Institutional Characteristics and the Relationship Between Student's Last-Year University and Final-Year Secondary School Academic Performance.

A study of academic results of a student cohort in a diverse faculty of a large multi-campus university indicates that students' first-year performance at university is related to their prior academic achievement at secondary school, both overall and discipline specific, but that the extent and form of the relationship can vary by subject area and institutional secondary school and university characteristics. This may have implications for university selection and specification of prerequisite subjects for courses.EDUCATION ; STUDENTS ; INSTITUTION BUILDING

Spin-2 Amplitudes in Black-Hole Evaporation

Quantum amplitudes for $s=2$ gravitational-wave perturbations of Einstein/scalar collapse to a black hole are treated by analogy with $s=1$ Maxwell perturbations. The spin-2 perturbations split into parts with odd and even parity. We use the Regge-Wheeler gauge; at a certain point we make a gauge transformation to an asymptotically-flat gauge, such that the metric perturbations have the expected falloff behaviour at large radii. By analogy with $s=1$, for $s=2$ natural 'coordinate' variables are given by the magnetic part $H_{ij} (i,j=1,2,3)$ of the Weyl tensor, which can be taken as boundary data on a final space-like hypersurface $\Sigma_F$. For simplicity, we take the data on the initial surface $\Sigma_I$ to be exactly spherically-symmetric. The (large) Lorentzian proper-time interval between $\Sigma_I$ and $\Sigma_F$, measured at spatial infinity, is denoted by $T$. We follow Feynman's $+i\epsilon$ prescription and rotate $T$ into the complex: $T\to{\mid}T{\mid} \exp(-i\theta)$, for $0<\theta\leq\pi/2$. The corresponding complexified {\it classical} boundary-value problem is expected to be well-posed. The Lorentzian quantum amplitude is recovered by taking the limit as $\theta\to 0_+$. For boundary data well below the Planck scale, and for a locally supersymmetric theory, this involves only the semi-classical amplitude $\exp(iS^{(2)}_{\rm class}$, where $S^{(2)}_{\rm class}$ denotes the second-variation classical action. The relations between the $s=1$ and $s=2$ natural boundary data, involving supersymmetry, are investigated using 2-component spinor language in terms of the Maxwell field strength $\phi_{AB}=\phi_{(AB)}$ and the Weyl spinor $\Psi_{ABCD}=\Psi_{(ABCD)}$

Constraining in situ cosmogenic nuclide paleo-production rates using sequential lava flows during a paleomagnetic field strength low

The geomagnetic field prevents a portion of incoming cosmic rays from reaching Earth’s atmosphere. During magnetic reversals and excursions, the field strength can decrease by up to 90% relative to the modern-day value. During such anomalies, cosmic ray bombardment to Earth’s atmosphere increases as evident from atmospheric ¹⁰Be anomalies recorded in sediment and ice cores. However, how the flux of cosmic rays to Earth’s surface varies during such geomagnetic anomalies is not well constrained. We measured fossil cosmogenic ³He in olivine from the tops of two pairs of ⁴⁰Ar/³⁹Ar age-dated Tahitian lava flows that erupted during the Matuyama-Brunhes reversal precursor event. We corrected these raw values for the diffusive loss of helium caused by heating from the overlying flow with a diffusion model using cooling rates and maximum temperature conditions based on field measurements of active lava flows from Kilauea, Hawaii. We assume the maximum temperature suggested by field measurements and thus present a limiting case for the highest diffusive loss corrections and thus the highest paleo-production rates. Based on paleomagnetic field strength reconstructions and scaling factor models, the upper limits of the corrected in situ 3He paleo-production rates (100 ± 23, 144 ± 35 atoms g⁻¹ a⁻¹) are in agreement with those expected during the period of a geomagnetic field strength low when these flow tops were exposed. However, the more plausible contact temperatures (<700°C maximum temperature in diffusion model) are associated with diffusion corrected paleo-production rates lower than those predicted by scalar models. This potential underestimation is likely a function of changes in local non-dipole field components, atmospheric density and/or an overestimation of the dipole field strength reduction during the M-B precursor event

Black hole evaporation in a spherically symmetric non-commutative space-time

Recent work in the literature has studied the quantum-mechanical decay of a Schwarzschild-like black hole, formed by gravitational collapse, into almost-flat space-time and weak radiation at a very late time. The relevant quantum amplitudes have been evaluated for bosonic and fermionic fields, showing that no information is lost in collapse to a black hole. On the other hand, recent developments in noncommutative geometry have shown that, in general relativity, the effects of non-commutativity can be taken into account by keeping the standard form of the Einstein tensor on the left-hand side of the field equations and introducing a modified energy-momentum tensor as a source on the right-hand side. Relying on the recently obtained non-commutativity effect on a static, spherically symmetric metric, we have considered from a new perspective the quantum amplitudes in black hole evaporation. The general relativity analysis of spin-2 amplitudes has been shown to be modified by a multiplicative factor F depending on a constant non-commutativity parameter and on the upper limit R of the radial coordinate. Limiting forms of F have been derived which are compatible with the adiabatic approximation.Comment: 8 pages, Latex file with IOP macros, prepared for the QFEXT07 Conference, Leipzig, September 200

Gravitational amplitudes in black-hole evaporation: the effect of non-commutative geometry

Recent work in the literature has studied the quantum-mechanical decay of a Schwarzschild-like black hole, formed by gravitational collapse, into almost-flat space-time and weak radiation at a very late time. The relevant quantum amplitudes have been evaluated for bosonic and fermionic fields, showing that no information is lost in collapse to a black hole. On the other hand, recent developments in noncommutative geometry have shown that, in general relativity, the effects of noncommutativity can be taken into account by keeping the standard form of the Einstein tensor on the left-hand side of the field equations and introducing a modified energy-momentum tensor as a source on the right-hand side. The present paper, relying on the recently obtained noncommutativity effect on a static, spherically symmetric metric, considers from a new perspective the quantum amplitudes in black hole evaporation. The general relativity analysis of spin-2 amplitudes is shown to be modified by a multiplicative factor F depending on a constant non-commutativity parameter and on the upper limit R of the radial coordinate. Limiting forms of F are derived which are compatible with the adiabatic approximation here exploited. Approximate formulae for the particle emission rate are also obtained within this framework.Comment: 14 pages, 2 figures, Latex macros. In the final version, section 5 has been amended, the presentation has been improved, and References 21-24 have been added. Last misprints amended in Section 5 and Ref. 2

Steady-state Engine Windmilling and Engine Speed Decay Characteristics of an Axial-flow Turbojet Engine

A wind tunnel investigation has been conducted to determine the steady-state windmilling and engine speed decay characteristics of the J34-WE-32 turbo-jet over a range of altitudes from 5000 to 50,000 feet and simulated flight Mach numbers from 0.19 to 1.06. The effect of an engine accessory load on the speed decay characteristics was also determined. The accessory load was about 7.8 horsepower for engine speeds above 4000 rpm and decreased with decreasing engine speed. An analysis of the speed decay data was made and engine speed decay rates were determined for hypothetical accessory loads up to 40 horsepower

Comprehension following silent and oral reading in grades two and three

Thesis (Ed.M.)--Boston Universit

Comprehension following silent and oral reading in grades two and three

Thesis (Ed.M.)--Boston Universit

Sclerostin does not play a major role in the pathogenesis of skeletal complications in type 2 diabetes mellitus

In contrast to previously reported elevations in serum sclerostin levels in diabetic patients, the present study shows that the impaired bone microarchitecture and cellular turnover associated with type 2 diabetes mellitus (T2DM)-like conditions in ZDF rats are not correlated with changes in serum and bone sclerostin expression. INTRODUCTION: T2DM is associated with impaired skeletal structure and a higher prevalence of bone fractures. Sclerostin, a negative regulator of bone formation, is elevated in serum of diabetic patients. We aimed to relate changes in bone architecture and cellular activities to sclerostin production in the Zucker diabetic fatty (ZDF) rat. METHODS: Bone density and architecture were measured by micro-CT and bone remodelling by histomorphometry in tibiae and femurs of 14-week-old male ZDF rats and lean Zucker controls (n = 6/group). RESULTS: ZDF rats showed lower trabecular bone mineral density and bone mass compared to controls, due to decreases in bone volume and thickness, along with impaired bone connectivity and cortical bone geometry. Bone remodelling was impaired in diabetic rats, demonstrated by decreased bone formation rate and increased percentage of tartrate-resistant acid phosphatase-positive osteoclastic surfaces. Serum sclerostin levels (ELISA) were higher in ZDF compared to lean rats at 9 weeks (+40 %, p < 0.01), but this difference disappeared as their glucose control deteriorated and by week 14, ZDF rats had lower sclerostin levels than control rats (-44 %, p < 0.0001). Bone sclerostin mRNA (qPCR) and protein (immunohistochemistry) were similar in ZDF, and lean rats at 14 weeks and genotype did not affect the number of empty osteocytic lacunae in cortical and trabecular bone. CONCLUSION: T2DM results in impaired skeletal architecture through altered remodelling pathways, but despite altered serum levels, it does not appear that sclerostin contributes to the deleterious effect of T2DM in rat bone