1,720,967 research outputs found
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
An interpretation of high-resolution aeromagnetic data over the Manitouwadge greenstone belt, Ontario, Canada.
No full textThe aim of this study is to interpret aeromagnetic data using 3D techniques. The data consist of eleven high resolution surveys over the Manitouwadge greenstone belt of the Superior Province, Ontario. The interpretation was calibrated to the detailed geological mapping of the area by Zaleski et. al. (1995) The study has three components. First, the data and grid quality were maximized to maintain as much of the high frequency component of the flight line data as possible while minimizing levelling errors and gridding artefacts. Second, a number of 3D interpretation techniques was investigated. Third, the 3D interpretation techniques were applied to the data over the Manitouwadge study area. Grid improvement techniques, particularly micro-levelling and trend reinforcement, were found to be necessary to maximize grid quality. The 3D interpretation techniques used included apparent magnetic susceptibility mapping, analytic signal, horizontal gradient of pseudo-gravity, potential field tilt and Euler deconvolution as well as first and second vertical derivatives. Each method enhances a different component of the total field intensity and complemented each other when interpreted in combination. The apparent susceptibility map combined with the horizontal gradient of pseudo-gravity maxima produced an image that approximates the mapped geology. Calibrating the magnetic interpretation to the known geology allowed the extrapolation of supracrustal rock units into areas of limited geological mapping. The presence of supracrustal units in the engulfing Black Pic tonalitic batholith extends the geological mapping and illustrates regional deformation
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
Tectonic framework and relative ages of structures within the Ottawa-Bonnechere graben.
No full textThe Ottawa-Bonnechere graben forms a 55 km wide topographic low extending from near Montreal through Ottawa. It is part of the St. Lawrence rift system, which also includes the Saguenay graben in Quebec. Cambrian to Ordovician carbonate and fine clastic sedimentary rocks of the St. Lawrence Platform overlie Grenvillian basement rocks and, in the Ottawa-Hull area, are cut by several generations of brittle faulting. Relative ages of faults and associated structures are determined or inferred from field studies of key outcrops. Three periods of faulting are defined, and the orientations of the paleostress fields associated with each period are modelled using fault and fault surface lineations orientation data. The oldest generation of fault structures, referred to as D\sb1, formed in response to a stress field in which the greatest principal horizontal stress was oriented northwest. The second and third periods of faulting (D\sb2, D\sb3) occurred when the greatest principal horizontal stress was oriented west-northwest and southwest, respectively. Both D\sb2 and D\sb3 involved the reactivation of the existing faults and the development of new faults. (Abstract shortened by UMI.
Structural and magnetic fabric study of the late Archean Sparrow and Prosperous plutons, Prosperous suite, Slave Province, Canada.
No full textThe late Archean (∼2595 Ma) Sparrow and Prosperous granite plutons near Yellowknife, NWT, intrude cordierite and andalusite bearing metagreywacke typical of the Slave Province. The objective of this thesis is to determine the structure of the plutons, mode of emplacement and timing in relation to regional deformation. Field and microstructural studies of the plutonic and host rocks are complemented by an analysis of the anisotropy of magnetic susceptibility (AMS) of the granites. Minor recrystallization of quartz within the plutons, with most grains showing subgrain development, suggests that the fabrics in the granites formed before the granites had completely cooled, probably during emplacement. Paramagnetic Fe-phyllosilicates (biotite and chlorite) and very fine-grained magnetite contribute to the magnetic susceptibility and its anisotropy. Magmatic mica-rich and mica-poor layers lie parallel to a shallow-dipping basal contact of the Prosperous pluton. The plutons are inferred to have been emplaced during a second phase of regional deformation (D2). It is proposed that the Sparrow and Prosperous plutons are laccoliths that were emplaced horizontally during D2 deformation, and subsequently were deformed as they crystallized during later stages of D2. (Abstract shortened by UMI.
Tectonic framework and relative ages of structures within the Ottawa-Bonnechere graben.
No full textThe Ottawa-Bonnechere graben forms a 55 km wide topographic low extending from near Montreal through Ottawa. It is part of the St. Lawrence rift system, which also includes the Saguenay graben in Quebec. Cambrian to Ordovician carbonate and fine clastic sedimentary rocks of the St. Lawrence Platform overlie Grenvillian basement rocks and, in the Ottawa-Hull area, are cut by several generations of brittle faulting. Relative ages of faults and associated structures are determined or inferred from field studies of key outcrops. Three periods of faulting are defined, and the orientations of the paleostress fields associated with each period are modelled using fault and fault surface lineations orientation data. The oldest generation of fault structures, referred to as D\sb1, formed in response to a stress field in which the greatest principal horizontal stress was oriented northwest. The second and third periods of faulting (D\sb2, D\sb3) occurred when the greatest principal horizontal stress was oriented west-northwest and southwest, respectively. Both D\sb2 and D\sb3 involved the reactivation of the existing faults and the development of new faults. (Abstract shortened by UMI.
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
The origins of magnetic anomaly lows associated with three impact structures.
No full textDrill cores from three Canadian impact structures were analysed for rock magnetic properties and mineralogy, in order to explain the reduced magnetizations associated with these structures. Samples from the drill cores were cut and measured for AMS and NRM parameters. Drill cores from the twin impact craters of the Clearwater structure exhibited different natural remanent magnetization (NRM) characteristics and samples from their respective drill cores were subject to demagnetization by alternating field and thermal techniques. The difference noted in their NRM characteristics was attributed to the acquisition of a viscous remanent magnetization (VRM) at depth in Clearwater East. Both magnetic susceptibilities and remanent magnetizations are well below regional values in impact generated breccias, melt rocks, shocked crystalline rocks, and in post-impact sedimentary infill. The processes of brecciation, alteration, shock, and infill by non-magnetic sediments contribute to the development of the magnetic lows. However, a significant component of the magnetic anomalies was found by forward modeling to derive from the unshocked basement rocks beneath the impact structures. This zone of reduced magnetization may be caused by the partial demagnetization of magnetite by the impact-induced transient stress wave travelling away from the point of impact, and the possible acquisition of a lower intensity shock remanent magnetization in the target rocks at depth. (Abstract shortened by UMI.
Tectonic evolution of the Late Archean Pontiac Subprovince, Superior Province, Canada: Structural, metamorphic, and geochronological studies.
No full textThe Pontiac Subprovince is a Late Archean (ca. 2.7 Ga) metasedimentary-metavolanic-granitoid-gneiss terrane situated along the southeastern margin of the Superior Province in Quebec. Detailed structural study of the northwestern part of this amphibolite facies metasedimentary belt has revealed a protracted history of deformation in Late Archean and Early Proterozoic time. An early contractional event (D\sb1) resulted in development of steep foliations now preserved as folded or straight relics within microlithons of S\sb2 foliation. During this stage, the Cadillac-Larder Lake fault zone acted as a major fault zone along which greenstones for the Abitibi Subprovince were thrust over the Pontiac Subprovince. Regional metamorphism resulted from both thickening of the crust, and intrusion of voluminous I-type graintes. D\sb2 structures record peak metamorphic high-temperature deformation of the crustal rocks during which large-scale D\sb2 nappes moved towards the south-southeast. The basal thrust faults of these nappes are preserved as high-strain shear zones within the study area. Second order east-trending recumbent F\sb2 folds, a penetrative S\sb2 crenulation foliation, and a north-northwest-trending L\sb2 elongation lineation are other important structures of this deformational event. A later D\sb3 contractional event superimposed east-trending upright folds on all earlier structures. Extensional D\sb4 structures are associated with reactivation of the Cadillac-Larder Lake fault zone as a normal fault zone, and are only recorded in or close to normal faults within this fault zone. Finally, brittle D\sb5 thrust faults and kink structures are superimposed on all older structures in the northwestern Pontiac Subprovince. Gneisses of the Lac Opasatica area record pre-D\sb1 penetrative structures that are not present within the other rock types of the study area. Increasing metamorphic grade from biotite zone to sillimanite zone is evident from north (the Cadillac-Larder Lake fault zone) to south in the study area, close to outcrops of the S-type granites. Thermobarometry of samples from the study area indicates that regional metamorphism of the rocks in the northwestern Pontiac Subprovince occurred at about 590\sp\circC and 6.2 kbar. Investigation of the metamorphic and structural history of these Late Archean rocks suggests a clockwise PT path similar to that of Phanerozoic collisional belts. \sp{40}Ar/\sp{39}Ar age constraints from this study combined with other geochronologic indicate a slow cooling rate of about 2\sp\circ to 6\sp\circC/Ma, and reveal that temperatures as high as 350\sp\circC and 280\sp\circC were persistent in crustal rocks of the area until ca. 150 Ma after attainment of peak metamorphic conditions. (Abstract shortened by UMI.
- …
