Théorie informationnelle du schéma

Schéma, schématisme, schématisation sont parmi les termes les plus fréquemment rencontrés dans le vocabulaire de l’activité créatrice. Le concept de schéma, défini comme une représentation simple et abstraite d’un phénomène ou d’un objet du monde extérieur, paraît prendre une importance de plus en plus grande au fur et à mesure que notre civilisation tend à être envahie par la pensée mécanique qui consomme et produit des schémas, et par l’inflation sémantique de ce qui, de près ou de loin, se..

Biblioteca pessoal, biblioteca universal

A partir de uma teoria funcional da biblioteca são examinadas as características específicas da biblioteca pessoal, do ponto de vista de sua estrutura e das relações entre ela e seu criador e usuário

Enantioselective aldol reactions with aqueous 2,2-dimethoxyacetaldehyde organocatalyzed by binam-prolinamides under solvent-free conditions

Aqueous 2,2-dimethoxyacetaldehyde (60% wt solution) is used as an acceptor in aldol reactions, with cyclic and acyclic ketones and aldehydes as donors, organocatalyzed by 10 mol % of N-tosyl-(Sa)-binam-l-prolinamide [(Sa)-binam-sulfo-l-Pro] at rt under solvent-free conditions. The corresponding monoprotected 2-hydroxy-1,4-dicarbonyl compounds are obtained in good yields and with high levels of diastereo- and enantioselectivity mainly as anti-aldols. In the case of 4-substituted cyclohexanones a desymmetrization process takes place to mainly afford the anti,anti-aldols. 2,2-Dimethyl-1,3-dioxan-5-one allows the synthesis of a useful intermediate for the preparation of carbohydrates in higher yield, de and ee than with l-Pro as the organocatalyst.We thank the financial support from the Spanish Ministerio de Economía y Competitividad (MINECO, Projects CTQ2010-20387 and Consolider Ingenio 2010, CSD2007-00006), FEDER, the Generalitat Valenciana (Prometeo/2009/039), the University of Alicante and the European Commission (ORCA action CM0905). A.B.-C. thanks Spanish MINECO for a predoctoral fellowship (FPU AP2009-3601)

Verbal Extensions: Valency Decreasing Extensions in The Basà Language

This work investigates verbal extensions that affect the valency of verbs in the Basà language (Western Kainji). It focuses on verbal inflections that result in the reduction of the verb’s valency by one argument with regard to the basic structure. This current study attempts to investigate the morphosyntactic effects of reciprocal and reflexive affixes in the Basà sentences. The significance of this work hinges on the fact that no known work has described these processes in Basà. The language is endangered because its native speakers neglect speaking it in favour of English and Hausa. Furthermore, there is dearth of information on Basà, especially in areas of morphology and syntax, which are basic to the study of language. This study will therefore attempt to fill this existing gap in the literature. In addition to the native intuitions of one of the researchers, as a native speaker of the Basà language, data collected for this work include discourse observation, staged and elicited spoken data from fluent native speakers. It was found in the study that affixes attached to the verb root result in deriving an intransitive verb from a transitive one, and a transitive verb from a bi- or ditransitive. Both operations are triggered by verbal extensions and move the internal argument (object) to the subject position. The derived structure, therefore, is headed by a complex noun phrase but the verb no longer subcategorizes an internal argument. The work explores the morphosyntax of Basà verbs and serves as a springboard for this aspect of Basà morphosyntax. It also contributes to the morphosyntactic literature

Morphological Number Counts and Redshift Distributions to I = 25 from the Hubble Deep Fields: Constraints on Cosmological Models from Early Type Galaxies

We combine magnitude and photometric redshift data on galaxies in the Hubble Deep Fields with morphological classifications in order to separate out the distributions for early type galaxies. The updated morphological galaxy number counts down to I = 25 and the corresponding redshift distributions are used as joint constraints on cosmological models, in particular on the values of the density parameter Omega_{0} and normalised cosmological constant Lambda_{0}. We find that an Einstein - de Sitter universe with simple passive evolution gives an excellent fit to the counts and redshift data at all magnitudes. An open, low Omega_{0}, model with no net evolution (and conservation of the number of ellipticals), which fits the counts equally well, is somewhat less successful, predicting slightly lower mean redshifts and, more significantly, the lack of a high--z tail. A number conserving model with a dominant contribution from Lambda_{0}, on the other hand, is far less successful, predicting a much narrower distribution than seen. More complex models are obviously possible, but we conclude that if large scale transmutation between types does {\it not} occur, then the lambda-dominated models provide a very poor fit to the current data.Comment: Accepted for publication in MNRA

Opacity effects and shock-in-jet modelling of low-level activity in Cygnus X-3

We present simultaneous dual-frequency radio observations of Cygnus X-3 during a phase of low-level activity. We constrain the minimum variability timescale to be 20 minutes at 43 GHz and 30 minutes at 15 GHz, implying source sizes of 2 to 4 AU. We detect polarized emission at a level of a few per cent at 43 GHz which varies with the total intensity. The delay of approximately 10 minutes between the peaks of the flares at the two frequencies is seen to decrease with time, and we find that synchrotron self-absorption and free-free absorption by entrained thermal material play a larger role in determining the opacity than absorption in the stellar wind of the companion. A shock-in-jet model gives a good fit to the lightcurves at all frequencies, demonstrating that this mechanism, which has previously been used to explain the brighter, longer-lived giant outbursts in this source, is also applicable to these low-level flaring events. Assembling the data from outbursts spanning over two orders of magnitude in flux density shows evidence for a strong correlation between the peak brightness of an event, and the timescale and frequency at which this is attained. Brighter flares evolve on longer timescales and peak at lower frequencies. Analysis of the fitted model parameters suggests that brighter outbursts are due to shocks forming further downstream in the jet, with an increased electron normalisation and magnetic field strength both playing a role in setting the strength of the outburst.Comment: Accepted for publication in MNRAS. 15 pages, 9 figure

Substructures in WINGS clusters

We search for and characterize substructures in the projected distribution of galaxies observed in the wide field CCD images of the 77 nearby clusters of the WIde-field Nearby Galaxy-cluster Survey (WINGS). This sample is complete in X-ray flux in the redshift range 0.04<z<0.07. We search for substructures in WINGS clusters with DEDICA, an adaptive-kernel procedure. We test the procedure on Monte-Carlo simulations of the observed frames and determine the reliability for the detected structures. DEDICA identifies at least one reliable structure in the field of 55 clusters. 40 of these clusters have a total of 69 substructures at the same redshift of the cluster (redshift estimates of substructures are from color-magnitude diagrams). The fraction of clusters with subclusters (73%) is higher than in most studies. The presence of subclusters affects the relative luminosities of the brightest cluster galaxies (BCGs). Down to L ~ 10^11.2 L_Sun, our observed differential distribution of subcluster luminosities is consistent with the theoretical prediction of the differential mass function of substructures in cosmological simulations.Comment: A&A accepted - figure 6 is available from http://adlibitum.oats.inaf.it/ramella/WINGSfig

The red-sequence of 72 WINGS local galaxy clusters

We study the color-magnitude red sequence and blue fraction of 72 X-ray selected galaxy clusters at z=0.04-0.07 from the WINGS survey, searching for correlations between the characteristics of the red sequence and the environment. We consider the slope and scatter of the red sequence, the number ratio of red luminous-to-faint galaxies, the blue fraction and the fractions of ellipticals, S0s and spirals that compose the red sequence. None of these quantities correlate with the cluster velocity dispersion, X-ray luminosity, number of cluster substructures, BCG prevalence over next brightest galaxies and spatial concentration of ellipticals. Instead, the properties of the red sequence depend strongly on local galaxy density. Higher density regions have a lower RS scatter, a higher luminous-to-faint ratio, a lower blue fraction, and a lower spiral fraction on the RS. Our results highlight the prominent effect of the local density in setting the epoch when galaxies become passive and join the red sequence, as opposed to the mass of the galaxy host structure.Comment: Accepted for publication in A&

Optical Intraday Variability Studies of Ten Low Energy Peaked Blazars

We have carried out optical (R band) intraday variability (IDV) monitoring of a sample of ten bright low energy peaked blazars (LBLs). Forty photometric observations, of an average of ~ 4 hours each, were made between 2008 September and 2009 June using two telescopes in India. Measurements with good signal to noise ratios were typically obtained within 1-3 minutes, allowing the detection of weak, fast variations using N-star differential photometry. We employed both structure function and discrete correlation function analysis methods to estimate any dominant timescales of variability and found that in most of the cases any such timescales were longer than the duration of the observation. The calculated duty cycle of IDV in LBLs during our observing run is ~ 52%, which is low compared to many earlier studies; however, the relatively short periods for which each source was observed can probably explain this difference. We briefly discuss possible emission mechanisms for the observed variability.Comment: 20 Pages, 9 Figures, 4 Tables, accepted for publication in MNRA