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At least 307 records · Page 17Linked to original sources
PubMed1999

Evaluation of washing with cold water to facilitate heat dissipation in horses exercised in hot, humid conditions.

OBJECTIVE: To determine whether body temperature of horses exercised in hot, humid conditions and then repetitively washed with cold water will decrease more rapidly than that of horses that are not washed, and to determine whether washing with cold water has deleterious effects on horses. ANIMALS: 5 physically fit Thoroughbred mares, 3 to 10 years old. PROCEDURES: Horses were exercised on a high-speed treadmill in hot (31.1+/-0.3 C), humid (relative humidity, 77.7+/-2%) conditions. Exercise was terminated when pulmonary artery temperature reached 41.5 C. Values for pulmonary artery, rectal, and left gluteal muscle temperatures were compared throughout a 30-minute recovery period after exercise during which horses stood quietly (passive cooling) or were cooled (active cooling) by repeated applications of cold (1 5.6+/-0.6 C) water. RESULTS: Pulmonary artery temperature was significantly less for actively cooled horses, compared with passively cooled horses 4 minutes into the recovery period. Left gluteal muscle temperature decreased significantly in actively cooled, but not passively cooled, horses during the recovery period. Heart rate and rectal temperature were significantly less for actively cooled horses by 15 minutes of the recovery period. Cooling technique did not effect hydration status, muscle health, or serum electrolyte concentrations. Active cooling did not cause obvious adverse effects. CONCLUSION AND CLINICAL RELEVANCE: Active cooling by washing with cold water is a safe, effective means for facilitating heat dissipation of horses after exercise in a hot, humid environment.

Animals↗
PubMed2000

Light scattering characteristics of aerosols as a function of relative humidity: Part I--A comparison of measured scattering and aerosol concentrations using the theoretical models.

The Southeastern Aerosol and Visibility Study (SEAVS) was undertaken to characterize the size-dependent composition, thermodynamic properties, and optical characteristics of the ambient atmospheric particles in the southeastern United States. The field portion of the study was carried out from July 15 to August 25, 1995. As part of the study a relative humidity controlled inlet was built to raise or lower the relative humidity to predetermined levels before the aerosol was passed into an integrating nephelometer or particle-sizing device. Five other integrating nephelometers were operated in various configurations, two of which were fitted with a 2.5 microns inlet. Fine particle (< 2.5 microns) samplers were operated to measure concentrations of sulfate, nitrate, and ammonium ions, organic and elemental carbon, and fine soil. Mass size distributions were measured with an eight-stage, single orifice cascade impactor. Four different strategies for estimating scattering were used. First, an externally mixed model with constant specific scattering coefficients, sulfate ion mass interpreted as ammonium bisulfate, and ammonium bisulfate growth as a function of relative humidity, is assumed. Second, an externally mixed aerosol model, assuming constant dry specific scattering but with sulfate ammoniation and associated composition-dependent hygroscopicity explicitly accounted for, is used. Third, an externally mixed aerosol model, but with sulfate ammoniation, associated growth as a function of relative humidity, and sulfate size distributions, is applied. Fourth, an internally mixed aerosol model with measured sulfur size distributions and estimated size distributions for other species is used with the growth characteristics of the mixture being estimated using the Zdanovskii-Stokes-Robinson (ZSR) assumptions. Only ionic species were considered to be hygroscopic. The second, third, and fourth approaches yield similar results with reconstructed scattering comparing quite favorably with measured scattering. Accounting for sulfate ammoniation and associated water uptake was the most important detail in achieving closure between measurements and modeled scattering. In general, differences between estimated scattering, assuming internally or externally mixed models, was small. These same models were used to estimate wet to dry scattering ratios. The R2 for an ordinary least-squares regression between measured and predicted ratios was high (0.71-0.92), and in most cases the scattering ratio was insensitive to modeling assumptions. However, during some sample periods differences between predicted scattering ratios for the different modeling assumptions were as high as 30%.

Aerosols↗
PubMed2002

[Dynamic changes of SOD and MDA in canine limbs with gunshot wound in hot and humid environment: an experimental study].

OBJECTIVE: To study the dynamic changes in lipid peroxidation and the activity of antioxidative enzyme in canine limbs with gunshot wound in hot and humid environment. METHODS: Eighteen dogs with gunshot wound were randomly assigned into 3 groups with equal numbers. Dogs observed after injury in normal environment was designated as NE group, those in hot and humid environment as HHE group and those in hot and humid environment with preceding heat acclimatization training as HA group. Contents of superoxide dismutase (SOD) and malonaldehyde (MDA) in both the peripheral blood and muscular tissues from gunshot wound tract were measured at 0, 1, 3, 4, 6, 8, 10, 14, 18 and 24 h respectively after the dogs had been wounded. RESULTS: Positive correlation between SOD and MDA contents was observed in each group. Three hours after injury, MDA level in HHE group began to ascend, reaching the peak level at 6 h that was significantly higher than those in the other 2 groups (P<0.05); SOD level underwent a reverse change, which was significantly lower in HHE group than in the other groups with that in HA group being the highest. Comparable SOD levels in the groups occurred at the time of 14 h, which happened to MDA levels 4 h later. CONCLUSION: Gunshot injuries in the limbs of dogs exposed to hot and humid environment induces increased free oxygen and aggravated the lipid peroxidation, which can be alleviated by heat acclimatization.

Animals↗
PubMed2004

[Pathological changes of cat brain tissues after cranial gunshot wound in hot and humid environment].

OBJECTIVE: To investigate pathological changes in cat brain tissues after gunshot wound in the head in hot and humid environments. METHODS: Sixteen cats were randomly divided into 4 groups, namely the normal environment (group 1), gunshot in normal environment (group 2), hot and humid environment (group 3), and gunshot wound in hot and humid environment (group 4) groups. Pathological changes of the cat brain tissues were observed with both optical and electron microscopes. RESULTS: The early-stage changes in group 2 were high-lighted by vasomotor dysfunction, with the coexistence of both vascular spasm and dilation. In group 3, vascular spasm was depressed while hemorrhagic changes increased. On the brain tissue sections in group 4 for optical microscopic observation and ultra-thin sections for electron microscopic examination, the number of viable neural cells was obviously reduced, and edema, degeneration of the organelle occurred; loosening of the capillary tight junction, rupture and bleeding of the blood vessels, as well as degeneration and loosening of the myelin sheath were observed by transmission and scanning electron microscopes, and such changes were more serious than those in group 2. CONCLUSION: The hot and humid environment can significantly affect the pathological changes in the brain tissues of cat with cranial gunshot wound.

Animals↗
PubMed2005

[Effect of early nutritional support on plasma superoxide dismutase, malondialdehyde and nitric oxide in rats with burns in a hot and humid environment].

OBJECTIVE: To observe the changes of plasma superoxide dismutase (SOD), malondialdehyde (MDA) and nitric oxide (NO) in rats with combined stress of burn injury and hot and humid environment. METHODS: The rats with superficial second-degree scald were subjected to intragastric administration of double-distilled water for one week (control group) or treated with ascorbic acid and L-arginine mixed with a-Tocopherol for one week (treatment group). All the rats were exposed to the same hot and humid environment of Td 37+/-0.5 degrees C with relative humidity of 65%+/-5% for 1-2 h. Observation was performed at 1, 2, 4, and 10 h after the heat exposure, respectively. RESULTS: SOD and MDA changes were significantly different between the two groups (P<0.01, P<0.05). In the control group, NO levels at 1 h were significantly different from those measured at 2 and 6 h after the exposure (P<0.01, P<0.05). CONCLUSION: Early nutritional support can significantly reduce the stress organ injuries, and prevent complications following injury in a hot and humid environment.

Animals↗
PubMed2005

[Changes of heat-shock protein 70 in the brain of rabbits with craniocerebral missile injury in hot and humid environment].

OBJECTIVE: To study the changes of heat shock protein 70 (HSP70) in the brain of rabbits with craniocerebral missile injury (CMI) and their impact on the injury in a hot and humid environment (HHE). METHODS: Twenty-four New Zealand white rabbits were randomized into 3 equal groups, namely normal temperature (NT) control group (subjected to treatment at temperature of 22.0+/-0.5 degrees C with relative humidity of 50%), NT gunshot group with CMI and HHE gunshot group with CMI. The rabbits in the latter two groups were subjected to normal temperature of 22.0+/-0.5 degrees C with relative humidity of 50% and environmental temperature of 39.0+/-0.5 degrees C with relative humidity of 80% to 85%, respectively, after establishment of CMI models. HSP70 in the brain tissues and lymphocytes was detected by Western blotting and visualized using chemoluminescence and X-ray films, followed by quantitative gel image analysis. RESULTS: Expressions of HSP70 in the cortex, hypothalamus and lymphocytes increased apparently in HHE gunshot group, and the changes of HSP70 in the lymphocytes were consistent with those in the cerebral cortex and hypothalamus. CONCLUSION: HSP70 expression in the brain tissues and the lymphocytes increase evidently after MCI in HHE.

Animals↗
PubMed1989

Humidity of the Bain and circle systems reassessed.

The humidity outputs of the Bain circuit, a traditional non-coaxial Mapleson D system, and a circle system with and without a soda lime absorber were evaluated in a laboratory model simulating a 70-kg subject. The breathing systems were tested with tidal volumes of 0.35 and 0.70 L and frequencies of 10-20 breaths/min to maintain an end-expiratory CO2 of 4.5%. There were small differences in inspiratory gas humidity between the Bain and the non-coaxial Mapleson D system. With a fresh gas flow of 5 L/min in the Bain circuit, the humidity was 9.8-16.5 mg H2O/L depending on tidal volume and respiratory frequency. The humidity output of the circle absorber system with fresh gas flows of 0.5 or 2 L/min was 21.6-25.2 mg H2O/L at 60 min. Therefore, this study does not support previous studies, which propose that the Bain circuit has superior humidifying properties compared with those of the circle absorber system.

Anesthesiology↗
PubMed1987

Acute modest changes in relative humidity do not affect energy expenditure at rest in human subjects.

Energy expenditure at rest was determined twice in 10 healthy subjects with a 2-d interval at a relative humidity of 32 and 66 per cent respectively. The relative humidity over the 2 d preceding each observation was estimated to be about 32 per cent. The average (+/- s.e.m.) difference between the RMR at a relative humidity of 32 and 66 per cent respectively was found to be 0.3 +/- 1.2 watt. The results presented here justify the commonly used practice of neglecting variations in humidity when reporting on results of observations of resting metabolic rates in apparently healthy subjects.

Body Weight↗
PubMed1986

Film-coated zinc sulphate tablets and the effect of humidity on tablet properties.

Preparation of film-coated zinc sulphate tablets and the effect of relative humidity and aging on the physical properties of these coated tablets were investigated in this study. Shellac; Eudragit E and L, hydroxypropyl methylcellulose (HPMC) and HPMC-Eudragit E mixture were used as film-forming materials. As zinc sulphate has efflorescent properties, the effect of humidity on the coated tablets was studied and physical stability tests were carried out. Coated tablets were kept in bottles and in open petri-dishes at different relative humidities (30, 55 and 85%) at room temperature over 12 weeks, and the weight loss, hardness, and disintegration times of these tablets were followed. Findings indicated that film-coated zinc sulphate tablets having good tablet quality can be prepared using the formulations (F-VI) HPMC-Eudragit E mixture and (F-III) Eudragit E as coating materials. Thus, the effect of relative humidity on tablet properties can be reduced.

Drug Stability↗
PubMed1978

[Changes in the biochemical and morphological indices of broiler chickens depending on the temperature and humidity conditions].

A varying temperature and humidity regime was tested on a total of 200 hybrid birds (White Plymouth Rock x Cornish crosses). Investigated were some indices of the carbohydrate metabolism and the deposition of vitamins in the organism as well as the effect of the temperature and humidity regime on the growth and development of broilers. It was established that the content of glycogen in the liver and the muscles in birds raised first at 32 degree C and relative air humidity of 65--70 per cent was higher than in birds raised at 36 degree C and relative air humidity of 45--50 per cent. Besides, these observations were coupled with some changes in the content of blood sugar and the amount of A and E vitamins in the liver. The body weight of the test broilers by the end of the experiment was 30 grams higher than that of the control group broilers.

Age Factors↗
PubMedDate not supplied

[Effect of air temperature and relative humidity on the preimaginal development of Ctenophthalmus teres fleas (Siphonaptera)].

The duration of the development and survival of preimaginal stages of fleas at a temperature of 5 to 30 degrees and relative humidity of 60 to 90% was studied. Minimal average duration of the development an the highest survival rate at all stages were registered at a temperature of 20 to 25 degrees and humidity of 85 to 90%. Under these conditions the whole cycle from egg to image lasts on an average 23 days. The threshold of the development for different stages falls within the limits of 3 to 6 degrees. The duration of the development of all stages was distinctly affected by temperature while the duration of larval development was affected as well by humidity. The survival of larvae was found to be affected by humidity while the survival of individuals in cocoons was considerably affected by temperature.

Animals↗
PubMed1994

Humidity regulation in the management of asthma patients sensitized to house dust mites.

Substances in the faeces of house dust mites are well-recognized as common allergens in the pathogenesis of asthma. There have been many trials of interventions aimed at reducing mite populations in the home, but most have been uncontrolled, too small, or too short to determine with confidence any beneficial effects. Of those which succeeded, very few used methods which reduced mite populations on a permanent basis. House dust mites are sensitive to humidity. Their geographical distribution is closely correlated to the availability of moisture. Very little work has been done on the effects of reducing humidity in the home environment in the long term, with a view to controlling dust mite populations. Two different methods which might reduce humidities to levels which could successfully reduce dust mite numbers are dehumidifiers, and mechanical ventilation with heat recovery (MVHR). To date there has been no work assessing the effectiveness of dehumidifiers and very little (although promising) work on MVHR. We discuss the potential of humidity control as an adjunct to the clinical treatment of asthma.

Animals↗
PubMed1993

Humidity effects on atomic force microscopy of gold-labeled DNA on mica.

Recent work in atomic force microscopy (AFM) of deoxyribonucleic acid (DNA) has relied on immobilizing DNA molecules by drying a small volume of buffered DNA solution onto cleaved mica. When imaging in air, relative humidity has been known to affect both the resolution and measured height of the DNA strands. We present data of measured height versus humidity for DNA and attached gold labels, and we propose a model for this data based on swelling of coadsorbed buffer salts upon exposure to moisture. In this model, small particles (e.g., DNA) stay near the top of the swelling salt layer, whereas larger particles (e.g., gold spheres) tend to be anchored down to the substrate until a moderate humidity is reached. At high humidity (around 65%), the salt layer becomes fluid-like and susceptible to tip-induced motion; the salts are either removed from the scan area or aggregate into island structures, depending on initial salt concentration on the surface.

Aluminum Silicates↗
PubMed1995

Effect of temperature and humidity on longevity of unfed adults and on oviposition of engorged females of Dermacentor reticulatus (Ixodidae).

The effect of ambient temperature and relative humidity on longevity of unfed adult ticks and on oviposition of engorged female ticks of Dermacentor reticulatus was examined. The 50% mortality time of unfed adult ticks, incubated at 5 degrees C, 10 degrees C, 20 degrees C and 27 degrees C and humidities of 15%, 50% and 100%, increased irrespective of their sex with rising relative humidity and decreasing temperature. It was longest at 5 degrees C and 100% r.h. being 617.8 days and shortest at 27 degrees C and 15% r.h. amounting only to 33.6 days. All unfed ticks survived an incubation of 150 days at -10 degrees C and 15%, 50% and 100% r.h. as well as an exposure of 180 days at 0 degrees C and 100% r.h. At 0 degrees C the percent survival was 75% for the males and 40% for the females at 50% r.h. but 100% for males and 95% for the females at 15% r.h. after exposure of 180 days. Oviposition of engorged females occurred at a temperature range of 10-27 degrees C, at 10 degrees C merely at 50% and 100% r.h. The percentage of ovipositioning females amounted to at least 80% apart from 10 degrees C and 50% r.h. being only 10%. The egg index and the egg conversion index as well as the larvae index and the larvae conversion index generally increased with rising temperature and relative humidity. The indices were lowest at 10 degrees C and 50% r.h. and were highest at 20 degrees C and 27 degrees C at 100% r.h. The reproduction capability of engorged female ticks, held at -10 degrees C, 0 degrees C and 5 degrees C and 15%, 50% and 100% r.h. and transferred to 20 degrees C and 95% r.h., persisted for 10 weeks at -10 degrees C and for 2 weeks at 0 degrees C at the most, but for at least 20 weeks at 5 degrees C. There were no significant differences of the preoviposition periods, egg indices and larvae indices as well as of the minimum embryonic developmental times and hatching rates with regard to the preceding incubation conditions and the length of the ticks' exposure.

Animals↗
PubMed1998

Measuring temperature and humidity in the breathing circuit.

Accurate measurement of temperature and humidity in the breathing circuit can be a difficult task. This article introduces basic humidity concepts, outlines the problems that are unique to the breathing circuit, and describes the various methods that are available to measure temperature and humidity. Recommendations are made on how to measure temperature and humidity in four commonly encountered situations.

Humans↗
PubMed1998

The effect of temperature and humidity on dengue virus propagation in Aedes aegypti mosquitos.

The effect of temperature and relative humidity on dengue virus propagation in the mosquito as one of the possible contributing factors to dengue hemorrhagic fever (DHF) outbreaks was studied. Ae. aegypti mosquitos were reared under standard conditions and inoculated intrathoracically with dengue virus. Virus propagation in the mosquitos was determined at the temperature and relative humidity of all 3 seasons of Yangon and for the simulated temperature and relative humidity of Singapore. The virus propagation was detected by direct fluorescent antibody technique (DFAT) with mosquito head squash and the virus titer was determined by plaque forming unit test (PFUT) in baby hamster kidney-21 cells. The results show that the infected mosquitos kept under the conditions of the rainy season and under the simulated conditions of Singapore had a significantly higher virus titer (p=<0.05) when compared with the other 2 seasons of Yangon. So it is thought that the temperature and relative humidity of the rainy season of Yangon and that of Singapore favors dengue virus propagation in the mosquito and is one of the contributing factors to the occurence of DHF outbreaks.

Aedes↗
PubMed2001

On-line measurement of the absolute humidity of air, breath and liquid headspace samples by selected ion flow tube mass spectrometry.

We describe how selected ion flow tube mass spectrometry (SIFT-MS) can be used to determine the absolute humidity of air, breath and liquid headspace samples. This involves the determination of the relative count rates of the H3O+ ions and those H3O+.(H2O)(1,2,3) hydrate ions that inevitably form in the helium carrier gas when humid samples are being analysed by SIFT-MS using H3O+ precursor ions. This requires an understanding of the kinetics of hydrated hydronium ion formation, the involvement of mass discrimination in the analytical quadrupole mass spectrometer and the decreased diffusive loss of the heavier hydrates along the flow tube. Thus, we show that the humidity of breath and liquid headspace samples, typically at the few percent level, can be directly obtained on-line to the SIFT-MS instrument along with the concentrations of trace gases, which are present at much lower levels. We emphasise the value of parallel humidity measurements in ensuring good real-time sampling of breath and liquid headspace and the value of such measurements to trace gas analysis using SIFT-MS.

Journal Article↗
PubMed1996

The Effect of Humidity on the Physical and Chemical Stability of Spray-Dried Aluminum Hydroxycarbonate

The moisture sorption isotherm of amorphous spray-dried aluminum hydroxycarbonate (SDAHC) at 25&deg;C revealed that moisture sorption increased sharply when the relative humidity exceeded 80%. The physical and chemical stability of SDAHC was studied for 1 year at 25&deg;C and 0, 11, 54, 84, or 100% RH. The results were interpreted to reveal that two mechanisms affect the properties of SDAHC at 25&deg;C. The sample stored at 0% RH did not exhibit any significant changes during the 1-year study period. The surface area and rate of acid neutralization decreased when samples were stored at 11 or 54% RH, but the material remained amorphous. This change is believed to be due to aggregation and cementation of particles. Much larger changes in surface area and the rate of acid neutralization occurred in the samples aged at 84 or 100% RH. Under these humidity conditions, polymorphic transformations occurred in addition to aggregation and cementation. X-ray diffraction indicated that microcrystalline boehmite was an intermediate phase. The stable polymorph was bayerite, which is believed to form due to the high surface pH produced by water sorption at 84 or 100% RH. The moisture sorption isotherm was useful in identifying the humidity conditions which resulted in high moisture sorption. Polymorphic transformations were only detected when the SDAHC was aged under these humidity conditions.

Journal Article↗