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Impurity Modes In Photonic Band Structures, Yi-Fen Chang Apr 1993

Impurity Modes In Photonic Band Structures, Yi-Fen Chang

Masters Theses

In this thesis I study a theoretical model of one-dimensional dielectric array (a layered system of dielectric slabs) which forms a periodic dielectric system in which band gaps are opened in the frequency spectrum. Specifically, we study such a one-dimensional array with linear impurities introduced in the periodic dielectric system. In these impurity structures narrow resonant modes are found in the band gaps as impurity modes and these impurity modes change with the dielectric constant. This impurity problem is similar to the donor and acceptor state problem in electronic semiconductors. The calculations presented in this thesis are based on numerically …

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Supersymmetry And The Tunneling Problem In An Asymmetric Double Well, Asim Gangopadhyaya, Prasanta K. Panigrahi, Uday P. Sukhatne Apr 1993

Supersymmetry And The Tunneling Problem In An Asymmetric Double Well, Asim Gangopadhyaya, Prasanta K. Panigrahi, Uday P. Sukhatne

Physics: Faculty Publications and Other Works

The techniques of supersymmetric quantum mechanics are applied to the calculation of the energy difference between the ground state and the first excited state of an asymmetric double well. This splitting, originating from the tunneling effect, is computed via a systematic, rapidly converging perturbation expansion. Perturbative calculations to any order can be easily carried out using a logarithmic perturbation theory. Our approach yield substantially better results than alternative widely used semiclassical analyses.

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The Effects Of Electron Radiation On The Glass Transition Temperature Of A Polyetherimide, Kristen Tulloch Kern Apr 1993

The Effects Of Electron Radiation On The Glass Transition Temperature Of A Polyetherimide, Kristen Tulloch Kern

Physics Theses & Dissertations

The effects of electron radiation on a polyetherimide (PEI), Ultem*, were investigated. In particular, the changes in the glass transition temperature (Tg) with absorbed radiation dose were studied. The polymer was exposed to mono-energetic beams of 100-keV electrons and 1.0-MeV electrons for doses up to 100 megagray (MGy). Dosimetry for the exposures was based on Monte-Carlo simulations of the transfer of energy from an energetic electron to the polymer and on comparison to Nylon standards. Dynamic mechanical analysis was used to determine the (Tg) for non-exposed PEI and the changes in (Tg) resulting from …

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Temperature Dependence Of Optical Properties For Amorphous Silicon At Wavelengths Of 632.8 And 752 Nm, P.T. Leung, Nhan Do, Oguz Yavas, Andrew C. Tam, Wing P. Leung, Hee K. Park, Costas P. Grigoropoulos, Johannes Boneberg, Paul Leiderer Apr 1993

Temperature Dependence Of Optical Properties For Amorphous Silicon At Wavelengths Of 632.8 And 752 Nm, P.T. Leung, Nhan Do, Oguz Yavas, Andrew C. Tam, Wing P. Leung, Hee K. Park, Costas P. Grigoropoulos, Johannes Boneberg, Paul Leiderer

Physics Faculty Publications and Presentations

The temperature dependence of the optical properties for amorphous silicon is studied at wavelengths of 632.8 and 752 nm. Both the refractive index and extinction coefficient increase linearly with temperature for 752 nm, while the refractive index decreases and the extinction coefficient increases for 632.8 nm. The rate of increase of the extinction coefficient at 632.8 nm is twice as much as that for 752 nm.

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Photodeflection Probing Of The Explosion Of A Liquid Film In Contact With A Solid Heated By Pulsed Excimer Laser Irradiation, P.T. Leung, Nhan Do, Leander Klees, Andrew C. Tam, Wing P. Leung Apr 1993

Photodeflection Probing Of The Explosion Of A Liquid Film In Contact With A Solid Heated By Pulsed Excimer Laser Irradiation, P.T. Leung, Nhan Do, Leander Klees, Andrew C. Tam, Wing P. Leung

Physics Faculty Publications and Presentations

The explosion or rapid vaporization of a liquid film on an opaque surface by a pulsed laser is studied experimentally. Using a probe-beam deflection sensing (PDS) scheme, together with a previously developed transmission monitor, the distortion of the PDS signal due to the generation of shock waves by the exploding liquid is investigated. Various liquids, including alcohols and pure water in contact with substrates such as polyimide, amorphous carbon, and silicon, are studied for a wide range of excimer laser fluences. It is concluded that the present PDS technique is highly sensitive to the explosion threshold.

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Magneto-Oscillatory Behavior And Magnetism In Quasi-Two-Dimensional Organic Conductors, J. S. Brooks, S. J. Klepper, C. C. Agosta, M. Tokumoto, N. Kinoshita, Y. Tanaka, S. Uji, H. Aoki, G. J. Athas, X. Chen, H. Anzai Mar 1993

Magneto-Oscillatory Behavior And Magnetism In Quasi-Two-Dimensional Organic Conductors, J. S. Brooks, S. J. Klepper, C. C. Agosta, M. Tokumoto, N. Kinoshita, Y. Tanaka, S. Uji, H. Aoki, G. J. Athas, X. Chen, H. Anzai

Physics

We have studied the magneto-oscillatory behavior of quasi-two-dimensional (quasi-2D) organic conductors of the type (BEDT-TTF)2XHg(SCN)4, where X = K, Rb, NH4, in order to probe the underlying magnetic behavior of these materials. The K and Rb compounds are metallic down to 50 mK, but are not superconducting. They both display a dual series of magneto-oscillations, a magnetic ordering at low temperatures, below about 10 K, and a sharp drop in the magnetoresistance associated with the destruction of this phase with the application of high magnetic fields at low temperatures. In contrast, the NH4 material is a superconductor at low temperatures …

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Electron Microscopy Study Of Magnetosomes In Two Cultured Vibrioid Magnetotactic Bacteria, Fiona C. Meldrum, Stephen Mann, Brigid R. Heywood, Richard B. Frankel, Dennis A. Bazylinski Mar 1993

Electron Microscopy Study Of Magnetosomes In Two Cultured Vibrioid Magnetotactic Bacteria, Fiona C. Meldrum, Stephen Mann, Brigid R. Heywood, Richard B. Frankel, Dennis A. Bazylinski

Physics

Magnetite (Fe304) crystals produced by two strains of cultured vibrioid magnetotactic bacteria were studied by high-resolution transmission electron microscopy (HRTEM). Both magnetotactic strains were characterized by single chains of magnetite crystals aligned along the long axes of the cells. The strains, designated as MV-2 and MV-4, produced crystals that differed markedly in size and morphology. Crystals present in MV-4 cells were generally larger than those in MV-2 cells and displayed significantly smaller aspect ratios. Crystallographic analysis of the magnetosomes of MV-2 revealed an elongated hexagonal habit based on a prism of {110} faces capped by {111} …

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Electron Microscopy Study Of Magnetosomes In A Cultured Coccoid Magnetotactic Bacterium, Fiona C. Meldrum, Stephen Mann, Brigid R. Heywood, Richard B. Frankel, D. A. Bazyllinski Mar 1993

Electron Microscopy Study Of Magnetosomes In A Cultured Coccoid Magnetotactic Bacterium, Fiona C. Meldrum, Stephen Mann, Brigid R. Heywood, Richard B. Frankel, D. A. Bazyllinski

Physics

Intracellular magnetite (Fe3O4) crystals produced by the magnetotactic bacterium MC-1 were analyzed by transmission electron microscopy (TEM). Strain MC-1 represents the first-reported isolation of a coccoid magnetotactic bacterium in axenic culture. The magnetosomes of this bacterium displayed a pseudo-hexagonal prismatic habit, were elongated along the crystallographic direction, and were truncated by {111}, {100} and {110} faces. The presence of {111} truncations represents a modification of the magnetosome morphology previously determined for those in other coccoid bacteria. Study of immature crystals produced by strain MC-1 showed that the crystal morphology was controlled even at early stages of …

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Distinguishing A Charged Higgs Signal From A Heavy Wr Signal, David I. Kaiser Mar 1993

Distinguishing A Charged Higgs Signal From A Heavy Wr Signal, David I. Kaiser

Dartmouth Scholarship

It is shown that non-Standard Model bosons should obey an observable asymmetry in their decays to taus. This asymmetry enables a distinction to be made between charged Higgsboson signalsand heavy right-handed Wboson signals,by reconstructing the orientation of the z with respect to the beam axis.

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Ta(110) Surface And Subsurface Core-Level Shifts And 4f7/2 Lineshapes, D. Mark Riffe, G. K. Wertheim Mar 1993

Ta(110) Surface And Subsurface Core-Level Shifts And 4f7/2 Lineshapes, D. Mark Riffe, G. K. Wertheim

All Physics Faculty Publications

High-resolution 4f core-level spectra of the Ta(110) surface region have been obtained at 80 and 300 K with 70- and 100-eV synchrotron radiation. The data show that the subsurface core-level binding-energy shift (compared to deeper-lying atoms) for a close-packed bcc(110) surface can be substantial: 65±15 meV for the first underlayer atoms of Ta(110). The surface core-level shift is 360±12 meV at 80 K and decreases by 13±2 meV at 300 K. Final-state screening in both the bulk and surface layers is well described by a constant singularity index of 0.133±0.012. An enhanced phonon broadening at the surface corresponds to a …

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On Spontaneous Symmetry Breaking In Discretized Light Cone Field Theory, David G. Robertson Mar 1993

On Spontaneous Symmetry Breaking In Discretized Light Cone Field Theory, David G. Robertson

Physics Faculty Scholarship

The problem of spontaneous symmetry breaking in scalar field theories quantized on the light cone is considered. Within the framework of "discretized" light-cone field theory, a constrained zero mode of the scalar field, which is necessary for obtaining a consistent dynamics, is responsible for supporting nonzero vacuum expectation values classically. This basic structure is shown to carry over to the quantum theory as well, and the consistency of the formalism is checked in an explicit perturbative calculation in (1+1)-dimensional φ4 theory.

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Influence Of Retardation On The Vibrational Wave Function And Binding Energy Of The Helium Dimer, Fei Luo, Geunsik Kim, George C. Mcbane, Clayton F. Giese, W. Ronald Gentry Mar 1993

Influence Of Retardation On The Vibrational Wave Function And Binding Energy Of The Helium Dimer, Fei Luo, Geunsik Kim, George C. Mcbane, Clayton F. Giese, W. Ronald Gentry

Peer Reviewed Articles

Because of the extremely small binding energy of the helium dimer, the nuclear wave function is delocalized over an extremely large range of separations. One might therefore expect the properties of this extraordinary species to be sensitive to the potential at very large internuclear distances, r, where relativistic corrections to the usual van der Waals interaction may be important. We have estimated the effect of retardation, which changes the r-6 dependence of the potential to r-7 in the limit of large r, and have found that the binding energy and expectation value (r) are …

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Heavy Quark Solitons, Joseph Schechter, Kumar S. Gupta, M. Arshad Momen, A. Subbaraman Mar 1993

Heavy Quark Solitons, Joseph Schechter, Kumar S. Gupta, M. Arshad Momen, A. Subbaraman

Physics - All Scholarship

We investigate the heavy baryons which arise as solitonic excitations in a ``heavy meson" chiral Lagrangian which includes the light vector particles. It is found that the effect of the light vectors may be substantial. We also present a simple derivation which clearly shows the connection to the Callan-Klebanov approach.

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Relative Effectiveness Of Mixed Radiation Fields, Robert Katz Mar 1993

Relative Effectiveness Of Mixed Radiation Fields, Robert Katz

Robert Katz Publications

For all one-hit detectors the relative effectiveness of a mixed radiation field may be found as the dose-weighted average of the relative effectiveness of its components, segregated according to the atomic number Z and the energy T. We emphasize that this procedure is incorrect for mammalian cells, whatever the nature of the segregation.

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Low Temperature Phase Formation Of Tl-Based Superconducting Thin Films In Reduced Oxygen Atmosphere, C.Y. Wu, F. Foong, Sy_Hwang Liou, J.C. Ho Mar 1993

Low Temperature Phase Formation Of Tl-Based Superconducting Thin Films In Reduced Oxygen Atmosphere, C.Y. Wu, F. Foong, Sy_Hwang Liou, J.C. Ho

Sy-Hwang Liou Publications

Tl-Ba-Cu-Cu-O superconducting thin films were prepared by magnetron sputtering with postannealing in a reduced oxygen atmosphere. Single-phase Tl2Ba2Ca2Cu3Oχ can form on the MgO substrate at 800°C under P(O2)≈0.1 atm. However, the phase formation temperature can be affected by the starting composition of the film. Tl1Ba2 Ca2Cu2Oχ phase can be formed by simply lowering the Tl2O pressure. The thermal stability of Tl1Ba2Ca2Cu3Oχ phase was studied by resistivity measurements at high temperatures.

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Angular Distributions For Near-Threshold (E,2E) Processes For Li And Mg, Cheng Pan, Anthony F. Starace Mar 1993

Angular Distributions For Near-Threshold (E,2E) Processes For Li And Mg, Cheng Pan, Anthony F. Starace

Anthony F. Starace Publications

Distorted-wave calculations of the triply differential cross sections for electron-impact ionization of Li and Mg are presented for the coplanar, θ12=π geometry in which the final-state electrons share 2 eV of excess energy equally. Our theoretical approach, described in detail elsewhere [C. Pan and A. F. Starace, Phys. Rev. A 45, 4588 (1992)], employs a partial-wave expansion of initial- and final-state wave functions, treats direct and exchange interactions of initial and final electrons with the target core, and treats the final-state interaction between the two continuum electrons by a screening potential. Li and Mg targets are found to …

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The Behlen Observatory Variable Star Survey, Paper Iii, Edward G. Schmidt, John R. Chab, Darwin E. Reiswig Mar 1993

The Behlen Observatory Variable Star Survey, Paper Iii, Edward G. Schmidt, John R. Chab, Darwin E. Reiswig

Edward Schmidt Publications

Finding charts, accurate coordinates and light curves are presented for 146 variable stars including three which are newly discovered. Parameters descriptive of the light curves arc tabulated including periods for eight stars which lacked them in the General Catalogue of Variable Stars (the GCVS). GCVS periods of twelve stars were found to be seriously in error. The classification of the stars is discussed. Revisions or refinements of the classifications from the General Catalogue of Variable of Stars are suggested for thirty-one stars. Of the nineteen stars classified as Bailey type c RR Lyrae stars in the General Catalogue of Variable …

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Doubly Differential Electron-Production Cross Sections For 200- 1500-Ev E- +H2 Collisions, M. Eugene Rudd, K. W. Hollman, J. K. Lewis, D. L. Johnson, R. R. Porter, E. L. Fagerquist Mar 1993

Doubly Differential Electron-Production Cross Sections For 200- 1500-Ev E- +H2 Collisions, M. Eugene Rudd, K. W. Hollman, J. K. Lewis, D. L. Johnson, R. R. Porter, E. L. Fagerquist

M. Eugene Rudd Publications

Ionization cross sections differential in the angle and energy of the detected electrons were measured for electron impact on hydrogen gas at 200, 500, 1000, and 1500 eV. Measurements were made from 15°-150° and from a few eV to T -I where T is the primary electron energy and I the ionization potential of hydrogen. The results are compared to earlier measurements and to available calculations.

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The Measurement Of Astronomical Parallaxes With Ccd Imaging Cameras On Small Telescopes, Stephen J. Ratcliff, Thomas J. Balonek, Laurence A. Marschall, David L. Dupuy, Carlton R. Pennypacker, Ritu Verma, Anastasia Alexov, Vivian Bonney Mar 1993

The Measurement Of Astronomical Parallaxes With Ccd Imaging Cameras On Small Telescopes, Stephen J. Ratcliff, Thomas J. Balonek, Laurence A. Marschall, David L. Dupuy, Carlton R. Pennypacker, Ritu Verma, Anastasia Alexov, Vivian Bonney

Physics and Astronomy Faculty Publications

Small telescopes equipped with charge-coupled device (CCD) imaging cameras are well suited to introductory laboratory exercises in positional astronomy (astrometry). An elegant example is the determination of the parallax of extraterrestrial objects, such as asteroids. For laboratory exercises suitable for introductory students, the astronomical hardware needs are relatively modest, and under the best circumstances, the analysis requires little more than arithmetic and a microcomputer with image display capabilities. Results from the first such coordinated parallax observations of asteroids ever made are presented. In addition, procedures for several related experiments, involving single-site observations and/or parallaxes of earth-orbiting artificial satellites, are outlined.

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Optical Activity In The Smectic-A Phase Of A Highly Chiral Liquid Crystal, Joshua D. Rosenzweig , '93, Peter J. Collings Mar 1993

Optical Activity In The Smectic-A Phase Of A Highly Chiral Liquid Crystal, Joshua D. Rosenzweig , '93, Peter J. Collings

Physics & Astronomy Faculty Works

Optical-activity measurements in the smectic-A phase of various chiral-racemic mixtures of S-4-(2'-methylbutyl)phenyl-4'-n-octylbiphenyl-4-carboxylate (CE8) demonstrate that contributions from fluctuations in more than one chiral structural mode are important near the transition to the smectic-C* phase. Although these results are similar to earlier measurements in the isotropic phase of highly chiral liquid crystals, previous theoretical work points out that the nature of these fluctuations and the reason for the importance of the second structural mode are very different. Because the present measurements are reported on mixtures of varying chirality, they provide a stringent test of the theory. Agreement between theory and experiment …

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Evolution Of Atomic Motion In An Intense Standing Wave, Jian Chen, J. Greg Story, Randall G. Hulet Mar 1993

Evolution Of Atomic Motion In An Intense Standing Wave, Jian Chen, J. Greg Story, Randall G. Hulet

Physics Faculty Research & Creative Works

We have investigated the effect of the dipole force and its fluctuation on the motion of Li atoms in an intense, one-dimensional, near-resonant standing light wave. The duration of the interaction of the atoms with the standing wave was varied from several tens of spontaneous-emission lifetimes to several hundreds. For a standing-wave frequency blue detuned from resonance, diffusive heating can dominate the time-averaged dissipative dipole force so that there is no steady-state momentum distribution. However, for sufficiently large blue detunings, the rate of diffusion is so slow that the resulting distribution approaches a quasisteady state. For red detunings, the diffusion …

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Low-Frequency Feature In The First-Order Raman Spectrum Of Amorphous Carbon, David D. Allred, Qi Wang, Jesus González-Hernández Mar 1993

Low-Frequency Feature In The First-Order Raman Spectrum Of Amorphous Carbon, David D. Allred, Qi Wang, Jesus González-Hernández

Faculty Publications

In the first-order Raman spectrum of amorphous carbon (a-C) there is a low-frequency feature in the 200-900-cm-1 region. This feature is characteristic of the highly disordered amorphous-carbon materials. We note that the intensity of this feature is very sensitive to the thermal history of samples, thus suggesting that it is an important measure of the degree of disorder of the a-C materials. We also discuss the relationship between this feature and the phonon density of states of graphite.

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Exponential Growth Of An Unstable L=1 Diocotron Mode For A Hollow Electron Column In A Warm-Fluid Model, S. Neil Rasband, Ross L. Spencer, Richard R. Vanfleet Mar 1993

Exponential Growth Of An Unstable L=1 Diocotron Mode For A Hollow Electron Column In A Warm-Fluid Model, S. Neil Rasband, Ross L. Spencer, Richard R. Vanfleet

Faculty Publications

Numerical investigations of a warm-fluid model with an isothermal equation of state for the perpendicular dynamics of an axisymmetric, magnetically confined pure electron plasma predict an exponentially unstable, l=1, diocotron mode for hollow density profiles. The unstable mode can be identified with a stable, nonsmooth mode that exists in cold drift models but which is destabilized by finite temperature effects. The unstable mode has many properties similar to the experimental results reported by Driscoll [Phys. Rev. Lett. 64, 645 (1990)].

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Self-Referenced Speckle Holography (Srsh) Image Reconstruction Performance, John R. Devey Mar 1993

Self-Referenced Speckle Holography (Srsh) Image Reconstruction Performance, John R. Devey

Theses and Dissertations

The Speckle Holography technique uses a series of short exposure images and associated wave front sensor measurements to reconstruct astronomical images. The reconstruction technique effectively boosts the amplitude of high spatial frequencies to allow for finer resolution of astronomical objects. A simulation package that calculates the optical transfer function (OTF) of a telescopic system was previously developed for the Phillips Laboratory. This software was modified slightly to provide the Speckle Holography system transfer function (STF) for a telescopic system under varying seeing conditions.

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Characterization Of Laboratory Generated Turbulence By Optical Phase Measurements, Eric P. Magee Mar 1993

Characterization Of Laboratory Generated Turbulence By Optical Phase Measurements, Eric P. Magee

Theses and Dissertations

The resolution achieved by an optical imaging system in the presence of the random effects of the atmosphere is severely degraded from the theoretical diffraction limit. Techniques exist for recovering near diffraction limited performance of an imaging system in the presence of atmospheric turbulence. As opposed to laboratory testing, testing image enhancement techniques in the Earth's atmosphere imposes many limitations. Unfavorable weather conditions could result in the loss of time and money invested in conducting the experiments. With a properly characterized turbulence generator, with statistics that match those of the atmosphere, experimental testing of image enhancement techniques can be conducted …

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Construction And Testing Of A Neutron And Gamma Spectrometry System Using Pulse Shape Discrimination With An Organic Scintillator, Robert S. Pope Mar 1993

Construction And Testing Of A Neutron And Gamma Spectrometry System Using Pulse Shape Discrimination With An Organic Scintillator, Robert S. Pope

Theses and Dissertations

The goal of this thesis was to construct and test a neutron detector to measure the energy spectrum of 1 to 14-MeV neutrons in the presence of gammas. A spectrometer based on the process of pulse shape discrimination (PSD) was constructed, in which the scintillator NE-213 was used. The primary neutron/ gamma sources used were 78-mCi and 4.7-Ci 239PuBe sources, while 4.7-µCi and 97.6-µCi 22Na gamma sources were used for energy calibration and additional testing of the detector. Proton recoil spectra and Compton electron spectra were unfolded with the neutron and gamma unfolding code FORIST to generate the …

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Design And Performance Evaluation Of A Gas Chromatograph Micromachined In A Single Crystal Silicon Substrate, Rocky R. Reston Mar 1993

Design And Performance Evaluation Of A Gas Chromatograph Micromachined In A Single Crystal Silicon Substrate, Rocky R. Reston

Theses and Dissertations

This investigation designed and developed a miniature gas chromatograph (GC) using silicon micromachining techniques. The GC is composed of a miniature sample injector (10 µl sample loop); a 0.9 m long, rectangular-shaped (300 µm width and 10 micrometers height) capillary column coated with a 0.2 µm thick copper phthalocyanine (CuPc) stationary phase; and a dual-detector scheme incorporating a CuPc-coated chemiresistor and a 125 µm diameter thermal conductivity detector bead. Micromachining was employed to fabricate the sample injector interface, the GC column, and the dual-detector cavity. A novel processing technique was developed to sublime the CuPc stationary phase coating on the …

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Magnetoresistance Of Multilayered Structures For Currents Perpendicular To The Plane Of The Layers, Horacio E. Camblong Feb 1993

Magnetoresistance Of Multilayered Structures For Currents Perpendicular To The Plane Of The Layers, Horacio E. Camblong

Physics and Astronomy

While most transport measurements on multilayered structures have been done for currents in the plane of the layers, there is an emerging interest in the geometry where the currents are perpendicular to the plane of the layers. We discuss the field and current patterns in these two cases. For the latter, the elastic mean free path is not a relevant length scale; rather, it is the spin-flip mean free path that is important. In the case of currents perpendicular to the plane of the layers, one must distinguish between models which allow spin mixing of the currents and those in …

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Multiple Evolutionary Origins Of Magnetotaxis In Bacteria, Edward F. Delong, Richard B. Frankel, Dennis A. Bazylinski Feb 1993

Multiple Evolutionary Origins Of Magnetotaxis In Bacteria, Edward F. Delong, Richard B. Frankel, Dennis A. Bazylinski

Physics

Magnetosomes are intracellular, iron-rich, membrane-enclosed magnetic particles that allow magnetotactic bacteria to orient in the earth's geomagnetic field as they swim. The magnetosomes of most magnetotactic bacteria contain iron oxide particles, but some magnetotactic species contain iron sulfide particles instead. Phylogenetic analyses of small subunit ribosomal RNA sequences showed that all known magnetotactic bacteria of the iron oxide type are associated with the a subgroup of the Proteobacteria in the domain Bacteria. In contrast, uncultured magnetotactic bacteria of the iron sulfide type are specifically related to the dissimilatory sulfate-reducing bacteria within the δ subdivision of the Proteobacteria. These findings indicate …

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Properties Of Photon Density Waves In Multiple-Scattering Media, Bruce J. Tromberg, Lars O. Svaasand, Tsong-Tseh Tsay, Richard C. Haskell Feb 1993

Properties Of Photon Density Waves In Multiple-Scattering Media, Bruce J. Tromberg, Lars O. Svaasand, Tsong-Tseh Tsay, Richard C. Haskell

All HMC Faculty Publications and Research

Amplitude-modulated light launched into multiple-scattering media, e.g., tissue, results in the propagation of density waves of diffuse photons. Photon density wave characteristics in turn depend on modulation frequency (ω) and media optical properties. The damped spherical wave solutions to the homogeneous form of the diffusion equation suggest two distinct regimes of behavior: (1) a highfrequency dispersion regime where density wave phase velocity Vp has a ω dependence and (2) a low-frequency domain where Vp is frequency independent. Optical properties are determined for various tissue phantoms by fitting the recorded phase (Φ) and modulation (m) response to …

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