A tiny mass of material composed of two protons and two neutrons.
Alpha particles do not travel very far from their radioactive source. They cannot pass through a piece of paper, clothes or even the layer of dead cells which normally protects the skin. Because alpha particles cannot penetrate human skin they are not considered an “external exposure hazard.” This means that if the alpha particles stay outside the human body they cannot harm it. However, alpha particle sources located within the body may pose an “internal” health hazard if they are present in great enough quantities.
For instance, the risk from indoor radon gas is due to inhaled alpha particle sources which irradiate lung tissue.
Alpha rays are streams of alpha particles.
Near the umbilicus (the “belly button”). The parumbilical veins are small veins in the front wall of the abdomen near the umbilicus.
- Parvovirus infection
There is no vaccine or medicine to prevent parvovirus B19 infection. Frequent hand washing is recommended as a practical and probably effective method to reduce the spread of parvovirus. Excluding persons with fifth disease from work, child care centers, schools, or other settings is not likely to prevent the spread of parvovirus B19, since ill […]
1. Physician-assisted suicide. 2. Personal alert system (an alarm system for an elderly or infirm person). 3. Periodic acid-Schiff (a stain used to detect carbohydrates in tissue).
- Passage, nasal
A channel for airflow through the nose. The walls of the nasal passages are coated with respiratory mucous membranes, which contain innumerable tiny hair-like cells that move waves of mucus toward the throat. Dust, bacteria, and other particles inhaled from the air are trapped by the mucus in the nose, carried back, swallowed, and dropped […]
- Passive exercise
Movement of the body, usually of the limbs, without effort by the patient. The patient is passive.