23,154 research outputs found

    Isostaticity in two dimensional pile of rigid disks

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    We study the static structure of piles made of polydisperse disks in the rigid limit with and without friction using molecular dynamic simulations for various elasticities of the disks and pile preparation procedures. The coordination numbers are calculated to examine the isostaticity of the pile structure. For the frictionless pile, it is demonstrated that the coordination number converges to 4 in the rigid limit, which implies that the structure of rigid disk pile is isostatic. On the other hand, for the frictional case with the infinite friction constant, the coordination number depends on the preparation procedure of the pile, but we find that the structure becomes very close to isostatic with the coordination number close to 3 in the rigid limit when the pile is formed through the process that tends to make a pile of random configuration.Comment: 3 pages, 3 figures, Submitted to J. Phys. Soc. Jp

    Quantum Walks with Entangled Coins

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    We present a mathematical formalism for the description of unrestricted quantum walks with entangled coins and one walker. The numerical behaviour of such walks is examined when using a Bell state as the initial coin state, two different coin operators, two different shift operators, and one walker. We compare and contrast the performance of these quantum walks with that of a classical random walk consisting of one walker and two maximally correlated coins as well as quantum walks with coins sharing different degrees of entanglement. We illustrate that the behaviour of our walk with entangled coins can be very different in comparison to the usual quantum walk with a single coin. We also demonstrate that simply by changing the shift operator, we can generate widely different distributions. We also compare the behaviour of quantum walks with maximally entangled coins with that of quantum walks with non-entangled coins. Finally, we show that the use of different shift operators on 2 and 3 qubit coins leads to different position probability distributions in 1 and 2 dimensional graphs.Comment: Two new sections and several changes from referees' comments. 12 pages and 12 (colour) figure

    Effectiveness of group-based self-management education for individuals with Type 2 diabetes:A systematic review with meta-analyses and meta-regression

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    Aims: Patient education for the management of Type 2 diabetes can be delivered in various forms, with the goal of promoting and supporting positive self-management behaviours. This systematic review aimed to determine the effectiveness of group-based interventions compared with individual interventions or usual care for improving clinical, lifestyle and psychosocial outcomes in people with Type 2 diabetes. Methods: Six electronic databases were searched. Group-based education programmes for adults with Type 2 diabetes that measured glycated haemoglobin (HbA1c) and followed participants for ≥ 6 months were included. The primary outcome was HbA1c, and secondary outcomes included fasting blood glucose, weight, body mass index, waist circumference, blood pressure, blood lipid profiles, diabetes knowledge and self-efficacy. Results: Fifty-three publications describing 47 studies were included (n = 8533 participants). Greater reductions in HbA1c occurred in group-based education compared with controls at 6–10 months [n = 30 studies; mean difference (MD) = 3 mmol/mol (0.3%); 95% confidence interval (CI): −0.48, −0.15; P = 0.0002], 12–14 months [n = 27 studies; MD = 4 mmol/mol (0.3%); 95% CI: −0.49, −0.17; P < 0.0001], 18 months [n = 3 studies; MD = 8 mmol/mol (0.7%); 95% CI: −1.26, −0.18; P = 0.009] and 36–48 months [n = 5 studies; MD = 10 mmol/mol (0.9%); 95% CI: −1.52, −0.34; P = 0.002], but not at 24 months. Outcomes also favoured group-based education for fasting blood glucose, body weight, waist circumference, triglyceride levels and diabetes knowledge, but not at all time points. Interventions facilitated by a single discipline, multidisciplinary teams or health professionals with peer supporters resulted in improved outcomes in HbA1c when compared with peer-led interventions. Conclusions: Group-based education interventions are more effective than usual care, waiting list control and individual education at improving clinical, lifestyle and psychosocial outcomes in people with Type 2 diabetes.No Full Tex

    Perturbative Part of the Non-Singlet Structure Function F_2 in the Large-N_F Limit

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    We have calculated MSˉ\bar{MS} Wilson coefficients and anomalous dimensions for the non-singlet part of the structure function F_2 in the large-N_F limit. Our result agrees with exact two and three loop calculations and gives the leading N_F dependence of the perturbative non-singlet Wilson coefficients to all orders in αS\alpha_S.Comment: 11 pages, including one figur

    Leading twist contribution to color singlet χc0,2→ωω\chi_{c0,2}\to\omega\omega decays

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    In this paper the leading twist contribution to χc0,2→ωω\chi_{c0,2}\to\omega\omega decays in the color singlet approximation is considered. It is shown, that the predictions for \Br(\chi_0\to\omega\omega) is in a good agreement with the experimental data, while \Br(\chi_{c2}\to\omega\omega) differs from the experiment significantly.Comment: 4 pages, RevTeX; minor changes, some refrences adde

    The Bs→KB_{s}\to K Form Factor in The Whole Kinematically Accessible Range

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    A systematic analysis is presented of the Bs→KB_{s}\to K form factor f(q2)f(q^{2}) in the whole range of momentum transfer q2q^{2}, which would be useful to analyzing the future data on Bs→KB_{s}\to K decays and extracting ∣Vub∣| V_{ub}|. With a modified QCD light cone sum rule (LCSR) approach, in which the contributions cancel out from the twist 3 wavefunctions of KK meson, we investigate in detail the behavior of f(q2)f(q^{2}) at small and intermediate q2q^{2} and the nonperturbative quantity fB∗gB∗BsKf_{B^{\ast}}g_{B^{\ast}B_{s}K} (fB∗(f_{B^{\ast}} is the decay constant of B∗B^{\ast} meson and gB∗BsKg_{B^{\ast}B_{s}K} the B∗BsKB^{\ast}B_{s}K strong coupling), whose numerical result is used to study q2q^{2} dependence of f(q2)f(q^{2}) at large q2q^{2} in the single pole approximation. Based on these findings, a form factor model from the best fit is formulated, which applies to the calculation on f(q2)f(q^{2}) in the whole kinematically accessible range. Also, a comparison is made with the standard LCSR predictions.Comment: 11 pages, Latex, 1 eps figure, Final version to appear in Phys.Rev.

    Heavy to Light Meson Exclusive Semileptonic Decays in Effective Field Theory of Heavy Quark

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    We present a general study on exclusive semileptonic decays of heavy (B, D, B_s) to light (pi, rho, K, K^*) mesons in the framework of effective field theory of heavy quark. Transition matrix elements of these decays can be systematically characterized by a set of wave functions which are independent of the heavy quark mass except for the implicit scale dependence. Form factors for all these decays are calculated consistently within the effective theory framework using the light cone sum rule method at the leading order of 1/m_Q expansion. The branching ratios of these decays are evaluated, and the heavy and light flavor symmetry breaking effects are investigated. We also give comparison of our results and the predictions from other approaches, among which are the relations proposed recently in the framework of large energy effective theory.Comment: 18 pages, ReVtex, 5 figures, added references and comparison of results, and corrected signs in some formula

    Benefits of Public R&D in U.S. Agriculture: Spill-Ins, Extension and Roads

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    This paper uses panel data for the 1980-2004 period to estimate the contributions of public research to US agricultural productivity growth. Local and social internal rates of return are estimated accounting for the effects of R & D spill-in, extension activities and road density. R & D spill-in proxies were constructed based on both geographic proximity and production profile to examine the sensitivity of the rates of return to these alternatives. We find that extension activities, road density, and R & D spill-ins, play an important role in enhancing the benefit of public R & D investments. We also find that the local internal rates of return, although high, have declined through time along with investments in extension, while the social rates have not. Yet, the social rates of return are not robust to the choice of spill-in proxy
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