(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.
Blood cell counts typically measure: 1  white blood cells, which function as the immune system cells that defend your body against foreign substances and âinvaders.â If you have a low white blood cell count, you have a higher risk of getting an infection. white blood cells, which function as the immune system cells that defend your body against foreign substances and âinvaders.â If you have a low white blood cell count, you have a higher risk of getting an infection.