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Search Results: 1 - 10 of 49 matches for " Niro; "
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Influence of a keV sterile neutrino on neutrino-less double beta decay -- how things changed in the recent years
Merle, Alexander;Niro, Viviana
High Energy Physics - Phenomenology , 2013,
Abstract: Earlier studies of the influence of Dark Matter keV sterile neutrinos on neutrino-less double beta decay concluded that there is no significant modification of the decay rate. These studies have focused only on a mass of the keV sterile neutrino above 2 and 4 keV, respectively, as motivated by certain production mechanisms. On the other hand, alternative production mechanisms have been proposed, which relax the lower limit for the mass, and new experimental/observational data is available, too. For this reason, an updated study is timely and worthwhile. We focus on the most recent data, i.e., the newest Chandra and XMM-Newton observational bounds on the X-ray line originating from radiative keV sterile neutrino decay, as well as the new measurement of the previously unknown leptonic mixing angle $\theta_{13}$ by the Daya Bay, RENO, and Double Chooz experiments. We find that, while the previous works had been too short-sighted, the new observational bounds do indeed render any influences of keV sterile neutrinos on neutrino-less double beta decay small. This conclusion even holds in case not all the Dark Matter is made up of keV sterile neutrinos. The bounds are so powerful that they strongly constrain form-dominant neutrino mixing, which is of interest for models of keV sterile neutrinos.
Lens subluxation grading system: predictive value for ectopia lentis surgical outcomes
Mauro Waiswol,Niro Kasahara
Einstein (S?o Paulo) , 2009,
Abstract: Objective: To present a classification system to grade ectopia lentis and to assess its usefulness as a predictor for surgical outcomes. Methods: Fifty-one eyes of 28 patients with either simple (19 patients) or Marfan syndrome-associated ectopia lentis (nine patients) with variable degrees of subluxation were operated on. Lens subluxation intensity was graded according to the lens subluxation grading system (LSGS) from grade 1 (lens on the whole pupillary area) up to grade 4 (lens absent from the pupillary area). Thirty eyes underwent cataract extraction (“dry” aspiration) with endocapsular ring and in-the-bag intraocular lens (IOL) implantation. Twenty-one eyes underwent cataract extraction (“dry” aspiration) with scleral fixation of the IOL. The predictive value of the LSGS was assessed by analyzing the post-operative outcomes, including visual acuity (VA), endothelial cell loss, and complications for each grade on the grading system. Rresults: Patients were classified into grade 1 (19.6%), grade 2 (51%) and grade 3 (29.4%). Post-operative VA was lower for eyes with larger degrees of subluxation. The higher the subluxation grade, the higher the endothelial cell loss, as well as, the frequency of vitreous loss and surgical time. Higher subluxation grades prevented optimal surgical outcomes with endocapsular ring and in-the-bag IOL implantation. Cconclusions: The LSGS provides an estimate of the surgical success of ectopia lentis. Adequate standardization of lens subluxation is crucial for understanding studies dealing with the surgical correction of this disorder.
Deriving Models for keV sterile Neutrino Dark Matter with the Froggatt-Nielsen mechanism
Alexander Merle,Viviana Niro
Physics , 2011, DOI: 10.1088/1475-7516/2011/07/023
Abstract: Sterile neutrinos with a mass around the keV scale are an attractive particle physics candidate for Warm Dark Matter. Although many frameworks have been presented in which these neutrinos can fulfill all phenomenological constraints, there are hardly any models known that can explain such a peculiar mass pattern, one sterile neutrino at the keV scale and the other two considerably heavier, while at the same time being compatible with low-energy neutrino data. In this paper, we present models based on the Froggatt-Nielsen mechanism, which can give such an explanation. We explain how to assign Froggatt-Nielsen charges in a successful way, and we give a detailed discussion of all conditions to be fulfilled. It turns out that the typical arbitrariness of the charge assignments is greatly reduced when trying to carefully account for all constraints. We furthermore present analytical calculations of a few simplified models, while quasi-perfect models are found numerically.
Produtividade de quatro espécies arbóreas de Terra Firme da Amaz?nia Central
Andrade, Eleonora Alvarenga;Higuchi, Niro;
Acta Amazonica , 2009, DOI: 10.1590/S0044-59672009000100011
Abstract: individual productivity analysis of species helps describe their comportment in forest ecosystems. the objective of this work was to analyze the productivity of four tree species during a period of six years (2000-2006) in a "terra firme" area near manaus, amazonas. the productivity was indirectly estimated by using individual allometric equations along with data from a continuous forest inventory. the following species were selected for this study: pouteria reticulata eyma (sapotaceae), micrandra siphonioides benth. (euphorbiaceae), protium hebetatum daly (burseraceae) and eschweilera wachenheimii sand (lecythidaceae). these were selected because they presented a very high importance value index in the area. the raw data used to developed specific equations were taken from an existing set of data. samples for each species numbered less than 30 individuals; for this reason, "jackknife" was used. the "jackknifed" equations were used to estimate aboveground biomass of individuals which occurred in two permanent sample plots measured in 2000, and re-measured in 2002, 2004 and 2006. the "jackknife" method was consistent and reliable, with high and significant determination coefficients (r2 > 0,93) and low values of standard error of estimates (sy.x < 0,692). the productivity rates of e. wachenheimii, p. reticulata e p. hebetatum were similar, different from m. siphonioides. the highest productivity was reported for m. siphonioides, and the lowest for p. hebetatum. the intra-specific productivity variability was superior to the inter-specific, with p. reticulata showing the highest variability coefficient.
Comparison of different analytic algorithms for interpretation of the Swedish interactive threshold algorithm strategy
Takahashi, Gustavo S.;Kasahara, Niro;
Clinics , 2008, DOI: 10.1590/S1807-59322008000300008
Abstract: objective: to compare 4 analytic algorithms for interpretation of the swedish interactive threshold algorithm. introduction: analytic algorithms were initially developed for interpretation of standard automated perimetry (using a full threshold strategy). the swedish interactive threshold algorithm is a novel strategy that was developed to shorten test duration. methods: one hundred forty-three printouts of normal and glaucomatous patients were analyzed using caprioli's (strict, moderate and liberal) criteria and anderson's modified criteria for perimetric defect. areas under the receiver operator characteristics (roc) curves, sensitivity, and specificity for each criteria were calculated. results: caprioli's strict and anderson's modified criteria presented similar sensitivity (94.5% and 92.3%, respectively) and specificity (63.5% and 61.5%, respectively). caprioli's liberal criteria were more sensitive (98.9%) and less specific (42.5%) than the other three criteria. conclusion: both caprioli's and anderson's modified criteria can be used for interpretation of the swedish interactive threshold algorithm.
An accurate analytic description of neutrino oscillations in matter
Akhmedov, E. Kh.;Niro, Viviana
High Energy Physics - Phenomenology , 2008, DOI: 10.1088/1126-6708/2008/12/106
Abstract: A simple closed-form analytic expression for the probability of two-flavour neutrino oscillations in a matter with an arbitrary density profile is derived. Our formula is based on a perturbative expansion and allows an easy calculation of higher order corrections. The expansion parameter is small when the density changes relatively slowly along the neutrino path and/or neutrino energy is not very close to the Mikheyev-Smirnov-Wolfenstein (MSW) resonance energy. Our approximation is not equivalent to the adiabatic approximation and actually goes beyond it. We demonstrate the validity of our results using a few model density profiles, including the PREM density profile of the Earth. It is shown that by combining the results obtained from the expansions valid below and above the MSW resonance one can obtain a very good description of neutrino oscillations in matter in the entire energy range, including the resonance region.
A conven??o do clima e a legisla??o brasileira pertinente, com ênfase para a legisla??o ambiental no Amazonas
Soares, Terezinha de Jesus;Higuchi, Niro;
Acta Amazonica , 2006, DOI: 10.1590/S0044-59672006000400021
Abstract: this work has analyzed the performance of brazil in relation to the fulfillment of the obligations defined by the united nations framework convention on climate change (article 4.1), from the point of view of the international law, internal positive law and especially the rules of environmental law. it compared the national legislation with the norms originated from the convention and the activities implemented by the national organisms, including policies and environmental programs, trying to identify the convergent and conflicting points in order to indicate what has to be done, and to allow, where necessary, norms to accomplish the objective planned. this work aimed to show the amazonas state commitments in relation to the convention, and to offer suggestions to the administration of public policies directed to the fulfillment of aims determined by the convention and undertaken by brazil.
Estimativa de sequestro de carbono em mata ciliar: projeto POMAR, S o Paulo (SP) / Estimate of carbon sequestration in riparian forests: the POMAR project case, S o Paulo (SP)
Giuliana Del Nero Velasco,Niro Higuchi
Ambiência , 2009,
Abstract: ResumoO objetivo do presente trabalho foi estimar a quantidade de carbono fixada (em plantio de três anos de idade) na vegeta o arbórea do projeto POMAR, na cidade de S o Paulo/SP, localizado às margens do Rio Pinheiros. Foram feitas medidas de altura e CAP (circunferência à altura do peito) de dezesseis espécies. Na área estudada de 4.612 m2havia 920 árvores. O estoque de carbono, três anos após o plantio, foi estimado em 67 t, que equivale a um estoque de 145,26 t de C ha-1. O carbono seqüestrado estimado por um hectare equivale à emiss o de vinte veículos. Concluiu-se que o plantio de árvores em cidades contribui para o sequestro de C devendo ser uma prática incentivada em conjunto com redu o de emiss es.AbstractThe research goal was to estimate the amount of Carbon that was fixed in a three-year-old plantation of tree species at the POMAR project in S o Paulo city, on the Pinheiros River banks. The diameter at breast height (DBH) and height of sixteen tree species were measured and recorded. The studied plot had 4,612.5 m2 and 920 trees. Carbon accumulation was 67t three years after planting, which corresponds to a stock of 145,26 t of C ha-1. The estimated carbon captured by 1 ha is equivalent to the emission of 20 vehicles. It was concluded that the planting of trees in cities contributes in the sequestration of Carbon and should be an encouraged practice in association with emission reduction.
Enhancing Dark Matter Annihilation into Neutrinos
Manfred Lindner,Alexander Merle,Viviana Niro
Physics , 2010, DOI: 10.1103/PhysRevD.82.123529
Abstract: We perform a detailed and quasi model-independent analysis of direct annihilation of Dark Matter into neutrinos. Considering different cases for scalar and fermionic Dark Matter, we identify several settings in which this annihilation is enhanced, contrary to some statements in the literature. They key point is that several restrictions of, e.g., a supersymmetric framework do not hold in general. The mass generation mechanism of the neutrinos plays an important role, too. We illustrate our considerations by two examples that are not (as usually) suppressed by the smallness of the neutrino mass, for which we also present a numerical analysis. Our results can be easily used as guidelines for model building.
On Probing theta_{23} in Neutrino Telescopes
Sandhya Choubey,Viviana Niro,Werner Rodejohann
Physics , 2008, DOI: 10.1103/PhysRevD.77.113006
Abstract: Among all neutrino mixing parameters, the atmospheric neutrino mixing angle theta_{23} introduces the strongest variation on the flux ratios of ultra high energy neutrinos. We investigate the potential of these flux ratio measurements at neutrino telescopes to constrain theta_{23}. We consider astrophysical neutrinos originating from pion, muon-damped and neutron sources and make a comparative study of their sensitivity reach to theta_{23}. It is found that neutron sources are most favorable for testing deviations from maximal theta_{23}. Using a chi^2 analysis, we show in particular the power of combining (i) different flux ratios from the same type of source, and also (ii) combining flux ratios from different astrophysical sources. We include in our analysis ``impure'' sources, i.e., deviations from the usually assumed initial (1 : 2 : 0), (0 : 1 : 0) or (1 : 0 : 0) flux compositions.
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