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In order to investigate the transverse flexural behavior of the UHPC waffle deck, a total of six T-shaped UHPC beams, with varying longitudinal reinforcement ratios, were tested and analyzed. The experiments, including material tests of UHPC and beam tests, were conducted. The material tests of UHPC revealed that strain-hardening behavior in tension was exhibited, and the ratio of uniaxial compressive strength-to-cubic compressive strength was 0.85. The beam tests showed that all the T-shaped UHPC beams, even without longitudinal rebar, exhibited ductile behavior that was similar to that of properly reinforced concrete beams. As the longitudinal reinforcement ratio increased, more flexural cracks developed and a larger load-carrying capacity was provided. Furthermore, the sectional analysis for the ultimate flexural capacity of T-shaped UHPC beams was conducted. Simplified material models, under tension and compression, for UHPC were developed. Based on the reverse calculation from the experimental result, the relation between reduction factor to the ultimate tensile strength of UHPC, and longitudinal reinforcement ratios was formulated. As a result, the predictive equations for the ultimate flexural capacity of T-shaped UHPC beams were proposed, and agreed well with the experimental results in this study and existing studies, which indicates good validity of the proposed equations.

Discharge gases have been used to detect terahertz (THz) waves, however, there are few relevant theoretical studies. The neon glow discharge model is established by COMSOL Multiphysics software, the characteristics of glow discharged neon and the interaction of the discharged gas with THz waves were investigated. The results show that with the increase of THz wave’s frequency, the transmittance increases, the change of plasma discharge characteristics caused by THz wave can be used for THz wave detection. The results provide a theoretical basis for the development of cheap, room temperature THz wave detector with fast response speed, and high sensitivity.

Steel fiber and Nano–SiO2 reinforced concrete is a novel material of concrete which has great potential to be used in practical engineering. However, there is relatively little literature available on the flexural behavior of steel fiber and Nano–SiO2 materials reinforced concrete (SFNMRC) beams. Hence, the main objective of this paper is to investigate the flexural performance of SFNMRC beams through combined experimental and theoretical studies. A total of 10 specimens were tested to investigate the flexural behavior and the effect of some key parameters, including concrete strength, the volume fraction of steel fiber, and the amount of Nano–SiO2. The load vs. deflection curves of SFNMRC beams during the whole loading process were analyzed in detail. The failure mode was discussed in detail, and the specimens all behaved in a very ductile manner. Furthermore, the test results indicated that bending cracks and concrete crushing were formed in the compression zone of all specimens. With the increase in concrete strength and the volume fraction of steel fiber, both the cracking load and ultimate load of beams increased. The amount of Nano–SiO2 had a limited effect on the flexure performance. Finally, the calculation formula for predicting the flexural bearing capacity of SFNMRC beams was derived with consideration of the effect of steel fiber on the cracked sections after beam cracking. The predicted results show satisfactory agreement with both experimental results. The studies may provide a considerable reference for designing this type of structure in engineering practice.

The radiation shielding competence was examined for a binary glass system xLa2O3 + (1 − x) TeO2 where x = 5, 7, 10, 15, and 20 mol% using MCNP-5 code. The linear attenuation coefficients (LACs) of the glasses were evaluated, and it was found that LT20 glass has the greatest LAC, while LT5 had the least LAC. The transmission factor (TF) of the glasses was evaluated against thicknesses at various selected energies and was observed to greatly decrease with increasing thickness, for example, at 1.332 MeV, the TF of the LT5 glass decreased from 0.76 to 0.25 as the thickness increased from 1 to 5 cm. The equivalent atomic number (Zeq) of the glasses gradually increased with increasing photon energy above 0.1 MeV, with the maximum values observed at around 1 MeV. The buildup factors were determined to evaluate the accumulation of photon flux, and it was found that the maximum values for both can be seen at around 0.8 MeV. This research concluded that LT20 has the greatest potential in radiation shielding applications out of the investigated glasses due to the glass having the most desirable parameters.

Basaran, Murat Alper/0000-0001-9887-5531 WOS: 000460758200048 In this theoretical study, calculations for the three types of the tetrazole which are 2-(1H-Tetrazole-5-yl)-3-phenylacrylonitrile, 2-(1H-Tetrazole-5-yl)-3-(4-nitrophenylacrylonitrile), and 2-(1H-Tetrazole-5-yl)-3-(4-hydroxyphenyl acrylonitrile) showing the corrosion inhibition efficiency on mild steel in 1M HCl were carried out with the Density Functional Theory (DFT) at the B3LYP functionals with the use of 6-311g (d, p) basis set. Calculated parameters such as E-HOMO, E-LUMO, energy gap, electronegativity (chi), chemical potential (mu), hardness (eta), softness (S), electrophilicity, electrofugality, nucleofugality, Proton affinity, polarizability and hyperpolarizability. The correlation and regression analysis have been conducted to determine which descriptors have effect on inhibition efficiency. Both the theoretical results and experimental data are in accordance based on the inhibition efficiency.

A brief review of experimental and theoretical studies of half-metallic ferromagnets (HMF) and spin gapless semiconductors (SGS) is given. The data on resistivity and magnetoresistivity are presented. An important role of non-quasiparticle states owing to electron-magnon scattering in transport properties is discussed. The problem of low-temperature resistivity in HMF is treated in terms of one-magnon and two-magnon scattering processes., Physics of Metals and Metallography, special issue, 4 pages

Introduction. The article presents new solutions for designing the equipment for final processing parts with a complex profile of working surface. The said solutions allow a planetary rotation of the part at a small center distance of the mandrel with the workpiece and the spindle of the installation. This solution improves the quality of the working surfaces and reduces energy costs. Materials and Methods. The disadvantage of modern devices for final processing of complex parts is the increased energy consumption and the large axial distance between the part and spindle. These factors reduce the quality of processing and the part range in terms of weight and dimension characteristics. The application of new solutions to change the design of the installation is relevant. When designing a new installation, the center distance between the part and the spindle was reduced. This contributed to the reduction of vibrations, improving the quality of surface treatment and increasing the product range. Results. The calculations to reduce the resistance of the abrasive medium affecting on the surface of the diesel engine turbo-compressor wheel blades confirmed the expediency of the solution. The calculations of the part for deflection by using Solid Works 2016 software were carried out. The calculations demonstrated the reliability of the installation when processing parts of medium and large sizes as compared to the basic installation option previously made by Penza State University for Penzadieselmash Company. Conclusions. The calculations made it possible to find that the reduction of the center distance reduces the deflection of parts and vibration in the process of finishing and allows stabilizing the quality and performance of processing the surfaces of a complex profile with less energy coast. A new design of the installation was developed and manufactured. It contributes to planetary rotation of the part at a small axial distance of the mandrel with the part and the spindle of the device. Keywords: theoretical study, result of study, complex surface, part surface, loose abrasive particles, performance, quality indicator, equipment design, design calculation automation For citation: Skryabin V. А. The Installation for Processing of Parts with a Complex Profile of Working Surface. Vestnik Mordovskogo universiteta = Mordovia University Bulletin. 2018; 28(4):552–561. DOI: https://doi.org/10.15507/0236-2910.028.201804.552-561

This paper develops a unified approach for assessing structural behaviour of austenitic and ferritic stainless steel circular hollow section (CHS) beam–columns​ under eccentric loading. This approach is based on combining a deformation-based method and collapse theory for stainless steel CHS beam–columns.A normalised M–N– Φ relationship of stainless steel CHS was derived based on a fibre model; the approach incorporated deformation capacity and strain hardening based on continuous strength method (CSM). The novelty of this paper is to present a closed-form solution for generating axial-load–end-moment interaction curves of the stainless steel CHS beam–column by combining the normalised M–N– Φ equation with a general beam–column equation. Besides, a critical normalised mid-height curvature was determined, which could be used to differentiate cross-section local buckling failure from global stability failure of stainless steel CHS beam–columns under combined loading. The proposed approach related the strengths of beam–columns to the effective column lengths by introducing a new non-dimensional slenderness ratio for stainless steel CHS beam–columns. It also provided an explicit way to consider the effect of column imperfections on the strengths of stainless steel CHS beam–columns. Accuracy of the derived normalised interaction curves was assessed by comparing the predictions against the test and numerical results for a wide range of non-dimensional slenderness ratios and different classes of CHS cross-sections for both stainless steel grades. A high level of accuracy and consistency was achieved in predicting the strengths of both short and long stainless steel CHS beam–columns for both types of steel grade.

Hydroxyphenyl-azoles are among the most popular ESIPT (Excited State Intramolecular Proton Transfer) scaffolds and as such, they have been thoroughly studied. Nevertheless, some aspects regarding the interplay between the emissive properties of these fluorophores and the size of their π-conjugated framework remain controversial. Previous studies have demonstrated that benzannulation of 2′-hydroxyphenyl-oxazole at the phenol group of the molecule can lead to either red- or blue-shifted fluorescence emission, depending on the site where it occurs. In this report, benzannulation at the heterocyclic unit (the oxazole site) is analysed in order to get the whole picture. The extension of π-conjugation does not significantly affect the ESIPT emission wavelength, but it leads instead to higher energy barriers for proton transfer in the first excited singlet state, as a consequence of dramatic changes in the charge transfer character of excitation caused by successive benzannulation. Theoretical calculations revealed an interesting connection between intramolecular charge transfer and excited-state aromaticity in the S1 state. The theoretical approach presented herein allows the behaviour of hydroxyphenyl-oxazoles in the excited state to be rationalized and, more generally, a deeper understanding of the factors governing the ESIPT process to be obtained, a crucial point in the design of new and efficient fluorophores. Fil: Mena, Leandro Daniel. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Vera, Domingo Mariano Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología; Argentina Fil: Baumgartner, Maria Teresa del V.. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina

Experiments show that clusters consisting of nano-sized ferromagnetic particles strongly affect the intensity of heat production during magnetic hyperthermia. In this paper, a theoretical study and mathematical modelling of the heat production by clusters of single-domain ferromagnetic particles, immobilized in a host medium, are presented. Two situations of strong and weak magnetic anisotropy of the particles are considered. Our results show that, in the case of strong anisotropy, the clusterization weakens the thermal effect, whereas in the case of weak anisotropy it enhances it. © 2020 The Author(s) Published by the Royal Society. All rights reserved. Ministry of Education and Science of the Russian Federation, Minobrnauka: FEUZ-2020-0051 Russian Foundation for Basic Research, RFBR: 18-08-00178, 20-02-00022, 19-52-45001 Data accessibility. This article has no additional data. Competing interests. We declare we have no competing interests. Funding. This work has been done with the financial support of a programme of the Ministry of Education and Science of the Russian Federation, projects 02.A03.21.0006 and FEUZ-2020-0051, as well as of the Russian Foundation of Basic Research, projects 18-08-00178, 19-52-45001 and 20-02-00022.

The thin interface limit of the phase-field model is extended to include transport via melt convection. A double-sided model (equal diffusivity in liquid and solid phases) is considered for the present analysis. For the coupling between phase-field and Navier-Stokes equations, two commonly used schemes are investigated using a matched asymptotic analysis: (i) variable viscosity and (ii) drag force model. While for the variable viscosity model, the existence of a thin interface limit can be shown up to the second order in the expansion parameter, difficulties arise in satisfying no-slip boundary condition at this order for the drag force model. Nevertheless, detailed numerical simulations in two dimensions show practically no difference in dendritic growth profiles in the presence of forced melt flow obtained for the two coupling schemes. This suggests that both approaches can be used for the purpose of numerical simulations. Simulation results are also compared to analytic theory, showing excellent agreement for weak flow. Deviations at higher fluid velocities are discussed in terms of the underlying theoretical assumptions. © 2020 The Author(s) Published by the Royal Society. All rights reserved. European Space Agency, ESA Deutsche Forschungsgemeinschaft, DFG Russian Science Foundation, RSF: 16-11-10095 Deutsche Forschungsgemeinschaft, DFG Data accessibility. This article has no additional data. Authors’ contributions. All the authors have contributed equally to this work. Competing interests. We declare we have no competing interest. Funding. P.K.G. acknowledges the support by the European Space Agency (ESA) under research project MULTIPHAS grant no. (AO-2004) and the German Aerospace Center (DLR) Space Management under contract no. 50WM1541 and also from the Russian Science Foundation under project no. 16-11-10095. A.S. and F.V. acknowledges financial support by the German Research Foundation (DFG) under the project no. Va205/17-1.

The adsorption of gas molecules (CO2, CH4, H2O, H2S and N2) on the “dense” (0 0 1) surface of α-quartz has been investigated by means of Density Functional Theory (DFT) for the molecular characterization of Enhanced Gas Recovery (EGR) processes by CO2 injection. Several configurations have been studied for the different compounds. Overall, the five molecules are weakly physisorbed on the surface; no charge transfer takes place and no new bonds are formed. The potential surface is quite flat, with all the different values falling into a range of less than 0.15 eV. Consequently, all the molecules can easily move from a configuration to the other. As for the order of preference, hydrogen sulfide adsorbs the most with a maximum adsorption energy of −0.23 eV, followed by carbon dioxide with −0.21 eV. For the other three molecules (H2O, CH4 and N2), there is no net sequence but values lower than that of CO2 are inferred. Coverage analysis of CO2 and CH4 show that carbon dioxide can replace methane on the surface improving its extraction, but high CO2 concentration could weaken its adsorption, hindering the whole process. These results could prove to be useful in designing the EGR process based on CO2 injection. This publication was made possible by NPRP Grant # 10-0125-170235 from Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors. Qatar University and the Gas Processing Center are acknowledged for their support. The authors would also like to thank Texas A&M University in Qatar for the use of their computational resources. Scopus

International audience; Thermoelectric colusites, one of the most recently identified and most promising family of complex Cu-S materials, have quickly attracted significant attention based on their outstanding performance. Herein, we investigate the effect of zinc for copper substitution on the thermoelectric properties of the high-performance Cr-Ge colusite, Cu26Cr2Ge6S32. We discuss the striking impact of the aliovalent Zn/Cu substitution on the charge carrier mobility and effective mass and the consequences on the electrical and thermal transport properties. The investigation is supported by first-principles calculations of the electronic density-of-states of doped colusites. The theoretical study reveals the removal of the sharp features at the top of the valence manifold with the incorporation of Zn in the conductive network, with a strong reduction in the estimated relaxation time. These theoretical and experimental observations confirm the importance of disorder within the conductive network and the high sensitivity of the Cu-S tetrahedral framework toward defects in high-performance thermoelectric colusites.

Introduction: The paper describes solutions of the problem raised during treating the turbine wheel of a turbocharger. The treatment of a complex surface with a hard grinding wheel requires a lot of time. This method does not provide the required quality because of the inaccessibility of some parts of the turbine blades. The problem is solved by polishing with loose abrasive grains. The abrasive medium is compressed with compressed air through a special device. Materials and Methods: The SolidWorks 2016 software was used to design the tool. The design of the part for determining actual loads and deflections was calculated taking into account the comparison of the operating parameters with the permissible values. Results: The main parameters of the part tratment are the pressure of the loose abrasive on the working surfaces of the blades and the speed of rotation of the part on the mandrel of the installation (cutting speed). During treating, the part experiences significant static and dynamic loads. The tension can lead to inadmissible deflection of the mandrel to secure the part, uneven treatment of its complex surfaces and defects. The performed calculations showed that in polishing the surfaces of parts of a complex, load profile and deflections on the workpiece and the mandrel are within the permissible values. Discussion and Conclusions: The presented method provides stable qualitative and productive treatment of the complex surfaces. The findings from this study contribute to the current technology of metal processing.

We present results of theoretical study of magnetorheological effect in ferrogels with magnetizable spherical particles chaotically distributed in a current gel. To avoid intuitive constructions with uncontrolled accuracy and adequacy, the analysis is done in the frames of the mathematically regular pair approximation. Our results demonstrate non monotonic increase of the composite shear modulus with the applied magnetic field. This effect is stronger for the systems with the soft gel, than for the relatively rigid ones., A.Z, L.I. and A.M are grateful to the program of the Ministry of Education and Science of the Russian Federation, projects 02.A03.21.0006; 3.1438.2017/4.6; 3.5214.2017/6.7 as well as to the Russian Fund of Basic Researches, projects 18-08-00178 and 19-52- 12028. M.T.L-L acknowledges financial support by project FIS2017- 85954-R (Ministerio de Economía, Industria y Competitividad, MINECO, and Agencia Estatal de Investigación, AEI, Spain, cofunded by Fondo Europeo de Desarrollo Regional, FEDER, European Union).

The paper deals with theoretical study of effect of ferrogels uniaxial elongation on magnetic susceptibilities of these composite materials. We have considered the systems with magnetically soft ellipsoidal and spherical particles. The results show that elongation of the composites with the ellipsoidal particles enhances the susceptibility in the direction of the elongation, whereas the deformation of ferrogels with the spherical particles decreases the susceptibility when the particles concentration is small enough and increases it when the concentration exceeds some threshold magnitude., This work has been supported by Russian Foundation for Basic Research (projects 18-08-00178, 19-52-12028); by the Program of the Ministry of Education and Science of the Russian Federation, projects 02.A03.21.0006; 3.1438.2017/4.6; 3.5214.2017/6.7. MTLL is grateful to proyect FIS2017-85954-R (Agencia Estatal de Investigación, AEI, Spain, co-funded by Fondo Europeo de Desarrollo Regional, ERDF, European Union).

A theoretical study of the influence of various technological factors on the force parameters of the hardening process of a cylindrical blank by a method of surface plastic deformation was performed. Based on the approximate model of plastic deformation propagation, an engineering technique has been developed that allows one to specify the force regimes of the surface hardening process with a toroidal roller, taking into account the required degree of deformation of the hardened layer, taking into account the mutual influence of the geometric parameters of the workpiece, the deforming roller and the required depth of cold work. The results of the theoretical study are in good agreement with the known experimental data and can be used in the development of technological operations for hardening machine parts by rolling in rollers or balls. © 2019 IOP Publishing Ltd. All rights reserved.

Fatima Aouidat,1 Sarah Boumati,2 Memona Khan,1 Frederik Tielens,3 Bich-Thuy Doan,2 Jolanda Spadavecchia1 1CNRS, UMR 7244, CSPBAT, Laboratory of Chemistry, Structures and Properties of Biomaterials And Therapeutic Agents University Paris 13, Sorbonne Paris Cité, Bobigny, France; 2UTCBS – Chimie ParisTech – University Paris Descartes - CNRS UMR 8258 – INSERM U1022 Equipe “Synthesis, Electrochemistry, Imaging and Analytical Systems for Diagnostics” SEISAD, Paris, France; 3General Chemistry (ALGC), Vrije University of Brussel (Free University Brussels-VUB), Brussel, BelgiumCorrespondence: Jolanda Spadavecchia Email jolanda.spadavecchia@univ-paris13.frIntroduction: The development of biopolymers for the synthesis of Gd(III) nanoparticles, as therapeutics, could play a key role in nanomedicine. Biocompatible polymers are not only used for complex monovalent biomolecules, but also for the realization of multivalent active targeting materials as diagnostic and/or therapeutic hybrid nanoparticles. In this article, it was reported for the first time, a novel synthesis of Gd(III)–biopolymer–Au(III) complex, acting as a key ingredient of core-shell gold nanoparticles (Gd(@AuNPs).Material and methods: The physical and chemical evaluation was carried out by spectroscopic analytical techniques (Raman spectroscopy, UV-visible and TEM). The theoretical characterization by DFT (density functional theory) analysis was carried out under specific conditions to investigate the interaction between the Au and the Gd precursors, during the first nucleation step. Magnetic features with relaxivity measurements at 7T were also performed as well as cytotoxicity studies on hepatocyte cell lines for biocompatibility studies. The in vivo detailed dynamic biodistribution studies in mice to characterize the potential applications for biology as MRI contrast agents were then achieved.Results: Physical–chemical evaluation confirms the successful design and reaction supposed. Viabilities of TIB-75 (hepatocytes) cells were evaluated using Alamar blue cytotoxic tests with increasing concentrations of nanoparticles. In vivo biodistribution studies were then accomplished to assess the kinetic behavior of the nanoparticles in mice and characterize their stealthiness property after intravenous injection.Conclusion: We demonstrated that Gd@AuNPs have some advantages to display hepatocytes in the liver. Particularly, these nanoconjugates give a good cellular uptake of several quantities of Gd@NPs into cells, while preserving a T1 contrast inside cells that provide a robust in vivo detection using T1-weighted MR images. These results will strengthen the role of gadolinium as complex to gold in order to tune Gd(@AuNPs) as an innovative diagnostic agent in the field of nanomedicine.Keywords: Gd-gold complex, theoretical study, MRI, relaxivity, biodistribution

The results of combined experimental and theoretical study of substitutional and clustering effects in Bi-doped TiO2 hosts (bulk and thin-film morphologies) are presented. Bi-doping of the bulk and thin-film titanium dioxide was made with help of pulsed ion-implantation (E(Bi+) = 30 keV, D = 1 * 1017 cm-2) without posterior tempering. The X-ray photoelectron spectroscopy (XPS) qualification (core-levels and valence bands) and Density-Functional Theory (DFT) calculations were employed in order to study the electronic structure of Bi-ion implanted TiO2 samples. According to XPS data obtained and DFT calculations, the Bi -> Ti cation substitution occurs in Bi-implanted bulk TiO2, whereas in the thin-film morphology of TiO2:Bi the Bi-atoms have metal-like clusters segregation tendency. Based on the combined XPS and DFT considerations the possible reasons and mechanism for the observed effects are discussed. It is believed that established peculiarities of bismuth embedding into employed TiO2 hosts are mostly the sequence of pleomorphic origin for the formed "bismuth-oxygen" chemical bonding., 19 pages, 6 figures, accepted in Appl. Surf. Sci

Embargo de 24 meses, The paper deals with theoretical study of deformation of a ferrogel filled by magnetizable particles united in the chain-like aggregates. The sample is placed in a magnetic field parallel to the chains. Uniaxial elongation of the sample along the field is studied. Analysis shows that interaction of the particles in the chains and rupture of the chains by the elastic forces lead to non linear dependence of the macroscopical stress on the elongation strain. The theoretical results are in principle agreement with known experimental study of the ferrogels deformation., Russian Scientific Foundation. project 14-19-00989. MINECO, Spain; co-funded by ERDF, European Union. Project FIS2013-41821-R

We present results of an experimental and theoretical study of the magnetic properties of soft magnetic gels consisting of micron-sized magnetizable particles embedded in a polymer matrix. Experiments demonstrate hysteretic dependences of composite magnetization on an applied magnetic field and non-monotonic, with maximum, dependence of the sample susceptibilities on the field. We propose a theoretical approach which describes the main physical features of these experimental results. © The Royal Society of Chemistry 2016.

The adsorption of gas molecules (CO2, CH4, H2O, H2S and N2) on calcite (104) has been studied by means of Density Functional Theory for molecular characterization of Enhanced Gas Recovery (EGR) CO2 injection. Results show that the geometry of both the surface and gas were not affected by the adsorption, highlighting the physisorption nature of the process. On average, water adsorbs the strongest followed by hydrogen sulfide, because of hydrogen bonding, and carbon dioxide comes next. Finally, nitrogen adsorption is stronger in average when compared to methane, with a certain degree of complexity. In general, all the configurations’ energies can be found in a range of less than 0.4 eV for each adsorbate. Nevertheless, the larger affinity of CO2 confirms the suitability of CO2 injection for methane release in EGR operations. The stronger water adsorption compared to carbon dioxide (−0.91 eV versus −0.38 eV) gives a quantitative estimate of the impact of water as impurity. Further investigations need to address the issue of water impurity, since this aspect could dramatically hinder the application of the whole technique. Coverage studies of methane and carbon dioxide further highlight the affinity of the latter to the carbonate surface. The authors would like to acknowledge the support of Qatar National Research Fund (a member of Qatar Foundation) through Grant # NPRP10-0125-170235. The findings achieved herein are solely the responsibility of the authors. In addition, we would like to thank Texas A&M University in Qatar for the use of their computational resources. Scopus

Prestressed concrete cylinder pipes (PCCPs) can suffer from prestress loss caused by wire-breakage, leading to a reduction in load-carrying capacity or a rupture accident. Reinforcement of PCCPs with external prestressed steel strands is an effective way to enhance a deteriorating pipe&rsquo, s ability to withstand the design load. One of the principal advantages of this reinforcement is that there is no need to drain the pipeline. A theoretical derivation is performed, and this tentative design method could be used to determine the area of prestressed steel strands and the corresponding center spacing in terms of prestress loss. The prestress losses of strands are refined and the normal stress between the strands and the pipe wall are assumed to be distributed as a trigonometric function instead of uniformly. This derivation configures the prestress of steel strands to meet the requirements of ultimate limit states, serviceability limit states, and quasi-permanent limit states, considering the tensile strength of the concrete core and the mortar coating, respectively. This theory was applied to the reinforcement design of a PCCP with broken wires (with a diameter of 2000 mm), and a prototype test is carried out to verify the effect of the reinforcement. The load-carrying capacity of the deteriorating PCCPs after reinforcement reached that of the original design level. The research presented in this paper could provide technical recommendations for the application of the reinforcement of PCCPs with external prestressed steel strands.

WOS: 000441821400079, In this study, the density functional theory (DFT) at the gradient-corrected correlation functional of Lee-Yang-Parr (B3LYP) functional with 6-311++G(2d,2p), correlation-consistent, polarized valence, X-zeta (cc-pVTZ) basis sets, BP86 functional with/6-311++G(2d,2p) basis set and ab initio calculations using the Hartree-Fock (HF)/6-311++G(2d, 2p) methods in gas and water phase of neutral and protonated forms of molecules were performed on six thiosemicarbazone derivatives, namely 4-methyl acetophenone thiosemicarbazone (Inh 1), 4-methoxy acetophenone thiosemicarbazone (Inh 2), Benzaldehyde thiosemicarbazone (Inh 3), 4-methoxy benzaldehyde thiosemicarbazone (Inh 4), 4-ethyl benzaldehyde thiosemicarbazone (Inh 5) and 4-bromo benzaldehyde thiosemicarbazone (Inh 6). The quantum chemical parameters/descriptors, namely, dipole moment (D), highest occupied molecular orbital energy (E-HOMO), lowest unoccupied molecular orbital energy (E-LUMO), HOMO-LUMO energy gap (Delta E), absolute electronegativity (chi), absolute hardness (eta), softness (sigma), proton affinity (PA), electrophilicity (omega) and nucleophilicity (epsilon) were calculated and correlated with the experimental inhibition efficiencies (% IE). It was observed that the theoretical and experimental results were in good agreement.

The paper deals with theoretical study of hysteretic magnetostriction of soft ferrogels – composite materials, consisting of the micron-sized magnetizable particles embedded into gel matrices. It is supposed that initially, before application of an external magnetic field, the particles are homogeneously and isotropically distributed in an elastic matrix. The theoretical explanation of the hysteresis phenomena is based on the conception that, under the field action, the particles rearrange into the linear chain-like aggregates. The typical length of the chains is determined by the competition between the force of magnetic attraction of the particles and the force of elastic deformation of the matrix., This work has been done under the financial support of the Russian Fund for Basic Research, 16-58-12003, 16-53- 12009, 16-32-00019 mol a, the Program of Russian Federation Ministry of Science and Education, projects 3.1438.2017/4.6, 11.10010.2017/5.2; 3.5214.2017/6.7; D.B. would like to acknowledge the financial support of the Deutsche Forschungsgemeinschaft (DFG) under Grant Bo 3343/1-1 within PAK 907. M.L-L was supported by the project FIS2013-41821-R (Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, Ministerio de Economía y Competitividad, Spain, co-funded by ERDF, European Union) and by the project FIS2017-85954-R (Agencia Estatal de Investigación, AEI, Spain, cofunded by Fondo Europeo de Desarrollo Regional, ERDF, European Union).

Potential applications of bulk GaN and AlN crystals have made possible single and multilayer allotropes of these III-V compounds to be a focus of interest recently. As of 2005, the theoretical studies have predicted that GaN and AlN can form two-dimensional (2D) stable, single-layer (SL) structures being wide band gap semiconductors and showing electronic and optical properties different from those of their bulk parents. Research on these 2D structures have gained importance with recent experimental studies achieving the growth of ultrathin 2D GaN and AlN on substrates. It is expected that these two materials will open an active field of research like graphene, silicene, and transition metal dichalcogenides. This topical review aims at the evaluation of previous experimental and theoretical works until 2018 in order to provide input for further research attempts in this field. To this end, starting from three-dimensional (3D) GaN and AlN crystals, we review 2D SL and multilayer (ML) structures, which were predicted to be stable in free-standing states. These are planar hexagonal (or honeycomb), tetragonal, and square-octagon structures. First, we discuss earlier results on dynamical and thermal stability of these SL structures, as well as the predicted mechanical properties. Next, their electronic and optical properties with and without the effect of strain are reviewed and compared with those of the 3D parent crystals. The formation of multilayers, hence prediction of new periodic layered structures and also tuning their physical properties with the number of layers are other critical subjects that have been actively studied and discussed here. In particular, an extensive analysis pertaining to the nature of perpendicular interlayer bonds causing planar GaN and AlN to buckle is presented. In view of the fact that SL GaN and AlN can be fabricated only on a substrate, the question of how the properties of free-standing, SL structures are affected if they are grown on a substrate is addressed. We also examine recent works treating the composite structures of GaN and AlN joined commensurately along their zigzag and armchair edges and forming heterostructures, delta-doping, single, and multiple quantum wells, as well as core/shell structures. Finally, outlooks and possible new research directions are briefly discussed. Published by AIP Publishing.

Total energy calculations based on density functional theory are performed for HgSe in the ambient and pressure induced phases. The electronic exchange and correlation effects are described by employing the generalized gradient approximation together with the projector augmented wave potentials. The equation of state parameters and the phase transition paths are obtained from the energy- volume landscape and enthalpy versus pressure data, correspondingly. The observed phase transition sequence of HgSe as ZB -> Cinnabar -> RS -> Cmcm and the final transition from Cmcm to CsCl structure predicted by the other theoretical study are confirmed by our calculations. The pressure dependence of elastic constants of the structures considered in this study is reported. Bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and Debye temperature as isotropic mechanical properties are evaluated for HgSe polymorphs. Our calculations of energy band structure reveal the inverted band structure evoking that HgSe in ZB phase is a semimetal. (c) 2018 Elsevier B. V. All rights reserved.

Gold is inert and forms very few compounds. One of the most interesting of those is calaverite AuTe2, which has incommensurate structure and which becomes superconducting when doped or under pressure. There exist a "sibling" of AuTe2 the mineral sylvanite AuAgTe4, which properties are almost unknown. In sylvanite Au and Ag ions are ordered in stripes, and Te6 octahedra around metals are distorted in such a way that Ag becomes linearly coordinated, what is typical for Ag^{1+}, whereas Au is square coordinated - it is typical for d^8 configurations, i.e. one can assign to Au the valence 3+. Our theoretical study shows that at pressure P_C ~ 5 GPa there should occur in it a structural transition such that above this critical pressure Te6 octahedra around Au and Ag become regular and practically identical. Simultaneously Te-Te dimers, existing at P = 0 GPa, disappear, and material from a bad metal becomes a usual metal with predominantly Te 5p states at the Fermi energy. We expect that, similar to AuTe2, AuAgTe4 should become superconducting above P_C., Comment: 8 pages, 4 figures

Tetradentate (1E,2E,1′E,2′E)-3,3′-bis[(4-bromophenyl)-3,3′-(4-methy-1,2-phenylene diimine)] acetaldehyde dioxime which possess N4 donor sets derived from the condensation of isonitroso-p-bromoacetophenone and 3,4-diaminotoluene are synthesized and characterized. The characterization of tetradentate Schiff base ligand has been deduced from LC-MS, FTIR, 13C and 1H NMR spectra and elemental analysis. Furthermore, the molecular geometry, infrared and NMR spectra of the title molecule in the ground state have been calculated by using the quantum chemical computational methods such as density functional theory (DFT) and ab initio Hartree-Fock (HF) methods with the 6–31G(d) and 6–311G(d) basis sets. The computed bond lengths and bond angles by using the both methods show the good agreement with each other. Moreover, the vibrational frequencies have been calculated and the scaled values have been compared with the experimental FTIR spectroscopic data. Assignments of the vibrational modes are made on the basis of potential energy distribution (PED) calculated from by using VEDA program. The correlations between the observed and calculated frequencies are in good agreement with each other as well as the correlation of the NMR data. © 2015, Pleiades Publishing, Ltd.

The paper deals with a theoretical study of the effective shear modulus of a magnetic gel, consisting of magnetizable particles randomly and isotropically distributed in an elastic matrix. The effect of an external magnetic field on the composite modulus is the focus of our consideration. We take into account that magnetic interaction between the particles can induce their spatial rearrangement and lead to internal anisotropy of the system. Our results show that, if this magnetically induced anisotropy is insignificant, the applied field reduces the total shear modulus of the composite. Strong anisotropy can qualitatively change the magnetomechanic effect and induce an increase of this modulus with the field., A.Y.Z. is grateful for financial support from the Russian Fund for Basic Research, through Grant No. 16-58-12003, the Program of Russian Federation Ministry of Science and Education, Project No. 3.1438.2017/4.6. M.T.L.-L. was supported by Project No. FIS2013-41821-R of Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, Ministerio de Economía y Competitividad, Spain, co-funded by ERDF, European Union. D.Y.B. would like to acknowledge support of from Deutsche Forschungsgemeinschaft under Grant No. Bo 3343/1-1.

The paper deals with theoretical study of elastic shear properties of a magnetic gel, consisting of spherical magnetizable particles, randomly (gas-like) distributed in an elastic matrix. We suppose that the composite is placed in a magnetic field, perpendicular to the direction of the sample shear. In order to get mathematically rigorous results, we have restricted ourselves by the analysis of the system with a low concentration of the particles. Magnetic and elastic (through the matrix deformation) interactions between them are considered in the framework of the regular pair approximation. Analysis shows that external magnetic field decreases the macroscopic shear modulus of the composite with a low concentration of the particles. The decreasing dependence of the modulus on the macroscopic shear is estimated. We believe that the suggested rigorous approach can be a robust background for the study of the systems with a high concentration of the particles., L Iskakova and A Zubarev are grateful for the financial support of the Russian Fund for Basic Research, 16-58- 12003; the Program of Russian Federation Ministry of Science and Education, project 3.1438.2017/4.6. M Lopez-Lopez was supported by the project FIS2013- 41821-R (Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, Ministerio de Economía y Competitividad, Spain, co-funded by ERDF, European Union). D Borin would like to acknowledge the support of DFG (Deutsche Forschungsgemeinschaft) under Grant Bo 3343/ 1-1.

The effects of particle-size polydispersity on the magnetostatic properties of concentrated ferrofluids are studied using theory and computer simulation. The second-order modified mean-field (MMF2) theory of Ivanov and Kuznetsova [Phys. Rev. E 64, 041405 (2001)1063-651X10.1103/PhysRevE.64.041405] has been extended by calculating additional terms of higher order in the dipolar coupling constant in the expansions of the initial magnetic susceptibility and the magnetization curve. The theoretical predictions have been tested rigorously against results from Monte Carlo simulations of model monodisperse, bidisperse, and highly polydisperse ferrofluids. Comparisons have been made between systems with the same Langevin susceptibility and the same saturation magnetization. In all cases, the new theoretical magnetization curve shows better agreement with simulation data than does the MMF2 theory. As for the initial susceptibility, MMF2 theory is most accurate for the monodisperse model, while the new theory works best for polydisperse systems with a significant proportion of large particles. These results are important for the analysis and characterization of recently synthesized polydisperse ferrofluids with record-breaking values of the initial magnetic susceptibility. © 2017 American Physical Society.

The current investigation is devoted to the theoretical study of orbital structure influence upon magnetic subsystem in half-doped charge-ordered manganites. The main interaction of magnetic subsystem is superexchange interaction. It forms spin-wave dispersion dependencies. Because of charge and orbital ordering, there are a lot of superexchange parameters in these compounds. That makes the dispersion rather complicated. This work clarifies some features of dispersion in terms of orbitally-dependent superexchange interactions.

The organic Rankine cycle (ORC) is efficient in using low-grade heat energy, while low pump efficiency and high pump leakage are usually serious problems. A gravity-driven organic power cycle (GDOPC) uses gravity instead of a pump to pressurize working fluid and has the potential to avoid problems associated with the pump. A theoretical method is used to study the performance and suitability of several fluids for GDOPC. The results show that the flow efficiency in high vertical pipes and the pump efficiency determine whether GDOPC gives better performance than ORC or not. When R245fa is selected as working fluid and evaporating temperature is 62 &deg, C, specific energy of GDOPC (flow efficiency is 80%) is 2.5% higher than that of ORC (pump efficiency is 60%). The improvement degree of specific energy and the liquid column height increase with increasing evaporating temperature. R1234yf and R227ea give good performance with specific energy of 4.84 kJ/kg and 4.82 kJ/kg, respectively, while they need a liquid column as much as 76.55 m and 45.65 m, respectively. Although R365mfc and cyclopentane do not give the most excellent cycle performance, they need liquid column height as low as 9.04 m and 10.88 m, respectively. Fluid with low saturated pressure and high density may need low liquid column height and has the advantage to be used in practical applications.

This article presents a simulation study on two integrated tuned vibration absorbers (TVAs) designed to control the global flexural vibration of lightly damped thin structures subject to broad frequency band disturbances. The first one consists of a single axial switching TVA composed by a seismic mass mounted on variable axial spring and damper elements so that the characteristic damping and natural frequency of the absorber can be switched iteratively to control the resonant response of three flexural modes of the hosting structure. The second one consists of a single three-axes TVA composed by a seismic mass mounted on axial and rotational springs and dampers, which are arranged in such a way that the suspended mass is characterized by uncoupled heave and pitch-rolling vibrations. In this case the three damping and natural frequency parameters of the absorber are tuned separately to control three flexural modes of the hosting structure. The simulation study shows that the proposed single-unit absorbers produce, respectively, 5.3 and 8.7 dB reductions of the global flexural vibration of a rectangular plate between 20 and 120 Hz.

The paper deals with the theoretical study of the effect of chain-like aggregates on diffusion and magnetophoretic transport in ferrofluids. Analysis shows that the appearance of the chains leads to a strong anisotropy of the diffusion transport-the coefficient of diffusion in the direction of applied magnetic field is significantly more than that in the perpendicular direction. The presence of the chains in a ferrofluid strongly affects the coefficient of the particle magnetophoresis. © 2012 Elsevier B.V. All rights reserved.

We have calculated the electronic structure and physical properties of metal thiophosphate compounds InPS4and AlPS4by means of pseudopotential density functional theory (DFT) coupled with the modern theory of polarization. The targeted physical properties are first and second order optical properties as well as elastic, piezoelectric and electro-optic coefficients. Furthermore, population analysis is presented in order to evaluate the covalent-ionic character of the constituent bonds. The calculated elastic constants, refractive indices and second order optical coefficients of InPS4are in good agreement with experimental values. With the absence of any theoretical or experimental physical properties of AlPS4, we predict that this compound has high piezoelectric coefficients with d14= − 73.82 pm/V, d25= − 10.96 pm/V and d36= 28.19 pm/V.

Fabrication of self-assembled arrays of nanocrystals (NCs) by physical vapor deposition (PVD) is a promising technique rated highly for its potential for various electronic, photonic, and sensing applications. However, the self-assembly process is not straightforward to control and direct in a desired way. A detailed understanding of how to control the size, shape, and density of self-assembled NCs by varying the accessible PVD process conditions, such as deposition rate, duration, or temperature, is critical for the potential of self-assembled nanofabrication to be fully realized. In this paper, we report a systematic kinetic Monte Carlo modeling that explicitly represents PVD synthesis of self-assembled metallic NCs on a crystalline substrate. We investigate how varying the duration of deposition, deposition rate, temperature, and substrate wetting conditions may affect the morphologies of arrays of self-assembled metallic islands and compare our results with previously reported experimentally observed surface morphologies generated by PVD and theoretical studies. © 2011 American Chemical Society.

The conditions for the application of taper angles of deforming rollers are considered in the article, which ensure a steady flow of the flow forming. With the help of the developed engineering technique, analytical and graphical dependences of the boundary values of the deformation degrees on the cone angle of the deforming roller are obtained. The results of the theoretical study are in good agreement with the known experimental data. The developed engineering technique can be used in designing the flow forming on the direct and reverse method, as well as for any process of pressure treatment with a local focus of deformation. © The Authors, published by EDP Sciences, 2018.

This contribution presents an electrochemical, Raman spectroscopic, and theoretical study probing the differences in molecular and electronic structure of two quinoidal oligothiophenes (3′,4′-dibutyl-5,5″-bis(dicyanomethylene)-5,5″-dihydro-2,2′:5′,2″-terthiophene and 5,5′-bis(dicyanomethylene)-3-hexyl-2,5-dihydro-4,4′-dihexyl-2,2′,5,5′-tetrahydro-tetrathiophene) with terminal tetracyanomethylene functionalization and aromatic oligothiophenes where acceptor moieties are positioned at lateral positions along the conjugated chain (6,6′-dibutylsulfanyl-[2,2′-bi-[4-dicyanovinylene-4H-cyclopenta[2,1-b:3,4-b′]dithiophene]). In this way, the consequences of linear and cross conjugation are compared and contrasted. From this analysis, it is apparent that organic field-effect transistors fabricated with cross-conjugated tetrathiophene semiconductors should combine the benefits of an electron-donor aromatic chain with strongly electron-accepting tetracyanomethylene substituents. The corresponding organic field-effect transistors exhibit ambipolar transport with rather similar hole and electron mobilities. Moreover, n-channel conduction is enhanced to yield one of the highest electron mobilities found to date for this type of material.

We present a theoretical study of the dynamics of H atoms adsorbed on graphene bilayers with Bernal stacking. First, through extensive density functional theory calculations, including van der Waals Interactions, we obtain the activation barriers involved in the desorption and migration processes of a single H atom. These barriers, along with attempt rates and the energetics of H pairs, are used as input parameters in kinetic Monte Carlo simulations to study the time evolution of an initial random distribution of adsorbed H atoms. The simulations reveal that, at room temperature, H atoms occupy only one sublattice before they completely desorb or form clusters. This sublattice selectivity in the distribution of H atoms may last for sufficiently long periods of time upon lowering the temperature down to 0 ◦C. The final fate of the H atoms, namely, desorption or cluster formation, depends on the actual relative values of the activation barriers which can be tuned by doping. In some cases, a sublattice selectivity can be obtained for periods of time experimentally relevant even at room temperature. This result shows the possibility for observation and applications of the ferromagnetic state associated with such distribution, This work was supported by MINECO under Grant Nos. FIS2013-47328 and FIS2012-37549, by CAM under Grant Nos. S2013/MIT-3007, P2013/MIT-2850, and by Generalitat Valenciana under Grant PROMETEO/2012/011

This paper investigates the effect of different orientations of fiber in the skins and different thicknesses of the skins and polypropylene honeycomb core (PPHC) on the transverse shear damping of the sandwich using experimental and theoretical studies. Three different sandwiches, SW1 (thickness of top and bottom FRP skin: 3.15 mm each with 10 mm thick PPHC), SW2 (thickness of top and bottom FRP skin: 1.575 mm each with 5 mm thick PPHC), SW3 (thickness of top and bottom FRP skin: 1.575 mm each with 10 mm thick PPHC) were fabricated for conducting experimental work. In order to study the effect of fiber orientation of the skin on the natural frequency and loss factors, five different orientations (all 0�, �30�, �45�, �60� and all 90�) were considered. An impulse technique was used to calculate the natural frequency and loss factor of the composites. The natural frequency and loss factor were also computed theoretically and compared. As the in-plane load of the strong FRP skins imposes on the soft honeycomb core under dynamic condition, it causes a large transverse shear deformation on the core. This shear deformation leads to a high energy dissipation/loss factor of the sandwich. At the 0� fiber oriented sandwich, the loss factor value (? = 0.0234) becomes significantly higher without losing its natural frequency (stiffness) value (fn = 142.12 Hz), which is not so in the case of FRP composites having the loss factor (?) value of 0.00218 and the natural frequency value (fn) of 114.23 Hz. It is also found that the transverse shear effect and damping loss factor increases with the increase in the thicknesses of the skins and core of the sandwich. � 2015 Elsevier Ltd. All rights reserved.

En este trabajo se revisan las técnicas de simulación molecular más habituales y potentes para la descripción de los polímeros a escala atómica y molecular, las cuales se han clasificado en cuánticas o clásicas dependiendo de cómo se describen las interacciones entre las partículas. Se presentan asimismo diversas aplicaciones de dichas metodologías, realizadas en nuestro laboratorio, en el contexto del estudio de la estructura y propiedades de polímeros. En particular, se muestran aplicaciones de las técnicas clásicas a la determinación de estructuras cristalinas, a estudio del plegamiento lamelar de los nylons, a la estabilidad de las estructuras supramoleculares observadas en algunos complejos tensioactivo·polielectrolito y a la difusión de gases en matrices poliméricas, mientras que el uso de técnicas cuánticas se ha ilustrado presentando estudios dedicados a la predicción de efectos cooperativos, interacciones específicas y parámetros espectroscópicos. The most important computational techniques employed to simulate the structure and properties of polymers at the miscroscopic level have been reviewed. They have been classified in quantum or classical methods depending on the expressions used to describe the interactions between the particles. Furthermore, the applicability of such modeling tools is shown with some results recently obtained by our group. More specifically, we show the applicability of classical methods to determine the crystal structure of polymers, to model the lamellar folding of nylons, to predict the stability of the supramolecular structures adopted by some surfactant·polyelectrolite self-assembled complexes and to investigate the diffusion of simple gases through polymeric matrices. The reliability of quantum methods has been illustrated displaying some studies devoted to study cooperative effects, specific interactions and spectroscopic parameters.

cited By 6; International audience; We present a complete analysis of the velocity of individual screw dislocations in pure iron, as a function of stress and temperature, by means of in situ straining experiments in a transmission electron microscope. The results show a very pronounced deviation from the classical laws of thermodynamics, which is at the origin of the discrepancy between experimental and calculated deformation stresses at low temperature. This strongly supports the occurrence of large quantum effects proposed in a recent theoretical study. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The present work, six different equations of state (EOS), have been used for studying Copper under high pressure at room temperature, by studying variation of different thermodynamical parameters in particular, variations in bulk modulus and Grüneisen parameter, which are represent a promising approach for modeling universal EOS for solids. On comparing our predicted results, obtained by using the different EOS, with experimental data, one notice that all the six EOS gives agreement with experimental data for relatively low pressure. The best agreement with experimental data, with increasing pressure, have been shown by the results calculated by Bardeen, Brennan – Stacey and Vinet EOS. While results predicted by using Birch – Murnaghan EOS shows slightly less agreement with experimental data. The results calculated by using both Murnaghan EOS and Thomsen EOS at higher pressure shows disagreement with experimental data and with our theoretical results.

This paper deals with a theoretical study of the shear thickening effects in concentrated suspensions of non-Brownian particles. Our analysis shows that an increase of the shear rate of the suspension flow leads to a decrease of the mean thickness of the gaps between the nearest particles in dense suspensions. In turn, this leads to the growth of energy dissipation in these gaps, which means an increase of the suspension effective viscosity with the shear rate. © 2013 American Physical Society.

The linear dispersion of the low-dimensional acoustic surface plasmon (ASP) opens perspectives in energy conversion, transport, and confinement far below optical frequencies. Although the ASP exists in a wide class of materials, ranging from metal surfaces and ultrathin films to graphene and topological insulators, its properties are still largely unexplored. Taking Au(111) as a model system, our combined experimental and theoretical study revealed an intriguing interplay between collective and single particle excitations, causing the ASP associated with the Shockley surface state to be embedded within the intraband transitions without losing its sharp character and linear dispersion., We acknowledge the partial support from the University of the Basque Country (Grant No. IT-366-07), the Departamento de Educación del Gobierno Vasco, the Spanish Ministerio de Ciencia e Innovación (Grant No. FIS2010-19609-C02-01), Italian PRIN-MIUR, and Compagnia di San Paolo.

This work reports both experimental and theoretical studies on the InGaN/GaN light-emitting diodes (LEDs) with optical output power and external quantum efficiency (EQE) levels substantially enhanced by incorporating p-GaN/n-GaN/p-GaN/n-GaN/p-GaN (PNPNP-GaN) current spreading layers in p-GaN. Each thin n-GaN layer sandwiched in the PNPNP-GaN structure is completely depleted due to the built-in electric field in the PNPNP-GaN junctions, and the ionized donors in these n-GaN layers serve as the hole spreaders. As a result, the electrical performance of the proposed device is improved and the optical output power and EQE are enhanced. © 2013 Optical Society of America.

The conformationally averaged mean-squared optical anisotropy ??? 2 of homopolymer chains under the theta solution condition is simulated using a rotational isomeric state (RIS) scheme with a generalized optical tensor description based on model bead-spring macromolecules. The effect of torsion angle values, number of minimum energy torsion states, probability (statistical weights) of the conformational states, and values of the components of the polarizability tensor for the bead are studied in this manner for the first time. Chains having either one or two interdependent rotatable bonds in the repeat unit are simulated. We find that under certain conditions of the relative orientations and values of the optical polarizability components with regards to the plane of the backbone bond angle, a higher probability for the gauche (less extended) conformation actually leads to a higher value of the optical anisotropy. In other cases, in conjunction with expectations from known experimental results, the optical anisotropy decreases with an increase in the probability of the gauche conformational state consistently over the range of values. We observe that, in most cases, higher values of the difference in the polarizability components lead to higher values of the chain optical anisotropy. � 2013 Copyright Taylor and Francis Group, LLC.

An experimental and theoretical study of the structural properties of monoclinic bismuth oxide (alpha-(BiO3)-O-2) under high pressures is here reported. Both synthetic and mineral bismite powder samples have been compressed up to 45 GPa and their equations of state have been determined with angle-dispersive x-ray diffraction measurements. Experimental results have been also compared with theoretical calculations which suggest the possibility of several phase transitions below 10 GPa. However, experiments reveal only a pressure-induced amorphization between 15 and 25 GPa, depending on sample quality and deviatoric stresses. The amorphous phase has been followed up to 45 GPa and its nature discussed., Financial support from the Spanish Consolider Ingenio 2010 Program (MALTA Project No. CSD2007-00045) is acknowledged. This work was also supported by Brazilian Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) under project 201050/2012-9, Spanish MICINN under projects MAT2010-21270-C04-01/03/04, Spanish MINECO under project CTQ2012-36253-C03-02, by Generalitat Valenciana through project GVA-ACOMP2013- 012 and from Vicerrectorado de Investigaci on de