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Results for “High temperature”

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PubMed1993

Property variations of stone casts following high-temperature sterilization.

The effects of high-temperature sterilization methods (boiling, dry-heating, autoclaving and chemiclaving) on the properties of four types of stone cast were determined. SEM observations were made of the cast surface before and after sterilization. High-temperature sterilization affected the properties of the stone casts. Boiling, dry-heating and autoclaving were considered to be unacceptable methods for sterilizing stone casts before making prosthetic restorations.

Calcium Sulfate↗

PubMed2005

Effect of seedling age and water depth on morphological and physiological aspects of transplanted rice under high temperature.

To study the effect of high temperature, rice seedlings 20, 30, 40 and 50 d were kept at 5, 10, 15 and 20 cm water depth in a water pool. Meteorological findings indicated that water temperature varied up to 10 cm but became stable below this depth. Deep water inflicted higher tiller mortality, minimal increase in dry weight of aerial parts and leaf area, decrease in root length, and decrease in root dry weight especially at 20 cm water depth and produced an unbalanced T/R ratio (top versus root dry weight). However, deep water tended to increase plant length. These parameters, however, excel in shallow water. Older seedlings, with the exception of root dry weight, could not perform well compared to young seedlings in all physiological and morphological aspects. The study revealed that seedlings, particularly young ones, stand well in shallow water and can cope with high temperature.

Desiccation↗

PubMed1986

Temperature and leaf osmotic potential as factors in the acclimation of photosynthesis to high temperature in desert plants.

Seasonal changes in the high temperature limit for photosynthesis of desert winter annuals growing under natural conditions in Death Valley, California were studied using an assay based upon chlorophyll fluorescence. All species of this group were 6 to 9 degrees C more tolerant of high temperature at the end of the growing season (May) than at its beginning (February). Over this same time period, the mean daily maximum air temperatures increased by 12 degrees C. Laboratory studies have demonstrated that increases in thermal tolerance could be induced by increasing growth temperature alone. For plants growing under field conditions there was also a good correlation between the thermal tolerance of leaves and the osmotic potential of leaf water, indicating that increases in the concentrations of some small molecules might also confer increased thermal tolerance. Isolated chloroplast thylakoids subjected to increasing concentrations of sorbitol could be demonstrated to have increased thermal tolerance.

Journal Article↗

PubMed1997

Filamentary microstructure and linear temperature dependence of normal state transport in optimized high temperature superconductors.

A filamentary model of "metallic" conduction in layered high temperature superconductive cuprates explains the concurrence of normal state resistivities (Hall mobilities) linear in T (T-2) with optimized superconductivity. The model predicts the lowest temperature T0 for which linearity holds and it also predicts the maximum superconductive transition temperature Tc. The theory abandons the effective medium approximation that includes Fermi liquid as well as all other nonpercolative models in favor of countable smart basis states.

Journal Article↗

PubMed2006

A vulnerability study of the low-income elderly in the context of high temperature and mortality in Seoul, Korea.

INTRODUCTION: We investigated the impact of environmental high temperature on mortality in Seoul, Korea, and the consequences of high temperature-induced mortality with a focus on the low-income elderly. METHODS: Changes in the risk of death by age and income were estimated by a 1 degrees C increase in temperature using a generalized additive model adjusting for non-temperature related factors: time trends, seasonality, and air pollution. The study covered the years of 2000, 2001, and 2002. RESULTS: We found that income and age were potential factors in high-temperature-induced excess mortality. Evidences to support these results are as follows: first, regarding the effect of an economic factor in the association between mortality and high temperature, the study shows that the mortality rate of the low-income group is higher, by as much as 1.3- to 1.7-fold, than that of the general population. Second, taking age into consideration, the mortality of low-income elderly people is 1.5-fold higher than that of the whole low-income group. The combined effect of income and age on mortality is estimated as 2.3-fold higher than that of the general population. But the results of the low-income and elderly group were not statistically significant due to wide standard deviation. CONCLUSIONS: The relationship between high-temperature-induced excess mortality, income, and age suggests the need for a public health message, yet many results were not statistically significant: preventive and health care interventions need to be administered to the elderly and low-income group during periods of high temperature.

Adaptation, Physiological↗

PubMed2005

High-temperature microfluidic synthesis of CdSe nanocrystals in nanoliter droplets.

The high-temperature synthesis of CdSe nanocrystals in nanoliter-volume droplets flowing in a perfluorinated carrier fluid through a microfabricated reactor is presented. A flow-focusing nanojet structure with a step increase in channel height reproducibly generated octadecene droplets in Fomblin Y 06/6 perfluorinated polyether at capillary numbers up to 0.81 and with a droplet:carrier fluid viscosity ratio of 0.035. Cadmium and selenium precursors flowing in octadecene droplets through a high-temperature (240-300 degrees C) glass microreactor produced high-quality CdSe nanocrystals, as verified by optical spectroscopy and transmission electron microscopy. Isolating the reaction solution in droplets prevented particle deposition and hydrodynamic dispersion, allowing the reproducible synthesis of nanocrystals at three different temperatures and four different residence times in the span of 4 h. Our synthesis of a wide range of nanocrystals at high temperatures, high capillary numbers, and low viscosity ratio illustrates the general utility of droplet-based microfluidic reactors to encapsulate nanoliter volumes of organic or aqueous solutions and to precisely control chemical or biochemical reactions.

Cadmium Compounds↗

PubMed2000

[High temperature Raman spectroscopic study of the structure of sodium disilicate crystal, glass and its melt].

The structure of Na2Si2O5 from room temperature up to 1,773 K are studied by high temperature Raman spectroscopy using copper vapor pulse laser and integral time-resolved detection technique without any black-body radiation effect on spectral record. Back-scattering optical configuration is coupled with confocal collection of Raman signal of macro-sample in the high temperature shaft tube furnace. Results show that temperature-dependent Raman spectra can clearly indicate phase transition during melting. Relative densities of various kinds of SiO4(n-4) (n, bridging-oxygen number binding to one tetrahedron former Si) tetrahedrons can be qualitatively and quantitatively resolved by Gaussian spectral deconvolution. Obviously high temperature Raman spectroscopy provides an useful tool for the micro-structure research of materials under high temperature.

Crystallization↗

PubMed2004

Increase in Ty1 cDNA recombination in yeast sir4 mutant strains at high temperature.

Transposition of the Ty1 element of the yeast Saccharomyces cerevisiae is temperature sensitive. We have identified a null allele of the silent information regulator gene SIR4 as a host mutant that allows for transposition at high temperature. We show that the apparent increase in transposition activity in sir4 mutant strains at high temperature is dependent on the RAD52 gene and is thus likely resulting from an increase in Ty1 cDNA recombination, rather than in IN-mediated integration. General cellular recombination is not increased at high temperature, suggesting that the increase in recombination at high temperature in sir4 mutants is specific for Ty1 cDNA. Additionally, this high-temperature Ty1 recombination was found to be dependent on functional Sir2p and Sir3p. We speculate that the increase in recombination seen in sir4 mutants at high temperature may be due to changes in chromatin structure or Ty1 interactions with chromosomal structures resulting in higher recombination rates.

DNA, Complementary↗

PubMed2005

Investigation on SAW properties of LGS and optimal cuts for high-temperature applications.

A promising perspective for surface acoustic wave (SAW) device applications at high temperature has been opened by langasite (LGS). The SAW properties of LGS in singly and doubly rotated cuts at 250 degrees C are investigated. Three noticeable regions for SAW-cut orientations and propagation directions at high temperature are put forward and are defined by Euler angles [0 degrees, 20 degrees --> 50 degrees, 35 degrees --> 45 degrees], [0 degrees, 85 degrees --> 110 degrees, 0 degrees --> 5 degrees], and [0 degrees, 138 degrees --> 145 degrees, 20 degrees --> 23 degrees], respectively. The first region includes zero or comparatively reduced temperature coefficient of delay (TCD) (<2 ppm) and smaller electromechanical coupling factor (K2) (0.2%-0.35%); the second one exhibits higher K2 (0.35%-0.45%) and moderate TCD (<5 ppm); and the highest K2 (>0.45%) and larger TCD (25-30 ppm) characterize the last region. For some typical orientations within the above-mentioned three regions, the temperature dependency of SAW characteristics (up to 1000 degrees C) is discussed. The second region [0 degrees, 85 degrees --> 110 degrees, 0 degrees --> 5 degrees], especially the orientation [0 degrees, 90 degrees, 0 degrees], has better comprehensive characteristics of SAW and is more suitable for high-temperature applications. Therefore, we should give a top priority to the orientation [0 degrees, 90 degrees, 0 degrees] in the design of SAW devices operating at high temperature. Comparison between published experimental results and numerical predictions based on LGS constants and their temperature coefficients available in the literature reveals that the theoretical results of TCD under 250 degrees C are in agreement with the experimental ones (the relative error of TCD is within 10%).

Journal Article↗

PubMedDate not supplied

Effect of pH on high-temperature production of bacterial penicillin acylase in Escherichia coli.

High-temperature-oriented production of bacterial penicillin acylase (PAC), which is usually expressed at low temperatures (less than 30 degrees C), was demonstrated in this study via heterologous expression of the Providencia rettgeri (P. rettgeri) pac gene in Escherichia coli (E. coli). While it is possible to produce PAC at a temperature as high as 37 degrees C, the environmental condition (specifically, culture pH) critically affected culture performance. Production of PAC at 37 degrees C was feasible only when culture pH was close to neutral (i.e., 6.5-7.5). Outside this pH range, cell physiology for the host/vector system was seriously affected, resulting in poor culture performance. In acidic culture environments, temperature significantly affected the pac expression level and specific PAC activity decreased with an increase in culture temperature. In basic culture environments, cell growth was seriously inhibited though the pac expression level was minimally affected by temperature. Such unusual types of pH and temperature effects on pac expression were never reported for bacterial PACs. The results suggest that culture pH should be precisely controlled for the current host/vector systems being applied on the overproduction of P. rettgeri PAC in E. coli at high temperatures.

Escherichia coli↗

PubMed2002

High-temperature gas chromatography-mass spectrometry with glass capillary columns for the screening of natural products.

High-temperature high resolution gas chromatography (HT-HRGC) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS) are powerful but relatively unexplored tools for the analysis of crude extracts and fractions of natural products. To illustrate the scope of the technique the direct characterization of several compounds, present in crude extracts of leaves and stems of Croton hemiargyreus Muell. Arg. var. hemiargyreus was undertaken, without derivatization or clean-up procedures. Both practical aspects and limitations of HT-HRGC and HT-HRGC-MS were evaluated resulting in a simple, straightforward and extremely powerful technique for the analysis of complex mixtures.

Biological Products↗

PubMed2004

Resistance of early midgut stages of natural Plasmodium falciparum parasites to high temperatures in experimentally infected Anopheles gambiae (Diptera: Culicidae).

We studied the effects of high temperature, 30 and 32 versus 27 C on early Plasmodium falciparum development in Anopheles gambiae experimentally infected with gametocytes from 30 volunteers with mean density of 264.1 gametocytes/microl blood (range: 16-1,536/microl). From several batches of mosquitoes, fed by membrane feeding, midguts of individual mosquitoes were dissected at 24 hr for ookinete enumeration and at 7 days to quantify oocysts. There were temperature-related differences in mean ookinete intensity per mosquito midgut, with 9.71 +/- 1.6 at 27 C, 9.85 +/- 2.32 at 30 C, and 3.89 +/- 0.81 at 32 C. The prevalence of oocyst infection decreased with an increase in temperatures from 15.9 to 8.5 to 6.4% at 27, 30, and 32 C, respectively. The average oocyst intensities for the infected mosquitoes increased with temperatures from 2.9 at 27 C to 3.5 at 30 C, and to 3.3 at 32 C. However, the success of infections was reduced at 30 and 32 C, and resulted in greater losses during consecutive inter-stage parasite development. The most significant impact of high temperatures occurred at the transition between macrogametocytes and ookinetes, whereas the transition between ookinetes and oocysts apparently was not affected. In contrast to other reports, exposure of mosquitoes infected with natural parasites to high temperatures did not eliminate preoocyst stages, as has been observed from laboratory studies using the NF-54 strain of P. falciparum. This observation of parasite resistance to high temperatures is consistent with the natural situation in tropical environments where perennial malaria transmission occurs during hot dry seasons.

Adolescent↗

PubMed2001

Evolutionary adaptation to temperature. IX. Preadaptation to novel stressful environments of Escherichia coli adapted to high temperature.

Stressful environments may be considered as those that reduce fitness, sometimes due in part to the increased metabolic expenditure required to sustain life. Direct adaptation to a stressor is expected to increase fitness and reduce maintenance metabolism, with the latter leading to increased biomass production. In this study, we test the general hypothesis that such adaptation to one stressor can preadapt organisms to novel stressful environments. Six lines of Escherichia coli propagated for 2,000 generations at 41-42 degrees C (42 group), a stressful temperature, were compared to six control lines propagated for 2,000 generations at 37degrees C (37 group) and to the common ancestor of both groups. We assayed biovolume yield (a measure of growth efficiency) and competitive fitness in the 42 group's selective high temperature environment as well as five novel stressful environments-acid, alkali, ethanol, high osmolarity and peroxide. As previously reported, at high temperature the 42 group had both higher yield and fitness than the 37 group and ancestor. In the novel environments, the 42 group generally produced yields higher than the 37 group (and marginally higher than the ancestor), but we found no differences in competitive fitness among the 37 and 42 groups and the ancestor. We also found that the performance of lines within groups was not correlated across stressful environments for either yield or relative fitness. Because previous adaptation to one stressor did not improve our measure of Darwinian fitness in novel stressful environments, we conclude that the 42 group shows no useful pre-adaptation, or cross-tolerance, to these types of environments.

Adaptation, Physiological↗

PubMed2025

High temperature induces MdGATA15 to suppress anthocyanin accumulation in apple peels.

Although GATA transcription factors are known to play broad roles in plant growth, development, and stress responses, their involvement in high-temperature-induced anthocyanin suppression remains largely unexplored. In this study, using "Otome" as the experimental material, we revealed the important role of MdGATA15 in inhibiting anthocyanin accumulation under high temperature through multiple molecular mechanisms. A series of physiological and biochemical experiments demonstrated that MdGATA15 directly binds to the promoters of anthocyanin activators MdMYB11, MdANS, and the transporter gene MdGSTF12, repressing their expression. Simultaneously, MdGATA15 activates the expression of the anthocyanin biosynthesis repressor MdMYB308, further enhancing the inhibition. Notably, MdGATA15 binds to its own promoter, forming a positive feedback loop that significantly enhances its expression under high-temperature conditions. This mechanism provides new insights into understanding how apple responds to high-temperature stress. Additionally, we identified the bHLH transcription factor MdPIF4-Like3 in apple as an interactor of MdGATA15, which stabilizes and enhances the transcriptional activity of MdGATA15, thereby further reinforcing the inhibition of anthocyanin biosynthesis. These findings highlight the central role of MdGATA15 in high-temperature-mediated suppression of anthocyanin synthesis in apple and provide significant advances in understanding the molecular mechanisms of apple's response to heat stress. This study provides a theoretical basis for breeding heat-resistant apple cultivars with improved fruit quality by targeting key transcription factors involved in high-temperature stress response.

Anthocyanins↗

PubMed1992

Effects of high temperature on growth and efficiency of male and female broilers from lines selected for high weight gain, favorable feed conversion, and high or low fat content.

Male and female broiler chicks from five different broiler crosses (WI, LF, and HF = Israeli chicks selected for high body weight gain, and low and high abdominal fat, respectively; FC and WN = Dutch chicks selected for favorable feed conversion and high body weight gain, respectively) were raised at a high ambient temperature (32 to 33 C). Weight gain, protein and fat content in the carcass and feed, and protein efficiency were determined at 4, 6, and 8 wk of age. The effect of the high temperature was evaluated by comparing these data with those of similar chicks raised at a normal temperature (20 to 33 C) up to 6 wk of age. The reductions in body weight, protein gain, and feed and protein efficiency due to the high temperature increased with age and were much larger in males than in females. This trend was more pronounced in WI and WN chicks than in LF, HF, and FC chicks. Females of WI and WN crosses were as heavy as males at 6 wk and heavier at 8 wk. In LF, HF, and FC crosses, both sexes had similar weights at 8 wk. Growth reduction due to the high temperature was largest in the groups with the highest growth rate at the normal temperature (WI and WN males). Chicks with a lower growth rate and a higher capacity for energy storage in fat depots (all females, HF chicks), or a higher capacity for heat loss (FC chicks), were less affected by the high temperature. The results suggest that females should be preferred over males for broiler production in hot facilities or locations. Broiler genotypes selected for feed efficiency at the expense of fast growth may allow for a more profitable broiler production in high-temperature regions.

Adipose Tissue↗

PubMed2005

Genetic engineering of the biosynthesis of glycinebetaine enhances photosynthesis against high temperature stress in transgenic tobacco plants.

Genetically engineered tobacco (Nicotiana tabacum) with the ability to synthesis glycinebetaine was established by introducing the BADH gene for betaine aldehyde dehydrogenase from spinach (Spinacia oleracea). The genetic engineering enabled the plants to accumulate glycinebetaine mainly in chloroplasts and resulted in enhanced tolerance to high temperature stress during growth of young seedlings. Moreover, CO2 assimilation of transgenic plants was significantly more tolerant to high temperatures than that of wild-type plants. The analyses of chlorophyll fluorescence and the activation of Rubisco indicated that the enhancement of photosynthesis to high temperatures was not related to the function of photosystem II but to the Rubisco activase-mediated activation of Rubisco. Western-blotting analyses showed that high temperature stress led to the association of Rubisco activase with the thylakoid membranes from the stroma fractions. However, such an association was much more pronounced in wild-type plants than in transgenic plants. The results in this study suggest that under high temperature stress, glycinebetaine maintains the activation of Rubisco by preventing the sequestration of Rubisco activase to the thylakoid membranes from the soluble stroma fractions and thus enhances the tolerance of CO2 assimilation to high temperature stress. The results seem to suggest that engineering of the biosynthesis of glycinebetaine by transformation with the BADH gene might be an effective method for enhancing high temperature tolerance of plants.

Betaine↗

PubMed2004

Response to water deficit and high temperature of transgenic peas (Pisum sativum L.) containing a seed-specific alpha-amylase inhibitor and the subsequent effects on pea weevil (Bruchus pisorum L.) survival.

The effects of water deficit and high temperature on the production of alpha-amylase inhibitor 1 (alpha-AI-1) were studied in transgenic peas (Pisum sativum L.) that were developed to control the seed-feeding pea weevil (Bruchus pisorum L., Coleoptera: Bruchidae). Transgenic and non-transgenic plants were subjected to water-deficit and high-temperature treatments under controlled conditions in the glasshouse and growth cabinet, beginning 1 week after the first pods were formed. In the water-deficit treatments, the peas were either adequately watered (control) or water was withheld after first pod formation. The high-temperature experiments were performed in two growth cabinets, one maintained at 27/22 degrees C (control) and one at 32/27 degrees C day/night temperatures, with the vapour pressure deficit maintained at 1.3 kPa. The plants exposure to high temperatures and water deficit produced 27% and 79% fewer seeds, respectively, than the controls. In the transgenic peas the level of alpha-AI-1 as a percentage of total protein was not influenced by water stress, but was reduced on average by 36.3% (the range in two experiments was 11-50%) in the high-temperature treatment. Transgenic and non-transgenic pods of plants grown at 27/22 degrees C and 32/27 degrees C were inoculated with pea weevil eggs to evaluate whether the reduction in level of alpha-AI-1 in the transgenic pea seeds affected pea weevil development and survival. At the higher temperatures, 39% of adult pea weevil emerged, compared to 1.2% in the transgenic peas grown at the lower temperatures, indicating that high temperature reduced the protective capacity of the transgenic peas.

Acclimatization↗

PubMed1983

Molecular cloning and expression of a gene that controls the high-temperature regulon of Escherichia coli.

The high-temperature production (HTP) regulon of Escherichia coli consists of a set of operons that are induced coordinately by a shift to a high temperature under the control of a single chromosomal gene called htpR or hin. To identify more components of this regulon, the rates of synthesis of many polypeptides resolved on two-dimensional polyacrylamide gels were measured in various strains by pulse-labeling after a temperature shift-up. A total of 13 polypeptides were found to be heat inducible only in cells bearing a normal htpR gene on the chromosome or on a plasmid; on this basis these polypeptides were designated products of the HTP regulon. Several hybrid plasmids that contain segments of the E. coli chromosome in the 75-min region were found to carry the htpR gene. A restriction map of this region was constructed, and selected fragments were subcloned and tested for the ability to complement an htpR mutant. The polypeptides encoded by these fragments were detected by permitting expression in maxicells, minicells, and chloramphenicol-treated cells. Complementation was accompanied by production of a polypeptide having a molecular weight of approximately 33,000. This polypeptide, designated F33.4, was markedly reduced in amount in an htpR mutant expected to contain very little htpR gene product. Polypeptide F33.4 is postulated to be the product of htpR and to be an effector that controls heat induction of the HTP regulon.

Bacterial Proteins↗