1,721,019 research outputs found
Lacalamita, M., Mesto, E., Mongelli, G., Mameli, P., Cerri, G., Pinto, D., Buccione, R., Schingaro, E. 2023. Characterization of Red Muds as valuable resource for sustainability. Convegno Nazionale Italiano sui Geopolimeri. Bari February, 16-17 2023.
No full textBuccione R., Cerri G., Cisullo C., Lacalamita M., Mameli P., Mesto E., Mongelli G., Pinto D. & Schingaro E. 2023. Geochemistry and mineralogy of bauxite residues (red muds) from Porto Vesme (Sardinia): from disposal material to new resource. Congresso congiunto SIMP-SGI-SOGEI-AIV “The Geoscience paradigm: resources, risk and future perspectives”, 19-21 Settembre 2023, Potenza.
No full textSpectroscopy and crystal chemical properties of NaCa2[Si4O10]F natural agrellite with tubular structure
No full textAgrellite is a rare inosilicate, having a crystal structure characterized by SiO4-tetrahedral tubes located between continuous wall layers formed by edge-sharing Ca-polyhedra. A detailed crystal chemical and physical study of agrellite specimens is carried out by means of electron probe microanalysis, Fourier transform infrared spectroscopy, electron-paramagnetic resonance, and single crystal X-ray diffraction. Additionally, the electronic structures of agrellite was calculated. Luminescence due to 5d-4f transition in Ce3+ ions is observed in both investigated samples. EPR analysis points out the Mn2+ replaces Ca2+ ion in Ca(1A) and Ca(2B) positions, coordinated by two F sites
Crystal-chemistry of micas belonging to the yangzhumingite-fluorophlogopite and phlogopite-fluorophlogopite series from the Apuan Alps (northern Tuscany, Italy)
No full textThe present work reports the crystal-chemical characterization of micas from the Monte Arsiccio and Buca della Vena mines (Apuan Alps, Italy) through electron microprobe analysis, single-crystal X-ray diffraction, and Raman spectroscopy. The sample from the Monte Arsiccio mine can be classifiedas an intermediate member of the yangzhumingite-fluorophlogopite series, with average crystal-chemical formula (K0.85Na0.01Ba0.09)Σ=0.95(Mg2.11Fe2+0.23Fe3+0.11Cr3+0.01Al0.20Ti0.04☐0.30)Σ=3.00(Si3.20Al0.80)Σ=4.00O10.00F1.90Cl0.02(OH)0.08. Unit-cell parameters are a ~ 5.30, b ~ 9.18, c ~ 10.14 Å, β ~ 100.12°, V ~ 486.22 Å3, corresponding to the 1M polytype. Structure refinements, performed in C2/m space group, converged to R1 = 3.54 and 4.46% and provided Mg plus Fe occupancy in the range 86–94% for the octahedral M1 and M2 sites. Raman spectroscopy shows very weak bands in the OH stretching region at ~ 3690 and 3580 cm−1. The sample from the Buca della Vena mine has been identified as an (OH)-rich fluorophlogopite, with average crystal-chemical formula (K0.84Na0.02Ca0.01)Σ=0.87(Mg2.12Fe2+0.55Fe3+0.10Al0.18☐0.05)Σ=3.00(Si2.99Al1.01)Σ=4.00O10.00F1.02Cl0.09(OH)0.89. Its unit-cell parameters are a ~ 5.33, b ~ 9.22, c ~ 10.23 Å, β ~ 100.09°, V ~ 494.39 Å3. Structure refinements gave good R1 values (3.27 and 4.37%) and revealed octahedral occupancy of 82–84% Mg and 16–18% Fe. Strong Raman signals at ~ 3702 cm−1 and 3595 cm−1 were observed in the OH stretching region. The findings allow to better understand not only the mineralogy of the Apuan Alps but, more generally, the crystal chemical details of intermediate dioctahedral-trioctahedral mica belonging to the yanzhumingite-fluorophlogopite series
Armstrongite at non ambient conditions: An in-situ high temperature single crystal X-ray diffraction study
Full text linkThe dehydration process of armstrongite, CaZr[Si6O15]·2H2O, from Khan Bogdo deposit (Gobi, Mongolia) was studied by in-situ High Temperature Single Crystal X-ray Diffraction (HT SCXRD) in air from 25 to 500 °C and in N2atmosphere from 25 to 375 °C. An abrupt discontinuity in the trend of the a and b parameters and of the unit-cell volume was observed at T = 275 °C in dry conditions and at T = 450 °C in air. This discontinuity is associated to dehydration and to a first-order transition. When compared to RT armstrongite, the dehydrated phase structure (obtained at 275 °C only under dry conditions) is characterized by the same space group (C2/m), cell volume decrease of ∼7.5%, compatible with the loss of the two water molecules, positional disorder of Ca over three sites, splitting of some of the heteropolyhedral framework oxygen atoms, tilting of Zr octahedra and Si tetrahedra and, distortion of four-, six- and eight-membered channels. Differently from other Zr-silicate structures, the channels dimension of the dehydrated structure (defined as the ratio between the longest and shortest diagonals of the channels) allowed the armstrongite structure to completely recover the structural water after 21 days exposure to humid conditions
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
Thermal stability and dehydration of armstrongite, a microporous zirconium silicate
No full textThe dehydration of armstrongite from Khan Bogdo (Mongolia) was investigated by combining thermal analysis, in situ HT X-ray powder diffraction (XRPD) and Fourier Transform InfraRed (FTIR) spectroscopy. The process starts at ∼380 °C and is completed within few tenths of degrees. It involves a mass loss of 6.1 wt% and a cell volume decrease of 7%. Armstrongite at RT has C2/m symmetry with (in Å) a = 14.010 (2), b = 14.115 (1), c = 7.838 (1), β = 109.387 (3)° V = 1462.2 (2) Å3. XRPD data in the T-range 370–400 °C show a significant contraction of the cell volume without any symmetry change. At 400 °C the dehydrated phase has cell dimensions (in Å): a = 13.425 (2), b = 13.752 (1), c = 7.818 (1), β = 110.246 (3)° V = 1354.2 (2) Å3. The patterns collected in the T-range from 800 to 30 °C show that armstrongite rehydrates quickly at T ∼320 °C; unit cell parameters and volume refined at the end of the heating/cooling cycle point to a complete reversibility of the dehydration process. Fast rehydration upon cooling is also evident in the FTIR spectra; a complete recovery of the OH-stretching and bending signals is observed at T ∼280–300 °C. Notably, this process can be monitored on single-crystals, while powders embedded in KBr pellets do not recover the structural water content. The thermal expansion of armstrongite is more pronounced along the b axis, with αa: αb: αc= 1.09 × 10−6: 1.69 × 10−5: 7.61 × 10−7at 90 °C and 7.73 × 10−6: 8.94 × 10−6: 5.85 × 10−6at 800 °C
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
- …
