Constant Stress Conditions Research Articles

Influence of personal and social characteristics on the formation of mental trauma in police officers in the context of the COVID-19 pandemic

Relevance. Due to the peculiarities of professional activity, the COVID-19 pandemic for police officers was associated not only with a high risk of infection, but also pronounced mental stress and emotional destabilization, with higher risk of developing severe psychological consequences. In police officers, incidence of a new coronavirus infection, according to departmental statistics, was 6.6 times higher than in general population and close to that of healthcare workers of the Ministry of Health of Russia. High risk of COVID-19 infection in police officers during performance of their duties contributes to the symptoms of psychoemotional maladjustment and a constant state of chronic tension and emotional stress. Identification of the causes of professional maladjustment is important for justification of preventive measures and search for markers of professional success in employees of internal affairs bodies.Intention. To identify the influence of personal and social characteristics on the formation of mental trauma in police officers in the context of the COVID-19 pandemic.Methodology. A complete empirical study of 371 male employees of the divisions of the Main Directorate of the Ministry of Internal Affairs of Russia in Moscow was conducted. Three groups were identified: 1st – 127 police officers with positive test results and clinical manifestations of COVID-19; 2nd – 118 persons released from duty and quarantined due to their contacts with COVID-19 patients; 3rd – 126 police officers who were on duty to protect public order in crowded places during the COVID-19 pandemic. An experimental psychological survey of the police officers was conducted using electronic digital resources to comply with anti-epidemic measures.Results and Discussion. Symptoms of emotional burnout against the background of stressful service were shown to contribute to the formation of mental trauma during the COVID-19 pandemic in all surveyed police officers. Specifically, Group 1 typically demonstrates anxiety-phobic reactions; Group 2 – dysthymic-pessimistic outlook; and Group 3 – decreased neuropsychiatric stability, pronounced exhaustion and fatigue associated with official duties.Conclusion. The obtained data should be taken into account when conducting psychocorrection and medical and psychological rehabilitation of police officers in emergency situations associated with the long-term psychosocial and occupational stress.

Impact of Sorption-Induced Strain and Effective Stress on the Evolution of Coal Permeability under Different Boundary Conditions

Coalbed methane (CBM) is a relatively common unconventional natural gas, which has great exploitation value. Coal permeability is an important parameter that affects the production and production efficiency of CBM, which is mainly controlled by the sorption expansion/contraction strain and effective stress. To study the seepage characteristics of coal in the process of CBM production, we have used CH4 and CO2 as test gases separately and conducted comparative seepage tests of different gases under constant pore pressure conditions. At the same time, the elastic modulus reduction coefficient Rm has been introduced to characterize the sorption strain of coal, following which the permeability models suitable for different boundary conditions were derived according to the stress–strain relationship. Under the two gases, the new model could not only better reflect the law of coal sorption strain but also better reflect the relationship among effective stress, pore pressure, and coal permeability. Under the conditions of constant pore pressure, coal permeability was mainly controlled by effective stress; with the increase of effective stress, permeability decreased sharply initially and then gradually. Under the conditions of uniaxial strain and constant external stress, with an increase of pore pressure and Rm, the matrix sorption expansion strain increased, resulting in a narrowing of the seepage channel, and Rm indirectly inhibited permeability. At this point, coal permeability was mainly controlled by sorption expansion/contraction strain and effective stress. In addition, compared with other permeability models, the new permeability model possesses higher applicability both in theoretical mechanism and in data matching. The general change trend concerning coal permeability, determined by rebound pressure prb, was consistent with the test results, which further verified the applicability of the model. It is believed that the results of this study could provide a basis for subsequent research on the stress–strain–permeability relationship and for the study of efficient development of CBM.

An experimental evaluation of the microstructure, mechanical and functional fatigue properties of the boron-doped Cu-Al-Be SMA wires

An experimental evaluation of the microstructure, mechanical and functional fatigue properties of the Cu-11.70Al-0.45Be doped with Bx (x = 0.05, 0.10, 0.12, and 0.14 wt%) SMA wires has been carried out. The experiments were performed to investigate microstructure, phase/precipitates, and transformation temperatures for both as-cast and wire samples. Furthermore, tensile properties, shape recovery ratio, and functional fatigue evaluation have also been carried out for the wire samples. The investigation shows that the addition of the minor amount of boron and secondary processes involved during the specimen preparation induced excellent grain refinement. The addition of boron decreased transformation temperatures; however, there was not a considerable change observed due to the secondary process. It was observed that tensile properties increases with the boron addition, and complete shape recovery was observed for all the selected alloys. Finally, functional fatigue tests were conducted under constant stress condition and observed that the number of cycles until the failure has increased and more distance recovery was achieved with an increase in boron doping.

COMPARATIVE ANALYSIS OF TECHNOLOGIES OF MICROPILES ARRANGEMENT DURING STRENGTHENING OF WEAK SOIL BASES

Purpose. Perform a comparative analysis of drill and injection (jet-grouting) and drill and mixing technologies of micropiles arrangement of weak soil bases with the identification of technological features that significantly effect on the design and calculation of weak soil bases strengthening. Methodology. To solve this problem, was conducted of the detailed analysis of the most effective methods of micropiles arrangement during the strengthening of weak soil bases (physical immersion, bored and packing of concrete, drill and injection of ground, drill and mixing soils and application of special effects). Peculiarities of technological parameters of jet-grouting and drill and mixing technologies are considered in detail. The advantages and disadvantages of each of the technologies are revealed. It is proved that the drill and mixing technology has a greater degree of prediction of the stress-strain state change of the inhomogeneous base. To determine the influence of deformation characteristics, a spatial finite-element model based on a flat prototype was created, which was built using automatic triangulation of the professional calculation complex SCAD. Findings. A significant reduction of the deformed state at an almost constant stress state is obtained. When the deformation characteristic increases by 3 times (the ratio of the modulus of elasticity of the soil cement pile and the weak soil), the vertical displacements of the foundation decrease by 1.23 times. Originality. It consists in obtaining the dependence of the change of vertical displacements and stresses on the modulus of elasticity of the soil cement micropile, created on the basis of drill and mixing technology. Practical value. It consists in the obtained results of comparative analysis of substantiation of micropile installation drill and mixing technology during strengthening of weak soil bases with definition of technological features and choice of drill and mixing as the most effective variant from the point of view of technology realization.

Spray-Dried Plasma Improves Body Weight, Intestinal Barrier Function, and Tibia Strength during Experimental Constant Heat Stress Conditions.

Simple SummaryBroilers are especially heat sensitive because of the absence of sweat glands and their elevated metabolism. Under commercial conditions, extremely high temperatures (heat stress) reduce their performance. This research aimed to assess spray-dried feeding plasma (SDP) during constant heat stress (HS) on the performance, intestinal permeability, and bone strength in broilers. Chickens fed with a diet supplemented with SDP increased both their body weight and body weight gain compared to the HS control group. At the end of the study (d 42 of age), chickens fed with SDP significantly alleviated the increased gut leakage induced by HS and showed a significant increase in tibia strength compared with control HS chickens. The results in the present study suggest SDP mends gut integrity, hence reducing chronic systemic inflammation.The aim of this study was to see how spray-dried plasma (SDP) supplementation affected broiler chicken performance, intestinal permeability, and bone strength during persistent heat stress. One-day-old chicks (n = 480) were randomly assigned into twelve environmental corrals; four thermoneutral (TN-negative control, maintained at 24 °C from d 21–42); four heat stress (HS, exposed to 35 °C from d 21–42); and four heat stress treated with 2% SDP in the feed until d 28 followed by 1% SDP until d 42 (HS-SDP). The performance and serum levels of fluorescein isothiocyanate-dextran (FITC-d) were evaluated at d 21, 28, 35, and 42. The tibias strength was evaluated on d 21 and 42. The increment in chicken temperature (p < 0.05) was observed two h following the increase in environmental temperature in both HS groups and was associated with decreased performance parameters compared with the TN group. At d 42 of age, the chickens exposed to HS had an impaired gut permeability and decreased tibia strength compared to the TN group (p < 0.05). However, partially feeding SDP mitigated these adverse effects significantly. These findings imply that using SDP strategically during stressful times, such as prolonged heat stress, may help mitigate its negative consequences.

A critical analysis of shale laboratory permeability evolution data

This review study aims to identify why current experimental measurements of shale permeability are not consistent with predictions of commonly-used permeability models and explore how the identified reason would guide future research. These goals are achieved through the collection of experimental permeability measured under constant confining pressure (CCP) and constant effective stress (CES) conditions. These data show that permeability ratios (k/k0) vary between an upper bound and a lower bound. A generic permeability model is developed to delineate the boundaries of k/k0 based on shale microstructural characteristics. It's found that for upper bounds are controlled primarily by the fracture behavior while for lower bounds are controlled by the matrix or intact shale behavior. These findings suggest that the model predictions represent only behaviors of either fracture system or matrix while the experimental measurements from CCP and CES observations are for real shales. For real shales the internal dependencies among these factors cannot be fully understood through the nature of the external boundary conditions in CCP and CES tests, alone, but require high-level knowledge of sample structure and process interactions. The nature of permeability time dependencies on the internal process interactions must be reflected in any future experimental and modeling research.

True Triaxial Study on Aeolian Sand Subgrade

The drained shear tests of aeolian sand in Tengger Desert were carried out by using the British GDS true triaxial apparatus, and the shear strength and stress-strain relationships of aeolian sand were studied under the conditions of constant average principal stress and different intermediate principal stress coefficients. The test results showed that the variation trends of principal strains in the three principal stress directions were correlated with the variation of the intermediate principal stress coefficient, and the stress-strain relationships in the three principal strain directions were hardening type. With the increase of intermediate principal stress coefficients, the shear strength of the specimen decreased, and the peak value of shear strength was the lowest when b = 0.8.

Myeloma Cell Addiction to the Transcription Factor TCF11

BACKGROUND: TCF11/NRF1 is a transcription factor transiently and post-translationally activated in response to metabolic challenges and endoplasmic reticulum (ER) stress. However, the genome-wide compendium of genes regulated by TCF11 has not been defined and its role in tumour biology has not been explored. Since malignant plasma cells (PC) in multiple myeloma are under a constant state of ER stress due to immunoglobulin secretion, we hypothesised that the expression and functional role of TCF11 would be altered in myeloma compared to normal cells.METHODS: We employed qPCR for mRNA quantitation, western blotting for protein expression analysis, constitutive and dox-inducible lentiviral shRNA-based knock-down of TCF11, DAPI staining and flow-cytometry for cell cycle analysis, RNA-seq for transcriptome analysis after TCF11knock-down, ChIP-seq against Flagx3-TCF11 in H929 myeloma cells, and a subcutaneous myeloma xenograft model in NSG mice following inducible TCF11 knock-down. Computational analysis of RNA-seq and ChIP-seq was performed using standard work-flows while cistrome-transcriptome integration was performed using the Binding and Expression Target Analysis package. Pathway enrichment analysis was performed using EnrichR and GSEA.RESULTS: We found that at the protein level TCF11 is undetectable in erythroblasts, monocytes, B and T cells but expressed at low level in normal PC and at higher levels in myeloma cell lines (n=5) as well as primary myeloma PC (n=10). Therefore, myeloma cells and to a lesser extent normal PC constitutively express TCF11. Depletion of TCF11 using 2 validated shRNAs (either constitutive or inducible) was toxic to 5/5 and 2/2 myeloma cell lines tested in vitro and in vivo respectively, revealing an absolute requirement for TCF11 expression for myeloma cell survival.Next we performed transcriptome analysis upon TCF11 depletion in 2 myeloma cell lines (H929 and U266) with divergent primary and secondary oncogenic events (CCND1 vs MMSET and MYC vs MYCL respectively). As well as its previously described role in the regulation of several metabolic processes, pathway enrichment analysis revealed in both cell lines a hitherto unknown function of TCF11 in cell cycle regulation. Indeed, inducible TCF11 depletion in myeloma cells resulted in a significant cell cycle arrest in G0/1 (n=5; p<0.01).To investigate whether TCF11 directly regulates genes involved in cell cycle and proliferation, we generated and analysed the first genome-wide maps of TCF11 binding in H929 cells (n=2). Significantly enriched peaks (n=3829) bind in roughly equal proportions to promoters, introns and enhancers and are highly enriched for the previously described TCF11-preferred ARE motif.Integrated transcriptome-cistrome maps revealed that 608 and 390 genes are directly activated or repressed by TCF11. Again, pathway enrichment analysis of TCF11 direct targets, as well as positive regulation of various metabolic processes (glycolysis, adipogenesis, unfolded protein response, oxidative phosphorylation), it also confirmed a direct role of TCF11 in the regulation of cell cycle and of the transcriptional programmes of MYC and E2F1/2. Low throughput ChIP-qPCR analysis validated TCF11 binding to the promoters of MYC and reciprocally, binding of MYC to the promoter of TCF11, thus establishing TCF11 as a novel co-operative factor of oncogenic MYC. Further, we confirmed that TCF11 binds to its own promoter and since TCF11 mRNA levels increase following proteasome inhibitor treatment, we conclude that TCF11 activates its own transcription.Finally, we detected constitutively high protein levels of TCF11 in several other haematological cancer cell lines, i.e., (ALL: BV173; AML: HL60 and KG1 and Burkitt lymphoma: Ramos) and solid tumour cell lines (breast: MCF7 and MCF7TR; prostate: DU145 and PC3; ovarian: SKOV3 and OVC433). In all cases, depletion of TCF11 was toxic to the cells.CONCLUSIONS: Myeloma cells are addicted to the constitutive expression of TCF11. As well as essential metabolic processes, TCF11 regulates cell cycle progression. At the transcriptional level, TCF11 regulated expression of MYC, E2F1/2 and of their respective transcriptional programmes in a direct co-operative fashion. These data establish a multifaceted role of TCF11 in tumour biology and link its function to cell cycle regulation in co-operation with oncogenic MYC in myeloma cells. DisclosuresAuner:Amgen: Honoraria, Research Funding. Karadimitris:GlaxoSmithKline: Research Funding.

Genome-wide analysis and functional characterization of the DELLA gene family associated with stress tolerance in B. napus

BackgroundBrassica napus is an essential crop for oil and livestock feed. Eventually, this crop's economic interest is at the most risk due to anthropogenic climate change. DELLA proteins constitute a significant repressor of plant growth to facilitate survival under constant stress conditions. DELLA proteins lack DNA binding domain but can interact with various transcription factors or transcription regulators of different hormonal families. Significant progress has been made on Arabidopsis and cereal plants. However, no comprehensive study regarding DELLA proteins has been delineated in rapeseed.ResultsIn our study, we have identified 10 BnaDELLA genes. All of the BnaDELLA genes are closely related to five AtDELLA genes, suggesting a relative function and structure. Gene duplication and synteny relationship among Brassica. napus, Arabidopsis. thaliana, Brassica rapa, Brassica oleracea, and Brassica nigra genomes were also predicted to provide valuable insights into the BnaDELLA gene family evolutionary characteristics. Chromosomal mapping revealed the uneven distribution of BnaDELLA genes on eight chromosomes, and site-specific selection assessment proposes BnaDELLA genes purifying selection. The motifs composition in all BnaDELLA genes is inconsistent; however, every BnaDELLA gene contains 12 highly conserved motifs, encoding DELLA and GRAS domains. The two known miRNAs (bna-miR6029 and bna-miR603) targets BnaC07RGA and BnaA09GAI, were also predicted. Furthermore, quantitative real-time PCR (qRT-PCR) analysis has exhibited the BnaDELLA genes diverse expression patterns in the root, mature-silique, leaf, flower, flower-bud, stem, shoot-apex, and seed. Additionally, cis-acting element prediction shows that all BnaDELLA genes contain light, stress, and hormone-responsive elements on their promoters. The gene ontology (GO) enrichment report indicated that the BnaDELLA gene family might regulate stress responses. Combine with transcriptomic data used in this study, we detected the distinct expression patterns of BnaDELLA genes under biotic and abiotic stresses.ConclusionIn this study, we investigate evolution feature, genomic structure, miRNAs targets, and expression pattern of the BnaDELLA gene family in B. napus, which enrich our understanding of BnaDELLA genes in B. napus and suggests modulating individual BnaDELLA expression is a promising way to intensify rapeseed stress tolerance and harvest index.

Investigation of the influence of intermediate principal stress on the dynamic responses of rocks subjected to true triaxial stress state

Precisely understanding the dynamic mechanical properties and failure modes of rocks subjected to true triaxial stress state (σ1 > σ2 > σ3, where σ1, σ2, and σ3 are the major principal stress, intermediate principal stress, and minor principal stress, respectively) is essential to the safety of underground engineering. However, in the laboratory, it is difficult to maintain the constant true triaxial stress state of rocks during the dynamic testing process. Herein, a numerical servo triaxial Hopkinson bar (NSTHB) was developed to study the dynamic responses of rocks confronted with a true triaxial stress state, in which lateral stresses can maintain constant. The results indicate that the dynamic strength and elastic modulus of rocks increase with the rise of intermediate principal stress σ2, while the dynamic elastic modulus is independent of the dynamic strain rate. Simulated acoustic emission distributions indicate that the intermediate principal stress σ2 dramatically affects dynamic failure modes of triaxial confined rocks. As σ2 increases, the failure pattern switches from a single diagonal shear zone into two parallel shear zones with a small slant. Moreover, a recent triaxial Hopkinson bar experimental system using three bar pairs is also numerically established, and the measuring discrepancies are identified between the two numerical bar systems. The proposed NSTHB system provides a controllable tool for studying the dynamic triaxial behavior of rocks.

Prevalence of fibromyalgia in medical students and its association with lifestyle factors - a cross-sectional study.

ObjectivesFibromyalgia (FM) is a chronic widespread pain syndrome, known to be associated with several other symptoms. Chronic stress is suspected to be a contributing factor in the pathogenesis of FM. It is known that medical students are under a constant state of stress originating from personal and social expectations. The aim of the study was to assess the prevalence of FM in this population and identify lifestyle parameters influencing FM severity.Material and methodsAn online survey of first- and final-year medical students was conducted using the ACR modified 2016 criteria and FANTASTIC checklist. The survey acquired demographic information such as age, gender, year, and division of studies. A subgroup analysis based on gender, year of studies, and division of studies was performed.Results439 medical students (71% females) completed the survey. The overall prevalence of FM in our cohort was 10.48%. The ratio of females to males was 3 : 1. A significant negative correlation between better quality of lifestyle and worse FM severity was observed in all subgroups. The “insight”, “sleep and stress”, “behavior” and “career” domains of lifestyle were found to have a significant negative correlation with FM severity on univariate analysis.ConclusionsThe prevalence of FM in medical students seems to be considerably higher than in the general population. Chronic stress levels, sleep problems, social support, and behavior seem to be the major factors influencing FM severity in this population. Our findings suggest that medical students must be considered a “high-risk” group for FM, and hence must be identified, educated, and managed accordingly. It is, therefore, important for medical universities to implement programs educating students about FM, the importance of a healthy lifestyle, and stress coping strategies, while also making systemic changes to curb stressors in medical training.

Two-Way Shape Memory Polymers: Evolution of Stress vs Evolution of Elongation

Stimuli-responsive polymers are a subject of numerous studies in recent decades due to its variety of possible applications ranging from nanomedicine, drug delivery systems, biosensing, to smart textile development and aerospace engineering. The current demand of reliable and easy-programmable polymeric-actuating components underlines the necessity to understand the mechanism that governs the actuation of materials. This work sheds new light on the understanding of the two-way shape memory effect (2W-SME) of cross-linked semicrystalline polymers. We investigated and compared melting/crystallization of cross-linked polycaprolactone under constant stress and constraint strain conditions. We observed three regions of behavior upon cooling: rubbery, semicrystalline, and an intermediate one associated with entropic softening of the network prior to crystallization. Based on obtained observations, we proposed possible mechanisms for the processes occurring in cross-linked polymers upon their crystallization/melting and quantitatively investigated the effects of applied stress, elongation, and cross-linking density to allow programmable design of reversible actuators.

Analysis of the stress distribution in a laminar direct simple shear device and implications for test data interpretation

Direct simple shear (DSS) testing allows observation of load-deformation response under rotation of the major principal stress plane, which is descriptive of many actual field problems. While the simplicity of the test configuration makes its use popular in research and industry, key uncertainties still remain regarding the interpretation of the laboratory data. This study uses laboratory validated discrete element method (DEM) models to examine the stress transmission in laminar-type direct simple shear devices under drained constant effective stress conditions. The DEM models (comprised of spheres) closely replicate physical specimens of precision chrome steel ball bearings for which the properties (e.g., shape, surface friction, and stiffness) were measured directly. The DEM models were also validated using experimental tests, so that conclusions regarding the system response can be derived with confidence from the available DEM data. The testing program included both loose and dense specimens, allowing for a comparison of the influence of density on stress state which has not been examined in previous simple shear DEM studies. Differences were observed between vertical effective stresses and shear stresses derived from boundary measurements (as commonly carried out in experimental programs) and those derived from force measurements within the DEM specimens. The failure state of the material in simple shear was also examined through Mohr’s circles of stress. The evolution of stresses on both the horizontally and vertically oriented planes were considered so that established methods of direct simple shear interpretation could be critically assessed. For the loose specimens, the angle of shearing resistance can be confidently estimated considering the maximum shear stress acting on the horizontal plane, which is easily inferred from measurements of the shear force during the physical test. This was true considering both internal and boundary calculated stresses. This approach, however, is inaccurate for the dense specimens. Analysis of the particle-scale kinematics of the response illustrates that the deformation field within the central portion of the specimen is in simple shear, although the magnitude of this shearing was significantly larger than what was measured on the boundary. This study and the conclusions derived focus on smooth spherical particle specimens; the objective was to examine the stress distribution within DSS devices and the implications for test interpretation using DEM models that more closely matched the physical laboratory specimens tested than in previous studies. When considered alongside the existing studies, the findings show that there is no broad conclusion that can be applied for all materials and all conditions in simple shear and that interpretation should be carefully tied to the physical conditions simulated.

The Impact of Structural Racism on Cardiovascular Health.

The Impact of Structural Racism on Cardiovascular Health.

Effect of sand grain size and boundary condition on the swelling behavior of bentonite–sand mixtures

Deep geological repository is a favorable choice for the long-term disposal of nuclear wastes. Bentonite–sand mixtures have been proposed as the potential engineered barrier materials because of their suitable swelling properties and good ability to seal under hydrated repository conditions. To investigate the effects of sand grain size on the engineering performance of bentonite–sand mixtures, we prepare five types of bentonite–sand mixtures by mixing bentonite with sand of varying particle size ranges (0.075–0.25 mm, 0.25–0.5 mm, 0.5–1 mm, 1–2 mm and 2–5 mm, respectively). We carry out sequential oedometer tests under different simulated repository conditions, including constant vertical stress (CVS), constant stiffness (CS) and constant volume (CV) conditions. The microstructural heterogeneity and anisotropy of these soil mixtures are characterized through the quantitative analysis of micro-CT scanning results. Experimental results reveal that both sand grain size and boundary condition significantly influence the swelling of soil mixtures. Under three conditions, the temporal evolutions of swelling stress and strain follow similar trends that they increase faster at the beginning and gradually stabilize afterward. Comparing the ultimate values, swelling strains follow CVS > CS > CV, while swelling stresses follow CV > CS > CVS. Under CS boundary conditions, as the stiffness coefficient increases, the swelling pressure increases and the swelling strain decreases. CT results further indicate that mixtures with larger sand inclusions are more structurally heterogeneous and anisotropic, resulting in increased inter-particle friction and collision and a higher energy dissipation during the swelling process. Moreover, the non-uniform distribution of bentonite in local zones would be intensified, which plays an important role in compromising swelling behavior. Therefore, soil samples mixed with larger sand particles present a smaller swelling stress and strain values. This study may guide the choice of engineered barrier materials toward an improved design and assessment of geological repository facilities.

Thermo-mechanical characterisation of NiTi-based shape memory alloy wires for civil engineering applications

Shape Memory Alloys (SMAs) exhibit a complex material behaviour due to thermo-mechanical coupling. At present, the understanding of their material behaviour under different thermo-mechanical loading conditions relevant to civil engineering applications is lacking even though they have been widely used in the past decade or so, for example mechanical behaviour at constant stress but variable temperature loading has not received much attention in civil engineering. In this study a comparative analysis of the mechanical behaviour of various NiTi-based SMAs is carried out to investigate: (1) stress-elongation and stress-temperature response under direct tensile loading; (2) thermo-mechanical behaviour under constant stress condition but under variable temperature loading (to investigate their ability to exhibit shape memory effect, if any, while carrying load); and (3) the ability to develop and retain recovery stress at room and sub-zero temperatures. Essentially, all these tests aim at investigating the potential/limitations of the SMAs in civil engineering in particular re-centring and heat-activated prestressing applications. The results from this study showed that at a constant stress of 600 MPa a large forward transformation strain, in the range of 5%–11%, is produced in NiTi-based SMAs when the temperature is lowered to or below the room temperature. This material behaviour of NiTi-based SMAs could be detrimental in many civil engineering applications of NiTi-based SMAs. However, all NiTi-based SMAs used in this study were found to have a good potential for re-centring applications, but only austenitic NiTi-based SMAs were found suitable for long-term prestressing applications. The maximum recovery stress developed on heating with constrained boundary conditions ranged between 230–750 MPa.

Improved predictions of thermal fluid pressurization in hydro-thermal models based on consistent incorporation of thermo-mechanical effects in anisotropic porous media

Coupled thermo-hydro-mechanical models are commonly used to model the evolution of temperature, pore pressure, and stress in a wide range of geotechnologies such as geothermal applications or around canisters of high-level radioactive waste in deep underground storage facilities. Their numerical modeling is often computationally highly demanding, especially if parameter identification, sensitivity analyses or uncertainty quantification require many model evaluations. Often, the thermally driven pore pressure evolution and the subsequently altered flow processes are the primary targets of an analysis. To benefit from the computational efficiency of hydro-thermal (HT) models while maintaining the accuracy of the thermo-hydro-mechanical (THM) model, we derived two cases of a simplified representation of mechanical deformations in a coupled hydro-thermal model. Deformations induced by pressure as well as temperature changes are consistently incorporated into the mass balance storage terms. We demonstrate the exact coincidence of THM and modified TH formulations in isotropic and orthotropic materials as long as the basic assumptions like constant hydrostatic stress conditions or uniaxial strain hold. By modeling of a point heat source in isotropic or anisotropic porous media it is shown that a good agreement between TH and THM models can be maintained even though the assumptions underlying the simplification are no longer valid exactly. On our test-machine, a significant speed-up could be achieved by the reduction of the problem size when transitioning from a THM to a TH model. The highest speed-ups were achieved when Taylor-Hood elements were employed in order to avoid the problem of spurious pressure oscillations in the fully coupled THM model.

Influence of Internal Friction Angle and Interface Roughness on Shear Behavior of Mortar-Rock Binary Medium Joint

The damage of the interface between mortar and rock often occurs in engineering projects. The stability of the binary medium joint is the key factor in judging the stability of a hydraulic structure foundation. The shear characteristics of the flat mortar-rock joint were numerically simulated under the direct shear test by finite element using FLAC3D software. The results showed that the internal friction angle of mortar has little influence on the shear strength, its corresponding displacement, strain softening degree and residual shear strength for flat joint. Therefore, considering the roughness of the structural surface, the joint with regular serrated mortar-rock binary medium was established in this paper, and the direct shear test under the condition of constant normal stress was carried out for comparative study. The results showed that the shear strength, residual strength, peak strength displacement and strain softening degree of the serrated structure were strongly correlated with the internal friction angle of mortar. For the regular serrated binary joint, improving the mortar performance can improve the shear performance and stability of the whole structure more effectively than the flat joint. The relationship between the shear strength, residual strength and the friction angle were established respectively.

THE ARMY BEHIND BARBED WIRE. PSYCHOLOGICAL ASPECTS OF BEHAVIOR IN CAPTIVITY

The article examines the psychological features of humans entering and the subsequent stay in a hostile environment and its consequences. We made the analysis of psychological factors influencing the behavior of a soldier in captivity. The genesis of captivity was analyzed, and the mechanisms of destructive psychological influence of captors on persons who were captured were investigated. The results of the research allow forming a holistic view of the psychological factors that affect military personnel from the moment of capture to the moment of their release. Activities of international humanitarian organizations and missions, does not fully protect prisoners of war from violence. The state of constant mental stress reduces the inner life of the individual to a primitive level. It was found that the events of the captivity were extreme. They go beyond the usual human experiences and cause intense fear for their lives, as well as create feelings of helplessness. Preparations for possible capture are mandatory for all servicemen. Post-captive reintegration will help to restore mental health and return the person to a full life and performance of duties. We identified the factors that help to endure conditions of the forced isolation with minimal loss to the physical and mental health.

The effect of secondary sawtooth height on shear properties of rock joints with rigid contact

A variety of joints of various shapes are widely developed in rock masses. An accurate account of the behavior of a joint rock mass requires a realistic model for the tribological behavior of joints, which requires further study to understand the influence of secondary asperities on shear strength and the shear failure mechanism of joints. In view of the current lack of research on the effects of secondary asperities, a test scheme including first-order and second-order sawteeth of different heights was developed. By means of a physical model test and numerical model test under different constant normal stress conditions, the macroscopic mechanical properties and the microscopic deformation failure process affected by secondary sawtooth of joint are revealed, respectively. The results of the direct shear tests under different normal stresses on these sawtooth profiles demonstrate that the height of the second-order asperity has a certain effect on the shear strength. When the secondary sawtooth height is less than half the height of the first-order sawtooth, the shear strength increases with secondary sawtooth height. Compared with the joint surface of the same sawtooth height, the presence of a secondary sawtooth causes local stress concentration of the joint under the direct shear test, resulting in different microcrack production, expansion sites, and numbers of microcracks. We believe that this study is useful for understanding the shear characteristics of saw-toothed joints.