Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Temperature environment”

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 613 records · Page 34Linked to original sources
PubMed1990

The influence of curing time and environment on the fracture properties of bone cement.

Fracture of bone cement at the bone-cement interface is considered to be of significance in the aseptic loosening of orthopaedic implants. The characterisation of the fracture properties of bone cement is influenced by the time and environment in which it is cured. Cement samples stored in air and water at 21 and 37 degrees C for 7 and 21 days were tested using the 'Chevron' test to determine the work of fracture. It was found that the storage temperature and environment had important influences on the fracture resistance of bone cement. In a physiological environment cement appears to take longer to attain a fracture resistance equivalent to that of cement stored at room temperature.

Bone Cements↗
PubMed2005

Effect of room temperature on percentage finger systolic blood pressure response to finger cooling.

Percentage finger systolic blood pressure (%FSBP) in response to finger cooling is used to assess vascular components of the hand-arm vibration syndrome and the measurement method is under discussion for standardization. It has been suggested that measurement circumstances including room temperature may affect %FSBP. We investigated the effect of room temperature on %FSBP response to finger cooling in healthy subjects. Six healthy male subjects who were medical students volunteered for the study. Multi-channel plethysmograph was used for simultaneous multi-finger FSBP measurements. The examination room was kept at 21 +/- 1 degrees C and 25 +/- 1 degrees C, and the subjects were randomly assigned. Percentage finger systolic blood pressures for the index, middle, ring and little fingers at 15 degrees C and 10 degrees C cuff-water temperatures were calculated. Four-way analysis of variance was performed to determine the independent effect of subject, room temperature, finger and cuff-water temperature factors on %FSBP. The room temperature as an independent factor affecting %FSBP was statistically significant (P < 0.01). From the results, it can be concluded that %FSBP response to finger cooling in healthy subjects may be affected by room temperature. Therefore, room temperature is expected to be controlled when assessing peripheral vascular components of the upper extremities using %FSBP response to finger cooling.

Adult↗
PubMed1985

Effect of high daytime temperatures on the intake and utilisation of water in lactating Friesian cows.

Four primiparous Friesian cows in mid-lactation and housed in climate chambers were simultaneously exposed to three sequential climate treatments: 1, a three-week period in a thermoneutral environment (ambient temperature Ta 14-21 degrees C and relative humidity r.h. 60-70%); 2, a similar period during which they were exposed to Ta max. 38 degrees C/r.h. max. 80% for up to 7 h and Ta 14-21 degrees C/r.h. 60-70% for 17 h each day; and 3, a three-week period during which they were subjected once more to the thermoneutral conditions described for 1. Water and a complete feed were constantly available. Compared with water intake (drinking water + feed water) under thermoneutral conditions cows exposed to treatment 2 significantly increased their mean intake by 12.2%; in three cows, this involved a phase-shift of greater than 20% in drinking habits from day (hot) to night (cool) time. Water balance trials conducted at the mid-point of each treatment revealed that the mean losses of water via urine, faeces, milk, sweat and saliva as a percentage of water intake changed significantly resulting in a net gain (retention) of body water. An accompanying significant increase in live weight despite a 9.1% decrease in DM intake during treatment 2 confirmed the water retention results. On return to thermoneutral conditions (3), the cows exhibited a marked weight loss and a significant increase in urinary water excretion over treatment 1 and 2 values, signifying that a large proportion of the water retained during 2 was of extracellular origin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Effects of a moderate nocturnal cold stress on daytime sleep in humans.

The effects of a nocturnal exposure to a cool environment on daytime recovery sleep was studied in eight young (20-25 years old) healthy volunteers. A set of standardized clothing (KSU ensemble type) was provided to each individual (estimated total thermal resistance: 0.6 clo). The subject kept awake was passively exposed from 22.30 to 07.30 hours to environments perceived as neutral (N) and comfortable or slightly cold (C) and uncomfortable. They were then allowed to sleep ad libitum (light out at 08.00 hours) under thermoneutral conditions (air temperature: 21 degrees C to 22 degrees C; clothing: cotton tee-shirt and pajama-pants; covering: one cotton sheet and one wool blanket). Sleep was recorded and scored according to the Rechtchaffen and Kales standard procedures. Esophageal temperature (T(es)) was recorded from 21.30 hours until the end of sleep. The nocturnal drops in T(es) were significantly different between N and C (p<0.01), this difference disappearing during sleep. No statistical difference was found between conditions for most of the sleep variables. Compared to N however, C resulted in a significant increase in rapid eye movement (REM) sleep duration (+35%, p<0.01) during the subsequent daytime sleep. It is hypothesized that the REM-sleep increase induced by the exposure to moderate cold is due to the thermal discomfort stress consciously perceived by the subject.

Adaptation, Physiological↗
PubMed2002

Supravital energy production in early post-mortem phase - estimate based on heat loss due to radiation and natural convection.

The temperature-based determination of the time since death in the early post-mortem (pm) period plays an important role in medico-legal practice. In contrast to the common opinion according to which convection and conduction are mainly responsible for post-mortem heat loss, a considerable part of energy is emitted by thermal radiation. The present paper concentrates on the heat loss due to radiation and natural convection. Since both heat transfer mechanisms depend on the temperature gradient between skin and environment, the skin temperature was measured in corpses of different constitution (lean, medium and obese) and its decrease fitted by a single-exponential model. Heat loss due to radiation was calculated according to the non-linearized form of the law of Stefan and Boltzmann, heat loss due to natural convection according to the semi-empirical thermodynamic laws; the shape of the body in supine position was approximated to a semi-cylinder of finite length. The power due to radiation ranged between 386kJ/h (lean) and 550kJ/h (obese), that due to natural convection between 307kJ/h (lean) and 429kJ/h (obese) initially. Cumulative energy loss amounted to 2167kJ (lean) and 4239kJ (obese) by radiation and 1485kJ (lean) and 2922kJ (obese) by natural convection up to 20h pm. The energy loss due to radiation plus natural convection initially exceeded the energy loss due the decrease of the energy content of the body (mass x heat capacity x temperature decrease). This surplus can be explained only by exothermal processes in the phase of intermediary life and directly provides lower bounds for supravital energy production. Cumulative supravital energy ranges between 1139kJ up to 5h pm in the lean and 2516kJ up to 10h pm in the obese corpses. The courses of supravital energies and powers are presented as functions of time. Under standard conditions like still air (no forced convection) and insulating ground (little conductive heat transfer), the lower bounds represent estimates for total supravital energy production.

Journal Article↗
PubMed2006

An evaluation of conditions that may affect the performance of houseboat exhaust stacks in prevention of carbon monoxide poisonings from generators.

National Institute for Occupational Safety and Health (NIOSH) researchers evaluated two exhaust stack designs for reducing carbon monoxide (CO) exposures from gasoline-powered generator exhaust on houseboats. Tests were conducted (a) after dark, (b) in high-temperature and high-humidity environments, (c) during temperature inversions, (d) under various generator loads, and (e) at different houseboat trim angles. Two different designs of houseboat exhaust stacks were evaluated and compared with the side-exhaust configuration, which is standard on many houseboats. The two designs were flagpole and vertical stack. Both exhaust stacks performed dramatically better than the standard water level, side-exhaust configuration. The highest mean CO concentrations on the upper and lower decks of the houseboat with the vertical exhaust stack were 27 ppm and 17 ppm. The highest mean CO concentrations on the upper and lower decks of the houseboat with the modified flagpole stack were 5 ppm and 2 ppm. These findings are much lower than the 67 ppm and 341 ppm for the highest mean CO concentrations found on the upper and lower decks of houseboats having the usual side-exhausted configuration. The NIOSH evaluation also indicated that high-temperature and high-humidity levels, temperature inversions, generator loading, and houseboat trim angles had little effect on the exhaust stack performance. It also demonstrated the importance of proper design and installation of exhaust stacks to ensure that all exhaust gases are released through the stack. Based on the results of this work, NIOSH investigators continue to recommend that houseboat manufacturers, rental companies, and owners retrofit their gasoline-powered generators with exhaust stacks to reduce the hazard of CO poisoning and death to individuals on or near the houseboat.

Air Pollutants↗
PubMed2004

[Range and ecology of Dermacentor reticulatus (Fabricius, 1794) in Mazuria focus. II. Seasonal activity patterns of the adults].

In the spring and fall of three consecutive years (1997, 1998 and 1999), a study of the seasonal activity patterns in hungry adult forms of Dermacentor reticulatus was conducted on experimental sites, supplemented by field observations beyond the sites in 2000 and 2001. The studies confirmed two periods of activity (spring and fall). The ticks' activity depended mostly on the average daily temperature of the environment, and was observed in temperatures ranging between +4 degrees C and +13 degrees C. Factors diminishing the ticks' activity also included day length and relative air humidity; no active ticks were observed during days longer than 16 hours, or in average relative air humidity lower than 65%.

Animals↗
PubMedDate not supplied

Infection by the warble fly Przhevalskiana silenus Brauer, 1858, in the Italian goats. An update up to 1988.

This paper is a review of the work done at the University of Bari on the goat warble fly Przhevalskiana silenus Brauer, 1858. It reports data concerning taxonomy, biology, and epidemiology of the goat warble fly, as well as therapy against the infection. Grunin in 1962, and later Madel in 1969, were the first researchers to reach the conclusion that the three species of Przhevalskiana up to then recognized--namely P. silenus, P. aegagri, and P. crossii--should be unified in just one--Przhevalskiana silenus. The genetical studies conducted by us on the third instar larvae with the use of 9 gene-enzyme systems confirmed the assumption that P. silenus is the only species which parasitizes goats. Studies were conducted on the external life-cycle of the parasite with the purpose of elucidating the relationship existing among time of dropping, length of time needed for adults to emerge from pupae, and temperature of the environment. Both total sum of temperature and length of time seem to play an important role in determining the duration of the pupal stage. Epidemiological data derived from a two-year survey carried out in six infected groups of goats are also reported. The interrelationship existing among prevalence, mean intensity, variance, variance/mean rate, and parameter K of the negative binomial are presented. It appears that age, parameter K, and variance of infection intensity are closely related. A trial experiment was also carried out to evaluate the efficacy of ivermectin against a natural infection with P. silenus larvae. A single subcutaneous injection of 1% ivermectin was given, at doses of 50, 100 or 200 micrograms/kg b.w. The drug was found to be fully effective at all three doses.

Animals↗
PubMed1977

Effective temperature scale useful for hypo- and hyperbaric environments.

Basic physics of man's heat exchange by radiation, convection, evaporation, and conduction through clothing is used to define and establish a Standard Effective Temperature Scale (SET), with which sensory and physiological responses of sedentary and active personnel can be related. The standard environment chosen is the Effective Temperature (ET) Scale, used by the American Society of Heating, Refrigerating and Air-Conditioning Engineers; namely, as the temperature of an isothermal enclosure at sea level with 50% rh and still air (0.1-0.15 m/s) in which a clothed (0.6 clo) sedentary subject would exchange the same total sensible and insensible heat as in the actual test environment. Mean skin temperature (Tsk) and skin wettedness (w) can be associated at sea level with thermal comfort and neutrality and with heat exchange. For hypo- and hyperbaric environments, thermal equivalence between SET and any test environment occurs when mean body temperature (Tb) for each is identical. Comprehensive data, developed for a 2-node model of human temperature regulation and of the associated partitional calorimetry, demonstrates the expected interaction between SET and the basic environmental and clothing factors over the barometric range 0.33 to 30 ATA.

Air Movements↗
PubMed1997

Dependence of human respiratory thermal washout on extrathoracic airway conditions.

Thermal washout curves have been proposed as noninvasive tools for analysing lower airway dimensions and pulmonary blood flow, but how upper airway heat transfer affects these washout curves is unclear. The present study was designed to compare extrathoracic and tracheobronchial contributions to thermal washout curves. Respiratory frequency, air ambient temperature, and body core temperature (tc) were varied in six male subjects before and after immersion in cold (1.1 degrees C) water for up to 2 h under three conditions: 1) control: ambient temperature (tamb) = 25 degrees C, rectal temperature change (delta tre) = 0 degrees C; 2) pre-immersion: tamb = 4 degrees C, delta tre = 0 degrees C; and 3) post-immersion: tamb = 25 degrees C, delta tre = -0.7 degrees C. Both peak expiratory nasal (tpn) and oral (tpo) airstream temperatures were measured. Each subject was tested twice. Expiratory tpo was generally higher than tpn in all conditions. Increasing breathing rates lowered tpn and tpo in the control and cold air environments. Orifice temperatures, which are presumed to reflect upper airway blood temperatures, correlated with both tpn and tpo. Lowering tc had no effect on washout curves during quiet breathing and affected only tpn during rapid breathing. The results suggest that while tracheobronchial conditions may contribute to thermal washout curves, extrathoracic conditions predominate. Strong correlations between orifice temperatures, peak expiratory nasal temperatures and peak expiratory oral temperature demonstrate the dominant role of upper airway heat exchange in determining thermal washout curves.

Adult↗
PubMed1990

Ecology of mesophilic Aeromonas spp. in aquatic environments of a temperate region and relationship with some biotic and abiotic environmental parameters.

The Ecology of mesophilic Aeromonas species has been investigated since January 1988 to examine their occurrence and distribution in aquatic environments of Okayama Prefecture. Water and plankton samples were quantitatively as well as qualitatively analyzed throughout the seasons from five selected stations including fresh, brackish, and saline environments. Analysis of variance and correlation coefficients among the biotic and abiotic parameters were sought. The organisms were found in all the environs with high densities through all the seasons. Plankton samples yielded higher counts of Aeromonas than the water samples in all the environs. Water temperature seemed to play a significant role on their growth during the winter months, however, no significant seasonal variation nor any correlation with fecal pollution were observed in most of the environments. A reciprocal relationship was seen with salt concentration in the saline environment. Among the currently recognized mesophilic species; A. caviae, A. hydrophila, A. sobria, and A. media were isolated with the predominance of anaerobic biovar. The present study reveals that Aeromonas are widely distributed in fresh, brackish and saline environments of this region. The study also reveals that Aeromonas are autochthonous members in aquatic ecosystems and are indigenous to these environs. Aeromonas species isolated from our environments were found to exhibit drug resistance potential which differed from that of isolates from diverse geographical locales. The high incidence of clinically significant Aeromonas species in this aquatic region could be of public health significance for the inhabitants of this region, as well as a challenge to their dependence on aquatic resources.

Aeromonas↗
PubMed2004

The measurement temperature: an important factor relating physicochemical and adhesive properties of yeast cells to biomaterials.

Flow chambers applied to the study of the initial adhesion process of Candida parapsilosis are rarely found in the literature. The ability of these microorganisms to proliferate and form biofilms in environments at temperatures around 22 or 37 degrees C is reflected in the contamination of laboratory instruments and material or in human implant infections, respectively. The initial interaction between yeasts and substrata is mediated by physicochemical forces, which in turn originate from the physicochemical surface properties of both interacting phases. In this context, this work aims to relate the initial rates of adhesion rates to glass and silicone of Candida parapsilosis, strains 294 and 289, grown at 22 and 37 degrees C with the theoretical predictions of the adhesion process, expressed by the interaction free energies and calculated through the physicochemical parameters, which are also measured at 22 and 37 degrees C. The results indicate that physicochemical parameters of yeasts are changed not only by the culture temperature but also by the measurement temperature; only when the measurement temperature is equal to the growth temperature a coherent relation between in vitro adhesion data and interaction free energies can be established. In this sense, the adhesion to glass is mediated by long-range forces or, what amounts to the same thing, by Lifshitz-van der Waals interaction free energy. On the other hand, the adhesion to silicone rubber seems to be moderated by acid-base interaction free energy, which involves the presence of short-range forces. Based on these results, it can be assumed that the substratum surface properties are directly related to the kind of force acting on the initial microbial adhesion process, while cell surface properties dictate the changes in the strength of the force between different samples.

Algorithms↗
PubMedDate not supplied

Crowding in extremophiles: linkage between solvation and weak protein-protein interactions, stability and dynamics, provides insight into molecular adaptation.

The study of the molecular adaptation of microorganisms to extreme environments (solvent, temperature, etc.) has provided tools to investigate the complex relationships between protein-solvent and protein-protein interactions, protein stability and protein dynamics, and how they are modulated by the crowded environment of the cell. We have evaluated protein-solvent and protein-protein interactions by solution experiments (analytical ultracentrifugation, small angle neutron and X-ray scattering, density) and crystallography, and protein dynamics by energy resolved neutron scattering. This review concerns work from our laboratory on (i) proteins from extreme halophilic Archaea, and (ii) psychrophile, mesophile, thermophile and hyperthermophile bacterial cells.

Adaptation, Biological↗
PubMed2003

Ryanodine and dihydropyridine receptor binding in ventricular cardiac muscle of fish with different temperature preferences.

Ca(2+)-induced Ca2+ release (CICR) mechanism of cardiac excitation-contraction (e-c) coupling is dependent on the close apposition between the sarcolemmal dihydropyridine receptors (DHPR) and the sarcoplasmic reticulum (SR) ryanodine receptors (RyR). In particular, high RyR/DHPR ratio is considered to reflect strong dependence on SR Ca2+ stores for the intracellular Ca2+ transient. To indirectly evaluate the significance of CICR in fish hearts, densities of cardiac DHPRs and RyRs were compared in ventricular homogenates of three fish species (burbot, rainbow trout, and crucian carp) and adult rat by [3H] PN200-110 and [3H] ryanodine binding. The density of RyRs was significantly (P<0.05) higher in the adult rat (124+/-10 channels/microm3 myocyte volume) than in any of the fish species. Among the fish species, cold-acclimated (4 degrees C) trout had more RyRs than burbot, and crucian carp. The density of DHPRs was highest in the trout heart. RyR/DHPR ratio was significantly (P<0.05) higher in rat (4.1+/-0.5) than in the fish hearts (varying from 0.97+/-0.16 to 1.91+/-0.49) suggesting that "mammalian type" CICR is less important during e-c coupling in fish ventricular myocytes. In rainbow trout, acclimation to cold did not affect the RyR/DHPR ratio, while in crucian carp it was depressed in cold-acclimated animals (4 degrees C; 0.97+/-0.16) when compared to warm-acclimated fish (23 degrees C; 1.91+/-0.49). Although RyR/DHPR ratios were relatively low in fish hearts, there was a close correlation (r2=0.78) between the RyR/DHPR ratio and the magnitude of the Ry-sensitive component of contraction in ventricular muscle among the fish species examined in this study.

Acclimatization↗
PubMed2006

Long-term change in the sensitivity of tree-ring growth to climate forcing in Larix decidua.

Tree rings are widely used long-term proxy data which, if combined with long-term instrumental climate records, can provide excellent information on global climate variability. This research aimed to determine whether interannual climate-growth responses in Alpine treeline forests are stationary over time. We used tree-ring width chronologies of Larix decidua (European larch) from 17 sites and monthly temperatures and precipitation data for the period 1800-1999. Climate-growth relationships were assessed with correlation and response functions, and their stationarity and consistency over time were measured using moving correlation. Tree-ring chronologies showed similar interannual variations over the last two centuries, suggesting that the same climatic factors synchronously limited growth at most sites. The most sensitive variables showed significant transient responses varying within the time period, indicating a possible deviation from the uniformitarian principle applied to dendroclimatology. If these findings are confirmed in future studies on other species and in other regions, we suggest that time-dependent variables should be taken into account to avoid overestimation of treeline advance, future forest carbon storage in temperature-limited environments and inaccurate reconstruction of past climate variability.

Carbon↗
PubMed2004

Dormancy release during hydrated storage in Lolium rigidum seeds is dependent on temperature, light quality, and hydration status.

The influence of temperature, light environment, and seed hydration on the rate of dormancy release in Lolium rigidum (annual ryegrass) seeds during hydrated storage (stratification) was investigated. In a series of experiments, seeds were subjected to a range of temperatures (nine between 5 degrees C and 37 degrees C), light (white, red, far-red, and dark), and hydration (4-70 g H(2)O 100 g(-1) FW) during stratification for up to 80 d. Samples were germinated periodically at 25/15 degrees C or constant 15, 20, or 25 degrees C with a 12 h photoperiod to determine dormancy status. Dark-stratification was an alternative, but not equivalent dormancy release mechanism to dry after-ripening in annual ryegrass seeds. Dormancy release during dark-stratification caused a gradual increase in sensitivity to light, but germination in darkness remained negligible. Germination, but not dormancy release, was greater under fluctuating diurnal temperatures than the respective mean temperatures delivered constantly. Dormancy release rate was a positive linear function of dark-stratification temperature above a base temperature for dormancy release of 6.9 degrees C. Dormancy release at temperatures up to 30 degrees C could be described in terms of thermal dark-stratification time, but the rate of dormancy release was slower at < or =15 degrees C (244 degrees Cd/probit increase in germination) than > or =20 degrees C (208 degrees Cd/probit). Stratification in red or white, but not far-red light, inhibited dormancy release, as did insufficient (<40 g H(2)O 100 g(-1) FW) seed hydration. The influence of dark-stratification on dormancy status in annual ryegrass seeds is discussed in terms of a hypothetical increase in available membrane-bound phytochrome receptors.

Animal Feed↗