Influence of thermal cycling treatment on the anneal hardening effect of Cu–10Zn Alloy

This paper reports the results of investigations on the influence of the so called thermal cycling treatment on the anneal hardening effect of the copper-based Cu–10 at.% Zn alloy. The quenched samples were subjected to cold rolling of 20, 40 and 60% in reduction, followed by annealing with and without thermocycling treatment below the recrystallization temperature. Anneal hardening effect was observed in both samples in the temperature range between 180 and 300 °C and was followed by an increase in the hardness and electrical conductivity. These investigations showed that the thermal cycling treatment some increased the intensity of anneal hardening effect.     

Mathematical model of gentamicin sulfate release from a bioactive textile material as a transdermal system under in vitro conditions

A mathematical model was developed to estimate the release of gentamicin sulfate from a bioactive textile material as a transdermal system for wound dressing. The gentamicin sulfate released from the antibiotic/chitosan hydrogel complexes was measured in vitro by the Franz diffusion cell technique. The diffusive transport of gentamicin sulfate through three connected compartments, that is, chitosan hydrogel, membrane, and solution, was considered by the formulation of a model based on Fick's second law. Initially, the total amount of gentamicin sulfate was placed within an already swollen chitosan hydrogel. The value of the diffusivity coefficient of the drug through the chitosan hydrogel was calculated for every initial amount of the active substance. For the initial concentration of gentamicin sulfate, which was lower than 2.81 × 10⁴ μg/mL, the diffusion coefficient was approximately constant. A higher amount of gentamicin sulfate in the hydrogel reduced its own transport as a consequence of an increase in the intensity of the interaction field between the molecules of gentamicin sulfate. The model provides the possibility of optimizing the process of drug release by ensuring a compromise between a higher value of the diffusivity coefficient and a desirable amount of gentamicin sulfate and a constant concentration within the solution over 48 h. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Highly bright and photostable cyanine dye-doped silica nanoparticles for optical imaging: Photophysical characterization and cell tests

Spherical silica nanoparticles containing fluorescent trimethine indocyanine dyes (λ_abs = 547 nm, λ_em = 570 nm) were prepared using a water-in-oil microemulsion method. The nanoparticles were of 50 nm diameter and were almost monodispersed in aqueous solution at pH 5.5. Entrapment of dye molecules in the silica matrix stabilised photoemission over several hours of continuous irradiation. The photoemission intensity of the indocyanine was increased 13-fold over that recorded in solution. As each nanoparticle contained 110 dye molecules, the photoemission brightness of each particle was enhanced by three orders of magnitude. The fluorescent nanoparticles have been tested as imaging tools in in vitro tests. As an example of non-macrophagic cells, a highly differentiated neuronal cell line (GT1-7) was used and the results showed that the prepared nanoparticles can be incorporated into these cells with no apparent toxicity for up to three days.     

Hydrodynemics of a cocurrent upflow liquid–liquid reciprocating plate reactor for homogeneously base-catalyzed methanolysis of vegetable oils

Hydrodynamics of a continuous cocurrent two-phase upflow reciprocating plate reactor (RPR) for homogeneously base-catalyzed methanolysis of sunflower oil was studied. Here, methanol constituted the dispersed phase and sunflower oil was the continuous phase. The measurements were performed in both the non-reactive (methanol–sunflower oil) and reactive (sunflower oil–methanol–KOH) systems. The main goal was to define the effects of the vibration intensity and the important reaction operating conditions on the pressure fluctuation at the reactor bottom, the power consumption, the dispersed phase holdup, the Sauter-mean drop diameter and the specific interfacial area. The power consumption under batch, single- and two-phase flow was proved to depend on the vibration intensity. The Sauter-mean drop diameter was found to depend on the specific power consumption in accordance with the turbulent model due to the turbulent energy dissipation in well-mixed regions around perforated plates. The simplified correlation of Kumar and Hartland could be used for estimating the Sauter-mean drop diameter. The energy dissipation due to reciprocating plate motion and the superficial dispersed phase velocity affected the dispersed phase holdup and the specific interfacial area. The present results are crucial for designing RPRs for application in continuous base-catalyzed methanolysis of vegetable oils.     

Probing enzyme promiscuity of SGNH hydrolases

Several hydrolases of the SGNH superfamily, including the lipase SrLip from Streptomyces rimosus (Q93MW7), the acyl-CoA thioesterase I TesA from Pseudomonas aeruginosa (Q9HZY8) and the two lipolytic enzymes EstA (from P. aeruginosa, O33407) and EstP (from Pseudomonas putida, Q88QS0), were examined for promiscuity. These enzymes were tested against four chemically different classes of a total of 34 substrates known to be hydrolysed by esterases, thioesterases, lipases, phospholipases, Tweenases and proteases. Furthermore, they were also analysed with respect to their amino acid sequences and structural homology, and their phylogenetic relationship was determined. The Pseudomonas esterases EstA and EstP each have an N-terminal domain with catalytic activity together with a C-terminal autotransporter domain, and so the hybrid enzymes EstA(N)-EstP(C) and EstP(N)-EstA(C) were constructed by swapping the corresponding N- and C-terminal domains, and their hydrolytic activities were compared. Interestingly, substrate specificity and kinetic measurements indicated a significant influence of the autotransporter domains on the catalytic activities of these enzymes in solution. TesA, EstA and EstP were shown to function as esterases with different affinities and catalytic efficacies towards p-nitrophenyl butyrate. Of all the enzymes tested, only SrLip revealed lipase, phospholipase, esterase, thioesterase and Tweenase activities.     

Absolute Determination of the Gelling Point of Gelatin under Quasi‐thermodynamic Equilibrium

Thermodynamic studies on phase transformation of biopolymers in solution are useful to understand their nature and to evaluate their technological potentials. Thermodynamic studies should be conducted avoiding time‐related phenomena. This condition is not easily achieved in hydrophilic biopolymers. In this contribution, the simultaneous effects of pH, salt concentration, and cooling rate (Cr) on the folding from random coil to triple helical collagen‐like structures of gelatin were systematically studied. The phase transformation temperature at the absolute invariant condition of Cr = 0 °C/min (T_T^Cr=0) is introduced as a conceptual parameter to study phase transformations in biopolymers under quasi‐thermodynamic equilibrium and avoiding interferences coming from time‐related phenomena. Experimental phase diagrams obtained at different Cr are presented. The T_T^Cr=0 compared with pH and T_T^Cr=0 compared with [NaCl] diagram allowed to explore the transformation process at Cr = 0 °C/min. The results were explained by electrostatic interactions between the biopolymers and its solvation milieu.     

Optimisation of puffing naked barley

The expansion of volume (the puffing index) of naked barley was investigated at various operating conditions of the puffing process. The purpose was to optimise the manufacture of expanded grains of the naked barley cultivars that have exceptional nutritional value for humans. The influence of the following parameters on the puffing index was investigated: the mass and the moisture content of the charge of the puffing barrel, pressure and temperature during the puffing process, the cultivar of barley, pre-processing of the grain (grinding and polishing), adding water into the barrel and the sensory quality of the product.

A regression equation was established for the calculation of the puffing index as a function of the operating parameters. The puffing index is influenced especially by the operating temperature and pressure. There was no influence found of mass of the charge, the cultivar of barley, the degree of grinding of barley, washing of the grains and adding water on the puffing index. The puffing index is not the sole indicator of the quality of the expanded product. It is necessary to take into account the sensory evaluation. A quality expanded naked barley was obtained at the operating temperature of 550 °C and pressure from 0.9 to 1.0 MPa with the moisture content of the charge around 16.5%.