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Study of the formation temperature of mixed LaREO3 (RE ≡ Dy, Ho, Er, Tm, Yb, Lu) and NdGdO3 oxides
No full textMixed LaREO3 (RE ≡ Dy, Ho, Er, Tm, Yb, Lu) and NdGdO 3 oxides were prepared by thermal decomposition of the corresponding co-precipitated mixed oxalates. The decomposition of La/RE and Nd/Gd oxalates was studied by means of differential thermal analysis and thermogravimetric (DTA-TG) measurements; in particular the last step, consisting of the loss of a CO2 molecule from the corresponding oxycarbonate, has been thoroughly investigated, as it is particularly interesting for the study of the formation temperature of mixed rare earth oxides. After the release of CO2, the oxides crystallize in a distorted perovskitic cell or one of the structures typical of rare earth sesquioxides, depending on the cationic size difference and on the average cationic radius. The mixed rare earth oxycarbonate decomposition has been studied in comparison to the decomposition of single rare earth oxycarbonates. A trend of the mixed oxides formation temperature as a function both of the average cationic size and of the cationic sizes difference has been observed and compared to the behaviour of single rare earth oxides. © 2010 Akadémiai Kiadó, Budapest, Hungary
Lo Scenario di un Pianeta in Crisi. Territori, Ambiente, Habitat Antropizzati
No full textIl tema del verde ritorna in molte discussioni sul futuro del mondo: il Great Green Wall in Africa, la piantumazione di alberi in India, le discussioni sull’Amazzonia, ma sembriamo non riuscire a parlarne in maniera efficace e coinvolgente riguardo alle nostre città : necessità di polmoni verdi, di sistemi alberali, di agricolture integrate anche per la città. La "Plant turn", una rinnovata svolta di attenzione per le piante e i loro comportamenti sembrerebbe indicare una rinnovata considerazione scientifica per le piante di cui però non si vede alcun effetto nei paesi e nelle città , come mostrano i continui sradicamenti e impoverimenti del verde in tutta Italia. Una lettura comparativa di questo tema
Synthesis and Characterization of the CeO2/Gd2O3 mixed system by XRD, SEM and magnetic measurements
No full textDC magnetic susceptibility and neutron powder diffraction analysis of the perovskite-type compounds LaYbO3 and LaHoO3
No full textMagnetization measurements and neutron powder diffraction analyses followed by Rietveld refinement have been carried out in order to investigate the magnetic structures of LaYbO3 and LaHoO3. Both compounds exhibit a negative thermal expansion along the a and b axes. In LaYbO3 Yb3+ spins order at 2.4 K according to a FyGz-type structure, belonging to the Pn’ma’ magnetic space group. Conversely, LaHoO3 is paramagnetic down to 1.5 K
Stability fields and structural properties of intra rare earths perovskites.
No full textA stability study of perovskitic LaREO3 oxides (RE = Dy, Ho, Er, Tm, Yb, Lu) as a function of temperature was undertaken. A correlation between the Goldschmidt t value and the perovskitic stability field amplitude was found: the latter widens as t increases. Magnetic measurements, performed on all the perovskitic samples, showed that t is also related to the exchange interactions.
LaREO3 oxides were synthesized by thermal decomposition of the corresponding coprecipitated oxalates at temperatures ranging between 600 and 1800 ◦C. Simultaneous differential thermal and thermogravimetric analyses showed that all the La–RE mixed oxalates decompose similarly. All the oxides, except LaDyO3, crystallize in the perovskitic form in a temperature range that depends on the ionic size difference between La and the smaller rare earth; above and below the perovskitic stability field, the B or C form, typical of rare earth sesquioxides, is present. Rietveld refinements, carried out on all the LaREO3 samples synthesized at 1200 ◦C, showed the occurrence of an orthorhombic distorted perovskitic structure belonging to the Pnma space group
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
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
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