University Of Valncia

Burjassot, Spain

University Of Valncia

Burjassot, Spain
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Gomez-Chova L.,University Of Valncia | Jenssen R.,University of Tromsø | Camps-Valls G.,University Of Valncia
IEEE Geoscience and Remote Sensing Letters | Year: 2012

This letter proposes the kernel entropy component analysis for clustering remote sensing data. The method generates nonlinear features that reveal structure related to the Ŕnyi entropy of the input space data set. Unlike other kernel feature-extraction methods, the top eigenvalues and eigenvectors of the kernel matrix are not necessarily chosen. Data are interestingly mapped with a distinct angular structure, which is exploited to derive a new angle-based spectral clustering algorithm based on the mapped data. An out-of-sample extension of the method is also presented to deal with test data. We focus on cloud screening from Medium Resolution Imaging Spectrometer images. Several images are considered to account for the high variability of the problem. Good results obtained show the suitability of the proposal. © 2006 IEEE.

Manzanares J.A.,University Of Valncia | Cervera J.,University Of Valncia | Mafe S.,University Of Valncia
Applied Physics Letters | Year: 2011

We explore the processing of weak electrical signals in parallel arrays of bio-inspired threshold nanostructureshowing a high variability in their threshold potentials. We consider a two-state canonical model that incorporates the basic properties demonstrated experimentally. The model is inspired by the voltage-gated ion channels in biological membranes and shows that the nanostructure variability can allow significant transmission of sub-threshold signals. Implications for the design of practical devices are briefly discussed. © 2011 American Institute of Physics.

Domenech A.,University Of Valncia | Montoya N.,University Of Valncia | Alarcon J.,University Of Valncia
Electrochimica Acta | Year: 2012

The voltammetry of immobilized particles methodology is applied to study solid state reaction kinetics on the basis of the electrocatalytic ability of solids toward selected electrochemical processes. Measurement of the time variation of catalytic current for oxygen evolution reaction in aqueous alkaline media provides a direct estimate of fractional conversion of the reactant in the course of the reaction for testing different reaction kinetic models. This methodology is applied to analyze the formation of monoclinic zirconia and praseodymia-doped zirconia from tetragonal precursors. Discrimination between competing and successive reactions mechanisms is obtained for reactions involving specimens with high praseodymium loadings, where a secondary pyrochlore phase is formed, combining the above data with those for the electrochemical reduction of dissolved oxygen. © 2012 Elsevier Ltd. All rights reserved.

Blay G.,University Of Valncia | Ceballos E.,University Of Valncia | Monleon A.,University Of Valncia | Pedro J.R.,University Of Valncia
Tetrahedron | Year: 2012

Chiral nonracemic N-(diphenylphosphinoyl)-protected propargylic amines have been prepared by addition of terminal alkynes to N-(diphenylphosphinoyl) aldimines in the presence of dimethylzinc and 3,3′-dibromo-BINOL as catalyst. The reaction works with a variety of aromatic and heteroaromatic aldimines and with different alkynes, providing the expected products in generally good yields and enantiomeric excesses (up to 96%). © 2011 Elsevier Ltd.

Parra J.,IATA CSIC | Mercader J.V.,IATA CSIC | Agullo C.,University Of Valncia | Abad-Fuentes A.,IATA CSIC | Abad-Somovilla A.,University Of Valncia
Tetrahedron | Year: 2011

The immune response to regioisomeric haptens of azoxystrobin with varied derivatization sites was studied. Based on the Sonogashira and Suzuki-Miyaura couplings and following a straightforward modular design, we have synthesized four haptens with the same linker anchored through C-C bonds and located at different sites of the molecule. The most stereoselective antibodies were produced from immunogens with the spacer arm at a distal position from the β-methoxyacrylate moiety characteristic of strobilurins. Moreover, we observed that assay cross-reactivity was reliant on the functionalization site of the competitor derivative. Finally, the antibody binding site was explored using synthetic chemical analogues. © 2010 Elsevier Ltd. All rights reserved.

Belenguer J.-M.,University Of Valncia | Benavent E.,University Of Valncia | Prins C.,University of Technology of Troyes | Prodhon C.,University of Technology of Troyes | Wolfler Calvo R.,CNRS Informatics Laboratory of Paris Nord
Computers and Operations Research | Year: 2011

Recent researches in the design of logistic networks have shown that the overall distribution cost may be excessive if routing decisions are ignored when locating depots. The Location-Routing Problem (LRP) overcomes this drawback by simultaneously tackling location and routing decisions. The aim of this paper is to propose an exact approach based on a Branch-and-Cut algorithm for solving the LRP with capacity constraints on depots and vehicles. The proposed method is based on a zero-one linear model strengthened by new families of valid inequalities. The computational evaluation on three sets of instances (34 instances in total), with 510 potential depots and 2088 customers, shows that 26 instances with five depots are solved to optimality, including all instances with up to 40 customers and three with 50 customers. © 2010 Elsevier Ltd. All rights reserved.

Rubert J.,University Of Valncia | Soler C.,University Of Valncia | Manes J.,University Of Valncia
Food Chemistry | Year: 2012

This article describes the validation of an analytical method for the detection of 21 mycotoxins in baby food. The analytical method is based on the simultaneous extraction of selected mycotoxins by matrix solid-phase dispersion (MSPD) followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) using a hybrid triple quadrupole-linear ion trap mass spectrometer (QTRAP®). Information Dependent Acquisition (IDA), an extra confirmation tool for samples that contain the selected mycotoxins, was used. The matrix effects were evaluated, and the corrections for the matrix effects were performed using two calibration approaches: external matrix-matched calibration and internal standard calibration. Matrix-matched calibration was ultimately used for accurate quantification, and the recoveries obtained were generally higher than 70%. The analytical method was applied to the analysis of 35 samples of commercial baby foods. No sample exceeded the maximum limit (ML) fixed by the European Union for these mycotoxins in baby food. However, this survey highlighted the occurrence of mycotoxins in cereal-based infant foods. © 2011 Elsevier Ltd. All rights reserved.

Ferrer E.,University Of Valncia | Santoni E.,University of Camerino | Vittori S.,University of Camerino | Font G.,University Of Valncia | And 2 more authors.
Food Chemistry | Year: 2011

A new analytical method, using pressurised liquid extraction (PLE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), was developed for the simultaneous determination of bisphenol A (BPA), octylphenol (OP) and nonylphenol (NP) in powdered infant formulas (IF) and powdered skimmed milk (PM). The analytes were extracted by PLE, using this optimised conditions: ethyl acetate as solvent, 70 °C of temperature, reversed-phase silica C 18 as dispersing agent and three cycles of extraction. The extracts were then injected in LC-MS/MS using a Gemini C18 column and a mixture of 5% water and 95% methanol/acetonitrile, both with 0.1% ammonia, as a mobile phase. Recoveries at different fortification levels (0.5 and 0.05 mg kg-1), were between 89% and 92% for BPA, 84 and 98% for OP, and 93% and 101% for NP. The method was applied to the analysis of samples of PM and IF, bought in Italian and Spanish markets. In positive samples, phenols concentration ranged from 0.07 to 1.29 mg kg-1 for BPA, from 0.028 to 1.55 mg kg-1 for OP and from 0.026 to 1.47 mg kg-1 for NP. © 2010 Elsevier Ltd. All rights reserved.

Andreu C.,University Of Valncia | Varea T.,University Of Valncia | Asensio G.,University Of Valncia
Tetrahedron | Year: 2011

The use of zinc salts as cocatalysts in aldol condensations catalyzed by single prolinamide (and in the extension by other more complex prolinamides) can prevent the formation of the parasitic intermediate imidazolidinone, with faster and also more stereoselective reactions than those catalyzed by the free amine. This new finding, together with this ion's already known properties, make zinc salts highly suitable additives for aldol reactions catalyzed for prolinamide derivatives. © 2011 Elsevier Ltd. All rights reserved.

Sagratini G.,University of Camerino | Fernandez-Franzon M.,University Of Valncia | De Berardinis F.,University of Camerino | Font G.,University Of Valncia | And 2 more authors.
Food Chemistry | Year: 2012

Biogenic amines on fish tissue are formed as a result of bacterial contamination and spoilage during storage. A new method based on liquid chromatography (LC) and tandem mass spectrometry (MS/MS) using a triple quadrupole (QqQ) analyser was developed for the analysis of eight biogenic amines (cadaverine, histamine, phenylethylamine, putrescine, spermine, spermidine, tyramine and tryptamine) in fish tissues. Sample preparation was performed by extraction with trichloroacetic acid 5% and solid phase extraction clean up with STRATA X cartridge. The MS/MS method was validated and compared with a method based on the analysis of dansyl derivatives by LC and fluorescence detector (FD). MS/MS achieved higher sensitivity (from 0.02 mg kg -1 for spermidine and phenylethylamine to 0.2 mg kg -1 for spermine) when compared to FD (from 1 mg kg -1 for putrescine and tyramine to 4 mg kg -1 for histamine); MS/MS method showed higher precision too, with intraday relative standard deviations (RSDs) from 1% to 4% with respect to those obtained with FD method (from 3% to 17%). Recovery study was conducted at two different fortification levels and the average ranged from 71% to 93% for all of the studied compounds with RSDs lower than 18%. Matrix-matched standards were used to counteract matrix effect observed in MS/MS determination. The applicability of the method was demonstrated by the analysis of biogenic amines in fish obtained from commercials of Valencia. © 2011 Elsevier Ltd. All rights reserved.

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