Dynamic assembly of a zinc-templated bifunctional organocatalyst in the presence of water for the asymmetric aldol reaction

A bifunctional organocatalytic system consisting of simple pyridine ligands containing separate catalytic functionalities was assembled using ZnCl2. This novel metal-templated catalyst furnished high yields and stereoselectivities towards the aldol reaction. The addition of controlled amounts of water turned out to be crucial to dissolve the system and achieve optimal results.Financial support from Mineco (CTQ2012-38594-C02-02 and CTQ2012-38543-C03-03), Generalitat de Catalunya (2014 SGR 231) and EU (FP7-PEOPLE-2012-CIG-321659) is gratefully acknowledged. CJ and JS are Ramón y Cajal fellows (RYC-2010-06750 and RYC-2011-08925). ASP thanks Mineco for a FPI predoctoral fellowship (BES-2013-067087).Peer reviewe

Has time come to switch from duty-cycled MAC protocols to wake-up radio for wireless sensor networks?

Duty-cycled Medium Access Control (MAC) protocols certainly improve the energy efficiency of wireless networks. However, most of these protocols still suffer from severe degrees of overhearing and idle listening. These two issues prevent optimum energy usage, a crucial aspect in energy-constrained wireless networks such as wireless sensor networks (WSNs). Wake-up radio (WuR) systems drastically reduce these problems by completely switching off the nodes' microcontroller unit (MCU) and main radio transceiver until a secondary, extremely low-power receiver is triggered by a particular wireless transmission, the so called wake-up call. Unfortunately, most WuR studies focus on theoretical platforms and/or custom-built simulators. Both these factors reduce the associated usefulness of the obtained results. In this paper, we model and simulate a real, recent, and promising WuR hardware platform developed by the authors. The simulation model uses time and energy consumption values obtained in the laboratory and does not rely on custom-built simulation engines, but rather on the OMNET++ simulator. The performance of the WuR platform is compared to four of the most well-known and widely employed MAC protocols for WSN under three real-world network deployments. The paper demonstrates how the use of our WuR platform presents numerous benefits in several areas, from energy efficiency and latency to packet delivery ratio and applicability, and provides the essential information for serious consideration of switching duty-cycled MAC-based networks to WuR.Peer ReviewedPostprint (author's final draft

Performance evaluation and comparative analysis of SubCarrier Modulation Wake-up radio systems for energy-efficient wireless sensor networks

Energy-efficient communication is one of the main concerns of wireless sensor networks nowadays. A commonly employed approach for achieving energy efficiency has been the use of duty-cycled operation of the radio, where the node’s transceiver is turned off and on regularly, listening to the radio channel for possible incoming communication during its on-state. Nonetheless, such a paradigm performs poorly for scenarios of low or bursty traffic because of unnecessary activations of the radio transceiver. As an alternative technology, Wake-up Radio (WuR) systems present a promising energy-efficient network operation, where target devices are only activated in an on-demand fashion by means of a special radio signal and a WuR receiver. In this paper, we analyze a novel wake-up radio approach that integrates both data communication and wake-up functionalities into one platform, providing a reconfigurable radio operation. Through physical experiments, we characterize the delay, current consumption and overall operational range performance of this approach under different transmit power levels. We also present an actual single-hop WuR application scenario, as well as demonstrate the first true multi-hop capabilities of a WuR platform and simulate its performance in a multi-hop scenario. Finally, by thorough qualitative comparisons to the most relevant WuR proposals in the literature, we state that the proposed WuR system stands out as a strong candidate for any application requiring energy-efficient wireless sensor node communications.Peer ReviewedPostprint (published version

La geografia a les aules: quin és el seu espai?

L'ensenyament de la geografia a les aules, tant a primària com a secundària, topa amb una sèrie de contradiccions que en fan necessari un profund replantejament. La formació del professorat i els màsters de formació, la predominança dels historiadors entre els professors de geografia, el seguiment dels llibres de text, la visió de la geografia com a ciència descriptiva, la pèrdua de continguts de la matèria al batxillerat i de pes específic a les PAU, el propi examen de les PAU, la lluita de les universitats per no perdre estudiants dels graus de geografia, els currículums i el nou model competencial... són els temes que aborda aquesta taula rodona a través de diferents visions, des de mestres de primària a coordinadors de la formació del professorat de secundària, passant per la percepció dels alumnes.Teaching geography in the classrooms, both in primary and secondary education, clashes with a series of contradictions that require a profound rethinking. Those are: teacher training and teacher training masters; the overwhelming predominance of historians among professors of geography; textbooks and the predominant vision of geography as a descriptive science; the reduction of geography contents in secondary education and its specific weight in the PAU (university access exams), or the PAU exam itself, the struggle of the universities not to lose students in geography degrees, the curricula and the new competence model… This paper summarizes the results of a round table around all these topics with contribution of different views from primary teachers to coordinators of secondary school teacher training, including the perception of students.La enseñanza de la geografía en las aulas, tanto en primaria como en secundaria, choca con una serie de contradicciones que hacen necesario un profundo replanteamiento. La formación del profesorado y los másters de formación, el predominio de los historiadores entre los profesores de geografía, el seguimiento de los libros de texto, la visión de la geografía como una ciencia descriptiva, la pérdida de contenidos de la materia en bachillerato y de peso específico en las PAU, el propio examen de las PAU, la lucha de las universidades para no perder estudiantes en los grados de geografía, los currículums i el nuevo modelo competencial… son los temas que aborda esta mesa redonda a través de diferentes visiones, desde maestros de primaria a coordinadores de la formación del profesorado de secundaria, pasando por la percepción de los alumnos

Dietary α‐Linolenic Acid, Marine ω‐3 Fatty Acids, and Mortality in a Population With High Fish Consumption: Findings From the PREvención con DIeta MEDiterránea (PREDIMED) Study

Background: Epidemiological evidence suggests a cardioprotective role of α‐linolenic acid (ALA), a plant‐derived ω‐3 fatty acid. It is unclear whether ALA is beneficial in a background of high marine ω‐3 fatty acids (long‐chain n‐3 polyunsaturated fatty acids) intake. In persons at high cardiovascular risk from Spain, a country in which fish consumption is customarily high, we investigated whether meeting the International Society for the Study of Fatty Acids and Lipids recommendation for dietary ALA (0.7% of total energy) at baseline was related to all‐cause and cardiovascular disease mortality. We also examined the effect of meeting the society's recommendation for long‐chain n‐3 polyunsaturated fatty acids (≥500 mg/day). Methods and Results: We longitudinally evaluated 7202 participants in the PREvención con DIeta MEDiterránea (PREDIMED) trial. Multivariable‐adjusted Cox regression models were fitted to estimate hazard ratios. ALA intake correlated to walnut consumption (r=0.94). During a 5.9‐y follow‐up, 431 deaths occurred (104 cardiovascular disease, 55 coronary heart disease, 32 sudden cardiac death, 25 stroke). The hazard ratios for meeting ALA recommendation (n=1615, 22.4%) were 0.72 (95% CI 0.56–0.92) for all‐cause mortality and 0.95 (95% CI 0.58–1.57) for fatal cardiovascular disease. The hazard ratios for meeting the recommendation for long‐chain n‐3 polyunsaturated fatty acids (n=5452, 75.7%) were 0.84 (95% CI 0.67–1.05) for all‐cause mortality, 0.61 (95% CI 0.39–0.96) for fatal cardiovascular disease, 0.54 (95% CI 0.29–0.99) for fatal coronary heart disease, and 0.49 (95% CI 0.22–1.01) for sudden cardiac death. The highest reduction in all‐cause mortality occurred in participants meeting both recommendations (hazard ratio 0.63 [95% CI 0.45–0.87]). Conclusions: In participants without prior cardiovascular disease and high fish consumption, dietary ALA, supplied mainly by walnuts and olive oil, relates inversely to all‐cause mortality, whereas protection from cardiac mortality is limited to fish‐derived long‐chain n‐3 polyunsaturated fatty acids. Clinical Trial Registration URL: http://www.Controlled-trials.com/. Unique identifier: ISRCTN35739639

A copper-templated, bifunctional organocatalyst: A strongly cooperative dynamic system for the aldol reaction

The study of novel metal-templated dynamic organocatalytic systems has led to the identification of CuSO4 as the most efficient template to assemble monofunctional prolinamide- and thiourea-modified pyridine ligands. The structural and electronic requirements to assemble an efficient catalyst have been disclosed: both pyridine ligands must bear a 1,3-substitution pattern, and the thiourea ligand serves as a reducing agent to copper(i) as well. Eventually, the cooperative effects achieved with such a simple system deliver high reaction rates and stereoselectivities at room temperature in the asymmetric aldol reaction, requiring only 1 mol% of copper salt. © 2017 The Royal Society of Chemistry.Financial support from MINECO/FEDER (Grant CTQ2015-70117-R) and Generalitat de Catalunya (Grant 2014SGR231) and the EU (FP7-PEOPLE-2012-CIG-321659) is gratefully acknowledged. ASP thanks MINECO for an FPI predoctoral fellowship (BES-2013-067087).Peer reviewe

Functional Bipyridine Ligands as Catalysts within a Metal-Templated Dynamic System

New types of supramolecular catalysts and strategies for their preparation are continuously being developed. Among them, metal-templating is a powerful tool for the design of new asymmetric organocatalysts. In these entities, the catalytic function is carried out solely by the cooperative action of the ligands, and the metal centre participates as an assembly point, providing the correct geometry for catalysis. This concept was used by us to design a pyridine-based system under fast ligand exchange for asymmetric catalysis. We have now designed a metal-templated system based on the action of functional bipyridine ligands and zinc trifluoroacetate as template. Slower ligand exchange is thus achieved. Bipyridine ligands containing prolinamide (bipyPro) or thiourea (bipyTU) groups assemble in situ on the metal centre to generate a bifunctional organocatalyst suitable for the asymmetric aldol reaction. However, ligand exchange still takes place, which results in a complex catalytic network involving several zinc complexes. The complexity of the system has been addressed by NMR and UV-Vis spectroscopy, allowing us to draw the system¿s network. As a result, the generation of the most active, bifunctional catalytic species could be optimized. Enhanced catalytic activity and stereoselectivity in the asymmetric direct aldol reaction can be achieved in this way: low catalyst loadings (5-10 mol%) in short reaction times (6-10 h) for the asymmetric aldol reaction talk in favor of this catalytic system

An efficient dynamic asymmetric catalytic system within a zinc-templated network

Enhanced cooperativity leading to high catalytic activity and stereoselectivity has been achieved through a complex network of simple species interacting reversibly. This novel dynamic catalytic system relies on bipyridine-based organocatalytic ligands and zinc(II) as the template. It demonstrates the effectiveness of dealing with mixtures rather than single species in asymmetric catalysis.We acknowledge support of the publication fee by the CSIC Open Access Support Initiative through its Unit of Information Resources for Research (URICI)Peer reviewe

Plasma modes, periodicity and symplectic structure

SIGLEAvailable from British Library Document Supply Centre- DSC:4672.262(JET-P--89/41) / BLDSC - British Library Document Supply CentreGBUnited Kingdo