859 research outputs found
B Physics on the Lattice: Present and Future
Recent experimental measurements and lattice QCD calculations are now
reaching the precision (and accuracy) needed to over-constrain the CKM
parameters and . In this brief review, I discuss the
current status of lattice QCD calculations needed to connect the experimental
measurements of meson properties to quark flavor-changing parameters.
Special attention is given to , which is becoming a competitive
way to determine , and to mixings, which now include
reliable extrapolation to the physical light quark mass. The combination of the
recent measurement of the mass difference and current lattice
calculations dramatically reduces the uncertainty in . I present an
outlook for reducing dominant lattice QCD uncertainties entering CKM fits, and
I remark on lattice calculations for other decay channels.Comment: Invited brief review for Mod. Phys. Lett. A. 15 pages. v2: typos
corrected, references adde
Smartlocks: Self-Aware Synchronization through Lock Acquisition Scheduling
As multicore processors become increasingly prevalent, system complexity is skyrocketing. The advent of the asymmetric multicore compounds this -- it is no longer practical for an average programmer to balance the system constraints associated with today's multicores and worry about new problems like asymmetric partitioning and thread interference. Adaptive, or self-aware, computing has been proposed as one method to help application and system programmers confront this complexity. These systems take some of the burden off of programmers by monitoring themselves and optimizing or adapting to meet their goals. This paper introduces an open-source self-aware synchronization library for multicores and asymmetric multicores called Smartlocks. Smartlocks is a spin-lock library that adapts its internal implementation during execution using heuristics and machine learning to optimize toward a user-defined goal, which may relate to performance, power, or other problem-specific criteria. Smartlocks builds upon adaptation techniques from prior work like reactive locks, but introduces a novel form of adaptation designed for asymmetric multicores that we term lock acquisition scheduling. Lock acquisition scheduling is optimizing which waiter will get the lock next for the best long-term effect when multiple threads (or processes) are spinning for a lock. Our results demonstrate empirically that lock scheduling is important for asymmetric multicores and that Smartlocks significantly outperform conventional and reactive locks for asymmetries like dynamic variations in processor clock frequencies caused by thermal throttling events
Preventing Falls with Vitamin D
Falls are the number one cause for injury-related morbidity and mortality in West Virginia’s seniors. Multiple independent variables contribute to the risk of a fall: previous falls, alterations in balance and vision, impairments in gait and strength, and medications most highly correlate with the risk for a fall. Vitamin D supplementation is emerging as an easy, safe and well-tolerated fall reduction/prevention strategy due to the beneficial effects on the musculoskeletal system with improvements in strength, function and navigational abilities. From meta-analysis data, maximal fall reduction benefit in seniors is achieved when correcting vitamin D deficiency and when using adjunctive calcium supplementation. It is therefore recommended that practitioners in our state screen for fall risks and consider the addition of supplementation protocols that provide sufficient vitamin D and calcium to our seniors
The Infinite Latent Events Model
We present the Infinite Latent Events Model, a nonparametric hierarchical Bayesian distribution over infinite dimensional Dynamic Bayesian Networks with binary state representations and noisy-OR-like transitions. The distribution can be used to learn structure in discrete timeseries data by simultaneously inferring a set of latent events, which events fired at each timestep, and how those events are causally linked. We illustrate the model on a sound factorization task, a network topology identification task, and a video game task.NTT Communication Science LaboratoriesUnited States. Air Force Office of Scientific Research (AFOSR FA9550-07-1-0075)United States. Office of Naval Research (ONR N00014-07-1-0937)National Science Foundation (U.S.) (Graduate Research Fellowship)United States. Army Research Office (ARO W911NF-08-1-0242)James S. McDonnell Foundation (Causal Learning Collaborative Initiative
The Omega- and the strange quark mass
Omega- correlators have been calculated on the MILC collaboration's archive
of three flavor improved staggered quark lattices. The Omega- is stable under
strong interactions (140 MeV below threshold). It provides a valuable
consistency check on a combination of strange quark mass and lattice scale
determination from other quantities. Alternatively, the Omega- mass could be
used to fix the strange quark mass, which gives a check on computations of the
strange quark mass based on the kaon mass.Comment: Three pages, proceedings of the Lattice-04 symposium. (Corrected
typographical errors
Baryonic sources using irreducible representations of the double-covered octahedral group
Irreducible representations (IRs) of the double-covered octahedral group are
used to construct lattice source and sink operators for three-quark baryons.
The goal is to achieve a good coupling to higher spin states as well as ground
states. Complete sets of local and nonlocal straight-link operators are
explicitly shown for isospin 1/2 and 3/2 baryons. The orthogonality relations
of the IR operators are confirmed in a quenched lattice simulation.Comment: Talk presented at Lattice2004(heavy), Fermilab, June 21-26, 2004, 3
page
Electrical activity of the sensory afferent pathway in the enteric nervous system
In this paper we develop a mathematical model for the electrical activity of the afferent pathway, formed from the coupled primary and secondary sensory neurons. The primary sensory neuron possesses the electrical properties of AH neurons and morphological characteristics of Dogiel type II neurons; the secondary sensory neuron displays the tonic type of electrical behavior and has morphological features of Dogiel type III neurons. Free nerve endings of the mechanoreceptor form the receptive field of the pathway. Based on the general principles of the Hodgkin-Huxley description of excitable cells, the model simulates the following sequence of events: stretch of the receptive field initiates the dendritic potential at the mechanoreceptors; the excitation causes soma action potential development at the primary sensory neuron which is followed by soma action potential generation at the secondary sensory neuron. Numerical calculations have shown that the model is capable of reproducing different electrical patterns within the pathway under normal physiological conditions and after treatment with charybdotoxin, iberiotoxin, tetrodotoxin, ω-conotoxin GVIA, A1-A2 purinoceptor agonists, a protein kinase C activator, and a δ-opioid receptor agonist. Comparison of the computational results with the results of experiments conducted on the neurons of the submucous and myenteric plexi of the small bowel demonstrates their good qualitative and quantitative agreement. © Springer-Verlag 1996
Heavy-Light Decay Constants: Conclusions from the Wilson Action
We report on the results of a MILC collaboration calculation of ,
, , and their ratios. We discuss the most important
errors in more detail than we have elsewhere.Comment: LATTICE98(heavyqk) 3 latex pages and 3 postscript figures. The
perturbative correction calculated by Kuramashi has been adjusted to take
into account the fact that we match to the continuum at the kinetic mass of
the heavy meson, not the pole mass. This produces a 2 to 4 MeV change in
final results for decay constants, and has negligible effect on decay
constant ratio
Implementation of the LANS-alpha turbulence model in a primitive equation ocean model
This paper presents the first numerical implementation and tests of the
Lagrangian-averaged Navier-Stokes-alpha (LANS-alpha) turbulence model in a
primitive equation ocean model. The ocean model in which we work is the Los
Alamos Parallel Ocean Program (POP); we refer to POP and our implementation of
LANS-alpha as POP-alpha. Two versions of POP-alpha are presented: the full
POP-alpha algorithm is derived from the LANS-alpha primitive equations, but
requires a nested iteration that makes it too slow for practical simulations; a
reduced POP-alpha algorithm is proposed, which lacks the nested iteration and
is two to three times faster than the full algorithm. The reduced algorithm
does not follow from a formal derivation of the LANS-alpha model equations.
Despite this, simulations of the reduced algorithm are nearly identical to the
full algorithm, as judged by globally averaged temperature and kinetic energy,
and snapshots of temperature and velocity fields. Both POP-alpha algorithms can
run stably with longer timesteps than standard POP.
Comparison of implementations of full and reduced POP-alpha algorithms are
made within an idealized test problem that captures some aspects of the
Antarctic Circumpolar Current, a problem in which baroclinic instability is
prominent. Both POP-alpha algorithms produce statistics that resemble
higher-resolution simulations of standard POP.
A linear stability analysis shows that both the full and reduced POP-alpha
algorithms benefit from the way the LANS-alpha equations take into account the
effects of the small scales on the large. Both algorithms (1) are stable; (2)
make the Rossby Radius effectively larger; and (3) slow down Rossby and gravity
waves.Comment: Submitted to J. Computational Physics March 21, 200
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