2,031 research outputs found
Physical properties of the jet from DG Tauri on sub-arcsecond scales with HST/STIS
We derive the physical properties at the base of the jet from DG Tau both
along and across the flow and as a function of velocity. We analysed seven
optical spectra of the DG Tau jet, taken with the Hubble Space Telescope
Imaging Spectrograph. The spectra were obtained by placing a long-slit parallel
to the jet axis and stepping it across the jet width. The resulting
position-velocity diagrams in optical forbidden emission lines allowed access
to plasma conditions via calculation of emission line ratios.
We find at the base of the jet high electron density, 10, and
very low ionisation, , which combine to give a total
density up to 3 10. This analysis confirms previous reports of
variations in plasma parameters along the jet, (i.e. decrease in density by
several orders of magnitude, increase of from 0.05 to a plateau at 0.7
downstream at 2 from the star). Furthermore, a spatial coincidence is
revealed between sharp gradients in the total density and supersonic velocity
jumps. This strongly suggests that the emission is caused by shock excitation.
The position-velocity diagrams indicate the presence of both fast accelerating
gas and slower, less collimated material. We derive the mass outflow rate,
, in the blue-shifted lobe in different velocity channels, that
contribute to a total of 8 4 10 M
yr. We estimate that a symmetric bipolar jet would transport at the low
and intermediate velocities probed by rotation measurements, an angular
momentum flux of 2.9 1.5 10 M yr
AU km s.
The derived properties of the DG Tau jet are demonstrated to be consistent
with magneto-centrifugal theory. However, non-stationary modelling is required
in order to explain all of the features revealed at high resolution.Comment: 16 pages, 18 figure
Digging in the megaproject's graveyard: Why do megaprojects die, and how to check their health?
The pressure to complete Infrastructure Megaprojects (IMs) is enormous; once started, IMs are commonly considered too costly to be stopped. Still, despite this widespread belief, several IMs are terminated during delivery/construction. Notwithstanding its empirical and theoretical relevance, few studies investigate IMs termination during delivery/construction. This paper aims to develop further the “reverse escalation of commitment” theory which sense-makes the termination of IMs. We take a critical confrontation of the existing literature addressing two questions: (1) Why are IMs terminated during delivery/construction? and (2) How does the project termination process occur in IMs? By analysing 30 unfinished IMs, we identified the six determinants for IMs termination, contributing to the development of reverse-escalation of commitment theory by providing a processual perspective of the four most common patterns leading to IMs termination. Finally, we provide a checklist for identifying key elements leading to IMs termination
Analysis of some global optimization algorithms for space trajectory design
In this paper, we analyze the performance of some global search algorithms on a number of space trajectory design problems. A rigorous testing procedure is introduced to measure the ability of an algorithm to identify the set of ²-optimal solutions. From the analysis of the test results, a novel algorithm is derived. The development of the novel algorithm starts from the redefinition of some evolutionary heuristics in the form of a discrete dynamical system. The convergence properties of this discrete dynamical system are used to derive a hybrid evolutionary algorithm that displays very good performance on the particular class of problems presented in this paper
Eficiência da irrigação e produtividade de feijão-caupi no cerrado Roraimense.
Suplemento. Edição dos Anais do 53 Congresso Brasileiro de Olericultura, jul. 2014
General practitioners' willingness to pay for continuing medical education in a fee-for-service universal coverage health care system [article]
Abstract: Background: Sponsoring of medical meetings by life science companies has led to reduced participation fees for physicians but questions potential drawbacks. Ongoing discussions are proposing to ban such sponsoring which may increase participation fees.
Objectives: To evaluate factors associated with general practitioners' willingness to pay for medical meetings, their support of a binding legislation prohibiting sponsoring and their opinion on alternative financing options.
Methods: An anonymous web-based questionnaire was sent to 447 general practitioners' of one state in Switzerland, identified through their affiliation to a medical association.
Results: Of the 115 physicians answering, 48% were willing to pay more than what they currently pay for medical meetings and 79% disagreed that sponsoring introduced a bias in their own prescription practices. In univariate analyses, factors most associated with physician's willingness to pay were perception of a bias in peers prescription practices (OR=6.67; 95% CI: 1.60-27.74), group practice (OR=3.01; 95% CI: 0.94-9.65) and having <4 meetings with sales representatives per month (OR=2.39; 95% CI: 0.91-6.33). 78% did not support the introduction of a binding legislation and 56% were in favor of creating a general fund set up by life science companies and centrally administered by an independent body as an alternative financing option.
Conclusions: Our results suggest that almost half of physicians surveyed were willing to pay more than what they currently pay for medical meetings and that an independent body that would centrally administer a general fund set up by life science companies might be better received by general practitioners' than a legislation banning the sponsoring of medical meetings by life science companies
Teste sorológico de imunofluorescência indireta para o diagnóstico da neosporose em bovinos.
Diagnóstico da neosporose. Métodos de diagnóstico sorológico. Reação de imunofluorescência indireta para Neospora caninum.bitstream/item/139526/1/COT-86.pdfCNPGC
Quantitative analysis of shadow X-ray Magnetic Circular Dichroism Photo-Emission Electron Microscopy
Shadow X-ray Magnetic Circular Dichroism Photo-Emission Electron Microscopy
(XMCD-PEEM) is a recent technique, in which the photon intensity in the shadow
of an object lying on a surface, may be used to gather information about the
three-dimensional magnetization texture inside the object. Our purpose here is
to lay the basis of a quantitative analysis of this technique. We first discuss
the principle and implementation of a method to simulate the contrast expected
from an arbitrary micromagnetic state. Text book examples and successful
comparison with experiments are then given. Instrumental settings are finally
discussed, having an impact on the contrast and spatial resolution : photon
energy, microscope extraction voltage and plane of focus, microscope background
level, electric-field related distortion of three-dimensional objects, Fresnel
diffraction or photon scattering
Publication trends of shared decision making in 15 high impact medical journals: a full-text review with bibliometric analysis.
BACKGROUND: Shared Decision Making (SDM) is increasingly advocated as a model for medical decision making. However, there is still low use of SDM in clinical practice. High impact factor journals might represent an efficient way for its dissemination. We aimed to identify and characterize publication trends of SDM in 15 high impact medical journals.
METHODS: We selected the 15 general and internal medicine journals with the highest impact factor publishing original articles, letters and editorials. We retrieved publications from 1996 to 2011 through the full-text search function on each journal website and abstracted bibliometric data. We included publications of any type containing the phrase "shared decision making" or five other variants in their abstract or full text. These were referred to as SDM publications. A polynomial Poisson regression model with logarithmic link function was used to assess the evolution across the period of the number of SDM publications according to publication characteristics.
RESULTS: We identified 1285 SDM publications out of 229,179 publications in 15 journals from 1996 to 2011. The absolute number of SDM publications by journal ranged from 2 to 273 over 16 years. SDM publications increased both in absolute and relative numbers per year, from 46 (0.32% relative to all publications from the 15 journals) in 1996 to 165 (1.17%) in 2011. This growth was exponential (P < 0.01). We found fewer research publications (465, 36.2% of all SDM publications) than non-research publications, which included non-systematic reviews, letters, and editorials. The increase of research publications across time was linear. Full-text search retrieved ten times more SDM publications than a similar PubMed search (1285 vs. 119 respectively).
CONCLUSION: This review in full-text showed that SDM publications increased exponentially in major medical journals from 1996 to 2011. This growth might reflect an increased dissemination of the SDM concept to the medical community
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