Thermostatic Chamber Research Articles

Temperature regulation of young coypus (Myocastor coypus) in air and water

Coypus (Myocastor coypus Molina) have recently colonized temperate regions of Europe in large numbers, originating from populations indigenous to subtropical regions of South America. Observations of coypu behavior in the wild and in enclosures under a temperate climate showed a preference for close proximity to water and frequent swimming bouts. Little change was observed in the semiaquatic habit in winter, despite high mortality during this period, particularly among young and adult male coypus. Evidence for constraints on thermal adaptation was sought from measurements in a thermostatic chamber of the resting metabolic rate (RMR) of young coypus caught from wild populations in France and of the body (Tb) and skin (Tsk) temperatures as a function of ambient temperature (Ta). A light heterothermic response with deep Tb falling by 0.8 degree C and stabilizing at a new level of 36.7 degrees C was observed in water and air at Ta below the lower critical temperatures. In common with other semiaquatic mammals, RMR (2.94 W/kg) was high relative to terrestrial mammals of equivalent body mass. Minimal thermal conductance was 0.10 W.kg-1.degree C-1 in air for Ta between -10 and +20 degrees C, and conductance varied in water from 0.24 to 1.18 W.kg-1.degrees C-1 for Ta between 5 and 35 degrees C. The physiological adaptations to cold and particularly the high insulative value of the fur (80-90% of the insulation) help to explain the successful extension of the coypu's range to temperate regions. Energetic costs were nevertheless high in cold water, suggesting that social factors may be implicated in severe winter mortality, particularly dominance hierarchy regulating the persistent use of water bodies even under freezing conditions.

Low-Temperature Convectors for Space Heating

Two convectors for space heating, designed for low-temperature operation, were built and tested. Both convectors consisted of an extended surface heating element placed at the bottom of an enclosure acting as a chimney. The first one was intended for an almost isothermal operation while the second one allowed an important cooling of the heating medium. A computer program was employed to optimize the heaters' geometry. Fin efficiency was found not to be accurately predicted by ordinary relationships in the case of unusual fin geometries: a finite difference analysis was employed as a more satisfactory computation tool. Tests were performed in a thermostatic test chamber and gave results in good agreement with the theoretical predictions. Owing to the influence of air temperature around the heater on chimney draft, ambient air temperature distribution is to be taken into account in the theoretical model in order to obtain accurate results. Both heaters tested gave a considerably better output than ordinary heaters of similar dimensions and working at the same temperature. In order to increase the heat delivery, one of the heaters was modified to accommodate a small fan. Even for extremely low electric power input, assuring a totally noise-free operation, a sizeable improvement of thermal power output was observed.

The Radiometer ABL300 blood gas analyzer

A modern blood gas analyzer such as the ABL300 directly accepts samples from syringes or capillary tubing. The ABL300 measures pH, carbon dioxide tension, and oxygen tension on 85-microliters samples by using specific electrodes, and estimates hemoglobin concentration from the optical density of a nonhemolyzed sample. From these it calculates bicarbonate, standard bicarbonate, total carbon dioxide, base excess, standard base excess, and oxygen saturation and content. The electrodes are automatically calibrated by pumping bicarbonate/phosphate buffer solutions, gas-equilibrated within the thermostatic chamber, into the measuring cuvettes. Samples are preheated in metal tubing before being pumped automatically into the measuring chamber. An open liquid junction to a half-saturated potassium chloride solution is renewed with each sample to complete the pH circuit. The electrodes are housed in a 37 degrees C circulated-air thermostat, which also contains the equilibrators for the calibration solutions. Two known carbon dioxide mixtures are made from pure carbon dioxide by dilution with room air, which is compressed continuously, avoiding the use of premixed calibration gases. The computer determines the derived variables and can correct pH, carbon dioxide tension, and oxygen tension values to a user-defined body temperature. Corrections are made for predicted discrepancy between the measured and true value caused by the small sample size. The corrections depend on the difference in gas tension between sample and rinse solution.

Model reference adaptive control of a thermostatic chamber

The design and the implementation of a model reference adaptive controller for continuous systems are presented. The algorithm has been developed taking into account: (1) the influence of discrete control on the behavior of continuous systems; (2) the possibility of working directly on the continuous representations of the plant and of the reference model; and (3) the need for concurrent implementation of the control software on multiple microprocessor architectures to obtain real-time response. The adaptive control algorithm has been implemented on a personal computer to control a thermostatic chamber. Results derived from this application show the effectiveness of the proposed algorithm. >

Influence of Radiation in Thermostatic Air Chamber

Influence of Radiation in Thermostatic Air Chamber

Experimental Studies of the Surface Tension of Nematic Liquid Crystals

Abstract Equilibrium measurements of surface tension have been carried out on nematic compounds using the pendant drop method. A drop of the liquid crystal is suspended at the tip of a capillary tube inside a completely enclosed thermostatic chamber filled with an inert gas and is maintained in equilibrium with its saturated vapour throughout the experiment. The surface tensiontemperature characteristic for all the compounds studied show anomalous behaviour. The slope in the nematic phase is initially negative but changes sign near the nematic-isotropic transition for p-azoxyanisole, p-anisaldazine and p-methoxy benzylidene-p'-n-butylaniline, whereas for p-azoxyphenetole the change of slope occurs in the isotropic phase. The original monotonically decreasing trend is regained in all the cases at higher temperatures in the isotropic phase. The data on p-azoxyanisole, p-azoxyphenetole and p-anisaldazine confirm the earlier measurements of Ferguson and Kennedy1 on the same compounds. The observed features ar...

A torsional creep instrument and a torsional pendulum, both with accurate temperature control

This paper describes a torsional pendulum and a torsional creep instrument. With the pendulum shear moduli between 106 and 1010N/m2 can be measured at frequencies from 0.1 to 20 Hz. The creep instrument is suitable for measurement of shear compliances lower than 10−7 m2/N in the time range from 1 to 105 seconds. In both instruments, specimens are kept at the right temperature by blowing heated nitrogen gas through a surrounding thermostatic chamber. The signal of a platinum resistance thermometer, provided in each chamber, automatically controls the heating of the gas. Temperatures from −180 to +300 °C can be maintained with an absolute accuracy of ±1 °C and a long term stability of ±0.05 °C. It is shown that one cannot directly compare one and the same shear property, calculated from the shear modulus as measured with the pendulum as well as from the shear compliance as measured with the creep instrument. This is due to differences in the temperature of one thermostatic chamber over against the other. Finally, the paper presents a method to reduce these differences to ±0.1 °C, although the absolute accuracy of temperature control remains ±1 °C.

A Thermostatic Chamber for the Measurement of Light Scattering from Solids at Elevated Temperatures

A chamber is described which, in conjunction with a Zimm type light scattering apparatus, may be used to determine the angular dependency of the scattering from polymer films at temperatures between 30°C and 200°C at scattering angles between 10° and 70° from the incident beam. The temperature is maintained by circulating heated air. The use of this chamber is illustrated with a series of measurements of scattering from a polythene film.

A new method of measuring oxygen consumed in the metabolism of small animals.

THE principle of replacing, by means of electrolysis, the oxygen consumed in measurements of metabolism offers the threefold possibility of having a high degree of sensitivity, of controlling the phenomenon for an unlimited time and avoiding calculation entirely. An electrolytic cell (30 per cent sodium hydroxide), capable of producing oxygen, is connected by means of a tube to the thermostatic chamber in which the animal is enclosed. The chamber is provided with a mechanical system for circulating the air and absorbing carbon dioxide, and comprises a pump and a purifier. The whole, including the metabolism chamber, the pump, the purifier, the bell-jar placed over the nickel electrode, and the connecting tubes, is hermetically sealed. Measurement and integration in time of the quantity of electricity supplied by the current generator to the electrolytic cell is done electrically.