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This research extensively used different progressive machine learning (ML) techniques to predict the compressive strength (CS) and tensile strain (TSt) of engineered cementitious composites (ECC) with 14 input variables and six algorithms. Specifically, random forest (RF), support vector machine, extreme gradient boosting (XGBoost), light gradient boosting machine, categorical gradient boosting (CatBoost), and natural gradient boosting techniques were used in the present study, to understand mechanical properties of ECC meanwhile these properties are crucial for design codes and developing new reliable models for mixtures. The discrepancy between the ML technique and specific ECC expected outputs is novel in this study and will aid researchers in better understanding of ECC features. To estimate the CS and TSt of the ECC, 2535 and 1469 input data points, respectively, were incorporated based on the material ratio, W/B, and different properties of the fibers. In addition, hyperparameter optimization techniques have also been used in ML to improve over fitting and make the model more accurate and robust. Moreover, an error analysis was highlighted between the actual and predicted CS and TSt of the ECC with each ML technique. Also, the significance and influence of the variable inputs that affect the CS and TSt were explained using the Shapley additive explanation (SHAP) approach. Among all approaches, CatBoost and XGBoost predicted the CS and TSt of ECC with greater accuracy than other techniques in terms of the coefficient of determination (R2), mean square error, mean absolute error, root mean square error, and symmetric mean absolute percentage error. The training and testing R2 values of CatBoost and XGBoost for predicting the CS and TSt of ECC were 0.96, 0.89, 0.89, and 0.76, respectively. SHAP analysis revealed that W/B and fiber elongation were the most significant input variables for the CS and TSt of the ECC. [ABSTRACT FROM AUTHOR]

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Context: In this paper, we systematically studied the effects of non-metallic element (B, C, N, O, F) doping and biaxial stretching on the photoelectric properties of ZrS2/ZrSe2 heterostructures by using the first-principles calculation method based on density functional theory. The results show that the p-type doping is realized by B, C, and N atom doping, and the n-type doping is realized by O and F atom doping. The doping of B and C atoms produces impurity energy levels in the band gap, which affects the conductivity of the heterostructure. The band gap of N and O atom–doped heterostructures increases under tensile strain, but it is still a direct band gap. The analysis of the optical properties of the heterostructures shows that the doping of non-metallic atoms can adjust the optical absorption rate and reflectivity of the heterostructures. Under the action of tensile strain, the optical properties of the doped heterostructures have changed significantly in the low-energy region. This article provides a theoretical basis for the future application of ZrS2/ZrSe2 heterostructures. Method: This paper uses the first-principles calculation method based on density functional theory. The PBE exchange-correlation functional based on generalized gradient approximation (GGA) is selected for the specific calculation, and the crystal structure is geometrically optimized by the ultrasoft pseudopotential method. It is verified that when the cutoff energy of the ZrS2/ZrSe2 heterostructure is 500 eV, the K-point grid is selected to be 10 × 10 × 2 with the lowest energy, so the cutoff energy is selected to be 500 eV. The K-point grid is selected to be 10 × 10 × 2. The convergence limits for structural optimization are as follows: the maximum force between atoms is 0.01 eV/Å, the convergence threshold of the maximum energy change is set to 10−9 eV/atom, and the convergence threshold of the maximum displacement is 0.001 Å. In order to avoid the influence of atomic periodic motion between different atomic layers, a vacuum layer of 20 Å is added in the vertical direction. Considering the interaction of vdW between the interfaces, the DFT-D2 method is used to verify. The optical properties were calculated by the random phase approximation method, and the K-point grid was selected as 12 × 12 × 2. [ABSTRACT FROM AUTHOR]

In this work, we report on a comparative study of the structural, optical, and elastic properties of SrTiSe3 and SrZrSe3 compounds using the DFT method. The lattice constants of the compounds are calculated using the GGA-PBE approximation and the hybrid functional Heyd, Scuseria, and Ernzerhof (HSE). The properties of the SrTiSe3 and SrZrSe3 materials in relation to electronic composition, elastic constants, and optical characteristics are deduced and analyzed. Both compounds display magnetic behavior, according to electronic calculations. SrTiSe3 shows metallic behavior, as the calculated bandgap value is zero. SrZrSe3, on the other hand, has a bandgap of 0.347 eV, which demonstrates its semiconducting nature. We have demonstrated that the plasma frequency of SrTiSe3 is around 1.77836. Using density functional theory, we report on the electronic characteristics of the compounds under mechanical stress. For SrZrSe3, the gap energy values rise with compressive stress and decrease with increasing tensile stress to zero. In addition, the study includes the extinction coefficient, optical conductivity, dielectric tensor, electron energy loss, and refractive index. [ABSTRACT FROM AUTHOR]

Context and results: In this work the first-principles calculations of the structural, electronic and thermoelectric properties of monolayer TiSe2 are presented. The optimized lattice parameter of monolayer TiSe2 shows excellent agreement with the experimental value. The computed band structure and density of states calculations predict metallic nature of monolayer TiSe2 with overlapping of 0.44 eV between the lowest conduction band and top valance band at high symmetry point M. The position of pseudogap formed by Ti-3d orbitals near the Fermi level confirms the mechanical stability of monolayer TiSe2. Due to the influence of positive strain (tensile strain), the Ti-Se bond length increases and the layer height decreases. The applied tensile strain changes the metallic nature of TiSe2 into a semiconductor with opening of bandgap. It has also been observed that the positions of conduction band minima and valance band maxima change with strain. The charge analysis shows that charge transfer from Ti to Se atom increases when tensile strain is applied, while an opposite trend is observed with compression. The computed thermoelectric coefficients i.e. Seeback coefficient, power factor and figure of merit are in good agreement with the experimental data. The temperature dependence of these coefficients is also reported. Computational method: The density functional theory based calculations are reported employing the PBE-GGA ansatz using the plane wave-pseudopotential method embodied in the Quantum ESPRESSO package. The self-consistent field calculations are performed over a dense Monkhorst–Pack net of 12 × 12 × 1 k-points. The energy convergence criteria for the self-consistent field calculation were set to 10–6 Ry/atom with a cutoff energy of 90 Ry. The thermoelectric properties are computed by combining the band structure calculations with the Boltzmann transport equation using Boltztrap2 package. [ABSTRACT FROM AUTHOR]

Context and results: In this work the first-principles calculations of the structural, electronic and thermoelectric properties of monolayer TiSe2 are presented. The optimized lattice parameter of monolayer TiSe2 shows excellent agreement with the experimental value. The computed band structure and density of states calculations predict metallic nature of monolayer TiSe2 with overlapping of 0.44 eV between the lowest conduction band and top valance band at high symmetry point M. The position of pseudogap formed by Ti-3d orbitals near the Fermi level confirms the mechanical stability of monolayer TiSe2. Due to the influence of positive strain (tensile strain), the Ti-Se bond length increases and the layer height decreases. The applied tensile strain changes the metallic nature of TiSe2 into a semiconductor with opening of bandgap. It has also been observed that the positions of conduction band minima and valance band maxima change with strain. The charge analysis shows that charge transfer from Ti to Se atom increases when tensile strain is applied, while an opposite trend is observed with compression. The computed thermoelectric coefficients i.e. Seeback coefficient, power factor and figure of merit are in good agreement with the experimental data. The temperature dependence of these coefficients is also reported. Computational method: The density functional theory based calculations are reported employing the PBE-GGA ansatz using the plane wave-pseudopotential method embodied in the Quantum ESPRESSO package. The self-consistent field calculations are performed over a dense Monkhorst–Pack net of 12 × 12 × 1 k-points. The energy convergence criteria for the self-consistent field calculation were set to 10–6 Ry/atom with a cutoff energy of 90 Ry. The thermoelectric properties are computed by combining the band structure calculations with the Boltzmann transport equation using Boltztrap2 package. [ABSTRACT FROM AUTHOR]

In this paper, we calculate the optical and electronic properties of ZrS2/ZrSe2 heterostructures under intrinsic and biaxial tensile strain using the first-principles calculation method based on plane wave density functional theory. The photoelectric properties of ZrS2/ZrSe2 heterojunction and single-layer ZrX2 (X = S, Se) structure are analyzed. The results show that the heterostructure has an adjustable band gap and stronger optical absorption capacity and light reflectivity in photoelectric properties. The ZrS2/ZrSe2 heterostructure under tensile strain significantly improves optical absorption capacity and light reflectivity. The ZrS2/ZrSe2 heterostructure under tensile strain has stronger optical absorption and reflection ability than the single-layer ZrX2 (X = S, Se) structure. The results provide a new theoretical reference for the applying ZrS2/ZrSe2 heterostructures in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Based on first principles, the effect of biaxial tensile strain on the electronic structure and optical properties of 1T-CrS2 doped with nonmetallic elements (B, C, and Si) has been studied. The monolayer CrS2 system exhibits an indirect band gap when subjected to tensile strain and Si doping. The direct bandgaps of the B and C doped systems are 0.125 and 0.167 eV, respectively, and the formation energies of both are negative, indicating that the systems are simple to form. Further bandgap modulation is accomplished under tensile strain for the doped systems. The B- and C-doped systems are capable of bandgap-type conversion under tensile strain. The study of the optical properties shows that atomic doping alters the optical response of the system, and a slight absorption band edge appears in the absorption spectrum. At minimal strain (2%), the optical properties of the doped system improved, thereby enhancing the photocatalytic activity of the compounds. The aforementioned findings inform the use of the material in microelectronics and particular optical domains. [ABSTRACT FROM AUTHOR]

Due to Silicon (Si) material abundance and specific properties, monolithic integration of III-V semiconductors on (Si) is of paramount importance for the next-generation in Optoelectronic devises. An alternative approach to lattice mismatched single silicon crystal substrates for heteroepitaxy is proposed. In this work, we have suggested a design of a compliant virtual substrate and we have explored the modulation of stress/lattice parameter of a window layer based on porous silicon pseudo-substrates allowing a defect free epitaxial growth. We prepared a silicon window layer with low porosity and variable thicknesses whose stress is modulated by the succession of several layers with gradual porosity. As a result, we evaluated the stress and the lattice parameter in compliant substrate before and after thermal annealing. The pores reorganization process was supported in Argon atmosphere at constant temperature (900 °C). The samples were studied morphologically by Field Emission scanning Electron Microscope (FE-SEM) and structurally by High Resolution X-Ray Diffraction (HR-XRD) and Nano-Raman. [ABSTRACT FROM AUTHOR]

We examined the fabrication process of uniaxial tensile-strained Ge wires in micro-bridge structures by utilizing the internal stresses in deposited metal thin films. This method enables strain control by adjusting film-deposition conditions, which is advantageous over previous methods that utilize internal stresses unintentionally applied to Ge-on-insulator substrates. We evaluated the internal stresses in W films formed by sputtering deposition methods. Tensile and compressive stresses were determined based on the Ar gas pressure during the deposition process. We applied tensile strain to Ge wires using 100-nm-thick W films, each with a tensile stress of 890 MPa, deposited in 1.5-Pa Ar gas. We confirmed that strains of up to 1.62% can be achieved and controlled by tuning the structural parameters of the bridge structure with the Ge wires. Photoluminescence peaks shifted to lower energies with increasing strain, in good agreement with theoretical predictions. We also used strained Ge wires to fabricate light-emitting diodes that exhibited clear electroluminescence peaks indicative of band structural modulation in the Ge wires. [ABSTRACT FROM AUTHOR]

This article presents the results of a study of the effect of the content of brand Printex XE 2B carbon black nanoparticles and a compatibilizer in the form of a graft copolymer of high density polyethylene with maleic anhydride on the basic physicomechanical characteristics of nanocomposites based on polyolefins. High density polyethylene, low density polyethylene, and polypropylene are used as a polyolefin. The following characteristics were studied: fracture stress, tensile yield strength, tensile strain, heat resistance, and flexural strength. The optimum ratios of the components of the mixture were established during the study, for which high physical and mechanical characteristics of polyolefin-based nanocomposites were obtained. [ABSTRACT FROM AUTHOR]

The cross-sectional morphology and atomic composition of samples before and after nitrogen ion implantation were compared and analyzed by high-resolution transmission electron microscopy and energy-dispersive x-ray. Results show that Ga and Al atoms diffuse among the quantum well, barrier, and waveguide layer during intermixing. The change of composition makes the heterojunction interfaces blurred from top to bottom. The implanted N ions are mainly distributed in the top GaInP barrier gradient layer and diffuse into the whole epitaxial layers after rapid thermal annealing. [ABSTRACT FROM AUTHOR]

Because of profound applications of two-dimensional molybdenum disulfide (MoS2) and its heterostructures in electronics, its thermal stability has been spurred substantial interest. We employ a precision muffle furnace at a series of increasing temperatures up to 340 °C to study the oxidation behavior of continuous MoS2 films by either directly growing mono- and few-layer MoS2 on SiO2/Si substrate, or by mechanically transferring monolayer MoS2 or hexagonal boron nitride (h-BN) onto monolayer MoS2 substrate. Results show that monolayer MoS2 can withstand high temperature at 340 °C with less oxidation while the few-layer MoS2 films are completely oxidized just at 280 °C, resulting from the growth-induced tensile strain in few-layer MoS2. When the tensile strain of films is released by transfer method, the stacked few-layer MoS2 films exhibit superior thermal stability and typical layer-by-layer oxidation behavior at similarly high temperature. Counterintuitively, for the MoS2/h-BN heterostructure, the h-BN film itself stacked on top is not damaged and forms many bubbles at 340 °C, whereas the underlying monolayer MoS2 film is oxidized completely. By comprehensively using various experimental characterization and molecular dynamics calculations, such anomalous oxidation behavior of MoS2/h-BN heterostructure is mainly due to the increased tensile strain in MoS2 film at elevated temperature. [ABSTRACT FROM AUTHOR]

Monolayer MoS2 is a typical transition metal dichalcogenides (TMDs), which is similar to graphene. However, MoS2 is a direct band gap semiconductor material. Based on the density functional theory, the changes of band structure, densities of states, phonon dispersion relations, and Raman spectrum of 2H monolayer MoS2 under ab biaxial strain are studied in this paper. The results show that the band gap, the structural stability, and the peak value of Raman spectrum of monolayer MoS2 are obviously changed under the biaxial strain. At compressive strain of 4%, monolayer MoS2 changed from direct band gap semiconductor to indirect band gap semiconductor, and at tensile strain of 10%, it changed from semiconductor material to metal material. During compressive strain above 4%, imaginary frequency appears in the phonon dispersion curve, and it means that the structure becomes unstable. [ABSTRACT FROM AUTHOR]

The results of studying the resistivity, magnetoresistance, and Hall coefficient of thin films of bismuth and the bismuth–antimony system on a borosilicate-glass substrate under plane tensile strain are presented. Deformation is created by a specially developed method that allows a change in its magnitude directly during measurement of the film properties. The films are obtained by thermal evaporation in vacuum. Varying the technological modes made it possible to obtain films of various structures: from small blocks to single crystal. Based on the experimental results, within the framework of the two-band approximation, the concentrations of charge carriers and the positions of the energy extrema of the valence and conduction bands relative to the chemical potential level are calculated. It is shown that the two-band approximation is insufficient for describing the properties of films of the studied compositions under plane tensile strain. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Orofacial Orthopedics/Fortschritte der Kieferorthopadie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Introduction: The goal of this study was to investigate how concurrent shear stress and tensile strain affect endothelial cell biomechanical responses. Methods: Human coronary artery endothelial cells were exposed to concurrent pulsatile shear stress and cyclic tensile strain in a programmable shearing and stretching device. Three shear stress–tensile strain conditions were used: (1) pulsatile shear stress at 1 Pa and cyclic tensile strain at 7%, simulating normal stress/strain conditions in a healthy coronary artery; (2) shear stress at 3.7 Pa and tensile strain at 3%, simulating pathological stress/strain conditions near a stenosis; (3) shear stress at 0.7 Pa and tensile strain at 5%, simulating pathological stress/strain conditions in a recirculation zone. Cell morphology was quantified using immunofluorescence microscopy. Cell surface PECAM-1 phosphorylation, ICAM-1 expression, ERK1/2 and NF-κB activation were measured using ELISA or Western blot. Results: Simultaneous stimulation from pulsatile shear stress and cyclic tensile strain induced a significant increase in cell area, compared to that induced by shear stress or tensile strain alone. The combined stimulation caused significant increases in PECAM-1 phosphorylation. The combined stimulation also significantly enhanced EC surface ICAM-1 expression (compared to that under shear stress alone) and transcriptional factor NF-κB activation (compared to that under control conditions). Conclusion: Pulsatile shear stress and cyclic tensile strain could induce increased but not synergistic effect on endothelial cell morphology or activation. The combined mechanical stimulation can be relayed from cell membrane to nucleus. Therefore, to better understand how mechanical conditions affect endothelial cell mechanotransduction and cardiovascular disease development, both shear stress and tensile strain need to be considered. [ABSTRACT FROM AUTHOR]

Ge emerges as a good candidate for the active layer in optoelectronic devices and is compatible with complementary metal oxide semiconductor technology. As the Ge band structure exhibits an indirect band gap with a small difference in energy between the direct and the indirect valleys (about 140 meV), the energy band structure can be modified by applying a tensile strain or by doping electrons into the film to turn Ge into a semiconductor material with a direct ban gap structure. In this work, Ge epilayers were grown on Si substrate by molecular beam epitaxy technique, and we show that the tensile strain value of the Ge epilayers increases by a factor of two by doping electrons into the films with two donor elements using GaP and Sb sources. The dopant concentration in Ge epilayers is 5.6 × 1019 at cm−3 for the P dopant and 6.4 × 1018 at cm−3 for the Sb dopant. The activated electron concentration was found to be up to 4.1019 cm−3 in the Ge film. A gain of photoluminescence (PL) intensity three times higher than the sample doped only with P atoms was obtained. This result contributes to the perspective that Ge films can be utilized in functional optoelectronic as well as photonic devices. [ABSTRACT FROM AUTHOR]

Increasing findings suggest that demyelination may play an important role in the pathophysiology of brain injury, but the exact mechanisms underlying such damage are not well known. Mechanical tensile strain of brain tissue occurs during traumatic brain injury. Several studies have investigated the cellular and molecular events following a static tensile strain of physiological magnitude on individual cells such as oligodendrocytes. However, the pathobiological impact of high-magnitude mechanical strain on oligodendrocytes and myelinated fibers remains under investigated. In this study, we reported that an applied mechanical tensile strain of 30% on mouse organotypic culture of cerebellar slices induced axonal injury and elongation of paranodal junctions, two hallmarks of brain trauma. It was also able to activate MAPK-ERK1/2 signaling, a stretch-induced responsive pathway. The same tensile strain applied to mouse oligodendrocytes in primary culture induced a profound damage to cell morphology, partial cell loss, and a decrease of myelin protein expression. The lower tensile strain of 20% also caused cell loss and the remaining oligodendrocytes appeared retracted with decreased myelin protein expression. Finally, high-magnitude tensile strain applied to 158N oligodendroglial cells altered myelin protein expression, dampened MAPK-ERK1/2 and MAPK-p38 signaling, and enhanced the production of reactive oxygen species. The latter was accompanied by increased protein oxidation and an alteration of anti-oxidant defense that was strain magnitude-dependent. In conclusion, mechanical stretch of high magnitude provokes axonal injury with significant alterations in oligodendrocyte biology that could initiate demyelination. [ABSTRACT FROM AUTHOR]

In a marine environment, the mechanical performance of Reinforced Concrete (RC) structures deteriorates mainly due to the coupling action of service load and/or the corrosion of steel bars. Here, the working conditions of RC columns in a marine environment were simulated in the laboratory. The chloride penetration and performance deterioration of RC columns with different widths for the maximum initial crack of 0, 50, 100 and 200 microns, induced by different levels of external sustained eccentric compressive load and environments of chloride corrosion, were simulated by seawater wet-dry cycles. The results showed that the yielding load and ultimate load of the RC column specimens were significantly decreased as the width of the initial cracks increased. Tensile strain and crack width were both parameters contributing to chloride penetration in the tensile area of the RC column specimens. During the seawater wet-dry cycles, the initial cracks on the column specimens changed. The initial cracks tended to vanish due to the self-healing capacity of concrete when the width of the initial crack was smaller than 50 microns. The initial cracks remained relatively constant when the crack widths were between 50 and 100 microns, and the crack widths increased when the initial crack width was larger than 100 microns. [ABSTRACT FROM AUTHOR]

Recent theoretical studies indicated that the Curie temperature of perovskite manganite thin films can be increased by more than an order of magnitude by applying appropriate interfacial strain to control orbital ordering. In this work, we demonstrate that the regular intercalation of BaTiO layers between LaSrMnO layers effectively enhances ferromagnetic order and increases the Curie temperature of LaSrMnO/BaTiO superlattices. The preferential orbital occupancy of e( x -y) in LaSrMnO layers induced by the tensile strain of BaTiO layers is identified by X-ray linear dichroism measurements. Our results reveal that controlling orbital ordering can effectively improve the Curie temperature of LaSrMnO films and that in-plane orbital occupancy is beneficial to the double exchange ferromagnetic coupling of thin-film samples. These findings create new opportunities for the design and control of magnetism in artificial structures and pave the way to a variety of novel magnetoelectronic applications that operate far above room temperature. [ABSTRACT FROM AUTHOR]

We theoretically investigate highly tensile-strained Ge nanowires laterally on GaSb. Finite element method has been used to simulate the residual elastic strain in the Ge nanowire. The total energy increment including strain energy, surface energy, and edge energy before and after Ge deposition is calculated in different situations. The result indicates that the Ge nanowire on GaSb is apt to grow along 〈100〉 rather than 〈110〉 in the two situations and prefers to be exposed by {105} facets when deposited a small amount of Ge but to be exposed by {110} when the amount of Ge exceeds a critical value. Furthermore, the conduction band minima in Γ-valley at any position in both situations exhibits lower values than those in L-valley, leading to direct bandgap transition in Ge nanowire. For the valence band, the light hole band maxima at Γ-point is higher than the heavy hole band maxima at any position and even higher than the conduction band minima for the hydrostatic strain more than ∼5.0%, leading to a negative bandgap. In addition, both electron and hole mobility can be enhanced by owing to the decrease of the effective mass under highly tensile strain. The results suggest that biaxially tensile-strained Ge nanowires hold promising properties in device applications. [ABSTRACT FROM AUTHOR]

Cellular therapies for the treatment of myocardial infarction have proven to be an invaluable tool in recent years and provide encouraging evidence for the possibility to restore normal heart function. However, questions still remain as to the optimal cell source, pre-conditioning methods and delivery techniques for such an application. This study explores the use of a population of stem cells arising from the neural crest and isolated from adult human periodontal ligament along with short-term mechanical strain as an inducer of cardiomyogenesis and possibly pre-conditioning stimulus for cellular cardiomyoplasty. Cells were subjected to a short-term dynamic mechanical tension in our custom-built bioreactor and analyzed for cardiomyogenic commitment. Mechanical strain elicited a cardiomyogenic response from the cells following just 2 h of stimulation. Mechanical strain activated and translocated cardiac-specific transcription factors GATA4, MEF2C and Nkx2.5, and induced expression of the sarcomeric actin and cardiac troponin T proteins. Mechanical strain induced production of significantly higher levels of nitric oxide when compared to static controls. Elimination of elevated ROS levels by free radical scavengers completely abolished the cardiomyogenic response of the cells. MicroRNA profile changes in stretched cells were detected for 39 miRNAs with 16 of the differentially expressed miRNAs related to heart development. The use of stem cells in combination with mechanical strain prior to their delivery in vivo may pose a valuable alternative for the treatment of myocardial infarction and merits further exploration for its capacity to augment the already observed beneficial effects of cellular therapies. [ABSTRACT FROM AUTHOR]

Rashba spin splitting (RSS) in quantum-spin Hall (QSH) insulators is of special importance for fabricating spintronic devices. By changing the stacking order, a unique bilayered fluorinated arsenene (AsF) system is demonstrated to simultaneously possess RSS and non-trivial topological electronic states. We show by first-principle calculations that tunable RSS can be realized in bilayered AsF. Intrinsic RSS of 25 meV is obtained in the AA-stacked AsF bilayer by considering the spin-orbit coupling effect. The RSS can be tuned in the range of 0 to 50 meV by applying biaxial strains and can be significantly enhanced up to 186 meV in the presence of an external electric field. The AB-stacked AsF bilayer is shown to be a two-dimensional topological insulator with a sizable bulk bandgap of 140 meV (up to 240 meV), which originates from the spin-orbit coupling within the p-p band inversion. Surprisingly, RSS up to 295 meV can be induced in the AB-stacked AsF bilayer by applying an external electric field, while the robust topology property without RSS can be retained under the applied strains. The AsF bilayers with tunable RSS and a nontrivial bandgap with AA- and AB-stacking orders can pave the way for designing spin field-effect transistors and new QSH devices. [ABSTRACT FROM AUTHOR]

The stability of high sidewalls of large-span underground powerhouses will be a major issue when the cavern axis forms a small angle to the steeply inclined rock strata. A synthetic test scheme composed of four experiments was performed on two rocks with clear bedding features, aiming at better understanding the otherwise confusing deformation behavior and failure patterns of bedded rocks. Bedding orientations with respect to stress direction impose significant effect on the mechanical behavior of bedded rocks. Excessive tensile strain is observed in the direction perpendicular to bedding or across material interface in uniaxial test. Under low confinement in true triaxial test, the σ angle mainly influences the deformation and fracture propagation but not strength. Deformation dependence of bedded rocks on two stress paths is thoroughly investigated. Confining pressure unloading leads to pronounced volumetric dilation accompanied by moduli drop. Samples with large bedding angle exhibit more obvious lateral dilation. Post-peak degradation of deformation parameters is confirmed by cyclic test. Fractures entirely or partly along bedding occurred under different stress states depend not only on the bonding strength between beds but on the anisotropic deformation field. Based on these observations, it is deduced that the possible reasons for the failure of steeply dipping rock mass after excavation are a combination of (1) the pervasive bedding planes, (2) the more pronounced deformation normal to bedding, and (3) the excavation-induced unloading of confinement. [ABSTRACT FROM AUTHOR]

The coupling of electrical and mechanical property measurements for thin films is a relatively new area of research. It is particularly useful to know how electrical resistance could be altered with mechanical straining for flexible electronic applications. While coupled resistance measurements have been made in conjunction with tensile straining, a clear description of the measurement technique is rarely provided. Explained here is a four-point probe resistance measurement that has been incorporated into tensile straining grips for accurate and repeatable in situ resistance measurements. Also described is an analytical explanation of how to correct for constant resistances that do not change during the experiment. The new technique has been employed on Cu films on polyethylene terephthalate (PET) to illustrate its use and to discuss how resistance will recover after 24 h. [ABSTRACT FROM AUTHOR]

The magnetic and electronic properties of both linear and dimerized nanochains of titanium at different atomic distances are calculated within density functional theory with the generalized gradient approximation. Titanium which is a nonmagnetic in its bulk form is shown to become magnetic in its nanochain structure. Also, a close relationship is found between magnetic state and geometry of chain structure and the dependence of electronic properties on the atomic structures of chains is revealed. It is found that, for dimerized nanochains from equilibrium constant, compressive strain leads to a reduction in magnetism. Moreover, characteristics of the systems near the Fermi level are investigated and the charge densities of both nanostructures are studied in the ferromagnetic order. The results show that metallic bonding is mainly responsible for the linear structure; however, for the dimerized structure, the bonding is more directional, i.e. has a more covalent character. With increasing tension along the axis of the nanostructures, a change in the types of bonding is found. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate the rationality of the suture locations of distal plantar fascia (DPF) after foot amputation to avoid the risk factors of re-amputation or plantar fasciitis.Methods: The tensile strain of plantar fascia (PF) in the different regions was measured by uni-axial tensile experiment. A three-dimensional (3D) finite element model was also developed to simulate tensile behaviour of PF in weight bearing conditions. The model includes 12 bones, ligaments, PF, cartilage and soft tissues. Four suture location models for the DPF were considered: the fourth and fifth DPF were sutured on the third metatarsal, the cuboid, and both the third metatarsal and the cuboid, and one un-sutured model.Results: The peak tensile strain of the first, second and third PF was 0.134, 0.128 and 0.138 based on the mechanical test, respectively. The fourth and fifth DPF sutured at the cuboid and the third metatarsal could offer more favourable outcomes. The peak strain of 4.859 × 10(-2), 2.347 × 10(-2) and 1.364 × 10(-2) in the first, second and third PF showed the least outcomes in stance phase. Also, peak strain and stress of the residual PF reduced to 4.859 × 10(-2) and 1.834 MPa, respectively. The stress region was redistributed on the mid-shaft of the first and third PF and the peak stress of medial cuneiform bone evidently decreased.Conclusions: The fourth and fifth DPF suture at the third metatarsal and cuboid was appropriate for the partial foot. The findings are expected to suggest optimal surgical plan of the DPF suture and guide further therapeutic planning of partial foot patients. [ABSTRACT FROM AUTHOR]

Objectives: Hepatic stellate cells (HSCs), the principal producers of extracellular matrix proteins, play a major role in the development of liver fibrosis which is accompanied with elevated sinusoidal pressure and portal hypertension. We have isolated primary rat HSCs and investigated the effect of mechanical pressure and tensile strain on retinol metabolism in the cells. Results: Mechanical force and tensile strain significantly increased the expression of α-smooth muscle actin (α-SMA) and collagen I, and notably inhibited the expression of cellular retinol-binding protein I (CRBP-I), lecithin-retinol acyltransferase (LRAT), retinyl ester hydrolase (REH), retinoic acid receptor-β (RAR-β) and retinoid X receptor-α (RXR-α). Such effects were partially reversed by the retinoid X receptor antagonist, HX531, and the retinoic acid receptor antagonist, LE135. Conclusion: Mechanical force and tensile strain significantly activate HSCs by regulating the retinoid metabolic pathway. Activation of HSCs can therefore be manipulated through mechanical force and tensile strain in vitro. [ABSTRACT FROM AUTHOR]

To investigate the effect of strain on bismuth telluride films, we applied different compressive and tensile strains to thin films by changing the bending radius of a flexible substrate so the strain ranged from −0.3% (compressive) to +0.3% (tensile). The structural properties of the strained thin films, composed of nanosized grains, were analyzed by x-ray diffraction and scanning electron microscopy. For all samples the main peak was the (015) diffraction peak; crystal orientation along the (015) growth direction was slightly enhanced by application of compressive strain. The thermoelectric properties of strained bismuth telluride thin films were evaluated by measurement of electrical conductivity, Seebeck coefficient, and power factor. The magnitude and direction of the applied strain did not significantly affect the power factor, because when the strain changed from compressive to tensile the electrical conductivity increased and the absolute Seebeck coefficient decreased. [ABSTRACT FROM AUTHOR]

Significant changes in the Raman spectrum of single-layer graphene grown on a copper film were observed after the spontaneous oxidation of the underlying substrate that occurred under ambient conditions. The frequencies of the graphene G and 2D Raman modes were found to undergo red shifts, while the intensities of the two bands change by more than an order of magnitude. To understand the origin of these effects, we further characterized the samples by scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and atomic force microscopy (AFM). The oxidation of the substrate produced an appreciable corrugation in the substrate without disrupting the crystalline order of the graphene overlayer and/or changing the carrier doping level. We explain the red shifts of the Raman frequencies in terms of tensile strain induced by corrugation of the graphene layer. The changes in Raman intensity with oxidation arise from the influence of the thin cuprous oxide film on the efficiency of light coupling with the graphene layer in the Raman scattering process. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Tensile-strained epitaxial La 0.67Ba 0.33MnO 3 (LBMO) film has been prepared by magnetron sputtering technique on (001) oriented spinel MgAl 2O 4 substrate. The transport and magnetic measurements give an insulator-metal transition and paramagnetic-ferromagnetic transition occurring at ∼150 K and 250 K respectively, which implies the phase separation in such a tensile-strained film. By analyzing the angular and temperature dependences of the ferromagnetic resonance (FMR), we determine the magnetocrystalline anisotropy of the film. It is found that the tensile-strained film is dominated by an easy-axis corresponding to the compressive out-of-plane direction, though the magnitudes of anisotropy constants are relatively small and their temperature dependences are some complex. Furthermore, the FMR spectra show additional spin wave resonance (SWR), and the field positions can be indexed to follow a linear dependence on the square of index n. The scaling gives a spin-wave exchange stiffness D of 20.7 meV Å 2 at low temperature, which is less than half of that in strain-free LBMO films, implying that the double exchange interaction is remarkably suppressed in the tensile-strained LBMO films. [ABSTRACT FROM AUTHOR]

Background: The clinical success of large class II resin-modified glass-ionomer cement/composite resin (RMGIC/CR) 'open-sandwich' restorations in permanent or primary molars may be influenced by certain bonding parameters. Aim: To examine in vitro the effect of placing/curing mode on the RMGIC/CR bond strength. Design: Two restoratives, a CR (Z250), a RMGIC (Vitremer) and a bonding agent (Adper Single Bond 2), all of 3M ESPE, were used for preparing five groups of seven specimen sticks each. The bond between the two restorative materials at the stick centre was created in the three test groups by: (A) 1-step placing RMGIC in contact with CR, then photocuring; (B) 2-step RMGIC placing/curing, then CR placement/curing; (C) 3-step RMGIC placing/curing, bonding agent placing/curing, CR placing/curing. Control groups consisted of sticks made of CR alone (D, positive) and RMGIC alone (E, negative). The specimens were subjected to tensile stress measurements in an Instron dynamometer and examined by scanning electron microscope for type of failure. Statistics: Tensile bond strength, tensile strain and elastic modulus differences were examined with one-way ANOVA and Tukey test. Results: Among experimental groups, Group C exhibited significantly higher tensile strength (MPa) means ( A = 12.11 ± 4.72, B = 15.69 ± 5.18, C = 19.08 ± 4.05) and significantly higher tensile strain (%) means ( A = 0.50 ± 0.11, B = 0.64 ± 0.19, C = 0.98 ± 0.24), compared to Group A, at p = 0.05. Group D had significantly higher tensile strength and strain than all other groups. No statistically significant differences were observed in the elastic modulus. The use of bonding agent (Group C) resulted in absence of adhesive failures as seen by SEM. Conclusion: The use of bonding agent improved the CR/RMGIC bond by tensile strength and strain tests. [ABSTRACT FROM AUTHOR]

This work describes a novel method for preparing electro-conductive rotor yarns by in situ oxidative chemical polymerization of pyrrole. The effects of different process parameters on electrical resistivity of the yarn were studied by using Box-Behnken response surface design. The concentration of monomer, polymerization time and polymerization temperature were found to influence the electrical resistivity of the yarn. It was observed that electrical resistivity of the yarn increased linearly with increase of measuring length of it. Whereas the effects of yarn twist and tensile strain found to had negative correlation with electrical resistivity of electro-conductive rotor yarns. Microscopic image analysis showed that there was uniform distribution of PPy polymer on the surface of cotton fibres and FTIR analysis depicted possible chemical interaction between polypyrrole and cellulose. [ABSTRACT FROM AUTHOR]

The development of the Brazilian disc test for determining indirect tensile strength and its applications in rock mechanics are reviewed herein. Based on the history of research on the Brazilian test by analytical, experimental, and numerical approaches, three research stages can be identified. Most of the early studies focused on the tensile stress distribution in Brazilian disc specimens, while ignoring the tensile strain distribution. The observation of different crack initiation positions in the Brazilian disc has drawn a lot of research interest from the rock mechanics community. A simple extension strain criterion was put forward by Stacey (Int J Rock Mech Min Sci Geomech Abstr 18(6):469-474, ) to account for extension crack initiation and propagation in rocks, although this is not widely used. In the present study, a linear elastic numerical model is constructed to study crack initiation in a 50-mm-diameter Brazilian disc using FLAC. The maximum tensile stress and the maximum tensile strain are both found to occur about 5 mm away from the two loading points along the compressed diameter of the disc, instead of at the center of the disc surface. Therefore, the crack initiation point of the Brazilian test for rocks may be located near the loading point when the tensile strain meets the maximum extension strain criterion, but at the surface center when the tensile stress meets the maximum tensile strength criterion. [ABSTRACT FROM AUTHOR]

The mechanotransduction of adipocytes is not well characterized in the literature. In this study, we employ stochastic modeling fitted to experiments for characterizing the influence of mechanical stretching delivered to adipocyte monolayers on the probabilities of commitment to the adipocyte lineage, mitosis, and growth after mitosis in 3T3-L1 adipocytes. We found that the probability of a cell to become committed to the adipocyte lineage in a single division when cultured on an elastic substrate was 0.025, which was indistinguishable between cultures that were radially stretched (to 12% strain) and control cultures. The probability of undergoing mitosis however was different between the groups, being 0.4 in the stretched cultures and 0.6 in the controls. The probability of growing after mitosis was affected by the stretching as well and was 0.9 and 0.8 in the stretched and control groups, respectively. We conclude that static stretching of the substrate of adipocyte cultures influences the mitotic potential of the cells as well as the growth potential post-mitosis. The present work provides better understanding of the mechanotransduction of adipocytes and in particular quantify how stretching influences the likelihood of cell proliferation and differentiation and, consequently, adipogenesis in the adipocyte cultures. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) magnetic kagome lattices are constructed using silicon carbide triangular nanoflakes (SiC-TNFs). Two types of structures with alternating Si and C atoms are studied: the first one is constructed using the C-edged SiC-TNFs as the building blocks and C atoms as the linkers of kagome sites (TNF-C-TNF) while the second one is composed of the Si-edged SiC-TNFs with Si atoms as linkers (TNF-Si-TNF). Using density functional theory-based calculations, we show that the fully relaxed TNF-C-TNF retains the morphology of regular kagome lattice and is ferromagnetism. On the other hand, the TNF-Si-TNF structure is deformed and antiferromagnetic. However, the ground state of TNF-Si-TNF structure can be transformed from the antiferromagnetic to ferromagnetic state by applying tensile strain. Monte Carlo simulations indicate that the SiC-TNFs-based kagome lattices can be ferromagnetic at room temperature. [ABSTRACT FROM AUTHOR]

Mammalian cells are sensitive to extracellular microenvironments. In order to precisely explore the physiological responses of cells to tensile loading, a stable and well-defined culture condition is required. In this study, a high-throughput perfusion-based microbioreactor platform capable of providing dynamic equibiaxial tensile loading to the cultured cells under a steady culture condition was proposed. The mechanism of generating tensile stimulation to cells is based on the pneumatically-driven deformation of an elastic polydimethylsiloxan (PDMS) membrane which exerts tensile loading to the attached cells. By modulating the magnitude and frequency of the applied pneumatic pressure, various tensile loading can be generated in a controllable manner. In this study, the microbioreactor platform was designed with the aid of the experimentally-validated finite element (FE) analysis to ensure the loading of tensile strain to cells is uniform and definable. Based on this design, the quantitative relationship between the applied pneumatic pressure and the generated tensile strain on the PDMS membrane was established via FE analysis. Results demonstrated that the proposed device was able to generate the tensile strain range (0~0.12), which covers the physiological condition that articular chondrocytes experience tensile strain under human walking condition. In this study, moreover, the effect of tensile loading on the metabolic, biosynthetic and proliferation activities of articular chondrocytes was investigated. Results disclosed that the dynamic tensile loading of 0.12 strain at 1 Hz might significantly up-regulate the synthesis of glycosaminoglycans while such stimulation was found no significant influence on the metabolic activity, the synthesis of collagen, and the proliferation of chondrocytes. Overall, this study has presented a high throughput perfusion micro cell culture device that is suitable for precisely exploring the effect of tensile loading on cell physiology. [ABSTRACT FROM AUTHOR]

general initial water penetration (seepage) fracture criterion for concrete is proposed to predict whether or not harmful water penetration (hydraulic fracturing), other than microcracking, will occur in concrete structures in a severe high water pressure environment. The final regression, of the different macroscopic failure types in concrete to microscopic Mode I cracking, allows the use of only one universal criterion to indicate the damage. Thus, a general initial water penetration fracture criterion is approximately defined as a strain magnitude of 1000×10, based on the concept of tensile strain derived from experimental results in the relevant literature. Then, the locations of harmful water penetration fracture (hydraulic fracture) in the high arch dam mass of the Jinping first class hydropower project are analyzed using the nonlinear finite element method (FEM) according to the proposed criterion. The proposed criterion also holds promise for other concrete structures in high water pressure environments. [ABSTRACT FROM AUTHOR]

Silver-coated fly ash cenospheres were embedded in silicone-rubber to form conductive composites. The electrical resistivity of the composites was examined and compared under different tensile strains. The electrical resistivity was a linear function of tensile strain under quasi-static load at linear viscoelastic area of the composites. Under cyclic strain, the peak of the electrical resistivity decreased and the offset was compared with the peak of strain and stress over time. For the stress relaxation test, the electrical resistivity displayed a change from linear to nonlinear under crescent transient strain. All of the changes were attributed to the breakup and rebuilding of the conductive networks in the composites. [ABSTRACT FROM AUTHOR]

The electronic properties of an armchair (4,4) single-walled silicon carbide nanotube (SWSiCNT) with the length and diameter of 22.4 and 6.93 Å, respectively under different tensile strains are investigated by density functional theory (DFT) calculation. The change of highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) gap of the nanotube has been observed during the elongation process. Our results show that the gap will significantly decrease linearly with the increase of axial strain. Two different slopes are found before and after an 11% strain in the profiles of the HOMO-LUMO gap. The radial buckling has been performed to investigate the radial geometry of nanotube. The partial density of states (PDOS) of two neighboring Si and C atoms of the nanotube are further studied to demonstrate the strain effect on the electronic structure of SiC nanotube. The PDOS results exhibit that the occupied states of Si atom and the unoccupied states of C atom are red-shifted and blue-shifted under stretching, respectively. Mulliken charge analysis reveals that Si and C atoms will become less ionic under the larger strain. The electron differences of silicon carbide nanotube (SiCNT) on tensile loading are also studied. [ABSTRACT FROM AUTHOR]

The paper investigates the effect of tensile strains on the field dependence of differential magnetic permeability of double-layer composite steel 45 specimens simulative of surface hardening and steel 45 specimens subjected to laser heat hardening. It is shown that the field dependence of differential magnetic permeability is representative of the multilayer micro structure and of the changes occurring in each layer under tension. It is found that significant shifts of the magnetic permeability peaks toward stronger magnetic fields and rapid decreases in peak heights result from the involvement of different layers of the specimens in plastic deformation and proceed in a strictly defined sequence as the stress corresponding to the yield limit of each layer is reached. It is demonstrated that the lost bimodal character of the field dependence of differential magnetic permeability after unloading suggests that the material with a hardened surface layer nears fracture. [Copyright &y& Elsevier]

A new tensile strained InGaAs/InGaAlAs quantum well structure in the 1.3 μm wavelength region is proposed for high temperature characteristics via quantum well band structure and optical gain calculations. To obtain such features, a tensile-strained InGaAs/InGaAlAs quantum well structure, which emits light dominated by TM polarization, is considered. This proposed structure has very high temperature characteristics ( T0 > 130 K) due to its high density of state at the first transition edge. This results clearly show the potential of tensile strained quantum well structure usage for the high temperature operation of quantum well semiconductor lasers. [ABSTRACT FROM AUTHOR]

Calculated relations for the geometric parameters of a spiral bar in elastic tension are proposed. A method is developed for taking into account the plastic properties of bar material, which appear to have a strong affect on the calculation results. [ABSTRACT FROM AUTHOR]

Mechanical strength of silicate glasses is known to decrease markedly due to the adsorption of molecules from the environment, especially in aqueous alkali solutions. This effect, known as the adsorption-induced reduction of strength (AIRS), has not yet been fully understood. Here, the dependence on the chemical nature and electronic properties of adsorbates of the AIRS of siloxane bonds in silica was studied by means of quantum-chemical calculations at the wB97X-D3/def2-TZVP level of theory. A siloxane bond was modelled by H3Si-O-SiH3 and (HO)3Si-O-Si(OH)3 clusters, and the AIRS was simulated by a linear tensile deformation of the siloxane bond in the presence of the following adsorbates: OH−, Cl−, H2O, H+ and H3O+. Potential energy profiles and derivative force curves of the siloxane bond rupture were obtained. The varying effect of the adsorbates on the energy-force characteristics of the AIRS can be explained by changes in the bond lengths and electron occupancy. It is shown that the AIRS of the siloxane bonds increases with an increase in the nucleophilicity of the adsorbates, and correlates with an adsorbate-induced redistribution of electron density. [ABSTRACT FROM AUTHOR]

We study the effects of tensile and compressive strain on the (LaMnO3)1/(SrTiO3)1 superlattice from density functional theory using Quantum-Espresso open source code. In the unstrained superlattice, electron interactions in out-of-plane Mn-O-Ti chains are dominated by superexchange interactions, giving rise to ferromagnetic and half-metallic conducting characters. We found that the most stable magnetic configuration is G-type antiferromagnetic configuration for strong compressive strain and for strong tensile strain it is A-type antiferromagnetic configuration. The results are in accordance with the experimental observations which show that the superlattices can be grown on different substrates, and due to the difference in lattice parameters of the substrate and the main layer, there are also changes in the amount of strain applied to the superlattice. [ABSTRACT FROM AUTHOR]

The coupling of electrical and mechanical property measurements for thin films is a relatively new area of research. It is particularly useful to know how electrical resistance could be altered with mechanical straining for flexible electronic applications. While coupled resistance measurements have been made in conjunction with tensile straining, a clear description of the measurement technique is rarely provided. Explained here is a four‐point probe resistance measurement that has been incorporated into tensile straining grips for accurate and repeatable in situ resistance measurements. Also described is an analytical explanation of how to correct for constant resistances that do not change during the experiment. The new technique has been employed on Cu films on polyethylene terephthalate (PET) to illustrate its use and to discuss how resistance will recover after 24 h. [ABSTRACT FROM AUTHOR]