On Salem numbers, expansive polynomials and Stieltjes continued fractions

A converse method to the Construction of Salem (1945) of convergent families of Salem numbers is investigated in terms of an association between Salem polynomials and Hurwitz quotients via expansive polynomials of small Mahler measure. This association makes use of Bertin-Boyd's Theorem A (1995) of interlacing of conjugates on the unit circle; in this context, a Salem number $\beta$ is produced and coded by an m-tuple of positive rational numbers characterizing the (SITZ) Stieltjes continued fraction of the corresponding Hurwitz quotient (alternant). The subset of Stieltjes continued fractions over a Salem polynomial having simple roots, not cancelling at $\pm 1$, coming from monic expansive polynomials of constant term equal to their Mahler measure, has a semigroup structure. The sets of corresponding generalized Garsia numbers inherit this semi-group structure.Comment: 35 pages, Journal de Th{\'e}orie des nombres de Bordeaux, Soumissio

The French Atlantic Littoral and the Massif Armoricain

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On the spectrum of the Thue-Morse quasicrystal and the rarefaction phenomenon

The spectrum of a weighted Dirac comb on the Thue-Morse quasicrystal is investigated, and characterized up to a measure zero set, by means of the Bombieri-Taylor conjecture, for Bragg peaks, and of another conjecture that we call Aubry-Godr\`eche-Luck conjecture, for the singular continuous component. The decomposition of the Fourier transform of the weighted Dirac comb is obtained in terms of tempered distributions. We show that the asymptotic arithmetics of the $p$-rarefied sums of the Thue-Morse sequence (Dumont; Goldstein, Kelly and Speer; Grabner; Drmota and Skalba,...), namely the fractality of sum-of-digits functions, play a fundamental role in the description of the singular continous part of the spectrum, combined with some classical results on Riesz products of Peyri\`ere and M. Queff\'elec. The dominant scaling of the sequences of approximant measures on a part of the singular component is controlled by certain inequalities in which are involved the class number and the regulator of real quadratic fields.Comment: 35 pages In honor of the 60-th birthday of Henri Cohe

Crystal Structure of the P Pilus Rod Subunit PapA

P pili are important adhesive fibres involved in kidney infection by uropathogenic Escherichia coli strains. P pili are assembled by the conserved chaperone-usher pathway, which involves the PapD chaperone and the PapC usher. During pilus assembly, subunits are incorporated into the growing fiber via the donor-strand exchange (DSE) mechanism, whereby the chaperone's G1 β-strand that complements the incomplete immunoglobulin-fold of each subunit is displaced by the N-terminal extension (Nte) of an incoming subunit. P pili comprise a helical rod, a tip fibrillum, and an adhesin at the distal end. PapA is the rod subunit and is assembled into a superhelical right-handed structure. Here, we have solved the structure of a ternary complex of PapD bound to PapA through donor-strand complementation, itself bound to another PapA subunit through DSE. This structure provides insight into the structural basis of the DSE reaction involving this important pilus subunit. Using gel filtration chromatography and electron microscopy on a number of PapA Nte mutants, we establish that PapA differs in its mode of assembly compared with other Pap subunits, involving a much larger Nte that encompasses not only the DSE region of the Nte but also the region N-terminal to it. Author Summary. Bacterial adhesion to a host is a crucial step that determines the onset of bacterial infection. It is mediated through recognition of a receptor on the host cell surface by a protein called an adhesin displayed on the surface of the bacterium. Many adhesins are displayed at the tip of specialized organelles called pili, some of which are assembled by the ubiquitous chaperone-usher pathway. In this pathway, each pilus subunit is assisted in folding by a chaperone. The resulting chaperone-subunit complex is targeted to a pore located in the outer membrane, called the usher, that serves as assembly platform. There, pilus subunits dissociate from the chaperone and polymerize, resulting in a surface organelle, the pilus, that protrudes out of the usher. Here, we have determined the structure of the major subunit of the P pilus, PapA. The P pilus, produced in uropathogenic Escherichia coli, displays the adhesin PapG responsible for targeting the bacterium to the kidney epithelium. We have determined the structure of PapA either bound to its cognate chaperone, PapD, or bound to another PapA subunit. These structures provide a view of PapA before and after its assembly in the pilus and shed light on the mechanism of PapA assembly.National Institutes of Health (DE 09761, GM040388, DE 09161); Committee of Scientific Research (3 PO4A 003 24, 2 P05A 137 24); Foundation for Polish Science (SUBSYDIUM PROFESORSKIE award); Swedish Rheumatism Association; Nanna Svartz Foundation; King Gustaf V Foundatio

The French Atlantic Littoral

There are no author-identified significant results in this report

The Printers’ Devices database of the University of Barcelona

Although the main subject of this conference is the discussion about the images of the printers’ devices, I think that in our case of the Printers’ Devices database an introduction and explanation are necessary. Image processing is integrated into the printer records and the connections between the printer and its devices are inseparable

Sistematizando experiencias : análisis y recreación de la acción colectiva desde la educación popular

El presente artículo explora en profundidad la Sistematización de Experiencias (SE), un método de investigación participativa muy próximo a la Educación Popular. La SE tiene sus orígenes en América Latina, donde se implementa desde la década de los ochenta. La propuesta de la SE conlleva un proceso colectivo de reconstrucción y reflexión analítica de experiencias mediante el cual interpretar, comprender e introducir mejoras en futuras prácticas. Si bien analizamos la aplicación de la propuesta en el ámbito de los movimientos sociales, ésta también se extiende a otras esferas donde interviene la acción colectiva, como son la organización escolar, el cooperativismo o los procesos participativos locales. A modo de conclusión, enmarcamos este método en las corrientes metodológicas de investigación para y desde los movimientos sociales. Además, pondremos de manifiesto las particularidades de la SE respecto a otras modalidades de investigación que contemplan la participación de los movimientos u otros sujetos de acción colectiva a lo largo del proceso analítico.This article explores the Experiences Systematisation (ES), i. e., a participatory research method related to Popular Education. ES has its roots in Latin America where it has been implemented since the 80's. ES proposal implies a reconstruction collective process and an analytical reflection of experiences aimed at interpreting, understanding and improving future practices. In this paper we analyse the application of ES in the social movements' field. Nevertheless, it may also be applied in other fields such as school organisation, cooperativism or local participatory processes. In the conclusion section, we frame the ES method in those research methodologies which are developed for and within social movements. Moreover, we also highlight the particularities of ES in relation to other participatory research methods

El rol de ideas e intereses en el proceso de transnacionalización de la educación superior

El Acuerdo General sobre Comercio de Servicios negociado en el marco de la Organización Mundial del Comercio (OMC) se ha convertido en uno de los principales instrumentos para la transnacionalización de la educación superior. Promueve la liberalización comercial de servicios, lo cual cristaliza en la eliminación, modificación y/o estandarización de un amplio abanico de regulaciones, tanto nacionales como locales, del ámbito educativo. Por este motivo, es considerado un elemento clave en el actual escenario de dirección educativa global. Este artículo se centra en el proceso de la negociación de la educación superior en el marco de este Acuerdo, explorando las estrategias, posiciones e ideas esgrimidas por los países a la hora de negociar y en qué medida éstas influyen en los resultados de la negociación.The General Agreement on Trade in Services (GATS) negotiated by means of the World Trade Organization (WTO) has become in one of the main instruments to make the higher education a transnational issue. The GATS promotes freedom on trade services, therefore, the educational field on domestics and local places need to eliminate, modify or standardize a huge range of regulations. That is why it is considered as a key figure on the current scene of the global education direction. The main interest of this article wants to focus on the negotiation process on higher education within the GATS. Specifically, this article explores the strategies, positions and ideas fenced by the countries when they need to negotiate this agreement and in how these terms influenced on the results obtaine