6,470 research outputs found

    Evaluation of the silver species nature in Ag-ITQ2 zeolites by the CO oxidation reaction

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    The authors thank the Spanish Ministry of Economy and Competitiveness through RTI2018-101784-B-I00 (MINECO/FEDER) and SEV-2016-0683 projects for the financial support. We gratefully acknowledge ALBA synchrotron for allocating beamtime (proposal 2015091414) and the CLAESS beamline staff for their help and technical support during our experiment. CG and NB thank the TUW Innovative Project GIP165CDGC. CG, SP, VT, NB and GR are thankful for financial support from the Austrian Science Fund (FWF) through projects DK+ Solids4Fun (W1243) and ComCat (I 1041-N28). I. Lopez Hernandez is grateful to Generalitat Valenciana and European Social Fund for the pre doctoral grant ACIF2017.López-Hernández, I.; García Yago, CI.; Truttmann, V.; Pollit, S.; Barrabés, N.; Rupprechter, G.; Rey Garcia, F.... (2020). Evaluation of the silver species nature in Ag-ITQ2 zeolites by the CO oxidation reaction. Catalysis Today. 345:22-26. https://doi.org/10.1016/j.cattod.2019.12.001S2226345Serhan, N., Tsolakis, A., Wahbi, A., Martos, F. J., & Golunski, S. (2019). Modifying catalytically the soot morphology and nanostructure in diesel exhaust: Influence of silver De-NOx catalyst (Ag/Al2O3). Applied Catalysis B: Environmental, 241, 471-482. doi:10.1016/j.apcatb.2018.09.068Góra-Marek, K., Tarach, K. A., Piwowarska, Z., Łaniecki, M., & Chmielarz, L. (2016). Ag-loaded zeolites Y and USY as catalysts for selective ammonia oxidation. Catalysis Science & Technology, 6(6), 1651-1660. doi:10.1039/c5cy01446hHu, X., Bai, J., Hong, H., & Li, C. (2016). Supercritical carbon dioxide anchored highly dispersed silver nanoparticles on 4A-zeolite and selective oxidation of styrene performance. CrystEngComm, 18(14), 2469-2476. doi:10.1039/c5ce02435hCerrillo, J. L., Palomares, A. E., Rey, F., Valencia, S., Pérez-Gago, M. B., Villamón, D., & Palou, L. (2018). Functional Ag-Exchanged Zeolites as Biocide Agents. ChemistrySelect, 3(17), 4676-4682. doi:10.1002/slct.201800432Dong, X.-Y., Gao, Z.-W., Yang, K.-F., Zhang, W.-Q., & Xu, L.-W. (2015). Nanosilver as a new generation of silver catalysts in organic transformations for efficient synthesis of fine chemicals. Catalysis Science & Technology, 5(5), 2554-2574. doi:10.1039/c5cy00285kSulaiman, K. O., Sudheeshkumar, V., & Scott, R. W. J. (2019). Activation of atomically precise silver clusters on carbon supports for styrene oxidation reactions. RSC Advances, 9(48), 28019-28027. doi:10.1039/c9ra05566eCoutiño-Gonzalez, E., Baekelant, W., Steele, J. A., Kim, C. W., Roeffaers, M. B. J., & Hofkens, J. (2017). Silver Clusters in Zeolites: From Self-Assembly to Ground-Breaking Luminescent Properties. Accounts of Chemical Research, 50(9), 2353-2361. doi:10.1021/acs.accounts.7b00295Liu, L., & Corma, A. (2018). Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles. Chemical Reviews, 118(10), 4981-5079. doi:10.1021/acs.chemrev.7b00776Zhao, J., & Jin, R. (2018). Heterogeneous catalysis by gold and gold-based bimetal nanoclusters. Nano Today, 18, 86-102. doi:10.1016/j.nantod.2017.12.009Zhang, B., Kaziz, S., Li, H., Hevia, M. G., Wodka, D., Mazet, C., … Barrabés, N. (2015). Modulation of Active Sites in Supported Au38(SC2H4Ph)24 Cluster Catalysts: Effect of Atmosphere and Support Material. The Journal of Physical Chemistry C, 119(20), 11193-11199. doi:10.1021/jp512022vZhang, B., Sels, A., Salassa, G., Pollitt, S., Truttmann, V., Rameshan, C., … Barrabés, N. (2018). Ligand Migration from Cluster to Support: A Crucial Factor for Catalysis by Thiolate‐protected Gold Clusters. ChemCatChem, 10(23), 5372-5376. doi:10.1002/cctc.201801474Natarajan, G., Mathew, A., Negishi, Y., Whetten, R. L., & Pradeep, T. (2015). A Unified Framework for Understanding the Structure and Modifications of Atomically Precise Monolayer Protected Gold Clusters. The Journal of Physical Chemistry C, 119(49), 27768-27785. doi:10.1021/acs.jpcc.5b08193Tsukuda, T., & Häkkinen, H. (2015). Introduction. Protected Metal Clusters - From Fundamentals to Applications, 1-7. doi:10.1016/b978-0-08-100086-1.00001-4Zhang, X., Qu, Z., Li, X., Wen, M., Quan, X., Ma, D., & Wu, J. (2010). Studies of silver species for low-temperature CO oxidation on Ag/SiO2 catalysts. Separation and Purification Technology, 72(3), 395-400. doi:10.1016/j.seppur.2010.03.012Kolobova, E., Pestryakov, A., Mamontov, G., Kotolevich, Y., Bogdanchikova, N., Farias, M., … Cortes Corberan, V. (2017). Low-temperature CO oxidation on Ag/ZSM-5 catalysts: Influence of Si/Al ratio and redox pretreatments on formation of silver active sites. Fuel, 188, 121-131. doi:10.1016/j.fuel.2016.10.037Ausavasukhi, A., Suwannaran, S., Limtrakul, J., & Sooknoi, T. (2008). Reversible interconversion behavior of Ag species in AgHZSM-5: XRD, 1H MAS NMR, TPR, TPHE, and catalytic studies. Applied Catalysis A: General, 345(1), 89-96. doi:10.1016/j.apcata.2008.04.026Shi, C., Cheng, M., Qu, Z., & Bao, X. (2005). On the correlation between microstructural changes of Ag-H-ZSM-5 catalysts and their catalytic performances in the selective catalytic reduction of NOx by methane. Journal of Molecular Catalysis A: Chemical, 235(1-2), 35-43. doi:10.1016/j.molcata.2004.10.045Afanasev, D. S., Yakovina, O. A., Kuznetsova, N. I., & Lisitsyn, A. S. (2012). High activity in CO oxidation of Ag nanoparticles supported on fumed silica. Catalysis Communications, 22, 43-47. doi:10.1016/j.catcom.2012.02.014Kolobova, E., Pestryakov, A., Shemeryankina, A., Kotolevich, Y., Martynyuk, O., Tiznado Vazquez, H. J., & Bogdanchikova, N. (2014). Formation of silver active states in Ag/ZSM-5 catalysts for CO oxidation. Fuel, 138, 65-71. doi:10.1016/j.fuel.2014.07.011Royer, S., & Duprez, D. (2010). Catalytic Oxidation of Carbon Monoxide over Transition Metal Oxides. ChemCatChem, 3(1), 24-65. doi:10.1002/cctc.201000378Soliman, N. K. (2019). Factors affecting CO oxidation reaction over nanosized materials: A review. Journal of Materials Research and Technology, 8(2), 2395-2407. doi:10.1016/j.jmrt.2018.12.012Du, M., Sun, D., Yang, H., Huang, J., Jing, X., Odoom-Wubah, T., … Li, Q. (2014). Influence of Au Particle Size on Au/TiO2 Catalysts for CO Oxidation. The Journal of Physical Chemistry C, 118(33), 19150-19157. doi:10.1021/jp504681fCorma, A., Fornés, V., Guil, J. ., Pergher, S., Maesen, T. L. ., & Buglass, J. . (2000). Preparation, characterisation and catalytic activity of ITQ-2, a delaminated zeolite. Microporous and Mesoporous Materials, 38(2-3), 301-309. doi:10.1016/s1387-1811(00)00149-9Joshi, C. P., Bootharaju, M. S., Alhilaly, M. J., & Bakr, O. M. (2015). [Ag25(SR)18]−: The «Golden» Silver Nanoparticle. Journal of the American Chemical Society, 137(36), 11578-11581. doi:10.1021/jacs.5b07088Aspromonte, S. G., Mizrahi, M. D., Schneeberger, F. A., López, J. M. R., & Boix, A. V. (2013). Study of the Nature and Location of Silver in Ag-Exchanged Mordenite Catalysts. Characterization by Spectroscopic Techniques. The Journal of Physical Chemistry C, 117(48), 25433-25442. doi:10.1021/jp4046269Veronesi, G., Deniaud, A., Gallon, T., Jouneau, P.-H., Villanova, J., Delangle, P., … Michaud-Soret, I. (2016). Visualization, quantification and coordination of Ag+ions released from silver nanoparticles in hepatocytes. Nanoscale, 8(38), 17012-17021. doi:10.1039/c6nr04381jVeronesi, G., Aude-Garcia, C., Kieffer, I., Gallon, T., Delangle, P., Herlin-Boime, N., … Carrière, M. (2015). Exposure-dependent Ag+release from silver nanoparticles and its complexation in AgS2sites in primary murine macrophages. Nanoscale, 7(16), 7323-7330. doi:10.1039/c5nr00353aHudson-Smith, N. V., Clement, P. L., Brown, R. P., Krause, M. O. P., Pedersen, J. A., & Haynes, C. L. (2016). Research highlights: speciation and transformations of silver released from Ag NPs in three species. Environmental Science: Nano, 3(6), 1236-1240. doi:10.1039/c6en90025aShimizu, K., Sugino, K., Kato, K., Yokota, S., Okumura, K., & Satsuma, A. (2007). Formation and Redispersion of Silver Clusters in Ag-MFI Zeolite as Investigated by Time-Resolved QXAFS and UV−Vis. The Journal of Physical Chemistry C, 111(4), 1683-1688. doi:10.1021/jp066995aChen, D., Qu, Z., Shen, S., Li, X., Shi, Y., Wang, Y., … Wu, J. (2011). Comparative studies of silver based catalysts supported on different supports for the oxidation of formaldehyde. Catalysis Today, 175(1), 338-345. doi:10.1016/j.cattod.2011.03.059Schuricht, F., & Reschetilowski, W. (2012). Simultaneous selective catalytic reduction (SCR) of NOx and N2O over Ag/ZSM-5 – Catalytic studies and mechanistic implications. Microporous and Mesoporous Materials, 164, 135-144. doi:10.1016/j.micromeso.2012.07.018Akolekar, D. B., & Bhargava, S. K. (2000). Adsorption of NO and CO on silver-exchanged microporous materials. Journal of Molecular Catalysis A: Chemical, 157(1-2), 199-206. doi:10.1016/s1381-1169(00)00055-8Liu, J., Krishna, K. S., Kumara, C., Chattopadhyay, S., Shibata, T., Dass, A., & Kumar, C. S. S. R. (2016). Understanding Au∼98Ag∼46(SR)60 nanoclusters through investigation of their electronic and local structure by X-ray absorption fine structure. RSC Advances, 6(30), 25368-25374. doi:10.1039/c5ra27396jChevrier, D. M., Yang, R., Chatt, A., & Zhang, P. (2015). Bonding properties of thiolate-protected gold nanoclusters and structural analogs from X-ray absorption spectroscopy. Nanotechnology Reviews, 4(2). doi:10.1515/ntrev-2015-0007Yamazoe, S., & Tsukuda, T. (2019). X-ray Absorption Spectroscopy on Atomically Precise Metal Clusters. Bulletin of the Chemical Society of Japan, 92(1), 193-204. doi:10.1246/bcsj.2018028

    Combinatorial RNA Design: Designability and Structure-Approximating Algorithm

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    In this work, we consider the Combinatorial RNA Design problem, a minimal instance of the RNA design problem which aims at finding a sequence that admits a given target as its unique base pair maximizing structure. We provide complete characterizations for the structures that can be designed using restricted alphabets. Under a classic four-letter alphabet, we provide a complete characterization of designable structures without unpaired bases. When unpaired bases are allowed, we provide partial characterizations for classes of designable/undesignable structures, and show that the class of designable structures is closed under the stutter operation. Membership of a given structure to any of the classes can be tested in linear time and, for positive instances, a solution can be found in linear time. Finally, we consider a structure-approximating version of the problem that allows to extend bands (helices) and, assuming that the input structure avoids two motifs, we provide a linear-time algorithm that produces a designable structure with at most twice more base pairs than the input structure.Comment: CPM - 26th Annual Symposium on Combinatorial Pattern Matching, Jun 2015, Ischia Island, Italy. LNCS, 201

    Pro-and Anti-Inflammatory Cytokines Release in Mice Injected with Crotalus durissus terrificus Venom

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    The effects of Crotalus durissus terrificus venom (Cdt) were analyzed with respect to the susceptibility and the inflammatory mediators in an experimental model of severe envenomation. BALB/c female mice injected intraperitoneally presented sensibility to Cdt, with changes in specific signs, blood biochemical and inflammatory mediators. The venom induced reduction of glucose and urea levels and an increment of creatinine levels in serum from mice. Significant differences were observed in the time-course of mediator levels in sera from mice injected with Cdt. The maximum levels of IL-6, NO, IL-5, TNF, IL-4 and IL-10 were observed 15 min, 30 min, 1, 2 and 4 hours post-injection, respectively. No difference was observed for levels of IFN-γ. Taken together, these data indicate that the envenomation by Cdt is regulated both pro-and anti-inflammatory cytokine responses at time-dependent manner. In serum from mice injected with Cdt at the two first hours revealed of pro-inflammatory dominance. However, with an increment of time an increase of anti-inflammatory cytokines was observed and the balance toward to anti-inflammatory dominance. In conclusion, the observation that Cdt affects the production of pro-and anti-inflammatory cytokines provides further evidence for the role played by Cdt in modulating pro/anti-inflammatory cytokine balance

    Isoscalar off-shell effects in threshold pion production from pd collisions

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    We test the presence of pion-nucleon isoscalar off-shell effects in the pdπ+tpd\to \pi^+ t reaction around the threshold region. We find that these effects significantly modify the production cross section and that they may provide the missing strength needed to reproduce the data at threshold.Comment: 6 pages, REVTeX, twocolumn, including 3 figures (Postscript), uses psfig, updated and extended versio

    Working towards a consensus on the oncological approach of breakthrough pain: A Delphi survey of Spanish experts

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    Purpose: There is a lack of standards for the diagnosis, assessment and management of breakthrough cancer pain (BTcP). La Fundación ECO (the Foundation for Excellence and Quality in Oncology) commissioned a study to establish a consensus and lay the foundations for the appropriate management of BTcP in oncology patients. Patients and methods: A modified Delphi survey comprising two rounds was used to gather and analyze data, which was conducted over the Internet. Each statement that reached a consensus with the respondents was defined as a median consensus score (MED) of =7, and agreement among panelists as an interquartile range (IQR) of =3. Results: In total, 69 medical oncologists responded, with a broad consensus that BTcP implied exacerbations of high-intensity pain, as opposed to moderate pain. Furthermore, they concurred that appropriate diagnostic equipment is needed, and that rapid-onset fentanyl formulations should be the preferred treatment for BTcP management. The panelists agreed that a lack of appropriate information and training to attend to patients, as well as limited patient visitation rights, were barriers to effective BTcP management. Regarding gaps in detected knowledge, the panelists were unsure of the measures necessary to assess the burden of the disease on the patient’s quality of life and associated medication costs. Alongside this, there was a lack of awareness of the technical specifics of the different formulations of rapid-onset fentanyl. Conclusion: These results represent the current status of BTcP management. They may inform recommendations and provide a framework for future research

    A primordial star in the heart of the Lion

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    Context: The discovery and chemical analysis of extremely metal-poor stars permit a better understanding of the star formation of the first generation of stars and of the Universe emerging from the Big Bang. aims: We report the study of a primordial star situated in the centre of the constellation Leo (SDSS J102915+172027). method: The star, selected from the low resolution-spectrum of the Sloan Digital Sky Survey, was observed at intermediate (with X-Shooter at VLT) and at high spectral resolution (with UVES at VLT). The stellar parameters were derived from the photometry. The standard spectroscopic analysis based on 1D ATLAS models was completed by applying 3D and non-LTE corrections. results: An iron abundance of [Fe/H]=--4.89 makes SDSS J102915+172927 one of the lowest [Fe/H] stars known. However, the absence of measurable C and N enhancements indicates that it has the lowest metallicity, Z<= 7.40x10^{-7} (metal-mass fraction), ever detected. No oxygen measurement was possible. conclusions: The discovery of SDSS J102915+172927 highlights that low-mass star formation occurred at metallicities lower than previously assumed. Even lower metallicity stars may yet be discovered, with a chemical composition closer to the composition of the primordial gas and of the first supernovae.Comment: To be published in A&

    Spitzer/IRAC view of Sh 2-284: Searching for evidence of triggered star formation in an isolated region in the outer Milky Way

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    Using Spitzer/IRAC observations of a region to be observed by the CoRoT satellite, we have unraveled a new complex star-forming region at low metallicity in the outer Galaxy. We perform a study of S284 in order to outline the chain of events in this star-forming region. We used four-band Spitzer/IRAC photometry as well as Halpha imaging obtained with INT/WFC. Combining these data with the optical photometry obtained in the frame of CoRoTs preparation and the 2MASS catalog we analysed the properties and distribution of young stellar objects (YSOs) associated with point-like sources. We also studied the SEDs of regions of extended emission, complementing our dataset with IRAS and MSX data. We find that S284 is unique in several ways: it is very isolated at the end of a spiral arm and both the diffuse dust and ionized emission are remarkably symmetric. We have partially resolved the central clusters of the three bubbles present in this region. Despite the different scales present in its multiple-bubble morphology, our study points to a very narrow spread of ages among the powering high-mass clusters. In contrast, the particular sawtooth structure of the extended emission at the rim of each ionized bubble harbours either small lower-mass clusters with a younger stellar population or individual young reddened protostars. In particular, triggered star formation is considered to be at work in these regions.Comment: Accepted by A&A. 13 pages, 10 figures, 2 Table

    Origin of the inverse spin-switch behavior in manganite/cuprate/manganite trilayers

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    We studied ferromagnet/superconductor/ferromagnet trilayers based on La_(0.7)Ca_(0.3)MnO_(3) manganite and YBa_(2)Cu_(3)O_(7−δ) (YBCO) high-T_(c) cuprate with magnetoresistance and magnetization measurements. We find an inverse superconducting spin-switch behavior, where superconductivity is favored for parallel alignment of the magnetization in the ferromagnetic layers. We argue that this inverse superconducting spin switch originates from the transmission of spin-polarized carriers into the superconductor. In this picture, the thickness dependence of the magnetoresistance yields the spin-diffusion length in YBCO as 13 nm. A comparison of bilayers and trilayers allows ruling out the effect of the stray fields of the domain structure of the ferromagnet as the source of the inverse superconducting spin switch

    Potential Use of Near-Infrared Spectroscopy to Predict Fatty Acid Profile of Meat from Different European Autochthonous Pig Breeds

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    Autochthonous pig breeds provide products of differentiated quality, among which quality control is difficult to perform and insufficient for current market requirements. The present research evaluates the predictive ability of near‐infrared (NIR) spectroscopy, combined with chemometric methods as a rapid and affordable tool to assure traceability and quality control. Thus, NIR technology was assessed for intact and minced muscle Longissimus thoracis et lumborum samples collected from 12 European autochthonous pig breeds for the quantification of lipid content and fatty acid composition. Different tests were performed using different numbers of samples for calibration and validation. The best predictive ability was found using minced presentation and set with 80% of the samples for the calibration and the remaining 20% for the external validation test for the following traits: lipid content and saturated and polyunsaturated fatty acids, which attained both the highest determination coefficients (0.89, 0.61, and 0.65, respectively) and the lowest root mean square errors in external validation (0.62, 1.82, and 1.36, respectively). Lower predictive ability was observed for intact muscles. These results could contribute to improve the management of autochthonous breeds and to ensure quality of their products by traditional meat industry chains
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