2,333 research outputs found

    The partition bundle of type A_{N-1} (2, 0) theory

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    Six-dimensional (2, 0) theory can be defined on a large class of six-manifolds endowed with some additional topological and geometric data (i.e. an orientation, a spin structure, a conformal structure, and an R-symmetry bundle with connection). We discuss the nature of the object that generalizes the partition function of a more conventional quantum theory. This object takes its values in a certain complex vector space, which fits together into the total space of a complex vector bundle (the `partition bundle') as the data on the six-manifold is varied in its infinite-dimensional parameter space. In this context, an important role is played by the middle-dimensional intermediate Jacobian of the six-manifold endowed with some additional data (i.e. a symplectic structure, a quadratic form, and a complex structure). We define a certain hermitian vector bundle over this finite-dimensional parameter space. The partition bundle is then given by the pullback of the latter bundle by the map from the parameter space related to the six-manifold to the parameter space related to the intermediate Jacobian.Comment: 15 pages. Minor changes, added reference

    Tuneable photoconductivity and mobility enhancement in printed MoS 2 /graphene composites

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    This is the author accepted manuscript. The final version is available from IOP Publishing via the DOI in this record.With the aim of increasing carrier mobility in nanosheet-network devices, we have investigated MoS2–graphene composites as active regions in printed photodetectors. Combining liquid exfoliation and inkjet-printing, we fabricated all-printed photodetectors with graphene electrodes and MoS2–graphene composite channels with various graphene mass fractions (0  ≤  M f  ≤  16 wt%). The increase in channel dark conductivity with M f was consistent with percolation theory for composites below the percolation threshold. While the photoconductivity increased with graphene content, it did so more slowly than the dark conductivity, such that the fractional photoconductivity decayed rapidly with increasing M f. We propose that both mobility and dark carrier density increase with graphene content according to percolation-like scaling laws, while photo-induced carrier density is essentially independent of graphene loading. This leads to percolation-like scaling laws for both photoconductivity and fractional photoconductivity—in excellent agreement with the data. These results imply that channel mobility and carrier density increase up to 100-fold with the addition of 16 wt% graphene.We acknowledge the Science Foundation Ireland (SFI/12/RC/2278), the European Commission (n° 696656, Graphene Flagship) and the European Research Council (FUTURE-PRINT)

    Focal epilepsy in SCN1A-mutation carrying patients: is there a role for epilepsy surgery?

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    Variants in the gene SCN1A are a common genetic cause for a wide range of epilepsy phenotypes ranging from febrile seizures to Dravet syndrome. Focal onset seizures and structural lesions can be present in these patients and the question arises whether epilepsy surgery should be considered. We report eight patients (mean age 13y 11mo [SD 8y 1mo], range 3–26y; four females, four males) with SCN1A variants, who underwent epilepsy surgery. Outcomes were variable and seemed to be directly related to the patient’s anatomo‐electroclinical epilepsy phenotype. Patients with Dravet syndrome had unfavourable outcomes, whilst patients with focal epilepsy, proven to arise from a single structural lesion, had good results. We conclude that the value of epilepsy surgery in patients with an SCN1A variant rests on two issues: understanding whether the variant is pathogenic and the patient’s anatomo‐electroclinical phenotype. Careful evaluation of epilepsy phenotype integrated with understanding the significance of genetic variants is essential in determining a patient’s suitability for epilepsy surgery. Patients with focal onset epilepsy may benefit from epilepsy surgery, whereas those with Dravet syndrome do not

    The biosocial event : responding to innovation in the life sciences

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    Innovation in the life sciences calls for reflection on how sociologies separate and relate life processes and social processes. To this end we introduce the concept of the ‘biosocial event’. Some life processes and social processes have more mutual relevance than others. Some of these relationships are more negotiable than others. We show that levels of relevance and negotiability are not static but can change within existing relationships. Such changes, or biosocial events, lie at the heart of much unplanned biosocial novelty and much deliberate innovation. We illustrate and explore the concept through two examples – meningitis infection and epidemic, and the use of sonic ‘teen deterrents’ in urban settings. We then consider its value in developing sociological practice oriented to critically constructive engagement with innovation in the life sciences

    Abundance, rarity and invasion debt among exotic species in a patchy ecosystem

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    Community assembly through species invasions is a long-term process, for which vital information regarding future trends can be contained in current patterns. Using comparative analyses of native and exotic plant assemblages from meadow patches on islands in British Columbia, Canada, we examined multiple lines of evidence for ‘invasion debt’, a latent expansion of exotic species populations. We show that: (1) short-dispersing species are underrepresented compared to their long-dispersing counterparts in exotic species only; (2) among species that are invasive elsewhere in North America, a greater proportion of long dispersers are common in the study area and a greater proportion of short dispersers are rare; and (3) time since arrival in the study region is positively related to number of occurrences in exotic species. In addition, we show that a suite of exotic species possesses the facility of rapid long-distance dispersal and ability to establish viable populations on even the most isolated and least disturbed patches. While some highly-dispersive exotic species can rapidly colonize new areas, short dispersers appear to exhibit invasion debt, with their potential distributions only being realized in the long term. Removing or even reducing populations of many rapid colonizers could be extremely difficult; however, for species exhibiting patterns most consistent with invasion debt, an opportunity exists for monitoring and removal to help reduce potential competition with native species

    Effects of intermediate scales on renormalization group running of fermion observables in an SO(10) model

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    In the context of non-supersymmetric SO(10) models, we analyze the renormalization group equations for the fermions (including neutrinos) from the GUT energy scale down to the electroweak energy scale, explicitly taking into account the effects of an intermediate energy scale induced by a Pati--Salam gauge group. To determine the renormalization group running, we use a numerical minimization procedure based on a nested sampling algorithm that randomly generates the values of 19 model parameters at the GUT scale, evolves them, and finally constructs the values of the physical observables and compares them to the existing experimental data at the electroweak scale. We show that the evolved fermion masses and mixings present sizable deviations from the values obtained without including the effects of the intermediate scale.Comment: Comments: 20 pages, 3 figures. Final version published in JHE

    Assessing the potential for dimethylsulfide enrichment at the sea surface and its influence on air–sea flux

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    The flux of dimethylsulfide (DMS) to the atmosphere is generally inferred using water sampled at or below 2 m depth, thereby excluding any concentration anomalies at the air–sea interface. Two independent techniques were used to assess the potential for near-surface DMS enrichment to influence DMS emissions and also identify the factors influencing enrichment. DMS measurements in productive frontal waters over the Chatham Rise, east of New Zealand, did not identify any significant gradients between 0.01 and 6 m in sub-surface seawater, whereas DMS enrichment in the sea-surface microlayer was variable, with a mean enrichment factor (EF; the concentration ratio between DMS in the sea-surface microlayer and in sub-surface water) of 1.7. Physical and biological factors influenced sea-surface microlayer DMS concentration, with high enrichment (EF > 1.3) only recorded in a dinoflagellate-dominated bloom, and associated with low to medium wind speeds and near-surface temperature gradients. On occasion, high DMS enrichment preceded periods when the air–sea DMS flux, measured by eddy covariance, exceeded the flux calculated using National Oceanic and Atmospheric Administration (NOAA) Coupled-Ocean Atmospheric Response Experiment (COARE) parameterized gas transfer velocities and measured sub-surface seawater DMS concentrations. The results of these two independent approaches suggest that air–sea emissions may be influenced by near-surface DMS production under certain conditions, and highlight the need for further study to constrain the magnitude and mechanisms of DMS production in the sea-surface microlayer

    Shorter leukocyte telomere length is associated with adverse COVID-19 outcomes: A cohort study in UK Biobank

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    Background Older age is the most powerful risk factor for adverse coronavirus disease-19 (COVID-19) outcomes. It is uncertain whether leucocyte telomere length (LTL), previously proposed as a marker of biological age, is also associated with COVID-19 outcomes. Methods We associated LTL values obtained from participants recruited into UK Biobank (UKB) during 2006–2010 with adverse COVID-19 outcomes recorded by 30 November 2020, defined as a composite of any of the following: hospital admission, need for critical care, respiratory support, or mortality. Using information on 130 LTL-associated genetic variants, we conducted exploratory Mendelian randomisation (MR) analyses in UKB to evaluate whether observational associations might reflect cause-and-effect relationships. Findings Of 6775 participants in UKB who tested positive for infection with SARS-CoV-2 in the community, there were 914 (13.5%) with adverse COVID-19 outcomes. The odds ratio (OR) for adverse COVID-19 outcomes was 1·17 (95% CI 1·05–1·30; P = 0·004) per 1-SD shorter usual LTL, after adjustment for age, sex and ethnicity. Similar ORs were observed in analyses that: adjusted for additional risk factors; disaggregated the composite outcome and reduced the scope for selection or collider bias. In MR analyses, the OR for adverse COVID-19 outcomes was directionally concordant but non-significant. Interpretation Shorter LTL is associated with higher risk of adverse COVID-19 outcomes, independent of several major risk factors for COVID-19 including age. Further data are needed to determine whether this association reflects causality. Funding UK Medical Research Council, Biotechnology and Biological Sciences Research Council and British Heart Foundation
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