1,721,002 research outputs found
The contribution of geoscience to cultural heritage studies
No full textThis issue of Elements celebrates the diverse contributions that the Earth sciences have made to characterizing, interpreting, conserving, and valorizing cultural heritage. Archaeometry and conservation science are connected to the geosciences at different levels. Earth scientists possess a profound perception of the complexity of natural materials, they have the necessary knowledge of the ancient and recent geological and physicochemical processes acting on natural materials and on the artifacts produced by human activities, and they master most of the techniques useful to investigate our common heritage. Therefore, Earth scientists can greatly contribute towards a better understanding and preservation of our past
XANES, UV-VIS and luminescence spectroscopic studyof chromophores in ancient HIMT glass
No full textThis work is aimed to the study of a series of Late Roman glass fragments belonging to the peculiar group called HIMT (High Iron Magnesium Titanium glass), characterized by different color nuances, and previously chemically characterized by our group. XANES, UV-VIS and luminescence spectroscopies are exploited for determining the distribution of the oxidation states ofthe two chromophores Fe and Mn. In all the ancient glass samples, Fe results to be mostly in its oxidate state 3+. The prevalent Mn oxidation state is 2+, however the presence of minor amounts of Mn3+ has been proved. The different spectroscopic techniques, used in a combined approach, areable to interpret the apparent anomalous colour of some of the ancient glass samples
The Influence of the Framework and Extraframework Content on the High Pressure Behavior of the GIS Type Zeolites: The Case of Amicite.
Get PDFThis paper reports a study, performed by in-situ synchrotron X-ray Powder Diffraction,
of the high pressure behavior of the natural zeolite amicite [K4 Na4 (Al8 Si8 O32 )·10H2 O], the GIS-type
phase with ordered (Si, Al) and (Na, K) distribution. The experiments were carried out up to
8.13(5) GPa in methanol:ethanol:water = 16:3:1 (m.e.w.) and 8.68(5) GPa in silicone oil (s.o.).
The crystal structure refinements of the patterns collected in m.e.w. were performed up to
4.71(5) GPa, while for the patterns collected in s.o. only the unit cell parameters were determined
as a function of pressure. The observed framework deformation mechanism—similar to that
reported for the other studied phases with GIS topology—is essentially driven by the distortion
of the “double crankshaft” chains and the consequent changed shape of the 8-ring channels.
The pressure-induced over-hydration observed in the experiment performed in aqueous medium
occurs without unit cell volume expansion, and is substantially reversible. A comparison is made with
the high pressure behavior of the other GIS-type phases, and the strong influence on compressibility
of the chemical composition of both framework and extraframework species is discussed
Dehydration Mechanism of Monastir Ferrierite: a High Resolution In-situ X-ray Powder Diffraction Study
No full textIrreversible Conversion of a Water-Ethanol Solution into an Organized Two-Dimensional Network of Alternating Supramolecular Units in a Hydrophobic Zeolite under Pressure
Get PDFTurning disorder into organization is a key issue in science. By making use of X-ray powder diffraction and modeling studies, we show herein that high pressures in combination with the shape and space constraints of the hydrophobic all-silica zeolite ferrierite separate an ethanol-water liquid mixture into ethanol dimer wires and water tetramer squares. The confined supramolecular blocks alternate in a binary two-dimensional (2D) architecture that remains stable upon complete pressure release. These results support the combined use of high pressures and porous networks as a viable strategy for driving the organization of molecules or nano-objects towards complex, pre-defined patterns relevant for the realization of novel functional nanocomposites.Unter hohem Druck trennt sich eine Ethanol/Wasser-Lösung in einem hydrophoben Zeolith in supramolekulare Einheiten ihrer Bestandteile, Ethanol-Reihen und Wasser-Quadrate, die sich zu einem zweidimensionalen Netzwerk anordnen. Dieses bleibt auch bei der Rückkehr zu Normaldruck stabil, so dass durch druckverstärkten Einschluss Mischungen einfacher Moleküle zu organisierten Materialien gebildet werden können
High temperature behavior of zeolite ferrierite: in situ synchrotron X-ray powder diffraction study
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
- …
