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The impact of different antiretroviral agents on the risk of developing or surviving CNS disease remains unknown. The aim of this study was to investigate whether using antiretroviral regimens with higher CNS penetration effectiveness (CPE) scores was associated with reduced incidence of CNS disease and improved survival in the UK Collaborative HIV Cohort (CHIC) Study.

Rate constants for the unimolecular thermal isomerization of gaseous 1,1-dimethylcyclopropane to isomeric methylbutenes have been measured, and Arrhenius parameters determined, over a wide temperature range, 683–1132 K, using a single-pulse shock tube and a static reactor. For the overall reaction, Ea = 61.8 ± 0.4 kcal/mol, and log10(A, s⁻¹) = 15.04 ± 0.10. These values are in good agreement with previously reported values obtained over a much narrower temperature range. Rate constants for formation of the two major products, 2-methylbut-2-ene and 3-methylbut-1-ene, are given by Ea = 61.9 kcal/mol, log A = 14.80 and Ea = 61.1 kcal/mol, log A = 14.54, respectively. A comparison of the activation parameters for structural isomerizations of cyclopropane, methylcyclopropane, and 1,1-dimethylcyclopropane confirms a trend toward lower activation energy values as hydrogen atoms in cyclopropane are replaced by CH3 groups. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 853–858, 2001

Gas samples containing either 0.20% or 1.0% cyclopentane plus 0.25% tert-butyl alcohol in argon have been heated to 1185–1257 K in a single pulse shock tube. The previously studied dehydration of the alcohol was used as an internal standard reaction for temperature measurement. Pyrolysis of the cyclopentane yielded a broad spectrum of C1–C5hydrocarbon products; however, the products and their concentration ratios were in good agreement with those recently reported by Tsang, in a comparative rate study of cyclopentane pyrolysis vs. cyclo-hexene decyclization. Thus strong support is offered for Tsang's proposed complex mechanism involving (a) molecular isomerization to 1-pentene and subsequent degradation of that product, (b) molecular decomposition to cyclopropane and ethene, followed by isomerization of cyclopropane to propene, and (c) induced decomposition to a variety of C1–C5hydrocarbons plus H2via hydrogen atom abstraction from cyclopentane by various radicals generated from 1-pentene. The only significant disagreement with Tsang's study is a ∼40° temperature discrepancy; possible sources of this are discussed.

Radiochemical and electrochemical evidence is presented that electrochemically generated tritium and hydrogen atoms permeate through lead foil at measureable rates at room temperature. The permeation process is controlled by diffusion through the metal lattice, Fick's First Law being obeyed by both H and 3H atoms. Using earlier measurements of the diffusivity of H in Pb, H and 3H concentrations of 4 × 10−7and 9 × 10−13 g-atom cm−3are computed for a current density of 53 mA cm−2at the Pb cathode surface.The overall hydrogen-tritium separation factor, STis apparently 0.3 ± 0.15, in contrast to Bockris and Srinivasan's 6.7 and 7.2 for cathodic gas evolution from acidic and alkaline media, respectively. Reasons are suggested for this large difference.

Conclusive evidence is reported for the permeation of electrolytic hydrogen through lead. The diffusion coefficient at 25 °C lies between 10−7and 10−6 cm2s−1while the bulk concentration of dissolved hydrogen is indicated to be 10−6 g-atom cm−3at current densities of 10 to 50 mA cm−2.

A case of leiomyoma of the female urethra arising from the anterior lip of the external urinary meatus is presented. The tumor was missed originally and, subsequently, increased in size. Although the neoplasm was suspected clinically, it was confirmed only by histopathology. The tumor was responsible for recurrent urinary tract infection, which ceased after the neoplasm was excised.

When high densities (three or more individuals per sq. cm.) of flour beetles, Tribolium confusum Duv. and Tl castaneum (Hbst.) were exposed to DDT or pyrethrins-treated surfaces in closed petri dishes the resulting mortality was much higher than with low densities (one individual or less per sq. cm.) of beetles. The mortality increase was progressive and did not show an abrupt change over the range of densities studied. The results were obtained from surfaces containing an excess of the insecticide in relation to the amount picked up. The differences in mortality did not occur in uncovered dishes or when the beetles were exposed to a thiocyanate insecticide, Lethane 384® (2-(2-butoxycthoxy)ethyl thiocyanate). The causes producing such differences in mortality would appear to be associated with some volatile material. Tests of the effects of the secreted quinone compounds and of accumulated carbon dioxide were negative. A critical level of oxygen need is probably reached. This probability is indicated based upon previous experiments in other laboratories that have shown a large increase in oxygen consumption following DDT or pyrethrins exposure. Conversely, a thiocyanate that depresses oxygen consumption did not produce greater mortality with a greater density of beetles. Open dishes would also permit an exchange of air and the differences in mortality did not occur under these conditions. Other possible influencing factors were studied but did not produce a positive correlation with the differences in mortality. These factors included the possible effect of rate of movement and pickup of the insecticide. Rate of movement was greater with a greater density of beetles, which occurred whether the dishes were covered or uncovered. No marked difference occurred in pickup.