6,340 research outputs found

    Genetic Variation in Resistance of Scotch Pine to Zimmerman Pine Moth

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    (excerpt) Scotch pine (Pinus sylvestris L.), a forest tree introduced from Eurasia, is commonly planted for Christmas tree and timber use in northeastern United States. In this country it has numerous insect enemies. Among the most important are European pine shoot moth, Rhyacionia buoliana (Schiffermiieller); pine root collar weevil, Hylobius radicis Buchanan;,European pine sawfly, Neodiprion sertifer (Geoffroy); and eastern white-pine shoot borer, Eucosma gloriola Heinrich. Previous studies (Wright et al., 1967; Wright and Wilson, 1972; Steiner, 1974) have revealed large genetic differences in resistance to some of these pests. Another destructive pest is the Zimmerman pine moth, Dioryctria zimmermani (Grote). In 1968 this insect, native to the United States, was found attacking trees in a Scotch pine provenance test in southwestern Michigan. The attack rate was heavy and by 1973 it was obvious that some rams or varieties were attacked more heavily than others. This is a report on those differences

    The Brauer-Manin Obstruction and Sha[2].

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    We discuss the Brauer-Manin obstruction on del Pezzo surfaces of degree 4. We outline a detailed algorithm for computing the obstruction and provide associated programs in magma. This is illustrated with the computation of an example with an irreducible cubic factor in the singular locus of the defining pencil of quadrics (in contrast to previous examples, which had at worst quadratic irreducible factors). We exploit the relationship with the Tate-Shafarevich group to give new types of examples of Sha[2], for families of curves of genus 2 of the form y^2 = f(x), where f(x) is a quintic containing an irreducible cubic factor

    The RCB star V854 Cen is surrounded by a hot dusty shell

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    Aims : The hydrogen-deficient supergiants known as R Coronae Borealis (RCB) stars might be the result of a double-degenerate merger of two white dwarfs (WDs), or a final helium shell flash in a planetary nebula central star. In this context, any information on the geometry of their circumstellar environment and, in particular, the potential detection of elongated structures, is of great importance. Methods : We obtained near-IR observations of V854 Cen with the AMBER recombiner located at the Very Large Telescope Interferometer (VLTI) array with the compact array (B\leq35m) in 2013 and the long array (B\leq140m) in 2014. At each time, V854 Cen was at maximum light. The HH- and KK-band continua were investigated by means of spectrally dependant geometric models. These data were supplemented with mid-IR VISIR/VLT images. Results : A dusty slightly elongated over density is discovered both in the HH- and KK-band images. With the compact array, the central star is unresolved (Θ2.5\Theta\leq2.5\,mas), but a flattened dusty environment of 8×118 \times 11 mas is discovered whose flux increases from about \sim20% in the HH band to reach about \sim50% at 2.3\micron, which indicates hot (T\sim1500\,K) dust in the close vicinity of the star. The major axis is oriented at a position angle (P.A.) of 126±\pm29deg\deg. Adding the long-array configuration dataset provides tighter constraints on the star diameter (Θ1.0\Theta\leq1.0 mas), a slight increase of the overdensity to 12×1512 \times 15 mas and a consistent P.A. of 133±\pm49deg\deg. The closure phases, sensitive to asymmetries, are null and compatible with a centro-symmetric, unperturbed environment excluding point sources at the level of 3% of the total flux in 2013 and 2014. The VISIR images exhibit a flattened aspect ratio at the 15-20% level at larger distances (\sim1\arcsec) with a position angle of 92±\pm19deg\deg, marginally consistent with the interferometric observations. Conclusions : This is the first time that a moderately elongated structure has been observed around an RCB star. These observations confirm the numerous suggestions for a bipolar structure proposed for this star in the literature, which were mainly based on polarimetric and spectroscopic observations.Comment: Accepted by A\&A, new version after language editing, Astronomy and Astrophysics (2014

    V838 Monocerotis: the central star and its environment a decade after outburst

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    Aims. V838 Monocerotis erupted in 2002, brightened in a series of outbursts, and eventually developed a spectacular light echo. A very red star emerged a few months after the outburst. The whole event has been interpreted as the result of a merger. Methods. We obtained near-IR and mid-IR interferometric observations of V838 Mon with the AMBER and MIDI recombiners located at the Very Large Telescope Interferometer (VLTI) array. The MIDI two-beam observations were obtained with the 8m Unit Telescopes between October 2011 and February 2012. The AMBER three-beam observations were obtained with the compact array (B\leqm) in April 2013 and the long array (B\leq140m) in May 2014, using the 1.8m Auxiliary Telescopes. Results. A significant new result is the detection of a compact structure around V838 Mon, as seen from MIDI data. The extension of the structure increases from a FWHM of 25 mas at 8 {\mu}m to 70 mas at 13 {\mu}m. At the adopted distance of D = 6.1 ±\pm 0.6 kpc, the dust is distributed from about 150 to 400 AU around V838 Mon. The MIDI visibilities reveal a flattened structure whose aspect ratio increases with wavelength. The major axis is roughly oriented around a position angle of -10 degrees, which aligns with previous polarimetric studies reported in the literature. This flattening can be interpreted as a relic of the 2002 eruption or by the influence of the currently embedded B3V companion. The AMBER data provide a new diameter for the pseudo-photosphere, which shows that its diameter has decreased by about 40% in 10yrs, reaching a radius R_* = 750 ±\pm 200 R_{\odot} (3.5 ±\pm 1.0 AU). Conclusions. After the 2002 eruption, interpreted as the merging of two stars, it seems that the resulting source is relaxing to a normal state. The nearby environment exhibits an equatorial over-density of dust up to several hundreds of AU.Comment: Astronomy and Astrophysics (2014) Will be set by the publishe

    The professional socialisation of headteachers in England: Further findings from the National Headteacher Survey

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    This paper reports on a further investigation of data first accumulated through a national survey of headteachers conducted in 1999. The survey was conducted by means of a self-completion postal questionnaire with a stratified random sample of 10 per cent serving headteachers in England, totalling 2285 potential respondents in all. Completed returns were received from 1405 headteachers, an overall response rate of 62 per cent. Initial findings from the survey have subsequently been published as conference papers and journal articles (Male, 2000; Male and Hvizdak, 2000; Male and Male, 2001, Male 2001). The survey primarily sought to establish the respondents’ perceived state of readiness for the demands of the headteacher position in a number of job categories and competencies. A secondary aim was to allow respondents to attribute reasons to their state of readiness where they perceived it to be adequate or better. A third aim was to seek opinion from the respondents as to what provision and support would be beneficial to headteachers in their first two years in post. This further investigation has been commissioned by the National College for School Leadership and has been conducted by the original author, aided by two serving headteachers who have been appointed as research associates by the college during the period January to July of 2002

    Total column CO_2 measurements at Darwin, Australia – site description and calibration against in situ aircraft profiles

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    An automated Fourier Transform Spectroscopic (FTS) solar observatory was established in Darwin, Australia in August 2005. The laboratory is part of the Total Carbon Column Observing Network, and measures atmospheric column abundances of CO_2 and O_2 and other gases. Measured CO_2 columns were calibrated against integrated aircraft profiles obtained during the TWP-ICE campaign in January–February 2006, and show good agreement with calibrations for a similar instrument in Park Falls, Wisconsin. A clear-sky low airmass relative precision of 0.1% is demonstrated in the CO2 and O2 retrieved column-averaged volume mixing ratios. The 1% negative bias in the FTS X_(CO_2) relative to the World Meteorological Organization (WMO) calibrated in situ scale is within the uncertainties of the NIR spectroscopy and analysis

    New observations regarding deterministic, time-reversible thermostats and Gauss's principle of least constraint

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    Deterministic thermostats are frequently employed in nonequilibrium molecular dynamics simulations in order to remove the heat produced irreversibly over the course of such simulations. The simplest thermostat is the Gaussian thermostat, which satisfies Gauss's principle of least constraint and fixes the peculiar kinetic energy. There are of course infinitely many ways to thermostat systems, e.g., by fixing [summation]i|pi|嫱. In the present paper we provide, for the first time, convincing arguments as to why the conventional Gaussian isokinetic thermostat (影) is unique in this class. We show that this thermostat minimizes the phase space compression and is the only thermostat for which the conjugate pairing rule holds. Moreover, it is shown that for finite sized systems in the absence of an applied dissipative field, all other thermostats (囮ot-equal]1) perform work on the system in the same manner as a dissipative field while simultaneously removing the dissipative heat so generated. All other thermostats (囮ot-equal]1) are thus autodissipative. Among all 場hermostats, only the 影 Gaussian thermostat permits an equilibrium state.Full Tex

    Probiotic effects of lactic acid bacteria against Vibrio alginolyticus in Penaeus (Fenneropenaeus) indicus (H. Milne Edwards)

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    Cell free extracts of four strains of Lactic acid bacteria (LAB) viz. Lactobacillus. acidophilus, Streptococcus.cremoris, Lactobacillus bulgaricus –56 and Lactobacillus bulgaricus –57 inhibited growth of Vibrio alginolyticus in nutrient broth. The antagonism of LAB to Vibrio alginolyticus was further confirmed by streak plating wherein suppression of growth of Vibrio was obtained. Juveniles of Penaeus indicus (average weight 0.985 ± 0.1 g) on administering orally a moist feed base containing 5 × 106 cells·g of the four LAB probionts for a period of four weeks showed better survival (56 to 72%) when challenged with V. alginolyticus by intra-muscular injection of 0.1 ml containing 3 × 109 cells·ml. Animals maintained on a diet devoid of bacterial biomass exhibited 80% mortality
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