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Stress, physiological thermal

The mechanisms by which polymers undergo degradation in the human body are not yet completely understood. Examples of breakdown of these materials are illustrated by the embrittlement and excessive wear of polyester sockets exposed to the mechanical, biochemical and thermal stresses of the physiological milieu, as well as by the fatigue fractures, excessive wear and additional cross-linking (embrittlement) that have been observed in polyethylene sockets. [Pg.470]

We don t know the basis of this loss of temperature control, but we do know that REM sleep is itself associated with failure of the central thermostat, and we know that REM sleep deprivation also causes a loss of temperature. A unifying hypothesis is that any condition that potentiates REM sleep physiology may also compromise the central regulation of body temperature. Relevant to this hypothesis is the fact that the two brain stem aminergic neuromodulators that are inactivated in REM sleep are active in responding to thermal stress. [Pg.200]

Most plants suffer damage, both physiological and biochemical by exposure to temperatures higher or lower than optimal for growth [99]. The results of these injuries, which are reflected in most metabolic processes may be a reduced growth capacity of the crops and therefore lower commercial yield [100]. It has been demontrated that thermal stress induces the production of phenolic compounds [3,4,101]. [Pg.667]

Because of the importance of pH in regulating so many physiological processes, any changes in pH that occur as a result of changes in body temperature would seem likely to add another element of thermal stress to the system. Thus, one might predict a priori that the pH values of the blood (pHB) and the cytosol would need to be closely conserved in the face of changes in body (cell) temperature if homeostasis is to be... [Pg.346]

The use of supercritical fluids in extraction processes has become well established. Until now, the extraction of liquids, as for example vitamins or vegetable edible oils, has been carried out in countercurrent columns. Dense gases offer several advantages over conventional solvents such as selective dissolving power, reduced thermal stress of the products or its physiological harmlessness. A supercritical fluid also has a density close to those for liquids, the viscosity is nearly 100 times lower and the diffusivity is up to 100 times higher than those of ordinary liquids as can be seen in table 1. [Pg.609]

Servicemen, however well trained, can only undertake strenuous duties wearing their full protective clothing for a limited period of time. They will experience physiological and thermal stress, especially in temperatures above 70 Fahrenheit. They will require rest and relief. They will have to complete various bodily functions and to shave, eat and drink. There are emergency drills to permit some of these activities, especially drinking, in a toxic environment but they are hardly ideal. Certain military specialists, moreover, like doctors, simply cannot perform their tasks in a contaminated, toxic environment. To meet these requirements, collective protection centres have to be established within buildings, vehicles and shelters, whether permanent or transportable. The internal areas are sealed by providing... [Pg.150]

The type and quantity of antioxidant is governed by the requirements imposed on the PEG. Thus, not only the temperature and dwell time but also the physiological properties of the antioxidant and its solubility or insolubUity in water must be taken into consideration. Where exposure to high thermal stress is involved, up to 3% antioxidant should be added. [Pg.255]

C.J. Gordon, L.R. Leon, Thermal stress and the physiological response to environmental toxicants. Rev. Environ. Health 20 (4) (2005) 235-263. [Pg.519]

Umminger, B.L. and Gist, D.H. (1973). Effects of thermal acclimation on physiological responses to handling stress, cortisol and aldosterone injections in the goldfish, Carassius auratus. Comparative Biochemistry and Physiology 44A, 967-977. [Pg.318]

Gliner, J.A., P.B.Raven, S.M.Horvath, B.L.Drinkwater, and I.C.Sutton. 1975. Man s physiologic response to long-term work during thermal and pollutant stress. J. Appl. Physiol. 39... [Pg.114]

In the peripheral nervous system, norepinephrine is an important neurotransmitter in the sympathetic branch of the autonomic system. Sympathetic nerve transmission operates below the level of consciousness in controlling physiological function of many organs and tissues of the body. The sympathetic system plays a particularly important role in regulating cardiovascular function in response to postural, exertional, thermal, and mental stress. With sympathetic activation, the heart rate is increased, peripheral arterioles are constricted, skeletal arterioles are dilated, and the blood pressure is elevated. In addition, sympathetic nerve stimulation dilates pupils inhibits smooth muscles of the intestines, bronchi, and bladder and closes the sphincters. Sympathetic signals work in balance with the parasympathetic portion of the autonomic nervous system to maintain a stable internal environment. [Pg.1041]

Desmelle and Schmid developed a set of tools to study the effects of exposure to hot water steam atmospheres on human physiology and to evaluate the protective capacities of fabrics under steam stress. However, their work involved lengthy time scales, wherein the skin would likely be destroyed, and unrealistically held the skin surface at constant temperatnre. Rossi et aV° and Reiser et al. found that steam protection depended on water vapour permeability, thermal insulation, and thickness of the samples tested. Like Lawson et al., - they also found that the presence of moisture in the fabric could have either a positive or negative effect on protection. [Pg.280]


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See also in sourсe #XX -- [ Pg.239 ]




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