Constant Ambient Temperature Research Articles

周囲温度一定条件下での減圧過程におけるメタンハイドレートコア分解挙動

周囲温度一定条件下での減圧過程におけるメタンハイドレートコア分解挙動

Constant ambient temperature of 24°C significantly reduces FDG uptake by brown adipose tissue in children scanned during the winter

The aim of this study was to determine if warming patients prior to and during (18)F-FDG uptake by controlling the room temperature could decrease uptake by brown adipose tissue (BAT). A group of 40 children underwent (18)F-FDG PET after being kept in the injection room at a constant temperature of 24 degrees C for half an hour before and 1 hour after intravenous tracer administration. The rate of uptake by BAT in this group was compared to the uptake in a control group of 45 patients who underwent PET when the injection room temperature was 21 degrees C. Uptake by BAT occurred in 5% of studies in the temperature-controlled room compared to 31% of studies performed when the injection room temperature was 21 degrees C (p<0.002). Maintaining room temperature at a constant 24 degrees C, half an hour prior to and during the period of FDG uptake significantly decreases accumulation of FDG in BAT in children.

Timed feeding synchronizes circadian rhythm in vertical swimming activity in cave loach, Nemacheilus evezardi

Subterranean cave ecosystems are characterized by perpetual darkness, almost constant ambient temperature, limited source of food supply and relatively high humidity. The occurrence of circadian rhythms in organisms living in such an ecosystem always attracts chronobiologists to understand the phenomena of time-measuring mechanisms. Few attempts have been made to correlate such rhythmic patterns of the organism with the putative periodicities in weak zeitgebers. In the present study, the effects of periodic feeding schedules on the characteristics of circadian rhythm in the vertical swimming activity of the cave loach Nemacheilus evezardi were examined. Results reveal that periodic feeding at 18:00 has the ability to synchronize the vertical swimming activity rhythm. It seems that periodic restricted feeding could act as a powerful zeitgeber of circadian rhythms in subterranean organisms.

Numerical investigation of hot air recirculation of air-cooled condensers at a large power plant

In order to minimize the hot air recirculation (HAR) to ensure normal operation of the air-cooled condensers (ACC) system, the hot air recirculation phenomenon and its dependence on ambient winds are numerically simulated by using the computational fluid dynamics code, FLUENT. Under the constant ambient temperature, the effects of different wind speed and wind direction on the HAR are qualitatively considered by applying the concept of the hot recirculation rate (HRR). The mechanism of occurrence of hot air recirculation are presented and analyzed. It was found that when considering about the existing and normally operating power plants, the HAR is more sensitive to wind direction and wind speed. Based on the above results, two improved measures increasing the wind-wall height and accelerating the rotational speed of the fans near the edge of the ACC platform are developed to effectively reduce the hot air recirculation.

Intracerebroventricular capsaicin influences the body weight increasing of rats

Adult rats were treated for ten days with capsaicin or with NaCl 0.9% directly injected into the lateral cerebral ventricles through a surgically implanted cannula. A third group of rats was implanted with the same cannula but did not receive any treatment. The food intake and the body weight were recorded for at least six weeks after stopping the treatment. The animals were always kept at constant ambient temperature of 22 °C. The body weight of the capsaicin-treated group was reduced by the treatment, and showed a regular but lower degree of recovery trend than the control groups after the treatment period. In fact the capsaicin treated animals never reached the body weight of the controls. Nevertheless, food intake did not significantly vary after the capsaicin treatment. On the basis of these and previous findings, we can assume that capsaicin injected into the cerebral ventricles to rats kept at constant ambient temperature can acts on hypothalamic neurons, but a permanent action on metabolic pathways can not be excluded.

Daily rhythms of body temperature and heat production of sibling mastomys species from different ecosystems — The response to photoperiod manipulations

We compared body temperature ( T b) and metabolic rates, measured as oxygen consumption (VO 2), daily rhythms of two sibling species of the genus Mastomys. We also studied their responses to long day (16L: 8D, LD) and short day (8L: 16D, SD) photoperiod manipulations at a constant ambient temperature of 26 + 1 °C. We noted significant differences in T b and VO 2 daily rhythm patterns, under SD and LD-acclimation between the sibling species. These differences explain adaptation to the climatic conditions that prevail in the different ecosystems where these species live. To the best of our knowledge, this is the first time that physiological differences between the two siblings are measured by using chronobiological methods.

Methodology of temperature prediction in an insulated container equipped with PCM

This study aims to present a methodology of product temperature prediction at various positions in an insulated container along a logistic chain. The container is equipped with Phase Change Material (PCM, melting point −0.5 °C) to maintain the recommended temperature in the loading. The following steps were undertaken: two experiments of product temperature monitoring in the loading were carried out. The loaded cavity, 5 °C initial temperature, was exposed to a constant external ambient temperature: 0 °C for the first experiment and 30 °C for the second. The experimental values of the temperature evolution, at various positions, were then used to develop a predictive model for a new ambient temperature varying from 0 °C to 30 °C. An excitation–response method, largely used in the signal treatment, was applied assuming linearity between the product temperature (response) and the external ambient temperature (excitation). A comparison was undertaken between the experimental product temperature in the container exposed to variable ambient temperature and the one predicted by the model. A good agreement was obtained. The predictive model is, thus, applicable for constant or variable external ambient temperature as occurs along a logistic chain as long as the PCM is not completely melted.

The study on estimation of time since death with proton magnetic resonance spectroscopy under different temperature

AbstractEstimation of the time of death (post-mortem interval, PMI) is occasionally a critical issue in adjudication of a criminal or civil action. But no objective and precise means has been derived for estimating PMI.One reason for this outcome may be the fact that most of these methods attempted to characterize PMI by a few or even just one specific parameter's variable in constant ambient temperature. It is crucial that we reduce or eliminate the effect of temperature variation in the estimation of PMI. Here we show the first results by using proton magnetic resonance spectroscopy (1H-MRS) technique to determine the order of degradation of certain substances, present in the brain tissue of a rabbit model, under different temperatures; our goal is to reduce or eliminate the temperature effect in the estimation of PMI.

Effects of photoperiod history on body mass and energy metabolism in Brandt's voles (Lasiopodomys brandtii)

Many small mammals respond to seasonal changes in photoperiod via alterations in morphology, physiology and behaviour. In the present study, we tested the hypothesis that the preweaning (from embryo to weaning) photoperiod experience can affect subsequent development in terms of body mass and thermogenesis. Brandt's voles (Lasiopodomys brandtii) were gestated and reared to weaning under either a short (SD, 8 h:16 h L:D) or a long photoperiod (LD, 16 h:8 h L:D) at a constant ambient temperature (23 degrees C). At weaning, male juveniles were either maintained in their initial photoperiod or transferred to the alternative photoperiod for 8 weeks. Postweaning SD voles had a lower body mass but higher thermogenic capacity compared with LD voles. At the same time, preweaning photoperiod conditions had long-lasting effects on thermogenic capacity later in life. Serum leptin concentration was positively correlated with body mass and body fat mass, whereas it was negatively correlated with energy intake and uncoupling protein 1 content in brown adipose tissue. Our results suggest that postweaning development in terms of body mass and thermogenesis is predominantly influenced by the postweaning photoperiod, while the preweaning photoperiod experience could chronically modify thermogenesis but not body mass. Furthermore, serum leptin, acting as a potential adipostatic signal, may be involved in the regulation of both energy intake and energy expenditure.

The influence of temperature on within-canopy acclimation and variation in leaf photosynthesis: spatial acclimation to microclimate gradients among climatically divergent Acer rubrum L. genotypes

Leaf gas exchange and temperature response were measured to assess temperature acclimation within a tree canopy in climatically contrasting genotypes of Acer rubrum L. Over the course of two 50 d continuous periods, growth temperature was controlled within tree crowns and the steady-state rate of leaf gas exchange was measured. Data were then modelled to calculate the influence of genotype variation and vertical distribution of physiological activity on carbon uptake. The maximal rate of Rubisco carboxylation (V(cmax)), the maximum rate of electron transport (J(max)), leaf dark respiration rate (R(d)), maximum photosynthesis (A(max)), and the CO(2) compensation point (Gamma) increased with temperature during both (i) a constant long-term (50 d) daytime temperature or (ii) ambient daytime temperature with short-term temperature control (25-38 degrees C). In addition, within-crown variation in the temperature response of photosynthesis and R(d) was influenced by acclimation to local microclimate temperature gradients. Results indicated that carbon uptake estimates could be overestimated by 22-25% if the vertical distribution of temperature gradients is disregarded. Temperature is a major factor driving photosynthetic acclimation and within-crown gas exchange variation. Thus, this study established the importance of including spatial acclimation to temperature- and provenance-, ecotype-, and/or genotype-specific parameter sets into carbon uptake models.

Meshless analysis of heat transfer due to viscous dissipation in polymer flow

This paper illustrates the results of meshless/meshfree solutions of a heat transfer to molten polymer flow in a tube with constant ambient temperature. Here, the rheological behaviors of the melt are based on a power law temperature-dependent model and heat produced by viscous dissipation, which satisfies an Arrhenius temperature-dependence law, is considered. Temperatures are obtained for different tube lengths, different inlet temperatures and different models. It shows that the temperature-dependent viscous disputation has significant impact on the heat transfer, and the limiting bulk temperature for both without viscosity dissipation model and with viscosity dissipation model is influenced by the wall boundary, but not by the inlet conditions of the melt. Meanwhile, the local Nusselt number is also presented for a variety of flow entry temperatures. Moreover, the element-free Galerkin solutions of steady state for different nodal distribution are validated by comparing with the analytical solution, which indicates that numerical solutions are excellent agreement with analytical solutions.

Effect of Chronic Heat Exposure on Fat Deposition and Meat Quality in Two Genetic Types of Chicken

The effects of chronic heat stress on growth, proportion of carcass and fat deposition, and meat quality were investigated in 2 genetic types of chickens. One hundred and eight 5-wk-old male chickens from a commercially fast-growing strain (Arbor Acres, AA) and a locally slow-growing species (Beijing You chicken, BJY) were kept in the following conditions: constant optimal ambient temperature at 21°C and ad libitum feeding (21AL), constant high ambient temperature at 34°C and ad libitum feeding (34AL), and constant optimal ambient temperature 21°C and pair-fed to the 34AL chickens (21PF). The results showed that feed intakes were decreased by heat exposure in both type of chickens at 8 wk of age (P < 0.001). At 34°C, AA broilers exhibited greatly decreased weight gain (22.38 vs. 61.45 g/d for 21AL) and lower breast proportion compared with 21AL, while the relevant indices of BJY chickens were not affected in hot condition. Abdominal fat deposition of BJY chickens was enhanced by heat exposure (P < 0.05). Fat deposition of AA broilers was decreased in heat-exposed and pair-fed chickens. Abdominal and intermuscular fat deposition in 34AL birds, however, were enhanced compared with 21PF birds (P < 0.01). The L* values, drip loss, initial pH, and shear force of breast meat in BJY chickens were not affected by treatments. In AA birds, chronic heat stress increased L* values and drip loss compared with 21AL, but pH and shear force were not affected by treatments. The results from this study indicated that the impact of heat stress was breed dependent and that BJY chickens showed higher resistance to high ambient temperature, which could be related to their increased feed efficiency and deposition of abdominal fat under heat exposure.

Fracture surface analysis on nano-SiO 2/epoxy composite

Fracture surface morphologies of nano-SiO 2/epoxy composite with different weight percentage of SiO 2 are investigated using scanning electron microscopy. Two types of curing agent, dimethylbenzanthracene (DMBA) and methyltetrahydrophthalic anhydride (MeTHPA), are individually used for preparing the composites. It is found that the fracture surface morphology of the composite cured by DMBA shows as radial striations, which suggests a rapid brittle fracture mode, while the fracture surface morphology of the composite cured by MeTHPA shows as regularly spaced ‘rib’ markings, which indicates a stick–slip motion during the fracture process. Furthermore, the uniaxial tensile behavior under constant loading rate and ambient temperature are investigated. It is shown that the elastic modulus of the composite cured by DMBA firstly increases, and then decreases with the mass fraction of nano-SiO 2 particles, but the elongation of the composite cured by MeTHPA is reversed with increasing fraction of nano-SiO 2 particles. For nano-SiO 2/epoxy composite cured with MeTHPA that possesses a suitable fraction of nano-SiO 2, an excellent synthetic mechanical property on elastic modulus and elongation is obtained.

Evaporative heat loss from group-housed growing pigs at high ambient temperatures

The effects of relative humidity and ambient temperature on evaporative heat loss were studied in 12 trials each with a group of 10 gilts with an initial BW of 61.7 kg (58.0–65.5 kg). The ambient temperature inside a respiration chamber was increased by 2 °C d −1 starting at 16 °C and ending at 32 °C. Relative humidity was set at 50%, 65% or 80% and remained constant within each trial. The animals had free access to feed and water. Skin temperature (SkinT), total heat production (HP), evaporative heat loss (EvapH), respiration rate (RR), and wallowing of the animals were recorded. SkinT was lowest at 80% relative humidity ( P<0.05). For each degree Celsius rise in SkinT, wallowing increased by 0.19% ( P<0.05). For each degree Celsius rise in ambient temperature, total HP decreased by 115 kJ pig −1 d −1 and EvapH increased by 290 kJ pig −1 d −1 ( P<0.05). It was concluded that under constant high ambient temperature and relative humidity, the pigs clearly employ respiratory evaporation to lose heat. Wallowing showed the importance of skin EvapH with higher temperatures, especially at high relative humidity. This study shows the importance of evaporative cooling from the skin. The implication is that pigs at high ambient temperatures, especially in combination with a high relative humidity, should be able to wet themselves. For animal welfare and environmental reasons, it is important that they are able to wet their skin.

Model predictive temperature control in long ducts by means of a neural network approximation tool

In this paper, a nonlinear model predictive control (MPC) configuration for hyperbolic distributed thermal systems is presented and applied in the flow-based temperature control in a long duct. At first, a radial basis function neural network is developed to estimate the temperature distribution along the duct with respect to flow velocity, assuming constant ambient temperature. The nonlinear model is then incorporated in the context of an MPC procedure. The use of the neural network model avoids the spatial discretization and decreases significantly the computational effort required to solve the optimization problem that is formulated in real time, compared to conventional modeling approaches. The proposed MPC scheme is able to overcome delay effects and accelerates the outlet temperature response. Reduced tuning effort is another advantage of the proposed control scheme.

Re-oxygenation of haemoglobin in livores after post-mortem exposure to a cold environment

When a body is exposed to a cold environment, the livid colour of livor mortis changes to cherry red. This colour change is due to an increase in the concentration of oxygenated haemoglobin. The chronological course and the extent of haemoglobin re-oxygenation associated with the exposure to low ambient temperatures have not been understood so far. The relations between refrigeration time under a constant ambient temperature (5 degrees C), skin temperature, body mass index (BMI), spectral reflectance curve and O2-Hb concentration in livor mortis were systematically investigated in 84 bodies brought to the Institute of Legal Medicine of the Freiburg University Hospital shortly after death. In the first measurements performed shortly after death, the reflectance curves of the livores of all bodies showed a broad minimum at 555 nm. After a refrigeration time of 44.9 +/- 17.9 h, the spectrum changed to the typical picture of O2-rich blood with 2 minima at 541 and 576 nm and a maximum at 560 nm in between. This qualitative change of the reflectance spectra was observed for a skin temperature of 10.3 +/- 2.7 degrees C. With the help of a physical skin model it was possible to calculate that due to the post-mortem exposure to cold the O2-Hb concentration in the livores rose from 0-1% to a value of up to 89.3%. The change in the reflectance curve was discernible from an oxygen saturation of 25 +/- 13.8%.

Comparison of ammonia and greenhouse gas emissions during the fattening of pigs, kept either on fully slatted floor or on deep litter

Five successive batches of fattening pigs were raised, each during a four month period, on a totally concrete slatted floor in one experimental room and on straw based deep litter in another. The rooms were automatically ventilated to maintain a constant ambient temperature. Available floor space was of 0.75 m 2 per pig kept on the slatted floor and 1.20 m 2 per pig kept on the deep litter. With this last system, about 46 kg of straw were supplied per pig throughout a fattening period. The slurry pit was emptied and the litter removed after each batch. Once a month, the emissions of ammonia (NH 3 ), nitrous oxide (N 2 O), methane (CH 4 ), carbon dioxide (CO 2 ), and water vapour (H 2 O) were measured continuously for 6 consecutive days by infra-red photoacoustic detection. The performance of the animals was not significantly different according to the floor type. Gaseous emissions from pigs raised on the slatted floor and on the deep litter were, respectively, 6.2 and 13.1 g per pig per day for NH 3 , 0.54 and 1.11 g per pig per day for N 2 O, 16.3 and 16.0 g per pig per day for CH 4 , 1.74 and 1.97 kg per pig per day for CO 2 and 2.48 and 3.70 kg per pig per day for H 2 O. Except for the CH 4 emissions, all the differences were significant ( P < 0.001). Thus, pig fattening on deep litter releases nearly 20% more greenhouse gases than on slatted floor, with 2.64 and 2.24 kg of CO 2 -equivalents, respectively ( P < 0.001). Whatever the floor type, emissions increased from the beginning to the end of the fattening periods by about 5 times for NH 3 , 4 times for N 2 O, 3 times for CH 4 and 2 times for CO 2 and H 2 O. Correlation coefficients between CO 2 -emissions and H 2 O, NH 3 and CH 4 emissions were, on average for both floor types, 0.82, 0.77 and 0.74, respectively. Although rearing pigs on straw generally has a good brand image for the consumer, this rearing system produces more pollutant gases than keeping pigs on slatted floors.

A temperature-compensated model for circadian rhythms that can be entrained by temperature cycles

From the viewpoint that reaction rates will change with temperature, we present a general method to build circadian clock models that generate circadian oscillations with almost constant period under different constant ambient temperature, and propose an algorithm estimating the parameter condition for compensated period against the change of temperature based on the PER single-feedback loop model of Goldbeter [1995. A model for circadian oscillations in the Drosophila period protein (PER). Proc. R. Soc. London Ser. B 261, 319–324] for Drosophila. We show that the model with derived parameters can realize the temperature compensation over a wide range of temperature, and simultaneously can realize the entrainment to temperature cycles.

Gaseous emissions during the fattening of pigs kept either on fully slatted floors or on straw flow

The aim of this study was to compare the environmental impact of the straw-flow system for fattening pigs with the slatted-floor system by measuring pollutant gas emissions such as ammonia (NH3), nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2), manure nitrogen (N) content and emissions of water vapour (H2O). Three successive batches of 32 pigs were fattened. For each batch, pigs were allotted to two groups raised in separated rooms fitted either with a concrete totally slatted-floor system (0.75 m2 per pig) or with a straw-flow system (0.79 m2 per pig). With this last system, pigs were kept on a sloped floor, straw being provided daily at the top of the pen. Throughout the fattening period, about 34.4 kg of straw were supplied per pig. The straw, mixed with dung, travelled down the slope by pig motion and went out of the pen to a scraped passage. The solid fraction was scraped every day, stored in a heap in the room and removed every month, 1 week before each period of gaseous emission measurement. The liquid fraction was automatically pumped from the scraped passage into a hermetic tank, which was emptied at the end of each fattening period. Rooms were ventilated mechanically in order to maintain a constant ambient temperature. Once a month, the emissions of NH3, N2O, CH4, CO2 and H2O were measured hourly for 6 consecutive days via infrared photoacoustic detection. Mean daily emissions per pig fattened on the slatted floor or on the sloped floor were, respectively, 4.98 and 13.31 g NH3, 0.67 and 0.68 g N2O, 15.2 and 8.88 g CH4, 548 g and 406 g CO2 equivalents, 1.61 and 1.77 kg CO2 and 2.33 and 2.95 kg H2O. Except for N2O emissions, all the differences were statistically significant (P < 0.001). From the slatted-floor system, the amount of slurry removed per fattening period was on average 256 kg per pig. From the straw-flow system, solid manure amounted on average to 209 kg per pig and liquid manure to 53 kg per pig. The total N-content of the manure was 2.23 kg N per pig with the straw-flow system (solid and liquid manure) v. 3.26 kg N per pig for slurry from the slatted-floor system. This reduction of 30% observed with the sloped floor was mainly explained by the higher level of NH3-N emissions.

The microwave-/photo-assisted degradation of bisphenol-A in aqueous TiO 2 dispersions revisited : Re-assessment of the microwave non-thermal effect

The microwave-assisted photodegradation of bisphenol-A (BPA) in the presence of TiO 2 was examined at ambient temperature to unravel some details on the importance of the microwave non-thermal effect. Normally, bisphenol-A photodegrades under microwave irradiation as a result of a thermal effect emanating from the microwave radiation which sees increase in temperature in the aqueous TiO 2 dispersion. However, on cooling the dispersion with circulating silicone oil at −20 °C, the temperature of the dispersion could be maintained constant at 21 °C. Under the latter irradiation conditions, the microwave-assisted photodegradation of BPA was shown to be not only due to a microwave thermal effect, but also to a significant non-thermal effect that might implicate hot-spots on the TiO 2 particle surface leading to enhanced photodegradation under constant ambient temperature. Other origins of the microwave non-thermal effect may include additional formation of charge carriers on the photomediator TiO 2 and formation of additional trap sites that may otherwise prolong the lifetimes of the charge carriers through diminished recombination and ultimately increase process kinetics.