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PubMed2002

A sandwich-designed temperature-gradient incubator for studies of microbial temperature responses.

A temperature-gradient incubator (TGI) is described, which produces a thermal gradient over 34 aluminium modules (15x30x5 cm) intersected by 2-mm layers of partly insulating graphite foil (SigraFlex Universal). The new, sandwich-designed TGI has 30 rows of six replicate sample wells for incubation of 28-ml test tubes. An electric plate heats one end of the TGI, and the other end is cooled by thermoelectric Peltier elements in combination with a liquid cooling system. The TGI is equipped with 24 calibrated Pt-100 temperature sensors and insulated by polyurethane plates. A PC-operated SCADA (Supervisory Control And Data Acquisition) software (Genesis 4.20) is applied for temperature control using three advanced control loops. The precision of the TGI temperature measurements was better than +/-0.12 degrees C, and for a 0-40 degrees C gradient, the temperature at the six replicate sample wells varied less than +/-0.04 degrees C. Temperatures measured in incubated water samples closely matched the TGI temperatures, which showed a linear relationship to the sample row number. During operation for 8 days with a gradient of 0-40 degrees C, the temperature at the cold end was stable within +/-0.02 degrees C, while the temperatures at the middle and the warm end were stable within +/-0.08 degrees C (n=2370). Using the new TGI, it was shown that the fine-scale (1 degrees C) temperature dependence of S(o) oxidation rates in agricultural soil (0-29 degrees C) could be described by the Arrhenius relationship. The apparent activation energy (E(a)) for S(o) oxidation was 79 kJ mol(-1), which corresponded to a temperature coefficient (Q(10)) of 3.1. These data demonstrated that oxidation of S(o) in soil is strongly temperature-dependent. In conclusion, the new TGI allowed a detailed study of microbial temperature responses as it produced a precise, stable, and certifiable temperature gradient by the new and combined use of sandwich-design, thermoelectric cooling, and advanced control loops. The sandwich-design alone reduced the disadvantageous thermal gradient over individual sample wells by 56%.

Bacteria↗
PubMed1998

Systemic hypothermia after spinal cord compression injury in the rat: does recorded temperature in accessible organs reflect the intramedullary temperature in the spinal cord?

This article addresses one basic issue regarding the use of systemic hypothermia in the acute management of spinal cord injury, namely, how to interpret temperature recordings in accessible organs such as the rectum or esophagus with reference to the spinal cord temperature. Thirty-six rats, divided into six groups, were randomized to laminectomy or to severe spinal cord compression trauma, and were further randomized to either a cooling/rewarming procedure or continuous normothermia (esophageal temperature 38 degrees C) for 90 min. The first procedure comprised normothermia during the surgical procedure, followed by lowering of the esophageal temperature from 38 degrees C to 30 degrees C (the hypothermic level), a 20-min steady-state period at 30 degrees C, rewarming to 38 degrees C, and finally a 20-min steady-state period at 38 degrees C. The esophageal, rectal, and epidural temperatures were recorded in all animals. The intramedullary temperature was also recorded invasively in four of the six groups. We conclude that the esophageal temperature is safe and easy to record and, in our setting, reflects the epidural temperature. The differences registrated may reflect a true deviation of the intramedullary temperature due to initial environmental exposure and secondary injury processes. Our results indicate that the esophageal temperature exceeds the intramedullary temperature during the initial recording and final steady state following rewarming, but not during the most crucial part of the experiment, the hypothermic period. The core temperature measured in the esophagus can therefore be used to evaluate the intramedullary temperature during alterations of the systemic temperature and during hypothermic periods.

Animals↗
PubMed1996

Comparison of infrared ear thermometer derived and equilibrated rectal temperatures in estimating pulmonary artery temperatures.

OBJECTIVES: To investigate the clinical accuracy of infrared ear thermometer derived and equilibrated rectal temperatures in estimating core body temperature. The clinical bias (i.e., mean difference between body sites), and variability (SD of the differences) of simultaneous temperatures were compared with pulmonary artery temperatures. Clinical repeatability (pooled SD of triplicate reading differences) was also examined for three ear infrared thermometers. DESIGN: Prospective clinical study. SETTING: A multidisciplinary, adult intensive care unit. PATIENTS: Twenty patients with an existing pulmonary artery catheter were studied in a multidisciplinary, adult intensive care unit. INTERVENTIONS: A single operator using optimum ear infrared technique and masked to ear and rectal temperatures recorded triplicate measurements with each of three infrared ear thermometers, each over a 4-min period with each infrared thermometer, while an assistant recorded temperatures. Infrared and rectal temperatures were compared with a simultaneous pulmonary artery temperature. MEASUREMENTS AND MAIN RESULTS: Infrared ear thermometers and rectal thermometers were calibrated daily, and pulmonary artery catheters were calibrated on removal from the patient. Patients were grouped into afebrile and febrile groups, based on initial pulmonary artery temperature. Bias and variability were compared between thermometers using analysis of variance. Clinical bias, but not variability, was significantly different between three ear infrared thermometers (0.16 +/- 0.46 degrees C, 0.07 +/- 0.38 degrees C, and -0.22 +/- 0.47 degrees C). The repeatability was not different between ear infrared thermometers (range 0.13 degrees C to 0.14 degrees C). Rectal temperature had a significantly greater bias (average 0.3 degrees C), but less variability (average 0.2 degrees C). Bias was increased, and variability decreased for both rectal and infrared ear temperatures when pulmonary artery temperature was increased. CONCLUSIONS: The three infrared ear thermometers studied provided a closer estimate of core body temperature than equilibrated rectal temperature. Clinical bias was greatest in febrile vs. afebrile intensive care unit patients.

Adult↗
PubMed2003

[Usefulness of monitoring forehead deep-tissue temperature as an index of core temperature in adult patients undergoing laparotomies under general anesthesia--investigation in operating rooms with air-movement control system using vertical flow].

BACKGROUND: Acute changes in air temperature in the vicinity of the patents' forehead may impair clinical usefulness of the forehead deep-tissue thermometry. We thus investigated usefulness of monitoring the forehead deep-tissue temperature as an index of core temperature in 12 adult patients undergoing laparotomies in operating rooms with air-movement control system using vertical flow. METHODS: Nasopharyngeal, forehead deep-tissue, palm deep-tissue, and fingertip skin-surface temperatures were recorded during surgery every 5 minutes in operating rooms where room temperature was thermostatically controlled at approximately 25 degrees C. The patients were not actively warmed with forced-air warmers, but covered with cotton blankets where possible. The deep-tissue and fingertip skin-surface temperatures were compared with the nasopharyngeal temperature using regression and Bland and Altman's analyses. RESULTS: The four temperatures continued decreasing during surgery, and the nasopharyngeal temperature decreased to below 36 degrees C 2 hours after induction of anesthesia. Only the forehead deep-tissue temperature satisfactorily correlated with the nasopharyngeal temperature (r = 0.76, n = 300, P < 0.0001). The difference between nasopharyngeal and forehead temperatures was +0.26 degree C, and its standard deviation was 0.34 degree C. CONCLUSIONS: The forehead deep-tissue temperature has sufficient accuracy and precision for clinical use in operating rooms with air-movement control system using vertical flow. However, the core temperature appears to be slightly underestimated with the forehead deep-tissue thermometry.

Adult↗
PubMedDate not supplied

Evaluation of manometric temperature measurement as a method of monitoring product temperature during lyophilization.

The objective of this study was to evaluate manometric temperature measurement as a non-invasive method of monitoring product temperature during the primary drying phase of lyophilization. This method is based on analysis of the transient response of the chamber pressure when the flow of water vapor from the chamber to the condenser is momentarily interrupted. Manometric temperature measurements (MTM) were compared to product temperature data measured by thermocouples during the lyophilization of water, mannitol, lactose and potassium chloride solutions. The transient pressure response was mathematically modeled by assuming that four mechanisms contribute to the pressure rise: 1) direct sublimation of ice through the dried product layer at a constant temperature, 2) an increase in the temperature at the sublimation interface due to equilibration of the temperature gradient across the frozen layer, 3) an increase in the ice temperature due to continued heating of the frozen matrix during the measurement, and 4) leaks in the chamber. Experimental transient pressure response data were fitted to an equation consisting of the sum of these terms containing three variables corresponding to the vapor pressure of ice, product resistance to vapor flow, and the vial heat transfer coefficient. Excellent fit between the mathematical model and the experimental data was observed, and the value of the variables was calculated from the measured transient pressure response by a least squares method. The product temperature measured by MTM, which measures the temperature at the sublimation interface, was compared with product temperature measured by thermocouples placed in the bottom center of the vials. Manometrically measured temperatures were consistently lower than the thermocouple measurements by about 2 degrees C, this difference being largely accounted for by the temperature gradient across the frozen layer. The resistance of the dried product to mass transfer calculated from MTM was found to agree reasonably well with values measured by a direct vial technique. Product resistance was observed to increase with increasing solute concentration, and to increase continuously as the depth of the dried product layer increases for mannitol and potassium chloride. For lactose, product resistance increases continuously with thickness up to the onset of collapse, at which point the product resistance becomes essentially independent of depth. Scanning electron microscopy was used to explain this observation based on changes in morphology of the solid. The vial heat transfer coefficients obtained from regression analysis were on the order of 10(-3)-10(-4) cal.sec-1. degrees C-1; however, the scatter in the vial heat transfer coefficient data prevents the method from being used for accurate measurement of the vial heat transfer coefficient. The results of the study show that the manometric method shows promise as a process development tool and as an alternative method of in-process product temperature measurement during primary drying.

Freeze Drying↗
PubMed1998

Embryonic temperature influences juvenile temperature choice and growth rate in snapping turtles Chelydra serpentina.

Snapping turtles (Chelydra serpentina) demonstrate temperature-dependent sex determination (TSD): intermediate egg incubation temperatures (23-27 degrees C) produce males, while extreme temperatures produce females. Snapping turtles are also sexually dimorphic: adult males are typically larger than females. Previous researchers hypothesized that male-producing egg temperatures enhanced the growth rate of juvenile turtles, resulting in the adult dimorphism and potentially providing an adaptive benefit for TSD. In reptiles, the choice of ambient temperature can also influence growth. I measured the effect of egg incubation temperature on juvenile growth rate and water temperature choice of C. serpentina. Eggs were incubated in the laboratory at 21.5, 24.5, 27.5 or 30.5 degrees C to produce both sexes, all males, both sexes or all females, respectively. Egg temperature was linearly and negatively correlated with growth rate of both male and female juveniles. Thus, growth was enhanced, but not maximized, by male-producing egg temperatures. Egg temperature was also negatively correlated with juvenile temperature choice such that, on average, turtles from 21.5 degrees C eggs selected 28 degrees C water, while turtles from 30.5 degrees C eggs chose 24.5 degrees C water. Additionally, these temperature choices were highly repeatable, even following a 6 month hibernation period at 7 degrees C. Thus, while male egg temperatures do not directly maximize growth, multiple effects of embryonic temperature may combine to create long-lasting differences in the behavioral physiology of male and female C. serpentina. Such differences could be important to the ecology and evolution of TSD.

Animals↗
PubMed2000

Acclimation of photosynthesis to temperature in eight cool and warm climate herbaceous C(3) species: Temperature dependence of parameters of a biochemical photosynthesis model.

To determine how parameters of a Farquhar-type photosynthesis model varied with measurement temperature and with growth temperature, eight cool and warm climate herbaceous crop and weed species were grown at 15 and 25 degrees C and single leaf carbon dioxide and water vapor exchange rates were measured over the range of 15 - 35 degrees C. Photosynthetic parameters examined were the initial slope of the response of assimilation rate (A) to substomatal carbon dioxide concentration (C(i)), A at high C(i), and stomatal conductance. The first two measurements allow calculation of V(Cmax), the maximum rate of carboxylation of ribulose bisphosphate carboxylase and J(max), the maximum rate of photosynthetic electron transport, of Farquhar-type photosynthesis models. In all species, stomatal conductance increased exponentially with temperature over the whole range of 15 - 35 degrees C, even when A decreased at high measurement temperature. There were larger increases in conductance over this temperature range in the warm climate species (4.3 x) than in the cool climate species (2.5 x). The initial slope of A vs. C(i) exhibited an optimum temperature which ranged from 20 to 30 degrees C. There was a larger increase in the optimum temperature of the initial slope at the warmer growth temperature in the cool climate species than in the warm climate species. The optimum temperature for A at high C(i) ranged from 25 to 30 degrees C among species, but changed little with growth temperature. The absolute values of both the initial slope of A vs. C(i) and A at high C(i) were increased about 10% by growth at the warmer temperature in the warm climate species, and decreased about 20% in the cool climate species. The ratio of J(max) - V(Cmax) normalized to 20 degrees C varied by more than a factor of 2 across species and growth temperatures, but differences in the temperature response of photosynthesis were more related to variation in the temperature dependencies of J(max) and V(Cmax) than to the ratio of their normalized values.

Journal Article↗
PubMed1998

Embryonic temperature influences juvenile temperature choice and growth rate in snapping turtles Chelydra serpentina.

Snapping turtles (Chelydra serpentina) demonstrate temperature-dependent sex determination (TSD): intermediate egg incubation temperatures (23-27 degreesC) produce males, while extreme temperatures produce females. Snapping turtles are also sexually dimorphic: adult males are typically larger than females. Previous researchers hypothesized that male-producing egg temperatures enhanced the growth rate of juvenile turtles, resulting in the adult dimorphism and potentially providing an adaptive benefit for TSD. In reptiles, the choice of ambient temperature can also influence growth. I measured the effect of egg incubation temperature on juvenile growth rate and water temperature choice of C. serpentina. Eggs were incubated in the laboratory at 21.5, 24.5, 27.5 or 30.5 degreesC to produce both sexes, all males, both sexes or all females, respectively. Egg temperature was linearly and negatively correlated with growth rate of both male and female juveniles. Thus, growth was enhanced, but not maximized, by male-producing egg temperatures. Egg temperature was also negatively correlated with juvenile temperature choice such that, on average, turtles from 21.5 degreesC eggs selected 28 degreesC water, while turtles from 30.5 degreesC eggs chose 24.5 degreesC water. Additionally, these temperature choices were highly repeatable, even following a 6 month hibernation period at 7 degreesC. Thus, while male egg temperatures do not directly maximize growth, multiple effects of embryonic temperature may combine to create long-lasting differences in the behavioral physiology of male and female C. serpentina. Such differences could be important to the ecology and evolution of TSD.

Journal Article↗
PubMed2001

Individual variation in the relation between body temperature and energy expenditure in response to elevated ambient temperature.

The question we address here is whether a mild increase in environmental temperature affects body temperature and energy expenditure, focusing on the individual variation in the relation between energy expenditure and body temperature. We studied eight normal weight healthy females, 48 h at an ambient temperature of 22 degrees C, and 48 h at 27 degrees C. Energy expenditure (EE) was measured in a respiration chamber. Subjects' skin temperature was measured continuously from 8:00 a.m. until 12:00 p.m.: forehead, infraclavicular zone, thigh, hand, and foot. Core temperature was determined tympanically. Body composition was determined by under water weighing. Exposure to 27 degrees C caused a significant increase in body temperature (both skin and core), a decrease in temperature gradients, and a decrease in energy expenditure. At 27 degrees C 24 h EE, adjusted for body composition, was significantly related to body tympanic temperature. The decrease in 24 h EE, at 27 degrees C ambient temperature, was significantly, negatively related to the increase in T(tym), indicating individual responses in adaptation to elevated ambient temperature. Changes in temperature gradient (comparing 27 degrees C with 22 degrees C) were negatively related to changes in EE. This shows that individuals differ in their response to an increase in environmental temperature regarding the relative contribution of insulative or metabolic adjustments.

Acclimatization↗
PubMed2001

Effects of baseline skin temperature on pain ratings to suprathreshold temperature-controlled stimuli.

Variations in baseline skin temperature can be encountered in experimental and clinical pain states. Such variations have been shown to greatly alter the response to radiant heat stimuli when the temperature of the stimulus is not controlled. We carried out a psychophysical investigation to examine the influence of baseline skin temperature on pain ratings to temperature-controlled heat stimuli. A CO(2) laser thermal stimulator was used to deliver heat stimuli under radiometer feedback temperature control to the volar forearm. Each stimulus consisted of a 30 s controlled baseline interval (at 34 or 38 degrees C) followed by a stepped increase in temperature (to 46 or 47 degrees C for 1, 2 or 4 s). A run comprised one presentation of each of these12 different stimuli to different locations. Each experiment contained three runs. In runs 2 and 3, the stimulus intensity and duration at a given location were not changed, but the baseline temperature was alternated between 34 degrees C and 38 degrees C. The intensity of pain was rated using the technique of magnitude estimation. Mean normalized pain ratings for suprathreshold stimuli applied from the higher base temperature (1.03+/-0.03) were slightly greater than from the lower base temperature (0.96+/-0.03). In contrast, pain ratings to the 47 degrees C stimuli (1.11+/-0.03) were substantially greater than to the 46 degrees C stimuli (0.88+/-0.03). Thus a 4 degrees C change in baseline temperature has a smaller affect (about 8%) on pain ratings than a 1 degrees C change in stimulus temperature (about 27%). This suggests that variations in baseline skin temperature encountered in experimental and clinical pain states have only a minor impact on pain sensitivity to suprathreshold temperature-controlled stimuli.

Adult↗
PubMed1984

Effect of ambient temperature on rectal temperature in normal and malnourished rats during early postnatal development.

Information on body temperature is frequently lacking in metabolic studies on normal and malnourished suckling rats although differences in their thermoregulatory efficiency may be expected. The aim of the present study was to evaluate the effect of different ambient temperatures on the rectal temperature of litters of normal and protein deprived rats to establish the ambient temperatures at which a normal rectal temperature can be expected at various postnatal ages. The offspring of normal rats and rats subjected to a dietary reduction of 50% of the protein intake were examined 10 days to 30 days postnatally. The pups were transferred from the nest cage to an incubator: the rectal temperature was measured immediately after transfer to the incubator and 30 and 60 min later at ambient temperatures of 35, 30 and 25 degrees C. Up to 15 days of age control pups showed a fall in rectal temperature after the short exposure to room temperature (22 degrees C) needed for transfer. A similar fall of rectal temperature was recorded in the malnourished pups up to 25 days age. The effects of the ambient temperatures on the malnourished pups indicated a delay in the control of body temperature of some 10 days. This is in agreement with a previous report on semi-starved rats (Heim & Szelenyi 1965). The conditions for the maintenance of a normal rectal temperature in litters of normal and malnourished suckling rats separated from their mother are out-lined.

Age Factors↗
PubMed1999

Core body temperature, skin temperature, and interface pressure. Relationship to skin integrity in nursing home residents.

OBJECTIVE: To ascertain the effects of 1-, 1 1/2-, and 2-hour turning intervals on nursing home residents' skin over the sacrum and trochanters. HYPOTHESES: (1) the higher the core body temperature, the higher the skin surface temperature; (2) the 2-hour turning interval would have significantly higher skin surface temperature; (3) there would be no relationship between skin surface temperature and interface pressure; and (4) the sacrum would have the lowest skin surface temperature. DESIGN: Modified Latin-square. SETTING: For-profit nursing home. PARTICIPANTS: Convenience sample of 26 residents who scored < 3 on the Short Portable Mini-Mental Status Questionnaire and did not have (1) open wounds; (2) albumin levels < 3.3 mg/dL; (3) severe arthritis; (4) cortisone, anticoagulation, insulin therapy or 3 medications for hypertension; and/or (5) were totally bedridden. MAIN OUTCOME MEASURE(S): First Temp measured core temperature; a disposable thermistor temperature probe, skin temperature; and a digital interface pressure evaluator, the interface pressure. RESULTS: Negative correlation (r = -.33, P = .003) occurred between core body temperature and skin surface temperature. Skin surface temperature rose at the end of the 2-hour turning interval but was not significant (F = (2.68) = .73, P = .49). Weak negative relationship (r = -12, P = .29) occurred between skin surface temperature and interface pressure, and sacral skin surface temperature was significantly lower for the left trochanter only (F = (8.68) = 7.05, P = .002). CONCLUSION: Although hypotheses were not supported, more research is needed to understand how time in position and multiple chronic illnesses interact to affect skin pressure tolerance.

Aged↗
PubMed2003

Temperature changes, temperature extremes, and their relationship to emergency department visits and hospitalizations for sickle cell crisis.

Weather changes are among the proposed precursors of painful sickle cell crises. However, epidemiologic data are mixed regarding the relationship between ambient temperature and crisis frequency. To study this relationship among a local sickle cell disease population, emergency department (ED) visits and admissions were evaluated in adults with sickle cell crisis as the primary diagnosis at a major teaching hospital in a temperate climate. Official daily ambient temperatures (average for that day) were obtained from the National Climate Data Center for the days patients visited the ED or were hospitalized, and for 24 or 48 hours prior. Daily ED visit counts and admission counts were correlated with the visit/admission day's ambient temperature, with the ambient temperature 24 hours before admission, and with the magnitude of change in daily ambient temperature over the prior 24 or 48 hours. For all correlations, statistical significance was defined as a p value of <0.01 and clinical significance was defined as a moderate or greater correlation, absolute value of r >/= 0.30. ED visits or admissions correlated statistically, but not clinically, with daily temperatures. On days when temperatures were <32 degrees F or >80 degrees F, these correlations were statistically significant, but clinical significance was variable. ED visits or admissions correlated only statistically with temperatures 24 hours prior, even on days when temperatures were <32 degrees F. When temperatures were >80 degrees F, the correlations were statistically significant, but there was a reverse, clinically significant correlation between admissions and temperatures. Finally, only statistically significant correlations were found between ED visits or admissions and change in temperature over the prior 24 or 48 hours. Weak or inconsistent confirmation of a relationship was found between daily ambient temperatures and ED visits or hospital admissions for sickle cell crises.

Academic Medical Centers↗
PubMedDate not supplied

Temperature control by the blood temperature monitor.

The rationale of temperature control during hemodialysis (HD) is to prevent heat accumulation, which increases body temperature and enhances hypotensive susceptibility. Treatments where thermal energy is neither delivered nor removed from the patient through the extracorporeal circulation (so-called extracorporeal thermoneutral treatments) lead to a marked increase in body temperature and to considerable heat accumulation during HD. Since this accumulation of heat cannot be explained by increased heat production, it must be related to reduced heat dissipation through the body surface. Peripheral vasoconstriction, and cutaneous vasoconstriction in particular, compensating for the ultrafiltration-induced decrease in blood volume is considered an important component in this setting. Therefore, to maintain temperature homeostasis, thermal energy has to be cleared from the patient by the extracorporeal system because cutaneous clearance of thermal energy is compromised intradialytically. The focus on dialysate temperature alone does not properly address the problem of controlled extracorporeal heat removal because dialysate temperature is only one of the variables involved in that process. These difficulties can be addressed by changing from the control of dialysate temperature to control of body temperature. Control of body temperature and temperature homeostasis is achievable by the physiologic feedback control system realized in the temperature control mode (T-mode) of the blood temperature monitor (BTM). The delivery of isothermic dialysis, that is, dialysis where body temperature is controlled to remain constant during the treatment, has impressively improved hemodynamic stability in hypotension prone patients.

Body Temperature Regulation↗
PubMed1995

Comparison of peripheral temperature measurements with core temperature.

The authors' objective of this study was to identify a peripheral method of measuring body temperature that approximates core body temperature. A cross-sectional design was used to compare peripheral measures of body temperature with core temperature. Peripheral temperatures were measured in the ear using two infrared thermometers, in the mouth using a mercury in glass thermometer, electronic thermometer, and chemical indicator thermometer, in the axilla using a mercury in glass thermometer, electronic thermometer, and chemical indicator thermometer, and in the rectum using a mercury in glass thermometer and electronic thermometer. A statistically significant difference was found between peripheral temperature measures and core temperature, except for the axillary chemical indicator temperature and both aural temperatures. Pearson correlation coefficients of > or = 0.79 were found for the association of pulmonary artery temperatures with oral mercury, oral electronic, axillary electronic, rectal mercury, and rectal electronic temperatures. Correlation coefficients were less than 0.20 between pulmonary artery and aural temperatures measured by both devices. Based on results from this study, there is no perfect instrument for approximating core temperature, although the electronic thermometer used orally has a low mean difference (0.18 degree C), low standard deviation of the difference (0.24 degree C), and a correlation coefficient of 0.79.

Adult↗
PubMedDate not supplied

Evaluation of setpoint temperature and pullback speed on vein adventitial temperature during endovenous radiofrequency energy delivery in an in-vitro model.

Endovenous occlusion of the greater saphenous vein with radiofrequency (RF) energy has been shown to be a safe and effective treatment for saphenofemoral reflux. Operating parameters initially developed for the VNUS Closure system were selected in order to provide sufficient energy to controllably and transmurally heat the vein wall to cause collagen contraction and destruction of the vein wall while limiting the degree of perivascular heating. Procedural advances, such as ultrasound-guided tumescent infiltration along the course of the vein to be treated, have provided an added level of thermal protection to the perivenous tissue during the application of RF energy. The purpose of this study was to evaluate the effect of raising the setpoint temperature from 85 degrees C to 90 degrees C while doubling the pullback speed from 3 to 6 cm/minute on vein adventitial temperature. An in vitro simulation of a peripheral vein surrounded by body tissue was created by fixing freshly excised bovine veins in beefsteak kept moist by normal saline. A VNUS RF generator, in conjunction with a VNUS Closure catheter, delivered temperature-controlled RF energy to the bovine vein intima. Adventitial temperatures were recorded as the catheter was withdrawn and peak temperatures from 4 treatment groups were analyzed. The mean peak adventitial temperatures for the groups in which the adventitia was lightly bathed in saline were 64.4 degrees C and 64.9 degrees C with a setpoint temperature of 85 degrees C at a pullback speed of 3 cm/minute and 90 degrees C at a pullback speed of 6 cm/minute, respectively. The mean peak adventitial temperatures for the groups in which the adventitia was bathed in a 2.0 mm layer of saline were 51.3 degrees C and 47.7 degrees C with a setpoint temperature of 85 degrees C at a pullback speed of 3 cm/minute and 90 degrees C at a pullback speed of 6 cm/minute, respectively. Temperature-controlled radiofrequency occlusion of the saphenous vein, performed using an intimal setpoint temperature of 90 degrees C and double the pullback speed of the historical VNUS Closure treatment (6 vs 3 cm/minute), produced comparable temperatures at the adventitial surface in an in vitro model. The addition of a 2.0 mm layer of saline significantly reduced the peak adventitial temperatures.

Animals↗
PubMed2005

Ambient air temperature effects on the temperature of sewage sludge composting process.

Using data obtained with a full-scale sewage sludge composting facility, this paper studied the effects of ambient air temperature on the composting temperature with varying volume ratios of sewage sludge and recycled compost to bulking agent. Two volume ratios were examined experimentally, 1: 0: 1 and 3: 1: 2. The results show that composting temperature was influenced by ambient air temperature and the influence was more significant when composting was in the temperature rising process: composting temperature changed 2.4-6.5 degrees C when ambient air temperature changed 13 degrees C. On the other hand, the influence was not significant when composting was in the high-temperature and/or temperature falling process: composting temperature changed 0.75-1.3 degrees C when ambient air temperature changed 8-15 degrees C. Hysteresis effect was observed in composting temperature's responses to ambient air temperature. When the ventilation capability of pile was excellent (at a volume ratio of 1:0:1), the hysteresis time was short and ranging 1.1-1.2 h. On the contrary, when the proportion of added bulking agent was low, therefore less porosity in the substrate (at a volume ratio of 3:1:2), the hysteresis time was long and ranging 1.9-3.1 h.

Regression Analysis↗
PubMed2005

Changes of body temperature and thermoregulatory responses of freely moving rats during GABAergic pharmacological stimulation to the preoptic area and anterior hypothalamus in several ambient temperatures.

Action of gamma-aminobutyric acid (GABA) in the preoptic area and anterior hypothalamus (PO/AH) has been implicated to regulate body temperature (T(b)). However, its precise role in thermoregulation remains unclear. Moreover, little is known about its release pattern in the PO/AH during active thermoregulation. Using microdialysis and telemetry techniques, we measured several parameters related to thermoregulation of freely moving rats during pharmacological stimulation of GABA in normal (23 degrees C), cold (5 degrees C), and hot (35 degrees C) ambient temperatures. We also measured extracellular GABA levels in the PO/AH during cold (5 degrees C) and heat (35 degrees C) exposure combined with microdialysis and high performance liquid chromatography (HPLC). Perfusion of GABA(A) agonist muscimol into the PO/AH increased T(b), which is associated with increased heart rate (HR), as an index of heat production in all ambient temperatures. Although tail skin temperature (T(tail)) as an index of heat loss increased only under normal ambient temperatures, its response was relatively delayed in comparison with HR and T(b), suggesting that the increase in T(tail) was a secondary response to increased HR and T(b). Locomotor activity also increased in all ambient temperatures, but its response was not extraordinary. Interestingly, thermoregulatory responses were different after perfusion of GABA(A) antagonist bicuculline at each ambient temperature. In normal ambient temperature conditions, perfusion of bicuculline had no effect on any parameter. However, under cold ambient temperature, the procedure induced significant hypothermia concomitant with a decrease in HR in spite of hyperactivity and increase of T(tail). It induced hyperthermia with the increase of HR but no additional change of T(tail) in hot ambient temperature conditions. Furthermore, the extracellular GABA level increased significantly during cold exposure. Its release was lower during heat exposure than in a normal environment. These results indicate that GABA in the PO/AH is an important neurotransmitter for disinhibition of heat production and inhibition of heat loss under cold ambient temperature. It is a neurotransmitter for inhibition of heat production under hot ambient temperature.

Analysis of Variance↗