1,617 research outputs found
The Nucleon-Nucleon Potential in the Chromo-Dielectric Soliton Model: Statics
We study the N-N interaction in the framework of the chromo-dielectric
soliton model. Here, the long-range parts of the nonabelian gluon
self-interactions are assumed to give rise to a color-dielectric function which
is parameterized in terms of an effective scalar background field. The
six-quark system is confined in a deformed mean field through an effective
non-linear interaction between the quarks and the scalar field. The CDM is
covariant, respects chiral invariance, leads to absolute color confinement and
is free of the spurious long range Van der Waals forces which trouble
non-relativistic investigations employing a confining potential. Six-quark
molecular-type configurations are generated as a function of deformation and
their energies are evaluated in a coupled channel analysis. By using molecular
states instead of cluster model wave functions, all important six-quark
configurations are properly taken into account. The corresponding Hamiltonian
includes the effective interaction between the quarks and the scalar background
field and quark-quark interactions generated through one gluon exchange treated
in Coulomb gauge. When evaluating the gluonic propagators, the inhomogeneity
and deformation of the dielectric medium are taken into account. Results for
the adiabatic nucleon-nucleon potential are presented, and the various
contributions are discussed. Finally, an outlook is given on how, in the next
stage of our investigation, the dynamical effects will be incorporated by
employing the generator coordinate method.Comment: 43 pages, REVTeX file followed by 11 uuencoded PostScript figures,
DOE/ER/40427-02-N9
Proceedings of the MECA Workshop on The Evoluation of the Martian Atmosphere
Topics addressed include: Mars' volatile budget; climatic implications of martian channels; bulk composition of Mars; accreted water inventory; evolution of CO2; dust storms; nonlinear frost albedo feedback on Mars; martian atmospheric evolution; effects of asteroidal and cometary impacts; and water exchange between the regolith and the atmosphere/cap system over obliquity timescales
New approach to He charge distribution
We present a study of the He charge distribution based on realistic
nucleonic wave functions and incorporation of the nucleon's quark substructure.
The central depression of the proton point density seen in modern four-body
calculations is too small by itself to lead to a correct description of the
charge distribution. We utilize six-quark structures calculated in the
Chromodielectric Model for N-N interactions, and we find a swelling of the
proton charge distribution as the internucleon distance decreases. These charge
distributions are combined with the He wave function using the Independent
Pair Approximation and two-body distributions generated from Green's Function
Monte Carlo calculations. We obtain a reasonably good fit to the experimental
charge distribution without including meson exchange currents.Comment: 9 pages, LaTeX, 4 figures (Figures 1 and 2 doesn't exist as
postscript files : they are only available on request
Ergonomics Case Study: EA-6B Aircraft Maintainer
Keeping our military aircraft mechanics healthy is essential for the defense of the country. To better understand the conditions which on-duty aircraft maintainers face, A series of ergonometric evaluations were performed on a retired United States Marine Corps mechanic as he simulated tasks performed while maintaining EA-6B Prowler aircraft. Four tasks were evaluated with either the Rapid Entire Body Assessment (REBA) tool, or the Washington State Risk Assessment Checklist (WAC). The tasks were grouped as being either strenuous or repetitive. The strenuous tasks involved high physical exertion. Repetitive tasks were less demanding but needed to be performed many times during a mechanic’s shift. Two strenuous tasks were examined, those being the replacement of engine Constant Speed Drive (CSD) units and engine access doors. The two repetitive tasks analyzed were the inspections of both cockpits and engine compressor blades. All tasks analyzed with the REBA scored within its two highest risk categories, and the weight of the CSD exceeded that recommended by the WAC by over 30lbs. Mechanics who perform these tasks should be aided by using mechanized jacks to lift heavy objects, while aspects of the repetitive tasks should be automated reduce their cumulative strain
Nested and dynamic documentation systems in/for teaching and teacher learning : re-conceptualising mathematics curriculum resources and their use.
Evaluating wildlife-cattle contact rates to improve the understanding of dynamics of bovine tuberculosis transmission in Michigan, USA
Direct and indirect contacts among individuals drive transmission of infectious disease. When multiple interacting species are susceptible to the same pathogen, risk assessment must include all potential host species. Bovine tuberculosis (bTB) is an example of a disease that can be transmitted among several wildlife species and to cattle, although the potential role of several wildlife species in spillback to cattle remains unclear. To better understand the complex network of contacts and factors driving disease transmission, we fitted proximity logger collars to beef and dairy cattle (n = 37), white-tailed deer (Odocoileus virginianus; n=29), raccoon (Procyon lotor; n=53), and Virginia opossum (Didelphis virginiana; n=79) for 16 months in Michigan\u27s Lower Peninsula, USA. We determined inter- and intra-species direct and indirect contact rates. Data on indirect contact was calculated when collared animals visited stationary proximity loggers placed at cattle feed and water resources. Most contact between wildlife species and cattle was indirect, with the highest contact rates occurring between raccoons and cattle during summer and fall. Nearly all visits (\u3e99%) to cattle feed and water sources were by cattle, whereas visitation to stored cattle feed was dominated by deer and raccoon (46% and 38%, respectively). Our results suggest that indirect contact resulting from wildlife species visiting cattle-related resources could pose a risk of disease transmission to cattle and deserves continued attention with active mitigation
Evaluating wildlife-cattle contact rates to improve the understanding of dynamics of bovine tuberculosis transmission in Michigan, USA
Direct and indirect contacts among individuals drive transmission of infectious disease. When multiple interacting species are susceptible to the same pathogen, risk assessment must include all potential host species. Bovine tuberculosis (bTB) is an example of a disease that can be transmitted among several wildlife species and to cattle, although the potential role of several wildlife species in spillback to cattle remains unclear. To better understand the complex network of contacts and factors driving disease transmission, we fitted proximity logger collars to beef and dairy cattle (n = 37), white-tailed deer (Odocoileus virginianus; n=29), raccoon (Procyon lotor; n=53), and Virginia opossum (Didelphis virginiana; n=79) for 16 months in Michigan\u27s Lower Peninsula, USA. We determined inter- and intra-species direct and indirect contact rates. Data on indirect contact was calculated when collared animals visited stationary proximity loggers placed at cattle feed and water resources. Most contact between wildlife species and cattle was indirect, with the highest contact rates occurring between raccoons and cattle during summer and fall. Nearly all visits (\u3e99%) to cattle feed and water sources were by cattle, whereas visitation to stored cattle feed was dominated by deer and raccoon (46% and 38%, respectively). Our results suggest that indirect contact resulting from wildlife species visiting cattle-related resources could pose a risk of disease transmission to cattle and deserves continued attention with active mitigation
SAM-2 ground-truth plan: Correlative measurements for the Stratospheric Aerosol Measurement-2 (SAM 2) sensor on the Nimbus G satellite
The SAM-2 will fly aboard the Nimbus-G satellite for launch in the fall of 1978 and measure stratospheric vertical profiles of aerosol extinction in high latitude bands. The plan gives details of the location and times for the simultaneous satellite/correlative measurements for the nominal launch time, the rationale and choice of the correlative sensors, their characteristics and expected accuracies, and the conversion of their data to extinction profiles. The SAM-2 expected instrument performance and data inversion results are presented. Various atmospheric models representative of polar stratospheric aerosols are used in the SAM-2 and correlative sensor analyses
Impact and collisional processes in the solar system
As impact cratered terrains have been successively recognized on certain planets and planetary satellites, it has become clear that impact processes are important to the understanding of the accretion and evolution of all solid planets. The noble gases in the normalized atmospheric inventories of the planets and the normalized gas content of meteorites are grossly similar, but demonstrate differences from each other which are not understood. In order to study shock devolatilization of the candidate carrier phases which are principally thought to be carbonaceous or hydrocarbons in planetesimals, experiments were conducted on noble gase implantation in various carbons: carbon black, activated charcoal, graphite, and carbon glass. These were candidate starting materials for impact devolatilization experiments. Initial experiments were conducted on vitreous amorphous carbon samples which were synthesized under vapor saturated conditions using argon as the pressurizing medium. An amino acid and surface analysis by laser ionization analyses were performed on three samples of shocked Murchison meteorite. A first study was completed in which a series of shock loading experiments on a porous limestone and on a non-porous gabbro in one and three dimensions were performed. Also a series of recovery experiments were conducted in which shocked molten basalt a 1700 C is encapsulated in molybdenum containers and shock recovered from up to 6 GPa pressures
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