668 research outputs found

    Dynamic Kinetic Resolution of Hetero biaryl Ketones by Zinc- Catalyzed Asymmetr ic Hydrosil ylation

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    Adiastereo- and highly enantioselective dynamic kinetic resolution (DKR) of configurationally labile hetero- biaryl ketones is described. The DKR proceeds by zinc- catalyze dhydrosilylation of the carbonyl group ,thus leading to secondary alcohols bearing axial and central chirality .The strategy relies on the labilization of the stereogenic axis that takes place thanks to aLewis acid–base interaction between anitrogen atom in the heterocycle and the ketone carbonyl group .The synthetic utility of the methodology is demonstrated through stereospecific transformations into either N,N-ligands or appealing axially chiral, bifunctional thiourea organocata- lysts.Ministerio de Ciencia e Innovación (Grants CTQ2016-76908-C2-1-P, CTQ2016-76908-C2-2-P, contract RYC-2013-12585)European FEDER FundsJunta de Andalucía (Grant 2012/FQM 10787)European Union - Marie Skłodowska-Curie (COFUND—Grant Agreement n 8 8 291780

    A Dynamic Kinetic Asymmetric Heck Reaction for the Simultaneous Generation of Central and Axial Chirality

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    A highly diastereo- and enantioselective, scalable Pd-catalyzed dynamic kinetic asymmetric Heck reaction of heterobiaryl sulfonates with electron-rich olefins is described. The coupling of 2,3-dihydrofuran or N-boc protected 2,3-dihydropyrrole with a variety of quinoline, quinazoline, phthalazine, and picoline derivatives takes place with simultaneous installation of central and axial chirality, reaching excellent diastereo- and enantiomeric excesses when in situ formed [Pd0/DM-BINAP] was used as the catalyst, with loadings reduced down to 2 mol % in large scale reactions. The coupling of acyclic, electron-rich alkenes can also be performed using a [Pd0/Josiphos ligand] to obtain axially chiral heterobiaryl α-substituted alkenes in high yields and enantioselectivities. Products from Boc-protected 2,3-dihydropyrrole can be easily transformed into N,N ligands or appealing axially chiral, bifunctional proline-type organocatalysts. Computational studies suggest that a β-hydride elimination is the stereocontrolling step, in agreement with the observed stereochemical outcome of the reaction.Ministerio de Ciencia e Innovación (Grants CTQ2016-76908-C2-1-P; CTQ2016-76908-C2-2-P; CTQ2016-78083-P; RYC-2013-12585)European Commission (FEDER Programme)Junta de Andalucía (Grant 2012/FQM 10787)Universidad de Sevilla (Grant No. 1800511201)European Union - Marie Skłodowska-Curie (COFUND—Grant Agreement nº 291780

    Impact of regulation fair disclosure on corporate communications with investors

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    In this study we report laser ablation–inductively coupled plasma–mass spectrometer U-Pb ages of granitoids from the so-called early granodiorites of the northwest Iberian Variscan belt. The U-Pb results attest to significant magmatic activity in Visean time (ca. 347–337 Ma) that generated a hitherto poorly constrained granitoid suite in the northwest Iberian tract of the western European Variscan belt realm. This early Carboniferous suite (ECS) is mainly composed of peraluminous cold and hot crustal granodiorites and monzogranites with minor associated mafic rocks that attest to minor involvement of mantle melting. Based on the geochronological and geochemical data, we compare the Visean granitoids with younger Variscan granitoids in northwest Iberia and, in view of the tectonothermal scenarios of the Variscan collision in northwest Iberia, propose a model for the genesis of the ECS in northwest Iberia that involves rapid melting upon fast exhumation of the thickened Gondwanan crust in the course of the protracted Variscan collision.This work has been funded by the Spanish Ministry of Economy and Competitiveness under the project ODRE III—Oroclines & Delamination: Relations & Effects (CGL2013-46061-P) and Происхождение, металлогения, климатические эффекты и цикличность Крупных Изверженных Провинций (КИП) (Origin, metallogeny, climatic effects, and cyclical large igneous provinces) (14.Y26.31.0012; Russian Federation) to Gutiérrez-Alonso and López-Carmona and CGL-2016-76438-P to Fernández-Suárez. López-Carmona was also funded by a “Juan de la Cierva” grant (reference FJCI-2014-20740).Peer reviewe

    Antiferromagnetism in four dimensions: search for non-triviality

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    We present antiferromagnetism as a mechanism capable of modifying substantially the phase diagram and the critical behaviour of statistical mechanical models. This is particularly relevant in four dimensions, due to the connection between second order transition points and the continuum limit as a quantum field theory. We study three models with an antiferromagnetic interaction: the Ising and the O(4) Models with a second neighbour negative coupling, and the \RP{2} Model. Different conclusions are obtained depending on the model.Comment: 4 pages LateX. Contribution to Lat9

    Phase diagram of d=4 Ising Model with two couplings

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    We study the phase diagram of the four dimensional Ising model with first and second neighbour couplings, specially in the antiferromagnetic region, by using Mean Field and Monte Carlo methods. From the later, all the transition lines seem to be first order except that between ferromagnetic and disordered phases in a region including the first-neighbour Ising transition point.Comment: Latex file and 4 figures (epsfig required). It replaces the preprint entitled "Non-classical exponents in the d=4 Ising Model with two couplings". New analysis with more statistical data is performed. Final version to appear in Phys. Lett.

    Maternal behaviour and welfare of the domestic and wild rabbit doe and its litter

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    El conejo europeo (Oryctolagus cuniculus), además de tener importancia faunística en el Mediterráneo occidental, es una especie ganadera relevante que es la base de un subsector pecuario industrializado orientado a la producción de carne en varios países, sobre todo europeos, mientras que en algunos pa- íses en vías de desarrollo se explota bajo sistemas alternativos orientados a la integración de renta y a la seguridad alimentaria. A la orientación cárnica se suman otras aptitudes productivas heterogéneas que configuran una gran diversidad de sistemas de producción cunícola. Este trabajo revisa el comportamiento materno de la coneja y de su camada, incluyendo su regulación endocrina, tanto en el animal silvestre como en la producción cunícola comercial y alternativa, y se relaciona con los factores de manejo, con la productividad en granja y con el bienestar de la especie. Se analizan también las implicaciones que las normativas sobre bienestar animal comportan respecto al alojamiento, manejo y satisfacción de las necesidades etológicas de las conejas reproductoras y de los gazapos durante la cría, caracterizadas, fundamentalmente, porque en algunos países tienden a proporcionar más espacio y enriquecimiento ambiental en las jaulas.The European rabbit (Oryctolagus cuniculus), in addition to its faunal interest in the western Mediterranean, is a relevant species which in several European countries is the basis of a meat-oriented, industrial livestock subsector, while in many developing countries rabbits are raised under alternative systems aimed at income integration and food security. In addition to meat production, other productive orientations exist that generate a variety of rabbit production systems. This paper reviews the ethology of maternal behaviour of the breeding doe and her litter, including its endocrine regulation, both in wild animal and in industrial and alternative farming systems, and its relation to management factors, productivity and performance as well as the welfare of the species. It also discusses the implications of the regulations concerning animal welfare on housing, management and satisfaction of behavioural needs of breeding does and their litters, which in some countries tend to provide more space and environmental enrichment in cage

    Sociedades fracturadas : la exclusión social en Centroamérica

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    El presente texto tiene un doble origen. Por un lado, desde hace ya varios años en la Facultad Latinoamericana de Ciencias Sociales (FLACSO), Sede de Costa Rica, se ha venido desarrollando un enfoque sobre las carencias materiales de la población, alternativo al de pobreza. Se ha elaborado una propuesta teórica y metodológica en torno al concepto de exclusión social que se ha aplicado en estudios tanto de alcance regional como nacional. Por otro lado, el Estado de la Región, para su IV Informe, identificó la problemática de la exclusión social como una de las cuestiones centrales a abordar en Centroamérica. En este sentido, ambas instituciones colaboraron para generar documentos a base de estudios tanto de tipo cuantitativo como cualitativo, que han servido de insumos para la elaboración del capítulo 10 de este IV informe

    Focal-plane generation of multi-resolution and multi-scale image representation for low-power vision applications

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    Comunicación presentada al "XXXVII Infrared Technology and Applications" celebrado en Orlando (USA) el 25 de Abril del 2011.Early vision stages represent a considerably heavy computational load. A huge amount of data needs to be processed under strict timing and power requirements. Conventional architectures usually fail to adhere to the specifications in many application fields, especially when autonomous vision-enabled devices are to be implemented, like in lightweight UAVs, robotics or wireless sensor networks. A bioinspired architectural approach can be employed consisting of a hierarchical division of the processing chain, conveying the highest computational demand to the focal plane. There, distributed processing elements, concurrent with the photosensitive devices, influence the image capture and generate a pre-processed representation of the scene where only the information of interest for subsequent stages remains. These focal-plane operators are implemented by analog building blocks, which may individually be a little imprecise, but as a whole render the appropriate image processing very efficiently. As a proof of concept, we have developed a 176x144-pixel smart CMOS imager that delivers lighter but enriched representations of the scene. Each pixel of the array contains a photosensor and some switches and weighted paths allowing reconfigurable resolution and spatial filtering. An energy-based image representation is also supported. These functionalities greatly simplify the operation of the subsequent digital processor implementing the high level logic of the vision algorithm. The resulting figures, 5.6m W@30fps, permit the integration of the smart image sensor with a wireless interface module (Imote2 from Memsic Corp.) for the development of vision-enabled WSN applications.This work is partially funded by the Andalusian regional government (Junta de Andalucía-CICE) through project 2006-TIC-2352 and the Spanish Ministry of Science (MICINN) through project TEC 2009-11812, co-funded by the European Regional Development Fund, and also supported by the Office of Naval Research (USA), through grant N000141110312.Peer Reviewe

    Boosting the visible-light photoactivity of Bi2WO6 using acidic carbon additives

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    We have explored the role of the physicohemical properties of carbon materials as additives to bismuth tungstate on its structure, optical properties, and photocatalytic activity for the degradation of rhodamine B under visible light. For this purpose, C/Bi2WO6 hybrid composites were prepared following two different routes: (i) physical mixture of the catalyst components, and (ii) one-pot hydrothermal synthesis of the semiconductor in the presence of the carbon additive. Three carbons with different properties were selected as additives: biomass-derived activated carbon, carbon nanotubes and carbon spheres obtained from polysaccharides. Data has shown the outstanding role of the acidic/basic nature of the carbon additive, and of the synthetic method on the photocatalytic performance of the resulting composites. For a given additive, the degradation rate of RhB is greatly improved for the catalysts prepared through a one-step hydrothermal synthesis, where there is low shielding effect of the carbon matrix. Carbon additives of acidic nature boost the surface acidity of the hybrid photocatalyst, thereby enhancing the photodegradation of RhB under visible light via a coupled mechanism (photosensitization, semiconductor photocatalysis and carbon-photon mediated reactions).The authors thank the financial support of MINECO (grants CTM2011/23378 and CTQ2011/26617) and PCTI Asturias (Fondos Feder 2007-2013, grant PC10-002). RJC thanks PCTI Asturias for her Severo Ochoa fellowshipPeer reviewe

    Demo: Real-time remote reporting of active regions with Wi-FLIP

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    This paper describes a real-time application programmed into Wi-FLIP, a wireless smart camera resulting from the integration of FLIP-Q, a focal-plane low-power image processor, and Imote2, a commercial WSN platform. The application, though simple, shows the potentiality of the reduced scene representations achievable at FLIP-Q to speed up the processing. It consists of detecting the active regions within the scene being surveyed, that is, those regions undergoing thresholded variations with respect to the background. If an activity pattern is prescribed, FLIP-Q enables the reconfigurability of the image plane accordingly, making its detection and tracking easier. For each frame, the number of active regions is calculated and wirelessly reported in real time. A base station picks up the radio signal and sends the information to a PC via USB, also in real time. Frame rates up to around 10fps have been achieved, although it greatly depends on the light conditions and the image plane division grid.Junta de Andalucía 2006-TIC-2352Ministerio de Ciencia TEC 2009-11812Office of Naval Research (USA) N00014111031
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