310 research outputs found
High energy gamma-ray constraints on decaying Dark Matter
New bounds on decaying Dark Matter are derived from the gamma-ray
measurements of (i) the isotropic residual (extragalactic) background by Fermi
and (ii) the Fornax galaxy cluster by H.E.S.S. We find that those from (i) are
among the most stringent constraints currently available, for a large range of
dark matter masses and a variety of decay modes, excluding half-lives up to
about 10^26 to few 10^27 seconds. In particular, they rule out the
interpretation in terms of decaying dark matter of the e+/- spectral features
in PAMELA, Fermi and H.E.S.S., unless very conservative choices are adopted. We
also discuss future prospects for CTA bounds from Fornax which, contrary to the
present H.E.S.S. constraints of (ii), may allow for an interesting improvement
and may become better than those from the current or future extragalactic Fermi
data.Comment: In Proceedings of the 33rd International Cosmic Ray Conference
(ICRC2013), ID622, Rio de Janeiro (Brazil
Neutrino decay as a possible interpretation to the MiniBooNE observation with unparticle scenario
In a new measurement on neutrino oscillation , the
MiniBooNE Collaboration observes an excess of electron-like events at low
energy and the phenomenon may demand an explanation which obviously is beyond
the oscillation picuture. We propose that heavier neutrino decaying
into a lighter one via the transition process
where denotes any light products, could be a natural mechanism. The
theoretical model we employ here is the unparticle scenario established by
Georgi. We have studied two particular modes \nu_\mu\to \nu_e+\Un and
. Unfortunately, the number coming out from
the computation is too small to explain the observation. Moreover, our results
are consistent with the cosmology constraint on the neutrino lifetime and the
theoretical estimation made by other groups, therefore we can conclude that
even though neutrino decay seems plausible in this case, it indeed cannot be
the source of the peak at lower energy observed by the MiniBooNE collaboration
and there should be other mechanisms responsible for the phenomenon.Comment: 14 pages, conclusions are changed; published version for EPJ
New Historical and Philosophical Perspectives on Quantitative Genetics
The aim of this collection is to bring together philosophical and historical perspectives to address long-standing issues in the interpretation, utility, and impacts of quantitative genetics methods and findings. Methodological approaches and the underlying scientific understanding of genetics and heredity have transformed since the field’s inception. These advances have brought with them new philosophical issues regarding the interpretation and understanding of quantitative genetic results. The contributions in this issue demonstrate that there is still work to be done integrating old and new methodological and conceptual frameworks. In some cases, new results are interpreted using assumptions based on old concepts and methodologies that need to be explicitly recognised and updated. In other cases, new philosophical tools can be employed to synthesise historical quantitative genetics work with modern methodologies and findings. This introductory article surveys three general themes that have dominated philosophical discussion of quantitative genetics throughout history: 1. How methodologies have changed and transformed our knowledge and interpretations; 2. Whether or not quantitative genetics can offer explanations relating to causation and prediction; 3. The importance of defining the phenotypes under study. We situate the contributions in this special issue within a historical framework addressing these three themes
Using BBN in cosmological parameter extraction from CMB: a forecast for Planck
Data from future high-precision Cosmic Microwave Background (CMB)
measurements will be sensitive to the primordial Helium abundance . At the
same time, this parameter can be predicted from Big Bang Nucleosynthesis (BBN)
as a function of the baryon and radiation densities, as well as a neutrino
chemical potential. We suggest to use this information to impose a
self-consistent BBN prior on and determine its impact on parameter
inference from simulated Planck data. We find that this approach can
significantly improve bounds on cosmological parameters compared to an analysis
which treats as a free parameter, if the neutrino chemical potential is
taken to vanish. We demonstrate that fixing the Helium fraction to an arbitrary
value can seriously bias parameter estimates. Under the assumption of
degenerate BBN (i.e., letting the neutrino chemical potential vary), the
BBN prior's constraining power is somewhat weakened, but nevertheless allows us
to constrain with an accuracy that rivals bounds inferred from present
data on light element abundances.Comment: 14 pages, 4 figures; v2: minor changes, matches published versio
Magnetization reversal driven by low dimensional chaos in a nanoscale ferromagnet
Energy-efficient switching of magnetization is a central problem in nonvolatile magnetic storage and magnetic neuromorphic computing. In the past two decades, several efficient methods of magnetic switching were demonstrated including spin torque, magneto-electric, and microwave-assisted switching mechanisms. Here we experimentally show that low-dimensional magnetic chaos induced by alternating spin torque can strongly increase the rate of thermally-activated magnetic switching in a nanoscale ferromagnet. This mechanism exhibits a well-pronounced threshold character in spin torque amplitude and its efficiency increases with decreasing spin torque frequency. We present analytical and numerical calculations that quantitatively explain these experimental findings and reveal the key role played by low-dimensional magnetic chaos near saddle equilibria in enhancement of the switching rate. Our work unveils an important interplay between chaos and stochasticity in the energy assisted switching of magnetic nanosystems and paves the way towards improved energy efficiency of spin torque memory and logic
Analysis of Risk Factors of Oral Cancer and Periodontitis from a Sex- and Gender-Related Perspective: Gender Dentistry
Gender-specific medicine studies how sexual biology and gender-related cultural and behavioral differences may influence a person's health and considers the differences in clinical features, prevention, therapies, prognosis, and psycho-social aspects of diseases with different impacts on women and men. The present work summarizes the main differential impact each risk factor for oral cancer and periodontitis has according to biological sex- and gender-oriented differences. It resulted in differences in epidemiology and the weight of various healthy determinants that may influence the incidence and prognosis of oral cancer and periodontitis. It is desirable to change the methodology of scientific studies with a higher focus on the weight that sexual variables may have on the well-being or the probability of getting ill of each person, thus promoting the development and diffusion of personalized gender dentistry
Report of a case of discoid lupus erythematosus localised to the oral cavity: immunofluorescence findings.
Discoid Lupus Erythematosus (DLE) is a chronic disease with a typical cutaneous involvement. This pathology rarely involves mucosa: oral cavity is interested in 20% of DLE patients. We describe a case of oral DLE in a 50-year-old woman with an anamnesis for autoimmune disorders. This study shows the helpful role of immunofluorescence in the diagnosis of autoimmune diseases. The first diagnostic step was the clinical observation of the oral mucosa: the lesion area was erythematous, athrophic and hyperkeratotic. The patient then underwent laboratory examination. We utilized human epithelial cells (Hep-2010) for Indirect Immuno-Fluorescence (IIF). Moreover, the biopsy site for Direct Immuno-Fluorescence (DIF) and histopathological analysis was the untreated oral lesion. IIF detected an increase of Anti-Nuclear Antibody (ANA) and positivity for SSA-RO. By DIF, we observed IgG/IgA/fibrinogen along basal layer. Multiple biopsies reported signs of chronic basal damage. Steroid systemic therapy induced a considerable lesion regression. We suggest the use of immunofluorescence with the integration of further data to improve diagnosis of rare diseases and to establish a suitable therapy
Primordial Nucleosynthesis
Primordial nucleosynthesis, or Big-Bang Nucleosynthesis (BBN), is one of the
three evidences for the Big-Bang model, together with the expansion of the
Universe and the Cosmic Microwave Background. There is a good global agreement
over a range of nine orders of magnitude between abundances of 4He, D, 3He and
7Li deduced from observations, and calculated in primordial nucleosynthesis.
This comparison was used to determine the baryonic density of the Universe. For
this purpose, it is now superseded by the analysis of the Cosmic Microwave
Background (CMB) radiation anisotropies. However, there remain, a yet
unexplained, discrepancy of a factor 3-5, between the calculated and observed
lithium primordial abundances, that has not been reduced, neither by recent
nuclear physics experiments, nor by new observations. We review here the
nuclear physics aspects of BBN for the production of 4He, D, 3He and 7Li, but
also 6Li, 9Be, 11B and up to CNO isotopes. These are, for instance, important
for the initial composition of the matter at the origin of the first stars.
Big-Bang nucleosynthesis, that has been used, to first constrain the baryonic
density, and the number of neutrino families, remains, a valuable tool to probe
the physics of the early Universe, like variation of "constants" or alternative
theories of gravity.Comment: Invited Plenary Talk given at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference
Series (JPCS
Mapping systematic errors in helium abundance determinations using Markov Chain Monte Carlo
Monte Carlo techniques have been used to evaluate the statistical and
systematic uncertainties in the helium abundances derived from extragalactic
H~II regions. The helium abundance is sensitive to several physical parameters
associated with the H~II region. In this work, we introduce Markov Chain Monte
Carlo (MCMC) methods to efficiently explore the parameter space and determine
the helium abundance, the physical parameters, and the uncertainties derived
from observations of metal poor nebulae. Experiments with synthetic data show
that the MCMC method is superior to previous implementations (based on flux
perturbation) in that it is not affected by biases due to non-physical
parameter space. The MCMC analysis allows a detailed exploration of
degeneracies, and, in particular, a false minimum that occurs at large values
of optical depth in the He~I emission lines. We demonstrate that introducing
the electron temperature derived from the [O~III] emission lines as a prior, in
a very conservative manner, produces negligible bias and effectively eliminates
the false minima occurring at large optical depth. We perform a frequentist
analysis on data from several "high quality" systems. Likelihood plots
illustrate degeneracies, asymmetries, and limits of the determination. In
agreement with previous work, we find relatively large systematic errors,
limiting the precision of the primordial helium abundance for currently
available spectra.Comment: 25 pages, 11 figure
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