Multifluid magnetohydrodynamic turbulent decay

It is generally believed that turbulence has a significant impact on the dynamics and evolution of molecular clouds and the star formation which occurs within them. Non-ideal magnetohydrodynamic effects are known to influence the nature of this turbulence. We present the results of a suite of 512-cubed resolution simulations of the decay of initially super-Alfvenic and supersonic fully multifluid MHD turbulence. We find that ambipolar diffusion increases the rate of decay of the turbulence while the Hall effect has virtually no impact. The decay of the kinetic energy can be fitted as a power-law in time and the exponent is found to be -1.34 for fully multifluid MHD turbulence. The power spectra of density, velocity and magnetic field are all steepened significantly by the inclusion of non-ideal terms. The dominant reason for this steepening is ambipolar diffusion with the Hall effect again playing a minimal role except at short length scales where it creates extra structure in the magnetic field. Interestingly we find that, at least at these resolutions, the majority of the physics of multifluid turbulence can be captured by simply introducing fixed (in time and space) resistive terms into the induction equation without the need for a full multifluid MHD treatment. The velocity dispersion is also examined and, in common with previously published results, it is found not to be power-law in nature.Comment: 16 pages, 15 figures, Accepted for publication in Ap

School Finance Reforms, Tax Limits, and Student Performance: Do Reforms Level Up or Dumb Down?

During the late 1970s and early 1980s, a majority of states substantially changed the ways in which schools were funded, either directly through court- or legislatively mandated school finance reform, or indirectly through tax and expenditure limits. To date, there have been few academic attempts to gauge the effects of these policy changes on actual outcomes of education. This paper is an attempt to fill this gap in the literature. We find compelling evidence that the imposition of tax or expenditure limits on local governments in a state results in a significant reduction in the mean for that state of student performance on standardized tests of mathematics skills. We also find that finance reforms in response to court mandates do not result in significant changes in either the mean level or the distribution of student performance on standardized tests of reading and mathematics. In addition, substantial finance reforms that are not legislative responses to explicit court mandates generally result in increases in mean student performance. Further, in those states that have implemented finance reforms of this type, the test performance of students residing in localities in which local revenues formed smaller shares of total revenue prior to the reforms improve relative to others after the reforms are implemented.

CVcat: an interactive database on cataclysmic variables

CVcat is a database that contains published data on cataclysmic variables and related objects. Unlike in the existing online sources, the users are allowed to add data to the catalogue. The concept of an ``open catalogue'' approach is reviewed together with the experience from one year of public usage of CVcat. New concepts to be included in the upcoming AstroCat framework and the next CVcat implementation are presented. CVcat can be found at http://www.cvcat.org.Comment: 5 pages A&A Latex, 4 figures, accepted for publication in A&

Quantum Communication with an Accelerated Partner

An unsolved problem in relativistic quantum information research is how to model efficient, directional quantum communication between localised parties in a fully quantum field theoretical framework. We propose a tractable approach to this problem based on solving the Heisenberg evolution of localized field observables. We illustrate our approach by analysing, and obtaining approximate analytical solutions to, the problem of communicating coherent states between an inertial sender, Alice and an accelerated receiver, Rob. We use these results to determine the efficiency with which continuous variable quantum key distribution could be carried out over such a communication channel.Comment: Additional explanatory text and typo in Eq.17 correcte

Embodied textiles for expression and wellbeing

To date, experiences with technical textiles have largely been focused on performance related aspects of a fabric developed for specific applications such as sports, health or safety (Shishoo 2005), and methodological problems remain with the techniques employed to measure what is a complex of effect and affect (Bartels 2005, Jordan 2000). However, there has been little in the way of empirical research into personal human experience with technical fabrics in context, with the notable exception perhaps of Entwistle who examines in depth the kinesthetic properties of particular garments, resulting in heightened awareness of the body (Entwistle & Wilson 2001) and Candy, who analyses feelings of well being and the performance of socially meaningful demeanours (Candy 2007a, Candy 2007b). We wish to extend this embodied view of textiles in order to realise the potential of smart and technical fabrics and sensory environments as tools for wellbeing, mental health and personal expression. This paper describes the work of an interdisciplinary group of practitioners and researchers investigating the development and application of textile stretch sensors on the body (Breedon et al 2008), figures 1 and 2. Understanding that such tactile products and materials may offer beneficial contexts for in-the-moment and expressive therapeutic techniques (Jones 2010, Jones & Wallis 2005), we describe the early stages of our collaborative development of an evaluation framework based on person-centred principles and outline the future work planned

Dense Molecular Gas and the Role of Star Formation in the Host Galaxies of Quasi-Stellar Objects

New millimeter-wave CO and HCN observations of the host galaxies of infrared-excess Palomar Green quasi-stellar objects (PG QSOs) previously detected in CO are presented. These observations are designed to assess the validity of using the infrared luminosity to estimate star formation rates of luminous AGN by determining the relative significance of dust-heating by young, massive stars and active galactic nuclei (AGN) in QSO hosts and IRAS galaxies with warm, AGN-like infrared colors. The HCN data show the PG QSO host IZw1 and most of the warm IRAS galaxies to have high L_IR / L'_HCN (>1600) relative to the cool IRAS galaxy population for which the median L_IR / L'_HCN ~ 890(+440,-470). If the assumption is made that the infrared emission from cool IRAS galaxies is reprocessed light from embedded star-forming regions, then high values of L_IR / L'_HCN are likely the result of dust heating by the AGN. Further, if the median ratio of L'_HCN / L'_CO ~ 0.06 observed for Seyfert galaxies and IZw1 is applied to the PG QSOs not detected in HCN, then the derived L_IR / L'_HCN correspond to a stellar contribution to the production of L_IR of ~ 7-39%, and star formation rates ~ 2-37 M_sun/yr are derived for the QSO hosts. Alternatively, if the far-infrared is adopted as the star formation component of the total infrared in cool galaxies, the stellar contributions in QSO hosts to their L_FIR are up to 35% higher than the percentages derived for L_IR. This raises the possibility that the L_FIR in several of the PG QSO hosts, including IZw1, could be due entirely to dust heated by young, massive stars. Finally, there is no evidence that the global HCN emission is enhanced relative to CO in galaxies hosting luminous AGN.Comment: LaTex, 31 pages, including 9 postscript figures, AJ, in press (December 2006