A Census of White Dwarfs Within 40 Parsecs of the Sun

Our aim is to compile a catalog of white dwarfs within 40 parsecs of the Sun, in which newly discovered objects would significantly increase the completeness of the current census. White dwarf candidates are identified from the SUPERBLINK proper motion database (Lepine & Shara 2005), which allows us to investigate stars down to a proper motion limit as low as 40 mas yr-1. The selection criteria and distance estimates are based on a combination of color-magnitude and reduced proper motion diagrams. Candidates with distances less than 50 parsecs are selected for spectroscopic follow-up. We present our preliminary sample of spectroscopically confirmed white dwarfs, as well as their atmospheric parameters. These parameters are obtained using the spectroscopic technique developed in Bergeron et al.(1992) for DA stars. DB, DQ, and DZ stars are also analyzed spectroscopically. For featureless spectra as well as those showing only Halpha, we perform a detailed photometric analysis of their energy distribution.Comment: 4 pages, 3 figures, to appear in AIP Conference Proceedings for the 17th European White Dwarf Worksho

Dans le cadre d’une insertion socioprofessionnelle, systématisation de la dimension « lieu »

L'article fait l'historique de la dimension « lieu » intégrée au modèle Trèfle chanceux et précise la double utilisation qui en a été faite dans le cadre d'une recherche menée à l'aide de deux instruments visant l'identification des positions d'employabilité, soit le logiciel Copilote Insertion et une entrevue semi-structurée. Ont participé à l'expérimentation 88 sujets répartis selon le sexe, la formation et l'expérience du marché du travail. Dans la majorité des comparaisons, à la fois instrumentales et interdimensionnelles, les corrélations sont significatives au seuil de 0,01. Pour chaque instrument, les quatre dimensions spécifiques au modèle reflètent bien l'ensemble des résultats. Toutefois, comme aucune corrélation n'est significative entre les deux instruments relativement à la dimension « lieu », l'auteur propose, pour la corriger, une resystématisation du modèle.Within the frame of the development of the dimension "lieu" as part of the "Trèfle chanceux" model, this article reports on a study of two instruments aimed at identifying employability positions. These instruments, the program "Copilot insertion" and a semi-structured interview, were administered to 88 subjects classified according to sex, training, and workplace experience. The results show that for a majority of comparisons, both inter-instrumental and inter-dimensional, the correlations were significant at the 0.01 level. For each instrument, the four dimensions that are specific to the model reflected these general results. However, as no significant correlation was noted between the two instruments regarding the dimension "lieu', the author proposes a re-working of his model.Este articulo traza la historia de la dimension "lugar" integrada al modelo de "Trébol de la suerte" y précisa el doble uso que se le dio en un estudio que utilize dos instrumentos para identificar la posibilidad de lograr empleo: el programa informatico "Copilote Insertion" y una entrevista semi-estructurada. Ochenta y ocho sujetos partidparon en este estudio, repartidos segun el sexo, la formacion y la experiencia en el mercado de trabajo. En la mayoria de las comparaciones, a lavez interinstrumentales e interdimensionales, las correlaciones resultaron significativas a un nivel de 0,05. Para cada instrumento, las cuatro dimensiones especificas del modelo reflejan bien el conjunto de resultados. Sin embargo, como ninguna correlaciôn es signifîcativa entre los dos instrumentos usados para la dimension "lugar", el autor propone la resistematizacion del modelo para corregirlo.Dieser Artikel beschreibt kurz die Entwicklung der Dimension "Ort" innerhalb des Kleeblatt-MoàéXs und geht auf ihre doppelte Anwendung ein im Rahmen eines Forschungsprojektes, das mit Hilfe von zwei Mitteln der Identifizierung der Chancen bei der Arbeitssuche - das Programm "Copilote Insertion" und ein halbstrukturiertes Interview - durchgefuhrt wurde. Achtundachzig Teilnehmer wurden nach Geschlecht, Ausbildung und Erfahrungauf dem Arbeitsmarkt gegliedert. Die meisten gleichzeitig interinstrumentalen und interdimensionalen Vergleiche ergaben Korrelationen mit bei 0.01 liegender Signifikanz. Bei beiden Mitteln decken die vier modellspezifischen Dimensionen wie erwartet aile Erge-bnisse. Nur war keine Korrelation zwischen den beiden Mitteln hinsichtlich der Dimension "Ort" signifikant, was den Verfasser dazu fuhrt, eine neue Systematisierung dieser Dimension vorzuschlagen

The 1.17-day orbit of the double-degenerate (DA+DQ) NLTT 16249

New spectroscopic observations show that the double degenerate system NLTT 16249 is in a close orbit (a = 5.6+/-0.3 R_sun) with a period of 1.17 d. The total mass of the system is estimated between 1.47 and 2.04 M_sun but it is not expected to merge within a Hubble time-scale (t_merge ~ 10^11 yr). Vennes & Kawka (2012, ApJ, 745, L12) originally identified the system because of the peculiar composite hydrogen (DA class) and molecular (C_2--DQ class--and CN) spectra and the new observations establish this system as the first DA plus DQ close double degenerate. Also, the DQ component was the first of its class to show nitrogen dredged-up from the core in its atmosphere. The star may be viewed as the first known DQ descendant of the born-again PG1159 stars. Alternatively, the presence of nitrogen may be the result of past interactions and truncated evolution in a close binary system.Comment: published in ApJ Letter

Cohomology and products of real weight filtrations

39 pagesWe associate to each algebraic variety defined over $\mathbb{R}$ a filtered cochain complex, which computes the cohomology with compact supports and $\mathbb{Z}_2$-coefficients of the set of its real points. This filtered complex is additive for closed inclusions and acyclic for resolution of singularities, and is unique up to filtered quasi-isomorphism. It is represented by the dual filtration of the geometric filtration on semialgebraic chains with closed supports defined by McCrory and Parusi\'nski, and leads to a spectral sequence which computes the weight filtration on cohomology with compact supports. This spectral sequence is a natural invariant which contains the additive virtual Betti numbers. We then show that the cross product of two varieties allows us to compare the product of their respective weight complexes and spectral sequences with those of their product, and prove that the cup and cap products in cohomology and homology are filtered with respect to the real weight filtrations

Natural solution to antibiotic resistance: bacteriophages ‘The Living Drugs’

Antibiotics have been a panacea in animal husbandry as well as in human therapy for decades. The huge amount of antibiotics used to induce the growth and protect the health of farm animals has lead to the evolution of bacteria that are resistant to the drug’s effects. Today, many researchers are working with bacteriophages (phages) as an alternative to antibiotics in the control of pathogens for human therapy as well as prevention, biocontrol, and therapy in animal agriculture. Phage therapy and biocontrol have yet to fulfill their promise or potential, largely due to several key obstacles to their performance. Several suggestions are shared in order to point a direction for overcoming common obstacles in applied phage technology. The key to successful use of phages in modern scientific, farm, food processing and clinical applications is to understand the common obstacles as well as best practices and to develop answers that work in harmony with nature

A Comprehensive Spectroscopic Analysis of DB White Dwarfs

We present a detailed analysis of 108 helium-line (DB) white dwarfs based on model atmosphere fits to high signal-to-noise optical spectroscopy. We derive a mean mass of 0.67 Mo for our sample, with a dispersion of only 0.09 Mo. White dwarfs also showing hydrogen lines, the DBA stars, comprise 44% of our sample, and their mass distribution appears similar to that of DB stars. As in our previous investigation, we find no evidence for the existence of low-mass (M < 0.5 Mo) DB white dwarfs. We derive a luminosity function based on a subset of DB white dwarfs identified in the Palomar-Green survey. We show that 20% of all white dwarfs in the temperature range of interest are DB stars, although the fraction drops to half this value above Teff ~ 20,000 K. We also show that the persistence of DB stars with no hydrogen features at low temperatures is difficult to reconcile with a scenario involving accretion from the interstellar medium, often invoked to account for the observed hydrogen abundances in DBA stars. We present evidence for the existence of two different evolutionary channels that produce DB white dwarfs: the standard model where DA stars are transformed into DB stars through the convective dilution of a thin hydrogen layer, and a second channel where DB stars retain a helium-atmosphere throughout their evolution. We finally demonstrate that the instability strip of pulsating V777 Her white dwarfs contains no nonvariables, if the hydrogen content of these stars is properly accounted for.Comment: 74 pages including 30 figures, accepted for publication in the Astrophysical Journa