243 research outputs found
Irish Ocean Climate and Ecosystem Status Report 2009
This report presents the results from the most comprehensive analysis to date of marine climate change in Irish waters. Using a variety of available datasets from Ireland and elsewhere, the status of Ireland's marine climate is described. These data sets are collected over varying time scales. The longest datasets extend back to the late 1950s while others have been initiated in the past 5-10 years. In some cases data have been put in a wider context by comparison with international data such as the HADSST sea surface temperature analysis and the Continuous Plankton Recorder (CPR) survey conducted by the Sir Alister Hardy Foundation for Ocean Science (SAHFOS). While the analysis to date has been considerable the brevity of some of the time series means that in 2009 we are relatively poorly equipped to make conclusions as to how climate change will affect Irish waters. This report describes key regulators of ocean climate around Ireland and examines relevant environmental datasets available in 2009. It therefore represents the current status of knowledge regarding the influence of climate on Irelandâs marine ecosystems and resources
Cylindrically symmetric inhomogeneous dust collapse with a zero expansion component
We investigate a class of cylindrically symmetric inhomogeneous Î-dust
spacetimes which have a regular axis and some zero expansion component.
For Π\neq 0, we obtain new exact solutions to the Einstein equations and show
that they are unique, within that class. For Î = 0, we recover the Senovillaâ
Vera metric and show that it can be locally matched to an EinsteinâRosen type
of exterior. Finally, we explore some consequences of the matching, such as
trapped surface formation and gravitational radiation in the exterior.We thank Jose Senovilla for suggesting solutions of the form (8) and (9) and for other very useful comments which led to substancial improvements in the paper. IB and FM are supported by Portuguese Funds through Fundacao para a Cincia e Tecnologia (FCT), within the Projects UID/MAT/00013/2013 and PTDC/MAT-ANA/1275/2014. FM and NOS acknowledge a grant received from UERJ and thank the warm hospitality from Instituto de Fisica, UERJ, Rio de Janeiro, where a great part of this work was completed. MFAdaSilva acknowledges the financial support from FAPERJ (no. E-26/171.754/2000, E-26/171.533.2002, E-26/170.951/2006, E-26/110.432/2009 and E-26/111.714/2010), Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) Brazil (no. 450572/2009-9, 301973/2009-1 and 477268/2010-2) and Financiadora de Estudos e Projetos (FINEP) Brazil.info:eu-repo/semantics/publishedVersio
An Introduction to the Chandra Carina Complex Project
The Great Nebula in Carina provides an exceptional view into the violent
massive star formation and feedback that typifies giant HII regions and
starburst galaxies. We have mapped the Carina star-forming complex in X-rays,
using archival Chandra data and a mosaic of 20 new 60ks pointings using the
Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer, as a testbed for
understanding recent and ongoing star formation and to probe Carina's regions
of bright diffuse X-ray emission. This study has yielded a catalog of
properties of >14,000 X-ray point sources; >9800 of them have multiwavelength
counterparts. Using Chandra's unsurpassed X-ray spatial resolution, we have
separated these point sources from the extensive, spatially-complex diffuse
emission that pervades the region; X-ray properties of this diffuse emission
suggest that it traces feedback from Carina's massive stars. In this
introductory paper, we motivate the survey design, describe the Chandra
observations, and present some simple results, providing a foundation for the
15 papers that follow in this Special Issue and that present detailed catalogs,
methods, and science results.Comment: Accepted for the ApJS Special Issue on the Chandra Carina Complex
Project (CCCP), scheduled for publication in May 2011. All 16 CCCP Special
Issue papers are available at
http://cochise.astro.psu.edu/Carina_public/special_issue.html through 2011 at
least. 43 pages; 18 figure
Search for gamma-ray emission from magnetars with the Fermi Large Area Telescope
We report on the search for 0.1-10 GeV emission from magnetars in 17 months
of Fermi Large Area Telescope (LAT) observations. No significant evidence for
gamma-ray emission from any of the currently-known magnetars is found. The most
stringent upper limits to date on their persistent emission in the Fermi-LAT
energy range are estimated between ~10^{-12}-10^{-10} erg/s/cm2, depending on
the source. We also searched for gamma-ray pulsations and possible outbursts,
also with no significant detection. The upper limits derived support the
presence of a cut-off at an energy below a few MeV in the persistent emission
of magnetars. They also show the likely need for a revision of current models
of outer gap emission from strongly magnetized pulsars, which, in some
realizations, predict detectable GeV emission from magnetars at flux levels
exceeding the upper limits identified here using the Fermi-LAT observations.Comment: ApJ Letters in press; Corresponding authors: Caliandro G. A., Hadasch
D., Rea N., Burnett
Detection of Gamma-Ray Emission from the Starburst Galaxies M82 and NGC 253 with the Large Area Telescope on Fermi
We report the detection of high-energy gamma-ray emission from two starburst
galaxies using data obtained with the Large Area Telescope on board the Fermi
Gamma-ray Space Telescope. Steady point-like emission above 200 MeV has been
detected at significance levels of 6.8 sigma and 4.8 sigma respectively, from
sources positionally coincident with locations of the starburst galaxies M82
and NGC 253. The total fluxes of the sources are consistent with gamma-ray
emission originating from the interaction of cosmic rays with local
interstellar gas and radiation fields and constitute evidence for a link
between massive star formation and gamma-ray emission in star-forming galaxies.Comment: Submitted to ApJ Letter
Fermi Large Area Telescope observations of PSR J1836+5925
The discovery of the gamma-ray pulsar PSR J1836+5925, powering the formerly
unidentified EGRET source 3EG J1835+5918, was one of the early accomplishments
of the Fermi Large Area Telescope (LAT). Sitting 25 degrees off the Galactic
plane, PSR J1836+5925 is a 173 ms pulsar with a characteristic age of 1.8
million years, a spindown luminosity of 1.1 erg s, and a
large off-peak emission component, making it quite unusual among the known
gamma-ray pulsar population. We present an analysis of one year of LAT data,
including an updated timing solution, detailed spectral results and a long-term
light curve showing no indication of variability. No evidence for a surrounding
pulsar wind nebula is seen and the spectral characteristics of the off-peak
emission indicate it is likely magnetospheric. Analysis of recent XMM
observations of the X-ray counterpart yields a detailed characterization of its
spectrum, which, like Geminga, is consistent with that of a neutron star
showing evidence for both magnetospheric and thermal emission.Comment: Accepted to Astrophysical Journa
Fermi Gamma-ray Imaging of a Radio Galaxy
The Fermi Gamma-ray Space Telescope has detected the gamma-ray glow emanating
from the giant radio lobes of the radio galaxy Centaurus A. The resolved
gamma-ray image shows the lobes clearly separated from the central active
source. In contrast to all other active galaxies detected so far in high-energy
gamma-rays, the lobe flux constitutes a considerable portion (>1/2) of the
total source emission. The gamma-ray emission from the lobes is interpreted as
inverse Compton scattered relic radiation from the cosmic microwave background
(CMB), with additional contribution at higher energies from the
infrared-to-optical extragalactic background light (EBL). These measurements
provide gamma-ray constraints on the magnetic field and particle energy content
in radio galaxy lobes, and a promising method to probe the cosmic relic photon
fields.Comment: 27 pages, includes Supplementary Online Material; corresponding
authors: C.C. Cheung, Y. Fukazawa, J. Knodlseder, L. Stawar
A change in the optical polarization associated with a gamma-ray flare in the blazar 3C 279
It is widely accepted that strong and variable radiation detected over all
accessible energy bands in a number of active galaxies arises from a
relativistic, Doppler-boosted jet pointing close to our line of sight. The size
of the emitting zone and the location of this region relative to the central
supermassive black hole are, however, poorly known, with estimates ranging from
light-hours to a light-year or more. Here we report the coincidence of a
gamma-ray flare with a dramatic change of optical polarization angle. This
provides evidence for co-spatiality of optical and gamma-ray emission regions
and indicates a highly ordered jet magnetic field. The results also require a
non-axisymmetric structure of the emission zone, implying a curved trajectory
for the emitting material within the jet, with the dissipation region located
at a considerable distance from the black hole, at about 10^5 gravitational
radii.Comment: Published in Nature issued on 18 February 2010. Corresponding
authors: Masaaki Hayashida and Greg Madejsk
Evaluation of the Indications for Sentinel Node Biopsy in Early-Stage Melanoma with the Advent of Adjuvant Systemic Therapy: An International, Multicenter Study
Background
Patients presenting with early-stage melanoma (AJCC pT1b-pT2a) reportedly have a relatively low risk of a positive SNB (~5â10%). Those patients are usually found to have low-volume metastatic disease after SNB, typically reclassified to AJCC stage IIIA, with an excellent prognosis of ~90% 5-year survival. Currently, adjuvant systemic therapy is not routinely recommended for most patients with AJCC stage IIIA melanoma. The purpose was to assess the SN-positivity rate in early-stage melanoma and to identify primary tumor characteristics associated with high-risk nodal disease eligible for adjuvant systemic therapy
Methods
An international, multicenter retrospective cohort study from 7 large-volume cancer centers identified 3,610 patients with early primary cutaneous melanomas 0.8â2.0 mm in Breslow thickness (pT1b-pT2a; AJCC 8th edition). Patient demographics, primary tumor characteristics, and SNB status/details were analyzed.
Results
The overall SNB-positivity rate was 11.4% (412/3610). Virtually all SNB-positive patients (409/412; 99.3%) were reclassified to AJCC stage IIIA. Multivariate analysis identified age, T-stage, mitotic rate, primary site and subtype, and lymphovascular invasion as independent predictors of sentinel node status. A mitotic rate of >1/mm2 was associated with a significantly increased SN-positivity rate and was the only significant independent predictor of high-risk SNB metastases (>1 mm maximum diameter).
Conclusions
The new treatment paradigm brings into question the role of SNB for patients with early-stage melanoma. The results of this large international cohort study suggest that a reevaluation of the indications for SNB for some patients with early-stage melanoma is required
Older patients' attitudes towards and experiences of patient-physician end-of-life communication: a secondary analysis of interviews from British, Dutch and Belgian patients
<p>Abstract</p> <p>Background</p> <p>Older patients often experience sub-standard communication in the palliative phase of illness. Due to the importance of good communication in patient-centred end-of-life care, it is essential to understand the factors which influence older patientsâ communication with physicians. This study examines older patientsâ attitudes towards, and experiences of, patient-physician end-of-life (EoL) communication in three European countries.</p> <p>Methods</p> <p>A secondary analysis of interviews from British, Dutch and Belgian patients over the age of 60 with a progressive terminal illness was conducted. Cross-cutting themes were identified using a thematic approach.</p> <p>Results</p> <p>Themes from 30 interviews (Male nâ=â20, Median age 78.5) included: confidence and trust; disclosure and awareness; and participation in decision-making. Confidence and trust were reinforced by physiciansâ availability, time and genuine attention and hindered by misdiagnoses and poor communication style. Most participants preferred full disclosure, though some remained deliberately ill-informed to avoid distress. Patients expressed a variety of preferences for and experiences of involvement in medical EoL decision-making and a few complained that information was only provided about the physician's preferred treatment.</p> <p>Conclusions</p> <p>A variety of experiences and attitudes regarding disclosure and participation in decision-making were reported from each country, suggesting that communication preferences are highly individual. It is important that physicians are sensitive to this diversity and avoid stereotyping. In regard to communication style, physicians are advised to provide clear explanations, avoid jargon, and continually check understanding. Both the âinformedâ and the âsharedâ patient-physician decision-making models assume patients make rational choices based on a clear understanding of treatment options. This idealized situation was often not reflected in patientsâ experiences.</p
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