9,807 research outputs found

    Study of psi' and chi_c decays as feed-down sources of J/psi hadro-production

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    The interpretation of the J/psi suppression patterns observed in nuclear collisions, at CERN and RHIC, as a signature of the formation of a deconfined phase of QCD matter, requires knowing which fractions of the measured J/psi yields, in pp collisions, are due to decays of heavier charmonium states. From a detailed analysis of the available mid-rapidity charmonium hadro-production cross sections, or their ratios, we determine that the J/psi feed-down contributions from psi' and chi_c decays are, respectively, (8.1 +/- 0.3) % and (25 +/- 5) %. These proton-proton values are derived from global averages of the proton-nucleus measurements, assuming that the charmonium states are exponentially absorbed with the length of matter they traverse in the nuclear targets.Comment: 12 pages, 4 figures, 3 table

    Absorption and J/psi Suppression in Heavy Ion Collisions

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    We discuss the J/psi suppression in the framework of multiple collision models. From the analysis of the Pb-Pb NA50 data we conclude that the strength of the absorption has increased, but we find no clear evidence for the formation of the quark-gluon plasma.Comment: 8 pages, 4 figure

    A Whole-Institution Approach Towards Sustainability at NOVA University: A Tangled Web of Engagement Schemes

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    Abstract. NOVA University Lisbon ambition to become a sustainable university following a whole-institution approach raises several challenges, due to the diversity of culture and governance of its nine schools spread over eight campuses in four municipalities. Engaging NOVA community is critical to achieve systemic changes, but very hard to carry coherently and at the same pace across all schools and throughout all its members. Different engagement schemes, interlinking a top-down one from the rector and the board of deans, who leads the vision, with several bottom-up schemes in education, research, value creation and operations are being implemented to carry out different purposes towards the common goal. NOVA for the Globe strategic platform and NOVA zero-waste task force are examples, among others, showing sustainability implementation at the university starts with people cooperation around the same ambition.Keyword: Strategic Thinking, Systemic Change, Engagement, University, Whole-Institution Approach

    From ‘creative cities’ to ‘urban creativity’? Space, creativity and governance in the contemporary city

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    DINÂMIA, Dezembro de 2009This paper derives from a broader research program studying the forms of governance associated with creative dynamics in cities (the “Creatcity” project) and draws on the first empirical results generated by the study following analysis of a set of exploratory interviews involving actors central to thinking and acting on the contemporary city (political decision makers, official structures and civil society) in the three metropolitan areas selected for the project: Lisbon (Portugal), São Paulo (Brazil) and Barcelona (Spain). Analysis of the responses sought to identify the different perspectives on the concepts of urban creativity and creative city and the relationship between creativity, vitality and competitivity within urban contexts while seeking to understand interviewee perspectives on the structural conditions necessary for the development of creativity in the city in terms of spatial/geographic configurations and the associated cultural ambiances and economic activities. In parallel, we aim to debate the means of fostering and supporting creativity in urban environments and discuss just which strategic policies and governance processes best achieve this.FC

    Synteny-based genome assembly for 16 species of Heliconius butterflies, and an assessment of structural variation across the genus

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    Heliconius butterflies (Lepidoptera: Nymphalidae) are a group of 48 neotropical species widely studied in evolutionary research. Despite the wealth of genomic data generated in past years, chromosomal level genome assemblies currently exist for only two species, Heliconius melpomene and H. erato, each a representative of one of the two major clades of the genus. Here, we use these reference genomes to improve the contiguity of previously published draft genome assemblies of 16 Heliconius species. Using a reference-assisted scaffolding approach, we place and order the scaffolds of these genomes onto chromosomes, resulting in 95.7-99.9% of their genomes anchored to chromosomes. Genome sizes are somewhat variable among species (270-422 Mb) and in one small group of species (H. hecale, H. elevatus and H. pardalinus) expansions in genome size are driven mainly by repetitive sequences that map to four small regions in the H. melpomene reference genome. Genes from these repeat regions show an increase in exon copy number, an absence of internal stop codons, evidence of constraint on non-synonymous changes, and increased expression, all of which suggest that at least some of the extra copies are functional. Finally, we conducted a systematic search for inversions and identified five moderately large inversions fixed between the two major Heliconius clades. We infer that one of these inversions was transferred by introgression between the lineages leading to the erato/sara and burneyi/doris clades. These reference-guided assemblies represent a major improvement in Heliconius genomic resources that enable further genetic and evolutionary discoveries in this genus

    The effect of gamma-cyclodextrin addition in the self-assembly behavior of pyrene labeled poly(acrylic) acid with different chain sizes

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    The interaction between poly(acrylic acid) polymers (PAA) of low- (2000 g/mol) and high- (450,000 g/mol) molecular weight (Mw) hydrophobically modified with pyrene (PAAMePy) and beta- and gamma-cyclodextrins (beta-CD, gamma-CD) was investigated with fluorescent techniques. The interaction with beta-CD promotes little variation in the spectral and photophysical behavior of the polymer, whereas significant changes are observed upon addition of gamma-CD. The degree of inclusion (between the pyrene groups of the polymer and the cyclodextrins) is followed through the observation of the changes in the absorption, excitation (collected in the monomer and excimer emission regions) and emission (IE/IM ratio) spectra and from time-resolved data. Within the studied range of gamma-CD concentration, the fluorescence decays of the long chain (high Mw) PAAMePy polymers were found tri-exponential in the monomer and excimer emission regions in agreement with previous studies. In the case of the low Mw PAAMePy polymers, tri-exponential decays were observed at the monomer and excimer emission wavelengths. However, when a gamma-CD concentration of 0.01 and 0.03 M is reached for, respectively, the low- and high-labeled pyrene short chain (low Mw) polymers, the fluorescence decays in the excimer region become biexponential (two excimers) with no rising component, thus showing that all pyrene groups are encapsulated (and preassociated) into the gamma-CD cavity. In the case of the high Mw polymers, the addition of gamma-CD has been found to change the level of polymer interaction from pure intramolecular (water in the absence of cyclodextrin) to a coexistence of intra- with intermolecular interactions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1402-1415, 200

    Feigenbaum networks

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    We study dynamical systems composed of a set of linearly coupled quadratic maps which, if uncoupled, would be on the Feigenbaum accumulation point. For two units we prove the existence of an infinite number of sinks for an open set of coupling parameters. In the limit of many units a mean field analysis also implies the stabilization in periodic orbits of, at least, a subset of the coupled units. Possible applications in the fields of control of chaos, signal processing through complex dynamics and as models of self-organization, are discussed