8,331 research outputs found

    Chiral Anomaly Effects and the BaBar Measurements of the γγπ0\gamma\gamma^{*}\to \pi^{0} Transition Form Factor

    Full text link
    The recent BaBar measurements of the γγπ0\gamma\gamma^{*}\to \pi^{0} transition form factor show spectacular deviation from perturbative QCD prediction for large space-like Q2Q^{2} up to 34GeV234\,\rm GeV^{2}. When plotted against Q2Q^{2}, Q2F(Q2)Q^{2}F(Q^{2}) shows steady increase with Q2Q^{2} in contrast with the flat Q2Q^{2} behavior predicted by perturbative QCD, and at 34GeV234\,\rm GeV^{2} is more than 50% larger than the QCD prediction. Stimulated by the BaBar measurements, we revisit our previous paper on the cancellation of anomaly effects in high energy processes Z0π0γZ^{0}\to \pi^{0}\gamma, e+eπ0γe^{+}e^{-}\to \pi^{0}\gamma and apply our results to the γγπ0\gamma^{*}\gamma\to \pi^{0} transition form factor measured in the e+ee+eπ0e^{+}e^{-}\to e^{+}e^{-}\pi^{0} process with one highly virtual photon. We find that, the transition form factor F(Q2)F(Q^{2}) behaves as (m2Q2)×(ln(Q2/m2))2(\frac{m^{2}}{Q^{2}})\times (\ln(Q^{2}/m^{2}))^{2} and produces a striking agreement with the BaBar data for Q2F(Q2)Q^{2}F(Q^{2}) with m=132MeVm=132\,\rm MeV which also reproduces very well the CLEO data at lower Q2Q^{2}.Comment: v4, LaTeX, 8 pages, one figure, minor changes(references), to appear in Int. J. Mod. Phys.

    Cattle as a consistently resilient agricultural commodity

    Get PDF
    This study compares a range of agricultural commodities over periods of varying economic circumstances. These commodities are examined over three categories, including returns, risk, and contribution to portfolio optimisation. Consistency in these categories is determined over four equal three-year stages which comprise pre-GFC (Global Financial Crisis), GFC, post-GFC and post-post GFC. To demonstrate resilience in the most extreme circumstances, the study uses Conditional Value at Risk (CVaR), which measures extreme risk in the tail of a distribution, as the risk measure and risk-return optimiser. The study thus provides a unique and comprehensive extreme-risk based focus which identifies and ranks the consistency of performance of agricultural commodities over a range of criteria and conditions. Cattle commodities consistently demonstrate the strongest overall performance in the categories examined

    Do nonparametric measures of extreme equity risk change the parametric ordinal ranking? Evidence from Asia

    Get PDF
    There has been much discussion in the literature about how central measures of equity risk such as standard deviation fail to account for extreme tail risk of equities. Similarly, parametric measures of value at risk (VaR) may also fail to account for extreme risk as they assume a normal distribution which is often not the case in practice. Nonparametric measures of extreme risk such as nonparametric VaR and conditional value at risk (CVaR) have often been found to overcome this problem by measuring actual tail risk without applying any predetermined assumptions. However, this article argues that it is not just the actual risk of equites that is important to investor choices, but also the relative (ordinal) risk of equities compared to each other. Using an applied setting of industry portfolios in a variety of Asian countries (benchmarked to the United States), over crisis and non-crisis periods, this article finds that nonparametric measures of VaR and CVaR may provide only limited new information to investors about relative risk in the portfolios examined as there is a high degree of similarity found in relative industry risk when using nonparametric metrics as compared to central or parametric measures such as standard deviation and parametric VaR

    Loss of Mfn2 results in progressive, retrograde degeneration of dopaminergic neurons in the nigrostriatal circuit

    Get PDF
    Mitochondria continually undergo fusion and fission, and these dynamic processes play a major role in regulating mitochondrial function. Studies of several genes associated with familial Parkinson's disease (PD) have implicated aberrant mitochondrial dynamics in the disease pathology, but the importance of these processes in dopaminergic neurons remains poorly understood. Because the mitofusins Mfn1 and Mfn2 are essential for mitochondrial fusion, we deleted these genes from a subset of dopaminergic neurons in mice. Loss of Mfn2 results in a movement defect characterized by reduced activity and rearing. In open field tests, Mfn2 mutants show severe, age-dependent motor deficits that can be rescued with L-3,4 dihydroxyphenylalanine. These motor deficits are preceded by the loss of dopaminergic terminals in the striatum. However, the loss of dopaminergic neurons in the midbrain occurs weeks after the onset of these motor and striatal deficits, suggesting a retrograde mode of neurodegeneration. In our conditional knockout strategy, we incorporated a mitochondrially targeted fluorescent reporter to facilitate tracking of mitochondria in the affected neurons. Using an organotypic slice culture system, we detected fragmented mitochondria in the soma and proximal processes of these neurons. In addition, we found markedly reduced mitochondrial mass and transport, which may contribute to the neuronal loss. These effects are specific for Mfn2, as the loss of Mfn1 yielded no corresponding defects in the nigrostriatal circuit. Our findings indicate that perturbations of mitochondrial dynamics can cause nigrostriatal defects and may be a risk factor for the neurodegeneration in PD

    Optimized FRP Wrapping Schemes for Circular Concrete Columns under Axial Compression

    Get PDF
    This study investigates the behavior and failure modes of fiber-reinforced polymer (FRP) confined concrete wrapped with different FRP schemes, including fully wrapped, partially wrapped, and nonuniformly-wrapped concrete cylinders. By using the same amount of FRP, this study proposes a new wrapping scheme that provides a higher compressive strength and strain for FRP-confined concrete, in comparison with conventional fully wrapping schemes. A total of 33 specimens were cast and tested, with three of these specimens acting as reference specimens and the remaining specimens wrapped with different types of FRP (CFRP and GFRP) by different wrapping schemes. For specimens that belong to the descending branch type, the partially-wrapped specimens had a lower compressive strength but a higher axial strain as compared to the corresponding fully-wrapped specimens. In addition, the nonuniformly-wrapped specimens achieved both a higher compressive strength and axial strain in comparison with the fully-wrapped specimens. Furthermore, the partially-wrapping scheme changes the failure modes of the specimens and the angle of the failure surface. A new equation that can be used to predict the axial strain of concrete cylinders wrapped partially with FRP is proposed

    Nano-scale reservoir computing

    Full text link
    This work describes preliminary steps towards nano-scale reservoir computing using quantum dots. Our research has focused on the development of an accumulator-based sensing system that reacts to changes in the environment, as well as the development of a software simulation. The investigated systems generate nonlinear responses to inputs that make them suitable for a physical implementation of a neural network. This development will enable miniaturisation of the neurons to the molecular level, leading to a range of applications including monitoring of changes in materials or structures. The system is based around the optical properties of quantum dots. The paper will report on experimental work on systems using Cadmium Selenide (CdSe) quantum dots and on the various methods to render the systems sensitive to pH, redox potential or specific ion concentration. Once the quantum dot-based systems are rendered sensitive to these triggers they can provide a distributed array that can monitor and transmit information on changes within the material.Comment: 8 pages, 9 figures, accepted for publication in Nano Communication Networks, http://www.journals.elsevier.com/nano-communication-networks/. An earlier version was presented at the 3rd IEEE International Workshop on Molecular and Nanoscale Communications (IEEE MoNaCom 2013

    Diffusivity and configurational entropy maxima in short range attractive colloids

    Full text link
    We study tagged particle diffusion at large packing fractions, for a model of particles interacting with a generalized Lennard-Jones 2n-n potential, with large n. The resulting short-range potential mimics interactions in colloidal systems. In agreement with previous calculations for short-range potential, we observe a diffusivity maximum as a function of temperature. By studying the temperature dependence of the configurational entropy -- which we evaluate with two different methods -- we show that a configurational entropy maximum is observed at a temperature close to that of the diffusivity maximum. Our findings suggest a relationbetween dynamics and number of distinct states for short-range potentials.Comment: 4 pages, 3 figures, submited to Physical Review Lette

    Review of potential and actual penetration of solar power in Vietnam

    Get PDF
    With the average solar radiation reaching up to 5 kWh/m2, Vietnam is considered as a country showing an excellent potential for solar power production. Since the year 2000, there have been a lot of studies about the potential of this source in Vietnam. So far, many applications of solar power have been implemented on small, medium, and large scales. In fact, the total capacity of current grid-connected solar power plants has exceeded the planned capacity by 2020 nearly 6 times. However, the studies of solar potential in Vietnam are still incomplete. The policies and mechanisms for developing solar power projects have received attention from the authorities but have not been really satisfactory. The infrastructure is still poor and the power system does not keep up with the development of modern grids. This paper reviewed the potential and actual implementation stage of photovoltaic projects in Vietnam. Moreover, the barriers and challenges of institution, technique, economy, and finance have been considered explicitly for the future development of solar energy in Vietnam
    corecore