316 research outputs found
Theory of the c-Axis Penetration Depth in the Cuprates
Recent measurements of the London penetration depth tensor in the cuprates
find a weak temperature dependence along the c-direction which is seemingly
inconsistent with evidence for d-wave pairing deduced from in-plane
measurements. We demonstrate in this paper that these disparate results are not
in contradiction, but can be explained within a theory based on incoherent
quasiparticle hopping between the CuO2 layers. By relating the calculated
temperature dependence of the penetration depth \lambda_c(T) to the c-axis
resistivity, we show how the measured ratio \lambda_c^2(0) / \lambda_c^2(T) can
provide insight into the behavior of c-axis transport below Tc and the related
issue of ``confinement.''Comment: 4 pages, REVTEX with psfig, 3 PostScript figures included in
compressed for
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At the extremes of exclusion: Deportation, detention and dispersal
Deportation, detention and dispersal have formed an occasional part of Britain's migration regime throughout the twentieth century, though they tended to be used in response to particular events or “crises”. By the end of the twentieth century, however, deportation, detention and, most recently, dispersal have become “normalized”, “essential” instruments in the ongoing attempt to control or manage immigration to Britain. This article outlines the use of detention, deportation and dispersal in the twentieth century exploring how they have evolved and then become an integral part of the migration regime into the twenty-first century. Where appropriate, British practices are compared with those of its European neighbours, where to differing degrees, deportation, detention and dispersal have also become everyday practices. In examining these practices in Britain, we consider the rationale and stated aims of their employment, as well as describing some of the consequences, where known, of detention, deportation and dispersal
Discovery of very high energy gamma rays from PKS 1424+240 and multiwavelength constraints on its redshift
We report the first detection of very-high-energy (VHE) gamma-ray emission
above 140 GeV from PKS 1424+240, a BL Lac object with an unknown redshift. The
photon spectrum above 140 GeV measured by VERITAS is well described by a power
law with a photon index of 3.8 +- 0.5_stat +- 0.3_syst and a flux normalization
at 200 GeV of (5.1 +- 0.9_stat +- 0.5_syst) x 10^{-11} TeV^-1 cm^-2 s^-1, where
stat and syst denote the statistical and systematical uncertainty,
respectively. The VHE flux is steady over the observation period between MJD
54881 and 55003 (2009 February 19 to June 21). Flux variability is also not
observed in contemporaneous high energy observations with the Fermi Large Area
Telescope (LAT). Contemporaneous X-ray and optical data were also obtained from
the Swift XRT and MDM observatory, respectively. The broadband spectral energy
distribution (SED) is well described by a one-zone synchrotron self-Compton
(SSC) model favoring a redshift of less than 0.1. Using the photon index
measured with Fermi in combination with recent extragalactic background light
(EBL) absorption models it can be concluded from the VERITAS data that the
redshift of PKS 1424+240 is less than 0.66.Comment: accepted for publication, Ap
Green function techniques in the treatment of quantum transport at the molecular scale
The theoretical investigation of charge (and spin) transport at nanometer
length scales requires the use of advanced and powerful techniques able to deal
with the dynamical properties of the relevant physical systems, to explicitly
include out-of-equilibrium situations typical for electrical/heat transport as
well as to take into account interaction effects in a systematic way.
Equilibrium Green function techniques and their extension to non-equilibrium
situations via the Keldysh formalism build one of the pillars of current
state-of-the-art approaches to quantum transport which have been implemented in
both model Hamiltonian formulations and first-principle methodologies. We offer
a tutorial overview of the applications of Green functions to deal with some
fundamental aspects of charge transport at the nanoscale, mainly focusing on
applications to model Hamiltonian formulations.Comment: Tutorial review, LaTeX, 129 pages, 41 figures, 300 references,
submitted to Springer series "Lecture Notes in Physics
Does social capital travel? Influences on the life satisfaction of young people living in England and Spain
<p>Abstract</p> <p>Background</p> <p>This study used a social capital framework to examine the relationship between a set of potential protective ('health assets') factors and the wellbeing of 15 year adolescents living in Spain and England. The overall purpose of the study was to compare the consistency of these relationships between countries and to investigate their respective relative importance.</p> <p>Methods</p> <p>Data were drawn from the 2002, English and Spanish components of the WHO Health Behaviour in School-Aged Children (HBSC) survey A total of 3,591 respondents (1884, Spain; 1707, England) aged 15, drawn from random samples of students in 215 and 80 schools respectively were included in the study. A series of univariate, bivariate and multivariate (general linear modelling and decision tree) analyses were used to establish the relationships.</p> <p>Results</p> <p>Results showed that the wellbeing of Spanish and English adolescents is similar and good. Three measures of social capital and 2 measures of social support were found to be important factors in the general linear model. Namely, family autonomy and control; family and school sense of belonging; and social support at home and school. However, there were differences in how the sub components of social capital manifest themselves in each country--feelings of autonomy of control, were more important in England and social support factors in Spain.</p> <p>Conclusions</p> <p>There is some evidence to suggest that social capital (and its related concept of social support) do travel and are applicable to young people living in Spain and England. Given the different constellation of assets found in each country, it is not possible to define exactly the precise formula for applying social capital across cultures. This should more appropriately be defined at the programme planning stage.</p
The Discovery of gamma-Ray Emission From The Blazar RGB J0710+591
The high-frequency-peaked BL Lacertae object RGB J0710+591 was observed in
the very high-energy (VHE; E > 100 GeV) wave band by the VERITAS array of
atmospheric Cherenkov telescopes. The observations, taken between 2008 December
and 2009 March and totaling 22.1 hr, yield the discovery of VHE gamma rays from
the source. RGB J0710+591 is detected at a statistical significance of 5.5
standard deviations (5.5{\sigma}) above the background, corresponding to an
integral flux of (3.9 +/- 0.8) x 10-12 cm-2 s-1 (3% of the Crab Nebula's flux)
above 300 GeV. The observed spectrum can be fit by a power law from 0.31 to 4.6
TeV with a photon spectral index of 2.69 +/- 0.26stat +/- 0.20sys. These data
are complemented by contemporaneous multiwavelength data from the Fermi Large
Area Telescope, the Swift X-ray Telescope, the Swift Ultra-Violet and Optical
Telescope, and the Michigan-Dartmouth-MIT observatory. Modeling the broadband
spectral energy distribution (SED) with an equilibrium synchrotron self-Compton
model yields a good statistical fit to the data. The addition of an
external-Compton component to the model does not improve the fit nor brings the
system closer to equipartition. The combined Fermi and VERITAS data constrain
the properties of the high-energy emission component of the source over 4
orders of magnitude and give measurements of the rising and falling sections of
the SED
A composite transcriptional signature differentiates responses towards closely related herbicides in Arabidopsis thaliana and Brassica napus
In this study, genome-wide expression profiling based on Affymetrix ATH1 arrays was used to identify discriminating responses of Arabidopsis thaliana to five herbicides, which contain active ingredients targeting two different branches of amino acid biosynthesis. One herbicide contained glyphosate, which targets 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), while the other four herbicides contain different acetolactate synthase (ALS) inhibiting compounds. In contrast to the herbicide containing glyphosate, which affected only a few transcripts, many effects of the ALS inhibiting herbicides were revealed based on transcriptional changes related to ribosome biogenesis and translation, secondary metabolism, cell wall modification and growth. The expression pattern of a set of 101 genes provided a specific, composite signature that was distinct from other major stress responses and differentiated among herbicides targeting the same enzyme (ALS) or containing the same chemical class of active ingredient (sulfonylurea). A set of homologous genes could be identified in Brassica napus that exhibited a similar expression pattern and correctly distinguished exposure to the five herbicides. Our results show the ability of a limited number of genes to classify and differentiate responses to closely related herbicides in A. thaliana and B. napus and the transferability of a complex transcriptional signature across species
Semiconductor Spintronics
Spintronics refers commonly to phenomena in which the spin of electrons in a
solid state environment plays the determining role. In a more narrow sense
spintronics is an emerging research field of electronics: spintronics devices
are based on a spin control of electronics, or on an electrical and optical
control of spin or magnetism. This review presents selected themes of
semiconductor spintronics, introducing important concepts in spin transport,
spin injection, Silsbee-Johnson spin-charge coupling, and spindependent
tunneling, as well as spin relaxation and spin dynamics. The most fundamental
spin-dependent nteraction in nonmagnetic semiconductors is spin-orbit coupling.
Depending on the crystal symmetries of the material, as well as on the
structural properties of semiconductor based heterostructures, the spin-orbit
coupling takes on different functional forms, giving a nice playground of
effective spin-orbit Hamiltonians. The effective Hamiltonians for the most
relevant classes of materials and heterostructures are derived here from
realistic electronic band structure descriptions. Most semiconductor device
systems are still theoretical concepts, waiting for experimental
demonstrations. A review of selected proposed, and a few demonstrated devices
is presented, with detailed description of two important classes: magnetic
resonant tunnel structures and bipolar magnetic diodes and transistors. In most
cases the presentation is of tutorial style, introducing the essential
theoretical formalism at an accessible level, with case-study-like
illustrations of actual experimental results, as well as with brief reviews of
relevant recent achievements in the field.Comment: tutorial review; 342 pages, 132 figure
The Prevalence of Sexually Transmitted Infections in Papua New Guinea: A Systematic Review and Meta-Analysis
Patellofemoral osteoarthritis (PF OA) is more prevalent than previously thought and contributes to patient's suffering from knee OA. Synthesis of prevalence data can provide estimates of the burden of PF OA
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