Europium-doped aluminum oxide phosphors as indicators for frontal polymerization dynamics.

In this study, we present an inexpensive and practical method that allows the monitoring and visualization of front polymerization, propagation, and dynamics. Commercially available europium-doped aluminum oxide powders were combined with video imaging to visualize free-radical propagating polymer fronts. In order to demonstrate the applicability of this method, frontal copolymerization reactions of propoxylated glycerin triacrylate (EB53), pentaerythritol triacrylate (PETA), and pentaerythritol tetra-acrylate (PETEA) with 1,1-Bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane (Luperox 231®) as an initiator were studied and compared to the results obtained by IR imaging. Systems exhibiting higher filler loading, higher EB53 content, and less acrylated monomers showed a marked decrease in front velocity, while those with more acrylated monomers and higher crosslinking density showed a marked increase in front velocity. Finally, in order to show the potential of the imaging technique, we studied fronts propagating in planar and spherical geometries.

Environmental radiological baseline in unconventional oil and gas areas of Mexico.

Environmental radioactivity study was performed in unconventional hydrocarbons areas for the first time in Mexico, where four unconventional hydrocarbon exploratory wells (UHEW) are planned. This study assesses natural radiological conditions in areas around UHEW. Equivalent dose rate distribution displayed in Geographic Information System (GIS) had a maximum of 1.83 mSv a-1 and minimum of 0.04 mSv a-1, GIS was also used for introducing land usage, water resources and population occupancy. Measurements of gross alpha and gross beta in water were below the national permissible limits for drinking water 0.5 and 1.0 Bq L-1 respectively, even though samples do not correspond to drinking water. Evaluation of 238U and 226Ra in groundwater were below minimum detectable concentration 1.3 and 1.0 Bq L-1, respectively. This study provides a radiological baseline for the impact of future industrial activities, especially if exploitation of unconventional hydrocarbons produces naturally occurring radioactive material.

pH wave-front propagation in the urea-urease reaction.

The urease-catalyzed hydrolysis of urea displays feedback that results in a switch from acid (pH ~3) to base (pH ~9) after a controllable period of time (from 10 to >5000 s). Here we show that the spatially distributed reaction can support pH wave fronts propagating with a speed of the order of 0.1-1 mm min(-1). The experimental results were reproduced qualitatively in reaction-diffusion simulations including a Michaelis-Menten expression for the urease reaction with a bell-shaped rate-pH dependence. However, this model fails to predict that at lower enzyme concentrations, the unstirred reaction does not always support fronts when the well-stirred reaction still rapidly switches to high pH.

Deep-Eutectic Solvents as MWCNT Delivery Vehicles in the Synthesis of Functional Poly(HIPE) Nanocomposites for Applications as Selective Sorbents.

We report an alternative green strategy based on deep-eutectic solvents (DES) to deliver multiwalled carbon nanotubes (MWCNTs) for a bottom-up approach that allows for the selective interfacial functionalization of nonaqueous poly(high internal phase emulsions), poly(HIPEs). The formation and polymerization of methacrylic and styrenic HIPEs were possible through stabilization with nitrogen doped carbon nanotube (CNX) and surfactant mixtures using a urea-choline chloride DES as a delivering phase. Subtle changes in CNX concentration (less than 0.2 wt % to the internal phase) produced important changes in the macroporous monolith functionalization, which in turn led to increased monolith hydrophobicity and pore openness. These materials displayed great oleophilicity with water contact angles as high as 140° making them apt for biodiesel, diesel, and gasoline fuel sorption applications. Overall, styrene divinylbenzene (StDvB) based poly(HIPEs) showed hydrophobicity and fuel sorption capacities as high as 4.8 (g/g). Pore hierarchy, namely pore openness, regulated sorption capacity, and sorption times where greater openness resulted in faster sorption and increased sorption capacity. Monoliths were subject to 20 sorption-desorption cycles demonstrating recyclability and stable sorption capacity. Finally, CNX/surfactant hybrids made it possible to reduce surfactant requirements for successful HIPE formation and stabilization during polymerization. All poly(HIPEs) retained acceptable conversion as a function of CNX loading nearing 90% or better with thermal stability as high as 283 °C.

Fundoplicatura de Nissen videolaparoscópica: experiencia de 104 casos / Laparoscopic Nissen fundoplication: experience in 104 cases

Introducción: Con el desarrollo de la Cirugía Laparoscópica la Enfermedad por Reflujo Gastroesofágico (ERGE) puede ser tratada de una manera invasiva, ofreciendo al paciente una recuperación rápida y definitiva a tan molesto problema. La Fundoplicatura de Nissen Video-laparoscópica es actualmente el procedimiento quirúrgico más frecuentemente realizado para el control del RGE. El objetivo del presente trabajo es presentar la experiencia del autor con ésta técnica en 104 casos. Material y Métodos: De diciembre de 1995 a octubre de 2002 el autor, ha efectuado fundoplicatura de Nissen por vía laparoscópica en 104 pacientes, 59 hombres y 45 mujeres, entre las edades de 9 a 71 años, todos con RGE crónico y con un mínimo de tratamiento médico de 18 meses cada uno. El protocolo pre-operatorio incluye: Historia de RGE crónico, Video-endoscopía superior más biopsias por gastroenterólogo, exámenes de laboratorio de rutina. La técnica quirúrgica es la descrita por Peters, DeMeester y Hinder en 1992. No se liberaron los vasos cortos en los primeros 25 casos, en los 79 restantes sí. Resultados: Se ha tenido un seguimiento en 102 casos, 2 pacientes se han ido a vivir al extranjero y ya no hay comunicación, se ha logrado controlar el RGE en los 102 casos. No hubo conversaciones a cirugía abierta, no hubo mortalidad. 1 paciente presentó disfagia postoperatoria al mes de operado la cual se resolvió con dos dilataciones esofágicas, 1 paciente presentó disfagia postoperativa al mes de operado la cual se resolvió con dos dilataciones esofágicas, 1 paciente presentó disfagia al 7o. día postoperatorio, misma que se resolvió con tratamiento médico. Conclusión: La Fundoplicatura de Nissen Video-laparoscópica controla de manera permanente la Enfermedad por reflujo gastroesofágico