Sequential plasma samples obtained from 16 individuals who seroconverted were tested for the presence of antibody to human immunodeficiency virus type 1 (HIV-1) by an antigen conjugate enzyme immunoassay (EIA) and a conventional antibody conjugate assay. In 11 of these individuals, the antigen conjugate assay detected antibody to HIV-1 2 to 11 days (mean, 5.5 days) earlier than the antibody conjugate assay. In 11 individuals, HIV-1 p24 antigen was detected a median of 6.5 days (range, 3 to 14 days) prior to positivity by the antigen conjugate EIA. Using class-specific probes, we determined the profiles of immunoglobulin M (IgM), IgG, and IgA antibodies for each individual and correlated these profiles with the ETA signals from both assays. In general, the appearance of IgM exhibited a peak at about 1 week postseroconversion, which was followed by gradually declining levels. Absorbance levels for IgG antibody, however, rose steadily and reached a plateau after 3 to 5 weeks. The levels of IgA were generally low and variable. In contrast to the progressive increase in ETA absorbance observed by the antibody conjugate assay, the antigen conjugate assay displayed a rapid early rise in absorbance which generally coincided with the transient expression of IgM antibody. The subsequent gradual increase coincided with rising levels of IgG. Because the configuration of the antigen

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The performance of an automatic spectroscopic ellipsometer, the SOPRA Multi-Layer Monitor (MLM) has been evaluated in the Defence Evaluation and Reasearch Agency's Cleanroom over a one-year period on representative CMOS/Bipolar wafer structures supplied by tC manufacturers. Precision, stability, throughput and accuracy have been assessed for ONO, OPO, oxide, Si/SiGe and PECVD nitride/metal wafers. Examples are given to illustrate the ability of the MLM to discriminate variations due to intrinsic and deliberately-induced process changes, as well as cross-wafer uniformity. Both monitor and patterned product wafers have been measured and the inadequacy of relying on monitor wafers demonstrated

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