Ambient Temperature Dependence Research Articles

Further demonstration of the ambient temperature dependence of the annual biological cycles in the edible dormouse, Glis glis.

In the male edible dormouse, it has been proposed that the annual temperature cycle is the major external factor triggering annual biological rhythms in this hibernating species. The present study was designed to explore (i) the effects of suppression of the annual thermoperiodic cycle under natural photoperiodic conditions, and (ii) the effects of acute exposure to a warm environment on basal plasma T4 levels observed during hibernation. The results of the first experiment demonstrate an absence of circannual cycles of hibernation, body weight, and endocrine thyroid and gonadal functions in the absence of annual fluctuations of temperature (constant warm environment at 24 degrees C) despite the maintenance of a normal photoperiodic cycle. On the other hand, acute exposure to 24 degrees C during the late stage of hibernation stimulated thyroid function as expressed by a consistent transitory rise in plasma T4 concentrations, which was maximal within 7 days and restored to basal levels after 14 days. These findings are in close agreement with the concept that in the edible dormouse, the annual thyroid cycle is synchronized with the annual temperature cycle. Moreover, the present study, combined with prior data indicating that the thyroid cycle induces the testis cycle, suggests that the ambient temperature cycle may be intricately involved in the control of neuroendocrine cycles in dormice, although the mechanism is still unknown.

Steady-state photoconductivity in glow-discharged amorphous hydrogenated silicon

The steady-state photoconductivity has been measured in glow-discharged amorphous hydrogenated silicon deposited at various substrate temperatures. The quantum efficiency ν in the photoconduction process is found to be unity at room temperature at the incident photon energy of 1.96 eV over the whole range of the substrate temperature. The mobility-lifetime product μτ is essentially the same as that obtained by time-of-flight measurement. The lifetime has a broad maximum of about 10 −6s at the substrate temperature of about 200°C. The ambient temperature dependence of the photoconductivity is explained on the basis of a model considering two sets of trap levels. The assumption that the tail states of the conduction band are responsible for both trap-controlled mobility and recombination seems to give a more plausible explanation. However, another possibility that cannot be ruled out is that the electron mobility is governed by potential barriers between quasi-crystalline zones.

On the Use of Wet Bulb Temperature as an Environmental Index

The cooling capacity of an atmospheric environment is examined with respect to a wet object of a given surface temperature. The maximum cooling capacity (MCC) is defined as the sum of the sensible and latent heat fluxes out of a unit area of the object. The MCC can be used as a quantitative measure of the upper limit of the sum of some internal energy dissipation (total internal energy production minus mechanical work) and the absorbed radiant flux in a given object in thermal equilibrium. It is found that, for a given surface temperature and wind speed, the MCC is essentially a function of the wet bulb temperature of the ambient air with a very weak dependence on the ambient air temperature and pressure. It is further shown that the ambient temperature and pressure dependence can be ignored for practical purposes. A simple equation relating the MCC to surface temperature and ambient wet bulb temperature has been derived. Thus, in a given environment the wet bulb temperature sets a quantitative upper limit for the intensity of prolonged exercise.

Ambient temperature dependence of the body temperature and of the duration of the hibernation periods in the garden dormouse, Eliomys quercinus L

Hibernation pattern in the garden dormouse ( Eliomys quercinus) was studied at T A's of 0, 4, 6.5, and 9 °C during 6 months in each study winter. The animals were kept in darkness without food or water. Body temperature and the mean duration of the hibernation periods were ambient temperature dependent. The comparison of hibernation at different T A's was based on three features: the mean duration of the hibernation periods during the midwinter plateau, the existence of the initial and terminal phases with the changing length of the hibernation periods, and the differences between the sexes. The T A of 4 °C was the optimal T A for long-term hibernation. The difference between 4 °C and other T A's was greater in males. The T A's of 0 and 9 °C were near the lower and higher T A limits for longterm hibernation. Signs of the existence of a circannual rhythm were detected in the males toward the end of the hibernation season.

Ion-induced silicide formation in niobium thin films

Abstract MeV 4He backscattering and X-ray diffraction analysis were used to examine the intermixing of niobium thin films on single-crystal silicon during 28Si+ ion bombardment. The ambient temperature dependence of the intermixing is reported. The dependence cannot be explained by either radiation-enhanced diffusion or cascade mixing alone. The silicides, NbSi2, and Nb5Si3, were both observed. Silicide growth was found to be proportional to the square root of the fluence for the case in which the ion range exceeds the film thickness.

Diamagnetism of Glassy Carbons

The diamagnetic susceptibility (χ) in the range down to liquid nitrogen temperature has been measured of glassy carbons prepared by stepwise heat treatments between 800 and 3000°C. The observed |χ| increases with heat treatment temperature similarly to those for various nongraphitizing carbons. The specimens treated under 1300°C exhibit a slight ambient-temperature (T) dependence indicating a maximum around room temperature, while those above 2000°C a monotonic trend decreasing with increase of T. The latter is accounted for in terms of the Haering-Wallace theory by assuming the Fermi level depressions of -0.16 to -0.11 eV. Discussions are given of the size effects, on the basis of a tangled-ribbon model for the crystalline structure.