Biomedical subjects

J P Hagen

Publications and source records attributed to J P Hagen.

3 recordsLinked to original sources

PubMed1997

Liquid-liquid immiscibility in lipid monolayers.

Some binary lipid mixtures form coexisting liquid phases when spread at the air/water interface. This work describes the pressure-composition phase diagrams of binary mixtures of four unsaturated phosphatidylcholines with dihydrocholesterol. These four binary mixtures have critical compositions of approximately fifty mole percent, and average critical exponents of 0.25 +/- 0.07. The data can also be approximated by a regular solution thermodynamic model, yielding parameters for the non-ideality of these mixtures.

Cholestanol↗

PubMed1997

Vision 21 Delphi panel: senior Army Medical Service Corps Officers' vision of behaviors for success of future Medical Service Corps officers.

A Delphi study was conducted of Army senior Medical Service Corps leaders (O6s) to identify the expected behaviors and competencies needed to ensure that junior officers will achieve successful careers as Medical Service Corps officers in the 21st century. A Delphi mailing was conducted in two phases. In the first iteration, 41 behaviors were identified to be of importance. In the second mailing, the 41 behaviors were rated for relative importance on a 7-point bipolar rating scale (1 = unimportant, 7 = most important). Comparisons were made between the ratings of administrative and biomedical scientific/technical (BS/T) series. Discriminant models developed to compare demographics between administrative and BS/T officers indicated that administrative officers had more time in grade, years of service, and professional military education, whereas BS/T officers reported significantly more civilian education. Minor differences among the two groups emerged for behavior ratings; however, the final priority order of behaviors reflected a high degree of consensus from both groups.

Clinical Competence↗

PubMed1996

Critical pressures in multicomponent lipid monolayers.

Epifluorescence microscopy has been used previously to study coexisting liquid phases in lipid monolayers of dihydrocholesterol and dimyristoylphosphatidylcholine at the air/water interface. This binary mixture has a critical point at room temperature (22 degrees C), a monolayer pressure of approx. 10 mN/m, and a composition in the vicinity of 20-30 mol% dihydrocholesterol. It is reported here that this critical pressure can be lowered, raised, or maintained constant by systematically replacing molecules of this phosphatidylcholine with molecules of a phosphatidylethanolamine, or an unsaturated phosphatidylcholine, or mixtures of the two, while maintaining the dihydrocholesterol concentration at 20 mol%. Thus, even complex mixtures of lipids may be characterized by a single, well-defined second-order phase transition. In principle, such transitions might be found in biological membranes.

Cholestanol↗