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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
Prospecting history leading to the discovery of Botswana’s diamond mines: from artifacts to Lesedi La Rona
Get PDFProspecting history leading to the discovery of Botswana’s diamond mines : from artefacts to Lesedi La Rona
Get PDFBechuanaland/Botswana has a long and colourful history in exploration and mining. Here these activities are subdivided into three phases: pre-historic, historic and modern. Quarrying stone in Botswana was ongoing 500,000 years ago during the Early Stone Age (ESA). Actual mining of stones probably only started during the Middle Stone Age (MSA) i.e. post 250,000 BP, and the first prehistoric hard rock mining of specularite and limonite, likely started during the Late Stone Age (LSA) 20,000 to 2,000 BP. In east Botswana iron and copper were mined from AD 800 onwards; the mining of gold started in the thirteenth century. Historic mining started with the re-discovery of gold close to Francistown in 1865 and lasted until the 1950s. Rumours of diamonds in Bechuanaland had already surfaced in the 1880s, and it was Ngamiland, in the northwest, that was first explored systematically for diamonds and gold between 1896 and 1899. A joint initiative between Anglo American and De Beers started serious prospecting parts of eastern Bechuanaland between 1932 and 1938; and in 1938 the first diamond finds in Bechuanaland were reported. Modern mining and exploration started with the signing of an agreement in 1959, allowing Consolidated African Selection Trust Ltd. (CAST) into the Bamangwato Tribal Reserve. CAST found a few diamonds in the Motloutse River, but concluded that these were reworked and dropped the exploration rights. De Beers believed that these diamonds had come from west of the Motloutse headwaters, across the watershed in the Kalahari. This ultimately led to the discovery of the Orapa kimberlite field in 1967, a year after Botswana became independent. This discovery triggered a major exploration boom across Botswana adding important diamond-bearing kimberlites such as at Letlhakane (1968), Jwaneng (1973), Gope (1981) and Lerala (1991).http://link.springer.com/journal/7102019-12-01hj2018Geolog
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
Early Permian diamond-bearing proximal eskers in the Lichtenburg/Ventersdorp area of the North West Province, South Africa
Get PDFDiamond-bearing gravels of the Lichtenburg-Ventersdorp area of the North West Province are associated with
north-south orientated sinuous 'runs' that occur almost entirely on a flat erosional surface of the Malmani dolomites
(Transvaal Supergroup) at some 1,500 m elevation. East to west, this dolomite plain measures 150 km, and northsouth
it is on average 40 km wide. This unconformity, which first developed before the Pretoria Group
sedimentation over a period of at least 80 Myr, is marked by siliceous breccias (palaeo-karst infill) and
conglomerates (reworked breccias). It was exhumed in pre-Karoo and post-Gondwana times. Glacial pavements
and remnants of thin Lower Karoo sediments are also found on this polyphase surface. The gravels that make up
these 'runs' and sinkholes directly or indirectly linked to these runs, are coarse-grained, very poorly-sorted, and are
best described as diamictites. The 'runs' are narrow, elongated, generally positive ridges that meander across the
dolomite surface and are up to 30 km long and between 80 to 300 m wide. They have always been regarded as post-
Cretaceous drainage features linked to southward-flowing river systems. Diamonds were discovered in these 'runs'
and they have produced some 12 million carats. However, no Cainozoic fossils or artefacts have ever been found
in almost 90 years of mining. From new field evidence, geomorphological studies, age dating from inclusions in
diamond and zircon and clay analyses, it is proposed that these coarse-grained runs represent proximal palaeoeskers
of the last deglaciation of the Dwyka continental ice sheet, that are preserved on this ancient 'palimpsest'
surface. The age of the deposit is constrained by two populations of agate within the diamictites that are linked to
two separate volcanic units of the Pretoria Group. In addition, the youngest crustal zircon ages from the gravels are
1 Ba, but mantle zircons from Lichtenburg suggest that these have been derived from Cambrian age kimberlites.
Analysis of inclusions in diamond support a Neoproterozoic to Cambrian source for the diamonds, so the absence of
diamonds from Mesozoic kimberlites and Cainozoic fossils within the gravels support the conclusion that the runs
are of Karoo age.http://sajg.geoscienceworld.orgam2018Geolog
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
Neoproterozoic to Early Paleozoic sequences of Congo Shield: comparison of Congo Basin with the surrounding marginal basins
No full textIn the Chap. 6, E. Kadima, D. Delvaux, M. Everaerts, S. Sebagenzi, and F. Lucazeau focus on these lowermost Neoproterozoic to Cambrian succession beneath the centre of the Congo Basin and use this to better constrain the early evolution of the Congo Basin. These authors draw on earlier work of Kadima and reinterpret the old drill core and seismic data, especially from the two fully cored, deep stratigraphic wells Gilson-1: 4,563 m and Mbandaka-1: 4,350 m) that appear to terminate in carbonates that contain intriguing evaporitic-like minerals at the base of the Congo Basin. With this information, they then correlate the successions with the carbonate-siliciclastic sequences along the peripheral margins of the Congo Basins (mentioned in the earlier chapters). The main findings of this work are the recognition of possible major Neoproterozoic (mechanical) rifts that underlie the overlying, but poorly dated, Phanerozoic cover, which they interpret as thermal subsidence sequences. This is an important contribution towards unravelling the origin of the Congo basin
Petroleum potential of the Congo Basin
No full textIn Chap. 18, D. Delvaux and M. Fernandez-Alonso evaluate the petroleum potential of the Congo Basin, probably the last continental-scale sedimentary basin that is still poorly known in terms of petroleum system and related hydrocarbon resources. Whilst some studies have speculated that there may be giant oil deposits in the Congo Basin, to date no evidence for the presence of oil reservoirs has been forthcoming, despite possible potential source-rock levels, petroleum systems, and possible plays designated as targets for exploration projects in the 1950s and 1970s. The authors of this chapter present results of their recent re-analyses of the geological archives and samples stored in the collections of the Royal Museum for Central Africa. Based on their new geochemical analyses, black shales from the Neoproterozoic and early Palaeozoic sequences appear to be barren. In contrast, the Permian black shales are gas prone, whilst younger Jurassic-Cretaceous source rocks are of excellent quality (with Total Organic Carbon up to 25 %), but too immature. The authors also describe oil seeps along the Lukenie River and Lake Inongo that have been previously linked to potential oil reservoirs, but these turn out to be anthropogenic. Thus, whilst there is still no clear indication presently of active petroleum systems in the Congo Basin, this is based on very limited data. New exploration projects are needed to identify areas where Mesozoic source rocks might have reached maturity. Thus, whether the Congo Basin may become an important oil (or shale gas) producer in the future remains unanswered
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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