Evolution and distribution of the anode overpotential and its oscillations in a polymer electrolyte membrane fuel cell exposed to carbon monoxide

Carbon monoxide (CO) poisoning of polymer electrolyte membrane fuel cells (PEMFCs) remains a challenge for their deployment, and a deeper understanding of the spatiotemporal dynamics involved is needed to develop effective mitigation strategies. In this work, localised reference electrodes were used to measure the anode overpotential at three locations across the active area of a galvanostatically operated cell (0.3 A cm−2) exposed to 100 ppm CO/H2. The anode region closest to the inlet was poisoned more rapidly than the rest of the cell, following a sigmoidal variation, and presented a higher CO coverage. The varying CO concentration, combined with local operating conditions, had a direct impact on the distribution of CO coverage. Additionally, complex self-sustained oscillations of the cell voltage and the anode overpotential were observed and correlated with the rate of CO oxidation in the overall cell. The coexistence of a dominant mean-field coupling area closer to the anode inlet, and a dominant migration coupling region closer to the outlet was identified, consistent with reported modelling predictions for a single straight channel cell. Finally, the cell recovery with pure H2 was shown to be a faster process than the CO adsorption, which follows first-order kinetics and is affected by local conditions

M dwarfs: effective temperatures, radii and metallicities

We empirically determine effective temperatures and bolometric luminosities for a large sample of nearby M dwarfs, for which high accuracy optical and infrared photometry is available. We introduce a new technique which exploits the flux ratio in different bands as a proxy of both effective temperature and metallicity. Our temperature scale for late type dwarfs extends well below 3000 K (almost to the brown dwarf limit) and is supported by interferometric angular diameter measurements above 3000 K. Our metallicities are in excellent agreement (usually within 0.2 dex) with recent determinations via independent techniques. A subsample of cool M dwarfs with metallicity estimates based on hotter Hipparcos common proper-motion companions indicates our metallicities are also reliable below 3000 K, a temperature range unexplored until now. The high quality of our data allow us to identify a striking feature in the bolometric luminosity versus temperature plane, around the transition from K to M dwarfs. We have compared our sample of stars with theoretical models and conclude that this transition is due to an increase in the radii of the M dwarfs, a feature which is not reproduced by theoretical models.Comment: 26 pages, 14 figures. Accepted by MNRAS. Landscape table available online at http://users.utu.fi/luccas/MOITE

Upbringing, interpersonal difficulties and drug use

Determinacin de la crianza parental y las dificultades interpersonales entre consumidores y no consumidores de drogas e identificacin de la relacin y efectos de la crianza parental y las dificultades interpersonales con el consumo de drogas, mediante un estudio descriptivo y correlativo a travs de una muestra de adolescentes seleccionados mediante conglomerados, en el que se descubri que para el consumo de alcohol alguna vez en la vida y en el ltimo ao, la crianza parental y las dificultades interpersonales son capaces de predecir el consumo de esta droga. Cuando existe una percepcin negativa de la crianza parental, existe consumo de alcohol; cuanto mayor es el nmero de dificultades interpersonales, mayor el consumo de alcohol por los adolescentes.Determining upbringing and interpersonal difficulties among those drug consumers and non consumers and identifying the relationship and effects of upbringing and interpersonal difficulties on drug consumption through a descriptive and correlative study using adolescents selected through cluster sampling. The study discovered that upbringing and interpersonal difficulties can predict having ever consumed alcohol and having consumed it within the last year. When a negative perception of upbringing exists, alcohol consumption exists; the greater the number of interpersonal difficulties, the greater the adolescents' alcohol consumption.Determinação da criação parental e as dificuldades interpessoais entre consumidores e não consumidores de drogas e identificação da relação e efeitos da criação parental e as dificuldades interpessoais com o consumo de drogas, mediante um estudo descritivo e correlativo através de uma amostra de adolescentes selecionados em grupos especficos, em que se descobriu que para o consumo de lcool alguma vez na vida e no último ano, a criação parental e as dificuldades interpessoais são capazes de predizer o consumo desta droga. Quando existe uma percepção negativa da criação parental, existe o consumo de álcool; quanto maior o número de dificuldades interpessoais, maior o consumo de álcool pelos adolescentes

Enzyme-Controlled Nanodevice for Acetylcholine-Triggered Cargo Delivery Based on Janus Au-Mesoporous Silica Nanoparticles

"This is the peer reviewed version of the following article: Llopis-Lorente, Antoni, Paula Díez, Cristina de la Torre, Alfredo Sánchez, Félix Sancenón, Elena Aznar, María D. Marcos, Paloma Martínez-Ruíz, Ramón Martínez-Máñez, and Reynaldo Villalonga. 2017. Enzyme-Controlled Nanodevice for Acetylcholine-Triggered Cargo Delivery Based on Janus Au-Mesoporous Silica Nanoparticles. Chemistry - A European Journal 23 (18). Wiley: 4276 81. doi:10.1002/chem.201700603, which has been published in final form at https://doi.org/10.1002/chem.201700603. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] This work reports a new gated nanodevice for acetylcholine-triggered cargo delivery. We prepared and characterized Janus Au-mesoporous silica nanoparticles functionalized with acetylcholinesterase on the Au face and with supramolecular b-cyclodextrin: benzimidazole inclusion complexes as caps on the mesoporous silica face. The nanodevice is able to selectively deliver the cargo in the presence of acetylcholine via enzyme-mediated acetylcholine hydrolysis, locally lowering the pH and opening the supramolecular gate. Given the key role played by ACh and its relation with Parkinson's disease and other nervous system diseases, we believe that these findings could help design new therapeutic strategies.A.L.L. is grateful to "La Caixa" Banking Foundation for his PhD fellowship. The authors are gratitude to the Spanish Government (MINECO Projects MAT2012-38429-C04-01, MAT2015-64139-C4-1, CTQ2014-58989-P and CTQ2015-71936-REDT) and the Generalitat Valencia (Project PROMETEOII/2014/047) for support. The Comunidad de Madrid (S2013/MIT-3029, Programme NANOAVANSENS) is also gratefully acknowledged.Llopis-Lorente, A.; Díez, P.; De La Torre-Paredes, C.; Sanchez, A.; Sancenón Galarza, F.; Aznar, E.; Marcos Martínez, MD.... (2017). Enzyme-Controlled Nanodevice for Acetylcholine-Triggered Cargo Delivery Based on Janus Au-Mesoporous Silica Nanoparticles. Chemistry - A European Journal. 23(18):4276-4281. https://doi.org/10.1002/chem.201700603S427642812318Gotti, C., & Clementi, F. (2004). Neuronal nicotinic receptors: from structure to pathology. Progress in Neurobiology, 74(6), 363-396. doi:10.1016/j.pneurobio.2004.09.006Lindstrom, J. (1997). Nicotinic acetylcholine receptors in health and disease. Molecular Neurobiology, 15(2), 193-222. doi:10.1007/bf02740634Descarries, L., Gisiger, V., & Steriade, M. (1997). Diffuse transmission by acetylcholine in the CNS. Progress in Neurobiology, 53(5), 603-625. doi:10.1016/s0301-0082(97)00050-6Leblond, L., Beaufort, C., Delerue, F., & Durkin, T. P. (2002). Differential roles for nicotinic and muscarinic cholinergic receptors in sustained visuo-spatial attention? A study using a 5-arm maze protocol in mice. 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Multifunctional Mesoporous Silica Nanoparticles as a Universal Platform for Drug Delivery. Chemistry of Materials, 26(1), 435-451. doi:10.1021/cm402592tYang, Y.-W., Sun, Y.-L., & Song, N. (2014). Switchable Host–Guest Systems on Surfaces. Accounts of Chemical Research, 47(7), 1950-1960. doi:10.1021/ar500022fPopat, A., Hartono, S. B., Stahr, F., Liu, J., Qiao, S. Z., & Qing (Max) Lu, G. (2011). Mesoporous silica nanoparticles for bioadsorption, enzyme immobilisation, and delivery carriers. Nanoscale, 3(7), 2801. doi:10.1039/c1nr10224aGuardado-Alvarez, T. M., Sudha Devi, L., Russell, M. M., Schwartz, B. J., & Zink, J. I. (2013). Activation of Snap-Top Capped Mesoporous Silica Nanocontainers Using Two Near-Infrared Photons. Journal of the American Chemical Society, 135(38), 14000-14003. doi:10.1021/ja407331nSancenón, F., Pascual, L., Oroval, M., Aznar, E., & Martínez-Máñez, R. (2015). Gated Silica Mesoporous Materials in Sensing Applications. 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The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Free-standing supercapacitors from Kraft lignin nanofibers with remarkable volumetric energy density

We have discovered a very simple method to address the challenge associated with the low volumetric energy density of free-standing carbon nanofiber electrodes for supercapacitors by electrospinning Kraft lignin in the presence of an oxidizing salt (NaNO₃) and subsequent carbonization in a reducing atmosphere. The presence of the oxidative salt decreases the diameter of the resulting carbon nanofibers doubling their packing density from 0.51 to 1.03 mg cm⁻² and hence doubling the volumetric energy density. At the same time, the oxidative NaNO₃ salt eletrospun and carbonized together with lignin dissolved in NaOH acts as a template to increase the microporosity, thus contributing to a good gravimetric energy density. By simply adjusting the process parameters (amount of oxidizing/reducing agent), the gravimetric and volumetric energy density of the resulting lignin free-standing carbon nanofiber electrodes can be carefully tailored to fit specific power to energy demands. The areal capacitance increased from 147 mF cm⁻² in the absence of NaNO₃ to 350 mF cm⁻² with NaNO₃ translating into a volumetric energy density increase from 949 μW h cm⁻³ without NaNO₃ to 2245 μW h cm⁻³ with NaNO₃. Meanwhile, the gravimetric capacitance also increased from 151 F g⁻¹ without to 192 F g⁻¹ with NaNO

Influence of composition, bonding characteristics and microstructure on the electrochemical and optical stability of AlOxNy thin films

Thin films of AlOxNy were deposited by magnetron sputtering in a wide composition range. Different structures and morphologies were observed, depending on the composition and bonding states, which opened the possibility to tailor the properties of this oxynitride system between those of pure Al and those of nitride and oxide films. In a wide range of stoichiometries, one can report the formation of nanocomposite porous films, where Al nanoparticles are dispersed in an amorphous matrix of AlOxNy. The electrochemical behaviour of the films was studied in isotonic NaCl solution. It was observed that the pitting 2 potential characteristic of aluminium disappears with the incorporation of oxygen and nitrogen in the films, being replaced by a smooth current increase. Electrochemical impedance spectroscopy performed during 35 days showed that the corrosion resistance of the films steadily increases. The unusual optical reflectance profile of some films is maintained after immersion for several months.Fundação para a Ciência e a TecnologiaPrograma Pessoa 2010/2011, Cooperação Portugal/França, Proc.º 441.00, Project“COLOURCLUSTER”