Comparación entre técnicas bilaminares y regenerativas para recubrir las raíces

El objetivo de este artículo en relación con los estudios publicados en la literatura internacional consiste en comparar las posibilidades terapéuticas que ofrecen las técnicas bilaminares y las de regeneración hística guiada (RHG) para recubrir las superficies radiculares expuestas a causa de las recesiones gingivales. La experimentación se ha realizado con 20 pacientes, 13 hombres y 7 mujeres, con edades de 25/39 años. Se dividió a los pacientes en dos grupos, A y B, según las técnicas quirúrgicas, bilaminar y regenerativa, respectivamente. Los sujetos con recesiones múltiples y adyacentes se asignaron al grupo A. Al considerar los datos de este estudio clínico, coincidentes con los de la literatura internacional, se puede afirmar que el injerto de tejido conectivo es una alternativa válida para la RHG en el tratamiento de las recesiones gingivales. De hecho, las técnicas bilaminares permiten aumentar la cantidad y el espesor de la encía insertada, tratar varias recesiones adyacentes y garantizar una gran predicibilidad en recubrimiento radicular

Bending properties in oxidized porous silicon waveguides

The greatest limit in high-speed communications between different circuit blocks is due to the delays introduced by metal interconnections. Knock-down wire communication bottleneck is, therefore, one of the best goals that current research could reach in the held of fast electronics. A possible solution is to build fast optical links and even better if the technology is based on silicon. To attain these ends, we have made studies into possibility to fabricate optical waveguide based on oxidized porous silicon. In the last few years, such a device: was realized and characterized. Waveguiding in the visible and in the near infrared was demonstrated, With propagation losses of about 3-5 dB/cm for a light with a wavelength of 632.8 nm. Moreover, a design feature of an integrated waveguide based on oxidized porous silicon is that it offers a spontaneous bending of the waveguiding layer at its ends. The edge bending is provided by a convex camber of a leading edge of forming porous silicon. This bending can be exploited to promote a vertical light output with no use of any additional devices. The paper discusses the properties of edge bending, evaluation of the light losses depending on the radius of curvature, and analysis of possibilities to reduce these losses. (C) 2001 Elsevier Science Ltd. All rights reserved

Er-doped Oxidized Porous Silicon Waveguides

The present work reports Er-doped channel oxidized porous silicon waveguides (OPSWG) formed from n+-type Si by the two-step anodisation process. Er has been introduced into porous silicon before oxidation by a cathodic treatment in 0.1 M Er (NO3)3 aqueous solution. A correlation between Er concentration and refractive index profiles has shown dominant core doping with Er relative to cladding regions. Reported Er concentration of 0.8 at.% in the OPSWG is large enough to attain the amplification effect

Gettering Technology Based on Porous Silicon

This paper briefly reviews a gettering technology based on porous silicon (PS). PS layers shown to have effecting gettering properties for fast-diffusing impurities. Samples saturated with Au or Cu on which the PS layer made on the wafer backside, increases the generation lifetime of minority carriers from 0.05 – 0.1 µs to 0.5 µs. The PS getter is demonstrated to be located either on the wafer backside or on the front side underneath an epitaxial layer. When formed on the wafer backside, the PS getter may be readily removed together with the absorbed impurities after the gettering process. When fabricated on the wafer front side underneath the epitaxial layer, the getter is brought closer to the wafer working regions as much as possible to provide the most effective gettering effect. At the same time, the epitaxial layer protects chemically active PS against all chemical attacks during device manufacturing. The buried PS getter may be designed as either the continuous or discontinuous layer configured as, for example, a pattern of insulating regions of VLSI. When properly adapted to the produced device conditions, the buried PS getter is shown to withstand successfully the whole VLSI production run providing advanced gain characteristics

Oxidized porous silicon waveguides losses

The Oxidized Porous Silicon Waveguides (OPSWG) present the chance to realize waveguide in the visible range compatible with integrated circuit (IC) fabrication technology. In OPSWG the light is confined in dense silica surrounded by a buffer of porous oxidized silicon. In this paper some of the results of the European project OLSI N degrees 28.934 are discussed. The waveguides were fabricated using p-doped (100) and n-doped (100) and (111) silicon wafers to investigate the influence of the doping type and of silicon crystal orientation on the guiding properties and the thickness of the buffer layer was varied from 1 mum to 2.5 mum changing the anodization regimes and the propagation losses were measured. Two different topology of mask have been used to determine propagation and planar bending losses. Buried OPSWG. realized depositing one micron poly-silicon layer on top of waveguides, have been thermally treated and measurements have not shown a great difference in terms of propagation losses with surface OPSWG

Sottostazioni elettriche con capacità di accumulo elettrochimico per l'alimentazione di linee metropolitane leggere

The possiblity of using lead-acid batteries in rapid transit systems for absorbing the energy regenerated by trains during the braking phase is analyzed in this article. The necessity arises in cases of partial or total lack of receptivity due to the absence of trains in traction phase. In particular a power supply system is examined in which electric substations with a. c. /d. c. converters and batteries are connected to common busbars. An analysis has been carried out by means of a digital computer program which simulates the operation of power supply networks for rapid-transit systems. Using a model system, based on a real case, a number of possible operating conditions have been simulated, for different values of train headways, no-load voltages, and battery storage levels. The simulation made it possible to outline the main characteristics of the system components, which could lead to a technical solution that is economical and resonably reliable

Eco-friendly urban transport systems. Comparison between energy demands of the trolleybus and tram systems

A computational code implementing experimentally tested mathematical models was used to conduct a study on an urban center of southern Italy comprising the cities of Cosenza and Rende that, seat of the University of Calabria, has recorded a systematic and significant expansion in recent years in terms of both urban and demographic development. In Italy the first electric tramway was built in Florence in 1890 and it linked Florence to Fiesole. In 1920 major tramway development was reached. In Europe, North America, South America and Australia, almost all medium and large size cities had urban and intercity networks. In the late 20s, North America first and then Europe reduced the tramway systems replacing them with trolleybuses and buses. The traction electric motor used in most new vehicles is the four-pole three-phase asynchronous motor, that with its control systems, has introduced a number of advantages compared to the DC motor in terms of reliability, less maintenance, high efficiency and control

Power quality disturbances in power supply system of the subway of Rome

The paper illustrates the results of a wide power quality (PQ) survey performed on the power supply installations of the metro-transit system in Rome. The system provides two railway lines supplied at 1.5 KV DC through several AC/DC converter substations (ESS). The power supply of the system is provided at medium voltage (MV-20 kV) from five different connections to the public grid. Fourteen electrical conversion substations provide the total demand of about 20 MW of the system. The survey has involved monitoring activities aimed at identifying possible PQ problems of various natures. Voltage and current wave shapes have been monitored during several weeks. PQ indices and PQ disturbances occurrence are illustrated