185 research outputs found
Magnetization states and switching in narrow-gapped ferromagnetic nanorings
We study permalloy nanorings that are lithographically fabricated with narrow
gaps that break the rotational symmetry of the ring while retaining the vortex
ground state, using both micromagnetic simulations and magnetic force
microscopy (MFM). The vortex chirality in these structures can be readily set
with an in-plane magnetic field and easily probed by MFM due to the field
associated with the gap, suggesting such rings for possible applications in
storage technologies. We find that the gapped ring edge characteristics (i.e.,
edge profile and gap shape) are critical in determining the magnetization
switching field, thus elucidating an essential parameter in the controls of
devices that might incorporate such structures
Towards the Development of a Framework for Socially Responsible Software by Analyzing Social Media Big Data on Cloud Through Ontological Engineering
AbstractA socially responsible internet is the need of the hour considering its huge potential and role in educating and transforming the society. Social computing is emerging as an important area as far as development of next generation web is concerned. With the proliferation of social networking applications, vast amount of data is available on cloud, which may be analyzed to gain useful insight into behavioral and linguistic patterns of different cultural and socio-economic groups further classified on the basis of gender and age etc. The idea is to come up with an appropriate framework for socially responsible software artifacts. These artifacts will monitor online social network data and analyze it from the perspective of socially responsible behavior based on ontological engineering concepts. Identification of socially responsible agents is such an example, though based on a different approach. More examples may be taken from literature dealing with microblog analytics, social semantic web, upper ontology for social web, and social-network-sourced big data analytics. In the present work, it is proposed to focus on analysis/monitoring of socially responsible behavior of social media big data and develop an upper level ontology as the framework/tool for such an analytics
Competing Gauge Fields and Entropically-Driven Spin Liquid to Spin Liquid Transition in non-Kramers Pyrochlores
Gauge theories are powerful tools in theoretical physics, allowing complex
phenomena to be reduced to simple principles, and are used in both high-energy
and condensed matter physics. In the latter context, gauge theories are
becoming increasingly popular for capturing the intricate spin correlations in
spin liquids, exotic states of matter in which the dynamics of quantum spins
never ceases, even at absolute zero temperature. We consider a spin system on a
three-dimensional pyrochlore lattice where emergent gauge fields not only
describe the spin liquid behaviour at zero temperature but crucially determine
the system's temperature evolution, with distinct gauge fields giving rise to
different spin liquid phases in separate temperature regimes. Focusing first on
classical spins, in an intermediate temperature regime, the system shows an
unusual coexistence of emergent vector and matrix gauge fields where the former
is known from classical spin ice systems while the latter has been associated
with fractonic quasiparticles, a peculiar type of excitation with restricted
mobility. Upon cooling, the system transitions into a low-temperature phase
where an entropic selection mechanism depopulates the degrees of freedom
associated with the matrix gauge field, rendering the system spin ice like. We
further provide numerical evidence that in the corresponding quantum model, a
spin liquid with coexisting vector and matrix gauge fields has a finite window
of stability in the parameter space of spin interactions down to zero
temperature. Finally, we discuss the relevance of our findings for non-Kramers
pyrochlore materials.Comment: 13 pages, 5 figure
Classical and quantum phases of the pyrochlore magnet with Heisenberg and Dzyaloshinskii-Moriya interactions
We investigate the ground state and critical temperature phase diagrams of
the classical and quantum pyrochlore lattice with nearest-neighbor
Heisenberg and Dzyaloshinskii-Moriya interactions (DMI). We consider
ferromagnetic and antiferromagnetic Heisenberg exchange as well as direct and
indirect DMI. Classically, three ground states are found: all-in/all-out,
ferromagnetic and a locally ordered phase, known as , which
displays an accidental classical U(1) degeneracy. Quantum zero-point energy
fluctuations are found to lift the classical ground state degeneracy and select
the state in most parts of the regime. Likewise, thermal
fluctuations treated classically, select the state at . In
contrast, classical Monte Carlo finds that the system orders at in the
state of for antiferromagnetic Heisenberg exchange and
indirect DMI with a transition from to at a temperature
. The same method finds that the system orders via a single
transition at directly into the state for most of the region
with ferromagnetic Heisenberg exchange and indirect DMI. Such ordering behavior
at for the quantum model is corroborated by high-temperature
series expansion. To investigate the quantum ground states, we apply the
pseudo-fermion functional renormalization group (PFFRG). The quantum
paramagnetic phase of the pure antiferromagnetic Heisenberg model is
found to persist over a finite region in the phase diagram for both direct or
indirect DMI. We find that near the boundary of ferromagnetism and
antiferromagnetism the system may potentially realize a quantum ground state
lacking conventional magnetic order. Otherwise, for the largest portion of the
phase diagram, PFFRG finds the same ordered phases as in the classical model.Comment: 26 pages, 14 figure
Diagnosing and managing sleep apnea in patients with chronic cerebrovascular disease: a randomized trial of a home-based strategy
Background
Obstructive sleep apnea is common and associated with poor outcomes after stroke or transient ischemic attack (TIA). We sought to determine whether the intervention strategy improved sleep apnea detection, obstructive sleep apnea (OSA) treatment, and hypertension control among patients with chronic cerebrovascular disease and hypertension.
Methods
In this randomized controlled strategy trial intervention, patients received unattended polysomnography at baseline, and patients with OSA (apnea-hypopnea index ≥5 events/h) received auto-titrating continuous positive airway pressure (CPAP) for up to 1 year. Control patients received usual care and unattended polysomnography at the end of the study, to identify undiagnosed OSA. Both groups received 24-h blood pressure assessments at baseline and end of the study. “Excellent” CPAP adherence was defined as cumulative use of ≥4 h/night for ≥70% of the nights.
Results
Among 225 randomized patients (115 control; 110 intervention), 61.9% (120/194) had sleep apnea. The strategy successfully diagnosed sleep apnea with 97.1% (102/105) valid studies; 90.6% (48/53, 95% CI 82.7–98.4%) of sleep apnea was undiagnosed among control patients. The intervention improved long-term excellent CPAP use: 38.6% (22/57) intervention versus 0% (0/2) control (p < 0.0001). The intervention did not improve hypertension control in this population with well-controlled baseline blood pressure: intervention, 132.7 mmHg (±standard deviation, 14.1) versus control, 133.8 mmHg (±14.0) (adjusted difference, −1.1 mmHg, 95% CI (−4.2, 2.0)), p = 0.48).
Conclusions
Patients with cerebrovascular disease and hypertension have a high prevalence of OSA. The use of portable polysomnography, and auto-titrating CPAP in the patients’ homes, improved both the diagnosis and the treatment for sleep apnea compared with usual care but did not lower blood pressure
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Nanoparticle Mediated Tumor Vascular Disruption: A Novel Strategy in Radiation Therapy
More than 50% of all cancer patients receive radiation therapy. The clinical delivery of curative radiation dose is strictly restricted by the proximal healthy tissues. We propose a dual-targeting strategy using vessel-targeted-radiosensitizing gold nanoparticles and conformal-image guided radiation therapy to specifically amplify damage in the tumor neoendothelium. The resulting tumor vascular disruption substantially improved the therapeutic outcome and subsidized the radiation/nanoparticle toxicity, extending its utility to intransigent or nonresectable tumors that barely respond to standard therapies
Challenging Conformity: A Case for Diversity * Willemien Kets †
Abstract Why do diverse groups outperform homogeneous groups in some settings, but not in others? We show that while diverse groups experience more frictions than homogeneous ones, they are also less conformist. Homogeneous groups minimize the risk of miscoordination, but they may get stuck in an inefficient equilibrium. Diverse groups may fail to coordinate, but if they do, they tend to attain efficiency. This fundamental tradeoff determines how the optimal level of diversity varies with social and economic factors. When it is vitally important to avoid miscoordination, homogeneous groups are optimal. However, when it is critical to implement new and efficient practices, diverse groups perform better. * Part of the material incorporated here was previously in a paper entitled "A belief-based theory of homophily" by the same authors (Kets and Sandroni, 2015a). We thank David Ahn, Larbi Alaoui, Sandeep Baliga, Vincent Crawford, Vessela Daskalova, Georgy Egorov, Tim Feddersen, Matthew Jackson, Wouter Kager, Rachel Kranton, George Mailath, Niko Matouschek, Friederike Mengel, Rosemarie Nagel, Alessandro Pavan, Antonio Penta, Nicola Persico, Debraj Ray, Yuval Salant, Larry Samuelson, Paola Sapienza, Rajiv Sethi, Eran Shmaya, Andy Skrzypacz, Jakub Steiner, Colin Stewart, Jeroen Swinkels, and numerous seminar audiences and conference participants for helpful comments and stimulating discussions
Association of the PHACTR1/EDN1 genetic locus with spontaneous coronary artery dissection
Background:
Spontaneous coronary artery dissection (SCAD) is an increasingly recognized cause of acute coronary syndromes (ACS) afflicting predominantly younger to middle-aged women. Observational studies have reported a high prevalence of extracoronary vascular anomalies, especially fibromuscular dysplasia (FMD) and a low prevalence of coincidental cases of atherosclerosis. PHACTR1/EDN1 is a genetic risk locus for several vascular diseases, including FMD and coronary artery disease, with the putative causal noncoding variant at the rs9349379 locus acting as a potential enhancer for the endothelin-1 (EDN1) gene.
Objectives:
This study sought to test the association between the rs9349379 genotype and SCAD.
Methods:
Results from case control studies from France, United Kingdom, United States, and Australia were analyzed to test the association with SCAD risk, including age at first event, pregnancy-associated SCAD (P-SCAD), and recurrent SCAD.
Results:
The previously reported risk allele for FMD (rs9349379-A) was associated with a higher risk of SCAD in all studies. In a meta-analysis of 1,055 SCAD patients and 7,190 controls, the odds ratio (OR) was 1.67 (95% confidence interval [CI]: 1.50 to 1.86) per copy of rs9349379-A. In a subset of 491 SCAD patients, the OR estimate was found to be higher for the association with SCAD in patients without FMD (OR: 1.89; 95% CI: 1.53 to 2.33) than in SCAD cases with FMD (OR: 1.60; 95% CI: 1.28 to 1.99). There was no effect of genotype on age at first event, P-SCAD, or recurrence.
Conclusions:
The first genetic risk factor for SCAD was identified in the largest study conducted to date for this condition. This genetic link may contribute to the clinical overlap between SCAD and FMD
Comprehensive Rare Variant Analysis via Whole-Genome Sequencing to Determine the Molecular Pathology of Inherited Retinal Disease
Inherited retinal disease is a common cause of visual impairment and represents a highly heterogeneous group of conditions. Here, we present findings from a cohort of 722 individuals with inherited retinal disease, who have had whole-genome sequencing (n = 605), whole-exome sequencing (n = 72), or both (n = 45) performed, as part of the NIHR-BioResource Rare Diseases research study. We identified pathogenic variants (single-nucleotide variants, indels, or structural variants) for 404/722 (56%) individuals. Whole-genome sequencing gives unprecedented power to detect three categories of pathogenic variants in particular: structural variants, variants in GC-rich regions, which have significantly improved coverage compared to whole-exome sequencing, and variants in non-coding regulatory regions. In addition to previously reported pathogenic regulatory variants, we have identified a previously unreported pathogenic intronic variant in in two males with choroideremia. We have also identified 19 genes not previously known to be associated with inherited retinal disease, which harbor biallelic predicted protein-truncating variants in unsolved cases. Whole-genome sequencing is an increasingly important comprehensive method with which to investigate the genetic causes of inherited retinal disease.This work was supported by The National Institute for Health Research England (NIHR) for the NIHR BioResource – Rare Diseases project (grant number RG65966). The Moorfields Eye Hospital cohort of patients and clinical and imaging data were ascertained and collected with the support of grants from the National Institute for Health Research Biomedical Research Centre at Moorfields Eye Hospital, National Health Service Foundation Trust, and UCL Institute of Ophthalmology, Moorfields Eye Hospital Special Trustees, Moorfields Eye Charity, the Foundation Fighting Blindness (USA), and Retinitis Pigmentosa Fighting Blindness. M.M. is a recipient of an FFB Career Development Award. E.M. is supported by UCLH/UCL NIHR Biomedical Research Centre. F.L.R. and D.G. are supported by Cambridge NIHR Biomedical Research Centre
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