12,429 research outputs found
Baryon Axial Charge in a Finite Volume
We compute finite-volume corrections to nucleon matrix elements of the
axial-vector current. We show that knowledge of this finite-volume dependence
--as well as that of the nucleon mass-- obtained using lattice QCD will allow a
clean determination of the chiral-limit values of the nucleon and
Delta-resonance axial-vector couplings.Comment: 11 pages, 8 figure
Two scenarios for avalanche dynamics in inclined granular layers
We report experimental measurements of avalanche behavior of thin granular
layers on an inclined plane for low volume flow rate. The dynamical properties
of avalanches were quantitatively and qualitatively different for smooth glass
beads compared to irregular granular materials such as sand. Two scenarios for
granular avalanches on an incline are identified and a theoretical explanation
for these different scenarios is developed based on a depth-averaged approach
that takes into account the differing rheologies of the granular materials.Comment: 4 pages, 4 figures, accepted to Phys. Rev. Let
Teaching grapheme-phoneme correspondences using a Direct Mapping Approach for at-risk Second Language Learners: A Randomized Controlled Trial
Reading interventions developed to teach grapheme–phoneme correspondences (GPCs) were evaluated among L2 at-risk readers. In the direct mapping of grapheme (DMG) condition, children’s attention was explicitly drawn to the application of a graphemes taught on that day to shared reading of words in authentic text. In the control condition there was no such systematic daily linkage of the GPCs and texts. The two reading interventions were otherwise identical. Two hundred fifty-three Chinese Grade 1 and Grade 2 students were screened, and those who scored in the bottom 30% of an English word-reading test were identified as L2 at-risk readers. Seventy-one L2 at-risk readers were thus randomly assigned to two conditions, both of which were small-group reading interventions: (a) DMG or (b) taught control. We hypothesized a significant main effect of Intervention condition and significant interaction of Intervention by Phonological Awareness (PA) effects on word reading, word attack, spelling, and sentence comprehension favoring the DMG intervention. Results showed that predicted interaction effects were significant for word reading, spelling, and sentence comprehension. No other effects were significant. Results suggest that the daily Direct Mapping of taught GPCs to shared book reading promotes reading development in at-risk English L2 readers with stronger phonological skills
Nucleon-Nucleon Scattering From Fully-Dynamical Lattice QCD
We present results of the first fully-dynamical lattice QCD determination of
nucleon-nucleon scattering lengths in the 1S0 channel and 3S1-3D1 coupled
channels. The calculations are performed with domain-wall valence quarks on the
MILC staggered configurations with lattice spacing of b=0.125 fm in the
isospin-symmetric limit, and in the absence of electromagnetic interactions.Comment: 4 pages, 4 figure
Calibration of the LIGO displacement actuators via laser frequency modulation
We present a frequency modulation technique for calibration of the
displacement actuators of the LIGO 4-km-long interferometric gravitational-wave
detectors. With the interferometer locked in a single-arm configuration, we
modulate the frequency of the laser light, creating an effective length
variation that we calibrate by measuring the amplitude of the frequency
modulation. By simultaneously driving the voice coil actuators that control the
length of the arm cavity, we calibrate the voice coil actuation coefficient
with an estimated 1-sigma uncertainty of less than one percent. This technique
enables a force-free, single-step actuator calibration using a displacement
fiducial that is fundamentally different from those employed in other
calibration methods.Comment: 10 pages, 5 figures, submitted to Classical and Quantum Gravit
Visual search for emotional expressions: Effect of stimulus set on anger and happiness superiority
Prior reports of preferential detection of emotional expressions in visual search have yielded inconsistent results, even for face stimuli that avoid obvious expression-related perceptual confounds. The current study investigated inconsistent reports of anger and happiness superiority effects using face stimuli drawn from the same database. Experiment 1 excluded procedural differences as a potential factor, replicating a happiness superiority effect in a procedure that previously yielded an anger superiority effect. Experiments 2a and 2b confirmed that image colour or poser gender did not account for prior inconsistent findings. Experiments 3a and 3b identified stimulus set as the critical variable, revealing happiness or anger superiority effects for two partially overlapping sets of face stimuli. The current results highlight the critical role of stimulus selection for the observation of happiness or anger superiority effects in visual search even for face stimuli that avoid obvious expression related perceptual confounds and are drawn from a single database
Neurogenic Fever after Acute Traumatic Spinal Cord Injury: A Qualitative Systematic Review.
STUDY DESIGN: Systematic review.
OBJECTIVE: To determine the incidence, pathogenesis, and clinical outcomes related to neurogenic fevers following traumatic spinal cord injury (SCI).
METHODS: A systematic review of the literature was performed on thermodysregulation secondary to acute traumatic SCI in adult patients. A literature search was performed using PubMed (MEDLINE), Cochrane Central Register of Controlled Trials, and Scopus. Using strict inclusion and exclusion criteria, seven relevant articles were obtained.
RESULTS: The incidence of fever of all origins (both known and unknown) after SCI ranged from 22.5 to 71.7% with a mean incidence of 50.6% and a median incidence of 50.0%. The incidence of fever of unknown origin (neurogenic fever) ranged from 2.6 to 27.8% with a mean incidence of 8.0% and a median incidence of 4.7%. Cervical and thoracic spinal injuries were more commonly associated with fever than lumbar injuries. In addition, complete injuries had a higher incidence of fever than incomplete injuries. The pathogenesis of neurogenic fever after acute SCI is not thoroughly understood.
CONCLUSION: Neurogenic fevers are relatively common following an acute SCI; however, there is little in the scientific literature to help physicians prevent or treat this condition. The paucity of research underscored by this review demonstrates the need for further studies with larger sample sizes, focusing on incidence rate, clinical outcomes, and pathogenesis of neurogenic fever following acute traumatic SCI
GHRS and ORFEUS-II Observations of the Highly Ionized Interstellar Medium Toward ESO141-055
We present Goddard High Resolution Spectrograph and ORFEUS-II measurements of
Si IV, CIV, N V, and O VI absorption in the interstellar medium of the Galactic
disk and halo toward the nucleus of the Seyfert galaxy ESO141-055. The high
ionization absorption is strong, with line strengths consistent with the
spectral signature expected for hot (log T = 5-6) collisionally ionized gas in
either a ``Galactic fountain'' or an inhomogeneous medium containing a mixture
of conductive interfaces and turbulent mixing layers. The total O VI column
density of log N ~ 15 suggests that the scale height of O VI is large (>3 kpc)
in this direction. Comparison of the high ion column densities with
measurements for other sight lines indicates that the highly ionized gas
distribution is patchy. The amount of O VI perpendicular to the Galactic plane
varies by at least a factor of ~4 among the complete halo sight lines thus far
studied. In addition to the high ion absorption, lines of low ionization
species are also present in the spectra. With the possible exception of Ar I,
which may have a lower than expected abundance resulting from partial
photoionization of gas along the sight line, the absorption strengths are
typical of those expected for the warm, neutral interstellar medium. The sight
line intercepts a cold molecular cloud with log N(H2) ~ 19. The cloud has an
identifiable counterpart in IRAS 100-micron emission maps of this region of the
sky. We detect a Ly-alpha absorber associated with ESO141-055 at z = 0.03492.
This study presents an enticing glimpse into the interstellar and intergalactic
absorption patterns that will be observed at high spectral resolution by the
Far Ultraviolet Spectroscopic Explorer.Comment: 24 pages + 8 figures, uses aaspp4.sty. Accepted for publication in
Ap
I=2 pi-pi Scattering from Fully-Dynamical Mixed-Action Lattice QCD
We compute the I=2 pi-pi scattering length at pion masses of m_pi ~ 294, 348
and 484 MeV in fully-dynamical lattice QCD using Luscher's finite-volume
method. The calculation is performed with domain-wall valence-quark propagators
on asqtad-improved MILC configurations with staggered sea quarks at a single
lattice spacing, b ~ 0.125 fm. Chiral perturbation theory is used to perform
the extrapolation of the scattering length from lattice quark masses down to
the physical value, and we find m_pi a_2 = -0.0426 +- 0.0006 +- 0.0003 +-
0.0018, in good agreement with experiment. The I=2 pi-pi scattering phase shift
is calculated to be delta = -43 +- 10 +- 5 degrees at |p| ~ 544 MeV for m_pi ~
484 MeV.Comment: 16 pages, 4 figure
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