2,029 research outputs found
Status of FNAL SciBooNE experiment
SciBooNE is a new experiment at FNAL which will make precision
neutrino-nucleus cross section measurements in the one GeV region. These
measurements are essential for the future neutrino oscillation experiments. We
started data taking in the antineutrino mode on June 8, 2007, and collected
5.19 \times 10^{19} protons on target (POT) before the accelerator shutdown in
August. The first data from SciBooNE are reported in this article.Comment: 3 pages, 3 figures. Proceedings of the 10th International Conference
on Topics in Astroparticle and Underground Physics (TAUP) 2007, Sendai,
Japan, September 11-15, 200
Magnus Expansion and Three-Neutrino Oscillations in Matter
We present a semi-analytical derivation of the survival probability of solar
neutrinos in the three generation scheme, based on the Magnus approximation of
the evolution operator of a three level system, and assuming a mass hierarchy
among neutrino mass eigenstates. We have used an exponential profile for the
solar electron density in our approximation. The different interesting density
regions that appear throughout the propagation are analyzed. Finally, some
comments on the allowed regions in the solar neutrino parameter space are
addressed.Comment: RevTex4 style, 5 pages including 5 figures. Presented at Mexican
School of Astrophysics 2002, Guanajuato, Mexico, 31 Jul - 7 Aug 2002. Final
version to appear in the Proceedings of IX Mexican Workshop on Particles and
Fields Physics Beyond the Standard Model, Colima Col. Mexico, November 17-22,
200
Diabetic Macular Edema: From Old Concepts to New Therapeutic Avenues
Diabetic macular edema (DME) is an important cause of blindness in the working population and is currently challenging to treat. Current interventions include focal laser or intravitreal injections. This article outlines a new treatment protocol based on the concept that peripheral ischemia is the introduction to angiogenesis, that will ultimately gather its momentum at the fovea. Performing extreme peripheral light laser panretinal photocoagulation (PRP) back to the equator reduces excessive expression of the vascular endothelial growth factor (VEGF) in the eye. Subsequently, this decreases VEGF-induced DME and provides long-term protection for the development of neovascularization. Initial exacerbation of DME often accompanies PRP, Therefore; first injections of anti-VEGF agents (with or without dexamethasone implant) can forestall worsening of DME preventing loss of vision. However, on the other hand, applying peripheral PRP and intraocular injections can induce posterior vitreous detachment (PVD). This could help release vitreomacular adhesions (VMA) and vitreomacular traction (VMT), decreasing DME severity and improving response to intravitreal injections. The current approach works by laser ablation of the peripheral retina that should stop the drive for VEGF release; moreover, laser ablation should produce secondary, accidental and beneficial PVD. This approach precludes focal laser therapy and paves the path for prolonged anti-VEGF therapy
Electron neutrino tagging through tertiary lepton detection
We discuss an experimental technique aimed at tagging electron neutrinos in
multi-GeV artificial sources on an event-by-event basis. It exploits in a novel
manner calorimetric and tracking technologies developed in the framework of the
LHC experiments and of rare kaon decay searches. The setup is suited for
slow-extraction, moderate power beams and it is based on an instrumented decay
tunnel equipped with tagging units that intercept secondary and tertiary
leptons from the bulk of undecayed \pi^+ and protons. We show that the taggers
are able to reduce the \nue contamination originating from K_e3 decays by about
one order of magnitude. Only a limited suppression (~60%) is achieved for \nue
produced by the decay-in-flight of muons; for low beam powers, similar
performance as for K_e3 can be reached supplementing the tagging system with an
instrumented beam dump.Comment: 19 pages, 7 figures; minor changes, version to appear in EPJ
Study of a Large NaI(Tl) Crystal
Using a narrow band positron beam, the response of a large high-resolution
NaI(Tl) crystal to an incident positron beam was measured. It was found that
nuclear interactions cause the appearance of additional peaks in the low energy
tail of the deposited energy spectrum
Gas Density Fluctuations in the Perseus Cluster: Clumping Factor and Velocity Power Spectrum
X-ray surface brightness fluctuations in the core of the Perseus Cluster are
analyzed, using deep observations with the Chandra observatory. The amplitude
of gas density fluctuations on different scales is measured in a set of radial
annuli. It varies from 8 to 12 per cent on scales of ~10-30 kpc within radii of
30-160 kpc from the cluster center and from 9 to 7 per cent on scales of ~20-30
kpc in an outer, 60-220 kpc annulus. Using a statistical linear relation
between the observed amplitude of density fluctuations and predicted velocity,
the characteristic velocity of gas motions on each scale is calculated. The
typical amplitudes of the velocity outside the central 30 kpc region are 90-140
km/s on ~20-30 kpc scales and 70-100 km/s on smaller scales ~7-10 kpc. The
velocity power spectrum is consistent with cascade of turbulence and its slope
is in a broad agreement with the slope for canonical Kolmogorov turbulence. The
gas clumping factor estimated from the power spectrum of the density
fluctuations is lower than 7-8 per cent for radii ~30-220 kpc from the center,
leading to a density bias of less than 3-4 per cent in the cluster core.
Uncertainties of the analysis are examined and discussed. Future measurements
of the gas velocities with the Astro-H, Athena and Smart-X observatories will
directly measure the gas density-velocity perturbation relation and further
reduce systematic uncertainties in these quantities.Comment: 16 pages, 15 figures, submitted to MNRAS, comments are welcom
Enhancement of urban pluvial flood risk management and resilience through collaborative modelling: a UK case study
This paper presents the main findings and lessons learned from the development and implementation of a new methodology for collaborative modelling, social learning and social acceptance of flood risk management technologies. The proposed methodology entails three main phases: (1) stakeholder analysis and engagement; (2) improvement of urban pluvial flood modelling and forecasting tools; and (3) development and implementation of web-based tools for collaborative modelling in flood risk management and knowledge sharing. The developed methodology and tools were tested in the Cranbrook catchment (London Borough of Redbridge, UK), an area that has experienced severe pluvial (surface) flooding in the past. The developed methodologies proved to be useful for promoting interaction between stakeholders, developing collaborative modelling and achieving social acceptance of new technologies for flood risk management. Some limitations for stakeholder engagement were identified and are discussed in the present paper
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