1,199 research outputs found
Lagrange Anchor and Characteristic Symmetries of Free Massless Fields
A Poincar\'e covariant Lagrange anchor is found for the non-Lagrangian
relativistic wave equations of Bargmann and Wigner describing free massless
fields of spin in four-dimensional Minkowski space. By making use of
this Lagrange anchor, we assign a symmetry to each conservation law and perform
the path-integral quantization of the theory
Giant Shapiro Resonances in a Flux Driven Josephson Junction Necklace
We present a detailed study of the dynamic response of a ring of equally
spaced Josephson junctions to a time-periodic external flux, including
screening current effects. The dynamics are described by the resistively
shunted Josephson junction model, appropriate for proximity effect junctions,
and we include Faraday's law for the flux. We find that the time-averaged
characteristics show novel {\em subharmonic giant Shapiro voltage resonances},
which strongly depend on having phase slips or not, on , on the inductance
and on the external drive frequency. We include an estimate of the possible
experimental parameters needed to observe these quantized voltage spikes.Comment: 8 pages RevTeX, 3 figures available upon reques
The Relationship Between Irrational Beliefs and Depressed Mood in Clinically Depressed Outpatients
Studies into the relationship between irrational beliefs and severity of depression have yielded variable results. Furthermore, there is a lack of information on the nature of this relationship within clinically depressed patients. The paper explores the relationship between BDI scores and individual irrational beliefs as measured by the Irrational Beliefs Test (IBT) in a clinical outpatient group (N=63) with major and minor depressive disorders diagnosed according to Research Diagnostic Criteria and in a comparison group of university students (N=43). The results of MANOVA analyses showed that the two groups differed significantly in overall level of irrational beliefs and in their endorsement of 7 out of 10 irrational belief scales. They also differed as to which irrational belief scale scores were predictive of BDI score. Findings suggested that several rational emotive therapy constructs lack explanatory and predictive power with respect to depressive relationships
Reverberation Mapping Results for Five Seyfert 1 Galaxies
We present the results from a detailed analysis of photometric and
spectrophotometric data on five Seyfert 1 galaxies observed as a part of a
recent reverberation mapping program. The data were collected at several
observatories over a 140-day span beginning in 2010 August and ending in 2011
January. We obtained high sampling-rate light curves for Mrk 335, Mrk 1501,
3C120, Mrk 6, and PG2130+099, from which we have measured the time lag between
variations in the 5100 Angstrom continuum and the H-beta broad emission line.
We then used these measurements to calculate the mass of the supermassive black
hole at the center of each of these galaxies. Our new measurements
substantially improve previous measurements of MBH and the size of the broad
line-emitting region for four sources and add a measurement for one new object.
Our new measurements are consistent with photoionization physics regulating the
location of the broad line region in active galactic nuclei.Comment: 45 pages, 5 figures. Accepted for publication in ApJ. For a brief
video explaining the key results of this paper, see
http://www.youtube.com/user/OSUAstronom
Einstein equations in the null quasi-spherical gauge
The structure of the full Einstein equations in a coordinate gauge based on
expanding null hypersurfaces foliated by metric 2-spheres is explored. The
simple form of the resulting equations has many applications -- in the present
paper we describe the structure of timelike boundary conditions; the matching
problem across null hypersurfaces; and the propagation of gravitational shocks.Comment: 12 pages, LaTeX (revtex, amssymb), revision 18 pages, contains
expanded discussion and explanations, updated references, to appear in CQ
Safetxt: a pilot randomised controlled trial of an intervention delivered by mobile phone to increase safer sex behaviours in young people.
OBJECTIVE: To test the procedures proposed for a main trial of a safer sex intervention for young people delivered by mobile phone text message ('safetxt'). DESIGN AND SETTING: Pilot randomised controlled trial. Participants were recruited through sexual health services in the UK. An independent online randomisation system allocated participants to receive the safetxt intervention or to receive the control text messages (monthly messages about participation in the study). Texting software delivered the messages in accordance with a predetermined schedule. PARTICIPANTS: Residents of England aged 16-24 who had received either a positive chlamydia test result or reported unsafe sex in the last year (defined as more than 1 partner and at least 1 occasion of sex without a condom). INTERVENTION: The safetxt intervention is designed to reduce sexually transmitted infection in young people by supporting them in using condoms, telling a partner about an infection and testing before unprotected sex with a new partner. Safetxt was developed drawing on: behavioural science; face-to-face interventions; the factors known to influence safer sex behaviours and the views of young people. OUTCOMES: The coprimary outcomes of the pilot trial were the recruitment rate and completeness of follow-up. RESULTS: We recruited 200 participants within our target of 3 months and we achieved 81% (162/200) follow-up response for the proposed primary outcome of the main trial, cumulative incidence of chlamydia at 12 months. CONCLUSIONS: Recruitment, randomisation, intervention delivery and follow-up were successful and a randomised controlled trial of the safetxt intervention is feasible. TRIAL REGISTRATION NUMBER: ISRCTN02304709; Results
Reverberation Mapping of the Seyfert 1 Galaxy NGC 7469
A large reverberation mapping study of the Seyfert 1 galaxy NGC 7469 has
yielded emission-line lags for Hbeta 4861 and He II 4686 and a central black
hole mass measurement of about 10 million solar masses, consistent with
previous measurements. A very low level of variability during the monitoring
campaign precluded meeting our original goal of recovering velocity-delay maps
from the data, but with the new Hbeta measurement, NGC 7469 is no longer an
outlier in the relationship between the size of the Hbeta-emitting broad-line
region and the AGN luminosity. It was necessary to detrend the continuum and
Hbeta and He II 4686 line light curves and those from archival UV data for
different time-series analysis methods to yield consistent results.Comment: 9 Pages, 7 figures, 6 tables. Accepted for publication in The
Astrophysical Journa
Flux Pinning and Phase Transitions in Model High-Temperature Superconductors with Columnar Defects
We calculate the degree of flux pinning by defects in model high-temperature
superconductors (HTSC's). The HTSC is modeled as a three-dimensional network of
resistively-shunted Josephson junctions in an external magnetic field,
corresponding to a HTSC in the extreme Type-II limit. Disorder is introduced
either by randomizing the coupling between grains (Model A disorder) or by
removing grains (Model B disorder). Three types of defects are considered:
point disorder, random line disorder, and periodic line disorder; but the
emphasis is on random line disorder. Static and dynamic properties of the
models are determined by Monte Carlo simulations and by solution of the
analogous coupled overdamped Josephson equations in the presence of thermal
noise. Random line defects considerably raise the superconducting transition
temperature T, and increase the apparent critical current density
J, in comparison to the defect-free crystal. They are more effective
in these respects than a comparable volume density of point defects, in
agreement with the experiments of Civale {\it et al}. Periodic line defects
commensurate with the flux lattice are found to raise T even more than
do random line defects. Random line defects are most effective when their
density approximately equals the flux density. Near T, our static and
dynamic results appear consistent with the anisotropic Bose glass scaling
hypotheses of Nelson and Vinokur, but with possibly different critical indices:Comment: 10 pages, LaTeX(REVTeX v3.0, twocolumn), 11 figures (not included
Evaluation of robustly optimised intensity modulated proton therapy for nasopharyngeal carcinoma
BACKGROUND AND PURPOSE: To evaluate the dosimetric changes occurring over the treatment course for nasopharyngeal carcinoma (NPC) patients treated with robustly optimised intensity modulated proton therapy (IMPT). MATERIALS AND METHODS: 25 NPC patients were treated to two dose levels (CTV1: 70Gy, CTV2: 54.25Gy) with robustly optimised IMPT plans. Robustness evaluation was performed over 28 error scenarios using voxel-wise minimum distributions to assess target coverage and voxel-wise maximum distributions to assess possible hotspots and critical organ doses. Daily CBCT was used for positioning and weekly repeat CTs (rCT) were taken, on which the plan dose was recalculated and robustly evaluated. Deformable image registration was used to warp and accumulate the nominal, voxel-wise minimum and maximum rCT dose distributions. Changes to target coverage, critical organ and normal tissue dose between the accumulated and planned doses were investigated. RESULTS: 2 patients required a plan adaptation due to reduced target coverage. The D98% in the accumulated voxel-wise minimum distribution was higher than planned for CTV1 in 24/25 patients and for CTV2 in 20/25 patients. Maximum doses to the critical organs remained acceptable in all patients. Other normal tissue doses showed some variation as a result of soft tissue deformations and weight change. Normal tissue complication probabilities for grade ≥2 dysphagia and grade ≥2 xerostomia remained similar to planned values. CONCLUSION: Robustly optimised IMPT plans, in combination with volumetric verification imaging and adaptive planning, provided robust target coverage and acceptable OAR dose variation in our NPC cohort when accumulated over longitudinal data
D1-D2 Dopamine Receptor Synergy Promotes Calcium Signaling via Multiple Mechanisms
The D1 dopamine receptor (D1R) has been proposed to form a hetero-oligomer with the D2 dopamine receptor (D2R), which in turn results in a complex that couples to phospholipase C–mediated intracellular calcium release. We have sought to elucidate the pharmacology and mechanism of action of this putative signaling pathway. Dopamine dose-response curves assaying intracellular calcium mobilization in cells heterologously expressing the D1 and D2 subtypes, either alone or in combination, and using subtype selective ligands revealed that concurrent stimulation is required for coupling. Surprisingly, characterization of a putative D1-D2 heteromer-selective ligand, 6-chloro-2,3,4,5-tetrahydro-3-methyl-1-(3-methylphenyl)-1H-3-benzazepine-7,8-diol (SKF83959), found no stimulation of calcium release, but it did find a broad range of cross-reactivity with other G protein–coupled receptors. In contrast, SKF83959 appeared to be an antagonist of calcium mobilization. Overexpression of Gqα with the D1 and D2 dopamine receptors enhanced the dopamine-stimulated calcium response. However, this was also observed in cells expressing Gqα with only the D1R. Inactivation of Gi or Gs with pertussis or cholera toxin, respectively, largely, but not entirely, reduced the calcium response in D1R and D2R cotransfected cells. Moreover, sequestration of Gβγ subunits through overexpression of G protein receptor kinase 2 mutants either completely or largely eliminated dopamine-stimulated calcium mobilization. Our data suggest that the mechanism of D1R/D2R–mediated calcium signaling involves more than receptor-mediated Gq protein activation, may largely involve downstream signaling pathways, and may not be completely heteromer-specific. In addition, SKF83959 may not exhibit selective activation of D1-D2 heteromers, and its significant cross-reactivity to other receptors warrants careful interpretation of its use in vivo
- …