The effects of urease immobilization on the transport characteristics and protein adsorption capacity of cellulose acetate based hemodialysis membranes

In this study, cellulose acetate (CA) based hemodialysis membranes were prepared by a dry phase inversion method and the influences of urease immobilization on the clearing performance and protein adsorption capacity of the membranes were investigated. Permeation experiments have shown that modification of CA membranes with urease immobilization not only enhanced the transport rate of urea but also increased the permeation coefficients of uric acid and creatinine by changing the structure of the membrane. Furthermore, the protein adsorption capacity of the CA membranes decreased. On the other hand, the mechanical strength of the modified CA membrane did not change significantly compared with that of the unmodified one. A mathematical model was derived to determine the rate of mass transfer of urea through modified CA membranes. Model predictions along with the experimental data suggest that urease immobilization can be used as an alternative method in preparing CA based hemodialysis membranes with improved transport characteristics and biocompatibility through reduced protein adsorption capacities.     

ASPHALTENE AND RESID PYROLYSIS: EFFECT OF REACTION ENVIRONMENT

Hondo and Maya vacuum resids and their isolated asphaltenes were pyrolyzed at 400, 425, and 450^°C (752, 797, 842^°F) for batch holding limes ranging from 20 to 180 minutes. Maltene, asphaltene, and coke product fractions were isolated by a solvent extraction sequence; gas yield was determined gravimetrically. Results were summarized in terms of a lumped reaction network. The variation of product yields, kinetics, and apparent activation energies with feedstock and asphaltene environment provided insight into asphaltene structure and thermal reaction pathways.     

Development of off‐flavour in non‐melting flesh peach genotypes

Studies performed to investigate the development of off‐flavour in some NMF peach genotypes revealed that there were certain chemical components that were consistently associated with the disorder. Generally there was a significant increase in total soluble phenolics, polyphenoloxidase (PPO) activity and ethanol with an increase in both the percentage of off‐flavoured fruit and the degree of off‐flavour with time in storage at 8 °C in NMF genotypes. Total soluble sugars and soluble solids decreased significantly during the storage period. These changes in chemical composition of NMF genotypes were not observed in MF and NMF genotypes that did not show off‐flavour development. Highly significant linear correlations were detected between off‐flavour development and soluble phenolics, PPO activity, ethanol, total soluble solids and soluble sugars in Fla 92‐21C and USDA 87P285, lines with the highest percentage of off‐flavoured fruit. Soluble phenolics, chlorogenic acid, PPO activity and ethanol were positively correlated but soluble sugars and soluble solids were negatively correlated with off‐flavour development. The accumulation of soluble phenolics and ethanol and the reduction in soluble solids and sugars appear to be associated with the development of off‐flavour in NMF peach genotypes. © 2000 Society of Chemical Industry     

Investigation of the adhesion of NbN coatings deposited by pulsed dc reactive magnetron sputtering using scratch tests

Scratch tests have been used to investigate the adhesion of niobium nitride (NbN) coatings that were deposited by pulsed dc reactive magnetron sputtering at target currents of 1.5, 2.5, and 3.5 A onto M2 tool steel and silicon wafer. The coating adhesion on each material substrate was investigated using a progressive load scratch tester (PLST) and a multi-pass scratch tester (MPST). Microhardness tests and scanning electron microscopy (SEM) were also used to examine the hardness and microstructure of the NbN coatings. These results have indicated that the structural, mechanical, and adhesion properties of the NbN coatings improve with increasing target currents. While performing PLST and MPST tests, the highest adhesion and lowest friction force were obtained for the coatings deposited at a target current of 3.5 A. In addition, the triboscobic behaviors that were observed from the MPST of the coatings indicated that the target currents affect the friction behavior of the coatings.     

Metal nanoparticle preparation within modifiable p(4-VP) microgels and their use in hydrogen production from NaBH4 hydrolysis

Composite poly(4-vinyl pyridine)-silica (p(4-VP)–Si) nanoparticles were synthesized, employing trimethoxy vinyl silane (TMVS) as silica forming agent using ethylene glycol dimethacrylate (EGDMA) as the cross-linker, and ammonium persulfate (APS) as the initiator in an oil-in-water micro emulsion system. Porous p(4-VP) nanoparticles were generated from p(4-VP)–Si by treatment with hydrofluoric acid (HF). The size of p(4-VP)-based particles ranged between 300 and 500 nm. The porous p(4-VP) particles have a surface area of 42.26 m²/g. We also report preparation of various metal nanoparticles, such as Co and Ni, inside bare p(4-VP), p(4-VP)–Si and porous p(4-VP) nanoparticles by absorption from the corresponding metal ions aqueous solution and then reduction with NaBH₄. Atomic Absorption Spectroscopy (AAS) was used to determine the metal particle content of the p(4-VP)-based nanoparticles. The hydrogen production rate of Co-containing p(4-VP) was found to be superior to Ni-containing p(4-VP) under the same conditions. Cobalt-containing p(4-VP)–Si and porous p(4-VP) microgel composites can generate hydrogen faster than Co-containing p(4-VP). Moreover, p(4-VP)-based microgels showed seven fold hydrogen production rate, and almost five fold turn over frequency (TOF) than p(AMPS) microgels in terms of catalytic performances reported earlier.     

An Android runtime security policy enforcement framework

Today, smart phone’s malwares are deceptive enough to spoof itself as a legal mobile application. The front-end service of Trojans is attractive enough to deceive mobile users. Mobile users download similar malwares without knowing their illegitimate background threat. Unlike other vendors, Android is an open-source mobile operating system, and hence, it lacks a dedicated team to analyze the application code and decide its trustworthiness. We propose an augmented framework for Android that monitors the dynamic behavior of application during its execution. Our proposed architecture called Security Enhanced Android Framework (seaf) validates the behavior of an application through its permissions exercising patterns. Based on the exercised permissions’ combination, the mobile user is intimated about the dangerous behavior of an application. We have implemented the proposed framework within Android software stack and ported it to device. Our initial investigation shows that our solution is practical enough to be used in the consumer market.