26,369 research outputs found
Rules for Minimal Atomic Multipole Expansion of Molecular Fields
A non-empirical minimal atomic multipole expansion (MAME) defines atomic
charges or higher multipoles that reproduce electrostatic potential outside
molecules. MAME eliminates problems associated with redundancy and with
statistical sampling, and produces atomic multipoles in line with chemical
intuition.Comment: 3.5 pages, 3 color PS figures embedde
The status of music education in the public junior high schools of Massachusetts as of the year 1945-1955
Thesis (Ed.M.)--Boston Universit
Relations Between Organizational Design and Information Processing Systems: A Passionate Affair or a Stormy Interlude?
“This paper considers the issues surrounding the fit between information systems and organization structures. The paper uses philosophical ideas concerning knowledge and applies them to organizational design and information processing in order to encourage alternative perspectives and new ideas. This is achieved by a discussion of the issues surrounding organizational design and the impact of design on information processing; an overview of the ideas concerning the theory of knowledge proposed from both a rational and an empirical viewpoint. The paper closes with a discussion of the means by which philosophical considerations can assist towards new forms of information processing.
Excitations in time-dependent density-functional theory
An approximate solution to the time-dependent density functional theory
(TDDFT) response equations for finite systems is developed, yielding
corrections to the single-pole approximation. These explain why allowed
Kohn-Sham transition frequencies and oscillator strengths are usually good
approximations to the true values, and why sometimes they are not. The
approximation yields simple expressions for G\"orling-Levy perturbation theory
results, and a method for estimating expectation values of the unknown
exchange-correlation kernel.Comment: 4 pages, 1 tabl
Electrical conductivity of chondritic meteorites
The electrical conductivity of samples of the Murchison and Allende carbonaceous chondrites is 4 to 6 orders of magnitude greater than rock forming minerals such as olivine for temperatures up to 700 C. The remarkably high electrical conductivity of these meteorites is attributed to carbon at the grain boundaries. Much of this carbon is produced by pyrolyzation of hydrocarbons at temperatures in excess of 150 C. As the temperature increases, light hydrocarbons are driven off and a carbon-rich residue or char migrates to the grain boundaries enhancing electrical conductivity. Assuming that carbon was present at the grain boundaries in the material which comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance during a hypothetical T-Tauri phase of the sun. Input conductivity data for the meteorite parent body were the present carbonaceous chondrite values for temperatures up to 840 C and the electrical conductivity values for olivine above 840 C
Average and worst-case specifications of precipitating auroral electron environment
The precipitation electrons in the auroral environment are highly variable in their energy and intensity in both space and time. As such they are a source of potential hazard to the operation of the Space Shuttle and other large spacecraft operating in polar orbit. In order to assess these hazards both the average and extreme states of the precipitating electrons must be determined. Work aimed at such a specification is presented. First results of a global study of the average characteristics are presented. In this study the high latitude region was divided into spatial elements in magnetic local time and corrected geomagnetic latitude. The average electron spectrum was then determined in each spatial element for seven different levels of activity as measured by K sub p using an extremely large data set of auroral observations. Second a case study of an extreme auroral electron environment is presented, in which the electrons are accelerated through field aligned potential as high as 30,000 volts and in which the spacecraft is seen to charge negatively to a potential approaching .5 kilovolts
A Component Based Heuristic Search Method with Evolutionary Eliminations
Nurse rostering is a complex scheduling problem that affects hospital
personnel on a daily basis all over the world. This paper presents a new
component-based approach with evolutionary eliminations, for a nurse scheduling
problem arising at a major UK hospital. The main idea behind this technique is
to decompose a schedule into its components (i.e. the allocated shift pattern
of each nurse), and then to implement two evolutionary elimination strategies
mimicking natural selection and natural mutation process on these components
respectively to iteratively deliver better schedules. The worthiness of all
components in the schedule has to be continuously demonstrated in order for
them to remain there. This demonstration employs an evaluation function which
evaluates how well each component contributes towards the final objective. Two
elimination steps are then applied: the first elimination eliminates a number
of components that are deemed not worthy to stay in the current schedule; the
second elimination may also throw out, with a low level of probability, some
worthy components. The eliminated components are replenished with new ones
using a set of constructive heuristics using local optimality criteria.
Computational results using 52 data instances demonstrate the applicability of
the proposed approach in solving real-world problems.Comment: 27 pages, 4 figure
Spectrophotometry of 2 complete samples of flat radio spectrum quasars
Spectrophotometry of two complete samples of flat-spectrum radio quasars show that for these objects there is a strong correlation between the equivalent width of the CIV wavelength 1550 emission line and the luminosity of the underlying continuum. Assuming Friedmann cosmologies, the scatter in this correlation is a minimum for q (sub o) is approximately 1. Alternatively, luminosity evolution can be invoked to give compact distributions for q (sub o) is approximately 0 models. A sample of Seyfert galaxies observed with IUE shows that despite some dispersion the average equivalent width of CIV wavelength 1550 in Seyfert galaxies is independent of the underlying continuum luminosity. New redshifts for 4 quasars are given
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