Simultaneous Refractive Index Sensing Using an Array of Suspended Porous Silicon Membranes

We propose a fast and cost-effective method for obtaining a miniaturized array-formatted sensor suitable for multiplexed detection. Our solution is based on the fabrication of multiple µm-sized suspended porous silicon (PSi) membranes working as independent transducers. Our process can potentially integrate an array of up to 1000 sensing spots per cm2 . We also propose a simple and user-friendly optical platform to simultaneously interrogate each element of the array in real-time. The feasibility of this idea was proved performing several sensing experiments where we were able to detect refractive index (RI) variations with different transducers at the same time. An average experimental sensitivity of 685 nm/RIU (Refractive Index Unit) was achieved, with a theoretical limit of detection (LoD) of 10-5 RIU. The analyzed sensing spots displayed similar behavior both in time and in magnitude. We believe that the high capabilities of the sensor presented in this work, along with the sensing mechanism, can be very useful for multi-parametric analysis and multi-target detection of biological samples

Sensitivity Comparison of a Self-Standing Porous Silicon Membrane Under Flow-Through and Flow-Over Conditions

An optical sensor based on a self-standing porous silicon (PS) membrane is presented. The sensor was created by electrochemically etching a heavily doped p-type silicon wafer with an organic electrolyte that contained dimethylformamide. After fabrication, a high-current density close to electropolishing was applied in order to allow the detachment from the substrate using a lift-off method. The PS membrane was integrated in a microfluidic cell for sensing purposes, and reflectance spectra were continuously obtained while the target substance was flowed. A comparison of the bulk sensitivity is achieved when flowing through and over the pores is reported. During the experiments, a maximum sensitivity of 770 nm/RIU measured at 1700 nm was achieved. Experimental sensitivity values are in good agreement with the theoretical calculations performed when flowing through the PS membrane, it means that the highest possible sensitivity of that sensor was achieved. In contrast, a drop in the sensitivity of around 25% was observed when flowing over the PS membrane

Dual refractive index and viscosity sensing using polymeric nanofibers optical structures

Porous materials have demonstrated to be ideal candidates for the creation of optical sensors with very high sensitivities. This is due both to the possibility of infiltrating the target substances into them and to their notable surface-to-volume ratio that provides a larger biosensing area. Among porous structures, polymeric nanofibers (NFs) layers fabricated by electrospinning have emerged as a very promising alternative for the creation of low-cost and easy-to-produce high performance optical sensors, for example, based on Fabry-Perot (FP) interferometers. However, the sensing performance of these polymeric NFs sensors is limited by the low refractive index contrast between the NFs porous structure and the target medium when performing in-liquid sensing experiments, which determines a very low amplitude of the FP interference fringes appearing in the spectrum. This problem has been solved with the deposition of a thin metal layer (∼ 3 nm) over the NFs sensing layer. We have successfully used these metal-coated FP NFs sensors to perform several real-time and in-flow refractive index sensing experiments. From these sensing experiments, we have also determined that the sponge-like structure of the NFs layer suffers an expansion/compression process that is dependent of the viscosity of the analyzed sample, what thus gives the possibility to perform a simultaneous dual sensing of refractive index and viscosity of a fluid

Thermo-Optic Coefficient of Porous Silicon in the Infrared Region and Oxidation Process at Low Temperatures

In this work, a porous silicon nanostructure has been fabricated by electrochemical means and used as a thermal sensor. The thermo-optic effect in the near infrared region has been experimentally studied based on spectroscopy measurements. Values of the thermo-optic coefficient between 3.2 and 7.9·10^{-5} K^{-1} have been obtained, depending on the porosity, reaching a maximum thermal sensitivity of 91 ± 3 pm/°C during the experiments carried out with the fabricated samples. Additionally, the oxidation process of the sensor at temperatures below 500 K has been studied, showing that the growth of the silicon oxide was dependent on the characteristics of the porous layers. Based on the experimental results, a mathematical model was developed to estimate the evolution of the oxidation process as a function of porosity and thickness

Effective elastic thickness in the Central Andes. Correlation to orogenic deformation styles and lower crust high-gravity anomaly

Global studies have assessed the importance of elastic thickness (Te) on orogenic evolution, showing that the style and nature of upper crustal shortening are influenced by the inherited lithospheric strength. Thus, pioneer works have identified that the upper crustal deformation style in the easternmost sector of the Central Andes in South America are related to the elastic thickness (Te). There, the thick-skinned and pure-shear style of Santa Bárbara system was initially related to the existence of low Te values. In contrast, the thin-skinned and simple-shear style of deformation in the Subandean system involves high Te values. However, more recent Te studies in the Central Andes present conflicting results which lead to question this straightforward relation. Results from these studies show a strong dependence on the applied methodology hampering the general understanding of the lithospheric thermo-mechanical state of the Central Andes. To contribute to this issue, we perform a high-resolution Te map, using forward modeling by solving flexural equation of infinite plate model in two dimensions. To achieve this, the crust-mantle interface was calculated using a high-resolution gravity anomaly dataset which combines satellite and terrestrial data, and an average density contrast. Additionally, the gravity anomaly and the foreland basin depth in the Central Andes were best predicted by considering that lower crustal rocks fill the space deflected downward in the plate model. The obtained Te values show an inverse correlation with previous heat flow studies, and a strong spatial correlation with the styles and mechanisms of deformation in the easternmost sector of the Central Andes. In the Santa Bárbara system Te values less than 10 km predominate, whereas in the Subandean system high Te values were observed. Such high values correlate with the orogenic curvature and with an shallower gravity Moho zone, which breaks the regional trend of the Central Andes. This shallower gravity Moho is linked to a high-gravity anomaly located in the east part of the Eastern Cordillera and Subandean system. These results are also correlated with a high-velocity zone in the upper mantle previously found by receiver functions studies. This correlation could indicate changes in the properties of the lower crustal rocks that justify the shallower gravity Moho zone and explain in part the highest Te values.Fil: Garcia, Hector Pedro Antonio. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gianni, Guido Martin. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lupari, Marianela Nadia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sanchez, Marcos Ariel. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Soler, Santiago Rubén. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ruiz, Francisco. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: Lince Klinger, Federico Gustavo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Macropore Formation and Pore Morphology Characterization of Heavily Doped p-Type Porous Silicon

Tuning the pore diameter of porous silicon films is essential for some applications such as biosensing, where the pore size can be used for filtering analytes or to control the biofunctionalization of its walls. However, macropore (>50nm) formation on p-type silicon is not yet fully controlled due to its strong dependence on resistivity. Electrochemical etching of heavily doped p-type silicon usually forms micropores (<5nm), but it has been found that bigger sizes can be achieved by adding an organic solvent to the electrolyte. In this work, we compare the results obtained when adding dimethylformamide (DMF) and dimethylsulfoxide (DMSO) to the electrolyte as well as the effect of a post-treatment of the sample with potasium hydroxide (KOH) and sodium hydroxide (NaOH) for macropore formation in p-type silicon with resistivities between 0.001 and 10Ω·cm, achieving pore sizes from 5 to 100nm

Efectos positivos del uso de blogs y wikis en variables psicoeducativas: revisión de estudios internacionales (2010-2013)

Se presenta una revisión de treinta y dos estudios empíricos internacionales publicados en los últimos cuatro años (2010-2013) en revistas científi - cas de impacto con la que se persigue dar respuesta a cuáles son las variables psicoeducativas más examinadas y cuáles son los efectos positivos que se producen en ellas como consecuencia del uso continuado de blogs y wikis. Los resultados demuestran que el uso de estas herramientas: i) promueve la colaboración, la participación, la interacción social y la socialización; ii) aumenta la motivación, la satisfacción, el rendimiento y la retroalimentación; y iii) favorece el desarrollo del pensamiento crítico y creativo. We describe the positive effects that the using of two Web 2.0 tools (blogs and wikis) produce in several psycho-educational variables through the literature review of thirty and two international empirical studies publish in last four years (2010-2013) in impacts journals. The results evidence that the use of blogs and wikis promotes the collaboration, the participation, the social interaction and socialization, at the same time these tools increase the motivation, the satisfaction, the performance and the feedback and this tools favour the developing of critical and creative thinking skills.

Optimización de gestión del tráfico para reducir la aglomeración vehicular en la Av. Perú en el intervalo de la Av. 12 de octubre y Universitaria con el programa SYNCHRO 11, Lima 2023.

En la presente investigación se trata el tema de la aplicación de herramientas tecnológicas, como en este caso con el software Synchro 11, para optimizar la gestión del tránsito vehicular de una concurrida avenida de la ciudad de Lima. En su desarrollo, se fijó como objetivo dar una oferta vial electiva a los usuarios que se sume a la agilización de los equipos de estimación de tráfico; entre ellos, el nivel de densidad de tránsito, el nivel de ayuda de las convergencias que son importantes para el estudio y las postergaciones por demoras en el tiempo. Para ello se utiliza Traffic Synchro 11, un programa de reproducción que mantiene el sistema del modelo de arreglo, completado a nivel mesoscópico. Para ello, se revisaron las teorías más actualizadas de investigación, como son las concernientes al software Synchro 11, el cual es viable con el Manual de Capacidad de Carretera HCM 2010. Se ha llegado a la conclusión de que es posible optimizar el flujo de tráfico vehicular mediante una propuesta elaborada que utiliza de manera adecuada el programa Traffic Synchro 11 junto con los sistemas de prueba de tráfico, en comparación con la situación actual del área de estudio. La importancia de la presente investigación radicó en optimizar la gestión del tránsito vehicular a través de un software especializado, mejorando los tiempos de circulación en la vía estudiada y reduciendo por lo tanto su saturación.This research deals with the application of technological tools, as in this case the Synchro 11 software, to optimize the management of vehicular traffic on a busy avenue in the city of Lima. In its development, the objective was set to provide an elective road offer to users that adds to the streamlining of traffic estimation equipment; among them, the level of traffic density, the level of help of the convergences that are important for the study and the postponements due to delays in time. For this, Traffic Synchro 11 is used, a playback program that maintains the arrangement model system, completed at the mesoscopic level. For this, the most up-to-date research theories were reviewed, such as those concerning the Synchro software, which is viable with the Highway Capacity Manual – HCM 2010. It has been concluded that it is possible to optimize the flow of vehicular traffic through an elaborate proposal that appropriately uses the Traffic Synchro 11 program together with traffic test systems, compared to the current situation in the study area. The importance of this research lies in optimizing the management of vehicular traffic through specialized software, improving circulation times on the studied road and therefore reducing its saturation.Trabajo de Suficiencia Profesiona