296 research outputs found
Neurological and rehabilitative problems in the demented elderly person and the web integrated organization of social and health service
Strategy for the risk of fall prevention: interventions on global population; specific interventions on selected high risk population
The dark matter profile of the milky way: A non-parametric reconstruction
Astrophysical Journal Letters 803.1 (2015) L3 reproduced by permission of the AASWe present the results of a new, non-parametric method to reconstruct the Galactic dark matter profile directly from observations. Using the latest kinematic data to track the total gravitational potential and the observed distribution of stars and gas to set the baryonic component, we infer the dark matter contribution to the circular velocity across the Galaxy. The radial derivative of this dynamical contribution is then estimated to extract the dark matter profile. The innovative feature of our approach is that it makes no assumption on the functional form or shape of the profile, thus allowing for a clean determination with no theoretical bias. We illustrate the power of the method by constraining the spherical dark matter profile between 2.5 and 25 kpc away from the Galactic center. The results show that the proposed method, free of widely used assumptions, can already be applied to pinpoint the dark matter distribution in the Milky Way with competitive accuracy, and paves the way for future developmentsF.I. acknowledges the support of the Spanish MINECO's "Centro de Excelencia Severo Ochoa" Programme under grant SEV-2012-0249 and the Consolider-Ingenio 2010 Programme under grant MultiDarkCSD2009-00064. Part of this work has been carried out during the workshop "What is the Dark Matter?" at NORDITA, Stockhol
The effect of early dark matter halos on reionization
The annihilation of dark matter particles releases energy, ionizing some of
the gas in the Universe. We investigate the effect of dark matter halos on
reionization. We show that the effect depends on the assumed density profile,
the particle mass, and the assumed minimum halo mass. For NFW halos and typical
WIMPs, we find the effect to be quite small. However, light dark matter
candidates in the MeV range can contribute significantly to reionization and
can make an important contribution to the measured optical depth. This effect
may be used to constrain light dark matter models. We also study the effect of
varying the halo density profile on reionization.Comment: Minor changes from v2. Accepted for publication in Phys. Rev.
Dark matter powered stars: Constraints from the extragalactic background light
The existence of predominantly cold non-baryonic dark matter is unambiguously
demonstrated by several observations (e.g., structure formation, big bang
nucleosynthesis, gravitational lensing, and rotational curves of spiral
galaxies). A candidate well motivated by particle physics is a weakly
interacting massive particle (WIMP). Self-annihilating WIMPs would affect the
stellar evolution especially in the early universe. Stars powered by
self-annihilating WIMP dark matter should possess different properties compared
with standard stars. While a direct detection of such dark matter powered stars
seems very challenging, their cumulative emission might leave an imprint in the
diffuse metagalactic radiation fields, in particular in the mid-infrared part
of the electromagnetic spectrum. In this work the possible contributions of
dark matter powered stars (dark stars; DSs) to the extragalactic background
light (EBL) are calculated. It is shown that existing data and limits of the
EBL intensity can already be used to rule out some DS parameter sets.Comment: Accepted for publication in ApJ; 7 pages, 5 figure
The risk of falling
Abstract: In the late 1960s, much interest was raised in regard to biomedical applications of various ceramic materials. A little bit later, such materials were named bioceramics. This review is limited to bioceramics prepared from calcium orthophosphates only, which belong to the categories of bioactive and bioresorbable compounds. There have been a number of important advances in this field during the past 30–40 years. Namely, by structural and compositional control, it became possible to choose whether calcium orthophosphate bioceramics were biologically stable once incorporated within the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of calcium orthophosphate bioceramics—which is able to promote regeneration of bones—was developed. Presently, calcium orthophosphate bioceramics are available in the form of particulates, blocks, cements, coatings, customized designs for specific applications and as injectable composites in a polymer carrier. Current biomedical applications include artificial replacements for hips, knees, teeth, tendons and ligaments, as well as repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jawbone, spinal fusion and bone fillers after tumor surgery. Exploratory studies demonstrate potential applications of calcium orthophosphate bioceramics as scaffolds, drug delivery systems, as well as carriers of growth factors, bioactive peptides and/or various types of cells for tissue engineering purposes
A robust estimate of the Milky Way mass from rotation curve data
We present a new estimate of the mass of the Milky Way, inferred via a Bayesian approach by making use of tracers of the circular velocity in the disk plane and stars in the stellar halo, as from the publicly available galkin compilation. We use the rotation curve method to determine the dark matter distribution and total mass under different assumptions for the dark matter profile, while the total stellar mass is constrained by surface stellar density and microlensing measurements. We also include uncertainties on the baryonic morphology via Bayesian model averaging, thus converting a potential source of systematic error into a more manageable statistical uncertainty. We evaluate the robustness of our result against various possible systematics, including rotation curve data selection, uncertainty on the Sun's velocity V0, dependence on the dark matter profile assumptions, and choice of priors. We find the Milky Way's dark matter virial mass to be log10M200DM/ Mo\u2d9 = 11.92+0.06-0.05(stat)\ub10.28\ub10.27(syst) (M200DM=8.3+1.2-0.9(stat)
71011 Mo\u2d9). We also apply our framework to Gaia DR2 rotation curve data and find good statistical agreement with the above results
Evidence for dark matter in the inner Milky Way
The ubiquitous presence of dark matter in the universe is today a central
tenet in modern cosmology and astrophysics. Ranging from the smallest galaxies
to the observable universe, the evidence for dark matter is compelling in
dwarfs, spiral galaxies, galaxy clusters as well as at cosmological scales.
However, it has been historically difficult to pin down the dark matter
contribution to the total mass density in the Milky Way, particularly in the
innermost regions of the Galaxy and in the solar neighbourhood. Here we present
an up-to-date compilation of Milky Way rotation curve measurements, and compare
it with state-of-the-art baryonic mass distribution models. We show that
current data strongly disfavour baryons as the sole contribution to the
galactic mass budget, even inside the solar circle. Our findings demonstrate
the existence of dark matter in the inner Galaxy while making no assumptions on
its distribution. We anticipate that this result will compel new
model-independent constraints on the dark matter local density and profile,
thus reducing uncertainties on direct and indirect dark matter searches, and
will shed new light on the structure and evolution of the Galaxy.Comment: First submitted version of letter published in Nature Physics on
Febuary 9, 2015:
http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3237.htm
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