Radiation radioactive emissions

A radioisotope is an atom the nucleus of which is not stable and which decays to a more stable state by the emission of various radiations. Radioactive isotopes, also called nucHdes or radionucHdes, are important to many areas of scientific research, as well as ia medical and iadustrial appHcations (see... 

Radiation Dosimetry. Radioactive materials cause damage to tissue by the deposition of energy via their radioactive emissions. Thus, when they are internally deposited, all emissions are important. When external, only those emissions that are capable of penetrating the outer layer of skin pose an exposure threat. The biological effects of radiation exposure and dose are generally credited to the formation of free radicals in tissue as a result of the ionization produced (17). 

The origin of the rays was initially a mystery, because the existence of the atomic nucleus was unknown at the time. However, in 1898, Ernest Rutherford took the first step to discover their origin when he identified three different types of radioactivity by observing the effect of electric fields on radioactive emissions (Fig. 17.4). Rutherford called the three types a (alpha), (3 (beta), and y (gamma) radiation. 

Shortly after Rutherford named those two emissions, a third one was discovered. It was named gamma, the third letter in the Greek alphabet. All of these names can be bewildering, but radioactive emissions actually come in only two fundamental forms electromagnetic radiation and particles. 

Alpha and beta radiation, on the other hand, are particles that possess mass and charge. If we set the weight of a hydrogen atom as 1 and the charge on its ion as +1, then the table below gives the corresponding properties of the radioactive emissions known in the early twentieth century. 

The changing of radioactive elements into other elements through radioactive emissions is called either radioactive decay or radioactive disintegration. By using radioactive rays, it is possible to detect whether a substance is radioactive or not. There are several methods to detect the types of radiations and their intensities. The most commonly used device to check the intensity of radioactivity is the Geiger-Mtiller counter. 

Some nuclei are unstable and emit particles and electromagnetic radiation. These emissions from the nucleus are known as radioactivity the unstable isotopes are known as radioisotopes and the nuclear reactions that spontaneously alter them are known as radioactive decay. Particles commonly involved in nuclear reactions are listed in the following table ... 

The fifth type of radioactive emission, gamma radiation, does not result in a change in the properties of the atoms. As a result, they are usually omitted from nuclear equations. Gamma emissions often accompany other alpha or beta reactions—any decay that has an excess of energy that is released. For example, when a positron collides with an electron, two gamma rays are emitted, a phenomenon usually referred to as annihilation radiation. 

In 1954, the book by Professor B.N. Tarusov "Principles of Biological Effects of Radioactive Emissions" was published [1] the book made a great impression on me. The author, an outstanding Soviet biophysicist. Head of the Biophysics Department at the Faculty of Biology of the Moscow State University, put forward a hypothesis that the development of radiation-induced disease is associated with the induction of ramified chain reaction of oxidation of fats of cellular shells (membranes), the oxidation products are very toxic for the cell. 

Various methods can be used to measure the intensity of radioactive emissions. These exploit the ability of radiation from radioactive isotopes to cause ionisation (Geiger-Miiller counting), to excite fluorophores (scintillation counting), or to cause exposure of light-sensitive photographic emulsion (autoradiography) (Slater 1990 Rickwood et al. 1993). 

Radioactive contamination Contamination with radioactive matter Radioactive decay Change of unstable atomic nuclei into other stable or unstable nuclei, associated with emission of nuclear radiation Radioactive equilibria Definite ratios between the activities of mother and daughter nuclides, given by their decay constants... 

There are many applications of radiochemistry in industry and engineering. When great precision is required in the manufacture of strips or sheets of metal of definite thicknesses, the penetrating powers of various kinds of radioactive emissions are utilized. The thickness of the metal is correlated with the intensity of radiation passing through it. The flow... 

Describe the types of tissues that are most sensitive to damage from radioactive emission, and explain why radiation treatments do more damage to cancer cells than to regular cells and why children are more affected by radiation than adults... 

Although iodine has several radioactive isotopes, greatest use has been made of I. It has a half-life of 8 days therefore, more than 99% of its radiation is expended within 56 days. Its radioactive emissions include both y rays P and particles. The short-lived radionuclide of iodine, I, is primarily a y-emitter with a half-life of only 13 hours. This permits a relatively brief exposure to radiation during thyroid scans. 

A stable nucleus remains intact indefinitely, but the great majority of nuclei are unstable. An unstable nucleus exhibits radioactivity it spontaneously disintegrates, or decays, by emitting radiation. In the next section, you ll see that each type of unstable nucleus has its own characteristic rate of radioactive decay, which can range from a fraction of a second to billions of years. This section introduces important terms and notation for nuclei, describes the common types of radioactive emissions and decay, and discusses how to predict whether and how a given nucleus will decay. 

When a nuclide decays, it forms a nuclide of lower energy, and the excess energy is carried off by the emitted radiation. The three most common types of radioactive emission are ... 

Figure 23.7 Penetrating power of radioactive emissions. Penetrating power is often measured in terms of the depth of water that stops 50% of the incoming radiation. (Water is the main component of living tissue.) Alpha particles, with the highest mass and charge, have the lowest penetrating power, and 7 rays have the highest. (Average values of actual penetrating distances are shown.)...

Except for the emission of gamma radiation, radioactive decay involves the conversion of an element into another element. Such a reaction, in which an atoms atomic number is altered, is called transmutation. Whether an atom spontaneously decays and what type of radiation it emits depends on its neutron-to-proton ratio. 

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