991 resultados para ENZYME STRUCTURE


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1. Landscape modification is often considered the principal cause of population decline in many bat species. Thus, schemes for bat conservation rely heavily on knowledge about species-landscape relationships. So far, however, few studies have quantified the possible influence of landscape structure on large-scale spatial patterns in bat communities. 2. This study presents quantitative models that use landscape structure to predict (i) spatial patterns in overall community composition and (ii) individual species' distributions through canonical correspondence analysis and generalized linear models, respectively. A geographical information system (GIS) was then used to draw up maps of (i) overall community patterns and (ii) distribution of potential species' habitats. These models relied on field data from the Swiss Jura mountains. 3. Fight descriptors of landscape structure accounted for 30% of the variation in bat community composition. For some species, more than 60% of the variance in distribution could be explained by landscape structure. Elevation, forest or woodland cover, lakes and suburbs, were the most frequent predictors. 4. This study shows that community composition in bats is related to landscape structure through species-specific relationships to resources. Due to their nocturnal activities and the difficulties of remote identification, a comprehensive bat census is rarely possible, and we suggest that predictive modelling of the type described here provides an indispensable conservation tool.

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Network airlines have been increasingly focusing their operations on hub airports through the exploitation of connecting traffic, allowing them to take advantage of economies of traffic density, which are unequivocal in the airline industry. Less attention has been devoted to airlines? decisions on point-to-point thin routes, which could be served using different aircraft technologies and different business models. This paper examines, both theoretically and empirically, the impact on airlines ?networks of the two major innovations in the airline industry in the last two decades: the regional jet technology and the low-cost business model. We show that, under certain circumstances, direct services on point-to-point thin routes can be viable and thus airlines may be interested in deviating passengers out of the hub.

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We describe a model structure for coloured operads with values in the category of symmetric spectra (with the positive model structure), in which fibrations and weak equivalences are defined at the level of the underlying collections. This allows us to treat R-module spectra (where R is a cofibrant ring spectrum) as algebras over a cofibrant spectrum-valued operad with R as its first term. Using this model structure, we give sufficient conditions for homotopical localizations in the category of symmetric spectra to preserve module structures.

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The geometry and kinematics of the map scale Maggia cross-fold structure has been studied by several generations of geologists over seventy years and different models have been proposed for its formation. New observations indicate that the Maggia structure is a SW-verging cross-fold created after earlier NW-directed overthrusting of the Maggia nappe onto the deeper Simano and Antigorio recumbent fold nappes. The nappe emplacement and later cross-folding occurred under amphibolite facies conditions by detachment of the upper European crust during its SE-directed underthrusting below the Adriatic plate.

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One hundred and ten specimens of Pseudoplatystoma corruscans (Pimelodidae) and 582 specimens of Schizodon borelli (Anostomidae) collected in the high Paraná River were analyzed. On necropsy 74% of P. corruscans were found to be parasitized; proteocephalidean cestodes presented the greatest number. With regard to S. borelli, the percentage of parasitism reached 19.42% and the nematode Cucullanus pinnai was the most abundant. The absence of correlation between the endoparasitic diversity and the standard length of the two host species indicates that each one presents homogeneity in alimentary behaviour during all its life time, permiting the uniform recruitment of the same species of endoparasites during all its ontogenetic development. Independence of diversity values in relation to sex of P. corruscans and S. borelli evidences that the ecological relationships are similar between males and females in these species. Both host's infrapopulations presented a typical overdispersed pattern of distribution with isolationist characteristics.

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La incorporació del Moodle com a eina de docència, i l’augment de hores no presencials a les diverses assignatures fa que calgui incorporar les noves tecnologies perquè els alumnes disposin de més material docent al seu abast. Però l’acumulació de material fa que només sigui útil aquell material que es guanyi a l’alumne. En aquest sentit, creiem que les animacions i les eines interactives poden ser materials atractius pels alumnes. En aquest projecte hem creat una eina d’animació interactiva perquè l’estudiant de Bioquímica practiqui i aprengui una de les rutes metabòliques principals: la glucòlisi. Aquesta eina consta d’una pantalla separada en 3 zones: 1) una zona lateral que inclou la ruta metabòlica completa, i en la que l’alumne pot prémer sobre cada un dels passos que estructuren la ruta (finestra del metabolisme); 2) una zona inferior que presenta la reacció individual de la ruta metabòlica, en la que s’observa l’estructura química de les molècules i informació de l’enzim implicat en la reacció (finestra de l’enzim); i 3) una zona central en la que a través d’una animació amb Macromedia Flash MX, l’alumne observa el mecanisme químic de la reacció (finestra del mecanisme químic). Les tres zones són interactives i en prémer sobre elles donen informació, respectivament sobre la ruta completa, l’enzim de cada pas en particular i el mecanisme d’acció. A més, la finestra del mecanisme químic permet aturar en qualsevol moment la animació, tornar enrere i veure els intermediaris. Durant el segon semestre del curs 2006-2007 hem avaluat l’eina amb alumnes de Bioquímica de la Llicenciatura de Química, incorporant-la als dossier electrònics. Creiem que hem assolit els objectius que es proposaven: aprendre una ruta metabòlica, de manera divertida; aprendre el mecanisme de cada un dels passos de la ruta i aprendre l’estructura química dels metabòlits intermediaris de la ruta.

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La incorporació del Moodle com a eina de docència, i l’augment de hores no presencials a les diverses assignatures fa que calgui incorporar les noves tecnologies perquè els alumnes disposin de més material docent al seu abast. Però l’acumulació de material fa que només sigui útil aquell material que es guanyi a l’alumne. En aquest sentit, creiem que les animacions i les eines interactives poden ser materials atractius pels alumnes. En aquest projecte hem creat una eina d’animació interactiva perquè l’estudiant de Bioquímica practiqui i aprengui dues rutes principals del metabolisme de hidrats de carboni: la glucòlisi i la gluconeogènesi. Aquesta eina consta d’una pantalla separada en 3 zones: 1) una zona lateral que inclou la ruta metabòlica completa, i en la que l’alumne pot prémer sobre cada un dels passos que estructuren la ruta (finestra del metabolisme); 2) una zona inferior que presenta la reacció individual de la ruta metabòlica, en la que s’observa l’estructura química de les molècules i informació de l’enzim implicat en la reacció (finestra de l’enzim); i 3) una zona central en la que a través d’una animació amb Macromedia Flash MX, l’alumne observa el mecanisme químic de la reacció (finestra del mecanisme químic). Les tres zones són interactives i en prémer sobre elles donen informació, respectivament sobre la ruta completa, l’enzim de cada pas en particular i el mecanisme d’acció. A més, la finestra del mecanisme químic permet aturar en qualsevol moment la animació, tornar enrere i veure els intermediaris. Durant el segon semestre del curs 2007-2008 hem avaluat l’eina amb alumnes de Bioquímica de la Llicenciatura de Química, incorporant-la als dossier electrònics i al Moodle. Creiem que hem assolit els objectius que es proposaven: que l’alumne aprengui les dues rutes metabòliques, de manera divertida; el mecanisme de cada un dels passos de les rutes i l’estructura química dels metabòlits intermediaris de les rutes.

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Morphological description of sand flies has remained a neglected area. The different organs used in taxonomy have not yet been described adequately with the scanning electron microscopy (SEM). We have examined the external genital structures of females of three Old World phlebotomine sand flies under SEM and recorded the morphological variations of the organs. We have found the female external genital structures of the three species varied considerably in morphology. The importance of the female external genital structures in sand fly identification is indicated

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In order to detect seasonal trends in the age structure of adult mosquitoes from Buenos Aires province, Argentina, female populations were sampled with CDC traps during 1989-1991 in Punta Lara and La Plata. The mosquitoes were dissected and age-grouped according to ovarian tracheation and ovariolar stages. All Runchomyia paranensis females were parous, suggesting that this species could be autogenous. Aedes albifasciatus showed parous peaks following population peaks, with shorter delays in spring-summmer and longer in fall-winter. Ae. crinifer and Culex dolosus showed wide fluctuations in age structure due to adult emergences during all months. Psorophora ferox showed high population replacement rates. Mansonia indubitans and Ma. titillans have few generations per year during their activity period. This is the first report on age-grading of adults of field mosquito populations from Argentina