3,304 research outputs found

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### Resonances in coupled πk,ηK scattering from lattice QCD

Coupled-channel $\pi K$ and $\eta K$ scattering amplitudes are determined by
studying the finite-volume energy spectra obtained from dynamical lattice QCD
calculations. Using a large basis of interpolating operators, including both
those resembling a $q\bar{q}$ construction and those resembling a pair of
mesons with relative momentum, a reliable excited-state spectrum can be
obtained. Working at ${m_\pi=391\,\mathrm{MeV}}$, we find a gradual increase in
the $J^P=0^+$ $\pi K$ phase-shift which may be identified with a broad scalar
resonance that couples strongly to $\pi K$ and weakly to $\eta K$. The
low-energy behavior of this amplitude suggests a virtual bound-state that may
be related to the $\kappa$ resonance. A bound state with $J^P=1^-$ is found
very close to the $\pi K$ threshold energy, whose coupling to the $\pi K$
channel is compatible with that of the experimental $K^\star(892)$. Evidence is
found for a narrow resonance in $J^P=2^+$. Isospin--3/2 $\pi K$ scattering is
also studied and non-resonant phase-shifts spanning the whole elastic
scattering region are obtained.We thank our colleagues within the Hadron Spectrum
Collaboration. We also thank R. Briceno, M.R. Pennington,
C.J.Shultz and A.P. Szczepaniak for fruitful discussions.
Chroma [63] and QUDA [64, 65] were used to perform
this work on clusters at Jefferson Laboratory under the
USQCD Initiative and the LQCD ARRA project. Gauge
configurations were generated using resources awarded
from the U.S. Department of Energy INCITE program
at Oak Ridge National Lab, the NSF Teragrid at the
Texas Advanced Computer Center and the Pittsburgh
Supercomputer Center, as well as at Jefferson Lab. RGE
and JJD acknowledge support from U.S. Department of
Energy contract DE-AC05-06OR23177, under which Jefferson
Science Associates, LLC, manages and operates
Jefferson Laboratory. JJD acknowledges support from
the U.S. Department of Energy Early Career award contract
DE-SC0006765. CET acknowledges partial support
from the Science and Technology Facilities Council
(U.K.) [grant number ST/L000385/1].This is the accepted manuscript. The final version is available at http://journals.aps.org/prd/abstract/10.1103/PhysRevD.91.054008

### Contrasting impacts of land use change on phylogenetic and functional diversity of tropical forest birds

1. Biodiversity conservation strategies increasingly target maintaining evolutionary history and the resilience of ecosystem function, not just species richness (SR). This has led to the emergence of two metrics commonly proposed as tools for decision making: phylogenetic diversity (PD) and functional diversity (FD). Yet the extent to which they are interchangeable remains poorly understood. 2. We explore shifts in and relationships between FD and PD of bird communities across a disturbance gradient in Borneo, from old-growth tropical forest to oil palm plantation. 3. We show a marked decline in PD, and an increase in phylogenetic mean nearest taxon distance (MNTD) from forest to oil palm, in line with declining SR across the gradient. However, phylogenetic mean pairwise distance (MPD) is constrained by forest logging more than by conversion to oil palm, taking account of SR. 4. The decline in FD across the gradient is less severe than in PD, with all metrics indicating relatively high trait diversity in oil palm despite low SR, although functional redundancy is much reduced. Accounting for SR, levels of functional over- or under-dispersion of bird communities are strongly coupled to habitat disturbance level rather than to any equivalent phylogenetic metric. 5. Policy Implications. We suggest that while phylogenetic diversity (PD) is an improvement on species richness as a proxy for functional diversity (FD), conservation decisions based on PD alone cannot reliably safeguard maximal FD. Thus, PD and FD are related but still complementary. Priority setting exercises should use these metrics in combination to identify conservation targets

### Extrapolating Monte Carlo Simulations to Infinite Volume: Finite-Size Scaling at ξ/L ≫1

We present a simple and powerful method for extrapolating finite-volume Monte Carlo data to infinite volume, based on finite-size-scaling theory. We discuss carefully its systematic and statistical errors, and we illustrate it using three examples: the two-dimensional three-state Potts antiferromagnet on the square lattice, and the two-dimensional $O(3)$ and $O(\infty)$ $\sigma$-models. In favorable cases it is possible to obtain reliable extrapolations (errors of a few percent) even when the correlation length is 1000 times larger than the lattice

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### B1 resonance in coupled πω, πφ scattering from lattice QCD

We present the first lattice QCD calculation of coupled $\pi\omega$ and
$\pi\phi$ scattering, incorporating coupled $S$ and $D$-wave $\pi\omega$ in
$J^P=1^+$. Finite-volume spectra in three volumes are determined via a
variational analysis of matrices of two-point correlation functions, computed
using large bases of operators resembling single-meson, two-meson and
three-meson structures, with the light-quark mass corresponding to a pion mass
of $m_\pi \approx 391$ MeV. Utilizing the relationship between the discrete
spectrum of finite-volume energies and infinite-volume scattering amplitudes,
we find a narrow axial-vector resonance ($J^{PC}=1^{+-}$), the analogue of the
$b_1$ meson, with mass $m_{R}\approx1380$ MeV and width $\Gamma_{R}\approx 91$
MeV. The resonance is found to couple dominantly to $S$-wave $\pi\omega$, with
a much-suppressed coupling to $D$-wave $\pi\omega$, and a negligible coupling
to $\pi\phi$ consistent with the `OZI rule'. No resonant behavior is observed
in $\pi\phi$, indicating the absence of a putative low-mass $Z_s$ analogue of
the $Z_c$ claimed in $\pi J/\psi$. In order to minimally present the contents
of a unitary three-channel scattering matrix, we introduce an $n$-channel
generalization of the traditional two-channel Stapp parameterization

### Decays of an exotic 1-+ hybrid meson resonance in QCD

We present the first determination of the hadronic decays of the lightest
exotic $J^{PC}=1^{-+}$ resonance in lattice QCD. Working with SU(3) flavor
symmetry, where the up, down and strange quark masses approximately match the
physical strange-quark mass giving $m_\pi \sim 700$ MeV, we compute
finite-volume spectra on six lattice volumes which constrain a scattering
system featuring eight coupled channels. Analytically continuing the scattering
amplitudes into the complex energy plane, we find a pole singularity
corresponding to a narrow resonance which shows relatively weak coupling to the
open pseudoscalar--pseudoscalar, vector--pseudoscalar and vector--vector decay
channels, but large couplings to at least one kinematically-closed
axial-vector--pseudoscalar channel. Attempting a simple extrapolation of the
couplings to physical light-quark mass suggests a broad $\pi_1$ resonance
decaying dominantly through the $b_1 \pi$ mode with much smaller decays into
$f_1 \pi$, $\rho \pi$, $\eta' \pi$ and $\eta \pi$. A large total width is
potentially in agreement with the experimental $\pi_1(1564)$ candidate state,
observed in $\eta \pi$, $\eta' \pi$, which we suggest may be heavily suppressed
decay channels

### Mechanism-based model characterizing bidirectional interaction between PEGylated liposomal CKD-602 (S-CKD602) and monocytes in cancer patients

S-CKD602 is a PEGylated liposomal formulation of CKD-602, a potent topoisomerase I inhibitor. The objective of this study was to characterize the bidirectional pharmacokinetic-pharmacodynamic (PK-PD) interaction between S-CKD602 and monocytes. Plasma concentrations of encapsulated CKD-602 and monocytes counts from 45 patients with solid tumors were collected following intravenous administration of S-CKD602 in the phase I study. The PK-PD models were developed and fit simultaneously to the PK-PD data, using NONMEM®. The monocytopenia after administration of S-CKD602 was described by direct toxicity to monocytes in a mechanism-based model, and by direct toxicity to progenitor cells in bone marrow in a myelosuppression-based model. The nonlinear PK disposition of S-CKD602 was described by linear degradation and irreversible binding to monocytes in the mechanism-based model, and Michaelis-Menten kinetics in the myelosuppression-based model. The mechanism-based PK-PD model characterized the nonlinear PK disposition, and the bidirectional PK-PD interaction between S-CKD602 and monocytes. © 2012 Cárdenas et al, publisher and licensee Dove Medical Press Ltd

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### An a0 resonance in strongly coupled πη, K K scattering from lattice QCD a0 RESONANCE in STRONGLY COUPLED ⋯ DUDEK, EDWARDS, and WILSON

We present the first calculation of coupled-channel meson-meson scattering in
the isospin $=1$, $G$-parity negative sector, with channels $\pi \eta$,
$K\overline{K}$ and $\pi \eta'$, in a first-principles approach to QCD. From
the discrete spectrum of eigenstates in three volumes extracted from lattice
QCD correlation functions we determine the energy dependence of the $S$-matrix,
and find that the $S$-wave features a prominent cusp-like structure in $\pi
\eta \to \pi \eta$ close to $K\overline{K}$ threshold coupled with a rapid turn
on of amplitudes leading to the $K\overline{K}$ final-state. This behavior is
traced to an $a_0(980)$-like resonance, strongly coupled to both $\pi \eta$ and
$K\overline{K}$, which is identified with a pole in the complex energy plane,
appearing on only a single unphysical Riemann sheet. Consideration of $D$-wave
scattering suggests a narrow tensor resonance at higher energy.This is the author accepted manuscript. The final version is available from the American Physical Society via http://dx.doi.org/10.1103/PhysRevD.93.09450

### Improved pregnancy rate with administration of hCG after intrauterine insemination: a pilot study

<p>Abstract</p> <p>Background</p> <p>In natural cycles, women conceive when intercourse takes place during a six-day period ending on the day of ovulation. The current practice in intrauterine insemination (IUI) cycles is to perform the IUI 24-36 hours after the hCG administration, when the ovulation is already imminent. In this study hCG was administered after the IUI, which more closely resembles the fertilisation process in natural cycles.</p> <p>Methods</p> <p>All the IUIs performed since the beginning of 2007 were analysed retrospectively. Our standard protocol has been to perform the IUI 24-32 hours after hCG administration. From the end of 2008, we started to inject hCG after the IUI at random. The main outcome measure was the result of a urinary pregnancy test. Generalized Estimating Equations (GEE) was used to identify independent factors affecting the cycle outcome.</p> <p>Results</p> <p>The analysis included 228 cycles with hCG administered before and 104 cycles hCG administered after the IUI. The pregnancy rates were 10.9% and 19.6% (P = 0.040), respectively. Independent factors (OR, 95% CI) affecting the cycle outcome were sperm count (2.65, 1.20-5.81), number of follicles > 16 mm at IUI (2.01, 1.07-3.81) and the time of hCG administration (2.21, 1.16-4.19).</p> <p>Conclusion</p> <p>Improved pregnancy rate was observed with administration of hCG after IUI.</p

### Glimpsing Colour in a World of Black and White

The past 40 years have taught us that nucleons are built of constituents that
carry colour charges with interactions governed by Quantum Chromodynamics
(QCD). How experiments (past, present and future) at Jefferson Lab probe
colourless nuclei to map out these internal colour degrees of freedom is
presented. When combined with theoretical calculations, these will paint a
picture of how the confinement of quarks and gluons, and the structure of the
QCD vacuum, determine the properties of all (light) strongly interacting
states.Comment: 8 pages, 9 figures. Invited talk at the Rutherford Centennial
Conference on Nuclear Physics, University of Manchester, 8-12 August 2011. To
appear in the Proceeding

### Power-law rheology in the bulk and at the interface: quasi-properties and fractional constitutive equations

Consumer products, such as foods, contain numerous polymeric and particulate additives that play critical roles in maintaining their stability, quality and function. The resulting materials exhibit complex bulk and interfacial rheological responses, and often display a distinctive power-law response under standard rheometric deformations. These power laws are not conveniently described using conventional rheological models, without the introduction of a large number of relaxation modes. We present a constitutive framework using fractional derivatives to model the power-law responses often observed experimentally. We first revisit the concept of quasi-properties and their connection to the fractional Maxwell model (FMM). Using Scott-Blair's original data, we demonstrate the ability of the FMM to capture the power-law response of ‘highly anomalous’ materials. We extend the FMM to describe the viscoelastic interfaces formed by bovine serum albumin and solutions of a common food stabilizer, Acacia gum. Fractional calculus allows us to model and compactly describe the measured frequency response of these interfaces in terms of their quasi-properties. Finally, we demonstrate the predictive ability of the FMM to quantitatively capture the behaviour of complex viscoelastic interfaces by combining the measured quasi-properties with the equation of motion for a complex fluid interface to describe the damped inertio-elastic oscillations that are observed experimentally.United States. National Aeronautics and Space Administration (Microgravity Fluid Sciences (Code UG) for support of this research under grant no. NNX09AV99G

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