1,720,961 research outputs found
In-situ high-temperature XRD and FTIR investigation of hohmannite, a water-rich Fe-sulfate, and its decomposition products
Full text linkThe thermal dehydration of hohmannite, Fe2[O(SO4)2]·8H2O, a secondary iron-bearing hydrous sulfate, was investigated by in situ high-temperature X-ray powder diffraction and in situ high-temperature Fourier transform infrared spectroscopy. Combination of the data from both techniques allowed determining the stability fields and reaction paths for this mineral and its high temperature products. Five main dehydration/transformation steps for hohmannite have been identified in the heating range of 25-800 °C. Temperature behavior of the different phases was analyzed, and the heating-induced structural changes are discussed
A revision of the Carnian/Norian boundary radiolarian assemblages: Insight from the biostratigraphic record of the Norian GSSP, Pizzo Mondello section (Sicily, Italy)
Full text linkThe Triassic was a critical period for a significant increase in the generic diversity of radiolarians after the disappearance of >80% of radiolarian genera during the Permian-Triassic mass extinction. In particular, the Upper Triassic radiolarian fauna is rich and has been documented in several world regions, such as North America, Western Europe, the Mediterranean area, Japan, the Philippines, Timor, and Far East Russia. In this study, a well-preserved and high-diversity fauna from a continuous pelagic-hemipelagic section deposited in western Tethys (Sicily, Italy) provides one of the most detailed radiolarian records of the Carnian-Norian boundary interval, which can be correlated worldwide, from high to low-latitude, from both sides of the Pangea and both Hemispheres. The 99 species belonging to 50 genera from this time interval have been collected from the Pizzo Mondello section (Sicanian Basin, Western Sicily), the selected GSSP for the base of the Norian stage, and then compared to the radiolarian associations documented in other coeval regions. Based on the occurrences of characteristic radiolarian species, we defined and proposed a new radiolarian biozonation across the Carnian-Norian boundary, which consists of five new assemblages (PM assemblage 1–5) that are correlated and calibrated to the already well-defined biozonation of bivalves, ammonoids, and conodonts
Short-range order-disorder in gem richterite and pargasite from Afghanistan: crystal-structure refinement and infrared spectroscopy
No full textGem amphiboles from Mogok, Myanmar: crystal-structure refinement, infrared spectroscopy and short-range order-disorder in gem pargasite and fluoro-pargasite
No full textKinetics of hydrogen diffusion in riebeckite, Na2Fe3+2Fe2+3Si8O22(OH)2: an HT-FTIR study
No full textCorrection to: Multi-scale minero-chemical analysis of biomass ashes: A key to evaluating their dangers vs. benefits (Sustainability 2021, 13, 6052)
No full textThe authors would like to make the following corrections to the published paper [1]. The changes are as follows: (1) Replacing the heading of “Section 2.2.5.” on page 3: “EMPA Analysis” with “EMPA and LA-ICP-MS Analyses” (2) The authors wish to add an explanation along with a reference in “Section 2.2.5.” on page 4. Replacing the original version: The glass pellets obtained after the quenching were embedded with epoxy resin; the mounts were cut, ground, and highly polished down to a 1 μm grade diamond polishing paste. with The glass pellets obtained after the quenching were embedded with epoxy resin; the mounts were cut, ground, and highly polished down to a 1 μm grade diamond polishing paste. Minor and trace elements were analysed at the Department of Physics and Geology (Perugia University) by LA-ICP-MS using the analytical protocol reported in Ref. [25]. Adding a reference into the citation list: 25. Petrelli, M.; Morgavi, D.; Vetere, F.; Perugini, D. Elemental Imaging and Petro-Volcanological Applications of an Improved Laser Ablation Inductively Coupled Quadrupole Plasma Mass Spectrometry. Period. Mineral. 2016, doi:10.2451/2015PM0465. (3) Replacing the caption of Table 4 on page 11: Table 4. Minor elements (ppm), measured with EMPA, in the four samples (2, 3, 4, and 5). with Table 4. Minor elements (ppm) measured with LA-ICP-MS in the four samples (2, 3, 4, and 5)
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
Oxidation or cation re-arrangement? Distinct behavior of riebeckite at high temperature
Full text linkIn this work we address the stability of riebeckite at high temperatures and compare the different behaviors observed under various oxidation conditions. For this purpose, we annealed powders of a sample from Mt. Malosa (Malawi), which is compositionally close to the end-member; the run products obtained after annealing in air vs. in vacuum were studied by Mossbauer spectroscopy and powder X-ray difraction. The results show that riebeckite follows two distinct paths depending on the external environment. Under oxidizing conditions, it is stable in the hydrous form up to relatively low temperatures (400-450 degrees C), then it undergoes a rapid (within similar to 50 degrees C) dehydrogenation, forming oxo-riebeckite, which is stable up to similar to 900 degrees C. The final breakdown products of the oxo-amphibole include aegirine + cristobalite + hematite. Based on the relative intensity of the (310) Bragg reflection, the activation energy (E-a) for the riebeckite to oxo-riebeckite transition is 166 +/- 6 kJ/mol.Under vacuum conditions, no Fe oxidation is observed, and riebeckite is stable up to much higher temperatures (750-800 degrees C); however, in the 550 < T < 700 degrees C range, it undergoes a significant rearrangement of the C cations (those hosted in the strip of octahedra). Indeed, the amphibole stable in the 700-800 degrees C range has the same chemical formula as riebeckite but has a disordered and non-standard cation distribution at the octahedra, i.e., (M(1))(Fe3+Fe2+)(M(2))(Fe3+Fe2+)Fe-M(3)(2+); we call this phase "R-C(3+) disordered riebeckite". For T >= 800 degrees C, it decomposes to aegirine + fayalite + cristobalite + H2O.External oxygen is required for the release of water into the surrounding system, being a prerequisite for the Fe-amphiboles to be a carrier of H2O in the lower crust and upper mantle. One important implication of our results is that characterization of the overall oxidation state of iron does not necessarily provide the redox conditions of the environment of formation because a crystal-chemical re-arrangement under reducing conditions allows riebeckite to maintain its Fe3+/Fe2+ composition up to higher temperatures
- …
