Abstract not found

Fluorine gas is produced industrially by electrolysing hydrogen fluoride in a potassium acid fluoride electrolyte. Fluorine is produced at the carbon anode, while hydrogen is produced at the mild-steel cathode. The fluorine produced has a wide range of uses, most notably in the nuclear industry where it is used to separate 235U and 238U. The South African Nuclear Energy Corporation (Necsa) is a producer of fluorine and requested an investigation into the hydrodynamics of their electrolysis cells as part of a larger national initiative to beneficiate more of South Africa’s large fluorspar deposits. Due to the extremely corrosive and toxic environment inside a typical fluorine electrolysis reactor, the fluid dynamics in the reactor are not understood well enough. The harsh conditions make detailed experimental investigation of the reactors extremely dangerous. The objective of this project is to construct a model that can accurately predict the physical processes involved in the production of fluorine gas. The results of the simulation will be compared to experimental results from tests done on a lab-scale reactor. A good correlation

Buoyancy-driven surface currents were generated in the laboratory by releasing buoy-ant fluid from a source adjacent to a vertical boundary in a rotating container. Dierent bottom topographies that simulate both a continental slope and a conti-nental ridge were introduced in the container. The topography modied the flow in comparison with the flat bottom case where the current grew in width and depth until it became unstable once to non-axisymmetric disturbances. However, when topogra-phy was introduced a second instability of the buoyancy-driven current was observed. The most important parameter describing the flow is the ratio of continental shelf width W to the width L of the current at the onset of the instability. The values of L for the rst instability, and L −W for the second instability were not influenced by the topography and were 2{6 times the Rossby radius. Thus, the parameter de-scribing the flow can be expressed as the ratio of the width of the continental shelf to the Rossby radius. When this ratio is larger than 2{6 the second instability was observed on the current front. A continental ridge allowed the disturbance to grow to larger amplitude with formation of eddies and fronts, while a gentle continental slope reduced the growth rate and amplitude of the most unstable mode, when compared to the continental ridge topography. When present, eddies did not separate from the main current, and remained near the shelf break. On the other hand, for the largest values of the Rossby radius the rst instability was suppressed and the flow was observed to remain stable. A small but signicant variation was found in the wavelength of the rst instability, which was smaller for a current over topography than over a flat bottom. 1.

Temperature sensitivity of soil organic matter decomposition in boreal soils

This report focuses on the evidence about the health.consequences of smoking for women, and is intended to serve.the public health and medical communities as 'a unified source of existing scientific research. The major issues about tobacco use and women's health are examined, including trends in consumption, biomedical evidence, and determinants of smoking ititiation, maintenance, and cessation. The biomedical aspects ofsmoking are presented in terms of mortality, morbiplity, cardiovasculaidiseases, cancer, pregnancy and infant,health,, Teptic ulcer disease, drug reactions and, interactions, food constituents, and responses to,diagnostic tests. The psychosocial and behavioraj. aspects, of smoking in women are discussed, along with the docffiented increases in- the risk of contracting lung cancer, heart,disease, or lung disease. The harmful effects of pregnant mothers smoking behaviors, are also docudented. Adhitionally, recent data are enumerated to indicate a trend of,decreasing tobacco usage among women in response to the warnings of the gavernMent, voluntary agencie, and physicrins. (Author /NRB)' DOCUMENT RESUME cc 015 465