11,521 research outputs found
Quenched Hadron Spectrum and Decay Constants on the lattice
In this talk we present the results obtained from a study of
(quenched) lattice configurations from the APE collaboration, at
, using both the Wilson and the SW-Clover fermion action.
We determine the light hadronic spectrum and the meson decay constants. For the
light-light systems we find an agreement with the experimental data of for mesonic masses and for baryonic masses and pseudoscalar
decay constants; a larger deviation is present for the vector decay constants.
For the heavy-light decay constants we find , in good agreement with previous estimates.Comment: 8 pages, latex, Talk given at XXV ITEP Winter School of Physics,
Moscow - Russia, 18-27 Feb 199
Investigation of the free flow electrophoretic process
The effects of gravity on the free flow electrophoretic process was demonstrated. The free flow electrophoresis chamber used to demonstrate the effects of gravity on the process was of a proprietary design. This chamber was 120 cm long, 16 cm wide, and 0.15 cm thick. Flow in this chamber was in the upward direction and exited through 197 outlets at the top of the chamber. During electrophoresis a stream of sample was injected into the flow near the bottom of the chamber and an electrical field was applied across the width of the chamber. The field caused a lateral force on particles in the sample proportional to the inherent change of the particle and the electric field strength. Particle lateral velocity was then dependent on the force due to viscous drag which was proportional to particle size and particle shape dependent
Investigation of the free flow electrophoretic process. Volume 1: Executive summary
The effect of gravity on the free flow electrophoretic process was investigated. The demonstrated effects were then compared with predictions made by mathematical models. Results show that the carrier buffer flow was affected by gravity induced thermal convection and that the movement of the separating particle streams was affected by gravity induced buoyant forces. It was determined that if gravity induced buoyant forces were included in the mathematical models, then effective predictions of electrophoresis chamber separation performance were possible
Granular Rheology in Zero Gravity
We present an experimental investigation on the rheological behavior of model
granular media made of nearly elastic spherical particles. The experiments are
performed in a cylindrical Couette geometry and the experimental device is
placed inside an airplane undergoing parabolic flights to cancel the effect of
gravity. The corresponding curves, shear stress versus shear rate, are
presented and a comparison with existing theories is proposed. The quadratic
dependence on the shear rate is clearly shown and the behavior as a function of
the solid volume fraction of particles exhibits a power law function. It is
shown that theoretical predictions overestimate the experiments. We observe, at
intermediate volume fractions, the formation of rings of particles regularly
spaced along the height of the cell. The differences observed between
experimental results and theoretical predictions are discussed and related to
the structures formed in the granular medium submitted to the external shear.Comment: 10 pages, 6 figures to be published in Journal of Physics : Condensed
Matte
Analysis of hadronic invariant mass spectrum in inclusive charmless semileptonic B decays
We make an analysis of the hadronic invariant mass spectrum in inclusive
charmless semileptonic B meson decays in a QCD-based approach. The decay width
is studied as a function of the invariant mass cut. We examine their
sensitivities to the parameters of the theory. The theoretical uncertainties in
the determination of from the hadronic invariant mass spectrum are
investigated. A strategy for improving the theoretical accuracy in the value of
is described.Comment: 13 pages, 5 Postscript figure
Decision and Discovery in Defining “Disease”
This version (May 17, 2005) was published in its final form as:
Schwartz PH. Decision and discovery in defining 'disease'. In: Kincaid H, McKitrick J, editors. Establishing medical reality: essays in the metaphysics and epistemology of biomedical science. Dordrecht: Springer; 2007. p. 47-63. http://dx.doi.org/10.1007/1-4020-5216-2_5The debate over how to analyze the concept of disease has often centered on the question of whether to include a reference to values, in particular the ‘disvalue’of diseases, or whether to avoid such notions. ‘Normativists,’such as King ([1954], 1981) and Culver and Gert (1982) emphasize the undesirability of diseases, while ‘Naturalists,’ most prominently Christopher Boorse (1977, 1987, 1997), instead require just the presence of biological dysfunction. The debate between normativism and naturalism often deteriorates into stalemate, with each side able to point out significant problems with the other. It starts to look as if neither approach can work. In this paper, I argue that the standoff stems from deeply questionable assumptions that have been used to formulate the opposing positions and guide the debate. In the end, I propose an alternative set of guidelines that offer a more constructive way to devise and compare theories
An invitation to grieve: reconsidering critical incident responses by support teams in the school setting
This paper proposes that consideration could be given to an invitational intervention rather than an expectational intervention when support personnel respond to a critical incident in schools. Intuitively many practitioners know that it is necessary for guidance/counselling personnel to intervene in schools in and following times of trauma. Most educational authorities in Australia have mandated the formulation of a critical incident intervention plan. This paper defines the term critical incident and then outlines current intervention processes, discussing the efficacy of debriefing interventions. Recent literature suggests that even though it is accepted that a planned intervention is necessary, there is scant evidence as to the effectiveness of debriefing interventions in stemming later symptoms of post traumatic stress disorder. The authors of this paper advocate for an expressive therapy intervention that is invitational rather than expectational, arguing that not all people respond to trauma in the same way and to expect that they will need to recall and retell what has happened is most likely a dangerous assumption. A model of invitation using Howard Gardner’s (1983) multiple intelligences is proposed so that students are invited to grieve and understand emotionally what is happening to them following a critical incident
Management of blunt extracranial traumatic cerebrovascular injury: a multidisciplinary survey of current practice
<p>Abstract</p> <p>Background</p> <p>Extracranial traumatic cerebrovascular injury (TCVI) is present in 1-3% of all blunt force trauma patients. Although options for the management of patients with these lesions include anticoagulation, antiplatelet agents, and endovascular treatment, the optimal management strategy for patients with these lesions is not yet established.</p> <p>Objective</p> <p>Multidisciplinary survey of clinicians about current management of TCVI.</p> <p>Methods</p> <p>A six-item multiple-choice survey was sent by electronic mail to a total of 11,784 neurosurgeons, trauma surgeons, stroke neurologists, and interventional radiologists. The survey included questions about their choice of imaging, medical management, and the use of endovascular techniques. Survey responses were analyzed according to stated specialty.</p> <p>Results</p> <p>Seven hundred eighty-five (6.7%) responses were received. Overall, a total of 325 (42.8%) respondents favored anticoagulation (heparin and/or warfarin), 247 (32.5%) favored antiplatelet drugs, 130 (17.1%) preferred both anticoagulation and antiplatelet drugs, and 57 (7.5%) preferred stenting and/or embolization. Anticoagulation was the most commonly preferred treatment among vascular surgeons (56.9%), neurologists (50.2%) and neurosurgeons (40.7%), whereas antiplatelet agents were the most common preferred treatment among trauma surgeons (41.5%). Overall, 158 (20.7%) of respondents recommended treatment of asymptomatic dissections and traumatic aneurysms, 211 (27.7%) did not recommend it, and 39.4% recommended endovascular treatment only if there is worsening of the lesion on follow-up imaging.</p> <p>Conclusions</p> <p>These data demonstrate the wide variability of physicians' management of traumatic cerebrovascular injury, both on an individual basis, and between specialties. These findings underscore the need for multicenter, randomized trials in this field.</p
Heavy- to light-meson transition form factors
Semileptonic heavy -> heavy and heavy -> light meson transitions are studied
as a phenomenological application of a heavy-quark limit of Dyson-Schwinger
equations. Employing two parameters: E, the difference between the mass of the
heavy meson and the effective-mass of the heavy quark; and Lambda, the width of
the heavy-meson Bethe-Salpeter amplitude, we calculate f_+(t) for all decays on
their entire kinematically accessible t-domain. Our study favours f_B in the
range 0.135-0.17 GeV and with E=0.44 GeV and 1/Lambda = 0.14 fm we obtain
f_+^{B pi}(0) = 0.46. As a result of neglecting 1/m_c-corrections, we estimate
that our calculated values of \rho^2 = 0.87 and f_+^{DK}(0)=0.62 are too low by
approximately 15%. However, the bulk of these corrections should cancel in our
calculated values of Br(D -> \pi l nu)/Br(D -> K l nu)=0.13 and f_+^{D
pi}(0)/f_+^{DK}(0) = 1.16.Comment: 26 pages, 3 figures, REVTE
First Constraints on the Ultra-High Energy Neutrino Flux from a Prototype Station of the Askaryan Radio Array
The Askaryan Radio Array (ARA) is an ultra-high energy ( eV) cosmic
neutrino detector in phased construction near the South Pole. ARA searches for
radio Cherenkov emission from particle cascades induced by neutrino
interactions in the ice using radio frequency antennas ( MHz)
deployed at a design depth of 200 m in the Antarctic ice. A prototype ARA
Testbed station was deployed at m depth in the 2010-2011 season and
the first three full ARA stations were deployed in the 2011-2012 and 2012-2013
seasons. We present the first neutrino search with ARA using data taken in 2011
and 2012 with the ARA Testbed and the resulting constraints on the neutrino
flux from eV.Comment: 26 pages, 15 figures. Since first revision, added section on
systematic uncertainties, updated limits and uncertainty band with
improvements to simulation, added appendix describing ray tracing algorithm.
Final revision includes a section on cosmic ray backgrounds. Published in
Astropart. Phys.
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