268 research outputs found
Factorizing the hard and soft spectator scattering contributions for the nucleon form factor F_1 at large Q^2
We investigate the soft spectator scattering contribution for the FF .
We focus our attention on factorization of the hard-collinear scale corresponding to transition from SCET-I to SCET-II. We compute the
leading order jet functions and find that the convolution integrals over the
soft fractions are logarithmically divergent. This divergency is the
consequence of the boost invariance and does not depend on the model of the
soft correlation function describing the soft spectator quarks. Using as
example a two-loop diagram we demonstrated that such a divergency corresponds
to the overlap of the soft and collinear regions. As a result one obtains large
rapidity logarithm which must be included in the correct factorization
formalism. We conclude that a consistent description of the factorization for
implies the end-point collinear divergencies in the hard and soft
spectator contributions, i.e. convolution integrals with respect to collinear
fractions are not well-defined. Such scenario can only be realized when the
twist-3 nucleon distribution amplitude has specific end-point behavior which
differs from one expected from the evolution of the nucleon distribution
amplitude. Such behavior leads to the violation of the collinear factorization
for the hard spectator scattering contribution. We suggest that the soft
spectator scattering and chiral symmetry breaking provide the mechanism
responsible for the violation of collinear factorization in case of form factor
.Comment: 25 pages, 6 figures, text is improved, few typos corrected, one
figure added, statement about end-point behavior of the nucleon DA is
formulated more accuratel
Comparative Natural History of Visual Function From Patients With Biallelic Variants in BBS1 and BBS10.
The purpose of this study was to compare the natural history of visual function change in cohorts of patients affected with retinal degeneration due to biallelic variants in Bardet-Biedl syndrome genes: BBS1 and BBS10.
Patients were recruited from nine academic centers from six countries (Belgium, Canada, France, New Zealand, Switzerland, and the United States). Inclusion criteria were: (1) female or male patients with a clinical diagnosis of retinal dystrophy, (2) biallelic disease-causing variants in BBS1 or BBS10, and (3) measures of visual function for at least one visit. Retrospective data collected included genotypes, age, onset of symptoms, and best corrected visual acuity (VA). When possible, data on refractive error, fundus images and autofluorescence (FAF), optical coherence tomography (OCT), Goldmann kinetic perimetry (VF), electroretinography (ERG), and the systemic phenotype were collected.
Sixty-seven individuals had variants in BBS1 (n = 38; 20 female patients and 18 male patients); or BBS10 (n = 29; 14 female patients and 15 male patients). Missense variants were the most common type of variants for patients with BBS1, whereas frameshift variants were most common for BBS10. When ERGs were recordable, rod-cone dystrophy (RCD) was observed in 82% (23/28) of patients with BBS1 and 73% (8/11) of patients with BBS10; cone-rod dystrophy (CORD) was seen in 18% of patients with BBS1 only, and cone dystrophy (COD) was only seen in 3 patients with BBS10 (27%). ERGs were nondetectable earlier in patients with BBS10 than in patients with BBS1. Similarly, VA and VF declined more rapidly in patients with BBS10 compared to patients with BBS1.
Retinal degeneration appears earlier and is more severe in BBS10 cases as compared to those with BBS1 variants. The course of change of visual function appears to relate to genetic subtypes of BBS
Inverse magnetic catalysis in field theory and gauge-gravity duality
We investigate the surface of the chiral phase transition in the
three-dimensional parameter space of temperature, baryon chemical potential and
magnetic field in two different approaches, the field-theoretical
Nambu-Jona-Lasinio (NJL) model and the holographic Sakai-Sugimoto model. The
latter is a top-down approach to a gravity dual of QCD with an asymptotically
large number of colors and becomes, in a certain limit, dual to an NJL-like
model. Our main observation is that, at nonzero chemical potential, a magnetic
field can restore chiral symmetry, in apparent contrast to the phenomenon of
magnetic catalysis. This "inverse magnetic catalysis" occurs in the
Sakai-Sugimoto model and, for sufficiently large coupling, in the NJL model and
is related to the physics of the lowest Landau level. While in most parts our
discussion is a pedagogical review of previously published results, we include
new analytical results for the NJL approach and a thorough comparison of
inverse magnetic catalysis in the two approaches.Comment: 37 pages, 11 figures, to appear in Lect. Notes Phys. "Strongly
interacting matter in magnetic fields" (Springer), edited by D. Kharzeev, K.
Landsteiner, A. Schmitt, H.-U. Ye
A Person-Centered Approach to Poststroke Care: The COMprehensive Post-Acute Stroke Services Model
Many individuals who have had a stroke leave the hospital without postacute care services in place. Despite high risks of complications and readmission, there is no standard in the United States for postacute stroke care after discharge home. We describe the rationale and methods for the development of the COMprehensive Post-Acute Stroke Services (COMPASS) care model and the structure and quality metrics used for implementation. COMPASS, an innovative, comprehensive extension of the TRAnsition Coaching for Stroke (TRACS) program, is a clinician-led quality improvement model providing early supported discharge and transitional care for individuals who have had a stroke and have been discharged home. The effectiveness of the COMPASS model is being assessed in a cluster-randomized pragmatic trial in 41 sites across North Carolina, with a recruitment goal of 6,000 participants. The COMPASS model is evidence based, person centered, and stakeholder driven. It involves identification and education of eligible individuals in the hospital; telephone follow-up 2, 30, and 60 days after discharge; and a clinic visit within 14 days conducted by a nurse and advanced practice provider. Patient and caregiver self-reported assessments of functional and social determinants of health are captured during the clinic visit using a web-based application. Embedded algorithms immediately construct an individualized care plan. The COMPASS model's pragmatic design and quality metrics may support measurable best practices for postacute stroke care
Big GABA II: Water-referenced edited MR spectroscopy at 25 research sites
Accurate and reliable quantification of brain metabolites measured in vivo using 1H magnetic resonance spectroscopy (MRS) is a topic of continued interest. Aside from differences in the basic approach to quantification, the quantification of metabolite data acquired at different sites and on different platforms poses an additional methodological challenge. In this study, spectrally edited γ-aminobutyric acid (GABA) MRS data were analyzed and GABA levels were quantified relative to an internal tissue water reference. Data from 284 volunteers scanned across 25 research sites were collected using GABA+ (GABA + co-edited macromolecules (MM)) and MM-suppressed GABA editing. The unsuppressed water signal from the volume of interest was acquired for concentration referencing. Whole-brain T1-weighted structural images were acquired and segmented to determine gray matter, white matter and cerebrospinal fluid voxel tissue fractions. Water-referenced GABA measurements were fully corrected for tissue-dependent signal relaxation and water visibility effects. The cohort-wide coefficient of variation was 17% for the GABA + data and 29% for the MM-suppressed GABA data. The mean within-site coefficient of variation was 10% for the GABA + data and 19% for the MM-suppressed GABA data. Vendor differences contributed 53% to the total variance in the GABA + data, while the remaining variance was attributed to site- (11%) and participant-level (36%) effects. For the MM-suppressed data, 54% of the variance was attributed to site differences, while the remaining 46% was attributed to participant differences. Results from an exploratory analysis suggested that the vendor differences were related to the unsuppressed water signal acquisition. Discounting the observed vendor-specific effects, water-referenced GABA measurements exhibit similar levels of variance to creatine-referenced GABA measurements. It is concluded that quantification using internal tissue water referencing is a viable and reliable method for the quantification of in vivo GABA levels
Supersymmetry beyond minimal flavour violation
We review the sources and phenomenology of non-minimal flavour violation in
the MSSM. We discuss in some detail the most important theoretical and
experimental constraints, as well as promising observables to look for
supersymmetric effects at the LHC and in the future. We emphasize the
sensitivity of flavour physics to the mechanism of supersymmetry breaking and
to new degrees of freedom present at fundamental scales, such as the grand
unification scale. We include a discussion of present data that may hint at
departures from the Standard Model.Comment: 23pp. Version to appear in the EPJC special volume "Supersymmetry on
the Eve of the LHC", dedicated to the memory of Julius Wess. References and
brief discussion on collider signatures adde
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The new Victorians? Celebrity charity and the demise of the welfare state
This article asks whether the expansion of celebrity involvement in charitable and humanitarian issues in Northern Europe and the US might be a comparable historical phenomenon with the philanthropic endeavours of prominent nineteenth-century persons. The article notes that the conspicuous nature of star philanthropy in both Victorian times and the present is fairly dramatic in comparison with that of the mid twentieth century, when the welfare state and the New Deal were at their peak: a welfare-oriented era which, to some, now increasingly looks like a ‘historical blip’. It asks whether the rise of contemporary celebrity involvement in charity can therefore be explained in terms of the contemporary political conjuncture, inasmuch as celebrities could be understood as individuals with large amounts of private capital seeking to intervene in – and gain forms of power through – involvement in humanitarian and charitable causes that might have formerly been the job of the state. Can celebrity involvement in charity be explained in these terms? Does the marriage of celebrity and charity today take a neoliberal form, one that parallels the liberal form of nineteenth-century interventions, bequests and donations? What might the key differences between forms of spectacular ‘philanthrocapitalism’ in these eras (particularly the contemporary insistence on the confessional and intimate modes of address) reveal about its workings, its internal traditions and about the specificity of our own age? This article draws on contemporary media discourse, debate in the voluntary sector, historical scholarship and Foucault’s distinctions between liberalism and neoliberalism to argue that whereas ‘celanthropy’ in the Victorian period eventually came to contribute to the welfare state, today it is more involved in privatising and dismantling it
Genome-Wide Association Study in BRCA1 Mutation Carriers Identifies Novel Loci Associated with Breast and Ovarian Cancer Risk
BRCA1-associated breast and ovarian cancer risks can be modified by common genetic variants. To identify further cancer risk-modifying loci, we performed a multi-stage GWAS of 11,705 BRCA1 carriers (of whom 5,920 were diagnosed with breast and 1,839 were diagnosed with ovarian cancer), with a further replication in an additional sample of 2,646 BRCA1 carriers. We identified a novel breast cancer risk modifier locus at 1q32 for BRCA1 carriers (rs2290854, P = 2.7×10-8, HR = 1.14, 95% CI: 1.09-1.20). In addition, we identified two novel ovarian cancer risk modifier loci: 17q21.31 (rs17631303, P = 1.4×10-8, HR = 1.27, 95% CI: 1.17-1.38) and 4q32.3 (rs4691139, P = 3.4×10-8, HR = 1.20, 95% CI: 1.17-1.38). The 4q32.3 locus was not associated with ovarian cancer risk in the general population or BRCA2 carriers, suggesting a BRCA1-specific associat
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