Monday, November 22, 2010

Surface Area Of Elliptical Dish End

I pericoli del nucleare: ma cos'è la radioattività? è veramente pericolosa?

addition to all the dilemmas that arise on the subject of nuceare, we believe that the most relevant and more sensitive to the population and the health.
Nuclear power plants emit small doses of nuclear radiation.
Some scientists say that they have no implication on human health while others report a large increase in leukemia and cancer for the populations living around the power stations.

radioactivity or radioactive decay, is a set of nuclear-physical processes by which some unstable atomic nuclei or radioactive decay (transmutation) into a lower-energy atomic species in accordance with the law of conservation of mass / energy, thus achieving a state of greater stability.

Historically (in the studies of Ernest Rutherford ) nuclear decays have been grouped into three main classes: alpha decay
  • beta decay
  • decay range

Effects of radioactivity
The effect of nuclear radiation on non-living material is mainly due to two causes: the ionization and subsequent breakdown of chemical bonds and the transmutation of nuclei in some other elements.

Biological effects
The biological effect is due largely to the properties instead of ionizing destroying the bonds between molecules, the radiation damages cells by generating free radicals. But mostly affect large macromolecules DNA and RNA, resulting in somatic and genetic damage, and this effect is mainly produced by gamma radiation, the most energetic and penetrating alpha and beta particles.

The time at which the cells are more vulnerable than ever to radiation is that of reproduction (mitosis or meiosis), in which DNA is being copied, the core structures are dissolved and the enzymes that ensure the integrity of the genetic material can not operate. The most obvious macroscopic effect of radiation on cells, then, is the slow speed breeding: populations of cells and reproduce very rapidly are more vulnerable than those who do it slowly. By virtue of this fact, the organs are more sensitive to radiation bone marrow hematopoietic and lymphatic system.

level instead of the whole organism, both in humans and higher animals we see a premature aging of the body related to the total dose of radiation absorbed, both with large doses snapshots that with prolonged exposure to low levels of radioactivity.

Bone marrow and blood.
is the tissue of the body most affected. The first consequence of irradiation is the decrease of white blood cells (leukopenia), followed by a decrease in platelets, causing bleeding and, if the damage is very serious, from the red blood cells (anemia). If the damage is not completely exterminate the hematopoietic stem cells this tissue recovers more quickly after irradiation.

lymphatic system lymphatic system in the main consequence of the radiation is infection of the lymph nodes and spleen following the death of lymphocytes present.

Digestive System
The intestine tenue è la porzione del tratto gastrointestinale radiosensibile, mentre l'esofago e lo stomaco lo sono meno. Con un danno lieve, le cellule della mucosa intestinale iniziano a riprodursi in modo discontinuo e a secernere più muco, che insieme alle cellule morte può dare origine ad occlusioni. Con l'aumentare della dose compaiono ulcerazioni che, per il ridotto numero di globuli bianchi, si infettano facilmente.

Organi genitali

Il danno può essere sia somatico (sterilità, permanente o meno) che genetico. Le femmine sono più sensibili dei maschi. Il danno genetico consists of mutations that can be transmitted to subsequent generations.

Nervous System The central nervous system is among the less radiosensitive tissues, while the spinal cord and peripheral nerves are more so. With high doses can be absorbed ischemia, because of damage sustained by the brain capillaries.

Thyroid and endocrine
The thyroid, pituitary gland, the adrenal and other glands are not particularly radiosensitive. For metabolic reasons, however, concentrates in the thyroid itself almost all the iodine in the body, since the isotope radioactive 131I very common, this body can absorb massive amounts of radioactivity in air if you breathe or ingest contaminated food.

The retina is very radiosensitive, but the lens, composed of dead cells and therefore can not repair itself quickly loses its transparency increasing dose absorbed by developing a cataract.

Lungs The lungs come into contact with the outside air is directly affected by radioactive particles inhaled through breathing which is deposited in his pockets: for this is absolutely necessary to wear gas masks during the operation in areas contaminated by dust, fumes or radioactive gases. The main source of pulmonary contamination is radon, a radioactive gas that being, it can easily be inhaled and deposited (it or its decay products) in the lungs.

liver, kidneys, heart and circulatory system
They are all very very radiosensitive organs. The liver and gallbladder can receive damages in case of contamination with specific radioactive isotopes such as gold, but in general there is a harm only with very high doses of radiation.

Skin and hair
The skin has a particular vulnerability, because, if not protected, received all three types of radiation (alpha, beta and gamma). The damage it receives is much higher, the less penetrating radiation: is little affected by gamma rays and more rays alpha and beta. For low levels of radiation you develop a rash, can occur if the radiation increases epithelial neoplasia. The ability to repair the damage is very high.
The hair growth stops completely, and those present fall into more or less according to the dose absorbed. After a few weeks they begin to grow, sometimes con caratteristiche diverse da quelle che avevano prima.

Apparato muscoloscheletrico
I muscoli e lo scheletro in genere sono in assoluto i tessuti meno danneggiati dalle radiazioni; tuttavia alcuni isotopi dello stronzio o del plutonio si concentrano proprio nel midollo osseo, nel qual caso il danno può essere molto grave e portare a leucemia o altre neoplasie.

Da notare che non tutte le specie animali e vegetali hanno la stessa suscettibilità alle radiazioni: per esempio gli scarafaggi possono sopportare senza gravi danni tassi di radioattività molto al di sopra di quelli letali per l'uomo, and a bacterium, Deinococcus radiodurans survives radiation doses 1000 times the lethal dose for humans

The effects of ionizing radiation are divided into "deterministic" and "stochastic effects (ICRP 60 International Commission on Radiological Protection), depending on whether or not they are directly related to the absorbed dose. Because of susceptibility to breast cancer, women have 40% more likely to acknowledge stochastic effects than men.


  • are directly attributable to radiation (there is a direct cause-effect);
  • derive from the inactivation of the vital structures of the cell;
  • is seen immediately after irradiation;
  • only occur if the absorption exceeds a definite dose-called "threshold dose"
  • Their severity increases with the dose absorbed (hence also known as "graduated effects").
deterministic effects are skin rash, dermatitis and specific (radiation dermatitis in fact), cataracts, anemia and leucopenia. In severe cases have mucosal bleeding and intestinal tract, hair loss and hair. If the absorbed dose was not lethal, the deterministic effects subside within a few weeks, with survival and recovery more or less complete.

Stochastic effects
  • not depend on the dose absorbed;
  • are derived from damage to the cell nucleus and in particular to DNA
  • not appear immediately, or there may be less in future unknown;
After irradiation, the DNA can be damaged in a reversible or irreversible, if the structure of DNA was not repaired (or repaired incorrectly), the cell would give rise to a progeny of cells GM, after a certain period of latency may lead to diseases such as cancer or leukemia. Simply increases the likelihood that the patient, sooner or later be affected by certain types of cancer.

The negative effects of radioactivity have been demonstrated, the problem is that there is no agreement on the levels of radiation that can be considered dangerous to humans.


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