Role Of High Temperature Research Articles

HSP70A promotes the photosynthetic activity of marine diatom Phaeodactylum tricornutum under high temperature.

With global climate change, the high-temperature environment has severely impacted the community structure and phenotype of marine diatoms. Phaeodactylum tricornutum, a model species of marine diatom, is sensitive to high temperature, which grow slowly under high temperature. However, the regulatory mechanism of P. tricornutum in response to high-temperature is still unclear. In this study, we found that the expression level of the HSP70A in the wild type (WT) increased 28 times when exposed to high temperature (26°C) for 1 h, indicating that HSP70A plays a role in high temperature in P. tricornutum. Furthermore, overexpression and interferenceof HSP70A have great impact on the exponential growth phase of P. tricornutum under 26°C. Moreover, the results of Co-immunoprecipitation (Co-IP) suggested that HSP70A potentially involved in the correct folding of the photosynthetic system-related proteins (D1/D2), preventing aggregation. The photosynthetic activity results demonstrated that overexpression of HSP70A improves non-photochemical quenching (NPQ) activity under high-temperature stress. These results reveal that HSP70A regulates the photosynthetic activity of P. tricornutum under high temperatures. This study not only helps us to understand the photosynthetic activity of marine diatoms to high temperature but also provides a molecular mechanism for HSP70A in P. tricornutum under high-temperature stress.

Effects and Mechanisms Investigation of Heat Stress on Egg Yolk Quality in Huaixiang Chickens.

The purpose of this study was to examine the effects of high temperature on internal egg yolk quality parameters and their possible mechanisms in Huaixiang chickens. This study consisted of two treatments, and each treatment had six replicates with six birds per cage. A total of seventy-two 26-week-old female Huaixiang chickens were randomly divided into a normal-temperature group (NT) and a high-temperature group (HT) for 6 weeks. And these hens were exposed to 25 ± 2 °C and 32 ± 2 °C, respectively. Their relative humidity was maintained at 55-65%. The results showed that the HT group significantly reduced yolk weight, yolk color, and egg weight compared to the NT group (p < 0.05). Heat stress caused vacuolar degeneration of the liver and reduced the absolute liver weight (p < 0.05). Both yolk triglyceride (TG) and liver TG in the HT group were significantly higher than in the NT group (p < 0.05). However, the liver total cholesterol (TC) level in the HT group was remarkably lower than that in the NT group (p < 0.05). Additionally, heat stress remarkably enhanced SREBP-1c, ACACA, and FASN lipid metabolism-related gene mRNA expression levels in Huaixiang chicken liver after 6 weeks of heat exposure (p < 0.05). Furthermore, the HT group had remarkably reduced total amino acid, Cys, and Tyr levels in the yolk when compared with the NT group in our experiment (p < 0.05). In conclusion, heat stress causes egg yolk quality reduction and abnormal lipid metabolism in Huaixiang chickens. These findings provided novel insights into the role of high temperature on egg yolk parameters and the underlying mechanisms in Chinese indigenous laying hens.

Optimizing chemistry for designing oxidation resistant FeCrAl alloys

Traditionally, FeCrAl alloys played an important role in high-temperature applications due to their ability to form a passive Al oxide film at temperatures above ~ 800 °C. Recently, FeCrAl alloys became of interest for the application of accident tolerant nuclear fuel cladding. This study covers work done at GE Research for better understanding the role of Al, Cr, and Mo in oxidation kinetics and thermodynamics. Several models and commercial prototype alloys have been tested in hydrothermal corrosion autoclave loops, at low temperature steam exposure (~ 400 °C), high temperature steam exposure (~ 1000 °C or higher), and high temperature air exposures. The results provide insights on how chromium and aluminum play a significant role in both high temperature and low temperature oxidation of FeCrAl. Additionally, machine learning tools are used to gain further insights on both predicting future optimized chemistries for balancing the properties of hydrothermal corrosion, low and high temperature steam oxidation, and thermal aging (which is exacerbated due to radiation in a nuclear reactor environment). GE plans to use this framework to further optimize the FeCrAl alloy system for use in nuclear reactor environments.Graphical abstract

Divacancy and silicon vacancy color centers in 4H-SiC fabricated by hydrogen and dual ions implantation and annealing

Silicon carbide (SiC), as a wide-band gap semiconductor, plays an important role in high temperature and high-power devices, and the spin defect has great application prospect in quantum technology. Divacancy in SiC (VCVSi, VV) has attracted more and more attention. There are a lot of experimental studies on color center preparation by ion implantation, but the mechanism of atomic scale defects in the experimental preparation process is not fully understood. EPI epitaxial 4H–SiC was implanted with 250 keV proton at room temperature under three fluence of 1E14 cm−2, 1E15 cm−2, 1E16 cm−2. Defects of implanted 4H–SiC samples were characterized by photoluminescence spectrum and electron paramagnetic resonance (EPR). The existence of the optimal implantation fluence for VSi and VCVSi (VV) color centers by hydrogen ion implantation was found. Molecular dynamics (MD) simulation by considering the ionization energy loss for swift ion implantation were used to study the defect distribution and transformation at atomic-scale during hydrogen ion implantation and post-annealing. The optimal implantation fluence was found and confirmed by comparing the atomic-scale implantation simulation with the experimental results. In the annealing simulation, the optimal annealing temperature for the color centers in 4H–SiC was verified, and its formation mechanism was analyzed by accurately calculating the defect transformation during the annealing process. Finally, in order to accurately control the depth of color center in 4H–SiC, dual ions implantation of carbon and proton has been studied to realize the optimal divacancy yield by SRIM and MD simulations. Molecular dynamics simulation results showed that low-fluence C pre-implantation is helpful to improve the color center yield for the dual ions implantation.

The effect of high temperature on kinetics of reactive species generation in patients with type 2 diabetes

The excessive amount of reactive species under chronic inflammation, which are accompanied by an increase body temperature, lead to diabetic complications. Phagocyte NADPH oxidase is the key enzyme in these processes. The role of high temperature in its regulation in diabetes is not clear. The aim was to investigate the effect of high temperature on NADPH-oxidase-dependent generation of reactive species in diabetic patients. Chemiluminescent method was applied to assess respiratory burst kinetics initiated by opsonized zymosan in blood or phorbol ester in isolated granulocytes. Analyzing ROC curves, the main predictors and changes in stages of activation of NADPH oxidase were determined. Phosphoisoforms of p47phox and p67phox were quantified by immunoblotting. Response to opsonized zymosan was lower in all subjects at 40 °C vs 37 °C, its kinetic parameters (except Tmax) were higher in blood of patients vs controls. Response rate was the main significant predictor to distinguish groups of subjects at 40 °C indicating NADPH oxidase upregulation in diabetes. Ca2+-dependent generation of reactive species by cells increased in both groups at 40 °C vs 37 °C, kinetic parameters were higher in patients. Initial phospho-p47phox level was higher in patient cells vs ones in controls. It was increased by ionomycin, phorbol ester, or 40 °C in control cells and unchanged in patient ones. Phospho-p67phox level was unchangeable in intact cells of healthy donors and patients at both temperatures. Excessive amounts of reactive species in patient cells were the consequence of granulocyte priming due to p47phox phosphorylation. Thus, high temperature decreased phagocytosis- and enhanced Ca2+-dependent generation of reactive species making the differences between controls and patients less pronounced. The effect of temperature on the generation of reactive species in blood granulocytes is associated with activity of NADPH oxidase that can be a prospective therapeutic target for pathologies accompanied by inflammation including type 2 diabetes.

Which factor determines the optical losses in refractory tungsten thin films at high temperatures?

Refractory tungsten (W) plays an important role in high temperature photonic/plasmonic applications. Previously room temperature bulk single/poly-crystalline optical constants were extensively used to calculate the optical properties of W nanostructures at high temperatures. This might lead to a significant deviation between the predicted and measured optical properties due to the exclusion of electron–phonon interaction, as well as grain-boundary and surface-scattering.Herein, we show experimentally, how film thickness and temperature affects the optical losses in W. A drastic increase in the effective electron collision frequency is observed with decreasing the film thickness down to 5 nm, due to the grain-boundary and surface-scattering mechanisms. At sufficiently high temperatures (greater than 200 °C for W), the electron–phonon interaction eventually becomes the dominant mechanism, linearly increasing collision frequency with temperature, and it is independent of the geometry of the thin film structure. The impact of thickness and temperature-dependent optical properties of W is showcased with a hyperbolic 1D metamaterial structure acting as a thermophotovoltaic emitter. This work opens new directions in accurate prediction of the optical properties of nanostructures and design of efficient devices in various applications, such as aerospace, energy-efficient lighting, radiative cooling and energy harvesting, by incorporating thickness and temperature-dependent optical constants.

Seed tolerance to post-fire temperature fluctuation of Cerrado legume shrubs with micromorphological implications

Multiple environmental cues may break seed physical dormancy (PY) in fire-prone ecosystems, but disentangling the roles of such cues remains challenging. Current research has mostly focused on the role of high temperatures (heat shocks) in PY alleviation, while post-fire environmental conditions are less understood. Here, we examined the role of post-fire temperature fluctuation on seed germination and viability of Cerrado legume shrubs. Specifically, we investigated (1) whether PY is broken by temperature fluctuation; (2) whether seed viability is affected by temperature fluctuations; and (3) micromorphological changes in the seed coat following exposure to temperature fluctuation. Seeds of nine legume species were collected in frequently burned Cerrado savannas. We simulated post-fire temperature fluctuation in germination chambers, with daily temperature fluctuation ranging from 18 to 55 °C for 90 days; controls consisted of untreated seeds (room temperature). We conducted germination trials with unblocked and blocked hilar region of seeds. In addition, seed samples were fixed and subjected to micromorphological analysis. Instead of dormancy break, three species showed decreased seed germination for both unblocked and blocked hilar regions, while other two species showed decreased germination in blocked seeds only. Nevertheless, random cracks formed across the seed coat were found in control and treated seeds, which displayed a proportion of nondormant seeds. Within nondormant seeds, both hilar and extra-hilar regions (such as the pleurogram) may take part on water uptake. Despite the lack of dormancy break, most Cerrado legume seeds persisted viable after post-fire temperature fluctuation, thus avoiding establishment under hazardous conditions. Seed tolerance to heat shocks and post-fire temperature fluctuation likely drives regeneration from seed in burned Cerrado areas.

Synthesis of crystalline Mg2Si films by ultrafast deposition of Mg on Si(111) and Si(001) at high temperatures. Mg/Si intermixing and reaction mechanisms

Mg2Si films have been grown on Si(111) and Si(001) surfaces at ~ 387–477 °C by ultra-fast deposition in vacuum. The original pulse-type evaporator used allows Mg deposition rates of ~103–104 nm/s which provide effective accumulation of Mg on hot Si surfaces despite its fast re-evaporation. The silicide films at different stages of formation and growth have been obtained by varying the pulse duration, Mg deposit amounts and substrate temperatures. The local structure and crystal quality of the obtained Mg2Si films have been studied. The mechanism of the Mg2Si film formation and growth process is considered. The role of high temperatures in the formation of film texture is demonstrated. The existing to date experimental data on Mg–Si intermixing and Mg2Si formation are explained. Technologies of Si/Mg2Si solar cells can be based on these results.

Possible Role of High Temperature and Soil Biological Fertility on Kiwifruit Early Decline Syndrome

Kiwifruit early decline is a disorder widespread worldwide in kiwifruit orchards, worsened in the last few years, seriously affecting economic sustainability of several rural areas where kiwifruit is an important crop. The symptoms include leaf epinasty, chlorosis, desiccation and abscission, reduced fruit production, anomalous root morphology and anatomy, followed by the plant collapse and death, usually in the same or the following year after symptoms occurrence. Even though several phytopathological or agronomical studies have been carried out, a clear and univocal explanation of the causes and the possible remedies are yet to be understood. A field trial has been carried out in an experimental kiwifruit orchard, in which several soil management practices (ridging, amendment with compost, bioinoculation with selected rhizospheric microorganisms) were tested to evaluate their effect on early decline symptoms occurrence. The analysis of plant growth parameters, root morphology and anatomy, and symptoms onset were related to environmental data (air and soil temperature, soil water tension). The results pointed to a possible role and interaction between agronomic soil management and climatic conditions as the triggering factors of kiwifruit early decline syndrome.

Study on distribution, chemical states and binding energy shifts of elements on the surface of gasification fine ash

Using feed coal as a reference, a series of modern advanced analysis and measurement technologies such as X-ray photoelectron spectroscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy and X-ray diffraction have been used to analyze the gasification fine ash obtained from a pulverized coal gasification unit. The results show that the fine ash mainly consists of elemental carbon, oxygen, silicon, and aluminum. The elemental carbon distributes primarily on the foams structure, while the spherical particles mainly consisted of silicon and aluminum are embedded in the foams structure. The C1s spectrum is composed of five components in which the content of graphitized carbon is up to 38.36%, and the content of aromatic C–C or C–H, the main existing form on coal surface, is only 25.75%. The 67.31% of elemental silicon is combined with bridging oxygen (Si–O) and 32.69% of that connected to non-bridging oxygen (Si–O2). The existence of aluminum is in the form of aluminum oxides with two coordinated modes ([AlO6] and [AlO4]), and the content of [AlO6] group is nearly double that of [AlO4]. Simultaneously, the binding energies of silicon and aluminum increase by approximately 3 eV, while that of carbon almost no change because of the number of carbon atoms is significantly higher than that of other elements. The silicon atoms and aluminum atoms are surrounded by masses of carbon atoms for the special microstructure of FA. The different chemical states of carbon with higher electronegativity along with the role of high temperature and pressure make the binding energies of silicon and aluminum changed dramatically.

Deep sequencing of small RNAs reveals ribosomal origin of microRNAs in Oryza sativa and their regulatory role in high temperature

MicroRNAs are small noncoding regulatory RNAs which control gene expression by mRNA degradation or translational repression. They are significant molecular players regulating important biological processes such as developmental timing and stress response. We report here the discovery of miRNAs derived from ribosomal DNA using the small RNA datasets of 16 deep sequencing libraries of rice. Twelve putative miRNAs were identified based on highly stringent criteria of novel miRNA prediction. Surprisingly, 10 putative miRNAs (mi_7403, mi_8435, mi_12675, mi_4266, mi_4758, mi_4218, mi_8200, mi_4644, mi_14291, mi_16235) originated from rDNA of rice chromosome 9. Expression analysis of putative miRNAs and their target genes in heat tolerant and susceptible rice cultivars in control and high temperature treated seedlings revealed differential regulation of rDNA derived miRNAs. This is the first report of rDNA derived miRNAs in rice which indicates their role in gene regulation during high temperature stress in plants. Further studies in this area will open new research challenges and opportunities to broaden our knowledge on gene regulation mechanisms.

Thermal enhancement of water affinity on the surface of undoped hematite photoelectrodes

Hematite is one of the most promising semiconductors used to convert solar irradiation directly into chemical energy (molecular hydrogen and oxygen) via water splitting. Although several methods have been developed in the last decades, the repertoire of a method to fabricate hematite electrodes with a large covered area, relative low cost, industrial viability and remarkable properties still remains a challenge. This paper describes a microwave-assisted hydrothermal process to produce hematite films. The photoelectrodes prepared consisted of rods of hematite on the FTO substrate (FTO-fluorine doped tin oxide) forming mesoporous nanostructured. According to the X-ray diffraction data, thin films thermally treated at high temperature grew preferentially to the [110] direction, i.e., growth perpendicular to the substrate. Moreover, high temperature of thermal treatment influenced positively on the stability, current density and charge transfer efficiency of photoelectrodes. The impedance spectroscopy (EIS) data aided us to understand the best photoelectrochemical performance exhibited by hematite electrode synthesized during 2h with additional thermal treatment at 750°C. The high temperature treatments seem to promote higher ND (charge density) and Vfb values estimated from EIS data, which are related to an efficient photogenerated charge separation (e−−h+). Additionally, our results suggested that the hematite surface roughness and wettability should be considered as important parameters for producing active electrodes for solar water oxidation. A quasi-super hydrophilic surface observed for electrode sintered at high temperature and illustrated by contact angle images could be favoring solid/liquid interface to increase the surface efficiency for chemical reaction. Finally, this work gives a new insight into the role of high temperatures in the sintering process for the activation of pure hematite photoelectrode surface.

Effect of sintering temperature and time on the mechanical properties of Co–Cr–Mo/58S bioglass porous nano-composite

In the present study, Co–Cr–Mo/58S bioglass porous nano-composite samples were successfully produced using 30 wt% carbonate hydrogen ammonium and polyvinyl alcohol solution as space holder and binder, respectively. The cold compacted samples were heated at 175°C for 2 h and then were heated to sinter at 1100, 1150, 1200 and 1250°C for 3, 6, 9 and 12 h. True porosity of samples was measured and the samples were characterized using the X-ray diffraction (XRD) technique, scanning electron microscopy (SEM) and compressive test. Although the results of compression test for samples sintered at 1200 and 1250°C showed that the shape of stress–strain curves were similar to each other, compacted powders sintered at 1100 and 1150°C exhibited some fluctuations. Moreover, the compressive strength increased by decreasing the true porosity, indicating the role of high temperature on the sintering process. In addition, volume diffusion was predominant mechanism for these samples at sintering temperature of 1250°C. SEM images of the porous sample sintered at 1250°C for 3 h showed an appropriate range of pore sizes and interconnectivity. The XRD results showed that there are no contaminations and new phase is detectable in the sintered porous samples.

SST and ADITYA tokamak research in India

Steady state operation of tokamaks plays an important role in high temperature magnetically confined plasma research. Steady state Superconducting Tokamak (SST) programme in India deals with the development of various technologies in this direction. SST-1 [1] machine has been engineered and is being fabricated at the Institute for Plasma Research. The objectives of the machine are to study physics of plasma processes under steady state condition and develop the technologies related to steadystate operation. Various sub-systems are being prototyped and developed. SST-1 is a large aspect ratio machine with a major radius of 1.1 m and a plasma minor radius of 0.2 m with elongation of 1.7 to 1.9 and triangularity of 0.5 to 0.7. It has been designed for 1000 sec operation at 3 T toroidal magnetic eld. Neutral beam Injection and Radio frequency heating systems are being developed to heat the plasma. Lower hybrid Current Drive system would sustain 200 kA of plasma current during 1000 sec operation. ADITYA tokamak [2] has been upgraded with new diagnostics and RF heating systems. Thomson Scattering and ECE diagnostics have been operated. 200 kW Ion Cyclotron Resonance Heating (ICRH) and 200 kW Electron Cyclotron Resonance Heating (ECRH) systems have been successfully commissioned. RF assisted initial breakdown experiments have been initiated with these systems.

Studies on the particulation and percolation in ultrafine ceramic reinforced barrier layers

Discusses the particulation of organic barrier layers, based on laboratory‐bench data, obtained from the exposure of painted panels in low, high or neutral pHelectrolytes. It also discusses their compatibility with the succeeding and preceding layers and the galvanic interactions at the layer substrate interfaces. Aspects like substrate effect, leaching of the micaceous iron powder, role of high temperature and hydrodynamic disturbances and distribution of ultrafine particulates have been highlighted using potential versus time plot, AAS data, and galvanic current measurements and XRD analysis. Exposure tests conducted under ambient conditions and under very strong hydrodynamic disturbances, revealed superior properties of the SiC particulated epoxy based barrier layers.

Human exposure to sulfur dioxide and ozone in a high temperature-humidity environment

In order to examine the role of high temperature and humidity in the possible synergistic action of ozone and sulfur dioxide on human pulmonary function previously reported by some investigators and repudiated by others, we randomly exposed eight healthy young male nonsmokers to filtered air, 0.4 ppm SO2, 0.4 ppm O3, and 0.4 ppm SO2 plus 0.4 ppm O3 at 35 degrees C--85% rh for 2 hours. Subjects exercised for 15 minutes of each half hour at a workload sufficient to elicit a minute ventilation of 30 liters (BTPS). Pulmonary function tests were performed prior to, during, and following exposure. Observed alterations in pulmonary functions in the SO2 + O3 exposure reflected the changes occurring during the O3 exposure, clearly indicating that no synergistic effects related to the additional presence of SO2 were evident in this study. We considered factors suggested as causes for a potential synergism in comparing the conflicting studies on O3 and SO2, and suggest that factors other than temperature-humidity and/or sulfate aerosol production must be sought.

Fatty acids in the thermophilic alga, Cyanidium caldarium

Lipids and fatty acids were compared in 20° and 45° photoautotrophically grown Cyanidium caldarium. Glycolipids were increased by 90% in 45° as compared to 20° grown cells. Linolenic acid was the most abundant fatty acid in the 20° grown cells but was very low in the 45° cultures. The replacement of linolenic acid in glycolipids might likely be met in 45° grown cells by linoleic acid since linoleic acid was increased several fold. If polyunsaturated fatty acids play a special role in photosynthesis, it would appear that linoleic acid has assumed this role in high temperature grown cells. On the other hand, phospholipids were decreased by 40% in 45° as compared with 20° grown cells. Yet, the marked decrease in linolenic acid in phospholipids is not replaced by linoleic acid.

HEAT TOLERANCE OF LAST-INSTAR LARVAE OF THE LARCH SAWFLY, PRISTIPHORA ERICHSONII (HYMENOPTERA: TENTHREDINIDAE)

AbstractLaboratory tests of heat tolerance of last-instar larvae of the larch sawfly, Pristiphora erichsonii (Htg.), were made to provide information for the evaluation of the role of high temperature as a mortality factor in field populations.Test larvae were reared from eggs at 21 ± 1.5 °C and 50 ± 10% relative humidity. LT50's were determined at 37°, 39°, 40°, and 41 °C for larvae conditioned at 30 °C and 75% relative humidity.Larvae were less heat resistant during the first 24 hours after molting than they were 24 to 48 hours after molting. The conditioning temperature and the duration of conditioning had very significant effects on heat tolerance. Differences in acclimation due to heat treatment could not be accounted for by differences in free water content.Temperature acclimation will occur in field populations and must be considered in evaluating the role of high temperature as a natural mortality factor.Larvae may encounter lethal temperatures when wandering on branches or tree trunks or crawling on dry ground in open sunshine.