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Previous Contributions (previous + contribution)
Selected AbstractsCan Electrophilicity Act as a Measure of the Redox Potential of First-Row Transition Metal Ions?CHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2007Jan Moens Abstract Previous contributions concerning the computational approach to redox chemistry have made use of thermodynamic cycles and Car,Parrinello molecular dynamics simulations to obtain accurate redox potential values, whereas this article adopts a conceptual density functional theory (DFT) approach. Conceptual DFT descriptors have found widespread use in the study of thermodynamic and kinetic aspects of a variety of organic and inorganic reactions. However, redox reactions have not received much attention until now. In this contribution, we prove the usefulness of global and local electrophilicity descriptors for the prediction of the redox characteristics of first row transition metal ions (from Sc3+|Sc2+ to Cu3+|Cu2+) and introduce a scaled definition of the electrophilicity based on the number of electrons an electrophile ideally accepts. This scaled electrophilicity concept acts as a good quantitative estimate of the redox potential. We also identify the first solvation sphere together with the metal ion as the primary active region during the electron uptake process, whereas the second solvation sphere functions as a non-reactive continuum region. [source] Performance evaluation of an autonomic network-aware metascheduler for GridsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2009A. Caminero Abstract Grid technologies have enabled the aggregation of geographically distributed resources in the context of a particular application. The network remains an important requirement for any Grid application, as entities involved in a Grid system (such as users, services, and data) need to communicate with each other over a network. The performance of the network must therefore be considered when carrying out tasks such as scheduling, migration or monitoring of jobs. Surprisingly, many existing quality of service efforts ignore the network and focus instead on processor workload and disk access time. Making use of the network in an efficient and fault-tolerant manner is challenging. In a previous contribution, we proposed an autonomic network-aware scheduling architecture that is capable of adapting its behavior to the current status of the environment. Now, we present a performance evaluation in which our proposal is compared with a conventional scheduling strategy. We present simulation results that show the benefits of our approach. Copyright © 2009 John Wiley & Sons, Ltd. [source] Addressing the Numbers Problem in Directed EvolutionCHEMBIOCHEM, Issue 11 2008Manfred T. Reetz Prof. Dr. Abstract Our previous contribution to increasing the efficiency of directed evolution is iterative saturation mutagenesis (ISM) as a systematic means of generating focused libraries for the control of substrate acceptance, enantioselectivity, or thermostability of enzymes. We have now introduced a crucial element to knowledge-guided targeted mutagenesis in general that helps to solve the numbers problem in directed evolution. We show that the choice of the amino acid (aa) alphabet, as specified by the utilized codon degeneracy, provides the experimenter with a powerful tool in designing "smarter" randomized libraries that require considerably less screening effort. A systematic comparison of two different codon degeneracies was made by examining the relative quality of the identically sized enzyme libraries in relation to the degree of oversampling required in the screening process. The specific example in our case study concerns the conventional NNK codon degeneracy (32 codons/20 aa) versus NDT (12 codons/12 aa). The model reaction is the hydrolytic kinetic resolution of a chiral trans -disubstituted epoxide, catalyzed by the epoxide hydrolase from Aspergillus niger. The NDT library proves to be of much higher quality, as measured by the dramatically higher frequency of positive variants and by the magnitude of catalyst improvement (enhanced rate and enantioselectivity). We provide a statistical analysis that constitutes a useful guide for the optimal design and generation of "smarter" focused libraries. This type of approach accelerates the process of laboratory evolution considerably and can be expected to be broadly applicable when engineering functional proteins in general. [source] An Urban Approach to Firm Entry: The Effect of Urban SizeGROWTH AND CHANGE, Issue 4 2005JOSEP-MARIA ARAUZO-CAROD ABSTRACT This article explores the determinants of firm entry in Spanish municipalities. The authors consider that size is an important determinant of a city's capacity to attract new manufacturing firms. Panel data were used to estimate the determinants of entry according to urban size in Spain (from 1994 to 1702). This article contributes to the literature on market entry because most previous contributions have focused on regional factors rather than urban ones. The results show that local characteristics affect the formation of new firms. However, more local data are needed to obtain more specific results. [source] The marketing profession: evolution and futureJOURNAL OF PUBLIC AFFAIRS, Issue 2 2006Michael Enright Marketing claims professional status and presents to the broader community as professional. The paper draws on previous contributions to the broader issue of professionalism and uses the examples from law, medicine and accounting to argue that the attempt has been neither completely successful nor easily demonstrable. Five criteria common to well-known and accepted professions are developed. The paper concludes that marketing is yet to achieve professional status and asks whether such status is essential for marketers. Copyright © 2006 John Wiley & Sons, Ltd. [source] Spatial and sectoral composition effects of agglomeration economies in the Netherlands,PAPERS IN REGIONAL SCIENCE, Issue 1 2007Frank G. Van Oort Agglomeration economies; spatial econometric models; dynamic externalities; urban growth; spatial regimes Abstract., In this article we test for dynamic inter- and intra-industry externalities on the urban level in the Netherlands. We argue that previous contributions might be sensitive to untested spatial and sectoral composition effects of urban data. We conclude that research results are better controlled when analysed on lower spatial scales, that results improve in robustness when spatial dependence in the form of spatially lagged versions of explained (growth) variables is introduced in the econometric models, and that results are more informative when hierarchical urban regimes are tested for. Introducing spatially lagged versions of explanatory agglomeration variables is informative but leads to less robust outcomes. In general our research results are more conclusive on inter-industry externalities circumstances when outcomes of city-industry as well as sectoral research designs are compared with the same dataset. [source] Caesarea Laus: Ciriaco d'Ancona praising Caesar to Leonardo BruniRENAISSANCE STUDIES, Issue 4 2008Hester Schadee In the 1430s, Poggio Bracciolini and Guarino Veronese conducted a heated epistolary exchange on the relative merits of the Roman republican paragon Scipio Africanus, and Julius Caesar, whom Poggio decried as destroyer of the Republic, whilst Guarino praised him as founder of the Empire. To this debate Ciriaco d'Ancona added his views, a defence of universal monarchy with Caesar as its herald, in his Caesarea Laus. This startling letter, addressed to Leonardo Bruni, is profoundly different in conception from the previous contributions to the Scipio-Caesar controversy, and is as yet not fully studied. In order to explain Ciriaco's argument, the present article examines his narrative tropes, his self-presentation, and his literary models in the Caesarea Laus. Foremost among these is Virgil, but behind him, Ciriaco's ultimate source appears: Dante. In choosing these models, Ciriaco also takes issue with Poggio, and Bruni, concerning the use of poetical allegory as a means to attain truth, of which both had been critical. Comparison with an earlier letter, in which Ciriaco defends such interpretations of poetry, sheds further light not only on his method, but also on the contents of his argument in the Caesarea Laus, and the importance he attached to it. Both Ciriaco's appraisal of Caesar and his espousal of allegorical exegesis, which for him are intimately linked, bespeak the continuing vitality, in early Quattrocento humanism, of medieval approaches, which underlie the originality of the Caesarea Laus. [source] | |||||||||||||