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PubMedDate not supplied

European Community controls for high temperature testing of food contact materials.

High temperature testing above 121 degrees C is currently in accordance with national legislation, although amended Council Directive 82/711/EEC will include a framework of temperatures and times, the most stringent of which will require 2 h testing of materials and articles at 175 degrees C with olive oil. The background debate that preceded the establishment of this proposed framework is described, as well as the difficulties that were encountered over agreeing the appropriate testing for microwave susceptors. The further work that will be required for implementation (and will need to be undertaken by groups such as CEN) is outlined as are areas such as testing above 175 degrees C that may require consideration for future EC control.

Cooking↗

PubMedDate not supplied

Determination of oligofructose, a soluble dietary fiber, by high-temperature capillary gas chromatography.

A high-temperature capillary gas chromatographic method was developed for the quantitative determination of oligofructose in foods and food products. Sample preparation involves oxymation and silylation of the extracted sugars. The oximetrimethylsilyl derivatives are analyzed on an apolar capillary column, with detection by flame ionization. The method is accurate, with recovery of spiked samples at >96%. Repeatability was excellent; RSD values of 1.1% were obtained. Other common oligosaccharides, such as malto-, isomalto-, and galactooligosaccharides, and levan do not interfere, making the method specific and reliable.

Chromatography, Gas↗

PubMed2002

[Effects on fine particles by the continued high temperature weather in Beijing].

The continued high temperature weather (CHTW) appeared in Beijing since June 23 1999. The measurements showed the PM2.5 mass concentrations were 2 to 3 times of that in non-CHTW period. However the diffusion conditions were still fine in these days. Both the highest hourly concentrations of O3 and the SO4(2-) composition in PM2.5 can identify that the photochemical action was very active. It is the very reason to produce more fine particles in atmosphere.

Air Pollutants↗

PubMed2000

Mutants of Arabidopsis thaliana defective in the acquisition of tolerance to high temperature stress.

The ability of organisms to acquire thermotolerance to normally lethal high temperatures is an ancient and conserved adaptive response. However, knowledge of cellular factors essential to this response is limited. Acquisition of thermotolerance is likely to be of particular importance to plants that experience daily temperature fluctuations and are unable to escape to more favorable environments. We developed a screen, based on hypocotyl elongation, for mutants of Arabidopsis thaliana that are unable to acquire thermotolerance to high-temperature stress and have defined four separate genetic loci, hot1-4, required for this process. hot1 was found to have a mutation in the heat shock protein 101 (Hsp101) gene, converting a conserved Glu residue in the second ATP-binding domain to a Lys residue, a mutation that is predicted to compromise Hsp101 ATPase activity. In addition to exhibiting a thermotolerance defect as assayed by hypocotyl elongation, 10-day-old hot1 seedlings were also unable to acquire thermotolerance, and hot1 seeds had greatly reduced basal thermotolerance. Complementation of hot1 plants by transformation with wild-type Hsp101 genomic DNA restored hot1 plants to the wild-type phenotype. The hot mutants are the first mutants defective in thermotolerance that have been isolated in a higher eukaryote, and hot1 represents the first mutation in an Hsp in any higher plant. The phenotype of hot1 also provides direct evidence that Hsp101, which is required for thermotolerance in bacteria and yeast, is also essential for thermotolerance in a complex eukaryote.

Adaptation, Physiological↗

PubMed1976

Protein synthesis in a cell-free system from an extreme thermophile. Effects of preincubation in the cold on polyuridylic acid-dependent polyphenylalanine synthesis at high temperature.

1. It was found that preincubation of the reaction mixture in the cold enhanced polyuridylic acid-directed polyphenylalanine synthesis by a cell-free extract of Thermus thermophilus HB8 at high temperature. 2. The effect of preincubation was most marked at 10-25 degrees in the presence of 20 mM Mg2+. Preincubation at 65 degrees failed to stimulate the incorporation. 3. The presence of phenylalanyl-tRNA, polyuridylic acid, and ribosomes was essential for preincubation in the cold to be effective. 4. A ternary complex of amino acyl-tRNA, polyuridylic acid, and a ribosome formed at low temperature was isolated by CPG-10 column chromatography; the isolated complex initiated polyphenylalanine synthesis effectively at high temperature. 5. The amount of the ternary complex formed depends on the preincubation time and the concentration of Mg2+. Since the amount of the complex correlated positively to the rate of polyphenylalanine synthesis at high temperature, the effectiveness of preincubation in the cold is presumably due to the formation of the ternary complex of phenylalanyl-tRNA, polyuridylic acid, and a ribosome.

Bacteria↗

PubMed2003

Effects of glycerol and high temperatures on structure and function of phycobilisomes in Synechocystis sp. PCC 6803.

The effects of glycerol and high temperatures on structure and function of phycobilisomes (PBSs) in vivo were investigated in a chlL deletion mutant of the cyanobacterium Synechocystis sp. PCC 6803. When the mutant was grown under light-activated heterotrophic growth conditions, it contained intact and functional PBSs, but essentially no chlorophyll and photosystems. So the structural and functional changes of the mutant PBSs in vivo can be handily detected by measurement of low temperature (77 K) fluorescence emission spectra. High concentration glycerol induced an obvious disassembly of PBSs and the dissociation of phycocyanins in the rod substructures into their oligomers and monomers. PBSs also disassembled at high temperatures and allophycocyanins were more sensitive to heat stress than phycocyanins. Our results demonstrate that the chlL(-) mutant strain is an advantageous model for studying the mechanisms of assembly and disassembly of protein complexes in vivo.

Bacterial Proteins↗

PubMed1992

Isolation and characterization of the Escherichia coli htrD gene, whose product is required for growth at high temperatures.

Those genes in Escherichia coli defined by mutations which result in an inability to grow at high temperatures are designated htr, indicating a high temperature requirement. A new htr mutant of E. coli was isolated and characterized and is designated htrD. The htrD gene has been mapped to 19.3 min on the E. coli chromosome. Insertional inactivation of htrD with a mini-Tn10 element resulted in a pleiotropic phenotype characterized by a severe inhibition of growth at 42 degrees C and decreased survival at 50 degrees C in rich media. Furthermore, htrD cells were sensitive to H2O2. Growth rate analysis revealed that htrD cells grow very slowly in minimal media supplemented with amino acids. This inhibitory effect has been traced to the presence of cysteine in the growth medium. Further studies indicated that the rate of cysteine transport is higher in htrD cells relative to the wild type. All of these results, taken together, indicate that the htrD gene product may be required for proper regulation of intracellular cysteine levels and that an increased rate of cysteine transport greatly affects the growth characteristics of E. coli.

Bacterial Proteins↗

PubMed1992

Limits of tolerance to high temperatures causing direct and indirect damage to black spruce.

The heat tolerance of actively growing 13-15-week-old black spruce (Picea mariana (Mill.) B.S.P.) was determined by exposing seedlings to temperatures of 40 to 60 degrees C for durations of 5 seconds to 3 hours by direct immersion in a hot water bath. Direct and indirect heat damage to needles were differentiated by assessing damage 5 minutes (direct) and 3 weeks (indirect) after exposure to high temperature. Both direct and indirect damage increased exponentially with the duration of exposure to high temperatures. However, indirect damage occurred at lower temperatures and with shorter periods of exposure than direct damage. Arrhenius plots of length of exposure versus exposure temperature revealed that the energy of activation for indirect damage was 384 kJ mol(-1), 36% higher than for direct damage. Both direct and indirect damage were less in seedlings preconditioned by a heat shock treatment (3 hours of exposure to an air temperature of 38 degrees C on each of 6 days prior to immersion in the water bath). Preconditioned seedlings withstood higher temperatures and longer durations of high temperature exposure than seedlings not preconditioned by heat shock.

Journal Article↗

PubMed2006

Cobalt-base high-temperature alloys.

We have identified cobalt-base superalloys showing a high-temperature strength greater than those of conventional nickel-base superalloys. The cobalt-base alloys are strengthened by a ternary compound with the L1(2) structure, gamma' Co3(Al,W), which precipitates in the disordered gamma face-centered cubic cobalt matrix with high coherency and with high melting points. We also identified a ternary compound, gamma' Ir3(Al,W), with the L1(2) structure, which suggests that the Co-Ir-Al-W-base systems with gamma+gamma' (Co,Ir)3(Al,W) structures offer great promise as candidates for next-generation high-temperature materials.

Journal Article↗

PubMed2005

[High temperature Raman spectra and structure character study of BSO crystal].

The structure character of BSO crystal at room temperature was generalized. The main Raman shifts of lattice vibration at room temperature were interpreted. The Raman spectra of BSO crystal were measured in a temperature range from 293 K to 1123 K with high temperature Raman spectroscopy and time-resolved detection techniques. Temperature-dependence character of the Raman spectra of the crystal was investigated. The vibration mode of the longest bond Bi-O(1) in crystal shifts from 542 cm(-1) to 512 cm(-1) with the temperature increasing from room temperature to 1123 K. It can be attributed to the fact that oxygen atoms are electrostatic bond to Bi atoms. The intensity of 88 cm(-1) modes, which belongs to combination mode of bending and stretching in Bi3O4 unit, changes not so noticeably as other modes, and even the 58 cm(-1) mode of Bi atoms motions in crystal lattice decreases rapidly when the temperature is higher than 873 K, which indicates that the framework structure of the crystal is broken down at high temperature, while the Bi3O4 unit still exists.

Bismuth↗

PubMed2003

Endometrial thermal balloon ablation using a high temperature, pulsed system: a mathematical model.

A new endometrial thermal balloon ablation treatment for menorrhagia is modeled mathematically to predict its efficacy and safety. A device preheats a fluid to 173 degrees C within a reservoir external to the uterus, and then pulses this fluid without further heating between the reservoir and the balloon for 2.1 min of treatment time. The model predicted this treatment to result in consistent immediate tissue death (coagulation) depths of 3.4 +/- 0.1 mm for uterine cavities of 7 to 26 mL, and that eventual necrosis (tissue death that would occur 1-5 days post burn) may occur to depths of 6.5 +/- 0.2 mm. Whereas, burn depths varied with uterine cavity volume when a low temperature treatment (constant 75 degrees C for 15 min) was modeled (2.3-2.9 mm and 6.8-8.2 mm, for immediate tissue death and eventual necrosis respectively). Similarly, the high temperature, pulsed treatment was less sensitive to blood perfusion rate than the low temperature treatment. Predicted eventual necrosis depth was 1.5 mm less for the high temperature, pulsed treatment than that predicted for a low temperature treatment (constant 87 degrees C for 7 min) for the same immediate tissue death depth (3.5 mm), indicating that the new high temperature treatment may result in less damage to non targeted tissues.

Body Temperature Regulation↗

PubMed1990

[Characteristics of recombination of heterosis hybrids of Drosophila melanogaster in high temperature conditions].

Spontaneous and high temperature-induced crossing over in regions b-cn and cn-vg of chromosome 2 was studied in Drosophila stocks and hybrids differing in fertility level and heat resistance. No essential distinction in recombination frequency was revealed in variants studied under the temperature 21-22 degrees C. The effect of temperature on 1- and 10-days imago during 4 or 7 h under 35 degrees C leads to increase in exchange frequency in the region b-cn. The hybrids show weaker reaction to this influence.

Animals↗

PubMed2001

Structure, properties, and bonding of ZrTe (MnP type), a low-symmetry, high-temperature modification of ZrTe (WC type).

ZrTe (MnP) was synthesized by high-temperature methods at 1570 K in Ta ampules. The structure of the telluride was determined by means of single-crystal X-ray diffraction to be orthorhombic, Pnma (No. 62), Z = 4, Pearson Symbol oP8, a = 739.15(15) pm, b = 377.23(8) pm, c = 694.34(14) pm. The orthorhombic MnP type structure is a distorted variant of the NiAs type structure with pronounced metal-metal zigzag chains. Zigzag chains are typical for phases with a d(2) metal atom electron configuration. According to extended Hückel calculations, the homonuclear interactions in the zigzag chains make up for 2/3 of the Zr-Zr interactions in ZrTe (MnP) and contribute decisively to the stability of the structure. The emergence of the distorted MnP type structure instead of the high-symmetry NiAs type ZrTe at high temperatures can be understood as the result of an optimization of homonuclear Zr-Zr interactions arising from states close to the Fermi level. The hexagonal WC type ZrTe transforms above 1438 +/- 5 K into ZrTe (MnP) (DeltaH = 8.3 +/- 1.0 kJ mol(-1)). The phase transition is reversible, although at room-temperature the reverse reaction is kinetically inhibited. Zr5Te4 and Zr5Te6 are the phases next to ZrTe. ZrTe (MnP) exhibits temperature-independent paramagnetic properties (chi(mol) = 0.14 x 10(-3) cm(3) mol(-1)), as typical for a metallic conductor. Resistivity measurements on ZrTe (MnP) imply metallic behavior.

Journal Article↗

PubMed1992

Impact of tropical conditions on thin layer chromatography in analytical toxicology: high temperatures and moderate humidities.

The impact of high temperatures (24 to 39 degrees C) and low to moderately high humidities (20 to 70%) on the applicability of TLC systems for drug identification was studied during a 6 month climatologic cycle in Burkina Faso (West Africa). In general, the Rf values as observed on the plates were found to be substantially affected as compared with values obtained at temperate climates. Some TLC systems were more affected than others and the largest deviations of up to 30 Rf units were at low humidities. Tropical conditions also had a negative effect on the reproducibility of Rf values. However, when an Rf-correction procedure was applied, using reference mixtures of known drugs on each plate, accuracy as well as reproducibility of the resulting Rfc values were drastically improved and data thus corrected were found to be compatible with existing TLC data bases developed under moderate climatological conditions. The impact of high to extremely high humidities (70 to 100%) remains to be investigated.

Burkina Faso↗

PubMed2006

Red soil as a regenerable sorbent for high temperature removal of hydrogen sulfide from coal gas.

In this study, hydrogen sulfide (H(2)S) was removed from coal gas by red soil under high temperature in a fixed-bed reactor. Red soil powders were collected from the northern, center and southern of Taiwan. They were characterized by XRPD, porosity analysis and DCB chemical analysis. Results show that the greater sulfur content of LP red soils is attributed to the higher free iron oxides and suitable sulfidation temperature is around 773K. High temperature has a negative effect for use red soil as a desulfurization sorbent due to thermodynamic limitation in a reduction atmosphere. During 10 cycles of regeneration, after the first cycle the red soil remained stable with a breakthrough time between 31 and 36 min. Hydrogen adversely affects sulfidation reaction, whereas CO exhibits a positive effect due to a water-shift reaction. COS was formed during the sulfidation stage and this was attributed to the reaction of H(2)S and CO. Results of XRPD indicated that, hematite is the dominant active species in fresh red soil and iron sulfide (FeS) is a product of the reaction between hematite and hydrogen sulfide in red soils. The spinel phase FeAl(2)O(4) was found during regeneration, moreover, the amount of free iron oxides decreased after regeneration indicating the some of the free iron oxide formed a spinel phase, further reducting the overall desulfurization efficiency.

Adsorption↗

PubMed2001

Potential of mass spectrometry for the analysis of inorganic high-temperature vapors.

Mass spectrometry is the most versatile method for the analysis of high-temperature vapors, because it enables the identification of the gaseous species and the determination of their partial pressures. If the vaporization processes are conducted under thermodynamic equilibrium, thermodynamic data can be evaluated from the partial pressures and their temperature-dependencies. The mass spectrometric methods used for the determination of thermodynamic data of high-temperature vapors are Knudsen effusion mass spectrometry (KEMS), transpiration mass spectrometry (TMS), and laser-induced vaporization mass spectrometry (LVMS). KEMS is used whenever possible. Limitations of KEMS and TMS are the container problem, which limits the measurement temperatures to approximately 2500 K. The container problem is overcome by LVMS, which enables measurements up to approximately 7,000 K. The upper limit of the partial pressure measurement by KEMS of approximately 10 Pa does not apply for TMS, which enables measurements up to pressures of approximately 0.1 MPa. The fundamentals of the different methods are described and results are presented. Emphasis is on KEMS.

Journal Article↗

PubMed2006

High-temperature micro liquid chromatography for lipid molecular species analysis with evaporative light scattering detection.

The need for a rapid and sensitive chromatographic technique for analyzing lipid molecular species, has led to the development of an high-temperature micro liquid chromatographic system (HTLC) coupled to an evaporative light scattering detector. The increased diffusion coefficients and reduced viscosity at higher temperatures allowed lipids to be analyzed rapidly with solvents differing from those classically used in lipids chemistry. Hypercarb, a reverse phase material, was used for its different properties including heat resistance in high temperature micro HPLC. We have investigated the temperature effect on kinetic performances in HTLC, established pure solvents eluent strength at high temperature and studied different classes of lipids with seven pure solvents. We found that it was possible to use alcohols solvents in the mobile phase to elute lipids without the use of chlorinated solvents. A quick and simple method was developed to analyze a complex lipid simple, ceramide type III and type IV.

Ceramides↗

PubMedDate not supplied

[High temperature "matè" infusion drinking in a population at risk for squamous cell carcinoma of the esophagus].

UNLABELLED: "Matè", a popular hot infusion of a herb (Ilex paraguayensis) drunk in large volumes, is a known risk factor for squamous cell carcinoma of the esophagus and there is a suspicion that high temperature of boiled water used for the infusion may contribute for carcinogenesis. METHODS: We measured the temperature of "matè" infusion drunk by a sample of the population at risk for this carcinoma in Taquara, southern Brazil. We interviewed inhabitants for drinking habits and the temperature of the infusion was measured with high precision thermometers. Temperature of the infusion was asked to consumers and their estimate compared to our measurements. We considered 60 degrees C or higher as "hot". RESULTS: In 36 residencies, 107 individuals were drinking "matè". Most individuals drank it daily (97.2%), and the medium daily volume was 1,265 ml (SD +/- 1,132 mL) ranging from 250 to 6,000 mL. The measured temperature was 60 degrees C or higher in 72% of residencies with medium of 63.4 degrees C (51-78 degrees C) and median 64.4 degrees C. CONCLUSION: In this study, "matè" was consumed in large volumes at high temperature and individuals did not estimate correctly the temperature of infusion. High temperatures of "matè" may contribute to carcinogenesis in this population.

Adult↗