3,134 research outputs found
Spacetime Supersymmetry in a nontrivial NS-NS Superstring Background
In this paper we consider superstring propagation in a nontrivial NS-NS
background. We deform the world sheet stress tensor and supercurrent with an
infinitesimal B_{\mu\nu} field. We construct the gauge-covariant super-Poincare
generators in this background and show that the B_{\mu\nu} field spontaneously
breaks spacetime supersymmetry. We find that the gauge-covariant spacetime
momenta cease to commute with each other and with the spacetime supercharges.
We construct a set of "magnetic" super-Poincare generators that are conserved
for constant field strength H_{\mu\nu\lambda}, and show that these generators
obey a "magnetic" extension of the ordinary supersymmetry algebra.Comment: 13 pages, Latex. Published versio
The energy of the high-temperature quark-gluon plasma
For the quark-gluon plasma, an energy-momentum tensor is found corresponding
to the high-temperature Braaten-Pisarski effective action. The tensor is found
by considering the interaction of the plasma with a weak gravitational field
and the positivity of the energy is studied. In addition, the complete
effective action in curved spacetime is written down.Comment: 13 pages, one figure, plain TeX forma
Towards measures of the eradicability of rain-splashed crop diseases
Controlling rain-splashed crop diseases is an extremely difficult task. Their spread is a complicated process and large-scale field surveys to determine the extent of an incursion over a large area are often economically intractable. A failed attempt at control or eradication of a pathogen can be very costly. In 1996 there was a major incursion of lupin anthracnose in Western Australia, which crippled the albus lupin industry. At the time of the outbreak a wide-spread survey was undertaken to estimate the extent of the incursion. A containment protocol involving broad-scale crop destruction was put into place with the view of eradicating the disease. This eradication attempt subsequently failed due to wild lupins acting as a reservoir for the disease from road verges and non-arable land outside the cropping area. There was also evidence of long distance dispersal vectors such as native budworm. Had all the relevant information related to spread and spatial habitat suitability been collected and taken into account, the decision to destroy the crops may not have been made and significant economic losses to growers may have been avoided. Estimates of the current extent of an incursion based solely on incomplete empirical data are likely to be inaccurate, as are predictions of the future trajectory of an incursion that do not take into account all available information. Therefore any control or eradication attempt based on these estimates and predictions may be ineffective.
Simulation modelling is an important method for making the best use of all available empirical data and integrating all available knowledge to predict the spread of rain-splashed crop diseases. With this prediction, an evaluation of the potential success of control or eradication measures may be estimated. This study describes a model that was built to simulate a situation analogous to that of the 1996 lupin anthracnose incursion in Western Australia, for the purpose of identifying general indicators of the eradicability of rain-splashed crop diseases.
We extended the spatiotemporal model AnthracnoseTracer to simulate the spread of lupin anthracnose in a heterogeneous paddock environment analogous to the 1996 conditions. Three control methods aimed at eradication were investigated. A simple detection model was assumed, where the probability of detecting the disease is dependent on the level of passive surveillance and the detectability of the disease.
As part of the preliminary analysis contained in this paper we investigated two scenarios to identify potential indicators of eradicability, based on the time taken to detect the disease. Our preliminary results indicate that rain-splashed pathogens are extremely difficult to eradicate and the chance of successful eradication appears strongly dependent on the level of surveillance of the susceptible areas and the detectability of the disease. The level of surveillance and detectability of the disease may both serve as general indicators of eradicability for rain-splashed crop diseases. We discuss further modelling analyses to be carried out to refine these indicators
Surface and capillary transitions in an associating binary mixture model
We investigate the phase diagram of a two-component associating fluid mixture
in the presence of selectively adsorbing substrates. The mixture is
characterized by a bulk phase diagram which displays peculiar features such as
closed loops of immiscibility. The presence of the substrates may interfere the
physical mechanism involved in the appearance of these phase diagrams, leading
to an enhanced tendency to phase separate below the lower critical solution
point. Three different cases are considered: a planar solid surface in contact
with a bulk fluid, while the other two represent two models of porous systems,
namely a slit and an array on infinitely long parallel cylinders. We confirm
that surface transitions, as well as capillary transitions for a large
area/volume ratio, are stabilized in the one-phase region. Applicability of our
results to experiments reported in the literature is discussed.Comment: 12 two-column pages, 12 figures, accepted for publication in Physical
Review E; corrected versio
Action at a distance as a full-value solution of Maxwell equations: basis and application of separated potential's method
The inadequacy of Li\'{e}nard-Wiechert potentials is demonstrated as one of
the examples related to the inconsistency of the conventional classical
electrodynamics. The insufficiency of the Faraday-Maxwell concept to describe
the whole electromagnetic phenomena and the incompleteness of a set of
solutions of Maxwell equations are discussed and mathematically proved. Reasons
of the introduction of the so-called ``electrodynamics dualism concept"
(simultaneous coexistence of instantaneous Newton long-range and
Faraday-Maxwell short-range interactions) have been displayed. It is strictly
shown that the new concept presents itself as the direct consequence of the
complete set of Maxwell equations and makes it possible to consider classical
electrodynamics as a self-consistent and complete theory, devoid of inward
contradictions. In the framework of the new approach, all main concepts of
classical electrodynamics are reconsidered. In particular, a limited class of
motion is revealed when accelerated charges do not radiate electromagnetic
field.Comment: ReVTeX file, 24pp. Small corrections which do not have influence
results of the paper. Journal reference is adde
How the composition of sandstone matrices affects rates of soil formation
Soils deliver multiple ecosystem services and their long-term sustainability is fundamentally controlled by the rates at which they form and erode. Our knowledge and understanding of soil formation is not commensurate with that of soil erosion, in part due to the difficulty of measuring the former. However, developments in cosmogenic radionuclide accumulation models have enabled soil scientists to more accurately constrain the rates at which soils form from bedrock. To date, all three major rock types – igneous, sedimentary and metamorphic lithologies – have been examined in such work. Soil formation rates have been measured and compared between these rock types, but the impact of rock characteristics on soil formation rates, such as rock matrices and mineralogy, have seldom been explored. In this UK-based study, we used cosmogenic radionuclide analysis to investigate whether the lithological variability of sandstone governs pedogenesis. Soil formation rates were measured on two arable hillslopes at Woburn and Hilton, which are underlain by different types of arenite sandstone. Rates were faster at Woburn, and we suggest that this is due to the fact that the Woburn sandstone formation is less cemented that that at Hilton. Similarly, rates at Woburn and Hilton were found to be faster than those measured at two other sandstone-based sites in the UK, and faster than those compiled in a global inventory of cosmogenic studies on sandstone-based soils. We suggest that the cementing agents present in matrix-abundant wackes studied previously may afford these sandstones greater structural integrity and resistance to weathering. This work points to the importance of factoring bedrock matrices into our understanding of soil formation rates, and the biogeochemical cycles these underpi
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Tank Vapor Characterization Project: Headspace vapor characterization of Hanford Waste Tank 241-S-103: Results from samples collected on 06/12/96
This report describes the analytical results of vapor samples taken from the headspace of the waste storage tank 241-S-103 (Tank S-103) at the Hanford Site in Washington State. The results described in this report were obtained to characterize the vapors present in the tank headspace and to support safety evaluations and tank farm operations. The results include air concentrations of selected inorganic and organic analytes and grouped compounds from samples obtained by Westinghouse Hanford Company (WHC) and provided for analysis to Pacific Northwest National Laboratory (PNNL). Analyses were performed by the Vapor Analytical Laboratory (VAL) at PNNL. Analyte concentrations were based on analytical results and, where appropriate, sample volumes provided by WHC. A summary of the inorganic analytes, permanent gases, and total non-methane organic compounds is listed in Table S.1. The three highest concentration analytes detected in SUMMA{trademark} canister and triple sorbent trap samples are also listed in Table S.1. Detailed descriptions of the analytical results appear in the appendices
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Permeability reduction by pyrobitumen, mineralization, and stress along large natural fractures in sandstones at 18,300 ft. depth: Destruction of a reservoir
Production of gas from the Frontier Formation at 18,300 R depth in the Frewen No. 4 Deep well, eastern Green River basin (Wyoming), was uneconomic despite the presence of numerous open natural fractures. Initial production tested at 500 MCFD, but dropped from 360 MCFD to 140 MCFD during a 10-day production test, and the well was abandoned. Examination of the fractures in the core suggests several probable reasons for this poor production. One factor is the presence of a hydrocarbon residue (carbon) which filled much of the porosity left in the smaller fractures after mineralization. An equally important factor is probably the reorientation of the in situ horizontal compressive stress to a trend normal to the main fractures, and which now acts to close fracture apertures rapidly during reservoir drawdown. This data set has unpleasant implications for the search for similar, deep fractured reservoirs
Withdrawal of water by industry in Illinois, 1970-1971
Includes bibliographical references (p. 17)
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