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Biomedical subjects

R S Chen

Publications and source records attributed to R S Chen.

At least 91 records · Page 5Linked to original sources
PubMed1987

The effect of water and ions on the energy band structure of periodic alpha-helical polypeptides.

The solvent structure around several periodic polypeptides in the alpha-helical conformation has been determined by Monte-Carlo simulations. The calculations of the water clusters have been performed in the presence and absence of Na+ ions. The resulting hydration shell has been used to calculate the band structure of the polymers in the effective field of the water molecules and ions. The results show that the maximum change of the band widths and the band gaps is about 0.7 eV in the presence of the hydration shell. The band positions are shifted by up to 4.1 eV in the presence of water molecules and ions. The results have been compared with the band structure results of periodic polypeptides in the beta-pleated sheet conformation.

Ions↗
PubMed1987

Survival of pathogenic bacteria in environmental microcosms.

The survival times of Salmonella enteritidis, Pseudomonas aeruginosa, Staphylococcus aureus, and Vibrio cholerae in natural soil and river water samples were monitored by using various differential media. S. aureus and V. cholerae failed to survive in samples of soil, groundwater, and river water with various degrees of eutrophication. The population of the introduced S. enteritidis remained fairly constant in all three samples of soils tested. In water samples, numbers of S. enteritidis and P. aeruginosa showed an initial rapid decline followed by a much lower rate of decrease. The results indicated that some allochthonous microorganisms, because of their insensitivity to various biotic and abiotic stresses, might persist for a long time in the environment and become a serious threat to public health.

Pseudomonas aeruginosa↗
PubMed1985

Duodenal somatostatin-containing tumor with psammoma bodies.

A duodenal tumor was found in a 68-year-old woman undergoing routine cholecystectomy for chronic cholecystitis associated with cholelithiasis. Microscopically, the tumor contained glandular structures and psammoma bodies. Electron microscopic examination demonstrated numerous intracytoplasmic neurosecretory granules consistent with endocrine D cells. Immunoperoxidase staining for somatostatin was positive in the tumor cells. The tumor appeared to be different from the somatostatinomas reported in the literature in that it was nonfunctional, located in the duodenum, and associated with psammoma bodies.

Adenocarcinoma↗