Africa, associations

Extensive volcanism can be found in eastern Africa associated with the East African rift system. Helium isotope ratios measured in basalts from the Ethiopian Rift Valley and Afar, near the triple junction of Red Sea, Aden, and Ethiopian rift systems, are 6-17/ a (Marty et al., 1993, 1996 Scarsi and Craig, 1996). These values include MORB ratios as well as indications of both contributions from radiogenic He and high He/ He hotspots. To the south, the rift system divides into eastern and western branches. Xenoliths from Tanzanian vents in the eastern branch... 

Nobel Prize, Presidential Medal of Freedom, and Congressional Gold Medal Laureate, Department of Soil and Crop Sciences, Texas A M University, College Station, Texas, USA International Maize and Wheat Improvement Center, Mexico Sasakawa Africa Association, The Nippon Foundation, Tokyo, Japan... 

Discovered in 1803 by Wollaston, Palladium is found with platinum and other metals of the platinum group in placer deposits of Russia, South America, North America, Ethiopia, and Australia. It is also found associated with the nickel-copper deposits of South Africa and Ontario. Palladium s separation from the platinum metals depends upon the type of ore in which it is found. 

Intrusive Deposits. Deposits included in the intmsive deposit type are those associated with intmsive or anatectic rocks of different chemical composition, eg, alaskite, granite, monzonite, peralkaline syenite, carbonatite, and pegmatite. Examples include the uranium occurrences in the porphyry copper deposits such as Bingham Canyon and Twin Butte in the United States, the Rossing Deposit in Namibia, and Ilimaussaq deposit in Greenland, Palabora in South Africa, and the deposits in the Bancroft area, Canada (15). 

Boehmite (OC-Aluminum Oxide-Hydroxide). Boehmite, the main constituent of bauxite deposits in Europe, is also found associated with gibbsite in tropical bauxites in Africa, Asia, and Austraha. Hydrothemial transformation of gibbsite at temperatures above 150 °C is a common method for the synthesis of weU-cry stalhzed boehmite. Higher temperatures and the presence of alkali increase the rate of transfomiation. Boehmite ciy stals of 5—10 ]liii size (Fig. 3) are produced by tliis method. Fibrous (acicular) boehmite is obtained under acidic hydrothemial conditions (6). Excess water, about 1% to 2% higher than the stoichiometric 15%, is usually found in hydrothemiaHy produced boehmite. 

Associated Manganese Mines (South Africa) Atlantic Equipment Engineers Atomergic Chemetals (France)... 

GCPF is the recognized worldwide representative of the Crop Protection Industry. Its network comprises six Regional Associations Africa/Middle-East, Asia-Pacific, Europe, Japan, Latin America and North America. GCPF promotes understanding of the Crop Protection Industry s contribution to society and to co-ordinate the membership network of member associations. 

The Africa/Middle-East Working Group represents Crop Protection Industiy Associations in Cameroun, Cote d Ivoire, Ghana, Kenya, Malawi, Nigeria, South Africa, Tanzania, Zambia, Zimbabwe, Algeria, Egypt, Jordan, Israel, Lebanon, Morocco and Syria. 

Associated Cement Companies Ltd., 169 Associated Manganese Mines of South Africa Ltd., 199 Association for the Development of Plastic Materials (AIMPLAS), 264... 

More than 200 ores are known to contain cobalt but only a few are of commercial value. The more important are arsenides and sulfides such as smaltite, C0AS2, cobaltite (or cobalt glance), CoAsS, and linnaeite, C03S4. These are invariably associated with nickel, and often also with copper and lead, and it is usually obtained as a byproduct or coproduct in the recovery of these metals. The world s major sources of cobalt are the African continent and Canada with smaller reserves in Australia and the former USSR. All the platinum metals are generally associated with each other and rhodium and iridium therefore occur wherever the other platinum metals are found. However, the relative proportions of the individual metals are by no means constant and the more important sources of rhodium are the nickel-copper-sulfide ores found in South Africa and in Sudbury, Canada, which contain about 0.1% Rh. Iridium is usually obtained from native osmiridium (Ir 50%) or iridiosmium (Ir 70%) found chiefiy in Alaska as well as South Africa. 

Sulfides such as pentlandite, (Ni,Fe)9Ss, associated with copper, cobalt and precious metals so that the ores typically contain about lt% Ni. These are found in more temperate regions such as Canada, the former Soviet Union and South Africa. 

Although estimates of their abundances vary considerably, Pd and Pt (approximately 0.015 and 0.01 ppm respectively) are much rarer than Ni. They are generally associated with the other platinum metals and occur either native in placer (i.e. alluvial) deposits or as sulfides or arsenides in Ni, Cu and Fe sulfide ores. Until the 1820s all platinum metals came from South America, but in 1819 the first of a series of rich placer deposits which were to make Russia the chief source of the metals for the next century, was discovered in the Urals. More recently however, the copper-nickel ores in South Africa and Russia (where the Noril sk-Talnakh deposits are well inside the Arctic Circle) have become the major sources, supplemented by supplies from Sudbury. 

Rotgieter, M., Davidowitz, B., Blom, B. (2005). Chemical concepts inventory of first year students at two tertiary institutions in South Africa. In the conference proceedings of the 13th Annual Conference Southern African Association of Research in Mathematics, Science and Technology Education. Namibia, pp. 664-675. 

Wilson, A. D. Prosser, H. J. (1982). Biocompatibility of the glass ionomer cement. Journal of the Dental Association of South Africa, 37, 872-9. 

By far the most important ores of iron come from Precambrian banded iron formations (BIF), which are essentially chemical sediments of alternating siliceous and iron-rich bands. The most notable occurrences are those at Hamersley in Australia, Lake Superior in USA and Canada, Transvaal in South Africa, and Bihar and Karnataka in India. The important manganese deposits of the world are associated with sedimentary deposits the manganese nodules on the ocean floor are also chemically precipitated from solutions. Phosphorites, the main source of phosphates, are special types of sedimentary deposits formed under marine conditions. Bedded iron sulfide deposits are formed by sulfate reducing bacteria in sedimentary environments. Similarly uranium-vanadium in sandstone-type uranium deposits and stratiform lead and zinc concentrations associated with carbonate rocks owe their origin to syngenetic chemical precipitation. 

Hepatitis E is associated with more than 50% of the acute hepatitis cases in endemic areas (Afghanistan, Bangladesh, Burma, China, India, Indonesia, Kazakhstan, Kyrgyzstan, Malaysia, Mongolia, Nepal, Pakistan, Tajikistan, Turkmenistan, Uzbekistan, Mexico, the Middle East, Northern Africa, and sub-Saharan Africa). The virus is primarily transmitted by the fecal-oral route. Transmission of HEV is more prominent in underdeveloped countries where sanitation is poor. 

---