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In addition to the well-known conventional acoustic wave propagation mode in three-dimensional solids, there exists the surface acoustic wave propagation mode where energy is only concentrated near the two-dimensional interface. In this work, utilizing the piezoelectric and inverse piezoelectric effects from GaAs substrates, we achieve the conversion between radiofrequency electromagnetic waves and surface acoustic waves with planar interdigital transducers, and successfully measure the surface acoustic wave velocity on a sample with a dimension of only 4 mm using superheterodyne-scheme lock-in technique, yielding a result of (2.9±0.1) km/s. We also fabricate a uniaxial stress cell with piezoelectric ceramics, capable of applying uniaxial strains up to approximately 10 -4 to the sample, and observe the influence of strain on the surface acoustic wave velocity. We measure the surface acoustic wave velocity of the important semiconductor GaAs under stress, demonstrating the capability of this velocity measurement technique to probe the internal mechanical properties of solids in situ. The wave velocity measurements based on planar interdigital transducers overcome the macroscopic size requirements of traditional time-of-flight and standing wave methods. The superheterodynescheme lock-in technique established in this article has replaced the commercial vector network analyzers for measuring surface acoustic wave velocity, enabling possible future applications with low power input and high phase stability. As the measurement setup can also be used for experimental teaching related to solid-state physics, this work provides detailed parameters and fabrication processes for surface acoustic wave devices and homemade stress cell. [ABSTRACT FROM AUTHOR]

Uniaxial stress has proven to be a powerful experimental tuning parameter for effectively controlling lattice, charge, orbital, and spin degrees of freedom in quantum materials. In addition, its ability to manipulate the symmetry of materials has garnered significant attention. Recent technical progress to combine uniaxial stress cells with quantum oscillation and angle-resolved photoemission techniques allowed to study the electronic structure as function of uniaxial stress. This review provides an overview on experimental advancements in methods and examines studies on diverse quantum materials, encompassing the semimetal WTe2, the unconventional superconductor Sr2RuO4, Fe-based superconductors, and topological materials. [ABSTRACT FROM AUTHOR]

Dielectric, ferroelectric, and piezoelectric properties of both random and textured Mn--PMN--PZT ceramics were characterized under uniaxial stress. Textured ceramics exhibit a large piezoelectric response under uniaxial pressure; the bias field piezoelectric constant is higher than 700 pC/N when pressure is below 50 MPa. Moreover, textured ceramics also show better depolarization resistance under uniaxial stress fields; overall, 30% of the origin performance will remain when stress approaches 200 MPa, but for random ceramics, it is only 10%. The ferroelectricity of both random and textured ceramics is suppressed by uniaxial compression. Ec, Pr, Ei, and dissipation energy all decrease with increasing uniaxial stress. In addition, phase-field simulation was used to better understand the polarization-changing effects on piezoelectric and dielectric performance. The uniaxial stress causes polarization rotation and increases the angle between polarization and the electric field, which is an important factor leading to the increase of the dielectric constant. [ABSTRACT FROM AUTHOR]

The ability to efficiently control charge and spin in the cuprate high-temperature superconductors is crucial for fundamental research and underpins technological development. Here, we explore the tunability of magnetism, superconductivity, and crystal structure in the stripe phase of the cuprate La2-xBaxCuO4, with x = 0.115 and 0.135, by employing temperature-dependent (down to 400 mK) muon-spin rotation and AC susceptibility, as well as X-ray scattering experiments under compressive uniaxial stress in the CuO2 plane. A sixfold increase of the three-dimensional (3D) superconducting critical temperature Tc and a full recovery of the 3D phase coherence is observed in both samples with the application of extremely low uniaxial stress of ~0.1 GPa. This finding demonstrates the removal of the well-known 1/8-anomaly of cuprates by uniaxial stress. On the other hand, the spin-stripe order temperature as well as the magnetic fraction at 400 mK show only a modest decrease under stress. Moreover, the onset temperatures of 3D superconductivity and spin-stripe order are very similar in the large stress regime. However, strain produces an inhomogeneous suppression of the spin-stripe order at elevated temperatures. Namely, a substantial decrease of the magnetic volume fraction and a full suppression of the low-temperature tetragonal structure is found under stress, which is a necessary condition for the development of the 3D superconducting phase with optimal Tc. Our results evidence a remarkable cooperation between the long-range static spin-stripe order and the underlying crystalline order with the three-dimensional fully coherent superconductivity. Overall, these results suggest that the stripe- and the SC order may have a common physical mechanism. [ABSTRACT FROM AUTHOR]

In the present study, we tried to understand the spatially distributed damage in sandstone samples under the coupled stress-freeze-thaw (SFT) conditions. Firstly, uniaxial compressive stresses (i.e. 0 MPa, 10 MPa, 20 MPa, and 25 MPa) were applied to the samples, and then freeze-thaw (FT) cycles (0, 8, 16, and 24) were performed on the uniaxially stressed samples to realize the SFT coupling. Next, real-time CT scanning was conducted to observe the induced damage. The total porosity was introduced to quantitatively evaluate the damage degree. The local porosity variation, with the distance from the center of the sandstone sample, was analyzed to understand the spatial distribution of damage. Finally, the coupling effects of SFT on the damage gradient were discussed. The results indicate that the porosity rises with FT cycles, and the applied stresses can accelerate the increase in porosity. The damage increases exponentially with the distance from the center of the sample. The damage presents a spatial gradient distribution, not the commonly used uniform distribution in various studies. The damage gradient increases with FT cycles, and the increasing rate in damage gradient decreases at uniaxial stress of 0 MPa and 10 MPa first, but the increasing rate in damage gradient increases with FT cycles then at stress increasing to 20 MPa.

Abstract Coal is the one of foundations of energy and economic structure in China, while the unsealing of coal mine fires would cause a great risk of coal re-ignition. In order to explore the influence of pressure-bearing state on the re-ignition characteristics for residual coal, the uniaxial compression equipped with a temperature-programmed device was built. The scanning electron microscope, synchronous thermal analyzer and Fourier transform infrared absorption spectrometer was applied to investigate the microscopic structure and thermal effect of the coal samples. Moreover, the microscopic effect of uniaxial stress on coal re-ignition is revealed, and the re-ignition mechanism is also obtained. As the uniaxial stress increasing, the number, depth and length of the fractures of the pre-treated coal increases. The application of uniaxial stress causes the thermal conductivity to change periodically, enhances the inhibition of injecting nitrogen on heat transfer and prolonges the duration of oxidation exothermic. The content of oxygen-containing functional groups has a high correlation with apparent activation energy, and coal samples at 6 MPa is more probability to re-ignite while the fire zone is unsealed. Uniaxial stress could control the re-ignition mechanism by changing the structure of fractures and pores. The side chains and functional groups of coal structure are easier to be broken by thermal-stress coupling. The higher the ·OH content, the more difficult coal samples would be re-ignited. The research results would lay a solid theoretical foundation for the safe unsealing of closed fire-areas underground, tighten the common bond between the actual industry and the experimental theory in closed fire-areas underground, and provide the theoretical guidance for coal re-ignition preventing.

• The H diffusivities in BCC-Fe with different uniaxial stress states are reported. • The greater the tensile stress, the stronger the inhibition of H diffusion. • Uniaxial stress causes varying H diffusion behaviors in different directions. Hydrogen diffusion in metals is of great significance for hydrogen embrittlement and requires comprehension on the atomic scale. In this study, molecular dynamics simulations are conducted to investigate hydrogen diffusion of atoms in α-Fe under different stresses. The increase in uniaxial tensile and compressive stress tends to reduce the diffusion coefficient, suppress the diffusion of hydrogen atoms in α-Fe, and lead to differences in diffusion behavior in different directions. The change in the migration barrier explains the differences in hydrogen atom diffusion behavior under different unidirectional stresses. [ABSTRACT FROM AUTHOR]

In order to explore the evolution law and mathematical characterization method of natural fissure structure of coal under uniaxial loading, a 3D numerical model was reconstructed based on computed tomography (CT) scanning experiment to accurately describe natural fissure structure, and the uniaxial compression numerical simulation of coal was carried out. The length, opening, fissure degree and fractal dimension were introduced to characterize the spatial morphology of fissure, and the variation of characterization parameters with increasing load was analyzed. The results reveal the evolution characteristics of fissure structure of coal under uniaxial loading. The study shows that the coal is mostly composed of small-scale fissure, and the fissure evolution can be divided into two stages during the loading process. In the first stage, namely the initial stage of loading, the fissure is compacted and closed. Compared with the non loading, the upper limit of fissure length decreases by -1-1%, the fissure degree decreases by 35%, and the fractal dimension decreases by 22%. In the second stage, fissure in the coal begin to develop with the increase of load. At peak load, the length increases by 10% on average, the distribution frequency of the minimum interval of fissure length increases by 12%, and the distribution frequency of the minimum interval of fissure opening increases by 50%. The research results provide a theoretical basis for revealing the laws of coal fissure propagation under loading and effectively implementing hydraulic fracturing technology. [ABSTRACT FROM AUTHOR]

This study reports on the behaviour of the thermoelectric properties of n- and p-type hydrogenated microcrystalline silicon thin films (µc-Si: H) as a function of applied uniaxial stress up to ±1.7%. µc-Si: H thin films were deposited via plasma enhanced chemical vapour deposition and thermoelectric properties were obtained through annealing at 200 °C (350 °C) for n-(p-) type samples, before the bending experiments. Tensile (compressive) stress was effective to increase the electrical conductivity of n-(p-) type samples. Likewise, stress induced changes in the Seebeck coefficient, however, showing an improvement only in electron-doped films under compressive stress. Overall, the addition of elevated temperature to the bending experiments resulted in a decrease in the mechanical stability of the films. These trends did not produce a significant enhancement of the overall thermoelectric power factor, rather it was largely preserved in all cases. [ABSTRACT FROM AUTHOR]

In order to further improve the high-frequency characteristics of highly scaled SiGe HBT and consider the compatibility with the mature CMOS technology, a new SiGe HBT structure is proposed by introducing an embedded Si1−yGey stress raiser to produce additional uniaxial stress in the bulk collector region. The energy-band configuration of multi-layered emitter has been investigated by the estimation of the strain effect, and then the influence of stress raiser on the electrical properties and frequency response has been studied by employing the SILVACO TCAD tools. The results show that the device performance has been enhanced to different degrees by altering the Ge fraction (y) in the stress raiser. At y = 0.3, the current gain is increased by approximately 6% compared to the case without stress in the collector region (y = 0). For the case of a uniform Si0.75Ge0.25 base, the cut-off frequency (fT) and the maximum oscillating frequency (fmax) are, respectively, peaked at 507.7 GHz and 730.7 GHz. Approximately 29.1% improvement in fT and 71.5% improvement in fmax have been achieved for the proposed HBT device in comparison with an equivalent traditional SiGe HBT. At y = 0.1, the frequency characteristic is considered the best due to the maximum of fT × fmax product. [ABSTRACT FROM AUTHOR]

Coal is the one of foundations of energy and economic structure in China, while the unsealing of coal mine fires would cause a great risk of coal re-ignition. In order to explore the influence of pressure-bearing state on the re-ignition characteristics for residual coal, the uniaxial compression equipped with a temperature-programmed device was built. The scanning electron microscope, synchronous thermal analyzer and Fourier transform infrared absorption spectrometer was applied to investigate the microscopic structure and thermal effect of the coal samples. Moreover, the microscopic effect of uniaxial stress on coal re-ignition is revealed, and the re-ignition mechanism is also obtained. As the uniaxial stress increasing, the number, depth and length of the fractures of the pre-treated coal increases. The application of uniaxial stress causes the thermal conductivity to change periodically, enhances the inhibition of injecting nitrogen on heat transfer and prolonges the duration of oxidation exothermic. The content of oxygen-containing functional groups has a high correlation with apparent activation energy, and coal samples at 6 MPa is more probability to re-ignite while the fire zone is unsealed. Uniaxial stress could control the re-ignition mechanism by changing the structure of fractures and pores. The side chains and functional groups of coal structure are easier to be broken by thermal-stress coupling. The higher the ·OH content, the more difficult coal samples would be re-ignited. The research results would lay a solid theoretical foundation for the safe unsealing of closed fire-areas underground, tighten the common bond between the actual industry and the experimental theory in closed fire-areas underground, and provide the theoretical guidance for coal re-ignition preventing. [ABSTRACT FROM AUTHOR]

To explore the influence of the oxidation and spontaneous combustion process of fractured coal at different burial depths under uniaxial stress, the spontaneous combustion characteristics of coal under loading was studied within the testing device of coal spontaneous combustion and loading. Bituminous coal from the Liuhuanggou mining area in Xinjiang was selected and oxidized in the oxygen-lean environment loaded at the range of 0–8 MPa. Based on the relationship between the gas generated in the experiment and the temperature, we calculated the apparent activation energy and oxygen consumption rate of coal samples under uniaxial stress. We combined the oxidation kinetics and pyrolysis parameters of spontaneous coal combustion to describe the nonlinear development of coal from slow to rapid oxidation under uniaxial stress. Based on catastrophe theory, the catastrophic temperature and critical temperature of bituminous coal oxidation-combustion process under test conditions were calculated, and four characteristic parameters were determined: catastrophic temperature \begin{document}$ {T}_{\mathrm{C}\mathrm{O}} $\end{document} (characterization of CO) and \begin{document}$ {T}_{\mathrm{H}\mathrm{Y}} $\end{document} (characterization of oxygen consumption rate), and critical temperature \begin{document}$ {T}_{\mathrm{C}\mathrm{O}}^{'} $\end{document} (characterization of CO) and \begin{document}$ {T}_{\mathrm{H}\mathrm{Y}}^{'} $\end{document} (characterization of oxygen consumption rate), and analyzed the variation of different characteristic parameters with uniaxial stress. The analysis results show that the pyrolysis gas concentration, apparent activation energy, and oxygen consumption rate follow a cubic function law that first increases, then decreases, and then increases with increases in the uniaxial stress (the critical axial pressures at 1.8 and 5.5 MPa). At 1.8 MPa, the apparent activation energy and various parameter values are lowest, the oxygen reaction rate of coal is fastest, and the oxygen consumption rate is the highest. When the uniaxial stress is 5.5 MPa, the oxygen consumption rate is the highest, the greatest number of new cracks is created, and the characteristic \begin{document}$ {T}_{\mathrm{C}\mathrm{O}} $\end{document} parameters have the greatest impact. The temperature index of spontaneous coal combustion slowly transitions to rapid oxidation, and the catastrophic temperature \begin{document}$ {T}_{\mathrm{C}\mathrm{O}} $\end{document} characterized by the CO concentration is the most accurate. The research results have important theoretical guiding significance for the early warning and prevention and control of spontaneous combustion of coal at different buried depths.

The existing researches do not consider that coal of different particle sizes in the goaf is affected by the axial stress generated by the collapsed coal rock and the residual coal pillars, which will cause major changes in the coal permeability, fracture structure and other parameters, thereby affecting the temperature rise process of coal spontaneous combustion and oxidation. In order to study the temperature rise characteristics of spontaneous combustion and oxidation of coal with different particle sizes under the effect of thermal-stress coupling, the change law of the temperature rise rate, oxygen consumption rate and heat production rate of coal with different particle sizes is measured by using load-and-pressure coal spontaneous combustion characteristic parameter measuring device and a gas chromatograph. The experiment show the results as follows. ① The temperature rise rate of coal samples of different particle sizes under different uniaxial stresses has a consistent trend with the increase of temperature, and the overall trend is to increase first and then decrease. When the uniaxial stress is 2, 4, 6, 8 MPa, as the particle size of the coal sample increases, the maximum temperature rise rate first increases and then decreases. When the uniaxial stress is 10 MPa, the maximum temperature rise rate increases with the increase of particle size. ② The oxygen consumption rate of coal samples with different particle sizes increases rapidly and then increases slowly during the temperature rise process. The oxygen consumption rate of coal samples with different particle sizes generally tends to increase with the increase of uniaxial stress. ③ The overall heat production rate of coal samples with different particle sizes tends to remain stable first and then increase and then decrease during the temperature rise process. As the particle size of coal samples increases, the maximum heat production rate of coal samples under appropriate uniaxial stress is greater than that without uniaxial stress.

Previous studies of analysis and prediction of marine risers responses usually focus on vortex-induced vibration (VIV) of cross-flow (CF) direction rather than in-line (IL). Recent studies show that responses of IL direction tend to dominate in some cases. Responses of long riser due to biaxial bending of IL and CF VIV are investigated. Closed-form formulas are derived for estimating maximum normal stress due to the biaxial moment of CF/IL VIV and relations for estimating biaxial stress using CF values are presented. Analytical results are compared with numerical results of the time domain model and a good correlation is observed. It is shown that for tension and bending-controlled modes of vibration if the ratio of displacement amplitude of IL to CF direction is, respectively, higher than 0.22 and 0.35, normal stress due to biaxial bending is noticeably more than one directional (CF) bending stress. For a case study, the maximum biaxial stress along the riser is about 20 and 40% higher than the maximum CF stress along the length of the riser for bending and tension-controlled modes of vibration, respectively. Such results can be important not only directly in design issues, but also they may be noticeable in fatigue analysis. [ABSTRACT FROM AUTHOR]

Q1N samples with different degrees of tempering were produced and changes in MBN energies in non-stressed and stressed samples was investigated. It was observed that while MBN energy decreased with increasing degree of tempering, it increased with applied uniaxial stress and the two opposing effects cannot be easily separated. MBN energy increased with stress along RD and decreased in the transverse direction (TD). Therefore, the ratio of MBN energy in RD to TD was examined. The value of the ratio at 0.3 T was successfully shown to be strongly correlated with applied uniaxial tensile stress level, regardless of the degree of tempering (pinning site density) in Q1N samples. [ABSTRACT FROM AUTHOR]

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We performed a systematic study on mechanical properties of boron nitride monolayer. We found that applying mechanical deformation on boron nitride monolayer induced pattern of ripples. The induced rippling in the boron nitride monolayer created different bending levels in the forbidden zone, which in turn significantly tune the electronic properties of the monolayer. We also found that the band gap of boron nitride monolayer decreased dramatically with increasing the bending angles. In other words, the combined effect of applying bending and uniaxial stress on the boron nitride monolayer significantly decreases the band gap. We believe that the ability to precisely control sharp local curvatures of boron nitride sheet brings forward opportunities for strain-assisted modification of chemical reactivity and local electronic structure in the boron nitride monolayer. Such modification may be of great interest to band gap engineered devices. [ABSTRACT FROM AUTHOR]

Concrete is a typical rate‐dependent material, and a direct tensile test is the most effective method by which to investigate its tensile performance. In this study, an additional loading device for direct uniaxial tensile tests was designed and fabricated to achieve central loading and determine the descending stage during direct tensile tests. Experimental results prove that the device is reliable and convenient for reuse; it is characterized by its ability to obtain complete stress–strain curves and to be used for many repetitive tests. Initially, 27 prismatic specimens were used to test the compressive strengths and elastic moduli of concrete specimens with designed compressive strengths of 25, 30, and 50 MPa. Next, a total of 256 uniaxial direct tensile tests were carried out, including 101 static tests at a loading strain rate of 10−5 s−1 and 155 dynamic tests at loading strain rates of 10−4 s−1 and 10−2 s−1. A total of 121 complete stress–strain curves were acquired for the 256 direct tensile tests. According to the test results, the SDs of the entire curves of the tensile stress of concrete are presented, and the energy absorption capacities of the specimens were also determined. The effects of the loading rate on the mean and variability of the peak stress, peak secant modulus, elastic modulus, and peak strain were analyzed. With the increase of the strain rate, the other indexes, excluding the peak strain, were found to notably increase. [ABSTRACT FROM AUTHOR]

The results of experimental and theoretical investigations of terahertz-emission-spectrum tuning by means of uniaxial stress of a silicon crystal doped with shallow bismuth donors are presented for the case of intracenter optical excitation. The frequency tuning of two emission lines of the bismuth donor is shown for the case of uniaxial strain along the [001] crystallographic direction. The cross sections of stimulated Raman scattering for uniaxially stressed bismuth-doped silicon are calculated. [ABSTRACT FROM AUTHOR]

In view of the lack of research on the interaction between hole and crack, the uniaxial compression numerical simulation test of porous and bifractured rock mass under uniaxial compression was carried out by using the numerical software RFPA. The crack propagation process, stress-time curve and acoustic emission law under different crack dip angles and different non-mean coefficients are obtained. The results show that under uniaxial stress conditions, the crack propagates near the tip of the orifice and the upper and lower side of the orifice, and then the crack propagates along the direction of the maximum principal stress and forms a macroscopic shear plane. The specimen experienced three stages of elastic deformation, nonlinear deformation and residual deformation under uniaxial stress, and prefabricated crack inclination. The larger the sample is, the lower the peak strength is, and the higher the homogeneity coefficient is, the higher the peak strength is. The rule of acoustic emission has a high consistency with crack propagation. The larger the average coefficient of specimen is, the greater the accumulative acoustic emission energy is, and the larger the accumulative number of acoustic emissions are, the greater the angle of precast crack is. The larger the acoustic emission energy produced by the specimen failure; The acoustical emission accumulative count increases slightly in the early stage of loading, but increases sharply during the failure of the specimen. The results provide a reference for the understanding of rock fracture law and oil resources exploitation. [ABSTRACT FROM AUTHOR]

In order to study the mechanical influence of different dip angles of colinear cracks on rock specimens. RFPA code is applied and numerical simulations are carried out. The crack propagation process, acoustic emission characteristics and stress-strain curves are obtained. Results show that three patterns of crack propagation which contains wing cracks, anti-wing cracks and colinear cracks are observed. Peak AE hits get larger with the increase of the inclination angles. The stress-strain curves undergoes three stages, the elastic deformation stage, the nonlinear deformation stage and the residual deformation stage and the peak stress becomes higher as the dip angles increase. The research results provide a reference for the understanding of rock failure process and the prevention of rock catastrophe. Future works should focus on the effect of the environmental contributions on the process of crack propagation. [ABSTRACT FROM AUTHOR]

Heavily doped semiconductors are well investigated and widely used in inorganic electronics. However, controlled heavy doping of organic crystalline semiconductors is yet to be studied because of the lack of suitable methods. This article reports on doping by electrolyte gating combined with bandwidth control by uniaxial stress using a bilayered nonstoichiometric κ–β'-type charge-transfer salt, in which the β' layer exhibits competition between metallic and charge-ordered insulating states. A change from insulating-like to metal-like conduction with a positive temperature coefficient of resistance is induced by the simultaneous application of a negative gate voltage and compressive stress applied by bending the substrate. The simultaneous heavy doping and bandwidth-control technique presents a novel approach for investigating nonstoichiometric doping of organic semiconductors for novel electronic functions using metal–insulator transitions and superconductivity of correlated electron systems. [ABSTRACT FROM AUTHOR]

Using X-ray luminescence spectra, the enhancement of both σ-luminescence of self-trapped excitons and Ех luminescence (band maxima at 3.89 and 3.1 eV, respectively) has been revealed for the first time in RbI single crystals exposed to elastic uniaxial stress at 93 K. The intensity of these emissions increases linearly with the relative degree of applied uniaxial deformation of the crystal up to ɛ = 1%, while the luminescence undergoes saturation at higher values of ɛ. The behavior of the I = f (ɛ) dependence for σ and Ех emissions suggests that Ех luminescence is intrinsic, and is connected with the radiative relaxation of self-trapped excitons in the field of local deformation of a RbI regular lattice. [ABSTRACT FROM AUTHOR]

A series of compression experiments characterising the elastic-plastic response of single crystal and polycrystalline tantalum from quasi-static to intermediate strain-rates (10−3 – 103 s−1) over a range of temperatures (233–438 K) are reported in this paper. The single crystal experiments show significant differences in the response of the three principle crystal orientations of tantalum in terms of yield, work hardening and ultimate deformed shapes. Modelling is undertaken using a dislocation mechanics based crystal plasticity finite element model giving insight into the underlying microscopic processes that govern the macroscopic response. The simulations show the importance of the dislocation mobility relations and laws governing the evolution of the mobile dislocation density for capturing the correct behaviours. The inclusion of the twinning/anti-twinning asymmetry is found to influence [100] orientation most strongly, and is shown to be critical for matching the relative yield strengths. In general the simulations are able to adequately match experimental trends although some specific details such as exact strain hardening evolution are not reproduced suggesting a more complex hardening model is required. 3D finite element simulations approximating the tests are also undertaken and are able to predict the final deformed sample shapes well once the twinning/anti-twinning asymmetry is included (particularly for the [100] orientation). The polycrystalline data in both as-received and cold rolled conditions shows the initial yield strength is highest and work hardening rate is lowest for the cold-rolled material due to the increase in mobile dislocation density caused by the prior work. The general behavioural trends with temperature and strain-rate of the polycrystalline materials are reproduced in the single crystal data however the specific form of stress versus strain curves are significantly different. This is discussed in terms of the similar active slip systems in polycrystalline material to high symmetry single crystals but with the significant added effect of grain boundary interactions. [ABSTRACT FROM AUTHOR]

When Heisenberg spins interact antiferromagnetically on a triangular lattice and nearest-neighbor interactions dominate, the ground state is 120° antiferromagnetism. In this work, we probe the response of this state to lifting the triangular symmetry, through investigation of the triangular antiferromagnet PdCrO _2 under uniaxial stress by neutron diffraction and resistivity measurements. The periodicity of the magnetic order is found to change rapidly with applied stress; the rate of change indicates that the magnetic anisotropy is roughly forty times the stress-induced bond length anisotropy. At low stress, the incommensuration period becomes extremely long, on the order of 1000 lattice spacings; no locking of the magnetism to commensurate periodicity is detected. Separately, the magnetic structure is found to undergo a first-order transition at a compressive stress of ∼0.4 GPa, at which the interlayer ordering switches from a double-to a single- q structure.

Highlights • TM optical gain spectra of InAs nanowires are calculated. • TE optical gain spectra of InAs nanowires are calculated. • Components of hole states under uniaxial stresses are analyzed. • Optical gain spectra under uniaxial stresses are calculated. Abstract We calculate the electronic structures and optical gain of InAs nanowires via the eight-band effective-mass k ⋅ p theory. It is found that there is one peak in TM gain spectra, and the peak value of TM gain spectra is much larger than that of TE gain spectra when the radius R of the nanowires is 3 nm. Meanwhile, as the radius increases, the peak value of TE gain spectra approaches that of TM gain spectra, and more peaks appear in both TM and TE gain spectra. We therefore predict that InAs nanowires with R smaller than 3 nm can be used to emit TM linearly polarized light. We find, however, with R being 6 nm or 10 nm, a tensile or compressive uniaxial stress along the c axis can be used to tune the optical gain of InAs nanowires, and we can obtain TE or TM linearly polarized light. Our calculation points out the possibility for the application of InAs nanowires in the field of infrared linearly polarized lasers. [ABSTRACT FROM AUTHOR]

Ligament wound healing involves the proliferation of a dense and disorganized fibrous matrix that slowly remodels into scar tissue at the injury site. This remodeling process does not fully restore the highly aligned collagen network that exists in native tissue, and consequently repaired ligament has decreased strength and durability. In order to identify treatments that stimulate collagen alignment and strengthen ligament repair, there is a need to develop in vitro models to study fibroblast activation during ligament wound healing. The objective of this study was to measure gene expression and matrix protein accumulation in fibroblast-collagen gels that were subjected to different static stress conditions (stress-free, biaxial stress, and uniaxial stress) for three time points (1, 2 or 3 weeks). By comparing our in vitro results to prior in vivo studies, we found that stress-free gels had time-dependent changes in gene expression (col3a1, TnC) corresponding to early scar formation, and biaxial stress gels had protein levels (collagen type III, decorin) corresponding to early scar formation. This is the first study to conduct a targeted evaluation of ligament healing biomarkers in fibroblast-collagen gels, and the results suggest that biomimetic in-vitro models of early scar formation should be initially cultured under biaxial stress conditions. [ABSTRACT FROM AUTHOR]

We report on first‐principles calculations of electric polarization in multiferroic rhombohedral BiFeO3 under the [111] uniaxial stress, and our results suggest that the polarization varies nearly linearly from 75.5  to 97.1 μC cm−2 within the stress range of 8 to −8 GPa. The change of polarization is mainly due to atomic displacements since the calculated Born effective charges barely change under stress. We also compute the elastic stiffness coefficients and the elastic compliance coefficients, and these results demonstrate that the rhombohedral structure of BiFeO3 remains stable under the uniaxial stress between 8 and −8 GPa. Because in a ferroelectric‐based photovoltaic cell the photocurrent is proportional to the magnitude of electric polarization, it is possible to improve the photovoltaic efficiency of BiFeO3 thin film by applying uniaxial stress. [ABSTRACT FROM AUTHOR]