Term Thermal Stress Research Articles

Transcriptomic analyses provide insights into the adaptive responses to heat stress in the ark shells, Scapharca subcrenata

The ark shell, Scapharca subcrenata, is susceptible to high temperature which may lead to mass mortality in hot summers. Herein, we conducted the transcriptomic analyses of haemocytes in ark shells under thermal stress, to reveal the underlying molecular mechanisms of heat resistance in these animals. The results showed that a total of 7773, 11,500 and 13,046 unigenes were expressed differentially at 12, 24 and 48 h post thermal stress, respectively. The expression levels of key DEGs as revealed by RNA-seq were confirmed by quantitative real-time PCR. GO and KEGG enrichment analyses showed that the DEGs were mainly associated with apoptosis, NF-kappa B signaling pathway, TNF signaling pathway and RIG-I-like receptor signaling pathway. Among the DEGs, 40 were candidate heat stress response-related genes and 169 were identified to be involved in antioxidant defense, cell detoxification, protein metabolism and endoplasmic reticulum stress responses. It seemed that ark shells may adapt to short term thermal stress through regulation of protein metabolism, DNA replication and anti-apoptotic system. However, if the stress sustains, it may cause irreparable injury gradually in the animals due to oxygen limitation and metabolic dysregulation. Noteworthily, the expression of DEGs involved in protein biosynthesis and proteolysis was significantly elevated in ark shells under heat stress. These findings may provide preliminary insights into the molecular response of ark shells to acute thermal stress and lay the groundwork for marker-assisted selection of heat-resistant strains in S. subcrenata.

Full-length transcriptome sequences of ridgetail white prawn Exopalaemon carinicauda provide insight into gene expression dynamics during thermal stress

Marine heat waves and extreme high temperature become more frequent and intense in these years, which affected the survival of aquaculture animals. The ridgetail white prawn Exopalaemon carinicauda is an important economic species in eastern China, which has remarkable thermal tolerance. However, there has been little study of its thermal-adaptation mechanisms due to the complex genetic structure and unknown genome. To better understand the molecular mechanisms of E. carinicauda to adapt to the changing temperature, a combination of Illumina-based short reads RNA-seq and single molecule real-time-based full-length transcriptome sequencing was used in this study. In total, 17,212 unigenes from high-quality transcripts of E. carinicauda were generated and 14,663 complete ORFs were detected with an average length of 1980 bp. In addition, the transcriptome profiles of E. carinicauda treated with 34 °C heat stress for 6 and 24 h were analyzed. These differentially expressed genes were primarily enriched in oxidation-reduction process (Gene Ontology enrichment, GO) and the pathways of starch and sucrose metabolism (Kyoto Encyclopedia of Genes and Genomes enrichment, KEGG) after 6 h thermal stress, which indicated that E. carinicauda was suffering the attack by reactive oxygen species. After 24 h thermal stress, these differentially expressed genes were enriched in the pathway of lysosome, glycine, serine and threonine metabolism, fatty acid metabolism (KEGG), which indicated the oxidative stress was decreased. Interestingly, 40 genes for hemocyanin were found to be downregulated after 6 h heat stress, which indicated that the immunocompetence of E. carinicauda decreased after short term thermal stress (6 h). After 24 h thermal stress, E. carinicauda showed transcriptional adaptation to high temperature by upregulating of 11 genes encoding molecular chaperones, including HSP40 and HSP90 which were firstly reported to be related to thermal stress in E. carinicauda. These results promote a better understanding of the thermal-adaptation mechanism of E. carinicauda.

Genetics of growth and survival under chronic heat stress and trade-offs with growth- and robustness-related traits in rainbow trout

Artificial selection can be advantageous for breeding fish that are better adapted to temperature changes induced by climate change. Selecting fish with better growth performance and survival under long term thermal stress would require an understanding of the level of additive genetic variation for these traits. Moreover, disentangling the genetic co-variation between growth- and robustness-related traits is key to understand potential antagonisms between selection for an increased performance and survivability. Thus, this study aimed at: i) assessing levels of genetic variation for growth and survival under chronic heat stress, and ii) evaluating the genetic relationship between these two traits and a broad range of growth- and robustness-related traits to identify potential trade-offs in rainbow trout. Phenotypic and pedigree records (n = 65,298 animals) from a rainbow trout breeding population were used. Growth and survival under chronic thermal stress were defined as the final body weight (FWHT) and days to death (TSR), after the experimental chronic exposure to high temperature (between 18 and 22 °C). Other growth-related traits analyzed here were: body weight at smolt stage (SW), harvest weight (HW), weight at processing plant (WPP), fillet weight (FW), weight of the eviscerated fish (GUW) and body weight at low temperature (FWLT). Robustness-related traits evaluated here were: resistance against Piscirickettsia salmonis (PSR) and Flavobacterium psychrophilum (FPR), and susceptibility to Caligus rogercresseyi (CS). The heritabilites estimated were: FWHT = 0.41 ± 0.14; TSR = 0.13 ± 0.05; SW = 0.54 ± 0.01; HW = 0.63 ± 0.01; WPP = 0.19 ± 0.02; FW = 0.03 ± 0.03; GUW = 0.18 ± 0.02; FWLT = 0.59 ± 0.17; FPR = 0.35 ± 0.05; PSR = 0.30 ± 0.05; and CS 0.08 ± 0.02. In general, strong compensations were identified between the robustness- and growth- related traits with genetic correlations that ranged from −0.28 to −0.98, except for resistance to F. psychrophilum and growth-related traits, which showed correlation values from 0.28 to 0.46. Genetic improvement for growth and survival under chronic upper thermal exposure is feasible. Compensations between growth- and robustness- related traits have to be accounted for when simultaneously including performance and disease resistance traits in the breeding objective.

Photoactive layer crosslinking in all-polymer solar cells: Stabilized morphology and enhanced thermal-stability

In recent years, a strong growth in power conversion efficiency of all-polymer solar cells (up to 11.0%) has been realized through extensive material and device research. For practical application, high intrinsic thermal stability of the photoactive layer is a crucial requirement for long lifetimes. In this study, two new vinyl-functionalized monomers (TPD-V, NDI-V) were synthesized as the third monomer to produce two new series of cross-linkable benzodithiophene (BDT)-thieno[3,4-c]pyrrole-4,6-dione (TPD)-based polymer donors and naphthalenediimide (NDI)-based polymer acceptors by random copolymerization. By synthetically tuning the molar content of vinyl units, the crosslinked properties of the polymers were explored. It is found that these crosslinkable polymers with small molar content of vinyl unit can be mostly crosslinked upon long-term heating. Meanwhile, by employing crosslinking of PA/PD blend, all-PSCs were fabricated and the thermal-stability were studied. As a result, the all-PSCs based both crosslinkable polymer donor PBDT-TPD-8 and acceptor PNDI-T-5 retained 86% of its highest PCE (106% of its initial PCE) without obvious burn-in efficiency loss under 24 h of continuous accelerated heating (150 °C), while the reference devices based non-crosslinkable PBDT-TPD-0/PNDI-T-0 only retained 40% of its highest PCE (51% of its initial PCE). The results demonstrate photoactive layer crosslinking can stabilize morphology under long term thermal stress leading to excellent thermal-stability of the devices.

Effect of thermal stress on the space charge distribution of 160 kV HVDC cable insulation material

The injection and accumulation of space charge in the bulk of XLPE insulation will be intensified due to the ageing of HVDC cable insulation which will affect the normal operation of the HVDC cable. In this paper, the effects of thermal stress of different endurance time and temperature on the space charge distribution of HVDC cable were studied. The samples used in the tests were all slices of 160 kV DC cable insulation and the thermal stress temperatures were 90 and 135 °C, which represented the low temperature thermal stress and high temperature stress, respectively. The Pulsed Electro-Acoustic (PEA) method was used to measure the space charge accumulation and decay characteristics of the samples. And then, the electron trap properties of the test samples were analyzed based on the PEA space charge decay model. Meanwhile, in order to further understand the influence of thermal stress on the physicochemical property of the samples, Fourier Transform Infrared Spectrum (FTIR) and Differential Scanning Calorimetry (DSC) tests were conducted in this paper. The results showed that the 90 °C thermal treating could help to improve the crystalline morphologies of the XLPE at the early stage which led to the decrease of electro traps and space charge density. However, for a much longer thermal stress, the total amount of space charge would trend to increase with the gradually degradation of the XLPE caused by long term thermal stress. Besides, the high temperature thermal stress of 135 °C caused the rapid degradation of the XLPE molecular structure, reducing the crystallinity, creating more deep traps in the insulation and resulting in the accumulation of space charge. With more deep electron traps, the de-trapping process became much more difficult and slower.

Antioxidant defenses of Onychostoma macrolepis in response to thermal stress: Insight from mRNA expression and activity of superoxide dismutase and catalase

Onychostoma macrolepis has becoming an endangered fish species in China, which population gradually declined in the past few decades due to the changing environment including elevated water temperature resulted from adverse weather events. The present study determined antioxidant defenses of O. macrolepis in response to thermal stress, aiming to understand the role of antioxidant system in adaptation of thermal stress for O. macrolepis. Experimental fish which were acclimated at 24 °C were stressed at 30 °C for 0 h, 1 h, 3 h, 6 h, 12 h, 24 h and 48 h, respectively. Change in mRNA expression of Cu/Zn superoxide dismutase (Cu/Zn-SOD) and catalase (CAT) and activity of SOD and CAT of the experimental fish with different stress time were determined. We cloned the full-length cDNA of Cu/Zn-SOD and CAT by means of RACE method, and analyzed their molecular characterization and tissue distribution. We discovered that the mRNA expression of the Cu/Zn-SOD in heart, liver, spleen, gill, intestine and the CAT in heart, liver, spleen, kidney, intestine and muscle of O. macrolepis significantly increased when water temperature increased from 24 °C to 30 °C, indicating a sensitive response of mRNA expression of Cu/Zn-SOD and CAT to the thermal stress. Moreover, the mRNA expression of the Cu/Zn-SOD and CAT were varied in different tissues, indicating different sensitivity of the tissues in response to thermal stress. Activity of the SOD in serum of O. macrolepis gradually increased from 1 h to 12 h sampling time, but significantly decreased at 24 h sampling time, compared to that of 0 h sampling time. And activity of the CAT in serum of O. macrolepis significantly decreased from 1 h to 12 h sampling time, and did not changed significantly at 24 h and 48 h sampling time, compared to that of 0 h sampling time. As such, MDA contents in the serum of O. macrolepis significantly decreased from 1 h to 6 h sampling time, but significantly increased at 12 h and 24 h sampling time, compared to that of 0 h sampling time. In summary, antioxidant system of the O. macrolepis can quickly response to short term thermal stress at 30 °C in form of both the mRNA expression of Cu/Zn-SOD and CAT and the activity of SOD and CAT, and consequently enhance the antioxidant defenses of O. macrolepis. However, thermal stress at 30 °C for 12 h-24 h seems to lead to oxidative damage of the O. macrolepis.

Temperature propagation in prismatic lithium-ion-cells after short term thermal stress

In this paper a 3D model based on the thermal material characteristics of an automotive prismatic Li–NiMnCoO2 (NMC) cell was created in COMSOL Multiphysics® in order to simulate the temperature propagation in the cell during short term thermal stress. The thermal characteristics of the battery components were experimentally determined via laser flash analysis (LFA) and differential scanning calorimetry (DSC) and used as an input parameter for the models. In order to validate the modelling approach, an experimental setup was built to measure the temperature propagation during thermal stresses within a dummy cell, equipped with temperature sensors. After validating, the model is used to describe the temperature propagation after a short-term temperature stress on automotive prismatic lithium-ion cells, simulating welding of the contact leads.

Simulation Model of a Prismatic Lithium-Ion-Battery for Temperature Propagation in the Cell after a Short Term Thermal Stress

For several years lithium-ion batteries have been commercially used in portable devices such as camcorders, laptop computers and cell phones. Battery lifetime plays only a minor role in such applications due to rapid product innovation and strong competition. However, the increasing demand for lithium-ion batteries for automotive traction applications requires drastic increase in battery life-time and safety.[1] The majority of the existing life-time and performance prognoses are based on accelerated aging tests at elevated temperatures such as 40 °C, since the temperature plays a crucial role on the battery performance, safety and life-time. However automotive lithium-ion cells must endure multiple production processes during the fabrication of a high-end traction battery system, such as contact welding, where the cells are exposed to elevated temperatures for a short period of time.[2] Up to date there is little information on the temperature propagation within the cell during the short-term thermal stress and also the influence of such short period thermal stress on the cell performance and cyclic ability. For a better understanding of the temperature propagation in the cell, a simulation model based on the thermal material characteristics of a prismatic Li-NiMnCoO2 cell was created in COMSOL Multiphysics®. The thermal characteristics of the battery components are experimentally determined using Laser Flash Analysis (LFA) and Differential Scanning Calorimetry (DSC). In order to validate the modeling approach in this work, we built an experimental setup to measure the temperature propagation within a dummy cell. This dummy cell includes a carbonate solution as electrolyte, yet without a lithium salt. After validating the model is used to describe the temperature propagation after a short-term temperature stress on automotive lithium-ion cells. Furthermore, it’s possible to predict the temperature propagation in the cell with this simulation model, after the short-term stress on different positions on the cell casing surface and at different SOC’s. [1] J. Vetter, P. Novák, M.R. Wagner, C. Veit, K.-C. Möller, J.O. Besenhard,M. Winter, M. Wohlfahrt-Mehrens, C. Vogler, A. Hammouche; Ageing mechanisms in lithium-ion batteries. J. Power Sources 147 (2005) 269–281 [2] M. Yoshio, R.J. Brodd, A. Kozawa; Lithium-Ion Batteries, Science and Technologies; Springer (2009)

Assessment of Long Term Thermal Stress on Egyptian Coral Reefs Based on Remotely Sensed Sea Surface Temperature Data

Assessment of Long Term Thermal Stress on Egyptian Coral Reefs Based on Remotely Sensed Sea Surface Temperature Data

Analysis of the Influence of a Short Term Thermal Stress on the Performance and the Characteristics of Lithium Ion Cells

For several years lithium-ion batteries have been commercially used in small portable devices such as camcorders, laptop computers, cell phones and other electronic devices. Battery lifetime plays only a minor role in such applications due to rapid innovation and strong competition. However, the increasing demand for lithium-ion batteries in the automobile market requires drastic increase in battery lifetime and safety.[1]All compounds in a lithium-ion battery are sensitive to higher temperatures. For example the electrolyte, which is critical in forming the Solid Electrolyte Interface (SEI), is extremely reactive with humid air and has the lowest boiling point of all battery compounds. Equally sensitive is the separator, which has a melting temperature of 130 to 165°C. [2] The majority of existing life-time and performance prognoses are based on long term temperature influences over numerous charging/discharging cycles (such as in a climate chamber at 40°C). Automotive lithium-ion cells must endure multiple production processes during the fabrication of a high-end battery system, such as contact welding, where the cells are exposed to elevated temperatures for a short period of time.This research analyzes the behavior and performance of lithium-ion cells after a short thermal stress. A new laboratory cell in two electrode arrangement has been developed in this study in order to perform in-situ short term thermal stress tests on both electrodes. For the current study commercially available lithium cobalt oxide (LiCoO2) cathodes, graphite anodes and an electrolyte consisting of a solution of lithium salt (e.g. LiPF6) in a mixed organic solvent have been used. This novel cell allows for the exact targeting of various components with heat. The thermal stress has been performed after the cell formation with different temperatures ranging from 60 to 250°C. Electrochemical impedance spectroscopy (EIS) has been used to detect changes, caused by the temporary thermal stress. The morphology and the 3D structure of the thermally stressed electrodes has been examined using Scanning Electron Microscope (SEM) and high resolution Computer Tomography (CT). In addition the thermal characteristics such as the thermal conductivity of the electrodes has been studied using Differential Scanning Calorimetry (DSC) and Laser Flash Analysis (LFA) in order to estimate the temperature propagation in automotive lithium-ion cells during pack assembly.[1] J. Vetter, P. Novák, M.R. Wagner, C. Veit, K.-C. Möller, J.O. Besenhard, M. Winter, M. Wohlfahrt-Mehrens, C. Vogler, A. Hammouche; Ageing mechanisms in lithium-ion batteries. J. Power Sources 147 (2005) 269–281[2] M. Yoshio, R.J. Brodd, A. Kozawa; Lithium-Ion Batteries, Science and Technologies; Springer (2009)

Regulation of Apoptotic Pathways by Stylophora pistillata (Anthozoa, Pocilloporidae) to Survive Thermal Stress and Bleaching

Elevated seawater temperatures are associated with coral bleaching events and related mortality. Nevertheless, some coral species are able to survive bleaching and recover. The apoptotic responses associated to this ability were studied over 3 years in the coral Stylophora pistillata from the Gulf of Eilat subjected to long term thermal stress. These include caspase activity and the expression profiles of the S. pistillata caspase and Bcl-2 genes (StyCasp and StyBcl-2-like) cloned in this study. In corals exposed to thermal stress (32 or 34°C), caspase activity and the expression levels of the StyBcl-2-like gene increased over time (6–48 h) and declined to basal levels within 72 h of thermal stress. Distinct transcript levels were obtained for the StyCasp gene, with stimulated expression from 6 to 48 h of 34°C thermal stress, coinciding with the onset of bleaching. Increased cell death was detected in situ only between 6 to 48 h of stress and was limited to the gastroderm. The bleached corals survived up to one month at 32°C, and recovered back symbionts when placed at 24°C. These results point to a two-stage response in corals that withstand thermal stress: (i) the onset of apoptosis, accompanied by rapid activation of anti-oxidant/anti-apoptotic mediators that block the progression of apoptosis to other cells and (ii) acclimatization of the coral to the chronic thermal stress alongside the completion of symbiosis breakdown. Accordingly, the coral's ability to rapidly curb apoptosis appears to be the most important trait affecting the coral's thermotolerance and survival.

長時間熱応力下における表面加工したSn-Ag-Cuろう付け部の寿命予測

長時間熱応力下における表面加工したSn-Ag-Cuろう付け部の寿命予測

Dopamine levels in the mosquito Aedes aegypti during adult development, following blood feeding and in response to heat stress

Dopamine, a catecholamine neurotransmitter, is important for insect development and is known to be involved in insect stress responses. In the current study, dopamine was analysed in Aedes aegypti heads by HPLC. We found that immediately after adult emergence, males have significantly higher concentrations of dopamine than females, and that dopamine concentrations decrease with age in both sexes. Dopamine levels increase in females following a blood meal suggesting that dopamine might be involved in ovarian- and/or egg-development. We also found that female mosquitoes have a higher tolerance to a short term thermal stress in a water bath than males up to 44 °C, however, both sexes die if exposed to short term temperatures between 44 and 45 °C. Finally, we did not find any indication that dopamine levels were associated with short time thermal stress response in female mosquitoes.

Hydrogen photoproduction ofA. Variabilis incorporated in a photobioreactor

H2 photoproduction and nitrogenase activities in two strains ofAnabaena variabilis marked wild type ATCC 29413 and mutant PK84 exposed to thermal stress (temperature higher than the normal incubation temperature of 30°C) were studied. Cultures of both strains collected from any interval of logarithmic growth phase exhibited high H2 photoproduction and nitrogenase activities when exposed to limited time heat shock during the assay process. In contrast, the algal H2 photoproduction rate of both strains fluctuated with long term thermal stress caused by increasing the growth temperature from 30°C to 36°C.