12,314 research outputs found

    Supersymmetric Open Wilson Lines

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    In this paper we study Open Wilson Lines (OWL's) in the context of two Supersymmetric Yang Mills theories. First we consider four dimensional N=2 Supersymmetric Yang Mills Theory with hypermultiplets transforming in the fundamental representation of the gauge group, and find supersymmetric OWL's only in the superconformal versions of these theories. We then consider four dimensional N=4 SYM coupled to a three dimensional defect hypermultiplet. Here there is a semi-circular supersymmetric OWL, which is related to the ray by a conformal transformation. We perform a perturbative calculation of the operators in both theories, and discuss using localization to compute them non-perturbatively.Comment: 26 pages, 3 figure

    Intramolecular H⋯S interactions in metal di-(isopropyl)dithiocarbamate complexes

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    © 2016 The Royal Society of Chemistry. Networks of C-H⋯S interactions have been discovered within the molecular structure of sodium di-(isopropyl)dithiocarbamate pentahydrate with the formula Na(C7H14NS2)·5H2O, revealed by single crystal X-ray diffraction. These interactions have also been investigated by ab initio and Hirshfeld surface analyses which show that the electron density is not symmetrical about the molecule. NMR spectroscopy in solution and solid the state showed temperature dependent restricted rotation of the isopropyl groups, which is attributed to the intramolecular C-H⋯S interactions. The ubiquitous nature of C-H⋯S intramolecular interactions in this class of compound is evident in the structures of other di-(isopropyl)dithiocarbamate complexes deposited in the CSD. In general, the restricted rotation in di-(isopropyl)dithiocarbamate complexes can be directly attributed to intramolecular C-H⋯S interactions, which subsequently influence the geometry in association with steric repulsion factors

    Neural crest migration is driven by a few trailblazer cells with a unique molecular signature narrowly confined to the invasive front

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    Neural crest (NC) cell migration is crucial to the formation of peripheral tissues during vertebrate development. However, how NC cells respond to different microenvironments to maintain persistence of direction and cohesion in multicellular streams remains unclear. To address this, we profiled eight subregions of a typical cranial NC cell migratory stream. Hierarchical clustering showed significant differences in the expression profiles of the lead three subregions compared with newly emerged cells. Multiplexed imaging of mRNA expression using fluorescent hybridization chain reaction (HCR) quantitatively confirmed the expression profiles of lead cells. Computational modeling predicted that a small fraction of lead cells that detect directional information is optimal for successful stream migration. Single-cell profiling then revealed a unique molecular signature that is consistent and stable over time in a subset of lead cells within the most advanced portion of the migratory front, which we term trailblazers. Model simulations that forced a lead cell behavior in the trailing subpopulation predicted cell bunching near the migratory domain entrance. Misexpression of the trailblazer molecular signature by perturbation of two upstream transcription factors agreed with the in silico prediction and showed alterations to NC cell migration distance and stream shape. These data are the first to characterize the molecular diversity within an NC cell migratory stream and offer insights into how molecular patterns are transduced into cell behaviors

    What do we know about how to do audit and feedback? Pitfalls in applying evidence from a systematic review

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    BACKGROUND: Improving the quality of health care requires a range of evidence-based activities. Audit and feedback is commonly used as a quality improvement tool in the UK National Health Service [NHS]. We set out to assess whether current guidance and systematic review evidence can sufficiently inform practical decisions about how to use audit and feedback to improve quality of care. METHODS: We selected an important chronic disease encountered in primary care: diabetes mellitus. We identified recommendations from National Institute for Clinical Excellence (NICE) guidance on conducting audit and generated questions which would be relevant to any attempt to operationalise audit and feedback in a healthcare service setting. We explored the extent to which a systematic review of audit and feedback could provide practical guidance about whether audit and feedback should be used to improve quality of diabetes care and, if so, how audit and feedback could be optimised. RESULTS: National guidance suggests the importance of securing the right organisational conditions and processes. Review evidence suggests that audit and feedback can be effective in changing healthcare professional practice. However, the available evidence says relatively little about the detail of how to use audit and feedback most efficiently. CONCLUSION: Audit and feedback will continue to be an unreliable approach to quality improvement until we learn how and when it works best. Conceptualising audit and feedback within a theoretical framework offers a way forward

    The fallacy of enrolling only high-risk subjects in cancer prevention trials: Is there a "free lunch"?

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    BACKGROUND: There is a common belief that most cancer prevention trials should be restricted to high-risk subjects in order to increase statistical power. This strategy is appropriate if the ultimate target population is subjects at the same high-risk. However if the target population is the general population, three assumptions may underlie the decision to enroll high-risk subject instead of average-risk subjects from the general population: higher statistical power for the same sample size, lower costs for the same power and type I error, and a correct ratio of benefits to harms. We critically investigate the plausibility of these assumptions. METHODS: We considered each assumption in the context of a simple example. We investigated statistical power for fixed sample size when the investigators assume that relative risk is invariant over risk group, but when, in reality, risk difference is invariant over risk groups. We investigated possible costs when a trial of high-risk subjects has the same power and type I error as a larger trial of average-risk subjects from the general population. We investigated the ratios of benefit to harms when extrapolating from high-risk to average-risk subjects. RESULTS: Appearances here are misleading. First, the increase in statistical power with a trial of high-risk subjects rather than the same number of average-risk subjects from the general population assumes that the relative risk is the same for high-risk and average-risk subjects. However, if the absolute risk difference rather than the relative risk were the same, the power can be less with the high-risk subjects. In the analysis of data from a cancer prevention trial, we found that invariance of absolute risk difference over risk groups was nearly as plausible as invariance of relative risk over risk groups. Therefore a priori assumptions of constant relative risk across risk groups are not robust, limiting extrapolation of estimates of benefit to the general population. Second, a trial of high-risk subjects may cost more than a larger trial of average risk subjects with the same power and type I error because of additional recruitment and diagnostic testing to identify high-risk subjects. Third, the ratio of benefits to harms may be more favorable in high-risk persons than in average-risk persons in the general population, which means that extrapolating this ratio to the general population would be misleading. Thus there is no free lunch when using a trial of high-risk subjects to extrapolate results to the general population. CONCLUSION: Unless the intervention is targeted to only high-risk subjects, cancer prevention trials should be implemented in the general population

    Understanding the Random Displacement Model: From Ground-State Properties to Localization

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    We give a detailed survey of results obtained in the most recent half decade which led to a deeper understanding of the random displacement model, a model of a random Schr\"odinger operator which describes the quantum mechanics of an electron in a structurally disordered medium. These results started by identifying configurations which characterize minimal energy, then led to Lifshitz tail bounds on the integrated density of states as well as a Wegner estimate near the spectral minimum, which ultimately resulted in a proof of spectral and dynamical localization at low energy for the multi-dimensional random displacement model.Comment: 31 pages, 7 figures, final version, to appear in Proceedings of "Spectral Days 2010", Santiago, Chile, September 20-24, 201

    Cervicogenic headache caused by myofascial trigger points in the sternocleidomastoid: a case report

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74754/1/j.1468-2982.2007.01296.x.pd

    Independent predictors of failure up to 7.5 years after 35 386 single-brand cementless total hip replacements: a retrospective cohort study using National Joint Registry data

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    The popularity of cementless total hip replacement (THR) has surpassed cemented THR in England and Wales. This retrospective cohort study records survival time to revision following primary cementless THR with the most common combination (accounting for almost a third of all cementless THRs), and explores risk factors independently associated with failure, using data from the National Joint Registry for England and Wales. Patients with osteoarthritis who had a DePuy Corail/Pinnacle THR implanted between the establishment of the registry in 2003 and 31 December 2010 were included within analyses. There were 35 386 procedures. Cox proportional hazard models were used to analyse the extent to which the risk of revision was related to patient, surgeon and implant covariates. The overall rate of revision at five years was 2.4% (99% confidence interval 2.02 to 2.79). In the final adjusted model, we found that the risk of revision was significantly higher in patients receiving metal-on-metal (MoM: hazard ratio (HR) 1.93, p < 0.001) and ceramic-on-ceramic bearings (CoC: HR 1.55, p = 0.003) compared with the best performing bearing (metal-on-polyethylene). The risk of revision was also greater for smaller femoral stems (sizes 8 to 10: HR 1.82, p < 0.001) compared with mid-range sizes. In a secondary analysis of only patients where body mass index (BMI) data were available (n = 17 166), BMI ≥ 30 kg/m2 significantly increased the risk of revision (HR 1.55, p = 0.002). The influence of the bearing on the risk of revision remained significant (MoM: HR 2.19, p < 0.001; CoC: HR 2.09, p = 0.001). The risk of revision was independent of age, gender, head size and offset, shell, liner and stem type, and surgeon characteristics. We found significant differences in failure between bearing surfaces and femoral stem size after adjustment for a range of covariates in a large cohort of single-brand cementless THRs. In this study of procedures performed since 2003, hard bearings had significantly higher rates of revision, but we found no evidence that head size had an effect. Patient characteristics, such as BMI and American Society of Anesthesiologists grade, also influence the survival of cementless components

    A systematic review of economic evaluations of whole genome sequencing for the surveillance of bacterial pathogens

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    Whole-genome sequencing (WGS) has unparalleled ability to distinguish between bacteria, with many public health applications. The generation and analysis of WGS data require significant financial investment. We describe a systematic review summarizing economic analyses of genomic surveillance of bacterial pathogens, reviewing the evidence for economic viability. The protocol was registered on PROSPERO (CRD42021289030). Six databases were searched on 8 November 2021 using terms related to ‘WGS’, ‘population surveillance’ and ‘economic analysis’. Quality was assessed with the Drummond–Jefferson checklist. Following data extraction, a narrative synthesis approach was taken. Six hundred and eighty-one articles were identified, of which 49 proceeded to full-text screening, with 9 selected for inclusion. All had been published since 2019. Heterogeneity was high. Five studies assessed WGS for hospital surveillance and four analysed foodborne pathogens. Four were cost–benefit analyses, one was a cost–utility analysis, one was a cost-effectiveness analysis, one was a combined cost-effectiveness and cost–utility analysis, one combined cost-effectiveness and cost–benefit analyses and one was a partial analysis. All studies supported the use of WGS as a surveillance tool on economic grounds. The available evidence supports the use of WGS for pathogen surveillance but is limited by marked heterogeneity. Further work should include analysis relevant to low- and middle-income countries and should use real-world effectiveness data
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