The world's second nuclear explosion was achieved with uranium-235. This isotope is unstable and fissions when struck by a neutron. It is, however, found in natural uranium at a concentration of only 0.7 percent. To be useful in nuclear weapons, the concentration must be increased.
Introduction. Influenza, or flu, is a caused by a virus infecting the respiratory system, meaning your nose, throat, bronchial tubes, and lungs. Flu symptoms are usually more severe than those of the common cold and are more likely to affect other parts of your body.
MYTH: The flu is just a bad cold. Influenza may cause bad cold symptoms, like sore throat, runny nose, sneezing, hoarseness, and cough. But in the United States alone, 36,000 people die and more than 200,000 are hospitalized each year because of the flu. MYTH: You can't spread the flu if you're feeling well. Actually, 20% to 30% of people carrying the influenza virus have no symptoms. MYTH: You don't need to get a flu shot every year. The influenza virus changes (mutates) each year.