6,215 research outputs found

    Rescattering effects in charmless B_{u,d,s} to P P decays

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    We study the final-state interaction (FSI) effects in charmless B_{u,d,s} to PP decays. We consider a FSI approach with both short- and long-distance contributions, where the former are from in-elastic channels and are contained in factorization amplitudes, while the latter are from the residual rescattering among PP states. Flavor SU(3) symmetry is used to constrain the residual rescattering S-matrix. We fit to all available data on the CP-averaged decay rates and CP asymmetries, and make predictions on unmeasured ones. Our main results are as follows: (i) Results are in agreement with data in the presence of FSI. (ii) For B decays, the pi^+pi^- and pi^0pi^0 rates are suppressed and enhanced respectively by FSI. (iii) The FSI has a large impact on direct CP asymmetries of many modes. (iv) The deviation (Delta A) between A(B{bar}^0 to K^-pi^+) and A(B^-to K^-\pi^0) can be understood in the FSI approach. (v) Sizable and complex color-suppressed tree amplitudes, which are crucial for the large \pi^0\pi^0 rate and Delta A, are generated through exchange rescattering. The correlation of the ratio B(pi^0pi^0)/B(pi^+pi^-) and Delta A is studied. (vi) The B^- to pi^-pi^0 direct CP violation is very small and is not affected by FSI. (vii) Several B_s decay rates are enhanced. In particular, the eta'eta' branching ratio is enhanced to the level of 1.0X10^{-4}, which can be checked experimentally. (viii) Time-dependent CP asymmetries S in B_{d,s} decays are studied. CP asymmetries in these modes will be useful to test the SM.Comment: 33 pages, 6 figures, version to appear in Phys. Rev.

    Evidence for Factorization in Three-body B --> D(*) K- K0 Decays

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    Motivated by recent experimental results, we use a factorization approach to study the three-body B --> D(*) K- K0 decay modes. Two mechanisms are proposed for kaon pair production: current-produced (from vacuum) and transition (from B meson). The Bbar0 --> D(*)+ K- K0 decay is governed solely by the current-produced mechanism. As the kaon pair can be produced only by the vector current, the matrix element can be extracted from e+ e- --> K Kbar processes via isospin relations. The decay rates obtained this way are in good agreement with experiment. Both current-produced and transition processes contribute to B- --> D(*)0 K- K0 decays. By using QCD counting rules and the measured B- --> D(*)0 K- K0 decay rates, the measured decay spectra can be understood.Comment: 17 pages, 6 figure

    Low-Mass Baryon-Antibaryon Enhancements in B Decays

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    The nature of low-mass baryon-antibaryon enhancements seen in B decays is explored. Three possibilities include (i) states near threshold as found in a model by Nambu and Jona-Lasinio, (ii) isoscalar states with JPC=0±+J^{PC} = 0^{\pm +} coupled to a pair of gluons, and (iii) low-mass enhancements favored by the fragmentation process. Ways of distinguishing these mechanisms using angular distributions and flavor symmetry are proposed.Comment: 8 pages, LaTeX, no figures, to be submitted to Phys. Rev. D. One reference adde

    Sampling rare fluctuations of height in the Oslo ricepile model

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    We have studied large deviations of the height of the pile from its mean value in the Oslo ricepile model. We sampled these very rare events with probabilities of order 1010010^{-100} by Monte Carlo simulations using importance sampling. These simulations check our qualitative arguement [Phys. Rev. E, {\bf 73}, 021303, 2006] that in steady state of the Oslo ricepile model, the probability of large negative height fluctuations Δh=αL\Delta h=-\alpha L about the mean varies as exp(κα4L3)\exp(-\kappa {\alpha}^4 L^3) as LL \to \infty with α\alpha held fixed, and κ>0\kappa > 0.Comment: 7 pages, 8 figure

    THE IN VITRO AND EX VIVO EFFECT OF PHYLLANTHUS NIRURI METHANOL EXTRACT ON HEPATIC UDP-GLUCURONYLTRANSFERASE ENZYME ACTIVITY IN STZ-INDUCED DIABETIC SPRAGUE DAWLEY RATS

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    Objective: The aim of the study was to investigate the in vitro and ex vivo (acute and sub-chronic doses) effect of Phyllanthus niruri methanol extract (PNME) on the microsomal UDP-glucuronyltransferase (UGT) enzyme activity in streptozotocin (STZ)-induced diabetic young female Sprague Dawley (SD) rats. Methods: Young female SD rats were induced type I diabetes mellitus using STZ (60 mg/kg i. v.). The in vitro study was performed on a microsomal fraction of diabetic rat livers using PNME in doses of (0.01 µg, 1 µg and 10 µg)/ml. While ex vivo studies were performed on the microsomal fraction of diabetic rats using PNME in doses of 500, 1000, 2000 and 5000 mg/kg p. o. for acute ex vivo study (one-day treatment) and 100, 500 and 2000 mg/kg/day p. o. for sub-chronic one (daily dose for two weeks). p-nitrophenol (p-NP), was used as a marker substrate for UGT enzyme activity and analyzed using the spectrophotometer to determine UGT enzyme activity. Results: The in vitro result showed that, there is no significant effect of the three concentrations of PNME versus control on UGT activity in the microsomal fraction of diabetic young female SD rat livers, while for ex vivo study, the result showed that UGT activity in the microsomal fraction of diabetic young female SD rats significantly and dose-independently increased at doses 1000, 2000 and 5000 mg/kg p. o in acute study (all p<0.05 vs control). However, no significant effect of PNME has been seen in the three doses used in the sub-chronic study. Conclusion: The three different concentrations of PNME have no significant effect as compared to control on UGT activity in the in vitro study. However, ex vivo study showed significant and dose-independent increased in UGT activity at doses 1000, 2000, and 5000 mg/kg p. o in acute study (all P<0.01 vs control), but no significant effect on sub-chronic study

    Psychometric properties of the five-level EuroQoL-5 dimension and Short Form-6 dimension measures of health-related quality of life in a population of pregnant women with depression

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    BACKGROUND: Although evidence suggests that the EuroQoL-5 dimension (EQ-5D) and Short Form-6 dimension (SF-6D) have equivalent psychometric properties in people with depression, there is some evidence that the EQ-5D may lack responsiveness in certain populations with depression. AIMS: To examine the psychometric properties of the five-level EQ-5D (EQ-5D-5L) and SF-6D measures of health-related quality of life in a representative sample of pregnant women with depression. METHOD: Data were taken from a cohort of pregnant women identified at or soon after the first antenatal care contact and followed-up at 3 months postpartum. Health-related quality of life was measured using both the EQ-5D-5L and the SF-6D at baseline and follow-up. We examined acceptability and conducted psychometric validation in the aspects of concurrent validity, convergent validity, known-group validity and responsiveness in 421 women with available data. RESULTS: The EQ-5D-5L and SF-6D have similarly high levels of acceptability. However, concurrent validation shows a lack of concordance between the EQ-5D-5L and SF-6D. The EQ-5D-5L tends to be higher than the SF-6D in individuals with better health states. The SF-6D tends to be higher than EQ-5D-5L in individuals with poorer health states. Convergent and known-group validity are comparable between the two utility measures. Longitudinally, women who recovered show larger increase in SF-6D utilities than those who did not recover at follow-up. With the EQ-5D-5L, this is not the case. Additionally, the ceiling effects were more apparent in the EQ-5D-5L. CONCLUSIONS: The effectiveness of perinatal mental health interventions may be better captured by the SF-6D than the EQ-5D-5L but this needs to be cross-validated in more studies. DECLARATION OF INTEREST: L.M.H. chaired the National Institute for Health and Care Excellence CG192 guidelines development group on antenatal and postnatal mental health in 2012-2014. L.M.H. reports grants from NIHR, MRC, Nuffield and the Stefanou Foundation, UK. K.T., M.H. and S.B. report funding by NIHR and the Stefanou Foundation, UK

    Further investigation on chaos of real digital filters

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    This Letter displays, via the numerical simulation of a real digital filter, that a finite-state machine may behave in a near-chaotic way even when its corresponding infinite-state machine does not exhibit chaotic behavior
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