1,748 research outputs found

    Which Bank is the "Central" Bank? An Application of Markov Theory to the Canadian Large Value Transfer System

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    We use a method similar to Google's PageRank procedure to rank banks in the Canadian Large Value Transfer System (LVTS). Along the way we obtain estimates of the payment processing speeds for the individual banks. These differences in processing speeds are essential for explaining why observed daily distributions of liquidity differ from the initial distributions, which are determined by the credit limits selected by banks.Payment, clearing, and settlement systems

    Evaluation of susceptibility of pear and plum varieties and rootstocks to Ca. P. pyri and Ca. P. prunorum using Real-Time PCR

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    Real-time PCR was used to quantify phytoplasma concentration in fifty inoculated trees from five Prunus rootstocks and in forty-eight symptomatic pear and Japanese plum trees from orchards. Seasonal fluctuation of Ca. P. prunorum in different Prunus rootstocks, over three years, showed that the highest percentage detected by nested-PCR was in the ‘Garnem’ rootstock on nearly all sampling dates. Intra-varietal differences were also observed. Phytoplasma titer could be estimated by real time PCR in some trees of the rootstocks ‘Garnem’, ‘Barrier’, ‘GF-677’ and ‘Marianna’, and ranged from 4.7x105 to 3.18x109 phytoplasmas per gram of tissue. Quantification by real-time PCR was not possible in the ‘Cadaman’ trees analyzed, probably due to a lower phytoplasma titer in this variety. Samples from infected trees from commercial plots had different phytoplasma concentration and detection percentage depending on the variety, both being lower in ‘Fortune’ and ‘606’ Japanese plum and in ‘Blanquilla’ pear trees.Keywords: Candidatus Phytoplasma pyri, Candidatus Phytoplasma prunorum, real time PCR, detectio

    Multisource data verification of a weather radar surface precipitation type product

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    Póster presentado en: 10th European Conference on Radar in Meteorology and Hydrology celebrado en Wageningen, Países Bajos, del 1 al 6 de julio de 2018.This study was partly supported by projects CGL2015-65627-C3-2-R (MINECO/FEDER), CGL2016-81828-REDT (MINECO) and DI065/2017 (Industrial Doctorate Programme of the Regional Government of Catalonia

    Fantappie's group as an extension of special relativity on Cantorian space-time

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    In this paper we will analyze the Fantappie group and its properties in connection with Cantorian space-time. Our attention will be focused on the possibility of extending special relativity. The cosmological consequences of such extension appear relevant, since thanks to the Fantappie group, the model of the Big Bang and that of stationary state become compatible. In particular, if we abandon the idea of the existence of only one time gauge, since we do not see the whole Universe but only a projection, the two models become compatible. In the end we will see the effects of the projective fractal geometry also on the galactic and extra-galactic dynamics.Comment: 14 pages, accepted in Chaos, Solitons and Fractal

    Improving QPF by blending techniques at the Meteorological Service of Catalonia

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    The current operational very short-term and short-term quantitative precipitation forecast (QPF) at the Meteorological Service of Catalonia (SMC) is made by three different methodologies: Advection of the radar reflectivity field (ADV), Identification, tracking and forecasting of convective structures (CST) and numerical weather prediction (NWP) models using observational data assimilation (radar, satellite, etc.). These precipitation forecasts have different characteristics, lead time and spatial resolutions. The objective of this study is to combine these methods in order to obtain a single and optimized QPF at each lead time. This combination (blending) of the radar forecast (ADV and CST) and precipitation forecast from NWP model is carried out by means of different methodologies according to the prediction horizon. Firstly, in order to take advantage of the rainfall location and intensity from radar observations, a phase correction technique is applied to the NWP output to derive an additional corrected forecast (MCO). To select the best precipitation estimation in the first and second hour (t+1 h and t+2 h), the information from radar advection (ADV) and the corrected outputs from the model (MCO) are mixed by using different weights, which vary dynamically, according to indexes that quantify the quality of these predictions. This procedure has the ability to integrate the skill of rainfall location and patterns that are given by the advection of radar reflectivity field with the capacity of generating new precipitation areas from the NWP models. From the third hour (t+3 h), as radar-based forecasting has generally low skills, only the quantitative precipitation forecast from model is used. This blending of different sources of prediction is verified for different types of episodes (convective, moderately convective and stratiform) to obtain a robust methodology for implementing it in an operational and dynamic wa

    Improvement after two sessions of electroconvulsive therapy predicts final remission in in-patients with major depression

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    Objective: To investigate whether early improvement, measured after two electroconvulsive therapy (ECT) sessions, is a good predictor of eventual remission in severely depressed in-patients receiving ECT. Method: A prospective cohort study was performed that included 89 major depressive disorder in-patients treated with bilateral ECT. Sensitivity, specificity, and predictive values were computed for various definitions of early improvement (15%, 20%, 25%, and 30% reduction on the Montgomery Asberg depression rating scale (MADRS) score) after 1 week (i.e. two sessions) of ECT regarding prediction of remission (final MADRS score ≤ 9). Results: A 15% reduction in MADRS score appeared to be the best definition of early improvement, with modest sensitivity (51%) and relatively good specificity (79%). Kaplan–Meier analysis showed a more than 2-week shorter time to remission in patients with early improvement compared with patients lacking early improvement. Conclusion: Early improvement during an ECT course may be assessed after two ECT sessions. Such improvement, defined as a 15% reduction in the MADRS score, is a moderately sensitive predictor for eventual remission in an in-patient population with severe major depression

    Hypsometric amplification and routing moderation of Greenland ice sheet meltwater release

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    Concurrent ice sheet surface runoff and proglacial discharge monitoring are essential for understanding Greenland ice sheet meltwater release. We use an updated, well-constrained river discharge time series from the Watson River in southwest Greenland, with an accurate, observation-based ice sheet surface mass balance model of the  ∼  12 000 km<sup>2</sup> ice sheet area feeding the river. For the 2006–2015 decade, we find a large range of a factor of 3 in interannual variability in discharge. The amount of discharge is amplified  ∼  56 % by the ice sheet's hypsometry, i.e., area increase with elevation. A good match between river discharge and ice sheet surface meltwater production is found after introducing elevation-dependent transit delays that moderate diurnal variability in meltwater release by a factor of 10–20. The routing lag time increases with ice sheet elevation and attains values in excess of 1 week for the upper reaches of the runoff area at  ∼  1800 m above sea level. These multi-day routing delays ensure that the highest proglacial discharge levels and thus overbank flooding events are more likely to occur after multi-day melt episodes. Finally, for the Watson River ice sheet catchment, we find no evidence of meltwater storage in or release from the en- and subglacial environments in quantities exceeding our methodological uncertainty, based on the good match between ice sheet runoff and proglacial discharge
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