36 research outputs found
Topological Non--connectivity Threshold in long-range spin systems
We demonstrate the existence of a topological disconnection threshold,
recently found in Ref. \cite{JSP}, for generic anisotropic Heisenberg
models interacting with an inter--particle potential when
(here is the distance among spins). We also show that if
is greater than the embedding dimension then the ratio between
the disconnected energy region and the total energy region goes to zero when
the number of spins becomes very large. On the other hand, numerical
simulations in for the long-range case support the
conclusion that such a ratio remains finite for large values. The
disconnection threshold can thus be thought as a distinctive property of
anisotropic long-range interacting systems.Comment: submitted to PR
MOFs as multifunctional catalysts: One-pot synthesis of menthol from citronellal over a bifunctional MIL-101 catalyst
A bifunctional MOF catalyst containing coordinatively unsaturated Cr3+ sites and palladium nanoparticles (Pd@MIL-101) has been used for the cyclization of citronellal to isopulegol and for the one-pot tandem isomerization/hydrogenation of citronellal to menthol. The MOF was found to be stable under the reaction conditions used, and the results obtained indicate that the performance of this bifunctional solid catalyst is comparable with other state-of-the-art materials for the tandem reaction: Full citronellal conversion was attained over Pd@MIL-101 in 18 h, with 86% selectivity to menthols and a diastereoselectivity of 81% to the desired (-)-menthol, while up to 30 h were necessary for attaining similar values over Ir/H-beta under analogous reaction conditions.Financial support by Ministerio de Educacion y Ciencia e Innovacion (Project MIYCIN, CSD2009-00050; PROGRAMA CONSOLIDER. INGENIO 2009), Generalidad Valenciana (GV PROMETEO/2008/130) and the CSIC (Proyectos Intramurales Especiales 201080I020) is gratefully acknowledged.GarcĂa Cirujano, F.; LlabrĂ©s I Xamena, FX.; Corma CanĂłs, A. (2012). MOFs as multifunctional catalysts: One-pot synthesis of menthol from citronellal over a bifunctional MIL-101 catalyst. Dalton Transactions. 41:4249-4254. https://doi.org/10.1039/c2dt12480gS4249425441Corma, A., GarciÌa, H., & LlabreÌs i Xamena, F. X. (2010). Engineering Metal Organic Frameworks for Heterogeneous Catalysis. Chemical Reviews, 110(8), 4606-4655. doi:10.1021/cr9003924Farrusseng, D., Aguado, S., & Pinel, C. (2009). Metal-Organic Frameworks: Opportunities for Catalysis. Angewandte Chemie International Edition, 48(41), 7502-7513. doi:10.1002/anie.200806063Lee, J., Farha, O. K., Roberts, J., Scheidt, K. A., Nguyen, S. T., & Hupp, J. T. (2009). Metalâorganic framework materials as catalysts. Chemical Society Reviews, 38(5), 1450. doi:10.1039/b807080fWang, Z., & Cohen, S. M. (2009). Postsynthetic modification of metalâorganic frameworks. Chemical Society Reviews, 38(5), 1315. doi:10.1039/b802258pBanerjee, M., Das, S., Yoon, M., Choi, H. J., Hyun, M. H., Park, S. M., ⊠Kim, K. (2009). Postsynthetic Modification Switches an Achiral Framework to Catalytically Active Homochiral MetalâOrganic Porous Materials. Journal of the American Chemical Society, 131(22), 7524-7525. doi:10.1021/ja901440gGASCON, J., AKTAY, U., HERNANDEZALONSO, M., VANKLINK, G., & KAPTEIJN, F. (2009). Amino-based metal-organic frameworks as stable, highly active basic catalysts. Journal of Catalysis, 261(1), 75-87. doi:10.1016/j.jcat.2008.11.010Hasegawa, S., Horike, S., Matsuda, R., Furukawa, S., Mochizuki, K., Kinoshita, Y., & Kitagawa, S. (2007). Three-Dimensional Porous Coordination Polymer Functionalized with Amide Groups Based on Tridentate Ligand: Selective Sorption and Catalysis. Journal of the American Chemical Society, 129(9), 2607-2614. doi:10.1021/ja067374yCho, S.-H., Ma, B., Nguyen, S. T., Hupp, J. T., & Albrecht-Schmitt, T. E. (2006). A metalâorganic framework material that functions as an enantioselective catalyst for olefin epoxidation. Chem. Commun., (24), 2563-2565. doi:10.1039/b600408cZhang, X., LlabrĂ©s i Xamena, F. X., & Corma, A. (2009). Gold(III) â metal organic framework bridges the gap between homogeneous and heterogeneous gold catalysts. Journal of Catalysis, 265(2), 155-160. doi:10.1016/j.jcat.2009.04.021Meilikhov, M., Yusenko, K., Esken, D., Turner, S., Van Tendeloo, G., & Fischer, R. A. (2010). Metals@MOFs - Loading MOFs with Metal Nanoparticles for Hybrid Functions. European Journal of Inorganic Chemistry, 2010(24), 3701-3714. doi:10.1002/ejic.201000473Henschel, A., Gedrich, K., Kraehnert, R., & Kaskel, S. (2008). Catalytic properties of MIL-101. Chemical Communications, (35), 4192. doi:10.1039/b718371bVermoortele, F., Ameloot, R., Vimont, A., Serre, C., & De Vos, D. (2011). An amino-modified Zr-terephthalate metalâorganic framework as an acidâbase catalyst for cross-aldol condensation. Chem. Commun., 47(5), 1521-1523. doi:10.1039/c0cc03038dWu, P., Wang, J., Li, Y., He, C., Xie, Z., & Duan, C. (2011). Luminescent Sensing and Catalytic Performances of a Multifunctional Lanthanide-Organic Framework Comprising a Triphenylamine Moiety. Advanced Functional Materials, 21(14), 2788-2794. doi:10.1002/adfm.201100115Pan, Y., Yuan, B., Li, Y., & He, D. (2010). Multifunctional catalysis by Pd@MIL-101: one-step synthesis of methyl isobutyl ketone over palladium nanoparticles deposited on a metalâorganic framework. Chemical Communications, 46(13), 2280. doi:10.1039/b922061eCliment, M. J., Corma, A., Guil-LĂłpez, R., Iborra, S., & Primo, J. (1998). Use of Mesoporous MCM-41 Aluminosilicates as Catalysts in the Preparation of Fine Chemicals. Journal of Catalysis, 175(1), 70-79. doi:10.1006/jcat.1998.1970Climent, M. J., Corma, A., Iborra, S., & Velty, A. (2002). Designing the adequate base solid catalyst with Lewis or Bronsted basic sites or with acidâbase pairs. Journal of Molecular Catalysis A: Chemical, 182-183, 327-342. doi:10.1016/s1381-1169(01)00501-5Boronat, M., Climent, M. J., Corma, A., Iborra, S., MontĂłn, R., & Sabater, M. J. (2010). Bifunctional Acid-Base Ionic Liquid Organocatalysts with a Controlled Distance Between Acid and Base Sites. Chemistry - A European Journal, 16(4), 1221-1231. doi:10.1002/chem.200901519Corma, A., DiÌaz, U., GarciÌa, T., Sastre, G., & Velty, A. (2010). Multifunctional Hybrid OrganicâInorganic Catalytic Materials with a Hierarchical System of Well-Defined Micro- and Mesopores. Journal of the American Chemical Society, 132(42), 15011-15021. doi:10.1021/ja106272zFerey, G. (2005). A Chromium Terephthalate-Based Solid with Unusually Large Pore Volumes and Surface Area. Science, 309(5743), 2040-2042. doi:10.1126/science.1116275Corma, A., & Renz, M. (2004). Sn-Beta zeolite as diastereoselective water-resistant heterogeneous Lewis-acid catalyst for carbonâcarbon bond formation in the intramolecular carbonylâene reaction. Chem. Commun., (5), 550-551. doi:10.1039/b313738dIosif, F., Coman, S., PĂąrvulescu, V., Grange, P., Delsarte, S., Vos, D. D., & Jacobs, P. (2004). Ir-Beta zeolite as a heterogeneous catalyst for the one-pot transformation of citronellal to menthol. Chem. Commun., (11), 1292-1293. doi:10.1039/b403692aNeaĆŁu, F., Coman, S., PĂąrvulescu, V. I., Poncelet, G., De Vos, D., & Jacobs, P. (2009). Heterogeneous Catalytic Transformation of Citronellal to Menthol in a Single Step on Ir-Beta Zeolite Catalysts. Topics in Catalysis, 52(9), 1292-1300. doi:10.1007/s11244-009-9270-9MERTENS, P., VERPOORT, F., PARVULESCU, A., & DEVOS, D. (2006). Pt/H-beta zeolites as productive bifunctional catalysts for the one-step citronellal-to-menthol conversion. Journal of Catalysis, 243(1), 7-13. doi:10.1016/j.jcat.2006.06.017Da Silva Rocha, K. A., Robles-Dutenhefner, P. A., Sousa, E. M. B., Kozhevnikova, E. F., Kozhevnikov, I. V., & Gusevskaya, E. V. (2007). Pdâheteropoly acid as a bifunctional heterogeneous catalyst for one-pot conversion of citronellal to menthol. Applied Catalysis A: General, 317(2), 171-174. doi:10.1016/j.apcata.2006.10.019Trasarti, A. F., Marchi, A. J., & ApesteguıÌa, C. R. (2004). Highly selective synthesis of menthols from citral in a one-step process. Journal of Catalysis, 224(2), 484-488. doi:10.1016/j.jcat.2004.03.016TRASARTI, A., MARCHI, A., & APESTEGUIA, C. (2007). Design of catalyst systems for the one-pot synthesis of menthols from citral. Journal of Catalysis, 247(2), 155-165. doi:10.1016/j.jcat.2007.01.016Alaerts, L., SĂ©guin, E., Poelman, H., Thibault-Starzyk, F., Jacobs, P. A., & De Vos, D. E. (2006). Probing the Lewis Acidity and Catalytic Activity of the MetalâOrganic Framework [Cu3(btc)2] (BTC=Benzene-1,3,5-tricarboxylate). Chemistry - A European Journal, 12(28), 7353-7363. doi:10.1002/chem.200600220Horcajada, P., SurblĂ©, S., Serre, C., Hong, D.-Y., Seo, Y.-K., Chang, J.-S., ⊠FĂ©rey, G. (2007). Synthesis and catalytic properties of MIL-100(Fe), an iron(iii) carboxylate with large pores. Chem. Commun., (27), 2820-2822. doi:10.1039/b704325bRavon, U., Chaplais, G., Chizallet, C., Seyyedi, B., Bonino, F., Bordiga, S., ⊠Farrusseng, D. (2010). Investigation of Acid Centers in MIL-53(Al, Ga) for BrĂžnsted-Type Catalysis: Inâ
Situ FTIR and Abâ
Initio Molecular Modeling. ChemCatChem, 2(10), 1235-1238. doi:10.1002/cctc.201000055Vimont, A., Leclerc, H., Maugé, F., Daturi, M., Lavalley, J.-C., Surblé, S., ⊠Férey, G. (2007). Creation of Controlled BrÞnsted Acidity on a Zeotypic Mesoporous Chromium(III) Carboxylate by Grafting Water and Alcohol Molecules. The Journal of Physical Chemistry C, 111(1), 383-388. doi:10.1021/jp064686
(So) Big Data and the transformation of the city
The exponential increase in the availability of large-scale mobility data has fueled the vision of smart cities that will transform our lives. The truth is that we have just scratched the surface of the research challenges that should be tackled in order to make this vision a reality. Consequently, there is an increasing interest among different research communities (ranging from civil engineering to computer science) and industrial stakeholders in building knowledge discovery pipelines over such data sources. At the same time, this widespread data availability also raises privacy issues that must be considered by both industrial and academic stakeholders. In this paper, we provide a wide perspective on the role that big data have in reshaping cities. The paper covers the main aspects of urban data analytics, focusing on privacy issues, algorithms, applications and services, and georeferenced data from social media. In discussing these aspects, we leverage, as concrete examples and case studies of urban data science tools, the results obtained in the âCity of Citizensâ thematic area of the Horizon 2020 SoBigData initiative, which includes a virtual research environment with mobility datasets and urban analytics methods developed by several institutions around Europe. We conclude the paper outlining the main research challenges that urban data science has yet to address in order to help make the smart city vision a reality
The Northern ROSAT All-Sky (NORAS) Galaxy Cluster Survey I: X-ray Properties of Clusters Detected as Extended X-ray Sources
In the construction of an X-ray selected sample of galaxy clusters for
cosmological studies, we have assembled a sample of 495 X-ray sources found to
show extended X-ray emission in the first processing of the ROSAT All-Sky
Survey. The sample covers the celestial region with declination and galactic latitude and comprises sources with
a count rate counts s and a source extent likelihood of 7. In
an optical follow-up identification program we find 378 (76%) of these sources
to be clusters of galaxies. ...Comment: 61 pages; ApJS in press; fixed bug in table file; also available at
(better image quality) http://www.xray.mpe.mpg.de/theorie/NORAS
Give more data, awareness and control to individual citizens, and they will help COVID-19 containment
Italian multicenter study on infection hazards during dental practice: Control of environmental microbial contamination in public dental surgeries
Background.
The present study assessed microbial contamination in Italian dental surgeries.
Methods.
An evaluation of water, air and surface microbial contamination in 102 dental units was carried out in eight Italian cities.
Results.
The findings showed water microbial contamination in all the dental surgeries; the proportion of water samples with microbial levels above those recommended decreased during working. With regard to Legionella spp., the proportion of positive samples was 33.3%. During work activity, the index of microbial air contamination (IMA) increased. The level of microbial accumulation on examined surfaces did not change over time.
Conclusion.
These findings confirm that some Italian dental surgeries show high biocontamination, as in other European Countries, which highlights the risk of occupational exposure and the need to apply effective measures to reduce microbial loads
MyWay: Location prediction via mobility profiling
Forecasting the future positions of mobile users is a valuable task allowing us to operate efficiently a myriad of different applications which need this type of information. We propose MyWay, a prediction system which exploits the individual systematic behaviors modeled by mobility profiles to predict human movements. MyWay provides three strategies: the individual strategy uses only the user individual mobility profile, the collective strategy takes advantage of all users individual systematic behaviors, and the hybrid strategy that is a combination of the previous two. A key point is that MyWay only requires the sharing of individual mobility profiles, a concise representation of the user's movements, instead of raw trajectory data revealing the detailed movement of the users. We evaluate the prediction performances of our proposal by a deep experimentation on large real-world data. The results highlight that the synergy between the individual and collective knowledge is the key for a better prediction and allow the system to outperform the state-of-art methods