2,306 research outputs found
Blue Boogie / words by John W. Schaum
Cover: caricature of an African American male face; Publisher: Belwin (New York)https://egrove.olemiss.edu/sharris_e/1067/thumbnail.jp
Cross Section For Excitation Of The Fourth Positive Band System In Carbon Monoxide By 20-120 KeV Protons
Excitation cross sections for the fourth positive band system in carbon monoxide have been determined from studies of the energy-loss spectra of 20-120-keV protons incident on gaseous CO targets. The energy-loss spectra had an energy resolution of about 2 eV. Prominent peaks in the spectra were observed at 8.5 and 13.8 eV. The first peak is believed to be due to excitation of the fourth positive band system of CO (X+1A 1, while the 13.8-eV peak covers a number of possible states, including the B+2 and the C+1 states. Changes in the slope of the ionization continuum were noted at 16.5 eV, corresponding to the A i2 state of CO+, and at 20.5 eV, corresponding to the B+2 state of CO+. Absolute excitation cross sections for the fourth positive band system of CO are presented, as well as the total inelastic cross sections and the total ionization cross sections for 20-120-keV protons incident on CO. © 1970 The American Physical Society
Shame On You / music by John Larkins; words by Chris Smith
Cover: drawing of an African American preacher stealing a chicken; photo inset of Lew Dockstader in blackface; Publisher: Jos. W. Stern and Co. (New York)https://egrove.olemiss.edu/sharris_b/1050/thumbnail.jp
System For Data Acquisition From High Voltage Terminals
An inexpensive data acquisition system has been designed to provide high voltage isolation for data acquisition in analog, digital, and pulse modes. The telemetry system uses GaAs light sources, fiber optics, and phototransistors to accomplish the data transmission. Prewired logic boards have been adapted to accomplish the timing and logic functions. Seven decades of digital data are transmitted error free, pulse data can be transmitted at rates up to 1 MHz, and analog data are transmitted with 0.05% full scale accuracy. © 1972 The American Institute of Physics
Evolving a puncture black hole with fixed mesh refinement
We present an algorithm for treating mesh refinement interfaces in numerical
relativity. We detail the behavior of the solution near such interfaces located
in the strong field regions of dynamical black hole spacetimes, with particular
attention to the convergence properties of the simulations. In our applications
of this technique to the evolution of puncture initial data with vanishing
shift, we demonstrate that it is possible to simultaneously maintain second
order convergence near the puncture and extend the outer boundary beyond 100M,
thereby approaching the asymptotically flat region in which boundary condition
problems are less difficult and wave extraction is meaningful.Comment: 18 pages, 12 figures. Minor changes, final PRD versio
Constraint and gauge shocks in one-dimensional numerical relativity
We study how different types of blow-ups can occur in systems of hyperbolic
evolution equations of the type found in general relativity. In particular, we
discuss two independent criteria that can be used to determine when such
blow-ups can be expected. One criteria is related with the so-called geometric
blow-up leading to gradient catastrophes, while the other is based upon the
ODE-mechanism leading to blow-ups within finite time. We show how both
mechanisms work in the case of a simple one-dimensional wave equation with a
dynamic wave speed and sources, and later explore how those blow-ups can appear
in one-dimensional numerical relativity. In the latter case we recover the well
known ``gauge shocks'' associated with Bona-Masso type slicing conditions.
However, a crucial result of this study has been the identification of a second
family of blow-ups associated with the way in which the constraints have been
used to construct a hyperbolic formulation. We call these blow-ups ``constraint
shocks'' and show that they are formulation specific, and that choices can be
made to eliminate them or at least make them less severe.Comment: 19 pages, 8 figures and 1 table, revised version including several
amendments suggested by the refere
Three dimensional numerical relativity: the evolution of black holes
We report on a new 3D numerical code designed to solve the Einstein equations
for general vacuum spacetimes. This code is based on the standard 3+1 approach
using cartesian coordinates. We discuss the numerical techniques used in
developing this code, and its performance on massively parallel and vector
supercomputers. As a test case, we present evolutions for the first 3D black
hole spacetimes. We identify a number of difficulties in evolving 3D black
holes and suggest approaches to overcome them. We show how special treatment of
the conformal factor can lead to more accurate evolution, and discuss
techniques we developed to handle black hole spacetimes in the absence of
symmetries. Many different slicing conditions are tested, including geodesic,
maximal, and various algebraic conditions on the lapse. With current
resolutions, limited by computer memory sizes, we show that with certain lapse
conditions we can evolve the black hole to about , where is the
black hole mass. Comparisons are made with results obtained by evolving
spherical initial black hole data sets with a 1D spherically symmetric code. We
also demonstrate that an ``apparent horizon locking shift'' can be used to
prevent the development of large gradients in the metric functions that result
from singularity avoiding time slicings. We compute the mass of the apparent
horizon in these spacetimes, and find that in many cases it can be conserved to
within about 5\% throughout the evolution with our techniques and current
resolution.Comment: 35 pages, LaTeX with RevTeX 3.0 macros. 27 postscript figures taking
7 MB of space, uuencoded and gz-compressed into a 2MB uufile. Also available
at http://jean-luc.ncsa.uiuc.edu/Papers/ and mpeg simulations at
http://jean-luc.ncsa.uiuc.edu/Movies/ Submitted to Physical Review
Understanding the Essex Junto: Fear, Dissent, and Propaganda in the Early Republic
Historians have never formed a consensus over the Essex Junto. In fact, though often associated with New England Federalists, propagandists evoked the Junto long after the Federalist Party’s demise in 1824. This article chronicles uses of the term Essex Junto and its significance as it evolved from the early republic through the 1840s
The toxicity of diquat, endothall, and fluridone to the early life stages of fish
ABSTRACT While most aquatic herbicides have undergone some toxicity testing for effects on non-target aquatic organisms, little of this testing has been conducted on early life stages of gamefish found in lakes undergoing treatment. Commercial formulations of diquat, endothall, and fluridone were selected for acute toxicity testing using very early life stages of walleye (Stizostedion vitreum), largemouth bass (Micropterus salmoides), and smallmouth bass (Micropterus dolomieu). In addition, the rates of diquat photodegradation and uptake by sediment were determined. These results were used to predict diquat concentrations in lakes of various depths. The results of the toxicity tests were compared to the predicted concentrations. Diquat, with 96-h LC50s of 0.74-4.9 mg/L, was more toxic to these early life stages than endothall or fluridone, with 96-h LC50s of 16-130 mg/L and 1.8-13 mg/L respectively. The LC50s for endothall and fluridone were at least one order of magnitude greater than the labeled application concentrations. As the LC50s for diquat were very close to the predicted concentration, the safety margin for the use of diquat appears to be very small
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