Recent advances in functionalization of mesoporous silica

Mesoporous silica with regular geometries have been recently paid much attention owing to their scientific importance and great potentials in practical applications such as catalysis, adsorption, separation, sensing, medical usage, ecology, and nanotechnology. Especially, applications often require immobilization of the related functional groups in the mesopores. In order to achieve desire applications, modification of these mesoporous silica are indispensable. In this review, recent progresses of functionalization of mesoporous silica are comprehensively summarized. In the first parts, advances in three major methods, grafting (post-synthetic modification), co-condensation (direct synthesis), and techniques related with periodic mesoporous organosilicates, are explained. In the latter parts, new concepts for functionalization of mesoporous silica including functional template method and lizard template method are introduced. Most of the examples described here have been published in a new millennium.     

Solution and interfacial behavior of hydrophobically modified water-soluble block copolymers of acrylamide and N-phenethylacrylamide

Hydrophobically modified water-soluble block copolymers were prepared by aqueous micellar copolymerization of acrylamide and small amounts (2 and 3 mol %) of a hydrophobe (N-phenethylacrylamide) that is characterized by a long spacer that places the aromatic ring far away from the backbone, with the objective of investigating the copolymers' rheological behavior and surface and interfacial activities under various conditions such as polymer concentration, shear rate, temperature, and salinity. As expected, the block copolymers exhibit improved thickening properties attributed to intermolecular hydrophobic associations as the solution viscosity of the copolymers increases sharply with increasing polymer concentration. Additional evidence for intermolecular association is provided by the effect of NaCl, the presence of which substantially enhances the viscosity. An almost shear rate–independent viscosity (Newtonian plateau) is also exhibited at high shear rate and a typical non-Newtonian shear thinning behavior appears at low shear rates and high temperatures. Furthermore, the block copolymers exhibit high air–liquid surface and liquid–liquid interfacial activities as the surface and interfacial tensions decrease with increasing polymer concentration, indicating strong adsorption of the copolymer at the interface. The surface and interfacial tensions exhibited by the copolymers were found to be relatively insensitive to the concentration of salt (NaCl). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 467–476, 2001     

Thermosonication: a potential technique that influences the quality of grapefruit juice

Thermosonication (TS) is an emerging nonthermal processing technique used for the liquid food preservation and is employed to improve the quality and acceptability of grapefruit juice. In this study, fresh grapefruit juice samples were subjected to TS treatment in an ultrasonic cleaner with different processing variables, including temperature (20, 30, 40, 50 and 60 °C), frequency (28 kHz), power (70%, 420 W) and processing time (30 and 60 min) for bioactive compounds, inactivation of enzymes pectin methylesterase (PME), peroxidase (POD) and polyphenolase (PPO) and micro‐organisms (total plate count, yeasts and moulds). The micro‐organism activity was completely inactivated in the treatment (60 °C for 60 min). The TS treatment at 60 °C for 60 min exposure reduced PME, PPO and POD activity by 91%, 90% and 89%, respectively. Results indicate that the advantages of TS for grapefruit juice processing at low temperature could enhance the inactivation of enzymes and micro‐organisms and it can be used as a potential technique to obtain better results as compared to alone .     

Modelling and kinetic study of microwave assisted drying of ginger and onion with simultaneous extraction of bioactive compounds

Food Science and Biotechnology - Onion and ginger are rich sources of bioactive compounds which are lost during conventional drying process. The present study was designed to optimize the novel...     

Spatiotemporal Variation in the Continental US Streamflow in Association with Large-Scale Climate Signals Across Multiple Spectral Bands

Water Resources Management - The study attempts to investigate the significant spatiotemporal variations in the continental United States’ streamflow as a response to large-scale climate...     

Molecular Determinants for Protein Stabilization by Insertional Fusion to a Thermophilic Host Protein

A universal method that improves protein stability and evolution has thus far eluded discovery. Recently, however, studies have shown that insertional fusion to a protein chaperone stabilized various target proteins with minimal negative effects. The improved stability was derived from insertion into a hyperthermophilic protein, Pyrococcus furiosus maltodextrin‐binding protein (PfMBP), rather than from changes to the target protein sequence. In this report, by evaluating the thermodynamic and kinetic stability of various inserted β‐lactamase (BLA) homologues, we were able to examine the molecular determinants of stability realized by insertional fusion to PfMBP. Results indicated that enhanced stability and suppressed aggregation of BLA stemmed from enthalpic and entropic mechanisms. This report also suggests that insertional fusion to a stable protein scaffold has the potential to be a useful method for improving protein stability, as well as functional protein evolution.     

Mobilization of arsenic during one-year incubations of grey aquifer sands from Araihazar, Bangladesh

Elevated As concentrations in shallow groundwater pose a major health threat in Bangladesh and similarly affected countries, yet there is little consensus on the mechanism of As release to groundwater or how it might be influenced by human activities. In this study, the rate of As release was measured directly with incubations lasting 11 months, using sediment and groundwater collected simultaneously in Bangladesh and maintained under anaerobic conditions throughout the study. Groundwater and gray sediment were collected as diluted slurries between 5 and 38 m in depth, a range over which ambient groundwater As concentrations increased from 20 to 100 microg L(-1). Arsenic was released to groundwater in slurries from 5 and 12 m in depth at a relatively constant rate of 21 +/- 4 (2 sigma) and 23 +/- 6 microg As kg(-1) yr(-1), respectively. Amendment with a modest level of acetate increased the rate of As release only at 12 m (82 +/- 18 mirog kg(-1) yr(-1)). Although the groundwater As concentration was initially highest at 38 m depth, no release of As was observed. These results indicate that the spatial distribution of dissolved As in Bangladesh and local rates of release to groundwater are not necessarily linked. Iron release during the incubations did not occur concurrently with As release, providing further confirmation thatthe two processes are not directly coupled. Small periodic additions of oxygen suppressed the release of As from sediments at all three depths, which supports the notion that anoxia is a prerequisite for accumulation of As in Bangladesh groundwater.