6,608 research outputs found
Cosmic e^\pm, \bar p, \gamma and neutrino rays in leptocentric dark matter models
Dark matter annihilation is one of the leading explanations for the recently
observed excesses in cosmic rays by PAMELA, ATIC, FERMI-LAT and HESS.
Any dark matter annihilation model proposed to explain these data must also
explain the fact that PAMELA data show excesses only in spectrum but
not in anti-proton. It is interesting to ask whether the annihilation mode into
anti-proton is completely disallowed or only suppressed at low energies. Most
models proposed have negligible anti-protons in all energy ranges. We show that
the leptocentric dark matter model can explain the
excesses with suppressed anti-proton mode at low energies, but at higher
energies there are sizable anti-proton excesses. Near future data from PAMELA
and AMS can provide crucial test for this type of models. Cosmic ray
data can further rule out some of the models. We also show that this model has
interesting cosmic neutrino signatures.Comment: Latex 20 pages and five figures. References adde
Perspective of Galactic dark matter subhalo detection on Fermi from the EGRET observation
The perspective of the detectability of Galactic dark matter subhaloes on the
Fermi satellite is investigated in this work. Under the assumptions that dark
matter annihilation accounts for the "GeV excess" of the Galactic diffuse
-rays discovered by EGRET and the -ray flux is dominated by the
contribution from subhaloes of dark matter, we calculate the expected number of
dark matter subhaloes that Fermi may detect. We show that Fermi may detect a
few tens to several hundred subhaloes in 1-year all sky survey. Since EGRET
observation is taken as a normalization, this prediction is independent of the
particle physics property of dark matter. The uncertainties of the prediction
are discussed in detail. We find that the major uncertainty comes from the mass
function of subhaloes, i.e., whether the subhaloes are "point like" (high-mass
rich) or "diffuse like" (low-mass rich). Other uncertainties like the
background estimation and the observational errors will contribute a factor of
.Comment: 16 pages, 4 figures and 1 table, accepted for publication in Chinese
Physics
Diffuse -rays and flux from dark matter annihilation -- a model for consistent results with EGRET and cosmic ray data
In this work we develop a new propagation model for the Galactic cosmic rays
based on the GALPROP code, including contributions from dark matter
annihilation. The model predicts compatible Galactic diffuse ray
spectra with EGRET data in all sky regions. It also gives consistent results of
the diffuse ray longitude and latitude distributions. Further the
results for B/C, Be/Be, proton, electron and antiproton spectra are
also consistent with cosmic ray measurements. In the model we have taken a
universal proton spectrum throughout the Galaxy without introducing large
fluctuation for the proton energy loss is negligible. The dark matter
annihilation signals are `boosted' after taking the contribution from subhalos
into account. Another interesting feature of the model is that it gives better
description of the diffuse rays when taking the source distribution
compatible with supernova remnants data, which is different from previous
studies.Comment: 29 pages, 13 figures; the published versio
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Analysis of Down syndrome failed to be diagnosed after prenatal screening: A multicenter study.
To analyze the characters of Down syndrome (DS) who failed to be diagnosed after prenatal screening and hope to be able to improve the programs of prenatal screening and reduce the missed diagnosis of DS. In this multicenter study, we collected the missed cases from 3 prenatal diagnosis centers and analyzed their characters. A total of 126 DS babies failed to be diagnosed after prenatal screening. Their mothers accepted the prenatal screening in second trimester. We collected the mothers' blood and detected the levels of alpha-fetoprotein (AFP) and the free beta subunit of human chorionic gonadotropin (fβhCG) by time-resolved fluoroimmunoassay. The values were also presented as multiples of the median (MoM) and determined the risk of carrying a fetus with DS by Wallace LifeCycle Elipse analysis software. Compared with normal control group, the level of fβhCG and hCG MoM were dramatically increased, while AFP and AFP MoM were decreased. The area under the receiver-operating-characteristic curve of trisomy 21 was 0.8387 for hCG-MoM and AFP-MoM testing. The sensitivity, specificity, positive predictive value, and negative predictive value were 84.6%, 74.8%, 75.4%, and 83.6%, respectively. Meanwhile, the prediction mode was "0.39957 + 1.90897HCG-MOM -3.32713AFP-MOM". It was worthwhile noting that the risk of 65.9% DS missed diagnosis group were higher than 1/1000, 92.9% higher than 1/3000. However, 72.5% cases in normal control group were lower than 1/3000. Only 9.2% mothers would be higher than the value of risk in 1/1000. The prediction mode of hCG MoM and AFP MoM might be able to help us reduce the missed diagnosis. It is also necessary to adjust more reasonable range of noninvasive prenatal testing with further clinical researches
Mesenchymal stem cells and induced pluripotent stem cells as therapies for multiple sclerosis.
Multiple sclerosis (MS) is a chronic, autoimmune, inflammatory demyelinating disorder of the central nervous system that leads to permanent neurological deficits. Current MS treatment regimens are insufficient to treat the irreversible neurological disabilities. Tremendous progress in the experimental and clinical applications of cell-based therapies has recognized stem cells as potential candidates for regenerative therapy for many neurodegenerative disorders including MS. Mesenchymal stem cells (MSC) and induced pluripotent stem cell (iPSCs) derived precursor cells can modulate the autoimmune response in the central nervous system (CNS) and promote endogenous remyelination and repair process in animal models. This review highlights studies involving the immunomodulatory and regenerative effects of mesenchymal stem cells and iPSCs derived cells in animal models, and their translation into immunomodulatory and neuroregenerative treatment strategies for MS
A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz
A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz is carried out
using the Shanghai Tian Ma 65 m Radio Telescope (TMRT-65m) with a sensitivity
of < 7 mK. Thirty-five spectral lines of 12 different molecules and radicals
are detected in total. Except for SiS, the detected molecules are all
carbon-chain molecules, including HC3N, HC5N, HC7N, HC9N, C6H, C6H-, C8H, SiC2,
SiC4, c-C3H2 and l-C5H. The presence of rich carbon-bearing molecules is
consistent with the identity of IRC +10216 as a carbon-rich AGB star. The
excitation temperatures and column densities of the observed species are
derived by assuming a local thermodynamic equilibrium and homogeneous
conditions.Comment: This is the authors' version of the manuscript; 16 pages, 5 figures,
6 tables; Accepted for publication in A&A 8/17/201
3-[(CycloÂhexylÂidene)amino]-1-(4-methylÂphenÂyl)thioÂurea
In the title compound, C14H19N3S, the cycloÂhexane ring has a chair conformation. The almost planar aminoÂthioÂurea unit (r.m.s. deviation = 0.0062 Å) is aligned at a dihedral angle of 45.23 (8)° with respect to the benzene ring. InterÂmolecular N—H⋯N and N—H⋯S hydrogen bonding stabilizes the crystal structure
Delayed Feedback Control on a Class of Generalized Gyroscope Systems under Parametric Excitation
AbstractThe nonlinear dynamics of the parametrically excited vibrations of a class of generalized gyroscope systems under delayed feedback control is investigated by the averaging method and simulations in this paper. The influence of feedback control on the stability of the trivial solution and the amplitude of the periodic vibrations is presented based on Routh-Hurwitz criterion and the Levenberg-Marquardt method respectively. It is shown that the stability of the trivial solution can be varied when feedback control and time delay are employed. The amplitudes of periodic solutions can also be modulated greatly by feedback gain and time delay. However, the influence of time delay on amplitudes is periodic. The simulations obtained by numerically integrating the original system are in good agreement with the analytical results
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