Temperature-induced changes, differential

Temperature also affects production rates but, through its influence on the thermal expansion of water, it also induces changes in the depth of vertical mixing and resistance to wind-stirring processes. Reactions to temperature of other components of the food chain are also important in the regulation of phytoplankton biomass by consumers. Different phytoplankton species, with important morphological differences, are differentiated selectively by the interplay of these factors. " ... 

When a material is heated or cooled, there is a change in its structure or composition. These transformations are connected with a heat exchange. Differential scanning calorimetry (DSC) is used for measuring the heat flow into and out of the sample, as well as for determining the temperature of the thermal phenomenon during a controlled change of temperature. The first method developed by Le Chatelier in 1887 was differential thermal analysis (DTA), where only the temperature induced in the sample was measured. 

Diffraction experiments at high pressures provide information concerning the compression-induced changes of lattice parameters and, thus, sample volume. In pure phases of constant chemical composition and in the absence of external fields, the thermodynamic parameters volume V, temperature T and pressure P are related by equations of state, i.e. each value of a state variable can be defined as a function of the other two parameters. Some macroscopic quantities are partial differentials of these equations of state, e.g. the frequently used isothermal bulk modulus Bq of a phase at a defined temperature and zero pressure 5q = — Fq (9P/9F) for T= constant and P = 0, with the reciprocal of Bq V) being the isothermal compressibility k. Equations of state can also be formulated as derivatives of thermodynamic functions like the internal energy U or the Helmholtz free-energy F. However, for practical use the macroscopic properties of solids are often described by means of semi-empirical equations, some of which will be discussed in more detail. 

Decker, M.W., M.J. Buckley, and J.D. Brioni. 1994. Differential effects of pretreatment with nicotine and lobeUne on nicotine-induced changes in body temperature and locomotor activity in mice. Drug Dev. Res. 31(l) 52-58. 

Thus, also a permanent dipole mechanism may be characterized by a transition of the X quantity from a quadratic field strength dependence to a linear one concomitant with the E dependence the temperature variation changes from T to T K Therefore the temperature dependence of equilibrium and rate constants may be used to differentiate between permanent and induced moments. 

The most extensively used methods for monitoring these heat induced changes in fibers are differential thermal analysis (DTA) and differential scanning calorimetry (DSC). In DTA, both sample and inert reference are heated at the same rate by the same heat source. When a thermally induced transition occurs in the sample, a temperature difference between the sample and reference results can be recognized. A plot of the difference in temperature between the two against increasing applied temperature exhibits deviations from the initial baseline, depending on... 

The variation of temperature induced by the laser pulses can be estimated through a veiy simple model, by considering that the fraction of the energy of the laser pulse that is not reflected on the surface, is converted immediately into heat at the surface of the electrode. ° ° Then, the temperature change can be calculated by solving the following partial differential equation ... 

The life-cycles of protozoa generally include several transformations between different cell types, and many of these transformations can be reproduced in vitro. Protozoan differentiation can often therefore be investigated in experimental systems which are well suited to detailed analysis at a number of levels. Unlike untransformed vertebrate cell lines which normally have a limited life-span, protozoan cells can be grown and manipulated indefinitely in vitro and often induced to differentiate by simple stimuli such as changes in temperature. 

The explosive phenomena produced by contact of liquefied gases with water were studied. Chlorodifluoromethane produced explosions when the liquid-water temperature differential exceeded 92°C, and propene did so at differentials of 96-109°C. Liquid propane did, but ethylene did not, produce explosions under the conditions studied [1], The previous literature on superheated vapour explosions has been critically reviewed, and new experimental work shows the phenomenon to be more widespread than had been thought previously. The explosions may be quite violent, and mixtures of liquefied gases may produce overpressures above 7 bar [2], Alternative explanations involve detonation driven by phase changes [3,4] and do not involve chemical reactions. Explosive phase transitions from superheated liquid to vapour have also been induced in chlorodifluoromethane by 1.0 J pulsed ruby laser irradiation. Metastable superheated states (of 25°C) achieved lasted some 50 ms, the expected detonation pressure being 4-5 bar [5], See LIQUEFIED NATURAL GAS, SUPERHEATED LIQUIDS, VAPOUR EXPLOSIONS... 

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