4,591 research outputs found
Soft Manifold Dynamics Behind Negative Thermal Expansion
Minimal models are developed to examine the origin of large negative thermal
expansion (NTE) in under-constrained systems. The dynamics of these models
reveals how underconstraint can organize a thermodynamically extensive manifold
of low-energy modes which not only drives NTE but extends across the Brillioun
zone. Mixing of twist and translation in the eigenvectors of these modes, for
which in ZrW2O8 there is evidence from infrared and neutron scattering
measurements, emerges naturally in our model as a signature of the dynamics of
underconstraint.Comment: 5 pages, 3 figure
Deformations of Fuchsian Systems of Linear Differential Equations and the Schlesinger System
We consider holomorphic deformations of Fuchsian systems parameterized by the
pole loci. It is well known that, in the case when the residue matrices are
non-resonant, such a deformation is isomonodromic if and only if the residue
matrices satisfy the Schlesinger system with respect to the parameter. Without
the non-resonance condition this result fails: there exist non-Schlesinger
isomonodromic deformations. In the present article we introduce the class of
the so-called isoprincipal deformations of Fuchsian systems. Every isoprincipal
deformation is also an isomonodromic one. In general, the class of the
isomonodromic deformations is much richer than the class of the isoprincipal
deformations, but in the non-resonant case these classes coincide. We prove
that a deformation is isoprincipal if and only if the residue matrices satisfy
the Schlesinger system. This theorem holds in the general case, without any
assumptions on the spectra of the residue matrices of the deformation. An
explicit example illustrating isomonodromic deformations, which are neither
isoprincipal nor meromorphic with respect to the parameter, is also given
Copyright and cultural work: an exploration
This article first discusses the contemporary debate on cultural âcreativityâ and the economy. Second, it considers the current state of UK copyright law and how it relates to cultural work. Third, based on empirical research on British dancers and musicians, an analysis of precarious cultural work is presented. A major focus is how those who follow their art by way of âportfolioâ work handle their rights in ways that diverge significantly from the current simplistic assumptions of law and cultural policy. Our conclusions underline the distance between present top-down conceptions of what drives production in the cultural field and the actual practice of dancers and musicians
Body mass index, abdominal fatness, fat mass and the risk of atrial fibrillation: a systematic review and doseâresponse meta-analysis of prospective studies
Different adiposity measures have been associ- ated with increased risk of atrial fibrillation, however, results have previously only been summarized for BMI. We therefore conducted a systematic review and meta- analysis of prospective studies to clarify the association between different adiposity measures and risk of atrial fibrillation. PubMed and Embase databases were searched up to October 24th 2016. Summary relative risks (RRs) were calculated using random effects models. Twenty-nine unique prospective studies (32 publications) were included. Twenty-five studies (83,006 cases, 2,405,381 participants) were included in the analysis of BMI and atrial fibrillation. The summary RR was 1.28 (95% confidence interval: 1.20â1.38, I 2 = 97%) per 5 unit increment in BMI, 1.18 (95% CI: 1.12â1.25, I 2 = 73%, n = 5) and 1.32 (95% CI: 1.16â1.51, I 2 = 91%, n = 3) per 10 cm increase in waist and hip circumference, respectively, 1.09 (95% CI: 1.02â1.16, I 2 = 44%, n = 4) per 0.1 unit increase in waist- to-hip ratio, 1.09 (95% CI: 1.02â1.16, I 2 = 94%, n = 4) per 5 kg increase in fat mass, 1.10 (95% CI: 0.92â1.33, I 2 = 90%, n = 3) per 10% increase in fat percentage, 1.10 (95% CI: 1.08â1.13, I 2 = 74%, n = 10) per 5 kg increase in weight, and 1.08 (95% CI: 0.97â1.19, I 2 = 86%, n = 2) per 5% increase in weight gain. The association between BMI and atrial fibrillation was non- linear, p nonlinearity \ 0.0001, with a stronger association at higher BMI levels, however, increased risk was observed even at a BMI of 22â24 compared to 20. In conclusion, general and abdominal adiposity and higher body fat mass increase the risk of atrial fibrillation
Substantiating a political public sphere in the Scottish press : a comparative analysis
This article uses content analysis to characterize the performance of the media in a national public sphere, by setting apart those qualities that typify internal press coverage of a political event. The article looks at the coverage of the 1999 devolved Scottish election from the day before the election until the day after. It uses a word count to measure the election material in Scottish newspapers the Herald, the Press and Journal and the Scotsman, and United Kingdom newspapers the Guardian, the Independent and The Times, and categorizes that material according to discourse type, day and page selection. The article finds a number of qualities that typify the Scottish sample in particular, and might be broadly indicative of a political public sphere in action. Firstly, and not unexpectedly, it finds that the Scottish newspapers carry significantly more election coverage. Just as tellingly, though, the article finds that the Scottish papers offer a greater proportion of advice and background information, in the form of opinion columns and feature articles. It also finds that the Scottish papers place a greater concentration of both informative and evaluative material in the period before the vote, consistent with their making a contribution to informed political action. Lastly, the article finds that the Scottish sample situates coverage nearer the front of the paper and places a greater proportion on recto pages. The article therefore argues that the Scottish papers display features that distinguish them from the UK papers, and are broadly consistent with their forming part of a deliberative public sphere, and suggests that these qualities might be explored as a means of judging future media performance
Non-Fermi liquid behavior of SrRuO_3 -- evidence from infrared conductivity
The reflectivity of the itinerant ferromagnet SrRuO_3 has been measured
between 50 and 25,000 cm-1 at temperatures ranging from 40 to 300 K, and used
to obtain conductivity, scattering rate, and effective mass as a function of
frequency and temperature. We find that at low temperatures the conductivity
falls unusually slowly as a function of frequency (proportional to
\omega^{-1/2}), and at high temperatures it even appears to increase as a
function of frequency in the far-infrared limit. The data suggest that the
charge dynamics of SrRuO_3 are substantially different from those of
Fermi-liquid metals.Comment: 4 pages, 3 postscript figure
Programming Protocol-Independent Packet Processors
P4 is a high-level language for programming protocol-independent packet
processors. P4 works in conjunction with SDN control protocols like OpenFlow.
In its current form, OpenFlow explicitly specifies protocol headers on which it
operates. This set has grown from 12 to 41 fields in a few years, increasing
the complexity of the specification while still not providing the flexibility
to add new headers. In this paper we propose P4 as a strawman proposal for how
OpenFlow should evolve in the future. We have three goals: (1)
Reconfigurability in the field: Programmers should be able to change the way
switches process packets once they are deployed. (2) Protocol independence:
Switches should not be tied to any specific network protocols. (3) Target
independence: Programmers should be able to describe packet-processing
functionality independently of the specifics of the underlying hardware. As an
example, we describe how to use P4 to configure a switch to add a new
hierarchical label
Measuring the vertical age structure of the Galactic disc using asteroseismology and SAGA
The existence of a vertical age gradient in the Milky Way disc has been
indirectly known for long. Here, we measure it directly for the first time with
seismic ages, using red giants observed by Kepler. We use Stroemgren photometry
to gauge the selection function of asteroseismic targets, and derive colour and
magnitude limits where giants with measured oscillations are representative of
the underlying population in the field. Limits in the 2MASS system are also
derived. We lay out a method to assess and correct for target selection effects
independent of Galaxy models. We find that low mass, i.e. old red giants
dominate at increasing Galactic heights, whereas closer to the Galactic plane
they exhibit a wide range of ages and metallicities. Parametrizing this as a
vertical gradient returns approximately 4 Gyr/kpc for the disc we probe,
although with a large dispersion of ages at all heights. The ages of stars show
a smooth distribution over the last 10 Gyr, consistent with a mostly quiescent
evolution for the Milky Way disc since a redshift of about 2. We also find a
flat age-metallicity relation for disc stars. Finally, we show how to use
secondary clump stars to estimate the present-day intrinsic metallicity spread,
and suggest using their number count as a new proxy for tracing the ageing of
the disc. This work highlights the power of asteroseismology for Galactic
studies; however, we also emphasize the need for better constraints on stellar
mass-loss, which is a major source of systematic age uncertainties in red giant
stars.Comment: MNRAS, accepted. SAGA website and data at
http://www.mso.anu.edu.au/saga/data_access.htm
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Beyond the Refugee Crisis how the UK news media represent asylum seekers across national boundaries
Migration is one of the most pressing, divisive issues in global politics today, and media play a crucial role in how communities understand and respond. This study examines how UK newspapers (n = 974) and popular news websites (n = 1044) reported on asylum seekers throughout 2017. It contributes to previous literature in two important ways. First, by examining the ânew normalâ of daily news coverage in the wake of the 2015 ârefugee crisisâ in Europe. Second, by looking at how asylum seekers from different regions are represented. The content analysis finds significant variations in how asylum seekers are reported, including terminology use and topics they are associated with. The paper also identifies important commonalities in how all asylum seekers are represented - most notably, the dominance of political elites as sources across all media content. It argues that Entmanâs âcascade network modelâ can help to explain this, with elites in one country able to influence transnational reports
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