Deep space network

Background, current status, and sites of Deep Space Network stations are briefly discussed

Monitoring the Health of Computer Networks with Visualization - VAST 2012 Mini Challenge 1 Award: "Efficient Use of Visualization"

The complex computer networks of large organisations contain many machines of many types, used in many geographic locations. Although system administrators should monitor the health of each machine, they need to do so within the context of the whole computer network. Our visualization presents the health of a fictitious financial institution's computer network at a snapshot in time and over a time range, and preserves the important aspects of each facility's administrative and geographic context. Using the "Bank of Money" VAST Challenge dataset, our visualization allowed us to correctly identify several areas of concern, as well as hypothesise about their causes

Measurement of the half-life of 198Au in a non-metal: High-precision measurement shows no host-material dependence

We have measured the half-life of the beta decay of 198Au to be 2.6948(9) d, with the nuclide sited in an insulating environment. Comparing this result with the half-life we measured previously with a metallic environment, we find the half-lives in both environments to be the same within 0.04%, thus contradicting a prediction that screening from a "plasma" of quasi-free electrons in a metal increases the half-life by as much as 7%

Kinematic Masses of Super Star Clusters in M82 from High-Resolution Near-Infrared Spectroscopy

Using high-resolution (R~22,000) near-infrared (1.51 -- 1.75 microns) spectra from Keck Observatory, we measure the kinematic masses of two super star clusters in M82. Cross-correlation of the spectra with template spectra of cool evolved stars gives stellar velocity dispersions of sigma_r=15.9 +/- 0.8 km/s for MGG-9 and sigma_r=11.4 +/- 0.8 km/s for MGG-11. The cluster spectra are dominated by the light of red supergiants, and correlate most closely with template supergiants of spectral types M0 and M4.5. We fit King models to the observed profiles of the clusters in archival HST/NICMOS images to measure the half-light radii. Applying the virial theorem, we determine masses of 1.5 +/- 0.3 x 10^6 M_sun for MGG-9 and 3.5 +/- 0.7 x 10^5 M_sun for MGG-11. Population synthesis modelling suggests that MGG-9 is consistent with a standard initial mass function, whereas MGG-11 appears to be deficient in low-mass stars relative to a standard IMF. There is, however, evidence of mass segregation in the clusters, in which case the virial mass estimates would represent lower limits.Comment: 16 pages, 8 figures; ApJ, in pres

The Dynamical Implications of Multiple Stellar Formation Events in Galactic Globular Clusters

Various galactic globular clusters display abundance anomalies that affect the morphology of their colour-magnitude diagrams. In this paper we consider the possibility of helium enhancement in the anomalous horizontal branch of NGC 2808. We examine the dynamics of a self-enrichment scenario in which an initial generation of stars with a top-heavy initial mass function enriches the interstellar medium with helium via the low-velocity ejecta of its asymptotic giant branch stars. This enriched medium then produces a second generation of stars which are themselves helium-enriched. We use a direct N-body approach to perform five simulations and conclude that such two-generation clusters are both possible and would not differ significantly from their single-generation counterparts on the basis of dynamics. We find, however, that the stellar populations of such clusters would differ from single-generation clusters with a standard initial mass function and in particular would be enhanced in white dwarf stars. We conclude, at least from the standpoint of dynamics, that two-generation globular clusters are feasible.Comment: 24 pages, 7 figures, 3 tables. Accepted for publication in Ap

The orbit structure of Dynkin curves

Let G be a simple algebraic group over an algebraically closed field k; assume that Char k is zero or good for G. Let \cB be the variety of Borel subgroups of G and let e in Lie G be nilpotent. There is a natural action of the centralizer C_G(e) of e in G on the Springer fibre \cB_e = {B' in \cB | e in Lie B'} associated to e. In this paper we consider the case, where e lies in the subregular nilpotent orbit; in this case \cB_e is a Dynkin curve. We give a complete description of the C_G(e)-orbits in \cB_e. In particular, we classify the irreducible components of \cB_e on which C_G(e) acts with finitely many orbits. In an application we obtain a classification of all subregular orbital varieties admitting a finite number of B-orbits for B a fixed Borel subgroup of G.Comment: 12 pages, to appear in Math

The effect of the dynamical state of clusters on gas expulsion and infant mortality

The star formation efficiency (SFE) of a star cluster is thought to be the critical factor in determining if the cluster can survive for a significant (>50 Myr) time. There is an often quoted critical SFE of ~30 per cent for a cluster to survive gas expulsion. I reiterate that the SFE is not the critical factor, rather it is the dynamical state of the stars (as measured by their virial ratio) immediately before gas expulsion that is the critical factor. If the stars in a star cluster are born in an even slightly cold dynamical state then the survivability of a cluster can be greatly increased.Comment: 6 pages, 2 figures. Review talk given at the meeting on "Young massive star clusters - Initial conditions and environments", E. Perez, R. de Grijs, R. M. Gonzalez Delgado, eds., Granada (Spain), September 2007, Springer: Dordrecht. Replacement to correct mistake in a referenc

Force-free magnetosphere of an aligned rotator with differential rotation of open magnetic field lines

Here we briefly report on results of self-consistent numerical modeling of a differentially rotating force-free magnetosphere of an aligned rotator. We show that differential rotation of the open field line zone is significant for adjusting of the global structure of the magnetosphere to the current density flowing through the polar cap cascades. We argue that for most pulsars stationary cascades in the polar cap can not support stationary force-free configurations of the magnetosphere.Comment: 5 pages, 4 figures. Presented at the conference "Isolated Neutron Stars: from the Interior to the Surface", London, April 24-28, 2006; to appear in Astrophysics and Space Science. Significantly revised version, a mistake found by ourselfs in the numerical code was corrected, all presented results are obtained with the correct version of the cod

Measurement equivalence of the newly developed Quality of Life in Childhood Epilepsy Questionnaire (QOLCE-55)

Summary Objective The aim of this study was to examine measurement equivalence of the newly developed Quality of Life in Childhood Epilepsy Questionnaire (QOLCE-55) across age, sex, and time in a representative sample of children with newly diagnosed epilepsy. Methods Data come from 373 children enrolled in the Health-related Quality of Life in Children with Epilepsy Study (HERQULES), a multisite prospective cohort study. Measurement equivalence was examined using a multiple-group confirmatory factor analysis framework, whereby increasingly stringent parameter constraints are imposed on the model. Comparison groups were stratified based on age (4-7 years vs. 8-12 years), sex (male vs. female), and time (measurement of health-related quality of life at diagnosis vs. 24 months later). Results The QOLCE-55 demonstrated measurement equivalence at the level of strict invariance for each model tested - age: χ2 (3,123) = 4,097.3, p \u3c 0.001; Comparative Fit Index (CFI) = 0.968; Root Mean Square Error of Approximation (RMSEA) = 0.042 (0.038, 0.045); sex: χ2 (3,124) = 4,188.3, p \u3c 0.001; CFI = 0.964; RMSEA = 0.044 (0.040, 0.047); and time: χ2 (3,121) = 5,185.0, p \u3c 0.001; CFI = 0.965; RMSEA = 0.046 (0.043, 0.048). Significance These findings suggest that items comprising the QOLCE-55 are perceived similarly among groups stratified by age, sex, and time and provide further evidence supporting the validity of the scale in children with epilepsy. Health professionals and researchers should be confident that group comparisons made using the QOLCE-55 are unbiased and that any group differences detected are meaningful; that is, not related to differences in the interpretation of items by informants. Future research replicating these findings is encouraged

Deep space network support of the Manned space flight network for Apollo, 1962 - 1968, volume 1

Deep Space Network support of Manned Space Flight Network for Apollo projec