Reconciling the Metallicity Distributions of Gamma-ray Burst, Damped Lyman-alpha, and Lyman-break Galaxies at z=3

We test the hypothesis that the host galaxies of long-duration gamma-ray bursts (GRBs) as well as quasar-selected damped Lyman-alpha (DLA) systems are drawn from the population of UV-selected star-forming, high-z galaxies (generally referred to as Lyman-break galaxies). Specifically, we compare the metallicity distributions of the GRB and DLA populations to simple models where these galaxies are drawn randomly from the distribution of star-forming galaxies according to their star-formation rate and HI cross-section respectively. We find that it is possible to match both observational distributions assuming very simple and constrained relations between luminosity, metallicity and HI sizes. The simple model can be tested by observing the luminosity distribution of GRB host galaxies and by measuring the luminosity and impact parameters of DLA selected galaxies as a function of metallicity. Our results support the expectation that GRB and DLA samples, in contrast to magnitude limited surveys, provide an almost complete census of z=3 star-forming galaxies that are not heavily dust-obscured.Comment: 31 pages, 6 figures. Accepted for publication in Ap

Reconciling the Metallicity Distributions of Gamma-ray Burst, Damped Lyman-α, and Lyman-break Galaxies at z ≈ 3

We test the hypothesis that the host galaxies of long-duration gamma-ray bursts (GRBs) as well as quasar-selected damped Lyman-α (DLA) systems are drawn from the population of UV-selected star-forming, high z galaxies (generally referred to as Lyman-break galaxies). Specifically, we compare the metallicity distributions of the GRB and DLA populations against simple disk models where these galaxies are drawn randomly from the distribution of star-forming galaxies according to their star-formation rate and HI cross-section respectively. We find that it is possible to match both observational distributions assuming very simple and constrained relations between luminosity, metallicity, metallicity gradients and HI sizes. The simple model can be tested by observing the luminosity distribution of GRB host galaxies and by measuring the luminosity and impact parameters of DLA selected galaxies as a function of metallicity. Our results support the expectation that GRB and DLA samples, in contrast with magnitude limited surveys, provide an almost complete census of star-forming galaxies at z ≈

Chasing Lyman alpha-emitting galaxies at z = 8.8

With a total integration time of 168 hours and a narrowband (NB) filter tuned to Lyman alpha at z = 8.8, the UltraVISTA survey has set out to find some of the most distant galaxies, on the verge of the Epoch of Reionization. Previous calculations of the expected number of detected Lya-emitting galaxies (LAEs) at this redshift did not explicitly take into account the radiative transfer (RT) of Lya. In this work we combine a theoretical model for the halo mass function with numerical results from high-res cosmological hydrosimulations with LyC+Lya RT, assessing the visibility of LAEs residing in these halos. Uncertainties such as cosmic variance and the anisotropic escape of Lya are taken into account, and it is predicted that once the survey has finished, the probabilities of detecting none, one, or more than one are ~90%, ~10%, and ~1%; a significantly smaller success rate compared to earlier predictions, due to the combined effect of a highly neutral IGM scattering Lya to such large distances from the galaxy that they fall outside the observational aperture, and to the actual depth of the survey being less than predicted. Because the IGM affects NB and broadband (BB) magnitudes differently, we argue for a relaxed color selection criterion of NB - BB ~ +0.85. But since the flux is continuum-dominated, even if a galaxy is detectable in the NB its probability of being selected as a NB excess object is <~35%. Various properties of galaxies at this redshift are predicted, e.g. UV and Lya LFs, M*-Mh relation, spectral shape, optimal aperture, and the anisotropic escape of Lya through both a dusty ISM and a partly neutral IGM. Finally, we describe and publish a fast numerical code for adding numbers with asymmetric uncertainties ("x_{-sigma_1}^{+sigma_2}") proving to be significantly better than the standard, but wrong, way of adding upper and lower uncertainties in quadrature separately.Comment: Submitted to A&A, comments are welcom

Broadband UBVRI Photometry of Horizontal-Branch and Metal-Poor Candidates from the HK and Hamburg/ESO Surveys. I

We report broadband UBV and/or BVRI CCD photometry for a total of 1857 stars in the thick-disk and halo populations of the Galaxy. The majority of our targets were selected as candidate field horizontal-branch or other A-type stars (FHB/A, N = 576), or candidate low-metallicity stars (N = 1221), from the HK and Hamburg/ESO objective-prism surveys. Similar data for a small number of additional stars from other samples are also reported. These data are being used for several purposes. In the case of the FHB/A candidates they are used to accurately separate the lower-gravity FHB stars from various higher-gravity A-type stars, a subsample that includes the so-called Blue Metal Poor stars, halo and thick-disk blue stragglers, main-sequence A-type dwarfs, and Am and Ap stars. These data are also being used to derive photometric distance estimates to high-velocity hydrogen clouds in the Galaxy and for improved measurements of the mass of the Galaxy. Photometric data for the metal-poor candidates are being used to refine estimates of stellar metallicity for objects with available medium-resolution spectroscopy, to obtain distance estimates for kinematic analyses, and to establish initial estimates of effective temperature for analysis of high-resolution spectroscopy of the stars for which this information now exists.Comment: 22 pages, including 3 figures, 5 tables, and two ascii files of full data, accepted for publication in the Astrophysical Journal (Supplements

Broadband UBVR_CI_C Photometry of Horizontal-Branch and Metal-poor Candidates from the HK and Hamburg/ESO Surveys. I.

We report broadband UBV and/or BVR_CI_C CCD photometry for a total of 1857 stars in the thick-disk and halo populations of the Galaxy. The majority of our targets were selected as candidate field horizontal-branch or other A-type stars (FHB/A, N = 576), or candidate low-metallicity stars (N = 1221), from the HK and Hamburg/ESO objective-prism surveys. Similar data for a small number of additional stars from other samples are also reported. These data are being used for several purposes. In the case of the FHB/A candidates they are used to accurately separate the lower gravity FHB stars from various higher gravity A-type stars, a subsample that includes the so-called blue metal poor stars, halo and thick-disk blue stragglers, main-sequence A-type dwarfs, and Am and Ap stars. These data are also being used to derive photometric distance estimates to high-velocity hydrogen clouds in the Galaxy and for improved measurements of the mass of the Galaxy. Photometric data for the metal-poor candidates are being used to refine estimates of stellar metallicity for objects with available medium-resolution spectroscopy, to obtain distance estimates for kinematic analyses, and to establish initial estimates of effective temperature for analysis of high-resolution spectroscopy of the stars for which this information now exists

Towards an Intelligent Tutor for Mathematical Proofs

Computer-supported learning is an increasingly important form of study since it allows for independent learning and individualized instruction. In this paper, we discuss a novel approach to developing an intelligent tutoring system for teaching textbook-style mathematical proofs. We characterize the particularities of the domain and discuss common ITS design models. Our approach is motivated by phenomena found in a corpus of tutorial dialogs that were collected in a Wizard-of-Oz experiment. We show how an intelligent tutor for textbook-style mathematical proofs can be built on top of an adapted assertion-level proof assistant by reusing representations and proof search strategies originally developed for automated and interactive theorem proving. The resulting prototype was successfully evaluated on a corpus of tutorial dialogs and yields good results.Comment: In Proceedings THedu'11, arXiv:1202.453

Kinematics of the Galactic Halo from Horizontal Branch stars in the Hamburg/ESO Survey

Large samples of Field Horizontal Branch (FHB) stars make excellent tracers of the Galactic halo; by studying their kinematics, one can infer important physical properties of our Galaxy. Here we present the results of a medium-resolution spectroscopic survey of 530 FHB stars selected from the Hamburg/ESO survey. The stars have a mean distance of ~7 kpc and thus probe the inner parts of the Milky Way halo. We measure radial velocities from the spectra in order to test the model of Sommer-Larsen et al., who suggested that the velocity ellipsoid of the halo changes from radially-dominated orbits to tangentially-dominated orbits as one proceeds from the inner to the outer halo. We find that the present data are unable to discriminate between this model and a more simple isothermal ellipsoid; we suggest that additional observations towards the Galactic centre might help to differentiate them.Comment: 7 pages, 7 figures. Accepted for publication in MNRA

Long-term outcomes of the pentaspline pulsed field ablation catheter for the treatment of paroxysmal atrial fibrillation: Results of the prospective, multicenter FARA-Freedom Study.

INTRODUCTION/OBJECTIVES Pulmonary vein isolation (PVI) is well-established strategy for the treatment of paroxysmal atrial fibrillation (PAF). Despite randomized controlled trials and real-world data showing the promise of pulsed-field ablation (PFA) for this treatment, long term efficacy and safety data demonstrating single procedure outcomes off antiarrhythmic drugs remain limited. The aim of the FARA-Freedom Study was to evaluate long-term efficacy and safety of PFA using the pentaspline catheter for PAF. METHODS FARA-Freedom, a prospective, non-randomized, multicenter study, enrolled patients with PAF undergoing de novo PVI with PFA, which were followed for 12 months with weekly transtelephonic monitoring (TTMs) and 72-hr Holter ECG at 6 and 12 months. The primary safety endpoint was a composite of device- or procedure-related serious adverse events out to 7 days post-ablation and PV stenosis or atrioesophageal (AE) fistula out to 12 months. Treatment success is a composite of acute PVI and chronic success; which includes freedom from any documented atrial tachyarrhythmia longer than 30 s, use of antiarrhythmic drugs or cardioversion after a 3-month blanking period, or use of amiodarone or repeat ablation at any time. RESULTS The study enrolled 179 PAF patients (62 ± 10 yr, 39% female) at 13 centers. At index procedure, all PVs were successfully isolated with the pentaspline PFA catheter. Procedure and left atrial dwell times, with a 20 min waiting period, were 71.9 ± 17.6 and 41.0 ± 13.3 min, respectively. Fluoroscopy time was 11.5 ± 7.4 min. Notably, monitoring compliance was high with 88.4% and 90.3% with weekly event and 72-hour Holter monitors, respectively. Freedom from composite primary effectiveness endpoint was 66.6%, 41 patients had atrial tachyarrhythmia recurrence: mostly recurrent atrial fibrillation (31 patients). The composite safety endpoint occurred in 2 patients (1.1%), 1 tamponade and 1 TIA. There was no coronary spasm, PV stenosis, or AE fistula. There were 4 cases of transient phrenic nerve palsy, but all resolved during index procedure. CONCLUSIONS In this prospective, non-randomized, multicenter study, PVI using a pentaspline PFA catheter was effective in treating PAF patients despite rigorous endpoint definitions and high monitoring compliance and demonstrated favorable safety

Broadband UBVR C I C Photometry of Horizontal-branch and Metal-poor Candidates from the HK and Hamburg/ESO Surveys. I

We report broadband UBVand/or BVRCIC CCD photometry for a total of 1857 stars in the thick-disk and halo populations of the Galaxy. The majority of our targets were selected as candidate field horizontal-branch or other A-type stars (FHB/A, N = 576), or candidate low-metallicity stars (N =1221), from the HK and Hamburg/ESO objective-prism surveys. Similar data for a small number of additional stars from other samples are also reported. These data are being used for several purposes. In the case of the FHB/A candidates they are used to accurately separate the lower gravity FHB stars from various higher gravity A-type stars, a subsample that includes the so-called blue metal poor stars, halo and thick-disk blue stragglers, main-sequence A-type dwarfs, and Am and Ap stars. These data are also being used to derive photometric distance estimates to high-velocity hydrogen clouds in the Galaxy and for improved measurements of the mass of the Galaxy. Photometric data for the metal-poor candidates are being used to refine estimates of stellar metallicity for objects with available medium-resolution spectroscopy, to obtain distance estimates for kinematic analyses, and to establish initial estimates of effective temperature for analysis of high-resolution spectroscopy of the stars for which this information now exists

The Gut Microbiota Modulates Energy Metabolism in the Hibernating Brown Bear Ursus arctos

Hibernation is an adaptation that helps many animals to conserve energy during food shortage in winter. Brown bears double their fat depots during summer and use these stored lipids during hibernation. Although bears seasonally become obese, they remain metabolically healthy. We analyzed the microbiota of free-ranging brown bears during their active phase and hibernation. Compared to the active phase, hibernation microbiota had reduced diversity, reduced levels of Firmicutes and Actinobacteria, and increased levels of Bacteroidetes. Several metabolites involved in lipid metabolism, including triglycerides, cholesterol, and bile acids, were also affected by hibernation. Transplantation of the bear microbiota from summer and winter to germ-free mice transferred some of the seasonal metabolic features and demonstrated that the summer microbiota promoted adiposity without impairing glucose tolerance, suggesting that seasonal variation in the microbiota may contribute to host energy metabolism in the hibernating brown bear