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Biomedical subjects

C Clasen

Publications and source records attributed to C Clasen.

8 recordsLinked to original sources
PubMed2006

Formation and characterization of chitosan membranes.

In this paper, hydrophilic polymer membranes based on macromolecular chitosan networks have been synthesized and characterized. The structure of the membrane has been altered in several ways during the formation to adjust the properties, particularly with regard to the elasticity, tensile strength, permeability, and surface structure. An alteration of the network structure was achieved by addition of flexibilizer, cross-linking with dialdehydes, symplex formation of the chitosan with the polyanion sulfoethyl cellulose, and the introduction of artificial pores on the micro- and nanometer scale into the chitosan matrix with silica particles or poly(ethylene glycol). The resulting network structures and morphologies of these unique membranes that combine the novel alteration techniques have been characterized in detail and correlated with molecular parameters of the chitosan as degree of deacetylation, molar mass, and charge density. Finally, we report on the impact of the new network structures on physical properties of the membranes, the water vapor and gas permeability and the tensile strength, to evaluate possible application of the membranes as a wet wound dressing material with microbial barrier function that actively assists the healing process of problematic wounds. Parts of the novel combined membrane alteration and formation techniques are now covered by the patent DE 102004047115.

Chitosan↗
PubMed2006

Ex vivo rheology of spider silk.

We investigate the rheological properties of microliter quantities of the spinning material extracted ex vivo from the major ampullate gland of a Nephila clavipes spider using two new micro-rheometric devices. A sliding plate micro-rheometer is employed to measure the steady-state shear viscosity of approximately 1 microl samples of silk dope from individual biological specimens. The steady shear viscosity of the spinning solution is found to be highly shear-thinning, with a power-law index consistent with values expected for liquid crystalline solutions. Calculations show that the viscosity of the fluid decreases 10-fold as it flows through the narrow spinning canals of the spider. By contrast, measurements in a microcapillary extensional rheometer show that the transient extensional viscosity (i.e. the viscoelastic resistance to stretching) of the spinning fluid increases more than 100-fold during the spinning process. Quantifying the properties of native spinning solutions provides new guidance for adjusting the spinning processes of synthetic or genetically engineered silks to match those of the spider.

Animals↗
PubMed2001

Service learning: integrating student learning and community service.

Health professions education is directly effected by changes in health care service delivery and financing systems. In the United States, as the health care industry increasingly shifts to a market economy, service delivery venues are moving away from acute care facilities and into community-based settings. Additionally, there is increased emphasis on primary prevention programs, often provided in public health settings. For health professions programs that traditionally provide clinical training in hospitals and long-term care facilities, there are unique challenges associated with identifying new venues in order to insure that students are exposed to a wide variety of patients with a range of chronic to acute disease conditions. One set of tools that has demonstrated usefulness during these kinds of transitions is service learning. This teaching methodology emphasizes increased partnership with clinical training sites, extensive orientation to patient populations and community resources, structured reflection and instilling the ethic of service in future health care providers. Although this article describes utilization of service learning in the context of current conditions in the United States, we hope that the principles presented here can be readily adapted in any setting.

Journal Article↗
PubMed1998

Three evaluation methods of a community health advocate program.

The title Community Health Advocate (CHA) is one of thirty or more titles used throughout the world for an indigenous outreach worker who is trusted and respected in his or her community and who serves as a bridge between peers and health professionals. In 1992, the Center for Healthy Communities in Dayton, Ohio developed a program to train as Advocates people indigenous to the communities in which they would be working. Since the first CHAs began work in January 1993, the effectiveness of the program has been evaluated from three perspectives: the Community Health Advocates, the managers/directors of the community sites at which the CHAs work, and the clients with whom the CHAs work. Advocates indicated that the training program adequately prepared them for their roles and functions. They also identified systematic frustrations and barriers that made it more difficult for them to perform their job. Community site directors and community leaders indicated that the CHAs were considered a positive force in meeting client needs and facilitating independence, and were very effective in outreach and coordination of resources. A survey of CHA clients revealed an overwhelmingly positive response to the Advocate's work, validating the belief that CHAs can fill an important niche in the health care community. The three evaluation processes described in this paper helped to document the need for and the effectiveness of this program and can serve as a model for similar programs.

Adolescent↗
PubMed1998

Unsatisfactory detection of an in vivo haemolytic anti-vel by the gel test.

BACKGROUND AND OBJECTIVES: A patient experienced a severe haemolytic transfusion reaction. Neither the haemolytic property nor the specificity of the causative antibody had been sufficiently recognised when performing a microcolumn gel test. MATERIALS AND METHODS: Subsequent to the transfusion reaction, the serological property and specificity of the causative antibody were analysed. Tube and gel test methods were compared, as were various reagent red cell specimens and their constituents. RESULTS: A haemolytic anti-Vel was detected in the tube test. In contrast, the particular commercial gel test kit used did not reveal the haemolytic property or specificity of the antibody. Our experiments suggest that this was apparently due to the presence of EDTA in the low ionic strength saline solution of the test kit. CONCLUSIONS: In rare cases life-treatening haemolytic activity of an irregular blood group antibody may be undetected by a commericial microcolum gel test kit in which EDTA is a constituent.

Aged↗