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The layers of the pelagic zone. All but the epipelagic zone make up the aphotic zone. Zones of the water column as defined by the amount of light penetration. The mesopelagic is sometimes referred to as the dysphotic zone. In the ocean, the aphotic zone is sometimes referred to as the dark ocean.
Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. [5] They are generally produced in the process of alpha decay but may also be produced in other ways. Alpha particles are named after the first letter in the Greek alphabet, α.
Small silt particles may also absorb blue light, further shifting the colour of water away from blue when there are high concentrations of suspended particles. [12] The ocean can be divided into depth layers depending on the amount of light penetration, as discussed in pelagic zone. The upper 200 metres is referred to as the photic or euphotic ...
This means that alpha particles from ordinary alpha decay do not penetrate the outer layers of dead skin cells and cause no damage to the live tissues below. Some very high energy alpha particles compose about 10% of cosmic rays, and these are capable of penetrating the body and even thin metal plates. However, they are of danger only to ...
Alpha particles are a strongly ionizing form of radiation, but when emitted by radioactive decay they have low penetration power and can be absorbed by a few centimeters of air, or by the top layer of human skin. More powerful alpha particles from ternary fission are three times as energetic, and penetrate proportionately farther in air. The ...
This increases the chance of double-strand breaks to the DNA in cases of internal contamination, when ingested, inhaled, injected or introduced through the skin. Otherwise, touching an alpha source is typically not harmful, as alpha particles are effectively shielded by a few centimeters of air, a piece of paper, or the thin layer of dead skin ...
But, according to this article, "Because of their charge and large mass, alpha particles are easily absorbed by materials and can travel only a few centimeters in air. They can be absorbed by tissue paper or the outer layers of human skin (about 40 micrometres, equivalent to a few cells deep)".
The maximum temperature can be found in the subskin layer, where the external heating per depth is lower than in the skin layer, but where the surface cooling has a smaller effect. With further increasing depth, the temperature declines, as the proportional heating is smaller and the layer is mixed via turbulent processes.