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At least 775 records · Page 43Linked to original sources
PubMed2004

[Effect of long-term suboptimal temperature and short-term low temperature under low light density on cucumber growth and its photosynthesis].

The study on the effects of long-term suboptimal temperature (T1) and short-term low temperature (T2) under low light density on cucumber seedling's growth and its photosynthesis showed that the growth speed, photosynthetic rate (Pn), carboxylation efficiency (CE), apparent quantum yield (AQY) and actual quantum yield of P(S II) electron transport (phi(PS II)) all declined remarkably, and the photochemical efficiency of PS II (Fnu/Fm) also decreased to some extent. The decreasing extents of Pn, CE and AQY of T1 were less than those of T2, while the recovery rate of T1 was slower than that of T2. The Fnu/Fm and phi(PS II) of T1 declined to less extent and resiled quickly, while those of T2 decreased to larger extent and recovered slowly. The contents of chlorophyll a, chlorophyll b and carotenoid of T1 increased remarkably after being treated, while those of T2 decreased evidently. The Chl a/b of both T1 and T2 declined remarkably. With recovery time going, the pigment of T1 declined under most conditions, while that of T2 increased gradually. Three days later, the pigment content of T1 and T2 were both higher than control. The Chl a/b had no significant change during the recovery period, and was still obviously lower than control.

Cucumis sativus↗
PubMed2005

[Comparison of non-protected fluid room temperature phosphorescence and micellar-stabilized room temperature phosphorescence properties of indole-3-butyric acid].

For indole-3-butyric acid (IBA), the non-protected fluid room temperature phosphorescence (NP-RTP) and the fluid room temperature phosphorescence with polymeric dispersant polyethyleneglycol-200 (PEG-200), PEG-400 or non-ionic surfactant Tween-20, Tween-40, Tween-80, Tween-85, Brij35 and emulsifier OP as a medium have been studied in detail. When the surfactants or polymeric dispersants were added to the NP-RTP system, the profile of RTP spectrum was not changed, but the RTP intensity and the pre-irradiation time required to attain a stable RTP signal were increased. Whether the surfactants or polymeric dispersants were added to the system or not, no RTP signal was observed when TlNO3 was used as a heavy atom perturber (HAP), but intense RTP emissions were observed when KI was present as HAP. Recoveries of 95.2%-104% with relative standard deviations of 2.4%-4.0% were obtained in spiked water and soil samples.

Indoles↗
PubMed1974

Temperature-sensitive mutants of Escherichia coli B which can grow in high-osmotic medium at the nonpermissive temperature.

Two temperature sensitive (TS) mutants (C4 tos and D2 tos) were isolated after mutagenesis of E. coli B/SM by N-methyl-N'-nitro-N-nitrosoguanidine (NMNG), which can grow even at 42 C in high-osmotic medium supplemented by addition of sucrose, NaCl or other compounds. Neither of the mutants lyzed when transferred to low-osmotic medium after growning at the nonpermissive temperature in high osmotic medium. One of these mutants, C4 tos, grew at 42 C in a long filamentous form. When bacteria growing exponentially at 30 C were shifted to 42 C, they continued to grow at a reduced rate even in low-osmotic medium. This strain could also grow or start to grow in low-osmotic medium when supplied with a factor or factors secreted from growing bacteria of another strain. This mutant strain could grow in low-osmotic medium at 42 C when it was cultured anaerobically. The other mutant strain obtained (D2 tos) displayed normal morphology even when grown at 42 C. When it was shifted from 30 to 42 C in low-osmotic medium, increase of mass, measured as optical density, continued for a while, but viability, measured as the number of colony-formers, stopped increasing and then decreased rapidly.

Acridines↗
PubMed1966

Environmental temperature and choline requirement in rats. I. Choline deficiency in rats at various temperatures.

Rats were maintained at 2 degrees, 21 degrees, and 33 degrees for 3 weeks on a choline-supplemented or a choline-deficient diet. In contrast to the findings of some other workers, choline deficiency produced fatty livers at all temperatures. The ratio of the total liver lipid to the total food intake was the same in all choline-supplemented rats. In choline-deficient rats this ratio was always higher and varied directly with temperature.

Animals↗
PubMed1980

Temperature sensitive phosphoproteins in rat cells transformed by a temperature sensitive mutant of rous sarcoma virus.

The localization of the src-encoded protein kinase was examined by fractionating cellular extracts from rat cells transformed by a wild type and a temperature-sensitive mutant of Rous sarcoma virus (SR-A 3Y1 and ts68 3Y1 cells). It was found to be specifically localized in the post-microsomal supernatant (PMS) fraction. Furthermore, it was noticed that a protein with a molecular weight of 16,000 (16K-protein) in the PMS fraction was phosphorylated in vitro when the PMS fraction from ts68 3Y1 cells was preincubated at 33 degrees C, but not at 42 degrees C. This protein was phosphorylated when the fraction from SR-A 3Y1 cells was preincubated at 33 degrees C and at 42 degrees C. Similar temperature-sensitive phosphorylation of 16K-protein was also observed in the PMS fraction from ts68 3Y1 cells labeled in vivo with [32P]orthophosphate at 33 degrees C. These results suggest that this 16K-protein might be a candidate for the endogenous acceptor for the src-encoded protein kinase.

Animals↗
PubMed1983

Effect of temperature changes in acrylic cement on prosthetic implant surgery. An investigation into the relationship between quantity and temperature changes at different levels on loosening of the implant.

Loosening of the prosthetic stem is one of the most frequent problems in arthroprosthetic replacement. Fixation at the bone/cement interface is therefore of crucial importance. This can be affected by several factors, one of which is the heat generated in the acrylic cement, which may exceed the level at which tissue viability is affected. The authors therefore investigated this phenomenon in theoretical models. These were related to the level and duration of temperature changes at four levels - inside the cement and at the interfaces between cement, implant, spongy bone and cortical bone. Graphs showing temperature peaks and duration are constructed in all the varying conditions and their implications discussed. These concern the viability of osteocytes and vascular tissue, and the mechanical strength of the cement. The implications on design and surgical technique are obvious and point to the need to use the thinnest layer of cement compatible with firm fixation.

Acrylates↗
PubMed1993

A temperature sensitive topoisomerase II allele confers temperature dependent drug resistance on amsacrine and etoposide: a genetic system for determining the targets of topoisomerase II inhibitors.

We have developed a simple system for determining the specific contribution of topoisomerase II targeting to the cytotoxic activity of a drug. We have constructed yeast strains that are permeable to anti-topoisomerase II drugs, carry a DNA repair mutation, rad52, and also have a temperature sensitive topoisomerase II mutation, top2-1. Strains carrying the top2-1 mutation have nearly normal topoisomerase II activity at 25 degrees C but less than 10% of wild type activity at 36 degrees C. We find that at a semi-permissive temperature (30 degrees C), there is sufficient topoisomerase II activity for viability; but since the topoisomerase II activity is greatly reduced, the cells are very resistant to anti-topoisomerase II drugs. Conversely, such cells are hypersensitive to the topoisomerase I inhibitor camptothecin. These results provide strong support for the model that drug stabilized DNA cleavage, rather than a lack of enzyme activity, is responsible for cell killing by eukaryotic anti-topoisomerase II agents. They also show that there is a minimum level of topoisomerase II activity in yeast that is consistent with viability but also allows a high degree of resistance to anti-topoisomerase II agents.

Alleles↗
PubMed1996

Heat-shock treatment reduces in situ temperature in yeast at sub-lethal high temperature.

Cells from the yeast Schizosaccharomyces pombe IFO-0342, once heat shocked and then treated with ultra-centrifugation showed a significant increase in tolerance compared to non heat-shocked control cells as estimated by colony forming unit (CFU). Fluorescence microscopical observation of these treated cells when stained with DAPI revealed that in non heat-shocked cells the chromatin regions were dislocated to one end due to the acceleration force of gravity. However, prior heat-shocked cells or 2.0 M glycerol suspended cells showed normal localization. From these results, it has been postulated that the interior part of the heat-shocked cells becomes viscous, and that in situ the temperature of the cell interior part might be reduced under semi-lethal high temperature.

Hot Temperature↗
PubMed1990

Brain and core temperatures and peripheral vasomotion during sleep and wakefulness at various ambient temperatures in the rat.

Changes in brain, core and tail skin temperatures (Tbr, Tc and Tt) associated with transitions in the arousal states were recorded in rats throughout the 24-h diurnal cycle at 10 degrees C, 21 degrees C and 29 degrees C. Falling asleep was accompanied by decreases in both Tbr and Tc and vasodilation at 10 degrees C and 21 degrees C. At 29 degrees C, tail vessels were permanently dilated, and further dilation was not found on sleep onset. Tbr and Tc, however, continued to decrease during non-rapid-eye-movement sleep (NREMS); these changes are likely to result from reductions in heat production and increased conductive heat loss. The changes in Tbr, Tc and Tt on awakening mirrored those on falling asleep. It is suggested that the suppression of sleep in the cold and the enhancement of NREMS in the heat promote thermoregulation. Rapid-eye-movement sleep (REMS) was associated with sharp rises in Tbr. The rise in Tbr was the largest in the cold and was attenuated at 29 degrees C. Tc decreased and Tt increased in the cold, whereas Tc tended to increase and Tt to decrease in the heat. The paradoxical peripheral vasomotion during REMS supports previous suggestions on severe thermoregulatory impairment during REMS in other species.

Animals↗
PubMed1995

Effect of adrenal medullectomy on responses in heat production, plasma catecholamines and body temperature of burned rats to changes in the temperature of the hypothalamus.

Burn (B) and control (C) rats with and without adrenal medullectomy (Adx) 9-11 days postburn underwent warning and cooling of the preoptic anterior hypothalamus (POAH) during calorimetry at 22 degrees and 28 degrees C ambient. Blood was drawn for catecholamine assay during each displacement of the POAH temperature (Thy). The heat production (Hp) for the AdxB group at 22 degrees and 28 degrees C was not different from the Hp for the sham AdxB group (80 +/- 4 vs 86 +/- 8 at 22 degrees C, 58 +/- 8 vs 64 +/- 7 W/m2 at 28 degrees C) in spite of there being no detectable circulating epinephrine (E) for the AdxB groups. Cooling of the POAH of the AdxB 22 degrees C group, however, did not induce a further increment in Hp, in contrast to all other groups. Thy demonstrated good significant negative linear correlation with Hp for all groups. The resulting slopes were not significantly different from one another, indicating no difference in thermal sensitivity of the POAH between the groups. In four of eight groups plasma norepinephrine (NE) demonstrated positive correlation with Hp and in five of eight groups negative correlation with Thy, Plasma E values did not correlate with Hp and demonstrated negative correlation with Thy in two of four possible groups. These data show that postburn hypermetabolism is not dependent on E in the rat and suggest that NE may be calorigenic in burned rats.

Adrenal Medulla↗
PubMed2005

High-temperature, high-pressure hydrothermal synthesis, crystal structure, and solid-state NMR spectroscopy of Cs2(UO2)(Si2O6) and variable-temperature powder X-ray diffraction study of the hydrate phase Cs2(UO2)(Si2O6) x 0.5H2O.

A new uranium(VI) silicate, Cs2(UO2)(Si2O6), has been synthesized by a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction and solid-state NMR spectroscopy. It crystallizes in the orthorhombic space group Ibca (No. 73) with a = 15.137(1) A, b = 15.295(1) A, c = 16.401(1) A, and Z = 16. Its structure consists of corrugated achter single chains of silicate tetrahedra extending along the c axis linked together via corner-sharing by UO6 tetragonal bipyramids to form a 3-D framework which delimits 8- and 6-ring channels. The Cs+ cations are located in the channels or at sites between channels. The 29Si and 133Cs MAS NMR spectra are consistent with the crystal structure as determined from X-ray diffraction, and the resonances in the spectra are assigned. Variable-temperature in situ powder X-ray diffraction study of the hydrate Cs2(UO2)(Si2O6) x 0.5H2O indicates that the framework structure is stable up to 800 degrees C and transforms to the structure of the title compound at 900 degrees C. A comparison of related uranyl silicate structures is made.

Journal Article↗
PubMed2006

Temperature-controlled growth of ZnO nanowires and nanoplates in the temperature range 250-300 degrees C.

Starting from a mixture of Zn and BiI3, we grew nanowires and nanoplates on an oxidized Si substrate at relatively low temperatures of 250 and 300 degrees C, respectively. The ZnO nanowires had diameters of approximately 40 nm and grew along the [110] direction rather than the conventional [0001] direction. The nanoplates had thicknesses of approximately 40 nm and lateral dimensions of 3-4 microm. The growth of both the nanowires and nanoplates is dominated by the synergy of vapor-liquid-solid (VLS) and direction conducting. Analysis of photoluminescence spectra suggested that the nanoplates contain more oxygen vacancies and have higher surface-to-volume ratios than the nanowires. The present results clearly demonstrate that the shapes of ZnO nanostructures formed by using BiI3 can be controlled by varying the temperature in the range 250-300 degrees C.

Journal Article↗
PubMed1999

Low-temperature sensitivity and enhanced Bohr effect in red deer (Cervus elaphus) haemoglobin: a molecular adaptive strategy to life at high altitude and low temperature.

A study of the functional properties of haemoglobin from red deer (Cervus elaphus) whose habitat varies over a wide range of latitude, was performed. The oxygen-binding properties of the most common haemoglobin phenotype from the species living in Sardinia were examined with particular attention to the effect of pH, chloride, 2, 3-bisphosphoglycerate and temperature. Results indicate that red deer haemoglobin, like all haemoglobins from ruminants so far examined, is characterized by a low intrinsic oxygen affinity, with chloride being its main physiological modulator in vivo. The functional results and the low temperature sensitivity of the oxygen affinity are discussed in the light of the amino acid sequence of closely related ruminant haemoglobins.

Adaptation, Physiological↗
PubMed2006

Electron attachment to POCl3: measurement and theoretical analysis of rate constants and branching ratios as a function of gas pressure and temperature, electron temperature, and electron energy.

Two experimental techniques, electron swarm and electron beam, have been applied to the problem of electron attachment to POCl3, with results indicating that there is a competition between dissociation of the resonant POCl3-* state and collisional stabilization of the parent anion. In the electron beam experiment at zero electron energy, the fragment ion POCl2- is the dominant ion product of attachment (96%), under single-collision conditions. Small amounts (approximately 2% each) of POCl3- and Cl- were observed. POCl3- and POCl2- ion products were observed only at zero electron energy, but higher-energy resonances were recorded for POCl-, Cl-, and Cl2- ion products. In the electron swarm experiment, which was carried out in 0.4-7 Torr of He buffer gas, the parent anion branching ratio increased significantly with pressure and decreased with temperature. The electron attachment rate constant at 297 K was measured to be (2.5+/-0.6)x10(-7) cm3 s(-1), with ion products POCl2- (71%) and POCl3- (29%) in 1 Torr of He gas. The rate constant decreased as the electron temperature was increased above 1500 K. Theory is developed for (a) the unimolecular dissociation of the nascent POCl3-* and (b) a stepladder collisional stabilization mechanism using the average energy transferred per collision as a parameter. These ideas were then used to model the experimental data. The modeling showed that D0 o(Cl-POCl2-) and EA(POCl3) must be the same within +/-0.03 eV.

Journal Article↗
PubMed1978

A temperature sensitive mutant of Escherichia coli which does not allow replication of RNA phage at a high temperature.

A conditional mutant, referred to as RepR43, was isolated from Escherichia coli W2252 by N-methyl-N'-nitro-N-nitroso-guanidine mutagenesis. Although RepR43 does not permit growth of RNA phage beta at the restrictive temperature, 43 degrees C, cell growth and synthesis of macromolecules such as RNA and protein continue at a somewhat reduced rate. Several lines of evidence indicate that a RepR43 function is indispensable for normal phage RNA replication. In addition, this function appears to be involved in the maintenance of the perpetuated phage genome. The addition of 10% sucrose to the medium at the restrictive temperature resulted in the production of the phage, suggesting that the mutant cell might have an altered membrane organization which interferes with normal viral replication.

Coliphages↗
PubMed1999

Trace rare gases optical emission spectroscopy: nonintrusive method for measuring electron temperatures in low-pressure, low-temperature plasmas.

Trace rare gases optical emission spectroscopy (TRG-OES) is a new, nonintrusive method for determining electron temperatures (T(e)) and, under some conditions, estimating electron densities (n(e)) in low-temperature, low-pressure plasmas. The method is based on a comparison of atomic emission intensities from trace amounts of rare gases (an equimixture of He, Ne, Ar, Kr, and Xe) added to the plasma, with intensities calculated from a model. For Maxwellian electron energy distribution functions (EEDFs), T(e) is determined from the best fit of theory to the experimental measurements. For non-Maxwellian EEDFs, T(e) derived from the best fit describes the high-energy tail of the EEDF. This method was reported previously, and was further developed and successfully applied to several laboratory and commercial plasma reactors. It has also been used in investigations of correlations between high-T(e) and plasma-induced damage to thin gate oxide layers. In this paper, we provide a refined mechanism for the method and include a detailed description of the generation of emission from the Paschen 2p manifold of rare gases both from the ground state and through metastable states, a theoretical model to calculate the number density of metastables (n(m)) of the rare gases, a practical procedure to compute T(e) from the ratios of experimental-to-theoretical intensity ratios, a way to determine the electron density (n(e)), a discussion of the range of sensitivity of TRG-OES to the EEDF, and an estimate of the accuracy of T(e). The values of T(e) obtained by TRG-OES in a transformer-coupled plasma reactor are compared with those obtained with a Langmuir probe for a wide range of pressures and powers. The differences in T(e) from the two methods are explained in terms of the EEDF dependence on pressure.

Journal Article↗
PubMed2005

Reciprocity relations between ordinary temperature and the Frieden-Soffer Fisher temperature.

Frieden and Soffer conjectured some years ago [Phys. Rev. E 52, 2274 (1995)] the existence of a "Fisher temperature" T(F) that would play, with regards to Fisher's information measure I , the same role that the ordinary temperature T plays in relation to Shannon's logarithmic measure. Here we exhibit the existence of reciprocity relations between T(F) and T and provide an interpretation with reference to the meaning of T(F) for the canonical ensemble.

Journal Article↗