Measurement of mean thickness of transparent samples using simultaneous phase shifting interferometry with four interferograms.

In this research a novel interferometric system is reported, which allows the generation of four simultaneous interferograms with phase shifts of π/2. The system consists of three coupled interferometers: a rectangular Sagnac interferometer which generates a primary pattern with crossed circular polarizations, coupled to two Michelson interferometers which operate as a multiplexing system, and generating replicas of the primary pattern. The two coupled Michelson interferometers generate four patterns retaining their polarization properties, which allow independent phase shifts by placing a linear polarizer over each pattern, thereby, four interferograms with relative phase shifts of π/2 are obtained. The optical phase is calculated using the well-known four-step algorithm. With knowledge of the optical phase, different properties of the samples can be calculated or analyzed; in this case, by knowing the mean refractive index, we can calculate the mean thickness of test objects. The results obtained for static transparent samples are presented. The capability of the system to analyze dynamic events is shown when results for the calculation of a temperature field of a heat flow are presented.

One-shot phase stepping with a pulsed laser and modulation of polarization: application to speckle interferometry.

For applications involving time varying optical phase distributions, fast cameras and/or pulsed lasers have to be used. To apply phase-shifting interferometry techniques (PSI) as well, single shot capture is required. Among others, modulation of polarization and phase grating interferometry is a possible technique to be considered. In this paper, a report about the use of this technique based on a double pulse laser system is presented. Single-pulse and twin-pulse operations are considered both in optical interferometers as well as in ESPI systems (mainly in subtraction mode). In ESPI a reduction of the degree of polarization appears due to scattering, so some measures have to be taken to prevent such deletereous effect. To show the feasibility of the proposed variants some experimental results are presented.

Optimum melanin production using recombinant Escherichia coli.

AIMS: A parametric study was conducted to define optimum conditions to achieve high yields in the conversion of tyrosine to eumelanin (EuMel) using recombinant Escherichia coli. METHODS AND RESULTS: Escherichia coli W3110 (pTrcMutmelA) expressing the tyrosinase coding gene from Rhizobium etli and glucose-mineral media were used to transform tyrosine into EuMel. Batch aerobic fermentor cultures were performed to study the effect of temperature, pH and inducer concentration (isopropyl-D-thio-galactopyranoside) on melanin production. Under optimum conditions, 0.1 mmol l(-1) of isopropyl-D-thio-galactopyranoside, temperature of 30 degrees C, and changing pH from 7.0 to 7.5 during the production phase, a 100% conversion of tyrosine into EuMel is obtained. Furthermore, tyrosine feeding allowed us to obtain the highest level (6 g l(-1)) of EuMel produced by recombinant E. coli reported until now. CONCLUSIONS: The most important factors affecting melanin formation and hence influencing the rate and efficiency in the conversion of tyrosine into EuMel in this system, are the temperature and pH. SIGNIFICANCE AND IMPACT OF THE STUDY: Maximum theoretical yield was obtained using a simple culture process and mineral media to convert tyrosine (a medium value compound) into melanin, a high value compound. The process reported here avoids the use of purified tyrosinase, expensive chemical methods or the cumbersome extraction of this polymer from animal or plant tissues.

Suicidio e intento de suicidio por salto desde altura en el Puente Villena / Suicide and attempt of suicide by jump from the heights of the Villena bridge

Objetivo. Estudiar las características de los individuos que intentaron o llegaron a suicidarse arrojándose desde un puente. Método. Se recopilaron los datos de los intentos y suicidios consumados ocurridos en el Puente Villena (Miraflores, Lima-Perú) que constan en los registros de la municipalidad de dicho distrito desde el primero de septiembre de 1988 hasta el 31 de agosto de 2003. Resultados. En el período estudiado ocurrió un total de 65 eventos (33 intentos de suicidio y 32 suicidios consumados). Los individuos que completan el suicidio son principalmente varones (65.6 por ciento), de 20 a 29 años (27.8 por ciento) con una edad promedio de 39.44 años, solteros (66.7 por ciento), limeños (66.7 por ciento), que no residen en el distrito de Miraflores (78.5 por ciento) y que escogen con mayor frecuencia el lunes (28.1 por ciento) para realizar su cometido. Los que intentan suicidarse son varones (81.81 por ciento), de 30 a 39 años (33.33 por ciento) con una edad promedio de 32.7 años, solteros (84.61 por ciento), limeños (55 por ciento), que no residen en el distrito de Miraflores (100 por ciento) y que escogen con mayor frecuencia los días jueves (30.30 por ciento) y lunes (24.24 por ciento) para llevar a cabo su cometido. Se observó un marcado aumento de casos en los últimos 2 años (37 eventos), ya que dicha cifra es mayor a todos los casos ocurridos en los primeros 13 años juntos (28 casos). Conclusiones. El perfil del sujeto que se suicida o que intenta hacerlo podría describirse así: un varón, soltero, limeño, no residente del distrito de Miraflores y que escoge los días lunes o jueves para realizar su acto.