3,347 research outputs found
Three Generation Long-wavelength Vacuum Oscillation Solution to the Solar Neutrino Problem
We investigate the current status of the long-wavelength vacuum oscillation
solution to the solar neutrino problem and to what extent the presence of a
third neutrino can affect and modify it. Assuming that the smaller mass squared
difference that can induce such oscillations, , is in the
range eV and the larger one, , in the
range relevant to atmospheric neutrino observations, we analyze the most recent
solar neutrino data coming from Homestake, SAGE, GALLEX, GNO and
Super-Kamiokande experiments in the context of three neutrino generations. We
include in our vacuum oscillation analysis the MSW effect in the Sun, which is
relevant for some of the parameter space scrutinized. We have also performed,
as an extreme exercise, the fit without Homestake data. % While we found that
the MSW effect basically does not affect the best fitted parameters, it
significantly modifies the allowed parameter space for larger
than eV, in good agreement with the result
obtained by A. Friedland in the case of two generations. % Although the
presence of a third neutrino does not essentially improve the quality of the
fit, the solar neutrino data alone can give an upper bound on ,
which is constrained to be less than at 95 % C.L.Comment: 35 pages, 14 png figures: good quality postscript figures can be
found in http://neutrinos.if.usp.br/gefan/papers/publicados/ps/GNZ
Searching for cavities of various densities in the Earth's crust with a low-energy electron-antineutrino beta-beam
We propose searching for deep underground cavities of different densities in
the Earth's crust using a long-baseline electron-antineutrino disappearance
experiment, realized through a low-energy beta-beam with highly-enhanced
luminosity. We focus on four cases: cavities with densities close to that of
water, iron-banded formations, heavier mineral deposits, and regions of
abnormal charge accumulation that have been posited to appear prior to the
occurrence of an intense earthquake. The sensitivity to identify cavities
attains confidence levels higher than and for exposures
times of 3 months and 1.5 years, respectively, and cavity densities below 1 g
cm or above 5 g cm, with widths greater than 200 km. We
reconstruct the cavity density, width, and position, assuming one of them known
while keeping the other two free. We obtain large allowed regions that improve
as the cavity density differs more from the Earth's mean density. Furthermore,
we demonstrate that knowledge of the cavity density is important to obtain
O(10%) error on the width. Finally, we introduce an observable to quantify the
presence of a cavity by changing the orientation of the electron-antineutrino
beam, with which we are able to identify the presence of a cavity at the
to C.L.Comment: 7 pages, 5 figures; matches published versio
Cuidados domiciliares – interacção do enfermeiro com a pessoa idosa/família
Objetivo: Compreender o processo de interacção com a pessoa idosa e família no domicílio desenvolvido pelos enfermeiros. Métodos: Estudo de natureza qualitativa, Grounded Theory, em uma comunidade onde 40% da população têm idade igual ou superior a 65 anos. A coleta dos dados foi pela observação não participante das práticas de enfermagem, durante 41 visitas domiciliárias e entrevistas semiestruturadas às enfermeiras, pessoa idosa e família. Resultados: Emergiram as categorias: organização estrutural dos cuidados domiciliares, avaliação diagnóstica em con- texto e intervenção terapêutica em contexto. Conclusão: A categoria central foi “Construindo a relação em contexto domiciliar” pelo fato da relação da enfermeira com o idoso e a família ser central em todo o processo de cuidados. A relação é simultaneamente o contexto de todos os cuidados, assim como é um instrumento terapêutico
Reversible Graphene decoupling by NaCl photo-dissociation
We describe the reversible intercalation of Na under graphene on Ir(111) by
photo-dissociation of a previously adsorbed NaCl overlayer. After room
temperature evaporation, NaCl adsorbs on top of graphene forming a bilayer.
With a combination of electron diffraction and photoemission techniques we
demonstrate that the NaCl overlayer dissociates upon a short exposure to an
X-ray beam. As a result, chlorine desorbs while sodium intercalates under the
graphene, inducing an electronic decoupling from the underlying metal. Low
energy electron diffraction shows the disappearance of the moir\'e pattern when
Na intercalates between graphene and iridium. Analysis of the Na 2p core-level
by X-ray photoelectron spectroscopy shows a chemical change from NaCl to
metallic buried Na at the graphene/Ir interface. The intercalation-decoupling
process leads to a n-doped graphene due to the charge transfer from the Na, as
revealed by constant energy angle resolved X-ray photoemission maps. Moreover,
the process is reversible by a mild annealing of the samples without damaging
the graphene
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