Application of auxiliary metal layers to e-beam and X-ray lithography

Micron and sub-micron gold lines have been produced by liftoff following e-beam and X-ray exposures of resist coated chromium layers on silicon. Etching a 0.1 micron chromium layer after development results in an undercut which aids the liftoff process. This approach has been used in e-beam lithography on PMMA (i.e. positive resist) to decouple the e-beam exposure from generation of the undercut. In this way 0.7 micron gold lines separated by less than 0.3 microns have been produced. A similar approach when used in X-ray lithography on OEBR (negative resist) yielded gold lines down to 0.3 microns in width and separation. Scanning electron micrographs of patterns at various stages of processing are presented and the profiles of the resist walls and the nature of the undercut are described.     

Potentiation of morphine-induced seizure by 6-hydroxydopamine

A retrospective study of sixteen patients with pelvic fractures compounded through the perineum, rectum, or vagina showed a mortality of 50 per cent. The cause of death in seven of the eight patients was sepsis and multisystem failure. The initial surgical management of these patients must include complete diversion of the fecal stream so that pelvic and systemic sepsis may be prevented.     

Perforated duodenal ulcer in Black patients

Sixteen cases of perforated duodenal ulcer in Black patients admitted to Tembisa Hospital during a 1-year period are reviewed. They constitute 0,4% of all surgical admissions. Duodenal ulcer has been considered a rare disease in South African Blacks, but we believe that the incidence is increasing in Black urban populations. The literature is reviewed and possible aetiological factors are discussed.     

Adsorption of Cu(II) onto silica gel-immobilized Schiff base derivative

4-chloroisonitroacetophenone 4-aminobenzylhydrazone (CAAH) chemically anchored on a silica gel surface, has been used for Cu(II) sorption from aqueous solution. The surface modification processes was performed after silanization of silica, then analyzed by elemental analysis, infrared spectroscopy, and thermogravimetry. The sorption behavior of copper(II) was evaluated by the use of batch and column methods. The influences of the concentration, temperature and pH for sorption on the immobilized silica gel with Schiff base were investigated. The obtained dynamic data were fitted to Freundlich, Langmuir and Dubinin-Raduskevich (D-R) isotherms. The mean sorption energy (E) of copper sorption onto silica gel was calculated from D-R isotherm indicating a chemical ion-exchange. The thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated from the adsorption isotherms which were used to explain the mechanism of the adsorption.     

A new pathway for transmembrane electron transfer in photosynthetic reaction centers of Rhodobacter sphaeroides not involving the excited special pair

It is generally accepted that electron transfer in bacterial photosynthesis is driven by the first singlet excited state of a special pair of bacteriochlorophylls (P*). We have examined the first steps of electron transfer in a mutant of the Rhodobacter sphaeroides reaction center in which charge separation from P* is dramatically slowed down. The results provide for the first time clear evidence that excitation of the monomeric bacteriochlorophyll in the active branch of the reaction center (B(A)) drives ultrafast transmembrane electron transfer without the involvement of P*, demonstrating a new and efficient mechanism for solar energy transduction in photosynthesis. The most abundant charge-separated intermediate state probably is P+B(A)-, which is formed within 200 fs from B(A)* and decays with a lifetime of 6.5 ps into P+H(A)-. We also see evidence for the involvement of a B(A)+H(A)- state in the alternative pathway.     

Increased lead absorption with anemia and slowed nerve conduction in children near a lead smelter

Studies to evaluate the prevalence, sources, and health consequences of lead absorption were conducted among children living near a primary lead smelter. Lead levels in air, soil, and dust were highest at the smelter and decreased with distance. Ninety-nine percent of one- to nine-year-old children living within 1.6 kilometers had blood lead levels greater than or equal 40 mug/dl, indicating increased absorption, and 22% had levels greater than or equal 80 mug/dl. The prevalence of lead levels greater than or equal 40 mug/dl decreased with distance; at 72 kilometers from the smelter it was 1%. Erythrocyte protoporphyrin levels increased with blood lead levels: 17% of children with lead levels of greater than or equal 80 mug/dl were anemic. There was no overt neurologic toxicity. Significant negative correlation was found in 202 five- to nine-year-old children between blood lead levels and motor nerve conduction velocity (r = 0.38, p less than 0.02).