Inflationary Hubble Parameter from the Gravitational Wave Spectrum in the General Slow-roll Approximation

Improved general slow-roll formulae giving the primordial gravitational wave spectrum are derived in the present work. Also the first and second order general slow-roll inverse formulae giving the Hubble parameter $H$ in terms of the gravitational wave spectrum are derived. Moreover, the general slow-roll consistency condition relating the scalar and tensor spectra is obtained

Quasi-geostrophic dynamics in the presence of moisture gradients

The derivation of a quasi-geostrophic (QG) system from the rotating shallow water equations on a midlatitude beta-plane coupled with moisture is presented. Condensation is prescribed to occur whenever the moisture at a point exceeds a prescribed saturation value. It is seen that a slow condensation time scale is required to obtain a consistent set of equations at leading order. Further, since the advecting wind fields are geostrophic, changes in moisture (and hence, precipitation) occur only via non-divergent mechanisms. Following observations, a saturation profile with gradients in the zonal and meridional directions is prescribed. A purely meridional gradient has the effect of slowing down the dry Rossby waves, through a reduction in the "equivalent gradient" of the background potential vorticity. A large scale unstable moist mode results on the inclusion of a zonal gradient by itself, or in conjunction with a meridional moisture gradient. For gradients that are are representative of the atmosphere, the most unstable moist mode propagates zonally in the direction of increasing moisture, matures over an intraseasonal timescale and has small phase speed.Comment: 9 pages, 8 figures, Quarterly Journal of the Royal Meteorological Society, DOI:10.1002/qj.2644, 201

The BOSS system for on-line submission and assessment of computing assignments

Practical computing courses which involve significant amounts of programming continue to suffer from increasing student numbers. This makes their delivery and management more difficult to achieve effectively with the available resources. One solution to this problem is to develop methods for automating the submission and testing of student programs to support the marking effort and to enable the division of marking tasks among several individuals while ensuring consistency and rigour throughout. We have developed such methods in our system, called BOSS, and have successfully deployed different versions of it on several courses over a number of years. Here, we describe the original system and its recent enhancements, and discuss the benefits it has provided us with, both in terms of administration and in improving the learning process

Blending of Cepheids in M33

A precise and accurate determination of the Hubble constant based on Cepheid variables requires proper characterization of many sources of systematic error. One of these is stellar blending, which biases the measured fluxes of Cepheids and the resulting distance estimates. We study the blending of 149 Cepheid variables in M33 by matching archival Hubble Space Telescope data with images obtained at the WIYN 3.5-m telescope, which differ by a factor of 10 in angular resolution. We find that 55+-4% of the Cepheids have no detectable nearby companions that could bias the WIYN V-band photometry, while the fraction of Cepheids affected below the 10% level is 73+-4%. The corresponding values for the I band are 60+-4% and 72+-4%, respectively. We find no statistically significant difference in blending statistics as a function of period or surface brightness. Additionally, we report all the detected companions within 2 arcseconds of the Cepheids (equivalent to 9 pc at the distance of M33) which may be used to derive empirical blending corrections for Cepheids at larger distances.Comment: v2: Fixed incorrect description of Figure 2 in text. Accepted for publication in AJ. Full data tables can be found in ASCII format as part of the source distribution. A version of the paper with higher-resolution figures can be found at http://faculty.physics.tamu.edu/lmacri/papers/chavez12.pd

Despite Regulatory Changes, Hospitals Cautious in Helping Physicians Purchase Electronic Medical Records

Examines hospitals' strategies to aid physicians' adoption of electronic medical records (EMRs) following regulatory changes facilitating hospital-subsidized EMRs. Looks at factors determining support for physicians' EMR adoption and their implications

A near-infrared study of the luminous merging galaxies NGC 2623 and ARP 148

As part of an investigation of the physical mechanisms which produce large infrared luminosities in interacting systems, multicolor near-infrared maps were obtained of the long tailed galaxy NGC 2623 and the ring galaxy Arp 148. The near-infrared broadband spectrum was decomposed to obtain the contribution of four processes: emission from evolved stars, nebular continuum emission, thermal reradiation, and extinction. This multicolor analysis, along with 2 micrometer maps and 10 micrometer measurements, is used to determine the structure of these interacting galaxies and to delineate regions of star formation