1,721,475 research outputs found
Compressibility of microporous materials with CHA topology: 1. Natural chabazite and SAPO-34
No full textThe HP behaviors of a natural chabazite and of SAPO-34 as synthesized wereinvestigated by means of in-situ synchrotron X-ray powder diffraction, with the aim of understandingthe role of the framework/extraframework content on the response to pressure. Compressibility wasdetermined with silicon oil, as non-penetrating P-transmitting medium, up to 7.6 GPa and 4.5 GPafor chabazite and SAPO-34, respectively. The isothermal Equation of States (EoS), refined with athird-order (chabazite) and a second order (SAPO-34) Birch-Murnagan EoS, yielded the followingparameters: V0=839(1) Å3, K0 = 41(3) GPa, Kp = 11(2) GPa, and V0=2439(4) Å3, K0 = 29(1)GPa, for chabazite and SAPO-34, respectively. These results indicate that chabazite is lesscompressible than SAPO-34. This is mainly ascribed to the more complex and hindering extraframeworkcontent of the natural sample. No complete structural refinements of the powderpatterns were performed, but the compressibility of these materials with CHA topology wastentatively interpreted on the basis of the deformation mechanism observed in the structurallyrelated zeolite levyne. The comparison between the volume decrease induced on chabazite by highpressure and by high temperature indicates that this zeolite is much more flexible undercompression than upon dehydration
Studio sperimentale del comportamento a taglio di travi in calcestruzzo armato rinforzate con FRCM
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Thermal behavior of Si-faujasite: new insights from in situ synchrotron X-ray powder diffraction study
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Thermal behaviour of siliceous faujasite: further structural interpretation of negative thermal expansion
No full textThe high-temperature behaviour of siliceous faujasite (Si-Y) was investigated by in situ synchrotron Xray powder diffraction from room temperature up to 1123 K. This porous phase is remarkably stable
when heated, and no phase transitions or changes in symmetry are observed. A marked negative thermal expansion (NTE), already reported in literature for a heating range from 25 to 573 K, was confirmed up to
about 923 K. Above this temperature a positive thermal expansion was observed. Si-Y’s thermal behaviour was interpreted on the basis of the transverse thermal vibrations of the oxygen atoms involved in
the T–O–T linkages and a series of other structural features characterizing the faujasite structure, namely the T–T distances between adjacent tetrahedral sites, the thickness of the double 6-membered rings, and
the ditrigonal index of the 6-membered rings. Moreover, the thermal behaviour of several other anhydrous porous materials with NTE behaviour is discussed and compared to that of Si-Y
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
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
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