Stable Thermal Environment Research Articles

Imaging chemiluminescence instrument for the study of heterogeneous oxidation effects in polymers

An imaging Chemiluminescence equipment used for studies of diffusion controlled oxidation effects in polymers is presented. The design involves an imaging photon counting system mounted on a cylindrical oven with a controlled atmosphere. The overshoot on heating is less than 2 °C and the temperature during isothermal conditions is maintained at ±0.4 °C, thus, a stable thermal environment is attained. To point out possible applications, the monitoring of oxidation profiles from aged nylon specimens and oxygen-barrier properties of an inorganic coating by chemical plasma deposition on a hydroxyl terminated polybutadiene substrate are presented. The results demonstrate the feasibility of studying diffusion controlled oxidation and also the possibility of the technique to estimate the function and durability of surface treatments on elastomers.

Research from the research utilization project: environmental temperatures.

Thermoregulation is one of the most common concerns for neonatal nurses. The literature contains limited information regarding the effects of environmental temperature during the transitioning process from the incubator to the crib for the premature infant weighing 1,500-1,800 g. The type and amount of insulation while in the incubator and open crib and the effects of the cooler environmental temperature may influence the success of the weaning process from the incubator. As an adjunct to the Transition of the Preterm Infant to an Open Crib Research Utilization Project, sponsored by the Association of Women's Health, Obstetric, and Neonatal Nurses (AWHONN), nurses collected data regarding environmental temperatures at 6 of the 10 project sites. The average correlation of infant's temperature to environmental temperature once the infant was out of the incubator for a weaning period was 0.09. In one-third of the cases, the environmental temperature never varied; however, in the rest of the infants, mean infant temperatures during weaning stayed constant, with little variance. There appears to be no association between neonatal intensive-care unit environmental temperature and infant's temperature during the weaning process when nurses followed a specific protocol of layering the infant with blankets.

Simple apparatus for the liquefaction of neon directly into a research Dewar

A simple apparatus for liquefying neon is described for use in experiments that require a stable thermal environment at 27 K. This apparatus makes use of a closed-cycle refrigerator attached to an insulated cold finger inserted into a conventional stainless steel Dewar to liquefy a quantity of neon gas stored previously in a tank. The system is inexpensive and easy to use. Furthermore, the neon is recovered for subsequent reuse upon completion of the experiment. Starting with a Dewar holding a small coil that had not been precooled, and using a refrigerator with rated cooling capacity of 15 W at 26 K, approximately 0.5 ℓ of liquid neon was condensed into the Dewar in ∼4 h. The apparatus has been used to measure the critical currents of high Tc oxide tape coils both with and without the application of an external magnetic field.

An oven design for torsional rheometers

A newly designed oven for rheological characterisation of polymer melts is presented which relies upon conduction and radiation rather than convection to heat the polymer. The design involves three concentric heating elements, all controlled independently to ensure a stable thermal atmosphere. The overshoot on heating is minimal (10 K, and this was due to opening the oven for sample trimming; the overshoot is 3 K if the oven is not opened) and the results of a typical dynamic shear test show that rheological properties attain their equilibrium values very rapidly (25 min after start-up of the oven fro room temperature, and 15 min after the sample was placed in the rheometer). The temperature of the sample was maintained at ±0.5 K, thus, a stable thermal environment was successfully attained.

Thermoregulation in neonatal ruminants

AbstractThis review is directed to thermoregulation in ruminants relative to weather and husbandry conditions of the United Kingdom in which the principal ruminant species are cattle and sheep. The main thermoregulatory demands for neonates, but not necessarily for older animals, are posed by cold rather than heat. Thermoregulation is critical to the survival of neonatal ruminants. On many farms, neonatal deaths are, for example, 20% of lambs born. Neonatal ruminants are precocial compared with many altrical neonatal mammals and have well developed thermoregulation which allows them to maintain homeothermy in many environments. However, at birth the neonatal ruminant moves from a very stable thermal environment, of similar temperature to its core body temperature, to a variable thermal environment which is 10 to 50°C colder than its core temperature. At birth the coat is wet and energy losses can be very high. To maintain homeothermy, heat production can usually be increased 3- to 5-fold above resting heat production. However, there are only limited quantities of tissue substrates available for this and the early intake of sufficient colostrum by the newborn is essential to continued heat production and survival. Nutrition in early and late pregnancy also affects the viability of, at least, young lambs: placental insufficiency may cause chronic prenatal hypoglycaemia and hypoxaemia which, postnatally, inhibits spontaneous respiration and restricts heat production. In calves, dystocia may cause acidosis and decreased heat production.The principal thermoregulatory mechanisms and some factors which affect their efficiency in newborn calves and lambs are presented, with consideration of the limitations of lower critical temperatures.

Preservation of oscillations in postocclusive reactive hyperemia

Oscillations in skin blood flow (SkBF) during postocclusive reactive hyperemia are believed to be due to locally mediated events in the microcirculation. We characterized the activity of these oscillations in nine healthy young men who underwent 0, 10, and 40 Torr of lower body negative pressure (LBNP). Postocclusive SkBF was estimated in both forearms simultaneously in a stable thermal environment with laser-Doppler velocimetry. Periodic behavior of SkBF was characterized by frequency-domain power spectral analysis. LBNP at 40 Torr increased heart rate, decreased forearm blood flow, and decreased postocclusive SkBF amplitude but did not change the periodicity of SkBF in the frequency response range that is characteristic of postischemic SkBF oscillations (0.11 +/- 0.04 Hz). We observed that LBNP did not alter the frequency response of the postocclusive SkBF as quantified in the periodogram, even though the amplitude of the SkBF was markedly diminished as a part of the general decrease in arm blood flow. We found inferential evidence for a disseminated common pacemaker mechanism that performs similarly at distant sites. We conclude that the LBNP baroreflex-mediated modulation of SkBF reduces the amplitude but does not change the frequency behavior of postocclusive SkBF. We propose on the basis of our findings that the preservation of vasomotion suggests that this phenomenon is an adaptation to the ischemic changes induced by disruption of blood flow.

蓄熱式床暖房システムの数値解析 : 床の蓄熱性,建物断熱性,室内温熱環境,温水投入熱量の関係に関するケーススタディ

Panel heating systems with floor heat storage, the thermal energy stored in which is gradually transferred to the room space, are considered effective in providing a stable and comfortable thermal environment. Sufficient insulation of the building envelopes is very important to enable us to have the panel heating systems that give such a thermally comfortable room space. However, the quantitative relationships between thermal characteristics of the building envelopes, thermal capacity of the floor, the thermal comfort and heating energy requirements have not been studied extensively. This paper describes the results of a numerical analysis on these relationships. We have found the following : the concrete floor of about 10cm is effective not only in reducing the heating energy demand but also in lowering the water temperature supplied to the floor ; the building envelopes should be covered with the foam-polystylene insulation of at least 4 cm or equivalent in case of Tokyo so that the floor surface temperature can be reduced to a desired level.

Neutron detection based on superheated materials

The environmental and radiation responses of the active personnel dosimeter/superheated drop detector (APD/SDD) combination have been evaluated at the Pacific Northwest Laboratory (PNL) for the US Department of Energy's Neutron Measurement and Evaluation Program. Results of the evaluation and possible improvements for the current system are discussed. The APD/SDD system provides real-time indication of dose equivalent resulting from neutron exposure. The APD/SDD has good neutron sensitivity and a practical readout system. The SDD is insensitive to moderate pressure changes and vibration and is not affected by M150 and H150 X-rays or intermittent use within a reasonable time period. The energy response of the SDD agrees well with recommended response. The linearity of the SDD decreases with increasing accumulated dose equivalent due to the reduction of superheated droplets. The SDD is also severely temperature-dependent. The useful range is roughly 0-150 mrem; use at higher levels requires a manufacturer-supplied calibration curve. The temperature sensitivity requires use in a relatively stable thermal environment, or the use of a thermal isolation chamber to keep the APD at a relatively constant temperature.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Incubator temperature control: effects on the very low birthweight infant.

We studied temperature stability in 22 infants of birthweight less than 1500 g in the first four days of life. Infants were nursed in incubators using either air mode control or skin temperature servo control. Data were collected continuously using a computer linked monitoring system. Skin temperature control resulted in a less stable thermal environment than air mode control. Increased thermal stability in the incubator on air mode control may well be beneficial, particularly to sick, very low birthweight infants.

Respiration in air and water of four mediterranean trochids

The oxygen consumption of inactive animals of four species of Mediterranean trochid was measured in air and sea water at temperatures commonly recorded on the shore. The loss of mantle cavity fluid significantly lowered the aerial oxygen consumption of all four species. The aquatic oxygen consumption of the four species after 12 h settlement in the respirometer was not significantly different from that measured after 1 h. The high-shore Monodonta lurbinata (Born) and M. articulata (Lamarck) experience a maximum of 60 to 70% aerial exposure, wide temperature fluctuations, and can maintain an aerial rate of oxygen consumption similar to the aquatic rate. They have temperature dependent rates of oxygen consumption with similar Q 10 values in both air and water between 20 and 30°C. The low-shore Gibbula richardi (Dayraudeau) and G. rarilineata (Michaud) are characterized by a low maximum percentage aerial exposure, a more stable thermal environment, an aerial rate of oxygen consumption lower than the aquatic rate, temperature dependent respiration rates between 20 and 30°C in sea water but a temperature coefficient not significantly different from 1 in air. These patterns of oxygen consumption are reflected in the 50% survival times of the trochids in air at 25°C. The pattern of respiration in air and water of a wide range of intertidal gastropods has been related to the maximum percentage aerial exposure experienced on the shore.

996 NEONATAL TRANSPORT IN SUB-ZERO AMBIENT CONDITIONS: CLINICAL THERMAL STABILITY WITH RADIANT WARMER

11 sick neonates (weighing 1150 - 2280g) have been studied during transport from sub-zero temperatures (0 to -34°C) in a radiant heat source incubator. This unit has been evaluated ‘in vitro’; our referral centre provided unique opportunities for clinical observation under extreme conditions. One observer monitored the infant's condition, core, skin and incubator air temperatures (4cm below the hood). Environmental temp. and wind speed were obtained. The radiant heater, in a curved transparent canopy generated heat at peak wave length of 8.7 micron over 180C of the infant's surface, servo-controlled from a skin thermistor. Core temperature never fell, and rose to normal in all (6) infants who were hypothermic (mean rise >0.5°C/hour for 3 hours) The greatest fall in skin temperature was <0.75°C (after 10 minutes unavoidable delay at -21°C with the heater control accidentally lowered to 35°C while unloading). Considerable flux in air temperature within the incubator occurred between periods of warmer activity. Once, a broken connection in the servo-control thermistor rendered the heating unit temporarily inoperable. Radiant heat can provide a stable thermal environment under adverse conditions; but data suggest an emergency manual override of thermistor control is mandatory and that heater controls should ‘lock’. Also, the optimum rate of rewarming after hypothermia, and the effects of a marked flux in air temperature must be established for small infants during radiant warming.

Temperature acclimation in Tribolium and Musca at locomotory, metabolic, and enzyme levels

The results of this study indicate that metabolic acclimation precedes locomotory acclimation. The effect of acclimation on the two species varies with respect to enzyme (Mg 2+-activated ATPase) activity. Tribolium confusum shows acclimative differences in ATPase activity throughout its normal temperature range. Enzyme activity of warm-acclimated beetles transferred to a low temperature showed little acclimation after more than 900 hr at the new temperature. This suggests that a rapid acclimation of ATPase activity is not essential to this insect and, perhaps, that other mechanisms are more important. The ATPase activity of Musca domestica shows no substantial acclimative differences in the temperature range of 15 to 30°C, but, at low temperatures near the chill-coma temperature, acclimative differences are evident. These differences increase the insect's sensitivity to temperature and are similar to interspecific differences found with the same enzyme in other insects. The results of this study also suggest that the rate of acclimation to temperature is dependent on the thermal environment of the insect being studied. Insects that live in a relatively stable thermal environment, like T. confusum, seem to acclimate slowly. M. domestica, which lives in a highly variable thermal environment, acclimates more rapidly.

The rate of thermal exchange in a teleost, Tilapia mossambica.

Excess tissue temperatures of a fish in a stable thermal environment were estimated. In fish weighing 40 to 200 g, mean excess muscle temperature was 0.44 °C and brain, 0.45 °C. A significant high local excess temperature (0.80 °C) was observed in the isthmus, immediately under the skin just anterior to the pelvic girdle. Mean excess muscle temperature in fish weighing less than 40 g was 0.15 °C.The rate of thermal exchange of fish was estimated by measuring the tissue temperature after the fish was placed m a bath 5 °C cooler than ambient. The slope of a double logarithmic plot of the coefficient of cooling versus body weight was −0.3. The coefficient was 1.8 °C/min per °C difference for fish weighing 1.0 g and was 0.4 for fish weighing 100 g.

Liquid metal solution calorimeter

A calorimeter is described, the operation of which involves the solution of samples in a liquid metal. The working temperature range is 240-500°C and, as a result of its highly stable thermal environment and small heat losses, high sensitivity and precision have been achieved. The calorimeter can be conveniently applied to the measurement of heats of formation and solution and energy changes accompanying solid state reactions in metallic systems.