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Investigating the scaling behavior of annealed Ga1-xMnxAs anomalous Hall coefficients, we note a universal crossover regime where the scaling behavior changes from quadratic to linear. Furthermore, measured anomalous Hall conductivities in the quadratic regime when properly scaled by carrier concentration remain constant, spanning nearly a decade in conductivity as well as over 100 K in T_[C] and comparing favorably to theoretically predicated values for the intrinsic origins of the anomalous Hall effect. Both qualitative and quantitative agreements strongly point to the validity of new equations of motion including the Berry phase contributions as well as the tunability of the anomalous Hall effect.

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The electronic structure of as-grown and post-annealed Ga(1-x)Mn(x)As epilayers (x≈0.055) has been investigated using resonant inelastic x-ray scattering. Mn L2,3 x-ray emission spectra show that the integral intensity ratio of Mn L2 to L3 emission lines increases with annealing temperature and comes close to that of manganese oxide. The oxygen K-emission/absorption spectra of post-annealed Ga0.945Mn0.055As show 1.5-3.0 times higher degree of oxidation on the film surface than that of the as-grown sample. These experimental findings are attributed to the diffusion of Mn impurity atoms from interstitial positions in the GaAs host lattice to the surface where they are passivated by oxygen.

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This study evaluated endothelin production by endothelial cells after exposure to nicotine or caffeine. Vasoconstrictive properties have been attributed to both nicotine and caffeine. The presence of endothelin, a potent vasoconstrictor itself, was determined using a radioimmunoassay. The optimal stimulatory doses for nicotine and caffeine were determined to be 1.0 micromol/L and 1.0 mmol/L, respectively. When endothelin production was evaluated over time after exposure to the optimal dose of each agent, it was determined that nicotine stimulated maximum endothelin production within 5 minutes. Caffeine failed to cause a distinct peak of endothelin production within 20 minutes. These results suggest that nicotine may have a possible acute and short-lived effect on the vasoconstrictive response associated with endothelin, while caffeine-induced endothelin release may require more long-term exposure.

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A survey was conducted from 1993 through 1995 to monitor organochlorine pesticides and their metabolite residues in milk available in local Hong Kong markets. Of 252 samples analyzed, including pasteurized milk, fresh milk, and raw milk, 42 contained organochloride pesticide residues at levels exceeding the Extraneous Maximum Residue Limits of the Codex Committee on Pesticide Residues. DDE and HCH isomer levels were substantially higher than those found in a 1984-1987 survey, probably because the source of cow's milk has shifted from local dairy industries to mainland China over the past decade. Although organochlorine pesticides such as DDT and HCH have been banned in China since 1983, residues of such compounds may still persist in the environment and cause contamination through the food chain.

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Over the past 7 years, acute food poisoning arising from the consumption of methamidophos-tainted vegetables has occurred sporadically in Hong Kong. To enable prompt remedial and regulatory actions to be taken, a simple and rapid gas chromatographic method was developed to determine methamidophos residues in food remnants. Samples were homogenized and extracted with acetone. Acetone in the resultant extract was removed by rotary evaporation, leaving behind an aqueous solution. After washing with petroleum ether and addition of sodium sulphate, the aqueous solution was re-extracted with chloroform. The chloroform extract was concentrated to dryness and the residue was reconstituted in absolute ethanol for determination by gas chromatography with flame photometric detection. The method was found to be applicable also to the determination of acephate, dimethoate, omethoate and trichlorfon. Mean recoveries of the five organo-phosphorus pesticides at two fortification levels, viz. 1 mg/kg and 10 mg/kg, ranged from 74 to 113%. Relative standard deviations lay between 1.3 and 6.1%. Method detection limits ranged from 0.02 to 0.04 mg/kg. In 1994, 75 food poisoning cases in Hong Kong were suspected to be related to the consumption of methamidophos-tainted vegetables; 13 food remnants were received for analysis, four of them were found to contain high concentrations of methamidophos.

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A simple and rapid method for the determination of bitertanol, metalaxyl, oxadixyl, propiconazole and triadimefon residues in cucumbers has been developed. The fungicide residues were extracted from the sample with ethyl acetate and determined, after an automated gel permeation chromatographic clean-up, by GC with nitrogen-phosphorus detection. Cucumbers fortified with fungicides in the laboratory were analysed using the proposed method and that of Luke, Frooberg, Masumoto and Doose (J. Assoc. Off. Anal. Chem., 1981, 64, 1187). For the proposed method, mean recoveries ranged from 87.9% for bitertanol to 96.5% for oxadixyl. For the method of Luke et al. mean recoveries ranged from 79.8% for triadimefon to 97.8% for bitertanol. Cucumbers treated with the fungicides in the field were also analysed by these two methods. For the determination of all these five fungicides, no difference was observed at the 5% significance level.

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Plasma exchange (PE) is considered the most effective nonsurgical treatment modality for the reduction of low-density lipoprotein (LDL) in patients with familial hypercholesterolemia (FH). However, the concomitant reduction of high-density lipoprotein (HDL) and the necessity and cost of using blood products are major drawbacks of PE. We studied the effects of selective LDL reduction using monoclonal anti-LDL antibodies in an investigational immunoadsorption (IA) system. Results were compared with the effects of PE. During the study period, two homozygous FH patients with baseline cholesterol levels greater than 10.34 mmol/L (400 mg/dL) were treated sequentially for a combined total of 37 IA treatments and the results were compared with a total of 19 sequential PE treatments. The IA system consisted of on-line plasma processing over two columns of monoclonal anti-LDL antibodies in alternating cycles of column adsorption and regeneration. No replacement solution was needed. PE was performed with a centrifugal plasma separator using 5% albumin as replacement solution. Results showed that the reduction of lipids with IA was 43% +/- 0.9% for cholesterol, 51% +/- 1.0% for LDL, and 19% +/- 1.3% for HDL, resulting in a reduction in the LDL to HDL ratio of 41% +/- 1.7%. Compared with IA, percent reduction by PE was significantly greater (P less than 0.001) for all lipids, but was nonselective (cholesterol, 74% +/- 1.0%; LDL, 77% +/- 1.2%; HDL, 73% +/- 2.7%), and therefore the reduction of the LDL to HDL ratio was only 6% +/- 3.6%, which was significantly less than for IA (P less than 0.001). Pretreatment HDL concentration appeared to increase with repetitive IA treatment, but decreased back to prestudy levels with repetitive PE.(ABSTRACT TRUNCATED AT 250 WORDS)

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