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Conférence de M. Michael V. Dmitriev
No full textDmitriev Mikhael V. Conférence de M. Michael V. Dmitriev. In: École pratique des hautes études, Section des sciences religieuses. Annuaire. Tome 110, 2001-2002. 2001. pp. 441-445
Elastic behavior and high pressure-induced phase transition in chabazite: new data from a sample from Nova Scotia
No full textRecently, the high pressure (HP) behavior of a natural chabazite from Vallerano [1] (VALL), and on the synthetic
phases SAPO-34 [1] and ALPO-34 [2], was investigated in the frame of a wider project aimed at understanding
the role of the framework/extraframework content on the compressibility of CHA-type porous materials.
In this work, further structural information is obtained studying the response to HP of another natural chabazite
sample from Nova Scotia (Canada) (NS) (s.g. R-3mR [3]), characterized by a different chemical composition with
respect to VALL. The study was performed by means of in situ synchrotron X-ray powder diffraction (XRPD) and
silicone oil as non-penetrating P-transmitting medium. XRPD experiments were performed in DAC at the BM01
beamline at ESRF (Grenoble, France) with a fixed =0.7355 Å. Powder patterns were collected from Pambup to 8.6
GPa and upon decompression. All the features of the Pamb pattern and the unit cell parameters are well recovered
upon P release. Below 2.1 GPa, a and cell parameters slightly decrease and increase respectively with a resulting
volume reduction of 3.6 %. Above 2.1 GPa, a transition to a triclinic P-1 pseudo-rhombohedral phase is observed.
The rhombohedral to triclinic phase transition is accompanied by an abrupt decrease in the unit cell parameters and
in the unit cell volume (V=-4.0%). Between 2.5 and 5.9 GPa, the triclinic/pseudo-rhombohedral cell parameters
decrease regularly and the unit cell volume variation (V=-3.0%) indicates a lower compressibility with respect to
that observed before the transition. In the highest P regime (5.9-7.2 GPa), a further slope change, with an increase
in compressibility, is observed. As a whole, V between Pamb and 7.2 GPa is -12.6%. The elastic parameters,
calculated with a second order BM-EoS, are V0 = 826 (1) Å3, K0 = 54(3) GPa and V0 = 784(2) Å3, K0 = 91(5)
GPa, for the rhombohedral and triclinic phase, respectively.
Preliminary results from Rietveld refinements up to about 1 GPa, suggest that the deformation mechanism acting
in the low-P regime is a cooperative tilting of the tetrahedra belonging to the double 6-ring – resulting in a decrease
of its thickness – accompanied by a simultaneous di-trigonalization of the two 6-rings. A similar mechanism was
previously observed during compression of levyne [4].
The HP-induced cell volume contraction of NS (12.6 %) is higher than that of VALL (10.3%) in the same P range.
This is congruent with the lower content in large extraframework potassium cations of NS, which contribute to
sustain the porous structure in VALL.
[1] L. Leardini, S. Quartieri, G. Vezzalini, Micropor. Mesopor. Mater. 127 (2010) 219-227
[2] L. Leardini, S. Quartieri, A. Martucci, G. Vezzalini, V. Dmitriev, Z. Kristallogr. (2012), doi:
10.1524/zkri.2012.1477.
[3] A. F. Gualtieri, E. Passaglia, Eur. J. Mineral. 18 (2006) 351–359.
[4] G. D. Gatta, P. Comodi, P. F. Zanazzi, T. F. Ballaran, Am. Miner. 90 (2005) 645-652
Elastic behavior and high pressure-induced phase transition in chabazite: New data from a natural sample from Nova Scotia
No full textThe high pressure behavior of a natural chabazite from Nova Scotia (Canada) [(Ca1.32K0.45Na0.13Sr0.10 [Si8.55Al3.45O24]11.30 H2O, s.g. R-3m, a = 9.38749(8) and a = 94.379(1)] was investigated by means of in situ synchrotron X-ray powder diffraction and silicone oil as non-penetrating P transmitting medium, in the P-range from Pamb to 7.2 GPa. Above 2.1 GPa, a phase transition from rhombohedral to triclinic
(pseudo-rhombohedral) symmetry is observed. The phase transition is accompanied by an abrupt decrease of most of the cell parameters and of the cell volume. Above the transition – between 2.5 and 5.9 GPa – the triclinic/pseudo-rhombohedral cell parameters decrease regularly, with a compressibility
decrease relative to the trend observed before the transition. A further increase in compressibility occurs in the highest P regime, between 5.9 and 7.2 GPa. Overall, the cell volume decrease in the investigated P-range is 12.6%. Notwithstanding the abrupt and marked cell volume decrease accompanying the phase transition, this is reversible upon decompression. The refined elastic parameters were V0 = 826(1) Å3, K0 = 54(3) GPa and V0 = 784(2) Å3, K0 = 91(5) GPa, for the rhombohedral and triclinic
phase, respectively. The results of the complete structural refinements performed up to 1.1 GPa indicated that: (i) the double-six-membered ring present in chabazite framework undergoes flattening as a result of a HP-induced cooperative tetrahedral anti-rotation; (ii) the 8-membered rings, limiting the channel apertures, become more circular and their crystallographic free area decreases; (iii) the extraframework
content does not exhibit relevant modifications under pressure – as concerns the site occupancies – while some significant changes are observed in the bond distances. The elastic behavior and deformation mechanism of chabazite from Nova Scotia are compared with those of another chabazite sample from Vallerano
and with those of other porous materials belonging to the 6-ring zeolite family
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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