801 research outputs found

    On the BKS pairing for Kahler quantizations of the cotangent bundle of a Lie group

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    A natural one-parameter family of K\"ahler quantizations of the cotangent bundle TKT^*K of a compact Lie group KK, taking into account the half-form correction, was studied in \cite{FMMN}. In the present paper, it is shown that the associated Blattner-Kostant-Sternberg (BKS) pairing map is unitary and coincides with the parallel transport of the quantum connection introduced in our previous work, from the point of view of \cite{AdPW}. The BKS pairing map is a composition of (unitary) coherent state transforms of KK, introduced in \cite{Ha1}. Continuity of the Hermitian structure on the quantum bundle, in the limit when one of the K\"ahler polarizations degenerates to the vertical real polarization, leads to the unitarity of the corresponding BKS pairing map. This is in agreement with the unitarity up to scaling (with respect to a rescaled inner product) of this pairing map, established by Hall.Comment: final version, to appear in Journ. Funct. Ana

    Geometric quantization, complex structures and the coherent state transform

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    It is shown that the heat operator in the Hall coherent state transform for a compact Lie group KK is related with a Hermitian connection associated to a natural one-parameter family of complex structures on TKT^*K. The unitary parallel transport of this connection establishes the equivalence of (geometric) quantizations of TKT^*K for different choices of complex structures within the given family. In particular, these results establish a link between coherent state transforms for Lie groups and results of Hitchin and Axelrod, Della Pietra and Witten.Comment: to appear in Journal of Functional Analysi

    O conceito de «Actividad Dirigida» inscrito no artigo 15.º, numero 1 alinea c). Do Regulamento «Bruxelas I» e a Internet: subsidios do Tribunal de Justiça por ocãsiao do acórdão Pammer/Alpenhof

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    Resumo: Para além do mais, a decisão pelo Tribunal de Justiça da União Europeia emitida nos casos apensos Pammer/Alpenhof versa a interpretação do conceito de «actividade dirigida» inscrito no artigo 15.º, número 1, alínea c), do Regulamento (CE) n.º 44/2001. De acordo com o pronunciamento do Tribunal, a circunstância de o sítio do profissional ser acessível a partir do Estado do domicílio do consumidor é insuficiente para dar por demonstrado que aquele profissional dirige a sua actividade ao Estado-Membro do domicílio do consumidor. A presente anotação passa em revista crítica a linha argumentativa desenvolvida pela instância jurisdicional.Palavras-chave: competência jurisdicional internacional, Regulamento (CE) n.º 44/2001, contratos celebrados por consumidores, o conceito de «actividade dirigida», internet.Abstract: Inter alia, the joint ruling issued by the EUCJ on 7th December 2010 addressed the applicability of Article 15(1)(c) of Regulation EC No 44/2001 («the Brussels I Regulation») vis-à-vis the use of web sites. In particular, the Court was summoned to clarify whether, in order to justify a finding that an activity is being «directed» within the terms of the aforesaid Article, it is sufficient that a website of the party with whom a consumer has concluded a contract can be consulted on the internet. The Court answered in the negative. Further, the Court catalogued a number of factors designed at helping national courts determine whether a business is directed towards consumers in other European states. This annotation provides for a detailed review and a critical analysis of the EUCJ’s decision.Key words: international jurisdiction, Regulation (EC) No 44/2001, consumer contracts, direction of activity, Internet

    Hsp70 and Hsp110 chaperones promote early steps of proteasome assembly

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    Whereas assembly of the 20S proteasome core particle (CP) in prokaryotes apparently occurs spontaneously, the efficiency of this process in eukaryotes relies on the dedicated assembly chaperones Ump1, Pba1-Pba2, and Pba3-Pba4. For mammals, it was reported that CP assembly initiates with formation of a complete alpha-ring that functions as a template for beta subunit incorporation. By contrast, we were not able to detect a ring composed only of a complete set of alpha subunits in S. cerevisiae. Instead, we found that the CP subunits alpha 1, alpha 2, and alpha 4 each form independent small complexes. Purification of such complexes containing alpha 4 revealed the presence of chaperones of the Hsp70/Ssa and Hsp110/Sse families. Consistently, certain small complexes containing alpha 1, alpha 2, and alpha 4 were not formed in strains lacking these chaperones. Deletion of the SSE1 gene in combination with deletions of PRE9 (alpha 3), PBA3, or UMP1 genes resulted in severe synthetic growth defects, high levels of ubiquitin-conjugates, and an accumulation of distinct small complexes with alpha subunits. Our study shows that Hsp70 and Hsp110 chaperones cooperate to promote the folding of individual alpha subunits and/or their assembly with other CP subunits, Ump1, and Pba1-Pba4 in subsequent steps.info:eu-repo/semantics/publishedVersio

    Genotype networks in metabolic reaction spaces

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    Background: A metabolic genotype comprises all chemical reactions an organism can catalyze via enzymes encoded in its genome. A genotype is viable in a given environment if it is capable of producing all biomass components the organism needs to survive and reproduce. Previous work has focused on the properties of individual genotypes while little is known about how genome-scale metabolic networks with a given function can vary in their reaction content. Results: We here characterize spaces of such genotypes. Specifically, we study metabolic genotypes whose phenotype is viability in minimal chemical environments that differ in their sole carbon sources. We show that regardless of the number of reactions in a metabolic genotype, the genotypes of a given phenotype typically form vast, connected, and unstructured sets -- genotype networks -- that nearly span the whole of genotype space. The robustness of metabolic phenotypes to random reaction removal in such spaces has a narrow distribution with a high mean. Different carbon sources differ in the number of metabolic genotypes in their genotype network; this number decreases as a genotype is required to be viable on increasing numbers of carbon sources, but much less than if metabolic reactions were used independently across different chemical environments. Conclusions: Our work shows that phenotype-preserving genotype networks have generic organizational properties and that these properties are insensitive to the number of reactions in metabolic genotypes.Comment: 48 pages, 10 main figures, 14 supplementary figure

    Environmental biofilms, consequences for health and disease

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    Ornamental waters of easy access and populated with animals are quite attractive and can hide threats to human health. Here we evaluated, during one year, the microbiota of ornamental waters in a Lisbon park in order to assess the risk for human health. A total of 26 different bacterial species were identified during the study. Among these are potential human pathogens such as Aeromonas, E. coli, K. pneumoniae, Pseudomonas and Raoutella. Aeromonas sobria is a resident bacterium whereas other species such as A. hydrophila and A. veronii were sporadically identified. A possible explanation for this result is the presence of a fish population. The presence of E. coli indicates water contamination with fecal materials. We first isolate this bacterium in June when the water temperature increased and then after it was a resident despite the natural temperature drop in the autumn. This might be explained by the replace of the fish population by ducks in October which lead to an increase in water tubirdity and total carbon content. Pseudomonas fluorescens, P. putida and P. oryzihabitans have been considered low-virulence bacteria but recently have been identified as ethiological agents of healthcare assotiated infections (HAI) mostly in immunosupressed individuals. Another recognized HAI agent present is K. pneumoniae. The same bacteria species were isolated from biofilm and water suggesting the existence of an equilibrium between planktonic and biofilm organized bacteria. The role played by biofilm assembly on the emergence of antibiotic resistance is still ongoing for the isolated bacteria, as well as the possible interaction between water chemical composition and bacteria isolates. Potential pathogens (biofilm or planktonic) represent a significant cause of acute bacterial infections mainly in specific populations (paediatric and geriatric). These results support a periodic control of ornamental water microbiota as simple preventive measure to avoid potential health issues.info:eu-repo/semantics/publishedVersio

    Pathogens in ornamental waters: a follow up study

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    Ornamental waters of easy access and populated with animals are quite attractive and can hide threats to human health. Here we evaluated the microbiota of ornamental waters in a Lisbon park. Water and biofilm samples where collected, in 2 lakes (L1-L2) and ornamental fountains (L3-L4) in February/2015. In May/2015 and monthly during a year (starting March/2016) samples from L4 where collected. Microbiota identification was performed as described previouslya. Biofilm assembly was monitored by crystal violet assay and SEMb and antibiotic susceptibility was performed by conventional methods. The results of the first water sampling (Feb/2015) revealed the presence of Enterobactereaceae and non-fermentative oxidase-positive bacteria. Fountains and lakes presented different microbota being the highest diversity found in L1 hosting a duck population. This result suggested the existence of an interplay between animal inhabitants and microbiota which was confirmed by the second sampling of L4 (May/2015). Between the 2 sampling events a fish population was introduced and the microbiota was completely altered with the appearance of a typical fish pathogen (Aeromonas spp). This tendency was also confirmed over 2016. K. pneumoniae and Aeromonas spp., present as planktonic and biofilm organized bacteria in 2015 showed an enhanced ability to assemble biofilms in vitro at 25 °C than at 37 °C. Bacteria recovered from biofilm showed an increased antibiotic resistance compared to planktonic counterparts. The pilot study conducted during 2015 and the follow up study (still in progress) support a periodic control of ornamental water microbiota as simple preventive measure to avoid potential health issues.Fundação para a Ciência e Tecnologia for the grant PEst-OE/CTM/UI0084/2011N/
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