Thermal Plasticity Research Articles

Convergence of life history and physiology during range expansion toward the phenotype of the native sister species

In our globally changing planet many species show range expansions whereby they encounter new thermal regimes that deviate from those of their source region. Pressing questions are to what extent and through which mechanisms, plasticity and/or evolution, species respond to the new thermal regimes and whether these trait changes are adaptive. Using a common-garden experiment, we tested for plastic and evolutionary trait changes in life history and a set of understudied biochemical/physiological traits during the range expansion of the damselfly Ischnura elegans from France into a warmer region in Spain. To assess the adaptiveness of the trait changes we used the phenotype of its native sister species in Spain, I. graellsii, as proxy for the locally adapted phenotype. While our design cannot fully exclude maternal effects, our results suggest that edge populations adapted to the local conditions in the newly invaded region through the evolution of a faster pace-of-life (faster development and growth rates), a smaller body size, a higher energy budget and increased expression levels of the heat shock gene DnaJ. Notably, based on convergence toward the phenotype of the native sister species and its thermal responses, and the fit with predictions of life history theory these potential evolutionary changes were likely adaptive. Nevertheless, the convergence toward the native sister species is incomplete for thermal plasticity in traits associated with anaerobic metabolism and melanization. Our results highlight that evolution might at least partly contribute in an adaptive way to the persistence of populations during range expansion into new thermal environments and should be incorporated when predicting and understanding species' range expansions.

Acclimation, duration and intensity of cold exposure determine the rate of cold stress accumulation and mortality in Drosophila suzukii

The spotted wing drosophila (SWD), Drosophila suzukii, is a major invasive fruit pest. There is strong consensus that low temperature is among the main drivers of SWD population distribution, and the invasion success of SWD is also linked to its thermal plasticity. Most studies on ectotherm cold tolerance focus on exposure to a single stressful temperature but here we investigated how cold stress intensity affected survival duration across a broad range of low temperatures (−7 to +3 °C). The analysis of Lt50 at different stressful temperatures (Thermal Death Time curve - TDT) is based on the suggestion that cold injury accumulation rate increases exponentially with the intensity of thermal stress. In accordance with the hypothesis, Lt50 of SWD decreased exponentially with temperature. Further, comparison of TDT curves from flies acclimated to 15, 19 and 23 °C, respectively, showed an almost full compensation with acclimation such that the temperature required to induce mortality over a fixed time decreased almost 1 °C per °C lowering of acclimation temperature. Importantly, this change in cold tolerance with acclimation was uniform across the range of moderate to intense cold stress exposures examined.To understand if cold stress at moderate and intense exposures affects the same physiological systems we examined how physiological markers/symptoms of chill injury developed at different intensities of the cold stress. Specifically, hsp23 expression and extracellular [K+] were measured in flies exposed to different intensities of cold stress (−6, −2 and +2 °C) and at various time points corresponding to the same progression of injury (equivalent to 1/3, 2/3 or 3/3 of Lt50). The different cold stress intensities all triggered hsp23 expression following 2 h of recovery, but patterns of expression differed. At the most intense cold stress (−6 and −2 °C) a gradual increase with time was found. In contrast, at +2 °C an initial increase was followed by a dissipating expression. A gradual perturbation of ion balance (hyperkalemia) was also found at all three cold stress intensities examined, with only slight dissimilarities between treatment temperatures. Despite some differences between the three cold intensities examined, the results generally support the hypothesis that intense and moderate cold stress induces the same physiological perturbation. This suggests that cold stress experienced during natural fluctuating conditions is additive and the results also illustrate that the rate of injury accumulation increases dramatically (exponentially) with decreasing temperature (increasing stress).

Mitigation of welding induced buckling with transient thermal tension and its application for accurate fabrication of offshore cabin structure

Offshore cabin structure is usually fabricated by welding with 6–8 mm steel plates as lightweight application, and welding distortion is inevitable generated to influence its dimensional accuracy. In particular, welding induced buckling will occur under conventional welding procedure due to the geometric feature of cabin structure. Typical fillet welded joints in considered cabin structure were numerically examined beforehand, while thermal and mechanical behaviors were represented with non-linear thermal elastic plastic FE computation. Then, welding inherent deformation was proposed as driving force for welding distortion prediction, which can be evaluated by integration of residual plastic strain for each typical welded joint. Since transient thermal tension is applied during fillet welding with numerical investigation, self-constraint supported by base materials on welding line will become weak. Thus, less plastic strain is generated during welding process, and magnitude of welding inherent deformation will be significantly reduced. Elastic FE computation with welding inherent deformation as mechanical load was carried out to predict out-of-plane welding distortion of considered cabin structure, while cases of conventional welding and welding with transient thermal tension were examined. Better fabrication accuracy can be obtained with application of transient thermal tension due to less welding inherent deformation.

Synthesis and Characterization of Epoxidized Silkworm Pupae Oil and Its Application as Polyvinyl Chloride.

More and more industries demand environmental friendliness. Silkworm pupae oil (SPO), extracted from the desilked silkworm pupae, can serve as a promising substrate alternative to use in plasticization. This study aimed to prepare epoxidized silkworm pupae oil (ESPO) and investigate their effects on the thermal stability and plasticization of polyvinyl chloride (PVC) films. A chemo-enzymatic method of ESPO was developed in the presence of Lipase SMG1-F278N and H2O2 in natural deep eutectic solvents (DESs). Lipase SMG1-F278N could initiate the epoxidation reaction effectively at room temperature with a negligible loss of activities 10 batches. A maximum oxirane value of 6.94% was obtained. The formation of oxirane ring in ESPO was confirmed by FTIR and 13C NMR spectra. Moreover, ESPO showed a better thermal stability and lower freezing point than epoxidized soybean oil (ESO). It was demonstrated that ESPO had a good frost resistance. In addition, ESPO showed a significantly improved plasticizing effect on flexible polyvinyl chloride (PVC). Compared with ESO, ESPO could increase the tensile elongation at break effectively. A significantly lower migration rate of plasticizer was observed in PVC plasticized with ESPO.

Plasma Membrane Fluidity: An Environment Thermal Detector in Plants.

The lipid matrix in cell membranes is a dynamic, bidimensional array of amphipathic molecules exhibiting mesomorphism, which contributes to the membrane fluidity changes in response to temperature fluctuation. As sessile organisms, plants must rapidly and accurately respond to environmental thermal variations. However, mechanisms underlying temperature perception in plants are poorly understood. We studied the thermal plasticity of membrane fluidity using three fluorescent probes across a temperature range of −5 to 41 °C in isolated microsomal fraction (MF), vacuolar membrane (VM), and plasma membrane (PM) vesicles from Arabidopsis plants. Results showed that PM were highly fluid and exhibited more phase transitions and hysteresis, while VM and MF lacked such attributes. These findings suggest that PM is an important cell hub with the capacity to rapidly undergo fluidity modifications in response to small changes of temperatures in ranges spanning those experienced in natural habitats. PM fluidity behaves as an ideal temperature detector: it is always present, covers the whole cell, responds quickly and with sensitivity to temperature variations, functions with a cell free-energy cost, and it is physically connected with potential thermal signal transducers to elicit a cell response. It is an optimal alternative for temperature detection selected for the plant kingdom.

Separating Paternal and Maternal Contributions to Thermal Transgenerational Plasticity

Climate change is rapidly altering the thermal environment in terrestrial and aquatic systems. Transgenerational thermal plasticity (TGP) – which occurs when the temperatures experienced by the parental generation prior to the fertilization of gametes results in a change in offspring reaction norms – may mitigate the effects of climate change. Although “maternal effects” have been widely studied, relatively little is known about TGP effects in vertebrates, particularly paternal contributions. We used artificial fertilization to cross sheepshead minnow (Cyprinodon variegatus) parents exposed to either low (26°C) or high (32°C) temperatures and measured growth rates of the offspring over the first 8 weeks of life at both low and high temperatures. A linear mixed effects model was employed to quantify the effects of maternal, paternal, and offspring temperatures on offspring growth and fecundity. We found that the offspring growth rate up to 63 days post-hatch was affected by both the temperature they experienced directly and parental temperatures prior to fertilization. Growth was lowest when neither parents’ temperature matched the offspring temperature, indicating a strong transgenerational effect. Notably, offspring growth was highest when all three (offspring, sire, and dam) temperatures matched [although the three-way interaction was found to be marginally non-significant (P = 0.155)], suggesting that TGP effects were additive across significant sire-offspring (P < 0.001) and dam-offspring interactions (P < 0.001). Transgenerational effects on fecundity (GSI) were suggestive for both maternal and paternal effects, but not significant. The finding that thermal TGP is contributed by both parents strongly suggests that it has an epigenetic basis.

A New Experimental Approach for Heat Transfer Coefficient and Adiabatic Wall Temperature Measurements on a Nozzle Guide Vane With Inlet Temperature Distortions

AbstractModern gas turbines lean combustors allow to limit NOx pollutant emissions by controlling the flame temperature, while maintaining high turbine inlet temperatures. On the other hand, their adoption presents other challenges, especially concerning the combustor–turbine interaction. Turbine inlet conditions are generally characterized by severe temperature distortions and swirl degree, which, in turn, is responsible for very high turbulence intensities. Several past studies have focused on the description of the effects of these phenomena on the behavior of the high pressure stages of the turbine, both considering them as separated aspects, and, in very recent years, accounting for their combined impact. Nevertheless, very limited experimental results are available when it comes to evaluate the heat transfer coefficient (HTC) on the nozzle guide vane (NGV) external surface, since relevant temperature distortions present a severe challenge for the commonly adopted measurement techniques. The work presented in this paper was carried out on a non-reactive, annular, three-sector test rig, made by a combustor simulator and a NGV cascade. Making use of three real hardware burners of a Baker Hughes heavy-duty gas turbine, operated in similitude conditions, it can reproduce a representative swirling flow, with temperature distortions at the combustor–turbine interface plane. This test apparatus was exploited to develop an experimental approach to retrieve reliable HTC and adiabatic wall temperature distributions simultaneously, in order to overcome the known limitations imposed by temperature gradients on state-of-the-art methods for HTC calculation from transient tests. A non-cooled mockup of a NGV doublet, manufactured using low thermal diffusivity plastic material, was used for the tests, carried out using infra-red thermography with a transient approach. In the authors’ knowledge, this presents the first experimental attempt of measuring a NGV HTC in the presence of relevant temperature distortions and swirl.

Membrane lipid metabolism, heat shock response and energy costs mediate the interaction between acclimatization and heat-hardening response in the razor clam Sinonovacula constricta.

Thermal plasticity on different time scales, including acclimation/acclimatization and heat-hardening response - a rapid adjustment for thermal tolerance after non-lethal thermal stress, can interact to improve the resilience of organisms to thermal stress. However, little is known about physiological mechanisms mediating this interaction. To investigate the underpinnings of heat-hardening responses after acclimatization in warm seasons, we measured thermal tolerance plasticity, and compared transcriptomic and metabolomic changes after heat hardening at 33 or 37°C followed by recovery of 3 or 24 h in an intertidal bivalve Sinonovacula constricta. Clams showed explicit heat-hardening responses after acclimatization in a warm season. The higher inducing temperature (37°C) caused less effective heat-hardening effects than the inducing temperature that was closer to the seasonal maximum temperature (33°C). Metabolomic analysis highlighted the elevated content of glycerophospholipids in all heat-hardened clams, which may help to maintain the structure and function of the membrane. Heat shock proteins (HSPs) tended to be upregulated after heat hardening at 37°C but not at 33°C, indicating that there was no complete dependency of heat-hardening effects on upregulated HSPs. Enhanced energy metabolism and decreased energy reserves were observed after heat hardening at 37°C, suggesting more energy costs during exposure to a higher inducing temperature, which may restrict heat-hardening effects. These results highlight the mediating role of membrane lipid metabolism, heat shock responses and energy costs in the interaction between heat-hardening response and seasonal acclimatization, and contribute to the mechanistic understanding of evolutionary change and thermal plasticity during global climate change.

Temperature Measurement and Control Application in a Laser Plastic Surgery Real Temperature Detection System

The purpose of this study was to grasp the development process of thermal image temperature measurement technology. It provides directional support for the optimization development of the thermal imagery and laser plastic surgery and laser treatment. This paper uses the infrared thermal image temperature measurement principle and performs infrared thermal image precise temperature measurement technology and its application research. The results showed that there was a correlation between 595 nm pulse dye laser, age, laser energy density, and skin temperature ( P < 0.05 ). There is a significant difference in the average ( P < 0.05 ). The infrared thermal imagery temperature monitoring system is a simple and relatively accurate temperature detection system that can be widely used in temperature measurement and control of laser plastic surgery.

High thermal plasticity, and vulnerability, in extreme environments at the warm distributional edge: The case of a tidepool shrimp

Climate change threatens the resilience of species, especially at their warm distributional edge in extreme environments. We investigated the thermal vulnerability of the tidepool shrimp, Palaemon elegans in the fast-warming southeastern Mediterranean Sea, its warm distributional edge. Tidepool organisms experience strong and fast thermal fluctuations. This might make them more resilient to change, but also bring them closer to their thermal limits during extreme conditions. To examine the shrimp's resilience, we tested three hypotheses: (1) P. elegance in the southeast Mediterranean has higher critical thermal maximum (CTMax) than in cooler regions, (2) the shrimp possess seasonal acclimatization, but (3) long exposure to extreme summer temperatures might erode its thermal performance making it vulnerable to future climate change. In a series of field observations and laboratory experiments we characterized the shrimp's thermal environment and population dynamics, determined its CTMax and tested diverse physiological performance attributes (respiration, digestion, activity, growth) under a wide range of temperatures during winter and summer. The thermal performance curves show that peak respiration rates occur at higher temperatures in the summer compared to winter, indicating seasonal acclimatization. The shrimp's CTMax was 38.1 °C; higher than its Atlantic counterparts, and an indication of biogeographic adaptation. However, its warming tolerance (the thermal safety margin: distance between maximum pool temperatures and CTMax) was only 0.3 °C, indicating low capacity for dealing with further warming in mostly isolated pools, compared to northeast Atlantic populations that have a wider safety margin. Performance also eroded with increase in exposure duration to high temperatures, and the optimum temperature reduces with time. We predict that prolonged exposure to current (~ 32 °C) and future mean summer values in open water would significantly reduce its performance and increase its mortality. Further, juvenile P. elegans were found to be more vulnerable to extreme (cold and hot) temperatures than adults. Together, these findings indicate that the population viability of this robust coastal water shrimp would eventually be reduced under continuous regional warming and the intensification of extreme events.

Developmental Temperature Affects Life-History Traits and Heat Tolerance in the Aphid Parasitoid Aphidius colemani.

Simple SummaryIndividual insects can experience different temperatures across their lives. In consequence, development of immature stages can take place at temperatures contrasting with those that the adult will encounter. In order to study the adaptation of organisms to warm environments, it is interesting to establish the links between developmental temperature and responses of the adult generation, in terms of physiology, morphology, and behavior. We exposed the parasitoid Aphidius colemani to three temperatures during larval development (10, 20, or 28 °C). We then measured the responses of adult parasitoids regarding their traits (physiology, morphology) and their tolerance to high temperatures. Mass, lipid reserves, survival, and heat tolerance of adults were affected by the rearing temperature regime. This means that, overall, developmental temperatures may affect how insects respond to a given temperature once they are adults, which may consequently influence the ability of parasitoids to control their aphid hosts. These results are important in the context of biological control in hot environments, such as the Maghreb, where this species of parasitoid is used in mass release techniques to control aphids in various crops.Developmental temperature plays important roles in the expression of insect traits through thermal developmental plasticity. We exposed the aphid parasitoid Aphidius colemani to different temperature regimes (10, 20, or 28 °C) throughout larval development and studied the expression of morphological and physiological traits indicator of fitness and heat tolerance in the adult. We showed that the mass decreased and the surface to volume ratio of parasitoids increased with the development temperature. Water content was not affected by rearing temperature, but parasitoids accumulated more lipids when reared at 20 °C. Egg content was not affected by developmental temperature, but adult survival was better for parasitoids reared at 20 °C. Finally, parasitoids developed at 20 °C showed the highest heat stupor threshold, whereas parasitoids developed at 28 °C showed the highest heat coma threshold (better heat tolerance CTmax1 and CTmax2, respectively), therefore only partly supporting the beneficial acclimation hypothesis. From a fundamental point of view, our study highlights the role of thermal plasticity (adaptive or not) on the expression of different life history traits in insects and the possible correlations that exist between these traits. From an applied perspective, these results are important in the context of biological control through mass release techniques of parasitoids in hot environments.

Limited plasticity in thermally tolerant ectotherm populations: evidence for a trade-off.

Many species face extinction risks owing to climate change, and there is an urgent need to identify which species' populations will be most vulnerable. Plasticity in heat tolerance, which includes acclimation or hardening, occurs when prior exposure to a warmer temperature changes an organism's upper thermal limit. The capacity for thermal acclimation could provide protection against warming, but prior work has found few generalizable patterns to explain variation in this trait. Here, we report the results of, to our knowledge, the first meta-analysis to examine within-species variation in thermal plasticity, using results from 20 studies (19 species) that quantified thermal acclimation capacities across 78 populations. We used meta-regression to evaluate two leading hypotheses. The climate variability hypothesis predicts that populations from more thermally variable habitats will have greater plasticity, while the trade-off hypothesis predicts that populations with the lowest heat tolerance will have the greatest plasticity. Our analysis indicates strong support for the trade-off hypothesis because populations with greater thermal tolerance had reduced plasticity. These results advance our understanding of variation in populations' susceptibility to climate change and imply that populations with the highest thermal tolerance may have limited phenotypic plasticity to adjust to ongoing climate warming.

Measurement of microscopic strain distributions of CFRP laminates with fiber discontinuities by sampling moiré method

Carbon fiber-reinforced plastics (CFRP) laminate structures manufactured using prepregs usually contain fiber discontinuities that result from the prepreg cutting for design and cost-efficiency. In this study, the sampling moiré method was used to measure the microscopic strain of unidirectional CFRP laminates with fiber discontinuities to investigate the deformation behavior that causes damage. In addition to the strain distributions of the laminate before and after cracking, the strain results due to thermal residual stress relaxation and residual plastic deformation during cracking were also obtained. The experimental results of this study were in good agreement with the finite element method results. Our results revealed that the sampling moiré method is an accurate method of measuring microscopic strain that can be used to evaluate the mechanical properties, damage behavior, residual strains in laminates with fiber discontinuities, and other different materials and structures.

The resistance welding of CF/epoxy laminate and 6063Al alloy: morphology, mechanical property and interface evolution

There is an increasing need for joining technologies of resin matrix composites and metals, in which resistance welding is one of the most promising methods. In this work, the resistance welding of 6063Al alloy and CF/epoxy laminate was realized through designing the thermoplastic layer on the surface of the base material. The welding process was conducted under different welding times (t w) in this research, while porous stainless steel (SS) mesh was selected as a heating implant. The microstructure of the welding interface formed at different t w was characterized by scanning electron microscopy (SEM), and the characteristic area showed a strong correlation with t w. The results of mechanical strength of the welding joint were obtained by tensile lap shear strength (LSS) test, which indicated that the LSS can reach a maximum value of 19.18 MPa when welding time (t w) was 6 mins. To further understand the joint formation process and strength changes law, the evolution process of the welding interface was described in detail according to the temperature distribution simulated by COMSOL. This work provided a technical foundation for large-area surface thermal plasticization in thermosetting composite materials and metals, and then achieve fusion bonding.

Strength of 3D prints with variable print orientation

The purpose of this paper is to present the analysis of the efficiency and strength of 3D printed parts due to the variation shown in print orientation. Fused deposition modeling (FDM) is a widely used technique in which the melt extrusion method is used to deploy the thermal plastics as filaments in a specific pattern. In recent years, the revolutionary method has changed the field of rapid manufacturing. This has become one of the most common methods for printing polymer-based composite components. The investigation is done based on the print orientation effects on the macrostructure, the mechanical properties, and the strain field behavior of PLA (polylactic acid) filament. Based on the analysis, the properties of an object are optimized to increase mechanical strength when manufactured. By fixing the similar print properties across all different orientations helps to identify the differences in the structural and other mechanical properties, which projects a clear understanding of the impact received and thus provides a way to enhance the structural strength of the prints.

Estimating the effect of aqueous cationic latex from the class of thermal elastic plastics on the properties of bitumen emulsions

To produce cationic bitumen emulsions, bitumen is used, whose penetration is not lower than 90 mm-1. Such bitumen has a small plasticity interval, which leads to a deterioration in its heat resistance at elevated temperatures and narrows the scope of application of emulsions based on it. Based on the review of emulsion modification methods, the modification has been proposed that involves mixing the finished bitumen emulsions with aqueous cationic latex. The process of interaction between a bituminous emulsion and an aqueous cationic latex has been considered. A mechanism for the disintegration of the modified bitumen emulsion on the surface of mineral materials was proposed. The emulsifiers have been selected and the composition of the aqueous phase has been chosen based on the analysis of surface tension isotherms. The influence of the modification on the properties of bitumen emulsions was investigated. It was established that the main physicochemical characteristics of the interphase surface accept similar values for the aqueous phase and emulsions based on it. It has been proven that the introduction of aqueous cationic latex quite moderately affects the basic physical-mechanical properties of emulsions, which makes it possible not to change the main technological parameters when using them. It was established that increasing the concentration of the polymer in the emulsion has a positive effect on the physical-mechanical properties of the binder. With an increase in the concentration of the polymer to 6 % the softening temperature increases by 16 °C, elasticity is 74 %, and the holding capacity at minus 25 °C is approaching 100 %. Improving the physical-mechanical properties of residual binder as a result of emulsion modification could increase the durability of layers in a roadbed based on bitumen emulsions and expand the scope of their application in the construction and repair of motorways

Genetic variation for upper thermal tolerance diminishes within and between populations with increasing acclimation temperature in Atlantic salmon.

Populations may counteract lasting temperature changes or recurrent extremes through plasticity or adaptation. However, it remains underexplored how outbreeding, either naturally, unintentionally, or facilitated, may modify a local response potential and whether genotype-by-environment interactions or between-trait correlations can restrict this potential. We quantified population differences and outbreeding effects, within-population genetic variation, and plasticity of these, for thermal performance proxy traits using 32 pedigreed wild, domesticated, and wild-domesticated Atlantic salmon families reared under common-garden conditions. Following exposure to ambient cold (11.6 °C) or ~4° and ~8° warmer summer temperatures, populations differed notably for body length and critical thermal maximum (CTmax) and for thermal plasticity of length, condition, and CTmax, but not for haematocrit. Line-cross analysis suggested mostly additive and some dominant outbreeding effects on means and solely additive outbreeding effects on plasticity. Heritability was detected for all traits. However, with increasing acclimation temperature, differences in CTmax between populations and CTmax heritability diminished, and CTmax breeding values re-ranked. Furthermore, CTmax and body size were negatively correlated at the genetic and phenotypic levels, and there was indirect evidence for a positive correlation between growth potential and thermal performance breadth for growth. Thus, population differences (including those between wild and domesticated populations) in thermal performance and plasticity may present a genetic resource in addition to the within-population genetic variance to facilitate, or impede, thermal adaptation. However, unfavourable genotype-by-environment interactions and negative between-trait correlations may generally hamper joint evolution in response to an increase in average temperature and temporary extremes.

Thermal tolerance of cyprinids along an urban-rural gradient: Plasticity, repeatability and effects of swimming and temperature shock.

Urbanization changes the thermal profile of streams in much the same way that climate change is predicted to with higher temperatures, more varied flow and rapid temperature pulses with precipitation events. Whether exceptional tolerance to these altered thermal conditions is a pre-requisite for a fish species to inhabit urban streams or if urbanization has changed the thermal physiology of those fish species that persist in urban streams is unknown, but could help predict the outcome of future climate disruption. To test whether residence in urban streams is associated with altered thermal tolerance, we compared thermal tolerance (CTMax) and phenotypic plasticity of thermal tolerance (ΔCTMax/Δ acclimation temperature) in five populations of an urban-tolerant cyprinid, the blacknose dace (Rhinichthys atratulus), from multiple watersheds along an urban/rural gradient. Thermal tolerance of these stream fish was tested while swimming at 10cm*s-1 but also in static water and after thermal shocks of 4°-6°C simulating precipitation events. To test whether blacknose dace as a species has unusual thermal tolerance or thermal plasticity, we also compared two blacknose dace populations with two co-resident, co-familiars (creek chub (Semotilus atromaculatus) and rosyside dace (Clinostomus funduloides), that don't persist in urban streams at three different acclimation temperatures. Thermal tolerance of blacknose dace, as measured by a critical thermal maximum test (CTMax), was independent of size and activity level, i.e. individuals had identical thermal tolerance whether swimming or resting and CTMax was significantly repeatable across two levels of activity. Although there was some variance among populations, blacknose dace from streams of varied urbanization generally exhibited comparable thermal tolerances, ability to acclimate to different temperatures and were unaffected by thermal shocks. Rosyside dace had significantly lower thermal tolerance than the other two species but plasticity of thermal tolerance was uniform across the three cyprinid species. Our conclusions are that exceptional thermal tolerance or ability to thermally acclimate are not pre-requisite characters for a given cyprinid species to survive in urban streams, nor has thermal tolerance undergone directional selection in this urban environment.

A Study on Strain Energy of Ellipsoidal Inclusion in Half-space

An inclusion refers to localized eigenstrains appearing in such processes as thermal expansion and plastic deformation. In view of micromechanics, the existence of inclusions may significantly influence the mechanical properties of the engineering materials. A micromechanical model is proposed to determine the variation of the strain energies in the presence of the near-surface inclusions. The corresponding inclusion problem in a half-space is usually difficult to be solved analytically. In this work, the strain energy is evaluated numerically via the method of images, which superposes the counterpart solutions in full-space and eliminates the tractions on the boundary surface of the half-space. The validity of the present work is confirmed by comparing with the published results and the finite element method (FEM).

Effect of Cullet on Firing Temperature and Dielectric Properties of Porcelain Insulator

In this study, porcelain insulators produced from locally available ceramic materials, Hosaena clay, Arero feldspar, and Arero quartz and cullet as alkaline materials. The chemical compositions of clay are determined using an atomic absorption spectrometer (AAS). The thermal response, mineralogy, morphology, and plasticity nature of the clay sample measured using TGA/DTA, XRD, SEM, and Atterberg test, respectively. Four test batches were prepared with progressive addition of cullet and sintered in the temperature range of 1100 ─1250°C at 50°C intervals. The physical and electrical properties of fired samples such as water absorption, apparent porosity, bulk density, and linear shrinkage; and dielectric strength as a function of firing temperature evaluated. The XRD and AAS results revealed that Hosaenna clay mainly belongs to kaolinite mineral with a sufficient SiO2 (45.60wt. %) and Al2O3 (35.52wt. %), and it possesses reasonable plasticity nature. The porcelain insulators fired at 1150°C & 1200°C showed homogenized primary and secondary mullets with optimum glassy phase and good dielectric strength for practical applications. The primary & secondary mullets and glassy phases were grown early at a firing temperature of 1150 and 1200°C, due to the partial replacement of feldspar by cullet. The porcelain insulators prepared from the composition of 45%clay, 35%feldspar, 10%quartz and 10%cullet and fired at 1200°C showed dielectric strength 8.9kv/mm, water absorption (0.459%), apparent porosity (1.530%), bulk density (4.29g/cm 3 ), and linear shrinkage (4.18%). Therefore, the addition of economic alkaline materials such as cullet in the locally available clay materials, Hosaenna clay, Arero feldspar, and Arero quartz reduces the firing temperature and with excellent dielectric strength.