Higher twists in the pion structure function

We calculate the QCD moments of the pion structure function using Drell-Yan data on the quark distributions in the pion and a phenomenological model for the resonance region. The extracted higher twist corrections are found to be larger than those for the nucleon, contributing around 50% of the lowest moment at Q^2=1 GeV^2.Comment: 8 pages, 3 figures, to appear in Phys. Rev.

Two-subband electron transport in nonideal quantum wells

Electron transport in nonideal quantum wells (QW) with large-scale variations of energy levels is studied when two subbands are occupied. Although the mean fluctuations of these two levels are screened by the in-plane redistribution of electrons, the energies of both levels remain nonuniform over the plane. The effect of random inhomogeneities on the classical transport is studied within the framework of a local response approach for weak disorder. Both short-range and small-angle scattering mechanisms are considered. Magnetotransport characteristics and the modulation of the effective conductivity by transverse voltage are evaluated for different kinds of confinement potentials (hard wall QW, parabolic QW, and stepped QW).Comment: 10 pages, 6 figure

Constraints on the pMSSM from LAT Observations of Dwarf Spheroidal Galaxies

We examine the ability for the Large Area Telescope (LAT) to constrain Minimal Supersymmetric Standard Model (MSSM) dark matter through a combined analysis of Milky Way dwarf spheroidal galaxies. We examine the Lightest Supersymmetric Particles (LSPs) for a set of ~71k experimentally valid supersymmetric models derived from the phenomenological-MSSM (pMSSM). We find that none of these models can be excluded at 95% confidence by the current analysis; nevertheless, many lie within the predicted reach of future LAT analyses. With two years of data, we find that the LAT is currently most sensitive to light LSPs (m_LSP < 50 GeV) annihilating into tau-pairs and heavier LSPs annihilating into b-bbar. Additionally, we find that future LAT analyses will be able to probe some LSPs that form a sub-dominant component of dark matter. We directly compare the LAT results to direct detection experiments and show the complementarity of these search methods.Comment: 24 pages, 9 figures, submitted to JCA

Diffusive Charge Transport in Graphene on SiO2

We review our recent work on the physical mechanisms limiting the mobility of graphene on SiO2. We have used intentional addition of charged scattering impurities and systematic variation of the dielectric environment to differentiate the effects of charged impurities and short-range scatterers. The results show that charged impurities indeed lead to a conductivity linear in density in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates [1]; increased dielectric screening reduces scattering from charged impurities, but increases scattering from short-range scatterers [2]. We evaluate the effects of the corrugations (ripples) of graphene on SiO2 on transport by measuring the height-height correlation function. The results show that the corrugations cannot mimic long-range (charged impurity) scattering effects, and have too small an amplitude-to-wavelength ratio to significantly affect the observed mobility via short-range scattering [3, 4]. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a resistivity linear in temperature and independent of carrier density [5]; at higher temperatures, polar optical phonons of the SiO2 substrate give rise to an activated, carrier density-dependent resistivity [5]. Together the results paint a complete picture of charge carrier transport in graphene on SiO2 in the diffusive regime.Comment: 28 pages, 7 figures, submitted to Graphene Week proceeding

Localizing Defects in Multithreaded Programs by Mining Dynamic Call Graphs

Writing multithreaded software for multicore computers confronts many developers with the difficulty of finding parallel programming errors. In the past, most parallel debugging techniques have concentrated on finding race conditions due to wrong usage of synchronization constructs. A widely unexplored issue, however, is that a wrong usage of non-parallel programming constructs may also cause wrong parallel application behavior. This paper presents a novel defect-localization technique for multithreaded shared-memory programs that is based on analyzing execution anomalies. Compared to race detectors that report just on wrong synchronization, this method can detect a wider range of defects affecting parallel execution. It works on a condensed representation of the call graphs of multithreaded applications and employs data-mining techniques to locate a method containing a defect. Our results from controlled application experiments show that we found race conditions, but also other programming errors leading to incorrect parallel program behavior. On average, our approach reduced in our benchmark the amount of code to be inspected to just 7.1% of all methods

Ancillary Therapy and Supportive Care of Chronic Graft-versus-Host Disease: National Institutes of Health Consensus Development Project on Criteria for Clinical Trials in Chronic Graft-versus-Host Disease: V. Ancillary Therapy and Supportive Care Working Group Report

AbstractThe Ancillary Therapy and Supportive Care Working Group had 3 goals: (1) to establish guidelines for ancillary therapy and supportive care in chronic graft-versus-host disease (GVHD), including treatment for symptoms and recommendations for patient education, preventive measures, and appropriate follow-up; (2) to provide guidelines for the prevention and management of infections and other common complications of treatment for chronic GVHD; and (3) to highlight the areas with the greatest need for clinical research. The definition of “ancillary therapy and supportive care” embraces the most frequent immunosuppressive or anti-inflammatory interventions used with topical intent and any other interventions directed at organ-specific control of symptoms or complications resulting from GVHD and its therapy. Also included in the definition are educational, preventive, and psychosocial interventions with this same objective. Recommendations are organized according to the strength and quality of evidence supporting them and cover the most commonly involved organs, including the skin, mouth, female genital tract, eyes, gastrointestinal tract, and lungs. Recommendations are provided for prevention of infections, osteoporosis, and steroid myopathy and management of neurocognitive and psychosocial adverse effects related to chronic GVHD. Optimal care of patients with chronic GVHD often requires a multidisciplinary approach

Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events

The $B^0$-$\bar B^0$ oscillation frequency has been measured with a sample of 23 million \B\bar B pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives $\Delta m_d = 0.493 \pm 0.012{(stat)}\pm 0.009{(syst)}$ ps$^{-1}$.Comment: 7 pages, 1 figure, submitted to Physical Review Letter

Limb Spicules from the Ground and from Space

We amassed statistics for quiet-sun chromosphere spicules at the limb using ground-based observations from the Swedish 1-m Solar Telescope on La Palma and simultaneously from NASA's Transition Region and Coronal Explorer (TRACE) spacecraft. The observations were obtained in July 2006. With the 0.2 arcsecond resolution obtained after maximizing the ground-based resolution with the Multi-Object Multi-Frame Blind Deconvolution (MOMFBD) program, we obtained specific statistics for sizes and motions of over two dozen individual spicules, based on movies compiled at 50-second cadence for the series of five wavelengths observed in a very narrow band at H-alpha, on-band and in the red and blue wings at 0.035 nm and 0.070 nm (10 s at each wavelength) using the SOUP filter, and had simultaneous observations in the 160 nm EUV continuum from TRACE. The MOMFBD restoration also automatically aligned the images, facilitating the making of Dopplergrams at each off-band pair. We studied 40 H-alpha spicules, and 14 EUV spicules that overlapped H-alpha spicules; we found that their dynamical and morphological properties fit into the framework of several previous studies. From a preliminary comparison with spicule theories, our observations are consistent with a reconnection mechanism for spicule generation, and with UV spicules being a sheath region surrounding the H-alpha spicules

Forest Biodiversity Assessment in Peruvian Andean Montane Cloud Forest

Cloud forests are unusual and fragile habitats, being one of the least studied and least understood ecosystems. The tropical Andean dominion is considered one of the most significant places in the world as rega rds biological diversity, with a very high level of endemism. The biodiversity was analysed in an isolated remnant area of a tropical montane cloud forest known as the ?Bosque de Neblina de Cuyas?, in the North of the Peruvian Andean range. Composition, structure and dead wood were measured or estimated. The values obtained were compared with other cloud forests. The study revealed a high level of forest biodiversity, although the level of biodiversity differs from one area to another: in the inner areas, where human pressure is almost inexistent, the biodiversity values increase. The high species richness and the low dominance among species bear testimony to this montane cloud forest as a real enclave of biodiversity