Viruses cause most cases of pneumonia in preschool-aged children (i.e., four months to five years of age).1, 9, 16, 24 Although most physicians start antibiotic therapy, guidelines allow for withholding treatment if a viral etiology is suspected and close follow-up can be ensured.1, 9, 13, 15, 16, 24 These children usually have associated symptoms of viral infection, such as pharyngitis, rhinorrhea, and diarrhea .1
Backgrounder on Plutonium. Printable Version. Plutonium is a radioactive metallic element with the atomic number 94. It was discovered in 1940 by scientists studying how to split atoms to make atomic bombs. Plutonium is created in a reactor when uranium atoms absorb neutrons.Nearly all plutonium is man-made.rintable Version. Plutonium is a radioactive metallic element with the atomic number 94. It was discovered in 1940 by scientists studying how to split atoms to make atomic bombs. Plutonium is created in a reactor when uranium atoms absorb neutrons. Nearly all plutonium is man-made.
In 1869 Russian chemist Dimitri Mendeleev started the development of the periodic table, arranging chemical elements by atomic mass. He predicted the discovery of other elements, and left spaces open in his periodic table for them.In 1886 French physicist Antoine Bequerel first discovered radioactivity.Thomson student from New Zealand Ernest Rutherford named three types of radiation; alpha, beta and gamma rays.n 1894 Sir William Ramsay and Lord Rayleigh discovered the noble gases, which were added to the periodic table as group 0. In 1897 English physicist J. J. Thomson first discovered electrons; small negatively charged particles in an atom. John Townsend and Robert Millikan determined their exact charge and mass.