16,024 research outputs found
The Effect of School District Consolidation on Student Achievement: Evidence from Arkansas
School district consolidation is one of the most widespread education reforms of the last century, but surprisingly little research has directly investigated its effectiveness. To examine the impact of consolidation on student achievement, this study takes advantage of a policy that requires the consolidation of all Arkansas school districts with enrollment of fewer than 350 students for two consecutive school years. Using a regression discontinuity model, we find that consolidation has either null or small positive impacts on student achievement in math and English Language Arts (ELA). We do not find evidence that consolidation in Arkansas results in positive economies of scale, either by reducing overall cost or allowing for a greater share of resources to be spent in the classroom
Wireless Power Transfer for Gas Pipe Inspection Robots
Wireless power transfer in metal pipes is a promising alternative to tethered exploration robots, with strong potential to enable longer operating times. Here we present experimental results, including rectification efficiency, for a prototype gas pipe inspection robot with wireless power receiver functionality
Effect of Solvent Extraction Parameters on the Recovery of Oil From Spent Coffee Grounds for Biofuel Production
Spent coffee grounds (SCG) are a potentially valuable source of lipids for sustainable production of biofuels. However, there are several feedstock properties and solvent extraction parameters that can impact on the oil yield and quality, potentially reducing the possible environmental benefits of deriving oils from this waste stream. This study presents results of laboratory and pilot plant scale experimental investigations into lipid recovery from spent coffee, determining the effects of solvent extraction variables including duration, SCG-to-solvent ratio and SCG residual moisture. SCG samples from both the industrial production of instant coffee and retail coffee shops were characterized in terms of moisture content, particle size distribution and oil content to identify the impact of these variables on the efficiency of lipid recovery by solvent extraction. The dry weight oil content of the instant SCG samples ranged from 24.2 to 30.4% w/w, while the retail SCG samples contained considerably lower amounts of lipids with their oil content ranging between 13.4 and 14.8% w/w. The highest oil yields were found at an extraction duration of 8 h, while a moisture content of ~2% w/w led to increased yields relative to completely dry samples. A pattern of increasing acidity with decreasing extraction duration was observed, suggesting preferential extraction of free fatty acids (FFA), with the fatty acid (FA) profile of the oil found to be similar to lipids commonly utilized for biofuel production
0103-72.6: A New Oxygen-Rich Supernova Remnant in the Small Magellanic Cloud
010372.6, the second brightest X-ray supernova remnant (SNR) in the Small
Magellanic Cloud (SMC), has been observed with the {\it Chandra X-Ray
Observatory}. Our {\it Chandra} observation unambiguously resolves the X-ray
emission into a nearly complete, remarkably circular shell surrounding bright
clumpy emission in the center of the remnant. The observed X-ray spectrum for
the central region is evidently dominated by emission from reverse shock-heated
metal-rich ejecta. Elemental abundances in this ejecta material are
particularly enhanced in oxygen and neon, while less prominent in the heavier
elements Si, S, and Fe. We thus propose that 010372.6 is a new
``oxygen-rich'' SNR, making it only the second member of the class in the SMC.
The outer shell is the limb-brightened, soft X-ray emission from the swept-up
SMC interstellar medium. The presence of O-rich ejecta and the SNR's location
within an H{\small II} region attest to a massive star core-collapse origin for
010372.6. The elemental abundance ratios derived from the ejecta suggest an
18 M progenitor star.Comment: 6 pages (ApJ emulator format), including 5 figures and 2 tables. For
high quality Figs.1,2, & 3, contact [email protected]. Accepted by the ApJ
Letter
Temperature and Magnetic Field Enhanced Hall Slope of a Dilute 2D Hole System in the Ballistic Regime
We report the temperature() and perpendicular magnetic field()
dependence of the Hall resistivity of dilute metallic
two-dimensional(2D) holes in GaAs over a broad range of
temperature(0.02-1.25K). The low Hall coefficient, , is found to be
enhanced when decreases. Strong magnetic fields further enhance the slope
of at all temperatures studied. Coulomb interaction corrections
of a Fermi liquid(FL) in the ballistic regime can not explain the enhancement
of which occurs in the same regime as the anomalous metallic
longitudinal conductivity. In particular, although the metallic conductivity in
2D systems has been attributed to electron interactions in a FL, these same
interactions should reduce, {\it not enhance} the slope of as
decreases and/or increases.Comment: Accepted for publication in Physical Review Letter
A Comprehensive Radio and Optical Study of Abell 2256: Activity from an Infalling Group
Abell 2256 is a nearby (z~0.06), rich cluster of galaxies with fascinating
observed properties across a range of wavelengths. Long believed to represent a
cluster merger, recent X-ray and optical results have suggested that in
addition to the primary cluster and subcluster there is evidence for a third,
poorer system. We present wide-field, high sensitivity 1.4 GHz VLA radio
observations of Abell 2256 in conjunction with optical imaging and additional
spectroscopy. Over 40 cluster radio galaxies are identified, with optical
spectroscopy indicating the emission source (star formation or AGN) for most of
them. While the overall fraction of galaxies exhibiting radio emission is
consistent with a large sample of other nearby clusters, we find an increase in
the activity level of galaxies belonging to the third system (hereafter, the
``Group''). Specifically, the Group has relatively more star formation than
both the primary cluster and main subcluster. The position of the Group is also
coincident with the observed cluster radio relic. We suggest that the Group
recently (~0.3 Gyr) merged with the primary cluster and that this merger, not
the ongoing merger of the primary and the main subcluster, might be responsible
for many of the unusual radio properties of Abell 2256. Furthermore, the
greater star formation activity of the Group suggests that the infall of groups
is an important driver of galaxy evolution in clusters.Comment: 21 pages plus 13 JPEG figures; to appear in the Astronomical Journa
The quantum metrology triangle and the re-definition of the SI ampere and kilogram; Analysis of a reduced set of observational equations
We have developed a set of seven observational equations that include all of
the physics necessary to relate the most important of the fundamental constants
to the definitions of the SI kilogram and ampere. We have used these to
determine the influence of alternative definitions being considered for the SI
kilogram and ampere on the uncertainty of three of the fundamental constants
(h, e and mu). We have also reviewed the experimental evidence for the
exactness of the quantum metrology triangle resulting from experiments
combining the quantum Hall effect, the Josephson effects and single-electron
tunnelling.Comment: 16 pages, 3 figures & 5 table
Granule Cell Dispersion in Human Temporal Lobe Epilepsy: Proteomics Investigation of Neurodevelopmental Migratory Pathways
Granule cell dispersion (GCD) is a common pathological feature observed in the
hippocampus of patients with Mesial Temporal Lobe Epilepsy (MTLE). Pathomechanisms
underlying GCD remain to be elucidated, but one hypothesis proposes aberrant
reactivation of neurodevelopmental migratory pathways, possibly triggered by febrile
seizures. This study aims to compare the proteomes of basal and dispersed granule
cells in the hippocampus of eight MTLE patients with GCD to identify proteins that
may mediate GCD in MTLE. Quantitative proteomics identified 1,882 proteins, of which
29% were found in basal granule cells only, 17% in dispersed only and 54% in both
samples. Bioinformatics analyses revealed upregulated proteins in dispersed samples
were involved in developmental cellular migratory processes, including cytoskeletal
remodeling, axon guidance and signaling by Ras homologous (Rho) family of GTPases
(P < 0.01). The expression of two Rho GTPases, RhoA and Rac1, was subsequently
explored in immunohistochemical and in situ hybridization studies involving eighteen
MTLE cases with or without GCD, and three normal post mortem cases. In cases with
GCD, most dispersed granule cells in the outer-granular and molecular layers have an
elongated soma and bipolar processes, with intense RhoA immunolabeling at opposite
poles of the cell soma, while most granule cells in the basal granule cell layer were devoid
of RhoA. A higher percentage of cells expressing RhoA was observed in cases with GCD
than without GCD (P < 0.004). In GCD cases, the percentage of cells expressing RhoA
was significantly higher in the inner molecular layer than the granule cell layer (P < 0.026),
supporting proteomic findings. In situ hybridization studies using probes against RHOA
and RAC1 mRNAs revealed fine peri- and nuclear puncta in granule cells of all cases. The density of cells expressing RHOA mRNAs was significantly higher in the inner
molecular layer of cases with GCD than without GCD (P = 0.05). In summary, our
study has found limited evidence for ongoing adult neurogenesis in the hippocampus of
patients with MTLE, but evidence of differential dysmaturation between dispersed and
basal granule cells has been demonstrated, and elevated expression of Rho GTPases
in dispersed granule cells may contribute to the pathomechanisms underpinning
GCD in MTLE
Generationing development
The articles in this special issue present a persuasive case for accounts of development to recognise the integral and fundamental roles played by age and generation. While the past two decades have witnessed a burgeoning of literature demonstrating that children and youth are impacted by development, and that they can and do participate in development, the literature has tended to portray young people as a special group whose perspectives should not be forgotten. By contrast, the articles collected here make the case that age and generation, as relational constructs, cannot be ignored. Appropriating the term ‘generationing’, the editors argue that a variety of types of age relations profoundly structure the ways in which societies are transformed through development – both immanent processes of neoliberal modernisation and the interventions of development agencies that both respond and contribute to these. Drawing on the seven empirical articles, I attempt to draw some of the ideas together into a narrative that further argues the case for ‘generationing’ but also identifies gaps, questions and implications for further research
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