1,721,009 research outputs found
Irreversible Conversion of a Water-Ethanol Solution into an Organized Two-Dimensional Network of Alternating Supramolecular Units in a Hydrophobic Zeolite under Pressure
No full textTurning disorder into organization is a key issue in science. By making use of X-ray powder diffraction and modeling studies, we show herein that high pressures in combination with the shape and space constraints of the hydrophobic all-silica zeolite ferrierite separate an ethanol-water liquid mixture into ethanol dimer wires and water tetramer squares. The confined supramolecular blocks alternate in a binary two-dimensional (2D) architecture that remains stable upon complete pressure release. These results support the combined use of high pressures and porous networks as a viable strategy for driving the organization of molecules or nano-objects towards complex, pre-defined patterns relevant for the realization of novel functional nanocomposites
Spectroscopic study of the product of thermal transformation of chrysotile-asbestos containing materials (ACM)
No full textIn Italy, reclamation of asbestos-containing materials (ACM) such as friable asbestos and cement-asbestos is accomplished by their removal, packaging and dumping in controlled landfills. An alternative way to landfill disposal is the thermal transformation of ACM and recycling of the transformation product as secondary raw material. The aim of this work is to integrate preliminary X-ray diffraction and microscopic investigations on the secondary raw material described earlier with a detailed study on the product of transformation at 1200 degrees C of friable chrysotile-asbestos and cement-asbestos, using (micro) Raman, (micro) FTIR, (57)Fe Mossbauer and XANES at the Fe K-edge. Micro-Raman spectra reveal that the absorption bands generated by chrysotile are no longer present in the high-temperature products, and this is further confirmed by micro-FTIR results. In the core of the former fibres of loose chrysotile asbestos, the newly formed phases are olivine and enstatite, whereas the product of transformation of cement-asbestos is composed of olivine together with several other phases such as hematite and (Ca, Mg, Al)-silicates. The Mossbauer absorption spectra of raw chrysotile reveal that iron is contained in a paramagnetic phase (40 %) as well as in accessory magnetite (60 %). The paramagnetic contribution, attributed to chrysotile, is represented by Fe(2+) (10 % of Fe(tot)) and Fe(3+) (30 % of Fe(tot)), both octahedrally coordinated. The spectrum of thermally treated chrysotile clearly shows that the magnetic phases are now oxidized magnetite/maghemite and hematite, and the paramagnetic contribution is quite unaltered, though likely due to the newly formed olivine. The spectrum of untreated cement-asbestos has no evidence of accessory magnetic phases and is made of Fe(2+) (15% of Fe(tot)) and Fe(3+) (85% of Fe(tot)), both octahedrally coordinated. In the thermally treated sample all iron is oxidized, but a phase transition occurred, because Fe(3+) is tetrahedrally coordinated. Also XANES spectra show that in all samples the dominant iron oxidation state is 3+. XANES data on standard chrysotile are compatible with the possible presence of magnetite. In the high-temperature product of cement-asbestos, the high intensity of the pre-edge peak is comparable with that of the reference compound Fe-silicalite, with ferric iron hosted in the framework. This result indicates that in this product ferric iron is likely hosted in a crystalline phase in four-fold coordination, in agreement with Mossbauer spectroscopy results. Such crystalline phase could be Fe-bearing akermanite-gehlenite
Recent advances in clean-up strategies of waters polluted with sulfonamide antibiotics: a review of sorbents and related properties
No full textSeveral strategies are available to reduce or eliminate recalcitrant sulfonamide antibiotics (sulfa drugs) from aqueous media. These contaminants are bioactive and ubiquitous pollutants of soils and watercourses and are known to induce bacterial resistance. Here the biological, chemical and physical methods developed over the last 5 years to decontaminate waters polluted with sulfa drugs are reviewed with special attention to procedures that make use of porous adsorbent materials and their applicability to real waters
Structural deformation mechanisms of zeolites under pressure
No full textGreen open access version of the paper:Structural deformation mechanisms of zeolites under pressure by: Rossella Arletti Orazio Ferro Simona Quartieri Alessandra Sani Gloria Tabacchi Giovanna VezzaliniPublished in:American Mineralogist (2003) 88 (10): 1416-1422.https://doi.org/10.2138/am-2003-1004ABSTRACTThe HP behavior of the natural zeolite yugawaralite and of the synthetic zeolite Na-A was studied by in situ synchrotron X-ray powder diffraction, using a non-penetrating P-transmitting medium. The unit-cell parameters of yugawaralite were refined up to the pressure of 10 GPa, at which reductions were found of about 7, 2.4, 7, 1.3, and 15% for a, b, c, β, and V, respectively. Contractions of 6.5 and 18.4% were found for a and V, respectively, for zeolite Na-A in the range 10−4 to 6.8 GPa. Diffraction patterns collected during decompression show that the effects induced by high pressure on both samples are almost completely reversible. These results are compared with those obtained under similar experimental conditions for other natural zeolites, with the aim of rationalizing the deformation mechanisms of these porous materials and comparing their flexibility under high-pressure and high-temperature conditions.</div
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Water and ethanol at high pressure in ferrierite - cover
No full textcover picture for the article:"Irreversible Conversion of a Water–Ethanol Solution into an Organized Two-Dimensional Network of Alternating Supramolecular Units in a Hydrophobic Zeolite under Pressure"by: Rossella Arletti, Ettore Fois, Lara Gigli, Giovanna Vezzalini, Simona Quartieri, Gloria Tabacchipublished in Angewandte Chemie,10.1002/anie.201610949DOI: 10.1002/anie.201610949 and 10.1002/ange.201610949and blogged at this link:https://yourmoleculardreams.blog/2017/01/18/under-pressure-from-chaos-to-order/An alternative popular summary is here: https://goo.gl/pS8rbUAuthor of the cover artwork: Andrea Stangoni (@andrea_stangoni) MRS-Bulletin has covered this research work with an excellent news article, freely available at this link:https://www.cambridge.org/core/journals/mrs-bulletin/article/div-classtitlehigh-pressure-and-small-spaces-create-order-from-disorderdiv/7DDFCC976A75CAC0684F7C8DD6723596/core-reader</div
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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