1,720,978 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
Transition metal complexes with functionalized aryl ligands
No full textReaction of [OsO4] with C7H7MgBr (C7H7 = 2-methylphenyl) followed by column chromatography afforded the reported osmium tetraaryl [Os(C7H7)4] along with the oxo-osmium(VI) [OsO(C7H7)2] (1) and the dioxo-osmium(VI) [OsO2(C7H7)4] (2) complexes. Treatment of [OsO4] with C8H9MgBr (C8H9 = 2,5-dimethylphenyl) gave a mixture of [Os(C8H9)4] (3) and [OsO(C8H9)4] (4) while that with C8H9OMgBr (C8H9O = 4-methoxy-2-methylphenyl) afforded [OsO(C8H9O)4] (5). Oxidation of 3 with 3-chloroperoxybenzoic acid afforded 4 in good yield. The solid-state structures of 1 and 4 have been established by X-ray crystallography.Direct functionalization of osmium(IV) tetraaryl complex [Os(C8H9)4] was studied. Reaction of 3 with CH3COCl and AlCl3 yielded [Os(C8H9)(C8H8-COMe-p)3] 10 and [Os(C8H9)3C8H8-COMe-p)] 11. Formylation of 3 with [TiCl4] and dichloromethyl methyl ether yielded [Os(C8H9)3(C8H8-CHO-p)] 12 and [Os(C8H9)2(C8H8-CHO-p)2] 13. Bromination of 3 with pyridinium tribromide in the presence of Fe powder to give [Os(C8H8-Br-p)4] 15, which undergoes Suzuki coupling with arylboronic acids to afford a series of homoleptic functionalised aryls of osmium(IV).Ir(III) orthometallated complexes [Ir2Cl2L4], (L = 4'-substituted 2-phenylpyridine Rppy), reacted with S-donor ligands to form monomeric [Ir(t-Buppy)(S^S)] (S^S = Et2NCS2- and (MeO)2PS2-).Treatment of lithium (4-oxazolinyl)phenyl prepared in situ from bromo(4-oxazolinyl)benzene and nBuLi with [Au(PPh3)Cl] and [Pt(COD)Cl2] (COD = 1,5 -cyclooctadiene) gave oxazolinylphenyl gold(I) and oxazolinylphenyl platinum(II) complexes respectively. These (oxazolinyl)phenyl complexes are capable for binding metal ions such as Pd(II), Zn(II) to give dinuclear and trinuclear complexes.</p
Denoising for surface reconstruction
No full textWe present an algorithm to denoise an unorganized point cloud which contains noise, white noise and outliers for surface reconstruction. Our algorithm first removes the outliers, white noise and very noisy points based on the point cloud behavior and simple statistical analysis. Afterwards, our algorithm denoises the remaining points by a modified Laplacian smoothing algorithm. Finally, we apply the Robust Cocone algorithm to reconstruct the surface from the denoised point cloud followed by some postprocessing on the reconstructed surface for constructing the boundaries and further smoothing. Our algorithm applies a variant of the standard octree structure to manipulate the points and this makes our algorithm very efficient. The experimental results show that our algorithm can generate a smooth surface even though the noise level is very high and the running time is fast. The data sets that we experimented with include some raw data contaminated by artificial noise, white noise and clusters of outliers. We also compare our algorithm with Robust Cocone, the Adaptive Moving Least-Squares (AMLS) algorithm, and the PoissonPU algorithm. The comparison results show that our algorithm can improve the surface reconstructed from Robust Cocone algorithm, and it gives better results than the AMLS algorithm and the PoissonPU algorithm.</p
Exploiting query distribution in planar point location
No full textPlanar point location is a classical problem in computational geometry. Several point location algorithms are known that achieve optimal worst-case query time. However, there is still a lot of research on this topic. In many applications, certain regions in a planar subdivision are more frequently queried. This raises the question of whether a better query time can be obtained by exploiting the query distribution. In this thesis, we study the point location algorithms that exploit the query distribution to acheive a better query time. We study both the static and dynamic cases. In the static case, the given subdivision is fixed. In the dynamic case, the subdivision can be updated using edge insertions and deletions. Any new edge to be inserted does not cross any existing one. In the static case, most of the existing solutions assume that the query distribution is fixed and can be accessed quickly. In the scenario that the query distribution is not known in advance, we propose point location algorithms for convex and connected subdivisions that can process any online query sequence σ in Ο(OPT + n) and O(OPT + n + │ σ │ log(log* n)) time, respectively, where n is the number of subdivision vertices and OPT is the minimum time to answer queries in σ by any linear decision tree. In the dynamic case, nothing is known about how to exploit the query distribution in answering point location queries. Suppose that there is a fixed query distribution in R2, and we are given an oracle that can return in O(1) time the probability of a query point falling into a polygonal region of constant complexity. A subdivision update is specified as a mixed sequence of k edge insertions and deletions. We can maintain a convex subdivision with n vertices such that it takes O(opt) expected time to answer a query and O(k log5 n) amortized time to perform a subdivision update, where opt is the minimum expected query time required by any linear decision tree to do a point location. The space and construction time are O(n log2 n). As a corollary, the randomized incremental construction of the Voronoi diagram of n sites can be performed in O(n log5 n) expected time so that, during the incremental construction, a nearest neighbor query can be answered optimally with respect to the intermediate Voronoi diagram at that time. Similarly, we can maintain a connected subdivision with n vertices such that it takes O(opt + log(log* n)) expected time to answer a query and O(k log8 n + log31 n) amortized time to perform a subdivision update.</p
Syntheses and downstream purification of 1,2,4-butanetriol
Get PDFThesis (Ph. D.)--Michigan State University. Dept. of Chemistry, 2007Includes bibliographical reference
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
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
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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