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83) Electrosecurity.

One of the major problems by development, industrial release and operation of the electromedical equipment is maintenance of a full electrosecurity for the attendants and patients. The basic safety means from action on an organism of an electric current is protective ground connection. Defeat of an organism by an electric current can be in the form of an electric trauma or electric impact. Electric trauma is a result of external local action of a current on a body: electric burns, electrometallization of skin, signs on a current. Electric burns are consequence of thermal action of the current which is passing through a body of the person, or occur under action of the electric arch, arising usually at short circuits in installations with a pressure above 1000 V. Electrometallization of a skin occurs at introduction in a skin of the smallest particles of metal fused under action of the current.

84) Primary stages of photobiological processes.

Depending on character of interaction of laser light with biological tissues it is possible to distinguish three kinds of photo-biological effects:

1) photo-destructive influence at which thermal, hydro-dynamical, photochemical effects of light cause destruction of tissues. This kind of laser interaction is used in laser surgery.

2) photo-physical and photochemical influence, at which light absorbed by biotissues raises in them atoms and molecules, causes photochemical and photophysical reactions. This laser radiation is used as therapeutic.

3) unperturbed influence, when the biosubstance does not change the properties during interaction with light. These are such effects, as dispersion, reflection and penetration. This kind use for diagnostics (laser spectroscopy).

Photobiological effects depend upon parameters of laser radiation: wave length, intensity of a stream of light energy, time of influence for biotissues. In laser therapy light streams of low intensity is applied, no more than 100 mW/cm2, that is comparable to intensity of radiation of the Sun on a surface of the Earth in clear day.

85) Photochemical reactions.

Photochemical reactions call such chemical reactions which proceed only under the influence of light.

Types of photochemical reactions:

Photodissociation (фотолиз) leads to decomposition of the initial substance which has absorbed light energy. Such are examples of reaction of photodecomposition: decomposition of halogenides of silver (basis of the silver photo), фотолиз vapors of CH3CO CH3 acetone → CO + other products.

Photosynthesis leads to formation of more difficult connections. Are examples of reactions of photosynthesis:

-the photosynthesis of ozone in an upper atmosphere creating a protective ozone layer:

-photosynthesis of organic compounds from carbon dioxide, water, mineral substances green plants.

High energy of photoexcitement also causes a possibility of course of such reactions which in usual conditions are impracticable.

Initial stage of any photochemical reaction absorption of a photon which transfers a molecule to an excited state is.

Photon excitement of a molecule starts one of two possible mechanisms of change of its chemical properties, each of which then generates a chain of regular chemical transformations. In the initiated molecule there is an electron on highly located free orbital. Such electron easily separates from a molecule, and it reacts photooxidations. In this case the initiated molecule becomes the donor of an electron. Products of primary oxidation-reduction reactions are free radicals also possess high chemical activity. They enter secondary reactions which come to an end with the corresponding physiological reaction- Molecule photoisomerization.Photoexcitation plays the predominating role in the course of photoisomerization; besides, the fotochromic applications is used in the lightsensible solar batteries, photochemistry, a luminescence, optically-excited lasers and others.

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