Estimating the upcrossings index

For stationary sequences, under general dependence restrictions, any limiting point process for time normalized upcrossings of high levels is a compound Poisson process, i.e., there is a clustering of high upcrossings, where the underlying Poisson points represent cluster positions and the multiplicities correspond to cluster sizes. For such classes of stationary sequences, there exists the upcrossings index η, 0≤η≤1, which is directly related to the extremal index θ, 0≤θ≤1, for suitable high levels. In this paper, we consider the problem of estimating the upcrossings index η for a class of stationary sequences satisfying a mild oscillation restriction. For the proposed estimator, properties such as consistency and asymptotic normality are studied. Finally, the performance of the estimator is assessed through simulation studies for autoregressive processes and case studies in the fields of environment and finance. Comparisons with other estimators derived from well known estimators of the extremal index are also presented.     

Chitosan amphiphiles provide new drug delivery opportunities

Chitosan, an acid soluble and renewable biopolymer, was first studied as a drug delivery agent in 1990. This review focuses on the relatively newer self‐assembling chitosan amphiphiles and their use as drug delivery agents. Chitosan amphiphiles, first introduced in the late 1990s, are prepared by conjugating hydrophobic and sometimes additional hydrophilic units to chitosan. These amphiphiles self‐assemble in aqueous media at neutral pH to form micelles, with critical micellar concentrations (CMCs) ranging from 0.09 to 700 µg mL^?1. The CMCs depend on the actual molecular architecture, molecular weight and hydrophobic character, but are typically lower than the values reported for block copolymer amphiphiles. As well as linear amphiphiles in which chitosan is derivatised with hydrophobic pendant groups, new claw amphiphiles have been prepared in which chitosan amphiphiles radiate geometrically from a dendrimer core. These chitosan amphiphiles (linear and claw) have been exploited as drug delivery agents and they increase the oral bioavailability of hydrophobic drugs up to sixfold, deliver hydrophobic drugs to tumours, genes to the liver via the intravenous route, genes to the muscle via the intramuscular routes and small interfering RNAs to tumours via the intratumoural route. Chitosan amphiphile nanoparticles also deliver peptides to the brain via the intravenous and oral routes. © 2014 Society of Chemical Industry     

Fresh-Cut Kiwifruit Structure and Firmness as Affected by Heat Pre-treatments and Post-cut Calcium Dips

The effect of heat pre-treatment (45 °C/25 min), applied to whole fruit, and post-cut calcium dips in 1 and 2 g/L CaCl₂ solutions on respiration rate and texture preservation of kiwifruit slices was studied. During a 9-day period, packages’ atmosphere composition, slices’ firmness, pectin content and sensory scores were evaluated. Histological observations of samples were also performed. Neither heat pre-treatment nor calcium dips alone were effective in diminishing respiration rate of the slices but the application of both treatments revealed a synergistic effect on respiration rate reduction. Calcium-dipped fruit slices showed better firmness preservation. Post-cut calcium dips, alone or combined with heat pre-treatments, yielded slices presenting higher insoluble/total galacturonic acid ratio, indicating formation of calcium pectates. Slices from heat-pre-treated fruits, even in the absence of calcium, also revealed insoluble/total galacturonic acid ratio similar to calcium-treated slices, supporting, despite the lower firmness value, a more structured tissue, as observed in SEM microphotographs. Sensory and physical–chemical parameters obtained were correlated. The effectiveness of calcium treatment was equally observed for both tested concentrations during a 9-day shelf life period.     

Automatic word naming recognition for an on-line aphasia treatment system

One of the most common effects among aphasia patients is the difficulty to recall names or words. Typically, word retrieval problems can be treated through word naming therapeutic exercises. In fact, the frequency and the intensity of speech therapy are key factors in the recovery of lost communication functionalities. In this sense, speech and language technology can have a relevant contribution in the development of automatic therapy methods. In this work, we present an on-line system designed to behave as a virtual therapist incorporating automatic speech recognition technology that permits aphasia patients to perform word naming training exercises. We focus on the study of the automatic word naming detector module and on its utility for both global evaluation and treatment. For that purpose, a database consisting of word naming therapy sessions of aphasic Portuguese native speakers has been collected. In spite of the different patient characteristics and speech quality conditions of the collected data, encouraging results have been obtained thanks to a calibration method that makes use of the patients’ word naming ability to automatically adapt to the patients’ speech particularities.     

Preliminary Developments of Miniplate-Type Fuel of U-2.5Zr-7.5Nb Alloy Dispersed and Cladded in Zircaloy

Nuclear fuel based on uranium metal alloys is utilized in research and test reactors. For the purpose of the reduction of fuel enrichment, high densities of uranium-235 in this kind of fuel are needed. This can be achieved when uranium alloys are used containing elements such as Zr, Mo and Nb. The construction of fuel element with high-uranium density requires materials with low cross sections for neutron absorption, stability under irradiation and absence of the chemical interactions between the fuel and cladding elements. In case of U-Zr-Nb alloys, Zry （zircaloy） cladding is a better option due to the fact that they have a higher chemical compatibility when compared with the use of aluminum alloys. This study aims to develop plate type nuclear fuel using the U-2.5Zr-7.5Nb alloy dispersed in Zry. Powders of this uranium based alloy and Zry were obtained by hydriding-dehydriding process. These powders were homogenized, compacted in pellet that was sandwiched in plates and frame of Zry. This assembly was hot rolled forming the dispersion fuel miniplate.