1,721,035 research outputs found
The map is not the territory: a spatial reading of Pynchon’s California trilogy
Full text linkMoving from a geocritical standpoint, this thesis analyzes the development of Thomas Pynchon’s spatial imagination in the so-called California trilogy. It argues that from the Crying of Lot 49 to Vineland and Inherent Vice, the author’s conceptualization of space develops in a constant and original way. To achieve this objective, the thesis addresses the theme of space on different levels. First, it delves into the urban/suburban aspect of Pynchon’s novels through a theoretical analysis of Edward Soja’s urban process “postmetropolitan transition.” Second, it deals with the representation of space in historical terms, as an instrument for the 1960s American counterculture against the political system of power and control. Finally, it investigates the change in Pynchon’s spatial vision through an examination of the role of mythical/fictional spaces in the trilogy, addressing a theoretical argument of the concept of “Thirdspace,” in relation to the question of alternative realities
Studio delle interazioni ruota-rotaia ai fini della sicurezza dell’esercizio e della manutenzione sviluppo di un sistema di misura sperimentale per il monitoraggio dei carichi trasversali
Full text linkIl presente lavoro, esaminando la situazione del settore ferroviario europeo in relazione alla sicurezza della circolazione ed alla manutenzione dei veicoli, affronta lo studio della misura delle forze di contatto, su base teorica e sperimentale, ai fini dello sviluppo di un sistema di misura sperimentale per il monitoraggio dei carichi trasversali (Y), lato infrastruttura. Attraverso una prima convenzione di ricerca con Rete Ferroviaria Italiana (RFI), è stato effettuato uno studio di fattibilità preliminare, confrontando tra loro due metodologie di misura differenti; successivamente la ricerca è proseguita a livello accademico approfondendo le potenzialità applicative di uno dei due metodi precedentemente analizzati. Infine, attraverso una seconda convenzione di ricerca, sempre con Rete Ferroviaria Italiana (RFI), si è sviluppato il sistema di misura a livello prototipale conducendo ulteriori prove sperimentali di laboratorio ed installando l’apparato direttamente in linea durante il normale esercizio
New insight into the crystal chemistry of alkali-poor beryl: the real topological configuration of the extra-framework content
No full textThe crystal chemistry of natural alkali/water-poor beryl from Gilgit, Pakistan (H2O+Na2O+Cs2O<1.2wt%) is reinvestigated by means of laser ablation inductively coupled plasma mass spectroscopy, thermogravimetric analysis, neutron diffraction and polarised infrared spectroscopy in order to determine the real topological configuration of the extra-framework content in the 6-membered ring channels. Fine chemical analysis was performed by means of laser ablation inductively coupled plasma mass spectroscopy with a laser ablation system made by Wave UP213 (Nd:YAG laser source) coupled with ICP-MS Thermo Electron X7. Calibration was performed using NIST SRM 612 as external calibration sample in conjunction with internal standardization using 29Si, previously measured by EMPA-WDS. The following masses (isotopes) have been analysed: 7Li, 9Be, 23Na, 24Mg, 27Al, 39K, 44Ca, 55Mn, 56Fe, 85Rb and 133Cs.
Thermal analysis were performed with a NETZSCH STA 449C instrument using 7.442 mg of powdered sample, previously dried at 130oC for 4h. The thermal curve (weight loss vs T, 1oC/min), showed a monotonic trend that became flat at about 1100 oC. The experiment was conducted up to 1200 oC. The calculated amount of H2O, on the basis of the weight loss, is 0.86 wt%. The chemical composition of sample is: Al1.93Fe0.03Be2.94Si5.93O18(Na 0.03 0.26H2O).
Single-crystal polarised IR-spectra were obtained with a Bruker IFS-120-HR spectrometer coupled with a Bruker IR-microscope. In order to avoid absorption bands due to external contaminants (H2O vapour or CO2), the optics of the spectrometer were kept under vacuum and the optics of the microscope were continuously purged with purified air (free of H2O and CO2) during the measurements. The resolution of the spectra was 1 cm-1. IR-spectra were obtained using radiation polarised parallel to the a and c axes of the beryl samples. To do this, two small single-crystals were oriented using a Huber four-circle X-ray diffractometer, and then cut and polished in thin platelets (50 μm thick) with the polished surfaces parallel to (001) and (100) respectively.
The single-crystal neutron diffraction experiment was performed at room T with a Huber four-circle diffractometer (SV28 beam-line) installed at the DIDO reactor - Forschungszentrum Juelich, Germany. The incident radiation (CW, λ=1.24126Å) was obtained using a Cu(200) monochromator. The unit-cell parameters of the neutron measurement are: a=b=9.2099(35)Å, c=9.1894(18)Å (c/a=0.9977). A total of 1534 reflections were recorded (2θmax = 100.78 ̊), of which 191 were unique. The systematic extinction rules agreed with the space group P6/mcc. Diffraction data were then corrected for Lorentz effect. No absorption correction was applied. Analysis of the nuclear density Fourier map suggests that the (water) oxygen is located along the 6-fold axis at the 2a-position site (0,0,1/4), whereas the (water) protons are at -0.028(7), -0.071(3), 0.332(1). The hydrogens are distributed in 6 x 2 equivalent positions, above and below the oxygen site. Geometrical configuration of the water molecule is well defined: the O-H bond distance is 0.949(18) Å and the H-O-H bond angle is 106.9(2.2) ̊. The H•••H vector is oriented at ~4 ̊ from [001]. This configuration is completely different from that found in alkali-rich beryl, where the H•••H vector is perpendicular to [001]. Na is also located, with the H2O-oxygen, at the 2a-position site. The final agreement index (R1) of the structural refinement was 0.037 for 34 refined parameters and 160 unique reflections with Fo > 4σ(Fo). The topological configuration of the H2O-molecule into the channel is confirmed by the spectroscopic investigation. Polarised single-crystal IR spectra show that the H2O-molecule is oriented with the molecular symmetry axis perpendicular to the hexagonal axis and H•••H vector parallel (or quasi-parallel) to [001]
NEW INSIGHT INTO THE EXTRA-FRAMEWORK CONTENT OF ZEOLITE LEVYNE
No full textLevyne is a rare zeolite [ideal chemical formula (Ca0.5,Na,K)6(Al6Si12O36)•18H2O] discovered almost two centuries ago in the Fær Øer Islands by Brewster [1]. It is usually found as secondary mineral into cavities of andesitic and basaltic rocks. Merlino et al. solved its crystal structure in the space group R-3m from an untwined crystal [2]. Later, Sacerdoti reported new refinements of the crystal structure of two different levynes, Na and Ca-rich respectively [3]. In all the aforementioned studies, all the extra framework cations (except the site C1 site), were described with isotropic thermal parameters [2,3]. The crystal chemistry of a large number of natural levynes was studied by Galli et al [4]. The framework of this zeolite can be described as a sequence of six-membered rings (AABCCABBC...), which build up the so-called “levyne-cage” and is characterized by the presence of three equivalent channel systems perpendicular to the threefold axis, confined by eight-membered rings. The six-membered single ring represents the secondary building unit (SBU) of this framework type. The topological symmetry is R-3m and corresponds to the general symmetry of the crystal structure.
In the present work we give new insights into the description of the extra framework population of two levynes, Ca-rich and Na-rich respectively, based on anisotropic structure refinement from single-crystal X-ray diffraction, wave-length dispersive electron microprobe analysis and laser-ablation ICP-MAS spectroscopy. The chemical composition of our crystals slightly differs from those of Sacerdoti [3]. In order to describe the thermal behaviour of the extra framework content, we collected intensity data for both the levynes at 298 and 150K.
The extra-framework content, represented by Ca, Na, K and water molecules, lies in the levyne-cages. At least five independent cation sites (C1, C2, C3, C4, C5, [2,3]) have been located. C1 is fully [2] or almost fully [3] occupied by Ca only. The C2, C3 and C4 sites are occupied by a mixture of Ca, Na and K. The C5 site is considered to be occupied by Ca, Na and K [2] or by K only [3].
Compared to previous studies, we observe different occupancies for the extra-framework sites that are in good agreement with the chemical analysis of the two samples. The high quality of the structural refinements allow a reliable description of the bonding environments based on a very good determination of bond-distances and bond-angles. Moreover, the low temperature data show that the thermo-elastic deformation of the structure is mainly accommodate by a re-arrangement of the extra-framework population.
The isotopes analysis performed by laser-ablation ICP-MAS show a high selection of trace elements with 71Ga, 85Rb, 88Sr, 137Ba and 24Mg above the detection limit. Among the major isotopes detected, levyne behaves as a “geochemical trap” for 88Sr displaying a selective character for Sr, with a content of 299 and 1497 ppm for Ca and Na-rich levyne respectively (ratio of about 1:5).
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References.
[1] M. Brewster, Edinb. J. Sci., 2, 332-334, 1825; [2] S. Merlino, E. Galli, A. Alberti, Tscher. Miner. Petrog., 22, 117-129, 1975; [3] M. Sacerdoti, Neues Jb. Miner. Monat., 3, 114-124, 1996; [4] E. Galli, R. Rinaldi, C. Modena, Zeolites, 1, 157-160, 198
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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