A Spin-Orbit Alignment for the Hot Jupiter HATS-3b

We have measured the alignment between the orbit of HATS-3b (a recently discovered, slightly inflated Hot Jupiter) and the spin-axis of its host star. Data were obtained using the CYCLOPS2 optical-fiber bundle and its simultaneous calibration system feeding the UCLES spectrograph on the Anglo-Australian Telescope. The sky-projected spin-orbit angle of $\lambda = 3\pm25^{\circ}$ was determined from spectroscopic measurements of Rossiter-McLaughlin effect. This is the first exoplanet discovered through the HATSouth transit survey to have its spin-orbit angle measured. Our results indicate that the orbital plane of HATS-3b is consistent with being aligned to the spin axis of its host star. The low obliquity of the HATS-3 system, which has a relatively hot mid F-type host star, agrees with the general trend observed for Hot Jupiter host stars with effective temperatures $>6250$K to have randomly distributed spin-orbit angles.Comment: 13 pages. Accepted for publication in the Astrophysical Journa

Ray methods for Free Boundary Problems

We discuss the use of the WKB ansatz in a variety of parabolic problems involving a small parameter. We analyse the Stefan problem for small latent heat, the Black--Scholes problem for an American put option, and some nonlinear diffusion equations, in each case constructing an asymptotic solution by the use of ray methods

New Estimates of the Effects of Minimum Wages in the U.S. Retail Trade Sector

This paper examines the impact of minimum wages on earnings and employment in selected branches of the retail-trade sector, 1990-2005, using county-level data on employment and a panel regression framework that allows for county-specific trends in sectoral outcomes. We focus on particular subsectors within retail trade that are identified as particularly low-wage. We find little evidence of disemployment effects once we allow for geographic-specific trends. Rather, in many sectors the evidence suggests modest (but robust) positive employment effects. One explanation we consider for these ‘perverse’ effects is that minimum wages may have significant influences on product demand shifts.border county analysis, spatial trends, county-level data, wages and employment, minimum wages, unions, right-to-work states

The Effect of Minimum Wages on Wages and Employment: County-Level Estimates for the United States

We use county-level data on employment and earnings in the restaurant-and-bar sector to evaluate the impact of minimum wage changes on low-wage labor markets. Our empirical approach is similar to the literature that has used state-level panel data to estimate minimum-wage impacts, with the difference that we focus on a particular sector rather than demographic group. Our estimated models are consistent with a simple competitive model of the restaurant-and-bar labor market in which supply-and-demand factors affect both the equilibrium outcome and the probability that a minimum wage will be binding in any given time period. Our evidence does not suggest that minimum wages reduce employment in the overall restaurant-and-bar sector, after controls for trends in sector employment at the county level are incorporated in the model. Employment in this sector appears to exhibit a downward long-term trend in states that have increased their minimum wages relative to states that have not, thereby predisposing fixed-effects estimates towards finding negative employment effects.county-level data, wages and employment, minimum wages, spatial trends

A Nearly Polar Orbit for the Extrasolar Hot Jupiter WASP-79b

We report the measurement of a spin-orbit misalignment for WASP-79b, a recently discovered, bloated transiting hot Jupiter from the WASP survey. Data were obtained using the CYCLOPS2 optical-fiber bundle and its simultaneous calibration system feeding the UCLES spectrograph on the Anglo-Australian Telescope. We have used the Rossiter-McLaughlin effect to determine the sky-projected spin-orbit angle to be lambda = -106+19-13 degrees. This result indicates a significant misalignment between the spin axis of the host star and the orbital plane of the planet -- the planet being in a nearly polar orbit. WASP-79 is consistent with other stars that have Teff > 6250K and host hot Jupiters in spin-orbit misalignment.Comment: 8 pages, 2 figures, in press ApJL (accepted 2 August 2013

Modelling the influence of the process inputs on the removal of surface contaminants from Ti-6Al-4V linear friction welds

The linear friction welding (LFW) process is finding increasing interest from industry for the fabrication of near-net-shape, titanium alloy Ti–6Al–4V, aerospace components. Currently, the removal of surface contaminants, such as oxides and foreign particles, from the weld interface into the flash is not fully understood. To address this problem, two-dimensional (2D) computational models were developed using the finite element analysis (FEA) software DEFORM and validated with experiments. The key findings showed that the welds made with higher applied forces required less burn-off to completely remove the surface contaminants from the interface into the flash; the interface temperature increased as the applied force was decreased or the rubbing velocity increased; and the boundary temperature between the rapid flash formation and negligible material flow was approximately 970 °C. An understanding of these phenomena is of particular interest for the industrialisation of near-net-shape titanium alloy aerospace components.EPSRC, Boeing Company, Welding Institut

Self-Diffusion in Sodium Single Crystals

The objective of this investigation was the study of self-diffusion in single-crystal sodium using tracer techniques and the determination of the diffusion constant and activation energy. Precise values of these quantities can be obtained by using Fick\u27s second law of diffusion and the relation D = D₀ exp (- Q/RT) provided the concentration of the diffusing isotope is kept very small. However, in the above relation, the quanties D₀ (diffusion constant) and Q (activation energy) may vary with the composition of the crystal and with impurity content but are independent of temperature

Minimum Wage Increases in a Soft U.S. Economy

Do apparently large minimum wage increases in an environment of straightened economic circumstances produce clearer evidence of disemployment effects than is typically reported in the new economics of the minimum wage? The present paper augments the sparse literature covering the very latest increases in the U.S. minimum wage, using three different data sets and the principal estimation strategies for handling geographically-disparate trends. Despite the seemingly more favorable milieu for identifying displacement effects, and although our treatment calls into question one well-received estimation strategy, our preferred specification generally fails to support a finding of negative employment effects. That is to say, minimum-wage workers are apparently concentrated in sectors of the economy for which the labor demand response to statutory wage hikes is minimal. Popular concern with a “recessionary multiplier” thus seems overdone.Minimum wages, Disemployment, Earnings, Low-wage sectors, Geographically-disparate employment trends, Recession