4,111 research outputs found
H.E.S.S. deeper observations on SNR RX J0852.0-4622
Supernova Remnants (SNRs) are believed to be acceleration sites of Galactic
cosmic rays. Therefore, deep studies of these objects are instrumental for an
understanding of the high energy processes in our Galaxy. RX J0852.0-4622, also
known as Vela Junior, is one of the few (4) shell-type SNRs resolved at Very
High Energies (VHE; E > 100 GeV). It is one of the largest known VHE sources (~
1.0 deg radius) and its flux level is comparable to the flux level of the Crab
Nebula in the same energy band. These characteristics allow for a detailed
analysis, shedding further light on the high-energy processes taking place in
the remnant. In this document we present further details on the spatial and
spectral morphology derived with an extended data set. The analysis of the
spectral morphology of the remnant is compatible with a constant power-law
photon index of 2.11 +/- 0.05_stat +/- 0.20_syst from the whole SNR in the
energy range from 0.5 TeV to 7 TeV. The analysis of the spatial morphology
shows an enhanced emission towards the direction of the pulsar PSR J0855-4644,
however as the pulsar is lying on the rim of the SNR, it is difficult to
disentangle both contributions. Therefore, assuming a point source, the upper
limit on the flux of the pulsar wind nebula (PWN) between 1 TeV and 10 TeV, is
estimated to be ~ 2% of the Crab Nebula flux in the same energy range
An integral model based on slender body theory, with applications to curved rigid fibers
We propose a novel integral model describing the motion of curved slender
fibers in viscous flow, and develop a numerical method for simulating dynamics
of rigid fibers. The model is derived from nonlocal slender body theory (SBT),
which approximates flow near the fiber using singular solutions of the Stokes
equations integrated along the fiber centerline. In contrast to other models
based on (singular) SBT, our model yields a smooth integral kernel which
incorporates the (possibly varying) fiber radius naturally. The integral
operator is provably negative definite in a non-physical idealized geometry, as
expected from PDE theory. This is numerically verified in physically relevant
geometries. We propose a convergent numerical method for solving the integral
equation and discuss its convergence and stability. The accuracy of the model
and method is verified against known models for ellipsoids. Finally, a fast
algorithm for computing dynamics of rigid fibers with complex geometries is
developed
SSR- and RAPD Analysis of a New Agropyron Repens Genotype
SSR-(single sequence repeat), and RAPD (randomly amplified polymorphic DNA) primer generated DNA fingerprints were used to distinguish a new genotype of quackgrass from its original type of Agropyron repenes L. Beauv. (= Elytrigia repens). Products of polymerase chain reactions (PCR) were separated by agarose (AGE) and denaturing gradient gel electrophoresis (DGGE). Although, both kinds of primers were found to be polymorphic, the microsatellite primer with sequence of 5í-AC(GACA)4-3í generated distinguishing fingerprints in the two types of quackgrasses. This result gives genetic evidence for the new genotype of quackgrass
The Genome Portal of the Department of Energy Joint Genome Institute
The Department of Energy (DOE) Joint Genome Institute (JGI) is a national user facility with massive-scale DNA sequencing and analysis capabilities dedicated to advancing genomics for bioenergy and environmental applications. Beyond generating tens of trillions of DNA bases annually, the Institute develops and maintains data management systems and specialized analytical capabilities to manage and interpret complex genomic data sets, and to enable an expanding community of users around the world to analyze these data in different contexts over the web. The JGI Genome Portal (http://genome.jgi.doe.gov) provides a unified access point to all JGI genomic databases and analytical tools. A user can find all DOE JGI sequencing projects and their status, search for and download assemblies and annotations of sequenced genomes, and interactively explore those genomes and compare them with other sequenced microbes, fungi, plants or metagenomes using specialized systems tailored to each particular class of organisms. We describe here the general organization of the Genome Portal and the most recent addition, MycoCosm (http://jgi.doe.gov/fungi), a new integrated fungal genomics resource
'Hole-digging' in ensembles of tunneling Molecular Magnets
The nuclear spin-mediated quantum relaxation of ensembles of tunneling
magnetic molecules causes a 'hole' to appear in the distribution of internal
fields in the system. The form of this hole, and its time evolution, are
studied using Monte Carlo simulations. It is shown that the line-shape of the
tunneling hole in a weakly polarised sample must have a Lorentzian lineshape-
the short-time half-width in all experiments done so far should be
, the half-width of the nuclear spin multiplet. After a time
, the single molecule tunneling relaxation time, the hole width begins
to increase rapidly. In initially polarised samples the disintegration of
resonant tunneling surfaces is found to be very fast.Comment: 4 pages, 5 figure
Absence of spin dependence in the final state interaction of the d(pol) p --> 3He eta reaction
The deuteron tensor analysing power t_{20} of the d(pol) p --> 3He eta
reaction has been measured at the COSY-ANKE facility in small steps in excess
energy Q up to Q = 11 MeV. Despite the square of the production amplitude
varying by over a factor of five through this range, t_{20} shows little or no
energy dependence. This is evidence that the final state interaction causing
the energy variation is not influenced by the spin configuration in the
entrance channel. The weak angular dependence observed for t_{20} provides
useful insight into the amplitude structure near threshold.Comment: 5 pages, 4 figure
Nonadiabatic Landau Zener tunneling in Fe_8 molecular nanomagnets
The Landau Zener method allows to measure very small tunnel splittings \Delta
in molecular clusters Fe_8. The observed oscillations of \Delta as a function
of the magnetic field applied along the hard anisotropy axis are explained in
terms of topological quantum interference of two tunnel paths of opposite
windings. Studies of the temperature dependence of the Landau Zener transition
rate P gives access to the topological quantum interference between exited spin
levels. The influence of nuclear spins is demonstrated by comparing P of the
standard Fe_8 sample with two isotopically substituted samples. The need of a
generalized Landau Zener transition rate theory is shown.Comment: 5 pages, 6 figure
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