Physical Sciences and Mathematics Commons^™

Spectral Features Of The Stimulated Raman Backscattering Of Modulated Laser Pulses In A Plasma, Nikolai E. Andreev, Serguei Y. Kalmykov

Serge Youri Kalmykov

The characteristic features of the stimulated Raman backscattering of short modulated (multi-frequency) laser pulses in an underdense plasma are investigated. A laser pulse consisting of a given pair of spectral components with the frequency difference close to the double plasma frequency is studied in the weak mode coupling approximation. The scattering of the component with the higher frequency is shown to be a five-wave resonant process, and the conditions under which this process is totally suppressed are found. The scattering of the component with the lower frequency is an ordinary three-wave decay process without any suppression. When the difference between …

"Wcfields": A Magnetic Rotating Stellar Wind Model From Wind Compression Theory., R. Ignace, J. P. Cassinelli, J. E. Bjorkman

Richard Ignace

A stellar wind model for a magnetic rotating star is presented. We use the semianalytic wind compression model that predicts the two-dimensional geometry of outflows from rotating stars and consider the addition of a magnetic field. In the limit of weak magnetic fields, in such a way that the fields are unimportant in accelerating the flow, the wind compression model can be used to predict the magnetic field distribution throughout the wind, which is shown to follow the mass flux distribution. A compression of field lines near the equator results as the flow of material from higher latitudes brings magnetic …

Emission Line Profile Shapes From Anisotropic Scattering In Planar Equatorial Disks., R. Ignace

Richard Ignace

The consequences of anisotropic resonance line scattering for the emission profiles of equatorial disks are considered. In particular the opportunity to infer the disk velocity field owing to the anisotropic scattering is discussed. Analytic expressions for the profile shapes are derived for the cases of constant expansion and rotation, and numerical results are given for more realistic disk velocity fields of linear expansion and Keplerian rotation. The essential result is that the anisotropic line scattering produces a different profile signature in expanding disks as compared to rotating disks, owing to the difference in the isovelocity pattern of the two cases …

Inference Of Steady Stellar Wind V(R) Laws From Optically Thin Emission Lines Iii. Inversion Of Total Line Intensity Distributions., R. Ignace, J. C. Brown, J. E. Milne, J. P. Cassinelli

Richard Ignace

The variation with wavelength for a sequence of total intensities of stellar wind lines is considered as a basis for deriving the wind velocity law v(r). In particular, we focus on the case where the continuum formation in the wind is dominated by the free-free opacity so that the inner radius increases with wavelength, as is realized in some massive winds like those of the Wolf-Rayet stars. The line emission in the wind occurs exterior to the continuum photosphere, hence lines observed at different wavelengths probe different regions of the wind acceleration. A major consequence of these physical conditions is …

2-Phenyl-3-(5,6,7,7a-Tetrahydro-1h,3h-Pyrrolo[1,2-C]Oxazol-3-Ylidene)-1-Propene-1,1-Dicarbonitrile And 4-(4-Methoxyphenyl)-2,6-Bis(Methylthio)Pyridine-3-Carbonitrile, M. George, S. Das, C.V. Ashokan, N.P. Rath, M.V. George

Nigam Rath

Sediment Control At Water Intakes Along Sand Bed Rivers, Fred L. Ogden

Fred L. Ogden

Results from five physical hydraulic model studies of riverside water intakes situated along the Missouri River reach between Sioux City, Iowa, and St. Louis, Missouri, are presented. Movable-bed, undistorted Froude-scale models are used to determine the effectiveness of structural modifications in the vicinity of the intake to limit the influx of bed-load sediments. Solutions developed in each case include a series of submerged flow-turning vanes located on the riverward side of the intake. A sediment-barrier wall between the vanes and intake ...

Resistivity Of Boron-Doped Diamond Microcrystals, M. D. Jaeger, S. Hyun, Anthony Roy Day, M. F. Thorpe, B. Golding

Anthony Roy Day

We describe measurements of the electrical resistivity of micron-size crystallites of boron-doped diamond. Electron-beam lithography was employed for writing sample-specific contacts on small, well-faceted diamond crystals grown by chemical-vapor deposition on silicon substrates. After generating a three-dimensional computer model of the crystallite, a finite-element analysis was used to calculate the internal electrostatic potential distribution. Multiterminal resistance measurements, in conjunction with a computed geometrical factor, enabled the absolute resistivity to be determined. We find that the resistivities obtained from two different crystallites agree to better than 10%. The results are compared with transport measurements on a large-area homoepitaxial diamond film grown …

Quantum-Statistical Properties Of Two Coupled Modes Of Electromagnetic Field, Serguei Y. Kalmykov, Mikhail E. Veisman

Serge Youri Kalmykov

Squeezing the quantum fluctuations of the two-mode light due to the nonstationary coupling between the quadrature components q_1 and q_2 is examined. The delta-function and step-function mode couplings are considered. The conditions of weak and strong step-function coupling are distinguished, the latter being the condition of the instability for the classical counterpart of the quantum system under study. Under the conditions of weak coupling the quadrature squeezing is established in both a two-mode electromagnetic noise in thermal equilibrium (the thermal state) and a two- mode correlated coherent state (CCS). Squeezing in the thermal state is suppressed at a high temperature. …

Attractor Systems And Analog Computation, Hava Siegelmann, Shmuel Fishman

Hava Siegelmann

Attractor systems are useful in neurodynamics, mainly in the modeling of associative memory. This paper presents a complexity theory for continuous phase space dynamical systems with discrete or continuous time update, which evolve to attractors. In our framework we associate complexity classes with different types of attractors. Fixed points belong to the class BPPd, while chaotic attractors are in NPd. The BPP=NP question of classical complexity theory is translated into a question in the realm of chaotic dynamical systems. This theory enables an algorithmic analysis of attractor networks and flows for the solution of various problem such as linear programming. …

A Re-Evaluation Of Profile Shapes From Resonance Line Scattering In Spherical Stellar Winds., R. Ignace

Richard Ignace

It is common to treat the scattering of light by resonance lines as isotropic, but in fact it has been known for some time that general resonance line scattering is partially isotropic and partially dipolar, the relative strength of the two components depending on the specific transition. As a result, the profile shapes of lines that scatter with strong dipole distributions could in principle differ markedly from those that scatter isotropically. This paper explores the consequences of general resonance line scattering in spherically symmetric stellar envelopes. As a simplified example, a resonance line profile arising in a constant expansion wind …

Sublimation Enthalpies At 298.15 K Using Correlation Gas Chromatography And Differential Scanning Calorimetry Measurements, James Chickos, Donald Hesse, Sarah Hosseini, Gary Nichols, Paul Webb

James Chickos

No abstract provided.

A Protocol For Correcting Experimental Fusion Enthalpies To 298.15 K And It's Application In Indirect Measurements Of Sublimation Enthalpy At 298.15 K, James S. Chickos

James Chickos

No abstract provided.

Density Fluctuations In Vibrated Granular Materials , E.R. Nowak, J.B. Knight, E. Ben-Naim, H.M Jaeger, S.R. Nagel

Eli Ben-Naim

We report systematic measurements of the density of a vibrated granular material as a function of time. Monodisperse spherical beads were confined to a cylindrical container and shaken vertically. Under vibrations, the density of the pile slowly reaches a final steady-state value about which the density fluctuates. We have investigated the frequency dependence and amplitude of these fluctuations as a function of vibration intensity Γ. The spectrum of density fluctuations around the steady state value provides a probe of the internal relaxation dynamics of the system and a link to recent thermodynamic theories for the settling of granular material. In …

Inference Of Steady Stellar Wind V(R) Laws From Optically Thin Emission Lines Ii. Occultation Effects And The Determination Of Intrinsic Stellar Properties., R. Ignace, J. C. Brown, L. L. Richardson, J. P. Cassinelli

Richard Ignace

This paper extends previous work on the inversion of line profiles to obtain wind velocity laws to a case that includes the occultation of light from the far side of the star. The velocity law v(r) is assumed to be from a wind that is steady and spherically symmetric. The wind is also assumed to be optically thin in the emission line profile. The major result here is the derivation of an analytic inversion formula. The effects of stellar occultation are shown to produce a significant change in the analysis from paper I, and by accounting for the occultation, the …

Crossing Of Disclinations In Nematic Slabs, T. Ishikawa, Oleg Lavrentovich

Oleg Lavrentovich

It is shown experimentally that crossing and intercommutation of disclinations in a bounded nematic cell depend on surface orientation of the director and the relative strength of disclinations. Lines of opposite strength switch the pinned ends between the bounding plates and vanish independently of each other if the surface orientation is tangential. In contrast, tilted surface orientation preserves the stability of lines.

Resistivity Determination From Small Crystallites, S. Hyun, M. Thorpe, B. Golding, M. Jaeger, Anthony Day

Anthony Roy Day

We determine the resistivity of small micrometer-sized conductors with arbitrary shapes. It is shown that with n terminals attached to the sample, there are n(n􏰝1)/2 independent measurements of the resistance that can be made; from which the sample resistivity and the contact resistances can be extracted. An image of the sample is digitized and a finite element analysis is used to determine the geometrical factors that arise from the nonuniform current flow and hence control the resistance measurements. It is shown that all the elements of the resistance matrix for the sample are generated from the diagonal elements alone for …

Measurements Of Kleinman-Disallowed Hyperpolarizability In Conjugated Chiral Molecules, S. Hubbard, R. Petschek, K. Singer, N. D'Sidocky, C. Hudson, Liang-Chy Chien, C. Henderson, P. Cahill

Liang-Chy Chien

We have designed a hyper-Rayleigh scattering scheme to measure six scalar invariants of the squared hyperpolarizability tensor beta(2). OUT theoretical approach expresses the rotational invariants of the irreducible beta components as scalars, which eliminates the need for difficult frame transformations. We applied our scheme to several conjugated chiral molecules and found that there are significant Kleinman-disallowed pseudotensor contributions to their hyperpolarizability. These components, along with a large optical rotation and the results of quantum-chemical calculations, indicate a handed nonplanar delocalization of the charge-transfer system in such molecules as predicted by quantum-chemical calculations and are expected to lead to macroscopic second-harmonic …

Dynamic Control Models As State Abstractions, Jefferson A. Coelho, Roderic Grupen

Roderic Grupen

This work proposes a methodology for the construction of state abstraction from a set of empirically derived models of system behavior. The idea is to treat the agent in its environment as a dynamical system and augment its observation space with contextual cues extracted empirically as the agent exercises each element out of the set of available control policies--the control bias. Contextual cues are provided by the correlation between dynamic features of the agent-environment interaction and agent performance. The resulting state abstraction (observations + context information) defines also a temporal abstraction, and offers interesting answers to some of the issues …

Biogeography Of The Late Paleocene Benthic Foraminiferal Extinction, Ellen Thomas

Ellen Thomas

During the Late Paleocene Thermal Maximum (LPTM) benthic foraminifera at middle bathyal and greater depths suffered extinction of 30-50% of species during a few thousand years. Extinction was less severe at neritic to upper bathyal depths, where temporary changes in faunal composition prevailed. Pre-extinction deep-sea faunas were cosmopolitan and diverse, and contained heavily calcified species. Immediate post-extinction faunas were more variable geographically, exhibited low diversity, and were dominated by thin-walled calcareous or agglutinated taxa, possibly because CaCO3 dissolution increased globally from neritic to abyssal depths just before the extinction. These assemblages were dominated either by long-lived taxa such as Nuttallides …

Ambiguity And Constraint In Mathematical Expression Recognition, Erik G. Learned-Miller, Paul A. Viola

Erik G Learned-Miller

The problem of recognizing mathematical expressions differs significantly from the recognition of standard prose. While in prose significant constraints can be put on the interpretation of a character by the characters immediately preceding and following it, few such simple constraints are present in a mathematical expression. In order to make the problem tractable, effective methods of recognizing mathematical expressions will need to put intelligent constraints on the possible interpretations. The authors present preliminary results on a system for the recognition of both handwritten and typeset mathematical expressions. While previous systems perform character recognition out of context, the current system maintains …

Trench's Canonical Form For A Disconjugate $N$Th-Order Linear Difference Equation, William F. Trench, Bennette Harris, Robert Krueger

William F. Trench

No abstract provided.

Additive Nonparametric Regression With Autocorrelated Errors, Michael S. Smith, C Wong, Robert Kohn

Michael Stanley Smith

A Bayesian approach is presented for nonparametric estimation of an additive regression model with autocorrelated errors. Each of the potentially nonlinear components is modelled as a regression spline using many knots, while the errors are modelled by a high order stationary autoregressive process parameterised in terms of its autocorrelations. The distribution of significant knots and partial autocorrelations is accounted for using subset selection. Our approach also allows the selection of a suitable transformation of the dependent variable. All aspects of the model are estimated simultaneously using Markov chain Monte Carlo. It is shown empirically that the proposed approach works well …

Conjugate Schema And Basis Representation Of Crossover And Mutation Operators, S. Kazadi

Sanza Kazadi

Strategies Of Representation, Relationship, And Resistance: British Women Travelers And Mormon Plural Wives, C. 1870-1890, Karen M. Morin, J.K. Guelke

Karen M. Morin

During the 1870s and 1880s, several British women writers traveled by transcontinental railroad across the American West via Salt Lake City, Utah, the capital of the Church of Jesus Christ of Latter-day Saints, or Mormons. These women subsequently wrote books about their travels for a home audience with a taste for adventures in the American West, and particularly for accounts of Mormon plural marriage, which was sanctioned by the Church before 1890. "The plight of the Mormon woman," a prominent social reform and literary theme of the period, situated Mormon women at the center of popular representations of Utah during …

Exo- And Endo-Tricarbonyl[(4b,5,6,7,8,8a-Η)-Cis-N-Methyl-2,3,4,4a,9,9a-Hexahydro-1h- Carbazole]Chromium(0), Nigam Rath, F. Christopher Pigge, Shiyue Fang

Nigam Rath