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Sample records for alleviate thermal stress

  1. Method for alleviating thermal stress damage in laminates

    NASA Technical Reports Server (NTRS)

    Hoffman, C. A.; Weeton, J. W.; Orth, N. W. (Inventor)

    1981-01-01

    The method is for metallic matrix composites, such as laminated sheet or foil composites. Non-intersecting discrete discontinuities are positively introduced into the interface between the layers so as to reduce the thermal stress produced by unequal expansion of the materials making up the composite. The discontinuities are preferably produced by drilling holes in the metallic matrix layer. However, a plurality of discrete elements may be used between the layers to carry out this purpose.

  2. Method for alleviating thermal stress damage in laminates. [metal matrix composites

    NASA Technical Reports Server (NTRS)

    Hoffman, C. A.; Weeton, J. W.; Orth, N. W. (Inventor)

    1980-01-01

    A method is provided for alleviating the stress damage in metallic matrix composites, such as laminated sheet or foil composites. Discontinuities are positively introduced into the interface between the layers so as to reduce the thermal stress produced by unequal expansion of the materials making up the composite. Although a number of discrete elements could be used to form one of the layers and thus carry out this purpose, the discontinuities are preferably produced by simply drilling holes in the metallic matrix layer or by forming grooves in a grid pattern in this layer.

  3. Thermal acclimation of the symbiotic alga Symbiodinium spp. alleviates photobleaching under heat stress.

    PubMed

    Takahashi, Shunichi; Yoshioka-Nishimura, Miho; Nanba, Daisuke; Badger, Murray R

    2013-01-01

    A moderate increase in seawater temperature causes coral bleaching, at least partially through photobleaching of the symbiotic algae Symbiodinium spp. Photobleaching of Symbiodinium spp. is primarily associated with the loss of light-harvesting proteins of photosystem II (PSII) and follows the inactivation of PSII under heat stress. Here, we examined the effect of increased growth temperature on the change in sensitivity of Symbiodinium spp. PSII inactivation and photobleaching under heat stress. When Symbiodinium spp. cells were grown at 25°C and 30°C, the thermal tolerance of PSII, measured by the thermal stability of the maximum quantum yield of PSII in darkness, was commonly enhanced in all six Symbiodinium spp. tested. In Symbiodinium sp. CCMP827, it took 6 h to acquire the maximum PSII thermal tolerance after transfer from 25°C to 30°C. The effect of increased growth temperature on the thermal tolerance of PSII was completely abolished by chloramphenicol, indicating that the acclimation mechanism of PSII is associated with the de novo synthesis of proteins. When CCMP827 cells were exposed to light at temperature ranging from 25°C to 35°C, the sensitivity of cells to both high temperature-induced photoinhibition and photobleaching was ameliorated by increased growth temperatures. These results demonstrate that thermal acclimation of Symbiodinium spp. helps to improve the thermal tolerance of PSII, resulting in reduced inactivation of PSII and algal photobleaching. These results suggest that whole-organism coral bleaching associated with algal photobleaching can be at least partially suppressed by the thermal acclimation of Symbiodinium spp. at higher growth temperatures. PMID:23170037

  4. Alleviating Stress for Women Administrators.

    ERIC Educational Resources Information Center

    Ten Elshof, Annette; Tomlinson, Elaine

    1981-01-01

    Describes a workshop designed to help women administrators assess individual stress levels. Stress can be alleviated through exercise, support groups or networking, sleep and diet, relaxation, guided fantasy, and planned activity. The long-term implications include preventing illness and making women more effective within the administrative…

  5. Strategies for Alleviating Teacher Stress.

    ERIC Educational Resources Information Center

    Luckner, John L.

    1990-01-01

    This article provides background information on stress and presents five strategies intended to help teachers of hearing-impaired students manage their stress levels. Strategies include increasing self-awareness, reducing isolation, restoring perspective and balance, redefining problem situations, and developing and implementing an action plan.…

  6. Arctigenin alleviates ER stress via activating AMPK

    PubMed Central

    Gu, Yuan; Sun, Xiao-xiao; Ye, Ji-ming; He, Li; Yan, Shou-sheng; Zhang, Hao-hao; Hu, Li-hong; Yuan, Jun-ying; Yu, Qiang

    2012-01-01

    Aim: To investigate the protective effects of arctigenin (ATG), a phenylpropanoid dibenzylbutyrolactone lignan from Arctium lappa L (Compositae), against ER stress in vitro and the underlying mechanisms. Methods: A cell-based screening assay for ER stress regulators was established. Cell viability was measured using MTT assay. PCR and Western blotting were used to analyze gene and protein expression. Silencing of the CaMKKβ, LKB1, and AMPKα1 genes was achieved by RNA interference (RNAi). An ATP bioluminescent assay kit was employed to measure the intracellular ATP levels. Results: ATG (2.5, 5 and 10 μmol/L) inhibited cell death and unfolded protein response (UPR) in a concentration-dependent manner in cells treated with the ER stress inducer brefeldin A (100 nmol/L). ATG (1, 5 and 10 μmol/L) significantly attenuated protein synthesis in cells through inhibiting mTOR-p70S6K signaling and eEF2 activity, which were partially reversed by silencing AMPKα1 with RNAi. ATG (1-50 μmol/L) reduced intracellular ATP level and activated AMPK through inhibiting complex I-mediated respiration. Pretreatment of cells with the AMPK inhibitor compound C (25 μmol/L) rescued the inhibitory effects of ATG on ER stress. Furthermore, ATG (2.5 and 5 μmol/L) efficiently activated AMPK and reduced the ER stress and cell death induced by palmitate (2 mmol/L) in INS-1 β cells. Conclusion: ATG is an effective ER stress alleviator, which protects cells against ER stress through activating AMPK, thus attenuating protein translation and reducing ER load. PMID:22705729

  7. Incorporation of coenzyme Q10 into bovine oocytes improves mitochondrial features and alleviates the effects of summer thermal stress on developmental competence.

    PubMed

    Gendelman, Mirit; Roth, Zvi

    2012-11-01

    Environmental stress-induced alterations in oocyte mitochondria are suggested to deleteriously affect developmental competence of the ovarian pool of oocytes. We examined the association between seasonal effects on oocyte developmental competence and mitochondrial distribution, polarization, mitochondrial DNA (mtDNA) content, and RNA expression, and whether the incorporation of coenzyme Q10 (CoQ10) might improve these effects. Bovine oocytes were collected during the summer (June-August), fall (September-November), and winter (December-May), matured in vitro with or without 50 μM CoQ10, fertilized, and cultured for 8 days. The proportion of developed blastocysts was highest in the winter, intermediate in the fall, and lowest in the summer. Matured oocytes were classified into categories I-IV according to their mitochondrial distribution pattern (MitoTracker green). The proportion of high- and low-polarized mitochondria (JC-1 assay) differed between oocyte categories but was not affected by season. On the other hand, oocyte distribution into categories differed between seasons and was affected by CoQ10, with an increased proportion of category I oocytes in the fall. Oocyte mtDNA did not differ between seasons, but expression of mitochondrion-associated genes involved in the respiratory chain (ND2, SDHD, CYTB, COXII, ATP5B, and TFAM) did. Coenzyme Q10 increased the expression of CYTB, COXII, and ATP5B and the proportions of blastocysts developed in the fall. In summary, season-induced alterations in mitochondrial functions might explain, in part, the reduced oocyte developmental competence. It seems that in the fall, under modest harm, CoQ10 incorporation can alleviate these deleterious effects somewhat. PMID:23018185

  8. Alleviating Stress in Parents of High-Risk Preterm Infants.

    ERIC Educational Resources Information Center

    Lowenthal, Barbara

    1989-01-01

    Possible sources of stress for parents of preterm high-risk infants are reviewed from a research perspective. Stages of parental attachment to their premature baby are spelled out. Strategies for special education teachers to use in alleviating parental stress are described. (JDD)

  9. Arbuscular mycorrhizal fungi in alleviation of salt stress: a review

    PubMed Central

    Evelin, Heikham; Kapoor, Rupam; Giri, Bhoopander

    2009-01-01

    Background Salt stress has become a major threat to plant growth and productivity. Arbuscular mycorrhizal fungi colonize plant root systems and modulate plant growth in various ways. Scope This review addresses the significance of arbuscular mycorrhiza in alleviation of salt stress and their beneficial effects on plant growth and productivity. It also focuses on recent progress in unravelling biochemical, physiological and molecular mechanisms in mycorrhizal plants to alleviate salt stress. Conclusions The role of arbuscular mycorrhizal fungi in alleviating salt stress is well documented. This paper reviews the mechanisms arbuscular mycorrhizal fungi employ to enhance the salt tolerance of host plants such as enhanced nutrient acquisition (P, N, Mg and Ca), maintenance of the K+ : Na+ ratio, biochemical changes (accumulation of proline, betaines, polyamines, carbohydrates and antioxidants), physiological changes (photosynthetic efficiency, relative permeability, water status, abscissic acid accumulation, nodulation and nitrogen fixation), molecular changes (the expression of genes: PIP, Na+/H+ antiporters, Lsnced, Lslea and LsP5CS) and ultra-structural changes. Theis review identifies certain lesser explored areas such as molecular and ultra-structural changes where further research is needed for better understanding of symbiosis with reference to salt stress for optimum usage of this technology in the field on a large scale. This review paper gives useful benchmark information for the development and prioritization of future research programmes. PMID:19815570

  10. Curcumin alleviates oxidative stress and mitochondrial dysfunction in astrocytes.

    PubMed

    Daverey, Amita; Agrawal, Sandeep K

    2016-10-01

    Oxidative stress plays a critical role in various neurodegenerative diseases, thus alleviating oxidative stress is a potential strategy for therapeutic intervention and/or prevention of neurodegenerative diseases. In the present study, alleviation of oxidative stress through curcumin is investigated in A172 (human glioblastoma cell line) and HA-sp (human astrocytes cell line derived from the spinal cord) astrocytes. H2O2 was used to induce oxidative stress in astrocytes (A172 and HA-sp). Data show that H2O2 induces activation of astrocytes in dose- and time-dependent manner as evident by increased expression of GFAP in A172 and HA-sp cells after 24 and 12h respectively. An upregulation of Prdx6 was also observed in A172 and HA-sp cells after 24h of H2O2 treatment as compared to untreated control. Our data also showed that curcumin inhibits oxidative stress-induced cytoskeleton disarrangement, and impedes the activation of astrocytes by inhibiting upregulation of GFAP, vimentin and Prdx6. In addition, we observed an inhibition of oxidative stress-induced inflammation, apoptosis and mitochondria fragmentation after curcumin treatment. Therefore, our results suggest that curcumin not only protects astrocytes from H2O2-induced oxidative stress but also reverses the mitochondrial damage and dysfunction induced by oxidative stress. This study also provides evidence for protective role of curcumin on astrocytes by showing its effects on attenuating reactive astrogliosis and inhibiting apoptosis. PMID:27423629

  11. Fluvoxamine alleviates ER stress via induction of Sigma-1 receptor.

    PubMed

    Omi, T; Tanimukai, H; Kanayama, D; Sakagami, Y; Tagami, S; Okochi, M; Morihara, T; Sato, M; Yanagida, K; Kitasyoji, A; Hara, H; Imaizumi, K; Maurice, T; Chevallier, N; Marchal, S; Takeda, M; Kudo, T

    2014-01-01

    We recently demonstrated that endoplasmic reticulum (ER) stress induces sigma-1 receptor (Sig-1R) expression through the PERK pathway, which is one of the cell's responses to ER stress. In addition, it has been demonstrated that induction of Sig-1R can repress cell death signaling. Fluvoxamine (Flv) is a selective serotonin reuptake inhibitor (SSRI) with a high affinity for Sig-1R. In the present study, we show that treatment of neuroblastoma cells with Flv induces Sig-1R expression by increasing ATF4 translation directly, through its own activation, without involvement of the PERK pathway. The Flv-mediated induction of Sig-1R prevents neuronal cell death resulting from ER stress. Moreover, Flv-induced ER stress resistance reduces the infarct area in mice after focal cerebral ischemia. Thus, Flv, which is used frequently in clinical practice, can alleviate ER stress. This suggests that Flv could be a feasible therapy for cerebral diseases caused by ER stress. PMID:25032855

  12. Coronatine alleviates water deficiency stress on winter wheat seedlings.

    PubMed

    Li, Xiangwen; Shen, Xuefeng; Li, Jianmin; Eneji, Anthony Egrinya; Li, Zhaohu; Tian, Xiaoli; Duan, Liusheng

    2010-07-01

    With the aim to determine whether coronatine (COR) alleviates drought stress on wheat, two winter wheat (Triticum aestivum L.) cultivars, ChangWu134 (drought-tolerant) and Shan253 (drought-sensitive) were studied under hydroponic conditions. Seedlings at the three-leaf stage were cultured in a Hoagland solution containing COR at 0.1 microM for 24 h, and then exposed to 20% polyethylene glycol 6000 (PEG-6000). Under simulated drought (SD), COR increased the dry weight of shoots and roots of the two cultivars significantly; the root/shoot ratio also increased by 30% for Shan253 and 40% for ChangWu134. Both cultivars treated with COR under SD (0.1COR+PEG) maintained significantly higher relative water content, photosynthesis, transpiration, intercellular concentration of CO(2) and stomatal conductance in leaves than those not treated with PEG. Under drought, COR significantly decreased the relative conductivity and malondialdehyde production, and the loss of 1,1-diphenyl-2-picrylhydrazyl scavenging activity in leaves was significantly alleviated in COR-treated plants. The activity of peroxidase, catalase, glutathione reductase and ascorbate peroxidase were adversely affected by drought. Leaves of plants treated with COR under drought produced less abscisic acid (ABA) than those not treated. Thus, COR might alleviate drought effects on wheat by reducing active oxygen species production, activating antioxidant enzymes and changing the ABA level. PMID:20590992

  13. Verminoside mediates life span extension and alleviates stress in Caenorhabditis elegans.

    PubMed

    Pant, A; Asthana, J; Yadav, A K; Rathor, L; Srivastava, S; Gupta, M M; Pandey, R

    2015-01-01

    The discovery of bioactive molecules modulating aging in living organism promotes development of natural therapeutics for curing age-related afflictions. The progression in age-related disorders can be attributed to increment in intracellular reactive oxygen species (ROS) and oxidative stress level. To this end, we isolated an iridoid verminoside (VMS) from Stereospermum suaveolens (Roxb.) DC. and evaluated its effect on Caenorhabditis elegans. The present study delineates VMS-mediated alteration of intracellular ROS, oxidative stress, and life span in C. elegans. The different tested doses of VMS (5 μM, 25 μM, and 50 μM) were able to enhance ROS scavenging and extend mean life span in C. elegans. The maximal life span extension was observed in 25 μM VMS, that is, 20.79% (P < 0.0001) followed by 9.84% (P < 0.0001) in 5 μM VMS and 8.54% (P < 0.0001) in 50 μM VMS. VMS was able to alleviate juglone-induced oxidative stress and enhanced thermotolerance in worms. The stress-modulating and ROS-scavenging potential of VMS was validated by increment in mean survival by 29.54% (P < 0.0001) in VMS-treated oxidative stress hypersensitive mev-1 mutant strain. Furthermore, VMS modulates expression of DAF-16 (a FoxO transcription factor) promoting stress resistance and longevity. Altogether, our results suggest that VMS attenuates intracellular ROS and stress (oxidative and thermal) level promoting longevity. The longevity and stress modulation can be attributed to VMS-mediated alterations in daf-16 expression which regulates insulin signaling pathway. This study opens doors for development of phytomolecule-based therapeutics for prolonging life span and managing age-related severe disorders. PMID:26189547

  14. Thermal stress and toxicity.

    PubMed

    Gordon, Christopher J; Johnstone, Andrew F M; Aydin, Cenk

    2014-07-01

    Elevating ambient temperature above thermoneutrality exacerbates toxicity of most air pollutants, insecticides, and other toxic chemicals. On the other hand, safety and toxicity testing of toxicants and drugs is usually performed in mice and rats maintained at sub-thermoneutral temperatures of ~22∘C. When exposed to chemical toxicants under these relatively cool conditions, rodents typically undergo a regulated hypothermic response, characterized by preference for cooler ambient temperatures and controlled reduction in core temperature. Reducing core temperature delays the clearance of most toxicants from the body; however, a mild hypothermia also improves recovery and survival from the toxicant. Raising ambient temperature to thermoneutrality and above increases the rate of clearance of the toxicant but also exacerbates toxicity. Furthermore, heat stress combined with work or exercise is likely to worsen toxicity. Body temperature of large mammals, including humans, does not decrease as much in response to exposure to a toxicant. However, heat stress can nonetheless worsen toxic outcome in humans through a variety of mechanisms. For example, heat-induced sweating and elevation in skin blood flow accelerates uptake of some insecticides. Epidemiological studies suggest that thermal stress may exacerbate the toxicity of airborne pollutants such as ozone and particulate matter. Overall, translating results of studies in rodents to that of humans is a formidable task attributed in part to the interspecies differences in thermoregulatory response to the toxicants and to thermal stress. PMID:24944028

  15. Exogenous Calcium Alleviates Low Night Temperature Stress on the Photosynthetic Apparatus of Tomato Leaves

    PubMed Central

    Ni, Yang; Meng, Zhaojuan; Lu, Tao; Li, Tianlai

    2014-01-01

    The effect of exogenous CaCl2 on photosystem I and II (PSI and PSII) activities, cyclic electron flow (CEF), and proton motive force of tomato leaves under low night temperature (LNT) was investigated. LNT stress decreased the net photosynthetic rate (Pn), effective quantum yield of PSII [Y(II)], and photochemical quenching (qP), whereas CaCl2 pretreatment improved Pn, Y(II), and qP under LNT stress. LNT stress significantly increased the non-regulatory quantum yield of energy dissipation [Y(NO)], whereas CaCl2 alleviated this increase. Exogenous Ca2+ enhanced stimulation of CEF by LNT stress. Inhibition of oxidized PQ pools caused by LNT stress was alleviated by CaCl2 pretreatment. LNT stress reduced zeaxanthin formation and ATPase activity, but CaCl2 pretreatment reversed both of these effects. LNT stress caused excess formation of a proton gradient across the thylakoid membrane, whereas CaCl2 pretreatment decreased the said factor under LNT. Thus, our results showed that photoinhibition of LNT-stressed plants could be alleviated by CaCl2 pretreatment. Our findings further revealed that this alleviation was mediated in part by improvements in carbon fixation capacity, PQ pools, linear and cyclic electron transports, xanthophyll cycles, and ATPase activity. PMID:24828275

  16. Adaptation to hot climate and strategies to alleviate heat stress in livestock production.

    PubMed

    Renaudeau, D; Collin, A; Yahav, S; de Basilio, V; Gourdine, J L; Collier, R J

    2012-05-01

    Despite many challenges faced by animal producers, including environmental problems, diseases, economic pressure, and feed availability, it is still predicted that animal production in developing countries will continue to sustain the future growth of the world's meat production. In these areas, livestock performance is generally lower than those obtained in Western Europe and North America. Although many factors can be involved, climatic factors are among the first and crucial limiting factors of the development of animal production in warm regions. In addition, global warming will further accentuate heat stress-related problems. The objective of this paper was to review the effective strategies to alleviate heat stress in the context of tropical livestock production systems. These strategies can be classified into three groups: those increasing feed intake or decreasing metabolic heat production, those enhancing heat-loss capacities, and those involving genetic selection for heat tolerance. Under heat stress, improved production should be possible through modifications of diet composition that either promotes a higher intake or compensates the low feed consumption. In addition, altering feeding management such as a change in feeding time and/or frequency, are efficient tools to avoid excessive heat load and improve survival rate, especially in poultry. Methods to enhance heat exchange between the environment and the animal and those changing the environment to prevent or limit heat stress can be used to improve performance under hot climatic conditions. Although differences in thermal tolerance exist between livestock species (ruminants > monogastrics), there are also large differences between breeds of a species and within each breed. Consequently, the opportunity may exist to improve thermal tolerance of the animals using genetic tools. However, further research is required to quantify the genetic antagonism between adaptation and production traits to evaluate

  17. Accurate Thermal Stresses for Beams: Normal Stress

    NASA Technical Reports Server (NTRS)

    Johnson, Theodore F.; Pilkey, Walter D.

    2003-01-01

    Formulations for a general theory of thermoelasticity to generate accurate thermal stresses for structural members of aeronautical vehicles were developed in 1954 by Boley. The formulation also provides three normal stresses and a shear stress along the entire length of the beam. The Poisson effect of the lateral and transverse normal stresses on a thermally loaded beam is taken into account in this theory by employing an Airy stress function. The Airy stress function enables the reduction of the three-dimensional thermal stress problem to a two-dimensional one. Numerical results from the general theory of thermoelasticity are compared to those obtained from strength of materials. It is concluded that the theory of thermoelasticity for prismatic beams proposed in this paper can be used instead of strength of materials when precise stress results are desired.

  18. Accurate Thermal Stresses for Beams: Normal Stress

    NASA Technical Reports Server (NTRS)

    Johnson, Theodore F.; Pilkey, Walter D.

    2002-01-01

    Formulations for a general theory of thermoelasticity to generate accurate thermal stresses for structural members of aeronautical vehicles were developed in 1954 by Boley. The formulation also provides three normal stresses and a shear stress along the entire length of the beam. The Poisson effect of the lateral and transverse normal stresses on a thermally loaded beam is taken into account in this theory by employing an Airy stress function. The Airy stress function enables the reduction of the three-dimensional thermal stress problem to a two-dimensional one. Numerical results from the general theory of thermoelasticity are compared to those obtained from strength of materials. It is concluded that the theory of thermoelasticity for prismatic beams proposed in this paper can be used instead of strength of materials when precise stress results are desired.

  19. Nutritional interventions to alleviate the negative consequences of heat stress.

    PubMed

    Rhoads, Robert P; Baumgard, Lance H; Suagee, Jessica K; Sanders, Sara R

    2013-05-01

    Energy metabolism is a highly coordinated process, and preferred fuel(s) differ among tissues. The hierarchy of substrate use can be affected by physiological status and environmental factors including high ambient temperature. Unabated heat eventually overwhelms homeothermic mechanisms resulting in heat stress, which compromises animal health, farm animal production, and human performance. Various aspects of heat stress physiology have been extensively studied, yet a clear understanding of the metabolic changes occurring at the cellular, tissue, and whole-body levels in response to an environmental heat load remains ill-defined. For reasons not yet clarified, circulating nonesterified fatty acid levels are reduced during heat stress, even in the presence of elevated stress hormones (epinephrine, glucagon, and cortisol), and heat-stressed animals often have a blunted lipolytic response to catabolic signals. Either directly because of or in coordination with this, animals experiencing environmental hyperthermia exhibit a shift toward carbohydrate use. These metabolic alterations occur coincident with increased circulating basal and stimulated plasma insulin concentrations. Limited data indicate that proper insulin action is necessary to effectively mount a response to heat stress and minimize heat-induced damage. Consistent with this idea, nutritional interventions targeting increased insulin action may improve tolerance and productivity during heat stress. Further research is warranted to uncover the effects of heat on parameters associated with energy metabolism so that more appropriate and effective treatment methodologies can be designed. PMID:23674792

  20. Residual stress alleviation of aircraft metal structures reinforced with filamentary composites

    NASA Technical Reports Server (NTRS)

    Kelly, J. B.; June, R. R.

    1973-01-01

    Methods to eliminate or reduce residual stresses in aircraft metal structures reinforced by filamentary composites are discussed. Residual stress level reductions were achieved by modifying the manufacturing procedures used during adhesive bonding. The residual stress alleviation techniques involved various forms of mechanical constraint which were applied to the components during bonding. Nine methods were evaluated, covering a wide range in complexity. All methods investigated during the program affected the residual stress level. In general, residual stresses were reduced by 70 percent or more from the stress level produced by conventional adhesive bonding procedures.

  1. Seed priming to alleviate salinity stress in germinating seeds.

    PubMed

    Ibrahim, Ehab A

    2016-03-15

    Salinity is one of the major abiotic stresses that affect crop production in arid and semiarid areas. Seed germination and seedling growth are the stages most sensitive to salinity. Salt stress causes adverse physiological and biochemical changes in germinating seeds. It can affect the seed germination and stand establishment through osmotic stress, ion-specific effects and oxidative stress. The salinity delays or prevents the seed germination through various factors, such as a reduction in water availability, changes in the mobilization of stored reserves and affecting the structural organization of proteins. Various techniques can improve emergence and stand establishment under salt conditions. One of the most frequently utilized is seed priming. The process of seed priming involves prior exposure to an abiotic stress, making a seed more resistant to future exposure. Seed priming stimulates the pre-germination metabolic processes and makes the seed ready for radicle protrusion. It increases the antioxidant system activity and the repair of membranes. These changes promote seed vigor during germination and emergence under salinity stress. The aim of this paper is to review the recent literature on the response of plants to seed priming under salinity stress. The mechanism of the effect of salinity on seed germination is discussed and the seed priming process is summarized. Physiological, biochemical and molecular changes induced by priming that lead to seed enhancement are covered. Plants' responses to some priming agents under salinity stress are reported based on the best available data. For a great number of crops, little information exists and further research is needed. PMID:26812088

  2. HUWE1 interacts with PCNA to alleviate replication stress.

    PubMed

    Choe, Katherine N; Nicolae, Claudia M; Constantin, Daniel; Imamura Kawasawa, Yuka; Delgado-Diaz, Maria Rocio; De, Subhajyoti; Freire, Raimundo; Smits, Veronique Aj; Moldovan, George-Lucian

    2016-06-01

    Defects in DNA replication, DNA damage response, and DNA repair compromise genomic stability and promote cancer development. In particular, unrepaired DNA lesions can arrest the progression of the DNA replication machinery during S-phase, causing replication stress, mutations, and DNA breaks. HUWE1 is a HECT-type ubiquitin ligase that targets proteins involved in cell fate, survival, and differentiation. Here, we report that HUWE1 is essential for genomic stability, by promoting replication of damaged DNA We show that HUWE1-knockout cells are unable to mitigate replication stress, resulting in replication defects and DNA breakage. Importantly, we find that this novel role of HUWE1 requires its interaction with the replication factor PCNA, a master regulator of replication fork restart, at stalled replication forks. Finally, we provide evidence that HUWE1 mono-ubiquitinates H2AX to promote signaling at stalled forks. Altogether, our work identifies HUWE1 as a novel regulator of the replication stress response. PMID:27146073

  3. Herbaspirillum sp. strain GW103 alleviates salt stress in Brassica rapa L. ssp. pekinensis.

    PubMed

    Lee, Gun Woong; Lee, Kui-Jae; Chae, Jong-Chan

    2016-05-01

    Mutual interactions between plant and rhizosphere bacteria facilitate plant growth and reduce risks of biotic and abiotic stresses. The present study demonstrates alleviation of salt stress in Brassica rapa L. ssp. perkinensis (Chinese cabbage) by Herbaspirillum sp. strain GW103 isolated from rhizosphere soil of Phragmites australis. The strain was capable of producing plant beneficial factors, such as auxin, siderophore, and 1-aminocylopropane-1-carboxylic acid deaminase. Treatment of strain GW103 on Chinese cabbage under salt stress increased K(+)/Na(+) ratio in roots generating balance in the ratio of ion homeostasis and consequently contributed to the increase of biomass. In addition, root colonization potential of the strain was observed by green fluorescent protein (GFP)-tagging approach. These results strongly suggest the beneficial impact of strain GW103 by inducing the alleviation of salt stress and development of stress tolerance in Chinese cabbage via plant-microbe interaction. PMID:26358119

  4. Alleviation of salt stress in lemongrass by salicylic acid.

    PubMed

    Idrees, Mohd; Naeem, M; Khan, M Nasir; Aftab, Tariq; Khan, M Masroor A; Moinuddin

    2012-07-01

    Soil salinity is one of the key factors adversely affecting the growth, yield, and quality of crops. A pot study was conducted to find out whether exogenous application of salicylic acid could ameliorate the adverse effect of salinity in lemongrass (Cymbopogon flexuosus Steud. Wats.). Two Cymbopogon varieties, Krishna and Neema, were used in the study. Three salinity levels, viz, 50, 100, and 150 mM of NaCl, were applied to 30-day-old plants. Salicylic acid (SA) was applied as foliar spray at 10(-5) M concentration. Totally, six SA-sprays were carried out at 10-day intervals, following the first spray at 30 days after sowing. The growth parameters were progressively reduced with the increase in salinity level; however, growth inhibition was significantly reduced by the foliar application of SA. With the increase in salt stress, a gradual decrease in the activities of carbonic anhydrase and nitrate reductase was observed in both the varieties. SA-treatment not only ameliorated the adverse effects of NaCl but also showed a significant improvement in the activities of these enzymes compared with the untreated stressed-plants. The plants supplemented with NaCl exhibited a significant increase in electrolyte leakage, proline content, and phosphoenol pyruvate carboxylase activity. Content and yield of essential oil was also significantly decreased in plants that received salinity levels; however, SA overcame the unfavorable effects of salinity stress to a considerable extent. Lemongrass variety Krishna was found to be more adapted to salt stress than Neema, as indicated by the overall performance of the two varieties under salt conditions. PMID:21882051

  5. Hyperoside Induces Endogenous Antioxidant System to Alleviate Oxidative Stress

    PubMed Central

    Park, Ji Young; Han, Xia; Piao, Mei Jing; Oh, Min Chang; Fernando, Pattage Madushan Dilhara Jayatissa; Kang, Kyoung Ah; Ryu, Yea Seong; Jung, Uhee; Kim, In Gyu; Hyun, Jin Won

    2016-01-01

    Background: Hyperoside, a flavonoid which is mainly found in Hypericum perforatum L., has many biological effects. One of the most important effects is to prevent the oxidative stress induced by reactive oxygen species. However, the molecular mechanisms underlying its effect are not fully understood. Oxidative stress is implicated in the occurrence of various physical diseases. A wide array of enzymatic antioxidant defense systems include NADH: quinone oxidoreductase 1, superoxide dismutase, and heme oxygenase-1 (HO-1). In the present study, the protective effects of hyperoside against hydrogen peroxide-induced oxidative stress in human lens epithelial cells, HLE-B3, were investigated in terms of HO-1 induction. Methods: The protein and mRNA expressions of HO-1 were examined by Western blotting and reverse transcriptase-PCR assays, respectively. To evaluate the ability of hyperoside to activate nuclear factor erythroid 2-related factor 2 (Nrf2), Western blotting and electrophoretic mobility shift assay were performed with nuclear extracts prepared from HLE-B3 cells treated with hyperoside. The activation of extracellular signal-regulated kinase (ERK), the upstream kinase of Nrf2 signaling, was monitored by Western blot analysis. The protective effect of hyperoside in HLE-B3 cells against hydrogen peroxide was performed by MTT assay. Results: Hyperoside increased both the mRNA and protein expression of HO-1 in a time- and dose-dependent manner. In addition, hyperoside elevated the level of of Nrf2 and its antioxidant response element-binding activity, which was modulated by upstream of ERK. Moreover, it activated ERK and restored cell viability which was decreased by hydrogen peroxide. Conclusions: Hyperoside is an effective compound to protect cells against oxidative stress via HO-1 induction. PMID:27051648

  6. Detection and classification of stress using thermal imaging technique

    NASA Astrophysics Data System (ADS)

    Hong, Kan; Yuen, Peter; Chen, Tong; Tsitiridis, Aristeidis; Kam, Firmin; Jackman, James; James, David; Richardson, Mark; Oxford, William; Piper, Jonathan; Thomas, Francis; Lightman, Stafford

    2009-09-01

    This paper reports how Electro-Optics (EO) technologies such as thermal and hyperspectral [1-3] imaging methods can be used for the detection of stress remotely. Emotional or physical stresses induce a surge of adrenaline in the blood stream under the command of the sympathetic nerve system, which, cannot be suppressed by training. The onset of this alleviated level of adrenaline triggers a number of physiological chain reactions in the body, such as dilation of pupil and an increased feed of blood to muscles etc. The capture of physiological responses, specifically the increase of blood volume to pupil, have been reported by Pavlidis's pioneer thermal imaging work [4-7] who has shown a remarkable increase of skin temperature in the periorbital region at the onset of stress. Our data has shown that other areas such as the forehead, neck and cheek also exhibit alleviated skin temperatures dependent on the types of stressors. Our result has also observed very similar thermal patterns due to physical exercising, to the one that induced by other physical stressors, apparently in contradiction to Pavlidis's work [8]. Furthermore, we have found patches of alleviated temperature regions in the forehead forming patterns characteristic to the types of stressors, dependent on whether they are physical or emotional in origin. These stress induced thermal patterns have been seen to be quite distinct to the one resulting from having high fever.

  7. Thermal stress and human performance.

    PubMed

    Enander, A E; Hygge, S

    1990-01-01

    There is evidence that the thermal stress encountered in many work environments may negatively affect various aspects of human performance and behavior. Evaluation of the empirical research is, however, complicated by differences in both the methodology and the definition of the basic stimulus. Effects of heat and cold stress are briefly reviewed, with particular regard to theoretical considerations. PMID:2189219

  8. Thermal anomalies in stressed Teflon.

    NASA Technical Reports Server (NTRS)

    Lee, S. H.; Wulff, C. A.

    1972-01-01

    In the course of testing polytetrafluoroethylene (Teflon) as a calorimetric gasketing material, serendipity revealed a thermal anomaly in stressed film that occurs concomitantly with the well-documented 25 C transition. The magnitude of the excess energy absorption - about 35 cal/g - is suggested to be related to the restricted thermal expansion of the film.

  9. Mechanisms of silicon-mediated alleviation of drought and salt stress in plants: a review.

    PubMed

    Rizwan, Muhammad; Ali, Shafaqat; Ibrahim, Muhammad; Farid, Mujahid; Adrees, Muhammad; Bharwana, Saima Aslam; Zia-Ur-Rehman, Muhammad; Qayyum, Muhammad Farooq; Abbas, Farhat

    2015-10-01

    Drought and salinity are the main abiotic stresses limiting crop yield and quality worldwide. Improving food production in drought- and salt-prone areas is the key to meet the increasing food demands in near future. It has been widely reported that silicon (Si), a second most abundant element in soil, could reduce drought and salt stress in plants. Here, we reviewed the emerging role of Si in enhancing drought and salt tolerance in plants and highlighted the mechanisms through which Si could alleviate both drought and salt stress in plants. Silicon application increased plant growth, biomass, photosynthetic pigments, straw and grain yield, and quality under either drought or salt stress. Under both salt and drought stress, the key mechanisms evoked are nutrient elements homeostasis, modification of gas exchange attributes, osmotic adjustment, regulating the synthesis of compatible solutes, stimulation of antioxidant enzymes, and gene expression in plants. In addition, Si application decreased Na(+) uptake and translocation while increased K(+) uptake and translocation under salt stress. However, these mechanisms vary with plant species, genotype, growth conditions, duration of stress imposed, and so on. This review article highlights the potential for improving plant resistance to drought and salt stress by Si application and provides a theoretical basis for application of Si in saline soils and arid and semiarid regions worldwide. This review article also highlights the future research needs about the role of Si under drought stress and in saline soils. PMID:26335528

  10. Thermal stresses in composite tubes

    NASA Technical Reports Server (NTRS)

    Hyer, M. W.

    1986-01-01

    This paper summarizes work to determine the thermally-induced stresses and deformations in specially-constructed angle-ply composite tubes subjected to a uniform temperature change relative to their stress-free cure state. The tubes are designed for application to space structures and have high axial stiffness. Four angle-ply designs are examined in an effort to determine which design might have the most favorable thermally-induced response. A planar elasticity solution is used, the solution being valid away from the ends of the tube. Of the four designs considered, none has any particular advantage as far as stress levels are concerned. However, despite the fact that the tube wall is a balanced laminate, one design exhibits a significant amount of thermally-induced twist.

  11. Role of Ulva lactuca extract in alleviation of salinity stress on wheat seedlings.

    PubMed

    Ibrahim, Wael M; Ali, Refaat M; Hemida, Khaulood A; Sayed, Makram A

    2014-01-01

    Seaweeds are potentially excellent sources of highly bioactive materials that could represent useful leads in the alleviation of salinity stress. The effects of presoaking wheat grains in water extract of Ulva lactuca on growth, some enzymatic activities, and protein pattern of salinized plants were investigated in this study. Algal presoaking of grains demonstrated a highly significant enhancement in the percentage of seed germination and growth parameters. The activity of superoxide dismutase (SOD) and catalase (CAT) increased with increasing the algal extract concentration while activity of ascorbate peroxidase (APX) and glutathione reductase (GR) was decreased with increasing concentration of algal extract more than 1% (w/v). The protein pattern of wheat seedling showed 12 newly formed bands as result of algal extract treatments compared with control. The bioactive components in U. lactuca extract such as ascorbic acid, betaine, glutathione, and proline could potentially participate in the alleviation of salinity stress. Therefore, algal presoaking is proved to be an effective technique to improve the growth of wheat seedlings under salt stress conditions. PMID:25436231

  12. Role of Ulva lactuca Extract in Alleviation of Salinity Stress on Wheat Seedlings

    PubMed Central

    Ibrahim, Wael M.; Ali, Refaat M.; Hemida, Khaulood A.; Sayed, Makram A.

    2014-01-01

    Seaweeds are potentially excellent sources of highly bioactive materials that could represent useful leads in the alleviation of salinity stress. The effects of presoaking wheat grains in water extract of Ulva lactuca on growth, some enzymatic activities, and protein pattern of salinized plants were investigated in this study. Algal presoaking of grains demonstrated a highly significant enhancement in the percentage of seed germination and growth parameters. The activity of superoxide dismutase (SOD) and catalase (CAT) increased with increasing the algal extract concentration while activity of ascorbate peroxidase (APX) and glutathione reductase (GR) was decreased with increasing concentration of algal extract more than 1% (w/v). The protein pattern of wheat seedling showed 12 newly formed bands as result of algal extract treatments compared with control. The bioactive components in U. lactuca extract such as ascorbic acid, betaine, glutathione, and proline could potentially participate in the alleviation of salinity stress. Therefore, algal presoaking is proved to be an effective technique to improve the growth of wheat seedlings under salt stress conditions. PMID:25436231

  13. Kinetin applications alleviate salt stress and improve the antioxidant composition of leaf extracts in Salvia officinalis.

    PubMed

    Tounekti, Taïeb; Hernández, Iker; Müller, Maren; Khemira, Habib; Munné-Bosch, Sergi

    2011-10-01

    A pot experiment was carried out under glasshouse conditions with common sage (Salvia officinalis L.) to investigate the interactive effects of salt stress and kinetin on growth attributes and the abundance of pigments, ions, phenolic diterpenes and α-tocopherol in leaf extracts of this species. The plants were subjected to the following four treatments: (i) control (nutrient solution), (ii) control + 10 μM kinetin, (iii) salt stress (nutrient solution + 100 mM NaCl), and (iv) salt stress + 10 μM kinetin. Kinetin was applied as a foliar fertilizer. Salt stress reduced water contents, photosynthetic activity and pigment contents of sage leaves. In addition, it increased Na(+) contents, and reduced those of Ca(2+) and K(+) in leaves. Salt stress reduced carnosic acid and 12-O-methyl carnosic acid contents in leaves, while it did not affect carnosol and α-tocopherol contents. Foliar applications of kinetin seemed to counterbalance or alleviate the stress symptoms induced by salinity, improving ion and pigment contents, while leaf phenolic diterpene (mainly carnosol) and α-tocopherol contents also increased in both control and NaCl-treated plants; still this effect was much more obvious in salt-treated plants. A similar effect was also obtained when plants were sprayed with KNO(3) or Ca(NO(3))(2), thus suggesting that kinetin effects were at least partly due to an improvement of ion homeostasis. Kinetin applications resulted in increased transcript levels of the isoprenoid and tocopherol biosynthetic genes, DXPRI and VTE2 and VTE4 in control plants, but not in NaCl-treated plants. We conclude that kinetin can alleviate the negative impact of salt on sage plants cultivated under arid environments with salinity problems. PMID:21856165

  14. Elevated CO2 alleviates high PAR and UV stress in the unicellular chlorophyte Dunaliella tertiolecta.

    PubMed

    García-Gómez, Candela; Gordillo, Francisco J L; Palma, Armando; Lorenzo, M Rosario; Segovia, María

    2014-09-01

    The effects of increased CO2 and irradiance on the physiological performance of the chlorophyte Dunaliella tertiolecta were studied at different PAR and UVR (UVA + UVB) irradiances, simulating the solar radiation at different depths, at present (390 ppmv, LC) and predicted CO2 levels for the year 2100 (1000 ppmv, HC). Elevated CO2 resulted in higher optimum and effective quantum yields (F(v)/F(m) and ϕPSII, respectively), electron transport rates (ETR) and specific growth rates (μ). Cell stress was alleviated in HC with respect to LC as evidenced by a decrease in reactive oxygen species (ROS) accumulation. DNA damage showed a 42-fold increase in cyclobutane-pyrimidine dimer (CPD) formation under the highest irradiance (1100 μmol quanta m(-2) s(-1)) in LC with respect to the lowest irradiance (200 μmol quanta m(-2) s(-1)). Photolyase (CII-PCD-PL) gene expression was upregulated under HC resulting in a drastic decrease in CPD accumulation to only 25% with respect to LC. Proliferating cell nuclear antigen (PCNA) accumulation was always higher in HC and the accumulation pattern indicated its involvement in repair or growth depending on the irradiance dose. The repressor of silencing (ROS1) was only marginally involved in the response, suggesting that photoreactivation was the most relevant mechanism to overcome UVR damage. Our results demonstrate that future scenarios of global change result in alleviation of irradiance stress by CO2-induced photoprotection in D. tertiolecta. PMID:25043601

  15. 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

  16. Proteomic study of β-aminobutyric acid-mediated cadmium stress alleviation in soybean.

    PubMed

    Hossain, Zahed; Makino, Takahiro; Komatsu, Setsuko

    2012-07-16

    The present study highlights the protective role of β-aminobutyric acid (BABA) in alleviating cadmium (Cd) stress in soybean. Proteomic analyses revealed that out of 66 differentially abundant protein spots in response to Cd challenge, 17 were common in the leaves of BABA-primed and non-primed plants. Oxygen-evolving enhancer protein 1 and ribulose bisphosphate carboxylase small chain 1 were detected in increase abundance in both groups of leaves. Among the 15 commonly decreased protein spots, the relative intensity levels of heat shock cognate 70-kDa protein, carbonic anhydrase, methionine synthase, and glycine dehydrogenase were partially restored after BABA treatment. Moreover, BABA priming significantly enhanced the abundance of the defense-related protein peroxiredoxin and glycolytic enzymes in response to Cd exposure. Additionally, the impact of Cd on the physiological state of BABA-primed and non-primed plants was analyzed using a biophoton technique. The finding of comparatively low biophoton emission in BABA-primed leaves under Cd stress indicates that these plants experienced less oxidative damage than that of non-primed plants. Proteomic study coupled with biophoton analysis reveals that BABA pretreatment helps the plants to combat Cd stress by modulating plants' defence mechanism as well as activating cellular detoxification system to protect the cells from Cd induced oxidative stress damages. PMID:22652489

  17. Black tea protects against hypertension-associated endothelial dysfunction through alleviation of endoplasmic reticulum stress

    PubMed Central

    San Cheang, Wai; Yuen Ngai, Ching; Yen Tam, Ye; Yu Tian, Xiao; Tak Wong, Wing; Zhang, Yang; Wai Lau, Chi; Chen, Zhen Yu; Bian, Zhao-Xiang; Huang, Yu; Ping Leung, Fung

    2015-01-01

    Hypertensive patients have been found to be associated with elevated levels of homocysteine, known as hyperhomocysteinemia. Homocysteine (Hcy) can induce endoplasmic reticulum (ER) stress in endothelial cells. This study aims to investigate whether black tea (BT) protects against hypertension-associated endothelial dysfunction through alleviation of ER stress. Rat aortae and cultured rat aortic endothelial cells were treated with Hcy, BT extract, and theaflavin-3,3’-digallate (TF3). Male Sprague Dawley rats were infused with angiotensin II (Ang II) to induce hypertension and orally administrated with BT extract at 15 mg/kg/day for 2 weeks. Hcy impaired endothelium-dependent relaxations of rat aortae and led to ER stress in endothelial cells, which were ameliorated by co-incubation of BT extract and TF3. The blood pressure of Ang II-infused rats and plasma Hcy level were normalized by BT consumption. Impaired endothelium-dependent relaxations in renal arteries, carotid arteries and aortae, and flow-mediated dilatations in third-order mesenteric resistance arteries were improved. Elevations of ER stress markers and ROS level, plus down-regulation of Hcy metabolic enzymes in aortae from Ang II-infused rats were prevented by BT treatment. Our data reveal the novel cardiovascular benefits of BT in ameliorating vascular dysfunctions, providing insight into developing BT into beneficial dietary supplements in hypertensive patients. PMID:25976123

  18. β-aminobutyric acid mediated drought stress alleviation in maize (Zea mays L.).

    PubMed

    Shaw, Arun K; Bhardwaj, Pardeep K; Ghosh, Supriya; Roy, Sankhajit; Saha, Suman; Sherpa, Ang R; Saha, Samir K; Hossain, Zahed

    2016-02-01

    The present study highlights the role of β-aminobutyric acid (BABA) in alleviating drought stress effects in maize (Zea mays L.). Chemical priming was imposed by pretreating 1-week-old plants with 600 μM BABA prior to applying drought stress. Specific activities of key antioxidant enzymes and metabolites (ascorbate and glutathione) levels of ascorbate-glutathione cycle were studied to unravel the priming-induced modulation of plant defense system. Furthermore, changes in endogenous ABA and JA concentrations as well as mRNA expressions of key genes involved in their respective biosynthesis pathways were monitored in BABA-primed (BABA+) and non-primed (BABA-) leaves of drought-challenged plants to better understand the mechanistic insights into the BABA-induced hormonal regulation of plant response to water-deficit stress. Accelerated stomatal closure, high relative water content, and less membrane damage were observed in BABA-primed leaves under water-deficit condition. Elevated APX and SOD activity in non-primed leaves found to be insufficient to scavenge all H2O2 and O2 (·-) resulting in oxidative burst as evident after histochemical staining with NBT and DAB. A higher proline accumulation in non-primed leaves also does not give much protection against drought stress. Increased GR activity supported with the enhanced mRNA and protein expressions might help the BABA-primed plants to maintain a high GSH pool essential for sustaining balanced redox status to counter drought-induced oxidative stress damages. Hormonal analysis suggests that in maize, BABA-potentiated drought tolerance is primarily mediated through JA-dependent pathway by the activation of antioxidant defense systems while ABA biosynthesis pathway also plays an important role in fine-tuning of drought stress response. PMID:26416125

  19. Naringin Alleviates Diabetic Kidney Disease through Inhibiting Oxidative Stress and Inflammatory Reaction

    PubMed Central

    Chen, Fenqin; Zhang, Ning; Ma, Xiaoyu; Huang, Ting; Shao, Ying; Wu, Can; Wang, Qiuyue

    2015-01-01

    Naringin, a flavanone glycoside extracted from Citrus grandis Osbeck, has a wide range of pharmacological effects. In the present study we aimed at demonstrating the protective effect of naringin against diabetic kidney disease (DKD) and elucidating its possible molecular mechanism underlying. The beneficial effect of naringin was assessed in rats with streptozotocin (STZ)-induced diabetes and high glucose-induced HBZY-1 cells. According to our results, first we found that naringin relieved kidney injury, improved renal function and inhibited collagen formation and renal interstitial fibrosis. Second, we confirmed that naringin restrained oxidative stress by activating Nrf2 antioxidant pathway. Moreover, the results suggested that naringin significantly resisted inflammatory reaction by inhibiting NF- κ B signaling pathway. Taken together, our results demonstrate that naringin effectively alleviates DKD, which provide theoretical basis for naringin clinically used to treatment of DKD. PMID:26619044

  20. Melatonin alleviates cadmium-induced cellular stress and germ cell apoptosis in testes.

    PubMed

    Ji, Yan-Li; Wang, Hua; Meng, Can; Zhao, Xian-Feng; Zhang, Cheng; Zhang, Ying; Zhao, Mei; Chen, Yuan-Hua; Meng, Xiu-Hong; Xu, De-Xiang

    2012-01-01

    Increasing evidence demonstrates that melatonin has an anti-apoptotic effect in somatic cells. However, whether melatonin can protect against germ cell apoptosis remains obscure. Cadmium (Cd) is a testicular toxicant and induces germ cell apoptosis. In this study, we investigated the effects of melatonin on Cd-evoked germ cell apoptosis in testes. Male ICR mice were intraperitoneally (i.p.) injected with melatonin (5 mg/kg) every 8 hr, beginning at 8 hr before CdCl(2) (2.0 mg/kg, i.p.). As expected, acute Cd exposure resulted in germ cell apoptosis in testes, as determined by terminal dUTP nick-end labeling (TUNEL) staining. Melatonin significantly alleviated Cd-induced testicular germ cell apoptosis. An additional experiment showed that spliced form of XBP-1, the target of the IRE-1 pathway, was significantly increased in testes of mice injected with CdCl(2). GRP78, an endoplasmic reticulum (ER) chaperone, and CHOP, a downstream target of the PERK pathway, were upregulated in testes of Cd-treated mice. In addition, acute Cd exposure significantly increased testicular eIF2α and JNK phosphorylation, indicating that the unfolded protein response (UPR) pathway was activated by CdCl(2). Interestingly, melatonin almost completely inhibited Cd-induced ER stress and the UPR in testes. In addition, melatonin obviously attenuated Cd-induced heme oxygenase (HO)-1 expression and protein nitration in testes. Taken together, these results suggest that melatonin alleviates Cd-induced cellular stress and germ cell apoptosis in testes. Melatonin may be useful as pharmacological agents to protect against Cd-induced testicular toxicity. PMID:21793897

  1. Nitrogen fertilizer improves boron phytoextraction by Brassica juncea grown in contaminated sediments and alleviates plant stress.

    PubMed

    Giansoldati, Virginia; Tassi, Eliana; Morelli, Elisabetta; Gabellieri, Edi; Pedron, Francesca; Barbafieri, Meri

    2012-06-01

    In this study we evaluated the effect of different fertilizer treatments on Brassica plants grown on boron-contaminated sediments. Experiments were conducted in the laboratory and on the lysimeter scale. At laboratory scale (microcosm), five different fertilizers were tested for a 35-d period. On the lysimeter scale, nitrogen fertilization was tested at three different doses and plants were allowed to grow until the end of the vegetative phase (70 d). Results showed that nitrogen application had effectively increased plant biomass production, while B uptake was not affected. Total B phytoextracted increased three-fold when the highest nitrogen dose was applied. Phytotoxicity on Brassica was evaluated by biochemical parameters. In plants grown in unfertilized B-contaminated sediments, the activity of antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX) and pyrogallol peroxidase (PPX) increased, whereas catalase (CAT) decreased with respect to control plants. Addition of N progressively mitigated the alteration of enzymatic activity, thus suggesting that N can aid in alleviating B-induced oxidative stress. SOD activity was restored to control levels just at the lowest N treatment, whereas the CAT inhibition was partially restored only at the highest one. N application also lowered the B-induced increase in APX and PPX activities. Increased glutathione reductase activity indicated the need to restore the oxidative balance of glutathione. Data also suggest a role of glutathione and phytochelatins in B defense mechanisms. Results suggest that the nitrogen fertilizer was effective in improving B phytoextraction by increasing Brassica biomass and by alleviating B-induced oxidative stress. PMID:22382070

  2. The unsaturation of phosphatidylglycerol in thylakoid membrane alleviates PSII photoinhibition under chilling stress.

    PubMed

    Sun, Xiao-lin; Yang, Sha; Wang, Li-Yan; Zhang, Qiu-Yu; Zhao, Shi-Jie; Meng, Qing-Wei

    2011-10-01

    Over-expression of chloroplast glycerol-3-phosphate acyltransferase gene (LeGPAT) in tomato increased cis-unsaturated fatty acid content in phosphatidylglycerol (PG) of the thylakoid membrane. Under chilling stress, the oxygen evolving activity, the maximal photochemical efficiency of PSII (F (v)/F (m)), and superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities decreased less in sense lines than in antisense lines compared to wild-type (WT) plants. Consistently, the relative electric conductivity, O⁻₂and H(2)O(2) contents in sense lines were lower than those of WT and antisense lines. The antisense lines with low level of unsaturated fatty acids in PG were extremely susceptible to photoinhibition of PSII and had a significant reduction in the D1 protein content of PSII reaction center under chilling stress. However, in the presence of streptomycin (SM), the degradation of D1 protein was faster in sense lines than in WT and antisense plants. These results suggested that, under chilling stress conditions, increasing cis-unsaturated fatty acids in PG through over-expression of LeGPAT can alleviate PSII photoinhibition by accelerating the repair of D1 protein and improving the activities of antioxidant enzymes in chloroplasts. PMID:21695527

  3. Rootstock alleviates PEG-induced water stress in grafted pepper seedlings: physiological responses.

    PubMed

    Penella, Consuelo; Nebauer, Sergio G; Bautista, Alberto San; López-Galarza, Salvador; Calatayud, Ángeles

    2014-06-15

    nitrate reductase activity in the roots was observed, mainly in plants grafted onto the sensitive rootstocks, as well as the ungrafted plants, and this was associated with the lessened flux to the leaves. This study suggests that PEG-induced water stress can be partially alleviated by using tolerant accessions as rootstocks. PMID:24877676

  4. Profiling of rutin-mediated alleviation of cadmium-induced oxidative stress in Zygophyllum fabago.

    PubMed

    Yildiztugay, Evren; Ozfidan-Konakci, Ceyda

    2015-07-01

    Zygophyllum fabago grows in arid, saline soil, or disturbed sites, such as former industrial or mining areas. This species is able to grow in coarse mineral substrates contaminated with heavy metals. To investigate the effects of the flavonoid rutin (Rtn) on certain heavy metal stress responses such as antioxidant defense systems and water status, seedlings were subjected to 100 and 200 μM CdCl2 treatment without or with 0.25 and 1 mM Rtn for 7 and 14 d (days). Cd stress decreased growth (RGR), water content (RWC), leaf osmotic potential (Ψ(Π)), and chlorophyll fluorescence, all of which could be partly alleviated by addition of Rtn. Activities of superoxide dismutase, peroxidase (POX), ascorbate peroxidase, and glutathione reductase increased within the first 7 d after exposure to Cd. However, failure of antioxidant defense in the scavenging of reactive oxygen species (ROS) was evidenced by an abnormal rise in superoxide anion radical ( O2(•-)) and hydrogen peroxide contents and a decline in hydroxyl radical (OH(•)) scavenging activity, resulting in enhancement of lipid peroxidation (TBARS) as a marker of Cd-induced oxidative stress. However, exogenously applied Rtn considerably improved the stress tolerance of plants via a reduction in Cd accumulation, modulation of POX activity, increase of proline (Pro) content, decrease in TBARS and ROS content and consequent lowering of oxidative damage of membrane. Overall, 0.25 and 1 mM Rtn could protect Z. fabago from the harmful effects of 100 μM Cd-induced oxidative stress throughout the experiment. PMID:24488808

  5. Alleviating effects of exogenous NO on tomato seedlings under combined Cu and Cd stress.

    PubMed

    Wang, Yi-Jun; Dong, Yu-Xiu; Wang, Juan; Cui, Xiu-Min

    2016-03-01

    To investigate the effect of NO on the different origin and regulation of oxidative stress of Cu and/or Cd, tomato seedlings were treated with Cu, Cd, or Cu + Cd in a nutrient solution culture system. The main effect of Cu(2+) was a significant reduction in root activity and nitrate reductase (NR) activity, which was similar to that under 50 μM Cd treatment, but promoted Cu accumulation. The supply of Cu under Cd treatment decreased Cd concentration, while not altered Cu concentration by contrast with Cu treatment, which is suggestive of a replacement of Cu(2+) with Cd(2+) and effective decrease in the boiotoxicity of 50 μM Cd(2+) to tomato seedlings. However, NO alleviated the restriction to NR activity significantly and made the biomass of tomato seedlings recover under Cd treatment, and also increased root activity under Cu and Cu + Cd treatment. Exogenous NO markedly reduced the absorption and transportation of Cu but did not obviously change the translocation of Cd to the aboveground parts under Cu + Cd treatment. Both metals induced lipid peroxidation via the decreasing activation of antioxidant enzymes. The antioxidant enzyme system worked differently under Cu, Cd, or Cu + Cd stress. The activities of peroxidase (POD) and catalase (CAT) were higher under single Cd stress than under the control. Meanwhile, Cu + Cd treatment decreased the activities of POD, superoxide dismutase (SOD), and ascorbic acid peroxidase (APX). Exogenous NO increased POD and SOD activities in the leaves and roots, and CAT activity in the roots under combined Cu and Cd stress. These results suggest that a different response and regulation mechanism that involves exogenous NO is present in tomato seedlings under Cu and Cd stress. PMID:26545885

  6. Reduction in Embryonic Malformations and Alleviation of Endoplasmic Reticulum Stress by Nitric Oxide Synthase Inhibition in Diabetic Embryopathy

    PubMed Central

    Eckert, Richard L.; Reece, E. Albert

    2012-01-01

    Maternal diabetes-induced neural tube defects (NTDs) are associated with increased programmed cell death (apoptosis) in the neuroepithelium, which is related to intracellular nitrosative stress. To alleviate nitrosative stress, diabetic pregnant mice were fed via gavage an inhibitor of nitric oxide (NO) synthase (NOS) 2, L-N6-(1-iminoethyl)-lysine (L-NIL; 80 mg/kg), once a day from embryonic (E) day 7.5 to 9.5 during early stages of neurulation. The treatment significantly reduced NTD rate in the embryos, compared with that in vehicle (normal saline)-treated diabetic group. In addition to alleviation of nitrosative stress, endoplasmic reticulum (ER) stress was also ameliorated, assessed by quantification of associated factors. Apoptosis was reduced, indicated by caspase 8 activation. These results show that nitrosative stress is important in diabetes-induced NTDs via exacerbating ER stress, leading to increased apoptosis. Oral treatment with NOS-2 inhibitor alleviates nitrosative and ER stress, decreases apoptosis, and reduces NTDs in the embryos, providing information for further interventional studies to reduce diabetes-associated birth defects. PMID:22534324

  7. Polyhydroxyfullerene Binds Cadmium Ions and Alleviates Metal-Induced Oxidative Stress in Saccharomyces cerevisiae

    PubMed Central

    Pradhan, Arunava; Pinheiro, José Paulo; Seena, Sahadevan; Pascoal, Cláudia

    2014-01-01

    The water-soluble polyhydroxyfullerene (PHF) is a functionalized carbon nanomaterial with several industrial and commercial applications. There have been controversial reports on the toxicity and/or antioxidant properties of fullerenes and their derivatives. Conversely, metals have been recognized as toxic mainly due to their ability to induce oxidative stress in living organisms. We investigated the interactive effects of PHF and cadmium ions (Cd) on the model yeast Saccharomyces cerevisiae by exposing cells to Cd (≤5 mg liter−1) in the absence or presence of PHF (≤500 mg liter−1) at different pHs (5.8 to 6.8). In the absence of Cd, PHF stimulated yeast growth up to 10.4%. Cd inhibited growth up to 79.7%, induced intracellular accumulation of reactive oxygen species (ROS), and promoted plasma membrane disruption in a dose- and pH-dependent manner. The negative effects of Cd on growth were attenuated by the presence of PHF, and maximum growth recovery (53.8%) was obtained at the highest PHF concentration and pH. The coexposure to Cd and PHF decreased ROS accumulation up to 36.7% and membrane disruption up to 30.7% in a dose- and pH-dependent manner. Two mechanisms helped to explain the role of PHF in alleviating Cd toxicity to yeasts: PHF decreased Cd-induced oxidative stress and bound significant amounts of Cd in the extracellular medium, reducing its bioavailability to the cells. PMID:25038095

  8. Strawberry consumption alleviates doxorubicin-induced toxicity by suppressing oxidative stress.

    PubMed

    Giampieri, Francesca; Alvarez-Suarez, Jose M; Gasparrini, Massimiliano; Forbes-Hernandez, Tamara Y; Afrin, Sadia; Bompadre, Stefano; Rubini, Corrado; Zizzi, Antonio; Astolfi, Paola; Santos-Buelga, Celestino; González-Paramás, Ana M; Quiles, Josè L; Mezzetti, Bruno; Battino, Maurizio

    2016-08-01

    Doxorubicin (Dox), one of the most used chemotherapeutic agents, is known to generate oxidative stress and block DNA synthesis, which result in severe dose-limiting toxicity. A strategy to protect against Dox toxic effects could be to use dietary antioxidants of which fruits and vegetable are a rich source. In this context, strawberry consumption is associated with the maintenance of good health and the prevention of several diseases, thanks to the antioxidant capacities of its bioactive compounds. The aim of the present study was to evaluate the protective effects of strawberry consumption against oxidative stress induced by Dox in rats. Animals were fed with strawberry enriched diet (15% of the total calories) for two months and Dox (10 mg/kg; i.p.) was injected at the end of the experimental period. Strawberry consumption significantly inhibited ROS production and oxidative damage biomarkers accumulation in plasma and liver tissue and alleviated histopathological changes in rat livers treated with Dox. The reduction of antioxidant enzyme activities was significantly mitigated after strawberry consumption. In addition, strawberry enriched diet ameliorated liver mitochondrial antioxidant levels and functionality. In conclusion, strawberry intake protects against Dox-induced toxicity, at plasma, liver and mitochondrial levels thanks to its high contents of bioactive compounds. PMID:27286747

  9. Transient thermal stress recovery for structural models

    NASA Technical Reports Server (NTRS)

    Walls, William

    1992-01-01

    A method for computing transient thermal stress vectors from temperature vectors is described. The three step procedure involves the use of NASTRAN to generate an influence coefficient matrix which relates temperatures to stresses in the structural model. The transient thermal stresses are then recovered and sorted for maximum and minimum values. Verification data for the procedure is also provided.

  10. Thermal stress studies using optical holographic interferometry

    NASA Technical Reports Server (NTRS)

    Harris, W. J.; Woods, D. C.

    1974-01-01

    The application of holography to thermal stress studies is discussed. Interference fringes as produced by holograms and their interpretation are reviewed in relation to workpiece displacement. Three potential mechanisms are given to explain thermal displacement as detected by holographic methods. Results of some thermal stressing studies are reported, including tests on a live rocket motor.

  11. Exogenous glycinebetaine alleviates the detrimental effect of Cd stress on perennial ryegrass.

    PubMed

    Lou, Yanhong; Yang, Yong; Hu, Longxing; Liu, Hongmei; Xu, Qingguo

    2015-08-01

    Glycinebetaine (GB) is an important organic osmolyte that accumulates in many plant species in response to abiotic stresses including heavy metals. The objective of this study was to investigate whether exogenous GB would ameliorate the adverse effect of cadmium (Cd) stress on perennial ryegrass (Lolium perenne). Fifty-three days old seedlings were exposed to hydroponic culture for 7 days with six treatments: T1 (control), T2 (0 mM Cd + 20 mM GB), T3 (0 mM Cd + 50 mM GB), T4 (0.5 mM Cd + 0 mM GB), T5 (0.5 mM Cd + 20 mM GB), T6 (0.5 mM Cd + 50 mM GB). Cd stress resulted in a remarkable decrease in turf quality, vertical shoot growth rate (VSGR), normalized relative transpiration (NRT) and Chlorophyll (Chl) content; with significant increases in electric conductivity (EL), malondialdehyde (MDA) content, superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) activity, oxalic and tartaric acid content. Exogenous application of GB decreased EL and MDA content in Cd stressed plants, and increased turf quality, VSGR, NRT, Chl content, SOD, CAT, POD activity, oxalic, tartaric acid content, and the gene expression level of SOD and POD when compared with Cd stressed without GB. Perennial ryegrass with 20 mM GB application suppressed the Cd accumulation in both shoots and roots. A lower translocation factor of Cd was found in GB treated plants than non-GB treated plants, and the lowest translocation factor was observed in the 20 mM GB application. These results suggested that GB could alleviate the detrimental effect of Cd on perennial ryegrass and the amelioration was mainly related to the elevation in SOD, CAT, and POD at enzyme and gene expression levels, which reduced Cd content in shoots and improved cell membrane stability by reducing oxidation of membrane lipids. These findings lead us to conclude that application of GB with 20 mM is the best strategy to ameliorate the detrimental impacts of Cd stress on perennial ryegrass. PMID:26135319

  12. Hand immersion in cold water alleviating physiological strain and increasing tolerance to uncompensable heat stress.

    PubMed

    Khomenok, Gennadi A; Hadid, Amir; Preiss-Bloom, Orahn; Yanovich, Ran; Erlich, Tomer; Ron-Tal, Osnat; Peled, Amir; Epstein, Yoram; Moran, Daniel S

    2008-09-01

    The current study examines the use of hand immersion in cold water to alleviate physiological strain caused by exercising in a hot climate while wearing NBC protective garments. Seventeen heat acclimated subjects wearing a semi-permeable NBC protective garment and a light bulletproof vest were exposed to a 125 min exercise-heat stress (35 degrees C, 50% RH; 5 km/h, 5% incline). The heat stress exposure routine included 5 min rest in the chamber followed by two 50:10 min work-rest cycles. During the control trial (CO), there was no intervention, whilst in the intervention condition the subjects immersed their hands and forearms in a 10 degrees C water bath (HI). The results demonstrated that hand immersion in cold water significantly reduced physiological strain. In the CO exposure during the first and second resting periods, the average rectal temperature (T (re)) practically did not decrease. With hand immersion, the mean (SD) T (re) decreased by 0.45 (0.05 degrees C) and 0.48 degrees C (0.06 degrees C) during the first and second rest periods respectively (P < 0.005). Significant decreases in skin temperature, sweat rate, heart rate, and heat storage was also noted in the HI vs. the CO trials. Tolerance time in the HI exposure were longer than in the CO exposure (only 12 subjects in the CO trial endured the entire heat exposure session, as opposed to all 17 subjects in the HI group). It is concluded that hand immersion in cold water for 10 min is an effective method for decreasing the physiological strain caused by exercising under heat stress while wearing NBC protective garments. The method is convenient, simple, and allows longer working periods in hot or contaminated areas with shorter resting periods. PMID:18478254

  13. Selenium and vitamin E together improve intestinal epithelial barrier function and alleviate oxidative stress in heat-stressed pigs.

    PubMed

    Liu, Fan; Cottrell, Jeremy J; Furness, John B; Rivera, Leni R; Kelly, Fletcher W; Wijesiriwardana, Udani; Pustovit, Ruslan V; Fothergill, Linda J; Bravo, David M; Celi, Pietro; Leury, Brian J; Gabler, Nicholas K; Dunshea, Frank R

    2016-07-01

    What is the central question of this study? Oxidative stress may play a role in compromising intestinal epithelial barrier integrity in pigs subjected to heat stress, but it is unknown whether an increase of dietary antioxidants (selenium and vitamin E) could alleviate gut leakiness in heat-stressed pigs. What is the main finding and its importance? Levels of dietary selenium (1.0 p.p.m.) and vitamin E (200 IU kg(-1) ) greater than those usually recommended for pigs reduced intestinal leakiness caused by heat stress. This finding suggests that oxidative stress plays a role in compromising intestinal epithelial barrier integrity in heat-stressed pigs and also provides a nutritional strategy for mitigating these effects. Heat stress compromises the intestinal epithelial barrier integrity of mammals through mechanisms that may include oxidative stress. Our objective was to test whether dietary supplementation with antioxidants, selenium (Se) and vitamin E (VE), protects intestinal epithelial barrier integrity in heat-stressed pigs. Female growing pigs (n = 48) were randomly assigned to four diets containing from 0.2 p.p.m. Se and 17 IU kg(-1) VE (control, National Research Council recommended) to 1.0 p.p.m. Se and 200 IU kg(-1) VE for 14 days. Six pigs from each dietary treatment were then exposed to either thermoneutral (20°C) or heat-stress conditions (35°C 09.00-17.00 h and 28°C overnight) for 2 days. Transepithelial electrical resistance and fluorescein isothiocyanate-dextran (4 kDa; FD4) permeability were measured in isolated jejunum and ileum using Ussing chambers. Rectal temperature, respiratory rate and intestinal HSP70 mRNA abundance increased (all P < 0.001), and respiratory alkalosis occurred, suggesting that pigs were heat stressed. Heat stress also increased FD4 permeability and decreased transepithelial electrical resistance (both P < 0.01). These changes were associated with changes indicative of oxidative stress, a decreased

  14. Treadmill exercise alleviates chronic mild stress-induced depression in rats

    PubMed Central

    Lee, Taeck-Hyun; Kim, Kijeong; Shin, Mal-Soon; Kim, Chang-Ju; Lim, Baek-Vin

    2015-01-01

    Depression is a major cause of disability and one of the most common public health problems. In the present study, antidepressive effect of treadmill exercise on chronic mild stress (CMS)-induced depression in rats was investigated. For this, sucrose intake test, immunohistochemistry for 5-bromo-2′-deoxyuridine, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining, and Western blot analysis for brain-derived neurotrophic factor, cyclic adenosine monophosphate response element binding protein, and endothelial nitric oxide synthase were conducted. Following adaptation to the animal vivarium and two baseline fluid intake tests, the animals were divided into four groups: the control group, the CMS-induced depression group, the CMS-induced depression and exercise group, and the CMS-induced depression and fluoxetine-treated group. The animals in the CMS groups were exposed to the CMS conditions for 8 weeks and those in the control group were exposed to the control conditions for 8 weeks. After 4 weeks of CMS, the rats in the CMS-induced depression and exercise group were made to run on a motorized treadmill for 30 min once a day for 4 weeks. In the present results, treadmill exercise alleviated CMS-induced depressive symptoms. Treadmill exercise restored sucrose consumption, increased cell proliferation, and decreased apoptotic cell death. The present results suggest the possibility that exercise may improve symptoms of depression. PMID:26730380

  15. Distinct physiological responses of tomato and cucumber plants in silicon-mediated alleviation of cadmium stress

    PubMed Central

    Wu, Jiawen; Guo, Jia; Hu, Yanhong; Gong, Haijun

    2015-01-01

    The alleviative effects of silicon (Si) on cadmium (Cd) toxicity were investigated in cucumber (Cucumis sativus L.) and tomato (Solanum lycopersicum L.) grown hydroponically. The growth of both plant species was inhibited by 100 μM Cd, but Si application counteracted the adverse effects on growth. Si application significantly decreased the Cd concentrations in shoots of both species and roots of cucumber. The root-to-shoot transport of Cd was depressed by added Si in tomato whereas it was increased by added Si in cucumber. The total content of organic acids was decreased in tomato leaves but increased in cucumber roots and leaves by Si application under Cd stress. Si application also increased the cell wall polysaccharide levels in the roots of both species under Cd toxicity. Si-mediated changes in levels of organic acids and cell wall polysaccharides might contribute to the differences in Cd transport in the two species. In addition, Si application also mitigated Cd-induced oxidative damage in both species. The results indicate that there were different mechanisms for Si-mediated decrease in shoot Cd accumulation: in tomato, Si supply decreased root-to-shoot Cd transport; whereas in cucumber, Si supply reduced the Cd uptake by roots. It is suggested that Si-mediated Cd tolerance is associated with different physiological responses in tomato and cucumber plants. PMID:26136764

  16. Prepubertal exposure to genistein alleviates di-(2-ethylhexyl) phthalate induced testicular oxidative stress in adult rats.

    PubMed

    Zhang, Lian-Dong; Li, He-Cheng; Chong, Tie; Gao, Ming; Yin, Jian; Fu, De-Lai; Deng, Qian; Wang, Zi-Ming

    2014-01-01

    Di-(2-ethylhexyl) phthalate (DEHP) is the most widely used plastizer in the world and can suppress testosterone production via activation of oxidative stress. Genistein (GEN) is one of the isoflavones ingredients exhibiting weak estrogenic and potentially antioxidative effects. However, study on reproductive effects following prepubertal multiple endocrine disrupters exposure has been lacking. In this study, DEHP and GEN were administrated to prepubertal male Sprague-Dawley rats by gavage from postnatal day 22 (PND22) to PND35 with vehicle control, GEN at 50 mg/kg body weight (bw)/day (G), DEHP at 50, 150, 450 mg/kg bw/day (D50, D150, D450) and their mixture (G + D50, G + D150, G + D450). On PND90, general morphometry (body weight, AGD, organ weight, and organ coefficient), testicular redox state, and testicular histology were studied. Our results indicated that DEHP could significantly decrease sex organs weight, organ coefficient, and testicular antioxidative ability, which largely depended on the dose of DEHP. However, coadministration of GEN could partially alleviate DEHP-induced reproductive injuries via enhancement of testicular antioxidative enzymes activities, which indicates that GEN has protective effects on DEHP-induced male reproductive system damage after prepubertal exposure and GEN may have promising future in its curative antioxidative role for reproductive disorders caused by other environmental endocrine disruptors. PMID:25530965

  17. Prepubertal Exposure to Genistein Alleviates Di-(2-ethylhexyl) Phthalate Induced Testicular Oxidative Stress in Adult Rats

    PubMed Central

    Zhang, Lian-Dong; Li, He-Cheng; Chong, Tie; Gao, Ming; Yin, Jian; Fu, De-Lai; Deng, Qian; Wang, Zi-Ming

    2014-01-01

    Di-(2-ethylhexyl) phthalate (DEHP) is the most widely used plastizer in the world and can suppress testosterone production via activation of oxidative stress. Genistein (GEN) is one of the isoflavones ingredients exhibiting weak estrogenic and potentially antioxidative effects. However, study on reproductive effects following prepubertal multiple endocrine disrupters exposure has been lacking. In this study, DEHP and GEN were administrated to prepubertal male Sprague-Dawley rats by gavage from postnatal day 22 (PND22) to PND35 with vehicle control, GEN at 50 mg/kg body weight (bw)/day (G), DEHP at 50, 150, 450 mg/kg bw/day (D50, D150, D450) and their mixture (G + D50, G + D150, G + D450). On PND90, general morphometry (body weight, AGD, organ weight, and organ coefficient), testicular redox state, and testicular histology were studied. Our results indicated that DEHP could significantly decrease sex organs weight, organ coefficient, and testicular antioxidative ability, which largely depended on the dose of DEHP. However, coadministration of GEN could partially alleviate DEHP-induced reproductive injuries via enhancement of testicular antioxidative enzymes activities, which indicates that GEN has protective effects on DEHP-induced male reproductive system damage after prepubertal exposure and GEN may have promising future in its curative antioxidative role for reproductive disorders caused by other environmental endocrine disruptors. PMID:25530965

  18. Treadmill exercise alleviates chronic mild stress-induced depression in rats.

    PubMed

    Lee, Taeck-Hyun; Kim, Kijeong; Shin, Mal-Soon; Kim, Chang-Ju; Lim, Baek-Vin

    2015-12-01

    Depression is a major cause of disability and one of the most common public health problems. In the present study, antidepressive effect of treadmill exercise on chronic mild stress (CMS)-induced depression in rats was investigated. For this, sucrose intake test, immunohistochemistry for 5-bromo-2'-deoxyuridine, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining, and Western blot analysis for brain-derived neurotrophic factor, cyclic adenosine monophosphate response element binding protein, and endothelial nitric oxide synthase were conducted. Following adaptation to the animal vivarium and two baseline fluid intake tests, the animals were divided into four groups: the control group, the CMS-induced depression group, the CMS-induced depression and exercise group, and the CMS-induced depression and fluoxetine-treated group. The animals in the CMS groups were exposed to the CMS conditions for 8 weeks and those in the control group were exposed to the control conditions for 8 weeks. After 4 weeks of CMS, the rats in the CMS-induced depression and exercise group were made to run on a motorized treadmill for 30 min once a day for 4 weeks. In the present results, treadmill exercise alleviated CMS-induced depressive symptoms. Treadmill exercise restored sucrose consumption, increased cell proliferation, and decreased apoptotic cell death. The present results suggest the possibility that exercise may improve symptoms of depression. PMID:26730380

  19. Contribution to encyclopedia of thermal stresses

    NASA Astrophysics Data System (ADS)

    Taler, Jan; Ocłoń, Pawel

    2015-06-01

    This paper lists the contribution in the international interdisciplinary reference - Encyclopedia of Thermal Stresses (ETS). The ETS, edited by the world famous expert in field of Thermal Stresses - Professor Richard Hetnarski from Rochester Institute of Technology, was published by Springer in 2014. This unique Encyclopedia, subdivided into 11 volumes is the most extensive and comprehensive work related to the Thermal Stresses topic. The entries were carefully prepared by specialists in the field of thermal stresses, elasticity, heat conduction, optimization among others. The Polish authors' contribution within this work is significant; over 70 entries were prepared by them.

  20. Atorvastatin alleviates experimental diabetic cardiomyopathy by suppressing apoptosis and oxidative stress.

    PubMed

    Abdel-Hamid, Ahmed A M; Firgany, Alaa El-Din L

    2015-10-01

    Diabetic hazard on the myocardium is a complication of diabetes that intensifies its morbidity and increases its mortality. Therefore, alleviation of diabetic cardiomyopathy (DCM) by a reliable drug remains a matter of interest in experimental research. The aim of this study was to explore the structural alterations in the myocardium induced by atorvastatin (ATOR) in DCM, induced by streptozotocin (STZ), along with the associated changes occurring in apoptosis and oxidative stress markers. Thirty-two rats were divided into four groups; group A (control), group B (non-diabetic, received ATOR, orally, 50 mg/kg daily), group C (DCM, received STZ 70 mg/kg, single i.p. injection) and group D (DCM + ATOR). After 6 weeks, left ventricle (LV) specimens were prepared for histological and immunohistochemical study by hematoxlyin and eosin, Masson`s trichrome, anti-cleaved caspase-3 stains as well as for assays of oxidative stress markers. All data were measured morphometrically and statistically analyzed. The DCM group showed disorganization of the cardiomyocytes, interstitial edema, numerous fibroblasts, significant increases in the collagen volume fraction (p < 0.001), cleaved caspase-3 expression % area (p < 0.001) and, malondialdehyde in blood (p < 0.001), in LV (p < 0.05) compared with DCM + ATOR group. The latter has LV wall thickness, relative heart weight and antioxidant activities nearly similar to the control, independent from ATOR lipid-lowering effect. Therefore, ATOR can preserve myocardial structure in DCM nearly similar to normal. This may be achieved by suppressing apoptosis that parallels the correction of the antioxidant markers, which can be considered as non-lipid lowering benefit of statins. PMID:26041576

  1. Arbuscular mycorrhizal fungi alleviate oxidative stress induced by ADOR and enhance antioxidant responses of tomato plants.

    PubMed

    García-Sánchez, Mercedes; Palma, José Manuel; Ocampo, Juan Antonio; García-Romera, Inmaculada; Aranda, Elisabet

    2014-03-15

    The behaviour of tomato plants inoculated with arbuscular mycorrhizal (AM) fungi grown in the presence of aqueous extracts from dry olive residue (ADOR) was studied in order to understand how this symbiotic relationship helps plants to cope with oxidative stress caused by ADOR. The influence of AM symbiosis on plant growth and other physiological parameters was also studied. Tomato plants were inoculated with the AM fungus Funneliformis mosseae and were grown in the presence of ADOR bioremediated and non-bioremediated by Coriolopsis floccosa and Penicillium chrysogenum-10. The antioxidant response as well as parameters of oxidative damage were examined in roots and leaves. The data showed a significant increase in the biomass of AM plant growth in the presence of ADOR, regardless of whether it was bioremediated. The establishment and development of the symbiosis were negatively affected after plants were exposed to ADOR. No differences were observed in the relative water content (RWC) or PS II efficiency between non-AM and AM plants. The increase in the enzymatic activities of superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6) and glutathione-S-transferase (GST; EC 2.5.1.18) were simultaneous to the reduction of MDA levels and H2O2 content in AM root growth in the presence of ADOR. Similar H2O2 levels were observed among non-AM and AM plants, although only AM plants showed reduced lipid peroxidation content, probably due to the involvement of antioxidant enzymes. The results highlight how the application of both bioremediated ADOR and AM fungi can alleviate the oxidative stress conditions, improving the growth and development of tomato plants. PMID:24594394

  2. [Alleviation of salt stress during maize seed germination by presoaking with exogenous sugar].

    PubMed

    Zhao, Ying; Yang, Ke-jun; Li, Zuo-tong; Zhao, Chang-jiang; Xu, Jing-yu; Hu, Xue- wei; Shi, Xin-xin; Ma, Li-feng

    2015-09-01

    The maize variety Kenyu 6 was used to study the effects of exogenous glucose (Glc) and sucrose (Suc) on salt tolerance of maize seeds at germination stage under 150 mmol · L(-1) NaCl treatment. Results showed that under salt stress condition, 0.5 mmol · L(-1) exogenous Glc and Suc presoaking could promote seed germination and early seedling growth. Compared with the salt treatment, Glc presoaking increased the shoot length, radicle length and corresponding dry mass up to 1.5, 1.3, 2.1 and 1.8 times, and those of the Suc presoaking treatment increased up to 1.7, 1.3. 2.7 and 1.9 times, respectively. Exogenous Glc and Suc presoaking resulted in decreased levels of thiobarbituric acid reactive substances (TBARS) and hydrogen peroxide (H2O2) content of maize shoot under salt stress, which were lowered by 24.9% and 20.6% respectively. Exogenous Glc and Suc presoaking could increase the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione peroxidase (GPX), glutathione reductase (GR) and induce glucose-6-phosphate dehydrogenase (G6PDH) activity of maize shoot under salt stress. Compared with the salt treatment. Glc presoaking increased the activity of SOD, APX, GPX, GR and G6PDH by 66.2%, 62.9%, 32.0%, 38.5% and 50.5%, and those of the Suc presoaking increased by 67.5%, 59.8%, 30.0%, 38.5% and 50.4%, respectively. Glc and Suc presoaking also significantly increased the contents of ascorbic acid (ASA) and glutathione (GSH), ASA/DHA and GSH/GSSG. The G6PDH activity was found closely related with the strong antioxidation capacity induced by exogenous sugars. In addition, Glc and Suc presoaking enhanced K+/Na+ in maize shoot by 1.3 and 1.4 times of water soaking salt treatment, respectively. These results indicated that exogenous Glc and Suc presoaking could improve antioxidation capacity of maize seeds and maintain the in vivo K+/Na+ ion balance to alleviate the inhibitory effect of salt stress on maize seed germination. PMID:26785556

  3. Bacillus amyloliquefaciens supplementation alleviates immunological stress in lipopolysaccharide-challenged broilers at early age.

    PubMed

    Li, Y; Zhang, H; Chen, Y P; Yang, M X; Zhang, L L; Lu, Z X; Zhou, Y M; Wang, T

    2015-07-01

    This study was conducted to investigate the effect of Bacillus amyloliquefaciens ( BA: ) on the immune function of broilers challenged with lipopolysaccharide ( LPS: ). 192 one-day-old male Arbor Acre broiler chickens were randomly distributed into four treatments: 1) broilers fed a basal diet; 2) broilers fed a basal diet supplemented with BA; 3) LPS-challenged broilers fed a basal diet; and 4) LPS-challenged broilers fed a basal diet supplemented with BA. Each treatment consisted of six replicates with eight broilers per replicate. Broilers were intraperitoneally injected with either 500 μg LPS per kg body weight or sterile saline at 16, 18 and 20 d of age. LPS decreased the average daily gain ( ADG: , P = 0.001) and average daily feed intake (P = 0.001). The decreased ADG (P = 0.009) and increased feed conversion ratio (P = 0.047) in LPS-challenged broilers were alleviated by BA. LPS increased the relative spleen weight (P = 0.001). Relative spleen (P = 0.014) and bursa (P = 0.024) weights in the LPS-challenged broilers were reduced by BA. LPS increased white blood cell ( WBC: ) numbers (P = 0.001). However, the WBC numbers (P = 0.042) and the ratio of lymphocytes to WBC (P = 0.020) in LPS-challenged broilers were decreased with BA treatment. LPS decreased plasma lysozyme activity (P = 0.001), but increased concentrations of plasma corticosterone (P = 0.012) and IL-2 (P = 0.020). In contrast, BA increased lysozyme activity in plasma (P = 0.040). LPS increased mRNA abundances of splenic toll-like receptor 4 (P = 0.046), interferon γ (P = 0.008), IL-1β (P = 0.045) and IL-6, (P = 0.006). IL-2 (P = 0.014) and IL-6 (P = 0.074) mRNA abundances in LPS-challenged broilers were reduced by BA, although BA had an opposite effect for IL-10 mRNA expression in those broilers (P = 0.004). In conclusion, BA supplementation could partially alleviate the compromised growth performance and immune status of broilers under immune stress induced by LPS challenge at early age. PMID

  4. Oxidative stress-related lung dysfunction by chromium(VI): alleviation by Citrus aurantium L.

    PubMed

    Soudani, Nejla; Rafrafi, Moez; Ben Amara, Ibtissem; Hakim, Ahmed; Troudi, Afef; Zeghal, Khaled Mounir; Ben Salah, Hichem; Boudawara, Tahia; Zeghal, Najiba

    2013-06-01

    Chromium(VI), a very strong oxidant, causes high cytotoxicity through oxidative stress in tissue systems. Our study investigated the potential ability of ethanolic Citrus aurantium L., family Rutaceae extract, used as a nutritional supplement, to alleviate lung oxidative damage induced by Cr(VI). A high-performance liquid chromatography coupled with a mass spectrometer method was developed to separate and identify flavonoids in C. aurantium L. Six flavonoids were identified, as (1) poncirin, (2) naringin, (3) naringenin, (4) quercetin, (5) isosinensetin, and (6) tetramethyl-o-isoscutellarein. Adult Wistar rats, used in this study, were divided into six groups of six animals each: group I served as controls which received standard diet, group II received via drinking water K2Cr2O7 alone (700 ppm), groups III and IV were pretreated for 10 days with ethanol extract of C. aurantium L. at doses of 100 and 300 mg/kg body weight/day, respectively, and then K2Cr2O7 was administrated during 3 weeks, and groups V and VI received during 10 days only C. aurantium L. ethanol extract at doses of 100 and 300 mg/kg/day, respectively. Ethanol extract of C. aurantium L. was administered orally. Rats exposed to Cr(VI) showed in lung an increase in malondialdehyde and protein carbonyl levels and a decrease in sulflydryl content, glutathione, nonprotein thiol, and vitamins C and E levels. Decreases in enzyme activities such as in Na(+)K(+) ATPase, catalase, glutathione peroxidase, and superoxide dismutase were noted. Pretreatment with C. aurantium L. of chromium-treated rats ameliorated all biochemical parameters. Lung histological studies confirmed the biochemical parameters and the beneficial role of C. aurantium L. PMID:22972417

  5. Involvement of ethylene in gibberellic acid-induced sulfur assimilation, photosynthetic responses, and alleviation of cadmium stress in mustard.

    PubMed

    Masood, Asim; Khan, M Iqbal R; Fatma, Mehar; Asgher, Mohd; Per, Tasir S; Khan, Nafees A

    2016-07-01

    The role of gibberellic acid (GA) or sulfur (S) in stimulation of photosynthesis is known. However, information on the involvement of ethylene in GA-induced photosynthetic responses and cadmium (Cd) tolerance is lacking. This work shows that ethylene is involved in S-assimilation, photosynthetic responses and alleviation of Cd stress by GA in mustard (Brassica juncea L.). Plants grown with 200 mg Cd kg(-1) soil were less responsive to ethylene despite high ethylene evolution and showed photosynthetic inhibition. Plants receiving 10 μM GA spraying plus 100 mg S kg(-1) soil supplementation exhibited increased S-assimilation and photosynthetic responses under Cd stress. Application of GA plus S decreased oxidative stress of plants grown with Cd and limited stress ethylene formation to the range suitable for promoting sulfur use efficiency (SUE), glutathione (GSH) production and photosynthesis. The role of ethylene in GA-induced S-assimilation and reversal of photosynthetic inhibition by Cd was substantiated by inhibiting ethylene biosynthesis with the use of aminoethoxyvinylglycine (AVG). The suppression of S-assimilation and photosynthetic responses by inhibiting ethylene in GA plus S treated plants under Cd stress indicated the involvement of ethylene in GA-induced S-assimilation and Cd stress alleviation. The outcome of the study is important to unravel the interaction between GA and ethylene and their role in Cd tolerance in plants. PMID:26998941

  6. Penehyclidine Hydrochloride Pretreatment Ameliorates Rhabdomyolysis-Induced AKI by Activating the Nrf2/HO-1 Pathway and Allevi-ating Endoplasmic Reticulum Stress in Rats

    PubMed Central

    Zhao, Wei; Huang, XuDong; Zhang, LiXia; Yang, XinJun; Wang, LiHui; Chen, YunShuang; Wang, JingHua; Wu, GuangLi

    2016-01-01

    Acute kidney injury (AKI) is one of the most severe complications of rhabdomyolysis (RM). The underlying mechanisms and potential preventions need to be investigated. Penehyclidine hydrochloride (PHC) was reported to ameliorate renal ischemia-reperfusion injury, but the effect of PHC on RM-reduced AKI is unknown. In this study, we established a rat model of RM-induced AKI using an intramuscular glycerol injection in the hind limbs. Rats were pretreated with PHC before the glycerol injection, and the heme oxygenase-1 (HO-1) inhibitor ZnPP was introduced to evaluate the effect of HO-1 on RM-induced AKI. PHC pretreatment ameliorated the pathological renal injury and renal dysfunction, and decreased the renal apoptosis rate in RM-induced AKI. PHC significantly up-regulated HO-1 expression, increased HO-1 enzymatic activity and decreased the accumulation of myoglobin in renal tissues. This effect was partly inhibited by ZnPP. PHC pretreatment also effectively up-regulated nuclear factor erythroid 2-related factor 2 (Nrf2) and down-regulated glucose regulated protein 78 (GRP78) and caspase-12 at both the gene and protein levels. These results suggest that the protective effects of PHC pretreatment on RM-induced AKI occur at least in part through activating the Nrf2/HO-1 pathway and alleviating endoplasmic reticulum stress (ERS) in rat renal tissues. PMID:26987113

  7. Yeast Culture and Vitamin E Supplementation Alleviates Heat Stress in Dairy Goats

    PubMed Central

    Wang, Lizhi; Wang, Zhisheng; Zou, Huawei; Peng, Quanhui

    2016-01-01

    This study was conducted to determine and compare the effects of yeast yeast culture (YC) and vitamin E (VE) supplementation on endotoxin absorption and antioxidant status in lactating dairy goats suffering from heat stress (HS). Three first lactation Saanen dairy goats (body weight 30±1.5 kg) were surgically fitted with indwelling catheters in the portal vein, mesenteric vein and carotid artery, and were randomly assigned to a 3×3 Latin square design. Dietary treatments were the basal diet, and the basal diet supplemented with either 100 IU VE or 30 g YC. Goats were kept in temperature and humidity-controlled room at 35°C from 8:00 to 20:00 and at 24°C from 20:00 till the next morning at 8:00. The relative humidity was kept at 55%. HS increased dairy goats’ rectum temperature and respiration frequency (p<0.01). HS reduced plasma flux rate of milk goats (p<0.01), but the plasma flux rate increased when the animal was under the conditions of the thermo-neutral period (p<0.01). The VE supplementation lowered dairy goats’ rectum temperature during thermo-neutral period (p<0.01). Meanwhile, no significant differences were observed between the control and YC treatment in rectum temperature and respiration frequency (p>0.05). Dietary supplementation of VE and YC reduced heat stressed dairy goats’ endotoxin concentration of the carotid artery and portal vein (p<0.01). However, the endotoxin concentration of the YC treatment was higher than that of the VE treatment (p<0.01). Both VE and YC supplementation decreased heat stressed dairy goats’ absorption of endotoxin in portal vein (p<0.01). The endotoxin absorption of YC treatment was higher than the VE treatment (p<0.01). The addition of VE and YC decreased dairy goats’ superoxide dismutase (SOD) concentration during HS and the whole experiment period (p<0.01). The addition of VE lowered SOD concentration during thermo-neutral period (p<0.01). Likewise, the addition of VE and YC lowered dairy goats

  8. Yeast Culture and Vitamin E Supplementation Alleviates Heat Stress in Dairy Goats.

    PubMed

    Wang, Lizhi; Wang, Zhisheng; Zou, Huawei; Peng, Quanhui

    2016-06-01

    This study was conducted to determine and compare the effects of yeast yeast culture (YC) and vitamin E (VE) supplementation on endotoxin absorption and antioxidant status in lactating dairy goats suffering from heat stress (HS). Three first lactation Saanen dairy goats (body weight 30±1.5 kg) were surgically fitted with indwelling catheters in the portal vein, mesenteric vein and carotid artery, and were randomly assigned to a 3×3 Latin square design. Dietary treatments were the basal diet, and the basal diet supplemented with either 100 IU VE or 30 g YC. Goats were kept in temperature and humidity-controlled room at 35°C from 8:00 to 20:00 and at 24°C from 20:00 till the next morning at 8:00. The relative humidity was kept at 55%. HS increased dairy goats' rectum temperature and respiration frequency (p<0.01). HS reduced plasma flux rate of milk goats (p<0.01), but the plasma flux rate increased when the animal was under the conditions of the thermo-neutral period (p<0.01). The VE supplementation lowered dairy goats' rectum temperature during thermo-neutral period (p<0.01). Meanwhile, no significant differences were observed between the control and YC treatment in rectum temperature and respiration frequency (p>0.05). Dietary supplementation of VE and YC reduced heat stressed dairy goats' endotoxin concentration of the carotid artery and portal vein (p<0.01). However, the endotoxin concentration of the YC treatment was higher than that of the VE treatment (p<0.01). Both VE and YC supplementation decreased heat stressed dairy goats' absorption of endotoxin in portal vein (p<0.01). The endotoxin absorption of YC treatment was higher than the VE treatment (p<0.01). The addition of VE and YC decreased dairy goats' superoxide dismutase (SOD) concentration during HS and the whole experiment period (p<0.01). The addition of VE lowered SOD concentration during thermo-neutral period (p<0.01). Likewise, the addition of VE and YC lowered dairy goats' malonaldehyde (MDA

  9. Thermal stress effects in intermetallic matrix composites

    NASA Technical Reports Server (NTRS)

    Wright, P. K.; Sensmeier, M. D.; Kupperman, D. S.; Wadley, H. N. G.

    1993-01-01

    Intermetallic matrix composites develop residual stresses from the large thermal expansion mismatch (delta-alpha) between the fibers and matrix. This work was undertaken to: establish improved techniques to measure these thermal stresses in IMC's; determine residual stresses in a variety of IMC systems by experiments and modeling; and, determine the effect of residual stresses on selected mechanical properties of an IMC. X ray diffraction (XRD), neutron diffraction (ND), synchrotron XRD (SXRD), and ultrasonics (US) techniques for measuring thermal stresses in IMC were examined and ND was selected as the most promising technique. ND was demonstrated on a variety of IMC systems encompassing Ti- and Ni-base matrices, SiC, W, and Al2O3 fibers, and different fiber fractions (Vf). Experimental results on these systems agreed with predictions of a concentric cylinder model. In SiC/Ti-base systems, little yielding was found and stresses were controlled primarily by delta-alpha and Vf. In Ni-base matrix systems, yield strength of the matrix and Vf controlled stress levels. The longitudinal residual stresses in SCS-6/Ti-24Al-llNb composite were modified by thermomechanical processing. Increasing residual stress decreased ultimate tensile strength in agreement with model predictions. Fiber pushout strength showed an unexpected inverse correlation with residual stress. In-plane shear yield strength showed no dependence on residual stress. Higher levels of residual tension led to higher fatigue crack growth rates, as suggested by matrix mean stress effects.

  10. Role of brassinosteroids in alleviation of phenanthrene–cadmium co-contamination-induced photosynthetic inhibition and oxidative stress in tomato

    PubMed Central

    Ahammed, Golam Jalal; Yu, Jingquan

    2013-01-01

    Heavy metal pollution often occurs together with organic contaminants. Brassinosteroids (BRs) induce plant tolerance to several abiotic stresses, including phenanthrene (PHE) and cadmium (Cd) stress. However, the role of BRs in PHE+Cd co-contamination-induced stress amelioration is unknown. Here, the interactive effects of PHE, Cd, and 24-epibrassinolide (EBR; a biologically active BR) were investigated in tomato plants. The application of Cd (100 µM) alone was more phytotoxic than PHE applied alone (100 µM); however, their combined application resulted in slightly improved photosynthetic activity and pigment content compared with Cd alone after a 40 d exposure. Accumulation of reactive oxygen species and membrane lipid peroxidation were induced by PHE and/or Cd; however, the differences in effect were insignificant between Cd and PHE+Cd. The foliar application of EBR (0.1 µM) to PHE- and/or Cd-stressed plants alleviated photosynthetic inhibition and oxidative stress by causing enhancement of the activity of the enzymes and related transcript levels of the antioxidant system, secondary metabolism, and the xenobiotic detoxification system. Additionally, PHE and/or Cd residues were significantly decreased in both the leaves and roots after application of EBR, more specifically in PHE+Cd-stressed plants when treated with EBR, indicating a possible improvement in detoxification of these pollutants. The findings thus suggest a potential interaction of EBR and PHE for Cd stress alleviation. These results advocate a positive role for EBR in reducing pollutant residues for food safety and also strengthening phytoremediation. PMID:23201830

  11. Assessing Cumulative Thermal Stress in Fish During Chronic Exposure to High Temperature

    SciTech Connect

    Bevelhimer, M.S.; Bennett, W.R.

    1999-11-14

    As environmental laws become increasingly protective, and with possible future changes in global climate, thermal effects on aquatic resources are likely to receive increasing attention. Lethal temperatures for a variety of species have been determined for situations where temperatures rise rapidly resulting in lethal effects. However, less is known about the effects of chronic exposure to high (but not immediately lethal) temperatures and even less about stress accumulation during periods of fluctuating temperatures. In this paper we present a modeling framework for assessing cumulative thermal stress in fish. The model assumes that stress accumulation occurs above a threshold temperature at a rate depending on the degree to which the threshold is exceeded. The model also includes stress recovery (or alleviation) when temperatures drop below the threshold temperature as in systems with large daily variation. In addition to non-specific physiological stress, the model also simulates thermal effects on growth.

  12. Thermal Stresses In Space-Shuttle Wing

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jenkins, Jerald M.

    1989-01-01

    Combined thermal deformations of wing-skin panel and TPS would not tear SIP layer. Report presents analysis of thermal stresses induced in skin panel, thermal-protection system (TPS), and strain-isolation pad (SIP) of Space Shuttle orbiter. Purpose of analysis to determine whether any part of above mentioned structures overstressed and overdeformed under reentry heating, assuming one TPS tile lost at end of reentry heating.

  13. Thermal stress in high temperature cylindrical fasteners

    NASA Technical Reports Server (NTRS)

    Blosser, Max L.

    1988-01-01

    Uninsulated structures fabricated from carbon or silicon-based materials, which are allowed to become hot during flight, are attractive for the design of some components of hypersonic vehicles. They have the potential to reduce weight and increase vehicle efficiency. Because of manufacturing contraints, these structures will consist of parts which must be fastened together. The thermal expansion mismatch between conventional metal fasteners and carbon or silicon-based structural materials may make it difficult to design a structural joint which is tight over the operational temperature range without exceeding allowable stress limits. In this study, algebraic, closed-form solutions for calculating the thermal stresses resulting from radial thermal expansion mismatch around a cylindrical fastener are developed. These solutions permit a designer to quickly evaluate many combinations of materials for the fastener and the structure. Using the algebraic equations developed, material properties and joint geometry were varied to determine their effect on thermal stresses. Finite element analyses were used to verify that the closed-form solutions derived give the correct thermal stress distribution around a cylindrical fastener and to investigate the effect of some of the simplifying assumptions made in developing the closed-form solutions for thermal stresses.

  14. Rotor thermal stress monitoring in steam turbines

    NASA Astrophysics Data System (ADS)

    Antonín, Bouberle; Jan, Jakl; Jindřich, Liška

    2015-11-01

    One of the issues of steam turbines diagnostics is monitoring of rotor thermal stress that arises from nonuniform temperature field. The effort of steam turbine operator is to operate steam turbine in such conditions, that rotor thermal stress doesn't exceed the specified limits. If rotor thermal stress limits are exceeded for a long time during machine operation, the rotor fatigue life is shortened and this may lead to unexpected machine failure. Thermal stress plays important role during turbine cold startup, when occur the most significant differences of temperatures through rotor cross section. The temperature field can't be measured directly in the entire rotor cross section and standardly the temperature is measured by thermocouple mounted in stator part. From this reason method for numerical solution of partial differential equation of heat propagation through rotor cross section must be combined with method for calculation of temperature on rotor surface. In the first part of this article, the application of finite volume method for calculation of rotor thermal stress is described. The second part of article deals with optimal trend generation of thermal flux, that could be used for optimal machine loading.

  15. Treadmill exercise alleviates stress-induced impairment of social interaction through 5-hydroxytryptamine 1A receptor activation in rats

    PubMed Central

    Kim, Tae-Woon; Lim, Baek-Vin; Kim, Kijeong; Seo, Jin-Hee; Kim, Chang-Ju

    2015-01-01

    Brain-derived neurotrophic factor (BDNF) and its receptors tyrosine kinase B (trkB), and cyclic adenosine monophosphate response element binding protein (CREB) have been suggested as the neurobiological risk factors causing depressive disorder. Serotonin (5-hydroxytryptamine, 5-HT) plays an important role in the pathogenesis of depression. We in-vestigated the effect of treadmill exercise on social interaction in relation with BDNF and 5-HT expressions following stress in rats. Stress was induced by applying inescapable 0.2 mA electric foot shock to the rats for 7 days. The rats in the exercise groups were forced to run on a motorized treadmill for 30 min once a day for 4 weeks. Social interaction test and western blot for BDNF, TrkB, pCREB, and 5-HT1A in the hippocampus were performed. The results indicate that the spend time with unfamiliar partner was decreased by stress, in contrast, treadmill exercise increased the spending time in the stress-induced rats. Expressions of BDNF, TrkB, and pCREB were decreased by stress, in contrast, treadmill exercise enhanced expressions of BDNF, TrkB, and pCREB in the stress-induced rats. In addition, 5-HT1A receptor expression was de-creased by stress, in contrast, treadmill exercise enhanced 5-HT1A expression in the stress-induced rats. In the present study, treadmill exercise alleviated stress-induced social interaction impairment through enhancing hippocampal plasticity and serotonergic function in the hippocampus. These effects of treadmill exercise are achieved through 5-HT1A receptor activation. PMID:26331133

  16. Treadmill exercise alleviates stress-induced impairment of social interaction through 5-hydroxytryptamine 1A receptor activation in rats.

    PubMed

    Kim, Tae-Woon; Lim, Baek-Vin; Kim, Kijeong; Seo, Jin-Hee; Kim, Chang-Ju

    2015-08-01

    Brain-derived neurotrophic factor (BDNF) and its receptors tyrosine kinase B (trkB), and cyclic adenosine monophosphate response element binding protein (CREB) have been suggested as the neurobiological risk factors causing depressive disorder. Serotonin (5-hydroxytryptamine, 5-HT) plays an important role in the pathogenesis of depression. We in-vestigated the effect of treadmill exercise on social interaction in relation with BDNF and 5-HT expressions following stress in rats. Stress was induced by applying inescapable 0.2 mA electric foot shock to the rats for 7 days. The rats in the exercise groups were forced to run on a motorized treadmill for 30 min once a day for 4 weeks. Social interaction test and western blot for BDNF, TrkB, pCREB, and 5-HT1A in the hippocampus were performed. The results indicate that the spend time with unfamiliar partner was decreased by stress, in contrast, treadmill exercise increased the spending time in the stress-induced rats. Expressions of BDNF, TrkB, and pCREB were decreased by stress, in contrast, treadmill exercise enhanced expressions of BDNF, TrkB, and pCREB in the stress-induced rats. In addition, 5-HT1A receptor expression was de-creased by stress, in contrast, treadmill exercise enhanced 5-HT1A expression in the stress-induced rats. In the present study, treadmill exercise alleviated stress-induced social interaction impairment through enhancing hippocampal plasticity and serotonergic function in the hippocampus. These effects of treadmill exercise are achieved through 5-HT1A receptor activation. PMID:26331133

  17. How Do You Spell Relief? Alleviating Job Stress Caused by Organizations and Executives.

    ERIC Educational Resources Information Center

    Ginsburg, Sigmund G.

    1991-01-01

    College business officers should examine whether they and their institutions are practicing stress-inducing activities, and modify current practice to reduce stress on employees. Stresses can originate in the organizational framework, managerial style, or manager personality. Review of individual and organizational actions possible causing stress…

  18. Teacher Stress: What It Is, Why It's Important, How It Can Be Alleviated

    ERIC Educational Resources Information Center

    Prilleltensky, Isaac; Neff, Marilyn; Bessell, Ann

    2016-01-01

    Teacher stress can be conceptualized as an imbalance between risk and protective factors. Stress emanates from risk factors at the personal, interpersonal, and organizational levels. When risk factors exceed protective factors, teacher ability to cope with adversity is inhibited, likely resulting in stress and pernicious consequences. In this…

  19. Carbon monoxide alleviates ethanol-induced oxidative damage and inflammatory stress through activating p38 MAPK pathway

    SciTech Connect

    Li, Yanyan; Gao, Chao; Shi, Yanru; Tang, Yuhan; Liu, Liang; Xiong, Ting; Du, Min; Xing, Mingyou; Liu, Liegang; Yao, Ping

    2013-11-15

    Stress-inducible protein heme oxygenase-1(HO-1) is well-appreciative to counteract oxidative damage and inflammatory stress involving the pathogenesis of alcoholic liver diseases (ALD). The potential role and signaling pathways of HO-1 metabolite carbon monoxide (CO), however, still remained unclear. To explore the precise mechanisms, ethanol-dosed adult male Balb/c mice (5.0 g/kg.bw.) or ethanol-incubated primary rat hepatocytes (100 mmol/L) were pretreated by tricarbonyldichlororuthenium (II) dimmer (CORM-2, 8 mg/kg for mice or 20 μmol/L for hepatocytes), as well as other pharmacological reagents. Our data showed that CO released from HO-1 induction by quercetin prevented ethanol-derived oxidative injury, which was abolished by CO scavenger hemoglobin. The protection was mimicked by CORM-2 with the attenuation of GSH depletion, SOD inactivation, MDA overproduction, and the leakage of AST, ALT or LDH in serum and culture medium induced by ethanol. Moreover, CORM-2 injection or incubation stimulated p38 phosphorylation and suppressed abnormal Tnfa and IL-6, accompanying the alleviation of redox imbalance induced by ethanol and aggravated by inflammatory factors. The protective role of CORM-2 was abolished by SB203580 (p38 inhibitor) but not by PD98059 (ERK inhibitor) or SP600125 (JNK inhibitor). Thus, HO-1 released CO prevented ethanol-elicited hepatic oxidative damage and inflammatory stress through activating p38 MAPK pathway, suggesting a potential therapeutic role of gaseous signal molecule on ALD induced by naturally occurring phytochemicals. - Highlights: • CO alleviated ethanol-derived liver oxidative and inflammatory stress in mice. • CO eased ethanol and inflammatory factor-induced oxidative damage in hepatocytes. • The p38 MAPK is a key signaling mechanism for the protective function of CO in ALD.

  20. Intradermal injection of Botulinum toxin type A alleviates infraorbital nerve constriction-induced thermal hyperalgesia in an operant assay.

    PubMed

    Kumada, A; Matsuka, Y; Spigelman, I; Maruhama, K; Yamamoto, Y; Neubert, J K; Nolan, T A; Watanabe, K; Maekawa, K; Kamioka, H; Yamashiro, T; Kuboki, T; Oguma, K

    2012-01-01

    Recent studies have shown that infraorbital nerve constriction (IoNC)-induced mechanical allodynia has been attenuated by administration of highly purified 150-kDa Botulinum neurotoxin type A (BoNT/A). Here, we extend these studies to determine whether BoNT/A could attenuate IoNC-induced symptoms of thermal hyperalgesia. Instead of testing head withdrawal thresholds, a thermal operant assay was used to evaluate cortical processing of sensory input following IoNC. In this assay, a fasted rat's desire to obtain a food reward (sweetened condensed milk) is coupled to its ability to tolerate facial contact with a warm (45 °C) thermode. Bilateral IoNC decreased the ratio of thermode contact duration/event, which is an indicative of thermal hyperalgesia. BoNT/A injection intradermally in the area of infraorbital nerve (IoN) innervation 7 days after IoNC resulted in decreased number of facial contacts and increased the ratio of contact duration/event (measured at 14 days after IoNC). The BoNT/A (2-200 pg) effects were dose dependent and statistically significant at 100 and 200 pg (P < 0·05). Complete reversal of thermal hyperalgesia symptoms was obtained with a 200-pg dose, without affecting sham rat behaviour. Off-site (neck) injection of BoNT/A did not relieve thermal hyperalgesia, while co-injection of BoNT/A with a neutralising antibody in the area of IoN innervation prevented relief of thermal hyperalgesia. Neither IoNC nor BoNT/A injection affected operant assay parameters with a 24 °C thermode, indicating selectivity of thermal hyperalgesia measurements. These results strongly suggest that intradermal injection of BoNT/A in the area of IoN innervation alleviates IoNC-induced thermal hyperalgesia in an operant assay. PMID:21793870

  1. Nitric oxide and hydrogen peroxide alleviate drought stress in marigold explants and promote its adventitious root development.

    PubMed

    Liao, Wei-Biao; Huang, Gao-Bao; Yu, Ji-Hua; Zhang, Mei-Ling

    2012-09-01

    Drought stress is one of the most important environmental factors that regulates plant growth and development. In this study, we examined the effects of nitric oxide (NO) and hydrogen peroxide (H(2)O(2)) on adventitious rooting in marigold (Tagetes erecta L.) under drought stress. The results showed that the promoting effect of NO or H(2)O(2) on rooting under drought stress was dose-dependent, with a maximal biological response at 10 μM NO donor sodium nitroprusside (SNP) or 600 μM H(2)O(2). Results also indicated that endogenous NO and H(2)O(2) may play crucial roles in rooting under drought conditions, and H(2)O(2) may be involved in rooting promoted by NO under drought stress. NO or H(2)O(2) treatment attenuated the destruction of mesophyll cells ultrastructure by drought stress. Similarly, NO or H(2)O(2) increased leaf chlorophyll content, chlorophyll fluorescence parameters (Fv/Fm, ΦPS II and qP), and hypocotyls soluble carbohydrate and protein content, while decreasing starch content. Results suggest that the protection of mesophyll cells ultrastructure by NO or H(2)O(2) under drought conditions improves the photosynthetic performance of leaves and alleviates the negative effects of drought on carbohydrate and nitrogen accumulation in explants, thereby adventitious rooting being promoted. PMID:22771430

  2. Thermal stresses in thick laminated composite shells

    NASA Technical Reports Server (NTRS)

    Yuan, F. G.

    1993-01-01

    The paper provides an analytical formulation to investigate the thermomechanical behavior of thick composite shells subjected to a temperature distribution which varies arbitrarily in the radial direction. For illustrative purposes, shells under uniform temperature change are presented. It is found that thermal twist would occur even for symmetric laminated shells. Under uniform temperature rise, results for off-axis graphite/epoxy shells show that extensional-shear coupling can cause tensile radial stress throughout the shell and tensile hoop stress in the inner region. Laminated graphite/epoxy shells can exhibit negative effective thermal expansion coefficients in the longitudinal and transverse directions. Finally, the stacking sequence has a strong influence on the thermal stress distributions.

  3. Nitric Oxide Alleviates Salt Stress Inhibited Photosynthetic Performance by Interacting with Sulfur Assimilation in Mustard.

    PubMed

    Fatma, Mehar; Masood, Asim; Per, Tasir S; Khan, Nafees A

    2016-01-01

    The role of nitric oxide (NO) and sulfur (S) on stomatal responses and photosynthetic performance was studied in mustard (Brassica juncea L.) in presence or absence of salt stress. The combined application of 100 μM NO (as sodium nitroprusside) and 200 mg S kg(-1) soil (S) more prominently influenced stomatal behavior, photosynthetic and growth performance both in the absence and presence of salt stress. The chloroplasts from salt-stressed plants had disorganized chloroplast thylakoids, but combined application of NO and S resulted in well-developed chloroplast thylakoids and properly stacked grana. The leaves from plants receiving NO plus S exhibited lower superoxide ion accumulation under salt stress than the plants receiving NO or S. These plants also exhibited increased activity of ATP-sulfurylase (ATPS), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) and optimized NO generation that helped in minimizing oxidative stress. The enhanced S-assimilation of these plants receiving NO plus S resulted in increased production of cysteine (Cys) and reduced glutathione (GSH). These findings indicated that NO influenced photosynthesis under salt stress by regulating oxidative stress and its effects on S-assimilation, an antioxidant system and NO generation. The results suggest that NO improves photosynthetic performance of plants grown under salt stress more effectively when plants received S. PMID:27200007

  4. Nitric Oxide Alleviates Salt Stress Inhibited Photosynthetic Performance by Interacting with Sulfur Assimilation in Mustard

    PubMed Central

    Fatma, Mehar; Masood, Asim; Per, Tasir S.; Khan, Nafees A.

    2016-01-01

    The role of nitric oxide (NO) and sulfur (S) on stomatal responses and photosynthetic performance was studied in mustard (Brassica juncea L.) in presence or absence of salt stress. The combined application of 100 μM NO (as sodium nitroprusside) and 200 mg S kg−1 soil (S) more prominently influenced stomatal behavior, photosynthetic and growth performance both in the absence and presence of salt stress. The chloroplasts from salt-stressed plants had disorganized chloroplast thylakoids, but combined application of NO and S resulted in well-developed chloroplast thylakoids and properly stacked grana. The leaves from plants receiving NO plus S exhibited lower superoxide ion accumulation under salt stress than the plants receiving NO or S. These plants also exhibited increased activity of ATP-sulfurylase (ATPS), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) and optimized NO generation that helped in minimizing oxidative stress. The enhanced S-assimilation of these plants receiving NO plus S resulted in increased production of cysteine (Cys) and reduced glutathione (GSH). These findings indicated that NO influenced photosynthesis under salt stress by regulating oxidative stress and its effects on S-assimilation, an antioxidant system and NO generation. The results suggest that NO improves photosynthetic performance of plants grown under salt stress more effectively when plants received S. PMID:27200007

  5. Glucocorticoids alleviate intestinal ER stress by enhancing protein folding and degradation of misfolded proteins

    PubMed Central

    Das, Indrajit; Png, Chin Wen; Oancea, Iulia; Hasnain, Sumaira Z.; Lourie, Rohan; Proctor, Martina; Eri, Rajaraman D.; Sheng, Yong; Crane, Denis I.; Florin, Timothy H.

    2013-01-01

    Endoplasmic reticulum (ER) stress in intestinal secretory cells has been linked with colitis in mice and inflammatory bowel disease (IBD). Endogenous intestinal glucocorticoids are important for homeostasis and glucocorticoid drugs are efficacious in IBD. In Winnie mice with intestinal ER stress caused by misfolding of the Muc2 mucin, the glucocorticoid dexamethasone (DEX) suppressed ER stress and activation of the unfolded protein response (UPR), substantially restoring goblet cell Muc2 production. In mice lacking inflammation, a glucocorticoid receptor antagonist increased ER stress, and DEX suppressed ER stress induced by the N-glycosylation inhibitor, tunicamycin (Tm). In cultured human intestinal secretory cells, in a glucocorticoid receptor-dependent manner, DEX suppressed ER stress and UPR activation induced by blocking N-glycosylation, reducing ER Ca2+ or depleting glucose. DEX up-regulated genes encoding chaperones and elements of ER-associated degradation (ERAD), including EDEM1. Silencing EDEM1 partially inhibited DEX’s suppression of misfolding-induced ER stress, showing that DEX enhances ERAD. DEX inhibited Tm-induced MUC2 precursor accumulation, promoted production of mature mucin, and restored ER exit and secretion of Winnie mutant recombinant Muc2 domains, consistent with enhanced protein folding. In IBD, glucocorticoids are likely to ameliorate ER stress by promoting correct folding of secreted proteins and enhancing removal of misfolded proteins from the ER. PMID:23650437

  6. Current developments in arbuscular mycorrhizal fungi research and its role in salinity stress alleviation: a biotechnological perspective.

    PubMed

    Kumar, Ashwani; Dames, Joanna F; Gupta, Aditi; Sharma, Satyawati; Gilbert, Jack A; Ahmad, Parvaiz

    2015-01-01

    Arbuscular mycorrhizal fungi (AMF) form widespread symbiotic associations with 80% of known land plants. They play a major role in plant nutrition, growth, water absorption, nutrient cycling and protection from pathogens, and as a result, contribute to ecosystem processes. Salinity stress conditions undoubtedly limit plant productivity and, therefore, the role of AMF as a biological tool for improving plant salt stress tolerance, is gaining economic importance worldwide. However, this approach requires a better understanding of how plants and AMF intimately interact with each other in saline environments and how this interaction leads to physiological changes in plants. This knowledge is important to develop sustainable strategies for successful utilization of AMF to improve plant health under a variety of stress conditions. Recent advances in the field of molecular biology, "omics" technology and advanced microscopy can provide new insight about these mechanisms of interaction between AMF and plants, as well as other microbes. This review mainly discusses the effect of salinity on AMF and plants, and role of AMF in alleviation of salinity stress including insight on methods for AMF identification. The focus remains on latest advancements in mycorrhizal research that can potentially offer an integrative understanding of the role of AMF in salinity tolerance and sustainable crop production. PMID:24708070

  7. Evaluation of Arbuscular Mycorrhizal Fungi Capacity to Alleviate Abiotic Stress of Olive (Olea europaea L.) Plants at Different Transplant Conditions

    PubMed Central

    Bompadre, María Josefina; Pérgola, Mariana; Fernández Bidondo, Laura; Colombo, Roxana Paula; Silvani, Vanesa Analía; Pardo, Alejandro Guillermo; Ocampo, Juan Antonio; Godeas, Alicia Margarita

    2014-01-01

    The capacity of roots to sense soil physicochemical parameters plays an essential role in maintaining plant nutritional and developmental functions under abiotic stress. These conditions generate reactive oxygen species (ROS) in plant tissues causing oxidation of proteins and lipids among others. Some plants have developed adaptive mechanisms to counteract such adverse conditions such as symbiotic association with arbuscular mycorrhizal fungi (AMF). AMF enhance plant growth and improve transplant survival by protecting host plants against environmental stresses. The aim of this study was to evaluate the alleviation of transplanting stress by two strains of Rhizophagus irregularis (GC2 and GA5) in olive. Our results show that olive plants have an additional energetic expense in growth due to an adaptative response to the growing stage and to the mycorrhizal colonization at the first transplant. However, at the second transplant the coinoculation improves olive plant growth and protects against oxidative stress followed by the GA5-inoculation. In conclusion, a combination of two AMF strains at the beginning of olive propagation produces vigorous plants successfully protected in field cultivation even with an additional cost at the beginning of growth. PMID:24688382

  8. Residual Stresses Modeled in Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Freborg, A. M.; Ferguson, B. L.; Petrus, G. J.; Brindley, W. J.

    1998-01-01

    Thermal barrier coating (TBC) applications continue to increase as the need for greater engine efficiency in aircraft and land-based gas turbines increases. However, durability and reliability issues limit the benefits that can be derived from TBC's. A thorough understanding of the mechanisms that cause TBC failure is a key to increasing, as well as predicting, TBC durability. Oxidation of the bond coat has been repeatedly identified as one of the major factors affecting the durability of the ceramic top coat during service. However, the mechanisms by which oxidation facilitates TBC failure are poorly understood and require further characterization. In addition, researchers have suspected that other bond coat and top coat factors might influence TBC thermal fatigue life, both separately and through interactions with the mechanism of oxidation. These other factors include the bond coat coefficient of thermal expansion, the bond coat roughness, and the creep behavior of both the ceramic and bond coat layers. Although it is difficult to design an experiment to examine these factors unambiguously, it is possible to design a computer modeling "experiment" to examine the action and interaction of these factors, as well as to determine failure drivers for TBC's. Previous computer models have examined some of these factors separately to determine their effect on coating residual stresses, but none have examined all the factors concurrently. The purpose of this research, which was performed at DCT, Inc., in contract with the NASA Lewis Research Center, was to develop an inclusive finite element model to characterize the effects of oxidation on the residual stresses within the TBC system during thermal cycling as well as to examine the interaction of oxidation with the other factors affecting TBC life. The plasma sprayed, two-layer thermal barrier coating that was modeled incorporated a superalloy substrate, a NiCrAlY bond coat, and a ZrO2-8 wt % Y2O3 ceramic top coat. We

  9. Haem oxygenase-1 is involved in salicylic acid-induced alleviation of oxidative stress due to cadmium stress in Medicago sativa

    PubMed Central

    Shen, Wenbiao

    2012-01-01

    This work examines the involvement of haem oxygenase-1 (HO-1) in salicylic acid (SA)-induced alleviation of oxidative stress as a result of cadmium (Cd) stress in alfalfa (Medicago sativa L.) seedling roots. CdCl2 exposure caused severe growth inhibition and Cd accumulation, which were potentiated by pre-treatment with zinc protoporphyrin (ZnPPIX), a potent HO-1 inhibitor. Pre-treatment of plants with the HO-1 inducer haemin or SA, both of which could induce MsHO1 gene expression, significantly reduced the inhibition of growth and Cd accumulation. The alleviation effects were also evidenced by a decreased content of thiobarbituric acid-reactive substances (TBARS). The antioxidant behaviour was confirmed by histochemical staining for the detection of lipid peroxidation and the loss of plasma membrane integrity. Furthermore, haemin and SA pre-treatment modulated the activities of ascorbate peroxidase (APX), superoxide dismutase (SOD), and guaiacol peroxidase (POD), or their corresponding transcripts. Significant enhancement of the ratios of reduced/oxidized homoglutathione (hGSH), ascorbic acid (ASA)/dehydroascorbate (DHA), and NAD(P)H/NAD(P)+, and expression of their metabolism genes was observed, consistent with a decreased reactive oxygen species (ROS) distribution in the root tips. These effects are specific for HO-1, since ZnPPIX blocked the above actions, and the aggravated effects triggered by SA plus ZnPPIX were differentially reversed when carbon monoxide (CO) or bilirubin (BR), two catalytic by-products of HO-1, was added. Together, the results suggest that HO-1 is involved in the SA-induced alleviation of Cd-triggered oxidative stress by re-establishing redox homeostasis. PMID:22915740

  10. Nutritional Interventions to Alleviate the Negative Consequences of Heat Stress12

    PubMed Central

    Rhoads, Robert P.; Baumgard, Lance H.; Suagee, Jessica K.; Sanders, Sara R.

    2013-01-01

    Energy metabolism is a highly coordinated process, and preferred fuel(s) differ among tissues. The hierarchy of substrate use can be affected by physiological status and environmental factors including high ambient temperature. Unabated heat eventually overwhelms homeothermic mechanisms resulting in heat stress, which compromises animal health, farm animal production, and human performance. Various aspects of heat stress physiology have been extensively studied, yet a clear understanding of the metabolic changes occurring at the cellular, tissue, and whole-body levels in response to an environmental heat load remains ill-defined. For reasons not yet clarified, circulating nonesterified fatty acid levels are reduced during heat stress, even in the presence of elevated stress hormones (epinephrine, glucagon, and cortisol), and heat-stressed animals often have a blunted lipolytic response to catabolic signals. Either directly because of or in coordination with this, animals experiencing environmental hyperthermia exhibit a shift toward carbohydrate use. These metabolic alterations occur coincident with increased circulating basal and stimulated plasma insulin concentrations. Limited data indicate that proper insulin action is necessary to effectively mount a response to heat stress and minimize heat-induced damage. Consistent with this idea, nutritional interventions targeting increased insulin action may improve tolerance and productivity during heat stress. Further research is warranted to uncover the effects of heat on parameters associated with energy metabolism so that more appropriate and effective treatment methodologies can be designed. PMID:23674792

  11. The wheat MAP kinase phosphatase 1 alleviates salt stress and increases antioxidant activities in Arabidopsis.

    PubMed

    Zaidi, Ikram; Ebel, Chantal; Belgaroui, Nibras; Ghorbel, Mouna; Amara, Imène; Hanin, Moez

    2016-04-01

    Mitogen-activated protein kinase phosphatases (MKPs) are important negative regulators in the MAPK signaling pathways, which play crucial roles in plant growth, development and stress responses. We have previously shown that the heterologous expression of a durum wheat MKP, TMKP1, results in increased tolerance to salt stress in yeast but its particular contribution in salt stress tolerance in plants was not investigated. Here, TMKP1 was overexpressed in Arabidopsis thaliana and physiological changes were assessed in transgenic plants exposed to stress conditions. Under salt stress and especially LiCl, the TMKP1 overexpressors displayed higher germination rates in comparison to wild type plants. The enhancement of salt stress tolerance was accompanied by increased antioxidant enzyme activities, namely superoxide dismutase, catalase and peroxydases. Such increases in antioxidant activities were concomitant with lower malondialdehyde, superoxide anion O2(-) and hydrogen peroxide levels in the TMKP1 transgenic seedlings. Moreover, we provide evidence that, in contrast to the Arabidopsis ortholog AtMKP1, TMKP1 acts as a positive regulator of salt stress tolerance via its ectopic expression in the Arabidopsis mkp1 mutant. PMID:26927025

  12. Overexpression of Arabidopsis AnnAt8 Alleviates Abiotic Stress in Transgenic Arabidopsis and Tobacco

    PubMed Central

    Yadav, Deepanker; Ahmed, Israr; Shukla, Pawan; Boyidi, Prasanna; Kirti, Pulugurtha Bharadwaja

    2016-01-01

    Abiotic stress results in massive loss of crop productivity throughout the world. Because of our limited knowledge of the plant defense mechanisms, it is very difficult to exploit the plant genetic resources for manipulation of traits that could benefit multiple stress tolerance in plants. To achieve this, we need a deeper understanding of the plant gene regulatory mechanisms involved in stress responses. Understanding the roles of different members of plant gene families involved in different stress responses, would be a step in this direction. Arabidopsis, which served as a model system for the plant research, is also the most suitable system for the functional characterization of plant gene families. Annexin family in Arabidopsis also is one gene family which has not been fully explored. Eight annexin genes have been reported in the genome of Arabidopsis thaliana. Expression studies of different Arabidopsis annexins revealed their differential regulation under various abiotic stress conditions. AnnAt8 (At5g12380), a member of this family has been shown to exhibit ~433 and ~175 fold increase in transcript levels under NaCl and dehydration stress respectively. To characterize Annexin8 (AnnAt8) further, we have generated transgenic Arabidopsis and tobacco plants constitutively expressing AnnAt8, which were evaluated under different abiotic stress conditions. AnnAt8 overexpressing transgenic plants exhibited higher seed germination rates, better plant growth, and higher chlorophyll retention when compared to wild type plants under abiotic stress treatments. Under stress conditions transgenic plants showed comparatively higher levels of proline and lower levels of malondialdehyde compared to the wild-type plants. Real-Time PCR analyses revealed that the expression of several stress-regulated genes was altered in AnnAt8 over-expressing transgenic tobacco plants, and the enhanced tolerance exhibited by the transgenic plants can be correlated with altered expressions of

  13. Thermal stress and diabetic complications

    NASA Astrophysics Data System (ADS)

    Ohtsuka, Yoshinori; Yabunaka, Noriyuki; Watanabe, Ichiro; Noro, Hiroshi; Fujisawa, Hiroyuki; Agishi, Yuko

    1995-06-01

    Activities of erythrocyte aldose reductase were compared in 34 normal subjects, 45 diabetic patients, and nine young men following immersion in water at 25, 39, and 42° C. Mean basal enzyme activity was 1.11 (SEM 0.12) U/g Hb and 2.07 (SEM 0.14) U/g Hb in normal controls and diabetic patients, respectively ( P<0.0001). Activities of the enzyme showed a good correlation with hemaglobin A1 (HbA1) concentrations ( P<0.01) but not with fasting plasma glucose concentrations. After immersion at 42° C for 10 min, enzyme activity was increased by 37.6% ( P<0.01); however, the activity decreased by 52.2% ( P<0.005) after immersion for 10 min at 39° C and by 47.0% ( P<0.05) at 25° C. These changes suggest that heat stress might aggravate diabetic complications, and body exposure to hot environmental conditions is not recommended for diabetic patients.

  14. Thermal analysis of thermoelectric power generator; Including thermal stresses

    NASA Astrophysics Data System (ADS)

    Al-Merbati, Abdulrahman Salman

    In recent years, the energy demand is increasing leads to use and utilization of clean energy becomes target of countries all over the world. Thermoelectric generator is one type of clean energy generators which is a solid-state device that converts heat energy into electrical energy through the Seebeck effect. With availability of, heat from different sources such as solar energy and waste energy from systems, thermoelectric research becomes important research topic and researchers investigates efficient means of generating electricity from thermoelectric generators. One of the important problems with a thermoelectric is development of high thermal stresses due to formation of temperature gradient across the thermoelectric generator. High thermal stress causes device failure through cracks or fractures and these short comings may reduce the efficiency or totally fail the device. In this thesis work, thermodynamic efficiency and thermal stresses developed in thermoelectric generator are analyzed numerically. The bismuth telluride (Bi2Te3) properties are used in simulation. Stress levels in thermoelectric device pins are computed for various pin geometric configurations. MASTER.

  15. Biochar alleviates combined stress of ammonium and acids by firstly enriching Methanosaeta and then Methanosarcina.

    PubMed

    Lü, Fan; Luo, Chenghao; Shao, Liming; He, Pinjing

    2016-03-01

    This investigation evaluated the effectiveness of biochar of different particle sizes in alleviating ammonium (NH4(+)) inhibition (up to 7 g-N/L) during anaerobic digestion of 6 g/L glucose. Compared to the control treatment without biochar addition, treatments that included biochar particles 2-5 mm, 0.5-1 mm and 75-150 μm in size reduced the methanization lag phase by 23.9%, 23.8% and 5.9%, respectively, and increased the maximum methane production rate by 47.1%, 23.5% and 44.1%, respectively. These results confirmed that biochar accelerated the initiation of methanization during anaerobic digestion under double inhibition risk from both ammonium and acids. Furthermore, fine biochar significantly promoted the production of volatile fatty acids (VFAs). Comparative analysis on the archaeal and bacterial diversity at the early and later stages of digestion, and in the suspended, biochar loosely bound, and biochar tightly bound fractions suggested that, in suspended fractions, hydrogenotrophic Methanobacterium was actively resistant to ammonium. However, acetoclastic Methanosaeta can survive at VFAs concentrations up to 60-80 mmol-C/L by improved affinity to conductive biochar, resulting in the accelerated initiation of acetate degradation. Improved methanogenesis was followed by the colonization of the biochar tightly bound fractions by Methanosarcina. The selection of appropriate biochar particles sizes was important in facilitating the initial colonization of microbial cells. PMID:26724437

  16. Salusins protect myocardium against ischemic injury by alleviating endoplasmic reticulum stress.

    PubMed

    Wang, Jianfei; Wang, Yin; Shan, Shifu; Hu, Tiantian; Chen, Huyan; Tian, Jing; Ren, Anjing; Zhou, Xu; Yuan, Wenjun; Lin, Li

    2012-04-01

    Salusins are regulatory peptides that affect cardiovascular function. We previously reported that salusin-α and -β protected cultured cardiomyocytes from serum deprivation-induced cell death through upregulating glucose-regulated protein 78 (GRP78), an endoplasmic reticulum (ER) resident protein whose overexpression acts as a marker and suppressor of ER stress. The present study examined whether salusin-α and -β inhibit ER stress in ischemic myocardium. In a rat model of myocardial infarction created by ligating the left anterior descending coronary artery (LAD), salusin-α or -β was intravenously injected at 5 or 15 nmol kg(-1) 15 min prior to 2 h of LAD occlusion. The high dose of salusin-α and -β significantly improved heart function and hemodynamics in LAD-occluded rats, but had no effects in sham-operated rats. The arrhythmias caused by LAD occlusion were markedly attenuated by salusin-α and -β. The apoptotic rate in ischemic myocardium was reduced from 31.5%±3.7% to 19.8%±2.2% and 12.3%±2.2%, and the infarct size was reduced from 53.4%±4.0% of the risk area to 26.5%±9.7% and 23.7%±8.9% by 15 nmol kg(-1) salusin-α and -β, respectively. Furthermore, salusin-α and -β prevented the activation of GRP78 and ER stress-specific apoptotic effectors caspase-12 and CHOP (C/EBP homologous protein), and attenuated the reduction of an ER stress-associated antiapoptotic protein Bcl-2 in ischemic cardiac tissue. The salusins also inhibited the ER stress induced by tunicamycin in cultured rat H9c2 cardiomyocytes. These results indicate that salusins protect myocardium against ischemic injury by inhibiting ER stress and ER stress-associated apoptosis. PMID:22566093

  17. Bilobalide alleviates depression-like behavior and cognitive deficit induced by chronic unpredictable mild stress in mice.

    PubMed

    Wu, Ruiyong; Shui, Li; Wang, Siyang; Song, Zhenzhen; Tai, Fadao

    2016-10-01

    Bilobalide (BB), a unique constituent of Ginkgo biloba, has powerful neuroprotection and stress-alleviating properties. However, whether BB exerts a positive effect on depression and cognitive deficit induced by chronic stress is not known. The present study was designed to investigate the influence of BB on depression and cognitive impairments induced by chronic unpredictable mild stress (CUMS) in mice. During daily exposure to stressors for 5 consecutive weeks, mice were administered BB at the doses of 0, 3, or 6 mg/kg/day intraperitoneally. We replicated the finding that CUMS induced depression-like behavior and cognitive deficits as the CUMS+vehicle (VEH) group showed a significant increase in immobility in the tail suspension test, a decrease in the discrimination index of the novel object recognition task, and increased latency to platform and decreased number of platform crossings in the Morris water maze compared with the control+VEH group. Chronic administration of BB effectively reversed these alterations. In addition, the CUMS+VEH group showed significantly higher levels of baseline serum corticosterone than those of the control+VEH group and BB dose-dependently inhibited this effect. Our results suggest that BB may be useful for inhibition of depression-like behavior and cognitive deficits, and this protective effect was possibly exerted partly through an action on the hypothalamic-pituitary-adrenal axis. PMID:27509313

  18. Thermal treatment and leaching of biochar alleviates plant growth inhibition from mobile organic compounds

    PubMed Central

    Sackett, Tara E.; Thomas, Sean C.

    2016-01-01

    Recent meta-analyses of plant responses to biochar boast positive average effects of between 10 and 40%. Plant responses, however, vary greatly across systems, and null or negative biochar effects are increasingly reported. The mechanisms responsible for such responses remain unclear. In a glasshouse experiment we tested the effects of three forestry residue wood biochars, applied at five dosages (0, 5, 10, 20, and 50 t/ha) to a temperate forest drystic cambisol as direct surface applications and as complete soil mixes on the herbaceous pioneers Lolium multiflorum and Trifolium repens. Null and negative effects of biochar on growth were found in most cases. One potential cause for null and negative plant responses to biochar is plant exposure to mobile compounds produced during pyrolysis that leach or evolve following additions of biochars to soil. In a second glasshouse experiment we examined the effects of simple leaching and heating techniques to ameliorate potentially phytotoxic effects of volatile and leachable compounds released from biochar. We used Solid Phase Microextraction (SPME)–gas chromatography–mass spectrometry (GC-MS) to qualitatively describe organic compounds in both biochar (through headspace extraction), and in the water leachates (through direct injection). Convection heating and water leaching of biochar prior to application alleviated growth inhibition. Additionally, growth was inhibited when filtrate from water-leached biochar was applied following germination. SPME-GC-MS detected primarily short-chained carboxylic acids and phenolics in both the leachates and solid chars, with relatively high concentrations of several known phytotoxic compounds including acetic acid, butyric acid, 2,4-di-tert-butylphenol and benzoic acid. We speculate that variable plant responses to phytotoxic organic compounds leached from biochars may largely explain negative plant growth responses and also account for strongly species-specific patterns of plant

  19. Physical and virtual water transfers for regional water stress alleviation in China

    PubMed Central

    Zhao, Xu; Liu, Junguo; Liu, Qingying; Tillotson, Martin R.; Guan, Dabo; Hubacek, Klaus

    2015-01-01

    Water can be redistributed through, in physical terms, water transfer projects and virtually, embodied water for the production of traded products. Here, we explore whether such water redistributions can help mitigate water stress in China. This study, for the first time to our knowledge, both compiles a full inventory for physical water transfers at a provincial level and maps virtual water flows between Chinese provinces in 2007 and 2030. Our results show that, at the national level, physical water flows because of the major water transfer projects amounted to 4.5% of national water supply, whereas virtual water flows accounted for 35% (varies between 11% and 65% at the provincial level) in 2007. Furthermore, our analysis shows that both physical and virtual water flows do not play a major role in mitigating water stress in the water-receiving regions but exacerbate water stress for the water-exporting regions of China. Future water stress in the main water-exporting provinces is likely to increase further based on our analysis of the historical trajectory of the major governing socioeconomic and technical factors and the full implementation of policy initiatives relating to water use and economic development. Improving water use efficiency is key to mitigating water stress, but the efficiency gains will be largely offset by the water demand increase caused by continued economic development. We conclude that much greater attention needs to be paid to water demand management rather than the current focus on supply-oriented management. PMID:25583516

  20. Blindness, Diabetes, and Amputation: Alleviation of Depression and Pain through Thermal Biofeedback Therapy.

    ERIC Educational Resources Information Center

    Needham, W. E.; And Others

    1993-01-01

    A 39-year-old man who was blind, diabetic, and had a double amputation with chronic renal failure and peripheral vascular disease was treated with thermal biofeedback to reduce his depression through increased self-control, to minimize pain, and to facilitate healing of a pregangrenous hand. On treatment discharge, his mental and physical states…

  1. Spermine Alleviates Drought Stress in White Clover with Different Resistance by Influencing Carbohydrate Metabolism and Dehydrins Synthesis

    PubMed Central

    Li, Zhou; Jing, Wen; Peng, Yan; Zhang, Xin Quan; Ma, Xiao; Huang, Lin Kai; Yan, Yan-hong

    2015-01-01

    The objective of this research was to analyse whether ameliorating drought stress through exogenously applied spermine (Spm) was related to carbohydrate metabolism, dehydrins accumulation and the transcription of genes encoding dehydrins in two white clovers (drought-susceptible cv. ‘Ladino’ and drought-resistant cv. ‘Haifa’) under controlled drying conditions for 10 days. The results show that the application of Spm effectively alleviates negative effects caused by drought stress in both cultivars. Exogenous Spm led to accumulation of more water-soluble carbohydrates (WSC), sucrose, fructose and sorbitol in both cultivars under drought stress, and also significantly elevated glucose content in leaves of drought-resistant cv. ‘Haifa’, but had no effect on drought-susceptible cv. ‘Ladino’. Accordingly, the key enzyme activities of sucrose and sorbitol metabolism changed along with the application of Spm under drought stress. Spm induced a significant increase in sucrose phosphate synthase (SPS) or sorbitol dehydrogenase (SDH) activity, but decrease in sucrose synthetase (SS) activity when two cultivars were subjected to drought. In addition, the improved accumulation of dehydrins induced by exogenous Spm coincided with three genes expression which was responsible for dehydrins synthesis. But Spm-induced transcript level of dehydrin genes increased earlier in cv. ‘Ladino’ than that in cv. ‘Haifa’. Thus, these results suggest that ameliorating drought stress through exogenously applied Spm may be associated with increased carbohydrate accumulation and dehydrins synthesis. There are differences between drought-susceptible and -resistant white clover cultivars related to Spm regulation of WSC metabolism and dehydrins expression. PMID:25835290

  2. A SAL1 Loss-of-Function Arabidopsis Mutant Exhibits Enhanced Cadmium Tolerance in Association with Alleviation of Endoplasmic Reticulum Stress.

    PubMed

    Xi, Hongmei; Xu, Hua; Xu, Wenxiu; He, Zhenyan; Xu, Wenzhong; Ma, Mi

    2016-06-01

    SAL1, as a negative regulator of stress response signaling, has been studied extensively for its role in plant response to environmental stresses. However, the role of SAL1 in cadmium (Cd) stress response and the underlying mechanism is still unclear. Using an Arabidopsis thaliana loss-of-function mutant of SAL1, we assessed Cd resistance and further explored the Cd toxicity mechanism through analysis of the endoplasmic reticulum (ER) stress response. The loss of SAL1 function greatly improved Cd tolerance and significantly attenuated ER stress in Arabidopsis. Exposure to Cd induced an ER stress response in Arabidopsis as evidenced by unconventional splicing of AtbZIP60 and up-regulation of ER stress-responsive genes. Damage caused by Cd was markedly reduced in the ER stress response double mutant bzip28 bzip60 or by application of the ER stress-alleviating chemical agents, tauroursodeoxycholic acid (TUDCA) and 4-phenyl butyric acid (4-PBA), in wild-type plants. The Cd-induced ER stress in Arabidopsis was also alleviated by loss of function of SAL1. These results identified SAL1 as a new component mediating Cd toxicity and established the role of the ER stress response in Cd toxicity. Additionally, the attenuated ER stress in the sal1 mutant might also shed new light on the mechanism of diverse abiotic stress resistance in the SAL1 loss-of-function mutants. PMID:27044671

  3. Multicyclic jet-flap control for alleviation of helicopter blade stresses and fuselage vibration

    NASA Technical Reports Server (NTRS)

    Mccloud, J. L., III; Kretz, M.

    1974-01-01

    Results of wind tunnel tests of a 12 meter-diameter-rotor utilizing multicyclic jet-flap control deflection are presented. Analyses of these results are shown, and experimental transfer functions are determined by which optimal control vectors are developed. These vectors are calculated to eliminate specific harmonic bending stresses, minimize rms levels (a measure of the peak-to-peak stresses), or minimize vertical vibratory loads that would be transmitted to the fuselage. Although the specific results and the ideal control vectors presented are for a specific jet-flap driven rotor, the method employed for the analyses is applicable to similar investigations. A discussion of possible alternative methods of multicyclic control by mechanical flaps or nonpropulsive jet-flaps is presented.

  4. Comparative proteomic analysis of β-aminobutyric acid-mediated alleviation of salt stress in barley.

    PubMed

    Mostek, Agnieszka; Börner, Andreas; Weidner, Stanisław

    2016-02-01

    The non-protein amino acid β-aminobutyric acid (BABA) is known to induce plant resistance to a broad spectrum of biotic and abiotic stresses. This is the first study describing the effect of BABA seed priming on physiological and proteomic changes under salt stress conditions in barley (Hordeum vulgare). The aim of our study was to investigate the changes of fresh weight, dry weight and relative water content (RWC) as well as root proteome changes of two barley lines contrasting in salt tolerance (DH14, DH 187) in response to salt stress after seed priming in water or in 800 μM BABA. Seed priming with BABA significantly increased (p ≤ 0.05) RWC in both barley lines, which indicates considerably lower water loss in BABA-primed plants than in the non-primed control plants. Dry and fresh matter increased significantly in line DH 187, whereas no changes were detected in line DH14. BABA-primed plants of both lines showed different proteomic patterns than the non-primed control plants. The root proteins exhibiting significant abundance changes (1.75-fold change, p ≤ 0.05) were separated by two-dimensional polyacrylamide gel electrophoresis (2D- PAGE). Thirty-one spots, representing 24 proteins, were successfully identified by MALDI TOF/TOF mass spectrometry. The most prominent differences include the up-regulation of antioxidant enzymes (catalase, peroxidase and superoxide dismutase), PR proteins (chitinase, endo-1,3-β-glucosidase), and chaperones (cyclophilin, HSC 70). Our results indicate that BABA induces defence and detoxification processes which may enable faster and more effective responses to salt stress, increasing the chances of survival under adverse environmental conditions. PMID:26760953

  5. Ageing-Associated Oxidative Stress and Inflammation Are Alleviated by Products from Grapes

    PubMed Central

    Petersen, K. S.

    2016-01-01

    Advanced age is associated with increased incidence of a variety of chronic disease states which share oxidative stress and inflammation as causative role players. Furthermore, data point to a role for both cumulative oxidative stress and low grade inflammation in the normal ageing process, independently of disease. Therefore, arguably the best route with which to address premature ageing, as well as age-associated diseases such as diabetes, cardiovascular disease, and dementia, is preventative medicine aimed at modulation of these two responses, which are intricately interlinked. In this review, we provide a detailed account of the literature on the communication of these systems in the context of ageing, but with inclusion of relevant data obtained in other models. In doing so, we attempted to more clearly elucidate or identify the most probable cellular or molecular targets for preventative intervention. In addition, given the absence of a clear pharmaceutical solution in this context, together with the ever-increasing consumer bias for natural medicine, we provide an overview of the literature on grape (Vitis vinifera) derived products, for which beneficial effects are consistently reported in the context of both oxidative stress and inflammation. PMID:27034739

  6. Overexpression of a tomato carotenoid ε-hydroxylase gene alleviates sensitivity to chilling stress in transgenic tobacco.

    PubMed

    Zhou, Bin; Deng, Yong-Sheng; Kong, Fan-Ying; Li, Bin; Meng, Qing-Wei

    2013-09-01

    Chilling is one of the most serious environmental stresses that disrupt the metabolic balance of cells and enhance the production of reactive oxygen species (ROS). Lutein plays important roles in dissipating excess excitation energy and eliminating ROS to maintain the normal physiological function of cells. A tomato carotenoid epsilon-ring hydroxylase gene (LeLUT1) was isolated, and the LeLUT1-GFP fusion protein was localized in the chloroplast of Arabidopsis mesophyll protoplast. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that the expression of LeLUT1 was the highest in the leaves and was down-regulated by various abiotic stresses in tomato. The transgenic tobacco plants overexpressing LeLUT1 had higher lutein content, which was decreased in cold condition. Under chilling stress, the non-photochemical quenching (NPQ) values were higher in the transgenic plants than in the wild type (WT) plants. Compared with the WT plants, the transgenic plants showed lower levels of hydrogen peroxide (H2O2), superoxide radical (O2(·-)), relative electrical conductivity, and malondialdehyde content (MDA), and relatively higher values of maximal photochemical efficiency of photosystem II (Fv/Fm), oxidizable P700 of PSI, and net photosynthetic rate (Pn). Therefore, the transgenic seedlings were less suppressed in growth and lost less cotyledon chlorophyll than the WT seedlings. These results suggested that the overexpression of LeLUT1 had a key function in alleviating photoinhibition and photooxidation, and decreased the sensitivity of photosynthesis to chilling stress. PMID:23796723

  7. Berberis vulgaris root extract alleviates the adverse effects of heat stress via modulating hepatic nuclear transcription factors in quails.

    PubMed

    Sahin, Kazim; Orhan, Cemal; Tuzcu, Mehmet; Borawska, Maria H; Jabłonski, Jakub; Guler, Osman; Sahin, Nurhan; Hayirli, Armagan

    2013-08-01

    To evaluate the action mode of Berberis vulgaris root extract in the alleviation of oxidative stress, female Japanese quails (n 180, aged 5 weeks) were reared, either at 22°C for 24 h/d (thermoneutral, TN) or 34°C for 8 h/d (heat stress, HS), and fed one of three diets: diets containing 0, 100 or 200 mg of B. vulgaris root extract per kg for 12 weeks. Exposure to HS depressed feed intake by 8·5% and egg production by 12·1%, increased hepatic malondialdehyde (MDA) level by 98·0% and decreased hepatic superoxide dismutase, catalase and glutathione peroxidase activities by 23·5, 35·4 and 55·7%, respectively (P<0·001 for all). There were also aggravations in expressions of hepatic NF-κB and heat-shock protein 70 (HSP70) by 42 and 43%, respectively and suppressions in expressions of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and haeme-oxygenase 1 (HO-1) by 57 and 61%, respectively, in heat-stressed quails (P<0·001 for all). As supplemental B. vulgaris extract increased, there were linear increases in performance parameters, activities of antioxidant enzymes and hepatic Nrf2 and HO-1 expressions (P<0·001 for all) and linear decreases in hepatic MDA level and NF-κB and HSP70 expressions at a greater extent in quails reared under TN condition and those reared under HS condition. In conclusion, dietary supplementation of B. vulgaris root extract to quails reduces the detrimental effects of oxidative stress and lipid peroxidation resulting from HS via activating the host defence system at the cellular level. PMID:23312115

  8. A nonmolecular derivation of Maxwell's thermal-creep boundary condition in gases and liquids via application of the LeChatelier-Braun principle to Maxwell's thermal stress

    NASA Astrophysics Data System (ADS)

    Brenner, Howard

    2009-05-01

    According to the LeChatelier-Braun principle, when a closed quiescent system initially in an equilibrium or unstressed steady state is subjected to an externally imposed "stress" it responds in a manner tending to alleviate that stress. Use of this entropically based qualitative rule, in combination with the notion of Maxwell thermal stresses existing in nonisothermal gases and liquids, enables one to (i) derive Maxwell's thermal-creep boundary condition prevailing at the boundary between a solid and a fluid (either gas or liquid) and (ii) rationalize the phenomenon of thermophoresis in liquids, for which, in contrast with the case of gases, an elementary explanation is currently lacking. These two objectives are achieved by quantitatively interpreting the heretofore qualitative LeChatelier-Braun notion of stress in the present context as being the fluid's stress tensor, the latter including Maxwell's thermal stress. In effect, thermophoretic particle motion is interpreted as the manifestation of the fluid's attempt to expel the particle from its interior so as to alleviate the thermal stress that would otherwise ensue were the particle to remain at rest (thus obeying the traditional no slip rather than thermal-creep boundary condition) following its introduction into the previously stress-free quiescent fluid. With Kn the Knudsen number in the case of rarefied gases, Maxwell's thermal stress constitutes a noncontinuum phenomenon of O(Kn2), whereas his thermal-creep phenomenon constitutes a continuum phenomenon of O(Kn). That these two phenomena can, nevertheless, be proved to be synonymous (in the sense, so to speak, of being two sides of the same coin), as is done in the present paper, supports the "ghost effect" findings of Sone [Y. Sone, "Flows induced by temperature fields in a rarefied gas and their ghost effect on the behavior of a gas in the continuum limit," Annu. Rev. Fluid Mech 32, 779 (2000)], which, philosophically, imply the artificiality of the

  9. Thermal stress fracturing of magma simulant materials

    SciTech Connect

    Wemple, R.P.; Longcope, D.B.

    1986-10-01

    Direct contact heat exchanger concepts for the extraction of energy from magma chambers are being studied as part of the DOE-funded Magma Energy Research Program at Sandia National Laboratories. These concepts require the solidification of molten material by a coolant circulated through a borehole drilled into the magma and subsequent fracture of the solid either as a natural consequence of thermal stress or by deliberate design (intentional flaws, high pressure, etc.). This report summarizes the results of several thermal stress fracturing experiments performed in the laboratory and compares the results with an analysis developed for use as a predictive tool. Information gained from this test series has been the basis for additional work now under way to simulate magma melt solidification processes.

  10. Lactobacillus rhamnosus GG improves glucose tolerance through alleviating ER stress and suppressing macrophage activation in db/db mice.

    PubMed

    Park, Kun-Young; Kim, Bobae; Hyun, Chang-Kee

    2015-05-01

    Although recent studies have reported that Lactobacillus rhamnosus GG (LGG), the most extensively studied probiotic strain, exerts an anti-hyperglycemic effect on several rodent models, the underlying mechanism remains unclear. In this study, twenty male C57BL/KsJ-db/db (db/db) mice were divided into 2 groups, LGG-treated and control group, which received a daily dose of LGG (1 × 10(8) CFU per mouse) and PBS orally for 4 weeks, respectively. We observed that glucose tolerance was significantly improved in LGG-treated db/db mice. Insulin-stimulated Akt phosphorylation and GLUT4 translocation were higher in skeletal muscle of LGG-treated mice relative to their controls. It was also observed that LGG treatment caused significant reductions in endoplasmic reticulum (ER) stress in skeletal muscle and M1-like macrophage activation in white adipose tissues. Our results indicate that the anti-diabetic effect of LGG in db/db mice is associated with alleviated ER stress and suppressed macrophage activation, resulting in enhanced insulin sensitivity. These findings suggest a therapeutic potential of probiotics for prevention and treatment of type 2 diabetes. PMID:26060355

  11. Lactobacillus rhamnosus GG improves glucose tolerance through alleviating ER stress and suppressing macrophage activation in db/db mice

    PubMed Central

    Park, Kun-Young; Kim, Bobae; Hyun, Chang-Kee

    2015-01-01

    Although recent studies have reported that Lactobacillus rhamnosus GG (LGG), the most extensively studied probiotic strain, exerts an anti-hyperglycemic effect on several rodent models, the underlying mechanism remains unclear. In this study, twenty male C57BL/KsJ-db/db (db/db) mice were divided into 2 groups, LGG-treated and control group, which received a daily dose of LGG (1 × 108 CFU per mouse) and PBS orally for 4 weeks, respectively. We observed that glucose tolerance was significantly improved in LGG-treated db/db mice. Insulin-stimulated Akt phosphorylation and GLUT4 translocation were higher in skeletal muscle of LGG-treated mice relative to their controls. It was also observed that LGG treatment caused significant reductions in endoplasmic reticulum (ER) stress in skeletal muscle and M1-like macrophage activation in white adipose tissues. Our results indicate that the anti-diabetic effect of LGG in db/db mice is associated with alleviated ER stress and suppressed macrophage activation, resulting in enhanced insulin sensitivity. These findings suggest a therapeutic potential of probiotics for prevention and treatment of type 2 diabetes. PMID:26060355

  12. Silymarin alleviates hepatic oxidative stress and protects against metabolic disorders in high-fat diet-fed mice.

    PubMed

    Feng, Bin; Meng, Ran; Huang, Bin; Shen, Shanmei; Bi, Yan; Zhu, Dalong

    2016-01-01

    Silymarin is a potent antioxidant medicine and has been widely used for the treatment of liver diseases over 30 years. Recent studies suggest that silymarin may benefit patients with glucose intolerance. However, the mechanism underlying the action of silymarin is not clarified. The aim of this work was to assess the impact of silymarin on glucose intolerance in high-fat diet (HFD)-fed mice, and explore the potential therapeutic mechanisms. C57BL/6 mice were fed with HFD for 12 weeks, randomized, and treated orally with vehicle saline or silymarin (30 mg/kg) daily for 30 days. We found that silymarin significantly improved HFD-induced body weight gain, glucose intolerance, and insulin resistance in mice. Silymarin treatment reduced HFD-increased oxidative stress indicators (reactive oxygen species, lipid peroxidation, protein oxidation) and restored HFD-down-regulated activities of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase) in the plasma and/or liver of the HFD-fed mice. Furthermore, silymarin decreased HFD-up-regulated hepatic NADPH oxidase expression and NF-κB activation in mice. Additionally, silymarin treatment mitigated HFD-increased plasma IL-1β, TNF-α levels, and HFD-enhanced hepatic NO, TLR4, and iNOS expression in mice. These novel data indicate that silymarin has potent anti-diabetic actions through alleviating oxidative stress and inflammatory response, partially by inhibiting hepatic NADPH oxidase expression and the NF-κB signaling. PMID:26758315

  13. 40 CFR 90.427 - Catalyst thermal stress resistance evaluation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 20 2011-07-01 2011-07-01 false Catalyst thermal stress resistance... Gaseous Exhaust Test Procedures § 90.427 Catalyst thermal stress resistance evaluation. (a) The purpose of the evaluation procedure specified in this section is to determine the effect of thermal stress...

  14. 40 CFR 91.427 - Catalyst thermal stress resistance evaluation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 20 2011-07-01 2011-07-01 false Catalyst thermal stress resistance... Procedures § 91.427 Catalyst thermal stress resistance evaluation. (a)(1) The purpose of the evaluation procedure specified in this section is to determine the effect of thermal stress on catalyst...

  15. 40 CFR 90.329 - Catalyst thermal stress test.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 20 2011-07-01 2011-07-01 false Catalyst thermal stress test. 90.329... Equipment Provisions § 90.329 Catalyst thermal stress test. (a) Oven characteristics. The oven used for... effect of thermal stress on catalyst conversion efficiency. (2) The synthetic exhaust gas mixture...

  16. 40 CFR 91.427 - Catalyst thermal stress resistance evaluation.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 21 2012-07-01 2012-07-01 false Catalyst thermal stress resistance... Procedures § 91.427 Catalyst thermal stress resistance evaluation. (a)(1) The purpose of the evaluation procedure specified in this section is to determine the effect of thermal stress on catalyst...

  17. 40 CFR 90.329 - Catalyst thermal stress test.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 21 2012-07-01 2012-07-01 false Catalyst thermal stress test. 90.329... Equipment Provisions § 90.329 Catalyst thermal stress test. (a) Oven characteristics. The oven used for... effect of thermal stress on catalyst conversion efficiency. (2) The synthetic exhaust gas mixture...

  18. 40 CFR 90.427 - Catalyst thermal stress resistance evaluation.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 21 2013-07-01 2013-07-01 false Catalyst thermal stress resistance... Gaseous Exhaust Test Procedures § 90.427 Catalyst thermal stress resistance evaluation. (a) The purpose of the evaluation procedure specified in this section is to determine the effect of thermal stress...

  19. 40 CFR 90.427 - Catalyst thermal stress resistance evaluation.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 21 2012-07-01 2012-07-01 false Catalyst thermal stress resistance... Gaseous Exhaust Test Procedures § 90.427 Catalyst thermal stress resistance evaluation. (a) The purpose of the evaluation procedure specified in this section is to determine the effect of thermal stress...

  20. 40 CFR 90.329 - Catalyst thermal stress test.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 20 2014-07-01 2013-07-01 true Catalyst thermal stress test. 90.329... Equipment Provisions § 90.329 Catalyst thermal stress test. (a) Oven characteristics. The oven used for... effect of thermal stress on catalyst conversion efficiency. (2) The synthetic exhaust gas mixture...

  1. 40 CFR 90.427 - Catalyst thermal stress resistance evaluation.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 20 2014-07-01 2013-07-01 true Catalyst thermal stress resistance... Gaseous Exhaust Test Procedures § 90.427 Catalyst thermal stress resistance evaluation. (a) The purpose of the evaluation procedure specified in this section is to determine the effect of thermal stress...

  2. 40 CFR 91.427 - Catalyst thermal stress resistance evaluation.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 21 2013-07-01 2013-07-01 false Catalyst thermal stress resistance... Procedures § 91.427 Catalyst thermal stress resistance evaluation. (a)(1) The purpose of the evaluation procedure specified in this section is to determine the effect of thermal stress on catalyst...

  3. 40 CFR 91.427 - Catalyst thermal stress resistance evaluation.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 20 2014-07-01 2013-07-01 true Catalyst thermal stress resistance... Procedures § 91.427 Catalyst thermal stress resistance evaluation. (a)(1) The purpose of the evaluation procedure specified in this section is to determine the effect of thermal stress on catalyst...

  4. 40 CFR 90.329 - Catalyst thermal stress test.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 21 2013-07-01 2013-07-01 false Catalyst thermal stress test. 90.329... Equipment Provisions § 90.329 Catalyst thermal stress test. (a) Oven characteristics. The oven used for... effect of thermal stress on catalyst conversion efficiency. (2) The synthetic exhaust gas mixture...

  5. 40 CFR 90.329 - Catalyst thermal stress test.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Catalyst thermal stress test. 90.329... Equipment Provisions § 90.329 Catalyst thermal stress test. (a) Oven characteristics. The oven used for... effect of thermal stress on catalyst conversion efficiency. (2) The synthetic exhaust gas mixture...

  6. 40 CFR 90.427 - Catalyst thermal stress resistance evaluation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Catalyst thermal stress resistance... Gaseous Exhaust Test Procedures § 90.427 Catalyst thermal stress resistance evaluation. (a) The purpose of the evaluation procedure specified in this section is to determine the effect of thermal stress...

  7. 40 CFR 91.427 - Catalyst thermal stress resistance evaluation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Catalyst thermal stress resistance... Procedures § 91.427 Catalyst thermal stress resistance evaluation. (a)(1) The purpose of the evaluation procedure specified in this section is to determine the effect of thermal stress on catalyst...

  8. Thermal stress analysis for a wood composite blade. [wind turbines

    NASA Technical Reports Server (NTRS)

    Fu, K. C.; Harb, A.

    1984-01-01

    Heat conduction throughout the blade and the distribution of thermal stresses caused by the temperature distribution were determined for a laminated wood wind turbine blade in both the horizontal and vertical positions. Results show that blade cracking is not due to thermal stresses induced by insulation. A method and practical example of thermal stress analysis for an engineering body of orthotropic materials is presented.

  9. Resveratrol alleviates endotoxemia-associated adrenal insufficiency by suppressing oxidative/nitrative stress.

    PubMed

    Duan, Guo-Li; Wang, Chang-Nan; Liu, Yu-Jian; Yu, Qing; Tang, Xiao-Lu; Ni, Xin; Zhu, Xiao-Yan

    2016-06-30

    We have recently demonstrated that endotoxin causes oxidative stress and overproduction of nitric oxide in adrenal glands, thereby leading to adrenocortical insufficiency. The aim of this study is to investigate the effects of resveratrol, a natural plant polyphenol with anti-oxidant and anti-nitrative properties, on endotoxemia-associated adrenocortical insufficiency. Resveratrol was administered immediately before injection of lipopolysaccharide (LPS). Twenty four hours later, the adrenocorticotropic hormone (ACTH) stimulation tests was been performed to measure the plasma corticosterone level and the adrenal gland tissues were collected for histopathologic examination, and determination of malondialdehyde (MDA), total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, catalase (CAT) activity, inducible nitric oxide synthase (iNOS) expression, nitric oxide (NO) and peroxynitrite production. Treatment with resveratrol significantly inhibited endotoxemia-induced iNOS expression, NO production, and peroxynitrite formation and also attenuated LPS-induced oxidative stress in the adrenal gland, as evidenced by the decrease of pro-oxidant biomarker (MDA), and the increases of anti-oxidant biomarkers (T-AOC, CAT and SOD activity). H&E staining demonstrated that administration of LPS resulted in increased into the adrenal gland. H&E-stained sections of adrenal glands demonstrated signs of leukocyte infiltration and hemorrhage during endotoxemia, which were significantly improved by resveratrol treatment. In addition, resveratrol reversed the LPS-induced downregulation of ACTH receptor and silent information regulator 1 (SIRT1) in adrenal gland, as well as adrenocortical hyporesponsiveness to ACTH. Resveratrol exerts protective effects against endotoxemia-associated adrenocortical insufficiency by suppressing oxidative/nitrative stress. These findings support the potential for resveratrol as a possible pharmacological agent to improve adrenocortical

  10. Mamao Pomace Extract Alleviates Hypertension and Oxidative Stress in Nitric Oxide Deficient Rats

    PubMed Central

    Kukongviriyapan, Upa; Kukongviriyapan, Veerapol; Pannangpetch, Patchareewan; Donpunha, Wanida; Sripui, Jintana; Sae-Eaw, Amporn; Boonla, Orachorn

    2015-01-01

    Reactive oxygen species (ROS)-induced oxidative stress plays a major role in pathogenesis of hypertension. Antidesma thwaitesianum (local name: Mamao) is a tropical plant distributed in the tropical/subtropical areas of the world, including Thailand. Mamao pomace (MP), a by-product generated from Mamao fruits, contains large amounts of antioxidant polyphenolic compounds. The aim of this study was to investigate the antihypertensive and antioxidative effects of MP using hypertensive rats. For this purpose, male Sprague-Dawley rats were given Nω-nitro-l-arginine methyl ester (l-NAME), an inhibitor of endothelial nitric oxide synthase (eNOS), in drinking water (50 mg/kg) for three weeks. MP extract was orally administered daily at doses of 100 and 300 mg/kg. l-NAME administration induced marked increase in blood pressure, peripheral vascular resistance, and oxidative stress. MP treatment significantly prevented the increase in blood pressure, hindlimb blood flow and hindlimb vascular resistance of l-NAME treated hypertensive rats (p < 0.05). The antihypertensive effect of MP treatment was associated with suppression of superoxide production from carotid strips and also with an increase in eNOS protein expression and nitric oxide bioavailability. The present results provide evidence for the antihypertensive effect of MP and suggest that MP might be useful as a dietary supplement against hypertension. PMID:26225998

  11. Dioscin alleviates dimethylnitrosamine-induced acute liver injury through regulating apoptosis, oxidative stress and inflammation.

    PubMed

    Zhang, Weixin; Yin, Lianhong; Tao, Xufeng; Xu, Lina; Zheng, Lingli; Han, Xu; Xu, Youwei; Wang, Changyuan; Peng, Jinyong

    2016-07-01

    In our previous study, the effects of dioscin against alcohol-, carbon tetrachloride- and acetaminophen-induced liver damage have been found. However, the activity of it against dimethylnitrosamine (DMN)-induced acute liver injury remained unknown. In the present study, dioscin markedly decreased serum ALT and AST levels, significantly increased the levels of SOD, GSH-Px, GSH, and decreased the levels of MDA, iNOS and NO. Mechanism study showed that dioscin significantly decreased the expression levels of IL-1β, IL-6, TNF-α, IκBα, p50 and p65 through regulating TLR4/MyD88 pathway to rehabilitate inflammation. In addition, dioscin markedly up-regulated the expression levels of SIRT1, HO-1, NQO1, GST and GCLM through increasing nuclear translocation of Nrf2 against oxidative stress. Furthermore, dioscin significantly decreased the expression levels of FasL, Fas, p53, Bak, Caspase-3/9, and upregulated Bcl-2 level through decreasing IRF9 level against apoptosis. In conclusion, dioscin showed protective effect against DMN-induced acute liver injury via ameliorating apoptosis, oxidative stress and inflammation, which should be developed as a new candidate for the treatment of acute liver injury in the future. PMID:27317992

  12. 40 CFR 91.329 - Catalyst thermal stress test.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 20 2011-07-01 2011-07-01 false Catalyst thermal stress test. 91.329....329 Catalyst thermal stress test. (a) Oven characteristics. The oven used for termally stressing the... stress on catalyst conversion efficiency. (2) The synthetic exhaust gas mixture must have the...

  13. 40 CFR 91.329 - Catalyst thermal stress test.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Catalyst thermal stress test. 91.329....329 Catalyst thermal stress test. (a) Oven characteristics. The oven used for termally stressing the... stress on catalyst conversion efficiency. (2) The synthetic exhaust gas mixture must have the...

  14. Carvedilol alleviates adjuvant-induced arthritis and subcutaneous air pouch edema: Modulation of oxidative stress and inflammatory mediators

    SciTech Connect

    Arab, Hany H.; El-Sawalhi, Maha M.

    2013-04-15

    Rheumatoid arthritis (RA) is a systemic inflammatory disease with cardiovascular complications as the leading cause of morbidity. Carvedilol is an adrenergic antagonist which has been safely used in treatment of several cardiovascular disorders. Given that carvedilol has powerful antioxidant/anti-inflammatory properties, we aimed to investigate its protective potential against arthritis that may add further benefits for its clinical usefulness especially in RA patients with concomitant cardiovascular disorders. Two models were studied in the same rat; adjuvant arthritis and subcutaneous air pouch edema. Carvedilol (10 mg/kg/day p.o. for 21 days) effectively suppressed inflammation in both models with comparable efficacy to the standard anti-inflammatory diclofenac (5 mg/kg/day p.o.). Notably, carvedilol inhibited paw edema and abrogated the leukocyte invasion to air pouch exudates. The latter observation was confirmed by the histopathological assessment of the pouch lining that revealed mitigation of immuno-inflammatory cell influx. Carvedilol reduced/normalized oxidative stress markers (lipid peroxides, nitric oxide and protein thiols) and lowered the release of inflammatory cytokines (TNF-α and IL-6), and eicosanoids (PGE{sub 2} and LTB{sub 4}) in sera and exudates of arthritic rats. Interestingly, carvedilol, per se, didn't present any effect on assessed biochemical parameters in normal rats. Together, the current study highlights evidences for the promising anti-arthritic effects of carvedilol that could be mediated through attenuation of leukocyte migration, alleviation of oxidative stress and suppression of proinflammatory cytokines and eicosanoids. - Highlights: ► Carvedilol possesses promising anti-arthritic properties. ► It markedly suppressed inflammation in adjuvant arthritis and air pouch edema. ► It abrogated the leukocyte invasion to air pouch exudates and linings. ► It reduced/normalized oxidative stress markers in sera and exudates of

  15. Vitamin C and vitamin E supplementation alleviates oxidative stress induced by dexamethasone and improves fertility of breeder roosters.

    PubMed

    Min, Yuna; Sun, Tongtong; Niu, Zhuye; Liu, Fuzhu

    2016-08-01

    This study was conducted to determine the effect of supplemental dietary vitamin C (VC) and vitamin E (VE) on improving semen quality and antioxidative status in breeder roosters challenged with dexamethasone (DEX). 120 45-week-old Lveyang black-boned breeder roosters were divided into 5 experimental treatments, including negative group, positive group, and three trial groups, which were fed basal diet supplemented with 300mg/kg VC, 200mg/kg VE, or 300mg/kg VC and 200mg/kg VE (VC+VE). At 49 weeks of age, the positive control and trial groups were subcutaneously injected 3 times every other day with DEX 4 mg/kg body weight, the negative control group was sham injected with saline. At 50 weeks of age, average daily feed intake of birds challenged with DEX significantly increased (P<0.05), however, serum testosterone significantly decreased (P<0.05). Dietary supplementation of VC+VE enhanced serum testosterone and sperm motility remarkably (P<0.05). There were no differences in sperm viability between the DEX-treated groups. During the post-stress recovery period (52 weeks of age), dietary supplementation of VE and VC+VE significantly increased the body weight of birds under oxidative stress (P<0.01). VC, VE, and VC+VE groups had greater sperm viability than control group (P<0.01). Additionally, there was a decrease in the semen plasma malondialdehyde content (P<0.05) of the VC and VC+VE groups, and in the testicular malondialdehyde content (P<0.01) of the VE and VC+VE groups. In summary, VC, VE, especially their combination alleviate the oxidative stress induced by DEX and are favorable for the fertility of breeder roosters. PMID:27297178

  16. Alleviative effect of myricetin on ochratoxin A-induced oxidative stress in rat renal cortex: histological and biochemical study.

    PubMed

    El-Haleem, Manal R Abdel; Kattaia, Asmaa A A; El-Baset, Samia A Abdel; Mostafa, Heba El Sayed

    2016-04-01

    Ochratoxins (OTA) are secondary metabolites of Aspergillus and Penicillium. The detoxification of OTA has been of major interest due to its widespread threat to human health. We aimed to investigate the possible alleviative effect of myricetin (MYR) against OTA-induced damage in renal cortex of rats. Thirty adult male albino rats were randomized into five equal groups: control (untreated), vehicle control (0.5 ml corn oil/day including dimethylsulfoxide [DMSO]), MYR (100 mg MYR/kg b.w./day in distilled water), OTA (0.5 mg OTA/kg b.w./day; dissolved in 10% DMSO and then corn oil) and OTA + MYR group (received OTA and MYR at similar doses). All treatments were given by oral gavage for 2 weeks. At the end of the experiment, renal cortices were processed for light and electron microscope examinations. Immunohistochemical staining for localization of proliferating cell nuclear antigen (PCNA), p53 and transforming growth factor beta 1 (TGF-β1) was carried out. Biochemical analysis of tissue glutathione peroxidase (GPX), catalase (CAT) and superoxide dismutase (SOD) were determined to evaluate oxidative stress. OTA administration induced deleterious renal injury evidenced by the structural and ultra-structural changes. Immunohistochemical expression of p53, PCNA and TGF-β1 were significantly up regulated compared with control. Alterations in antioxidant parameters supported that oxidative stress was one of the mechanisms involved in OTA toxicity. On the contrary, co-administration of MRY partially ameliorated OTA-induced renal injury. We suggest the potential effectiveness of MYR to counteract OTA-induced toxic oxidative stress on the renal cortex. PMID:26571153

  17. Polysaccharides from Angelica sinensis alleviate neuronal cell injury caused by oxidative stress

    PubMed Central

    Lei, Tao; Li, Haifeng; Fang, Zhen; Lin, Junbin; Wang, Shanshan; Xiao, Lingyun; Yang, Fan; Liu, Xin; Zhang, Junjian; Huang, Zebo; Liao, Weijing

    2014-01-01

    Angelica sinensis has antioxidative and neuroprotective effects. In the present study, we aimed to determine the neuroprotective effect of polysaccharides isolated from Angelica sinensis. In a preliminary experiment, Angelica sinensis polysaccharides not only protected PC12 neuronal cells from H2O2-induced cytotoxicity, but also reduced apoptosis and intracellular reactive oxygen species levels, and increased the mitochondrial membrane potential induced by H2O2 treatment. In a rat model of local cerebral ischemia, we further demonstrated that Angelica sinensis polysaccharides enhanced the antioxidant activity in cerebral cortical neurons, increased the number of microvessels, and improved blood flow after ischemia. Our findings highlight the protective role of polysaccharides isolated from Angelica sinensis against nerve cell injury and impairment caused by oxidative stress. PMID:25206810

  18. Thymoquinone alleviates nonalcoholic fatty liver disease in rats via suppression of oxidative stress, inflammation, apoptosis.

    PubMed

    Awad, Azza S M; Abd Al Haleem, Ekram N; El-Bakly, Wesam M; Sherief, Mohie A

    2016-04-01

    Nonalcoholic steatohepatitis (NAFLD) is a progressive form of liver disease that leads to advanced fibrosis. The present study was designed to assess the hepatoprotective effect of thymoquinone (TQ) on liver functions, insulin resistance, and PPAR-γ expression in NAFLD. Rats were divided into two main groups: one fed with normal rat chow diet and the other with high-fat high-cholesterol diet group for 6 weeks. Every group was subdivided into three subgroups (n = 8): treated with saline, low dose TQ (10 mg/kg), high dose TQ (20 mg/kg). High fat high cholesterol diet caused marked liver damage as noted in histopathology and significant increase in liver index, liver enzymes. There was significant increase in the insulin resistance, serum cholesterol, triglyceride, PPAR-γ gene overexpression with significant decrease in HDL. Additionally, oxidative stress increased by measuring MDA associated with significant decrease in serum total antioxidant capacity. As markers of inflammation, hepatic TNF-α was significantly increased with decrease in IL10. Further, there was increase in BAX protein with decrease in Bcl as compared to control group. This model of 6 weeks high-fat high-cholesterol diet showed minimal fibrosis as noticed by increase MMP2 and Masson trichrome satin. Co-treatment with TQ improved all previous parameters. High dose was more effective, although mostly non-statistically significant. TQ may have a promising agent to improve hepatic steatosis, oxidative stress; inflammatory, apoptotic status, fibrosis and so prevent liver damage in patients with NAFLD. Although PPAR-γ was significantly under-expressed by TQ, insulin resistance was improved significantly suggesting a role of liver damage. PMID:26753695

  19. Arbuscular mycorrhizal symbiosis elicits shoot proteome changes that are modified during cadmium stress alleviation in Medicago truncatula

    PubMed Central

    2011-01-01

    Background Arbuscular mycorrhizal (AM) fungi, which engage a mutualistic symbiosis with the roots of most plant species, have received much attention for their ability to alleviate heavy metal stress in plants, including cadmium (Cd). While the molecular bases of Cd tolerance displayed by mycorrhizal plants have been extensively analysed in roots, very little is known regarding the mechanisms by which legume aboveground organs can escape metal toxicity upon AM symbiosis. As a model system to address this question, we used Glomus irregulare-colonised Medicago truncatula plants, which were previously shown to accumulate and tolerate heavy metal in their shoots when grown in a substrate spiked with 2 mg Cd kg-1. Results The measurement of three indicators for metal phytoextraction showed that shoots of mycorrhizal M. truncatula plants have a capacity for extracting Cd that is not related to an increase in root-to-shoot translocation rate, but to a high level of allocation plasticity. When analysing the photosynthetic performance in metal-treated mycorrhizal plants relative to those only Cd-supplied, it turned out that the presence of G. irregulare partially alleviated the negative effects of Cd on photosynthesis. To test the mechanisms by which shoots of Cd-treated mycorrhizal plants avoid metal toxicity, we performed a 2-DE/MALDI/TOF-based comparative proteomic analysis of the M. truncatula shoot responses upon mycorrhization and Cd exposure. Whereas the metal-responsive shoot proteins currently identified in non-mycorrhizal M. truncatula indicated that Cd impaired CO2 assimilation, the mycorrhiza-responsive shoot proteome was characterised by an increase in photosynthesis-related proteins coupled to a reduction in glugoneogenesis/glycolysis and antioxidant processes. By contrast, Cd was found to trigger the opposite response coupled the up-accumulation of molecular chaperones in shoot of mycorrhizal plants relative to those metal-free. Conclusion Besides drawing a

  20. Autophagy protects intestinal epithelial cells against deoxynivalenol toxicity by alleviating oxidative stress via IKK signaling pathway.

    PubMed

    Tang, Yulong; Li, Jianjun; Li, Fengna; Hu, Chien-An A; Liao, Peng; Tan, Kunrong; Tan, Bie; Xiong, Xia; Liu, Gang; Li, Tiejun; Yin, Yulong

    2015-12-01

    Autophagy is an intracellular process of homeostatic degradation that promotes cell survival under various stressors. Deoxynivalenol (DON), a fungal toxin, often causes diarrhea and disturbs the homeostasis of the intestinal system. To investigate the function of intestinal autophagy in response to DON and associated mechanisms, we firstly knocked out ATG5 (autophagy-related gene 5) in porcine intestinal epithelial cells (IPEC-J2) using CRISPR-Cas9 technology. When treated with DON, autophagy was induced in IPEC-J2 cells but not in IPEC-J2.Atg5ko cells. The deficiency in autophagy increased DON-induced apoptosis in IPEC-J2.atg5ko cells, in part, through the generation of reactive oxygen species (ROS). The cellular stress response can be restored in IPEC-J2.atg5ko cells by overexpressing proteins involved in protein folding. Interestingly, we found that autophagy deficiency downregulated the expression of endoplasmic reticulum folding proteins BiP and PDI when IPEC-J2.atg5ko cells were treated with DON. In addition, we investigated the molecular mechanism of autophagy involved in the IKK, AMPK, and mTOR signaling pathway and found that Bay-117082 and Compound C, specific inhibitors for IKK and AMPK, respectively, inhibited the induction of autophagy. Taken together, our results suggest that autophagy is pivotal for protection against DON in pig intestinal cells. PMID:26456059

  1. Epalrestat protects against diabetic peripheral neuropathy by alleviating oxidative stress and inhibiting polyol pathway

    PubMed Central

    Li, Qing-rong; Wang, Zhuo; Zhou, Wei; Fan, Shou-rui; Ma, Run; Xue, Li; Yang, Lu; Li, Ya-shan; Tan, Hong-li; Shao, Qing-hua; Yang, Hong-ying

    2016-01-01

    Epalrestat is a noncompetitive and reversible aldose reductase inhibitor used for the treatment of diabetic neuropathy. This study assumed that epalrestat had a protective effect on diabetic peripheral nerve injury by suppressing the expression of aldose reductase in peripheral nerves of diabetes mellitus rats. The high-fat and high-carbohydrate model rats were established by intraperitoneal injection of streptozotocin. Peripheral neuropathy occurred in these rats after sustaining high blood glucose for 8 weeks. At 12 weeks after streptozotocin injection, rats were intragastrically administered epalrestat 100 mg/kg daily for 6 weeks. Transmission electron microscope revealed that the injuries to myelinated nerve fibers, non-myelinated nerve fibers and Schwann cells of rat sciatic nerves had reduced compared to rats without epalrestat administuation. Western blot assay and immunohistochemical results demonstrated that after intervention with epalrestat, the activities of antioxidant enzymes such as superoxide dismutase, catalase and glutathione peroxidase gradually increased, but aldose reductase protein expression gradually diminished. Results confirmed that epalrestat could protect against diabetic peripheral neuropathy by relieving oxidative stress and suppressing the polyol pathway. PMID:27073391

  2. Oxidative Stress Alleviation by Sage Essential Oil in Co-amoxiclav induced Hepatotoxicity in Rats

    PubMed Central

    El-Hosseiny, L. S.; Alqurashy, N. N.; Sheweita, S. A.

    2016-01-01

    Clinical studies have shown that several classes of antibiotics are evidenced in drug induced liver injury. The combination of amoxicillin with clavulanic acid is commonly cited in such cases. Accordingly, the present study investigated the potential hepatoprotective and in vivo antioxidant efficacy of sage essential oil in Co-amoxiclav induced hepatotoxicity in rats. Sage essential oil was hydrodistilled from the aerial parts of Salvia officinalis L. and its compositional analysis was characterized by Gas chromatography-Mass spectroscopy. Rats were treated singly or concomitantly with Co-amoxiclav and sage essential oil for a period of seven days. The major components of sage oil as identified by GC-MS were 1,8-cineole, β-pinene, camphor, β-caryophyllene, α-pinene and α-caryophyllene comprising 26.3%, 14.4%, 10.9%, 7.8%, 6% and 2.5% respectively. The in vivo exposure of rats to Co-amoxiclav resulted in hepatotoxicity biochemically evidenced by the significant elevation of serum AST, ALT, ALP, γ-GT, total bilirubin and histologically conveyed by hydropic, inflammatory and cholestatic changes in rats’ liver. Oxidative stress mediated the hepatic injury as indicated by the significant escalation in lipid peroxidation, as well as, the significant depletion of both glutathione level and glutathione dependent enzymes’ activities. The concomitant administration of sage essential oil with Co-amoxiclav exerted a hepatoprotective effect via inducing an in vivo antioxidant defense response eventually regressing, to some extent, the hepatoarchitectural changes induced by Co-amoxiclav. Results suggest that sage essential oil is a potential candidate for counteracting hepatic injury associating Co-amoxiclav and this effect is in part related to the complexity of its chemical composition. PMID:27493593

  3. Oxidative Stress Alleviation by Sage Essential Oil in Co-amoxiclav induced Hepatotoxicity in Rats.

    PubMed

    El-Hosseiny, L S; Alqurashy, N N; Sheweita, S A

    2016-06-01

    Clinical studies have shown that several classes of antibiotics are evidenced in drug induced liver injury. The combination of amoxicillin with clavulanic acid is commonly cited in such cases. Accordingly, the present study investigated the potential hepatoprotective and in vivo antioxidant efficacy of sage essential oil in Co-amoxiclav induced hepatotoxicity in rats. Sage essential oil was hydrodistilled from the aerial parts of Salvia officinalis L. and its compositional analysis was characterized by Gas chromatography-Mass spectroscopy. Rats were treated singly or concomitantly with Co-amoxiclav and sage essential oil for a period of seven days. The major components of sage oil as identified by GC-MS were 1,8-cineole, β-pinene, camphor, β-caryophyllene, α-pinene and α-caryophyllene comprising 26.3%, 14.4%, 10.9%, 7.8%, 6% and 2.5% respectively. The in vivo exposure of rats to Co-amoxiclav resulted in hepatotoxicity biochemically evidenced by the significant elevation of serum AST, ALT, ALP, γ-GT, total bilirubin and histologically conveyed by hydropic, inflammatory and cholestatic changes in rats' liver. Oxidative stress mediated the hepatic injury as indicated by the significant escalation in lipid peroxidation, as well as, the significant depletion of both glutathione level and glutathione dependent enzymes' activities. The concomitant administration of sage essential oil with Co-amoxiclav exerted a hepatoprotective effect via inducing an in vivo antioxidant defense response eventually regressing, to some extent, the hepatoarchitectural changes induced by Co-amoxiclav. Results suggest that sage essential oil is a potential candidate for counteracting hepatic injury associating Co-amoxiclav and this effect is in part related to the complexity of its chemical composition. PMID:27493593

  4. Gypenosides alleviate myocardial ischemia-reperfusion injury via attenuation of oxidative stress and preservation of mitochondrial function in rat heart.

    PubMed

    Yu, Haijie; Guan, Qigang; Guo, Liang; Zhang, Haishan; Pang, Xuefeng; Cheng, Ying; Zhang, Xingang; Sun, Yingxian

    2016-05-01

    Gypenosides (GP) are the predominant components of Gynostemma pentaphyllum, a Chinese herb medicine that has been widely used for the treatment of chronic inflammation, hyperlipidemia, and cardiovascular disease. GP has been demonstrated to exert protective effects on the liver and brain against ischemia-reperfusion (I/R) injury, yet whether it is beneficial to the heart during myocardial I/R is unclear. In this study, we demonstrate that pre-treatment with GP dose-dependently limits infarct size, alleviates I/R-induced pathological changes in the myocardium, and preserves left ventricular function in a rat model of cardiac I/R injury. In addition, GP pre-treatment reduces oxidative stress and protects the intracellular antioxidant machinery in the myocardium. Further, we show that the cardioprotective effect of GP is associated with the preservation of mitochondrial function in the cardiomyocytes, as indicated by ATP level, enzymatic activities of complex I, II, and IV on the mitochondrial respiration chain, and the activity of citrate synthase in the citric acid cycle for energy generation. Moreover, GP maintains mitochondrial membrane integrity and inhibits the release of cytochrome c from the mitochondria to the cytosol. The cytoprotective effect of GP is further confirmed in vitro in H9c2 cardiomyoblast cell line with oxygen-glucose deprivation and reperfusion (OGD/R), and the results indicate that GP protects cell viability, reduces oxidative stress, and preserves mitochondrial function. In conclusion, our study suggests that GP may be of clinical value in cytoprotection during acute myocardial infarction and reperfusion. PMID:26800973

  5. Dietary supplementation with L-glutamate and L-aspartate alleviates oxidative stress in weaned piglets challenged with hydrogen peroxide.

    PubMed

    Duan, Jielin; Yin, Jie; Ren, Wenkai; Liu, Ting; Cui, Zhijie; Huang, Xingguo; Wu, Li; Kim, Sung Woo; Liu, Gang; Wu, Xi; Wu, Guoyao; Li, Tiejun; Yin, Yulong

    2016-01-01

    This study was to evaluate the protective roles of L-glutamate (Glu) and L-aspartate (Asp) in weaned piglets challenged with H2O2. Forty weaned piglets were assigned randomly into one of five groups (8 piglets/group): (1) control group (NC) in which pigs were fed a corn- and soybean meal-based diet and received intraperitoneal administration of saline; (2) H2O2 group (PC) in which pigs were fed the basal diet and received intraperitoneal administration of 10 % H2O2 (1 ml/kg body weight once on days 8 and repeated on day 11); (3) PC + Glu group (PG) in which pigs were fed the basal diet supplemented with 2.0 % Glu before intraperitoneal administration of 10 % H2O2; (4) PC + Asp group (PA) in which pigs were fed the basal diet supplemented with 1.0 % Asp before intraperitoneal administration of 10 % H2O2; (5) PC + Glu + Asp group (PGA) in which pigs were fed the basal diet supplemented with 2.0 % Glu plus 1.0 % Asp before intraperitoneal administration of 10 % H2O2. Measured parameters included daily feed intake (DFI), average daily gain (ADG), feed conversion rate (FCR), and serum anti-oxidative enzyme activities (catalase, superoxide dismutase, glutathione peroxidase-1), serum malondialdehyde and H2O2 concentrations, serum amino acid (AA) profiles, and intestinal expression of AA transporters. Dietary supplementation with Glu, Asp or their combination attenuated the decreases in DFI, ADG and feed efficiency, the increase in oxidative stress, the alterations of serum AA concentrations, and the changed expression of intestinal AA transporters in H2O2-challenged piglets. Thus, dietary supplementation with Glu or Asp alleviates growth suppression and oxidative stress, while restoring serum the amino acid pool in H2O2-challenged piglets. PMID:26255283

  6. Physiological Responses to Thermal Stress and Exercise

    NASA Astrophysics Data System (ADS)

    Iyota, Hiroyuki; Ohya, Akira; Yamagata, Junko; Suzuki, Takashi; Miyagawa, Toshiaki; Kawabata, Takashi

    The simple and noninvasive measuring methods of bioinstrumentation in humans is required for optimization of air conditioning and management of thermal environments, taking into consideration the individual specificity of the human body as well as the stress conditions affecting each. Changes in human blood circulation were induced with environmental factors such as heat, cold, exercise, mental stress, and so on. In this study, the physiological responses of human body to heat stress and exercise were investigated in the initial phase of the developmental research. We measured the body core and skin temperatures, skin blood flow, and pulse wave as the indices of the adaptation of the cardiovascular system. A laser Doppler skin blood flowmetry using an optical-sensor with a small portable data logger was employed for the measurement. These results reveal the heat-stress and exercise-induced circulatory responses, which are under the control of the sympathetic nerve system. Furthermore, it was suggested that the activity of the sympathetic nervous system could be evaluated from the signals of the pulse wave included in the signals derived from skin blood flow by means of heart rate variability assessments and detecting peak heights of velocity-plethysmogram.

  7. Thermal stress analysis of wrapped pipes in steady temperature state

    SciTech Connect

    Kawaguchi, Kouji; Sawa, Toshiyuki

    1995-11-01

    Thermal stress distributions of wrapped pipes subjected to heat loading are analyzed using an axisymmetrical theory of elasticity. The wrapped pipes consist of two finite hollow pipes of dissimilar material. In the numerical calculations, the effects of the thermal expansion coefficient and Young`s modulus on the interface thermal stress distributions are investigated. The residual thermal stress distributions are examined in the case of alumina-metal wrapped pipes. Experiments on the strains were conducted. It is found that the interface thermal stresses increase with an increase of the ratios of the thermal expansion coefficient and of Young`s modulus between the inner and the outer pipes. Moreover, it is demonstrated that the residual thermal stress in the case of alumina-metal wrapped pipes decreases as Young`s modulus of the outer pipe decreases and the thermal expansion coefficient of the outer pipe increases. The analytical results show good agreement with the experiments.

  8. Analysis of thermal stresses and metal movement during welding

    NASA Technical Reports Server (NTRS)

    Muraki, T.; Masubuchi, K.

    1973-01-01

    The research is reported concerning the development of a system of mathematical solutions and computer programs for one- and two-dimensional analyses for thermal stresses. Reports presented include: the investigation of thermal stress and buckling of tantalum and columbium sheet; and analysis of two dimensional thermal strains and metal movement during welding.

  9. Modeling conductive cooling for thermally stressed dairy cows.

    PubMed

    Gebremedhin, Kifle G; Wu, Binxin; Perano, K

    2016-02-01

    Conductive cooling, which is based on direct contact between a cow lying down and a cooled surface (water mattress, or any other heat exchanger embedded under the bedding), allows heat transfer from the cow to the cooled surface, and thus alleviate heat stress of the cow. Conductive cooling is a novel technology that has the potential to reduce the consumption of energy and water in cooling dairy cows compared to some current practices. A three-dimensional conduction model that simulates cooling thermally-stressed dairy cows was developed. The model used a computational fluid dynamics (CFD) method to characterize the air-flow field surrounding the animal model. The flow field was obtained by solving the continuity and the momentum equations. The heat exchange between the animal and the cooled water mattress as well as between the animal and ambient air was determined by solving the energy equation. The relative humidity was characterized using the species transport equation. The conduction 3-D model was validated against experimental temperature data and the agreement was very good (average error is 4.4% and the range is 1.9-8.3%) for a mesh size of 1117202. Sensitivity analyses were conducted between heat losses (sensible and latent) with respect to air temperature, relative humidity, air velocity, and level of wetness of skin surface to determine which of the parameters affect heat flux more than others. Heat flux was more sensitive to air temperature and level of wetness of the skin surface and less sensitive to relative humidity. PMID:26857982

  10. Alleviation of salt stress in citrus seedlings inoculated with arbuscular mycorrhizal fungi depends on the rootstock salt tolerance.

    PubMed

    Navarro, Josefa M; Pérez-Tornero, Olaya; Morte, Asunción

    2014-01-01

    Seedlings of Cleopatra mandarin (Citrus reshni Hort. ex Tan.) and Alemow (Citrus macrophylla Wester) were inoculated with a mixture of AM fungi (Rhizophagus irregularis and Funneliformis mosseae) (+AM), or left non-inoculated (-AM). From forty-five days after fungal inoculation onwards, half of +AM or -AM plants were irrigated with nutrient solution containing 50 mM NaCl. Three months later, AM significantly increased plant growth in both Cleopatra mandarin and Alemow rootstocks. Plant growth was higher in salinized +AM plants than in non-salinized -AM plants, demonstrating that AM compensates the growth limitations imposed by salinity. Whereas AM-inoculated Cleopatra mandarin seedlings had a very good response under saline treatment, inoculation in Alemow did not alleviate the negative effect of salinity. The beneficial effect of mycorrhization is unrelated with protection against the uptake of Na or Cl and the effect of AM on these ions did not explain the different response of rootstocks. This response was related with the nutritional status since our findings confirm that AM fungi can alter host responses to salinity stress, improving more the P, K, Fe and Cu plant nutrition in Cleopatra mandarin than in Alemow plants. AM inoculation under saline treatments also increased root Mg concentration but it was higher in Cleopatra mandarin than in Alemow. This could explain why AM fungus did not completely recovered chlorophyll concentrations in Alemow and consequently it had lower photosynthesis rate than control plants. AM fungi play an essential role in citrus rootstock growth and biomass production although the intensity of this response depends on the rootstock salinity tolerance. PMID:23859560

  11. Thermal-Stress Reducer For Metal/Composite Joint

    NASA Technical Reports Server (NTRS)

    Glinski, Robert L.

    1993-01-01

    Simple insert called "thermal link" reduces stresses caused by mismatches between thermal expansions of metal part and nonmetallic part made of fiber/matrix composite material. Link conceived for use in casing of advanced jet engine.

  12. Argirein alleviates stress-induced and diabetic hypogonadism in rats via normalizing testis endothelin receptor A and connexin 43

    PubMed Central

    Xu, Ming; Hu, Chen; Khan, Hussein-hamed; Shi, Fang-hong; Cong, Xiao-dong; Li, Qing; Dai, Yin; Dai, De-zai

    2016-01-01

    Aim: Argirein (rhein-arginine) is a derivative of rhein isolated from Chinese rhubarb (Rheum Officinale Baill.) that exhibits antioxidant and anti-inflammatory activities. In the present study we investigated the effects of argirein on stress-induced (hypergonadotrophic) and diabetic (hypogonadotrophic) hypogonadism in male rats. Methods: Stress-induced and diabetic hypogonadism was induced in male rats via injection of isoproterenol (ISO) or streptozotocin (STZ). ISO-injected rats were treated with argirein (30 mg·kg−1·d−1, po) or testosterone replacement (0.5 mg·kg−1·d−1, sc) for 5 days, and STZ-injected rats were treated with argirein (40–120 mg·kg−1·d−1, po) or aminoguanidine (100 mg·kg−1·d−1, po) for 4 weeks. After the rats were euthanized, blood samples and testes were collected. Serum hormone levels were measured, and the expression of endothelin receptor A (ETA), connexin 43 (Cx43) and other proteins in testes was detected. For in vitro experiments, testis homogenate was prepared from normal male rats, and incubated with ISO (1 μmol/L) or high glucose (27 mmol/L). Results: ISO injection induced hyper-gonadotrophic hypogonadism characterized by low testosterone and high FSH and LH levels in the serum, whereas STZ injection induced hypogonadotrophic hypogonadism as evidenced by low testosterone and low FSH and LH levels in the serum. In the testes of ISO- and STZ-injected rats, the expression of ETA, MMP-9, NADPH oxidase and pPKCε was significantly increased, and the expression of Cx43 was decreased. Administration of argirein attenuated both the abnormal serum hormone levels and the testis changes in ISO- and STZ-injected rats, and aminoguanidine produced similar actions in STZ-injected rats; testosterone replacement reversed the abnormal serum hormone levels, but did not affect the testis changes in ISO-injected rats. Argirein (0.3–3 μmol/L) exerted similar effects in testis homogenate incubated with ISO or high glucose in

  13. Higher Ammonium Transamination Capacity Can Alleviate Glutamate Inhibition on Winter Wheat (Triticum aestivum L.) Root Growth under High Ammonium Stress

    PubMed Central

    Liu, Yang; Tian, Zhongwei; Muhammad, Abid; Zhang, Yixuan; Jiang, Dong; Cao, Weixing; Dai, Tingbo

    2016-01-01

    Most of the studies about NH4+ stress mechanism simply address the effects of free NH4+, failing to recognize the changed nitrogen assimilation products. The objective of this study was to elucidate the effects of glutamate on root growth under high ammonium (NH4+) conditions in winter wheat (Triticum aestivum L.). Hydroponic experiments were conducted using two wheat cultivars, AK58 (NH4+-sensitive) and Xumai25 (NH4+-tolerant) with either 5 mM NH4+ nitrogen (AN) as stress treatment or 5 mM nitrate (NO3-) nitrogen as control. To evaluate the effects of NH4+-assimilation products on plant growth, 1 μM L-methionine sulfoximine (MSO) (an inhibitor of glutamine synthetase (GS)) and 1 mM glutamates (a primary N assimilation product) were added to the solutions, respectively. The AN significantly reduced plant biomass, total root length, surface area and root volume in both cultivars, but less effect was observed in Xumai25. The inhibition effects were alleviated by the application of MSO but strengthened by the application of glutamate. The AN increased the activities of GS, glutamate dehydrogenase (GDH) in both cultivars, resulting in higher glutamate contents. However, its contents were decreased by the application of MSO. Compared to AK58, Xumai25 showed lower glutamate contents due to its higher activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT). With the indole-3-acetic acid (IAA) contents decreasing in roots, the ratio of shoot to root in IAA was increased, and further increased by the application of glutamate, and reduced by the application of MSO, but the ratio was lower in Xumai25. Meanwhile, the total soluble sugar contents and its root to shoot ratio also showed similar trends. These results indicate that the NH4+-tolerant cultivar has a greater transamination ability to prevent glutamate over-accumulation to maintain higher IAA transport ability, and consequently promoted soluble sugar transport to roots, further

  14. Higher Ammonium Transamination Capacity Can Alleviate Glutamate Inhibition on Winter Wheat (Triticum aestivum L.) Root Growth under High Ammonium Stress.

    PubMed

    Wang, Feng; Gao, Jingwen; Liu, Yang; Tian, Zhongwei; Muhammad, Abid; Zhang, Yixuan; Jiang, Dong; Cao, Weixing; Dai, Tingbo

    2016-01-01

    Most of the studies about NH4+ stress mechanism simply address the effects of free NH4+, failing to recognize the changed nitrogen assimilation products. The objective of this study was to elucidate the effects of glutamate on root growth under high ammonium (NH4+) conditions in winter wheat (Triticum aestivum L.). Hydroponic experiments were conducted using two wheat cultivars, AK58 (NH4+-sensitive) and Xumai25 (NH4+-tolerant) with either 5 mM NH4+ nitrogen (AN) as stress treatment or 5 mM nitrate (NO3-) nitrogen as control. To evaluate the effects of NH4+-assimilation products on plant growth, 1 μM L-methionine sulfoximine (MSO) (an inhibitor of glutamine synthetase (GS)) and 1 mM glutamates (a primary N assimilation product) were added to the solutions, respectively. The AN significantly reduced plant biomass, total root length, surface area and root volume in both cultivars, but less effect was observed in Xumai25. The inhibition effects were alleviated by the application of MSO but strengthened by the application of glutamate. The AN increased the activities of GS, glutamate dehydrogenase (GDH) in both cultivars, resulting in higher glutamate contents. However, its contents were decreased by the application of MSO. Compared to AK58, Xumai25 showed lower glutamate contents due to its higher activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT). With the indole-3-acetic acid (IAA) contents decreasing in roots, the ratio of shoot to root in IAA was increased, and further increased by the application of glutamate, and reduced by the application of MSO, but the ratio was lower in Xumai25. Meanwhile, the total soluble sugar contents and its root to shoot ratio also showed similar trends. These results indicate that the NH4+-tolerant cultivar has a greater transamination ability to prevent glutamate over-accumulation to maintain higher IAA transport ability, and consequently promoted soluble sugar transport to roots, further

  15. Coupled thermal stress simulations of ductile tearing

    DOE PAGESBeta

    Neilsen, Michael K.; Dion, Kristin

    2016-03-01

    Predictions for ductile tearing of a geometrically complex Ti-6Al-4V plate were generated using a Unified Creep Plasticity Damage model in fully coupled thermal stress simulations. Uniaxial tension and butterfly shear tests performed at displacement rates of 0.0254 and 25.4 mm/s were also simulated. Results from these simulations revealed that the material temperature increase due to plastic work can have a dramatic effect on material ductility predictions in materials that exhibit little strain hardening. Furthermore, this occurs because the temperature increase causes the apparent hardening of the material to decrease which leads to the initiation of deformation localization and subsequent ductilemore » tearing earlier in the loading process.« less

  16. Intra-hippocampal administration of ZIP alleviates depressive and anxiety-like responses in an animal model of posttraumatic stress disorder

    PubMed Central

    2014-01-01

    Background Given that impairment of fear extinction has been implicated in the pathogenesis of posttraumatic stress disorder (PTSD), effective pharmacological interventions that facilitate fear extinction may provide alternative strategies to conventional treatment. It is generally accepted that the zeta inhibitory peptide (ZIP), a controversial inhibitor of protein kinase M zeta (PKMζ), could erase certain types of previously established long-term memories. However, it is unclear whether ZIP administration may alleviate PTSD-associated depressive and anxiety-like abnormalities. Methods Here we developed a re-stressed single-prolonged stress (SPS) paradigm, a modified prevalent animal model of PTSD, and assayed the expressions of PKMζ in the hippocampus after SPS procedure. Next, Seven days prior to re-stress, ZIP was injected into the hippocampus, and the depressive and anxiety-like behavior was examined by the subsequent forced swim (FS), open-field and elevated plus maze (EPM) test. Results Rats given ZIP prior to FS exhibited a reduction of immobility time in FS test, and more open arms (OA) entries and longer OA duration in EPM. They also spent longer time in the center of the open field. Conclusions Our results suggested that re-stressed SPS could reproduce behavioral alteration similar to that observed in patients with PTSD, and these behavioral symptoms co-morbid with PTSD could be effectively alleviated by the intro-hippocampal administration of ZIP. PMID:25178800

  17. Alleviating salt stress in tomato seedlings using Arthrobacter and Bacillus megaterium isolated from the rhizosphere of wild plants grown on saline-alkaline lands.

    PubMed

    Fan, Pengfei; Chen, Daitao; He, Yanan; Zhou, Qingxia; Tian, Yongqiang; Gao, Lihong

    2016-11-01

    Salt-induced soil degradation is common in farmlands and limits the growth and development of numerous crop plants in the world. In this study, we isolated salt-tolerant bacteria from the rhizosphere of Tamarix chinensis, Suaeda salsa and Zoysia sinica, which are common wild plants grown on a saline-alkaline land, to test these bacteria's efficiency in alleviating salt stress in tomato plants. We screened out seven strains (TF1-7) that are efficient in reducing salt stress in tomato seedlings. The sequence data of 16S rRNA genes showed that these strains belong to Arthrobacter and Bacillus megaterium. All strains could hydrolyze casein and solubilize phosphate, and showed at least one plant growth promotion (PGP)-related gene, indicating their potential in promoting plant growth. The Arthrobacter strains TF1 and TF7 and the Bacillus megaterium strain TF2 and TF3 could produce indole acetic acid under salt stress, further demonstrating their PGP potential. Tomato seed germination, seedling length, vigor index, and plant fresh and dry weight were enhanced by inoculation of Arthrobacter and B. megaterium strains under salt stress. Our results demonstrated that salt-tolerant bacteria isolated from the rhizosphere of wild plants grown on saline-alkaline lands could be used for alleviating salt stress in crop plants. PMID:27196364

  18. Evaluation of Transient Pin-Stress Requirements for Spacecraft Launching in Lightning Environments. Pain Free Analysis to Alleviate Those Pin Stress Headaches

    NASA Technical Reports Server (NTRS)

    Edwards, Paul; Terseck, Alex; Trout, Dawn

    2016-01-01

    Spacecraft are generally protected from direct lightning attachment by encapsulation within the payload fairing of a launch vehicle and the ground structures that exist at the launch site. Regardless of where lightning strikes, potentially damaging indirect effects prevail from the coupling of electromagnetic fields into a loop created by outer shield of the payload umbilical. The energy coupled into individual spacecraft circuits is dependent on the umbilical current drive, the cable transfer impedance and the source/ load circuitry, and the reference potential used. Lightning induced transient susceptibility of the spacecraft avionics needs to be fully understood in order to define realistic re-test criteria in the event of a lightning occurrence during the launch campaign. Use of standards such as RTCA/DO-160 & SAE 5412 has some applicability but do not represent the indirect environment adequately. This paper evaluates the launch pad environments, the measurement data available, and computer simulations to provide pain-free analysis to alleviate the transient pin-stress headaches for spacecraft launching in Lightning environments.

  19. Thermal-stress-free fasteners for joining orthotropic materials

    NASA Technical Reports Server (NTRS)

    Blosser, Max L.

    1987-01-01

    Hot structures fabricated from orthotropic materials are an attractive design option for future high speed vehicles. Joining subassemblies of these materials with standard cylindrical fasteners can lead to loose joints or highly stressed joints due to thermal stress. A method has been developed to eliminate thermal stress and maintain a tight joint by shaping the fastener and mating hole. This method allows both materials (fastener and structure), with different coefficients of thermal expansion (CTE's) in each of the three principal material directions, to expand freely with temperature yet remain in contact. For the assumptions made in the analysis, the joint will remain snug, yet free of thermal stress at any temperature. Finite element analysis was used to verify several thermal-stress-free fasteners and to show that conical fasteners, which are thermal-stress-free for isotropic materials, can reduce thermal stresses for transversely isotropic materials compared to a cylindrical fastener. Equations for thermal-stress-free shapes are presented and typical fastener shapes are shown.

  20. Thermal-stress-free fasteners for joining orthotropic materials

    NASA Technical Reports Server (NTRS)

    Blosser, M. L.

    1987-01-01

    Hot structures fabricated from orthotropic materials are an attractive design option for future high speed vehicles. Joining subassemblies of these materials with standard cylindrical fasteners can lead to loose joints or highly stressed joints due to thermal stress. A method has been developed to eliminate thermal stresses and maintain a tight joint by shaping the fastener and mating hole. This method allows both materials (fastener and structure), with different coefficients of thermal expansion (CTEs) in each of the three material directions, to expand freely with temperature yet remain in contact. For the assumptions made in the analysis, the joint will remain snug, yet free of thermal stress at any temperature. Finite element analysis was used to verify several thermal-stress-free fasteners and to show that conical fasteners, which are thermal-stress-free for isotropic materials, can reduce thermal stresses for transversely isotropic materials compared to a cylindrical fastener. Equations for thermal-stress-free shapes are presented and typical fastener shapes are shown.

  1. Stress-Induced Depression Is Alleviated by Aerobic Exercise Through Up-Regulation of 5-Hydroxytryptamine 1A Receptors in Rats

    PubMed Central

    Kim, Tae Woon; Lim, Baek Vin; Baek, Dongjin; Ryu, Dong-Soo; Seo, Jin Hee

    2015-01-01

    Purpose: Stress is associated with depression, which induces many psychiatric disorders. Serotonin, also known as 5-hydroxy-tryptamine (5-HT), acts as a biochemical messenger and regulator in the brain. It also mediates several important physiological functions. Depression is closely associated with an overactive bladder. In the present study, we investigated the effect of treadmill exercise on stress-induced depression while focusing on the expression of 5-HT 1A (5-H1A) receptors in the dorsal raphe. Methods: Stress was induced by applying a 0.2-mA electric foot shock to rats. Each set of electric foot shocks comprised a 6-second shock duration that was repeated 10 times with a 30-second interval. Three sets of electric foot shocks were applied each day for 7 days. For the confirmation of depressive state, a forced swimming test was performed. To visualize the expression of 5-HT and tryptophan hydroxylase (TPH), immunohistochemistry for 5-HT and TPH in the dorsal raphe was performed. Expression of 5-H1A receptors was determined by western blot analysis. Results: A depressive state was induced by stress, and treadmill exercise alleviated the depression symptoms in the stress-induced rats. Expressions of 5-HT, TPH, and HT 1A in the dorsal raphe were reduced by the induction of stress. Treadmill exercise increased 5-HT, TPH, and HT 1A expressions in the stress-induced rats. Conclusions: Treadmill exercise enhanced 5-HT synthesis through the up-regulation of 5-HT1A receptors, and improved the stress-induced depression. In the present study, treadmill exercise improved depression symptoms by enhancing 5-HT1A receptor expression. The present results suggest that treadmill exercise might be helpful for the alleviation of overactive bladder and improve sexual function. PMID:25833478

  2. Thermal Residual Stress in Environmental Barrier Coated Silicon Nitride - Modeled

    NASA Technical Reports Server (NTRS)

    Ali, Abdul-Aziz; Bhatt, Ramakrishna T.

    2009-01-01

    When exposed to combustion environments containing moisture both un-reinforced and fiber reinforced silicon based ceramic materials tend to undergo surface recession. To avoid surface recession environmental barrier coating systems are required. However, due to differences in the elastic and thermal properties of the substrate and the environmental barrier coating, thermal residual stresses can be generated in the coated substrate. Depending on their magnitude and nature thermal residual stresses can have significant influence on the strength and fracture behavior of coated substrates. To determine the maximum residual stresses developed during deposition of the coatings, a finite element model (FEM) was developed. Using this model, the thermal residual stresses were predicted in silicon nitride substrates coated with three environmental coating systems namely barium strontium aluminum silicate (BSAS), rare earth mono silicate (REMS) and earth mono di-silicate (REDS). A parametric study was also conducted to determine the influence of coating layer thickness and material parameters on thermal residual stress. Results indicate that z-direction stresses in all three systems are small and negligible, but maximum in-plane stresses can be significant depending on the composition of the constituent layer and the distance from the substrate. The BSAS and REDS systems show much lower thermal residual stresses than REMS system. Parametric analysis indicates that in each system, the thermal residual stresses can be decreased with decreasing the modulus and thickness of the coating.

  3. Temperature, Thermal Stress, And Creep In A Structure

    NASA Technical Reports Server (NTRS)

    Jenkins, Jerald M.

    1991-01-01

    Report presents comparison of predicted and measured temperatures, thermal stresses, and residual creep stresses in heated and loaded titanium structure. Study part of continuing effort to develop design capability to predict and reduce deleterious effects of creep, which include excessive deformations, residual stresses, and failure.

  4. Alleviation of Salt Stress by Enterobacter sp. EJ01 in Tomato and Arabidopsis Is Accompanied by Up-Regulation of Conserved Salinity Responsive Factors in Plants

    PubMed Central

    Kim, Kangmin; Jang, Ye-Jin; Lee, Sang-Myeong; Oh, Byung-Taek; Chae, Jong-Chan; Lee, Kui-Jae

    2014-01-01

    Microbiota in the niches of the rhizosphere zones can affect plant growth and responses to environmental stress conditions via mutualistic interactions with host plants. Specifically, some beneficial bacteria, collectively referred to as Plant Growth Promoting Rhizobacteria (PGPRs), increase plant biomass and innate immunity potential. Here, we report that Enterobacter sp. EJ01, a bacterium isolated from sea china pink (Dianthus japonicus thunb) in reclaimed land of Gyehwa-do in Korea, improved the vegetative growth and alleviated salt stress in tomato and Arabidopsis. EJ01 was capable of producing 1-aminocy-clopropane-1-carboxylate (ACC) deaminase and also exhibited indole-3-acetic acid (IAA) production. The isolate EJ01 conferred increases in fresh weight, dry weight, and plant height of tomato and Arabidopsis under both normal and high salinity conditions. At the molecular level, short-term treatment with EJ01 increased the expression of salt stress responsive genes such as DREB2b, RD29A, RD29B, and RAB18 in Arabidopsis. The expression of proline biosynthetic genes (i.e. P5CS1 and P5CS2) and of genes related to priming processes (i.e. MPK3 and MPK6) were also up-regulated. In addition, reactive oxygen species scavenging activities were enhanced in tomatoes treated with EJ01 in stressed conditions. GFP-tagged EJ01 displayed colonization in the rhizosphere and endosphere in the roots of Arabidopsis. In conclusion, the newly isolated Enterobacter sp. EJ01 is a likely PGPR and alleviates salt stress in host plants through multiple mechanisms, including the rapid up-regulation of conserved plant salt stress responsive signaling pathways. PMID:24598995

  5. Thermal stress fracture in elastic-brittle materials

    NASA Technical Reports Server (NTRS)

    Emery, A. F.

    1980-01-01

    The reported investigation shows that the assessment of the possibility of the thermal fracture of brittle materials depends upon an accurate evaluation of the thermal stresses and the determination of the resulting stress intensity factors. The stress intensity factors can be calculated in a variety of ways ranging from the very precise to approximate, but only for a limited number of geometries. The main difficulty is related to the determination of the thermal stress field because of its unusual character and its dependence upon boundary conditions at points far from the region of thermal activity. Examination of a number of examples suggests that the best visualization of the thermal stresses and any associated fracture can be made by considering the problem to be the combination of thermal and isothermal problems or by considering that the prime effect of the temperature is in the generation of thermal strains and that the thermal stresses are simply the result of the region trying to accommodate these strains.

  6. Thermal stress effects in intermetallic matrix composites. Final report

    SciTech Connect

    Wright, P.K.; Sensmeier, M.D.; Kupperman, D.S.; Wadley, H.N.G.

    1993-09-01

    Intermetallic matrix composites develop residual stresses from the large thermal expansion mismatch (delta-alpha) between the fibers and matrix. This work was undertaken to: establish improved techniques to measure these thermal stresses in IMC's; determine residual stresses in a variety of IMC systems by experiments and modeling; and, determine the effect of residual stresses on selected mechanical properties of an IMC. X ray diffraction (XRD), neutron diffraction (ND), synchrotron XRD (SXRD), and ultrasonics (US) techniques for measuring thermal stresses in IMC were examined and ND was selected as the most promising technique. ND was demonstrated on a variety of IMC systems encompassing Ti- and Ni-base matrices, SiC, W, and Al2O3 fibers, and different fiber fractions (Vf). Experimental results on these systems agreed with predictions of a concentric cylinder model. In SiC/Ti-base systems, little yielding was found and stresses were controlled primarily by delta-alpha and Vf. In Ni-base matrix systems, yield strength of the matrix and Vf controlled stress levels. The longitudinal residual stresses in SCS-6/Ti-24Al-llNb composite were modified by thermomechanical processing. Increasing residual stress decreased ultimate tensile strength in agreement with model predictions. Fiber pushout strength showed an unexpected inverse correlation with residual stress. In-plane shear yield strength showed no dependence on residual stress. Higher levels of residual tension led to higher fatigue crack growth rates, as suggested by matrix mean stress effects.

  7. Transient thermal stress analysis of a laminated composite beam

    SciTech Connect

    Tanigawa, Y.; Murakami, H.; Ootao, Y. California Univ., La Jolla Osaka Prefectural Industrial Technology Research Institute )

    1989-01-01

    This paper considers a transient thermal stress analysis of a laminated beam made of different materials in multilayers. To simplify the problem, the heat conduction problem is treated as a one-dimensional case in the direction of thickness; then, the transient temperature solution is evaluated using the Laplace transform method. For the thermoelastic fields, thermal stress distributions are obtained using the elementary beam theory and Airy's thermal stress function method. As an example, numerical calculations are carried out for a laminated beam made of five layers, and the numerical results are examined.

  8. Measuring of residual stresses in thermal sprayed coatings

    SciTech Connect

    Brandt, O.C.

    1995-12-31

    The Modified Almen Method (MAM) uses the deformation of test samples for measuring the residual stress and with small mathematical expenditure it yields the distribution in the coating. This paper presents the basic theory of MAM and the boundary conditions for using this method for the classification of thermal sprayed coatings with respect to the residual stress. The residual stress distribution of different HVOF coatings are shown in this work. Typical spray parameters are compared. The results are also compared with the ones calculated with other methods for the determination of the residual stress in thermal sprayed coatings.

  9. Phase composition and residual stresses in thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Betsofen, S. Ya.; Ryabenko, B. V.; Ashmarin, A. A.; Molostov, D. E.

    2015-10-01

    The phase composition and the residual stresses in multilayer thermal barrier coatings, which consist of an external ZrO2-8Y2O3 ceramic layer, an intermediate gradient (metal ceramic) layer, and a transient metallic NiCrAlY sublayer, are studied. It is shown that an increase in the specific volume of the metallic sublayer as a result of the formation of thermal growing oxide Al2O3 generates high compressive stresses in this sublayer. The ceramic layer undergoes tensile stresses in this case. A method is proposed to estimate the stresses in gradient coatings from X-ray diffraction results.

  10. Lipid biomarkers in Symbiodinium dinoflagellates: new indicators of thermal stress

    NASA Astrophysics Data System (ADS)

    Kneeland, J.; Hughen, K.; Cervino, J.; Hauff, B.; Eglinton, T.

    2013-12-01

    Lipid content and fatty acid profiles of corals and their dinoflagellate endosymbionts are known to vary in response to high-temperature stress. To better understand the heat-stress response in these symbionts, we investigated cultures of Symbiodinium goreauii type C1 and Symbiodinium sp. clade subtype D1 grown under a range of temperatures and durations. The predominant lipids produced by Symbiodinium are palmitic (C16) and stearic (C18) saturated fatty acids and their unsaturated analogs, the polyunsaturated fatty acid docosahexaenoic acid (C22:6, n-3; DHA), and a variety of sterols. Prolonged exposure to high temperature causes the relative amount of unsaturated acids within the C18 fatty acids in Symbiodinium tissue to decrease. Thermal stress also causes a decrease in abundance of fatty acids relative to sterols, as well as the more specific ratio of DHA to an algal 4-methyl sterol. These shifts in fatty acid unsaturation and fatty acid-to-sterol ratios are common to both types C1 and D1, but the apparent thermal threshold of lipid changes is lower for type C1. This work indicates that ratios among free fatty acids and sterols in Symbiodinium can be used as sensitive indicators of thermal stress. If the Symbiodinium lipid stress response is unchanged in hospite, the algal heat-stress biomarkers we have identified could be measured to detect thermal stress within the coral holobiont. These results provide new insights into the potential role of lipids in the overall Symbiodinium thermal stress response.

  11. Thermal stresses due to cooling of a viscoelastic oceanic lithosphere

    SciTech Connect

    Denlinger, R.P. ); Savage, W.Z. )

    1989-01-10

    Theories based upon thermal contraction of cooling oceanic lithosphere provide a successful basis for correlating seafloor bathymetry and heat flow. The horizontal components of the contraction of the lithosphere as it cools potentially give rise to large thermal stresses. Current methods to calculate these stresses assume that on the time scales of cooling, the lithosphere initially behaves as an inviscid fluid and instantly freezes into an elastic solid at some critical temperature. These instant-freezing methods inaccurately predict transient thermal stresses in rapidly cooling silicate glass plates because of the temperature dependent rheology of the material. The temperature dependent rheology of the lithosphere may affect the transient thermal stress distribution in a similar way, and for this reason the authors use a thermoviscoelastic model to estimate thermal stresses in young oceanic lithosphere. This theory is formulated here for linear creep processes that have an Arrhenius rate dependence on temperature. Results show that the stress differences between instant freezing and linear thermoviscoelastic theory are most pronounced at early times (0-20 m.y.) when the instant freezing stresses may be twice as large. The solutions for the two methods asymptotically approach the same solution with time. A comparison with intraplate seismicity shows that both methods underestimate the depth of compressional stresses inferred from the seismicity in a systematic way.

  12. Thermal stresses due to cooling of a viscoelastic oceanic lithosphere

    NASA Astrophysics Data System (ADS)

    Denlinger, Roger P.; Savage, William Z.

    1989-01-01

    Theories based upon thermal contraction of cooling oceanic lithosphere provide a successful basis for correlating seafloor bathymetry and heat flow. The horizontal components of the contraction of the lithosphere as it cools potentially give rise to large thermal stresses. Current methods to calculate these stresses assume that on the time scales of cooling, the lithosphere initially behaves as an inviscid fluid and instantly freezes into an elastic solid at some critical temperature. These instant-freezing methods inaccurately predict transient thermal stresses in rapidly cooling silicate glass plates because of the temperature dependent rheology of the material. The temperature dependent rheology of the lithosphere may affect the transient thermal stress distribution in a similar way, and for this reason we use a thermoviscoelastic model to estimate thermal stresses in young oceanic lithosphere. This theory is formulated here for linear creep processes that have an Arrhenius rate dependence on temperature. Our results show that the stress differences between instant freezing and linear thermoviscoelastic theory are most pronounced at early times (0-20 m.y.) when the instant freezing stresses may be twice as large. The solutions for the two methods asymptotically approach the same solution with time. A comparison with intraplate seismicity shows that both methods underestimate the depth of compressional stresses inferred from the seismicity in a systematic way.

  13. Thermal stress vs. thermal transpiration: A competition in thermally driven cavity flows

    NASA Astrophysics Data System (ADS)

    Mohammadzadeh, Alireza; Rana, Anirudh Singh; Struchtrup, Henning

    2015-11-01

    The velocity dependent Maxwell (VDM) model for the boundary condition of a rarefied gas, recently presented by Struchtrup ["Maxwell boundary condition and velocity dependent accommodation coefficient," Phys. Fluids 25, 112001 (2013)], provides the opportunity to control the strength of the thermal transpiration force at a wall with temperature gradient. Molecular simulations of a heated cavity with varying parameters show intricate flow patterns for weak, or inverted transpiration force. Microscopic and macroscopic transport equations for rarefied gases are solved to study the flow patterns and identify the main driving forces for the flow. It turns out that the patterns arise from a competition between thermal transpiration force at the boundary and thermal stresses in the bulk.

  14. Thermal stress tectonics on the satellites of Saturn and Uranus

    NASA Technical Reports Server (NTRS)

    Hillier, John; Squyres, Steven W.

    1991-01-01

    Thermal stress histories of the Saturnian and Uranian satellites are investigated. To this end, the thermal evolution of an icy satellite subjected to accretional and radiogenic heating, thermal conduction, and solid-state convection is modeled, and changes in the internal stress that occur during satellite evolution are examined. Results show that internal temperature changes that occur during normal evolution of many of the satellites of Saturn and Uranus can be expected to generate large extensional stresses in the satellites' outer regions. These stresses arise from three sources: (1) radiogenic warming, causing thermal expansion of materials in the satellite's deep interior; (2) radiogenic warming in larger satellites that can induce a phase transition from ice II to ice I and to produce a volume increase in the deep interior; and (3) accretional heating depositing heat in the satellite'e outer regions.

  15. Transient thermal stress problem for a circumferentially cracked hollow cylinder

    NASA Technical Reports Server (NTRS)

    Nied, H. F.; Erdogan, F.

    1983-01-01

    The paper is concerned with the transient thermal stress problem for a long hollow circular cylinder containing an internal axisymmetric circumferential edge crack that is suddenly cooled from inside. It is assumed that the transient thermal stress problem is quasi-static, i.e., the inertial effects are negligible. Also, all thermoelastic coupling effects and the possible temperature dependence of the thermoelastic constants are neglected. The problem is considered in two parts. The first part is the evaluation of transient thermal stresses in an uncracked cylinder; the second part is the isothermal perturbation problem for the cracked cylinder in which the crack surface tractions, equal and opposite to the thermal stresses obtained from the first problem, are the only external loads. The superposition of the two solutions gives results for the cracked cylinder.

  16. Observation of silicon-mediated alleviation of cadmium stress in maize (Zea mays L.) seedlings via LED-induced chlorophyll fluorescence

    NASA Astrophysics Data System (ADS)

    Gouveia-Neto, Artur S.; Silva, Elias A.; da Silva, Airon José; do Nascimento, Clístenes W. A.

    2013-02-01

    LED-induced chlorophyll fluorescence analysis is exploited to observe, and monitor the time evolution of silicon-induced alleviation of toxicity in maize (Zea mays L.) seedlings in cadmium contaminated soil. Red, and far-red emissions were examined as a function of cadmium-silicon concentrations, during the 20 days period of the seedlings growing process under stress. The chlorophyll fluorescence spectral analysis provided detection, and evaluation of the damage imposed by the metal stress in the early stages of the plant growing process. The technique also provided the time evolution evaluation of the silicon-induced tolerance enhancement of maize plants to cadmium, which is not viable using conventional in vitro spectral analysis techniques

  17. Nitrogen Nutrition Improves the Potential of Wheat (Triticum aestivum L.) to Alleviate the Effects of Drought Stress during Vegetative Growth Periods

    PubMed Central

    Abid, Muhammad; Tian, Zhongwei; Ata-Ul-Karim, Syed Tahir; Cui, Yakun; Liu, Yang; Zahoor, Rizwan; Jiang, Dong; Dai, Tingbo

    2016-01-01

    Efficient nitrogen (N) nutrition has the potential to alleviate drought stress in crops by maintaining metabolic activities even at low tissue water potential. This study was aimed to understand the potential of N to minimize the effects of drought stress applied/occur during tillering (Feekes stage 2) and jointing (Feekes stage 6) growth stages of wheat by observing the regulations and limitations of physiological activities, crop growth rate during drought periods as well as final grain yields at maturity. In present study, pot cultured plants of a wheat cultivar Yangmai-16 were exposed to three water levels [severe stress at 35–40% field capacity (FC), moderate stress at 55–60% FC and well-watered at 75–80% FC] under two N rates (0.24 g and 0.16 g/kg soil). The results showed that the plants under severe drought stress accompanied by low N exhibited highly downregulated photosynthesis, and chlorophyll (Chl) fluorescence during the drought stress periods, and showed an accelerated grain filling rate with shortened grain filling duration (GFD) at post-anthesis, and reduced grain yields. Severe drought-stressed plants especially at jointing, exhibited lower Chl and Rubisco contents, lower efficiency of photosystem II and greater grain yield reductions. In contrast, drought-stressed plants under higher N showed tolerance to drought stress by maintaining higher leaf water potential, Chl and Rubisco content; lower lipid peroxidation associated with higher superoxide dismutase and ascorbate peroxidase activities during drought periods. The plants under higher N showed delayed senescence, increased GFD and lower grain yield reductions. The results of the study suggested that higher N nutrition contributed to drought tolerance in wheat by maintaining higher photosynthetic activities and antioxidative defense system during vegetative growth periods. PMID:27446197

  18. Thermal stress analysis of a planar SOFC stack

    NASA Astrophysics Data System (ADS)

    Lin, Chih-Kuang; Chen, Tsung-Ting; Chyou, Yau-Pin; Chiang, Lieh-Kwang

    The aim of this study is, by using finite element analysis (FEA), to characterize the thermal stress distribution in a planar solid oxide fuel cell (SOFC) stack during various stages. The temperature profiles generated by an integrated thermo-electrochemical model were applied to calculate the thermal stress distributions in a multiple-cell SOFC stack by using a three-dimensional (3D) FEA model. The constructed 3D FEA model consists of the complete components used in a practical SOFC stack, including positive electrode-electrolyte-negative electrode (PEN) assembly, interconnect, nickel mesh, and gas-tight glass-ceramic seals. Incorporation of the glass-ceramic sealant, which was never considered in previous studies, into the 3D FEA model would produce more realistic results in thermal stress analysis and enhance the reliability of predicting potential failure locations in an SOFC stack. The effects of stack support condition, viscous behavior of the glass-ceramic sealant, temperature gradient, and thermal expansion mismatch between components were characterized. Modeling results indicated that a change in the support condition at the bottom frame of the SOFC stack would not cause significant changes in thermal stress distribution. Thermal stress distribution did not differ significantly in each unit cell of the multiple-cell stack due to a comparable in-plane temperature profile. By considering the viscous characteristics of the glass-ceramic sealant at temperatures above the glass-transition temperature, relaxation of thermal stresses in the PEN was predicted. The thermal expansion behavior of the metallic interconnect/frame had a greater influence on the thermal stress distribution in the PEN than did that of the glass-ceramic sealant due to the domination of interconnect/frame in the volume of a planar SOFC assembly.

  19. Postnatal Treadmill Exercise Alleviates Prenatal Stress-Induced Anxiety in Offspring Rats by Enhancing Cell Proliferation Through 5-Hydroxytryptamine 1A Receptor Activation

    PubMed Central

    2016-01-01

    Purpose: Stress during pregnancy is a risk factor for the development of anxiety-related disorders in offspring later in life. The effects of treadmill exercise on anxiety-like behaviors and hippocampal cell proliferation were investigated using rats exposed to prenatal stress. Methods: Exposure of pregnant rats to a hunting dog in an enclosed room was used to induce stress. Anxiety-like behaviors of offspring were evaluated using the elevated plus maze test. Immunohistochemistry for the detection of 5-bromo-2ʹ- deoxyuridine and doublecortin (DCX) in the hippocampal dentate gyrus and 5-hydroxytryptamine 1A receptors (5-HT1A) in the dorsal raphe was conducted. Brain-derived neurotrophic factor (BDNF) and tyrosine kinase B (TrkB) levels in the hippocampus were evaluated by western blot analysis. Results: Offspring of maternal rats exposed to stress during pregnancy showed anxiety-like behaviors. Offspring also showed reduced expression of BDNF, TrkB, and DCX in the dentate gyrus, decreased cell proliferation in the hippocampus, and reduced 5-HT1A expression in the dorsal raphe. Postnatal treadmill exercise by offspring, but not maternal exercise during pregnancy, enhanced cell proliferation and expression of these proteins. Conclusions: Postnatal treadmill exercise ameliorated anxiety-like behaviors in offspring of stressed pregnant rats, and the alleviating effect of exercise on these behaviors is hypothesized to result from enhancement of cell proliferation through 5-HT1A activation in offspring rats. PMID:27230461

  20. Low thermal stress ceramic turbine nozzle

    DOEpatents

    Glezer, Boris; Bagheri, Hamid; Fierstein, Aaron R.

    1996-01-01

    A turbine nozzle vane assembly having a preestablished rate of thermal expansion is positioned in a gas turbine engine and being attached to conventional metallic components. The metallic components having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine nozzle vane assembly. The turbine nozzle vane assembly includes an outer shroud and an inner shroud having a plurality of vanes therebetween. Each of the plurality of vanes have a device for heating and cooling a portion of each of the plurality of vanes. Furthermore, the inner shroud has a plurality of bosses attached thereto. A cylindrical member has a plurality of grooves formed therein and each of the plurality of bosses are positioned in corresponding ones of the plurality of grooves. The turbine nozzle vane assembly provides an economical, reliable and effective ceramic component having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the other component.

  1. Thermally induced micromechanical stresses in ceramic/ceramic composites

    SciTech Connect

    Li, Zhuang; Bradt, R.C.

    1992-11-01

    The internal micromechanical stresses which develop in ceramic-ceramic composites as a consequence of temperature changes and thermoelastic property differences between the reinforcing and matrix phases are addressed by the Eshelby method. Results for two whisker reinforced ceramic matrix composites and for quartz particles in porcelain are discussed. It is concluded that the stresses which develop in the second phase reinforcing inclusions are quite substantial (GPa-levels) and may be highly anisotropic in character. These stresses are additive to the macroscopic thermal stresses from temperature gradients which are encountered during heating and cooling, and also to externally apphed mechanical stresses (loads). These micromechanical stresses are expected to be highly significant for thermal cycling fatigue and other failure processes.

  2. Behavior of Materials Under Conditions of Thermal Stress

    NASA Technical Reports Server (NTRS)

    Manson, S S

    1954-01-01

    A review is presented of available information on the behavior of brittle and ductile materials under conditions of thermal stress and thermal shock. For brittle materials, a simple formula relating physical properties to thermal-shock resistance is derived and used to determine the relative significance of two indices currently in use for rating materials. For ductile materials, thermal-shock resistance depends upon the complex interrelation among several metallurgical variables which seriously affect strength and ductility. These variables are briefly discussed and illustrated from literature sources. The importance of simulating operating conditions in tests for rating materials is especially to be emphasized because of the importance of testing conditions in metallurgy. A number of practical methods that have been used to minimize the deleterious effects of thermal stress and thermal shock are outlined.

  3. Thermal stress analysis of a silicon carbide/aluminum composite

    NASA Technical Reports Server (NTRS)

    Gdoutos, E. E.; Karalekas, D.; Daniel, I. M.

    1991-01-01

    Thermal deformations and stresses were studied in a silicon-carbide/aluminum filamentary composite at temperatures up to 370 C (700 F). Longitudinal and transverse thermal strains were measured with strain gages and a dilatometer. An elastoplastic micromechanical analysis based on a one-dimensional rule-of-mixtures model and an axisymmetric two-material composite cylinder model was performed. It was established that beyond a critical temperature thermal strains become nonlinear with decreasing longitudinal and increasing transverse thermal-expansion coefficients. This behavior was attributed to the plastic stresses in the aluminum matrix above the critical temperature. An elastoplastic analysis of both micromechanical models was performed to determine the stress distributions and thermal deformation in the fiber and matrix of the composite. While only axial stresses can be determined by the rule-of-mixtures model, the complete triaxial state of stress is established by the composite cylinder model. Theoretical predictions for the two thermal-expansion coefficients were in satisfactory agreement with experimental results.

  4. Analysis of thermal stresses in polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Bowles, David E.; Griffin, O. H., Jr.

    1989-01-01

    In the present micromechanics study of the thermally-induced stress field which emerges at very low temperatures in the matrix and fibers of continuous fiber-reinforced polymer composites, the results obtained by a specialized FEM analysis are compared to an analytical solution of the composite cylinder model for several composite materials. Attention is given to the influence of microstructural geometry and constituent properties; it is established that the distributions and magnitudes of the thermally-induced stresses are affected by the assumed microstructural geometry of the sample. While matrix stresses are not a strong function of fiber properties, the temperature dependence of the matrix properties significantly affects the magnitudes of thermally-induced matrix stresses.

  5. Ectotherm thermal stress and specialization across altitude and latitude.

    PubMed

    Buckley, Lauren B; Miller, Ethan F; Kingsolver, Joel G

    2013-10-01

    Gradients of air temperature, radiation, and other climatic factors change systematically but differently with altitude and latitude. We explore how these factors combine to produce altitudinal and latitudinal patterns of body temperature, thermal stress, and seasonal overlap that differ markedly from patterns based solely on air temperature. We use biophysical models to estimate body temperature as a function of an organism's phenotype and environmental conditions (air and surface temperatures and radiation). Using grasshoppers as a case study, we compare mean body temperatures and the incidence of thermal extremes along altitudinal gradients both under past and current climates. Organisms at high elevation can experience frequent thermal stress despite generally cooler air temperatures due to high levels of solar radiation. Incidences of thermal stress have increased more rapidly than have increases in mean conditions due to recent climate change. Increases in air temperature have coincided with shifts in cloudiness and solar radiation, which can exacerbate shifts in body temperature. We compare altitudinal thermal gradients and their seasonality between tropical and temperate mountains to ask whether mountain passes pose a greater physiological barrier in the tropics (Janzen's hypothesis). We find that considering body temperature rather than air temperature generally increases the amount of overlap in thermal conditions along gradients in elevation and thus decreases the physiological barrier posed by tropical mountains. Our analysis highlights the limitations of predicting thermal stress based solely on air temperatures, and the importance of considering how phenotypes influence body temperatures. PMID:23620253

  6. 3,4-Dihydroxyphenylethanol alleviates early brain injury by modulating oxidative stress and Akt and nuclear factor-κB pathways in a rat model of subarachnoid hemorrhage

    PubMed Central

    FU, PENG; HU, QUAN

    2016-01-01

    3,4-Dihydroxyphenylethanol (DOPET) is a naturally occurring polyphenolic compound, present in olive oil and in the wastewater generated during olive oil processing. DOPET has various biological and pharmacological activities, including anticancer, antibacterial and anti-inflammatory effects. This study was designed to determine whether DOPET alleviates early brain injury (EBI) associated with subarachnoid hemorrhage (SAH) through suppression of oxidative stress and Akt and nuclear factor (NF)-κB pathways. Rats were randomly divided into the following groups: Sham group, SAH group, SAH + vehicle group and SAH + DOPET group. Mortality, blood-brain barrier (BBB) permeability and brain water content were assessed. Oxidative stress, Akt, NF-κB p65 and caspase-3 assays were also performed. DOPET induced a reduction in brain water content, and decreased the BBB permeability of SAH model rats. Furthermore, DOPET effectively controlled oxidative stress, NF-κB p65 and caspase-3 levels, in addition to significantly increasing Akt levels in the cortex following SAH. These results provide evidence that DOPET attenuates apoptosis in a rat SAH model through modulating oxidative stress and Akt and NF-κB signaling pathways. PMID:27168841

  7. Low thermal stress ceramic turbine nozzle

    DOEpatents

    Glezer, B.; Bagheri, H.; Fierstein, A.R.

    1996-02-27

    A turbine nozzle vane assembly having a preestablished rate of thermal expansion is positioned in a gas turbine engine and is attached to conventional metallic components, the metallic components having a preestablished rate of thermal expansion greater than the preestablished rate of thermal expansion of the turbine nozzle vane assembly. The turbine nozzle vane assembly includes an outer shroud and an inner shroud having a plurality of vanes there between. Each of the plurality of vanes have a device for heating and cooling a portion of each of the plurality of vanes. Furthermore, the inner shroud has a plurality of bosses attached thereto. A cylindrical member has a plurality of grooves formed therein and each of the plurality of bosses are positioned in corresponding ones of the plurality of grooves. The turbine nozzle vane assembly provides an economical, reliable and effective ceramic component having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the other component. 4 figs.

  8. Micromechanics thermal stress analysis of composites for space structure applications

    NASA Technical Reports Server (NTRS)

    Bowles, David E.

    1991-01-01

    This paper presents results from a finite element micromechanics analysis of thermally induced stresses in composites at cryogenic temperatures typical of spacecraft operating environments. The influence of microstructural geometry, constituent and interphase properties, and laminate orientation were investigated. Stress field results indicated that significant matrix stresses occur in composites exposed to typical spacecraft thermal excursions; these stresses varied with laminate orientation and circumferential position around the fiber. The major difference in the predicted response of unidirectional and multidirectional laminates was the presence of tensile radial stresses, at the fiber/matrix interface, in multidirectional laminates with off-axis ply angles greater than 15 deg. The predicted damage initiation temperatures and modes were in good agreement with experimental data for both low (207 GPa) and high (517 GPa) modulus carbon fiber/epoxy composites.

  9. Alleviation of cadmium stress in Solanum lycopersicum L. by arbuscular mycorrhizal fungi via induction of acquired systemic tolerance.

    PubMed

    Hashem, Abeer; Abd Allah, E F; Alqarawi, A A; Al Huqail, Asma A; Egamberdieva, D; Wirth, S

    2016-03-01

    Experiments were conducted to evaluate cadmium (Cd) stress-induced changes in growth, antioxidants and lipid composition of Solanum lycopersicum with and without arbuscular mycorrhizal fungi (AMF). Cadmium stress (50 μM) caused significant changes in the growth and physio-biochemical attributes studied. AMF mitigated the deleterious impact of Cd on the parameters studied. Cadmium stress increased malonaldehyde and hydrogen peroxide production but AMF reduced these parameters by mitigating oxidative stress. The activity of antioxidant enzymes enhanced under Cd treatment and AMF inoculation further enhanced their activity, thus strengthening the plant's defense system. Proline and phenol content increased in Cd-treated as well as AMF-inoculated plants providing efficient protection against Cd stress. Cadmium treatment resulted in great alterations in the main lipid classes leading to a marked change in their composition. Cadmium stress caused a significant reduction in polyunsaturated fatty acids resulting in enhanced membrane leakage. The present study supports the use of AMF as a biological means to ameliorate Cd stress-induced changes in tomato. PMID:26981010

  10. Alleviation of cadmium stress in Solanum lycopersicum L. by arbuscular mycorrhizal fungi via induction of acquired systemic tolerance

    PubMed Central

    Hashem, Abeer; Abd_Allah, E.F.; Alqarawi, A.A.; Al Huqail, Asma A.; Egamberdieva, D.; Wirth, S.

    2015-01-01

    Experiments were conducted to evaluate cadmium (Cd) stress-induced changes in growth, antioxidants and lipid composition of Solanum lycopersicum with and without arbuscular mycorrhizal fungi (AMF). Cadmium stress (50 μM) caused significant changes in the growth and physio-biochemical attributes studied. AMF mitigated the deleterious impact of Cd on the parameters studied. Cadmium stress increased malonaldehyde and hydrogen peroxide production but AMF reduced these parameters by mitigating oxidative stress. The activity of antioxidant enzymes enhanced under Cd treatment and AMF inoculation further enhanced their activity, thus strengthening the plant’s defense system. Proline and phenol content increased in Cd-treated as well as AMF-inoculated plants providing efficient protection against Cd stress. Cadmium treatment resulted in great alterations in the main lipid classes leading to a marked change in their composition. Cadmium stress caused a significant reduction in polyunsaturated fatty acids resulting in enhanced membrane leakage. The present study supports the use of AMF as a biological means to ameliorate Cd stress-induced changes in tomato. PMID:26981010

  11. Salicylic Acid Alleviates the Adverse Effects of Salt Stress in Torreya grandis cv. Merrillii Seedlings by Activating Photosynthesis and Enhancing Antioxidant Systems

    PubMed Central

    Du, Xuhua; Tang, Hui; Shen, Chaohua; Wu, Jiasheng

    2014-01-01

    Background Salt stress is a major factor limiting plant growth and productivity. Salicylic acid (SA) has been shown to ameliorate the adverse effects of environmental stress on plants. To investigate the protective role of SA in ameliorating salt stress on Torreya grandis (T. grandis) trees, a pot experiment was conducted to analyze the biomass, relative water content (RWC), chlorophyll content, net photosynthesis (Pn), gas exchange parameters, relative leakage conductivity (REC), malondialdehyde (MDA) content, and activities of superoxide dismutase (SOD) and peroxidase (POD) of T. grandis under 0.2% and 0.4% NaCl conditions with and without SA. Methodology/Principal Findings The exposure of T. grandis seedlings to salt conditions resulted in reduced growth rates, which were associated with decreases in RWC and Pn and increases in REC and MDA content. The foliar application of SA effectively increased the chlorophyll (chl (a+b)) content, RWC, net CO2 assimilation rates (Pn), and proline content, enhanced the activities of SOD, CAT and POD, and minimized the increases in the REC and MDA content. These changes increased the capacity of T. grandis in acclimating to salt stress and thus increased the shoot and root dry matter. However, when the plants were under 0% and 0.2% NaCl stress, the dry mass of the shoots and roots did not differ significantly between SA-treated plants and control plants. Conclusions SA induced the salt tolerance and increased the biomass of T. grandis cv. by enhancing the chlorophyll content and activity of antioxidative enzymes, activating the photosynthetic process, and alleviating membrane injury. A better understanding about the effect of salt stress in T. grandis is vital, in order gain knowledge over expanding the plantations to various regions and also for the recovery of T. grandis species in the future. PMID:25302987

  12. Growth performance and reproductive traits at first parity of New Zealand white female rabbits as affected by heat stress and its alleviation under Egyptian conditions.

    PubMed

    Marai, I F; Ayyat, M S; Abd el-Monem, U M

    2001-12-01

    Exposing growing and adult New Zealand White (NZW) female rabbits to severe heat stress (temperature-humidity index = 28.9) during summer adversely affected their growth and reproductive traits. The traits that declined significantly (p < 0.01) were the live body weight, daily weight gain and feed intake of growing rabbits, and the litter size and litter weight at weaning (p < 0.05) and the pre-weaning weight gain of pups (p < 0.01) for adult females. The conception rate declined considerably with heat stress. The declines in the values of the digestibility coefficients due to heat stress were 7.9% (p < 0.05) for dry matter (DM), 8.1% (p < 0.05) for crude protein (CP) and 1.0% for crude fibre (CF). The traits that increased significantly (p < 0.01) due to heat stress were water intake, water/feed ratio and rectal temperature in growing rabbits and pre-weaning mortality for adult females. Alleviation of heat stress in the growing and adult female NZW rabbits was more efficient with drinking cool water (10-15 degrees C; between 10:00 and 17:00) than with supplementation with palm oil (as a source of energy) or natural clay (as a natural enhancer to growth and milk production). Supplying the animals with cool drinking water gave the highest body weight and weight gain, conception rate, litter size and weight and digestibility coefficients for DM and CP and the lowest rectal temperature, respiration rate and pre-weaning mortality. The loss in rabbit production pertaining to heat stress estimated from the percentages of decline in conception rate x pre-weaning mortality x litter weight at weaning was 73.0%. The provision of cool water restored 11/12 of heat loss. PMID:11770200

  13. ZPPR FUEL ELEMENT THERMAL STRESS-STRAIN ANALYSIS

    SciTech Connect

    Charles W. Solbrig; Jason Andrus; Chad Pope

    2014-04-01

    The design temperature of high plutonium concentration ZPPR fuel assemblies is 600 degrees C. Cladding integrity of the 304L stainless steel cladding is a significant concern with this fuel since even small holes can lead to substantial fuel degradation. Since the fuel has a higher coefficient of thermal expansion than the cladding, an investigation of the stress induced in the cladding due to the differential thermal expansion of fuel and cladding up to the design temperature was conducted. Small holes in the cladding envelope would be expected to lead to the fuel hydriding and oxidizing into a powder over a long period of time. This is the same type of chemical reaction chain that exists in the degradion of the high uranium concentration ZPPR fuel. Unfortunately, the uranium fuel was designed with vents which allowed this degradation to occur. The Pu cladding is sealed so only fuel with damaged cladding would be subject to this damage. The thermal stresses that can be developed in the fuel cladding have been calculated in in this paper and compared to the ultimate tensile stress of the cladding. The conclusion is drawn that thermal stresses cannot induce holes in the cladding even for the highest storage temperatures predicted in calculations (292°C). In fact, thermal stress can not cause cladding failure as long as the fuel temperatures are below the design limit of 600 degrees C (1,112 degrees F).

  14. Thermal stresses in the microchannel heatsink cooled by liquid nitrogen

    SciTech Connect

    Riddle, R.A.

    1993-06-30

    Microchannel heatsinks represent a highly efficient and compact method for heat removal in high heat flux components. Excellent thermal performance of a silicon microchannel heatsink has been demonstrated using liquid nitrogen as the coolant. For the heating of a 1 square centimeter area, at a heat dissipation of 500 W, a typical silicon heatsink cooled by liquid nitrogen has a thermal resistance of 0.046 cm{sup 2}{degrees}K/W. The actual heatsink structure in this case is only 0.1 cm high. Silicon, although it has excellent thermal properties at liquid nitrogen temperatures, may fracture with very little plastic deformation due to mechanical and thermal stresses. Because the fracture strength of silicon depends on the presence of small defects, strength of the heatsink structures must be addressed to insure highly reliable heatsink devices. Microchannel heatsink reliability can be affected by thermal stresses that arise due to temperature gradients between the base and fin and along the film length. These stresses are combined with the bonding stresses that arise in attaching components at elevated temperatures to the silicon heatsink and then cooling the structure to the cryogenic operating temperatures. These bonding stresses are potentially large because of the differences in the values of the coefficients of thermal expansion in silicon heatsink material, and the attached component materials. The stress results are shown for a 17:1 aspect ratio heatsink cooled in liquid nitrogen. The temperature gradients are a result of a surface heat flux of 1.3 kW/cm{sup 2}, approximating the heat dissipation of an RF power chip. The chip is connected to an aluminum nitride substrate, then the chip and substrate module are attached to the heatsink at a bonding temperature of 600{degrees}K, as for a gold tin eutectic bond. The stresses are shown to be within the allowables of the materials involved.

  15. Alleviation of Drought Stress and Metabolic Changes in Timothy (Phleum pratense L.) Colonized with Bacillus subtilis B26

    PubMed Central

    Gagné-Bourque, François; Bertrand, Annick; Claessens, Annie; Aliferis, Konstantinos A.; Jabaji, Suha

    2016-01-01

    Drought is a major limiting factor of crop productivity worldwide and its incidence is predicted to increase under climate change. Drought adaptation of cool-season grasses is thus a major challenge to secure the agricultural productivity under current and future climate conditions. Endophytes are non-pathogenic plant-associated bacteria that can play an important role in conferring resistance and improving plant tolerance to drought. In this study, the effect of inoculation of the bacterial endophyte Bacillus subtilis strain B26 on growth, water status, photosynthetic activity and metabolism of timothy (Phleum pratense L.) subjected to drought stress was investigated under controlled conditions. Under both drought-stress and non-stressed conditions, strain B26 successfully colonized the internal tissues of timothy and had a positive impact on plant growth. Exposure of inoculated plant to a 8-week drought-stress led to significant increase in shoot and root biomass by 26.6 and 63.8%, and in photosynthesis and stomatal conductance by 55.2 and 214.9% respectively, compared to non-inoculated plants grown under similar conditions. There was a significant effect of the endophyte on plant metabolism; higher levels of several sugars, notably sucrose and fructans and an increase of key amino acids such as, asparagine, glutamic acid and glutamine were recorded in shoots and roots of colonized plants compared to non-colonized ones. The accumulation of the non-protein amino acid GABA in shoots of stressed plants and in roots of stressed and unstressed plants was increased in the presence of the endophyte. Taken together, our results indicate that B. subtilis B26 improves timothy growth under drought stress through the modification of osmolyte accumulation in roots and shoots. These results will contribute to the development of a microbial agent to improve the yield of grass species including forage crops and cereals exposed to environmental stresses. PMID:27200057

  16. Alleviation of Drought Stress and Metabolic Changes in Timothy (Phleum pratense L.) Colonized with Bacillus subtilis B26.

    PubMed

    Gagné-Bourque, François; Bertrand, Annick; Claessens, Annie; Aliferis, Konstantinos A; Jabaji, Suha

    2016-01-01

    Drought is a major limiting factor of crop productivity worldwide and its incidence is predicted to increase under climate change. Drought adaptation of cool-season grasses is thus a major challenge to secure the agricultural productivity under current and future climate conditions. Endophytes are non-pathogenic plant-associated bacteria that can play an important role in conferring resistance and improving plant tolerance to drought. In this study, the effect of inoculation of the bacterial endophyte Bacillus subtilis strain B26 on growth, water status, photosynthetic activity and metabolism of timothy (Phleum pratense L.) subjected to drought stress was investigated under controlled conditions. Under both drought-stress and non-stressed conditions, strain B26 successfully colonized the internal tissues of timothy and had a positive impact on plant growth. Exposure of inoculated plant to a 8-week drought-stress led to significant increase in shoot and root biomass by 26.6 and 63.8%, and in photosynthesis and stomatal conductance by 55.2 and 214.9% respectively, compared to non-inoculated plants grown under similar conditions. There was a significant effect of the endophyte on plant metabolism; higher levels of several sugars, notably sucrose and fructans and an increase of key amino acids such as, asparagine, glutamic acid and glutamine were recorded in shoots and roots of colonized plants compared to non-colonized ones. The accumulation of the non-protein amino acid GABA in shoots of stressed plants and in roots of stressed and unstressed plants was increased in the presence of the endophyte. Taken together, our results indicate that B. subtilis B26 improves timothy growth under drought stress through the modification of osmolyte accumulation in roots and shoots. These results will contribute to the development of a microbial agent to improve the yield of grass species including forage crops and cereals exposed to environmental stresses. PMID:27200057

  17. Histone hyperacetylation modulates spinal type II metabotropic glutamate receptor alleviating stress-induced visceral hypersensitivity in female rats

    PubMed Central

    Cao, Dong-Yuan; Bai, Guang; Ji, Yaping; Karpowicz, Jane

    2016-01-01

    Stress is often a trigger to exacerbate chronic pain including visceral hypersensitivity associated with irritable bowel syndrome, a female predominant functional bowel disorder. Epigenetic mechanisms that mediate stress responses are a potential target to interfere with visceral pain. The purpose of this study was to examine the effect of a histone deacetylase inhibitor, suberoylanilide hydroxamic acid, on visceral hypersensitivity induced by a subchronic stressor in female rats and to investigate the involvement of spinal glutamate receptors. Three daily sessions of forced swim induced visceral hypersensitivity. Intrathecal suberoylanilide hydroxamic acid prevented or reversed the stress-induced visceral hypersensitivity, increased spinal histone 3 acetylation and increased mGluR2 and mGluR3 expression. Chromatin immunoprecipitation (ChIP) analysis revealed enrichment of H3K9Ac and H3K18Ac at several promoter Grm2 and Grm3 regions. The mGluR2/3 antagonist LY341495 reversed the inhibitory effect of suberoylanilide hydroxamic acid on the stress-induced visceral hypersensitivity. In surprising contrast, stress and/or suberoylanilide hydroxamic acid had no effect on spinal NMDA receptor expression or function. These data reveal histone modification modulates mGluR2/3 expression in the spinal cord to attenuate stress-induced visceral hypersensitivity. HDAC inhibitors may provide a potential approach to relieve visceral hypersensitivity associated with irritable bowel syndrome. PMID:27385724

  18. Non-thermal Plasma and Oxidative Stress

    NASA Astrophysics Data System (ADS)

    Toyokuni, Shinya

    2015-09-01

    Thermal plasmas and lasers have been used in medicine to cut and ablate tissues and for coagulation. Non-equilibrium atmospheric pressure plasma (NEAPP; non-thermal plasma) is a recently developed, non-thermal technique with possible biomedical applications. Although NEAPP reportedly generates reactive oxygen/nitrogen species, electrons, positive ions, and ultraviolet radiation, few research projects have been conducted to merge this technique with conventional free radical biology. Recently, Prof. Masaru Hori's group (Plasma Nanotechnology Research Center, Nagoya University) developed a NEAPP device with high electron density. Here electron spin resonance revealed hydroxyl radicals as a major product. To merge non-thermal plasma biology with the preexisting free radical biology, we evaluated lipid peroxidation and DNA modifications in various in vitro and ex vivo experiments. Conjugated dienes increased after exposure to linoleic and alfa-linolenic acids. An increase in 2-thiobarbituric acid-reactive substances was also increased after exposure to phosphatidylcholine, liposomes or liver homogenate. Direct exposure to rat liver in medium produced immunohistochemical evidence of 4-hydroxy-2-nonenal- and acrolein-modified proteins. Exposure to plasmid DNA induced dose-dependent single/double strand breaks and increased the amounts of 8-hydroxy-2'-deoxyguanosine and cyclobutane pyrimidine dimers. These results indicate that oxidative biomolecular damage by NEAPP is dose-dependent and thus can be controlled in a site-specific manner. Simultaneous oxidative and UV-specific DNA damage may be useful in cancer treatment. Other recent advancements in the related studies of non-thermal plasma in Nagoya University Graduate School of Medicine will also be discussed.

  19. Nonsteady thermal stress analysis and thermal fatigue strength of metal-CFRP bonded joints

    NASA Astrophysics Data System (ADS)

    Yu, Qiang; Shiratori, Masaki; Mori, Takao

    1993-01-01

    In this paper, a finite-element method (FEM) system of nonsteady thermal stress analysis has been developed to analyze the problem of metal-fiber-reinforced plastic (FRP) bonded joints. The authors have presented a new algorithm for the system, which can provide an effective thermal stress analysis for metal-carbon-FRP (CFRP) bonded joints. The effectiveness, in terms of the accuracy and central processing unit (CPU) time, has been discussed by analyzing some typical problems. The thermal fatigue strength of Al-CFRP bonded joints has been studied through a series of thermal cyclic fatigue tests. It has been shown that the thermal fatigue strength of the joints can be well described by the maximum equivalent stress at the adhesive layer, which can be calculated by the developed FEM system.

  20. Antioxidant potential of Cymbopogon citratus extract: alleviation of carbon tetrachloride-induced hepatic oxidative stress and toxicity.

    PubMed

    Koh, Pei Hoon; Mokhtar, Ruzaidi Azli Mohd; Iqbal, Mohammad

    2012-01-01

    This study was aimed to evaluate the effect of Cymbopogon citratus against carbon tetrachloride (CCl(4))-mediated hepatic oxidative damage in rats. Rats were administrated with C. citratus extract (100, 200 and 300 mg/kg b.w.) for 14 days before the challenge of CCl(4) (1.2 ml/kg b.w. p.o) on 13th and 14th days. Hepatic damage was evaluated by employing serum biochemical parameters (alanine aminotransferase-ALT, aspartate aminotransferase-AST and lactate dehydrogenase-LDH), malondialdehye (MDA) level, reduced GSH and antioxidant enzymes (catalase: CAT, glutathione peroxidase: GPX, quinone reductase: QR, glutathione S-transferase: GST, glutathione reductase: GR, glucose-6-phosphate dehyrogenase: G6PD). In addition, CCl(4)-mediated hepatic damage was further evaluated by histopathological examination. However, most of these changes were alleviated by prophylactic treatment of animals with C. citratus dose dependently (p < 0.05). The protection was further evident through decreased histopathological alterations in liver. The results of the present study indicated that the hepatoprotective effect of C. citratus might be ascribable to its antioxidant and free radical scavenging property. PMID:21508074

  1. Lipopolysaccharide-Induced Behavioral Alterations Are Alleviated by Sodium Phenylbutyrate via Attenuation of Oxidative Stress and Neuroinflammatory Cascade.

    PubMed

    Jangra, Ashok; Sriram, Chandra Shaker; Lahkar, Mangala

    2016-08-01

    Oxido-nitrosative stress, neuroinflammation, and reduced level of neurotrophins are implicated in the pathophysiology of anxiety and depressive illness. A few recent studies have revealed the role of endoplasmic reticulum (ER) stress in the pathophysiology of stress and depression. The aim of the present study is to investigate the neuroprotective potential of sodium phenylbutyrate (SPB), an ER stress inhibitor against lipopolysaccharide (LPS)-induced anxiety and depressive-like behavior in Swiss albino mice. Anxiety and depressive-like behavior was induced by LPS (0.83 mg/kg; i.p.) administration. Various behavioral tests were conducted to evaluate the anxiety and depressive-like behavior in mice. Real-time PCR was employed for the detection and expression of ER stress markers (78-kDa glucose-regulated protein (GRP78) and CCAAT/enhancer binding protein homologous protein (CHOP)). Pretreatment with SPB significantly ameliorated the LPS-induced anxiety and depressive-like behavior as revealed by behavioral paradigm results. LPS-induced oxidative stress was ameliorated by SPB pretreatment in hippocampus (HC) and prefrontal cortex (PFC) region. Neuroinflammation was significantly reduced by SPB pretreatment in LPS-treated mice as evident from reduction in proinflammatory cytokines (IL-1β and TNF-α). Importantly, LPS administration significantly up-regulated the GRP78 mRNA expression level in the HC which suggests the involvement of unfolded protein response (UPR) in LPS-evoked behavioral anomalies. These results highlight the neuroprotective potential of SPB in LPS-induced anxiety and depressive illness model which may be partially due to inhibition of oxidative stress-neuroinflammatory cascade. PMID:27192986

  2. Alleviation of aflatoxin B1-induced oxidative stress in HepG2 cells by volatile extract from Allii Fistulosi Bulbus.

    PubMed

    Lee, Joon-Kyoung; Choi, Eun Hye; Lee, Kwang-Geun; Chun, Hyang Sook

    2005-10-21

    The volatile extract from Allii Fistulosi Bulbus (VEAF) was isolated by steam distillation under reduced pressure, followed by continuous liquid-liquid extraction, and its effects on aflatoxin B1 (AFB1)-induced oxidative stress were investigated in human hepatoma cells (HepG2). The main constituents of the VEAF, identified by gas chromatography/mass spectrometry, were 2-octyl-5-methyl-3(2H)-furanone, 2-hexyl-5-methyl-3(2H)-furanone, 2,5-dimethylthiophene, 3,5-diethyl-1,2,4-trithiolane and 3,4-dimethyl-2,5-dihydro-thiophene-2-one. VEAF significantly inhibited the formation of intracellular reactive oxygen species caused by AFB1 in a dose-dependent manner, concomitant with a significant decrease in the AFB1-induced cytotoxicity. VEAF pretreatment significantly reduced the levels of thiobarbituric acid reactive substances, an indicator of lipid peroxidation, whereas increased the level of reduced glutathione. The level of 8-hydroxy-2'-deoxyguanosine, a DNA oxidative stress marker, was also decreased by 49-59% with pretreatment of VEAF. With respect to the activity of AFB1 metabolizing enzymes, VEAF significantly increased the activity of glutathione S-transferase, and significantly decreased the cytochrome (CYP) P450 3A4 activity, but had a little effect on the CYP1As. These results suggest that VEAF may be selectively effective in alleviating the AFB1-induced oxidative stress, and lead to cytoprotection against AFB1 exposure. PMID:15970298

  3. Identification of a novel putative non-selenocysteine containing phospholipid hydroperoxide glutathione peroxidase (NPGPx) essential for alleviating oxidative stress generated from polyunsaturated fatty acids in breast cancer cells.

    PubMed

    Utomo, Ahmad; Jiang, Xianzhi; Furuta, Saori; Yun, Jeanho; Levin, David S; Wang, Yi-Chun J; Desai, Kartiki V; Green, Jeffrey E; Chen, Phang-Lang; Lee, Wen-Hwa

    2004-10-15

    A dramatic reduction in the expression of a novel phospholipid hydroperoxide glutathione peroxidase (PHGPx), which incorporates cysteine instead of selenocysteine in the conserved catalytic motif was observed in a microarray analysis using cDNAs amplified from mRNA of Brca1-null mouse embryonic fibroblasts. This non-selenocysteine PHGPx named NPGPx is a cytoplasmic protein with molecular mass of approximately 22 kDa and has little detectable glutathione peroxidase activity in vitro. Ectopic expression of NPGPx in Brca1-null cells that were sensitive to oxidative stress induced by hydrogen peroxide conferred a similar resistance level to that of the wild-type cells, suggesting the importance of this protein in reducing oxidative stress. Expression of NPGPx was found in many tissues, including developing mammary gland. However, the majority of breast cancer cell lines studied (11 of 12) expressed very low or undetectable levels of NPGPx irrespective of BRCA1 status. Re-expression of NPGPx in breast cancer lines, MCF-7 and HCC1937, which have very little or no endogenous NPGPx, induced resistance to eicosapentaenoic acid (an omega-3 type of polyunsaturated fatty acid)-mediated cell death. Conversely, inhibition of the expression of NPGPx by the specific small interfering RNA in HS578T breast cancer cells that originally express substantial amounts of endogenous NPGPx increased their sensitivity to eicosapentaenoic acid-mediated cell death. Thus, NPGPx plays an essential role in breast cancer cells in alleviating oxidative stress generated from polyunsaturated fatty acid metabolism. PMID:15294905

  4. Analysis of thermal stresses in composite laminates by assumed stress hybrid multilayer element

    SciTech Connect

    Wang Liangzhong; Wang Cheng )

    1993-03-01

    Based on Hellinger-Reissner principle, a hybrid multilayer element is presented in this article. This element can be used for analyzing thermoelastic stresses in composite laminates induced by nonuniform temperature distribution. The thermal loads are derived from the functional directly in the element model. Numerical results show that this multilayer element model is suitable for thermal stress analysis of laminated composite structures. 9 refs.

  5. EXPRESS: Histone hyperacetylation modulates spinal type II metabotropic glutamate receptor alleviating stress-induced visceral hypersensitivity in female rats.

    PubMed

    Cao, Dong-Yuan; Bai, Guang; Ji, Yaping; Karpowicz, Jane M; Traub, Richard J

    2016-01-01

    Stress is often a trigger to exacerbate chronic pain including visceral hypersensitivity associated with irritable bowel syndrome, a female predominant functional bowel disorder. Epigenetic mechanisms that mediate stress responses are a potential target to interfere with visceral pain. The purpose of this study was to examine the effect of a histone deacetylase inhibitor, suberoylanilide hydroxamic acid, on visceral hypersensitivity induced by a subchronic stressor in female rats and to investigate the involvement of spinal glutamate receptors. Three daily sessions of forced swim induced visceral hypersensitivity. Intrathecal suberoylanilide hydroxamic acid prevented or reversed the stress-induced visceral hypersensitivity, increased spinal histone 3 acetylation and increased mGluR2 and mGluR3 expression. Chromatin immunoprecipitation (ChIP) analysis revealed enrichment of H3K9Ac and H3K18Ac at several promoter Grm2 and Grm3 regions. The mGluR2/3 antagonist LY341495 reversed the inhibitory effect of suberoylanilide hydroxamic acid on the stress-induced visceral hypersensitivity. In surprising contrast, stress and/or suberoylanilide hydroxamic acid had no effect on spinal NMDA receptor expression or function. These data reveal histone modification modulates mGluR2/3 expression in the spinal cord to attenuate stressinduced visceral hypersensitivity. HDAC inhibitors may provide a potential approach to relieve visceral hypersensitivity associated with irritable bowel syndrome. PMID:27385724

  6. Thermal stresses investigation of a gas turbine blade

    NASA Astrophysics Data System (ADS)

    Gowreesh, S.; Pravin, V. K.; Rajagopal, K.; Veena, P. H.

    2012-06-01

    The analysis of structural and thermal stress values that are produced while the turbine is operating are the key factors of study while designing the next generation gas turbines. The present study examines structural, thermal, modal analysis of the first stage rotor blade of a two stage gas turbine. The design features of the turbine segment of the gas turbine have been taken from the preliminary design of a power turbine for maximization of an existing turbojet engine with optimized dump gap of the combustion chamber, since the allowable temperature on the turbine blade dependents on the hot gas temperatures from the combustion chamber. In the present paper simplified 3-D Finite Element models are developed with governing boundary conditions and solved using the commercial FEA software ANSYS. As the temperature has a significant effect on the overall stress on the rotor blades, a detail study on mechanical and thermal stresses are estimated and evaluated with the experimental values.

  7. Modeling of thermal stresses in elastic multilayer coating systems

    NASA Astrophysics Data System (ADS)

    Gao, Chunxue; Zhao, Zhiwei; Li, Xuehua

    2015-02-01

    The performance and reliability of multilayer coating systems are strongly influenced by thermal stresses. The present study develops an alternative analytical model to predict the thermal stresses in elastic multilayer coating systems. An exact closed-form solution is obtained which is independent of the number of coating layers. In addition, with the definition of the coordinate system, the closed-form solution is concisely formulated. Specific results are calculated for thermal stresses in HfO2/SiO2 multilayer optical coatings, and a finite element analysis is performed to confirm the analytical results. The two results agree fairly well with each other. Also, when the thicknesses of the coating layers are much less than the substrate thickness, the approximate solution is obtained based on the exact closed-form solution, and its accuracy is examined.

  8. Potential of casein as a nutrient intervention to alleviate lead (Pb) acetate-mediated oxidative stress and neurotoxicity: First evidence in Drosophila melanogaster.

    PubMed

    Venkareddy, Lalith Kumar; Muralidhara

    2015-05-01

    Understanding the interaction between dietary protein deficits and neurotoxicants such as lead (Pb) is critical since oxidative stress is a common denominator under such conditions. The Drosophila system is an extensively used model to investigate the interaction between nutrients and environmental toxicants. Accordingly, we have examined the hypothesis that casein (CSN) enrichment has the propensity to attenuate Pb-associated phenotype, oxidative stress and neurotoxicity in Drosophila melanogaster. Exposure of young (2-3 d) and adult flies (10-12 d old) to Pb acetate (0-20 mM, 7 d) in the medium resulted in a concentration dependent mortality and the survivors exhibited a hyperactive phenotype. While males showed higher susceptibility to Pb among both age groups, young flies were relatively more susceptible than adults. Pb exposure (5-10 mM, 5 d) among young flies caused robust oxidative stress as evidenced by markedly elevated levels of reactive oxygen species with concomitant perturbations in the activities of antioxidant enzymes (diminished SOD and elevated thioredoxin reductase) and altered redox state. Further, Pb caused significant elevation in the activity of acetylcholinesterase and dopamine levels. In a satellite study, we assessed the modulatory effect of CSN-enriched diet (1-2%) on Pb intoxication in terms of lethality, hyperactivity, oxidative stress and neurotoxicity. CSN markedly offset Pb-induced lethality and diminished the hyperactivity response. While CSN enrichment among Pb (5 mM) treated flies caused further elevation in ROS levels and thioredoxin reductase activity, the SOD levels were restored to normalcy. Further, CSN improved the activity levels of complex I-III and restored the dopamine levels. Our data suggest that Pb-induced toxicity in the Drosophila system may be predominantly mediated through oxidative stress mechanisms and the propensity of casein-enriched diet to abrogate such responses. Hence, we propose that enrichment of diet

  9. Treadmill exercise alleviates prenatal noise stress-induced impairment of spatial learning ability through enhancing hippocampal neurogenesis in rat pups

    PubMed Central

    Kim, Tae-Woon; Shin, Mal-Soon; Park, Joon-Ki; Shin, Mi-Ai; Lee, Hee-Hyuk; Lee, Sam-Jun

    2013-01-01

    Stress alters brain cell properties and then disturbs cognitive processes, such as learning and memory. In this study, we investigated the effect of postnatal treadmill exercise on hippocampal neurogenesis and spatial learning ability of rat pups following prenatal noise stress. The impact of exercise intensity (mild-intensity exercise vs heavy-intensity exercise) was also compared. The pregnant rats in the stress-applied group were exposed to a 95 dB supersonic machine sound for 1 h once a day from the 15th day after mating until delivery. After birth, the rat pups in the exercise groups were made to run on a treadmill for 30 min once a day for 7 consecutive days, starting 4 weeks after birth. The spatial learning ability was tested using radial-arm maze task and hippocampal neurogenesis was determined by 5-bromo-2′-deoxyuridine (BrdU) immunohistochemistry. The rat pups born from the stress-applied maternal rats spent more time for the seeking of water and showed higher number of error in the radial-arm maze task compared to the control group. These rat pups showed suppressed neurogenesis in the hippocampus. In contrast, the rat pups performed postnatal treadmill exercise saved time for seeking of water and showed lower number of error compared to the stress-applied group. Postnatal treadmill exercise also enhanced neurogenesis in the hippocampus. The mild-intensity exercise showed more potent impact compared to the heavy-intensity exercise. The present results reveal that postnatal treadmill exercise lessens prenatal stress-induced deterioration of brain function in offspring. PMID:24282804

  10. Residual stress within nanoscale metallic multilayer systems during thermal cycling

    SciTech Connect

    Economy, David Ross; Cordill, Megan Jo; Payzant, E. Andrew; Kennedy, Marian S.

    2015-09-21

    Projected applications for nanoscale metallic multilayers will include wide temperature ranges. Since film residual stress has been known to alter system reliability, stress development within new film structures with high interfacial densities should be characterized to identify potential long-term performance barriers. To understand factors contributing to thermal stress evolution within nanoscale metallic multilayers, stress in Cu/Nb systems adhered to Si substrates was calculated from curvature measurements collected during cycling between 25 °C and 400 °C. Additionally, stress within each type of component layers was calculated from shifts in the primary peak position from in-situ heated X-ray diffraction. The effects of both film architecture (layer thickness) and layer order in metallic multilayers were tracked and compared with monolithic Cu and Nb films. Analysis indicated that the thermoelastic slope of nanoscale metallic multilayer films depends on thermal expansion mismatch, elastic modulus of the components, and also interfacial density. The layer thickness (i.e. interfacial density) affected thermoelastic slope magnitude while layer order had minimal impact on stress responses after the initial thermal cycle. When comparing stress responses of monolithic Cu and Nb films to those of the Cu/Nb systems, the nanoscale metallic multilayers show a similar increase in stress above 200 °C to the Nb monolithic films, indicating that Nb components play a larger role in stress development than Cu. Local stress calculations from X-ray diffraction peak shifts collected during heating reveal that the component layers within a multilayer film respond similarly to their monolithic counterparts.

  11. Residual stress within nanoscale metallic multilayer systems during thermal cycling

    DOE PAGESBeta

    Economy, David Ross; Cordill, Megan Jo; Payzant, E. Andrew; Kennedy, Marian S.

    2015-09-21

    Projected applications for nanoscale metallic multilayers will include wide temperature ranges. Since film residual stress has been known to alter system reliability, stress development within new film structures with high interfacial densities should be characterized to identify potential long-term performance barriers. To understand factors contributing to thermal stress evolution within nanoscale metallic multilayers, stress in Cu/Nb systems adhered to Si substrates was calculated from curvature measurements collected during cycling between 25 °C and 400 °C. Additionally, stress within each type of component layers was calculated from shifts in the primary peak position from in-situ heated X-ray diffraction. The effects ofmore » both film architecture (layer thickness) and layer order in metallic multilayers were tracked and compared with monolithic Cu and Nb films. Analysis indicated that the thermoelastic slope of nanoscale metallic multilayer films depends on thermal expansion mismatch, elastic modulus of the components, and also interfacial density. The layer thickness (i.e. interfacial density) affected thermoelastic slope magnitude while layer order had minimal impact on stress responses after the initial thermal cycle. When comparing stress responses of monolithic Cu and Nb films to those of the Cu/Nb systems, the nanoscale metallic multilayers show a similar increase in stress above 200 °C to the Nb monolithic films, indicating that Nb components play a larger role in stress development than Cu. Local stress calculations from X-ray diffraction peak shifts collected during heating reveal that the component layers within a multilayer film respond similarly to their monolithic counterparts.« less

  12. Transient thermal stress problem for a circumferentially cracked hollow cylinder

    NASA Technical Reports Server (NTRS)

    Nied, H. F.; Erdogan, F.

    1982-01-01

    The transient thermal stress problem for a hollow elasticity cylinder containing an internal circumferential edge crack is considered. It is assumed that the problem is axisymmetric with regard to the crack geometry and the loading, and that the inertia effects are negligible. The problem is solved for a cylinder which is suddenly cooled from inside. First the transient temperature and stress distributions in an uncracked cylinder are calculated. By using the equal and opposite of this thermal stress as the crack surface traction in the isothermal cylinder the crack problem is then solved and the stress intensity factor is calculated. The numerical results are obtained as a function of the Fourier number tD/b(2) representing the time for various inner-to-outer radius ratios and relative crack depths, where D and b are respectively the coefficient of diffusivity and the outer radius of the cylinder.

  13. Thermal mechanical stress modeling of GCtM seals

    SciTech Connect

    Dai, Steve Xunhu; Chambers, Robert

    2015-09-01

    Finite-element thermal stress modeling at the glass-ceramic to metal (GCtM) interface was conducted assuming heterogeneous glass-ceramic microstructure. The glass-ceramics were treated as composites consisting of high expansion silica crystalline phases dispersed in a uniform residual glass. Interfacial stresses were examined for two types of glass-ceramics. One was designated as SL16 glass -ceramic, owing to its step-like thermal strain curve with an overall coefficient of thermal expansion (CTE) at 16 ppm/ºC. Clustered Cristobalite is the dominant silica phase in SL16 glass-ceramic. The other, designated as NL16 glass-ceramic, exhibited clusters of mixed Cristobalite and Quartz and showed a near-linear thermal strain curve with a same CTE value.

  14. Thermal-stress fatigue behavior of twenty-six superalloys

    NASA Technical Reports Server (NTRS)

    Bizon, P. T.; Spera, D. A.

    1976-01-01

    The comparative thermal-stress fatigue resistances of 26 nickeland cobalt-base alloys were determined by fluidized bed tests. Cycles to cracking differed by almost three orders of magnitude for these materials, with directional solidification and surface protection showing definite benefit. The alloy-coating combination with the highest thermal-stress fatigue resistance was directionally solidified NASA TAZ-8A with an RT-SP coating. Its oxidation resistance was also excellent, showing approximately a 1/2 percent weight loss after 14,000 fluidized bed cycles.

  15. Recurrent Water Level Fluctuation Alleviates the Effects of Submergence Stress on the Invasive Riparian Plant Alternanthera philoxeroides

    PubMed Central

    Zhang, Haijie; Wang, Renqing; Wang, Xiao; Du, Ning; Ge, Xiuli; Du, Yuanda; Liu, Jian

    2015-01-01

    Recurrent water level fluctuation and submergence of plants are common in riparian zones. Our study objectives were to test the independent and interactive effects of submergence level and fluctuation frequency on a globally important riparian invasive plant, Alternanthera philoxeroides. To this end, we conducted a greenhouse experiment, in which ramets of the plants, obtained from a wetland in China, were treated with four fluctuation frequencies (0, 3, 6, and 12 cycles over a 96-day experimental period) under three water levels (0, 10, and 30 cm). We found that effects of fluctuation frequency were non-significant, negative, and positive under water levels of 0, 10 and 30 cm, respectively. As fluctuation frequency increased, the effects of increasing water level decreased significantly. When water levels were high, A. philoxeroides allocated greater biomass to shoot production probably in order to elongate and escape from submergence. However, as fluctuation frequency increased, biomass investment in roots and leaves also increased, probably in order to maximize nutrient absorption and photosynthesis, respectively. These results suggest that water level fluctuation may alleviate the effects of submergence on A. philoxeroides. In addition, A. philoxeroides showed significant phenotypic plasticity, adjusting its functional traits, such as number of nodes and leaves per stem, as well as stem diameter and pith cavity diameter, according to recurrent water level fluctuation. We conclude that A. philoxeroides may perform better in shallow water zones under conditions of disturbance that include recurrent water level fluctuation. This ability to adapt to disturbance likely promotes its growth and invasion in disturbed habitats. PMID:26066509

  16. Thermal stress analysis of reusable surface insulation for shuttle

    NASA Technical Reports Server (NTRS)

    Ojalvo, I. U.; Levy, A.; Austin, F.

    1974-01-01

    An iterative procedure for accurately determining tile stresses associated with static mechanical and thermally induced internal loads is presented. The necessary conditions for convergence of the method are derived. An user-oriented computer program based upon the present method of analysis was developed. The program is capable of analyzing multi-tiled panels and determining the associated stresses. Typical numerical results from this computer program are presented.

  17. Cinnamon intake alleviates the combined effects of dietary-induced insulin resistance and acute stress on brain mitochondria.

    PubMed

    Couturier, Karine; Hininger, Isabelle; Poulet, Laurent; Anderson, Richard A; Roussel, Anne-Marie; Canini, Frédéric; Batandier, Cécile

    2016-02-01

    Insulin resistance (IR), which is a leading cause of the metabolic syndrome, results in early brain function alterations which may alter brain mitochondrial functioning. Previously, we demonstrated that rats fed a control diet and submitted to an acute restraint stress exhibited a delayed mitochondrial permeability transition pore (mPTP) opening. In this study, we evaluated the combined effects of dietary and emotional stressors as found in western way of life. We studied, in rats submitted or not to an acute stress, the effects of diet-induced IR on brain mitochondria, using a high fat/high fructose diet (HF(2)), as an IR inducer, with addition or not of cinnamon as an insulin sensitizer. We measured Ca(2+) retention capacity, respiration, ROS production, enzymatic activities and cell signaling activation. Under stress, HF(2) diet dramatically decreased the amount of Ca(2+) required to open the mPTP (13%) suggesting an adverse effect on mitochondrial survival. Cinnamon added to the diet corrected this negative effect and resulted in a partial recovery (30%). The effects related to cinnamon addition to the diet could be due to its antioxidant properties or to the observed modulation of PI3K-AKT-GSK3β and MAPK-P38 pathways or to a combination of both. These data suggest a protective effect of cinnamon on brain mitochondria against the negative impact of an HF(2) diet. Cinnamon could be beneficial to counteract deleterious dietary effects in stressed conditions. PMID:26878796

  18. Hepatitis C Virus Infection Induces Autophagy as a Prosurvival Mechanism to Alleviate Hepatic ER-Stress Response

    PubMed Central

    Dash, Srikanta; Chava, Srinivas; Aydin, Yucel; Chandra, Partha K.; Ferraris, Pauline; Chen, Weina; Balart, Luis A.; Wu, Tong; Garry, Robert F.

    2016-01-01

    Hepatitis C virus (HCV) infection frequently leads to chronic liver disease, liver cirrhosis and hepatocellular carcinoma (HCC). The molecular mechanisms by which HCV infection leads to chronic liver disease and HCC are not well understood. The infection cycle of HCV is initiated by the attachment and entry of virus particles into a hepatocyte. Replication of the HCV genome inside hepatocytes leads to accumulation of large amounts of viral proteins and RNA replication intermediates in the endoplasmic reticulum (ER), resulting in production of thousands of new virus particles. HCV-infected hepatocytes mount a substantial stress response. How the infected hepatocyte integrates the viral-induced stress response with chronic infection is unknown. The unfolded protein response (UPR), an ER-associated cellular transcriptional response, is activated in HCV infected hepatocytes. Over the past several years, research performed by a number of laboratories, including ours, has shown that HCV induced UPR robustly activates autophagy to sustain viral replication in the infected hepatocyte. Induction of the cellular autophagy response is required to improve survival of infected cells by inhibition of cellular apoptosis. The autophagy response also inhibits the cellular innate antiviral program that usually inhibits HCV replication. In this review, we discuss the physiological implications of the HCV-induced chronic ER-stress response in the liver disease progression. PMID:27223299

  19. The physical effects of aromatherapy in alleviating work-related stress on elementary school teachers in taiwan.

    PubMed

    Liu, Shing-Hong; Lin, Tzu-Hsin; Chang, Kang-Ming

    2013-01-01

    People use aromatherapy to relieve the symptoms of physical and psychological stress. However, previous studies have not precisely clarified a scientific basis for the beneficial effects of aromatherapy. Therefore, the overall purpose of this study was to elucidate the beneficial effect of aromatherapy in relieving work-related stress. Twenty-nine elementary school teachers from Taiwan participated in this study. The experimental procedures comprised 2 phases. First, we verified the effect of aromatherapy by conducting 2 blind tests. We used natural bergamot essential oil extracted from plants and synthesized a chemical essential oil as the placebo to do the aromatherapy. Second, we analyzed the performance of the aromatherapy treatment on the teachers who had various workloads. We measured the teachers' heart rate variability to evaluate their autonomic nervous system activity. The results show that only the natural bergamot essential oil had an effect and that the aromatherapy treatment relieved work-related stress of teachers with various workloads. However, the aromatherapy treatment had a weak effect on young teachers who had a heavy workload. Moreover, the aromatherapy treatment exhibited no effect on teachers who belong to the abnormal body mass index subgroup having a heavy workload. PMID:24228065

  20. 18-β Glycyrrhetinic acid alleviates 2-acetylaminofluorene-induced hepatotoxicity in Wistar rats: Role in hyperproliferation, inflammation and oxidative stress.

    PubMed

    Hasan, S K; Khan, R; Ali, N; Khan, A Q; Rehman, M U; Tahir, M; Lateef, A; Nafees, S; Mehdi, S J; Rashid, S; Shahid, A; Sultana, S

    2015-06-01

    2-Acetylaminofluorene (2-AAF) is a known hepatic carcinogen which leads to tumour formation in rodents. 18-β Glycyrrhetinic acid (18β-GA) derived from liquorice plant has various pharmacological properties such as anti-ulcer, anti-inflammatory, antiviral, hepatoprotective and antioxidant. This study is designed to elucidate the chemopreventive properties of 18β-GA against 2-AAF-induced liver toxicity in Wistar rats and evaluated its effect on inflammatory and tumour promotion marker and activities of different oxidative stress enzymes. Administration of 2-AAF at the dose of (50 mg/kg body weight (b.w.) intraperitoneally (i.p.)) for five consecutive days induces hepatic toxicity, inflammation, oxidative stress and hyperproliferation. Pretreatment with 18β-GA at two different doses (45 and 75 mg kg(-1) b.w.) significantly ameliorates 2-AAF-induced increased lipid peroxidation, alanine transaminase and aspartate transaminase, xanthine oxidase activities and activities of phase-II detoxifying enzymes along with the levels of glutathione content. Administration of 18β-GA also significantly restored the expressions of proliferating cell nuclear antigen, cyclooxygenase 2, inducible nitric oxide synthase and nuclear factor κB. Furthermore, histological observations also support the preventive effects of 18β-GA. Our findings suggest that pretreatment with 18β-GA showed potential hepatoprotective effects via attenuation of oxidative stress, inflammation and hyperproliferation. PMID:25352648

  1. The Edible Marine Alga Gracilariopsis chorda Alleviates Hypoxia/Reoxygenation-Induced Oxidative Stress in Cultured Hippocampal Neurons.

    PubMed

    Mohibbullah, Md; Hannan, Md Abdul; Choi, Ji-Young; Bhuiyan, Mohammad Maqueshudul Haque; Hong, Yong-Ki; Choi, Jae-Suk; Choi, In Soon; Moon, Il Soo

    2015-09-01

    Age-related neurological disorders are of growing concern among the elderly, and natural products with neuroprotective properties have been attracting increasing attention as candidates for the prevention or treatment of neurological disorders induced by oxidative stress. In an effort to explore natural resources, we collected some common marine seaweed from the Korean peninsula and Indonesia and screened them for neuroprotective activity against hypoxia/reoxygenation (H/R)-induced oxidative stress. Of the 23 seaweeds examined, the ethanol extract of Gracilariopsis chorda (GCE) provided maximum neuroprotection at an optimum concentration of 15 μg/mL, followed by Undaria pinnatifida. GCE increased cell viability after H/R, decreased the formation of reactive oxygen species (measured by 2',7'-dichlorodihydrofluorescein diacetate [DCF-DA] staining), and inhibited the double-stranded DNA breaks (measured by H2AX immunocytochemistry), apoptosis (measured by Annexin V/propidium iodide staining), internucleosomal DNA fragmentation (measured by DNA laddering), and dissipation of mitochondrial membrane potential (measured by JC-1 staining). Using reverse-phase high-pressure liquid chromatography, we quantitated the arachidonic acid (AA) in GCE, which provides neuroprotection against H/R-induced oxidative stress. This neuroprotective effect of AA was comparable to that of GCE. These findings suggest that the neuroprotective effect of GCE against H/R-induced neuronal death is due, at least in part, to the AA content that suppresses neuronal apoptosis. PMID:26106876

  2. Dietary rosemary oil alleviates heat stress-induced structural and functional damage through lipid peroxidation in the testes of growing Japanese quail.

    PubMed

    Türk, Gaffari; Çeribaşı, Ali O; Şimşek, Ülkü G; Çeribaşı, Songül; Güvenç, Mehmet; Özer Kaya, Şeyma; Çiftçi, Mehmet; Sönmez, Mustafa; Yüce, Abdurrauf; Bayrakdar, Ali; Yaman, Mine; Tonbak, Fadime

    2016-01-01

    Supplementation of natural antioxidants to diets of male poultry has been reported to be effective in reducing or completely eliminating heat stress (HS)-induced reproductive failures. In this study, the aim is to investigate whether rosemary oil (RO) has a protective effect on HS-induced damage in spermatozoa production, testicular histologic structures, apoptosis, and androgenic receptor (AR) through lipid peroxidation mechanisms in growing Japanese quail. Male chicks (n=90) at 15-days of age were assigned to two groups. The first group (n=45) was kept in a thermo-neutral (TN) room at 22°C for 24h/d. The second group (n=45) was kept in a room with a greater ambient temperature of 34°C for 8h/d (from 9:00 AM to 5:00 PM) and 22°C for 16h/d. Animals in each of these two groups were randomly assigned to three subgroups (RO groups: 0, 125, 250ppm), consisting of 15 chicks (six treatment groups in 2×3 factorial design). Each of subgroups was replicated three times with each replicate including five chicks. The HS treatment significantly reduced the testicular spermatogenic cell counts, amount of testicular Bcl-2 (anti-apoptotic marker) and amount of AR. In addition, it significantly increased testicular lipid peroxidation, Bax (apoptotic marker) immunopositive staining, and the Bax/Bcl-2 ratio in conjunction with some histopathologic damage. Dietary supplementation of RO to diets of quail where the HS treatment was imposed alleviated HS-induced almost all negative changes such as increased testicular lipid peroxidation, decreased numbers of spermatogenic cells, and decreased amounts of Bcl-2 and AR, increased ratio of Bax/Bcl-2 and some testicular histopathologic lesion. In conclusion, dietary supplementation of RO for growing male Japanese quail reared in HS environmental conditions alleviates the HS-induced structural and functional damage by providing a decrease in lipid peroxidation. PMID:26656503

  3. Thermal lensing and stress in Cr,Er:YSGG

    NASA Astrophysics Data System (ADS)

    Gollihar, William A.; Margo, Satrijo T.; DeShazer, Larry G.; Kennedy, Chandler J.

    1995-04-01

    Thermal and stress lensing effects have been measured in a Cr,Er:YSGG rod by observing a transmitted 1064 nm Nd:YAG beam diverging from an operating Cr,Er:YSGG laser. The results compare favorably with theory and estimated thermal-optic properties of YSGG, which is intermediate between YAG and GSGG. Numerical simulations of the laser agree substantially with the threshold and power observed and show a heat generation rate which is consistent with our observations of lensing. Thermal fracture of the rod has been observed on several occasions, leading to an estimate of the thermal fracture figure of merit which is also intermediate between YAG and GSGG. Back focal distances of less than 20 cm occur in the vicinity of half the thermal rupture limit.

  4. Thermal diffusion by Brownian-motion-induced fluid stress

    NASA Astrophysics Data System (ADS)

    Kreft, Jennifer; Chen, Yeng-Long

    2007-08-01

    The Ludwig-Soret effect, the migration of a species due to a temperature gradient, has been extensively studied without a complete picture of its cause emerging. Here we investigate the dynamics of DNA and spherical particles subjected to a thermal gradient using a combination of Brownian dynamics and the lattice Boltzmann method. We observe that the DNA molecules will migrate to colder regions of the channel, an observation also made in experiments. In fact, the thermal diffusion coefficient found agrees quantitatively with the experimentally measured value. We also observe that the thermal diffusion coefficient decreases as the radius of the studied spherical particles increases. Furthermore, we observe that the thermal-fluctuation-fluid-momentum-flux coupling induces a gradient in the stress which leads to thermal migration in both systems.

  5. Exogenous proline mediates alleviation of cadmium stress by promoting photosynthetic activity, water status and antioxidative enzymes activities of young date palm (Phoenix dactylifera L.).

    PubMed

    Zouari, M; Ben Ahmed, Ch; Zorrig, W; Elloumi, N; Rabhi, M; Delmail, D; Ben Rouina, B; Labrousse, P; Ben Abdallah, F

    2016-06-01

    The ability of exogenous compatible solutes, such as proline, to counteract cadmium (Cd) inhibitory effects in young date palm plants (Phoenix dactylifera L. cv Deglet Nour) was investigated. Two-year-old date palm plants were subjected for five months at different Cd stress levels (0, 10 and 30 mg CdCl2 kg(-1) soil) whether supplied or not with exogenous proline (20mM) added through the irrigation water. Different levels of Cd stress altered plant growth, gas exchanges and chlorophyll content as well as water status, but at different extent among them. In contrast, an increase of antioxidant enzymes activities of Cd-treated plants in association with high amounts of proline content, hydrogen peroxide (H2O2), thiobarbituric acid reactive substances (TBARS) and electrolyte leakage (EL) were observed. Interestingly, exogenous proline mitigated the adverse effects of Cd on young date palm. Indeed, it alleviated the oxidative damage induced by Cd accumulation and established better levels of plant growth, water status and photosynthetic activity. Moreover, proline-treated plants showed high antioxidant enzymes activities (superoxide dismutase, catalase and glutathione peroxydase) in roots and leaves as compared to Cd-treated plants. PMID:26901506

  6. Hydroalcoholic seed extract of Coriandrum sativum (Coriander) alleviates lead-induced oxidative stress in different regions of rat brain.

    PubMed

    Velaga, Manoj Kumar; Yallapragada, Prabhakara Rao; Williams, Dale; Rajanna, Sharada; Bettaiya, Rajanna

    2014-06-01

    Lead exposure is known to cause apoptotic neurodegeneration and neurobehavioral abnormalities in developing and adult brain by impairing cognition and memory. Coriandrum sativum is an herb belonging to Umbelliferae and is reported to have a protective effect against lead toxicity. In the present investigation, an attempt has been made to evaluate the protective activity of the hydroalcoholic extract of C. sativum seed against lead-induced oxidative stress. Male Wistar strain rats (100-120 g) were divided into four groups: control group: 1,000 mg/L of sodium acetate; exposed group: 1,000 mg/L lead acetate for 4 weeks; C. sativum treated 1 (CST1) group: 250 mg/kg body weight/day for seven consecutive days after 4 weeks of lead exposure; C. sativum treated 2 (CST2) group: 500 mg/kg body weight/day for seven consecutive days after 4 weeks of lead exposure. After the exposure and treatment periods, rats were sacrificed by cervical dislocation, and the whole brain was immediately isolated and separated into four regions: cerebellum, hippocampus, frontal cortex, and brain stem along with the control group. After sacrifice, blood was immediately collected into heparinized vials and stored at 4 °C. In all the tissues, reactive oxygen species (ROS), lipid peroxidation products (LPP), and total protein carbonyl content (TPCC) were estimated following standard protocols. An indicator enzyme for lead toxicity namely delta-amino levulinic acid dehydratase (δ-ALAD) activity was determined in the blood. A significant (p<0.05) increase in ROS, LPP, and TPCC levels was observed in exposed rat brain regions, while δ-ALAD showed a decrease indicating lead-induced oxidative stress. Treatment with the hydroalcoholic seed extract of C. sativum resulted in a tissue-specific amelioration of oxidative stress produced by lead. PMID:24793421

  7. Thermal Stress Behavior of Aluminum Nanofilms under Heat Cycling

    SciTech Connect

    Kusaka, Kazuya; Hanabusa, Takao; Shingubara, Shoso; Matsue, Tatsuya; Sakata, Osami; Noda, Kazuhiro; Hataya, Mitsuhiko

    2004-12-08

    In-situ thermal stress in aluminum nanofilms with silicon oxide glass (SOG) passivation was investigated by using synchrotron radiation at the SPring-8. Aluminum films of varying thickness (10, 20, 50 nm) were deposited on thermally oxidized silicon wafers by RF magnetron sputtering. Each specimen was heated in air over two cycles between room temperature and 300 deg. C. The following results were obtained: (1) {l_brace}111{r_brace} planes of aluminum nanofilm crystals were oriented parallel to the substrate normal; (2) the intensity of 111 diffraction was almost independent of temperature except in the case of the 50-nm-thick film; (3) the FWHM of 111 diffraction was almost independent of temperature at any given film thickness; and (4) for all films, the thermal stress varied linearly with heating temperature, and the hysteresis between the heating and cooling steps disappeared.

  8. Combined thermal and herbicide stress in functionally diverse coral symbionts.

    PubMed

    van Dam, J W; Uthicke, S; Beltran, V H; Mueller, J F; Negri, A P

    2015-09-01

    Most reef building corals rely on symbiotic microalgae (genus Symbiodinium) to supply a substantial proportion of their energy requirements. Functional diversity of different Symbiodinium genotypes, endorsing the host with physiological advantages, has been widely reported. Yet, the influence of genotypic specificity on the symbiont's susceptibility to contaminants or cumulative stressors is unknown. Cultured Symbiodinium of presumed thermal-tolerant clade D tested especially vulnerable to the widespread herbicide diuron, suggesting important free-living populations may be at risk in areas subjected to terrestrial runoff. Co-exposure experiments where cultured Symbiodinium were exposed to diuron over a thermal stress gradient demonstrated how fast-growing clade C1 better maintained photosynthetic capability than clade D. The mixture toxicity model of Independent Action, considering combined thermal stress and herbicide contamination, revealed response additivity for inhibition of photosynthetic yield in both tested cultures, emphasizing the need to account for cumulative stressor impacts in ecological risk assessment and resource management. PMID:25989453

  9. Thermal stresses, differential subsidence, and flexure at oceanic fracture zones

    NASA Technical Reports Server (NTRS)

    Wessel, Pal; Haxby, William F.

    1990-01-01

    Geosat geoid undulations over four Pacific fracture zones have been analyzed. After correcting for the isostatic thermal edge effect, the amplitudes of the residuals are shown to be proportional to the age offset. The shape of the residuals seems to broaden with increasing age. Both geoid anomalies and available ship bathymetry data suggest that slip must sometimes occur on the main fracture zone or secondary faults. Existing models for flexure at fracture zones cannot explain the observed anomalies. A combination model accounting for slip and including flexure from thermal stresses and differential subsidence is presented. This model accounts for lateral variations in flexural rigidity from brittle and ductile yielding due to both thermal and flexural stresses and explains both the amplitudes and the shape of the anomalies along each fracture zone. The best fitting models have mechanical plate thicknesses that are described by the depth to the 600-700 C isotherms.

  10. Growth instabilities in mechanical breakdown under mechanical and thermal stresses

    NASA Astrophysics Data System (ADS)

    Zhang, S.-Z.; Louis, E.; Plá, O.; Guinea, F.

    1995-12-01

    A linear stability analysis is used to investigate crack growth in two dimensional elastic media, and under mechanical or thermal stresses. Although in most cases a circular geometry is considered, the instability of a planar crack is also discussed. Several boundary conditions and size effects are considered. The results indicate that the tendency towards instabilities in mechanical breakdown is stronger than in the case of growth in fields governed by the Laplace equation (diffusion or electrostatic fields), in line with the smaller fractal dimensions obtained in the first case. Instabilities under thermal stresses are shown to depend on the actual thermal gradients. Finally, a model previously investigated numerically is used to show that plasticity decreases the strength of the instability. (c) 1995 The American Physical Society

  11. Minimizing Thermal Stress for Data Center Servers through Thermal-Aware Relocation

    PubMed Central

    Ling, T. C.; Hussain, S. A.

    2014-01-01

    A rise in inlet air temperature may lower the rate of heat dissipation from air cooled computing servers. This introduces a thermal stress to these servers. As a result, the poorly cooled active servers will start conducting heat to the neighboring servers and giving rise to hotspot regions of thermal stress, inside the data center. As a result, the physical hardware of these servers may fail, thus causing performance loss, monetary loss, and higher energy consumption for cooling mechanism. In order to minimize these situations, this paper performs the profiling of inlet temperature sensitivity (ITS) and defines the optimum location for each server to minimize the chances of creating a thermal hotspot and thermal stress. Based upon novel ITS analysis, a thermal state monitoring and server relocation algorithm for data centers is being proposed. The contribution of this paper is bringing the peak outlet temperatures of the relocated servers closer to average outlet temperature by over 5 times, lowering the average peak outlet temperature by 3.5% and minimizing the thermal stress. PMID:24987743

  12. Melatonin alleviates hyperthyroidism induced oxidative stress and neuronal cell death in hippocampus of aged female golden hamster, Mesocricetus auratus.

    PubMed

    Rao, Geeta; Verma, Rakesh; Mukherjee, Arun; Haldar, Chandana; Agrawal, Neeraj Kumar

    2016-09-01

    Oxidative stress is a well known phenomenon under hyperthyroid condition that induces various physiological and neural problems with a higher prevalence in females. We, therefore investigated the antioxidant potential of melatonin (Mel) on hyperthyroidism-induced oxidative stress and neuronal cell death in the hippocampus region of brain (cognition and memory centre) of aged female golden hamster, Mesocricetus auratus. Aged female hamsters were randomly divided into four experimental groups (n=7); group-I: control, group-II: Melatonin (5mgkg(-1)day(-1), i.p., for one week), group-III: Hyperthyroid (100μg kg(-1)day(-1), i.p., for two weeks) and group-IV- Hyper+Mel. Hormonal profiles (thyroid and melatonin), activity of antioxidant enzymes (SOD, CAT and GPX), lipid peroxidation level (TBARS) and the specific apoptotic markers (Bax/Bcl-2 ratio and Caspase-3) expression were evaluated. A significant increase in the profile of total thyroid hormone (tT3 and tT4) in hyperthyroidic group as compared to control while tT3 significantly decreased in melatonin treated hyperthyroidic group. However, Mel level significantly decreased in hyperthyroidic group but increased in melatonin treated hyperthyroidic group. Further, the number of immune-positive cells for thyroid hormone receptor-alpha (TR-α) decreased in the hippocampus of hyperthyroidic group and increased in melatonin treated hyperthyroidic group. Profiles of antioxidant enzymes showed a significant decrease in hyperthyroidic group with a simultaneous increase in lipid peroxidation (TBARS). Melatonin treatment to hyperthyroidic group lead to decreased TBARS level with a concomitant increase in antioxidant enzyme activity. Moreover, increased expression of Bax/Bcl-2 ratio and Caspase-3, in hyperthyroidic group had elevated neuronal cell death in hippocampal area and melatonin treatment reduced its expression in hyperthyroidic group. Our findings thus indicate that melatonin reduced the hyperthyroidism

  13. OBIC analysis of stressed, thermally-isolated polysilicon resistors

    SciTech Connect

    Cole, E.I. Jr.; Peterson, K.A.; Campbell, A.N.; Snyder, E.S.; Pierce, D.G.; Suehle, J.S.; Chaparala, P.

    1994-12-31

    High gain Optical Beam Induced Current (OBIC) imaging has been used for the first time to examine the internal structural effects of electrical stress on thermally-isolated polysilicon resistors. The resistors are examined over a wide range of current densities, producing Joule heating up to {approximately}1200{degrees}C. Throughout this current density range, the OBIC images indicate a clustering of dopant under dc stress and a more uniform distribution under ac conditions. The OBIC images also reveal areas that are precursors to catastrophic resistor failure. In addition to OBIC imaging, conventional electrical measurements were performed, examining the polysilicon resistance degradation and time-to-failure as a function of electrical stress. The electrical measurements show a monotonic increase in polysilicon resistor lifetime with frequency (up to 2 kHz) when subjected to a bipolar ac stress. The enhanced lifetime was observed even under high temperature (from Joule heating) stress conditions previously reported to be electromigration-free. The dopant redistribution indicated by the OBIC images is consistent with an electromigration stress experienced by the polysilicon resistors. The implications for thermally-isolated polysilicon resistor reliability are examined briefly.

  14. Diagnostic gene expression biomarkers of coral thermal stress.

    PubMed

    Kenkel, C D; Sheridan, C; Leal, M C; Bhagooli, R; Castillo, K D; Kurata, N; McGinty, E; Goulet, T L; Matz, M V

    2014-07-01

    Gene expression biomarkers can enable rapid assessment of physiological conditions in situ, providing a valuable tool for reef managers interested in linking organism physiology with large-scale climatic conditions. Here, we assessed the ability of quantitative PCR (qPCR)-based gene expression biomarkers to evaluate (i) the immediate cellular stress response (CSR) of Porites astreoides to incremental thermal stress and (ii) the magnitude of CSR and cellular homeostasis response (CHR) during a natural bleaching event. Expression levels largely scaled with treatment temperature, with the strongest responses occurring in heat-shock proteins. This is the first demonstration of a 'tiered' CSR in a coral, where the magnitude of expression change is proportional to stress intensity. Analysis of a natural bleaching event revealed no signature of an acute CSR in normal or bleached corals, indicating that the bleaching stressor(s) had abated by the day of sampling. Another long-term stress CHR-based indicator assay was significantly elevated in bleached corals, although assay values overall were low, suggesting good prospects for recovery. This study represents the first step in linking variation in gene expression biomarkers to stress tolerance and bleaching thresholds in situ by quantifying the severity of ongoing thermal stress and its accumulated long-term impacts. PMID:24354729

  15. The relationship between bioclimatic thermal stress and subjective thermal sensation in pedestrian spaces

    NASA Astrophysics Data System (ADS)

    Pearlmutter, David; Jiao, Dixin; Garb, Yaakov

    2014-12-01

    Outdoor thermal comfort has important implications for urban planning and energy consumption in the built environment. To better understand the relation of subjective thermal experience to bioclimatic thermal stress in such contexts, this study compares micrometeorological and perceptual data from urban spaces in the hot-arid Negev region of Israel. Pedestrians reported on their thermal sensation in these spaces, whereas radiation and convection-related data were used to compute the Index of Thermal Stress (ITS) and physiologically equivalent temperature (PET). The former is a straightforward characterization of energy exchanges between the human body and its surroundings, without any conversion to an "equivalent temperature." Although the relation of ITS to subjective thermal sensation has been analyzed in the past under controlled indoor conditions, this paper offers the first analysis of this relation in an outdoor setting. ITS alone can account for nearly 60 % of the variance in pedestrians' thermal sensation under outdoor conditions, somewhat more than PET. A series of regressions with individual contextual variables and ITS identified those factors which accounted for additional variance in thermal sensation, whereas multivariate analyses indicated the considerable predictive power ( R-square = 0.74) of models including multiple contextual variables in addition to ITS. Our findings indicate that pedestrians experiencing variable outdoor conditions have a greater tolerance for incremental changes in thermal stress than has been shown previously under controlled indoor conditions, with a tapering of responses at high values of ITS. However, the thresholds of ITS corresponding to thermal "neutrality" and thermal "acceptability" are quite consistent regardless of context.

  16. Thermal stresses from large volumetric expansion during freezing of biomaterials.

    PubMed

    Shi, X; Datta, A K; Mukherjee, Y

    1998-12-01

    Thermal stresses were studied in freezing of biomaterials containing significant amounts of water. An apparent specific heat formulation of the energy equation and a viscoelastic model for the mechanics problem were used to analyze the transient axi-symmetric freezing of a long cylinder. Viscoelastic properties were measured in an Instron machine. Results show that, before phase change occurs at any location, both radial and circumferential stresses are tensile and keep increasing until phase change begins. The maximum principal tensile stress during phase change increases with a decrease in boundary temperature (faster cooling). This is consistent with experimentally observed fractures at a lower boundary temperature. Large volumetric expansion during water to ice transformation was shown to be the primary contributor to large stress development. For very rapid freezing, relaxation may not be significant, and an elastic model may be sufficient. PMID:10412455

  17. Plant protein 2-Cys peroxiredoxin TaBAS1 alleviates oxidative and nitrosative stresses incurred during cryopreservation of mammalian cells.

    PubMed

    Chow-Shi-Yée, Mélanie; Grondin, Mélanie; Averill-Bates, Diana A; Ouellet, François

    2016-07-01

    There is increasing demand for cryopreserved cells such as liver and pancreatic cells for clinical applications. Cryopreservation at ultra-low temperatures requires use of cryoprotectants (e.g., dimethyl sulfoxide (DMSO)) to maintain cell integrity during freezing and thawing processes. Standard cryoprotectants are cytotoxic and more effective cryopreservation technologies are urgently needed for long-term storage of cells. As an alternative, soluble protein extracts (WPE) from winter wheat successfully replaced DMSO as a cryoprotectant for several mammalian cell types. To identify novel cryoactive proteins, the WPE was separated by chromatography and cryoactive fractions were analyzed by mass spectrometry. The wheat protein 2-Cys peroxiredoxin BAS1 (renamed TaBAS1) was identified as a potential cryoactive candidate. Recombinant proteins were prepared and found to possess dual functions as a peroxidase antioxidant and molecular chaperone, and display cryoprotective properties for hepatocytes and insulin-secreting INS832/13 cells. Following cryopreservation with TaBAS1, cells were plateable and showed high post-thaw viability, good adhesion properties, and well-maintained cell-specific metabolic functions. The overall quality of these cell types was equivalent or improved compared to cells that were cryopreserved with DMSO. The antioxidant and chaperone functions of TaBAS1 likely explain its efficacy in reducing oxidative/nitrosative stresses in cryopreserved cells. The plant protein TaBAS1 could be a promising molecule to include in cryostorage protocols. Biotechnol. Bioeng. 2016;113: 1511-1521. © 2015 Wiley Periodicals, Inc. PMID:26724792

  18. Diosmin abrogates chemically induced hepatocarcinogenesis via alleviation of oxidative stress, hyperproliferative and inflammatory markers in murine model.

    PubMed

    Tahir, Mir; Rehman, Muneeb U; Lateef, Abdul; Khan, Abdul Quaiyoom; Khan, Rehan; Qamar, Wajhul; O'Hamiza, Oday; Ali, Farrah; Hasan, Syed Kazim; Sultana, Sarwat

    2013-07-18

    Hepatocellular carcinoma (HCC) is a global health problem and is fourth leading cause of cancer related deaths. Now-a-days new strategies have been accounted for the chemoprevention of liver cancer due to ineffective traditional treatments against HCC. In the present study, we have shown that diosmin attenuates 2-AAF induced hepatic toxicity and early tumor promotion markers (ODC, PCNA and Ki67), its chemopreventive efficacy against DEN initiated and 2-AAF promoted hyper-proliferation and hepatocarcinogenesis in Wistar rats. Hepatocarcinogenesis has been characterized by the presence of apparent hepatic nodules, hepatic proliferation, elevation in the levels of proliferation markers (PCNA and Ki67), and inflammatory markers (COX-2 and iNOS) in DEN and 2-AAF administered rats. Protective efficacy of diosmin has been investigated in terms of its potential in reducing the percentage of visible hepatic nodules and the restoration of early tumor markers (PCNA, Ki67 and ODC), oxidative stress biomarkers, serum cytotoxicity markers (AST, ALT and LDH), cell necrosis markers (NF-kappa B and TNF-α) and inflammatory markers (COX-2 and iNos). Our study demonstrates that the inhibition of cell proliferation and down regulation of inflammatory markers may be, at least in part, the underlying mechanisms related to the liver tumor inhibition by diosmin. The present study allows us to conclude that diosmin being a dietary supplement, could be used as chemopreventive agent to prevent hepatocarcinogenesis. PMID:23665045

  19. Alleviation of salt stress by halotolerant and halophilic plant growth-promoting bacteria in wheat (Triticum aestivum).

    PubMed

    Orhan, Furkan

    2016-01-01

    In the current study, 18 halotolerant and halophilic bacteria have been investigated for their plant growth promoting abilities in vitro and in a hydroponic culture. The bacterial strains have been investigated for ammonia, indole-3-acetic acid and 1-aminocyclopropane-1-carboxylate-deaminase production, phosphate solubilisation and nitrogen fixation activities. Of the tested bacteria, eight were inoculated with Triticum aestivum in a hydroponic culture. The investigated bacterial strains were found to have different plant-growth promoting activities in vitro. Under salt stress (200mM NaCl), the investigated bacterial strains significantly increased the root and shoot length and total fresh weight of the plants. The growth rates of the plants inoculated with bacterial strains ranged from 62.2% to 78.1%. Identifying of novel halophilic and halotolerant bacteria that promote plant growth can be used as alternatives for salt sensitive plants. Extensive research has been conducted on several halophilic and halotolerant bacterial strains to investigate their plant growth promoting activities. However, to the best of my knowledge, this is the first study to inoculate these bacterial strains with wheat. PMID:27133557

  20. Formation of mountains on Io: Variable volcanism and thermal stresses

    NASA Astrophysics Data System (ADS)

    Kirchoff, Michelle R.; McKinnon, William B.

    2009-06-01

    Thermal stresses are potentially important drivers of Io's tectonics and mountain building. It has been hypothesized that sustained local or regional shut down of heat-pipe volcanism on Io could lead to deep crustal heating and large compressive stresses [McKinnon, W.B., Schenk, P.M., Dombard, A.J., 2001. Geology 29, 103-106]. Such large stresses would then be relieved by thrust faulting and uplifting of crustal blocks, producing mountains like those observed on Io. Here we analyze the tectonic consequences of the heat-pipe model in detail, considering both the initial thermal stress state of a basalt or peridotite crust created by heat-pipe volcanism, and relative roles of subsidence stresses (due to burial of preexisting layers) and thermal stresses arising from variable volcanism and changes in crustal (˜lithosphere) thickness. We limit the magnitude of the potential subsidence stresses in our study, because the magnitude of subsidence stresses can be quite large, if not dominant. Results indicate that for a fixed crustal thickness, the region of failure and faulting moves closer to the surface as eruption rate decreases and time increases. When the crust melts at its base as volcanism decreases (as might occur under steady state tidal heating), resulting in crustal thinning, the region of failure is brought even closer to the surface. Naturally, when compressive, subsidence stresses are included, the vertical extent of crust in brittle failure thickens to include most of the lithosphere. In contrast, increases in eruption rate cause the extent of the region in compressional failure to decrease and be driven very deep in the crust (in the absence of sufficient subsidence stress). Therefore, regions of declining volcanism are more likely to produce mountains, whereas regions of extensive or increasing volcanism are less likely to do so. This is consistent with the observation of a global anticorrelation between mountains and volcanic centers on Io. Finally, we

  1. Thermal stress cycling of GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Francis, Robert W.

    1987-01-01

    Thermal stress cycling was performed on gallium arsenide solar cells to investigate their electrical, mechanical, and structural integrity. Cells were cycled under low Earth orbit (LEO) simulated temperature conditions in vacuum. Cell evaluations consisted of power output values, spectral response, optical microscopy and ion microprobe mass analysis, and depth profiles on both front surface inter-grid areas and metallization contact grid lines. Cells were examined for degradation after 500, 5,000, 10,000 and 15,245 thermal cycles. No indication of performance degradation was found for any vendor's cell lot.

  2. Correlation of predicted and measured thermal stresses on an advanced aircraft structure with similar materials

    NASA Technical Reports Server (NTRS)

    Jenkins, J. M.

    1979-01-01

    A laboratory heating test simulating hypersonic heating was conducted on a heat-sink type structure to provide basic thermal stress measurements. Six NASTRAN models utilizing various combinations of bar, shear panel, membrane, and plate elements were used to develop calculated thermal stresses. Thermal stresses were also calculated using a beam model. For a given temperature distribution there was very little variation in NASTRAN calculated thermal stresses when element types were interchanged for a given grid system. Thermal stresses calculated for the beam model compared similarly to the values obtained for the NASTRAN models. Calculated thermal stresses compared generally well to laboratory measured thermal stresses. A discrepancy of signifiance occurred between the measured and predicted thermal stresses in the skin areas. A minor anomaly in the laboratory skin heating uniformity resulted in inadequate temperature input data for the structural models.

  3. Thermal stress analysis of space shuttle orbiter wing skin panel and thermal protection system

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jenkins, Jerald M.

    1987-01-01

    Preflight thermal stress analysis of the space shuttle orbiter wing skin panel and the thermal protection system (TPS) was performed. The heated skin panel analyzed was rectangular in shape and contained a small square cool region at its center. The wing skin immediately outside the cool region was found to be close to the state of elastic instability in the chordwise direction based on the conservative temperature distribution. The wing skin was found to be quite stable in the spanwise direction. The potential wing skin thermal instability was not severe enough to tear apart the strain isolation pad (SIP) layer. Also, the preflight thermal stress analysis was performed on the TPS tile under the most severe temperature gradient during the simulated reentry heating. The tensile thermal stress induced in the TPS tile was found to be much lower than the tensile strength of the TPS material. The thermal bending of the TPS tile was not severe enough to cause tearing of the SIP layer.

  4. Transient winter leaf reddening in Cistus creticus characterizes weak (stress-sensitive) individuals, yet anthocyanins cannot alleviate the adverse effects on photosynthesis

    PubMed Central

    Zeliou, Konstantina; Manetas, Yiannis; Petropoulou, Yiola

    2009-01-01

    Under apparently similar field conditions individual plants of Cistus creticus turn transiently red during winter, while neighbouring plants remain green. These two phenotypes provide a suitable system for comparing basic photosynthetic parameters and assessing critically two hypotheses, i.e. anthocyanins afford photoprotection and anthocyanins induce shade characteristics on otherwise exposed leaves. With that aim, pigment levels and in vivo chlorophyll fluorescence parameters were monitored in dark-acclimated (JIP-test) and light-acclimated (saturation pulse method) leaves during both the green and the red period of the year. No evidence for actual photoprotection by anthocyanins was obtained. On the contrary, all fluorescence parameters related to yields and probabilities of photochemical energy conversion and electron flow, from initial light trapping to final reduction of ultimate electron acceptors in PSI, declined in the red phenotype after leaf reddening. Moreover, the pool sizes of final electron acceptors of PSII diminished, indicating that both photosystems were negatively affected. Vulnerability to winter stress was also indicated by sustained chlorophyll loss, inability to increase the levels of photoprotective xanthophylls and increased quantum yield of non-regulated energy loss during reddening. However, during the same period, the relative PSII antenna size increased, indicating an apparent shade acclimation after anthocyanin accumulation, while changes in the photosynthetic pigment ratios were also compatible to the shade acclimation hypothesis. All parameters recovered to pre-reddening values upon re-greening. It is concluded that the photosynthetic machinery of the red leaf phenotype has an inherently low capacity for winter stress tolerance, which is not alleviated by anthocyanin accumulation. PMID:19420284

  5. Transient winter leaf reddening in Cistus creticus characterizes weak (stress-sensitive) individuals, yet anthocyanins cannot alleviate the adverse effects on photosynthesis.

    PubMed

    Zeliou, Konstantina; Manetas, Yiannis; Petropoulou, Yiola

    2009-01-01

    Under apparently similar field conditions individual plants of Cistus creticus turn transiently red during winter, while neighbouring plants remain green. These two phenotypes provide a suitable system for comparing basic photosynthetic parameters and assessing critically two hypotheses, i.e. anthocyanins afford photoprotection and anthocyanins induce shade characteristics on otherwise exposed leaves. With that aim, pigment levels and in vivo chlorophyll fluorescence parameters were monitored in dark-acclimated (JIP-test) and light-acclimated (saturation pulse method) leaves during both the green and the red period of the year. No evidence for actual photoprotection by anthocyanins was obtained. On the contrary, all fluorescence parameters related to yields and probabilities of photochemical energy conversion and electron flow, from initial light trapping to final reduction of ultimate electron acceptors in PSI, declined in the red phenotype after leaf reddening. Moreover, the pool sizes of final electron acceptors of PSII diminished, indicating that both photosystems were negatively affected. Vulnerability to winter stress was also indicated by sustained chlorophyll loss, inability to increase the levels of photoprotective xanthophylls and increased quantum yield of non-regulated energy loss during reddening. However, during the same period, the relative PSII antenna size increased, indicating an apparent shade acclimation after anthocyanin accumulation, while changes in the photosynthetic pigment ratios were also compatible to the shade acclimation hypothesis. All parameters recovered to pre-reddening values upon re-greening. It is concluded that the photosynthetic machinery of the red leaf phenotype has an inherently low capacity for winter stress tolerance, which is not alleviated by anthocyanin accumulation. PMID:19420284

  6. Using thermal stress to model aspects of disease states.

    PubMed

    Wilson, Thad E; Klabunde, Richard E; Monahan, Kevin D

    2014-07-01

    Exposure to acute heat or cold stress elicits numerous physiological responses aimed at maintaining body temperatures. Interestingly, many of the physiological responses, mediated by the cardiovascular and autonomic nervous systems, resemble aspects of, or responses to, certain disease states. The purpose of this Perspective is to highlight some of these areas in order to explore how they may help us better understand the pathophysiology underlying aspects of certain disease states. The benefits of using this human thermal stress approach are that (1) no adjustments for inherent comparative differences in animals are needed, (2) non-medicated healthy humans with no underlying co-morbidities can be studied in place of complex patients, and (3) more mechanistic perturbations can be safely employed without endangering potentially vulnerable populations. Cold stress can be used to induce stable elevations in blood pressure. Cold stress may also be used to model conditions where increases in myocardial oxygen demand are not met by anticipated increases in coronary blood flow, as occurs in older adults. Lower-body negative pressure has the capacity to model aspects of shock, and the further addition of heat stress improves and expands this model because passive-heat exposure lowers systemic vascular resistance at a time when central blood volume and left-ventricular filling pressure are reduced. Heat stress can model aspects of heat syncope and orthostatic intolerance as heat stress decreases cerebral blood flow and alters the Frank-Starling mechanism resulting in larger decreases in stroke volume for a given change in left-ventricular filling pressure. Combined, thermal perturbations may provide in vivo paradigms that can be employed to gain insights into pathophysiological aspects of certain disease states. PMID:24956954

  7. Alleviation of Photoinhibition by Co-ordination of Chlororespiration and Cyclic Electron Flow Mediated by NDH under Heat Stressed Condition in Tobacco

    PubMed Central

    Li, Qinghua; Yao, Zheng-Ju; Mi, Hualing

    2016-01-01

    much more in the mutant. The results suggest that chlororespiration and cyclic electron flow mediated by NDH may coordinate to alleviate the over-reduction of stroma, thus to keep operation of CO2 assimilation at certain extent under heat stress condition. PMID:27066014

  8. Alleviation of Photoinhibition by Co-ordination of Chlororespiration and Cyclic Electron Flow Mediated by NDH under Heat Stressed Condition in Tobacco.

    PubMed

    Li, Qinghua; Yao, Zheng-Ju; Mi, Hualing

    2016-01-01

    decreased much more in the mutant. The results suggest that chlororespiration and cyclic electron flow mediated by NDH may coordinate to alleviate the over-reduction of stroma, thus to keep operation of CO2 assimilation at certain extent under heat stress condition. PMID:27066014

  9. Effect of element density on the NASTRAN calculated mechanical and thermal stresses of a spar

    NASA Technical Reports Server (NTRS)

    Jenkins, J. M.

    1979-01-01

    A NASTRAN model of a spar was examined to determine the sensitivity of calculated axial thermal stresses and bending stresses to changes in element density of the model. The thermal stresses calculated with three different element densities resulted in drastically differing values. The position of the constraint also significantly affected the value of the calculated thermal stresses. Mechanical stresses calculated from an applied loading were insensitive to element density.

  10. Reduction of thermal stresses in continuous fiber reinforced metal matrix composites with interface layers

    NASA Technical Reports Server (NTRS)

    Jansson, S.; Leckie, F. A.

    1992-01-01

    The potential of using interface layer to reduce thermal stresses in the matrix of composites with a mismatch in coefficients of thermal expansion of fiber and matrix has been investigated. It was found that compliant layers, with properties of readily available materials, do not have the potential to reduce thermal stresses significantly. However, interface layers with high coefficient of thermal expansion can compensate for the mismatch and reduce thermal stresses in the matrix significantly.

  11. Reduction of thermal stresses in continuous fiber reinforced metal matrix composites with interface layers

    NASA Technical Reports Server (NTRS)

    Jansson, S.; Leckie, F. A.

    1990-01-01

    The potential of using an interface layer to reduce thermal stresses in the matrix of composites with a mismatch in coefficients of thermal expansion of fiber and matrix was investigated. It was found that compliant layers, with properties of readily available materials, do not have the potential to reduce thermal stresses significantly. However, interface layers with high coefficient of thermal expansion can compensate for the mismatch and reduce thermal stresses in the matrix significantly.

  12. Thermal isostasy, elevation of continental North America and intraplate stresses

    NASA Astrophysics Data System (ADS)

    Mareschal, J.; Perry, C.

    2009-12-01

    We determine variations in gravitational potential energy (GPE) in North America due to internal loads associated with lithospheric density anomalies. To constrain GPE estimates within the continental interior, we calculate the predicted elevation of North America assuming local isostatic equilibrium due to crustal density variations and thermal isostasy. The contribution of internal loads to intraplate stresses are determined and compared to other tectonic stresses. Internal horizontal stresses are calculated from the gradient of the GPE, and follow variations in topography. Transient thermal models are developed for the tectonically active zones of the Basin&Range Province, the Colorado Plateau and Canadian Cordillera, and the validity of these models is tested through comparison of the observed and predicted topography and gravity in each region. Standard steady-state thermal models are used for non-active regions. We do not calculate here the dynamic component of observed surface topography, however the misfit between the predicted and observed surface topography is largely associated with the dynamic mantle signal. The RMS difference in observed and predicted topography over all North America is found to be ~250 m which is close to the average North American dynamic component of topography inferred from seismic-geodynamic inversion techniques.

  13. Coefficient of thermal expansion dependent thermal stress analysis of thermal barrier coatings (TBCs) using finite element model

    NASA Astrophysics Data System (ADS)

    Coker, Omotola

    Thermal barrier coatings (TBCs) are highly sophisticated micro scale ceramic insulation applied on high temperature components such as gas turbine blades. TBCs create a large temperature drop between the gas turbine environment and the underlying metal blades. TBC lifetime is finite and influenced by several factors such as: Bond Coat (BC) oxidation, BC roughness, Coefficient of thermal expansion (CTE) mismatch between the layers, and creep properties of the TBC system. However, there is a lack of reliable methods of TBC life prediction which result in under utilization of these coatings. This research study focuses on modeling the steady state thermal stresses in TBC systems of various oxide thicknesses, and BC roughness, using Finite Element Analysis (FEA). The model factors into it the temperature dependent thermo mechanical properties of each layer, as well as the creep properties. The steady state model results show similar results to the existing transient models: an increase in tensile stresses as the oxide thickness increases, an increase in tensile stresses with BC roughness and stress relaxation in the ceramic BC interface due to creep. It also shows in each model, initially compressive stresses in the BC - Top Coat (TC) interface, and its evolution into higher tensile stresses which lead to crack formation and ultimately failure of the TBC by spallation.

  14. Modeling Oxidation Induced Stresses in Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Ferguson, B. L.; Freborg, A. M.; Petrus, G. J.; Brindley, William J.

    1998-01-01

    The use of thermal barrier coatings (TBC's) in gas turbines has increased dramatically in recent years, due mainly to the need for component protection from ever increasing service temperatures. Oxidation of the bond coat has been identified as an important contributing factor to spallation of the ceramic top coat during service. Additional variables found to influence TBC thermal cycle life include bond coat coefficient of thermal expansion, creep behavior of both the ceramic and bond coat layers, and modulus of elasticity. The purpose of this work was to characterize the effects of oxidation on the stress states within the TBC system, as well as to examine the interaction of oxidation with other factors affecting TBC life.

  15. Thermally induced stresses and deformations in layered composite tubes

    NASA Technical Reports Server (NTRS)

    Cooper, D. E.; Cohen, D.; Rousseau, C. Q.; Hyer, M. W.; Tompkins, S. S.

    1985-01-01

    The thermally induced stresses and deformations in layered, orthotropic tubes are studied. The motivation for studying tubes is their likely application for use in space structures. Tubes are a strong candidate for this application because of their high structural efficiency, as measured by stiffness per unit weight, and their relative ease of fabrication. Also, tubes have no free edges to deteriorate or delaminate. An anticipated thermal condition for tubes in space is a circumferential temperature gradient. This type of gradient will introduce dimensional changes into the structure and may cause stresses large enough to cause damage to the material. There are potentially large differences in temperatures at different circumferential locations on the tube. Because of this, the effects of temperature dependent material properties on the stresses and deformations may be important. The study is composed of three parts: experiments to determine the functional form of the circumferential gradient and to measure tube deflections; an elasticity solution to compute the stresses and deformations; and an approximate approach to determine the effects of temperature dependent material properties.

  16. Analytical Model for Thermal Elastoplastic Stresses of Functionally Graded Materials

    SciTech Connect

    Zhai, P. C.; Chen, G.; Liu, L. S.; Fang, C.; Zhang, Q. J.

    2008-02-15

    A modification analytical model is presented for the thermal elastoplastic stresses of functionally graded materials subjected to thermal loading. The presented model follows the analytical scheme presented by Y. L. Shen and S. Suresh [6]. In the present model, the functionally graded materials are considered as multilayered materials. Each layer consists of metal and ceramic with different volume fraction. The ceramic layer and the FGM interlayers are considered as elastic brittle materials. The metal layer is considered as elastic-perfectly plastic ductile materials. Closed-form solutions for different characteristic temperature for thermal loading are presented as a function of the structure geometries and the thermomechanical properties of the materials. A main advance of the present model is that the possibility of the initial and spread of plasticity from the two sides of the ductile layers taken into account. Comparing the analytical results with the results from the finite element analysis, the thermal stresses and deformation from the present model are in good agreement with the numerical ones.

  17. INFLUENCE OF THERMAL STRESS ON MARGINAL INTEGRITY OF RESTORATIVE MATERIALS

    PubMed Central

    Cenci, Maximiliano Sérgio; Pereira-Cenci, Tatiana; Donassollo, Tiago Aurélio; Sommer, Leandro; Strapasson, André; Demarco, Flávio Fernando

    2008-01-01

    The aim of this study was to evaluate the influence of thermal stress on the marginal integrity of restorative materials with different adhesive and thermal properties. Three hundred and sixty Class V cavities were prepared in buccal and lingual surfaces of 180 bovine incisors. Cervical and incisal walls were located in dentin and enamel, respectively. Specimens were restored with resin composite (RC); glass ionomer (GI) or amalgam (AM), and randomly assigned to 18 groups (n=20) according to the material, number of cycles (500 or 1,000 cycles) and dwell time (30 s or 60 s). Dry and wet specimens served as controls Specimens were immersed in 1% basic fuchsine solution (24 h), sectioned, and microleakage was evaluated under x40 magnification. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests: Thermal cycling regimens increased leakage in all AM restorations (p<0.05) and its effect on RC and GI restorations was only significant when a 60-s dwell time was used (p<0.05). Marginal integrity was more affected in AM restorations under thermal cycling stress, whereas RC and GI ionomer restoration margins were only significantly affected only under longer dwell times. PMID:19089200

  18. Investigation of Thermal Stress Convection in Nonisothermal Gases Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Mackowski, Daniel W.; Knight, Roy W.

    1996-01-01

    Microgravity conditions offer an environment in which convection in a nonisothermal gas could be driven primarily by thermal stress. A direct examination of thermal stress flows would be invaluable in assessing the accuracy of the Burnett terms in the fluid stress tensor. We present a preliminary numerical investigation of the competing effects of thermal stress, thermal creep at the side walls, and buoyancy on gas convection in nonuniformly heated containers under normal and reduced gravity levels. Conditions in which thermal stress convection becomes dominant are identified, and issues regarding the experimental measurement of the flows are discussed.

  19. Surface Residual Stresses in Ti-6Al-4V Friction Stir Welds: Pre- and Post-Thermal Stress Relief

    NASA Astrophysics Data System (ADS)

    Edwards, P.; Ramulu, M.

    2015-09-01

    The purpose of this study was to determine the residual stresses present in titanium friction stir welds and if a post-weld thermal stress relief cycle would be effective in minimizing those weld-induced residual stresses. Surface residual stresses in titanium 6Al-4V alloy friction stir welds were measured in butt joint thicknesses ranging from 3 to 12 mm. The residual stress states were also evaluated after the welds were subjected to a post-weld thermal stress relief cycle of 760 °C for 45 min. High (300-400 MPa) tensile residual stresses were observed in the longitudinal direction prior to stress relief and compressive residual stresses were measured in the transverse direction. After stress relief, the residual stresses were decreased by an order of magnitude to negligible levels.

  20. Treatment with bone marrow mesenchymal stem cells combined with plumbagin alleviates spinal cord injury by affecting oxidative stress, inflammation, apoptotis and the activation of the Nrf2 pathway.

    PubMed

    Yang, Wencheng; Yang, Yan; Yang, Jian-Yi; Liang, Ming; Song, Jiangtao

    2016-04-01

    The aim of the present study was to investigate the protective effect exerted by bone marrow mesenchymal stem cells (BMSCs) in combination with plumbagin on spinal cord injury (SCI) and explore the mechanism behind this protective effect. Firstly, BMSCs were extracted from male Sprague-Dawley rats, cultured in vitro, and identified by hematoxylin. Sprague-Dawley rats were then randomly divided into a control group, SCI model group, BMSC-treated group, a plumbagin-treated group, and a BMSC and plumbagin-treated group. After treatment with BMSCs combined with plumbagin, a Basso, Beattie and Bresnahan (BBB) test was carried out and the spinal cord water content was examined in order to analyze the effect of BMSCs combined with plumbagin on SCI. The myeloperoxidase (MPO), superoxide dismutase (SOD), malondialdehyde (MDA), nuclear factor-κB (NF-κB) p65 unit, tumor necrosis factor-α (TNF-α) levels were also detected. Moreover, nuclear factor erythroid 2‑related factor 2 (Nrf2), phosphoinositide 3-kinase (PI3K), phosphorylated (p-)Akt, p-p38 mitogen-activated protein kinase (MAPK), and p-extracellular-signal-regulated kinase (ERK) protein expression levels were measured using western blot analysis. Treatment with BMSCs combined with plumbagin significantly improved locomotor recovery and reduced the spinal cord water content after SCI. The increased MPO, MDA, NF-κB p65 and TNF-α levels were significantly suppressed and the decreased SOD was significantly increased in SCI rats. The suppression of Nrf2, p-Akt and p-ERK, as well as the promotion of p-p38 MAPK, were reversed by treatment with BMSCs combined with plumbagin. These effects suggest that treatment with BMSCs combined with plumbagin alleviates SCI through its effects on oxidative stress, inflammation, apoptotis and activation of the Nrf2 pathway. PMID:26936518

  1. Long Chain Omega-3 Polyunsaturated Fatty Acid Supplementation Alleviates Doxorubicin-Induced Depressive-Like Behaviors and Neurotoxicity in Rats: Involvement of Oxidative Stress and Neuroinflammation

    PubMed Central

    Wu, Yan-Qin; Dang, Rui-Li; Tang, Mi-Mi; Cai, Hua-Lin; Li, Huan-De; Liao, De-Hua; He, Xin; Cao, Ling-Juan; Xue, Ying; Jiang, Pei

    2016-01-01

    Doxorubicin (DOX) is a chemotherapeutic agent widely used in human malignancies. Its long-term use can cause neurobiological side-effects associated with depression. Omega-3 polyunsaturated fatty acids (ω-3 PUFAs), the essential fatty acids found in fish oil, possess neuroprotecitve and antidepressant activities. Thus, the aim of this study was to explore the potential protective effects of ω-3 PUFAs against DOX-induced behavioral changes and neurotoxicity. ω-3 PUFAs were given daily by gavage (1.5 g/kg) over three weeks starting seven days before DOX administration (2.5 mg/kg). Open-field test (OFT) and forced swimming test (FST) were conducted to assess exploratory activity and despair behavior, respectively. Our data showed that ω-3 PUFAs supplementation significantly mitigated the behavioral changes induced by DOX. ω-3 PUFAs pretreatment also alleviated the DOX-induced neural apoptosis. Meanwhile, ω-3 PUFAs treatment ameliorated DOX-induced oxidative stress in the prefrontal cortex and hippocampus. Additionally, gene expression of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α, and the protein levels of NF-κB and iNOS were significantly increased in brain tissues of DOX-treated group, whereas ω-3 PUFAs supplementation significantly attenuated DOX-induced neuroinflammation. In conclusion, ω-3 PUFAs can effectively protect against DOX-induced depressive-like behaviors, and the mechanisms underlying the neuroprotective effect are potentially associated with its anti-oxidant, anti-inflammatory, and anti-apoptotic properties. PMID:27120616

  2. Genome Analysis of Pseudomonas fluorescens PCL1751: A Rhizobacterium that Controls Root Diseases and Alleviates Salt Stress for Its Plant Host

    PubMed Central

    Cho, Shu-Ting; Chang, Hsing-Hua; Egamberdieva, Dilfuza; Kamilova, Faina; Lugtenberg, Ben; Kuo, Chih-Horng

    2015-01-01

    Pseudomonas fluorescens PCL1751 is a rod-shaped Gram-negative bacterium isolated from the rhizosphere of a greenhouse-grown tomato plant in Uzbekistan. It controls several plant root diseases caused by Fusarium fungi through the mechanism of competition for nutrients and niches (CNN). This mechanism does not rely on the production of antibiotics, so it avoids the concerns of resistance development and is environmentally safe. Additionally, this bacterium promotes plant growth by alleviating salt stress for its plant host. To investigate the genetic mechanisms that may explain these observations, we determined the complete genome sequence of this bacterium, examined its gene content, and performed comparative genomics analysis with other Pseudomonas strains. The genome of P. fluorescens PCL1751 consisted of one circular chromosome that is 6,143,950 base-pairs (bp) in size; no plasmid was found. The annotation included 19 rRNA, 70 tRNA, and 5,534 protein-coding genes. The gene content analysis identified a large number of genes involved in chemotaxis and motility, colonization of the rhizosphere, siderophore biosynthesis, and osmoprotectant production. In contrast, the pathways involved in the biosynthesis of phytohormones or antibiotics were not found. Comparison with other Pseudomonas genomes revealed extensive variations in their genome size and gene content. The presence and absence of secretion system genes were highly variable. As expected, the synteny conservation among strains decreased as a function of phylogenetic divergence. The integration of prophages appeared to be an important driver for genome rearrangements. The whole-genome gene content analysis of this plant growth-promoting rhizobacterium (PGPR) provided some genetic explanations to its phenotypic characteristics. The extensive and versatile substrate utilization pathways, together with the presence of many genes involved in competitive root colonization, provided further support for the finding

  3. Genome Analysis of Pseudomonas fluorescens PCL1751: A Rhizobacterium that Controls Root Diseases and Alleviates Salt Stress for Its Plant Host.

    PubMed

    Cho, Shu-Ting; Chang, Hsing-Hua; Egamberdieva, Dilfuza; Kamilova, Faina; Lugtenberg, Ben; Kuo, Chih-Horng

    2015-01-01

    Pseudomonas fluorescens PCL1751 is a rod-shaped Gram-negative bacterium isolated from the rhizosphere of a greenhouse-grown tomato plant in Uzbekistan. It controls several plant root diseases caused by Fusarium fungi through the mechanism of competition for nutrients and niches (CNN). This mechanism does not rely on the production of antibiotics, so it avoids the concerns of resistance development and is environmentally safe. Additionally, this bacterium promotes plant growth by alleviating salt stress for its plant host. To investigate the genetic mechanisms that may explain these observations, we determined the complete genome sequence of this bacterium, examined its gene content, and performed comparative genomics analysis with other Pseudomonas strains. The genome of P. fluorescens PCL1751 consisted of one circular chromosome that is 6,143,950 base-pairs (bp) in size; no plasmid was found. The annotation included 19 rRNA, 70 tRNA, and 5,534 protein-coding genes. The gene content analysis identified a large number of genes involved in chemotaxis and motility, colonization of the rhizosphere, siderophore biosynthesis, and osmoprotectant production. In contrast, the pathways involved in the biosynthesis of phytohormones or antibiotics were not found. Comparison with other Pseudomonas genomes revealed extensive variations in their genome size and gene content. The presence and absence of secretion system genes were highly variable. As expected, the synteny conservation among strains decreased as a function of phylogenetic divergence. The integration of prophages appeared to be an important driver for genome rearrangements. The whole-genome gene content analysis of this plant growth-promoting rhizobacterium (PGPR) provided some genetic explanations to its phenotypic characteristics. The extensive and versatile substrate utilization pathways, together with the presence of many genes involved in competitive root colonization, provided further support for the finding

  4. Thermal imaging to detect physiological indicators of stress in humans

    NASA Astrophysics Data System (ADS)

    Cross, Carl B.; Skipper, Julie A.; Petkie, Douglas T.

    2013-05-01

    Real-time, stand-off sensing of human subjects to detect emotional state would be valuable in many defense, security and medical scenarios. We are developing a multimodal sensor platform that incorporates high-resolution electro-optical and mid-wave infrared (MWIR) cameras and a millimeter-wave radar system to identify individuals who are psychologically stressed. Recent experiments have aimed to: 1) assess responses to physical versus psychological stressors; 2) examine the impact of topical skin products on thermal signatures; and 3) evaluate the fidelity of vital signs extracted from thermal imagery and radar signatures. Registered image and sensor data were collected as subjects (n=32) performed mental and physical tasks. In each image, the face was segmented into 29 non-overlapping segments based on fiducial points automatically output by our facial feature tracker. Image features were defined that facilitated discrimination between psychological and physical stress states. To test the ability to intentionally mask thermal responses indicative of anxiety or fear, subjects applied one of four topical skin products to one half of their face before performing tasks. Finally, we evaluated the performance of two non-contact techniques to detect respiration and heart rate: chest displacement extracted from the radar signal and temperature fluctuations at the nose tip and regions near superficial arteries to detect respiration and heart rates, respectively, extracted from the MWIR imagery. Our results are very satisfactory: classification of physical versus psychological stressors is repeatedly greater than 90%, thermal masking was almost always ineffective, and accurate heart and respiration rates are detectable in both thermal and radar signatures.

  5. YoeB toxin is activated during thermal stress.

    PubMed

    Janssen, Brian D; Garza-Sánchez, Fernando; Hayes, Christopher S

    2015-08-01

    Type II toxin-antitoxin (TA) modules are thought to mediate stress-responses by temporarily suppressing protein synthesis while cells redirect transcription to adapt to environmental change. Here, we show that YoeB, a ribosome-dependent mRNase toxin, is activated in Escherichia coli cells grown at elevated temperatures. YoeB activation is dependent on Lon protease, suggesting that thermal stress promotes increased degradation of the YefM antitoxin. Though YefM is efficiently degraded in response to Lon overproduction, we find that Lon antigen levels do not increase during heat shock, indicating that another mechanism accounts for temperature-induced YefM proteolysis. These observations suggest that YefM/YoeB functions in adaptation to temperature stress. However, this response is distinct from previously described models of TA function. First, YoeB mRNase activity is maintained over several hours of culture at 42°C, indicating that thermal activation is not transient. Moreover, heat-activated YoeB does not induce growth arrest nor does it suppress global protein synthesis. In fact, E. coli cells proliferate more rapidly at elevated temperatures and instantaneously accelerate their growth rate in response to acute heat shock. We propose that heat-activated YoeB may serve a quality control function, facilitating the recycling of stalled translation complexes through ribosome rescue pathways. PMID:26147890

  6. Sympathetic regulation during thermal stress in human aging and disease.

    PubMed

    Greaney, Jody L; Kenney, W Larry; Alexander, Lacy M

    2016-04-01

    Humans control their core temperature within a narrow range via precise adjustments of the autonomic nervous system. In response to changing core and/or skin temperature, several critical thermoregulatory reflex effector responses are initiated and include shivering, sweating, and changes in cutaneous blood flow. Cutaneous vasomotor adjustments, mediated by modulations in sympathetic nerve activity (SNA), aid in the maintenance of thermal homeostasis during cold and heat stress since (1) they serve as the first line of defense of body temperature and are initiated before other thermoregulatory effectors, and (2) they are on the efferent arm of non-thermoregulatory reflex systems, aiding in the maintenance of blood pressure and organ perfusion. This review article highlights the sympathetic responses of humans to thermal stress, with a specific focus on primary aging as well as impairments that occur in both heart disease and type 2 diabetes mellitus. Age- and pathology-related changes in efferent muscle and skin SNA during cold and heat stress, measured directly in humans using microneurography, are discussed. PMID:26627337

  7. YoeB toxin is activated during thermal stress

    PubMed Central

    Janssen, Brian D; Garza-Sánchez, Fernando; Hayes, Christopher S

    2015-01-01

    Type II toxin-antitoxin (TA) modules are thought to mediate stress-responses by temporarily suppressing protein synthesis while cells redirect transcription to adapt to environmental change. Here, we show that YoeB, a ribosome-dependent mRNase toxin, is activated in Escherichia coli cells grown at elevated temperatures. YoeB activation is dependent on Lon protease, suggesting that thermal stress promotes increased degradation of the YefM antitoxin. Though YefM is efficiently degraded in response to Lon overproduction, we find that Lon antigen levels do not increase during heat shock, indicating that another mechanism accounts for temperature-induced YefM proteolysis. These observations suggest that YefM/YoeB functions in adaptation to temperature stress. However, this response is distinct from previously described models of TA function. First, YoeB mRNase activity is maintained over several hours of culture at 42°C, indicating that thermal activation is not transient. Moreover, heat-activated YoeB does not induce growth arrest nor does it suppress global protein synthesis. In fact, E. coli cells proliferate more rapidly at elevated temperatures and instantaneously accelerate their growth rate in response to acute heat shock. We propose that heat-activated YoeB may serve a quality control function, facilitating the recycling of stalled translation complexes through ribosome rescue pathways. PMID:26147890

  8. Methodology for assessment of amount and amplitude of thermal stress cycles in masonry

    NASA Astrophysics Data System (ADS)

    Beran, Pavel

    2016-06-01

    Analysis of amount and amplitude of thermal stress cycles in historic masonry has been made by means of combination of three 2-D numerical models of heterogeneous ashlar masonry. The numerical models were used to simulate thermal stress cycles during June, July and August in reference climatic year valid for Prague Castle, Czech Republic. For evaluation of amplitude and amount of the thermal stress cycles the effective stress in selected point in masonry was used. Afterwards rainflow method was used to count the amplitude and amount of the stress cycles. The results show that during summer quite a lot of significant thermal stress cycles originate in masonry, especially during sunny hot days. The results presented in this paper confirm the significant fatigue character of the thermal stress cycles and the method presented here could be suitable to evaluate thermal stress in building materials and structures.

  9. Exogenous IAA differentially affects growth, oxidative stress and antioxidants system in Cd stressed Trigonella foenum-graecum L. seedlings: Toxicity alleviation by up-regulation of ascorbate-glutathione cycle.

    PubMed

    Bashri, Gausiya; Prasad, Sheo Mohan

    2016-10-01

    In the present study, effect of exogenous indole-3-acetic acid at their different levels (i.e. low; IAAL, 10µM and high; IAAH, 100µM) were studied on growth, oxidative stress biomarkers and antioxidant enzymes (SOD, POD, CAT and GST), and metabolites (AsA and GSH) as well as enzymes (APX, GR and DHAR) of ascorbate-glutathione cycle in Trigonella foenum-graecum L. seedlings grown under cadmium (Cd1, 3mgCd kg(-1) soil and Cd2, 9mgCd kg(-1) soil) stress. Cadmium (Cd) at both doses caused reduction in growth which was correlated with enhanced lipid peroxidation and damage to membrane as a result of excess accumulation of O2(•-) and H2O2. Cd also enhanced the oxidation of AsA and GSH to DHA and GSSG, respectively which give a clear sign of oxidative stress, despite of accelerated activity of enzymatic antioxidants: SOD, CAT, POD, GST as well as APX, DHAR (except in Cd2 stress) and GR. Exogenous application of IAAL resulted further rise in the activities of these enzymes, and maintained the redox status (> ratios: AsA/DHA and GSH/GSSG) of cells. The maintained redox status of cells under IAAL treatment declined the level of ROS in Cd1 and Cd2 treated seedlings thereby alleviated the Cd toxicity and this effect was more pronounced under Cd1 stress. Contrary to this, exogenous IAAH suppressed the activity of DHAR and GR and disturbed the redox status (< ratios: AsA/DHA and GSH/GSSG) of cells, hence excess accumulation of ROS further aggravated the Cd induced damage. Thus, overall results suggest that IAA at low (IAAL) and high (IAAH) doses affected the Cd toxicity differently by regulating the ascorbate-glutathione cycle as well as activity of other antioxidants in Trigonella seedlings. PMID:27344401

  10. Effects of Dietary Arginine and Glutamine on Alleviating the Impairment Induced by Deoxynivalenol Stress and Immune Relevant Cytokines in Growing Pigs

    PubMed Central

    Zhou, Ting; Yin, Jie; Li, Tiejun; Yang, Lin; He, Liuqin; Yang, Xiaojian; Zhang, Hongfu; Wang, Qi; Huang, Ruilin; Yin, Yulong

    2013-01-01

    glutamine on alleviating the impairment induced by DON stress and immune relevant cytokines in growing pigs. PMID:23922725

  11. PARP INHIBITION ALLEVIATES DIABETES-INDUCED SYSTEMIC OXIDATIVE STRESS AND NEURAL TISSUE 4-HYDROXYNONENAL ADDUCT ACCUMULATION: CORRELATION WITH PERIPHERAL NERVE FUNCTION

    PubMed Central

    Lupachyk, Sergey; Shevalye, Hanna; Maksimchyk, Yury; Drel, Viktor R.; Obrosova, Irina G.

    2011-01-01

    This study evaluated the role of poly(ADP-ribose) polymerase in systemic oxidative stress and 4-hydoxynonenal adduct accumulation in diabetic peripheral neuropathy. Control and streptozotocin-diabetic rats were maintained with or without treatment with the PARP inhibitor, 1,5-isoquinolinediol, 3 mg kg−1d−1, for 10 weeks after initial 2 weeks. Treatment efficacy was evaluated by poly(ADP-ribosyl)ated protein content in peripheral nerve and spinal cord (Western blot analysis) and dorsal root ganglion neurons and non-neuronal cells (fluorescent immunohistochemistry), as well as by indices of peripheral nerve function. Diabetic rats displayed increased urinary isoprostane and 8-hydroxy-2'-deoxyguanosine excretion (ELISA), 4-hydroxynonenal adduct accumulation in endothelial and Schwann cells of the peripheral nerve, neurons, astrocytes, and oligodendrocytes of the spinal cord, and neurons and glial cells of the dorsal root ganglia (double-label fluorescent immunohistochemistry) as well as motor and sensory nerve conduction velocity deficits, thermal hypoalgesia, and tactile allodynia. PARP inhibition counteracted diabetes-induced systemic oxidative stress and 4-hydroxynonenal adduct accumulation in peripheral nerve and spinal cord (Western blot analysis) and dorsal root ganglion neurons (perikarya, fluorescent immunohistochemistry) which correlated with improvement of large and small nerve fiber function. The findings reveal the important role of PARP activation in systemic oxidative stress and 4-hydroxynonenal adduct accumulation in diabetic peripheral neuropathy. PMID:21300148

  12. Deposition stress effects on thermal barrier coating burner rig life

    NASA Technical Reports Server (NTRS)

    Watson, J. W.; Levine, S. R.

    1984-01-01

    A study of the effect of plasma spray processing parameters on the life of a two layer thermal barrier coating was conducted. The ceramic layer was plasma sprayed at plasma arc currents of 900 and 600 amps onto uncooled tubes, cooled tubes, and solid bars of Waspalloy in a lathe with 1 or 8 passes of the plasma gun. These processing changes affected the residual stress state of the coating. When the specimens were tested in a Mach 0.3 cyclic burner rig at 1130 deg C, a wide range of coating lives resulted. Processing factors which reduced the residual stress state in the coating, such as reduced plasma temperature and increased heat dissipation, significantly increased coating life.

  13. Crack Growth in First Wall by Cyclic Thermal Stress

    SciTech Connect

    Nishimura, T.; Hatano, T.; Honda, T.; Saito, M.

    2003-07-15

    The long pulse operation is assumed in ITER and future reactors. If the first wall has a defect, the crack may be propagated by cyclic thermal loads. In addition, flattop of more than 300 sec during plasma burning is expected, therefore, an effect of transient creep must be included. In order to simulate a severe temperature gradient in the first wall, an experimental facility was designed using an electron beam (EB) as a heat source, which has a distinct feature that the various plasma burning scenarios can be simulated by controlling the beam power so as to make surface temperature of the specimen to be fixed. To clarify the crack growth mechanism and the effects of transient creep, elastic-plastic stress analysis and creep analysis were performed. It is concluded that the creep effect during the operation duration period enlarges the residual tensile stress in the cooling period, and that consequently the crack propagation length increases.

  14. Crop water-stress assessment using an airborne thermal scanner

    NASA Technical Reports Server (NTRS)

    Millard, J. P.; Jackson, R. D.; Reginato, R. J.; Idso, S. B.; Goettelman, R. C.

    1978-01-01

    An airborne thermal scanner was used to measure the temperature of a wheat crop canopy in Phoenix, Arizona. The results indicate that canopy temperatures acquired about an hour and a half past solar noon were well correlated with presunrise plant water tension, a parameter directly related to plant growth and development. Pseudo-colored thermal images reading directly in stress degree days, a unit indicative of crop irrigation needs and yield potential, were produced. The aircraft data showed significant within-field canopy temperature variability, indicating the superiority of the synoptic view provided by aircraft over localized ground measurements. The standard deviation between airborne and ground-acquired canopy temperatures was 2 C or less.

  15. Bond strength and stress measurements in thermal barrier coatings

    SciTech Connect

    Gell, M.; Jordan, E.

    1995-10-01

    Thermal barrier coatings have been used extensively in aircraft gas turbines for more than 15 years to insulate combustors and turbine vanes from the hot gas stream. Plasma sprayed thermal barrier coatings (TBCs) provide metal temperature reductions as much as 300{degrees}F, with improvements in durability of two times or more being achieved. The introduction of TBCs deposited by electron beam physical vapor deposition (EB-PVD) processes in the last five years has provided a major improvement in durability and also enabled TBCs to be applied to turbine blades for improved engine performance. To meet the aggressive Advanced Turbine Systems goals for efficiency, durability and the environment, it will be necessary to employ thermal barrier coatings on turbine airfoils and other hot section components. For The successful application of TBCs to ATS engines with 2600{degrees}F turbine inlet temperatures and required component lives 10 times greater than those for aircraft gas turbine engines, it is necessary to develop quantitative assessment techniques for TBC coating integrity with time and cycles in ATS engines. Thermal barrier coatings in production today consist of a metallic bond coat, such as an MCrAlY overlay coating or a platinum aluminide (Pt-Al) diffusion coating. During heat treatment, both these coatings form a thin, tightly adherent alumina (Al{sub 2}O{sub 3}) film. Failure of TBC coatings in engine service occurs by spallation of the ceramic coating at or near the bond coat to alumina or the alumina to zirconia bonds. Thus, it is the initial strength of these bonds and the stresses at the bond plane, and their changes with engine exposure, that determines coating durability. The purpose of this program is to provide, for the first time, a quantitative assessment of TBC bond strength and bond plane stresses as a function of engine time and cycles.

  16. The effect of thermal stresses on the integrity of three built-up aircraft structures

    NASA Technical Reports Server (NTRS)

    Jenkins, J. M.

    1980-01-01

    A Mach 6 flight was simulated in order to examine heating effects on three frame/skin specimens. The specimens included: a titanium truss frame with a lockalloy skin; a stainless steel z-frame with a lockalloy skin; and a titanium z-frame with a lockalloy skin. Thermal stresses and temperature were measured on these specimens for the purpose of examining their efficiency, performance, and integrity. Measured thermal stresses were examined with respect to material yield strengths, buckling criteria, structural weight, and geometric locations. Principal thermal stresses were studied from the standpoint of uniaxial stress assumptions. Measured thermal stresses were compared to predicted values.

  17. Fluid shifts during thermal stress with and without fluid replacement

    NASA Technical Reports Server (NTRS)

    Myhre, L. G.; Robinson, S.

    1977-01-01

    Six unacclimatized men rested for 4 hr in a hot, dry environment without fluid replacement (DH). Another group of six men were exposed to the same thermal stress, replacing evaporative fluid loss with warm 0.1% NaCl solution (FRP). Total grams of circulating hemoglobin, determined by CO immediately prior to and again during the last minutes of heat exposure, increased an insignificant 1.6 and 1.3% during DH and FRP, respectively. With DH, body weight loss of 2.6% was accompanied by a 7.8% reduction in calculated plasma volume (PV). Even when body weight was maintained (FRP), PV decreased 2.9% during the heat exposure. Total circulating serum protein did not change as a result of the heat stress with either DH or FRP. In a test-retest series of experiments on four men, DH was not detrimental to sweat rate. It is shown that hemodilution is not a general response to acute heat exposure. The disproportionately large reduction in PV during thermal dehydration is confirmed.

  18. Graphite having improved thermal stress resistance and method of preparation

    DOEpatents

    Kennedy, Charles R.

    1980-01-01

    An improved method for fabricating a graphite article comprises the steps of impregnating a coke article by first heating the coke article in contact with a thermoplastic pitch at a temperature within the range of 250.degree.-300.degree. C. at a pressure within the range of 200-2000 psig for at least 4-10 hours and then heating said article at a temperature within the range of 450.degree.-485.degree. C. at a pressure of 200-2000 psig for about 16-24 hours to provide an impregnated article; heating the impregnated article for sufficient time to carbonize the impregnant to provide a second coke article, and graphitizing the second coke article. A graphite having improved thermal stress resistance results when the coke to be impregnated contains 1-3 wt.% sulfur and no added puffing inhibitors. An additional improvement in thermal stress resistance is achieved when the second coke article is heated above about 1400.degree. C. at a rate of at least 10.degree. C./minute to a temperature above the puffing temperature.

  19. Prognostics Approach for Power MOSFET Under Thermal-Stress

    NASA Technical Reports Server (NTRS)

    Galvan, Jose Ramon Celaya; Saxena, Abhinav; Kulkarni, Chetan S.; Saha, Sankalita; Goebel, Kai

    2012-01-01

    The prognostic technique for a power MOSFET presented in this paper is based on accelerated aging of MOSFET IRF520Npbf in a TO-220 package. The methodology utilizes thermal and power cycling to accelerate the life of the devices. The major failure mechanism for the stress conditions is dieattachment degradation, typical for discrete devices with leadfree solder die attachment. It has been determined that dieattach degradation results in an increase in ON-state resistance due to its dependence on junction temperature. Increasing resistance, thus, can be used as a precursor of failure for the die-attach failure mechanism under thermal stress. A feature based on normalized ON-resistance is computed from in-situ measurements of the electro-thermal response. An Extended Kalman filter is used as a model-based prognostics techniques based on the Bayesian tracking framework. The proposed prognostics technique reports on preliminary work that serves as a case study on the prediction of remaining life of power MOSFETs and builds upon the work presented in [1]. The algorithm considered in this study had been used as prognostics algorithm in different applications and is regarded as suitable candidate for component level prognostics. This work attempts to further the validation of such algorithm by presenting it with real degradation data including measurements from real sensors, which include all the complications (noise, bias, etc.) that are regularly not captured on simulated degradation data. The algorithm is developed and tested on the accelerated aging test timescale. In real world operation, the timescale of the degradation process and therefore the RUL predictions will be considerable larger. It is hypothesized that even though the timescale will be larger, it remains constant through the degradation process and the algorithm and model would still apply under the slower degradation process. By using accelerated aging data with actual device measurements and real

  20. Thermal stress prediction in mirror and multilayer coatings.

    PubMed

    Cheng, Xianchao; Zhang, Lin; Morawe, Christian; Sanchez Del Rio, Manuel

    2015-03-01

    Multilayer optics for X-rays typically consist of hundreds of periods of two types of alternating sub-layers which are coated on a silicon substrate. The thickness of the coating is well below 1 µm (tens or hundreds of nanometers). The high aspect ratio (∼10(7)) between the size of the optics and the thickness of the multilayer can lead to a huge number of elements (∼10(16)) for the numerical simulation (by finite-element analysis using ANSYS code). In this work, the finite-element model for thermal-structural analysis of multilayer optics has been implemented using the ANSYS layer-functioned elements. The number of meshed elements is considerably reduced and the number of sub-layers feasible for the present computers is increased significantly. Based on this technique, single-layer coated mirrors and multilayer monochromators cooled by water or liquid nitrogen are studied with typical parameters of heat-load, cooling and geometry. The effects of cooling-down of the optics and heating of the X-ray beam are described. It is shown that the influences from the coating on temperature and deformation are negligible. However, large stresses are induced in the layers due to the different thermal expansion coefficients between the layer and the substrate materials, which is the critical issue for the survival of the optics. This is particularly true for the liquid-nitrogen cooling condition. The material properties of thin multilayer films are applied in the simulation to predict the layer thermal stresses with more precision. PMID:25723932

  1. Effect of thermal stress on the vestibulosympathetic reflexes in humans.

    PubMed

    Wilson, Thad E; Ray, Chester A

    2004-10-01

    Both heat stress and vestibular activation alter autonomic responses; however, the interaction of these two sympathetic activators is unknown. To determine the effect of heat stress on the vestibulosympathetic reflex, eight subjects performed static head-down rotation (HDR) during normothermia and whole body heating. Muscle sympathetic nerve activity (MSNA; peroneal microneurography), mean arterial blood pressure (MAP), heart rate (HR), and internal temperature were measured during the experimental trials. HDR during normothermia caused a significant increase in MSNA (Delta5 +/- 1 bursts/min; Delta53 +/- 14 arbitrary units/min), whereas no change was observed in MAP, HR, or internal temperature. Whole body heating significantly increased internal temperature (Delta0.9 +/- 0.1 degrees C), MSNA (Delta10 +/- 3 bursts/min; Delta152 +/- 44 arbitrary units/min), and HR (Delta25 +/- 6 beats/min), but it did not alter MAP. HDR during whole body heating increased MSNA (Delta16 +/- 4 bursts/min; Delta233 +/- 90 arbitrary units/min from normothermic baseline), which was not significantly different from the algebraic sum of HDR during normothermia and whole body heating (Delta15 +/- 4 bursts/min; Delta205 +/- 55 arbitrary units/min). These data suggest that heat stress does not modify the vestibulosympathetic reflex and that both the vestibulosympathetic and thermal reflexes are robust, independent sympathetic nervous system activators. PMID:15169749

  2. Daily oral intake of theanine prevents the decline of 5-bromo-2'-deoxyuridine incorporation in hippocampal dentate gyrus with concomitant alleviation of behavioral abnormalities in adult mice with severe traumatic stress.

    PubMed

    Takarada, Takeshi; Nakamichi, Noritaka; Kakuda, Takami; Nakazato, Ryota; Kokubo, Hiroshi; Ikeno, Shinsuke; Nakamura, Saki; Hinoi, Eiichi; Yoneda, Yukio

    2015-03-01

    Posttraumatic stress disorder is a long-lasting psychiatric disease with the consequence of hippocampal atrophy in humans exposed to severe fatal stress. We demonstrated a positive correlation between the transient decline of 5-bromo-2'-deoxyuridine (BrdU) incorporation in the hippocampal dentate gyrus (DG) and long-lasting behavioral abnormalities in mice with traumatic stress. Here, we investigated pharmacological properties of theanine on the declined BrdU incorporation and abnormal behaviors in mice with traumatic stress. Prior daily oral administration of theanine at 50-500 mg/kg for 5 days significantly prevented the decline of BrdU incorporation, while theanine significantly prevented the decline in the DG even when administered for 5 days after stress. Consecutive daily administration of theanine significantly inhibited the prolonged immobility in mice with stress in forced swimming test seen 14 days later. Although traumatic stress significantly increased spontaneous locomotor activity over 30 min even when determined 14 days later, the increased total locomotion was significantly ameliorated following the administration of theanine at 50 mg/kg for 14 days after stress. These results suggest that theanine alleviates behavioral abnormalities together with prevention of the transient decline of BrdU incorporation in the hippocampal DG in adult mice with severe traumatic stress. PMID:25837925

  3. Thermal effects of fiber sensing coils in different winding pattern considering both thermal gradient and thermal stress

    NASA Astrophysics Data System (ADS)

    Ling, Weiwei; Li, Xuyou; Xu, Zhenlong; Zhang, Zhiyong; Wei, Yanhui

    2015-12-01

    By studying the temperature gradient and thermal stress of the difference-winding interferometric fiber optic gyroscope (IFOG) sensing coils, the improvement of the IFOG's temperature performance is realized. A new turn-by-turn quantization thermal-induced bias error model including the traditional "pure Shupe effect", elastic strain interactions and elasto-optical interactions are established. Compared with the traditional "pure Shupe effect" model, the experimental results show that the new model can more fully describe the thermal effect of the coils. Based on the temperature and stress distribution models mentioned above, the effects of the fiber coils with the quadrupolar (QAD) winding pattern, octupolar winding pattern and cross winding pattern on the temperature performance of IFOG are simulated under the same temperature gradient, respectively. The results show that the elastic strain and the elasto-optical effect must be considered when calculated the thermal-induced bias error of the fiber coil. Furthermore, we also come to the conclusion that cross-winding coil of the IFOG have more wonderful temperature performance than the fiber coil with quadruple winding and octupole-winding.

  4. Buffet Load Alleviation

    NASA Technical Reports Server (NTRS)

    Ryall, T. G.; Moses, R. W.; Hopkins, M. A.; Henderson, D.; Zimcik, D. G.; Nitzsche, F.

    2004-01-01

    High performance aircraft are, by their very nature, often required to undergo maneuvers involving high angles of attack. Under these conditions unsteady vortices emanating from the wing and the fuselage will impinge on the twin fins (required for directional stability) causing excessive buffet loads, in some circumstances, to be applied to the aircraft. These loads result in oscillatory stresses, which may cause significant amounts of fatigue damage. Active control is a possible solution to this important problem. A full-scale test was carried out on an F/A-18 fuselage and fins using piezoceramic actuators to control the vibrations. Buffet loads were simulated using very powerful electromagnetic shakers. The first phase of this test was concerned with the open loop system identification whereas the second stage involved implementing linear time invariant control laws. This paper looks at some of the problems encountered as well as the corresponding solutions and some results. It is expected that flight trials of a similar control system to alleviate buffet will occur as early as 2001.

  5. Thermal-stress analysis for wood composite blade. [horizontal axis wind turbines

    NASA Technical Reports Server (NTRS)

    Fu, K. C.; Harb, A.

    1984-01-01

    The thermal-stress induced by solar insolation on a wood composite blade of a Mod-OA wind turbine was investigated. The temperature distribution throughout the blade (a heat conduction problem) was analyzed and the thermal-stress distribution of the blades caused by the temperature distribution (a thermal-stress analysis problem) was then determined. The computer programs used for both problems are included along with output examples.

  6. Thermal Hyperspectral Remote Sensing for Plant Species and Stress Detection

    NASA Astrophysics Data System (ADS)

    Schlerf, M.; Rock, G.; Ullah, S.; Gerhards, M.; Udelhoven, T.; Skidmore, A. K.

    2014-12-01

    Thermal infrared (TIR) spectroscopy offers a novel opportunity for measuring emissivity spectra of natural surfaces. Emissivity spectra are not directly measured, they first have to be retrieved from the raw measurements. Once retrieved, the spectra can be used, for example, to discriminate plant species or to detect plant stress. Knowledge of plant species distribution is essential for the sustainable management of ecosystems. Remote sensing of plant species has so far mostly been limited to data in the visible and near-infrared where, however, different species often reveal similar reflectance curves. Da Luz and Crowley showed in a recent paper that in the TIR plants indeed have distinct spectral features. Also with a certain species, subtle changes of emissivity in certain wavebands may occur, when biochemical compounds change due to osmotic adjustment induced by water stress. Here we show, that i) emissive imaging spectroscopy allows for reliable and accurate retrieval of plant emissivity spectra, ii) emissivity spectra are well suited to discriminate plant species, iii) a reduction in stomatal conductance (caused by stress) changes the thermal infrared signal. For 13 plant species in the laboratory and for 8 plant species in a field setup emissivity spectra were retrieved. A comparison shows, that for most species the shapes of the emissivity curves agree quite well, but that clear offsets between the two types of spectra exist. Discrimination analysis revealed that based on the lab spectra, 13 species could be distinguished with an average overall classification accuracy of 92% using the 6 best spectral bands. For the field spectra (8 species), a similar high OAA of 89% was achieved. Species discrimination is likely to be possible due to variations in the composition of the superficial epidermal layer of plant leaves and in internal chemical concentrations producing unique emissivity features. However, to date, which spectral feature is responsible for which

  7. Thermal stress-relief treatments for 2219 aluminum alloy are evaluated

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Evaluation of three thermal stress relief treatments for 2219 aluminum alloy in terms of their effect on residual stress, mechanical properties, and stress corrosion resistance. The treatments are post aging and stress relieving fullscale and subscale parts formed in the aged T81 condition, and aging subscale parts formed in the unaged T31 condition.

  8. A model for residual stress evolution in air-plasma-sprayed zirconia thermal barrier coatings

    SciTech Connect

    Nair, B. G.; Singh, J. P.; Grimsditch, M.

    2000-02-28

    Ruby fluorescence spectroscopy indicates that residual stress in air-plasma-sprayed zirconia thermal barrier coatings is a function of the local interface geometry. The stress profile of a simulated rough interface characterized by ``peaks'' and ``valleys'' was modeled with a finite-element approach that accounted for thermal mismatch, oxide scale growth, and top coat sintering. Dependence of the stress profile on interface geometry and microstructure was investigated, and the results were compared with measured stresses.

  9. Preliminary Thermal Stress Analysis of a High-Pressure Cryogenic Storage Tank

    NASA Technical Reports Server (NTRS)

    Baker, J. Mark

    2003-01-01

    The thermal stresses on a cryogenic storage tank strongly affect the condition of the tank and its ability to withstand operational stresses. These thermal stresses also affect the growth of any surface damage that might occur in the tank walls. These stresses are particularly of concern during the initial cooldown period for a new tank placed into service, and during any subsequent thermal cycles. A preliminary thermal stress analysis of a high-pressure cryogenic storage tank was performed. Stresses during normal operation were determined, as well as the transient temperature distribution. An elastic analysis was used to determine the thermal stresses in the inner wall based on the temperature data. The results of this elastic analysis indicate that the inner wall of the storage tank will experience thermal stresses of approximately 145,000 psi (1000 MPa). This stress level is well above the room-temperature yield strength of 304L stainless steel, which is about 25,000 psi (170 MPa). For this preliminary analysis, several important factors have not yet been considered. These factors include increased strength of 304L stainless steel at cryogenic temperatures, plastic material behavior, and increased strength due to strain hardening. In order to more accurately determine the thermal stresses and their affect on the tank material, further investigation is required, particularly in the area of material properties and their relationship to stress.

  10. Cracking of coated materials under transient thermal stresses

    NASA Technical Reports Server (NTRS)

    Rizk, A. A.; Erdogan, F.

    1989-01-01

    The crack problem for a relatively thin layer bonded to a very thick substrate under thermal shock conditions is considered. The effect of surface cooling rate is studied by assuming the temperature boundary condition to be a ramp function. Among the crack geometries considered are the edge crack in the coating layer, the broken layer, the edge crack going through the interface, the undercoat crack in the substrate and the embedded crack crossing the interface. The primary calculated quantity is the stress intensity factor at various singular points and the main variables are the relative sizes and locations of cracks, the time, and the duration of the cooling ramp. The problem is solved and rather extensive results are given for two material pairs, namely a stainless steel layer welded on a ferritic medium and a ceramic coating on a steel substrate.

  11. Cracking of coated materials under transient thermal stresses

    SciTech Connect

    Rizk, A.A.; Erdogan, F. )

    1989-01-01

    The crack problem for a relatively thin layer bonded to a very thick substrate under thermal shock conditions is considered. The effect of surface cooling rate is studied by assuming the temperature boundary condition to be a ramp function. Among the crack geometries considered are the edge crack in the coating layer, the broken layer, the edge crack going through the interface, the undercoat crack in the substrate and the embedded crack crossing the interface. The primary calculated quantity is the stress intensity factor at various singular points and the main variables are the relative sizes and locations of cracks, the time, and the duration of the cooling ramp. The problem is solved and rather extensive results are given for two material pairs, namely a stainless steel layer welded on a ferritic medium and a ceramic coating on a steel substrate. 12 refs.

  12. Cracking of coated materials under transient thermal stresses

    NASA Technical Reports Server (NTRS)

    Rizk, A. A.; Erdogan, Fazil

    1988-01-01

    The crack problem for a relatively thin layer bonded to a very thick substrate under thermal shock conditions is considered. The effect of surface cooling rate is studied by assuming the temperature boundary condition to be a ramp function. Among the crack geometries considered are the edge crack in the coating layer, the broken layer, the edge crack going through the interface, the undercoat crack in the substrate and the embedded crack crossing the interface. The primary calculated quantity is the stress intensity factor at various singular points and the main variables are the relative sizes and locations of cracks, the time, and the duration of the cooling ramp. The problem is solved and rather extensive results are given for two material pairs, namely a stainless steel layer welded on a ferritic medium and a ceramic coating on a steel substrate.

  13. The effect of water on thermal stresses in polymer composites

    NASA Technical Reports Server (NTRS)

    Sullivan, Roy M.

    1994-01-01

    The fundamentals of the thermodynamic theory of mixtures and continuum thermochemistry are reviewed for a mixture of condensed water and polymer. A specific mixture which is mechanically elastic with temperature and water concentration gradients present is considered. An expression for the partial pressure of water in the mixture is obtained based on certain assumptions regarding the thermodynamic state of the water in the mixture. Along with a simple diffusion equation, this partial pressure expression may be used to simulate the thermostructural behavior of polymer composite materials due to water in the free volumes of the polymer. These equations are applied to a specific polymer composite material during isothermal heating conditions. The thermal stresses obtained by the application of the theory are compared to measured results to verify the accuracy of the approach.

  14. Exploring the Use of Thermal Infrared Imaging in Human Stress Research

    PubMed Central

    Grant, Joshua A.; Cardone, Daniela; Tusche, Anita; Singer, Tania

    2014-01-01

    High resolution thermal infrared imaging is a pioneering method giving indices of sympathetic activity via the contact-free recording of facial tissues (thermal imprints). Compared to established stress markers, the great advantage of this method is its non-invasiveness. The goal of our study was to pilot the use of thermal infrared imaging in the classical setting of human stress research. Thermal imprints were compared to established stress markers (heart rate, heart rate variability, finger temperature, alpha-amylase and cortisol) in 15 participants undergoing anticipation, stress and recovery phases of two laboratory stress tests, the Cold Pressor Test and the Trier Social Stress Test. The majority of the thermal imprints proved to be change-sensitive in both tests. While correlations between the thermal imprints and established stress markers were mostly non-significant, the thermal imprints (but not the established stress makers) did correlate with stress-induced mood changes. Multivariate pattern analysis revealed that in contrast to the established stress markers the thermal imprints could not disambiguate anticipation, stress and recovery phases of both tests. Overall, these results suggest that thermal infrared imaging is a valuable method for the estimation of sympathetic activity in the stress laboratory setting. The use of this non-invasive method may be particularly beneficial for covert recordings, in the study of special populations showing difficulties in complying with the standard instruments of data collection and in the domain of psychophysiological covariance research. Meanwhile, the established stress markers seem to be superior when it comes to the characterization of complex physiological states during the different phases of the stress cycle. PMID:24675709

  15. Thermal stress analysis of symmetric shells subjected to asymmetric thermal loads

    NASA Technical Reports Server (NTRS)

    Negaard, G. R.

    1980-01-01

    The performance of the NASTRAN level 16.0 axisymmetric solid elements when subjected to both symmetric and asymmetric thermal loading was investigated. A ceramic radome was modeled using both the CTRAPRG and the CTRAPAX elements. The thermal loading applied contained severe gradients through the thickness of the shell. Both elements were found to be more sensitive to the effect of the thermal gradient than to the aspect ratio of the elements. Analysis using the CTRAPAX element predicted much higher thermal stresses than the analysis using the CTRAPRG element, prompting studies of models for which theoretical solutions could be calculated. It was found that the CTRAPRG element solutions were satisfactory, but that the CTRAPAX element was very geometry dependent. This element produced erroneous results if the geometry was allowed to vary from a rectangular cross-section. The most satisfactory solution found for this type of problem was to model a small segment of a symmetric structure with isoparametric solid elements and apply the cyclic symmetry option in NASTRAN.

  16. Thermal Indices and Thermophysiological Modeling for Heat Stress.

    PubMed

    Havenith, George; Fiala, Dusan

    2015-01-01

    The assessment of the risk of human exposure to heat is a topic as relevant today as a century ago. The introduction and use of heat stress indices and models to predict and quantify heat stress and heat strain has helped to reduce morbidity and mortality in industrial, military, sports, and leisure activities dramatically. Models used range from simple instruments that attempt to mimic the human-environment heat exchange to complex thermophysiological models that simulate both internal and external heat and mass transfer, including related processes through (protective) clothing. This article discusses the most commonly used indices and models and looks at how these are deployed in the different contexts of industrial, military, and biometeorological applications, with focus on use to predict related thermal sensations, acute risk of heat illness, and epidemiological analysis of morbidity and mortality. A critical assessment is made of tendencies to use simple indices such as WBGT in more complex conditions (e.g., while wearing protective clothing), or when employed in conjunction with inappropriate sensors. Regarding the more complex thermophysiological models, the article discusses more recent developments including model individualization approaches and advanced systems that combine simulation models with (body worn) sensors to provide real-time risk assessment. The models discussed in the article range from historical indices to recent developments in using thermophysiological models in (bio) meteorological applications as an indicator of the combined effect of outdoor weather settings on humans. PMID:26756633

  17. Crack propagation and fracture in silicon wafers under thermal stress

    PubMed Central

    Danilewsky, Andreas; Wittge, Jochen; Kiefl, Konstantin; Allen, David; McNally, Patrick; Garagorri, Jorge; Elizalde, M. Reyes; Baumbach, Tilo; Tanner, Brian K.

    2013-01-01

    The behaviour of microcracks in silicon during thermal annealing has been studied using in situ X-ray diffraction imaging. Initial cracks are produced with an indenter at the edge of a conventional Si wafer, which was heated under temperature gradients to produce thermal stress. At temperatures where Si is still in the brittle regime, the strain may accumulate if a microcrack is pinned. If a critical value is exceeded either a new or a longer crack will be formed, which results with high probability in wafer breakage. The strain reduces most efficiently by forming (hhl) or (hkl) crack planes of high energy instead of the expected low-energy cleavage planes like {111}. Dangerous cracks, which become active during heat treatment and may shatter the whole wafer, can be identified from diffraction images simply by measuring the geometrical dimensions of the strain-related contrast around the crack tip. Once the plastic regime at higher temperature is reached, strain is reduced by generating dislocation loops and slip bands and no wafer breakage occurs. There is only a small temperature window within which crack propagation is possible during rapid annealing. PMID:24046487

  18. Epoetin beta pegol alleviates oxidative stress and exacerbation of renal damage from iron deposition, thereby delaying CKD progression in progressive glomerulonephritis rats.

    PubMed

    Hirata, Michinori; Tashiro, Yoshihito; Aizawa, Ken; Kawasaki, Ryohei; Shimonaka, Yasushi; Endo, Koichi

    2015-12-01

    The increased deposition of iron in the kidneys that occurs with glomerulopathy hinders the functional and structural recovery of the tubules and promotes progression of chronic kidney disease (CKD). Here, we evaluated whether epoetin beta pegol (continuous erythropoietin receptor activator: CERA), which has a long half-life in blood and strongly suppresses hepcidin-25, exerts renoprotection in a rat model of chronic progressive glomerulonephritis (cGN). cGN rats showed elevated urinary total protein excretion (uTP) and plasma urea nitrogen (UN) from day 14 after the induction of kidney disease (day 0) and finally declined into end-stage kidney disease (ESKD), showing reduced creatinine clearance with glomerulosclerosis, tubular dilation, and tubulointerstitial fibrosis. A single dose of CERA given on day 1, but not on day 16, alleviated increasing uTP and UN, thereby delaying ESKD. In the initial disease phase, CERA significantly suppressed urinary 8-OHdG and liver-type fatty acid-binding protein (L-FABP), a tubular damage marker. CERA also inhibited elevated plasma hepcidin-25 levels and alleviated subsequent iron accumulation in kidneys in association with elevated urinary iron excretion and resulted in alleviation of growth of Ki67-positive tubular and glomerular cells. In addition, at day 28 when the exacerbation of uTP occurs, a significant correlation was observed between iron deposition in the kidney and urinary L-FABP. In our study, CERA mitigated increasing kidney damage, thereby delaying CKD progression in this glomerulonephritis rat model. Alleviation by CERA of the exacerbation of kidney damage could be attributable to mitigation of tubular damage that might occur with lowered iron deposition in tubules. PMID:26634903

  19. Stress analysis in curved composites due to thermal loading

    NASA Astrophysics Data System (ADS)

    Polk, Jared Cornelius

    Many structures in aircraft, cars, trucks, ships, machines, tools, bridges, and buildings, consist of curved sections. These sections vary from straight line segments that have curvature at either one or both ends, segments with compound curvatures, segments with two mutually perpendicular curvatures or Gaussian curvatures, and segments with a simple curvature. With the advancements made in multi-purpose composites over the past 60 years, composites slowly but steadily have been appearing in these various vehicles, compound structures, and buildings. These composite sections provide added benefits over isotropic, polymeric, and ceramic materials by generally having a higher specific strength, higher specific stiffnesses, longer fatigue life, lower density, possibilities in reduction of life cycle and/or acquisition cost, and greater adaptability to intended function of structure via material composition and geometry. To be able to design and manufacture a safe composite laminate or structure, it is imperative that the stress distributions, their causes, and effects are thoroughly understood in order to successfully accomplish mission objectives and manufacture a safe and reliable composite. The objective of the thesis work is to expand upon the knowledge of simply curved composite structures by exploring and ascertaining all pertinent parameters, phenomenon, and trends in stress variations in curved laminates due to thermal loading. The simply curved composites consist of composites with one radius of curvature throughout the span of the specimen about only one axis. Analytical beam theory, classical lamination theory, and finite element analysis were used to ascertain stress variations in a flat, isotropic beam. An analytical method was developed to ascertain the stress variations in an isotropic, simply curved beam under thermal loading that is under both free-free and fixed-fixed constraint conditions. This is the first such solution to Author's best knowledge

  20. On thermal stress failure of the SNAP-19A RTG heat shield

    NASA Technical Reports Server (NTRS)

    Pitts, W. C.; Anderson, L. A.

    1974-01-01

    Results of a study on thermal stress problems in an amorphous graphite heat shield that is part of the launch-abort protect system for the SNAP-19A radio-isotope thermoelectric generators (RTG) that will be used on the Viking Mars Lander are presended. The first result is from a thermal stress analysis of a full-scale RTG heat source that failed to survive a suborbital entry flight test, possibly due to thermal stress failure. It was calculated that the maximum stress in the heat shield was only 50 percent of the ultimate strength of the material. To provide information on the stress failure criterion used for this calculation, some heat shield specimens were fractured under abort entry conditions in a plasma arc facility. It was found that in regions free of stress concentrations the POCO graphite heat shield material did fracture when the local stress reached the ultimate uniaxial stress of the material.

  1. Anisotropic internal thermal stress in sea ice from the Canadian Arctic Archipelago

    NASA Astrophysics Data System (ADS)

    Hata, Y.; Tremblay, L. B.

    2015-08-01

    Results from an ice stress buoy deployed near the center of a multi-year floe in the Viscount Melville Sound of the Canadian Arctic Archipelago between 10 October 2010 and 17 August 2011 are presented. The position record indicates the landlocked season was approximately 5 months, from 18 January to 22 June, when the sea ice was fast to Melville Island and Victoria Island. Thermal stresses (ranging from -84 to 66 kPa) dominate the internal stress record, with only a few dynamic stress events (˜50 kPa) recorded before the landlocked season. Intriguingly, the thermal stresses are isotropic before the landlocked ice onset and anisotropic during the landlocked season. Two possible causes to explain anisotropy in thermal stresses are considered: preferred c axis alignment of the ice crystal, and land confinement associated with the nearby coastline. The orientation of the principal stresses indicates that land confinement is responsible for the anisotropy. The stress record also clearly shows the presence of residual compressive stresses at the melt onset, suggesting a viscous creep relaxation time constant of several days. Finally, results show an interesting reversal in the sign of the correlation (from negative to positive) between surface air temperature and thermal stress after the onset of surface melt. We attribute this to the onset of water infiltration within sea ice after which colder night temperature leads to refreezing and compressive stresses. To the best of the authors' knowledge, this is the first time that anisotropic thermal stresses have been reported in sea ice.

  2. Analysis of thermal stresses and metal movement during welding. I - Analytical study

    NASA Technical Reports Server (NTRS)

    Muraki, T.; Masubuchi, K.; Bryan, J. J.

    1974-01-01

    This is the first part of a study of thermal stresses and metal movement during welding. This part discusses analysis of two-dimensional thermal stresses and metal movement during bead-on-plate and butt welding. A finite-element formulation has been derived, based on the variational principle. The formulation includes temperature dependence of material properties as well as the yield criterion.

  3. Thermal stress and predation risk trigger distinct transcriptomic responses in the intertidal snail Nucella lapillus.

    PubMed

    Chu, Nathaniel D; Miller, Luke P; Kaluziak, Stefan T; Trussell, Geoffrey C; Vollmer, Steven V

    2014-12-01

    Thermal stress and predation risk have profound effects on rocky shore organisms, triggering changes in their feeding behaviour, morphology and metabolism. Studies of thermal stress have shown that underpinning such changes in several intertidal species are specific shifts in gene and protein expression (e.g. upregulation of heat-shock proteins). But relatively few studies have examined genetic responses to predation risk. Here, we use next-generation RNA sequencing (RNA-seq) to examine the transcriptomic (mRNA) response of the snail Nucella lapillus to thermal stress and predation risk. We found that like other intertidal species, N. lapillus displays a pronounced genetic response to thermal stress by upregulating many heat-shock proteins and other molecular chaperones. In contrast, the presence of a crab predator (Carcinus maenas) triggered few significant changes in gene expression in our experiment, and this response showed no significant overlap with the snail's response to thermal stress. These different gene expression profiles suggest that thermal stress and predation risk could pose distinct and potentially additive challenges for N. lapillus and that genetic responses to biotic stresses such as predation risk might be more complex and less uniform across species than genetic responses to abiotic stresses such as thermal stress. PMID:25377436

  4. Residual stresses in a multi-pass weld in an austenitic stainless steel plate before and after thermal stress relief

    SciTech Connect

    Spooner, S.; Wang, X.L.; Hubbard, C.R.; David, S.A.

    1994-06-01

    Changes in residual stresses due to thermal stress relief were determined in a welded 1/2 in. thick 304 stainless steel plate from two residual stress maps determined with the neutron diffraction technique. The 304 stainless plate was made from two 6 {times} 12 {times} 1/2 in. pieces joined along the length by a gas tungsten arc welding process. Multi-pass welds were made with a semiautomatic welding machine employing cold-wire feed of type 308 stainless steel filler alloy. The thermal stress relief treatment consisted of heating to 1150 F, holding for one hour at temperature and then air cooling. Strain components were measured along the weld direction (longitudinal), perpendicular to the weld line in the plate (transverse), and normal to the plate. Measurements were confined to the plane bisecting the weld at the center of the plate. The strain components were converted to stresses assuming that the measured strains were along the principal axes of the strain tensor. Parameters used in the calculation were E=224 GPa and v=0.25. As-welded longitudinal stresses are compressive in the base metal and become strongly tensile through the heat affected zone and into the fusion zone. The transverse stresses follow the longitudinal trend but with a lower magnitude while the normal stresses are small throughout. The stress relief treatment reduced the magnitudes of all the stresses. In the weld zone the longitudinal stress was lowered by 30% and the spatial range of residual stresses was reduced as well.

  5. Investigation of Thermal Stress Convection in Nonisothermal Gases under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Mackowski, Daniel W.

    1999-01-01

    The project has sought to ascertain the veracity of the Burnett relations, as applied to slow moving, highly nonisothermal gases, by comparison of convection and stress predictions with those generated by the DSMC method. The Burnett equations were found to provide reasonable descriptions of the pressure distribution and normal stress in stationary gases with a 1-D temperature gradient. Continuum/Burnett predictions of thermal stress convection in 2-D heated enclosures, however, are not quantitatively supported by DSMC results. For such situations, it appears that thermal creep flows, generated at the boundaries of the enclosure, will be significantly larger than the flows resulting from thermal stress in the gas.

  6. Study on three dimensional transient thermal stress analysis for laminated composite materials

    SciTech Connect

    Matsumoto, Kin`ya; Zako, Masaru

    1995-11-01

    Transient heat conduction and thermal stress analysis of laminated composite materials are very important because they are hated during manufacturing process. Anisotropy of thermal conductivity has to be considered for heat conduction analysis of composite materials such as FRP. Assuming that heat conducts uniformly in normal direction in thin structures, laminated plates can be modeled as single layers with the equivalent heat conductivities. With this assumption, FEM three dimensional transient heat conduction and thermal stress analysis programs for laminated composite materials are developed. As numerical examples, the heat conduction and thermal stresses of laminated CFRP structure are investigated.

  7. EVALUATION OF THERMAL STRESS ANALYSIS FOR SIDE WALLS OF CUT-AND-COVER TUNNELS

    NASA Astrophysics Data System (ADS)

    Iwanami, Motoi; Sadato, Seiichiro; Ikarashi, Yuki

    Cracks due to thermal stresses that occur in the side walls of large cut-and-cover tunnels adversely affect tunnel durability. In many cases, therefore, thermal stress is analyzed to control thermal stress cracking. However, the analytical accuracy is not good enough for estimation. This paper discusses methods for improvmg the accuracy of thermal stress analyses, taking as an example a side wall about 1.0 m thick of a large cut-and-cover tunnel. The methods involve the following three points: consideration of drying shrinkage, utilization of the diagrams in the Standard Specifications for Concrete Structures-Design(JSCE), and three dimensional thermal stress analysis considering drying shrinkage induced by humidity migration.

  8. Study of the thermal stress in a Pb-free half-bump solder joint under current stressing

    SciTech Connect

    Wu, B. Y.; Chan, Y. C.; Zhong, H. W.; Alam, M. O.; Lai, J. K. L.

    2007-06-04

    The thermal stress in a Sn3.5Ag1Cu half-bump solder joint under a 3.82x10{sup 8} A/m{sup 2} current stressing was analyzed using a coupled-field simulation. Substantial thermal stress accumulated around the Al-to-solder interface, especially in the Ni+(Ni,Cu){sub 3}Sn{sub 4} layer, where a maximal stress of 138 MPa was identified. The stress gradient in the Ni layer was about 1.67x10{sup 13} Pa/m, resulting in a stress migration force of 1.82x10{sup -16} N, which is comparable to the electromigration force, 2.82x10{sup -16} N. Dissolution of the Ni+(Ni,Cu){sub 3}Sn{sub 4} layer, void formation with cracks at the anode side, and extrusions at the cathode side were observed.

  9. Stress generation in thermally grown oxide films. [oxide scale spalling from superalloy substrates

    NASA Technical Reports Server (NTRS)

    Kumnick, A. J.; Ebert, L. J.

    1981-01-01

    A three dimensional finite element analysis was conducted, using the ANSYS computer program, of the stress state in a thin oxide film thermally formed on a rectangular piece of NiCrAl alloy. The analytical results indicate a very high compressive stress in the lateral directions of the film (approximately 6200 MPa), and tensile stresses in the metal substrate that ranged from essentially zero to about 55 MPa. It was found further that the intensity of the analytically determined average stresses could be approximated reasonably well by the modification of an equation developed previously by Oxx for stresses induced into bodies by thermal gradients.

  10. Factors Influencing Residual Stresses in Yttria Stabilized Zirconia Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    McGrann, Roy T. R.; Rybicki, Edmund F.; Shadley, John R.; Brindley, William J.

    1997-01-01

    To improve gas turbine and diesel engine performance using thermal barrier coatings (TBC's) requires an understanding of the factors that influence the in-service behavior of thermal barrier coatings. One of the many factors related to coating performance is the state of stress in the coating. The total stress state is composed of the stresses due to the in-service loading history and the residual stresses. Residual stresses have been shown to affect TBC life, the bond strength of thermal spray coatings, and the fatigue life of tungsten carbide coatings. Residual stresses are first introduced in TBC's by the spraying process due to elevated temperatures during processing and the difference in coefficients of thermal expansion of the top coat, bond coat, and substrate. Later, the residual stresses can be changed by the in-service temperature history due to a number of time and temperature dependent mechanisms, such as oxidation, creep, and sintering. Silica content has also been shown to affect sintering and the cyclic life of thermal barrier coatings. Thus, it is important to understand how the spraying process, the in-service thermal cycles, and the silica content can create and alter residual stresses in thermal barrier coatings.

  11. Coupling Mechanism of Electromagnetic Field and Thermal Stress on Drosophila melanogaster.

    PubMed

    Zhang, Zi-Yan; Zhang, Jing; Yang, Chuan-Jun; Lian, Hui-Yong; Yu, Hui; Huang, Xiao-Mei; Cai, Peng

    2016-01-01

    Temperature is an important factor in research on the biological effects of extremely low-frequency electromagnetic field (ELF-EMF), but interactions between ELF-EMF and temperature remain unknown. The effects of ELF-EMF (50 Hz, 3 mT) on the lifespan, locomotion, heat shock response (HSR), and oxidative stress (OS) of Canton-Special (CS) and mutant w1118 flies were investigated at 25°C and 35°C (thermal stress). Results showed that thermal stress accelerated the death rates of CS and w1118 flies, shortened their lifespan, and influenced their locomotion rhythm and activity. The upregulated expression levels of heat shock protein (HSP) 22, HSP26, and HSP70 indicated that HSR was enhanced. Thermal stress-induced OS response increased malondialdehyde content, enhanced superoxide dismutase activity, and decreased reactive oxygen species level. The effects of thermal stress on the death rates, lifespan, locomotion, and HSP gene expression of flies, especially w1118 line, were also enhanced by ELF-EMF. In conclusion, thermal stress weakened the physiological function and promoted the HSR and OS of flies. ELF-EMF aggravated damages and enhanced thermal stress-induced HSP and OS response. Therefore, thermal stress and ELF-EMF elicited a synergistic effect. PMID:27611438

  12. Elastic-Plastic Thermal Stress Analysis of a High-Pressure Cryogenic Storage Tank

    NASA Technical Reports Server (NTRS)

    Barker, J. Mark; Field, Robert E. (Technical Monitor)

    2003-01-01

    The thermal stresses on a cryogenic storage tank contribute strongly to the state of stress of the tank material and its ability to withstand operational stresses. These thermal stresses also affect the growth of any surface damage that might occur in the tank walls. These stresses are particularly of concern during the initial cooldown period for a new tank placed into service, and during any subsequent thermal cycles. A previous preliminary elastic analysis showed that the thermal stress on the inner wall would reach approximately 1,000MPa (145,000 psi). This stress far exceeds the ASTM specified room temperature values for both yield (170MPa) and ultimate (485 MPa) strength for 304L stainless steel. The present analysis determines the thermal stresses using an elastic-plastic model. The commercial software application ANSYS was used to determine the transient spatial temperature profile and the associated spatial thermal stress profiles in a segment of a thick-walled vessel during a typical cooldown process. A strictly elastic analysis using standard material properties for 304L stainless steel showed that the maximum thermal stress on the inner and outer walls was approximately 960 MPa (tensile) and - 270 MPa (compressive) respectively. These values occurred early in the cooldown process, but at different times, An elastic-plastic analysis showed significantly reducing stress, as expected due to the plastic deformation of the material. The maximum stress for the inner wall was approximately 225 MPa (tensile), while the maximum stress for the outer wall was approximately - 130 MPa (compressive).

  13. Large-amplitude internal waves benefit corals during thermal stress

    PubMed Central

    Wall, M.; Putchim, L.; Schmidt, G. M.; Jantzen, C.; Khokiattiwong, S.; Richter, C.

    2015-01-01

    Tropical scleractinian corals are particularly vulnerable to global warming as elevated sea surface temperatures (SSTs) disrupt the delicate balance between the coral host and their algal endosymbionts, leading to symbiont expulsion, mass bleaching and mortality. While satellite sensing of SST has proved a reliable predictor of coral bleaching at the regional scale, there are large deviations in bleaching severity and mortality on the local scale that are poorly understood. Here, we show that internal waves play a major role in explaining local coral bleaching and mortality patterns in the Andaman Sea. Despite a severe region-wide SST anomaly in May 2010, frequent upslope intrusions of cold sub-pycnocline waters due to breaking large-amplitude internal waves (LAIW) mitigated coral bleaching and mortality in shallow waters. In LAIW-sheltered waters, by contrast, bleaching-susceptible species suffered severe bleaching and total mortality. These findings suggest that LAIW benefit coral reefs during thermal stress and provide local refugia for bleaching-susceptible corals. LAIW are ubiquitous in tropical stratified waters and their swash zones may thus be important conservation areas for the maintenance of coral diversity in a warming climate. Taking LAIW into account can significantly improve coral bleaching predictions and provide a valuable tool for coral reef conservation and management. PMID:25473004

  14. Tensile stress and creep in thermally grown oxide.

    PubMed

    Veal, Boyd W; Paulikas, Arvydas P; Hou, Peggy Y

    2006-05-01

    Structural components that operate at high temperatures (for example, turbine blades) rely on thermally grown oxide (TGO), commonly alumina, for corrosion protection. Strains that develop in TGOs during operation can reduce the protectiveness of the TGO. However, the occurrence of growth strains in TGOs, and mechanisms that cause them, are poorly understood. It is accepted that compressive strains can develop as oxygen and metal atoms meet to form new growth within constrained oxide. More controversial is the experimental finding that large tensile stresses, close to 1 GPa, develop during isothermal growth conditions in alumina TGO formed on a FeCrAlY alloy. Using a novel technique based on synchrotron radiation, we have confirmed these previous results, and show that the tensile strain develops as the early oxide, (Fe,Cr,Al)(2)O(3), converts to alpha-Al2O3 during the growth process. This allows us to model the strain behaviour by including creep and this diffusion-controlled phase change. PMID:16604078

  15. Large-amplitude internal waves benefit corals during thermal stress.

    PubMed

    Wall, M; Putchim, L; Schmidt, G M; Jantzen, C; Khokiattiwong, S; Richter, C

    2015-01-22

    Tropical scleractinian corals are particularly vulnerable to global warming as elevated sea surface temperatures (SSTs) disrupt the delicate balance between the coral host and their algal endosymbionts, leading to symbiont expulsion, mass bleaching and mortality. While satellite sensing of SST has proved a reliable predictor of coral bleaching at the regional scale, there are large deviations in bleaching severity and mortality on the local scale that are poorly understood. Here, we show that internal waves play a major role in explaining local coral bleaching and mortality patterns in the Andaman Sea. Despite a severe region-wide SST anomaly in May 2010, frequent upslope intrusions of cold sub-pycnocline waters due to breaking large-amplitude internal waves (LAIW) mitigated coral bleaching and mortality in shallow waters. In LAIW-sheltered waters, by contrast, bleaching-susceptible species suffered severe bleaching and total mortality. These findings suggest that LAIW benefit coral reefs during thermal stress and provide local refugia for bleaching-susceptible corals. LAIW are ubiquitous in tropical stratified waters and their swash zones may thus be important conservation areas for the maintenance of coral diversity in a warming climate. Taking LAIW into account can significantly improve coral bleaching predictions and provide a valuable tool for coral reef conservation and management. PMID:25473004

  16. Prior stress exposure increases pain behaviors in a rat model of full thickness thermal injury.

    PubMed

    Nyland, Jennifer E; McLean, Samuel A; Averitt, Dayna L

    2015-12-01

    Thermal burns among individuals working in highly stressful environments, such as firefighters and military Service Members, are common. Evidence suggests that pre-injury stress may exaggerate pain following thermal injury; however current animal models of burn have not evaluated the potential influence of pre-burn stress. This sham-controlled study evaluated the influence of prior stress exposure on post-burn thermal and mechanical sensitivity in male Sprague-Dawley rats. Rats were exposed to 20 min of inescapable swim stress or sham stress once per day for three days. Exposure to inescapable swim stress (1) increased the intensity and duration of thermal hyperalgesia after subsequent burn and (2) accelerated the onset of thermal hyperalgesia and mechanical allodynia after subsequent burn. This stress-induced exacerbation of pain sensitivity was reversed by pretreatment and concurrent treatment with the serotonin-norepinephrine reuptake inhibitor (SNRI) duloxetine. These data suggest a better understanding of mechanisms by which prior stress augments pain after thermal burn may lead to improved pain treatments for burn survivors. PMID:26432505

  17. Interfacial stress in a carbon-to-metal bond joint under thermal shock loading

    SciTech Connect

    You, J.H.

    1998-02-01

    The duplex bond joint consisting of a metallic substrate armored with carbon-base materials is a promising candidate configuration for application to high heat flux operations. When a bond joint is subjected to thermal loadings, significant thermal stresses may develop due to mismatch of the thermal expansion coefficients. Stress intensification occurs near the free surface edge of the interface, sometimes showing singularity. The singular stress fields are critical for understanding the loading nature of the bond interface in a joint system. In this paper, thermal stresses in the bond interface of a carbon-to-molybdenum joint element were investigated. A high heat flux (HHF) pulse was assumed as the reference load history to simulate the thermal shock condition. The thermomechanical behavior was described quantitatively in terms of the stress intensity factor. The stress solutions of the singular field computed by the theoretical approach showed a good agreement with the numerical results of the finite element analysis. The stress intensity factor of the singular stress fields near the free surface edge of the interface showed a time variation similar to that of the bulk stress. The temperature gradient induced by the transient HHF load affected the overall interfacial stress only slightly.

  18. Estimation of thermal stress in concentrator cells using structural mechanics simulation

    NASA Astrophysics Data System (ADS)

    Ota, Yasuyuki; Nishioka, Kensuke

    2014-09-01

    Under the concentration conditions, it is important to manage the operating temperature of a concentrator photovoltaic (CPV) module, because a high-density solar energy enters into the solar cell. The estimation of operating temperature and mechanical stress is important for the solution of failure mechanisms. We estimated the operating temperature and thermal stress of the CPV module using structural mechanics simulation. In the case of the non-uniform light condition, inhomogeneous temperature distribution was generated in the solar cell and the highest thermal stress at the center of the finger electrode was observed. In the case of uniform light condition, the maximum temperature and thermal stress were suppressed. The developed model can be applied to the design optimization of CPV module which achieves low operating temperature and low thermal stress.

  19. Effect of Thermal Stresses Along Crack Surface on Ultrasonic Response

    SciTech Connect

    Virkkunen, I.; Haenninen, H.; Kemppainen, M.; Pitkaenen, J.

    2004-02-26

    Artificial flaws can be manufactured by controlled thermal fatigue loading. The produced cracks can be introduced to a wide variety of materials. This technology gives also a unique opportunity to monitor the ultrasonic response of a crack during thermal loading. This paper reports studies on the effects of different thermal load cycles on the ultrasonic response. The loads are analyzed with FEM. Two cracked samples were loaded with different thermal load cycles.

  20. Free vibrations of thermally stressed orthotropic plates with various boundary conditions

    NASA Technical Reports Server (NTRS)

    Bailey, C. D.; Greetham, J. C.

    1973-01-01

    An analytical investigation of the vibrations of thermally stressed orthotropic plates in the prebuckled region is presented. The investigation covers the broad class of trapezoidal plates with two opposite sides parallel. Each edge of the plate may be subjected to different uniform boundary conditions. variable thickness and arbitrary temperature distributions (analytical or experimental) for any desired combination of boundary conditions may be prescribed. Results obtained using this analysis are compared to experimental results obtained for isotropic plates with thermal stress, and to results contained in the literature for orthotropic plates without thermal stress. Good agreement exists for both sets of comparisons.

  1. Environmental and societal consequences of a possible CO/sub 2/-induced climate change. Volume II, Part 9. Alleviation of environmental stress on renewable resource productivity

    SciTech Connect

    Howell, G. S.

    1982-09-01

    It is pointed out that temperature and water stress are the key factors that will be influenced by a rise in ambient CO/sub 2/ concentration. Improvement of the capacity of crop plants to withstand water and temperature stress will require an undergirding effort in basic research, to support required advances in plant breeding and development of novel crop management systems. The most important considerations for future research on environmental stress in crops are: the need for interdisciplinary approaches in all aspects of stress research; the need for centralized stress testing capabilities; plant-breeding, the long-term solution with greatest potential benefit and least cost; improvement in management techniques, becoming more effective as increased attention is directed to the management of specific genotypes; the need for understanding of more stress effects closer to the optimum than to lethality; the need to optimize rather than maximize production; the need for understanding different stress effects during different, critical developmental stages; the need for development of usable, physiologically-based crop models to serve as predictive tools for agronomists and breeders; the recognition that improvement options in annual crops are greater than in perennial crops; efforts to culture perennial crops as annuals as a means of avoiding winter stress; and the need for a major effort to devise techniques to shorten the breeding cycle in perennials so that genetic solutions can be more readily employed.

  2. Simplified micromechanical equations for thermal residual stress analysis of coated fiber composites

    NASA Technical Reports Server (NTRS)

    Naik, R. A.

    1991-01-01

    The fabrication of metal matrix composites poses unique problems to the materials engineer. The large thermal expansion coefficient (CTE) mismatch between the fiber and matrix leads to high tensile residual stresses at the fiber/matrix (F/M) interface which could lead to premature matrix cracking during cooldown. Fiber coatings could be used to reduce thermal residual stresses. A simple closed form analysis, based on a three phase composite cylinder model, was developed to calculate thermal residual stresses in a fiber/interphase/matrix system. Parametric studies showed that the tensile thermal residual stresses at the F/M interface were very sensitive to the CTE and thickness of the interphase layer. The modulus of the layer had only a moderate effect on tensile residual stresses. For a silicon carbide titanium aluminide composite, the tangential stresses were 20 to 30 pct. larger than the axial stresses, over a wide range of interphase layer properties, indicating a tendency to form radial matrix cracks during cooldown. Guidelines for the selection of appropriate material properties of the fiber coating were also derived in order to minimize thermal residual stresses in the matrix during fabrication.

  3. Simplified micromechanical equations for thermal residual stress analysis of coated fiber composites

    NASA Technical Reports Server (NTRS)

    Naik, Rajiv A.

    1992-01-01

    The fabrication of metal matrix composites poses unique problems to the materials engineer. The large thermal expansion coefficient mismatch between the fiber and matrix leads to high tensile residual stresses at the fiber/matrix interface which could lead to premature matrix cracking during cooldown. Fiber coating could be used to reduce thermal residual stresses. A simple closed-form analysis, based on a three-phase composite cylinder model, was developed to calculate thermal residual stresses in a fiber/interface/matrix system. Guidelines, in the form of simple equations, for the selection of appropriate material properties of the fiber coating, were also derived to minimize thermal residual stresses in the matrix during fabrication.

  4. Micromechanics analysis of space simulated thermal deformations and stresses in continuous fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Bowles, David E.

    1990-01-01

    Space simulated thermally induced deformations and stresses in continuous fiber reinforced composites were investigated with a micromechanics analysis. The investigation focused on two primary areas. First, available explicit expressions for predicting the effective coefficients of thermal expansion (CTEs) for a composite were compared with each other, and with a finite element (FE) analysis, developed specifically for this study. Analytical comparisons were made for a wide range of fiber/matrix systems, and predicted values were compared with experimental data. The second area of investigation focused on the determination of thermally induced stress fields in the individual constituents. Stresses predicted from the FE analysis were compared to those predicted from a closed-form solution to the composite cylinder (CC) model, for two carbon fiber/epoxy composites. A global-local formulation, combining laminated plate theory and FE analysis, was used to determine the stresses in multidirectional laminates. Thermally induced damage initiation predictions were also made.

  5. Thermal stresses in the wall of pipes caused by periodic change of temperature of medium fluid

    NASA Astrophysics Data System (ADS)

    Atefi, Gholamali; Mahmoudi, Hamid

    2012-06-01

    The problem of thermal stresses induced in pipes due to periodic change of medium fluid temperature has never been considered completely. In this paper an analytical solution for obtaining thermal stresses in a pipe caused by periodic time varying of temperature of medium fluid is offered. Transient heat conduction equation in cylindrical coordinates for a long hollow cylinder under periodic change of ambient temperature condition is solved analytically using Fourier series and Temperature distribution in the wall of pipe as a function of time and radial direction is specified. Then resulting thermal stresses are obtained using thermoelasticity relations. Because of the use of Fourier series expansion in obtaining the transient temperature field the proposed method is very comprehensive and covers many theoretical and practical problems. The results for thermal stresses have been compared with former works and show excellent agreement for the same conditions.

  6. Thermal stress analysis of the NASA Dryden hypersonic wing test structure

    NASA Technical Reports Server (NTRS)

    Morris, Glenn

    1990-01-01

    Present interest in hypersonic vehicles has resulted in a renewed interest in thermal stress analysis of airframe structures. While there are numerous texts and papers on thermal stress analysis, practical examples and experience on light gage aircraft structures are fairly limited. A research program has been undertaken at General Dynamics to demonstrate the present state of the art, verify methods of analysis, gain experience in their use, and develop engineering judgement in thermal stress analysis. The approach for this project has been to conduct a series of analyses of this sample problem and compare analysis results with test data. This comparison will give an idea of how to use our present methods of thermal stress analysis, and how accurate we can expect them to be.

  7. SO2 protects the amino nitrogen metabolism of Saccharomyces cerevisiae under thermal stress

    PubMed Central

    Ancín‐Azpilicueta, Carmen; Barriuso‐Esteban, Blanca; Nieto‐Rojo, Rodrigo; Aristizábal‐López, Nerea

    2012-01-01

    Summary Thermal stress conditions during alcoholic fermentation modify yeasts' plasma membrane since they become more hyperfluid, which results in a loss of bilayer integrity. In this study, the influence of elevated temperatures on nitrogen metabolism of a Saccharomyces cerevisiae strain was studied, as well as the effect of different concentrations of SO2 on nitrogen metabolism under thermal stress conditions. The results obtained revealed that amino nitrogen consumption was lower in the fermentation sample subjected to thermal stress than in the control, and differences in amino acid consumption preferences were also detected, especially at the beginning of the fermentation. Under thermal stress conditions, among the three doses of SO2 studied (0, 35, 70 mg l−1 SO2), the highest dose was observed to favour amino acid utilization during the fermentative process, whereas sugar consumption presented higher rates at medium doses. PMID:22452834

  8. Three-phase inclusions of arbitrary shape with internal uniform hydrostatic thermal stresses

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Chen, Weiqiu

    2013-08-01

    We investigate the internal thermal stress field of a three-phase inclusion of arbitrary shape which is bonded to an infinite matrix through an interphase layer. The three phases have different thermoelastic constants. It is found that the internal thermal stress field induced by a uniform change in temperature can be uniform and hydrostatic within an inclusion of elliptical or hypotrochoidal shape when the thickness of the interphase layer is properly designed for given material parameters of the three-phase composite. Several examples are presented to demonstrate the solution. The thermal stress analysis of a ( Q + 2)-phase inclusion of arbitrary shape with Q ≥ 2 is also carried out under the assumption that all the phases except the internal inclusion share the same elastic constants. It is found that the irregular inclusion shape permitting internal uniform hydrostatic thermal stresses becomes really arbitrary if a sufficiently large number of interphase layers are added between the inclusion and the matrix.

  9. Regulation of bovine pyruvate carboxylase mRNA and promoter expression by thermal stress.

    PubMed

    White, H M; Koser, S L; Donkin, S S

    2012-09-01

    Pyruvate carboxylase (PC) catalyzes the rate-limiting step in gluconeogenesis from lactate and is a determinant of tricarboxylic acid cycle carbon flux. Bovine PC 5' untranslated region (UTR) mRNA variants are the products of a single PC gene containing 3 promoter regions (P3, P2, and P1, 5' to 3') that are responsive to physiological and nutritional stressors. The objective of this study was to determine the direct effects of thermal stress on PC mRNA and gene expression in bovine hepatocyte monolayer cultures, rat hepatoma (H4IIE) cells, and Madin-Darby bovine kidney epithelial (MDBK) cells. Hepatocytes were isolated from 3 Holstein bull calves and used to prepare monolayer cultures. Rat hepatoma cells and MDBK cells were obtained from American Type Culture Collection, Manassas, VA. Beginning 24 h after initial seeding, cells were subjected to either 37°C (control) or 42°C (thermal stress) for 24 h. Treatments were applied in triplicate in a minimum of 3 independent cell preparations. For bovine primary hepatocytes, endogenous expression of bovine PC mRNA increased (P < 0.1) with 24 h of thermal stress (1.31 vs. 2.79 ± 0.49, arbitrary units, control vs. thermal stress, respectively), but there was no change (P ≥ 0.1) in cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) mRNA expression. Similarly, exposure of MDBK cells to thermal stress increased (P < 0.1) expression of bovine PC mRNA without altering (P ≥ 0.1) PEPCK-C mRNA expression. Conversely, there was no effect (P ≥ 0.1) of thermal stress on endogenous rat PC (0.47 vs. 0.30 ± 0.08, control vs. thermal stress) or PEPCK-C (1.61 vs. 1.20 ± 0.48, arbitrary units, control vs. thermal stress, respectively) mRNA expressions in H4IIE cells. To further investigate the regulation of PC, H4IIE cells were transiently transfected with bovine promoter-luciferase constructs containing either P1, P2, or P3, and exposed to thermal stress for 23 h. Activity of P1 was suppressed (P < 0.1) 5-fold, activity of P2

  10. Thermal surface free energy and stress of iron

    NASA Astrophysics Data System (ADS)

    Schönecker, Stephan; Li, Xiaoqing; Johansson, Börje; Kwon, Se Kyun; Vitos, Levente

    2015-10-01

    Absolute values of surface energy and surface stress of solids are hardly accessible by experiment. Here, we investigate the temperature dependence of both parameters for the (001) and (110) surface facets of body-centered cubic Fe from first-principles modeling taking into account vibrational, electronic, and magnetic degrees of freedom. The monotonic decrease of the surface energies of both facets with increasing temperature is mostly due to lattice vibrations and magnetic disorder. The surface stresses exhibit nonmonotonic behaviors resulting in a strongly temperature dependent excess surface stress and surface stress anisotropy.

  11. Laser welding of low carbon steel and thermal stress analysis

    NASA Astrophysics Data System (ADS)

    Yilbas, B. S.; Arif, A. F. M.; Abdul Aleem, B. J.

    2010-07-01

    Laser welding of mild steel sheets is carried out under nitrogen assisting gas ambient. Temperature and stress fields are computed in the welding region through the finite element method. The residual stress developed in the welding region is measured using the XRD technique and the results are compared with the predictions. Optical microscopy and the SEM are used for the metallurgical examination of the welding sites. It is found that von Mises stress attains high values in the cooling cycle after the solidification of the molten regions. The residual stress predicted agreed well with the XRD results.

  12. Thermal stresses and deflections of cross-ply laminated plates using refined plate theories

    SciTech Connect

    Khdeir, A.A.; Reddy, J.N. Virginia Polytechnic Institute and State University, Blacksburg )

    1991-12-01

    Exact analytical solutions of refined plate theories are developed to study the thermal stresses and deflections of cross-ply rectangular plates. The state-space approach in conjunction with the Levy method is used to solve exactly the governing equations of the theories under various boundary conditions. Numerical results of the higher-order theory of Reddy for thermal stresses and deflections are compared with those obtained using the classical and first-order plate theories. 14 refs.

  13. Finite element modeling of the effect of interface anomalies on thermal stresses in alumina scales

    SciTech Connect

    Wright, J.K.; Williamson, R.L.; Hou, P.Y.; Cannon, R.M.; Renusch, D.; Veal, B.; Grimsditch, M.

    1998-07-01

    The scales that grow from oxidation often develop a convoluted morphology or interface pores. High thermal stresses can develop locally and are potentially detrimental to the scale or interface integrity. Finite element simulations are used to examine residual thermal stresses and strains that result when these deviations from a flat interface have formed, and the resulting geometry is subsequently cooled to room temperature. A variety of geometries will be considered for alumina scales on a FeCrAl substrate.

  14. Finite element modeling of the effect of interface anomalies on thermal stresses in alumina scales.

    SciTech Connect

    Wright, J. K.

    1998-06-10

    The scales that grow from oxidation often develop a convoluted morphology or interface pores. High thermal stresses can develop locally and are potentially detrimental to the scale or interface integrity. Finite element simulations are used to examine residual thermal stresses and strains that result when these deviations from a flat interface have formed, and the resulting geometry is subsequently cooled to room temperature. A variety of geometries will be considered for alumina scales on a FeCrAl substrate.

  15. Thermal-stress modeling of an optical microphone at high temperature.

    SciTech Connect

    Barnard, Casey Anderson

    2010-08-01

    To help determine the capability range of a MEMS optical microphone design in harsh conditions computer simulations were carried out. Thermal stress modeling was performed up to temperatures of 1000 C. Particular concern was over stress and strain profiles due to the coefficient of thermal expansion mismatch between the polysilicon device and alumina packaging. Preliminary results with simplified models indicate acceptable levels of deformation within the device.

  16. Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium) from Corals

    PubMed Central

    Fujise, Lisa; Yamashita, Hiroshi; Suzuki, Go; Sasaki, Kengo; Liao, Lawrence M.; Koike, Kazuhiko

    2014-01-01

    The foundation of coral reef biology is the symbiosis between corals and zooxanthellae (dinoflagellate genus Symbiodinium). Recently, coral bleaching, which often results in mass mortality of corals and the collapse of coral reef ecosystems, has become an important issue around the world as coral reefs decrease in number year after year. To understand the mechanisms underlying coral bleaching, we maintained two species of scleractinian corals (Acroporidae) in aquaria under non-thermal stress (27°C) and moderate thermal stress conditions (30°C), and we compared the numbers and conditions of the expelled Symbiodinium from these corals. Under non-thermal stress conditions corals actively expel a degraded form of Symbiodinium, which are thought to be digested by their host coral. This response was also observed at 30°C. However, while the expulsion rates of Symbiodinium cells remained constant, the proportion of degraded cells significantly increased at 30°C. This result indicates that corals more actively digest and expel damaged Symbiodinium under thermal stress conditions, likely as a mechanism for coping with environmental change. However, the increase in digested Symbiodinium expulsion under thermal stress may not fully keep up with accumulation of the damaged cells. There are more photosynthetically damaged Symbiodinium upon prolonged exposure to thermal stress, and corals release them without digestion to prevent their accumulation. This response may be an adaptive strategy to moderate stress to ensure survival, but the accumulation of damaged Symbiodinium, which causes subsequent coral deterioration, may occur when the response cannot cope with the magnitude or duration of environmental stress, and this might be a possible mechanism underlying coral bleaching during prolonged moderate thermal stress. PMID:25493938

  17. Pre-storage application of oxalic acid alleviates chilling injury in mango fruit by modulating proline metabolism and energy status under chilling stress.

    PubMed

    Li, Peiyan; Zheng, Xiaolin; Liu, Yan; Zhu, Yuyan

    2014-01-01

    Effects of oxalic acid on chilling injury, proline metabolism and energy status in mango fruit were investigated after mango fruit (Mangifera indica L. cv. Zill) were dipped in 5mM oxalic acid solution for 10min at 25°C and then stored at low temperature (10±0.5°C) for 49days thereafter transferred to 25°C for 4days. Pre-storage application of oxalic acid apparently inhibited the development of chilling injury, notably elevated proline accumulation actually associated with increase in Δ(1)-pyrroline-5-carboxylate synthetase (P5CS) activity and decrease in proline dehydrogenase (PDH) activity in the peel and the flesh, without activation of ornithine-δ-aminotransferase (OAT) activity, and maintained high ATP level and energy charge in the flesh during storage. It was suggested that these effects of oxalic acid might collectively contribute to improving chilling tolerance, thereby alleviating chilling injury and maintaining quality of mango fruit in long term cold storage. PMID:24001814

  18. Effects of melatonin on the proliferation and apoptosis of sheep granulosa cells under thermal stress.

    PubMed

    Fu, Yao; He, Chang-Jiu; Ji, Peng-Yun; Zhuo, Zhi-Yong; Tian, Xiu-Zhi; Wang, Feng; Tan, Dun-Xian; Liu, Guo-Shi

    2014-01-01

    The cross-talk between oocyte and somatic cells plays a crucial role in the regulation of follicular development and oocyte maturation. As a result, granulosa cell apoptosis causes follicular atresia. In this study, sheep granulosa cells were cultured under thermal stress to induce apoptosis, and melatonin (MT) was examined to evaluate its potential effects on heat-induced granulosa cell injury. The results demonstrated that the Colony Forming Efficiency (CFE) of granulosa cells was significantly decreased (heat 19.70% ± 1.29% vs. control 26.96% ± 1.81%, p < 0.05) and the apoptosis rate was significantly increased (heat 56.16% ± 13.95% vs. control 22.80% ± 12.16%, p < 0.05) in granulosa cells with thermal stress compared with the control group. Melatonin (10⁻⁷ M) remarkably reduced the negative effects caused by thermal stress in the granulosa cells. This reduction was indicated by the improved CFE and decreased apoptotic rate of these cells. The beneficial effects of melatonin on thermal stressed granulosa cells were not inhibited by its membrane receptor antagonist luzindole. A mechanistic exploration indicated that melatonin (10⁻⁷ M) down-regulated p53 and up-regulated Bcl-2 and LHR gene expression of granulosa cells under thermal stress. This study provides evidence for the molecular mechanisms of the protective effects of melatonin on granulosa cells during thermal stress. PMID:25405739

  19. Thermal stress analyses of multilayered films on substrates and cantilever beams for micro sensors and actuators

    SciTech Connect

    Hsueh, Chun-Hway; Luttrell, Claire Roberta; Cui, Tianhong

    2006-01-01

    Thermal stress-induced damage in multilayered films formed on substrates and cantilever beams is a major reliability issue for the fabrication and applications of micro sensors and actuators. Using closed-form predictive solutions for thermal stresses in multilayered systems, specific results are calculated for the thermal stresses in PZT/Pt/Ti/SiO2/Si3N4/SiO2 film layers on Si substrates and PZT/Pt/Ti/SiO2 film layers on Si3N4 cantilever beams. When the thickness of the film layer is negligible compared to the substrate, thermal stresses in each film layer are controlled by the thermomechanical mismatch between the individual film layer and the substrate, and the modification of thermal stresses in each film layer by the presence of other film layers is insignificant. On the other hand, when the thickness of the film layer is not negligible compared to the cantilever beam, thermal stresses in each film layer can be controlled by adjusting the properties and thickness of each layer. The closed-form solutions provide guidelines for designing multilayered systems with improved reliability.

  20. Determination of Creep Behavior of Thermal Barrier Coatings Under Laser Imposed High Thermal and Stress Gradient Conditions

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1999-01-01

    A laser sintering/creep technique has been established to determine the creep behavior of thermal barrier coatings under steady-state high heat flux conditions. For a plasma sprayed zirconia-8 wt. % yttria coating, a significant primary creep strain and a low apparent creep activation energy were observed. Possible creep mechanisms involved include stress induced mechanical sliding and temperature and stress enhanced cation diffusion through the splat and grain boundaries. The elastic modulus evolution, stress response, and total accumulated creep strain variation across the ceramic coating are simulated using a finite difference approach. The modeled creep response is consistent with experimental observations.

  1. A comparison of measured and calculated thermal stresses in a hybrid metal matrix composite spar cap element

    NASA Technical Reports Server (NTRS)

    Jenkins, J. M.; Taylor, A. H.; Sakata, I. F.

    1985-01-01

    A hybrid spar of titanium with an integrally brazed composite, consisting of an aluminum matrix reinforced with boron-carbide-coated fibers, was heated in an oven and the resulting thermal stresses were measured. Uniform heating of the spar in an oven resulted in thermal stresses arising from the effects of dissimilar materials and anisotropy of the metal matrix composite. Thermal stresses were calculated from a finite element structural model using anisotropic material properties deduced from constituent properties and rules of mixtures. Comparisons of calculated thermal stresses with measured thermal stresses on the spar are presented. It was shown that failure to account for anisotropy in the metal matrix composite elements would result in large errors in correlating measured and calculated thermal stresses. It was concluded that very strong material characterization efforts are required to predict accurate thermal stresses in anisotropic composite structures.

  2. Experimental determination of thermal and adhesion stress in particle filled thermoplasts

    SciTech Connect

    Vollenberg, P.; Heikens, D.; Ladan, H.C.B.

    1988-12-01

    The phenomena of dewetting in filled thermoplastics were studied by light microscopy and were correlated with variations in the slope of stress-strain diagrams in constant strain rate tests. In such diagrams, kinks in the plots were found to correspond to the dewetting stress. The corresponding local stress at a filler particle is then equal to the sum of the thermal compressive stress and the adhesion stress. It was shown that the adhesion stress was proportional to the reciprocal root of the particle radius. Also, values of dewetting stress predicted for inorganic particles with radii smaller than 2-4 micrometers are higher than the stresses at which crazes and shear-bands are formed near such particles, indicating that dewetting will not occur in those cases, and adhesion aids may be superfluous. 10 references.

  3. High intensity acoustic tests of a thermally stressed aluminum plate in TAFA

    NASA Technical Reports Server (NTRS)

    Ng, Chung Fai; Clevenson, Sherman A.

    1989-01-01

    An investigation was conducted in the Thermal Acoustic Fatigue Apparatus at the Langley Research Center to study the acoustically excited random motion of an aluminum plate which is buckled due to thermal stresses. The thermal buckling displacements were measured and compared with theory. The general trends of the changes in resonances frequencies and random responses of the plate agree with previous theoretical prediction and experimental results for a mechanically buckled plate.

  4. Compressional stress effect on thermal conductivity of powdered materials: Measurements and their implication to lunar regolith

    NASA Astrophysics Data System (ADS)

    Sakatani, Naoya; Ogawa, Kazunori; Iijima, Yu-ichi; Arakawa, Masahiko; Tanaka, Satoshi

    2016-03-01

    Thermal conductivity of powdered materials under vacuum conditions is a valuable physical parameter in the context of planetary sciences. We report results of thermal conductivity measurements of 90-106 μm and 710-1000 μm glass beads, and lunar regolith simulant using two different experimental setups for varying the compressional stress and the temperature, respectively. We found the thermal conductivity increase with the compressional stress, for example, from 0.003 to 0.008 W m-1 K-1 for the glass beads of 90-106 μm in diameter at the compressional stress less than 20 kPa. This increase of the thermal conductivity is attributed the areal enlargement of the contacts between particles due to their elastic deformation. The thermal conductivity increased also with temperature, which primarily represented enhancement of the radiative heat conduction between particles. Reduction of the estimated radiative conductivity from the effective thermal conductivity obtained in the first experiment yields the relation between the solid conductivity (conductive contribution through inter-particle contacts) and the compressional stress. We found that the solid conductivity is proportional to approximately 1/3 power of the compressional stress for the glass beads samples, while the regolith simulant showed a weaker exponent than that of the glass beads. We developed a semi-empirical expression of the thermal conductivity of the lunar regolith using our data on the lunar regolith simulant. This model enabled us to estimate a vertical distribution of the lunar subsurface thermal conductivity. Our model provides an examination for the density and compressional stress relationships to thermal conductivity observed in the in-situ measurements in Apollo 15 and 17 Heat Flow Experiments.

  5. Biogenic amines and acute thermal stress in the rat

    NASA Technical Reports Server (NTRS)

    Williams, B. A.; Moberg, G. P.

    1975-01-01

    A study is summarized which demonstrates that depletion of the biogenic amines 5-hydroxytryptamine (5-HT) or norepinephrine (NE) alters the normal thermoregulatory responses to acute temperature stress. Specifically, NE depletion caused a significant depression in equilibrium rectal temperature at 22 C and a greater depression in rectal temperature than controls in response to cold (6 C) stress; NE depletion also resulted in a significantly higher rectal temperature response to acute heat (38 C) stress. Depletion of 5-HT had less severe effects. It remains unclear whether the primary site of action of these agents is central or peripheral.

  6. Pinus densiflora Sieb. et Zucc. Alleviates Lipogenesis and Oxidative Stress during Oleic Acid-Induced Steatosis in HepG2 Cells

    PubMed Central

    Hwang, Yu-Jin; Wi, Hae-Ri; Kim, Haeng-Ran; Park, Kye Won; Hwang, Kyung-A

    2014-01-01

    Excess accumulation of lipids and oxidative stress in the liver contribute to nonalcoholic fatty liver disease (NAFLD). We hypothesized that Pinus densiflora Sieb. et Zucc. (PSZ) can protect against NAFLD by regulating lipid accumulation and oxidative stress in the liver. To investigate the effect of PSZ upon NAFLD, we used an established cellular model: HepG2 cells treated with oleic acid. Then, the extent of hepatic steatosis and oxidative stress was assessed and levels of inflammatory markers measured. Oleic acid-treated HepG2 cells, compared with controls, had greater lipid accumulation. PSZ decreased lipid accumulation by 63% in oleic acid-treated HepG2 cells. Additionally, PSZ decreased the target gene expression of lipogenesis such as sterol regulatory element binding protein-1c, fatty acid synthase, stearoyl-CoA desaturase-1, diacylglycerol O-acyltransferase-1, and acetyl-CoA carboxylase-1 by 1.75, 6.0, 2.32, 1.93 and 1.81 fold, respectively. In addition, Oleic acid-treated HepG2 cells elicited extensive accumulation of tumor necrosis factor-α (TNFα) by 4.53 fold, whereas PSZ-treated cells decreased the expression of TNFα mRNA by 1.76 fold. PSZ significantly inhibited oxidative stress induced by reactive oxygen species. These results suggest that PSZ has effects on steatosis in vitro and further studies are needed in vivo to verify the current observations. PMID:25057104

  7. Stress analysis in thermal barrier coatings subjected to long-term exposure in simulated turbine conditions.

    SciTech Connect

    Nair, B. G.; Singh, J. P.; Grimsditch, M.; Ceramatec, Inc.

    2004-03-15

    In recent years, ruby fluorescence spectroscopy has been demonstrated as a powerful technique for monitoring residual stress evolution in the thermally grown oxide scale in thermal barrier coating (TBC) systems. The measured residual stresses, in turn, can be used to monitor evolution of damage in the coatings. Effective use of this technology for real-time damage monitoring requires the identification of trends in measured stresses that can be used as indicators of damage evolution. The present work focuses on studying the evolution of residual stresses in TBC systems during long-term exposure to turbine operating conditions. The coatings are electron beam physical vapor deposited (EBPVD) and atmospheric plasma sprayed (APS) zirconia. The stress evolution in both EBPVD and APS coatings is analytically modeled by an approach that takes into consideration contributions due to both thermal mismatch and oxide growth. Microstructural changes in the TBC system are correlated with measured stress trends through comparison with the modeled stresses. The stress measurements and modeling provide insight into failure modes and mechanisms, and to identify critical features in the measured stress data that can be used as indicators of failure in TBCs.

  8. Measurement and computation of thermal stresses in injection molding of amorphous and crystalline polymers

    NASA Astrophysics Data System (ADS)

    Farhoudi, Yalda

    1998-12-01

    An integrated experimental and theoretical study of the residual thermal stresses has been carried out. The final stress profiles along the thickness were measured in an amorphous and a semi-crystalline injection molded polymer using the layer removal technique. The two materials exhibited drastically distinct residual profiles. Furthermore, processing parameters such as melt and coolant temperatures, pressure history, and mold thickness were found to modify the profiles. In order to elucidate the findings, two models were derived. The two-dimensional free mold shrinkage model was developed to provide a rapid estimation of thermal stresses and the main features of their profile. A more complex model was developed by integrating the stress analysis with the simulation of the complete injection molding cycle by McKam. This model accounts for the fountain flow effect, the crystallization, and the PVT behavior of the material. With the help of the model predictions, explanations were provided for the occurrence of various regions in the residual stress profiles. Transitions or reversal of the regions under variable conditions or material properties were observed to be mainly determined by the ratio of the thermal to the pressure effects. Using these concepts, practical conclusions were drawn for controlling the residual stresses. As an alternative for optimization of injection molding with respect to residual stresses, inverse methods were developed to calculate the pressure history or the initial temperature distribution required to produce a prescribed residual stress distribution. These methods were tested using direct solutions with added errors and experimental stress data.

  9. Transient thermal stresses in a reinforced hollow disk or cylinder containing a radial crack

    NASA Technical Reports Server (NTRS)

    Tang, R.; Erdogan, F.

    1983-01-01

    The transient thermal stress problem in a hollow cylinder or a disk containing a radial crack is considered. It is assumed that the cylinder is reinforced on its inner boundary by a membrane which has thermoelastic constants different than those of the base material. The transient temperature, thermal stresses and the crack tip stress intensity factors are calculated in a cylinder which is subjected to a sudden change of temperature on the inside surface. The results are obtained for various dimensionless parameters and material constants. The special cases of the crack terminating at the cylinder-membrane interface and of the broken membrane are separately considered and some examples are given.

  10. Transient thermal stresses in a reinforced hollow disk or cylinder containing a radial crack

    NASA Technical Reports Server (NTRS)

    Tang, R.; Erdogan, F.

    1984-01-01

    The transient thermal stress problem in a hollow cylinder or a disk containing a radial crack is considered. It is assumed that the cylinder is reinforced on its inner boundary by a membrane which has thermoelastic constants different than those of the base material. The transient temperature, thermal stresses and the crack tip stress intensity factors are calculated in a cylinder which is subjected to a sudden change of temperature on the inside surface. The results are obtained for various dimensionless parameters and material constants. The special cases of the crack terminating at the cylinder-membrane interface and of the broken membrane are separately considered and some examples are given.

  11. Rock properties and their effect on thermally-induced displacements and stresses

    SciTech Connect

    Chan, T.; Hood, M.; Board, M.

    1980-02-01

    A discussion is given of the importance of material properties in the finite-element calculations for thermally induced displacements and stresses resulting from a heating experiment in an in-situ granitic rock, at Stripa, Sweden. Comparisons are made between field measurements and finite element method calculations using (1) temperature independent, (2) temperature dependent thermal and thermomechanical properties and (3) in-situ and laboratory measurements for Young's modulus. The calculations of rock displacements are influenced predominantly by the temperature dependence of the thermal expansion coefficient, whereas the dominant factor affecting predictions for rock stresses is the in-situ modulus.

  12. Rock properties and their effect on thermally induced displacements and stresses

    SciTech Connect

    Chan, T.; Mood, M.

    1982-12-01

    A discussion is given of the importance of material properties in the finite-element calculations for thermally induced displacements and stresses resulting from a heating experiment in an in-situ granitic rock, at Stripa, Sweden. Comparisons are made between field measurements and finite element method calculations using (i) temperature independent, (ii) temperature dependent thermal and thermomechanical properties, and (iii) in-situ and laboratory measurements for Young's modulus. The calculations of rock displacements are influenced predominantly by the temperature dependence of the thermal expansion coefficient, whereas the dominant factor affecting predictions or rock stresses is the in-situ modulus.

  13. Mapping Evaporative Stress at Continental Scales Using GOES Thermal Imagery

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Robust, operational methodologies for mapping daily evapotranspiration (ET), soil moisture, and moisture stress over large areas using satellite remote sensing will have widespread utility in applications such as drought detection, crop yield forecasting, irrigation scheduling, water resource manage...

  14. Analytical Predictions of Thermal Stress in the Stardust PICA Heatshield Under Reentry Flight Conditions

    NASA Technical Reports Server (NTRS)

    Squire, Thomas; Milos, Frank; Agrawal, Parul

    2009-01-01

    We performed finite element analyses on a model of the Phenolic Impregnated Carbon Ablator (PICA) heatshield from the Stardust sample return capsule (SRC) to predict the thermal stresses in the PICA material during reentry. The heatshield on the Stardust SRC was a 0.83 m sphere cone, fabricated from a single piece of 5.82 cm-thick PICA. The heatshield performed successfully during Earth reentry of the SRC in January 2006. Material response analyses of the full, axisymmetric PICA heatshield were run using the Two-Dimensional Implicit Ablation, Pyrolysis, and Thermal Response Program (TITAN). Peak surface temperatures were predicted to be 3385K, while the temperature at the PICA backface remained at the estimated initial cold-soak temperature of 278K. Surface recession and temperature distribution results from TITAN, at several points in the reentry trajectory, were mapped onto an axisymmetric finite element model of the heatshield. We used the finite element model to predict the thermal stresses in the PICA from differential thermal expansion. The predicted peak compressive stress in the PICA heatshield was 1.38 MPa. Although this level of stress exceeded the chosen design limit for compressive stresses in PICA tiles for the design of the Orion crew exploration vehicle heatshield, the Stardust heatshield exhibited no obvious mechanical failures from thermal stress. The analyses of the Stardust heatshield were used to assess and adjust the level of conservatism in the finite element analyses in support of the Orion heatshield design.

  15. Effect of Rotor Diameter on the Thermal Stresses of a Turbine Rotor Model

    NASA Astrophysics Data System (ADS)

    Dávalos, J. O.; García, J. C.; Urquiza, G.; Castro-Gómez, L. L.; Rodríguez, J. A.; De Santiago, O.

    2016-04-01

    Thermal stresses in a simplified steam turbine rotor model during a cold startup are analyzed using finite element analysis (FEA). In order to validate the numerical model, an experimental array is developed in which a hollow cylinder is heated with hot air in the external surface. At the thick wall of the cylinder, temperature distribution is measured in real time, while at the same time an algorithm computes thermal stresses. Additional computational fluid dynamics (CFD) calculations are made to obtain magnitudes of velocity and pressure in order to compute convective heat transfer coefficient. The experimental results show good agreement with the FEA computations. To evaluate the effect of rotor diameter size, FEA computations with variation in external and internal diameters are performed. Results show that thermal stresses are proportional to rotor diameter size. Also, zones of higher stress concentration are found in the external and internal surfaces of the rotor.

  16. Modeling of thermal stress development during the vacuum arc remelting process

    SciTech Connect

    Ali, Z.; Alam, M.K.; Semiatin, S.L.

    1995-12-31

    The development of thermal stresses during the vacuum arc remelting (VAR) process was investigated through numerical solution of the two-dimensional, non-steady state heat conduction and stress equilibrium equations. Solutions were obtained for various levels of input power efficiency, values of the crucible-ingot interface heat transfer coefficients, and lengths of the melted and resolidified ingot. Model predictions revealed that the maximum tensile thermal stresses are developed at the bottom of the ingot for cases involving low input power efficiency and high interface heat transfer coefficients. The predicted development of large tensile stresses at the mid-radius position correlates well with observations of thermal cracking during VAR of near-gamma titanium aluminide alloy ingots.

  17. Thermally induced stresses and deformations in angle-ply composite tubes

    NASA Technical Reports Server (NTRS)

    Hyer, M. W.; Rousseau, Carl Q.

    1987-01-01

    Cure-induced uniform temperature change effects on the stresses, axial expansion, and thermally-induced twist of four specific angle-ply tube designs are discussed with a view to the tubes' use as major space structure components. The stresses and deformations in the tubes are studied as a function of the four designs, the off-axis angle, and the single-material and hybrid reinforcing-material construction used. It is found that tube design has a minor influence on the stresses, axial stiffness, and axial thermal expansion characteristics, which are more directly a function of off-axis angle and material selection; tube design is, however, the primary influence in the definition of thermally-induced twist and torsional stiffness characteristics. None of the designs is free of thermally induced twist.

  18. Temperature propagation in prismatic lithium-ion-cells after short term thermal stress

    NASA Astrophysics Data System (ADS)

    Bohn, Pamina; Liebig, Gerd; Komsiyska, Lidiya; Wittstock, Gunther

    2016-05-01

    In this paper a 3D model based on the thermal material characteristics of an automotive prismatic Li-NiMnCoO2 (NMC) cell was created in COMSOL Multiphysics® in order to simulate the temperature propagation in the cell during short term thermal stress. The thermal characteristics of the battery components were experimentally determined via laser flash analysis (LFA) and differential scanning calorimetry (DSC) and used as an input parameter for the models. In order to validate the modelling approach, an experimental setup was built to measure the temperature propagation during thermal stresses within a dummy cell, equipped with temperature sensors. After validating, the model is used to describe the temperature propagation after a short-term temperature stress on automotive prismatic lithium-ion cells, simulating welding of the contact leads.

  19. Transient thermal stresses due to periodically moving line heat source of composite hollow cylinder

    SciTech Connect

    Chen, L.S.; Chu, H.S. )

    1990-01-01

    The transient thermal stress distribution of a finite composite hollow cylinder, which is heated by a periodically moving line source on its inner boundary and cooled convectively on the outer surface, is analyzed in this paper. The heat sources are assumed to be axisymmetric, moving along the axis of the hollow cylinder with constant velocity. To solve the temperature distribution of the hollow cylinder, the Laplace transform and eigenfunction expansion methods are used. The associated thermal stress distributions are then obtained by solving the thermoelastic displacement function and the Love function. Finally, a numerical scheme, the Fourier series technique, is utilized to calculate the inverse transform. The numerical results of the temperature and thermal stress distribution are presented, which demonstrate the effects of thermal conductivity ratio, shear modulus ratio, Biot number, and period of the moving heat source. 13 refs.

  20. Thymoquinone effectively alleviates lung fibrosis induced by paraquat herbicide through down-regulation of pro-fibrotic genes and inhibition of oxidative stress.

    PubMed

    Pourgholamhossein, Fatemeh; Sharififar, Fariba; Rasooli, Rokhsana; Pourgholi, Leyla; Nakhaeipour, Fatemeh; Samareh-Fekri, Hojjat; Iranpour, Maryam; Mandegary, Ali

    2016-07-01

    The potential preventive and therapeutic effects of thymoquinone (TQ) and its molecular mechanism were evaluated in paraquat (PQ)-induced pulmonary fibrosis in mice. TQ was administered orally at the doses of 20 and 40mg/kg during the course and after development of fibrosis. Pathological changes, expressions of genes involved in fibrogenesis, hydroxyproline (HP) and oxidative stress parameters were determined in the lung tissues. TQ dose-dependently recovered the pathological changes induced by PQ. TQ decreased hydroxyproline content, lipid peroxidation and restored the antioxidant enzymes to the normal values. In molecular level, expressions of TGF-β1, α-SMA, collagen 1a1 and collagen 4a1 genes were also returned to the control level by TQ. This study indicated that TQ has the preventive and therapeutic potentials for the treatment of lung fibrosis by inhibition of oxidative stress and down-regulation of profibrotic genes. PMID:27375216

  1. Proline over-accumulation alleviates salt stress and protects photosynthetic and antioxidant enzyme activities in transgenic sorghum [Sorghum bicolor (L.) Moench].

    PubMed

    Surender Reddy, P; Jogeswar, Gadi; Rasineni, Girish K; Maheswari, M; Reddy, Attipalli R; Varshney, Rajeev K; Kavi Kishor, P B

    2015-09-01

    Shoot-tip derived callus cultures of Sorghum bicolor were transformed by Agrobacterium tumefaciens as well as by bombardment methods with the mutated pyrroline-5-carboxylate synthetase (P5CSF129A) gene encoding the key enzyme for proline biosynthesis from glutamate. The transgenics were selfed for three generations and T4 plants were examined for 100 mM NaCl stress tolerance in pot conditions. The effect of salt stress on chlorophyll and carotenoid contents, photosynthetic rate, stomatal conductance, internal carbon dioxide concentration, transpiration rates, intrinsic transpiration and water use efficiencies, proline content, MDA levels, and antioxidant enzyme activities were evaluated in 40-day-old transgenic lines and the results were compared with untransformed control plants. The results show that chlorophyll content declines by 65% in untransformed controls compared to 30-38% loss (significant at P < 0.05) in transgenics but not carotenoid levels. Photosynthetic rate (PSII activity) was reduced in untransformed controls almost completely, while it declined by 62-88% in different transgenic lines. Salinity induced ca 100% stomatal closure in untransformed plants, while stomatal conductance was decreased only by 64-81% in transgenics after 4 days. The intercellular CO2 decreased by ca 30% in individual transgenic lines. Malondialdehyde (MDA) content was lower in transgenics compared to untransformed controls. The activities of superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6) and glutathione reductase (GR; EC1.8.1.7) were quantified in leaves exposed to 100 mM NaCl stress and found higher in transgenics. The results suggest that transgenic lines were able to cope better with salt stress than untransformed controls by protecting photosynthetic and antioxidant enzyme activities. PMID:26065619

  2. Mannitol alleviates chromium toxicity in wheat plants in relation to growth, yield, stimulation of anti-oxidative enzymes, oxidative stress and Cr uptake in sand and soil media.

    PubMed

    Adrees, Muhammad; Ali, Shafaqat; Iqbal, Muhammad; Aslam Bharwana, Saima; Siddiqi, Zeenat; Farid, Mujahid; Ali, Qasim; Saeed, Rashid; Rizwan, Muhammad

    2015-12-01

    Chromium (Cr) is one of the most phytotoxic metals in the agricultural soils and its concentration is continuously increasing mainly through anthropogenic activities. Little is known on the role of mannitol (M) on plant growth and physiology under metal stress. The aim of this study was to investigate the mechanism of growth amelioration and antioxidant enzyme activities in Cr-stressed wheat (Triticum aestivum L. cv. Lasani 2008) by exogenously applied mannitol. For this, wheat seedlings were sown in pots containing soil or sand and subjected to increasing Cr concentration (0, 0.25 and 0.5mM) in the form of of K2Cr2O7 with and without foliar application of 100mM mannitol. Plants were harvested after four months and data regarding growth characteristics, biomass, photosynthetic pigments, and antioxidant enzymes were recorded. Mannitol application increased plant biomass, photosynthetic pigments and antioxidant enzymes while decreased Cr uptake and accumulation in plants as compared to Cr treatments alone. In this study, we observed that M applied exogenously to Cr-stressed wheat plants, which normally cannot synthesize M, improved their Cr tolerance by increasing growth, photosynthetic pigments and enhancing activities of antioxidant enzymes and by decreasing Cr uptake and translocation in wheat plants. From this study, it can be concluded that M could be used to grow crops on marginally contaminated soils for which separate remediation techniques are time consuming and not cost effective. PMID:26164268

  3. Role of plant growth regulators and a saprobic fungus in enhancement of metal phytoextraction potential and stress alleviation in pearl millet.

    PubMed

    Firdaus-e-Bareen; Shafiq, Muhammad; Jamil, Sidra

    2012-10-30

    "Assisted phytoextraction" involving application of chemical additives such as plant growth regulators (PGRs) has become a trend in phytoremediation technology. This study identifies a cost-effective, naturally available crude PGR (PGR1) that produces the same effects as the commercial PGR (PGR2), increasing metal uptake by plants and the reduction of metal stress. Assisted phytoextraction by pearl millet (Pennisetum glaucum) from a multi-metal (Cd, Cr, Cu, Fe, Na and Zn) contaminated soil medium with tannery solid waste (TSW) soil amendments of 5 and 10%, was evaluated in a full-factorial pot trial with PGR1, PGR2 and Trichoderma pseudokoningii as factors. The effects of these phytoextraction assistants were measured through dry biomass production, heavy metal uptake, stress tolerance enzymes catalase (CAT) and superoxide dismutase (SOD), soluble protein content of plant, and phytoextraction efficiency. Dry biomass and multi-metal accumulation were the highest in the soil treatments with a combined application of PGR1, PGR2 and T. pseudokoningii and the lowest in the control. The soluble protein contents and the SOD and CAT values were the highest in the 10% TSW treatment provided with PGR2+T. pseudokoningii, while the lowest were in the control. Thus, application of crude PGR in combination with other phytoextraction assistants can increase biomass production as well as multi-metal accumulation in plants. However, the biochemical properties of the plant depend on the level of TSW stress in the soil treatment as well as the type of phytoextraction assistants. PMID:22959131

  4. Vitamin C modulates the metabolic and cytokine profiles, alleviates hepatic endoplasmic reticulum stress, and increases the life span of Gulo−/− mice

    PubMed Central

    Aumailley, Lucie; Warren, Alessandra; Garand, Chantal; Dubois, Marie Julie; Paquet, Eric R.; Le Couteur, David G.; Marette, André; Cogger, Victoria C.; Lebel, Michel

    2016-01-01

    Suboptimal intake of dietary vitamin C (ascorbate) increases the risk of several chronic diseases but the exact metabolic pathways affected are still unknown. In this study, we examined the metabolic profile of mice lacking the enzyme gulonolactone oxidase (Gulo) required for the biosynthesis of ascorbate. Gulo−/− mice were supplemented with 0%, 0.01%, and 0.4% ascorbate (w/v) in drinking water and serum was collected for metabolite measurements by targeted mass spectrometry. We also quantified 42 serum cytokines and examined the levels of different stress markers in liver. The metabolic profiles of Gulo−/− mice treated with ascorbate were different from untreated Gulo−/− and normal wild type mice. The cytokine profiles of Gulo−/− mice, in return, overlapped the profile of wild type animals upon 0.01% or 0.4% vitamin C supplementation. The life span of Gulo−/− mice increased with the amount of ascorbate in drinking water. It also correlated significantly with the ratios of serum arginine/lysine, tyrosine/phenylalanine, and the ratio of specific species of saturated/unsaturated phosphatidylcholines. Finally, levels of hepatic phosphorylated endoplasmic reticulum associated stress markers IRE1α and eIF2α correlated inversely with serum ascorbate and life span suggesting that vitamin C modulates endoplasmic reticulum stress response and longevity in Gulo−/− mice. PMID:26922388

  5. L-Theanine alleviates the neuropathological changes induced by PCB (Aroclor 1254) via inhibiting upregulation of inflammatory cytokines and oxidative stress in rat brain.

    PubMed

    Sumathi, Thangarajan; Asha, Deivasigamani; Nagarajan, Ganesan; Sreenivas, Arivazhagan; Nivedha, Rajendran

    2016-03-01

    The present study is aimed at evaluating the protective role of L-theanine on aroclor 1254-induced oxidative stress in rat brain. Intraperitoneal administration of Aroclor 1254 (2 mg/kg b.wt. for 30 days) caused oxidative stress in rat brain and also caused neurobehavioral changes. Oxidative stress was assessed by determining the levels of lipid peroxide (LPO), protein carbonyl content, and changes in activities of creatine kinase (CK), acetylcholinesterase (AchE), and ATPases in the hippocampus, cerebellum and cerebral cortex of control and experimental rats. Histopathological results showed that PCB caused neuronal loss in all three regions. PCB upregulated the mRNA expressions of inflammatory cytokines. Oral administration of L-theanine (200 mg/kg b.wt.) increased the status of antioxidants, decreased the levels of LPO, nitric oxide (NO) and increased the activities of CK, AchE and ATPases. L-Theanine restored normal architecture of brain regions and downregulated the expression of inflammatory cytokines. In conclusion, L-theanine shows a protective role against PCBs-induced oxidative damage in rat brain. PMID:26826962

  6. Small molecule compounds alleviate anisomycin-induced oxidative stress injury in SH-SY5Y cells via downregulation of p66shc and Aβ1–42 expression

    PubMed Central

    WANG, YUN; LIU, TE; PAN, WEIDONG; CHI, HUIYING; CHEN, JIULIN; YU, ZHIHUA; CHEN, CHUAN

    2016-01-01

    Oxidative stress and ageing are important factors contributing to the pathogenesis of Alzheimer's disease (AD), which is associated with neuronal damage and β-amyloid (Aβ) deposition. The p66shc adaptor protein is important for the regulation of oxidative stress and ageing. In the present study, SH-SY5Y human neuroblastoma cells were treated with anisomycin in order to establish a cell model of oxidative stress-induced neuronal damage. The results from quantitative polymerase chain reaction, enzyme-linked immunosorbent assay and western blotting demonstrated that anisomycin was able to stimulate the secretion of Aβ1–42 from SH-SY5Y cells and upregulate the expression levels of p66shc, which was associated with concomitant damage to SH-SY5Y cells. In addition, the protective effects of various small molecule compounds with antioxidant properties against neuronal damage were evaluated. Notably, treatment of SH-SY5Y cells with gallic acid was associated with significant downregulation of p66shc protein expression levels, reduced anisomycin-induced secretion of Aβ1–42, and increased superoxide dismutase activity and acetylcholine secretion levels. The results of the present study suggested that anisomycin is able to promote oxidative neuronal damage by inducing the secretion of Aβ1–42 from neurons and increasing the neuronal expression of p66shc, and this damage may be attenuated by treatment with gallic acid. Therefore, gallic acid and similar small molecule compounds may be considered for the alleviation of neuronal oxidative stress injury in patients with AD. PMID:26893652

  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. Thermal stress, human performance, and physical employment standards.

    PubMed

    Cheung, Stephen S; Lee, Jason K W; Oksa, Juha

    2016-06-01

    Many physically demanding occupations in both developed and developing economies involve exposure to extreme thermal environments that can affect work capacity and ultimately health. Thermal extremes may be present in either an outdoor or an indoor work environment, and can be due to a combination of the natural or artificial ambient environment, the rate of metabolic heat generation from physical work, processes specific to the workplace (e.g., steel manufacturing), or through the requirement for protective clothing impairing heat dissipation. Together, thermal exposure can elicit acute impairment of work capacity and also chronic effects on health, greatly contributing to worker health risk and reduced productivity. Surprisingly, in most occupations even in developed economies, there are rarely any standards regarding enforced heat or cold safety for workers. Furthermore, specific physical employment standards or accommodations for thermal stressors are rare, with workers commonly tested under near-perfect conditions. This review surveys the major occupational impact of thermal extremes and existing employment standards, proposing guidelines for improvement and areas for future research. PMID:27277564

  9. Granular chains for the assessment of thermal stress in slender structures

    NASA Astrophysics Data System (ADS)

    Bagheri, Abdollah; La Malfa Ribolla, Emma; Rizzo, Piervincenzo

    2015-03-01

    Slender beams subjected to compressive stress are common in civil and mechanical engineering. The rapid in-situ measurement of this stress may prevent structural anomalies. In this paper, we describe the coupling mechanism between highly nonlinear solitary waves (HNSWs) propagating along an L-shaped granular system and a beam in contact with the granular medium. We evaluate the use of HNSWs as a tool to measure stress in thermally loaded structures and to estimate the neutral temperature, i.e. the temperature at which this stress is null. We investigated numerically and experimentally one and two L-shaped chains of spherical particles in contact with a prismatic beam subjected to heat. We found that certain features of the solitary waves are affected by the beam's stress. In the future, these findings may help developing a novel sensing system for the nondestructive prediction of neutral temperature and thermal buckling.

  10. Thermal Stability of Residual Stresses in Ti-6Al-4V components

    NASA Astrophysics Data System (ADS)

    Stanojevic, A.; Angerer, P.; Oberwinkler, B.

    2016-03-01

    The need for light weight design while maintaining a high safety is essential for many components, especially in the aircraft industry. Therefore, it's important to consider every aspect to reduce weight, improve fatigue life and maintain safety of crucial components. Residual stresses are a major factor which can positively influence components and fulfil all three requirements. However, due to the inconstancy of the behaviour of residual stresses during the life time of a component, residual stresses are often neglected. If the behaviour of residual stresses could be described reliably over the entire life time of a component, residual stresses could be taken into account and components could be optimized even further. Mechanical and thermal loads are the main reason for relaxation of residual stresses. This work covers the thermal stability of residual stresses in Ti-6Al-4V components. Therefore, exposure tests at raised temperatures were performed on specimens with different surface conditions. Residual stresses were measured by x-ray diffraction before and after testing. Creep tests were also carried out to describe the creep behaviour and thereby the ability for residual stress relaxation. A correlation between the creep rate and amount of relaxed stress was found. The creep behaviour of the material was described by using a combination of the Norton Power law and the Arrhenius equation. The Zener-Wert-Avrami model was used to describe the residual stress relaxation. With these models a satisfying correlation between measured and calculated data was found. Hence, the relaxation of residual stresses due to thermal load was described reliably.

  11. Phase composition and residual stresses in thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Lozovan, A. A.; Betsofen, S. Ya; Ashmarin, A. A.; Ryabenko, B. V.; Ivanova, S. V.

    2016-07-01

    X-ray study of the phase composition and residual stresses distribution in two-layer APS coatings showed that the ceramic layer consists of t-ZrO2 phase with tetragonal lattice and the metal underlayer γ-solid solution based on nickel. In the transition zone thickness of ∼ 100 pm as the distance from the surface was revealed a gradual transition from t-ZrO2 to γ-solid solution. Increase in the specific volume of the metal underlayer resulting TGO growing leads to the formation of this layer high compressive stresses up to 600 MPa. In this case, the ceramic layer contains tensile stress up to 200 MPa.

  12. Control of Thermal Stress in Dendritic Web Growth

    NASA Technical Reports Server (NTRS)

    Seidensticker, R. G.; Schruben, J. S.

    1984-01-01

    The temperature distributions which are present during the growth of ribbon crystals generate stresses which can adversely affect the growth or perfection of the material. Several different effects occur which depend on the magnitude and distribution of these stresses. In most cases, the observed phenomena are the result of complex interactions of a number of mechanisms. In many instances, however, one mechanism predominates to such an extent that a simplified distinction between the various effects can be made. Definitions based on observed behavior in dendritic web growth are outlined.

  13. Thermal Stress Analysis of RCG-Tempered TUFI Tile TPS for Hypersonic Vehicles

    NASA Technical Reports Server (NTRS)

    Milos, Frank S.; Squire, Thomas H.

    1995-01-01

    This paper presents detailed results from linear and nonlinear finite-element thermal stress analyses of a new tile, Thermal Protection Systems (TPS) concept. A very thin coating of Reaction Cured Glass (RCG) is used to "temper" the surface of Toughened Uni-Piece Fibrous Insulation (TUFI) tiles to improve resistance to thermal shock and thermal cycling effects. The coating also serves to reduce catalytic heating and may improve waterproofing. Calculations include trajectory-based aerothermal heating environments for X-34 wing leading edge TPS designs and arc jet environments for TPS test articles. The nonlinear analyses include the high temperature plasticity of RCG to demonstrate the reuseability of the material.

  14. Thermal stress and the physiological response to environmental toxicants.

    PubMed

    Gordon, Christopher J; Leon, Lisa R

    2005-01-01

    Most toxicological and pharmacological studies are performed in laboratory animals maintained under comfortable environmental conditions. Yet, the exposure to environmental toxicants as well as many drugs can occur under stressful environmental conditions during rest or while exercising. The intake and biological efficacy of many toxicants is exacerbated by exposure to heat stress, which can occur in several ways. The increase in pulmonary ventilation during exposure to hot environments results in an increase in the uptake of airborne toxicants. Furthermore, the transcutaneous absorption of pesticides on the skin as well as drugs delivered by skin patches is increased during heat stress because of the combined elevation in skin blood flow coupled with moist skin from sweat. The thermoregulatory response to toxicant exposure, such as hypothermia in relatively small rodents and fever in humans, also modulates the physiological response to most chemical agents. This paper endeavors to review the issue of environmental heat stress and exercise and how they influence thermoregulatory and related pathophysiological responses to environmental toxicants, as well as exposure to drugs. PMID:16422347

  15. Discrimination of plant stress caused by oil pollution and waterlogging using hyperspectral and thermal remote sensing

    NASA Astrophysics Data System (ADS)

    Emengini, Ebele Josephine; Blackburn, George Alan; Theobald, Julian Charles

    2013-01-01

    Remote sensing of plant stress holds promise for detecting environmental pollution by oil. However, in oil-rich delta regions, waterlogging is a frequent source of plant stress that has similar physiological effects to oil pollution. This study investigated the capabilities of remote sensing for discriminating between these two sources of plant stress. Bean plants were subjected to oil pollution, waterlogging, and combined oil and waterlogging treatments. Canopy physiological, hyperspectral, and thermal measurements were taken every two to three days after treatment to follow the stress responses. For plants treated with oil, spectral and thermal responses were evident six days before symptoms could be observed visually. In waterlogged plants, only spectral responses were observed, but these were present up to eight days before visual symptoms. A narrowband reflectance ratio was efficient in detecting stress caused by oil and waterlogging. Canopy temperature and a thermal index were good indicators of oil and combined oil and waterlogging stress, but insensitive to waterlogging alone. Hence, this study provides evidence that combined hyperspectral and thermal remote sensing of vegetation has potential for monitoring oil pollution in environments that are also subjected to waterlogging.

  16. Thermal stress measurement in continuous welded rails using the hole-drilling method

    NASA Astrophysics Data System (ADS)

    Zhu, Xuan; Lanza di Scalea, Francesco; Fateh, Mahmood

    2016-04-01

    The absence of expansion joints in Continuous Welded Rail (CWR) has created the need for the railroad industry to determine the in-situ level of thermal stresses so as to prevent train accidents caused by rail buckling in hot weather and by rail breakage in cold weather. The development of non-destructive or semi-destructive methods for determining the level of thermal stresses in rails is today a high research priority. This study explores the known hole-drilling method as a possible solution to this problem. A new set of calibration coefficients to compute the relieved stress field with the finer hole depth increments was determined by a 3D Finite Element Analysis that modeled the entire hole geometry, including the mechanics of the hole bottom and walls. To compensate the residual stress components, a linear relationship was experimentally established between the longitudinal and the vertical residual stresses of two common sizes of rails, the 136RE and the 141RE, with statistical significance. This result was then utilized to isolate the longitudinal thermal stress component in hole-drilling tests conducted on the 136RE and 141RE thermally-loaded rails at the Large-scale CWR Test-bed of UCSD's Powell Research Laboratories. The results from the Test-bed showed that the hole-drilling procedure, with the appropriate residual stress compensation, can indeed estimate the in-situ thermal stresses to achieve a +/-5°F accuracy of Neutral Temperature determination with a 90% statistical confidence, which is the desired industry gold standard.

  17. When depth is no refuge: cumulative thermal stress increases with depth in Bocas del Toro, Panama

    NASA Astrophysics Data System (ADS)

    Neal, B. P.; Condit, C.; Liu, G.; dos Santos, S.; Kahru, M.; Mitchell, B. G.; Kline, D. I.

    2014-03-01

    Coral reefs are increasingly affected by high-temperature stress events and associated bleaching. Monitoring and predicting these events have largely utilized sea surface temperature data, due to the convenience of using large-scale remotely sensed satellite measurements. However, coral bleaching has been observed to vary in severity throughout the water column, and variations in coral thermal stress across depths have not yet been well investigated. In this study, in situ water temperature data from 1999 to 2011 from three depths were used to calculate thermal stress on a coral reef in Bahia Almirante, Bocas del Toro, Panama, which was compared to satellite surface temperature data and thermal stress calculations for the same area and time period from the National Oceanic and Atmospheric Administration Coral Reef Watch Satellite Bleaching Alert system. The results show similar total cumulative annual thermal stress for both the surface and depth-stratified data, but with a striking difference in the distribution of that stress among the depth strata during different high-temperature events, with the greatest thermal stress unusually recorded at the deepest measured depth during the most severe bleaching event in 2005. Temperature records indicate that a strong density-driven temperature inversion may have formed in this location in that year, contributing to the persistence and intensity of bleaching disturbance at depth. These results indicate that depth may not provide a stress refuge from high water temperature events in some situations, and in this case, the water properties at depth appear to have contributed to greater coral bleaching at depth compared to near-surface locations. This case study demonstrates the importance of incorporating depth-stratified temperature monitoring and small-scale oceanographic and hydrologic data for understanding and predicting local reef responses to elevated water temperature events.

  18. Lipocalin 2 regulation by thermal stresses: Protective role of Lcn2/NGAL against cold and heat stresses

    SciTech Connect

    Roudkenar, Mehryar Habibi; Halabian, Raheleh; Roushandeh, Amaneh Mohammadi; Nourani, Mohammad Reza; Masroori, Nasser; Ebrahimi, Majid; Nikogoftar, Mahin; Rouhbakhsh, Mehdi; Bahmani, Parisa; Najafabadi, Ali Jahanian; Shokrgozar, Mohammad Ali

    2009-11-01

    Environmental temperature variations are the most common stresses experienced by a wide range of organisms. Lipocalin 2 (Lcn2/NGAL) is expressed in various normal and pathologic conditions. However, its precise functions have not been fully determined. Here we report the induction of Lcn2 by thermal stresses in vivo, and its role following exposure to cold and heat stresses in vitro. Induction of Lcn2 in liver, heart and kidney was detected by RT-PCR, Western blot and immunohistochemistry following exposure of mice to heat and cold stresses. When CHO and HEK293T cells overexpressing NGAL were exposed to cold stress, cell proliferation was higher compared to controls. Down-regulatrion of NGAL by siRNA in A549 cells resulted in less proliferation when exposed to cold stress compared to control cells. The number of apoptotic cells and expression of pro-apoptotic proteins were lower in the NGAL overexpressing CHO and HEK293T cells, but were higher in the siRNA-transfected A549 cells compared to controls, indicating that NGAL protects cells against cold stress. Following exposure of the cells to heat stress, ectopic expression of NGAL protected cells while addition of exogenous recombinant NGAL to the cell culture medium exacerbated the toxicity of heat stress specially when there was low or no endogenous expression of NGAL. It had a dual effect on apoptosis following heat stress. NGAL also increased the expression of HO-1. Lcn2/NGAL may have the potential to improve cell proliferation and preservation particularly to prevent cold ischemia injury of transplanted organs or for treatment of some cancers by hyperthermia.

  19. Thermal stress induced voids in nanoscale copper interconnects by in-situ TEM heating

    NASA Astrophysics Data System (ADS)

    An, Jin Ho

    Stress induced void formation in Cu interconnects, due to thermal stresses generated during the processing of semiconductors, is an increasing reliability issue in the semiconductor industry as Cu interconnects are being downscaled to follow the demand for faster chip speed. In this work, 1.8 micron and 180 nm wide Cu interconnects, fabricated by Freescale Semiconductors, were subjected to thermal cycles, in-situ in the TEM, to investigate the stress relaxation mechanisms as a function of interconnect linewidth. The experiments show that the 1.8 micron Cu interconnect lines relax the thermal stresses through dislocation nucleation and motion while the Cu interconnect 180 nm lines exhibit void formation. Void formation in 180 nm lines occurs predominantly at triple junctions where the Ta diffusion barrier meets a Cu grain boundary. In order to understand void formation in 180 nm lines, the grain orientation and local stresses are determined. In particular, Nanobeam Diffraction (NBD) in the TEM is used to obtain the diffraction pattern of each grain, from which the crystal orientation is evaluated by the ACT (Automated Crystallography for TEM) software. In addition, 2D Finite Element Method (FEM) simulations are performed using the Object Oriented Finite Modeling (OOF2) software to correlate grain orientation with local stresses, and consequently void formation. According to the experimental and simulation results obtained, void formation in 180nm Cu interconnects does not seem to be solely dependent on local stresses, but a combination of diffusion paths available, stress gradients and possibly the presence of defects. In addition, based on the in-situ TEM observations, void growth seems to occur through grain boundary and/or interfacial diffusion. However, in-situ STEM observations of fully opened voids post-failure show pileup of material at the Cu grain surfaces. This means that surface or interface diffusion is also very active during void growth in the presence

  20. Chloroplastic NAD(P)H Dehydrogenase in Tobacco Leaves Functions in Alleviation of Oxidative Damage Caused by Temperature Stress1[OA

    PubMed Central

    Wang, Peng; Duan, Wei; Takabayashi, Atsushi; Endo, Tsuyoshi; Shikanai, Toshiharu; Ye, Ji-Yu; Mi, Hualing

    2006-01-01

    In this study, the function of the NAD(P)H dehydrogenase (NDH)-dependent pathway in suppressing the accumulation of reactive oxygen species in chloroplasts was investigated. Hydrogen peroxide accumulated in the leaves of tobacco (Nicotiana tabacum) defective in ndhC-ndhK-ndhJ (ΔndhCKJ) at 42°C and 4°C, and in that of wild-type leaves at 4°C. The maximum quantum efficiency of PSII decreased to a similar extent in both strains at 42°C, while it decreased more evidently in ΔndhCKJ at 4°C. The parameters linked to CO2 assimilation, such as the photochemical efficiency of PSII, the decrease of nonphotochemical quenching following the initial rise, and the photosynthetic O2 evolution, were inhibited more significantly in ΔndhCKJ than in wild type at 42°C and were seriously inhibited in both strains at 4°C. While cyclic electron flow around PSI mediated by NDH was remarkably enhanced at 42°C and suppressed at 4°C. The proton gradient across the thylakoid membranes and light-dependent ATP synthesis were higher in wild type than in ΔndhCKJ at either 25°C or 42°C, but were barely formed at 4°C. Based on these results, we suggest that cyclic photophosphorylation via the NDH pathway might play an important role in regulation of CO2 assimilation under heat-stressed condition but is less important under chilling-stressed condition, thus optimizing the photosynthetic electron transport and reducing the generation of reactive oxygen species. PMID:16428601

  1. Bond strength and stress measurements in thermal barrier coatings

    SciTech Connect

    Gell, M.; Jordan, E.

    1995-12-31

    Thermal barrier coatings have been used extensively in aircraft gas turbines for more than 15 years to insulate combustors and turbine vanes from the hot gas stream. Plasma sprayed thermal barrier coatings (TBCs) provide metal temperature reductions as much as 300{degrees}F, with improvements in durability of two times or more being achieved. The introduction of TBCs deposited by electron beam physical vapor deposition (EB-PVD) processes in the last five years has provided a major improvement in durability and also enabled TBCs to be applied to turbine blades for improved engine performance. This program evaluates the bond strength of yttria stabilized zirconia coatings with MCrAlY and Pt-Al bond coats utilizing diffraction and fluorescence methods.

  2. Effect of thermal stresses on the dielectric properties of strontium titanate thin films

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Weiss, C. V.; Alpay, S. P.

    2011-07-01

    We develop a quantitative thermodynamic model to understand the role of thermal stresses on the dielectric permittivity and tunability of (001)-textured polycrystalline monodomain strontium titanate (SrTiO3) films. This methodology is used to compute the dielectric constant and tunability of SrTiO3 films on Si, c-sapphire, LaAlO3, and MgO substrates. Results show that dielectric properties of SrTiO3 depend strongly on the growth/processing temperature TG. For substrates such as MgO that induce compressive in-plane thermal stresses, the dielectric response of SrTiO3 is enhanced. However, for SrTiO3 films on IC-compatible substrates (Si and c-sapphire), thermal stresses can significantly degrade the dielectric permittivity and tunability.

  3. Stress Evolution in Sn Thin Films During Thermal Cycling

    SciTech Connect

    Stevens, K. J.; Cheong, K. C.; Cai Zhonghou; Ingham, B.; Toney, M. F.

    2009-07-23

    Finite Element Modelling and corresponding X-ray and Electron Back-Scatter Diffraction measurements have been used to investigate the development of strain in thin tin films during thermal cycling. The modeled average strain in the film was found to agree within 20% to the experimental result, although the strain within individual grains was found to vary dramatically as observed by electron backscatter diffraction and synchrotron microdiffraction.

  4. Lipid biomarkers of thermal stress in scleractinian corals

    NASA Astrophysics Data System (ADS)

    Kneeland, J. M.; Hughen, K.; Cervino, J.; Eglinton, T. I.; Bartels, E.

    2007-12-01

    Lipid content and fatty acid profiles of corals and their symbiotic dinoflagellates are known to vary in response to heat stress and bleaching. To develop lipid biomarkers of heat stress and bleaching response in scleractinian corals, clones of Symbiodinium algae of clade subtypes C1 and D1 were cultured under a range of temperatures. The predominant lipids produced are palmitic (C16) and stearic (C18) saturated fatty acids and their unsaturated analogs. Other important compounds included a C22 penta-unsaturated fatty acid, which is thought to be a specific dinoflagellate marker, and a variety of sterols. Analysis of lipids extracted from coral skeleton indicated that palmitic and stearic acids were the most abundant compounds. The amount of unsaturated C16 and C18 fatty acids in coral skeleton relative to the saturated versions of those acids was much lower in coral skeleton than in the zooxanthellae tissue. This could indicate the incorporation of lipids from outside the coral host-symbiont system into the coral aragonite, or it could reflect diagenesis. A comparison between the lipids found in cloned zooxanthellae, coral tissue, and aragonitic skeleton will be presented to assess the usefulness of lipid biomarkers as indicators of temperature stress on corals.

  5. Thermal stress cycling of GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Janousek, B. K.; Francis, R. W.; Wendt, J. P.

    1985-01-01

    A thermal cycling experiment was performed on GaAs solar cells to establish the electrical and structural integrity of these cells under the temperature conditions of a simulated low-Earth orbit of 3-year duration. Thirty single junction GaAs cells were obtained and tests were performed to establish the beginning-of-life characteristics of these cells. The tests consisted of cell I-V power output curves, from which were obtained short-circuit current, open circuit voltage, fill factor, and cell efficiency, and optical micrographs, spectral response, and ion microprobe mass analysis (IMMA) depth profiles on both the front surfaces and the front metallic contacts of the cells. Following 5,000 thermal cycles, the performance of the cells was reexamined in addition to any factors which might contribute to performance degradation. It is established that, after 5,000 thermal cycles, the cells retain their power output with no loss of structural integrity or change in physical appearance.

  6. Shot Peening and Thermal Stress Relaxation in 17-4 PH Stainless Steel

    NASA Astrophysics Data System (ADS)

    Qin, Enwei; Chen, Guoxing; Tan, Ziming; Wu, Shuhui

    2015-11-01

    Shot peening is an effective process to enhance the fatigue performance of turbine blades. In this study, the effect of peening pressures was discussed in terms of the residual stress distribution and the surface morphology. Shot peening processes were designed at varying pressures on a 17-4 PH martensitic stainless steel. The profiles of hardness and residual stress were characterized in the cross section. The thermal stress relaxation was further carried out to evaluate the stability of the compressive residual stress under service temperatures of turbine blades. Results show that a maximum stress depth is obtained with peening pressure of 0.40 MPa, and the residual stress can be maintained up to 400 °C, which ensures the service in low-pressure turbine blades.

  7. Satellite Thermal Infrared Stress Field and Earthquake Prediction in Short-term and Imminent

    NASA Astrophysics Data System (ADS)

    Qiang, Z.; Zhao, X.; Xie, H.; Zeng, Z.

    2007-12-01

    It has been recognized that there is a temperature-increase anomaly before earthquake. Meteorological satellite based thermal infrared (IR) radiation in detecting ground surface temperature, thus anomaly, has its advantages, such as data accuracy, large areal coverage, a large amount of information and capability of capturing the time- space dynamic variation of the temperature - increase before earthquakes (Qiang Zuji et al., 1996). Earthquake precursors should enable a predicator to give the three elements of a future earthquake: location, magnitude and time, (Max Wyss, 1993) in which the method of thermal anomaly detection can provide all three elements. Practice is the only criterion to examine a truth. Chinese scientists in the satellite thermal-infrared earthquake-prediction group led by QIANG Zuji and DIAN Changgong have carried on practicing short and imminent earthquake prediction since 1990. Over the years we have made steady and exciting progress. During the 11 years from 1990 to 2000, we made 119 predictions. of which 58 were valid and 15 were false alarms. The success rate of those predictions increases from 24% during period of 1990-1995, to 46% in 1996, 53% in 1997, 76% in 1998, to 80% in 1999 and 2000, summarized by Wang (2005). The satellite infrared detected thermal stress field is a reflection of the earth's crust stress condition when rock stress increases the spot along the stress to produce micro fissures in rock. Therefore, hot plane and line that have the closet relation with the stress condition and the rock faulted structure can demonstrate the compression stress direction. The thermal stress types have been recognized over years include isolated X shear structure, en echelon, single arm form, the string of beads shape, ~{!J~} type, rotation shear ellipse, and the advancement rotation shear ellipse (Wu Li-xin, Liu Shan-jun, 2006,Qiang Zuji et al 1991,1993,1995,1996,1997,2001)

  8. Waste Package Outer Barrier Stress Due to Thermal Expansion with Various Barrier Gap Sizes

    SciTech Connect

    M. M. Lewis

    2001-11-27

    The objective of this activity is to determine the tangential stresses of the outer shell, due to uneven thermal expansion of the inner and outer shells of the current waste package (WP) designs. Based on the results of the calculation ''Waste Package Barrier Stresses Due to Thermal Expansion'', CAL-EBS-ME-000008 (ref. 10), only tangential stresses are considered for this calculation. The tangential stresses are significantly larger than the radial stresses associated with thermal expansion, and at the WP outer surface the radial stresses are equal to zero. The scope of this activity is limited to determining the tangential stresses the waste package outer shell is subject to due to the interference fit, produced by having two different shell coefficients of thermal expansions. The inner shell has a greater coefficient of thermal expansion than the outer shell, producing a pressure between the two shells. This calculation is associated with Waste Package Project. The calculations are performed for the 21-PWR (pressurized water reactor), 44-BWR (boiling water reactor), 24-BWR, 12-PWR Long, 5 DHLW/DOE SNF - Short (defense high-level waste/Department of Energy spent nuclear fuel), 2-MCO/2-DHLW (multi-canister overpack), and Naval SNF Long WP designs. The information provided by the sketches attached to this calculation is that of the potential design for the types of WPs considered in this calculation. This calculation is performed in accordance with the ''Technical Work Plan for: Waste Package Design Description for SR (Ref.7). The calculation is documented, reviewed, and approved in accordance with AP-3.12Q, Calculations (Ref.1).

  9. High precision thermal stress study on flip chips by synchrotron polychromatic x-ray microdiffraction

    SciTech Connect

    Chen, Kai; Tamura, Nobumichi; Tang, Wei; Kunz, Martin; Chou, Yi-Chia; Tu, King-Ning; Lai, Yi-Shao

    2010-01-01

    The bending and residual stress of flip chips caused by the mismatch of thermal expansion between the chip and the substrate have been measured by polychromatic microfocused synchrotron x-ray beam. Precise orientation information as a function of position on the chip was obtained from Laue diffraction patterns, so that the bending angle with respect to a reference position at the center of the chip can be calculated at each position. This in turn allows deducing the local curvature of the entire flip chip. Local stress distribution was then mapped by applying a modified Stoney's stress-strain equation to the measured curvature. Our study shows that thermal stress on the circuits and the solder joints in a flip chip strongly depend on temperature and the distance from the center of the chip, indicating that interconnects at the corner and edge of a flip chip are of reliability concerns.

  10. NMR-based metabolomic analysis of Haliotis diversicolor exposed to thermal and hypoxic stresses.

    PubMed

    Lu, Jie; Shi, Yanyan; Wang, Shuhong; Chen, Hao; Cai, Shuhui; Feng, Jianghua

    2016-03-01

    Haliotis diversicolor is a commercially important cultured shellfish. It is also an important marine model organism for environmental science. High temperature accompanied with hypoxia frequently induces diseases or even death to abalones. In present study, (1)H NMR spectroscopy together with pattern recognition methods was used to investigate the responses of muscle and gill of H. diversicolor to thermal and hypoxic stresses. It was found that obvious gender-, time- and tissue-specific metabolic responses were induced by thermal and hypoxic stresses. In combination with the changes of H. diversicolor in physiological features, the dual-modal stresses were suggested to mainly cause the disturbance in energy metabolism and osmotic balance in muscle and gill tissues with different mechanisms. Further, the corresponding correlation networks and metabolic pathways derived from the characteristic metabolites were used to assess the major metabolic functions of these characteristic metabolites. These findings shed some lights on the metabolic influences of environmental stresses on marine organisms. PMID:26747992

  11. Cracks in Martian boulders exhibit preferred orientations that point to solar-induced thermal stress.

    PubMed

    Eppes, Martha-Cary; Willis, Andrew; Molaro, Jamie; Abernathy, Stephen; Zhou, Beibei

    2015-01-01

    The origins of fractures in Martian boulders are unknown. Here, using Mars Exploration Rover 3D data products, we obtain orientation measurements for 1,857 cracks visible in 1,573 rocks along the Spirit traverse and find that Mars rock cracks are oriented in statistically preferred directions similar to those compiled herein for Earth rock cracks found in mid-latitude deserts. We suggest that Martian directional cracking occurs due to the preferential propagation of microfractures favourably oriented with respect to repeating geometries of diurnal peaks in sun-induced thermal stresses. A numerical model modified here with Mars parameters supports this hypothesis both with respect to the overall magnitude of stresses as well as to the times of day at which the stresses peak. These data provide the first direct field and numerical evidence that insolation-related thermal stress potentially plays a principle role in cracking rocks on portions of the Martian surface. PMID:25813699

  12. In Situ Measurement of Stress and Whisker/Hillock Density During Thermal Cycling of Sn Layers

    NASA Astrophysics Data System (ADS)

    Pei, Fei; Chason, Eric

    2014-01-01

    Compressive stress is believed to be the primary driving force that makes Sn whiskers/hillocks grow, but the mechanisms that create the stress (e.g., intermetallic compound growth) are difficult to control. As an alternative, the thermal expansion mismatch between the Sn layer and the substrate can be used to induce stress in a controlled way via heating and cooling. In this work, we describe real-time experiments which quantify the whiskering behavior and stress evolution during cyclic heating. The density of whiskers/hillocks is measured with an optical microscope, while the stress is measured simultaneously with a wafer-curvature-based multi-beam optical stress sensor. Results from three thermal cycles are described in which the samples are heated from room temperature to 65 °C at rates of 10, 30, and 240 °C/h. In each case, we find that the whisker/hillock formation is the primary source of stress relaxation. At fast heating rates, the relaxation is proportional to the number of hillocks, indicating that the stress is relaxed by the nucleation of many small surface features. At slower heating rates, the whisker/hillock density is lower, and continual growth of the features is suggested after nucleation. Long whiskers are found to be more likely to form in the slow heating cycle.

  13. An analytical model of thermal mechanical stress induced by through silicon via

    NASA Astrophysics Data System (ADS)

    Dong, Gang; Shi, Tao; Zhao, Ying-Bo; Yang, Yin-Tang

    2015-05-01

    We present an accurate through silicon via (TSV) thermal mechanical stress analytical model which is verified by using finite element method (FEM). The results show only a very small error. By using the proposed analytical model, we also study the impacts of the TSV radius size, the thickness, the material of Cu diffusion barrier, and liner on the stress. It is found that the liner can absorb the stress effectively induced by coefficient of thermal expansion mismatch. The stress decreases with the increase of liner thickness. Benzocyclobutene (BCB) as a liner material is better than SiO2. However, the Cu diffusion barrier has little effect on the stress. The stress with a smaller TSV has a smaller value. Based on the analytical model, we explore and validate the linear superposition principle of stress tensors and demonstrate the accuracy of this method against detailed FEM simulations. The analytic solutions of stress of two TSVs and three TSVs have high precision against the finite element result. Project supported by the National Natural Science Foundation of China (Grant No. 61334003) and the Kunshan Innovation Institute of Xidian University.

  14. Changes in laser-induced fluorescence responses of 3T3 fibroblasts to repetitive thermal stress

    NASA Astrophysics Data System (ADS)

    Beuthan, J.; Dressler, C.; Zabarylo, U.; Minet, O.

    2009-04-01

    The combined experimental use of laser-induced autofluorescence of cellular metabolites and methodological fundamentals of systems biology will provide access to biological thermal stress analysis on a sub cellular level. A test setup incorporating a pulsed nitrogen laser was realized with which autofluorescence of the coenzyme NADH could be measured in living 3T3 cells. The cells were subjected to different temperature stress at repetitive time intervals. When subjected to a simple mathematical analysis, the NADH concentration change measured through autofluorescence in biological cells exhibited approximate concentration-equivalent balance curves. These results add up to the fundamental know-how about the dosimetry of thermally therapeutic methods.

  15. Thermally-induced stresses in graphite-epoxy tubes coated with aluminum foil

    NASA Technical Reports Server (NTRS)

    Knott, Tamara W.; Hyer, M. W.

    1989-01-01

    Thermally-induced stresses in the foil, adhesive, and graphite-epoxy layers of composite tubes with aluminum foil bonded to the inner and outer surface are computed. The thermal effects are due to a temperature decrease from the processing temperature of the material to a temperature felt to represent the space environment, the intended operating environment of the tubes. Tubes fabricated from T300/934 and P75s/934 material systems are considered. The results indicate that the presence of the foil and adhesive have no detrimental effect on the stresses in the tube.

  16. Thermal stress response of General Purpose Heat Source (GPHS) aeroshell material

    NASA Technical Reports Server (NTRS)

    Grinberg, I. M.; Hulbert, L. E.; Luce, R. G.

    1980-01-01

    A thermal stress test was conducted to determine the ability of the GPHS aeroshell 3 D FWPF material to maintain physical integrity when exposed to a severe heat flux such as would occur from prompt reentry of GPHS modules. The test was performed in the Giant Planetary Facility at NASA's Ames Research Center. Good agreement was obtained between the theoretical and experimental results for both temperature and strain time histories. No physical damage was observed in the test specimen. These results provide initial corroboration both of the analysis techniques and that the GPHS reentry member will survive the reentry thermal stress levels expected.

  17. Fiber-matrix interface effects in the presence of thermally induced residual stresses

    SciTech Connect

    Nimmer, R.P. )

    1990-01-01

    The mechanics of transversely loaded high-temperature composites with a thermally induced residual stress field and a vanishingly weak fiber-matrix interface strength was investigated using two analytical models. In particular, the effects of several physical properties defining the performance of the constituent fiber, matrix, and interface are examined relative to their effect on composite's behavior. Both models demonstrate that, if there is a thermally induced residual stress field in the composite, the initial transverse modulus for the composite will be the same regardless of whether there is a well-bonded or an unbonded interface. 10 refs.

  18. Thermal stress modeling of in situ vitrified barriers for hazardous waste containment

    SciTech Connect

    Garnich, M.R.

    1991-09-01

    Development of In Situ Vitrification technology has included the concept of subsurface barriers. Structural integrity of vitrified soil bodies is important to barrier performance. Analytical methods are under development for predicting thermal-structural performance during melt cooldown. A thermal modeling capability has been developed for predicting the cooling transient of subsurface molten masses using the finite element method. A computationally efficient instant freezing model'' was demonstrated to give qualitative agreement for predicted stresses with a more sophisticated creep model. A method for predicting stress relief due to cracking, as a preliminary step to predicting crack densities, has been demonstrated. 8 refs., 10 figs.

  19. Thermal stresses of a wind turbine blade made of orthotropic material

    NASA Technical Reports Server (NTRS)

    Fu, Kuan-Chen; Harb, Awad

    1987-01-01

    This study is to investigate the thermal stress of a wind turbine blade made of wood composite material. First, the governing partial differential equation on heat conduction is stated, then, a finite element procedure using a variational approach is employed for the solution of the governing equation. Thus, the temperature field throughout the blade is determined. Next, based on the temperature field, a finite element procedure using potential energy approach is applied to determine the thermal stress field. A set of results is obtained through the use of a computer, which is considered to be satisfactory.

  20. Transient thermal stress analysis and bending behavior of an angle-ply laminated slab

    SciTech Connect

    Ootao, Y.; Tanigawa, Y.; Murakami, H. Osaka Prefecture Univ., Sakai California Univ., La Jolla )

    1990-01-01

    This paper is concerned with a theoretical treatment of thermal stress and bending behavior in a transient state of a multilayered nonisotropic laminated slab. Consideration is given to an infinitely long laminated slab which consists of obliquely directed layers with orthotropic material properties. The thermoelastic problem for the slab under the condition of uniformly distributed heat supply from its one surface is solved in order to obtain the temperature solution and to evaluate the thermal stresses in a transient state. As an example, numerical calculations are carried out for the five-layered angle-ply laminate.

  1. Axisymmetric transient thermal stress analysis of a multilayered composite hollow cylinder

    SciTech Connect

    Ootao, Y.; Tanigawa, Y.; Fukuda, T. Osaka Prefecture, University, Sakai Hitachi, Ltd., Yokohama )

    1991-06-01

    This article is concerned with axisymmetric, transient, thermal stress analysis of a hollow cylinder composed of multilayered composite laminates with temperature changes in the radial and axial directions due to axisymmetric heating from the outer and/or inner surfaces. The methods of Fourier cosine transform and Laplace transform are applied to the temperature field and the thermoelastic potential function, and Love's displacement function is applied to the thermoelastic field. Exact solutions are obtained for the temperature and thermal stress distributions in a transient state. Moreover, the theoretical developments proposed in the present article are applied to the analysis of a hollow cylinder with nonhomogeneous material properties, such as a functionally gradient material.

  2. Stress, on the rocks: Thermally induced stresses in rocks and microstructures on airless bodies, implications for breakdown

    NASA Astrophysics Data System (ADS)

    Molaro, Jamie

    This dissertation investigates the role of thermomechanical processes in the production of regolith on airless body surfaces. Thermally induced breakdown may provide a significant contribution to their surface evolution, by breaking down rocks and degrading craters. In Chapter 1, we use the traditional terrestrial methodology of evaluating the efficacy of this process by modeling the rate of surface temperature change (dT/dt) on various airless surfaces, using a damage threshold of 2 K/min. We find that the magnitude of dT/dt values is primarily controlled by sunrise/set durations on quickly rotating bodies, such as Vesta, and by distance to the sun on slowly rotating bodies, such as Mercury. The strongest rates of temperature change occur on slopes normal to the sun when a sunrise or sunset occurs, either naturally or because of daytime shadowing. We find, however, that high dT/dt values are not always correlated with high temperature gradients within the surface. This adds to the ambiguity of the poorly understood damage threshold, emphasizes the need further research on this topic that goes beyond the simple 2 K/min criterion. We further investigate this shortcoming in the terrestrial literature in Chapter two by modeling stresses induced by diurnal temperature variations at the mineral grain scale on these bodies. We find that the resulting stresses are controlled by mismatches in material properties between adjacent mineral grains. Peak stresses (on the order of 100s of MPa) are controlled by the coefficient of thermal expansion and Young's modulus of the mineral constituents, and the average stress within the microstructure is determined by relative volume of each mineral. Amplification of stresses occurs at surface-parallel boundaries between adjacent mineral grains and at the tips of pore spaces. We also find that microscopic spatial and temporal surface temperature gradients do not correlate with high stresses, making them inappropriate proxies for

  3. Elastoplastic analysis of process induced residual stresses in thermally sprayed coatings

    SciTech Connect

    Chen Yongxiong; Liang Xiubing; Liu Yan; Xu Binshi

    2010-07-15

    The residual stresses induced from thermal spraying process have been extensively investigated in previous studies. However, most of such works were focused on the elastic deformation range. In this paper, an elastoplastic model for predicting the residual stresses in thermally sprayed coatings was developed, in which two main contributions were considered, namely the deposition induced stress and that due to differential thermal contraction between the substrate and coating during cooling. The deposition induced stress was analyzed based on the assumption that the coating is formed layer-by-layer, and then a misfit strain is accommodated within the multilayer structure after the addition of each layer (plastic deformation is induced consequently). From a knowledge of specimen dimensions, processing temperatures, and material properties, residual stress distributions within the structure can be determined by implementing the model with a simple computer program. A case study for the plasma sprayed NiCoCrAlY on Inconel 718 system was performed finally. Besides some similar phenomena observed from the present study as compared with previous elastic model reported in literature, the elastoplastic model also provides some interesting features for prediction of the residual stresses.

  4. Phosphodiesterase-4D Knock-down in the Prefrontal Cortex Alleviates Chronic Unpredictable Stress-Induced Depressive-Like Behaviors and Memory Deficits in Mice

    PubMed Central

    Wang, Zhen-Zhen; Yang, Wei-Xing; Zhang, Yi; Zhao, Nan; Zhang, You-Zhi; Liu, Yan-Qin; Xu, Ying; Wilson, Steven P.; O'Donnell, James M.; Zhang, Han-Ting; Li, Yun-Feng

    2015-01-01

    Phosphodiesterase 4 (PDE4) has four isoforms (PDE4A-D) with at least 25 splice variants. PDE4 subtype nonselective inhibitors produce potent antidepressant-like and cognition-enhancing effects via increased intracellular cyclic AMP (cAMP) signaling in the brain. Our previous data have demonstrated that long-form PDE4Ds appear to be involved in these pharmacological properties of PDE4 inhibitors in the normal animals. However, it is not clear whether long-form PDE4Ds are critical for the behaviors and related cellular signaling/neuronal plasticity/neuroendocrine alterations in the depressed animals. In the present study, animals exposed to the chronic unpredictable stress (CUS), a rodent model of depression, exhibited elevated corticosterone, depressive-like behavior, memory deficits, accompanied with decreased cAMP-PKA-CREB and cAMP-ERK1/2-CREB signaling and neuroplasticity. These alterations induced by CUS were reversed by RNA interference (RNAi)-mediated prefrontal cortex long-form PDE4Ds (especially PDE4D4 and PDE4D5) knock-down, similar to the effects of the PDE4 subtype nonselective inhibitor rolipram. Furthermore, these effects of RNAi were not enhanced by rolipram. These data indicate a predominant role of long-form PDE4Ds in the pharmacotherapies of PDE4 inhibitors for depression and concomitant memory deficits. Long-form PDE4Ds, especially PDE4D4 and PDE4D5, appear to be the promising targets for the development of antidepressants with high therapeutic indices. PMID:26161529

  5. Melatonin alleviates brain injury in mice subjected to cecal ligation and puncture via attenuating inflammation, apoptosis, and oxidative stress: the role of SIRT1 signaling.

    PubMed

    Zhao, Lei; An, Rui; Yang, Yang; Yang, Xiangmin; Liu, Haixiao; Yue, Liang; Li, Xia; Lin, Yan; Reiter, Russel J; Qu, Yan

    2015-09-01

    Sepsis is a systemic inflammatory response to infection that causes severe neurological complications. Previous studies have suggested that melatonin is protective during sepsis. Additionally, silent information regulator 1 (SIRT1) was reported to be beneficial in sepsis. However, the role of SIRT1 signaling in the protective effect of melatonin against septic encephalopathy remains unclear. This study aimed to investigate the role of SIRT1 in the protective effect of melatonin. EX527, a SIRT1 inhibitor, was used to reveal the role of SIRT1 in melatonin's action. Cecal ligation and puncture or sham operation was performed in male C57BL/6J mice. Melatonin was administrated intraperitoneally (30 mg/kg). The survival rate of mice was recorded for the 7-day period following the sham or CLP operation. The blood-brain barrier (BBB) integrity, brain water content, levels of inflammatory cytokines (TNF-α, IL-1β, and HMGB1), and the level of oxidative stress (superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA)) and apoptosis were assessed. The expression of SIRT1, Ac-FoxO1, Ac-p53, Ac-NF-κB, Bcl-2, and Bax was detected by Western blot. The results suggested that melatonin improved survival rate, attenuated brain edema and neuronal apoptosis, and preserved BBB integrity. Melatonin decreased the production of TNF-α, IL-1β, and HMGB1. Melatonin increased the activity of SOD and CAT and decreased the MDA production. Additionally, melatonin upregulated the expression of SIRT1 and Bcl-2 and downregulated the expression of Ac-FoxO1, Ac-p53, Ac-NF-κB, and Bax. However, the protective effects of melatonin were abolished by EX527. In conclusion, our results demonstrate that melatonin attenuates sepsis-induced brain injury via SIRT1 signaling activation. PMID:26094939

  6. Rockfall triggering by cyclic thermal stressing of exfoliation fractures

    NASA Astrophysics Data System (ADS)

    Collins, Brian D.; Stock, Greg M.

    2016-05-01

    Exfoliation of rock deteriorates cliffs through the formation and subsequent opening of fractures, which in turn can lead to potentially hazardous rockfalls. Although a number of mechanisms are known to trigger rockfalls, many rockfalls occur during periods when likely triggers such as precipitation, seismic activity and freezing conditions are absent. It has been suggested that these enigmatic rockfalls may occur due to solar heating of rock surfaces, which can cause outward expansion. Here we use data from 3.5 years of field monitoring of an exfoliating granite cliff in Yosemite National Park in California, USA, to assess the magnitude and temporal pattern of thermally induced rock deformation. From a thermodynamic analysis, we find that daily, seasonal and annual temperature variations are sufficient to drive cyclic and cumulative opening of fractures. Application of fracture theory suggests that these changes can lead to further fracture propagation and the consequent detachment of rock. Our data indicate that the warmest times of the day and year are particularly conducive to triggering rockfalls, and that cyclic thermal forcing may enhance the efficacy of other, more typical rockfall triggers.

  7. Rockfall triggering by cyclic thermal stressing of exfoliation fractures

    USGS Publications Warehouse

    Collins, Brian; Stock, Greg M.

    2016-01-01

    Exfoliation of rock deteriorates cliffs through the formation and subsequent opening of fractures, which in turn can lead to potentially hazardous rockfalls. Although a number of mechanisms are known to trigger rockfalls, many rockfalls occur during periods when likely triggers such as precipitation, seismic activity and freezing conditions are absent. It has been suggested that these enigmatic rockfalls may occur due to solar heating of rock surfaces, which can cause outward expansion. Here we use data from 3.5 years of field monitoring of an exfoliating granite cliff in Yosemite National Park in California, USA, to assess the magnitude and temporal pattern of thermally induced rock deformation. From a thermodynamic analysis, we find that daily, seasonal and annual temperature variations are sufficient to drive cyclic and cumulative opening of fractures. Application of fracture theory suggests that these changes can lead to further fracture propagation and the consequent detachment of rock. Our data indicate that the warmest times of the day and year are particularly conducive to triggering rockfalls, and that cyclic thermal forcing may enhance the efficacy of other, more typical rockfall triggers.

  8. Transcriptional expression levels of cell stress marker genes in the Pacific oyster Crassostrea gigas exposed to acute thermal stress

    PubMed Central

    Farcy, Émilie; Voiseux, Claire; Lebel, Jean-Marc

    2008-01-01

    During the annual cycle, oysters are exposed to seasonal slow changes in temperature, but during emersion at low tide on sunny summer days, their internal temperature may rise rapidly, resulting in acute heat stress. We experimentally exposed oysters to a 1-h acute thermal stress and investigated the transcriptional expression level of some genes involved in cell stress defence mechanisms, including chaperone proteins (heat shock proteins Hsp70, Hsp72 and Hsp90 (HSP)), regulation of oxidative stress (Cu-Zn superoxide dismutase, metallothionein (MT)), cell detoxification (glutathione S-transferase sigma, cytochrome P450 and multidrug resistance (MDR1)) and regulation of the cell cycle (p53). Gene mRNA levels were quantified by reverse transcription-quantitative polymerase chain reaction and expressed as their ratio to actin mRNA, used as a reference. Of the nine genes studied, HSP, MT and MDR1 mRNA levels increased in response to thermal stress. We compared the responses of oysters exposed to acute heat shock in summer and winter and observed differences in terms of magnitude and kinetics. A larger increase was observed in September, with recovery within 48 h, whereas in March, the increase was smaller and lasted more than 2 days. The results were also compared with data obtained from the natural environment. Though the functional molecule is the protein and information at the mRNA level only has limitations, the potential use of mRNAs coding for cell stress defence proteins as early sensitive biomarkers is discussed. PMID:19002605

  9. Coping with Commitment: Projected Thermal Stress on Coral Reefs under Different Future Scenarios

    PubMed Central

    Donner, Simon D.

    2009-01-01

    Background Periods of anomalously warm ocean temperatures can lead to mass coral bleaching. Past studies have concluded that anthropogenic climate change may rapidly increase the frequency of these thermal stress events, leading to declines in coral cover, shifts in the composition of corals and other reef-dwelling organisms, and stress on the human populations who depend on coral reef ecosystems for food, income and shoreline protection. The ability of greenhouse gas mitigation to alter the near-term forecast for coral reefs is limited by the time lag between greenhouse gas emissions and the physical climate response. Methodology/Principal Findings This study uses observed sea surface temperatures and the results of global climate model forced with five different future emissions scenarios to evaluate the “committed warming” for coral reefs worldwide. The results show that the physical warming commitment from current accumulation of greenhouse gases in the atmosphere could cause over half of the world's coral reefs to experience harmfully frequent (p≥0.2 year−1) thermal stress by 2080. An additional “societal” warming commitment, caused by the time required to shift from a business-as-usual emissions trajectory to a 550 ppm CO2 stabilization trajectory, may cause over 80% of the world's coral reefs to experience harmfully frequent events by 2030. Thermal adaptation of 1.5°C would delay the thermal stress forecast by 50–80 years. Conclusions/Significance The results suggest that adaptation – via biological mechanisms, coral community shifts and/or management interventions – could provide time to change the trajectory of greenhouse gas emissions and possibly avoid the recurrence of harmfully frequent events at the majority (97%) of the world's coral reefs this century. Without any thermal adaptation, atmospheric CO2 concentrations may need to be stabilized below current levels to avoid the degradation of coral reef ecosystems from frequent thermal

  10. Technological thermal stresses in the shrink fitting of cylindrical bodies with consideration of plastic flows

    NASA Astrophysics Data System (ADS)

    Dats, E. P.; Tkacheva, A. V.

    2016-05-01

    This paper presents a solution of a sequence of one-dimensional boundary-value problems of thermal stresses defining the elastic-plastic deformation processes used in the shrink fitting of cylindrical bodies. The initiation and development of plastic flow in the materials of the assembly elements are studied taking into account the temperature dependence of the yield stress of these materials. During temperature equalization, the flow can slow down, followed by unloading and formation of a residual stress field providing tension. The conditions of formation and motion of the boundaries of the elastic and plastic states in plastic flow and during unloading are determined.

  11. The competition between thermal contraction and differentiation in the stress history of the moon

    NASA Astrophysics Data System (ADS)

    Kirk, Randolph L.; Stevenson, David J.

    1989-09-01

    The stress history of the moon is discussed, taking into consideration the effects of thermal contraction and differentiation. The amount of expansion caused by extracting basalt from undifferentiated lunar material is estimated taking account of the uncertainty in the knowledge of the appropriate compositions, and the resulting estimate of the expansion is used to compare the relative importance of the thermal and differentiation effects in the moon's volumetric history. The results of calculations show that differentiation is likely to be of major importance and, thus, thermal expansion is not the sole possible contributor to evolutionary changes in the lunar radius.

  12. Passive load alleviation bi-stable morphing concept

    NASA Astrophysics Data System (ADS)

    Arrieta, A. F.; Bilgen, O.; Friswell, M. I.; Hagedorn, P.

    2012-09-01

    In wind turbines, large loads caused by fluid structure interaction leading to fatigue failure and added robustness to withstand high bending stresses on the root of blades constitute important design bottlenecks. Implementation of morphing offers a potential solution for such challenges in wind turbine blades. In this letter, a passive load alleviating bi-stable morphing concept is proposed. A bi-stable specimen designed to have different stiffness and dynamic response characteristics on each stable state is devised as a compliant structure. Passive alleviation mechanisms require no active components to achieve the load alleviation objective, resulting in lighter and simpler designs in comparison to actively morphed solutions.

  13. Stress determination in thermally grown alumina scales using ruby luminescence

    SciTech Connect

    Renusch, D.; Veal, B.W.; Koshelev, I.; Natesan, K.; Grimsditch; Hou, P.Y.

    1996-06-01

    By exploiting the strain dependence of the ruby luminescence line, we have measured the strain in alumina scales thermally grown on Fe-Cr- Al alloys. Results are compared and found to be reasonably consistent with strains determined using x rays. Oxidation studies were carried out on alloys Fe - 5Cr - 28Al and Fe - 18Cr - 10Al (at.%). Significantly different levels of strain buildup were observed in scales on these alloys. Results on similar alloys containing a ``reactive element`` (Zr or Hf) in dilute quantity are also presented. Scales on alloys containing a reactive element (RE) can support significantly higher strains than scales on RE-free alloys. With the luminescence technique, strain relief associated with spallation thresholds is readily observed.

  14. Thermal stress analysis of planar solid oxide fuel cell stacks: Effects of sealing design

    NASA Astrophysics Data System (ADS)

    Lin, Chih-Kuang; Huang, Ling-Hao; Chiang, Lieh-Kwang; Chyou, Yau-Pin

    A three-dimensional multi-cell model based on a prototypical, planar solid oxide fuel cell (pSOFC) stack design using compliant mica-based seal gaskets was constructed in this study to perform comprehensive thermal stress analyses by using a commercial finite element analysis (FEA) code. Effects of the applied assembly load on the thermal stress distribution in the given integrated pSOFC stack with such a compressive sealing design were characterized. A comparison was made with a previous study for a similar comprehensive multi-cell pSOFC stack model but using only a rigid type of glass-ceramic sealant instead. Simulation results indicate that stress distributions in the components such as positive electrode-electrolyte-negative electrode (PEN) plate, PEN-supporting window frame, nickel mesh, and interconnect were mainly governed by the thermal expansion mismatch rather than by the applied compressive load. An applied compressive load of 0.6 MPa could eliminate the bending deformation in the PEN-frame assembly plate leading to a well joined structure. For a greater applied load, the critical stresses in the glass-ceramic and mica sealants were increased to a potential failure level. In this regard, a 0.6 MPa compressive load was considered an optimal assembly load. Changing the seal between the connecting metallic PEN-supporting frame and interconnect from a rigid type of glass-ceramic sealant to a compressive type of mica gasket would significantly influence the thermal stress distribution in the PEN plate. The critical stress in the PEN was favorably decreased at room temperature but considerably increased at operating temperature due to such a change in sealing design. Such differences in the stress distribution could be ascribed to the differences in the constrained conditions at the interfaces of adjacent components under various sealing designs.

  15. Effect of Residual Stress on the Wear Resistance of Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Luo, W.; Selvadurai, U.; Tillmann, W.

    2016-01-01

    The wear resistance of thermal spray coatings mainly depends on coating properties such as the microstructure, hardness, and porosity, as well as on the residual stress in the coating. The residual stress is induced by a variety of influences e.g., temperature gradients, difference of the thermal expansion coefficient of the coating/substrate materials, and the geometry of the components. To investigate the residual stress, the impulse excitation technique was employed to measure the Young's and shear moduli. The residual stress was determined by the hole-drilling method and x-ray diffraction. Pin-on-Disk and Pin-on-Tube tests were used to investigate the wear behavior. After the wear tests, the wear volume was measured by means of a 3D-profilometer. The results show that the value of the residual stress can be modified by varying the coating thickness and the substrate geometry. The compressive stress in the HVOF-sprayed WC-Co coatings has a significant positive influence on the wear resistance whereas the tensile stress has a negative effect.

  16. Gene expression under thermal stress varies across a geographical range expansion front.

    PubMed

    Lancaster, Lesley T; Dudaniec, Rachael Y; Chauhan, Pallavi; Wellenreuther, Maren; Svensson, Erik I; Hansson, Bengt

    2016-03-01

    Many ectothermic species are currently expanding their distributions polewards due to anthropogenic global warming. Molecular genetic mechanisms facilitating range expansion under these conditions are largely unknown, but understanding these could help mitigate expanding pests and disease vectors, or help explain why some species fail to track changing climates. Here, using RNA-seq data, we examine genomewide changes in gene expression under heat and cold stress in the range-expanding damselfly Ischnura elegans in northern Europe. We find that both the number of genes involved and levels of gene expression under heat stress have become attenuated during the expansion, consistent with a previously reported release from selection on heat tolerances as species move polewards. Genes upregulated under cold stress differed between core and edge populations, corroborating previously reported rapid adaptation to cooler climates at the expansion front. Expression of sixty-nine genes exhibited a region x treatment effect; these were primarily upregulated in response to heat stress in core populations but in response to cold stress at the range edge, suggesting that some cellular responses originally adapted to heat stress may switch to cold-stress functionality upon encountering novel thermal selection regimes during range expansion. Transcriptional responses to thermal stress involving heat-shock and neural function genes were largely geographically conserved, while retrotransposon, regulatory, muscle function and defence gene expression patterns were more variable. Flexible mechanisms of cold-stress response and the ability of some genes to shift their function between heat and cold stress might be key mechanisms facilitating rapid poleward expansion in insects. PMID:26821170

  17. Pipeline design and thermal stress analysis of a 10kW@20K helium refrigerator

    NASA Astrophysics Data System (ADS)

    Xu, D.; Gong, L. H.; Xu, P.; Liu, H. M.; Li, L. F.; Xu, X. D.

    2014-01-01

    This paper is based on the devices and pipeline in the horizontal cryogenic cold-box of a 10kW@20K helium refrigerator developed by Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. Four devices, six valves, supporting components and pipe lines are positioned in the cold-box. At operating state, the temperature of these devices and pipeline is far below the room temperature, and the lowest temperature is 14K. Due to different material and temperature, the shrinkage of devices and pipes is different. Finite element analysis software SOLIDWORKS SIMULATION was used to numerically simulate the thermal stress and deformation. The results show that the thermal stress of pipe A is a little large. So we should change the pipe route or use a bellows expansion joint. Bellows expansion joints should also be used in the pipes connected to three of the six valves to protect them by decreasing the deformation. At last, the effect of diameter, thickness and bend radius on the thermal stress was analyzed. The results show that the thermal stress of the pipes increases with the increase of the diameter and the decrease of the bend radius.

  18. Modeling of thermal stresses in a microtubular Solid Oxide Fuel Cell stack

    NASA Astrophysics Data System (ADS)

    Pianko-Oprych, Paulina; Zinko, Tomasz; Jaworski, Zdzisław

    2015-12-01

    A modeling study was carried out to analyze thermal stresses in a microtubular Solid Oxide Fuel Cell (mSOFC) stack and to estimate thermal expansion of the fuel cells inside the stack. A joint analysis by Computational Fluid Dynamics (CFD) and Computational Structural Mechanics Finite Element Method (FEM) was performed. Temperature profiles generated by the thermo-hydrodynamic model were applied in the thermo-mechanical model to calculate thermal stress distributions in the mSOFC stack. The results yield maximum thermal axial elongation equal to 1.34 mm for the mSOFC stack, while the maximum radial elongation was equal to 0.496 mm. Modeled maximum equivalent (von Mises) stress was equal to 538 MPA in the contact areas of the cylindrical housing and manifold on the fuel inlet side. Based on comparison of the total axial stresses and the residual ones with the material strength it was noticed that the anode and electrolyte layers should not be critically deformed, but there is a risk of damage for cathode layers at chosen fuel cell configurations. A high risk of damage was also noticed for the outer housing, near contact points with manifolds as well as at the air distributor due to large number of cut-outs in the material.

  19. Examining rapid onset drought development using the thermal infrared based evaporative stress index

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reliable indicators of rapid drought onset are necessary to improve the utility of drought early warning systems. In this study, the Evaporative Stress Index (ESI), which uses remotely-sensed thermal infrared imagery to estimate evapotranspiration (ET), is compared to meteorological data and United...

  20. Influence of thermal residual stresses on the elastic phase-strain

    SciTech Connect

    Shi, N.; Bourke, M.A.M.; Goldstone, J.A.

    1996-04-01

    The development of elastic lattice phase strains in a 15 vol. pct TiC particulate reinforced 2219-T6 Al composite was modeled as a function of tensile uniaxial loading by finite element method (FEM). In the relationship of applied stress vs. elastic lattice phase strain, the slopes vary with the applied load even before the macroscopic yielding. The slopes for the phase-strain perpendicular to loading follow nonmonotonic changes with loading, while, in the direction parallel to loading, the slopes change monotonically with the applied load. In this investigation, we have demonstrated via FEM that thermal residual stresses from thermal expansion mismatch between phases affect initiation of matrix plasticity. And the differences in the matrix plasticity initiation influence the internal stress distribution. The changes in the slope are dictated by the internal stress transfer between phases. FEM models with and without thermal history show significant differences in the response of elastic strain component, a mechanics equivalent of the lattice elastic strain. Agreement with experiment can only be obtained by including the thermal history. From a simple elasto-plastic spring model we are able to demonstrate that, with matrix plasticity propagating as predicted by FEM, the elastic strain component responds similarly to the more rigorous numerical predictions, suggesting that the morphology of elastic strain evolution is dictated by the development of matrix plasticity.

  1. Effect of non-homogenous thermal stress during sub-lethal photodynamic antimicrobial chemotherapy

    NASA Astrophysics Data System (ADS)

    Gadura, N.; Kokkinos, D.; Dehipawala, S.; Cheung, E.; Sullivan, R.; Subramaniam, R.; Schneider, P.; Tremberger, G., Jr.; Holden, T.; Lieberman, D.; Cheung, T.

    2012-03-01

    Pathogens could be inactivated via a light source coupled with a photosensitizing agent in photodynamic antimicrobial chemotherapy (PACT). This project studied the effect of non-homogenous substrate on cell colony. The non-homogeneity could be controlled by iron oxide nano-particles doping in porous glassy substrates such that each cell would experience tens of hot spots when illuminated with additional light source. The substrate non-homogeneity was characterized by Atomic Force Microscopy, Transmission Electron Microscopy and Extended X-Ray Absorption Fine Structure at Brookhaven Synchrotron Light Source. Microscopy images of cell motion were used to study the motility. Laboratory cell colonies on non-homogenous substrates exhibit reduced motility similar to those observed with sub-lethal PCAT treatment. Such motility reduction on non-homogenous substrate is interpreted as the presence of thermal stress. The studied pathogens included E. coli and Pseudomonas aeruginosa. Non-pathogenic microbes Bacillus subtilis was also studied for comparison. The results show that sub-lethal PACT could be effective with additional non-homogenous thermal stress. The use of non-uniform illumination on a homogeneous substrate to create thermal stress in sub-micron length scale is discussed via light correlation in propagation through random medium. Extension to sub-lethal PACT application complemented with thermal stress would be an appropriate application.

  2. Release of bacterial spores from inner walls of a stainless steel cup subjected to thermal stress

    NASA Technical Reports Server (NTRS)

    Wolochow, H.; Chatigny, M. A.; Herbert, J.

    1974-01-01

    In an earlier report thermal stresses, simulating those expected on a Mars Lander, dislodged approximately 0.01% of an aerosol deposited surface burden, as did a landing shock of 8-10 G deceleration. This work confirms earlier results and demonstrates that release rate is not dependent on surface burden.

  3. A biharmonic relaxation method for calculating thermal stress in cooled irregular cylinders

    NASA Technical Reports Server (NTRS)

    Holms, Arthur G

    1952-01-01

    A numerical method was developed for calculating thermal stresses in irregular cylinders cooled by one or more internal passages. The use of relaxation methods and elementary methods of finite differences was found to give approximations to the correct values when compared with previously known solutions for concentric circular cylinders possessing symmetrical and asymmetrical temperature distributions.

  4. Estimating maize water stress by standard deviation of canopy temperature in thermal imagery

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new crop water stress index using standard deviation of canopy temperature as an input was developed to monitor crop water status. In this study, thermal imagery was taken from maize under various levels of deficit irrigation treatments in different crop growing stages. The Expectation-Maximizatio...

  5. Contrasting Patterns of Coral Bleaching Susceptibility in 2010 Suggest an Adaptive Response to Thermal Stress

    PubMed Central

    Guest, James R.; Baird, Andrew H.; Maynard, Jeffrey A.; Muttaqin, Efin; Edwards, Alasdair J.; Campbell, Stuart J.; Yewdall, Katie; Affendi, Yang Amri; Chou, Loke Ming

    2012-01-01

    Background Coral bleaching events vary in severity, however, to date, the hierarchy of susceptibility to bleaching among coral taxa has been consistent over a broad geographic range and among bleaching episodes. Here we examine the extent of spatial and temporal variation in thermal tolerance among scleractinian coral taxa and between locations during the 2010 thermally induced, large-scale bleaching event in South East Asia. Methodology/Principal Findings Surveys to estimate the bleaching and mortality indices of coral genera were carried out at three locations with contrasting thermal and bleaching histories. Despite the magnitude of thermal stress being similar among locations in 2010, there was a remarkable contrast in the patterns of bleaching susceptibility. Comparisons of bleaching susceptibility within coral taxa and among locations revealed no significant differences between locations with similar thermal histories, but significant differences between locations with contrasting thermal histories (Friedman = 34.97; p<0.001). Bleaching was much less severe at locations that bleached during 1998, that had greater historical temperature variability and lower rates of warming. Remarkably, Acropora and Pocillopora, taxa that are typically highly susceptible, although among the most susceptible in Pulau Weh (Sumatra, Indonesia) where respectively, 94% and 87% of colonies died, were among the least susceptible in Singapore, where only 5% and 12% of colonies died. Conclusions/Significance The pattern of susceptibility among coral genera documented here is unprecedented. A parsimonious explanation for these results is that coral populations that bleached during the last major warming event in 1998 have adapted and/or acclimatised to thermal stress. These data also lend support to the hypothesis that corals in regions subject to more variable temperature regimes are more resistant to thermal stress than those in less variable environments. PMID:22428027

  6. Cross-Sectional Residual Stresses in Thermal Spray Coatings Measured by Moiré Interferometry and Nanoindentation Technique

    NASA Astrophysics Data System (ADS)

    Zhu, Jianguo; Xie, Huimin; Hu, Zhenxing; Chen, Pengwan; Zhang, Qingming

    2012-09-01

    A plasma-sprayed thermal barrier coating (TBC) was deposited on a stainless steel substrate. The residual stresses were firstly measured by moiré interferometry combined with a cutting relaxation method. The fringe patterns in the cross-section of the specimen clearly demonstrate the deformation caused by the residual stress in thermal spray coatings. However, restricted by the sensitivity of moiré interferometry, there are few fringes in the top coat, and large errors may exist in evaluating the residual stress in the top coat. Then, the nanoindentation technique was used to estimate the residual stresses across the coating thickness. The stress/depth profile shows that the process-induced stresses after thermal spray are compressive in the top coat and a tendency to a more compressive state toward the interface. In addition, the stress gradient in the substrate is nonlinear, and tensile and compressive stresses appear simultaneously for self-equilibrium in the cross-section.

  7. Coupled melt flow and thermal stress predictions for Czochralski crystal growth

    SciTech Connect

    Zou, Y.F.; Zhang, H.; Prasad, V.

    1995-12-31

    A coupled finite volume-finite element algorithm is developed to simulate the melt flows and predict the temperature distributions and thermal stresses in the Czochralski grown crystals. The computer model employs a multizone adaptive grid generation scheme together with curvilinear finite column discretization (MASTRAPP) to predict the transport phenomena associated with the crystal growth processes as well as the nonplanar melt/crystal interface shape and its dynamics (Zhang and Prasad, 1995a). The MASTRAPP has proven to be a robust and efficient scheme for the problems involving moving interfaces and free surfaces. Thermal stresses in the crystal are obtained by using a commercial finite element code, ALGOR, that uses the curvilinear mesh generated by the MASTRAPP. The numerical results show that the melt flows have a strong influence on thermal stresses in the crystal near the melt/crystal interface, and hence, melt convection must be included in the computer model for accurate stress predictions. The predicted stress phenomena agrees qualitatively with the report results.

  8. Diluent sensitivity in thermally stressed cells of pseudomonas fluorescens.

    PubMed

    Gray, R J; Ordal, Z J; Witter, L D

    1977-05-01

    Thermally injured cells of Pseudomonas fluorescens were unable to produce colonies on Trypticase soy agar (TSA) after dilution with 0.1% peptone. Nutritional exigency could not be used as the criterion for this injury, since varying the composition of the plating medium had little effect on the number of colonies that developed. The injured cells had no requirement for compounds known to leak out during the heat treatment in order to recover. The cells did not exhibit injury if dilution preceded heat treatment on the plating medium, demonstrating that the heat treatment sensitized the cells to the trauma of dilution. Substitution of 0.1% peptone with growth medium as the diluent largely offset the previously observed drop in TSA count. Little difference in survival was observed when monosodium glutamate or the balance of the defined medium was used as the diluent. The diluent effect was ionic rather than osmotic. The presence of cations was important in maintaining the integrity of the injured cell, and divalent cations enhanced this protective effect. The role of these cations at the level of the cell envelope is discussed. PMID:406839

  9. Evaluation of Transverse Thermal Stresses in Composite Plates Based on First-Order Shear Deformation Theory

    NASA Technical Reports Server (NTRS)

    Rolfes, R.; Noor, A. K.; Sparr, H.

    1998-01-01

    A postprocessing procedure is presented for the evaluation of the transverse thermal stresses in laminated plates. The analytical formulation is based on the first-order shear deformation theory and the plate is discretized by using a single-field displacement finite element model. The procedure is based on neglecting the derivatives of the in-plane forces and the twisting moments, as well as the mixed derivatives of the bending moments, with respect to the in-plane coordinates. The calculated transverse shear stiffnesses reflect the actual stacking sequence of the composite plate. The distributions of the transverse stresses through-the-thickness are evaluated by using only the transverse shear forces and the thermal effects resulting from the finite element analysis. The procedure is implemented into a postprocessing routine which can be easily incorporated into existing commercial finite element codes. Numerical results are presented for four- and ten-layer cross-ply laminates subjected to mechanical and thermal loads.

  10. Adaptive bimaterial lattices to mitigate thermal expansion mismatch stresses in satellite structures

    NASA Astrophysics Data System (ADS)

    Toropova, Marina M.; Steeves, Craig A.

    2015-08-01

    Earth-orbiting satellites regularly pass from sunlight to shade and back; these transitions are typically accompanied by significant temperature changes. When adjoining parts of a satellite that are made of different materials are subjected to large temperature changes, thermal mismatch stresses arise that are a function of the temperature change and the difference in coefficients of thermal expansion (CTEs) between the two materials. These thermal stresses are linked to undesirable deformation and, through long-term cycling, fatigue and failure of the structure. This paper describes a type of anisotropic lattice that can serve as a stress-free adaptor between two materials, eliminating thermal mismatch stresses and their concomitant consequences. The lattices consist of planar nonidentical anisotropic bimaterial cells, each designed based on a virtual triangle. Physically the cells consist of a triangle made of material with higher CTE surrounded by a hexagon made of material with lower CTE. Different skew angles of the hexagon make a particular cell and the whole lattice anisotropic. The cells can be designed and combined in a lattice in such a way that one edge of the lattice has CTE that coincides with the CTE of the first part of the structure (substrate 1), while the other edge of the lattice has CTE equal to the CTE of the second part of the structure (substrate 2). If all joints between the parts of each cell, neighbouring cells, and the lattice and the substrates are pinned, the whole structure will be free of thermal stresses. This paper will discuss the fundamental principles governing such lattices, their refinement for special circumstances, and opportunities for improving the structural performance of the lattices. This will be presented coupled to a rational strategy for lattice design.

  11. Mucus Sugar Content Shapes the Bacterial Community Structure in Thermally Stressed Acropora muricata

    PubMed Central

    Lee, Sonny T. M.; Davy, Simon K.; Tang, Sen-Lin; Kench, Paul S.

    2016-01-01

    It has been proposed that the chemical composition of a coral’s mucus can influence the associated bacterial community. However, information on this topic is rare, and non-existent for corals that are under thermal stress. This study therefore compared the carbohydrate composition of mucus in the coral Acropora muricata when subjected to increasing thermal stress from 26 to 31°C, and determined whether this composition correlated with any changes in the bacterial community. Results showed that, at lower temperatures, the main components of mucus were N-acetyl glucosamine and C6 sugars, but these constituted a significantly lower proportion of the mucus in thermally stressed corals. The change in the mucus composition coincided with a shift from a γ-Proteobacteria- to a Verrucomicrobiae- and α-Proteobacteria-dominated community in the coral mucus. Bacteria in the class Cyanobacteria also started to become prominent in the mucus when the coral was thermally stressed. The increase in the relative abundance of the Verrucomicrobiae at higher temperature was strongly associated with a change in the proportion of fucose, glucose, and mannose in the mucus. Increase in the relative abundance of α-Proteobacteria were associated with GalNAc and glucose, while the drop in relative abundance of γ-Proteobacteria at high temperature coincided with changes in fucose and mannose. Cyanobacteria were highly associated with arabinose and xylose. Changes in mucus composition and the bacterial community in the mucus layer occurred at 29°C, which were prior to visual signs of coral bleaching at 31°C. A compositional change in the coral mucus, induced by thermal stress could therefore be a key factor leading to a shift in the associated bacterial community. This, in turn, has the potential to impact the physiological function of the coral holobiont. PMID:27047481

  12. Mucus Sugar Content Shapes the Bacterial Community Structure in Thermally Stressed Acropora muricata.

    PubMed

    Lee, Sonny T M; Davy, Simon K; Tang, Sen-Lin; Kench, Paul S

    2016-01-01

    It has been proposed that the chemical composition of a coral's mucus can influence the associated bacterial community. However, information on this topic is rare, and non-existent for corals that are under thermal stress. This study therefore compared the carbohydrate composition of mucus in the coral Acropora muricata when subjected to increasing thermal stress from 26 to 31°C, and determined whether this composition correlated with any changes in the bacterial community. Results showed that, at lower temperatures, the main components of mucus were N-acetyl glucosamine and C6 sugars, but these constituted a significantly lower proportion of the mucus in thermally stressed corals. The change in the mucus composition coincided with a shift from a γ-Proteobacteria- to a Verrucomicrobiae- and α-Proteobacteria-dominated community in the coral mucus. Bacteria in the class Cyanobacteria also started to become prominent in the mucus when the coral was thermally stressed. The increase in the relative abundance of the Verrucomicrobiae at higher temperature was strongly associated with a change in the proportion of fucose, glucose, and mannose in the mucus. Increase in the relative abundance of α-Proteobacteria were associated with GalNAc and glucose, while the drop in relative abundance of γ-Proteobacteria at high temperature coincided with changes in fucose and mannose. Cyanobacteria were highly associated with arabinose and xylose. Changes in mucus composition and the bacterial community in the mucus layer occurred at 29°C, which were prior to visual signs of coral bleaching at 31°C. A compositional change in the coral mucus, induced by thermal stress could therefore be a key factor leading to a shift in the associated bacterial community. This, in turn, has the potential to impact the physiological function of the coral holobiont. PMID:27047481

  13. Food availability promotes rapid recovery from thermal stress in a scleractinian coral

    NASA Astrophysics Data System (ADS)

    Connolly, S. R.; Lopez-Yglesias, M. A.; Anthony, K. R. N.

    2012-12-01

    Bleaching in corals due to environmental stress represents a loss of energy intake often leading to an increase in mortality risk. Successful coral recovery from severe bleaching events may depend on the rate of replenishment of algal symbiont populations following the period of thermal stress, the supply of an alternative food source, or both. Here, we explore the role of food availability in promoting the survival and recovery of a common coral ( Acropora intermedia) following acute experimentally induced thermal stress. Fed corals were provided with live rotifers daily, to maintain densities of zooplankton in tanks that are typical of coral reefs. After a 6-week acclimation phase, heated corals were subjected to a +4 °C thermal anomaly for a 7-day period (bleaching phase) then temperatures were returned to normal for a further 2 weeks (recovery phase). Results demonstrated that heated corals had higher survival when they were provided with heterotrophic food. Fed corals experienced reduced loss of chlorophyll a, relative to unfed corals. During the recovery phase, both fed and unfed corals recovered within a few days; however, fed corals recovered to pre-bleaching phase levels of chlorophyll a, whereas unfed corals stabilized approximately one-third below this level. Protein levels of fed corals declined markedly during the bleaching phase, but recovered all of their losses by the end of the recovery phase. In contrast, unfed corals had low protein levels that were maintained throughout the experiment. To the extent that these results are representative of corals' responses to thermal anomalies in nature, the findings imply that availability of particulate food matter has the potential to increase corals' capacity to survive thermally induced bleaching and to ameliorate its sub-lethal effects. They also support the hypothesis that different rates of heterotrophy are an important determinant of variation in resilience to thermal stress among reef environments.

  14. Correlation of predicted and measured thermal stresses on an advanced aircraft structure with dissimilar materials. [hypersonic heating simulation

    NASA Technical Reports Server (NTRS)

    Jenkins, J. M.

    1979-01-01

    Additional information was added to a growing data base from which estimates of finite element model complexities can be made with respect to thermal stress analysis. The manner in which temperatures were smeared to the finite element grid points was examined from the point of view of the impact on thermal stress calculations. The general comparison of calculated and measured thermal stresses is guite good and there is little doubt that the finite element approach provided by NASTRAN results in correct thermal stress calculations. Discrepancies did exist between measured and calculated values in the skin and the skin/frame junctures. The problems with predicting skin thermal stress were attributed to inadequate temperature inputs to the structural model rather than modeling insufficiencies. The discrepancies occurring at the skin/frame juncture were most likely due to insufficient modeling elements rather than temperature problems.

  15. Thermal- and electromigration-induced stresses in passivated Al- and AlSiCu-interconnects

    SciTech Connect

    Beckers, D.; Schroeder, H.; Schilling, W.; Eppler, I.

    1997-05-01

    Mechanical stresses in microelectronic devices are of special interest because of degradation effects in microelectronic circuits such as stress induced voiding or electromigration. Al and al-alloys are commonly used as interconnect materials in integrated electronic devices. Stress induced voiding and degradation of metal lines by electromigration are closely related to the stresses in the lines. The authors have studied the strain and stress evolution during thermal cycling, isothermal relaxation and due to electromigration in passivated Al and AlSi(1%)Cu(0.5%) lines by X-Ray diffraction with variation of experimental parameters such as the aspect ratio and the electrical current density. Furthermore the extent of voiding and plastic shear deformation has been determined from the experimental metal strains with the help of finite element calculations. Main results are: (1) During thermal cycling the voiding is less than 2 {center_dot} 10{sup {minus}3}. The extent of plastic shear deformation increases with increasing line width and with decreasing flowstress. (2) During isothermal relaxation void growth occurs but no significant change in the plastic shear deformation. (3) An electric current in the lines causes no measurable additional change of the volume averaged stresses up to line failure.

  16. Reduction of spinal PGE2 concentrations prevents swim stress-induced thermal hyperalgesia.

    PubMed

    Guevara, Coram; Fernandez, Ana Cristina; Cardenas, Ricardo; Suarez-Roca, Heberto

    2015-03-30

    We evaluated the association between spinal PGE2 and thermal hyperalgesia following repeated stress. Thermal nociception was determined in male Sprague-Dawley rats using the hot-plate test, before and after forced-swimming; non-conditioned rats served as controls. Animals were pretreated with ketoprofen or meloxicam, preferential COX-1 and COX-2 inhibitors, respectively. After the second hot-plate test, we measured serum corticosterone (stress marker), and lumbar spinal PGE2 (neuroinflammation marker) under peripheral inflammation (1% formalin plantar injection). Stressed rats displayed response latencies 40% shorter and inflammatory spinal PGE2 levels 95% higher than controls. Pretreatment with ketoprofen or meloxicam prevented hyperalgesia and elevation of spinal PGE2, increasing the escape behavior time during forced swimming 95% respect to saline-treated rats. Corticosterone levels in stressed rats were 97% higher than controls; COX inhibitors reduced them by 84%. PGE2 could participate in stress-induced hyperalgesia, learned helplessness, and corticosterone production, supporting the use of non-steroidal anti-inflammatory drugs (NSAIDs) for persistent pain associated with chronic stress and depression. PMID:25703222

  17. Thermal imaging of soybean response to drought stress: the effect of Ascophyllum nodosum seaweed extract.

    PubMed

    Martynenko, Alex; Shotton, Katy; Astatkie, Tessema; Petrash, Gerry; Fowler, Christopher; Neily, Will; Critchley, Alan T

    2016-01-01

    Previous experiments have demonstrated positive effect of Acadian(®) extract of Ascophyllum nodosum on plant stress-resistance, however the mode of action is not fully understood. The aim of this study was to understand the physiological effect of Acadian(®) seaweed extract on the plant response to drought stress. Leaf temperature and leaf angle were measured as early-stage indicators of plant stress with thermal imaging "in situ" over a 5-day stress-recovery trial. The early stress-response of control became visible on the third day as a rapid wilting of leaves, accompanied with the asymptotic increase of leaf temperature on 4-5 °C to the thermal equilibrium with ambient air temperature. At the same time Acadian(®) treated plants still maintained turgor, accompanied with the linear increase in leaf temperature, which indicated better control of stomatal closure. Re-watering on the fifth day showed better survival of treated plants compared to control. This study demonstrated the ability of Acadian(®) seaweed extract to improve resistance of soybean plants to water stress. PMID:27610312

  18. Effects of WC size and amount on the thermal residual stress in WC–Ni composites

    SciTech Connect

    Seol, K.; Krawitz, A. D.; Richardson, J. W.; Weisbrook, C. M.

    2005-05-01

    We studied the effects of WC particle size and volume fraction on the magnitude and distribution of thermal residual stresses (TRS) in WC–Ni cemented carbide composites by neutron powder diffraction. Samples of high (0.3) and low (0.1) Ni volume fraction and coarse (1.7 m) and fine (0.5 m) WC particle size were employed. Thermal residual strain and stress values were obtained at temperatures between 100 and 900 K. Moreover, the magnitude of the mean (compressive) WC stress increased as WC fraction decreased, while the mean (tensile) Ni stress did the opposite. For both phases, stresses were highest for fine WC particles, reaching over 3 GPa in Ni. Elastic strain distributions, due to the sharp edges and corners of WC particles, were characterized by analyzing diffraction peak widths. The range of stress increased with the magnitude of the TRS. Even though the mean TRS is compressive in WC, regions of tension exist, and, for Ni, regions of compression are present.

  19. A geometrically nonlinear analysis of interlaminar stresses in unsymmetrically laminated plates subjected to uniform thermal loading

    NASA Technical Reports Server (NTRS)

    Norwood, D. S.; Shuart, Mark J.; Herakovich, Carl T.

    1991-01-01

    An analytical study of interlaminar stresses in unsymmetrically laminated plates is presented. The study examines the linear elastic, large deflection response of square laminated composite plates subjected to uniform thermal loading. Both cross-ply and angle-ply, symmetric and unsymmetric, laminates are examined to evaluate the effects of mismatch between adjacent layers in elastic constants and coefficients of thermal expansion. A geometrically nonlinear kinematic description is used to predict the large out-of-plane (transverse) deflections. The nonlinear, three-dimensional boundary value problems are formulated from elasticity theory and approximate solutions are determined using the finite element method. A global/local analysis procedure is used to obtain improved free edge stress predictions. For the laminates and loading conditions considered, the results indicate that the out-of-plane deflections of the unsymmetric laminates reduce interlaminar shear stresses. These deflections also reduce interlaminar normal stresses in some laminates and increase these stresses for others. The results indicate that as the out-of-plane deflections become large, the differences in interlaminar stress predictions between linear and nonlinear theory can become quite large.

  20. Finite element analysis of the residual thermal stresses on functionally gradated dental restorations.

    PubMed

    Henriques, B; Miranda, G; Gasik, M; Souza, J C M; Nascimento, R M; Silva, F S

    2015-10-01

    The aim of this work was to study, using the finite element method (FEM), the distribution of thermal residual stresses arising in metal-ceramic dental restorations after cooling from the processing temperature. Three different interface configurations were studied: with conventional sharp transition; one with a 50% metal-50% ceramic interlayer; and one with a compositionally functionally gradated material (FGM) interlayer. The FE analysis was performed based on experimental data obtained from Dynamic Mechanical Analysis (DMA) and Dilatometry (DIL) studies of the monolithic materials and metal/ceramic composites. Results have shown significant benefits of using the 50% metal-50% ceramic interlayer and the FGM interlayer over the conventional sharp transition interface configuration in reduction of the thermal residual stress and improvement of stress profiles. Maximum stresses magnitudes were reduced by 10% for the crowns with 50% metal-50% ceramic interlayer and by 20% with FGM interlayer. The reduction in stress magnitude and smoothness of the stress distribution profile due to the gradated architectures might explain the improved behavior of these novel dental restorative systems relative to the conventional one, demonstrated by in-vitro studies already reported in literature. PMID:26122789

  1. Dependence of thermal residual stress on temperature in a SiC particle-reinforced 6061Al alloy

    NASA Astrophysics Data System (ADS)

    Li, H.; Wang, D. Z.; Li, J. B.; Wang, Z. G.; Chen, C. R.

    1998-07-01

    The thermal stresses (TS) in the matrix of a SiC p /6061Al composite during thermal cycling were measured by X-ray diffraction. Also, the TS during thermal cycling and residual stress distribution (RSD) at room temperature in the two phases of composite were calculated by finite element modeling (FEM). The measured and calculated results indicated that the closed stress-temperature loop was formed during thermal cycling. The stress state in the matrix changed from tension to compression during heating and from compression to tension during cooling. Plastic deformation took place in the matrix of the composite during thermal cycling. The general change trend of TS with temperature during thermal cycling was in agreement between the experiment and calculation.

  2. Effects of coating spray speed and convective heat transfer on transient thermal stress in thermal barrier coating system during the cooling process of fabrication

    NASA Astrophysics Data System (ADS)

    Song, Yan; Lv, Zhichao; Liu, Yilun; Zhuan, Xin; Wang, T. J.

    2015-01-01

    The coating spray speed and the convective heat transfer have significant effects on transient thermal stress in TBCs (Thermal Barrier Coating system) during the cooling process of fabrication. In this work, a simplified analytical model is developed firstly, to predict the transient thermal stress in YSZ (ZrO2-8%Y2O3) coating and shear stress at the coating-substrate interface during the cooling process of fabrication. Then, based on this simplified model, the effects of coating spray speed which determines the initial temperature field of YSZ coating, and the convective heat transfer coefficient between YSZ coating and the environment on transient thermal stress in TBCs during the cooling process have been studied. The results indicate that the YSZ coating spray speed has a significant effect on the transient thermal stress in YSZ coating and the shear stress near the edge of YSZ-substrate interface; effect of convective heat transfer on the thermal stress is more significant when convective heat transfer coefficient is bigger enough, and for a given convective heat transfer the effect becomes smaller as the cooling down process going on.

  3. Steady thermal stress analysis in two-dimensional problems by thermoelastic displacement potential and boundary-element method

    SciTech Connect

    Ochiai, Y.; Ishida, R.; Sekiya, T. Osaka Prefecture Univ., Sakai Osaka Electro-Communication University, Neyagawa )

    1990-01-01

    A new numerical method to analyze steady thermal stresses in two-dimensional problems is proposed. Thermoelastic displacement potential is introduced for the analysis. The discontinuities of stresses on the boundary are investigated, and a completely analytic formulation is carried out. In order to investigate the accuracy of this method, steady thermal stress distributions in a square column and a circular cylinder with an eccentric circular hole are obtained.

  4. Quantifying the Rates of Sn Whisker Growth and Plastic Strain Relaxation Using Thermally-Induced Stress

    NASA Astrophysics Data System (ADS)

    Pei, Fei; Bower, Allan F.; Chason, Eric

    2016-01-01

    Whiskers and hillocks that grow out of Sn-based coatings are a critical reliability issue in Pb-free electronics. Although their growth is widely regarded as a stress-relaxation mechanism, quantitative understanding of the relationship between the stress, growth kinetics, and strain relaxation is still lacking. In this work, the well-controlled strain induced by thermal-expansion mismatch was used to study the whiskering behavior of electroplated Sn films. Stress was quantified by monitoring wafer-curvature and the density of whiskers and hillocks was measured simultaneously by use of optical microscopy. Evolution of the volume of individual features was also measured by scanning electron microscopy after different periods of heating. The measurements were used to develop a model for temperature-dependent and stress-dependent growth kinetics of whiskers and hillocks and to determine the amount of strain relaxation which occurs as a result of their formation.

  5. Thermal stresses in chemically hardening elastic media with application to the molding process

    NASA Technical Reports Server (NTRS)

    Levitsky, M.; Shaffer, B. W.

    1974-01-01

    A method has been formulated for the determination of thermal stresses in materials which harden in the presence of an exothermic chemical reaction. Hardening is described by the transformation of the material from an inviscid liquid-like state into an elastic solid, where intermediate states consist of a mixture of the two, in a ratio which is determined by the degree of chemical reaction. The method is illustrated in terms of an infinite slab cast between two rigid mold surfaces. It is found that the stress component normal to the slab surfaces vanishes in the residual state, so that removal of the slab from the mold leaves the remaining residual stress unchanged. On the other hand, the residual stress component parallel to the slab surfaces does not vanish. Its distribution is described as a function of the parameters of the hardening process.

  6. The stress heat-flow paradox and thermal results from Cajon Pass

    USGS Publications Warehouse

    Lachenbruch, A.H.; Sass, J.H.

    1988-01-01

    Conventional friction models predict a substantial thermal anomaly associated with active traces of strike-slip faults, but no such anomaly is observed from over 100 heat-flow determinations along 1000 km of the San Andreas fault. The Cajon Pass well is being drilled to bring deep heat-flow and stress data to bear on this paradox. Preliminary stress results from Cajon Pass and a new interpretation of regional data by Mark D. Zoback and colleagues suggests that the maximum compressive stress near the fault is almost normal to the trace, and hence the resolved shear stress is low and the fault, weak. The heat-flow data show large variability with depth, probably from three-dimensional structure, and an overall decrease from over 90 mW/m2 in the upper kilometer to less than 80 mW/m2 in the lower 300 m with no evidence of advective heat transfer. -from Authors

  7. Impact of the medical clothing on the thermal stress of surgeons.

    PubMed

    Zwolińska, M; Bogdan, A

    2012-11-01

    The aim of the presented experiments was to determine thermal stress of surgeons performing their work with a high metabolic rate, wearing clothing characterized by high insulation and impermeability protecting them against water vapour but also in thermal conditions of a warm climate protecting patients against hypothermia. The experiments were conducted with the participation of 8 volunteers. Each subject took part in the experiment four times, i.e. in each of the four tested surgical gowns. The experiments were conducted in a climatic chamber where thermal conditions characteristic of an operating theatre were simulated. The parameters to be measured included: skin temperature, temperature measured in the auditory canal, sweat rate as well as temperature and humidity between clothing and a human body. The conducted experiments provided the grounds to conclude that medical clothing can be regarded as barrier clothing and it can influence thermal load of a human body. PMID:22575493

  8. Through-thickness determination of phase composition and residual stresses in thermall barrier coatings using high- energy x-rays.

    SciTech Connect

    Weyant, , C. M.; Almer, J. D.; Faber, K. T.; Stony Brook Univ.

    2009-01-01

    High-energy X-rays were used to determine the local phase composition and residual stresses through the thickness of as-sprayed and heat-treated plasma-sprayed thermal barrier coatings consisting of a NiCoCrAlY bond coat and an yttria-stabilized zirconia (YSZ) topcoat produced with through-thickness segmentation cracks. The as-sprayed residual stresses reflected the combined influence of quenching stresses from the plasma spray process, thermal expansion mismatch between the topcoat, bond coat and substrate, and stress relief from the segmentation cracks. Heat treatments led to the formation of a thermally grown oxide (TGO) which was in compression in the plane, as well as relief of quenching stresses and development of a stress gradient in the YSZ topcoat. The high-energy X-ray technique used in this study revealed the effects that TGO and segmentation cracks have on the in-plane stress state of the entire coating.

  9. Temperature-time distribution and thermal stresses on the RTG fins and shell during water cooling

    NASA Technical Reports Server (NTRS)

    Turner, R. H.

    1983-01-01

    Radioisotope thermoelectric generator (RTG) packages designed for space missions generally do not require active cooling. However, the heat they generate cannot remain inside of the launch vehicle bay and requires active removal. Therefore, before the Shuttle bay door is closed, the RTG coolant tubes attached to the heat rejection fins must be filled with water, which will circulate and remove most of the heat from the cargo bay. There is concern that charging a system at initial temperature around 200 C with water at 24 C can cause unacceptable thermal stresses in the RTG shell and fins. A computer model is developed to estimate the transient temperature distribution resulting from such charging. The thermal stresses resulting from the temperature gradients do not exceed the elastic deformation limit for the material. Since the simplified mathematical model for thermal stresses tends to overestimate stresses, it is concluded that the RTG can be cooled by introducing water at 24 C to the initially hot fin coolant tubes while the RTG is in the Shuttle cargo bay.

  10. Thermal stress analysis of pipe flange connections with raised-face gasket subjected to heat conduction

    SciTech Connect

    Sawa, Toshiyuki; Kotani, Kenichi

    1996-12-01

    This paper deals with thermal stress analysis of a pipe flange connection with a raised-face gasket subjected to heat conduction. In the analysis, pipe flange, hubs of the flanges and a raised-face gasket are replaced by finite hollow cylinders. When the inner surface is subjected to heat conduction due to contained fluid and the outer surface are kept at a constant temperature, temperature distribution of the connection is analyzed. Using the temperature distribution, thermoelastic displacement potential is determined. Thermal stresses and displacements are analyzed by using the thermoelastic displacement potential and axisymmetrical theory of elasticity. Experiments are performed. The analytical results are in fairly good agreement with the experimental results concerning the variation of axial bolt force and the axial strain at the hubs of pipe flange. In the numerical calculations, the effects of the ratios of Young`s modulus and the gasket thickness between the flanges and the gaskets on the contact stress distribution are examined. As the results, it is seen that the thermal stress at the inner surface increases with a decrease of the ratio of Young`s modulus and that it increases with a decrease of the gasket thickness.

  11. Boundary layer thermal stresses in angle-ply composite laminates, part 1. [graphite-epoxy composites

    NASA Technical Reports Server (NTRS)

    Wang, S. S.; Choi, I.

    1981-01-01

    Thermal boundary-layer stresses (near free edges) and displacements were determined by a an eigenfunction expansion technique and the establishment of an appropriate particular solution. Current solutions in the region away from the singular domain (free edge) are found to be excellent agreement with existing approximate numerical results. As the edge is approached, the singular term controls the near field behavior of the boundary layer. Results are presented for cases of various angle-ply graphite/epoxy laminates with (theta/-theta/theta/theta) configurations. These results show high interlaminar (through-the-thickness) stresses. Thermal boundary-layer thicknesses of different composite systems are determined by examining the strain energy density distribution in composites. It is shown that the boundary-layer thickness depends on the degree of anisotropy of each individual lamina, thermomechanical properties of each ply, and the relative thickness of adjacent layers. The interlaminar thermal stresses are compressive with increasing temperature. The corresponding residual stresses are tensile and may enhance interply delaminations.

  12. Calculation of Local Stress and Fatigue Resistance due to Thermal Stratification on Pressurized Surge Line Pipe

    SciTech Connect

    Bandriyana, B.; Utaja

    2010-06-22

    Thermal stratification introduces thermal shock effect which results in local stress and fatigue problems that must be considered in the design of nuclear power plant components. Local stress and fatigue calculation were performed on the Pressurize Surge Line piping system of the Pressurize Water Reactor of the Nuclear Power Plant. Analysis was done on the operating temperature between 177 to 343 deg. C and the operating pressure of 16 MPa (160 Bar). The stagnant and transient condition with two kinds of stratification model has been evaluated by the two dimensional finite elements method using the ANSYS program. Evaluation of fatigue resistance is developed based on the maximum local stress using the ASME standard Code formula. Maximum stress of 427 MPa occurred at the upper side of the top half of hot fluid pipe stratification model in the transient case condition. The evaluation of the fatigue resistance is performed on 500 operating cycles in the life time of 40 years and giving the usage value of 0,64 which met to the design requirement for class 1 of nuclear component. The out surge transient were the most significant case in the localized effects due to thermal stratification.

  13. Calculation of Local Stress and Fatigue Resistance due to Thermal Stratification on Pressurized Surge Line Pipe

    NASA Astrophysics Data System (ADS)

    Bandriyana, B.; Utaja

    2010-06-01

    Thermal stratification introduces thermal shock effect which results in local stress and fatique problems that must be considered in the design of nuclear power plant components. Local stress and fatique calculation were performed on the Pressurize Surge Line piping system of the Pressurize Water Reactor of the Nuclear Power Plant. Analysis was done on the operating temperature between 177 to 343° C and the operating pressure of 16 MPa (160 Bar). The stagnant and transient condition with two kinds of stratification model has been evaluated by the two dimensional finite elements method using the ANSYS program. Evaluation of fatigue resistance is developed based on the maximum local stress using the ASME standard Code formula. Maximum stress of 427 MPa occurred at the upper side of the top half of hot fluid pipe stratification model in the transient case condition. The evaluation of the fatigue resistance is performed on 500 operating cycles in the life time of 40 years and giving the usage value of 0,64 which met to the design requirement for class 1 of nuclear component. The out surge transient were the most significant case in the localized effects due to thermal stratification.

  14. Thermal conductivity of silicon nitride membranes is not sensitive to stress

    NASA Astrophysics Data System (ADS)

    Ftouni, Hossein; Blanc, Christophe; Tainoff, Dimitri; Fefferman, Andrew D.; Defoort, Martial; Lulla, Kunal J.; Richard, Jacques; Collin, Eddy; Bourgeois, Olivier

    2015-09-01

    We have measured the thermal properties of suspended membranes from 10 to 300 K for two amplitudes of internal stress (about 0.1 and 1 GPa) and for two different thicknesses (50 and 100 nm). The use of the original 3 ω -Volklein method has allowed the extraction of both the specific heat and the thermal conductivity of each SiN membrane over a wide temperature range. The mechanical properties of the same substrates have been measured at helium temperatures using nanomechanical techniques. Our measurements show that the thermal transport in freestanding SiN membranes is not affected by the presence of internal stress. Consistently, mechanical dissipation is also unaffected even though Q 's increase with increasing tensile stress. We thus demonstrate that the theory developed by Wu and Yu [J. Wu and C. C. Yu, Phys. Rev. B 84, 174109 (2011), 10.1103/PhysRevB.84.174109] does not apply to this amorphous material in this stress range. On the other hand, our results can be viewed as a natural consequence of the "dissipation dilution" argument [Y. L. Huang and P. R. Saulson, Rev. Sci. Instrum. 69, 544 (1998), 10.1063/1.1148692], which has been introduced in the context of mechanical damping.

  15. Perturbation of baseline thermal stress in the Mound 9516 Shipping Package primary containment vessel

    NASA Astrophysics Data System (ADS)

    Sansalone, Keith H. F.

    1995-01-01

    Full-capacity loading of heat sources into the Mound 9516 Shipping Package primary containment vessel (PCV) results in temperature gradients which are symmetric, due to the axisymmetry of the package design. Concern over the change in thermal gradients (and therefore, stress) in the PCV due to sub-capacity loading led to the analytical examination of this phenomenon. The PCVs are cylindrical in shape and are loaded into the package such that they and all containment components are concentrically arranged along a common longitudinal axis. If the design full-capacity loading of the PCVs in this package assumes the axisymmetric (or more precisely, cyclicly symmetric) arrangement of its heat-producing contents, then sub-capacity loading implies that in many cases, the load arrangement could be asymmetric with respect to the longitudinal axis. It is then feasible that the departure from heat load axisymmetry could perturb the nominal thermal gradients so that thermally-induced stress within the PCV might increase to levels deemed unacceptable. This study applies Finite Element analysis (FEA) to the problem and demonstrates that no such unacceptable thermal stress increase occurs in the PCV material due to the asymmetric arrangement of contents.

  16. Perturbation of baseline thermal stress in the Mound 9516 Shipping Package primary containment vessel

    SciTech Connect

    Sansalone, K.H.F.

    1995-01-20

    Full-capacity loading of heat sources into the Mound 9516 Shipping Package primary containment vessel (PCV) results in temperature gradients which are symmetric, due to the axisymmetry of the package design. Concern over the change in thermal gradients (and therefore, stress) in the PCV due to sub-capacity loading led to the analytical examination of this phenomenon. The PCVs are cylindrical in shape and are loaded into the package such that they and all containment components are concentrically arranged along a common longitudinal axis. If the design full-capacity loading of the PCVs in this package assumes the axisymmetric (or more precisely, cyclicly symmetric) arrangement of its heat-producing contents, then sub-capacity loading implies that in many cases, the load arrangement could be asymmetric with respect to the longitudinal axis. It is then feasible that the departure from heat load axisymmetry could perturb the nominal thermal gradients so that thermally-induced stress within the PCV might increase to levels deemed unacceptable. This study applies Finite Element analysis (FEA) to the problem and demonstrates that no such unacceptable thermal stress increase occurs in the PCV material due to the asymmetric arrangement of contents. {copyright} 1995 {ital American} {ital Institute} {ital of} {ital Physics}

  17. Evaluation of an improved finite-element thermal stress calculation technique

    NASA Technical Reports Server (NTRS)

    Camarda, C. J.

    1982-01-01

    A procedure for generating accurate thermal stresses with coarse finite element grids (Ojalvo's method) is described. The procedure is based on the observation that for linear thermoelastic problems, the thermal stresses may be envisioned as being composed of two contributions; the first due to the strains in the structure which depend on the integral of the temperature distribution over the finite element and the second due to the local variation of the temperature in the element. The first contribution can be accurately predicted with a coarse finite-element mesh. The resulting strain distribution can then be combined via the constitutive relations with detailed temperatures from a separate thermal analysis. The result is accurate thermal stresses from coarse finite element structural models even where the temperature distributions have sharp variations. The range of applicability of the method for various classes of thermostructural problems such as in-plane or bending type problems and the effect of the nature of the temperature distribution and edge constraints are addressed. Ojalvo's method is used in conjunction with the SPAR finite element program. Results are obtained for rods, membranes, a box beam and a stiffened panel.

  18. Thermal Stress of Surface Oxide Layer on Micro Solder Bumps During Reflow

    NASA Astrophysics Data System (ADS)

    Key Chung, C.; Zhu, Z. X.; Kao, C. R.

    2015-02-01

    Micro-bumps are now being developed with diameters smaller than 10 μm. At these dimensions, only very small amounts of solder are used to form the interconnections. Surface oxidation of such small micro-bumps is a critical issue. The key question is whether the oxide film on the solder bumps acts as a barrier to formation of solder joints. In this work, the mechanical stability of the oxide layer on solder bumps was investigated. Solder bumps with 35- μm radii were heated for different times. Auger electron spectroscopy was used to determine the thickness of the oxide layer on the solder bumps. Solder bumps with known oxide layer thicknesses were then heated in a low-oxygen environment (<50 ppm) until they melted. The mechanical stability of the oxide layer was observed by use of a high-speed camera. Results showed that a 14-nm-thick oxide layer on a solder bump of radius 35 μm was able to withstand the molten solder without cracking, leading to a non-wetting solder joint. A thermal stress model of the surface oxide layer revealed that the stress varied substantially with bump size and temperature, and increased almost linearly with temperature. Upon melting, the thermal stress on the oxide increased abruptly, because of the higher thermal expansion of molten solder compared with its solid state. On the basis of the experimental results and the thermal stress model of the oxide film, the maximum oxide thickness that can be tolerated to form a solder joint was determined, e.g. 14 nm oxide can support liquid solder, and thus lead to a non-wetting condition. This work provided a new method of determination of the maximum stress of oxide film for solder joint formation.

  19. Anisotropy analysis of the thermal stresses and strain energies in BCC metal films

    NASA Astrophysics Data System (ADS)

    Zhang, Jian-Min; Zhang, Yan; Xu, Ke-Wei

    2005-11-01

    A thin polycrystalline film tightly bonded to a thick substrate of different thermal expansion coefficients will experience thermal stresses when the temperature is changed in applications. Calculations of these stresses and the corresponding strain energies for grains having various crystallographic orientations (hkl) relative to the film surface were made for a polycrystalline film composed of the BCC metal Cr, Fe, K, Li, Mo, Na, Nb, Ta, V and W, respectively. Neglecting W, which is isotropic, the stresses and strain energy densities are not grain orientation (hkl) dependence. The remaining BCC metals may be grouped into two classes. In the first group (Cr, Mo, Nb and V), the (1 0 0)-oriented grains have the highest stresses and strain energy densities and (1 1 1)-oriented grains the lowest, the stresses σ1 and σ2 in the film surface and strain energy densities in other (hkl)-oriented grains decrease linearly with increasing angle between (hkl) and (1 0 0), and have σ1<σ2 excepting in (1 0 0)- and (1 1 1)-oriented grains. The contrary conclusions are obtained for the second group (Fe, K, Li, Na and Ta).

  20. Exploring thermal imaging variables for the detection of stress responses in grapevine under different irrigation regimes.

    PubMed

    Grant, Olga M; Tronina, Lukasz; Jones, Hamlyn G; Chaves, M Manuela

    2007-01-01

    Temperatures of leaves or canopies can be used as indicators of stomatal closure in response to soil water deficit. In 2 years of field experiments with grapevines (Vitis vinifera L., cvs Castelão and Aragonês), it was found that thermal imaging can distinguish between irrigated and non-irrigated canopies, and even between deficit irrigation treatments. Average canopy temperature was inversely correlated with stomatal conductance measured with a porometer. Variation of the distribution of temperatures within canopies was not found to be a reliable indicator of stress. A large degree of variation between images was found in reference 'wet' and 'dry' leaves used in the first year for the calculation of an index proportional to stomatal conductance. In the second year, fully irrigated (FI) (100% Et(c)) and non-irrigated (NI) canopies were used as alternatives to wet and dry leaves. A crop water stress index utilizing these FI and NI 'references', where stressed canopies have the highest values and non-stressed canopies have the lowest values, was found to be a suitable measure for detecting stress. It is suggested that the average temperatures of areas of canopies containing several leaves may be more useful for distinguishing between irrigation treatments than the temperatures of individual leaves. Average temperatures over several leaves per canopy may be expected to reduce the impact of variation in leaf angles. The results are discussed in relation to the application of thermal imaging to irrigation scheduling and monitoring crop performance. PMID:17032729

  1. Thermal and physical stresses induce a short-term immune priming effect in Galleria mellonella larvae.

    PubMed

    Browne, Niall; Surlis, Carla; Kavanagh, Kevin

    2014-04-01

    Exposure of larvae of Galleria mellonella larvae to mild physical (i.e. shaking) or thermal stress for 24h increased their ability to survive infection with Aspergillus fumigatus conidia however larvae stressed in a similar manner but incubated for 72h prior to infection showed no elevation in their resistance to infection with A. fumigatus. Stressed larvae demonstrated an elevated haemocyte density 24h after initiation of the stress event but this declined at 48 and 72h. Larval proteins such as apolipophorin, arylophorin and prophenoloxidase demonstrated elevated expression at 24h but not at 72h. Larvae maintained at 37°C showed increased expression of a range of antimicrobial and immune-related proteins at 24h but these decreased in expression thereafter. The results presented here indicate that G. mellonella larvae are capable of altering their immune response following exposure to mild thermal or physical stress to mount a response capable of counteracting microbial infection which reaches a peak 24h after the initiation of the priming event and then declines by 72h. A short-term immune priming effect may serve to prevent infection but maintaining an immune priming effect for longer periods may be metabolically costly and unnecessary while living within the colony of another insect. PMID:24561359

  2. The role of D-GADD45 in oxidative, thermal and genotoxic stress resistance.

    PubMed

    Moskalev, Alexey; Plyusnina, Ekaterina; Shaposhnikov, Mikhail; Shilova, Lyubov; Kazachenok, Alexey; Zhavoronkov, Alexander

    2012-11-15

    There is a relationship between various cellular stress factors and aging. In earlier studies, we demonstrated that overexpression of the D-GADD45 gene increases the life span of Drosophila melanogaster. In this study, we investigate the relationship between D-GADD45 activity and resistance to oxidative, genotoxic and thermal stresses as well as starvation. In most cases, flies with constitutive and conditional D-GADD45 overexpression in the nervous system were more stress-resistant than ones without overexpression. At the same time, most of the studied stress factors increased D-GADD45 expression in the wild-type strain. The lifespan-extending effect of D-GADD45 overexpression was also retained after exposure to chronic and acute gamma-irradiation, with doses of 40 сGy and 30 Gy, respectively. However, knocking out D-GADD45 resulted in a significant reduction in lifespan, lack of radiation hormesis and radioadaptive response. A dramatic decrease in the spontaneous level of D-GADD45 expression was observed in the nervous system as age progressed, which may be one of the causes of the age-related deterioration of organismal stress resistance. Thus, D-GADD45 expression is activated by most of the studied stress factors, and D-GADD45 overexpression resulted in an increase of stress resistance. PMID:23095639

  3. Thermal stress analysis of ceramic gas-path seal components for aircraft turbines

    NASA Technical Reports Server (NTRS)

    Kennedy, F. E.; Bill, R. C.

    1979-01-01

    Stress and temperature distributions were evaluated numerically for a blade-tip seal system proposed for gas turbine applications. The seal consists of an abradable ceramic layer on metallic backing with intermediate layers between the ceramic layer and metal substrate. The most severe stresses in the seal, as far as failure is concerned, are tensile stresses at the top of the ceramic layer and shear and normal stresses at the layer interfaces. All these stresses reach their maximum values during the deceleration phase of a test engine cycle. A parametric study was carried out to evaluate the influence of various design parameters on these critical stress values. The influences of material properties and geometric parameters of the ceramic, intermediate, and backing layers were investigated. After the parametric study was completed, a seal system was designed which incorporated materials with beneficial elastic and thermal properties in each layer of the seal. An analysis of the proposed seal design shows an appreciable decrease in the magnitude of the maximum critical stresses over those obtained with earlier configurations.

  4. Reactive oxygen species in pregnant rats: effects of exercise and thermal stress.

    PubMed

    Osorio, R A L; Christofani, J S; D'Almeida, V; Russo, A K; Piçarro, I C

    2003-05-01

    With the aim of evaluating the effect of interaction between physical training or exercise only during pregnancy and thermal stress on oxidative stress, and antioxidant mechanism sedentary pregnant rats (PS), exercised pregnant rats only during pregnancy (PE) and trained rats submitted to also exercise during pregnancy (PT) were compared (N=63). Exercise sessions consisted of swimming at 80% of maximal work load supported into water at 28 degrees C (hypothermia, PS 28, PE28, PT28) or 35 degrees C (thermal neutrality, PS35, PE35, PT35) or 39 degrees C (hyperthermia, PS39, PE39, PT39), for 30 min. The initial body weight in all groups of rats was from 177 to 207 g. On the 20th day of pregnancy, 24 h after the last immersion or swimming session venous blood was collected to determine oxidative stress. Plasma concentrations of means malondialdehyde (MDA) values measured as thiobarbituric acid reactive substances (TBARS); total glutathione (GSH) and vitamin E were determined. The oxidative stress index was calculated from the ratio TBARS/GSH and TBARS/Vitamin E. TBARS did not change on the group PE at different temperatures of water; TBARS were higher for PS28 than PS35 and PS39; PT35 had higher values than PT28 and PT39. For GSH, PS39 was lower than PS35; PE28 was higher than PE35 and PE39 and PT35 were lower than PT28 and PT39. Plasma concentration of vitamin E did not present any difference for sedentary rats at different water temperatures, but for PE28, the values were lower than for PE35 and PE39, whereas PT39 was lower than PT35 and PT28. In relation to TBARS/GSH, it was verified an increase in oxidative stress for PS28 (in relation to PS35 and PS39), PE35, and PT35 (in relation to PE28 and PE39 or PT28 and PT39); regarding the ratio TBARS/vitamin E, the highest values were obtained at 35 degrees C for PS and PT groups and at 39 for PE group. These results have shown the great complexity of the interaction between physical training, thermal stress and pregnancy

  5. Substructure procedure for including tile flexibility in stress analysis of shuttle thermal protection system

    NASA Technical Reports Server (NTRS)

    Giles, G. L.

    1980-01-01

    A substructure procedure to include the flexibility of the tile in the stress analysis of the shuttle thermal protection system (TPS) is described. In this procedure, the TPS is divided into substructures of (1) the tile which is modeled by linear finite elements and (2) the SIP which is modeled as a nonlinear continuum. This procedure was applied for loading cases of uniform pressure, uniform moment, and an aerodynamic shock on various tile thicknesses. The ratios of through-the-thickness stresses in the SIP which were calculated using a flexible tile compared to using a rigid tile were found to be less than 1.05 for the cases considered.

  6. 3D numerical thermal stress analysis of the high power target for the SLC Positron Source

    SciTech Connect

    Reuter, E.M.; Hodgson, J.A.

    1991-05-01

    The volumetrically nonuniform power deposition of the incident 33 GeV electron beam in the SLC Positron Source Target is hypothesized to be the most likely cause target failure. The resultant pulsed temperature distributions are known to generate complicated stress fields with no known closed-form analytical solution. 3D finite element analyses of these temperature distributions and associated thermal stress fields in the new High Power Target are described here. Operational guidelines based on the results of these analyses combined with assumptions made about the fatigue characteristics of the exotic target material are proposed. 6 refs., 4 figs.

  7. Use of thermal infrared and colour infrared imagery to detect crop moisture stress. [Alberta, Canada

    NASA Technical Reports Server (NTRS)

    Mckenzie, R. C.; Clark, N. F.; Cihlar, J. (Principal Investigator)

    1979-01-01

    The author has identified the following significant results. In the presence of variable plant cover (primarily percent cover) and variable available water content, the remotely sensed apparent temperatures correlate closely with plant cover and poorly with soil water. To the extent that plant cover is not systematically related to available soil water, available water in the root zone values may not be reliably predicted from the thermal infrared data. On the other hand, if plant cover is uniform and the soil surface is shown in a minor way, the thermal data indicate plant stress and consequently available water in the soil profile.

  8. Piezotronic Effect Enhanced Photocatalysis in Strained Anisotropic ZnO/TiO₂ Nanoplatelets via Thermal Stress.

    PubMed

    Wang, Longfei; Liu, Shuhai; Wang, Zheng; Zhou, Yongli; Qin, Yong; Wang, Zhong Lin

    2016-02-23

    Effective piezoelectric semiconductor based hybrid photocatalysts are successfully developed by assembling TiO2 nanoparticles on ZnO monocrystalline nanoplatelets. The piezopotential can be introduced and tuned by thermal stress on the piezoelectric material of ZnO monocrystalline nanoplatelets through cooling hybrid photocatalysts from high temperature to room temperature with different rates based on the mismatched thermal expansion coefficient of the two materials, which can be used to engineer the heterojunction band structure and significantly enhance the photocatalytic performance in a wide range by improving charge separation. It is proposed that the piezotronic effect enhanced photocatalyst will provide a strategy for high-performance photocatalysis applications. PMID:26745209

  9. Apparatus and method for reducing thermal stress in a turbine rotor

    NASA Technical Reports Server (NTRS)

    Heller, J. A. (Inventor)

    1978-01-01

    A gas turbine is described wherein the thermal stresses in the turbine rotor are reduced. The rotor includes a central disc with a peripheral rim, and a plurality of blades extending radially outward from the rim. To reduce thermal stresses, a duct arrangement is provided which selectively directs hot gases from the turbine combustor to the rim during the turbine start up. The hot gases from the combustor serve to heat the rim, and decrease the start up period necessary to bring the temperature profile of the rotor into the operating temperature range. After the start up period, the duct arrangement is then used to direct cool gases from the turbine compressor to the rim of the rotor in order to maintain a lower rotor equilibrium temperature.

  10. Metallurgical characterization and determination of residual stresses of coatings formed by thermal spraying

    NASA Astrophysics Data System (ADS)

    Laribi, M.; Mesrati, N.; Vannes, A. B.; Treheux, D.

    2003-06-01

    This work presents an experimental determination of residual stresses in 35CrMo4 (Euronorm) low alloyed steel substrates with thermally sprayed coatings. Two different materials were separately deposited. The first one consisted of a blend of two superalloys: Cr-Ni steel and Cr-Mn steel, designated 55E and 65E, respectively. The second material was molybdenum. In a first part, basic characteristics of the deposited layers (metallographic analysis, hardness, and adhesion) are presented. In a second part, the determination of the residual stresses, in both substrate and thermal sprayed layers is performed using an extensometric method in combination with a simultaneous progressive electrolytic polishing. The influence of a nickel-aluminum (80:20%) bond-coat and/or a post-annealing at 850 °C in air for 1 h is studied.

  11. Effects study on the thermal stresses in a LEU metal foil annular target.

    PubMed

    Govindarajan, Srisharan G; Solbrekken, Gary L

    2015-09-01

    The effects of fission gas pressure, uranium swelling and thermal contact conductance on the thermal-mechanical behavior of an annular target containing a low-enriched uranium foil (LEU) encapsulated in a nickel foil have been presented in this paper. The draw-plug assembly method is simulated to obtain the residual stresses, which are applied to the irradiation model as initial inputs, and the integrated assembly-irradiation process is simulated as an axisymmetric problem using the commercial finite element code Abaqus FEA. Parametric studies were performed on the LEU heat generation rate and the results indicate satisfactory irradiation performance of the annular target. The temperature and stress margins have been provided along with a discussion of the results. PMID:26036440

  12. Packaging strategies for printed circuit board components. Volume I, materials & thermal stresses.

    SciTech Connect

    Neilsen, Michael K.; Austin, Kevin N.; Adolf, Douglas Brian; Spangler, Scott W.; Neidigk, Matthew Aaron; Chambers, Robert S.

    2011-09-01

    Decisions on material selections for electronics packaging can be quite complicated by the need to balance the criteria to withstand severe impacts yet survive deep thermal cycles intact. Many times, material choices are based on historical precedence perhaps ignorant of whether those initial choices were carefully investigated or whether the requirements on the new component match those of previous units. The goal of this program focuses on developing both increased intuition for generic packaging guidelines and computational methodologies for optimizing packaging in specific components. Initial efforts centered on characterization of classes of materials common to packaging strategies and computational analyses of stresses generated during thermal cycling to identify strengths and weaknesses of various material choices. Future studies will analyze the same example problems incorporating the effects of curing stresses as needed and analyzing dynamic loadings to compare trends with the quasi-static conclusions.

  13. On the transition thermal discomfort to heat stress as a function of the PMV value.

    PubMed

    D'Ambrosio Alfano, Francesca Romana; Palella, Boris Igor; Riccio, Giuseppe

    2013-01-01

    ISO 15265 Standard - Ergonomics of the thermal environment - Risk assessment strategy for the prevention of stress or discomfort in thermal working conditions - can be considered as a key document for helping responsible for the health protection and prevention of working situations. According to the SOBANE strategy, this standard provides a three-step protocol aimed to the prevention, elimination or reduction of risks affecting the workplaces. Although both methods and procedures suggested by ISO 15265 appear very clear, this standard could bring in confusion both beginners and not specialists in occupational health concerning Predicted Mean Vote (PMV) threshold values consistent with comfort - hot discomfort and the discomfort - hot stress transitions. In this work such matter has been extensively discussed showing a certain difficulty in the definition of an unambiguous PMV threshold value for each working situation in any microclimate. PMID:23385432

  14. Thermal Characterization and Spatial Analysis of Water Stress in Cotton (Gossypium Hirsutum) and Phytochemical Composition Related to Water Stress in Soybean (Glycine Max)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Studies were designed to explore spatial relationships of water and/or heat stress in cotton and soybeans and to assess factors that may influence yield potential. Investigations focused on detecting the onset of water/heat stress in row crops using thermal and multispectral imagery with ancillary p...

  15. Modeling technique to simulate thermally-induced stress in an assembly consisting of components made of different materials

    SciTech Connect

    Raab, W.; Weigand, M.; Renneisen, A.; Hoeerl, S. )

    1991-06-01

    A modeling technique based on the stress-freezing procedure of three-dimensional photoelasticity is presented. This technique makes it possible to freeze the state of stress caused by a restraint in thermal expansion. The method simulates the restraint using the glass-transition effect during the stress-freezing procedure, so that the state of stress can be measured quantitatively. Cured epoxy resins were used as model materials. To achieve the necessary difference between the coefficients of thermal expansion, a prestressing method was used. The experimental stress analysis shows that the prestressing method can be applied when different thermal expansion properties associated with multiple components are required. The modeling technique is illustrated by an example in which the stress in the bottom of a light metal-alloy cylinder head is simulated.

  16. Numerical Parametric Analysis of Bond Coat Thickness Effect on Residual Stresses in Zirconia-Based Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Abbas, Musharaf; Hasham, Hasan Junaid; Baig, Yasir

    2016-02-01

    Numerical-based finite element investigation has been conducted to explain the effect of bond coat thickness on stress distribution in traditional and nanostructured yttria-stabilized zirconia (YSZ)-based thermal barrier coatings (TBC). Stress components have been determined to quantitatively analyze the mechanical response of both kinds of coatings under the thermal shock effect. It has been found that maximum radial tensile and compressive stresses that exist at thermally grown oxide (TGO)/bond coat interface and within TGO respectively decrease with an increase in bond coat thickness. Effect of bond coat thickness on axial tensile stresses is not significant. However, axial compressive stresses that exist at the edge of the specimen near bond coat/substrate interface decrease appreciably with the increase in bond coat thickness. Residual stress profile as a function of bond coat thickness is further explained for comparative analysis of both coatings to draw some useful conclusions helpful in failure studies of TBCs.

  17. Correlation of predicted and measured thermal stresses on a truss-type aircraft structure

    NASA Technical Reports Server (NTRS)

    Jenkins, J. M.; Schuster, L. S.; Carter, A. L.

    1978-01-01

    A test structure representing a portion of a hypersonic vehicle was instrumented with strain gages and thermocouples. This test structure was then subjected to laboratory heating representative of supersonic and hypersonic flight conditions. A finite element computer model of this structure was developed using several types of elements with the NASA structural analysis (NASTRAN) computer program. Temperature inputs from the test were used to generate predicted model thermal stresses and these were correlated with the test measurements.

  18. Numerical Investigation of Thermal Stress Convention in Nonisothermal Gases Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Mackowski, D. W.

    1999-01-01

    Reported here are our results of our numerical/theoretical investigation into the effects of thermal stress in nonisothermal gases under microgravity conditions. The first part of the report consists of a brief summary of the accomplishments and conclusions of our work. The second part consists of two manuscripts, one being a paper presented at the 1998 MSAD Fluid Physics workshop, and the other to appear in Physics of Fluids.

  19. Coupled convection, segregation, and thermal stress modeling of low and high pressure Czochralski crystal growth

    NASA Astrophysics Data System (ADS)

    Zou, Yunfeng

    Czochralski (Cz) method is a dominant single crystal growth technology for microelectronics applications. The demand for large diameter, low defect density, and uniform single crystals has motivated extensive research on Cz Si growth as well as high pressure liquid-encapsulated Czochralski (HPLEC) growth of III-V compound crystals, e.g., GaAs and InP. The transport phenomena of Cz growth is quite complex, particularly under the industrial growth conditions. The relationship between the process parameters and material properties is further complicated by convective flows of the gas if a high pressure condition is to be maintained for the growth. Two important factors that greatly influence the quality of the crystals, are: (a) impurity and dopant distributions and (b) thermal stresses in the crystal. A comprehensive model which incorporates all of the major physical mechanisms of HPLEC growth, has been developed. For numerical simulation, a novel scheme of combined finite volume (FVM) and finite element (FEM) methods has been devised for thermal-mechanical calculations, that uses multizone adaptive grid generation (MAGG) technique for both FVM and FEM modules. By combining the FVM for thermal transport modeling and FEM for solid stress calculations, valuable experiences in both fields have been employed, and a reliable and robust predictive tool for a large class of problems has been developed. This requires minimum effort and cost in both software development and computing environment and shows a great promise. It makes the investigation of coupled thermal convection and stress phenomena much easier to perform. A two time-scale, mass conserving scheme has also been developed to perform macro-segregation calculations. Both Cz and HPLEC (high pressure liquid-encapsulant Czochralski) processes have been investigated. It is found that both melt and gas convective flows have significant influence on stress distribution in the crystal. It is shown that pure conduction

  20. A protocol for analysing thermal stress in insects using infrared thermography.

    PubMed

    Gallego, Belén; Verdú, José R; Carrascal, Luis M; Lobo, Jorge M

    2016-02-01

    The study of insect responses to thermal stress has involved a variety of protocols and methodologies that hamper the ability to compare results between studies. For that reason, the development of a protocol to standardize thermal assays is necessary. In this sense, infrared thermography solves some of the problems allowing us to take continuous temperature measurements without handling the individuals, an important fact in cold-blooded organisms like insects. Here, we present a working protocol based on infrared thermography to estimate both cold and heat thermal stress in insects. We analyse both the change in the body temperature of individuals and their behavioural response. In addition, we used partial least squares regression for the statistical analysis of our data, a technique that solves the problem of having a large number of variables and few individuals, allowing us to work with rare or endemic species. To test our protocol, we chose two species of congeneric, narrowly distributed dung beetles that are endemic to the southeastern part of the Iberian Peninsula. With our protocol we have obtained five variables in the response to cold and twelve in the response to heat. With this methodology we discriminate between the two flightless species of Jekelius through their thermal response. In response to cold, Jekelius hernandezi showed a higher rate of cooling and reached higher temperatures of stupor and haemolymph freezing than Jekelius punctatolineatus. Both species displayed similar thermoregulation ranges before reaching lethal body temperature with heat stress. Overall, we have demonstrated that infrared thermography is a suitable method to assess insect thermal responses with a high degree of sensitivity, allowing for the discrimination between closely related species. PMID:26857985

  1. A study of the effect of apparent strain on thermal stress measurement for two types of elevated temperature strain gages

    NASA Technical Reports Server (NTRS)

    Jenkins, J. M.

    1983-01-01

    A weldable type strain gage was used to measure low level thermal stress in an elevated temperature environment. Foil strain gages used in a comparative manner reveal that the apparent strain of weldable strain gages is not sufficiently known to acquire accurate low level thermal stress data. Apparent strain data acquired from coupon tests reveals a large scatter in apparent strain characteristics among the weldable strain gages. It is concluded that apparent strain data for individual weldable strain gages must be required prior to installation if valid thermal stress data is to be obtained through the temperature range of room temperature to 755 K (900 F).

  2. Thermal Stress-Induced Depolarization Loss in Conventional and Panda-Shaped Photonic Crystal Fiber Lasers

    NASA Astrophysics Data System (ADS)

    Mousavi, Seyedeh Laleh; Sabaeian, Mohammad

    2016-07-01

    We report on the modeling of the depolarization loss in the conventional and panda-shaped photonic crystal fiber lasers (PCFLs) due to the self-heating of the fiber, which we call it thermal stress-induced depolarization loss (TSIDL). We first calculated the temperature distribution over the fiber cross sections and then calculated the thermal stresses/strains as a function of heat load per meter. Thermal stress-induced birefringence (TSIB), which is defined as |n x - n y |, in the core and cladding regions was calculated. Finally, TSIDL was calculated for the conventional and panda-shaped PCFLs as a function of fiber length and, respectively, saturated values of 22 and 25 % were obtained which were independent of heat load per meter. For panda-shaped PCFLs, prior to being saturated, an oscillating and damping behavior against the fiber length was seen where in some lengths reached 35 %. The results are close to an experimental value of 30 % reported for a pulsed PCFL (Limpert et al., Opt Express 12:1313-1319, 2004) where the authors reported a degree of polarization of 70 % (i.e., a depolarization of 30 %). The most important result of this work is a saturation behavior of TSIDL at long-enough lengths of the fiber laser which is independent of heat load per meter. To our knowledge, this the first report of TSIBL for PCFLs.

  3. Expression analysis of NOS family and HSP genes during thermal stress in goat (Capra hircus).

    PubMed

    Yadav, Vijay Pratap; Dangi, Satyaveer Singh; Chouhan, Vikrant Singh; Gupta, Mahesh; Dangi, Saroj K; Singh, Gyanendra; Maurya, Vijay Prakash; Kumar, Puneet; Sarkar, Mihir

    2016-03-01

    Approximately 50 genes other than heat shock protein (HSP) expression changes during thermal stress. These genes like nitric oxide synthase (NOS) need proper attention and investigation to find out their possible role in the adaptation to thermal stress in animals. So, the present study was undertaken to demonstrate the expressions of inducible form type II NOS (iNOS), endothelial type III NOS (eNOS), constitutively expressed enzyme NOS (cNOS), HSP70, and HSP90 in peripheral blood mononuclear cells (PBMCs) during different seasons in Barbari goats. Real-time polymerase chain reaction, western blot, and immunocytochemistry were applied to investigate messenger RNA (mRNA) expression, protein expression, and immunolocalization of examined factors. The mRNA and protein expressions of iNOS, eNOS, cNOS, HSP70, and HSP90 were significantly higher (P < 0.05) during peak summer, and iNOS and eNOS expressions were also observed to be significantly higher (P < 0.05) during peak winter season as compared with moderate season. The iNOS, eNOS, cNOS, HSP70, and HSP90 were mainly localized in plasma membrane and cytoplasm of PBMCs. To conclude, data generated in the present study indicate the possible involvement of the NOS family genes in amelioration of thermal stress so as to maintain cellular integrity and homeostasis in goats. PMID:26205811

  4. Thermal stresses in small meteoroids. II. Effects of an insulating surface layer

    NASA Astrophysics Data System (ADS)

    Čapek, D.; Vokrouhlický, D.

    2012-03-01

    Aims: We extend our previous analysis of thermal stresses in small, spherical and homogeneous meteoroids by taking into account the effects of a surface insulating layer. Methods: Using analytical computations, we determine the temperature distribution in a spherical inhomogeneous body smaller than ~10 cm with a high-conductivity core and a low-conductivity surface layer. Our main approximation consists in (i) linearization of the surface energy-conservation constraint and (ii) omission of the seasonal effects in the Fourier spectrum of the incident solar radiation flux. Using the temperature solution, we analytically compute the mechanical (thermal) stress field in the core, neglecting its effects in the particulate surface layer. Conditions for material failure in the whole volume of the body are analyzed. In particular, we pay attention to whether the surface layer depth evolves toward an equilibrium situation. Results: As the meteoroid approaches the Sun, the thermal stress first exceeds the material strength at the surface of meteoroid. If the fractured material is able to stay on meteoroid, a particulate shell begins to form. After one revolution about the Sun, this process is roughly completed. We determine the dependence of its thickness on perihelion distance, spin axis orientation with respect to the Sun, and the size of meteoroid. We estimate the distribution of the final depths of the surface layer for eight major meteoroid showers with perihelion distances smaller than 1 AU.

  5. Expression analysis of NOS family and HSP genes during thermal stress in goat ( Capra hircus)

    NASA Astrophysics Data System (ADS)

    Yadav, Vijay Pratap; Dangi, Satyaveer Singh; Chouhan, Vikrant Singh; Gupta, Mahesh; Dangi, Saroj K.; Singh, Gyanendra; Maurya, Vijay Prakash; Kumar, Puneet; Sarkar, Mihir

    2016-03-01

    Approximately 50 genes other than heat shock protein (HSP) expression changes during thermal stress. These genes like nitric oxide synthase (NOS) need proper attention and investigation to find out their possible role in the adaptation to thermal stress in animals. So, the present study was undertaken to demonstrate the expressions of inducible form type II NOS (iNOS), endothelial type III NOS (eNOS), constitutively expressed enzyme NOS (cNOS), HSP70, and HSP90 in peripheral blood mononuclear cells (PBMCs) during different seasons in Barbari goats. Real-time polymerase chain reaction, western blot, and immunocytochemistry were applied to investigate messenger RNA (mRNA) expression, protein expression, and immunolocalization of examined factors. The mRNA and protein expressions of iNOS, eNOS, cNOS, HSP70, and HSP90 were significantly higher ( P < 0.05) during peak summer, and iNOS and eNOS expressions were also observed to be significantly higher ( P < 0.05) during peak winter season as compared with moderate season. The iNOS, eNOS, cNOS, HSP70, and HSP90 were mainly localized in plasma membrane and cytoplasm of PBMCs. To conclude, data generated in the present study indicate the possible involvement of the NOS family genes in amelioration of thermal stress so as to maintain cellular integrity and homeostasis in goats.

  6. The correct lens mount lightweighting design and thermal stress OPD analysis in Cassegrain telescope

    NASA Astrophysics Data System (ADS)

    Hsu, Ming-Ying; Chan, Chia-Yen; Lin, Wei-Cheng; Chang, Shenq-Tsong; Huang, Ting-Ming

    2013-09-01

    This study is trying to evaluate different lens barrel material, caused lens stress OPD (Optical Path Different) in different temperature condition. The Cassegrain telescope's correct lens assembly are including as correct lens, lens mount, spacer, mount barrel and retainer. The lens barrel initial design is made by invar, but system mass limit is need to lightweighting to meet requirement. Therefore, the lens barrel material is tried to replace to lower density material, such as aluminum and titanium alloy. Meanwhile, the aluminum or titanium alloy material properties CTE (Coefficient of Thermal Expansion) are larger then invar. Thus, the high CTE material will introduce larger thermal stress into the optical system in different temperature condition. This article is analysis the correct lens assembly thermal stress and optical performance in different lens mount material. From above conditions, using FEM (Finite Element Method) and optical software, simulation and optimization the lens mount to achieve system mass requirement.

  7. Residual thermal and moisture influences on the free-edge delamination of laminated composites

    NASA Technical Reports Server (NTRS)

    Armanios, Erian A.; Mahler, Mary A.

    1988-01-01

    A simple delamination analysis method is developed. It is based on a shear-type deformation theory and includes hygrothermal effects. The method is applied to mixed-mode edge delamination specimens made of T300/5208 graphite/epoxy. It is found that residual thermal influences were alleviated when moisture stresses were included. Thermal effects on the interlaminar shear stress and total energy release rate were totally alleviated for the same specific moisture content. Moreover, this value of moisture content was not significantly affected by the stacking sequence for the laminates considered.

  8. Modeling and experimental verification of thermally induced residual stress in RF-MEMS

    NASA Astrophysics Data System (ADS)

    Somà, Aurelio; Mubasher Saleem, Muhammad

    2015-05-01

    Electrostatically actuated radio frequency microelectromechanical systems (RF-MEMS) generally consist of microcantilevers and clamped-clamped microbeams. The presence of residual stress in these microstructures affects the static and dynamic behavior of the device. In this study, nonlinear finite element method (FEM) modeling and the experimental validation of residual stress induced in the clamped-clamped microbeams and the symmetric toggle RF-MEMS switch (STS) is presented. The formation of residual stress due to plastic deformation during the thermal loading-unloading cycle in the plasma etching step of the microfabrication process is explained and modeled using the Bauschinger effect. The difference between the designed and the measured natural frequency and pull-in voltage values for the clamped-clamped microbeams is explained by the presence of the nonhomogenous tensile residual stress. For the STS switch specimens, three-dimensional (3D) FEM models are developed and the initial deflection at zero bias voltage, observed during the optical profile measurements, is explained by the residual stress developed during the plasma etching step. The simulated residual stress due to the plastic deformation is included in the STS models to obtain the switch pull-in voltage. At the end of the simulation process, a good correspondence is obtained between the FEM model results and the experimental measurements for both the clamped-clamped microbeams and the STS switch specimens.

  9. Thermal residual stresses in silicon-carbide/titanium (0/90) laminate

    NASA Technical Reports Server (NTRS)

    Bigelow, C. A.

    1992-01-01

    The current work formulated a micromechanical analysis of a cross-ply laminate and calculated the thermal residual stress in a very thick (0/90)(sub 2n) silicon-carbide/titanium laminate. Results were also shown for a unidirectional laminate of the same material. Discrete fiber-matrix models assuming a rectangular array of fibers with a fiber volume fraction of 32.5 percent and a three-dimensional, finite-element analysis were used. Significant differences in the trends and magnitudes for the fiber, matrix, and interface stresses were calculated for unidirectional and (0/90) models. Larger hoop stresses calculated for the (0/90) model indicate that it may be more susceptible to radial cracking when subjected to mechanical loading than the unidirectional model. The axial stresses in the matrix were calculated to be slightly larger for the (0/90) model. The compressive axial stresses in the fiber were significantly larger in the (0/90) model. The presence of the cross-ply in the (0/90) model reduced the constraint on the fiber, producing radial interface stresses that were less compressive, which could lead to earlier failure of the fiber-matrix interface.

  10. Thermal infrared as a tool to detect tree water stress in a coniferous forest

    NASA Astrophysics Data System (ADS)

    Nourtier, M.; Chanzy, A.; Bes, B.; Davi, H.; Hanocq, J. F.; Mariotte, N.; Sappe, G.

    2009-04-01

    In the context of climatic change, species area may move and so, a study of forest species vulnerability is on interest. In Mediterranean regions, trees can suffer of water stress due to drought during summer. Responses to environmental constraints are delayed in forest so it is necessary to anticipate risks in order to adapt management. It would be therefore interesting to localize areas where trees might be vulnerable to water stress. To detect such areas, the idea developed in this study is to map the severity of water stress, which may be linked to soil. Because vegetation surface temperature is linked to transpiration and so to water stress, the relevance of thermal infrared as a tool to detect water stress was explored. Past studies about surface temperature of forests at the planting scale did not lead to conclusive results. At this scale, important spatial and temporal variations of surface temperature, with a magnitude of about 10°C, can be registered but there is possibly a sizeable contribution of the undergrowth (Duchemin, 1998a, 1998b). In the other hand, important stress are not detectable, probably due to meteorological conditions (Pierce et al., 1990). During spring and summer 2008, an experimentation was carried out on the silver fir (Abies alba) forest of Mont Ventoux (south of France) to evaluate temporal variations at tree scale of the surface temperature in relation to water stress and climatic conditions. Two sites and three trees were chosen for measurements of surface temperature with a view to have different levels of water stress. Transpiration deficit is characterised by the ratio of actual transpiration to potential transpiration which is computed by the ISBA model (Noilhan et al., 1989) implemented by climatic observations made at the top of tree canopy. Sap flow measurements needed to calculate this ratio were completed on different trees of the sites. Climatic datas also allows building reference temperature and then surface

  11. Thermal stress characterization using the impedance-based structural health monitoring system

    NASA Astrophysics Data System (ADS)

    Zhu, Xuan; Lanza di Scalea, Francesco; Fateh, Mahmood

    2016-04-01

    Structural health monitoring (SHM) has attracted researchers' interests for the past two decades to reinforce the maintenance of the aging infrastructure systems all over the world. As one of the potential solutions, the electro-mechanical impedance (EMI) method was introduced in the early 1990s and has a great number of potential applications in the SHM of civil, mechanical and aerospace industries. This paper studied the impedance-based technique with the presence of environmental/operational variability, especially the influences of temperature and uniaxial stress on the admittance signature-based features. A comprehensive analytical model is established and provides satisfactory agreements with the experimental results. The stress and temperature sensitivities of all the proposed features are quantified using the experimental measurements, with discussions on their advantages and disadvantages. The final results illustrate that the EMI method can potentially provide effective measure for thermal stress.

  12. Computer program for nonlinear static stress analysis of shuttle thermal protection system: User's manual

    NASA Technical Reports Server (NTRS)

    Giles, G. L.; Wallas, M.

    1981-01-01

    User documentation is presented for a computer program which considers the nonlinear properties of the strain isolator pad (SIP) in the static stress analysis of the shuttle thermal protection system. This program is generalized to handle an arbitrary SIP footprint including cutouts for instrumentation and filler bar. Multiple SIP surfaces are defined to model tiles in unique locations such as leading edges, intersections, and penetrations. The nonlinearity of the SIP is characterized by experimental stress displacement data for both normal and shear behavior. Stresses in the SIP are calculated using a Newton iteration procedure to determine the six rigid body displacements of the tile which develop reaction forces in the SIP to equilibrate the externally applied loads. This user documentation gives an overview of the analysis capabilities, a detailed description of required input data and an example to illustrate use of the program.

  13. A New Model to Calculate Friction Coefficients and Shear Stresses in Thermal Drilling

    SciTech Connect

    Qu, Jun; Blau, Peter Julian

    2008-01-01

    A new analytical model for thermal drilling (also known as friction drilling) has been developed. The model distinguishes itself from recent work of other investigators by improving on two aspects: (1) the new model defines material plastic flow in terms of the yield in shear rather than the yield in compression, and (2) it uses a single, variable friction coefficient instead of assuming two unrelated friction coefficients in fixed values. The time dependence of the shear stress and friction coefficient at the hole walls, which cannot be measured directly in thermal drilling, can be calculated using this model from experimentally-measured values of the instantaneous thrust force and torque. Good matches between the calculated shear strengths and the handbook values for thermally drilling low carbon steel confirm the model's validity.

  14. Role of mechanical loads in inducing in-cycle tensile stress in thermally grown oxide

    SciTech Connect

    Diaz, R.; Jansz, M.; Mossaddad, M.; Raghavan, S.; Okasinski, J.S.; Almer, J.D.; Perez, H.P.; Imbrie, P.

    2012-01-01

    Experimental in situ synchrotron x-ray diffraction results tracking the strain behavior of the various layers during a cycle, under thermo-mechanical conditions are presented in this work. The quantitative strain measurements here show that the thermally grown oxide briefly experiences in-plane tensile stress ({sigma}{sub 22} = +36.4 MPa) with increased mechanical loading during ramp-up in the thermal cycle. These findings are the first in situ experimental observations of these strains under thermo-mechanical conditions, envisaged to serve as a catalyst for crack initiation. The depth resolved measurements of strain taken during applied thermal and mechanical load in this work are a significant step towards achieving realistic testing conditions.

  15. Drought stress determination of crops by means of ground based thermal remote sensing

    NASA Astrophysics Data System (ADS)

    Weihs, P.; Linke, R.; Richter, K.; Eitzinger, J.; Berger, L.; Besnard, T.

    2009-04-01

    Drought stress is known to have a restricting effect on plant growth and thus inevitably decreases crop yield. In the presence of drought stress, occurring whenever the evaporative demand of the atmosphere can no longer be met by the water uptake of the plant, transpiration rates of the leaves are reduced leading to higher leaf-temperatures. Remote Sensing in the thermal infrared region has been proved to be useful for acquiring information about canopy temperature and thus crop condition. Consequently, the adequate interpretation of these observations provides an instrument for irrigation scheduling, needed to avoid the negative effects of yield losses and to support a sustainable use of water in agriculture. In this study, thermal measurements by means of CIR-5 were routinely performed during the growth period from May to July 2006, on an irrigated and a rainfed wheat (Triticum aestivum L. (cv. Xenos)) plot at the study test site ‘Augarten', Vienna. Physiological measurements, such as leaf water potential and relative water content, were performed on the youngest fully expanded leaf at the three developmental stages. Additionally, spectral measurements with a portable field spectrometer were performed and meteorological data including net radiation and shortwave global radiation were continuously recorded. The objective of the present study was to assess the potential of crop water stress indices (CWSI, WDI) to determine the level of drought stress and thus irrigation needs. The results of the analyses will be presented and discussed, also in terms of a potential application in irrigation management systems.

  16. NDT&E using shearography with impulsive thermal stressing and clustering phase extraction

    NASA Astrophysics Data System (ADS)

    Huang, Y. H.; Ng, S. P.; Liu, L.; Li, C. L.; Chen, Y. S.; Hung, Y. Y.

    2009-07-01

    Shearography has been widely adopted for nondestructive testing and evaluation of various materials, especially in the rubber industry and aerospace industry. It detects flaws and defects by identifying deformation anomalies when the specimen is stressed by a certain means. Conventional stressing methods for shearography include pressurization, mechanical or acoustic loading and vibration excitation. These stressing techniques are favorably applied in various applications. In this study, we propose a novel impulsive thermal stressing method using high-power flash lamps for convenient nondestructive testing and evaluation in both laboratory and industrial environment. The proposed technique employs a high-energy heat flux to excite the specimen and detects the thermal deformation anomaly using a shearographic setup. By incorporating a novel clustering phase extraction method, the movement of the continuously deforming object is obtained using only one single deformed speckle image at each deformed stage, thus enabling both qualitative and quantitative measurement. Experiments conducted on various samples with cracks and debonds demonstrate the practicability of proposed technique for both laboratory and industrial applications.

  17. Simulation of residual stresses and their effects on thermal barrier coating systems using finite element method

    NASA Astrophysics Data System (ADS)

    Zhu, JianGuo; Chen, Wei; Xie, HuiMin

    2015-03-01

    Thermal barrier coating (TBC) systems are widely used in industrial gas-turbine engines. However, premature failures have impaired the use of TBCs and cut down their lifetime, which requires a better understanding of their failure mechanisms. In the present study, experimental studies of isothermal cycling are firstly carried out with the observation and estimation of microstructures. According to the experimental results, a finite element model is established for the analysis of stress perpendicular to the TBC/BC interface. Detailed residual stress distributions in TBC are obtained to reflect the influence of mechanical properties, oxidation, and interfacial roughness. The calculated results show that the maximum tensile stress concentration appears at the peak of TBC and continues to increase with thermal cycles. Because of the microstructural characteristics of plasma-sprayed TBCs, cracks initialize in tensile stress concentration (TSC) regions at the peaks of TBC and propagate along the TBC/BC interface resulting in the spallation of TBC. Also, the inclusion of creep is crucial to failure prediction and is more important than the inclusion of sintering in the simulation.

  18. 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.

  19. Stress intensity factors for an underclad nozzle corner crack subjected to pressure and thermal loading

    SciTech Connect

    Wilkening, W.W.

    1991-06-01

    The opening mode linear elastic stress intensity factor, K{sub I}, was computed, via 3-D elastic finite element techniques, for an embedded elliptical crack located just beneath the cladding at the nozzle corner in a pressure vessel. Pressure loading and several thermal transient loading conditions were analyzed. The underclad crack was explicitly modeled and K{sub I} was computed explicitly, from the energy release rate, J. The variation of the maximum principal stress along the minor axis of the elliptical crack was determined for a companion set of thermal/structural analyses that were performed in the absence of the crack. These stress distributions were linearized into equivalent membrane and bending stress components that were used to compute K{sub I} from the Shah and Kobayashi solutions for near-surface embedded elliptical cracks. The explicitly computed K{sub I} values were found to be in very good agreement with the K{sub I} values computed from the flat plate'' solutions of Reference 1, for all the loading cases analyzed. An additional comparison was made between the energy release rate results and the results obtained by fitting the 1/{radical}r stress singularity to the crack tip stress field at the Gaussian integration points nearest to the crack front. The observed excellent agreement between the two independent explicit'' computational methods served to verify each of the methods and also demonstrated the adequacy of the refinement of the finite element mesh. These observations support the use of the Shah and Kobayashi flat plate K{sub I} solutions for analyzing underclad cracks at the nozzle corner. 7 refs., 11 figs.

  20. Changes in thermal infrared spectra of plants caused by temperature and water stress

    NASA Astrophysics Data System (ADS)

    Buitrago, Maria F.; Groen, Thomas A.; Hecker, Christoph A.; Skidmore, Andrew K.

    2016-01-01

    Environmental stress causes changes in leaves and the structure of plants. Although physiological adaptations to stress by plants have been explored, the effect of stress on the spectral properties in the thermal part of the electromagnetic spectrum (3-16 μm) has not yet been investigated. In this research two plant species (European beech, Fagus sylvatica and rhododendron, Rhododendron cf. catawbiense) that both grow naturally under temperature limited conditions were selected, representing deciduous and evergreen plants respectively. Besides TIR spectra, Leaf Water Content (LWC) and cuticle thickness were measured as possible variables that can explain the changes in TIR spectra. The results demonstrated that both species, when exposed to either water or temperature stress, showed significant changes in their TIR spectra. The changes in TIR in response to stress were similar within a species, regardless of the stress imposed on them. However, changes in TIR spectra differed between species. For rhododendron emissivity in TIR increased under stress while for beech it decreased. Both species showed depletion of Leaf Water Content (LWC) under stress, ruling LWC out as a main cause for the change in the TIR spectra. Cuticle thickness remained constant for beech, but increased for rhododendron. This suggests that changes in emissivity may be linked to changes in the cuticle thickness and possibly the structure of cuticle. It is known that spectral changes in this region have a close connection with microstructure and biochemistry of leaves. We propose detailed measurements of these changes in the cuticle to analyze the effect of microstructure on TIR spectra.