Effects Of Different Stresses Research Articles

Creep Rupture Behavior and Microscopic Analysis of 304HCu Austenitic Stainless Steel Under Multiaxial State of Stresses at 973 K

As a part of materials development for the application of 304HCu SS in advanced ultra super critical power plants, an experimental study has been carried out to understand the response of material under various states of stresses at 973 K. In order to introduce the multiaxial state of stress, notches of different root radii ranging from 0.25 to 2.5 mm were incorporated in smooth specimens. The comparison of rupture life of the smooth and notched specimen revealed the ability of the steel to ‘notch-strengthen’. In order to understand and substantiate the above observations, detailed FE analysis has been carried out. The decrease in von-Mises stress below the net applied stress resulted in notch strengthening in the steel in presence of a notch. The rupture life of the steel was found to increase with notch sharpness. Detailed scanning electron microscopy investigation carried out on fracture surfaces of smooth and notched specimens exhibited ductile fracture for smooth and shallow notches; whereas mixed mode fracture for relatively sharper notches. Further, the effect of different stresses on fracture morphology has also been discussed.

Priming of pathogenesis related-proteins and enzymes related to oxidative stress by plant growth promoting rhizobacteria on rice plants upon abiotic and biotic stress challenge

Two plant growth promoting rhizobacteria (PGPR) were tested to evaluate their capacity to prime rice seedlings against stress challenge (salt and Xanthomonas campestris infection). As is accepted that plants respond to biotic and abiotic stresses by generation of reactive oxygen species (ROS), enzyme activities related to oxidative stress (ascorbate peroxidase (APX, EC 1.11.1.11), guaiacol peroxidase (GPX, EC 1.11.1.7), glutathione reductase (GR, EC 1.6.4.2) and superoxide dismutase (SOD, EC 1.15.1.1)) as well as the pathogenesis-related proteins (PRs) ß-1,3-glucanase (PR2, EC 3.2.1.6) and chitinase (PR3, EC 3.2.1.14) were measured at 3 time points after stress challenge. In addition, photosynthetic parameters related with fluorescence emission of photosystem II (F0, Fv/Fm, ΦPSII and NPQ) were also measured although they were barely affected. Both strains were able to protect rice seedlings against salt stress. AMG272 reduced the salt symptoms over 47% with regard to control, and L81 over 90%. Upon pathogen challenge, 90% protection was achieved by both strains. All enzyme activities related to oxidative stress were modified by the two PGPR, especially APX and SOD upon salinity stress challenge, and APX and GR upon pathogen presence. Both bacteria induced chitinase activity 24 and 48h after pathogen inoculation, and L81 induced ß-1,3-Glucanase activity 48h after pathogen inoculation, evidencing the priming effect. These results indicate that these strains could be used as bio-fortifying agents in biotechnological inoculants in order to reduce the effects of different stresses, and indirectly reduce the use of agrochemicals.

Product Level Accelerated Reliability Testing of Motor Drives With Input Power Interruptions

Motor drives utilizing power semiconductors play an important role in modern day electric motor control. Although the reliability of power semiconductors is widely studied, the product level reliability of motor drives has been studied markedly less even though their more complex control and measuring electronics often make them more vulnerable to environmental stresses. In order to advance product level accelerated reliability testing, customized test methods with multiple simultaneous or sequential stresses can be used. However, the knowledge of combined effects of different stresses is still largely unknown. In this research the reliability of a commercial motor drive was studied. Environmental conditions used included an 85 °C constant temperature test and an 85 °C test with 85% relative humidity. Additionally, input power interruptions were included to study the effect of sudden shortages of electricity. The results of the study showed that the mean time to failure for the devices tested with the input power interruptions was notably shorter than that for the test series without them. An especially clear effect of the input power interruptions was seen on the power MOSFETs of the motor drives. Moreover, the humidity was found to play an important role in the reliability of the motor drives.

Investigation of purification process stresses on erythropoietin peptide mapping profile.

Background:Full compliance of recombinant protein peptide mapping chromatogram with the standard reference material, is one of the most basic quality control tests of biopharmaceuticals. Changing a single amino acid substitution or side chain diversity for a given peptide changes protein hydrophobicity and causes peak shape or retention time alteration in a peptide mapping assay. In this work, the effect of different stresses during the recombinant erythropoietin (EPO) purification process, including pH 4, pH 5, and room temperature were checked on product peptide mapping results.Materials and Methods:Cell culture harvest was purified under stress by different chromatographic techniques consisting of gel filtration, anionic ion exchange, concentration by ultrafiltration, and high resolution size exclusion chromatography. To induce more pH stresses, the purified EPO was exposed to pH stress 4 and 5 by exchanging buffer by a 10 KDa dialysis sac overnight. The effects of temperature and partial deglycosylation (acid hydrolysis) on purified EPO were also studied by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and peptide mapping analysis. Removal of sialic acid by mild hydrolysis was performed by exposure to two molar acetic acid at 80°C for 3 h.Results:No significant effect was observed between intact and stressed erythropoietin peptide mapping profiles and SDS-PAGE results. To validate the sensibility of the technique, erythropoietin was partially acid hydrolyzed and significant changes in the chromatographic peptide map of the intact form and a reduction on its molecular weight were detected, which indicates some partial deglycosylation.Conclusions:Purification process does not alter the peptide mapping profile and purification process stresses are not the cause of peptide mapping noncompliance.

Regulation of root water uptake under abiotic stress conditions

A common effect of several abiotic stresses is to cause tissue dehydration. Such dehydration is caused by the imbalance between root water uptake and leaf transpiration. Under some specific stress conditions, regulation of root water uptake is more crucial to overcome stress injury than regulation of leaf transpiration. This review first describes present knowledge about how water is taken up by roots and then discusses how specific stress situations such as drought, salinity, low temperature, and flooding modify root water uptake. The rate of root water uptake of a given plant is the result of its root hydraulic characteristics, which are ultimately regulated by aquaporin activity and, to some extent, by suberin deposition. Present knowledge about the effects of different stresses on these features is also summarized. Finally, current findings regarding how molecular signals such as the plant hormones abscisic acid, ethylene, and salicylic acid, and how reactive oxygen species may modulate the final response of root water uptake under stress conditions are discussed.

System-level reliability testing a frequency converter with simultaneous stresses

Because the time available for product design is usually much shorter than the projected operating life of the product, accelerated stress testing is commonly used to study the reliability of components, devices or larger systems. Under normal use conditions, products can be subjected to multiple simultaneous stressors. Consequently, it is also useful to use concurrent stresses during reliability testing. However, the combinatory effects of multiple stressors can be quite complex, which complicates failure analysis after testing. The usage of concurrent environmental stresses as a system-level reliability testing method is studied with the help of a frequency converter. The effects of different stresses on the failure modes and on the overall testing time were examined separately and simultaneously. The results show that with concurrent stresses the same kind of failure modes may be observed during testing as in normal service conditions and, more importantly, a significant reduction in testing time could be achieved when compared to that of single stress tests.

Quantitative Proteomic Approaches and Their Application in the Study of Yeast Stress Responses

The increasing popularity of proteomics has created a need for quantitative analysis methods. As a result, many different techniques are now available for performing gel-based or gel-free quantitative proteomic analysis of biological samples. These techniques provide an insight into global protein expression from identification to quantification, taking into account the highly dynamic status of the proteome. With its relatively small and compact genome, yeast is widely used as a model organism for molecular genetics, cell biology, and proteomic studies. In this review, we will show how quantitative proteomics has been used to study the effect of different stresses on yeast.

Effect of different stresses on trehalose levels in Rhizopus oryzae

Rhizopus oryzae accumulates and degrades trehalose in response to environmental stress conditions such as heat, osmotic stress, nitrogen starvation and pH. When heat stress was applied to R. oryzae, the trehalose content of the cells was increased from 0.9 to 4.8 mg/g dw and when the stress was relieved it decreased back to 1.1 mg/g dw. Under osmotic stress and nitrogen starvation, trehalose content was increased by 3.5 and 3 fold, respectively. The decrease in external pH increased trehalose level up to 2.6 mg/g dw from 1.1 mg/g dw. Increased trehalose level decreased back to normal after pH stress was relieved. These results indicate that trehalose accumulates and acts as a stress protectant in R. oryzae.

Stress-specific response of the p53-Mdm2 feedback loop

BackgroundThe p53 signalling pathway has hundreds of inputs and outputs. It can trigger cellular senescence, cell-cycle arrest and apoptosis in response to diverse stress conditions, including DNA damage, hypoxia and nutrient deprivation. Signals from all these inputs are channeled through a single node, the transcription factor p53. Yet, the pathway is flexible enough to produce different downstream gene expression patterns in response to different stresses.ResultsWe construct a mathematical model of the negative feedback loop involving p53 and its inhibitor, Mdm2, at the core of this pathway, and use it to examine the effect of different stresses that trigger p53. In response to DNA damage, hypoxia, etc., the model exhibits a wide variety of specific output behaviour - steady states with low or high levels of p53 and Mdm2, as well as spiky oscillations with low or high average p53 levels.ConclusionsWe show that even a simple negative feedback loop is capable of exhibiting the kind of flexible stress-specific response observed in the p53 system. Further, our model provides a framework for predicting the differences in p53 response to different stresses and single nucleotide polymorphisms.

Effects of systemic potato response to wounding and jasmonate on the aphid Macrosiphum euphorbiae (Sternorryncha: Aphididae)

AbstractPlant induced responses are activated by multiple biotic and abiotic stresses, and may affect the interactions between a plant and phytophagous insects. The objective of this work was to evaluate the effects of different stresses inflicted to potato plants (Solanum tuberosum) on the potato aphid (Macrosiphum euphorbiae). Abiotic wounding, biotic wounding by Leptinotarsa decemlineata and treatment with volatile methyl jasmonate (MeJA) were evaluated with regard to the orientation behaviour, the feeding behaviour and the development of the potato aphids. Dual‐choice olfactometry showed that plants treated with MeJA lost their attractiveness for the potato aphids, while both abiotic and biotic wounding did not alter the orientation of aphids. Electropenetrography revealed that the feeding behaviour of aphids was only slightly disturbed by a previous L. decemlineata wounding, while it was highly disturbed by mechanical wounding and MeJA treatment. Aphid nymph survival was reduced on mechanically wounded plants, the pre‐reproductive period was lengthened and the fecundity reduced on plants treated with MeJA. Our results bring new information about the effects of various stresses inflicted to S. tuberosum on M. euphorbiae. We showed that wounding and MeJA treatment induced an antixenosis resistance in potato plants against M. euphorbiae, which may influence aphid colonization processes.

Effect of Ag addition on the creep characteristics of Sn–8.8 wt%Zn solder alloy

Full implementation of the new generation of lead-free solders requires detailed knowledge and understanding of their mechanical behavior. The materials used in the present study are Sn–8.8 wt%Zn (binary) and Sn–8.8 wt%Zn–1.5 wt%Ag (tertiary) alloys. Effect of Ag addition, deformation temperature T and the applied stress, σ, on the creep characteristics have been studied. Creep tests were performed under the effect of different stresses ranged from 17.8 to 26 MPa at the deformation temperatures 291, 303, 323 and 343 K. The transient creep parameters β and n were found to be markedly affected by the creep test conditions, T and σ. The parameter β was found to be decreased by increasing T and/or σ while n was found to increase by increasing T irrespective of the applied stress σ. The steady-state creep rate έ st was found to increase with increasing both T and σ in both solder alloys. The steady-state creep rate έ st was related to the stress σ with the relationship έ st = Cσ m where m = (∂ln έ st/∂ln σ) is the stress exponent. This exponent is decreased with increasing T in both alloys. Addition of 1.5 wt%Ag to the binary alloy increased its creep resistance. This behavior was attributed to the formation of the intermetallic compounds (IMCs) AgZn and Ag 3Sn during solidification. These IMCs played the role of pinning action for the moving dislocations and consequently leading to the increase of its creep resistance. Micro-structural changes were investigated by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis.

Stress and Memory: Behavioral Effects and Neurobiological Mechanisms

Stress is a potent modulator of learning and memory processes. Although there have been a few attempts in the literature to explain the diversity of effects (including facilitating, impairing, and lack of effects) described for the impact of stress on memory function according to single classification criterion, they have proved insufficient to explain the whole complexity of effects. Here, we review the literature in the field of stress and memory interactions according to five selected classifying factors (source of stress, stressor duration, stressor intensity, stressor timing with regard to memory phase, and learning type) in an attempt to develop an integrative model to understand how stress affects memory function. Summarizing on those conditions in which there was enough information, we conclude that high stress levels, whether intrinsic (triggered by the cognitive challenge) or extrinsic (induced by conditions completely unrelated to the cognitive task), tend to facilitate Pavlovian conditioning (in a linear-asymptotic manner), while being deleterious for spatial/explicit information processing (which with regard to intrinsic stress levels follows an inverted U-shape effect). Moreover, after reviewing the literature, we conclude that all selected factors are essential to develop an integrative model that defines the outcome of stress effects in memory processes. In parallel, we provide a brief review of the main neurobiological mechanisms proposed to account for the different effects of stress in memory function. Glucocorticoids were found as a common mediating mechanism for both the facilitating and impairing actions of stress in different memory processes and phases. Among the brain regions implicated, the hippocampus, amygdala, and prefrontal cortex were highlighted as critical for the mediation of stress effects.

Degradation of supercoiled plasmid DNA within a capillary device

Supercoiled plasmid DNA is susceptible to fluid stress in large-scale manufacturing processes. A capillary device was used to generate controlled shear conditions and the effects of different stresses on plasmid DNA structure were investigated. Computational fluid dynamics (CFD) analysis was employed to characterize the flow environment in the capillary device and different analytical techniques were used to quantify the DNA breakage. It was found that the degradation of plasmid DNA occurred at the entrance of the capillary and that the shear stress within the capillary did not affect the DNA structure. The degradation rate of plasmids was well correlated with the average elongational strain rate or the pressure drop at the entrance region. The conclusion may also be drawn that laminar shear stress does not play a significant role in plasmid DNA degradation.

Stress Response of Escherichia coli

ABSTRACT: Escherichia coli encounter numerous different stresses during their growth, survival, and infection. These stresses are relevant to survival in foods and food processing environments. E. coli and other bacteria respond to stress conditions by activating small or large groups of genes under the control of common regulator proteins. Stress conditions result in the accumulation of these regulator proteins and subsequent transcription of many genes allows cells to cope with specific stress situations, conferring stress tolerance and survival. In addition, induced stress tolerance of cells is attributed to enhanced virulence and enhanced tolerance to other stresses (cross‐protection). In this review, regulation of stress and the stress tolerance response of E. coli to heat, acid, starvation, and cold stresses that are commonly used in food preservation and food production will be addressed. The effect of different stress on survival, adaptation, and cross‐protection of E. coli studied using laboratory media, and real foods will be briefly summarized. Finally, the relationship of stress response and subsequent virulence and cross‐protection will also be discussed.

Microstructure and growth mechanism of stressed complex oxide thin films in strain-modulation

A series of experiments of strain modulations in heterostructures of SrTiO3/LaAlO3 and LaAlO3/SrTiO3 perovskite thin films fabricated by laser molecular beam epitaxy (L-MBE) were performed to study the effect of the compressive stress and tensile stress on the growth and microstructure of the films. The growth process of the films was in-situ monitored by reflective high-energy electron diffraction (RHEED). The morphology of the films was studied by ex-situ atomic force microscopy (AFM). We demonstrated that the compressive stress-induced self-organized SrTiO3 films deposited on LaAlO3 (100) single crystal substrates exhibited a periodic well-ordered ripple-shaped structure, forming a unique nanopatterning tool to fabricate 1D/2D arrays of confined nanostructures (i.e., islands and wires). Small angle X-ray scattering technique was employed to investigate the superstructure. Symmetric satellite peaks were observed, which also revealed the well-aligned self-organized structures. In contrast, the similar superstructure was not observed during the growth of the tensile stress-induced LaAlO3 films on SrTiO3 substrates. Based on the experimental data, the compressive stress was estimated as the main reason of the self-organized growth. A growth model about the formation mechanisms of compressive stress-induced nanostructure was put forward and systematical kinetics elucidations about the growth processes were also discussed to illustrate the effects of different stresses on the growth and microstructures of the films.

Modelling the variability of lag times and the first generation times of single cells of E. coli

A mathematical model combining deterministic and stochastic elements describes the growth and division of single cells. Its deterministic part is based on the model of Baranyi and Roberts [ International Journal of Food Microbiology 23 (1994) 277] modelling the gradual adjustment of the cells to a new environment. The stochastic part assumes a random threshold size for the division of a single cell, which accounts for the variability of the individual generation times. Experimental results of the first division times of thousands of single cells using a microscopic flow system could be reproduced with this model, and it has the potential to be used to study the effects of different stress and environmental factors on the distribution of the lag and generation times of individual cells.

The effects of different stresses on reactivation of latently infected HSV-1 in mice

目的 探讨不同应激对小鼠三叉神经节潜伏感染的单纯疱疹病毒再激活的影响,以期对疱疹病毒复发性感染的发病机制有更深的了解.方法给潜伏感染单纯疱疹病毒I型的小鼠施加高热、过度疲劳、寒冷等不同刺激,然后检测小鼠应激反应后三叉神经节单纯疱疹病毒I型抗原的表达.结果高热、过度疲劳和寒冷应激在小鼠三叉神经节均不同程度地检测到活化的病毒,以高热应激组病毒再激活的数目最多.结论应激可以诱发小鼠三叉神经节内潜伏感染的单纯疱疹病毒I型再激活,是单纯疱疹病毒复发性感染的重要诱因。

ステンレス鋼粒界での照射誘起偏析を模擬した合金のマルテンサイト変態と磁性

We have investigated the magnetic properties of four model alloys (18Cr8Ni0.5Si, 16Cr10Ni1Si, 13Cr20Ni2Si, and 10Cr30Ni3Si) for simulating radiation induced segregation in SUS304 austenitic stainless steels. All alloys are paramagnetic at room temperature. With reduction of temperature, a structural transition was occurred for alloys with lower Ni content (18Cr8Ni0.5Si and 16Cr10Ni1Si), which produced ferromagnetic martensite. Alloys with higher Ni content (13Cr20Ni2Si, and 10Cr30Ni3Si) became ferromagnetic at low temperature without martensitic transformation. Different effects of stress on the structure and magnetism were found also. Martensitic transformations and magnetic properties of austenitic stainless steels depend strongly on its chemical composition and can be classified by the value of Ni equivalent. This study suggests the possibility of applying magnetic methods to the nondestructive detection of radiation induced segregation.

Quantitative study of charge trapping in SiO 2 during bipolar Fowler–Nordheim injection

This work deals with the programming window closure observed in electrically erasable programmable read only memories as the number of write/erase cycles increases. This aging phenomenon is attributed to the build-up of oxide charge in the tunnel area. Capacitance–voltage and current–voltage measurements on 8.5 nm thick oxide MOS capacitors performed after constant current Fowler–Nordheim (FN) stresses showed interface states generation at both the anode and the cathode. A linear build-up of ‘slow’ states with the total injected charge was also observed at the cathode. Bulk oxide trapped charge and normalized centroid were deduced from the DiMaria technique. The bulk oxide charge build-up after FN stress is shown to follow a power law as a function of injected electron density over several decades. The charging kinetics have been explained by two components: trapping by native and generated traps. We have determined the different trap parameters (densities, capture cross-sections, generation rates and locations). By varying the stress current (polarity and density), we have noticed that the change in generated trap parameters is linear with the stress bias. We take finally a particular interest in the cumulating effects of different stresses. To our knowledge, such a complete study is absent from the literature and has to be done to predict the charge trapping kinetics due to non-constant stress which occur during memory write and erase operations.

Domain behavior and polarization changes in ferroelectric films under stress

The effect of stress on the ferroelectric properties of SBT and PZT thin films has been investigated. In SBT films, both Remnant polarization (Pr) and spontaneous polarization (Ps) increase with the application of tensile stress, but decrease with the application of compressive stress. While PZT films exhibit just the opposite behavior. The changes of polarity under stress with testing voltage in the two kinds of films also show different characteristics. The different effects of stress on the two kinds of materials are compared, and the change of domains under stress is put forward as the possible cause.