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Safe Sr confinement in feldspar structures
No full textSamples of synthetic Na-A zeolite, pre-exchanged in Sr form, were heat treated at various temperatures up to 1150◦C, in order to entrap the toxic cation in a non-exchanging ceramic matrix. It has been demonstrated that the Sr-loaded zeolite undergoes the following sequence of transformations: zeolite →amorphous phase (at 900◦C) → hexagonal strontium aluminosilicate (at 1000◦C)→ monoclinic strontium aluminosilicate (above 1100◦C). Strontium retention performances of the above Sr-based compounds were compared to each other, estimating cation leaching either by a back-exchange with NaCl solution or by a prolonged contact with distilled water at different pHs (availability test). Thermal treatments from 900◦C onwards were able to safely immobilize Sr2+. The immobilization level depended on the relevant phase formed and resulted the highest (only 0.14% of theinitial Sr concentration), when monoclinic Sr-aluminosilicate structure (Sr-feldspar) was obtained
Monoclinic Sr-celsian by thermal treatment of Sr-exchanged zeolite A, LTA-type framework
No full textAn unconventional method for preparing monoclinic Sr-feldspar starting from a synthetic Na-A zeolite is presented. Accordingly, samples of Sr2+-exchanged zeolite A (Sr-A), containing a residual 5% content of Na+, were thermally treated at temperatures up to 1150 °C for times up to 24 h. Sr-A zeolitic structure breakdown, occurred at about 900 °C and followed by the crystallization of the hexagonal formof Sr-feldspar (Sr-hexacelsian) at about 950 °C, resulted in the final conversion, in 1 h at 1150 °C, of the original zeolitic material into a monoclinic polymorph of Sr-feldspar. Increasing the duration of the thermal treatment up to about 5 h gave rise to the crystallization of monoclinic Sr-celsian at only 1000 °C
Thermal conversion of (Ba,Sr)-exchanged zeolite A in BaAl2Si2O8-SrAl2Si2O8 solid solutions
No full textPreparazione di soluzioni solide (Ba, Sr)Al2Si2O8 per conversione termica di zeolite A [LTA] pre-scambiata al bario e allo stronzio
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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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