125,659 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Evolving multimedia ontologies: the BSM tool environment
No full textGoal of this paper is to present the BOEMIE Semantic Manager (BSM) tool environment providing advanced tool-assisted functionalities for domain experts and content managers to support design and evolution of ontology knowledge about multimedia resources. In particular, key features of the tool are i) the capability to figure out the different situations where available background knowledge is not sufficient for multimedia resource interpretation, and ii) the capability to support the design of the missing knowledge not only through the traditional "from scratch" approach, but also by enforcing the (re)use of externally harvested matching knowledge chunks
How structural modifications can tune the asymmetric cyclopropanations catalyzed by Cu(I) complexes of chiral pyridine containing macrocylcic ligands (Pc-L*)
No full textWe have recently reported that copper(I) complexes of the new C1-symmetric pyridine-based 12-membered tetraaza macrocycles, Pyridine Containing Ligands (Pc-L*), are competent catalysts in the asymmetric cyclopropanation.[1] We report here the synthesis of new C1- and C2-symmetric Pc-L* macrocycles and the use of their Cu(I) complexes as catalysts for the title reaction. The synthetic paths, reportedi in Scheme 1, are very simple and they take advantage of commercially available, enantiomerically pure, chiral amino-alcohols and/or primary amines. These last compounds can react either with 2,6-bis(chloromethyl)pyridine(path A) or with the stereochemically pure forms of the alkyl pyridines obtained by the Lipase-catalyzed kinetic acetylation of 2,6-bis(1-hydroxyethyl)pyridine [2] (path B).
Ligands with different structures have been obtained in moderate to good yields (40-80%) and they have been fully characterized. The Cu(I) complexes of those ligands showed good catalytic activities in the cyclopropanation of differently substituted olefins employing ethyl diazoacetate (EDA) as carbene precursor.
In all cases a complete conversion of EDA was observed and, depending on the employed ligand, cyclopropanes were obtained with tunable cis/trans stereoselectivities and e.e. up to 96%.
[1] Caselli, A.; Cesana, F.; Gallo, E.; Casati, N.; Macchi, P.; Sisti, M.; Celentano, G.; Cenini, S. Dalton Trans. 2008, 4202-4205. [2] Uenishi, J.; Aburatani, S.; Takami, V. J. Org. Chem., 2007, 72, 132-138
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Modular approach to chiral pyridine-containing macrocyclic ligands (Pc-L*) : application of their Copper(I) complexes in asymmetric cyclopropanations
No full textWe have recently reported that copper(I) complexes of the new C1-symmetric pyridine-based 12-membered tetraaza macrocycles, Pyridine Containing Ligands (Pc-L*), are competent catalysts in asymmetric cyclopropanations.1 Herein we report the synthesis of new C1- and C2-symmetric Pc-L* macrocycles and the use of their Cu(I) complexes as catalysts for the title reaction.
The synthetic path is very simple and it takes advantage of commercially available, enantiomerically pure, chiral amino-alcohols and/or primary amines. Compounds 1a-b have been obtained in a quantitative yield employing naturally occurring L-valinol as starting material.2 Differently substituted macrocyclic ligands 4a-d have been obtained in moderate to good yields (20-70%) and they have been fully characterized including elemental analysis, MS, 1H-NMR, 13C-NMR. The Cu(I) complexes of those ligands have been isolated and characterized, and they showed good catalytic activities in the cyclopropanation of differently substituted olefins employing ethyl diazoacetate (EDA) as carbene precursor.
In all cases a complete conversion of EDA was observed and, depending on the employed ligand, cyclopropanes have been obtained with tunable cis/trans stereoselectivities and e.e. up to 96%. Moreover, the obtained results allow a direct comparison of the reaction stereoselective outcome between C1- and C2-symmetric ligands having the same molecular structure
Some piece-wise smooth Lagrangian fibrations
No full textThis paper was motivated by the Strominger-Yau-Zaslow [A. Strominger, S.-T. Yau and E. Zaslow, Nuclear Phys. B 479 (1996), no. 1-2, 243–259; MR1429831 (97j:32022)] conjecture and work surrounding it. This conjecture predicts that mirror symmetry can be explained in terms of dualizing special Lagrangian fibrations on Calabi-Yau manifolds. The paper under review deals with the question of constructing Lagrangian, rather than special Lagrangian, fibrations.
One way to construct a smooth Lagrangian torus bundle is to start with an affine manifold, i.e., a real manifold with transition maps in , whose transition maps in fact have integral linear part. Then there is a local system contained in the cotangent bundle of , generated locally by where are local affine coordinates. Because of the restriction on transition maps, is well-defined, and inherits the canonical symplectic form on and is a Lagrangian torus bundle over .
Now the basic problem is that interesting Lagrangian fibrations will have singular fibres. One considers affine manifolds with singularities, i.e., topological manifolds with a dense open set which has an affine structure. Ideally, should have codimension two in . One then seeks compactifications as symplectic manifolds. Of course, one's ability to do this will depend on the nature of the affine structure around . It is not difficult to carry this out in two dimensions for some standard types of singularities [see, for example, M. Symington, in Topology and geometry of manifolds (Athens, GA, 2001), 153–208, Proc. Sympos. Pure Math., 71, Amer. Math. Soc., Providence, RI, 2003; MR2024634 (2005b:53142)]. The paper under review is concerned with aspects which only arise in higher dimensions. In particular, it appears that in higher dimensions there are some naturally occurring singularities which can only be compactified using piecewise smooth fibrations. This phenomenon was first seen in work of W.-D. Ruan [in Winter School on Mirror Symmetry, Vector Bundles and Lagrangian Submanifolds (Cambridge, MA, 1999), 297–332, Amer. Math. Soc., Providence, RI, 2001; MR1876075 (2002m:32041)] and was demonstrated by D. D. Joyce [see, for example, Comm. Anal. Geom. 11 (2003), no. 5, 859–907; MR2032503 (2004m:53094)] to be crucial in understanding the Strominger-Yau-Zaslow conjecture.
The paper under review is partly expository and partly an introduction to some new ideas of the authors. It begins with a nice exposition of the basic problems and examples that arise in this context, and then proceeds to give some general constructions for producing piecewise smooth Lagrangian fibrations, including ones which have the correct topology for compactifying the "negative vertex'', one of the two basic singularities which occur in three-dimensional Calabi-Yaus. This is the hard case; local models for the "positive vertex'' have been known for a long time. This example has the feature that the discriminant locus is not codimension two, but is a codimension one fattening of a trivalent graph. This appears to be a necessary feature of such examples. The authors then consider periods of such piecewise smooth fibrations, and give some hints at upcoming work on more powerful methods of constructing piecewise smooth fibrations
Pragmatic Case Studies as a Source of Unity in Applied Psychology
No full textTo unify or not to unify applied psychology: that is the question. In this article we review pendulum swings in the historical efforts to answer this question—from a comprehensive, positivist, “top-down,” deductive yes between the 1930s and the early 60s, to a postmodern no since then. A rationale and proposal for a limited, “bottom-up,” inductive yes in applied psychology is then presented, employing a case-based paradigm that integrates both positivist and postmodern themes and components. This paradigm is labeled “pragmatic psychology” and, its specific use of case studies, the “Pragmatic Case Study Method” (“PCS Method”). We call for the creation of peer-reviewed journal-databases of pragmatic case studies as a foundational source of unifying applied knowledge in our discipline. As one example, the potential of the PCS Method for unifying different angles of theoretical regard is illustrated in an area of applied psychology, psychotherapy, via the case of Mrs. B. The article then turns to the broader historical and epistemological arguments for the unifying nature of the PCS Method in both applied and basic psychology.Peer reviewe
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