5,150 research outputs found
Extragalactic Planetary Nebulae: Observational Challenges & Future Prospects
The study of extragalactic planetary nebulae (EPN) is a rapidly expanding
field. The advent of powerful new instrumentation such as the PN spectrograph
has led to an avalanche of new EPN discoveries both within and between
galaxies. We now have thousands of EPN detections in a heterogeneous selection
of nearby galaxies and their local environments, dwarfing the combined galactic
detection efforts of the last century. Key scientific motivations driving this
rapid growth in EPN research and discovery have been the use of the PNLF as a
standard candle, as dynamical tracers of their host galaxies and dark matter
and as probes of Galactic evolution. This is coupled with the basic utility of
PN as laboratories of nebula physics and the consequent comparison with theory
where population differences, abundance variations and star formation history
within and between stellar systems informs both stellar and galactic evolution.
Here we pose some of the burning questions, discuss some of the observational
challenges and outline some of the future prospects of this exciting,
relatively new, research area as we strive to go fainter, image finer, see
further and survey faster than ever before and over a wider wavelength regimeComment: 4 pages, no figures, LaTeX, to be published in Proceedings of the ESO
workshop on Planetary Nebulae beyond the Milky Way held at ESO, Garching, May
19-21, 200
Flesh on the Bones: Animal Bodies in Atlantic Roundhouses
This volume presents the state of research across Europe to illustrate how comparable interpretative frameworks are used by archaeologists working with both prehistoric and historical societies
Central Stars of Planetary Nebulae in Galactic Open Clusters: Providing additional data for the White Dwarf Initial-to-Final-Mass Relation
Accurate (<10%) distances of Galactic star clusters allow precise estimation
of the physical parameters of any physically associated Planetary Nebula (PN)
and also that of its central star (CSPN) and its progenitor. The progenitor's
mass can be related to the PN's chemical characteristics and furthermore,
provides additional data for the widely used white dwarf (WD) initial-to-final
mass relation (IFMR) that is crucial for tracing the development of both carbon
and nitrogen in entire galaxies. To date there is only one PN (PHR1315- 6555)
confirmed to be physically associated with a Galactic open cluster (ESO 96
-SC04) that has a turn-off mass 2 M. Our deep HST photometry
was used for the search of the CSPN of this currently unique PN. In this work,
we present our results.Comment: 2 pages, 1 figure, IAU343 Synposiu
The Unusual Variability of the Large Magellanic Cloud Planetary Nebula RPJ 053059-683542
We present images and light curves of the bipolar Planetary Nebula RPJ
053059-683542 that was discovered in the Reid-Parker AAO/UKST H-alpha survey of
the Large Magellanic Cloud (LMC). The emission from this object appears
entirely nebular, with the central star apparently obscured by a central band
of absorption that bisects the nebula. The light curves, which were derived
from images from the SuperMACHO project at CTIO, showed significant, spatially
resolved variability over the period 2002 January through 2005 December.
Remarkably, the emission from the two bright lobes of the nebula vary either
independently, or similarly but with a phase lag of at least one year. The
optical spectra show a low level of nebular excitation, and only modest N
enrichment. Infrared photometry from the 2MASS and SAGE surveys indicates the
presence of a significant quantity of dust. The available data imply that the
central star has a close binary companion, and that the system has undergone
some kind of outburst event that caused the nebular emission to first brighten
and then fade. Further monitoring, high-resolution imaging, and detailed IR
polarimetry and spectroscopy would uncover the nature of this nebula and the
unseen ionizing source.Comment: Accepted for ApJ Letters; 6 page
Response to Letter from Wong on determining the target difference in sample size calculations for randomised controlled trials.
Recommended from our members
Implementing a perioperative efficiency initiative for orthopedic surgery instrumentation at an academic center: A comparative before-and-after study.
Optimizing surgical instrumentation may contribute to value-based care, particularly in commonly performed procedures. We report our experience in implementing a perioperative efficiency program in 2 types of orthopedic surgery (primary total-knee arthroplasty, TKA, and total-hip arthroplasty, THA).A comparative before-and-after study with 2 participating surgeons, each performing both THA and TKA, was conducted. Our objective was to evaluate the effect of surgical tray optimization on operating and processing time, cost, and waste associated with preparation, delivery, and staging of sterile surgical instruments. The study was designed as a prospective quality improvement initiative with pre- and postimplementation operational measures and a provider satisfaction survey.A total of 96 procedures (38 preimplementation and 58 postimplementation) were assessed using time-stamped performance endpoints. The number and weight of trays and instruments processed were reduced substantially after the optimization intervention, particularly for TKA. Setup time was reduced by 23% (6 minutes, P = .01) for TKA procedures but did not differ for THA. The number of survey respondents was small, but satisfaction was high overall among personnel involved in implementation.Optimizing instrumentation trays for orthopedic procedures yielded reduction in processing time and cost. Future research should evaluate patient outcomes and incremental/additive impact on institutional quality measures
Confirmation of New Planetary Nebulae in the Large Magellanic Cloud
We present Hubble Space Telescope (HST) images of new planetary nebulae (PNe)
that were discovered in the Reid-Parker AAO/UKST H-alpha survey of the Large
Magellanic Cloud. These serendipitous observations from various HST programs
yield independent confirmations of 6 PNe; one other detected nebula may also be
a PN, and one appears to be a region of diffuse emission. The high resolution
HST archival images enable us to determine the physical sizes, the nebular
morphology, and related features of these new PNe in detail for the first time.
In a few cases we were also able to identify the central star, which was
impossible with the lower resolution, wide-field discovery data. The
confirmation of faint, extended halos surrounding many PNe in the RP catalog
must await the acquisition of new deep, high-resolution, narrow-band imagery.Comment: 6 figures. To appear in PASP, 2007 Januar
Evidence for quantum confinement in the photoluminescence of porous Si and SiGe
We have used anodization techniques to process porous surface regions in p-type Czochralski Si and in p-type Si0.85Ge0.15 epitaxial layers grown by molecular beam epitaxy. The SiGe layers were unrelaxed before processing. We have observed strong near-infrared and visible light emission from both systems. Analysis of the radiative and nonradiative recombination processes indicate that the emission is consistent with the decay of excitons localized in structures of one or zero dimensions
Stability of empathy among undergraduate medical students: a longitudinal study at one UK medical school.
BACKGROUND: Empathy is important to patient care. The prevailing view is that empathy declines during university medical education. The significance of that decline has been debated.This paper reports the findings in respect of two questions relating to university medical education: 1. Do men and women medical students differ in empathy? 2. Does empathy change amongst men and women over time? METHODS: The medical course at the University of Cambridge comprises two components: Core Science (Years 1-3) and Clinical (Years 4-6). Data were obtained from repeated questionnaire surveys of medical students from each component over a period of four years: 2007-2010. Participation in the study was voluntary.Empathy was measured using two subscales of the Interpersonal Reactivity Index: IRI-EC (affective empathy) and IRI-PT (cognitive empathy). We analysed data separately for men and women from the Core Science and Clinical components. We undertook missing value analyses using logistic regression separately, for each measure of empathy, to examine non-response bias. We used Student's t-tests to examine gender differences and linear mixed effects regression analyses to examine changes over time. To assess the influence of outliers, we repeated the linear mixed effects regression analyses having excluded them. RESULTS: Women displayed statistically significant higher mean scores than men for affective empathy in all 6 years of medical training and for cognitive empathy in 4 out of 6 years - Years 1 and 2 (Core Science component) and Years 4 and 5 (Clinical component).Amongst men, affective empathy declined slightly during both Core Science and Clinical components. Although statistically significant, both of these changes were extremely small. Cognitive empathy was unchanged during either component. Amongst women, neither affective empathy nor cognitive empathy changed during either component of the course.Analysis following removal of outliers showed a statistically significant slight increase in men's cognitive empathy during the Core Science component and slight decline in women's affective empathy during the Clinical component. Again, although statistically significant, these changes were extremely small and do not influence the study's overall conclusions. CONCLUSIONS: Amongst medical students at the University of Cambridge, women are more empathetic than men (a generally observed phenomenon). Men's affective empathy declined slightly across the course overall, whilst women's affective empathy showed no change. Neither men nor women showed any change in cognitive empathy during the course. Although statistically significant, the size of such changes as occurred makes their practical significance questionable. Neither men nor women appear to become meaningfully less empathetic during their medical education at the University of Cambridge.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are
Neutron spectroscopy as a tool in catalytic science
Catalytic science currently has access to a range of advanced experimental methods for the study of molecular behaviour in chemical processes. Neutron spectroscopy, however, is uniquely placed to gain detailed insight into such systems, particularly through techniques such as vibrational spectroscopy with neutrons (INS) which gives access to vibrational modes unavailable to conventional spectroscopy techniques, and quasielastic neutron scattering (QENS) which studies molecular motion on a range of timescales. The present article illustrates the role of these techniques in advancing the field of catalysis. We first provide a brief introduction to the basic principles of the techniques, and then discuss their use in the study of three key catalytic systems: the behaviour of hydrocarbons confined in zeolite catalysts; the methanol-to-hydrocarbons process; and methane reforming. We demonstrate the importance of neutron spectroscopy in understanding established catalytic processes, but also consider its role in the design of future catalytic systems
- …