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Using a realistic model for line emission from the broad emission line regions of quasars, we are able to reproduce the previously observed correlations of emission-line ratios with the shape of the spectral energy distribution (SED). In agreement with previous studies, we find that the primary driving force behind the Baldwin Effect (EW ~ L^beta, beta < 0) is a global change in the SED with quasar luminosity, in that more luminous quasars must have characteristically softer ionizing continua. This is completely consistent with observations that show correlations between L_uv, alpha_ox, alpha_uvx, line ratios and EWs. However, to explain the complete lack of a correlation in the EW(NV)--L_uv diagram we propose that the more luminous quasars have characteristically larger gas metallicities (Z). As a secondary element, nitrogen's rapid...
Comment: 24 pages, 10 figures, accepted by ApJ. Preprint utilizes emulateapj.cls v. 4/12/04 (included)
Comment: 11 pages AAS-LATeX aaspp4.sty format, including 1 figure; accepted for publication in ApJ
Alpha-toxin from five strains of Staphylococcus aureus, including Wood 46, was purified by isoelectric focusing. The alpha-toxins obtained from different strains were similar. The isoelectric point of the purified toxins was 8.65 ± 0.15. Sharp concentration peaks were not always obtained. In the ultracentrifuge the alpha-toxins migrated usually as three peaks which could be dissociated with propionic acid to yield one peak. A single line of identity was obtained in immunoelectrophoresis when a heterologous antiserum was reacted with the five purified toxins. It was concluded that the widespread use of the Wood 46 strain for the production of alpha-toxin is justified.
Although there are a number of existing assays for monitoring the activity of both isopenicillin N synthase (IPNS) and deacetoxycephalosporin C synthase (DAOCS), none have demonstrated the qualities required for screening a mutant library. Hence, enzyme-linked immunosorbent assays (ELISAs) for IPNS and DAOCS were developed based on the detection of the catalytic turnover products isopenicillin N and cephalexin/phenylacetyl-7-aminodeacetoxycephalosporanic acid (G-7-ADCA), respectively. These assays are relatively fast compared to existing assays, such as the hole-plate bioassay, and are amenable with high-throughput screening. Both the IPNS and DAOCS-ELISAs were optimised for use with crude protein extracts rather than purified protein, thereby eliminating any additional time required for purification. The ELISA developed for the ...
Comment: 42 pages, 16 figures, Accepted for publication in ApJS
Comment: 54 pages, 21 figures, Accepted for publication in the Astrophysical Journal
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