Effect of crosslinker length on the elastic and compression modulus of poly(acrylamide) nanocomposite hydrogels

Polymer hydrogelshave shown to exhibit improved properties upon the addition of nanoparticles; however, the mechanical underpinnings behind these enhancements have not been fully elucidated. Moreover, fewer studies have focused on developing an understanding of how polymer parameters affect the nanoparticle-mediated enhancements. In this study, we investigated the elastic properties of silica nanoparticle-reinforced poly(acrylamide) hydrogels synthesized using crosslinkers of various lengths. Crosslinker length positively affected the mechanical properties of hydrogels that were synthesized with or without nanoparticles. However the degree of nanoparticle enhancement was negatively correlated to crosslinker length. Our findings enable the understanding of the respective roles of nanoparticle and polymer properties on nanoparticle-mediated enhancement of hydrogels and thereby the development of next-generation nanocomposite materials

Aplicación del modelo de calidad del servicio Servqual en el área de recursos humanos de la empresa National Car Rental en México (Grupo Antyr)

Este trabajo presenta un estudio de las dimensiones de calidad del servicio de la franquicia National Car Rental en México operada por Grupo Antyr para 23 estados del país, mediante el modelo de brechas o Servqual. El objetivo es lograr aplicar un modelo de calidad del servicio para detectar cuáles son los temas más importantes a corregir con el fin de mejorar la satisfacción y percepción que el personal tiene respecto al área de recursos humanos

Integration and optimization of pressure retarded osmosis with reverse osmosis for power generation and high efficiency desalination

© 2016 Elsevier Ltd. Salinity gradient power is proposed as a source of renewable energy when two solutions of different salinity are mixed. In particular, Pressure Retarded Osmosis (PRO) coupled with a Reverse Osmosis process (RO) has been previously suggested for power generation, using RO brine as the draw solution. However, integration of PRO with RO may have further value for increasing the extent of water recovery in a desalination process. Consequently, this study was designed to model the impact of various system parameters to better understand how to design and operate practical PRO-RO units. The impact of feed salinity and recovery rate for the RO process on the concentration of draw solution, feed pressure, and membrane area of the PRO process was evaluated. The PRO system was designed to operate at maximum power density of δP=δπ2. Model results showed that the PRO power density generated intensified with increasing seawater salinity and RO recovery rate. For an RO process operating at 52% recovery rate and 35 g/L feed salinity, a maximum power density of 24 W/m2 was achieved using 4.5 M NaCl draw solution. When seawater salinity increased to 45 g/L and the RO recovery rate was 46%, the PRO power density increased to 28 W/m2 using 5 M NaCl draw solution. The PRO system was able to increase the recovery rate of the RO by up to 18% depending on seawater salinity and RO recovery rate. This result suggested a potential advantage of coupling PRO process with RO system to increase the recovery rate of the desalination process and reduce brine discharge

Evaluating human neural tuning curves from a mechanical model of the cochlea by relating them to psychophysical masking data

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (leaves 40-42).by Peter A.Z. Garbes.M.S

A Short and Improved Synthesis of the Antiprotozoal Abietane Diterpenoid (-)-Sugikurojin A

Financial support from the Spanish Government [Consejo Superior de Investigaciones Cientificas (201680I008)] is gratefully acknowledgedGonzález-Cardenete, MA.; Zaragoza, RJ. (2017). A Short and Improved Synthesis of the Antiprotozoal Abietane Diterpenoid (-)-Sugikurojin A. Synthesis. 49(6):1315-1318. https://doi.org/10.1055/s-0036-1588353S1315131849

Identification guide for cephalopod paralarvae from the Mediterranean Sea

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Commercial scale membrane distillation for solar desalination

Abstract Membrane distillation is an attractive technology for solar-powered decentralized desalination that has not yet reached commercial breakthrough on a large scale. The main barriers are energy consumption and cost. Since the latter are mostly related to the former, thermal energy efficiency is key to assessing the potential of the different available membrane distillation systems at a commercial scale. As discussed here, existing membrane distillation technologies use mostly flat sheet membranes in plate and frame and spiral-wound modules. Modules based on hollow fibre membranes are also considered, as well as the concept of multi-effect vacuum membrane distillation for improved heat recovery. The heat efficiency of each system is analysed based on available experimental results. Better internal heat recovery and capacity for upscaling are found to be important elements of distinction which make multi-channelled spiral-wound modules working in air-gap configuration stand out currently, with the lowest heat consumption of all large scale modules. Potential for improvement of this and other technologies is also discussed, and an estimation based on the associated costs for solar energy is used for establishing boundary conditions towards the implementation of membrane distillation for solar desalination