3,436 research outputs found

    Kahler Moduli Inflation Revisited

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    We perform a detailed numerical analysis of inflationary solutions in Kahler moduli of type IIB flux compactifications. We show that there are inflationary solutions even when all the fields play an important role in the overall shape of the scalar potential. Moreover, there exists a direction of attraction for the inflationary trajectories that correspond to the constant volume direction. This basin of attraction enables the system to have an island of stability in the set of initial conditions. We provide explicit examples of these trajectories, compute the corresponding tilt of the density perturbations power spectrum and show that they provide a robust prediction of n_s approximately 0.96 for 60 e-folds of inflation.Comment: 27 pages, 9 figure

    Optimized intermolecular potential for nitriles based on Anisotropic United Atoms model

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    An extension of the Anisotropic United Atoms intermolecular potential model is proposed for nitriles. The electrostatic part of the intermolecular potential is calculated using atomic charges obtained by a simple Mulliken population analysis. The repulsion-dispersion interaction parameters for methyl and methylene groups are taken from transferable AUA4 literature parameters [Ungerer et al., J. Chem. Phys., 2000, 112, 5499]. Non-bonding Lennard-Jones intermolecular potential parameters are regressed for the carbon and nitrogen atoms of the nitrile group (–C≡N) from experimental vapor-liquid equilibrium data of acetonitrile. Gibbs Ensemble Monte Carlo simulations and experimental data agreement is very good for acetonitrile, and better than previous molecular potential proposed by Hloucha et al. [J. Chem. Phys., 2000, 113, 5401]. The transferability of the resulting potential is then successfully tested, without any further readjustment, to predict vapor-liquid phase equilibrium of propionitrile and n-butyronitrile

    The relationship between anxiety and acute mountain sickness.

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    INTRODUCTION: Whilst the link between physical factors and risk of high altitude (HA)-related illness and acute mountain sickness (AMS) have been extensively explored, the influence of psychological factors has been less well examined. In this study we aimed to investigate the relationship between 'anxiety and AMS risk during a progressive ascent to very HA. METHODS: Eighty health adults were assessed at baseline (848m) and over 9 consecutive altitudes during a progressive trek to 5140m. HA-related symptoms (Lake Louise [LLS] and AMS-C Scores) and state anxiety (State-Trait-Anxiety-Score [STAI Y-1]) were examined at each altitude with trait anxiety (STAI Y-2) at baseline. RESULTS: The average age was 32.1 ± 8.3 years (67.5% men). STAI Y-1 scores fell from 848m to 3619m, before increasing to above baseline scores (848m) at ≥4072m (p = 0.01). STAI Y-1 scores correlated with LLS (r = 0.31; 0.24-0.3; P<0.0001) and AMS-C Scores (r = 0.29; 0.22-0.35; P<0.0001). There was significant main effect for sex (higher STAI Y-1 scores in women) and altitude with no sex-x-altitude interaction on STAI Y-1 Scores. Independent predictors of significant state anxiety included female sex, lower age, higher heart rate and increasing LLS and AMS-C scores (p<0.0001). A total of 38/80 subjects (47.5%) developed AMS which was mild in 20 (25%) and severe in 18 (22.5%). Baseline STAI Y-2 scores were an independent predictor of future severe AMS (B = 1.13; 1.009-1.28; p = 0.04; r2 = 0.23) and STAI Y-1 scores at HA independently predicted AMS and its severity. CONCLUSION: Trait anxiety at low altitude was an independent predictor of future severe AMS development at HA. State anxiety at HA was independently associated with AMS and its severity

    Segond's fracture: a biomechanical cadaveric study using navigation

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    Background Segond’s fracture is a well-recognised radiological sign of an anterior cruciate ligament (ACL) tear. While previous studies evaluated the role of the anterolateral ligament (ALL) and complex injuries on rotational stability of the knee, there are no studies on the biomechanical effect of Segond’s fracture in an ACL deficient knee. The aim of this study was to evaluate the effect of a Segond’s fracture on knee rotation stability as evaluated by a navigation system in an ACL deficient knee. Materials and methods Three different conditions were tested on seven knee specimens: intact knee, ACL deficient knee and ACL deficient knee with Segond’s fracture. Static and dynamic measurements of anterior tibial translation (ATT) and axial tibial rotation (ATR) were recorded by the navigation system (2.2 OrthoPilot ACL navigation system B. Braun Aesculap, Tuttlingen, Germany). Results Static measurements at 30 showed that the mean ATT at 30 of knee flexion was 5.1 ± 2.7 mm in the ACL intact condition, 14.3 ± 3.1 mm after ACL cut (P = 0.005), and 15.2 ± 3.6 mm after Segond’s fracture (P = 0.08). The mean ATR at 30 of knee flexion was 20.7 ± 4.8 in the ACL intact condition, 26.9 ± 4.1 in the ACL deficient knee (P[0.05) and 30.9 ± 3.8 after Segond’s fracture (P = 0.005). Dynamic measurements during the pivot-shift showed that the mean ATT was 7.2 ± 2.7 mm in the intact knee, 9.1 ± 3.3 mm in the ACL deficient knee(P = 0.04) and 9.7 ± 4.3 mm in the ACL deficient knee with Segond’s fracture (P = 0.07). The mean ATR was 9.6 ± 1.8 in the intact knee, 12.3 ± 2.3 in the ACL deficient knee (P[0.05) and 19.1 ± 3.1 in the ACL deficient knee with Segond’s lesion (P = 0.016). Conclusion An isolated lesion of the ACL only affects ATT during static and dynamic measurements, while the addition of Segond’s fracture has a significant effect on ATR in both static and dynamic execution of the pivot-shift test, as evaluated with the aid of navigation

    Epidemics on contact networks: a general stochastic approach

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    Dynamics on networks is considered from the perspective of Markov stochastic processes. We partially describe the state of the system through network motifs and infer any missing data using the available information. This versatile approach is especially well adapted for modelling spreading processes and/or population dynamics. In particular, the generality of our systematic framework and the fact that its assumptions are explicitly stated suggests that it could be used as a common ground for comparing existing epidemics models too complex for direct comparison, such as agent-based computer simulations. We provide many examples for the special cases of susceptible-infectious-susceptible (SIS) and susceptible-infectious-removed (SIR) dynamics (e.g., epidemics propagation) and we observe multiple situations where accurate results may be obtained at low computational cost. Our perspective reveals a subtle balance between the complex requirements of a realistic model and its basic assumptions.Comment: Main document: 16 pages, 7 figures. Electronic Supplementary Material (included): 6 pages, 1 tabl

    F-theory and Neutrinos: Kaluza-Klein Dilution of Flavor Hierarchy

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    We study minimal implementations of Majorana and Dirac neutrino scenarios in F-theory GUT models. In both cases the mass scale of the neutrinos m_nu ~ (M_weak)^2/M_UV arises from integrating out Kaluza-Klein modes, where M_UV is close to the GUT scale. The participation of non-holomorphic Kaluza-Klein mode wave functions dilutes the mass hierarchy in comparison to the quark and charged lepton sectors, in agreement with experimentally measured mass splittings. The neutrinos are predicted to exhibit a "normal" mass hierarchy, with masses m_3,m_2,m_1 ~ .05*(1,(alpha_GUT)^(1/2),alpha_GUT) eV. When the interactions of the neutrino and charged lepton sectors geometrically unify, the neutrino mixing matrix exhibits a mild hierarchical structure such that the mixing angles theta_23 and theta_12 are large and comparable, while theta_13 is expected to be smaller and close to the Cabibbo angle: theta_13 ~ theta_C ~ (alpha_GUT)^(1/2) ~ 0.2. This suggests that theta_13 should be near the current experimental upper bound.Comment: v2: 83 pages, 10 figures, references adde

    Susceptibility to tuberculosis is associated with variants in the ASAP1 gene encoding a regulator of dendritic cell migration

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    Human genetic factors predispose to tuberculosis (TB). We studied 7.6 million genetic variants in 5,530 people with pulmonary TB and in 5,607 healthy controls. In the combined analysis of these subjects and the follow-up cohort (15,087 TB patients and controls altogether), we found an association between TB and variants located in introns of the ASAP1 gene on chromosome 8q24 (P = 2.6 × 10−11 for rs4733781; P = 1.0 × 10−10 for rs10956514). Dendritic cells (DCs) showed high ASAP1 expression that was reduced after Mycobacterium tuberculosis infection, and rs10956514 was associated with the level of reduction of ASAP1 expression. The ASAP1 protein is involved in actin and membrane remodeling and has been associated with podosomes. The ASAP1-depleted DCs showed impaired matrix degradation and migration. Therefore, genetically determined excessive reduction of ASAP1 expression in M. tuberculosis–infected DCs may lead to their impaired migration, suggesting a potential mechanism of predisposition to TB

    Self-assembly, Self-organization, Nanotechnology and vitalism

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    International audienceOver the past decades, self-assembly has attracted a lot of research attention and transformed the relations between chemistry, materials science and biology. The paper explores the impact of the current interest in self-assembly techniques on the traditional debate over the nature of life. The first section describes three different research programs of self-assembly in nanotechnology in order to characterize their metaphysical implications: -1- Hybridization ( using the building blocks of living systems for making devices and machines) ; -2- Biomimetics (making artifacts mimicking nature); -3- Integration (a composite of the two previous strategies). The second section focused on the elusive boundary between selfassembly and self-organization tries to map out the various positions adopted by the promoters of self-assembly on the issue of vitalism

    Canine respiratory coronavirus employs caveolin-1-mediated pathway for internalization to HRT-18G cells

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    Canine respiratory coronavirus (CRCoV), identified in 2003, is a member of the Coronaviridae family. The virus is a betacoronavirus and a close relative of human coronavirus OC43 and bovine coronavirus. Here, we examined entry of CRCoV into human rectal tumor cells (HRT-18G cell line) by analyzing co-localization of single virus particles with cellular markers in the presence or absence of chemical inhibitors of pathways potentially involved in virus entry. We also targeted these pathways using siRNA. The results show that the virus hijacks caveolin-dependent endocytosis to enter cells via endocytic internalization
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