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New paradigms for the statistics profession

Description: This paper is a presentation made in support of the statistics profession. This field can say it has had a major impact in most major fields of study presently undertaken by man, yet it is not perceived as an important, or critical field of study. It is not a growth field either, witness the almost level number of faculty and new PhD`s produced over the past twenty years. The author argues the profession must do a better job of selling itself to the students it educates. Awaken them to the impact of statistics in their lives and their business worlds, so that they see beyond the formulae to the application of these principles.
Date: February 1, 1995
Creator: Iman, R. L.
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Partner: UNT Libraries Government Documents Department

Properties of multiple event gamma ray bursts

Description: We present results from a study of 37 multiple event gamma ray bursts found in the monitoring data of the PVO gamma ray burst detector. We define these bursts as those which have two or more distinct emission events separated by a return to the background intensity. Significant correlation exists between the duration of the first event and the duration of the second event, while some correlation exists between the hardness of the events and only weak correlation exists in the intensity of the events. Although the time profiles of events in a burst may be similar, as measured in the phase portrait, there is no general rule about the degree of similarity of the time profiles. Subdividing the data according to the recurrence time, we find a tendency for the strength of the correlation in the hardness to increase with decreasing separation between the events. 2 refs., 2 figs., 1 tab.
Date: December 31, 1991
Creator: Lochner, J. C.
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Radial and nonradial periods and growth rates of an AI Velorum model

Description: Walraven, Walraven, and Balona recently discovered several new periodicities in addition to the well-known fundamental and first overtone periods of the high-amplitude {delta} Scuti star AI Velorum. Linear nonadiabatic pulsation calculations were performed for an AI Velorum model of mass 1.96 M{sub {circle_dot}}, 24.05 L{sub {circle_dot}}, and T{sub eff}7566 K for the radial and low-degree nonradial modes to help verify the tentative identifications made by Walraven, et al. Comparison of the calculated periods with the observations suggests some alternatives to the identifications proposed by Walraven, et al.
Date: May 1, 1992
Creator: Guzik, J. A.
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A survey of surveys

Description: A new era for the field of Galactic structure is about to be opened with the advent of wide-area digital sky surveys. In this article, the author reviews the status and prospects for research for 3 new ground-based surveys: the Sloan Digital Sky Survey (SDSS), the Deep Near-Infrared Survey of the Southern Sky (DENIS) and the Two Micron AU Sky Survey (2MASS). These surveys will permit detailed studies of Galactic structure and stellar populations in the Galaxy with unprecedented detail. Extracting the information, however, will be challenging.
Date: November 1, 1994
Creator: Kent, S. M.
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Do the Pop II field blue stragglers have a collisional origin?

Description: The hypothesis that the Pop II field blue stragglers have a collisional origin is considered. It appears unlikely that the majority of these stragglers were formed via collisions, but it is difficult to rule out the possibility that a small, but observable, fraction of them were.
Date: March 1, 1993
Creator: Leonard, P. J. T.
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Working group 1: Coronal streamers

Description: The working group on colonel streamers convened on the first day of the 2nd SOHO Workshop, which took place in Marciana Marina, Isola d`Elba, 27 September--1 October 1993. Recent progress in streamer observational techniques and theoretical modeling was reported. The contribution of streamers to the mass and energy supply for the solar wind was discussed. Moreover, the importance of thin electric current sheets for determining both the gross dynamical properties of streamers and the fine-scale filamentary structure within streamers, was strongly emphasized. Potential advances to our understanding of these areas of colonel physics that could be made by the contingent of instruments aboard SOHO were pointed out.
Date: April 1, 1994
Creator: Kopp, R. A.
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Angular momentum in the Local Group

Description: We briefly review models for the Local Group and the acquisition of its angular momentum. We describe early attempts to understand the origin of the spin of the galaxies discussing the hypothesis that the Local Group has little angular momentum. Finally we show that using Peebles` least action principle there should be a rather large amount of orbital angular momentum compared to the magnitude of the spin of its galaxies. Therefore the Local Group cannot be thought as tidally isolated. Using Peebles` trajectories we give a possible set of trajectories for Local Group galaxies which would predict their spin.
Date: April 1, 1994
Creator: Dunn, A. & Laflamme, R.
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Do the Pop II field blue stragglers have a collisional origin

Description: The hypothesis that the Pop II field blue stragglers have a collisional origin is considered. It appears unlikely that the majority of these stragglers were formed via collisions, but it is difficult to rule out the possibility that a small, but observable, fraction of them were.
Date: January 1, 1993
Creator: Leonard, P.J.T.
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Partner: UNT Libraries Government Documents Department

The influence of CDM on the dynamical estimate of {Omega} in the local neighborhood

Description: Peebles has suggested an interesting method to trace back in time positions of galaxies called the least action method. This method applied on the Local Group galaxies seems to indicate that we live in an {Omega}{approx} 0.1 Universe. We have studied a CDM N-body simulation with {Omega} = 0.2 and H = 50kms{sup {minus}1}/Mpc and compare trajectories traced back from the Least Action Principle and the center of mass of the particle forming CDM halos. We have shown that the agreement between these set of trajectories is at best qualitative. We have also shown that the line of sight peculiar velocities are underestimated. This discrepancy is due to orphans, CDM particles which do not end up in halos. By varying the density parameter {Omega} in the least action principle we show that using this method we would underestimate the density of the Universe by a factor of 4--5.
Date: December 31, 1994
Creator: Dunn, A. M. & Laflamme, R.
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Convection in RR Lyrae stars

Description: Convection undoubtedly plays a strong role in defining the RR Lyrae instability strip, but its effects on amplitude, mode of pulsation, and light curve have always been problematical. One reason is simple that convective models are difficult to compute, and their accuracy is difficult to ascertain. We present results of a new convective survey of RR Lyrae stars that constitute the best models available at this time, with better boundary conditions, physics, zoning, and length of computational run than previous results.
Date: October 1, 1992
Creator: Stellingwerf, R. F. & Bono, G.
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Nonlinear optics and organic materials

Description: We shall consider an interesting topic relating nonlinear optics and organic materials: how nonlinear optics can be used to study organic materials. One of the main differences between linear and nonlinear responses of a medium to incoming radiation is in their symmetries. It leads to the possibility that some properties of the medium could be more sensitively probed by nonlinear, rather than linear, optical means, or vise versa. A well-known example is that some vibrational modes of a medium could be Raman-active but infrared-inactive, and would be more readily observed by Raman scattering, which is a two-photon transition process. In this paper, we shall discuss, with the help of three examples, how we can use second harmonic generation (SHG) and sum frequency generation (SFG) to obtain unique information about a material. We shall focus on thin films, surfaces, and interfaces.
Date: July 1, 1994
Creator: Shen, Y. R.
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Morphology of Laplacian growth processes and statistics of equivalent many-body systems

Description: The authors proposes a theory for the nonlinear evolution of two dimensional interfaces in Laplacian fields. The growing region is conformally mapped onto the unit disk, generating an equivalent many-body system whose dynamics and statistics are studied. The process is shown to be Hamiltonian, with the Hamiltonian being the imaginary part of the complex electrostatic potential. Surface effects are introduced through the Hamiltonian as an external field. An extension to a continuous density of particles is presented. The results are used to study the morphology of the interface using statistical mechanics for the many-body system. The distribution of the curvature and the moments of the growth probability along the interface are calculated exactly from the distribution of the particles. In the dilute limit, the distribution of the curvature is shown to develop algebraic tails, which may, for the first time, explain the origin of fractality in diffusion controlled processes.
Date: November 1, 1994
Creator: Blumenfeld, R.
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Cratering rates from lunar xenospherules

Description: The goal of this project is to obtain the time history of impacts on the moon, with emphasis on recent impacts. In particular, the project could prove (or disprove) the existence of comet sores and provide the dates when they occurred.
Date: May 25, 1993
Creator: Muller, R. A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Radio galaxies and their environment

Description: The relationships between radio galaxies and their environment are varied, complex, and evolve with cosmic epoch. Basic questions are what role the environment plays in triggering and fuelling (radio) galaxy activity what the effects of this activity are on its environment, and how radio galaxies and environment evolve. Clearly, this could be the topic of a workshop all in itself and the scope of this review will necessarily be limited. A review of the connections between environment and galaxy activity in general has been given by Heckman. First, I will briefly summarize the relationships between parent galaxy and cluster environments, and radio galaxies. A more detailed discussion of various aspects of this will be given elsewhere by F. Owen, J.0. Burns and R. Perley. I will then discuss the current status of investigations of extended emission-line regions in radio galaxies, again referring elsewhere in this volume for more detailed discussions of some particular aspects (kinematics and ionization mechanisms by K. Meisenheimer; polarization and spectral index lobe asymmetries by G. Pooley). I will conclude with a brief discussion of the current status of observations of high redshift radio galaxies.
Date: February 24, 1993
Creator: van Breugel, W.
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Partner: UNT Libraries Government Documents Department

High gain GaAs Photoconductive Semiconductor Switches (PCSS): Device lifetime, high current testing, optical pulse generators

Description: This paper presents results from three areas of GaAs PCSS research and development: device lifetime, high current switching, and PCSS-driven laser diode arrays (LDA). The authors have performed device lifetime tests on both lateral and vertical switches as a function of current amplitude, pulse width, and charging time. At present, their longest-lived switch reached 4 {times} 10{sup 6} pulses. Scanning electron microscope (SEM) images show damage near the contacts even after only 5 pulses. They are presently searching for the threshold at which no damage is evident after a single shot. In high current tests, they have reached 5.2 kA at 4.2 kV. This was achieved using twenty fiber-optic coupled lasers to distribute current filaments over a 5 mm wide PCSS. Current waveforms and images of the current filaments as a function of current amplitude will be presented. The lasers used to trigger the high current PCSS were driven with a miniature PCSS. Low inductance, high speed GaAs PCSS are very effective as short pulse laser diode array drivers. Some types of arrays gain switch, producing a compressed optical pulse which is only 75 ps wide. Results from tests with a variety of laser diode arrays will be presented.
Date: December 31, 1995
Creator: Zutavern, F. J.; Loubriel, G. M.; Helgeson, W. D.; O`Malley, M. W.; Gallegos, R. R.; Hjalmarson, H. P. et al.
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Partner: UNT Libraries Government Documents Department

Recent results from sage

Description: A radiochemical {sup 71}Ga-{sup 71}Ge experiment to determine the primary flux of neutrinos from the Sun began measurements of the solar neutrino flux at the Baksan Neutrino Observatory in 1990. The number of {sup 71}Ge atoms extracted from initially 30 and later 57 tons of metallic gallium was measured in fifteen runs during the period of January 1990 to May 1992. The observed capture rate is 70{plus_minus}19 (stat){plus_minus}10 (syst) SNU. This is to be compared with 132 SNU predicted by the Standard Solar Model.
Date: December 31, 1993
Creator: Gavrin, V. N.; Faizov, E. L. & Kalikhov, A. V.
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Rapid cooling and structure of neutron stars

Description: This report discusses the following topics on neutron stars: direct URCA neutrino emission; thermal evolution models; analytic model for diffusion through the crust; and core superfluidity. (LSP).
Date: July 1, 1992
Creator: Van Riper, K. A. & Lattimer, J. M.
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Views of the solar system

Description: Views of the Solar System has been created as an educational tour of the solar system. It contains images and information about the Sun, planets, moons, asteroids and comets found within the solar system. The image processing for many of the images was done by the author. This tour uses hypertext to allow space travel by simply clicking on a desired planet. This causes information and images about the planet to appear on screen. While on a planet page, hyperlinks travel to pages about the moons and other relevant available resources. Unusual terms are linked to and defined in the Glossary page. Statistical information of the planets and satellites can be browsed through lists sorted by name, radius and distance. History of Space Exploration contains information about rocket history, early astronauts, space missions, spacecraft and detailed chronology tables of space exploration. The Table of Contents page has links to all of the various pages within Views Of the Solar System.
Date: February 1, 1995
Creator: Hamilton, C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

The effects of internal fluctuations on a class of nonequilibrium statistical field theories

Description: A class of models with applications to swarm behavior as well as many other types of spatially extended complex biological and physical systems is studied. Internal fluctuations can play an active role in the organization of the phase structure of such systems. In particular, for the class of models studied here the effect of internal fluctuations due to finite size is a renormalized decrease in the temperature near the point of spontaneous symmetry breaking.
Date: July 1, 1993
Creator: Millonas, M. M.
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Discussion of stress tensor nonuniqueness with application to nonuniform, particulate systems

Description: The indeterminacy of the mechanical stress tensor has been noted in several developments of expressions for stress in a system of particles. It is generally agreed that physical quantities related to the stress tensor must be insensitive to this nonuniqueness, but there is no definitive prescription for insuring it. Kroener`s tensor decomposition theorem is applied to the mechanical stress tensor {sup {sigma}}{sub ij} to show that its complete determination requires specification of its ``incompatibility,`` {epsilon}{sub ijk} {epsilon}{sub lmn} {sup {partial_derivative}}{sub j} {sup {partial_derivative}}{sub m} {sup {sigma}}{sub kn}, in addition to its divergence, which is obtained from the momentum conservation relation. For a particulate system, stress tensor incompatibility is shown to vanish to recover the correct expression for macroscopically observable traction. This result removes concern about nonuniqueness without requiring equilibrium or arbitrarily-defined force lines.
Date: June 1, 1993
Creator: Aidun, J. B.
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Notes on the Landau, Pomeranchuk, Midgel effect: Experiment and theory

Description: The status of the Landau, Pomeranchuk, Migdal Effect is briefly reviewed. A recent experiment at the Stanford Linear Accelerator Center substantially agrees with the existing theoretical formulation. However, that formulation suffers from an imprecise foundation and a lack of generality. The difficulty of finding a simple, explanatory picture of the 1/{radical}K behavior of the Effect is also noted.
Date: May 1, 1994
Creator: Perl, M. L.
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Partner: UNT Libraries Government Documents Department