Brane worlds and dark matter

Two problems related to dark matter is considered in the context of a brane world model in which the confinement of gauge fields on the brane is achieved by invoking a confining potential. First, we show that the virial mass discrepancy can be addressed if the conserved geometrical term appearing in this model is considered as an energy momentum tensor of an unknown type of matter, the so-called X-matter whose equation of state is also obtained. Second, the galaxy rotation curves are explained by assuming an anisotropic energy momentum tensor for the X-matter.Comment: 13 pages, 1 figure, to appear in IJMP

An overview of Space Communication Artificial Intelligence for Link Evaluation Terminal (SCAILET) Project

A software application to assist end-users of the link evaluation terminal (LET) for satellite communications is being developed. This software application incorporates artificial intelligence (AI) techniques and will be deployed as an interface to LET. The high burst rate (HBR) LET provides 30 GHz transmitting/20 GHz receiving (220/110 Mbps) capability for wideband communications technology experiments with the Advanced Communications Technology Satellite (ACTS). The HBR LET can monitor and evaluate the integrity of the HBR communications uplink and downlink to the ACTS satellite. The uplink HBR transmission is performed by bursting the bit-pattern as a modulated signal to the satellite. The HBR LET can determine the bit error rate (BER) under various atmospheric conditions by comparing the transmitted bit pattern with the received bit pattern. An algorithm for power augmentation will be applied to enhance the system's BER performance at reduced signal strength caused by adverse conditions

Space Communication Artificial Intelligence for Link Evaluation Terminal (SCAILET)

A software application to assist end-users of the high burst rate (HBR) link evaluation terminal (LET) for satellite communications is being developed. The HBR LET system developed at NASA Lewis Research Center is an element of the Advanced Communications Technology Satellite (ACTS) Project. The HBR LET is divided into seven major subsystems, each with its own expert. Programming scripts, test procedures defined by design engineers, set up the HBR LET system. These programming scripts are cryptic, hard to maintain and require a steep learning curve. These scripts were developed by the system engineers who will not be available for the end-users of the system. To increase end-user productivity a friendly interface needs to be added to the system. One possible solution is to provide the user with adequate documentation to perform the needed tasks. With the complexity of this system the vast amount of documentation needed would be overwhelming and the information would be hard to retrieve. With limited resources, maintenance is another reason for not using this form of documentation. An advanced form of interaction is being explored using current computer techniques. This application, which incorporates a combination of multimedia and artificial intelligence (AI) techniques to provided end-users with an intelligent interface to the HBR LET system, is comprised of an intelligent assistant, intelligent tutoring, and hypermedia documentation. The intelligent assistant and tutoring systems address the critical programming needs of the end-user

On modular signs

We consider some questions related to the signs of Hecke eigenvalues or Fourier coefficients of classical modular forms. One problem is to determine to what extent those signs, for suitable sets of primes, determine uniquely the modular form, and we give both individual and statistical results. The second problem, which has been considered by a number of authors, is to determine the size, in terms of the conductor and weight, of the first sign-change of Hecke eigenvalues. Here we improve significantly the recent estimate of Iwaniec, Kohnen and Sengupta.Comment: 23 pages, 1 figure; new version with new coauthor and strong improvements of two of the two main results

Talent Identification and Development in Youth Sports: A Systematic Review

Introduction: Talent has traditionally been associated with the concept of an athlete's essential conditions for success. Longitudinal studies can assess characteristics associated with performance while evaluating changes and developments over time. Therefore, the goal of this review was to identify and summarize the longitudinal literature that addresses the impact of the development of potential talent indicators in childhood/adolescence on later success in elite sports. Methods: Accordingly, the search methodology of this systematic synthesis review was guided by the preferred reporting points for systematic reviews. Articles were included that examined child/adolescent development over time of potential talent indicators for success in future elite athletes. A total of six manuscripts were fully reviewed. Results: Overall, the results of these studies show that the findings are inconclusive and that talent indicators have changed over time, with this change having a different pace and intensity depending on the growth spurt. Conclusion: The result of this systematic review shows that it is not possible to say whether talent can be identified in children/adolescents in relation to success in elite sports. This is due to the non-linear development of adolescents and the emerging, dynamic, and symbiotic conceptualization of talent.Introducción: El talento se ha asociado tradicionalmente al concepto de condiciones esenciales para el éxito del deportista. Los estudios longitudinales pueden evaluar las características asociadas con el desempeño mientras evalúan los cambios y desarrollos a lo largo del tiempo. Por lo tanto, el objetivo de esta revisión fue identificar y resumir la literatura longitudinal que aborda el impacto del desarrollo de indicadores de talento potencial en la infancia/adolescencia sobre el éxito posterior en los deportes de élite. Métodos: En consecuencia, la metodología de búsqueda de esta revisión de síntesis sistemática se guió por los puntos de notificación preferidos para las revisiones sistemáticas. Se incluyeron artículos que examinaron el desarrollo de niños/adolescentes a lo largo del tiempo de los posibles indicadores de talento para el éxito en futuros atletas de élite. Se revisaron completamente un total de seis manuscritos. Resultados: En general, los resultados de estos estudios muestran que los hallazgos no son concluyentes y que los indicadores de talento han cambiado con el tiempo, y este cambio tiene un ritmo e intensidad diferente según el crecimiento acelerado. Conclusión: El resultado de esta revisión sistemática muestra que no es posible afirmar si se puede identificar o no el talento en niños/adolescentes en relación con el éxito en el deporte de élite. Esto se debe al desarrollo no lineal de los adolescentes ya la emergente, dinámica y simbiótica conceptualización del talento

How does the driver's Perception Reaction Time affect the performances of crash surrogate measures?

© 2015 Kuang et al. With the merit on representing traffic conflict through examining the crash mechanism and causality proactively, crash surrogate measures have long been proposed and applied to evaluate the traffic safety. However, the driver's Perception-Reaction Time (PRT), an important variable in crash mechanism, has not been considered widely into surrogate measures. In this regard, it is important to know how the PRT affects the performances of surrogate indicators. To this end, three widely used surrogate measures are firstly modified by involving the PRT into their crash mechanisms. Then, in order to examine the difference caused by the PRT, a comparative study is carried out on a freeway section of the Pacific Motorway, Australia. This result suggests that the surrogate indicators' performances in representing rear-end crash risks are improved with the incorporating of the PRT for the investigated section