Glossary

Author: Glossary

  • Urban legend

    Urban legends about health care are widely disseminated by patients and practitioners. One favorite is the internet prank that states that dihydrogen monoxide is a deadly toxin widely consumed by human beings. Its chemical formula is H20.  

  • Uranyl

    The bivalent uranium radical U02+. It forms salts with many acids. An example is uranyl nitrate, U02 (N03)2.  

  • Enriched uranium

    Uranium with a higher concentration of the radioisotope than is found in natural uranium ore. The isotope is used to manufacture nuclear fuel rods (for electrical power generation) and nuclear weapons.  

  • Depleted uranium

    The metal remaining after the most active radioisotope has been extracted from uranium. A heavy metal, depleted uranium is used in munitions, e.g., in armor-piercing weapons. Its radioactivity is about 40% that of natural uranium.  

  • Uranium

    A radioactive element, the parent of radium and other radio elements; atomic weight, 238.029; atomic number, 92. A radioactive metallic element, not naturally found in its pure state, but commonly extracted from ores like pitchblende, carnotite, and uraninite. Radioactive decay of uranium leads to radiation emission and produces a sequence of radioactive byproducts, such as…

  • Upstream

    In descriptions of genetic material, codons or base pairs that are on the 5′ side of a specific gene.  

  • Upregulate

    To increase the responsiveness of a cell or organ to a stimulus.  

  • Upper motor neuron lesion

    Neurological damage to the corticospinal or pyramidal tract in the brain or spinal cord. This lesion results in hemiplegia, paraplegia, or quadriplegia, depending on its location and extent. Clinical signs include loss of voluntary movement, spasticity, sensory loss, and pathological reflexes.  

  • Upper airway resistance syndrome

    A type of sleep-disordered breathing, caused by increased airflow obstruction, in which a person awakens multiple times and then suffers daytime drowsiness or fatigue.  

  • Upper airway obstruction

    Any potentially life-threatening abnormality in which the flow of air into and out of the lungs is partially or completely blocked by such conditions as laryngeal swelling, foreign bodies, or angioedema.