Biomedical subjects
Publications and source records attributed to AS Chan.
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A method for measuring the asymmetry parameter gamma arising from dipole-quadrupole interference in core-level photoemission is proposed which is based on condensed thin films and exploits the influence of this asymmetry in photoemission monitoring of x-ray standing wave field absorption. The high density of material in this method offers some advantages over a conventional gas-phase measurement. Results are presented for C, O, and F 1s photoemission at photon energies around 3 keV. The combined nondipole asymmetry factor (delta+gamma/3) for non- s-states can be determined in a similar way.
A new polymer-supported BINOL (1,1'-Bi-2-naphthol) was synthesized by coupling of aminomethyl polystyrene resin and (S)-2, 2'-dihydroxy-1,1'-binaphthyl-3,3'-dicarboxylic acid. This new ligand was found to be more enantioselective for the asymmetric addition of diethylzinc to aldehydes than its "free" analog [Ti(BINOL)(i)PrO(2)]. A range of 57-99% ee's as well as 78-97% yields was obtained, and the electronic properties of the enantioselectivity were also observed.
Studying the interaction of CH3SH, methanethiol, with Cu(111) as a model system, we demonstrate the ability of chemical-shift normal incidence x-ray standing wave field measurements to identify the local adsorption geometries of coadsorbed reaction products at different temperatures, a technical problem of broad chemical significance. In the present case the local geometries of four distinct S-containing adsorbate species (intact CH3SH, two thiolate (CH3S-) reaction intermediates and atomic S) are determined.
Event schemas, the conceptualization of past experience, in schizophrenic patients were examined based upon script theory. Forty schizophrenic patients and 40 age- and education-matched normal control subjects participated in this study. This experiment consisted of three tasks. In the recall task, subjects recalled a typical scenario of going to a formal restaurant. In the frequency judgment task, subjects determined whether the given events happen frequently, occasionally or rarely in a restaurant. In the sequencing task, the subjects put the randomly presented events in the correct order. The responses of the schizophrenic patients in the recall task, when compared with those of the normal control subjects, had significantly fewer concepts and a greater proportion of highest-frequency concepts. In addition, the sequence of their responses was less accurate than that of normal individuals. This abnormality is unlikely due primarily to a retrieval deficit (i.e. generating fewer concepts in the recall task) given that their performances on the frequency judgment and sequencing tasks, tasks that require less retrieval effort, were consistent with those of the recall task. These results suggest that event schemas in schizophrenic patients contain little detailed information and are incoherent in organization.