14,141 research outputs found
The Decay Properties of the 1^{-+} Hybrid State
Within the framework of the QCD sum rules, we consider the three-point
correlation function, work at the limit q^2 -> 0 and m_\pi -> 0, and pick out
the singular term ~ {1\over q^2} to extract the pionic coupling constants of
the 1^{-+} hybrid meson. Then we calculate the decay widths of different modes.
The decay width of the S-wave modes b_1 \pi, f_1\pi increases quickly as the
hybrid meson mass and decay momentum increase. But for the low mass hybrid
meson around 1.6 GeV, the P-wave decay mode \rho \pi is very important and its
width is around 180 MeV, while the widths of \eta \pi and \eta^\prime \pi are
strongly suppressed. We suggest the experimental search of \pi_1(1600) through
the decay chains at BESIII: e^+e^- -> J/\psi(\psi') -> \pi_1 +\gamma or e^+e^-
-> J/\psi(\psi') -> \pi_1 +\rho where the \pi_1 state can be reconstructed
through the decay modes \pi_1 -> \rho\pi -> \pi^+\pi^-\pi^0 or \pi_1 ->
f_1(1285)\pi^0. It is also interesting to look for \pi_1 using the available
BELLE/BABAR data through the process e^+e^- -> \gamma^\ast -> \rho\pi_1,
b_1\pi_1, \gamma \pi_1 etc.Comment: one reference correcte
Diffusion of Lexical Change in Social Media
Computer-mediated communication is driving fundamental changes in the nature
of written language. We investigate these changes by statistical analysis of a
dataset comprising 107 million Twitter messages (authored by 2.7 million unique
user accounts). Using a latent vector autoregressive model to aggregate across
thousands of words, we identify high-level patterns in diffusion of linguistic
change over the United States. Our model is robust to unpredictable changes in
Twitter's sampling rate, and provides a probabilistic characterization of the
relationship of macro-scale linguistic influence to a set of demographic and
geographic predictors. The results of this analysis offer support for prior
arguments that focus on geographical proximity and population size. However,
demographic similarity -- especially with regard to race -- plays an even more
central role, as cities with similar racial demographics are far more likely to
share linguistic influence. Rather than moving towards a single unified
"netspeak" dialect, language evolution in computer-mediated communication
reproduces existing fault lines in spoken American English.Comment: preprint of PLOS-ONE paper from November 2014; PLoS ONE 9(11) e11311
Structure-Aware Dynamic Scheduler for Parallel Machine Learning
Training large machine learning (ML) models with many variables or parameters
can take a long time if one employs sequential procedures even with stochastic
updates. A natural solution is to turn to distributed computing on a cluster;
however, naive, unstructured parallelization of ML algorithms does not usually
lead to a proportional speedup and can even result in divergence, because
dependencies between model elements can attenuate the computational gains from
parallelization and compromise correctness of inference. Recent efforts toward
this issue have benefited from exploiting the static, a priori block structures
residing in ML algorithms. In this paper, we take this path further by
exploring the dynamic block structures and workloads therein present during ML
program execution, which offers new opportunities for improving convergence,
correctness, and load balancing in distributed ML. We propose and showcase a
general-purpose scheduler, STRADS, for coordinating distributed updates in ML
algorithms, which harnesses the aforementioned opportunities in a systematic
way. We provide theoretical guarantees for our scheduler, and demonstrate its
efficacy versus static block structures on Lasso and Matrix Factorization
Scale Setting Using the Extended Renormalization Group and the Principle of Maximum Conformality: the QCD Coupling Constant at Four Loops
A key problem in making precise perturbative QCD predictions is to set the
proper renormalization scale of the running coupling. The extended
renormalization group equations, which express the invariance of physical
observables under both the renormalization scale- and scheme-parameter
transformations, provide a convenient way for estimating the scale- and
scheme-dependence of the physical process. In this paper, we present a solution
for the scale-equation of the extended renormalization group equations at the
four-loop level. Using the principle of maximum conformality (PMC) /
Brodsky-Lepage-Mackenzie (BLM) scale-setting method, all non-conformal
terms in the perturbative expansion series can be summed into the
running coupling, and the resulting scale-fixed predictions are independent of
the renormalization scheme. Different schemes lead to different effective
PMC/BLM scales, but the final results are scheme independent. Conversely, from
the requirement of scheme independence, one not only can obtain
scheme-independent commensurate scale relations among different observables,
but also determine the scale displacements among the PMC/BLM scales which are
derived under different schemes. In principle, the PMC/BLM scales can be fixed
order-by-order, and as a useful reference, we present a systematic and
scheme-independent procedure for setting PMC/BLM scales up to NNLO. An explicit
application for determining the scale setting of up to four
loops is presented. By using the world average , we obtain the asymptotic scale for the 't Hooft associated
with the scheme, MeV, and
the asymptotic scale for the conventional scheme,
MeV.Comment: 9 pages, no figures. The formulas in the Appendix are correcte
More Straightforward Extraction of the Fundamental Lepton Mixing Parameters from Long-Baseline Neutrino Oscillations
We point out the simple reversibility between the fundamental neutrino mixing
parameters in vacuum and their effective counterparts in matter. The former can
therefore be expressed in terms of the latter, allowing more straightforward
extraction of the genuine lepton mixing quantities from a variety of
long-baseline neutrino oscillation experiments. In addition to the
parametrization-independent results, we present the formulas based on the
standard parametrization of the lepton flavor mixing matrix and give a typical
numerical illustration.Comment: RevTex 10 pages. Minor changes. Phys. Rev. D in printin
Supercritical fluid coating of API on excipient enhances drug release
A process to coat particles of active pharmaceutical ingredient (API) onto microcrystalline cellulose (MCC) excipient shows promise as a new way to dosage forms showing enhanced drug release. The process consists of a fluidized bed operated at elevated pressure in which API particles are precipitated from a Supercritical Anti-Solvent process (SAS). MCC particles were used as an excipient in the fluidized bed and collect the SAS-generated API particles. Naringin was selected as the model API to coat onto MCC. A number of operational parameters of the process were investigated: fluidization velocity, coating pressure, temperature, concentration of drug solution, drug solution flow rate, drug mass, organic solvent, MCC mass and size and CO2-to-organic solution ratio. SEM and SPM analyses showed that the MCC particle surfaces were covered with near-spherical nanoparticles with a diameter of approximately 100–200 nm, substantially smaller than the as-received API material. XRD showed that naringin changed from crystalline to amorphous during processing. The coated particles resulting from the SAS fluidized bed process have a higher loading of API, gave faster release rates and higher release ratios in comparison with those produced using a conventional fluidized bed coating process. The approach could be transferred to other industries where release is important such as agrochemical, cosmetic and food
Phases and Transitions in Phantom Nematic Elastomer Membranes
Motivated by recently discovered unusual properties of bulk nematic
elastomers, we study a phase diagram of liquid-crystalline polymerized phantom
membranes, focusing on in-plane nematic order. We predict that such membranes
should enerically exhibit five phases, distinguished by their conformational
and in-plane orientational properties, namely isotropic-crumpled,
nematic-crumpled, isotropic-flat, nematic-flat and nematic-tubule phases. In
the nematic-tubule phase, the membrane is extended along the direction of {\em
spontaneous} nematic order and is crumpled in the other. The associated
spontaneous symmetries breaking guarantees that the nematic-tubule is
characterized by a conformational-orientational soft (Goldstone) mode and the
concomitant vanishing of the in-plane shear modulus. We show that long-range
orientational order of the nematic-tubule is maintained even in the presence of
harmonic thermal luctuations. However, it is likely that tubule's elastic
properties are ualitatively modified by these fluctuations, that can be studied
using a nonlinear elastic theory for the nematic tubule phase that we derive at
the end of this paper.Comment: 12 pages, 4 eps figures. To appear in PR
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