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Articles 8491 - 8520 of 8913

Full-Text Articles in Physical Sciences and Mathematics

Oh Emission In The Direction Of Tv Gem And Bi Cyg, L. W. Brown, R. W. Hobbs, A. G. Michalitsianos, Menas Kafatos Jan 1981

Oh Emission In The Direction Of Tv Gem And Bi Cyg, L. W. Brown, R. W. Hobbs, A. G. Michalitsianos, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

OH maser main-line emission at 1665 MHz has been detected in the direction of two late-type supergiants, TV Gem (Mllab) and BI Cyg (M3Iab), with the 43-m telescope and 18-cm receiver at NRAO-Green Bank. Detection of two new OH maser sources here is particularly interesting in view of the relatively small number of late-type supergiants that are known as molecular radio sources or associated in close proximity with OH emission clouds. The infrared, ultraviolet, and radio properties of these stars are discussed briefly.

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Magnetohydrodynamics In An Open Universe, Oscar Norris Dec 1980

Magnetohydrodynamics In An Open Universe, Oscar Norris

Masters Theses & Specialist Projects

A study of magnetohydrodynamics (MHD) in an open universe is presented. We discuss the data and justification behind our choice of an open universe for investigation in this thesis, as opposed to the closed universe theory, which is more appealing in some ways. We explicitly define all parameters used in the analysis of magnetohydrodynamic Bianchi Type V cosmologies and outline the formulation behind them. We then proceed to present a solution to a Bianchi Type V magnetohydrodynamic cosmology with a diagonal metric. After that, the results are compared with present observations. Lastly, we conclude with an assessment of the model …

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Influence Of Nonequilibrium Radiation And Shape Change On The Flowfield Of A Jupiter Probe With Ablation And Mass Injection, Sundaresa Venkata Subramanian Apr 1980

Influence Of Nonequilibrium Radiation And Shape Change On The Flowfield Of A Jupiter Probe With Ablation And Mass Injection, Sundaresa Venkata Subramanian

Mechanical & Aerospace Engineering Theses & Dissertations

The influence of nonequilibrium radiative energy transfer and the effect of probe configuration changes on the flow phenomena around a Jovian entry body is investigated. The radiating shock-layer flow is assumed to be axisymmetric, viscous, laminar and in chemical equilibrium. The radiative transfer equations are derived under nonequilibrium conditions which include multi-level energy transitions. The equilibrium radiative transfer is calculated with an existing nongray radiation model which accounts for molecular band, atomic line and continuum transitions. The nonequilibrium results are obtained with and without ablation injection in the shock layer. The nonequilibrium results are found to be influenced greatly by …

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Iue Observations Of Circumstellar Emission From The Late Type Variable R Aquarii (M7 + Pec), A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs Jan 1980

Iue Observations Of Circumstellar Emission From The Late Type Variable R Aquarii (M7 + Pec), A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs

Mathematics, Physics, and Computer Science Faculty Articles and Research

IUE observations of R Aquarii (M7 + pec) have been obtained in low dispersion in order to study its circumstellar emission. Strong permitted, semiforbidden, and forbidden emission lines are identified that are superposed on a bright ultraviolet continuum. From our analysis we deduce that the strong emission-line spectrum that involves C III], C IV, Si III], [0 II], and [0 III] probably arises from a dense compact nebula the size of which is comparable to the binary system of which R Aqr is the primary star. Low-excitation emission lines of Fe II, Mg II, 0 1, and Si II suggest …

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Gamma Rays From Penrose Powered Black Holes In Centaurus A, 3c 273, And Ngc 4151, Menas Kafatos Jan 1980

Gamma Rays From Penrose Powered Black Holes In Centaurus A, 3c 273, And Ngc 4151, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

Gamma-ray observations of active galaxies have important consequences for theories of the activity in their nuclei. The observations of Cen A, 3C 273, and NGC 4151 are examined under the assumption that Penrose collision processes in the ergospheres of massive black holes power their nuclei. The observed sharp break in the MeV region of the NGC 4151 spectrum cannot be due to the γ-γ pair production process. We attribute this break to the Penrose Compton scattering (PCS), in which γ-rays escape from the ergosphere as a result of Penrose processes involving electrons and lower energy X-ray photons in the ergosphere …

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Iue Observations Of A Luminous M Supergiant That Exhibits Emission Continuum In The Far Ultraviolet, A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs Jan 1980

Iue Observations Of A Luminous M Supergiant That Exhibits Emission Continuum In The Far Ultraviolet, A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs

Mathematics, Physics, and Computer Science Faculty Articles and Research

IUE observations of the late-type M supergiant TV Gem (M1 lab) have been obtained that reveal strong UV continuum between 1200 and 3200 A. The continuum is essentially featureless with the exception of a number of broad absorption features in the short wavelength spectral range. UV emission from this star is unexpected because earlier ground-based observations give no indication of a possible association with an early companion or circumstellar ionized nebulosity. We find that a B9 or A1 III-IV type star approximately 2-3 magnitudes fainter than the M star could explain the level of UV continuum observed, but a fully …

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The Evolution Of Supernova Remnants In Different Galactic Environments, And Its Effects On Supernova Statistics, Menas Kafatos, S. Sofia, C. Bruhweilier, T. R. Gull Jan 1980

The Evolution Of Supernova Remnants In Different Galactic Environments, And Its Effects On Supernova Statistics, Menas Kafatos, S. Sofia, C. Bruhweilier, T. R. Gull

Mathematics, Physics, and Computer Science Faculty Articles and Research

By examining the interaction between supernova (SN) ejecta and the various environments in which the explosive event might occur, we conclude that only a small fraction of the many SNs produce observable supernova remnants (SNRs). This fraction, which is found to depend weakly upon the lower mass limit of the SN progenitors, and more strongly on the specific characteristics of the associated interstellar medium, decreases from approximately 15% near the galactic center to 10% at R8a1 -10 kpc and drops nearly to zero for Rga~> 15 kpc. Generally, whether a SNR is detectable is determined by the density of the …

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Iue Observations Of Two Late Type Stars: R Aql And W Hya, Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs Jan 1980

Iue Observations Of Two Late Type Stars: R Aql And W Hya, Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs

Mathematics, Physics, and Computer Science Faculty Articles and Research

Ultraviolet spectra of two late type M stars R Aql and W Hya were obtained with the International Ultraviolet Explorer (IUE). Spectra were obtained of R Aql near maximum (cf>=0.21) and minimum (cf>=0.65) of the visible light curve. We find that the absolute flux intensity of the Mgn resonance doublet (2796 A, 2803 A) is essentially the same at these phases in the visible light curve. A nebular emission feature at 3133 A is detected at minimum light in R Aql that is possibly due to 0 III. Mg II emission is totally absent in W Hya, which …

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150 Ghz Observations Of Three Radio Galaxies, Menas Kafatos, R. W. Hobbs, S. P. Maran, L. W. Brown Jan 1980

150 Ghz Observations Of Three Radio Galaxies, Menas Kafatos, R. W. Hobbs, S. P. Maran, L. W. Brown

Mathematics, Physics, and Computer Science Faculty Articles and Research

Radio galaxies were observed for the first time at 150 GHz. The central sources in Cyg A and 3C Ill were detected, as were the two radio lobes of Cyg A. No emission was found from the central source in 3C 236. Each of these three central sources has been previously discussed as the site of the energy supply for the associated distant components. The millimeter-wavelength emission from the central sources in Cyg A and 3C 111 is probably due in each case to a compact component that is optically thin to synchrotron radiation above about 35 GHz. These components …

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Iue Observations Of Rw Hydrae (Gm2 + Pec), Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs Jan 1980

Iue Observations Of Rw Hydrae (Gm2 + Pec), Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs

Mathematics, Physics, and Computer Science Faculty Articles and Research

IUE observations of the late type star RW Hya (gM2 + pec) have been obtained. Analysis of the intense UV continuum observed between 1100 and 2000 A suggests that this object is a binary system in which the secondary is identified as the central star of a planetary nebula with Teff 105 K. The ultraviolet spectrum is characterized by semiforbidden and allowed transition lines, of which the C IV (1548 A, 1550 A) doublet is particularly strong. A general absence of strong forbidden line emission suggests that the compact nebula in which both primary and secondary stars are embedded has …

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Saturated Solar Ponds: Modified Equations And Results Of A Laboratory Experiment, Markus Karl Rothmeyer Dec 1979

Saturated Solar Ponds: Modified Equations And Results Of A Laboratory Experiment, Markus Karl Rothmeyer

Physics & Astronomy ETDs

The diffusion equation for salt gradient solar ponds has been modified to include the Soret effect (a thermal cross-effect due to the temperature gradient). The contribution of the Soret effect to the diffusion flux of salt is shown to be on the order of 4% in the winter and 28% in the summer for the UNM NaCl solar pond. The traditional stability criterion for solar ponds remains practically unchanged by the Soret effect. However, the contribution of non-constant properties (diffusion coefficient, thermal diffusivity and viscosity)--which have been neglected so far--seems to be significant. Saturated solar ponds are described by a …

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Program For New Observatory Facility For Brigham Young University, Provo, Utah, Byu Department Of Physics And Astronomy Nov 1979

Program For New Observatory Facility For Brigham Young University, Provo, Utah, Byu Department Of Physics And Astronomy

BYU West Mountain Observatory Project

No abstract provided.

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Magnetohydrodynamic Effects On The Growth Of Condensations In An Expanding Universe & The Formation Of Galaxies, Charles Evans Aug 1979

Magnetohydrodynamic Effects On The Growth Of Condensations In An Expanding Universe & The Formation Of Galaxies, Charles Evans

Masters Theses & Specialist Projects

We review the evidence for existence of a magnetic field of the galaxy and whatever evidence there is of an intergalactic magnetoionic medium. We then consider the magnetohydrodynamics (MHD) of such a medium. The formation of galaxies through purely gravitational means in an expanding universe is then reviewed. Next the role of magnetohydrodynamics in such a universe is analyzed for their effects on galaxy formation. Finally, the importance of MED behavior in the early universe is emphasized from physical considerations and from present day evidence. Appendices discuss isotropic cosmologies, magnetic fields in such a background, the detailed MHD perturbations, and …

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Simulative Investigation Of The Detection Of Modes Of Luminosity Variation In Astrophysical Sources, James Collins May 1979

Simulative Investigation Of The Detection Of Modes Of Luminosity Variation In Astrophysical Sources, James Collins

Masters Theses & Specialist Projects

Five astronomical data analysis methods were evaluated, using computer simulation techniques, for minimum detection levels, periodicity detection, and parameter estimation sensitivities. The evaluation of these methods was accomplished using three basic waveforms with the addition of ten “random” noise samples from a Gaussian distribution of known parameters. The chi-square and t-test methods were evaluated in detecting low-amplitude variability and brightness level shifts. Results indicate both methods have a strong dependence on the estimation of the standard deviation (σ) where a 0.1 change in σ will affect detection rates by ten to twenty-five percent at the ninety-five percent confidence level. The …

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Ca Ii H And K And Hydrogen-Line Variations In V471 Tauri (=Bd + 16°516), Terry D. Oswalt Apr 1979

Ca Ii H And K And Hydrogen-Line Variations In V471 Tauri (=Bd + 16°516), Terry D. Oswalt

Publications

Spectroscopic and narrow-band photoelectric observations of the white dwarf eclipsing binary V471 Tau (= BD + 16°516) are reported. Periodic fluctuations in Ca IIH and K emission and Ha absorption, and a wave-like distortion of the light curve mimic the characteristics of several well-observed RS CVn binaries. A probable correlation between maximum emission-line strength and wave minimum is shown to exist.

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Interplanetary Magnetic Field Sector Polarity And Neuropsychiatric Adaption: A Reanalysis, Hans W. Wendt Jan 1979

Interplanetary Magnetic Field Sector Polarity And Neuropsychiatric Adaption: A Reanalysis, Hans W. Wendt

Journal of the Minnesota Academy of Science

Recent Russian studies reported associations between adaptation syndromes and (solar activity-related) interplanetary magnetic field (IMF) sector polarity. Certain ambiguities in the original work suggested some reanalyses, based on the graphs and data made available. Syndrome status exhibited a biphasic (semi annual) trend. It also correlated with specific geomagnetic changes during magnetic storms and possibly after sudden impulses. Moreover, lag effects and higher order interactions were noted among all parameters investigated. The restudy tends to support some of the original findings but also suggests new conclusions regarding potential relationships between geophysical/solar and psychophysiological processes.

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Ionization, Luminosity, And Heating Of The Upper Atmosphere Of Mars, Jane L. Fox, Alexander Dalgarno Jan 1979

Ionization, Luminosity, And Heating Of The Upper Atmosphere Of Mars, Jane L. Fox, Alexander Dalgarno

Physics Faculty Publications

A model based upon Viking data is constructed of the Martian atmosphere, and a comprehensive quantitative discussion is given of the measurements of the ultraviolet dayglow. A detailed assessment is made of the heating of the neutral and ionized components of the atmosphere arising from the absorption of ultraviolet solar radiation.

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Identification Of Cosmic Particles 3695 Mev/C2 And 3105 Mev/C2, Frank H. Meyer, Ronald W. Satz Jan 1979

Identification Of Cosmic Particles 3695 Mev/C2 And 3105 Mev/C2, Frank H. Meyer, Ronald W. Satz

Journal of the Minnesota Academy of Science

No abstract provided.

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Sporadic Mass Ejection In Red Supergiants, Menas Kafatos, A. G. Michalitsianos Jan 1979

Sporadic Mass Ejection In Red Supergiants, Menas Kafatos, A. G. Michalitsianos

Mathematics, Physics, and Computer Science Faculty Articles and Research

We have applied a general mechanism first proposed by J. A. Burke to red supergiants for determining the spin-down rate and angular momentum loss of rotating stars. This model relies principally on sporadic mass ejection, which is assumed to be the result of turbulent elements accelerating material in cool supergiant.atmospheres. Mass is preferentially expelled in the forward direction of rotation, resulting in a rapid loss of angular momentum on time scales of 1Q^4-10^6 years in the supergiant evolutionary phase. Such rotational breaking will occur if the turbulent elements have characteristic sizes a few percent of the stellar radius, and rms …

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Penrose Pair Production As A Power Source Of Quasars And Active Galactic Nuclei, Menas Kafatos, D. Leiter Jan 1979

Penrose Pair Production As A Power Source Of Quasars And Active Galactic Nuclei, Menas Kafatos, D. Leiter

Mathematics, Physics, and Computer Science Faculty Articles and Research

In this paper we propose a new mechanism, Penrose pair production in massive, canonical (with a/M = 0.998) Kerr black holes, as a power source in quasars, Seyfert galaxies, radio galaxies, and BL Lac objects (i.e., what one usually refers to as active nuclei). As a working hypothesis, we postulate that massive (10^8 M0 or around this value) Kerr black holes reside in the centers of these objects. We also postulate that an accretion disk is formed. In a variety of models, hot, inner disks are expected. If the temperature is sufficiently high-as, for example, in the two-temperature model-then MeV …

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Chemical Vapor Deposited Amorphous Silicon For Use In Photothermal Conversion, David D. Allred, D. C. Booth, M. Janai, G. Weiser, B. O. Seraphin Nov 1978

Chemical Vapor Deposited Amorphous Silicon For Use In Photothermal Conversion, David D. Allred, D. C. Booth, M. Janai, G. Weiser, B. O. Seraphin

Faculty Publications

Efficient photothermal conversion requires surfaces of high solar absorptance and low thermal emittance. This can be accomplished by the tandem action of a good infrared reflector overlaid by a film of sufficient solar absorptance that is transparent in the infrared. Crystalline silicon is a suitable candidate for the absorber layer. Its indirect band gap, however, results in a shallow absorption edge that extends to far into the visible. In contrast, the absorption edge of amorphous silicon is steeper and located farther into the infrared, resulting in a larger solar absorptance. We report on the fabrication of amorphous silicon absorbers by …

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Chemical Vapor Deposited Molybdenum Films For Use In Photothermal Conversion, David D. Allred, G. E. Carver, B. O. Seraphin Nov 1978

Chemical Vapor Deposited Molybdenum Films For Use In Photothermal Conversion, David D. Allred, G. E. Carver, B. O. Seraphin

Faculty Publications

High infrared reflectance, coupled with higher solar absorptance, is required for efficient photothermal conversion. Converters can be fabricated by depositing an absorber on a highly reflecting metal. The absorber functions in the visible, yet becomes transparent in the near infrared, allowing the metal to suppress the thermal emittance. Economic considerations demand the use of thin films, rather than bulk materials. The thin film reflector must be capable of withstanding high temperatures of operation. Compatibility of the reflector with the substrate below, and the absorber above, is required for long-time service. Highly reflective silver films suffer reflectance losses by agglomeration, and …

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"Needed Social Innovations (Lecture 2)", John Rader Platt Jul 1978

"Needed Social Innovations (Lecture 2)", John Rader Platt

Special Collections: Oregon Public Speakers

No abstract provided.

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"Space Settlements", John Billingham Jun 1978

"Space Settlements", John Billingham

Special Collections: Oregon Public Speakers

No abstract provided.

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Recipe For A Moon, Edwin J. Geels Jun 1978

Recipe For A Moon, Edwin J. Geels

Pro Rege

No abstract provided.

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Energy And Angular Distribution Of Neutrons From Proton-Proton Inelastic Scattering At 800 Mev, Ted Dean Rupp Apr 1978

Energy And Angular Distribution Of Neutrons From Proton-Proton Inelastic Scattering At 800 Mev, Ted Dean Rupp

Physics & Astronomy ETDs

The neutron energy spectra from the reaction p + p → n + p + π+ for an incident proton energy of 800 MeV was measured for all phase space. ++ The channels were dominated by △++. (1232) resonance and had a total cross section of 16 ± 1.5 mb. Also, the data demonstrated the dominance of Sand P waves. The experimental results were compared to isobar, phase space and a one pion exchange model. The isobar and phase space models failed to predict the experimental results; however, the one pion exchange model fit the data for …

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Polynomial And Rational Fraction Representations Of A Diatomic Molecular Potential, Paul R. Findley Apr 1978

Polynomial And Rational Fraction Representations Of A Diatomic Molecular Potential, Paul R. Findley

Physics & Astronomy ETDs

A method is presented for approximating a diatomic molecular vibrational potential by fitting to modified forms of the potential. Power's numerical Born-Oppenheimer potential for the H2+ electronic ground state is the potential used in this thesis. The modification procedure is to multiply the potential by various powers of the internuclear separation. This removes the troublesome Coulomb pole at zero internuclear separation. Graphs of the modified forms are presented. Polynomials were fitted directly to the potential, to the modified forms, and to the pure electronic energy. Comparisons are made among the various representations of the potential obtained from the …

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Mass Loss And Oh Maser Emission From Mira Variables, A. G. Michalitsianos, Menas Kafatos Jan 1978

Mass Loss And Oh Maser Emission From Mira Variables, A. G. Michalitsianos, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

We have estimated the mass, radius, and luminosity of 26 Mira variables that are known OH sources of radio emission at 1612 MHz. The time-independent solution of Salpeter's stellar wind equation and a period-density relation are used to solve for basic stellar parameters, with the aid of the terminal expansion velocity of the OH maser cloud. Masses obtained from these calculations are consistent with other estimated values for masses of Mira variables. Good agreement is obtained when comparing the rate of mass loss as determined from Reimers's semiempirical relation to estimates of the mass loss rate as deduced from theoretical …

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Penrose Pair Production In Massive, Extreme Kerr Black Holes, D. Leiter, Menas Kafatos Jan 1978

Penrose Pair Production In Massive, Extreme Kerr Black Holes, D. Leiter, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

We show that in the case of very massive (M > 108 M0 ) Kerr black holes with extreme ranges of angular momentum 1 ≥ a/M > 0.998, the possibility of photon-induced Penrose pair production (PPP) in the ergosphere is very plausible. The pairs that escape the ergosphere are very high energy and on the order of the GeV rest mass of the Penrose accreted protons which participate in the photon-induced pair production process. Application of this model to the case of quasistellar objects (QSOs) is shown to lead to reasonable predictions about their masses, lifetimes, and luminosities. The physical mechanism is …

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The Central, Compact Source In The Cygnus A Galaxy, Menas Kafatos Jan 1978

The Central, Compact Source In The Cygnus A Galaxy, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

Single, optically thin, component models as well as double, optically thick at low frequencies, component models have been examined in trying to explain the central source in the nucleus of Cygnus A. In the course of exploring those models, it is found that this compact radio source may be quite similar to other compact and variable sources in Seyfert galaxies and quasars. Double component models generally do better because they fit the X-rays, and there is a good chance that the X-rays arise in the central source; these models can naturally explain variability which may already have been detected in …

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