1,824 research outputs found
Newspaper competition and content diversity: a comparison of regional media markets in Sweden
This article discusses the relationship between the newspaper market structure in a region and the diversity of local news. It introduces some partial results on studies based on substantial media concentration within two very different regional newspaper markets in the North and in the South of Sweden. The findings suggest that the relationship between newspaper competition and local news diversity is rather complicated. The study gives some support to the thought that ruinous competition sometimes could be as bad for news diversity as monopoly media
Effects of Cutoff Functions of Tersoff Potentials on Molecular Dynamics Simulations of Thermal Transport
Past molecular dynamics studies of thermal transport have predominantly used
Stillinger-Weber potentials. As materials continuously shrink, their properties
increasingly depend on defect and surface effects. Unfortunately,
Stillinger-Weber potentials are best used for diamond-cubic-like bulk crystals.
They cannot represent the energies of many metastable phases, nor can they
accurately predict the energetics of defective and surface regions. To study
nanostructured materials, where these regions can dominate thermal transport,
the accuracy of Tersoff potentials in representing these structures is more
desirable. Based upon an analysis of thermal transport in a GaN system, we
demonstrate that the cutoff function of the existing Tersoff potentials may
lead to problems in determining the thermal conductivity. To remedy this issue,
improved cutoff schemes are proposed and evaluated
Newspaper competition and content diversity: a comparison of regional media markets in Sweden
This article discusses the relationship between the newspaper market structure in a region and the diversity of local news. It introduces some partial results on studies based on substantial media concentration within two very different regiona newspaper markets in the North and in the South of Sweden. The findings suggest that the relationship between newspaper competition and local news diversity is rather complicated. The study gives some support to the thought that ruinous competition sometimes could be as bad for news diversity as monopoly media.Este artículo trata sobre la relación entre la estructura de mercado regional para los periódicos impresos y la diversidad de las noticias locales. Presenta los resultados parciales de algunos estudios basados en la concentración de medios impresos en dos mercados regionales muy diferentes en el Norte y el Sur de Suecia. Los hallazgos sugieren que la relación entre la competencia entre los diarios y la diversidad de las noticias locales es más bien compleja. El estudio sustenta, asimismo, la idea de que la competencia destructiva en ocasiones puede ser tan negativa para la diversidad en la información como los mercados monopolísticos
Strategy for reliable strain measurement in InAs/GaAs materials from high-resolution Z-contrast STEM images
Geometric phase analysis (GPA), a fast and simple Fourier space method for strain analysis, can give useful information on accumulated strain and defect propagation in multiple layers of semiconductors, including quantum dot materials. In this work, GPA has been applied to high resolution Z-contrast scanning transmission electron microscopy (STEM) images. Strain maps determined from different g vectors of these images are compared to each other, in order to analyze and assess the GPA technique in terms of accuracy. The SmartAlign tool has been used to improve the STEM image quality getting more reliable results. Strain maps from template matching as a real space approach are compared with strain maps from GPA, and it is discussed that a real space analysis is a better approach than GPA for aberration corrected STEM images
The L_X--M relation of Clusters of Galaxies
We present a new measurement of the scaling relation between X-ray luminosity
and total mass for 17,000 galaxy clusters in the maxBCG cluster sample.
Stacking sub-samples within fixed ranges of optical richness, N_200, we measure
the mean 0.1-2.4 keV X-ray luminosity, , from the ROSAT All-Sky Survey.
The mean mass, , is measured from weak gravitational lensing of SDSS
background galaxies (Johnston et al. 2007). For 9 <= N_200 < 200, the data are
well fit by a power-law, /10^42 h^-2 erg/s = (12.6+1.4-1.3 (stat) +/- 1.6
(sys)) (/10^14 h^-1 M_sun)^1.65+/-0.13. The slope agrees to within 10%
with previous estimates based on X-ray selected catalogs, implying that the
covariance in L_X and N_200 at fixed halo mass is not large. The luminosity
intercent is 30%, or 2\sigma, lower than determined from the X-ray flux-limited
sample of Reiprich & Bohringer (2002), assuming hydrostatic equilibrium. This
difference could arise from a combination of Malmquist bias and/or systematic
error in hydrostatic mass estimates, both of which are expected. The intercept
agrees with that derived by Stanek et al. (2006) using a model for the
statistical correspondence between clusters and halos in a WMAP3 cosmology with
power spectrum normalization sigma_8 = 0.85. Similar exercises applied to
future data sets will allow constraints on the covariance among optical and hot
gas properties of clusters at fixed mass.Comment: 5 pages, 1 figure, MNRAS accepte
Towards More Accurate Molecular Dynamics Calculation of Thermal Conductivity. Case Study: GaN Bulk Crystals
Significant differences exist among literature for thermal conductivity of
various systems computed using molecular dynamics simulation. In some cases,
unphysical results, for example, negative thermal conductivity, have been
found. Using GaN as an example case and the direct non-equilibrium method,
extensive molecular dynamics simulations and Monte Carlo analysis of the
results have been carried out to quantify the uncertainty level of the
molecular dynamics methods and to identify the conditions that can yield
sufficiently accurate calculations of thermal conductivity. We found that the
errors of the calculations are mainly due to the statistical thermal
fluctuations. Extrapolating results to the limit of an infinite-size system
tend to magnify the errors and occasionally lead to unphysical results. The
error in bulk estimates can be reduced by performing longer time averages using
properly selected systems over a range of sample lengths. If the errors in the
conductivity estimates associated with each of the sample lengths are kept
below a certain threshold, the likelihood of obtaining unphysical bulk values
becomes insignificant. Using a Monte-Carlo approach developed here, we have
determined the probability distributions for the bulk thermal conductivities
obtained using the direct method. We also have observed a nonlinear effect that
can become a source of significant errors. For the extremely accurate results
presented here, we predict a [0001] GaN thermal conductivity of 185 at 300 K, 102 at 500 K, and 74
at 800 K. Using the insights obtained in the work, we have achieved a
corresponding error level (standard deviation) for the bulk (infinite sample
length) GaN thermal conductivity of less than 10 , 5 , and 15 at 300 K, 500 K, and 800 K respectively
Nonthermal Emission from the Arches Cluster (G0.121+0.017) and the Origin of -ray Emission from 3EG J1746-2851
High resolution VLA observations of the Arches cluster near the Galactic
center show evidence of continuum emission at 3.6, 6, 20 and 90cm. The
continuum emission at 90cm is particularly striking because thermal
sources generally become optically thick at longer wavelengths and fall off in
brightness whereas non-thermal sources increase in brightness. It is argued
that the radio emission from this unique source has compact and diffuse
components produced by thermal and nonthermal processes, respectively. Compact
sources within the cluster arise from stellar winds of mass-losing stars (Lang,
Goss & Rodriguez 2001a) whereas diffuse emission is likely to be due to
colliding wind shocks of the cluster flow generating relativistic particles due
to diffuse shock acceleration. We also discuss the possibility that
-ray emission from 3EG J1746--2851, located within 3.3 of the Arches
cluster, results from the inverse Compton scattering of the radiation field of
the cluster.Comment: 15 pages, four figures, ApJL (in press
New Nonthermal Filaments at the Galactic Center: Are They Tracing a Globally Ordered Magnetic Field?
New high-resolution, wide-field 90 cm VLA observations of the Galactic center (GC) region by Nord and coworkers have revealed 20 nonthermal filament (NTF) candidates. We report 6 cm polarization observations of six of these. All of the candidates have the expected NTF morphology, and two show extended polarization, confirming their identification as NTFs. One of the new NTFs appears to be part of a system of NTFs located in the Sgr B region, 64 pc in projection north of Sgr A. These filaments cross the Galactic plane with an orientation similar to the filaments in the Galactic center radio arc. They extend the scale over which the NTF phenomena is known to occur to almost 300 pc along the Galactic plane. Another NTF was found in the Galactic plane south of the Sgr C filament but with an orientation of 45° to the Galactic plane. This is only the second of 12 confirmed NTFs that is not oriented perpendicular to the Galactic plane. An additional candidate in the Sgr C region was resolved into multiple filamentary structures. Polarization was detected only at the brightness peak of one of the filaments. Several of these filaments run parallel to the Galactic plane and can be considered additional evidence for nonpoloidal magnetic fields at the GC. Together the 90 and 6 cm observations indicate that the GC magnetic field may be more complex than a simple globally ordered dipolar field
The social value of a QALY : raising the bar or barring the raise?
Background: Since the inception of the National Institute for Health and Clinical Excellence (NICE) in England,
there have been questions about the empirical basis for the cost-per-QALY threshold used by NICE and whether
QALYs gained by different beneficiaries of health care should be weighted equally. The Social Value of a QALY
(SVQ) project, reported in this paper, was commissioned to address these two questions. The results of SVQ were
released during a time of considerable debate about the NICE threshold, and authors with differing perspectives
have drawn on the SVQ results to support their cases. As these discussions continue, and given the selective use of
results by those involved, it is important, therefore, not only to present a summary overview of SVQ, but also for
those who conducted the research to contribute to the debate as to its implications for NICE.
Discussion: The issue of the threshold was addressed in two ways: first, by combining, via a set of models, the
current UK Value of a Prevented Fatality (used in transport policy) with data on fatality age, life expectancy and
age-related quality of life; and, second, via a survey designed to test the feasibility of combining respondents’
answers to willingness to pay and health state utility questions to arrive at values of a QALY. Modelling resulted in
values of £10,000-£70,000 per QALY. Via survey research, most methods of aggregating the data resulted in values
of a QALY of £18,000-£40,000, although others resulted in implausibly high values. An additional survey, addressing
the issue of weighting QALYs, used two methods, one indicating that QALYs should not be weighted and the
other that greater weight could be given to QALYs gained by some groups.
Summary: Although we conducted only a feasibility study and a modelling exercise, neither present compelling
evidence for moving the NICE threshold up or down. Some preliminary evidence would indicate it could be
moved up for some types of QALY and down for others. While many members of the public appear to be open to
the possibility of using somewhat different QALY weights for different groups of beneficiaries, we do not yet have
any secure evidence base for introducing such a system
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