Episodic release

The principal shortcoming with SCREENS is the lack of graphical displays. Interactive graphics that enable plume tracking are invaluable in assessing potential environmental impacts and public health risks from episodic releases. There are a... 

When spills and releases of hazardous gases or liquids occur, the concentration of the hazardous material in the vicinity of the release is often the greatest concern, since potential health effects on those nearby will be determined by the concentration of the substance at the time of the acute exposure. There are many models of routine continuous discharges (e.g., discharges arising from leaky valves in chemical plants), but these carmot be applied to single episodic events. Research on the ambient behavior of short-term environmental releases and the development of models for concentration profiles in episodic releases are cmcial if we are to plan appropriate safety and abatement measures. 

The episodic release of growth hormone is the most pronounced among the pituitary hormones. Serum levels between bursts of release are usually low (<5... 

The type of model to be used in a given situation depends on the nature of the release and on the properties of the ecosystem. When releases of metals or radionuclides are continuous and steady-state conditions are present, an equilibrium model such as a concentration factor model can be used. In this case,the important parameter needed for the model is the concentration factor, the ratio of the concentration in the animal to that in the water. The concentration in the animal is determined then by multiplying the concentration in the water by the concentration factor. In the case of accidental episodic releases, a dynamic situation exists in which organisms accumulate the material for a relatively short period and then lose it with a characteristic time constant. In this case,the important parameters needed for the model are biological turnover rate constants and concentration factors. 

Point source and episodic releases of primarily radioisotopes from nuclear fuel reprocessing (e.g., Windscale effluent) and from accidents (e.g., the Chernobyl disaster). 

In the case of carbon isotopes the 6 C is the complex result of the relative importance of organic carbon sequestration or release by weathering compared to calcium carbonate deposition since the former has a 6 C of about —25 and the latter a 6 C of —0. A further effect can be the episodic release of extremely light carbon (6 C... 

Measurement of Urinary Gonadotropins Chnically, the pulsatEe and episodic release of gonadotropins make a single blood concentration of FSH or LH difficult to interpret. In normal adults, the concentrations of gonadotropins in blood, particularly LH, have been known to ... 

The primary stimulus for oxytocin release is suclding. Stimulation of tactile receptors located around the nipples of the breasts initiates an action potential that propagates along afferent nerve fibers through the spinal cord and mid-bram to the hypothalamus. The cell bodies in the paraventricular nucleus are then stimulated, resulting in the episodic release of oxytocin. Stretch receptors in the uterus and possibly in the vaginal mucosa may also initiate action potentials in afferent nerve fibers that ultimately stimulate the release of oxytocin from the neurohypophysis. Estrogens enhance the response of oxytocin to these stimuli. The influence of other parts of the brain on the release of oxytocin has been reported emotional stress, for instance, inhibits lactation. 

A single component, such as contaminated sediments, may have an episodic release of toxics that could push an entire system beyond its resihency. Ecotoxicological tests in microcosms and/or mesocosms can reduce uncertainty about this threshold. 

Episodic release A release of limited duration, usually associated with an accident. 

Level of concern The concentration of an airborne chemical above which there may be adverse human health effects experienced as a result of a short-term exposure during an episodic release. 

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