Showing papers by "Polytechnic University of Valencia published in 2006"

Chemoselective Hydrogenation of Nitro Compounds with Supported Gold Catalysts

Abstract: The selective reduction of a nitro group when other reducible functions are present is a difficult process that often requires stoichiometric amounts of reducing agents or, if H2 is used, the addition of soluble metals. Gold nanoparticles supported on TiO2 or Fe2O3 catalyzed the chemoselective hydrogenation of functionalized nitroarenes with H2 under mild reaction conditions that avoided the accumulation of hydroxylamines and their potential exothermic decomposition. These chemoselective hydrogenation gold catalysts also provide a previously unknown route for the synthesis of the industrially relevant cyclohexanone oxime from 1-nitro-1-cyclohexene.

Silica-Bound Homogenous Catalysts as Recoverable and Reusable Catalysts in Organic Synthesis

Abstract: Very frequently the most costly components in a chemical reaction are not the starting materials or the reaction products, but the catalyst. In addition to the advantages from the economic point of view, recovery and reuse of the catalyst is equally important in order to avoid wastes, so improving the greenness of the process. There is a current tendency to transform homogeneous into heterogeneous catalysis, that will even be accelerated in the near future. Starting from a successful homogeneous catalyst, one general methodology allowing its recovery and reuse is to immobilize a suitable derivative of the active catalyst on an insoluble solid support. When the catalyst does not deactivate and is sufficiently stable under the reaction conditions, the ultimate immobilization methodology is to attach covalently the catalytically active species to the support. In this contribution, after introducing some general principles describing the fundamentals of the covalent anchoring, the emphasis is placed more on giving an overview of the most important types of covalently anchored catalysts, including Bronsted and Lewis acids, covalently anchored bases and hydrogenation complexes. Hot topics such as silica-bound organocatalysts and the application of periodic mesoporous organosilicas as heterogeneous catalysts is also covered.

The supramolecular chemistry of organic-inorganic hybrid materials.

Abstract: The combination of nanomaterials as solid supports and supramolecular concepts has led to the development of hybrid materials with improved functionalities. These "hetero-supramolecular" ideas provide a means of bridging the gap between molecular chemistry, materials sciences, and nanotechnology. In recent years, relevant examples have been reported on functional aspects, such as enhanced recognition and sensing by using molecules on preorganized surfaces, the reversible building of nanometer-sized networks and 3D architectures, as well as biomimetic and gated chemistry in hybrid nanomaterials for the development of advanced functional protocols in three-dimensional frameworks. This approach allows the fine-tuning of the properties of nanomaterials and offers new perspectives for the application of supramolecular concepts.

Consumer perceptions of product packaging

Abstract: Purpose – This paper seeks to discuss the need to understand consumer perceptions in order to correctly design product packing and to achieve the desired position in the minds of consumers.Design/methodology/approach – Data collection was divided into two phases. The first, (based on designers' opinions), to determine the key graphic variables in the design of packaging. The second, (based on consumers' opinions), to associate each packaging with a positioning strategy. The seven product‐positioning strategies selected were represented from the consumers' standpoint using multidimensional scaling. Four maps were obtained related to: alternative packaging colours; alternative packaging typography; alternative packaging graphical forms; alternative packaging imagesFindings – Each positioning strategy appears associated with particular packaging dimensions.Research limitations/implications – Consumers have exhibited harmonious perceptions towards products‐packaging strategies, so one can conclude that a gene...

High-throughput synthesis and catalytic properties of a molecular sieve with 18- and 10-member rings

Abstract: Zeolites are porous materials with potential uses in electronics, catalysis and gas storage. A new zeolite named ITQ-33 has now been synthesized with the advantage over previous compounds of a very large micropore volume. The conditions for synthesis were identified using high-throughput techniques. The new material has two pore systems, one with a very large diameter ring structure (relative to pores found in other zeolites), intersected by a second of medium diameter. This open architecture will be particularly suited to catalysis. Crystalline molecular sieves with large pores and high adsorption capacities have many potential applications1,2,3,4. Of these materials, zeolites are of particular interest owing to their stability in a wide range of experimental conditions. An aluminophosphate with very large circular channels5 containing 18 oxygen atoms (18-ring channels) has been synthesized, but in the search for large-pore zeolites, most of the materials which have been synthesized up to now contain only 14-ring channels; the synthesis of zeolites with larger ring structures has been believed to be hindered by the low Si-O-Si bond angles available. A silicogaloaluminate (ECR-34) with unidirectional 18-ring channels12 was recently reported, but exhibited low micropore volume, thus rendering the material less attractive for catalytic applications. Here we report the structure and catalytic activity of the silicogermanate zeolite ITQ-33; this material exhibits straight large pore channels with circular openings of 18-rings along the c axis interconnected by a bidirectional system of 10-ring channels, yielding a structure with very large micropore volume. The conditions for synthesis are easily accessible, but are not typical, and were identified using high-throughput techniques.

Autonomous artificial nanomotor powered by sunlight

Abstract: Light excitation powers the reversible shuttling movement of the ring component of a rotaxane between two stations located at a 1.3-nm distance on its dumbbell-shaped component. The photoinduced shuttling movement, which occurs in solution, is based on a “four-stroke” synchronized sequence of electronic and nuclear processes. At room temperature the deactivation time of the high-energy charge-transfer state obtained by light excitation is ≈10 μs, and the time period required for the ring-displacement process is on the order of 100 μs. The rotaxane behaves as an autonomous linear motor and operates with a quantum efficiency up to ≈12%. The investigated system is a unique example of an artificial linear nanomotor because it gathers together the following features: (i) it is powered by visible light (e.g., sunlight); (ii) it exhibits autonomous behavior, like motor proteins; (iii) it does not generate waste products; (iv) its operation can rely only on intramolecular processes, allowing in principle operation at the single-molecule level; (v) it can be driven at a frequency of 1 kHz; (vi) it works in mild environmental conditions (i.e., fluid solution at ambient temperature); and (vii) it is stable for at least 103 cycles.

Two new robust genetic algorithms for the flowshop scheduling problem

Abstract: The flowshop scheduling problem (FSP) has been widely studied in the literature and many techniques for its solution have been proposed. Some authors have concluded that genetic algorithms are not suitable for this hard, combinatorial problem unless hybridization is used. This work proposes new genetic algorithms for solving the permutation FSP that prove to be competitive when compared to many other well known algorithms. The optimization criterion considered is the minimization of the total completion time or makespan ( C max ). We show a robust genetic algorithm and a fast hybrid implementation. These algorithms use new genetic operators, advanced techniques like hybridization with local search and an efficient population initialization as well as a new generational scheme. A complete evaluation of the different parameters and operators of the algorithms by means of a Design of Experiments approach is also given. The algorithm's effectiveness is compared against 11 other methods, including genetic algorithms, tabu search, simulated annealing and other advanced and recent techniques. For the evaluations we use Taillard's well known standard benchmark. The results show that the proposed algorithms are very effective and at the same time are easy to implement.

maSigPro: a method to identify significantly differential expression profiles in time-course microarray experiments

Abstract: Motivation: Multi-series time-course microarray experiments are useful approaches for exploring biological processes. In this type of experiments, the researcher is frequently interested in studying gene expression changes along time and in evaluating trend differences between the various experimental groups. The large amount of data, multiplicity of experimental conditions and the dynamic nature of the experiments poses great challenges to data analysis. Results: In this work, we propose a statistical procedure to identify genes that show different gene expression profiles across analytical groups in time-course experiments. The method is a two-regression step approach where the experimental groups are identified by dummy variables. The procedure first adjusts a global regression model with all the defined variables to identify differentially expressed genes, and in second a variable selection strategy is applied to study differences between groups and to find statistically significant different profiles. The methodology is illustrated on both a real and a simulated microarray dataset. Availability: The method has been implemented in the statistical language R and is freely available from the Bioconductor contributed packages repository and from http://www.ivia.es/centrogenomica/bioinformatics.htm Contact:[email protected]; [email protected]

A Network of Local and Redundant Gene Regulation Governs Arabidopsis Seed Maturation

Abstract: In Arabidopsis thaliana, four major regulators (ABSCISIC ACID INSENSITIVE3 [ABI3], FUSCA3 [FUS3], LEAFY COTYLEDON1 [LEC1], and LEC2) control most aspects of seed maturation, such as accumulation of storage compounds, cotyledon identity, acquisition of desiccation tolerance, and dormancy. The molecular basis for complex genetic interactions among these regulators is poorly understood. By analyzing ABI3 and FUS3 expression in various single, double, and triple maturation mutants, we have identified multiple regulatory links among all four genes. We found that one of the major roles of LEC2 was to upregulate FUS3 and ABI3. The lec2 mutation is responsible for a dramatic decrease in ABI3 and FUS3 expression, and most lec2 phenotypes can be rescued by ABI3 or FUS3 constitutive expression. In addition, ABI3 and FUS3 positively regulate themselves and each other, thereby forming feedback loops essential for their sustained and uniform expression in the embryo. Finally, LEC1 also positively regulates ABI3 and FUS3 in the cotyledons. Most of the genetic controls discovered were found to be local and redundant, explaining why they had previously been overlooked. This works establishes a genetic framework for seed maturation, organizing the key regulators of this process into a hierarchical network. In addition, it offers a molecular explanation for the puzzling variable features of lec2 mutant embryos.

A New Simplified Multilevel Inverter Topology for DC–AC Conversion

Abstract: Multilevel converters offer high power capability, associated with lower output harmonics and lower commutation losses. Their main disadvantage is their complexity, requiring a great number of power devices and passive components, and a rather complex control circuitry. This work reports a new multilevel inverter topology using an H-bridge output stage with a bidirectional auxiliary switch. The new topology produces a significant reduction in the number of power devices and capacitors required to implement a multilevel output. The new topology is used in the design of a five-level inverter; only five controlled switches, eight diodes, and two capacitors are required to implement the five-level inverter using the proposed topology. The new topology achieves a 37.5% reduction in the number of main power switches required (five in the new against eight in any of the other three configurations) and uses no more diodes or capacitors that the second best topology in the literature, the Asymmetric Cascade configuration. Additionally, the dedicated modulator circuit required for multilevel inverter operation is implemented using a FPGA circuit, reducing overall system cost and complexity. Theoretical predictions are validated using simulation in SPICE, and satisfactory circuit operation is proved with experimental tests performed on a laboratory prototype

Transcriptional regulation of gibberellin metabolism genes by auxin signaling in Arabidopsis.

Abstract: Auxin and gibberellins (GAs) overlap in the regulation of multiple aspects of plant development, such as root growth and organ expansion. This coincidence raises questions about whether these two hormones interact to regulate common targets and what type of interaction occurs in each case. Auxins induce GA biosynthesis in a range of plant species. We have undertaken a detailed analysis of the auxin regulation of expression of Arabidopsis (Arabidopsis thaliana) genes encoding GA 20-oxidases and GA 3-oxidases involved in GA biosynthesis, and GA 2-oxidases involved in GA inactivation. Our results show that auxin differentially up-regulates the expression of various genes involved in GA metabolism, in particular several AtGA20ox and AtGA2ox genes. Up-regulation occurred very quickly after auxin application; the response was mimicked by incubations with the protein synthesis inhibitor cycloheximide and was blocked by treatments with the proteasome inhibitor MG132. The effects of auxin treatment reflect endogenous regulation because equivalent changes in gene expression were observed in the auxin overproducer mutant yucca. The results suggest direct regulation of the expression of GA metabolism genes by Aux/IAA and ARF proteins. The physiological relevance of this regulation is supported by the observation that the phenotype of certain gain-of-function Aux/IAA alleles could be alleviated by GA application, which suggests that changes in GA metabolism mediate part of auxin action during development.

Metodologías activas para la formación de competencias.

Abstract: The Bolonia process may be considered an “opportunity” to improve our educational practices. In this scenario of change, one of the most fruitful debates has focused on the reflection on the renovation of methodologies. The diagnosis made on the state of the matter in the area is rather discouraging: lectures continue to be the predominant method used at the university. This article first poses the question of what learning competences efficiently really means and the role of methodology as the vehicle to make this objective posible. Second, it offers a synthetic description of different methodologies pertinent to the new educational model. Third, different citeria for selecting methodologies are presented. Fourth, recommendations on the design of learning activities are given. And last, the paper discusses considerations on how to guarantee the efficient use of “active methodologies”.

Enhancement of Abscisic Acid Sensitivity and Reduction of Water Consumption in Arabidopsis by Combined Inactivation of the Protein Phosphatases Type 2C ABI1 and HAB1

Abstract: Abscisic acid (ABA) plays a key role in plant responses to abiotic stress, particularly drought stress. A wide number of ABA-hypersensitive mutants is known, however, only a few of them resist/avoid drought stress. In this work we have generated ABA-hypersensitive drought-avoidant mutants by simultaneous inactivation of two negative regulators of ABA signaling, i.e. the protein phosphatases type 2C (PP2Cs) ABA-INSENSITIVE1 (ABI1) and HYPERSENSITIVE TO ABA1 (HAB1). Two new recessive loss-of-function alleles of ABI1, abi1-2 and abi1-3, were identified in an Arabidopsis (Arabidopsis thaliana) T-DNA collection. These mutants showed enhanced responses to ABA both in seed and vegetative tissues, but only a limited effect on plant drought avoidance. In contrast, generation of double hab1-1 abi1-2 and hab1-1 abi1-3 mutants strongly increased plant responsiveness to ABA. Thus, both hab1-1 abi1-2 and hab1-1 abi1-3 were particularly sensitive to ABA-mediated inhibition of seed germination. Additionally, vegetative responses to ABA were reinforced in the double mutants, which showed a strong hypersensitivity to ABA in growth assays, stomatal closure, and induction of ABA-responsive genes. Transpirational water loss under drought conditions was noticeably reduced in the double mutants as compared to single parental mutants, which resulted in reduced water consumption of whole plants. Taken together, these results reveal cooperative negative regulation of ABA signaling by ABI1 and HAB1 and suggest that fine tuning of ABA signaling can be attained through combined action of PP2Cs. Finally, these results suggest that combined inactivation of specific PP2Cs involved in ABA signaling could provide an approach for improving crop performance under drought stress conditions.

Photonic microwave tunable single-bandpass filter based on a Mach-Zehnder interferometer

Abstract: The authors present the theoretical analysis and experimental demonstration of a novel single-bandpass tunable microwave filter. The filter is based on a broadband optical source and a fiber Mach-Zehnder interferometer and shows a high Q factor over a tuning range of 5-17 GHz. A generalized analysis considering that the optical signal propagates along optical delay lines with a dispersion slope different from zero is presented.

Agroinjection of tomato fruits. A tool for rapid functional analysis of transgenes directly in fruit.

Abstract: Transient expression of foreign genes in plant tissues is a valuable tool for plant biotechnology To shorten the time for gene functional analysis in fruits, we developed a transient methodology that could be applied to tomato (Solanum lycopersicum cv Micro Tom) fruits It was found that injection of Agrobacterium cultures through the fruit stylar apex resulted in complete fruit infiltration This infiltration method, named fruit agroinjection, rendered high levels of 35S Cauliflower mosaic virus-driven β-glucuronidase and yellow fluorescence protein transient expression in the fruit, with higher expression levels around the placenta and moderate levels in the pericarp Usefulness of fruit agroinjection was assayed in three case studies: (1) the heat shock regulation of an Arabidopsis (Arabidopsis thaliana) promoter, (2) the production of recombinant IgA antibodies as an example of molecular farming, and (3) the virus-induced gene silencing of the carotene biosynthesis pathway In all three instances, this technology was shown to be efficient as a tool for fast transgene expression in fruits

Analysis of surface electrocardiograms in atrial fibrillation: techniques, research, and clinical applications

Abstract: Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice. Neither the natural history of AF nor its response to therapy is sufficiently predictable by clinical and echocardiographic parameters. The purpose of this article is to describe technical aspects of novel electrocardiogram (ECG) analysis techniques and to present research and clinical applications of these methods for characterization of both the fibrillatory process and the ventricular response during AF. Atrial fibrillatory frequency (or rate) can reliably be assessed from the surface ECG using digital signal processing (extraction of atrial signals and spectral analysis). This measurement shows large inter-individual variability and correlates well with intra-atrial cycle length, a parameter which appears to have primary importance in AF maintenance and response to therapy. AF with a low fibrillatory rate is more likely to terminate spontaneously and responds better to antiarrhythmic drugs or cardioversion, whereas high-rate AF is more often persistent and refractory to therapy. Ventricular responses during AF can be characterized by a variety of methods, which include analysis of heart rate variability, RR-interval histograms, Lorenz plots, and non-linear dynamics. These methods have all shown a certain degree of usefulness, either in scientific explorations of atrioventricular (AV) nodal function or in selected clinical questions such as predicting response to drugs, cardioversion, or AV nodal modification. The role of the autonomic nervous system for AF sustenance and termination, as well as for ventricular rate responses, can be explored by different ECG analysis methods. In conclusion, non-invasive characterization of atrial fibrillatory activity and ventricular response can be performed from the surface ECG in AF patients. Different signal processing techniques have been suggested for identification of underlying AF pathomechanisms and prediction of therapy efficacy.

Both abscisic acid (ABA)‐dependent and ABA‐independent pathways govern the induction of NCED3, AAO3 and ABA1 in response to salt stress

Abstract: The responsiveness of plants to osmotic stress is critically mediated by the increase in abscisic acid (ABA) levels. Osmotic stress induces the biosynthesis of ABA, whose increased levels subsequently exert a positive feedback on its own biosynthetic pathway. As only qualitative or semi-quantitative analyses were performed to test the inducibility of ABA biosynthetic genes in Arabidopsis thaliana, we used quantitative reverse transcriptase-polymerase chain reaction to re-examine the induction of the ABA1, ABA2, ABA3, NCED3 and AAO3 genes by NaCl and ABA. Quantitative gene expression data obtained from wild-type plants and severely ABA-deficient mutants support the prevailing notion that the 9-cis-epoxycarotenoid cleavage reaction is the key regulatory step in NaCl-induced ABA biosynthesis. Interestingly, strong induction by NaCl of NCED3 was still observed in severe ABA-deficient mutants, pointing to an ABA-independent induction pathway for NCED3 that is NaCl-dependent. Therefore, in the absence of the ABA-mediated positive feedback on ABA biosynthesis, the ABA-independent pathway makes a major contribution to the induction of key ABA biosynthetic genes, such as NCED3, AAO3 and ABA1. In addition, and in contrast to some previous reports, our data do not support the limited ability of ABA to induce NCED3 expression. Under our experimental conditions, the induction of NCED3 by ABA, either in wild-type plants or ABA-deficient mutants, was predominant over that of other ABA biosynthetic genes. Natural variability was found in the induction by NaCl and ABA of NCED3 and ABA1 expression in different Arabidopsis accessions, although NCED3 expression was clearly predominant.

Mechanism of the Meerwein-Ponndorf-Verley-Oppenauer (MPVO) redox equilibrium on Sn- and Zr-beta zeolite catalysts.

Abstract: The mechanism of the Meerwein-Ponndorf-Verley (MPV) reduction of cyclohexanone with 2-butanol catalyzed by Sn-beta and Zr-beta zeolites has been theoretically investigated using density functional theory (DFT) and the cluster approach. An experimental catalytic study has shown that the active sites in the MPV reaction catalyzed by Sn-beta are the same partially hydrolyzed Sn-OH groups that were found to be active for the Baeyer-Villiger (BV) reaction. The computational study indicates that the mechanism of Sn-beta and Zr-beta catalysis is similar, and involves the following steps: adsorption of both the ketone and the alcohol on the Lewis acid center, deprotonation of the alcohol, carbon-to-carbon hydride transfer, proton transfer from the catalyst, and products exchange. As in the aluminum alkoxide catalyzed reaction, the hydride shift occurs through a six-membered transition state, and the role of the hydrolyzed and therefore more flexible M-OH bond is just to facilitate the initial deprotonation of the alcohol.

Heterogeneous Gold‐Catalysed Synthesis of Phenols

Abstract: Nanoparticles of gold supported on nanocrystalline CeO 2 catalyse the isomerisation of ω-alkynylfurans to phenols. Initial leaching of gold was observed, which could be minimised by calcining. Subsequent runs showed that once all soluble species had leached, the surface-bound, cationic gold species is still active and can reach turnover numbers of up to 391. This is the first time that a heterogeneous gold catalyst showed activity in the gold-catalysed phenol synthesis.

Genetic and physiological characterization of tomato cv. Micro-Tom

Abstract: Based on its compact habit, Micro-Tom, a dwarf cultivar of tomato (Solanum lycopersicum L.), has been proposed as a preferred variety to carry out molecular research in tomato. This cultivar, however, is poorly characterized. It is shown here that Micro-Tom has mutations in the SELF-PRUNING (SP) and DWARF (D) genes. In addition to this, it is also shown that Micro-Tom harbours at least two independently segregating resistance loci to the plant pathogen Cladosporium fulvum. The presence of the self-pruning mutation in Micro-Tom, that generates a determinate phenotype, was confirmed by crossing and sequence analysis. It was also found that Micro-Tom has a mutation in the DWARF gene (d) that leads to mis-splicing and production of at least two shorter mRNAs. The d mutation is predicted to generate truncated DWARF protein. The d sequence defect co-segregates with dark-green and rugose leaves, characteristics of brassinosteroid biosynthesis mutants. Micro-Tom also carries at least another mutation producing internode length reduction that affects plant height but not active gibberellin (GA) levels, which were similar in dwarf and tall Micro-TomxSeverianin segregants. GAs and brassinosteroids act synergistically in Micro-Tom, and the response to GA depends on brassinosteroids because the elongation of internodes was at least six times higher when GA(3) was applied simultaneously with brassinolide. A novel variety, Micro-0 that is fully susceptible to C. fulvum and almost as dwarf as Micro-Tom, has been generated from the cross of Cf0xMicro-Tom. This line represents a valuable resource for future analysis of Cf resistance genes through breeding or transformation.