String equations in Whitham hierarchies: tau-functions and Virasoro constraints

A scheme for solving Whitham hierarchies satisfying a special class of string equations is presented. The tau-function of the corresponding solutions is obtained and the differential expressions of the underlying Virasoro constraints are characterized. Illustrative examples of exact solutions of Whitham hierarchies are derived and applications to conformal maps dynamics are indicated.Comment: 26 pages, 2 figure

Influence of the fiber direction on the tribological behavior of carbon-fiber reinforced epoxy composites manufactured by prepeg laminates

In this work, friction behavior of different carbon fiber-epoxy composites is evaluated. Linear friction tests are carried out and wear behaviour has been established from several parameters as wear depth, wear band width and macrostructural observation. The experimental variables considered were load (10-40N) and the fiber orientation with respect to the sliding direction (0°, 90° and multidirectional). Layers with the fiber oriented in the sliding direction showed larger wear due to cracks existing in the fibermatrix interface once the wear depth reached the fibers. The best results were obtained in those cases in which no influence of the resin matrix existed

Exercise addiction and satisfaction of fitness center users as precursors to the intention of continuing to engage in physical activity

Exercise addiction occurs when a person engages in excessive physical activity until they lose control. Among individuals attending fitness centers, the risk of developing exercise addiction has been estimated to be close to 10%. The objective of this study was to determine whether exercise addiction may be an antecedent of satisfaction with the service received and/or of the intention of continuing to partake in leisure-time physical activity at fitness centers in a direct or indirect manner. A total of 361 individuals (29.05 ± 11.40 years old) who were physically active at Spanish fitness centers were asked to respond to a questionnaire on exercise addiction, satisfaction with the sports service, and their intention to continue to engage in physical activity. A multi-group analysis was conducted to check for differences in relationships by sex. The results show the relationships between addiction, satisfaction, and intention to continue physical activity. The standardized values display differences between men and women, with women exhibiting the highest values for the relationships between addiction and the rest of the constructs. Satisfaction with the sports service is a mediator in the relationship between exercise addiction and intention to engage in leisure-time physical activity

Evaluación de la resistencia del ácaro Varroa destructor al fluvalinato en colonias de abejas (Apis mellifera) en Yucatán, México

The constant application of pyrethroids for controlling the mite Varroa destructor has caused the appearance of populations of resistant mites to this product in several parts of the world. With the purpose of detecting the possible existence of populations of resistant mites to the fluvalinate in the State of Yucatan, one of the main honey producer states in Mexico, 12 samples were gathered from each apiary, selecting four apiaries where fluvalinate was used in constant way for the control of V. destructor during five years, and a similar quantity of samples coming from apiaries where methods of alternative control have been used during a similar time.La constante aplicación de piretroides para el control del ácaro Varroa destructor ha ocasionado la aparición de poblaciones de ácaros resistentes a este producto en diversas partes del mundo. Con la finalidad de detectar la posible existencia de poblaciones de ácaros resistentes al fluvalinato en el estado de Yucatán, uno de los principales estados productores de miel en México, se colectó un total de 12 muestras por cada apiario, seleccionando cuatro apiarios donde se ha utilizado de manera constante el fluvalinato para el control de V. destructor por un periodo de cinco años, y una cantidad de muestras similar provenientes de apiarios donde se han utilizado métodos de control alternativo durante un tiempo similar

La Iniciativa Mérida: un problema común de seguridad

A partir de 2006 la política exterior mexicana tendrá entre sus prioridades combatir los problemas de seguridad vinculados al comercio de drogas ilegales, tráfico de armas y trata de personas, generando un mayor apoyo en recursos materiales y asesoría por parte de los Estados Unidos de América. Como resultado de esta colaboración, se resolvió implementar la Iniciativa Mérida. A pesar de los esfuerzos de México y Estados Unidos para erradicar el comercio de drogas por medio de la ejecución de la Iniciativa Mérida, los resultados no han sido los esperados. Esto se debe a que se han olvidado que la salida no debe limitarse al combate de las organizaciones de traficantes; sino que también necesitan atender necesidades como el deterioro en la calidad de vida de la población, la falta de oportunidades educativas y la insuficiente política de generación de empleo. A la vez, resulta necesaria la cooperación eficaz de los EE.UU. en materia de reducción en la demanda de los consumidores, así como del compromiso real de cortar el flujo de armas que abastece a los cárteles mexicanos; no olvidando que si bien éste es un problema que circula por México, su fin último es fluir fuera de las fronteras, haciendo de la cooperación y el compromiso bilateral una herramienta necesaria para enfrentar la situación. Palabras clave: Iniciativa Mérida, narcotráfico, México-Estados Unidos

Una Nueva Política De Recursos Humanos En I+D: El Programa Ramón y Cajal

Publicado en: Economía Industrial, 343 (1): 149-160, 2000Peer reviewe

Revising the diversity within the Dwarf Dog-faced Bat, Molossops temminckii (Chiroptera, Molossidae), with the revalidation of the endangered Molossops griseiventer

The genus Molossops includes two monotypic species of insectivore bats distributed in South America: Molossops neglectus and Molossops temminckii. Both can be differentiated, based on sizes, M. temminckii being smaller (forearm less than 33 mm). Despite being monotypic, at least two additional subspecies have been described for M. temminckii, of which M. temminckii griseiventer from the inter-Andean Valley of the Magdalena River in Colombia might represent a valid taxon. To test the taxonomic status of M. t. griseiventer, we reviewed specimens of M. temminckii from cis- and trans-Andean localities in Colombia. We used Cytochrome-b and Cytochrome Oxidase I comparisons to test the phylogenetic position of cis- and trans-Andean samples and compared qualitative morphology, morphometric and bioacoustics. Our results show that M. t. griseiventer is differentiated from cis-Andean specimens, providing further evidence of its validity at the species level. Furthermore, M. temminckii (sensu stricto) is also distributed in Colombia, but both M. griseiventer and M. temminckii are allopatric, with the Andes acting as a barrier. The specific identity of the specimens from the Caribbean Region of Colombia needs a new evaluation, but our results clearly show that the diversity of Molossops is underestimated