612 research outputs found
Galactic secondary positron flux at the Earth
Secondary positrons are produced by spallation of cosmic rays within the
interstellar gas. Measurements have been typically expressed in terms of the
positron fraction, which exhibits an increase above 10 GeV. Many scenarios have
been proposed to explain this feature, among them some additional primary
positrons originating from dark matter annihilation in the Galaxy. The PAMELA
satellite has provided high quality data that has enabled high accuracy
statistical analyses to be made, showing that the increase in the positron
fraction extends up to about 100 GeV. It is therefore of paramount importance
to constrain theoretically the expected secondary positron flux to interpret
the observations in an accurate way. We find the secondary positron flux to be
reproduced well by the available observations, and to have theoretical
uncertainties that we quantify to be as large as about one order of magnitude.
We also discuss the positron fraction issue and find that our predictions may
be consistent with the data taken before PAMELA. For PAMELA data, we find that
an excess is probably present after considering uncertainties in the positron
flux, although its amplitude depends strongly on the assumptions made in
relation to the electron flux. By fitting the current electron data, we show
that when considering a soft electron spectrum, the amplitude of the excess
might be far lower than usually claimed. We provide fresh insights that may
help to explain the positron data with or without new physical model
ingredients. PAMELA observations and the forthcoming AMS-02 mission will allow
stronger constraints to be aplaced on the cosmic--ray transport parameters, and
are likely to reduce drastically the theoretical uncertainties.Comment: 15 pages, 12 figures. The recent PAMELA data on the positron fraction
(arXiv:0810.4995) have been included and the ensuing discussion has been
extended. Accepted version in A&
LASER SCANNER AND CAMERA-EQUIPPED UAV ARCHITECTURAL SURVEYS
ABSTRACT: The paper reports the workflow of 3D modelling and photorealistic texture mapping based on close range imagery acquired through a terrestrial laser scan and a camera mounted on a mini Unmanned Aerial Vehicle (UAV). The 3D models of the same architectural object -a watchtower named "Torre Pelosa" (Bari, Italy) -were compared in order to evaluate strengths and weaknesses of the used instruments and methods. The evaluated parameters where geo-referencing capability, manageability, manoeuvrability, operational constraint, survey completeness and costs. Despite a lower accuracy of the results, the use of a UAV mounted camera is essential to obtain a whole representation of the tower
Polyethylene imine-based receptor immobilization for label free bioassays
Polyethylene imine (PEI) based immobilization of antibodies is described and the concept is proved on the
label free assay of C-Reactive Protein (CRP). This novel immobilization method is composed of a hyperbranched
PEI layer which was deposited at a high pH (9.5) on the sensor surface. The free amino groups
of PEI were derivatized with neutravidin by Biotin N-hydroxysuccinimide ester and the biotinylated
anti-CRP antibody immobilized on this layer. Direct binding assay of recombinant CRP was successfully
performed in the low ÎŒg/ml concentrations using a label free optical waveguide biosensor
Topological spin excitations of Heisenberg antiferromagnets in two dimensions
In this paper we discuss the construction and the dynamics of vortex-like
topological spin excitations in the Schwinger-boson description of Heisenberg
antiferromagnets in two dimensions. The topological spin excitations are Dirac
fermions (with gap) when spin value is a half-integer. Experimental and
theoretical implications of these excitations are being investigated.Comment: Latex file, no figur
Anomalous finite size spectrum in the S=1/2 two dimensional Heisenberg model
We study the low energy spectrum of the nearest neighbor Heisenberg model on
a square lattice as a function of the total spin S. By quantum Monte Carlo
simulation we compute this spectrum for the s=1/2, s=1 and s=3/2 Heisenberg
models. We conclude that the nonlinear sigma model prediction for the low
energy spectrum is always verified for large enough system size. However the
crossover to the correct scaling regime is particularly slow just for the s=1/2
Heisenberg model. The possibility to detect this unexpected anomaly with finite
temperature experiments on s=1/2 isotropic quantum antiferromagnets is also
discussed.Comment: 4 pages, RevTeX + 5 encapsulated postscript figure
On the Sunyaev-Zel'dovich effect from dark matter annihilation or decay in galaxy clusters
We revisit the prospects for detecting the Sunyaev Zel'dovich (SZ) effect
induced by dark matter (DM) annihilation or decay. We show that with standard
(or even extreme) assumptions for DM properties, the optical depth associated
with relativistic electrons injected from DM annihilation or decay is much
smaller than that associated with thermal electrons, when averaged over the
angular resolution of current and future experiments. For example, we find:
(depending on the assumptions) for \mchi
= 1 GeV and a density profile for a template cluster
located at 50 Mpc and observed within an angular resolution of , compared
to . This, together with a full spectral
analysis, enables us to demonstrate that, for a template cluster with generic
properties, the SZ effect due to DM annihilation or decay is far below the
sensitivity of the Planck satellite. This is at variance with previous claims
regarding heavier annihilating DM particles. Should DM be made of lighter
particles, the current constraints from 511 keV observations on the
annihilation cross section or decay rate still prevent a detectable SZ effect.
Finally, we show that spatial diffusion sets a core of a few kpc in the
electron distribution, even for very cuspy DM profiles, such that improving the
angular resolution of the instrument, e.g. with ALMA, does not necessarily
improve the detection potential. We provide useful analytical formulae
parameterized in terms of the DM mass, decay rate or annihilation cross section
and DM halo features, that allow quick estimates of the SZ effect induced by
any given candidate and any DM halo profile.Comment: 27 p, 6 figs, additional section on spatial diffusion effects.
Accepted for publication in JCA
Screening, prevalence, treatment and control of kidney disease in patients with type 1 and type 2 diabetes in low-to-middle-income countries (2005â2017): the International Diabetes Management Practices Study (IDMPS)
Diabetes is the leading cause of kidney disease worldwide. There is limited information on screening, treatment and control of kidney disease in patients with diabetes in low-to-middle-income countries (LMICs).Fil: Mbanya, Jean Claude. UniversitĂ© de YaoundĂ© ; CamerĂșnFil: Aschner, Pablo. Hospital Universitario San Ignacio; Colombia. Pontificia Universidad Javeriana; ColombiaFil: Gagliardino, Juan Jose. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Centro de EndocrinologĂa Experimental y Aplicada. Universidad Nacional de La Plata. Facultad de Ciencias MĂ©dicas. Centro de EndocrinologĂa Experimental y Aplicada; ArgentinaFil: Ilkova, Hasan. Ä°stanbul S. Zaim Ăniversitesi; TurquĂaFil: Lavalle, Fernando. Universidad AutĂłnoma de Nuevo Leon, Facultad de Medicina; MĂ©xicoFil: Ramachandran, Ambady. India Diabetes Research Foundation; IndiaFil: Chantelot, Jean Marc. Sanofi; FranciaFil: Chan, Juliana C. N.. Prince of Wales Hospital; Chin
Persistent poor glycaemic control in individuals with type 2 diabetes in developing countries: 12Â years of real-world evidence of the International Diabetes Management Practices Study (IDMPS)
We evaluated the secular trend of glycaemic control in individuals with type 2 diabetes in developing countries, where data are limited. Erratum in Correction to: Persistent poor glycaemic control in individuals with type 2 diabetes in developing countries: 12 years of real-world evidence of the International Diabetes Management Practices Study (IDMPS). Aschner P, Gagliardino JJ, Ilkova H, Lavalle F, Ramachandran A, Mbanya JC, Shestakova M, Chantelot JM, Chan JCN. Diabetologia. 2020 May;63(5):1088-1089. doi: 10.1007/s00125-020-05118-3.Fil: Aschner, Pablo. Pontificia Universidad Javeriana; ColombiaFil: Gagliardino, Juan Jose. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Centro de EndocrinologĂa Experimental y Aplicada. Universidad Nacional de La Plata. Facultad de Ciencias MĂ©dicas. Centro de EndocrinologĂa Experimental y Aplicada; ArgentinaFil: Ilkova, Hasan. Ä°stanbul Ăniversitesi; TurquĂaFil: Lavalle, Fernando. universidad AutĂłnoma de Nueva LeĂłn; MĂ©xicoFil: Ramachandran, Ambady. India Diabetes Research Foundation; IndiaFil: Mbanya, Jean Claude. UniversitĂ© de YaoundĂ© I; CamerĂșnFil: Shestakova, Marina. Endocrinology Research Center Moscow; RusiaFil: Chantelot, Jean Marc. Sanofi; FranciaFil: Chan, Juliana C. N.. The Chinese University of Hong Kong; Chin
Galactic electrons and positrons at the Earth:new estimate of the primary and secondary fluxes
We analyse predictions of the CR lepton fluxes at the Earth of both secondary
and primary origins, evaluate the theoretical uncertainties, and determine
their level of consistency with respect to the available data. For propagation,
we use a relativistic treatment of the energy losses for which we provide
useful parameterizations. We compute the secondary components by improving on
the method that we derived earlier for positrons. For primaries, we estimate
the contributions from astrophysical sources (supernova remnants and pulsars)
by considering all known local objects within 2 kpc and a smooth distribution
beyond. We find that the electron flux in the energy range 5-30 GeV is well
reproduced by a smooth distant distribution of sources with index , while local sources dominate the flux at higher energy. For
positrons, local pulsars have an important effect above 5-10 GeV. Uncertainties
affecting the source modeling and propagation are degenerate and each
translates into about one order of magnitude error in terms of local flux. The
spectral shape at high energy is weakly correlated with the spectral indices of
local sources, but more strongly with the hierarchy in their distance, age and
power. Despite the large theoretical errors that we describe, our global and
self-consistent analysis can explain all available data without over-tuning the
parameters, and therefore without the need to consider any exotic physics.
Though a \emph{standard paradigm} of Galactic CRs is well established, our
results show that we can hardly talk about any \emph{standard model} of CR
leptons, because of the very large theoretical uncertainties. Our analysis
provides details about the impact of these uncertainties, thereby sketching a
roadmap for future improvements.Comment: 34 pages, 14 figures. V2: few changes, results unchanged; matches the
version accepted in Astron. Astrophy
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