1,721,174 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
Acetate-Bridged Platinum(III) Complexes Derived from Cisplatin
No full textOxidation of the acetate-bridged half-lantern platinum(II) complex cis-[Pt[superscript II](NH[subscript 3])[subscript 2](μ-OAc)[subscript 2]Pt[superscript II](NH[subscript 3])[subscript 2]](NO[subscript 3])[subscript 2], [1](NO[subscript 3])[subscript 2], with iodobenzene dichloride or bromine generates the halide-capped platinum(III) species cis-[XPt[superscript III](NH[subscript 3])[subscript 2](μ-OAc)[subscript 2]Pt[superscript III](NH[subscript 3])[subscript 2]X](NO[subscript 3])[subscript 2], where X is Cl in [2](NO[subscript 3])[subscript 2] or Br in [3](NO[subscript 3])[subscript 2], respectively. These three complexes, characterized structurally by X-ray crystallography, feature short (≈2.6 Å) Pt–Pt separations, consistent with formation of a formal metal–metal bond upon oxidation. Elongated axial Pt–X distances occur, reflecting the strong trans influence of the metal–metal bond. The three structures are compared to those of other known dinuclear platinum complexes. A combination of [superscript 1]H, [superscript 13]C, [superscript 14]N, and [superscript 195]Pt NMR spectroscopy was used to characterize [1][superscript 2+]–[3][superscript 2+] in solution. All resonances shift downfield upon oxidation of [1][superscript 2+] to [2][superscript 2+] and [3][superscript 2+]. For the platinum(III) complexes, the [superscript 14]N and [superscript 195]Pt resonances exhibit decreased line widths by comparison to those of [1][superscript 2+]. Density functional theory calculations suggest that the decrease in the [superscript 14]N line width arises from a diminished electric field gradient at the [superscript 14]N nuclei in the higher valent compounds. The oxidation of [1](NO[subscript 3])[subscript 2] with the alternative oxidizing agent bis(trifluoroacetoxy)iodobenzene affords the novel tetranuclear complex cis-[(O[subscript 2]CCF[subscript 3])Pt[superscript III](NH[subscript 3])[subscript 2](μ-OAc)[subscript 2]Pt[superscript III](NH[subscript 3])(μ-NH[subscript 2])][subscript 2](NO[subscript 3])[subscript 4], [4](NO[subscript 3])[subscript 4], also characterized structurally by X-ray crystallography. In solution, this complex exists as a mixture of species, the identities of which are proposed.National Cancer Institute (U.S.) (Grant CA034992)National Institutes of Health (U.S.) (Grant 1S10RR13886-01)David H. Koch Cancer Research Fund (Fellowship
Synthetic Methods for the Preparation of Platinum Anticancer Complexes
Get PDFThe demonstration in the 1960s that cis-diammine-dichloroplatinum(II), or cisplatin, inhibits cellular division of Escherichia coli led to the subsequent discovery that this simple coordination compound is also an effective antitumor agent in mouse models. Subsequent studies validated cisplatin as an effective anticancer agent in humans as well, and FDA approval of cisplatin for the treatment of metastatic ovarian and testicular cancers was granted in 1978. Its introduction as a chemotherapeutic agent significantly improved the survival outlook for many cancer patients; the cure rate for testicular cancer before the approval of cisplatin was less than 10%, significantly lower than the 90% cure rate attained with modern platinum chemotherapy.National Cancer Institute (U.S.) (Grant CA034992)David H. Koch Institute for Integrative Cancer Research at MIT (Graduate Fellowship
A Dual-Targeting, P53-Independent, Apoptosis-Inducing Platinum( Ii ) Anticancer Complex, [Pt(BDI [superscript QQ] )]Cl
Get PDFThe therapeutic index and cellular mechanism of action of [Pt(BDI[superscript QQ])]Cl, a monocationic, square-planar platinum(II) complex, are reported. [Pt(BDI[superscript QQ])]Cl was used to treat several cell lines, including wild type and cisplatin-resistant ovarian carcinoma cells (A2780 and A2780CP70) and non-proliferating lung carcinoma cells (A549). [Pt(BDI[superscript QQ])]Cl selectively kills cancer cells over healthy cells and exhibits no cross-resistance with cisplatin. The mechanism of cell killing was established through detailed cell-based assays. [Pt(BDI[superscript QQ])]Cl exhibits dual-threat capabilities, targeting nuclear DNA and mitochondria simultaneously. [Pt(BDI[superscript QQ])]Cl induces DNA damage, leading to p53 enrichment, mitochondrial membrane potential depolarisation, and caspase-mediated apoptosis. [Pt(BDI[superscript QQ])]Cl also accumulates in the mitochondria, resulting in direct mitochondrial damage. Flow cytometric studies demonstrated that [Pt(BDI[superscript QQ])]Cl has no significant effect on cell cycle progression. Remarkably, p53-status is a not a determinant of [Pt(BDI[superscript QQ])]Cl activity. In p53-null cells, [Pt(BDI[superscript QQ])]Cl, induces cell death through mitochondrial dysfunction. Cancers with p53-null status could therefore be targeted using [Pt(BDI[superscript QQ])]Cl.National Cancer Institute (U.S.) (R01-CA034992
Oxidative reactivity and cytotoxic properties of a platinum(II) complex prepared by outer-sphere amide bond coupling
No full textBenzyl amine was coupled to the dangling carboxylic acid groups of the platinum(II) complex [Pt(edda)Cl[subscript 2]], where edda = ethylenediamine-N,N′-diacetic acid, to give the diamide-tethered complex [Pt(L)Cl[subscript 2]] (1), where L = ethylenediamine-N,N′-bis(N-benzylacetamide). Complex 1 was oxidized with both PhICl[subscript 2] and Br[subscript 2]. Oxidation with PhICl[subscript 2] cleanly afforded the tetrachloride complex, [Pt(L)Cl[subscript 4]] (2), whereas oxidation with Br[subscript 2] gave rise to several mixed halide complexes of the general formula, [Pt(L)Cl[subscript x]Br[subscript 4-x]], where x = 1, 2, or 3. Complexes 1 and 2 were fully characterized by [superscript 1]H, [superscript 13]C, and [superscript 195]Pt NMR spectroscopy, as well as by ESI-MS. These compounds exist as a mixture of diastereomers that arise from the chirality of the two coordinated nitrogen atoms. Crystal structures of 1, 2, and [Pt(L)Cl[subscript x]Br[subscript y]] (3) are reported. Although refined as the tetrabromide complex [Pt(L)Br[subscript 4]], the crystal structure of 3 is a mixture of species with site-occupancy disorder of chloride and bromide ligands. DFT calculations indicate that the two sets of diastereomers of 1 and 2 are effectively thermoneutral, a conclusion that is also supported by the observation of both members of each pair by NMR spectroscopy. The cytotoxicity of 1 and 2 was measured by the MTT assay in HeLa cells and compared to that of cisplatin. Both exhibit IC[subscript 50] values close to 50 μM and are therefore substantially less toxic than cisplatin, for which the IC[subscript 50] is 1 μM.National Cancer Institute (U.S.) (grant CA034992
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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