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Articles 2191 - 2220 of 2389
Full-Text Articles in Entire DC Network
Secular Variations Of Atomic Oxygen In The Mesopause Region Induced By Transient Gravity Wave Packets, Michael P. Hickey Ph.D., R. L. Walterscheid, Philip G. Richards
Secular Variations Of Atomic Oxygen In The Mesopause Region Induced By Transient Gravity Wave Packets, Michael P. Hickey Ph.D., R. L. Walterscheid, Philip G. Richards
Publications
We employ a 2-dimensional, time-dependent, fully nonlinear model of minor species in the mesopause region and our Spectral Full-Wave Model to simulate the response of atomic oxygen (O) to a gravity wave packet in the mesopause region. We demonstrate that gravity waves affect the time-averaged distribution of O in the mesosphere and lower thermosphere (MLT) region through the constituent fluxes the waves induce. Our conclusions are based on simulations of two wave packets that violate the non-acceleration conditions through transience and dissipation. The net cycle-averaged effect of the waves is to significantly increase (by as much as 50%) the O …
Resolving Ambiguities In Gravity Wave Propagation Directions Inherent In Satellite Observations: A Simulation Study, Michael P. Hickey Ph.D., Jason S. Brown
Resolving Ambiguities In Gravity Wave Propagation Directions Inherent In Satellite Observations: A Simulation Study, Michael P. Hickey Ph.D., Jason S. Brown
Publications
We simulate space-based, sub-limb viewing observations of airglow brightness fluctuations caused by atmospheric gravity wave interactions with the O2 atmospheric airglow, and we demonstrate that, due to the geometry associated with such observations, the brightness fluctuations observed for the optically thick 0–0 band emission will always appear stronger for waves traveling towards the observer (satellite). The effect should be most noticeable for waves having relatively small vertical wavelengths (∼10 km) and horizontal wavelengths of 50 km or greater. For waves of short (∼100 km) horizontal wavelength, the brightness fluctuation anisotropy with respect to viewing direction may also be evident in …
The White Dwarf Cooling Age Of The Open Cluster Ngc 2420, Ted Von Hippel, Gerard Gilmore
The White Dwarf Cooling Age Of The Open Cluster Ngc 2420, Ted Von Hippel, Gerard Gilmore
Publications
We have used deep HST WFPC2 observations of two fields in NGC 2420 to produce a cluster color-magnitude diagram down to V ≈ 27. After imposing morphological selection criteria we find eight candidate white dwarfs in NGC 2420. Our completeness estimates indicate that we have found the terminus of the WD cooling sequence. We argue that the cluster distance modulus is likely to be close to 12.10 with E(B-V) = 0.04. With these parameters we find a white dwarf cooling age for NGC 2420 of 2.0 ± 0.20 (1 σ) Gyr. The 0.20 Gyr uncertainty includes errors in the photometry, …
Characterization Of An Isolate That Uses Vinyl Chloride As A Growth Substrate Under Aerobic Conditions, Matthew F. Verce, Ricky L. Ulrich, David L. Freedman
Characterization Of An Isolate That Uses Vinyl Chloride As A Growth Substrate Under Aerobic Conditions, Matthew F. Verce, Ricky L. Ulrich, David L. Freedman
Publications
An aerobic enrichment culture was developed by using vinyl chloride (VC) as the sole organic carbon and electron donor source. VC concentrations as high as 7.3 mM were biodegraded without apparent inhibition. VC use did not occur when nitrate was provided as the electron acceptor. A gram-negative, rod-shaped, motile isolate was obtained from the enrichment culture and identified based on biochemical characteristics and the sequence of its 16S rRNA gene as Pseudomonas aeruginosa, designated strain MF1. The observed yield of MF1 when it was grown on VC was 0.20 mg of total suspended solids (TSS)/mg of VC. Ethene, acetate, glyoxylate, …
Mpi Collective Operations Over Ip Multicast, Amy Apon, H A. Chen, Y O. Carrasco
Mpi Collective Operations Over Ip Multicast, Amy Apon, H A. Chen, Y O. Carrasco
Publications
Many common implementations of Message Passing Inter- face (MPI) implement collective operations over point-to-point operations. This work examines IP multicast as a framework for collective operations. IP multicast is not reliable. If a receiver is not ready when a message is sent via IP multicast, the message is lost. Two techniques for ensuring that a message is not lost due to a slow receiving process are examined. The techniques are implemented and compared experimentally over both a shared and a switched Fast Ethernet. The average performance of collective operations is improved as a function of the number of participating processes …
An Elliptic Equation With Spike Solutions Concentrating At Local Minima Of The Laplacian Of The Potential, Gregory S. Spradlin
An Elliptic Equation With Spike Solutions Concentrating At Local Minima Of The Laplacian Of The Potential, Gregory S. Spradlin
Publications
We consider the equation −ԑ2∆u + V (z)u = f(u) which arises in the study of nonlinear Schrödinger equations. We seek solutions that are positive on RN and that vanish at infinity. Under the assumption that f satisfies super-linear and sub-critical growth conditions, we show that for small ԑ there exist solutions that concentrate near local minima of V. The local minima may occur in unbounded components, as long as the Laplacian of V achieves a strict local minimum along such a component. Our proofs employ vibrational mountain-pass and concentration compactness arguments. A penalization technique developed by Felmer and del …
Accountability Policy At The Street Level In Kentucky: Teachers And Administrators Debate The Fairness Of Continuous Improvement Versus Relative Standing, Jane Clark Lindle
Accountability Policy At The Street Level In Kentucky: Teachers And Administrators Debate The Fairness Of Continuous Improvement Versus Relative Standing, Jane Clark Lindle
Publications
While scholars of educational accountability policy will not be surprised at the power of local implementers in modifying accountability efforts, Kentucky's street-level debate splits two constituencies in defining a fair system. Advocates for the education of all children including the poor and minorities support the continuous improvement model, while elite advocates support recognition of relative standing of schools. This paper includes data from teachers and administrators in four schools identified as eligible for state assistance under Kentucky's testing and accountability system. Of particular interest are the perceptions of accountability held by teachers and administrators in one school that had received …
Climate Change: The Next Dimension, Lakshman Guruswamy
Climate Change: The Next Dimension, Lakshman Guruswamy
Publications
No abstract provided.
A Case Study In The Intersection Of Law And Science: The 1999 Report Of The Committee Of Scientists, Charles F. Wilkinson
A Case Study In The Intersection Of Law And Science: The 1999 Report Of The Committee Of Scientists, Charles F. Wilkinson
Publications
No abstract provided.
A Normative Analysis Of New Financially Engineered Derivatives, Peter H. Huang
A Normative Analysis Of New Financially Engineered Derivatives, Peter H. Huang
Publications
This Article analyzes whether the introduction of new derivative assets makes a society better or worse off. Because trading such non-redundant derivatives produces new distributions of income across time and over possible future contingencies, individuals can utilize such financial instruments to hedge risks not possible before the introduction of these assets. Thus, it may seem that new derivatives unambiguously benefit society. In fact, introducing sufficiently many new derivatives completes asset markets. Asset markets are complete if trading on them can attain every possible payoff pattern of wealth across time and over possible future contingencies. The first fundamental theorem of welfare …
Book Review: The Birth Of Time: How Astronomers Measured The Age Of The Universe, T. D. Oswalt
Book Review: The Birth Of Time: How Astronomers Measured The Age Of The Universe, T. D. Oswalt
Publications
This document is Dr. Oswalt’s review of The Birth of Time : How Astronomers Measured the Age of the Universe by John Gribbin. Yale, 2000 237p, 0-300-08346-7 $22.50.
The Wiyn Open Cluster Study: A New Color-Magnitude Diagram For M35 - A Twin Of The Pleiades, Ted Von Hippel, Vera Kozhurina-Platais, Imants Platais, Pierre Demarque, Ata Sarajedini
The Wiyn Open Cluster Study: A New Color-Magnitude Diagram For M35 - A Twin Of The Pleiades, Ted Von Hippel, Vera Kozhurina-Platais, Imants Platais, Pierre Demarque, Ata Sarajedini
Publications
M35 (NGC 2168) is rich, young, and in some regards a better laboratory for stellar cluster research at 100 million years than the Pleiades. Yet, while M35 has been the subject of intriguing photometric, astrometric, and theoretical studies, to the best of our knowledge no published CCD-based photometry exists for this cluster. We have obtained relatively wide-field (23' x23') precise UBVRJ CCD photometry for M35 as part of the WIYN Open Cluster Study (WOCS) at the 0.9m telescope at Kitt Peak National Observatory. The photometry extends from the main sequence turn off to beyond V = 19. We find that …
Public Education And Greenwood County: A Benchmarking Tool, 1999 December 31, Louis R. Lanier, Ellen Weeks Saltzman
Public Education And Greenwood County: A Benchmarking Tool, 1999 December 31, Louis R. Lanier, Ellen Weeks Saltzman
Publications
No abstract provided.
(Teff,Log G,[Fe/H]) Classification Of Low-Resolution Stellar Spectra Using Artificial Neural Networks, Shawn Snider, Yuan Qu, Carlos Allende Prieto, Ted Von Hippel, Timothy C. Beers, Christopher Sneden, David L. Lambert, Silvia Rossi
(Teff,Log G,[Fe/H]) Classification Of Low-Resolution Stellar Spectra Using Artificial Neural Networks, Shawn Snider, Yuan Qu, Carlos Allende Prieto, Ted Von Hippel, Timothy C. Beers, Christopher Sneden, David L. Lambert, Silvia Rossi
Publications
New generation large-aperture telescopes, multi-object spectrographs, and large format detectors are making it possible to acquire very large samples of stellar spectra rapidly. In this context, traditional star-by-star spectroscopic analysis are no longer practical. New tools are required that are capable of extracting quickly and with reasonable accuracy important basic stellar parameters coded in the spectra. Recent analyses of Artificial Neural Networks (ANNs) applied to the classification of astronomical spectra have demonstrated the ability of this concept to derive estimates of temperature and luminosity. We have adapted the back-propagation ANN technique developed by von Hippel et al. (1994) to predict …
Wiyn Open Cluster Study. Ii. Ubvri Ccd Photometry Of The Open Cluster Ngc 188, Ata Sarajedini, Ted Von Hippel, Vera Kozhurina-Platais, Pierre Demarque
Wiyn Open Cluster Study. Ii. Ubvri Ccd Photometry Of The Open Cluster Ngc 188, Ata Sarajedini, Ted Von Hippel, Vera Kozhurina-Platais, Pierre Demarque
Publications
We present high-precision UBVRI CCD photometry of the old open cluster NGC 188. Our color-magnitude diagram extends from near the red giant branch tip to as faint as ~5 mag below the main-sequence turnoff. From an analysis of these data along with published photometry for M67, we draw the following conclusions: (1) From the UBV two-color diagram, we find a reddening of E(B ̶ V) = 0.04 ± 0.02 for M67 and E(B ̶ V) = 0.09 ± 0.02 for NGC 188. (2) Based on main-sequence fitting to solar abundance isochrones, the distance moduli …
An Elliptic Partial Differential Equation With A Symmetrical Almost Periodic Term, Gregory S. Spradlin
An Elliptic Partial Differential Equation With A Symmetrical Almost Periodic Term, Gregory S. Spradlin
Publications
In [STT], a Hamiltonian system of the form (1.0)− u′′+ u= h (t)∇ F (u) was studied, where h is an almost periodic (defined in a moment) function, and F: RN→ R a “superquadratic” potential. That is, F (q) behaves like q to a power greater than 2, with F (q)/| q| 2→ 0 as| q|→ 0 and F (q)/| q| 2→∞ as| q|→∞. For example, F (q)=| q| p− 1q with p> 1 would qualify. The authors found that (1.0) must have a nonzero solution homoclinic to zero. Since this result, many papers (see [CMN],[R1], and [ACM], for example) …
A Singularly Perturbed Elliptic Partial Differential Equation With An Almost Periodic Term, Gregory S. Spradlin
A Singularly Perturbed Elliptic Partial Differential Equation With An Almost Periodic Term, Gregory S. Spradlin
Publications
In [STT], a Hamiltonian system of the form (1. 0)− u+ u= h (t)∇ F (u) was studied, where h is an almost periodic (defined in a moment) function, and F: Rn→ R a “superquadratic” potential. That is, F (q) behaves like q to a power greater than 2, with F (q)/| q| 2→ 0 as| q|→ 0 and F (q)/| q| 2→∞ as| q|→∞. For example, F (q)=| q| p− 1q with p> 1 would qualify. The authors found that (1.0) must have a nonzero solution homoclinic to zero. Since this result, many papers (see [CMN],[R1], and [ACM], for …
Enhanced Biotransformation Of Carbon Tetrachloride By Acetobacterium Woodii Upon Addition Of Hydroxocobalamin And Fructose, Syed A. Hashsham, David L. Freedman
Enhanced Biotransformation Of Carbon Tetrachloride By Acetobacterium Woodii Upon Addition Of Hydroxocobalamin And Fructose, Syed A. Hashsham, David L. Freedman
Publications
The objective of this study was to evaluate the effect of hydroxocobalamin (OH-Cbl) on transformation of high concentrations of carbon tetrachloride (CT) by Acetobacterium woodii (ATCC 29683). Complete transfor-mation of 470 M (72 mg/liter [aqueous]) CT was achieved by A. woodii within 2.5 days, when 10 M OH-Cbl was added along with 25.2 mM fructose. This was approximately 30 times faster than A. woodii cultures (live or autoclaved) and medium that did not receive OH-Cbl and 5 times faster than those controls that did receive OH-Cbl, but either live A. woodii or fructose was missing. CT transformation in treatments with …
A Review Of Automated Stellar Spectral Classification And Surveys, Ted Von Hippel, Coryn A.L. Bailer-Jones
A Review Of Automated Stellar Spectral Classification And Surveys, Ted Von Hippel, Coryn A.L. Bailer-Jones
Publications
Modern spectroscopic surveys and automated classifiers are becoming so inextricably linked that it is difficult even to summarize one without discussing the other. Some of the automated classifiers are being built because of current analysis needs, though with a clear anticipation of future, larger surveys. Other automated classifiers are being designed specifically for future surveys. Automated classifiers may be applied to databases already in hand, to real-time analysis at the telescope, or one day to on-board satellite analysis where the raw data are too bulky to save and transmit. In addition, many current spectroscopic surveys target galaxies. These surveys may …
Observations And Interpretation Of Gravity Wave Induced Fluctuations In The O I (557.7 Nm) Airglow, G. Schubert, R. L. Walterscheid, Michael P. Hickey Ph.D., C. A. Tepley
Observations And Interpretation Of Gravity Wave Induced Fluctuations In The O I (557.7 Nm) Airglow, G. Schubert, R. L. Walterscheid, Michael P. Hickey Ph.D., C. A. Tepley
Publications
Observations of fluctuations in the intensity and temperature of the O I (557.7 nm) airglow taken at Arecibo in 1989 are reported and interpreted on the assumption that they are caused by gravity waves propagating through the emission layer. The data give the magnitude of Krassovsky's ratio as 3.5 ± 2.2, at periods between about 5 and 10 hours. Comparison with theory shows that the gravity waves responsible for the measured airglow variations must have long wavelengths of several thousand kilometers. The observed phases of Krassovsky's ratio are in good agreement with theoretically predicted values at the long wavelengths and …
Evaluation Of Real-Time Fiber Communications For Parallel Collective Operations, Amy Apon, Parvathi Rajagopal
Evaluation Of Real-Time Fiber Communications For Parallel Collective Operations, Amy Apon, Parvathi Rajagopal
Publications
Real-Time Fiber Communications (RTFC) is a gigabit speed network that has been designed for damage tolerant local area networks. In addition to its damage tolerant characteristics, it has several features that make it attractive as a possible interconnection technology for parallel applications in a cluster of workstations. These characteristics include support for broadcast and multicast messaging, memory cache in the network interface card, and support for very fine grain writes to the network cache. Broadcast data is captured in network cache of all workstations in the network providing a distributed shared memory capability. In this paper, RTFC is introduced. The …
Load Dependent Single Chain Models Of Multichain Closed Queueing Networks, Amy Apon, Lawrence Dowdy
Load Dependent Single Chain Models Of Multichain Closed Queueing Networks, Amy Apon, Lawrence Dowdy
Publications
No abstract provided.
A Note On Gravity Wave-Driven Volume Emission Rate Weighted Temperature Perturbations Inferred From O₂ Atmospheric And O I 5577 Airglow Observations, Michael P. Hickey Ph.D., Richard L. Walterscheid
A Note On Gravity Wave-Driven Volume Emission Rate Weighted Temperature Perturbations Inferred From O₂ Atmospheric And O I 5577 Airglow Observations, Michael P. Hickey Ph.D., Richard L. Walterscheid
Publications
A full-wave dynamical model and chemistry models that simulate ground-based observations of gravity wave-driven O₂ atmospheric and O I 5577 airglow fluctuations in the mesopause region are used to demonstrate that for many observable gravity waves modeling is required to infer temperature perturbation amplitudes from airglow observations. We demonstrate that the amplitude of the altitude-integrated volume emission rate weighted temperature perturbation differs by at least about 30% from the amplitude of the temperature perturbation of the major gas in the vicinity of the peak of the airglow volume emission rate for gravity waves with horizontal phase speeds less than about …
Simple Mathematics: South Carolina's State Property Tax Relief Is Unsustainable, 1999, James C. Hite
Simple Mathematics: South Carolina's State Property Tax Relief Is Unsustainable, 1999, James C. Hite
Publications
No abstract provided.
What The Twins Saw, Paul F. Campos
The Roth Ira Cuts Federal Revenues, With No Benefit To Taxpayers, Michael Waggoner
The Roth Ira Cuts Federal Revenues, With No Benefit To Taxpayers, Michael Waggoner
Publications
No abstract provided.
Thermal Plasmaspheric Morphology: Effect Of Geomagnetic And Solar Activity, Mark Anthony Reynolds, G. Ganguli, J.A. Fedder, J. Lemaire, R.R. Meier, D.J. Melendez-Alvira
Thermal Plasmaspheric Morphology: Effect Of Geomagnetic And Solar Activity, Mark Anthony Reynolds, G. Ganguli, J.A. Fedder, J. Lemaire, R.R. Meier, D.J. Melendez-Alvira
Publications
A multispecies kinetic model of the thermal plasma in the plasmasphere is used to predict the spatial dependence of the hydrogen ion and helium ion density and temperature for different levels of geomagnetic and solar activity. The particular convection electric field model chosen is intended for the time intervals between substorms. The plasma density and temperature in the equatorial plane are found to exhibit a local-time variation that is sensitive to the details of the convection electric field. In particular, the parallel temperature increases with altitude and the perpendicular temperature decreases with altitude, except in the postmidnight sector, features that …
Site Index Of Balsam Poplar/Western Black Cottonwood In Interior And Southcentral Alaska, John D. Shaw, Edmond C. Packee
Site Index Of Balsam Poplar/Western Black Cottonwood In Interior And Southcentral Alaska, John D. Shaw, Edmond C. Packee
Publications
Stem analysis data were obtained from 268 balsam poplar (populus balsamifera L.) and black cottonwood (P. trichocarpa Torr. & Gray) trees on 67 sites in interior and southcentral Alaska during 1988-1990 for the purpose of height and volume growth analysis. A modifiedform of the Chapman-Richards growth model was used to produce polymorphic site index curves. Wide variations in curve shape, which were evident in region-to-region comparisons, required stratification ofthe data. Site index curves for balsam poplar north ofthe Alaska Range were produced using one equation and data from 35 sites. The remaining 32 sites, located south ofthe Range, were divided …
Site Index Of Balsam Poplar/Western Black Cottonwood In Interior And Southcentral Alaska, John D. Shaw, Edmond C. Packee
Site Index Of Balsam Poplar/Western Black Cottonwood In Interior And Southcentral Alaska, John D. Shaw, Edmond C. Packee
Publications
Stem analysis data were obtained from 268 balsam poplar (populus balsamifera L.) and black cottonwood (P. trichocarpa Torr. & Gray) trees on 67 sites in interior and southcentral Alaska during 1988-1990 for the purpose of height and volume growth analysis. A modifiedform of the Chapman-Richards growth model was used to produce polymorphic site index curves. Wide variations in curve shape, which were evident in region-to-region comparisons, required stratification ofthe data. Site index curves for balsam poplar north ofthe Alaska Range were produced using one equation and data from 35 sites. The remaining 32 sites, located south ofthe Range, were divided …
Wiyn Open Cluster Study. I. Deep Photometry Of Ngc188, Ted Von Hippel, Ata Sarajedini
Wiyn Open Cluster Study. I. Deep Photometry Of Ngc188, Ted Von Hippel, Ata Sarajedini
Publications
We have employed precise and carefully calibrated V - and I - band photometry of NGC 188 at WIYN Observatory to explore the cluster luminosity function (LF) and study the cluster white dwarfs. Our photometry is offset by V = 0.052 (fainter) from that of Sandage and Eggen & Sandage. All published photometry for the past three decades has been based on these two calibrations, which are in error by 0.05 ± 0.01. We employ the Pinsonneault et al. fiducial open cluster main sequence to derive a distance modulus of 11.43 ± 0.08 and E(B - V )=0.09, with …