Rational Topological Design for Fluorescence Enhancement upon Aggregation of Distyrylfuran Derivatives

A series of 2,5-distyrylfuran derivatives bearing pentafluorophenyl- and cyanovinyl units have been synthesized for aggregation-induced emission (AIE). The effect of the type and extent of the supramolecular connections on the AIE of the furan derivatives were examined and correlated with their X-ray crystal structures. It was found that the simultaneous presence of cyano and perfluorophenyl units strongly enhances the fluorescence upon aggregation. Single-crystal X-ray diffraction analysis confirmed that C — H⋅⋅⋅F, F⋅⋅⋅F, C — H⋅⋅⋅nitrile, Ar⋅⋅⋅ArF (Ar=aryl, ArF=fluoroaryl), and nitrile⋅⋅⋅ArF intra- and intermolecular interactions drive the topology of the molecule and that solid-state supramolecular contacts favor AIE of the furan derivatives

La escultura antropomorfa en piedra de Teotihuacan, México : problemáticas, antecedentes y nuevas propuestas

Jornadas de Jóvenes en Investigación Arqueológica, JIA (3as : 5-7 de mayo 2010 : Universitat Autònoma de Barcelona). Sesión 4. Cultura material y transdisciplinariedad en la investigación arqueológica de Latinoamérica .La escultura de la antigua metrópolis de Teotihuacan ha sido un tema que ha suscitado poco interés en la investigación, a pesar que en numerosas colecciones de museos se cuentan con algunos ejemplares. Entre las problemáticas a las que nos enfrentamos se encuentran por un lado, la gran cantidad de esculturas que no proceden de un contexto arqueológico fiable y que llegaron a los museos mediante la adquisición o cesión de particulares. Otro grupo lo constituye las que fueron excavadas a principios del siglo pasado y carecen de datos suficientes que permitan situarlas en una cronología. En conjunto estas esculturas que se hallan en los museos son mayores en número si las comparamos con las que proceden de excavaciones controladas. Consideramos que la ausencia en la definición de unos rasgos que permitan identificar por un lado la filiación a la ciudad de las esculturas y por otro su probable anclaje temporal, dificulta en su mayor parte su estudio. De hecho las cronologías que se manejan en la actualidad para fechar una esculturano procedente de excavación comprenden un período de más de 500 años. En este artículo se pretende ofrecer una revisión del estado de la cuestión y se propone un nuevo enfoque para tratar de dar con la idiosincrasia de la litoescultura antropomorfa teotihuacana.The sculpture of the ancient metropolis of Teotihuacan has been a topic that has attracted little interest in research, although numerous museum collections have some copies. Amongst the issues to deal with, it could be said that the first is the large number of sculptures that did not come from a reliable archaeological context but came to the museum through the acquisition or disposal of individuals. Another group is those that were excavated at the beginning of the 20th century and they lacked sufficient data to propose them into a chronology. Taken together, these sculptures are greater in number when compared with those from controlled excavations. We believe that the absence in the definition of features which can be identified, on one hand the relationship of the sculptures with the city and the other its probably time, mostly hinder their study. In fact chronologies are used at present for placing a sculpture dating from the excavation not include a period of more than 500 years. This article aims to provide a status review of the issue and proposes a new approach to try to come up with the idiosyncrasies of anthropomorphic stone sculpture in Teotihuacan.L'escultura de l'antiga ciutat de Teotihuacan ha generat poc interès en la investigació, malgrat que en nombroses col·leccions de museus es conserven exemplars que procedeixen d'aquesta cultura. Entre les problemàtiques a les quals ens enfrontem es troba la gran quantitat d'escultures que no procedeixen d'un context arqueològic fiable i que van arribar als museus mitjançant l'adquisició o la cessió per part de particulars. Un altre grup el constitueix aquells que compren les escultures que foren excavades a començaments del segle passat i que no disposen de dades suficients per poder-les ubicar en una cronologia. En conjunt, aquestes escultures que es troben en els museus son majors en nombre si les comparem amb aquelles que procedeixen d'excavacions controlades. Considerem que l'absència en la definició d'uns trets que permetin identificar per una banda la filiació a la ciutat de les escultures i per una altra, el seu probable anclatge temporal, en dificulten el seu estudi. De fet, les cronologies emprades actualment per situar una escultura no procedent d'excavació compren un període de 500 anys. En aquest article es proposa una revisió de l'estat de la qüestió i oferir un nou enfocament per apropar-nos a la idiosincrasia de la litoescultura antropomorfa teotihuacana

Space occupation by tree crowns obeys fractals laws: evidence from 3D digitized plants

International audienceno abstrac

Hunting lesions caused by osseous projectile points: experimental results and archaeological implications.

International audienceThe identification of projectile impact traces on archaeological faunal remains is an important issue for understanding prehistoric hunting behavior, especially in the Paleolithic and Mesolithic. From the beginning of the Upper Paleolithic in Europe, and earlier in Africa, projectiles tipped with osseous points were of great importance for subsistence; but thus far, no specific experimental reference has been developed to help identify the traces left by these points. In 2003 and 2004 two series of projectile experiments with antler points of Magdalenian design were organized, involving two ox calves and two female fallow deer as targets for bow and spearthrower shooting. The subsequent study demonstrates that positive identifications of impact traces left by osseous points can be made. The observation of 127 impact traces allowed us to distinguish three main types of traces: notches, punctures and perforations. The relationships between the nature of the impact traces and the (i) target species, (ii) characteristics of the impacted bones, and (iii) type of weapon are presented. Synthesized results are then discussed within the context of the European Upper Paleolithic and Mesolithic

Lascaux, grotte

Le siteDécouverte en 1940, la grotte de Lascaux, peut-être le plus célèbre des sites ornés au monde, s’ouvre dans le calcaire coniacien, sur la commune de Montignac, un peu à l’écart des sanctuaires paléolithiques concentrés autour des Eyzies et dans la vallée des Beunes.Implanté non pas à flanc de falaise, mais sur un versant lissé, le porche devait être très discret au Paléolithique récent, alors qu’existait sans doute une seconde entrée, colmatée aujourd’hui. Elle fait partie des premiers..

Metacognitive and Non-Metacognitive Processes in Arithmetic Performance: Can There Be More than One Meta-Level?

The nature of the development of arithmetic performance has long been intensively studied, and available scientific evidence can be evaluated and synthesized in light of Nelson and Narens' model of metacognition. According to the Nelson-Narens model, human cognition can be split into two or more interrelated levels. Obviously, in the case of more than two levels, cognitive processes from at least one level can be described as both meta- and object-level processes. The question arises whether it is possible that the very same cognitive processes are both controlled and controlling. The feasibility of owning the same cognitive processes-which are considered the same from an external point of view of assessment-as both meta- and object-level processes within the same individual opens the possibility of investigating the transition from meta-level to object-level. Modeling cognitive development by means of a series of such transitions calls forth an understanding of possible developmental phases in a given domain of learning. The developmental phases of arithmetic performance are described as a series of transitions from arithmetical facts to strategies of arithmetic word problem solving. For school learning and instruction, the role of metacognitive scaffolding as a powerful educational approach is emphasized