2,533 research outputs found

    WSRT and VLA Observations of the 6 cm and 2 cm lines of H2CO in the direction of W 58 C1(ON3) and W 58 C2

    Get PDF
    Absorption in the J{K-K+} = 2{11}-2{12} transition of formaldehyde at 2 cm towards the ultracompact HII regions C1 and C2 of W 58 has been observed with the VLA with an angular resolution of ~0.2'' and a velocity resolution of ~1 km/s. The high resolution continuum image of C1 (ON 3) shows a partial shell which opens to the NE. Strong H2CO absorption is observed against W 58 C1. The highest optical depth (tau > 2) occurs in the SW portion of C1 near the edge of the shell, close to the continuum peak. The absorption is weaker towards the nearby, more diffuse compact HII region C2, tau<~0.3. The H2CO velocity (-21.2 km/s) towards C1 is constant and agrees with the velocity of CO emission, mainline OH masers, and the H76 alpha recombination line, but differs from the velocity of the 1720 MHz OH maser emission (~-13 km/s). Observations of the absorption in the J{K-K+} = 1{10}-1{11} transition of formaldehyde at 6 cm towards W 58 C1 and C2 carried out earlier with the WSRT at lower resolution (~4''x7'') show comparable optical depths and velocities to those observed at 2 cm. Based on the mean optical depth profiles at 6 cm and 2 cm, the volume density of molecular hydrogen n(H2) and the formaldehyde column density N(H2CO) were determined. The n(H2) is ~6E4 /cm**3 towards C1. N(H2CO) for C1 is ~8E14 /cm**2 while that towards C2 is ~8E13 /cm**2.Comment: AJ in press Jan 2001, 14 pages plus 6 figures (but Fig. 1 has 4 separate parts, a through d). Data are available at http://adil.ncsa.uiuc.edu/document/00.HD.0

    Ionized Gas Kinematics and Morphology in Sgr B2 Main on 1000 AU Scales

    Full text link
    We have imaged the Sgr B2 Main region with the Very Large Array in the BnA configuration (θbeam\theta_{beam} = 0\farcs13) in both the H52α\alpha (45.453 GHz) radio recombination line (RRL) and 7 mm continuum emission. At a distance of 8500 pc, this spatial resolution corresponds to a physical scale of 0.005 pc (\sim1100 AU). The current observations detect H52α\alpha emission in 12 individual ultracompact (UC) and hypercompact (HC) HII regions. Two of the sources with detected H52 α\alpha emission have broad (Δ\DeltaVFWHM_{FWHM}\sim50 \kms) recombination lines, and two of the sources show lines with peaks at more than one velocity. We use line parameters from the H52α\alpha lines and our previous H66α\alpha line observations to determine the relative contribution of thermal, pressure and kinematic broadening, and electron density. These new observations suggest that pressure broadening can account for the broad lines in some of the sources, but that gas motions (e.g. turbulence, accretion or outflow) contribute significantly to the broad lines in at least one of the sources (Sgr B2 F3).Comment: 10 pages, 2 figure

    Scale and intensity of intertidal habitat use by knots Calidris canutus in the Western Wadden Sea in relation to food, friends and foes

    Get PDF
    In August-October 1988-1992 we studied the distribution and abundance of knots Calidris canutus around Griend in the western Wadden Sea, and the extent to which these can be explained by benthic prey availability and presence of avian predators. Numbers in the nonbreeding season showed monthly averages of 10000 to 25000 birds. Over 100000 knots were recorded on three occasions. Knots feed in large flocks, individual birds usually experiencing 4000 to 15000 flock-mates. The Siberian-breeding/west-African wintering canutus subspecies passed through in late July and early August. Otherwise the Greenlandic/Canadian breeding islandica subspecies was present. Over the period 1964-1992 there were no clear trends in the number of knots, but canutus-knots were particularly abundant in July-August 1991, whereas in 1992 both subspecies were absent. Macoma balthica was the preferred prey of both subspecies. Hydrobia ulvae, Mytilus edulis and Cerastoderma edule were eaten when Macoma was absent close to the surface of the sediment. As Macoma buried deeper from July onwards, canutus faced better average feeding conditions than islandica later in the year. The spatial distribution of knots feeding on the intertidal flats around Griend was best explained by the harvestable biomass of the prevalent prey species in a particular year and season, i.e. Macoma (main prey when their harvestable biomass densities were greater than ca 0.8 g AFDM per m2) and Cerastoderma, and by the avoidance of situations where they run the risk of attack by bird-eating birds. Flocks of knots covered most of the intertidal flats in the western Dutch Wadden Sea in a couple of tidal cycles. This is about 800 km2, much larger than the equivalent area used by knots on their wintering grounds in Mauritania (10-15 km2), a difference that is correlated with prey spectrum, prey availability and predictability.

    VLA Limits for Intermediate Mass Black Holes in Three Globular Clusters

    Full text link
    The observational evidence for central black holes in globular clusters has been argued extensively, and their existence has important consequences for both the formation and evolution of the cluster. Most of the evidence comes from dynamical arguments, but the interpretation is difficult, given the short relaxation times and old ages of the clusters. One of the most robust signatures for the existence of a black hole is radio and/or X-ray emission. We observed three globular clusters, NGC6093 (M80), NGC6266 (M62), and NGC7078 (M15), with the VLA in the A and C configuration with a 3-sigma noise of 36, 36 and 25 microJy, respectively. We find no statistically-significant evidence for radio emission from the central region for any of the three clusters. NGC6266 shows a 2-sigma detection. It is difficult to infer a mass from these upper limits due to uncertainty about the central gas density, accretion rate, and accretion model.Comment: 5 pages, accepted for publication in the Astronomical Journa

    Why Local Party Leaders Don't Support Nominating Centrists

    Get PDF
    Would giving party leaders more influence in primary elections in the United States decrease elite polarization? Some scholars have argued that political party leaders tend to support centrist candidates in the hopes of winning general elections. In contrast, the authors argue that many local party leaders - especially Republicans - may not believe that centrists perform better in elections and therefore may not support nominating them. They test this argument using data from an original survey of 1,118 county-level party leaders. In experiments, they find that local party leaders most prefer nominating candidates who are similar to typical co-partisans, not centrists. Moreover, given the choice between a more centrist and more extreme candidate, they strongly prefer extremists: Democrats do so by about 2 to 1 and Republicans by 10 to 1. Likewise, in open-ended questions, Democratic Party leaders are twice as likely to say they look for extreme candidates relative to centrists; Republican Party leaders are five times as likely. Potentially driving these partisan differences, Republican leaders are especially likely to believe that extremists can win general elections and overestimate the electorate's conservatism by double digits

    Flickering of 1.3 cm Sources in Sgr B2: Towards a Solution to the Ultracompact HII Region Lifetime Problem

    Full text link
    Accretion flows onto massive stars must transfer mass so quickly that they are themselves gravitationally unstable, forming dense clumps and filaments. These density perturbations interact with young massive stars, emitting ionizing radiation, alternately exposing and confining their HII regions. As a result, the HII regions are predicted to flicker in flux density over periods of decades to centuries rather than increasing monotonically in size as predicted by simple Spitzer solutions. We have recently observed the Sgr B2 region at 1.3 cm with the VLA in its three hybrid configurations (DnC, CnB and BnA) at a resolution of 0.25''. These observations were made to compare in detail with matched continuum observations from 1989. At 0.25'' resolution, Sgr B2 contains 41 UC HII regions, 6 of which are hypercompact. The new observations of Sgr B2 allow comparison of relative peak flux densites for the HII regions in Sgr B2 over a 23 year time baseline (1989-2012) in one of the most source-rich massive star forming regions in the Milky Way. The new 1.3 cm continuum images indicate that four of the 41 UC HII regions exhibit significant changes in their peak flux density, with one source (K3) dropping in peak flux density, and the other 3 sources (F10.303, F1 and F3) increasing in peak flux density. The results are consistent with statistical predictions from simulations of high mass star formation, suggesting that they offer a solution to the lifetime problem for ultracompact HII regions.Comment: 12 pages, 3 figures, Accepted for publication in the Astrophysical Journal Letter

    Memórias de um sobrevivente e o direito: o sistema penal em discurso

    Get PDF
    Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Jurídicas. Programa de Pós-Graduação em DireitoO presente trabalho tem como objeto o estudo da relação entre literatura e direito, mais especificamente o sistema penal. A evolução do pensamento sobre o crime é abordada por seus principais pensadores e obras, com mais ênfase nas correntes críticas da Criminologia. No campo da literatura, a obra Memórias de um Sobrevivente destaca-se entre aquelas escritas de oriundos das prisões paulistas. Preocupada em mostrar a dissociação entre o que a teoria prevê e a prática impõe, vários narradores procuraram fazer relatos fiéis do que se passa atrás das grades. Dentro dessa literatura, destacam-se os testemunhos de presos das casas de detenção paulistas, que seguem as tradições do testemunho mundial, mas inovam na maneira de abordar o assunto, porque operam a partir do marginalizado, ou seja, são produzidos pelos próprios encarcerados.The present work has as its object the study of the relationship between literature and law, specifically the criminal justice system. The evolution of thinking about crime is addressed by leading thinkers and their works, with more amphasis on critical currents of Criminology. In literature, the book Memorias de um Sobrevivente stands among those written from prison in São Paulo. Keen to show the dissociation between what the theory predicts and requires practice, several narrators sought to faithful accounts of what goes on behind bars. Within this literature, we highlight the testimonies of prisoners from detention facilities in São Paulo, following the traditions of the witnessing world but innovated in the way ofapproaching the subject, because they operate from themarginalized, or are produced by the prisoners

    Below ground interactions for sustainable cropping systems.

    Get PDF
    Key aspects of cropping systems are described in terms of their impacts on soil, water and air resources. The importance of microbial symbiotic relations with crop plants are briefly considered in the context of nutrient resource use efficiency and the resilience of plants to biotic and abiotic stress. It is argued that cropping systems need to include crops with fibrous root systems and legumes in the rotation to ensure sustainable use of resources. Three series of experiments are discussed that considered how the efficacy of rhizobia and indigenous arbuscular mycorrhizal fungi could be enhanced in sustainable cropping systems. Evidence is presented to demonstrate that there are potential benefits to crop production from improved management of soil resources through the adoption of reduced tillage practices coupled with suitable crop rotation and weed control
    corecore