Low-Temperature Preparation and Magnetic Properties of Nanoparticle Iron-Doped Anatase TiO2

Nanoparticle iron (Fe)-doped anatase TiO₂ was prepared at a low temperature (100°C) and at room pressure. The product was obtained from a boiling solution of an amorphous TiO₂ gel mixed with an iron nitrate solution and stirred for 5 h. An amorphous TiO₂ gel was obtained from TiCl₃ solution and NH₄OH as a precipitating agent stirred at room temperature for 1 day. EDAX results on different selected areas of as-prepared Fe-doped anatase TiO₂ revealed a homogeneous composition of 17 at.% Fe. Fe–TiO₂ has a superparamagnetic state with a possibility of antiferromagnetism at low temperatures. Fe seems to substitute titanium ions without any evidence of other impurities such as Fe nanoclusters or Fe-based oxides.     

Purification and Biochemical Characterization of Lipase from <Emphasis Type="Italic">Ficus carica</Emphasis> Latex of Tunisian East Coast Zidi Variety

Lipase from Ficus carica L. (Moraceae) latex of the Zidi variety was purified 80.5-fold with 68.5 % recovery using silica gel chromatography. The molecular weight of the enzyme was 29 kDa as determined by SDS-PAGE. High lipolytic activity was found in the crude extract during the fruit ripening process. The activity of purified lipase (ZL) seemed to depend strongly on chain length and showed a preference to long chain triacylglycerols. Indeed, ZL specific activity was 370.3 UI/mg using olive oil as a substrate at 45 °C and pH 5.5. In contrast, activity towards short chain triacylglycerols (tributyrin) was 12-fold lower (32 UI/mg). The enzyme was quite stable in the pH range 4–8, and thermally stable at 60 °C displaying t _1/2 about 90 min using olive oil as a substrate. The values of K _m app and V _m were found to be 14.3 mM and 294.1 μmol/min/mg, respectively. ZL activity was strongly reduced by Fe²⁺, Mg²⁺ and Zn²⁺, while significantly increased by Ca²⁺ and Cu²⁺. The enzyme was stimulated by sodium dodecyl sulfate, and Tween-80, while Triton X-100 and EDTA had a slight inhibitory effect. No Effect was observed in addition of PMSF and iodoacetic acid.     

Enhanced fructose oxidase activity in a galactose oxidase variant

Galactose oxidase (GO; EC 1.1.3.9) catalyses the oxidation of a wide range of primary alcohols including mono-, oligo- and polysaccharides. High-resolution structures have been determined for GO, but no structural information is available for the enzyme with bound substrate or inhibitor. Previously, computer-aided docking experiments have been used to develop a plausible model for interactions between GO and the D-galactose substrate. Residues implicated in such interactions include Arg330, Gln406, Phe464, Phe194 and Trp290. In the present study we describe an improved expression system for recombinant GO in the methylotrophic yeast Pichia pastoris. We use this system to express variant proteins mutated at Arg330 and Phe464 to explore the substrate binding model. We also demonstrate that the Arg330 variants display greater fructose oxidase activity than does wild-type GO.     

Electrochemical behavior of copper-nickel alloys in acidic chloride solutions

The electrochemical behavior of Cu-Ni alloys in acidic chloride medium was investigated. Commercial Cu-Ni alloys were investigated using potentiodynamic techniques, complemented by electrochemical impedance spectroscopy. The influence of alloy composition, chloride ion concentration and immersion time on the electrochemical response of the alloys was analyzed. Results of present investigations with pure metals (Cu and Ni) are also considered in this paper for the sake of comparison. Potentiodynamic measurements reveal that the increase in nickel content decreases the corrosion rate of the alloy and when the nickel content exceeds 30%, an increase in the corrosion rate was recorded. Also, the corrosion current density increases with increasing the concentration of chloride ions up to 0.6 M.The experimental impedance data were fitted to an equivalent circuit model representing the electrode/electrolyte interface. The relevance of the proposed model to the corrosion/passivation phenomena occurring at the electrode/solution interface was discussed.     

Lightning protection — A proven system

A unique integrated lightning protection system is described, which uses an electrode assembly enhanced by electron sources. The electrode is coupled to a high voltage coaxial grounding conductor to offer hitherto unattainable performance. Note: The system discussed in this paper is registered under U.S. Patent 3919956.     

Simulation and experimental study for an inverted trickle solar still

An experimental study for an inverted trickle solar still was performed. The still was basically composed of an inclined absorber plate painted black on the top. Saline water flowed at the backside of the plate and was kept attached to the plate. The water flow rate was kept low so that its temperature was raised to produce vapor. Condensation took place in another compartment where a heat exchanger was placed to provide heat recovery. The still was tested using brackish water of 6000 ppm salinity during the month of November at 47° and 32° tilt angles. The condensate obtained was 2.8 and 2 L/d at the above angles, respectively. This represents an 18% increase in this kind of output over previous work, which is due to reduction in the salinity of feed water. However, the intermediate header production, which is saline water of reduced salinity (3600 ppm), was also reduced by 13%. A computer simulation program was developed to predict the performance of the still.     

Inhibitory action of purified hydroxytyrosol from stored olive mill waste on intestinal disaccharidases and lipase activities and pancreatic toxicity in diabetic rats

This study was established that after 3 months storage, olive mill waste (OMW) was enriched with hydroxytyrosol (HT) (2,652 mg/L) and contained only phenolic monomers. It also showed that HT supplementation to surviving diabetic rats decreases considerably intestinal maltase, lactase, sucrose, and lipase activities by 49, 31, 42, and 40%, respectively. In addition, HT enhanced the superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities by 330, 170, and 301%, respectively and reduced gluthation (GSH) level by 79% in pancreas compared to diabetic rats. Moreover, a significant decrease in the thiobarbituric acid reactive substances (TBARs) level and lactate dehydrogenase (LDH) activity in diabetic rats pancreas by 34 and 49% respectively after administration of HT. In addition, HT improved plasma triglyceride and cholesterol levels in diabetic rats by lowering low density lipoprotein (LDL)-cholesterol and triglycerides (TG) by 27 and 53%, respectively and increasing high density lipoprotein (HDL)-cholesterol content by 72%. These properties of HT are interesting regarding its use as therapeutic agent in biotechnological applications, especially in developing anti-diabetic and hypocholesterolemic drugs.     

Nanostructure fabrication on germanium and silicon by nanocoining imprint technique

Germanium (Ge) and silicon (Si) material response to indentation with a nanostructured die is investigated. A diamond die attached to a high speed actuator previously used to create large arrays of nanofeatures on metallic surfaces was used to create nanofeatures on Ge and Si samples. The pressure induced transformation of Ge and Si from a diamond cubic brittle phase to a more ductile beta-tin metallic phase due to the nanofeatures on the die was investigated. Results using the dynamic nanocoining method showed chip-like deformation around the individual nanofeatures indicative of the beta-tin phase transformation at the nanofeature level. Micro-Raman measurements confirmed the metallic transition from evidence including metastable and amorphous phases after indentation. Indents created using a common linear indentation method exhibited similar behavior. The Si nanofeature deformation was compared to electroless (EL) nickel and the deformation differed as dictated by the mechanism of material flow. Although not observed in Si, fracture occurred in some Ge indents at higher loads as a result of the lower fracture toughness compared to Si.     

Chitosan: A new route for increasing the efficiency of stannate/phosphate flame retardants on cotton

Sodium stannate/phosphate is an ideal eco-friendly flame retardant agent for cotton fabric. Development of this technique is an essential way to overcome some of its disadvantages such as the harsh feeling as a result of using high concentration of sodium stannate. Chitosan is added in the phosphorylation bath as a nitrogen source and to facilitate the phosphorylation process. Incorporation of 1% chitosan could decrease the sodium stannate concentration to the one-third of the amount that is used in the conventional method. Increasing the stannate concentration in the finishing bath from 10 to 30% could enhance the flame retardancy of the cotton fabric. Thermogravimetric analysis of the treated cotton fabric shows an increase in the residual percent of the fabric and decrease in both thermal degradation onset point (TDOP) and maximum degradation rate point as a function of stannate concentration. Increasing diammonium hydrogen phosphate (DAHP) from 2 to 10% in the finishing bath shows an increase in the residue at 500°C to 39.24%. Phosphorus and nitrogen percentages show an increase in their values till reaches to 1.39 and 1.72, respectively. The effect of curing temperature and time, chitosan concentration, and the sequence of treatment are studied in detail.     

Location-aware downlink and uplink power control and throughput optimization in cellular cognitive radio networks

In this paper, we consider throughput maximization in cognitive radio systems with proper power control. In particular, we incorporate location-awareness into the power control design and maximize the average throughput of the cognitive system. As we shall show, the proposed approach effectively utilizes the “spatial opportunity” to maximize the system throughput, which clearly outperforms traditional power control methods. Further, the proposed approach still exhibits significant throughput gain even considering imperfect position information, with appropriate robust design modifications.