4,024 research outputs found
Improving Rural Educational Attainment
More often than not, policymakers focus on school-based strategies to spur improvements in the educational progress of students. The 2002 No Child Left Behind Act, which demands greater school accountability for student performance, is a case in point. Yet, what happens in the classroom is only part of the story.In fact, as Lionel J. Beaulieu, Glenn D. Israel and Ronald C. Wimberley show in their chapter in "Challenges for Rural America in the Twenty-First Century", family characteristics have from 5 to 10 times as much impact as school characteristics on reading and math scores of rural U.S. eighth graders.In addition, community characteristics have as much impact as school characteristics on test scores, although both community and chool characteristics tend to be more important in geographically isolated rural areas than those adjacent to metropolitan areas. Clearly, helping rural youth succeed academically is the collective responsibility of families, schools, and communities.This issue brief is a joint product of the Rural Sociological Society and the National Coalition for Rural Entrepreneurship, a collaboration of four Regional Rural Development Centers: The Northeast Regional Center for Rural Development, the Southern Rural Development Center, the North Central Regional Center for Rural Development, and the Western Rural Development Center. Funding was also made available from the Ford Foundation.This brief is part of a policy brief series by the Rural Sociological Society and the Regional Rural Development Centers that stresses the importance of community collective action and developing the capacity of people and organizations to meet the community's needsThe Rural Sociological Society and the Regional Rural Development Centers creates new Public Policy Issue Brief series based on its recent book, "Challenges for Rural America in the Twenty-First Century".The briefs synthesize the context and substance of important issues raised in the book and address alternative policy options, with the goal of bringing important research to the policy community
High-contrast imaging at small separation: impact of the optical configuration of two deformable mirrors on dark holes
The direct detection and characterization of exoplanets will be a major
scientific driver over the next decade, involving the development of very large
telescopes and requires high-contrast imaging close to the optical axis. Some
complex techniques have been developed to improve the performance at small
separations (coronagraphy, wavefront shaping, etc). In this paper, we study
some of the fundamental limitations of high contrast at the instrument design
level, for cases that use a combination of a coronagraph and two deformable
mirrors for wavefront shaping. In particular, we focus on small-separation
point-source imaging (around 1 /D). First, we analytically or
semi-analytically analysing the impact of several instrument design parameters:
actuator number, deformable mirror locations and optic aberrations (level and
frequency distribution). Second, we develop in-depth Monte Carlo simulation to
compare the performance of dark hole correction using a generic test-bed model
to test the Fresnel propagation of multiple randomly generated optics static
phase errors. We demonstrate that imaging at small separations requires large
setup and small dark hole size. The performance is sensitive to the optic
aberration amount and spatial frequencies distribution but shows a weak
dependence on actuator number or setup architecture when the dark hole is
sufficiently small (from 1 to 5 /D).Comment: 13 pages, 18 figure
The first radial velocity measurements of a microlensing event: no evidence for the predicted binary
The gravitational microlensing technique allows the discovery of exoplanets
around stars distributed in the disk of the galaxy towards the bulge. However,
the alignment of two stars that led to the discovery is unique over the
timescale of a human life and cannot be re-observed. Moreover, the target host
is often very faint and located in a crowded region. These difficulties hamper
and often make impossible the follow-up of the target and study of its possible
companions. Gould et al. (2013) predicted the radial-velocity curve of a binary
system, OGLE-2011-BLG-0417, discovered and characterised from a microlensing
event by Shin et al. (2012). We used the UVES spectrograph mounted at the VLT,
ESO to derive precise radial-velocity measurements of OGLE-2011-BLG-0417. To
gather high-precision on faint targets of microlensing events, we proposed to
use the source star as a reference to measure the lens radial velocities. We
obtained ten radial velocities on the putative V=18 lens with a dispersion of
~100 m/s, spread over one year. Our measurements do not confirm the
microlensing prediction for this binary system. The most likely scenario is
that the assumed V=18 mag lens is actually a blend and not the primary lens
that is 2 magnitude fainter. Further observations and analyses are needed to
understand the microlensing observation and infer on the nature and
characteristics of the lens itself.Comment: submitted on 3rd June 2015 to A&ALette
A Novel Weighted-Counter Method for Simulating Coherent TWDP Fading Channels
New channel simulation models are needed for the study of future wireless networks, 5G and beyond. A novel simulation technique dubbed weighted-counting is proposed. It is used to generate random variates having the two-wave with diffuse power (TWDP) fading amplitude distribution. The TWDP channel model describes high-speed train, femtocell, sea surface, heterogeneous and other channels having two different dominant line-of-sight waves as well as scatter power components
Optimal Diversity Combining Based on Noisy Channel Estimation
The performances of coherent diversity receivers with noisy channel estimation are examined. Fading channel gain estimates are modeled as sums of the true fading channel gain values plus independent Gaussian distributed estimation errors. The optimal diversity receiver for coherent reception with noisy channel state information and independent and identically distributed fading channels is derived. Exact expressions for the average error probability of optimal diversity MPSK with noisy channel estimation are derived for Rayleigh and Ricean fading channels; closed-form expressions are obtained for some special cases. Some interesting observations regarding practical diversity receiver design for higher-order modulation formats are drawn
Comparaison de techniques d’identification des Erwinia et des Pseudomonas responsables de la pourriture molle
Trois méthodes, soit la caractérisation physiologique, l'utilisation de systèmes miniaturisés d'identification (API 20E, API NFT et Biolog) et l'analyse du profil électrophorétique des protéines sécrétées, ont été expérimentées afin de déterminer une technique précise et rapide d'identification des Pseudomonas et des Erwinia responsables de la pourriture molle. L'analyse des patrons électrophorétiques des protéines sécrétées est une méthode très efficace pour identifier les différentes espèces pectinolytiques de Pseudomonas fluorescents. Le système Biolog reconnaît efficacement le P. marginalis et le P. viridiflava. Le système API NFT est efficace pour l'identification du P. marginalis, du P. viridiflava et du P. syringae. C'est le système API 20E qui s'est avéré le plus efficace pour l'identification des Erwinia. L'électrophorèse des protéines sécrétées et le système API NFT permettent une identification rapide et efficace des Pseudomonas, tandis que pour les Erwinia, seul le système API20E est performant.Three methods, namely physiological characterization, the use of miniaturized identification Systems (API 20E, API NFT, and Biolog) and the analysis of the electrophoretic profile of proteins secreted by the bacteria, were used in order to determine a precise and quick identification technique for the Pseudomonas and Erwinia species causing soft rots in several plant species. The analysis of the electrophoretic profile of the proteins secreted is a very efficient method of identification for the various pectinolytic species of fluorescent Pseudomonas. The Biolog System accurately recognizes P. marginalisand P. viridiflava. The API NFT System is efficient for the identification of P. marginalis, P. viridiflava and P. syringae. The API 20E System was found to be the most reliable System for identifying Erwinia species. The electrophoresis of proteins secreted and the API NFT system allow a quick and efficient identification of Pseudomonas species, while for Erwinia species, only the API 20E System is efficient
- …