Pre-exposure prophylaxis (PrEP) is a course of HIV drugs taken daily by HIV negative people most at risk of HIV to reduce their risk of HIV infection. Truvada is currently the only drug approved for use as PrEP. Truvada is a single pill that is a combination of two anti-HIV drugs, tenofovir and emtricitabine.
Astronomical spectroscopy is one of the most powerful tools used by astronomers to gain a fundamental understanding of our universe. Astronomical spectroscopy is a technique in which the absorption and emission of electromagnetic radiation from stars and other celestial objects are studied.he absorption and or emission spectra of a molecule generally consist of a number of lines. These lines correspond to the discrete differences in the internal energy modes of a molecule.
1 A given atom will absorb and emit the SAME frequencies of electromagnetic (E-M) radiation. 2  A gas of hydrogen atoms will produce an absorption line spectrum if it is between you (your telescope+spectrograph) and a continuum light source, and an emission line spectrum if viewed from a different angle. This is called an emission spectrum (just peaks, not continuous). 2  The E-M radiation frequencies absorbed and emitted match the allowed energy levels in the atom. 3  The allowed energy levels in an atom depend mostly on the electric field configuration.