47,922 research outputs found
An imaging and spectroscopic study of the planetary nebulae in NGC 5128 (Centaurus A): Planetary nebulae catalogues
Imaging and spectroscopic observations of planetary nebulae (PNe) in the
nearest large elliptical galaxy NGC 5128 (Centaurus A), were obtained to find
more PNe and measure their radial velocities. NTT imaging was obtained in 15
fields in NGC 5128 over an area of about 1 square degree with EMMI using [O
III] and off-band filters. Newly detected sources, combined with literature
PNe, were used as input for VLT FLAMES multi-fibre spectroscopy in MEDUSA mode.
Spectra of the 4600-5100A region were analysed and velocities measured based on
emission lines of [O III]4959,5007A and often H-beta. The chief results are
catalogues of 1118 PN candidates and 1267 spectroscopically confirmed PNe in
NGC 5128. The catalogue of PN candidates contains 1060 PNe discovered with EMMI
imaging and 58 from literature surveys. The spectroscopic PN catalogue has
FLAMES radial velocity and emission line measurements for 1135 PNe, of which
486 are new. Another 132 PN radial velocities are available from the
literature. For 629 PNe observed with FLAMES, H-beta was measured in addition
to [O III]. Nine targets show double-lined or more complex profiles, and their
possible origin is discussed. FLAMES spectra of 48 globular clusters were also
targetted: 11 had emission lines detected (two with multiple components), but
only 3 are PNe likely to belong to the host globular. The total of 1267
confirmed PNe in NGC 5128 with radial velocity measurements (1135 with small
velocity errors) is the largest collection of individual kinematic probes in an
early-type galaxy. This PN dataset, as well as the catalogue of PN candidates,
are valuable resources for detailed investigation of the stellar population of
NGC 5128. [Abridged]Comment: 19 pages, 11 figures. Accepted for publication in Astronomy and
Astrophysics. Tables 7 - 11 available in electronic form at CDS. Replaced
with a few typos fixe
A Content Analysis of Youth Internet Safety Programs: Are Effective Prevention Strategies Being Used?
ABSTRACT: Almost half of youth in the U.S. report receiving internet safety education (ISE) in their schools. Unfortunately, we know little about what educational messages make a difference in problems such as cyberbullying, sexting, or online predators. To consider directions for improving effectiveness, a content analysis was conducted on materials from four ISE programs. Results indicate that ISE programs are mostly not incorporating proven educational strategies. Common ISE messages have proliferated without a clear rationale for why they would be effective. It is recommended that program developers and other stakeholders reconsider ISE messages, improve educational strategies, and participate in evaluation. The field must also consider whether ISE messages would be better delivered through broader youth safety prevention programs versus stand-alone lessons
Trauma and repair in the museum: an introduction
Despite its considerable investment in questions of memory, attachments between subjects and objects, and trauma and its treatment, psychoanalysis has been largely sidelined in the unfolding reassessment of museums. This introduction to the special issue on ‘Trauma and Repair in the Museum’, which aims to reintroduce psychoanalytic perspectives in these debates, outlines the issues around reparation that surround the modern museum due to the traumatic legacies of coloniality. Timothy P. Brown’s notion of how the trauma of displacement and dissociation effects both objects and communities is key to our consideration of the museum as symptomatic of trauma, as is Cathy Caruth’s reading of history as trauma. Referring to several artists’ practices, such as Lisa Reihana, Erika Tan, and especially Kader Attia’s concept of repair, as well as a number of museological approaches to restitution, we expand on the complexities of ongoing coloniality and its implication with museums as institutions, practices of collection and display, and highly charged psychoactive spaces. Eve Kosofsky Sedgwick’s rereading of Melanie Klein’s notion of reparation allows us to posit a form of decolonial repair that involves the assembling of damaged part-objects into ‘something like a whole [but] not necessarily like any preexisting whole’ (2003, p. 128, original emphasis). This approach enables a reckoning with trauma and its legacies that keeps them visible without ruling out processes of reparation. We follow our outline of trauma and repair in the museum with summaries of our contributors’ articles, which expose and unpack the mutual implication of collections, institutions and displays with patriarchy, colonialism and racial capitalism through the critical discourse of contestation, while also acknowledging the potential of museums to overcome their traumatic origins
A Systematic Review of Effective Youth Prevention Education: Implications for Internet Safety Education.
ABSTRACT: Over the past two decades, a wide array of internet safety education materials and programs have developed to increase positive youth behavior and safety online. Although it is a new area of prevention, programs should incorporate practices that prior prevention evaluation studies tell us work best. To inform internet safety education, 31 youth prevention education meta-analyses across a wide range of youth prevention (substance abuse, risky sex behavior, delinquency, etc.) were coded to identify prevention program characteristics shown by research to be most effective. The review identified that active, skill-based lessons, focused on research based causal and risk factors, and provided with adequate dosage were key. Such strategies must be included as a starting place when developing prevention in new areas of youth risk concerns. Implications of the finding suggest some need for reevaluating how internet safety education is delivered in the future
HeI in the central Giant HII Region of NGC 5253. A 2D observational approach to collisional and radiative transfer effects
ABRIDGED: NGC5253 is an ideal laboratory for detailed studies of starburst
galaxies. We present for the first time in a starburst galaxy a 2D study of the
spatial behavior of collisional and radiative transfer effects in He^+. The HeI
lines are analysed based on data obtained with FLAMES and GMOS. Collisional
effects are negligible for transitions in the singlet cascade while relatively
important for those in the triplet cascade. In particular, they can contribute
up to 20% of the flux in the HeIl7065 line. Radiative transfer effects are
important over an extended and circular area of 30pc in diameter centered at
the Super Star Clusters. HeI abundance, y^+, has been mapped using extinction
corrected fluxes of six HeI lines, realistic assumptions for T_e, n_e, and the
stellar absorption equivalent width as well as the most recent emissivities. We
found a mean of 10^3 y^+ ~80.3 over the mapped area. The relation between the
excitation and the total helium abundance, y_tot, is consistent with no
abundance gradient. Uncertainties in the derivation of He abundances are
dominated by the adopted assumptions. We illustrated the difficulty of
detecting a putative He enrichment due to the presence of Wolf-Rayet stars in
the main GHIIR. Data are marginally consistent with an excess in the N/He ratio
in the N enriched area of the order of both, the atmospheric N/He ratios in WR
stars and the uncertainties estimated for the N/He ratios.Comment: Accepted in Astronomy and Astrophysics; the emissivities presented in
the Corrigendum, Porter et al. 2013, arXiv:1303.5115, have been include
Kinematics of a hot massive accretion disk candidate
Characterizing rotation, infall and accretion disks around high-mass
protostars is an important topic in massive star formation research. With the
Australia Telescope Compact Array and the Very Large Array we studied a massive
disk candidate at high angular resolution in ammonia (NH3(4,4) & (5,5)) tracing
the warm disk but not the envelope. The observations resolved at ~0.4''
resolution (corresponding to ~1400AU) a velocity gradient indicative of
rotation perpendicular to the molecular outflow. Assuming a Keplerian accretion
disk, the estimated protostar-disk mass would be high, similar to the
protostellar mass. Furthermore, the position-velocity diagram exhibits
additional deviation from a Keplerian rotation profile which may be caused by
infalling gas and/or a self-gravitating disk. Moreover, a large fraction of the
rotating gas is at temperatures >100K, markedly different to typical low-mass
accretion disks. In addition, we resolve a central double-lobe cm continuum
structure perpendicular to the rotation. We identify this with an ionized,
optically thick jet.Comment: 5 pages, 3 figures, accepted for Astrophysical Journal Letters, a
high-resolution version of the draft can be found at
http://www.mpia.de/homes/beuther/papers.htm
Review of operational aspects of initial experiments utilizing the U.S. MLS
An exercise to support the Federal Aviation Administration in demonstrating the U.S. candidate for an international microwave landing system (MLS) was conducted by NASA. During this demonstration the MLS was utilized to provide the TCV Boeing 737 research airplane with guidance for automatic control during transition from conventional RNAV to MLS RNAV in curved, descending flight; flare; touchdown; and roll-out. Flight profiles, system configuration, displays, and operating procedures used in the demonstration are described, and preliminary results of flight data analysis are discussed. Recent experiences with manually controlled flight in the NAFEC MLS environment are also discussed. The demonstration shows that in automatic three-dimensional flight, the volumetric signal coverage of the MLS can be exploited to enable a commercial carrier class airplane to perform complex curved, descending paths with precision turns into short final approaches terminating in landing and roll-out, even when subjected to strong and gusty tail and cross wind components and severe wind shear
A comparison of Olpidium isolates from a range of host plants using internal transcribed spacer sequence analysis and host range studies
Olpidium brassicae is a ubiquitous obligate root-infecting fungal pathogen. It is an important vector of a wide range of plant viruses. Olpidium isolates that infected brassica plants did not infect lettuce plants and vice-versa. Host range tests, PCR amplification and sequencing of the internal transcribed spacer (ITS) and 5.8S regions of 25 Olpidium isolates from brassica, carrot, cucumber and lettuce originating from four continents revealed differences between isolates. Based on their ability to infect lettuce and brassicas and the differences between their ITS1, 5.8S and ITS2 regions they could be separated into a number of distinct groups. Comparisons with other published sequences revealed two distinct genetic groups of brassica-infecting isolates, two distinct groups of lettuce-infecting isolates, one of which contained a carrot-infecting isolate and a distinct group comprising a cucumber-infecting isolate and a melon-infecting isolate. The possibility of the isolates belonging to three distinct species is discussed
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