17,842 research outputs found
Spin Observables for Polarizing Antiprotons
The PAX project at GSI Darmstadt plans to polarize an antiproton beam by
repeated interaction with a hydrogen target in a storage ring. Many of the beam
particles are required to remain within the ring after interaction with the
target, so small scattering angles are important. Hence we concentrate on low
momentum transfer (small t), a region where electromagnetic effects dominate
the hadronic effects. A colliding beam of polarized electrons with energy
sufficient to provide scattering of antiprotons beyond ring acceptance may
polarize an antiproton beam by spin filtering. Expressions for spin observables
are provided and are used to estimate the rate of buildup of polarization of an
antiproton beam.Comment: 4 pages, 2 figures, to be published in the Proceedings of the 17th
International Spin Physics Symposium (SPIN 2006), Kyoto, Japan; October 2-7,
200
Dynamics of polarization buildup by spin filtering
There has been much recent research into polarizing an antiproton beam,
instigated by the recent proposal from the PAX (Polarized Antiproton
eXperiment) project at GSI Darmstadt. It plans to polarize an antiproton beam
by repeated interaction with a polarized internal target in a storage ring. The
method of polarization by spin filtering requires many of the beam particles to
remain within the ring after scattering off the polarized internal target via
electromagnetic and hadronic interactions. We present and solve sets of
differential equations which describe the buildup of polarization by spin
filtering in many different scenarios of interest to projects planning to
produce high intensity polarized beams. These scenarios are: 1) spin filtering
of a fully stored beam, 2) spin filtering while the beam is being accumulated,
i.e. unpolarized particles are continuously being fed into the beam, 3) the
particle input rate is equal to the rate at which particles are being lost due
to scattering beyond ring acceptance angle, the beam intensity remaining
constant, 4) increasing the initial polarization of a stored beam by spin
filtering, 5) the input of particles into the beam is stopped after a certain
amount of time, but spin filtering continues. The rate of depolarization of a
stored polarized beam on passing through an electron cooler is also shown to be
negligible.Comment: 15 pages, references added, introduction elaborated on, some
variables defined in more detail. Submitted to Eur. Phys. J.
An anotated list of the Curculionoidea (Coleoptera) of Dominica (excluding Scolytinae and Platypodidae)
Curculionoidea (Coleoptera) of the West Indian island of Dominica are composed of 111 genera and 214 species and subspecies. Some of the species listed are morphospecies, or are known to be undescribed, but all are identified at least to genus. Previously the fauna was recorded as 31 species. Numbers presented herein represent a seven-fold increase in species diversity. Furthermore, the widespread nature of many species demonstrates that the supposedly endemic faunas of many West Indian islands may be based on collecting biases or a lack of people capable of providing species level identifications
Deposit insurance, bank incentives, and the design of regulatory policy
This paper was presented at the conference "Financial services at the crossroads: capital regulation in the twenty-first century" as part of session 6, "The role of capital regulation in bank supervision." The conference, held at the Federal Reserve Bank of New York on February 26-27, 1998, was designed to encourage a consensus between the public and private sectors on an agenda for capital regulation in the new century.Deposit insurance ; Bank investments ; Bank supervision ; Bank capital
Simulation of subseismic joint and fault networks using a heuristic mechanical model
Flow simulations of fractured and faulted reservoirs require representation of subseismic structures about which subsurface data are limited. We describe a method for simulating fracture growth that is mechanically based but heuristic, allowing for realistic modelling of fracture networks with reasonable run times. The method takes a triangulated meshed surface as input, together with an initial stress field. Fractures initiate and grow based on the stress field, and the growing fractures relieve the stress in the mesh. We show that a wide range of bedding-plane joint networks can be modelled simply by varying the distribution and anisotropy of the initial stress field. The results are in good qualitative agreement with natural joint patterns. We then apply the method to a set of parallel veins and demonstrate how the variations in thickness of the veins can be represented. Lastly, we apply the method to the simulation of normal fault patterns on salt domes. We derive the stress field on the bedding surface using the horizon curvature. The modelled fault network shows both radial and concentric faults. The new method provides an effective means of modelling joint and fault networks that can be imported to the flow simulator
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The role of blanket peat moorland management in the generation and amelioration of discolouration of surface water supplies
Discolouration of surface waters in upland catchments (with associated costs of water treatment and resources) has increased particularly since the severe droughts in the 1970s and mid 1990s. Such discolouration is a major concern for many water companies whose catchment areas include upland moorland, particularly those areas located on deep blanket peat soils. The principal aim of this study was to evaluate the role of catchment management in the production of discoloured surface runoff and DOC flux from catchments used as gathering grounds for public water supply. The investigation focused on blanket peat moorlands in the Ladybower catchment from which water is treated at Bamford Treatment Works. Whilst other workers have considered management techniques for water colour amelioration at laboratory and plot scale, no previous study had evaluated the impact of these approaches at a catchment scale with a sufficient degree of experimental control. Baseline relationships between meteorological inputs and hydrological responses were established during a calibration period prior to intervention in management. Six catchments were instrumented and the relationships between water discolouration and hydrological and land management characteristics were identified. Suitable pairings of catchments were determined with similar characteristics. One catchment was then treated to a management practice, whilst the management on another was not affected. It was then possible to assess the impact of management on the treated catchment in comparison with the untreated catchment
The precision of international market sampling for North Sea herring and its influence on assessment
Market sampling is a key source of data for catch-at-age-based assessment. Little has been documented about the influence of potential error in these data on the precision of assessments and the management information they produce. This paper presents the results of a study of the precision of North Sea herring fish market sampling carried out by the UK, Denmark and the Netherlands. Data from eight years of market sampling were analysed to obtain the precision of estimated numbers-at-age in the catch. The market sample data was then used to estimate 1000 realisations of the international catch-at-age and mean weightsat- age in the catch. Three methods of estimating the variability of missing catch data were used and three options for the catch-at-age matrices were computed. These base datasets were utilised to obtain 1000 assessments conditional on the ICA (Integrated Catch-at-age Analysis) model. From the outcome of these assessments the influence of the market sampling programmes on the management of the stock are presented as 95âonfidence intervals on the main management parameters (recruitment, SSB, F0-1 and F2-6). In addition, the influence of missing data is estimated. The implications of our conclusions on the requirements from a market sampling programme are discusse
A Buffer Stocks Model for Stabilizing Price of Staple Food with Considering the Expectation of Non Speculative Wholesaler
This paper is a study of price stabilization in the
staple food distribution system. All stakeholders experience
market risks due to some possibility causes of price volatility.
Many models of price stabilization had been developed by
employing several approaches such as floor-ceiling prices,
buffer funds, export or import taxes, and subsidies. In the
previous researches, the models were expanded to increase the
purchasing price for producer and decrease the selling price
for consumer. Therefore, the policy can influence the losses for
non-speculative wholesaler that is reflected by the descending
of selling quantity and ascending of the stocks. The objective of
this model is not only to keep the expectation of both producer
and consumer, but also to protect non-speculative wholesaler
from the undesirable result of the stabilization policy. A
nonlinear programming model was addressed to determine the
instruments of intervention program. Moreover, the result
shows that the wholesaler behavior affects the intervention
costs.
Index Terms Buffer stocks, Price stabilization, Nonlinear
programming, Wholesaler behavior
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