9,467 research outputs found
Joint H.E.S.S. and Fermi-LAT analysis of the region around PSR J1813-1749
HESS J1813-178 is one of the brightest sources detected during the first HESS
Galactic Plane survey. The compact source, also detected by MAGIC, is believed
to be a pulsar wind nebula powered by one of the most powerful pulsars known in
the Galaxy, PSR J1813-1749 with a spin-down luminosity of . With its extreme physical
properties, as well as the pulsar's young age of 5.6 kyrs, the -rays
detected in this region allow us to study the evolution of a highly atypical
system. Previous studies of the region in the GeV energy range show emission
extended beyond the size of the compact H.E.S.S. source. Using the archival
H.E.S.S. data with improved background methods, we perform a detailed
morphological and spectral analysis of the region. Additionally to the compact,
bright emission component, we find significantly extended emission, whose
position is coincident with HESS J1813-178. We reanalyse the region in GeV and
derive a joint-model in order to find a continuous description of the emission
in the region from GeV to TeV. Using the results derived in this analysis, as
well as X-ray and radio data of the region, we perform multi-wavelength
spectral modeling. Possible hadronic or leptonic origins of the -ray
emission are investigated, and the diffusion parameters necessary to explain
the extended emission are examined.Comment: 8 pages, 4 figures, 1 table, In proceedings of ICRC202
Dark matter annihilation and decay in dwarf spheroidal galaxies: The classical and ultrafaint dSphs
Dwarf spheroidal (dSph) galaxies are prime targets for present and future
gamma-ray telescopes hunting for indirect signals of particle dark matter. The
interpretation of the data requires careful assessment of their dark matter
content in order to derive robust constraints on candidate relic particles.
Here, we use an optimised spherical Jeans analysis to reconstruct the
`astrophysical factor' for both annihilating and decaying dark matter in 21
known dSphs. Improvements with respect to previous works are: (i) the use of
more flexible luminosity and anisotropy profiles to minimise biases, (ii) the
use of weak priors tailored on extensive sets of contamination-free mock data
to improve the confidence intervals, (iii) systematic cross-checks of binned
and unbinned analyses on mock and real data, and (iv) the use of mock data
including stellar contamination to test the impact on reconstructed signals.
Our analysis provides updated values for the dark matter content of 8
`classical' and 13 `ultrafaint' dSphs, with the quoted uncertainties directly
linked to the sample size; the more flexible parametrisation we use results in
changes compared to previous calculations. This translates into our ranking of
potentially-brightest and most robust targets---viz., Ursa Minor, Draco,
Sculptor---, and of the more promising, but uncertain targets---viz., Ursa
Major 2, Coma---for annihilating dark matter. Our analysis of Segue 1 is
extremely sensitive to whether we include or exclude a few marginal member
stars, making this target one of the most uncertain. Our analysis illustrates
challenges that will need to be addressed when inferring the dark matter
content of new `ultrafaint' satellites that are beginning to be discovered in
southern sky surveys.Comment: 19 pages, 14 figures, submitted to MNRAS. Supplementary material
available on reques
Investigation of preparative possibilities of iodinating systems on the basis of N-iodoacetamide
N-iodoacetamide in organic solvents with H2SО4 iodinates successfully alkylbenzenes, aromatic amines and phenol ether. Electrophilic iodine activity is controlled by medium acidity. Super electrophilic iodine formed at N-iodoacetamide dissolution in sulfuric acid reacts easily with electron-deficient arenes at 0...20 °C forming iodinated product
Search for axions in streaming dark matter
A new search strategy for the detection of the elusive dark matter (DM) axion
is proposed. The idea is based on streaming DM axions, whose flux might get
temporally enormously enhanced due to gravitational lensing. This can happen if
the Sun or some planet (including the Moon) is found along the direction of a
DM stream propagating towards the Earth location. The experimental requirements
to the axion haloscope are a wide-band performance combined with a fast axion
rest mass scanning mode, which are feasible. Once both conditions have been
implemented in a haloscope, the axion search can continue parasitically almost
as before. Interestingly, some new DM axion detectors are operating wide-band
by default. In order not to miss the actually unpredictable timing of a
potential short duration signal, a network of co-ordinated axion antennae is
required, preferentially distributed world-wide. The reasoning presented here
for the axions applies to some degree also to any other DM candidates like the
WIMPs.Comment: 5 page
Radical Scavenging of Poly(Methyl Methacrylate) Bone Cement by Rifampin and Clinically Relevant Properties of the Rifampin-Loaded Cement
Objectives: The objective of this study was to characterize the effect of rifampin incorporation into poly(methyl methacrylate) (pMMA) bone cement. While incompatibilities between the two materials have been previously noted, we sought to identify and quantify the cause of rifampin\u27s effects, including alterations in curing properties, mechanical strength, and residual monomer content.
Methods: Four cement groups were prepared using commercial pMMA bone cement: a control; one with 1 g of rifampin; and one each with equimolar amounts of ascorbic acid or hydroquinone relative to the amount of rifampin added. The handling properties, setting time, exothermic output, and monomer loss were measured throughout curing. The mechanical strength of each group was tested over 14 days. A radical scavenging assay was used to assess the scavenging abilities of rifampin and its individual moieties.
Results: Compared with control, the rifampin-incorporated cement had a prolonged setting time and a reduction in exothermic output during polymerization. The rifampin cement showed significantly reduced strength and was below the orthopaedic weight-bearing threshold of 70 Mpa. Based on the radical scavenging assay and strength tests, the hydroquinone structure within rifampin was identified as the polymerization inhibitor.
Conclusion: The incorporation of rifampin into pMMA bone cement interferes with the cement\u27s radical polymerization. This interference is due to the hydroquinone moiety within rifampin. This combination alters the cement\u27s handling and curing properties, and lowers the strength below the threshold for weight-bearing applications. Additionally, the incomplete polymerization leads to increased toxic monomer output, which discourages its use even in non-weight-bearing applications
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