Biomedical subjects

S M Hansen

Publications and source records attributed to S M Hansen.

11 recordsLinked to original sources

PubMed2001

Headspace solvent microextraction.

A hanging microliter drop of 1-octanol is shown to be an excellent preconcentration medium for headspace analysis of volatile compounds in an aqueous matrix by gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS). Model compounds benzene, toluene, ethylbenzene, and o-xylene (BTEX) are conveniently and rapidly preconcentrated in the microdrop. An internal standard, decane, is present in the organic extracting solvent, and linear calibration curves of relative peak area versus aqueous concentration are obtained for the four model compounds. Detailed kinetic studies reveal that the overall rate of mass transfer is limited by both the aqueous-phase stirring rate and the degree of convection within the organic phase. The very low vapor pressure of 1-octanol results in minimal evaporation of the microdrop during the extraction time. This system represents an inexpensive, convenient, and precise sample cleanup and preconcentration method for the determination of volatile organic compounds at trace levels.

Journal Article↗

PubMed1992

A model for an outpatient imaging center.

U.S. federally imposed efforts to regulate joint venturing are a result of certain physician strategies to circumvent anti-kickback statutes by investing in clinics, labs, and facilities for self-referral. This article addresses the ethical debate on physician ownership, MRI as an evolving modality, the 1989 Ethics in Patient Referrals Act and the subsequently released "safe harbors," and finally, describes an existing model for physician/hospital ownership in an outpatient MRI facility.

Ethics, Medical↗

PubMed1989

Prognosis after the first episode of gastrointestinal bleeding or coma in cirrhosis. Survival and prognostic factors.

Hepatic encephalopathy and gastrointestinal (GI) bleeding are the most serious complications in cirrhosis. The purpose of this study was to examine survival after the first episode of GI bleeding or coma, or both, and to identify variables associated with the subsequent survival in 284 consecutive patients with cirrhosis admitted to one division of hepatology over a period of 81 months. Patients who only bled had markedly longer survival than those who only had coma, whereas those who had both bleeding and coma had by far the poorest survival, only 15% being alive 1 year later. Several other variables showed a significant association with survival. In a Cox multiple regression analysis the following four variables showed significant association with a short survival: coma and bleeding at the episode, ascites, low prothrombin index, and high serum creatinine. The prognostic index derived from the Cox model, which was validated by a split-sample testing technique, may be used to refine prognostic estimation in this subgroup of severely ill cirrhotic patients.

Adult↗

PubMed1985