Thermal Response Curves Research Articles

Geographic variation in the response of Culex pipiens life history traits to temperature.

BackgroundClimate change is predicted to alter the transmission of many vector-borne pathogens. The quantitative impact of climate change is usually estimated by measuring the temperature-performance relationships for a single population of vectors, and then mapping this relationship across a range of temperatures or locations. However, life history traits of different populations often differ significantly. Specifically, performance across a range of temperatures is likely to vary due to local adaptation to temperature and other factors. This variation can cause spatial variation in pathogen transmission and will influence the impact of climate change on the transmission of vector-borne pathogens.MethodsWe quantified variation in life history traits for four populations of Culex pipiens (Linnaeus) mosquitoes. The populations were distributed along altitudinal and latitudinal gradients in the eastern United States that spanned ~3 °C in mean summer temperature, which is similar to the magnitude of global warming expected in the next 3–5 decades. We measured larval and adult survival, development rate, and biting rate at six temperatures between 16 and 35 °C, in a common garden experiment.ResultsTemperature had strong and consistent non-linear effects on all four life history traits for all four populations. Adult female development time decreased monotonically with increasing temperature, with the largest decrease at cold temperatures. Daily juvenile and adult female survival also decreased with increasing temperature, but the largest decrease occurred at higher temperatures. There was significant among-population variation in the thermal response curves for the four life history traits across the four populations, with larval survival, adult survival, and development rate varying up to 45, 79, and 84 % among populations, respectively. However, variation was not correlated with local temperatures and thus did not support the local thermal adaptation hypothesis.ConclusionThese results suggest that the impact of climate change on vector-borne disease will be more variable than previous predictions, and our data provide an estimate of this uncertainty. In addition, the variation among populations that we observed will shape the response of vectors to changing climates.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1402-z) contains supplementary material, which is available to authorized users.

Hormonal and metabolic responses to upper temperature extremes in divergent life-history ecotypes of a garter snake.

Extreme temperatures constrain organismal physiology and impose both acute and chronic effects. Additionally, temperature-induced hormone-mediated stress response pathways and energetic trade-offs are important drivers of life-history variation. This study employs an integrative approach to quantify acute physiological responses to high temperatures in divergent life-history ecotypes of the western terrestrial garter snake (Thamnophis elegans). Using wild-caught animals, we measured oxygen consumption rate and physiological markers of hormonal stress response, energy availability and anaerobic respiration in blood plasma across five ecologically relevant temperatures (24, 28, 32, 35 and 38°C; 3h exposure). Corticosterone, insulin and glucose concentrations all increased with temperature, but with different thermal response curves, suggesting that high temperatures differently affect energy-regulation pathways. Additionally, oxygen consumption rate increased without plateau and lactate concentration did not increase with temperature, challenging the recent hypothesis that oxygen limitation sets upper thermal tolerance limits. Finally, animals had similar physiological thermal responses to high-temperature exposure regardless of genetic background, suggesting that local adaptation has not resulted in fixed differences between ecotypes. Together, these results identify some of the mechanisms by which higher temperatures alter hormonal-mediated energy balance in reptiles and potential limits to the flexibility of this response.

Tolerance of Flexible MOFs toward Repeated Adsorption Stress.

The adsorption/desorption cyclability of four flexible MOFs, namely, MIL-53(Al), ELM-11, DUT-8(Ni), and SNU-9, was studied at 298 K using n-butane as adsorptive. The detailed analysis of thermal response curves, physisorption isotherm data, powder X-ray diffraction patterns, as well as SEM images revealed the highly stable switching performance of MIL-53(Al) and ELM-11 materials during 100 adsorption/desorption cycles. In contrast, for DUT-8(Ni) and SNU-9, the multiple adsorption/desorption stress leads to the reduction of crystallite size, causing changes in the switching behavior in the initial 10 physisorption runs, and a characteristic shift of the "gate-opening" pressure to higher values is observed.

Variable effects of temperature on insect herbivory.

Rising temperatures can influence the top-down control of plant biomass by increasing herbivore metabolic demands. Unfortunately, we know relatively little about the effects of temperature on herbivory rates for most insect herbivores in a given community. Evolutionary history, adaptation to local environments, and dietary factors may lead to variable thermal response curves across different species. Here we characterized the effect of temperature on herbivory rates for 21 herbivore-plant pairs, encompassing 14 herbivore and 12 plant species. We show that overall consumption rates increase with temperature between 20 and 30 °C but do not increase further with increasing temperature. However, there is substantial variation in thermal responses among individual herbivore-plant pairs at the highest temperatures. Over one third of the herbivore-plant pairs showed declining consumption rates at high temperatures, while an approximately equal number showed increasing consumption rates. Such variation existed even within herbivore species, as some species exhibited idiosyncratic thermal response curves on different host plants. Thus, rising temperatures, particularly with respect to climate change, may have highly variable effects on plant-herbivore interactions and, ultimately, top-down control of plant biomass.

Response of chironomid species (Diptera, Chironomidae) to water temperature: effects on species distribution in specific habitats

The response of 443 chironomid species to water temperature was analyzed, with the aim of defining their thermal optimum, tolerance limits and thermal habitat. The database included 4442 samples mainly from Italian river catchments collected from the 1950s up to date. Thermal preferences were calculated separately for larval and pupal specimens and for different habitats: high altitude and lowland lakes in the Alpine ecoregion; lowland lakes in the Mediterranean ecoregion; heavily modified water bodies; kryal, krenal, rhithral and potamal in running waters. Optimum response was calculated as mean water temperature, weighted by species abundances; tolerance as weighted standard deviation; skewness and kurtosis as 3<sup>rd</sup> and 4<sup>th</sup> moment statistics. The responses were fitted to normal uni- or plurimodal Gaussian models. Cold stenothermal species showed: i) unimodal response, ii) tolerance for a narrow temperature range, iii) optima closed to their minimum temperature values, iv) leptokurtic response. Thermophilous species showed: i) optima at different temperature values, ii) wider tolerance, iii) optima near their maximum temperature values, iv) platikurtic response, often fitting a plurimodal model. As expected, lower optima values and narrower tolerance were obtained for kryal and krenal, than for rhithral, potamal and lakes. Thermal response curves were produced for each species and were discussed according to species distribution (<em>i.e. </em>altitudinal range in running water and water depth in lakes), voltinism and phylogeny. Thermal optimum and tolerance limits and the definition of the thermal habitat of species can help predicting the impact of global warming on freshwater ecosystems.

Temperature dependence of trophic interactions are driven by asymmetry of species responses and foraging strategy

Environmental temperature has systematic effects on rates of species interactions, primarily through its influence on organismal physiology. We present a mechanistic model for the thermal response of consumer-resource interactions. We focus on how temperature affects species interactions via key traits - body velocity, detection distance, search rate and handling time - that underlie per capita consumption rate. The model is general because it applies to all foraging strategies: active-capture (both consumer and resource body velocity are important), sit-and-wait (resource velocity dominates) and grazing (consumer velocity dominates). The model predicts that temperature influences consumer-resource interactions primarily through its effects on body velocity (either of the consumer, resource or both), which determines how often consumers and resources encounter each other, and that asymmetries in the thermal responses of interacting species can introduce qualitative, not just quantitative, changes in consumer-resource dynamics. We illustrate this by showing how asymmetries in thermal responses determine equilibrium population densities in interacting consumer-resource pairs. We test for the existence of asymmetries in consumer-resource thermal responses by analysing an extensive database on thermal response curves of ecological traits for 309 species spanning 15 orders of magnitude in body size from terrestrial, marine and freshwater habitats. We find that asymmetries in consumer-resource thermal responses are likely to be a common occurrence. Overall, our study reveals the importance of asymmetric thermal responses in consumer-resource dynamics. In particular, we identify three general types of asymmetries: (i) different levels of performance of the response, (ii) different rates of response (e.g. activation energies) and (iii) different peak or optimal temperatures. Such asymmetries should occur more frequently as the climate changes and species' geographical distributions and phenologies are altered, such that previously noninteracting species come into contact. 6. By using characteristics of trophic interactions that are often well known, such as body size, foraging strategy, thermy and environmental temperature, our framework should allow more accurate predictions about the thermal dependence of consumer-resource interactions. Ultimately, integration of our theory into models of food web and ecosystem dynamics should be useful in understanding how natural systems will respond to current and future temperature change.

The thermal dependence of biological traits

Environmental temperature has strong and systematic effects on biological processes at all levels of organization, ranging from cells to ecosystems. The large temporal and spatial variation in Earth's temperature creates a complex thermal landscape within which life evolves and operates. Here, we present a data set on how diverse biological rates and times respond to temperature, which we hope will aid in the search for general mechanisms of thermal dependence.For nearly a century, intraspecific studies (within single species' populations) of thermal responses have been conducted on a wide range of organismal traits. Comparative studies of these data are essential for elucidating mechanisms underlying thermal response curves. However, such comparative intraspecific studies have been limited because of a lack of a comprehensive database that organizes these data with consistent units and trait definitions. Here, we present a database of 2352 thermal responses for 220 traits for microbes, plants, and animals compiled from 270 published sources. This represents the most diverse and comprehensive thermal response data set ever compiled. The traits in this database span levels of biological organization from internal physiology to species interactions and were measured in marine, freshwater, and terrestrial habitats for 411 species. Although we include some physiological rates, most data are for ecological traits, which we define here to mean any organismal trait that directly determines interactions between individuals within or across species.We hope that publication of our data set will encourage others to compile complementary data sets, especially on individual physiology and life history traits. Intraspecific and interspecific (across species' populations) analyses of our data set should provide new insights into generalities and deviations in the thermal dependence of biological traits, and thus how biological systems, from cells to ecosystems, respond to temperature change. Such insights are essential for understanding how natural biological systems function, and how life is responding to Earth's complex and rapidly changing thermal landscape.

Method of evaluating thermal diffusivity near lossy boundaries as an alternative to the Parker method

We describe an analysis of a flash thermographic method to measure thermal diffusivity that is particularly insensitive to heat loss mechanisms near thermal boundaries. This approach is an alternative to the “Parker method” which requires that a plate-like region subject to a uniform energy flux must reach a maximum constant temperature in order to obtain an accurate measurement of thermal diffusivity at the half-temperature point in time. The present approach relies on evaluating another unique point, the inflection point, of the same back-side thermal response curve as Parker's or, from the front side, using a contrast versus time curve in the sample region of interest. This inflection point occurs so early in the response history that little heat loss, for example, near heat-sink boundaries or surface convection, is expressed. Since the method is insensitive to the achieved temperature, it is also insensitive to surface emissivity variations.

Numerical and experimental evaluation on methods for parameter identification of thermal response tests

Several parameter identification methods of thermal response test were evaluated through numerical and experimental study. A three-dimensional finite-volume numerical model was established under the assumption that the soil thermal conductivity had been known in the simulation of thermal response test. The thermal response curve was firstly obtained through numerical calculation. Then, the accuracy of the numerical model was verified with measured data obtained through a thermal response test. Based on the numerical and experimental thermal response curves, the thermal conductivity of the soil was calculated by different parameter identification methods. The calculated results were compared with the assumed value and then the accuracy of these methods was evaluated. Furthermore, the effects of test time, variable data quality, borehole radius, initial ground temperature, and heat injection rate were analyzed. The results show that the method based on cylinder-source model has a low precision and the identified thermal conductivity decreases with an increase in borehole radius. For parameter estimation, the measuring accuracy of the initial temperature of the deep ground soil has greater effect on identified thermal conductivity.

Heat transfer from small objects in microgravity: Experiments and analysis

Heat transfer over a sub-millimeter spheroidal solid is of interest in many engineering processes. One important mechanism of heat transfer in the above processes is natural convection which leads to heat transfer rates many times larger than that of pure conduction. Despite the huge literature devoted to natural convection heat transfer rates over spheres (and to a smaller extent over spheroids) there is not a generally accepted correlation especially for small Rayleigh numbers. Existing correlations for external geometries predict a progressively increasing contribution of natural convection to heat transfer with respect to gravity (starting from zero gravity). To test the validity of these correlations, experiments are performed for the estimation of heat transfer rates at low gravity. Heat pulses are given to a miniature thermistor with a nearly spheroidal shape immersed in a liquid and its thermal response is registered during heating in parabolic flights. The contribution of natural convection to heat transfer is undoubtedly estimated from runs in which acceleration varies from 0 to 1.8 g. Surprisingly enough, the experiments showed that the Rayleigh number must take a minimum value before non-negligible effect of natural convection on heat transfer appears (existence of a threshold Rayleigh number). In the absence of natural convection (below Ra thr) the experimental thermal response curves can be successfully described by approximating solutions of the transient heat conduction equation for the spheroidal geometry of the thermistor. Apparently, additional research is needed regarding the natural convection around sub-millimeter objects for small Rayleigh numbers.

Genetic correlation between temperature-induced plasticity of life-history traits in a soil arthropod

Temperature is considered one of the most important mediators of phenotypic plasticity in ectotherms. However, the costs and benefits shaping the evolution of different thermal responses are poorly elucidated. One of the possible constraints to phenotypic plasticity is its intrinsic genetic cost, such as genetic linkage or pleiotropy. Genetic coupling of the thermal response curves for different life history traits may significantly affect the evolution of thermal sensitivity in thermally fluctuating environments. We used the collembolan Orchesella cincta to study if there is genetic variation in temperature-induced phenotypic plasticity in life history traits, and if the degree of temperature-induced plasticity is correlated across traits. Egg development rate, juvenile growth rate and egg size of 19 inbred isofemale lines were measured at two temperatures. Our results show that temperature was a highly significant factor for all three traits. Egg development rate and juvenile growth rate increased with increasing temperature, while egg size decreased. Line by temperature interaction was significant for all traits tested; indicating that genetic variation for temperature-induced plasticity existed. The degree of plasticity was significantly positively correlated between egg development rate and growth rate, but plasticity in egg size was not correlated to the other two plasticity traits. The findings suggest that the thermal plasticities of egg development rate and growth rate are partly under the control of the same genes or genetic regions. Hence, evolution of the thermal plasticity of traits cannot be understood in isolation of the response of other traits. If traits have similar and additive effects on fitness, genetic coupling between these traits may well facilitate the evolution of optimal phenotypes. However, for this we need to know the selective forces under field conditions.

An analysis of transient thermal properties for high power GaN‐based laser diodes

AbstractThermal properties of 405 nm GaN‐based laser diodes were investigated by employing a transient heating response method based on the temperature dependence of diode forward voltage. Thermal resistances of materials consisting of packaged laser diodes were differentiated in transient thermal response curves at a current below threshold current. With a current above threshold current, no significant change in thermal resistances and difference between junction‐up and junction‐down laser diodes was observed at pulses shorter than 3 sec. From an analysis with long current injections, thermal resistance of a packaged laser diode with a junction‐up bonding was ∼45 °C/W which was higher than that of a junction‐down bonded laser diode by ∼10 °C/W. Further analyses based on parameters obtained from voltage recovery curves indicated that the time constant for cooling is directly related to the thermal resistance and thermal capacitance of a laser diode package. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Thermal Adaptation of Viruses and Bacteria

A previously established multiscale population genetics model posits that fitness can be inferred from the physical properties of proteins under the physiological assumption that a loss of stability by any protein confers the lethal phenotype to an organism. Here, we develop this model further by positing that replication rate (fitness) of a bacterial or viral strain directly depends on the copy number of folded proteins, which determine its replication rate. Using this model, and both numerical and analytical approaches, we studied the adaptation process of bacteria and viruses at varied environmental temperatures. We found that a broad distribution of protein stabilities observed in the model and in experiment is the key determinant of thermal response for viruses and bacteria. Our results explain most of the earlier experimental observations: the striking asymmetry of thermal response curves; the absence of evolutionary tradeoff, which was expected but not found in experiments; correlation between denaturation temperature for several protein families and the optimal growth temperature of their carrier organisms; and proximity of bacterial or viral optimal growth temperatures to their evolutionary temperatures. Our theory quantitatively and with high accuracy described thermal response curves for 35 bacterial species using, for each species, only two adjustable parameters—the number of rate-determining genes and the energy barrier for metabolic reactions.

Self Organising Maps for distinguishing polymer groups using thermal response curves obtained by dynamic mechanical analysis

Self Organising Maps are described including the U-Matrix, component planes, hit histograms, quality indicators as mean quantisation error and topological error. Software was written in Matlab and several new approaches for visualising multiclass maps are employed. The method is applied to a dataset consisting of the Dynamic Mechanical Analysis of 293 polymers, involving heating the polymers over a temperature range of -51 degrees C to 270 degrees C. These can be characterised in three different ways (a) amorphous or semi-crystalline (b) as 9 groups (c) as 30 grades.

Thermal adaptation of Arctic charr: experimental studies of growth in eleven charr populations from Sweden, Norway and Britain

Summary1. Experimental growth data for Arctic charr (Salvelinus alpinusL.), all fed on excess rations, from 11 European watercourses between 54 and 70°N were analysed and fitted to a new general growth model for fish. The model was validated by comparing its predictions with the growth rate of charr in the wild.2. Growth performance varied among populations, mainly because of variation in the maximum growth potential, whereas the thermal response curves were similar. The estimated lower and upper temperatures for growth varied between −1.7 to 5.3 and 20.8–23.2 °C, respectively, while maximum growth occurred between 14.4 and 17.2 °C.3. There was no geographical or climatic trend in growth performance among populations and therefore no indication of thermal adaptation. The growth potential of charr from different populations correlated positively with fish body length at maturity and maximum weight in the wild. Charr from populations including large piscivorous fish had higher growth rates under standardised conditions than those from populations feeding on zoobenthos or zooplankton. Therefore, the adaptive variation in growth potential was related to life‐history characteristics and diet, rather than to thermal conditions.

Thermal expansion behaviour of aluminium/SiC composites with bimodal particle distributions

The thermal response and the coefficient of thermal expansion (CTE) of aluminium matrix composites having high volume fractions of SiC particulate have been investigated. The composites were produced by infiltrating liquid aluminium into preforms made either from a single particle size, or by mixing and packing SiC particulate of two largely different average diameters (170 and 16 μm, respectively). The experimental results for composites with a single particle size indicate that the hysteresis in the thermal strain response curves is proportional to the square root of the particle surface area per unit volume of metal matrix, in agreement with current theories. Instead, no simple relationship is found between the hysteresis and any of the system parameters for composites with bimodal particle distributions. On the other hand, the overall CTE is shown to be mainly determined by the composite compactness or total particle volume fraction; neither the particle average size nor the particle size distribution seem to affect the overall CTE. This result is in full agreement with published numerical results obtained from finite element analyses of the effective CTE of aluminum matrix composites. Our results also indicate that the CTE varies with particle volume fraction at a pace higher than predicted by theory.

Determination of RNase A/2′-Cytidine Monophosphate Binding Affinity and Enthalpy by a Global Fit of Thermal Unfolding Curves

A spectropolarimeter was used to measure the thermal response curves of RNase A in the presence and absence of the ligand cytidine 2′-monophosphate. A coupled equilibrium model was used to describe the dissociation of the protein–ligand complex (NL ⇄ N + L) and the thermal unfolding of the free protein (N ⇄ U). The unfolding curves of the protein in the presence of several different concentrations of ligand were fit to this coupled equilibrium model using global linkage analysis. The best-fitted values for the thermal unfolding of the apo-protein were 60.9 ± 0.2°C (Tm) and 105.5 ± 1.4 kcal/mol (ΔH), while the fitted values for the dissociation of the protein–ligand complex were 1.6 ± 0.4 μM (KD) and 18.7 ± 1.0 kcal mol−1 (ΔHL). These values were in excellent agreement with values obtained by other methods. The sensitivity of the data fitting was compared using linear or quadratic temperature dependence for the response curves of the free ligand (L), native apo-protein (N), native ligand–bound protein (NL), and unfolded apo-protein (U). There was no significant improvement in the precision of the fitted data when the temperature-dependent response for each species (N, L, NL, and U) was expressed as quadratic functions of temperature.

On the modeling of the transient thermal behavior of semiconductor devices

A mathematical model of the transient temperature response of integrated devices is presented which takes into account the three-dimensional (3-D) nature of heat flow and the physical structure of the device. Simple analytical relations for the transient thermal impedance and thermal time constants are derived for the first time. The impact of device geometry on the transient thermal response curve is discussed, and simple guidelines for the thermal design of solid-state devices operated in transient or pulsed regime are given.

The mechanical and thermal expansion behavior of an Al–Si alloy composite reinforced with potassium titanate whisker

Composites of aluminum–silicon (Al–12 wt.%Si) alloy reinforced with potassium titanate whiskers were prepared by the squeeze casting process. The tensile behavior, thermal expansion and dimensional stability of such composites were investigated. Tensile tests showed that the tensile strength of the composites at room temperature is slightly inferior to that of the Al–12Si alloy However, potassium titanium whiskers exert a beneficial effect in improving the tensile strength of Al–12Si alloy at higher temperatures. Dilatometric measurements revealed that the coefficient of thermal expansion of Al–12Si alloy tends to decrease with increasing whisker content. Strain hysteresis was observed in Al–12Si alloy and its composites subjected to thermal cycling. The thermal response curves indicated that the Al–12Si alloy exhibits the largest thermal and residual plastic strains subjected to heating and cooling cycles between 50 and 280°C. The Al–12Si alloy reinforced with 30 vol.% whiskers had little dimensional change owing to the absence of residual plastic strain. Finally, we conclude that the thermal strain response curves can be used to predict the thermal stability and failure of the structural materials on exposure to fluctuating temperature environments.

Estimation of the IGBT Silicon Temperature During Short-Circuit Condition in Order to Determine the Failure Mode

AbstractDesigners in power electronics use IGBT because of its attractive electrical characteristics and its short-circuit withstand capability. Unfortunately. if is very difficult to forecast the IGBT safe operating area in short-circuit conditions (short duration and large power) because the thermal response curves obtained with the classical thermal model are not accurate in such conditions. The aim of this paper is to present a study of the device temperature rise during the short-circuit. The values of the silicon temperature inform the user on the possible damage occurring in the device. Furthermore this can help the user to determine the physical failure mode and to design an appropriate fault protection scheme.