Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network™

Open Access. Powered by Scholars. Published by Universities.®

2002

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 12121 - 12150 of 14400

Full-Text Articles in Entire DC Network

Principles Of Forecasting: A Handbook For Researchers And Practitioners, Jaishankar Ganesh Jan 2002

Principles Of Forecasting: A Handbook For Researchers And Practitioners, Jaishankar Ganesh

Faculty Bibliography 2000s

No abstract provided.

Go to article

Identification Of Omi/Htra-2 As A Mitochondrial Apoptotic Serine Protease That Disrupts Inhibitor Of Apoptosis Protein-Caspase Interaction, Ramesh Hegde, Srinivasa M. Srinivasula, Zhi-Jia Zhang, Richard Wassell, Rula Mukattash, Lucia Cilenti, Garrett Dubois, Yuri Lazebnik, Anthonis S. Zervos, Teresa Fernandes-Alnemri, Emad S. Alnemri Jan 2002

Identification Of Omi/Htra-2 As A Mitochondrial Apoptotic Serine Protease That Disrupts Inhibitor Of Apoptosis Protein-Caspase Interaction, Ramesh Hegde, Srinivasa M. Srinivasula, Zhi-Jia Zhang, Richard Wassell, Rula Mukattash, Lucia Cilenti, Garrett Dubois, Yuri Lazebnik, Anthonis S. Zervos, Teresa Fernandes-Alnemri, Emad S. Alnemri

Faculty Bibliography 2000s

To identify human proteins that bind to the Smac and caspase-9 binding pocket on the baculoviral inhibitor of apoptosis protein (IAP) repeat 3 (BIR3) domain of human XIAP, we used BIR3 as an affinity reagent, followed by elution with the BIR3 binding peptide AVPIA microsequencing, and mass spectrometry. The mature serine protease Omi (also known as HtrA2) was identified as a mitochondrial direct BIR3-binding protein and a caspase activator. Like mature Smac (also known as Diablo), mature Omi contains a conserved LAP-binding motif (AVPS) at its N terminus, which is exposed after processing of its N-terminal mitochondrial targeting sequence upon …

Go to article

The Birth Of Homological Algebra, Peter Hilton Jan 2002

The Birth Of Homological Algebra, Peter Hilton

Faculty Bibliography 2000s

No abstract provided.

Go to article

Theoretically Exact Filtered Backprojection-Type Inversion Algorithm For Spiral Ct, Alexander Katsevich Jan 2002

Theoretically Exact Filtered Backprojection-Type Inversion Algorithm For Spiral Ct, Alexander Katsevich

Faculty Bibliography 2000s

Proposed is a theoretically exact formula for inversion of data obtained by a spiral computed tomography ( CT) scan with a two- dimensional detector array. The detector array is supposed to be of limited extent in the axial direction. The main property of the formula is that it can be implemented in a truly filtered backprojection fashion. First, one performs shift- invariant filtering of a derivative of the cone beam projections, and, second, the result is backprojected in order to form an image. Another property is that the formula solves the so- called long object problem. Limitations of the algorithm …

Go to article

Comparative Evaluation Of Protective Coatings And Focused Ion Beam Chemical Vapor Deposition Processes, B. W. Kempshall, L. A. Giannuzzi, B. I. Prenitzer, F. A. Stevie, S. X. Da Jan 2002

Comparative Evaluation Of Protective Coatings And Focused Ion Beam Chemical Vapor Deposition Processes, B. W. Kempshall, L. A. Giannuzzi, B. I. Prenitzer, F. A. Stevie, S. X. Da

Faculty Bibliography 2000s

Dual-beam instruments incorporate both an electron column and an ion column into a single instrument, and therefore allow the chemical vapor deposition (CVD) process to be either ion- or electron-beam assisted. Damage has been observed in the surface layers of specimens in which ion-beam assisted CVD processes have been employed. Cross-section transmission electron microscopy (TEM) has been used to compare (100) Si substrates on which Pt metal lines have been grown by ion- and electron-beam assisted CVD processes. The micrographs show that a 30 keV Ga+ ion beam, a 5 keV ion beam, and a 3 keV electron beam imparts …

Go to article

Second-Harmonic Generation Tuning Curves With Narrow, High-Intensity Beams For Quasiphase-Matched Potassium Titanyl Phosphate, Hongki Kim, Ladislav Jankovic, George Stegeman, Mordechai Katz, Silvia Carrasco, Lluis Torner Jan 2002

Second-Harmonic Generation Tuning Curves With Narrow, High-Intensity Beams For Quasiphase-Matched Potassium Titanyl Phosphate, Hongki Kim, Ladislav Jankovic, George Stegeman, Mordechai Katz, Silvia Carrasco, Lluis Torner

Faculty Bibliography 2000s

The tuning curves with temperature and incidence angle for second-harmonic generation were asymmetrically distorted and broadened with increasing intensity for narrow input fundamental beams in periodically poled KTiOPO4. Multiple phenomena including mutual self-focusing of the fundamental and harmonic, cascading, quadratic soliton generation, and artificially induced walk-off (for light incidence away from the poling axis) contribute, in good agreement with theory.

Go to article

Influence Of Elevated Co2 On The Fungal Community In A Coastal Scrub Oak Forest Soil Investigated With Terminal-Restriction Fragment Length Polymorphism Analysis, Morten Klamer, Michael S. Roberts, Lanfang H. Levine, Bert G. Drake, Jay L. Garland Jan 2002

Influence Of Elevated Co2 On The Fungal Community In A Coastal Scrub Oak Forest Soil Investigated With Terminal-Restriction Fragment Length Polymorphism Analysis, Morten Klamer, Michael S. Roberts, Lanfang H. Levine, Bert G. Drake, Jay L. Garland

Faculty Bibliography 2000s

Sixteen open-top chambers (diameter, 3.66 m) were established in a scrub oak habitat in central Florida where vegetation was removed in a planned burn prior to chamber installation. Eight control chambers have been continuously exposed to ambient air and eight have been continuously exposed to elevated CO2 at twice-ambient concentration (similar to700 ppm) for 5 years. Soil cores were collected from each chamber to examine the influence of elevated atmospheric CO, on the fungal community in different soil fractions. Each soil sample was physically fractionated into bulk soil, rhizosphere soil, and roots for separate analyses. Changes in relative fungal biomass …

Go to article

Effects Of Environmental And Land Use Regulation In The Oil And Gas Industry Using The Wyoming Checkerboard As An Experimental Design (Retracted Article. See Vol 97, Pg 1032, 2007), Shelby Gerking, William E. Morgan Jan 2002

Effects Of Environmental And Land Use Regulation In The Oil And Gas Industry Using The Wyoming Checkerboard As An Experimental Design (Retracted Article. See Vol 97, Pg 1032, 2007), Shelby Gerking, William E. Morgan

Faculty Bibliography 2000s

No abstract provided.

Go to article

Investigation Of Recycled Concrete Made With Limestone Aggregate For A Base Course In Flexible Pavement, Shiou-San Kuo, Hesham S. Mahgoub, Abdenour Nazef Jan 2002

Investigation Of Recycled Concrete Made With Limestone Aggregate For A Base Course In Flexible Pavement, Shiou-San Kuo, Hesham S. Mahgoub, Abdenour Nazef

Faculty Bibliography 2000s

The research objectives were to investigate the feasibility of using recycled concrete aggregate (RCA) as a base course material in asphalt pavement, to evaluate the physical properties of RCA, and to develop practical and reliable guidelines and specifications. The tasks included literature review, sample collection, laboratory testing, accelerated performance testing and pavement distresses monitoring, failing weight deflectometer (FWD) test, theoretical analysis of pavement, and development of guidelines and specifications for the use of Florida RCA. Three test sections of asphalt pavement were constructed at the University of Central Florida's circular accelerated test track. Two sections of different thicknesses were constructed …

Go to article

X-Ray Photoelectron Spectroscopic Investigation Of Surface Chemistry Of Ternary As-S-Se Chalcogenide Glasses, Wenyan Li, Sudipta Seal, Cedric Lopez, Kathleen A. Richardson Jan 2002

X-Ray Photoelectron Spectroscopic Investigation Of Surface Chemistry Of Ternary As-S-Se Chalcogenide Glasses, Wenyan Li, Sudipta Seal, Cedric Lopez, Kathleen A. Richardson

Faculty Bibliography 2000s

Chalcogenide glasses belong to an important class of materials, due to their good infrared transmission, and low-phonon energy as compared to other oxide glasses. Structural and chemical variations imposed by glass processing conditions, e.g., film deposition, can lead to changes in the linear and nonlinear optical properties. X-ray photoelectron spectroscopy (XPS) has been employed to study As-S-Se glasses of differing chemical compositions, in the film and the bulk form, to understand any variations in chemical bond configuration and their electronic structure. The molecular environments of As and Se for As-S-Se samples with varying S/Se ratio (fixed As content) and As …

Go to article

Polymer Depletion Interaction Between A Colloid Particle And A Wall: A Monte Carlo Study, Andrey Milchev, Aniket Bhattacharya Jan 2002

Polymer Depletion Interaction Between A Colloid Particle And A Wall: A Monte Carlo Study, Andrey Milchev, Aniket Bhattacharya

Faculty Bibliography 2000s

An off-lattice bead-spring model of a polymer solution in a container with impenetrable walls is used to study the depletion interaction of a colloid particle with the planar wall by means of a Monte Carlo simulation. As expected, this interaction is found to depend essentially on the ratio rho=R/R-g of the particle radius R to the mean radius of gyration R-g of the polymer chains in the case of dilute and semidilute solutions. For large particle to polymer size ratio rho > 1 this effective force is attractive and decreases steadily with growing distance D of the colloid from the wall. …

Go to article

Regulation Of Prostasin By Aldosterone In The Kidney, Takefumi Narikiyo, Kenichiro Kitamura, Masataka Adachi, Taku Miyoshi, Kozo Iwashita, Naoki Shiraishi, Hiroshi Nonoguchi, Li-Mei Chen, Karl X. Chai, Julie Chao, Kimio Tomita Jan 2002

Regulation Of Prostasin By Aldosterone In The Kidney, Takefumi Narikiyo, Kenichiro Kitamura, Masataka Adachi, Taku Miyoshi, Kozo Iwashita, Naoki Shiraishi, Hiroshi Nonoguchi, Li-Mei Chen, Karl X. Chai, Julie Chao, Kimio Tomita

Faculty Bibliography 2000s

Prostasin is a serine protease present in mammalian urine that increases the activity of the epithelial sodium channel (ENaC) when the two are coexpressed in Xenopus oocytes. To determine if aldosterone, one of the principal regulators of urinary Na reabsorption by the distal nephron, affects prostasin expression, we examined prostasin mRNA and protein in a cultured mouse cortical collecting duct cell line (M-1), whole rats, and patients with primary aldosteronism. Aldosterone treatment of M-1 cells substantially increased prostasin expression and stimulated Na-22 uptake. Urinary excretion of prostasin in rats that were infused with aldosterone likwise increased by similar to4-fold when …

Go to article

Correlations Between Spatially Resolved Raman Shifts And Dislocation Density In Gan Films, G. Nootz, A. Schulte, L. Chernyak, A. Osinky, J. Jasinski, M. Benamara, Z. Liliental-Weber Jan 2002

Correlations Between Spatially Resolved Raman Shifts And Dislocation Density In Gan Films, G. Nootz, A. Schulte, L. Chernyak, A. Osinky, J. Jasinski, M. Benamara, Z. Liliental-Weber

Faculty Bibliography 2000s

Spatially resolved Raman spectra were measured on thick GaN samples with known dislocation density grown by hydride vapor phase epitaxy. The frequencies of the E-2 (high) and E-1 (transverse optical) phonons shift to lower wave number over a distance of 30 mum from the sapphire substrate/GaN interface. The shifts are linearly correlated with the dislocation density suggesting that the strain due to the lattice mismatch at the interface determines both quantities.

Go to article

Existence And Properties Of Quadratic Solitons In Anisotropic Media: Variational Approach, Sergey V. Polyakov, George I. Stegeman Jan 2002

Existence And Properties Of Quadratic Solitons In Anisotropic Media: Variational Approach, Sergey V. Polyakov, George I. Stegeman

Faculty Bibliography 2000s

Stationary quadratic solitons associated with second harmonic generation in optically anisotropic media have been investigated both numerically and analytically using the variational approach. The solitons were found to have elliptical shapes, both for the fundamental and second harmonic, and their approximate beam waists and amplitudes as a function of the anisotropy and the soliton parameter were found. The important limits of anisotropic diffraction were compared to the well-known model of isotropic diffraction. The stability of anisotropic solitons was addressed via the Vakhitov-Kolokolov criterion and the regions of parameter space for which the solitons are stable were identified. Direct numerical simulations …

Go to article

Spatially Resolved Microrheology Using Localized Coherence Volumes, G. Popescu, A. Dogariu, R. Rajagopalan Jan 2002

Spatially Resolved Microrheology Using Localized Coherence Volumes, G. Popescu, A. Dogariu, R. Rajagopalan

Faculty Bibliography 2000s

We propose an optical technique, based on dynamic light scattering, for investigating the local rheological response of a complex fluid over a frequency range larger than that provided by standard mechanical instrumentation. The low-coherence radiation used in a fiber optics configuration allows the measurements to be confined to a small volume around a tenth of a picoliter. The ability of the method to accurately measure both loss and storage moduli has been tested using both simple Newtonian liquids and viscoelastic, complex fluids. The possibility to monitor liquid-gel transitions in polymer solutions has also been demonstrated. The unique capability of the …

Go to article

Reflective Reversed-Mode Polymer Stabilized Cholesteric Texture Light Switches, Hongwen Ren, Shin-Tson Wu Jan 2002

Reflective Reversed-Mode Polymer Stabilized Cholesteric Texture Light Switches, Hongwen Ren, Shin-Tson Wu

Faculty Bibliography 2000s

Light-switching behavior of reflective reserved-mode polymer-stabilized-cholesteric-texture (PSCT) was analyzed and validated experimentally. Our results indicate that the reflective reversed-mode PSCT offers a much higher contrast ratio and lower operating voltage than its transmissive counterpart. Effects of cell gap, birefringence, and pitch length on the contrast ratios of the reversed-mode PSCT cells were investigated. Potential applications of this device as variable optical attenuator and light shutter for telecommunication are emphasized.

Go to article

Anisotropic Liquid Crystal Gels For Switchable Polarizers And Displays, Hongwen Ren, Shin-Tson Wu Jan 2002

Anisotropic Liquid Crystal Gels For Switchable Polarizers And Displays, Hongwen Ren, Shin-Tson Wu

Faculty Bibliography 2000s

An anisotropic liquid crystal gel with low operating voltage, high contrast ratio, broad bandwidth, wide viewing angle, and fast response time was demonstrated. In the voltage-off state, the gel is highly transparent. When the gel is activated by an electric field, light scattering occurs for the polarization along the molecular axis. By incorporating a lambda/4 film between the gel and a reflector, this reflective device is useful for modulating unpolarized light. Potential applications of such anisotropic gel as a broadband switchable polarizer, reflective display, and transflective display are emphasized.

Go to article

Inhomogeneous Nanoscale Polymer-Dispersed Liquid Crystals With Gradient Refractive Index, Hongwen Ren, Shin-Tson Wu Jan 2002

Inhomogeneous Nanoscale Polymer-Dispersed Liquid Crystals With Gradient Refractive Index, Hongwen Ren, Shin-Tson Wu

Faculty Bibliography 2000s

Inhomogeneous polymer-dispersed liquid crystal devices having gradient droplet distribution were fabricated and their phase retardation characterized. The gradient refractive index profile can be used as switchable prism gratings, and positive and negative lenses with tunable focal lengths. Such a tunable electronic lens is a broadband device and can be used for unpolarized light.

Go to article

Down-Regulation Of Cdc6, A Cell Cycle Regulatory Gene, In Prostate Cancer, Liza D. Robles, Andra R. Frost, Monica Davila, Alan D. Hutson, William E. Grizzle, Ratna Chakrabarti Jan 2002

Down-Regulation Of Cdc6, A Cell Cycle Regulatory Gene, In Prostate Cancer, Liza D. Robles, Andra R. Frost, Monica Davila, Alan D. Hutson, William E. Grizzle, Ratna Chakrabarti

Faculty Bibliography 2000s

CDC6 plays a critical role in regulation of the onset of DNA replication in eukaryotic cells. We have found that Cdc6 expression is down-regulated in prostate cancer as detected by semiquantitative reverse transcriptase-PCR of prostate cell lines and laser-captured microdissected prostate tissues. This result was substantiated by immunohistochemical analysis of paraffin-embedded tissue sections and immunoblot analysis of benign (BPH-1) and adenocarcinomatous prostatic cells. Furthermore, a 100-fold reduction in the transcription efficiency of the Cdc6 promoter-luciferase construct was noted in the metastatic PC3 cells compared with that in BPH-1 cells. Concentration of the E2F and Oct1 transcription factors that have putative …

Go to article

Method Of Adjustments Versus Method Of Constant Stimuli In The Quantification Of Accuracy And Precision Of Rendered Depth In Head-Mounted Displays, J. P. Rolland, C. Meyer, K. Arthur, E. Rinalducci Jan 2002

Method Of Adjustments Versus Method Of Constant Stimuli In The Quantification Of Accuracy And Precision Of Rendered Depth In Head-Mounted Displays, J. P. Rolland, C. Meyer, K. Arthur, E. Rinalducci

Faculty Bibliography 2000s

The utilization of head-mounted displays (HMDs) in high-end applications such as medical, engineering, and scientific visualization necessitates that the position of objects be rendered accurately and precisely. Accuracy and precision of rendered depth for near-field visualization were measured in a custom-designed bench prototype HMD. Experimental results were compared to theoretical predictions established from a computational model for rendering and presenting virtual images by Robinett and Rolland (1992). Such a theoretical model provided the necessary graphics transformations required so that rendered virtual objects be perceived at the rendered depth in binocular HMDs, Three object shapes of various sizes were investigated under …

Go to article

Photoelectron Angular Distribution Of 3s Photoionization Of Atomic Chlorine, H. P. Saha Jan 2002

Photoelectron Angular Distribution Of 3s Photoionization Of Atomic Chlorine, H. P. Saha

Faculty Bibliography 2000s

The photoelectron angular distribution asymmetry parameter beta for 3s electrons of atomic chlorine has been calculated using the multiconfiguration Hartree-Fock method for both bound and continuum wave functions. It is determined in the electric dipole approximation within the framework of the angular-momentum-transfer formulation. The effects of electron correlation are investigated, and it is shown that electron correlations are very important for beta values corresponding to both P-3 and P-1 ionic states. Our results confirm the recent experimental prediction that beta for s subshell photoionization in open-shell atoms, is, in general, term and photon energy dependent and, in addition, in the …

Go to article

Reflective Liquid-Crystal Display Using An In-Plane-Switching Super-Twisted Nematic Cell, Yubao Sun, Hongmei Ma, Zhidong Zhang, Shin-Tson Wu Jan 2002

Reflective Liquid-Crystal Display Using An In-Plane-Switching Super-Twisted Nematic Cell, Yubao Sun, Hongmei Ma, Zhidong Zhang, Shin-Tson Wu

Faculty Bibliography 2000s

Two in-plane-switching (IPS) super-twisted nematic (STN) cells are proposed for reflective liquid-crystal displays. The IPS 180degrees-STN cell exhibits a normally black display with a relatively low-operating voltage, fast response time, and wide viewing angle. Potential applications for large screen reflective displays are foreseeable.

Go to article

Optimal Rubbing Angle For Reflective In-Plane-Switching Liquid Crystal Displays, Yubao Sun, Zhidong Zhang, Hongmei Ma, Xinyu Zhu, Shin-Tson Wu Jan 2002

Optimal Rubbing Angle For Reflective In-Plane-Switching Liquid Crystal Displays, Yubao Sun, Zhidong Zhang, Hongmei Ma, Xinyu Zhu, Shin-Tson Wu

Faculty Bibliography 2000s

Rubbing angle effects on the response time and optical threshold voltage of the reflective in-plane-switching homogeneous liquid crystal displays were analyzed. As the rubbing angle increases, the rise time decreases except that its operating voltage also increases. The optimal rubbing angle is around 30degrees-40degrees.

Go to article

Selective Mode Excitation By Nonaxial Evanescent Coupling For Bandwidth Enhancement Of Multimode Fiber Links, Laurent Vaissié, Eric G. Johnson Jan 2002

Selective Mode Excitation By Nonaxial Evanescent Coupling For Bandwidth Enhancement Of Multimode Fiber Links, Laurent Vaissié, Eric G. Johnson

Faculty Bibliography 2000s

We present an analysis of conditioned launch in a gradient-index multimode fiber (MMF). Selective mode excitation is obtained by nonaxial evanescent coupling between two highly asymmetric side-polished fibers: a single-mode fiber and an MMF with an exposed core. An index-matching slab improves the coupling efficiency and selectivity. The simulation shows that about 40% of modes, only high-order modes, are excited in the MMF. When compared to an overfilled launch, the bandwidth of a perturbed index fiber is enhanced more than twofold for large parameter variations.

Go to article

Angular Distributions Of The Atomic Scandium 3d And 4s Photoelectrons In The Region Of The 3p - > 3d Giant Resonance, S. B. Whitfield, T. Myers, M. Bjelland, R. Wehlitz, J. Jiménez-Mier, P. Olalde-Velasco, M. O. Krause Jan 2002

Angular Distributions Of The Atomic Scandium 3d And 4s Photoelectrons In The Region Of The 3p - > 3d Giant Resonance, S. B. Whitfield, T. Myers, M. Bjelland, R. Wehlitz, J. Jiménez-Mier, P. Olalde-Velasco, M. O. Krause

Faculty Bibliography 2000s

A determination of the angular distribution parameter beta of the 3d and 4s main lines of atomic scandium in the resonance region of the 3p-- > nd,ms excitations has been carried out using electron spectrometry in conjunction with monochromatized synchrotron radiation., These measurements reveal strong variations of beta8 throughout the entire resonance region, highlighting the complicated nature of the ionization process for this first and seemingly simple 3d transition metal. The beta values-of the photoelectrons resulting in 4s subshell, ionization deviate significantly from 2.0 in qualitative, but not-quantitative, agreement with recent many-body perturbation-theory calculations.

Go to article

Ve-Based Training Strategies For Acquiring Survey Knowledge, Bob G. Witmer, Wallace J. Sadowski, Neal M. Finkelstein Jan 2002

Ve-Based Training Strategies For Acquiring Survey Knowledge, Bob G. Witmer, Wallace J. Sadowski, Neal M. Finkelstein

Faculty Bibliography 2000s

Virtual environments (VEs) have been used successfully to train wayfinders to navigate through buildings and learn their layout. However, at the same time, for many, the VE deficiencies have reduced the effectiveness of VEs for training spatial tasks. In an effort to improve VE effectiveness, we conducted research to determine if certain unique capabilities of VEs could compensate for its deficiencies. Research participants were required to learn the layout or configuration of one floor of an office building as portrayed in a VE. To improve spatial learning, we developed three VE navigation training aids: local and global orientation cues, aerial …

Go to article

Perdeuterated Cyanobiphenyl Liquid Crystals For Infrared Applications, Shin-Tson Wu, Qiong-Hua Wang, Michael D. Kempe, Julia A. Kornfield Jan 2002

Perdeuterated Cyanobiphenyl Liquid Crystals For Infrared Applications, Shin-Tson Wu, Qiong-Hua Wang, Michael D. Kempe, Julia A. Kornfield

Faculty Bibliography 2000s

Perdeuterated 4'-pentyl-4-cyanobiphenyl (D5CB) was synthesized and its physical properties evaluated and compared to those of 5CB. D5CB retains physical properties similar to those of 5CB, such as phase transition temperatures, dielectric constants, and refractive indices. An outstanding feature of D5CB is that it exhibits a much cleaner and reduced infrared absorption. Perdeuteration, therefore, extends the usable range of liquid crystals to the mid infrared by significantly reducing the absorption in the near infrared, which is essential for telecom applications.

Go to article

Field Detection And Monitoring Of Explosives, Jehuda Yinon Jan 2002

Field Detection And Monitoring Of Explosives, Jehuda Yinon

Faculty Bibliography 2000s

Detection of explosives in situ is of major importance in several applications: finding hidden explosives in airport luggage and in mail; screening of personnel for concealed explosives; environmental monitoring of explosives-contaminated sites; and, detection of buried landmines. Mobile and hand-held detectors have been developed for the various applications. They can be sub-divided into three classes: vapor and particle detectors; radiation detectors; and, biochemical detectors. An overview of the various explosives detectors and their principles of operation is presented. (C) 2002 Published by Elsevier Science B.V. All rights reserved.

Go to article

Turbulence Induced Beam Spreading Of Higher Order Mode Optical Waves, Cynthia Y. Young, Yadira V. Gilchrest, Brian R. Macon Jan 2002

Turbulence Induced Beam Spreading Of Higher Order Mode Optical Waves, Cynthia Y. Young, Yadira V. Gilchrest, Brian R. Macon

Faculty Bibliography 2000s

It is well known that laser beams spread as they propagate through free space due to natural diffraction, and that there is additional spreading when optical waves propagate through atmospheric turbulence. Previous studies on Gaussian beams have mainly involved the lowest order mode (zero order). The study of higher order mode Gaussian beams has involved Hermite-Gaussian and Laguerre-Gaussian beams for rectangular and cylindrical geometry, respectively, These studies have developed expressions for the field and intensity in free space, in addition to developing new definitions of beam size in the receiver plane for the higher order modes. We calculate the mean …

Go to article

New Phasing Algorithm For Large Segmented Telescope Mirrors, Weiyao Zou Jan 2002

New Phasing Algorithm For Large Segmented Telescope Mirrors, Weiyao Zou

Faculty Bibliography 2000s

We propose a new phase calibration method, called the sensor-by-sensor phase calibration method (SSPC), which is applied for the phasing of a large segmented telescope mirror. Instead of making the entire segmented mirror in phase at one time and obtaining the desired sensor readings accordingly, we serially make the local areas in phase at each sensor location and thus obtain the desired sensor readings one by one. Then we run the telescope active control system to make the segments cophase. For the case of Keck telescopes, the SSPC method uses all the 168 phase measurements at 168 phase sensor locations; …

Go to article

First Prev Next Last