Digital Commons Network^™

Time-Resolved Studies Of Ultracold Ionizing Collisions, Scott D. Bergeson, C. Orzel, S. Kulin, S. L. Rolston

Faculty Publications

Using 40 ns laser pulses, we probe the real-time dynamics of ultracold ionizing collisions in metastable xenon. We time resolve both shielding and enhancement effects, and observe the production of Xe2^+ molecular ions through associative ionization. We estimate the rate of molecule formation in excited-state collisions, and directly measure the role of both flux enhancement and excited state survival in the collisional enhancement process. Conceptually simple theoretical models are used to predict the dynamics of the collisional shielding.

Cell Size Dependence Of Transport Coefficients In Stochastic Particle Algorithms, Alejandro Garcia, F. Alexander, B. Alder

Faculty Publications

Using the Green–Kubo theory, the dependence of the viscosity and thermal conductivity on cell size is obtained explicitly for stochastic particle methods such as direct simulation Monte Carlo (DSMC) and its generalization, the consistent Boltzmann algorithm (CBA). These analytical results confirm empirical observations that significant errors occur when the cell dimensions are larger than a mean free path.

Diversity Within Streptomyces Ipomoeae Based On Inhibitory Interactions, Rep-Pcr, And Plasmid Profiles, C. A. Clark, C. Chen, N. Ward-Rainey, G. S. Pettis

Faculty Publications

Streptomyces soil rot is a destructive disease of sweetpotato (Ipomoea batatas) that causes yield loss resulting from decay of the feeder root system and reduced quality due to the presence of necrotic lesions on the storage roots. It is managed by the use of resistant cultivars, but variability of the pathogen has not been previously assessed. This study compared 36 strains of the pathogen Streptomyces ipomoeae from different locations in the United States and Japan. The strains could be separated into three groups on the basis of their ability to inhibit the growth of one another in in vitro assays. …

Performance And Metabolic Responses Of Young Dairy Calves Fed Diets Supplemented With Chromium Tripicolinate, C. L. Depew, L. D. Bunting, J. M. Fernandez, D. L. Thompson, R. W. Adkinson

Faculty Publications

Forty-two Holstein calves were used to study performance and metabolic responses when milk replacer and then postweaning starter were supplemented with 1 ppm of Cr as Cr-tripicolinate. From birth through 8 wk of age, supplemental Cr tended to improve the growth performance of bull calves but not of heifer calves. Starter intake and feed efficiency were not affected by supplemental Cr. From 1 to 5 wk of age, plasma cortisol concentrations sampled just prior to feeding decreased, and concentrations of insulinlike growth factor-I increased. All calves appeared to become less sensitive to insulin as they aged. From 1 to 5 …

Antiferromagnetic Hedgehogs With Superconducting Cores, Paul M. Goldbart, Daniel E. Sheehy

Faculty Publications

Excitations of the antiferromagnetic state that resemble antiferromagnetic hedgehogs at large distances but are predominantly superconducting inside a core region are discussed within the context of Zhang’s SO(5)-symmetry-based approach to the physics of high-temperature superconducting materials. Nonsingular, in contrast with their hedgehog cousins in pure antiferromagnetism, these texture excitations are what hedgehogs become when the antiferromagnetic order parameter is permitted to “escape” into superconducting directions. The structure of such excitations is determined in a simple setting, and a number of their experimental implications are examined. © 1998 The American Physical Society.

Single-Head Spin Modes In Frontal Polymerization, Victor M. Ilyashenko, John A. Pojman

Faculty Publications

The single-head spin mode is the first two-dimensional pattern of self-propagating thermal reaction fronts observed after the planar front loses stability. A "hot spot" is observed to propagate around the periphery of the front. The dynamics of the single-head frontal polymerization regime were studied experimentally, and two novel results were found. The "hot spot" was measured and found to be superadiabatic. The relationship between the rotational velocity and the propagating velocity was found. Experimental data were also compared with the theoretical results based on the linear stability analysis and found to be in a reasonable agreement. © 1998 American Institute …

The Effect Of Convection On A Propagating Front With A Liquid Product: Comparison Of Theory And Experiments, B. Mccaughey, J. A. Pojman, C. Simmons, V. A. Volpert

Faculty Publications

This work is devoted to the investigation of propagating polymerization fronts converting a liquid monomer into a liquid polymer. We consider a simplified mathematical model which consists of the heat equation and equation for the depth of conversion for one-step chemical reaction and of the Navier-Stokes equations under the Boussinesq approximation. We fulfill the linear stability analysis of the stationary propagating front and find conditions of convective and thermal instabilities. We show that convection can occur not only for ascending fronts but also for descending fronts. Though in the latter case the exothermic chemical reaction heats the cold monomer from …

Accelerated Degradation Tests: Modeling And Analysis, William Q. Meeker, Luis A. Escobar, C. Joseph Lu

Faculty Publications

High reliability systems generally require individual system components having extremely high reliability over long periods of time. Short product development times require reliability tests to be conducted with severe time constraints. Frequently few or no failures occur during such tests, even with acceleration. Thus, it is difficult to assess reliability with traditional life tests that record only failure times. For some components, degradation measures can be taken over time. A relationship between component failure and amount of degradation makes it possible to use degradation models and data to make inferences and predictions about a failure-time distribution. This article describes degradation …

Computation On Metric Spaces Via Domain Theory, Jimmie Lawson

Faculty Publications

The purpose of this paper is to survey recent approaches to realizing (or embedding) a Polish space as the set of maximal points of a continuous domain. Such realizations provide a convenient framework in which to model certain computational algorithms on the space and a useful alternate approach via the probabilistic power domain to measure theory and integraion on the space. © 1998 Elsevier Science B.V.

Heat Conduction In Fine Scale Mixtures With Interfacial Contact Resistance, Robert Lipton

Faculty Publications

Heat conduction in a fine scale mixture of two conductors is examined in the presence of a contact resistance between phases. The problem is studied rigorously in the context of periodic homogenization. Unlike the case of perfect heat transmission between phases, the temperature gradients converge weakly as Radon measures. The strict ellipticity of the homogenized transport equation depends upon the geometry of the interface. The effective conductivity associated with the overall heat dissipation rate inside a composite cube is considered. It is shown that this property exhibits a size effect under rescaling.

The Second Stekloff Eigenvalue And Energy Dissipation Inequalities For Functionals With Surface Energy, Robert Lipton

Faculty Publications

A functional with both bulk and interfacial surface energy is considered. It corresponds to the energy dissipated inside a two-phase electrical conductor in the presence of an electrical contact resistance at the two-phase interface. The effect of embedding a highly conducting particle into a matrix of lesser conductivity is investigated. We find the criterion that determines when the increase in surface energy matches or exceeds the reduction in bulk energy associated with the particle. This criterion is general and applies to any particle with Lipschitz continuous boundary. It is given in terms of the of the second Stekloff eigenvalue of …

Influence Of Interfacial Surface Conduction On The Dc Electrical Conductivity Of Particle Reinforced Composites, Robert Lipton

Faculty Publications

We describe new effects associated with electrical conduction along phase interfaces for particle reinforced conductors. For particles of general shape we introduce a new quantity β1 called the 'surface to volume dissipation' of a particle. This quantity is a measure of the particle's ability to dissipate energy on its surface relative to the energy dissipated in its interior. It is described mathematically as the minimum value of a suitably defined Rayleigh quotient and is related to an eigenvalue problem posed on the particle surface. We consider the overall conductivity of a particle reinforced conductor when the particle conductivities are less …

On Weak Maps Of Ternary Matroids, James Oxley, Geoff Whittle

Faculty Publications

Let M and N be ternary matroids having the same rank and the same ground set, and assume that every independent set in N is also independent in M. The main result of this paper proves that if M is 3-connected and N is connected and non-binary, then M = N. A related result characterizes precisely when a matroid that is obtained by relaxing a circuit-hyperplane of a ternary matroid is also ternary. © 1998 Academic Press Limited.

On Packing 3-Connected Restrictions Into 3-Connected Matroids, James Oxley

Faculty Publications

Let M1,M2,...,Mn be 3-connected restrictions of a 3-connected matroid M on disjoint ground sets E1,E2,...,En, respectively. This paper proves that M has a 3-connected minor N that contains E1 UE2 U ··· UEn, has its restriction to each Ei, being Mi, and has at most 2n - 2 additional elements.

On Summability Of Distributions And Spectral Geometry, R. Estrada, J. M. Gracia-Bondía, J. C. Várilly

Faculty Publications

Modulo the moment asymptotic expansion, the Cesàro and parametric behaviours of distributions at infinity are equivalent. On the strength of this result, we construct the asymptotic analysis for spectral densities arising from elliptic pseudodifferential operators. We show how Cesàro developments lead to efficient calculations of the expansion coefficients of counting number functionals and Green functions. The bosonic action functional proposed by Chamseddine and Connes can more generally be validated as a Cesàro asymptotic development.

Complementary Group Resolution Of The Su(N) Outer Multiplicity Problem. I. The Littlewood Rules And A Complementary U(2n-2) Group Structure, Feng Pan, J. P. Draayer

Faculty Publications

A complementary group to SU(n) is found that realizes all features of the Littlewood rules for Kronecker products of SU(n) representations. This is accomplished by considering a state of SU(n) to be a special Gel'fand state of the complementary group U(2n-2) with labels of the latter used to distinguish multiple occurrences of irreducible representations of SU(n) (irreps) in the SU(n)×SU(n)↓SU(n) decomposition that is obtained from the Littlewood rules. Furthermore, this realization also helps us to determine SU(n)⊃SU(n - 1) × U(1) Reduced Wigner Coefficients (RWCs, frequently called Isoscalar Factors) and Clebsch-Gordan Coefficients [CGCs, or full (nonreduced) Wigner Coefficients] of SU(n), …

Wavelets And Quantum Algebras, A. Ludu, M. Greiner, J. P. Draayer

Faculty Publications

Wavelets, known to be useful in nonlinear multiscale processes and in multiresolution analysis, are shown to have a q-deformed algebraic structure. The translation and dilation operators associate to any scaling equation a nonlinear, two parameter algebra. This structure can be mapped onto the quantum group slq(2) in one limit, and approaches a Fourier series generating algebra, in another limit. A duality between any scaling function and its corresponding nonlinear algebra is obtained. Examples for the Haar and B-wavelets are worked out in detail. © 1998 American Institute of Physics.

Complementary Group Resolution Of The Su(N) Outer Multiplicity Problem. Ii. Recoupling Approach For Su(3)⊃U(2) Reduced Wigner Coefficients, Feng Pan, J. P. Draayer

Faculty Publications

A general procedure for the derivation of SU(3)⊃U(2) reduced Wigner coefficients (RWCs) for the coupling (λ1μ1) × (λ2μ2) ↓ (λ μ)η, where η is the outer multiplicity label required in the decomposition, is proposed based on a recoupling approach that follows the complementary group technique for a resolution of the outer multiplicity of SU(n) introduced in Part (I) of this series. RWCs of SU(n) are not unique under a canonical resolution of the outer multiplicity; the transformation from one set to another are elements of SO(m), where m is the number of occurrences of the (λ μ) irrep in the …

A Physical Model Of Warped Galaxy Disks, Kimberly C.B. New, Joel E. Tohline, Juhan Frank, Horst M. Väth

Faculty Publications

Warped H 1 gas layers in the outer regions of spiral galaxies usually display a noticeably twisted structure. This structure almost certainly arises primarily as a result of differential precession in the H I disk as it settles toward a preferred orientation in an underlying dark halo potential well that is not spherically symmetric. In an attempt to better understand the structure and evolution of these twisted, warped disk structures, we have adopted the "twist equation" formalism originally developed by Petterson to study accretion onto compact objects. Utilizing more recent treatments of this formalism, we have generalized the twist equation …

Correlation Function Formulation For The State Selected Total Reaction Probability, Sophya V. Garashchuk, D. J. Tannor

Faculty Publications

A correlation function formulation for the state-selected total reaction probability, Nα(E), is suggested. A wave packet, correlating with a specific set of internal reactant quantum numbers, α, is propagated forward in time until bifurcation is complete at which time the nonreactive portion of the amplitude is discarded. The autocorrelation function of the remaining amplitude is then computed and Fourier transformed to obtain a reactivity spectrum. Dividing by the corresponding spectrum of the original, unfiltered, wave packet normalizes the reactivity spectrum, yielding the total reaction probability from the internal state, α. The procedure requires negligible storage and just one time-energy Fourier …

Chaos, Complexity, And Coevolution: The Web Of Law, Management Theory, And Law Related Services At The Millenium, Thomas Geu

Faculty Publications

No abstract provided.

Spatiotemporal Autoregressive Models Of Neighborhood Effects, R. Kelley Pace, Ronald Barry, John M. Clapp, Mauricio Rodriquez

Faculty Publications

Using 70,822 observations on housing prices from 1969 to 1991 from Fairfax County Virginia, this article demonstrates the substantial benefits obtained by modeling the spatial as well as the temporal dependence of the data. Specifically, the spatiotemporal autoregression with twelve variables reduced median absolute error by 37.35% relative to an indicator-based model with twenty-six variables. One-step ahead forecasts also document the improved performance of the proposed spatiotemporal model. In addition, the article illustrates techniques for rapidly computing the estimates and shows how to compute indices for any location.

Evaluation Of The Acoustic Doppler Velocimeter (Adv) For Turbulence Measurements, George Voulgaris, John H. Trowbridge

Faculty Publications

Accuracy of the acoustic Doppler velocimeter (ADV) is evaluated in this paper. Simultaneous measurements of open-channel flow were undertaken in a 17-m flume using an ADV and a laser Doppler velocimeter. Flow velocity records obtained by both instruments are used for estimating the true (‘‘ground truth’’) flow characteristics and the noise variances encountered during the experimental runs. The measured values are compared with estimates of the true flow characteristics and values of variance (^u92&, ^w92&) and covariance (^u9w9&) predicted by semiempirical models for open-channel flow. The analysis showed that the ADV sensor can measure mean velocity and Reynolds stress within …

A Mathematical Model For Fibroblast And Collagen Orientation, J. C. Dallon, J. A. Sherratt

Faculty Publications

Due to the increasing importance of the extracellular matrix in many biological problems, in this paper we develop a model for fibroblast and collagen orientation with the ultimate objective of understanding how fibroblasts form and remodel the extracellular matrix, in particular its collagen component. The model uses integro-differential equations to describe the interaction between the cells and fibers at a point in space with various orientations. The equations are studied both analytically and numerically to discover different types of solutions and their behavior. In particular we examine solutions where all the fibroblasts and collagen have discrete orientations, a localized continuum …

Proton Diffusion In Nickel Hydroxide: Prediction Of Active Material Utilization, Sathya Motupally, Christopher C. Streinz, John W. Weidner

Faculty Publications

Galvanostatic charge and discharge experiments reveal that the active material in nickel electrodes cannot be fully accessed at high currents or for thick films. It has been proposed that the utilization of the active material is controlled by the diffusion rate of protons through the film. This hypothesis is supported by the good agreement between mathematical simulations of material utilization and experimental data over a range of charge and discharge currents and film thicknesses. Furthermore, the fraction of material utilized is larger on charge than on discharge. The asymmetry on charge and discharge is due to a diffusion coefficient that …

Ab Initio Study Of Formazan And 3-Nitroformazan, G. Buemi, F. Zuccarello, P. Venuvanalingam, M. Ramalingam, Salai Cheettu Ammal

Faculty Publications

Formazan and 3-nitroformazan have been investigated at abinitio level (MP2/6-31G** and B3LYP/6-31G**) in all their possible conformations, for studying the various possibilities of intramolecular hydrogen bonding formation. The trans-syn-s-cis (TSSC), known also asyellowform, has been found to be the most stable conformer (at least in the gas phase) in both compounds. This particular structure is strongly stabilized by a N–H···N hydrogen bridge, which gives rise to a hexatomic chelate ring, with the possibility of a proton transfer process.This closely resembles that of malondialdehyde, previously studied, in the evolution of the …

Chaos, Complexity, And Coevolution: The Web Of Law, Management Theory, And Law Related Services At The Millennium, Thomas Geu

Faculty Publications

No abstract provided.

Cognitive Agents, Michael N. Huhns, Munindar P. Singh

Faculty Publications

Several researchers have proposed using cognitive concepts as a semantic basis for agent communications (M.N. Huhns and M.P. Singh, 1997). One of the leading candidates for such a semantics is based on Arcol, the communication language used within Artimis. Interestingly, this application (not only of Arcol, but also in general) appears extremely misguided. The intentional concepts are well suited to designing agents, but are not suited to giving a basis to a public, standardizable view of communication. A challenge for using the cognitive concepts is that although they are natural in several respects and can guide implementations, full blown implementations …

Teaching Law Students Through Individual Learning Styles, Robin A. Boyle, Rita Dunn

Faculty Publications

(Excerpt)

Teaching can be rewarding, but it can also be frustrating when some students fail to grasp the material. Professor Robin A. Boyle of St. John’s University School of Law has been teaching Legal Research and Writing in small sections of approximately twenty to thirty students for four years. She, like many of her similarly exasperated colleagues, has repeated the same course content by using either lecture or collaborative learning, and has observed some students doing well, whereas others continued to perform poorly. Then, Dr. Rita Dunn was introduced to the law school faculty and suggested that law professors incorporate …

An Investigation Of The Amount Of Emphasis Placed On Content And Delivery By Instructors Of Public Speaking, Paul J. Siddens Iii

Faculty Publications

A study examined how much emphasis instructors of public speaking place on content and delivery when teaching and delivering oral and written critiques. The study sought to determine whether when teaching a hybrid introduction to communication course; or public speaking course; instructors are challenged with teaching their students about issues related to the content of the speech; such as the introduction and conclusion; organization; supporting evidence; and issues related to physical and vocal delivery such as appearance; gestures; eye contact; volume; rate; and vocal variety. This was a pilot study to test the research questions; survey instrument; and methodology used …