Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Heating”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed1981

Heat shock phenomena in Chironomus tentans I. In vivo effects of heat, overheat, and quenching on salivary chromosome puffing.

Incubation of 4th instar larvae of Chironomus tentans at elevated temperatures leads in salivary and Malpighian chromosomes to the appearance of 4-5 new puffs. Previously present puffs, particularly Balbiani rings in salivary chromosomes, become drastically reduced. The reactions of region IV-5C and Balbiani ring 1 and 2 in salivary glands are quantitatively analyzed. Statistically significant heat shock effects are observed already after 5 min and reach a maximum between 30 and 60 min. The effective temperature range is small (between 33 to 40 degrees C) with an optimum at 37 degrees C. Above 40 degrees C, i.e., at overheat shock temperatures, heat shock reactions are suppressed. Larvae heat or overheat shocked for 1-7 h or 15-30 min, respectively, survive when returned to normal culturing temperatures. The recovery from heat shock of the puffing pattern occurs in two phases: a fast one (10-20 min) and a slow one (up to 5 h) sometimes separated by a period of backlash. Quenching of overheat shocked larvae does not result in a delayed heat shock reaction.

Animals↗
PubMed1991

An evaluation of heat stress indices (ISO 7243, ISO/DIS 7933) in the prediction of heat strain in unacclimated men.

The ISO 7243 heat stress standard based on the wet bulb globe temperature (WBGT) heat stress index and the analytical standard proposal ISO/DIS 7933 were evaluated in eight physically trained and eight untrained, unacclimated men during prolonged light exercise carried out while wearing industrial work clothing. The exercise tests were done in a thermoneutral (20 degrees C/40%), a warm humid (30 degrees C/80% humidity), and a hot dry (40 degrees C/20% humidity) environment. Both of the standards were effective in predicting the excessive thermal strain observed in the dry and humid heat (WBGT, 28 degrees C). In dry heat, neither of the standards took into account the higher sweating capacities of the physically trained men. The large inter-individual variability in the physiological responses to heat stress questioned the calculations of definite allowable exposure times (ISO/DIS 7933).

Acclimatization↗
PubMed1981

Heat-stable alkaline phosphatase in uterine cancer, with special reference to its histochemical heat-stability and the L-phenylalanine inhibition test.

We report a histochemical study of alkaline phosphatase (ALP) in normal cells of the female reproductive system, in pre-cancerous and cancerous lesions of the uterine cervix and in endometrial cancer to ascertain the incidence of ALP and its isoenzyme type. For this purpose, serial sections were subjected to heat stability and L-phenylalanine (LP) inhibition tests. The Regan-like isoenzyme, a heat-stable and LP-sensitive ALP, which has been thought to derive only from cancer or the placenta, was found in uterine cervical reserve cells and endometrial luminal surface lining cells. In contrast, ALP activity in endometrial glandular cells was found to be heat and LP sensitive. Of 183 cases of cervical neoplasia, 60 (33%) manifested non-specific ALP activity. One dysplasia and two invasive cancer cases manifested the Regan-like isoenzyme. The other 36 classifiable lesions had small-intestine ALP-like activity (marked heat and LP sensitivity) or a liver ALP-like isoenzyme (marked heat and slight LP sensitivity). Of 42 cases of endometrial cancer, all cases manifested non-specific ALP activity. Seven endometrial cancers exhibited the Regan-like isoenzyme. The other 19 cases manifested either small intestine or liver ALP-like isoenzyme. Our findings indicate that in the course of uterine carinogenesis, the ALP isoenzyme of reserve cell and endometrial glandular cells undergo a change and that enzyme deviation occurs.

Alkaline Phosphatase↗
PubMed2003

The effect of passive heating and face cooling on perceived exertion during exercise in the heat.

Increased body temperature is thought to be an important component of the higher perception of exertion that is a feature of fatigue during exercise in the heat but a causal relationship has yet to be demonstrated. We have investigated the effect of passive heating on the perception of exertion during a standard bout of exercise and also assessed the effect of cooling the head on compensating for the increased body temperature on the feelings of exertion. Ten male subjects performed a 14-min cycling exercise [average power approximately 63% of maximum power output ( W(max))] at an ambient temperature of 35 degrees C at resting rectal temperature [mean (SD): 37.49 (0.27) degrees C; control (CON) trial] on one occasion, and after sitting in a sauna to raise rectal temperature [mean (SD): 38.95(0.13) degrees C; sauna (SAU) trial]. During the exercise, subjects reported their ratings of overall perceived exertion (RPE), perceived exertion of the legs (RPE(legs)) and thermal comfort (TC). A blood sample was collected by the end of the exercise for determination of plasma glucose, lactate and prolactin and haematocrit. RPE values were significantly elevated after passive heating [mean (SE): 14.5 (0.7) units in CON and 17.2 (0.5) units in SAU, at the end of exercise; P<0.001] as were the RPE(legs) ( P<0.01), while ratings of TC were similar in CON and SAU trials. Passive heating increased blood glucose ( P<0.05) but had no effect on lactate at the end of the exercise. Plasma prolactin was markedly elevated as a result of the sauna exposure [mean (SE): 1598 (152) versus 225 (31) mU l(-1) in SAU and CON trials, respectively; P<0.001]. Six of the subjects repeated the two trials but with the face cooled during exercise (trials CON(FAN) and SAU(FAN)) that was achieved by combining face fanning and spraying the face with a mist of cooled water. Face cooling decreased RPE values after sauna to a point that no differences between the two conditions existed. RPE(legs) scores and heart rate, however, remained higher in SAU(FAN) compared with CON(FAN) ( P<0.05). We conclude that hyperthermia is a causative element of the increased perception of exertion during submaximal exercise in the heat and that the effect of increased core temperature on the feelings of exertion is modulated by face cooling.

Adult↗
PubMed1977

Deletions of two heat-activated loci in Drosophila melanogaster and their effects on heat-induced protein synthesis.

Deficiencies that delete two heat-induced puffs in Drosophila melanogaster have been isolated. Two deficiencies delete the puff arising from 87C1, and one deletes the two puffs at 87A and 87C1. Homozygotes for these deletions can be recognized by their abnormal, transparent malpighian tubules. The influence on heat-induced protein synthesis of deleting one or both of these puffs has been examined. Unexpectedly, deleting only the 87C1 puff has no apparent effect. Deleting both the 87A and 87C1 puffs eliminates synthesis of a 71,000 dalton protein. We map a coding locus for the 71,000 dalton heat-induced protein to 87A7-B3, a seven band region which also contains a heat-induced puff. The roles of the 87A and 87C1 puffs in coding for heat-induced proteins are discussed in the light of these results.

Animals↗
PubMed1993

A differential heat-conduction microcalorimeter for heat-capacity measurements of fluids.

A heat-conduction calorimeter has been developed for measuring small changes in heat capacity of milligram samples of membrane lipid dispersed in water as a function of temperature. The operation of the instrument is based on the principle that the thermal response of the sample to a short (10 s), electrically generated heat burst is a function of the diffusivity of the sample. Modeling studies of the instrument's performance have revealed that the output response after the heat burst is a function of only the heat capacity, rho Cp. Calibration of the instrument experimentally confirmed this behavior. This feature obviated the need to measure the thermal conductivity in order to determine rho Cp from the diffusivity equation, eta = lambda/rho Cp. The calorimeter has the following characteristics: reproducibility of loading: +/- 400 microJ/C degrees.cm3; baseline stability: +/- 10 microJ/C degrees.cm3 per 36 h; resolution (+/- 1 S.D.): +/- 50 microJ/C degrees.cm3; sample size 600 microliters.

Calibration↗
PubMed2006

Modelling the influence of the sporulation temperature upon the bacterial spore heat resistance, application to heating process calculation.

Environmental conditions of sporulation influence bacterial heat resistance. For different Bacillus species a linear Bigelow type relationship between the logarithm of D values determined at constant heating temperature and the temperature of sporulation was observed. The absence of interaction between sporulation and heating temperatures allows the combination of this new relationship with the classical Bigelow model. The parameters zT and zT(spo) of this global model were fitted to different sets of data regarding different Bacillus species: B. cereus, B. subtilis, B. licheniformis, B. coagulans and B. stearothermophilus. The origin of raw products or food process conditions before a heat treatment can lead to warm temperature conditions of sporulation and to a dramatic increase of the heat resistance of the generated spores. In this case, provided that the temperature of sporulation can be assessed, this model can be easily implemented to rectify F values on account of possible increase of thermal resistance of spores and to ensure the sterilisation efficacy.

Bacillus↗
PubMed1990

Heat capacity of proteins. I. Partial molar heat capacity of individual amino acid residues in aqueous solution: hydration effect.

The partial molar heat capacities of various peptides and various organic compounds that model the amino acid side-chains or their parts in aqueous solution have been determined by precise scanning microcalorimetry in the temperature range from 5 to 125 degrees C. This provides an estimate of the partial molar heat capacity of the peptide--CHCONH--group and the side-chains of all amino acid residues. The values obtained are compared with the values found for these substances in the gaseous phase, in order to define the hydration effect. It has been shown that the partial heat capacity of the non-polar groups is positive at low temperature (5 degrees C) and decreases with increasing temperature, while for the polar and charged groups it is negative at low temperature, becomes zero at room temperature and increases further with increasing temperature. This leads to a hydrophobicity scale of the amino acid side-chains based upon the temperature dependences of their heat capacities. Due to the observed specificity in the temperature dependence, at room temperature, the heat capacities of amino acid side-chains correlate well with the non-polar surface areas.

Amino Acid Sequence↗
PubMed2002

Theoretical calculation of heat of formation and heat of combustion for several flammable gases.

Heats of formation have been calculated by the Gaussian-2 (G2) and/or G2MP2 method for a number of flammable gases. As a result, it has been found that the calculated heat of formation for compounds containing, such atoms as fluorine and chlorine tends to deviate from the observed values more than calculations for other molecules do. A simple atom additivity correction (AAC) has been found effective to improve the quality of the heat of formation calculation from the G2 and G2MP2 theories for these molecules. The values of heat of formation thus obtained have been used to calculate the heat of combustion and related constants for evaluating the combustion hazard of flammable gases.

Fires↗
PubMed2005

Electrically heated, air-cooled thermal modulator and at-column heating for comprehensive two-dimensional gas chromatography.

An instrument for comprehensive two-dimensional gas chromatography (GCxGC) is described using an electrically heated and air-cooled thermal modulator requiring no cryogenic materials or compressed gas for modulator operation. In addition, at-column heating is used to eliminate the need for a convection oven and to greatly reduce the power requirements for column heating. The single-stage modulator is heated by current pulses from a dc power supply and cooled by a conventional two-stage refrigeration unit. The refrigeration unit, together with a heat exchanger and a recirculating pump, cools the modulator to about -30 degrees C. The modulator tube is silica-lined stainless steel with an internal film of dimethylpolysiloxane. The modulator tube is 0.18 mm i.d. x 8 cm in length. The modulator produces an injection plug width as small as 15 ms.

Journal Article↗
PubMedDate not supplied

Modeling conductive heat transfer during high-pressure thawing processes: determination of latent heat as a function of pressure.

A numerical heat transfer model for predicting product temperature profiles during high-pressure thawing processes was recently proposed by the authors. In the present work, the predictive capacity of the model was considerably improved by taking into account the pressure dependence of the latent heat of the product that was used (Tylose). The effect of pressure on the latent heat of Tylose was experimentally determined by a series of freezing experiments conducted at different pressure levels. By combining a numerical heat transfer model for freezing processes with a least sum of squares optimization procedure, the corresponding latent heat at each pressure level was estimated, and the obtained pressure relation was incorporated in the original high-pressure thawing model. Excellent agreement with the experimental temperature profiles for both high-pressure freezing and thawing was observed.

Freezing↗
PubMed2006

Enterocyte and M-cell transport of native and heat-denatured bovine beta-lactoglobulin: significance of heat denaturation.

The three-dimensional structure, digestibility, and immunological properties of bovine beta-lactoglobulin (beta-lg) are modified by heat treatments used in processing of liquid milk products. Because it is not known if such treatments also modify the intestinal transport properties of beta-lg, the transport of native and heat-denatured bovine beta-lg was investigated in experimental cell models using Caco-2 cells and M cells. Transport of beta-lg labeled with a fluorescent marker was followed with fluorometric measurements, electrophoretic analyses, and fluorescence microscopy. The data show that both cell types transported native beta-lg more efficiently than they did heat-denatured beta-lg. In addition, M cells transported native beta-lg more than Caco-2 cells. Transport of native and heat-denatured beta-lg was transcellular. The electrophoretic data also suggest that heat-denatured beta-lg may have degraded more than native beta-lg during the transport.

Animals↗
PubMed2002

Poleward heat transport by the atmospheric heat engine.

The atmospheric heat transport on Earth from the Equator to the poles is largely carried out by the mid-latitude storms. However, there is no satisfactory theory to describe this fundamental feature of the Earth's climate. Previous studies have characterized the poleward heat transport as a diffusion by eddies of specified horizontal length and velocity scales, but there is little agreement as to what those scales should be. Here we propose instead to regard the baroclinic zone--the zone of strong temperature gradients and active eddies--as a heat engine which generates eddy kinetic energy by transporting heat from a warmer to a colder region. This view leads to a new velocity scale, which we have tested along with previously proposed length and velocity scales, using numerical climate simulations in which the eddy properties have been varied by changing forcing and boundary conditions. The experiments show that the eddy velocity varies in accordance with the new scale, while the size of the eddies varies with the well-known Rhines beta-scale. Our results not only give new insight into atmospheric eddy heat transport, but also allow simple estimates of the intensities of mid-latitude storms, which have hitherto only been possible with expensive general circulation models.

Journal Article↗
PubMed2003

Joule heating and heat transfer in poly(dimethylsiloxane) microfluidic systems.

Joule heating is a significant problem in electrokinetically driven microfluidic chips, particularly polymeric systems where low thermal conductivities amplify the difficulty in rejecting this internally generated heat. In this work, a combined experimental (using a microscale thermometry technique) and numerical (using a 3D "whole-chip" finite element model) approach is used to examine Joule heating and heat transfer at a microchannel intersection in poly(dimethylsiloxane)(PDMS), and hybrid PDMS/Glass microfluidic systems. In general the numerical predictions and the experimental results agree quite well (typically within +/- 3 degree C), both showing dramatic temperature gradients at the intersection. At high potential field strengths a nearly five fold increase in the maximum buffer temperature was observed in the PDMS/PDMS chips over the PDMS/Glass systems. The detailed numerical analysis revealed that the vast majority of steady state heat rejection is through lower substrate of the chip, which was significantly impeded in the former case by the lower thermal conductivity PDMS substrate. The observed higher buffer temperature also lead to a number of significant secondary effects including a near doubling of the volume flow rate. Simple guidelines are proposed for improving polymeric chip design and thereby extend the capabilities of these microfluidic systems.

Computer Simulation↗
PubMed2001

Local heat-shock priming-induced improvement in microvascular perfusion in osteomyocutaneous flaps is mediated by heat-shock protein 32.

BACKGROUND: Stress conditioning is thought to improve microvascular free flap survival but the mechanisms of protection are not clear. The aim of this study was to determine whether local induction of heat-shock protein (HSP) 32 improves microvascular perfusion in transferred osteomyocutaneous flaps. METHODS: The hindlimb harvest region of osteomyocutaneous flaps in Wistar rats was subjected to stress conditioning by local heating (30 min, 42.5 degrees C) 24 h before microvascular flap transfer. In a second group of animals, after heat-shock priming, the action of HSP-32 was inhibited by tin protoporphyrin IX. Animals with unconditioned flaps served as controls. After transfer, the microcirculation of the muscle, cutaneous, subcutaneous and periosteal tissue of the flap was analysed quantitatively for 6 h using intravital fluorescence microscopy. RESULTS: Immunohistochemistry revealed that HSP-32 was detectable only after priming and not in unconditioned flaps. Priming did not alter functional capillary density or capillary red blood cell velocity compared with that in unconditioned flaps. However, heat-shock priming induced significant capillary dilatation (P < 0.05) and thus a substantial increase in capillary blood flow volume (P < 0.05) in all tissues of the transferred flaps. Inhibition of HSP-32 by tin protoporphyrin IX completely abolished the priming-induced improvement in capillary perfusion, as indicated by the lack of increased capillary diameters and volumetric blood flow. CONCLUSION: The present study demonstrated that stress conditioning by local heat-shock priming improves nutritive perfusion in osteomyocutaneous flaps by capillary dilatation, probably mediated through the vasoactive action of HSP-32.

Animals↗
PubMed2000

Sensitivity of nisin-resistant Listeria monocytogenes to heat and the synergistic action of heat and nisin.

Nisin, a bacteriocin produced by some strains of Lactococcus lactis, acts against foodborne pathogen Listeria monocytogenes. A single exposure of cells to nisin can generate nisin-resistant (Nisr) mutants, which may compromise the use of nisin in the food industry. The objective of this research was to compare the heat resistance of Nisr and wild type (WT) Listeria monocytogenes. The synergistic effect of heat-treatment (55 degrees C) and nisin (500 IU ml-1) on the Nisr cells and the WT L. monocytogenes Scott A was also studied. When the cells were grown in the absence of nisin, there was no significant (alpha = 0.05) difference in heat resistance between WT and Nisr cells of L. monocytogenes at 55, 60 and 65 degrees C. However, when the Nisr cells were grown in the presence of nisin, they were more sensitive to heat at 55 degrees C than the WT cells. The D-values at 55 degrees C were 2.88 and 2.77 min for Nisr ATCC 700301 and ATCC 700302, respectively, which was significantly (alpha = 0.05) lower than the D-value for WT, 3.72 min. When Nisr cells were subjected to a combined treatment of heat and nisin, there was approximately a four log reduction during the first 7 min of treatment.

Culture Media↗
PubMedDate not supplied

Hypnosis increases heat detection and heat pain thresholds in healthy volunteers.

BACKGROUND AND OBJECTIVES: Hypnosis has been reported to induce analgesia and to facilitate anesthesia. To date, hypnotic-induced analgesia has had little explanation and it has even been questioned. The current study was thus designed to investigate the effect of hypnotic suggestion on thermal-detection thresholds, heat pain, and heat-pain tolerance thresholds. METHODS: In 15 healthy volunteers, enrolled in a randomized cross-over study, thermal thresholds were investigated in 2 sequences of measurements, under waking and hypnotic states, using a thermal stimulator. RESULTS: Heat detection and heat-pain thresholds were increased under hypnosis (from 34.3 +/-.9 degrees C to 36.0 +/- 2.9 degrees C and 45.0 +/- 3.7 degrees C to 46.7 +/- 2.7 degrees C, respectively, P <.05), whereas heat-pain tolerance and cold-detection thresholds were not statistically changed. CONCLUSION: These results indicate that hypnosis may partly impair the detection of A delta and C fibers stimulation, potentially explaining its analgesic effect.

Adult↗
PubMed2001

A randomized clinical trial to compare the effects of a heat and moisture exchanger with a heated humidifying system on the occurrence rate of ventilator-associated pneumonia.

BACKGROUND: The purpose of this study was to compare the performance of heat and moisture exchanger filters with heated humidifying systems in the mechanical ventilator circuit on the incidence of ventilator-associated pneumonia (VAP) and bacterial colonization. METHOD: Two hundred and forty-three consecutive patients who required mechanical ventilation for 48 hours or more in the adult intensive care unit were randomized to either a heat and moisture exchanger (HME) or a heated humidifying breathing circuit. RESULTS: The VAP rate among the group with HME was 11.4%; the rate among the group with heated humidifying system (HHS) was 15.8%. The difference was not statistically significant. Approximately 68% of the patients in the HME group had no pathogen isolated compared with 50% of the patients in the HHS group. This difference was statistically significant (P =.006). However, the distribution of the pathogens among those patients who had the isolated pathogens was mostly identical in the 2 groups. CONCLUSION: Even though the study did not find HME to be significantly advantageous over the HHS, in as much as VAP rate is concerned, other advantages such as reduced nurses workload, reduced financial cost, and better safety made HME a more favorable device for use in our adult intensive care unit.

Bacteria↗