681 research outputs found
Supervised fully polarimetric classification of the Black Forest test site: From MAESTROI to MAC Europe
A study on the performance of a supervised fully polarimetric maximum likelihood classifier for synthetic aperture radar (SAR) data when applied to a specific classification context: forest classification based on age classes and in the presence of a sloping terrain is presented. For the experimental part, the polarimetric AIRSAR data at P, L, and C-band, acquired over the German Black Forest near Freiburg in the frame of the 1989 MAESTRO-1 campaign and the 1991 MAC Europe campaign was used, MAESTRO-1 with an ESA/JRC sponsored campaign, and MAC Europe (Multi-sensor Aircraft Campaign); in both cases the multi-frequency polarimetric JPL Airborne Synthetic Aperture Radar (AIRSAR) radar was flown over a number of European test sites. The study is structured as follows. At first, the general characteristics of the classifier and the dependencies from some parameters, like frequency bands, feature vector, calibration, using test areas lying on a flat terrain are investigated. Once it is determined the optimal conditions for the classifier performance, we then move on to the study of the slope effect. The bulk of this work is performed using the Maestrol data set. Next the classifier performance with the MAC Europe data is considered. The study is divided into two stages: first some of the tests done on the Maestro data are repeated, to highlight the improvements due to the new processing scheme that delivers 16 look data. Second we experiment with multi images classification with two goals: to assess the possibility of using a training set measured from one image to classify areas in different images; and to classify areas on critical slopes using different viewing angles. The main points of the study are listed and some of the results obtained so far are highlighted
Cosmic-ray antiproton constraints on light dark matter candidates
Some direct detection experiments have recently collected excess events that
could be interpreted as a dark matter (DM) signal, pointing to particles in the
10 GeV mass range. We show that scenarios in which DM can self-annihilate
with significant couplings to quarks are likely excluded by the cosmic-ray (CR)
antiproton data, provided the annihilation is S-wave dominated when DM
decouples in the early universe. These limits apply to most of supersymmetric
candidates, eg in the minimal supersymmetric standard model (MSSM) and in the
next-to-MSSM (NMSSM), and more generally to any thermal DM particle with
hadronizing annihilation final states.Comment: Contribution to the proceedings of TAUP-2011 (Munich, 5-9 IX 2011). 4
page
Antimatter signals of singlet scalar dark matter
We consider the singlet scalar model of dark matter and study the expected
antiproton and positron signals from dark matter annihilations. The regions of
the viable parameter space of the model that are excluded by present data are
determined, as well as those regions that will be probed by the forthcoming
experiment AMS-02. In all cases, different propagation models are investigated,
and the possible enhancement due to dark matter substructures is analyzed. We
find that the antiproton signal is more easily detectable than the positron one
over the whole parameter space. For a typical propagation model and without any
boost factor, AMS-02 will be able to probe --via antiprotons-- the singlet
model of dark matter up to masses of 600 GeV. Antiprotons constitute,
therefore, a promising signal to constraint or detect the singlet scalar model.Comment: 24 pages, 8 figures. v2: minor improvements. Accepted for publication
in JCA
Rivaroxaban in atrial fibrillation cardioversion: an update
Currently, atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, with a prevalence of about 2-3% in the general population, representing a powerful risk factor for stroke and systemic thromboembolism and increased mortality and morbidity. Restoration of sinus rhythm is an important treatment option in AF and has a high success rate, but there is the need for an effective anticoagulation strategy to reduce the risk of embolic events. Anticoagulation with vitamin K antagonists is often associated with failure to achieving effective international normalized ratio. In this setting, recent data have led to extended approval for rivaroxaban in clinical practice, because it is effective and safe in patients with AF undergoing cardioversion, avoiding additional health costs and related time loss, while improving patient satisfaction. The present report provides an overview of the main randomized controlled trial and the main real-life studies, documenting the use of rivaroxaban in patients with non-valvular AF who underwent the cardioversion procedure. Considering that novel non-vitamin K antagonist oral anticoagulants in left atrial appendage thrombi resolution is still unknown in the real-world practice, the main findings on the use of rivaroxaban in this setting are also discussed
Gender differences in vaccine therapy: where are we in Covid-19 pandemic?
Vaccination is one of the greatest achievements of public health. Vaccination programs have contributed to the decline in mortality and morbidity of various infectious diseases. This review aims to investigate the impact of sex/gender on the vaccine acceptance, responses, and outcomes. The studies were identified by using PubMed, until 30th June 2020. The search was performed by using the following keywords: SARS-CoV-2, Covid-19, gender, sex, vaccine, adverse reaction. Clinical trials, retrospective and prospective studies were included. Studies written in languages other than English were excluded. Three authors (TC, EB and IA) reviewed all study abstracts. Studies were included if gender differences in response to vaccination trials were reported. All selected studies were qualitatively analyzed. Innate recognition and response to viruses, as well as, adaptive immune responses during viral infections, differ between females and males. Unfortunately, a majority of vaccine trials have focused on healthy people, with ages between 18 to 65 years, excluding the elderly, pregnant women, post-menopausal female and children. In conclusion, it is apparent that the design of vaccines and vaccine strategies should be sex-specific, to reduce adverse reactions in females and increase immunogenicity in males. It should be mandatory to examine sex-related variables in pre-clinical and clinical vaccine trials, such as their crucial role for successful prevention of pandemic Covid-19
High energy photon flux prediction from neutralino annihilation in the globular cluster Palomar 13
The distant globular cluster Palomar 13 has been found to have a very high
mass-to-light ratio and its profile can be well fitted either by a King model
with a tail, or with a NFW model. This cluster may be the first case of the
many clumps predicted by CDM simulations that would not be disrupted by the
galactic halo potential. We make the hypothesis that Pal 13 is made of
neutralinos and run the DarkSuspect code to estimate the high-energy photon
flux due to the annihilation of neutralinos through various channels in some
benchmark scenarios. These low fluxes may be used as targets to be reached in
proposals for future ground-based high altitude Cerenkov telescopes.Comment: A 2-page poster to be published in ``Astronomy, Cosmology and
Fundamental Physics'', the proceedings of the ESO-CERN-ESA Symposium, eds. P.
A. Shaver, L. Di Lella, and A. Gimene
Scalar Multiplet Dark Matter
We perform a systematic study of the phenomenology associated to models where
the dark matter consists in the neutral component of a scalar SU(2)_L n-uplet,
up to n=7. If one includes only the pure gauge induced annihilation
cross-sections it is known that such particles provide good dark matter
candidates, leading to the observed dark matter relic abundance for a
particular value of their mass around the TeV scale. We show that these values
actually become ranges of values -which we determine- if one takes into account
the annihilations induced by the various scalar couplings appearing in these
models. This leads to predictions for both direct and indirect detection
signatures as a function of the dark matter mass within these ranges. Both can
be largely enhanced by the quartic coupling contributions. We also explain how,
if one adds right-handed neutrinos to the scalar doublet case, the results of
this analysis allow to have altogether a viable dark matter candidate,
successful generation of neutrino masses, and leptogenesis in a particularly
minimal way with all new physics at the TeV scale.Comment: 43 pages, 20 figure
Dirac gaugino as leptophilic dark matter
We investigate the leptophilic properties of Dirac gauginos in an
R--symmetric N=2 supersymmetric model with extended gauge and Higgs sectors.
The annihilation of Dirac gauginos to leptons requires no chirality flip in the
final states so that it is not suppressed as in the Majorana case. This implies
that it can be sizable enough to explain the positron excess observed by the
PAMELA experiment with moderate or no boost factors. When squark masses are
heavy, the annihilation of Dirac gauginos to hadrons is controlled by their
Higgsino fraction and is driven by the and final states.
Moreover, at variance with the Majorana case, Dirac gauginos with a
non-vanishing higgsino fraction can also have a vector coupling with the
gauge boson leading to a sizable spin--independent scattering cross section off
nuclei. Saturating the current antiproton limit, we show that Dirac gauginos
can leave a signal in direct detection experiments at the level of the
sensitivity of dark matter searches at present and in the near future.Comment: 24 pages, 10 figures, typos corrected, final version published on
JCA
Supersymmetry in models with strong on-site Coulomb repulsion - application to t-J model
A supersymmetric way of imposing the constraint of no double occupancy in
models with strong on-site Coulomb repulsion is presented in this paper. In
this formulation the physical operators in the constrainted Hilbert space are
invariant under local unitary transformations mixing boson and fermion
representations. As an illustration the formulation is applied to the
model. The model is studied in the mean-field level in the J=0 limit where we
show how both the slave-boson and slave-fermion formulations are included
naturally in the present approach and how further results beyond both
approaches are obtained.Comment: 12 pages, Latex file, 1 figur
Direct oral anticoagulants versus vitamin K antagonists in patients with atrial fibrillation and cancer a meta-analysis
Background: Direct oral anticoagulants (DOACs) are recommended as first-line anticoagulants in patients with atrial fibrillation (AF). However, in patients with cancer and AF the efficacy and safety of DOACs are not well established. Objective: We performed a meta-analysis comparing available data regarding the efficacy and safety of DOACs vs vitamin K antagonists (VKAs) in cancer patients with non-valvular AF. Methods: An online search of Pubmed and EMBASE libraries (from inception to May, 1 2020) was performed, in addition to manual screening. Nine studies were considered eligible for the meta-analysis involving 46,424 DOACs users and 182,797 VKA users. Results: The use of DOACs was associated with reduced risks of systemic embolism or any stroke (RR 0.65; 95% CI 0.52–0.81; p 0.001), ischemic stroke (RR 0.84; 95% CI 0.74–0.95; p 0.007) and hemorrhagic stroke (RR 0.61; 95% CI 0.52–0.71; p 0.00001) as compared to VKA group. DOAC use was associated with significantly reduced risks of major bleeding (RR 0.68; 95% CI 0.50–0.92; p 0.01) and intracranial or gastrointestinal bleeding (RR 0.64; 95% CI 0.47–0.88; p 0.006). Compared to VKA, DOACs provided a non-statistically significant risk reduction of the outcomes major bleeding or non-major clinically relevant bleeding (RR 0.94; 95% CI 0.78–1.13; p 0.50) and any bleeding (RR 0.91; 95% CI 0.78–1.06; p 0.24). Conclusions: In comparison to VKA, DOACs were associated with a significant reduction of the rates of thromboembolic events and major bleeding complications in patients with AF and cancer. Further studies are needed to confirm our results
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