Environmental chemistry of chromium.

The processes that control the environmental chemistry of chromium include redox transformation, precipitation/dissolution, and adsorption/desorption reactions. Commonly occurring reductants, such as ferrous iron and organic material, can transform Cr(VI) to Cr(III), but manganese oxides are the only inorganic oxidants found in the environment that cause the rapid oxidation of Cr(III) to Cr(VI). In the trivalent state, chromium readily forms compounds such as Cr(OH)3 and (Cr,Fe)(OH)3. These solids show amphoteric solubility behavior, with hydroxo complexes being the dominant aqueous species of Cr(III). The relatively low solubilities of Cr(OH)3 and (Cr,Fe)(OH)3 limit Cr(III) concentrations to less than the drinking water limit over much of the pH range of environmental interest. In the hexavalent state, the formation of the Ba(S,Cr)O4 solid solution controls the dissolved chromium concentrations in environments that contain BaSO4. In the absence of solubility-controlling Cr(VI) solids, Cr(VI) concentrations in acidic to slightly alkaline conditions are expected to be limited by adsorption. Iron oxides are the most important absorbents for aqueous Cr(VI) species in most soil environments. Although these processes are complex and interrelated, each must be considered to predict the aqueous concentrations, mobility, and toxicity of chromium in the environment.

Continuity, family involvement, and clinical content in a year-long ambulatory care clerkship.

Entries in student logbooks for the Ambulatory Care Clerkship at the Michigan State University College of Human Medicine were tabulated by microcomputer for 38,430 patient encounters in five community campuses in 1985 and 1986, and by hand for 32,182 patient encounters in Grand Rapids from 1983 to 1987. The repeat visit rate recorded toward the end of the clerkship by students in family practice settings was approximately 60% of the rate recorded by students taking the clerkship with internists or pediatricians. Students in family practice and in pediatrics had the same degree of exposure to patient families; however, family exposure in internal medicine and in pediatrics was limited to other family members of the same generation as the patient. Distributions of the kinds of patient problems seen were distinctive by specialty and were stable across 5 years.

Pilot experience of a family practice-based combined clerkship.

In order to explore alternatives in clinical undergraduate medical education, an experimental Combined Clerkship was developed and implemented on the Grand Rapids campus of Michigan State University. Two third-year medical students spent three half-days per week for 36 weeks seeing patients in the family practice office, of a facluty member. Hospitalized patients from this practice were worked-up and used as the source of inpatient specialty learning. The students attended lectures and took oral and written examinations of all required clerkships, but had no specific hospital assignment during this time. Two hundred nineteen patients were followed by these students, compared to 174 required by the clerkships. All written and oral examinations were passed. In addition to meeting all clerkship objectives, the students cared for 680 outpatients presenting 1,035 ICHPPC-coded problems. The top ten diagnoses were identified collectively and individually, and were compared to other published studies for corroboration of representative patient problems. This project demonstrates that the objectives of required clerkships can be met in an alternative setting that allows the addition of other important experiences.