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Artigos de revistas sobre o assunto "Species thermal stress"
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WHITE, R. R., e M. D. HANIGAN. "Modelling cross-species feed intake responses to thermal stress". Journal of Agricultural Science 154, n.º 1 (5 de novembro de 2015): 136–50. http://dx.doi.org/10.1017/s0021859615001033.
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SUMMARYThe objectives of the current study were to compare and model feed intake responses to ambient temperature across species and to assess opportunities to use cross-species (CS) data to parameterize models when species-specific (SS) data were limited. Literature searches were conducted to identify studies reporting intake during thermal stress compared with thermoneutral (TN) conditions. The resulting data set comprised 614 treatment means from 108 studies on livestock responses to thermal stress. An analysis of variance was conducted with the CS data set to identify the effects of species, temperature and species by temperature interactions on intake as (fractional feed intake; FFI). Four models were derived from the CS data set and root mean squared prediction error (RMSPE) and concordance correlation coefficients (CCC) of these models were compared with models of the same form derived from SS data sets. Models used explanatory variables for (1) duration of exposure; (2) mean temperature; (3) minimum and maximum temperatures; or (4) difference between minimum and maximum temperatures. An additional model accounting for temperature and stage of production was derived from the SS data. Analysis of variance demonstrated that the species by temperature interaction did not have a significant effect on FFI. Across species, intake decreased with temperature. Notably, all species demonstrated a constant decrease in intake across the TN zone indicating the previous assumption of constant intake during thermoneutrality may be not fully valid. When compared on a SS basis, SS-derived models had marginally lower RMSPE and higher CCC when compared with models derived from the CS data sets. The model fit with production data had the lowest RMSPE and highest CCC within the study. When compared over temperature ranges with minimal data available in some species (e.g., cold stress), using CS models often resulted in decreased RMSPE and improved CCC when compared with SS models. Although fitting models based on SS data allows for incorporating unique covariates, like level of production, fitting responses based on CS data can help to improve model estimates when knowledge gaps exist.
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Bard, Brittany, e James D. Kieffer. "The effects of repeat acute thermal stress on the critical thermal maximum (CTmax) and physiology of juvenile shortnose sturgeon (Acipenser brevirostrum)". Canadian Journal of Zoology 97, n.º 6 (junho de 2019): 567–72. http://dx.doi.org/10.1139/cjz-2018-0157.
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The shortnose sturgeon (Acipenser brevirostrum Lesueur, 1818) is a species of special concern in Canada, but little is known about their thermal biology. Information on the upper thermal tolerance of shortnose sturgeon becomes valuable for predicting future survival particularly with climate change and improving species management. Using a modified critical thermal maximum (CTmax) methodology, the objective is to determine whether previous thermal stress affects the thermal tolerance of juvenile shortnose sturgeon when exposed to a second thermal stress event. Prior exposure to thermal stress (CTmax1) did not affect the thermal tolerance (CTmax2) of juvenile shortnose sturgeon when a 24 h recovery period was allotted between tests. However, a significant increase in thermal tolerance occurred when the recovery time between the two thermal challenges was 1 h. Plasma glucose, lactate, and osmolality were all significantly affected by thermal stress, but values returned to control levels within 24 h. Hematocrit and plasma chloride concentrations were not significantly affected by thermal stress. All fish survived the CTmax testing. The data indicate that the thermal tolerance of juvenile shortnose sturgeon is modified when multiple thermal stresses occur closer together (1 h) but not if separated by a longer time period (24 h).
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DeVito, Jill, Jesse M. Meik, Marina M. Gerson e Daniel R. Formanowicz, Jr. "Physiological tolerances of three sympatric riparian wolf spiders (Araneae: Lycosidae) correspond with microhabitat distributions". Canadian Journal of Zoology 82, n.º 7 (1 de julho de 2004): 1119–25. http://dx.doi.org/10.1139/z04-090.
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Coexisting species from the same ecological guild often exhibit different adaptations to discontinuous, abiotic environmental factors. In the laboratory, we compared tolerance to thermal and desiccation stress among three sympatric wolf spiders (Pirata sedentarius Montgomery, 1904, Pardosa lapidicina Emerton, 1885, and Pardosa fuscula Thorell, 1875). In the field, we examined spatial structure across a microhabitat (moisture) gradient in a streamside cobble habitat where these three species are abundant. Female P. sedentarius succumbed more quickly to desiccation stress than females of either Pardosa species. In the absence of thermal stress, desiccation tolerance was high for both Pardosa species. However, P. fuscula appears to be more resistant to combined thermal and desiccation stress than P. lapidicina. These findings correspond with the results of the field survey; the distribution of P. sedentarius was the most restricted (by proximity to the shoreline) among the three species. Contingency analyses also revealed greater relative abundance of P. fuscula than P. lapidicina farther away from the creek. Further examination of spatial structure suggests that neither of these two species was restricted by proximity to the shoreline within the sampling grid.
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Klepac, C. N., e D. J. Barshis. "Reduced thermal tolerance of massive coral species in a highly variable environment". Proceedings of the Royal Society B: Biological Sciences 287, n.º 1933 (19 de agosto de 2020): 20201379. http://dx.doi.org/10.1098/rspb.2020.1379.
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Coral bleaching events are increasing in frequency and severity, resulting in widespread losses in coral cover. However, branching corals native to highly variable (HV) thermal environments can have higher bleaching resistance than corals from more moderate habitats. Here, we investigated the response of two massive corals, Porites lobata and Goniastrea retiformis , from a moderately variable (MV) and a low variability (LV) pool transplanted into a HV pool on Ofu Island in American Samoa. Paired transplant and native ramets were exposed to an acute thermal stress after 6 and 12 months of exposure to the HV pool to evaluate changes in thermal tolerance limits. For both species, photosynthetic efficiency and chlorophyll loss following acute heat stress did not differ between ramets transplanted into the HV pool and respective native pool. Moreover, HV native P. lobata exhibited the greatest bleaching susceptibility compared to MV and LV natives and there was no effect of acute heat stress on MV P. lobata . There was also a thermal anomaly during the study, where Ofu's backreef thermal regime surpassed historical records—2015 had 8 degree heating weeks (DHW) and 2016 had up to 5 DHW (in comparison to less than or equal to 3 over the last 10 years)—which may have exceeded the upper thermal limits of HV native P. lobata . These results strongly contrast with other research on coral tolerance in variable environments, potentially underscoring species-specific mechanisms and regional thermal anomalies that may be equally important in shaping coral responses to extreme temperatures.
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Fordyce, Alexander J., Emma F. Camp e Tracy D. Ainsworth. "Polyp bailout in Pocillopora damicornis following thermal stress". F1000Research 6 (10 de agosto de 2017): 687. http://dx.doi.org/10.12688/f1000research.11522.2.
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Polyp bailout is an established but understudied coral stress response that involves the detachment of individual polyps from the colonial form as a means of escaping unfavourable conditions. This may influence both the mortality and asexual recruitment of coral genotypes across a range of species. It has been observed in response to numerous stressors including high salinity and low pH. Polyp expulsion in association with thermal stress has once been described in a geographically restricted, temperate species. We therefore cannot reliably apply this observation to tropical coral reefs around the world, which are increasingly under threat from thermal stress events. We present the first qualitative observation of polyp bailout following acute temperature shock in a near-natural mesocosm experiment. Detached polyps show similar characteristics to those described in previous studies, including the retention of endosymbiotic zooxanthellae and the ability to disperse across short distances. This finding strongly suggests that polyp bailout occurs in tropical coral reef environments and warrants further detailed research into the implication of this response in terms of individual survival, rapid migration into cooler micro-habitats and local recruitment within the reef environment and its coral community.
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Williams, Amanda, Jananan S. Pathmanathan, Timothy G. Stephens, Xiaoyang Su, Eric N. Chiles, Dennis Conetta, Hollie M. Putnam e Debashish Bhattacharya. "Multi-omic characterization of the thermal stress phenome in the stony coral Montipora capitata". PeerJ 9 (10 de novembro de 2021): e12335. http://dx.doi.org/10.7717/peerj.12335.
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Background Corals, which form the foundation of biodiverse reef ecosystems, are under threat from warming oceans. Reefs provide essential ecological services, including food, income from tourism, nutrient cycling, waste removal, and the absorption of wave energy to mitigate erosion. Here, we studied the coral thermal stress response using network methods to analyze transcriptomic and polar metabolomic data generated from the Hawaiian rice coral Montipora capitata. Coral nubbins were exposed to ambient or thermal stress conditions over a 5-week period, coinciding with a mass spawning event of this species. The major goal of our study was to expand the inventory of thermal stress-related genes and metabolites present in M. capitata and to study gene-metabolite interactions. These interactions provide the foundation for functional or genetic analysis of key coral genes as well as provide potentially diagnostic markers of pre-bleaching stress. A secondary goal of our study was to analyze the accumulation of sex hormones prior to and during mass spawning to understand how thermal stress may impact reproductive success in M. capitata. Methods M. capitata was exposed to thermal stress during its spawning cycle over the course of 5 weeks, during which time transcriptomic and polar metabolomic data were collected. We analyzed these data streams individually, and then integrated both data sets using MAGI (Metabolite Annotation and Gene Integration) to investigate molecular transitions and biochemical reactions. Results Our results reveal the complexity of the thermal stress phenome in M. capitata, which includes many genes involved in redox regulation, biomineralization, and reproduction. The size and number of modules in the gene co-expression networks expanded from the initial stress response to the onset of bleaching. The later stages involved the suppression of metabolite transport by the coral host, including a variety of sodium-coupled transporters and a putative ammonium transporter, possibly as a response to reduction in algal productivity. The gene-metabolite integration data suggest that thermal treatment results in the activation of animal redox stress pathways involved in quenching molecular oxygen to prevent an overabundance of reactive oxygen species. Lastly, evidence that thermal stress affects reproductive activity was provided by the downregulation of CYP-like genes and the irregular production of sex hormones during the mass spawning cycle. Overall, redox regulation and metabolite transport are key components of the coral animal thermal stress phenome. Mass spawning was highly attenuated under thermal stress, suggesting that global climate change may negatively impact reproductive behavior in this species.
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Da-Anoy, Jeric, Niño Posadas e Cecilia Conaco. "Interspecies differences in the transcriptome response of corals to acute heat stress". PeerJ 12 (10 de dezembro de 2024): e18627. https://doi.org/10.7717/peerj.18627.
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Rising sea surface temperatures threaten the survival of corals worldwide, with coral bleaching events becoming more commonplace. However, different coral species are known to exhibit variable levels of susceptibility to thermal stress. To elucidate genetic mechanisms that may underlie these differences, we compared the gene repertoire of four coral species, Favites colemani, Montipora digitata, Acropora digitifera, and Seriatopora caliendrum, that were previously demonstrated to have differing responses to acute thermal stress. We found that more tolerant species, like F. colemani and M. digitata, possess a greater abundance of antioxidant protein families and chaperones. Under acute thermal stress conditions, only S. caliendrum showed a significant bleaching response, which was accompanied by activation of the DNA damage response network and drastic upregulation of stress response genes (SRGs). This suggests that differences in SRG orthologs, as well as the mechanisms that control SRG expression response, contribute to the ability of corals to maintain stability of physiological functions required to survive shifts in seawater temperature.
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Ataíde, Glauciana da Mata, Eduardo Euclydes de Lima e. Borges e Andressa Vasconcelos Flores. "Enzymatic activity in braúna seeds subjected to thermal stress". Ciência Rural 46, n.º 6 (junho de 2016): 1044–49. http://dx.doi.org/10.1590/0103-8478cr20141800.
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ABSTRACT: To occur seed germination distinct hydrolytic enzymes work together, enabling primary root protrusion. The objective of this study was to investigate changes in the activities of α-amylase, β-amylase, and glucose-6-phosphate dehydrogenase (G6PdH) during germination of Melanoxylon brauna Schott. seeds under thermal stress. To this end, seeds of this species were germinated under constant temperature (10, 25, 30 or 40°C) and samples were collected every 24h during a 96-h period, in which the activity of the enzymes were evaluated. At 25 and 30°C, optimal temperatures for the germination of the species, the activities of α-amylase, β-amylase, and G6PdH increased with seed imbibitions. At 10 and 40°C, enzyme activities decreased, impairing the germination process.
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FitzGerald, Alyssa M., Sara N. John, Travis M. Apgar, Nathan J. Mantua e Benjamin T. Martin. "Quantifying thermal exposure for migratory riverine species: Phenology of Chinook salmon populations predicts thermal stress". Global Change Biology 27, n.º 3 (4 de dezembro de 2020): 536–49. http://dx.doi.org/10.1111/gcb.15450.
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Berrigan, David. "Correlations between measures of thermal stress resistance within and between species". Oikos 89, n.º 2 (maio de 2000): 301–4. http://dx.doi.org/10.1034/j.1600-0706.2000.890211.x.
Texto completo da fonteTeses / dissertações sobre o assunto "Species thermal stress"
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Walsh, Desmond. "The detection, properties, and stress responses of Listeria monocytogenes and other Listeria species". Thesis, University of Ulster, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342425.
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Hidalgo, Galiana Amparo. "Evolution of thermal tolerance and size of the geographic range in closely related species of water beetles". Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/286361.
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This thesis studies a group of aquatic beetles (Agabus brunneus complex) that present important differences in the size of their geographic ranges. This complex is composed by an insular species (A. rufulus), a continental species with restricted range (A. ramblae) and another continental species (A. brunneus) that posses a wide range of distribution (A. brunneus) with the aim of study the factors implied in those differences. For this purpose we integrated the phylogeny/ phylogeography of the group and the evolution of the ecological niche together with morphological study and thermal tolerance of species. This complex of species diversified at the end of Pleistocene in Iberian Peninsula probably after the colonization of A. ramblae from Morocco. One of the resultant species (A. brunneus) at some point of the diversification acquired the ability to resist colder temperatures and was able to disperse to colder climates. To understand range variability from another perspective we used population proteomics to analyse the response of several populations for A. ramblae and A. bruneus facing temperatures that they might experience on field. We decided to analyse the variability at several levels in two populations of (A. ramblae) when working with natural populations obtaining satisfactory results for the reproducibility of our experimental methodology. When we analysed globally two populations for each species (one from Morocco and one from Iberian peninsula for each) we saw that the diversification observed in the phylogeny was encompassed with changes at the proteomic response. The more common proteins identified belong to energetic metabolism and stress proteins. The latter were detected to express differentially between the two species studied, showing a different response to thermal stress. This work address the possibility of employing population proteomics in natural populations of non-model species and being able of recovering the stress response facing an environmental factor like temperature. We show as well that differences in range size can be encompassing with the acquisition of capacity to face thermal stress.Esta tesis parte del estudio de un grupo de especies de escarabajos acuáticos (Agabus brunneus complex) que poseen diferencias importantes en el tamaño de sus rangos geográficos, contando con una especie insular (A. rufulus), una continental de rango restringido (A. ramblae) y una continental de rango amplio (A. brunneus) para estudiar los factores implicados en esas diferencias. Este complejo de especies diversificó a finales del Pleistoceno en la península ibérica posiblemente tras la colonización de A. ramblae desde Marruecos. Una de las especies resultantes A. brunneus en algún momento de la diversificación desarrolló la capacidad de resistencia a bajas temperaturas lo que le facilitó el poder extender su rango hacia climas más fríos. Se empleó la proteómica de poblaciones para analizar la respuesta de varias poblaciones de A. brunneus y A. ramblae frente a temperaturas que pueden experimentar en la naturaleza. Al estudiar la variabilidad a distintos niveles entre dos poblaciones naturales de A. ramblae obtuvimos una buena reproducibilidad de nuestros experimentos. Al analizar de forma global dos poblaciones para cada especie (Marruecos y península ibérica para ambas) descubrimos que la diversificación de la filogenia ha ido acompañada de cambios en la respuesta a nivel de expresión proteínica. La mayoría de las proteínas identificadas están relacionadas con el metabolismo energético y con proteínas del estrés, estas últimas se expresan diferencialmente entre las dos especies analizadas, indicando una diferente respuesta al estrés térmico. El presente trabajo abre la posibilidad de realizar este tipo de experimentos empleando poblaciones naturales de especies no modelo y demuestra que la respuesta frente al estrés de un factor ambiental, en este caso la temperatura, puede recuperarse empleando para ello la proteómica. Así mismo las diferencias en el tamaño del rango pueden ir acompañadas de la adquisición de distinta capacidad de respuesta frente al estrés térmico.
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Guibourd, de Luzinais Vianney. "L'impact des vagues de chaleurs marines sur le fonctionnement des écosystèmes de l'océan à l'échelle mondiale". Electronic Thesis or Diss., Rennes, Agrocampus Ouest, 2024. http://www.theses.fr/2024NSARH121.
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Le changement climatique affecte de plus en plus la vie marine. Les vagues de chaleur marines (MHWs), liées au réchauffement, devraient augmenter en durée, intensité et fréquence, amplifiant leurs impacts sur les écosystèmes marins au 21e siècle. Cette thèse explore les effets du changement climatique et des MHWs sur les flux de biomasse dans les réseaux trophiques marins et leurs conséquences sur la structure et le fonctionnement des écosystèmes. J’ai développé EcoTroph-Dyn, une version dynamique du modèle EcoTroph, représentant le fonctionnement des écosystèmes marins comme un flux de biomasse continu, des producteurs primaires aux prédateurs supérieurs. Basé sur une approche virtuelle d’EcoTroph-Dyn, j'ai mis en évidence que, les MHWs pourraient avoir impacté les flux de biomasse par la perturbation de la cinétique, de l'efficacité de transfert et induire des pertes de biomasse. Ensuite, en utilisant EcoTroph-Dyn, j’ai reconstitué les biomasses des consommateurs marins de 1998 à 2021 en intégrant les variations de température et de production primaire.La biomasse animale marine, estimée à chaque niveau trophique sur une grille mondiale de 1° x 1°, révèle des pertes significatives dues aux MHWs, avec des impacts accentués aux niveaux trophiques supérieurs. Enfin, les projections de la biomasse animale des océans de 1950 à 2100 indiquent que les altérations des flux de biomasse due aux MHWs pourrait entraîner une diminution globale supplémentaire de la biomasse des consommateurs proportionnelle au réchauffement des océans, avec des impacts plus prononcés que ceux dû au changement climatique de fond. Cette thèse démontre que le changement climatique et les MHWs perturbent conjointement les flux de biomasse, réduisant la biomasse océanique future avec des répercussions majeures sur les pêcheriesIntensifying climate change is increasingly affecting marine life in the world's oceans. Extreme events like marine heatwaves (MHWs), associated with climate change, are projected to grow in duration, intensity, and frequency, further impacting marine ecosystems throughout the 21st century. In this dissertation, I investigated the effects of climate change and MHWs on biomass flows in marine food webs and their consequences on ecosystem structure and functioning. I developed a dynamic version of the EcoTroph model, named EcoTroph-Dyn, which represents the functioning of marine ecosystems as a single flow of biomass from primary producers to top predators. To study MHW effects using EcoTroph-Dyn, I estimated MHW-induced mortality from 1982 to 2021 based on the thermal preferences of various taxa. The results reveal that MHWs may have impacted biomass flow through the perturbation of the kinetics of biomassflow and transfer efficiency and caused biomass loss through instantaneous mortality. Secondly, using EcoTroph-Dyn, I hindcasted consumer biomass in marine food webs from 1998 to 2021. By integrating changes in temperature and primary production, marine animal biomass was estimated at each trophic level on a 1° x 1° grid of the global ocean. Findings show significant biomass loss due to MHWs, with more pronounced impacts at higher trophic levels. Finally, projections from 1950 to 2100 indicate that MHW-induced changes in biomass flows could drive a global consumer biomass decline, surpassing the impacts of background climate change. Overall, this dissertation demonstrates that climate change and MHWs jointly disrupt biomass flows in marine ecosystems, leading to reduced future ocean animal biomass with direct repercussions on fisheries
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Turschwell, Mischa Peter. "Thermal and Habitat Characteristics of a Headwater Fish Species: Predicting Population Success Under Climate Change". Thesis, Griffith University, 2017. http://hdl.handle.net/10072/367629.
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Streams are becoming increasingly fragmented by anthropogenic impacts related to altered thermal and hydrological regimes, dispersal barriers, land-use, introductions of non-native fish, habitat degradation, and altered disturbance regimes. Furthermore, relatively little is known about the ecology and spatio-temporal dynamics of a large proportion of freshwater fish populations and assemblages, making their conservation challenging. The general goal of my research was to improve ecological understanding of the drivers of fish distribution in upland streams, using the threatened Northern river blackfish (Gadopsis marmoratus - hereinafter blackfish) in the upper Condamine River and Spring Creek tributaries in Queensland, as a case study. While blackfish are still widespread throughout the Murray Darling Basin, anecdotal evidence suggests that historically, they were widely distributed throughout the entire upper catchment of the
Condamine River, extending into the lowlands. In addition, results from contemporary research suggests that these fish may now be restricted to headwaters and tributaries. The aim of my research was to identify the variables that influence blackfish distribution in this upland system. More specifically, I tested the hypothesis that these fish are thermally restricted to their current habitat range. I asked whether there are different processes governing their occurrence versus abundance, and whether these vary between life-stages. In addition to examining static population structure I also examined the environmental determinants of juvenile recruitment in this system, and examined the spatial scales at which these take place.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Lin, Sen. "Evaluation of HMA fracture mechanics-based thermal cracking model". Thesis, KTH, Transportvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-50945.
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Low temperature cracking is an important form of asphalt pavement deterioration in cold regions. The cracks develop when thermally induced stresses exceed the fracture resistance of the asphalt pavement. In this study, by incorporating HMA fracture mechanics into thermal cracking model, a new integrated model is introduced to investigate low temperature cracking performance. To evaluate its reliability and accuracy, the predicted thermally induced stress and failure temperature are compared with the fracture stress and fracture temperature obtained from thermal stress restrained specimen test. The findings indicate that this HMA fracture mechanics-based thermal cracking model has a great potential to reliably evaluate the performance of asphalt mixtures subjected to thermally induced damage.
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Parker, Donald Scott. "Fracture and residual-stress characterization of tungsten-carbide 17%-cobalt thermal-spray coatings applied to high-strength steel fatigue specimens". [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000763.
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Qadir, Adnan. "Investigation Of Low Temperature Cracking In Asphalt Concrete Pavement". Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612696/index.pdf.
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In this study, low temperature cracking of asphalt concrete is investigated based on a laboratory experimental program including the design variables of aggregate type, gradation, asphalt content, binder grading, binder modification, and the experimental variables of cooling rate, and specimen size. The design of experiment is proposed according to the fractional factorial design principles to reduce the required number of test specimens. Mix designs are performed according to the Superpave mix design guidelines using materials obtained from the Turkish General Directorate of High-ways. In the course of this study, a test setup for thermal stress restrained specimen test for asphalt concrete is developed and used successfully to test a number of as-phalt concrete beam specimens. The same setup is also used for measuring the glass transition temperatures to obtain various thermo-volumetric properties of mixtures. Statistical methods are used to identify the effect of experimental variables on frac-ture strength, fracture temperature and other dependent variables obtained from the testing program. Statistical models are also developed to predict the fracture strength, fracture temperature and other thermo-volumetric properties of mixtures. Results of analyses show that aggregate type, binder modification, and asphalt content significantly affect both the fracture strength and fracture temperature of asphalt concrete. While the glass transition temperature is affected by only aggregate type, coefficients of contraction before and after the glass transition temperature are not influenced by any of the experimental variables. The results of this study provide an important basis to prevent low temperature cracking in asphalt concrete pavements.
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Nassar, Saif. "Evaluation of the Ohio CTE Device for Low Temperature Characterization of Hot Mix Asphalt". University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1597158023589419.
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Oliveira, Ronald Fred Alves de. "Proposta de Complementação do Método de Avaliação da Exposição Ocupacional ao Calor: estudo de caso da atividade de manutenção de linhas energizadas". Universidade Federal da Paraíba, 2009. http://tede.biblioteca.ufpb.br:8080/handle/tede/5229.
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This thesis had the objective of proposing a complementation, with proactive character, to method and procedures of evaluation concerning occupational exposure to heat predicted in the norms NR-15/1978 and NHO 06/2002, respectively. The electricians of the maintenance team of energized lines at potential, in tension of 69 kV, from Companhia Energética de Alagoas (CEAL) composed the group of workers monitored. The main objective was achieved by measuring climate variables (dry bulb temperature, natural wet bulb temperature, globe temperature and air speed), calculating Wet Bulb Globe Temperature (WBGT), estimating personal variables (metabolism rate and thermal isolation of clothing being used at the time of work development), investigating weight loss rate caused by work accomplishment and evaluating through Norm ISO 7933/89. Besides measures, it was made a comparison between different norms (ISO 7243/89; ISO 7933/89; ISO 8996/90; ISO 7730/94; ISO 9920/95) and recommendations (ABHO/98) in order to fill any gaps still remaining in Brazilian norms that rule the subject. One of the main assumptions proved through the evaluations is related to the significant water loss the worker is submitted every working hour, when work accomplishment demands the use of special protective clothing. When water loss exceeds the limits specified in the Norm ISO 7933/89, it is reasonable to conclude that physiological consequences harmful to worker s health may occur. Considering that specific approach, Brazilian legal documents fail. From the working regimes specified in NR-15/1978, the one that admits the work may be performed continuously shows the most agreeable conditions in relation to insalubrity. In one of the working situations examined simply with the use of WBGT, the working regime defined was continuous. However, when based on Norm ISO 7933/89, that same working situation demands that work execution should be interrupted after approximately 30 (thirty) minutes from the beginning, as a way of limiting heat accumulation in the body. For the latter protection requirement may be considered by NR-15/1978, it is necessary that WBGT index moves from 26,7º C, value that defines the work is likely to be executed continuously, at least to 28,1º C, which is the low limit of the range that defines a pause after 30 (thirty) minutes from the very beginning of work execution. As the difference between the above-mentioned WBGT s is 1,4º C, this is the value that should be added to WBGT index acquired, as a way of compensating the effects produced by the clothing. Besides the pauses provided, another significant result of the evaluation according to Norm ISO 7933/89 is time limitation of exposure due to water loss. The maximum of a day s work for all the situations investigated was stipulated in 300 (three hundred) minutes (five hours). The results of the research should be understood as restricted to climate and personal conditions described in the present paper. Yet, they may serve as a demarcation in order to specify proper conditions of execution of labor activities in situations distinct from the ones examined.
Esta tese teve como objetivo propor uma complementação, com caráter proativo, ao método e aos procedimentos de avaliação da exposição ocupacional ao calor previstos nas normas NR-15/1978 e NHO 06/2002, respectivamente. A população escolhida para este estudo de caso foi aquela composta pelos eletricistas da turma de manutenção de linhas energizadas ao potencial, na tensão de 69 kV, da Companhia Energética de Alagoas (CEAL). O objetivo principal foi alcançado através das medidas das variáveis climáticas (temperatura de bulbo seco, de bulbo úmido natural, de globo e da velocidade do ar), do cálculo do Índice de Bulbo Úmido Termômetro de Globo (IBUTG), da estimativa das variáveis pessoais (taxa de metabolismo e isolamento térmico das vestes utilizadas quando do desenvolvimento das atividades), da apuração da taxa de perda de peso provocada pela realização das tarefas e da avaliação através da Norma ISO 7933/89. Além das medidas efetuadas, houve a confrontação de diferentes normas (ISO 7243/89; ISO 7933/89; ISO 8996/90; ISO 7730/94; ISO 9920/95) e recomendações (ABHO/98) relacionadas à matéria, de tal forma que as lacunas existentes nas normas brasileiras que regem o assunto pudessem ser preenchidas. Uma das principais constatações obtidas com as avaliações que integram esta pesquisa diz respeito à significativa perda hídrica por hora de trabalho a que pode ser submetido o organismo do trabalhador, quando a realização das tarefas exige a utilização de vestimentas especiais de proteção. Quando essa perda hídrica suplanta os limites especificados na Norma ISO 7933/89, é razoável concluir, com base nesta norma, que poderão ocorrer conseqüências fisiológicas danosas à saúde do trabalhador. Sobre essa abordagem específica os documentos legais brasileiros são omissos. Dos regimes de trabalho previstos pela NR-15/1978, o que reflete as condições mais amenas em relação à insalubridade é aquele que permite que as tarefas sejam executadas de forma contínua. Em uma das situações de trabalho avaliadas com a simples utilização do IBUTG, o regime de trabalho definido foi contínuo. No entanto, essa mesma situação de trabalho quando avaliada com base na Norma ISO 7933/89 exige que a execução das tarefas seja interrompida depois de transcorridos aproximadamente 30 minutos do seu início, como forma de limitar a acumulação de calor no organismo. Para que este último requisito de proteção seja contemplado pela NR-15/1978, há necessidade de que o IBUTG utilizado na avaliação avance de 26,7ºC, valor que define a possibilidade das tarefas serem realizadas de forma contínua, até, pelo menos, 28,1 ºC, que é o limite inferior da faixa que define a pausa depois de transcorridos 30 min (trinta minutos) do início da execução das tarefas. Como a diferença entre aqueles IBUTG s é de 1,4 ºC, este é o valor que deverá ser adicionado ao IBUTG lido/apurado, como forma de se compensar os efeitos provocados pelas vestes. Além de providenciar as pausas, outro resultado significativo da avaliação pela Norma ISO 7933/89 é a limitação do tempo de exposição em função da perda de água. A jornada máxima de trabalho, para todas as situações avaliadas, foi estipulada em 300 minutos (5 horas). Os resultados da pesquisa devem ser entendidos como restritos às condições climáticas e pessoais descritas no presente trabalho, podendo servir, no entanto, de balizamento para que se procure especificar condições adequadas de execução das atividades laborais em situações distintas daquelas avaliadas.
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Tran, Duc Thang. "Endommagement des enrobés bitumineux soumis à des cycles de gel / dégel". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSET011.
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Cette thèse s’inscrit dans le cadre d’une collaboration entre l’École Nationale des Travaux Publics de l’État (ENTPE) et l’entreprise EUROVIA au sein du projet national DVDC. Elle contribue aux travaux du sous-thème 1.5, sur les dégradations hivernales, du thème 1 du projet national sur les mécanismes de dégradation des chaussées. Elle s’intéresse à l’endommagement des enrobés bitumineux à l’eau et au gel. Une étude bibliographique sur l’endommagement des enrobés bitumineux à l’eau et au gel a d’abord été réalisée. Après cette étude, deux campagnes expérimentales ont été proposées puis réalisées : une campagne principale et une campagne complémentaire. La campagne complémentaire étudie les évolutions des éprouvettes cylindriques lors des phases de conditionnement avec la saturation en eau, les cycles de gel/dégel et le séchage des éprouvettes sous vide. La campagne principale étudie les effets de la saturation en eau, de cycles de gel/dégel (cycle Freezing/Thaw - FT), de cycles avec réchauffement (cycle Heating/Freezing-HF et cycle Heating /Cooling- HC) sur les matériaux bitumineux non-vieilli et vieilli, dans des domaines de comportement différents. Elle se concentre sur trois grands domaines de comportement : le comportement viscoélastique, le comportement à la fatigue et le couplage thermomécanique. Pour le comportement viscoélastique linéaire (VEL), les éprouvettes soumises à des conditionnements différents ont été étudiées à l’aide de l’essai de module complexe. Le comportement VEL du matériau étudié a été ensuite simulé à l’aide du modèle 2S2P1D (2 Springs, 2 Parabolic elements, 1 Dashpot) développé à l’ENTPE. Le comportement à la fatigue des enrobés bitumineux soumis à 50 cycles FT et à la saturation en eau a été étudié. L’essai de traction-compression en déformation à température contrôlée et à fréquence donnée a été utilisé. Les effets des cycles de gel/dégel et de l’eau ont été analysés en traçant des courbes de fatigue de Wöhler. Un modèle a été proposé pour décrire l’endommagement à la fatigue. Dans le domaine de comportement à basse température, les éprouvettes ont été étudiées à l’aide de l’essai de retrait thermique empêché (TSRST) et de l’essai de retrait thermique libre (TUST). Des analyses ont été réalisées sur la température, la contrainte et aussi la déformation radiale à la rupture. Les résultats obtenus montrent des effets non-significatifs des cycles de gel/dégel et de l’eau sur les enrobés bitumineux pour les domaines étudiés, surtout pour des sollicitations à faible déformation (moins de 120μdef) et à température positive. Cependant, l’effet de l’eau devient dominant et significatif à basse température, en particulier dans l’essai TSRST. Pour un conditionnement avec des cycles intégrant une période de réchauffement (type HF et HC, où la température atteint 50°C), un vieillissement du bitume a été mis en évidence à l’aide des courbes du module complexe normaliséThis PhD thesis is part of a collaboration between “l’École Nationale des Travaux Publics de l’État” (ENTPE) and the research center of Eurovia within the national project DVDC. PhD works contribute to the sub-theme 1.5 dealing with winter degradations included in Theme 1 of the national project, on the mechanisms of pavement degradation. PhD thesis studies damages in bituminous mixtures, which might be caused by water and freeze/thaw cycles. A literature review on the effect of water and frost on bituminous mixtures was carried out as a first part of the thesis. After the literature review, two experimental campaigns were proposed and realized: a main campaign and a complementary campaign. The main campaign studies the effects of water saturation, freezing/thaw cycles (FT), thermal cycles with heating (Heating/Freezing-HF cycle and Heating/Cooling- HC cycle) on non-aged and aged bituminous mixtures. It focuses on three main behaviours of bituminous mixture : viscoelastic behaviour, fatigue behaviour and thermomechanical coupling. In the domain of linear viscoelastic behaviour (VEL), the complex module test was performed on a bituminous mixture subjected to different conditions : water conditioning, FT cycles, HF cycles or HC cycles. The VEL behaviour of the tested material was then modeled using the 2S2P1D model (2 Springs, 2 Parabolic elements, 1 Dashpot) developed at ENTPE. The fatigue behaviour of bituminous mixture subjected to 50 FT cycles and water saturation was studied. Sinusoidal loading in controlled axial strain mode was applied at 10 Hz and 10°C. The effects of water saturation and FT conditioning were then analyzed by using the Wöhler fatigue curves. A model was used to simulate the damage evolution. In the low temperature behaviour domain, the specimens were studied by using the Thermal Stress Restrained Specimen Test (TSRST) and Thermal Unstressed Specimen Test (TUST). The temperature, the stress and the radial strain at failure were analyzed to investigate the conditioning effects. The results show a non-significant effect of the FT cycles and water conditioning on the bituminous mixture behaviour, for small strain loading (less than 120μdef) and at positive testing temperature. However, the effect of water conditioning becomes dominant and significant at low temperatures, especially in the TSRST. For the non-aged material conditioned with HF and HC cycles, the aging of the bitumen was observed by using the normalized curves of complex modulus
Livros sobre o assunto "Species thermal stress"
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Johnson, W. S. Stress analysis of the cracked lap shear specimen: An ASTM round robin. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1986.
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Crews, John H. Factors influencing elastic stresses in double cantilever beam specimens. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1987.
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Sheppard, Charles R. C., Simon K. Davy, Graham M. Pilling e Nicholas A. J. Graham. Symbiotic interactions. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198787341.003.0004.
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Symbiosis, where different species live together for prolonged periods, is ubiquitous and extremely important on coral reefs. The most important symbiosis is between corals and the microalgae (zooxanthellae) that live in their cells, without which coral reefs would not exist. This chapter focuses on the diversity of zooxanthellae, the linkage with coral calcification and the nutrition of the symbiosis, particularly the supply of photosynthetically fixed carbon to coral, and the conservation and recycling of essential nutrients (especially nitrogen and phosphorus) by this symbiosis. The acquisition and breakdown of the symbiosis, particularly under thermal stress (i.e. coral bleaching), is described. Other important coral–microbe symbioses involve cyanobacteria, heterotrophic bacteria, viruses, protozoans and endolithic algae and fungi that live in the coral skeleton. Symbioses between sponges and bacteria or algae are also important, as are the iconic associations between fish and various invertebrates (e.g. the sea anemone–anemonefish symbiosis) or other fish species.
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Influence of supporting conditions on stress intensity factors for single-edge-cracked specimens under bending. Washington, DC: National Aeronautics and Space Administration, 1987.
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Kanerva, Hannele K. Prediction of low temperature cracking of asphalt concrete mixtures with thermal stress restrained specimen test results. 1993.
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Inelastic strain analysis of solder joint in NASA fatigue specimen: Final report. College Park, MD: University of Maryland, 1991.
Encontre o texto completo da fonteCapítulos de livros sobre o assunto "Species thermal stress"
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Häkkinen, Henry, Silviu O. Petrovan, Nigel G. Taylor, William J. Sutherland e Nathalie Pettorelli. "7. Skuas (Stercorariidae)". In Seabirds in the North-East Atlantic, 164–79. Cambridge, UK: Open Book Publishers, 2023. http://dx.doi.org/10.11647/obp.0343.07.
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With key information linked to thematic maps, this section evaluates the climate change vulnerability of three skuas (Stercorariidae) species – Great Skua, Long-tailed Jaeger, and Arctic Jaeger – in the North-East Atlantic. The assessments for every species cover three categories each: the exposure, or the magnitude in percentage and the characteristics of climate change; the sensitivity, or how much and by which climatic events the species are affected, depending on their biological features; the adaptive capacity, or the potential of species to respond to climate change. Assessments of local conservation actions against climate change impacts are listed here in readily consultable tables. Interventions are evaluated by evidence of effectiveness and grouped by types of impacts on skuas: increased avian predation, thermal stress, competition due to mortality, and reduced prey availability. Criteria of relevance, strength, and transparency measure the effectiveness of the actions.
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Häkkinen, Henry, Silviu O. Petrovan, Nigel G. Taylor, William J. Sutherland e Nathalie Pettorelli. "1. Auks (Alcidae)". In Seabirds in the North-East Atlantic, 18–47. Cambridge, UK: Open Book Publishers, 2023. http://dx.doi.org/10.11647/obp.0343.01.
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With key information linked to thematic maps, this section evaluates the climate change vulnerability of six auks (Alcidae) species – Razorbill, Little Auk, Black Guillemot, Atlantic Puffin, Common Murre, and Thick-billed Murre – in the North-East Atlantic. The assessments for every species cover three categories each: the exposure, or the magnitude in percentage and the characteristics of climate change; the sensitivity, or how much and by which climatic events the species are affected, depending on their biological features; the adaptive capacity, or the potential of species to respond to climate change. Assessments of local conservation actions against climate change impacts are listed here in readily consultable tables. Interventions are evaluated by evidence of effectiveness and grouped by types of impacts on auks: mammal predation, storms causing foraging difficulty and mortality, thermal stress, and reduced prey availability. Criteria of relevance, strength, and transparency measure the actions’ effectiveness.
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Srivastava, Hari M. "Special Functions". In Encyclopedia of Thermal Stresses, 4519–29. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-007-2739-7_30.
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Suhir, Ephraim. "Analysis of a Prestressed Bi-Material Accelerated-Life-Test (ALT) Specimen". In Encyclopedia of Thermal Stresses, 112–22. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-007-2739-7_1010.
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Pei, Eujin, e Israt Kabir. "Development of FGM and FGAM". In A Guide to Additive Manufacturing, 307–19. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-05863-9_8.
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AbstractFGM is a special class of composite material that was first developed in Japan around 1984 for the propulsion system and airframe of space planes. The challenge was to create a thermal barrier that would be capable of withstanding a temperature of 1000 °C over a cross-section of 10 mm. A sharp interface between the matrix and the reinforcement in a traditional composite material would cause cracking in high temperatures. The cracks occur due to the generation of interfacial stress induced by the mismatch of thermal expansion between two different materials.
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Ranglack, Dustin H., Glenn E. Plumb e Luke R. Rogers. "American Bison (Bison bison): A Rangeland Wildlife Continuum". In Rangeland Wildlife Ecology and Conservation, 791–827. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-34037-6_23.
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AbstractAmerican bison (Bison bison) are the largest extant land animal in North America and have an important history and contemporary role in modern conservation. Bison historically had the widest continental distribution of all native ungulates but now only function as wildlife under natural selection on < 1.2% of the original range. Bison as rangeland wildlife occur on an array of exclusive and overlapping governance jurisdictions (e.g., Federal, State, Provincial, County, and Tribes and First Nations), private not-for-profit conservation lands enterprises, zoo and education enterprises, and for-profit commodity production. The historical and prevailing relationships within and between these higher order sectors are very complex and often conflicting, yet each sector has invested tremendous effort and public and private resources to increase the total abundance of bison to present levels. Despite long-term public investment in wild bison conservation, the private sector has far out-stripped wild bison, resulting in a potentially divergent evolution trajectory towards species domestication. The primary ecosystem function of plains bison on rangelands is contributing to plant community heterogeneity through patchily distributed grazing events that create mosaics of grazing pressure. Additionally, bison exhibit a myriad of other roles in their environment through direct and indirect interactions. Perhaps more than with other rangeland wildlife species, genetics play an outsized role in current bison population management given historical bottlenecks and intentional cross breeding of bison and cattle. However, moving forward the interplay between population size, isolation, and genetic diversity is more important. Along the continuum of bison management there exist a wide variety of rangeland management techniques. However, as a wildlife species, the rangeland management practices associated with bison have generally focused on disturbance ecology with a more recent push to understand the impacts of bison grazing at scale. The question of scale is important given that every bison is behind a barrier, thus restricting their impacts on rangeland ecology and processes. Bison and cattle are considered by many to be potential competitors, due to large overlaps in diet and body size, and much research has focused on the ecological equivalence of the two species. While this is still not without controversy, bison and cattle are not incompatible when properly managed. Chronic infection of wild bison populations with diseases that can be transmitted to livestock and humans is an important factor affecting potential recovery of bison outside existing reserve boundaries. Climate change may represent the next major challenge to bison, as it is expected to directly affect bison through decreased forage and water availability and increased thermal stress. These threats, combined with the differences in bison management practices between sectors have led some to classify bison as moderately vulnerable to climate change, recommending the creation of a ‘bison coalition’ that could seek climate change adaptation solutions through shared stewardship. While much of the continental historical range is no longer available for bison restoration, there are exciting conservation opportunities that are finding voice through the vision of “Shared Stewardship” that embraces innovative collaboration to work together across jurisdictions and sectors to successfully address the scale, complexity, and ecological and cultural significance of wild bison.
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Crisp, D. T. "Thermal “Resetting” of Streams by Reservoir Releases with Special Reference to Effects on Salmonid Fishes". In Regulated Streams, 163–82. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4684-5392-8_11.
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Abendroth, Martin, Shahin Takht Firouzeh, Meinhard Kuna e Bjoern Kiefer. "Determination of the Temperature-Dependent Fracture and Damage Properties of Ceramic Filter Materials from Small Scale Specimens". In Multifunctional Ceramic Filter Systems for Metal Melt Filtration, 577–603. Cham: Springer International Publishing, 2024. http://dx.doi.org/10.1007/978-3-031-40930-1_23.
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AbstractOpen cell ceramic foam filters are used to improve the quality of metallic cast products. They play a major role on reducing the number of inclusions within the microstructure of the cast product and restraining the liquid flow inside the mold. The newly developed carbon-bonded alumina ceramics are investigated considering the mechanical and thermal loads of the filtration process. The aim of this project is to assess the strength, the fracture mechanical behavior, and the damage properties of the filter material. Since the tiny struts of the foam have different properties than the common bulk material specimen, small specimens of millimeter size are needed. Within this work, a combination of experiments and numerical simulations are conducted for various mechanical tests at temperatures up to 1500 $${}^{\circ }\text {C}$$ ∘ C . The first test is the small punch test (SPT), where a small disk-like specimen is supported on a circular die and loaded with a spherical tipped punch until failure of the disk occurs. The small punch fracture stress is obtained from the experiments, as well as the corresponding parameters of the Weibull distribution necessary for the evaluation of the cold modulus of rupture (CMOR). Furthermore, a modified version of the SPT, the so called ball on three ball test (B3B), is carried out. In the B3B test, miniaturized disk-shaped specimens are supported with three spherical balls and loaded with a spherical tipped punch until failure. Hereby, the fracture mechanical parameters, such as the fracture toughness, are identified with the help of numerical simulations. Moreover, the Chevron notched beam test (CNB) is used to determine the fracture toughness of the ceramics. The final test is the Brazilian disc test (BDT), where compressive loads are exerted on the specimen leading to tensile stresses along the specimen diameter, perpendicular to the applied load direction. This test is employed to determine the Young’s modulus, the yield stress and the fracture toughness. In general the simplicity of all these tests, their setup, application, and results evaluation, in addition to the ease of specimens production, make them very attractive. The size of these specimens is about one order of magnitude smaller than that of common standard tests. The accompanying numerical simulations are inevitable to extract from the measurements the wanted mechanical properties.
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Ramteke, A. L., F. Meyer-Olbersleben e F. Rézai-Aria. "Three Dimensional Thermal Strain and Stress Analysis of Single Edge Wedge Specimens". In Low Cycle Fatigue and Elasto-Plastic Behaviour of Materials—3, 281–86. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2860-5_46.
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van Santen, Victor M., Hussam Amrouch, Thomas Wild, Jörg Henkel e Andreas Herkersdorf. "Thermal Management and Communication Virtualization for Reliability Optimization in MPSoCs". In Dependable Embedded Systems, 181–205. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-52017-5_8.
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AbstractThis chapter covers the interdependencies of temperature and the reliable operation of multiprocessor systems on chip (MPSoC). Starting with the assessment of temperature values for the different cores either through measurement or estimation, it is shown which methods on system level can be applied to balance the thermal stress in the system and thus to come to an evenly distributed probability of errors. Special focus is given to task migration as a system-level means, which is supported by an on-chip interconnect virtualization technique that eases fast and transparent switch-over of communication channels. Overall, it is shown how mechanisms on different levels of the system stack can be combined to cooperate across layers for improving system reliability.
Trabalhos de conferências sobre o assunto "Species thermal stress"
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Wu, Bei, Ronghui Ma, Hui Zhang, Michael Dudley, Raoul Schlesser e Zlatko Sitar. "Growth Kinetics and Thermal Stress in AlN Bulk Crystal Growth". In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33700.
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Group III nitrides, such as GaN, AlN and InGaN, have attracted a lot of attention due to the development of blue-green and ultraviolet light emitting diodes (LEDs) and lasers. In this paper, an integrated model has developed based on the conservation of momentum, mass, chemical species and energy together with necessary boundary conditions that account for heterogeneous chemical reactions both at the source and seed surfaces. The simulation results have been compared with temperature measurements for different power levels and flow rates in a reactor specially designed for nitride crystal growth at NCSU. It is evident that the heat power level affects the entire temperature distribution greatly while the flow rate has minor effect on the temperature distribution. The results also show that the overall thermal stress level is higher than the critical resolved shear stress, which means thermal elastic stress can be a major source of dislocation density in the as-grown crystal. The stress level is strongly dependent on the temperature gradient in the as-grown crystal. Results are correlated well with defects showing in an X-ray topograph for the AlN wafer.
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Zhu, Zhenjin, Steven Cooper e Brian Cooper. "Modeling of Thermal Cycling on Initiation of Stress Corrosion Cracking". In 2024 15th International Pipeline Conference. American Society of Mechanical Engineers, 2024. https://doi.org/10.1115/ipc2024-130933.
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Abstract This paper develops a theoretical model to investigate the impact of thermal cycling on the initiation of stress corrosion cracking (SCC). Prior to commissioning, coatings may be disbonded in places due to poor material selection or application. Corrosive gases (i.e., O2, CO2) and water vapor diffuse into coating disbondment areas from the soil side. The diffused amount of each species is governed by Fick’s First Law. The accumulation of condensed water vapor depends on the solubility change of water vapor with respect to thermal cycling frequency and magnitude. The concentrations of [H+], [HCO3−], and [CO32−] are dependent on CO2 partial pressure. The metal surface potential is predicted using a resistance circuit model. When an open coating holiday occurs, the cathodic protection (CP) current arrives at the metal surface directly through the exposed electrolyte. The local surface potentials inside the crevice are simulated using a parametric equation. The pH value at an open holiday obeys Faraday’s Second Law of Electrolysis. Local tensile stress may come from hoop stress from design, residual stress from manufacturing and fabrication, thermal stress from operation, geotechnical stress from soil movement, and mechanical stress from deformation. When the pH value, surface potential, and tensile stress are within certain bounds, stress corrosion cracking may take place longitudinally or circumferentially depending on stress orientation. Types of SCC such as high-pH SCC or near-neutral pH SCC can be characterized. The findings should be useful for stakeholders in proactively developing preventive and mitigative measures for effective SCC threat management.
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Osman, Sameer, e Mahmoud Ahmed. "Mass Transport and Thermal Stresses Evaluation of Micro Solid-Oxide Fuel Cells: A Numerical Study". In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-72922.
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Abstract Solid-oxide fuel cell (SOFC) are among the highest types of fuel cells in terms of efficiency, reaching as high as 65%. However, poor mechanical robustness and thermal cycling stability are the major disadvantages of these fuel cells due to high thermal stresses between layers. A new concept of a micro-monolithic ceramic cell was previously introduced that had extremely high power-densities (> 10 W/cm3) as well as high mechanical robustness and thermal cycling stability. In this study, a 3D comprehensive theoretical model is presented for ceramic fuel cells, which includes species, charge, momentum, and energy transport. Moreover, the bilinear elastoplastic material model is used to estimate thermal stresses in ceramics at high temperatures. This model is then used to simulate two new geometries for the cell and anode flow channels. Results indicate that circular anode channels are best in terms of thermal stresses, while being inferior in terms of electrochemical performance. A hexagonal cell with trapezoidal flow channels yielded the highest volumetric power density with an increase of 15% compared to the plain circular arrangement. On the other hand, circular sector flow channel increased the power density by only 9%. The increased current of the cell with the circular sectors and trapezoidal sections is due to the more efficient distribution of flow channel area such that the travel path for hydrogen gas is less restricted in terms of diffusion. As for the thermal stress, the newly introduced configurations increased the values of stress by 64% for the circular sector channels, compared to only 16% for the trapezoidal flow channels. This study is meant as an initial step in the optimization process for the microtubular SOFC with high volumetric power density, creating an opportunity for performance enhancement of this type of fuel cell.
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Fan, Pengfei, Xiongwen Zhang e Guojun Li. "Numerical Study on Electric Characteristics and Thermal Stresses of Solid Oxide Fuel Cells". In ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology collocated with the ASME 2012 6th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/fuelcell2012-91121.
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A generalized, three-dimensional (3D) mathematical model of solid oxide fuel cells (SOFCs) for various geometries is constructed in this paper. A finite-volume method is applied to calculate the electric characteristics, which is based on the fundamental conservation law of mass, energy and electrical charge. The electrical potential distribution, the current density distribution, the concentrations distribution of the chemical species and the temperature profile are calculated by solving the governing equations of a single-unit model with double channels of co-flow and counter-flow pattern using the commercial computational fluid dynamic software Fluent. The internal steam reforming and the water shift reactions are taken into account in the mathematical model. The Knudsen diffusion is considered for computation of the gases diffusion in the porous electrodes and the concentration overpotential. The Butler-Volmer equation and the function of the reaction gases composition for the exchange density are used in the model to analyze the activation overpotential. Numerical simulations are performed for a planar geometry solid oxide fuel cell and the detailed features of the temperature, the electrical potential distribution and the gases composition are illustrated. The simulation results agree well with the Benchmark results for planar configuration. With the simulated temperature profile in the planar SOFC, the finite-element method is employed to calculate the thermal stress distribution in the planar solid oxide fuel cell. A 3D finite-element model consists of positive electrode-electrolyte-negative electrode (PEN) and interconnects assembly is constructed by using commercial finite-element code Abaqus. The effects of temperature profile, electrodes and electrolyte thickness, and coefficients of thermal expansion (CTE) mismatch between components are characterized. The calculated results indicate that the maximum stress appears on the electrode and electrolyte interface. The value and distribution of the thermal stress are the functions of the applied materials CTE, applied temperature profiles and the thicknesses of electrode and electrolyte. The calculated results can be applied as the guide for the SOFC materials selection and the SOFC structure design.
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Kawamura, M., H. Okado e K. Suzuki. "Effect of Interface Roughness on Internal Stress of Ceramic Thermal Barrier Coating". In ITSC2004, editado por Basil R. Marple e Christian Moreau. ASM International, 2004. http://dx.doi.org/10.31399/asm.cp.itsc2004p1082.
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Abstract An investigation was carried out into the effect of the interface roughness between the metallic bond coat and the ceramic topcoat on internal stresses in a thermal sprayed ceramic thermal barrier coating (TBC). To evaluate the effect of the interface roughness on the residual stress in the top coat, the specimens with two kinds of bondcoat roughness (rough type and smooth type) were prepared. The in-plane stresses of the specimens were measured with laboratory X-rays. The in-plane stresses for the both of the rough and smooth specimens were about 60MPa and independent of the roughness of the bond coat. Using high energy X-ray, the stress of the rough specimen was compressive and the stress of smooth specimen was tensile. This tendency is different from the result measured by laboratory X-ray. This difference in the stress value is coursed by the out-of-plane stress. Theses stresses in the topcoat were estimated by the hybrid method, that is to estimate out-of-plane stress using laboratory X-rays and high-energy synchrotron X-rays. As a result, the larger the roughness of the bond coat became the larger out-of-plane-stress become.
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Moravcova, Vendula, Jana Moravcova, Petra Kosova e Jiri Slama. "GREEN INFRASTRUCTURE IN URBAN PLANNING IN THE CZECH REPUBLIC". In 22nd SGEM International Multidisciplinary Scientific GeoConference 2022. STEF92 Technology, 2022. http://dx.doi.org/10.5593/sgem2022v/6.2/s27.70.
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The inclusion of greenery in spatial planning has an irreplaceable function. Not only do these areas fulfill an aesthetic function in otherwise monotonous areas of villages and towns, but they also significantly affect the quality of life of local citizens. These are primarily areas that provide a space for people to meet in a pleasant green environment and, thus, an opportunity to relax and recharge their batteries as a result of the positive effect of greenery on the human psyche. At the same time, green areas supplemented by water features provide the necessary shade and a more pleasant climate on hot summer days, when city centers tend to be hot and expose citizens to excessive temperatures and high thermal stress. For this reason, studies on thermal comfort analyses are still being carried out, especially in large cities, to determine the impact of green spaces and accompanying water features on thermal comfort and the health and psyche of residents. In addition to the role of greenery itself on public life in communities and its aesthetic function, blue-green infrastructure has a significant impact on the enrichment of local biodiversity, serving as an interactive element with the surrounding nature and thus providing a refuge for various species, from insects to songbirds and small mammals.
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Domae, Masafumi, Kosho Hojo e Wataru Sugino. "Water Chemistry Technology of Methanol Addition in PWR Primary Systems: Radiolysis of Methanol Solution at 320 °C". In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-30954.
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Primary Water Stress Corrosion Cracking (PWSCC) is one of important ageing issues in PWR (Pressurized Water Reactor) primary systems. It has been pointed out that high concentration dissolved hydrogen may lead to occurrence of PWSCC. The authors have proposed to substitute hydrogen by methanol as a fundamental countermeasure of PWSCC. So far corrosion tests of stainless steels and Zircaloy-4 in methanol solutions at 320 °C were conducted under γ-ray irradiation and without irradiation. The test results show that methanol is promising. In the present paper, γ-ray irradiation experiments of methanol solution at 320 °C were done up to 100 kGy. A study on the radiolysis of methanol solution is important from two aspects. One concerns corrosion of structural materials. The radiolysis of methanol may result in formation of harmful compounds to the structural materials, such as carboxylic acids. It is necessary to know the yields of such compounds. The other concern is possible polymerization of methanol and formation of organic polymer deposit on fuel claddings. Large amount of the deposit on fuel claddings should be avoided to keep integrity of fuel claddings. Therefore, it should be clarified whether gaseous species are major products and whether polymerized species of methanol such as ethylene glycol is formed. After the γ-ray irradiation of methanol solution, following species were analyzed: CO2 and H2, methanol, formaldehyde, formate and acetate, and ethylene glycol and glycerin. Without γ-ray irradiation, the major process of the thermal decomposition of methanol at 320 °C is oxidation of methanol by water and generation of one CO2 molecule and three H2 molecules. Under γ-ray irradiation, the decomposition of methanol is accelerated; little methanol remains after 10 kGy irradiation. The major product is CO2, and polymerization of methanol unlikely occurs. After methanol is completely decomposed, the hydrogen yield still increases. The reducing environment is maintained. Probably, transient organic species play important roles. The addition of low concentration methanol may be sufficient to maintain reducing environment of the PWR primary systems.
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Tuncer, Onur. "Cavity Flame Holding for High Speed Reacting Flows". In ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-25081.
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Combustion phenomena in a ramjet combustor with cavity flame-holder is studied numerically. Combustor follows a constant area isolator and comprises of hydrogen fuel injected sonically upstream of the cavity. Secondary fuel injection is performed at the cavity backwall. A diverging section follows the cavity to prevent thermal choking. These concepts are also utilized in practice. Calculations were performed for an entrance Mach number of 1.4. Stagnation temperature is 702 K, corresponding to a flight Mach number of 3.3 at an altitude of 12.5 km. Detailed chemical kinetics are taken into account with a reaction mechanism comprising of 9 species and 25 reaction steps. Turbulence is modeled using Menter’s k–ω shear stress transport model, which is appropriate for high speed internal flows. It is observed that flame anchors at the leading edge of the cavity, and the flame is stabilized in the cavity mode rather than the jet-wake mode. Numerical simulation captures all the essential features of the reacting flowfield.
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Mirzaee-Sisan, Ali, Christopher E. Truman e David J. Smith. "Characterising Residual Stresses in Rectangular Beam Specimens Following Thermo-Mechanical Loading". In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93675.
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The neutron diffraction (ND) technique was used to characterise residual stress fields in thin rectangular beam specimens containing residual stresses induced thermo-mechanically by partial quenching. Two types of material were considered, type 316H stainless steel and A533B ferritic steel. The work was motivated by a need to investigate the influence of residual stress on the fracture behaviour of steels. During quenching, specimens experienced a severe temperature gradient which induced thermal stresses resulting in plastic strains and a subsequent residual stress field. An extensive finite element (FE) analysis was undertaken to predict the residual stress following thermo-mechanical loading. It was shown that partial quenching generated a considerable residual stress field in 316H stainless steel. However, the level of residual stresses in the A533B steel specimens was lower than that 316H stainless steel specimens. There was acceptable agreement between the finite element simulations and measurements with simulations generally predicting higher tensile residual stresses following partial quenching than those measured in the 316H stainless steel, and lower tensile residual stresses than those measured in the A533B ferritic steel.
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Kim, W. T., M. Y. Choi, J. H. Park e K. S. Kang. "Thermal stress analysis of a circular holed specimen". In SPIE Defense and Security Symposium, editado por Vladimir P. Vavilov e Douglas D. Burleigh. SPIE, 2008. http://dx.doi.org/10.1117/12.777986.
Texto completo da fonteRelatórios de organizações sobre o assunto "Species thermal stress"
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Rogers, Caroline. A synthesis of coral reef research at Buck Island Reef National Monument and Salt River Bay National Historical Park and Ecological Preserve, St. Croix, U.S. Virgin Islands: 1961 to 2022. National Park Service, setembro de 2022. http://dx.doi.org/10.36967/2294235.
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This synthesis focuses on the history of research on coral reefs within two U.S. National Park Service units in St. Croix, U.S. Virgin Islands: Buck Island Reef National Monument (from 1961 to 2022) and Salt River Bay National Historical Park and Ecological Preserve (from 1980 to 2022). Buck Island Reef National Monument (BUIS) is off the north shore of the island of St. Croix, in the U.S. Virgin Islands. Established in 1961 and expanded in 2001, it is under the jurisdiction of the National Park Service (NPS). Long-term monitoring programs maintained by the NPS and jointly by the University of the Virgin Islands (UVI) and the Virgin Islands Department of Planning and Natural Resources (VIDPNR) provide data on trends in living coral cover and specific coral species from 2000 and 2001, respectively. Disease, thermal stress (indicated by coral bleaching), and hurricanes reduced total coral cover periodically, but cover remained relatively stable from 2007 through the end of 2020. Salt River Bay National Historical Park and Ecological Preserve (SARI) is a national park on the north shore of the island of St. Croix, in the U.S. Virgin Islands. Established in 1992, it is co-managed by the NPS and the Government of the Virgin Islands. Long-term monitoring programs maintained by the NPS and by the UVI with the VIDPNR provide data on trends in living coral cover and individual coral species from 2011 and 2001, respectively. In spite of thermal stress (indicated by coral bleaching), disease, and hurricanes, total coral cover remained relatively stable through the end of 2020. This document also includes results from extensive investigations by the National Oceanic and Atmospheric Administration (NOAA) and from many individual projects including those based out of the underwater saturation habitats Hydrolab and Aquarius from 1977 to 1989, as well as studies from researchers at Fairleigh Dickinson University’s West Indies Laboratory. While not possible to review all of these in detail, this report highlights information considered useful to managers, and scientists planning future research. In 2021, a particularly virulent disease called stony coral tissue loss disease (SCTLD), first noted in 2014 in Florida, and then in 2019 in the U.S. Virgin Islands, started killing corals in BUIS and SARI with the different species showing a gradient of susceptibility. An exact cause or link between this disease and human actions has not been discovered to date. The losses associated with this disease have now exceeded those from any other stressors in these national parks.
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Gill. L51675 Effects of Weldment Property Variations on the Behavior of Line Pipe. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), janeiro de 1993. http://dx.doi.org/10.55274/r0010133.
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A steel weldment is a composite of zones or layers of different microstructures that possess different material properties. The zones include the base metal (or the sections of pipe), the weld metal, and a complex heat-affected zone (HAZ) of base metal that has been exposed to a variety of thermal cycles resulting in varying microstructures. The material properties of primary concern with respect to the mechanical behavior of the pipe are the stress-strain response (the constitutive properties) and the resistance to initiation and propagation of cracks or tears in the presence of a crack, notch, or other stress concentrator (the fracture toughness properties). Most of the experimental data on the behavior of welds with significant discontinuities were obtained from test specimens with surface or through-thickness notches or cracks. These data typically show an increase in load or nominal ductility for overmatched welds and a decrease in load or nominal ductility for undermatched welds. However, there are cases where the presence of a soft zone may enhance the nominal ductility and cases where overmatched welds will decrease the nominal ductility. The latter is especially likely in a girth weld with a circumferential crack in the HAZ.
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Miller, Gad, e Jeffrey F. Harper. Pollen fertility and the role of ROS and Ca signaling in heat stress tolerance. United States Department of Agriculture, janeiro de 2013. http://dx.doi.org/10.32747/2013.7598150.bard.
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The long-term goal of this research is to understand how pollen cope with stress, and identify genes that can be manipulated in crop plants to improve reproductive success during heat stress. The specific aims were to: 1) Compare heat stress dependent changes in gene expression between wild type pollen, and mutants in which pollen are heat sensitive (cngc16) or heat tolerant (apx2-1). 2) Compare cngc16 and apx2 mutants for differences in heat-stress triggered changes in ROS, cNMP, and Ca²⁺ transients. 3) Expand a mutant screen for pollen with increased or decreased thermo-tolerance. These aims were designed to provide novel and fundamental advances to our understanding of stress tolerance in pollen reproductive development, and enable research aimed at improving crop plants to be more productive under conditions of heat stress. Background: Each year crop yields are severely impacted by a variety of stress conditions, including heat, cold, drought, hypoxia, and salt. Reproductive development in flowering plants is highly sensitive to hot or cold temperatures, with even a single hot day or cold night sometimes being fatal to reproductive success. In many plants, pollen tube development and fertilization is often the weakest link. Current speculation about global climate change is that most agricultural regions will experience more extreme environmental fluctuations. With the human food supply largely dependent on seeds, it is critical that we consider ways to improve stress tolerance during fertilization. The heat stress response (HSR) has been intensively studied in vegetative tissues, but is poorly understood during reproductive development. A general paradigm is that HS is accompanied by increased production of reactive oxygen species (ROS) and induction of ROS-scavenging enzymes to protect cells from excess oxidative damage. The activation of the HSR has been linked to cytosolic Ca²⁺ signals, and transcriptional and translational responses, including the increased expression of heat shock proteins (HSPs) and antioxidative pathways. The focus of the proposed research was on two mutations, which have been discovered in a collaboration between the Harper and Miller labs, that either increase or decrease reproductive stress tolerance in a model plant, Arabidopsis thaliana (i.e., cngc16--cyclic nucleotide gated channel 16, apx2-1--ascorbate peroxidase 2,). Major conclusions, solutions, achievements. Using RNA-seq technology, the expression profiles of cngc16 and apx2 pollen grains were independently compared to wild type under favourable conditions and following HS. In comparison to a wild type HSR, there were 2,776 differences in the transcriptome response in cngc16 pollen, consistent with a model in which this heat-sensitive mutant fails to enact or maintain a normal wild-type HSR. In a comparison with apx2 pollen, there were 900 differences in the HSR. Some portion of these 900 differences might contribute to an improved HSR in apx2 pollen. Twenty-seven and 42 transcription factor changes, in cngc16 and apx2-1, respectively, were identified that could provide unique contributions to a pollen HSR. While we found that the functional HS-dependent reprogramming of the pollen transcriptome requires specific activity of CNGC16, we identified in apx2 specific activation of flavonol-biosynthesis pathway and auxin signalling that support a role in pollen thermotolerance. Results from this study have identified metabolic pathways and candidate genes of potential use in improving HS tolerance in pollen. Additionally, we developed new FACS-based methodology that can quantify the stress response for individual pollen in a high-throughput fashion. This technology is being adapted for biological screening of crop plant’s pollen to identify novel thermotolerance traits. Implications, both scientific and agricultural. This study has provided a reference data on the pollen HSR from a model plant, and supports a model that the HSR in pollen has many differences compared to vegetative cells. This provides an important foundation for understanding and improving the pollen HSR, and therefor contributes to the long-term goal of improving productivity in crop plants subjected to temperature stress conditions. A specific hypothesis that has emerged from this study is that pollen thermotolerance can be improved by increasing flavonol accumulation before or during a stress response. Efforts to test this hypothesis have been initiated, and if successful have the potential for application with major seed crops such as maize and rice.
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Graville, B. A. L51707 Factors Affecting Heat Affected Zone Root Strains in Pipeline Girth Welds and Repairs. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), novembro de 1993. http://dx.doi.org/10.55274/r0010219.
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A previous study on hydrogen cracking in the heat affected zone of pipeline girth welds and repairs found that large strains in the HAZ transverse to the weld played a major role in causing cracking. Large transverse strains were believed to arise from bending of the weld due to the thermal contraction of the weld around the pipe circumference. Large root strains were simulated in the laboratory using a bend test which enabled the effect of material composition and strength to be studied. In the bend test, the specimen deflection at the onset of cracking, indicated by a drop in load, was used as a measure of susceptibility to cracking. The study showed that increasing the base metal strength for the same HAZ (achieved experimentally by heat treating the same base metal) resulted in a decrease in the critical deflection. This suggested that considerable strain concentration was occuring in the HAZ which increased as the base metal strength increased. Although the study succeeded in quantifying the effects of base metal composition and strength on the sensitivity to cracking, the program did not attempt to address the factors that influence the degree of strain applied to the weld. Specifically, the study only considered a single weld metal strength, and only one pipe wall thickness was addressed. Thus it was not clear whether the move to higher strength pipes welded with higher strength electrodes or a change in the dimensions of the pipe might increase the exposure to cracking risks. Furthermore, if bend tests are used to screen materials, the question is raised as to whether the acceptance level of critical deflection should be changed for higher strength materials. Heat affected zone cracking was observed in both complete circumferential welds (tie-in welds) and in part-circumferential welds (repairs). Various procedural details, such as heat input and length of repair, could influence the root strain and might warrant specific controls to minimize risk of cracking. This study assessed the effects of weld metal strength, pipe thickness, pipe diameter, heat input, and weld (repair) length on root strains in girth welds. A literature review was conducted and simple analysis methods were applied to identify areas with a high risk for cracking. The results show that high tensile stresses in the axial direction on the inside surface of the pipe result from the radial contraction of the weld and consequent bending of the pipe. Welding procedures with high heat inputs and few weld passes tend to have the greatest effect on stress. Multipass welds decrease the tensile stress, which becomes compressive after a certain thickness. Base metal and weld metal strength were shown to significantly impact strain in the heat-affect zone.
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Brosh, Arieh, David Robertshaw, Yoav Aharoni, Zvi Holzer, Mario Gutman e Amichai Arieli. Estimation of Energy Expenditure of Free Living and Growing Domesticated Ruminants by Heart Rate Measurement. United States Department of Agriculture, abril de 2002. http://dx.doi.org/10.32747/2002.7580685.bard.
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Research objectives were: 1) To study the effect of diet energy density, level of exercise, thermal conditions and reproductive state on cardiovascular function as it relates to oxygen (O2) mobilization. 2) To validate the use of heart rate (HR) to predict energy expenditure (EE) of ruminants, by measuring and calculating the energy balance components at different productive and reproductive states. 3) To validate the use of HR to identify changes in the metabolizable energy (ME) and ME intake (MEI) of grazing ruminants. Background: The development of an effective method for the measurement of EE is essential for understanding the management of both grazing and confined feedlot animals. The use of HR as a method of estimating EE in free-ranging large ruminants has been limited by the availability of suitable field monitoring equipment and by the absence of empirical understanding of the relationship between cardiac function and metabolic rate. Recent developments in microelectronics provide a good opportunity to use small HR devices to monitor free-range animals. The estimation of O2 uptake (VO2) of animals from their HR has to be based upon a consistent relationship between HR and VO2. The question as to whether, or to what extent, feeding level, environmental conditions and reproductive state affect such a relationship is still unanswered. Studies on the basic physiology of O2 mobilization (in USA) and field and feedlot-based investigations (in Israel) covered a , variety of conditions in order to investigate the possibilities of using HR to estimate EE. In USA the physiological studies conducted using animals with implanted flow probes, show that: I) although stroke volume decreases during intense exercise, VO2 per one heart beat per kgBW0.75 (O2 Pulse, O2P) actually increases and measurement of EE by HR and constant O2P may underestimate VO2unless the slope of the regression relating to heart rate and VO2 is also determined, 2) alterations in VO2 associated with the level of feeding and the effects of feeding itself have no effect on O2P, 3) both pregnancy and lactation may increase blood volume, especially lactation; but they have no effect on O2P, 4) ambient temperature in the range of 15 to 25°C in the resting animal has no effect on O2P, and 5) severe heat stress, induced by exercise, elevates body temperature to a sufficient extent that 14% of cardiac output may be required to dissipate the heat generated by exercise rather than for O2 transport. However, this is an unusual situation and its affect on EE estimation in a freely grazing animal, especially when heart rate is monitored over several days, is minor. In Israel three experiments were carried out in the hot summer to define changes in O2P attributable to changes in the time of day or In the heat load. The animals used were lambs and young calves in the growing phase and highly yielding dairy cows. In the growing animals the time of day, or the heat load, affected HR and VO2, but had no effect on O2P. On the other hand, the O2P measured in lactating cows was affected by the heat load; this is similar to the finding in the USA study of sheep. Energy balance trials were conducted to compare MEI recovery by the retained energy (RE) and by EE as measured by HR and O2P. The trial hypothesis was that if HR reliably estimated EE, the MEI proportion to (EE+RE) would not be significantly different from 1.0. Beef cows along a year of their reproductive cycle and growing lambs were used. The MEI recoveries of both trials were not significantly different from 1.0, 1.062+0.026 and 0.957+0.024 respectively. The cows' reproductive state did not affect the O2P, which is similar to the finding in the USA study. Pasture ME content and animal variables such as HR, VO2, O2P and EE of cows on grazing and in confinement were measured throughout three years under twenty-nine combinations of herbage quality and cows' reproductive state. In twelve grazing states, individual faecal output (FO) was measured and MEI was calculated. Regression analyses of the EE and RE dependent on MEI were highly significant (P<0.001). The predicted values of EE at zero intake (78 kcal/kgBW0.75), were similar to those estimated by NRC (1984). The EE at maintenance condition of the grazing cows (EE=MEI, 125 kcal/kgBW0.75) which are in the range of 96.1 to 125.5 as presented by NRC (1996 pp 6-7) for beef cows. Average daily HR and EE were significantly increased by lactation, P<0.001 and P<0.02 respectively. Grazing ME significantly increased HR and EE, P<0.001 and P<0.00l respectively. In contradiction to the finding in confined ewes and cows, the O2P of the grazing cows was significantly affected by the combined treatments (P<0.00l ); this effect was significantly related to the diet ME (P<0.00l ) and consequently to the MEI (P<0.03). Grazing significantly increased O2P compared to confinement. So, when EE of grazing animals during a certain season of the year is estimated using the HR method, the O2P must be re measured whenever grazing ME changes. A high correlation (R2>0.96) of group average EE and of HR dependency on MEI was also found in confined cows, which were fed six different diets and in growing lambs on three diets. In conclusion, the studies conducted in USA and in Israel investigated in depth the physiological mechanisms of cardiovascular and O2 mobilization, and went on to investigate a wide variety of ruminant species, ages, reproductive states, diets ME, time of intake and time of day, and compared these variables under grazing and confinement conditions. From these combined studies we can conclude that EE can be determined from HR measurements during several days, multiplied by O2P measured over a short period of time (10-15 min). The study showed that RE could be determined during the growing phase without slaughtering. In the near future the development microelectronic devices will enable wide use of the HR method to determine EE and energy balance. It will open new scopes of physiological and agricultural research with minimizes strain on animals. The method also has a high potential as a tool for herd management.