Effect Of Stress Conditions Research Articles

Experiments on internal erosion in sandy gravel foundations containing a suspended cutoff wall under complex stress states

Internal erosion is one of the most common failure modes of embankment dams or foundations, and the simplest and most effective preventive measure is to build a cutoff wall. The soil at the bottom of the cutoff wall is usually under complex stress states. The deeper the cutoff wall, the higher is the stress. In this study, the effects of stress conditions on the evolution of internal erosion were investigated in sandy gravel foundations containing a suspended cutoff wall using a newly developed stress-controlled erosion apparatus. Three series of erosion tests were conducted on gap-graded soil under different confining stresses, different deviatoric stresses, and different confining and deviatoric stresses. The results of these tests are as follows: (1) The discharge and permeability decrease with an increase in the confining stress, but the critical hydraulic gradient increases. (2) In the second series of erosion tests, the specimen is compressed under low deviatoric stress; the specimen undergoes shear expansion under high deviatoric stress. (3) In the third series of erosion tests, the confining and deviatoric stresses synchronously change, and therefore, their combined effect on the evolution of internal erosion is complicated. Under low stress, the soil is compressed in the early stage of the experiment, and its structure may change during internal erosion. When the stress level is high, the specimen also undergoes shear expansion, and the degree of expansion is controlled by both confining and deviatoric stresses.

Effect of stress conditions on the activity and isozyme composition of peroxidase of vacuoles and tissue extract of red beet roots

Changes in the enzymatic activity of phenol-dependent peroxidase (PO) of vacuoles and tissue extract of red beet (Beta vulgaris L.) roots in different phases of plant development and in hyperosmotic stress and pathogen infection were found. The highest activity was observed during root growth and the lowest PO activity occurred in dormancy, respectively. Activation of the enzyme was observed in infected roots. The isozyme composition of PO was characterized by lability, and the number of cationic isoforms varied significantly. The optimum pH of the enzyme changed depending on the growth phase and stressor, tending to shift towards low values at rest and in hyperosmotic stress. The shift in the optimum pH coincided with the appearance of additional cationic PO isoforms.

Effects of stress conditions on the generation of negative bias temperature instability-associated interface traps

The exponent n of the generation of an interface trap (Nit), which contributes to the power-law negative bias temperature instability (NBTI) degradation, and the exponent's time evolution are investigated by simulations with varying the stress voltage Vg and temperature T. It is found that the exponent n in the diffusion-limited phase of the degradation process is irrelevant to both Vg and T. The time evolution of the exponent n is affected by the stress conditions, which is reflected in the shift of the onset of the diffusion-limited phase. According to the diffusion profiles, the generation of the atomic hydrogen species, which is equal to the buildup of Nit, is strongly correlated with the stress conditions, whereas the diffusion of the hydrogen species shows Vg-unaffected but T-affected relations through the normalized results.

Effects of stress condition in beef cattle

Abstract: The knowledge about cattles behavior and the factors that promote animal stress has been the focus of several publications that seek to equate the relationship between environment / welfare / animal production. Thus, the mechanisms involving the adaptation of animals to the environment in which they are exposed are complex and multivariate, resulting in a complex analysis of the subject and often poorly elucidated by researchers. The aim of this review was to bring information related stress conditions and their relationship in cattle. Keywords: Bovine, Stress, Welfare, Management

EFFECT OF STRESS CONDITIONS ON STABILITY AND BIOLOGICAL ACTIVITY OF A RECOMBINANT Escherichia Coli AGAINST THE COTTON LEAFWORM SPODOPTERA LITTORALIS (BOISD)

The effect of stress conditions on viability and activity of the recombinant E. coli, that contains cryIAC gene, which encodes a crystal toxin specific to Spodoptera littoralis, was tested. Solar radiation showed the worst effect on both viability and activity against the larvae of S. littoralis. The drastic effect also happened when recombinant E. coli was exposed to heat treatment at 50oC for more than 5 min. and to high concentrations of sucrose (> 20 % for more than 2 days). Also, the same effect happened when cells were exposed to NaCl > 5 %, even after one day of exposure. The viability of E. coli cells after preservation by freezing under glycerol, lyophilization and encapsulation indicated that, freezing was the best method for keeping both viability and activity of cells till 9 months post preparation.

Mechanism of zonal disintegration in surrounding rock mass around deep rock engineering and its application

The mechanical behaviors of deep rock mass are different from those of shallow rock mass. Through cases of Jinping II Hydropower Station, the special phenomenon of zonal disintegration in the surrounding rock mass around the diversion tunnels, is analyzed. On the basis of fracture mechanics, a new strength criterion for deep rock mass is derived. The new nonlinear strength criterion that is relative to the rock mass rating classification can be applied to the study of the tensile failure of deep rock mass. Subsequently, zonal disintegration model is established, and the radius of fractured zone and none-fractured zone of deep surrounding rock mass around cylindrical tunnel are obtained, their exact positions and the evolution law of zonal disintegration of surrounding rock mass is determined. To validate the present model, comparison between calculation results and the experiment observation on facture and failure around underground openings is carried out. It is found that the numerical simulation result is in good agreement with the experimental one on failure modes around the hole. Through sensitivity analysis, the effects of stress condition, cohesion and the angle of internal friction on the phenomenon of zonal disintegration are determined. Finally, the present model is adopted in the analysis of the zonal disintegration in the surrounding rock mass around the diversion tunnels in Jinping II Hydropower Station. Meanwhile, the magnitude and distributions of fractured zones are determined by numerical simulation.

Effect of loading environment on the human osteochondral allograft preserved by tissue culture

Objective To study the effect of the loading environment on the chondrocytes and the collagen ultrastructure at articular cartilage of the osteochondral allograft graft preserved by tissue culture method so as to improve the preservation effect. Methods A kind of shaking table was used as a dynamic loading device for storage of the osteochondral allograft to simulate the mechanical environment of normal articular cartilage in vivo. The device worked in an incubator at 3711 and the frequency was 1Hz. Western blotting was used for analysis of β-actin at the articular cartilage of the graft for investigating the effects of stress condition on the chondrocyte function. Transmission electron microscopy was used to observe the collagen ultrastructure at the articular cartilage of the graft two weeks after storage and compared with the control group. Results The dynamic loading condition could significantly increase the expression of β-actin and keep the ultrastructure of the collagen fibril in articular cartilage compared with the static condition. Conclusions The loading condition benefits the chondrocyte function and collagen ultrastructure of the articular cartilage in human osteochondral allograft. The dynamic mechanical loading may provide a better method in preservation of the human osteochondral allograft. Key words: Articular cartilage; Allograft; Tissue preservation; Stress

Reliability studies on Ta2O5 high-κ dielectric metal-insulator-metal capacitors prepared by wet anodization

The temperature dependence of leakage current for tantalum oxide metal-insulator-metal capacitors has been investigated over the temperature range 20–160 °C. The leakage current shows an increase with temperature and the conduction mechanism at medium to high electric fields is in agreement with the modified Poole–Frenkel model. The activation energy of the dominant deep trapping center in the oxide is calculated using this model. Constant voltage and constant current stress have been applied to the devices and the effect of stress conditions on leakage current, breakdown voltage, and high frequency capacitance-voltage have been investigated. Early oxide breakdown or time-dependent dielectric breakdown was observed during constant voltage and constant current stress, in which the former is a function of stress time and applied voltage or current. There is an increase in leakage current with time during the constant voltage stress, presumably due to generation of positive defect states. This is also apparent from the decrease in voltage with time during constant current stress. Degradation of the oxides by constant current stress and its effect on the oxide leakage current (or stress induced leakage current) at various constant current values and stress times has also been investigated and is discussed in this article.

A Shear Wave Velocity Tomography System for Geotechnical Centrifuge Testing

Abstract In physical model tests using geotechnical centrifuge, it is important to evaluate soil properties during centrifugal acceleration due to the effect of stress conditions. A crosshole type shear wave velocity tomography testing system has been developed, and the distribution of maximum shear modulus in sand layers could be evaluated in the centrifuge. Piezoelectric bender elements are installed in the system as shear wave transmitters and receivers for travel time measurement. A driving and measurement system for bender element tests is prepared to be used under centrifuge operating environment. A series of tests using this system has been conducted with uniform sand samples, and the testing procedure and typical signals from bender elements are presented. Tomography inversion considering curved raypaths has been conducted using a total of 256 travel time data determined by measured signals because the first arrivals follow curved raypaths under a stress related linear variation in stiffness with depth. The maximum shear modulus variation with depth, or vertical effective stress, has been verified through comparison with resonant column test results, and the applicability of this system in general centrifuge testing has been confirmed.

MTORC1 Links Protein Quality and Quantity Control by Sensing Chaperone Availability

Balanced protein synthesis and degradation are crucial for proper cellular function. Protein synthesis is tightly coupled to energy status and nutrient levels by the mammalian target of rapamycin complex 1 (mTORC1). Quality of newly synthesized polypeptides is maintained by the molecular chaperone and ubiquitin-proteasome systems. Little is known about how cells integrate information about the quantity and quality of translational products simultaneously. We demonstrate that cells distinguish moderate reductions in protein quality from severe protein misfolding using molecular chaperones to differentially regulate mTORC1 signaling. Moderate reduction of chaperone availability enhances mTORC1 signaling, whereas stress-induced complete depletion of chaperoning capacity suppresses mTORC1 signaling. Molecular chaperones regulate mTORC1 assembly in coordination with nutrient availability. This mechanism enables mTORC1 to rapidly detect and respond to environmental cues while also sensing intracellular protein misfolding. The tight linkage between protein quality and quantity control provides a plausible mechanism coupling protein misfolding with metabolic dyshomeostasis.

Zonal disintegration of surrounding rock mass around the diversion tunnels in Jinping II Hydropower Station, Southwestern China

By means of numerical simulation, the special phenomenon of zonal disintegration of surrounding rock mass around the diversion tunnels of Jinping II Hydropower Station is analyzed in this paper. In order to model the growth and coalescence of cracks within rock mass in Jinping II Hydropower Station, the weak-element is adopted. When cracks coalesce, failure of deep crack-weakened rock masses occurs and fractured zone is formed. The present result is different from the one obtained by the traditional elasto-plastic theory. The numerical results show that the slip-line zonal fracture is created within rock mass around the diversion tunnels in Jinping II Hydropower Station. Meanwhile, the magnitude and distributions of fractured zones are determined by numerical simulation. It is shown that the present results are in good agreement with the one observed by model tests. Through sensitivity analysis, the effects of stress condition, cohesion and the angle of internal friction on the phenomenon of zonal disintegration is determined.

Effects of stress conditions on rheological properties of granular soil in large triaxial rheology laboratory tests

In order to study the rheological properties of red stone granular soil, a series of rheological experiments were executed on large tri-axial rheological apparatus. Under 100, 200 and 300 kPa confining stress conditions, the rheological tests were carried out. These experiment results showed that the stress conditions, especially the stress level were the critical influencing factors of the rheological deformation properties. Under the low stress level (S=0.1), the granular soil showed the elastic properties, and there was no obvious rheological deformation. Under the middle stress level (0.2 0.8) creep curves showed the non-linear viscous plastic rheological properties. Especially, under the stress level of S=1.0, the accelerated rheological phase of creep curves occurred at early time with a trend of failure. The stress level had obvious effects on the final rheological deformation of the soil sample, and the final rheological deformation increments nonlinearly increased with stress level. The final rheological deformation increment and step was little under low stress level, while it became large under high stress level, which showed the nonlinearly rheological properties of the granular soil. The confining pressure also had direct effects on final rheological deformation, and the final rheological deformation linearly increased with confining pressure increments.

Responses of Azospirillum brasilense to Nitrogen Deficiency and to Wheat Lectin: A Diffuse Reflectance Infrared Fourier Transform (DRIFT) Spectroscopic Study

For the rhizobacterium Azospirillum brasilense, the optimal nutritional range of C:N ratios corresponds to the presence of malate (ca. 3 to 5 g l(-1) of its sodium salt) and ammonium (ca. 0.5 to 3 g l(-1) of NH4Cl) as preferred carbon and nitrogen sources, respectively. This microaerophilic aerotactic bacterium is known to have a narrow optimal oxygen concentration range of ca. 3 to 5 microM, which is 1.2% to 2% of oxygen solubility in air-saturated water under normal conditions. In this work, the effects of stress conditions (bound-nitrogen deficiency related to a high C:N ratio in the medium; excess of oxygen) on aerobically grown A. brasilense Sp245, a native wheat-associated endophyte, were investigated in the absence and presence of wheat germ agglutinin (WGA, plant stress protein and a molecular host-plant signal for the bacterium) using FTIR spectroscopy of whole cells in the diffuse reflectance mode (DRIFT). The nutritional stress resulted in the appearance of prominent spectroscopic signs of poly-3-hydroxybutyrate (PHB) accumulation in the bacterial cells; in addition, splitting of the amide I band related to bacterial cellular proteins indicated some stress-induced alterations in their secondary structure components. Similar structural changes were observed in the presence of nanomolar WGA both in stressed A. brasilense cells and under normal nutritional conditions. Comparative analysis of the data obtained and the relevant literature data indicated that the stress conditions applied (which resulted in the accumulation of PHB involved in stress tolerance) and/or the presence of nanomolar concentrations of WGA induced synthesis of bacterial cell-surface (glyco)proteins rich in beta-structures, that could be represented by hemagglutinin and/or porin.

Analysis of skeletal muscle tissue expression profiles in pig to identify genes involved in meat quality traits: effect of stress conditions before slaughtering in different pig breeds

The knowledge of genes and molecular processes involved in the stress susceptibility and reaction could be important for the improvement of meat quality traits. The aim of the research was the identification by microarray analysis of skeletal muscle genes differentially expressed in pigs divergent for meat quality. The expression profiles were studied in subjects exposed or not exposed to a physical stress (a run in controlled conditions) before slaughtering. Semimembranosus muscle samples were collected at slaughtering and stored at -80°C before RNA extraction. These samples were obtained from 38 unrelated castrated male pigs belonging to 3 different breeds and reared up to 120 kg in the University of Bologna experimental farm: 10 Italian Duroc and 10 Italian Large White pigs with genotype CC at the RYR 1 1843 polymorphic site and18 Pietrain pigs (CC, CT and TT in the not stressed group and only CC and CT in the stressed group). Microarray analysis was performed using two platforms: a cDNA based microarray produce by the University of Aarhus (~27,000 porcine cDNAs) and the Operon/Qiagen pig 11k Oligo set (version 1.0) (10,665 70mers oligos). Total RNA extracted from the samples was reverse transcribed, labelled with fluorescent Alexa Fluor 555 dye and individually hybridized to both cDNA and Oligo microarrays. The labelled samples were hybridised together with a common reference sample consisting of Alexa Fluor 647 labelled total RNA extracted from skeletal muscle and heart tissue from a pig not related with those of the experiment. ScanArray Gx (Perkin Elmer) scanner and ScanArray Express software were used for image acquisition and data normalization. ANOVA has been performed without to include 3 Pietrain pigs not stressed with genotype CC at RYR 1. Using the Mixed procedure of SAS that consider fixed and random factors the adjustment for overall effects of array and dye across genes was performed. The residuals from this normalization process were used to test the effects of the factors included in the model on gene expression. Differences in the least square means were obtained and tested for significant differences by using a t-test. The false discovery rate was used to account for multiple testing. A false discovery rate of 5% was accepted. Preliminary results of the comparison between stressed and not stressed pigs obtained with the Oligo array showed that more than 20% of the genes upregulated in the group of stressed pigs belong to functional categories involved in regulation of cellular physiological processes. The first results from the comparison between treatments within breed seems to evidence differences among breeds in stress response and can provide indication on potentially interesting genes influencing pig meat quality.

A time contraction effect of acute tail-pinch stress on the associative learning of rats

The effect of tail-pinch stress interpolated between the saccharin conditioned stimulus (CS) and the illness-inducing unconditioned stimulus (US) during long-trace taste-aversion conditioning was examined in young- and old adult rats with a two-cylinder (saccharin versus water) test. A 2 x 2 x 4 factorial ANOVA was performed on percent-preference-for-saccharin data, with age (young, old), stress condition (stressed, non-stressed), and CS-US interval (22.5-, 45-, 90-, and 180-min) being the factors under consideration. The ANOVA yielded only significant main effects of stress condition and CS-US interval. These findings indicate that stress weakens the CS-US association as evidenced by a higher percent preference for saccharin in the stressed rats than in non-stressed rats at all CS-US intervals. A comparison of the stressed and non-stressed conditioned rats with pseudo-conditioned controls showed that the non-stressed rats formed strong aversions up to the 45-min CS-US interval whereas the stressed rats showed no conditioning beyond the 22.5 min CS-US interval, indicating that stress decreases the effective CS-US interval. Results were interpreted in terms of time-contraction and an internal biological countdown timer hypothesized to govern processes involved in associative learning over long delays.

Thin-Layer Chromatography-Densitometry and Liquid Chromatography Analysis of Alkaloids in Leaves of Papaver somniferum Under Stress Conditions

The effect of stress conditions on the concentrations of secondary metabolites were examined during various developmental stages of Papaver somniferum plants. P. somniferum plants were grown in laboratory conditions (Budakalász). The experiment consisted of 22 treatments. Significantly different alkaloid contents can be observed under different stress conditions. In general, the alkaloid contents of plants are very low; therefore, a highly sensitive and reliable method has to be developed for analysis. The amount of alkaloids was measured by 2 separation and detection techniques. Accuracy of the thin-layer chromatography method for quantitative analysis is limited. Without purification of samples the background is too noisy. Column liquid chromatography is a sensitive and relatively inexpensive method that allows precise quantitative determination of the alkaloid content.

Controlling Foliar Blights of Wheat in the Rice-Wheat Systems of Asia.

Foliar blight caused by Cochliobolus sativus and Pyrenophora tritici-repentis is the main biotic stress of wheat in the rice-wheat systems of South Asia, where it causes, on average, up to 15% yield loss. Increases in food production have to come from higher and sustainable productivity. It requires a multidisciplinary approach combining novel resistance sources and adapted agronomic practices. Better host plant resistance has been achieved by crossing genetic resistance sources or wild relatives to high-yielding cultivars. Germ plasm improvement methods centered on regional partnerships are now more specifically addressing the needs of warmer areas. Observations in long-term trials underline the increasing role of soil fertility in reducing disease severity. Studies focusing on the effect of stress conditions on disease development increase knowledge about the stability of resistance. This makes breeding more efficient and helps recommend better-adapted crop management practices. The adoption of reduced tillage methods and soil conservation practices imply farmers' direct participation in the research process. Foliar fungicide treatments are not a viable alternative for small farmers, but seed treatment may prove useful as part of an integrated disease management approach based on improved genetic resistance and good agronomy.

The Effects of Stressful Conditions on an Artificial Aeromonas hydrophilia Challenge in Hybrid Catfish (Clarias gariepinus x Clarias batrachus)

The Effects of Stressful Conditions on an Artificial Aeromonas hydrophilia Challenge in Hybrid Catfish (Clarias gariepinus x Clarias batrachus)

On the weibull shape factor of intrinsic breakdown of dielectric films and its accurate experimental determination-part II: experimental results and the effects of stress conditions

For pt. I see ibid., vol. 49, no. 12, p.2131 (2002).The Weibull slope measurement techniques described in Part I are used to determine Weibull slopes as function of thickness, voltage, and temperature. The effect of stress temperature and voltage on Weibull slopes is investigated over a wide range of voltage and temperatures for several different oxide thickness values. It was found that Weibull slopes show a strong thickness dependence while Weibull slopes are essentially independent of stress conditions such as voltages and temperature. The implications of the voltage-independent Weibull slope on voltage-dependent acceleration factors are discussed. In addition, the impact of electron injection polarity on Weibull slopes is studied in detail. To further advance understanding, we compare the measured Weibull slopes with different nitrogen incorporation processes under gate injection mode. It was found that for ultrathin oxides below 3 nm to the first order, the Weibull slopes are relatively insensitive to the nitrogen incorporation process for which we investigated. Finally, we discuss the validity of the stress-induced leakage current measurement as an experimental means to measure the critical defect density.

A quantitative analysis of the chlorophyll fluorescence induction in terms of electron transfer rates at donor and acceptor sides of photosystem II

The light-induced chlorophyll fluorescence increase in dark-adapted leaves and chloroplasts upon a 1s light pulse shows the following characteristics: i) the half time of the initial fluorescence increase is not inversely related to the light intensity at excitation rates above 5*103 s-1; ii) the sigmoidal fluorescence rise at excitation rates of the order of 103 s-1 converts into an exponential rise upon an increase in the range above 104-105 s-1, and iii) the rate constant of the fluorescence rise becomes invariable at high excitation rates and modulates with the redox state of the oxygen evolving complex (OEC). Numerical solutions of differential equations for the double hit requiring closure of reaction centers (RC) are derived. Experimental induction curves can be resolved in terms of the rate constants of the oxidation of the four OEC redox states, the rate constants of QA- oxidation by QB and QB-, the excitation rate and the S0/S1 heterogeneity constant of the system. Analysis of the induction curve offers a supreme tool for localizing and quantifying the effect of stress conditions (UV, drought, heat, and inhibitors) on photosynthetic performance. Current classification of RC?s differing in fluorescence properties will require renewed attention and analysis