The use of radiant energy. radiant energy

A significant part of the solar radiation entering the Earth covers the wave range within 0.15 - 4.0 mmk. The amount of solar energy that strikes the Earth's surface at a right angle is called the solar constant. It is equal to 1.4 10-3 J (m2/s).

Most of the radiation in the visible region of the spectrum reaches the earth's surface, 30

% - infrared and long-wave ultraviolet. The surface of the earth reaches:

Infrared rays (f - 3 10v11 Hz, - 3 10v12, λ from 710 - 3000 nm) - 45% (IR-

radiation is 50% of the radiation of the sun).

Visible rays (3 10v12 - 7.5 10v 16, λ 400 - 710 nm,) - 48%

Ultraviolet rays (7.5 10v 16-10v17, λ 400-10 nm) -7%.

A small part of the solar radiation goes back into the atmosphere. The amount of reflected radiation depends on the reflectivity (albedo) of the surface. For example, snow can reflect 80% of the sun's radiation, so it heats up slowly. A grassy surface reflects 20%, and dark soils only 10 5 of the incoming radiation.

Most of the solar energy absorbed by the soil and water bodies is spent on the evaporation of water. When water condenses, heat is released, which warms the atmosphere. The heating of the atmosphere also occurs due to the absorption of 20-25% of solar radiation.

Infrared radiation.

Infrared radiation (IR radiation) is electromagnetic radiation invisible to human eyes. The optical properties of a substance in IR radiation are significantly different from those in the visible spectrum. For example, a few cm layer of water is impervious to IR radiation with λ >1 µm.

About 20% of the infrared radiation of the solar spectrum is absorbed by dust, carbon dioxide and water vapor in the 10 km layer of the atmosphere adjacent to the Earth's surface. In this case, the absorbed energy is converted into heat.

IR radiation makes up most of the radiation from incandescent lamps (unbearable heat when shooting in studios), gas discharge lamps. IR radiation is emitted by ruby ​​lasers.

The long-wave part of infrared radiation (> 1.4 microns) is retained mainly by the superficial layers of the skin, causing burning (hot rays). The medium and short-wave part of the infrared rays and the red part of the optical radiation penetrates to a depth of 3 cm. With large amounts of energy, overripeness can be caused. Sunstroke is the result of local overheating of the brain.

Visible radiation is light.

Approximately half of the radiation comes from waves with a wavelength between 0.38 and 0.87 microns. It's visible human eye spectrum perceived as light.

One of the visible aspects of the impact of radiant energy is illumination. It is known that light heals the environment (including bactericidal action). Half of all the thermal energy of the sun is contained in the optical part of the radiant energy of the sun. Light is necessary for the normal course of physiological processes.

Effect on the body:

Stimulates vitality;

Enhances metabolism;

Improves overall well-being;

Improves mood;

Increases performance.

lack of light:

Negative effect on the functions of the nervous analyzer (its fatigue increases):

Increased fatigue of the central nervous system;

Decreased productivity;

Increasing industrial trauma;

Depressive states develop.

WITH insufficient illumination is currently associated with a disease that has several names:"autumn-winter depression", "emotional seasonal illness", "affective seasonal disorder" (Seasonal Affective Disorder - SAD). The less natural illumination of the area, the more common this disorder. According to statistics, 5-10% of people have signs of this symptom complex (75% are women).

Darkness leads to the synthesis of melatonin, which in healthy people regulates the timing of nighttime sleep cycles so that it is healing and promotes long life. However, if melatonin production does not stop in the morning due to the effect of light on the pineal gland, lethargy and depression develop during the day due to inadequately high daytime levels of this hormone.

Signs of SAD:

signs of depression;

Difficulty waking up;

Decreased productivity at work;

Decrease in social contacts;

Increased need for carbohydrates;

Weight gain.

May cause a decrease in the activity of the immune system, which is manifested by an increase in susceptibility to infectious (viral and bacterial) diseases.

These signs disappear in spring and summer, when the length of daylight hours increases significantly.

Autumn-winter depression is currently being treated with light. Light therapy with an intensity of 10,000 lux in the morning gives a good effect. This exceeds about 20 times the normal internal illumination. The choice of the duration of therapy is individual for each person. Most often, the duration of the procedure lasts 15 minutes. During this time, you can do any business (read, eat, clean the apartment, etc.). A positive effect is noted after a few days. All symptoms completely disappear after a few weeks. side effect may have headaches.

The effect of treatment is associated with the regulation of the activity of the pineal gland, which modulates the production of melatonin and serotonin. Melatonin is responsible for falling asleep, and serotonin is responsible for waking up.

Shown also:

Psychotherapy;

Antidepressants.

IN At the same time, another type of disturbance of biological rhythms associated with the modern way of life can now be observed. Prolonged artificial light leads to a decrease in the inhibitory effect of melatonin on the activity of the gonads. This contributes to the acceleration of puberty.

Ultraviolet (UV) radiation

Ultraviolet radiation belongs to the short-wavelength part of the solar spectrum. It borders on one side with the softest part of ionizing radiation (X-ray), on the other - with the visible part of the spectrum. It makes up 9% of all energy emitted by the Sun. At the border with the atmosphere, 5% of natural sunlight is present, and 1% reaches the Earth's surface.

The ultraviolet radiation of the Sun ionizes the gases of the upper layers of the Earth's atmosphere, which leads to the formation of the ionosphere. Short UV rays are stopped by a layer of ozone at an altitude of about 200 km. Therefore, only rays of 400-290 nm reach the earth's surface. Ozone holes contribute to the penetration of the short-wave part of the UV spectrum.

The intensity of the action depends on:

Geographic location (latitude);

time of day,

weather conditions.

The biological properties of UV radiation depend on the wavelength. There are 3 ranges of UV radiation:

1. Area A (400-320 nm) - fluorescent, tan. This long-wave radiation, which is the dominant part, is practically not absorbed in the atmosphere, therefore it reaches the Earth's surface. It is also emitted by special lamps used in solariums.

Action:

Causes the glow of certain substances (phosphors, some vitamins);

Weak general stimulating effect;

The conversion of tyrosine to melanin (protection of the body from excess UV radiation).

The conversion of tyrosine to melanin occurs in melanocytes. These cells are located in the basal layer of the epidermis. Melanocytes are pigment cells of neuroectodermal origin. They are unevenly distributed throughout the body. For example, in the skin of the forehead there are 3 times more of them than in the upper limbs. Pale people and swarthy people contain the same number of pigment cells, but the melanin content in them is different. Melanocytes contain the enzyme tyrazinase, which is involved in the conversion of tyrosine to melanin.

2. Region B (320 - 280 nm) - medium-wave, tan UV radiation. A significant part of this range is absorbed by stratospheric ozone.

Action:

Improving physical and mental performance;

Increased nonspecific immunity;

Increasing the body's resistance to the action of infectious, toxic, carcinogenic agents.

Strengthening tissue regeneration;

Strengthening growth.

This is due to the excitation of amino acids (tyrosine, tryptophan, phenylalanine, etc.), primidine and purine bases (thymine, cytosine, etc.). This leads to the breakdown of protein molecules (photolysis) with the formation of biologically active substances (choline, acetylcholine, histamine, etc.). BAS activate metabolic and trophic processes.

3. Region C (280 - 200 nm) - short-wave, bactericidal radiation. Actively absorbed by the ozone layer of the atmosphere.

Action:

Synthesis of vitamin D;

bactericidal action.

Bactericidal action, although less pronounced, have other ranges of UV radiation, as well as visible radiation.

N!B! UV rays of the medium and short wavelength spectrum in high doses can cause changes in nucleic acids and lead to cellular mutations. At the same time, long-wave radiation contributes to the recovery of nucleic acids.

4. The D region (315 - 265 nm) is also distinguished, which has a pronounced antirachi-

tic action.

It has been shown that to meet the daily requirement for ittamin D, about 60 minimal erythemal doses (MED) are needed for exposed areas of the body (face, neck, hands). To do this, you need to stay in sunlight daily for 15 minutes.

Lack of UV radiation leads to:

rickets;

Decreased overall resistance;

Violation of metabolic processes (including osteoporosis?).

Excess UV radiation leads to:

Increased body's need for essential amino acids, vitamins, Ca salts, etc.;

Inactivation of vitamin D (transfer of cholecalceferol into indifferent and toxic substances);

The formation of peroxide compounds and epoxy substances, which can cause chromosomal aberrations, mutagenic and carcinogenic effects.

Exacerbation of certain chronic diseases (tuberculosis, gastric ulcer, rheumatism, glomerulonephritis, etc.);

Development of photophthalmia (photoconjunctivitis and photokeratitis) 2-14 hours after irradiation. The development of photophthalmia can be the result of the action of: A - direct sunlight, B - scattered and reflected (snow, sand in the desert), C

– when working with artificial sources;

Dimerization of the crystallin protein (crystallin), which induces the development of cataracts;

Increased risk of retinal damage in individuals with a removed lens (even area A).

In persons with fermentopathy to dermatitis;

Development of malignant neoplasms of the skin (melanoma, basal cell carcinoma, squamous cell carcinoma)

Immunosuppression (change in the ratio of lymphocyte subpopulations, a decrease in the number of Langerhans cells in the skin and a decrease in their functional activity) → to a decrease in resistance to infectious diseases,

Accelerated skin aging.

The body's natural defense against UV radiation:

1. The formation of sunburn associated with the appearance of melanin, which:

able to absorb photons and thus weaken the effect of radiation;

is a trap for free radicals formed during skin irradiation.

2. Keratinization of the upper layer of the skin, followed by peeling.

3. Formation of trans-cis-form of urocanic (urocaic) acid. This compound is capable of capturing UV radiation quanta. Excreted in human sweat. In the dark, a reverse reaction occurs with the release of heat.

The criterion for the sensitivity of the skin to UV radiation is the burn threshold of tanning. It is characterized by the time of primary exposure to UV radiation (that is, until the formation of pigmentation), after which error-free DNA repair is possible.

IN middle latitudes distinguish 4 skin types :

5. Particularly sensitive bright skin. Blushes quickly, tans badly. Individuals are distinguished by blue or in green eyes, the presence of freckles, sometimes red hair. Burn threshold for tanning 5-10 minutes.

6. Sensitive skin. People of this type have blue, green or gray eyes, light brown or brown hair. The burn threshold for tanning is 10-20 minutes.

7. Normal skin (20-30 min.). People with gray or light brown eyes, dark blond or brown hair.

8. Insensitive skin(30-45 min.). Individuals with dark eyes, swarthy skin and dark color hair.

It is possible to modify the photosensitivity of the skin. Substances that increase the sensitivity of the skin to light are called photosensitizers.

Photosensitizers: aspirin, brufen, indocide, librium, bactrim, lasix, penicillin, plant furanocoumarins (celery).

Risk groups for the development of skin tumors:

light, poorly pigmented skin,

sunburns received before the age of 15,

Availability a large number birthmarks,

the presence of birthmarks more than 1.5 cm in diameter.

Although ultraviolet radiation is of priority importance in the development of malignant neoplasms,

skin, a significant risk factor is contact with carcinogens -

mi, such as contained in atmospheric dust nickel and its mobile forms in the soil.

Protection against excessive UV exposure:

1. It is necessary to limit the time spent under intense sunlight, especially in the time interval 10.00 - 14.00 hours, peak for UV activity. The shorter the shadow, the more damaging the UV activity.

2. Sunglasses (glass or plastic with UV protection) should be worn.

3. The use of photoprotectors.

4. The use of sunscreen.

5. Nutrition with a high content of essential amino acids, vitamins, macro- and microelements (primarily nutritious with antioxidant activity).

6. Regular examination by a dermatologist by persons at risk for developing skin cancer. The appearance of new ro-

dark spots, loss of clear boundaries, changing pigmentation, itching and bleeding.

It must be remembered that UV radiation is intensively reflected from sand, snow, ice, concrete, which can increase the intensity of UV exposure by 10-50%. It should be remembered that UV radiation, especially UVA, affects a person even on cloudy days.

Photoprotectors are substances with a protective effect against damaging UV radiation. The protective effect is associated with the absorption or dissipation of photon energy.

Photoprotectors;

Para-aminobenzoic acid and its esters;

Melanin obtained from natural sources (for example, mushrooms). Photoprotectors are added to sunscreens and lotions.

Sunscreens.

There are 2 types - with a physical effect and with a chemical effect. The cream should be applied 15-30 minutes before taking sunbathing, and again - every 2 subsequent hours.

Sunscreens with a physical effect contain compounds such as titanium dioxide, zinc oxide and talc. Their presence leads to the reflection of UVA and UVB rays.

Sunscreens with a chemical effect include products containing 2-5% benzophenone or its derivatives (oxybenzone, benzophenone-3). These compounds absorb UV radiation and as a result break into 2 parts, which leads to the absorption of UV energy. A side effect is the formation of two free radical fragments that can damage cells.

Sunscreen SPF-15 filters out about 94% of UV rays, SPF-30 blocks out 97% of UV rays, predominantly UVB. UVA filtration in chemical sunscreens is low, accounting for 10% of UVB absorption.

It is no coincidence that we begin our review with this environmental factor. The radiant energy of the sun, or solar radiation, is the main source of heat and life on our planet. Only thanks to this, in the distant past on Earth, organic matter could originate and, in the process of evolution, achieve those degrees of perfection that we observe in nature at the present time. The main properties of radiant energy as an ecological factor are determined by the wavelength. On this basis, within the entire light spectrum, visible light, its ultraviolet and infrared parts are distinguished (Fig. 10). Ultraviolet rays have a chemical effect on living organisms, infrared rays have a thermal effect.

Rice. 10. Spectra of solar radiation c. various conditions (according to: Odum, 1975).
1 - not changed by the atmosphere; 2 - at sea level on a clear day; 3 - passed through continuous cloudiness; 4 - passed through the vegetation canopy.

The main parameters of the environmental impact of this factor include the following: 1) photoperiodism - a regular change of daylight and darkness (in hours); 2) lighting intensity (in lux); 3) voltage of direct and scattered radiation (calories per unit surface per unit time); 4) chemical action of light energy (wavelength).

The sun continuously radiates great amount radiant energy. Its power, or radiation intensity, at the upper limit of the atmosphere is from 1.98 to 2.0 cal / cm 2 -min. This indicator is called the solar constant. However, the solar constant, apparently, can vary somewhat. It is noted that for last years The brightness of the Sun has increased by about 2%. As it approaches the Earth's surface, solar energy undergoes profound transformations. Most of it is retained by the atmosphere. Further, vegetation gets in the way of light waves, and if it represents a multi-tiered closed tree plantation, then a very small part of the initial solar energy reaches the soil surface. Under the canopy of a dense beech forest, this number is 20-25 times less than in the open. But the point is not only in a sharp decrease in the amount of light, but also in the fact that in the process of penetrating into the depths of the forest, the spectral composition of light changes. Consequently, it undergoes qualitative changes that are very significant for plants and animals.

Speaking about the ecological significance of light, it must be emphasized that the most important thing here is its role in the photosynthesis of green plants, because the result is the creation of organic matter, plant biomass. The latter represents the primary biological products, on the use and transformation of which everything else living on Earth depends. The intensity of photosynthesis varies greatly in different geographic areas and depends on the season of the year, as well as on local environmental conditions. Additional lighting allows you to significantly increase the growth of even tree and shrub species, not to mention herbaceous plants. I. I. Nikitin germinated acorns for 10 days under continuous illumination, then 5 months. grew seedlings in the light with a brightness of 4 thousand lux. As a result, the oaks reached a height of 2.1 m. After transplanting into the ground, the 8-year-old experimental oak gave an annual growth in height of 82 cm, while the control trees - only 18 cm.

It is noteworthy that although the vital activity and productivity of animals are directly (for phytophages) or indirectly (for zoophages) dependent on the primary production of plants, nevertheless, the relationship between maenads and animals is far from one-sided. It has been established that phytophagous animals, such as moose, eating green plant mass and damaging photosynthetic organs, are capable of
significantly reduce the intensity of photosynthesis and plant productivity. So, in the Central Chernozem Reserve (Kursk region), moose ate only 1-2% of the phytomass of young oak forests, but their productivity fell by 46%. Thus, in the forage plant - phytophage system, there is both a direct and a feedback relationship.

Photoperiodism plays a huge role in the life of all living beings. As this factor is studied, it becomes clear that the photoperiodic reaction underlies many biological phenomena, being a direct factor determining them or performing signal functions. The outstanding significance of the photoperiodic reaction is to a large extent due to its astronomical origin and, because of this, a high degree of stability, which, for example, cannot be said about the temperature of the medium, which is also extremely important, but extremely unstable.

The very fact that animals are divided into two large groups according to the time of activity - daytime and nocturnal - clearly indicates their deep dependence on photoperiodic conditions. The same is evidenced by the regularity established in 1920 by American scientists W. Garner and G. Allard, according to which plants are divided into types of long and short day. Later, it was found that a similar photoperiodic reaction is also characteristic of animals and, therefore, is of a general ecological character.

A regular change in the length of daylight hours by seasons determines the time of the onset of the state of diapause of numerous species of insects and other arthropods, in particular ticks. Through subtle experiments, A. S. Danilevsky and his coworkers proved that diapause is stimulated precisely by the shortening of the day, and not by a decrease in air temperature, as previously thought (Fig. 11). Accordingly, the regular increase in the length of daylight hours in spring serves as a clear signal for the termination of the state of diapause. At the same time, species populations living at different latitudes differ in specific photoperiodic requirements. For example, for a butterfly of the oxalic shooter (A crony eta rumicis), in Abkhazia, a day length of at least 14 hours 30 minutes is required, in the Belgorod region - 16 hours 30 minutes, in the Vitebsk region - 18 hours and near Leningrad - 19 hours. In other words, with advancement to the north for every 5° of latitude, the duration of the day required to emerge from diapause in this species lengthens by about an hour and a half.

Rice. 11. Photoperiodic reaction of the long-day type - the cabbage butterfly (1) and the short-day type - the silkworm (2) (according to: Danilevsky, 1961).

Thus, photoperiodism is the main factor in the seasonal activity of arthropods. Moreover, similar studies by botanists have shown that many phenomena in the seasonal life of plants, the dynamics of their growth and development, are also related to photoperiodic reactions. For example, the photoperiodic factor serves as a signal for early preparation of plants for winter, regardless of the weather. All this makes photoperiodism a very important factor in the introduction of agricultural plants into new areas, in their cultivation in greenhouses, etc.

Finally, a comparison of the results of experiments on the photoperiodism of phytophagous insects and their food plants revealed a deep interdependence between them. Both of them respond to the impact of the same environmental factor in a similar way, therefore, their trophic relationships have a deep ecological and physiological basis.

The study of photoperiodic reactions in higher vertebrates has also brought extremely interesting results. So, in autumn, fur-bearing animals develop an increasingly dense and lush hairline. In winter, it reaches its greatest development and maximum thermal insulation properties. These protective functions of the fur are enhanced by a thick layer of fat that forms under the skin in late summer and autumn. In winter, the mentioned morphophysiological adaptations are fully functional. It has long been believed that the main factor determining the seasonal development of fur and fat is the air temperature, its fall in the autumn-winter months. However, experiments have shown that the triggering mechanism of this process is associated not so much with temperature as with photoperiodism. In a laboratory vivarium and even on a fur farm, you can place American minks or other animals in cages with adjustable lighting and artificially reduce daylight hours starting in mid-summer. As a result, the process of molting in experimental animals begins much earlier than in nature, goes more intensively and, accordingly, ends not by winter, but at the beginning of autumn.

The most important seasonal phenomenon in the life of migratory birds also rests on a photoperiodic basis - their migration and closely related processes of plumage molting, accumulation of fat under the skin and on internal organs and others. Of course, all these are adaptations for enduring unfavorable temperature and food conditions by “avoiding” them. However, in this case, the main signaling role is played by changes not in the temperature, but in the light regime - a reduction in the length of the day, which can be proved by experiments. In the laboratory, by acting on the photoperiodic response of birds, it is not too difficult to bring them into a specific pre-migratory state and then into migratory excitement, although the temperature conditions will remain stable.

It turns out that the cyclical nature of the sexual activity of animals, the cyclical nature of their reproduction, is also photoperiodic. Perhaps this is especially surprising, since the biology of reproduction belongs to the properties of the organism, the most finely formed, with the most complex coordination of relationships.

Experiments on many types of birds and mammals have shown that by increasing the length of daylight hours, it is possible to activate the gonads (Fig. 12), bring animals into a state of sexual arousal and achieve productive mating even in the autumn-winter months, if, of course, a positive reaction to light Both sexes will be affected. Meanwhile, females in some species (for example, sparrows) in this respect are much more inert than males, and require additional ethological stimulation.

Rice. 12. Influence of light on the development of gonads in male and female house sparrows slaughtered after keeping at different conditions(after: Polikarpova, 1941).
a - from the will on January 31; b - from a chamber with room temperature on January 29; c - from a camera with additional light on January 28.

Some mammals - sable, marten, a number of other mustelid species, as well as roe deer - are characterized by interesting feature reproduction biology. In them, the fertilized egg does not first implant in the uterine wall, but<в течение длительного времени находится в состоянии покоя, так называемой латентной стадии. У соболя эта стадия продолжается несколько месяцев и лишь приблизительно за полтора месяца до рождения щенков происходит имплантация яйца и очень быстрое эмбриональное развитие. Таким образом, беременность распадается как бы на длительный период предбеременности, или латентный, и короткий, порядка 35-45 дней, период вынашивания, т. е. собственно эмбрионального развития. Благодаря этому замечательному приспособлению животные получают возможность с минимальными энергетическими затратами переживать тяжелое зимнее время. Оказывается, что продолжительность латентного периода также регулируется фотопериодической реакцией и, если воспользоваться последней, может быть существенно сокращена.

The influence of the ratio of the periods of illumination and darkness and the change in the intensity of illumination during the day on the activity of animals is very great. For example, diurnal birds wake up at dawn at a certain intensity of "awakening illumination", depending on the height of the sun in relation to the horizon. The onset of the proper "awakening light" serves as a signal that stimulates the activation of the birds. Thrushes begin to show signs of life at 0.1 lux, when it is still almost completely dark in the forest; the cuckoo requires 1 lux for its awakening, the black-headed warbler - 4, the finch-12, the house sparrow - 20 lux. In accordance with this, in good weather, birds in a given area wake up at a certain time and in a certain order, which allows us to speak of the existence of "bird clocks". For example, in the Les na Vorskla uchleskhoz of the Belgorod Region, in May-June, the first calls of birds are heard on average at the following time: nightingale - at 2 h 31 min, black and song thrushes - 2 h 31 min, cuckoo - 3 h 00 min, black-headed warbler - 3 h 30 min, great tit - 3 h 36 min, tree sparrow - 3 h 50 min.

Daily changes in the illumination regime have a profound effect on the vital activity of plants, and above all on the rhythm and intensity of photosynthesis, which stops during the dark hours of the day, during bad weather and in winter (Fig. 13).

Finally, solar energy can play a very important role as a source of heat, affecting living beings directly or profoundly influencing their environment on a local or global scale.

In general, from the above fragmentary information it is clear that the light factor plays an extremely important and versatile role in the life of organisms.

Rice. 13. Dependence of photosynthesis on light energy in different plant populations (according to: Odum, 1975).
1 - trees in the forest; 2 - leaves illuminated by the sun; 3 - shaded leaves.

Radiant energy from the sun coming to Earth is the most significant source of energy available to mankind. The sun, like other stars, is a hot gas. Inside the Sun there is a region of high pressure, where the temperature reaches 15 - 20 million degrees. The Sun has an insignificant amount of oxygen, and therefore combustion processes, understood in the usual sense, do not proceed in any noticeable way. Huge energy is generated on the Sun due to the synthesis of the light elements hydrogen and helium.

The radiant energy of the sun, absorbed by the soil surface, turns into heat and is transferred to the underlying soil layers. Part of the solar energy is reflected by the soil surface. If the temperature of the soil surface is lower than the temperature of the surface layer of the atmosphere, then the soil gives off the heat accumulated due to the incoming solar radiation.

Radiant energy from the sun coming to Earth is the most significant source of energy available to mankind. The sun, like other stars, is a hot gas. Inside the Sun there is a region of high pressure, where the temperature reaches 15 - 20 million degrees.

The radiant energy of the sun, converted into heat, can be used, bypassing electrolysis, directly for the thermochemical decomposition of water. Previously, it was shown that two-stage thermochemical cycles are unlikely when using the heat of nuclear reactors. But the temperatures required for the two-stage thermochemical cycle of water decomposition can be reached using solar energy.

The radiant energy of the sun, primarily the ultraviolet part of the solar spectrum, has significant biological effects. Mod its influence in the skin produces vitamin I), which is necessary for the correct exchange in the body of phosphorus and calcium, the most important components of bone and brain tissues.

Quantity radiant energy from the sun, which arrives in 1 min on an area of ​​1 cm2, placed outside the earth's atmosphere perpendicular to the sun's rays at an average distance from the Earth to the Sun, is called the solar constant. It is assumed that at the maximum solar activity, the radiation of the Sun increases somewhat, but it does not exceed fractions of a percent. I Solar activity significantly influences terrestrial processes, manifested through solar-terrestrial relations in the response of the Earth (its outer shells, including the biosphere) to changes in this activity.

WITH radiant energy from the sun the illumination of the earth's surface is related, which is determined by the duration and intensity of the light flux. Due to the rotation of the Earth, there is a periodic alternation of dark and daylight hours, as well as a change in the duration of daylight hours. Since this factor has the correct periodicity, its significance for life is exceptionally great.

During photosynthesis radiant energy of the sun is converted into chemical and in the form of potential energy is in the plant organic mass - a product of photosynthesis.

They call it radiation radiant energy from the sun falling on the irradiated surface.

Increasing Flux Density radiant energy from the sun, as already noted, can be carried out by mirror and lens systems, however, in what follows, the main attention will be paid to mirror concentrating systems, which does not reduce the generality of the fundamental provisions of the developed approach to a formalized description of the process under consideration.

The source of natural light is radiant energy from the sun. The natural average outdoor illumination during the year varies sharply by months and hours of the day, reaching a maximum in June and a minimum in December in the middle zone of our country.

An inexhaustible source of thermal energy is radiant energy from the sun, which also causes the formation of wind, water flows and other types of energy. However, the industrial use of the energy of solar radiation in the form of heat is still limited.

SOLAR CONSTANT - total amount radiant energy from the sun falling outside the Earth's atmosphere onto an area of ​​unit area located perpendicular to the sun's rays on cf.

Source of natural light - stream radiant energy from the sun reaching the earth's surface in the form of direct and diffused light. It is the most hygienic - it has a favorable spectral composition. Depending on the geographical latitude, season, weather conditions, the level of natural light can change dramatically and within a fairly wide range.

SOLAR - a device that captures radiant energy from the sun and transforming it into others, convenient for practical.

The main source of heat for the soil is radiant energy from the sun. Of some importance may be the heat released during exothermic reactions caused in the soil layer by microorganisms.

The first thermal factor is due to uneven distribution radiant energy from the sun over the surface of the earth. In the polar regions, up to 95% of the sun's rays are reflected from snow and ice. This is explained by the fact that at high latitudes the rays enter the atmosphere at an oblique angle, which means that their light energy is distributed over a large area of ​​the earth's surface. The gliding rays of the sun, which do not enter the atmosphere at a right angle, pass through a thicker layer of air. Therefore, it is always cold here, constantly high pressure is formed. Conversely, in the equatorial zone, the sun's rays fall on the Earth's surface at a right angle, strongly heating it. As a result, a low pressure zone is formed here. Therefore, there is a movement of air from the polar regions to the equator, i.e. from high to low pressure areas. Equatorial air masses, intensively and quickly heating up, rise and in the high layers of the atmosphere diverge to the north and south and cool.

HELIOELECTRIC POWER PLANT - a solar power plant that converts radiant energy from the sun in electric

Let's say we can collect radiant energy from the sun, which falls on the surface of the earth in a year; if we can transform this radiant energy into such an energy that would be useful for us, then it turns out that with such a transformation we will cover all the sources of energy that are currently available on earth.

The use of energy sources such as radiant energy of the sun in semiconductor installations and photocells, the use of the internal heat of the Earth, the energy of sea tides, etc. All this, taken together, along with the development of controlled thermonuclear reactions, will allow many times to increase the amount of generated electrical energy compared to the current level.

Such a mode (QI constancy) is actually implemented in thermogenerators using radiant energy from the sun or the decay heat of radioactive isotopes.

High emissivity coatings are widely used in installations using radiant energy from the sun. Practical solar technology is currently developing at a rapid pace.

Among climatic factors, an important place in the life of plants is occupied by light and heat, associated with radiant energy from the sun; water; composition and movement of air. Atmospheric pressure and some other phenomena included in the concept of climate do not have significant significance in the life and distribution of plants.

In the future, it is possible to build more economical solar stations using semiconductors (solar batteries) for direct conversion radiant energy from the sun into electrical energy. ]

Light is the main environmental factor that determines the basis of the vital activity of a plant organism - photosynthesis, the process of transformation by green plants. radiant energy from the sun into the energy of the chemical bonds of organic substances. This process occurs with the absorption of carbon dioxide and the release of free oxygen. With the participation of light-absorbing pigments - chlorophyll and some others - carbon dioxide and water, reacting, form the main food of plants - carbohydrates.]

In our studies, we proceed from the considerations that by changing the optical properties of the soil surface, it is possible to increase the absorption radiant energy from the sun during the day and reduce heat radiation at night. Our experiments last year with cellulose acetate film showed that this film can serve as an excellent protection against radiation, but so far it is too expensive for field cultivation.

On a large scale, work is underway in the direction of creating solar power plants based either on the use of solar concentrators in conjunction with a thermodynamic (steam turbine) cycle, or on the use of direct conversion technology. radiant energy from the sun into electricity.

Thus, the energy delivered by the Sun can only be used to produce work in a wind turbine, provided that there is a temperature difference between the individual parts of the atmosphere created by absorption radiant energy from the sun and its partial emission into the world space. So, not all the heat received from the heater goes to work, but only part of it, while the rest of the heat is given to the refrigerator.

The atmosphere determines the light and regulates the thermal regimes of the Earth, contributes to the redistribution of heat on the globe. Radiant energy from the sun- practically the only source of heat for the Earth's surface - is partially absorbed by the atmosphere. The energy reaching the Earth's surface is partially absorbed by soil and water bodies, seas and oceans, and partially reflected into the atmosphere.

Electromagnetic radiation ( radiant energy of the sun) - electromagnetic waves propagating at a speed of 300 thousand km / s. Corpuscular radiation consists mainly of protons moving at a speed of 300 - 1500 km / s and almost completely captured by the Earth's magnetosphere.

Solar radiation is an essential factor in climate formation. Due to the dustiness of the cities radiant energy of the sun absorbed by dust particles. According to American and British researchers, large cities receive 15% less solar radiation, 10% more rain, 10% more cloudy days, and over the past 80 years, the frequency of fogs has doubled.

Ionizing radiation acts on the body from both external and internal sources of radiation (in the case of penetration of radioactive substances into the body with food, water, air or through the skin). Combined exposure to external and internal radiation is possible.

The damaging effect of various types of radioactive rays depends on their penetrating activity and, consequently, on the density of ionization in the tissues. The shorter the beam path, the greater the ionization density and the stronger the damaging effect (Table 7).

However, physically identical amounts of absorbed energy often produce different biological effects, depending on the type of radiant energy. Therefore, to assess the degree of damaging effect of ionizing radiation on biological objects, the coefficient of relative biological effectiveness (RBE) is used.

As can be seen from Table. 8, the damaging effect of alpha rays, neutrons and protons is 10 times greater than that of X-rays, the biological effect of which is conditionally taken as 1. However, it should be remembered that these coefficients are conditional. Much depends on the choice of indicator, which is taken to compare biological effectiveness. For example, RBE can be set by the percentage of mortality, by the degree of hematogenous changes, by the sterilizing effect on the sex glands, etc.

The reaction of the organism to the action of ionizing radiation depends on the received dose of radiation, the duration of action and the general condition of the irradiated organism (Table 9).

For humans, the absolute lethal dose in a single exposure is about 600 r.

Irradiation duration plays a role in the development of radioactive damage. With a short-term exposure, measured in seconds, the degree of damaging effect is somewhat reduced. When exposed to the same dose of radiation, but lasting several tens of minutes, the damaging effect increases. Fractional (fractionated) action reduces mortality. The total dose of multiple exposures can significantly exceed a single lethal dose.

Individual and species reactivity of the organism is also of great importance in determining the severity of radioactive damage. In the experiment on animals, wide limits of individual sensitivity are noted - some dogs survive with a single irradiation of 600 r, while others die from 275 r. Young and also pregnant animals are more sensitive to ionizing radiation. Older animals are also less resistant due to the weakening of their recovery processes.

Mechanisms of the pathogenic action of ionizing radiation. In the mechanism of radiation damage to the human and animal body, three important stages can be distinguished:

• a) the primary effect of radioactive radiation;
• b) the effect of radiation on cells;
• c) the effect of radiation on the whole organism.

The mechanism of the primary action of ionizing radiation is determined by the physical, physicochemical and chemical processes that occur in any biological substrate that is under the influence of radiation.

physical processes - ionizing radiation, having high energy, knocks out electrons from atoms and molecules on its way or causes them to move. This leads within a negligibly short time (10 -16 seconds) to ionization and the formation of excited atoms and molecules. Physical and chemical processes consist in the fact that ionized and excited atoms and molecules, having a high reactivity, cause the formation of free radicals. In living structures, water undergoes ionization most quickly.

Ionization is accompanied by phenomena of recombination of particles that have arisen. It is especially pronounced under the action of such types of radiation that have a high ionization density (alpha rays, neutrons). In the process of water radiation, the following free atoms and radicals arise: atomic hydrogen (H +), hydroxyl (OH +), hydroperoxide (HO 2) and hydrogen peroxide (H 2 O 2).

The action of ionizing radiation on substances dissolved in water is mainly due to the products of water radiolysis. Thus, the high radioresistance of substances in a frozen state or enzymes in a dried powder state is known.

The ionization process also applies to macromolecules. The absorbed energy can migrate along the macromolecule, being realized in its most vulnerable places. In proteins, these places can be SH-groups, in DNA - the chromophore groups of thymine, in lipids - unsaturated bonds.

The effect of radiation on cells arises as a result of the interaction of radicals of proteins, nucleic acids and lipids with water, oxygen, hydrogen, etc., when, as a result of all these processes, organic peroxides are formed and fast oxidation reactions occur. A lot of modified molecules accumulate, as a result of which the initial radiation effect is greatly enhanced. All this is reflected primarily in the structure of biological membranes, their sorption properties change and permeability increases (including the membranes of lysosomes and mitochondria). Changes in lysosome membranes lead to the release and activation of DNase, RNase, cathepsins, phosphatase, muconblisaccharide hydrolysis enzymes, and a number of other enzymes.

The released hydrolytic enzymes can, by simple diffusion, reach any cell organelle, into which they easily penetrate due to the increase in membrane permeability. Under the action of these enzymes, the macromolecular components of the cell, including nucleic acids and proteins, are further degraded. The uncoupling of oxidative phosphorylation as a result of the release of a number of enzymes from mitochondria, in turn, leads to inhibition of ATP synthesis, and hence to a violation of protein biosynthesis.

Thus, the basis of radiation damage to the cell is a violation of the ultrastructures of cell organelles and the associated changes in metabolism. In addition, ionizing radiation causes the formation in the tissues of the body of a whole complex of toxic products that enhance the radiation effect - the so-called radiotoxins. Among them, the most active products of lipoid oxidation are peroxides, epoxides, aldehydes and ketones. Formed immediately after irradiation, lipid radiotoxins stimulate the formation of other biologically active substances - quinones, choline, histamine - and cause increased protein breakdown. When administered to non-irradiated animals, lipid radiotoxins have an effect reminiscent of radiation injury.

At sufficiently high radiation doses, changes in cells and tissues are determined mainly by the development of degenerative-destructive processes and structural changes in the chromosomal apparatus, which leads to cell death during mitosis or to the emergence of non-viable cell progeny. Inhibition of the mitotic activity of cells is one of the specific manifestations of the biological action of ionizing radiation.

Ionizing radiation acts on cells the stronger, the greater their reproducing ability, the longer the passage of the mitotic process, the younger and less differentiated the cells. Based on the morphological signs of susceptibility, organs and tissues are distributed in the following descending order: lymphoid organs (lymph nodes, spleen, thymus, lymphoid tissue of other organs), bone marrow, testicles, ovaries, mucous membrane of the gastrointestinal tract. Skin with appendages, cartilage, growing bones, and vascular endothelium are even less affected. Parenchymal organs have high radioresistance: liver, adrenal glands, kidneys, salivary glands, lungs.

The degree of radiation damage to cells of the same type depends on a number of factors:

• 1) degree of differentiation - embryonic and undifferentiated cells are affected to a greater extent than the differentiated cells formed from them;
• 2) metabolism - an increase in the intensity of cellular metabolism is accompanied by an increase in radiosensitivity;
• 3) mitotic activity - actively dividing cells, as a rule, are more sensitive than non-dividing ones. The cell nucleus is more sensitive to radiation than the cytoplasm;
• 4) stages of mitosis - the sensitivity of cells is highest in the stage of prophase and metaphase.

Radiosensitivity changes dramatically at different stages of phylogenetic development. The susceptibility of animals to radiation decreases in the following order: embryo, fetus, young animal, adult organism.

The effect of ionizing radiation on the body as a whole. The morbid effect of ionizing radiation as a whole is determined both by a direct damaging effect on the cells and tissues of the body, and by irritation of the nervous system and the resulting general reactions of the body, referred to as radiation sickness.

Radiation sickness. Distinguish with the flow acute and chronic radiation sickness. Acute radiation sickness can occur in mild, moderate and severe forms. Four periods are distinguished in its course.

The first period is the initial (primary reactions), observed immediately after irradiation, lasts from several hours to 1-2 days. A sign of radiation damage during this period is a delay in mitotic activity in hematopoietic cells. During this period, metabolic processes intensify and the functions of the main organs and systems increase.

Second period - latent, hidden (a period of apparent well-being), is characterized by changes in the patient's blood associated with the beginning oppression of hematopoiesis. The duration of this period depends on the absorbed dose. So, at doses of 20-100 I am glad, the disease can end with this period. At a dose of 150-200 rads, the latent period can last several weeks, at 300-500 rads - only a few days, and at a dose of over 500 rads, the latent period lasts only a few hours.

The third period - pronounced phenomena, or the height of the disease . In mild cases, it lasts a few days, in severe cases - 2-3 weeks. This period is characterized by hemorrhages in the internal organs, a sharp suppression of hematopoiesis (Fig. 5), an increase in the permeability of cell membranes, and suppression of immunity. It is during this period that death occurs. The causes of death can be bleeding, infection and other complications.

The fourth period is the period of exodus or recovery .

chronic radiation sickness occurs with weak long-term irradiation of the body, it can also be the outcome of acute radiation sickness. During chronic radiation sickness, three periods are distinguished: the period of early changes, the development of complications, and the period of severe, irreversible changes with a fatal outcome.

The mechanism of development of radiation sickness It is determined along with the direct damage to cells mainly by the reaction of the body from the nervous, endocrine and connective tissue systems to damaging radioactive radiation.

The reaction of the nervous system can be observed in all phases of the development of radiation sickness. At the beginning of its development, when water and biosubstrates of the body are ionized, the receptors of the nervous system react to changes in the internal environment of the body, leading to excitation of all parts of the nervous system.

Disorders of the function of the central nervous system are manifested in violations of conditioned reflex connections, weakening of the process of internal inhibition. Functional changes in the cerebral cortex at different times of irradiation are associated with an increase in impulses flowing into the higher parts of the nervous system through the reticular formation. The functions of all subcortical centers also change. Thus, damage to the vegetative centers is manifested by a violation of thermoregulation, regulation of vascular tone, and heart rhythm in an irradiated organism. Thus, during radiation sickness, the earliest and most intense functional changes are found in the nervous system, and structural disturbances in it are not as pronounced as, for example, in the bone marrow (P. D. Horizontov).

In the development of radiation sickness, endocrine disorders are also of considerable importance. The functions of all endocrine glands are violated to some extent under the influence of ionizing radiation. The most pronounced changes are observed in the gonads, pituitary and adrenal glands. These changes depend on the dose of radiation and can be manifested as an increase in secretion or its suppression. Of great importance, apparently, is the violation of the usual consistency in the secretion of various endocrine glands.

Radiation damage to the gonads under chronic exposure to penetrating radiation can occur very early - before the onset of clinical symptoms of radiation sickness. Changes that occur in the sex glands lead to sterility, a decrease in offspring, and an increase in stillbirth.

Violation of the function of the pituitary gland, accompanied by a change in the secretion of a number of triple hormones, leads to a variety of secondary consequences due to a violation of the function of the corresponding glands. Especially important is the insufficiency of the adrenal glands, which sharply reduces the reactivity of the body and resistance to all kinds of damaging effects of the external environment.

Long-term effects of exposure. Among the long-term consequences of irradiation, the most studied (except for chronic radiation sickness) are the reduction in average life expectancy, the development of cataracts, disturbances in embryonic development, and the occurrence of malignant tumors.

Irradiation increases the number of malignant tumors and accelerates their occurrence (experimentally). Most often, tumors of the hematopoietic tissue (leukemia), breast, skin, liver, and thyroid gland are formed.

Tumors can occur with both general and local irradiation.

Exposure to ionizing radiation is also used as a powerful antitumor agent. Irradiation is always carried out locally. The exposure mode is selected in such a way that most of the radiation energy is absorbed in the tumor and near it. The effect of radio emission is most effective in the case of tumors with increased mitotic activity and low radioresistance.

Sun rays

Ultraviolet rays (UFL). Ultraviolet rays (wavelength from 1880 to 3800 A) penetrate only the most superficial layers of the skin and have a biological and pathological effect on the body.

The general biological effect of ultraviolet rays on a person is expressed in three ways:

1. Reaction from the skin - ultraviolet rays of the medium wave range (2800-3150 A) cause erythema. Erythema occurs as a result of the formation of histamine at the site of irradiation, which is a strong vasodilator. It has sharply defined boundaries, occurs after a certain period of time (from tens of minutes to several hours) and, as a rule, goes over to pigmentation - tan with the formation and deposition of melanin pigment in the skin. Sunburn is caused mainly by long-wave ultraviolet rays (3150-3800 A).

• 2. Under the influence of ultraviolet rays, vitamin D 3 is formed in the skin from provitamin 7-dehydrocholesterol by photochemical means. The minimum amount of ultraviolet rays required for this is 1/8-1/10 of the erythemal dose per day.

• 3. The bactericidal effect of ultraviolet rays is most pronounced within the wavelength range from 2000 to 2800 A (short-wave ultraviolet). The bactericidal effect is also accompanied by stimulation of immunological reactivity: the production of antibodies increases, the complementary activity of blood serum increases.

Ultraviolet rays of the shortest range (less than 2000 A) have an ozonizing effect (vacuum ultraviolet).

Pathogenic effect of UV manifests itself with excessive irradiation of the body or in the presence of hypersensitivity (photosensitization).

Sunburns strictly at the site of irradiation occur due to the chemical action of UV - excessive formation of histamine and other biologically active substances in the irradiated tissues and their subsequent toxic effects, both local and general.

Eye damage UFL - photophthalmia - occurs more often in the absence of protection of the sclera of the eyes in conditions of increased radiation (for electric welders, when working in phototherapy rooms, in arctic and high-mountain regions, etc.); appears after 2-6 hours, is expressed in pain in the eyes, hyperemia, swelling of the conjunctiva and eyelids, decreased visual acuity. There is also a general reaction of the body - headache, fatigue, insomnia, tachycardia. Usually after 5-6 days these symptoms disappear.

General action UFL can also manifest itself as general reactions with the leading role of local symptoms, as well as an independent reaction to general ultraviolet irradiation - sunstroke, where the leading one is a violation of the general condition of the body, primarily the functions of the central nervous system and circulatory organs.

In the mechanism of the general pathogenic action of UFL, two ways are of the greatest importance: humoral and neurogenic .

Humoral mechanisms . At the site of irradiation, under the influence of UV radiation, toxic products are formed - histamine, acetylcholine, irradiated cholesterol, ergosterol, protein-lipoid complexes, which have a toxic effect on the capillary wall at the site of their formation, on nerve cells and sensitive nerve endings due to absorption into the general circulation.

Intense skin irradiation with UV radiation causes hemolysis of erythrocytes - the so-called photohemolysis, which is especially enhanced in the presence of photosensitizers. Photosensitizers - some dyes (eosin, fluorescein), porphyrins, lecithin, cholesterol - increase the damaging effect of UV radiation.

Some people with impaired porphyrin metabolism (porphyria) have burns and a state of severe collapse due to poisoning by toxic products of irradiated porphyrin even with insignificant solar radiation.

Neurogenic mechanisms . Perhaps reflex excitation of some autonomic centers (vasomotor, vagal, thermoregulatory centers) through skin receptors irritated by chemicals at the site of their formation.

Perhaps the centrogenic effect of these same toxic products on the vital nerve centers as a result of absorption into the bloodstream, lymph and cerebrospinal fluid - hence circulatory disorders such as collapse, which can sometimes result in death (sunstroke).

Blastomogenic action a person can be exposed to UV radiation with a wavelength of 2900 to 3841 A with prolonged exposure. In animals, tumors can be caused by broader wavelength radiation. The absorption of UV light by the upper layers of the skin determines to a certain extent the localization of tumors developing under their action in humans, for example, squamous and basal cell skin cancer. In animals with thinner skin, sarcomas also occur in a significant percentage of cases. In humans, tumors develop on open, unprotected areas of the body, and in experimental animals - on parts of the body that are devoid of hair.

The frequency of skin tumors increases with the amount of absorbed energy. Thus, it is estimated that in the United States between 42° and 30° north latitude, the incidence of skin cancer doubles every 4° closer to the equator. UV-induced skin cancer occurs after a long latency period. The appearance of cancer is preceded by long-term destructive and inflammatory changes in the skin, called solar keratosis.

The mechanism of the blastomogenic action of ultraviolet rays is far from clear. There are two possible ways to do this:

• a) UFL, like radioactive radiation, have a mutagenic property (see "The role of heredity, constitution and age in pathology");
• b) Under the influence of UV radiation, some carcinogenic substances can form in the skin.

purple rays (3800-4500 A) can have a chemical effect on the body, like ultraviolet, but much less pronounced.

Visible rays of the solar spectrum with a wavelength of 5000-7000 A, they do not have a significant damaging effect, since they are mainly absorbed by the skin and do not penetrate deep into the body.

Through the eye - an organ specialized for the perception of the rays of the solar spectrum ranging from 4000 to 7600 A, light stimuli can affect the entire body. Irritation of the visual receptors by light rays is transmitted, in addition to the visual centers, to the vegetative centers of the hypothalamus and leads them to a state of weak excitation, which in turn contributes to an increase in oxidative processes, an increase in blood pressure and even the appearance of some euphoria (on a bright, sunny day, people are more smiling and sociable than on gloomy, cloudy days).

The natural rhythm of lighting determines the daily rhythm of the activity of animals and humans, the rhythm of a number of physiological processes that are closely connected by reflex and conditioned reflex mechanisms with the rhythm of the change of day and night, the rhythm of seasonal fluctuations in illumination. Violations of the normal rhythm of physiological functions associated with the rhythm of the natural change of day and night, in some cases lead to the development of painful conditions (neuroses), the treatment of which requires the restoration of the normal rhythm of light stimuli. Such violations may be the result of an incorrect construction of the working and domestic regime, round-the-clock day and round-the-clock night beyond the Arctic Circle, etc.

infrared rays. Infrared rays have a thermal effect on the body. Beams with a wavelength from 7600 to 14,000 A have a high penetrating power and warm the tissues as if from the inside. Rays with a wavelength of more than 14,000 A are absorbed by superficial tissues and can produce a burning effect.

An increase in temperature as a result of the absorption of infrared energy by tissues is accompanied by an acceleration of various physicochemical and physiological reactions of the body, both local (increased vascular permeability, their expansion - passive hyperemia, exudation, etc.), and general (increased metabolism, body temperature, in severe cases - violations of the mechanisms of thermoregulation and heat stroke) character.

Laser radiation

A laser, or optical quantum generator, is a physical device that allows you to emit monochromatic beams of light of extraordinary intensity with a small angle of their divergence. The unfocused laser beam has a width of 1-2 cm, and with induced focus from 1 to 0.01 mm or less. Therefore, it is possible to concentrate enormous light energy on an area of ​​several microns and at the same time reach very high temperatures. The energy of each laser flash can be measured in hundreds and thousands of joules. The laser beam is capable of melting diamond, steel and other materials.

There are pulsed and continuous lasers; both are used in medicine. The action of the laser beam on living tissues occurs for very short intervals (hundred-thousandths of a second), and, apparently, therefore, there is no sensation of pain. The penetration depth can be adjusted using an optical system and usually reaches 20-25 mm.

The degree of absorption of laser beams depends on the color of the irradiated object. Most of all, they are absorbed by pigmented tissues, erythrocytes, melanomas, etc. Laser beams destroy, melt living tissues; Tumor tissues are especially sensitive to them.

The mechanism of the damaging effect of laser beams on biological objects consists of a number of factors:

• 1) the thermal effect of the beam itself and the secondary increase in the temperature of the underlying tissues as a result of the absorption of thermal energy;
• 2) mechanical action as a result of the occurrence of elastic vibrations such as ultrasonic or even shock waves. There is a kind of "explosive effect" due to the instantaneous transition of solid and liquid substances of the body into a gaseous state and a sharp increase in interstitial pressure (up to several tens and hundreds of atmospheres):
• 3) biological effect - toxic substances are formed in tissues and cells after exposure to a laser beam. Perhaps, the progressive necrosis of cells after irradiation depends on them;
• 4) inactivation or change in the specific action of tissue enzymes.

The possibility of ionization of the constituent elements of tissues and the occurrence of magnetic fields is allowed.

The degree and result of exposure to a laser beam depend on the characteristics of the radiation itself (laser type, power, duration of action, radiation density, pulse frequency), physicochemical and biological characteristics of the irradiated tissues (degree of pigmentation, blood circulation, tissue heterogeneity, their elasticity, thermal conductivity, etc.). .).

Due to their biological and physicochemical characteristics, tumor cells are more sensitive to the laser beam than healthy ones. It is in oncology that this type of radiation still finds the greatest application. In addition, the laser is used for bloodless operations in surgery, ophthalmology, etc.

The impact on microorganisms of various forms of radiant energy manifests itself in different ways. The action is based on certain chemical or physical changes that occur in the cells of microorganisms and in the environment.

The impact of radiant energy obeys the general laws of photochemistry - changes can only be caused by absorbed rays. Therefore, for the effectiveness of irradiation, the penetrating power of the rays is of great importance.

Light. In nature, microorganisms are constantly exposed to solar radiation. Light is necessary for the life of only photosynthetic microbes that use light energy in the process of assimilation of carbon dioxide. Microorganisms that are not capable of photosynthesis grow well in the dark. Direct sunlight is harmful to microorganisms; even diffused light suppresses their growth to some extent. However, the development of many molds in the dark proceeds abnormally: in the constant absence of light, only the mycelium develops well, and sporulation is inhibited.

Pathogenic bacteria (with rare exceptions) are less resistant to light than saprophytic ones.

It is known that radiant energy is transferred in "portions" - quanta. The action of a quantum depends on the content of energy in it. The amount of energy varies depending on the wavelength: the longer it is, the smaller the energy of the quantum.

Infra-red rays (IR rays) have a relatively long wavelength. The energy of these radiations is insufficient to cause photochemical changes in the substances that absorb them. Basically, it turns into heat, which has a detrimental effect on microorganisms when using infrared radiation for thermal processing of products.

Ultra-violet rays. These rays are the most active part of the solar spectrum, which determines its bactericidal action. They have high energy,

accurate in order to cause photochemical changes in the molecules of the substrate and the cell that absorb them.

Rays with a wavelength of 250–260 nm have the greatest bactericidal effect.

The effectiveness of exposure to UV rays on microorganisms depends on the dose of radiation, that is, on the amount of absorbed energy. In addition, the nature of the irradiated substrate matters: its pH, the degree of contamination with microbes, and also the temperature.

Very small doses of radiation even stimulate individual functions of microorganisms. Higher

but doses that do not lead to death cause inhibition of individual metabolic processes, change the properties of microorganisms, up to hereditary changes. This is used in practice to obtain variants of microorganisms with a high ability to produce antibiotics, enzymes and other biologically active substances. A further increase in the dose" leads to death. At a dose below the lethal dose, restoration (reactivation) of normal life is possible.

Different microorganisms are not equally sensitive to the same radiation dose (Fig. 24, 25).

Among non-spore bacteria, pigment bacteria are especially sensitive to irradiation, releasing pigment in the environment.

living environment. Pigment bacteria containing carotenoid pigments are extremely resistant, as carotenoid pigments have protective properties against UV rays.

Bacterial spores are much more resistant to UV rays than vegetative cells. It takes 4–5 times more energy to kill spores (see Table 9). Mushroom spores are more hardy than mycelium.

The death of microorganisms can be a consequence of both the direct action of UV rays on cells and the unfavorable change in the irradiated substrate for them.

UV rays inactivate enzymes, they are adsorbed by the most important substances

cells (proteins, nucleic acids) and cause changes - damage to their molecules. Substances (hydrogen peroxide, ozone, etc.) can be formed in the irradiated environment, which have a detrimental effect on microorganisms.

Currently, UV rays are quite widely used in practice. An artificial source of ultraviolet radiation is often argon-mercury lamps of low pressure, called bactericidal (BUV-15,

Ultraviolet rays disinfect the air of refrigeration chambers, medical and industrial premises. Treatment with UV rays for 6 hours destroys up to 80% of bacteria and molds in the air. Such rays can be used to prevent infection from the outside during bottling, packaging and packaging of food products, medical preparations, as well as to disinfect containers, packaging materials, equipment, utensils (in public catering establishments).

Recently, the bactericidal properties of UV rays have been successfully used to disinfect drinking water.

Sterilization of food products with UV rays is hampered by their low penetrating power, and therefore the effect of these rays is manifested only on the surface or in a very thin layer. Nevertheless, it is known that irradiation of chilled meat and meat products prolongs their shelf life. at 2–3 times.