11,844 research outputs found
Quasiquarks in two stream system
We study the collective quark excitations in an extremely anisotropic system
of two interpenetrating streams of the quark-gluon plasma. In contrast to the
gluon modes, all quark ones appear to be stable in such a system. Even more,
the quark modes in the two-stream system are very similar to those in the
isotropic plasma.Comment: 4 pages, 2 figures, minor corrections, to appear in Phys. Rev.
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Influence of convection and biomass burning outflow on tropospheric chemistry over the tropical Pacific
Observations over the tropics from the Pacific Exploratory Mission-Tropics A Experiment are analyzed using a one-dimensional model with an explicit formulation for convective transport. Adopting tropical convective mass fluxes from a general circulation model (GCM) yields a large discrepancy between observed and simulated CH3I concentrations. Observations of CH3I imply the convective mass outflux to be more evenly distributed with altitude over the tropical ocean than suggested by the GCM. We find that using a uniform convective turnover lifetime of 20 days in the upper and middle troposphere enables the model to reproduce CH3I observations. The model reproduces observed concentrations of H2O2 and CH3OOH. Convective transport of CH3OOH from the lower troposphere is estimated to account for 40-80% of CH3OOH concentrations in the upper troposphere. Photolysis of CH3OOH transported by convection more than doubles the primary HOx source and increases OH concentrations and O3 production by 10-50% and 0.4 ppbv d-1, respectively, above 11 km. Its effect on the OH concentration and O3 production integrated over the tropospheric column is, however, small. The effects of pollutant import from biomass burning regions are much more dominant. Using C2H2 as a tracer, we estimate that biomass burning outflow enhances O3 concentrations, O3 production, and concentrations of NOx and OH by 60%, 45%, 75%, and 7%, respectively. The model overestimates HNO3 concentrations by about a factor of 2 above 4 km for the upper one-third quantile of C2H2 data while it generally reproduces HNO3 concentrations for the lower and middle one-third quantiles of C2H2 data. Copyright 2000 by the American Geophysical Union
Optimization Coaching for JavaScript
The performance of dynamic object-oriented programming languages such as JavaScript depends heavily on highly optimizing just-in-time compilers. Such compilers, like all compilers, can silently fall back to generating conservative, low-performance code during optimization. As a result, programmers may inadvertently cause performance issues on users\u27 systems by making seemingly inoffensive changes to programs. This paper shows how to solve the problem of silent optimization failures. It specifically explains how to create a so-called optimization coach for an object-oriented just-in-time-compiled programming language. The development and evaluation build on the SpiderMonkey JavaScript engine, but the results should generalize to a variety of similar platforms
Algorithms for detecting dependencies and rigid subsystems for CAD
Geometric constraint systems underly popular Computer Aided Design soft-
ware. Automated approaches for detecting dependencies in a design are critical
for developing robust solvers and providing informative user feedback, and we
provide algorithms for two types of dependencies. First, we give a pebble game
algorithm for detecting generic dependencies. Then, we focus on identifying the
"special positions" of a design in which generically independent constraints
become dependent. We present combinatorial algorithms for identifying subgraphs
associated to factors of a particular polynomial, whose vanishing indicates a
special position and resulting dependency. Further factoring in the Grassmann-
Cayley algebra may allow a geometric interpretation giving conditions (e.g.,
"these two lines being parallel cause a dependency") determining the special
position.Comment: 37 pages, 14 figures (v2 is an expanded version of an AGD'14 abstract
based on v1
Optimization Coaching for JavaScript (Artifact)
This artifact is based on our prototype optimization coach for the SpiderMonkey (https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey) JavaScript engine. An optimization coach is a performance tool that aims to provide programmers with insight into how their compiler optimizes their programs and to help them better harness the optimization process. It does so by reporting optimization near misses, i.e., reports of optimizations that the compiler did not apply, but could apply if the program were to be modified slightly.
This artifact provides the necessary environment, programs and data to repeat our experiments, and to allow readers to run our tool on JavaScript programs of their choic
Neurochemical characterization of pERK-expressing spinal neurons in histamine-induced itch
Date of Acceptance: 08/07/2015 Acknowledgements This work was supported by grants from the Ministry of Science and Technology of China (2012CB966904, 2011CB51005), National Natural Science Foundation of China (31271182, 81200692, 91232724, 81200933, 81101026), Shanghai Natural Science Foundation (12ZR1434300), Key Specialty Construction Project of Pudong Health Bureau of Shanghai (PWZz2013-17), Shenzhen Key Laboratory for Molecular Biology of Neural Development (ZDSY20120617112838879), Fundamental Research Funds for the Central Universities (1500219072) and Sino-UK Higher Education Research Partnership for PhD Studies.Peer reviewedPublisher PD
Controlled generation and steering of spatial gap solitons
We demonstrate the first fully controlled generation of immobile and slow
spatial gap solitons in nonlinear periodic systems with band-gap spectra, and
reveal the key features of gap solitons which distinguish them from
conventional counterparts, including a dynamical transformation of gap solitons
due to nonlinear inter-band coupling. We also predict theoretically and confirm
experimentally the effect of anomalous steering of gap solitons in
optically-induced photonic lattices.Comment: 4 pages, 5 figure
Discussion: behaviour of jacked and driven piles in sandy soil
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