The acid properties of a series of alumina‐supported tungsten oxide (WO3/Al2O3) catalysts with loadings of 5–50 wt % WO3 calcined at various temperatures were investigated by acid‐catalyzed reactions (benzylation of anisole and isomerization of α‐pinene) and FTIR spectroscopy. The relationships between acid properties, structures, and catalytic performances were evaluated. Both the catalytic activity and amount of Brønsted acid sites depend on the calcination temperature and WO3 loading. High‐temperature calcination (1123 K) generated Brønsted acid properties, and 20 wt % WO3/Al2O3 calcined at 1123 K exhibited the highest activity among the catalysts tested. The activities for the benzylation of anisole and α‐pinene isomerization over WO3/Al2O3 calcined at 1123 K were proportional to the Brønsted acidity, which indicates that these reactions occurred on the Brønsted acid sites. Tungsten oxide, which has distorted octahedral symmetry, was loaded as 2 D monolayer domains below 20 wt %, and these domains covered most of the alumina surface at 20 wt %. If the WO3 loading was sufficient to form 2 D tungsten oxide monolayer sheets (>20 wt %), some of the Brønsted acid sites on WO3/Al2O3 were obscured by monoclinic WO3 that has no Brønsted acid sites, which resulted in a decrease of the catalytic activity. This suggests that Brønsted acid sites are generated at the boundaries between tungsten oxide monolayer domains.
An automatic fluorescence microphotometer using an image dissector tube as the fluorescence detector is described. The image dissector tube is used in the photon-counting mode of operation to allow precise intensity measurements of weak fluorescent spots. With the support of a laboratory-built microcomputer system, the instrument can automatically search for cells stained with fluorescent dye in the microscope field; then the detected cells are individually put in the measuring probe region to have their fluorescence intensities measured. Finally a fluorescence distribution histogram of stained cells is automatically generated and graphically presented. The instrument also allows a fluorescence intensity mapping operation utilizing the conventional raster scanning technique. To demonstrate the system's performance, DNA in rat liver nuclei stained with Feulgen dye was measured.
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