics and Biomedical Engineering, ISSN: 0208-5216, DOI: 10.1016/j.bbe.2020.04.002, Vol.40, No.3, pp.977-986, 2020

Abstract:
We propose a novel approach to breast mass classification based on deep learning models that utilize raw radio-frequency (RF) ultrasound (US) signals. US images, typically displayed by US scanners and used to develop computer-aided diagnosis systems, are reconstructed using raw RF data. However, information related to physical properties of tissues present in RF signals is partially lost due to the irreversible compression necessary to make raw data readable to the human eye. To utilize the information present in raw US data, we develop deep learning models that can automatically process small 2D patches of RF signals and their amplitude samples. We compare our approach with classification method based on the Nakagami parameter, a widely used quantitative US technique utilizing RF data amplitude samples. Our better performing deep learning model, trained using RF signals and their envelope samples, achieved good classification performance, with the area under the receiver attaining operating characteristic curve (AUC) and balanced accuracy of 0.772 and 0.710, respectively. The proposed method significantly outperformed the Nakagami parameter-based classifier, which achieved AUC and accuracy of 0.64 and 0.611, respectively. The developed deep learning models were used to generate parametric maps illustrating the level of mass malignancy. Our study presents the feasibility of using RF data for the development of deep learning breast mass classification models.

Keywords:
breast lesion classification, convolutional neural networks, deep learning, radio-frequency signals, ultrasound imaging

37.Kovalchuk V., Gołubowska B., Rożko E.E., Mechanics of incompressible test bodies moving in Riemannian spaces, MATHEMATICAL METHODS IN THE APPLIED SCIENCES, ISSN: 0170-4214, DOI: 10.1002/mma.6651, pp.1-15, 2020
Kovalchuk V., Gołubowska B., Rożko E.E., Mechanics of incompressible test bodies moving in Riemannian spaces, MATHEMATICAL METHODS IN THE APPLIED SCIENCES, ISSN: 0170-4214, DOI: 10.1002/mma.6651, pp.1-15, 2020

Abstract:
In the present paper, we have discussed the mechanics of incompressible test bodies moving in Riemannian spaces with nontrivial curvature tensors. For Hamilton's equations of motion, the solutions have been obtained in the parametrical form and the special case of the purely gyroscopic motion on the sphere has been discussed. For the geodetic case when the potential is equal to zero, the comparison between the geodetic and geodesic solutions has been done and illustrated in details for the case of a particular choice of the constants of motion of the problem. The obtained results could be applied, among others, in geophysical problems, for example, for description of the movement of continental plates or the motion of a drop of fat or a spot of oil on the surface of the ocean (e.g., produced during some "ecological disaster"), or generally in biomechanical problems, for example, for description of the motion of objects with internal structure on different curved two-dimensional surfaces (e.g., transport of proteins along the curved biological membranes).

Keywords:
geodesics, geodetics, gyroscopic motion, incompressibility constraints, mechanics of infinitesimal test bodies, Riemannian spaces

38.Sankaran A., Pawłowska S., Pierini F., Kowalewski T.A., Yarin A.L., Dynamics of electrospun hydrogel filaments in oscillatory microchannel flows: a theoretical and experimental approach, PHYSICS OF FLUIDS, ISSN: 1070-6631, DOI: 10.1063/5.0011005, Vol.32, No.7, pp.072008-1-13, 2020
Sankaran A., Pawłowska S., Pierini F., Kowalewski T.A., Yarin A.L., Dynamics of electrospun hydrogel filaments in oscillatory microchannel flows: a theoretical and experimental approach, PHYSICS OF FLUIDS, ISSN: 1070-6631, DOI: 10.1063/5.0011005, Vol.32, No.7, pp.072008-1-13, 2020

Abstract:
The dynamics of highly flexible micro- and nano-filaments are important to a variety of biological, medical, and industrial problems. The filament configuration variation and cross-stream migration in a microchannel are affected by thermal fluctuations in addition to elastic and viscous forces. Here, hydrogel nano-filaments with small bending Young's moduli are utilized to elucidate the transitional behavior of elastic Brownian filaments in an oscillatory microchannel flow. A numerical model based on chain elastic dumbbells similar to the Rouse-Zimm model accounting for elastic, viscous, and random Brownian forces is proposed and implemented. In addition, a theoretical model to describe the average orientation–deformation tensor evolution for an ensemble of filaments in an oscillatory flow is proposed. The results are compared with the evolution observed in the experiments.

39.Lee B.Y., Chu C.T., Krajewski M., Michalska M., Lin J.Y., Temperature-controlled synthesis of spinel lithium nickel manganese oxide cathode materials for lithium-ion batteries, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2020.05.124, Vol.46, No.13, pp.20856-20864, 2020
Lee B.Y., Chu C.T., Krajewski M., Michalska M., Lin J.Y., Temperature-controlled synthesis of spinel lithium nickel manganese oxide cathode materials for lithium-ion batteries, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2020.05.124, Vol.46, No.13, pp.20856-20864, 2020

Abstract:
In this work, we successfully synthesized series of LiNi0.5Mn1.5O4 (LNMO) cathode materials with spinel structure by using a facile sol-gel method and then calcined at various temperature ranging from 600 to 1000 °C. The application of different calcination temperatures significantly influenced the surface morphology, stoichiometry and crystalline nature of the as-synthesized LNMO material. According to the results of physical characterizations, the LNMO materials calcined at various temperatures mainly revealed the stoichiometric disordered Fd-3m structure with a small amount of well-ordered P4332 phase. The structural analysis also exhibited that the control of the calcination temperature contributed to the higher crystalline nature. Moreover, the morphological investigations indicated that the increasing calcination temperatures caused the formation of large micron-sized LNMO material. In turn, the electrochemical evaluations revealed the impact of the calcination temperatures on enhancing the electrochemical performances of the LNMO electrode materials up to 900 °C. The LNMO electrode calcined at 900 °C exhibited an impressive initial discharge specific capacity of ca. 142 mAh g^−1 between 3.5 and 4.9 V vs. Li/Li+, and remarkably improved capacity retention of 97% over 50 cycles. Those excellent electrochemical properties were associated with the presence of the dominant Fd-3m phase over the P4332 phase. Additionally, the results of the corrosion and dissolution tests which were performed for all calcined LNMO materials in order to estimate the amount of manganese and nickel ions leached from them, proved that the micro-sized LNMO calcined at 900 °C was the most stable.

Keywords:
spinel LiNi0.5Mn1.5O4, sol-gel synthesis, calcination temperature, cathode material, lithium-ion batteries

40.Hou J., Li Z., Zhang Q., Jankowski Ł., Zhang H., Local mass addition and data fusion for structural damage identification using approximate models, International Journal of Structural Stability and Dynamics, ISSN: 1793-6764, DOI: 10.1142/S0219455420501242, pp.1-24, 2020
Hou J., Li Z., Zhang Q., Jankowski Ł., Zhang H., Local mass addition and data fusion for structural damage identification using approximate models, International Journal of Structural Stability and Dynamics, ISSN: 1793-6764, DOI: 10.1142/S0219455420501242, pp.1-24, 2020

Abstract:
In practical civil engineering, structural damage identification is difficult to implement due to the shortage of measured modal information and the influence of noise. Furthermore, typical damage identification methods generally rely on a precise Finite Element (FE) model of the monitored structure. Pointwise mass alterations of the structure can effectively improve the quantity and sensitivity of measured data, while the data fusion methods can adequately utilize various kinds of data and identification results. This paper proposes a damage identification method that requires only approximate FE models and combines the advantages of pointwise mass additions and data fusion. First, an additional mass is placed at different positions throughout the structure to collect the dynamic response and obtain the corresponding modal information. The resulting relation between natural frequencies and the position of the added mass is sensitive to local damage, and it is thus utilized to form a new objective function based on the modal assurance criterion (MAC) and l1-based sparsity promotion. The proposed objective function is mostly insensitive to global structural parameters, but remains sensitive to local damage. Several approximate FE models are then established and separately used to identify the damage of the structure, and then the Dempster-Shafer method of data fusion is applied to fuse the results from all the approximate models. Finally, fractional data fusion is proposed to combine the results according to the parametric probability distribution of the approximate FE models, which allows the natural weight of each approximate model to be determined for the fusion process. Such an approach circumvents the need for a precise FE model, which is usually not easy to obtain in real application, and thus enhances the practical applicability of the proposed method, while maintaining the damage identification accuracy. The proposed approach is verified numerically and experimentally. Numerical simulations of a simply supported beam and a long-span bridge confirm that it can be used for damage identification, including a single damage and multiple damages, with a high accuracy. Finally, an experiment of a cantilever beam is successfully performed.

Keywords:
structural health monitoring (SHM), damage identification, adding mass, data fusion, objective function, modal assurance criterion (MAC)

41.Luo L., Akinoglu E.M., Wu W., Dodge T., Wang X., Zhou G., Naughton M.J., Kempa K., Giersig M., Nano-bridged nanosphere lithography, NANOTECHNOLOGY, ISSN: 0957-4484, DOI: 10.1088/1361-6528/ab7c4c, Vol.31, pp.245302-1-6, 2020
Luo L., Akinoglu E.M., Wu W., Dodge T., Wang X., Zhou G., Naughton M.J., Kempa K., Giersig M., Nano-bridged nanosphere lithography, NANOTECHNOLOGY, ISSN: 0957-4484, DOI: 10.1088/1361-6528/ab7c4c, Vol.31, pp.245302-1-6, 2020

Abstract:
We develop nano-bridged nanosphere lithography (NB-NSL), a modification to the widely used conventional nanosphere lithography (NSL). Nano-bridges between polystyrene (PS) spheres of a pristine NSL template are controllably formed in a two-step process: (i) spin-coating of a dilute styrene solution on top of the template, followed by (ii) oxygen plasma etching of the template. We show that the nanobridge dimensions can be precisely tuned by controlling the pre-processing conditions and the plasma etching time. The resulting lithography templates feature control over the shape and size of the apertures, which determine the morphology of the final nano-island arrays after material deposition and template removal. The unique advantage of NB-NSL is that PS particle templates based on a single PS particle diameter can be utilized for the fabrication of a variation of nano-island shapes and sizes, whereas conventional NSL yields only bowtie-shaped nano-islands, with their size being predetermined by the PS particle diameter of the template.

Keywords:
nanofabrication, nanosphere lithography, colloid lithography

42.Kołbuk D., Jeznach O., Wrzecionek M., Gadomska-Gajadhur A., Poly(glycerol succinate) as an eco-friendly component of PLLA and PLCL fibres towards medical applications, Polymers, ISSN: 2073-4360, DOI: 10.3390/polym12081731, Vol.12, No.8, pp.1731-1-17, 2020
Kołbuk D., Jeznach O., Wrzecionek M., Gadomska-Gajadhur A., Poly(glycerol succinate) as an eco-friendly component of PLLA and PLCL fibres towards medical applications, Polymers, ISSN: 2073-4360, DOI: 10.3390/polym12081731, Vol.12, No.8, pp.1731-1-17, 2020

Abstract:
This study was conducted as a first step in obtaining eco-friendly fibres for medical applications using a synthesised oligomer poly(glycerol succinate) (PGSu) as an additive for synthetic poly(L-lactic acid) (PLLA) and poly (L-lactide-co-caprolactone) (PLCL). The effects of the oligomer on the structure formation, morphology, crystallisation behaviour, and mechanical properties of electrospun bicomponent fibres were investigated. Nonwovens were investigated by means of scanning electron microscopy (SEM), wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and mechanical testing. The molecular structure of PLLA fibres is influenced by the presence of PGSu mainly acting as an enhancer of molecular orientation. In the case of semicrystalline PLCL, chain mobility was enhanced by the presence of PGSu molecules, and the crystallinity of bicomponent fibres increased in relation to that of pure PLCL. The mechanical properties of bicomponent fibres were influenced by the level of PGSu present and the extent of crystal formation of the main component. An in vitro study conducted using L929 cells confirmed the biocompatible character of all bicomponent fibres.

Keywords:
poly(glycerol succinate), plasticiser, eco-friendly polymer, electrospinning, hyperbranched polyester

43.Gupta A., Jain A., Tripathi S., Structural and electrochemical studies of bromide derived ionic liquid-based gel polymer electrolyte for energy storage application, Journal of Energy Storage, ISSN: 2352-152X, DOI: 10.1016/j.est.2020.101723, Vol.32, pp.101723-1-7, 2020
Gupta A., Jain A., Tripathi S., Structural and electrochemical studies of bromide derived ionic liquid-based gel polymer electrolyte for energy storage application, Journal of Energy Storage, ISSN: 2352-152X, DOI: 10.1016/j.est.2020.101723, Vol.32, pp.101723-1-7, 2020

Abstract:
In the present studies, poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), ionic liquid {1-Ethyl-3-methylimidazolium bromide} (EMIM)(Br), and magnesium perchlorate Mg(ClO4)2 as salt were used to synthesize free standing electrolyte films by using solution cast technique. The prepared electrolyte films were investigated by using various structural and electrochemical techniques like scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) as well as ionic and temperature dependence studies. It has been observed that addition of ionic liquid significantly increases the properties like ionic conductivity, thermal stability, transparency etc. The maximum room temperature ionic conductivity for the optimized system was found to be of the order of 2.05 × 10^−2 S cm^−1 which is suitable for device fabrication point of view. The optimized electrolyte films are suitable for supercapacitor application.

Keywords:
gel polymer electrolytes, ionic liquid, solution cast technique, supercapacitors

44.Magliulo M., Lengiewicz J., Zilian A., Beex L.A.A., Beam-inside-beam contact: mechanical simulations of slender medical instruments inside the human body, Computer Methods and Programs in Biomedicine, ISSN: 0169-2607, DOI: 10.1016/j.cmpb.2020.105527, Vol.196, pp.105527-1-14, 2020
Magliulo M., Lengiewicz J., Zilian A., Beex L.A.A., Beam-inside-beam contact: mechanical simulations of slender medical instruments inside the human body, Computer Methods and Programs in Biomedicine, ISSN: 0169-2607, DOI: 10.1016/j.cmpb.2020.105527, Vol.196, pp.105527-1-14, 2020

Abstract:
This contribution presents a rapid computational framework to mechanically simulate the insertion of a slender medical instrument in a tubular structure such as an artery, the cochlea or another slender instrument.

Keywords:
surgical simulation, contact mechanics, beam-inside-beam, artery, cochlea

45.Pnevmatikos N., Konstandakopoulou F., Błachowski B., Papavasileiou G., Broukos P., Multifractal analysis and wavelet leaders for structural damage detection of structures subjected to earthquake excitation, Soil Dynamics and Earthquake Engineering, ISSN: 0267-7261, DOI: 10.1016/j.soildyn.2020.106328, Vol.139, pp.106328-1-4, 2020
Pnevmatikos N., Konstandakopoulou F., Błachowski B., Papavasileiou G., Broukos P., Multifractal analysis and wavelet leaders for structural damage detection of structures subjected to earthquake excitation, Soil Dynamics and Earthquake Engineering, ISSN: 0267-7261, DOI: 10.1016/j.soildyn.2020.106328, Vol.139, pp.106328-1-4, 2020

Abstract:
This work is an effort to join, for the first-time, multifractal analysis and damage detection in civil structures subjected to strong ground seismic motions. Specifically, based on the singularity spectrum quantitative and qualitative criteria are proposed. The qualitative criteria are based on the concave of singularity spectrum of damage and undamaged structure. The proposed quantitative criterion is based on calculation of damage index taken the parameters of singularity spectrum. In order to achieve the above goal, a robust signal processing method, which is known as multifractal wavelet leader (MFWL) is used. The multifractal analysis is a tool to calculate fractal properties as well as scaling behavior of the structural response excited by an earthquake. The singularity spectrum is obtained from the Legendre-transformation to Holder exponents. In this paper, a parameter which is based on the shape of singularity spectrum and can identify the damage in the structure is proposed. The proposed method is an output-only approach for damage detection. Considering that the dynamic behavior of an inelastic system subjected to strong ground motion appears to be a non-stationary process, the above procedure of multifractal wavelet leader is suitable to retrieve the simulation response data. The findings from the analysis show that the MFWL is an appropriate scheme for structural damage detection.

Keywords:
multifractal wavelet leader, damage detection, singularity spectrum, earthquake engineering, structural safety

46.Meissner M., Wiśniewski K., Investigation of damping effects on low-frequency steady-state acoustical behaviour of coupled spaces, Royal Society Open Science, ISSN: 2054-5703, DOI: 10.1098/rsos.200514, Vol.7, No.8, pp.200514-1-14, 2020
Meissner M., Wiśniewski K., Investigation of damping effects on low-frequency steady-state acoustical behaviour of coupled spaces, Royal Society Open Science, ISSN: 2054-5703, DOI: 10.1098/rsos.200514, Vol.7, No.8, pp.200514-1-14, 2020

Abstract:
In the low-frequency range, the acoustical behaviour of enclosed spaces is strongly influenced by excited acoustic modes resulting in a spatial irregularity of a steady-state sound field. In the paper, this problem has been examined theoretically and numerically for a system of coupled spaces with complex-valued conditions on boundary surfaces. Using a modal expansion method, an analytic formula for the Green's function was derived allowing to predict the interior sound field for a pure-tone excitation. To quantify the spatial irregularity of steady-state sound field, the parameter referred to as the mean spatial deviation was introduced. A numerical simulation was carried out for the system consisting of two coupled rectangular subspaces. Eigenfunctions and eigenfrequencies for this system were determined using the high-accuracy eigenvalue solver. As was evidenced by computational data, for small sound damping on absorptive walls the mean spatial deviation peaks at frequencies corresponding to eigenfrequencies of strongly localized modes. However, if the sound damping is much higher, the main cause of spatial irregularity of the interior sound field is the appearance of sharp valleys in a spatial distribution of a sound pressure level.

Keywords:
interior acoustics, coupled spaces, steady-state sound field, modal expansion method, sound damping, Green's function

47.Szymczak T., Kowalewski Z.L., Strength tests of polymer-glass composite to evaluate its operational suitability for ballistic shield plates, EKSPLOATACJA I NIEZAWODNOŚĆ - MAINTENANCE AND RELIABILITY, ISSN: 1507-2711, DOI: 10.17531/ein.2020.4.2, Vol.22, No.4, pp.592-600, 2020
Szymczak T., Kowalewski Z.L., Strength tests of polymer-glass composite to evaluate its operational suitability for ballistic shield plates, EKSPLOATACJA I NIEZAWODNOŚĆ - MAINTENANCE AND RELIABILITY, ISSN: 1507-2711, DOI: 10.17531/ein.2020.4.2, Vol.22, No.4, pp.592-600, 2020

Abstract:
The paper concerns the study of polymer-glass composite under tensile loading in order to determine changes in the tensile characteristics. Mechanical properties and features of damage zones important for operation and assessment of the technical conditions of the components made of this material are considered. Selected details of the experimental technique used are presented. The tensile characteristics of the polymer-glass composite are given. They were determined using specimens taken from various directions, with the main focus on the Young's modulus, elastic limit, yield point and ultimate tensile strength. An influence of the number of reinforcement layers, percentage content of the glass fibres as well as the resin quantity, on the mechanical parameters, are discussed.

Keywords:
composite, reinforcement, anisotropy, tensile curve, mechanical properties, structure, degradation, cracking, delamination

48.Orłowska A., Gałęzia A., Świercz A., Jankowski Ł., Mitigation of vibrations in sandwich-type structures by a controllable constrained layer, JOURNAL OF VIBRATION AND CONTROL, ISSN: 1077-5463, DOI: 10.1177/1077546320946130, pp.1-11, 2020
Orłowska A., Gałęzia A., Świercz A., Jankowski Ł., Mitigation of vibrations in sandwich-type structures by a controllable constrained layer, JOURNAL OF VIBRATION AND CONTROL, ISSN: 1077-5463, DOI: 10.1177/1077546320946130, pp.1-11, 2020

Abstract:
This study presents and tests a method for semi-active control of vibrations in sandwich-type beam structures. This method adapts a strategy called prestress accumulation release. The prestress accumulation release strategy is based on structural reconfiguration: it uses short time, impulsive and localised changes of actuator properties (such as stiffness or damping), which are applied to a part of the system in the moments, when its strain energy attains a local maximum. The method has been earlier applied as a global control scheme to mitigate the fundamental vibration mode of a cantilever beam (by stiffness control) and in the task of mitigating the first four modes of a frame structure (by damping control). This study proposes a prestress accumulation release strategy and tests its effectiveness for the case of a three-layered sandwich structure, with the internal layer fabricated from a material with dissipative characteristic locally controllable through the material damping coefficient. In contrast to the earlier research, the control is applied thus at the level of material characteristics instead of a discrete set of dedicated actuators. Based on the finite element method, a numerical experiment involving a passively damped, as well as prestress accumulation release-controlled, three-layered cantilever beam excited by initial displacements was performed. The effectiveness of the approach was studied for a broad range of internal layer damping parameters. The presented results revealed a high potential of the prestress accumulation release strategy in semi-active damping of vibrations of sandwich-type structures.

Keywords:
vibration control, sandwich structure, semi-active control, decentralised control, smart structures, constrained layer method

49.Byra M., Hentzen E., Du J., Andre M., Chang E.Y., Shah S., Assessing the performance of morphologic and echogenic features in median nerve ultrasound for carpal tunnel syndrome diagnosis, Journal of Ultrasound in Medicine, ISSN: 0278-4297, DOI: 10.1002/jum.15201, Vol.39, No.6, pp.1165-1174, 2020
Byra M., Hentzen E., Du J., Andre M., Chang E.Y., Shah S., Assessing the performance of morphologic and echogenic features in median nerve ultrasound for carpal tunnel syndrome diagnosis, Journal of Ultrasound in Medicine, ISSN: 0278-4297, DOI: 10.1002/jum.15201, Vol.39, No.6, pp.1165-1174, 2020

Abstract:
Objectives: To assess the feasibility of using ultrasound (US) image features related to the median nerve echogenicity and shape for carpal tunnel syndrome (CTS) diagnosis. Methods: In 31 participants (21 healthy participants and 10 patients with CTS), US images were collected with a 30-MHz transducer from median nerves at the wrist crease in 2 configurations: a neutral position and with wrist extension. Various morphologic features, including the cross-sectional area (CSA), were calculated to assess the nerve shape. Carpal tunnel syndrome commonly results in loss of visualization of the nerve fascicular pattern on US images. To assess this phenomenon, we developed a nerve-tissue contrast index (NTI) method. The NTI is a ratio of average brightness levels of surrounding tissue and the median nerve, both calculated on the basis of a US image. The area under the curve (AUC) from a receiver operating characteristic curve analysis and t test were used to assess the usefulness of the features for differentiation of patients with CTS from control participants. Results: We obtained significant differences in the CSA and NTI parameters between the patients with CTS and control participants (P < .01), with the corresponding highest AUC values equal to 0.885 and 0.938, respectively. For the remaining investigated morphologic features, the AUC values were less than 0.685, and the differences in means between the patients and control participants were not statistically significant (P > .10). The wrist configuration had no impact on differences in average parameter values (P > .09). Conclusions: Patients with CTS can be differentiated from healthy individuals on the basis of the median nerve CSA and echogenicity. Carpal tunnel syndrome is not manifested in a change of the median nerve shape that could be related to circularity or contour variability.

Keywords:
carpal tunnel syndrome, cross-sectional area, echogenicity, median nerve, morphologic features, ultrasound

50.Caporale R., Darban H., Luciano R., Exact closed-form solutions for nonlocal beams with loading discontinuities, MECHANICS OF ADVANCED MATERIALS AND STRUCTURES, ISSN: 1537-6494, DOI: 10.1080/15376494.2020.1787565, pp.1-11, 2020
Caporale R., Darban H., Luciano R., Exact closed-form solutions for nonlocal beams with loading discontinuities, MECHANICS OF ADVANCED MATERIALS AND STRUCTURES, ISSN: 1537-6494, DOI: 10.1080/15376494.2020.1787565, pp.1-11, 2020

Abstract:
A novel mathematical formulation is presented for the applications of the stress-driven nonlocal theory of elasticity to engineering nano-scale problems requiring longitudinal discretization. Specifically, a differential formulation accompanied with novel constitutive continuity conditions is provided for determining exact closed-form solutions of nonlocal Euler-Bernoulli beams with loading discontinuities, i.e. points of discontinuity for external loads and internal forces. Constitutive continuity conditions have to be satisfied in interior points where a loading discontinuity occurs and contain integral convolutions of the stress over suitable parts of the nonlocal beam. Several results show the effectiveness of the proposed method.

Keywords:
closed-form solutions, discretization, Euler-Bernoulli beams, nanobeams

51.Luciano R., Caporale A., Darban H., Bartolomeo C., Variational approaches for bending and buckling of non-local stress-driven Timoshenko nano-beams for smart materials, Mechanics Research Communications, ISSN: 0093-6413, DOI: 10.1016/j.mechrescom.2019.103470, Vol.103, pp.103470-1-7, 2020
Luciano R., Caporale A., Darban H., Bartolomeo C., Variational approaches for bending and buckling of non-local stress-driven Timoshenko nano-beams for smart materials, Mechanics Research Communications, ISSN: 0093-6413, DOI: 10.1016/j.mechrescom.2019.103470, Vol.103, pp.103470-1-7, 2020

Abstract:
In this work, variational formulations are proposed for solving numerically the problem of bending and buckling of Timoshenko nano-beams. The present work belongs to research branch in which the non-local theory of elasticity has been used for analysis of beam-like elements in smart materials, micro-electro-mechanical (MEMS) or nano-electro-mechanical systems (NEMS). In fact, the local beam theory is not adequate to describe the behavior of beam-like elements of smart materials at the nano-scale, so that different non-local models have been proposed in last decades for nano-beams. The nano-beam model considered in this work is a convex combination (mixture) of local and non-local phases. In the non-local phase, the kinematic entities in a point of the nano-beam are expressed as integral convolutions between internal forces and an exponential kernel. The aim is to construct a functional whose stationary condition provides the solution of the problem. Two different functionals are defined: one for the pure non-local model, where the local fraction of the mixture is absent, and the other for the mixture with both local and non-local phases. The Euler equations of the two functionals are derived; then, attention focuses on the mixture model. The functional of the mixture depends on unknown Lagrange multipliers and the Euler equations of the functional provide not only the governing equations of the problem but also the relationships between these Lagrange multipliers and the other variables on which the functional depends. In fact, approximations of the variables of the functional can not be chosen arbitrarily in numerical analyzes but have to satisfy suitable conditions. The Euler equations involving the Lagrange multipliers are essential in the numerical analyzes and suggest the correct approximations that have to be adopted for Lagrange multipliers and the other unknown variables of the functional. The proposed method is verified by comparing numerical solutions with exact solutions in bending problem. Finally, the method is used to determine the buckling load of Timoshenko nano-beams with mixture of phases.

Keywords:
non-local elasticity, variational methods, Timoshenko beam, buckling load, smart materials

52.Luciano R., Darban H., Bartolomeo C., Fabbrocino F., Scorza D., Free flexural vibrations of nanobeams with non-classical boundary conditions using stress-driven nonlocal model, Mechanics Research Communications, ISSN: 0093-6413, DOI: 10.1016/j.mechrescom.2020.103536, Vol.107, pp.103536-1-5, 2020
Luciano R., Darban H., Bartolomeo C., Fabbrocino F., Scorza D., Free flexural vibrations of nanobeams with non-classical boundary conditions using stress-driven nonlocal model, Mechanics Research Communications, ISSN: 0093-6413, DOI: 10.1016/j.mechrescom.2020.103536, Vol.107, pp.103536-1-5, 2020

Abstract:
Free flexural vibrations of nanobeams with non-rigid edge supports are studied by means of the stress-driven nonlocal elasticity model and Euler-Bernoulli kinematics. The elastic deformations of the supports are modelled by transversal and flexural springs, so that, in the limit conditions when the springs stiffnesses tend to zero or infinity, the classical free, pinned, and clamped boundary conditions may be recovered. An analytical procedure is used to derive the closed form solution of the spatial differential equation. The problem of finding the natural frequencies is then reduced to find the roots of the determinant of a matrix, whose elements are explicitly given. The proposed technique, then, avoids the numerical instabilities usually arising when the numerical techniques are used to obtain the solution. The effects of both non-rigid supports elastic deformations and nonlocal parameter on the natural frequencies are studied also for higher vibrations modes. The comparison between the solutions of the proposed model and those available in the literature shows an excellent agreement, and new insightful results and discussions are presented.

Keywords:
elastically constrained beam, nanostructures, natural frequency, size effects, well-posed nonlocal formulation

53.Darban H., Fabbrocino F., Feo L., Luciano R., Size-dependent buckling analysis of nanobeams resting on two-parameter elastic foundation through stress-driven nonlocal elasticity model, MECHANICS OF ADVANCED MATERIALS AND STRUCTURES, ISSN: 1537-6494, DOI: 10.1080/15376494.2020.1739357, pp.1-9, 2020
Darban H., Fabbrocino F., Feo L., Luciano R., Size-dependent buckling analysis of nanobeams resting on two-parameter elastic foundation through stress-driven nonlocal elasticity model, MECHANICS OF ADVANCED MATERIALS AND STRUCTURES, ISSN: 1537-6494, DOI: 10.1080/15376494.2020.1739357, pp.1-9, 2020

Abstract:
The instability of nanobeams rested on two-parameter elastic foundations is studied through the Bernoulli-Euler beam theory and the stress-driven nonlocal elasticity model. The size-dependency is incorporated into the formulation by defining the strain at each point as an integral convolution in terms of the stresses in all the points and a kernel. The nonlocal elasticity problem in a bounded domain is well-posed and inconsistencies within the Eringen nonlocal theory are overcome. Excellent agreement is found with the results in the literature, and new insightful results are presented for the buckling loads of nanobeams rested on the Winkler and Pasternak foundations.

Keywords:
buckling, closed form solution, nanobeam, nonlocal elasticity, Pasternak foundation, stress-driven

54.Kruk A., Gadomska-Gajadhur A., Dulnik J., Ruśkowski P., The influence of the molecular weight of polymer on the morphology, functional properties and L929 fibroblasts growth on polylactide membranes for tissue engineering, International Journal of Polymeric Materials and Polymeric Biomaterials, ISSN: 0091-4037, DOI: 10.1080/00914037.2020.1798440, pp.1-13, 2020
Kruk A., Gadomska-Gajadhur A., Dulnik J., Ruśkowski P., The influence of the molecular weight of polymer on the morphology, functional properties and L929 fibroblasts growth on polylactide membranes for tissue engineering, International Journal of Polymeric Materials and Polymeric Biomaterials, ISSN: 0091-4037, DOI: 10.1080/00914037.2020.1798440, pp.1-13, 2020

Abstract:
The main goal of tissue engineering (TE) is supporting the regeneration of damaged tissues that are difficult to regenerate. The experimental results of the preparation of semi-permeable membranes for cell cultures are presented. The effect of the PLA molecular weight and addition of pore precursors on the morphology of the membranes was studied. The pore precursor of choice was polyvinylpyrrolidone (PVP). It was found that semi-permeable membranes for application in tissue engineering can be prepared with polylactides of molecular weight more significant than 37,000 g/mol. Moreover, it was observed that the growth of the molecular weight of the polymer, the porosity, the size of the pores, the Young modulus and maximum tensile increased. Additionally, to obtain a better morphology of the membranes, PVP should be added to the polymeric solution. Positive growth of L929 fibroblast cells on the obtained scaffolds was shown.

Keywords:
biodegradable polymers, cell cultures, L929 fibroblasts, polylactide, scaffolds, tissue engineering

55.Gadomska‐Gajadhur A., Kruk A., Ruśkowski P., Sajkiewicz P., Dulnik J., Chwojnowski A., Original method of imprinting pores in scaffolds for tissue engineering, Polymers for Advanced Technologies, ISSN: 1042-7147, DOI: 10.1002/pat.5091, pp.1-13, 2020
Gadomska‐Gajadhur A., Kruk A., Ruśkowski P., Sajkiewicz P., Dulnik J., Chwojnowski A., Original method of imprinting pores in scaffolds for tissue engineering, Polymers for Advanced Technologies, ISSN: 1042-7147, DOI: 10.1002/pat.5091, pp.1-13, 2020

Abstract:
Results of the preparation of biodegradable porous scaffolds using an original modification of a wet phase inversion method were presented. Influence of gelatin non‐woven as a non‐classic pore precursor and polyvinylpyrrolidone, Pluronic as classic pore precursors on the structure of obtained scaffolds was analyzed. It was shown that the addition of gelatin non‐wovens enables the preparation of scaffolds, which allow for the growth of cells (size, distribution, and shape of pores). Mechanical properties of the obtained cell scaffolds were determined. The influence of pore precursors on mass absorption of scaffolds against isopropanol and plasma was investigated. Interaction of scaffolds with a T‐lymphocyte line (Jurkat) and with fibroblasts (L929) was investigated. Obtained scaffolds are not cytotoxic and can be used as implants, for example, the regeneration of cartilage tissue.

Keywords:
cell cultures, cytotoxic, fibroblasts, imprinted scaffolds

56.Dziedzic K., Dąbrowski M., Antolik A., Glinicki A., Characteristics of concrete mix air-entrainment applying the sequential pressure method / Charakterystyka napowietrzenia mieszanki betonowej metodą sekwencyjno-cioenieniową, Roads and Bridges - Drogi i Mosty, ISSN: 1643-1618, DOI: 10.7409/rabdim.020.007, Vol.19, No.2, pp.107-118, 2020
Dziedzic K., Dąbrowski M., Antolik A., Glinicki A., Characteristics of concrete mix air-entrainment applying the sequential pressure method / Charakterystyka napowietrzenia mieszanki betonowej metodą sekwencyjno-cioenieniową, Roads and Bridges - Drogi i Mosty, ISSN: 1643-1618, DOI: 10.7409/rabdim.020.007, Vol.19, No.2, pp.107-118, 2020

Abstract:
The purpose of introducing air into the concrete mix is to increase the freeze-thaw and scaling resistance of hardened concrete. The utility of the sequential pressure method (Super Air Meter - SAM) for assessment of the air entrainment quality was verified by comparing the results obtained with this method with the results of the air-void analysis of hardened concrete. The results of the tests carried out on mixes designed and produced at a laboratory and the mixes produced on an industrial scale during expressway construction are considered. Furthermore, the relationships between the SAM number and the micro air-void content A300 in hardened concrete and the freeze-thaw and de-icing salt resistance are analysed as part of this research. A clear co-relation between the SAM number, a parameter that characterises the air-entrainment of the concrete mix, and the microvoid content has been demonstrated.
Napowietrzenie mieszanki betonowej stosuje się w celu podwyższenia mrozoodporności betonu i jego odporności na złuszczenia powierzchniowe. Przeprowadzono badania możliwości charakteryzowania jakości napowietrzenia mieszanki betonowej za pomocą pomiarów metodą sekwencyjno-ciśnieniową, oceniając zgodność jej wyników z wynikami pomiaru charakterystyki porów w betonie stwardniałym. Przedstawiono wyniki badań mieszanek zaprojektowanych i wykonanych w laboratorium, jak i mieszanek wykonanych przemysłowo na budowie drogi ekspresowej. Analizowano relację tzw. liczby SAM mieszanki betonowej w odniesieniu do zawartości mikroporów A300 w stwardniałym betonie oraz odporności na cykliczne działanie mrozu w obecności soli odladzających. Wykazano wyraźną korelację między parametrem charakteryzującym napowietrzenie mieszanki betonowej (liczba SAM) a zawartością mikroporów w betonie stwardniałym.

Keywords:
air-entrainment, air-void parameters, concrete, freeze-thaw resistance, microvoid content, sequential pressure method, surface scaling / beton, charakterystyka porów, metoda sekwencyjno-cioenieniowa, mrozoodporność, napowietrzenie, zawartość mikroporów, złuszczenia powierzchniowe

57.Auguścik-Królikowska M., Ryszkowska J., Szczepkowski L., Kwiatkowski D., Kołbuk-Konieczny D., Szymańska J., Viscoelastic polyurethane foams with the addition of mint, POLIMERY, ISSN: 0032-2725, DOI: 10.14314/polimery.2020.3.4, Vol.65, No.3, pp.196-207, 2020
Auguścik-Królikowska M., Ryszkowska J., Szczepkowski L., Kwiatkowski D., Kołbuk-Konieczny D., Szymańska J., Viscoelastic polyurethane foams with the addition of mint, POLIMERY, ISSN: 0032-2725, DOI: 10.14314/polimery.2020.3.4, Vol.65, No.3, pp.196-207, 2020

Abstract:
The article presents an assessment of the possibilities of producing viscoelastic open cell polyurethane (PUR) foams produced with a natural filler in the form of mint leaves. PUR foams containing from 10 to 30 wt % of mint were produced. Chemical structure, thermal and mechanical properties of the foams were assessed. It was found that the filler containing 7 wt % of water caused significant changes in the foam characteristics. In composite foams, the content of urea and hydrogen bonds increased with higher mint contents. The hardness and comfort factor of composite foams also increased. The introduction of a filler containing a significant amount of water caused a change in the porosity and wall thickness of composite foams resulting in a significant increase in their permanent deformations.

Keywords:
open cell viscoelastic polyurethane foams, mint, cytocompatibility

58.Fantilli A.P., Jóźwiak-Niedźwiedzka D., Influence of Portland cement alkalinity on wool reinforced mortar, Proceedings of the Institution of Civil Engineers - Construction Materials, ISSN: 1747-650X, DOI: 10.1680/jcoma.20.00003, pp.1-10, 2020
Fantilli A.P., Jóźwiak-Niedźwiedzka D., Influence of Portland cement alkalinity on wool reinforced mortar, Proceedings of the Institution of Civil Engineers - Construction Materials, ISSN: 1747-650X, DOI: 10.1680/jcoma.20.00003, pp.1-10, 2020

Abstract:
Natural wool is a good insulating material, both thermal and acoustic. Nevertheless, with the increase in demand for the use of waste materials, other applications, such as the use of wool as a fibre-reinforcement in mortars and concretes, have been found. Unfortunately, wool, like other natural organic materials, dissolve in alkaline environment and, consequently, the performances of the reinforcement cannot be guaranteed for a long time. To solve the above issue, three series of reinforced mortar beams, with various contents of alkalis in cement, are investigated herein. The chemical compatibility, and the effects of alkalinity on the mechanical performances, are investigated by testing the beams in three point bending and, subsequently, by analysing the microstructure of the mortars through a scanning electron microscope equipped with energy dispersive X-ray spectroscopy. The results reveal that the lower the alkalinity of the cement paste, the better the resistance of wool fibres in cementitious matrix, which guarantees larger post-cracking residual stresses in the wool reinforced mortars.

Keywords:
fibre-reinforcement, fracture & fracture mechanics, microstructure, waste valorisation

59.Proniewska K., Pręgowska A., Dołęga-Dołęgowski D., Dudek D., Immersive technologies as a solution for general data protection regulation in Europe and impact on the COVID-19 pandemic, Cardiology Journal, ISSN: 1897-5593, DOI: 10.5603/CJ.a2020.0102, pp.1-21, 2020
Proniewska K., Pręgowska A., Dołęga-Dołęgowski D., Dudek D., Immersive technologies as a solution for general data protection regulation in Europe and impact on the COVID-19 pandemic, Cardiology Journal, ISSN: 1897-5593, DOI: 10.5603/CJ.a2020.0102, pp.1-21, 2020

Abstract:
Background: General data protection regulation (GDPR) provides rules according to which data should be managed and processed in a secure and appropriate way for patient requirements and security. Currently, everyone in Europe is covered by GDPR. Thus, the medical practice also requires access to patient data in a safe and secure way. Methods: Holographic technology allows users to see everything visible ona computer screen in a new and less restricted way, i. e. without the limitations of traditional computers and screens. Results: In this study, a three-dimensional holographic doctors' assistant is designed and implemented in a way that meets the GDPR requirements. The HoloView application, which is tailored to run on Microsoft HoloLens, is proposed toallow display and access to personal data and so-called sensitive information of all individual patients without the risk that it will be presented to unauthorized persons. Conclusions: To enhance the user experience and remain consistent with GSPR, a holographic desk is proposed that allows displaying patient data and sensitive information only in front of the doctor's eyes using mixed reality glasses. Last but not least, it boasts of a reduction in infection risk for the staff during the COVID-19 pandemic, affording medical care to be carried out by as few doctors as possible.

Keywords:
augmented reality, mixed reality, pandemic

60.Popławski B., Mikułowski G., Orłowska A., Jankowski Ł., On/off nodal reconfiguration for global structural control of ‎smart 2D frames, Journal of Applied and Computational Mechanics, ISSN: 2383-4536, DOI: 10.22055/jacm.2020.32454.2016, pp.1-9, 2020
Popławski B., Mikułowski G., Orłowska A., Jankowski Ł., On/off nodal reconfiguration for global structural control of ‎smart 2D frames, Journal of Applied and Computational Mechanics, ISSN: 2383-4536, DOI: 10.22055/jacm.2020.32454.2016, pp.1-9, 2020

Abstract:
This paper proposes an on/off semi-active control approach for mitigation of free structural vibrations, designed for application in 2D smart frame structures. The approach is rooted in the Prestress-Accumulation Release (PAR) control strategies. The feedback signal is the global strain energy of the structure, or its approximation in the experimental setup. The actuators take the form of on/off nodes with a controllable ability to transfer moments (blockable hinges). Effectiveness of the approach is confirmed in a numerical simulation, as well as using a laboratory experimental test stand.

Keywords:
structural reconfiguration, structural control, semi-active control, frame structures, controllable nodes‎

61.Golasiński K.M., Pieczyska E.A., Kowalczyk-Gajewska K., Maj M., Kuramoto S., Furuta T., Mechanical behavior of gum metal under tension at various strain rates - full-field deformation measurements and simulations, International Conference on Plasticity, Damage, and Fracture 2020, 2020-01-03/01-09, Riviera Maya (MX), pp.1-1, 2020
62.Gupta A., Jain A., Kumari M., Tripathi S.K., Structural, electrical and electrochemical studies of sodium ion conducting blend polymer electrolytes, Materials Today: Proceedings, ISSN: 2214-7853, DOI: 10.1016/j.matpr.2020.05.030, pp.1-7, 2020
Gupta A., Jain A., Kumari M., Tripathi S.K., Structural, electrical and electrochemical studies of sodium ion conducting blend polymer electrolytes, Materials Today: Proceedings, ISSN: 2214-7853, DOI: 10.1016/j.matpr.2020.05.030, pp.1-7, 2020

Abstract:
In the present study sodium ion conducting polymer blend electrolytes has been prepared using poly (vinylidene fluoride – hexafluoro – propylene) (PVdF-HFP), poly (methyl methacrylate) (PMMA), and sodium thiocyanate (NaSCN) salt by solution-cast technique. The highest ionic conductivity of the optimized blend polymer electrolyte system [PVdF(HFP)-PMMA (4:1)] (20 wt%)-[NaSCN (1 M)] (80 wt%) has been found to be 4.54 × 10^−2 S cm^−1 at room temperature. The temperature dependence conductivity plot shows the Arrhenius behaviour and its activation energy calculated from the plot were found to be 0.13 eV. The structural and morphological studies of polymer blend electrolyte were investigated by XRD, SEM and FTIR spectroscopy. Complex formation between polymer and salt has been confirmed by these studies. The thermal properties of optimized electrolyte system were examined by differential scanning calorimetry (DSC) techniques. The ionic transport number was calculated using d.c polarization techniques and was found to be 0.92, which shows that electrolyte system is predominantly ionic in nature. The electrochemical potential window of optimized polymer blend electrolyte was tested and observed to be ~2.8 V.

Keywords:
polymer blends electrolyte, solution cast technique, sodium ion, FTIR, DSC

63.Fantilli A.P., Jóźwiak-Niedźwiedzka D., The effect of hydraulic cements on the flexural behavior of wool reinforced mortars, Academic Journal of Civil Engineering, ISSN: 2680-1000, DOI: 10.26168/icbbm2019.41, Vol.37, No.2, pp.287-292, 2020
Fantilli A.P., Jóźwiak-Niedźwiedzka D., The effect of hydraulic cements on the flexural behavior of wool reinforced mortars, Academic Journal of Civil Engineering, ISSN: 2680-1000, DOI: 10.26168/icbbm2019.41, Vol.37, No.2, pp.287-292, 2020

Abstract:
It is known that natural wool is a good thermal insulating material, but recent results suggest another application: the use of wool as a fiber-reinforcement in mortars and concretes. Indeed, the mechanical properties of wool filaments are comparable to those of some synthetic polymeric fibers (e.g., made with polypropylene). However, wool can dissolve in alkaline environments and, therefore, the performances of reinforced cement-based matrixes cannot be guaranteed for a long time. Accordingly, three series of reinforced mortar beams have been made with low alkali, high alkali, and sulfoaluminate cements. To investigate the chemical compatibility, and the subsequent effects on the mechanical performances, the beams have been tested in three point bending. As a result, the lower the alkalinity of the cement paste, the better the post-cracking capability of wool fibers to arrest the growth of cracks.

Keywords:
wool reinforcement, low alkali cement, high alkali cement, sulfoaluminate cement

64.Glinicki M.A., Materiałowe aspekty równości nawierzchni betonowej, DROGOWNICTWO, ISSN: 0012-6357, Vol.LXXV, No.4, pp.99-108, 2020
Glinicki M.A., Materiałowe aspekty równości nawierzchni betonowej, DROGOWNICTWO, ISSN: 0012-6357, Vol.LXXV, No.4, pp.99-108, 2020

Abstract:
Zgodnie z definicją podaną w MEPDG 2020, równość nawierzchni odzwierciedla profil nawierzchni w śladach kół. W artykule przestawiono przegląd materiałowych i technologicznych czynników wpływających na równość nawierzchni drogowej z betonu cementowego, dyblowanej i kotwionej, przeznaczonej do kategorii ruchu KR5-KR7. Omówiono specyfikę metody ślizgowej, która jest procesem ekstruzji betonu, pozwalającym na monolityczne ułożenie warstwy przy jednym przejeździe układarki. Omówiono właściwości reologiczne mieszanki betonowej oraz jej praktyczne cechy techniczne, mające decydujące znaczenie przy formowaniu powierzchni jezdni.Utrzymanie stałego profilu nawierzchni w projektowanym 30-letnim okresie eksploatacji jest możliwe dzięki wysokiej odporności betonu na silne oddziaływania mechaniczne, termiczne i agresję środowiska.
According to the definition given in MEPDG 2020, the evenness of pavement reflects the surface profile in the wheel tracks. A review of material and technological factors influencing the evenness of the road pavement made of cement concrete, doweled and anchored, designed for traffic category KR5-KR7 is presented. The specificity of the slip-form method, which is a process of concrete extrusion, allowing for monolithic paving at one pass of the paver is discussed. Rheological properties of the concrete mixture and its practical technical features, which are decisive for the formation of roadway surface, are discussed. Maintaining a constant surface profile over the designed 30-year service life is possible due to the high resistance of concrete to strong mechanical, thermal and environmental influences.

Keywords:
beton cementowy, IRI, MEPDG, metoda ślizgowa, nawierzchnia drogowa, projektowanie składu, równość, trwałość, właściwosci reologiczne cement concrete, IRI, MEPDG, sliding method, road pavement, composition design, evenness, durability, rheological properties

65.Kucharczyk K., Rybka J.D., Hilgendorff M., Krupinski M., Slachcinski M., Mackiewicz A., Giersig M., Dams-Kozlowska H., Composite spheres made of bioengineered spider silk and iron oxide nanoparticles for theranostics applications, PLOS ONE, ISSN: 1932-6203, DOI: 10.1371/journal.pone.0219790, Vol.14, No.7, pp. e0219790-1-20, 2019
Kucharczyk K., Rybka J.D., Hilgendorff M., Krupinski M., Slachcinski M., Mackiewicz A., Giersig M., Dams-Kozlowska H., Composite spheres made of bioengineered spider silk and iron oxide nanoparticles for theranostics applications, PLOS ONE, ISSN: 1932-6203, DOI: 10.1371/journal.pone.0219790, Vol.14, No.7, pp. e0219790-1-20, 2019

Abstract:
Bioengineered spider silk is a biomaterial that has exquisite mechanical properties, biocompatibility, and biodegradability. Iron oxide nanoparticles can be applied for the detection and analysis of biomolecules, target drug delivery, as MRI contrast agents and as therapeutic agents for hyperthermia-based cancer treatments. In this study, we investigated three bioengineered silks, MS1, MS2 and EMS2, and their potential to form a composite material with magnetic iron oxide nanoparticles (IONPs). The presence of IONPs did not impede the self-assembly properties of MS1, MS2, and EMS2 silks, and spheres formed. The EMS2 spheres had the highest content of IONPs, and the presence of magnetite IONPs in these carriers was confirmed by several methods such as SEM, EDXS, SQUID, MIP-OES and zeta potential measurement. The interaction of EMS2 and IONPs did not modify the superparamagnetic properties of the IONPs, but it influenced the secondary structure of the spheres. The composite particles exhibited a more than two-fold higher loading efficiency for doxorubicin than the plain EMS2 spheres. For both the EMS2 and EMS2/IONP spheres, the drug revealed a pH-dependent release profile with advantageous kinetics for carriers made of the composite material. The composite spheres can be potentially applied for a combined cancer treatment via hyperthermia and drug delivery.

66.Rybka J.D., Mieloch A.A., Plis A., Pyrski M., Pniewski T., Giersig M., Assembly and characterization of HBc derived virus-like particles with magnetic core, Nanomaterials, ISSN: 2079-4991, DOI: 10.3390/nano9020155, Vol.9, No.2, pp.155-1-11, 2019
Rybka J.D., Mieloch A.A., Plis A., Pyrski M., Pniewski T., Giersig M., Assembly and characterization of HBc derived virus-like particles with magnetic core, Nanomaterials, ISSN: 2079-4991, DOI: 10.3390/nano9020155, Vol.9, No.2, pp.155-1-11, 2019

Abstract:
Core-virus like particles (VLPs) assembly is a kinetically complex cascade of interactions between viral proteins, nanoparticle's surface and an ionic environment. Despite many in silico simulations regarding this process, there is still a lack of experimental data. The main goal of this study was to investigate the capsid protein of hepatitis B virus (HBc) assembly into virus-like particles with superparamagnetic iron oxide nanoparticles (SPIONs) as a magnetic core in relation to their characteristics. The native form of HBc was obtained via agroinfection of Nicotiana benthamiana with pEAQ-HBc plasmid. SPIONs of diameter of 15 nm were synthesized and functionalized with two ligands, providing variety in ζ-potential and hydrodynamic diameter. The antigenic potential of the assembled core-VLPs was assessed with enzyme-linked immunosorbent assay (ELISA). Morphology of SPIONs and core-VLPs was evaluated via transmission electron microscopy (TEM). The most successful core-VLPs assembly was obtained for SPIONs functionalized with dihexadecyl phosphate (DHP) at SPIONs/HBc ratio of 0.2/0.05 mg/mL. ELISA results indicate significant decrease of antigenicity concomitant with core-VLPs assembly. In summary, this study provides an experimental assessment of the crucial parameters guiding SPION-HBc VLPs assembly and evaluates the antigenicity of the obtained structures.

Keywords:
virus-like particles, VLPs, hepatitis B virus capsid protein, HBc, viral self-assembly, magnetic core, HBcAg

67.Brinkert K., Akay Ö., Richter M.H., Liedtke J., Fountaine K.T., Lewerenz H-J., Giersig M., Experimental methods for efficient solar hydrogen production in microgravity environment, Journal of Visualized Experiments, ISSN: 1940-087X, DOI: 10.3791/59122, Vol.154, pp.e59122-1-9, 2019
Brinkert K., Akay Ö., Richter M.H., Liedtke J., Fountaine K.T., Lewerenz H-J., Giersig M., Experimental methods for efficient solar hydrogen production in microgravity environment, Journal of Visualized Experiments, ISSN: 1940-087X, DOI: 10.3791/59122, Vol.154, pp.e59122-1-9, 2019

Abstract:
Long-term space flights and cis-lunar research platforms require a sustainable and light life-support hardware which can be reliably employed outside the Earth's atmosphere. So-called 'solar fuel' devices, currently developed for terrestrial applications in the quest for realizing a sustainable energy economy on Earth, provide promising alternative systems to existing air-revitalization units employed on the International Space Station (ISS) through photoelectrochemical water-splitting and hydrogen production. One obstacle for water (photo-) electrolysis in reduced gravity environments is the absence of buoyancy and the consequential, hindered gas bubble release from the electrode surface. This causes the formation of gas bubble froth layers in proximity to the electrode surface, leading to an increase in ohmic resistance and cell-efficiency loss due to reduced mass transfer of substrates and products to and from the electrode. Recently, we have demonstrated efficient solar hydrogen production in microgravity environment, using an integrated semiconductor-electrocatalyst system with p-type indium phosphide as the light-absorber and a rhodium electrocatalyst. By nanostructuring the electrocatalyst using shadow nanosphere lithography and thereby creating catalytic 'hot spots' on the photoelectrode surface, we could overcome gas bubble coalescence and mass transfer limitations and demonstrated efficient hydrogen production at high current densities in reduced gravitation. Here, the experimental details are described for the preparations of these nanostructured devices and further on, the procedure for their testing in microgravity environment, realized at the Bremen Drop Tower during 9.3 s of free fall.

Keywords:
chemistry, issue 154, solar fuels, hydrogen, microgravity, photoelectrocatalysis, drop tower, shadow nanosphere lithography, semiconductor-electrocatalyst systems

68.Akinoglu G.E., Akinoglu E.M., Kempa K., Giersig M., Plasmon resonances in coupled Babinet complementary arrays in the mid-infrared range, OPTICS EXPRESS, ISSN: 1094-4087, DOI: 10.1364/OE.27.022939, Vol.27, No.16, pp.22939-22950, 2019
Akinoglu G.E., Akinoglu E.M., Kempa K., Giersig M., Plasmon resonances in coupled Babinet complementary arrays in the mid-infrared range, OPTICS EXPRESS, ISSN: 1094-4087, DOI: 10.1364/OE.27.022939, Vol.27, No.16, pp.22939-22950, 2019

Abstract:
A plasmonic structure with transmission highly tunable in the mid-infrared spectra range is developed. This structure consists of a hexagonal array of metallic discs located on top of silicon pillars protruding through holes in a metallic Babinet complementary film. We reveal with FDTD simulations that changing the hole diameter tunes the main plasmonic resonance frequency of this structure throughout the infrared range. Due to the underlying Babinet physics of these coupled arrays, the spectral width of these plasmonic resonances is strongly reduced, and the higher harmonics are suppressed. Furthermore, we demonstrate that this structure can be easily produced by a combination of the nanosphere lithography and the metal-assisted chemical etching technique.

69.Henglein A., Giersig M., Formation of colloidal silver nanoparticles: capping action of citrate, JOURNAL OF PHYSICAL CHEMISTRY B, ISSN: 1520-6106, DOI: 10.1021/jp9925334, Vol.103, pp.9533-9539, 1999
Henglein A., Giersig M., Formation of colloidal silver nanoparticles: capping action of citrate, JOURNAL OF PHYSICAL CHEMISTRY B, ISSN: 1520-6106, DOI: 10.1021/jp9925334, Vol.103, pp.9533-9539, 1999

Abstract:
Colloidal silver sols of long-time stability are formed in the γ-irradiation of 1.0 x 10^-4 M AgClO4 solutions, which also contain 0.3 M 2-propanol, 2.5 x 10^-2 M N2O, and sodium citrate in various concentrations. The reduction of Ag+ in these solutions is brought about by the 1-hydroxyalkyl radical generated in the radiolysis of 2-propanol; citrate does not act as a reductant but solely as a stabilizer of the colloidal particles formed. Its concentration is varied in the range from 5.0 x 10^-5 to 1.5 x 10^-3 M, and the size and size distribution of the silver particles are studied by electron microscopy. At low citrate concentration, partly agglomerated large particles are formed that have many imperfections. In an intermediate range (a few 10^-4 M), wellseparated particles with a rather narrow size distribution and little imperfections are formed, the size slightly decreasing with increasing citrate concentration. At high citrate concentrations, large lumps of coalesced silver particles are present, due to destabilization by the high ionic strength of the solution. These findings are explained by two growth mechanisms: condensation of small silver clusters (type-I growth), and reduction of Ag+ on silver particles via radical-to-particle electron transfer (type-II growth). The particles formed in the intermediate range of citrate concentration were studied by high-resolution electron microscopy and computer simulations. They constitute icosahedra and cuboctahedra.

70.Liz-Marzán L.M., Giersig M., Mulvaney P., Synthesis of nanosized gold-silica core-shell particles, LANGMUIR, ISSN: 0743-7463, DOI: 10.1021/la9601871, Vol.12, No.18, pp.4329-4335, 1996
Liz-Marzán L.M., Giersig M., Mulvaney P., Synthesis of nanosized gold-silica core-shell particles, LANGMUIR, ISSN: 0743-7463, DOI: 10.1021/la9601871, Vol.12, No.18, pp.4329-4335, 1996

Abstract:
Gold colloids have been homogeneously coated with silica using the silane coupling agent (3-aminopropyl)- trimethoxysilane as a primer to render the gold surface vitreophilic. After the formation of a thin silica layer in aqueous solution, the particles can be transferred into ethanol for further growth using the Stöber method. The thickness of the silica layer can be completely controlled, and (after surface modification) the particles can be transferred into practically any solvent. Varying the silica shell thickness and the refractive index of the solvent allows control over the optical properties of the dispersions. The optical spectra of the coated particles are in good agreement with calculations using Mie's theory for core-shell particles.

71.Vossmeyer T., Katsikas L., Giersig M., Popovic G., Diesner K., Chemseddine A., Eychmüller A., Weller H., CdS nanoclusters: synthesis, characterization, size dependent oscillator strength, temperature shift of the excitonic transition energy, and reversible absorbance shift, JOURNAL OF PHYSICAL CHEMISTRY B, ISSN: 1520-6106, DOI: 10.1021/j100082a044, Vol.98, No.31, pp.7665-7673, 1994
Vossmeyer T., Katsikas L., Giersig M., Popovic G., Diesner K., Chemseddine A., Eychmüller A., Weller H., CdS nanoclusters: synthesis, characterization, size dependent oscillator strength, temperature shift of the excitonic transition energy, and reversible absorbance shift, JOURNAL OF PHYSICAL CHEMISTRY B, ISSN: 1520-6106, DOI: 10.1021/j100082a044, Vol.98, No.31, pp.7665-7673, 1994

Abstract:
Improved synthetic routes and size-selective precipitation have enabled the preparation of almost monodisperse CdS clusters. Six samples of 1-thioglycerol stabilized clusters with diameters of approximately 13,14,16,19, 23, and 39 A have been prepared as fully redispersible powders and were characterized by elemental analysis, powder X-ray diffraction, electron microscopy, thermogravimetric analysis, and UV-vis spectroscopy. Smallangle X-ray scattering was used to determine the mean cluster size. The well-structured UV-vis spectra reveal that the size-dependent shift of the 1s-1s excitonic transition is in agreement with the tight-binding theory and the pseudopotential theory. Moreover, as expected by quantum mechanical calculations the oscillator strength of the transition increases proportional to 1/r^3. UV-vis spectra taken at various temperatures between 4 and 295 K have shown that the temperature shift of the excitonic transition energy becomes stronger with decreasing particle size. Strong, reversible absorbance shifts were observed, upon transferring the clusters from their solutions onto quartz plates and vice versa.

72.Kacprzyk Z., Postek E., Plastoshell. Program for static elastic-plastic analysisof plates and shells, Metody Komputerowe w Inżynierii Lądowej, ISSN: 0867-5007, Vol.3, No.3-4, pp.89-94, 1993
Kacprzyk Z., Postek E., Plastoshell. Program for static elastic-plastic analysisof plates and shells, Metody Komputerowe w Inżynierii Lądowej, ISSN: 0867-5007, Vol.3, No.3-4, pp.89-94, 1993

Abstract:
The modern structural mechanics is strictly computer oriented. To prepare a part of a course considering nonlinear analysis of shells a published finite element program PLASTOSHELL of Figueiras and Owen is used. The following finite elements ar implemented: 8-node Serendipidity, 9-node Lagrangian and 9-node Heterosis. The program was tested to check if it may be used in an accurate analysis of shells.

Keywords:
nonlinear analysis, plates and shells, graduate courses

73.Kacprzyk Z., Postek E., Plast. Program for static elastic-plastic analysis of plates and shells, Metody Komputerowe w Inżynierii Lądowej, ISSN: 0867-5007, Vol.3, No.3-4, pp.83-87, 1993
Kacprzyk Z., Postek E., Plast. Program for static elastic-plastic analysis of plates and shells, Metody Komputerowe w Inżynierii Lądowej, ISSN: 0867-5007, Vol.3, No.3-4, pp.83-87, 1993

Abstract:
The not deals with a short description of a finite element program for elastic-plastic analysis of plaes and shells. The code is published in [1] and is distributed with he book. It is possible to use it in the analysis of anizotropic, layered, elastic-plastic plates and shells undergoing large displacements. The Huber Mises yield condition is applied.

Keywords:
nonlinear analysis, plates and shells, graduate courses

74.Giersig M., Mulvaney P., Preparation of ordered colloid monolayers by electrophoretic deposition, LANGMUIR, ISSN: 0743-7463, DOI: 10.1021/la00036a014, Vol.9, No.12, pp.3408-3413, 1993
Giersig M., Mulvaney P., Preparation of ordered colloid monolayers by electrophoretic deposition, LANGMUIR, ISSN: 0743-7463, DOI: 10.1021/la00036a014, Vol.9, No.12, pp.3408-3413, 1993

Abstract:
Citrate- and alkanethiol-stabilized gold colloids have been electrophoretically deposited onto carboncoated copper grids. The colloid particles form ordered monolayers, and the core-to-core interparticle spacing is determined by the size of the alkane chains on the stabilizers used in the preparation of the sols. In the case of longer alkane chains, some interpenetration of the chains occurs when the gold particles form monolayers. When the gold sols are stabilized by sodium 3-thiopropionate, they can be reversibly coagulated and peptized by cycling the pH between 3 and 7. The method has also been used to form ordered monolayers and bilayers of latex particles.