6,828 research outputs found
Duality and Light Cone Symmetries of the Equations of Motion
The matrix theory description of the discrete light cone quantization of
theory on a is studied. In terms of its super Yang- Mills description,
we identify symmetries of the equations of motion corresponding to independent
rescalings of one of the world sheet light cone coordinates, which show how the
duality of Type IIB string theory is realized as a Nahm-type
transformation. In the theory description this corresponds to a simple
flip.Comment: 13 pages, uses harvmac. An expanded and clarified versio
A preliminary evaluation of a manualised intervention to improve early literacy skills in children with developmental language disorder
Children with Developmental Language Disorder (DLD) commonly present with oral language weaknesses which disrupt the development of literacy and impede related academic progress. While there is evidence to support the delivery of manualised Tier 2 interventions with this population, little is known about the effects of Tier 1 interventions. A retrospective cohort comparison was used to evaluate whether there was an observable effect of a manualised Tier 1 intervention compared to ‘business-as-usual’ on early literacy skills for children with DLD. Participants were 140 children attending a specialised education program with equivalent oral language skills and alphabetic knowledge at baseline. After 18 months formal literacy intervention, both groups were assessed on measures of early literacy skills. The differences between group means on all measures favoured the manualised intervention group, and they performed significantly better on a measure of nonword reading fluency. The findings indicate that a manualised Tier 1 intervention may be advantageous for children with DLD in developing proficiency in phonological recoding. This research contributes to the sparse evidence-base supporting the implementation of Tier 1 interventions for at risk populations, and findings warrant future research using experimental designs with tighter controls
A Search for Cold Dust around Neutron Stars
We present observations of nine radio pulsars using the
Heinrich-Hertz-Telescope at \lambda 0.87mm and the IRAM 30-m telescope at
\lambda 1.2mm in search for a cold dust around these sources. Five of the
program pulsars have been observed for the first time at the mm-wavelengths.
The results are consistent with the absence of circumpulsar disks that would be
massive enough () to support planet formation according to
the scenarios envisioned for solar-type stars, but they do not exclude lower
mass () disks for a wide range of grain sizes. These
conclusions confirm the previously published results and, together with the
current lack of further detections of pulsar planets, they suggest that planet
formation around neutron stars is not a common phenomenon.Comment: 5 pages, 1 figure, accepted for publication in A&
Under which conditions is quantum brownian motion observable in a microscope?
We investigate under which conditions we can expect to observe quantum
brownian motion in a microscope. Using the fluctuation-dissipation theorem, we
investigate quantum brownian motion in an ohmic bath, and estimate temporal and
spatial accuracy required to observe a crossover from classical to quantum
behavior
A possible optical counterpart to the old nearby pulsar J0108-1431
The multi-wavelength study of old (>100 Myr) radio pulsars holds the key to
understanding the long-term evolution of neutron stars, including the advanced
stages of neutron star cooling and the evolution of the magnetosphere.
Optical/UV observations are particularly useful for such studies because they
allow one to explore both thermal and non-thermal emission processes. In
particular, studying the optical/UV emission constrains temperature of the bulk
of the neutron star surface, too cold to be measured in X-ray observations.Aim
of this work is to identify the optical counterpart of the very old (166 Myr)
radio pulsar J0108-1431. We have re-analyzed our original VLT observations
(Mignani et al. 2003), where a very faint object was tentatively detected close
to the radio position, near the edge of a field galaxy. We found that the
backward extrapolation of the PSR J0108-1431 proper motion recently measured by
CHANDRA(Pavlov et al. 2008) nicely fits the position of this object. Based on
that, we propose it as a viable candidate for the optical counterpart to PSR
J0108-1431. The object fluxes (U =26.4+/-0.3; B =27.9; V >27.8) are consistent
with a thermal spectrum with a brightness temperature of 9X10^4 K (for R = 13
km at a distance of 130 pc), emitted from the bulk of the neutron star surface.
New optical observations are required to confirm the optical identification of
PSR J0108-1431 and measure its spectrum.Comment: 5 pages, 4 figures, submitted to A&
Using Immediate Feedback to Improve Short-Term Learning in Extension
Program evaluation is an important part of any extension program and is often a required component by funding agencies. Given declining resources in land-grant universities, we must be creative in evaluating the learning and adoption of our research-based recommendations. I used a survey tool to give immediate feedback to participants in a wide variety of situations. Results indicate adults were receptive to this evaluation method, and close-ended questions can provide reliable evaluation data in an extension program. People showed improved significant learning with this technique and it is a model for other extension personnel
Phase Diagram for Turbulent Transport: Sampling Drift, Eddy Diffusivity and Variational Principles
We study the long-time, large scale transport in a three-parameter family of
isotropic, incompressible velocity fields with power-law spectra. Scaling law
for transport is characterized by the scaling exponent and the Hurst
exponent , as functions of the parameters. The parameter space is divided
into regimes of scaling laws of different {\em functional forms} of the scaling
exponent and the Hurst exponent. We present the full three-dimensional phase
diagram.
The limiting process is one of three kinds: Brownian motion (),
persistent fractional Brownian motions () and regular (or smooth)
motion (H=1).
We discover that a critical wave number divides the infrared cutoffs into
three categories, critical, subcritical and supercritical; they give rise to
different scaling laws and phase diagrams. We introduce the notions of sampling
drift and eddy diffusivity, and formulate variational principles to estimate
the eddy diffusivity. We show that fractional Brownian motions result from a
dominant sampling drift
Airborne Wind Profiling Algorithms for the Pulsed 2-Micron Coherent Doppler Lidar at NASA Langley Research Center
Two versions of airborne wind profiling algorithms for the pulsed 2-micron coherent Doppler lidar system at NASA Langley Research Center in Virginia are presented. Each algorithm utilizes different number of line-of-sight (LOS) lidar returns while compensating the adverse effects of different coordinate systems between the aircraft and the Earth. One of the two algorithms APOLO (Airborne Wind Profiling Algorithm for Doppler Wind Lidar) estimates wind products using two LOSs. The other algorithm utilizes five LOSs. The airborne lidar data were acquired during the NASA's Genesis and Rapid Intensification Processes (GRIP) campaign in 2010. The wind profile products from the two algorithms are compared with the dropsonde data to validate their results
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