1,721,897 research outputs found
FTIR spectroscopy of hydrogen in minerals: detection, structural environment, quantitative analysis and thermal behaviour
No full textHydrogen can be a major, a minor or a trace constituent of a large variety of minerals. It is usually bonded to oxygen to give H2O, OH-, or more rarely H3O+, H3O2- H5O2+ units, but also NH4+ or organic compounds. It can be a structural component in stoichiometric hydrates, hydroxides, and in many silicate minerals, or can be non-stoichiometrically present as a major extraframework component in microporous minerals (e.g. zeolites). Hydrogen also occur as a minor constituent in structural defects of nominally anhydrous minerals (NAMs) [1]. H exerts a strong influence on the chemical and physical properties of minerals; hence it has a controlling effect on many high-temperature geological processes (e.g. magma genesis, kinetic of phase transformations, etc.), as well as low-temperature alteration processes. Unfortunately, H is a rather elusive element, specially when it occurs in very low amounts, as in NAMs. Conventional micro-analytical techniques (EMPA) and X-ray diffraction are generally unsuitable to characterize this element; secondary ion mass spectrometry (SIMS) and neutron diffraction are not easily accessible and requires complex, time-consuming, analytical procedures. A possible alternative is offered by spectroscopy: Raman, Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR). FTIR is particularly suitable for hydrogen, since the O-H (C-H and N-H) bond absorbs the infrared radiation very efficiently. The relatively low cost, ease of use and ease of sample preparation makes the FTIR technique an extremely powerful tool for the study of H-bearing minerals [2]. Using FTIR spectroscopy we can: a) quantify hydrogen, b) study its distribution [3], c) distinguish its speciation, d) define the structural orientation of the O-H dipole, e) study phase transitions associated with H loss, and f) study thermal processes [4]. We present here the recent developments of the FTIR activities at Roma Tre and describe the new facilities which are currently available in our laboratories (high temperature stages, Focal Plane Array detectors). We will use, as examples, the most recent results obtained by our group, including studies on beryl, cordierite, feldspathoids, phospates and hydrocarbons-bearing materials.
[1] H. Keppler, J.R. Smyth (Eds.) Reviews in Mineralogy and Geochemistry 62 (2006) pp. 478.
[2] E. Libowitky, A. Beran, Emu Notes in Mineralogy 6 (2004) 227-279.
[3] G. Della Ventura, F. Bellatreccia, A. Marcelli, M. Cestelli Guidi, M. Piccinini, A. Cavallo, M. Piochi, Anal. Bioanal. Chem. 397 (2004) 2039-2049.
[4] E. Bonaccorsi, G. Della Ventura, F. Bellatreccia, S. Merlino, Micropor. Mesopor. Mater. 99 (2006) 225-235
Il Paleolitico medio
No full textIl capitolo, ospitato all'interno del volume Italia preistorica, fornisce un dettagliato e accurato inquadramento del Paleolitico medio italiano, dal punto di vista cronologico e cultural
Giulio Schmiedt, Il livello antico del Mar Tirreno. Testimonianze dei resti archeologici, con la collaborazione di M. Caputo, G. Conta, F. Guidi, M. Pellegrini, L. Pieri
No full textVan Wonterghem Frank. Giulio Schmiedt, Il livello antico del Mar Tirreno. Testimonianze dei resti archeologici, con la collaborazione di M. Caputo, G. Conta, F. Guidi, M. Pellegrini, L. Pieri. In: L'antiquité classique, Tome 43, fasc. 1, 1974. pp. 660-662
Optical performances of SINBAD, the Synchrotron INfrared Beamline At DANE. 22, J) CESTELLI GUIDI, M., PICCININI, M., MARCELLI, A., NUCARA, A., CALVANI, P., BURATTINI. E.,
No full textSINBAD (Synchrotron Infrared Beamline At DANE) is the first Italian synchrotron radiation beamline operating in the infrared range. It collects the radiation emitted by DANE, an electron-positron collider designed to work at 0.51 GeV with a beam current I > 1 A. Here, the actual performances of the beamline, in terms of brilliance gain with respect to black bodies and polarization properties, are presented and discussed. Finally, the stability of the SINBAD source, a critical issue for Fourier transform infrared spectroscopy, is discussed
Modelli culturali di fruizione del servizio e livelli di soddisfazione del servizio scolastico presso le famiglie, Progetto P.A.S.- Sviluppo di un modello psicosociale di autovalutazione della qualità dei processi d’efficacia ed efficienza nell’azione formativa;
No full textreport di ricerca inteistituzional
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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