WorldWideScience

Sample records for thermal stress resistance

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

    Science.gov (United States)

    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... catalyst conversion efficiency for Phase 1 engines. The thermal stress is imposed on the test catalyst by...

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

    Science.gov (United States)

    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 conversion...

  3. Coral thermal tolerance: tuning gene expression to resist thermal stress.

    Directory of Open Access Journals (Sweden)

    Anthony J Bellantuono

    Full Text Available The acclimatization capacity of corals is a critical consideration in the persistence of coral reefs under stresses imposed by global climate change. The stress history of corals plays a role in subsequent response to heat stress, but the transcriptomic changes associated with these plastic changes have not been previously explored. In order to identify host transcriptomic changes associated with acquired thermal tolerance in the scleractinian coral Acropora millepora, corals preconditioned to a sub-lethal temperature of 3°C below bleaching threshold temperature were compared to both non-preconditioned corals and untreated controls using a cDNA microarray platform. After eight days of hyperthermal challenge, conditions under which non-preconditioned corals bleached and preconditioned corals (thermal-tolerant maintained Symbiodinium density, a clear differentiation in the transcriptional profiles was revealed among the condition examined. Among these changes, nine differentially expressed genes separated preconditioned corals from non-preconditioned corals, with 42 genes differentially expressed between control and preconditioned treatments, and 70 genes between non-preconditioned corals and controls. Differentially expressed genes included components of an apoptotic signaling cascade, which suggest the inhibition of apoptosis in preconditioned corals. Additionally, lectins and genes involved in response to oxidative stress were also detected. One dominant pattern was the apparent tuning of gene expression observed between preconditioned and non-preconditioned treatments; that is, differences in expression magnitude were more apparent than differences in the identity of genes differentially expressed. Our work revealed a transcriptomic signature underlying the tolerance associated with coral thermal history, and suggests that understanding the molecular mechanisms behind physiological acclimatization would be critical for the modeling of reefs

  4. Thermal stress resistance of ion implanted sapphire crystals

    International Nuclear Information System (INIS)

    Gurarie, V.N.; Jamieson, D.N.; Szymanski, R.; Orlov, A.V.; Williams, J.S.; Conway, M.

    1999-01-01

    Monocrystals of sapphire have been subjected to ion implantation with 86 keV Si - and 80 keV Cr - ions to doses in the range of 5x10 14 -5x10 16 cm -2 prior to thermal stress testing in a pulsed plasma. Above a certain critical dose ion implantation is shown to modify the near-surface structure of samples by introducing damage, which makes crack nucleation easier under the applied stress. The effect of ion dose on the stress resistance is investigated and the critical doses which produce a noticeable change in the stress resistance are determined. The critical dose for Si ions is shown to be much lower than that for Cr - ions. However, for doses exceeding 2x10 16 cm -2 the stress resistance parameter decreases to approximately the same value for both implants. The size of the implantation-induced crack nucleating centers and the density of the implantation-induced defects are considered to be the major factors determining the stress resistance of sapphire crystals irradiated with Si - and Cr - ions

  5. Thermal Stress

    Science.gov (United States)

    2011-01-01

    and Science in Sports and Exercise 37: 1328--1334. Coris EE, Ramirez AM, and Van Durme DJ (2004) Heat illness in athletes : The dangerous combination...of heat, humidity and exercise. Sports Medicine 34: 9--16. Gordon CJ and Leon LR (2005) Thermal stress and the physiological response to environmental...code) 2011 Book Chapter-Enc. of Environmental Health Thermal Stress L.R. Leon, C.J. Gordon Thermal and Mountain Medicine Division U.S. Research

  6. Carbon-Starvation Induces Cross-Resistance to Thermal, Acid, and Oxidative Stress in Serratia marcescens

    Science.gov (United States)

    Pittman, Joseph R.; Kline, La’Kesha C.; Kenyon, William J.

    2015-01-01

    The broad host-range pathogen Serratia marcescens survives in diverse host and non-host environments, often enduring conditions in which the concentration of essential nutrients is growth-limiting. In such environments, carbon and energy source starvation (carbon-starvation) is one of the most common forms of stress encountered by S. marcescens. Related members of the family Enterobacteriaceae are known to undergo substantial changes in gene expression and physiology in response to the specific stress of carbon-starvation, enabling non-spore-forming cells to survive periods of prolonged starvation and exposure to other forms of stress (i.e., starvation-induced cross-resistance). To determine if carbon-starvation also results in elevated levels of cross-resistance in S. marcescens, both log-phase and carbon-starved cultures, depleted of glucose before the onset of high cell-density stationary-phase, were grown in minimal media at either 30 °C or 37 °C and were then challenged for resistance to high temperature (50 °C), low pH (pH 2.8), and oxidative stress (15 mM H2O2). In general, carbon-starved cells exhibited a higher level of resistance to thermal stress, acid stress, and oxidative stress compared to log-phase cells. The extent of carbon-starvation-induced cross-resistance was dependent on incubation temperature and on the particular strain of S. marcescens. In addition, strain- and temperature-dependent variations in long-term starvation survival were also observed. The enhanced stress-resistance of starved S. marcescens cells could be an important factor in their survival and persistence in many non-host environments and within certain host microenvironments where the availability of carbon sources is suboptimal for growth. PMID:27682115

  7. Carbon-Starvation Induces Cross-Resistance to Thermal, Acid, and Oxidative Stress in Serratia marcescens

    Directory of Open Access Journals (Sweden)

    Joseph R. Pittman

    2015-10-01

    Full Text Available The broad host-range pathogen Serratia marcescens survives in diverse host and non-host environments, often enduring conditions in which the concentration of essential nutrients is growth-limiting. In such environments, carbon and energy source starvation (carbon-starvation is one of the most common forms of stress encountered by S. marcescens. Related members of the family Enterobacteriaceae are known to undergo substantial changes in gene expression and physiology in response to the specific stress of carbon-starvation, enabling non-spore-forming cells to survive periods of prolonged starvation and exposure to other forms of stress (i.e., starvation-induced cross-resistance. To determine if carbon-starvation also results in elevated levels of cross-resistance in S. marcescens, both log-phase and carbon-starved cultures, depleted of glucose before the onset of high cell-density stationary-phase, were grown in minimal media at either 30 °C or 37 °C and were then challenged for resistance to high temperature (50 °C, low pH (pH 2.8, and oxidative stress (15 mM H2O2. In general, carbon-starved cells exhibited a higher level of resistance to thermal stress, acid stress, and oxidative stress compared to log-phase cells. The extent of carbon-starvation-induced cross-resistance was dependent on incubation temperature and on the particular strain of S. marcescens. In addition, strain- and temperature-dependent variations in long-term starvation survival were also observed. The enhanced stress-resistance of starved S. marcescens cells could be an important factor in their survival and persistence in many non-host environments and within certain host microenvironments where the availability of carbon sources is suboptimal for growth.

  8. Theoretical Research on Thermal Shock Resistance of Ultra-High Temperature Ceramics Focusing on the Adjustment of Stress Reduction Factor

    Directory of Open Access Journals (Sweden)

    Daining Fang

    2013-02-01

    Full Text Available The thermal shock resistance of ceramics depends on not only the mechanical and thermal properties of materials, but also the external constraint and thermal condition. So, in order to study the actual situation in its service process, a temperature-dependent thermal shock resistance model for ultra-high temperature ceramics considering the effects of the thermal environment and external constraint was established based on the existing theory. The present work mainly focused on the adjustment of the stress reduction factor according to different thermal shock situations. The influences of external constraint on both critical rupture temperature difference and the second thermal shock resistance parameter in either case of rapid heating or cooling conditions had been studied based on this model. The results show the necessity of adjustment of the stress reduction factor in different thermal shock situations and the limitations of the applicable range of the second thermal shock resistance parameter. Furthermore, the model was validated by the finite element method.

  9. Impact of thermal stress on evolutionary trajectories of pathogen resistance in three-spined stickleback (Gasterosteus aculeatus).

    Science.gov (United States)

    Schade, Franziska M; Shama, Lisa N S; Wegner, K Mathias

    2014-07-26

    Pathogens are a major regulatory force for host populations, especially under stressful conditions. Elevated temperatures may enhance the development of pathogens, increase the number of transmission stages, and can negatively influence host susceptibility depending on host thermal tolerance. As a net result, this can lead to a higher prevalence of epidemics during summer months. These conditions also apply to marine ecosystems, where possible ecological impacts and the population-specific potential for evolutionary responses to changing environments and increasing disease prevalence are, however, less known. Therefore, we investigated the influence of thermal stress on the evolutionary trajectories of disease resistance in three marine populations of three-spined sticklebacks Gasterosteus aculeatus by combining the effects of elevated temperature and infection with a bacterial strain of Vibrio sp. using a common garden experiment. We found that thermal stress had an impact on fish weight and especially on survival after infection after only short periods of thermal acclimation. Environmental stress reduced genetic differentiation (QST) between populations by releasing cryptic within-population variation. While life history traits displayed positive genetic correlations across environments with relatively weak genotype by environment interactions (GxE), environmental stress led to negative genetic correlations across environments in pathogen resistance. This reversal of genetic effects governing resistance is probably attributable to changing environment-dependent virulence mechanisms of the pathogen interacting differently with host genotypes, i.e. GPathogenxGHostxE or (GPathogenxE)x(GHostxE) interactions, rather than to pure host genetic effects, i.e. GHostxE interactions. To cope with climatic changes and the associated increase in pathogen virulence, host species require wide thermal tolerances and pathogen-resistant genotypes. The higher resistance we found

  10. Numerical Simulation for Thermal Shock Resistance of Ultra-High Temperature Ceramics Considering the Effects of Initial Stress Field

    Directory of Open Access Journals (Sweden)

    Weiguo Li

    2011-01-01

    Full Text Available Taking the hafnium diboride ceramic as an example, the effects of heating rate, cooling rate, thermal shock initial temperature, and external constraint on the thermal shock resistance (TSR of ultra-high temperature ceramics (UHTCs were studied through numerical simulation in this paper. The results show that the external constraint has an approximately linear influence on the critical rupture temperature difference of UHTCs. The external constraint prepares a compressive stress field in the structure because of the predefined temperature field, and this compressive stress field relieves the tension stress in the structure when it is cooled down and then it improves the TSR of UHTCs. As the thermal shock initial temperature, a danger heating rate (or cooling rate exists where the critical temperature difference is the lowest.

  11. Theory of thermal stresses

    CERN Document Server

    Boley, Bruno A

    1997-01-01

    Highly regarded text presents detailed discussion of fundamental aspects of theory, background, problems with detailed solutions. Basics of thermoelasticity, heat transfer theory, thermal stress analysis, more. 1985 edition.

  12. Resistance to thermal stress in corals without changes in symbiont composition.

    Science.gov (United States)

    Bellantuono, Anthony J; Hoegh-Guldberg, Ove; Rodriguez-Lanetty, Mauricio

    2012-03-22

    Discovering how corals can adjust their thermal sensitivity in the context of global climate change is important in understanding the long-term persistence of coral reefs. In this study, we showed that short-term preconditioning to higher temperatures, 3°C below the experimentally determined bleaching threshold, for a period of 10 days provides thermal tolerance for the symbiosis stability between the scleractinian coral, Acropora millepora and Symbiodinium. Based on genotypic analysis, our results indicate that the acclimatization of this coral species to thermal stress does not come down to simple changes in Symbiodinium and/or the bacterial communities that associate with reef-building corals. This suggests that the physiological plasticity of the host and/or symbiotic components appears to play an important role in responding to ocean warming. The further study of host and symbiont physiology, both of Symbiodinium and prokaryotes, is of paramount importance in the context of global climate change, as mechanisms for rapid holobiont acclimatization will become increasingly important to the long-standing persistence of coral reefs.

  13. Environmental thermal stress.

    Science.gov (United States)

    Keim, Samuel M; Guisto, John A; Sullivan, John B

    2002-01-01

    Thermal stress from cold and heat can affect health and productivity in a wide range of environmental and workload conditions. Health risks typically occur in the outer zones of heat and cold stress, but are also related to workload. Environmental factors related to thermal stress are reviewed. Individuals undergo thermoregulatory physiologic changes to adapt and these changes are reviewed. Heat and cold related illnesses are reviewed as well as their appropriate therapy. Published standards, thresholds and recommendations regarding work practices, personal protection and types of thermal loads are reviewed.

  14. Thermal stress and seismogenesis

    International Nuclear Information System (INIS)

    Zhou Huilan; Wei Dongping

    1989-05-01

    In this paper, the Fourier stress method was applied to deal with the problem of plane thermal stress, and a computing formula was given. As an example, we set up a variate temperature field to describe the uplifted upper mantle in Bozhong area of China, and the computing results shows that the maximum value of thermal plane shear stress is up to nearly 7x10 7 P α in two regions of this area. Since the Bohai earthquake (18 July, 1969, M s = 7.4) occurred at the edge of one of them and Tangshan earthquake (28 July, 1976, M s = 7.8) within another, their occurrences can be related reasonably to the thermal stress. (author). 15 refs, 7 figs

  15. Evolution of Escherichia coli rifampicin resistance in an antibiotic-free environment during thermal stress.

    Science.gov (United States)

    Rodríguez-Verdugo, Alejandra; Gaut, Brandon S; Tenaillon, Olivier

    2013-02-22

    Beneficial mutations play an essential role in bacterial adaptation, yet little is known about their fitness effects across genetic backgrounds and environments. One prominent example of bacterial adaptation is antibiotic resistance. Until recently, the paradigm has been that antibiotic resistance is selected by the presence of antibiotics because resistant mutations confer fitness costs in antibiotic free environments. In this study we show that it is not always the case, documenting the selection and fixation of resistant mutations in populations of Escherichia coli B that had never been exposed to antibiotics but instead evolved for 2000 generations at high temperature (42.2°C). We found parallel mutations within the rpoB gene encoding the beta subunit of RNA polymerase. These amino acid substitutions conferred different levels of rifampicin resistance. The resistant mutations typically appeared, and were fixed, early in the evolution experiment. We confirmed the high advantage of these mutations at 42.2°C in glucose-limited medium. However, the rpoB mutations had different fitness effects across three genetic backgrounds and six environments. We describe resistance mutations that are not necessarily costly in the absence of antibiotics or compensatory mutations but are highly beneficial at high temperature and low glucose. Their fitness effects depend on the environment and the genetic background, providing glimpses into the prevalence of epistasis and pleiotropy.

  16. Computational analysis of heat transfer, thermal stress and dislocation density during resistively Czochralski growth of germanium single crystal

    Science.gov (United States)

    Tavakoli, Mohammad Hossein; Renani, Elahe Kabiri; Honarmandnia, Mohtaram; Ezheiyan, Mahdi

    2018-02-01

    In this paper, a set of numerical simulations of fluid flow, temperature gradient, thermal stress and dislocation density for a Czochralski setup used to grow IR optical-grade Ge single crystal have been done for different stages of the growth process. A two-dimensional steady state finite element method has been applied for all calculations. The obtained numerical results reveal that the thermal field, thermal stress and dislocation structure are mainly dependent on the crystal height, heat radiation and gas flow in the growth system.

  17. Consequences of acclimation on the resistance to acute thermal stress: Proteomic focus on mussels from pristine site.

    Science.gov (United States)

    Péden, Romain; Rocher, Béatrice; Chan, Philippe; Vaudry, David; Poret, Agnès; Olivier, Stéphanie; Le Foll, Frank; Bultelle, Florence

    2016-10-01

    Climate change constitutes an additional threat for intertidal species that already have to cope with a challenging environment. The present study focuses on the blue mussel Mytilus edulis and aims at investigating the importance of thermal acclimation in heat stress response. Microcosm exposures were performed with mussels submitted to an identical acute thermal stress following two thermal summer acclimations standing for present or future temperature conditions. Gill proteomes were analyzed by 2DE and 96 differentially expressed proteoforms were identified. Our results show that cell integrity appears to be maintained by the rise in molecular protective systems (i.e. Heat Shock Proteins), and by the reallocation of energy production via a switch to anaerobic metabolism and the setting up of alternative energy pathways. Finally, our results indicate that the response of mussels to acute thermal stress is conditioned by the acclimation temperature with an improved response in organisms acclimated to higher temperatures. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Electrical resistivity and strain recovery studies on the effect of thermal cycling under constant stress on R-phase in NiTi shape memory alloy

    International Nuclear Information System (INIS)

    Uchil, J.; Mahesh, K.K.; Kumara, K. Ganesh

    2002-01-01

    In this paper, the results of electrical resistivity and strain recovery measurements involved in the study of the stability of R-phase in NiTi shape memory alloy upon thermal cycling under a constant tensile stress of 100 and 200 MPa are presented. Two wire samples are chosen such that the one heat-treated at 560 deg. C exhibits a pure martensitic phase and the other heat-treated at 380 deg. C consists of a mixture of R-phase and martensitic phase with residual austenites at ambient temperature. In both cases, the applied stress has been found to promote the R→A transformation during the heating part of the thermal cycling unlike the case of stress free condition in which R-phase is found to exist only in the cooling part of thermal cycling. R-phase is found to become more prominent with increasing applied stress. It is also found that the applied tensile stress enables the development of R-phase in the cooling part of the first thermal cycle itself in the sample heat-treated at 560 deg. C whereas under stress-free condition it requires about 15 thermal cycles to develop R-phase. The NiTi wire heat-treated at 560 deg. C exhibits more recoverable strain in the initial cycles than the wire heat-treated at 380 deg. C, but after a large number of thermal cycles of the order of 1000 the recoverable strain in both samples is found to be almost the same. Under tensile stress, the sample heat-treated at 380 deg. C is found to be more stable against plastic deformation with thermal cycling and hence can be preferred over the sample heat-treated at 560 deg. C for two-way applications of SMA

  19. Encyclopedia of thermal stresses

    CERN Document Server

    2014-01-01

    The Encyclopedia of Thermal Stresses is an important interdisciplinary reference work.  In addition to topics on thermal stresses, it contains entries on related topics, such as the theory of elasticity, heat conduction, thermodynamics, appropriate topics on applied mathematics, and topics on numerical methods. The Encyclopedia is aimed at undergraduate and graduate students, researchers and engineers. It brings together well established knowledge and recently received results. All entries were prepared  by leading experts from all over the world, and are presented in an easily accessible format. The work is lavishly illustrated, examples and applications are given where appropriate, ideas for further development abound, and the work will challenge many students and researchers to pursue new results of their own. This work can also serve as a one-stop resource for all who need succinct, concise, reliable and up to date information in short encyclopedic entries, while the extensive references will be of inte...

  20. Thermal stress resistance of the brown alga Fucus serratus along the North-Atlantic coast: acclimatization potential to climate change.

    Science.gov (United States)

    Jueterbock, Alexander; Kollias, Spyros; Smolina, Irina; Fernandes, Jorge M O; Coyer, James A; Olsen, Jeanine L; Hoarau, Galice

    2014-02-01

    Seaweed-dominated communities are predicted to disappear south of 45° latitude on North-Atlantic rocky shores by 2200 because of climate change. The extent of predicted habitat loss, however, could be mitigated if the seaweeds' physiology is sufficiently plastic to rapidly acclimatize to the warmer temperatures. The main objectives of this study were to identify whether the thermal tolerance of the canopy-forming seaweed Fucus serratus is population-specific and where temperatures are likely to exceed its tolerance limits in the next 200 years. We measured the stress response of seaweed samples from four populations (Norway, Denmark, Brittany and Spain) to common-garden heat stress (20 °C-36 °C) in both photosynthetic performance and transcriptomic upregulation of heat shock protein genes. The two stress indicators did not correlate and likely measured different cellular components of the stress response, but both indicators revealed population-specific differences, suggesting ecotypic differentiation. Our results confirmed that thermal extremes will regularly reach physiologically stressful levels in Brittany (France) and further south by the end of the 22nd century. Although heat stress resilience in photosynthetic performance was higher at the species' southern distributional edge in Spain, the hsp expression pattern suggested that this edge-population experienced reduced fitness and limited responsiveness to further stressors. Thus, F. serratus may be unable to mitigate its predicted northward shift and may be at high risk to lose its center of genetic diversity and adaptability in Brittany (France). As it is an important intertidal key species, the disappearance of this seaweed will likely trigger major ecological changes in the entire associated ecosystem. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. Thermal stress mitigation by Active Thermal Control

    DEFF Research Database (Denmark)

    Soldati, Alessandro; Dossena, Fabrizio; Pietrini, Giorgio

    2017-01-01

    This work proposes an Active Thermal Control (ATC) of power switches. Leveraging on the fact that thermal stress has wide impact on the system reliability, controlling thermal transients is supposed to lengthen the lifetime of electronic conversion systems. Indeed in some environments......, such as transportation, reliability and lifetime are still obstacles to widespread adoption of electric and electronic actuators, despite a general trend of electrification spreading in many different areas of interest. Active thermal control is attained leaving the electric parameters of load untouched, while acting...... results of control schemes are presented, together with evaluation of the proposed loss models. Experimental proof of the ability of the proposed control to reduce thermal swing and related stress on the device is presented, too....

  2. Temperature distribution and thermal stress

    Indian Academy of Sciences (India)

    Abstract. Thermal effects of a double-end-pumped cubic Nd:YVO4 laser crystal are investigated in this paper. A detailed analysis of temperature distribution and thermal stress in cubic crystal with circular shape pumping is discussed. It has been shown that by considering the total input powers as constant, the ...

  3. Thermal Stresses in Welding

    DEFF Research Database (Denmark)

    Hansen, Jan Langkjær

    1998-01-01

    Studies of the transient temperature fields and the hereby induced deformations and stressses in a butt-welded mild steel plate modelledrespectively in 2D plane stress state (as well as plane strain state) and in full 3D have been done. The model has been implemented in the generalpurpose FE-soft......-software package ABAQUS. In this work, the results have been qualitatively evaluated....

  4. Residual thermal stresses in injection moulded products

    NARCIS (Netherlands)

    Zoetelief, W.F.; Douven, L.F.A.; Ingen Housz, A.J.; Ingen housz, A.J.

    1996-01-01

    Nonisothermal flow of a polymer melt in a cold mold cavity introduces stresses that are partly frozen-in during solidification. Flow-induced stresses cause anisotropy of mechanical, thermal, and optical properties, while the residual thermal stresses induce warpage and stress-cracking. In this

  5. Thermal Shock-resistant Cement

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Pyatina, T.; Gill, S.

    2012-02-01

    We studied the effectiveness of sodium silicate-activated Class F fly ash in improving the thermal shock resistance and in extending the onset of hydration of Secar #80 refractory cement. When the dry mix cement, consisting of Secar #80, Class F fly ash, and sodium silicate, came in contact with water, NaOH derived from the dissolution of sodium silicate preferentially reacted with Class F fly ash, rather than the #80, to dissociate silicate anions from Class F fly ash. Then, these dissociated silicate ions delayed significantly the hydration of #80 possessing a rapid setting behavior. We undertook a multiple heating -water cooling quenching-cycle test to evaluate the cement’s resistance to thermal shock. In one cycle, we heated the 200 and #61616;C-autoclaved cement at 500 and #61616;C for 24 hours, and then the heated cement was rapidly immersed in water at 25 and #61616;C. This cycle was repeated five times. The phase composition of the autoclaved #80/Class F fly ash blend cements comprised four crystalline hydration products, boehmite, katoite, hydrogrossular, and hydroxysodalite, responsible for strengthening cement. After a test of 5-cycle heat-water quenching, we observed three crystalline phase-transformations in this autoclaved cement: boehmite and #61614; and #61543;-Al2O3, katoite and #61614; calcite, and hydroxysodalite and #61614; carbonated sodalite. Among those, the hydroxysodalite and #61614; carbonated sodalite transformation not only played a pivotal role in densifying the cementitious structure and in sustaining the original compressive strength developed after autoclaving, but also offered an improved resistance of the #80 cement to thermal shock. In contrast, autoclaved Class G well cement with and without Class F fly ash and quartz flour failed this cycle test, generating multiple cracks in the cement. The major reason for such impairment was the hydration of lime derived from the dehydroxylation of portlandite formed in the autoclaved

  6. Thermal stresses and their possible limits

    International Nuclear Information System (INIS)

    Montfort, C.

    1974-01-01

    The method proposed is not restricted to heat exchangers. It concerns the means of determining the behaviour of materials subjected to thermal and mechanical stresses. The paper has two parts: I. Method for the rapid determination of thermal stresses. II. Possible limits of stresses. Field of elasticity and plasticity [fr

  7. Contribution to encyclopedia of thermal stresses

    Science.gov (United States)

    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.

  8. Thermal stress relaxation in magnesium composites during thermal cycling

    Energy Technology Data Exchange (ETDEWEB)

    Trojanova, Z.; Lukac, P. (Karlova Univ., Prague (Czech Republic)); Kiehn, J.; Kainer, K.U.; Mordike, B.L. (Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany))

    1998-01-01

    It has been shown that the internal friction of Mg - Saffil metal matrix composites can be influenced by thermal stresses, if MMCc are submitted to thermal cycling between room temperature and an upper temperature of cycling. These stresses can be accommodated by generation and motion of dislocations giving the formation of the microplastic zones. The thermal stress relaxation depends on the upper temperature of cycling, the volume fraction of reinforcement and the matrix composition and can result in plastic deformation and strain hardening of the matrix without applied stress. The internal friction measurements can be used for non destructive investigation of processes which influence the mechanical properties. (orig.)

  9. Thermal Stress Awareness, Self-Study #18649

    Energy Technology Data Exchange (ETDEWEB)

    Chochoms, Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-11-15

    Thermal stresses can expose individuals to a variety of health hazards at work, home, and play. Every year thermal stresses cause severe injuries and death to a large range of people, from elderly people in cities during summer heat waves to young people engaged in winter mountaineering. Awareness is the key to preventing the health hazards associated with thermal stresses. This course is designed for personnel at Los Alamos National Laboratory (LANL). It addresses both heat and cold stresses and discusses their factors, signs and symptoms, treatments, and controls.

  10. Correlation of physical properties of ceramic materials with resistance to fracture by thermal shock

    Science.gov (United States)

    Lidman, W G; Bobrowsky, A R

    1949-01-01

    An analysis is made to determine which properties of materials affect their resistance to fracture by thermal stresses.From this analysis, a parameter is evaluated that is correlated with the resistance of ceramic materials to fracture by thermal shock as experimentally determined. This parameter may be used to predict qualitatively the resistance of a material to fracture by thermal shock. Resistance to fracture by thermal shock is shown to be dependent upon the following material properties: thermal conductivity, tensile strength, thermal expansion, and ductility modulus. For qualitative prediction of resistance of materials to fracture by thermal shock, the parameter may be expressed as the product of thermal conductivity and tensile strength divided by the product of linear coefficient of thermal expansion and ductility modulus of the specimen.

  11. Resistance of functional Lactobacillus plantarum strains against food stress conditions.

    Science.gov (United States)

    Ferrando, Verónica; Quiberoni, Andrea; Reinhemer, Jorge; Suárez, Viviana

    2015-06-01

    The survival of three Lactobacillus plantarum strains (Lp 790, Lp 813 and Lp 998) with functional properties was studied taking into account their resistance to thermal, osmotic and oxidative stress factors. Stress treatments applied were: 52 °C-15 min (Phosphate Buffer pH 7, thermal shock), H2O2 0.1% (p/v) - 30 min (oxidative shock) and NaCl aqueous solution at 17, 25 and 30% (p/v) (room temperature - 1 h, osmotic shock). The osmotic stress was also evaluated on cell growth in MRS broth added of 2, 4, 6, 8 and 10% (p/v) of NaCl, during 20 h at 30 °C. The cell thermal adaptation was performed in MRS broth, selecting 45 °C for 30 min as final conditions for all strains. Two strains (Lp 813 and Lp 998) showed, in general, similar behaviour against the three stress factors, being clearly more resistant than Lp 790. An evident difference in growth kinetics in presence of NaCl was observed between Lp 998 and Lp 813, Lp998 showing a higher optical density (OD570nm) than Lp 813 at the end of the assay. Selected thermal adaptation improved by 2 log orders the thermal resistance of both strains, but cell growth in presence of NaCl was enhanced only in Lp 813. Oxidative resistance was not affected with this thermal pre-treatment. These results demonstrate the relevance of cell technological resistance when selecting presumptive "probiotic" cultures, since different stress factors might considerably affect viability or/and performance of the strains. The incidence of stress conditions on functional properties of the strains used in this work are currently under research in our group. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Heat transfer and thermal stress analysis in grooved tubes

    Indian Academy of Sciences (India)

    The maximum thermal stress ratio positions inside the tube have been indicated as MX for all investigated cases. In the light of the thermal stress values, various designs can be applied to reduce thermal stress in grooved tubes. Keywords. Heat transfer; thermal stress; grooved tubes. 1. Introduction. Heat transfer in pipe flow ...

  13. Sunflower breeding for resistance to abiotic stresses

    OpenAIRE

    Škorić D.

    2009-01-01

    Due to a specific structure of its main organs (root, stem, leaves, head), sunflower can be successfully grown on marginal soils and in semi-arid conditions and it is more resistant to abiotic stresses than other field crops. In sunflower breeding for resistance to abiotic stresses, the greatest progress has been made in selection for drought resistance. Breeders use over 30 different parameters in sunflower screening for drought resistance, with physiological ones being the predominant type....

  14. Thermal conductivity and thermal boundary resistance of nanostructures

    Directory of Open Access Journals (Sweden)

    Merabia Samy

    2011-01-01

    Full Text Available Abstract We present a fabrication process of low-cost superlattices and simulations related with the heat dissipation on them. The influence of the interfacial roughness on the thermal conductivity of semiconductor/semiconductor superlattices was studied by equilibrium and non-equilibrium molecular dynamics and on the Kapitza resistance of superlattice's interfaces by equilibrium molecular dynamics. The non-equilibrium method was the tool used for the prediction of the Kapitza resistance for a binary semiconductor/metal system. Physical explanations are provided for rationalizing the simulation results. PACS 68.65.Cd, 66.70.Df, 81.16.-c, 65.80.-g, 31.12.xv

  15. Thermal stress relieving of dilute uranium alloys

    International Nuclear Information System (INIS)

    Eckelmeyer, K.H.

    1981-01-01

    The kinetics of thermal stress relieving of uranium - 2.3 wt % niobium, uranium - 2.0 wt % molybdenum, and uranium - 0.75 wt % titanium are reported and discussed. Two temperature regimes of stress relieving are observed. In the low temperature regime (T 0 C) the process appears to be controlled by an athermal microplasticity mechanism which can be completely suppressed by prior age hardening. In the high temperature regime (300 0 C 0 C) the process appears to be controlled by a classical diffusional creep mechanism which is strongly dependent on temperature and time. Stress relieving is accelerated in cases where it occurs simultaneously with age hardening. The potential danger of residual stress induced stress corrosion cracking of uranium alloys is discussed

  16. Ecologically relevant stress resistance: from microarrays and ...

    Indian Academy of Sciences (India)

    2004-10-15

    Oct 15, 2004 ... Home; Journals; Journal of Biosciences; Volume 29; Issue 4. Ecologically relevant stress resistance: from microarrays and quantitative trait loci to candidate genes – A research plan and preliminary results using Drosophila as a model organism and climatic and genetic stress as model stresses.

  17. Performance Analysis and Modeling of Thermally Sprayed Resistive Heaters

    Science.gov (United States)

    Lamarre, Jean-Michel; Marcoux, Pierre; Perrault, Michel; Abbott, Richard C.; Legoux, Jean-Gabriel

    2013-08-01

    Many processes and systems require hot surfaces. These are usually heated using electrical elements located in their vicinity. However, this solution is subject to intrinsic limitations associated with heating element geometry and physical location. Thermally spraying electrical elements directly on surfaces can overcome these limitations by tailoring the geometry of the heating element to the application. Moreover, the element heat transfer is maximized by minimizing the distance between the heater and the surface to be heated. This article is aimed at modeling and characterizing resistive heaters sprayed on metallic substrates. Heaters were fabricated by using a plasma-sprayed alumina dielectric insulator and a wire flame-sprayed iron-based alloy resistive element. Samples were energized and kept at a constant temperature of 425 °C for up to 4 months. SEM cross-sectional observations revealed the formation of cracks at very specific locations in the alumina layer after thermal use. Finite-element modeling shows that these cracks originate from high local thermal stresses and can be predicted according to the considered geometry. The simulation model was refined using experimental parameters obtained by several techniques such as emissivity and time-dependent temperature profile (infra-red camera), resistivity (four-probe technique), thermal diffusivity (laser flash method), and mechanical properties (micro and nanoindentation). The influence of the alumina thickness and the substrate material on crack formation was evaluated.

  18. Effects of Screening on the Thermal Resistivity And Compressibility ...

    African Journals Online (AJOL)

    Models for computing thermal resistivity, compressibility ratio, and screening parameter of metals was developed and used to study the effects of screening on the thermal resistivity and compressibility ratio of metals. The results obtained revealed that the thermal resistivity of metals increases with an increase in the electron ...

  19. Thermal Shock Resistance of Stabilized Zirconia/Metal Coat on Polymer Matrix Composites by Thermal Spraying Process

    Science.gov (United States)

    Zhu, Ling; Huang, Wenzhi; Cheng, Haifeng; Cao, Xueqiang

    2014-12-01

    Stabilized zirconia/metal coating systems were deposited on the polymer matrix composites by a combined thermal spray process. Effects of the thicknesses of metal layers and ceramic layer on thermal shock resistance of the coating systems were investigated. According to the results of thermal shock lifetime, the coating system consisting of 20 μm Zn and 125 μm 8YSZ exhibited the best thermal shock resistance. Based on microstructure evolution, failure modes and failure mechanism of the coating systems were proposed. The main failure modes were the formation of vertical cracks and delamination in the outlayer of substrate, and the appearance of coating spallation. The residual stress, thermal stress and oxidation of substrate near the substrate/metal layer interface were responsible for coating failure, while the oxidation of substrate near the substrate/coating interface was the dominant one.

  20. Thermal barrier coating resistant to sintering

    Science.gov (United States)

    Subramanian, Ramesh; Seth, Brij B.

    2004-06-29

    A device (10) is made, having a ceramic thermal barrier coating layer (16) characterized by a microstructure having gaps (18) with a sintering inhibiting material (22) disposed on the columns (20) within the gaps (18). The sintering resistant material (22) is stable over the range of operating temperatures of the device (10), is not soluble with the underlying ceramic layer (16) and is applied by a process that is not an electron beam physical vapor deposition process.

  1. Determination of Thermal Contact Resistances for Small TENV Electrical Machine

    OpenAIRE

    Olfa MEKSI; Mohd Azri Hizami RASID; Alejandro OSPINA; Vincent LANFRANCHI

    2016-01-01

    In this paper, a thermal study of Synchronous Reluctant motor is proposed. A specific experimental method is applied in order to identify the thermal parameters, this method focus on the study of contact resistances and total thermal capacity. Generally, in the classical thermal modeling, the thermal contact resistance (TCR) is estimated by empirical values and the thermal capacities are calculated by analytical solutions. The originality of the proposed model is based on the complementarity ...

  2. Effect of cold working and applied stress on the stress corrosion cracking resistance of nickel-chromium-iron alloys

    International Nuclear Information System (INIS)

    Yonezawa, T.; Onimura, K.; Itoh, H.; Saito, I.; Takamatsu, H.; Fujitani, T.

    1992-01-01

    In order to grasp the stress corrosion cracking quantitative resistance of Alloys 600 and 690 in PWR primary water, the authors have studied the effect of cold working and applied stress on the stress corrosion cracking resistance of Alloys 600 and 690, in high temperature water. Stress corrosion cracking tests were conducted at 360 degrees C (633K) in a simulated PWR primary water for about 12,000 hours or 24,000 hours. From the test results, it is concluded that the stress corrosion cracking resistance in the cold worked Alloy 600 at the same applied stress level increases with an increase in cold working ratio, and the cold worked Alloys of thermally treated 690 have the excellent stress corrosion cracking resistance. Further, in this paper, the planning of stress corrosion cracking test for weld joints and weld metal of Alloy 600 is described

  3. 40 CFR 90.329 - Catalyst thermal stress test.

    Science.gov (United States)

    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 thermally stressing the test catalyst must be capable of maintaining a temperature of 500 ±5 °C and 1000 ±10...

  4. Induced thermal resistance in the mouse ear

    International Nuclear Information System (INIS)

    Law, M.P.; Coultas, P.G.; Field, S.B.

    1979-01-01

    The mouse ear (pinna) was used to investigate the effect of two hyperthermic treatments. Heating was by immersion in hot water at 43.5 0 C. A single treatment of about 50 minutes was required to cause necrosis in 50% of the ears treated. When heat treatment was given in two equal fractions the total heating time had to be increased if the interval between fractions was greater than four hours. By 24 hours a total treatment of about 100 minutes was required, indicating almost complete recovery from the first heating. Priming treatments at 43.5 0 C induced thermal resistance to a second heat treatment at 43.5 0 C. Maximum resistance was observed one day after a 20 minute priming and two days after a 40 minute priming, when the heating time had to be increased to 120 minutes, an increase by a factor of 2.4. Shorter priming treatments induced less resistance, the minimum heating time to produce an effect being two minutes. In all cases the effect decreased during the next four to five days. These results indicate that the reduced response of tissues to fractionated hyperthermia is due both to the repair of sublethal heat damage and induction of thermal resistance. (author)

  5. Stress analysis in multilayered FGM plates under thermal shock

    Energy Technology Data Exchange (ETDEWEB)

    Jin, G.; Nishikawa, T.; Honda, S.; Awaji, H. [Dept. of Material Science and Engineering, Nagoya Inst. of Tech. (Japan)

    2003-07-01

    In this study, one-dimensional calculation was employed to evaluate the steady-state and transient temperature/stress distributions in a multilayered functionally graded ceramic-metal composite materials. The residual thermal stress raised from fabrication process because of the macroscopic variation of constituent across the thickness was also evaluated. The alumina/nickel FGM disks were fabricated using a powder stacking method and a pulse electric current sintering technique. The thermal shock tests on the fabricated FGM disks were performed and the stress distributions in the FGM plates under thermal shock were calculated using a critical temperature difference where cracks appeared on the ceramic surface. Then the thermal shock properties of FGM plates were evaluated under the consideration of both the thermal stress and the residual thermal stress distribution. It was indicated that the thermal shock properties of the multilayered alumina-nickel FGM plate were strongly influenced by the residual thermal stress distribution on the alumina surface. (orig.)

  6. Thermal stress analysis of FIRE divertor

    International Nuclear Information System (INIS)

    Baxi, C.B.; Reis, E.E.; Ulrickson, M.A.; Heizenroeder, P.; Driemeyer, D.

    2003-01-01

    The fusion engineering research experiment (FIRE) device is designed for high power density and advanced physics operating modes. Due to the short distance of the divertor from the X-point, the connection lengths are short and the scrape off layer thickness is small. A relatively high peak heat flux of 25 MW/m 2 is expected on the divertor. The FIRE divertor engineering design is based on the design approaches developed for international thermonuclear experimental reactor (ITER). The geometry of the FIRE divertor consists of water cooled copper fingers and a tungsten brush armor as plasma facing material. The divertor assembly consists of modular units for remote handling. A 316 stainless steel back plate is used for support and manifolding. The backing plate is joined to the copper fingers by pins. The coolant channel diameter is 8 mm at a pitch of 14 mm. The total power flow to the outer divertor is 35 MW. Water at an inlet temperature of 30 deg.C, 1.5 MPa and a flow velocity of 10 m/s is used with two channels in series. A margin of ∼1.6 is obtained on the critical heat flux. A three dimensional thermal stress finite element (FE) analysis of this geometry was performed. Thermal hydraulic correlations derived for ITER were used to perform the thermal analysis. Design changes were implemented to reduce the stresses and temperatures to acceptable levels

  7. Proliferation resistance assessment of thermal recycle systems

    International Nuclear Information System (INIS)

    1979-02-01

    This paper examines the major proliferation aspects of thermal recycle systems and the extent to which technical or institutional measures could increase the difficulty or detectability of misuse of the system by would-be proliferators. It does this by examining the various activities necessary to acquire weapons-usable material using a series of assessment factors; resources required, time required, detectability. It is concluded that resistance to proliferation could be improved substantially by collecting reprocessing, conversion and fuel fabrication plants under multi national control and instituting new measures to protect fresh MOX fuel. Resistance to theft at sub-national level could be improved by co-location of sensitive facilities high levels of physical protection at plants and during transportation and possibly by adding a radiation barrier to MOX prior to shipment

  8. The Potential Link between Thermal Resistance and Virulence in Salmonella: A Review

    Directory of Open Access Journals (Sweden)

    Turki M. Dawoud

    2017-06-01

    Full Text Available In some animals, the typical body temperature can be higher than humans, for example, 42°C in poultry and 40°C in rabbits which can be a potential thermal stress challenge for pathogens. Even in animals with lower body temperatures, when infection occurs, the immune system may increase body temperature to reduce the chance of survival for pathogens. However, some pathogens can still easily overcome higher body temperatures and/or rise in body temperatures through expression of stress response mechanisms. Salmonella is the causative agent of one of the most prevalent foodborne illnesses, salmonellosis, and can readily survive over a wide range of temperatures due to the efficient expression of the heat (thermal stress response. Therefore, thermal resistance mechanisms can provide cross protection against other stresses including the non-specific host defenses found within the human body thus increasing pathogenic potential. Understanding the molecular mechanisms associated with thermal responses in Salmonella is crucial in designing and developing more effective or new treatments for reducing and eliminating infection caused by Salmonella that have survived heat stress. In this review, Salmonella thermal resistance is assessed followed by an overview of the thermal stress responses with a focus on gene regulation by sigma factors, heat shock proteins, along with the corresponding thermosensors and their association with virulence expression including a focus on a potential link between heat resistance and potential for infection.

  9. Sustainably Sourced, Thermally Resistant, Radiation Hard Biopolymer

    Science.gov (United States)

    Pugel, Diane

    2011-01-01

    This material represents a breakthrough in the production, manufacturing, and application of thermal protection system (TPS) materials and radiation shielding, as this represents the first effort to develop a non-metallic, non-ceramic, biomaterial-based, sustainable TPS with the capability to also act as radiation shielding. Until now, the standing philosophy for radiation shielding involved carrying the shielding at liftoff or utilizing onboard water sources. This shielding material could be grown onboard and applied as needed prior to different radiation landscapes (commonly seen during missions involving gravitational assists). The material is a bioplastic material. Bioplastics are any combination of a biopolymer and a plasticizer. In this case, the biopolymer is a starch-based material and a commonly accessible plasticizer. Starch molecules are composed of two major polymers: amylase and amylopectin. The biopolymer phenolic compounds are common to the ablative thermal protection system family of materials. With similar constituents come similar chemical ablation processes, with the potential to have comparable, if not better, ablation characteristics. It can also be used as a flame-resistant barrier for commercial applications in buildings, homes, cars, and heater firewall material. The biopolymer is observed to undergo chemical transformations (oxidative and structural degradation) at radiation doses that are 1,000 times the maximum dose of an unmanned mission (10-25 Mrad), indicating that it would be a viable candidate for robust radiation shielding. As a comparison, the total integrated radiation dose for a three-year manned mission to Mars is 0.1 krad, far below the radiation limit at which starch molecules degrade. For electron radiation, the biopolymer starches show minimal deterioration when exposed to energies greater than 180 keV. This flame-resistant, thermal-insulating material is non-hazardous and may be sustainably sourced. It poses no hazardous

  10. Thermal Barrier Coatings Resistant to Glassy Deposits

    Science.gov (United States)

    Drexler, Julie Marie

    Engineering of alloys has for years allowed aircraft turbine engines to become more efficient and operate at higher temperatures. As advancements in these alloy systems have become more difficult, ceramic thermal barrier coatings (TBCs), often yttria (7 wt %) stabilized zirconia (7YSZ), have been utilized for thermal protection. TBCs have allowed for higher engine operating temperatures and better fuel efficiency but have also created new engineering problems. Specifically, silica based particles such as sand and volcanic ash that enter the engine during operation form glassy deposits on the TBCs. These deposits can cause the current industrial 7YSZ thermal barrier coatings to fail since the glass formed penetrates and chemically interacts with the TBC. When this occurs, coating failure may occur due to a loss of strain tolerance, which can lead to fracture, and phase changes of the TBC material. There have been several approaches used to stop calcium-magnesium aluminio-silcate (CMAS) glasses (molten sand) from destroying the entire TBC, but overall there is still limited knowledge. In this thesis, 7YSZ and new TBC materials will be examined for thermochemical and thermomechanical performance in the presence of molten CMAS and volcanic ash. Two air plasma sprayed TBCs will be shown to be resistant to volcanic ash and CMAS. The first type of coating is a modified 7YSZ coating with 20 mol% Al2O3 and 5 mol% TiO2 in solid solution (YSZ+20Al+5Ti). The second TBC is made of gadolinium zirconate. These novel TBCs impede CMAS and ash penetration by interacting with the molten CMAS or ash and drastically changing the chemistry. The chemically modified CMAS or ash will crystallize into an apatite or anorthite phase, blocking the CMAS or ash from further destroying the coating. A presented mechanism study will show these coatings are effective due to the large amount of solute (Gd, Al) in the zirconia structure, which is the key to creating the crystalline apatite or

  11. Modelling and analysis of radial thermal stresses and temperature ...

    African Journals Online (AJOL)

    A theoretical investigation has been undertaken to study operating temperatures, heat fluxes and radial thermal stresses in the valves of a modern diesel engine with and without air-cavity. Temperatures, heat fluxes and radial thermal stresses were measured theoretically for both cases under all four thermal loading ...

  12. Prognostics Approach for Power MOSFET Under Thermal-Stress

    Science.gov (United States)

    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

  13. 40 CFR 91.329 - Catalyst thermal stress test.

    Science.gov (United States)

    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 test catalyst must be capable of maintaining a temperature of 500 ±5 °C and 1000 ±10 °C. (b) Evaluation...

  14. Final Project Report for "Interfacial Thermal Resistance of Carbon Nanotubes”

    Energy Technology Data Exchange (ETDEWEB)

    Cumings, John [Univ. of Maryland, College Park, MD (United States)

    2016-04-15

    This report describes an ongoing project to comprehensively study the interfacial thermal boundary resistance (Kapitza resistance) of carbon nanotubes. It includes a list of publications, personnel supported, the overall approach, accomplishments and future plans.

  15. Thermal stresses in long prisms by relaxation methods

    International Nuclear Information System (INIS)

    Cummins, J.D.

    1959-07-01

    A general method is presented for calculating the elastic thermal stresses in long prisms which are producing heat and are not solvable by simple analytical methods. The problem of an inverted lattice i.e. an hexagonal coolant passage surrounded by hexagonal fuel elements is considered and the temperature and principal thermal stress distributions evaluated for the particular case of 20% coolant. The maximum thermal stress for this type of fuel element is about the same as the maximum thermal stress in a cylindrical fuel element surrounded by a sea of coolant assuming the existence of the same maximum temperature drop and material properties. (author)

  16. Freeze-dried EchiTAb+ICP antivenom formulated with sucrose is more resistant to thermal stress than the liquid formulation stabilized with sorbitol.

    Science.gov (United States)

    Herrera, María; Segura, Álvaro; Sánchez, Adriana; Sánchez, Andrés; Vargas, Mariángela; Villalta, Mauren; Harrison, Robert A; Gutiérrez, José María; León, Guillermo

    2017-07-01

    EchiTAb + ICP is a pan-African antivenom used for the treatment of snakebite envenomation in rural sub-Saharan African communities, where the cold chain can be difficult to maintain. To develop a formulation of EchiTAb + ICP that can be distributed and stored without refrigeration, we submitted three different formulations of EchiTAb + ICP: control (i.e. liquid antivenom formulated without stabilizer), liquid antivenom stabilized with sorbitol, and freeze-dried antivenom formulated with sucrose, to an accelerated stability study (i.e. 38 ± 2 °C and 75% relative humidity for 6 months). We analyzed changes in color, residual humidity, reconstitution time (for freeze-dried preparation), pH, osmolality, total protein concentration, antibody monomers content, turbidity, bacterial endotoxins, and pre-clinical neutralizing efficacy of the lethal effect of Echis ocellatus venom at 0, 3 and 6 months. In the control formulation, instability was evidenced by the development of a yellow coloration and an increment in aggregation and turbidity, without change in its neutralizing activity. The sorbitol-stabilized formulation did not develop marked aggregation or turbidity, but instability was evidenced by the development of yellow coloration and a drop in the neutralizing potency. The freeze-dried formulation maintained its neutralizing potency and did not show marked signs of instability, thus indicating that freeze-drying could confer EchiTAb + ICP with improved thermal stability required for distribution and storage at room temperature in sub-Saharan Africa. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Random thermal stress in concrete containments

    International Nuclear Information System (INIS)

    Singh, M.P.; Heller, R.A.

    1980-01-01

    Currently, the overly conservative thermal design forces are obtained on the basis of simplified assumptions made about the temperature gradient across the containment wall. Using the method presented in this paper, a more rational and better estimate of the design forces can be obtained. Herein, the outside temperature is considered to consist of a constant mean on which yearly and daily harmonic changes plus a randomly varying part are superimposed. The random part is modeled as a stationary random process. To obtain the stresses due to random and harmonic temperatures, the complex frequency response function approach has been used. Numerical results obtained for a typical containment show that the higher frequency temperature variations, though of large magnitude, induce relatively small forces in a containment. Therefore, in a containment design, a rational separation of more effective, slowly varying temperatures, such as seasonal cycle from less effective but more frequently occuring daily and hourly changes, is desirable to obtain rational design forces. 7 refs

  18. Kapitza thermal resistance studied by high-frequency photothermal radiometry

    International Nuclear Information System (INIS)

    Horny, Nicolas; Chirtoc, Mihai; Hamaoui, Georges; Fleming, Austin; Ban, Heng

    2016-01-01

    Kapitza thermal resistance is determined using high-frequency photothermal radiometry (PTR) extended for modulation up to 10 MHz. Interfaces between 50 nm thick titanium coatings and silicon or stainless steel substrates are studied. In the used configuration, the PTR signal is not sensitive to the thermal conductivity of the film nor to its optical absorption coefficient, thus the Kapitza resistance is directly determined from single thermal parameter fits. Results of thermal resistances show the significant influence of the nature of the substrate, as well as of the presence of free electrons at the interface.

  19. Physiological Response of Siderastrea siderea to Thermal Stress

    Science.gov (United States)

    Bruno-Laureano, Y.; Mercado-Molina, A. E.; Fonseca, J. S.

    2016-02-01

    Warming of the ocean water is one of the major causes of coral bleaching, a phenomenon that disrupt the obligate endosymbiotic relationships that corals has with dinoflagellates of the genus Symbiodinium. Because it is predicted that sea surface temperature are going to increase 1-3°C in the next 10 years, it is important to understand how coral species will respond to such changes. It is known that the coral Siderastrea siderea is a scleractinian coral common to the Caribbean reefs that has shown to be very resistant to environmental stressors such as sedimentation and water contamination. However, little is known about its capacity to overcome high temperatures. But several studies suggest that Siderastrea siderea can recover faster than other corals from thermal-stress. The purpose of this study is to determine whether the physiology S. siderea varies with respect to an increase in water temperature. We conducted a controlled laboratory experiments where the coral were exposed to typical (27.5°C) and elevated temperatures (31.5°C). We quantified the densities of the endosymbiotic Symbiodinium spp. as well as physiological parameters such as protein and chlorophyll concentration to determine whether they change in response to an increase in temperature. Results show no significant differences or a direct relation between the thermal stress and the physiological mechanisms studied. Which would suggest that S. siderea indeed has the mechanisms to cope to high temperature scenarios.

  20. Measurement of thermal stress in graphite intercalated with bromine

    Energy Technology Data Exchange (ETDEWEB)

    Chung, D.D.L.; Wong, L.W.

    1988-03-01

    The thermal stress of graphite intercalated with bromine was found to increase from zero at about 100/degree/C to about 1.3 MPa at 200/degree/C. The effect was reversible with hysteresis. The thermal stress increase had a sharp temperature dependence due to its association with the exfoliation phase transition.

  1. Effect of cold working on the stress corrosion cracking resistance of nickel-chromium-iron alloys

    International Nuclear Information System (INIS)

    Yonezawa, T.; Onimura, K.

    1987-01-01

    In order to grasp the stress corrosion cracking resistance of cold worked nickel base alloys in PWR primary water, the effect of cold working on the stress corrosion cracking resistance of alloys 600, X-750 and 690, in high temperature water, have been studied. Stress corrosion cracking tests were conducted at 360 0 C (633K) in a simulated PWR primary water for about 12,000 hours (43.2Ms). From the test results, it is concluded that the stress corrosion cracking resistance in the cold worked Alloy 600 at the same applied stress level increases with an increase in cold working ratio, and the cold worked alloys of thermally treated 690 and X-750 have excellent stress corrosion cracking resistance. (Author)

  2. Thermal shock resistance behavior of a functionally graded ceramic: Effects of finite cooling rate

    Directory of Open Access Journals (Sweden)

    Zhihe Jin

    2014-01-01

    Full Text Available This work presents a semi-analytical model to explore the effects of cooling rate on the thermal shock resistance behavior of a functionally graded ceramic (FGC plate with a periodic array of edge cracks. The FGC is assumed to be a thermally heterogeneous material with constant elastic modulus and Poisson's ratio. The cooling rate applied at the FGC surface is modeled using a linear ramp function. An integral equation method and a closed form asymptotic temperature solution are employed to compute the thermal stress intensity factor (TSIF. The thermal shock residual strength and critical thermal shock of the FGC plate are obtained using the SIF criterion. Thermal shock simulations for an Al2O3/Si3N4 FGC indicate that a finite cooling rate leads to a significantly higher critical thermal shock than that under the sudden cooling condition. The residual strength, however, is relatively insensitive to the cooling rate.

  3. The thermal fatigue resistance of H-13 Die Steel for aluminum die casting dies

    Science.gov (United States)

    1982-01-01

    The effects of welding, five selected surface coatings, and stress relieving on the thermal fatigue resistance of H-13 Die Steel for aluminum die casting dies were studied using eleven thermal fatigue specimens. Stress relieving was conducted after each 5,000 cycle interval at 1050 F for three hours. Four thermal fatigue specimens were welded with H-13 or maraging steel welding rods at ambient and elevated temperatures and subsequently, subjected to different post-weld heat treatments. Crack patterns were examined at 5,000, 10,000, and 15,000 cycles. The thermal fatigue resistance is expressed by two crack parameters which are the average maximum crack and the average cracked area. The results indicate that a significant improvement in thermal fatigue resistance over the control was obtained from the stress-relieving treatment. Small improvements were obtained from the H-13 welded specimens and from a salt bath nitrogen and carbon-surface treatment. The other surface treatments and welded specimens either did not affect or had a detrimental influence on the thermal fatigue properties of the H-13 die steel.

  4. Thermal stress analysis of composites in the space environment

    Science.gov (United States)

    Bowles, David E.

    1993-01-01

    A finite element micromechanics approach was utilized to investigate the thermally induced stress fields in continuous fiber reinforced polymer matrix composites at temperatures typical of spacecraft operating environments. The influence of laminate orientation was investigated with a simple global/local formulation. Thermal stress calculations were used to predict probable damage initiation locations, and the results were compared to experimentally observed damage in several epoxy matrix composites. The influence of an interphase region on the interfacial stress states was investigated.

  5. Oxylipins and plant abiotic stress resistance.

    Science.gov (United States)

    Savchenko, T V; Zastrijnaja, O M; Klimov, V V

    2014-04-01

    Oxylipins are signaling molecules formed enzymatically or spontaneously from unsaturated fatty acids in all aerobic organisms. Oxylipins regulate growth, development, and responses to environmental stimuli of organisms. The oxylipin biosynthesis pathway in plants includes a few parallel branches named after first enzyme of the corresponding branch as allene oxide synthase, hydroperoxide lyase, divinyl ether synthase, peroxygenase, epoxy alcohol synthase, and others in which various biologically active metabolites are produced. Oxylipins can be formed non-enzymatically as a result of oxygenation of fatty acids by free radicals and reactive oxygen species. Spontaneously formed oxylipins are called phytoprostanes. The role of oxylipins in biotic stress responses has been described in many published works. The role of oxylipins in plant adaptation to abiotic stress conditions is less studied; there is also obvious lack of available data compilation and analysis in this area of research. In this work we analyze data on oxylipins functions in plant adaptation to abiotic stress conditions, such as wounding, suboptimal light and temperature, dehydration and osmotic stress, and effects of ozone and heavy metals. Modern research articles elucidating the molecular mechanisms of oxylipins action by the methods of biochemistry, molecular biology, and genetics are reviewed here. Data on the role of oxylipins in stress signal transduction, stress-inducible gene expression regulation, and interaction of these metabolites with other signal transduction pathways in cells are described. In this review the general oxylipin-mediated mechanisms that help plants to adjust to a broad spectrum of stress factors are considered, followed by analysis of more specific responses regulated by oxylipins only under certain stress conditions. New approaches to improvement of plant resistance to abiotic stresses based on the induction of oxylipin-mediated processes are discussed.

  6. Oxidative stress resistance in Porphyromonas gingivalis

    Science.gov (United States)

    Henry, Leroy G; McKenzie, Rachelle ME; Robles, Antonette; Fletcher, Hansel M

    2012-01-01

    Porphyromonas gingivalis, a black-pigmented, Gram-negative anaerobe, is an important etiologic agent of periodontal disease. The harsh inflammatory condition of the periodontal pocket implies that this organism has properties that will facilitate its ability to respond and adapt to oxidative stress. Because the stress response in the pathogen is a major determinant of its virulence, a comprehensive understanding of its oxidative stress resistance strategy is vital. We discuss multiple mechanisms and systems that clearly work in synergy to defend and protect P. gingivalis against oxidative damage caused by reactive oxygen species. The involvement of multiple hypothetical proteins and/or proteins of unknown function in this process may imply other unique mechanisms and potential therapeutic targets. PMID:22439726

  7. Microstructural effects associated to CTE mismatch for enhancing the thermal shock resistance of refractories

    Science.gov (United States)

    Huger, M.; Ota, T.; Tessier-Doyen, N.; Michaud, P.; Chotard, T.

    2011-10-01

    This work is devoted to the study of thermomechanical properties of several industrial and model refractory materials in relation with the evolution of their microstructure during thermal treatments. The aim is, in particular, to highlight the role of thermal expansion mismatches existing between phases which can induce damage at local scale. The resulting network of microcracks is well known to improve thermal shock resistance of materials, since it usually involves a significant decrease in elastic properties. Moreover, this network of microcracks can strongly affect the thermal expansion at low temperature and the stress-strain behaviour in tension. Even if these two last aspects are not so much documented in the literature, they certainly also constitute key points for the improvement of the thermal shock resistance of refractory materials. Evolution of damage during thermal cycling has been monitored by a specific ultrasonic device at high temperature. Beyond its influence on Young's modulus, this damage also allows to decrease the thermal expansion and to improve the non-linear character of the stress-strain curves determined in tension. The large increase in strain to rupture, which results from this non-linearity, is of great interest for thermal shock application.

  8. Microstructural effects associated to CTE mismatch for enhancing the thermal shock resistance of refractories

    International Nuclear Information System (INIS)

    Huger, M; Tessier-Doyen, N; Michaud, P; Chotard, T; Ota, T

    2011-01-01

    This work is devoted to the study of thermomechanical properties of several industrial and model refractory materials in relation with the evolution of their microstructure during thermal treatments. The aim is, in particular, to highlight the role of thermal expansion mismatches existing between phases which can induce damage at local scale. The resulting network of microcracks is well known to improve thermal shock resistance of materials, since it usually involves a significant decrease in elastic properties. Moreover, this network of microcracks can strongly affect the thermal expansion at low temperature and the stress-strain behaviour in tension. Even if these two last aspects are not so much documented in the literature, they certainly also constitute key points for the improvement of the thermal shock resistance of refractory materials. Evolution of damage during thermal cycling has been monitored by a specific ultrasonic device at high temperature. Beyond its influence on Young's modulus, this damage also allows to decrease the thermal expansion and to improve the non-linear character of the stress-strain curves determined in tension. The large increase in strain to rupture, which results from this non-linearity, is of great interest for thermal shock application.

  9. Residual stress evolution regularity in thermal barrier coatings under thermal shock loading

    Directory of Open Access Journals (Sweden)

    Ximin Chen

    2014-01-01

    Full Text Available Residual stress evolution regularity in thermal barrier ceramic coatings (TBCs under different cycles of thermal shock loading of 1100°C was investigated by the microscopic digital image correlation (DIC and micro-Raman spectroscopy, respectively. The obtained results showed that, as the cycle number of the thermal shock loading increases, the evolution of the residual stress undergoes three distinct stages: a sharp increase, a gradual change, and a reduction. The extension stress near the TBC surface is fast transformed to compressive one through just one thermal cycle. After different thermal shock cycles with peak temperature of 1100°C, phase transformation in TBC does not happen, whereas the generation, development, evolution of the thermally grown oxide (TGO layer and micro-cracks are the main reasons causing the evolution regularity of the residual stress.

  10. Imposed Thermal Fatigue and Post-Thermal-Cycle Wear Resistance of Biomimetic Gray Cast Iron by Laser Treatment

    Science.gov (United States)

    Sui, Qi; Zhou, Hong; Zhang, Deping; Chen, Zhikai; Zhang, Peng

    2017-08-01

    The present study aims to create coupling biomimetic units on gray cast iron substrate by laser surface treatment (LST). LSTs for single-step (LST1) and two-step (LST2) processes, were carried out on gray cast iron in different media (air and water). Their effects on microstructure, thermal fatigue, and post-thermal-cycle wear (PTW) resistance on the specimens were studied. The tests were carried out to examine the influence of crack-resistance behavior as well as the biomimetic surface on its post-thermal-cycle wear behavior and different units, with different laser treatments for comparison. Results showed that LST2 enhanced the PTW behaviors of gray cast iron, which then led to an increase in its crack resistance. Among the treated cast irons, the one treated by LST2 in air showed the lowest residual stress, due to the positive effect of the lower steepness of the thermal gradient. Moreover, the same specimen showed the best PTW performance, due to its superior crack resistance and higher hardness as a result of it.

  11. Thermal stresses in composite tubes using complementary virtual work

    Science.gov (United States)

    Hyer, M. W.; Cooper, D. E.

    1988-01-01

    This paper addresses the computation of thermally induced stresses in layered, fiber-reinforced composite tubes subjected to a circumferential gradient. The paper focuses on using the principle of complementary virtual work, in conjunction with a Ritz approximation to the stress field, to study the influence on the predicted stresses of including temperature-dependent material properties. Results indicate that the computed values of stress are sensitive to the temperature dependence of the matrix-direction compliance and matrix-direction thermal expansion in the plane of the lamina. There is less sensitivity to the temperature dependence of the other material properties.

  12. Modelling of thermal stress in vapor generator supports

    International Nuclear Information System (INIS)

    Halpert, S.; Vazquez, L.

    1997-01-01

    To assure safety and availability of a nuclear power plant components or equipment stress analysis are done. When thermal loads are involved it's necessary to know the temperature field of the component or equipment. This paper describes the structural analysis of a steam generator lug with thermal load including the model used for computer simulation and presents the evolution of the temperature profile, the stress intensity and principal stress during start up and shut down of a nuclear power reactor. Temperature field obtained from code calculation show good agreement with the experimental data while stress analysis results are in agreement with a preview estimation. (author) [es

  13. Reducing Contact Resistance Errors In Measuring Thermal ...

    African Journals Online (AJOL)

    Values of thermal conductivity (k) of glass beads, quartz sand, stone dust and clay were determined using a thermal probe with and without heat sink compounds (arctic silver grease (ASG) and white grease (WG)) at different water contents, bulk densities and particle sizes. The heat sink compounds (HSC) increased k at ...

  14. Thermal and stress analyses in thermoelectric generator with tapered and rectangular pin configurations

    International Nuclear Information System (INIS)

    Yilbas, Bekir Sami; Akhtar, S.S.; Sahin, A.Z.

    2016-01-01

    Thermal stress developed in thermoelectric generators is critical for long service applications. High temperature gradients, due to a large temperature difference across the junctions, causes excessive stress levels developed in the device pins and electrodes at the interfaces. In the present study, a thermoelectric generator with horizontal pin configuration is considered and thermal stress analysis in the device is presented. Ceramic wafer is considered to resemble the high temperature plate and copper electrodes are introduced at the pin junctions to reduce the electrical resistance between the pins and the high and low temperature junction plates during the operation. Finite element code is used to simulate temperature and stress fields in the thermoelectric generator. In the simulations, convection and radiation losses from the thermoelectric pins are considered and bismuth telluride pin material with and without tapering is incorporated. It is found that von Mises stress attains high values at the interface between the hot and cold junctions and the copper electrodes. Thermal stress developed in tapered pin configuration attains lower values than that of rectangular pin cross-section. - Highlights: • Different cold junction temperatures improves thermoelectric generator performance. • von Mises stress remains high across copper electrodes and hot junction ceramics. • von Mises stress reduces along pin length towards cold junction. • Pin tapering lowers stress levels in thermoelectric generator.

  15. Heat transfer and thermal stress analysis in grooved tubes

    Indian Academy of Sciences (India)

    grooved tubes and three different mean inlet water velocities. Constant temperature was applied from the external surface of the tube. Energy and governing flow equations were solved using finite difference scheme. Finite element method (FEM) was used to compute the thermal stress fields. Grooving effects on the thermal ...

  16. About the determination of the thermal and athermal stress

    Czech Academy of Sciences Publication Activity Database

    Kruml, Tomáš; Coddet, O.; Martin, J. L.

    2008-01-01

    Roč. 56, č. 3 (2008), s. 333-340 ISSN 1359-6454 Institutional research plan: CEZ:AV0Z20410507 Keywords : Internal stresses * Compression test * Thermally activated processes * Plastic deformation * Stress-relaxation experiments Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.729, year: 2008

  17. Thermal stresses in the space shuttle orbiter: Analysis versus test

    International Nuclear Information System (INIS)

    Grooms, H.R.; Gibson, W.F. Jr.; Benson, P.L.

    1984-01-01

    Significant temperature differences occur between the internal structure and the outer skin of the Space Shuttle Orbiter as it returns from space. These temperature differences cause important thermal stresses. A finite element model containing thousands of degrees of freedom is used to predict these stresses. A ground test was performed to verify the prediction method. The analysis and test results compare favorably. (orig.)

  18. Thermal and mechanical stresses in a functionally graded thick sphere

    International Nuclear Information System (INIS)

    Eslami, M.R.; Babaei, M.H.; Poultangari, R.

    2005-01-01

    In this paper, a general solution for the one-dimensional steady-state thermal and mechanical stresses in a hollow thick sphere made of functionally graded material is presented. The temperature distribution is assumed to be a function of radius, with general thermal and mechanical boundary conditions on the inside and outside surfaces of the sphere. The material properties, except Poisson's ratio, are assumed to vary along the radius r according to a power law function. The analytical solution of the heat conduction equation and the Navier equation lead to the temperature profile, radial displacement, radial stress, and hoop stress as a function of radial direction

  19. Analytical method for thermal stress analysis of plasma facing materials

    International Nuclear Information System (INIS)

    You, J.H.; Bolt, H.

    2001-01-01

    The thermo-mechanical response of plasma facing materials (PFMs) to heat loads from the fusion plasma is one of the crucial issues in fusion technology. In this work, a fully analytical description of the thermal stress distribution in armour tiles of plasma facing components is presented which is expected to occur under typical high heat flux (HHF) loads. The method of stress superposition is applied considering the temperature gradient and thermal expansion mismatch. Several combinations of PFMs and heat sink metals are analysed and compared. In the framework of the present theoretical model, plastic flow and the effect of residual stress can be quantitatively assessed. Possible failure features are discussed

  20. Analytical method for thermal stress analysis of plasma facing materials

    Science.gov (United States)

    You, J. H.; Bolt, H.

    2001-10-01

    The thermo-mechanical response of plasma facing materials (PFMs) to heat loads from the fusion plasma is one of the crucial issues in fusion technology. In this work, a fully analytical description of the thermal stress distribution in armour tiles of plasma facing components is presented which is expected to occur under typical high heat flux (HHF) loads. The method of stress superposition is applied considering the temperature gradient and thermal expansion mismatch. Several combinations of PFMs and heat sink metals are analysed and compared. In the framework of the present theoretical model, plastic flow and the effect of residual stress can be quantitatively assessed. Possible failure features are discussed.

  1. A simplified model to estimate thermal resistance between carbon nanotube and sample in scanning thermal microscopy

    Science.gov (United States)

    Nazarenko, Maxim; Rosamond, Mark C.; Gallant, Andrew J.; Kolosov, Oleg V.; Dubrovskii, Vladimir G.; Zeze, Dagou A.

    2017-12-01

    Scanning thermal microscopy (SThM) is an attractive technique for nanoscale thermal measurements. Multiwalled carbon nanotubes (MWCNT) can be used to enhance a SThM probe in order to drastically increase spatial resolution while keeping required thermal sensitivity. However, an accurate prediction of the thermal resistance at the interface between the MWCNT-enhanced probe tip and a sample under study is essential for the accurate interpretation of experimental measurements. Unfortunately, there is very little literature on Kapitza interfacial resistance involving carbon nanotubes under SThM configuration. We propose a model for heat conductance through an interface between the MWCNT tip and the sample, which estimates the thermal resistance based on phonon and geometrical properties of the MWCNT and the sample, without neglecting the diamond-like carbon layer covering the MWCNT tip. The model considers acoustic phonons as the main heat carriers and account for their scattering at the interface based on a fundamental quantum mechanical approach. The predicted value of the thermal resistance is then compared with experimental data available in the literature. Theoretical predictions and experimental results are found to be of the same order of magnitude, suggesting a simplified, yet realistic model to approximate thermal resistance between carbon nanotube and sample in SThM, albeit low temperature measurements are needed to achieve a better match between theory and experiment. As a result, several possible avenues are outlined to achieve more accurate predictions and to generalize the model.

  2. Non-linear elastic thermal stress analysis with phase changes

    International Nuclear Information System (INIS)

    Amada, S.; Yang, W.H.

    1978-01-01

    The non-linear elastic, thermal stress analysis with temperature induced phase changes in the materials is presented. An infinite plate (or body) with a circular hole (or tunnel) is subjected to a thermal loading on its inner surface. The peak temperature around the hole reaches beyond the melting point of the material. The non-linear diffusion equation is solved numerically using the finite difference method. The material properties change rapidly at temperatures where the change of crystal structures and solid-liquid transition occur. The elastic stresses induced by the transient non-homogeneous temperature distribution are calculated. The stresses change remarkably when the phase changes occur and there are residual stresses remaining in the plate after one cycle of thermal loading. (Auth.)

  3. Coherent gradient sensing method for measuring thermal stress field of thermal barrier coating structures

    Directory of Open Access Journals (Sweden)

    Kang Ma

    2017-01-01

    Full Text Available Coherent gradient sensing (CGS method can be used to measure the slope of a reflective surface, and has the merits of full-field, non-contact, and real-time measurement. In this study, the thermal stress field of thermal barrier coating (TBC structures is measured by CGS method. Two kinds of powders were sprayed onto Ni-based alloy using a plasma spraying method to obtain two groups of film–substrate specimens. The specimens were then heated with an oxy-acetylene flame. The resulting thermal mismatch between the film and substrate led to out-of-plane deformation of the specimen. The deformation was measured by the reflective CGS method and the thermal stress field of the structure was obtained through calibration with the help of finite element analysis. Both the experiment and numerical results showed that the thermal stress field of TBC structures can be successfully measured by CGS method.

  4. Non-thermal Plasma and Oxidative Stress

    Science.gov (United States)

    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.

  5. Experimental and analytical study of thermal stresses during pipe freezing

    OpenAIRE

    Keary, A.C.; Syngellakis, S.; Bowen, R.J.

    2001-01-01

    A review of experimental investigations on stress development during the blockage of a water-filled pipe by freezing was undertaken with the parallel development of an effective finite element thermal stress model. A wide spread of measured stress values was noted as well as a degree of uncertainty in the cases when the gauge output did not return to zero at the end of the freezing cycle. A methodical examination of stress- and temperature-time histories showed that it is possible to divide a...

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

    KAUST Repository

    Kneeland, J.

    2013-08-30

    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. © 2013 Springer-Verlag Berlin Heidelberg.

  7. Structural studies of thermally stable, combustion-resistant polymer composites

    OpenAIRE

    Smith, G.N.; Hallett, J.E.; Joseph, P.; Tretsiakova-McNally, S.; Zhang, T.; Blum, F.D.; Eastoe, J.

    2017-01-01

    Composites of the industrially important polymer, poly(methyl methacrylate) (PMMA), were prepared by free-radical polymerization of MMA with varying amounts (1–30 wt. %) of sodium dioctylsulfosuccinate (Aerosol OT or AOT) surfactant added to the reaction mixture. The composites with AOT incorporated show enhanced resistance to thermal degradation compared to pure PMMA homopolymer, and micro-cone combustion calorimetry measurements also show that the composites are combustion-resistant. The ph...

  8. Thermal mechanical stress modeling of GCtM seals

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Steve Xunhu [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Chambers, Robert [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    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.

  9. Mesopredator trophodynamics on thermally stressed coral reefs

    Science.gov (United States)

    Hempson, Tessa N.; Graham, Nicholas A. J.; MacNeil, M. Aaron; Hoey, Andrew S.; Almany, Glenn R.

    2018-03-01

    Ecosystems are becoming vastly modified through disturbance. In coral reef ecosystems, the differential susceptibility of coral taxa to climate-driven bleaching is predicted to shift coral assemblages towards reefs with an increased relative abundance of taxa with high thermal tolerance. Many thermally tolerant coral species are characterised by low structural complexity, with reduced habitat niche space for the small-bodied coral reef fishes on which piscivorous mesopredators feed. This study used a patch reef array to investigate the potential impacts of climate-driven shifts in coral assemblages on the trophodynamics of reef mesopredators and their prey communities. The `tolerant' reef treatment consisted only of coral taxa of low susceptibility to bleaching, while `vulnerable' reefs included species of moderate to high thermal vulnerability. `Vulnerable' reefs had higher structural complexity, and the fish assemblages that established on these reefs over 18 months had higher species diversity, abundance and biomass than those on `tolerant' reefs. Fish assemblages on `tolerant' reefs were also more strongly influenced by the introduction of a mesopredator ( Cephalopholis boenak). Mesopredators on `tolerant' reefs had lower lipid content in their muscle tissue by the end of the 6-week experiment. Such sublethal energetic costs can compromise growth, fecundity, and survivorship, resulting in unexpected population declines in long-lived mesopredators. This study provides valuable insight into the altered trophodynamics of future coral reef ecosystems, highlighting the potentially increased vulnerability of reef fish assemblages to predation as reef structure declines, and the cost of changing prey availability on mesopredator condition.

  10. Early resistance change and stress/electromigrationmodeling in aluminium interconnects

    NARCIS (Netherlands)

    Petrescu, V.; Mouthaan, A.J.; Schoenmaker, W.

    1997-01-01

    A complete description for early resistance change and two dimensional simulation of mechanical stress evolution in confined Al interconnects, related to the electromigration, is given in this paper. The model, combines the stress/ vacancy concentration evolution with the early resistance change of

  11. Resistance of Some Steels to Stress Corrosion Cracking

    Science.gov (United States)

    Humphries, T. S.; Nelson, E. E.

    1982-01-01

    Evaluations of stress-corrosion cracking resistance of five high-strength low-alloy steels described in report now available. Steels were heat-treated to various tensile strengths and found to be highly resistant to stress-corrosion cracking.

  12. Decay fungi resistance in thermally treated OSB panels

    Directory of Open Access Journals (Sweden)

    Rafael Farinassi Mendes

    2013-12-01

    Full Text Available This study evaluated the effect of pre and post thermal treatment on the resistance of OSB panels to attack by decay fungi, and compared these two forms of thermal treatment with some production variables. The experimental design consisted of seven treatments, with the evaluation of two temperatures of pre thermal treatment of the particles (200 and 240 ºC for a 60 minutes period; post thermal treatment of the panels, produced with and without the application of paraffin, at 220 ºC of temperature for a period of 12 minutes; and increasing the content of adhesive and application of paraffin in panels without thermal treatment. For each treatment three panels were produced with nominal density of 0.65 g/cm3 and phenol-formaldehyde adhesive. By analyzing the results it was concluded that the panels with pre thermal treatment at 240 º C presented great potential for inhibiting the attack of Trametes versicolor fungi and Gloeophyllum trabeum, but with equivalent effect to that obtained with the increasing the content phenol-formaldehyde adhesive. The post thermal treatment did not increase significantly the biological resistance of the OSB panels.

  13. Theory of elasticity and thermal stresses explanations, problems and solutions

    CERN Document Server

    Eslami, M Reza; Ignaczak, Józef; Noda, Naotake; Sumi, Naobumi; Tanigawa, Yoshinobu

    2013-01-01

    This book contains the elements of the theory and the problems of Elasticity and Thermal Stresses with full solutions. The emphasis is placed on problems and solutions and the book consists of  four parts: one part is on The Mathematical Theory of Elasticity, two parts are on Thermal Stresses and one part is on Numerical Methods. The book is addressed to higher level undergraduate students, graduate students and engineers and it is an indispensable companion to all who study any of the books published earlier by the authors. This book links the three previously published books by the authors into one comprehensive entity.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    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. - Highlights: • Water quality influences thermal stress thresholds in different Symbiodinium types. • Photosystem of clade D tested more sensitive than C1 to a common herbicide. • Increased thermal tolerance quickly countered in presence of herbicide. • Mixture toxicity approach demonstrated response additivity for combined stressors. • Symbiotic partnership may be compromised in areas subjected to terrestrial runoff. - Thermal-tolerant Symbiodinium type D tested especially vulnerable to a common herbicide, emphasizing the significance of cumulative stressors in ecological risk management

  15. Coupled stress-strain and electrical resistivity measurements on copper based shape memory single crystals

    Directory of Open Access Journals (Sweden)

    Gonzalez Cezar Henrique

    2004-01-01

    Full Text Available Recently, electrical resistivity (ER measurements have been done during some thermomechanical tests in copper based shape memory alloys (SMA's. In this work, single crystals of Cu-based SMA's have been studied at different temperatures to analyse the relationship between stress (s and ER changes as a function of the strain (e. A good consistency between ER change values is observed in different experiments: thermal martensitic transformation, stress induced martensitic transformation and stress induced reorientation of martensite variants. During stress induced martensitic transformation (superelastic behaviour and stress induced reorientation of martensite variants, a linear relationship is obtained between ER and strain as well as the absence of hys teresis. In conclusion, the present results show a direct evidence of martensite electrical resistivity anisotropy.

  16. Quantitative scanning thermal microscopy based on determination of thermal probe dynamic resistance.

    Science.gov (United States)

    Bodzenta, J; Juszczyk, J; Chirtoc, M

    2013-09-01

    Resistive thermal probes used in scanning thermal microscopy provide high spatial resolution of measurement accompanied with high sensitivity to temperature changes. At the same time their sensitivity to variations of thermal conductivity of a sample is relatively low. In typical dc operation mode the static resistance of the thermal probe is measured. It is shown both analytically and experimentally that the sensitivity of measurement can be improved by a factor of three by measuring the dynamic resistance of a dc biased probe superimposed with small ac current. The dynamic resistance can be treated as a complex value. Its amplitude represents the slope of the static voltage-current U-I characteristic for a given I while its phase describes the delay between the measured ac voltage and applied ac current component in the probe. The phase signal also reveals dependence on the sample thermal conductivity. Signal changes are relatively small but very repeatable. In contrast, the difference between dynamic and static resistance has higher sensitivity (the same maximum value as that of the 2nd and 3rd harmonics), and also much higher amplitude than higher harmonics. The proposed dc + ac excitation scheme combines the benefits of dc excitation (mechanical stability of probe-sample contact, average temperature control) with those of ac excitation (base-line stability, rejection of ambient temperature influence, high sensitivity, lock-in signal processing), when the experimental conditions prohibit large ac excitation.

  17. Residual stress of particulate polymer composites with reduced thermal expansion

    International Nuclear Information System (INIS)

    Nishino, T; Kotera, M; Sugiura, Y

    2009-01-01

    Thermal expansion behavior was investigated for tangusten zirconium phosphate (Zr 2 (WO 4 )(PO 4 ) 2 (ZWP)) particulate filled poly(ether ether ketone) (PEEK) composite. ZWP is known as ceramic filler with a negative thermal expansion. By incorporating ZWP with 40 volume %, the linear thermal expansion coefficient of the PEEK composite was reduced to almost same value (2.53 X 10 -5 K -1 ) with that of aluminum. This decrease was found to be quite effective for the decrease of the residual stress at the interface between aluminum plate and the composite.

  18. Plasticity in behavioural responses and resistance to temperature stress in Musca domestica

    DEFF Research Database (Denmark)

    Kjaersgaard, Anders; Blackenhorn, Wolf U.; Pertoldi, Cino

    2015-01-01

    , at the stressful high temperature Spanish flies flew the furthest and Danish flies the shortest distance. Neither body size nor wing loading affected flight performance, although flies with narrower wings tended to fly further (wing shape effect). Swiss flies were most active in terms of locomotor activity......Organisms can respond to and cope with stressful environments in a number of ways including behavioural, morphological and physiological adjustments. To understand the role of behavioural traits in thermal adaptations we compared heat resistance, locomotor (walking and flying) activity, flight...... performance and morphology of three European populations of Musca domestica (Diptera: Muscidae) originating from different thermal conditions (Spain, Switzerland and Denmark) at benign and stressful high temperatures. Spanish flies showed greater heat resistance than Swiss and Danish flies. Similarly...

  19. Numerical Simulation for Thermal Shock Resistance of Thermal Protection Materials Considering Different Operating Environments

    Directory of Open Access Journals (Sweden)

    Weiguo Li

    2013-01-01

    Full Text Available Based on the sensitivities of material properties to temperature and the complexity of service environment of thermal protection system on the spacecraft, ultrahigh-temperature ceramics (UHTCs, which are used as thermal protection materials, cannot simply consider thermal shock resistance (TSR of the material its own but need to take the external constraint conditions and the thermal environment into full account. With the thermal shock numerical simulation on hafnium diboride (HfB2, a detailed study of the effects of the different external constraints and thermal environments on the TSR of UHTCs had been made. The influences of different initial temperatures, constraint strengths, and temperature change rates on the TSR of UHTCs are discussed. This study can provide a more intuitively visual understanding of the evolution of the TSR of UHTCs during actual operation conditions.

  20. Measurements of clothing evaporative resistance using a sweating thermal manikin: an overview

    Science.gov (United States)

    WANG, Faming

    2017-01-01

    Evaporative resistance has been widely used to describe the evaporative heat transfer property of clothing. It is also a critical variable in heat stress models for predicting human physiological responses in various environmental conditions. At present, sweating thermal manikins provide a fast and cost-effective way to determine clothing evaporative resistance. Unfortunately, the measurement repeatability and reproducibility of evaporative resistance are rather low due to the complicated moisture transfer processes through clothing. This review article presents a systematical overview on major influential factors affecting the measurement precision of clothing evaporative resistance measurements. It also illustrates the state-of-the-art knowledge on the development of test protocol to measure clothing evaporative resistance by means of a sweating manikin. Some feasible and robust test procedures for measurement of clothing evaporative resistance using a sweating manikin are described. Recommendations on how to improve the measurement accuracy of clothing evaporative resistance are addressed and expected future trends on development of advanced sweating thermal manikins are finally presented. PMID:28566566

  1. The Kapitza thermal boundary resistance between two solids

    International Nuclear Information System (INIS)

    Andersen, A.C.

    1981-01-01

    In this article, the author develops a model of the Kapitza resistance between two solids in which this resistance is seen to be related to the refraction of thermal phonons at the interface, which is a function of the accoustic properties of the two solids. By calculating a kapitza boundary resistance for the two solids in an ideal case (with ideal temperature, ideal interface, and phonon scattering produced only by the interface) and then producing a summation of the three phonon modes, the angles of incidence, and the phonon frequencies, the author produces an equation which expresses the resistance; this equation is known as the accoustic-mis-match model. By then removing the conditions of ideality and adjusting the equation accordingly, the author finds that the acoustic mismatch model is successful in describing the resistance behavior

  2. Thermal stresses in functionally graded materials caused by a laser thermal shock

    Science.gov (United States)

    Elperin, T.; Rudin, G.

    Mathematical simulation of a thermal shock method for reliability testing of functionally graded material (FGM) is performed with the end to determine operating parameters of the testing device (power of a laser, laser beam radius, duration of heating) and to investigate the effect of the composition of FGM on a magnitude of thermal stresses in a coating. An analytical method for solution of the thermal elasticity problem is developed whereby the approach of a multilayer plate is used for determining temperature and thermal stresses distributions in a coating. We considered the limiting case of the obtained solution when the thickness of a layer is infinitesimally small and the number of layers tends to infinity. This procedure allowed us to obtain the thermal stresses distribution in a FGM coating. The results for the FGM coating composed of WC (tungsten carbide) ceramics and HS-steel are presented. It is showed that variation of the volume content of ceramics strongly affects thermal stresses in a coating and they decrease significantly in the case of the uniform spatial distribution of ceramics.

  3. Crack growth resistance under thermal shock loading of alumina

    Energy Technology Data Exchange (ETDEWEB)

    Saadaoui, M. [Ecole Mohammadia d`Ingenieurs (EMIL), Rabat (Morocco); Fantozzi, G. [GEMPPM-UMR CNRS 5510, INSA Lyon, Villeurbanne (France)

    1998-06-01

    Thermal shock experiments, conducted in an apparatus in which all the parameters can be controlled, are modelled by a two dimensional cooling model, allowing a precise determination of the induced stress intensity factors (SIF). Fracture mechanics analysis in terms of stress intensity factors is applied to determine R-curve behaviour of indentation cracks in alumina materials subjected to thermal shock. The instant of unstable crack growth was obtained by acoustic emission (AE). As in bending tests, the coarse grained material showed a more pronounced R-curve behaviour than the fine grained material. The results are discussed considering the influence of the R-curve behaviour on the retained strength after thermal shock. (orig.) 25 refs.

  4. Pre-cold stress increases acid stress resistance and induces amino ...

    African Journals Online (AJOL)

    Pre-cold stress increases acid stress resistance and induces amino acid homeostasis in Lactococcus lactis NZ9000. ... Compared to exposure to acid stress only, pre-adaptation to cold stress decreased the redox balance ratio and the formation of hydroxyl radicals, indicating a change in aerobic respiration and oxidative ...

  5. An expression for transient thermal stress in a nonhomogeneous plate with temperature variation through thickness

    International Nuclear Information System (INIS)

    Sugano, Y.

    1987-01-01

    An expression for nonzero thermal stress in a nonhomogeneous flat plate with arbitrary variation in mechanical properties is presented under a transient temperature distribution. Especially an equation for nonzero thermal stress and its numerical calculation showing the effect of nonhomogeneous thermal and mechanical properties on temperature and thermal stress distribution, is given for the case of an exponentially varying thermal conductivity and Young's modulus, but for a homogeneous Poisson's ratio and coefficient of linear thermal expansion. (orig.) [de

  6. Trait Stress Resistance and Dynamic Stress Dissipation on Health and Well-Being: The Reservoir Model

    OpenAIRE

    Bergeman, C. S.; Deboeck, Pascal R.

    2014-01-01

    Daily data from the NDHWB (n = 783; age range 37–90) were analyzed to produce ‘dynamic characteristic’ estimates of stress input and dissipation. These were used in multi-level modeling (with age and trait stress resistance) to predict depression and health trajectories. Main effects suggest that dissipation and stress resistance predict lower depression and better health, but lower stress input was only related to lower depression. Interactions revealed that subjects with above average stres...

  7. Aging causes decreased resistance to multiple stresses and a failure to activate specific stress response pathways

    Science.gov (United States)

    Bergsma, Alexis L.; Senchuk, Megan M.; Van Raamsdonk, Jeremy M.

    2016-01-01

    In this work, we examine the relationship between stress resistance and aging. We find that resistance to multiple types of stress peaks during early adulthood and then declines with age. To dissect the underlying mechanisms, we use C. elegans transcriptional reporter strains that measure the activation of different stress responses including: the heat shock response, mitochondrial unfolded protein response, endoplasmic reticulum unfolded protein response, hypoxia response, SKN-1-mediated oxidative stress response, and the DAF-16-mediated stress response. We find that the decline in stress resistance with age is at least partially due to a decreased ability to activate protective mechanisms in response to stress. In contrast, we find that any baseline increase in stress caused by the advancing age is too mild to detectably upregulate any of the stress response pathways. Further exploration of how worms respond to stress with increasing age revealed that the ability to mount a hormetic response to heat stress is also lost with increasing age. Overall, this work demonstrates that resistance to all types of stress declines with age. Based on our data, we speculate that the decrease in stress resistance with advancing age results from a genetically-programmed inactivation of stress response pathways, not accumulation of damage. PMID:27053445

  8. Aging causes decreased resistance to multiple stresses and a failure to activate specific stress response pathways.

    Science.gov (United States)

    Dues, Dylan J; Andrews, Emily K; Schaar, Claire E; Bergsma, Alexis L; Senchuk, Megan M; Van Raamsdonk, Jeremy M

    2016-04-01

    In this work, we examine the relationship between stress resistance and aging. We find that resistance to multiple types of stress peaks during early adulthood and then declines with age. To dissect the underlying mechanisms, we use C. elegans transcriptional reporter strains that measure the activation of different stress responses including: the heat shock response, mitochondrial unfolded protein response, endoplasmic reticulum unfolded protein response, hypoxia response, SKN-1-mediated oxidative stress response, and the DAF-16-mediated stress response. We find that the decline in stress resistance with age is at least partially due to a decreased ability to activate protective mechanisms in response to stress. In contrast, we find that any baseline increase in stress caused by the advancing age is too mild to detectably upregulate any of the stress response pathways. Further exploration of how worms respond to stress with increasing age revealed that the ability to mount a hormetic response to heat stress is also lost with increasing age. Overall, this work demonstrates that resistance to all types of stress declines with age. Based on our data, we speculate that the decrease in stress resistance with advancing age results from a genetically-programmed inactivation of stress response pathways, not accumulation of damage.

  9. Analytical model of transient temperature and thermal stress in ...

    Indian Academy of Sciences (India)

    failure stress) and to suitably choose a crystal that achieves this task. The result of this work is compared with a well-verified finite element solution and a good agreement has been found. Some conclusions are obtained: Tm:YAP crystal, which has high thermal conductivity, low expansion coefficient, low absorption ...

  10. Finite element analysis of thermal stress distribution in different ...

    African Journals Online (AJOL)

    This cavity was restored with three different materials (Group I: Resin composite, Group II: Glass ionomer cement, and Group III: Amalgam). Loads of 400 N were applied at an angle of 90° to the longitudinal axis of the tooth on the restorative material at 5 and 55°C temperatures. Von Mises and thermal stress distributions.

  11. Non-uniform temperature gradients and thermal stresses produced ...

    Indian Academy of Sciences (India)

    Abstract. This work presents numerical analyses of transient temperature and thermally-induced stress distributions in a hollow steel sphere heated by a moving uniform heat source applied on a certain zenithal segment (the heated zenithal segment, H ) of its outer surface (the processed surface) under stagnant ambient.

  12. Heat transfer and thermal stress analysis in grooved tubes

    Indian Academy of Sciences (India)

    Heat transfer and thermal stresses, induced by temperature differencesin the internally grooved tubes of heat transfer equipment, have been analysed numerically. The analysis has been conducted for four different kinds of internally grooved tubes and three different mean inlet water velocities. Constant temperature was ...

  13. Contrasting patterns of coral bleaching susceptibility in 2010 suggest an adaptive response to thermal stress.

    Directory of Open Access Journals (Sweden)

    James R Guest

    Full Text Available 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.

  14. Thermal Super-Pixels for Bimodal Stress Recognition

    DEFF Research Database (Denmark)

    Irani, Ramin; Nasrollahi, Kamal; Dhall, Abhinav

    2016-01-01

    Stress is a response to time pressure or negative environmental conditions. If its stimulus iterates or stays for a long time, it affects health conditions. Thus, stress recognition is an important issue. Traditional systems for this purpose are mostly contact-based, i.e., they require a sensor...... to be in touch with the body which is not always practical. Contact-free monitoring of the stress by a camera [1, 2] can be an alternative. These systems usually utilize only an RGB or a thermal camera to recognize stress. To the best of our knowledge, the only work on fusion of these two modalities for stress...... recognition is [3] which uses a feature level fusion of the two modalities. The features in [3] are extracted directly from pixel values. In this paper we show that extracting the features from super-pixels, followed by decision level fusion results in a system outperforming [3]. The experimental results...

  15. Laser hole cutting into bronze: Thermal stress analysis

    Science.gov (United States)

    Yilbas, B. S.; Ahktar, S. S.; Chatwin, C.

    2011-10-01

    Laser hole cutting in bronze is carried out and the thermal stress formed in the cutting section is examined using a finite element code. The cut geometry and microstructural changes in the cutting section are examined using optical microscope, scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS). It is found that the high conductivity of bronze increases the cooling rates within the cutting section, which influences the thermal stress field in the cutting region. The residual stress predicted is in the order of 200 MPa within the vicinity of the hole circumference. The striation pattern at the kerf surface changes towards the hole exit, which is associated with the drag forces developed in this region.

  16. First wall thermal stress analysis for suddenly applied heat fluxes

    International Nuclear Information System (INIS)

    Dalessandro, J.A.

    The failure criterion for a solid first wall of an inertial confinement reactor is investigated. Analytical expressions for induced thermal stresses in a plate are given. Two materials have been chosen for this investigation: grade H-451 graphite and chemically vapor deposited (CVD) β-silicon carbide. Structural failure can be related to either the maximum compressive stress produced on the surface or the maximum tensile stress developed in the interior of the plate; however, it is shown that compressive failure would predominate. A basis for the choice of the thermal shock figure of merit, k(1 - ν) sigma/E α kappa/sup 1/2/, is identified. The result is that graphite and silicon carbide rank comparably

  17. First wall thermal stress analysis for suddenly applied heat fluxes

    Energy Technology Data Exchange (ETDEWEB)

    Dalessandro, J A

    1978-01-01

    The failure criterion for a solid first wall of an inertial confinement reactor is investigated. Analytical expressions for induced thermal stresses in a plate are given. Two materials have been chosen for this investigation: grade H-451 graphite and chemically vapor deposited (CVD) ..beta..-silicon carbide. Structural failure can be related to either the maximum compressive stress produced on the surface or the maximum tensile stress developed in the interior of the plate; however, it is shown that compressive failure would predominate. A basis for the choice of the thermal shock figure of merit, k(1 - ..nu..) sigma/E ..cap alpha.. kappa/sup 1/2/, is identified. The result is that graphite and silicon carbide rank comparably.

  18. Thermal strain measurement of EAST W/Cu divertor structure using electric resistance strain gauges

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xingli [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Science Island Branch of Graduate School, University of Science & Technology of China, Hefei, 230031 (China); Wang, Wanjing, E-mail: wjwang@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Wang, Jichao [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Wei, Ran; Sun, Zhaoxuan [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Science Island Branch of Graduate School, University of Science & Technology of China, Hefei, 230031 (China); Li, Qiang; Xie, Chunyi [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Chen, Hong-En; Wang, Kaiqiang; Wu, Lei; Chen, Zhenmao [State Key Lab for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University (China); Luo, Guang-Nan [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Science Island Branch of Graduate School, University of Science & Technology of China, Hefei, 230031 (China); Hefei Center for Physical Science and Technology, Hefei, 230022 (China); Hefei Science Center of Chinese Academy of Sciences, Hefei, 230027 (China)

    2016-12-15

    Highlights: • To understand the service behavior of W/Cu divertor, an electrical resistance strain gauge system had been introduced in a thermal strain measurement experiment. • The measurement system successfully finished the experiment and obtained valued thermal strain data. • Two thermomechanical analyses had also been carried out and compared with the measurement results. • Experiment results corresponded well to simulations and threw a light upon the failure of W/Cu divertor in the previous baking tests. - Abstract: W/Cu divertor has complex structure and faces extreme work environment in EAST Tokamak device. To measure its thermal strain shall be a valued way to understand its service behavior and then optimize its design and manufacturing process. This work presents a preliminary study on measuring thermal strain of EAST W/Cu divertor structure using electric resistance strain gauges. Eight gauges had been used in the experiment and the heating temperature had been set to 230 °C with respect to the work temperature. To realize the measuring experiment, an appropriate fixing method of gauges in divertor narrow spaces had been taken and tested, which could not only withstand high temperature but also had no damage to the divertor sample. The measurement results were that three gauges showed positive strain while other three showed negative strain after having been compensated, which corresponded to tensile stress and compressed stress respectively. Two thermomechanical simulations had also been carried out and used for comparing with the experiment.

  19. Effect of Air Gap Entrapped in Firefighter Protective Clothing on Thermal Resistance and Evaporative Resistance

    Directory of Open Access Journals (Sweden)

    He Hualing

    2018-03-01

    Full Text Available Heat and water vapor transfer behavior of thermal protective clothing is greatly influenced by the air gap entrapped in multilayer fabric system. In this study, a sweating hot plate method was used to investigate the effect of air gap position and size on thermal resistance and evaporative resistance of firefighter clothing under a range of ambient temperature and humidity. Results indicated that the presence of air gap in multilayer fabric system decreased heat and water vapor transfer abilities under normal wear. Moreover, the air gap position slightly influenced the thermal and evaporative performances of the firefighter clothing. In this study, the multilayer fabric system obtained the highest thermal resistance, when the air space was located at position B. Furthermore, the effect of ambient temperature on heat and water vapor transfer properties of the multilayer fabric system was also investigated in the presence of a specific air gap. It was indicated that ambient temperature did not influence the evaporative resistance of thermal protective clothing. A thermographic image was used to test the surface temperature of multilayer fabric system when an air gap was incorporated. These results suggested that a certain air gap entrapped in thermal protective clothing system could affect wear comfort.

  20. Dynamic thermal characteristics of heat pipe via segmented thermal resistance model for electric vehicle battery cooling

    Science.gov (United States)

    Liu, Feifei; Lan, Fengchong; Chen, Jiqing

    2016-07-01

    Heat pipe cooling for battery thermal management systems (BTMSs) in electric vehicles (EVs) is growing due to its advantages of high cooling efficiency, compact structure and flexible geometry. Considering the transient conduction, phase change and uncertain thermal conditions in a heat pipe, it is challenging to obtain the dynamic thermal characteristics accurately in such complex heat and mass transfer process. In this paper, a ;segmented; thermal resistance model of a heat pipe is proposed based on thermal circuit method. The equivalent conductivities of different segments, viz. the evaporator and condenser of pipe, are used to determine their own thermal parameters and conditions integrated into the thermal model of battery for a complete three-dimensional (3D) computational fluid dynamics (CFD) simulation. The proposed ;segmented; model shows more precise than the ;non-segmented; model by the comparison of simulated and experimental temperature distribution and variation of an ultra-thin micro heat pipe (UMHP) battery pack, and has less calculation error to obtain dynamic thermal behavior for exact thermal design, management and control of heat pipe BTMSs. Using the ;segmented; model, the cooling effect of the UMHP pack with different natural/forced convection and arrangements is predicted, and the results correspond well to the tests.

  1. Development of structural response diagram approach to evaluation of thermal stress caused by thermal striping

    Energy Technology Data Exchange (ETDEWEB)

    Kasahara, Naoto; Yacumpai, Apisara [Japan Nuclear Cycle Development Inst., Oarai, Ibaraki (Japan). Oarai Engineering Center; Takasho, Hideki

    1999-02-01

    At incomplete mixing area of high temperature and low temperature fluids near the surface of structures, temperature fluctuation of fluid gives thermal fatigue damage to wall structures. This thermohydraulic and thermomechanical coupled phenomenon is called thermal striping, which has so complex mechanism and sometimes causes crack initiation on the structural surfaces that rational evaluation methods are required for screening rules in design codes. In this study, frequency response characteristics of structures and its mechanism were investigated by both numerical and theoretical methods. Based on above investigation, a structural response diagram was derived, which can predict stress amplitude of structures from temperature amplitude and frequency of fluids. Furthermore, this diagram was generalized to be the Non-dimensional structural response diagram by introducing non-dimensional parameters such as Biot number, non-dimensional frequency, and non-dimensional stress. The use of the Non-dimensional structural response diagram appears to evaluate thermal stress caused by thermal striping, rapidly without structural analysis, and rationally with considering attenuation by non-stationary heat transfer and thermal unloading. This diagram can also give such useful information as sensitive frequency range to adjust coupled thermohydraulic and thermomechanical analysis models taking account of four kinds of attenuation factors: turbulent mixing, molecular diffusion, non-stationary heat transfer, and thermal unloading. (author)

  2. Thermal stress evaluation of the Viking RTG heat shield

    International Nuclear Information System (INIS)

    Stadter, J.T.; Weiss, R.O.

    1976-03-01

    Thermal stress analyses of the Viking RTG heat shield are presented. The primary purpose of the analyses was to determine the effects of the end cap and the finite length of the heat shield on the peak tensile stress in the barrel wall. The SAAS III computer code was used to calculate the thermal stresses; axisymmetric and plane section analyses were performed for a variety of temperature distributions. The study consisted of three parts. In the first phase, the influence of the end cap on the barrel wall stresses was examined by parametrically varying the modulus of elasticity of the contact zone between the end cap and the barrel. The second phase was concerned with stresses occurring as a result of an orbital decay reentry trajectory, and the effects of the magnitude and shape of the axial temperature gradient. The final part of the study was concerned with the circumferentially nonuniform temperature distribution which develops during a side-on stable reentry. The last part includes a comparison of stresses generated for a hexagonal cross section with those generated for a circular cross section

  3. Ecologically relevant stress resistance: from microarrays and ...

    Indian Academy of Sciences (India)

    Unknown

    2004-10-15

    Oct 15, 2004 ... senting both cosmopolitan species such as D. melanogaster with a known genome map, and more specialized and ecologically well described .... gene regulation in stress selected and inbred lines, map. QTL responsible for stress ..... psychophysiological stress in rats; Brain Res. 757 146–. 148. Goodnight ...

  4. Assessment of thermal spray coatings for wear and abrasion resistance applications

    Science.gov (United States)

    Karode, Ishaan Nitin

    Thermal spray cermet and metallic coatings are extensively used for wear, abrasion and corrosion control in a variety of industries. The first part of the thesis focuses mainly on testing of sand erosion resistance of thermal spray coatings on carbon composites used in the manufacture of helicopter rotor blades. The test set-up employed is a sand blasting machine and is an effort to duplicate the in-flight conditions especially those encountered in hot arid conditions. The technique adopted follows the Department of Defence test method standard. Carbon Composites have excellent stiffness, strength and low weight/density. The strength to weight ratio is high. Hence, these are used in aerospace applications to a large extent. However, the biggest problem encountered with carbon composites is its low abrasion resistance as its surface is very weak. Hence, thermal spray coatings are used to improve the surface properties of CFRP. Zinc bond coats and WC-Co coatings were tested. However, high amount of thermal stresses were developed between the substrate and the coating due to large differences in the CTE's of the both, leading to high mass losses within two minutes and just 130 grams of sand sprayed on to the coatings with the sand blasting machine built; and hence the coatings with CC as a substrate could not qualify for the application. The second part of the thesis focuses on the assessment of different thermal spray coatings used for manufacture of mechanical seals in pumps and analyze the best coating material for the wear resistance application through detail quantification of material loss by block-on-ring test set-up. A machine based on Block-on-ring test set-up following ASTM G77 (Measurement of Adhesive wear resistance of thermal spray coatings) standards was built to duplicate the pump conditions. Thermally sprayed coated materials were tested in different conditions (Load, time, abrasive). WC-Co had the highest wear resistance (lower volume losses) and

  5. The thermal fatigue behaviour of creep-resistant Ni-Cr cast steel

    Directory of Open Access Journals (Sweden)

    B. Piekarski

    2007-12-01

    Full Text Available The study gives a summary of the results of industrial and laboratory investigations regarding an assessment of the thermal fatigue behaviour of creep-resistant austenitic cast steel. The first part of the study was devoted to the problem of textural stresses forming in castings during service, indicating them as a cause of crack formation and propagation. Stresses are forming in carbides and in matrix surrounding these carbides due to considerable differences in the values of the coefficients of thermal expansion of these phases. The second part of the study shows the results of investigations carried out to assess the effect of carbon, chromium and nickel on crack resistance of austenitic cast steel. As a criterion of assessment the amount and propagation rate of cracks forming in the specimens as a result of rapid heating followed by cooling in running water was adopted. Tests were carried out on specimens made from 11 alloys. The chemical composition of these alloys was comprised in a range of the following values: (wt-%: 18-40 %Ni, 17-30 %Cr, 1.2-1.6%Si and 0.05-0.6 %C. The specimens were subjected to 75 cycles of heating to a temperature of 900oC followed by cooling in running water. After every 15 cycles the number of the cracks was counted and their length was measured. The results of the measurements were mathematically processed. It has been proved that the main factor responsible for an increase in the number of cracks is carbon content in the alloy. In general assessment of the results of investigations, the predominant role of carbon and of chromium in the next place in shaping the crack behaviour of creep-resistant austenitic cast steel should be stressed. Attention was also drawn to the effect of high-temperature corrosion as a factor definitely deteriorating the cast steel resistance to thermal fatigue.

  6. Gene Expression Dynamics Accompanying the Sponge Thermal Stress Response

    Science.gov (United States)

    Guzman, Christine; Conaco, Cecilia

    2016-01-01

    Marine sponges are important members of coral reef ecosystems. Thus, their responses to changes in ocean chemistry and environmental conditions, particularly to higher seawater temperatures, will have potential impacts on the future of these reefs. To better understand the sponge thermal stress response, we investigated gene expression dynamics in the shallow water sponge, Haliclona tubifera (order Haplosclerida, class Demospongiae), subjected to elevated temperature. Using high-throughput transcriptome sequencing, we show that these conditions result in the activation of various processes that interact to maintain cellular homeostasis. Short-term thermal stress resulted in the induction of heat shock proteins, antioxidants, and genes involved in signal transduction and innate immunity pathways. Prolonged exposure to thermal stress affected the expression of genes involved in cellular damage repair, apoptosis, signaling and transcription. Interestingly, exposure to sublethal temperatures may improve the ability of the sponge to mitigate cellular damage under more extreme stress conditions. These insights into the potential mechanisms of adaptation and resilience of sponges contribute to a better understanding of sponge conservation status and the prediction of ecosystem trajectories under future climate conditions. PMID:27788197

  7. Gene Expression Dynamics Accompanying the Sponge Thermal Stress Response.

    Directory of Open Access Journals (Sweden)

    Christine Guzman

    Full Text Available Marine sponges are important members of coral reef ecosystems. Thus, their responses to changes in ocean chemistry and environmental conditions, particularly to higher seawater temperatures, will have potential impacts on the future of these reefs. To better understand the sponge thermal stress response, we investigated gene expression dynamics in the shallow water sponge, Haliclona tubifera (order Haplosclerida, class Demospongiae, subjected to elevated temperature. Using high-throughput transcriptome sequencing, we show that these conditions result in the activation of various processes that interact to maintain cellular homeostasis. Short-term thermal stress resulted in the induction of heat shock proteins, antioxidants, and genes involved in signal transduction and innate immunity pathways. Prolonged exposure to thermal stress affected the expression of genes involved in cellular damage repair, apoptosis, signaling and transcription. Interestingly, exposure to sublethal temperatures may improve the ability of the sponge to mitigate cellular damage under more extreme stress conditions. These insights into the potential mechanisms of adaptation and resilience of sponges contribute to a better understanding of sponge conservation status and the prediction of ecosystem trajectories under future climate conditions.

  8. Thermal cycling fatigue behavior of hardfacing heat-resistant stainless steel for continuous caster rolls

    International Nuclear Information System (INIS)

    Jung, Jae Young; Sung, Hwan Jin; Ahn, Sang Ho

    1998-01-01

    The variation of tensile properties and hardness as a function of tempering temperature and time has been investigated using a hardfacing 12%Cr stainless steel. The mechanical properties of the hardfacing 12%Cr stainless steel could be generalized by the Larson-Miller parameter, which concurrently considers the effects of tempering temperature and time. Thermal cycling fatigue behavior of a hardfacing 12%Cr stainless steel has been investigated using a special thermal fatigue testing apparatus. The resistance of thermal fatigue was deteriorated mainly by the low ductility and true fracture strength of material. The temperature distribution in the specimen was calculated using finite element program and compared to experimental results. The strain and stress distributions were evaluated taking into account the temperature distribution and the temperature dependence of the material properties. The results showed that maximum values of strain and stress were produced within the induction-heating region. The strain amplitude obtained in this study was much smaller than that of fully constrained case, which corresponds to thermal expansion due to temperature difference. This result arises from the reduction of the temperature gradient due to thermal conduction to the neighboring region. The magnitude of strain raised with the increase in the temperature gradient, which is due to the rapid cooling and heating rates in the induction-heating region

  9. Experimental determination of satellite bolted joints thermal resistance

    Science.gov (United States)

    Mantelli, Marcia Barbosa Henriques; Basto, Jose Edson

    1990-01-01

    The thermal resistance was experimentally determined of the bolted joints of the first Brazilian satellite (SCD 01). These joints, used to connect the satellite structural panels, are reproduced in an experimental apparatus, keeping, as much as possible, the actual dimensions and materials. A controlled amount of heat is forced to pass through the joint and the difference of temperature between the panels is measured. The tests are conducted in a vacuum chamber with liquid nitrogen cooled walls, that simulates the space environment. Experimental procedures are used to avoid much heat losses, which are carefully calculated. Important observations about the behavior of the joint thermal resistance with the variation of the mean temperature are made.

  10. Variation in adult life history and stress resistance across five ...

    Indian Academy of Sciences (India)

    Unknown

    Dry weight at eclosion, adult lifespan, lifetime fecundity, lipid and carbohydrate content at eclosion, and starvation and desiccation ... Keywords. life-history evolution; lifespan; fecundity; starvation; desiccation; lipid; glycogen; sexual dimorphism; laboratory ...... Rapid loss of stress resistance in Drosophila melanogaster.

  11. Transient thermal stresses in a circular cylinder with constrained ends

    International Nuclear Information System (INIS)

    Goshima, Takahito; Miyao, Kaju

    1986-01-01

    This paker deals with the transient thermal stresses in a finite circular cylinder constrained at both end surfaces and subjected to axisymmetric temperature distribution on the lateral surface. The thermoelastic problem is formulated in terms of a thermoelastic displacement potential and three harmonic stress functions. Numerical calculations are carried out for the case of the uniform temperature distribution on the lateral surface. The stress distributions on the constrained end and the free suface are shown graphically, and the singularity in stresses appearing at the circumferencial edge is considered. Moreover, the approximate solution based upon the plane strain theory is introduced in order to compare the rigorous one, and it is considered how the length of the cylinder and the time proceeds affect on the accuracy of the approximation. (author)

  12. Effects of pressure and temperature on thermal contact resistance between different materials

    Directory of Open Access Journals (Sweden)

    Zhao Zhe

    2015-01-01

    Full Text Available To explore whether pressure and temperature can affect thermal contact resistance, we have proposed a new experimental approach for measurement of the thermal contact resistance. Taking the thermal contact resistance between phenolic resin and carbon-carbon composites, cuprum, and aluminum as the examples, the influence of the thermal contact resistance between specimens under pressure is tested by experiment. Two groups of experiments are performed and then an analysis on influencing factors of the thermal contact resistance is presented in this paper. The experimental results reveal that the thermal contact resistance depends not only on the thermal conductivity coefficient of materials, but on the interfacial temperature and pressure. Furthermore, the thermal contact resistance between cuprum and aluminum is more sensitive to pressure and temperature than that between phenolic resin and carbon-carbon composites.

  13. INVESTIGATION OF THERMAL BEHAVIOR OF MULTILAYERED FIRE RESISTANT STRUCTURE

    Directory of Open Access Journals (Sweden)

    R. GUOBYS

    2016-09-01

    Full Text Available This paper presents experimental and numerical investigations of thermal behavior under real fire conditions of new generation multilayered fire resistant structure (fire door, dimensions H × W × D: 2090 × 980 × 52 mm combining high strength and fire safety. This fire door consists of two steel sheets (thickness 1.5 and 0.7 mm with stone wool ( = 33 kg/m3, k = 0.037 W/mK, E = 5000 N/m2,  = 0.2 insulating layer in between. One surface of the structure was heated in fire furnace for specified period of time of 60 min. Temperature and deformation of opposite surface were measured from outside at selected measuring points during fire resistance test. Results are presented as temperature-time and thermal deformation-time graphs. Experimental results were compared with numerical temperature field simulation results obtained from SolidWorks®Simulation software. Numerical results were found to be in good agreement with experimental data. The percent differences between door temperatures from simulation and fire resistance test don’t exceed 8%. This shows that thermal behaviour of such multilayered structures can be investigated numerically, thus avoiding costly and time-consuming fire resistance tests. It is established that investigated structure should be installed in a way that places thicker steel sheet closer to the potential heat source than thinner one. It is also obtained that stone wool layer of higher density should be used to improve fire resistance of the structure.

  14. Aging causes decreased resistance to multiple stresses and a failure to activate specific stress response pathways

    OpenAIRE

    Dues, Dylan J.; Andrews, Emily K.; Schaar, Claire E.; Bergsma, Alexis L.; Senchuk, Megan M.; Van Raamsdonk, Jeremy M.

    2016-01-01

    In this work, we examine the relationship between stress resistance and aging. We find that resistance to multiple types of stress peaks during early adulthood and then declines with age. To dissect the underlying mechanisms, we use C. elegans transcriptional reporter strains that measure the activation of different stress responses including: the heat shock response, mitochondrial unfolded protein response, endoplasmic reticulum unfolded protein response, hypoxia response, SKN-1-mediated oxi...

  15. Screening for Stress Resistance Mutations in the Mouse

    Directory of Open Access Journals (Sweden)

    Wallace S Chick

    2014-09-01

    Full Text Available Longevity is correlated with stress resistance in many animal models. However, previous efforts through the boosting of the antioxidant defense system did not extend life span, suggesting that longevity related stress resistance is mediated by other uncharacterized pathways. We have developed a high-throughput platform for screening and rapid identification of novel genetic mutants in the mouse that are stress-resistant. Selection for resistance to stressors occurs in mutagenized mouse embryonic stem (ES cells, which are carefully treated so as to maintain pluripotency for mouse production. Initial characterization of these mutant ES cells revealed mutations in Pigl, Tiam1, and Rffl, among others. These genes are implicated in glycosylphosphatidylinositol biosynthesis, NADPH oxidase function, and inflammation. These mutants: (1 are resistant to two different oxidative stressors, paraquat and the omission of 2-mercaptoethanol, (2 have reduced levels of endogenous reactive oxygen species (ROS, (3 are capable of generating live mice, and (4 transmit the stress resistance phenotype to the mice. This strategy offers an efficient way to select for new mutants expressing a stress resistance phenotype, to rapidly identify the causative genes, and to develop mice for in vivo studies.

  16. Thermal stress analysis of the SLAC moveable mask. Addendum 2

    International Nuclear Information System (INIS)

    Johnson, G.L.

    1985-01-01

    X-ray beams emerging from the new SLAC electron-positron storage ring (PEP) can impinge on the walls of tangential divertor channels. A moveable mask made of 6061-T6 aluminum is installed in the channel to limit wall heating. The mask is cooled with water flowing axially at 30 0 C. Beam strikes on the mask cause highly localized heating in the channel structure. Analyses were completed to determine the temperatures and thermally-induced stresses due to this heating. The current design and operating conditions should result in the entrance to the moveable mask operating at a peak temperature of 88 0 C with a peak thermal stress at 19% of the yield of 6061-T6 aluminum

  17. Increased resistance to stress corrosion of aluminum alloys

    Science.gov (United States)

    Brummer, S. B.; Cocks, F. H.

    1970-01-01

    Stress corrosion resistance is increased by distorting surface grain-boundary structure and by interrupting the corrosion and stress corrosion. The first is accomplished by machining or shot peening and the second by removal from and later reexposure to the corrosive environment.

  18. Plant resistance to cold stress: Mechanisms and environmental ...

    Indian Academy of Sciences (India)

    Unknown

    temperature was an even more effective signal than day-length. [Beck E H, Heim R and Hansen J 2004 Plant resistance to cold stress: Mechanisms and environmental signals triggering frost hardening and dehardening; J. Biosci. 29 449–459]. 1. Introduction. 1.1 Ecophysiological aspects of plant cold stress and acclimation.

  19. Influence of thermal stress on marginal integrity of restorative materials

    Directory of Open Access Journals (Sweden)

    Maximiliano Sérgio Cenci

    2008-04-01

    Full Text Available 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.

  20. Thermal and physical stresses induce a short-term immune priming effect in Galleria mellonella larvae.

    Science.gov (United States)

    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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Effects of location, thermal stress and residual stress on corner cracks in nozzles with cladding

    International Nuclear Information System (INIS)

    McLean, J.L.; Cohen, L.M.; Besuner, P.M.

    1979-01-01

    The stress intensity factors (K 1 ) for corner cracks in a boiling water reactor feedwater nozzle with stainless steel cladding are obtained for loading by internal pressure and a fluid quench in the nozzle. Conditions both with and without residual stress in the component are considered. The residual stress is simulated by means of a reference temperature change. The stress distribution for the uncracked structure is obtained from a three-dimensional finite element model. A three-dimensional influence function (IF) method, in conjunction with the boundary-integral equation method for structural analysis, is employed to compute K 1 values from the uncracked stress distribution. For each type of loading K 1 values are given for cracks at 15 nozzle locations and for 6 crack depths. Reasonable agreement is noted between calculated and previously published pressure-induced K 1 values. Comparisons are made to determine the effect on K 1 of crack location, thermal stress and residual stress, as compared with pressure stress. For the thermal transient it is shown that K 1 for small crack depths is maximised early in the transient, while K 1 for large cracks is maximised later under steady state conditions. Computation should, therefore, be made for several transient time points and the maximum K 1 for a given crack depth should be used for design analysis. It is concluded that the effects on K 1 of location, thermal stresses and residual stresses are significant and generally too complex to evaluate without advanced numerical procedures. The utilised combination of finite element analysis of the uncracked structure and three-dimensional influence function analysis of the cracked structure is demonstrated and endorsed. (author)

  2. The biochar effect: plant resistance to biotic stresses

    Directory of Open Access Journals (Sweden)

    YIGAL ELAD

    2012-01-01

    Full Text Available Biochar (charcoal is the solid co-product of pyrolysis, the thermal degradation of biomass in the absence of oxygen. Pyrolysis also yields gaseous and liquid biofuel products. There is a growing interest worldwide in the pyrolysis platform, for at least four reasons: (i pyrolysis can be a source of renewable biofuels; (ii many biomass waste materials can be treated by pyrolysis and thus converted into a fuel resource; (iii long-term sequestration of carbon dioxide which originated in the atmosphere may result from adding biochar to soil; and (iv biochar soil amendment contributes to improved soil fertility and crop productivity. Currently, however, very little biochar is utilized in agriculture, in part because its agronomic value in terms of crop response and soil health benefits have yet to be quantified, and because the mechanisms by which it improves soil fertility are poorly understood. The positive effects of biochar on crop productivity under conditions of extensive agriculture are frequently attributed to direct effects of biochar-supplied nutrients and to several other indirect effects, including increased water and nutrient retention, improvements in soil pH, increased soil cation exchange capacity, effects on P and S transformations and turnover, neutralization of phytotoxic compounds in the soil, improved soil physical properties, promotion of mycorrhizal fungi, and alteration of soil microbial populations and functions. Yet, the biochar effect is also evident under conditions of intensive production where many of these parameters are not limited. Biochar addition to soil alters microbial populations in the rhizosphere, albeit via mechanisms not yet understood, and may cause a shift towards beneficial microorganism populations that promote plant growth and resistance to biotic stresses. In addition to some scant evidence for biochar-induced plant protection against soilborne diseases, the induction of systemic resistance towards

  3. Stress corrosion cracking resistance of aluminum alloy 7000 series after two-step aging

    Directory of Open Access Journals (Sweden)

    Jegdić Bore V.

    2015-01-01

    Full Text Available The effect of one step-and a new (short two-step aging on the resistance to stress corrosion cracking of an aluminum alloy 7000 series was investigated, using slow strain rate test and fracture mechanics method. Aging level in the tested alloy was evaluated by means of scanning electron microscopy and measurements of electrical resistivity. It was shown that the alloy after the new two-step aging is significantly more resistant to stress corrosion cracking. Values of tensile properties and fracture toughness are similar for both thermal states. Processes that take place at the crack tip have been considered. The effect of the testing solution temperature on the crack growth rate on the plateau was determined. Two values of the apparent activation energy were obtained. These values correspond to different processes that control crack growth rate on the plateau at higher and lower temperatures. [Projekat Ministarstva nauke Republike Srbije, br. TR 34028 i br. TR 34016

  4. Effect of ion implantation on thermal shock resistance of magnesia and glass

    International Nuclear Information System (INIS)

    Gurarie, V.N.; Williams, J.S.; Watt, A.J.

    1995-01-01

    Monocrystals of magnesia together with glass samples have been subjected to ion implantation prior to thermal shock testing in an impulse plasma of continuously varied intensity. Measurements of the separation between fragments have been used to estimate the surface temperature. Fracture and deformation characteristics of the surface layer are measured in ion implanted and unimplanted samples using optical and scanning electron microscopy. Implantation-induced near-surface damage is analysed by ion channeling using 2 MeV He + ions. Ion implantation is shown to modify the near-surface structure of magnesia samples by introducing damage, which makes crack initiation easier under thermal stresses. The fracture threshold and maximum crack density are shifted towards the lower temperature range. Ion implanted MgO crystals show a ten fold increase in surface crack density. An increased crack density results in a decreased degree of damage characterised by the depth of crack penetration. The thermal stress resistance parameter of glass samples is increased at relatively small doses and decreased at higher doses. The results suggest that crack density and the degree of fracture damage in brittle ceramics operating under thermal shock conditions can be effectively controlled by ion implantation which provides crack initiating defects in the near-surface region. 23 refs., 7 figs

  5. Thermally Bonded PET–Basalt Sandwich Composites for Heat Pipeline Protection: Preparation, Stab Resisting, and Thermal-Insulating Properties

    Directory of Open Access Journals (Sweden)

    Ting-Ting Li

    2018-03-01

    Full Text Available In order to solve the cost and bulky problems of buried thermal pipeline insulating materials, this study adopts basalt fabric and low-melting PET nonwoven to construct low-cost and light-weight pipeline thermal-insulating composites after needle punching and thermal bonding processes. Research result shows that thermal-bonded temperature affected the stab resistance and burst energy more significantly. As thermal-bonded temperature increased, knife resistance and spike resistance presented the upward and then downward trends, but the burst energy gradually decreased. Yarn pull-out result shows that the enhancement of stab resistance of intra-/inter-thermal-bonded structure resulted from the increment in the coefficient of friction between yarns. When PET–basalt sandwich composites were thermal-bonded at 140 °C for 5 min, the maximum knife and spike resistance were 147.00 N (1.99 J and 196.30 N (1.11 J, respectively, and burst energy was 4.79 J, thermal conductivity reduced to 0.0073 W/(m∙K. The resultant thermally bonded sandwich composites can be used as thermal-insulating protection for buried thermal pipeline.

  6. Effect of thermal aging on the erosion resistance of air plasma sprayed zirconia thermal barrier coating

    International Nuclear Information System (INIS)

    Janos, B.Z.; Lugscheider, E.; Remer, P.

    1999-01-01

    To increase the performance, efficiency and reliability of thermal barrier coatings, it is important to understand the influence of the microstructure on the erosion resistance. Therefore, the erosion behavior of air-plasma-sprayed 7 wt% yttria stabilized zirconia (7YSZ) thermal barrier coatings (TBC) at elevated temperatures was investigated. The paper focuses on both the porosity of the coating as well as the thermal pre-treatment of the ceramic. To simulate operating conditions on the ceramic samples, high-temperature erosion experiments at 1093 C were carried out on as-sprayed samples as well as on samples, thermally aged at different temperatures up to 1482 C in air prior to erosion testing. A significant dependence of erosion rate on porosity and thermal pre-treatment was found. Finally, a technique was developed to predict the erosion rates of air-plasma-sprayed 7YSZ TBCs independent of aging conditions or porosity levels. Erosion rates seem to be highly correlated to the micro-hardness of the zirconia TBC. A power-law model was empirically derived to estimate erosion rates of plasma-sprayed 7YSZ ceramic thermal barrier coatings. (orig.)

  7. Progress in engineering acid stress resistance of lactic acid bacteria.

    Science.gov (United States)

    Wu, Chongde; Huang, Jun; Zhou, Rongqing

    2014-02-01

    Lactic acid bacteria (LAB) are widely used for the production of a variety of fermented foods, and are considered as probiotic due to their health-promoting effect. However, LAB encounter various environmental stresses both in industrial fermentation and application, among which acid stress is one of the most important survival challenges. Improving the acid stress resistance may contribute to the application and function of probiotic action to the host. Recently, the advent of genomics, functional genomics and high-throughput technologies have allowed for the understanding of acid tolerance mechanisms at a systems level, and many method to improve acid tolerance have been developed. This review describes the current progress in engineering acid stress resistance of LAB. Special emphasis is placed on engineering cellular microenvironment (engineering amino acid metabolism, introduction of exogenous biosynthetic capacity, and overproduction of stress response proteins) and maintaining cell membrane functionality. Moreover, strategies to improve acid tolerance and the related physiological mechanisms are also discussed.

  8. Numerical methods for calculating thermal residual stresses and hydrogen diffusion

    International Nuclear Information System (INIS)

    Leblond, J.B.; Devaux, J.; Dubois, D.

    1983-01-01

    Thermal residual stresses and hydrogen concentrations are two major factors intervening in cracking phenomena. These parameters were numerically calculated by a computer programme (TITUS) using the FEM, during the deposition of a stainless clad on a low-alloy plate. The calculation was performed with a 2-dimensional option in four successive steps: thermal transient calculation, metallurgical transient calculation (determination of the metallurgical phase proportions), elastic-plastic transient (plain strain conditions), hydrogen diffusion transient. Temperature and phase dependence of hydrogen diffusion coefficient and solubility constant. The following results were obtained: thermal calculations are very consistent with experiments at higher temperatures (due to the introduction of fusion and solidification latent heats); the consistency is not as good (by 70 degrees) for lower temperatures (below 650 degrees C); this was attributed to the non-introduction of gamma-alpha transformation latent heat. The metallurgical phase calculation indicates that the heat affected zone is almost entirely transformed into bainite after cooling down (the martensite proportion does not exceed 5%). The elastic-plastic calculations indicate that the stresses in the heat affected zone are compressive or slightly tensile; on the other hand, higher tensile stresses develop on the boundary of the heat affected zone. The transformation plasticity has a definite influence on the final stress level. The return of hydrogen to the clad during the bainitic transformation is but an incomplete phenomenon and the hydrogen concentration in the heat affected zone after cooling down to room temperature is therefore sufficient to cause cold cracking (if no heat treatment is applied). Heat treatments are efficient in lowering the hydrogen concentration. These results enable us to draw preliminary conclusions on practical means to avoid cracking. (orig.)

  9. Relationship between negative differential thermal resistance and asymmetry segment size

    Science.gov (United States)

    Kong, Peng; Hu, Tao; Hu, Ke; Jiang, Zhenhua; Tang, Yi

    2018-03-01

    Negative differential thermal resistance (NDTR) was investigated in a system consisting of two dissimilar anharmonic lattices exemplified by Frenkel-Kontorova (FK) lattices and Fremi-Pasta-Ulam (FPU) lattices (FK-FPU). The previous theoretical and numerical simulations show the dependence of NDTR are the coupling constant, interface and system size, but we find the segment size also to be an important element. It’s interesting that NDTR region depends on FK segment size rather than FPU segment size in this coupling FK-FPU model. Remarkably, we could observe that NDTR appears in the strong interface coupling strength case which is not NDTR in previous studies. The results are conducive to further developments in designing and fabricating thermal devices.

  10. Overexpression of VOZ2 confers biotic stress tolerance but decreases abiotic stress resistance in Arabidopsis.

    Science.gov (United States)

    Nakai, Yusuke; Fujiwara, Sumire; Kubo, Yasuyuki; Sato, Masa H

    2013-03-01

    VOZ (vascular plant one zinc-finger protein) is a plant specific one-zinc finger type transcriptional activator, which is highly conserved through land plant evolution. We have previously shown that loss-of-function mutations in VOZ1 and VOZ2 showed increased cold and drought stress tolerances whereas decreased biotic stress resistance in Arabidopsis. Here, we demonstrate that transgenic plants overexpressing VOZ2 impairs freezing and drought stress tolerances but increases resistance to a fungal pathogen, Colletoricum higginsianum. Consistent with changes in the tolerance to biotic and abiotic stresses, the expression of marker genes for these stresses is significantly altered compared with those of the wild-type plant. These results indicate that a overexpression of VOZ2 confers biotic stress tolerance but impairs abiotic stress tolerances in Arabidopsis.

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

    Science.gov (United States)

    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. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  12. Highly defective oxides as sinter resistant thermal barrier coating

    Science.gov (United States)

    Subramanian, Ramesh

    2005-08-16

    A thermal barrier coating material formed of a highly defective cubic matrix structure having a concentration of a stabilizer sufficiently high that the oxygen vacancies created by the stabilizer interact within the matrix to form multi-vacancies, thereby improving the sintering resistance of the material. The concentration of stabilizer within the cubic matrix structure is greater than that concentration of stabilizer necessary to give the matrix a peak ionic conductivity value. The concentration of stabilizer may be at least 30 wt. %. Embodiments include a cubic matrix of zirconia stabilized by at least 30-50 wt. % yttria, and a cubic matrix of hafnia stabilized by at least 30-50 wt. % gadolinia.

  13. Thermal Stress Analysis of W/Cu Functionally Graded Materials by Using Finite Element Method

    Science.gov (United States)

    Yang, Zhenxiao; Liu, Min; Deng, Chunming; Zhang, Xiaofeng; Deng, Changguang

    2013-03-01

    Copper alloys with tungsten coating shows an excellent plasma irradiation resistance, however, the difference of coefficient thermal expansion between W and Cu makes it really a difficult job to prepare over 1 mm W coating with high adhesive strength. Functionally graded material (FGM) seems to be an effective method to improve the adhesive strength of thick W coating. This paper focused on the finite element simulation on thermal stress for W/Cu FGM with different graded layers, composition and thicknesses. In addition, the variance of stresses for functionally graded coatings with the steady state heat flux were simulated by finite element analysis (ANSYS Workbench). The results showed that the W/Cu FGM was effectively beneficial for the stress relief of W coating. Meanwhile, the maximum von mises stress decreased approximately by 52.8 % compared to monolithic W plasma facing material. And the four-layer FGM with a compositional exponent of 2 was optimum for 1.5 mm W coating.

  14. Alloy SCR-3 resistant to stress corrosion cracking

    International Nuclear Information System (INIS)

    Kowaka, Masamichi; Fujikawa, Hisao; Kobayashi, Taiki

    1977-01-01

    Austenitic stainless steel is used widely because the corrosion resistance, workability and weldability are excellent, but the main fault is the occurrence of stress corrosion cracking in the environment containing chlorides. Inconel 600, most resistant to stress corrosion cracking, is not necessarily safe under some severe condition. In the heat-affected zone of SUS 304 tubes for BWRs, the cases of stress corrosion cracking have occurred. The conventional testing method of stress corrosion cracking using boiling magnesium chloride solution has been problematical because it is widely different from actual environment. The effects of alloying elements on stress corrosion cracking are remarkably different according to the environment. These effects were investigated systematically in high temperature, high pressure water, and as the result, Alloy SCR-3 with excellent stress corrosion cracking resistance was found. The physical constants and the mechanical properties of the SCR-3 are shown. The states of stress corrosion cracking in high temperature, high pressure water containing chlorides and pure water, polythionic acid, sodium phosphate solution and caustic soda of the SCR-3, SUS 304, Inconel 600 and Incoloy 800 are compared and reported. (Kako, I.)

  15. Thermal Stress Effect on Density Changes of Hemp Hurds Composites

    Science.gov (United States)

    Schwarzova, Ivana; Cigasova, Julia; Stevulova, Nadezda

    2016-12-01

    The aim of this article is to study the behavior of prepared biocomposites based on hemp hurds as a filling agent in composite system. In addition to the filler and water, an alternative binder, called MgO-cement was used. For this objective were prepared three types of samples; samples based on untreated hemp hurds as a referential material and samples based on chemically (with NaOH solution) and physically (by ultrasonic procedure) treated hemp hurds. The thermal stress effect on bulk density changes of hemp hurds composites was monitored. Gradual increase in temperature led to composites density reduction of 30-40 %. This process is connected with mass loss of the adsorbed moisture and physically bound water and also with degradation of organic compounds present in hemp hurds aggregates such as pectin, hemicelluloses and cellulose. Therefore the changes in the chemical composition of treated hemp hurds in comparison to original sample and its thermal decomposition were also studied.

  16. Thermal expansion and thermal stress in the moon and terrestrial planets - Clues to early thermal history

    Science.gov (United States)

    Solomon, S. C.; Chaiken, J.

    1976-01-01

    The paper discusses how features of the surface geology of the moon and also Mars and Mercury impose constraints on the volumetric expansion or contraction of a planet and consequently provide a test of thermal history models. The moon has changed very little in volume over the last 3.8 b.y. Thermal models satisfying this constraint involve early heating and perhaps melting of the outer 200 km of the moon and an initially cold interior. Mercury has contracted by about 2 km in radius since emplacement of its present surface, so core formation must predate that surface. A hot initial temperature distribution is implied.

  17. Study of thermal stress in heat affected zones during welding

    International Nuclear Information System (INIS)

    Devaux, J.C.

    1979-01-01

    The importance of applications of welding in the nuclear industry leads to the study of the main problem concerning metal welding: sensibility to cracking. The development of computation methods allows the numerical simulation of welding effects. Due to the complexity of this problem, it is divided in three steps: thermal, metallurgical and mechanical calculus. Interactions between the 3 steps are examined. Mathematical models necessary to get residual stress (i.e. stress remaining when welding is completed and structure at ambient temperature) are described. Then parameters for metallurgical structure determination are given and compared to experiments. A508 and A533 type steels of primary coolant circuit of PWR reactors are taken as examples and the numerical simulation of a test is presented [fr

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

    Science.gov (United States)

    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.

  19. Heterogeneity in induced thermal resistance of rat tumor cell clones

    International Nuclear Information System (INIS)

    Tomasovic, S.P.; Rosenblatt, P.L.; Heitzman, D.

    1983-01-01

    Four 13762NF rat mammary adenocarcinoma clones were examined for their survival response to heating under conditions that induced transient thermal resistance (thermotolerance). Clones MTC and MTF7 were isolated from the subcutaneous locally growing tumor, whereas clones MTLn2 and MTLn3 were derived from spontaneous lung metastases. There was heterogeneity among these clones in thermotolerance induced by either fractionated 45 0 C or continuous 42 0 C heating, but the order of sensitivity was not necessarily the same. The clones developed thermal resistance at different rates and to different degrees within the same time intervals. There was heterogeneity between clones isolated from within either the primary site or metastatic lesions. However, clones derived from metastatic foci did not intrinsically acquire more or less thermotolerance to fractionated 45 0 C or continuous 42 0 C heating than did clones from the primary tumor. Further, there was no apparent relationship between any phenotypic properties that conferred more or less thermotolerance in vitro and any phenotypic properties that conferred enhanced metastatic success of these same clones by spontaneous (subcutaneous) or experimental (intravenous) routes in vivo. These tumor clones also differ in their karyotype, metastatic potential, cell surface features, sensitivity to x-irradiation and drugs, and ability to repair sublethal radiation damage. These results provide further credence to the concept that inherent heterogeneity within tumors may be as important in therapeutic success as other known modifiers of outcome such as site and treatment heterogeneity

  20. Intermittent hypoxic resistance training: is metabolic stress the key moderator?

    Science.gov (United States)

    Scott, Brendan R; Slattery, Katie M; Dascombe, Ben J

    2015-02-01

    Traditionally, researchers and practitioners have manipulated acute resistance exercise variables to elicit the desired responses to training. However, recent research indicates that altering the muscular environment during resistance training, namely by implementing a hypoxic stimulus, can augment muscle hypertrophy and strength. Intermittent hypoxic resistance training (IHRT), whereby participants inspire hypoxic air during resistance training, has been previously demonstrated to increase muscle cross-sectional area and maximum strength by significantly greater amounts than the equivalent training in normoxia. However, some recent evidence has provided conflicting results, reporting that the use of systemic hypoxia during resistance training provided no added benefit. While the definitive mechanisms that may augment muscular responses to IHRT are not yet fully understood, an increased metabolic stress is thought to be important for moderating many downstream processes related to hypertrophy. It is likely that methodological differences between conflicting IHRT studies have resulted in different degrees of metabolic stress during training, particularly when considering the inter-set recovery intervals used. Given that the most fundamental physiological stresses resulting from hypoxia are disturbances to oxidative metabolism, it becomes apparent that resistance training may only benefit from additional hypoxia if the exercise is structured to elicit a strong metabolic response. We hypothesize that for IHRT to be more effective in producing muscular hypertrophy and increasing strength than the equivalent normoxic training, exercise should be performed with relatively brief inter-set recovery periods, with the aim of providing a potent metabolic stimulus to enhance anabolic responses. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Methods of evaluating protective clothing relative to heat and cold stress: thermal manikin, biomedical modeling, and human testing.

    Science.gov (United States)

    O'Brien, Catherine; Blanchard, Laurie A; Cadarette, Bruce S; Endrusick, Thomas L; Xu, Xiaojiang; Berglund, Larry G; Sawka, Michael N; Hoyt, Reed W

    2011-10-01

    Personal protective equipment (PPE) refers to clothing and equipment designed to protect individuals from chemical, biological, radiological, nuclear, and explosive hazards. The materials used to provide this protection may exacerbate thermal strain by limiting heat and water vapor transfer. Any new PPE must therefore be evaluated to ensure that it poses no greater thermal strain than the current standard for the same level of hazard protection. This review describes how such evaluations are typically conducted. Comprehensive evaluation of PPE begins with a biophysical assessment of materials using a guarded hot plate to determine the thermal characteristics (thermal resistance and water vapor permeability). These characteristics are then evaluated on a thermal manikin wearing the PPE, since thermal properties may change once the materials have been constructed into a garment. These data may be used in biomedical models to predict thermal strain under a variety of environmental and work conditions. When the biophysical data indicate that the evaporative resistance (ratio of permeability to insulation) is significantly better than the current standard, the PPE is evaluated through human testing in controlled laboratory conditions appropriate for the conditions under which the PPE would be used if fielded. Data from each phase of PPE evaluation are used in predictive models to determine user guidelines, such as maximal work time, work/rest cycles, and fluid intake requirements. By considering thermal stress early in the development process, health hazards related to temperature extremes can be mitigated while maintaining or improving the effectiveness of the PPE for protection from external hazards.

  2. Effect of Layer-Graded Bond Coats on Edge Stress Concentration and Oxidation Behavior of Thermal Barrier Coatings

    Science.gov (United States)

    Zhu, Dongming; Ghosn, Louis J.; Miller, Robert A.

    1998-01-01

    Thermal barrier coating (TBC) durability is closely related to design, processing and microstructure of the coating Z, tn systems. Two important issues that must be considered during the design of a thermal barrier coating are thermal expansion and modulus mismatch between the substrate and the ceramic layer, and substrate oxidation. In many cases, both of these issues may be best addressed through the selection of an appropriate bond coat system. In this study, a low thermal expansion and layer-graded bond coat system, that consists of plasma-sprayed FeCoNiCrAl and FeCrAlY coatings, and a high velocity oxyfuel (HVOF) sprayed FeCrAlY coating, is developed to minimize the thermal stresses and provide oxidation resistance. The thermal expansion and oxidation behavior of the coating system are also characterized, and the strain isolation effect of the bond coat system is analyzed using the finite element method (FEM). Experiments and finite element results show that the layer-graded bond coat system possesses lower interfacial stresses. better strain isolation and excellent oxidation resistance. thus significantly improving the coating performance and durability.

  3. Thermal stress analysis of sulfur deactivated solid oxide fuel cells

    Science.gov (United States)

    Zeng, Shumao; Parbey, Joseph; Yu, Guangsen; Xu, Min; Li, Tingshuai; Andersson, Martin

    2018-03-01

    Hydrogen sulfide in fuels can deactivate catalyst for solid oxide fuel cells, which has become one of the most critical challenges to stability. The reactions between sulfur and catalyst will cause phase changes, leading to increase in cell polarization and mechanical mismatch. A three-dimensional computational fluid dynamics (CFD) approach based on the finite element method (FEM) is thus used to investigate the polarization, temperature and thermal stress in a sulfur deactivated SOFC by coupling equations for gas-phase species, heat, momentum, ion and electron transport. The results indicate that sulfur in fuels can strongly affect the cell polarization and thermal stresses, which shows a sharp decrease in the vicinity of electrolyte when 10% nickel in the functional layer is poisoned, but they remain almost unchanged even when the poisoned Ni content was increased to 90%. This investigation is helpful to deeply understand the sulfur poisoning effects and also benefit the material design and optimization of electrode structure to enhance cell performance and lifetimes in various hydrocarbon fuels containing impurities.

  4. Cemented carbide cutting tool: Laser processing and thermal stress analysis

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S. [Mechanical Engineering Department, KFUPM, Box 1913, Dhahran 31261 (Saudi Arabia)]. E-mail: bsyilbas@kfupm.edu.sa; Arif, A.F.M. [Mechanical Engineering Department, KFUPM, Box 1913, Dhahran 31261 (Saudi Arabia); Karatas, C. [Engineering Faculty, Hacettepe University, Ankara (Turkey); Ahsan, M. [Mechanical Engineering Department, KFUPM, Box 1913, Dhahran 31261 (Saudi Arabia)

    2007-04-15

    Laser treatment of cemented carbide tool surface consisting of W, C, TiC, TaC is examined and thermal stress developed due to temperature gradients in the laser treated region is predicted numerically. Temperature rise in the substrate material is computed numerically using the Fourier heating model. Experiment is carried out to treat the tool surfaces using a CO{sub 2} laser while SEM, XRD and EDS are carried out for morphological and structural characterization of the treated surface. Laser parameters were selected include the laser output power, duty cycle, assisting gas pressure, scanning speed, and nominal focus setting of the focusing lens. It is found that temperature gradient attains significantly high values below the surface particularly for titanium and tantalum carbides, which in turn, results in high thermal stress generation in this region. SEM examination of laser treated surface and its cross section reveals that crack initiation below the surface occurs and crack extends over the depth of the laser treated region.

  5. Thermal stress failure criteria for a structural epoxy

    Science.gov (United States)

    Côté, Patrice; Desnoyers, Nichola

    2011-09-01

    Representative failure data for structural epoxies can be very difficult to find for the optomechanical engineer. Usually, test data is only available for shear configuration at room temperature and fast pull rate. On the other hand, the slowly induced stress at extreme temperature is for many optical systems the worse-case scenario. Since one of the most referenced epoxy for optical assembly is the 3M™ Scotch-Weld™ Epoxy Adhesive EC-2216 B/A Gray, better understanding its behavior can benefit a broad range of applications. The objective of this paper is two-fold. First, review data for critical parameters such as Young's modulus and coefficient of thermal expansion. Secondly, derive failure criteria from correlation between a thermal stress experiment and a finite element model. Instead of pulling out a standard tensile specimen, it is proposed to test thin bondline geometry to replicate an optical device usage. Four test plates are assembled at the Institut National d'Optique (INO) in Quebec City, Canada with bondlines of 50 μm and 133 μm. To detect the failure of the epoxy, the low level vibration signature of a cantilever Invar plate is monitored as temperature changes. Following the finite element analysis, a failure criterion is found to better match the experimental results than generic lap shear data.

  6. Thermal Shock Resistance of Si3N4/h -BN Composites Prepared via Catalytic Reaction-Bonding Route

    Science.gov (United States)

    Yang, Wanli; Peng, Zhigang; Dai, Lina; Shi, Zhongqi; Jin, Zhihao

    2017-09-01

    Si3N4/h-BN ceramic matrix composites were prepared via a catalytic reaction-bonding route by using ZrO2 as nitridation catalyst, and the water quenching (fast cooling) and molten aluminum quenching tests (fast heating) were carried out to evaluate the thermal shock resistance of the composites. The results showed that the thermal shock resistance was improved obviously with the increase in h-BN content, and the critical thermal shock temperature difference (Δ T c) reaches as high as 780 °C when the h-BN content was 30 wt.%. The improvement of thermal shock resistance of the composites was mainly due to the crack tending to quasi static propagating at weak bonding interface between Si3N4 and h-BN with the increase in h-BN content. For the molten aluminum quenching test, the residual strength showed no obvious decrease compared with water quenching test, which could be caused by the mild stress condition on the surface. In addition, a calculated parameter, volumetric crack density ( N f), was presented to quantitative evaluating the thermal shock resistance of the composites in contrast to the conventional R parameter.

  7. The effects of location, thermal stress, and residual stress on corner cracks in nozzles with cladding

    International Nuclear Information System (INIS)

    Besuner, P.M.; Cohen, L.M.; McLean, J.L.

    1977-01-01

    The stress intensity factors (Ksub(I)) for corner cracks in a boiling water reactor feedwater nozzle with stainless steel cladding are obtained for loading by internal pressure, and a fluid quench in the nozzle. Conditions with and without residual stress in the component are considered. The residual stress is simulated by means of a reference temperature change. The stress distribution for the uncracked structure is obtained from a three-dimensional finite element model. A three-dimensional influence function (IF) method, in conjunction with the boundary-integral equation method for structural analysis is employed to compute Ksub(I) values from the uncracked structure's stress distribution. It is concluded that the effects on Ksub(I) of location, thermal stresses, and residual stresses are significant and generally too complex to evaluate without advanced numerical procedures. The ulilized combination of finite element analysis of the uncracked structure and three-dimensional influence function analysis of the cracked structure is demonstrated and endorsed. (Auth.)

  8. Treatment increases stress-corrosion resistance of aluminum alloys

    Science.gov (United States)

    Jacobs, A. J.

    1966-01-01

    Overaging during heat treatment of the aluminum alloys immediately followed by moderate plastic deformation, preferably by shock loading achieves near optimum values of both yield strength and resistance to stress corrosion. Similar results may be obtained by substituting a conventional deformation process for the shock loading step.

  9. Biochemical basis of the high resistance to oxidative stress in ...

    Indian Academy of Sciences (India)

    Unknown

    Higher resistance to oxidative stress in D. discoideum. 583 each culture being assayed and incubated for 3–4 h. At the end of the incubation period, isopropanol was added directly and the dissolution was accomplished by titura- tion. Absorbance of the reduced dye was measured at. 570 nm with background subtraction at ...

  10. Variation in adult life history and stress resistance across five ...

    Indian Academy of Sciences (India)

    Unknown

    higher adult lifespan and stress resistance in recently wild-caught flies, relative to flies maintained for a long time in discrete- generation laboratory cultures. ... as preadult development time, age-specific female fecun- dity and adult lifespan ...... ween fecundity and longevity in Drosophila melanogaster. Physiol. Zool.

  11. Modeling thermal stress propagation during hydraulic stimulation of geothermal wells

    Science.gov (United States)

    Jansen, Gunnar; Miller, Stephen A.

    2017-04-01

    A large fraction of the world's water and energy resources are located in naturally fractured reservoirs within the earth's crust. Depending on the lithology and tectonic history of a formation, fracture networks can range from dense and homogeneous highly fractured networks to single large scale fractures dominating the flow behavior. Understanding the dynamics of such reservoirs in terms of flow and transport is crucial to successful application of engineered geothermal systems (also known as enhanced geothermal systems or EGS) for geothermal energy production in the future. Fractured reservoirs are considered to consist of two distinct separate media, namely the fracture and matrix space respectively. Fractures are generally thin, highly conductive containing only small amounts of fluid, whereas the matrix rock provides high fluid storage but typically has much smaller permeability. Simulation of flow and transport through fractured porous media is challenging due to the high permeability contrast between the fractures and the surrounding rock matrix. However, accurate and efficient simulation of flow through a fracture network is crucial in order to understand, optimize and engineer reservoirs. It has been a research topic for several decades and is still under active research. Accurate fluid flow simulations through field-scale fractured reservoirs are still limited by the power of current computer processing units (CPU). We present an efficient implementation of the embedded discrete fracture model, which is a promising new technique in modeling the behavior of enhanced geothermal systems. An efficient coupling strategy is determined for numerical performance of the model. We provide new insight into the coupled modeling of fluid flow, heat transport of engineered geothermal reservoirs with focus on the thermal stress changes during the stimulation process. We further investigate the interplay of thermal and poro-elastic stress changes in the reservoir

  12. Mechanisms of Brain Glucocorticoid Resistance in Stress-Induced Psychopathologies.

    Science.gov (United States)

    Merkulov, V M; Merkulova, T I; Bondar, N P

    2017-03-01

    Exposure to stress activates the hypothalamic-pituitary-adrenal axis and leads to increased levels of glucocorticoid (GC) hormones. Prolonged elevation of GC levels causes neuronal dysfunction, decreases the density of synapses, and impairs neuronal plasticity. Decreased sensitivity to glucocorticoids (glucocorticoid resistance) that develops as a result of chronic stress is one of the characteristic features of stress-induced psychopathologies. In this article, we reviewed the published data on proposed molecular mechanisms that contribute to the development of glucocorticoid resistance in brain, including changes in the expression of the glucocorticoid receptor (GR) gene, biosynthesis of GR isoforms, and GR posttranslational modifications. We also present data on alterations in the expression of the FKBP5 gene encoding the main component of cell ultra-short negative feedback loop of GC signaling regulation. Recent discoveries on stress- and GR-induced changes in epigenetic modification patterns as well as normalizing action of antidepressants are discussed. GR and FKBP5 gene polymorphisms associated with stress-induced psychopathologies are described, and their role in glucocorticoid resistance is discussed.

  13. Thermal Stress and Toxicity | Science Inventory | US EPA

    Science.gov (United States)

    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 subthermoneutral 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 tan 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

  14. Thermal stresses in an orthotropic rectangular plate with a rigid ribbonlike inclusion

    International Nuclear Information System (INIS)

    Sumi, N.

    1981-01-01

    On the basis of the complex variable method for determining the stationary two-dimensional thermal stresses, the thermal stresses in an orthotropic rectangular plate with a rigid ribbonlike inclusion under a steady state temperature field is considered. The solution is found by the analytic continuation argument and the modified mapping-collocation technique. Numerical results indicate a dependence of the orthotropic stress intensity factors on the thermal, elastic and geometrical constants over a certain parameter range. (orig.)

  15. Inclusion of copepod Acartia tonsa nauplii in the feeding of Centropomus undecimalis larvae increases stress resistance

    Directory of Open Access Journals (Sweden)

    Wanessa de Melo-Costa

    2015-09-01

    Full Text Available This research represents the first result of studies of the common snook Centropomus undecimalis larvae from broodstock matured in captivity in Brazil. The aim of this study was to evaluate if the inclusion of Acartia tonsa nauplii improves stress resistance of common snook larvae. The larvae were fed with: rotifers Brachionus plicatilis (10 to 15 mL-1; A. tonsa nauplii (0.25 to 0.5 mL-1 and rotifers (5 to 7.5 mL-1, and A. tonsa nauplii (0.12 to 0.25 mL-1. The average percentage of survival of the treatments was 11.9%. At 20 days of age, larvae were subjected to thermal stress. Subsequently, the stress resistance was evaluated. Common snook larvae fed B. plicatilis+A. tonsa reached a higher weight and length (7.5 ± 0.00 mg and 9.1 ± 0.23 mm, respectively and resisted more heat stress (87.4% than larvae fed other foods, indicating that the feed mixture is satisfactory as a starter diet for larvae of common snook. However, more research is needed to confirm these results.

  16. Reduced resistance to oxidative stress during reproduction as a cost of early-life stress.

    Science.gov (United States)

    Zimmer, Cédric; Spencer, Karen A

    2015-05-01

    Stress exposure during early-life development can have long-term consequences for a variety of biological functions including oxidative stress. The link between early-life stress and oxidative balance is beginning to be explored and previous studies have focused on this link in adult non-breeding or immature individuals. However, as oxidative stress is considered as the main physiological mechanism underlying the trade-off between self-maintenance and investment in reproduction, it is necessary to look at the consequences of early-life stress on oxidative status during reproduction. Here, we investigated the effects of exposure to pre- and/or post-natal stress on oxidative balance during reproduction under benign or stressful environmental conditions in an avian model species, the Japanese quail. We determined total antioxidant status (TAS), total oxidant status (TOS) and resistance to a free-radical attack in individual exposed to pre-natal stress, post-natal stress or both and in control individuals exposed to none of the stressors. TAS levels decreased over time in all females that reproduced under stressful conditions. TOS decreased between the beginning and the end of reproductive period in pre-natal control females. In all females, resistance to a free-radical attack decreased over the reproductive event but this decrease was more pronounced in females from a pre-natal stress development. Our results suggest that pre-natal stress may be associated with a higher cost of reproduction in terms of oxidative stress. These results also confirm that early-life stress can be associated with both benefits and costs depending of the life-history stage or environmental context. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Role of the thermal boundary resistance of the quantum well interfaces on the degradation of high power laser diodes

    Science.gov (United States)

    Martín-Martín, A.; Iñiguez, P.; Jiménez, J.; Oudart, M.; Nagle, J.

    2011-08-01

    The influence of the quantum well (QW) interfaces with the barrier layers on the rapid degradation of AlGaAs based high power laser bars (808 nm) is investigated. Thermal stresses induced in the device by the local heating produced by nonradiative recombination areas at the facet mirror are calculated by means of a thermomechanical model. Results show that the laser power density threshold necessary to achieve the plastic deformation, leading to the generation of dislocations and to the failure of these devices, is reduced as the quality of the QW interfaces worsens in terms of thermal boundary resistance.

  18. Survival of juvenile fishes receiving thermal and mechanical stresses in a simulated power plant condenser

    International Nuclear Information System (INIS)

    Kedl, R.J.; Coutant, C.C.

    Experiments were conducted in a water-recirculating loop to determine the effects of fluid-induced stresses (e.g., turbulence, pressure, and vacuum) on six species of larval fish and one species each of frog tadpoles and zooplankton. These stresses simulate the insults developed in the condenser portion, but not including the pump, of a steam power plant. Some experiments were conducted with thermal stresses superimposed on fluid-induced stresses. Fluid-induced stresses of the magnitude developed in these experiments were generally not fatal to the larval fish within the precision of the experiments, although some sublethal effects were noted. When thermal stress was superimposed on the fluid-induced stresses, the mortalities were equivalent to those resulting from thermal stress alone. Fluid-induced stresses of low magnitude were not fatal to Daphnia magna, but fluid-induced stresses of higher magnitude were responsible for significant mortalities. (U.S.)

  19. Transient stress control of aeroengine disks based on active thermal management

    International Nuclear Information System (INIS)

    Ding, Shuiting; Wang, Ziyao; Li, Guo; Liu, Chuankai; Yang, Liu

    2016-01-01

    Highlights: • The essence of cooling in turbine system is a process of thermal management. • Active thermal management is proposed to control transient stress of disks. • The correlation between thermal load and transient stress of disks is built. • Stress level can be declined by actively adjusting the thermal load distribution. • Artificial temperature gradient can be used to counteract stress from rotating. - Abstract: The physical essence of cooling in the turbine system is a process of thermal management. In order to overcome the limits of passive thermal management based on thermal protection, the concept of active thermal management based on thermal load redistribution has been proposed. On this basis, this paper focuses on a near real aeroengine disk during a transient process and studies the stress control mechanism of active thermal management in transient conditions by a semi-analytical method. Active thermal management is conducted by imposing extra heating energy on the disk hub, which is represented by the coefficient of extra heat flow η. The results show that the transient stress level can be effectively controlled by actively adjusting the thermal load distribution. The decline ratio of the peak equivalent stress of the disk hub can be 9.0% for active thermal management load condition (η = 0.2) compared with passive condition (η = 0), even at a rotation speed of 10,000 r/min. The reason may be that the temperature distribution of the disk turns into an artificial V-shape because of the extra heating energy on the hub, and the resulting thermal stresses induced by the negative temperature gradients counteract parts of the stress from rotating.

  20. Anisotropic Horizontal Thermal Contraction of Young Oceanic Lithosphere Inferred From Stress Release Due To Oceanic Intraplate Earthquakes

    Science.gov (United States)

    Sasajima, Ryohei; Ito, Takeo

    2017-10-01

    How freely the oceanic lithosphere contracts horizontally due to thermal contraction is important information, because it reflects the boundary condition of the oceanic lithosphere, which includes information regarding the magnitude of driving/resisting forces of plate tectonics. We investigated the horizontal thermal contraction of young oceanic lithosphere using an analysis of the intraplate stress release due to oceanic intraplate earthquakes (OCEQs) and numerical simulations. The stress release due to OCEQs in young oceanic lithosphere (5-15 Ma) shows significant differences between the spreading directional component and the ridge-parallel component. The extensional stress release of the ridge-parallel component is 6 times as large as that of the spreading directional component, while the compressional stress release of the ridge-parallel component is one seventh that of the spreading directional component. We conducted a numerical simulation of the thermal stress evolution of the oceanic lithosphere to investigate how the difference in the horizontal contraction rates between the spreading direction and the ridge-parallel direction can explain the observed anisotropic stress release. The result indicates that young oceanic lithosphere (5-15 Ma) barely contracts in the ridge-parallel direction (only 0-30% of the spreading directional contraction rate), while it contracts freely in the spreading direction due to the weakness of the oceanic ridge strength and the low-viscosity asthenosphere. From the results, we constrained the magnitude of the basal traction working on the bottom of the oceanic lithosphere to be smaller than 0.44 MPa.

  1. Calculation of Thermal Strains and Stresses in Composite Conical Fairing

    Directory of Open Access Journals (Sweden)

    B. S. Sarbaev

    2015-01-01

    Full Text Available Fairings in the form of thin-walled circular conical shells made from composite materials are a commonly used structural element of the cutting-edge rocketry. In the course of operation they are subjected to intense thermal and force loading. To calculate them the unnecessarily time consuming (laborious methods using complicated finite element software systems are often applied. The article proposes an analytical method to calculate thermal strains and stresses in composite conically shaped fairing under uneven heating. The proposed method of calculation can be useful at the preliminary stage of design process. The article describes a design model. For its construction the theory of thin orthotropic conical shells under axisymmetric loading, based on the Kirchhoff-Love hypotheses, is used. The article considers uneven heating of the fairing, when the temperature varies nonlinearly along the slant height and across the thickness. The fairing is made from composite material with woven filler. Duhamel-Neumann relations describe thermo-elastic properties of the material. Boundary conditions are formulated. The system of resolving ordinary nonhomogeneous differential equations of the second order with respect to the rotation angle of the normal in the meridian direction and shearing forces is obtained. The system of equations is transformed to the Bessel equation via auxiliary complex function. Its order is determined by the ratio of the elasticity modulus along the weft to the modulus of elasticity along the warp. For the practically important case when this ratio is equal approximately to 0.5, the analytical solution of the homogeneous system of equations is obtained. This solution is expressed by elementary functions. The variant of a particular solution for the nonhomogeneous system of differential equations is proposed. For the "long" conical shell a simplified solution is given. Using the obtained relations for the displacements and internal

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

    Science.gov (United States)

    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

  3. The etiology of oxidative stress in insulin resistance

    Directory of Open Access Journals (Sweden)

    Samantha Hurrle

    2017-10-01

    Full Text Available Insulin resistance is a prevalent syndrome in developed as well as developing countries. It is the predisposing factor for type 2 diabetes mellitus, the most common end stage development of metabolic syndrome in the United States. Previously, studies investigating type 2 diabetes have focused on beta cell dysfunction in the pancreas and insulin resistance, and developing ways to correct these dysfunctions. However, in recent years, there has been a profound interest in the role that oxidative stress in the peripheral tissues plays to induce insulin resistance. The objective of this review is to focus on the mechanism of oxidative species generation and its direct correlation to insulin resistance, to discuss the role of obesity in the pathophysiology of this phenomenon, and to explore the potential of antioxidants as treatments for metabolic dysfunction.

  4. Anion exchanger and the resistance against thermal haemolysis.

    Science.gov (United States)

    Ivanov, I T; Zheleva, A; Zlatanov, I

    2011-01-01

    4,4'-Diiso-thiocyanato stilbene-2,2'-disulphonic acid (DIDS) is a membrane-impermeable, highly specific covalent inhibitor and powerful thermal stabiliser of the anion exchanger (AE1), the major integral protein of erythrocyte membrane (EM). Suspensions of control and DIDS-treated (15 µM, pH 8.2) human erythrocytes were heated from 20° to 70°C using various but constant heating rates (1-8°C/min). The cellular electrolyte leakage exhibited a sigmoidal response to temperature as detected by conductometry. The critical midpoint temperature of leakage, T(mo), extrapolated to low heating rate (0.5°C/min) was used as a measure for EM thermostability. T(mo) was greater for DIDS-treated erythrocytes, 63.2° ± 0.3°C, than for intact erythrocytes, 60.7° ± 0.2°C. The time, t(1/2), for 50% haemolysis of erythrocytes, exposed to 53°C was used as a measure for the resistance of erythrocytes against thermal haemolysis. The t(1/2) was also greater for DIDS-treated erythrocytes, 63 ± 3 min, than for intact erythrocytes, 38 ± 2 min. The fluorescent label N-(3-pyrenyl)maleimide and EPR spin label 3-maleimido-proxyl, covalently bound to sulphydryl groups of major EM proteins, were used to monitor the changes in molecular motions during transient heating. Both labels reported an intensification of the motional dynamics at the denaturation temperatures of spectrin (50°C) and AE1 (67°C), and, surprisingly, immobilisation of a major EM protein, presumably the AE1, at T(mo). The above results are interpreted in favour of the possible involvement of a predenaturational rearrangement of AE1 copies in the EM thermostability and the resistance against thermal haemolysis.

  5. Thermal stress control using waste steel fibers in massive concretes

    Science.gov (United States)

    Sarabi, Sahar; Bakhshi, Hossein; Sarkardeh, Hamed; Nikoo, Hamed Safaye

    2017-11-01

    One of the important subjects in massive concrete structures is the control of the generated heat of hydration and consequently the potential of cracking due to the thermal stress expansion. In the present study, using the waste turnery steel fibers in the massive concretes, the amount of used cement was reduced without changing the compressive strength. By substituting a part of the cement with waste steel fibers, the costs and the generated hydration heat were reduced and the tensile strength was increased. The results showed that by using 0.5% turnery waste steel fibers and consequently, reducing to 32% the cement content, the hydration heat reduced to 23.4% without changing the compressive strength. Moreover, the maximum heat gradient reduced from 18.5% in the plain concrete sample to 12% in the fiber-reinforced concrete sample.

  6. Compressive strength evolution of thermally-stressed Saint Maximin limestone.

    Science.gov (United States)

    Farquharson, J.; Griffiths, L.; Baud, P.; Wadsworth, F. B.; Heap, M. J.

    2017-12-01

    The Saint Maximin quarry (Oise, France) opened in the early 1600s, and its limestone has been used extensively as masonry stone, particularly during the classical era of Parisian architecture from the 17th century onwards. Its widespread use has been due to a combination of its regional availability, its high workability, and its aesthetic appeal. Notable buildings completed using this material include sections of the Place de la Concorde and the Louvre in Paris. More recently, however, it has seen increasing use in the construction of large private residences throughout the United States as well as extensions to private institutions such as Stanford University. For any large building, fire hazard can be a substantial concern, especially in tectonically active areas where catastrophic fires may arise following large-magnitude earthquakes. Typically, house fires burn at temperatures of around 600 °C ( 1000 F). Given the ubiquity of this geomaterial as a building stone, it is important to ascertain the influence of heating on the strength of Saint Maximin limestone (SML), and in turn the structural stability of the buildings it is used in. We performed a series of compressive tests and permeability measurements on samples of SML to determine its strength evolution in response to heating to incrementally higher temperatures. We observe that the uniaxial compressive strength of SML decreases from >12 MPa at room temperature to 400 °C). We anticipate that this substantial weakening is in part a result of thermal microcracking, whereby changes in temperature induce thermal stresses due to a mismatch in thermal expansion between the constituent grains. This mechanism is compounded by the volumetric increase of quartz through its alpha - beta transition at 573 °C, and by the thermal decomposition of calcite. To track the formation of thermal microcracks, we monitor acoustic emissions, a common proxy for microcracking, during the heating of an SML sample. The

  7. Exploring the use of thermal infrared imaging in human stress research.

    Directory of Open Access Journals (Sweden)

    Veronika Engert

    Full Text Available 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.

  8. Thermal stress and creep fatigue limitations in first wall design

    International Nuclear Information System (INIS)

    Majumdar, S.; Misra, B.; Harkness, S.D.

    1977-01-01

    The thermal-hydraulic performance of a lithium cooled cylindrical first wall module has been analyzed as a function of the incident neutron wall loading. Three criteria were established for the purpose of defining the maximum wall loading allowable for modules constructed of Type 316 stainless steel and a vanadium alloy. Of the three, the maximum structural temperature criterion of 750 0 C for vanadium resulted in the limiting wall loading value of 7 MW/m 2 . The second criterion limited thermal stress levels to the yield strength of the alloy. This led to the lowest wall loading value for the Type 316 stainless steel wall (1.7 MW/m 2 ). The third criterion required that the creep-fatigue characteristics of the module allow a lifetime of 10 MW-yr/m 2 . At wall temperatures of 600 0 C, this lifetime could be achieved in a stainless steel module for wall loadings less than 3.2 MW/m 2 , while the same lifetime could be achieved for much higher wall loadings in a vanadium module

  9. Thermal stability of nafion membranes under mechanical stress

    Energy Technology Data Exchange (ETDEWEB)

    Quintilii, M.; Struis, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The feasibility of adequately modified fluoro-ionomer membranes (NAFION{sup R}) is demonstrated for the selective separation of methanol synthesis products from the raw reactor gas at temperatures around 200{sup o}C. For an economically relevant application of this concept on a technical scale the Nafion membranes should be thin ({approx_equal}10 {mu}m) and thermally stable over a long period of time (1-2 years). In cooperation with industry (Methanol Casale SA, Lugano (CH)), we test the thermal stability of Nafion hollow fibers and supported Nafion thin sheet membranes at temperatures between 160 and 200{sup o}C under mechanical stress by applying a gas pressure difference over the membrane surface ({Delta}P{<=} 40 bar). Tests with the hollow fibers revealed that Nafion has visco-elastic properties. Tests with 50 {mu}m thin Nafion sheets supported by a porous metal carrier at 200{sup o}C and {Delta}P=39 bar showed no mechanical defects over a period of 92 days. (author) 5 figs., 4 refs.

  10. Thermal Stress Effect on Density Changes of Hemp Hurds Composites

    Directory of Open Access Journals (Sweden)

    Schwarzova Ivana

    2016-12-01

    Full Text Available The aim of this article is to study the behavior of prepared biocomposites based on hemp hurds as a filling agent in composite system. In addition to the filler and water, an alternative binder, called MgO-cement was used. For this objective were prepared three types of samples; samples based on untreated hemp hurds as a referential material and samples based on chemically (with NaOH solution and physically (by ultrasonic procedure treated hemp hurds. The thermal stress effect on bulk density changes of hemp hurds composites was monitored. Gradual increase in temperature led to composites density reduction of 30-40 %. This process is connected with mass loss of the adsorbed moisture and physically bound water and also with degradation of organic compounds present in hemp hurds aggregates such as pectin, hemicelluloses and cellulose. Therefore the changes in the chemical composition of treated hemp hurds in comparison to original sample and its thermal decomposition were also studied.

  11. Time-dependent analytical thermal model to investigate thermally induced stresses in quasi-CW-pumped laser rods

    CSIR Research Space (South Africa)

    Bernhardi, EH

    2008-01-01

    Full Text Available that determines the temperature and the thermally induced stresses in isotropic rods is presented. Even though the model is developed for isotropic rods, it is shown that it can also be used to accurately estimate the thermal effects in anisotropic rods...

  12. Thermally induced rock stress increment and rock reinforcement response

    International Nuclear Information System (INIS)

    Hakala, M.; Stroem, J.; Nujiten, G.; Uotinen, L.; Siren, T.; Suikkanen, J.

    2014-07-01

    This report describes a detailed study of the effect of thermal heating by the spent nuclear fuel containers on the in situ rock stress, any potential rock failure, and associated rock reinforcement strategies for the Olkiluoto underground repository. The modelling approach and input data are presented together repository layout diagrams. The numerical codes used to establish the effects of heating on the in situ stress field are outlined, together with the rock mass parameters, in situ stress values, radiogenic temperatures and reinforcement structures. This is followed by a study of the temperature and stress evolution during the repository's operational period and the effect of the heating on the reinforcement structures. It is found that, during excavation, the maximum principal stress is concentrated at the transition areas where the profile changes and that, due to the heating from the deposition of spent nuclear fuel, the maximum principal stress rises significantly in the tunnel arch area of NW/SW oriented central tunnels. However, it is predicted that the rock's crack damage (CD, short term strength) value of 99 MPa will not be exceeded anywhere within the model. Loads onto the reinforcement structures will come from damaged and loosened rock which is assumed in the modelling as a free rock wedge - but this is very much a worst case scenario because there is no guarantee that rock cracking would form a free rock block. The structural capacity of the reinforcement structures is described and it is predicted that the current quantity of the rock reinforcement is strong enough to provide a stable tunnel opening during the peak of the long term stress state, with damage predicted on the sprayed concrete liner. However, the long term stability and safety can be improved through the implementation of the principles of the Observational Method. The effect of ventilation is also considered and an additional study of the radiogenic heating effect on the brittle

  13. Decay and termite resistance, water absorption and swelling of thermally compressed wood panels

    Science.gov (United States)

    Oner Unsal; S. Nami Kartal; Zeki Candan; Rachel A. Arango; Carol A. Clausen; Frederick Green

    2009-01-01

    This study evaluated decay and termite resistance of thermally compressed pine wood panels under pressure at either 5 or 7 MPa and either 120 or 150 °C for 1 h. Wood specimens from the panels were exposed to laboratory decay resistance by using the wood degrading fungi, Gloeophyllum trabeum and Trametes versicolor. The thermal compression process caused increases in...

  14. Responses To Thermal Stresses in Psoriasis of Hand

    Directory of Open Access Journals (Sweden)

    Soma Mukherjee

    1989-01-01

    Full Text Available Fifteen subjects having psoriasis on the hand, comprising both sexes, between 22 and 56 years in age and suffering for durations varying from 10 months to 20 years each with a sex and age niatched control were studied. A thermistor thermometer measured the skin temperature in ambient condition at the finger tip and at selected sites on the dorsa of hands and fingers, both at lesion site and lesion-free adjacent ones. In all cases except one, the thermistor readings were significantly lower (p in the psoriatic lesions than in the uninvolved adjacent skin. The hands were next subjected to thermal stresses: first by immersion in an ice-water bath at O′C (cold challenge and later in a hot water bath at 450C (heat challenge each for a period of 60 seconds. Immediately after each stress period,ithe fingertip temperatures were recorded, in psoriatic subjects, the finger-tip temperature dropped on cold challenge and the amount of drop expressed as percentage of the basal temperature was significantly less (p than the corresponding value for the control. There was no significant difference (p 0.05 in the respo se to the heat challenge between psoriat c and normal subjects. It appears that there is some fault in the local vasomotor tone in subjects with hand psoriasis.

  15. A laboratory study of the correlation between the thermal conductivity and electrical resistivity of soil

    Science.gov (United States)

    Wang, Jie; Zhang, Xiaopei; Du, Lizhi

    2017-10-01

    Thermal conductivity k (Wm- 1 K- 1) and electrical resistivity ρ (Ω·m) depend on common parameters such as grain size, dry density and saturation, allowing the finding of a relationship between both parameters. In this paper, we found a linear quantitative formula between thermal conductivity and electrical resistivity of soil. To accomplish this, we measured the thermal conductivity and electrical resistivity of 57 soil samples in the laboratory; samples included 8 reconstructed soils from the Changchun area (clay, silt, and sand) with approximately 7 different saturation levels. A linear relationship between thermal conductivity and electrical resistivity was found excluding the parameter of soil saturation, and the linear model was validated with undisturbed soils in Changchun area. To fully use this relationship (e.g., by imaging the thermal conductivity of soils with electrical resistivity tomography), further measurements with different soils are needed.

  16. Thermal resistance investigations on new leadframe-based LED packages and boards

    NARCIS (Netherlands)

    Pardo, B.; Gasse, A.; Fargeix, A.; Jakovenko, J.; Werkhoven, R.J.; Perpiñà, X.; Jordà, X.; Vellhevi, M.; Weelden, T. van; Bancken, P.

    2013-01-01

    In Solid State Lighting, thermal management is a key issue. Within the C-SSL consortium, we have developed an advanced leadframe based package to reduce the thermal resistance of the component. Numerical simulations have been implemented using Ansys® software and thermal measurements have been

  17. Preliminary investigation of biological resistance, water absorption and swelling of thermally compressed pine wood panels

    Science.gov (United States)

    Oner Unsal; S. Nami Kartal; Zeki Candan; Rachel Arango; Carol A. Clausen; Frederick Green

    2008-01-01

    Wood can be modified by compressive, thermal and chemical treatments. Compression of wood under thermal conditions is resulted in densification of wood. This study evaluated decay and termite resistance of thermally compressed pine wood panels at either 5 or 7 MPa and at either 120 or 150°C for one hour. The process caused increases in density and decreases in...

  18. The importance of interfacial resistance on the thermal behavior of carbon nanofiber/epoxy composites

    Science.gov (United States)

    Gardea, Frank; Naraghi, Mohammad; Lagoudas, Dimitris C.

    2014-04-01

    This research addresses the thermal transport in carbon nanofiber (CNF)/epoxy composites via finite element modeling. The effects of nanofiber orientation on thermal transport are investigated through Fourier's Law of heat conduction and through simulation of a high magnitude, short heat pulse. The effect of interface thermal resistance on the effective composite thermal conductivity is also quantified. In addition, a simplified lightning strike simulation is modeled in order to analyze the effect of interfacial thermal resistance on composite behavior when subjected to multiple short heat pulses.

  19. A neutron scattering study on the stability of trehalose mycolates under thermal stress

    International Nuclear Information System (INIS)

    Migliardo, F.; Salmeron, C.; Bayan, N.

    2013-01-01

    Highlights: ► Neutron scattering measurements have been performed on mycolate water mixtures. ► A comparison with lecithin lipid water mixtures has been carried out. ► Mycolates show a lower mobility and flexibility compared to lecithin. ► The observed peculiarities of mycolic acids could be ascribed to trehalose. ► The results could justify the high resistance to thermal stress of mycobacteria. - Abstract: The present paper is focused on the study of the dynamics of mycolic acids, which are fundamental components of the outer membrane (mycomembrane) of Mycobacterium tuberculosis. An elastic neutron scattering study of mycolic acid/H 2 O and lecithin/H 2 O mixtures as a function of temperature and exchanged wavevector Q has been carried out. This study provides an effective way for characterizing the dynamical properties, furnishing a set of parameters characterizing the different flexibility and rigidity of the investigated lipids. The behavior of the elastically scattered intensity profiles and the derived mean square displacements as a function of temperature shows a more marked temperature dependence for lecithin lipids in comparison with mycolic acids, so revealing a higher thermal stability of these latter. These findings could be useful for understanding the dynamics-function relation in the mycomembrane and then to relate it to the low permeability and high resistance of mycobacteria to many antibiotics

  20. A neutron scattering study on the stability of trehalose mycolates under thermal stress

    Energy Technology Data Exchange (ETDEWEB)

    Migliardo, F., E-mail: fmigliardo@unime.it [Department of Physics, University of Messina, Viale D’Alcontres 31, 98166 Messina (Italy); Salmeron, C.; Bayan, N. [Laboratoire de Microbiologie Moléculaire et Cellulaire, IBBMC, Bat 430, Université de Paris Sud XI, 15 rue Georges Clémenceau, 91405 Orsay Cedex (France)

    2013-10-16

    Highlights: ► Neutron scattering measurements have been performed on mycolate water mixtures. ► A comparison with lecithin lipid water mixtures has been carried out. ► Mycolates show a lower mobility and flexibility compared to lecithin. ► The observed peculiarities of mycolic acids could be ascribed to trehalose. ► The results could justify the high resistance to thermal stress of mycobacteria. - Abstract: The present paper is focused on the study of the dynamics of mycolic acids, which are fundamental components of the outer membrane (mycomembrane) of Mycobacterium tuberculosis. An elastic neutron scattering study of mycolic acid/H{sub 2}O and lecithin/H{sub 2}O mixtures as a function of temperature and exchanged wavevector Q has been carried out. This study provides an effective way for characterizing the dynamical properties, furnishing a set of parameters characterizing the different flexibility and rigidity of the investigated lipids. The behavior of the elastically scattered intensity profiles and the derived mean square displacements as a function of temperature shows a more marked temperature dependence for lecithin lipids in comparison with mycolic acids, so revealing a higher thermal stability of these latter. These findings could be useful for understanding the dynamics-function relation in the mycomembrane and then to relate it to the low permeability and high resistance of mycobacteria to many antibiotics.

  1. Numerical simulations on the temperature gradient and thermal stress of a thermoelectric power generator

    International Nuclear Information System (INIS)

    Wu, Yongjia; Ming, Tingzhen; Li, Xiaohua; Pan, Tao; Peng, Keyuan; Luo, Xiaobing

    2014-01-01

    Highlights: • An appropriate ceramic plate thickness is effective in alleviating the thermal stress. • A smaller distance between thermo-pins can help prolong lifecycle of the TE module. • Either a thicker or a thinner copper conducting strip effectively reduces thermal stress. • A suitable tin soldering thickness will alleviate thermal stress intensity and increase thermal efficiency. - Abstract: Thermoelectric generator is a device taking advantage of the temperature difference in thermoelectric material to generate electric power, where the higher the temperature difference of the hot-cold ends, the higher the efficiency will be. However, higher temperature or higher heat flux upon the hot end will cause strong thermal stress which will negatively influence the lifecycle of the thermoelectric module. This phenomenon is very common in industrial applications but seldom has research work been reported. In this paper, numerical analysis on the thermodynamics and thermal stress performance of the thermoelectric module has been performed, considering the variation on the thickness of materials; the influence of high heat flux on thermal efficiency, power output, and thermal stress has been examined. It is found that under high heat flux imposing upon the hot end, the thermal stress is so strong that it has a decisive effect on the life expectation of the device. To improve the module’s working condition, different geometrical configurations are tested and the optimum sizes are achieved. Besides, the side effects on the efficiency, power output, and open circuit voltage output of the thermoelectric module are taken into consideration

  2. Thermal preference, thermal resistance, and metabolic rate of juvenile Chinese pond turtles Mauremys reevesii acclimated to different temperatures.

    Science.gov (United States)

    Xu, Wei; Dang, Wei; Geng, Jun; Lu, Hong-Liang

    2015-10-01

    The thermal acclimatory capacity of a particular species may determine its resilience to environmental change. Evaluating the physiological acclimatory responses of economically important species is useful for determining their optimal culture conditions. Here, juvenile Chinese three-keeled pond turtles (Mauremys reevesii) were acclimated to one of three different temperatures (17, 25 or 33°C) for four weeks to assess the effects of thermal acclimation on some physiological traits. Thermal acclimation significantly affected thermal resistance, but not thermal preference, of juvenile M. reevesii. Turtles acclimated to 17°C were less resistant to high temperatures than those acclimated to 25°C and 33°C. However, turtles increased resistance to low temperatures with decreasing acclimation temperature. The acclimation response ratio of the critical thermal minimum (CTMin) was lower than that of the critical thermal maximum (CTMax) for acclimation temperatures between 17 and 25°C, but slightly higher between 25 and 33°C. The thermal resistance range (i.e., the difference between CTMax and CTMin) was widest in turtles acclimated to the intermediate temperature (25°C), and narrowest in those acclimated to low temperature (17°C). The standard metabolic rate increased as body temperature and acclimation temperature increased, and the temperature quotient (Q10) between acclimation temperatures 17 and 25°C was higher than the Q10 between 25 and 33°C. Our results suggest that juvenile M. reevesii may have a greater resistance under mild thermal conditions resembling natural environments, and better physiological performance at relatively warm temperatures. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Multi-stress resistance in Lactococcus lactis is actually escape from purine-induced stress sensitivity

    DEFF Research Database (Denmark)

    Ryssel, Mia; Hviid, Anne-Mette Meisner; Dawish, Mohamed S.

    2014-01-01

    in the rich and complex M17 medium. When salvage of purines and subsequent conversion to GTP was permitted in various genetic backgrounds of L. lactis MG1363, the cells became sensitive to acid stress, indicating that an excess of guanine nucleotides induces stress sensitivity. The addition of phosphate...... nucleotides is formed as a result of an improved conversion of guanosine in the salvage pathway. Based upon our findings, we suggest that L. lactis MG1363 is naturally multi-stress resistant in habitats devoid of any purine source. However, any exogenous purine that results in increased guanine nucleotide...

  4. Thermal resistances of crystalline and amorphous few-layer oxide thin films

    Directory of Open Access Journals (Sweden)

    Liang Chen

    2017-11-01

    Full Text Available Thermal insulation at nanoscale is of crucial importance for non-volatile memory devices such as phase change memory and memristors. We perform non-equilibrium molecular dynamics simulations to study the effects of interface materials and structures on thermal transport across the few-layer dielectric nanostructures. The thermal resistance across few-layer nanostructures and thermal boundary resistance at interfaces consisting of SiO2/HfO2, SiO2/ZrO2 or SiO2/Al2O3 are obtained for both the crystalline and amorphous structures. Based on the comparison temperature profiles and phonon density of states, we show that the thermal boundary resistances are much larger in crystalline few-layer oxides than the amorphous ones due to the mismatch of phonon density of state between distinct oxide layers. Compared with the bulk SiO2, the increase of thermal resistance across crystalline few-layer oxides results from the thermal boundary resistance while the increase of thermal resistance across amorphous few-layer oxides is attributed to the lower thermal conductivity of the amorphous thin films.

  5. Experimental study of thermal comfort on stab resistant body armor.

    Science.gov (United States)

    Ji, Tingchao; Qian, Xinming; Yuan, Mengqi; Jiang, Jinhui

    2016-01-01

    This research aims to investigate the impacts of exercise intensity and sequence on human physiology parameters and subjective thermal sensation when wearing stab resistant body armor under daily working conditions in China [26 and 31 °C, 45-50 % relative humidity (RH)], and to investigate on the relationship between subjective judgments and objective parameters. Eight male volunteers were recruited to complete 3 terms of exercises with different velocity set on treadmill for 90 min at 26 °C and 31 °C, 45-50 % RH. In Exercise 1 volunteers were seated during the test. In Exercise 2, volunteers walked with the velocity of 3 km/h in the first 45 min and 6 km/h in the left 45 min. In Exercise 3, volunteers walked with the velocity of 6 km/h in the first 45 min and 3 km/h in the left 45 min. The body core temperature, skin temperature and subjective judgments were recorded during the whole process. Analysis of variance was performed among all the tests. Individual discrepancy of Exercise 1 is larger than that of Exercise 2 and 3. On the premise of the same walking distance and environmental conditions, core temperature in Exercise 3 is about 0.2 °C lower than that in Exercise 2 in the end; and with the velocity decrease from 6 km/h to 3 km/h in the end, thermal tolerance of Exercise 3 is about 1 degree lower than that in Exercise 2. Skin temperatures of human trunk were at least 1 °C higher than that of limbs. Activity narrows the individual discrepancy on core temperature. Within experimental conditions, decreasing of intensity at last stage makes the core temperature lower and the whole process much tolerable. The core temperature is more sensitive to the external disturbance on the balance of the whole body, and it can reflect the subjective thermal sensation and physical exertion.

  6. Thermal resistance of indium coated sapphire-copper contacts below 0.1 K

    Science.gov (United States)

    Eisel, T.; Bremer, J.; Koettig, T.

    2014-11-01

    High thermal resistances exist at ultra-low temperatures for solid-solid interfaces. This is especially true for pressed metal-sapphire joints, where the heat is transferred by phonons only. For such pressed joints it is difficult to achieve good physical, i.e. thermal contacts due to surface irregularities in the microscopic or larger scale. Applying ductile indium as an intermediate layer reduces the thermal resistance of such contacts. This could be proven by measurements of several researchers. However, the majority of the measurements were performed at temperatures higher than 1 K. Consequently, it is difficult to predict the thermal resistance of pressed metal-sapphire joints at temperatures below 1 K. In this paper the thermal resistances across four different copper-sapphire-copper sandwiches are presented in a temperature range between 30 mK and 100 mK. The investigated sandwiches feature either rough or polished sapphire discs (Ø 20 mm × 1.5 mm) to investigate the phonon scattering at the boundaries. All sandwiches apply indium foils as intermediate layers on both sides of the sapphire. Additionally to the indium foils, thin indium films are vapour deposited onto both sides of one rough and one polished sapphire in order to improve the contact to the sapphire. Significantly different thermal resistances have been found amongst the investigated sandwiches. The lowest total thermal resistivity (roughly 26 cm2 K4/W at 30 mK helium temperature) is achieved across a sandwich consisting of a polished sapphire with indium vapour deposition. The thermal boundary resistance between indium and sapphire is estimated from the total thermal resistivity by assuming the scattering at only one boundary, which is the warm sapphire boundary where phonons impinge, and taking the scattering in the sapphire bulk into account. The so derived thermal boundary resistance agrees at low temperatures very well with the acoustic mismatch theory.

  7. Effect of thermal acclimation on thermal preference, resistance and locomotor performance of hatchling soft-shelled turtle

    Directory of Open Access Journals (Sweden)

    Mei-Xian WU,Ling-Jun HU, Wei DANG, Hong-Liang LU, Wei-Guo DU

    2013-12-01

    Full Text Available The significant influence of thermal acclimation on physiological and behavioral performance has been documented in many ectothermic animals, but such studies are still limited in turtle species. We acclimated hatchling soft-shelled turtles Pelodiscus sinensis under three thermal conditions (10, 20 and 30 °C for 4 weeks, and then measured selected body temperature (Tsel, critical thermal minimum (CTMin and maximum (CTMax, and locomotor performance at different body temperatures. Thermal acclimation significantly affected thermal preference and resistance of P. sinensis hatchlings. Hatchling turtles acclimated to 10 °C selected relatively lower body temperatures and were less resistant to high temperatures than those acclimated to 20 °C and 30 °C. The turtles’ resistance to low temperatures increased with a decreasing acclimation temperature. The thermal resistance range (i.e. the difference between CTMax and CTMin, TRR was widest in turtles acclimated to 20 °C, and narrowest in those acclimated to 10 °C. The locomotor performance of turtles was affected by both body temperature and acclimation temperature. Hatchling turtles acclimated to relatively higher temperatures swam faster than did those acclimated to lower temperatures. Accordingly, hatchling turtles acclimated to a particular temperature may not enhance the performance at that temperature. Instead, hatchlings acclimated to relatively warm temperatures have a better performance, supporting the “hotter is better” hypothesis [Current Zoology 59 (6 : 718–724, 2013 ].

  8. Evaluation of the of thermal shock resistance of a castable containing andalusite aggregates by thermal shock cycles

    International Nuclear Information System (INIS)

    Garcia, G.C.R.; Santos, E.M.B.; Ribeiro, S.; Rodrigues, J.A.

    2011-01-01

    The thermal shock resistance of refractory materials is one of the most important characteristics that determine their performance in many applications, since abrupt and drastic differences in temperature can damage them. Resistance to thermal shock damage can be evaluated based on thermal cycles, i.e., successive heating and cooling cycles followed by an analysis of the drop in Young's modulus occurring in each cycle. The aim of this study was to evaluate the resistance to thermal shock damage in a commercial refractory concrete with andalusite aggregate. Concrete samples that were sintered at 1000 deg C and 1450 deg C for 5 hours to predict and were subjected to 30 thermal shock cycles, soaking in the furnace for 20 minutes at a temperature of 1000 deg C, and subsequent cooling in circulating water at 25 deg C. The results showed a decrease in Young's modulus and rupture around 72% for samples sintered at 1000 ° C, and 82% in sintered at 1450 ° C. The refractory sintered at 1450 deg C would show lower thermal shock resistance than the refractory sintered at 1000 deg C. (author)

  9. Consistent effects of a major QTL for thermal resistance in field-released Drosophila melanogaster

    DEFF Research Database (Denmark)

    Loeschcke, Volker; Kristensen, Torsten Nygård; Norry, Fabian M

    2011-01-01

    Molecular genetic markers can be used to identify quantitative trait loci (QTL) for thermal resistance and this has allowed characterization of a major QTL for knockdown resistance to high temperature in Drosophila melanogaster. The QTL showed trade-off associations with cold resistance under lab...

  10. Porous polymeric membranes with thermal and solvent resistance

    KAUST Repository

    Pulido, Bruno

    2017-05-30

    Polymeric membranes are highly advantageous over their ceramic counterparts in terms of the simplicity of the manufacturing process, cost and scalability. Their main disadvantages are low stability at temperatures above 200 °C, and in organic solvents. We report for the first time porous polymeric membranes manufactured from poly(oxindolebiphenylylene) (POXI), a polymer with thermal stability as high as 500 °C in oxidative conditions. The membranes were prepared by solution casting and phase inversion by immersion in water. The asymmetric porous morphology was characterized by scanning electronic microscopy. The pristine membranes are stable in alcohols, acetone, acetonitrile and hexane, as well as in aqueous solutions with pH between 0 and 14. The membrane stability was extended for application in other organic solvents by crosslinking, using various dibromides, and the efficiency of the different crosslinkers was evaluated by thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). POXI crosslinked membranes are stable up to 329 °C in oxidative conditions and showed organic solvent resistance in polar aprotic solvents with 99% rejection of Red Direct 80 in DMF at 70 °C. With this development, the application of polymeric membranes could be extended to high temperature and harsh environments, fields currently dominated by ceramic membranes.

  11. An antidiabetic polyherbal phytomedicine confers stress resistance and extends lifespan in Caenorhabditis elegans.

    Science.gov (United States)

    Rathor, Laxmi; Pant, Aakanksha; Awasthi, Harshika; Mani, Dayanandan; Pandey, Rakesh

    2017-02-01

    An Ayurvedic polyherbal extract (PHE) comprising six herbs viz. Berberis aristata, Cyperus rotundus, Cedrus deodara, Emblica officinalis, Terminalia chebula and Terminalia bellirica is mentioned as an effective anti-hyperglycemic agent in 'Charaka Samhita', the classical text of Ayurveda. Previously, antidiabetic drug metformin was found to elicit antiaging effects and PHE was also found to exhibit antidiabetic effects in humans. Therefore, we screened it for its in vivo antioxidant antiaging effect on stress and lifespan using human homologous Caenorhabditis elegans model system. The effect on aging is evaluated by studying effect of PHE on mean survival in worms. The stress modulatory potential was assessed by quantification of intracellular ROS level, autofluorescent age pigment lipofuscin, oxidative and thermal stress assays. Additionally, stress response was quantified using gene reporter assays. The 0.01 µg/ml dose of PHE was able to enhance mean lifespan by 16.09% (P elegans. Furthermore, PHE treated worms demonstrated oxidative stress resistance in both wild type and stress hypersensitive mev-1 mutant along with upregulation of stress response genes sod-3 and gst-4. The delayed aging under stress can be attributed to its direct reactive oxygen species-scavenging activity and regulation of some age associated genes like daf-2, daf-16, skn-1, sod-3 and gst-4 in wild-type worms. Additonally, PHE delayed age related paralysis phenotype in CL4176 transgenic worms. Altogether, our results suggest PHE significantly improves the oxidative stress and life span in C. elegans. Overall the present study suggests this polyherbal formulation might play important role in regultaing aging and related complications like diabetes.

  12. Modeling conductive cooling for thermally stressed dairy cows.

    Science.gov (United States)

    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. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

    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.

  14. Early life thermal stress: Impact on future thermotolerance, stress response, behavior, and intestinal morphology in piglets exposed to a heat stress challenge during simulated transport

    Science.gov (United States)

    Study objectives were to evaluate the impact of early life thermal stress (ELTS) on thermoregulation, stress, and intestinal health of piglets subjected to a future heat stress (HS) challenge during simulated transport. Approximately 7 d after farrowing, 12 first parity gilts and their litters were ...

  15. The heat shock protein/chaperone network and multiple stress resistance

    KAUST Repository

    Jacob, Pierre

    2016-11-15

    Crop yield has been greatly enhanced during the last century. However, most elite cultivars are adapted to temperate climates and are not well suited to more stressful conditions. In the context of climate change, stress resistance is a major concern. To overcome these difficulties, scientists may help breeders by providing genetic markers associated with stress resistance. However, multi-stress resistance cannot be obtained from the simple addition of single stress resistance traits. In the field, stresses are unpredictable and several may occur at once. Consequently, the use of single stress resistance traits is often inadequate. Although it has been historically linked with the heat stress response, the heat shock protein (HSP)/chaperone network is a major component of multiple stress responses. Among the HSP/chaperone

  16. Thermal stress dependence of magnetic hysteretic processes in core–shell nanoparticles

    International Nuclear Information System (INIS)

    Dumitru, Ioan; Astefanoaei, Iordana; Stancu, Alexandru

    2013-01-01

    The control of thermal stresses in the core–shell structures is an important task in order to understand their temperature dependent magnetization processes. This paper is dedicated to a theoretical and micromagnetic study of the thermal stresses on the hysteretic processes in core–shell nanoparticles. The analytical model can predict the thermal and elastic behavior of the core–shell nanoparticle supposed to a forced cooling process. The temperature and thermal stresses values obtained by direct computation from the analytical model were used to evaluate the magneto-elastic energy of the core–shell system. A micromagnetic model was used to compute the equilibrium positions of the particle magnetization as function of the applied field. The model allows an evaluation of the increase of the particle coercive field and of the blocking temperature as an effect of the thermal stress

  17. A viewpoint on considering physiological principles to study stress resistance and resilience with aging.

    Science.gov (United States)

    Miller, Benjamin F; Seals, Douglas R; Hamilton, Karyn L

    2017-09-01

    Adaptation to stress is identified as one of the seven pillars of aging research. Our viewpoint discusses the importance of the distinction between stress resistance and resilience, highlights how integration of physiological principles is critical for further understanding in vivo stress resistance and resilience, and advocates for the use of early warning signs to prevent a tipping point in stress resistance and resilience. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. l-Arginine Enhances Resistance against Oxidative Stress and Heat Stress in Caenorhabditis elegans

    Directory of Open Access Journals (Sweden)

    Heran Ma

    2016-09-01

    Full Text Available The antioxidant properties of l-arginine (l-Arg in vivo, and its effect on enhancing resistance to oxidative stress and heat stress in Caenorhabditis elegans were investigated. C. elegans, a worm model popularly used in molecular and developmental biology, was used in the present study. Here, we report that l-Arg, at a concentration of 1 mM, prolonged C. elegans life by 26.98% and 37.02% under oxidative and heat stress, respectively. Further experiments indicated that the longevity-extending effects of l-Arg may be exerted by its free radical scavenging capacity and the upregulation of aging-associated gene expression in worms. This work is important in the context of numerous recent studies that concluded that environment stresses are associated with an increased population death rate.

  19. l-Arginine Enhances Resistance against Oxidative Stress and Heat Stress in Caenorhabditis elegans

    Science.gov (United States)

    Ma, Heran; Ma, Yudan; Zhang, Zhixian; Zhao, Ziyuan; Lin, Ran; Zhu, Jinming; Guo, Yi; Xu, Li

    2016-01-01

    The antioxidant properties of l-arginine (l-Arg) in vivo, and its effect on enhancing resistance to oxidative stress and heat stress in Caenorhabditis elegans were investigated. C. elegans, a worm model popularly used in molecular and developmental biology, was used in the present study. Here, we report that l-Arg, at a concentration of 1 mM, prolonged C. elegans life by 26.98% and 37.02% under oxidative and heat stress, respectively. Further experiments indicated that the longevity-extending effects of l-Arg may be exerted by its free radical scavenging capacity and the upregulation of aging-associated gene expression in worms. This work is important in the context of numerous recent studies that concluded that environment stresses are associated with an increased population death rate. PMID:27690079

  20. Thermal expansion coefficients of obliquely deposited MgF2 thin films and their intrinsic stress.

    Science.gov (United States)

    Jaing, Cheng-Chung

    2011-03-20

    This study elucidates the effects of columnar angles and deposition angles on the thermal expansion coefficients and intrinsic stress behaviors of MgF2 films with columnar microstructures. The behaviors associated with temperature-dependent stresses in the MgF2 films are measured using a phase-shifting Twyman-Green interferometer with a heating stage and the application of a phase reduction algorithm. The thermal expansion coefficients of MgF2 films at various columnar angles were larger than those of glass substrates. The intrinsic stress in the MgF2 films with columnar microstructures was compressive, while the thermal stress was tensile. The thermal expansion coefficients of MgF2 films with columnar microstructures and their intrinsic stress evidently depended on the deposition angle and the columnar angle.

  1. Simplified calculation of thermal stresses - on the reduction of effort in the stress analysis of reactor components

    International Nuclear Information System (INIS)

    Karow, K.

    1984-01-01

    The fatigue behaviour of reactor components is predominantly determined from the in-service thermal stresses. The calculation of such stresses for a number of temperature transients in the adjacent fluid may be expensive, particularly with complicated structures. Under certain conditions this expense can be reduced considerably with the aid of a rule, which permits interpolation of thermal stresses from known reference values instead of calculation. This paper presents the derivation and method of application of this interpolation rule. The derivation procedure is based on well-known proportionalities between thermal stress range Δsigma in the structure and temperature change ΔT and rate of change T of the fluid in the extreme cases of an ideal thermal shock and quasi-steady-state conditions, respectively. For the real transients in between the relationship Δsigma proportional (ΔT)sup(x) Tsup(1-x)αsup(y) is proposed, where x is the shock-degree and lies between 0 and 1, and, additionally, y designates the influence of the heat transfer coefficient α. This formula yields the interpolation rule. The rule permits interpolation of stress ranges for additional thermal transients from at least 3 reference stresses via x and y. The procedure is applicable to any metallic structure, reduces fatigue analysis effort considerably and yields excellent results. The paper is split up into 2 parts. In the following the derivation of the rule is presented. The second part describes its application and will be published shortly. (orig.)

  2. Infrared nondestructive measurement of thermal resistance between liner and engine block: design of experiment

    Energy Technology Data Exchange (ETDEWEB)

    Laloue, P.; L' Ecolier, J.; Nigon, F. [PSA Peugeot Citroen, Laboratoire Optique et Thermique, 45 rue Jean-Pierre Timbaud, 78 300 Poissy (France); Bissieux, C.; Henry, J.-F.; Pron, H. [Universite de Reims, Unite de Thermique et Analyse Physique, EA 3802, Laboratoire de Thermophysique, UFR Sciences, Moulin de la Housse, BP 1039, 51 687 Reims Cedex 2 (France)

    2008-03-15

    Thermal resistances between liners and engine blocks are nondestructively studied by photothermal infrared thermography. Under controlled sinusoidal light irradiation, the thermal response of the sample is measured by means of an infrared camera. A numerical lock-in procedure yields amplitude and absolute phase maps of the thermal field periodic component. Then, apart from classical qualitative detection of air layers, a quantitative characterization of thermal resistance becomes available. An analytical modeling, associated with an inverse procedure using the Gauss-Newton parameter estimation method, allows to identify the thermal resistance on academic samples representative of the liner-engine block interface. Simply joined cast iron and aluminum plates present thermal resistances about 2 x 10{sup -3} K m{sup 2} W{sup -1}. The implementation of a numerical modeling allows to study two-dimensional defects. When the samples are pressed on their periphery, thus straightened, contact resistances ranging from 2 x 10{sup -4} to 7 x 10{sup -4} K m{sup 2} W{sup -1} have been measured. Then, the method is applied to liner-engine block interfaces where the thermal resistances fall to about 2 x 10{sup -5} K m{sup 2} W{sup -1}, matching the values obtained when a cast iron plate is locally pressed against an aluminum plate. (author)

  3. Numerical simulation of high-temperature thermal contact resistance and its reduction mechanism

    Science.gov (United States)

    Zhang, Jing

    2018-01-01

    High-temperature thermal contact resistance (TCR) plays an important role in heat-pipe-cooled thermal protection structures due to the existence of contact interface between the embedded heat pipe and the heat resistive structure, and the reduction mechanism of thermal contact resistance is of special interests in the design of such structures. The present paper proposed a finite element model of the high-temperature thermal contact resistance based on the multi-point contact model with the consideration of temperature-dependent material properties, heat radiation through the cavities at the interface and the effect of thermal interface material (TIM), and the geometry parameters of the finite element model are determined by simple surface roughness test and experimental data fitting. The experimental results of high-temperature thermal contact resistance between superalloy GH600 and C/C composite material are employed to validate the present finite element model. The effect of the crucial parameters on the thermal contact resistance with and without TIM are also investigated with the proposed finite element model. PMID:29547651

  4. Thermal Stress of Surface of Mold Cavities and Parting Line of Silicone Molds

    OpenAIRE

    Bajčičák Martin; Šuba Roland

    2014-01-01

    The paper is focused on the study of thermal stress of surface of mold cavities and parting line of silicone molds after pouring. The silicone mold White SD - THT was thermally stressed by pouring of ZnAl4Cu3 zinc alloy with pouring cycle 20, 30 and 40 seconds. The most thermally stressed part of surface at each pouring cycle is gating system and mold cavities. It could be further concluded that linear increase of the pouring cycle time leads to the exponential increasing of the maximum tempe...

  5. Insulin resistance as a physiological defense against metabolic stress

    DEFF Research Database (Denmark)

    Nolan, Christopher J; Ruderman, Neil B; Kahn, Steven E

    2015-01-01

    challenging subgroup of patients with T2D who are overweight or obese with insulin resistance (IR) and the most refractory hyperglycemia due to an inability to change lifestyle to reverse positive energy balance. For this subgroup of patients with T2D, we question the dogma that IR is primarily harmful...... with intensive insulin therapy, could therefore be harmful. Treatments that nutrient off-load to lower glucose are more likely to be beneficial. The concepts of "IR as an adaptive defense mechanism" and "insulin-induced metabolic stress" may provide explanation for some of the unexpected outcomes of recent major...

  6. Transgenic plants: resistance to abiotic and biotic stresses

    Directory of Open Access Journals (Sweden)

    Akila Wijerathna-Yapa

    2017-06-01

    Full Text Available Today’s crop breeding combined with improved agricultural management has brought substantial increases in food production. But irrigation, fertilizers pest management requires a high energy input that creates a drain on the already scare fossil fuels. It is thus clear that different strategy has to be adopted to increase crop productivity further to meet the needs of rapidly increasing world population. Crop breeders are endeavoring to meet this challenge by developing crops with higher yield, better resistance to pest, disease and weedicides, tolerance to various stress conditions.

  7. High performance thermal stress analysis on the earth simulator

    International Nuclear Information System (INIS)

    Noriyuki, Kushida; Hiroshi, Okuda; Genki, Yagawa

    2003-01-01

    In this study, the thermal stress finite element analysis code optimized for the earth simulator was developed. A processor node of which of the earth simulator is the 8-way vector processor, and each processor can communicate using the message passing interface. Thus, there are two ways to parallelize the finite element method on the earth simulator. The first method is to assign one processor for one sub-domain, and the second method is to assign one node (=8 processors) for one sub-domain considering the shared memory type parallelization. Considering that the preconditioned conjugate gradient (PCG) method, which is one of the suitable linear equation solvers for the large-scale parallel finite element methods, shows the better convergence behavior if the number of domains is the smaller, we have determined to employ PCG and the hybrid parallelization, which is based on the shared and distributed memory type parallelization. It has been said that it is hard to obtain the good parallel or vector performance, since the finite element method is based on unstructured grids. In such situation, the reordering is inevitable to improve the computational performance [2]. In this study, we used three reordering methods, i.e. Reverse Cuthil-McKee (RCM), cyclic multicolor (CM) and diagonal jagged descending storage (DJDS)[3]. RCM provides the good convergence of the incomplete lower-upper (ILU) PCG, but causes the load imbalance. On the other hand, CM provides the good load balance, but worsens the convergence of ILU PCG if the vector length is so long. Therefore, we used the combined-method of RCM and CM. DJDS is the method to store the sparse matrices such that longer vector length can be obtained. For attaining the efficient inter-node parallelization, such partitioning methods as the recursive coordinate bisection (RCM) or MeTIS have been used. Computational performance of the practical large-scale engineering problems will be shown at the meeting. (author)

  8. Thermal shock resistances of a bonding material of C/C composite and copper

    International Nuclear Information System (INIS)

    Kurumada, Akira; Oku, Tatsuo; Kawamata, Kiyohiro; Motojima, Osamu; Noda, Nobuaki; McEnaney, B.

    1997-01-01

    The purpose of this study is to contribute to the development and the safety design of plasma facing components for fusion reactor devices. We evaluated the thermal shock resistance and the thermal shock fracture toughness of a bonding material which was jointed a carbon-fiber-reinforced carbon composite (C/C composite) to oxygen-free copper. We also examined the microstructures of the bonding layers using a scanning electron microscope before and after thermal shock tests. The bonding material did not fracture during thermal shock tests. However, thermal cracks and delamination cracks were observed in the bonding layers. (author)

  9. Progranulin causes adipose insulin resistance via increased autophagy resulting from activated oxidative stress and endoplasmic reticulum stress.

    Science.gov (United States)

    Guo, Qinyue; Xu, Lin; Li, Huixia; Sun, Hongzhi; Liu, Jiali; Wu, Shufang; Zhou, Bo

    2017-01-31

    Progranulin (PGRN) has recently emerged as an important regulator for insulin resistance. However, the direct effect of progranulin in adipose insulin resistance associated with the autophagy mechanism is not fully understood. In the present study, progranulin was administered to 3T3-L1 adipocytes and C57BL/6 J mice with/without specific inhibitors of oxidative stress and endoplasmic reticulum stress, and metabolic parameters, oxidative stress, endoplasmic reticulum stress and autophagy markers were assessed. Progranulin treatment increased iNOS expression, NO synthesis and ROS generation, and elevated protein expressions of CHOP, GRP78 and the phosphorylation of PERK, and caused a significant increase in Atg7 and LC3-II protein expression and a decreased p62 expression, and decreased insulin-stimulated tyrosine phosphorylation of IRS-1 and glucose uptake, demonstrating that progranulin activated oxidative stress and ER stress, elevated autophagy and induced insulin insensitivity in adipocytes and adipose tissue of mice. Interestingly, inhibition of iNOS and ER stress both reversed progranulin-induced stress response and increased autophagy, protecting against insulin resistance in adipocytes. Furthermore, the administration of the ER stress inhibitor 4-phenyl butyric acid reversed the negative effect of progranulin in vivo. Our findings showed the clinical potential of the novel adipokine progranulin in the regulation of insulin resistance, suggesting that progranulin might mediate adipose insulin resistance, at least in part, by inducing autophagy via activated oxidative stress and ER stress.

  10. Stem and stripe rust resistance in wheat induced by gamma rays and thermal neutrons

    International Nuclear Information System (INIS)

    Skorda, E.A.

    1977-01-01

    Attempts were made to produce rust-resistant mutants in wheat cultivars. Seeds of G-38290 and G-58383 (T. aestivum), Methoni and Ilectra (T. durum) varieties were irradiated with different doses of γ-rays (3.5, 5, 8, 11, 15 and 21 krad) and thermal neutrons (1.7, 4, 5.5, 7.5, 10.5 and 12.5x10 12 ) and the M 1 plants were grown under isolation in the field. The objective was mainly to induce stripe, leaf and stem rust resistance in G-38290, Methoni and Ilectra varieties and leaf rust resistance in G-58383. Mutations for rust resistance were detected by using the ''chimera method'' under natural and artificial field epiphytotic conditions in M 2 and successive generations. The mutants detected were tested for resistance to a broad spectrum of available races. Mutants resistant or moderately resistant to stripe and stem rusts but not to leaf rust, were selected from G-38290. From the other three varieties tested no rust-resistant mutants were detected. The frequency of resistant mutants obtained increased with increased γ-ray dose-rate, but not with increased thermal neutron doses. Some mutants proved to be resistant or moderately resistant to both rusts and others to one of them. Twenty of these mutants were evaluated for yield from M 5 to M 8 . Some of them have reached the final stage of regional yield trials and one, induced by thermal neutrons, was released this year. (author)

  11. Effects of Melatonin on Adrenal Cortical Functions of Indian Goats under Thermal Stress

    Directory of Open Access Journals (Sweden)

    Veerasamy Sejian

    2010-01-01

    Full Text Available The study was conducted with the primary objective to establish the influence of melatonin on adrenocortical functions to ameliorate thermal stress in goats. Endocrine secretions and several other blood biochemical parameters reflecting the animals adrenocortical stress response were determined over a one-week period after goats had been exposed to 40C∘ and 60%RH for 10 days. The study was conducted for a period of 17 days in psychrometric chamber. The animals served as self-controls prior to start of the experiment. Blood samples were drawn on day 10 to establish effect of thermal stress. Chemical adrenalectomy was achieved using metyrapone followed by exogenous melatonin treatment. 40C∘ of thermal stress which is quite normal in tropical zone significantly (P≤.05 influenced all parameters except plasma insulin. Metyrapone treatment significantly (P≤.05 affected plasma levels of glucose, total protein, total cholesterol, cortisol, and aldosterone. Metyrapone aggravated thermal stress by decreasing cortisol level in goats. Melatonin treatment at 11:00 AM significantly (P≤.05 influenced plasma levels of glucose, total protein, total cholesterol, cortisol, aldosterone and insulin. Metyrapone treatment aggravated thermal stress although administration of melatonin could ameliorate the condition. This establishes the role of melatonin in relieving thermal stress in goats.

  12. Verification of the Simultaneous Local Extraction Method of Base and Thermal Resistance of Bipolar Transistors

    OpenAIRE

    Robert Setekera; Luuk Tiemeijer; Ramses van der Toorn

    2014-01-01

    In this paper an extensive verification of the extraction method (published earlier) that consistently accounts for self-heating and Early effect to accurately extract both base and thermal resistance of bipolar junction transistors is presented. The method verification is demonstrated on advanced RF SiGe HBTs were the extracted results for the thermal resistance are compared with those from another published method that ignores the effect of Early effect on internal base...

  13. Wafer-scale fabrication of scanning thermal probes with integrated metal nanowire resistive elements for sensing and heating

    NARCIS (Netherlands)

    Hatakeyama, Kodai; Sarajlic, Edin; Siekman, Martin Herman; Jalabert, L.; Fujita, H.; Tas, Niels Roelof; Abelmann, Leon

    2014-01-01

    Scanning Thermal Microscopy (SThM) and micro-thermal analysis allow the study of thermal phenomena at micro- and nanoscale. We present a novel scanning resistive probe aimed for thermal imaging and localized thermal analysis. The probe features an AFM cantilever with a sharp pyramidal tip. Metal

  14. Effects of burn-off on thermal shock resistances of nuclear carbon materials

    International Nuclear Information System (INIS)

    Kurumada, A.; Oku, T.; Kawamata, K.; Hiraoka, T.; McEnaney, B.

    1997-01-01

    The purpose of this study is to evaluate the effects of burn-off on thermal shock resistance and thermal shock fracture toughness of a carbon fiber reinforced carbon composite (C/C composite) and three fine-grained isotropic graphites. The thermal shock resistance and thermal shock fracture toughness was degraded slightly by air oxidation at 500 o C. The extent of degradations of the thermal shock parameters were less than those of the mechanical and fracture mechanics properties, however, they were larger than that of the thermal diffusivity. In observations of the microstructures of the fracture surfaces after oxidation of the graphites, the size and the number of pores were increased and the fracture surfaces were rough due to oxidation of boundaries of graphite particles. After oxidation of the C/C composite, there were preferential removal of the boundary layer between carbon fiber and pyrolytic carbon matrix and pull out of carbon fiber. (author)

  15. Differential Glycosylation and Modulation of Camel and Human HSP Isoforms in Response to Thermal and Hypoxic Stresses

    Directory of Open Access Journals (Sweden)

    Abdullah Hoter

    2018-01-01

    Full Text Available Increased expression of heat shock proteins (HSPs following heat stress or other stress conditions is a common physiological response in almost all living organisms. Modification of cytosolic proteins including HSPs by O-GlcNAc has been shown to enhance their capabilities for counteracting lethal levels of cellular stress. Since HSPs are key players in stress resistance and protein homeostasis, we aimed to analyze their forms at the cellular and molecular level using camel and human HSPs as models for efficient and moderate thermotolerant mammals, respectively. In this study, we cloned the cDNA encoding two inducible HSP members, HSPA6 and CRYAB from both camel (Camelus dromedarius and human in a Myc-tagged mammalian expression vector. Expression of these chaperones in COS-1 cells revealed protein bands of approximately 25-kDa for both camel and human CRYAB and 70-kDa for camel HSPA6 and its human homologue. While localization and trafficking of the camel and human HSPs revealed similar cytosolic localization, we could demonstrate altered glycan structure between camel and human HSPA6. Interestingly, the glycoform of camel HSPA6 was rapidly formed and stabilized under normal and stress culture conditions whereas human HSPA6 reacted differently under similar thermal and hypoxic stress conditions. Our data suggest that efficient glycosylation of camel HSPA6 is among the mechanisms that provide camelids with a superior capability for alleviating stressful environmental circumstances.

  16. On plane stress state and stress free deformation of thick plate with FGM interface under thermal loading

    Science.gov (United States)

    Szubartowski, Damian; Ganczarski, Artur

    2016-10-01

    This paper demonstrates the plane stress state and the stress free thermo-elastic deformation of FGM thick plate under thermal loading. First, the Sneddon-Lockett theorem on the plane stress state in an isotropic infinite thick plate is generalized for a case of FGM problem in which all thermo-mechanical properties are optional functions of depth co-ordinate. The proof is based on application of the Iljushin thermo-elastic potential to displacement type system of equations that reduces it to the plane stress state problem. Then an existence of the purely thermal deformation is proved in two ways: first, it is shown that the unique solution fulfils conditions of simultaneous constant temperature and linear gradation of thermal expansion coefficient, second, proof is based directly on stress type system of equations which straightforwardly reduces to compatibility equations for purely thermal deformation if only stress field is homogeneous in domain and at boundary. Finally, couple examples of application to an engineering problem are presented.

  17. Thermal Stress Analysis of Medium-Voltage Converters for Smart Transformers

    DEFF Research Database (Denmark)

    Andresen, Markus; Ma, Ke; De Carne, Giovanni

    2017-01-01

    A smart transformer (ST) can take over an important managing role in the future electrical distribution grid system and can provide many advanced grid services compared to the traditional transformer. However, the risk is that the advanced functionality is balanced out by a lower reliability....... To address this concern, this work conducts thermal stress analysis for a modular multilevel converter (MMC), which is a promising solution for the medium voltage stage of the ST. The focus is put on the mission profiles of the transformer and the impact on the thermal stress of power semiconductor devices....... Normal operation at different power levels and medium voltage grid faults in a feeder fed by a traditional transformer are considered as well as the electrical and the thermal stress of the disconnection and the reconnection procedures. For the validation, the thermal stress of one MMC cell is reproduced...

  18. Characterization of a Silicon-Micromachined Thermal Shear-Stress Sensor

    National Research Council Canada - National Science Library

    Sheplak, Mark; Chandrasekaran, Venkataraman; Cain, Anthony; Nishida, Toshikazu; Cattafesta, Louis N

    2002-01-01

    A detailed characterization is presented of a silicon-micromachined thermal shear-stress sensor employing a thin-film platinum-sensing element on top of a silicon-nitride membrane that is stretched over a vacuum cavity...

  19. Microstructural evolution and stress-corrosion-cracking behavior of thermally aged Ni-Cr-Fe alloy

    International Nuclear Information System (INIS)

    Yoo, Seung Chang; Choi, Kyoung Joon; Kim, Taeho; Kim, Si Hoon; Kim, Ju Young; Kim, Ji Hyun

    2016-01-01

    Highlights: • Effects of long-term thermal aging on the nickel-based Alloy 600 were investigated. • Heat treatments simulating thermal aging were conducted by considering Cr diffusion. • Nano-indentation test results show hardening of thermally aged materials. • Thermally aged materials are more susceptible to stress corrosion cracking. • The property changes are attributed to the formation and evolution of precipitates. - Abstract: To understand the effect of long-term thermal aging in power plant systems, representative thick-walled Alloy 600 was prepared and thermally aged at 400 °C to fabricate samples with thermal aging effects similar to service operating conditions. Changes of microstructures, mechanical properties, and stress corrosion cracking susceptibility were investigated mainly through electron backscatter diffraction, nanoindentation, and high-temperature slow strain rate test. The formation of abundant semi-continuous precipitates with chromium depletion at grain boundaries was observed after thermally aged for 10 equivalent years. Also, alloys thermally aged for 10 equivalent years of thermal aging exhibited the highest susceptibility to stress corrosion cracking.

  20. Characterization of Contact and Bulk Thermal Resistance of Laminations for Electric Machines

    Energy Technology Data Exchange (ETDEWEB)

    Cousineau, J. Emily [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Bennion, Kevin [National Renewable Energy Laboratory (NREL), Golden, CO (United States); DeVoto, Doug [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Mihalic, Mark [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Narumanchi, Sreekant [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2015-06-30

    The ability to remove heat from an electric machine depends on the passive stack thermal resistances within the machine and the convective cooling performance of the selected cooling technology. This report focuses on the passive thermal design, specifically properties of the stator and rotor lamination stacks. Orthotropic thermal conductivity, specific heat, and density are reported. Four materials commonly used in electric machines were tested, including M19 (29 and 26 gauge), HF10, and Arnon 7 materials.

  1. Study on Stress Development in the Phase Transition Layer of Thermal Barrier Coatings

    Directory of Open Access Journals (Sweden)

    Yijun Chai

    2016-09-01

    Full Text Available Stress development is one of the significant factors leading to the failure of thermal barrier coating (TBC systems. In this work, stress development in the two phase mixed zone named phase transition layer (PTL, which grows between the thermally grown oxide (TGO and the bond coat (BC, is investigated by using two different homogenization models. A constitutive equation of the PTL based on the Reuss model is proposed to study the stresses in the PTL. The stresses computed with the proposed constitutive equation are compared with those obtained with Voigt model-based equation in detail. The stresses based on the Voigt model are slightly higher than those based on the Reuss model. Finally, a further study is carried out to explore the influence of phase transition proportions on the stress difference caused by homogenization models. Results show that the stress difference becomes more evident with the increase of the PTL thickness ratio in the TGO.

  2. An anisotropic thermal-stress model for through-silicon via

    Science.gov (United States)

    Liu, Song; Shan, Guangbao

    2018-02-01

    A two-dimensional thermal-stress model of through-silicon via (TSV) is proposed considering the anisotropic elastic property of the silicon substrate. By using the complex variable approach, the distribution of thermal-stress in the substrate can be characterized more accurately. TCAD 3-D simulations are used to verify the model accuracy and well agree with analytical results (Manufacturing Technology Research Joint Fund (No. U1537208).

  3. Thermal stress in flexible interdigital transducers with anisotropic electroactive cellulose substrates

    Science.gov (United States)

    Yoon, Sean J.; Kim, Jung Woong; Kim, Hyun Chan; Kang, Jinmo; Kim, Jaehwan

    2017-12-01

    Thermal stress in flexible interdigital transducers a reliability concern in the development of flexible devices, which may lead to interface delamination, stress voiding and plastic deformation. In this paper, a mathematical model is presented to investigate the effect of material selections on the thermal stress in interdigital transducers. We modified the linear relationships in the composite materials theory with the effect of high curvature, anisotropic substrate and small substrate thickness. We evaluated the thermal stresses of interdigital transducers, fabricated with various electrodes, insulators and substrate materials for the comparison. The results show that, among various insulators, organic polymer developed the highest stress level while oxide showed the lowest stress level. Aluminium shows a higher stress level and curvature as an electrode than gold. As substrate materials, polyimide and electroactive cellulose show similar stress levels except the opposite sign convention to each other. Polyimide shows positive curvatures while electroactive cellulose shows negative curvatures, which is attributed to the stress and thermal expansion state of the metal/insulator composite. The results show that the insulator is found to be responsible for the confinement across the metal lines while the substrate is responsible for the confinement along the metal lines.

  4. Tasco®, a Product of Ascophyllum nodosum, Imparts Thermal Stress Tolerance in Caenorhabditis elegans

    Directory of Open Access Journals (Sweden)

    Franklin Evans

    2011-11-01

    Full Text Available Tasco®, a commercial product manufactured from the brown alga Ascophyllum nodosum, has been shown to impart thermal stress tolerance in animals. We investigated the physiological, biochemical and molecular bases of this induced thermal stress tolerance using the invertebrate animal model, Caenorhabiditis elegans. Tasco® water extract (TWE at 300 µg/mL significantly enhanced thermal stress tolerance as well as extended the life span of C. elegans. The mean survival rate of the model animals under thermal stress (35 °C treated with 300 µg/mL and 600 µg/mL TWE, respectively, was 68% and 71% higher than the control animals. However, the TWE treatments did not affect the nematode body length, fertility or the cellular localization of daf-16. On the contrary, TWE under thermal stress significantly increased the pharyngeal pumping rate in treated animals compared to the control. Treatment with TWE also showed differential protein expression profiles over control following 2D gel-electrophoresis analysis. Furthermore, TWE significantly altered the expression of at least 40 proteins under thermal stress; among these proteins 34 were up-regulated while six were down-regulated. Mass spectroscopy analysis of the proteins altered by TWE treatment revealed that these proteins were related to heat stress tolerance, energy metabolism and a muscle structure related protein. Among them heat shock proteins, superoxide dismutase, glutathione peroxidase, aldehyde dehydrogenase, saposin-like proteins 20, myosin regulatory light chain 1, cytochrome c oxidase RAS-like, GTP-binding protein RHO A, OS were significantly up-regulated, while eukaryotic translation initiation factor 5A-1 OS, 60S ribosomal protein L18 OS, peroxiredoxin protein 2 were down regulated by TWE treatment. These results were further validated by gene expression and reporter gene expression analyses. Overall results indicate that the water soluble components of Tasco® imparted thermal stress

  5. Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium from Corals.

    Directory of Open Access Journals (Sweden)

    Lisa Fujise

    Full Text Available 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.

  6. Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium) from Corals.

    Science.gov (United States)

    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.

  7. On Residual Stresses in Resistance Spot-Welded Aluminum Alloy 6061-T6: Experimental and Numerical Analysis

    Science.gov (United States)

    Afshari, D.; Sedighi, M.; Karimi, M. R.; Barsoum, Z.

    2013-12-01

    In this study, an electro-thermal-structural-coupled finite element (FE) model and x-ray diffraction residual stress measurements have been utilized to analyze distribution of residual stresses in an aluminum alloy 6061-T6 resistance spot-welded joint with 2-mm-thickness sheet. Increasing the aluminum sheet thickness to more than 1 mm leads to creating difficulty in spot-welding process and increases the complexity of the FE model. The electrical and thermal contact conductances, as mandatory factors are applied in contact areas of electrode-workpiece and workpiece-workpiece to resolve the complexity of the FE model. The physical and mechanical properties of the material are defined as thermal dependent to improve the accuracy of the model. Furthermore, the electrodes are removed after the holding cycle using the birth-and-death elements method. The results have a good agreement with experimental data obtained from x-ray diffraction residual stress measurements. However, the highest internal tensile residual stress occurs in the center of the nugget zone and decreases toward nugget edge; surface residual stress increases toward the edge of the welding zone and afterward, the area decreases slightly.

  8. Effect of posture positions on the evaporative resistance and thermal insulation of clothing.

    Science.gov (United States)

    Wu, Y S; Fan, J T; Yu, W

    2011-03-01

    Evaporative resistance and thermal insulation of clothing are important parameters in the design and engineering of thermal environments and functional clothing. Past work on the measurement of evaporative resistance of clothing was, however, limited to the standing posture with or without body motion. Information on the evaporative resistance of clothing when the wearer is in a sedentary or supine posture and how it is related to that when the wearer is in a standing posture is lacking. This paper presents original data on the effect of postures on the evaporative resistance of clothing, thermal insulation and permeability index, based on the measurements under three postures, viz. standing, sedentary and supine, using the sweating fabric manikin-Walter. Regression models are also established to relate the evaporative resistance and thermal insulation of clothing under sedentary and supine postures to those under the standing posture. The study further shows that the apparent evaporated resistances of standing and sedentary postures measured in the non-isothermal condition are much lower than those in the isothermal condition. The apparent evaporative resistances measured using the mass loss method are generally lower than those measured using the heat loss method due to moisture absorption or condensation within clothing. STATEMENT OF RELEVANCE: The thermal insulation and evaporative resistance values of clothing ensembles under different postures are essential data for the ergonomics design of thermal environments (e.g. indoors or a vehicle's interior environment) and functional clothing. They are also necessary for the prediction of thermal comfort or duration of exposure in different environmental conditions.

  9. Role of the Stringent Stress Response in the Antibiotic Resistance Phenotype of Methicillin-Resistant Staphylococcus aureus.

    Science.gov (United States)

    Aedo, Sandra; Tomasz, Alexander

    2016-04-01

    Resistance to beta-lactam antibiotics in methicillin-resistantStaphylococcus aureus(MRSA) requires the presence of an acquired genetic determinant,mecAormecC, which encode penicillin-binding protein PBP2A or PBP2A', respectively. Although all MRSA strains share a mechanism of resistance, the phenotypic expression of beta-lactam resistance shows considerable strain-to-strain variation. The stringent stress response, a stress response that results from nutrient limitation, was shown to play a key role in determining the resistance level of an MRSA strain. In the present study, we validated the impact of the stringent stress response on transcription and translation ofmecAin the MRSA clinical isolate strain N315, which also carries known regulatory genes (mecI/mecR1/mecR2andblaI/blaR1) formecAtranscription. We showed that the impact of the stringent stress response on the resistance level may be restricted to beta-lactam resistance based on a "foreign" determinant such asmecA, as opposed to resistance based on mutations in the nativeS. aureusdeterminantpbpB(encoding PBP2). Our observations demonstrate that high-level resistance mediated by the stringent stress response follows the current model of beta-lactam resistance in which the native PBP2 protein is also essential for expression of the resistance phenotype. We also show that theStaphylococcus sciuri pbpDgene (also calledmecAI), the putative evolutionary precursor ofmecA, confers oxacillin resistance in anS. aureusstrain, generating a heterogeneous phenotype that can be converted to high and homogenous resistance by induction of the stringent stress response in the bacteria. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  10. Effects of melatonin on the proliferation and apoptosis of sheep granulosa cells under thermal stress.

    Science.gov (United States)

    Fu, Yao; He, Chang-Jiu; Ji, Peng-Yun; Zhuo, Zhi-Yong; Tian, Xiu-Zhi; Wang, Feng; Tan, Dun-Xian; Liu, Guo-Shi

    2014-11-14

    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 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.

  11. ABOUT THE STUDY OF THE THERMAL STRESS FOR NAVAL SYSTEMS

    Directory of Open Access Journals (Sweden)

    ANASASE PRUIU

    2016-06-01

    Full Text Available In this paper are presented and analyzed the effects of thermal expansion on gas evacuation piping from naval power plants an d technical protection possibilities to prevent structures from deformations; also are analyzed the possibilities for the use of thermal expansion for tightening the main screws for power plant propulsion.

  12. Effect of Thermal Stresses on the Failure Criteria of Fiber Composites

    DEFF Research Database (Denmark)

    Leong, Martin Klitgaard; Sankar, Bhavani V.

    2010-01-01

    When composite laminates are operated at cryogenic temperatures, thermal stresses arise. This is due to the difference in coefficients of thermal expansion of different plies and also between the fiber and matrix. While the former is taken into account in the composite structural analysis, the la...

  13. Effect of thermal stress of short duration on the red blood cell ...

    African Journals Online (AJOL)

    African Journal of Biotechnology ... After period of adaptation (three weeks), half of the fish (24) were used as a control group while the other 24 were subjected to thermal stress by raising the water ... In both control and thermally treated, fish blood was collected by heart puncture according to “Animal welfare act“. Analyses ...

  14. Stressful life events are associated with insulin resistance among Chinese immigrant women in the United States

    Directory of Open Access Journals (Sweden)

    Carolyn Y. Fang

    2015-01-01

    Conclusions: This is one of the first studies to examine the associations between psychosocial stress and insulin resistance in Chinese immigrant women. These findings contribute to a growing body of literature on stress and diabetes risk in an immigrant population.

  15. A thermal plasmonic sensor platform: resistive heating of nanohole arrays.

    Science.gov (United States)

    Virk, Mudassar; Xiong, Kunli; Svedendahl, Mikael; Käll, Mikael; Dahlin, Andreas B

    2014-06-11

    We have created a simple and efficient thermal plasmonic sensor platform by letting a DC current heat plasmonic nanohole arrays. The sensor can be used to determine thermodynamic parameters in addition to monitoring molecular reactions in real-time. As an application example, we use the thermal sensor to determine the kinetics and activation energy for desorption of thiol monolayers on gold. Further, the temperature of the metal can be measured optically by the spectral shift of the bonding surface plasmon mode (0.015 nm/K). We show that this resonance shift is caused by thermal lattice expansion, which reduces the plasma frequency of the metal. The sensor is also used to determine the thin film thermal expansion coefficient through a theoretical model for the expected resonance shift.

  16. DETERMINING THE THERMAL RESISTANCE OF A VENTILATED HINGED FACADE SYSTEM LAYER

    Directory of Open Access Journals (Sweden)

    Gagarin Vladimir Gennad'evich

    2015-03-01

    Full Text Available Enveloping structures with hinged façade systems are nowadays widely used for moisture control of enveloping structures, prevention of overheating of the structures by insolation, saving the constructions from atmospheric moisture and also for correspondence with the raised requirements to thermal protection of the enveloping structures, aimed also at reducing energy consumption. In the winter conditions the influence of air layer on the thermal insulation parameters is usually neglected. In the article the thermal resistance of an air gap and is considered and its effect in the calculation of the heat resistance of a building envelope with hinged facade system is analyzed in the conditions of cold weather. The thermal resistance of the air layer determines how the heat losses decrease.

  17. Development of the variety for resistance against bacterial leaf-blight in rice with thermal neutrons

    International Nuclear Information System (INIS)

    Nakai, Hirokazu

    1990-01-01

    In search for the development of genes for resistance against bacterial leaf-blight in rice, thermal neutrons generated from the Research Reactor at the Kyoto University have been applied to the breeding. In this paper, the developmental outcome is described, and a potential application of thermal neutrons for breeding the variety of resistance against bacterial leaf-blight in rice is reviewed. When thermal neutrons were delivered to the rice, the ratio of absorbed doses by B-10, which is contained in a small quantity in the plant, was found to be larger than expected. This implies characteristic effects of thermal neutrons on the plant. When boric acid was incorporated into the plant before irradiation, the effect of thermal neutrons per irradiation time was considered to become great. The frequency of mutations for resistance was significantly higher by thermal neutron, as compared with that induced by other mutagens, such as gamma radiation, ethylene-imine, ethyl-methane-sulfonate, and nitroso-methyl-urea. Genetic analysis of mutants for resistance revealed recessive genes and polygenes. Finally, the application of thermal neutrons and other radiations would contribute greatly to a resolution of serious pollution problems in global food and environment. (N.K.)

  18. Calculation of thermal stress condition in long metal cylinder under heating by continuous laser radiation

    International Nuclear Information System (INIS)

    Uglov, A.A.; Uglov, S.A.; Kulik, A.N.

    1997-01-01

    The method of determination of temperature field and unduced thermal stresses in long metallic cylinder under its heating by cw-laser normally distributed heat flux is offered. The graphically presented results of calculation show the stress maximum is placed behind of center of laser heat sport along its movement line on the cylinder surface

  19. A numerical analysis method on thermal and shrinkage stress of concrete

    International Nuclear Information System (INIS)

    Takiguchi, Katsuki; Hotta, Hisato

    1991-01-01

    Thermal stress often causes cracks in large scale concrete such as that for dam construction. The drying shrinkage of concrete causes cracks in concrete structures. These thermal stress and drying shrinkage stress may be the main reasons cracks occur in concrete, however there is few research which dealt with both stresses together. The problems on the thermal stress and the drying shrinkage are not independent, and should be dealt with together, because both temperature and water content of concrete affect hydration reaction, and the degree of hydration determines all the characteristics of concrete at early age. In this study, the degree of hydration is formulated experimentally, and a numerical stress analysis method taking the hydration reaction in consideration is presented. The formulation of the rate of hydration reaction, the method of analyzing thermal and drying shrinkage stresses, the analytical results for a concrete column and the influence that continuous load exerted to the tensile strength of concrete are reported. The relatively high stress nearly equal to the tensile strength of concrete arises near the surface. (K.I.)

  20. Using High-Resolution Hand-Held Radiometers To Measure In-Situ Thermal Resistance

    Science.gov (United States)

    Burch, Douglas M.; Krintz, Donald F.

    1984-03-01

    A field study was carried out to investigate the accuracy of using high-resolution radiometers to determine the in situ thermal resistance of building components having conventional residential construction. Two different types of radiometers were used to determine the thermal resistances of the walls of six test buildings located at the National Bureau of Standards. These radiometer thermal resistance measurements were compared to reference thermal resistance values determined from steady-state series resistance predictions, time-averaged heat-flow-sensor measurements, and guarded-hot-box measurements. When measurements were carried out 5 hours after sunset when the outdoor temperature was relatively steady and the heating plant was operated in a typical cyclic fashion, the following results were obtained: for lightweight wood-frame cavity walls, the radiometer procedures were found to distinguish wall thermal resistance 4.4 h.ft2- °F/Btu (0.77 m2•K/W) systematically higher than corresponding reference values. Such a discrimination will per-mit insulated and uninsulated walls to be distinguished. However, in the case of walls having large heat capacity (e.g., masonry and log), thermal storage effects produced large time lags between the outdoor diurnal temperature variation and the heat-flow response at the inside surface. This phenomenon caused radiometer thermal resistances to deviate substantially from corresponding reference values. This study recommends that the ANSI/ASHRAE Standard 101-1981 be modified requiring the heating plant to be operated in a typical cyclic fashion instead of being turned off prior to and during radiometer measurements.

  1. Bidirectional negative differential thermal resistance in three-segment Frenkel–Kontorova lattices

    International Nuclear Information System (INIS)

    Ou, Ya-li; Lu, Shi-cai; Hu, Cai-tian; Ai, Bao-quan

    2016-01-01

    By coupling three nonlinear 1D lattice segments, we demonstrate a thermal insulator model, where the system acts like an insulator for large temperature bias and a conductor for very small temperature bias. We numerically investigate the parameter range of the thermal insulator and find that the nonlinear response (the role of on-site potential), the weakly coupling interaction between each segment, and the small system size collectively contribute to the appearance of bidirectional negative differential thermal resistance (BNDTR). The corresponding exhibition of BNDTR can be explained in terms of effective phonon-band shifts. Our results can provide a new perspective for understanding the microscopic mechanism of negative differential thermal resistance and also would be conducive to further developments in designing and fabricating thermal devices and functional materials. (paper)

  2. Improved resistance of chemically-modified nanocellulose against thermally-induced depolymerization.

    Science.gov (United States)

    Agustin, Melissa B; Nakatsubo, Fumiaki; Yano, Hiroyuki

    2017-05-15

    The study demonstrated the improvement in the resistance of nanocellulose against thermally-induced depolymerization by esterification with benzoyl (BNZ) and pivaloyl (PIV). The change in the degree of polymerization (DP) and molecular weight distribution (MWD) after thermal treatment in nitrogen and in air was investigated using viscometry and gel permeation chromatography. BNZ and PIV nanocellulose esters without α-hydrogens gave higher DP and narrower MWD than pure bacterial cellulose; and the acetyl and myristoyl esters, which possess α-hydrogens. Results also showed that when depolymerization is suppressed, thermal discoloration is also reduced. Resistance against depolymerization inhibits the formation of reducing ends which can be active sites for thermal discoloration. Finally, the findings suggest that benzoylation and pivaloylation can be an excellent modification technique to improve the thermal stability of nanocellulose. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Rock properties and their effect on thermally-induced displacements and stresses

    International Nuclear Information System (INIS)

    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

  4. Preliminary thermal and stress analysis of the SINQ window

    International Nuclear Information System (INIS)

    Heidenreich, G.

    1991-01-01

    Preliminary results of a finite element analysis for the SINQ proton beam window are presented. Temperatures and stresses are calculated in an axisymmetric model. As a result of these calculations, the H 2 O-cooled window (safety window) could be redesigned in such a way that plastic deformation resulting from excessive stress in some areas is avoided. (author)

  5. Thermal Stress of Surface of Mold Cavities and Parting Line of Silicone Molds

    Directory of Open Access Journals (Sweden)

    Bajčičák Martin

    2014-06-01

    Full Text Available The paper is focused on the study of thermal stress of surface of mold cavities and parting line of silicone molds after pouring. The silicone mold White SD - THT was thermally stressed by pouring of ZnAl4Cu3 zinc alloy with pouring cycle 20, 30 and 40 seconds. The most thermally stressed part of surface at each pouring cycle is gating system and mold cavities. It could be further concluded that linear increase of the pouring cycle time leads to the exponential increasing of the maximum temperature of mold surface after its cooling. The elongated pouring cycle increases the temperature accumulated on the surface of cavities and the ability of silicone mold to conduct the heat on its surface decreases, because the low thermal conductivity of silicone molds enables the conduction of larger amount of heat into ambient environment.

  6. Thermal Stress of Surface of Mold Cavities and Parting Line of Silicone Molds

    Science.gov (United States)

    Bajčičák, Martin; Šuba, Roland

    2014-06-01

    The paper is focused on the study of thermal stress of surface of mold cavities and parting line of silicone molds after pouring. The silicone mold White SD - THT was thermally stressed by pouring of ZnAl4Cu3 zinc alloy with pouring cycle 20, 30 and 40 seconds. The most thermally stressed part of surface at each pouring cycle is gating system and mold cavities. It could be further concluded that linear increase of the pouring cycle time leads to the exponential increasing of the maximum temperature of mold surface after its cooling. The elongated pouring cycle increases the temperature accumulated on the surface of cavities and the ability of silicone mold to conduct the heat on its surface decreases, because the low thermal conductivity of silicone molds enables the conduction of larger amount of heat into ambient environment.

  7. Thermal properties and thermal shock resistance of liquid phase sintered ZrC-Mo cermets

    International Nuclear Information System (INIS)

    Landwehr, Sean E.; Hilmas, Gregory E.; Fahrenholtz, William G.; Talmy, Inna G.; Wang Hsin

    2009-01-01

    The linear thermal expansion coefficient (CTE), heat capacity, and thermal conductivity, were investigated as a function of temperature for hot pressed ZrC and liquid phase sintered ZrC-Mo cermets. The ZrC and the ZrC-Mo cermets had the same CTE at 50 deg. C (∼5.1-5.5 ppm deg. C -1 ), but the CTE of ZrC increased to ∼12.2 ppm deg. C -1 at 1000 deg. C compared to ∼7.2-8.5 ppm deg. C -1 for the ZrC-Mo cermets. Heat capacity was calculated using a rule of mixtures and previously reported thermodynamic data. Thermal diffusivity was measured with a laser flash method and was, in turn, used to calculate thermal conductivity. Thermal conductivity increased linearly with increasing temperature for all compositions and was affected by solid solution formation and carbon deficiency of the carbide phases. Hot pressed ZrC had the highest thermal conductivity (∼30-37 W m -1 K -1 ). The nominally 20 and 30 vol% Mo compositions of the ZrC-Mo cermets had a lower thermal conductivity, but the thermal conductivity generally increased with increasing Mo content. Water quench thermal shock testing showed that ZrC-30 vol% Mo had a critical temperature difference of 350 deg. C, which was ∼120 deg. C higher than ZrC. This increase was due to the increased toughness of the cermet compared to ZrC.

  8. Investigation of effective factors of transient thermal stress of the MONJU-System components

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Masaaki; Hirayama, Hiroshi; Kimura, Kimitaka; Jinbo, M. [Toshiba Corp., Kawasaki, Kanagawa (Japan)

    1999-03-01

    Transient thermal stress of each system Component in the fast breeder reactor is an uncertain factor on it's structural design. The temperature distribution in a system component changes over a wide range in time and in space. An unified evaluation technique of thermal, hydraulic, and structural analysis, in which includes thermal striping, temperature stratification, transient thermal stress and the integrity of the system components, is required for the optimum design of tho fast reactor plant. Thermal boundary conditions should be set up by both the transient thermal stress analysis and the structural integrity evaluation of each system component. The reasonable thermal boundary conditions for the design of the MONJU and a demonstration fast reactor, are investigated. The temperature distribution analysis models and the thermal boundary conditions on the Y-piece structural parts of each system component, such as reactor vessel, intermediate heat exchanger, primary main circulation pump, steam generator, superheater and upper structure of reactor core, are illustrated in the report. (M. Suetake)

  9. Study on the Thermal Resistance of Multi-chip Module High Power LED Packaging Heat Dissipation System

    Directory of Open Access Journals (Sweden)

    Kailin Pan

    2014-10-01

    Full Text Available Thermal resistance is a key technical index which indicates the thermal management of multi-chip module high power LED (MCM-LED packaging heat dissipation system. In this paper, the prototype structure of MCM-LED packaging heat dissipation system is proposed to study the reliable thermal resistance calculation method. In order to analyze the total thermal resistance of the MCM-LED packaging heat dissipation system, three kinds of thermal resistance calculation method including theoretical calculation, experimental testing and finite element simulation are developed respectively. Firstly, based on the thermal resistance network model and the principle of steady state heat transfer, the theoretical value of total thermal resistance is 6.111 K/W through sum of the thermal resistance of every material layer in the major direction of heat flow. Secondly, the thermal resistance experiment is carried out by T3Ster to obtain the experimental result of total thermal resistance, and the value is 6.729 K/W. Thirdly, a three-dimensional finite element model of MCM-LED packaging heat dissipation system is established, and the junction temperature experiment is also performed to calculated the finite element simulated result of total thermal resistance, the value is 6.99 K/W. Finally, by comparing the error of all the three kinds of result, the error of total thermal resistance between the theoretical value and experimental result is 9.2 %, and the error of total thermal resistance between the experimental result and finite element simulation is only about -3.9 %, meanwhile, the main reason of each error is discussed respectively.

  10. Average thermal stress in the Al+SiC composite due to its manufacturing process

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Carlos A.J.; Libardi, Rosani M.P.; Marcelino, Sergio; Boari, Zoroastro M., E-mail: cmiranda@ipen.br, E-mail: rmpenha@ipen.br, E-mail: sergio.marcelino@gmail.com, E-mail: zoroastr@uol.com.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Engenharia Nuclear

    2013-07-01

    The numerical analyses framework to obtain the average thermal stress in the Al+SiC Composite due to its manufacturing process is presented along with the obtained results. The mixing of Aluminum and SiC powders is done at elevated temperature and the usage is at room temperature. A thermal stress state arises in the composite due to the different thermal expansion coefficients of the materials. Due to the particles size and randomness in the SiC distribution, some sets of models were analyzed and a statistical procedure used to evaluate the average stress state in the composite. In each model the particles position, form and size are randomly generated considering a volumetric ratio (VR) between 20% and 25%, close to an actual composite. The obtained stress field is represented by a certain number of iso stress curves, each one weighted by the area it represents. Systematically it was investigated the influence of: (a) the material behavior: linear x non-linear; (b) the carbide particles form: circular x quadrilateral; (c) the number of iso stress curves considered in each analysis; and (e) the model size (the number of particles). Each of above analyzed condition produced conclusions to guide the next step. Considering a confidence level of 95%, the average thermal stress value in the studied composite (20% ≤ VR ≤ 25%) is 175 MPa with a standard deviation of 10 MPa. Depending on its usage, this value should be taken into account when evaluating the material strength. (author)

  11. Average thermal stress in the Al+SiC composite due to its manufacturing process

    International Nuclear Information System (INIS)

    Miranda, Carlos A.J.; Libardi, Rosani M.P.; Marcelino, Sergio; Boari, Zoroastro M.

    2013-01-01

    The numerical analyses framework to obtain the average thermal stress in the Al+SiC Composite due to its manufacturing process is presented along with the obtained results. The mixing of Aluminum and SiC powders is done at elevated temperature and the usage is at room temperature. A thermal stress state arises in the composite due to the different thermal expansion coefficients of the materials. Due to the particles size and randomness in the SiC distribution, some sets of models were analyzed and a statistical procedure used to evaluate the average stress state in the composite. In each model the particles position, form and size are randomly generated considering a volumetric ratio (VR) between 20% and 25%, close to an actual composite. The obtained stress field is represented by a certain number of iso stress curves, each one weighted by the area it represents. Systematically it was investigated the influence of: (a) the material behavior: linear x non-linear; (b) the carbide particles form: circular x quadrilateral; (c) the number of iso stress curves considered in each analysis; and (e) the model size (the number of particles). Each of above analyzed condition produced conclusions to guide the next step. Considering a confidence level of 95%, the average thermal stress value in the studied composite (20% ≤ VR ≤ 25%) is 175 MPa with a standard deviation of 10 MPa. Depending on its usage, this value should be taken into account when evaluating the material strength. (author)

  12. Thermal stress and topography control on the exfoliation of spheroidal granite boulders in Pricopan Ridge, Macin Mountains, Romania

    Science.gov (United States)

    Vasile, Mirela; Vespremeanu-Stroe, Alfred

    2017-04-01

    Exfoliation is one of the most frequent processes of granite landforms shaping, its intensity being usually associated with the cumulated action of thermal stresses. Although exfoliation microforms are present on granite landforms in most of the warm-climates, the controlling factors of this process are not yet well defined. Within this study, we investigated the distribution pattern of the exfoliation microforms identified on the surface of 40 rounded granite boulders mapped on the western slope of Pricopan Ridge (Macin Mountains), in a semi-arid temperate environment (Northern Dobrogea, Romania). Continuous rock near-surface temperature measurement on a reference boulder over a four years period allowed us to evaluate the frequency and intensity of the rock thermal oscillations, taking into account (as control factors) (i) the fast temperature changes generated by convective summer rain events, (ii) the day-night temperature variations and (iii) the occurrence of freeze-thaw oscillations during winter. The relative rock strength at the rock surface was determined by Schmidt Hammer tests, which highlighted a reduced resistance of the boulder areas oriented towards South (mean rebound values of 27-33) compared to the North-exposed ones (mean rebound values of 43-50). Over a North-South profile of the boulders, the lowest resistance of the rock surface corresponds to their gently sloping southern faces (at slope values of 0-45 degrees (°)), which indicates a higher susceptibility of these sectors to be affected by weathering processes. These specific areas (gently-sloping faces of the rounded granite boulders) overlap the sector of high frequency and intensity of the investigated thermal-stress inducing processes, all three of them reaching the highest peak on the South-face of the boulders at slopes of 20°-30°. Correspondently, the exfoliation microforms mapped and morphometrically described in this study are developed most frequently in the area delimited by

  13. Effects of Thermal Resistance on One-Dimensional Thermal Analysis of the Epidermal Flexible Electronic Devices Integrated with Human Skin

    Science.gov (United States)

    Li, He; Cui, Yun

    2017-12-01

    Nowadays, flexible electronic devices are increasingly used in direct contact with human skin to monitor the real-time health of human body. Based on the Fourier heat conduction equation and Pennes bio-heat transfer equation, this paper deduces the analytical solutions of one - dimensional heat transfer for flexible electronic devices integrated with human skin under the condition of a constant power. The influence of contact thermal resistance between devices and skin is considered as well. The corresponding finite element model is established to verify the correctness of analytical solutions. The results show that the finite element analysis agrees well with the analytical solution. With bigger thermal resistance, temperature increase of skin surface will decrease. This result can provide guidance for the design of flexible electronic devices to reduce the negative impact that exceeding temperature leave on human skin.

  14. Thermal Cyclic Resistance Polyester Resin Composites Reinforce Fiber Nut Shell

    Science.gov (United States)

    Fahmi, Hendriwan

    2017-12-01

    The purpose of study is to determine the effect of fiber length and thermal cyclic of the bending strength of polyester resin composite reinforced by fibers nut shell. The materials used in this study is a nut shell fibers with fiber length of 1 cm, 2 cm and 3 cm and polyester resin with composition 70-30%wt. Fiber nut shell treated soaking in NaOH 30% for 30 minutes, then rinse with clean water so that the fiber free of alkali and then dried. Furthermore, the composite is heated in an oven to a temperature of 100°C for 1 hour and then cooled in the open with a variety of thermal cyclic 30, 40, and 50 times. Bending properties of composites known through the testing process using a three-point bending test equipment universal testing machine. The test results show that the bending strength bending highest in fiber length of 3 cm with 30 treatment cycles of thermal to the value of 53.325 MPa, while the lowest occurred in bending strength fiber length of 1 cm with no cycles of thermal treatment to the value of 30.675 MPa.

  15. Thermal resistance and conductivity of recycled construction and demolition waste (RCDW concrete blocks

    Directory of Open Access Journals (Sweden)

    Ivan Julio Apolonio Callejas

    Full Text Available Abstract In Brazil, studies to reuse construction and demolition waste are a special issue because a large amount of this material has been delivered to the public landfills and in illegal places. Some researchers have suggested reusing this material in building elements, such as bricks or blocks. It is possible to find a lot of researches in physical/mechanical characterization, while little effort has been made to characterize recycled construction and demolition waste blocks (RCDW for their thermal properties. The aim of this work was to characterize the RCDW thermal resistance and conductivity in order to provide subsidies for a building's thermal performance analysis. The hot-box method was adapted, together with measuring techniques with a heat-flow meter to determine the RCDW thermal properties. The results indicated that the RCDW block overall thermal resistance and thermal conductivity in the solid region was within the intervals of 0.33≤RT≤0.41m2KW-1 and 0.60≤l≤0.78Wm-1K-1, respectively. The lower resistance and conductivity values are justified by the presence of aggregate with a lower density and lower thermal conductivity than the natural aggregate.

  16. Non-uniform temperature gradients and thermal stresses produced ...

    Indian Academy of Sciences (India)

    induced stress distributions in a hollow steel sphere heated by a moving uniform heat source applied on a certain zenithal segment (the heated zenithal segment, Θ H ) of its outer surface (the processed surface) under stagnant ambient ...

  17. [Advances in molecular mechanisms of bacterial resistance caused by stress-induced transfer of resistance genes--a review].

    Science.gov (United States)

    Sun, Dongchang; Wang, Bing; Zhu, Lihong

    2013-07-04

    The transfer of resistance gene is one of the most important causes of bacterial resistance. Recent studies reveal that stresses induce the transfer of antibiotic resistance gene through multiple mechanisms. DNA damage stresses trigger bacterial SOS response and induce the transfer of resistance gene mediated by conjugative DNA. Antibiotic stresses induce natural bacterial competence for transformation in some bacteria which lack the SOS system. In addition, our latest studies show that the general stress response regulator RpoS regulates a novel type of resistance gene transfer which is mediated by double-stranded plasmid DNA and occurs exclusively on the solid surface. In this review, we summarized recent advances in SOS dependent and independent stress-induced DNA transfer which is mediated by conjugation and transformation respectively, and the transfer of double-stranded plasmid DNA on the solid surface which is regulated by RpoS. We propose that future work should address how stresses activate the key regulators and how these regulators control the expression of gene transfer related genes. Answers to the above questions would pave the way for searching for candidate targets for controlling bacterial resistance resulted from the transfer of antibiotic genes.

  18. Early resistance change and stress/electromigration evolution in near bamboo interconnects

    NARCIS (Netherlands)

    Petrescu, V.; Mouthaan, A.J.; Dima, G.; Govoreanu, B.; Mitrea, O.; Profirescu, M.

    1997-01-01

    A complete description for early resistance change and mechanical stress evolution in near-bamboo interconnects, related to the electromigration, is given in this paper. The proposed model, for the first time, combines the stress/vacancy concentration evolution with the early resistance change of

  19. Assessing thermal conductivity of composting reactor with attention on varying thermal resistance between compost and the inner surface.

    Science.gov (United States)

    Wang, Yongjiang; Niu, Wenjuan; Ai, Ping

    2016-12-01

    Dynamic estimation of heat transfer through composting reactor wall was crucial for insulating design and maintaining a sanitary temperature. A model, incorporating conductive, convective and radiative heat transfer mechanisms, was developed in this paper to provide thermal resistance calculations for composting reactor wall. The mechanism of thermal transfer from compost to inner surface of structural layer, as a first step of heat loss, was important for improving insulation performance, which was divided into conduction and convection and discussed specifically in this study. It was found decreasing conductive resistance was responsible for the drop of insulation between compost and reactor wall. Increasing compost porosity or manufacturing a curved surface, decreasing the contact area of compost and the reactor wall, might improve the insulation performance. Upon modeling of heat transfers from compost to ambient environment, the study yielded a condensed and simplified model that could be used to conduct thermal resistance analysis for composting reactor. With theoretical derivations and a case application, the model was applicable for both dynamic estimation and typical composting scenario. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Human Thermal Comfort and Heat Stress in an Outdoor Urban Arid Environment: A Case Study

    Directory of Open Access Journals (Sweden)

    A. M. Abdel-Ghany

    2013-01-01

    Full Text Available To protect humans from heat stress risks, thermal comfort and heat stress potential were evaluated under arid environment, which had never been made for such climate. The thermal indices THI, WBGT, PET, and UTCI were used to evaluate thermal comfort and heat stress. RayMan software model was used to estimate the PET, and the UTCI calculator was used for UTCI. Dry and wet bulb temperatures (Td, Tw, natural wet bulb temperature (Tnw, and globe temperature (Tg were measured in a summer day to be used in the calculation. The results showed the following. (i The thermal sensation and heat stress levels can be evaluated by either the PET or UTCI scales, and both are valid for extremely high temperature in the arid environment. (ii In the comfort zone, around 75% of individuals would be satisfied with the surrounding environment and feel comfortable during the whole day. (iii Persons are exposed to strong heat stress and would feel uncomfortable most of the daytime in summer. (iv Heat fatigue is expected with prolonged exposure to sun light and activity. (v During the daytime, humans should schedule their activities according to the highest permissible values of the WBGT to avoid thermal shock.

  1. Thermal resistances of air in cavity walls and their effect upon the thermal insulation performance

    Energy Technology Data Exchange (ETDEWEB)

    Bekkouche, S.M.A.; Cherier, M.K.; Hamdani, M.; Benamrane, N. [Application of Renewable Energies in Arid and Semi Arid Environments /Applied Research Unit on Renewable Energies/ EPST Development Center of Renewable Energies, URAER and B.P. 88, ZI, Gart Taam Ghardaia (Algeria); Benouaz, T. [University of Tlemcen, BP. 119, Tlemcen R.p. 13000 (Algeria); Yaiche, M.R. [Development Center of Renewable Energies, CDER and B.P 62, 16340, Route de l' Observatoire, Bouzareah, Algiers (Algeria)

    2013-07-01

    The optimum thickness in cavity walls in buildings is determined under steady conditions; the heat transfer has been calculated according to ISO 15099:2003. Two forms of masonry units are investigated to conclude the advantage of high thermal emissivity. The paper presents also some results from a study of the thermal insulation performance of air cavities bounded by thin reflective material layer 'eta = 0.05'. The results show that the most economical cavity configuration depends on the thermal emissivity and the insulation material used.

  2. Renal sympathetic nerve, blood flow, and epithelial transport responses to thermal stress.

    Science.gov (United States)

    Wilson, Thad E

    2017-05-01

    Thermal stress is a profound sympathetic stress in humans; kidney responses involve altered renal sympathetic nerve activity (RSNA), renal blood flow, and renal epithelial transport. During mild cold stress, RSNA spectral power but not total activity is altered, renal blood flow is maintained or decreased, and epithelial transport is altered consistent with a sympathetic stress coupled with central volume loaded state. Hypothermia decreases RSNA, renal blood flow, and epithelial transport. During mild heat stress, RSNA is increased, renal blood flow is decreased, and epithelial transport is increased consistent with a sympathetic stress coupled with a central volume unloaded state. Hyperthermia extends these directional changes, until heat illness results. Because kidney responses are very difficult to study in humans in vivo, this review describes and qualitatively evaluates an in vivo human skin model of sympathetically regulated epithelial tissue compared to that of the nephron. This model utilizes skin responses to thermal stress, involving 1) increased skin sympathetic nerve activity (SSNA), decreased skin blood flow, and suppressed eccrine epithelial transport during cold stress; and 2) increased SSNA, skin blood flow, and eccrine epithelial transport during heat stress. This model appears to mimic aspects of the renal responses. Investigations of skin responses, which parallel certain renal responses, may aid understanding of epithelial-sympathetic nervous system interactions during cold and heat stress. Copyright © 2016 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    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(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(2) laser are inspected by optical microscope. The cracks are observed initiating at r=0.5 mm and extending along the radial direction. © 2011 Optical Society of America

  4. Effect of Ionizing Beta Radiation on the Mechanical Properties of Poly(ethylene under Thermal Stress

    Directory of Open Access Journals (Sweden)

    Bednarik Martin

    2016-01-01

    Full Text Available It was found in this study, that ionizing beta radiation has a positive effect on the mechanical properties of poly(ethylene. In recent years, there have been increasing requirements for quality and cost effectiveness of manufactured products in all areas of industrial production. These requirements are best met with the polymeric materials, which have many advantages in comparison to traditional materials. The main advantages of polymer materials are especially in their ease of processability, availability, and price of the raw materials. Radiation crosslinking is one of the ways to give the conventional plastics mechanical, thermal, and chemical properties of expensive and highly resistant construction polymers. Several types of ionizing radiation are used for crosslinking of polymers. Each of them has special characteristics. Electron beta and photon gamma radiation are used the most frequently. The great advantage is that the crosslinking occurs after the manufacturing process at normal temperature and pressure. The main purpose of this paper has been to determine the effect of ionizing beta radiation on the tensile modulus, strength and elongation of low and high density polyethylene (LDPE and HDPE. These properties were examined in dependence on the dosage of the ionizing beta radiation (non-irradiated samples and those irradiated by dosage 99 kGy were compared and on the test temperature. Radiation cross-linking of LDPE and HDPE results in increased tensile strength and modulus, and decreased of elongation. The measured results indicate that ionizing beta radiation treatment is effective tool for improvement of mechanical properties of LDPE and HDPE under thermal stress.

  5. The heat-shock protein/chaperone network and multiple stress resistance.

    Science.gov (United States)

    Jacob, Pierre; Hirt, Heribert; Bendahmane, Abdelhafid

    2017-04-01

    Crop yield has been greatly enhanced during the last century. However, most elite cultivars are adapted to temperate climates and are not well suited to more stressful conditions. In the context of climate change, stress resistance is a major concern. To overcome these difficulties, scientists may help breeders by providing genetic markers associated with stress resistance. However, multistress resistance cannot be obtained from the simple addition of single stress resistance traits. In the field, stresses are unpredictable and several may occur at once. Consequently, the use of single stress resistance traits is often inadequate. Although it has been historically linked with the heat stress response, the heat-shock protein (HSP)/chaperone network is a major component of multiple stress responses. Among the HSP/chaperone 'client proteins', many are primary metabolism enzymes and signal transduction components with essential roles for the proper functioning of a cell. HSPs/chaperones are controlled by the action of diverse heat-shock factors, which are recruited under stress conditions. In this review, we give an overview of the regulation of the HSP/chaperone network with a focus on Arabidopsis thaliana. We illustrate the role of HSPs/chaperones in regulating diverse signalling pathways and discuss several basic principles that should be considered for engineering multiple stress resistance in crops through the HSP/chaperone network. © 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

  6. Abnormal contact resistance reduction of bonded copper interconnects in three-dimensional integration during current stressing

    Science.gov (United States)

    Chen, K. N.; Tan, C. S.; Fan, A.; Reif, R.

    2005-01-01

    Bonded copper interconnects were stressed with current to measure the specific contact resistance. For bonded copper interconnects without a prebonding HCl clean, the corresponding specific contact resistance did not change while increasing the stress current. However, for some interconnects with the prebonding HCl clean, an abnormal contact resistance reduction was observed during the increase of the stress current. The rise of temperature at the bonding interface area due to Joule heating under high current density may have caused the decrease of contact resistance. This behavior may be one option for quality enhancement in 3D integration at low temperature.

  7. Thermal Stability of Residual Stresses in Ti-6Al-4V components

    International Nuclear Information System (INIS)

    Stanojevic, A; Angerer, P; Oberwinkler, B

    2016-01-01

    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. (paper)

  8. Development and Life Prediction of Erosion Resistant Turbine Low Conductivity Thermal Barrier Coatings

    Science.gov (United States)

    Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

    2010-01-01

    Future rotorcraft propulsion systems are required to operate under highly-loaded conditions and in harsh sand erosion environments, thereby imposing significant material design and durability issues. The incorporation of advanced thermal barrier coatings (TBC) in high pressure turbine systems enables engine designs with higher inlet temperatures, thus improving the engine efficiency, power density and reliability. The impact and erosion resistance of turbine thermal barrier coating systems are crucial to the turbine coating technology application, because a robust turbine blade TBC system is a prerequisite for fully utilizing the potential coating technology benefit in the rotorcraft propulsion. This paper describes the turbine blade TBC development in addressing the coating impact and erosion resistance. Advanced thermal barrier coating systems with improved performance have also been validated in laboratory simulated engine erosion and/or thermal gradient environments. A preliminary life prediction modeling approach to emphasize the turbine blade coating erosion is also presented.

  9. Thermal Inactivation of Bacillus anthracis Spores Using Rapid Resistive Heating

    Science.gov (United States)

    2016-03-24

    persist in the environment over millennial time spans in a metabolically inactive state (Nicholson et al., 2000)." Once favorable conditions arise...for the prototyping/initial testing, the collection of 1586 data points, and to ensure quality agar plates were used for the thermal inactivation...removal process yielded some broken filament samples and required inspection for cracks of still intact filament samples to ensure quality samples

  10. Transient thermal stresses in composite hollow circular cylinder due to partial heat generation

    International Nuclear Information System (INIS)

    Goshima, Takahito; Miyao, Kaju

    1979-01-01

    Clad materials are adopted for the machines and structures used in contact with high temperature, corrosive atmosphere in view of their strength and economy. Large thermal stress sometimes arises in clad cylinders due to uneaven temperature field and the difference in linear thermal expansion. Vessels are often heated uneavenly, and shearing stress occurs, which is not observed in uniform heating. In this study, infinitely long, concentric cylinders of two layers were analyzed, when the internal heat changing in stepped state is generated in cylindrical form. The unsteady thermal stress occurred was determined, using thermo-elastic potential and stress functions, and assuming the thermal properties and elastic modulus of materials as constant regardless of the temperature. Laplace transformation was used, and the basic equations for thermo-elastic displacement were employed as the basis of calculation. The analysis of the temperature distribution and stress is explained. Numerical calculation was carried out on the example of an internal cylinder of SUS 304 stainless steel and an external cylinder of mild steel. The maximum shearing stress occurred in the direction of 40 deg from the heat source, and was affected largely by the position of heat generation. The effect became remarkable as time elapsed. (Kako, I.)

  11. In situ Weak Magnetic-Assisted Thermal Stress Field Reduction Effect in Laser Welding

    Science.gov (United States)

    Liang, Lvjie; Pang, Shengyong; Shao, Xinyu; Wang, Chunming; Jiang, Ping; Chen, Xin

    2018-01-01

    For decades, post-welding magnetic treatment has been used to reduce residual stress of welds by improving the crystal structure of solid-state welds. In this paper, we propose a new magnetic treatment method, which can reduce the time-dependent thermal stress field in situ and reduce the final residual stress of welds by simply exerting an assisted weak magnetic field perpendicular to the welding direction and workpiece during laser welding. A new finite-element model is developed to understand the thermal-mechanical physical process of the magnetic-assisted laser welding. For the widely used 304 austenite stainless steel, we theoretically observed that this method can reduce around 10 pct of the time-dependent thermal stress field, and finally reduce approximately 20 MPa of residual stress near the heat-affected zone with a 415-mT magnetic field for typical welding process parameters. A new mechanism based on magneto-fluid dynamics is proposed to explain the theoretical predications by combining high-speed imaging experiments of the transient laser welding process. The developed method is very simple but surprisingly effective, which opens new avenues for thermal stress reduction in laser welding of metals, particularly heat-sensitive metallic materials.

  12. Thermal resistance analysis and optimization of photovoltaic-thermoelectric hybrid system

    International Nuclear Information System (INIS)

    Yin, Ershuai; Li, Qiang; Xuan, Yimin

    2017-01-01

    Highlights: • A detailed thermal resistance analysis of the PV-TE hybrid system is proposed. • c-Si PV and p-Si PV cells are proved to be inapplicable for the PV-TE hybrid system. • Some criteria for selecting coupling devices and optimal design are obtained. • A detailed process of designing the practical PV-TE hybrid system is provided. - Abstract: The thermal resistance theory is introduced into the theoretical model of the photovoltaic-thermoelectric (PV-TE) hybrid system. A detailed thermal resistance analysis is proposed to optimize the design of the coupled system in terms of optimal total conversion efficiency. Systems using four types of photovoltaic cells are investigated, including monocrystalline silicon photovoltaic cell, polycrystalline silicon photovoltaic cell, amorphous silicon photovoltaic cell and polymer photovoltaic cell. Three cooling methods, including natural cooling, forced air cooling and water cooling, are compared, which demonstrates a significant superiority of water cooling for the concentrating photovoltaic-thermoelectric hybrid system. Influences of the optical concentrating ratio and velocity of water are studied together and the optimal values are revealed. The impacts of the thermal resistances of the contact surface, TE generator and the upper heat loss thermal resistance on the property of the coupled system are investigated, respectively. The results indicate that amorphous silicon PV cell and polymer PV cell are more appropriate for the concentrating hybrid system. Enlarging the thermal resistance of the thermoelectric generator can significantly increase the performance of the coupled system using amorphous silicon PV cell or polymer PV cell.

  13. Coping with commitment: Projecting future thermal stress on coral reefs worldwide and the potential importance of the Central Equatorial Pacific

    Science.gov (United States)

    Donner, S. D.

    2009-05-01

    Sea surface temperatures of only 1-2°C greater than the usual summer maximum can cause mass coral bleaching, a paling of the reef-building animals caused by a breakdown of the symbiosis with the colourful dinoflagellates Symbiodinium. A range of recent studies have concluded that anthropogenic climate change may rapidly increase the frequency of mass coral bleaching events, leading to declines in coral cover, shifts in the composition of corals and other reef-dwelling organisms, and stress on the human populations that depend on coral reef ecosystems for food, income and shoreline protection. Recent analysis with AVHRR observed sea surface temperatures and the results of two global climate models (GFDL CM2.0 and CM2.1) shows physical warming commitment from current accumulation of greenhouse gases in the atmosphere will cause over half of the world's coral reefs to experience harmfully frequent (p > 0.2 year-1) severe thermal stress events (DHM > 2°C/month) 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 percent of the world's coral reefs to experience harmfully frequent events by 2030. Thermal adaptation or acclimation of 1.5°C - whether accomplished via biological mechanisms, coral community shifts and/or management interventions - would postpone the forecast by 50-80 years, possibly providing time for the world to shift from the business-as-usual emissions trajectory to a stabilization trajectory which could protect the majority of reefs from harmfully frequent thermal stress events. Sensitivity analysis using historical sea surface temperatures, bleaching reports and coral cover observations indicates that coral reefs in regions which experience high year-to-year SST variability, in particular the atolls of the central equatorial Pacific, may possess higher thermal stress thresholds and greater resistance to

  14. Perceived Thermal Discomfort and Stress Behaviours Affecting Students’ Learning in Lecture Theatres in the Humid Tropics

    Directory of Open Access Journals (Sweden)

    Tamaraukuro Tammy Amasuomo

    2016-04-01

    Full Text Available The study investigated the relationship between students’ perceived thermal discomfort and stress behaviours affecting their learning in lecture theatres in the humid tropics. Two lecture theatres, LTH-2 and 3, at the Niger Delta University, Nigeria, were used for the study. Two groups of students from the Faculties of Agriculture and Engineering and the Department of Technology Education constituted the population. The sample size selected through random sampling for Groups A and B was 210 and 370 students, respectively. Objective and self-report instruments were used for data collection. The objective instrument involved physical measurement of the two lecture theatres and of the indoor temperature, relative humidity and air movement. The self-report instrument was a questionnaire that asked for the students perceived indoor thermal discomfort levels and the effect of indoor thermal comfort level on perceived stress behaviours affecting their learning. The objective indoor environmental data indicated thermal discomfort with an average temperature of 29–32 °C and relative humidity of 78% exceeding the ASHARE [1] and Olgyay [2].The students’ experienced a considerable level of thermal discomfort and also perceived that stress behaviours due to thermal discomfort affected their learning. Further, there were no significant differences in the perceived thermal discomfort levels of the two groups of students in LTH-2 and 3. Furthermore, stress behaviours affecting learning as perceived by the two groups of students did not differ significantly. In addition, no correlation existed between the perceived indoor thermal discomfort levels and stress behaviour levels affecting learning for students in LTH-2, because the arousal level of the students in the thermal environment was likely higher than the arousal level for optimal performance [3,4]. However, a correlation existed in the case of students in LTH-3, which was expected because it only

  15. Transient, heat-induced thermal resistance in the small intestine of mouse

    International Nuclear Information System (INIS)

    Hume, S.P.; Marigold, J.C.L.

    1980-01-01

    Heat-induced thermal resistance has been investigated in mouse jejunum by assaying crypt survival 24 h after treatment. Hyperthermia was achieved by immersing an exteriorized loop of intestine in a bath of Krebs-Ringer solution. Two approaches have been used. In the first, thermal survival curves were obtained following single hyperthermal treatments at temperatures in the range 42 to 44 0 C. Transient thermal resistance, inducted by a plateau in the crypt survival curve, developed during heating at temperatures around 42.5 0 C after 60 to 80 min. In the second series of experiments, a priming heat treatment (40.0, 41.0, 41.5, or 42.0 0 C for 60 min) was followed at varying intervals by a test treatment at 43.0 0 C. A transient resistance to the second treatment was induced, the extent and time of development being dependent upon the priming treatment. Crypt survival curves for thermally resistant intestine showed an increase in thermal D 0 and a decrease in n compared with curves from previously unheated intestine

  16. Thermal resistance of indium coated sapphire–copper contacts below 0.1K

    CERN Document Server

    Eisel, T; Koettig, T

    2014-01-01

    High thermal resistances exist at ultra-low temperatures for solid-solid interfaces. This is especially true for pressed metal-sapphire joints, where the heat is transferred by phonons only. For such pressed joints it is difficult to achieve good physical, i.e. thermal contacts due to surface irregularities in the microscopic or larger scale. Applying ductile indium as an intermediate layer reduces the thermal resistance of such contacts. This could be proven by measurements of several researchers. However, the majority of the measurements were performed at temperatures higher than 1 K. Consequently, it is difficult to predict the thermal resistance of pressed metal-sapphire joints at temperatures below 1 K. In this paper the thermal resistances across four different copper-sapphire-copper sandwiches are presented in a temperature range between 30 mK and 100 mK. The investigated sandwiches feature either rough or polished sapphire discs (empty set 20 mm x 1.5 mm) to investigate the phonon scattering at the bo...

  17. Thermal resistance of buffer layer in a ceramic wall of MHD generation channel

    International Nuclear Information System (INIS)

    Nomura, Osami; Ebata, Yoshihiro; Hijikata, Kenichi.

    1982-01-01

    A wal l model is composed for obtaining the thermal resistance of the buffer layer. A buffer layer of the model is consisted to an adhesive layer and a buffer body. The adhesive layer is made of a copper plate, which is 0.3 mm thick, and adhered to the element by Refractory Method. The adhesive layer is consisted to three layers, i.e., Cu, Cu 2 O and CuO. These three layers seems to give rise to the thermal resistance. The buffer body is made of nickel wires of which radious is 0.4 mm and purity is 99.7%. All of the nickel wires are assembled in one direction which is parallel to a center line of the element, and bundled all together. Occupation ratio of nickel is about 78% in a sectional area of the buffer body. One end of the buffer body is soldered to adhesive layer by silver solder and opposite and is soldered to holder by lead solder. An element of the model is made of magnesia ceramics of which purity is about 99.9% and porosity is about 3%. A holder of the model is made of copper block. Results are as follows: (1) Thermal resistance of the buffer layer is from 1.9 to 2.5K/(W/cm 2 ). (2) Thermal resistance of the adhesive layer is from 0.43 to 0.87K/(W/cm 2 ). (3) Thermal resistance of the buffer body is calculated to about 0.7K/(W/cm 2 ) under the estimation at which the heat flows in the nickel wires only. (4) From above results, thermal resistance of silver soldering layer seems to be same as that of the adhesive layers. The buffer layer needs more value of the thermal resistance in order to apply to the MHD generation channel. Value of the thermal resistance is easily satisfied by changing of material of the buffer body, increase of thickness of the buffer layer and etc. Then this wall appears to be useful to an MHD generation channel wall. (author)

  18. Nanolayering around and thermal resistivity of the water-hexagonal boron nitride interface

    Science.gov (United States)

    Akıner, Tolga; Mason, Jeremy K.; Ertürk, Hakan

    2017-07-01

    The water-hexagonal boron nitride interface was investigated by molecular dynamics simulations. Since the properties of the interface change significantly with the interatomic potential, a new method for calibrating the solid-liquid interatomic potential is proposed based on the experimental energy of the interface. The result is markedly different from that given by Lorentz-Berthelot mixing for the Lennard-Jones parameters commonly used in the literature. Specifically, the extent of nanolayering and interfacial thermal resistivity is measured for several interatomic potentials, and the one calibrated by the proposed method gives the least thermal resistivity.

  19. Tungsten Oxide Resistive Memory Using Rapid Thermal Oxidation of Tungsten Plugs

    Science.gov (United States)

    Lai, Erh-Kun; Chien, Wei-Chih; Chen, Yi-Chou; Hong, Tian-Jue; Lin, Yu-Yu; Chang, Kuo-Pin; Yao, Yeong-Der; Lin, Pang; Horng, Sheng-Fu; Gong, Jeng; Tsai, Shih-Chang; Lee, Ching-Hsiung; Hsieh, Sheng-Hui; Chen, Chun-Fu; Shih, Yen-Hao; Hsieh, Kuang-Yeu; Liu, Rich; Lu, Chih-Yuan

    2010-04-01

    A complementary metal oxide semiconductor (CMOS)-compatible WOx based resistive memory has been developed. The WOx memory layer is made from rapid thermal oxidation of W plugs. The device performs excellent electrical properties. The switching speed is extremely fast (˜2 ns) and the programming voltage (endurance. For multi-level cell (MLC) operation, it demonstrates 2-bit/cell storage with the endurance up to 10000 times. The rapid thermal oxidation (RTO) WOx resistance random access memory (RRAM) is very promising for both high-density and embedded memory applications.

  20. Damage assessment of low-cycle fatigue by crack growth prediction. Fatigue life under cyclic thermal stress

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2013-01-01

    The number of cycles to failure of specimens in fatigue tests can be estimated by predicting crack growth. Under a cyclic thermal stress caused by fluctuation of fluid temperature, due to the stress gradient in the thickness direction, the estimated fatigue life differs from that estimated for mechanical fatigue tests. In this paper, the influence of crack growth under cyclic thermal loading on the fatigue life was investigated. First, the thermal stress was derived by superposing analytical solutions, and then, the stress intensity factor was obtained by the weight function method. It was shown that the thermal stress depended not on the rate of the fluid temperature change but on the rise time, and the magnitude of the stress was increased as the rise time was decreased. The stress intensity factor under the cyclic thermal stress was smaller than that under the uniform stress distribution. The change in the stress intensity factor with the crack depth was almost the same regardless of the rise time. The estimated fatigue life under the cyclic thermal loading could be 1.6 times longer than that under the uniform stress distribution. The critical size for the fatigue life determination was assumed to be 3 mm for fatigue test specimens of 10 mm diameter. By evaluating the critical size by structural integrity analyses, the fatigue life was increased and the effect of the critical size on the fatigue life was more pronounced for the cyclic thermal stress. (author)

  1. Damage assessment of low-cycle fatigue by crack growth prediction. Fatigue life under cyclic thermal stress

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2013-01-01

    The number of cycles to failure of specimens in fatigue tests can be estimated by predicting crack growth. Under a cyclic thermal stress caused by fluctuation of fluid temperature, due to the stress gradient in the thickness direction, the estimated fatigue life differs from that estimated for mechanical fatigue tests. In this paper, the influence of crack growth under cyclic thermal loading on the fatigue life was investigated. First, the thermal stress was derived by superposing analytical solutions, and then, the stress intensity factor was obtained by the weight function method. It was shown that the thermal stress depended not on the rate of the fluid temperature change but on the rise time, and the magnitude of the stress was increased as the rise time was decreased. The stress intensity factor under the cyclic thermal stress was smaller than that under the uniform stress distribution. The change in the stress intensity factor with the crack depth did not depend on the heat transfer coefficient and only slightly depended on the rise time. The estimated fatigue life under the cyclic thermal loading could be 1.6 times longer than that under the uniform stress distribution. The critical size for the fatigue life determination was assumed to be 3 mm for fatigue test specimens of 10 mm diameter. By evaluating the critical size by structural integrity analyses, the fatigue life was increased and the effect of the critical size on the fatigue life was more pronounced for the cyclic thermal stress. (author)

  2. Increase of resistance to cracking on stress relieving of hardened steel

    International Nuclear Information System (INIS)

    Velichko, V.V.; Zabil'skij, V.V.; Mikheev, G.M.

    1995-01-01

    Regularities of increase of resistance to cracking during stress relieving of hardened low-alloyed steels were studied, using complex of methods. Effect of carbon, stress concentrator radius, duration and temperature of stress relieving was studies in particular. Results of investigating kinetics of change of physicomechanical properties, hydrogen desorption from hardened specimens showed, that increase of resistance to cracking was caused by desorption from grain boundaries of diffusion-mobile hydrogen, formed during hardening. 18 refs., 8 figs

  3. Effects of N+ implantation on polysaccharide and osmosis stress resistance of liquorice

    International Nuclear Information System (INIS)

    Wei Shenglin; Wu Lijun; Yu Zengliang

    2007-01-01

    In order to study the effects of N + implantation on osmosis stress resistance of plant, the experiment was taken with liquorice as plant model and 15% PEG as the osmosis stress agent. The results showed that the stem height growth of liquorice increased by 40.2% compared with controls (p + implantation parameters may be useful to increase osmosis stress resistance cultivation of liquorice and to make it mutated with ions beam implantation. (authors)

  4. The correct lens mount lightweighting design and thermal stress OPD analysis in Cassegrain telescope

    Science.gov (United States)

    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.

  5. Microstructure, Tensile Adhesion Strength and Thermal Shock Resistance of TBCs with Different Flame-Sprayed Bond Coat Materials Onto BMI Polyimide Matrix Composite

    Science.gov (United States)

    Abedi, H. R.; Salehi, M.; Shafyei, A.

    2017-10-01

    In this study, thermal barrier coatings (TBCs) composed of different bond coats (Zn, Al, Cu-8Al and Cu-6Sn) with mullite top coats were flame-sprayed and air-plasma-sprayed, respectively, onto bismaleimide matrix composites. These polyimide matrix composites are of interest to replace PMR-15, due to concerns about the toxicity of the MDA monomer from which PMR-15 is made. The results showed that pores and cracks appeared at the bond coat/substrate interface for the Al-bonded TBC because of its high thermal conductivity and diffusivity resulting in transferring of high heat flux and temperature to the polymeric substrate during top coat deposition. The other TBC systems due to the lower conductivity and diffusivity of bonding layers could decrease the adverse thermal effect on the polymer substrate during top coat deposition and exhibited adhesive bond coat/substrate interfaces. The tensile adhesion test showed that the adhesion strength of the coatings to the substrate is inversely proportional to the level of residual stress in the coatings. However, the adhesion strength of Al bond-coated sample decreased strongly after mullite top coat deposition due to thermal damage at the bond coat/substrate interface. TBC system with the Cu-6Sn bond coat exhibited the best thermal shock resistance, while Al-bonded TBC showed the lowest. It was inferred that thermal mismatch stresses and oxidation of the bond coats were the main factors causing failure in the thermal shock test.

  6. Analytical model of transient temperature and thermal stress in ...

    Indian Academy of Sciences (India)

    for certain tensile strain as modulus of elasticity increases. The most effective factor that may influence maximum hoop stress is the absorption coefficient, since it is the reciprocal of the effective depth that absorbs power. Increasing absorption power within a small depth means high temperature gradient and consequently, ...

  7. Temperature/Stress Distributions in a Stress-Relief-Type Plate of Functionally Graded Materials under Thermal Shock

    Science.gov (United States)

    Awaji, Hideo; Takenaka, Hiromitsu; Honda, Sawao; Nishikawa, Tadahiro

    This paper presents a numerical technique for analyzing one-dimensional transient temperature and stress distributions in a stress-relief-type plate of functionally graded ceramic-metal based materials (FGMs), in relation to both the temperature-dependent thermal properties and continuous and gradual variation of the thermo-mechanical properties of the FGM. The FGM plate is assumed to be initially in steady state of temperature gradient, suffering high temperature at the ceramic side and low temperature at the metallic side associated with its in-service performance. The FGM plate is then rapidly cooled at the ceramic side of the plate by a cold medium. The transient temperature and related thermal stresses in the FGM plate are analyzed numerically for a model alumina-nickel FGM system. The proposed analytical technique for determining the temperature distribution is quite simple and widely applicable for various boundary conditions of FGMs, compared with methods recently proposed by other researchers. The optimum composition of FGMs is also discussed to reduce the thermal stresses in the FGM plate, relating to the function of the volume fraction of the metal across the thickness.

  8. Effects of striated laser tracks on thermal fatigue resistance of cast iron samples with biomimetic non-smooth surface

    International Nuclear Information System (INIS)

    Tong, Xin; Zhou, Hong; Liu, Min; Dai, Ming-jiang

    2011-01-01

    In order to enhance the thermal fatigue resistance of cast iron materials, the samples with biomimetic non-smooth surface were processed by Neodymium:Yttrium Aluminum Garnet (Nd:YAG) laser. With self-controlled thermal fatigue test method, the thermal fatigue resistance of smooth and non-smooth samples was investigated. The effects of striated laser tracks on thermal fatigue resistance were also studied. The results indicated that biomimetic non-smooth surface was benefit for improving thermal fatigue resistance of cast iron sample. The striated non-smooth units formed by laser tracks which were vertical with thermal cracks had the best propagation resistance. The mechanisms behind these influences were discussed, and some schematic drawings were introduced to describe them.

  9. A Numerical Investigation of the Thermal Stresses of a Planar Solid Oxide Fuel Cell

    Directory of Open Access Journals (Sweden)

    Paulina Pianko-Oprych

    2016-09-01

    Full Text Available A typical operating temperature of a solid oxide fuel cell (SOFC is quite high above 750 °C and affects the thermomechanical behavior of the cell. Thermal stresses may cause microstructural instability and sub-critical cracking. Therefore, a joint analysis by the computational fluid dynamics (CFD and computational structural mechanics based on the finite element method (FEM was carried out to analyze thermal stresses in a planar SOFC and to predict potential failure locations in the cell. A full numerical model was based on the coupling of thermo-fluid model with the thermo-mechanical model. Based on a temperature distribution from the thermo-fluid model, stress distribution including the von Mises stress, shear stress as well as the operating principal stress were derived in the thermo-mechanical model. The FEM calculations were performed under different working conditions of the planar SOFC. The highest total stress was noticed at the lower operating voltage of 0.3 V, while the lowest total stress was determined at the voltage of 0.7 V. The obtained stress distributions allowed a better understanding of details of internal processes occurring within the SOFC and provided helpful guidance in the optimization of a new SOFC design.

  10. A Numerical Investigation of the Thermal Stresses of a Planar Solid Oxide Fuel Cell

    Science.gov (United States)

    Pianko-Oprych, Paulina; Zinko, Tomasz; Jaworski, Zdzisław

    2016-01-01

    A typical operating temperature of a solid oxide fuel cell (SOFC) is quite high above 750 °C and affects the thermomechanical behavior of the cell. Thermal stresses may cause microstructural instability and sub-critical cracking. Therefore, a joint analysis by the computational fluid dynamics (CFD) and computational structural mechanics based on the finite element method (FEM) was carried out to analyze thermal stresses in a planar SOFC and to predict potential failure locations in the cell. A full numerical model was based on the coupling of thermo-fluid model with the thermo-mechanical model. Based on a temperature distribution from the thermo-fluid model, stress distribution including the von Mises stress, shear stress as well as the operating principal stress were derived in the thermo-mechanical model. The FEM calculations were performed under different working conditions of the planar SOFC. The highest total stress was noticed at the lower operating voltage of 0.3 V, while the lowest total stress was determined at the voltage of 0.7 V. The obtained stress distributions allowed a better understanding of details of internal processes occurring within the SOFC and provided helpful guidance in the optimization of a new SOFC design. PMID:28773935

  11. The effect of acute mental stress on limb vasodilation is unrelated to total peripheral resistance

    NARCIS (Netherlands)

    Paine, N.J.; Ring, C.; Bosch, J.A.; McIntyre, D.; Veldhuijzen van Zanten, J.J.C.S.

    2013-01-01

    Mental stress can trigger myocardial infarction, with poor vascular responses to stress implicated as a pathway. Vascular stress reactivity can be assessed by different methods, such as total peripheral resistance (TPR) and forearm blood flow (FBF). Little is known about how these vascular

  12. Haemoglobin-mediated response to hyper-thermal stress in the keystone species Daphnia magna.

    Science.gov (United States)

    Cuenca Cambronero, Maria; Zeis, Bettina; Orsini, Luisa

    2018-01-01

    Anthropogenic global warming has become a major geological and environmental force driving drastic changes in natural ecosystems. Due to the high thermal conductivity of water and the effects of temperature on metabolic processes, freshwater ecosystems are among the most impacted by these changes. The ability to tolerate changes in temperature may determine species long-term survival and fitness. Therefore, it is critical to identify coping mechanisms to thermal and hyper-thermal stress in aquatic organisms. A central regulatory element compensating for changes in oxygen supply and ambient temperature is the respiratory protein haemoglobin (Hb). Here, we quantify Hb plastic and evolutionary response in Daphnia magna subpopulations resurrected from the sedimentary archive of a lake with known history of increase in average temperature and recurrence of heat waves. By measuring constitutive changes in crude Hb protein content among subpopulations, we assessed evolution of the Hb gene family in response to temperature increase. To quantify the contribution of plasticity in the response of this gene family to hyper-thermal stress, we quantified changes in Hb content in all subpopulations under hyper-thermal stress as compared to nonstressful temperature. Further, we tested competitive abilities of genotypes as a function of their Hb content, constitutive and induced. We found that Hb-rich genotypes have superior competitive abilities as compared to Hb-poor genotypes under hyper-thermal stress after a period of acclimation. These findings suggest that whereas long-term adjustment to higher occurrence of heat waves may require a combination of plasticity and genetic adaptation, plasticity is most likely the coping mechanism to hyper-thermal stress in the short term. Our study suggests that with higher occurrence of heat waves, Hb-rich genotypes may be favoured with potential long-term impact on population genetic diversity.

  13. GaN on Diamond with Ultra-Low Thermal Barrier Resistance

    Science.gov (United States)

    2016-03-31

    GaN-on-Diamond with Ultra -Low Thermal Barrier Resistance Xing Gu1, Cathy Lee1, Jinqiao Xie1, Edward Beam1, Michael Becker2, Timothy A. Grotjohn2...previously reported best data, and close to the limit predicted by theoretical models for GaN-diamond interfaces Keywords: GaN-on-Diamond; ultra -low...is yet to be realized, mainly due to thermal limitations. Diamond, which offers superior thermal conductivity of ~ 2000 W/ mK , is a natural choice

  14. Numerical simulation of near surface rail cracks subject to thermal contact stress

    OpenAIRE

    Fletcher, D.I.

    2014-01-01

    Boundary element modelling was conducted to investigate rail cracks subject to combined thermal and contact loading such as occurs in 'stud' or 'squat type' defects in which white etching layer lies above shallow cracks formed without evidence of plastic flow. An embedded crack at 0.5. mm below the rail surface was modelled, revealing a thermal mechanism of crack opening. Stress intensity values for a range of contact temperatures were calculated. © 2013 Elsevier B.V.

  15. Mitochondrial Adaptations to Oxidative Stress Confer Resistance to Apoptosis in Lymphoma Cells

    Directory of Open Access Journals (Sweden)

    Margaret M. Briehl

    2012-08-01

    Full Text Available Acquired resistance to drugs commonly used for lymphoma treatment poses a significant barrier to improving lymphoma patient survival. Previous work with a lymphoma tissue culture model indicates that selection for resistance to oxidative stress confers resistance to chemotherapy-induced apoptosis. This suggests that adaptation to chronic oxidative stress can contribute to chemoresistance seen in lymphoma patients. Oxidative stress-resistant WEHI7.2 cell variants in a lymphoma tissue culture model exhibit a range of apoptosis sensitivities. We exploited this phenotype to test for mitochondrial changes affecting sensitivity to apoptosis in cells made resistant to oxidative stress. We identified impaired release of cytochrome c, and the intermembrane proteins adenylate kinase 2 and Smac/DIABLO, indicating inhibition of the pathway leading to permeabilization of the outer mitochondrial membrane. Blunting of a glucocorticoid-induced signal and intrinsic mitochondrial resistance to cytochrome c release contributed to both points of resistance. The level of Bcl-2 family members or a difference in Bim induction were not contributing factors. The extent of cardiolipin oxidation following dexamethasone treatment, however, did correlate with apoptosis resistance. The differences found in the variants were all proportionate to the degree of resistance to glucocorticoid treatment. We conclude that tolerance to oxidative stress leads to mitochondrial changes that confer resistance to apoptosis.

  16. Lumped thermal capacitance analysis of transient heat conduction and induced stresses in Ghana Research Reactor vessel

    International Nuclear Information System (INIS)

    Annor-Nyarko, M.; Ayensu Gyeabour, I.; Akaho, E. H. K.

    2013-01-01

    Lumped thermal capacitance analysis has been undertaken to investigate the transient temperature variations, associated induced thermal stress distributions, and the structural integrity of Ghana Research Reactor-I (GHAR R-I) vessel after 15 years of operation. The beltline configuration of the cylindrical vessel of the Miniature Neutron Source Reactor (MNSR) was based on thin-shell and axi-symmetric assumptions with small temperature gradient and low Biot number. The thermal energy transferred by unsteady flow of the coolant to the vessel was determined as internal energy change. Numerical algorithms for Matlab Code were implemented to generate data for transient analysis and simulation. The simulations indicated that the temperature variations and the thermal stresses were below the limits imposed by the vessel material (Aluminium alloy LT 21) specifications of 933 K melting point and allowable yield stress of 480 MPa. The low level of induced thermal stresses indicated that the structural integrity of the reactor vessel has been maintained to forestall any incidence of crack propagation and fatigue failure over the operation period. (au)

  17. Biochemical basis of the high resistance to oxidative stress in ...

    Indian Academy of Sciences (India)

    Unknown

    D. discoideum to enter cell death as a function of oxida- tive stress, NO stress and nutrient stress. This was achieved by intracellular build up of H2O2 or directly treating. D. discoideum cells with cumene hydroperoxide; or in situ NO generation by sodium nitroprusside treatment as well as nutrient stress by starvation.

  18. Transient thermal stresses in multiple connected region exhibiting temperature dependence of material properties

    International Nuclear Information System (INIS)

    Sugano, Yoshihiro; Maekawa, Toshiya.

    1983-01-01

    The examples of the analysis of thermal stress in multiple connection regions such as heat exchangers, nuclear reactor cores, ingot cases and polygonal region with elliptic holes are not few, but the temperature dependence of material constants was neglected in these researches because of the difficulty of analysis though the industrial problems related to thermal stress are apt to occur in the condition of relatively large temperature gradient. Also, the analysis of heat conduction problems taking the temperature dependence of material constants into account was limited to one-dimensional problems for which Kirchhoff's transmission can be used. The purpose of this study is to derive the equation of condition which assures the one-value property of rotation and displacement, taking the temperature dependence of material constants into account, and to complete the formulation of the plane thermal stress problems in multiple connection regions by stress function method. Also the method of numerical analysis using difference method is shown to examine the effectiveness of various formulated equations and the effect of the temperature dependence of material constants on temperature and thermal stress. The example of numerical calculation on a thin rectangular plate with a rectangular hole is shown. (Kako, I.)

  19. ON THE INFLUENCE OF COLD WORK ON RESISTIVITY VARIATIONS WITH THERMAL EXPOSURE IN IN-718 NICKEL-BASE SUPERALLOY

    International Nuclear Information System (INIS)

    Madhi, Elhoucine; Nagy, Peter B.

    2010-01-01

    In nickel-base superalloys, irreversible electrical conductivity changes occur above a transition temperature where thermally-activated microstructural evolution initiates. The electrical conductivity first decreases above about 450 deg. C then increases above 600 deg. C. However, the presence of plastic deformation results in accelerated microstructure evolution at an earlier transition temperature. It was recently suggested that this well-known phenomenon might explain the notable conductivity difference between the peened near-surface part and the intact part at sufficiently large depth in surface-treated specimens. The influence of cold work on the electrical conductivity change with thermal exposure offers a probable answer to one of the main remaining questions in eddy current residual stress assessment, namely unusually fast and occasionally even non-monotonic decay of the apparent eddy current conductivity (AECC) change that was observed at temperatures as low as 400 deg. C. To validate this explanation, the present study investigates the influence of cold work on low-frequency Alternating Current Potential Drop (ACPD) resistivity variations with thermal exposure. In-situ resistivity monitoring was conducted throughout various heating cycles using the ACPD technique. IN-718 nickel-base superalloy specimens with different levels of cold work were exposed to gradually increasing peak temperatures from 400 deg. C to 800 deg. C. The results indicate that the initial irreversible rise in resistivity is approximately one order of magnitude higher and occurs at about 50 deg. C lower temperature in cold-worked samples of 30% plastic strain than in the intact material.

  20. Coupled heat conduction and thermal stress formulation using explicit integration

    International Nuclear Information System (INIS)

    Marchertas, A.H.; Kulak, R.F.

    1982-06-01

    The formulation needed for the conductance of heat by means of explicit integration is presented. The implementation of these expressions into a transient structural code, which is also based on explicit temporal integration, is described. Comparisons of theoretical results with code predictions are given both for one-dimensional and two-dimensional problems. The coupled thermal and structural solution of a concrete crucible, when subjected to a sudden temperature increase, shows the history of cracking. The extent of cracking is compared with experimental data

  1. The competition between thermal contraction and differentiation in the stress history of the moon

    Science.gov (United States)

    Kirk, Randolph L.; Stevenson, David J.

    1989-01-01

    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.

  2. Thermal cycling of stress-induced martensite for high-performance shape memory effect

    International Nuclear Information System (INIS)

    Casati, Riccardo; Vedani, Maurizio; Tuissi, Ausonio

    2014-01-01

    A novel approach to achieve an extraordinary high stress recovery shape memory effect based on thermal cycling of stress-induced martensite is proposed. An alternative thermodynamic path is considered in order to achieve outstanding functional properties of Ni-rich NiTi alloys, which are commonly used at room or body temperature as superelastic materials. Fatigue tests revealed excellent stability of the material subjected to the novel thermomechanical path, confirming its suitability for employment in high-performance shape memory actuators

  3. Thermal stress analysis of a Fort St. Vrain core support block under accident conditions

    International Nuclear Information System (INIS)

    Carruthers, L.M.; Butler, T.A.; Anderson, C.A.

    1982-01-01

    A thermoelastic stress analysis of a graphite core support block in the Fort St. Vrain High Temperature Gas Cooled Reactor is described. The support block is subjected to thermal stresses caused by a loss of forced circulation accident of the reactor system. Two- and three-dimensional finite element models of the core suport block are analyzed using the ADINAT and ADINA codes, and results are given that verify the integrity of this structural component under the given accident condition

  4. Thermal-stress analysis of a Fort St. Vrain core-support block under accident conditions

    International Nuclear Information System (INIS)

    Carruthers, L.M.; Butler, T.A.; Anderson, C.A.

    1982-01-01

    A thermoelastic stress analysis of a graphite core support block in the Fort St. Vrain High Temperature Gas Cooled Reactor is described. The support block is subjected to thermal stresses caused by a loss of forced circulation accident of the reactor system. Two- and three-dimensional finite element models of the core support block are analyzed using the ADINAT and ADINA codes, and results are given that verify the integrity of this structural component under the given accident condition

  5. Thermographic registration of thermal effects in plants exposed to cold stress

    Directory of Open Access Journals (Sweden)

    Kovchavtcev A.P.

    2011-12-01

    Full Text Available In present paper the possibility of continuous measurement of thermal effects of plants by thermography was investigated. The problems of measurement precision decreasing and thermograph calibration to cold-restraint stress process temperature region was discussed. The possibility of fast temperature measurement of plants in cold-restraint stress process was investigated. The dead temperature region of winter wheat was find out.

  6. Physiological parameters for thermal stress in dairy cattle

    Directory of Open Access Journals (Sweden)

    Vanessa Calderaro Dalcin

    Full Text Available ABSTRACT The objective of this study was to investigate changes in physiological parameters of dairy cows and understand which physiological parameters show greater reliability for verification of heat stress. Blood samples were collected for analysis and included hematocrit (Ht, erythrocyte count (ERY, and hemoglobin count (HEMO. In addition, physiological variables, including rectal temperature (RT, heart rate (HR, respiratory rate (RR, and panting score (PS were recorded in 38 lactating cows. These varied according to genetic group (1/2, 3/4, and pure bred Holstein (HO. Analysis of variance considering the effects of genetic group, days, and their interaction as well as linear and quadratic effect of the black globe humidity index (BGHI was performed, as well as broken-line regression. These values were higher in pure HO than in 3/4 and 1/2 groups. The average BGHI during the morning was 74, when 70, 43, and 13% of pure HO, 3/4, and 1/2, respectively, presented RR above reference value. The RR was the best indicator of heat stress and its critical value was 116 breaths/min for 1/2, 140 for 3/4, and 168 breaths/min for pure HO cows. In the HO group, physiological variables increased linearly with BGHI, without presenting inflection in the regression. The inflection point occurred at a higher BGHI for the 1/2 group compared with the other groups. Hematocrit and HEMO were different among genetic groups and did not vary with BGHI, showing that stress was not sufficient to alter these hematological parameters. The 1/2 HO group was capable of maintaining normal physiological parameters for at least 3 BGHI units above that of HO and 1 to 3 units higher than 3/4 HO for RR and RT, respectively. Respiratory rate is the physiological parameter that best predicts heat stress in dairy cattle, and the 1/2 Holstein group is the best adapted to heat stress.

  7. Mechanical spectroscopy of thermal stress relaxation in aluminium alloys reinforced with short alumina fibres

    Energy Technology Data Exchange (ETDEWEB)

    Carreno-Morelli, E.; Schaller, R. [Ecole Polytechnique Federale, Lausanne (Switzerland). Inst. de Genie Atomique; Urreta, S.E.

    1998-05-01

    The mechanical behaviour under low temperature thermal cycling of aluminium-based composites reinforced with short Al{sub 2}O{sub 3} SAFFIL fibres has been investigated by mechanical spectroscopy (mechanical loss and elastic shear modulus measurements). A mechanical loss maximum has been observed during cooling which originates in the relaxation of thermal stresses at the interfaces due to the differential thermal expansion between matrix and reinforcement. The maximum height increases with the volumetric fibre content. In addition, if the matrix strength is increased by the appropriated choice of alloy and thermal treatment, the maximum diminishes and shifts to lower temperatures. No damage accumulation at the interfaces has been detected during long period thermal cycling in the range 100 to 500 K. A description of the damping behaviour is made in terms of the development of microplastic zones which surround the fibres. (orig.) 9 refs.

  8. An analytical model of thermal mechanical stress induced by through silicon via

    International Nuclear Information System (INIS)

    Dong Gang; Shi Tao; Zhao Ying-Bo; Yang Yin-Tang

    2015-01-01

    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 SiO 2 . 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. (paper)

  9. An investigation on thermal residual stresses in a cylindrical functionally graded WC-Co component

    Energy Technology Data Exchange (ETDEWEB)

    Tahvilian, L. [Metallurgical Engineering, University of Utah, 135 South 1460 East, Salt Lake City, UT 84112 (United States); Fang, Z. Zak, E-mail: zak.fang@utah.edu [Metallurgical Engineering, University of Utah, 135 South 1460 East, Salt Lake City, UT 84112 (United States)

    2012-11-15

    The thermal residual stress distribution in a functionally graded cemented tungsten carbide (FG WC-Co) hollow cylinder was examined with an emphasis on the effects of key variables, such as gradient profile and gradient thickness on the magnitude and distribution of the stress field. An analytical direct solution based on solving the governing equations of a cylinder composed of a uniform inner core and a functionally graded outer shell was developed, considering the cylindrical compound as two separate elements: a homogeneous cylinder and a functionally graded shell. Through the graded shell, material properties such as the modulus of elasticity and the coefficient of thermal expansion (CTE), except Poisson's ratio, were considered to vary as a power function of the radius, and proper mechanical boundary conditions were imposed at the interface of the two cylinders. Practical values for the two variables, gradient profile and gradient thickness, were evaluated in the mathematical solution for the FG WC-Co compound, and their effects on the stress distribution were studied. An examination of different gradient profiles showed that with excess Co content in the graded region, compressive radial stresses were created, while with decreasing Co content through the graded region tensile stresses were generated at the interface. The effect of gradient thickness was shown to have a greater effect on radial stress, compared to hoop stress, and increasing the gradient thickness significantly increased the radial stress magnitude.

  10. Rockfall triggering by cyclic thermal stressing of exfoliation fractures

    Science.gov (United States)

    Collins, Brian D.; 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.

  11. Effect of magnesium aluminum silicate glass on the thermal shock resistance of BN matrix composite ceramics

    NARCIS (Netherlands)

    Cai, Delong; Jia, Dechang; Yang, Zhihua; Zhu, Qishuai; Ocelik, Vaclav; Vainchtein, Ilia D.; De Hosson, Jeff Th M.; Zhou, Yu

    The effects of magnesium aluminum silicate (MAS) glass on the thermal shock resistance and the oxidation behavior of h-BN matrix composites were systematically investigated at temperature differences from 600 degrees C up to 1400 degrees C. The retained strength rate of the composites rose with the

  12. Modelling of Dynamic Transmission Cable Temperature Considering Soil-Specific Heat, Thermal Resistivity, and Precipitation

    DEFF Research Database (Denmark)

    Olsen, Rasmus; Anders, George J.; Holboell, Joachim

    2013-01-01

    This paper presents an algorithm for the estimation of the time-dependent temperature evolution of power cables, when real-time temperature measurements of the cable surface or a point within its vicinity are available. The thermal resistivity and specific heat of the cable surroundings are varied...

  13. Analytical 1D models of the wall thermal resistance of rectangular minichannels applied in heat exchangers

    Directory of Open Access Journals (Sweden)

    Rybiński Witold

    2016-09-01

    Full Text Available The paper presents four 1-dimensional models of thermal resistance of walls in a heat exchanger with rectangular minichannels. The first model is the simplest one, with a single wall separating two fluids. The second model of the so called equivalent wall takes into account total volume of intermediate walls between layers of minichannels and of side walls of minichannels. The next two more complicated models take separately into account thermal resistance of these walls. In these two models side walls are treated as fins. The results of models comparison are presented. It is shown that thermal resistance may be neglected for metal walls but it should be taken into account for the walls made of plastics. For the case of non-neglected wall thermal resistance the optimum wall thickness was derived. Minichannel heat exchangers made of plastic are larger than those built of metal, but are significantly cheaper. It makes possible to use of such exchangers in inexpensive microscale ORC installations.

  14. Structure Analysis Of Corrosion Resistant Thermal Sprayed Coatings On Low Alloy Steels

    Science.gov (United States)

    Chaliampalias, D.; Vourlias, G.; Pistofidis, N.; Pavlidou, E.; Stergiou, A.; Stergioudis, G.; Polychroniadis, E. K.

    2007-04-01

    Metallic coatings have been proved to reduce the rate of corrosion of steel in various atmospheres. In this work the structure of Al, Cu-Al and Zn thermal sprayed coatings is examined. The as formed coatings are extremely rough, and they are composed of several phases which increase corrosion resistance as it was determined Salt Spray Chamber tests.

  15. Genome-wide association analysis of oxidative stress resistance in Drosophila melanogaster.

    Directory of Open Access Journals (Sweden)

    Allison L Weber

    Full Text Available Aerobic organisms are susceptible to damage by reactive oxygen species. Oxidative stress resistance is a quantitative trait with population variation attributable to the interplay between genetic and environmental factors. Drosophila melanogaster provides an ideal system to study the genetics of variation for resistance to oxidative stress.We used 167 wild-derived inbred lines of the Drosophila Genetic Reference Panel for a genome-wide association study of acute oxidative stress resistance to two oxidizing agents, paraquat and menadione sodium bisulfite. We found significant genetic variation for both stressors. Single nucleotide polymorphisms (SNPs associated with variation in oxidative stress resistance were often sex-specific and agent-dependent, with a small subset common for both sexes or treatments. Associated SNPs had moderately large effects, with an inverse relationship between effect size and allele frequency. Linear models with up to 12 SNPs explained 67-79% and 56-66% of the phenotypic variance for resistance to paraquat and menadione sodium bisulfite, respectively. Many genes implicated were novel with no known role in oxidative stress resistance. Bioinformatics analyses revealed a cellular network comprising DNA metabolism and neuronal development, consistent with targets of oxidative stress-inducing agents. We confirmed associations of seven candidate genes associated with natural variation in oxidative stress resistance through mutational analysis.We identified novel candidate genes associated with variation in resistance to oxidative stress that have context-dependent effects. These results form the basis for future translational studies to identify oxidative stress susceptibility/resistance genes that are evolutionary conserved and might play a role in human disease.

  16. Coping with commitment: projected thermal stress on coral reefs under different future scenarios.

    Directory of Open Access Journals (Sweden)

    Simon D Donner

    Full Text Available 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> or =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 CO(2 stabilization trajectory, may cause over 80% of the world's coral reefs to experience harmfully frequent events by 2030. Thermal adaptation of 1.5 degrees 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 CO(2 concentrations may need to be stabilized below current levels to avoid the degradation of coral reef ecosystems

  17. An investigation of characteristics of thermal stress caused by fluid temperature fluctuation at a T-junction pipe

    International Nuclear Information System (INIS)

    Miyoshi, Koji; Nakamura, Akira; Utanohara, Yoichi

    2014-01-01

    Thermal fatigue cracking may initiate at a T-junction pipe where high and low temperature fluids flow in from different directions and mix. Thermal stress is caused by a temperature gradient in a structure and by its variation. It is possible to obtain stress distributions if the temperature distributions at the pipe inner surface are obtained by experiments. The wall temperature distributions at a T-junction pipe were measured by experiments. The thermal stress distributions were calculated using the experimental data. The circumferential and axial stress fluctuations were larger than the radial stress fluctuation range. The stress fluctuation at the position of the maximum stress fluctuation had 10sec period. The distribution of the stress fluctuation was similar to that of the temperature fluctuation. The large stress fluctuations were caused by the time variation of the heating region by the hot jet flow. (author)

  18. Lipocalin 2 regulation by thermal stresses: Protective role of Lcn2/NGAL against cold and heat stresses

    Energy Technology Data Exchange (ETDEWEB)

    Roudkenar, Mehryar Habibi, E-mail: roudkenar@ibto.ir [Research Center, Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Halabian, Raheleh [Research Center, Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Roushandeh, Amaneh Mohammadi [Department of Anatomy, Faculty of Medicine, Medical University of Tabriz, Tabriz (Iran, Islamic Republic of); Nourani, Mohammad Reza [Chemical Injury Research Center, Baqiyatallah Medical Science University, Tehran (Iran, Islamic Republic of); Masroori, Nasser [Research Center, Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Ebrahimi, Majid [Research Center, Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Chemical Injury Research Center, Baqiyatallah Medical Science University, Tehran (Iran, Islamic Republic of); Nikogoftar, Mahin; Rouhbakhsh, Mehdi; Bahmani, Parisa [Research Center, Iranian Blood Transfusion Organization, Tehran (Iran, Islamic Republic of); Najafabadi, Ali Jahanian [Department of Molecular Biology, Pasteur Institute of Iran, Tehran (Iran, Islamic Republic of); Shokrgozar, Mohammad Ali [National Cell Bank of Iran, Pasteur institute of Iran, Tehran (Iran, Islamic Republic of)

    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. Lipocalin 2 regulation by thermal stresses: Protective role of Lcn2/NGAL against cold and heat stresses

    International Nuclear Information System (INIS)

    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

    2009-01-01

    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.

  20. Machine-Thermal Coupling Stresses Analysis of the Fin-Type Structural Thermoelectric Generator

    Science.gov (United States)

    Zhang, Zheng; Yue, Hao; Chen, Dongbo; Qin, Delei; Chen, Zijian

    2017-05-01

    The design structure and heat-transfer mechanism of a thermoelectric generator (TEG) determine its body temperature state. Thermal stress and thermal deformation generated by the temperature variation directly affect the stress state of thermoelectric modules (TEMs). Therefore, the rated temperature and pressing force of TEMs are important parameters in TEG design. Here, the relationships between structural of a fin-type TEG (FTEG) and these parameters are studied by modeling and "machine-thermal" coupling simulation. An indirect calculation method is adopted in the coupling simulation. First, numerical heat transfer calculations of a three-dimensional FTEG model are conducted according to an orthogonal simulation table. The influences of structural parameters for heat transfer in the channel and outer fin temperature distribution are analyzed. The optimal structural parameters are obtained and used to simulate temperature field of the outer fins. Second, taking the thermal calculation results as the initial condition, the thermal-solid coupling calculation is adopted. The thermal stresses of outer fin, mechanical force of spring-angle pressing mechanism, and clamping force on a TEM are analyzed. The simulation results show that the heat transfer area of the inner fin and the physical parameters of the metal materials are the keys to determining the FTEG temperature field. The pressing mechanism's mechanical force can be reduced by reducing the outer fin angle. In addition, a corrugated cooling water pipe, which has cooling and spring functionality, is conducive to establishing an adaptable clamping force to avoid the TEMs being crushed by the thermal stresses in the body.

  1. A shift to organismal stress resistance in programmed cell death mutants.

    Directory of Open Access Journals (Sweden)

    Meredith E Judy

    Full Text Available Animals have many ways of protecting themselves against stress; for example, they can induce animal-wide, stress-protective pathways and they can kill damaged cells via apoptosis. We have discovered an unexpected regulatory relationship between these two types of stress responses. We find that C. elegans mutations blocking the normal course of programmed cell death and clearance confer animal-wide resistance to a specific set of environmental stressors; namely, ER, heat and osmotic stress. Remarkably, this pattern of stress resistance is induced by mutations that affect cell death in different ways, including ced-3 (cell death defective mutations, which block programmed cell death, ced-1 and ced-2 mutations, which prevent the engulfment of dying cells, and progranulin (pgrn-1 mutations, which accelerate the clearance of apoptotic cells. Stress resistance conferred by ced and pgrn-1 mutations is not additive and these mutants share altered patterns of gene expression, suggesting that they may act within the same pathway to achieve stress resistance. Together, our findings demonstrate that programmed cell death effectors influence the degree to which C. elegans tolerates environmental stress. While the mechanism is not entirely clear, it is intriguing that animals lacking the ability to efficiently and correctly remove dying cells should switch to a more global animal-wide system of stress resistance.

  2. Thermal-shock Resistance of a Ceramic Comprising 60 Percent Boron Carbide and 40 Percent Titanium Diboride

    Science.gov (United States)

    Yeomans, C M; Hoffman, C A

    1953-01-01

    Thermal-shock resistance of a ceramic comprising 60 percent boron carbide and 40 percent titanium diboride was investigated. The material has thermal shock resistance comparable to that of NBS body 4811C and that of zirconia, but is inferior to beryllia, alumina, and titanium-carbide ceramals. It is not considered suitable for turbine blades.

  3. Investigation of the thermal resistance of timber attic spaces with reflective foil and bulk insulation, heat flow up

    Energy Technology Data Exchange (ETDEWEB)

    Belusko, M.; Bruno, F.; Saman, W. [Institute for Sustainable Systems and Technologies, University of South Australia, Mawson Lakes Boulevard, SA 5095 (Australia)

    2011-01-15

    An experimental investigation was undertaken in which the thermal resistance for the heat flow through a typical timber framed pitched roofing system was measured under outdoor conditions for heat flow up. The measured thermal resistance of low resistance systems such as an uninsulated attic space and a reflective attic space compared well with published data. However, with higher thermal resistance systems containing bulk insulation within the timber frame, the measured result for a typical installation was as low as 50% of the thermal resistance determined considering two dimensional thermal bridging using the parallel path method. This result was attributed to three dimensional heat flow and insulation installation defects, resulting from the design and construction method used. Translating these results to a typical house with a 200 m{sup 2} floor area, the overall thermal resistance of the roof was at least 23% lower than the overall calculated thermal resistance including two dimensional thermal bridging. When a continuous layer of bulk insulation was applied to the roofing system, the measured values were in agreement with calculated resistances representing a more reliable solution. (author)

  4. Thermal stress intensity factor for an axial crack in a clad cylinder

    International Nuclear Information System (INIS)

    Kuo, An Yu; Deardorf, A.F.; Riccardella, P.C.

    1993-01-01

    Many clad pressure vessels have been found to have cracks running through the inside surface cladding and into the base material. Although Young's moduli and Poisson's ratios of the clad and base materials are about the same for most of the industrial applications, coefficients of thermal expansion of the two dissimilar materials, clad and base materials, are usually quite different. For example, low alloy ferritic steel is a common base material for reactor pressure vessels (RPV) and the vessels are usually clad with austenitic stainless steel. Young's moduli for the low alloy steel and stainless steel at 350 F are 29,000 ksi and 28,000 ksi, respectively, while their coefficients of thermal expansion are 7.47x10 -6 in/in and 9.50x10 -6 in/in-degree F, respectively. The mismatch in coefficients of thermal expansion will cause high residual thermal stress even when the entire vessel is at a uniform temperature. This residual stress is one of the primary reasons why so many cracks have been found in the cladded components. In performing reactor pressure vessel integrity evaluation, such as computing probability of brittle fracture of the RPV, it is necessary to calculate stress intensity factors for cracks, which initiate from the clad material and run into the base metal. This paper presents a convenient method of calculating stress intensity factor for an axial crack emanating from the inside surface of a cladded cylinder under thermal loading. A J-integral like line integral was derived and used to calculate the stress intensity factors from finite element stress solutions of the problem

  5. Standard Test Method for Thermal Oxidative Resistance of Carbon Fibers

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1982-01-01

    1.1 This test method covers the apparatus and procedure for the determination of the weight loss of carbon fibers, exposed to ambient hot air, as a means of characterizing their oxidative resistance. 1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units which are provided for information only and are not considered standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard information, see Section 8.

  6. Endoplasmic reticulum stress epigenetics is related to adiposity, dyslipidemia, and insulin resistance.

    Science.gov (United States)

    Ramos-Lopez, Omar; Riezu-Boj, Jose I; Milagro, Fermin I; Moreno-Aliaga, Maria J; Martinez, J Alfredo

    2018-03-23

    Unresolved ER stress is involved in the onset and progression of several obesity-related metabolic disorders, including dyslipidemia and insulin resistance. Different epigenetic modifications may regulate ER stress response and consequently disease risks. These epigenetic phenomena encompass DNA and histone methylation patterns in ER stress genes and downstream signaling molecules, as well as microRNA expression. Our results suggest potential associations of methylation signatures at ER regulatory genes in white blood cells with an abdominal/central obesity marker (waist circumference), dyslipidemia, and insulin resistance. Interestingly, most of these genes were implicated in ER stress, as revealed by pathway enrichment analysis. Together, these findings add knowledge into the current understanding of relationships between obesity and accompanying complications with epigenetics and ER stress. Here, we comment about the implication of ER stress in central/abdominal adiposity, dyslipidemia, and insulin resistance, with an emphasis on the role that epigenetics may play on these pathological processes.

  7. One-dimensional models of thermal activation under shear stress

    CSIR Research Space (South Africa)

    Nabarro, FRN

    2003-01-01

    Full Text Available - dimensional models presented here may illuminate the study of more realistic models. For the model in which as many dislocations are poised for backward jumps as for forward jumps, the experimental activation volume Vye(C27a) under applied stresses close to C...27a is different from the true activation volume V(C27) evaluated at C27 ?C27a. The relations between the two are developed. A model is then discussed in which fewer dislocations are available for backward than for forward jumps. Finally...

  8. Effect of power history on the shape and the thermal stress of a large sapphire crystal during the Kyropoulos process

    Science.gov (United States)

    Nguyen, Tran Phu; Chuang, Hsiao-Tsun; Chen, Jyh-Chen; Hu, Chieh

    2018-02-01

    In this study, the effect of the power history on the shape of a sapphire crystal and the thermal stress during the Kyropoulos process are numerically investigated. The simulation results show that the thermal stress is strongly dependent on the power history. The thermal stress distributions in the crystal for all growth stages produced with different power histories are also studied. The results show that high von Mises stress regions are found close to the seed of the crystal, the highly curved crystal surface and the crystal-melt interface. The maximum thermal stress, which occurs at the crystal-melt interface, increases significantly in value as the crystal expands at the crown. After this, there is reduction in the maximum thermal stress as the crystal lengthens. There is a remarkable enhancement in the maximum von Mises stress when the crystal-melt interface is close to the bottom of the crucible. There are two obvious peaks in the maximum Von Mises stress, at the end of the crown stage and in the final stage, when cracking defects can form. To alleviate this problem, different power histories are considered in order to optimize the process to produce the lowest thermal stress in the crystal. The optimal power history is found to produce a significant reduction in the thermal stress in the crown stage.

  9. Thermally-treated Pt-coated silicon AFM tips for wear resistance in ferroelectric data storage

    International Nuclear Information System (INIS)

    Bhushan, Bharat; Palacio, Manuel; Kwak, Kwang Joo

    2008-01-01

    In ferroelectric data storage, a conductive atomic force microscopy (AFM) probe with a noble metal coating is placed in contact with a lead zirconate titanate (PZT) film. The understanding and improvement of probe tip wear, particularly at high velocities, is needed for high data rate recording. A commercial Pt-coated silicon AFM probe was thermally treated in order to form platinum silicide at the near-surface. Nanoindentation, nanoscratch and wear experiments were performed to evaluate the mechanical properties and wear performance at high velocities. The thermally treated tip exhibited lower wear than the untreated tip. The tip wear mechanism is adhesive and abrasive wear with some evidence of impact wear. The enhancement in mechanical properties and wear resistance in the thermally treated film is attributed to silicide formation in the near-surface. Auger electron spectroscopy and electrical resistivity measurements confirm the formation of platinum silicide. This study advances the understanding of thin film nanoscale surface interactions

  10. Baicalein modulates stress-resistance and life span in C. elegans via SKN-1 but not DAF-16.

    Science.gov (United States)

    Havermann, Susannah; Humpf, Hans-Ulrich; Wätjen, Wim

    2016-09-01

    The flavonoid baicalein has been demonstrated to be an activator of the transcription factor Nrf2 in mammalian cell lines. We show that it further modulates the Nrf2 homolog SKN-1 in Caenorhabditis elegans and by this pathway mediates beneficial effects in the nematode: baicalein enhances the resistance of C. elegans against lethal thermal and sodium arsenite stress and dose-dependently prolongs the life span of the nematode. Using RNA interference against SKN-1 we were able to show that the induction of longevity and the enhanced stress-resistance were dependent on this transcription factor. DAF-16 (homolog to mammalian FOXO) is another pivotal aging-related transcription factor in the nematode. We demonstrate that DAF-16 does not participate in the beneficial effects of baicalein: since baicalein causes no increase in the nuclear translocation of DAF-16 (DAF-16::GFP expressing strain, incubation time: 1h) and it still induces longevity even in a DAF-16 loss-of-function strain, we conclude, that baicalein increases stress-resistance and life span in C. elegans via SKN-1 but not DAF-16. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Investigation of the Use of Laser Shock Peening for Enhancing Fatigue and Stress Corrosion Cracking Resistance of Nuclear Energy Materials

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Vijay K. [Univ. of Cincinnati, OH (United States); Jackson, John [Idaho National Lab. (INL), Idaho Falls, ID (United States); Teysseyre, Sebastien [Idaho National Lab. (INL), Idaho Falls, ID (United States); Alexandreanu, Bogdan [Argonne National Lab. (ANL), Argonne, IL (United States); Chen, Yiren [Argonne National Lab. (ANL), Argonne, IL (United States)

    2017-03-07

    The objective of this project, which includes close collaboration with scientists from INL and ANL, is to investigate and demonstrate the use of advanced mechanical surface treatments like laser shock peening (LSP) and ultrasonic nanocrystal surface modification (UNSM) and establish baseline parameters for enhancing the fatigue properties and SCC resistance of nuclear materials like nickel-based alloy 600 and 304 stainless steel. The research program includes the following key elements/tasks: 1) Procurement of Alloy 600 and 304 SS, heat treatment studies; 2) LSP and UNSM processing of base metal and welds/HAZ of alloys 600 and 304; (3) measurement and mapping of surface and sub-surface residual strains/stresses and microstructural changes as a function of process parameters using novel methods; (4) determination of thermal relaxation of residual stresses (macro and micro) and microstructure evolution with time at high temperatures typical of service conditions and modeling of the kinetics of relaxation; (5) evaluation of the effects of residual stress, near surface microstructure and temperature on SCC and fatigue resistance and associated microstructural mechanisms; and (6) studies of the effects of bulk and surface grain boundary engineering on improvements in the SCC resistance and associated microstructural and cracking mechanisms

  12. The anomalous low temperature resistivity of thermally evaporated α-Mn thin film

    International Nuclear Information System (INIS)

    Ampong, F.K.; Boakye, F.; Nkum, R.K.

    2010-01-01

    Electrical resistivity measurements have been carried out on thermally evaporated α-Mn thin film between 300 and 1.4 K using the van der Pauw four probe technique. The film was grown on a glass substrate held at a temperature of 373 K, in an ambient pressure of 5x10 -6 Torr. The results show a resistance minimum, a notable characteristic of α-Mn but at a (rather high) temperature of 194±1 K. Below the resistivity maximum which corresponds to 70 K, the resistivity drops by only 0.02 μΩm indicating a rather short range magnetic ordering. The low temperature results show a tendency towards saturation of the resistivity as the temperature approaches zero suggesting a Kondo scattering.

  13. The anomalous low temperature resistivity of thermally evaporated alpha-Mn thin film

    Energy Technology Data Exchange (ETDEWEB)

    Ampong, F.K., E-mail: kampxx@yahoo.co [Department of Physics, Kwame Nkrumah University of Science and Technology, Kumasi (Ghana); Boakye, F.; Nkum, R.K. [Department of Physics, Kwame Nkrumah University of Science and Technology, Kumasi (Ghana)

    2010-08-15

    Electrical resistivity measurements have been carried out on thermally evaporated alpha-Mn thin film between 300 and 1.4 K using the van der Pauw four probe technique. The film was grown on a glass substrate held at a temperature of 373 K, in an ambient pressure of 5x10{sup -6} Torr. The results show a resistance minimum, a notable characteristic of alpha-Mn but at a (rather high) temperature of 194+-1 K. Below the resistivity maximum which corresponds to 70 K, the resistivity drops by only 0.02 muOMEGAm indicating a rather short range magnetic ordering. The low temperature results show a tendency towards saturation of the resistivity as the temperature approaches zero suggesting a Kondo scattering.

  14. Mitofusin 2 in POMC neurons connects ER stress with leptin resistance and energy imbalance

    DEFF Research Database (Denmark)

    Schneeberger, Marc; Dietrich, Marcelo O; Sebastián, David

    2013-01-01

    Mitofusin 2 (MFN2) plays critical roles in both mitochondrial fusion and the establishment of mitochondria-endoplasmic reticulum (ER) interactions. Hypothalamic ER stress has emerged as a causative factor for the development of leptin resistance, but the underlying mechanisms are largely unknown....... This previously unrecognized role for MFN2 argues for a crucial involvement in mediating ER stress-induced leptin resistance........ Here, we show that mitochondria-ER contacts in anorexigenic pro-opiomelanocortin (POMC) neurons in the hypothalamus are decreased in diet-induced obesity. POMC-specific ablation of Mfn2 resulted in loss of mitochondria-ER contacts, defective POMC processing, ER stress-induced leptin resistance...

  15. Effect of air confinement on thermal contact resistance in nanoscale heat transfer

    Science.gov (United States)

    Pratap, Dheeraj; Islam, Rakibul; Al-Alam, Patricia; Randrianalisoa, Jaona; Trannoy, Nathalie

    2018-03-01

    Here, we report a detailed analysis of thermal contact resistance (R c) of nano-size contact formed between a Wollaston wire thermal probe and the used samples (fused silica and titanium) as a function of air pressure (from 1 Pa to 105 Pa). Moreover, we suggest an analytical model using experimental data to extract R c. We found that for both samples, the thermal contact resistance decreases with increasing air pressure. We also showed that R c strongly depends on the thermal conductivity of materials keeping other parameters the same, such as roughness of the probe and samples, as well as the contact force. We provide a physical explanation of the R c trend with pressure and thermal conductivity of the materials: R c is ascribed to the heat transfer through solid-solid (probe-sample) contact and confined air at nanoscale cavities, due to the rough nature of the materials in contact. The contribution of confined air on heat transfer through the probe sample contact is significant at atmospheric pressure but decreases as the pressure decreases. In vacuum, only the solid-solid contact contributes to R c. In addition, theoretical calculations using the well-known acoustic and diffuse mismatch models showed a high thermal conductivity material that exhibits high heat transmission and consequently low R c, supporting our findings.

  16. Irradiation effects on thermal shock resistance and its fracture toughness of HTGR graphites

    International Nuclear Information System (INIS)

    Sato, Sennosuke; Imamura, Yoshio; Kawamata, Kiyohiro; Awaji, Hideo; Oku, Tatsuo.

    1979-01-01

    This paper describes changes in the thermal shock resistance delta = σsub(t)k / E alpha (σsub(t): tensile strength, k: thermal conductivity, E: Young's modulus, alpha : coefficient of thermal expansion) and the thermal shock fracture toughness delta = K sub( ic)k / E alpha (K sub( ic): fracture toughness value of the mode I) in addition to usual mechanical properties including the diametral compressive strength and fracture toughness of four varieties of graphite (IM2-24, 7477, H327 and SMG) for the high temperature gas-cooled reactor due to neutron irradiations of (1.6 -- 2.3) x 10 21 n/cm 2 ( gt 0.18 MeV) at 600 -- 850 0 C. These experiments are carried out by means of our recently developed techniques using small disk type specimens which are very effective for a capsule irradiation in the JMTR. Both the thermal shock resistance and the thermal shock fracture toughness of graphites after irradiation are expressed to decrease remarkably in contrast with the increase of the usual mechanical strength. (author)

  17. Swimming performance and thermal resistance of juvenile and adult newts acclimated to different temperatures

    Directory of Open Access Journals (Sweden)

    Hong-Liang Lu

    2016-12-01

    Full Text Available Thermal acclimatory adjustments of locomotor performance and thermal tolerance occur commonly in ectothermic animals. However, few studies have investigated ontogenetic differences in these acclimatory responses, and thus, their causes remain unclear. In this study, juvenile and adult Chinese fire-bellied newts (Cynops orientalis were acclimated to one of two temperatures (16 or 24 °C for 4 weeks to examine ontogenetic differences in acclimation effect on burst swimming speed, and critical thermal minimum (CTMin and maximum (CTMax. Swimming performance was thermally acclimated in both juvenile and adult C. orientalis. Adult newts had greater absolute swimming speeds than juveniles, which may simply result from their larger sizes. Cold acclimation enhanced low-temperature resistance, and warm acclimation enhanced high-temperature resistance in both juveniles and adults. Despite no ontogenetic difference in CTMin, adult newts had greater CTMax and acclimation response ratio than juveniles, indicating their greater abilities to withstand extreme high temperatures and manage rapid temperature shifts. Ontogenetic change in the thermal acclimatory responses of newts may be related to changes in the thermal environment they experience.

  18. Is phenotypic plasticity a key mechanism for responding to thermal stress in ants?

    Science.gov (United States)

    Oms, Cristela Sánchez; Cerdá, Xim; Boulay, Raphaël

    2017-06-01

    Unlike natural selection, phenotypic plasticity allows organisms to respond quickly to changing environmental conditions. However, plasticity may not always be adaptive. In insects, body size and other morphological measurements have been shown to decrease as temperature increases. This relationship may lead to a physiological conflict in ants, where larger body size and longer legs often confer better thermal resistance. Here, we tested the effect of developmental temperature (20, 24, 28 or 32 °C) on adult thermal resistance in the thermophilic ant species Aphaenogaster senilis. We found that no larval development occurred at 20 °C. However, at higher temperatures, developmental speed increased as expected and smaller adults were produced. In thermal resistance tests, we found that ants reared at 28 and 32 °C had half-lethal temperatures that were 2 °C higher than those of ants reared at 24 °C. Thus, although ants reared at higher temperatures were smaller in size, they were nonetheless more thermoresistant. These results show that A. senilis can exploit phenotypic plasticity to quickly adjust its thermal resistance to local conditions and that this process is independent of morphological adaptations. This mechanism may be particularly relevant given current rapid climate warming.

  19. Is phenotypic plasticity a key mechanism for responding to thermal stress in ants?

    Science.gov (United States)

    Oms, Cristela Sánchez; Cerdá, Xim; Boulay, Raphaël

    2017-06-01

    Unlike natural selection, phenotypic plasticity allows organisms to respond quickly to changing environmental conditions. However, plasticity may not always be adaptive. In insects, body size and other morphological measurements have been shown to decrease as temperature increases. This relationship may lead to a physiological conflict in ants, where larger body size and longer legs often confer better thermal resistance. Here, we tested the effect of developmental temperature (20, 24, 28 or 32 °C) on adult thermal resistance in the thermophilic ant species Aphaenogaster senilis. We found that no larval development occurred at 20 °C. However, at higher temperatures, developmental speed increased as expected and smaller adults were produced. In thermal resistance tests, we found that ants reared at 28 and 32 °C had half-lethal temperatures that were 2 °C higher than those of ants reared at 24 °C. Thus, although ants reared at higher temperatures were smaller in size, they were nonetheless more thermoresistant. These results show that A. senilis can exploit phenotypic plasticity to quickly adjust its thermal resistance to local conditions and that this process is independent of morphological adaptations. This mechanism may be particularly relevant given current rapid climate warming.

  20. Enhancing stress resistance and production phenotypes through transcriptome engineering.

    Science.gov (United States)

    Lam, Felix H; Hartner, Franz S; Fink, Gerald R; Stephanopoulos, Gregory

    2010-01-01

    As Saccharomyces cerevisiae is engineered further as a microbial factory for industrially relevant but potentially cytotoxic molecules such as ethanol, issues of cell viability arise that threaten to place a biological limit on output capacity and/or the use of less refined production conditions. Evidence suggests that one naturally evolved mode of survival in deleterious environments involves the complex, multigenic interplay between disparate stress response and homeostasis mechanisms. Rational engineering of such resistance would require a systems-level understanding of cellular behavior that is, in general, not yet available. To circumvent this limitation, we have developed a phenotype discovery approach termed global transcription machinery engineering (gTME) that allows for the generation and selection of nonphysiological traits. We alter gene expression on a genome-wide scale by selecting for dominant mutations in a randomly mutagenized general transcription factor. The gene encoding the mutated transcription factor resides on a plasmid in a strain carrying the unaltered chromosomal allele. Thus, although the dominant mutations may destroy the essential function of the plasmid-borne variant, alteration of the transcriptome with minimal perturbation to normal cellular processes is possible via the presence of the native genomic allele. Achieving a phenotype of interest involves the construction and diversity evaluation of yeast libraries harboring random sequence variants of a chosen transcription factor and the subsequent selection and validation of mutant strains. We describe the rationale and procedures associated with each step in the context of generating strains possessing enhanced ethanol tolerance. Copyright © 2010 Elsevier Inc. All rights reserved.

  1. effect of thermal stress of short duration on the red blood cell

    African Journals Online (AJOL)

    Dr Ivanc

    2013-05-01

    May 1, 2013 ... an acute increase of temperature and metabolic rate on basic blood parameters as oxygen transport system. The effect of thermal stress was studied on the Barbus balcanicus, a species inhabiting smaller water bodies often exposed to temperature fluctuatiation. During the experiment, the fish were ...

  2. Quasi-static transient thermal stresses in a thick annular disc

    Indian Academy of Sciences (India)

    in a thin annular disc. Also Deshmukh 2002 studied transient heat conduction problem in a thin hollow cylinder and determined thermal stresses. ... containers for hot gases or liquids, in the foundations for furnaces, etc. 2. Formulation of the problem. Consider a thick a annular disc of thickness 2h occupying space D defined ...

  3. Impact of thermal stress on the growth, size-distribution and biomass ...

    African Journals Online (AJOL)

    This paper reports an in-vivo account of the impact of thermal stress on the biomass and sizedistribution of estuarine populations of Pachymelania aurita in Epe Lagoon, Nigeria. Off all physicochemical variables investigated only water temperature was statistically different among study stations. A total of 7626 individuals of ...

  4. Reliability-oriented environmental thermal stress analysis of fuses in power electronics

    DEFF Research Database (Denmark)

    Bahman, A. S.; Iannuzzo, F.; Holmgaard, T.

    2017-01-01

    This paper investigates the thermo-mechanical stress experienced by axial lead fuses used in power electronics. Based on some experience, the approach used in this paper is pure thermal cycling, and the found failure mechanisms have been investigated through X-ray imaging. A two-step analysis, i...

  5. Thermal stress analysis and operational characteristics of a bellows-seal globe valve

    International Nuclear Information System (INIS)

    Kim, Kwang Su; Kim, Youn Jae

    2005-01-01

    Because of design and manufacturing costs, it is important to predict an expected life of bellows with component stresses of bellows as its design factors and material characteristics. In this study, numerical analyses are carried out to elucidate the thermal and flow characteristics with 0.1 m (4 inch) bellows-seal globe valve for high temperature (max. 600 .deg. C) and for high pressure (max. 104 kgf/cm 2 , 10.2 MPa) conditions. Using commercial codes, FLUENT, which uses FVM and SIMPLE algorithm, and ANSYS, which uses FEM, the pressure and temperature fields are calculated and the results are graphically depicted. In addition, when bellows have an axial displacement, thermal stress affecting bellows life is studied. The pressure and temperature values obtained from the flow analyses are adopted as the boundary conditions for thermal stress analyses. As the result of this study, we get the reasonable coefficients for valve and thermal stress for bellows, compared with existing coefficients and calculated values

  6. Involvement of polyhydroxyalkanoates in stress resistance of microbial cells: Biotechnological consequences and applications.

    Science.gov (United States)

    Obruca, Stanislav; Sedlacek, Petr; Koller, Martin; Kucera, Dan; Pernicova, Iva

    2017-12-14

    Polyhydroxyalkanoates (PHA) are polyesters accumulated by numerous prokaryotes as storage materials; they attract attention as "green" alternatives to petrochemical plastics. Recent research has demonstrated that their biological role goes beyong their storage function, since they presence in cytoplasm enhances stress resistance of microorganisms. To address these complex functions, this review summarizes the protective effects of PHA for microrganisms; the involvement of PHA in stress resistance is discussed also from a praxis-oriented perspective. The review discourses the controlled application of stress to improve PHA productivity. Also the manifold advantages of using stress adapted microbes - extremophiles as PHA producers are discussed. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. [Regulating acid stress resistance of lactic acid bacteria--a review].

    Science.gov (United States)

    Wu, Chongde; Huang, Jun; Zhou, Rongqing

    2014-07-04

    As cell factories, lactic acid bacteria are widely used in food, agriculture, pharmaceutical and other industries. Acid stress is one the important survival challenges encountered by lactic acid bacteria both in fermentation process and in the gastrointestinal tract. Recently, the development of systems biology and metabolic engineering brings unprecedented opportunity for further elucidating the acid tolerance mechanisms and improving the acid stress resistance of lactic acid bacteria. This review addresses physiological mechanisms of lactic acid bacteria during acid stress. Moreover, strategies to improve the acid stress resistance of lactic acid were proposed.

  8. Identification of plant genes for abiotic stress resistance

    NARCIS (Netherlands)

    Dixit, S.A.

    2008-01-01

    As water and salt stresses occur frequently and can affect many habitats, plants have developed several strategies to cope with these challenges: either adaptation mechanisms, which allow them to survive the adverse conditions, or specific growth habits to avoid stress conditions. Stress-tolerant

  9. Biochemical basis of the high resistance to oxidative stress

    Indian Academy of Sciences (India)

    Aerobic organisms experience oxidative stress due to generation of reactive oxygen species during normal aerobic metabolism. In addition, several chemicals also generate reactive oxygen species which induce oxidative stress. Thus oxidative stress constitutes a major threat to organisms living in aerobic environments.

  10. Biochemical basis of the high resistance to oxidative stress in ...

    Indian Academy of Sciences (India)

    Aerobic organisms experience oxidative stress due to generation of reactive oxygen species during normal aerobic metabolism. In addition, several chemicals also generate reactive oxygen species which induce oxidative stress. Thus oxidative stress constitutes a major threat to organisms living in aerobic environments.

  11. Excessive caloric intake acutely causes oxidative stress, GLUT4 carbonylation, and insulin resistance in healthy men.

    Science.gov (United States)

    Boden, Guenther; Homko, Carol; Barrero, Carlos A; Stein, T Peter; Chen, Xinhua; Cheung, Peter; Fecchio, Chiara; Koller, Sarah; Merali, Salim

    2015-09-09

    Obesity-linked insulin resistance greatly increases the risk for type 2 diabetes, hypertension, dyslipidemia, and non-alcoholic fatty liver disease, together known as the metabolic or insulin resistance syndrome. How obesity promotes insulin resistance remains incompletely understood. Plasma concentrations of free fatty acids and proinflammatory cytokines, endoplasmic reticulum ( ER) stress, and oxidative stress are all elevated in obesity and have been shown to induce insulin resistance. However, they may be late events that only develop after chronic excessive nutrient intake. The nature of the initial event that produces insulin resistance at the beginning of excess caloric intake and weight gain remains unknown. We show that feeding healthy men with ~6000 kcal/day of the common U.S. diet [~50% carbohydrate (CHO), ~ 35% fat, and ~15% protein] for 1 week produced a rapid weight gain of 3.5 kg and the rapid onset (after 2 to 3 days) of systemic and adipose tissue insulin resistance and oxidative stress but no inflammatory or ER stress. In adipose tissue, the oxidative stress resulted in extensive oxidation and carbonylation of numerous proteins, including carbonylation of GLUT4 near the glucose transport channel, which likely resulted in loss of GLUT4 activity. These results suggest that the initial event caused by overnutrition may be oxidative stress, which produces insulin resistance, at least in part, via carbonylation and oxidation-induced inactivation of GLUT4. Copyright © 2015, American Association for the Advancement of Science.

  12. KLF15 is a molecular link between endoplasmic reticulum stress and insulin resistance.

    Directory of Open Access Journals (Sweden)

    Dae Young Jung

    Full Text Available Obesity places major demands on the protein folding capacity of the endoplasmic reticulum (ER, resulting in ER stress, a condition that promotes hepatic insulin resistance and steatosis. Here we identify the transcription factor, Kruppel-like factor 15 (KLF15, as an essential mediator of ER stress-induced insulin resistance in the liver. Mice with a targeted deletion of KLF15 exhibit increased hepatic ER stress, inflammation, and JNK activation compared to WT mice; however, KLF15 (-/- mice are protected against hepatic insulin resistance and fatty liver under high-fat feeding conditions and in response to pharmacological induction of ER stress. The mammalian target of rapamycin complex 1 (mTORC1, a key regulator of cellular energy homeostasis, has been shown to cooperate with ER stress signaling pathways to promote hepatic insulin resistance and lipid accumulation. We find that the uncoupling of ER stress and insulin resistance in KLF15 (-/- liver is associated with the maintenance of a low energy state characterized by decreased mTORC1 activity, increased AMPK phosphorylation and PGC-1α expression and activation of autophagy, an intracellular degradation process that enhances hepatic insulin sensitivity. Furthermore, in primary hepatocytes, KLF15 deficiency markedly inhibits activation of mTORC1 by amino acids and insulin, suggesting a mechanism by which KLF15 controls mTORC1-mediated insulin resistance. This study establishes KLF15 as an important molecular link between ER stress and insulin action.

  13. KLF15 is a molecular link between endoplasmic reticulum stress and insulin resistance.

    Science.gov (United States)

    Jung, Dae Young; Chalasani, Umadevi; Pan, Ning; Friedline, Randall H; Prosdocimo, Domenick A; Nam, Minwoo; Azuma, Yoshihiro; Maganti, Rajanikanth; Yu, Kristine; Velagapudi, Ashish; O'Sullivan-Murphy, Bryan; Sartoretto, Juliano L; Jain, Mukesh K; Cooper, Marcus P; Urano, Fumihiko; Kim, Jason K; Gray, Susan

    2013-01-01

    Obesity places major demands on the protein folding capacity of the endoplasmic reticulum (ER), resulting in ER stress, a condition that promotes hepatic insulin resistance and steatosis. Here we identify the transcription factor, Kruppel-like factor 15 (KLF15), as an essential mediator of ER stress-induced insulin resistance in the liver. Mice with a targeted deletion of KLF15 exhibit increased hepatic ER stress, inflammation, and JNK activation compared to WT mice; however, KLF15 (-/-) mice are protected against hepatic insulin resistance and fatty liver under high-fat feeding conditions and in response to pharmacological induction of ER stress. The mammalian target of rapamycin complex 1 (mTORC1), a key regulator of cellular energy homeostasis, has been shown to cooperate with ER stress signaling pathways to promote hepatic insulin resistance and lipid accumulation. We find that the uncoupling of ER stress and insulin resistance in KLF15 (-/-) liver is associated with the maintenance of a low energy state characterized by decreased mTORC1 activity, increased AMPK phosphorylation and PGC-1α expression and activation of autophagy, an intracellular degradation process that enhances hepatic insulin sensitivity. Furthermore, in primary hepatocytes, KLF15 deficiency markedly inhibits activation of mTORC1 by amino acids and insulin, suggesting a mechanism by which KLF15 controls mTORC1-mediated insulin resistance. This study establishes KLF15 as an important molecular link between ER stress and insulin action.

  14. Two-dimensional simulation of the thermal stress effect on static and dynamic VDMOS characteristics

    International Nuclear Information System (INIS)

    Alwan, M.; Beydoun, B.; Ketata, K.; Zoaeter, M.

    2005-01-01

    Using a two-dimensional simulator, the effect of the thermal stress on static and dynamic vertical double-diffusion metal oxide semiconductor (VDMOS) characteristics have been investigated. The use of the device under certain thermal stress conditions can produce modifications of its physical and electrical properties. Based on physics and 2D simulations, this paper proposes an analysis of this stress effect observed on the electrical characteristics of the device. Parameters responsible of these modifications are determined. Approximate expressions of the ionization coefficients and breakdown voltage in terms of temperature are proposed. Non-punch-through junction theory is used to express the breakdown voltage and the space charge extension with respect to the impurity concentration and the temperature. The capacitances of the device have been also studied. The effect of the stress on C-V characteristics is observed and analyzed. We notice that the drain-gate, drain-source and gate-source capacitances are shifted due to the degradation of device physical properties versus thermal stress

  15. Thermal Stress Analyses for a Multislug Beam NLC Positron Target(LCC-0090)

    International Nuclear Information System (INIS)

    Stein, W.

    2003-01-01

    The power deposition of an incident multislug electron beam in a tungsten-rhenium target and the resultant thermal shock stresses in the material have been modeled with a transient, dynamic, structural response finite element code. The Next Linear Collider electron beam is assumed split into two parts, with each part impinging on a 4 radiation lengths thick target. Two targets are required to avoid excessive thermal stresses in the targets. Each of the two beam parts is assumed broken up into four slugs, each two microseconds apart. Energy deposition from each slug occurs over 265 nanoseconds and results in heating of the target and pressure pulses straining the material. The rapid power deposition of the electron beam and the resultant temperature profile in the target generates stress and pressure waves in the material that are considerably larger than those calculated by a static analysis. The 6.22 GeV electron beam has a spot radius size of 1.6 mm and results in a maximum temperature jump of 438 C. Stress pressure pulses are induced in the material from the rapid thermal expansion of the hotter material with peak effective stresses reaching 78 ksi (5.3 x 10 8 Pa) on the back side of the target, which is less than one half of the yield strength of the tungsten/rhenium alloy and below the material fatigue limit

  16. Thermal Stress Analyses for an NLC Positron Target with a 3 mm Spot Radius Beam

    International Nuclear Information System (INIS)

    Stein, W.; Sunwoo, A.; Sheppard, J. C.; Bharadwaj, V.; Schultz, D.

    2002-01-01

    The power deposition of an incident electron beam in a tungsten-rhenium target and the resultant thermal shock stresses in the material have been modeled with a transient, dynamic, structural response finite element code. The Next Linear Collider electron beam is assumed split into three parts, with each part impinging on a 4 radiation lengths thick target. Three targets are required to avoid excessive thermal stresses in the targets. Energy deposition from each beam pulse occurs over 265 nanoseconds and results in heating of the target and pressure pulses straining the material. The rapid power deposition of the electron beam and the resultant temperature profile in the target generates stress and pressure waves in the material that are considerably larger than those calculated by a static analysis. The 6.22 GeV electron beam has a spot radius size of 3 mm and results in a maximum temperature jump of 147 C. Stress pressure pulses are induced in the material from the rapid thermal expansion of the hotter material with peak effective stresses reaching 83 ksi (5.77 x 10 8 Pa) on the back side of the target, which is less than one half of the yield strength of the tungsten/rhenium alloy and below the material fatigue limit

  17. Effect of electrical pulse treatment on the thermal fatigue resistance of bionic compacted graphite cast iron processed in water

    International Nuclear Information System (INIS)

    Liu, Yan; Zhou, Hong; Su, Hang; Yang, Chunyan; Cheng, Jingyan; Zhang, Peng; Ren, Luquan

    2012-01-01

    Highlights: ► Electrical pulse treatment can reduce cracks on bionic units before thermal fatigue tests. ► Electrical pulse treatment can reduce crack sources during thermal fatigue tests. ► Thermal fatigue resistance of bionic units processed in water is enhanced. ► Thermal fatigue resistance of bionic CGI processed in water is improved. -- Abstract: In order to further enhance the thermal fatigue resistance of bionic compacted graphite cast iron (CGI) which is processed by laser in water, the electrical pulse treatment is applied to improve the thermal fatigue resistance of bionic units. The results show that the electrical pulse treatment causes the supersaturated carbon atoms located in the lattice of austenite to react with the iron atoms to form the Fe 3 C. The microstructures of the bionic units processed in water are refined by the electrical pulse treatment. The cracks on the bionic units are reduced by the electrical pulse treatment before the thermal fatigue tests; and during the tests, the thermal fatigue resistance of bionic units is therefore enhanced by reducing the crack sources. By this way, the thermal fatigue resistance of bionic CGI processed in water is improved.

  18. Mucus sugar content shapes the bacterial community structure in thermally stressed Acropora muricata

    Directory of Open Access Journals (Sweden)

    Sonny T.M. Lee

    2016-03-01

    Full Text Available 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°C 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.

  19. Assessment of thermal fatigue damage caused by local fluid temperature fluctuation (part I: characteristics of constraint and stress caused by thermal striation and stratification)

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2014-01-01

    Highlights: • The source of the membrane constraint due to local temperature fluctuation was shown. • Thermal fatigue that occurred at a mixing tee and branched elbow was analyzed. • Cracking occurrence was reasonably explained by the constraint and stress conditions. - Abstract: This study was aimed at identifying the constraint conditions under local temperature fluctuation by thermal striping at a mixing tee and by thermal stratification at an elbow pipe branched from the main pipe. Numerical and analytical approaches were made to derive the thermal stress and its fluctuation. It was shown that an inhomogeneous temperature distribution in a straight pipe caused thermal stress due to a membrane constraint even if an external membrane constraint did not act on the pipe. Although the membrane constraint increased the mean stress at the mixing tee, it did not contribute to fluctuation of the thermal stress. On the other hand, the membrane constraint played an important role in the fatigue damage accumulation near the stratification layer of the branched elbow. Based on the constraint and stress conditions analyzed, the characteristics of the cracking observed in actual nuclear power plants were reasonably explained. Namely, at the mixing tee, where thermal crazing has been found, the lack of contribution of the membrane constraint to stress fluctuation caused a stress gradient in the thickness direction and arrested crack growth. On the other hand, at the branched elbow, where axial through-wall cracks have been found, the relatively large hoop stress fluctuation was brought about by movement of the stratified layer together with the membrane constraint even under a relatively low frequency of stress fluctuation

  20. Thermal Stress Analysis for a Transfer Line of Hydrogen Moderator in J-Parc

    Science.gov (United States)

    Tatsumoto, H.; Teshigawara, M.; Aso, T.; Ohtsu, K.; Maekawa, F.; Kato, T.

    2008-03-01

    An intense spallation neutron source (JSNS) driven by a 1-MW proton beam was constructed, as one of the main experimental facilities in J-PARC. In JSNS, supercritical hydrogen (1.5 MPa, 20 K) was selected as a moderator material. Three kinds of hydrogen moderator are installed (coupled, decoupled, and poisoned) to provide pulsed neutron beam with higher neutronic performance. The moderators contain cryogenic hydrogen transfer lines located in a radioactive area. Therefore, the transfer lines should be designed to have minimum pipe size and elbow-type bend sections to reduce the potential for radiation dose by radiation streaming. The design should also consider mechanical stress concentrations, deformation, and touching between the pipes due to the thermal shrinkage at the cryogenic hydrogen temperature. A FEM code analysis determined the appropriate locations of piping supporting spacers to keep the thermal stress below the allowable stress and to also avoid touching between the pipes.

  1. Transcriptome analysis and identification of significantly differentially expressed genes in Holstein calves subjected to severe thermal stress

    Science.gov (United States)

    Srikanth, Krishnamoorthy; Lee, Eunjin; Kwan, Anam; Lim, Youngjo; Lee, Junyep; Jang, Gulwon; Chung, Hoyoung

    2017-11-01

    RNA-Seq analysis was used to characterize transcriptome response of Holstein calves to thermal stress. A total of eight animals aged between 2 and 3 months were randomly selected and subjected to thermal stress corresponding to a temperature humidity index of 95 in an environmentally controlled house for 12 h consecutively for 3 days. A set of 15,787 unigenes were found to be expressed and after a threshold of threefold change, and a Q value physiological and metabolic processes to survive. Many of the genes identified in this study have not been previously reported to be involved in thermal stress response. The results of this study extend our understanding of the animal's response to thermal stress and some of the identified genes may prove useful in the efforts to breed Holstein cattle with superior thermotolerance, which might help in minimizing production loss due to thermal stress.

  2. Simulation of thermal stresses in SiC-Al2O3 composite tritium penetration barrier by finite-element analysis

    International Nuclear Information System (INIS)

    Liu, Hongbing; Tao, Jie; Gautreau, Yoann; Zhang, Pingze; Xu, Jiang

    2009-01-01

    Tritium penetration barrier (TPB) composed of Al 2 O 3 and SiC on 316L stainless steel was proposed to improve the tritium penetration resistance of the substrate in this work. At the same time, the concept of functionally graded materials (FGM) was applied to manage to decrease residual stresses between Al 2 O 3 and 316L stainless steel substrate due to the mismatch of their thermal expansion coefficients. The effects of system architecture on the residual stresses developed in the composite coatings were investigated numerically by means of finite-element analysis (FEA). Modeling results showed that the presence of the graded properties and the compositions within the coating did reduce the stress discontinuity at the interfaces between the coating and the substrate. Also, the magnitudes of the residual stresses on the coating surface and at the coating/substrate interface were dependent on the Al 2 O 3 and SiC coating thickness.

  3. Thermal barrier coatings for thermal insulation and corrosion resistance in industrial gas turbine engines

    Science.gov (United States)

    Vogan, J. W.; Hsu, L.; Stetson, A. R.

    1981-01-01

    Four thermal barrier coatings were subjected to a 500-hour gas turbine engine test. The coatings were two yttria stabilized zirconias, calcium ortho silicate and calcium meta titanate. The calcium silicate coating exhibited significant spalling. Yttria stabilized zirconia and calcium titanate coatings showed little degradation except in blade leading edge areas. Post-test examination showed variations in the coating due to manual application techniques. Improved process control is required if engineering quality coatings are to be developed. The results indicate that some leading edge loss of the coating can be expected near the tip.

  4. Solvent and Thermally Resistant Polymeric Membranes for Different Applications

    KAUST Repository

    Taghreeed, Jalal

    2016-11-01

    In this work polymeric materials were developed to be used as a solvent and heat resistance membrane for different applications. In ultrafiltration, poly (ether imide sulfone) membranes were manufactured by combining phase inversion and functionalization reaction between epoxy groups and amine modified polyether oligomers (Jeffamine®). Polysilsesquioxanes or oligo silsesquioxanes containing epoxy functionalities were in-situ grown in the casting solution and made available for further reaction with amines in the coagulation/annealing baths. Water permeances up to 1500 l m-2 h-1 bar-1 were obtained with sharp pore size distribution and a pore diameter peak at 66 nm, confirmed by porosimetry, allowing 99.2 % rejection of γ-globulin. The membranes were stable in 50:50 dimethylformamide/water, 50:50 N-methyl pyrrolidone/water and 100 % tetrahydrofuran. In pervaporation, Novel hydrophobic Hyflon®/Extem® and Hyflon®/PVDF were developed and investigated for ethylene glycol dehydration and n-butanol dehydration respectively. For ethylene glycol different Extem® concentrations were evaluated with regard to both flux and amount of water in the permeate side. Eighteen (18) wt% gave more than 90 wt% water in the permeate. Increasing feed temperature from 25 to 85°C increased the water flux from 31 to 91 g m-2 h-1 when using 5 wt% water in ethylene glycol as feed. The water flux of 40 wt% water:ethylene glycol at 45°C was found to be 350 g m-2 h-1. And for n-butanol dehydration the coating protocols for thin defect-free Hyflon® selective layer on the PVDF support was optimized. Water and n-butanol transport was measured, analyzing the effect of operating conditions. The water flux through the newly developed membranes was higher than 150 g m-2 h-1 with selectivity for water higher than 99 wt%. The membrane application can be extended to other solvents, supporting an effective and simple method for dehydration with hydrophobic membranes. In membrane distillation, PVDF

  5. Thermal resistance between low-dimensional nanostructures and semi-infinite media

    Science.gov (United States)

    Panzer, Matthew A.; Goodson, Ken E.

    2008-05-01

    Nanostructured electronic and photonic devices include a high density of material interfaces, which can strongly impede heat conduction and influence performance and reliability. Thermal conduction through interfaces is a very mature discipline for the traditional geometry, in which the lateral interface dimensions are large compared to the phonon wavelength. In nanostructures, however, the localization of phonons in the directions parallel to the interface may strongly influence the effective thermal resistance. The present work investigates model problems of abrupt junctions between a harmonic one-dimensional (1D) and a three-dimensional (3D) fcc lattice and between a 1D and a two-dimensional square lattice. The abrupt change in geometry modifies the phonon modes participating in energy transmission and creates an additional thermal resistance that is comparable with that occurring due to the acoustic mismatch at the interface of bulk media. For both cases, varying the impedance mismatch at the junction suggests that engineering an intentional impedance mismatch at a nanostructured interface may enhance the transmission of energy. The lattice dynamics calculations are used to develop qualitative arguments for the interface resistances in the practical geometries involving carbon nanotubes, silicon nanopillars, and graphene. This research provides foundations for detailed investigations of the impact of localized phonon modes on the acoustic mismatch resistance.

  6. 3-D thermal modelling applied to stress-induced anisotropy of thermal conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Pron, H.; Bissieux, C. [Universite de Reims, Unite de Thermique et Analyse Physique, EA 2061, Laboratoire de Thermophysique (URCA/UTAP/LTP), UFR Sciences, Moulin de la Housse, B.P 1039, 51687 cedex 2, Reims (France)

    2004-12-01

    The present work consists in the development of a three-dimensional model of heat diffusion in orthotropic media, based on numerical Fourier transforms, and taking into account the extent of the source. This model has been applied, together with a Gauss-Newton parameter estimation procedure, to identify the components of the conductivity tensor of a steel bar under uniaxial loading. Few percent variations of the conductivity components have been observed for applied stresses remaining in the elastic domain. (authors)

  7. Exponentially Increased Thermal Resistance of Salmonella spp. and Enterococcus faecium at Reduced Water Activity.

    Science.gov (United States)

    Liu, Shuxiang; Tang, Juming; Tadapaneni, Ravi Kiran; Yang, Ren; Zhu, Mei-Jun

    2018-04-15

    Salmonella spp. exhibit prolonged survivability and high tolerance to heat in low-moisture foods. The reported thermal resistance parameters of Salmonella spp. in low-moisture foods appear to be unpredictable due to various unknown factors. We report here that temperature-dependent water activity (a w, treatment temperature ) plays an important role in the sharply increased thermal resistance of Salmonella enterica serovar Enteritidis PT 30 and its potential surrogate Enterococcus faecium NRRL B-2354. In our study, silicon dioxide granules, as carriers, were separately inoculated with these two microorganisms and were heated at 80°C with controlled relative humidity between 18 and 72% (resulting in corresponding a w,80°C values for bacteria between 0.18 and 0.72) in custom-designed test cells. The inactivation kinetics of both microorganisms fitted a log-linear model ( R 2 , 0.83 to 0.97). Reductions in the a w,80°C values of bacterial cells exponentially increased the D 80°C (the time needed to achieve a 1-log reduction in a bacterial population at 80°C) values for S Enteritidis and E. faecium on silicon dioxide. The log-linear relationship between the D 80°C values for each strain in silicon dioxide and its a w,80°C values was also verified for organic wheat flour. E. faecium showed consistently higher D 80°C values than S Enteritidis over the a w,80°C range tested. The estimated z aw (the change in a w,80°C needed to change D 80°C by 1 log) values of S Enteritidis and E. faecium were 0.31 and 0.28, respectively. This study provides insight into the interpretation of Salmonella thermal resistance that could guide the development and validation of thermal processing of low-moisture foods. IMPORTANCE In this paper, we established that the thermal resistance of the pathogen S Enteritidis and its surrogate Enterococcus faecium , as reflected by D values at 80°C, increases sharply with decreasing relative humidity in the environment. The log

  8. High-Performance Corrosion-Resistant Materials: Iron-Based Amorphous-Metal Thermal-Spray Coatings

    International Nuclear Information System (INIS)

    Farmer, J C; Haslam, J J; Wong, F; Ji, X; Day, S D; Branagan, D J; Marshall, M C; Meacham, B E; Buffa, E J; Blue, C A; Rivard, J K; Beardsley, M B; Weaver, D T; Aprigliano, L F; Kohler, L; Bayles, R; Lemieux, E J; Wolejsza, T M; Martin, F J; Yang, N; Lucadamo, G; Perepezko, J H; Hildal, K; Kaufman, L; Heuer, A H; Ernst, F; Michal, G M; Kahn, H; Lavernia, E J

    2004-01-01

    The multi-institutional High Performance Corrosion Resistant Materials (HPCRM) Team is cosponsored by the Defense Advanced Projects Agency (DARPA) Defense Science Office (DSO) and the Department of Energy (DOE) Office of Civilian Radioactive Waste Management (OCRWM), and has developed new corrosion-resistant, iron-based amorphous metals that can be applied as coatings with advanced thermal spray technology. Two compositions have corrosion resistance superior to wrought nickel-based Alloy C-22 (UNS No. N06022) in very aggressive environments, including concentrated calcium-chloride brines at elevated temperature. Corrosion costs the Department of Defense billions of dollars every year, with an immense quantity of material in various structures undergoing corrosion. For example, in addition to fluid and seawater piping, ballast tanks, and propulsions systems, approximately 345 million square feet of structure aboard naval ships and crafts require costly corrosion control measures. The use of advanced corrosion-resistant materials to prevent the continuous degradation of this massive surface area would be extremely beneficial. The Fe-based corrosion-resistant, amorphous-metal coatings under development may prove of importance for applications on ships. Such coatings could be used as an ''integral drip shield'' on spent fuel containers, as well as protective coatings that could be applied over welds, thereby preventing exposure to environments that might cause stress corrosion cracking. In the future, such new high-performance iron-based materials could be substituted for more-expensive nickel-based alloys, thereby enabling a reduction in the $58-billion life cycle cost for the long-term storage of the Nation's spent nuclear fuel by tens of percent

  9. Study of thermal stability and degradation of fire resistant candidate polymers for aircraft interiors

    Science.gov (United States)

    Hsu, M. T. S.

    1976-01-01

    The thermochemistry of bismaleimide resins and phenolphthalein polycarbonate was studied. Both materials are fire-resistant polymers and may be suitable for aircraft interiors. The chemical composition of the polymers has been determined by nuclear magnetic resonance and infrared spectroscopy and by elemental analysis. Thermal properties of these polymers have been characterized by thermogravimetric analyses. Qualitative evaluation of the volatile products formed in pyrolysis under oxidative and non-oxidative conditions has been made using infrared spectrometry. The residues after pyrolysis were analyzed by elemental analysis. The thermal stability of composite panel and thermoplastic materials for aircraft interiors was studied by thermogravimetric analyses.

  10. Testing of thermal fatigue resistance of tools and rolls for hot working

    Science.gov (United States)

    Terčelj, Milan; Fazarinc, Matevž; Kugler, Goran

    2017-09-01

    In the present contribution two tests for thermal fatigue testing, which have been developed in our group, are presented. First test has provided internal cooling system of sample, while second has external cooling. For both tests heating and cooling of samples are computer guided that enables very reliable results of testing. The first test is more appropriate for testing the base material, i.e. roll cast irons, roll steels, tool steels. The second test is more appropriate for experiments that are aimed for selection of appropriate tool surface treatment, i.e. laser cladding, nitriding, coating, etc., and to compare and to achieve improved resistance against thermal fatigue of produced surface layers.

  11. Blocking iNOS and endoplasmic reticulum stress synergistically improves insulin resistance in mice

    Directory of Open Access Journals (Sweden)

    Tamires M. Zanotto

    2017-02-01

    Conclusions: Taken together, these results reinforce the tissue-specific regulation of insulin signaling in obesity, with iNOS being sufficient to account for insulin resistance in muscle, but in liver and adipose tissue ER stress and insulin resistance can be induced by both iNOS-dependent and iNOS-independent mechanisms.

  12. A unified momentum equation approach for computing thermal residual stresses during melting and solidification

    Science.gov (United States)

    Yeo, Haram; Ki, Hyungson

    2018-03-01

    In this article, we present a novel numerical method for computing thermal residual stresses from a viewpoint of fluid-structure interaction (FSI). In a thermal processing of a material, residual stresses are developed as the material undergoes melting and solidification, and liquid, solid, and a mixture of liquid and solid (or mushy state) coexist and interact with each other during the process. In order to accurately account for the stress development during phase changes, we derived a unified momentum equation from the momentum equations of incompressible fluids and elastoplastic solids. In this approach, the whole fluid-structure system is treated as a single continuum, and the interaction between fluid and solid phases across the mushy zone is naturally taken into account in a monolithic way. For thermal analysis, an enthalpy-based method was employed. As a numerical example, a two-dimensional laser heating problem was considered, where a carbon steel sheet was heated by a Gaussian laser beam. Momentum and energy equations were discretized on a uniform Cartesian grid in a finite volume framework, and temperature-dependent material properties were used. The austenite-martensite phase transformation of carbon steel was also considered. In this study, the effects of solid strains, fluid flow, mushy zone size, and laser heating time on residual stress formation were investigated.

  13. Experimental Study of Laser - enhanced 5A03 Aluminum Alloy and Its Stress Corrosion Resistance

    Science.gov (United States)

    Wang, Guicheng; Chen, Jing; Pang, Tao

    2018-02-01

    Based on the study of improving the stress corrosion resistance of 5A03 aluminum alloy for ship, this paper mainly studied the tensile test, surface morphology and residual stress under laser shock, high temperature and stress corrosion. It is found that the residual compressive stress and the grain refinement on the surface of the material during the heat strengthening process increase the breaking strength of the sample in the stress corrosion environment. Appropriate high temperature maintenance helps to enhance the effect of deformation strengthening. In the 300°C environment insulation, due to recrystallization of the material, the performance decreased significantly. This study provides an experimental basis for effectively improving the stress corrosion resistance of 5A03 aluminum alloy.

  14. Variation in adult life history and stress resistance across five ...

    Indian Academy of Sciences (India)

    In particular, the expected positive relationships between fecundity and size/lipid content, lipid content and starvation resistance, carbohydrate (glycogen) content and desiccation resistance, and the expected negative relationship between lifespan and fecundity were not observed. Most traits were strongly positively ...

  15. Quantifying Cyclic Thermal Stresses Due to Solar Exposure in Rock Fragments in Gale Crater, Mars

    Science.gov (United States)

    Hallet, B.; Mackenzie-Helnwein, P.; Sletten, R. S.

    2017-12-01

    Curiosity and earlier rovers on Mars have revealed in detail rocky landscapes with decaying outcrops, rubble, stone-littered regolith, and bedrock exposures that reflect the weathering processes operating on rock exposed to Mars' cold and hyperarid environment. Evidence from diverse sources points to the importance of thermal stresses driven by cyclic solar exposure in contributing to the mechanical weathering of exposed rock and generation of regolith in various settings on Earth [1,2,3], and even more so on extraterrestrial bodies where large, rapid cyclic temperature variations are frequent (e.g. Mars [4], as well as comets [5], asteroids [6] and other airless bodies [7]). To study these thermal stresses, we use a 3d finite element (FE) model constrained by ground-based surface temperature measurements from Curiosity's Environmental Monitoring Station (REMS). The numerical model couples radiation and conduction with elastic response to determine the temperature and stress fields in individual rocks on the surface of Mars based on rock size and thermo-mechanical properties. We provide specific quantitative results for boulder-size basalt rocks resting on the ground using a realistic thermal forcing that closely matches the REMS temperature observations, and related thermal inertia data. Moreover, we introduce analytical studies showing that these numerical results can readily be generalized. They are quite universal, informing us about thermal stresses due to cyclic solar exposure in general, for rock fragments of different sizes, lithologies, and fracture- thermal- and mechanical-properties. Using Earth-analogue studies to gain insight, we also consider how the shapes, fractures, and surface details of rock fragments imaged by Curiosity likely reflect the importance of rock breakdown due to thermal stresses relative to wind-driven rock erosion and other surface processes on Mars. References:[1] McFadden L et al. (2005) Geol. Soc.Am. Bull. 117(1-2): 161-173 [2

  16. Ecogenomics of plant resistance to biotic and abiotic stresses

    NARCIS (Netherlands)

    Davila Olivas, N.H.

    2016-01-01

    Summary

    In natural and agricultural ecosystems, plants are exposed to a wide diversity of abiotic and biotic stresses such as drought, salinity, pathogens and insect herbivores. Under natural conditions, these stresses do not occur in isolation but commonly occur simultaneously.

  17. Finite Element Simulation of Residual Stress Development in Thermally Sprayed Coatings

    Science.gov (United States)

    Elhoriny, Mohamed; Wenzelburger, Martin; Killinger, Andreas; Gadow, Rainer

    2017-04-01

    The coating buildup process of Al2O3/TiO2 ceramic powder deposited on stainless-steel substrate by atmospheric plasma spraying has been simulated by creating thermomechanical finite element models that utilize element death and birth techniques in ANSYS commercial software and self-developed codes. The simulation process starts with side-by-side deposition of coarse subparts of the ceramic layer until the entire coating is created. Simultaneously, the heat flow into the material, thermal deformation, and initial quenching stress are computed. The aim is to be able to predict—for the considered spray powder and substrate material—the development of residual stresses and to assess the risk of coating failure. The model allows the prediction of the heat flow, temperature profile, and residual stress development over time and position in the coating and substrate. The proposed models were successfully run and the results compared with actual residual stresses measured by the hole drilling method.

  18. Effect of the combined stress on the life of components under thermal cycling conditions

    International Nuclear Information System (INIS)

    Zuchowski, R.; Zietkowski, L.

    1987-01-01

    The life of structural components subjected to temperature changes is affected, among other factors, by the nature of the stress field. If life prediction for axially stressed components can be accomplished with a number of well established techniques, the behaviour under a complex state of stress and varying temperature conditions still is the object of intensive research. The present study was aimed at assessing the influence of the stress field upon the life of specimens made of chromium-nickel H23N18 steel under thermal cycling conditions. The designation of steel is in accordance with Polish Standards. The experiments were made on thin-walled tubular specimens loaded with various combinations of a static axial force and a static torque. (orig./GL)

  19. Transient thermal stresses analysis and thermal fatigue damage evaluation for skirt attachment of coke drum

    Science.gov (United States)

    Ambarita, H.; Siahaan, A. S.; Kawai, H.; Daimaruya, M.

    2018-02-01

    In the last decade, the demand for delayed coking capacity has been steadily increasing. The trend in the past 15 to 20 years has been for operators to try to maximize the output of their units by reducing cycle times. This mode of operation can result in very large temperature gradients within the drums during preheating stage and even more so during the quench cycle. This research provide the optimization estimation of fatigue life due to each for the absence of preheating stage and cutting stage. In the absence of preheating stage the decreasing of fatigue life is around 19% and the increasing of maximum stress in point 5 of shell-to-skirt junction is around 97 MPa. However for the absence of cutting stage it was found that is more severe compare to normal cycle. In this adjustment fatigue life reduce around 39% and maximum stress is increased around 154 MPa. It can concluded that for cycle optimization, eliminating preheating stage possibly can become an option due to the increasing demand of delayed coking process.

  20. Thermally oxidized titania nanotubes enhance the corrosion resistance of Ti6Al4V.

    Science.gov (United States)

    Grotberg, John; Hamlekhan, Azhang; Butt, Arman; Patel, Sweetu; Royhman, Dmitry; Shokuhfar, Tolou; Sukotjo, Cortino; Takoudis, Christos; Mathew, Mathew T

    2016-02-01

    The negative impact of in vivo corrosion of metallic biomedical implants remains a complex problem in the medical field. We aimed to determine the effects of electrochemical anodization (60V, 2h) and thermal oxidation (600°C) on the corrosive behavior of Ti-6Al-4V, with serum proteins, at physiological temperature. Anodization produced a mixture of anatase and amorphous TiO2 nanopores and nanotubes, while the annealing process yielded an anatase/rutile mixture of TiO2 nanopores and nanotubes. The surface area was analyzed by the Brunauer-Emmett-Teller method and was estimated to be 3 orders of magnitude higher than that of polished control samples. Corrosion resistance was evaluated on the parameters of open circuit potential, corrosion potential, corrosion current density, passivation current density, polarization resistance and equivalent circuit modeling. Samples both anodized and thermally oxidized exhibited shifts of open circuit potential and corrosion potential in the noble direction, indicating a more stable nanoporous/nanotube layer, as well as lower corrosion current densities and passivation current densities than the smooth control. They also showed increased polarization resistance and diffusion limited charge transfer within the bulk oxide layer. The treatment groups studied can be ordered from greatest corrosion resistance to least as Anodized+Thermally Oxidized > Anodized > Smooth > Thermally Oxidized for the conditions investigated. This study concludes that anodized surface has a potential to prevent long term implant failure due to corrosion in a complex in-vivo environment. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Silicon nitride: A ceramic material with outstanding resistance to thermal shock and corrosion

    Science.gov (United States)

    Huebner, K. H.; Saure, F.

    1983-01-01

    The known physical, mechanical and chemical properties of reaction-sintered silicon nitride are summarized. This material deserves interest especially because of its unusually good resistance to thermal shock and corrosion at high temperatures. Two types are distinguished: reaction-sintered (porous) and hot-pressed (dense) Si3N4. Only the reaction-sintered material which is being produced today in large scale as crucibles, pipes, nozzles and tiles is considered.

  2. The Analysis Of Accuracy Of Selected Methods Of Measuring The Thermal Resistance Of IGBTs

    Directory of Open Access Journals (Sweden)

    Górecki Krzysztof

    2015-09-01

    Full Text Available In the paper selected methods of measuring the thermal resistance of an IGBT (Insulated Gate Bipolar Transistor are presented and the accuracy of these methods is analysed. The analysis of the measurement error is performed and operating conditions of the considered device, at which each measurement method assures the least measuring error, are pointed out. Theoretical considerations are illustrated with some results of measurements and calculations.

  3. Experimental DC extraction of the thermal resistance of bipolar transistors taking into account the Early effect

    Science.gov (United States)

    d'Alessandro, Vincenzo

    2017-01-01

    This paper presents three methods to experimentally extract the thermal resistance of bipolar transistors taking into account the Early effect. The approaches are improved variants of recently-proposed techniques relying on common-base DC measurements. The accuracy is numerically verified by making use of a compact model calibrated on I-V characteristics of state-of-the-art SOG BJTs and SiGe:C HBTs.

  4. Residual thermal stress simulation in three-dimensional molar crown systems: a finite element analysis.

    Science.gov (United States)

    Bonfante, Estevam A; Rafferty, Brian T; Silva, Nelson R F A; Hanan, Jay C; Rekow, Elizabeth Dianne; Thompson, Van P; Coelho, Paulo G

    2012-10-01

    To simulate coefficient of thermal expansion (CTE)-generated stress fields in monolithic metal and ceramic crowns, and CTE mismatch stresses between metal, alumina, or zirconia cores and veneer layered crowns when cooled from high temperature processing. A 3D computer-aided design model of a mandibular first molar crown was generated. Tooth preparation comprised reduction of proximal walls by 1.5 mm and of occlusal surfaces by 2.0 mm. Crown systems were monolithic (all-porcelain, alumina, metal, or zirconia) or subdivided into a core (metallic, zirconia, or alumina) and a porcelain veneer layer. The model was thermally loaded from 900°C to 25°C. A finite element mesh of three nodes per edge and a first/last node interval ratio of 1 was used, resulting in approximately 60,000 elements for both solids. Regions and values of maximum principal stress at the core and veneer layers were determined through 3D graphs and software output. The metal-porcelain and zirconia-porcelain systems showed compressive fields within the veneer cusp bulk, whereas alumina-porcelain presented tensile fields. At the core/veneer interface, compressive fields were observed for the metal-porcelain system, slightly tensile for the zirconia-porcelain, and higher tensile stress magnitudes for the alumina-porcelain. Increasingly compressive stresses were observed for the metal, alumina, zirconia, and all-porcelain monolithic systems. Variations in residual thermal stress levels were observed between bilayered and single-material systems due to the interaction between crown configuration and material properties. © 2012 by the American College of Prosthodontists.

  5. The emerging role of the mitochondrial-derived peptide humanin in stress resistance.

    Science.gov (United States)

    Yen, Kelvin; Lee, Changhan; Mehta, Hemal; Cohen, Pinchas

    2013-02-01

    The discovery of humanin, a novel, mitochondrial-derived peptide, has created a potentially new category of biologically active peptide. As more research unravels the endogenous role of humanin as well as its potential pharmacological use, its role in stress resistance has become clearer. Humanin protects cells from oxidative stress, serum starvation, hypoxia, and other insults in vitro and also improves cardiovascular disease as well as Alzheimer's disease in vivo. In this review, we discuss the emerging role of humanin in stress resistance and its proposed mechanism of action.

  6. Enhanced stress corrosion resistance from steels having a dual-phase austenite-martensite microstructure

    International Nuclear Information System (INIS)

    Venkatasubramanian, T.V.; Baker, T.J.

    1983-01-01

    A high strength steel with an austenite-martensite duplex microstructure has been produced by extruding nickel coated steel powder. The austenite is present as a continuous network surrounding a high strength martensite. The steel exhibits superior resistance to stress corrosion cracking in 3.5 pct NaCl solution, the effectiveness of the austenite in improving stress corrosion cracking resistance increases as yield strength increases. The austenite reduces the effective stress intensity at the advancing crack tip and at the same time shields the crack tip from the corrosive environment

  7. Thermal stress in the edge cladding of Nova glass laser disks

    International Nuclear Information System (INIS)

    Pitts, J.H.; Kong, M.K.; Gerhard, M.A.

    1987-01-01

    We calculated thermal stresses in Nova glass laser disks having light-absorbing edge cladding glass attached to the periphery with an epoxy adhesive. Our closed-form solutions indicated that, because the epoxy adhesive is only 25 μm across, it does not significantly affect the thermal stress in the disk or cladding glass. Our numerical results showed a peak tensile stress in the cladding glass of 24 MPa when the cladding glass had a uniform absorption coefficient of 7.5 cm -1 . This peak value is reduced to 19 MPa if surface parasitic oscillation heating is eliminated by tilting the disk edges. The peak tensile stresses exceed the typical 7 to 14-MPa working stress for glass; however, we have not observed any disk or cladding glass failures at peak Nova fluences of 20 J/cm 2 . We have observed delamination of the epoxy adhesive bond at fluences several times that which would occur on Nova. Replacement laser disks will incorporate cladding with a reduced absorption coefficient of 4.5 cm -1 . Recent experiments show that this reduced absorption coefficient is satisfactory

  8. 3D numerical thermal stress analysis of the high power target for the SLC Positron Source

    International Nuclear Information System (INIS)

    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

  9. Prediction of Short-Circuit-Related Thermal Stress in Aged IGBT Modules

    DEFF Research Database (Denmark)

    Bahman, Amir Sajjad; Iannuzzo, Francesco; Uhrenfeldt, Christian

    2016-01-01

    In this paper, the thermal stress on bond wires of aged IGBT modules under short-circuit conditions has been studied with respect to different solder delamination levels. To ensure repeatable test conditions, ad-hoc DBC (direct bond copper) samples with delaminated solder layers have been purposely...... fabricated. The temperature distribution produced by such abnormal conditions has been modelled first by means of FEM simulations and then experimentally validated by means of a non-destructive testing technique including an ultra-fast infrared camera. Results demonstrate a significant imbalance...... in the surface temperature distribution which confirms the hypothesis that short-circuit events produce significantly uneven stresses on bond wires....

  10. Modeling of Short-Circuit-Related Thermal Stress in Aged IGBT Modules

    DEFF Research Database (Denmark)

    Bahman, Amir Sajjad; Iannuzzo, Francesco; Uhrenfeldt, Christian

    2017-01-01

    In this paper, the thermal stress on bond wires of aged IGBT modules under short-circuit conditions has been studied with respect to different solder delamination levels. To ensure repeatable test conditions, ad-hoc DBC (direct bond copper) samples with delaminated solder layers have been purposely...... fabricated. The temperature distribution produced by such abnormal conditions has been modelled first by means of FEM simulations and then experimentally validated by means of a non-destructive testing technique including an ultra-fast infrared camera. Results demonstrate a significant imbalance...... in the surface temperature distribution, which confirms the hypothesis that short-circuit events produce significantly uneven stresses on bond wires....

  11. Combinatorial Strategies for Improving Multiple-Stress Resistance in Industrially Relevant Escherichia coli Strains

    DEFF Research Database (Denmark)

    Lennen, Rebecca; Herrgard, Markus

    2014-01-01

    conditions and two combinations of individual stresses. A subset of the identified loss-of-function mutants were selected for a combinatorial approach, where strains with combinations of two and three gene deletions were systematically constructed and tested for single and multistress resistance....... These approaches allowed identification of (i) strain-background-specific stress resistance phenotypes, (ii) novel gene deletion mutants in E. coli that confer single and multistress resistance in a strain-background-dependent manner, and (iii) synergistic effects of multiple gene deletions that confer improved...... resistance over single deletions. The results of this study underscore the suboptimality and strain-specific variability of the genetic network regulating growth under stressful conditions and suggest that further exploration of the combinatorial gene deletion space in multiple strain backgrounds is needed...

  12. High-resolution and high-conductive electrode fabrication on a low thermal resistance flexible substrate

    International Nuclear Information System (INIS)

    Kang, Bongchul; Kno, Jinsung; Yang, Minyang

    2011-01-01

    Processes based on the liquid-state pattern transfer, like inkjet printing, have critical limitations including low resolution and low electrical conductivity when fabricating electrodes on low thermal resistance flexible substrates such as polyethylene terephthalate (PET). Those are due to the nonlinear transfer mechanism and the limit of the sintering temperature. Although the laser direct curing (LDC) of metallic inks is an alternative process to improve the resolution, it is also associated with the disadvantages of causing thermal damage to the polymer substrate. This paper suggests the laser induced pattern adhesion transfer method to fabricate electrodes of both high electrical conductivity and high resolution on a PET substrate. First, solid patterns are cost-effectively created by the LDC of the organometallic silver ink on a glass that is optically and thermally stable. The solid patterns sintered on the glass are transferred to the PET substrate by the photo-thermally generated adhesion force of the substrate. Therefore, we achieved electrodes with a minimum line width of 10 µm and a specific resistance of 3.6 μΩcm on the PET substrate. The patterns also showed high mechanical reliability

  13. High-resolution and high-conductive electrode fabrication on a low thermal resistance flexible substrate

    Science.gov (United States)

    Kang, Bongchul; Kno, Jinsung; Yang, Minyang

    2011-07-01

    Processes based on the liquid-state pattern transfer, like inkjet printing, have critical limitations including low resolution and low electrical conductivity when fabricating electrodes on low thermal resistance flexible substrates such as polyethylene terephthalate (PET). Those are due to the nonlinear transfer mechanism and the limit of the sintering temperature. Although the laser direct curing (LDC) of metallic inks is an alternative process to improve the resolution, it is also associated with the disadvantages of causing thermal damage to the polymer substrate. This paper suggests the laser induced pattern adhesion transfer method to fabricate electrodes of both high electrical conductivity and high resolution on a PET substrate. First, solid patterns are cost-effectively created by the LDC of the organometallic silver ink on a glass that is optically and thermally stable. The solid patterns sintered on the glass are transferred to the PET substrate by the photo-thermally generated adhesion force of the substrate. Therefore, we achieved electrodes with a minimum line width of 10 µm and a specific resistance of 3.6 μΩcm on the PET substrate. The patterns also showed high mechanical reliability.

  14. Local strain field engineering on interfacial thermal resistance of graphene nanoribbon

    Science.gov (United States)

    Xue, Yixuan; Chen, Yang; Cai, Kun; Liu, Zi-Yu; Zhang, Yingyan; Wei, Ning

    2018-01-01

    Strain engineering shows distinct advantages in thermal management by tuning thermal resistance in a wide range. Till now, most of the relative studies were concentrated in uniform deformation, wherein the effects of the localized strain field are rarely exploited. Herein, by using non-equilibrium molecular dynamics simulations, we explore the local strain field engineering effects on the interfacial thermal resistance (ITR) of graphene nanoribbons (GNRs). The model of GNRs employed in this work contains extended drag threads, which are used to create a local strain field. Our simulation results show that the ITR has a quasi-linear relationship with the local tensile strain. GNRs are very sensitive to the local strain field in terms of ITR with a maximum enhancement factor of ˜1.5 at the strain of 10%. The ITR is found to depend linearly on the local strain. This phenomenon is thoroughly explained by micro-structure deformation, heat flux scattering, and phonon density of state overlapping. Our findings here offer a simple yet useful tool in modulating the thermal properties of graphene and other two-dimensional materials by using local strain engineering.

  15. A new method for testing thermal shock resistance properties of soapstone – Effects of microstructures and mineralogical variables

    Directory of Open Access Journals (Sweden)

    A. Huhta

    2016-09-01

    Full Text Available Soapstone industry utilizes different types of soapstone mainly as a construction material for fireplaces. In this application soapstone has to meet different temperature requirements in different parts of fireplaces. Mineralogical and structural information is needed for placing an appropriate type of soapstone in an appropriate position in the fireplace construction. This allows employment of higher temperatures resulting in more particulate-free combustion, which makes it possible for soapstone industry to develop more efficient and environmentally friendly fireplaces. Of many soapstone types, which differ from each other in their chemical composition and thermal properties, carbonate soapstone and its microstructural variations were investigated in this study. A new method was developed to measure thermal shock resistant of natural stones. By exposing carbonate soapstone samples of different textural types to rapid temperature changes, it was possible to determine the parameters that affect the capacity of the rock to resist thermal shock. The results indicate that the type of microtexture is an important factor in controlling the thermal shock resistance of carbonate soapstone. The soapstone samples with a high thermal shock resistance show deformation textures, such as crenulation cleavage and S/C mylonite. A strong negative correlation was observed between the thermal shock resistance and length of cleavage domains in foliated rocks. Also a slight elevation in the iron concentration of talc and magnesite was discovered to improve the thermal shock resistance of carbonate soapstone. Attention should especially be paid to the length and planarity of cleavage domains of spaced foliation.

  16. Analysis technology on the temperature and thermal stress of the cask for radioactive material transport

    International Nuclear Information System (INIS)

    Shin, L.Y.; Jin, C.Y.; Soo, K.H.; Hwan, C.S.

    2005-01-01

    The cask is used to transport the radioactive materials. It is required to withstand for the thirty minute under the hypothetical fire accident condition of the 800□. According to development of the computer simulation, finite element analysis is applied to the calculation widely. But finite element method for the hypothetical accident conditions is not established in domestic regulations. In this study, the temperature and thermal stress analysis of KSC-4 cask under 800□ fire condition is conducted using by ANSYS 7.0 code. In order to analyze finite elements, two-dimensional model of KSC-4 cask is used. Symmetric boundary, convection, and radiation condition are applied in the analysis. As the results, maximum temperature and thermal stress of the KSC-4 cask is evaluated. (orig.)

  17. Study of Thermal Stress Influence on Dimensional Stability of Silicone Molds

    Science.gov (United States)

    Bajčičák, Martin; Šuba, Roland

    2014-06-01

    The paper is focused on the study of temperature influence on dimensional stability of silicone molds used for spin casting of the low melting points alloys. The silicone material denoted as TEKSIL Silicone-GP-S was used to produce samples during experiments. The samples were heated to temperatures in the range from 100 up to 250oC for 30 up to 120 min. Dimensional changes of the samples in the radial and axial directions aa well as their change of weight were evaluated. The results of experiments proved that thermal stress of silicone molds can influence the size and shape of mold cavities. These results can also explain the possible mechanism of degradation process of silicone molds under thermal stress.

  18. Effects study on the thermal stresses in a LEU metal foil annular target.

    Science.gov (United States)

    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. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Packaging strategies for printed circuit board components. Volume I, materials & thermal stresses.

    Energy Technology Data Exchange (ETDEWEB)

    Neilsen, Michael K. (Kansas City Plant, Kansas City, MO); 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.

  20. Study of Thermal Stress Influence on Dimensional Stability of Silicone Molds

    Directory of Open Access Journals (Sweden)

    Bajčičák Martin

    2014-06-01

    Full Text Available The paper is focused on the study of temperature influence on dimensional stability of silicone molds used for spin casting of the low melting points alloys. The silicone material denoted as TEKSIL Silicone-GP-S was used to produce samples during experiments. The samples were heated to temperatures in the range from 100 up to 250oC for 30 up to 120 min. Dimensional changes of the samples in the radial and axial directions aa well as their change of weight were evaluated. The results of experiments proved that thermal stress of silicone molds can influence the size and shape of mold cavities. These results can also explain the possible mechanism of degradation process of silicone molds under thermal stress.

  1. Stress recovery and cyclic behaviour of an Fe-Mn-Si shape memory alloy after multiple thermal activation

    Science.gov (United States)

    Hosseini, E.; Ghafoori, E.; Leinenbach, C.; Motavalli, M.; Holdsworth, S. R.

    2018-02-01

    The stress recovery and cyclic deformation behaviour of Fe-17Mn-5Si-10Cr-4Ni-1(V,C) shape memory alloy (Fe-SMA) strips, which are often used for pre-stressed strengthening of structural members, were studied. The evolution of recovery stress under different constraint conditions was studied. The results showed that the magnitude of the tensile stress in the Fe-SMA member during thermal activation can have a signification effect on the final recovery stress. The higher the tensile load in the Fe-SMA (e.g., caused by dead load or thermal expansion of parent structure during heating phase), the lower the final recovery stress. Furthermore, this study investigated the cyclic behaviour of the activated SMA followed by a second thermal activation. Although the magnitude of the recovery stress decreased during the cyclic loading, the second thermal activation could retrieve a significant part of the relaxed recovery stress. This observation suggests that the relaxation of recovery stress during cyclic loading is due to a reversible phase transformation-induced deformation (i.e., forward austenite-to-martensite transformation) rather than an irreversible dislocation-induced plasticity. Retrieval of the relaxed recovery stress by the reactivation process has important practical implications as the prestressing loss in pre-stressed civil structures can be simply recovered by reheating of the Fe-SMA elements.

  2. THE STRESS RESISTANCE OF STUDENTS. THE PARADIGM OF SUBJECT PERSONALITY SELF- ORGANIZATION

    Directory of Open Access Journals (Sweden)

    Sergey I. Dyakov

    2016-01-01

    Full Text Available The aim of the investigation is to consider a problem of stress resistance of students in the context of subject self-organization of the personality. Methods. The following methods of research are used: questioning; psychological and diagnostic tests «Tolerance of Uncertainty» (NTN and «Personal Factors of Decisions» (PFD by T. V. Kornilova; original experimental experiences – «Coding», a technique of a self-assessment (scaling and «A locus control». While data processing the methods of mathematical statistics (SPSS 12 package – the correlation analysis of Pearson and the factorial analysis with rotation use a component by «verimax» method are applied. Results and scientific novelty. Types of subjectivity and strategy of stress resistance are allocated. The nature and a role of the emotional and stressful mechanism having information and semantic properties in its basis are disclosed. Communication of irresponsible mechanisms of mentality with the sphere of consciousness in the context of subjectivity of the personality is shown. Mechanisms of emotional and rational self-control of system of mental self-organization of the person are presented. The statistical and qualitative data opening communications between properties of subjectivity and stress resistance of the personality are empirically obtained. Variation of the relations and also types of subjectivity and stress resistance emphasized based on the results of the presented research. Original (author’s methods of studying of subjectivity and factors of stress resistance are presented. Practical significance. The revealed factors of subject self-organization reveal the stress-producing directions of the environment and the relation of the personality to situations of changes and uncertainty: and also indicate subject properties of resistance to stress which need to be developed to increase the level of health of students, to reduce risk of deviance and delinquency of

  3. A study of the effect of apparent strain on thermal stress measurement for two types of elevated temperature strain gages

    Science.gov (United States)

    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).

  4. A protocol for analysing thermal stress in insects using infrared thermography.

    Science.gov (United States)

    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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. STRESSES IN CEMENT-CONCRETE PAVEMENT SURFACING CAUSED BY THERMAL SHOCK

    Directory of Open Access Journals (Sweden)

    M. K. Pshembaev

    2016-01-01

    Full Text Available It is necessary to mention specially so-called thermal shock among various impacts on highway surface. Ice layer is formed on a concrete surface during the winter period of pavement surfacing operation. Sodium chloride which lowers temperature of water-ice transition temperature and causes ice thawing at negative temperature is usually used to remove ice from the pavement surface. Consequently, temperature in the concrete laying immediately under a thawing ice layer is coming down with a run that leads to significant stresses. Such phenomenon is known as a thermal shock with a meaning of local significant change in temperature. This process is under investigation, it has practical importance for an estimation of strength and longevity of a cement-concrete pavement surfacing and consequently it is considered as rather topical issue. The purpose of investigations is to develop a mathematical model and determination of shock blow permissible gradients for a cementconcrete road covering. Finite difference method has been used in order to determine stressed and deformed condition of the cement-concrete pavement surfacing of highways. A computer program has been compiled and it permits to carry out calculation of a road covering at various laws of temperature distribution in its depth. Regularities in distribution of deformation and stresses in the cement-concrete pavement surfacing of highways at thermal shock have been obtained in the paper. A permissible parameter of temperature distribution in pavement surfacing thickness has been determined in the paper. A strength criterion based on the process of micro-crack formation and development in concrete has been used for making calculations. It has been established that the thermal shock causes significant temperature gradients on the cement-concrete surfacing that lead to rather large normal stresses in the concrete surface layer. The possibility of micro-crack formation in a road covering is

  6. Measuring the thermal insulation and evaporative resistance of sleeping bags using a supine sweating fabric manikin

    International Nuclear Information System (INIS)

    Wu, Y S; Fan, Jintu

    2009-01-01

    For testing the thermal insulation of sleeping bags, standard test methods and procedures using heated manikins are provided in ASTM F1720-06 and EN 13537:2002. However, with regard to the evaporative resistance of sleeping bags, no instrument or test method has so far been established to give a direct measurement. In this paper, we report on a novel supine sweating fabric manikin system for directly measuring the evaporative resistance of sleeping bags. Eleven sleeping bags were tested using the manikin under the isothermal condition, namely, both the mean skin temperature of the manikin and that of the environment were controlled to be the same at 35 °C, with the wind speed and ambient relative humidity at 0.3 m s −1 and 50%, respectively. The results showed that the novel supine sweating fabric manikin is reproducible and accurate in directly measuring the evaporative resistance of sleeping bags, and the measured evaporative resistance can be combined with thermal insulation to calculate the moisture permeability index of sleeping bags

  7. Transcriptome response to thermal stress in two key zooplankton species, Calanus finmarchicus and C. Glacialis

    DEFF Research Database (Denmark)

    Smolina, I.; Kollias, S.; Møller, Eva Friis

    dominated by C. glacialis. Temperature-mediated shifts in gene expression may be critical in thermal acclimation. Thus, in order to identify genes associated with thermal stress in Calanus spp. on a genome-wide scale, we conducted a whole transcriptome profiling using RNA-Seq. Samples of C. finmarchicus......Copepods of the genus Calanus are key zooplankton species in subarctic and arctic marine food webs. As a response to ocean warming, a northward movement of warm-water Calanus species has been detected. A further northward shift of C. finmarchicus is predicted into arctic waters traditionally....... glacialis resulted in 4,894,166 and 3,412,784 reads respectively. Difference in the thermal responses of the two species is linked to acclimatory potential to ocean warming and possible changes in the marine communities....

  8. Decay Resistance Variability of European Wood Species Thermally Modified by Industrial Process

    Directory of Open Access Journals (Sweden)

    Kevin CANDELIER

    2017-06-01

    Full Text Available Thermal modification is now considered as a new ecofriendly industrial wood modification process improving mainly the material decay resistance and its dimensional stability. Most industrial thermal treatment processes use convection heat transfer which induces sometimes heterogeneous treatment temperature propagation within the oven and lead to the heterogeneity in treatment efficiency. Thus, it is common that treatment is not completely effective on several stack boards, in a same batch. The aim of this paper was to study the decay resistance variability of various European wood species thermally modified. Thermal modifications were performed around 240°C during 4h, on about 10m3 of 27x152x2000mm3 wood planks placed in an industrial oven having a volume of 20m3 , on the following wood species: spruce, ash, beech and poplar. All of the tests concerning the decay resistance were carried out in the laboratory using untreated beech and pine woods as reference materials. An agar block test was used to determine the resistance of thermally modified woods, leached beforehand according to EN 84 standard or not, to brownrot and white-rot fungi, according to XP CEN/TS 15083-1. A large selection of treated wood samples was tested in order to estimate the variability of treatment efficiency. Thermal treatment increased the biological durability of all leached and un-leached modified wood samples, compared with native wood species. The treatment temperature of 240°C used in this study is sufficient to reach durability classes ‘‘durable’’ or ‘‘very durable’’ for the four wood species. However, the dispersion of weight loss values, due to the fungal attacks was very important and showed a large variability of the durability of wood which has been treated in a single batch. These results showed that there is a substantial need to develop process control and indicator in order to insure that the quality of treated timber is properly evaluated

  9. FEM thermal and stress analysis of bonded GaN-on-diamond substrate

    Directory of Open Access Journals (Sweden)

    Wenbo Zhai

    2017-09-01

    Full Text Available A three-dimensional thermal and stress analysis of bonded GaN on diamond substrate is investigated using finite element method. The transition layer thickness, thermal conductivity of transition layer, diamond substrate thickness and the area ratio of diamond and GaN are considered and treated appropriately in the numerical simulation. The maximum channel temperature of GaN is set as a constant value and its corresponding heat power densities under different conditions are calculated to evaluate the influences that the diamond substrate and transition layer have on GaN. The results indicate the existence of transition layer will result in a decrease in the heat power density and the thickness and area of diamond substrate have certain impact on the magnitude of channel temperature and stress distribution. Channel temperature reduces with increasing diamond thickness but with a decreasing trend. The stress is reduced by increasing diamond thickness and the area ratio of diamond and GaN. The study of mechanical and thermal properties of bonded GaN on diamond substrate is useful for optimal designs of efficient heat spreader for GaN HEMT.

  10. Thermal Stress-Induced Depolarization Loss in Conventional and Panda-Shaped Photonic Crystal Fiber Lasers

    Science.gov (United States)

    Mousavi, Seyedeh Laleh; Sabaeian, Mohammad

    2016-10-01

    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.

  11. Evaluations of thermal shock resistance and fracture toughness of SiC as a gas turbine blade at high temperatures. Gas turbine yo SiC yokuzai no koon ni okeru tainetsu shogekisei no hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Sato, S.; Kurumada, A.; Kudo, Y.; Chikahata, H.; Shibano, M.; Miyata, H. (Ibaraki Univ., Ibaraki (Japan). Faculty of Engineering Hitachi Ltd., Tokyo (Japan))

    1989-12-20

    This paper shows the results of the experiments on the thermal shock resistance and the thermal shock fracture toughness of ceramic blade used for high quality high temperature gas turbines. Using disk specimens of alpha SiC blade, the thermal shock resistance and the thermal shock fracture toughness are determined by means of Joule {prime} s heating at a central area of disk specimens at 1000 {degree} C (4.3 sec.) and at 1200 {degree} C, 1300 {degree} C, and 1600 {degree} C (4.5 sec.) . Both of the thermal shock resistance and fracture toughness decreases as the temperature increases until 1300 {degree} C, and then increases from 1300 to 1600 {degree} C. Both show maximum values at 1600 {degree} C. The writers consider that this is due to the stress release by the increase of ductility at high temperature. The experiments were also performed for SC-101 which is used for semiconductor base as reference material. The thermal shock resistance and fracture toughness of SC-101 at 1200 {degree} C is three times and 1.4 times larger respectively than SiC. The writers considered that it is caused by the high thermal conductivity three times larger than alpha SiC. 11 refs., 12 figs.

  12. Light induced intraspecific variability in response to thermal stress in the hard coral Stylophora pistillata

    Directory of Open Access Journals (Sweden)

    Arjen Tilstra

    2017-10-01

    Full Text Available Recent research suggests that prior exposure of several months to elevated irradiance induces enhanced thermal tolerance in scleractinian corals. While this tolerance has been reported at the species level, individual coral colonies may react differently due to individual variability in thermal tolerance. As thermal anomalies are predicted to become common in the upcoming future, intraspecific variation may be key to the survival of coral populations. In order to study light-history based thermal stress responses on individual colonies, we developed a preliminary microcosm experiment where three randomly chosen, aquacultured colonies of the model coral Stylophora pistillata were exposed to two irradiance treatments (200 and 400 μmol photons m−2 s−1 for 31 days, followed by artificially induced heat stress (∼33.4 °C. We found different responses to occur at both the intraspecific and the intracolonial levels, as indicated by either equal, less severe, delayed, and/or even non-necrotic responses of corals previously exposed to the irradiance of 400 compared to 200 μmol photons m−2 s−1. In addition, all individual colonies revealed light-enhanced calcification. Finally, elevated irradiance resulted in a lower chlorophyll a concentration in one colony compared to the control treatment, and the same colony displayed more rapid bleaching compared to the other ones. Taken together, this study highlights the potential importance of intra-individual variability in physiological responses of scleractinian corals and provides recommendations for improving methodological designs for future studies.

  13. Design of a Resistively Heated Thermal Hydraulic Simulator for Nuclear Rocket Reactor Cores

    Science.gov (United States)

    Litchford, Ron J.; Foote, John P.; Ramachandran, Narayanan; Wang, Ten-See; Anghaie, Samim

    2007-01-01

    A preliminary design study is presented for a non-nuclear test facility which uses ohmic heating to replicate the thermal hydraulic characteristics of solid core nuclear reactor fuel element passages. The basis for this testing capability is a recently commissioned nuclear thermal rocket environments simulator, which uses a high-power, multi-gas, wall-stabilized constricted arc-heater to produce high-temperature pressurized hydrogen flows representative of reactor core environments, excepting radiation effects. Initially, the baseline test fixture for this non-nuclear environments simulator was configured for long duration hot hydrogen exposure of small cylindrical material specimens as a low cost means of evaluating material compatibility. It became evident, however, that additional functionality enhancements were needed to permit a critical examination of thermal hydraulic effects in fuel element passages. Thus, a design configuration was conceived whereby a short tubular material specimen, representing a fuel element passage segment, is surrounded by a backside resistive tungsten heater element and mounted within a self-contained module that inserts directly into the baseline test fixture assembly. With this configuration, it becomes possible to create an inward directed radial thermal gradient within the tubular material specimen such that the wall-to-gas heat flux characteristics of a typical fuel element passage are effectively simulated. The results of a preliminary engineering study for this innovative concept are fully summarized, including high-fidelity multi-physics thermal hydraulic simulations and detailed design features.

  14. Grafting as a tool to improve tolerance of vegetables to abiotic stresses : Thermal stress, water stress and organic pollutants

    NARCIS (Netherlands)

    Schwarz, Dietmar; Rouphael, Youssef; Colla, Giuseppe; Venema, Jan Henk

    2010-01-01

    Due to limited availability of arable land and the high market demand for vegetables around the world, cucurbit (cucumber, melon, and watermelon) and solanaceous (eggplant, pepper and tomato) crops are frequently cultivated under unfavourable soil and environmental conditions. These include thermal

  15. A high thermal resistance MEMS-based Pirani vacuum sensor chip

    Science.gov (United States)

    Dams, Florian; Schreiner, Rupert

    2013-05-01

    The performance of thermal conductivity vacuum gauges can be improved by a well-designed geometry. The lower measurement range limit is determined by the size of the active sensing area and the thermal conduction heat losses through the supporting structures. The upper measurement range is limited by the distance between the heated element and the cold reference plane. Silicon based MEMS-technology gives the possibility to fabricate both sensing structures with suitable areas out of low thermal conductive materials and narrow gaps in order to extend the measurement range in both directions. In this work we present a MEMS-process to fabricate high thermal resistance sensor structures. The rectangular sensitive areas are anchored by four beams and are structured out of low thermal conductive PECVD-siliconnitride films with 1 µm in thickness. The metallic heating structure is completely embedded in the SiN-layer. Both sensitive area and its support beams were released from the silicon bulk material by anisotropic underetching. In this way a free-supporting structure with a gap of 150 μm to the silicon substrate was formed. The influence of the filament geometry and temperature was systematically investigated to determine the properties of the chips as thermal conductivity vacuum gauges. The temperature of the sensitive area was held constant by a self-balancing bridge circuit and the heating power was measured by a Δ-Σ-ADC. The average solid state thermal conductivity is in the order of 106WK1. The measuring range of the most sensitive structures covers 8 orders of magnitude from 105 mbar to 1000mbar.

  16. Eumelanin- and pheomelanin-based colour advertise resistance to oxidative stress in opposite ways.

    Science.gov (United States)

    Roulin, A; Almasi, B; Meichtry-Stier, K S; Jenni, L

    2011-10-01

    The control mechanisms and information content of melanin-based colourations are still debated among evolutionary biologists. Recent hypotheses contend that molecules involved in melanogenesis alter other physiological processes, thereby generating covariation between melanin-based colouration and other phenotypic attributes. Interestingly, several molecules such as agouti and glutathione that trigger the production of reddish-brown pheomelanin have an inhibitory effect on the production of black/grey eumelanin, whereas other hormones, such as melanocortins, have the opposite effect. We therefore propose the hypothesis that phenotypic traits positively correlated with the degree of eumelanin-based colouration may be negatively correlated with the degree of pheomelanin-based colouration, or vice versa. Given the role played by the melanocortin system and glutathione on melanogenesis and resistance to oxidative stress, we examined the prediction that resistance to oxidative stress is positively correlated with the degree of black colouration but negatively with the degree of reddish colouration. Using the barn owl (Tyto alba) as a model organism, we swapped eggs between randomly chosen nests to allocate genotypes randomly among environments and then we measured resistance to oxidative stress using the KRL assay in nestlings raised by foster parents. As predicted, the degree of black and reddish pigmentations was positively and negatively correlated, respectively, with resistance to oxidative stress. Our results reveal that eumelanin- and pheomelanin-based colourations can be redundant signals of resistance to oxidative stress. © 2011 The Authors. Journal of Evolutionary Biology © 2011 European Society For Evolutionary Biology.

  17. Determination of clothing evaporative resistance on a sweating thermal manikin in an isothermal condition: heat loss method or mass loss method?

    Science.gov (United States)

    Wang, Faming; Gao, Chuansi; Kuklane, Kalev; Holmér, Ingvar

    2011-08-01

    This paper addresses selection between two calculation options, i.e heat loss option and mass loss option, for thermal manikin measurements on clothing evaporative resistance conducted in an isothermal condition (T(manikin) = T(a) = T(r)). Five vocational clothing ensembles with a thermal insulation range of 1.05-2.58 clo were selected and measured on a sweating thermal manikin 'Tore'. The reasons why the isothermal heat loss method generates a higher evaporative resistance than that of the mass loss method were thoroughly investigated. In addition, an indirect approach was applied to determine the amount of evaporative heat energy taken from the environment. It was found that clothing evaporative resistance values by the heat loss option were 11.2-37.1% greater than those based on the mass loss option. The percentage of evaporative heat loss taken from the environment (H(e,env)) for all test scenarios ranged from 10.9 to 23.8%. The real evaporative cooling efficiency ranged from 0.762 to 0.891, respectively. Furthermore, it is evident that the evaporative heat loss difference introduced by those two options was equal to the heat energy taken from the environment. In order to eliminate the combined effects of dry heat transfer, condensation, and heat pipe on clothing evaporative resistance, it is suggested that manikin measurements on the determination of clothing evaporative resistance should be performed in an isothermal condition. Moreover, the mass loss method should be applied to calculate clothing evaporative resistance. The isothermal heat loss method would appear to overestimate heat stress and thus should be corrected before use.

  18. Rooting and early growth of red mangrove seedlings from thermally stressed trees

    International Nuclear Information System (INIS)

    Banus, M.D.; Kolehmainen, S.E.

    At Guayanilla on the south coast of Puerto Rico a fossil fueled electric generating station of 1100 MW(e) discharges its cooling water into a nearly enclosed lagoon of about 25 hectares area. The plume and lagoon typically have water temperatures 10 0 C and 8 0 C above ambient so that the winter and summer lagoon temperatures are 34 and 39 0 C, respectively. The north, east, and south shores of this lagoon have extensive stands of red and black mangrove trees which are visibly stressed by the elevated temperatures. Ripe red mangrove seedlings from the bearing trees are significantly smaller than those from trees in Guayanilla Bay not thermally stressed and in unpolluted bays from western Puerto Rico. Seedlings from thermally stressed trees developed negative buoyancy and initial roots faster but first pair of leaves slower than seedlings from control areas. This behavior will be discussed in relation to the propagation of seedlings from non-stressed areas. (U.S.)

  19. Drought stress determination of crops by means of ground based thermal remote sensing

    Science.gov (United States)

    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.

  20. Laser circular cutting of Kevlar sheets: Analysis of thermal stress filed and assessment of cutting geometry

    Science.gov (United States)

    Yilbas, B. S.; Akhtar, S. S.; Karatas, C.

    2017-11-01

    A Kevlar laminate has negative thermal expansion coefficient, which makes it difficult to machine at room temperaures using the conventional cutting tools. Contararily, laser machining of a Kevlar laminate provides advantages over the conventional methods because of the non-mechanical contact between the cutting tool and the workpiece. In the present study, laser circular cutting of Kevlar laminate is considered. The experiment is carried out to examine and evaluate the cutting sections. Temperature and stress fields formed in the cutting section are simulated in line with the experimental study. The influence of hole diameters on temperature and stress fields are investigated incorporating two different hole diameters. It is found that the Kevlar laminate cutting section is free from large size asperities such as large scale sideways burnings and attachemnt of charred residues. The maximum temperature along the cutting circumference remains higher for the large diameter hole than that of the small diameter hole. Temperature decay is sharp around the cutting section in the region where the cutting terminates. This, in turn, results in high temperature gradients and the thermal strain in the cutting region. von Mises stress remains high in the region where temperature gradients are high. von Mises stress follows similar to the trend of temperature decay around the cutting edges.

  1. High hydrostatic pressure resistance of Campylobacter jejuni after different sublethal stresses.

    Science.gov (United States)

    Sagarzazu, N; Cebrián, G; Condón, S; Mackey, B; Mañas, P

    2010-07-01

    To study the development of resistance responses in Campylobacter jejuni to high hydrostatic pressure (HHP) treatments after the exposure to different stressful conditions that may be encountered in food-processing environments, such as acid pH, elevated temperatures and cold storage. Campylobacter jejuni cells in exponential and stationary growth phase were exposed to different sublethal stresses (acid, heat and cold shocks) prior to evaluate the development of resistance responses to HHP. For exponential-phase cells, neither of the conditions tested increased nor decreased HHP resistance of C. jejuni. For stationary-phase cells, acid and heat adaptation-sensitized C. jejuni cells to the subsequent pressure treatment. On the contrary, cold-adapted stationary-phase cells developed resistance to HHP. Whereas C. jejuni can be classified as a stress sensitive micro-organism, our findings have demonstrated that it can develop resistance responses under different stressing conditions. The resistance of stationary phase C. jejuni to HHP was increased after cells were exposed to cold temperatures. The results of this study contribute to a better knowledge of the physiology of C. jejuni and its survival to food preservation agents. Results here presented may help in the design of combined processes for food preservation based on HHP technology. © 2009 The Authors. Journal compilation © 2009 The Society for Applied Microbiology.

  2. Growth on Alpha-Ketoglutarate Increases Oxidative Stress Resistance in the Yeast Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Maria Bayliak

    2017-01-01

    Full Text Available Alpha-ketoglutarate (AKG is an important intermediate in cell metabolism, linking anabolic and catabolic processes. The effect of exogenous AKG on stress resistance in S. cerevisiae cells was studied. The growth on AKG increased resistance of yeast cells to stresses, but the effects depended on AKG concentration and type of stressor. Wild-type yeast cells grown on AKG were more resistant to hydrogen peroxide, menadione, and transition metal ions (Fe2+ and Cu2+ but not to ethanol and heat stress as compared with control ones. Deficiency in SODs or catalases abolished stress-protective effects of AKG. AKG-supplemented growth led to higher values of total metabolic activity, level of low-molecular mass thiols, and activities of catalase and glutathione reductase in wild-type cells compared with the control. The results suggest that exogenous AKG may enhance cell metabolism leading to induction of mild oxidative stress. It turn, it results in activation of antioxidant system that increases resistance of S. cerevisiae cells to H2O2 and other stresses. The presence of genes encoding SODs or catalases is required for the expression of protective effects of AKG.

  3. Alterations in neuronal morphology in infralimbic cortex predict resistance to fear extinction following acute stress

    Directory of Open Access Journals (Sweden)

    Kelly M. Moench

    2016-06-01

    Full Text Available Dysfunction in corticolimbic circuits that mediate the extinction of learned fear responses is thought to underlie the perseveration of fear in stress-related psychopathologies, including post-traumatic stress disorder. Chronic stress produces dendritic hypertrophy in basolateral amygdala (BLA and dendritic hypotrophy in medial prefrontal cortex, whereas acute stress leads to hypotrophy in both BLA and prelimbic cortex. Additionally, both chronic and acute stress impair extinction retrieval. Here, we examined the effects of a single elevated platform stress on extinction learning and dendritic morphology in infralimbic cortex, a region considered to be critical for extinction. Acute stress produced resistance to extinction, as well as dendritic retraction in infralimbic cortex. Spine density on apical and basilar terminal branches was unaffected by stress. However, animals that underwent conditioning and extinction had decreased spine density on apical terminal branches. Thus, whereas dendritic morphology in infralimbic cortex appears to be particularly sensitive to stress, changes in spines may more sensitively reflect learning. Further, in stressed rats that underwent conditioning and extinction, the level of extinction learning was correlated with spine densities, in that rats with poorer extinction retrieval had more immature spines and fewer thin spines than rats with better extinction retrieval, suggesting that stress may have impaired learning-related spine plasticity. These results may have implications for understanding the role of medial prefrontal cortex in learning deficits associated with stress-related pathologies.

  4. Thermal infrared as a tool to detect tree water stress in a coniferous forest

    Science.gov (United States)

    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

  5. High temperature thermal creep under variable stress and temperature loading conditions

    International Nuclear Information System (INIS)

    Bocek, M.

    1985-01-01

    The present paper is concerned with thermal creep of cavitating materials subjected to time variable stresses and/or temperatures. Creep cavitation damage, because reducing the load bearing capability will influence the creep behavior of structures loaded by tension. The calculations are based on a phenomenological cavitation damage model, from which the life fraction rule (LFR) is deduced. For complex stress/temperature loading conditions by means of the LFR analytical expressions for the corresponding lifetimes are derived. Only stationary stress rupture data together with the loading conditions enter the computations. In the present procedure the damage function A(t), as a variable structure parameter, enters a constitutive strain rate/stress equation through an effective (true) stress. The latter, for given loading conditions, is derived from the solution of the general tensile test equation. Solving the strain rate/stress equation in terms of strain or time, the constitutive creep equation for ideally plastic cavitating materials exposed to non-stationary loading conditions are derived

  6. Modeling and experimental verification of thermally induced residual stress in RF-MEMS

    International Nuclear Information System (INIS)

    Somà, Aurelio; Saleem, Muhammad Mubasher

    2015-01-01

    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. (paper)

  7. Habitat pollution and thermal regime modify molecular stress responses to elevated temperature in freshwater mussels (Anodonta anatina: Unionidae)

    International Nuclear Information System (INIS)

    Falfushynska, H.; Gnatyshyna, L.; Yurchak, I.; Ivanina, A.; Stoliar, O.; Sokolova, I.

    2014-01-01

    Elevated temperature and pollution are common stressors in freshwater ecosystems. We study cellular stress response to acute warming in Anodonta anatina (Unionidae) from sites with different thermal regimes and pollution levels: a pristine area and an agriculturally polluted site with normal temperature regimes (F and A, respectively) and a polluted site with elevated temperature (N) from the cooling pond of an electrical power plant. Animals were exposed to different temperatures for 14 days and stress response markers were measured in gills, digestive gland and hemocytes. Mussels from site N and A had elevated background levels of lactate dehydrogenase activity indicating higher reliance on anaerobic metabolism for ATP production and/or redox maintenance. Exposure to 25 °C and 30 °C induced oxidative stress (indicated by elevated levels of lipid peroxidation products) in digestive gland and gills of mussels from A and F sites, while in mussels from N sites elevated oxidative stress was only apparent at 30 °C. Temperature-induced changes in levels of antioxidants (superoxide dismutase, metallothioneins and glutathione) were tissue- and population-specific. Acute warming led to destabilization of lysosomal membranes and increased frequencies of nuclear lesions in mussels from F and A sites but not in their counterparts from N site. Elevated temperature led to an increase in the frequency of micronuclei in hemocytes in mussels from F and A sites at 25 °C and 30 °C and in mussels from N site at 30 °C. The mussels from N site also demonstrated better survival at elevated temperature (30 °C) than their counterparts from the F and A sites. Taken together, these data indicate that long-term acclimation and/or adaptation of A. anatina to elevated temperatures result in increased thermotolerance and alleviate stress response to moderate temperature rise. In contrast, extreme warming (30 °C) is harmful to mussels from all populations indicating limit to this induced

  8. Habitat pollution and thermal regime modify molecular stress responses to elevated temperature in freshwater mussels (Anodonta anatina: Unionidae)

    Energy Technology Data Exchange (ETDEWEB)

    Falfushynska, H.; Gnatyshyna, L.; Yurchak, I. [Research Laboratory of Comparative Biochemistry and Molecular Biology, Ternopil National Pedagogical University, Kryvonosa Str 2, 46027 Ternopil (Ukraine); Ivanina, A. [Department of Biological Sciences, University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28223 (United States); Stoliar, O. [Research Laboratory of Comparative Biochemistry and Molecular Biology, Ternopil National Pedagogical University, Kryvonosa Str 2, 46027 Ternopil (Ukraine); Sokolova, I., E-mail: isokolov@uncc.edu [Department of Biological Sciences, University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28223 (United States)

    2014-12-01

    Elevated temperature and pollution are common stressors in freshwater ecosystems. We study cellular stress response to acute warming in Anodonta anatina (Unionidae) from sites with different thermal regimes and pollution levels: a pristine area and an agriculturally polluted site with normal temperature regimes (F and A, respectively) and a polluted site with elevated temperature (N) from the cooling pond of an electrical power plant. Animals were exposed to different temperatures for 14 days and stress response markers were measured in gills, digestive gland and hemocytes. Mussels from site N and A had elevated background levels of lactate dehydrogenase activity indicating higher reliance on anaerobic metabolism for ATP production and/or redox maintenance. Exposure to 25 °C and 30 °C induced oxidative stress (indicated by elevated levels of lipid peroxidation products) in digestive gland and gills of mussels from A and F sites, while in mussels from N sites elevated oxidative stress was only apparent at 30 °C. Temperature-induced changes in levels of antioxidants (superoxide dismutase, metallothioneins and glutathione) were tissue- and population-specific. Acute warming led to destabilization of lysosomal membranes and increased frequencies of nuclear lesions in mussels from F and A sites but not in their counterparts from N site. Elevated temperature led to an increase in the frequency of micronuclei in hemocytes in mussels from F and A sites at 25 °C and 30 °C and in mussels from N site at 30 °C. The mussels from N site also demonstrated better survival at elevated temperature (30 °C) than their counterparts from the F and A sites. Taken together, these data indicate that long-term acclimation and/or adaptation of A. anatina to elevated temperatures result in increased thermotolerance and alleviate stress response to moderate temperature rise. In contrast, extreme warming (30 °C) is harmful to mussels from all populations indicating limit to this induced

  9. Effects of thermal stress on the immune and oxidative stress responses of juvenile sea cucumber Holothuria scabra.

    Science.gov (United States)

    Kamyab, Elham; Kühnhold, Holger; Novais, Sara C; Alves, Luís M F; Indriana, Lisa; Kunzmann, Andreas; Slater, Matthew; Lemos, Marco F L

    2017-01-01

    Holothuria scabra is the most valued and cultured tropical sea cucumber, given the great demand of this species for human consumption. However, despite its ecological and economic relevance, little is known regarding its immune responses under thermal stress. Here, the main goal was to study the response of sea cucumbers to temperature stress, assessing sub-organismal alterations and acclimation capacities of juveniles to temperature changes. After changing temperature (1 °C/day) for 6 days, organisms were exposed to temperature conditions of 21 °C (cold), 27 °C (control), and 33 °C (warm) over a 30 day period. At each 15-day interval (T0, T15, and T30), six replicates per condition were killed for biochemical analysis. Immune responses were addressed by studying the activity of phenoloxidase (PO) and prophenoloxidase (ProPO) in the coelomic fluid. Antioxidant defence responses-catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GR) enzymatic activities-were measured in the muscle and respiratory tree tissues, whereas oxidative damage was evaluated by measuring levels of superoxide radicals (ROS), DNA-strand breaks and lipid peroxidation (LPO). Juvenile H. scabra increased SOD and PO activities when temperature was elevated, and revealed low levels of ROS and damage in both cold and warm treatments throughout the experiment, confirming the organism's moderate thermal stress. After the short acclimation period, the immune and antioxidant responses prevented damage and maintained homeostasis. This multi-biomarker approach highlights its usefulness to monitor the health of H. scabra and to gain insight concerning the use of this high-valued species in global-scale aquaculture from different temperature regions.

  10. Rapid growth reduces cold resistance: evidence from latitudinal variation in growth rate, cold resistance and stress proteins.

    Science.gov (United States)

    Stoks, Robby; De Block, Marjan

    2011-02-24

    Physiological costs of rapid growth may contribute to the observation that organisms typically grow at submaximal rates. Although, it has been hypothesized that faster growing individuals would do worse in dealing with suboptimal temperatures, this type of cost has never been explored empirically. Furthermore, the mechanistic basis of the physiological costs of rapid growth is largely unexplored. Larvae of the damselfly Ischnura elegans from two univoltine northern and two multivoltine southern populations were reared at three temperatures and after emergence given a cold shock. Cold resistance, measured by chill coma recovery times in the adult stage, was lower in the southern populations. The faster larval growth rates in the southern populations contributed to this latitudinal pattern in cold resistance. In accordance with their assumed role in cold resistance, Hsp70 levels were lower in the southern populations, and faster growing larvae had lower Hsp70 levels. Yet, individual variation in Hsp70 levels did not explain variation in cold resistance. WE PROVIDE EVIDENCE FOR A NOVEL COST OF RAPID GROWTH: reduced cold resistance. Our results indicate that the reduced cold resistance in southern populations of animals that change voltinism along the latitudinal gradient may not entirely be explained by thermal selection per se but also by the costs of time constraint-induced higher growth rates. This also illustrates that stressors imposed in the larval stage may carry over and shape fitness in the adult stage and highlights the importance of physiological costs in the evolution of life-histories at macro-scales.

  11. High Thermal Conductivity and High Wear Resistance Tool Steels for cost-effective Hot Stamping Tools

    Science.gov (United States)

    Valls, I.; Hamasaiid, A.; Padré, A.

    2017-09-01

    In hot stamping/press hardening, in addition to its shaping function, the tool controls the cycle time, the quality of the stamped components through determining the cooling rate of the stamped blank, the production costs and the feasibility frontier for stamping a given component. During the stamping, heat is extracted from the stamped blank and transported through the tool to the cooling medium in the cooling lines. Hence, the tools’ thermal properties determine the cooling rate of the blank, the heat transport mechanism, stamping times and temperature distribution. The tool’s surface resistance to adhesive and abrasive wear is also an important cost factor, as it determines the tool durability and maintenance costs. Wear is influenced by many tool material parameters, such as the microstructure, composition, hardness level and distribution of strengthening phases, as well as the tool’s working temperature. A decade ago, Rovalma developed a hot work tool steel for hot stamping that features a thermal conductivity of more than double that of any conventional hot work tool steel. Since that time, many complimentary grades have been developed in order to provide tailored material solutions as a function of the production volume, degree of blank cooling and wear resistance requirements, tool geometries, tool manufacturing method, type and thickness of the blank material, etc. Recently, Rovalma has developed a new generation of high thermal conductivity, high wear resistance tool steel grades that enable the manufacture of cost effective tools for hot stamping to increase process productivity and reduce tool manufacturing costs and lead times. Both of these novel grades feature high wear resistance and high thermal conductivity to enhance tool durability and cut cycle times in the production process of hot stamped components. Furthermore, one of these new grades reduces tool manufacturing costs through low tool material cost and hardening through readily

  12. Estimation of Fracture Conditions of Ceramics by Thermal Shock with Laser Beams based on the Maximum Compressive Stress Criterion

    OpenAIRE

    AKIYAMA, Shigeru; AMADA, Shigeyasu

    1995-01-01

    Structural ceramics are attracting attention in the development of space planes, aircraft and nuclear fusion reactors because they have excellent wear-resistant and heat-resistant characteristics. However, in some applications it is anticipated that they will be exposed to very-high-temperature environments of the order of thousands of degrees. Therefore, it is very important to investigate their thermal shock characteristics. In this report, the distributions of temperatures and thermal stre...

  13. Pneumococcal Gene Complex Involved in Resistance to Extracellular Oxidative Stress

    NARCIS (Netherlands)

    Farshchi Andisi, Vahid; Hinojosa, Cecilia A.; de Jong, Anne; Kuipers, Oscar P.; Orihuela, Carlos J.; Bijlsma, Jetta J. E.

    Streptococcus pneumoniae is a Gram-positive bacterium which is a member of the normal human nasopharyngeal flora but can also cause serious disease such as pneumonia, bacteremia, and meningitis. Throughout its life cycle, S. pneumoniae is exposed to significant oxidative stress derived from

  14. Utilizing Genetic Resources and Precision Agriculture to Enhance Resistance to Biotic and Abiotic Stress in Watermelon

    Directory of Open Access Journals (Sweden)

    Mihail KANTOR

    2018-03-01

    Full Text Available Originally from Africa, watermelon is a staple crop in South Carolina and rich source of important phytochemicals that promote human health. As a result of many years of domestication and selection for desired fruit quality, modern watermelon cultivars are susceptible to biotic and abiotic stress. The present review discusses how genetic selection and breeding combined with geospatial technologies (precision agriculture may help enhance watermelon varieties for resistance to biotic and abiotic stress. Gene loci identified and selected in undomesticated watermelon accessions are responsible for resistance to diseases, pests and abiotic stress. Vegetable breeding programs use traditional breeding methodologies and genomic tools to introduce gene loci conferring biotic or abiotic resistance into the genome background of elite watermelon cultivars. This continuous approach of collecting, evaluating and identifying useful genetic material is valuable for enhancing genetic diversity and tolerance and combined with precision agriculture could increase food security in the Southeast.

  15. Isoxanthohumol, a constituent of hop (Humulus lupulus L.), increases stress resistance in Caenorhabditis elegans dependent on the transcription factor DAF-16.

    Science.gov (United States)

    Büchter, Christian; Havermann, Susannah; Koch, Karoline; Wätjen, Wim

    2016-02-01

    The flavanone isoxanthohumol (IX) has gained attention as antioxidative and chemopreventive agent, but the molecular mechanism of action remains unclear. We investigated effects of this secondary plant compound in vivo using the model organism Caenorhabditis elegans. Adult C. elegans nematodes were incubated with IX, and then, the stress resistance was analysed in the SYTOX assay; lifespan was monitored by touch-provoked movement method, the amount of reactive oxygen species (ROS) was measured in the DCF assay, and the nuclear localisation of the transcription factor DAF-16 was analysed by using a transgenic strain. By the use of a DAF-16 loss-of-function strain, we analysed whether the effects are dependent on DAF-16. IX increases the resistance of the nematode against thermal stress. Additionally, a reduction in ROS in vivo was caused by IX. Since the flavanone only has a marginal radical-scavenging capacity (TEAC assay), we suggest that IX mediates its antioxidative effects indirectly via activation of DAF-16 (homologue to mammalian FOXO proteins). The nuclear translocation of this transcription factor is increased by IX. In the DAF-16-mutated strain, the IX-mediated increase in stress resistance was completely abolished; furthermore, an increased formation of ROS and a reduced lifespan was mediated by IX. IX or a bacterial metabolite of IX causes antioxidative effects as well as an increased stress resistance in C. elegans via activation of DAF-16. The homologous pathway may have implications in the molecular mechanism of IX in mammals.

  16. Behavior of oxygen in zinc oxide films through thermal annealing and its effect on sheet resistance

    International Nuclear Information System (INIS)

    Hiramatsu, Takahiro; Furuta, Mamoru; Matsuda, Tokiyoshi; Li, Chaoyang; Hirao, Takashi

    2011-01-01

    Behavior of oxygen in sputtering deposited ZnO films through thermal annealing and its effect on sheet resistance of the films were investigated. The crystallinities of the ZnO film were improved by post-deposition annealing in vacuum. However, the sheet resistance of ZnO film was dramatically decreased after post-deposition annealing in vacuum at more than 300 deg. C, while O 2 desorbed from the film. The oxygen vacancies which acted as donors were formed by the thermal annealing in vacuum. The sheet resistance of the films was recovered by annealing in oxygen ambient. In this paper, 18 O 2 gas as an oxygen isotope was used as the annealing ambient in order to distinguish from 16 O, which was constituent atom of the ZnO films. SIMS analysis revealed that 18 O diffused into the ZnO film from the top surface by 18 O 2 annealing. Therefore oxygen vacancies formed by the post-deposition annealing in vacuum could be compensated by the annealing in oxygen ambient.

  17. Rec-8 dimorphism affects longevity, stress resistance and X-chromosome nondisjunction in C. elegans, and replicative lifespan in yeast

    Directory of Open Access Journals (Sweden)

    Srinivas eAyyadevara

    2014-08-01

    Full Text Available A quantitative trait locus (QTL in the nematode C. elegans, lsq4, was recently implicated by mapping longevity genes. QTLs for lifespan and 3 stress-resistance traits coincided within a span of <300 kbp, later narrowed to <200 kbp. A single gene in this interval is now shown to modulate all lsq4-associated traits. Full-genome analysis of transcript levels indicates that lsq4 contains a dimorphic gene governing expression of sperm-specific genes, suggesting effects on spermatogenesis. Quantitation of allele-specific transcripts encoded within the lsq4 interval revealed significant, 2- to 15-fold expression differences for 10 of 33 genes. Fourteen genes, implicated by both position and expression, were tested for RNA-interference effects on QTL-linked traits. In a strain carrying the shorter-lived allele, knockdown of rec-8 (encoding a meiotic cohesin reduced its transcripts 4-fold, to a level similar to the longer-lived strain, and extended lifespan 25–26% whether begun before fertilization or at maturity. The short-lived lsq4 allele also conferred sensitivity to oxidative and thermal stresses, and lower male frequency, traits reversed uniquely by rec-8 knockdown. A strain bearing the longer-lived lsq4 allele, differing from the short-lived strain at <0.3% of its genome, derived no lifespan or stress-survival benefit from rec-8 knockdown. We consider two possible explanations: high rec-8 expression may include increased leaky expression in mitotic cells, leading to deleterious destabilization of somatic genomes; or REC-8 may act entirely in germ-line meiotic cells to reduce aberrations such as nondisjunction, thereby blunting a stress-resistance response mediated by innate immunity. Replicative lifespan was extended 20% in haploid S. cerevisiae (BY4741 by deletion of REC8, orthologous to nematode rec-8, implying that REC8 disruption of mitotic-cell survival is widespread, reflecting antagonistic pleiotropy and/or balancing selection.

  18. Comparison of different test methods to assess thermal stresses of metal oxide surge arresters under pollution conditions

    International Nuclear Information System (INIS)

    Bargigia, A.; de Nigris, M.; Pigini, A.; Sironi, A.

    1992-01-01

    The report deals with the research conducted by ENEL, the Italian Electricity Board, to assess the performance of zinc oxide surge arresters under pollution condition, with special reference to the consequent thermal stress on internal active parts which can affect the energy handling capabality of the arrester and may lead, in particular conditions, even to thermal runaway

  19. Effects of silicon on plant resistance to environmental stresses: review

    Science.gov (United States)

    Balakhnina, T.; Borkowska, A.

    2013-03-01

    The role of exogenous silicon in enhancing plant resistance to various abiotic stressors: salinity, drought, metal toxicities and ultraviolet radiation are presented. The data on possible involvement of silicon in reducing the reactive oxygen species generation, intensity of lipid peroxidation, and in some cases, increasing the activity of enzymes of the reactive oxygen species detoxificators: superoxide dismutase, ascorbate peroxidase, glutathione reductase, guaiacol peroxidase and catalase are analyzed.

  20. Endophytic fungi: resource for gibberellins and crop abiotic stress resistance.

    Science.gov (United States)

    Khan, Abdul Latif; Hussain, Javid; Al-Harrasi, Ahmed; Al-Rawahi, Ahmed; Lee, In-Jung

    2015-03-01

    The beneficial effects of endophytes on plant growth are important for agricultural ecosystems because they reduce the need for fertilizers and decrease soil and water pollution while compensating for environmental perturbations. Endophytic fungi are a novel source of bioactive secondary metabolites; moreover, recently they have been found to produce physiologically active gibberellins as well. The symbiosis of gibberellins producing endophytic fungi with crops can be a promising strategy to overcome the adverse effects of abiotic stresses. The association of such endophytes has not only increased plant biomass but also ameliorated plant-growth during extreme environmental conditions. Endophytic fungi represent a trove of unexplored biodiversity and a frequently overlooked component of crop ecology. The present review describes the role of gibberellins producing endophytic fungi, suggests putative mechanisms involved in plant endophyte stress interactions and discusses future prospects in this field.

  1. Laser welded versus resistance spot welded bone implants: analysis of the thermal increase and strength.

    Science.gov (United States)

    Fornaini, Carlo; Meleti, Marco; Bonanini, Mauro; Lagori, Giuseppe; Vescovi, Paolo; Merigo, Elisabetta; Nammour, Samir

    2014-01-01

    The first aim of this "ex vivo split mouth" study was to compare the thermal elevation during the welding process of titanium bars to titanium implants inserted in pig jaws by a thermal camera and two thermocouples. The second aim was to compare the strength of the joints by a traction test with a dynamometer. Six pigs' jaws were used and three implants were placed on each side of them for a total of 36 fixtures. Twelve bars were connected to the abutments (each bar on three implants) by using, on one side, laser welding and, on the other, resistance spot welding. Temperature variations were recorded by thermocouples and by thermal camera while the strength of the welded joint was analyzed by a traction test. For increasing temperature, means were 36.83 and 37.06, standard deviations 1.234 and 1.187, and P value 0.5763 (not significant). For traction test, means were 195.5 and 159.4, standard deviations 2.00 and 2.254, and P value 0.0001 (very significant). Laser welding was demonstrated to be able to connect titanium implant abutments without the risk of thermal increase into the bone and with good results in terms of mechanical strength.

  2. Laser Welded versus Resistance Spot Welded Bone Implants: Analysis of the Thermal Increase and Strength

    Directory of Open Access Journals (Sweden)

    Carlo Fornaini

    2014-01-01

    Full Text Available Introduction. The first aim of this “ex vivo split mouth” study was to compare the thermal elevation during the welding process of titanium bars to titanium implants inserted in pig jaws by a thermal camera and two thermocouples. The second aim was to compare the strength of the joints by a traction test with a dynamometer. Materials and Methods. Six pigs’ jaws were used and three implants were placed on each side of them for a total of 36 fixtures. Twelve bars were connected to the abutments (each bar on three implants by using, on one side, laser welding and, on the other, resistance spot welding. Temperature variations were recorded by thermocouples and by thermal camera while the strength of the welded joint was analyzed by a traction test. Results. For increasing temperature, means were 36.83 and 37.06, standard deviations 1.234 and 1.187, and P value 0.5763 (not significant. For traction test, means were 195.5 and 159.4, standard deviations 2.00 and 2.254, and P value 0.0001 (very significant. Conclusion. Laser welding was demonstrated to be able to connect titanium implant abutments without the risk of thermal increase into the bone and with good results in terms of mechanical strength.

  3. Induced thermal stress on serotonin levels in the blue swimmer crab, Portunus pelagicus

    Directory of Open Access Journals (Sweden)

    Saravanan Rajendiran

    2016-03-01

    Full Text Available The temperature of habitat water has a drastic influence on the behavioral, physiological and biochemical mechanisms of crustaceans. Hyperglycemia is a typical response of many aquatic animals to harmful physical and chemical environmental changes. In crustaceans increased circulating crustacean hyperglycemic hormone (CHH and hyperglycemia are reported to occur following exposure to several environmental stress. The biogenic amine, serotonin has been found to modulate the CHH levels and oxidation of serotonin into its metabolites is catalysed by monoamine oxidase. The blue swimmer crab, Portunus pelagicus is a dominant intertidal species utilized throughout the indo-pacific region and is a particularly important species of Palk bay. It has high nutritional value and delicious taste and hence their requirements of capture and cultivation of this species are constantly increasing. This species experiences varying and increasing temperature levels as it resides in an higher intertidal zone of Thondi coast. The present study examines the effect of thermal stress on the levels of serotonin and crustacean hyperglycemic hormone in the hemolymph of P. pelagicus and analyzes the effect of the monoamine oxidase inhibitor, pargyline on serotonin and CHH level after thermal stress. The results showed increased levels of glucose, CHH and serotonin on exposure to 26 °C in control animals. Pargyline injected crabs showed highly significant increase in the levels of CHH and serotonin on every 2 °C increase or decrease in temperature. A greater CHH level of 268.86±2.87 fmol/ml and a greater serotonin level of 177.69±10.10 ng/ml was observed at 24 °C. This could be due to the effect of in maintaining the level of serotonin in the hemolymph and preventing its oxidation, which in turn induces hyperglycemia by releasing CHH into hemolymph. Thus, the study demonstrates the effect of thermal stress on the hemolymph metabolites studied and the role of

  4. Induced thermal stress on serotonin levels in the blue swimmer crab, Portunus pelagicus.

    Science.gov (United States)

    Rajendiran, Saravanan; Muhammad Iqbal, Beema Mahin; Vasudevan, Sugumar

    2016-03-01

    The temperature of habitat water has a drastic influence on the behavioral, physiological and biochemical mechanisms of crustaceans. Hyperglycemia is a typical response of many aquatic animals to harmful physical and chemical environmental changes. In crustaceans increased circulating crustacean hyperglycemic hormone (CHH) and hyperglycemia are reported to occur following exposure to several environmental stress. The biogenic amine, serotonin has been found to modulate the CHH levels and oxidation of serotonin into its metabolites is catalysed by monoamine oxidase. The blue swimmer crab, Portunus pelagicus is a dominant intertidal species utilized throughout the indo-pacific region and is a particularly important species of Palk bay. It has high nutritional value and delicious taste and hence their requirements of capture and cultivation of this species are constantly increasing. This species experiences varying and increasing temperature levels as it resides in an higher intertidal zone of Thondi coast. The present study examines the effect of thermal stress on the levels of serotonin and crustacean hyperglycemic hormone in the hemolymph of P. pelagicus and analyzes the effect of the monoamine oxidase inhibitor, pargyline on serotonin and CHH level after thermal stress. The results showed increased levels of glucose, CHH and serotonin on exposure to 26 °C in control animals. Pargyline injected crabs showed highly significant increase in the levels of CHH and serotonin on every 2 °C increase or decrease in temperature. A greater CHH level of 268.86±2.87 fmol/ml and a greater serotonin level of 177.69±10.10 ng/ml was observed at 24 °C. This could be due to the effect of in maintaining the level of serotonin in the hemolymph and preventing its oxidation, which in turn induces hyperglycemia by releasing CHH into hemolymph. Thus, the study demonstrates the effect of thermal stress on the hemolymph metabolites studied and the role of pargyline in elevating the

  5. Variation in adult stress resistance does not explain vulnerability to climate change in copper butterflies.

    Science.gov (United States)

    Klockmann, Michael; Wallmeyer, Leonard; Fischer, Klaus

    2017-03-15

    Ongoing climate change is a major threat to biodiversity. However, although many species clearly suffer from ongoing climate change, others benefit from it, for example, by showing range expansions. However, which specific features determine a species' vulnerability to climate change? Phenotypic plasticity, which has been described as the first line of defence against environmental change, may be of utmost importance here. Against this background, we here compare plasticity in stress tolerance in 3 copper butterfly species, which differ arguably in their vulnerability to climate change. Specifically, we investigated heat, cold and desiccation resistance after acclimatization to different temperatures in the adult stage. We demonstrate that acclimation at a higher temperature increased heat but decreased cold tolerance and desiccation resistance. Contrary to our predictions, species did not show pronounced variation in stress resistance, though plastic capacities in temperature stress resistance did vary across species. Overall, our results seemed to reflect population-rather than species-specific patterns. We conclude that the geographical origin of the populations used should be considered even in comparative studies. However, our results suggest that, in the 3 species studied here, vulnerability to climate change is not in the first place determined by stress resistance in the adult stage. As entomological studies focus all too often on adults only, we argue that more research effort should be dedicated to other developmental stages when trying to understand insect responses to environmental change. © 2017 Institute of Zoology, Chinese Academy of Sciences.

  6. Molecular Events Linking Oxidative Stress and Inflammation to Insulin Resistance and β-Cell Dysfunction

    OpenAIRE

    Keane, Kevin Noel; Cruzat, Vinicius Fernandes; Carlessi, Rodrigo; de Bittencourt, Paulo Ivo HomemJr.; Newsholme, Philip

    2015-01-01

    The prevalence of diabetes mellitus (DM) is increasing worldwide, a consequence of the alarming rise in obesity and metabolic syndrome (MetS). Oxidative stress and inflammation are key physiological and pathological events linking obesity, insulin resistance, and the progression of type 2 DM (T2DM). Unresolved inflammation alongside a “glucolipotoxic” environment of the pancreatic islets, in insulin resistant pathologies, enhances the infiltration of immune cells which through secretory activ...

  7. JNK at the crossroad of obesity, insulin resistance, and cell stress response

    OpenAIRE

    Solinas, Giovanni; Becattini, Barbara

    2016-01-01

    Background: The cJun-N-terminal-kinase (JNK) plays a central role in the cell stress response, with outcomes ranging from cell death to cell proliferation and survival, depending on the specific context. JNK is also one of the most investigated signal transducers in obesity and insulin resistance, and studies have identified new molecular mechanisms linking obesity and insulin resistance. Emerging evidence indicates that whereas JNK1 and JNK2 isoforms promote the development of obesity and in...

  8. Effect of anisotropic thermal transport on the resistive plasma response to resonant magnetic perturbation field

    Science.gov (United States)

    Bai, Xue; Liu, Yueqiang; Gao, Zhe

    2017-10-01

    Plasma response to the resonant magnetic perturbation (RMP) field is numerically investigated by an extended toroidal fluid model, which includes anisotropic thermal transport physics parallel and perpendicular to the total magnetic field. The thermal transport is found to be effective in eliminating the toroidal average curvature induced plasma screening (the so called Glasser-Green-Johnson, GGJ screening) in a slow toroidal flow regime, whilst having minor effect on modifying the conventional plasma screening regimes at faster flow. This physics effect of interaction between thermal transport and GGJ screening is attributed to the modification of the radial structure of the shielding current, which resulted from the plasma response to the applied field. The modification of the plasma response (shielding current, response field, plasma displacement, and the perturbed velocity) also has direct consequence on the toroidal torques produced by RMP. Modelling results show that thermal transport reduces the resonant electromagnetic torque as well as the torque associated with the Reynolds stress, but enhances the neoclassical toroidal viscous torque at slow plasma flow.

  9. Stress resistance of biofilm and planktonic Lactobacillus plantarum subsp. plantarum JCM 1149

    OpenAIRE

    Kubota, Hiromi; Senda, Shouko; Tokuda, Hajime; Uchiyama, Hiroo; Nomura, Nobuhiko

    2009-01-01

    The purpose of this study was to investigate the change in resistance of biofilm and planktonic food spoilage lactic acid bacteria (LAB) to environmental stresses, which strongly inhibit bacterial growth and are important in food preservation or in disinfection. The stress responses of biofilm and planktonic cells of Lactobacillus plantarum subsp. plantarum JCM 1149, which was used as a model spoilage bacterium, in various organic acids (namely, acetic acid, citric acid, lactic acid, and mali...

  10. Refuge behaviour from outdoor thermal environmental stress and seasonal differences of thermal sense in tropical urban climate

    Science.gov (United States)

    Kurazumi, Y.; Ishii, J.; Fukagawa, K.; Kondo, E.; Aruninta, A.

    2017-12-01

    Thermal sensation affects body temperature regulation. As a starting point for behavioral body temperature regulation taken to improve from a poor thermal environment to a more pleasant environment, thermal sense of thermal environment stimulus is important. The poupose of this sutudy is to use the outdoor thermal environment evaluation index ETFe to quantify effects on thermal sensations of the human body of a tropical region climate with small annual temperature differences, and to examine seasonal differences in thermal sensation. It was found temperature preferences were lower in the winter season than in the dry season, and that a tolerance for higher temperatures in the dry season than in the winter season. It was found effects of seasonal differences of the thermal environment appear in quantitative changes in thermal sensations. It was found that effects of seasonal differences of the thermal environment do not greatly affect quantitative changes in thermal comfort.

  11. Replacement by Caenis diminuta walker (ephemeroptera:caenidae) in the mayfly community structure of a thermally-stressed, southeastern stream

    Energy Technology Data Exchange (ETDEWEB)

    Poff, N L; Matthews, R A

    1984-01-01

    Mayfly community structure on sycamore and sweetgum leaf packs in a thermally-stressed, post-thermal and an unstressed stream were compared. Leaves were colonized over an 11 wk (77 d) period from December 1982 to March 1983. Degree-days (> 0/sup 0/C) accumulated were 1014, 638 and 627 for the thermally-stressed, post-thermal and unstressed streams, respectively. Significant differences in mayfly community structure were found between the thermally-stressed vs. the post-thermal and unstressed streams with respect to both Stenonema spp. and Caenis diminuta Walker. No significant differences in community structure were found between the two leaf species. Stenonema spp. dominated the mayfly fauna over the sampling period for both the unstressed (68%) and post-thermal (98%) streams; however, C. diminuta replaced Stenonema spp. as the dominant mayfly (88%) within leaf packs from the stream receiving thermal effluent. Additional data suggest C. diminuta is tolerant of rapidly fluctuating thermal regimes (..delta.. T of up to 11/sup 0/C in 1 h) and high temperatures (up to 40/sup 0/C). 30 references, 3 figures, 3 tables.

  12. Bandgap tuning with thermal residual stresses induced in a quantum dot.

    Science.gov (United States)

    Kong, Eui-Hyun; Joo, Soo-Hyun; Park, Hyun-Jin; Song, Seungwoo; Chang, Yong-June; Kim, Hyoung Seop; Jang, Hyun Myung

    2014-09-24

    Lattice distortion induced by residual stresses can alter electronic and mechanical properties of materials significantly. Herein, a novel way of the bandgap tuning in a quantum dot (QD) by lattice distortion is presented using 4-nm-sized CdS QDs grown on a TiO2 particle as an application example. The bandgap tuning (from 2.74 eV to 2.49 eV) of a CdS QD is achieved by suitably adjusting the degree of lattice distortion in a QD via the tensile residual stresses which arise from the difference in thermal expansion coefficients between CdS and TiO2. The idea of bandgap tuning is then applied to QD-sensitized solar cells, achieving ≈60% increase in the power conversion efficiency by controlling the degree of thermal residual stress. Since the present methodology is not limited to a specific QD system, it will potentially pave a way to unexplored quantum effects in various QD-based applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Numerical Analysis of Thermal Stresses around Fasteners in Composite Metal Foils

    Science.gov (United States)

    Nammi, S. K.; Butt, J.; –L Mauricette, J.; Shirvani, H.

    2017-12-01

    The process of composite metal foil manufacturing (CMFM) has reduced a number of limitations associated with commercial additive manufacturing (AM) methods. The existing metal AM machines are restricted by their build envelope and there is a growing market for the manufacture of large parts using AM. These parts are subsequently manufactured in fragments and are fastened together. This paper analyses the thermal stresses around cylindrical fasteners for three layered metal composite parts consisting of aluminium foil, brazing paste and copper foil layers. The investigation aims to examine the mechanical integrity of the metallurgically bonded aluminium/copper foils of 100 micron thickness manufactured in a disc shape. A cylindrical fastener set at an elevated temperature of 100 °C is fitted in the middle of the disc which results in a steady-state thermal distribution. Radial and shear stresses are computed using finite element method which shows that non-zero shear stresses developed by the copper layer inhibit the axial slippage of the fastener and thereby establishing the suitability of rivet joints for CMFM parts.

  14. Thermal and stress analysis of hot isostatically pressed, alumina ceramic, nuclear waste containers

    International Nuclear Information System (INIS)

    Chang, Yun; Hoenig, C.L.

    1990-01-01

    The Yucca Mountain Project is studying design and fabrication options for a safe durable container in which to store nuclear waste underground at Yucca Mountain, Nevada. The ceramic container discussed here is an alternative to using a metal container. This ceramic alternative would be selected if site conditions prove too corrosive to use metals for nuclear waste storage. Some of the engineering problems addressed in this study were: the stress generated in the alumina container by compressive loads when 4000 to 40,000 psi of external pressure is applied; the thermal stress in the container during the heating and cooling processes; the temperature histories of the container in various production scenarios and the power required for typical heaters; the fastest possible turnaround time to heat, seal, and cool the container commensurate with preserving the structural integrity of the ceramic and the closure; the testing of some commercial heating elements to determine the maximum available heat output; and the trade-offs between the minimization in thermal stress and cycle time for closure. 2 refs., 23 figs., 2 tabs

  15. The effect of thermal contact resistance on the thermosetting pultrusion process

    DEFF Research Database (Denmark)

    Baran, Ismet; Tutum, Cem Celal; Hattel, Jesper Henri

    2013-01-01

    In the present study the control volume based finite difference (CV/FD) method is utilized to perform thermo-chemical simulation of the pultrusion process of a composite rod. Preliminary, the model is applied for a simple setup without die and heaters and the results match well with those obtained...... experimentally in the literature. In order to study the effects of the thermal contact resistance (TCR), which can also be expressed by the heat transfer coefficient (HTC), on the pultrusion process, a cylindrical die block and heaters are added to the original problem domain. The significance of using the TCR...

  16. FLCN and AMPK Confer Resistance to Hyperosmotic Stress via Remodeling of Glycogen Stores.

    Directory of Open Access Journals (Sweden)

    Elite Possik

    2015-10-01

    Full Text Available Mechanisms of adaptation to environmental changes in osmolarity are fundamental for cellular and organismal survival. Here we identify a novel osmotic stress resistance pathway in Caenorhabditis elegans (C. elegans, which is dependent on the metabolic master regulator 5'-AMP-activated protein kinase (AMPK and its negative regulator Folliculin (FLCN. FLCN-1 is the nematode ortholog of the tumor suppressor FLCN, responsible for the Birt-Hogg-Dubé (BHD tumor syndrome. We show that flcn-1 mutants exhibit increased resistance to hyperosmotic stress via constitutive AMPK-dependent accumulation of glycogen reserves. Upon hyperosmotic stress exposure, glycogen stores are rapidly degraded, leading to a significant accumulation of the organic osmolyte glycerol through transcriptional upregulation of glycerol-3-phosphate dehydrogenase enzymes (gpdh-1 and gpdh-2. Importantly, the hyperosmotic stress resistance in flcn-1 mutant and wild-type animals is strongly suppressed by loss of AMPK, glycogen synthase, glycogen phosphorylase, or simultaneous loss of gpdh-1 and gpdh-2 enzymes. Our studies show for the first time that animals normally exhibit AMPK-dependent glycogen stores, which can be utilized for rapid adaptation to either energy stress or hyperosmotic stress. Importantly, we show that glycogen accumulates in kidneys from mice lacking FLCN and in renal tumors from a BHD patient. Our findings suggest a dual role for glycogen, acting as a reservoir for energy supply and osmolyte production, and both processes might be supporting tumorigenesis.

  17. Studying the Phenotypic and Genotypic Expression of Antibiotic Resistance in Campylobacter jejuni under Stress Conditions.

    Science.gov (United States)

    Efimochkina, N R; Stetsenko, V V; Bykova, I V; Markova, Yu M; Polyanina, A S; Aleshkina, A I; Sheveleva, S A

    2018-03-01

    Specific features for the development of resistance in Campylobacter jejuni strains were studied after treatment with antibiotics of 6 pharmacological groups. Populations of 18 native strains of C. jejuni (isolated from raw poultry products) and their subcultures (obtained after 2-3-fold stress exposures to antimicrobial agents in subinhibitory doses) were examined to evaluate the expression of phenotypic antibiotic resistance. Genotypic properties of strains were studied by the PCR with primers that detect the presence of genes for resistance to aminoglycosides (aphA-1, aphA-3, and aphA-7), tetracyclines (tetO), and quinolones (GZgyrA). The majority of test strains of C. jejuni exhibited a high resistance to nalidixic acid, ciprofloxacin, and tetracycline, which reached the maximum value after numerous passages. The expression of antibiotic resistance was greatest in the presence of nalidixic acid and tetracycline. Ciprofloxacin resistance of 33% strains, which were initially resistant to this antibiotic, was increased after 2-3-fold treatment. We revealed a high degree of correspondence between phenotypic and genotypic profiles of antibiotic resistance in food isolates of Campylobacter. One, two, or more genes of aphA were identified in 85% strains phenotypically resistant to aminoglycosides. The tetO gene was found nearly in all strains resistant to tetracycline. Studying the biofilm matrix in C. jejuni after culturing with antibiotics in subinhibitory doses showed that quinolones (particularly nalidixic acid) and tetracyclines potentiate the formation of biofilms and increase the tolerance of Campylobacter to stress exposures. The intensity of biofilm growth was shown to depend little on the effect of macrolides and aminoglycosides. Therefore, the presence of these agents in residual concentrations is associated with a lower risk for the development of antibiotic resistance in C. jejuni populations.

  18. On the thermally-induced residual stresses in thick fiber-thermoplastic matrix (PEEK) cross-ply laminated plates

    Science.gov (United States)

    Hu, Shoufeng; Nairn, John A.

    1992-01-01

    An analytical method for calculating thermally-induced residual stresses in laminated plates is applied to cross-ply PEEK laminates. We considered three cooling procedures: slow cooling (uniform temperature distribution); convective and radiative cooling; and rapid cooling by quenching (constant surface temperature). Some of the calculated stresses are of sufficient magnitude to effect failure properties such as matrix microcracking.

  19. Effects of current stress and thermal storage on polymeric heterojunction P3HT:PCBM solar cell

    DEFF Research Database (Denmark)

    Rizzo, Antonio; Cester, Andrea; Torto, Lorenzo

    2016-01-01

    We subjected P3HT:PCBM solar cells to electrical constant current stress and thermal storage. We employed the impedance spectroscopy technique combined to conventional DC measurements for device characterization during all stresses. We identified and separated different contributions affecting...

  20. The GATA Transcription Factor egl-27 Delays Aging by Promoting Stress Resistance in Caenorhabditis elegans

    Science.gov (United States)

    Xu, Xiao; Kim, Stuart K.

    2012-01-01

    Stress is a fundamental aspect of aging, as accumulated damage from a lifetime of stress can limit lifespan and protective responses to stress can extend lifespan. In this study, we identify a conserved Caenorhabditis elegans GATA transcription factor, egl-27, that is involved in several stress responses and aging. We found that overexpression of egl-27 extends the lifespan of wild-type animals. Furthermore, egl-27 is required for the pro-longevity effects from impaired insulin/IGF-1 like signaling (IIS), as reduced egl-27 activity fully suppresses the longevity of worms that are mutant for the IIS receptor, daf-2. egl-27 expression is inhibited by daf-2 and activated by pro-longevity factors daf-16/FOXO and elt-3/GATA, suggesting that egl-27 acts at the intersection of IIS and GATA pathways to extend lifespan. Consistent with its role in IIS signaling, we found that egl-27 is involved in stress response pathways. egl-27 expression is induced in the presence of multiple stresses, its targets are significantly enriched for many types of stress genes, and altering levels of egl-27 itself affects survival to heat and oxidative stress. Finally, we found that egl-27 expression increases between young and old animals, suggesting that increased levels of egl-27 in aged animals may act to promote stress resistance. These results identify egl-27 as a novel factor that links stress and aging pathways. PMID:23271974

  1. Thermohydraulic and thermal stress aspects of a porous blockage in an LMFBR fuel assembly

    International Nuclear Information System (INIS)

    Kuzay, T.M.; Marr, W.W.; Helenberg, H.W.; Ariman, T.; Wilson, R.E.; Pedersen, D.R.

    1979-01-01

    The current safety scenarios of Liquid Metal Fast Breeder Reactors (LMFBR) under local fault propagation include the study of a hypothetical accident initiated by the formation of an external debris porous blockage in a fuel subassembly. In this preliminary experimental and analytical investigation, a non-heat-generating porous blockage was postulated to cover 18 flow channels of a 37 pin Fast Test Reactor (FTR) type fuel subassembly. The axial extent of the blockage is 50 mm. The blockage material is stainless steel (SS 316) with 30 percent average porosity (percent void volume). The blockage and the pins were modeled with a finite element technique and the thermal field in the blockage was predicted. This thermal field was utilized to do a planar thermal stress analysis of the postulated blockage. To verify the analytical model and also to better understand the thermal-hydraulics of such a porous blockage out-of-pile tests were conducted in a sodium loop. Data from the out-of-pile tests was utilized to calibrate and improve the analytical model

  2. Thermal shock behaviour of ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Fantozzi, G.; Saadaoui, M.; Chevalier, J.; Olagnon, C. [Groupe d' Etude de Metallurgie Physique UMR, Institut National des Sciences Appliquees de Lyon, Villeurbanne (France)

    2000-07-01

    Thermal shock of ceramics is complex to analyse because of the important number of parameters to take into account. Thermal shock analysis has been refined by considering the dependence with temperature of the different parameters. From the temperature evolution in the specimen, the stress and stress intensity factor (SIF) profiles can be calculated. This allows the prediction of the crack evolution during thermal shock. Thermal shock experiments conducted by using an in-situ acoustic emission (AE) apparatus allow the determination of the time of unstable crack growth. The effect of crack growth resistance (R-curve behaviour) can be taken into account and, if it is significant, the thermal shock resistance of ceramics can be improved. The fracture mechanical analysis was used to determine the R-curve behaviour of alumina material subjected to thermal shock. A good agreement is observed between predictions of thermal fracture theory based on fracture mechanics and experimental results. (orig.)

  3. A dome-shaped BE window for x-rays and its thermal and thermal stress analysis

    International Nuclear Information System (INIS)

    Wang, Z.; Kuzay, T.M.

    1994-01-01

    Synchrotron x-ray windows are vacuum separators and are usually made of thin (about 10 μm to 300 μm in thickness) beryllium foil that is brazed onto a cooled frame. Beryllium (Be) is a low-atomic-number material so that a thin beryllium window will let useful x-rays pass through. Because beryllium has a relatively high strength and good plasticity, the thin beryllium window can keep the vacuum system tight without failure when carefully engineered. Even if the majority of high-energy photons from x-rays is transmitted through the window, some low-energy photons will be absorbed. This absorbed part turns into heat in the window. A good design of a beryllium window should be as thin as possible so that more low-energy photons can be transmitted through the window while it can still withstand the heat load and vacuum pressure. Due to the high heat load from the third-generation synchrotron radiation X-ray beams, it becomes a very challenging problem to design a safe window. This paper presents a new dome-shaped Be window concept. A novel dome-shaped Be window design with varying cross section is proposed, and its thermal and thermal stress analyses are presented in this paper. All the safety criteria for the window are checked after a full understanding of this window's behavior under heat and pressure. The dome Be window analyses are based on the assumption that the low-energy photon transmission at the first harmonic of APS Undulator A (4.09 keV) through the filter/window assembly should be at least 50 percent of the original photon flux. The results promise that a feasible filter/window assembly for APS Undulator A can be designed and built

  4. Effect of substrate properties and thermal annealing on the resistivity of molybdenum thin films

    International Nuclear Information System (INIS)

    Schmid, U.; Seidel, H.

    2005-01-01

    In this study, the influence of substrate properties (e.g. roughness characteristics and chemical composition) on the electrical resistivity of evaporated molybdenum thin films is investigated as a function of varying parameters, such as film thickness (25-115 nm) and post-deposition annealing with temperatures up to T PDA = 900 deg. C. A thermally oxidized silicon wafer with very low surface roughness was used as one substrate type. In contrast, a low temperature co-fired ceramics substrate with a glass encapsulant printed in thick film technology is the representative for rough surface morphology. The electrical resistivity follows the prediction of the size effect up to T PDA = 600 deg. C independent of substrate nature. On the silicon-based substrate, the thickness-independent portion of the film resistivity ρ g in the 'as deposited' state is about 29 times higher than the corresponding bulk value for a mono-crystalline sample. Thin films of this refractory metal on the SiO 2 /Si substrate exhibit an average grain size of 4.9 nm and a negative temperature coefficient of resistivity (TCR). On the glass/ceramic-based substrate, however, ρ g is half the value as compared to that obtained on the SiO 2 /Si substrate and the TCR is positive

  5. Design and Performance Optimizations of Advanced Erosion-Resistant Low Conductivity Thermal Barrier Coatings for Rotorcraft Engines

    Science.gov (United States)

    Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

    2012-01-01

    Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future rotorcraft engine higher fuel efficiency and lower emission goals. For thermal barrier coatings designed for rotorcraft turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability, because the rotorcraft are often operated in the most severe sand erosive environments. Advanced low thermal conductivity and erosion-resistant thermal barrier coatings are being developed, with the current emphasis being placed on thermal barrier coating toughness improvements using multicomponent alloying and processing optimization approaches. The performance of the advanced thermal barrier coatings has been evaluated in a high temperature erosion burner rig and a laser heat-flux rig to simulate engine erosion and thermal gradient environments. The results have shown that the coating composition and architecture optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic oxidation durability

  6. Analysis of the Thermal Stress for Combined Electrode of Soldered Crystalline Silicon Solar Cells under Temperature Field

    Directory of Open Access Journals (Sweden)

    He Wang

    2016-01-01

    Full Text Available Based on the theory of material mechanics and thermal stress analysis, the stress distribution of combined electrode for crystalline silicon solar module was studied for the first time. The shear stress and normal stress distribution of soldered structure for crystalline silicon solar cells under the thermal field were discussed. And the results show that the stress distribution is not simply linear relationship as some results found. But there is a stress concentration at the edge, which was considered as the true reason that caused microcracks at the edge of soldered solar cells. The conclusions we got in this paper provide a theoretical basis for deceasing the breakage rates of soldered crystalline silicon solar cells and improving the reliability of crystalline silicon solar modules.

  7. DIFFERENTIAL BLOOD COUNT OF TENCH Tinca tinca (Linnaeus, 1758 IN CONDITIONS OF THERMAL STRESS

    Directory of Open Access Journals (Sweden)

    Edhem Hasković

    2014-03-01

    Full Text Available Defining the physiological feature provides an understanding of functional adaptation of species to its ecological niche as well as the various forms of stress factors. This paper gives an overview of changes in certain forms of leukocytes (WBC differential under the influence of thermal stress (increased temperature. In our experiment, we used 46 specimens of tench (Tinca tinca fished in the Jablanica Lake reservoir. Specimens had previously been adapted in specially prepared tanks for 20 days.  The control group of animals (16 was exposed to constant water temperature of 10 0C, while in the treated groups (30, the water temperature was gradually risen to 28 0C and, as such, held for 30 minutes. All specimens were aged 2+ and 3+.It was found that the thermal regime change causes adaptive response of tench specimens by increasing the number of neutrophils and pseudoeosinophils but reduction in the number of lymphocytes. Observed were statistically significant differences in the number of segmented granulocytes, pseudoeosinophils and lymphocytes between the control and the experimental group. However, a significantly higher number of segmented granulocytes and pseudoeosinophils was at the experimental group, while in the control group a number of lymphocytes was significantly higher compared with the experimental group. Neither form of leukocytes showed any significant difference between males and females of the experimental group. It is interesting to note that among individuals from both the control and experimental group, eosinophils and monocytes were rarely noticed, while basophils were not found at all. Key words: thermal stress, tench, Tinca tinca, pseudoeosinophils

  8. Thermal Stress Cracking of Slide-Gate Plates in Steel Continuous Casting

    Science.gov (United States)

    Lee, Hyoung-Jun; Thomas, Brian G.; Kim, Seon-Hyo

    2016-04-01

    The slide-gate plates in a cassette assembly control the steel flow through the tundish nozzle, and may experience through-thickness cracks, caused by thermal expansion and/or mechanical constraint, leading to air aspiration and safety concerns. Different mechanisms for common and rare crack formation are investigated with the aid of a three-dimensional finite-element model of thermal mechanical behavior of the slide-gate plate assembly during bolt pretensioning, preheating, tundish filling, casting, and cooling stages. The model was validated with previous plant temperature measurements of a ladle plate during preheating and casting, and then applied to a typical tundish-nozzle slide-gate assembly. The formation mechanisms of different types of cracks in the slide-gate plates are investigated using the model and evaluated with actual slide-gate plates at POSCO. Common through-thickness radial cracks, found in every plate, are caused during casting by high tensile stress on the outside surfaces of the plates, due to internal thermal expansion. In the upper plate, these cracks may also arise during preheating or tundish filling. Excessive bolt tightening, combined with thermal expansion during casting may cause rare radial cracks in the upper and lower plates. Rare radial and transverse cracks in middle plate appear to be caused during tundish filling by impingement of molten steel on the middle of the middle plate that generates tensile stress in the surrounding refractory. The mechanical properties of the refractory, the bolt tightening conditions, and the cassette/plate design are all important to service life.

  9. Heat resistance of Monascus ruber ascospores isolated from thermally processed green olives of the Conservolea variety.

    Science.gov (United States)

    Panagou, Efstathios Z; Katsaboxakis, Constantinos Z; Nychas, George-John E

    2002-06-05

    A heat-resistant fungus identified as Monascus ruber was isolated from thermally processed green olives of the Conservolea variety. Thermal death parameters of the ascospores were determined using Baranyi's primary predictive model in phosphate buffer (pH 7.0), citrate buffer (pH 4.0) and brine (pH 3.8) at two different NaCl levels (5.6% and 10.5%). The decimal reduction times (D values) at 70, 75 and 80 degrees C in phosphate buffer (pH 7.0) were 37.31, 7.14 and 1.66 min, respectively, and the calculated z value was 7.4 degrees C. In citrate buffer (pH 4.0), the relative D values were 38.61, 7.83 and 2.10 min and the z value was 7.9 degrees C. In brine, the D(70 degrees C), D75(75 degrees C) and D(80 degrees C) values increased from 46.08, 4.91 and 0.88 min to 72.99, 7.98 and 1.04 min, respectively, as the level of NaCl in brine increased from 5.6% to 10.5%, indicating a protective effect in ascospore inactivation. This effect was more pronounced at lower heating temperatures. It was concluded that a thermal process of F(80 degrees C) = 5 min could be considered as an effective thermal processing treatment. Results from this research could assist the table olive industry in designing an effective pasteurization plan to eliminate the fungus in thermally processed table olives.

  10. A comparison of the fracture resistance of three machinable ceramics after thermal and mechanical fatigue.

    Science.gov (United States)

    Yang, Rui; Arola, Dwayne; Han, Zhihui; Zhang, Xiuyin

    2014-10-01

    Mechanical and thermal fatigue may affect ceramic restorations in the oral environment. The purpose of this study was to determine the influence of thermal and mechanical cycling on the fracture load and fracture patterns of 3 machinable ceramics. Seventy-two human third molar teeth were prepared for bonding ceramic specimens of Sirona CEREC Blocs, IPS e.maxCAD, or inCoris ZI meso blocks. The 24 specimens of each ceramic were divided into 4 groups (n=6), which underwent no preloading (control), thermocycling (5°C-55°C, 2000 cycles), mechanical cycling (10(5) cycles, 100 N), and thermocycling (5°C-55°C, 2000 cycles) plus mechanical cycling (10(5) cycles, 100 N). The specimens were subsequently loaded to failure, and both stereomicroscopy and scanning electron microscopy were used to investigate the fracture patterns. The data were analyzed with 2-way ANOVA and the Fisher exact probability test (α=.05). Mechanical and thermal cycling had a significant influence on the critical load to failure of the 3 ceramics. No significant difference was found between mechanical cycling for 10(5) times and thermocycling for 2000 times within the same ceramic. The specimens of inCoris ZI experienced significantly higher fracture loads for all the groups. The fracture patterns of the 3 machinable ceramics showed that failure mainly occurred at the cement-dentin interface. The effects of combined thermal and mechanical cycling on the fracture load of ceramics were more significant than any individual mode of cyclic fatigue. Overall, the inCoris ZI resisted thermal and mechanical fatigue better than the Sirona CEREC and IPS e.maxCAD. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  11. Effect of a marginal inclination on pattern formation in a binary liquid mixture under thermal stress.

    Science.gov (United States)

    Croccolo, Fabrizio; Scheffold, Frank; Vailati, Alberto

    2013-07-05

    Convective motions in a fluid layer are affected by its orientation with respect to the gravitational field. We investigate the long-term stability of a thermally stressed layer of a binary liquid mixture and show that pattern formation is strongly affected by marginal inclinations as small as a few milliradians. At small Rayleigh numbers, the mass transfer is dominated by the induced large scale shear flow, while at larger Rayleigh numbers, it is dominated by solutal convection. At the transition, the balance between the solutal and shear flows gives rise to drifting columnar flows moving in opposite directions along parallel lanes in a superhighway configuration.

  12. Stress induced conditioning and thermal relaxation in the simulation of quasi-static compression experiments

    CERN Document Server

    Scalerandi, M; Johnson, P A

    2003-01-01

    Local interaction simulation approach simulations of the ultrasonic wave propagation in multi-grained materials have succeeded in reproducing most of the recently observed nonclassical nonlinear effects, such as stress-strain hysteresis and discrete memory in quasi-static experiments and a downwards shift of the resonance frequency and the generation of odd harmonics at specific amplitude rates in dynamics experiments. By including a simple mechanism of thermally activated random transitions, we can predict the occurrence of experimentally observed effects, such as the conditioning and relaxation of the specimen. Experiments are also suggested for a quantitative assessment of the validity of the model.

  13. Stress induced conditioning and thermal relaxation in the simulation of quasi-static compression experiments

    International Nuclear Information System (INIS)

    Scalerandi, M; Delsanto, P P; Johnson, P A

    2003-01-01

    Local interaction simulation approach simulations of the ultrasonic wave propagation in multi-grained materials have succeeded in reproducing most of the recently observed nonclassical nonlinear effects, such as stress-strain hysteresis and discrete memory in quasi-static experiments and a downwards shift of the resonance frequency and the generation of odd harmonics at specific amplitude rates in dynamics experiments. By including a simple mechanism of thermally activated random transitions, we can predict the occurrence of experimentally observed effects, such as the conditioning and relaxation of the specimen. Experiments are also suggested for a quantitative assessment of the validity of the model

  14. Simulation of thermal stress and buckling instability in Si/Ge and Ge/Si core/shell nanowires.

    Science.gov (United States)

    Das, Suvankar; Moitra, Amitava; Bhattacharya, Mishreyee; Dutta, Amlan

    2015-01-01

    The present study employs the method of atomistic simulation to estimate the thermal stress experienced by Si/Ge and Ge/Si, ultrathin, core/shell nanowires with fixed ends. The underlying technique involves the computation of Young's modulus and the linear coefficient of thermal expansion through separate simulations. These two material parameters are combined to obtain the thermal stress on the nanowires. In addition, the thermally induced stress is perceived in the context of buckling instability. The analysis provides a trade-off between the geometrical and operational parameters of the nanostructures. The proposed methodology can be extended to other materials and structures and helps with the prediction of the conditions under which a nanowire-based device might possibly fail due to elastic instability.

  15. A 1-D Analytical Model for the Thermally Induced Stresses in the Mould Surface During Die Casting

    DEFF Research Database (Denmark)

    Hattel, Jesper; Hansen, Preben

    1994-01-01

    This paper presents an anlytically based method for predicting the normal stresses in a die mold surface exposed to a thermal load. A example of application of the method is the high-pressure di casting process where the surface stresses in critical cases lead to cracks. Expressions for the normal...... stresses as afunction of the thermal and mechanical properties have been developed for a casting both without and with a coating. Finally, the resulting relationships are derived and evaluated, with particular emphasis on the effect of the heat transfer coefficient between the casting and the mold....

  16. Prediction of thermal and mechanical stress-strain responses of TMC's subjected to complex TMF histories

    Science.gov (United States)

    Johnson, W. S.; Mirdamadi, M.

    1994-01-01

    This paper presents an experimental and analytical evaluation of cross-plied laminates of Ti-15V-3Cr-3Al-3Sn (Ti-15-3) matrix reinforced with continuous silicon-carbide fibers (SCS-6) subjected to a complex TMF loading profile. Thermomechanical fatigue test techniques were developed to conduct a simulation of a generic hypersonic flight profile. A micromechanical analysis was used. The analysis predicts the stress-strain response of the laminate and of the constituents in each ply during thermal and mechanical cycling by using only constituent properties as input. The fiber was modeled as elastic with transverse orthotropic and temperature-dependent properties. The matrix was modeled using a thermoviscoplastic constitutive relation. The fiber transverse modulus was reduced in the analysis to simulate the fiber-matrix interface failures. Excellent correlation was found between measured and predicted laminate stress-strain response due to generic hypersonic flight profile when fiber debonding was modeled.

  17. Service Life Of Main Piping Component Due To Low Thermal Stresses.Fatigue

    International Nuclear Information System (INIS)

    Miroshnik, R.; Jeager, A.; Ben Haim, H.

    1998-01-01

    The paper deals with estimating the service life of the power station Main piping component and describing the repair process for extending of its service life. After a long period of service, several circular fatigue cracks have been discovered at the bottom of the Main piping component chamber. Finite element analyses of transient thermal stresses, caused by power station startup, are carried out in the paper. The calculation results show good agreement between the theoretical locations of the maximum stresses and the actual locations of the cracks. There is a good agreement between theoretical evaluation and actual service life, as well. The possibility of machining out the cracks in order to prevent their growing is examined here. The machining enables us to extend the power station component's life service

  18. Heightened reward learning under stress in generalized anxiety disorder: a predictor of depression resistance?

    Science.gov (United States)

    Morris, Bethany H; Rottenberg, Jonathan

    2015-02-01

    Stress-induced anhedonia is associated with depression vulnerability (Bogdan & Pizzagalli, 2006). We investigated stress-induced deficits in reward learning in a depression-vulnerable group with analogue generalized anxiety disorder (GAD, n = 34), and never-depressed healthy controls (n = 41). Utilizing a computerized signal detection task, reward learning was assessed under stressor and neutral conditions. Controls displayed intact reward learning in the neutral condition, and the expected stress-induced blunting. The GAD group as a whole also showed intact reward learning in the neutral condition. When GAD subjects were analyzed as a function of prior depression history, never-depressed GAD subjects showed heightened reward learning in the stressor condition. Better reward learning under stress among GAD subjects predicted lower depression symptoms 1 month later. Robust reward learning under stress may indicate depression resistance among anxious individuals. (PsycINFO Database Record (c) 2015 APA, all rights reserved).

  19. Resistance to early-life stress in mice: effects of genetic background and stress duration

    Directory of Open Access Journals (Sweden)

    Helene M. Savignac

    2011-04-01

    Full Text Available Early-life stress can induce marked behavioural and physiological impairments in adulthood including cognitive deficits, depression, anxiety and gastrointestinal dysfunction. Although robust rat models of early-life stress exist there are few established effective paradigms in the mouse. Genetic background and protocol parameters used are two critical variables in such model development.Thus we investigated the impact of two different early-life stress protocols in two commonly used inbred mouse strains. C57BL/6 and innately anxious BALB/c male mice were maternally deprived 3 hrs daily, either from postnatal day 1 to 14 (Protocol 1 or 6 to 10 (Protocol 2. Animals were assessed in adulthood for cognitive performance (spontaneous alternation behaviour test, anxiety (open field, light/dark box and elevated plus maze tests and depression-related behaviours (forced swim test in addition to stress-sensitive physiological changes. Overall, the results showed that early-life stressed mice from both strains displayed good cognitive ability and no elevations in anxiety. However, paradoxical changes occurred in C57BL/6 mice as the longer protocol (protocol 1 decreased anxiety in the light-dark box and increased exploration in the elevated plus maze. In BALB/c mice there were also limited effects of maternal separation with both separation protocols inducing reductions in stress-induced defecation and protocol 1 reducing the colon length. These data suggest that, independent of stress duration, mice from both strains were on the whole resilient to the maladaptive effects of early-life stress. Thus maternal-separation models of brain-gut axis dysfunction should rely on either different stressor protocols or other strains of mice.

  20. Correlation between corrosion resistance properties and thermal cycles experienced by gas tungsten arc welding and laser beam welding Alloy 690 butt weldments

    International Nuclear Information System (INIS)

    Lee, H T; Wu, J L

    2009-01-01

    This study investigates the correlation between the thermal cycles experienced by Alloy 690 weldments fabricated using gas tungsten arc welding (GTAW) and laser beam welding (LBW) processes, and their corresponding corrosion resistance properties. The corrosion resistance of the weldments is evaluated using a U-bend stress corrosion test in which the specimens are immersed in a boiling, acid solution for 240 h. The experimental results reveal that the LBW inputs significantly less heat to the weldment than the GTAW, and therefore yields a far faster cooling rate. Moreover, the corrosion tests show that in the GTAW specimen, intergranular corrosion (IGC) occurs in both the fusion zone (FZ) and the heat affected zone (HAZ). By contrast, the LBW specimen shows no obvious signs of IGC.