1,180 research outputs found
Experimental evidence of a change of exchange anisotropy sign with temperature in Zn-substituted Cu2OSeO3
We report small-angle neutron scattering from the conical state in a single crystal of Zn-substituted Cu 2 OSeO 3 . Using a 3D vector-field magnet to reorient the conical wave vector, our measurements show that the magnitude of the conical wave vector changes as a function of crystallographic direction. These changes are explained using the anisotropic exchange interaction (AEI) within the continuum model, whose magnitude in free-energy transitions from a maxima to a minima along the ⨠111 ⊠and ⨠100 ⊠crystallographic directions respectively. We further find that the AEI free-energy constant undergoes a change of sign from positive to negative with decreasing temperature. Unlike in the related compound FeGe, where similar behavior of the AEI induces a reorientation of the helical wave vector, we show that the zero field helical wave vector in ( Cu 0.98 Zn 0.02 ) 2 OSeO 3 remains along the ⨠100 ⊠directions at all temperatures due to the competing fourth-order magnetocrystalline anisotropy becoming dominant at lower temperatures
Identification and safety evaluation of <em>Bacillus species </em>occurring in high numbers during spontaneous fermentations to produce Gergoush, a traditional Sudanese bread snack
Testing the near field/far field model performance for prediction of particulate matter emissions in a paint factory
Here we tested how well a NF/FF dispersion model predicts particulate matter concentrations when source emission potency was estimated using a material dustiness index.</p
Are and the Roper resonance diquark-diquark-antiquark states?
We consider a current in the QCD sum rule framework to study
the mass of the recently observed pentaquark state , obtaining
good agreement with the experimental value. We also study the mass of the
pentaquark . Our results are compatible with the interpretation
of the state as being the Roper resonance N(1440), as suggested
by Jaffe and Wilczek.Comment: 9 pages RevTex4 and 3 eps figures. Revised version accepted for
publication in Phys. Lett.
From Network Structure to Dynamics and Back Again: Relating dynamical stability and connection topology in biological complex systems
The recent discovery of universal principles underlying many complex networks
occurring across a wide range of length scales in the biological world has
spurred physicists in trying to understand such features using techniques from
statistical physics and non-linear dynamics. In this paper, we look at a few
examples of biological networks to see how similar questions can come up in
very different contexts. We review some of our recent work that looks at how
network structure (e.g., its connection topology) can dictate the nature of its
dynamics, and conversely, how dynamical considerations constrain the network
structure. We also see how networks occurring in nature can evolve to modular
configurations as a result of simultaneously trying to satisfy multiple
structural and dynamical constraints. The resulting optimal networks possess
hubs and have heterogeneous degree distribution similar to those seen in
biological systems.Comment: 15 pages, 6 figures, to appear in Proceedings of "Dynamics On and Of
Complex Networks", ECSS'07 Satellite Workshop, Dresden, Oct 1-5, 200
Sex Chromosome Turnover in Bent-Toed Geckos (\u3cem\u3eCyrtodactylus\u3c/em\u3e)
Lizards and snakes (squamates) are known for their varied sex determining systems, and gecko lizards are especially diverse, having evolved sex chromosomes independently multiple times. While sex chromosomes frequently turnover among gecko genera, intrageneric turnovers are known only from Gekko and Hemidactylus. Here, we used RADseq to identify sex-specific markers in two species of Burmese bent-toed geckos. We uncovered XX/XY sex chromosomes in Cyrtodactylus chaunghanakwaensis and ZZ/ZW sex chromosomes in Cyrtodactylus pharbaungensis. This is the third instance of intrageneric turnover of sex chromosomes in geckos. Additionally, Cyrtodactylus are closely related to another genus with intrageneric turnover, Hemidactylus. Together, these data suggest that sex chromosome turnover may be common in this clade, setting them apart as exceptionally diverse in a group already known for diverse sex determination systems
Continuity of the Maximum-Entropy Inference
We study the inverse problem of inferring the state of a finite-level quantum
system from expected values of a fixed set of observables, by maximizing a
continuous ranking function. We have proved earlier that the maximum-entropy
inference can be a discontinuous map from the convex set of expected values to
the convex set of states because the image contains states of reduced support,
while this map restricts to a smooth parametrization of a Gibbsian family of
fully supported states. Here we prove for arbitrary ranking functions that the
inference is continuous up to boundary points. This follows from a continuity
condition in terms of the openness of the restricted linear map from states to
their expected values. The openness condition shows also that ranking functions
with a discontinuous inference are typical. Moreover it shows that the
inference is continuous in the restriction to any polytope which implies that a
discontinuity belongs to the quantum domain of non-commutative observables and
that a geodesic closure of a Gibbsian family equals the set of maximum-entropy
states. We discuss eight descriptions of the set of maximum-entropy states with
proofs of accuracy and an analysis of deviations.Comment: 34 pages, 1 figur
Impurity state in the vortex core of d-wave superconductors: Anderson impurity model versus unitary impurity model
Using an extended Anderson/Kondo impurity model to describe the magnetic
moments around an impurity doped in high- d-wave cuprates and in
the framework of the slave-boson meanfield approach, we study numerically the
impurity state in the vortex core by exact diagonalization of the
well-established Bogoliubov-de Gennes equations. The low-energy impurity state
is found to be good agreement with scanning tunnelingmicroscopy observation.
After pinning a vortex on the impurity site, we compare the unitary impurity
model with the extended Anderson impurity model by examining the effect of the
magnetic field on the impurity state. We find that the impurity resonance in
the unitary impurity model is strongly suppressed by the vortex; while it is
insensitive to the field in the extended Anderson impurity model.Comment: 8 pages, 3 figure
Progress in the determination of the cross section
Improving previous calculations, we compute the cross section using QCD sum rules. Our sum rules for the , , and hadronic
matrix elements are constructed by using vaccum-pion correlation functions, and
we work up to twist-4 in the soft-pion limit. Our results suggest that, using
meson exchange models is perfectly acceptable, provided that they include form
factors and that they respect chiral symmetry. After doing a thermal average we
get mb at T=150\MeV.Comment: 22 pages, RevTeX4 including 7 figures in ps file
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