19,610 research outputs found
An improved study of the kappa resonance and the non-exotic wave scatterings up to GeV of LASS data
We point out that the dispersion relation for the left hand cut integral
presented in one of our previous paper (Nucl. Phys. {\bf A}733(2004)235) is
actually free of subtraction constant, even for unequal mass elastic
scatterings. A new fit to the LASS data~\cite{Aston} is performed and firm
evidence for the existence of pole is found. The correct use of
analyticity also put strong constraints on threshold parameters -- which are
found to be in good agreement with those obtained from chiral theories. We also
determined the pole parameters of on the second sheet, and
reconfirm the existence of on the third sheet. We stress that the
LASS data do not require them to have the twin pole structure of a typical
Breit--Wigner resonance.Comment: 14 pages + 4 postscript figures; discussions largely expanded;
references added; version to appear in NPA; title changed in the journa
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Patterns of spatial genetic structures in Aedes albopictus (Diptera: Culicidae) populations in China.
BACKGROUND:The Asian tiger mosquito, Aedes albopictus, is one of the 100 worst invasive species in the world and the vector for several arboviruses including dengue, Zika and chikungunya viruses. Understanding the population spatial genetic structure, migration, and gene flow of vector species is critical to effectively preventing and controlling vector-borne diseases. Little is known about the population structure and genetic differentiation of native Ae. albopictus in China. The aim of this study was to examine the patterns of the spatial genetic structures of native Ae. albopictus populations, and their relationship to dengue incidence, on a large geographical scale. METHODS:During 2016-2018, adult female Ae. albopictus mosquitoes were collected by human landing catch (HLC) or human-bait sweep-net collections in 34 localities across China. Thirteen microsatellite markers were used to examine the patterns of genetic diversity, population structure, and gene flow among native Ae. albopictus populations. The correlation between population genetic indices and dengue incidence was also examined. RESULTS:A total of 153 distinct alleles were identified at the 13 microsatellite loci in the tested populations. All loci were polymorphic, with the number of distinct alleles ranging from eight to sixteen. Genetic parameters such as PIC, heterozygosity, allelic richness and fixation index (FST) revealed highly polymorphic markers, high genetic diversity, and low population genetic differentiation. In addition, Bayesian analysis of population structure showed two distinct genetic groups in southern-western and eastern-central-northern China. The Mantel test indicated a positive correlation between genetic distance and geographical distance (R2Â =Â 0.245, PÂ =Â 0.01). STRUCTURE analysis, PCoA and GLS interpolation analysis indicated that Ae. albopictus populations in China were regionally clustered. Gene flow and relatedness estimates were generally high between populations. We observed no correlation between population genetic indices of microsatellite loci in Ae. albopictus populations and dengue incidence. CONCLUSION:Strong gene flow probably assisted by human activities inhibited population differentiation and promoted genetic diversity among populations of Ae. albopictus. This may represent a potential risk of rapid spread of mosquito-borne diseases. The spatial genetic structure, coupled with the association between genetic indices and dengue incidence, may have important implications for understanding the epidemiology, prevention, and control of vector-borne diseases
Ni/Ni3C Core-Shell Nanochains and Its Magnetic Properties: One-Step Synthesis at low temperature
One-dimensional Ni/Ni3C core-shell nanoball chains with an average diameter
by around 30 nm were synthesized by means of a mild chemical solution method
using a soft template of trioctylphosphineoxide (TOPO). It was revealed that
the uniform Ni nanochains were capped with Ni3C thin shells by about 1 to 4 nm
in thickness and each Ni core consists of polygrains. The coercivity of the
core-shell nanochains is much enhanced (600 Oe at 5 K) and comparable with
single Ni nanowires due to the one-dimensional shape anisotropy. Deriving from
the distinctive structure of Ni core and Ni3C shell, this architecture may
possess a possible bi-functionality. This unique architecture is also useful
for the study on the magnetization reversal mechanism of one-dimensional
magnetic nanostructure.Comment: 17 pages, 6 figur
Suppressing longitudinal double-layer oscillations by using elliptically polarized laser pulses in the hole-boring radiation pressure acceleration regime
It is shown that well collimated mono-energetic ion beams with a large
particle number can be generated in the hole-boring radiation pressure
acceleration regime by using an elliptically polarized laser pulse with
appropriate theoretically determined laser polarization ratio. Due to the
effect, the double-layer charge separation region is
imbued with hot electrons that prevent ion pileup, thus suppressing the
double-layer oscillations. The proposed mechanism is well confirmed by
Particle-in-Cell simulations, and after suppressing the longitudinal
double-layer oscillations, the ion beams driven by the elliptically polarized
lasers own much better energy spectrum than those by circularly polarized
lasers.Comment: 6 pages, 5 figures, Phys. Plasmas (2013) accepte
The Deconfined Phase Transition under the Fuzzy Sphere Microscope: Approximate Conformal Symmetry, Pseudo-Criticality, and Operator Spectrum
The deconfined quantum critical point (DQCP) is an example of phase
transitions beyond the Landau symmetry breaking paradigm that attracts wide
interest. However, its nature has not been settled after decades of study. In
this paper, we apply the recently proposed fuzzy sphere regularization to study
the non-linear sigma model (NLM) with a topological
Wess-Zumino-Witten term, which serves as a dual description of the DQCP with an
exact symmetry. We demonstrate that the fuzzy sphere functions
as a powerful microscope, magnifying and revealing a wealth of crucial
information about the DQCP, ultimately paving the way towards its final answer.
In particular, through exact diagonalization, we provide clear evidence that
the DQCP exhibits approximate conformal symmetry. The evidence includes the
existence of a conserved symmetry current, a stress tensor,
and integer-spaced levels between conformal primaries and their descendants.
Most remarkably, we have identified 19 conformal primaries and their 82
descendants. Furthermore, by examining the renormalization group flow of the
lowest symmetry singlet, we demonstrate that the DQCP is more likely
pseudo-critical, with the approximate conformal symmetry plausibly emerging
from nearby complex fixed points. Our computed primary spectrum also has
important implications, including the conclusion that the DQCP
cannot describe a direct transition from the N\'eel to valence bond solid phase
on the honeycomb lattice.Comment: 17 pages, 6 figures and 6 table
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