More recent studies by physical anthropologists have substantiated and extended these observations; a recent review and analysis of data from more than 100 populations (Relethford 1997) found that skin reflectance is lowest at the equator, then gradually increases, about 8% per 10° of latitude in the Northern Hemisphere and about 4% per 10° of latitude in the Southern Hemisphere. This pattern is inversely correlated with levels of UV irradiation, which are greater in the Southern than in the Northern Hemisphere. An important caveat is that we do not know how patterns of UV irradiation have changed over time; more importantly, we do not know when skin color is likely to have evolved, with multiple migrations out of Africa and extensive genetic interchange over the last 500,000 years (Templeton 2002).Regardless, most anthropologists accept the notion that differences in UV irradiation have driven selection for dark human skin at the equator and for light human skin at greater latitudes. What remains controversial are the exact mechanisms of selection. The most popular theory posits that protection offered by dark skin from UV irradiation becomes a liability in more polar latitudes due to vitamin D deficiency (Murray 1934). UVB (short-wavelength UV) converts 7-dehydrocholesterol into an essential precursor of cholecaliferol (vitamin D3); when not otherwise provided by dietary supplements, deficiency for vitamin D causes rickets, a characteristic pattern of growth abnormalities and bony deformities.
Contraindications
Hypersensitivity

Society and culture
Availability
Gatifloxacin is currently available in the US and Canada only as an ophthalmic solution.In 2011, the Union Health and Family Welfare Ministry of India banned the manufacture, sale, and distribution of gatifloxacin because of its adverse side effects.In China, gatifloxacin is sold in tablet as well as in eye drop formulations. Brand names
Bristol-Myers Squibb introduced gatifloxacin in 1999 under the proprietary name Tequin for the treatment of respiratory tract infections, having licensed the medication from Kyorin Pharmaceutical Company of Japan. Allergan produces it in eye-drop formulation under the names Zymar, Zymaxid and Zylopred. In many countries, gatifloxacin is also available as tablets and in various aqueous solutions for intravenous therapy. == References ==