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.
Viruses will also spread to nearby cells and begin the process again. The human body does have some natural defenses against a virus. A cell can initiate RNA interference when it detects viral infection, which works by decreasing the influence of the virus's genetic material in relation to the cell's usual material.nd some viruses, such as HIV, work essentially by tricking the immune system. Viruses cause many diseases, including colds, measles, chicken pox, HPV, herpes, rabies, SARS and the flu. Though they're small, they pack a big punch -- and they can only sometimes be sent into exile. Launch Video Body Invaders: Virus.