(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.
White blood cells, or WBC, are produced in the bone marrow and are the disease-fighting cells of the body. According to MedLinePlus, a low WBC count, also called leukopenia or neutropenia, is when the concentration of white blood cells in the body are less than 4,500 cells per microliter of blood.hite blood cells, or WBC, are produced in the bone marrow and are the disease-fighting cells of the body. According to MedLinePlus, a low WBC count, also called leukopenia or neutropenia, is when the concentration of white blood cells in the body are less than 4,500 cells per microliter of blood.