Refractive index evaluation of porous silicon using Bragg reflectors

There are two main physical properties needed to fabricate 1D photonic structures and form perfect photonic bandgaps: the quality of the thickness periodicity and the refractive index of their components. Porous silicon (PS) is a nano-structured material widely used to prepare 1D photonic crystals due to the ease of tuning its porosity and its refractive index by changing the fabrication conditions. Since the morphology of PS changes with porosity, the determination of PS's refractive index is no easy task. To find the optical properties of PS we can use different effective medium approximations (EMA). In this work we propose a method to evaluate the performance of the refractive index of PS layers to build photonic Bragg reflectors. Through a quality factor we measure the agreement between theory and experiment and therein propose a simple procedure to determine the usability of the refractive indices. We test the obtained refractive indices in more complicated structures, such as a broadband Vis-NIR mirror, and by means of a Merit function we find a good agreement between theory and experiment. With this study we have proposed quantitative parameters to evaluate the refractive index for PS Bragg reflectors. This procedure could have an impact on the design and fabrication of 1D photonic structures for different applications

Transient situations in traffic flow: Modelling the Mexico City Cuernavaca Highway

In this paper a recent variable anticipation cellular automata model for single-lane traffic flow is extended to analyze the situation of free and congested flow in the Highway from Mexico City to Cuernavaca. This highway presents free flow in standard days; but in the returning day of long weekends or holidays it exhibits congested flow and in rush hours jamming appears. We illustrate how our CA model for traffic flow can deal appropriately with transient situations and can be used to search new alternatives that allow to improve the traffic flow in Mexican highways.Comment: Paper accepted to be published in the Proceedings of Second Mexican Meeting on Mathematical and Experimental Physics (September 2004), El Colegio Nacional, Mexico City, Mexic

Electromiograph Study of Patients Treated with Overdentures Retined with Implants

INTRODUCTION: Long Term edentulous patients present severe bone loss in their alveolar ridges, as a consequence there is serious compromise in esthetics and function. A therapeutic alternative which we can offer to these patients is an overdenture retined with dental implants, in order to improve retention and stability. AIM OF THE WORK: The aim of the study was to determine by electromiography whether the muscular groups involved in masticatory function present any special activity in patients treated with overdentures retined with dental implants. MATERIAL AND METHODS: We selected ten complete edentulous patients with inferior overdentures retined with two implants and a bar.Myotronics K6-I with eight channels, and registration of anterior and posterior temporalis muscle maseter and dygastric muscles. We performed recordings in rest positions and maximum force bite. RESULTS AND CONCLUSION: The results obtained indicate an increase in activity in the rest position of the posterior temporalis group