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PubMed2006

Determining heats of detonation of non-aromatic energetic compounds without considering their heats of formation.

A new procedure is introduced for calculating heats of detonation of non-aromatic energetic compounds through ratios of oxygen to carbon and hydrogen to oxygen as well as the contribution of some structural parameters. There is no need to use heats of formation of non-aromatic energetic compounds that are usually needed by the other methods. Moreover, this much simple method does not use any experimental and computed data of energetic materials. Predicted heats of detonation for 28 non-aromatic energetic compounds have a root mean square (rms) of deviation of 0.54 kJ/g from experiment, which show good agreement with respect to measured values. The new method is the simplest procedure for predicting heats of detonation and provides reliable results which are comparable with the other methods.

Carbon↗
PubMed2004

Heat acclimation affects the neuromodulatory role of AngII and nitric oxide during combined heat and hypohydration stress.

We studied the effect of heat acclimation on the neuromodulatory role of angiotensin (AngII) and nitric oxide during combined heat (39 degrees C) and hypohydration (water deprivation, -10% body weight) stress. Rats were divided into control (C), short (2d-STHA) or long (30d-LTHA) acclimation (34 degrees C) groups. AngII, 7-nitroindazole (7NI)-nNOS blocker, or both were centrally administered (5 mul, bolus) under light chloroform anesthesia prior to each experimental paradigms: (1) In vivo: measurements of skin-vasodilatation (VTsh) and salivation-cooling (STsh) thresholds, and heat endurance in conscious heat/hypohydrated stressed rats; (2) expression of AT(1) and AT(2) AngII receptors and nNOS were measured in the hypothalamus (Western blot); (3) transcript levels of the coding genes were measured using real-time PCR. A synthesis of the results shows a biphasic acclimatory profile of VTsh, STsh, and transcript levels of all studied genes, with transient up/down-regulatory changes on STHA. AngII affected the physiological integrative outcome primarily during euhydration, although AT membranal changes (except in LTHA) were confined to hypohydration. 7NI had an impact during hypohydration. Evidence is provided that AngII and 7NI modulate thermoregulation primarily via AT(1) and AT(2) receptors, with predominance of AT(2) signaling following LTHA and/or hypohydration, opposing a drop in AT(1)-mediated thresholds. The final shaping of AngII signaling depends on cross-talk between nNOS and AngII receptors at both molecular and protein levels. Hypohydration induces transcriptional responses but desensitizes AngII receptors signaling, attenuating their effect on VTsh and STsh, and abolishing the beneficial thermoregulatory effects achieved by heat acclimation. nNOS, AngII receptor-independent pathway is also implicated.

Acclimatization↗
PubMed1998

Reversibility of heat-induced conformational changes and surface exposed hydrophobic clusters of beta-lactoglobulin: their role in heat-induced sol-gel state transition.

The effects of heat-treatment on the conformational changes of beta-lactoglobulin were monitored by differential scanning calorimetry (DSC), binding properties to 1-anilino-8-naphthalenesulphonic acid (ANS) and to 5,5'-dithio-bis (2-nitrobenzoic acid) (DTNB). The thermal transition of beta-lactoglobulin was 100% reversible on re-heating and its binding properties to the ANS fluorescent-dye and to the DTNB probe did not significantly change when the first heating was made to a temperature T < Tmax, that of the DSC maximal peak deviation of unheated solutions. When the solutions were heated to higher temperatures, the degree of reversibility of the thermal transition decreased, while the beta-lactoglobulin surface hydrophobicity increased. Furthermore, the time (tg) needed for the sol-gel state transitions was highly temperature-dependent for the solutions showing no significant reactivity with the DTNB probe, a high percentage of residual tertiary structure but a low surface hydrophobicity. For beta-lactoglobulin showing < 50% residual tertiary structure but high surface hydrophobicity, tg values were hardly temperature-dependent. The results are discussed in terms of the role of hydrophobic interactions in the aggregation process of denatured beta-lg molecules.

Anilino Naphthalenesulfonates↗
PubMed1986

Complementary nature of heat production and heat intake during behavioral thermoregulation in the rat.

Rats were trained to work for radiant heat in a cold environment in an apparatus that permitted the simultaneous measurement of metabolic heat production. Reductions in behavioral efficacy produced either by a decrease in reward duration or intensity or by an increase in response effort resulted in a reduction in behavioral heat intake, an increase in metabolic heat production, and no change in body temperature. Thus, autonomic and behavioral temperature regulation interact to produce a constant body temperature.

Animals↗
PubMed1982

Heat stability of milk: influence of modification of lysine and arginine on the heat stability-pH profile.

Several dicarbonyl compounds (glyoxal, substituted glyoxals, diacetyl and 1, 2-cyclohexanedione) had a marked stabilizing effect on the heat stability of milk, especially in the presence of urea. These reagents are believed to modify arginine more or less specifically suggesting an important role for arginine residues in heat stability. In contrast, modification of lysine residues with dansyl chloride, acetic anhydride or cyanoborohydride had little effect on maximum heat stability although it did alter the HCT-pH profile. Since diacetyl is a natural constituent of fermented milks and cheese, it may be acceptable as an additive to increase the heat stability of milk.

Acetic Anhydrides↗
PubMed2000

Response of Micromonospora echinospora (NCIMB 12744) spores to heat treatment with evidence of a heat activation phenomenon.

The effects of heat treatment on spores of the actinomycete Micromonospora echinospora were investigated. The percentage of culturable spores in untreated spore stocks was found to be approximately 20%. A 60 degrees C treatment of spores in phosphate buffer for 10 min led to an approximately five-fold increase in the number of culturable units. This indicated that a large proportion of the spores were constitutively dormant. Within 10 min and in the absence of an external energy-yielding substrate, the heat treatment was found to stimulate spore respiration suggesting that endogenous storage compounds were being utilized. Heating spores at 70 degrees C shortened the time period required for activation; holding times greater than 10 min, however, resulted in a reduction of culturable cells. Classic thermal death characteristics were seen at temperatures of 80 degrees C and above with D-values of 21.43, 2.67, 0.45 and 0.09 min being recorded at 70, 80, 90 and 100 degrees C, respectively. Spores of this organism, while being weakly heat resistant in comparison with bacterial endospores, are significantly more resistant than vegetative cells.

Colony Count, Microbial↗
PubMed1993

Enteroaggregative Escherichia coli heat-stable enterotoxin 1 represents another subfamily of E. coli heat-stable toxin.

Enteroaggregative Escherichia coli (EAggEC) are associated with persistent diarrhea in young children. Some of these organisms produce a low-molecular-weight, heat-stable, plasmid-encoded enterotoxin that has been named EAggEC heat-stable enterotoxin 1 (EAST1). We have cloned a 4.4-kb DNA fragment from the virulence plasmid of prototype EAggEC strain 17-2, which expresses enterotoxic activity as measured by electrogenic response in Ussing chambers mounted with rabbit ileal tissue. DNA-sequence analysis of this fragment identified an open reading frame (ORF) encoding a cysteine-rich polypeptide of 38 amino acids (M(r), 4100). Insertional and deletional mutations in this ORF resulted in loss of enterotoxic activity. The ORF was cloned into a T7 expression vector, and postinduction culture filtrates exhibited enterotoxic activity and increased ileal tissue cGMP levels. A synthetic peptide consisting of predicted amino acid residues 8-29 also showed enterotoxic activity. These data indicate that this ORF, named astA (EAggEC heat-stable enterotoxin), represents the EAST1 structural gene. EAST1 shows significant homology with the enterotoxic domain of heat-stable enterotoxin a (STa) of enterotoxigenic E. coli and with guanylin, a mammalian analog of STa. Unlike STa, which requires six cysteines and three disulfide linkages for full biological activity, both EAST1 and guanylin contain four cysteine residues. Based on the cGMP data and the sequence homology to STa and guanylin, it is predicted that EAST1 stimulates the particulate form of guanylate cyclase through the same receptor-binding region as STa and guanylin.

Amino Acid Sequence↗
PubMed1981

Sensible heat transfer from the fowl: radiative and convective heat losses from a flock of broiler chickens.

1. Measurements of the micro-climate within a poultry house and physical models of heat loss produced estimates of the sensible heat losses from broilers. The partition between radiative and convective heat losses changed with age and bird activity. 2. The birds spent approximately 67% of ;their time in a cluster, in which their sensible heat losses were between 30 and 60% of those of an individual bird. 3. body plus plumage resistance was constant at 0.09 m2K/W up to 30 d and increased linearly to 0.40 m2K/W at 54 d.

Animals↗
PubMed1987

Heat strain and heat stress for workers wearing protective suits at a hazardous waste site.

In order to evaluate the effects of heat stress when full body protective suits are worn, heart rates, oral temperatures and environmental parameters were measured for five unacclimatized male workers (25-33 years of age) who performed sampling activities during hazardous waste clean-up operations. The protective ensembles included laminated PVC-Tyvec chemical resistant hood suits with rubber boots, gloves full facepiece dual cartridge respirators and hard hats. For comparison, measurements also were performed when the men worked at a similar level of activity while they wore ordinary work clothes. A comparison of the heart rates for the men working with and without suits indicated that wearing the suits imposed a heat stress equivalent to adding 6 degrees to 11 degrees C (11 degrees to 20 degrees F) to the ambient WBGT index. A similar result was obtained by calculating the WBGT in the microclimate inside the suits and comparing it to the ambient WBGT. These results indicate the following: 1) there exists a significant risk of heat injury during hazardous waste work when full body protective clothing is worn, and 2) threshold limit values for heat stress established by the ACGIH must be lowered substantially before extending them to cover workers under these conditions.

Adult↗
PubMed1979

A microwave heating system for improving temperature uniformity in heated tissue.

A microwave heating system, designed to improve temperature uniformity in heated tissue, is described. The system employs parallel-opposed waveguide applicators, operating in the TE10 mode at 2450 MHz with the tissue to be heated (i.e. mouse intestine) immersed in a liquid which is both biologically compatible with and dielectrically similar to the tissue. The liquid improves the microwave coupling and avoids shape and size dependent absorption characteristics of the irregularly shaped tissue. Also, by maintaining this liquid at a suitable temperature with respect to that required in the tissue, the thermal losses and hence temperature gradients in the tissue are reduced compared with heating in hot liquid alone.

Animals↗
PubMed1991

[Energy metabolism of growing broiler chickens kept in groups in relation to the environmental temperature. 2. Heat production, thermoregulatory heat production and thermoneutral temperature (short term measurement)].

In 5 experiments the weekly rhythm of the heat production of growing young broiler chickens kept in groups between their 5th and 57th days of life was measured according to the method of short-time measuring (30-minute measuring periods) in dependence on environmental temperature (ET) between 40 and 5 degrees C in stages of 5 K by means of gas exchange and indirect calorimetry. The keeping temperature ranged from one experiment to the other from 35, 30, 25, 20 to 15 degrees C. The dependence of heat production on ET is parabolic in the medium and high ranges of temperature. As a rule, heat production increases progressively with very low ET. Thermoneutral temperature depends on both, the age (live weight) of the chickens and environmental temperature. Thermoregulatory heat production decreases with growing age. It changed from 24 kJ/kg LW0.75.d.K at the beginning to 8 kJ/kg LW0.75.d.K at the end of the experiments.

Age Factors↗
PubMed1978

Thermal design of a heat exchanger for heating or cooling blood.

Experimental data, and their correlation with predictions from theory, are presented for the thermal design of a countercurrent heat exchanger for heating or cooling blood. The thermal design considers the influence on the Nusselt number of blood and the heat exchanger effectiveness of variables such as the blood flow rate, tube diameter and length, and the thermal properties of blood. The data presented are compared with data from the literature and with predictions from theory. Insofar as the design of a blood heat exchanger is concerned, flowing blood can be considered a single-phase fluid. Results of the thermal design analysis are applicable to attempts to produce and control blood hyperthermia for applications such as the perfusion of tumours of the extremities, and to efforts to induce hypothermia during open-heart surgery.

Blood↗
PubMed2004

Effect of excessive environmental heat on core temperature in critically ill patients. An observational study during the 2003 European heat wave.

BACKGROUND: The primary goal of this study was to investigate the relation between the core temperature of critically ill patients and hot ambient temperatures during a heat wave. The second goal was to evaluate the impact of such a heat wave on the number of microbiological tests ordered. METHODS: During a heat wave, from August 3 to 22, 2003, we conducted an observational study in the surgical intensive care unit (ICU) of a French hospital that had no air-conditioning at the time. The core temperature of 18 critically ill patients and 36 health-care workers was measured with a non-contact, infrared tympanic membrane thermometer. The association between the core body temperature in infected and non-infected critically ill patients and the staff members, and the ambient temperature in the ICU was analysed using linear regression. The number of microbiological tests ordered was also recorded and compared with the same period in the previous year. RESULTS: The equation of the regression line for infected critically ill patients was: core temperature=33.5+0.16 x ambient temperature (R(2)=0.53; P<0.0001). The regression line was steeper than that for the non-infected patients (0.077; P<0.0001). The slopes of the regression lines for non-infected and control patients were similar (P=0.20). More blood cultures were carried out during the heat wave than at the same period during the year 2002 (4.80 blood cultures per 1000 patient-days vs 2.47 per 1000 patient-days; P=0.0006). CONCLUSION: During a sustained high ambient temperature, hyperthermia can occur in critically ill infected patients and to a lesser extent in non-infected patients and health-care workers. The number of blood cultures requested rises substantially, leading to increased costs. Installation of air-conditioning is therefore recommended.

Adult↗
PubMed1997

Heat-induced longevity extension in Drosophila. I. Heat treatment, mortality, and thermotolerance.

Survival data were collected on a total of 28,000 Drosophila melanogaster adults in order to investigate mortality patterns and induced physiological responses after a mild thermal stress. A brief, nonlethal heat treatment extends adult life span at normal temperatures by an average of 2 days (64), compared to nontreated controls of the same genotypes. Life expectancy is extended as a demographic consequence of reduced age-specific mortality over a period of up to several weeks after the heat treatment. Heat treatment also increases tolerance to subsequent, more severe thermal stress. Observations on single-sex populations suggest that heat-induced longevity extension is independent of the suppression of reproductive activity.

Acclimatization↗
PubMed2000

Effects of a heat and moisture exchanger and a heated humidifier on respiratory mucus in patients undergoing mechanical ventilation.

OBJECTIVE: To evaluate the effects of a heat and moisture exchanger and a heated humidifier on respiratory mucus and transportability by cilia and cough in patients undergoing invasive mechanical ventilation (up to 72 hrs). DESIGN: Prospective, randomized, clinical study. SETTING: General intensive care unit and university research laboratory. PATIENTS: A total of 32 consecutive patients with acute respiratory failure, who were intubated and mechanically ventilated in the intensive care unit setting, were enrolled in the study. INTERVENTIONS: Patients were randomly assigned to receive as a humidifying system a heat and moisture exchanger (HME) or heated humidified water (HHW) at the onset of mechanical ventilation (time 0). Respiratory mucus samples were collected by suction using a sterile technique at time 0, 24, 48, and 72 hrs of mechanical ventilation. MEASUREMENTS AND MAIN RESULTS: Eleven patients were excluded from this study because of either extubation or death before 72 hrs of mechanical ventilation, leaving 12 patients in the HME group and nine patients in the HHW group. Ventilatory variables including minute volume, mean airway pressure, positive end-expiratory pressure, Fio2, as well as Pao2/Fio2 ratio, fluid balance (last 6 hrs), furosemide, and inotrope administration (last 4 hrs) were recorded. In vitro mucus transportability by cilia was evaluated on the mucus-depleted frog palate model, and the results were expressed as the mucus transport rate. Cough clearance (an estimation of the interaction between the flow of air and the mucus lining the bronchial walls) was measured using a simulated cough machine, the results being expressed in millimeters. Mucus wettability was measured by the contact angle between a mucus sample drop and a flat glass surface. Mucus rheologic properties (mechanical impedance [log G*] and the ratio between viscosity and elasticity [tan delta]) were measured using a magnetic microrheometer at 1 and 100 cGy/sec deformation frequency. The two humidification groups were comparable in terms of the Acute Physiology and Chronic Health Evaluation II score, age, gender, ventilatory variables, fluid balance, use of inotropes, and furosemide. CONCLUSION: Ours results indicate that air humidification with either HME or HHW at 32 degrees C (89.6 degrees F) has similar effects on mucus rheologic properties, contact angle, and transportability by cilia in patients undergoing mechanical ventilation, except for transportability by cough, which diminished after 72 hrs of mechanical ventilation in the HME group (p = .0441).

APACHE↗
PubMed2002

Influence of the electron distribution function shape on nonlocal electron heat transport in laser-heated plasmas.

A nonlocal model of electron heat flow in laser-heated plasmas taking into account the super-Gaussian deformation of the electron velocity distribution function by the laser heating was developed. Based on comparisons to Fokker-Planck simulations of hot spot heating, it performs better than previous models. The growth rate of thermal filamentation is considerably changed by this thermal conductivity modification. First results from a formula describing the isotropic component, f(0)(x,v), of the electron velocity distribution function as a spatial convolution over local Maxwellians are also presented.

Journal Article↗
PubMed2000

Enhanced heat capacity and a new temperature instability in superfluid 4He in the presence of a constant heat flux near t(lambda)

We present the first experimental evidence that the heat capacity of superfluid 4He, at temperatures very close to the lambda point T(lambda), is enhanced by a constant heat flux Q. The heat capacity at constant Q, C(Q), is predicted to diverge at a temperature T(c)(Q)<T(lambda) at which superflow becomes unstable. In agreement with previous measurements, we find that dissipation enters our cell at a temperature, T(DAS)(Q), below the theoretical value, T(c)(Q). We argue that T(DAS)(Q) can be accounted for by a temperature instability at the cell wall, and is therefore distinct from T(c)(Q). The excess heat capacity we measure has the predicted scaling behavior as a function of T and Q, but it is much larger than predicted by current theory.

Journal Article↗
PubMed2005

Heat pinches in electron-heated Tokamak plasmas: theoretical turbulence models versus experiments.

Two fluid turbulence models, the drift wave based quasilinear 1.5D Weiland model and the electromagnetic global 3D nonlinear model CUTIE, have been used to account for heat pinch evidence in off-axis modulated electron cyclotron heating experiments in the Rijnhuizen Tokamak Project. Both models reproduce the main features indicating inward heat convection in mildly off-axis cases. In far-off-axis cases with hollow electron temperature profiles, the existence of outward convection was reproduced only by CUTIE. Turbulence mechanisms driving heat convection in the two models are discussed.

Journal Article↗