Directionality in van der Waals Interactions: the Case of 4-Acetylbiphenyl Adsorbed on Au(111)

We report on a theoretical study of adsorption of 4-Acetylbiphenyl molecule and its diffusion properties in the main directions of the Au(111) surface. Structural changes of the molecule, which are induced by adsorption lead to stronger conjugation of the $\pi$-system. The molecule is adsorbed in a flat configuration on the surface with roughly the same binding energy along the [110] and [112] directions, in good agreement with experiments. Furthermore, the diffusion barriers imply an important directionality of the molecule-surface interactions. This is somewhat surprising because our calculations show that the prevailing interaction is the long-range molecule-surface van der Waals interaction. Despite of its weakness, the van der Waals interaction discriminates the preferential adsorption sites as well as imposes a molecular geometry that needs to be considered when rationalizing the diffusion barriers

Lenguajes de Scripting

Los lenguajes de scripting son una subcategoría de los lenguajes de programación. Este tipo de lenguajes son interpretados, es decir, que para ejecutar las instrucciones existe un programa o intérprete que se encarga de procesar cada una de las órdenes y producir los resultados deseados. Algunos ejemplos de este tipo de lenguajes son: JavaScript, Lisp, P. H. P., Python, Ruby, etc. En el otro caso, en los lenguajes que no son interpretadosexiste un compilador que toma esas instrucciones y genera un archivo ejecutable. Tenemos en esta categoría a C, C++, Java, Microsoft Visual Basic, etc. Recientemente hemos visto dos enguajes de scripting orientados a objetos que han tenido una gran acogida por la comunidad de programadores: Ruby y Groovy

Diagnostic Theory of Information as a Testing Technique to Ascertain Spanish Reading Proficiency

The purpose of this study was to investigate the use of information theory as a testing reading proficiency of bilingual students. This study is not an attempt to analyze mistakes or to debate which reading proficiency test is the best in testing Spanish language abilities or expertise. This test was constructed to determine the readability and the validity of information theory as a testing tool. A second purpose was to determine whether this technique could help increase the student\u27s ability to comprehend reading material at his/her level of language learning. A third purpose was to try to develop a Spanish reading proficiency test that could be used in the classroom. This study of Spanish reading proficiency consisted of three experimental groups. The first was composed of ten fourth, fifth and sixth grade students from Dr. Martin Luther King Jr. #9 School in the city of Rochester. All of the students in this group were raised in the United States. This group was at an intermediate level and has been in a bilingual program no less than three years. They all received an equal amount of English reading and Spanish reading during the day. This group is categorized as English dominant in a bilingual setting. The second group consisted of ten fourth, fifth, and sixth grade students who were more recent arrivals in the United States. This group was also at an intermediate level and the students selected have been in a bilingual program since at least September of 1989. This group is categorized as Spanish dominant in a bilingual setting. Finally, the third group was composed of ten students from Spanish-speaking homes, but are enrolled in an all-day English only classroom. This particular group is also at an intermediate level. Each group was tested with a variety of reading materials in the target language. The materials used were poems with part of the information deleted. The objective of the test was for the subjects to encode the missing letters within a five minute, four minute, and three minute time frame. All three groups were presented with a similar procedure at different levels of difficulty. The passages consisted of approximately 300 to 400 bits of information each

El efecto competitivo de las importaciones recientes en México

Uno de los beneficios esperados de un proceso de liberalización y apertura comercial es la imposición de restricciones al poder de fijación de precios que tienen los monopolios o los oligopolios internos. Es decir, la disminución de las barreras arancelarias y el desmantelamiento de las no tarifarias, como permisos de importación y precios oficiales de importación, y su sustitución por aranceles, puede aumentar la competencia efectiva y la potencial que enfrentan los productores locales. Algunos autores (Esposito y Esposito, 1971) sugieren incluso que la liberalización comercial puede ser utilizada para disminuir las presiones inflacionarias de los bienes manufactureros locales, gracias al efecto competitivo que debe ser mayor en las industrias más concentradas (De Rosa y Goldstein, 1981). El comportamiento competitivo de la industria local es reforzado también por los consumidores. En efecto, una apertura comercial modificará la estructura de sus preferencias, y cuando éstas se desplacen hacia los productos importados, la elasticidad-precio de la demanda de los bienes nacionales tiende a menos infinito y en consecuencia el precio interno debe tender a su costo marginal (Zeelemberg, 1986).

Diseño estructural : unidad 4

1 archivo PDF (77 páginas) ; 2a ediciónSe ilustra el análisis del equilibrio de estructuras sujetas a distintos tipos de acciones

Características sedimentológicas y paleogeográficas del fan-delta albiense de la Formación Monte Grande y sus relaciones con el Flysh Negro (Arminza-Górliz, Vizcaya)

La Fm. Monte Grande (Albiense inferior-medio, Vizcaya) posee más de 500 m de conglomerados, areniscas, lutitas y calizas urgonianas, sedimentadas en un «fan-delta» retrogradante. Importantes disconformidades limitando la unidad sugieren dos variaciones relativas bruscas del nivel del mar