A methodology to allow avalanche forecasting on an information retrieval system

This paper presents adaptations and tests undertaken to allow an information retrieval (IR) system to forecast the likelihood of avalanches on a particular day. The forecasting process uses historical data of the weather and avalanche conditions for a large number of days. A method for adapting these data into a form usable by a text-based IR system is first described, followed by tests showing the resulting system’s accuracy to be equal to existing ‘custom built’ forecasting systems. From this, it is concluded that the adaptation methodology is effective at allowing such data to be used in a text-based IR system. A number of advantages in using an IR system for avalanche forecasting are also presented

Evidence-based management options for women at increased breast/ovarian cancer risk

Recent developments in our ability to predict breast cancer risk necessitates primary care physicians learn to evaluate breast cancer risk and its importance in shaping decisions concerning surveillance and risk reduction measures. This article reviews the current opinion on risk assessment and management of women with an increased risk of breast/ovarian cancer. Management options are given for women at slightly, moderately and highly elevated breast cancer risk, as well as for BRCA1/2 carriers, based on currently available evidenc

Optimization of imaging before pulmonary vein isolation by radiofrequency ablation: breath-held ungated versus ECG/breath-gated MRA

Isolation of the pulmonary veins has emerged as a new therapy for atrial fibrillation. Pre-procedural magnetic resonance (MR) imaging enhances safety and efficacy; moreover, it reduces radiation exposure of the patients and interventional team. The purpose of this study was to optimize the MR protocol with respect to image quality and acquisition time. In 31 patients (23-73years), the anatomy of the pulmonary veins, left atrium and oesophagus was assessed on a 1.5-Tesla scanner with four different sequences: (1) ungated two-dimensional true fast imaging with steady precession (2D-TrueFISP), (2) ECG/breath-gated 3D-TrueFISP, (3) ungated breath-held contrast-enhanced three-dimensional turbo fast low-angle shot (CE-3D-tFLASH), and (4) ECG/breath-gated CE-3D-TrueFISP. Image quality was scored from 1 (structure not visible) to 5 (excellent visibility), and the acquisition time was monitored. The pulmonary veins and left atrium were best visualized with CE-3D-tFLASH (scores 4.50 ± 0.52 and 4.59 ± 0.43) and ECG/breath-gated CE-3D-TrueFISP (4.47 ± 0.49 and 4.63 ± 0.39). Conspicuity of the oesophagus was optimal with CE-3D-TrueFISP and 2D-TrueFISP (4.59 ± 0.35 and 4.19 ± 0.46) but poor with CE-3D-tFLASH (1.03 ± 0.13) (p < 0.05). Acquisition times were shorter for 2D-TrueFISP (44 ± 1s) and CE-3D-tFLASH (345 ± 113s) compared with ECG/breath-gated 3D-TrueFISP (634 ± 197s) and ECG/breath-gated CE-3D-TrueFISP (636 ± 230s) (p < 0.05). In conclusion, an MR imaging protocol comprising CE-3D-tFLASH and 2D-TrueFISP allows assessment of the pulmonary veins, left atrium and oesophagus in less than 7 min and can be recommended for pre-procedural imaging before electric isolation of pulmonary vein

Stellar pollution and [Fe/H] in the Hyades

The Hyades open cluster presents a unique laboratory for planet formation and stellar pollution studies because all of the stars have essentially the same age and were born from the same cloud of gas. Furthermore, with an age of roughly 650 Myr most of the intermediate and low mass stars are on the main sequence. Given these assumptions, the accretion of metal rich material onto the surface of a star during and shortly after the formation of planetary systems should be evident via the enhanced metallicity of the star. Building on previous work, stellar evolution models which include the effects of stellar pollution are applied to the Hyades. The results of several Monte Carlo simulations, in which the amount of accreted material is drawn at random from a Gaussian distribution with standard deviation equal to half the mean, are presented. An effective temperature-[Fe/H] relation is produced and compared to recent observations. The theoretical predictions presented in this letter will be useful in future searches for evidence of stellar pollution due to planet formation. It is concluded that stellar pollution effects at the mean level of >=2 Earth masses of iron are ruled out by current observational data.Comment: 10 pages, 3 figures, AASTeX, accepted to the ApJ

On the kinematic deconvolution of the local neighbourhood luminosity function

A method for inverting the statistical star counts equation, including proper motions, is presented; in order to break the degeneracy in that equation it uses the supplementary constraints required by dynamical consistency. The inversion gives access to both the kinematics and the luminosity function of each population in three r\'egimes: the singular ellipsoid, the constant ratio Schwarzschild ellipsoid plane parallel models and the epicyclic model. This more realistic model is taylored to account for local neighbourhood density and velocity distribution. The first model is fully investigated both analytically and via means of a non-parametric inversion technique, while the second model is shown to be formally its equivalent. The effect of noise and incompleteness in apparent magnitude is investigated. The third model is investigated via a 5D+2D non-parametric inversion technique where positivity of the underlying luminosity function is explicitely accounted for. It is argued that its future application to data such as the Tycho catalogue (and in the upcoming satellite GAIA) could lead -- provided the vertical potential, and/or the asymmetric drift or w_0 are known -- to a non-parametric determination of the local neighbourhood luminosity function without any reference to stellar evolution tracks. It should also yield the proportion of stars for each kinematic component and a kinematic diagnostic to split the thin disk from the thick disk or the halo.Comment: 18 pages, LateX (or Latex, etc), mnras, accepted for publicatio

New frontiers at the interface of general relativity and quantum optics

In the present paper we follow three major themes: (i) concepts of rotation in general relativity, (ii) effects induced by these generalized rotations, and (iii) their measurement using interferometry. Our journey takes us from the Foucault pendulum via the Sagnac interferometer to manifestations of gravito-magnetism in double binary pulsars and in Gödel\u27s Universe. Throughout our article we emphasize the emerging role of matter wave interferometry based on cold atoms or Bose-Einstein condensates leading to superior inertial sensors. In particular, we advertise recent activities directed towards the operation of a coherent matter wave interferometer in an extended free fall. © 2009 Springer Science+Business Media B.V

Exploring the Local Milky Way: M Dwarfs as Tracers of Galactic Populations

We have assembled a spectroscopic sample of low-mass dwarfs observed as part of the Sloan Digital Sky Survey along one Galactic sightline, designed to investigate the observable properties of the thin and thick disks. This sample of ~7400 K and M stars also has measured ugriz photometry, proper motions, and radial velocities. We have computed UVW space motion distributions, and investigate their structure with respect to vertical distance from the Galactic Plane. We place constraints on the velocity dispersions of the thin and thick disks, using two-component Gaussian fits. We also compare these kinematic distributions to a leading Galactic model. Finally, we investigate other possible observable differences between the thin and thick disks, such as color, active fraction and metallicity.Comment: 11 pages, 12 figures, Accepted by A

The age of the oldest globular clusters

The age of three of the oldest clusters -- M15, M68, M92 -- has been redetermined. We use the latest EOS and opacity data available for calculating both isochrones and zero age horizontal branches and employ the brightness difference between turn-off and horizontal branch to determine the cluster age. Our best ages for all three clusters are about 13 Gyr, and even smaller ages are possible. Our results help to reconcile cluster ages with recent results on the age of the universe determined from the Hubble constant.Comment: submitted to The Astrophysical Journal Letter

HST/FOS Eclipse Observations of the Nova-like Cataclysmic Variable UX Ursae Majoris

[abridged abstract] We present and analyze Hubble Space Telescope observations of the eclipsing nova-like cataclysmic variable UX UMa obtained with the Faint Object Spectrograph. Two eclipses each were observed with the G160L grating (covering the ultraviolet waveband) in August of 1994 and with the PRISM (covering the near-ultraviolet to near-infrared) in November of the same year. The system was 50% brighter in November than in August, which, if due to a change in the accretion rate, indicates a fairly substantial increase in Mdot_acc by >~ 50%. Model disk spectra constructed as ensembles of stellar atmospheres provide poor descriptions of the observed post-eclipse spectra, despite the fact that UX UMa's light should be dominated by the disk at this time. Suitably scaled single temperature model stellar atmospheres with T_eff = 12,500-14,500 K actually provide a better match to both the ultraviolet and optical post-eclipse spectra. Evidently, great care must be taken in attempts to derive accretion rates from comparisons of disk models to observations. One way to reconcile disk models with the observed post-eclipse spectra is to postulate the presence of a significant amount of optically thin material in the system. Such an optically thin component might be associated with the transition region (``chromosphere'') between the disk photosphere and the fast wind from the system, whose presence has been suggested by Knigge & Drew (1997).Comment: 35 pages, including 12 figures; to appear in the ApJ (Vol. 499