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Full-Text Articles in Physics

Impedance Spectroscopy Of Bilayer Lipid Membranes And Tio₂ Based Solar Cells, Uwe Hermes Nov 1997

Impedance Spectroscopy Of Bilayer Lipid Membranes And Tio₂ Based Solar Cells, Uwe Hermes

Dissertations and Theses

It has been proposed in the literature that a novel class of biosensors can be based on a bimolecular layer of lipids supported on one side by a metallic surface. In order to estimate the potential of this system for the design of membrane sensors, we have studied properties of a two-electrode system consisting of a tefion insulated metallic wire and a Ag/ AgCl electrode, both immersed in KCl solution. The lipid bimolecular layer was formed on the metal surface of the cut tefion insulated wire. The electrical conductivity properties of such a device were studied in the frequency range …


Molecular Fluorescence At A Rough Surface: The Orientation Effects, P.T. Leung, W. L. Blacke Nov 1997

Molecular Fluorescence At A Rough Surface: The Orientation Effects, P.T. Leung, W. L. Blacke

Physics Faculty Publications and Presentations

The problem of the dynamical interaction between an emitting dipole and a metallic grating surface is considered with particular interest in the effects due to different orientations of the dipole with respect to the substrate surface. Our previous perturbative theory is extended to treat both parallel and perpendicular dipoles and the results are applied to the study of modified fluorescence characteristics for admolecules in the vicinity of a rough metal surface modeled as a grating. Numerical results show that some of the characteristics are very sensitive to the molecular orientation and the one along the grating direction is manifested with …


Symmetry, Symmetry Breaking, And The Current View Of The Dirac Monopole, Erik Kristian Leder Aug 1997

Symmetry, Symmetry Breaking, And The Current View Of The Dirac Monopole, Erik Kristian Leder

Dissertations and Theses

The ideas of symmetry and symmetry breaking are considered in the context of classical gauge theory. Local U(l) symmetry is developed for a complex scalar field and electromagnetism is identified as the associated gauge field. Local S0(3) theory for a triplet of real scalar fields is derived and the incorporation of additional gauge fields is demonstrated. Symmetry breaking for the S0(3) gauge theory is performed and the gauge fields are shown to acquire mass by the Higgs mechanism. The equations of the t'Hooft-Polyakov monopole are derived and compared to those of the magnetic monopole of Dirac.


Molecular Fluorescence At A Rough Surface: The Orientation Effects, William Lee Blacke May 1997

Molecular Fluorescence At A Rough Surface: The Orientation Effects, William Lee Blacke

Dissertations and Theses

The interaction between an emitting molecular dipole and a conducting substrate with a periodic surface roughness is looked at with particular interest in the different orientations of the dipole with respect to the substrate surface. A previous dynamical, perturbative theory for the effects of perpendicular dipole is extended to treat a dipole oriented parallel to the surface of the substrate. The results are then applied to study the modified fluorescence characteristics of the emitting dipoles. Numerical results demonstrate that some fluorescence characteristics are extremely sensitive to the molecular orientation with the dipole oriented along the grating (x direction) exhibiting unique …


Measurement Of The Focal Properties Of A Magnetic Electron Lens Using The Shadowgraph Method, Luis Thomas Almaraz Jan 1997

Measurement Of The Focal Properties Of A Magnetic Electron Lens Using The Shadowgraph Method, Luis Thomas Almaraz

Dissertations and Theses

A method of experimentally determining the properties of a magnetic electron lens is presented. The method uses the shadows cast by two meshes, one placed in front of the lens and one behind the lens, to study the properties of the image of a point source. The lens properties are then calculated from the image properties. The paraxial values of focal length and focal distance as well as their spherical aberrations, are determined. The relationship between image and lens properties are discussed. The method is used here for the first time in determining the focal properties of a magnetic lens.


The Interaction Of Naphthoquinones With The Calcium Release Channel Of Skeletal Muscle Sarcoplasmic Reticulum, Ruohong Xia Jan 1997

The Interaction Of Naphthoquinones With The Calcium Release Channel Of Skeletal Muscle Sarcoplasmic Reticulum, Ruohong Xia

Dissertations and Theses

The sarcoplasmic reticulum (SR) is an intracellular membrane system which regulates cytoplasmic calcium concentration in muscle and controls the contractile state of muscle. In this thesis, the interaction between naphthoquinone and the Ca2+ release mechanism of SR is described. 1,4-naphthoquinone (1,4NQ) is shown to stimulate Ca2+ release and to modify high-affinity ryanodine binding to skeletal muscle sarcoplasmic reticulum. The interaction between 1,4NQ and the SR involves the oxidation ofcritical sulfhydryl groups associated with the Ca2+ release mechanism. The modulation of ryanodine binding by 1,4NQ is biphasic. At low concentrations of 1,4NQ (<10 >μM) ryanodine binding is stimulated, …


Optical Imaging Of Carrier Dynamics In Silicon With Subwavelength Resolution, Andres H. La Rosa, B. I. Yakobson, H. D. Hallen Jan 1997

Optical Imaging Of Carrier Dynamics In Silicon With Subwavelength Resolution, Andres H. La Rosa, B. I. Yakobson, H. D. Hallen

Physics Faculty Publications and Presentations

Characteristic rate variations of carrier processes are imaged using near-field scanning optical microscopy. We couple both a visible pump and an infrared probe light through a subwavelength aperture to investigate the interband recombination and intraband diffusion of excess carriers in oxidized silicon. Typical values of the locally measured life time constants agree well with those obtained by conventional space-averaged techniques. Moreover, the images locate defects, reveal variations, and can map the regions in which a recombination process is active.


General Remarks On Spectral Entropy Vs. Statistical Entropy, John D. Ramshaw Jan 1997

General Remarks On Spectral Entropy Vs. Statistical Entropy, John D. Ramshaw

Physics Faculty Publications and Presentations

Crepeau and Herzel [1] (CH) have recently compared the spectral entropy of Powell and Percival [2] with the standard statistical (Boltzmann-Gibbs-Shannon) entropy in three simple physical systems. Here we compare and contrast these two entropies in a more general way by considering their values for an arbitrary stationary process X(t).