Decomposability and modularity of economic interactions

No abstract availabl

Appropriability, Patents, and Rates of Innovation in Complex Products Industries

The economic theory of intellectual property rights is based on a rather narrow view of both competition and technological knowledge. We suggest some ways of enriching this framework with a more empirically grounded view of both and, by means of a simulation model, we analyze the impact of different property right regimes on the dynamics of a complex product industry, that is an industry where products are complex multi-component objects and competition takes place mainly through differentiation and component innovation. We show that, as the complexity of the product spaces increases, stronger patent regimes yield lower rates of innovation, lower product quality and lower consumers' welfare. localized ones.patents; appropriability of innovation; complex product industries; industrial dynamics

Supporti alla programmazione Grid-aware - esperienze di allocazione dinamica di programmi ASSIST a componenti

In questa tesi viene proposta e sperimentata una metodologia per il supporto di applicazioni grid-aware espresse come moduli paralleli ASSIST puri e incapsulati in componenti CCM (CORBA Component Model). La metodologia oggetto della tesi prevede il monitoraggio del tempo di servizio di applicazioni, basate su stream di dati, e la riconfigurazione da parte di un Application Manager, che può autonomamente decidere quali moduli/componenti paralleli utilizzare per bilanciare il carico, rispettando quindi il contratto di performance o evitando uno spreco inutile di risorse. A conclusione della sperimentazione, viene fatto un confronto tra i due approcci proposti (ASSIST puro ed integrato CCM), valutando l'impatto dei componenti CCM in una applicazione in esecuzione su una griglia, e valutando la bontà dell'Application Manager nei due casi

Wolf-Rayet nebulae as tracers of stellar ionizing fluxes: I. M1-67

We use WR124 (WN8h) and its associated nebula M1-67, to test theoretical non-LTE models for Wolf-Rayet (WR) stars. Lyman continuum ionizing flux distributions derived from a stellar analysis of WR124, are compared with nebular properties via photo-ionization modelling. Our study demonstrates the significant role that line blanketing plays in affecting the Lyman ionizing energy distribution of WR stars, of particular relevance to the study of HII regions containing young stellar populations. We confirm previous results that non-line blanketed WR energy distributions fail to explain the observed nebular properties of M1-67, such that the predicted ionizing spectrum is too hard. A line blanketed analysis of WR124 is carried out using the method of Hillier & Miller (1998), with stellar properties in accord with previous results, except that the inclusion of clumping in the stellar wind reduces its wind performance factor to only approx2. The ionizing spectrum of the line blanketed model is much softer than for a comparable temperature unblanketed case, such that negligible flux is emitted with energy above the HeI 504 edge. Photo-ionization modelling, incorporating the observed radial density distribution for M1-67 reveals excellent agreement with the observed nebular electron temperature, ionization balance and line strengths. An alternative stellar model of WR124 is calculated, following the technique of de Koter et al. (1997), augmented to include line blanketing following Schmutz et al. (1991). Good consistency is reached regarding the stellar properties of WR124, but agreement with the nebular properties of M1-67 is somewhat poorer than for the Hillier & Miller code.Comment: 12 pages, 5 figures, latex2e style file, Astronomy & Astrophysics (accepted

Synthesis and characterization of non-bridging mono- and bis-σ-η1-alkynyl derivatives of the phosphido-bridged hexaplatinum core [Pt6(μ-PBut2)4(CO)4]2+

Several mono- or bis-alkynyl derivatives of general formula Pt6(μ-PBut2)4(CO)4X(CC–R), Pt6(μ-PBut2)4(CO)4(CC–R)2 or Pt6(μ-PBut2)4(CO)4(CC–R)(CC–R′) were obtained under Sonogashira type conditions. The new clusters have been characterized with microanalysis and using IR and multinuclear NMR spectroscopy. The crystal and molecular structures of Pt6(μ-PBut2)4(CO)4(CC–R)2 (R = H, C6H4-4-n-C5H11) are presented and electrochemical and spectroelectrochemical studies of some representative compounds are also reported

Galaxy Groups in the SDSS DR4: I. The Catalogue and Basic Properties

We use a modified version of the halo-based group finder developed by Yang et al. to select galaxy groups from the Sloan Digital Sky Survey (SDSS DR4). In the first step, a combination of two methods is used to identify the centers of potential groups and to estimate their characteristic luminosity. Using an iterative approach, the adaptive group finder then uses the average mass-to-light ratios of groups, obtained from the previous iteration, to assign a tentative mass to each group. This mass is then used to estimate the size and velocity dispersion of the underlying halo that hosts the group, which in turn is used to determine group membership in redshift space. Finally, each individual group is assigned two different halo masses: one based on its characteristic luminosity, and the other based on its characteristic stellar mass. Applying the group finder to the SDSS DR4, we obtain 301237 groups in a broad dynamic range, including systems of isolated galaxies. We use detailed mock galaxy catalogues constructed for the SDSS DR4 to test the performance of our group finder in terms of completeness of true members, contamination by interlopers, and accuracy of the assigned masses. This paper is the first in a series and focuses on the selection procedure, tests of the reliability of the group finder, and the basic properties of the group catalogue (e.g. the mass-to-light ratios, the halo mass to stellar mass ratios, etc.). The group catalogues including the membership of the groups are available at http://gax.shao.ac.cn/data/Group.html and http://www.astro.umass.edu/~xhyang/Group.htmlComment: 19 pages, 12 figures, Accepted for publication in ApJ. Group catalogues are available at http://gax.shao.ac.cn/data/Group.html and http://www.astro.umass.edu/~xhyang/Group.htm