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Full-Text Articles in Biomedical Engineering and Bioengineering

Scanning Electrochemical Mapping Of Spatially Localized Electrochemical Reactions Induced By Surface Potential Gradients, Shrisudersan Jayaraman, Erin L. May, Andrew C. Hillier Aug 2006

Scanning Electrochemical Mapping Of Spatially Localized Electrochemical Reactions Induced By Surface Potential Gradients, Shrisudersan Jayaraman, Erin L. May, Andrew C. Hillier

Chemical and Biological Engineering Publications

The influence of a surface potential gradient on the location and extent of electrochemical reactions was examined using a scanning electrochemical microscope. A linear potential gradient was imposed on the surface of a platinum-coated indium tin oxide electrode by applying two different potential values at the edges of the electrode. The applied potentials were used to control the location and extent of several electrochemical reactions, including the oxidation of Ru(NH3)62+, the oxidation of H2, and the oxidation of H2 in the presence of adsorbed CO. Scanning electrochemical mapping of these reactions was achieved by ...


Precision And Accuracy Of Thermal Calibration Of Atomic Force Microscopy Cantilevers, Nancy Burnham, G Matei, E Thoreson, J Pratt, D Newell Jul 2006

Precision And Accuracy Of Thermal Calibration Of Atomic Force Microscopy Cantilevers, Nancy Burnham, G Matei, E Thoreson, J Pratt, D Newell

Nancy A. Burnham

To have confidence in force measurements made with atomic force microscopes(AFMs), the spring constant of the AFM cantilevers should be known with good precision and accuracy, a topic not yet thoroughly treated in the literature. In this study, we compared the stiffnesses of uncoated tipless uniform rectangular silicon cantilevers among thermal, loading, and geometric calibration methods; loading was done against an artifact from the National Institute of Standards and Technology (NIST). The artifact was calibrated at NIST using forces that were traceable to the International System of units. The precision and accuracy of the thermal method were found to ...


Substrate Rigidity Regulates The Formation And Maintenance Of Tissues, Nancy Burnham, Wei-Hui Guo, Margo Frey, Yu-Li Wang Mar 2006

Substrate Rigidity Regulates The Formation And Maintenance Of Tissues, Nancy Burnham, Wei-Hui Guo, Margo Frey, Yu-Li Wang

Nancy A. Burnham

The ability of cells to form tissues represents one of the most fundamental issues in biology. However, it is unclear what triggers cells to adhere to one another in tissues and to migrate once a piece of tissue is planted on culture surfaces. Using substrates of identical chemical composition but different flexibility, we show that this process is controlled by substrate rigidity: on stiff substrates, cells migrate away from one another and spread on surfaces, whereas on soft substrates they merge to form tissue-like structures. Similar behavior was observed not only with fibroblastic and epithelial cell lines but also explants ...


Analysis And Control Theory Of Some Cochlear Models , Isaac Chepkwony Jan 2006

Analysis And Control Theory Of Some Cochlear Models , Isaac Chepkwony

Retrospective Theses and Dissertations

The standard 2-dimensional cochlear model consists of a 1-dimensional elastic structure, modeling the basilar membrane, surrounded by an incompressible 2-dimensional fluid within a 2-dimensional cochlear cavity. The dynamics are typically driven by a pressure differential across the basilar membrane transmitted through the round and oval windows (a portion of the boundary of the cochlear). First we describe a model in which the basilar membrane is modeled as an infinite array of oscillators and the fluid is described by Laplace's equation. In this setting, we show that the coupled system is approximately controllable with control acting on an arbitrary open ...


Electrochemically Modulated Permeability Of Poly(Aniline) And Composite Poly(Aniline)−Poly(Styrenesulfonate) Membranes, D. L. Pile, Y. Zhang, Andrew C. Hillier Jan 2006

Electrochemically Modulated Permeability Of Poly(Aniline) And Composite Poly(Aniline)−Poly(Styrenesulfonate) Membranes, D. L. Pile, Y. Zhang, Andrew C. Hillier

Chemical and Biological Engineering Publications

The influence of oxidation state on the permeability of several probe molecules through conducting polymer membranes comprising composites of poly(aniline) and poly(styrenesulfonate) was examined in aqueous solution. Pure poly(aniline) membranes displayed a characteristic increase in permeability between reduced and half-oxidized states for neutrally charged phenol and negatively charged 4-hydroxybenzenesulfonate. In contrast, positively charged pyridine experienced decreased permeability through the membrane when poly(aniline) was switched from the reduced to the half-oxidized state. This behavior can be explained by a combination of oxidation-induced film swelling and the anion-exchange character of the positively charged membrane. The membrane composition was ...