1,284 research outputs found

    Stability Conditions, Wall-crossing and weighted Gromov-Witten Invariants

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    We extend B. Hassett's theory of weighted stable pointed curves ([Has03]) to weighted stable maps. The space of stability conditions is described explicitly, and the wall-crossing phenomenon studied. This can be considered as a non-linear analog of the theory of stability conditions in abelian and triangulated categories. We introduce virtual fundamental classes and thus obtain weighted Gromov-Witten invariants. We show that by including gravitational descendants, one obtains an \LL-algebra as introduced in [LM04] as a generalization of a cohomological field theory.Comment: 28 pages; v2: references added and updated, addressed referee comments; to appear in Moscow Math Journa

    Gyrification in relation to cortical thickness in the congenitally blind

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    Greater cortical gyrification (GY) is linked with enhanced cognitive abilities and is also negatively related to cortical thickness (CT). Individuals who are congenitally blind (CB) exhibits remarkable functional brain plasticity which enables them to perform certain non-visual and cognitive tasks with supranormal abilities. For instance, extensive training using touch and audition enables CB people to develop impressive skills and there is evidence linking these skills to cross-modal activations of primary visual areas. There is a cascade of anatomical, morphometric and functional-connectivity changes in non-visual structures, volumetric reductions in several components of the visual system, and CT is also increased in CB. No study to date has explored GY changes in this population, and no study has explored how variations in CT are related to GY changes in CB. T1-weighted 3D structural magnetic resonance imaging scans were acquired to examine the effects of congenital visual deprivation in cortical structures in a healthy sample of 11 CB individuals (6 male) and 16 age-matched sighted controls (SC) (10 male). In this report, we show for the first time an increase in GY in several brain areas of CB individuals compared to SC, and a negative relationship between GY and CT in the CB brain in several different cortical areas. We discuss the implications of our findings and the contributions of developmental factors and synaptogenesis to the relationship between CT and GY in CB individuals compared to SC. F

    Simulation of photo-excited adenine in water with a hierarchy of equations of motion approach

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    We present a theoretical method to simulate the electronic dynamics and two-dimensional ultraviolet spectra of the nucleobase adenine in water. The method is an extension of the hierarchy of equation of motion approach to treat a model with one or more conical intersections. The application to adenine shows that a two-level model with a direct conical intersection between the optically bright state and the ground state, generating a hot ground state, is not consistent with experimental observations. This supports a three-level model for the decay of electronically excited adenine in water as was previously proposed in [Prokhorenko et al., J. Phys. Chem. Lett. 7, 4445 (2016)]

    Peer versus staff tutoring in problem-based learning

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    Effects of student versus staff tutoring on student learning in a problem-based, health sciences curriculum were studied. Academic achievement of 334 tutorial groups guided by staff tutors was compared with achievement of 400 groups guided by student tutors. In addition, students rated their tutor''s performance on four behaviors considered critical to facilitating student learning. Overall, students guided by a staff tutor achieved somewhat better. In terms of practical significance, the difference was, however, fairly small. Staff tutors were rated as more knowledgeable and their contributions as more relevant. In addition, they asked stimulating questions to a larger extent. However, an interaction effect was found between the ratings and the year of study: Peer tutors displayed the supportive behaviors more extensively in the first year, whereas staff tutors'' ratings were higher as the curriculum advanced. These results were interpreted in terms of the cognitive congruence framework

    Diffusion mechanisms of localised knots along a polymer

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    We consider the diffusive motion of a localized knot along a linear polymer chain. In particular, we derive the mean diffusion time of the knot before it escapes from the chain once it gets close to one of the chain ends. Self-reptation of the entire chain between either end and the knot position, during which the knot is provided with free volume, leads to an L^3 scaling of diffusion time; for sufficiently long chains, subdiffusion will enhance this time even more. Conversely, we propose local ``breathing'', i.e., local conformational rearrangement inside the knot region (KR) and its immediate neighbourhood, as additional mechanism. The contribution of KR-breathing to the diffusion time scales only quadratically, L^2, speeding up the knot escape considerably and guaranteeing finite knot mobility even for very long chains.Comment: 7 pages, 2 figures. Accepted to Europhys. Let

    Energy transfer in structured and unstructured environments: Master equations beyond the Born-Markov approximations

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    We explore excitonic energy transfer dynamics in a molecular dimer system coupled to both structured and unstructured oscillator environments. By extending the reaction coordinate master equation technique developed by Iles-Smith et al. [Phys. Rev. A 90, 032114 (2014)], we go beyond the commonly used Born-Markov approximations to incorporate system-environment correlations and the resultant non-Markovian dynamical effects. We obtain energy transfer dynamics for both underdamped and overdamped oscillator environments that are in perfect agreement with the numerical hierarchical equations of motion over a wide range of parameters. Furthermore, we show that the Zusman equations, which may be obtained in a semiclassical limit of the reaction coordinate model, are often incapable of describing the correct dynamical behaviour. This demonstrates the necessity of properly accounting for quantum correlations generated between the system and its environment when the Born-Markov approximations no longer hold. Finally, we apply the reaction coordinate formalism to the case of a structured environment comprising of both underdamped (i.e., sharply peaked) and overdamped (broad) components simultaneously. We find that though an enhancement of the dimer energy transfer rate can be obtained when compared to an unstructured environment, its magnitude is rather sensitive to both the dimer-peak resonance conditions and the relative strengths of the underdamped and overdamped contributions

    The incidence of osteopenia of prematurity in preterm infants without phosphate supplementation A prospective, observational study:A prospective, observational study

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    ABSTRACT: To meet their requirements for bone mineralization, it is recommended that preterm infants receive nutritional support containing calcium and phosphate. There are no clear data on the incidence of osteopenia of prematurity (OFP) in preterm infants without phosphate supplementation.This study aimed to investigate the incidence of OFP in preterm infants without phosphate supplementation and its relationship with the duration of parenteral nutrition (PN).This was a prospective and observational study.This study included 30 infants aged 15 days significantly increased the risk of OFP (odds ratio, 5.40; 95% confidence interval, 1.12-26.04; P = .035).We found a high incidence of OFP in preterm infants without phosphate supplementation. An association was found between the duration of PN and the incidence of OFP. Further research is needed to prevent the development of osteopenia in preterm infants

    First-in-Man Open Clinical Trial of a Combined rdESAT-6 and rCFP-10 Tuberculosis Specific Skin Test Reagent

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    Tuberculin is still the only available skin test reagent for the diagnosis of mycobacterial infection. The product has a remarkable sensitivity, but poor specificity. Previous studies, including two human phase I clinical trials, have indicated that rdESAT-6 has a potential as an improved skin test reagent. Animal studies have shown that the sensitivity may be increased by inclusion of the genetically related CFP-10 antigen in the preparation without loosing specificity.In this study a Lactococcus fermented, recombinant skin test reagent consisting of a 1ratio1 wt/wt of rdESAT-6 and CFP-10 was manufactured according to GMP standards and tested for the first time in 42 healthy adult volunteers. The two doses of 0.01 microg or 0.1 microg were injected intradermally by the Mantoux technique with 6 or 12 weeks interval. No serious adverse events and only mild adverse reactions were reported. The reagent elicited a positive skin test reaction after the first injection in one participant, who most likely was latently infected with M. tuberculosis as indicated by an appreciable IFN gamma response just below the Quantiferon(R) cut-off level at the screening visit. None of the remaining participants in the four groups had any skin test reactions and sensitisation by the reagent could therefore be excluded.The investigational skin test reagent rdESAT-6 and CFP-10 appeared safe and non-sensitising in this first-in-man clinical trial in human volunteers and can now be tested in larger clinical trials involving individuals with latent M. tuberculosis infection or active TB disease.ClinicalTrials.gov NCT00793702
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