999 resultados para Quadratic term
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The propagation of small amplitude stationary profile nonlinear electrostatic excitations in a pair plasma is investigated, mainly drawing inspiration from experiments on fullerene pair-ion plasmas. Two distinct pair ion species are considered of opposite polarity and same mass, in addition to a massive charged background species, which is assumed to be stationary, given the frequency scale of interest. In the pair-ion context, the third species is thought of as a background defect (e.g. charged dust) component. On the other hand, the model also applies formally to electron-positron-ion (e-p-i) plasmas, if one neglects electron-positron annihilation. A two-fluid plasma model is employed, incorporating both Lorentz and Coriolis forces, thus taking into account the interplay between the gyroscopic (Larmor) frequency ?c and the (intrinsic) plasma rotation frequency O0. By employing a multi-dimensional reductive perturbation technique, a Zakharov-Kuznetsov (ZK) type equation is derived for the evolution of the electric potential perturbation. Assuming an arbitrary direction of propagation, with respect to the magnetic field, we derive the exact form of nonlinear solutions, and study their characteristics. A parametric analysis is carried out, as regards the effect of the dusty plasma composition (background number density), species temperature(s) and the relative strength of rotation to Larmor frequencies. It is shown that the Larmor and mechanical rotation affect the pulse dynamics via a parallel-to-transverse mode coupling diffusion term, which in fact diverges at ?c ? ±2O0. Pulses collapse at this limit, as nonlinearity fails to balance dispersion. The analysis is complemented by investigating critical plasma compositions, in fact near-symmetric (T- ˜ T+) “pure” (n- ˜ n+) pair plasmas, i.e. when the concentration of the 3rd background species is negligible, case in which the (quadratic) nonlinearity vanishes, so one needs to resort to higher order nonlinear theory. A modified ZK equation is derived and analyzed. Our results are of relevance in pair-ion (fullerene) experiments and also potentially in astrophysical environments, e.g. in pulsars.
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This paper examines (i) whether value-growth characteristics have more power than past performance in predicting return reversals; and (ii) whether typical rational behaviour such as incentives to delay paying capital gain taxes can better explain long-term reversals than past performance. We find that value-growth characteristics generally provide better explanations for long-term stock returns than past performance. The evidence also shows that winners identified by capital gains dominate past performance winners in predicting reversals in the cross-sectional comparison. However, in the time-series analysis, when returns on capital gain winners are adjusted by the Fama and French (1996) risk factors, the predictive power of capital gain winners disappears. Our results show that capital gain winners are heavily featured as growth stocks. Return reversals in capital gain winners potentially reflect market price corrections for growth stocks. We conclude that investors’ incentives to delay paying capital gain taxes cannot fully rationalise long-term reversals in the UK market. Our results also imply that the long-term return pattern potentially reflects a mixture of investor rational and irrational behaviour.
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An experimental investigation of the effect of conductor-to-substrate interface on distributed passive intermodulation (PIM) generation in printed microstrip lines has been undertaken using the custom-designed microwave laminates with removed surface bonding layers and with the commercial adhesion promotion applied to the conductor underside. The study of long-term stability of PIM performance of the printed circuits is reported for the first time. The comprehensive measurement results, observations of the selfimprovement of the PIM performance and the effect of panel bending on PIM generation in printed boards with different finishing are presented. A consistent physical interpretation of the observed phenomena is proposed. The results of this study provide new important considerations for the design and characterisation of low-PIM printed circuits.
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The aim of this study was to determine bow nutrient intake is affected by a short-term phytoestrogen-rich diet. Ten healthy volunteers consumed 100 g soya chunks, 150 g lentils, and 250 g kidney beans daily for 3 days. Urine was collected during the 2 days before, 3 intervention days, and 2 days after the intervention and analyzed for phytoestrogen status. Subjects filled in food diaries throughout the study period. Urinary daidzein, but not equol and enterolactone, levels increased during the 7-day period. There was no change in energy, protein, sugar, or total fat intake, but an increase in carbohydrate, fiber, and starch intake. There was a change in the distribution of fat intake with a fall in saturated fat and cholesterol intake. Iron intake significantly increased, although vitamin B-12 fell significantly. The long-term effects of this diet and the associated health benefits of these changes require further study. (C) 2006 Elsevier Inc. All rights reserved.
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Phytoestrogens are plant compounds that have been proposed to have a variety of health benefits. The aim of this study was to assess the effects of these compounds on a number of physiological endpoints. Subjects were given a single intake of a phytoestrogen-rich (80 mg total phytoestrogens) supplement containing soy, rye and linseed (Phase 1), followed by a week-long intervention using the same supplement (Phase 2) (80 mg total phytoestrogens daily). A number of biochemical endpoints were assessed including urinary phytoestrogen metabolites, lipids, antioxidant status, DNA damage and insulin-like growth factor-1 (IGF-1) and IGF binding protein-1 (IGFBP-1) and -3 (IGFBP-3). Ten healthy female subjects took part in the study. Excretion of the isoflavones genistein, daidzein and equol in urine increased in both phases of the study. No other endpoint was altered in Phase 1. However, in Phase 2, concentrations of IGF-1 and IGFBP-3 were increased by phytoestrogen supplementation [IGF-1, median (IQ range), baseline 155 (123, 258), postweek 265 (228, 360) ng/ml, P
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Introduction: Our objective was to determine which factors were predictive of good long-term outcomes after fixed appliance treatment of Class II Division 1 malocclusion. Methods: Two hundred seven patients with Class II Division 1 malocclusion were examined in early adulthood at a mean of 4.6 years after treatment with fixed appliances. The peer assessment rating index was used to evaluate dental alignment and occlusal relationships. The soft-tissue profile was assessed with the Holdaway angle. Results: Logistic regression identified 3 pretreatment variables that were predictive of a good facial profile (Holdaway angle) at recall: the lower lip to E-plane distance (P
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Because of their critical location adjacent to brain, cranial nerve, and vascular structures, petroclival meningiomas remain a clinical challenge. As first author, I evaluated outcomes in 168 patients with petroclival meningiomas who underwent Gamma Knife surgery (GKS) during a 21-year interval at the University of Pittsburgh.