Contraction Stress Research Articles

IVIVC for Extended Release Hydrophilic Matrix Tablets in Consideration of Biorelevant Mechanical Stress

PurposeWhen establishing IVIVC, a special problem arises by interpretation of averaged in vivo profiles insight of considerable individual variations in term of time and number of mechanical stress events in GI-tract. The objective of the study was to investigate and forecast the effect of mechanical stress on in vivo behavior in human of hydrophilic matrix tablets.MethodsDissolution profiles for the marketed products were obtained at different conditions (stirring speed, single- or repeatable mechanical stress applied) and convoluted into C-t profiles. Vice versa, published in vivo C-t profiles of the products were deconvoluted into absorption profiles and compared with dissolution profiles by similarity factor.ResultsInvestigated hydrophilic matrix tablets varied in term of their resistance against hydrodynamic stress or single stress during the dissolution. Different scenarios, including repeatable mechanical stress, were investigated on mostly prone Seroquel® XR 50 mg. None of the particular scenarios fits to the published in vivo C-t profile of Seroquel® XR 50 mg representing, however, the average of individual profiles related to scenarios differing by number, frequency and time of contraction stress. When different scenarios were combined in different proportions, the profiles became closer to the original in vivo profile including a burst between 4 and 5 h, probably, due to stress-events in GI-tract.ConclusionFor establishing IVIVC of oral dosage forms susceptible mechanical stress, a comparison of the deconvoluted individual in vivo profiles with in vitro profiles of different dissolution scenarios can be recommended.

Stiffness Sensing by Aortic Smooth Muscle Cells: Continuum Mechanics Modeling of the Acto-Myosin Role

Smooth Muscle Cells (SMCs) play a vital role in maintaining homeostasis in the aorta by sensing and responding to mechanical stimuli. However, the mechanisms that underlie the ability of SMCs to sense and respond to stiffness change in their environment are still partially unclear. In this study, we focus on the role of acto-myosin contractility in stiffness sensing and introduce a novel continuum mechanics approach based on the principles of thermal strains. Each stress fiber satisfies a universal stress-strain relationship driven by a Young’s modulus, a contraction coefficient scaling the fictitious thermal strain, a maximum contraction stress and a softening parameter describing slipping effects at the weakest links. To account for the inherent variability of cellular responses, large populations of SMCs are modeled with the finite-element method, each cell having a random number and a random arrangement of stress fibers. Moreover, the level of myosin activation in each stress fiber satisfies a Weibull probability density function. Model predictions are compared to traction force measurements on different SMC lineages. It is demonstrated that the model not only predicts well the effects of substrate stiffness on cellular traction, but it can also successfully approximate the statistical variations of cellular tractions induced by intercellular variability. Finally, stresses in the nuclear envelope and in the nucleus are computed with the model, showing that the variations of cytoskeletal forces induced by substrate stiffness directly induce deformations of the nuclear envelope and of the nucleus, which can potentially alter gene expression. The predictability of the model combined to its relative simplicity are promising assets for further investigation of stiffness sensing in multicellular 3D environments. Eventually, this could contribute to decipher the effects of mechanosensitivity impairment, which are known to be at the root of aortic aneurysms.

Evaluation of the Plio-Quaternary tectonic stress regime from fault kinematic analysis in the lake Van Basin (Eastern Anatolia)

We focus on the Neogene–Quaternary tectonic evolution of the Lake Van Basin located within the Turkish-Iranian Plateau. To better understand the complex tectonic history of the region and determine the paleostress patterns, we investigate and report on the geometric, structural, and kinematic characteristics of the Basin based on field observations of fault-slip orientations which are classified according to radiometric ages of the basin stratigraphy.The analysis of large-scale structures and fault kinematics indicate that three different deformation phases prevailed in the Lake Van Basin during the Neogene-Quaternary periods. Phase 1 is characterized by NW-SE extension and NE-SW contraction that gave rise to the development of strike-slip faults with thrust or normal components during the late Miocene, deforming the fluvial sediments which expose at east/northeast of the Basin. Phase 2 is characterized in fluvial and lake deposits of the Middle Pleistocene, deformed by dominant contraction stress regime effective along NW-SE direction. The late Pleistocene tectonic regime (Phase 3) consists of transpressional deformation that develops under NNW-SSE compression and ENE-WSW extension. According to our analysis, the present-day deformation pattern of the Lake Van Basin is dominated by compression at east, while at the northern part is transtensional.

A human hair-based platform for long-term maintenance of 3D engineered cardiac tissues in vitro

In vitro cardiac models constructed with human cardiomyocytes and appropriate biomaterial scaffolds are still in pressing need for drug testing and disease modeling. Here, we describe a platform based on human hair to generate 3D cardiac tissues, termed cardiowire, from human induced pluripotent stem cell-derived cardiomyocytes. The cardiowire was cultivated for an extended period of time (up to 118 days). To monitor the contractile motion of the cardiac tissue, video-based analysis was performed throughout the time course of cultivation. After an appreciably long time (52 days) of culture, the cardiowire remained its strong contractility. Although the gel compaction went on with time, the width of the cardiowire was as large as 1 mm after 100 days. Moreover, it was demonstrated that human hair not only could support cell attachment, but also had long-term mechanical strength to sustain the highly repetitive mechanical stress of the cardiac tissue contraction. This platform could be easily combined with electrical and mechanical stimulation and serve as an in vitro cardiac model for drug screening and other therapeutic applications.

Structural control and genesis of gold deposits in the Liaodong Peninsula, northeastern North China Craton

Two distinct styles of gold mineralization occurred in the Liaodong Peninsula, in the northeastern North China Craton. One formed an altered rock-type gold deposit in the west, and the other formed a quartz vein-type deposit in the east. Geological investigations and structural analysis show that these deposits may have originated from two distinct tectono-magmatic hydrothermal systems. The former is an E–W-trending contractional–extensional structural system formed in the Late Triassic, which includes the deposits in Baiyun, Jianshangou, and Maoling. The latter is related to high-angle strike-slip faults formed in the Early Cretaceous, and includes the Wulong gold deposit. Stress-induced tectonic analyses show that the principal stress in the western district was nearly N–S-oriented contractional stress initially, which subsequently changed to extensional stress; this might have been the result of the collision and subsequent extension of the Siberia Craton, North China Craton, and Yangzi Craton in the Late Triassic. The principal stress in the eastern district was nearly NW–SE-oriented contractional and sinistral shear stress initially, which subsequently changed to extensional stress, which may be the result of regional extension associated with the westward subduction of the Paleo-Pacific Plate in the Early Cretaceous.The structural control of the gold mineralization is manifested at all scales from regional to mines to orebodies; that is, the grading of the ores was controlled by different generations or orders of deformation. Gold ores were mainly formed under brittle or brittle-shear deformation conditions; in particular with extensive ore-bearing catalasite flows; which were generated by both the brittle or brittle-shear failure along major fault systems and related Late Triassic and Early Cretaceous magmatic hydrothermal activity. This genetic origin for gold mineralization and ore-bearing catalasite flows may provide support for the mechanism of flash vaporization in mineralization processes that form mesothermal gold systems.

Spin stress contribution to the lattice dynamics of FePt.

Invar-behavior occurring in many magnetic materials has long been of interest to materials science. Here, we show not only invar behavior of a continuous film of FePt but also even negative thermal expansion of FePt nanograins upon equilibrium heating. Yet, both samples exhibit pronounced transient expansion upon laser heating in femtosecond x-ray diffraction experiments. We show that the granular microstructure is essential to support the contractive out-of-plane stresses originating from in-plane expansion via the Poisson effect that add to the uniaxial contractive stress driven by spin disorder. We prove the spin contribution by saturating the magnetic excitations with a first laser pulse and then detecting the purely expansive response to a second pulse. The contractive spin stress is reestablished on the same 100-ps time scale that we observe for the recovery of the ferromagnetic order. Finite-element modeling of the mechanical response of FePt nanosystems confirms the morphology dependence of the dynamics.

Расчетный метод оценки морозостойкости лакокрасочных покрытий воздушных судов

The paper considers the issues of temperature cycling and ice accretion on external paint coatings of aircraft as well as the negative effects of these processes expressed in periodic tension-compression strain and absorption of atmospheric moisture by surface microasperities with its subsequent freezing resulting in gradual cavity wedging. We note that laboratory testing methods recreating the temperature cycling that simulates actual operating conditions of aircraft paint coatings are increasingly labour-intensive. We substantiate the feasibility of developing a computational method for frost resistance estimation in specific operating conditions. The method takes into account the combination of contraction stresses, excessive cooling and wedging caused by ice build-up. We assume the main physical and mechanical properties of ice and paint to be homogeneous and equal to cumulative average values, and the linear thermal expansion coefficients of the substrate and coating to be constant and not dependent on temperature. We disregard ice friction over the microasperity cavities and in-flight loads on the paint coating caused by incident air flows and structural deformations of the aircraft. We present a method of computing frost resistance of aircraft paint coating subjected to cyclical ice accretion, which is based on the method of equivalent stresses. We tested frost resistance of a polyesterurethane coating over a duralumin plate in the range of --50 to 25 °C for F = 2000 freezing and thawing cycles. We performed a temperature cycling computation of the factor of safety for frost resistance in the case of periodic ice accretion. The results obtained are in good agreement with experimental data

The role of non-stress test as a method to evaluate the outcome of high-risk pregnancy: a tertiary care center experience

Background: Non-stress test (NST) is a graphical recording of changes in fetal heart activity and uterine contraction along with fetal movement when uterus is quiescent. NST is primarily a test of fetal condition and it differs from contraction stress test which is a test of uteroplacental function. The present study aimed at evaluating the efficacy and diagnostic value of NST for antenatal surveillance in high-risk pregnancy and comparing the mode of delivery with test results.Methods: A clinical study of NST was done between November 2014 to October 2015. NST was used for their surveillance from 32 weeks of gestation and NST was recorded weekly, biweekly, on alternate days or even on daily basis depending on high risk factors and were followed up.Results: A total of 100 cases were enrolled in the study. The mean age of patients was 25.09±3.78 years. In all 14 cases (23.3%) with reactive NST underwent lower caesarean section (LSCS) whereas 36 cases (90%) with non-reactive NST underwent LSCS. The mean NST delivery interval with reactive NST was 9.8±7.1 hours and in cases with non-reactive NST it was 9.2±8.6 hours, the difference was statistically not significant (p=0.70).Conclusions: NST tells about acute fetal hypoxia and decision to delivery time can be made for those patients with fetal distress so that a major improvement in the outcome among parturient can be achieved with abnormal NST results. An abnormal NST should alert the clinician of fetal compromise and has to be followed up by other biophysical tests.

Unconventional picosecond strain pulses resulting from the saturation of magnetic stress within a photoexcited rare earth layer.

Optical excitation of spin-ordered rare earth metals triggers a complex response of the crystal lattice since expansive stresses from electron and phonon excitations compete with a contractive stress induced by spin disorder. Using ultrafast x-ray diffraction experiments, we study the layer specific strain response of a dysprosium film within a metallic heterostructure upon femtosecond laser-excitation. The elastic and diffusive transport of energy to an adjacent, non-excited detection layer clearly separates the contributions of strain pulses and thermal excitations in the time domain. We find that energy transfer processes to magnetic excitations significantly modify the observed conventional bipolar strain wave into a unipolar pulse. By modeling the spin system as a saturable energy reservoir that generates substantial contractive stress on ultrafast timescales, we can reproduce the observed strain response and estimate the time- and space dependent magnetic stress. The saturation of the magnetic stress contribution yields a non-monotonous total stress within the nanolayer, which leads to unconventional picosecond strain pulses.

Pre‐Stretched Double Network Polymer Films Based on Agarose and Polyacrylamide with Sensitive Humidity‐Responsive Deformation, Shape Memory, and Self‐Healing Properties

AbstractA series of pre‐stretched double network (DN) polymer films based on agarose and polyacrylamide (Agar/PAM) are prepared. These films show the rapid and large deformation in response to humidity due to the release of contraction stress. The pre‐stretched dry film can curl toward the humidity direction into a scroll‐like structure in an extremely short time. The deformation direction can be also well controlled by the stretching direction. The released contraction stress increases with the increase of tensile strain. The DN Agar/PAM hydrogel film shows good water‐induced shape memory effect. It can be stretched to form various temporary shapes such as circle, square, and spiral. The shape fixing and recovery ratios are both close to 100%. The released large contraction stress accelerates the shape recovery process. The recovery time increases with the increase of film thickness. The DN dry film shows the good water‐induced self‐healing ability. The healed film maintains about 88% tensile strength (103 MPa) of the original film. Due to these good properties, the pre‐stretched DN dry films can be fabricated into a soft robot jack which can easily lift up to ≈20 times its own weight within 8 s.

Evaluation of the correlation between job stress and sleep quality in community nurses.

Chronic sleep deprivation may worsen many medical and mental health conditions, causing difficulty in the ability to function at work. Job stress may be a factor that directly correlates with the poorer sleep quality of nurses from different departments in a general hospital. However, epidemiological evaluations of sleep problems among community nurses in China are scarce, and an association between sleep problems and occupational stress has not been investigated. This study investigated the association between nurses’ job stress and sleep quality in a community hospital in China. This cross-sectional study was conducted from September to November 2017 and involved 180 nurses who had worked for more than 1 year in 12 community hospitals. The Job Stress Questionnaire was administered to evaluate occupational stress. The Pittsburgh Sleep Quality Index was used to evaluate sleep disorder status. Logistic regression was performed to investigate the association between job stress and sleep disorder among these community nurses in China. For the 155 nurses who completed the study, the job stress score was 58 ± 18, and 72 nurses (46%) had a Pittsburgh Sleep Quality Index (PSQI > 7). The type of nurse contract and total job stress scores were related to sleep disturbances within the previous month. The job stress scores were negatively associated with sleep quality; in other words, the higher the job stress scores were, the worse the quality of sleep. The logistic regression analysis showed that the type of nurse contract and self-reported job stress were significant factors affecting sleep quality. Sleep disturbances in nurses were highly associated with job difficulty factor, doctor-patient relationships, psychosomatic state, environment or events, promotion or competition and total pressure scores. Sleep problems were prevalent among clinical nurses in community hospitals in China. Occupational stress negatively affects sleep quality in Chinese community nurses; the higher the stress is, the worse the sleep quality.

Investigation on the Shape Distortions of Pultruded Profiles at Different Pulling Speed

Pultrusion is a continuous technique for manufacturing of polymer composites which combines automation and versatility. The main factors behind the wide application of the process are the enhanced productivity and the remarkable mechanical properties achievable. Nevertheless, the quality of pultruded products dramatically depends on the choice of the process parameters. As a matter of fact, pultrusion presents numerous tunable parameters, such as the temperature of the heating plates or the pulling speed, because most of the polymerization reaction of the resin occurs within the curing-forming die in a short time. Resin shrinkage, thermal contraction and residual internal stresses change the geometry of the profiles after their production. Process related stresses typically result in distortions evolving for months after the process, which can lead to out of geometrical tolerances. The present paper discusses an experimental/numerical investigation of the shape distortions of L-shaped profiles made of epoxy-based resin reinforced with E-glass rovings and unidirectional glass fabrics. The samples were pultruded at three different pulling speeds, namely 200, 400 and 600 mm/min. For each of them, the spring-in angle was periodically measured for the 90 days following production. The results show the dependence of the shape distortions on pulling speed and on time.

Strength Behaviour of Blended Self Cured Concrete made with Cement by partial replacement of Supplementary Cementitious Materials (SCM’s)

At Present Water is the most essential material in the modern era. In general, Curing of concrete is retaining moisture in the concrete for the period of early ages precisely within 28 days of placing concrete, to improve anticipated properties. Appropriate curing of concrete is crucial to obtain extreme durability, especially if the concrete is exposed to serve conditions where the surface will be imperiled to excessive wear, assertive solutions, and severe environmental circumstances. Poor curing practices adversely affect the desirable properties of concrete which constitutes a major influence on the permeability of a given concrete.Unpredicted shrinkage and temperature cracks be able to diminish the strength, durability and serviceability properties of the concrete. The surface zone will be critically damaged by increased permeability expected to poor curing. The improvement of shrinkage in concrete is proportionate to the rate of moisture loss in concrete. When concrete is correctly cured, water preserved in concrete would facilitate continuous hydration and enhancement of enough compressive and tensile strength to withstand contraction stresses. The incessant development of strength reduces shrinkage and initial cracks or micro-cracks. As a part of this study, SCMs like Flyash (FA), Ground Granulated furnace Slag (GGBS), Silica Fume (SF). Concrete may be a mixture of cement, aggregates and water with / without suitable admixtures with self-curing agents and various proportions, which resulted in the early strength to reduce the autogenous shrinkage and increase in durability.

Genetic and functional implications of an exonic TRIM55 variant in heart failure

BackgroundTo tackle the missing heritability of sporadic heart failure, we screened for novel heart failure-associated genetic variants in the Finnish population and functionally characterized a novel variant in vitro and in vivo. Methods and resultsHeart failure-associated variants were screened in genotyping array data of the FINRISK study, consisting of 994 cases and 20,118 controls. Based on logistic regression analysis, a potentially damaging variant in TRIM55 (rs138811034), encoding an E140K variant, was selected for validations. In HL-1 cardiomyocytes, we used CRISPR/Cas9 technology to introduce the variant in the endogenous locus, and additionally TRIM55 wildtype or E140K was overexpressed from plasmid. Functional responses were profiled using whole-genome RNA sequencing, RT-PCR and Western analyses, cell viability and cell cycle assays and cell surface area measurements. In zebrafish embryos, cardiac contractility was measured using videomicroscopy after CRISPR-mediated knockout of trim55a or plasmid overexpression of TRIM55 WT or E140K. Genes related to muscle contraction and cardiac stress were highly regulated in Trim55 E140K/− cardiomyocytes. When compared to the WT/WT cells, the variant cells demonstrated reduced viability, significant hypertrophic response to isoproterenol, p21 protein overexpression and impaired cell cycle progression. In zebrafish embryos, the deletion of trim55a or overexpression of TRIM55 E140K reduced cardiac contractility as compared to embryos with wildtype genotype or overexpression of WT TRIM55, respectively. ConclusionsA previously uncharacterized TRIM55 E140K variant demonstrated a number of functional implications for cardiomyocyte functions in vitro and in vivo. These findings suggest a novel role for TRIM55 polymorphism in predisposing to heart failure.

Adult human cardiac stem cell supplementation effectively increases contractile function and maturation in human engineered cardiac tissues

BackgroundDelivery of stem cells to the failing heart is a promising therapeutic strategy. However, the improvement in cardiac function in animal studies has not fully translated to humans. To help bridge the gap between species, we investigated the effects of adult human cardiac stem cells (hCSCs) on contractile function of human engineered cardiac tissues (hECTs) as a species-specific model of the human myocardium.MethodsHuman induced pluripotent stem cell-derived cardiomyoctes (hCMs) were mixed with Collagen/Matrigel to fabricate control hECTs, with an experimental group of hCSC-supplemented hECT fabricated using a 9:1 ratio of hCM to hCSC. Functional testing was performed starting on culture day 6, under spontaneous conditions and also during electrical pacing from 0.25 to 1.0 Hz, measurements repeated at days 8 and 10. hECTs were then frozen and processed for gene analysis using a Nanostring assay with a cardiac targeted custom panel.ResultsThe hCSC-supplemented hECTs displayed a twofold higher developed force vs. hCM-only controls by day 6, with approximately threefold higher developed stress and maximum rates of contraction and relaxation during pacing at 0.75 Hz. The spontaneous beat rate characteristics were similar between groups, and hCSC supplementation did not adversely impact beat rate variability. The increased contractility persisted through days 8 and 10, albeit with some decrease in the magnitude of the difference of the force by day 10, but with developed stress still significantly higher in hCSC-supplemented hECT; these findings were confirmed with multiple hCSC and hCM cell lines. The force-frequency relationship, while negative for both, control (− 0.687 Hz− 1; p = 0.013 vs. zero) and hCSC-supplemented (− 0.233 Hz− 1;p = 0.067 vs. zero) hECTs, showed a significant rectification in the regression slope in hCSC-supplemented hECT (p = 0.011 vs. control). Targeted gene exploration (59 genes) identified a total of 14 differentially expressed genes, with increases in the ratios of MYH7/MHY6, MYL2/MYL7, and TNNI3/TNNI1 in hCSC-supplemented hECT versus controls.ConclusionsFor the first time, hCSC supplementation was shown to significantly improve human cardiac tissue contractility in vitro, without evidence of proarrhythmic effects, and was associated with increased expression of markers of cardiac maturation. These findings provide new insights about adult cardiac stem cells as contributors to functional improvement of human myocardium.

An investigation on solidification path and hot tearing tendency of Mg−2Zn−3Y−xAl alloys

AbstractBased on the improved Clyne‐Davies’ model (CSCT), the hot tearing tendency of Mg−2Zn−3Y−xAl (x = 0, 0.5, 1, 2, wt.%) alloys were predicted. The concretion path, the solidification characteristic temperature, the dendrite coherent solid fraction were studied by the double thermocouples thermal analysis. The curve of solidification contraction stress with temperature (or time) was measured with a “T” type hot tearing permanent‐mold. The experimental results show that the modified Clyne‐Davies’ model prediction values are in good agreement with the experimental results. Al2Y phase can be used as the heterogeneous nucleation core of α‐Mg matrix and refine the α‐Mg grain size. It is found that Al2Y increases, grain refinement is more obvious, dendrite coherence is postponed, and the hot tearing susceptibility of the alloy decreases significantly with increasing aluminum content.

Role of spot weld electrode geometry on liquid metal embrittlement crack development

Advanced high strength steels (AHSS) used in automotive structural components are commonly protected using zinc coatings. However, the steel/zinc system creates the potential for liquid metal embrittlement (LME) during welding. Recent studies have examined the impact of the welding electrode geometry on LME cracking severity and found there to be some effect, but did not explore the responsible mechanisms for the changes. This work shows that a radius tip electrode provides minimal cracking while a truncated cone shape showed severe LME, particularly in the shoulder region. Thermo-mechanical simulations showed the significance of the thermal contact at the outer region of the electrode/sheet interface (weld shoulder). It was observed that when the water-cooled electrode presses into the steel during the welding, causing a contact between the steel surface and the electrode sidewall, a sudden local cooling of the weld shoulder occurs. This cooling causes contraction and tensile stresses on the material surface, leading to LME. Additionally, the magnitude and location of heat transfer between the steel and electrode is controlled by the thermal contact conductance.

Extensive Polygonal Fracture Network in Siccar Point group Strata: Fracture Mechanisms and Implications for Fluid Circulation in Gale Crater, Mars

AbstractRock fractures are indicators of stress release within geologic systems, and fracture morphologies can commonly be used to infer formation conditions. Polygonal fractures are common in isotropic, contractional stress regimes such as in rocks exposed at the surface of a planet undergoing thermal cycling or in sedimentary substrates undergoing repeated wetting and drying. Such polygonal fracture systems, on centimeter to decameter scales, have been widely documented on Mars. Utilizing a combination of orbital‐ and ground‐based images, we report a laterally extensive polygonal fracture network that occurs within siliciclastic rocks of the lowermost Siccar Point group, Gale crater, Mars. The Siccar Point group is exposed over approximately 20 km2 in northwest Gale crater, where it unconformably overlies eroded strata of Mount Sharp (Aeolis Mons) and reflects likely aeolian deposition along the lower flanks of Mount Sharp. Images reveal an extensive network of erosionally resistant polygons, approximately 7.5 m across, that exhibit interior angles (i.e., fracture intersections) with modes at 90° and 120°. Polygon morphology indicates that fractures formed during multiple cycles of expansion and contraction, which is attributed to desiccation and subsequent recharge of near‐surface groundwater. The erosional resistance of preserved fractures is inferred to reflect postfracture diagenetic fluid flow along the sub–Siccar Point group unconformity and cementation. Evidence for multiple fluid events in the relatively young strata of the Siccar Point group requires a protracted history of fluid stability in Gale crater.

Theoretical elastic tensile behavior of muscle fiber bundles in traumatic loading events

BackgroundThe mechanical characterization of skeletal muscle under high-rate loading regimes is important for predicting traumatic injuries due to traffic accidents and contact sports. However, it is difficult to perform dynamic mechanical tests at rates relevant to such rapid loading events. MethodsIn the present study, a series of stress relaxation tests were conducted on rabbit hind-limb muscle fiber bundles using a custom tensile tester. Using relatively moderate loading conditions compared to those typically associated with traumatic injuries, the passive stress-decaying mechanical properties of muscle fiber bundles were characterized. In addition, stress relaxation responses to various ramp-hold stretches were theoretically predicted by a custom-built code. FindingsThe results showed that the muscle fiber bundles exhibit greater stress relaxation at higher loading rates and greater stretch magnitudes. Based on these results, the data points representing the “elastic” stress–strain tensile behavior typical of traumatic injury were extrapolated using curve fitting. The theoretical model revealed rate-dependent characteristics of the muscle fiber bundles under traumatic loading conditions, which would result in tensile strengths of 300–500 kPa at the maximum engineering strain of 54%. This strength is on the order of magnitude as the maximum isometric stress of an active muscle contraction. InterpretationThe proposed numerical model is expected to serve as a powerful research tool to investigate injury mechanisms of the skeletal muscle. Moreover, the elastic response that was theoretically predicted here will be useful in the development of effective countermeasures to prevent traumatic injuries due to rapid loading events.

Response of building to shallow tunnel excavation in different types of soil

This research investigates the tunneling induced building responses in different types of soil via finite element (FE) method. Different simulation techniques, namely contraction factor method and stress reduction method, are applied in FE-model to simulate the volume loss during the excavation process. A wide range of soils, including limestone, dense/loose sand, stiff/soft clay and silt, are taken into account in this study. The considered building responses include the surface settlement profile, position of inflection point, deflection ratio in sagging/hogging zone, horizontal compressive/tensile strain, etc. The relationship between these building responses and soil/building properties is investigated. Local sensitivity analysis is further applied to distinguish the relative importance of soil stiffness and strength in determining the deflection ratio of the building settlement profile. The results show that soil properties play a significant role in determining the building responses. Generally, soil with larger initial elastic modulus results in higher deflection ratios and horizontal strains of the building. Furthermore, in order to provide a guideline for practical tunneling design, an upper bound design curve of modification factor to greenfield deflection ratio or horizontal strain for different types of building is derived in both sagging and hogging zones.