(thÃ»r'mÄ«'Én) An electrically charged particle or ion that is emitted by a heated conducting material. The electrons emitted from the cathodes of electron tubes (such as cathode ray tubes) are thermions.
A low white blood cell count (leukopenia) is a decrease in disease-fighting cells (leukocytes) in your blood. Leukopenia is almost always related to a decrease in a certain type of white blood cell (neutrophil). The definition of low white blood cell count varies from one medical practice to another. In general, for adults a count lower than 4,000 white blood cells per microliter of blood is considered a low white blood cell count. For children, that threshold varies with age.
A normal white blood cell count is between about 4,500 and 10,000 cells per microliter. Many conditions can cause a low white blood cell count: â¢ Infection (which usually increases the white blood cell count, but may decrease it). â¢ Drugs, especially chemotherapy. â¢ Human immunodeficiency virus (HIV).