Search results for "SELE"
showing 10 items of 4721 documents
Proton Acid-Catalysed Transformations of Estrogen Derivatives: New Results and Some Mechanistic Aspects of theKober Colour Reaction
1994
The 3-O-methylated estrogen derivatives 1a-d and α-estradiol (1e) underwent sulfuric acid-catalysed transformations to furnish the steroids 2–6. The processes involved in the reaction sequence are regioselective sulfonation and, above all, the Wagner-Meerwein rearrangement of the methyl group at C-13. With the objective of obtaining further information on the course of the Kober colour reaction of estrogens, some UV/VIS and ESR spectroscopic investigations were also carried out. Protonenkatalysierte Transformationen von Estrogen-Derivaten: Neue Ergebnisse und einige mechanistische Aspekte der Kober-Farbreaktion Die O-methylierten Estrogenderivate 1a-d und α-Estradiol (1e) reagieren in Schwe…
Efficient analysis of in-line waveguide filters and frequency-selective surfaces with stepped holes
2003
This paper presents a novel method for the analysis of large classes of microwave and mm-wave passive components, including in-line waveguide filters, single- and multi-layer frequency selective surfaces, and open-ended waveguide array antennas. This method is based on the segmentation technique, which permits us to reduce complex components to cascaded waveguide step discontinuities, which are separately characterized through their generalized impedance matrices, as calculated by the integral equation (IE) technique and the boundary integral-resonant mode expansion (BI-RME) method. Some examples demonstrate the flexibility and efficiency of the IE/BI-RME method, and its utility in investig…
Feature selection: A multi-objective stochastic optimization approach
2020
The feature subset task can be cast as a multiobjective discrete optimization problem. In this work, we study the search algorithm component of a feature subset selection method. We propose an algorithm based on the threshold accepting method, extended to the multi-objective framework by an appropriate definition of the acceptance rule. The method is used in the task of identifying relevant subsets of features in a Web bot recognition problem, where automated software agents on the Web are identified by analyzing the stream of HTTP requests to a Web server.
Identifying legitimate Web users and bots with different traffic profiles — an Information Bottleneck approach
2020
Abstract Recent studies reported that about half of Web users nowadays are intelligent agents (Web bots). Many bots are impersonators operating at a very high sophistication level, trying to emulate navigational behaviors of legitimate users (humans). Moreover, bot technology continues to evolve which makes bot detection even harder. To deal with this problem, many advanced methods for differentiating bots from humans have been proposed, a large part of which relies on supervised machine learning techniques. In this paper, we propose a novel approach to identify various profiles of bots and humans which combines feature selection and unsupervised learning of HTTP-level traffic patterns to d…
Mercury and selenium in fish and shellfish: Occurrence, bioaccessibility and uptake by Caco-2 cells
2012
This study evaluates Hg and Se concentrations and bioaccessibility (element solubilised after simulated gastrointestinal digestion) in 16 raw seafood species consumed in Spain. The concentrations varied greatly (Hg, 3.8-1621 ng/g wet weight, ww; Se, 84-1817 ng/g ww). Only one sample of swordfish exceeded the Hg limit permitted in Spain (1mg/kg), and for this sample the Hg/Se molar ratio and Se Health Benefit Value food safety criteria also indicated the presence of a risk. Bioaccessibility of Hg (35-106%) and Se (17-125%) was very variable and the Hg/Se molar ratio in the bioaccessible fraction was less than one for all samples. Transport by Caco-2 cells, an intestinal epithelium model, was…
Didáctica (lengua y literatura)
2017
La diversidad siempre ha estado presente en nuestro alumnado, no obstante, la incorporación de culturas poco presentes en España, fue un revulsivo en los años 90 para la revitalización de la educación intercultural. Pero a nuestro parecer, existe una carencia importante de estudios acerca de cómo esta nueva multiculturalidad ha hecho mella en la sociedad, y en especial en los materiales no curriculares entre los cuales la Literatura Infantil y Juvenil (LIJ) es un componente fundamental. Es importante, pues, y necesario comprobar qué tratamiento se ha hecho de la multiculturalidad en la LIJ y el estereotipo es, sin duda, uno de los aspectos más sensibles que se reflejan en las obras.Nuestro …
A New Neighbour Selection Strategy for Group-Based Wireless Sensor Networks
2008
In any type of networks a neighbour selection method is needed to form the topology of the network and to know which node the information has to be sent to reach a destination. Nowadays, several selection strategies exist that are based on different aspects and mainly designed to work in common networks. In this paper we will show our study about those different methods and, then we show the development of a suitable neighbour selection strategy for group-based wireless sensor networks (WSN) that is based on a capacity parameter defined by us and the new neighbour distance. We also present the proposal architecture for WSNs and the protocol when a new node joins a group and has to select it…
Energy efficient and distributed resource allocation for wireless powered OFDMA multi-cell networks
2017
In this paper, we investigate the energy efficient resource allocation problem for the wireless powered OFDMA multi-cell networks. In the considered system, the users who have data to transmit in the uplink can only be empowered by the wireless power obtained from multiple base stations (BSs) with a large scale of multiple antennas in the downlink. A time division protocol is considered to divide the time of wireless power transfer (WPT) in the downlink and wireless information transfer (WIT) in the uplink into separate time slot. With the objective to improve the energy efficiency (EE) of the system, we propose the antenna selection, time allocation, subcarrier and power allocation schemes…
Wind Speed Forecasting by Box-Jenkins Models
2008
The possibility of modelling observed wind speed time series and forecasting their future values is presented in this paper. Seasonal autoregressive integrated moving average (SARIMA) models are applied to time series formed by four years hourly average wind speed measurements in thirty sites of Sicily. Our approach is considerably different from the original one (the Box-Jenkins approach) since it is completely automatic. We use a peculiar feature of wind speed on a land area, its daily period, to identify a class of SARIMA models within which to find the best fitting model by information criteria (here we employ AICC). Here we report the results, concerning the fit and forecast accuracy, …
Do upscale restaurant owners use wine lists as a differentiation strategy?
2009
Abstract The present paper studies various criteria used by upscale restaurant owners to differentiate their restaurants and to define their positioning. In particular, we studied several wine list attributes. Through a cluster analysis and a correspondence factor analysis based on different objective wine list characteristics, we obtain two main differentiated profiles of restaurants according to the relative importance of their wine list in comparison with food menu: wine selection and complementarity. Upscale restaurants need to define their positioning strategy and elaborate their wine lists according to their strategy.