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Sample records for compressive stress induced

  1. IL-13 Augments Compressive Stress-Induced Tissue Factor Expression in Human Airway Epithelial Cells.

    PubMed

    Mitchel, Jennifer A; Antoniak, Silvio; Lee, Joo-Hyeon; Kim, Sae-Hoon; McGill, Maureen; Kasahara, David I; Randell, Scott H; Israel, Elliot; Shore, Stephanie A; Mackman, Nigel; Park, Jin-Ah

    2016-04-01

    Tissue factor (TF) is best known as a cellular initiator of coagulation, but it is also a multifunctional protein that has been implicated in multiple pathophysiologic conditions, including asthma. In the lung, airway epithelial cells express TF, but it is unknown how TF expression is regulated by asthma-associated mediators. We investigated the role of IL-13, a type 2 cytokine, alone and in combination with compressive stress, which mimics asthmatic bronchoconstriction, on TF expression and release of TF-positive extracellular vesicles from primary normal human bronchial epithelial cells. Well-differentiated normal human bronchial epithelial cells were treated with IL-13 and compressive stress, alone and in combination. TF mRNA, protein and activity were measured in the cells and conditioned media. TF was also measured in the bronchoalveolar lavage (BAL) fluid of allergen-challenged mice and patients with asthma. IL-13 and compressive stress increased TF expression, but only compressive stress induced TF-positive extracellular vesicle release. Pretreatment with IL-13 augmented compressive stress-induced TF expression and release. TF protein and activity in BAL fluid were increased in allergen-sensitized and -challenged mice. TF was elevated in the BAL fluid of patients with mild asthma after an allergen challenge. Our in vitro and in vivo data indicate close cooperation between mechanical and inflammatory stimuli on TF expression and release of TF-positive extracellular vesicles in the lungs, which may contribute to pathophysiology of asthma. PMID:26407210

  2. Compression loading-induced stress responses in intervertebral disc cells encapsulated in 3D collagen constructs

    PubMed Central

    Chooi, Wai Hon; Chan, Barbara Pui

    2016-01-01

    Cells protect themselves from stresses through a cellular stress response. In the interverebral disc, such response was also demonstrated to be induced by various environmental stresses. However, whether compression loading will cause cellular stress response in the nucleus pulposus cells (NPCs) is not well studied. By using an in vitro collagen microencapsulation model, we investigated the effect of compression loading on the stress response of NPCs. Cell viability tests, and gene and protein expression experiments were conducted, with primers for the heat shock response (HSR: HSP70, HSF1, HSP27 and HSP90), and unfolded protein response (UPR: GRP78, GRP94, ATF4 and CHOP) genes and an antibody to HSP72. Different gene expression patterns occurred due to loading type throughout experiments. Increasing the loading strain for a short duration did not increase the stress response genes significantly, but over longer durations, HSP70 and HSP27 were upregulated. Longer loading durations also resulted in a continuous upregulation of HSR genes and downregulation of UPR genes, even after load removal. The rate of apoptosis did not increase significantly after loading, suggesting that stress response genes might play a role in cell survival following mechanical stress. These results demonstrate how mechanical stress might induce and control the expression of HSR and UPR genes in NPCs. PMID:27197886

  3. Compression loading-induced stress responses in intervertebral disc cells encapsulated in 3D collagen constructs.

    PubMed

    Chooi, Wai Hon; Chan, Barbara Pui

    2016-01-01

    Cells protect themselves from stresses through a cellular stress response. In the interverebral disc, such response was also demonstrated to be induced by various environmental stresses. However, whether compression loading will cause cellular stress response in the nucleus pulposus cells (NPCs) is not well studied. By using an in vitro collagen microencapsulation model, we investigated the effect of compression loading on the stress response of NPCs. Cell viability tests, and gene and protein expression experiments were conducted, with primers for the heat shock response (HSR: HSP70, HSF1, HSP27 and HSP90), and unfolded protein response (UPR: GRP78, GRP94, ATF4 and CHOP) genes and an antibody to HSP72. Different gene expression patterns occurred due to loading type throughout experiments. Increasing the loading strain for a short duration did not increase the stress response genes significantly, but over longer durations, HSP70 and HSP27 were upregulated. Longer loading durations also resulted in a continuous upregulation of HSR genes and downregulation of UPR genes, even after load removal. The rate of apoptosis did not increase significantly after loading, suggesting that stress response genes might play a role in cell survival following mechanical stress. These results demonstrate how mechanical stress might induce and control the expression of HSR and UPR genes in NPCs. PMID:27197886

  4. Axisymmetric deformations and stresses of unsymmetrically laminated composite cylinders in axial compression with thermally-induced preloading effects

    NASA Technical Reports Server (NTRS)

    Paraska, Peter J.

    1993-01-01

    This report documents an analytical study of the response of unsymmetrically laminated cylinders subjected to thermally-induced preloading effects and compressive axial load. Closed-form solutions are obtained for the displacements and intralaminar stresses and recursive relations for the interlaminar shear stress were obtained using the closed-form intralaminar stress solutions. For the cylinder geometries and stacking sequence examples analyzed, several important and as yet undocumented effects of including thermally-induced preloading in the analysis are observed. It should be noted that this work is easily extended to include uniform internal and/or external pressure loadings and the application of strain and stress failure theories.

  5. Measurement and control for mechanical compressive stress

    NASA Astrophysics Data System (ADS)

    Li, Qing; Ye, Guang; Pan, Lan; Wu, Xiushan

    2001-12-01

    At present, the indirect method is applied to measuring and controlling mechanical compressive stress, which is the measurement and control of rotating torque of screw with torque transducer during screw revolving. Because the friction coefficient between every screw-cap and washer, of screw-thread is different, the compressive stress of every screw may is different when the machinery is equipped. Therefore, the accurate measurement and control of mechanical compressive stress is realized by the direct measurement of mechanical compressive stress. The author introduces the research of contrast between compressive stress and rotating torque in the paper. The structure and work principle of a special washer type transducer is discussed emphatically. The special instrument cooperates with the washer type transducer for measuring and controlling mechanical compressive stress. The control tactics based on the rate of compressive stress is put to realize accurate control of mechanical compressive stress.

  6. Finite element stress analysis of a compression mold. Final report. [Using SASL and WILSON codes

    SciTech Connect

    Watterson, C.E.

    1980-03-01

    Thermally induced stresses occurring in a compression mold during production molding were evaluated using finite element analysis. A complementary experimental stress analysis, including strain gages and thermocouple arrays, verified the finite element model under typical loading conditions.

  7. Compressive stress system for a gas turbine engine

    DOEpatents

    Hogberg, Nicholas Alvin

    2015-03-24

    The present application provides a compressive stress system for a gas turbine engine. The compressive stress system may include a first bucket attached to a rotor, a second bucket attached to the rotor, the first and the second buckets defining a shank pocket therebetween, and a compressive stress spring positioned within the shank pocket.

  8. Turbulent shear stresses in compressible boundary layers

    NASA Technical Reports Server (NTRS)

    Laderman, A. J.; Demetriades, A.

    1979-01-01

    Hot-wire anemometer measurements of turbulent shear stresses in a Mach 3 compressible boundary layer were performed in order to investigate the effects of heat transfer on turbulence. Measurements were obtained by an x-probe in a flat plate, zero pressure gradient, two dimensional boundary layer in a wind tunnel with wall to freestream temperature ratios of 0.94 and 0.71. The measured shear stress distributions are found to be in good agreement with previous results, supporting the contention that the shear stress distribution is essentially independent of Mach number and heat transfer for Mach numbers from incompressible to hypersonic and wall to freestream temperature ratios of 0.4 to 1.0. It is also found that corrections for frequency response limitations of the electronic equipment are necessary to determine the correct shear stress distribution, particularly at the walls.

  9. Estimation of the Iron Loss in Deep-Sea Permanent Magnet Motors considering Seawater Compressive Stress

    PubMed Central

    Wei, Yanyu; Zou, Jibin; Li, Jianjun; Qi, Wenjuan; Li, Yong

    2014-01-01

    Deep-sea permanent magnet motor equipped with fluid compensated pressure-tolerant system is compressed by the high pressure fluid both outside and inside. The induced stress distribution in stator core is significantly different from that in land type motor. Its effect on the magnetic properties of stator core is important for deep-sea motor designers but seldom reported. In this paper, the stress distribution in stator core, regarding the seawater compressive stress, is calculated by 2D finite element method (FEM). The effect of compressive stress on magnetic properties of electrical steel sheet, that is, permeability, BH curves, and BW curves, is also measured. Then, based on the measured magnetic properties and calculated stress distribution, the stator iron loss is estimated by stress-electromagnetics-coupling FEM. At last the estimation is verified by experiment. Both the calculated and measured results show that stator iron loss increases obviously with the seawater compressive stress. PMID:25177717

  10. Polymer-induced compression of biological hydrogels

    NASA Astrophysics Data System (ADS)

    Datta, Sujit; Preska Steinberg, Asher; Ismagilov, Rustem

    Hydrogels - such as mucus, blood clots, and the extracellular matrix - provide critical functions in biological systems. However, little is known about how their structure is influenced by many of the polymeric materials they come into contact with regularly. Here, we focus on one critically important biological hydrogel: colonic mucus. While several biological processes are thought to potentially regulate the mucus hydrogel structure, the polymeric composition of the gut environment has been ignored. We use Flory-Huggins solution theory to characterize polymer-mucus interactions. We find that gut polymers, including those small enough to penetrate the mucus hydrogel, can in fact alter mucus structure, changing its equilibrium degree of swelling and forcing it to compress. The extent of compression increases with increasing polymer concentration and size. We use experiments on mice to verify these predictions with common dietary and therapeutic gut polymers. Our results provide a foundation for investigating similar, previously overlooked, polymer-induced effects in other biological hydrogels.

  11. Toward compression of small cell population: harnessing stress in passive regions of dielectric elastomer actuators

    NASA Astrophysics Data System (ADS)

    Poulin, Alexandre; Rosset, Samuel; Shea, Herbert

    2014-03-01

    We present a dielectric elastomer actuator (DEA) for in vitro analysis of mm2 biological samples under periodic compressive stress. Understanding how mechanical stimuli affect cell functions could lead to significant advances in diseases diagnosis and drugs development. We previously reported an array of 72 micro-DEAs on a chip to apply a periodic stretch to cells. To diversify our cell mechanotransduction toolkit we have developed an actuator for periodic compression of small cell populations. The device is based on a novel design which exploits the effects of non-equibiaxial pre-stretch and takes advantage of the stress induced in passive regions of DEAs. The device consists of two active regions separated by a 2mm x 2mm passive area. When connected to an AC high-voltage source, the two active regions periodically compress the passive region. Due to the non-equibiaxial pre-stretch it induces uniaxial compressive strain greater than 10%. Cells adsorbed on top of this passive gap would experience the same uniaxial compressive stain. The electrodes configuration confines the electric field and prevents it from reaching the biological sample. A thin layer of silicone is casted on top of the device to ensure a biocompatible environment. This design provides several advantages over alternative technologies such as high optical transparency of the area of interest (passive region under compression) and its potential for miniaturization and parallelization.

  12. Gravity-induced stresses in finite slopes

    USGS Publications Warehouse

    Savage, W.Z.

    1994-01-01

    An exact solution for gravity-induced stresses in finite elastic slopes is presented. This solution, which is applied for gravity-induced stresses in 15, 30, 45 and 90?? finite slopes, has application in pit-slope design, compares favorably with published finite element results for this problem and satisfies the conditions that shear and normal stresses vanish on the ground surface. The solution predicts that horizontal stresses are compressive along the top of the slopes (zero in the case of the 90?? slope) and tensile away from the bottom of the slopes, effects which are caused by downward movement and near-surface horizontal extension in front of the slope in response to gravity loading caused by the additional material associated with the finite slope. ?? 1994.

  13. The elastic moduli and diametrical compressive fracture stress of ? - ? ceramics

    NASA Astrophysics Data System (ADS)

    Tan, K. S.; Hing, P.; Ramalingam, P.

    1997-03-01

    Young's moduli of green and sintered unstabilized 0022-3727/30/6/017/img8 - 0022-3727/30/6/017/img9 ceramics have been determined by measuring compression and shear velocities through the material and, from separate measurements, the associated bulk density. Young's modulus and sintered density of 0022-3727/30/6/017/img8 - 0022-3727/30/6/017/img9 ceramics can be enhanced by increasing the compacting pressure when forming the green ceramics and with the addition of <5 wt% of unstabilized 0022-3727/30/6/017/img9. For a particular green compacting pressure, the trend in the diametrical compressive fracture stress is similar to that of Young's modulus. The fracture stress also increases with a higher green compacting pressure at a constant wt% 0022-3727/30/6/017/img9.

  14. Does stress induce bowel dysfunction?

    PubMed

    Chang, Yu-Ming; El-Zaatari, Mohamad; Kao, John Y

    2014-08-01

    Psychological stress is known to induce somatic symptoms. Classically, many gut physiological responses to stress are mediated by the hypothalamus-pituitary-adrenal axis. There is, however, a growing body of evidence of stress-induced corticotrophin-releasing factor (CRF) release causing bowel dysfunction through multiple pathways, either through the HPA axis, the autonomic nervous systems, or directly on the bowel itself. In addition, recent findings of CRF influencing the composition of gut microbiota lend support for the use of probiotics, antibiotics, and other microbiota-altering agents as potential therapeutic measures in stress-induced bowel dysfunction. PMID:24881644

  15. The surgically induced stress response.

    PubMed

    Finnerty, Celeste C; Mabvuure, Nigel Tapiwa; Ali, Arham; Kozar, Rosemary A; Herndon, David N

    2013-09-01

    The stress response to surgery, critical illness, trauma, and burns encompasses derangements of metabolic and physiological processes that induce perturbations in the inflammatory, acute phase, hormonal, and genomic responses. Hypermetabolism and hypercatabolism result, leading to muscle wasting, impaired immune function and wound healing, organ failure, and death. The surgery-induced stress response is largely similar to that triggered by traumatic injuries; the duration of the stress response, however, varies according to the severity of injury (surgical or traumatic). This spectrum of injuries and insults ranges from small lacerations to severe insults such as large poly-traumatic and burn injuries. Burn injuries provide an extreme model of trauma induced stress responses that can be used to study the long-term effects of a prolonged stress response. Although the stress response to acute trauma evolved to confer improved chances of survival following injury, in modern surgical practice the stress response can be detrimental. PMID:24009246

  16. Intermittent Compressive Stress Enhanced Insulin-Like Growth Factor-1 Expression in Human Periodontal Ligament Cells

    PubMed Central

    Pumklin, Jittima; Manokawinchoke, Jeeranan; Bhalang, Kanokporn; Pavasant, Prasit

    2015-01-01

    Mechanical force was shown to promote IGF-1 expression in periodontal ligament both in vitro and in vivo. Though the mechanism of this effect has not yet been proved, here we investigated the molecular mechanism of intermittent mechanical stress on IGF-1 expression. In addition, the role of hypoxia on the intermittent compressive stress on IGF-1 expression was also examined. In this study, human periodontal ligament cells (HPDLs) were stimulated with intermittent mechanical stress for 24 hours. IGF-1 expression was examined by real-time polymerase chain reaction. Chemical inhibitors were used to determine molecular mechanisms of these effects. For hypoxic mimic condition, the CoCl2 supplementation was employed. The results showed that intermittent mechanical stress dramatically increased IGF-1 expression at 24 h. The pretreatment with TGF-β receptor I or TGF-β1 antibody could inhibit the intermittent mechanical stress-induced IGF-1 expression. Moreover, the upregulation of TGF-β1 proteins was detected in intermittent mechanical stress treated group. Correspondingly, the IGF-1 expression was upregulated upon being treated with recombinant human TGF-β1. Further, the hypoxic mimic condition attenuated the intermittent mechanical stress and rhTGF-β1-induced IGF-1 expression. In summary, this study suggests intermittent mechanical stress-induced IGF-1 expression in HPDLs through TGF-β1 and this phenomenon could be inhibited in hypoxic mimic condition. PMID:26106417

  17. The Surgically Induced Stress Response

    PubMed Central

    Finnerty, Celeste C.; Mabvuure, Nigel Tapiwa; Ali, Arham; Kozar, Rosemary A.; Herndon, David N.

    2013-01-01

    The stress response to surgery, critical illness, trauma, and burns encompasses derangements of metabolic and physiological processes which induce perturbations in the inflammatory, acute phase, hormonal, and genomic responses. Hypermetabolism and hypercatabolism result, leading to muscle wasting, impaired immune function and wound healing, organ failure, and death. The surgery-induced stress response is largely similar to that triggered by traumatic injuries; the duration of the stress response, however, varies according to the severity of injury (surgical or traumatic). This spectrum of injuries and insults ranges from small lacerations to severe insults such as large poly-traumatic and burn injuries. Although the stress response to acute trauma evolved to improve chances of survival following injury, in modern surgical practice the stress response can be detrimental. PMID:24009246

  18. A study of turbulence on compression ramps with k-epsilon and Reynolds stress models

    NASA Technical Reports Server (NTRS)

    Lee, J.; Taulbee, D. B.; Holden, M. S.

    1990-01-01

    A theoretical study was conducted to determine the effects of adverse pressure gradient and compressibility in modeling turbulent compressible flows. The kinetic energy/dissipation and Reynolds stress model predictions are presented and compared with experimental data. The effects of compressibility, which include the mass averaged fluctuation term, the pressure dilatation term, and the dilatation dissipation, are important in modeling the turbulent compressible flows. The normal stresses and longitudinal strain rates also have an effect in the prediction of turbulent energy productions on the curved surfaces. A new compressible formulation of the pressure strain term, which includes the dilatation effects, in the Reynolds stress equation is presented.

  19. Effect of Compressive Stresses on Leakage Currents in Microchip Tantalum Capacitors

    NASA Technical Reports Server (NTRS)

    Teverovsky, Alexander

    2012-01-01

    Microchip tantalum capacitors are manufactured using new technologies that allow for production of small size capacitors (down to EIA case size 0402) with volumetric efficiency much greater than for regular chip capacitors. Due to a small size of the parts and leadless design they might be more sensitive to mechanical stresses that develop after soldering onto printed wiring boards (PWB) compared to standard chip capacitors. In this work, the effect of compressive stresses on leakage currents in capacitors has been investigated in the range of stresses up to 200 MPa. Significant, up to three orders of magnitude, variations of currents were observed after the stress exceeds a certain critical level that varied from 10 MPa to 180 MPa for capacitors used in this study. A stress-induced generation of electron traps in tantalum pentoxide dielectric is suggested to explain reversible variations of leakage currents in tantalum capacitors. Thermo-mechanical characteristics of microchip capacitors have been studied to estimate the level of stresses caused by assembly onto PWB and assess the risk of stress-related degradation and failures. Keywords: tantalum capacitors, leakage current, soldering, reliability, mechanical stress.

  20. Stress-induced cervical lesions.

    PubMed

    Braem, M; Lambrechts, P; Vanherle, G

    1992-05-01

    The increasing occurrence of dental lesions at the cervical surfaces requires more knowledge of the causes of the process. Acidic and abrasive mechanisms have clearly been documented as causes but the stress theory by Lee and Eakle is still controversial. This report describes several incidences of possible stress-induced lesions according to the characteristics described by Lee and Eakle. The occurrences of subgingival lesions lend credence to the stress-induction theory by exclusion of other superimposing etiologic factors. With the current concepts, a perceptive approach to the treatment of cervical lesions can be executed. PMID:1527763

  1. Antioxidant-Induced Stress

    PubMed Central

    Villanueva, Cleva; Kross, Robert D.

    2012-01-01

    Antioxidants are among the most popular health-protecting products, sold worldwide without prescription. Indeed, there are many reports showing the benefits of antioxidants but only a few questioning the possible harmful effects of these “drugs”. The normal balance between antioxidants and free radicals in the body is offset when either of these forces prevails. The available evidence on the harmful effects of antioxidants is analyzed in this review. In summary, a hypothesis is presented that “antioxidant-induced stress” results when antioxidants overwhelm the body’s free radicals. PMID:22408440

  2. Impact of local compressive stress on the optical transitions of single organic dye molecules

    NASA Astrophysics Data System (ADS)

    Stöttinger, Sven; Hinze, Gerald; Diezemann, Gregor; Oesterling, Ingo; Müllen, Klaus; Basché, Thomas

    2014-03-01

    The ability to mechanically control the optical properties of individual molecules is a grand challenge in nanoscience and could enable the manipulation of chemical reactivity at the single-molecule level. In the past, light has been used to alter the emission wavelength of individual molecules or modulate the energy transfer quantum yield between them. Furthermore, tensile stress has been applied to study the force dependence of protein folding/unfolding and of the chemistry and photochemistry of single molecules, although in these mechanical experiments the strength of the weakest bond limits the amount of applicable force. Here, we show that compressive stress modifies the photophysical properties of individual dye molecules. We use an atomic force microscope tip to prod individual molecules adsorbed on a surface and follow the effect of the applied force on the electronic states of the molecule by fluorescence spectroscopy. Applying a localized compressive force on an isolated molecule induces a stress that is redistributed throughout the structure. Accordingly, we observe reversible spectral shifts and even shifts that persist after retracting the microscope tip, which we attribute to transitions to metastable states. Using quantum-mechanical calculations, we show that these photophysical changes can be associated with transitions among the different possible conformers of the adsorbed molecule.

  3. Induced groundwater flux by increases in the aquifer's total stress.

    PubMed

    Chang, Ching-Min; Yeh, Hund-Der

    2015-01-01

    Fluid-filled granular soils experience changes in total stress because of earth and oceanic tides, earthquakes, erosion, sedimentation, and changes in atmospheric pressure. The pore volume may deform in response to the changes in stress and this may lead to changes in pore fluid pressure. The transient fluid flow can therefore be induced by the gradient in excess pressure in a fluid-saturated porous medium. This work demonstrates the use of stochastic methodology in prediction of induced one-dimensional field-scale groundwater flow through a heterogeneous aquifer. A closed-form of mean groundwater flux is developed to quantify the induced field-scale mean behavior of groundwater flow and analyze the impacts of the spatial correlation length scale of log hydraulic conductivity and the pore compressibility. The findings provided here could be useful for the rational planning and management of groundwater resources in aquifers that contain lenses with large vertical aquifer matrix compressibility values. PMID:25178834

  4. Numerical Simulation of Airfoil Vibrations Induced by Compressible Flow

    NASA Astrophysics Data System (ADS)

    Feistauer, Miloslav; Kučera, Václav; Šimánek, Petr

    2010-09-01

    The paper is concerned with the numerical solution of interaction of compressible flow and a vibrating airfoil with two degrees of freedom, which can rotate around an elastic axis and oscillate in the vertical direction. Compressible flow is described by the Euler or Navier-Stokes equations written in the ALE form. This system is discretized by the semi-implicit discontinuous Galerkin finite element method (DGFEM) and coupled with the solution of ordinary differential equations describing the airfoil motion. Computational results showing the flow induced airfoil vibrations are presented.

  5. One-dimensional patterning of cells in silicone wells via compression-induced fracture

    PubMed Central

    Dixon, Angela R.; Moraes, Christopher; Csete, Marie E.; Thouless, M. D.; Philbert, Martin A.; Takayama, Shuichi

    2014-01-01

    We have adapted our existing compression-induced fracture technology to cell culture studies, by generating linear patterns on a complex cell culture well structure, rather than on simple solid constructs. We present a simple method to create 1D, submicron, linear patterns of extracellular matrix on a multilayer silicone material. We identified critical design parameters necessary to optimize compression-induced fracture patterning on the wells, and applied stresses using compression Hoffman clamps. Finite-element analyses show that the incorporation of the well improves stress homogeneity (stress variation = 25%), and, thus, crack uniformity over the patterned region. Notably, a shallow well with a thick base (vs. deeper wells with thinner bases) reduces out-of-plane deflections by greater than a sixth in the cell culture region, improving clarity for optical imaging. The comparison of cellular and nuclear shape indices of a neuroblast line cultured on patterned 1D lines and unpatterned 2D surfaces reveals significant differences in cellular morphology, which could impact many cellular functions. Since 1D cell cultures recapitulate many important phenotypical traits of 3D cell cultures, our culture system offers a simple means to further study the relationship between 1D and 3D cell culture environments, without demanding expensive engineering techniques and expertise. PMID:23733484

  6. Drilling-induced core fractures and in situ stress

    NASA Astrophysics Data System (ADS)

    Li, Yongyi; Schmitt, Douglas R.

    1998-03-01

    The relationship between the shapes of drilling-induced core fractures and the in situ state of stress is developed. The stress concentrations at the well bore bottom are first determined using a complete three-dimensional finite element analysis. Existing in situ compressional stresses generate large tensions in the immediate vicinity of the bottom hole which are sufficient to rupture the rock. Tensile fracture trajectories within these concentrated stress fields are predicted using a simple model of fracture propagation. These modeled fracture trajectories resemble well the observed shapes of drilling-induced core disking, petal, and petal-centerline fractures. Further, this agreement suggests that both the shape of the drilling-induced fracture and the location at which it initiates depends on the in situ stress state existing in the rock mass prior to drilling; the core fractures contain substantial information on in situ stress conditions. In all faulting regimes the coring-induced fractures initiate near the bit cut except for most cases under thrust faulting regime where the fracture initiates on the well bore axis. Further, under thrust faulting conditions only disk fractures appear possible. Both petal and disking fractures can be produced in strike-slip and normal faulting regimes depending upon the relative magnitudes between the least compressive horizontal principal stress and the vertical overburden stress. The predicted fracture shapes are in good qualitative agreement with observations of drilling-induced fractures described in the literature from laboratory experiments and field programs in which in situ stresses are measured by other means. The relationship of the morphology of coring induced fractures and in situ stresses suggests that the fractures can be used as independent complementary indicators in identifying stress regimes.

  7. Change in dynamic young's modulus of nuclear-grade isotropic graphite during tensile and compressive stressing

    NASA Astrophysics Data System (ADS)

    Yoda, S.; Eto, M.; Oku, T.

    1983-12-01

    The effect of mechanical stresses on the dynamic Young's modulus measured by the ultrasonic wave method was examined for an isotropic graphite. Young's modulus of the graphite decreased with increasing applied stress, though the amount of its decrease was different between tensile and compressive stresses. The change in Young's modulus under mechanical stresses clearly corresponded to the stress-strain behavior of the graphite. Change in pore volume caused by mechanical stressing plays an important role in the decrease in Young's modulus under tension and compression. The change in Young's modulus was well represented by the formula E/E 0 = exp(- Aɛ + B) within a limited strain. A and B in the equation appeared to differ between tension and compression. The strain above which the formula showed deviation would be associated with the formation of cracks as observed in previous work.

  8. Chronic sciatic nerve compression induces fibrosis in dorsal root ganglia

    PubMed Central

    LI, QINWEN; CHEN, JIANGHAI; CHEN, YANHUA; CONG, XIAOBIN; CHEN, ZHENBING

    2016-01-01

    In the present study, pathological alterations in neurons of the dorsal root ganglia (DRG) were investigated in a rat model of chronic sciatic nerve compression. The rat model of chronic sciatic nerve compression was established by placing a 1 cm Silastic tube around the right sciatic nerve. Histological examination was performed via Masson's trichrome staining. DRG injury was assessed using Fluoro Ruby (FR) or Fluoro Gold (FG). The expression levels of target genes were examined using reverse transcription-quantitative polymerase chain reaction, western blot and immunohistochemical analyses. At 3 weeks post-compression, collagen fiber accumulation was observed in the ipsilateral area and, at 8 weeks, excessive collagen formation with muscle atrophy was observed. The collagen volume fraction gradually and significantly increased following sciatic nerve compression. In the model rats, the numbers of FR-labeled DRG neurons were significantly higher, relative to the sham-operated group, however, the numbers of FG-labeled neurons were similar. In the ipsilateral DRG neurons of the model group, the levels of transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF) were elevated and, surrounding the neurons, the levels of collagen type I were increased, compared with those in the contralateral DRG. In the ipsilateral DRG, chronic nerve compression was associated with significantly higher levels of phosphorylated (p)-extracellular signal-regulated kinase 1/2, and significantly lower levels of p-c-Jun N-terminal kinase and p-p38, compared with those in the contralateral DRGs. Chronic sciatic nerve compression likely induced DRG pathology by upregulating the expression levels of TGF-β1, CTGF and collagen type I, with involvement of the mitogen-activated protein kinase signaling pathway. PMID:26820076

  9. Chronic sciatic nerve compression induces fibrosis in dorsal root ganglia.

    PubMed

    Li, Qinwen; Chen, Jianghai; Chen, Yanhua; Cong, Xiaobin; Chen, Zhenbing

    2016-03-01

    In the present study, pathological alterations in neurons of the dorsal root ganglia (DRG) were investigated in a rat model of chronic sciatic nerve compression. The rat model of chronic sciatic nerve compression was established by placing a 1 cm Silastic tube around the right sciatic nerve. Histological examination was performed via Masson's trichrome staining. DRG injury was assessed using Fluoro Ruby (FR) or Fluoro Gold (FG). The expression levels of target genes were examined using reverse transcription‑quantitative polymerase chain reaction, western blot and immunohistochemical analyses. At 3 weeks post‑compression, collagen fiber accumulation was observed in the ipsilateral area and, at 8 weeks, excessive collagen formation with muscle atrophy was observed. The collagen volume fraction gradually and significantly increased following sciatic nerve compression. In the model rats, the numbers of FR‑labeled DRG neurons were significantly higher, relative to the sham‑operated group, however, the numbers of FG‑labeled neurons were similar. In the ipsilateral DRG neurons of the model group, the levels of transforming growth factor‑β1 (TGF‑β1) and connective tissue growth factor (CTGF) were elevated and, surrounding the neurons, the levels of collagen type I were increased, compared with those in the contralateral DRG. In the ipsilateral DRG, chronic nerve compression was associated with significantly higher levels of phosphorylated (p)‑extracellular signal‑regulated kinase 1/2, and significantly lower levels of p‑c‑Jun N‑terminal kinase and p‑p38, compared with those in the contralateral DRGs. Chronic sciatic nerve compression likely induced DRG pathology by upregulating the expression levels of TGF‑β1, CTGF and collagen type I, with involvement of the mitogen‑activated protein kinase signaling pathway. PMID:26820076

  10. High Compressive Stresses Near the Surface of the Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Martel, S. J.; Logan, J. M.; Stock, G. M.

    2012-12-01

    Observations and stress measurements in granitic rocks of the Sierra Nevada, California reveal strong compressive stresses parallel to the surface of the range at shallow depths. New overcoring measurements show high compressive stresses at three locations along an east-west transect through Yosemite National Park. At the westernmost site (west end of Tenaya Lake), the mean compressive stress is 1.9. At the middle site (north shore of Tenaya Lake) the mean compressive stress is 6.8 MPa. At the easternmost site (south side of Lembert Dome) the mean compressive stress is 3.0 MPa. The trend of the most compressive stress at these sites is within ~30° of the strike of the local topographic surface. Previously published hydraulic fracturing measurements by others elsewhere in the Sierra Nevada indicate surface-parallel compressive stresses of several MPa within several tens of meters of the surface, with the stress magnitudes generally diminishing to the west. Both the new and the previously published compressive stress magnitudes are consistent with the presence of sheeting joints (i.e., "exfoliation joints") in the Sierra Nevada, which require lateral compressive stresses of several MPa to form. These fractures are widespread: they are distributed in granitic rocks from the north end of the range to its southern tip and across the width of the range. Uplift along the normal faults of the eastern escarpment, recently measured by others at ~1-2 mm/yr, probably contributes to these stresses substantially. Geodetic surveys reveal that normal faulting flexes a range concave upwards in response to fault slip, and this flexure is predicted by elastic dislocation models. The topographic relief of the eastern escarpment of the Sierra Nevada is 2-4 km, and since alluvial fill generally buries the bedrock east of the faults, the offset of granitic rocks is at least that much. Compressive stresses of several MPa are predicted by elastic dislocation models of the range front

  11. Compressive intrinsic stress originates in the grain boundaries of dense refractory polycrystalline thin films

    NASA Astrophysics Data System (ADS)

    Magnfält, D.; Fillon, A.; Boyd, R. D.; Helmersson, U.; Sarakinos, K.; Abadias, G.

    2016-02-01

    Intrinsic stresses in vapor deposited thin films have been a topic of considerable scientific and technological interest owing to their importance for functionality and performance of thin film devices. The origin of compressive stresses typically observed during deposition of polycrystalline metal films at conditions that result in high atomic mobility has been under debate in the literature in the course of the past decades. In this study, we contribute towards resolving this debate by investigating the grain size dependence of compressive stress magnitude in dense polycrystalline Mo films grown by magnetron sputtering. Although Mo is a refractory metal and hence exhibits an intrinsically low mobility, low energy ion bombardment is used during growth to enhance atomic mobility and densify the grain boundaries. Concurrently, the lateral grain size is controlled by using appropriate seed layers on which Mo films are grown epitaxially. The combination of in situ stress monitoring with ex situ microstructural characterization reveals a strong, seemingly linear, increase of the compressive stress magnitude on the inverse grain size and thus provides evidence that compressive stress is generated in the grain boundaries of the film. These results are consistent with models suggesting that compressive stresses in metallic films deposited at high homologous temperatures are generated by atom incorporation into and densification of grain boundaries. However, the underlying mechanisms for grain boundary densification might be different from those in the present study where atomic mobility is intrinsically low.

  12. Stress relaxation in vanadium under shock and shockless dynamic compression

    SciTech Connect

    Kanel, G. I.; Razorenov, S. V.; Garkushin, G. V.; Savinykh, A. S.; Zaretsky, E. B.

    2015-07-28

    Evolutions of elastic-plastic waves have been recorded in three series of plate impact experiments with annealed vanadium samples under conditions of shockless and combined ramp and shock dynamic compression. The shaping of incident wave profiles was realized using intermediate base plates made of different silicate glasses through which the compression waves were entered into the samples. Measurements of the free surface velocity histories revealed an apparent growth of the Hugoniot elastic limit with decreasing average rate of compression. The growth was explained by “freezing” of the elastic precursor decay in the area of interaction of the incident and reflected waves. A set of obtained data show that the current value of the Hugoniot elastic limit and plastic strain rate is rather associated with the rate of the elastic precursor decay than with the local rate of compression. The study has revealed the contributions of dislocation multiplications in elastic waves. It has been shown that independently of the compression history the material arrives at the minimum point between the elastic and plastic waves with the same density of mobile dislocations.

  13. Noise variation by compressive stress on the model core of power transformers

    NASA Astrophysics Data System (ADS)

    Mizokami, Masato; Kurosaki, Yousuke

    2015-05-01

    The reduction of audible noise generated by cores for power transformers has been required due to environmental concern. It is known that compressive stress in the rolling direction of electrical steel affects magnetostriction and it can result in an increase in noise level. In this research, the effect of compressive stress to noise was investigated on a 3-phase 3-limb model core. Compressive stress was applied in the rolling direction of the limbs from the outside of the core. It increased the sound pressure levels and the slope of the rise was about 2 dBA/MPa. Magnetostriction on single sheet samples was also measured under compressive stress and the harmonic components of the magnetostriction were compared with those of noise. It revealed that the variation in magnetostriction with compressive stress did not entirely correspond to that in noise. In one of the experiments, localized bending happened on one limb during compressing the core. While deformation of the core had not been intended, the noise was measured. The deformation increased the noise by more than 10 dBA and it occurred on most of the harmonic components.

  14. Band-Moment Compression of AVIRIS Hyperspectral Data and its Use in the Detection of Vegetation Stress

    NASA Technical Reports Server (NTRS)

    Estep, L.; Davis, B.

    2001-01-01

    A remote sensing campaign was conducted over a U.S. Department of Agriculture test farm at Shelton, Nebraska. An experimental field was set off in plots that were differentially treated with anhydrous ammonia. Four replicates of 0-kg/ha to 200-kg/ha plots, in 50-kg/ha increments, were set out in a random block design. Low-altitude (GSD of 3 m) Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) hyperspectral data were collected over the site in 224 bands. Simultaneously, ground data were collected to support the airborne imagery. In an effort to reduce data load while maintaining or enhancing algorithm performance for vegetation stress detection, band-moment compression and analysis was applied to the AVIRIS image cube. The results indicated that band-moment techniques compress the AVIRIS dataset significantly while retaining the capability of detecting environmentally induced vegetation stress.

  15. Stress Relaxation for Granular Materials near Jamming under Cyclic Compression

    NASA Astrophysics Data System (ADS)

    Farhadi, Somayeh; Zhu, Alex Z.; Behringer, Robert P.

    2015-10-01

    We have explored isotropically jammed states of semi-2D granular materials through cyclic compression. In each compression cycle, systems of either identical ellipses or bidisperse disks transition between jammed and unjammed states. We determine the evolution of the average pressure P and structure through consecutive jammed states. We observe a transition point ϕm above which P persists over many cycles; below ϕm, P relaxes slowly. The relaxation time scale associated with P increases with packing fraction, while the relaxation time scale for collective particle motion remains constant. The collective motion of the ellipses is hindered compared to disks because of the rotational constraints on elliptical particles.

  16. Compressive stress effects on nanoparticle modulus and fracture

    NASA Astrophysics Data System (ADS)

    Mook, W. M.; Nowak, J. D.; Perrey, C. R.; Carter, C. B.; Mukherjee, R.; Girshick, S. L.; McMurry, P. H.; Gerberich, W. W.

    2007-06-01

    Individual nanoparticles of silicon and titanium having diameters in the range of 40-140nm have been repeatedly compressed by a nanoindenter. Even at low loads, the small tip-particle and particle-substrate contacts generate extreme pressures within the confined particle, influencing its stiffness and fracture toughness. The effect of these high pressures on the measured modulus is taken into account by invoking a Murnaghan equation-of-state-based analysis. Fracture toughness of the silicon particles is found to increase by a factor of 4 in compression for a 40-nm -diam particle when compared to bulk silicon. Additionally, strain energy release rates increase by more than an order of magnitude for particles of this size when compared to bulk Si.

  17. Compression stress relaxation apparatus for the long-time monitoring of the incremental modulus

    NASA Astrophysics Data System (ADS)

    Horst, Roland H.; Stephens, Thomas S.; Coons, James E.; Winter, H. Henning

    2003-11-01

    A compression apparatus for aging experiments on soft rubbers and foams is presented. The sample is compressed between two parallel surfaces and held there for long-time relaxation studies. The specific purpose of the test is twofold: possible exposure of the sample to aggressive environment under compression during aging and measurement of sample modulus without unloading, i.e., while leaving the sample under constant compression at all times. To determine the restoring force in the compressed sample, the compression strain is modulated with an incremental strain while measuring the force response. The total force gives the compression modulus, and the slope of the force-strain curve allows the determination of the incremental modulus. Stress relaxation data for silicon foam, Dow Corning S-5370 RTV, with 68% void fraction are shown. The modulus of the compressed sample decays over long experimental times of several days. The decay can be described by two relaxation modes, a short mode at 1500 s and a long mode at about 105 s. The incremental modulus changes sharply in the first 1000 s (first mode) and then levels off. The apparatus consists of two self-contained components, the removable sample holder (compression jig) and the stationary test station, which performs the modulation of the strain and all measurements (restoring force and incremental modulus). This allows separation of functions. The apparatus design specifically focused on the control of the incremental strain modulation.

  18. Induced compression wood formation in Douglas fir (Pseudotsuga menziesii) in microgravity

    NASA Technical Reports Server (NTRS)

    Kwon, M.; Bedgar, D. L.; Piastuch, W.; Davin, L. B.; Lewis, N. G.

    2001-01-01

    In the microgravity environment of the Space Shuttle Columbia (Life and Microgravity Mission STS-78), were grown 1-year-old Douglas fir and loblolly pine plants in a NASA plant growth facility. Several plants were harnessed (at 45 degrees ) to establish if compression wood biosynthesis, involving altered cellulose and lignin deposition and cell wall structure would occur under those conditions of induced mechanical stress. Selected plants were harnessed at day 2 in orbit, with stem sections of specific plants harvested and fixed for subsequent microscopic analyses on days 8, 10 and 15. At the end of the total space mission period (17 days), the remaining healthy harnessed plants and their vertical (upright) controls were harvested and fixed on earth. All harnessed (at 45 degrees ) plant specimens, whether grown at 1 g or in microgravity, formed compression wood. Moreover, not only the cambial cells but also the developing tracheid cells underwent significant morphological changes. This indicated that the developing tracheids from the primary cell wall expansion stage to the fully lignified maturation stage are involved in the perception and transduction of the stimuli stipulating the need for alteration of cell wall architecture. It is thus apparent that, even in a microgravity environment, woody plants can make appropriate corrections to compensate for stress gradients introduced by mechanical bending, thereby enabling compression wood to be formed. The evolutionary implications of these findings are discussed in terms of "variability" in cell wall biosynthesis.

  19. Development, characterization, and modeling of ballistic impact on composite laminates under compressive pre-stress

    NASA Astrophysics Data System (ADS)

    Kerr-Anderson, Eric

    Structural composite laminates were ballistically impacted while under in-plane compressive pre-stress. Residual properties, damage characterization, and energy absorption were compared to determine synergistic effects of in-plane compressive pre-stress and impact velocity. A fixture was developed to apply in-plane compressive loads up to 30 tons to structural composites during an impact event using a single-stage light-gas gun. Observed failure modes included typical conical delamination, the development of an impact initiated shear crack (IISC), and the shear failure of a pre-stressed composite due to impact. It was observed that the compressive failure threshold quadratically decreased in relation to the impact velocity up to velocities that caused partial penetration. For all laminates impacted at velocities causing partial or full penetration up to 350 ms-1, the failure threshold was consistent and used as an experimental normalization. Samples impacted below 65% of the failure threshold witnessed no significant change in damage morphology or residual properties when compared to typical conical delamination. Samples impacted above 65% of the failure threshold witnessed additional damage in the form of a shear crack extending perpendicular to the applied load from the point of impact. The presence of an IISC reduced the residual properties and even caused failure upon impact at extreme combinations. Four failure envelopes have been established as: transient failure, steady state failure, impact initiated shear crack, and conical damage. Boundaries and empirically based equations for residual compressive strength have been developed for each envelope with relation to two E-glass/vinyl ester laminate systems. Many aspects of pre-stressed impact have been individually examined, but there have been no comprehensive examinations of pre-stressed impact. This research has resulted in the exploration and characterization of compressively pre-stressed damage for impact

  20. Corrosion Product Film-Induced Stress Facilitates Stress Corrosion Cracking

    PubMed Central

    Wang, Wenwen; Zhang, Zhiliang; Ren, Xuechong; Guan, Yongjun; Su, Yanjing

    2015-01-01

    Finite element analyses were conducted to clarify the role of corrosion product films (CPFs) in stress corrosion cracking (SCC). Flat and U-shaped edge-notched specimens were investigated in terms of the CPF-induced stress in the metallic substrate and the stress in the CPF. For a U-shaped edge-notched specimen, the stress field in front of the notch tip is affected by the Young’s modulus of the CPF and the CPF thickness and notch geometry. The CPF-induced tensile stress in the metallic substrate is superimposed on the applied load to increase the crack tip strain and facilitate localized plasticity deformation. In addition, the stress in the CPF surface contributes to the rupture of the CPFs. The results provide physical insights into the role of CPFs in SCC. PMID:26066367

  1. Corrosion Product Film-Induced Stress Facilitates Stress Corrosion Cracking.

    PubMed

    Wang, Wenwen; Zhang, Zhiliang; Ren, Xuechong; Guan, Yongjun; Su, Yanjing

    2015-01-01

    Finite element analyses were conducted to clarify the role of corrosion product films (CPFs) in stress corrosion cracking (SCC). Flat and U-shaped edge-notched specimens were investigated in terms of the CPF-induced stress in the metallic substrate and the stress in the CPF. For a U-shaped edge-notched specimen, the stress field in front of the notch tip is affected by the Young's modulus of the CPF and the CPF thickness and notch geometry. The CPF-induced tensile stress in the metallic substrate is superimposed on the applied load to increase the crack tip strain and facilitate localized plasticity deformation. In addition, the stress in the CPF surface contributes to the rupture of the CPFs. The results provide physical insights into the role of CPFs in SCC. PMID:26066367

  2. Laser induced surface stress on water droplets.

    PubMed

    Wang, Neng; Lin, Zhifang; Ng, Jack

    2014-10-01

    Laser induced stress on spherical water droplets is studied. At mechanical equilibrium, the body stress vanishes therefore we consider only the surface stress. The surface stress on sub-wavelength droplets is slightly weaker along the light propagation direction. For larger droplets, due to their light focusing effect, the forward stress is significantly enhanced. For a particle roughly 3 micron in radius, when it is excited at whispering gallery mode with Q ∼ 10⁴ by a 1 Watt Gaussian beam, the stress can be enhanced by two orders of magnitude, and can be comparable with the Laplace pressure. PMID:25321955

  3. Pre-stressed/pre-compressed gas turbine nozzle

    DOEpatents

    Jang, Hoyle; Itzel, Gary Michael; Yu, Yufeng Phillip

    2002-01-01

    A method of increasing low cycle fatigue life of a turbine nozzle comprising a plurality of stationary airfoils extending between radially inner and outer ring segments comprising a) providing at least one radial passage in each of the plurality of airfoils; b) installing a rod in the radial passage extending between the radially inner and outer ring segments and fixing one end of the rod to one of the inner and outer rings; and c) pre-loading the rod to compress the airfoil between the inner and outer ring segments.

  4. Quantitative measurement of CO2 laser-induced residual stress in fused silica optics

    NASA Astrophysics Data System (ADS)

    Yang, Liang; Liao, Wei; Miao, Xinxiang; Yuan, Xiaodong; Zheng, Wanguo; Lv, Haibin; Zhou, Guorui; Zu, Xiaotao; Xiang, Xia

    2015-05-01

    The residual stress field of fused silica induced by continuous wave CO2 laser irradiation is investigated with specific photoelastic methods. Both hoop stress and axial stress in the irradiated zone are measured quantitatively. For the hoop stress along the radial direction, the maximum phase retardance of 30 nm appears at the boundary of the laser distorted zone (680-μm distance to center), and the phase retardance decreases rapidly and linearly inward, and decreases slowly and exponentially outward. For the axial stress, tensile stress lies in a thin surface layer (<280 μm) and compressive stress lies just below the tensile region. Both tensile and compressive stresses increase first and then decrease along the depth direction. The maximum phase retardance induced by axial tensile stress is 150 nm, and the maximum phase retardance caused by axial compression stress is about 75 nm. In addition, the relationship between the maximum axial stress and the deformation height of the laser irradiated zone is also discussed.

  5. Fluid Production Induced Stress Analysis Surrounding an Elliptic Fracture

    NASA Astrophysics Data System (ADS)

    Pandit, Harshad Rajendra

    Hydraulic fracturing is an effective technique used in well stimulation to increase petroleum well production. A combination of multi-stage hydraulic fracturing and horizontal drilling has led to the recent boom in shale gas production which has changed the energy landscape of North America. During the fracking process, highly pressurized mixture of water and proppants (sand and chemicals) is injected into to a crack, which fractures the surrounding rock structure and proppants help in keeping the fracture open. Over a longer period, however, these fractures tend to close due to the difference between the compressive stress exerted by the reservoir on the fracture and the fluid pressure inside the fracture. During production, fluid pressure inside the fracture is reduced further which can accelerate the closure of a fracture. In this thesis, we study the stress distribution around a hydraulic fracture caused by fluid production. It is shown that fluid flow can induce a very high hoop stress near the fracture tip. As the pressure gradient increases stress concentration increases. If a fracture is very thin, the flow induced stress along the fracture decreases, but the stress concentration at the fracture tip increases and become unbounded for an infinitely thin fracture. The result from the present study can be used for studying the fracture closure problem, and ultimately this in turn can lead to the development of better proppants so that prolific well production can be sustained for a long period of time.

  6. Stress induced obesity: lessons from rodent models of stress

    PubMed Central

    Patterson, Zachary R.; Abizaid, Alfonso

    2013-01-01

    Stress was once defined as the non-specific result of the body to any demand or challenge to homeostasis. A more current view of stress is the behavioral and physiological responses generated in the face of, or in anticipation of, a perceived threat. The stress response involves activation of the sympathetic nervous system and recruitment of the hypothalamic-pituitary-adrenal (HPA) axis. When an organism encounters a stressor (social, physical, etc.), these endogenous stress systems are stimulated in order to generate a fight-or-flight response, and manage the stressful situation. As such, an organism is forced to liberate energy resources in attempt to meet the energetic demands posed by the stressor. A change in the energy homeostatic balance is thus required to exploit an appropriate resource and deliver useable energy to the target muscles and tissues involved in the stress response. Acutely, this change in energy homeostasis and the liberation of energy is considered advantageous, as it is required for the survival of the organism. However, when an organism is subjected to a prolonged stressor, as is the case during chronic stress, a continuous irregularity in energy homeostasis is considered detrimental and may lead to the development of metabolic disturbances such as cardiovascular disease, type II diabetes mellitus and obesity. This concept has been studied extensively using animal models, and the neurobiological underpinnings of stress induced metabolic disorders are beginning to surface. However, different animal models of stress continue to produce divergent metabolic phenotypes wherein some animals become anorexic and lose body mass while others increase food intake and body mass and become vulnerable to the development of metabolic disturbances. It remains unclear exactly what factors associated with stress models can be used to predict the metabolic outcome of the organism. This review will explore a variety of rodent stress models and discuss the

  7. Inducing dynamical bistability by reversible compression of an optical piston

    NASA Astrophysics Data System (ADS)

    Schnoering, Gabriel; Genet, Cyriaque

    2015-04-01

    We study the reversible crossover between stable and bistable phases of an overdamped Brownian bead inside an optical piston. The interaction potentials are solved developing a method based on Kramers's theory that exploits the statistical properties of the stochastic motion of the bead. We evaluate precisely the energy balance of the crossover. We show that the deformation of the optical potentials induced by the compression of the piston is related to a production of heat balanced between potential energy changes and the total amount of work performed by the piston. This reveals how specific thermodynamic processes can be designed and controlled with a high level of precision by tailoring the optical landscapes of the piston.

  8. Numerical study of Reynolds stress in compressible flows

    NASA Technical Reports Server (NTRS)

    Vandromme, D.; Hamin, H.

    1985-01-01

    A second order closure has been implemented in an implicit Navier-Stokes solver to study the behavior of the Reynolds stresses under the influence of severe pressure gradients. In the boundary layer zone, the strongly sheared character of the mean flow dominates the turbulence generation mechanisms. However, the pressure gradients also play a very important role for these processes, but at different locations within the boundary layer.

  9. Optimum Injection Pressure of a Cavitating Jet for Introducing Compressive Residual Stress into Stainless Steel

    NASA Astrophysics Data System (ADS)

    Soyama, Hitoshi; Nagasaka, Kazuya; Takakuwa, Osamu; Naito, Akima

    Introducing compressive residual stress by a cavitating jet into the sub-surface of components used in nuclear power plants can mitigate stress corrosion cracking in these components. Although applying the jet is an effective method for this purpose, it should be used without causing damage to the surface from water jet droplets arising from high-pressure injection of the water jet. Thus, in introducing compressive residual stress, the injection pressure needs to be optimized. In this paper, in order to determine the optimum injection pressure, the residual stress of stainless steel treated by a jet at various injection pressures was measured using an X-ray diffraction method. The injection pressure of the jet was varied from 5 MPa to 300 MPa, and the diameter of the nozzle throat of the jet was varied from 0.35 mm to 2.0 mm. The variation of residual stress with depth was measured by alternating X-ray diffraction measurements with electropolishing. It was revealed that a cavitating jet at an injection pressure of 10 MPa with a nozzle diameter of 2.0 mm can introduce higher compressive residual stress to deeper into stainless steel compared with a jet at 300 MPa with a nozzle diameter of 0.35 mm when the downstream pressure of the nozzle was constant.

  10. The deformation units in metallic glasses revealed by stress-induced localized glass transition

    NASA Astrophysics Data System (ADS)

    Huo, L. S.; Ma, J.; Ke, H. B.; Bai, H. Y.; Zhao, D. Q.; Wang, W. H.

    2012-06-01

    We report that even in quasi-static cyclic compressions in the apparent elastic regimes of the bulk metallic glasses, the precisely measured stress-strain curve presents a mechanical hysteresis loop, which is commonly perceived to occur only in high-frequency dynamic tests. A phenomenological viscoelastic model is established to explain the hysteresis loop and demonstrate the evolutions of the viscous zones in metallic glasses during the cyclic compression. The declining of the viscosity of the viscous zones to at least 1 × 1012 Pa s when stress applied indicates that stress-induced localized glass to supercooled liquid transition occurs. We show that the deformation units of metallic glasses are evolved from the intrinsic heterogeneous defects in metallic glasses under stress and the evolution is a manifestation of the stress-induced localized glass transition. Our study might provide a new insight into the atomic-scale mechanisms of plastic deformation of metallic glasses.

  11. Drug-Induced Oxidative Stress and Toxicity

    PubMed Central

    Deavall, Damian G.; Martin, Elizabeth A.; Horner, Judith M.; Roberts, Ruth

    2012-01-01

    Reactive oxygen species (ROS) are a byproduct of normal metabolism and have roles in cell signaling and homeostasis. Species include oxygen radicals and reactive nonradicals. Mechanisms exist that regulate cellular levels of ROS, as their reactive nature may otherwise cause damage to key cellular components including DNA, protein, and lipid. When the cellular antioxidant capacity is exceeded, oxidative stress can result. Pleiotropic deleterious effects of oxidative stress are observed in numerous disease states and are also implicated in a variety of drug-induced toxicities. In this paper, we examine the nature of ROS-induced damage on key cellular targets of oxidative stress. We also review evidence implicating ROS in clinically relevant, drug-related side effects including doxorubicin-induced cardiac damage, azidothymidine-induced myopathy, and cisplatin-induced ototoxicity. PMID:22919381

  12. Explosion-induced stress changes estimated from vibrating-wire stressmeter measurements near the Mighty Epic event, Nevada Test Site

    USGS Publications Warehouse

    Ellis, William L.; Kibler, J.D.

    1983-01-01

    Explosion-induced compressive stress increases near an underground nuclear explosion are believed to contribute significantly to the containment of high-pressure gases within the explosion-produced cavity. These induced compressive stresses are predicted by computer calculations, but have never been adequately confirmed by field measurements, owing primarily to the unique difficulties of obtaining such field data. Vibrating-wire stressmeter measurements made near the Mighty Epic nuclear detonation, however, qualitatively indicate that within 150 meters of the working point, permanent compressive stress increases of several megapascals were present 15 weeks after the event. Additionally, stress-change magnitudes interpreted from the stressmeter data between the 75- and 260-meter range from the working point compare favorably with calculational predictions of the stress changes believed to be present shortly after detonation of the event. The measurements and calculations differ, however, with regard to the pattern of stress change radial and transverse to the explosion source. For the range of the field measurements from the working point, computer models predict the largest compressive-stress increase to be radial to the explosion source, while the field data indicate the transverse component of. stress change to be the most compressive. The significance of time-dependent modification of the initial explosion-induced stress distribution is, however, uncertain with regard to the comparison of the field measurements and theoretical predictions.

  13. A PZT-based smart aggregate for compressive seismic stress monitoring

    NASA Astrophysics Data System (ADS)

    Hou, S.; Zhang, H. B.; Ou, J. P.

    2012-10-01

    A PZT-based smart aggregate (SA) for compressive seismic stress monitoring is proposed in this paper. The proposed SA consists of a piece of PZT (lead zirconate titanate) patch sandwiched between a pair of marble cubes through epoxy. A soft PZT is selected, rendering the SA as a potential actuator in active sensing. Finite element analysis (FEA) was conducted to investigate the stress distribution in the SA under compression, which is used for calculating its sensitivity to compressive stresses. With a commercially available charge amplifier, the frequency response of both the amplitude and the phase shift of the sensing system are investigated by applying the frequency sweep loading scheme on the proposed SA. The frequency ranges from 0.01 to 10 Hz, corresponding to the range of seismic frequency response of most building structures. The alternating load for evaluating SA sensitivity was applied by the servo-hydraulic machine. The lower limit of frequency response is determined to be 0.5 Hz. The depolarization process of the piezoelectric coefficient of the selected PZT material was investigated to decide the load-holding time in calibration tests. The degradation of the piezoelectric coefficient with a series of compressive pre-stresses from 4.8 to 24 MPa was evaluated, and the experimental results showed that the influence from the considered range of pre-stresses is negligible. Using a commercially available charge amplifier, the proposed SA-based sensing system can monitor the seismic stress of low- and middle-rise building structures under moderate earthquakes.

  14. Damage and Plastic Deformation Modeling of Beishan Granite Under Compressive Stress Conditions

    NASA Astrophysics Data System (ADS)

    Chen, L.; Wang, C. P.; Liu, J. F.; Liu, J.; Wang, J.; Jia, Y.; Shao, J. F.

    2015-07-01

    Based on experimental investigations, we propose a coupled elastoplastic damage model to simulate the mechanical behavior of granite under compressive stress conditions. The granite is taken from the Beishan area, a preferable region for China's high-level radioactive waste repository. Using a 3D acoustic emission monitoring system in mechanical tests, we focus on the cracking process and its influence on the macroscopic mechanical behavior of the granite samples. It is verified that the crack propagation coupled with fractional sliding along the cracks is the principal mechanism controlling the failure process and nonlinear mechanical behavior of granite under compressive stress conditions. Based on this understanding, the coupled elastoplastic damage model is formulated in the framework of the thermodynamics theory. In the model, the coupling between damage and plastic deformation is simulated by introducing the independent damage variable in the plastic yield surface. As a preliminary validation of the model, a series of numerical simulations are performed for compressive tests conducted under different confining pressures. Comparisons between the numerical and simulated results show that the proposed model can reproduce the main features of the mechanical behavior of Beishan granite, particularly the damage evolution under compressive stress conditions.

  15. Inducible NO synthase inhibition attenuates shear stress-induced pulmonary vasodilation in the ovine fetus.

    PubMed

    Rairigh, R L; Storme, L; Parker, T A; le Cras, T D; Kinsella, J P; Jakkula, M; Abman, S H

    1999-03-01

    Recent studies have suggested that type II (inducible) nitric oxide (NO) synthase (NOS II) is present in the fetal lung, but its physiological roles are uncertain. Whether NOS II activity contributes to the NO-mediated fall in pulmonary vascular resistance (PVR) during shear stress-induced pulmonary vasodilation is unknown. We studied the hemodynamic effects of two selective NOS II antagonists [aminoguanidine (AG) and S-ethylisothiourea (EIT)], a nonselective NOS antagonist [nitro-L-arginine (L-NNA)], and a nonselective vasoconstrictor (U-46619) on PVR during partial compression of the ductus arteriosus (DA) in 20 chronically prepared fetal lambs (mean age 132 +/- 2 days, term 147 days). At surgery, catheters were placed in the left pulmonary artery (LPA) for selective drug infusion, an ultrasonic flow transducer was placed on the LPA to measure blood flow, and an inflatable vascular occluder was placed loosely around the DA for compression. On alternate days, a brief intrapulmonary infusion of normal saline (control), AG, EIT, L-NNA, or U-46619 was infused in random order into the LPA. The DA was compressed to increase mean pulmonary arterial pressure (MPAP) 12-15 mmHg above baseline values and held constant for 30 min. In control studies, DA compression reduced PVR by 42% from baseline values (P < 0.01). L-NNA treatment completely blocked the fall in PVR during DA compression. AG and EIT attenuated the decrease in PVR by 30 and 19%, respectively (P < 0.05). Nonspecific elevation in PVR by U-46619 did not affect the fall in PVR during DA compression. Immunostaining for NOS II identified this isoform in airway epithelium and vascular smooth muscle in the late-gestation ovine fetal lung. We conclude that selective NOS II antagonists attenuate but do not block shear stress-induced vasodilation in the fetal lung. We speculate that stimulation of NOS II activity, perhaps from smooth muscle cells, contributes in part to the NO-mediated fall in PVR during shear stress-induced

  16. Processing-induced-transformations (PITs) during direct compression: impact of compression speeds on phase transition of caffeine.

    PubMed

    Juban, Audrey; Briancon, Stephanie; Puel, François

    2016-11-01

    For pharmaceutical industry, understanding solid-phase transition of the active pharmaceutical ingredient (API) induced by the manufacturing process is a key issue. Caffeine was chosen as a model API since it exhibits a polymorphic transformation during tableting. This study investigated the impact of the compression speed on the phase transition of anhydrous Form I (CFI) into Form II. Tablets were made from pure CFI and binary mixtures of CFI/microcrystalline cellulose, with an electric press well instrumented at three different compression speeds (50, 500 and 4500 mm min(-1)). For each velocity of the mobile punch studied, tablets made from three compression pressures (50, 100 and 200 MPa) were analyzed. The determination of the CFI transition degree was performed using a Differential Scanning Calorimetry (DSC). The CFI transition degree was monitored during three months in order to obtain the transformation profile of the API in tablets and in uncompressed powder. The modeling of the profile with a stretched exponential kinetic law (Johnson-Mehl-Avrami model) was used for the identification of the transition mechanism. The direct compression process triggered the polymorphic transformation in tablet when a sufficient compression pressure is applied. The velocity of the punch did neither impact the transition degree just after compression nor the transformation profile. The transition mechanism remained driven by nucleation for several operating conditions. Consequently, the punch velocity is not a decisive process parameter for avoiding such phase transition in tableting. As already observed, the compression pressure did not influence the transition whatever the compression speed and the velocity. PMID:27109544

  17. A compressible Navier-Stokes solver with two-equation and Reynolds stress turbulence closure models

    NASA Technical Reports Server (NTRS)

    Morrison, Joseph H.

    1992-01-01

    This report outlines the development of a general purpose aerodynamic solver for compressible turbulent flows. Turbulent closure is achieved using either two equation or Reynolds stress transportation equations. The applicable equation set consists of Favre-averaged conservation equations for the mass, momentum and total energy, and transport equations for the turbulent stresses and turbulent dissipation rate. In order to develop a scheme with good shock capturing capabilities, good accuracy and general geometric capabilities, a multi-block cell centered finite volume approach is used. Viscous fluxes are discretized using a finite volume representation of a central difference operator and the source terms are treated as an integral over the control volume. The methodology is validated by testing the algorithm on both two and three dimensional flows. Both the two equation and Reynolds stress models are used on a two dimensional 10 degree compression ramp at Mach 3, and the two equation model is used on the three dimensional flow over a cone at angle of attack at Mach 3.5. With the development of this algorithm, it is now possible to compute complex, compressible high speed flow fields using both two equation and Reynolds stress turbulent closure models, with the capability of eventually evaluating their predictive performance.

  18. The interactions of compressive stress and weathering in driving rock fracture.

    NASA Astrophysics Data System (ADS)

    de Vilder, Saskia; Brain, Matthew; Rosser, Nick; Vann Jones, Emma

    2016-04-01

    Weathering plays an important role in weakening a rock mass before failure. The stresses generated by failure triggering events are often an order of magnitude smaller than those required to fracture rock. The compressive stresses of the slope resulting from gravitational load are also in themselves insufficient to result in fracture. Therefore, the rock must have been weakened prior to failure. Recent studies have shown that local stress concentrations within a slope can determine the effectiveness of weathering events. Currently however, the exact impact of this is not well constrained with few studies undertaken to analyse rock weathering under stress. To address this, we report the results of a laboratory testing programme designed to assess the influence of compressive stress on the effectiveness of weathering, specifically saltwater wetting and drying. In these laboratory tests, rock cores were placed under a constant 2 MPa uniaxial compressive stress, corresponding to the approximate compressive stresses at the base of a 60 m high, near-vertical rock slope. The cores consist of moderately strong grey Staithes Siltstone (unconfined compressive stress, UCS, range of 20 - 30 MPa), found along the North Yorkshire coastline, United Kingdom. The samples were subjected to saltwater wetting and drying cycles of 6 hours, designed to mimic the submersion of a coastal cliff by the tide. Modified oedometers were used to place the samples under stress as wetting and drying occurred. We tested 4 samples which had been 'preloaded' in unconfined compression to 13.5 MPa (i.e. exceeding the crack initiation threshold but insufficient to cause fracture) to simulate the role of accumulated damage (i.e. creating a population of microcracks) in the rock slope, along with 4 samples which were not 'preloaded', and 8 samples with varying geometries to simulate the role of cliff-face topography in concentrating stress. Each test had a corresponding control sample which was not placed

  19. Effect of residual stresses induced by prestressing on rolling element fatigue life

    NASA Technical Reports Server (NTRS)

    Parker, R. J.; Zaretsky, E. V.

    1972-01-01

    A mechanical prestress cycle suitable to induce compressive stress beneath the surface of the inner race of radially loaded 207-size bearings was determined. Compressive residual stress in excess 0.69 x 10 to the 9th power N/sq m (100,000 psi), as measured by X-ray diffraction, were induced at the depth of maximum shearing stress. The prestress cycle consisted of running the bearings for 25 hours at 2750 rpm at a radial load which produced a maximum Hertz stress of 3.3 x 10 to the 9th power N/sq m (480,000 psi) at the contact of the inner race and the heaviest loaded ball. Bearings subjected to this prestress cycle and subsequently fatigue tested gave a 10 percent fatigue life greater than twice that of a group of baseline bearings.

  20. Stress Drops for Potentially Induced Earthquake Sequences

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Beroza, G. C.; Ellsworth, W. L.

    2015-12-01

    Stress drop, the difference between shear stress acting across a fault before and after an earthquake, is a fundamental parameter of the earthquake source process and the generation of strong ground motions. Higher stress drops usually lead to more high-frequency ground motions. Hough [2014 and 2015] observed low intensities in "Did You Feel It?" data for injection-induced earthquakes, and interpreted them to be a result of low stress drops. It is also possible that the low recorded intensities could be a result of propagation effects. Atkinson et al. [2015] show that the shallow depth of injection-induced earthquakes can lead to a lack of high-frequency ground motion as well. We apply the spectral ratio method of Imanishi and Ellsworth [2006] to analyze stress drops of injection-induced earthquakes, using smaller earthquakes with similar waveforms as empirical Green's functions (eGfs). Both the effects of path and linear site response should be cancelled out through the spectral ratio analysis. We apply this technique to the Guy-Greenbrier earthquake sequence in central Arkansas. The earthquakes migrated along the Guy-Greenbrier Fault while nearby injection wells were operating in 2010-2011. Huang and Beroza [GRL, 2015] improved the magnitude of completeness to about -1 using template matching and found that the earthquakes deviated from Gutenberg-Richter statistics during the operation of nearby injection wells. We identify 49 clusters of highly similar events in the Huang and Beroza [2015] catalog and calculate stress drops using the source model described in Imanishi and Ellsworth [2006]. Our results suggest that stress drops of the Guy-Greenbrier sequence are similar to tectonic earthquakes at Parkfield, California (the attached figure). We will also present stress drop analysis of other suspected induced earthquake sequences using the same method.

  1. High-temperature, multi-atmosphere, constant stress compression creep apparatus

    NASA Astrophysics Data System (ADS)

    Carter, C. H., Jr.; Stone, C. A.; Davis, R. F.; Schaub, D. R.

    1980-10-01

    A creep apparatus is presented in which uniaxial compressive stresses, constant to within 1% for strains up to 10%, can be applied to the sample and strains can be read with an accuracy of 5 x 10 to the -7th m. Loads as great as 440 kg can be applied, and the furnace can be operated in vacuum or inert gas to 2573 K or used with a muffle tube. Data acquisition, manipulation, and plotting is computer controlled.

  2. Diabetic Cardiovascular Disease Induced by Oxidative Stress

    PubMed Central

    Kayama, Yosuke; Raaz, Uwe; Jagger, Ann; Adam, Matti; Schellinger, Isabel N.; Sakamoto, Masaya; Suzuki, Hirofumi; Toyama, Kensuke; Spin, Joshua M.; Tsao, Philip S.

    2015-01-01

    Cardiovascular disease (CVD) is the leading cause of morbidity and mortality among patients with diabetes mellitus (DM). DM can lead to multiple cardiovascular complications, including coronary artery disease (CAD), cardiac hypertrophy, and heart failure (HF). HF represents one of the most common causes of death in patients with DM and results from DM-induced CAD and diabetic cardiomyopathy. Oxidative stress is closely associated with the pathogenesis of DM and results from overproduction of reactive oxygen species (ROS). ROS overproduction is associated with hyperglycemia and metabolic disorders, such as impaired antioxidant function in conjunction with impaired antioxidant activity. Long-term exposure to oxidative stress in DM induces chronic inflammation and fibrosis in a range of tissues, leading to formation and progression of disease states in these tissues. Indeed, markers for oxidative stress are overexpressed in patients with DM, suggesting that increased ROS may be primarily responsible for the development of diabetic complications. Therefore, an understanding of the pathophysiological mechanisms mediated by oxidative stress is crucial to the prevention and treatment of diabetes-induced CVD. The current review focuses on the relationship between diabetes-induced CVD and oxidative stress, while highlighting the latest insights into this relationship from findings on diabetic heart and vascular disease. PMID:26512646

  3. Heat Stress-Induced DNA Damage

    PubMed Central

    Kantidze, O.L.; Velichko, A.K.; Luzhin, A.V.; Razin, S.V.

    2016-01-01

    Although the heat-stress response has been extensively studied for decades, very little is known about its effects on nucleic acids and nucleic acid-associated processes. This is due to the fact that the research has focused on the study of heat shock proteins and factors (HSPs and HSFs), their involvement in the regulation of transcription, protein homeostasis, etc. Recently, there has been some progress in the study of heat stress effects on DNA integrity. In this review, we summarize and discuss well-known and potential mechanisms of formation of various heat stress-induced DNA damage. PMID:27437141

  4. Lead induced testicular hypersensitivity in stressed rats.

    PubMed

    Saxena, D K; Lal, B; Srivastava, R S; Chandra, S V

    1990-01-01

    Rats were immobilized for 2 h and treated i.p. with lead Pb2+ (8 mg/kg/day) for 45 d to investigate the testicular effects of lead on rats kept under immobilization stress. Marked alteration in SDH. G6PDH activity, cholesterol and ascorbic acid contents and reduced sperm counts associated with marked pathological changes in the testis of rats were observed after combined treatment with lead and immobilization stress in comparison to either alone. An increase in the disturbances of testicular androgen synthesis seems to be responsible for enhanced testicular injury in lead induced stressed rats. PMID:2401350

  5. CO2 laser scribe of chemically strengthened glass with high surface compressive stress

    NASA Astrophysics Data System (ADS)

    Li, Xinghua; Vaddi, Butchi R.

    2011-03-01

    Chemically strengthened glass is finding increasing use in handheld, IT and TV cover glass applications. Chemically strengthened glass, particularly with high (>600MPa) compressive stress (CS) and deeper depth of layer (DOL), enable to retain higher strength after damage than non-strengthened glass when its surface is abraded. Corning Gorilla® Glass has particularly proven to be advantageous over competition in this attribute. However, due to high compressive stress (CS) and Central Tension (CT) cutting ion-exchanged glass is extremely difficult and often unmanageable where ever the applications require dicing the chemically strengthened mother glass into smaller parts. We at Corning have developed a CO2 laser scribe and break method (LSB) to separate a single chemically strengthened glass sheet into plurality of devices. Furthermore, CO2 laser scribe and break method enables debris-free separation of glass with high edge strength due to its mirror-like edge finish. We have investigated laser scribe and break of chemically strengthened glass with surface compressive stress greater than 600 MPa. In this paper we present the results of CO2 scribe and break method and underlying laser scribing mechanisms. We demonstrated cross-scribe repetitively on GEN 2 size chemically strengthened glass substrates. Specimens for edge strength measurements of different thickness and CS/DOL glass were prepared using the laser scribe and break technique. The specimens were tested using the standard 4-point bend method and the results are presented.

  6. Experimental study on properties of methane diffusion of coal block under triaxial compressive stress.

    PubMed

    Zhao, Hong-Bao

    2014-01-01

    Taking the standard size coal block samples defined by ISRM as research objects, both properties of methane diffusion of coal block under triaxial compressive stress and characteristic influences caused by methane pressure were systematically studied with thermo-fluid-solid coupling with triaxial servocontrolled seepage equipment of methane-containing coal. The result shows the methane diffusion property of coal block under triaxial compressive stress was shown in four-stage as follow, first is sharply reduce stage, second is hyperbolic reduce stage, third is close to a fixed value stage, fourth stage is 0. There is a special point making the reduced rate of characteristic curve of methane diffusion speed become sharply small; the influences of shape of methane diffusion speed characteristic curve caused by methane pressure are not obvious, which only is shown in numerical size of methane diffusion speed. Test time was extended required by appear of the special point makes the reduce rate of methane diffusion speed become sharply small. The fitting four-phase relation of methane diffusion of coal block under triaxial compressive stress was obtained, and the idea is proposed that influences of the fitting four-phase relation caused by methane pressure were only shown in value of fitting parameters. PMID:25531000

  7. Experimental Study on Properties of Methane Diffusion of Coal Block under Triaxial Compressive Stress

    PubMed Central

    Zhao, Hong-Bao

    2014-01-01

    Taking the standard size coal block samples defined by ISRM as research objects, both properties of methane diffusion of coal block under triaxial compressive stress and characteristic influences caused by methane pressure were systematically studied with thermo-fluid-solid coupling with triaxial servocontrolled seepage equipment of methane-containing coal. The result shows the methane diffusion property of coal block under triaxial compressive stress was shown in four-stage as follow, first is sharply reduce stage, second is hyperbolic reduce stage, third is close to a fixed value stage, fourth stage is 0. There is a special point making the reduced rate of characteristic curve of methane diffusion speed become sharply small; the influences of shape of methane diffusion speed characteristic curve caused by methane pressure are not obvious, which only is shown in numerical size of methane diffusion speed. Test time was extended required by appear of the special point makes the reduce rate of methane diffusion speed become sharply small. The fitting four-phase relation of methane diffusion of coal block under triaxial compressive stress was obtained, and the idea is proposed that influences of the fitting four-phase relation caused by methane pressure were only shown in value of fitting parameters. PMID:25531000

  8. Design of a squeeze film magnetorheological brake considering compression enhanced shear yield stress of magnetorheological fluid

    NASA Astrophysics Data System (ADS)

    Sarkar, C.; Hirani, H.

    2013-02-01

    A magnetorheological brake, consisting of rotating disks immersed in a MR fluid and enclosed in an electromagnet, is proposed to replace the conventional heavy weight low response hydraulic disk brake. The frictional characteristics of the proposed brake can be controlled by regulating the yield stress of the MR fluid as function of magnetic field and normal compressive force. The controllable yield stress retards the surfaces of rotating disks, thus MR fluid can be used as a brake lining material. The present research work attempts designing a squeeze film MR brake by accounting compression enhanced shear yield stress of magnetorheological fluid. Theoretical calculations indicate that the estimated braking torque of the six plate squeeze film MR brake, under compression, is in the order of 600Nm. To validate the theoretical design and its findings, a prototype of single-plate squeeze film MR disk brake has been developed. Experimental test setup helps to illustrate braking torque under different control currents (0.0 to 1.25 A).

  9. Shear veins observed within anisotropic fabric at high angles to the maximum compressive stress

    NASA Astrophysics Data System (ADS)

    Fagereng, Åke; Remitti, Francesca; Sibson, Richard H.

    2010-07-01

    Some faults seem to slip at unusually high angles (>45°) relative to the orientation of the greatest principal compressive stress. This implies that these faults are extremely weak compared with the surrounding rock. Laboratory friction experiments and theoretical models suggest that the weakness may result from slip on a pre-existing frictionally weak surface, weakening from chemical reactions, elevated fluid pressure or dissolution-precipitation creep. Here we describe shear veins within the Chrystalls Beach accretionary mélange, New Zealand. The mélange is a highly sheared assemblage of relatively competent rock within a cleaved, anisotropic mudstone matrix. The orientation of the shear veins-compared with the direction of hydrothermal extension veins that formed contemporaneously-indicates that they were active at an angle of 80°+/-5° to the greatest principal compressive stress. We show that the shear veins developed incrementally along the cleavage planes of the matrix. Thus, we suggest that episodic slip was facilitated by the anisotropic internal fabric, in a fluid-overpressured, heterogeneous shear zone. A similar mechanism may accommodate shear at high angles to the greatest principal compressive stress in a range of tectonic settings. We therefore conclude that incremental slip along a pre-existing planar fabric, coupled to high fluid pressure and dissolution-precipitation creep, may explain active slip on severely misoriented faults.

  10. Stress-Induced Nanoparticle Crystallization

    PubMed Central

    2015-01-01

    We demonstrate for the first time a new mechanical annealing method that can significantly improve the structural quality of self-assembled nanoparticle arrays by eliminating defects at room temperature. Using in situ high-pressure small-angle X-ray scattering, we show that deformation of nanoparticle assembly in the presence of gigapascal level stress rebalances interparticle forces within nanoparticle arrays and transforms the nanoparticle film from an amorphous assembly with defects into a quasi-single crystalline superstructure. Our results show that the existence of the hydrostatic pressure field makes the transformation both thermodynamically and kinetically possible/favorable, thus providing new insight for nanoparticle self-assembly and integration with enhanced mechanical performance. PMID:24829089

  11. Stress-induced martensitic transformation in metastable austenitic stainless steels: Effect on fatigue crack growth rate

    NASA Astrophysics Data System (ADS)

    Khan, Z.; Ahmed, M.

    1996-04-01

    This paper addresses the influence of cyclic stress-induced martensitic transformation on fatigue crack growth rates in metastable austenitic stainless steels. At low applied stress and mean stress values in AISI type 301 stainless steel, fatigue crack growth rate is substantially retarded due to a cyclic stress-induced γ-α' and γ-ɛ martensitic transformation occurring at the crack-tip plastic zone. It is suggested that the transformation products produce a compressive residual stress at the tip of the fatigue crack, which essentially lowers the effective stress intensity and hence retards the fatigue crack growth rate. At high applied stress or mean stress values, fatigue crack growth rates in AISI type 301 steels become almost equal to those of stable AISI type 302 alloy. As the amount of transformed products increases (with an increase in applied or mean stress), the strain-hardening effect brought about by the transformed martensite phase appears to accelerate fatigue crack growth, offsetting the contribution from the compressive residual stress produced by the positive volume change of γ → α' or ɛ transformation.

  12. Fault activation due to glacially induced stresses

    NASA Astrophysics Data System (ADS)

    Steffen, R.; Lund, B.; Wu, P. P.

    2013-12-01

    Melting glaciers worldwide have an effect on sea level, but also on the stability of pre-existing faults. The load due to continental ice sheets or glaciers depresses the surface below, leading to changes in the lithospheric stresses. The accumulation of ice mass increases the vertical stress, and the horizontal stresses increase due to the accompanying flexure of the lithosphere. During deglaciation, ice-mass loss causes a simultaneous decrease in vertical stress; however, horizontal stresses decrease only slowly due to the slow readjusting of the Earth. After the end of deglaciation, only the induced horizontal stresses remain as the process of glacial isostatic adjustment (GIA) proceeds visco-elastically. The modelling of this process and the estimation of fault slip is enabled by a new GIA-fault model. However, this finite-element model is only available in two dimensions, and the extension to three dimensions is a necessary step further to allow the comparison of obtained fault slips to observations of glacially induced faults in Europe and North America. The model has several input parameters, which affect the activation time of faults and their resulting slip (e.g. ice history, rheology of the Earth, frictional properties, pore-fluid pressure). We will present the results of the new 3D model and show the sensitivity of faults with respect to modelling parameters. Furthermore, a comparison to observations will be presented.

  13. Fault activation due to glacially induced stresses

    NASA Astrophysics Data System (ADS)

    Steffen, Rebekka; Lund, Björn

    2014-05-01

    Melting glaciers worldwide have an effect on sea level, but also on the stability of pre-existing faults. The load due to continental ice sheets or glaciers depresses the surface below, leading to changes in the lithospheric stresses. The accumulation of ice mass increases the vertical stress, and the horizontal stresses increase due to the accompanying flexure of the lithosphere. During deglaciation, ice-mass loss causes a simultaneous decrease in vertical stress; however, horizontal stresses decrease only slowly due to the slow readjusting of the Earth. After the end of deglaciation, only the induced horizontal stresses remain as the process of glacial isostatic adjustment (GIA) proceeds visco-elastically. The modelling of this process and the estimation of fault slip is enabled by a new GIA-fault model. However, this finite-element model is only available in two dimensions, and the extension to three dimensions is a necessary step further to allow the comparison of obtained fault slips to observations of glacially induced faults in Europe and North America. The model has several input parameters, which affect the activation time of faults and their resulting slip (e.g. ice history, rheology of the Earth, frictional properties, pore-fluid pressure). We will present the results of the new 3D model and show the sensitivity of faults with respect to modelling parameters. Furthermore, a comparison to observations will be presented.

  14. Stress-Induced Mutagenesis in Bacteria

    PubMed Central

    Foster, Patricia L.

    2009-01-01

    Bacteria spend their lives buffeted by changing environmental conditions. To adapt to and survive these stresses, bacteria have global response systems that result in sweeping changes in gene expression and cellular metabolism. These responses are controlled by master regulators, which include: alternative sigma factors, such as RpoS and RpoH; small molecule effectors, such as ppGpp; gene repressors such as LexA; and, inorganic molecules, such as polyphosphate. The response pathways extensively overlap and are induced to various extents by the same environmental stresses. These stresses include nutritional deprivation, DNA damage, temperature shift, and exposure to antibiotics. All of these global stress responses include functions that can increase genetic variability. In particular, up-regulation and activation of error-prone DNA polymerases, down-regulation of error-correcting enzymes, and movement of mobile genetic elements are common features of several stress responses. The result is that under a variety of stressful conditions, bacteria are induced for genetic change. This transient mutator state may be important for adaptive evolution. PMID:17917873

  15. Stress-Induced Cardiomyopathy Presenting as Shock

    PubMed Central

    Yoo, Tae Kyung; Lee, Jong-Young; Oh, Sam Sae; Song, Young Seok; Lee, Seung Jae; Ko, Kyung Jin

    2016-01-01

    Stress-induced cardiomyopathy has become a more recognized and reported entity. It can be caused by emotional or physical stress, which causes excessive catecholamine release. Typically, the clinical course is benign with conservative treatment being effective. However, stress-induced cardiomyopathy can be fatal. A 41-year-old female presented with cardiogenic shock followed by sudden back pain. Initial echocardiographic finding showed severely decreased ejection fraction with akinesia at all mid-to-apical walls with relatively preserved basal wall contractility. The coronary artery was intact on coronary angiography. Cardiac resuscitation and extra-corporeal membrane oxygenation was needed to manage the cardiogenic shock. Recovery was complete after 2 weeks. PMID:27081451

  16. Plastic cap evolution law derived from induced transverse isotropy in dilatational triaxial compression.

    SciTech Connect

    Macon, David James; Brannon, Rebecca Moss; Strack, Otto Eric

    2014-02-01

    Mechanical testing of porous materials generates physical data that contain contributions from more than one underlying physical phenomenon. All that is measurable is the (3z(Bensemble(3y (Bhardening modulus. This thesis is concerned with the phenomenon of dilatation in triaxial compression of porous media, which has been modeled very accurately in the literature for monotonic loading using models that predict dilatation under triaxial compression (TXC) by presuming that dilatation causes the cap to move outwards. These existing models, however, predict a counter-intuitive (and never validated) increase in hydrostatic compression strength. This work explores an alternative approach for modeling TXC dilatation based on allowing induced elastic anisotropy (which makes the material both less stiff and less strong in the lateral direction) with no increase in hydrostatic strength. Induced elastic anisotropy is introduced through the use of a distortion operator. This operator is a fourth-order tensor consisting of a combination of the undeformed stiffness and deformed compliance and has the same eigenprojectors as the elastic compliance. In the undeformed state, the distortion operator is equal to the fourth-order identity. Through the use of the distortion operator, an evolved stress tensor is introduced. When the evolved stress tensor is substituted into an isotropic yield function, a new anisotropic yield function results. In the case of the von Mises isotropic yield function (which contains only deviatoric components), it is shown that the distortion operator introduces a dilatational contribution without requiring an increase in hydrostatic strength. In the thesis, an introduction and literature review of the cap function is given. A transversely isotropic compliance is presented, based on a linear combination of natural bases constructed about a transverse-symmetry axis. Using a probabilistic distribution of cracks constructed for the case of transverse isotropy

  17. Strain Rate Dependence of Compressive Stress-Strain Loops of Several Polymers

    NASA Astrophysics Data System (ADS)

    Nakai, Kenji; Yokoyama, Takashi

    The compressive stress-strain loops of several commercial polymers at strain rates of nearly 700/s are determined in the standard split Hopkinson pressure bar. Four different polymers or typical thermoplastics: ABS, PA-6, PA-66 and PC are tested at room temperature. Cylindrical specimens with a slenderness ratio (= height l /diameter d) of 0.5 are used in the Hopkinson bar tests, and those with l/d = 1.5 as specified in the ASTM Designation E9-89a are used in the static tests. The stress-strain loops in compression at low and intermediate strain rates are measured in an Instron testing machine. The influences of strain rate on the Young's modulus, 2.5% flow stress and dissipation energy are investigated. It is demonstrated that the area within the stress-strain loop (or dissipation energy) increases with increasing strain rate as well as given strain, that is, all polymers tested exhibit intrinsic dynamic viscoelasticity and a high elastic aftereffect following complete unloading.

  18. Phase Stability and Stress-Induced Transformations in Beta Titanium Alloys

    NASA Astrophysics Data System (ADS)

    Kolli, R. Prakash; Joost, William J.; Ankem, Sreeramamurthy

    2015-06-01

    In this article, we provide a brief review of the recent developments related to the relationship between phase stability and stress-induced transformations in metastable body-centered-cubic β-phase titanium alloys. Stress-induced transformations occur during tensile, compressive, and creep loading and influence the mechanical response. These transformations are not fully understood and increased understanding of these mechanisms will permit future development of improved alloys for aerospace, biomedical, and energy applications. In the first part of this article, we review phase stability and discuss a few recent developments. In the second section, we discuss the current status of understanding stress-induced transformations and several areas that require further study. We also provide our perspective on the direction of future research efforts. Additionally, we address the occurrence of the hcp ω-phase and the orthorhombic α″-martensite phase stress-induced transformations.

  19. Tensile and compressive stress-strain behavior of heat treated boron-aluminum

    NASA Technical Reports Server (NTRS)

    Kennedy, J. M.; Tenney, D. R.; Herakovich, C. T.

    1978-01-01

    An experimental study was conducted to assess the effects of heat treatment and cyclic mechanical loading on the tensile and compressive stress-strain behavior of six boron-aluminum composites having different laminate orientations and being subjected to different heat treatments. The heat treatments were as-fabricated, T6, and T6N consisting of T6 treatment followed by cryogenic quench in liquid nitrogen prior to testing. All laminates were tested in monotonic and cyclic compression, while the tensile-test data are taken from the literature for comparison purposes. It is shown that the linear elastic range of the T6- and T6N-condition specimens is larger than that of the as-fabricated specimens, and that cyclic loading in tension or compression strain hardens the specimens and extends the linear elastic range. For laminates containing 0-deg plies, the stress-strain behavior upon unloading is found to be nonlinear, whereas the other laminates exhibit a linear behavior upon unloading. Specimens in the T6 and T6N conditions show higher strain hardening than the as-fabricated specimens.

  20. Piezoresistance in silicon at uniaxial compressive stresses up to 3 GPa.

    PubMed

    Milne, J S; Favorskiy, I; Rowe, A C H; Arscott, S; Renner, Ch

    2012-06-22

    The room-temperature longitudinal piezoresistance of n-type and p-type crystalline silicon along selected crystal axes is investigated under uniaxial compressive stresses up to 3 GPa. While the conductance (G) of n-type silicon eventually saturates at ≈ 45% of its zero-stress value (G(0)) in accordance with the charge transfer model, in p-type material G/G(0) increases above a predicted limit of ≈ 4.5 without any significant saturation, even at 3 GPa. Calculation of G/G(0) using ab initio density functional theory reveals that neither G nor the mobility, when properly averaged over the hole distribution, saturate at stresses lower than 3 GPa. The lack of saturation has important consequences for strained-silicon technologies. PMID:23004630

  1. Stress response of bovine artery and rat brain tissue due to combined translational shear and fixed unconfined compression

    NASA Astrophysics Data System (ADS)

    Leahy, Lauren

    During trauma resulting from impacts and blast waves, sinusoidal waves permeate the brain and cranial arterial tissue, both non-homogeneous biological tissues with high fluid contents. The experimental shear stress response to sinusoidal translational shear deformation at 1 Hz and 25% strain amplitude and either 0% or 33% compression is compared for rat brain tissue and bovine aortic tissue. Both tissues exhibit Mullins effect in shear. Harmonic wavelet decomposition, a novel application to the mechanical response of these tissues, shows significant 1 Hz and 3 Hz components. The 3 Hz component magnitude in brain tissue, which is much larger than in aortic tissue, may correlate to interstitial fluid induced drag forces that decrease on subsequent cycles perhaps because of damage resulting in easier fluid movement. The fluid may cause the quasiperiodic, viscoelastic behavior of brain tissue. The mechanical response differences under impact may cause shear damage between arterial and brain connections.

  2. Deformation failure characteristics of coal body and mining induced stress evolution law.

    PubMed

    Wen, Zhijie; Qu, Guanglong; Wen, Jinhao; Shi, Yongkui; Jia, Chuanyang

    2014-01-01

    The results of the interaction between coal failure and mining pressure field evolution during mining are presented. Not only the mechanical model of stope and its relative structure division, but also the failure and behavior characteristic of coal body under different mining stages are built and demonstrated. Namely, the breaking arch and stress arch which influence the mining area are quantified calculated. A systematic method of stress field distribution is worked out. All this indicates that the pore distribution of coal body with different compressed volume has fractal character; it appears to be the linear relationship between propagation range of internal stress field and compressed volume of coal body and nonlinear relationship between the range of outburst coal mass and the number of pores which is influenced by mining pressure. The results provide theory reference for the research on the range of mining-induced stress and broken coal wall. PMID:24967438

  3. Deformation Failure Characteristics of Coal Body and Mining Induced Stress Evolution Law

    PubMed Central

    Wen, Zhijie; Wen, Jinhao; Shi, Yongkui; Jia, Chuanyang

    2014-01-01

    The results of the interaction between coal failure and mining pressure field evolution during mining are presented. Not only the mechanical model of stope and its relative structure division, but also the failure and behavior characteristic of coal body under different mining stages are built and demonstrated. Namely, the breaking arch and stress arch which influence the mining area are quantified calculated. A systematic method of stress field distribution is worked out. All this indicates that the pore distribution of coal body with different compressed volume has fractal character; it appears to be the linear relationship between propagation range of internal stress field and compressed volume of coal body and nonlinear relationship between the range of outburst coal mass and the number of pores which is influenced by mining pressure. The results provide theory reference for the research on the range of mining-induced stress and broken coal wall. PMID:24967438

  4. The influence of uniaxial compressive stress on the phase transitions and dielectric properties of NaNO2

    NASA Astrophysics Data System (ADS)

    Seyidov, MirHasan Yu.; Mikailzade, Faik A.; Suleymanov, Rauf A.; Bulut, Nebahat; Salehli, Ferid

    2016-06-01

    The effect of uniaxial stress on dielectric properties of sodium nitrite (NaNO2) ferroelectric has been investigated. The real part of the dielectric susceptibility was measured at the frequency of 1 kHz without and on applying compressive uniaxial stress along different crystallographic directions using a uniaxial compress meter. Extraordinary changes in the dielectric constant of NaNO2 under the influence of applied uniaxial stresses were observed for the first time. The shifts of the phase transition points Ti and Tc under the uniaxial stresses σyy and σzz were investigated. The "uniaxial pressure-temperature" phase diagram of NaNO2 was obtained from these results. The observed phenomena were interpreted on the base of the phenomenological Landau theory of phase transitions in NaNO2 by taking into account the uniaxial compressive stress effect. A best agreement between the theoretical predictions and experimental results has been revealed.

  5. Acute stress may induce ovulation in women

    PubMed Central

    2010-01-01

    Background This study aims to gather information either supporting or rejecting the hypothesis that acute stress may induce ovulation in women. The formulation of this hypothesis is based on 2 facts: 1) estrogen-primed postmenopausal or ovariectomized women display an adrenal-progesterone-induced ovulatory-like luteinizing hormone (LH) surge in response to exogenous adrenocorticotropic hormone (ACTH) administration; and 2) women display multiple follicular waves during an interovulatory interval, and likely during pregnancy and lactation. Thus, acute stress may induce ovulation in women displaying appropriate serum levels of estradiol and one or more follicles large enough to respond to a non-midcycle LH surge. Methods A literature search using the PubMed database was performed to identify articles up to January 2010 focusing mainly on women as well as on rats and rhesus monkeys as animal models of interaction between the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes. Results Whereas the HPA axis exhibits positive responses in practically all phases of the ovarian cycle, acute-stress-induced release of LH is found under relatively high plasma levels of estradiol. However, there are studies suggesting that several types of acute stress may exert different effects on pituitary LH release and the steroid environment may modulate in a different way (inhibiting or stimulating) the pattern of response of the HPG axis elicited by acute stressors. Conclusion Women may be induced to ovulate at any point of the menstrual cycle or even during periods of amenorrhea associated with pregnancy and lactation if exposed to an appropriate acute stressor under a right estradiol environment. PMID:20504303

  6. Stress induced neuroendocrine-immune plasticity

    PubMed Central

    Liezmann, Christiane; Stock, Daniel; Peters, Eva M. J.

    2012-01-01

    Research over the past decade has revealed close interaction between the nervous and immune systems in regulation of peripheral inflammation linking psychosocial stress with chronic somatic disease and aging. Moreover emerging data suggests that chronic inflammations lead to a pro-inflammatory status underlying premature aging called inflammaging. In this context, the spleen can be seen as a switch board monitoring peripherally derived neuroendocrine-immune mediators in the blood and keeping up a close communication with the central stress response via its mainly sympathetic innervation. The effect aims at balanced and well-timed stress axis activation and immune adaptation in acute peripheral inflammatory events. Constant adjustment to the needs generated by environmental and endogenous challenges is provided by neuroendocrine-immune plasticity. However, maladaptive plasticity induced e.g., by chronic stress-axis activation and excessive non-neuronal derived neuroendocrine mediators may be at the heart of the observed stress sensitivity promote inflammaging under chronic inflammatory conditions. We here review the role of neurotransmitters, neuropeptides and neurotrophins as stress mediators modulating the immune response in the spleen and their potential role in inflammaging. PMID:23467333

  7. Numerical and experimental study of the thermal stress of silicon induced by a millisecond laser

    SciTech Connect

    Wang Xi; Qin Yuan; Wang Bin; Zhang Liang; Shen Zhonghua; Lu Jian; Ni Xiaowu

    2011-07-20

    A spatial axisymmetric finite element model of single-crystal silicon irradiated by a 1064 nm millisecond laser is used to investigate the thermal stress damage induced by a millisecond laser. The transient temperature field and the thermal stress field for 2 ms laser irradiation with a laser fluence of 254 J/cm{sup 2} are obtained. The numerical simulation results indicate that the hoop stresses along the r axis on the front surface are compressive stress within the laser spot and convert to tensile stress outside the laser spot, while the radial stresses along the r axis on the front surface and on the z axis are compressive stress. The temperature of the irradiated center is the highest temperature obtained, yet the stress is not always highest during laser irradiation. At the end of the laser irradiation, the maximal hoop stress is located at r=0.5 mm and the maximal radial stress is located at r=0.76 mm. The temperature measurement experiments are performed by IR pyrometer. The numerical result of the temperature field is consistent with the experimental result. The damage morphologies of silicon under the action of a 254 J/cm{sup 2} laser are inspected by optical microscope. The cracks are observed initiating at r=0.5 mm and extending along the radial direction.

  8. Motor commands induce time compression for tactile stimuli.

    PubMed

    Tomassini, Alice; Gori, Monica; Baud-Bovy, Gabriel; Sandini, Giulio; Morrone, Maria Concetta

    2014-07-01

    Saccades cause compression of visual space around the saccadic target, and also a compression of time, both phenomena thought to be related to the problem of maintaining saccadic stability (Morrone et al., 2005; Burr and Morrone, 2011). Interestingly, similar phenomena occur at the time of hand movements, when tactile stimuli are systematically mislocalized in the direction of the movement (Dassonville, 1995; Watanabe et al., 2009). In this study, we measured whether hand movements also cause an alteration of the perceived timing of tactile signals. Human participants compared the temporal separation between two pairs of tactile taps while moving their right hand in response to an auditory cue. The first pair of tactile taps was presented at variable times with respect to movement with a fixed onset asynchrony of 150 ms. Two seconds after test presentation, when the hand was stationary, the second pair of taps was delivered with a variable temporal separation. Tactile stimuli could be delivered to either the right moving or left stationary hand. When the tactile stimuli were presented to the motor effector just before and during movement, their perceived temporal separation was reduced. The time compression was effector-specific, as perceived time was veridical for the left stationary hand. The results indicate that time intervals are compressed around the time of hand movements. As for vision, the mislocalizations of time and space for touch stimuli may be consequences of a mechanism attempting to achieve perceptual stability during tactile exploration of objects, suggesting common strategies within different sensorimotor systems. PMID:24990936

  9. Pulverization Texturein Fault Damage Zones: A result of Implosion Damage or Dynamic Compressive Stresses?

    NASA Astrophysics Data System (ADS)

    Rockwell, T. K.; Girty, G.; Whearty, J.; Mitchell, T. M.

    2015-12-01

    Micro-brecciation, or pulverization, is recognized as a fundamental component of the architecture and damage products of many large faults, although the precise mechanisms to produce this damage are debated, with both compressive and tensile mechanisms proposed. We characterized several sites along the San Jacinto fault, southern California, where the total depth of exhumation for the life history of the fault can be determined, to study the confining stresses required for pulverization. In basement rock near Anza, where exhumation is less than 100 m, granitic dikes injected into schist of the Burnt Valley Complex are pulverized out to several meters from the fault core, whereas the schist is brecciated at the macro-scale and contains narrow centimeter-thick seams of black cataclasite. Similar relationships are observed in Horse Canyon, which is exhumed about 400 m below a regional Tertiary erosion surface, where granitic dikes emplaced into schist are pulverized out to distances of several tens of meters from the fault core. These observations imply that very low confining stress is required for micro-brecciation in granitic rock. Unconsolidated sandstones (alluvial fan deposits) along the SJF in Rock House Canyon are undeformed where the deposits are exhumed by about 70 m, but show incipient pulverization (high-density, sub-grain cracking) at 120 m depth of exhumation. Cracks oriented perpendicular to the fault formed in individual quartz and feldspar grains out to a few meters from the fault core. These observations suggest that the confining stress required for onset of pulverization in unconsolidated deposits is on the order of 2-2.5 MPa. As the tensile strength of quartz is an order of magnitude higher than these confining stresses, the most likely mechanism that is producing this damage is dynamic compressive stresses during passage of the rupture front.

  10. Design and fabrication of a large area freestanding compressive stress SiO2 optical window

    NASA Astrophysics Data System (ADS)

    Van Toan, Nguyen; Sangu, Suguru; Ono, Takahito

    2016-07-01

    This paper reports the design and fabrication of a 7.2 mm  ×  9.6 mm freestanding compressive stress SiO2 optical window without buckling. An application of the SiO2 optical window with and without liquid penetration has been demonstrated for an optical modulator and its optical characteristic is evaluated by using an image sensor. Two methods for SiO2 optical window fabrication have been presented. The first method is a combination of silicon etching and a thermal oxidation process. Silicon capillaries fabricated by deep reactive ion etching (deep RIE) are completely oxidized to form the SiO2 capillaries. The large compressive stress of the oxide causes buckling of the optical window, which is reduced by optimizing the design of the device structure. A magnetron-type RIE, which is investigated for deep SiO2 etching, is the second method. This method achieves deep SiO2 etching together with smooth surfaces, vertical shapes and a high aspect ratio. Additionally, in order to avoid a wrinkling optical window, the idea of a Peano curve structure has been proposed to achieve a freestanding compressive stress SiO2 optical window. A 7.2 mm  ×  9.6 mm optical window area without buckling integrated with an image sensor for an optical modulator has been successfully fabricated. The qualitative and quantitative evaluations have been performed in cases with and without liquid penetration.

  11. Compressive forces induce osteogenic gene expression in calvarial osteoblasts.

    PubMed

    Rath, Bjoern; Nam, Jin; Knobloch, Thomas J; Lannutti, John J; Agarwal, Sudha

    2008-01-01

    Bone cells and their precursors are sensitive to changes in their biomechanical environment. The importance of mechanical stimuli has been observed in bone homeostasis and osteogenesis, but the mechanisms responsible for osteogenic induction in response to mechanical signals are poorly understood. We hypothesized that compressive forces could exert an osteogenic effect on osteoblasts and act in a dose-dependent manner. To test our hypothesis, electrospun poly(epsilon-caprolactone) (PCL) scaffolds were used as a 3-D microenvironment for osteoblast culture. The scaffolds provided a substrate allowing cell exposure to levels of externally applied compressive force. Pre-osteoblasts adhered, proliferated and differentiated in the scaffolds and showed extensive matrix synthesis by scanning electron microscopy (SEM) and increased Young's modulus (136.45+/-9.15 kPa) compared with acellular scaffolds (24.55+/-8.5 kPa). Exposure of cells to 10% compressive strain (11.81+/-0.42 kPa) resulted in a rapid induction of bone morphogenic protein-2 (BMP-2), runt-related transcription factor 2 (Runx2), and MAD homolog 5 (Smad5). These effects further enhanced the expression of genes and proteins required for extracellular matrix (ECM) production, such as alkaline phosphatase (Akp2), collagen type I (Col1a1), osteocalcin/bone gamma carboxyglutamate protein (OC/Bglap), osteonectin/secreted acidic cysteine-rich glycoprotein (ON/Sparc) and osteopontin/secreted phosphoprotein 1 (OPN/Spp1). Exposure of cell-scaffold constructs to 20% compressive strain (30.96+/-2.82 kPa) demonstrated that these signals are not osteogenic. These findings provide the molecular basis for the experimental and clinical observations that appropriate physical activities or microscale compressive loading can enhance fracture healing due in part to the anabolic osteogenic effects. PMID:18191137

  12. Inhomogeneous relaxation of a molecular layer on an insulator due to compressive stress.

    PubMed

    Bocquet, F; Nony, L; Mannsfeld, S C B; Oison, V; Pawlak, R; Porte, L; Loppacher, Ch

    2012-05-18

    We discuss the inhomogeneous stress relaxation of a monolayer of hexahydroxytriphenylene (HHTP) which adopts the rare line-on-line (LOL) coincidence on KCl(001) and forms moiré patterns. The fact that the hexagonal HHTP layer is uniaxially compressed along the LOL makes this system an ideal candidate to discuss the influence of inhomogeneous stress relaxation. Our work is a combination of noncontact atomic force microscopy experiments, density functional theory and potential energy calculations, and a thorough interpretation by means of the Frenkel-Kontorova model. We show that the assumption of a homogeneous molecular layer is not valid for this organic-inorganic heteroepitaxial system since the best calculated energy configuration correlates with the experimental data only if inhomogeneous relaxations of the layer are taken into account. PMID:23003159

  13. Inhomogeneous Relaxation of a Molecular Layer on an Insulator due to Compressive Stress

    NASA Astrophysics Data System (ADS)

    Bocquet, F.; Nony, L.; Mannsfeld, S. C. B.; Oison, V.; Pawlak, R.; Porte, L.; Loppacher, Ch.

    2012-05-01

    We discuss the inhomogeneous stress relaxation of a monolayer of hexahydroxytriphenylene (HHTP) which adopts the rare line-on-line (LOL) coincidence on KCl(001) and forms moiré patterns. The fact that the hexagonal HHTP layer is uniaxially compressed along the LOL makes this system an ideal candidate to discuss the influence of inhomogeneous stress relaxation. Our work is a combination of noncontact atomic force microscopy experiments, density functional theory and potential energy calculations, and a thorough interpretation by means of the Frenkel-Kontorova model. We show that the assumption of a homogeneous molecular layer is not valid for this organic-inorganic heteroepitaxial system since the best calculated energy configuration correlates with the experimental data only if inhomogeneous relaxations of the layer are taken into account.

  14. Modeling of Flow Stress of High Titanium Content 6061 Aluminum Alloy Under Hot Compression

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Guan, Yingping; Wang, Zhenhua

    2016-07-01

    Hot compression tests were performed on high titanium content 6061 aluminum alloy (AA 6061-Ti) using a Gleeble-3500 thermomechanical testing system at temperatures from 350 to 510 °C with a constant strain rate in the range of 0.001-10 s-1. Three types of flow stress models were established from the experimental stress-strain curves, the correlation coefficient (R), mean absolute relative error (MARE), and root mean square deviation (RMSD) between the predicted data and the experimental data were also calculated. The results show that the Fields-Backofen model, which includes a softening factor, was the simplest mathematical expression with a level of precision appropriate for the numerical simulations. However, the Arrhenius and artificial neural network (ANN) models were also consistent with the experimental results but they are more limited in their application in terms of their accuracy and the mathematical expression of the models.

  15. Long-term prediction of creep strains of mineral wool slabs under constant compressive stress

    NASA Astrophysics Data System (ADS)

    Gnip, Ivan; Vaitkus, Saulius; Keršulis, Vladislovas; Vėjelis, Sigitas

    2012-02-01

    The results obtained in determining the creep strain of mineral wool slabs under compressive stress, used for insulating flat roofs and facades, cast-in-place floors, curtain and external basement walls, as well as for sound insulation of floors, are presented. The creep strain tests were conducted under a compressive stress of σ c =0.35 σ 10%. Interval forecasting of creep strain was made by extrapolating the creep behaviour and approximated in accordance with EN 1606 by a power equation and reduced to a linear form using logarithms. This was performed for a lead time of 10 years. The extension of the range of the confidence interval due to discount of the prediction data, i.e. a decrease in their informativity was allowed for by an additional coefficient. Analysis of the experimental data obtained from the tests having 65 and 122 days duration showed that the prediction of creep strains for 10 years can be made based on data obtained in experiments with durations shorter than the 122 days as specified by EN 13162. Interval prediction of creep strains (with a confidence probability of 90%) was based on using the mean square deviation of the actual direct observations of creep strains in logarithmic form to have the linear trend in a retrospective area.

  16. Injectant mole-fraction imaging in compressible mixing flows using planar laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Abbitt, John D., III; Mcdaniel, James C.

    1989-01-01

    A technique is described for imaging the injectant mole-fraction distribution in nonreacting compressible mixing flow fields. Planar fluorescence from iodine, seeded into air, is induced by a broadband argon-ion laser and collected using an intensified charge-injection-device array camera. The technique eliminates the thermodynamic dependence of the iodine fluorescence in the compressible flow field by taking the ratio of two images collected with identical thermodynamic flow conditions but different iodine seeding conditions.

  17. Magneto-rotatory compressible couple-stress fluid heated from below in porous medium

    NASA Astrophysics Data System (ADS)

    Mehta, Chander Bhan

    2016-03-01

    The study is aimed at analysing thermal convection in a compressible couple stress fluid in a porous medium in the presence of rotation and magnetic field. After linearizing the relevant equations, the perturbation equations are analysed in terms of normal modes. A dispersion relation governing the effects of rotation, magnetic field, couple stress parameter and medium permeability have been examined. For a stationary convection, the rotation postpones the onset of convection in a couple stress fluid heated from below in a porous medium in the presence of a magnetic field. Whereas, the magnetic field and couple stress postpones and hastens the onset of convection in the presence of rotation and the medium permeability hastens and postpones the onset of convection with conditions on Taylor number. Further the oscillatory modes are introduced due to the presence of rotation and the magnetic field which were non-existent in their absence, and hence the principle of exchange stands valid. The sufficient conditions for nonexistence of over stability are also obtained.

  18. Stress-induced formation mechanism of stacking fault tetrahedra in nano-cutting of single crystal copper

    NASA Astrophysics Data System (ADS)

    Wang, Quanlong; Bai, Qingshun; Chen, Jiaxuan; Guo, Yongbo; Xie, Wenkun

    2015-11-01

    Stacking fault tetrahedra commonly existed in subsurface of deformed face center cubic metals, has great influence on machining precision and surface roughness in nano-cutting. Here we report, a stacking fault tetrahedra is formed in subsurface of workpiece during nano-cutting. The variation of cutting force and subsurface defects distribution are studied by using molecular dynamics simulation. The stress distribution is investigated which is calculated by virial stress and analyzed by static compression. The result shows that the cutting force has a rapidly increase in the initial stage and fluctuates at their equilibrium position at stable cutting stage, which is because of the energy accumulation and release leading to the dislocation emission. A typically stacking fault tetrahedra is nucleated in the subsurface defect layer, which is induced by the complex tension and compression stress. The stress-induced mechanism of stacking fault tetrahedra formation is investigated by atomic scale evolution and local stress distribution.

  19. Laser-induced generation of pure tensile stresses

    SciTech Connect

    Niemz, M.H.; Lin, C.P.; Pitsillides, C.; Cui, J.; Doukas, A.G.; Deutsch, T.F.

    1997-05-01

    While short compressive stresses can readily be produced by laser ablation, the generation of pure tensile stresses is more difficult. We demonstrate that a 90{degree} prism made of polyethylene can serve to produce short and pure tensile stresses. A compressive wave is generated by ablating a thin layer of strongly absorbing ink on one surface of the prism with a Q-switched frequency-doubled Nd:YAG laser. The compressive wave driven into the prism is reflected as a tensile wave by the polyethylene-air interface at its long surface. The low acoustic impedance of polyethylene makes it ideal for coupling tensile stresses into liquids. In water, tensile stresses up to {minus}200bars with a rise time of the order of 20 ns and a duration of 100 ns are achieved. The tensile strength of water is determined for pure tensile stresses lasting for 100 ns only. The technique has potential application in studying the initiation of cavitation in liquids and in comparing the effect of compressive and tensile stress transients on biological media. {copyright} {ital 1997 American Institute of Physics.}

  20. Quantification of Transmission of Vertical stress and Soil Structure under Partially Confined Uniaxial Compression using X-ray CT

    NASA Astrophysics Data System (ADS)

    Naveed, Muhammad; Schjønning, Per; Keller, Thomas; de Jonge, Lis; Moldrup, Per; Lamandé, Mathieu

    2015-04-01

    Soil compaction can seriously damage soil-pore architecture. Accurate estimation of stress transmission through soil is therefore utmost important for efficient soil use and management. Continuous mechanics has been applied for agricultural soils so far, even if their structure is regularly disrupted by tillage. The main objective of the study was to quantify the transmission of vertical stress through topsoil with various initial soil-pore architecture. Partially confined uniaxial compression tests were carried out on intact topsoil columns (20cm diameter and 20cm height) placed on separately sampled subsoil columns in order to simulate field conditions. Stress transmission patterns within the top soil columns were quantified using X-ray CT, while a tactile sensor mat was employed for measuring stresses at the interface of the top and subsoil columns. Resulting soil-pore architecture under applied stresses was quantified using X-ray CT and air permeability measurements. Compression index (Cc) was linearly correlated with initial void ratio of the soils. Discrete stress transmission patterns through top soil were observed at 275 kPa applied stress, whereas elastic stress transmission patterns were observed at 625 kPa applied stress. This means at lower applied stress most of the load is transmitted through aggregates and with increasing applied stresses aggregated soil were deformed toward a more isotropic soil. This reflects that models following the elasticity theory are not able to predict stress transmission through aggregated soil particularly at lower applied stresses. Soil-pore architecture was greatly damaged with increasing applied stresses. X-ray CT analyzed macroporosity, macropore connectivity, and width of macropore size distribution was greatly reduced with increasing applied stresses. Air permeability was tremendously reduced under applied stresses, and all soils showed similar air permeability under 620 kPa stress irrespective of their initial

  1. Diffusion induced stresses in buckling battery electrodes

    NASA Astrophysics Data System (ADS)

    Bhandakkar, Tanmay K.; Johnson, Harley T.

    2012-06-01

    Highly networked nanostructured battery electrode materials offer the possibility of achieving both rapid battery charge-discharge rates and high storage capacity. Recently, lithium ion battery (LIB) electrodes based on a 2-D honeycomb architecture were shown to undergo remarkable and reversible morphological changes during the lithiation process. Charge-discharge rates in 3-D composite electrode have also been shown to benefit from sandwiching the electrolytically active material between highly conductive ion and electron transport pathways to reduce electrical resistance and solid-state diffusion lengths. In the present work we simulate and analyze the observed morphological changes in honeycomb electrodes, with and without the presence of conductive pathways, during the lithiation-delithiation process. Diffusion induced stresses are analyzed for such structures undergoing elastic-plastic deformation during cycling. The results show that such a periodic, nanostructured electrode geometry allows for the presence of buckling-like deformation modes, which effectively reduce the resulting mechanical stresses that lead to electrode failure.

  2. Stress state in turbopump bearing induced by shrink fitting

    NASA Technical Reports Server (NTRS)

    Sims, P.; Zee, R.

    1991-01-01

    The stress generated by shrink fitting in bearing-like geometries is studied. The feasibility of using strain gages to determine the strain induced by shrink fitting process is demonstrated. Results from a ring with a uniform cross section reveal the validity of simple stress mechanics calculations for determining the stress state induced in this geometry by shrink fitting.

  3. SIRT1-dependent myoprotective effects of resveratrol on muscle injury induced by compression

    PubMed Central

    Sin, Thomas K.; Yung, Benjamin Y.; Yip, Shea P.; Chan, Lawrence W.; Wong, Cesar S.; Tam, Eric W.; Siu, Parco M.

    2015-01-01

    Our current understanding on the molecular mechanisms by which sustained compression induces skeletal muscle injury is very limited. This study aimed to test the hypothesis that activation of SIRT1 by the natural antioxidant resveratrol could deactivate apoptotic and catabolic signaling in skeletal muscle exposed to moderate compression. Two cycles of 6-h constant pressure at 100 mmHg was applied to the tibialis region of right, but not left hindlimbs of Sprague Dawley rats pre-treated with DMSO (vehicle control) or resveratrol with/without sirtinol. Skeletal muscle tissues lying underneath and spatially corresponding to the compressed sites were collected for analyses. Resveratrol prevented the compression-induced manifestations of pathohistological damages including elevations of the number of interstitial nuclei and area of interstitial space and ameliorated oxidative damages measured as 4-hydroxy-2-nonenal (4HNE) and nitrotyrosine in skeletal muscle. In parallel, resveratrol augmented the expression level and activity of SIRT1 and phosphorylation levels of Foxo3a and Akt while suppressed the increases in protein abundances of p53, Bax, MAFbx, and ubiquitin, enzymatic activities of caspase 3 and 20S proteasome, and apoptotic DNA fragmentation in the compressed muscle. These favorable myoprotective effects of resveratrol were diminished upon pharmacological blockade of SIRT1 by using sirtinol. These novel data support the hypothesis that the anti-apoptotic and anti-catabolic effects of resveratrol on compression injury in skeletal muscle required the action of SIRT1. PMID:26557094

  4. Melamine Induces Oxidative Stress in Mouse Ovary

    PubMed Central

    Dai, Xiao-Xin; Duan, Xing; Cui, Xiang-Shun; Kim, Nam-Hyung; Xiong, Bo; Sun, Shao-Chen

    2015-01-01

    Melamine is a nitrogen heterocyclic triazine compound which is widely used as an industrial chemical. Although melamine is not considered to be acutely toxic with a high LD50 in animals, food contaminated with melamine expose risks to the human health. Melamine has been reported to be responsible for the renal impairment in mammals, its toxicity on the reproductive system, however, has not been adequately assessed. In the present study, we examined the effect of melamine on the follicle development and ovary formation. The data showed that melamine increased reactive oxygen species (ROS) levels, and induced granulosa cell apoptosis as well as follicle atresia. To further analyze the mechanism by which melamine induces oxidative stress, the expression and activities of two key antioxidant enzymes superoxide dismutase (SOD) and glutathi-one peroxidase (GPX) were analyzed, and the concentration of malondialdehyde (MDA) were compared between control and melamine-treated ovaries. The result revealed that melamine changed the expression and activities of SOD and GPX in the melamine-treated mice. Therefore, we demonstrate that melamine causes damage to the ovaries via oxidative stress pathway. PMID:26545251

  5. Electrochemical behavior of single-walled carbon nanotube supercapacitors under compressive stress.

    PubMed

    Li, Xin; Rong, Jiepeng; Wei, Bingqing

    2010-10-26

    The effect of compressive stress on the electrochemical behavior of flexible supercapacitors assembled with single-walled carbon nanotube (SWNT) film electrodes and 1 M aqueous electrolytes with different anions and cations were thoroughly investigated. The under-pressed capacitive and resistive features of the supercapacitors were studied by means of cyclic voltammetry measurements and electrochemical impedance analysis. The results demonstrated that the specific capacitance increased first and saturated in corresponding decreases of the series resistance, the charge-transfer resistance, and the Warburg diffusion resistance under an increased pressure from 0 to 1723.96 kPa. Wettability as well as ion-size effect of different aqueous electrolytes played important roles to determine the pressure dependence behavior of the suerpcapacitors under an applied pressure. An improved high-frequency capacitive response with 1172 Hz knee frequency, which is significantly higher compared to reported values, was observed under the compressive pressure of 1723.96 kPa, indicating an improving and excellent high-power capability of the supercapacitors under the pressure. The experimental results and the thorough analysis described in this work not only provide fundamental insight of pressure effects on supercapacitors but also give an important guideline for future design of next generation flexible/stretchable supercapacitors for industrial and consumer applications. PMID:20828214

  6. New method for predicting lifetime of seals from compression-stress relaxation experiments

    SciTech Connect

    Gillen, K.T.; Keenan, M.R.; Wise, J.

    1998-06-01

    Interpretation of compression stress-relaxation (CSR) experiments for elastomers in air is complicated by (1) the presence of both physical and chemical relaxation and (2) anomalous diffusion-limited oxidation (DLO) effects. For a butyl material, the authors first use shear relaxation data to indicate that physical relaxation effects are negligible during typical high temperature CSR experiments. They then show that experiments on standard CSR samples ({approximately}15 mm diameter when compressed) lead to complex non-Arrhenius behavior. By combining reaction kinetics based on the historic basic autoxidation scheme with a diffusion equation appropriate to disk-shaped samples, they derive a theoretical DLO model appropriate to CSR experiments. Using oxygen consumption and permeation rate measurements, the theory shows that important DLO effects are responsible for the observed non-Arrhenius behavior. To minimize DLO effects, they introduce a new CSR methodology based on the use of numerous small disk samples strained in parallel. Results from these parallel, minidisk experiments lead to Arrhenius behavior with an activation energy consistent with values commonly observed for elastomers, allowing more confident extrapolated predictions. In addition, excellent correlation is noted between the CSR force decay and the oxygen consumption rate, consistent with the expectation that oxidative scission processes dominate the CSR results.

  7. Martensitic transformation of FeNi nanofilm induced by interfacial stress generated in FeNi/V nanomultilayered structure

    PubMed Central

    2014-01-01

    FeNi/V nanomultilayered films with different V layer thicknesses were synthesized by magnetron sputtering. By adjusting the thickness of the V layer, different interfacial compressive stress were imposed on FeNi layers and the effect of interfacial stress on martensitic transformation of the FeNi film was investigated. Without insertion of V layers, the FeNi film exhibits a face-centered cubic (fcc) structure. With the thickness of V inserted layers up to 1.5 nm, under the coherent growth structure in FeNi/V nanomultilayered films, FeNi layers bear interfacial compressive stress due to the larger lattice parameter relative to V, which induces the martensitic transformation of the FeNi film. As the V layer thickness increases to 2.0 nm, V layers cannot keep the coherent growth structure with FeNi layers, leading to the disappearance of interfacial compressive stress and termination of the martensitic transformation in the FeNi film. The interfacial compressive stress-induced martensitic transformation of the FeNi nanofilm is verified through experiment. The method of imposing and modulating the interfacial stress through the epitaxial growth structure in the nanomultilayered films should be noticed and utilized. PMID:25232296

  8. Cell death induced by mechanical compression on engineered muscle results from a gradual physiological mechanism.

    PubMed

    Wu, Yabin; van der Schaft, Daisy W J; Baaijens, Frank P; Oomens, Cees W J

    2016-05-01

    Deep tissue injury (DTI), a type of pressure ulcer, arises in the muscle layers adjacent to bony prominences due to sustained mechanical loading. DTI presents a serious problem in the clinic, as it is often not visible until reaching an advanced stage. One of the causes can be direct mechanical deformation of the muscle tissue and cell. The mechanism of cell death induced by mechanical compression was studied using bio-artificial skeletal muscle tissues. Compression was applied by placing weights on top of the constructs. The morphological changes of the cytoskeleton and the phosphorylation of mitogen-activated protein kinases (MAPK) under compression were investigated. Moreover, inhibitors for each of the three major MAPK groups, p38, ERK, and JNK, were applied separately to look at their roles in the compression caused apoptosis and necrosis. The present study for the first time showed that direct mechanical compression activates MAPK phosphorylation. Compression also leads to a gradual destruction of the cytoskeleton. The percentage apoptosis is strongly reduced by p38 and JNK inhibitors down to the level of the unloaded group. This phenomenon could be observed up to 24h after initiation of compression. Therefore, cell death in bio-artificial muscle tissue caused by mechanical compression is primarily caused by a physiological mechanism, rather than through a physical mechanism which kills the cell directly. These findings reveal insight of muscle cell death under mechanical compression. Moreover, the result indicates a potential clinical solution to prevent DTI by pre-treating with p38 or/and JNK inhibitors. PMID:26961799

  9. DHEA administration modulates stress-induced analgesia in rats.

    PubMed

    Cecconello, Ana Lúcia; Torres, Iraci L S; Oliveira, Carla; Zanini, Priscila; Niches, Gabriela; Ribeiro, Maria Flávia Marques

    2016-04-01

    An important aspect of adaptive stress response is the pain response suppression that occurs during or following stress exposure, which is often referred to as acute stress-induced analgesia. Dehydroepiandrosterone (DHEA) participates in the modulation of adaptive stress response, changing the HPA axis activity. The effect of DHEA on the HPA axis activity is dependent on the state and uses the same systems that participate in the regulation of acute stress-induced analgesia. The impact of DHEA on nociception has been studied; however, the effect of DHEA on stress-induced analgesia is not known. Thus, the aim of the present study was to evaluate the effect of DHEA on stress-induced analgesia and determine the best time for hormone administration in relation to exposure to stressor stimulus. The animals were stressed by restraint for 1h in a single exposure and received treatment with DHEA by a single injection before the stress or a single injection after the stress. Nociception was assessed with a tail-flick apparatus. Serum corticosterone levels were measured. DHEA administered before exposure to stress prolonged the acute stress-induced analgesia. This effect was not observed when the DHEA was administered after the stress. DHEA treatment in non-stressed rats did not alter the nociceptive threshold, suggesting that the DHEA effect on nociception is state-dependent. The injection of DHEA had the same effect as exposure to acute stress, with both increasing the levels of corticosterone. In conclusion, acute treatment with DHEA mimics the response to acute stress indexed by an increase in activity of the HPA axis. The treatment with DHEA before stress exposure may facilitate adaptive stress response, prolonging acute stress-induced analgesia, which may be a therapeutic strategy of interest to clinics. PMID:26852948

  10. Adaptation-Induced Compression of Event Time Occurs Only for Translational Motion

    PubMed Central

    Fornaciai, Michele; Arrighi, Roberto; Burr, David C.

    2016-01-01

    Adaptation to fast motion reduces the perceived duration of stimuli displayed at the same location as the adapting stimuli. Here we show that the adaptation-induced compression of time is specific for translational motion. Adaptation to complex motion, either circular or radial, did not affect perceived duration of subsequently viewed stimuli. Adaptation with multiple patches of translating motion caused compression of duration only when the motion of all patches was in the same direction. These results show that adaptation-induced compression of event-time occurs only for uni-directional translational motion, ruling out the possibility that the neural mechanisms of the adaptation occur at early levels of visual processing. PMID:27003445

  11. Stress-relaxation response of human menisci under confined compression conditions.

    PubMed

    Martin Seitz, Andreas; Galbusera, Fabio; Krais, Carina; Ignatius, Anita; Dürselen, Lutz

    2013-10-01

    The objective of this study was to determine the viscoelastic properties of human meniscal tissue during stress-relaxation under confined compression conditions. Lateral and medial longitudinal meniscus plugs of 25 donor knees (ntotal=150) were exposed to stress-relaxation tests under confined compression conditions at three compression levels (ε=0.1; 0.15; 0.2). Mathematical modelling using an exponential 1D-diffusion equation was used to predict the viscoelastic properties. Subsequently, finite element (FE) models were created using identical geometry, properties and test conditions as used for the in-vitro tests. Two constitutively different underlying mathematical formulations were applied to the FE models to reveal possible differences in their predictions for the relaxation response. While the first FE model mimicked the analytical model (FE1), the second FE model used a different biphasic, non-linear approach (FE2). Regression analyses showed promising coefficients of determination (R(2)>0.73) between the experimental data and the predictions obtained from the diffusion equation and the two FE models. Mean aggregate modulus, predicted with the diffusion equation (HA=64.0 kPa) was lower than those obtained with the two FE analyses (HA,FE1=91.9 kPa; HA,FE2=81.5 kPa). Mean hydraulic permeability (kFE2=1.5×10(-15)m(4)/Ns) of the second FE2 approach was statistically lower (p<0.01) than the other permeability values (k=3.9×10(-15)m(4)/Ns; kFE1=3.4×10(-15)m(4)/Ns). These differences are mainly due to the different underlying mathematical models used. However, when compared with corresponding literature, the results of the present study indicated good agreement. The results of the present study contribute to a better understanding of the complex nature of meniscal tissue and might also have an impact on the design of future meniscal substitutes. PMID:23811278

  12. The relaxation of intrinsic compressive stress in complementary metal-oxide-semiconductor transistors by additional N ion implantation treatment with atomic force microscope-Raman stress extraction

    NASA Astrophysics Data System (ADS)

    Liao, M.-H.; Chen, C.-H.; Chang, L.-C.; Yang, C.; Kao, S.-C.

    2012-05-01

    Based on the stress extraction and measurement by atomic force microscope-Raman technique with the nanometer level space resolution, the high compressive stress about 550 MPa on the Si active region (OD) is observed for the current complementary metal-oxide-semiconductor (CMOS) transistor. During the thermal budget for the standard manufacture process of the current CMOS transistor, the difference of thermal expansion coefficients between Si and Shallow Trench Isolation (STI) oxide results in this high compressive stress in Si OD and further degrades the electron carrier mobility seriously. In order to relax this intrinsic processed compressive stress in Si OD and try to recover this performance loss, the novel process is proposed in this work in addition to the usage of one-side pad SiN layer. With this novel process of additional N-ion implantation (IMP) treatment in STI oxide, it can be found that the less compressive stress about 438 MPa in Si OD can be achieved by the smaller difference of thermal expansion coefficients between Si and N-doped SiO2 STI oxide. The formation of Si-N bonding in N-doped SiO2 STI region can be monitored by Fourier transform infrared spectroscopy spectra and thermal expansion coefficients for Si, SiO2, and SiN are 2.6 ppm/K, 0.4 ppm/K, and 2.87 ppm/K, respectively. The effective relaxation of intrinsic processed compressive stress in Si OD about 112 MPa (from 550 MPa to 438 MPa) by this proposed additional N IMP treatment contributes ˜14% electron carrier mobility enhancement/recovery. The experimental electrical data agree well with the theoretical piezoelectricity calculation for the strained-Si theory.

  13. Critical Compressive Stress for Flat Rectangular Plates Supported Along All Edges and Elastically Restrained Against Rotation along the Unloaded Edges

    NASA Technical Reports Server (NTRS)

    Lundquist, Eugene E; Stowell, Elbridge Z

    1942-01-01

    A chart is presented for the values of the coefficient in the formula for the critical compressive stress at which buckling may be expected to occur in flat rectangular plates supported along all edges and, in addition, elastically restrained against rotation along the unloaded edges. The mathematical derivations of the formulas required in the construction of the chart are given.

  14. Antiamnesic effect of acyl-prolyl-containing dipeptide (GVS-111) in compression-induced damage to frontal cortex.

    PubMed

    Romanova, G A; Mirzoev, T K; Barskov, I V; Victorov, I V; Gudasheva, T A; Ostrovskaya, R U

    2000-09-01

    Antiamnestic effect of acyl-prolyl-containing dipeptide GVS-111 was demonstrated in rats with bilateral compression-induced damage to the frontal cortex. Both intraperitoneal and oral administration of the dipeptide improved retrieval of passive avoidance responses in rats with compression-induced cerebral ischemia compared to untreated controls. PMID:11177261

  15. Conduction-only transport phenomena in compressible bivelocity fluids: Diffuse interfaces and Korteweg stresses

    NASA Astrophysics Data System (ADS)

    Brenner, Howard

    2014-04-01

    "Diffuse interface" theories for single-component fluids—dating back to van der Waals, Korteweg, Cahn-Hilliard, and many others—are currently based upon an ad hoc combination of thermodynamic principles (built largely upon Helmholtz's free-energy potential) and so-called "nonclassical" continuum-thermomechanical principles (built largely upon Newtonian mechanics), with the latter originating with the pioneering work of Dunn and Serrin [Arch. Ration. Mech. Anal. 88, 95 (1985)]. By introducing into the equation governing the transport of energy the notion of an interstitial work-flux contribution, above and beyond the usual Fourier heat-flux contribution, namely, jq=-k∇T, to the energy flux, Dunn and Serrin provided a rational continuum-thermomechanical basis for the presence of Korteweg stresses in the equation governing the transport of linear momentum in compressible fluids. Nevertheless, by their failing to recognize the existence and fundamental need for an independent volume transport equation [Brenner, Physica A 349, 11 (2005), 10.1016/j.physa.2004.10.033]—especially for the roles played therein by the diffuse volume flux jv and the rate of production of volume πv at a point of the fluid continuum—we argue that diffuse interface theories for fluids stand today as being both ad hoc and incomplete owing to their failure to recognize the need for an independent volume transport equation for the case of compressible fluids. In contrast, we point out that bivelocity hydrodynamics, as it already exists [Brenner, Phys. Rev. E 86, 016307 (2012), 10.1103/PhysRevE.86.016307], provides a rational, non-ad hoc, and comprehensive theory of diffuse interfaces, not only for single-component fluids, but also for certain classes of crystalline solids [Danielewski and Wierzba, J. Phase Equilib. Diffus. 26, 573 (2005), 10.1007/s11669-005-0002-y]. Furthermore, we provide not only what we believe to be the correct constitutive equation for the Korteweg stress in the

  16. Cell cytoskeletal changes effected by static compressive stress lead to changes in the contractile properties of tissue regenerative collagen membranes.

    PubMed

    Gellynck, K; Shah, R; Deng, D; Parkar, M; Liu, W; Knowles, J C; Buxton, P

    2013-01-01

    Static compressive stress can influence the matrix, which subsequently affects cell behaviour and the cell's ability to further transform the matrix. This study aimed to assess response to static compressive stress at different stages of osteoblast differentiation and assess the cell cytoskeleton's role as a conduit of matrix-derived stimuli. Mouse bone marrow mesenchymal stem cells (MSCs) (D1 ORL UVA), osteoblastic cells (MC3T3-E1) and post-osteoblast/pre-osteocyte-like cells (MLO-A5) were seeded in hydrated and compressed collagen gels. Contraction was quantified macroscopically, and cell morphology, survival, differentiation and mineralisation assessed using confocal microscopy, alamarBlue® assay, real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and histological stains, respectively. Confocal microscopy demonstrated cell shape changes and favourable microfilament organisation with static compressive stress of the collagen matrix; furthermore, cell survival was greater compared to the hydrated gels. The stage of osteoblast differentiation determined the degree of matrix contraction, with MSCs demonstrating the greatest amount. Introduction of microfilament disrupting inhibitors confirmed that pre-stress and tensegrity forces were under the influence of gel density, and there was increased survival and differentiation of the cells within the compressed collagen compared to the hydrated collagen. There was also relative stiffening and differentiation with time of the compressed cell-seeded collagen, allowing for greater manipulation. In conclusion, the combined collagen chemistry and increased density of the microenvironment can promote upregulation of osteogenic genes and mineralisation; MSCs can facilitate matrix contraction to form an engineered membrane with the potential to serve as a 'pseudo-periosteum' in the regeneration of bone defects. PMID:23813054

  17. Relaxation of curvature-induced elastic stress by the Asaro-Tiller-Grinfeld instability

    NASA Astrophysics Data System (ADS)

    Köhler, C.; Backofen, R.; Voigt, A.

    2015-08-01

    A two-dimensional crystal on the surface of a sphere experiences elastic stress due to the incompatibility of the crystal axes and the curvature. A common mechanism to relax elastic stress is the Asaro-Tiller-Grinfeld (ATG) instability. With a combined numerical and analytical approach, we demonstrate that also curvature-induced stress in surface crystals can be relaxed by the long-wavelength ATG instability. The numerical results are obtained using a surface phase-field crystal (PFC) model, from which we determine the characteristic wave numbers of the ATG instability for various surface coverages corresponding to different curvature-induced compressions. The results are compared with an analytic expression for the characteristic wave number, obtained from a continuum approach which accounts for hexagonal crystals and intrinsic PFC symmetries. We find our numerical results in accordance with the analytical predictions.

  18. An Analytical Solution for Mechanical Responses Induced by Temperature and Air Pressure in a Lined Rock Cavern for Underground Compressed Air Energy Storage

    NASA Astrophysics Data System (ADS)

    Zhou, Shu-Wei; Xia, Cai-Chu; Du, Shi-Gui; Zhang, Ping-Yang; Zhou, Yu

    2015-03-01

    Mechanical responses induced by temperature and air pressure significantly affect the stability and durability of underground compressed air energy storage (CAES) in a lined rock cavern. An analytical solution for evaluating such responses is, thus, proposed in this paper. The lined cavern of interest consists of three layers, namely, a sealing layer, a concrete lining and the host rock. Governing equations for cavern temperature and air pressure, which involve heat transfer between the air and surrounding layers, are established first. Then, Laplace transform and superposition principle are applied to obtain the temperature around the lined cavern and the air pressure during the operational period. Afterwards, a thermo-elastic axisymmetrical model is used to analytically determine the stress and displacement variations induced by temperature and air pressure. The developments of temperature, displacement and stress during a typical operational cycle are discussed on the basis of the proposed approach. The approach is subsequently verified with a coupled compressed air and thermo-mechanical numerical simulation and by a previous study on temperature. Finally, the influence of temperature on total stress and displacement and the impact of the heat transfer coefficient are discussed. This paper shows that the temperature sharply fluctuates only on the sealing layer and the concrete lining. The resulting tensile hoop stresses on the sealing layer and concrete lining are considerably large in comparison with the initial air pressure. Moreover, temperature has a non-negligible effect on the lined cavern for underground compressed air storage. Meanwhile, temperature has a greater effect on hoop and longitudinal stress than on radial stress and displacement. In addition, the heat transfer coefficient affects the cavern stress to a higher degree than the displacement.

  19. Planar temperature measurement in compressible flows using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.

    1991-01-01

    A laser-induced iodine fluorescence technique that is suitable for the planar measurement of temperature in cold nonreacting compressible air flows is investigated analytically and demonstrated in a known flow field. The technique is based on the temperature dependence of the broadband fluorescence from iodine excited by the 514-nm line of an argon-ion laser. Temperatures ranging from 165 to 245 K were measured in the calibration flow field. This technique makes complete, spatially resolved surveys of temperature practical in highly three-dimensional, low-temperature compressible flows.

  20. Mantle-induced subsidence and compression in SE Asia since the early Miocene

    NASA Astrophysics Data System (ADS)

    Yang, Ting; Gurnis, Michael; Zahirovic, Sabin

    2016-03-01

    Rift basins developed extensively across Sundaland, the continental core of Southeast Asia, since the Eocene. Beginning in the early Miocene, basins in southern Sundaland experienced widespread synchronous compression (inversion) and marine inundation, despite a large drop in long-term global sea level. The mechanism for this large-scale synchronous regional sea level rise, basin inversion, and subsidence is not well understood and contrary to expectations from traditional basin models and eustatic sea level trends. We present geodynamic models of mantle convection with both deformable and rigid plate reconstructions to investigate this enigma. Models suggest that a slab stagnates within the transition zone beneath Southeast Asia before the Miocene. The stagnant slab penetrated through the 660 km mantle discontinuity during the early Miocene and formed a slab avalanche event, due to continuous subduction and accumulation of negatively buoyant slabs. This avalanche may have induced large-scale marine inundation, regional compression, and basin inversion across southern Sundaland. We argue mantle convection induced large-scale basin compression, in contrast to conventional plate margin-induced compression; this suggests mantle convection may exert a much stronger control on surface processes than previously recognized.

  1. Investigation of stress-induced (100) platelet formation and surface exfoliation in plasma hydrogenated Si

    SciTech Connect

    Di Zengfeng; Wang Yongqiang; Nastasi, Michael; Rossi, Francois; Lee, Jung-Kun; Shao, Lin; Thompson, Phillip E.

    2007-12-10

    We have studied the mechanisms underlying stress-induced platelet formation during plasma hydrogenation. The stress is purposely introduced by a buried SiGe stained layer in a Si substrate. During plasma hydrogenation, diffusing H is trapped in the region of the SiGe layer and H platelets are formed. The platelet orientation is controlled by the in-plane compressive stress, which favors nucleation and growth of platelets in the plane of stress and parallel to the substrate surface, and ultimately leads to controlled fracture along the SiGe layer. Also, the Si/SiGe/Si structure is found to be more efficient in utilizing H for platelet formation and growth compared to H ion implanted Si because there are fewer defects to trap H (e.g., V{sub n}H{sub m} and I{sub n}H{sub m}); therefore, the total H dose needed for layer exfoliation is greatly reduced.

  2. Uncemented Total Hip Replacement Stem Loosening after Long Term Compressive Stress Application: A Simulated FEA Study of Cortical Bone Remodeling

    NASA Astrophysics Data System (ADS)

    Jung, Duk-Young; Tsutsumi, Sadami; Nakai, Ryusuke; Ikeuchi, Ken; Sekel, Ron

    The purpose of this study is to predict with the use of FEA, the differing predisposition to cortical bone resorption and subsequent distal migration of an un-cemented femoral hip replacement stem subjected to long term biomechanical high compressive stresses, while varying the load angles, the material properties of the stem, and the stem length. A two-dimensional hip model was constructed to estimate the minimum principle stresses (P3) and migration magnitudes. Bone remodeling at the interface between the bone and the prosthesis was performed by comparison of the local compressive stress to physiological stress values governing bone resorption. With respect to load angles, migrations of the hip prosthesis did not occur with load angles between 63° and 74° load angle in relation to the longitudinal axis of the bony femur, as the compressive stress generated on the cortical bone was under the criteria threshold for bone resorption (-50MPa). In addition, the magnitude of migration (17%decrease) was relatively more sensitive to changes in stem length than those (92%decrease) of changes of material properties. In conclusion, using an FEA model for bone remodeling, based on the high compressive stresses exerted on distal cortical bone, it is possible to estimate migration magnitudes of cementless hip prostheses in the long term. The load angles have been shown to be an important parameter affecting the migration magnitudes and furthermore, it can be demonstrated that the stiffer materials and reduction of stem length can decrease the migration of cementless hip prosthesis in the long term.

  3. Extracting Constitutive Stress-Strain Behavior of Microscopic Phases by Micropillar Compression

    SciTech Connect

    Williams, J. J.; Walters, Jennifer; Wang, Mingyue; Chawla, N.; Rohatgi, Aashish

    2013-02-01

    The manuscript describes how micropillar compression technique can be used to perform uniaxial compression tests within individual grains so as to generate local-scale constitutive behavior which, otherwise cannot be ascertained from the conventional macroscale compression test techniques. The manuscript uses steel and magnesium alloys as an example. A portion of the magnesium work was performed at PNNL.

  4. Investigation on Residual Stress Induced by Shot Peening

    NASA Astrophysics Data System (ADS)

    Zhao, Chunmei; Gao, Yukui; Guo, Jing; Wang, Qiang; Fu, Lichao; Yang, Qingxiang

    2015-03-01

    The high strength steel widely used in the aviation industry was chosen in this paper. The shot peening (SP) tests with different technical parameters were carried out, and compressive residual stress (CRS) distribution along the depth was determined. The phase structures before and after SP were analyzed by XRD and TEM. Microhardness and fatigue life were measured, and the morphology of fatigue fracture was also observed. The effects of different technical parameters on CRS field were investigated, and the CRS features with the characteristic parameters were analyzed deeply to summarize the rules. The results show that the CRS field induced by SP can be expressed by four characteristic parameters: the surface CRS σsrs, the maximum CRS σmrs, the depth of maximum CRS ξm and the depth of CRS (strengthened depth) ξ0. Martensite matrix is not changed by SP, while its boundary changes ambiguous with the formation of dislocations. After SP, the microhardness of the specimen increase, and the fatigue crack source moves inwards. The SP saturated time is 1 min. With the increase of SP intensity, σsrs, σmrs, ξm, and ξ0 all increase. While with the increase of SP angle, ξ0 grows gradually. The strengthen effect behaves more obviously as the shot size increases, and the shot material with larger hardness cause higher level of CRS field. Dual SP mainly increases σsrs value.

  5. Salubrious effects of oxytocin on social stress-induced deficits

    PubMed Central

    Smith, Adam S.; Wang, Zuoxin

    2012-01-01

    Social relationships are a fundamental aspect of life, affecting social, psychological, physiological, and behavioral functions. While social interactions can attenuate stress and promote health, disruption, confrontations, isolation, or neglect in the social environment can each be major stressors. Social stress can impair the basal function and stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis, impairing function of multiple biological systems and posing a risk to mental and physical health. In contrast, social support can ameliorate stress-induced physiological and immunological deficits, reducing the risk of subsequent psychological distress and improving an individual's overall well-being. For better clinical treatment of these physiological and mental pathologies, it is necessary to understand the regulatory mechanisms of stress-induced pathologies as well as determine the underlying biological mechanisms that regulate social buffering of the stress system. A number of ethologically relevant animal models of social stress and species that form strong adult social bonds have been utilized to study the etiology, treatment, and prevention of stress-related disorders. While undoubtedly a number of biological pathways contribute to the social buffering of the stress response, the convergence of evidence denotes the regulatory effects of oxytocin in facilitating social bond-promoting behaviors and their effect on the stress response. Thus, oxytocin may be perceived as a common regulatory element of the social environment, stress response, and stress-induced risks on mental and physical health. PMID:22178036

  6. TIA1 oxidation inhibits stress granule assembly and sensitizes cells to stress-induced apoptosis

    PubMed Central

    Arimoto-Matsuzaki, Kyoko; Saito, Haruo; Takekawa, Mutsuhiro

    2016-01-01

    Cytoplasmic stress granules (SGs) are multimolecular aggregates of stalled translation pre-initiation complexes that prevent the accumulation of misfolded proteins, and that are formed in response to certain types of stress including ER stress. SG formation contributes to cell survival not only by suppressing translation but also by sequestering some apoptosis regulatory factors. Because cells can be exposed to various stresses simultaneously in vivo, the regulation of SG assembly under multiple stress conditions is important but unknown. Here we report that reactive oxygen species (ROS) such as H2O2 oxidize the SG-nucleating protein TIA1, thereby inhibiting SG assembly. Thus, when cells are confronted with a SG-inducing stress such as ER stress caused by protein misfolding, together with ROS-induced oxidative stress, they cannot form SGs, resulting in the promotion of apoptosis. We demonstrate that the suppression of SG formation by oxidative stress may underlie the neuronal cell death seen in neurodegenerative diseases. PMID:26738979

  7. Stress, stress-induced cortisol responses, and eyewitness identification performance.

    PubMed

    Sauerland, Melanie; Raymaekers, Linsey H C; Otgaar, Henry; Memon, Amina; Waltjen, Thijs T; Nivo, Maud; Slegers, Chiel; Broers, Nick J; Smeets, Tom

    2016-07-01

    In the eyewitness identification literature, stress and arousal at the time of encoding are considered to adversely influence identification performance. This assumption is in contrast with findings from the neurobiology field of learning and memory, showing that stress and stress hormones are critically involved in forming enduring memories. This discrepancy may be related to methodological differences between the two fields of research, such as the tendency for immediate testing or the use of very short (1-2 hours) retention intervals in eyewitness research, while neurobiology studies insert at least 24 hours. Other differences refer to the extent to which stress-responsive systems (i.e., the hypothalamic-pituitary-adrenal axis) are stimulated effectively under laboratory conditions. The aim of the current study was to conduct an experiment that accounts for the contemporary state of knowledge in both fields. In all, 123 participants witnessed a live staged theft while being exposed to a laboratory stressor that reliably elicits autonomic and glucocorticoid stress responses or while performing a control task. Salivary cortisol levels were measured to control for the effectiveness of the stress induction. One week later, participants attempted to identify the thief from target-present and target-absent line-ups. According to regression and receiver operating characteristic analyses, stress did not have robust detrimental effects on identification performance. Copyright © 2016 John Wiley & Sons, Ltd. © 2016 The Authors Behavioral Sciences & the Law Published by John Wiley & Sons Ltd. PMID:27417874

  8. Shape modification of phospholipid vesicles induced by high pressure: influence of bilayer compressibility.

    PubMed

    Beney, L; Perrier-Cornet, J M; Hayert, M; Gervais, P

    1997-03-01

    Giant vesicles composed of pure egg yolk phosphatidylcholine (EYPC) or containing cholesterol (28 mol%) have been studied during a high hydrostatic pressure treatment to 285 MPa by microscopic observation. During pressure loading the vesicles remain spherical. A shape transition consisting of budding only occurs on the cholesterol-free vesicles during pressure release. The decrease in the volume delimited by the pure EYPC bilayer between 0.1 and 285 MPa was found to be 16% of its initial volume, whereas the bulk compression of water in this pressure range is only 10%. So the compression at 285 MPa induced a water exit from the pure EYPC vesicle. The shape transition of the EYPC vesicle during pressure release is attributed to an increase in its area-to-volume ratio caused by the loss of its water content during compression. Because bulk compression of the cholesterol-containing vesicle is close to that of water, no water transfer would be induced across the bilayer and the vesicle remains spherical during the pressure release. PMID:9138571

  9. Shape modification of phospholipid vesicles induced by high pressure: influence of bilayer compressibility.

    PubMed Central

    Beney, L; Perrier-Cornet, J M; Hayert, M; Gervais, P

    1997-01-01

    Giant vesicles composed of pure egg yolk phosphatidylcholine (EYPC) or containing cholesterol (28 mol%) have been studied during a high hydrostatic pressure treatment to 285 MPa by microscopic observation. During pressure loading the vesicles remain spherical. A shape transition consisting of budding only occurs on the cholesterol-free vesicles during pressure release. The decrease in the volume delimited by the pure EYPC bilayer between 0.1 and 285 MPa was found to be 16% of its initial volume, whereas the bulk compression of water in this pressure range is only 10%. So the compression at 285 MPa induced a water exit from the pure EYPC vesicle. The shape transition of the EYPC vesicle during pressure release is attributed to an increase in its area-to-volume ratio caused by the loss of its water content during compression. Because bulk compression of the cholesterol-containing vesicle is close to that of water, no water transfer would be induced across the bilayer and the vesicle remains spherical during the pressure release. Images FIGURE 1 FIGURE 2 FIGURE 3 PMID:9138571

  10. Stress-induced piezoelectric field in GaN-based 450-nm light-emitting diodes

    SciTech Connect

    Tawfik, Wael Z.; Hyeon, Gil Yong; Lee, June Key

    2014-10-28

    We investigated the influence of the built-in piezoelectric field induced by compressive stress on the characteristics of GaN-based 450-nm light-emitting diodes (LEDs) prepared on sapphire substrates of different thicknesses. As the sapphire substrate thickness was reduced, the compressive stress in the GaN layer was released, resulting in wafer bowing. The wafer bowing-induced mechanical stress altered the piezoelectric field, which in turn reduced the quantum confined Stark effect in the InGaN/GaN active region of the LED. The flat-band voltage was estimated by measuring the applied bias voltage that induced a 180° phase shift in the electro-reflectance (ER) spectrum. The piezoelectric field estimated by the ER spectra changed by ∼110 kV/cm. The electroluminescence spectral peak wavelength was blue-shifted, and the internal quantum efficiency was improved by about 22% at a high injection current of 100 mA. The LED on the 60-μm-thick sapphire substrate exhibited the highest light output power of ∼59 mW at an injection current of 100 mA, with the operating voltage unchanged.

  11. Stress-induced piezoelectric field in GaN-based 450-nm light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Tawfik, Wael Z.; Hyeon, Gil Yong; Lee, June Key

    2014-10-01

    We investigated the influence of the built-in piezoelectric field induced by compressive stress on the characteristics of GaN-based 450-nm light-emitting diodes (LEDs) prepared on sapphire substrates of different thicknesses. As the sapphire substrate thickness was reduced, the compressive stress in the GaN layer was released, resulting in wafer bowing. The wafer bowing-induced mechanical stress altered the piezoelectric field, which in turn reduced the quantum confined Stark effect in the InGaN/GaN active region of the LED. The flat-band voltage was estimated by measuring the applied bias voltage that induced a 180° phase shift in the electro-reflectance (ER) spectrum. The piezoelectric field estimated by the ER spectra changed by ˜110 kV/cm. The electroluminescence spectral peak wavelength was blue-shifted, and the internal quantum efficiency was improved by about 22% at a high injection current of 100 mA. The LED on the 60-μm-thick sapphire substrate exhibited the highest light output power of ˜59 mW at an injection current of 100 mA, with the operating voltage unchanged.

  12. Cracking Process and Stress Field Evolution in Specimen Containing Combined Flaw Under Uniaxial Compression

    NASA Astrophysics Data System (ADS)

    Liu, Ting; Lin, Baiquan; Yang, Wei; Zou, Quanle; Kong, Jia; Yan, Fazhi

    2016-08-01

    Hydraulic slotting, an efficient technique for underground enhanced coal bed methane (ECBM) recovery, has been widely used in China. However, its pressure relief mechanism is unclear. Thus far, only limited research has been conducted on the relationships among the mechanical properties, flaw parameters, and crack propagation patterns of coal after hydraulic slotting. In addition, because of the limitations of test methods, an in-depth information is not available for this purpose. In this work, numerical models of specimens containing combined flaws are established based on particle flow code method. Our results provide insights into the effects of flaw inclination angle on the mechanical properties, crack propagation patterns, and temporal and spatial evolution rules of stress field in specimens containing combined flaws during the loading process. Besides, based on the initiation position and underlying mechanism, three types of crack initiation modes are identified from the failure processes of specimens. Finally, the crack propagation pattern is quantitatively described by the fractal dimension, which is found to be inversely proportional to the uniaxial compressive strength and elastic modulus of the specimen. To verify the rationality of the numerical simulation results, laboratory tests were conducted and their results match well with those obtained from the numerical simulation.

  13. Thermal convection of magneto compressible couple-stress fluid saturated in a porous medium with Hall current

    NASA Astrophysics Data System (ADS)

    Mehta, C. B.; Singh, M.; Kumar, S.

    2016-02-01

    An investigation is made on the effect of Hall currents on thermal instability of a compressible couple-stress fluid in the presence of a horizontal magnetic field saturated in a porous medium. The analysis is carried out within the framework of the linear stability theory and normal mode technique. A dispersion relation governing the effects of viscoelasticity, Hall currents, compressibility, magnetic field and porous medium is derived. For the stationary convection a couple-stress fluid behaves like an ordinary Newtonian fluid due to the vanishing of the viscoelastic parameter. Compressibility, the magnetic filed and couple-stress parameter have stabilizing effects on the system whereas Hall currents and medium permeability have a destabilizing effect on the system, but in the absence of Hall current couple-stress has a destabilizing effect on the system. It has been observed that oscillatory modes are introduced due to the presence of viscoelasticity, magnetic field porous medium and Hall currents which were non-existent in their absence.

  14. Glucagon orchestrates stress-induced hyperglycaemia.

    PubMed

    Harp, J B; Yancopoulos, G D; Gromada, J

    2016-07-01

    Hyperglycaemia is commonly observed on admission and during hospitalization for medical illness, traumatic injury, burn and surgical intervention. This transient hyperglycaemia is referred to as stress-induced hyperglycaemia (SIH) and frequently occurs in individuals without a history of diabetes. SIH has many of the same underlying hormonal disturbances as diabetes mellitus, specifically absolute or relative insulin deficiency and glucagon excess. SIH has the added features of elevated blood levels of catecholamines and cortisol, which are not typically present in people with diabetes who are not acutely ill. The seriousness of SIH is highlighted by its greater morbidity and mortality rates compared with those of hospitalized patients with normal glucose levels, and this increased risk is particularly high in those without pre-existing diabetes. Insulin is the treatment standard for SIH, but new therapies that reduce glucose variability and hypoglycaemia are desired. In the present review, we focus on the key role of glucagon in SIH and discuss the potential use of glucagon receptor blockers and glucagon-like peptide-1 receptor agonists in SIH to achieve target glucose control. PMID:27027662

  15. Differentiating stress to wheat fields induced by Diuraphis noxia from other stress causing factors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to develop a method to differentiate two categories of stress to wheat fields, stress induced by the Russian wheat aphid, Diuraphis noxia (Mordvilko), and stress caused by other factors. The study used a set of 11 spatial pattern metrics derived from multispectral im...

  16. Isentropic Compression Loading of HMX and the Pressure-induced Phase Transition at 27 GPa

    SciTech Connect

    Hare, D E; Reisman, D B; Dick, J J; Forbes, J W

    2004-02-25

    The 27 GPa pressure-induced epsilon-phi phase transition in HMX is explored using the Isentropic Compression Experiment (ICE) technique at the Sandia National Laboratories Z-machine facility. Our data indicate that this phase transition is sluggish and if it does occur to any extent under the time scales (200-500 ns) and strain rates (5 x 10{sup 5}) typical of ICE loading conditions, the amount of conversion is small.

  17. Beam and shell modes of buckling of buried pipes induced by compressive ground failure

    SciTech Connect

    Chiou, Y.J.; Chi, S.Y.

    1995-12-31

    The buckling of buried pipeline induced by compressive ground failure was investigated. Both the beam mode of buckling and local shell mode of buckling, and their interactions were studied. The pipeline response was analyzed numerically. The results agree qualitatively with past researches and possess satisfactory comparisons with actual case histories. The relations of critical buried depth versus ratio of pipe diameter to thickness for buried pipe with different imperfections and various soil foundations were established.

  18. Unpredictable chronic mild stress not chronic restraint stress induces depressive behaviours in mice.

    PubMed

    Zhu, Shenghua; Shi, Ruoyang; Wang, Junhui; Wang, Jun-Feng; Li, Xin-Min

    2014-10-01

    The chronic stress model was developed on the basis of the stress-diathesis hypothesis of depression. However, these behavioural responses associated with different stress paradigms are quite complex. This study examined the effects of two chronic stress regimens on anxiety-like and depressive behaviours. C57BL/6 mice were subjected to unpredictable chronic mild stress or to chronic restraint stress for 4 weeks. Subsequently, both anxiety-like behaviours (open field, elevated plus maze and novelty suppressed feeding) and depression-like behaviours (tail suspension, forced swim and sucrose preference) were evaluated. Both chronic stress models generated anxiety-like behaviours, whereas only unpredictable chronic mild stress could induce depressive behaviours such as increased immobility and decreased sucrose consumption. These results of the present study provide additional evidence on how chronic stress affects behavioural responses and point to the importance of the validity of animal models of chronic stress in studying depression. PMID:25089805

  19. Stress- and Allostasis-Induced Brain Plasticity

    PubMed Central

    McEwen, Bruce S.; Gianaros, Peter J.

    2014-01-01

    The brain is the key organ of stress processes. It determines what individuals will experience as stressful, it orchestrates how individuals will cope with stressful experiences, and it changes both functionally and structurally as a result of stressful experiences. Within the brain, a distributed, dynamic, and plastic neural circuitry coordinates, monitors, and calibrates behavioral and physiological stress response systems to meet the demands imposed by particular stressors. These allodynamic processes can be adaptive in the short term (allostasis) and maladaptive in the long term (allostatic load). Critically, these processes involve bidirectional signaling between the brain and body. Consequently, allostasis and allostatic load can jointly affect vulnerability to brain-dependent and stress-related mental and physical health conditions. This review focuses on the role of brain plasticity in adaptation to, and pathophysiology resulting from, stressful experiences. It also considers interventions to prevent and treat chronic and prevalent health conditions via allodynamic brain mechanisms. PMID:20707675

  20. Experimentally Induced Stress Validated by EMG Activity

    PubMed Central

    Luijcks, Rosan; Hermens, Hermie J.; Bodar, Lonneke; Vossen, Catherine J.; Os, Jim van.; Lousberg, Richel

    2014-01-01

    Experience of stress may lead to increased electromyography (EMG) activity in specific muscles compared to a non-stressful situation. The main aim of this study was to develop and validate a stress-EMG paradigm in which a single uncontrollable and unpredictable nociceptive stimulus was presented. EMG activity of the trapezius muscles was the response of interest. In addition to linear time effects, non-linear EMG time courses were also examined. Taking into account the hierarchical structure of the dataset, a multilevel random regression model was applied. The stress paradigm, executed in N = 70 subjects, consisted of a 3-minute baseline measurement, a 3-minute pre-stimulus stress period and a 2-minute post-stimulus phase. Subjects were unaware of the precise moment of stimulus delivery and its intensity level. EMG activity during the entire experiment was conform a priori expectations: the pre-stimulus phase showed a significantly higher mean EMG activity level compared to the other two phases, and an immediate EMG response to the stimulus was demonstrated. In addition, the analyses revealed significant non-linear EMG time courses in all three phases. Linear and quadratic EMG time courses were significantly modified by subjective anticipatory stress level, measured just before the start of the stress task. Linking subjective anticipatory stress to EMG stress reactivity revealed that subjects with a high anticipatory stress level responded with more EMG activity during the pre-stimulus stress phase, whereas subjects with a low stress level showed an inverse effect. Results suggest that the stress paradigm presented here is a valid test to quantify individual differences in stress susceptibility. Further studies with this paradigm are required to demonstrate its potential use in mechanistic clinical studies. PMID:24736740

  1. Induced stresses due to fluid extraction from axisymmetric reservoirs

    USGS Publications Warehouse

    Segall, P.

    1992-01-01

    Earthquakes can be induced by fluid extraction, as well as by fluid injection. Segall (1989) proposed that poroelastic stresses are responsible for inducing earthquakes associated with fluid extraction. Here, I present methods for computing poroelastic stress changes due to fluid extraction for general axisymmetric reservoir geometries. The results of Geertsma (1973) for a thin disk reservoir with uniform pressure drop are recovered as a special case. Predicted surface subsidence agrees very well with measured leveling changes over the deep Lacq gas field in southwestern France. The induced stresses are finite if the reservoir pressure changes are continuous. Computed stress changes are on the order of several bars, suggesting that the preexisting stress states in regions of extraction induced seismicity are very close to frictional instability prior to production. ?? 1992 Birkha??user Verlag.

  2. Horizontal stresses induced by vertical processes in planetary lithospheres

    NASA Technical Reports Server (NTRS)

    Banerdt, W. B.

    1993-01-01

    Understanding the state of stress in the elastic lithosphere is of fundamental importance for planetary geophysics, as it is the link between the observed geologic structures on the surface and the processes which form and modify these structures. As such, it can provide valuable constraints for the difficult problem of determining interior structure and processes. On the Earth, most large scale, organized deformation can be related to lateral tectonics associated with plate dynamics; however, the tectonics on many extraterrestrial bodies (such as the Moon, Mars, and most of the outer-planet satellites) appears to be primarily vertical in nature, and the horizontal stresses induced by vertical motions and loads are expected to dominate the deformation of their lithospheres. The largest stress contributions from vertical loading come from the flexure of the lithosphere, which induces both bending moments and membrane stresses. We are concerned here only with nonflexural changes in the state of stress induced by processes such as sedimentary and volcanic deposition, erosional denudation, and changes in the thermal gradient that induce uplift or subsidence. This analysis is important both for evaluating stresses for specific regions in which the vertical stress history can be estimated, as well as for applying the proper loading conditions to global stress models. It is also of interest for providing a reference state of stress for interpreting stress measurements in the crust of the Earth.

  3. Biological effects of laser-induced stress waves

    SciTech Connect

    Doukas, A.; Lee, S.; McAuliffe, D.

    1995-12-31

    Laser-induced stress waves can be generated by one of the following mechanisms: Optical breakdown, ablation or rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to stress waves with different characteristics and under different conditions. The most widely studied phenomena are those of the collateral damage seen in photodisruption in the eye and in 193 run ablation of cornea and skin. On the other hand, the therapeutic application of laser-induced stress waves has been limited to the disruption of noncellular material such as renal stones, atheromatous plaque and vitreous strands. The effects of stress waves to cells and tissues can be quite disparate. Stress waves can fracture tissue, damage cells, and increase the permeability of the plasma membrane. The viability of cell cultures exposed to stress waves increases with the peak stress and the number of pulses applied. The rise time of the stress wave also influences the degree of cell injury. In fact, cell viability, as measured by thymidine incorporation, correlates better with the stress gradient than peak stress. Recent studies have also established that stress waves induce a transient increase of the permeability of the plasma membrane in vitro. In addition, if the stress gradient is below the damage threshhold, the cells remain viable. Thus, stress waves can be useful as a means of drug delivery, increasing the intracellular drug concentration and allowing the use of drugs which are impermeable to the cell membrane. The present studies show that it is important to create controllable stress waves. The wavelength tunability and the micropulse structure of the free electron laser is ideal for generating stress waves with independently adjustable parameters, such as rise time, duration and peak stress.

  4. Ultrasonic evaluation of the effects of compressive residual stresses on aircraft engine turbine blades subjected to high cycle fatigue

    NASA Astrophysics Data System (ADS)

    Bray, Don E.; Suh, Ui; Hough, C. L. ``Mickey''

    2002-05-01

    Experiments conducted on titanium (Ti-64) turbine blades with the LCR ultrasonic wave at 20 MHz showed significant differences in untreated blades and blades treated to increase the subsurface compressive residual stress. Group 1 showed significant differences in the treated and untreated areas, the top and bottom of the blades, high cycle fatigue and cracked and uncracked conditions. Group 2 blades showed significant difference between untreated and treated travel-times at probes located at the blade leading edge.

  5. Compression failure of fibrous laminated composites in the presence of stress gradients : experiment and analysis

    NASA Astrophysics Data System (ADS)

    Waas, Anthony M.

    A series of experiments were performed to determine the mechanism of failure in compressively loaded laminated plates in the presence of stress gradients generated by a circular cutout. Real time holographic interferometry and in-situ photomicrography of the hole surface, were used to observe the progression of failure.The test specimens are multi-layered composite flat plates, which are loaded in compression. The plates are made of two material systems, T300/BP907 and IM7/8551-7. Two different lay-ups of T300/BP907 and four different lay-ups of IM7/8551-7 are investigated.The load on the specimen is slowly increased and a series of interferograms are produced during the load cycle. These interferograms are video-recorded. The results obtained from the interferograms and photo-micrographs are substantiated by sectioning studies and ultrasonic C-scanning of some specimens which are unloaded prior to catastrophic failure, but beyond failure initiation. This is made possible by the servo-controlled loading mechanism that regulates the load application and offers the flexibility of unloading a specimen at any given instance in the loadtime history.An underlying objective of the present investigation is the identification of the physics of the failure initiation process. This required testing specimens with different stacking sequences, for a fixed hole diameter, so that consistent trends in the failure process could be identified.It is revealed that the failure is initiated as a localized instability in the 0? plies at the hole surface, approximately at right angles to the loading direction. This instability emanating at the hole edge and propagating into the interior of the specimen within the 0? plies is found to be fiber microbuckling. The microbuckling is found to occur at a local strain level of [...]8600 [mu]strain at the hole edge for the IM material system. This initial failure renders a narrow zone of fibers within the 0? plies to loose structural integrity

  6. Stress antagonizes morphine-induced analgesia in rats

    NASA Technical Reports Server (NTRS)

    Vernikos, J.; Shannon, L.; Heybach, J. P.

    1981-01-01

    Exposure to restraint stress resulted in antagonism of the analgesic effect of administered morphine in adult male rats. This antagonism of morphine-induced analgesia by restraint stress was not affected by adrenalectomy one day prior to testing, suggesting that stress-induced secretion of corticosteroids is not critical to this antagonism. In addition, parenteral administration of exogenous adrenocorticotropin (ACTH) mimicked the effect of stress in antagonizing morphine's analgesic efficacy. The hypothesis that ACTH is an endogenous opiate antagonist involved in modulating pain sensitivity is supported.

  7. Stress-induced martensitic transformations in NiTi and NiTi-TiC composites investigated by neutron diffraction

    SciTech Connect

    Vaidyanathan, R.; Bourke, M.A.M.; Dunand, D.C.

    1998-12-31

    Superelastic NiTi (51.0 at% Ni) with 0, 10 and 20 vol% TiC particles were deformed under uniaxial compression as neutron diffraction spectra were simultaneously obtained. The experiments yielded in-situ measurements of the thermoelastic stress-induced transformation. A detailed Rietveld determination is made of the phase fractions and the evolving strains in the reinforcing TiC particles and the austenite as it transforms to martensite on loading (and its subsequent back transformation on unloading). These strains are used to shed light on the phenomenon of load transfer in composites where the matrix undergoes a stress-induced phase transformation.

  8. Psychological Stress, Cocaine and Natural Reward Each Induce Endoplasmic Reticulum Stress Genes in Rat Brain

    PubMed Central

    Pavlovsky, Ashly A.; Boehning, Darren; Li, Dingge; Zhang, Yafang; Fan, Xiuzhen; Green, Thomas A.

    2013-01-01

    Our prior research has shown that the transcription of endoplasmic reticulum (ER) stress transcription factors Activating Transcription Factor 3 (ATF3) and ATF4 are induced by amphetamine and restraint stress in rat striatum. However, presently it is unknown the full extent of ER stress responses to psychological stress or cocaine, and which of the three ER stress pathways is activated. The current study examines transcriptional responses of key ER stress target genes subsequent to psychological stress or cocaine. Rats were subjected to acute or repeated restraint stress or cocaine treatment and mRNA was isolated from dorsal striatum, medial prefrontal cortex and nucleus accumbens brain tissue. ER stress gene mRNA expression was measured using quantitative PCR and RNA sequencing. Restraint stress and cocaine induced transcription of the classic ER stress-induced genes (BIP, CHOP, ATF3 and GADD34) and of two other ER stress components XBP1 and ATF6. In addition, rats living in an enriched environment (large group cage with novel toys changed daily) exhibited rapid induction of GADD34 and ATF3 after 30 min of exploring novel toys, suggesting these genes are also involved in normal non-pathological signaling. However, environmental enrichment, a paradigm that produces protective addiction and depression phenotypes in rats, attenuated the rapid induction of ATF3 and GADD34 after restraint stress. These experiments provide a sensitive measure of ER stress and, more importantly, these results offer good evidence of the activation of ER stress mechanisms from psychological stress, cocaine and natural reward. Thus, ER stress genes may be targets for novel therapeutic targets for depression and addiction. PMID:23644055

  9. Psychological stress, cocaine and natural reward each induce endoplasmic reticulum stress genes in rat brain.

    PubMed

    Pavlovsky, A A; Boehning, D; Li, D; Zhang, Y; Fan, X; Green, T A

    2013-08-29

    Our prior research has shown that the transcription of endoplasmic reticulum (ER) stress transcription factors activating transcription factor 3 (ATF3) and ATF4 are induced by amphetamine and restraint stress in rat striatum. However, presently the full extent of ER stress responses to psychological stress or cocaine, and which of the three ER stress pathways is activated is unknown. The current study examines transcriptional responses of key ER stress target genes subsequent to psychological stress or cocaine. Rats were subjected to acute or repeated restraint stress or cocaine treatment and mRNA was isolated from dorsal striatum, medial prefrontal cortex and nucleus accumbens brain tissue. ER stress gene mRNA expression was measured using quantitative polymerase chain reaction (PCR) and RNA sequencing. Restraint stress and cocaine-induced transcription of the classic ER stress-induced genes (BIP, CHOP, ATF3 and GADD34) and of two other ER stress components x-box binding protein 1 (XBP1) and ATF6. In addition, rats living in an enriched environment (large group cage with novel toys changed daily) exhibited rapid induction of GADD34 and ATF3 after 30 min of exploring novel toys, suggesting these genes are also involved in normal non-pathological signaling. However, environmental enrichment, a paradigm that produces protective addiction and depression phenotypes in rats, attenuated the rapid induction of ATF3 and GADD34 after restraint stress. These experiments provide a sensitive measure of ER stress and, more importantly, these results offer good evidence of the activation of ER stress mechanisms from psychological stress, cocaine and natural reward. Thus, ER stress genes may be targets for novel therapeutic targets for depression and addiction. PMID:23644055

  10. Charts relating the compressive buckling stress of longitudinally supported plates to the effective deflectional and rotational stiffness of the supports

    NASA Technical Reports Server (NTRS)

    Anderson, Roger A; Semonian, Joseph W

    1954-01-01

    A stability analysis is made of a long flat rectangular plate subjected to a uniform longitudinal compressive stress and supported along its longitudinal edges and along one or more longitudinal lines by elastic line supports. The elastic supports possess deflectional and rotational stiffness. Such configuration is an idealization of the compression cover skin and internal structure of a wing and tail surfaces. The results of the analysis are presented in the form of charts in which the buckling-stress coefficient is plotted against the buckle length of the plate for a wide range of support stiffnesses. The charts make possible the determination of the compressive buckling stress of plates supported by members whose stiffness may or may not be defined by elementary beam bending and twisting theory but yet whose effective restraint is amenable to evaluation. The deflectional and rotational stiffness provided by longitudinal stiffeners and full-depth webs is discussed and numerical examples are given to illustrate the application of the charts to the design of wing structures.

  11. Low stress ion-assisted coatings on fused silica substrates for large aperture laser pulse compression gratings

    NASA Astrophysics Data System (ADS)

    Smith, Douglas J.; McCullough, Mike; Smith, Claire; Mikami, Takuya; Jitsuno, Takahisa

    2008-10-01

    Large aperture laser pulse compressor designs use several diffraction gratings in series and sometimes tiled together to compress an amplified 1 to 10 ns pulse to 0.1 to 10 ps. The wavefront of the compressed pulse must be well controlled to allow focusing to a small spot on a target. Traditionally, multilayer dielectric gratings (MLDG) have been fabricated onto high thermal expansion substrates such as BK7 glass to prevent crazing and excessive bending due to tensile coating stress when operated in high vacuum. However, the high CTE of the BK7 can cause wavefront distortion and changes in the period of the grating. This work uses ion-assisted deposition of HfO2/SiO2 films to increase the compressive stress in MLD layers to allow use of silica substrates in the compressor vacuum environment. Stress, coating uniformity, and damage results are reported. The process was scaled to full size (91cm × 42cm) MLD gratings for use in the Osaka University LFEX laser system. Diffracted wavefront results from the full scale gratings is presented.

  12. In situ x-ray diffraction of fast compressed iron: Analysis of strains and stress under non-hydrostatic pressure

    NASA Astrophysics Data System (ADS)

    Konôpková, Zuzana; Rothkirch, André; Singh, Anil K.; Speziale, Sergio; Liermann, Hanns-Peter

    2015-04-01

    Series of high-pressure x-ray diffraction patterns of iron and its high-pressure polymorphs were collected with 0.1-0.2-s exposure time utilizing a membrane diamond anvil cell (DAC) for compression at various loading and unloading rates to a maximum pressure of 70 GPa. Strain rates of 10-2s-1 at a maximum pressurization rate of 4.1 GPa/s were achieved in non-hydrostatic compression of hcp Fe. Linewidth analysis was used to retrieve strain and uniaxial stress of Fe as a function of pressure upon both compression and decompression. Analysis of the lattice parameters ratio c /a of hcp Fe indicates the presence of complex non-hydrostatic stress states, which developed as a function of strain rate, relaxation time, and various levels of hydrostaticity. Our results emphasize the importance of a controlled pressurization in DACs because the experimental loading rate strongly influences the stress state of the sample, particularly on decompression. Our time-resolved x-ray diffraction of the phase transition from bcc Fe to hcp Fe reveals residual grains of bcc Fe capable of surviving to very high pressures (>35 GPa) for a few minutes after the transition.

  13. Hypoxia-induced compression in the tracheal system of the tobacco hornworm caterpillar, Manduca sexta.

    PubMed

    Greenlee, Kendra J; Socha, John J; Eubanks, Haleigh B; Pedersen, Paul; Lee, Wah-Keat; Kirkton, Scott D

    2013-06-15

    Abdominal pumping in caterpillars has only been documented during molting. Using synchrotron X-ray imaging in conjunction with high-speed flow-through respirometry, we show that Manduca sexta caterpillars cyclically contract their bodies in response to hypoxia, resulting in significant compressions of the tracheal system. Compression of tracheae induced by abdominal pumping drives external gas exchange, as evidenced by the high correlation between CO2 emission peaks and body movements. During abdominal pumping, both the compression frequency and fractional change in diameter of tracheae increased with body mass. However, abdominal pumping and tracheal compression were only observed in larger, older caterpillars (>0.2 g body mass), suggesting that this hypoxic response increases during ontogeny. The diameters of major tracheae in the thorax increased isometrically with body mass. However, tracheae in the head did not scale with mass, suggesting that there is a large safety margin for oxygen delivery in the head in the youngest animals. Together, these results highlight the need for more studies of tracheal system scaling and suggest that patterns of tracheal investment vary regionally in the body. PMID:23531813

  14. Compression of a multiphase mantle assemblage: Effects of undesirable stress and stress annealing on the iron spin state crossover in ferropericlase

    NASA Astrophysics Data System (ADS)

    Glazyrin, Konstantin; Miyajima, Nobuyoshi; Smith, Jesse S.; Lee, Kanani K. M.

    2016-05-01

    Using synchrotron-based X-ray diffraction, we explore characteristic signatures for nonhydrostatic stresses and their effect on the spin state crossover of ferrous iron in (Mg, Fe)O ferropericlase (Fp) upon compression in a two-phase mixture which includes an Al- and Fe-bearing bridgmanite (Bm). We observe an influence of nonhydrostatic stresses on the spin state crossover starting pressure and width. The undesirable stresses discussed here include uniaxial deviatoric stress evolving in the diamond anvil cell and effects of intergrain interaction. While the former leads to a pressure overestimation, the latter one lowers the pressure of the onset for the high-spin to low-spin electronic transition in Fe2+ in ferropericlase (Mg, Fe)O with respect to hydrostatic conditions.

  15. Radiation Induced Stress Relaxation in Silicone and Polyurethane Elastomers

    SciTech Connect

    Spellman, G; Gourdin, W; Jensen, W; Pearson, M; Fine, I

    2007-08-22

    Many different materials are used in the National Ignition Facility, NIF, located at Lawrence Livermore National Laboratory, LLNL. Some of these are exposed to significant doses of ionizing radiation. Two elastomers are of special interest because they are used in sealing applications with long expected lifetimes. These are LPU4, a polyurethane formulated at LLNL, and Dow Corning DC93-500, a silicone RTV elastomer. In 2004 a program to determine the impact of ionizing radiation on the stress relaxation and compression set characteristics of these two elastomers was undertaken. Since the materials are used in continuous compression and must reliably seal, the primary test utilized was a stress relaxation test. This test provides insight into the ability of a seal to remain functional in a static seal. The test determines how much residual force remains after a certain period of time under compression. The temperature and absorbed radiation dose can dramatically impact this property. In this study the only independent environmental variable studied is the effect of radiation at ambient temperatures. Two levels of radiation exposure were studied, 1 MRad, and 10 MRad. One of the independent test parameters is the compression deflection during storage and in this test the value used was 25%. The need for a compression retention mechanism ruled out radiation exposure in the compressed direction since the high atomic number materials for that device would block the radiation. Therefore, an annular ring was chosen for the specimen shape. The procedures are, as closely as possible, based on ASTM D 6147-97. Since the data is readily obtained at the end of the stress relaxation test, the samples were also evaluated for compression set. Compression set is the essentially permanent deformation incurred in a seal after the seal is compressed for some period of time and then unloaded. Though this is indicative of potential sealing reliability, it is not as direct an indicator of

  16. FEM calculation of residual stresses induced by laser shock processing in stainless steels

    NASA Astrophysics Data System (ADS)

    Peyre, P.; Chaieb, I.; Braham, C.

    2007-04-01

    Laser shock processing, also known as laser shock peening, generates through a laser-induced plasma, plastic deformation and compressive residual stresses in materials for improved fatigue or stress corrosion cracking resistances. The calculation of mechanical effects is rather complex, due to the severity of the pressure loading imparted in a very short time period (in the ns regime). This produces very high strain rates (106 s-1), which necessitate a precise determination of dynamic properties. Finite element techniques have been applied to predict the residual stress fields induced in two different stainless steels, combining shock wave hydrodynamics and strain rate dependent mechanical behaviour. The predicted residual stress fields for single or multiple laser processes were correlated with those from experimental data, with a specific focus on the influence of process parameters such as pressure pulse amplitude and duration, laser spot size or sacrificial overlay. Among other results, simulations confirmed that the affected depths increased with pulse duration, peak pressure and cyclic deformations, thus reaching much deeper layers (> 0.5 mm) than with any other conventional surface processing. To improve simulations, the use of experimental VISAR determinations to determine pressure loadings and elastic limits under shock conditions (revealing different strain-rate dependences for the two stainless steels considered) was shown to be a key point. Finally, the influence of protective coatings and, more precisely, the simulation of a thermo-mechanical uncoated laser shock processing were addressed and successfully compared with experiments, exhibiting a large tensile surface stress peak affecting a few tenths of micrometres and a compressive sub-surface stress field.

  17. An experimental study on the effects of compressive stress on the fatigue crack growth of low-alloy steel

    SciTech Connect

    Jones, D.P.; Hoppe, R.G.; Hechmer, J.L.; James, B.A.

    1993-12-01

    A series of fatigue crack growth rate tests was conducted in order to study effects of negative stress ratio on fatigue crack growth rate of low-alloy steel in air. Four-point bend specimens were used to simulate linear stress distributions typical of pressure vessel applications. This type of testing adds to knowledge on negative stress ratio effects for low-alloy steels obtained in the past from uniform tension-compression tests. Applied bending stress range was varied over twice the yield strength. Load control was used for tests for which the stress range was less than twice the yield strength and deflection control was used for the higher stress range tests. Crack geometries were both short and long fatigue cracks started at notches and tight fatigue cracks for which crack closure could occur over the full crack face. Results are presented in terms of the stress intensity factor ratio R = K{sub MIN}/K{sub MAX}. The negative R-ratio test results were correlated to an equation of the form da/dN = C[{Delta}K/(A-R)]{sup n}, where A, C, and n are curve fitting parameters. It was found that effects of negative R-ratio on fatigue crack growth rates for even the high stress range tests could be bounded by correlating the above equation to only positive R-ratio test results and extending the resulting equation into the negative R-ratio regime.

  18. Neurobiology of Stress-Induced Reproductive Dysfunction In Female Macaques

    PubMed Central

    Bethea, Cynthia L.; Centeno, Maria Luisa; Cameron, Judy L.

    2012-01-01

    It is now well accepted that stress can precipitate mental and physical illness. However, it is becoming clear that given the same stress, some individuals are very vulnerable and will succumb to illness while others are more resilient and cope effectively, rather than becoming ill. This difference between individuals is called stress sensitivity. Stress-sensitivity of an individual appears to be influenced by genetically inherited factors, early life (even prenatal) stress, and by the presence or absence of factors that provide protection from stress. In comparison to other stress-related diseases, the concept of sensitivity versus resilience to stress-induced reproductive dysfunction has received relatively little attention. The studies presented herein were undertaken to begin to identify stable characteristics and the neural underpinnings of individuals with sensitivity to stress-induced reproductive dysfunction. Female cynomolgus macaques with normal menstrual cycles either stop ovulating (Stress Sensitive) or to continue to ovulate (Stress Resilient) upon exposure to a combined metabolic and psychosocial stress. However, even in the absence of stress, the stress sensitive animals have lower secretion of the ovarian steroids, estrogen and progesterone, have higher heart rates, have lower serotonin function, have fewer serotonin neurons and lower expression of pivotal serotonin-related genes, have lower expression of 5HT2A and 2C genes in the hypothalamus, have higher gene expression of GAD67 and CRH in the hypothalamus and have reduced GnRH transport to the anterior pituitary. Altogether, the results suggest that the neurobiology of reproductive circuits in stress sensitive individuals is compromised. We speculate that with the application of stress, the dysfunction of these neural systems becomes exacerbated and reproductive function ceases. PMID:18931961

  19. Grinding Induced Changes in Residual Stresses of Carburized Gears

    SciTech Connect

    Lemaster, Robert A; Boggs, Bryan L; Bunn, Jeffrey R; Hubbard, Camden R; Watkins, Thomas R

    2009-01-01

    This paper presents the results of a study performed to measure the change in residual stress that results from the finish grinding of carburized gears. Residual stresses were measured in five gears using the x-ray diffraction equipment in the Large Specimen Residual Stress Facility at Oak Ridge National Laboratory. Two of the gears were hobbed, carburized, quenched and tempered, but not finished. The remaining three gears were processed similarly, but were finish ground. The residual stresses were measured at 64 different locations on a tooth from each gear. Residual stresses were also measured at fewer points on other teeth to determine the tooth-to-tooth variation. Tooth profile measurements were made of the finished and unfinished gear samples. The results show a fairly uniform and constant compressive residual field in the nonfinished gears. There was a significant reduction in the average residual stress measured in the finished gears. Additionally, there was a significant increase in the variability of the residual stress that was introduced by the grinding process. Analysis of the data suggests a linear relationship between the change in average residual stress and the amount of material removed by the grinding process.

  20. Social factors modulate restraint stress induced hyperthermia in mice.

    PubMed

    Watanabe, Shigeru

    2015-10-22

    Stress-induced hyperthermia (SIH) was examined in three different social conditions in mice by thermographic measurement of the body surface temperature. Placing animals in cylindrical holders induced restraint stress. I examined the effect of the social factors in SIH using the thermograph (body surface temperature). Mice restrained in the holders alone showed SIH. Mice restrained in the holders at the same time as other similarly restrained cage mates (social equality condition) showed less hyperthermia. Interestingly, restrained mice with free moving cage mates (social inequality condition) showed the highest hyperthermia. These results are consistent with a previous experiment measuring the memory-enhancing effects of stress and the stress-induced elevation of corticosterone, and suggest that social inequality enhances stress. PMID:26232073

  1. Shock Compression Induced Hot Spots in Energetic Material Detected by Thermal Imaging Microscopy

    NASA Astrophysics Data System (ADS)

    Chen, Ming-Wei; Dlott, Dana

    2014-06-01

    The chemical reaction of powder energetic material is of great interest in energy and pyrotechnic applications since the high reaction temperature. Under the shock compression, the chemical reaction appears in the sub-microsecond to microsecond time scale, and releases a large amount of energy. Experimental and theoretical research progresses have been made in the past decade, in order to characterize the process under the shock compression. However, the knowledge of energy release and temperature change of this procedure is still limited, due to the difficulties of detecting technologies. We have constructed a thermal imaging microscopy apparatus, and studied the temperature change in energetic materials under the long-wavelength infrared (LWIR) and ultrasound exposure. Additionally, the real-time detection of the localized heating and energy concentration in composite material is capable with our thermal imaging microscopy apparatus. Recently, this apparatus is combined with our laser driven flyer plate system to provide a lab-scale source of shock compression to energetic material. A fast temperature increase of thermite particulars induced by the shock compression is directly observed by thermal imaging with 15-20 μm spatial resolution. Temperature change during the shock loading is evaluated to be at the order of 10^9K/s, through the direct measurement of mid-wavelength infrared (MWIR) emission intensity change. We observe preliminary results to confirm the hot spots appear with shock compression on energetic crystals, and will discuss the data and analysis in further detail. M.-W. Chen, S. You, K. S. Suslick, and D. D. Dlott, {Rev. Sci. Instr., 85, 023705 (2014) M.-W. Chen, S. You, K. S. Suslick, and D. D. Dlott, {Appl. Phys. Lett., 104, 061907 (2014)} K. E. Brown, W. L. Shaw, X. Zheng, and D. D. Dlott, {Rev. Sci. Instr., 83, 103901 (2012)}

  2. Origin of compression-induced failure in brittle solids under shock loading

    NASA Astrophysics Data System (ADS)

    Huang, J. Y.; Li, Y.; Liu, Q. C.; Zhou, X. M.; Liu, L. W.; Liu, C. L.; Zhu, M. H.; Luo, S. N.

    2015-10-01

    The origin of compression-induced failure in brittle solids has been a subject of debate. Using in situ, high-speed, strain field mapping of a representative material, polymethylmethacrylate, we reveal that shock loading leads to heterogeneity in a compressive strain field, which in turn gives rise to localized lateral tension and shear through Poisson's effects, and, subsequently, localized microdamage. A failure wave nucleates from the impact surface and its propagation into the microdamage zone is self-sustained, triggering interior failure. Its velocity increases with increasing shock strength and eventually approaches the shock velocity. The seemingly puzzling phenomena observed in previous experiments, including incubation time, failure wave velocity variations, and surface roughness effects, can all be explained consistently with the nucleation and growth of the microdamage, and the effects of loading strength and preexisting defects.

  3. Possible Biomarkers of Chronic Stress Induced Exhaustion - A Longitudinal Study

    PubMed Central

    Wallensten, Johanna; Åsberg, Marie; Nygren, Åke; Szulkin, Robert; Wallén, Håkan; Mobarrez, Fariborz; Nager, Anna

    2016-01-01

    Background Vascular endothelial growth factor (VEGF), epidermal growth factor (EGF) and monocyte chemotactic protein-1 (MCP-1) have previously been suggested to be potential biomarkers for chronic stress induced exhaustion. The knowledge about VEGF has increased during the last decades and supports the contention that VEGF plays an important role in stress and depression. There is scarce knowledge on the possible relationship of EGF and MCP-1 in chronic stress and depression. This study further examines the role of VEGF, EGF and MCP-1 in women with chronic stress induced exhaustion and healthy women during a follow-up period of two years. Methods and Findings Blood samples were collected from 105 women with chronic stress induced exhaustion on at least 50% sick leave for at least three months, at inclusion (T0), after 12 months (T12) and after 24 months (T24). Blood samples were collected at inclusion (T0) in 116 physically and psychiatrically healthy women. The plasma levels of VEGF, EGF and MCP-1 were analyzed using Biochip Array Technology. Women with chronic stress induced exhaustion had significantly higher plasma levels of VEGF and EGF compared to healthy women at baseline, T12 and at T24. There was no significant difference in plasma levels of MCP-1. Plasma levels of VEGF and EGF decreased significantly in women with chronic stress induced exhaustion during the two years follow-up. Conclusions The replicated findings of elevated levels of VEGF and EGF in women with chronic stress induced exhaustion and decreasing plasma levels of VEGF and EGF during the two years follow-up add important knowledge to the pathophysiology of chronic stress induced exhaustion. PMID:27145079

  4. Biomechanics of Sports-Induced Axial-Compression Injuries of the Neck

    PubMed Central

    Ivancic, Paul C.

    2012-01-01

    Context Head-first sports-induced impacts cause cervical fractures and dislocations and spinal cord lesions. In previous biomechanical studies, researchers have vertically dropped human cadavers, head-neck specimens, or surrogate models in inverted postures. Objective To develop a cadaveric neck model to simulate horizontally aligned, head-first impacts with a straightened neck and to use the model to investigate biomechanical responses and failure mechanisms. Design Descriptive laboratory study. Setting Biomechanics research laboratory. Patients or Other Participants Five human cadaveric cervical spine specimens. Intervention(s) The model consisted of the neck specimen mounted horizontally to a torso-equivalent mass on a sled and carrying a surrogate head. Head-first impacts were simulated at 4.1 m/s into a padded, deformable barrier. Main Outcome Measure(s) Time-history responses were determined for head and neck loads, accelerations, and motions. Average occurrence times of the compression force peaks at the impact barrier, occipital condyles, and neck were compared. Results The first local compression force peaks at the impact barrier (3070.0 ± 168.0 N at 18.8 milliseconds), occipital condyles (2868.1 ± 732.4 N at 19.6 milliseconds), and neck (2884.6 ± 910.7 N at 25.0 milliseconds) occurred earlier than all global compression peaks, which reached 7531.6 N in the neck at 46.6 milliseconds (P < .001). Average peak head motions relative to the torso were 6.0 cm in compression, 2.4 cm in posterior shear, and 6.4° in flexion. Neck compression fractures included occipital condyle, atlas, odontoid, and subaxial comminuted burst and facet fractures. Conclusions Neck injuries due to excessive axial compression occurred within 20 milliseconds of impact and were caused by abrupt deceleration of the head and continued forward torso momentum before simultaneous rebound of the head and torso. Improved understanding of neck injury mechanisms during sports-induced impacts

  5. Altered Gravity Induces Oxidative Stress in Drosophila Melanogaster

    NASA Technical Reports Server (NTRS)

    Bhattacharya, Sharmila; Hosamani, Ravikumar

    2015-01-01

    Altered gravity environments can induce increased oxidative stress in biological systems. Microarray data from our previous spaceflight experiment (FIT experiment on STS-121) indicated significant changes in the expression of oxidative stress genes in adult fruit flies after spaceflight. Currently, our lab is focused on elucidating the role of hypergravity-induced oxidative stress and its impact on the nervous system in Drosophila melanogaster. Biochemical, molecular, and genetic approaches were combined to study this effect on the ground. Adult flies (2-3 days old) exposed to acute hypergravity (3g, for 1 hour and 2 hours) showed significantly elevated levels of Reactive Oxygen Species (ROS) in fly brains compared to control samples. This data was supported by significant changes in mRNA expression of specific oxidative stress and antioxidant defense related genes. As anticipated, a stress-resistant mutant line, Indy302, was less vulnerable to hypergravity-induced oxidative stress compared to wild-type flies. Survival curves were generated to study the combined effect of hypergravity and pro-oxidant treatment. Interestingly, many of the oxidative stress changes that were measured in flies showed sex specific differences. Collectively, our data demonstrate that altered gravity significantly induces oxidative stress in Drosophila, and that one of the organs where this effect is evident is the brain.

  6. Emotional Intelligence, Personality, and Task-Induced Stress

    ERIC Educational Resources Information Center

    Matthews, Gerald; Emo, Amanda K.; Funke, Gregory; Zeidner, Moshe; Roberts, Richard D.; Costa, Paul T.; Schulze, Ralf

    2006-01-01

    Emotional intelligence (EI) may predict stress responses and coping strategies in a variety of applied settings. This study compares EI and the personality factors of the Five Factor Model (FFM) as predictors of task-induced stress responses. Participants (N = 200) were randomly assigned to 1 of 4 task conditions, 3 of which were designed to be…

  7. Influence of the drying medium parameters on drying induced stresses

    SciTech Connect

    Musielak, G.

    2000-03-01

    A thermomechanical model of drying of capillary-porous materials whose material constants depend on moisture content and temperature is presented in the paper. The finite element method is used for the solution of two-dimensional problem of convective drying of a prismatic bar. The moisture distributions, temperature distributions, drying induced strains and stresses for various drying medium parameters are determined. The effect of these parameters on moisture distribution and in particular on drying induced stresses is discussed.

  8. Investigation of Shock-Induced Chemical Reactions in Mo-Si Powder Mixtures Using Instrumented Experiments with PVDF Stress Gauges

    SciTech Connect

    Vandersall, K S; Thadhani, N N

    2001-05-29

    Shock-induced chemical reactions in {approx}58% dense Mo+2Si powder mixtures were investigated using time-resolved instrumented experiments, employing PVDF-piezoelectric stress gauges placed at the front and rear surfaces of the powders to measure the input and propagated stresses, and wave speed through the powder mixture. Experiments performed on the powders at input stresses less than 4 GPa, showed characteristics of powder densification and dispersed propagated wave stress profiles with rise time > {approx}40 nanoseconds. At input stress between 4-6 GPa, the powder mixtures showed a sharp rise time (<{approx}10 ns) of propagated wave profile and an expanded state of products revealing evidence of shock-induced chemical reaction. At input stresses greater than 6 GPa, the powder mixtures showed a slower propagated-stress-wave rise time and transition to a low-compressibility (melt) state indicating lack of shock-induced reaction. The results illustrate that premature melting of Si, at input stresses less than the crush-strength of the powder mixtures, restricts mixing between reactants and inhibits ''shock-induced'' reaction initiation.

  9. [Nitric oxide and prostaglandin E2 secretion in osteocytes induced by intermittent cyclic compressive force].

    PubMed

    Yin, Jian; Hao, Zhichao; Liao, Shuang; Liu, Ying; Shen, Jiefei; Liao, Yunmao; Wang, Hang

    2014-06-01

    This paper is aimed to investigate the effect of rest-inserted loading on the mechanosensitivity of osteocytes. In the investigation, cultured MLO-Y4 osteocyte-like cells were strained on cyclic compressive force (CCF) by the self-made compressive loading device. Then we observed the effect of different rest periods-inserted loading (5 s, 15 s, 30 s, respectively) on the mechanosensitivity of osteocytes. We then determined the levels of secreted nitric oxide (NO) and prostaglandin E2 (PGE2) by Griess method and enzyme linked immunosorbent assay (ELISA), respectively. We then stained the cytoskeleton F-actin using immunofluorescence. We found that the expressions of NO and PGE2 in rest-inserted strained groups (> 15 s) were significantly increased compared to those in the continuous strained group. And rest-inserted loading promoted the parallel alignment of stress fibers. It indicates that rest-inserted loading could promote the mechanosensitivity of osteocytes, and this might be related to the parallel alignment of stress fibers. PMID:25219246

  10. ATR inhibition rewires cellular signaling networks induced by replication stress.

    PubMed

    Wagner, Sebastian A; Oehler, Hannah; Voigt, Andrea; Dalic, Denis; Freiwald, Anja; Serve, Hubert; Beli, Petra

    2016-02-01

    The slowing down or stalling of replication forks is commonly known as replication stress and arises from multiple causes such as DNA lesions, nucleotide depletion, RNA-DNA hybrids, and oncogene activation. The ataxia telangiectasia and Rad3-related kinase (ATR) plays an essential role in the cellular response to replication stress and inhibition of ATR has emerged as therapeutic strategy for the treatment of cancers that exhibit high levels of replication stress. However, the cellular signaling induced by replication stress and the substrate spectrum of ATR has not been systematically investigated. In this study, we employed quantitative MS-based proteomics to define the cellular signaling after nucleotide depletion-induced replication stress and replication fork collapse following ATR inhibition. We demonstrate that replication stress results in increased phosphorylation of a subset of proteins, many of which are involved in RNA splicing and transcription and have previously not been associated with the cellular replication stress response. Furthermore, our data reveal the ATR-dependent phosphorylation following replication stress and discover novel putative ATR target sites on MCM6, TOPBP1, RAD51AP1, and PSMD4. We establish that ATR inhibition rewires cellular signaling networks induced by replication stress and leads to the activation of the ATM-driven double-strand break repair signaling. PMID:26572502

  11. Algebraic Reynolds stress modeling of turbulence subject to rapid homogeneous and non-homogeneous compression or expansion

    NASA Astrophysics Data System (ADS)

    Grigoriev, I. A.; Wallin, S.; Brethouwer, G.; Grundestam, O.; Johansson, A. V.

    2016-02-01

    A recently developed explicit algebraic Reynolds stress model (EARSM) by Grigoriev et al. ["A realizable explicit algebraic Reynolds stress model for compressible turbulent flow with significant mean dilatation," Phys. Fluids 25(10), 105112 (2013)] and the related differential Reynolds stress model (DRSM) are used to investigate the influence of homogeneous shear and compression on the evolution of turbulence in the limit of rapid distortion theory (RDT). The DRSM predictions of the turbulence kinetic energy evolution are in reasonable agreement with RDT while the evolution of diagonal components of anisotropy correctly captures the essential features, which is not the case for standard compressible extensions of DRSMs. The EARSM is shown to give a realizable anisotropy tensor and a correct trend of the growth of turbulence kinetic energy K, which saturates at a power law growth versus compression ratio, as well as retaining a normalized strain in the RDT regime. In contrast, an eddy-viscosity model results in a rapid exponential growth of K and excludes both realizability and high magnitude of the strain rate. We illustrate the importance of using a proper algebraic treatment of EARSM in systems with high values of dilatation and vorticity but low shear. A homogeneously compressed and rotating gas cloud with cylindrical symmetry, related to astrophysical flows and swirling supercritical flows, was investigated too. We also outline the extension of DRSM and EARSM to include the effect of non-homogeneous density coupled with "local mean acceleration" which can be important for, e.g., stratified flows or flows with heat release. A fixed-point analysis of direct numerical simulation data of combustion in a wall-jet flow demonstrates that our model gives quantitatively correct predictions of both streamwise and cross-stream components of turbulent density flux as well as their influence on the anisotropies. In summary, we believe that our approach, based on a proper

  12. Potential role of punicalagin against oxidative stress induced testicular damage

    PubMed Central

    Rao, Faiza; Tian, Hui; Li, Wenqing; Hung, Helong; Sun, Fei

    2016-01-01

    Punicalagin is isolated from pomegranate and widely used for the treatment of different diseases in Chinese traditional medicine. This study aimed to evaluate the effect of Punicalagin (purity ≥98%) on oxidative stress induced testicular damage and its effect on fertility. We detected the antioxidant potential of punicalagin in lipopolysaccharide (LPS) induced oxidative stress damage in testes, also tried to uncover the boosting fertility effect of Punicalagin (PU) against oxidative stress-induced infertility. Results demonstrated that 9 mg kg−1 for 7 days treatment significantly decreases LPS induced oxidative damage in testes and nitric oxide production. The administration of oxidative stress resulted in a significant reduction in testes antioxidants GSH, T-SOD, and CAT raised LPO, but treatment with punicalagin for 7 days increased antioxidant defense GSH, T-SOD, and CAT by the end of the experiment and reduced LPO level as well. PU also significantly activates Nrf2, which is involved in regulation of antioxidant defense systems. Hence, the present research categorically elucidates the protective effect of punicalagin against LPS induced oxidative stress induced perturbation in the process of spermatogenesis and significantly increased sperm health and number. Moreover, fertility success significantly decreased in LPS-injected mice compared to controls. Mice injected with LPS had fertility indices of 12.5%, while others treated with a combination of PU + LPS exhibited 75% indices. By promoting fertility and eliminating oxidative stress and inflammation, PU may be a useful nutrient for the treatment of infertility. PMID:26763544

  13. Potential role of punicalagin against oxidative stress induced testicular damage.

    PubMed

    Rao, Faiza; Tian, Hui; Li, Wenqing; Hung, Helong; Sun, Fei

    2016-01-01

    Punicalagin is isolated from pomegranate and widely used for the treatment of different diseases in Chinese traditional medicine. This study aimed to evaluate the effect of Punicalagin (purity ≥98%) on oxidative stress induced testicular damage and its effect on fertility. We detected the antioxidant potential of punicalagin in lipopolysaccharide (LPS) induced oxidative stress damage in testes, also tried to uncover the boosting fertility effect of Punicalagin (PU) against oxidative stress-induced infertility. Results demonstrated that 9 mg kg-1 for 7 days treatment significantly decreases LPS induced oxidative damage in testes and nitric oxide production. The administration of oxidative stress resulted in a significant reduction in testes antioxidants GSH, T-SOD, and CAT raised LPO, but treatment with punicalagin for 7 days increased antioxidant defense GSH, T-SOD, and CAT by the end of the experiment and reduced LPO level as well. PU also significantly activates Nrf2, which is involved in regulation of antioxidant defense systems. Hence, the present research categorically elucidates the protective effect of punicalagin against LPS induced oxidative stress induced perturbation in the process of spermatogenesis and significantly increased sperm health and number. Moreover, fertility success significantly decreased in LPS-injected mice compared to controls. Mice injected with LPS had fertility indices of 12.5%, while others treated with a combination of PU + LPS exhibited 75% indices. By promoting fertility and eliminating oxidative stress and inflammation, PU may be a useful nutrient for the treatment of infertility. PMID:26763544

  14. Stress-induced phase transformation and optical coupling of silver nanoparticle superlattices into mechanically stable nanowires.

    PubMed

    Li, Binsong; Wen, Xiaodong; Li, Ruipeng; Wang, Zhongwu; Clem, Paul G; Fan, Hongyou

    2014-01-01

    One-dimensional silver materials display unique optical and electrical properties with promise as functional blocks for a new generation of nanoelectronics. To date, synthetic approaches and property engineering of silver nanowires have primarily focused on chemical methods. Here we report a simple physical method of metal nanowire synthesis, based on stress-induced phase transformation and sintering of spherical Ag nanoparticle superlattices. Two phase transformations of nanoparticles under stress have been observed at distinct length scales. First, the lattice dimensions of silver nanoparticle superlattices may be reversibly manipulated between 0-8 GPa compressive stresses to enable systematic and reversible changes in mesoscale optical coupling between silver nanoparticles. Second, stresses greater than 8 GPa induced an atomic lattice phase transformation, which induced sintering of silver nanoparticles into micron-length scale nanowires. The nanowire synthesis mechanism displays a dependence on both nanoparticle crystal surface orientation and presence of particular grain boundaries to enable nanoparticle consolidation into nanowires. PMID:24957078

  15. An experimental study on the effects of compressive stress on the fatigue crack growth of low-alloy steel

    SciTech Connect

    Jones, D.P.; Hoppe, R.G. . Bettis Atomic Power Lab.); Hechmer, J.L. ); James, B.A. . Metallurgy Dept.)

    1994-08-01

    A series of fatigue crack growth rate tests was conducted in order to study the effects of negative stress ratio upon the fatigue crack growth rate of low-alloy steel in air environment. The tests used four-point bend specimens in order to simulate linear stress distributions typical of many pressure vessel applications. This type of testing adds to the knowledge on negative stress ratio effects for low-alloy steels that in the past have been obtained from uniform tension-compression tests. Additionally, the applied bending stress range was varied from low values of applied stress to high values of applied stress over twice the yield strength. Load control was used for tests for which the stress range was less than twice the yield strength and deflection control was used for the higher stress range tests. The crack geometries involved were both short and long fatigue cracks started at notches and tight fatigue cracks for which crack closure could occur over the full crack face. The results are presented in terms of the stress intensity factor ratio R = K[sub MIN]/K[sub MAX]. The negative R-ratio test results were correlated to an equation of the form da/dN = C[[delta]K/(A-R)][sup n] where A, C and n are curve-fitting parameters. It was found that the effects of negative R-ratio on the fatigue crack growth rates for even the high stress range tests could be bounded by correlating the foregoing equation to only positive R-ratio test results and extending the resulting equation into the negative R-ratio regime.

  16. A representation for the turbulent mass flux contribution to Reynolds-stress and two-equation closures for compressible turbulence

    NASA Technical Reports Server (NTRS)

    Ristorcelli, J. R.

    1993-01-01

    The turbulent mass flux, or equivalently the fluctuating Favre velocity mean, appears in the first and second moment equations of compressible kappa-epsilon and Reynolds stress closures. Mathematically it is the difference between the unweighted and density-weighted averages of the velocity field and is therefore a measure of the effects of compressibility through variations in density. It appears to be fundamental to an inhomogeneous compressible turbulence, in which it characterizes the effects of the mean density gradients, in the same way the anisotropy tensor characterizes the effects of the mean velocity gradients. An evolution equation for the turbulent mass flux is derived. A truncation of this equation produces an algebraic expression for the mass flux. The mass flux is found to be proportional to the mean density gradients with a tensor eddy-viscosity that depends on both the mean deformation and the Reynolds stresses. The model is tested in a wall bounded DNS at Mach 4.5 with notable results.

  17. A unified planar measurement technique for compressible flows using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.

    1992-01-01

    A unified laser-induced fluorescence technique for conducting planar measurements of temperature, pressure and velocity in nonreacting, highly compressible flows has been developed, validated and demonstrated. Planar fluorescence from iodine, seeded into air, was induced by an argon-ion laser and collected using a liquid-nitrogen cooled CCD camera. In the measurement technique, temperature is determined from the fluorescence induced with the laser operated broad band. Pressure and velocity are determined from the shape and position of the fluorescence excitation spectrum which is measured with the laser operated narrow band. The measurement approach described herein provides a means of obtaining accurate, spatially-complete maps of the primary flow field parameters in a wide variety of cold supersonic and transonic flows.

  18. Uniaxial Compression Experiments on Lead Zirconate Titanate 95/5-2Nb Ceramic: Evidence for an Orientation-Dependent, ''Maximum Compressive Stress'' Criterion for Onset of the Ferroelectric - Antiferroelectric Polymorphic Transformation

    SciTech Connect

    Zeuch, D.H.; Montgomery, S.T.; Holcomb, D.J.

    1999-07-26

    Some time ago we presented evidence that, under nonhydrostatic loading, the F{sub R1} {r_arrow} A{sub O} polymorphic transformation of unpoled PZT 95/5-2Nb (PNZT) ceramic began when the maximum compressive stress equaled the hydro-static pressure at which the transformation otherwise took place. Recently we showed that this simple criterion did not apply to nonhydrostatically compressed, poled ceramic. However, unpoled ceramic is isotropic, whereas poled ceramic has a preferred crystallographic orientation and is mechanically anisotropic. If we further assume that the transformation depends not only on the magnitude of the compressive stress, but also its orientation relative to some feature(s) of PNZT's crystallography, then these disparate results can be qualitatively resolved. It has long been known that this transformation can be triggered in uniaxial compression. Our modified hypothesis makes two predictions for transformation of unpoled polycrystals under uniaxial stress: (i) the transformation should begin when the maximum compressive stress, {sigma}{sub 1}, equals the hydrostatic pressure for transformation, and (ii) a steadily increasing axial stress should be required to drive the transformation.

  19. Stress induced topographic patterning in thin diblock copolymer films

    NASA Astrophysics Data System (ADS)

    Croll, Andrew; Crosby, Alfred

    2011-03-01

    When a thin rigid polymer film is attached to a soft elastic substrate and placed in a state of compressive stress, the system wrinkles as a critical stress is surpassed. This simple deformation pattern contains information about the mechanical state of both the polymer film and substrate. Although classical mechanics can be used to relate the global deformation of the film/substrate to the local wrinkle geometry as a function of materials properties, relatively little is known about how the thin capping film material accommodates the localized bending (and therefore localized stress). Here we conduct wrinkling experiments using a model diblock copolymer/elastomer composite. Wrinkling a homogeneous, disordered block copolymer film places the film in a well-defined initial stress state. When heated above its glass transition, the wrinkled film flows, microphase separates, and relaxes from the stress imposed by local wrinkle deformations. The periodic stress relaxation leads to the emergence of a new pattern in the microphase separated surface structure, thus providing new insight into how block copolymers react to stress.

  20. A computer program for plotting stress-strain data from compression, tension, and torsion tests of materials

    NASA Technical Reports Server (NTRS)

    Greenbaum, A.; Baker, D. J.; Davis, J. G., Jr.

    1974-01-01

    A computer program for plotting stress-strain curves obtained from compression and tension tests on rectangular (flat) specimens and circular-cross-section specimens (rods and tubes) and both stress-strain and torque-twist curves obtained from torsion tests on tubes is presented in detail. The program is written in FORTRAN 4 language for the Control Data 6000 series digital computer with the SCOPE 3.0 operating system and requires approximately 110000 octal locations of core storage. The program has the capability of plotting individual strain-gage outputs and/or the average output of several strain gages and the capability of computing the slope of a straight line which provides a least-squares fit to a specified section of the plotted curve. In addition, the program can compute the slope of the stress-strain curve at any point along the curve. The computer program input and output for three sample problems are presented.

  1. Stress-Shielding Effect of Nitinol Swan-Like Memory Compressive Connector on Fracture Healing of Upper Limb

    NASA Astrophysics Data System (ADS)

    Fu, Q. G.; Liu, X. W.; Xu, S. G.; Li, M.; Zhang, C. C.

    2009-08-01

    In this article, the stress-shielding effect of a Nitinol swan-like memory compressive connector (SMC) is evaluated. Patients with fracture healing of an upper limb after SMC internal fixation or stainless steel plate fixation were randomly selected and observed comparatively. With the informed consent of the SMC group, minimal cortical bone under the swan-body and swan-neck was harvested; and in the steel plate fixation group, minimal cortical bone under the steel plate and opposite side to the steel plate was also harvested for observation. Main outcome measurements were taken such as osteocyte morphology, Harversian canal histological observation under light microscope; radiographic observation of fracture healing, and computed tomography quantitative scanning of cortical bone. As a conclusion, SMC has a lesser stress-shielding effect to fixed bone than steel plate. Finally, the mechanism of the lesser stress-shielding effect of SMC is discussed.

  2. A new paradigm to induce mental stress: the Sing-a-Song Stress Test (SSST)

    PubMed Central

    Brouwer, Anne-Marie; Hogervorst, Maarten A.

    2014-01-01

    We here introduce a new experimental paradigm to induce mental stress in a quick and easy way while adhering to ethical standards and controlling for potential confounds resulting from sensory input and body movements. In our Sing-a-Song Stress Test, participants are presented with neutral messages on a screen, interleaved with 1-min time intervals. The final message is that the participant should sing a song aloud after the interval has elapsed. Participants sit still during the whole procedure. We found that heart rate and skin conductance during the 1-min intervals following the sing-a-song stress message are substantially higher than during intervals following neutral messages. The order of magnitude of the rise is comparable to that achieved by the Trier Social Stress Test. Skin conductance increase correlates positively with experienced stress level as reported by participants. We also simulated stress detection in real time. When using both skin conductance and heart rate, stress is detected for 18 out of 20 participants, approximately 10 s after onset of the sing-a-song message. In conclusion, the Sing-a-Song Stress Test provides a quick, easy, controlled and potent way to induce mental stress and could be helpful in studies ranging from examining physiological effects of mental stress to evaluating interventions to reduce stress. PMID:25120425

  3. Stress- and pressure-induced iron spin-state crossover in lower mantle minerals

    NASA Astrophysics Data System (ADS)

    Glazyrin, K.; Miyajima, N.; Smith, J.; Lee, K. K.

    2013-12-01

    The spin-state crossover of ferric and ferrous iron is an important feature of major lower mantle minerals, namely magnesium silicate perovskite (Pv) and ferropericlase (Fp). This electronic transition observed in compressed Pv and Fp was initially discovered at ambient temperatures, however it is also expected for the extreme high pressure-high temperature (HP-HT) conditions endemic to planetary interiors, in particular to the Earth's lower mantle. The pressure-induced spin-state crossover of iron in Pv and Fp has been under focus of many studies, however, some aspects have not been explored in great detail. One of these aspects is the influence of non-hydrostatic macro and micro stresses on the spin-state transitions. Hydrostatic pressure is the important thermodynamic property and distinguishing effects of undesirable stresses is important from both a theoretical and experimental point of view. In this work we compress a two-phase polycrystalline mixture containing magnesium silicate Pv (Fe, Al bearing) and Fp. Using high-resolution synchrotron diffraction on laser-heated diamond-anvil cell samples, we explore characteristic signatures for non-hydrostatic stresses and their influence on the spin-state crossover of ferrous and ferric iron in Pv and Fp. We demonstrate how non-hydrostatic stresses affect the starting pressure and width of the ferrous iron spin-state crossover in Fp and compare available literature data with our results with powder and single crystal diffraction data. Finally, we use the dependence of high-spin to low-spin crossover on the ferrous iron concentration in Fp to support a recently predicted gradual decrease of ferrous iron partitioning coefficient value for Pv and Fp under compression. Our results suggest that this change occurs at HP-HT conditions even before the actual spin-state crossover of ferrous iron in Fp.

  4. Compressibility and pressure-induced phase transformation of Ti3GeC2

    NASA Astrophysics Data System (ADS)

    Wang, Zhongwu; Zha, C. S.; Barsoum, M. W.

    2004-10-01

    In order to explore the large shear-strain-induced polymorph, α-Ti3GeC2 polycrystals were investigated by using a synchrotron radiation source to 64GPa under nonhydrostatic state. Upon compression to 26.6GPa, α-Ti3GeC2 starts to transform to β-Ti3GeC2. As compared to α-Ti3GeC2, the cell parameter a of β-Ti3GeC2 is slightly shorter, and both c and c /a larger. These two polymorphs exhibit similar compressibility. The bulk modulus is calculated to be 179(±10)GPa at a fixed K'=4.0. This is lower than that of Ti3SiC2, and close to that of Ti3Si0.5Ge0.5C2. The compressibilities of these two Ti3GeC2 polymorphs do not display an apparent anisotropy, and differ from the large anisotropies observed from Ti3SiC2 and Ti3Si0.5Ge0.5C2.

  5. Cellular characterization of compression induced-damage in live biological samples

    NASA Astrophysics Data System (ADS)

    Bo, Chiara; Balzer, Jens; Hahnel, Mark; Rankin, Sara M.; Brown, Katherine A.; Proud, William G.

    2011-06-01

    Understanding the dysfunctions that high-intensity compression waves induce in human tissues is critical to impact on acute-phase treatments and requires the development of experimental models of traumatic damage in biological samples. In this study we have developed an experimental system to directly assess the impact of dynamic loading conditions on cellular function at the molecular level. Here we present a confinement chamber designed to subject live cell cultures in liquid environment to compression waves in the range of tens of MPa using a split Hopkinson pressure bars system. Recording the loading history and collecting the samples post-impact without external contamination allow the definition of parameters such as pressure and duration of the stimulus that can be related to the cellular damage. The compression experiments are conducted on Mesenchymal Stem Cells from BALB/c mice and the damage analysis are compared to two control groups. Changes in Stem cell viability, phenotype and function are assessed flow cytometry and with in vitro bioassays at two different time points. Identifying the cellular and molecular mechanisms underlying the damage caused by dynamic loading in live biological samples could enable the development of new treatments for traumatic injuries.

  6. Microscopic studies of cellular damage induced by compression waves in different environments

    NASA Astrophysics Data System (ADS)

    Bo, Chiara; Balzer, Jens; Brown, Katherine A.; Proud, William G.

    2011-06-01

    The cellular basis of induced-damage in biological samples under dynamic loading conditions is largely uncharacterized. In this study we propose a new approach to investigate the effects of compression waves on in-vitro grown Stem cells extracted from BALB/c mice. A modified split Hopkinson pressure bar system is used to simulate damage in the biological samples: the cells are inserted in a confinement chamber either in their growing media or on a 3D scaffold, they are subjected to compression waves and finally recovered for further analysis. The difference in mechanical impedance between the cells and the hosting environments is believed to be a key point in the generation of damage. To discriminate the effects of the different mechanical supports on cell morphology pre and after compression, membrane and cytoskeletal proteins disruptions are investigated using fluorescence confocal microscopy. Understanding the underlying mechanism of damage at the microscopic scale could set the basis for the development of therapeutic applications at the cellular level.

  7. Environmental stress induces trinucleotide repeat mutagenesis in human cells.

    PubMed

    Chatterjee, Nimrat; Lin, Yunfu; Santillan, Beatriz A; Yotnda, Patricia; Wilson, John H

    2015-03-24

    The dynamic mutability of microsatellite repeats is implicated in the modification of gene function and disease phenotype. Studies of the enhanced instability of long trinucleotide repeats (TNRs)-the cause of multiple human diseases-have revealed a remarkable complexity of mutagenic mechanisms. Here, we show that cold, heat, hypoxic, and oxidative stresses induce mutagenesis of a long CAG repeat tract in human cells. We show that stress-response factors mediate the stress-induced mutagenesis (SIM) of CAG repeats. We show further that SIM of CAG repeats does not involve mismatch repair, nucleotide excision repair, or transcription, processes that are known to promote TNR mutagenesis in other pathways of instability. Instead, we find that these stresses stimulate DNA rereplication, increasing the proportion of cells with >4 C-value (C) DNA content. Knockdown of the replication origin-licensing factor CDT1 eliminates both stress-induced rereplication and CAG repeat mutagenesis. In addition, direct induction of rereplication in the absence of stress also increases the proportion of cells with >4C DNA content and promotes repeat mutagenesis. Thus, environmental stress triggers a unique pathway for TNR mutagenesis that likely is mediated by DNA rereplication. This pathway may impact normal cells as they encounter stresses in their environment or during development or abnormal cells as they evolve metastatic potential. PMID:25775519

  8. Environmental stress induces trinucleotide repeat mutagenesis in human cells

    PubMed Central

    Chatterjee, Nimrat; Lin, Yunfu; Santillan, Beatriz A.; Yotnda, Patricia; Wilson, John H.

    2015-01-01

    The dynamic mutability of microsatellite repeats is implicated in the modification of gene function and disease phenotype. Studies of the enhanced instability of long trinucleotide repeats (TNRs)—the cause of multiple human diseases—have revealed a remarkable complexity of mutagenic mechanisms. Here, we show that cold, heat, hypoxic, and oxidative stresses induce mutagenesis of a long CAG repeat tract in human cells. We show that stress-response factors mediate the stress-induced mutagenesis (SIM) of CAG repeats. We show further that SIM of CAG repeats does not involve mismatch repair, nucleotide excision repair, or transcription, processes that are known to promote TNR mutagenesis in other pathways of instability. Instead, we find that these stresses stimulate DNA rereplication, increasing the proportion of cells with >4 C-value (C) DNA content. Knockdown of the replication origin-licensing factor CDT1 eliminates both stress-induced rereplication and CAG repeat mutagenesis. In addition, direct induction of rereplication in the absence of stress also increases the proportion of cells with >4C DNA content and promotes repeat mutagenesis. Thus, environmental stress triggers a unique pathway for TNR mutagenesis that likely is mediated by DNA rereplication. This pathway may impact normal cells as they encounter stresses in their environment or during development or abnormal cells as they evolve metastatic potential. PMID:25775519

  9. Folate levels modulate oncogene-induced replication stress and tumorigenicity

    PubMed Central

    Lamm, Noa; Maoz, Karin; Bester, Assaf C; Im, Michael M; Shewach, Donna S; Karni, Rotem; Kerem, Batsheva

    2015-01-01

    Chromosomal instability in early cancer stages is caused by replication stress. One mechanism by which oncogene expression induces replication stress is to drive cell proliferation with insufficient nucleotide levels. Cancer development is driven by alterations in both genetic and environmental factors. Here, we investigated whether replication stress can be modulated by both genetic and non-genetic factors and whether the extent of replication stress affects the probability of neoplastic transformation. To do so, we studied the effect of folate, a micronutrient that is essential for nucleotide biosynthesis, on oncogene-induced tumorigenicity. We show that folate deficiency by itself leads to replication stress in a concentration-dependent manner. Folate deficiency significantly enhances oncogene-induced replication stress, leading to increased DNA damage and tumorigenicity in vitro. Importantly, oncogene-expressing cells, when grown under folate deficiency, exhibit a significantly increased frequency of tumor development in mice. These findings suggest that replication stress is a quantitative trait affected by both genetic and non-genetic factors and that the extent of replication stress plays an important role in cancer development. PMID:26197802

  10. Mechanical stress induced voltage shift in polycrystalline Bi3.25La0.75Ti3O12 thin films

    NASA Astrophysics Data System (ADS)

    Wu, Xiumei; Zhai, Ya; Kan, Yi; Lu, Xiaomei; Zhu, Jinsong

    2009-10-01

    Imprint behavior of polycrystalline Bi3.25La0.75Ti3O12 thin films under stress was studied. The voltage shift along the positive voltage axis can be depressed by tensile stress while increased by compressive stress. With the measured voltage increasing, the voltage shift referred above increases and the increase trend gets enhanced under both compressive and tensile stress compared with that at zero stress. The asymmetric distribution of the trapped charged in films, which is caused by the increase of the in-plane polarization component for the domain reorientation induced by stress or for the voltage-assisted domain walls depinning, was considered the contribution to the voltage shift.

  11. Multiple Stress Signals Induce p73β Accumulation1

    PubMed Central

    Lin, Kai Wei; Nam, Shin Yuen; Toh, Wen Hong; Dulloo, Iqbal; Sabapathy, Kanaga

    2004-01-01

    Abstract Although p73 is a structural and functional homologue of the tumor-suppressor gene p53, it is not mutated in many human cancers as p53. Besides, p73 was shown to be activated by only a subset of signals that activate p53, such as γ-irradiation and cisplatin, but not by other common genotoxic stress-inducing agents such as ultraviolet (UV) irradiation, although many of these signals are also capable of inducing p53-independent cell death. Using a p73-specific antibody, we confirmed that c-Abl is required for cisplatin-induced p73 upregulation, and further demonstrate that the p73 protein is upregulated by UV irradiation and other stress stimuli including sorbitol, hydrogen peroxide, nocodazol, and taxol. These stress signals upregulate both p73 mRNA and increases the stability of p73, indicating that p73 is regulated transcriptionally and posttranslationally. Cells stably expressing the dominant-negative p73 inhibitor protein (p73DD) and p73-/- fibroblasts are more resistant than control cells to apoptosis induced by these stress signals, suggesting that p73 contributes to apoptosis induction. Together, the data demonstrate that several stress signals can signal to p73 in vivo, which raises the possibility of eradicating cancers with an unmutated p73 gene by activating them with stress-inducing agents or their mimetics. PMID:15548364

  12. Role of endoplasmic reticulum stress in drug-induced toxicity.

    PubMed

    Foufelle, Fabienne; Fromenty, Bernard

    2016-02-01

    Drug-induced toxicity is a key issue for public health because some side effects can be severe and life-threatening. These adverse effects can also be a major concern for the pharmaceutical companies since significant toxicity can lead to the interruption of clinical trials, or the withdrawal of the incriminated drugs from the market. Recent studies suggested that endoplasmic reticulum (ER) stress could be an important event involved in drug liability, in addition to other key mechanisms such as mitochondrial dysfunction and oxidative stress. Indeed, drug-induced ER stress could lead to several deleterious effects within cells and tissues including accumulation of lipids, cell death, cytolysis, and inflammation. After recalling important information regarding drug-induced adverse reactions and ER stress in diverse pathophysiological situations, this review summarizes the main data pertaining to drug-induced ER stress and its potential involvement in different adverse effects. Drugs presented in this review are for instance acetaminophen (APAP), arsenic trioxide and other anticancer drugs, diclofenac, and different antiretroviral compounds. We also included data on tunicamycin (an antibiotic not used in human medicine because of its toxicity) and thapsigargin (a toxic compound of the Mediterranean plant Thapsia garganica) since both molecules are commonly used as prototypical toxins to induce ER stress in cellular and animal models. PMID:26977301

  13. Stress-induced obesity and the emotional nervous system

    PubMed Central

    Dallman, Mary F

    2009-01-01

    Stress and emotional brain networks foster eating behaviors that may lead to obesity. The neural networks underlying the complex interactions among stressors, body, brain and food intake are now better understood. Stressors, by activating a neural stress-response network, bias cognition toward increased emotional activity and degraded executive function. This causes formed habits to be used rather than a cognitive appraisal of responses. Stress also induces secretion of both glucocorticoids, which increases motivation for food, and insulin, which promotes food intake and obesity. Pleasurable feeding then reduces activity in the stress-response network, reinforcing the feeding habit. These effects of stressors emphasize the importance of teaching mental reappraisal techniques to restore responses from habitual to thoughtful, thus battling stress-induced obesity. PMID:19926299

  14. Oxidative stress-induced autophagy: Role in pulmonary toxicity

    SciTech Connect

    Malaviya, Rama; Laskin, Jeffrey D.; Laskin, Debra L.

    2014-03-01

    Autophagy is an evolutionarily conserved catabolic process important in regulating the turnover of essential proteins and in elimination of damaged organelles and protein aggregates. Autophagy is observed in the lung in response to oxidative stress generated as a consequence of exposure to environmental toxicants. Whether autophagy plays role in promoting cell survival or cytotoxicity is unclear. In this article recent findings on oxidative stress-induced autophagy in the lung are reviewed; potential mechanisms initiating autophagy are also discussed. A better understanding of autophagy and its role in pulmonary toxicity may lead to the development of new strategies to treat lung injury associated with oxidative stress. - Highlights: • Exposure to pulmonary toxicants is associated with oxidative stress. • Oxidative stress is known to induce autophagy. • Autophagy is upregulated in the lung following exposure to pulmonary toxicants. • Autophagy may be protective or pathogenic.

  15. HCV-Induced Oxidative Stress: Battlefield-Winning Strategy

    PubMed Central

    Rebbani, Khadija; Tsukiyama-Kohara, Kyoko

    2016-01-01

    About 150 million people worldwide are chronically infected with hepatitis C virus (HCV). The persistence of the infection is controlled by several mechanisms including the induction of oxidative stress. HCV relies on this strategy to redirect lipid metabolism machinery and escape immune response. The 3β-hydroxysterol Δ24-reductase (DHCR24) is one of the newly discovered host markers of oxidative stress. This protein, as HCV-induced oxidative stress responsive protein, may play a critical role in the pathogenesis of HCV chronic infection and associated liver diseases, when aberrantly expressed. The sustained expression of DHCR24 in response to HCV-induced oxidative stress results in suppression of nuclear p53 activity by blocking its acetylation and increasing its interaction with MDM2 in the cytoplasm leading to its degradation, which may induce hepatocarcinogenesis. PMID:27293514

  16. Stress proteins are induced by space environment

    NASA Astrophysics Data System (ADS)

    Takahashi, Akihisa; Ohnishi, Takeo

    The space environment contains two major biologically significant influences such as space radiations and microgravity. Almost all organisms possess essential recognition and response systems for environmental changes. The famous one of cellular stress responses is the gene induction of heat shock protein (HSP). HSP expression is increased under elevated temperatures, and also increased by other sources of cellular stress, including ionizing radiation, oxidative injury, osmotic stress and the unfolded protein response. HSPs assist in the folding and maintenance of newly translated proteins, the refolding of denatured proteins and the further unfolding of misfolded or destabilized proteins to protect the cell from crisis. Based on our space experiment, we report the results and discussion from the viewpoint of HSP expression after exposure to space environment.

  17. Juvenile stress impairs body temperature regulation and augments anticipatory stress-induced hyperthermia responses in rats.

    PubMed

    Yee, Nicole; Plassmann, Kerstin; Fuchs, Eberhard

    2011-09-01

    Clinical studies have implicated adolescence as an important and vulnerable period during which traumatic experiences can predispose individuals to anxiety and mood disorders. As such, a stress model in juvenile rats (age 27-29 d) was previously developed to investigate the long-term effects of stress exposure during adolescence on behavior and physiology. This paradigm involves exposing rats to different stressors on consecutive days over a 3-day period. Here, we studied the effects of juvenile stress on long-term core body temperature regulation and acute stress-induced hyperthermia (SIH) responses using telemetry. We found no differences between control and juvenile stress rats in anxiety-related behavior on the elevated plus maze, which we attribute to stress associated with surgical implantation of telemetry devices. This highlights the severe impact of surgical stress on the results of subsequent behavioral measurements. Nonetheless, juvenile stress disrupted the circadian rhythmicity of body temperature and decreased circadian amplitude. It also induced chronic hypothermia during the dark phase of the day, when rats are most active. When subjected to acute social defeat stress as adults, juvenile stress had no impact on the SIH response relative to controls. However, 24 h later, juvenile stress rats displayed an elevated SIH response in anticipation of social defeat when re-exposed to the social defeat environment. Taken together, our findings indicate that juvenile stress can induce long-term alterations in body temperature regulation and heighten the increase in temperature associated with anticipation of social defeat. The outcomes of behavioral measurements in these experiments, however, are severely affected by surgical stress. PMID:21557956

  18. Cracking and Stress-Strain Behavior of Rock-Like Material Containing Two Flaws Under Uniaxial Compression

    NASA Astrophysics Data System (ADS)

    Zhao, Yanlin; Zhang, Lianyang; Wang, Weijun; Pu, Chengzhi; Wan, Wen; Tang, Jingzhou

    2016-07-01

    This paper investigates the cracking and stress-strain behavior, especially the local strain concentration near the flaw tips, of rock-like material containing two flaws. A series of uniaxial compression tests were carried out on rock-like specimens containing two flaws, with strain gauges mounted near the flaw tips to measure the local strain concentration under the uniaxial compressive loading. Four different types of cracks (wing cracks, anti-wing cracks, coplanar shear cracks and oblique shear cracks) and seven patterns of crack coalescences (T1 and T2; S1 and S2; and TS1, TS2 and TS3) are observed in the experiments. The type of crack coalescence is related to the geometry of the flaws. In general, the crack coalescence varies from the S-mode to the TS-mode and then to the T-mode with the increase of the rock bridge ligament angle. The stress-strain curves of the specimens containing two flaws are closely related to the crack development and coalescence process. The strain measurements indicate that the local tensile strain concentration below or above the pre-existing flaw tip causes wing or anti-wing cracks, while the local compressive strain concentration near the flaw tip is related to the shear crack. The measured local tensile strain shows a jump at the initiation of wing- and anti-wing cracks, reflecting the instant opening of the wing- and anti-wing crack propagating through the strain gauge. During the propagation of wing- and anti-wing cracks, the measured local tensile strain gradually increases with few jumps, implying that the opening deformation of wing- and anti-wing cracks occurs in a stable manner. The shear cracks initiate followed by a large and abrupt compressive strain jump and then quickly propagate in an unstable manner resulting in the failure of specimens.

  19. Phloroglucinol Attenuates Free Radical-induced Oxidative Stress

    PubMed Central

    So, Mi Jung; Cho, Eun Ju

    2014-01-01

    The protective role of phloroglucinol against oxidative stress and stress-induced premature senescence (SIPS) was investigated in vitro and in cell culture. Phloroglucinol had strong and concentration-dependent radical scavenging effects against nitric oxide (NO), superoxide anions (O2−), and hydroxyl radicals. In this study, free radical generators were used to induce oxidative stress in LLC-PK1 renal epithelial cells. Treatment with phloroglucinol attenuated the oxidative stress induced by peroxyl radicals, NO, O2−, and peroxynitrite. Phloroglucinol also increased cell viability and decreased lipid peroxidation in a concentration-dependent manner. WI-38 human diploid fibroblast cells were used to investigate the protective effect of phloroglucinol against hydrogen peroxide (H2O2)-induced SIPS. Phloroglucinol treatment attenuated H2O2-induced SIPS by increasing cell viability and inhibited lipid peroxidation, suggesting that treatment with phloroglucinol should delay the aging process. The present study supports the promising role of phloroglucinol as an antioxidative agent against free radical-induced oxidative stress and SIPS. PMID:25320709

  20. Angina and Mental Stress-Induced Myocardial Ischemia

    PubMed Central

    Pimple, Pratik; Shah, Amit J.; Rooks, Cherie; Bremner, J. Douglas; Nye, Jonathon; Ibeanu, Ijeoma; Raggi, Paolo; Vaccarino, Viola

    2015-01-01

    Objective Mental stress-induced myocardial ischemia is a common phenomenon in patients with coronary artery disease (CAD) and an emerging prognostic factor. Mental stress ischemia is correlated with ambulatory ischemia. However, whether it is related to angina symptoms during daily life has not been examined. Methods We assessed angina-frequency (past month) in 98 post-myocardial infarction (MI) subjects (age 18-60 years) using the Seattle Angina Questionnaire. Patients underwent [99mTc]sestamibi SPECT perfusion imaging at rest, after mental stress, and after exercise/pharmacological stress. Summed scores of perfusion abnormalities were obtained by observer-independent software. A summed-difference score (SDS), the difference between stress and rest scores, was used to quantify myocardial ischemia under both stress conditions. Results The mean age was 50 years, 50% were female and 60% were non-white. After adjustment for age, sex, smoking, CAD-severity, depressive, anger and anxiety symptoms, each 1-point increase in mental-stress SDS was associated with 1.73-unit increase in the angina-frequency score (95% CI: 0.09-3.37) and 17% higher odds of being in a higher angina-frequency category (OR: 1.17, 95% CI: 1.00-1.38). Depressive symptoms were associated with 12% higher odds of being in a higher angina-frequency category (OR: 1.12, 95% CI: 1.03-1.21). In contrast, exercise/pharmacological stress-induced SDS was not associated with angina-frequency. Conclusion Among young and middle-aged post-MI patients, myocardial ischemia induced by mental stress in the lab, but not by exercise/pharmacological stress, is associated with higher frequency of retrospectively reported angina during the day. Psychosocial stressors related to mental stress ischemia may be important contributory factor to daily angina. PMID:25727240

  1. Oxidative stress induced carbonylation in human plasma.

    PubMed

    Madian, Ashraf G; Diaz-Maldonado, Naomi; Gao, Qiang; Regnier, Fred E

    2011-10-19

    The focus of this study was on the assessment of technology that might be of clinical utility in identification, quantification, characterization of carbonylation in human plasma proteins. Carbonylation is widely associated with oxidative stress diseases. Breast cancer patient samples were chosen as a stress positive case based on the fact that oxidative stress has been reported to be elevated in this disease. Measurements of 8-isoprostane in plasma confirmed that breast cancer patients in this study were indeed experiencing significant oxidative stress. Carbonyl groups in proteins from freshly drawn blood were derivatized with biotin hydrazide after which the samples were dialyzed and the biotinylated proteins subsequently selected, digested and labeled with iTRAQ™ heavy isotope coding reagent(s). Four hundred sixty proteins were identified and quantified, 95 of which changed 1.5 fold or more in concentration. Beyond confirming the utility of the analytical method, association of protein carbonylation was examined as well. Nearly one fourth of the selected proteins were of cytoplasmic, nuclear, or membrane origin. Analysis of the data by unbiased knowledge assembly methods indicated the most likely disease associated with the proteins was breast neoplasm. Pathway analysis showed the proteins which changed in carbonylation were strongly associated with Brca1, the breast cancer type-1 susceptibility protein. Pathway analysis indicated the major molecular functions of these proteins are defense, immunity and nucleic acid binding. PMID:21856457

  2. Water deficit stress induced gene expression

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water deficit stress is one of the most challenging agricultural issues limiting sustainable cotton production. Many efforts have been incorporated using genetic and genomic approaches to identify valuable molecular resources. In this study, we aimed to identify a global set of transcript fragments ...

  3. Oxidative stress induced carbonylation in human plasma

    PubMed Central

    Madian, Ashraf G.; Diaz-Maldonado, Naomi; Gao, Qiang; Regnier, Fred E.

    2011-01-01

    The focus of this study was on the assessment of technology that might be of clinical utility in identification, quantification, characterization of carbonylation in human plasma proteins. Carbonylation is widely associated with oxidative stress diseases. Breast cancer patient samples were chosen as a stress positive case based on the fact that oxidative stress has been reported to be elevated in this disease. Measurements of 8-isoprostane in plasma confirmed that breast cancer patients in this study were indeed experiencing significant oxidative stress. Carbonyl groups in proteins from freshly drawn blood were derivatized with biotin hydrazide after which the samples were dialyzed and the biotinylated proteins subsequently selected, digested and labeled with iTRAQ™ heavy isotope coding reagent(s). Four hundred sixty proteins were identified and quantified, 95 of which changed 1.5 fold or more in concentration. Beyond confirming the utility of the analytical method, association of protein carbonylation was examined as well. Nearly one fourth of the selected proteins were of cytoplasmic, nuclear, or membrane origin. Analysis of the data by unbiased knowledge assembly methods indicated the most likely disease associated with the proteins was breast neoplasm. Pathway analysis showed the proteins which changed in carbonylation were strongly associated with Brca1, the breast cancer type-1 susceptibility protein. Pathway analysis indicated the major molecular functions of these proteins are defense, immunity and nucleic acid binding. PMID:21856457

  4. Humidity-dependent compression-induced glass transition of the air-water interfacial Langmuir films of poly(D,L-lactic acid-ran-glycolic acid) (PLGA).

    PubMed

    Kim, Hyun Chang; Lee, Hoyoung; Jung, Hyunjung; Choi, Yun Hwa; Meron, Mati; Lin, Binhua; Bang, Joona; Won, You-Yeon

    2015-07-28

    Constant rate compression isotherms of the air-water interfacial Langmuir films of poly(D,L-lactic acid-ran-glycolic acid) (PLGA) show a distinct feature of an exponential increase in surface pressure in the high surface polymer concentration regime. We have previously demonstrated that this abrupt increase in surface pressure is linked to the glass transition of the polymer film, but the detailed mechanism of this process is not fully understood. In order to obtain a molecular-level understanding of this behavior, we performed extensive characterizations of the surface mechanical, structural and rheological properties of Langmuir PLGA films at the air-water interface, using combined experimental techniques including the Langmuir film balance, X-ray reflectivity and double-wall-ring interfacial rheometry methods. We observed that the mechanical and structural responses of the Langmuir PLGA films are significantly dependent on the rate of film compression; the glass transition was induced in the PLGA film only at fast compression rates. Surprisingly, we found that this deformation rate dependence is also dependent on the humidity of the environment. With water acting as a plasticizer for the PLGA material, the diffusion of water molecules through the PLGA film seems to be the key factor in the determination of the glass transformation properties and thus the mechanical response of the PLGA film against lateral compression. Based on our combined results, we hypothesize the following mechanism for the compression-induced glass transformation of the Langmuir PLGA film; (1) initially, a humidified/non-glassy PLGA film is formed in the full surface-coverage region (where the surface pressure shows a plateau) during compression; (2) further compression leads to the collapse of the PLGA chains and the formation of new surfaces on the air side of the film, and this newly formed top layer of the PLGA film is transiently glassy in character because the water evaporation rate

  5. FEM analysis of deformation localization mechanisms in a 3-D fractured medium under rotating compressive stress orientations

    NASA Astrophysics Data System (ADS)

    Strijker, Geertje; Beekman, Fred; Bertotti, Giovanni; Luthi, Stefan M.

    2013-05-01

    Stress distributions and deformation patterns in a medium with a pre-existing fracture set are analyzed as a function of the remote compressive stress orientation (σH) using finite element models with increasingly complex fracture configurations. Slip along the fractures causes deformation localization at the tips as wing cracks or shear zones. The deformation intensity is proportional to the amount of slip, attaining a peak value for α = 45° (α: angle between the fracture strike and σH) and slip is linearly proportional with fracture length. Wing cracks develop for high deformation intensities for 30° < α < 60°, whereas primary plastic shear zones develop for low deformation intensities. Additionally, two types of secondary shear zones develop for α < 30° and α > 60°, with constant angles of 135° and - 60° with σH, respectively. Mechanical interaction between fractures in a fracture zone, quantified as change in slip compared to an isolated fracture, decreases with increasing fracture separation. Fracture underlap elongates the fracture length and therefore increases the amount of slip, while fracture overlap exhibits the opposite effect. Fracture slip decreases with an increasing amount of directly adjacent fractures. Mechanical interaction becomes negligible for fracture configurations with spacing-to-length and spacing-to-overlap ratios exceeding 0.5 and that in this case fractures are decoupled. Independent of the pre-existing fracture configuration, the development of a secondary systematic fracture set driven by a remote stress rotation is dominated by σH; development of wing cracks or shear zones is restricted to the fracture tips. Blocks with tapered geometries are present in models with a variable fracture strike, where the maximum principal stress (σ1, applying the geological convention that compressive stresses are positive) trajectories consistently deviate from σH; the presence of two systematic σ1 trajectory orientations suggests

  6. Cross-Sectional TEM and X-ray Examination of Radiation-Induced Stress Relaxation of Peened Stainless Steel Surfaces

    SciTech Connect

    Sencer, Bulent; Was, Gary S.; Yuya, Hideki; Isobe, Y; Sagisaka, M.; Garner, Francis A.

    2005-02-01

    Neutron irradiation-induced relaxation was emulated using proton irradiation in order to determine the expected amount of stress relaxation in the peened surface layer of a BWR core shroud during its 40 year lifetime. Samples of 304 SS were shot peened to induce a compressive residual stress, and then irradiated with 3.2 MeV protons at 288 C to four dose levels spanning 0.1-2.0 dpa. One set of specimens was as-peened and a second was pre-injected with 25 appm He. Depth-dependent measurements of internal stress were conducted using successive steps of X-ray line broadening measurement and electropolishing. Results showed that the compressive stress state was progressively relaxed, but was maintained at some level for the majority of the 2 dpa target dose. Helium pre-injection did not significantly affect the relaxation, but the magnitude of thermally-induced relaxation was somewhat greater, although it was observed to be largely a transient, saturable process. A new cross-section technique was developed that allows multiple observations to be made in one specimen at all depths, both in and beyond the peen-damaged range. The as-peened microstructure varies strongly with depth, consisting of deformation twins and dense dislocation networks. The radiation-induced relaxation on the microstructural level was expressed primarily in modification and reduction of the dislocation structure. A comparison was made between the proton-induced relaxation of internal stresses and predictions based on neutron-induced relaxation of externally-applied stresses. The relatively good agreement indicates that proton irradiation is a valid emulation of neutron irradiation for this application.

  7. Cross-Sectional TEM and X-ray Examination of Radiation-Induced Stress Relaxation of Peened Stainless Steel Surfaces

    SciTech Connect

    Sencer, Bulent H.; Was, Gary S.; Yuya, Hideki; Isobe, Y; Sagisaka, M.; Garner, Francis A.

    2005-02-01

    Neutron irradiation-induced relaxation was emulated using proton irradiation in order to determine the expected amount of stress relaxation in the peened surface layer of a BWR core shroud during its 40 year lifetime. Samples of 304 SS were shot peened to induce a compressive residual stress, and then irradiated with 3.2 MV protons at 288 C to four dose levels spanning 0.1-2.0 dpa. One set of specimens was as-peened and a second was pre-injected with 25 appm He. Depth-dependent measurements of internal stress were conducted using successive steps of X-ray line broadening measurement and electropolishing. Results showed that the compressive stress state was progressively relaxed, but was maintained at some level for the majority of the 2 dpa target dose. Helium pre-injection did not significantly affect the relaxation, but the magnitude of thermally-induced relaxation was somewhat greater, although it was observed to be largely a transient, saturable process. A new cross-section technique was developed that allows multiple observations to be made in one specimen at all depths, both in and beyond the peen-damaged range. The as-peened microstructure varies strongly with depth, consisting of deformation twins and dense dislocation networks. The radiation-induced relaxation on the microstructural level was expressed primarily in modification and reduction of the dislocation structure. A comparison was made between the proton-induced relaxation of internal stresses and predictions based on neutron-induced relaxation of externally-applied stresses. The relatively good agreement indicates that proton irradiation is a valid emulation of neutron irradiation for this application.

  8. Cross-sectional TEM and X-ray examination of radiation-induced stress relaxation of peened stainless steel surfaces

    NASA Astrophysics Data System (ADS)

    Sencer, B. H.; Was, G. S.; Yuya, H.; Isobe, Y.; Sagisaka, M.; Garner, F. A.

    2005-02-01

    Neutron irradiation-induced relaxation was emulated using proton irradiation in order to determine the expected amount of stress relaxation in the peened surface layer of a BWR core shroud during its 40 year lifetime. Samples of 304 SS were shot peened to induce a compressive residual stress, and then irradiated with 3.2 MeV protons at 288 °C to four dose levels spanning 0.1-2.0 dpa. One set of specimens was as-peened and a second was pre-injected with 25 appm He. Depth-dependent measurements of internal stress were conducted using successive steps of X-ray line broadening measurement and electropolishing. Results showed that the compressive stress state was progressively relaxed, but was maintained at some level for the majority of the 2 dpa target dose. Helium pre-injection did not significantly affect the relaxation, but the magnitude of thermally-induced relaxation was somewhat greater, although it was observed to be largely a transient, saturable process. A new cross-section technique was developed that allows multiple observations to be made in one specimen at all depths, both in and beyond the peen-damaged range. The as-peened microstructure varies strongly with depth, consisting of deformation twins and dense dislocation networks. The radiation-induced relaxation on the microstructural level was expressed primarily in modification and reduction of the dislocation structure. A comparison was made between the proton-induced relaxation of internal stresses and predictions based on neutron-induced relaxation of externally-applied stresses. The relatively good agreement indicates that proton irradiation is a valid emulation of neutron irradiation for this application.

  9. Temporal pore pressure induced stress changes during injection and depletion

    NASA Astrophysics Data System (ADS)

    Müller, Birgit; Heidbach, Oliver; Schilling, Frank; Fuchs, Karl; Röckel, Thomas

    2016-04-01

    Induced seismicity is observed during injection of fluids in oil, gas or geothermal wells as a rather immediate response close to the injection wells due to the often high-rate pressurization. It was recognized even earlier in connection with more moderate rate injection of fluid waste on a longer time frame but higher induced event magnitudes. Today, injection-related induced seismicity significantly increased the number of events with M>3 in the Mid U.S. However, induced seismicity is also observed during production of fluids and gas, even years after the onset of production. E.g. in the Groningen gas field production was required to be reduced due to the increase in felt and damaging seismicity after more than 50 years of exploitation of that field. Thus, injection and production induced seismicity can cause severe impact in terms of hazard but also on economic measures. In order to understand the different onset times of induced seismicity we built a generic model to quantify the role of poro-elasticity processes with special emphasis on the factors time, regional crustal stress conditions and fault parameters for three case studies (injection into a low permeable crystalline rock, hydrothermal circulation and production of fluids). With this approach we consider the spatial and temporal variation of reservoir stress paths, the "early" injection-related induced events during stimulation and the "late" production induced ones. Furthermore, in dependence of the undisturbed in situ stress field conditions the stress tensor can change significantly due to injection and long-term production with changes of the tectonic stress regime in which previously not critically stressed faults could turn to be optimally oriented for fault reactivation.

  10. External compression-induced fracture patterning on the surface of poly(dimethylsiloxane) cubes and microspheres

    PubMed Central

    Uchida, Tomoyuki; Mills, K.L.; Kuo, Chuan-Hsien; Roh, Whijae; Tung, Yi-Chung; Garner, Amanda L.; Koide, Kazunori; Thouless, M.D.; Takayama, Shuichi

    2009-01-01

    This paper describes a method for creating sub-micron surface patterns on cubes and microspheres. In this method, PDMS cubes and microspheres are exposed to oxygen plasma, which creates a very thin, hard, surface-modified layer on a compliant substrate. These are then compressed, causing the layer to crack in patterns dictated by the distribution of tensile stresses in the surface layer. Cracks with sub-micron widths were generated on 1 cm3 cubes and 800 µm-diameter microspheres, and the resulting crack patterns were observed. Finite-element simulations of the tensile stress distributions reveal that the fracture patterns arise from different mechanisms in the cubes and spheres. In particular, pattern formation is associated with frictional contact in the cubes; but not in the microspheres where geometrical effects associated with changes in the cross-sectional area along the axis lead to generation of tensile stress. These observations and analyses provide a foundation on which to predict and guide crack pattern formation on a wide variety of small 3D objects. In anticipation of future applications in materials science and biology, we demonstrate selective deposition of compounds into the cracks to make them functionally differentiable from the rest of the surface. PMID:19437776

  11. Gravity-induced stresses in stratified rock masses

    USGS Publications Warehouse

    Amadei, B.; Swolfs, H.S.; Savage, W.Z.

    1988-01-01

    This paper presents closed-form solutions for the stress field induced by gravity in anisotropic and stratified rock masses. These rocks are assumed to be laterally restrained. The rock mass consists of finite mechanical units, each unit being modeled as a homogeneous, transversely isotropic or isotropic linearly elastic material. The following results are found. The nature of the gravity induced stress field in a stratified rock mass depends on the elastic properties of each rock unit and how these properties vary with depth. It is thermodynamically admissible for the induced horizontal stress component in a given stratified rock mass to exceed the vertical stress component in certain units and to be smaller in other units; this is not possible for the classical unstratified isotropic solution. Examples are presented to explore the nature of the gravity induced stress field in stratified rock masses. It is found that a decrease in rock mass anisotropy and a stiffening of rock masses with depth can generate stress distributions comparable to empirical hyperbolic distributions previously proposed in the literature. ?? 1988 Springer-Verlag.

  12. Ethanol Induces Endoplasmic Reticulum Stress in the Developing Brain

    PubMed Central

    Ke, Zunji; Wang, Xin; Liu, Ying; Fan, Zhiqin; Chen, Gang; Xu, Mei; Bower, Kimberley A.; Frank, Jacqueline A.; Li, Mingtao; Fang, Shengyun; Shi, Xianglin; Luo, Jia

    2016-01-01

    Background Ethanol exposure during brain development causes profound damages to the central nervous system (CNS). The underlying cellular/molecular mechanisms remain unclear. The endoplasmic reticulum (ER) is involved in posttranslational protein processing and transport. The accumulation of unfolded or misfolded proteins in the ER lumen triggers ER stress, which is characterized by translational attenuation, synthesis of ER chaperone proteins, and activation of transcription factors. Sustained ER stress ultimately leads to cell death. ER stress is implicated in various neurodegenerative processes. Methods Using a third trimester equivalent mouse model of ethanol exposure, we tested the hypothesis that ethanol induces ER stress in the developing brain. Seven-day-old C57BL/6 mice were acutely exposed to ethanol by subcutaneous injection and the expression of ER stress-inducible proteins (ERSIPs) and signaling pathways associated with ER stress were examined. Results Ethanol exposure significantly increased the expression of ERSIPs and activated signaling pathways associated with ER stress; these include ATF6, CHOP/GADD153, GRP78, and mesencephalic astrocyte-derived neurotrophic factor as well as the phosphorylation of IRE1α, eIF2α, PERK, and PKR. The ethanol-induced increase in ERSIPs occurred within 4 hours of ethanol injection, and levels of some ERSIPs remained elevated after 24 hours of ethanol exposure. Ethanol-induced increase in phosphorylated eIF2α, caspase-12, and CHOP was distributed in neurons of specific areas of the cerebral cortex, hippocampus, and thalamus. Conclusions Our finding indicates that ethanol induces ER stress in immature neurons, providing novel insight into ethanol’s detrimental effect on the developing CNS. PMID:21599712

  13. (+)-Catechin protects dermal fibroblasts against oxidative stress-induced apoptosis

    PubMed Central

    2014-01-01

    Background Oxidative stress has been suggested as a mechanism underlying skin aging, as it triggers apoptosis in various cell types, including fibroblasts, which play important roles in the preservation of healthy, youthful skin. Catechins, which are antioxidants contained in green tea, exert various actions such as anti-inflammatory, anti-bacterial, and anti-cancer actions. In this study, we investigated the effect of (+)-catechin on apoptosis induced by oxidative stress in fibroblasts. Methods Fibroblasts (NIH3T3) under oxidative stress induced by hydrogen peroxide (0.1 mM) were treated with either vehicle or (+)-catechin (0–100 μM). The effect of (+)-catechin on cell viability, apoptosis, phosphorylation of c-Jun terminal kinases (JNK) and p38, and activation of caspase-3 in fibroblasts under oxidative stress were evaluated. Results Hydrogen peroxide induced apoptotic cell death in fibroblasts, accompanied by induction of phosphorylation of JNK and p38 and activation of caspase-3. Pretreatment of the fibroblasts with (+)-catechin inhibited hydrogen peroxide-induced apoptosis and reduced phosphorylation of JNK and p38 and activation of caspase-3. Conclusion (+)-Catechin protects against oxidative stress-induced cell death in fibroblasts, possibly by inhibiting phosphorylation of p38 and JNK. These results suggest that (+)-catechin has potential as a therapeutic agent for the prevention of skin aging. PMID:24712558

  14. ER Stress-induced Aberrant Neuronal Maturation and Neurodevelopmental Disorders.

    PubMed

    Kawada, Koichi; Iekumo, Takaaki; Kaneko, Masayuki; Nomura, Yasuyuki; Okuma, Yasunobu

    2016-01-01

    Neurodevelopmental disorders, which include autism spectrum disorder, are congenital impairments in the growth and development of the central nervous system. They are mainly accentuated during infancy and childhood. Autism spectrum disorder may be caused by environmental factors, genomic imprinting of chromosome 15q11-q13 regions, and gene defects such as those in genes encoding neurexin and neuroligin, which are involved in synaptogenesis and synaptic signaling. However, regardless of the many reports on neurodevelopmental disorders, the pathogenic mechanism and treatment of neurodevelopmental disorders remain unclear. Conversely, it has been reported that endoplasmic reticulum (ER) stress is involved in neurodegenerative diseases. ER stress is increased by environmental factors such as alcohol consumption and smoking. Here we show the recent results on ER stress-induced neurodevelopmental disorders. ER stress led to a decrease in the mRNA levels of the proneural factors Hes1/5 and Pax6, which maintain an undifferentiated state of the neural cells. This stress also led to a decrease in nestin expression and an increase in beta-III tubulin expression. In addition, dendrite length was shortened by ER stress in microtubule-associated protein-2 (MAP-2) positive cells. However, the ubiquitin ligase HRD1 expression was increased by ER stress. By suppressing HRD1 expression, the ER stress-induced decrease in nestin and MAP-2 expression and increase in beta-III tubulin returned to control levels. Therefore, we suggest that ER stress induces abnormalities in neuronal differentiation and maturation via HRD1 expression. These results suggest that targeting ER stress may facilitate quicker approaches toward the prevention and treatment of neurodevelopmental disorders. PMID:27252060

  15. Compression-induced changes on physical structures and calcification of the aromatic polyether polyurethane composite.

    PubMed

    Tang, Z G; Teoh, S H; McFarlane, W; Poole-Warren, L; Umezu, M

    2003-01-01

    It is generally accepted that stress causes calcification in both bio-prosthetic and polyurethane heart valves. However, simple uni-axially- and bi-axially-stretched samples did not yield a feasible model for the elaboration of the stress-induced calcification. In this study, heat compaction combined with the incorporation of polyethylene has been explored. Specimens of polyurethane were solution cast onto a porous bi-axially-drawn ultra-high-molecular-weight polyethylene film and then heat compacted under a pressure of 18 MPa at a chosen temperature for 1.5 h. The heat-compaction-induced calcification and physical changes of the polyurethane composite were evaluated using a 28-day in vitro calcification model and Attenuated Total Reflection-Fourier Transform-Infrared (ATR-FT-IR) spectroscopy. The calcification results indicated that heat-compaction-induced calcification was double that achieved without heat compaction. Heat-compacted polyurethane composite showed higher affinity to calcium ions than the non-heat compacted sample. The ATR-FT-IR results showed that the heat-compaction-induced physical changes include distortions of polymeric molecules and permanent changes of microstructures. The distortions of polymeric molecules could be deteriorated in contact with different media. The relaxation of the stressed structures of the polyether moiety might serve as a calcium trap and a heterogeneous nucleation site for calcification. The permanent changes of microstructures resulted from high distortions also served as affinity sites attracting calcification. PMID:14661883

  16. Compressive/Tensile Stresses and Lignified Cells as Resistance Components in Joints between Cladodes of Opuntia laevis (Cactaceae).

    PubMed

    Kahn-Jetter; Evans; Grzan; Frenz

    2000-05-01

    The Cactaceae are a diverse group of plants with a wide variety of morphologies. Many species of Opuntia have segmented stems in which terminal cladodes may be separated from main-stem cladodes with varying amounts of resistance. From a geometric approach, derivations were used to calculate normal (axial and bending) and shear (transverse force and torque) stresses at joints due to the weight of the cladodes. Normal and shear stresses act perpendicular and parallel to (along) the cross sections of joints, respectively. Normal stress caused by bending was >10 times that of the mean value of any other stress. Analyses were performed to determine the relationship between maximum normal stress and the amount of lignified xylem cells. Such cells had thicker cell walls compared with the various other cells of stem joints that had thin cell walls and that thus would provide the most resistance to normal stresses. An analogy was made between cactus joints and a composite beam with reinforcing rods. In such joints, thin-walled parenchyma cells might be analogous to concrete that has little resistance to tensile stress, while the thick-walled, lignified xylem cells would be analogous to reinforcing rods. There were statistically significant relationships between normal stresses (from bending and axial loads) and mean percentage of lignified xylem cells (r=0.73) and between normal stresses and total areas of lignified xylem cells (r=0.65) (more stress, more reinforcing xylem cells). Tensile portions of cactus joints had 23% lignified xylem cells, while compressive portions had only 10% lignified xylem cells in joint areas (more tension, more reinforcing xylem cells). In addition, tensile joint tissues had two to three times more thick-walled, lignified xylem cells in the outer 30% of the radius compared with other joint tissues types (more reinforcing near the surface). To our knowledge, this is the first publication to present mechanical stresses at stem joints of cacti and

  17. Processing-induced-transformations (PITs) during direct compression: Impact of tablet composition and compression load on phase transition of caffeine.

    PubMed

    Juban, Audrey; Briançon, Stéphanie; Puel, François

    2016-03-30

    In the pharmaceutical field, solid-state transitions that may occur during manufacturing of pharmaceuticals are of great importance. The phase transition of a model API, caffeine Form I (CFI), was studied during direct compression process by analysing the impacts of the operating conditions (process and formulation). This work is focused on two formulation parameters: nature of the diluent and impact of the caffeine dilution, and one process parameter: the compression pressure that may impact the phase transition of CFI. Tablets were made from pure CFI and from binary mixture of CFI/diluent (microcrystalline cellulose or anhydrous dicalcium phosphate). A kinetic study performed during six months helped to highlight the influence of these parameters on the CFI transition degree. Results showed a triggering effect of the direct compression process, transformation was higher in tablets than in uncompressed powders. Whatever the pressure applied, CFI transition degree was almost constant and uniformly occurring throughout the tablet volume. Nevertheless, several differences on the evolution of the CFI transition degree were observed between binary mixtures of CFI/diluent. An analysis of the transition mechanism with a stretched exponential law of the Johnson-Mehl-Avrami model shows that tableting accelerates the polymorphic transition without modifying its mechanism controlled by nucleation only. PMID:26853314

  18. Mechanical Stress Induces Biotic and Abiotic Stress Responses via a Novel cis-Element

    PubMed Central

    Walley, Justin W; Coughlan, Sean; Hudson, Matthew E; Covington, Michael F; Kaspi, Roy; Banu, Gopalan; Harmer, Stacey L; Dehesh, Katayoon

    2007-01-01

    Plants are continuously exposed to a myriad of abiotic and biotic stresses. However, the molecular mechanisms by which these stress signals are perceived and transduced are poorly understood. To begin to identify primary stress signal transduction components, we have focused on genes that respond rapidly (within 5 min) to stress signals. Because it has been hypothesized that detection of physical stress is a mechanism common to mounting a response against a broad range of environmental stresses, we have utilized mechanical wounding as the stress stimulus and performed whole genome microarray analysis of Arabidopsis thaliana leaf tissue. This led to the identification of a number of rapid wound responsive (RWR) genes. Comparison of RWR genes with published abiotic and biotic stress microarray datasets demonstrates a large overlap across a wide range of environmental stresses. Interestingly, RWR genes also exhibit a striking level and pattern of circadian regulation, with induced and repressed genes displaying antiphasic rhythms. Using bioinformatic analysis, we identified a novel motif overrepresented in the promoters of RWR genes, herein designated as the Rapid Stress Response Element (RSRE). We demonstrate in transgenic plants that multimerized RSREs are sufficient to confer a rapid response to both biotic and abiotic stresses in vivo, thereby establishing the functional involvement of this motif in primary transcriptional stress responses. Collectively, our data provide evidence for a novel cis-element that is distributed across the promoters of an array of diverse stress-responsive genes, poised to respond immediately and coordinately to stress signals. This structure suggests that plants may have a transcriptional network resembling the general stress signaling pathway in yeast and that the RSRE element may provide the key to this coordinate regulation. PMID:17953483

  19. Pneumococcal Hydrogen Peroxide–Induced Stress Signaling Regulates Inflammatory Genes

    PubMed Central

    Loose, Maria; Hudel, Martina; Zimmer, Klaus-Peter; Garcia, Ernesto; Hammerschmidt, Sven; Lucas, Rudolf; Chakraborty, Trinad; Pillich, Helena

    2015-01-01

    Microbial infections can induce aberrant responses in cellular stress pathways, leading to translational attenuation, metabolic restriction, and activation of oxidative stress, with detrimental effects on cell survival. Here we show that infection of human airway epithelial cells with Streptococcus pneumoniae leads to induction of endoplasmic reticulum (ER) and oxidative stress, activation of mitogen-associated protein kinase (MAPK) signaling pathways, and regulation of their respective target genes. We identify pneumococcal H2O2 as the causative agent for these responses, as both catalase-treated and pyruvate oxidase-deficient bacteria lacked these activities. Pneumococcal H2O2 induced nuclear NF-κB translocation and transcription of proinflammatory cytokines. Inhibition of translational arrest and ER stress by salubrinal or of MAPK signaling pathways attenuate cytokine transcription. These results provide strong evidence for the notion that inhibition of translation is an important host pathway in monitoring harmful pathogen-associated activities, thereby enabling differentiation between pathogenic and nonpathogenic bacteria. PMID:25183769

  20. Intermittent Noise Induces Physiological Stress in a Coastal Marine Fish

    PubMed Central

    Nichols, Tye A.; Anderson, Todd W.; Širović, Ana

    2015-01-01

    Anthropogenic noise in the ocean has increased substantially in recent decades, and motorized vessels produce what is likely the most common form of underwater noise pollution. Noise has the potential to induce physiological stress in marine fishes, which may have negative ecological consequences. In this study, physiological effects of increased noise (playback of boat noise recorded in the field) on a coastal marine fish (the giant kelpfish, Heterostichus rostratus) were investigated by measuring the stress responses (cortisol concentration) of fish to increased noise of various temporal dynamics and noise levels. Giant kelpfish exhibited acute stress responses when exposed to intermittent noise, but not to continuous noise or control conditions (playback of recorded natural ambient sound). These results suggest that variability in the acoustic environment may be more important than the period of noise exposure for inducing stress in a marine fish, and provide information regarding noise levels at which physiological responses occur. PMID:26402068

  1. Intermittent Noise Induces Physiological Stress in a Coastal Marine Fish.

    PubMed

    Nichols, Tye A; Anderson, Todd W; Širović, Ana

    2015-01-01

    Anthropogenic noise in the ocean has increased substantially in recent decades, and motorized vessels produce what is likely the most common form of underwater noise pollution. Noise has the potential to induce physiological stress in marine fishes, which may have negative ecological consequences. In this study, physiological effects of increased noise (playback of boat noise recorded in the field) on a coastal marine fish (the giant kelpfish, Heterostichus rostratus) were investigated by measuring the stress responses (cortisol concentration) of fish to increased noise of various temporal dynamics and noise levels. Giant kelpfish exhibited acute stress responses when exposed to intermittent noise, but not to continuous noise or control conditions (playback of recorded natural ambient sound). These results suggest that variability in the acoustic environment may be more important than the period of noise exposure for inducing stress in a marine fish, and provide information regarding noise levels at which physiological responses occur. PMID:26402068

  2. Study of inducer load and stress, volume 2

    NASA Technical Reports Server (NTRS)

    1972-01-01

    A program of analysis, design, fabrication and testing has been conducted to develop computer programs for predicting rocket engine turbopump inducer hydrodynamic loading, stress magnitude and distribution, and vibration characteristics. Methods of predicting blade loading, stress, and vibration characteristics were selected from a literature search and used as a basis for the computer programs. An inducer, representative of typical rocket engine inducers, was designed, fabricated, and tested with special instrumentation selected to provide measurements of blade surface pressures and stresses. Data from the tests were compared with predicted values and the computer programs were revised as required to improve correlation. For Volume 1 see N71-20403. For Volume 2 see N71-20404.

  3. Stress induced telomere shortening: longer life with less mutations?

    PubMed Central

    2014-01-01

    Background Mutations accumulate as a result of DNA damage and imperfect DNA repair machinery. In higher eukaryotes the accumulation and spread of mutations is limited in two primary ways: through p53-mediated programmed cell death and cellular senescence mediated by telomeres. Telomeres shorten at every cell division and cell stops dividing once the shortest telomere reaches a critical length. It has been shown that the rate of telomere attrition is accelerated when cells are exposed to DNA damaging agents. However the implications of this mechanism are not fully understood. Results With the help of in silico model we investigate the effect of genotoxic stress on telomere attrition and apoptosis in a population of non-identical replicating cells. When comparing the populations of cells with constant vs. stress-induced rate of telomere shortening we find that stress induced telomere shortening (SITS) increases longevity while reducing mutation rate. Interestingly, however, the effect takes place only when genotoxic stresses (e.g. reactive oxygen species due to metabolic activity) are distributed non-equally among cells. Conclusions Our results for the first time show how non-equal distribution of metabolic load (and associated genotoxic stresses) combined with stress induced telomere shortening can delay aging and minimize mutations. PMID:24580844

  4. Silver nanoparticles induce endoplasmatic reticulum stress response in zebrafish

    SciTech Connect

    Christen, Verena; Capelle, Martinus; Fent, Karl

    2013-10-15

    Silver nanoparticles (AgNPs) find increasing applications, and therefore humans and the environment are increasingly exposed to them. However, potential toxicological implications are not sufficiently known. Here we investigate effects of AgNPs (average size 120 nm) on zebrafish in vitro and in vivo, and compare them to human hepatoma cells (Huh7). AgNPs are incorporated in zebrafish liver cells (ZFL) and Huh7, and in zebrafish embryos. In ZFL cells AgNPs lead to induction of reactive oxygen species (ROS), endoplasmatic reticulum (ER) stress response, and TNF-α. Transcriptional alterations also occur in pro-apoptotic genes p53 and Bax. The transcriptional profile differed in ZFL and Huh7 cells. In ZFL cells, the ER stress marker BiP is induced, concomitant with the ER stress marker ATF-6 and spliced XBP-1 after 6 h and 24 h exposure to 0.5 g/L and 0.05 g/L AgNPs, respectively. This indicates the induction of different pathways of the ER stress response. Moreover, AgNPs induce TNF-α. In zebrafish embryos exposed to 0.01, 0.1, 1 and 5 mg/L AgNPs hatching was affected and morphological defects occurred at high concentrations. ER stress related gene transcripts BiP and Synv are significantly up-regulated after 24 h at 0.1 and 5 mg/L AgNPs. Furthermore, transcriptional alterations occurred in the pro-apoptotic genes Noxa and p21. The ER stress response was strong in ZFL cells and occurred in zebrafish embryos as well. Our data demonstrate for the first time that AgNPs lead to induction of ER stress in zebrafish. The induction of ER stress can have several consequences including the activation of apoptotic and inflammatory pathways. - Highlights: • Effects of silver nanoparticles (120 nm AgNPs) are investigated in zebrafish. • AgNPs induce all ER stress reponses in vitro in zebrafish liver cells. • AgNPs induce weak ER stress in zebrafish embryos. • AgNPs induce oxidative stress and transcripts of pro-apoptosis genes.

  5. Aneuploidy-induced cellular stresses limit autophagic degradation

    PubMed Central

    Santaguida, Stefano; Vasile, Eliza; White, Eileen; Amon, Angelika

    2015-01-01

    An unbalanced karyotype, a condition known as aneuploidy, has a profound impact on cellular physiology and is a hallmark of cancer. Aneuploid cells experience a number of stresses that are caused by aneuploidy-induced proteomic changes. How the aneuploidy-associated stresses affect cells and whether cells respond to them are only beginning to be understood. Here we show that autophagosomal cargo such as protein aggregates accumulate within lysosomes in aneuploid cells. This causes a lysosomal stress response. Aneuploid cells activate the transcription factor TFEB, a master regulator of autophagic and lysosomal gene expression, thereby increasing the expression of genes needed for autophagy-mediated protein degradation. Accumulation of autophagic cargo within the lysosome and activation of TFEB-responsive genes are also observed in cells in which proteasome function is inhibited, suggesting that proteotoxic stress causes TFEB activation. Our results reveal a TFEB-mediated lysosomal stress response as a universal feature of the aneuploid state. PMID:26404941

  6. Calculation of radiation-induced creep and stress relaxation

    NASA Astrophysics Data System (ADS)

    Nagakawa, Johsei

    1995-08-01

    Numerical calculation based on a computer simulation of point defect kinetics under stress was performed to predict radiation-induced deformation in an Inconel X-750 bolt in a LWR core and for a 316 stainless steel blanket in experimental fusion reactors with the water-coolant scenario. Although the displacement rate is rather low, modest irradiation creep with nearly linear stress dependence was predicted below 200 MPa at 300°C in the LWR core. This low stress dependence causes significant stress relaxation, which coincides with the experimental data to 2 dpa. An almost equal amount of enhanced irradiation creep strain was predicted at 60°C in both solution annealed and cold worker 316 stainless steel in the water-cooled blanket. The stress relaxation is practically not expected without irradiation in both the cases, but the calculation predicts that it is definitely expected under irradiation.

  7. Tau protein is essential for stress-induced brain pathology.

    PubMed

    Lopes, Sofia; Vaz-Silva, João; Pinto, Vitor; Dalla, Christina; Kokras, Nikolaos; Bedenk, Benedikt; Mack, Natalie; Czisch, Michael; Almeida, Osborne F X; Sousa, Nuno; Sotiropoulos, Ioannis

    2016-06-28

    Exposure to chronic stress is frequently accompanied by cognitive and affective disorders in association with neurostructural adaptations. Chronic stress was previously shown to trigger Alzheimer's-like neuropathology, which is characterized by Tau hyperphosphorylation and missorting into dendritic spines followed by memory deficits. Here, we demonstrate that stress-driven hippocampal deficits in wild-type mice are accompanied by synaptic missorting of Tau and enhanced Fyn/GluN2B-driven synaptic signaling. In contrast, mice lacking Tau [Tau knockout (Tau-KO) mice] do not exhibit stress-induced pathological behaviors and atrophy of hippocampal dendrites or deficits of hippocampal connectivity. These findings implicate Tau as an essential mediator of the adverse effects of stress on brain structure and function. PMID:27274066

  8. Gravity-induced stresses near a vertical cliff

    USGS Publications Warehouse

    Savage, W.Z.

    1993-01-01

    The exact solution for gravity-induced stresses beneath a vertical cliff presented here has application to the design of cut slopes in rock, compares favorably with published photoelastic and finite-element results for this problem, and satisfies the condition that shear and normal stresses vanish on the ground surface, except at the bottom corner where stress concentrations exist. The solution predicts that horizontal stresses are tensile away from the bottom of the cliff-effects caused by movement below the cliff in response to the gravity loading of the cliff. Also, it is shown that along the top of the cliff normal stresses reduce to those predicted for laterally constrained flat-lying topography. ?? 1993.

  9. OGG1 is essential in oxidative stress induced DNA demethylation.

    PubMed

    Zhou, Xiaolong; Zhuang, Ziheng; Wang, Wentao; He, Lingfeng; Wu, Huan; Cao, Yan; Pan, Feiyan; Zhao, Jing; Hu, Zhigang; Sekhar, Chandra; Guo, Zhigang

    2016-09-01

    DNA demethylation is an essential cellular activity to regulate gene expression; however, the mechanism that triggers DNA demethylation remains unknown. Furthermore, DNA demethylation was recently demonstrated to be induced by oxidative stress without a clear molecular mechanism. In this manuscript, we demonstrated that 8-oxoguanine DNA glycosylase-1 (OGG1) is the essential protein involved in oxidative stress-induced DNA demethylation. Oxidative stress induced the formation of 8-oxoguanine (8-oxoG). We found that OGG1, the 8-oxoG binding protein, promotes DNA demethylation by interacting and recruiting TET1 to the 8-oxoG lesion. Downregulation of OGG1 makes cells resistant to oxidative stress-induced DNA demethylation, while over-expression of OGG1 renders cells susceptible to DNA demethylation by oxidative stress. These data not only illustrate the importance of base excision repair (BER) in DNA demethylation but also reveal how the DNA demethylation signal is transferred to downstream DNA demethylation enzymes. PMID:27251462

  10. In situ measurement of electromigration-induced transient stress in Pb-free Sn-Cu solder joints by synchrotron radiation based X-ray polychromatic microdiffraction

    SciTech Connect

    Chen, Kai; Tamura, Nobumichi; Kunz, Martin; Tu, King-Ning; Lai, Yi-Shao

    2009-05-15

    Electromigration-induced hydrostatic elastic stress in Pb-free SnCu solder joints was studied by in situ synchrotron X-ray white beam microdiffraction. The elastic stresses in two different grains with similar crystallographic orientation, one located at the anode end and the other at the cathode end, were analyzed based on the elastic anisotropy of the {beta}-Sn crystal structure. The stress in the grain at the cathode end remained constant except for temperature fluctuations, while the compressive stress in the grain at the anode end was built-up as a function of time during electromigration until a steady state was reached. The measured compressive stress gradient between the cathode and the anode is much larger than what is needed to initiate Sn whisker growth. The effective charge number of {beta}-Sn derived from the electromigration data is in good agreement with the calculated value.

  11. In situ measurement of electromigration-induced transient stress in Pb-free Sn-Cu solder joints by synchrotron radiation based X-ray polychromatic microdiffraction

    SciTech Connect

    Chen, Kai; Tamura, Nobumichi; Kunz, Martin; Tu, King-Ning; Lai, Yi-Shao

    2009-12-01

    Electromigration-induced hydrostatic elastic stress in Pb-free SnCu solder joints was studied by in situ synchrotron X-ray white beam microdiffraction. The elastic stresses in two different grains with similar crystallographic orientation, one located at the anode end and the other at the cathode end, were analyzed based on the elastic anisotropy of the Beta-Sn crystal structure. The stress in the grain at the cathode end remained constant except for temperature fluctuations, while the compressive stress in the grain at the anode end was built-up as a function of time during electromigration until a steady state was reached. The measured compressive stress gradient between the cathode and the anode is much larger than what is needed to initiate Sn whisker growth. The effective charge number of Beta-Sn derived from the electromigration data is in good agreement with the calculated value.

  12. In situ measurement of electromigration-induced transient stress in Pb-free Sn-Cu solder joints by synchrotron radiation based x-ray polychromatic microdiffraction

    NASA Astrophysics Data System (ADS)

    Chen, Kai; Tamura, N.; Kunz, M.; Tu, K. N.; Lai, Yi-Shao

    2009-07-01

    Electromigration-induced hydrostatic elastic stress in Pb-free SnCu solder joints was studied by in situ synchrotron x-ray white beam microdiffraction. The elastic stresses in two different grains with similar crystallographic orientation, one located at the anode end and the other at the cathode end, were analyzed based on the elastic anisotropy of the β-Sn crystal structure. The stress in the grain at the cathode end remained constant except for temperature fluctuations, while the compressive stress in the grain at the anode end was builtup as a function of time during electromigration until a steady state was reached. The measured compressive stress gradient between the cathode and the anode is much larger than what is needed to initiate Sn whisker growth. The effective charge number of β-Sn derived from the electromigration data is in good agreement with the calculated value.

  13. Pressure-induced shape change of phospholipid vesicles: implication of compression and phase transition.

    PubMed

    Perrier-Cornet, J-M; Baddóuj, K; Gervais, P

    2005-04-01

    A microscopic study has allowed the analysis of modifications of various shapes acquired by phospholipid vesicles during a hydrostatic pressure treatment of up to 300 MPa. Giant vesicles of dimyristoylphosphatidylcholine / phosphatidylserine (DMPC/PS) prepared at 40 degrees C mainly presented a shape change resembling budding during pressure release. This comportment was reinforced by the incorporation of 1,2-dioleyl-sn-glycero-3-phosphatidylethanolamine (DOPE) or by higher temperature (60 degrees C) processing. The thermotropic main phase transition (L alpha to P beta') of the different vesicles prepared was determined under pressure through a spectrofluorimetric study of 6-dodecanoyl-2-dimethylamino-naphtalene (Laurdan) incorporated into the vesicles' bilayer. This analysis was performed by microfluorescence observation of single vesicles. The phase transition was found to begin at about 80 MPa and 120 MPa for DMPC/PS vesicles at, respectively, 40 degrees C and 60 degrees C. At 60 degrees C the liquid-to-gel transition phase was not complete within 250 MPa. Addition of DMPE at 40 degrees C does not significantly shift the onset boundary of the phase transition but extends the transition region. At 40 degrees C, the gel phase was obtained at, respectively, 110 MPa and 160 MPa for DMPC/PS and DMPC/PS/DOPE vesicles. In comparing volume data obtained from image analysis and Laurdan signal, we assume the shape change is a consequence of the difference between lateral compressibility of the membrane and bulk water. The phase transition contributes to the membrane compression but seems not necessary to induce shape change of vesicles. The high compressibility of the L alpha phase at 60 degrees C allows induction on DMPC/PS vesicles of a morphological transition without phase change. PMID:16245032

  14. Tensile strain / transverse compressive stress effects in Nb{sub 3}Sn multifilamentary wires with CuNb reinforcing stabilizer

    SciTech Connect

    Katagiri, K.; Shoji, Y.; Noto, K.

    1997-06-01

    In order to improve the strain/stress characteristics of the critical current I{sub c}, the use of external CuNb reinforcing stabilizer, instead of the conventional Cu stabilizer, with bronze processed Nb{sub 3}Sn multifilamentary superconducting wires was examined up to the magnetic field of 14T and at a temperature of 4.2K. Although the axial tensile strain sensitivity of I{sub c} was not changed, the strain for peak I{sub c} as well as the reversible strain limit increased by 0.14% when the Cu stabilizer was replaced by the CuNb reinforcing stabilizer. On the other hand, the transverse compressive stress sensitivity of I{sub c} decreased and the reversible stress limit increased. An increase in both a bronze to Nb ratio and Sn content in bronze matrix resulted in a higher stress tolerance and, as a consequence, the contribution of the CuNb reinforcement became relatively small.

  15. Stress Induces Pain Transition by Potentiation of AMPA Receptor Phosphorylation

    PubMed Central

    Li, Changsheng; Yang, Ya; Liu, Sufang; Fang, Huaqiang; Zhang, Yong; Furmanski, Orion; Skinner, John; Xing, Ying; Johns, Roger A.

    2014-01-01

    Chronic postsurgical pain is a serious issue in clinical practice. After surgery, patients experience ongoing pain or become sensitive to incident, normally nonpainful stimulation. The intensity and duration of postsurgical pain vary. However, it is unclear how the transition from acute to chronic pain occurs. Here we showed that social defeat stress enhanced plantar incision-induced AMPA receptor GluA1 phosphorylation at the Ser831 site in the spinal cord and greatly prolonged plantar incision-induced pain. Interestingly, targeted mutation of the GluA1 phosphorylation site Ser831 significantly inhibited stress-induced prolongation of incisional pain. In addition, stress hormones enhanced GluA1 phosphorylation and AMPA receptor-mediated electrical activity in the spinal cord. Subthreshold stimulation induced spinal long-term potentiation in GluA1 phosphomimetic mutant mice, but not in wild-type mice. Therefore, spinal AMPA receptor phosphorylation contributes to the mechanisms underlying stress-induced pain transition. PMID:25297100

  16. Mechanisms of Nanoparticle-Induced Oxidative Stress and Toxicity

    PubMed Central

    Wang, Liying

    2013-01-01

    The rapidly emerging field of nanotechnology has offered innovative discoveries in the medical, industrial, and consumer sectors. The unique physicochemical and electrical properties of engineered nanoparticles (NP) make them highly desirable in a variety of applications. However, these novel properties of NP are fraught with concerns for environmental and occupational exposure. Changes in structural and physicochemical properties of NP can lead to changes in biological activities including ROS generation, one of the most frequently reported NP-associated toxicities. Oxidative stress induced by engineered NP is due to acellular factors such as particle surface, size, composition, and presence of metals, while cellular responses such as mitochondrial respiration, NP-cell interaction, and immune cell activation are responsible for ROS-mediated damage. NP-induced oxidative stress responses are torch bearers for further pathophysiological effects including genotoxicity, inflammation, and fibrosis as demonstrated by activation of associated cell signaling pathways. Since oxidative stress is a key determinant of NP-induced injury, it is necessary to characterize the ROS response resulting from NP. Through physicochemical characterization and understanding of the multiple signaling cascades activated by NP-induced ROS, a systemic toxicity screen with oxidative stress as a predictive model for NP-induced injury can be developed. PMID:24027766

  17. Asg1 is a stress-inducible gene which increases stomatal resistance in salt stressed potato.

    PubMed

    Batelli, Giorgia; Massarelli, Immacolata; Van Oosten, Michael; Nurcato, Roberta; Vannini, Candida; Raimondi, Giampaolo; Leone, Antonella; Zhu, Jian-Kang; Maggio, Albino; Grillo, Stefania

    2012-12-15

    The identification of critical components in plant salt stress adaptation has greatly benefitted, in the last two decades, from fundamental discoveries in Arabidopsis and close model systems. Nevertheless, this approach has also highlighted a non-complete overlap between stress tolerance mechanisms in Arabidopsis and agricultural crops. Within a long-running research program aimed at identifying salt stress genetic determinants in potato by functional screening in Escherichia coli, we isolated Asg1, a stress-related gene with an unknown function. Asg1 is induced by salt stress in both potato and Arabidopsis and by abscisic acid in Arabidopsis. Asg1 is actively transcribed in all plant tissues. Furthermore, Asg1 promoter analysis confirmed its ubiquitous expression, which was remarkable in pollen, a plant tissue that undergoes drastic dehydration/hydration processes. Fusion of Asg1 with green fluorescent protein showed that the encoded protein is localized close to the plasma membrane with a non-continuous pattern of distribution. In addition, Arabidopsis knockout asg1 mutants were insensitive to both NaCl and sugar hyperosmotic environments during seed germination. Transgenic potato plants over-expressing the Asg1 gene revealed a stomatal hypersensitivity to NaCl stress which, however, did not result in a significantly improved tuber yield in stress conditions. Altogether, these data suggest that Asg1 might interfere with components of the stress signaling pathway by promoting stomatal closure and participating in stress adaptation. PMID:22854180

  18. Asg1 is a stress-inducible gene which increases stomatal resistance in salt stressed potato

    PubMed Central

    Batelli, Giorgia; Massarelli, Immacolata; Van Oosten, Michael; Nurcato, Roberta; Vannini, Candida; Raimondi, Giampaolo; Leone, Antonella; Zhu, Jian-Kang; Maggio, Albino; Grillo, Stefania

    2013-01-01

    The identification of critical components in plant salt stress adaptation has greatly benefitted, in the last two decades, from fundamental discoveries in Arabidopsis and close model systems. Nevertheless, this approach has also highlighted a non-complete overlap between stress tolerance mechanisms in Arabidopsis and agricultural crops. Within a long-running research program aimed at identifying salt stress genetic determinants in potato by functional screening in Escherichia coli, we isolated Asg1, a stress-related gene with an unknown function. Asg1 is induced by salt stress in both potato and Arabidopsis and by abscisic acid in Arabidopsis. Asg1 is actively transcribed in all plant tissues. Furthermore, Asg1 promoter analysis confirmed its ubiquitous expression, which was remarkable in pollen, a plant tissue that undergoes drastic dehydration/hydration processes. Fusion of Asg1 with green fluorescent protein showed that the encoded protein is localized close to the plasma membrane with a non-continuous pattern of distribution. In addition, Arabidopsis knockout asg1 mutants were insensitive to both NaCl and sugar hyperosmotic environments during seed germination. Transgenic potato plants over-expressing the Asg1 gene revealed a stomatal hypersensitivity to NaCl stress which, however, did not result in a significantly improved tuber yield in stress conditions. Altogether, these data suggest that Asg1 might interfere with components of the stress signaling pathway by promoting stomatal closure and participating in stress adaptation. PMID:22854180

  19. Endoplasmic reticulum stress and oxidative stress are involved in ZnO nanoparticle-induced hepatotoxicity

    PubMed Central

    Yang, Xia; Shao, Huali; Liu, Weirong; Gu, Weizhong; Shu, Xiaoli; Mo, Yiqun; Chen, Xuejun; Zhang, Qunwei; Jiang, Mizu

    2015-01-01

    Zinc oxide nanoparticles (Nano-ZnO) are widely used in sunscreens, clothes, medicine and electronic devices. However, the potential risks of human exposure and the potential for adverse health impacts are not well understood. Previous studies have demonstrated that exposure to Nano-ZnO caused liver damage and hepatocyte apoptosis through oxidative stress, but the molecular mechanisms that are involved in Nano-ZnO-induced hepatotoxicity are still unclear. Endoplasmic reticulum (ER) is sensitive to oxidative stress, and also plays a crucial role in oxidative stress-induced damage. Previous studies showed that ER stress was involved in many chemical-induced liver injuries. We hypothesized that exposure to Nano-ZnO caused oxidative stress and ER stress that were involved in Nano-ZnO-induced liver injury. To test our hypothesis, mice were gavaged with 200 mg/kg or 400 mg/kg of Nano-ZnO once a day for a period of 90 days, and blood and liver tissues were obtained for study. Our results showed that exposure to Nano-ZnO caused liver injury that was reflected by focal hepatocellular necrosis, congestive dilation of central veins, and significantly increased alanine transaminase (ALT) and aspartate transaminase (AST) levels. Exposure to Nano-ZnO also caused depletion of glutathione (GSH) the liver tissues. In addition, our electron microscope results showed that ER swelling and ribosomal degranulation were observed in the liver tissues from mice treated with Nano-ZnO. The mRNA expression levels of ER stress-associated genes (grp78, grp94, pdi-3, xbp-1) were also up-regulated in Nano-ZnO-treated mice. Nano-ZnO caused increased phosphorylation of RNA-dependent protein kinase-like ER kinase (PERK) and eukaryotic initiation factor 2α (eIF2α). Finally, we found that exposure to Nano-ZnO caused increased ER stress-associated apoptotic protein levels, such as caspase-3, caspase-9, caspase-12, phosphorylation of JNK, and CHOP/GADD153, and up-regulation of pro-apoptotic genes (chop

  20. Association between Anger and Mental Stress-Induced Myocardial Ischemia

    PubMed Central

    Pimple, Pratik; Shah, Amit; Rooks, Cherie; Bremner, J. Douglas; Nye, Jonathon; Ibeanu, Ijeoma; Murrah, Nancy; Shallenberger, Lucy; Kelley, Mary; Raggi, Paolo; Vaccarino, Viola

    2014-01-01

    Background Mental stress-induced myocardial ischemia is associated with adverse prognosis in coronary artery disease patients. Anger is thought to be a trigger of acute coronary syndromes and is associated with increased cardiovascular risk; however, little direct evidence exists for a link between anger and myocardial ischemia. Methods [99mTc]sestamibi single-photon emission tomography was performed at rest, after mental stress (a social stressor with a speech task), and after exercise/pharmacological stress. Summed scores of perfusion abnormalities were obtained by observer-independent software. A summed difference score, the difference between stress and rest scores, was used to quantify myocardial ischemia under both stress conditions. The Spielberger's State-Trait Anger Expression Inventory was used to assess different anger dimensions. Results The mean age was 50 years, 50% were female and 60% were non-white. After adjusting for demographic factors, smoking, coronary artery disease severity, depressive and anxiety symptoms, each interquartile range increment in state-anger score was associated with 0.36 units adjusted increase in ischemia as measured by the summed difference score (95% CI: 0.14-0.59); the corresponding association for trait-anger was 0.95 (95% CI: 0.21-1.69). Anger expression scales were not associated ischemia. None of the anger dimensions were related to ischemia during exercise/pharmacological stress. Conclusion Anger, both as an emotional state and as a personality trait, is significantly associated with propensity to develop myocardial ischemia during mental stress, but not during exercise/pharmacological stress. Patients with this psychological profile may be at increased risk for silent ischemia induced by emotional stress and this may translate into worse prognosis. PMID:25497256

  1. Investigation of laser-induced iodine fluorescence for the measurement of density in compressible flows

    NASA Technical Reports Server (NTRS)

    Mcdaniel, J. C., Jr.

    1982-01-01

    Laser induced fluorescence is an attractive nonintrusive approach for measuring molecular number density in compressible flows although this technique does not produce a signal that is directly related to the number density. Saturation and frequency detuned excitation are explored as means for minimizing the quenching effect using iodine as the molecular system because of its convenient absorption spectrum. Saturation experiments indicate that with available continuous wave laser sources of Gaussian transverse intensity distribution only partial saturation could be achieved in iodine at the pressures of interest in gas dynamics. Using a fluorescence lineshape theory, it is shown that for sufficiently large detuning of a narrow bandwidth laser from a molecular transition, the quenching can be cancelled by collisional broadening over a large range of pressures and temperatures. Experimental data obtained in a Mach 4.3 underexpanded jet of nitrogen seeded with iodine for various single mode argon laser detunings from a strong iodine transition at 5145 A are discussed.

  2. Oxidative stress induces mitochondrial fragmentation in frataxin-deficient cells

    SciTech Connect

    Lefevre, Sophie; Sliwa, Dominika; Rustin, Pierre; Camadro, Jean-Michel; Santos, Renata

    2012-02-10

    Highlights: Black-Right-Pointing-Pointer Yeast frataxin-deficiency leads to increased proportion of fragmented mitochondria. Black-Right-Pointing-Pointer Oxidative stress induces complete mitochondrial fragmentation in {Delta}yfh1 cells. Black-Right-Pointing-Pointer Oxidative stress increases mitochondrial fragmentation in patient fibroblasts. Black-Right-Pointing-Pointer Inhibition of mitochondrial fission in {Delta}yfh1 induces oxidative stress resistance. -- Abstract: Friedreich ataxia (FA) is the most common recessive neurodegenerative disease. It is caused by deficiency in mitochondrial frataxin, which participates in iron-sulfur cluster assembly. Yeast cells lacking frataxin ({Delta}yfh1 mutant) showed an increased proportion of fragmented mitochondria compared to wild-type. In addition, oxidative stress induced complete fragmentation of mitochondria in {Delta}yfh1 cells. Genetically controlled inhibition of mitochondrial fission in these cells led to increased resistance to oxidative stress. Here we present evidence that in yeast frataxin-deficiency interferes with mitochondrial dynamics, which might therefore be relevant for the pathophysiology of FA.

  3. Stress stimulus induced resistance to Cladosporium cucumerinum in cucumber seeding.

    PubMed

    Zhao, Huan; Wang, Bo-Chu; Zhao, Hu-Cheng; Wang, Jing Bo

    2005-07-25

    Up to date, the studies of plant induced resistance have become the focus in plant pathology and physiology. During the course of pathogens penetrating the plant cell, besides of chemical secretion, the pathogens may generate mechanical signal caused by the physical pressure on the plant cell. In the non-host resistance, both the chemical signal and the mechanical stress signal are considered to have contribution to the entire defense reaction acted by the plant. The penetration of pathogen Cladosporium cucumerinum to cucumber is thought to be one of the model in research of plant induced resistance. In the current study, as a mechanical signal elicitor, the appropriate stress stimulus was proved to effectually induce the resistance of cucumber seedling to C. cucumerinum. After the treatment of the stress stimulus on leaves, the activities of resistance-related enzymes were significantly increased, such as phenylanine ammonia lyase (PAL), peroxidase (POD). Also, we found that stress stimulation may cause synthesis of lignin, which acts as the physical barrier to defense the pathogens. The results suggest that stress stimulation may not only enhance ability of the plant cell resistance to pathogen penetration but also elicit the accumulation of pathogens suppression or antimicrobial chemical substance in the plant cell. PMID:16002268

  4. Activation of the hypothalamic-pituitary-adrenal stress axis induces cellular oxidative stress

    PubMed Central

    Spiers, Jereme G.; Chen, Hsiao-Jou Cortina; Sernia, Conrad; Lavidis, Nickolas A.

    2015-01-01

    Glucocorticoids released from the adrenal gland in response to stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis induce activity in the cellular reduction-oxidation (redox) system. The redox system is a ubiquitous chemical mechanism allowing the transfer of electrons between donor/acceptors and target molecules during oxidative phosphorylation while simultaneously maintaining the overall cellular environment in a reduced state. The objective of this review is to present an overview of the current literature discussing the link between HPA axis-derived glucocorticoids and increased oxidative stress, particularly focussing on the redox changes observed in the hippocampus following glucocorticoid exposure. PMID:25646076

  5. Mechanical consequences of allergic induced remodeling on mice airway resistance and compressibility.

    PubMed

    Novali, Mauro; Shalaby, Karim H; Robichaud, Annette; Benedetti, Andrea; Fereydoonzad, Liah; McGovern, Toby K; Schuessler, Thomas F; Martin, James G

    2015-11-01

    The effect of remodeling on airway function is uncertain. It may affect airway compressibility during forced expirations differently than airflow resistance, providing a tool for its assessment. The aim of the current study was to compare the effects of acute and chronic antigen challenge on methacholine-induced bronchoconstriction assessed from resistance and maximal tidal expiratory flow. Balb/C mice were sensitized with ovalbumin (OVA) and challenged either daily for three days with intra-nasal OVA or daily for 5 days and three times a week for 5 subsequent weeks. Acute and chronic allergen challenge induced airway hyperresponsiveness (AHR) to methacholine. However the relationship between maximal tidal expiratory flow and resistance during methacholine challenge was different between the two conditions, suggesting that the determinants of AHR are not identical following acute and chronic allergen exposure. We conclude that the contrast of changes in maximal tidal expiratory flow and respiratory resistance during methacholine-induced bronchoconstriction may allow the detection of the mechanical consequences of airway remodeling. PMID:26213118

  6. Diaphragmatic breathing reduces exercise-induced oxidative stress.

    PubMed

    Martarelli, Daniele; Cocchioni, Mario; Scuri, Stefania; Pompei, Pierluigi

    2011-01-01

    Diaphragmatic breathing is relaxing and therapeutic, reduces stress, and is a fundamental procedure of Pranayama Yoga, Zen, transcendental meditation and other meditation practices. Analysis of oxidative stress levels in people who meditate indicated that meditation correlates with lower oxidative stress levels, lower cortisol levels and higher melatonin levels. It is known that cortisol inhibits enzymes responsible for the antioxidant activity of cells and that melatonin is a strong antioxidant; therefore, in this study, we investigated the effects of diaphragmatic breathing on exercise-induced oxidative stress and the putative role of cortisol and melatonin hormones in this stress pathway. We monitored 16 athletes during an exhaustive training session. After the exercise, athletes were divided in two equivalent groups of eight subjects. Subjects of the studied group spent 1 h relaxing performing diaphragmatic breathing and concentrating on their breath in a quiet place. The other eight subjects, representing the control group, spent the same time sitting in an equivalent quite place. Results demonstrate that relaxation induced by diaphragmatic breathing increases the antioxidant defense status in athletes after exhaustive exercise. These effects correlate with the concomitant decrease in cortisol and the increase in melatonin. The consequence is a lower level of oxidative stress, which suggests that an appropriate diaphragmatic breathing could protect athletes from long-term adverse effects of free radicals. PMID:19875429

  7. TRIB2 regulates normal and stress-induced thymocyte proliferation

    PubMed Central

    Liang, Kai Ling; O’Connor, Caitriona; Veiga, J Pedro; McCarthy, Tommie V; Keeshan, Karen

    2016-01-01

    TRIB2, a serine/threonine pseudokinase identified as an oncogene, is expressed at high levels in the T-cell compartment of hematopoiesis. The proliferation of developing thymocytes is tightly controlled to prevent leukemic transformation of T cells. Here we examine Trib2 loss in murine hematopoiesis under steady state and proliferative stress conditions, including genotoxic and oncogenic stress. Trib2−/− developing thymocytes show increased proliferation, and Trib2−/− mice have significantly higher thymic cellularity at steady state. During stress hematopoiesis, Trib2−/− developing thymocytes undergo accelerated proliferation and demonstrate hypersensitivity to 5-fluorouracil (5-FU)-induced cell death. Despite the increased cell death post 5-FU-induced proliferative stress, Trib2−/− mice exhibit accelerated thymopoietic recovery post treatment due to increased cell division kinetics of developing thymocytes. The increased proliferation in Trib2−/− thymocytes was exacerbated under oncogenic stress. In an experimental murine T-cell acute lymphoblastic leukemia (T-ALL) model, Trib2−/− mice had reduced latency in vivo, which associated with impaired MAP kinase (MAPK) activation. High and low expression levels of Trib2 correlate with immature and mature subtypes of human T-ALL, respectively, and associate with MAPK. Thus, TRIB2 emerges as a novel regulator of thymocyte cellular proliferation, important for the thymopoietic response to genotoxic and oncogenic stress, and possessing tumor suppressor function. PMID:27462446

  8. Mechanical Stress Promotes Cisplatin-Induced Hepatocellular Carcinoma Cell Death

    PubMed Central

    Riad, Sandra; Bougherara, Habiba

    2015-01-01

    Cisplatin (CisPt) is a commonly used platinum-based chemotherapeutic agent. Its efficacy is limited due to drug resistance and multiple side effects, thereby warranting a new approach to improving the pharmacological effect of CisPt. A newly developed mathematical hypothesis suggested that mechanical loading, when coupled with a chemotherapeutic drug such as CisPt and immune cells, would boost tumor cell death. The current study investigated the aforementioned mathematical hypothesis by exposing human hepatocellular liver carcinoma (HepG2) cells to CisPt, peripheral blood mononuclear cells, and mechanical stress individually and in combination. HepG2 cells were also treated with a mixture of CisPt and carnosine with and without mechanical stress to examine one possible mechanism employed by mechanical stress to enhance CisPt effects. Carnosine is a dipeptide that reportedly sequesters platinum-based drugs away from their pharmacological target-site. Mechanical stress was achieved using an orbital shaker that produced 300 rpm with a horizontal circular motion. Our results demonstrated that mechanical stress promoted CisPt-induced death of HepG2 cells (~35% more cell death). Moreover, results showed that CisPt-induced death was compromised when CisPt was left to mix with carnosine 24 hours preceding treatment. Mechanical stress, however, ameliorated cell death (20% more cell death). PMID:25685789

  9. Metallothionein Alleviates Oxidative Stress-Induced Endoplasmic Reticulum Stress and Myocardial Dysfunction

    PubMed Central

    Guo, Rui; Ma, Heng; Gao, Feng; Zhong, Li; Ren, Jun

    2009-01-01

    Oxidative stress and endoplasmic reticulum (ER) stress have been implicated in cardiovascular diseases although the interplay between the two is not clear. This study was designed to examine the influence of oxidative stress through glutathione depletion on myocardial ER stress and contractile function in the absence or presence of the heavy metal scavenger antioxidant metallothionein (MT). FVB and MT overexpression transgenic mice received the GSH synthase inhibitor buthionine sulfoximine (BSO, 30 mM) in drinking water for 2 weeks. Oxidative stress, ER stress, apoptosis, cardiac function and ultrastructure were assessed using GSH/GSSG assay, reactive oxygen species (ROS), immunoblotting, caspase-3 activity, Langendorff perfused heart function (LVDP and ± dP/dt), and transmission electron microscopy. BSO led to a robust decrease in the GSH/GSSG ratio and increased ROS production, consolidating oxidative stress. Cardiac function and ultrastructure were compromised following BSO treatment, the effect of which was obliterated by MT. BSO promoted overt ER stress as evidenced by upregulated BiP, calregulin, phospho-IRE1α and phospho-eIF2α without affecting total IRE1α and eIF2α. BSO treatment led to apoptosis manifested as elevated expression of CHOP/GADD153, caspase-12 and Bax as well as caspase-3 activity, reduced Bcl-2 expression and JNK phosphorylation, all of which was ablated by MT. Moreover, both antioxidant N-acetylcysteine and the ER stress inhibitor tauroursodeoxycholic acid reversed the oxidative stress inducer menadione-elicited depression in cardiomyocyte contractile function. Taken together, these data suggested that ER stress occurs likely downstream of oxidative stress en route to cardiac dysfunction. PMID:19344729

  10. Neuromodulator and Emotion Biomarker for Stress Induced Mental Disorders.

    PubMed

    Gu, Simeng; Wang, Wei; Wang, Fushun; Huang, Jason H

    2016-01-01

    Affective disorders are a leading cause of disabilities worldwide, and the etiology of these many affective disorders such as depression and posttraumatic stress disorder is due to hormone changes, which includes hypothalamus-pituitary-adrenal axis in the peripheral nervous system and neuromodulators in the central nervous system. Consistent with pharmacological studies indicating that medical treatment acts by increasing the concentration of catecholamine, the locus coeruleus (LC)/norepinephrine (NE) system is regarded as a critical part of the central "stress circuitry," whose major function is to induce "fight or flight" behavior and fear and anger emotion. Despite the intensive studies, there is still controversy about NE with fear and anger. For example, the rats with LC ablation were more reluctant to leave a familiar place and took longer to consume the food pellets in an unfamiliar place (neophobia, i.e., fear in response to novelty). The reason for this discrepancy might be that NE is not only for flight (fear), but also for fight (anger). Here, we try to review recent literatures about NE with stress induced emotions and their relations with mental disorders. We propose that stress induced NE release can induce both fear and anger. "Adrenaline rush or norepinephrine rush" and fear and anger emotion might act as biomarkers for mental disorders. PMID:27051536