103 research outputs found

    A theoretical insight into the catalytic effect of a mixed-metal oxide at the nanometer level: The case of the highly active metal/CeOx/TiO2(110) catalysts

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    The structural and electronic properties of CeOx species supported on the rutile TiO2 110 surface have been examined by means of periodic density-functional calculations that use a generalized gradient approximation functional including a Hubbard-like type correction. Deposition of Ce atoms leads in a first step to Ce3+ ions bound to the surface through bridge and in-plane oxygen atoms, the released electrons occupying the Ti 3d empty orbitals. Further addition of Ce and molecular oxygen gives place to Ce2O3 dimers diagonally arranged on the surface, in agreement with the spots observed in the scanning tunnel microscope images. The formation process of CeOx nanoparticles NPs on the TiO2 surface is highly exothermic and our calculations show that the redox properties of the Ce III-Ce IV couple are significantly altered when it is supported on TiO2. In particular the reactivity against CO/O2 indicates that on the surface the presence of Ce III is favored over Ce IV species. Our results also indicate that the CeOx /TiO2 interface should be seen like a real mixed-metal oxide rather than a supported NP of ceria. Finally, in the context of the high catalytic activity of the M /CeOx /TiO2 M =Au,Cu,Pt systems in the water-gas shift reaction, we have examined the dissociation of water on the CeOx /TiO2 surface and estimated a barrier as small as 0.04 eV, i.e. 8 times smaller than that computed for a TiO2 oxygen vacancy. This result agrees with the experimental superior catalytic activity of the M /CeOx /TiO2 systems over M /TiO2.Gobierno de España. Ministerio Ciencia e Innovación (MICINN) MAT2005-01872 y CSD2008-0023Junta de Andalucía FQM-132Departamento de Energía de EE. UU. División de Subvención de Ciencias Químicas DE-AC02-98CH1088

    GROWTH AND SEX RATIO OF OCTOPUS Paroctopus digueti (PERRIER & ROCHEBRUNE, 1894) IN A WILD POPULATION

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    Istraživanja hobotnice Paroctopus digueti u Meksiku su rijetka te je stoga cilj ovog istraživanja procijeniti neke od bioloških karakteristika navedene vrste u zaljevu Ohuira, Ahome, Sinaloa, u Meksiku. Tijekom jeseni 2016. do jeseni 2017. g. uzorkovano je 217 hobotnica P. digueti od kojih su 166 bile ženke, 31 ovigerne ženke i 20 mužjaka. Svakoj hobotnici je zabilježena dužina plašta (ML) i krakova (AL), ukupna dužina (TL) i ukupna masa (TW), a korišten je FiSAT II program za dobivanje parametara rasta posredstvom frekvencija sezonskih veličina. S obzirom na oba spola, prosječna dužina plašta bila je 40,31 ± 2,5 mm. Za analizu odnosa ML-TL i ML-AL, podaci su prilagođeni modelu linearnog tipa. Za odnos između ML-TL, najmanji je koeficijent determinacije zabilježen tijekom proljeća R2 = 0,34, a najviši je zabilježen zimi R2 = 0,65. Što se tiče koeficijenta alometrije (b), bio je različit u četiri klimatske sezone. Teorijska krivulja rasta ML pokazala je oba spola ML∞ = 73,50 mm, K = 1,30 godina-1 i t0 = 0,10. Procijenjene vrijednosti iz jednadžbe rasta pokazale su brži rast (ML∞ = 63 mm) unutar 1,2 godine njihova života, dostižući maksimalnu duljinu u dobi od 2,5 godine. Krivulja rasta ukupne mase hobotnice P. digueti formirana je eksponencijalnim rastom u prvom stadiju do šest mjeseci, te u drugom, logaritamskom stadiju od sedam mjeseci do približno 1,8 godina. Ljeti su zabilježeni nešto niži koeficijenti i postoci trenutačnog koeficijenata rasta (IGC) za duljine i ukupnu masu hobotnice. Najviši Fultonov indeks kondicije (K) zabilježen je zimi. Omjer spola bio je značajno na strani ženki 9,85 F: 1 M.In Mexico, studies of octopus Paroctopus digueti are scarce, thus the objective of this research is to evaluate some of its biological aspects in Ohuira Bay, Ahome, Sinaloa, Mexico. From autumn 2016 to autumn 2017, a total of 217 organisms of P. digueti were collected, from which 166 were females, 31 ovigerous females and 20 males. The lengths of the mantle (ML), tentacles or arms (AL) and total length (TL) were recorded as well as the total weight (TW) of each organism. The software FiSAT II was used to obtain the growth parameters by mediating seasonal size frequencies. Considering both sexes, the average registered mantle length was 40.31±2.5 mm. For the analysis of ML-TL y ML-AL, the data were adjusted to a linear-type model. For the relationship between ML-TL, the minimum determination coefficient was observed during spring R2 = 0.335, and the highest was registered in winter R2 = 0.6452. With regards to the allometry coefficient (b), it was different among the 4 climatic seasons. The theoretical ML growth curve showed both sexes of ML∞= 73.50 mm, K = 1.30 year-1 and t0= 0.10. The estimated values from the growth equation revealed faster growth (ML∞= 63 mm) within the 1.2 years of their lives, reaching a maximum length at 2.5 years of age. The total weight growth curve of P. digueti octopus was formed by an exponential first stage up to six months and the second logarithmic stage from seven months to approximately 1.8 years. In the summer there were slightly lower coefficients and percentages of instantaneous growth coefficients (IGC) for the lengths and total weight of octopus P. digueti. The highest Fulton’s condition index (k) was recorded in winter. The sex ratio was significant in a proportion of 9.85 F:1 M

    Novel computational protocol to support transfemoral prosthetic alignment procedure using machine learning techniques

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    The prosthetic alignment procedure considers biomechanical, anatomical and comfort characteristics of the amputee to achieve an acceptable gait. Prosthetic malalignment induces long-term disease. The assessment of alignment is highly variable and subjective to the experience of the prosthetist, so the use of machine learning could assist the prosthetist during the judgment of optimal alignment.Peer ReviewedPostprint (published version

    Cu Deposited on CeOx-Modified TiO2(110): Synergistic Effects at the Metal-Oxide Interface and the Mechanism of the WGS Reaction

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    Experimental techniques and DFT calculations have been combined to study and compare the effect of the metal-substrate interaction in Cu/TiO2(110) and Cu/CeOx/TiO2(110) catalysts for the water-gas shift (WGS) reaction. Experiments and theory show that CeOx nanoparticles affect the dispersion of copper on titania, and on the formed copper-ceria interface, there are synergistic effects which favor water dissociation and the WGS reaction. The minimum energy path for the WGS reaction on the new highly active catalytic system Cu/CeOx/TiO2(110) has been predicted by theoretical calculations. Main steps such as adsorption-dissociation of water and∗OCOH carboxyl intermediate formation-deprotonation have been characterized. In this very particular system, water splitting is no longer the rate-limiting step because it can dissociate overcoming an energy barrier of only 0.92 kcal/mol. One important insight of the present work is to show that easy full hydration of the ceria particles strongly lowers the reaction barrier for the deprotonation of the∗OCOH intermediate and facilitates the evolution of the WGS reaction. For the first time, a system has been found on which the WGS reaction is able to work with all the involved energy barriers below 12 kcal/mol. This remarkable behavior makes the metal/CeOx/TiO2 family a potential candidate for industrial application as catalysts in the WGS reaction. The change in the metal-support interactions when going from Cu/TiO2 to Cu/CeOx/TiO2 illustrates the importance of optimizing the oxide phase when improving the performance of metal/oxide catalysts for the WGS.Ministerio de Economía y Competitividad MAT2012-31526, CSD2008-0023U.S. Department of Energy DE-SC001270

    Biodiversity of Gastropod in the Southeastern Gulf of California, Mexico

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    Currently, studying the environment is important because of the phenomena that take place on the earth every day. That is why it is a priority to carry out studies that relate environmental changes to the biology of organisms. This allows us to know the interactions with the environment, and in this way solve, reduce or prevent ecological and economic problems, if they are organisms with a commercial value. The objective of this investigation is to determine ecological parameters of the gastropod community from the intertidal zone on five islands from the Gulf of California, México, to model the diversity, distribution and abundance of malacological fauna. We considered to evaluate the Shannon-Wiener diversity (H′), Pielou’s of evenness (J) and the Margalef species richness indexes, in order to evaluate through an analysis from biotic and abiotic factors, the species status that was collected from the exposed and non-exposed zone tidal. The generated data were contemplated from a year-based biodiversity project (2016–2017) on the following islands: Patos, Bledos, Bleditos, Tunosa, and Mazocahui which belong to the Ohuira lagoon in Ahome, Sinaloa, southeast of the Gulf of California, México. Likewise a status about the importance of gastropods is mentioned for the study area

    Nature of the mixed-oxide interface in ceria-titania catalysts: Clusters, chains, and nanoparticles

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    The ceria-titania mixed metal oxide is an important component of catalysts active for the production of hydrogen through the water-gas shift reaction (CO + H2O → H2 + CO2) and the photocatalytic splitting of water (H2O + hv → H2 + 0.5O 2). We have found that ceria-titania catalysts prepared through wet chemical methods have a unique hierarchal architecture. Atomic resolution imaging by high-angle annular dark field scanning transmission electron microscopy (HAADF STEM) reveals that ceria supported on titania exhibits a range of morphologies. One can clearly identify ceria structures involving clusters, chains, and nanoparticles, which are distributed inhomogeneously on the titania support. These structures are often below the sensitivity limit of techniques such as X-ray diffraction (XRD), which in this case identifies the average particle size of the ceria and titania nanoparticles (via the Debye-Scherer equation) to be 7.5 and 36 nm, respectively. The fluorite-structured ceria grows epitaxially on the anatase-structured titania, and this epitaxial growth influences the morphology of the nanoparticles. The presence of defects in the ceria - such as dislocations and surface steps - was routinely observed in HAADF STEM. Density functional theory (DFT) calculations indicate an energetic preference for the formation of O vacancies and the corresponding Ce 3+ sites at the ceria-titania interface. Experimental corroboration by soft X-ray absorption spectroscopy (SXAS) does suggest the presence of Ce3+ sites at the interface. © 2013 American Chemical Society.The research carried out at the Center for Functional Nanomaterials and the Chemistry Department of Brookhaven National Laboratory was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. The theoretical studies were funded by the Ministry of Economy and Competitiveness (Spain, grants MAT2012-31526 and CSD2008-0023) and EU FEDER. Computational resources were provided by the Barcelona Supercomputing Center/Centro Nacional de Supercomputación (Spain).Peer Reviewe

    Poesía de sátira política y clandestina del Siglo de Oro. Antología esencial. Volumen I. Reinados de Felipe III y Felipe IV

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    En el marco del proyecto de investigación "La burla como diversión y arma social en el Siglo de Oro (II). Poesía política y clandestina. Recuperación patrimonial y contexto histórico y cultural" (AEI/FEDER, UE, PID2020-116009GB-I00), del Ministerio de Ciencia e Innovación (MICINN) del Gobierno de España, este volumen aborda el corpus correspondiente a los reinados de Felipe III y Felipe IV, ampliando sustancialmente el material disponible hasta el momento del abundante repertorio de la poesía clandestina y de sátira política del Siglo de Oro. Incluye esta entrega 381 poemas procedentes de numerosos manuscritos, acompañados de un aparato de notas que intenta aclarar las claves complejas de sus alusiones satíricas y precedidos de un estudio introductorio en el que, además de establecerse el estado de la cuestión sobre la materia, se ofrecen reflexiones teóricas sobre los criterios y retos de edición de este difícil y fascinante corpus de enorme interés literario, histórico, social y cultural

    Low exposure long-baseline neutrino oscillation sensitivity of the DUNE experiment

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    The Deep Underground Neutrino Experiment (DUNE) will produce world-leading neutrino oscillation measurements over the lifetime of the experiment. In this work, we explore DUNE's sensitivity to observe charge-parity violation (CPV) in the neutrino sector, and to resolve the mass ordering, for exposures of up to 100 kiloton-megawatt-years (kt-MW-yr). The analysis includes detailed uncertainties on the flux prediction, the neutrino interaction model, and detector effects. We demonstrate that DUNE will be able to unambiguously resolve the neutrino mass ordering at a 3σ\sigma (5σ\sigma) level, with a 66 (100) kt-MW-yr far detector exposure, and has the ability to make strong statements at significantly shorter exposures depending on the true value of other oscillation parameters. We also show that DUNE has the potential to make a robust measurement of CPV at a 3σ\sigma level with a 100 kt-MW-yr exposure for the maximally CP-violating values \delta_{\rm CP}} = \pm\pi/2. Additionally, the dependence of DUNE's sensitivity on the exposure taken in neutrino-enhanced and antineutrino-enhanced running is discussed. An equal fraction of exposure taken in each beam mode is found to be close to optimal when considered over the entire space of interest

    A Gaseous Argon-Based Near Detector to Enhance the Physics Capabilities of DUNE

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    This document presents the concept and physics case for a magnetized gaseous argon-based detector system (ND-GAr) for the Deep Underground Neutrino Experiment (DUNE) Near Detector. This detector system is required in order for DUNE to reach its full physics potential in the measurement of CP violation and in delivering precision measurements of oscillation parameters. In addition to its critical role in the long-baseline oscillation program, ND-GAr will extend the overall physics program of DUNE. The LBNF high-intensity proton beam will provide a large flux of neutrinos that is sampled by ND-GAr, enabling DUNE to discover new particles and search for new interactions and symmetries beyond those predicted in the Standard Model
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