Uncle traps: harvesting rewards in a queue-based ethereum Mining Pool

Mining pools in Proof-of-Work cryptocurrencies allow miners topool their computational resources as a means of reducing payoutvariance. In Ethereum,uncle blocksare valid Proof-of-Work solu-tions which do not become the head of the blockchain, yet yieldrewards if later referenced by main chain blocks. Mining pool opera-tors are faced with the non-trivial task of fairly distributing rewardsfor both block types among pool participants.Inspired by empirical observations, we formally reconstruct aSybil attack exploiting the uncle block distribution policy in a queue-based mining pool. To ensure fairness of the queue-based payoutscheme, we propose a mitigation. We examine the effectiveness ofthe attack strategy under the current and the proposed policy via adiscrete-event simulation. Our findings show that the observed attackcan indeed be obviated by altering the current reward scheme

Improving interval estimation of binomial proportions

In this paper, we propose one new confidence interval for the binomial proportion; our interval is based on the Edgeworth expansion of a logit transformation of the sample proportion. We provide theoretical justification for the proposed interval and also compare the finite-sample performance of the proposed interval with the three best existing intervals—the Wilson interval, the Agresti–Coull interval and the Jeffreys interval—in terms of their coverage probabilities and expected lengths. We illustrate the proposed method in two real clinical studies

Zimosis en vinos

We have isolated one sporulate yeast strain that produce a thick pellicle on the top of a disease wine. lt has been made the taxonomyc study in pure culture and it was analysed it's probable systematic position. It has been reproduced the disease in a lot of wines. The analitie results revea that the alcohol is kept without harmfull but the total accidity is considerably reduced by the yeast effect.Se aísla una levadura esporulada que forma gruesa película en la superficie de un vino alterado. Se hace el estudio taxonómico en cultivo puro. Se analiza su probable ubicación sistemática. Se reproduce la formación de película en una serie de vinos del comercio. Los datos analíticos revelan que el alcohol no es oxidado, pero sí la acción zimógeno modifica la proporción de ácidos totales que se reducen apreciablemente. Para mayores detalles sobre los métodos empleados nos remitirnos a nuestros trabajos citados en la bibliografía con los n% 4 y 5.Fil: De Pritz, María J. R.. Universidad Nacional de Cuyo. Facultad de Ciencias AgrariasFil: Llop, Armando A.

A simplified transfer matrix approach for the determination of the complex modulus of viscoelastic materials

Nowadays, several analytical and numerical approaches are available for analysing the performance of materials used in noise and vibration control applications. All these methodologies require knowledge of a set of input parameters which, in the case of viscoelastic materials, could exhibit strong dependence on frequency in the entire audible range. The aim of this paper is to present a simplified transfer matrix approach for the determination of the complex modulus for longitudinal waves of isotropic viscoelastic materials as a function of frequency. To that effect, the tested material is excited by an electromagnetic shaker and longitudinal waves are investigated. Using a frequency sweep as an excitation signal, the time domain response is measured downstream and upstream of the sample itself. A velocity transfer function is measured and, by using a transfer matrix model of the experimental setup, the complex wave number for longitudinal waves and, consequently, the complex modulus can be determined once the Poisson’s ratio is known in advance. The results are presented and discussed for different materials and compared with well-established quasi-static and dynamic techniques

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The following report provides results from a geochemical survey for Thomas Range-Wasatch, Utah. Field and laboratory data are presented for 15 groundwater and 79 stream sediment samples

Protein-Protein Fusion Catalyzed by Sortase A

Chimeric proteins boast widespread use in areas ranging from cell biology to drug delivery. Post-translational protein fusion using the bacterial transpeptidase sortase A provides an attractive alternative when traditional gene fusion fails. We describe use of this enzyme for in vitro protein ligation and report the successful fusion of 10 pairs of protein domains with preserved functionality — demonstrating the robust and facile nature of this reaction

Evaluation of ELISA and haemagglutination inhibition as screening tests in serosurveillance for H5/H7 avian influenza in commercial chicken flocks

Avian influenza virus (AIV) subtypes H5 and H7 can infect poultry causing low pathogenicity (LP) AI, but these LPAIVs may mutate to highly pathogenic AIV in chickens or turkeys causing high mortality, hence H5/H7 subtypes demand statutory intervention. Serological surveillance in the European Union provides evidence of H5/H7 AIV exposure in apparently healthy poultry. To identify the most sensitive screening method as the first step in an algorithm to provide evidence of H5/H7 AIV infection, the standard approach of H5/H7 antibody testing by haemagglutination inhibition (HI) was compared with an ELISA, which detects antibodies to all subtypes. Sera (n = 1055) from 74 commercial chicken flocks were tested by both methods. A Bayesian approach served to estimate diagnostic test sensitivities and specificities, without assuming any 'gold standard'. Sensitivity and specificity of the ELISA was 97% and 99.8%, and for H5/H7 HI 43% and 99.8%, respectively, although H5/H7 HI sensitivity varied considerably between infected flocks. ELISA therefore provides superior sensitivity for the screening of chicken flocks as part of an algorithm, which subsequently utilises H5/H7 HI to identify infection by these two subtypes. With the calculated sensitivity and specificity, testing nine sera per flock is sufficient to detect a flock seroprevalence of 30% with 95% probability

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Results of the Chinati Mountains project area of the detailed geochemical survey fro Trans-Pecos, Texas are reported

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Results of the Dryden project area of the detailed geochemical survey for Trans-Pecos, Texas are reported