Size and morphology-controlled synthesis of mesoporous hydroxyapatite nanocrystals by microwave-assisted hydrothermal method

We report the rapid microwave-assisted hydrothermal synthesis of mesoporous hydroxyapatite (HAp) nanocrystals with controlled size, morphology, and surface area using various organic modifiers as regulators. The products were analyzed for their crystalline nature, phase purity, morphology, particle size and pore size distribution. Results indicated that ascorbic acid, cetyltrimethyl ammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) play an important role to obtain needle like, rod like and fiber like mesoporous HAp nanocrystals with different specific surface area by controlling growth habit of HAp along c-axis. In addition, the prepared samples were B-type carbonated HAp similar to bone minerals. Therefore, the present approach can be a promising way to obtain precursor for making tissue engineering scaffolds, drug/protein delivery carriers and bone fillers with tunable characteristics.     

Enantioselectivity of recombinant Rhizomucor miehei lipase in the ring opening of oxazolin-5(4H)-ones

Enantioselectivity of enzyme catalysis is often rationalizedvia active site models. These models are constructed on thebasis of comparing the enantiomeric excess of product observedin a series of reactions which are conducted with a range ofhomologous substrates, typically carrying various side chainsubstitutions. Surprisingly the practical application of thesesimple but informative `pocket size' models has been rarelytested in genetic engineering experiments. In this paper wereport the construction, purification and enantioselectivityof two recombinant Rhizomucor miehei lipases which were designedto check the validity of such a model in reactions of ring openingof oxazolin-5(4H)-ones.     

Field enhancement factor and field emission from a hemi-ellipsoidal metallic needle

We present an exact solution for the electrostatic field between a metallic hemi-ellipsoidal needle on a plate (as a cathode) and a flat anode. The basic idea is to replace the cathode by a linearly charged thread in a uniform electric field and to use a set of “image” charges to reproduce the anode. We calculate the field enhancement factor on the needle surface and ponderomotive force acting on the needle. Using the Fowler–Nordheim theory we obtain an exact analytical formula for the total current.     

Numerical study of the effect of the doping profile on the threshold voltage of narrow-channel MOS transistor

A two-dimensional MOS process and device simulator, called IMPEDANCE, is used to study the influence of various doping profiles of stopper and channel implantations on the threshold voltage of narrow-channel MOS transistor (made with LOCOS isolation technology). For enhancement-mode transistors without channel implantation the lateral spread of the stopper implantation is the main factor for the threshold voltage increase with decreasing channel width. However the increase of the channel implantation dose reduces the dependence of the threshold voltage on the width especially at higher ion energies. In case of depletion-mode transistors the dependence of the threshold voltage on width is stronger owing to: (1) the existence of a lateral p-n junction between the channel and the stopper region and (2) the weaker gate control of the channel carriers.     

Ascorbic Acid-Assisted Eco-friendly Synthesis of NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanoparticles as an Anode Material for High-Performance Lithium-Ion Batteries

We have synthesized NiCo₂O₄ nanoparticles (NCO NPs) using an ascorbic acid-assisted co-precipitation method for the first time. When NCO NPs are used as an anode material for lithium-ion batteries, the cell exhibits superior lithium storage properties, such as high capacity (700 mA h g^?1 after 300 cycles at 200 mA g^?1), excellent rate capabilities (applied current density range 100–1200 mA g^?1), and impressive cycling stability (at 1200 mA g^?1 up to 650 cycles). The enhanced electrochemical properties of NCO NPs are due to the nanometer dimensions which not only offers a smooth charge-transport pathway and short diffusion paths of the lithium ions but also adequate spaces for volume expansion during Li storage. Hence, this eco-friendly synthesis approach will provide a new strategy for the synthesis of various nanostructured metal oxide compounds, for energy conversion and storage systems applications.     

Digital Fluid Technologies for the Steel Industry

Digital fluid systems are controlled solely by on-off valves, in contrast to analogue fluid systems which use continuously adjustable valves. Many digital fluid systems have been in practical use for some decades. The steel industry relies on several fluid technologies. Apart from the handling of the liquid steel, several other fluid processes exist to fulfill indispensable functions; examples include cooling, motion control, torch cutting, descaling, and lubricating. Many of these processes need better control concerning precision, dynamics, resource demand, reliability, and environmental impact or must offer additional functionalities for use in factories of the future. In several cases digital fluid systems are the better solutions. In this paper this is demonstrated by four examples, ranging from proven simple solutions and concepts going currently into industrial application to promising concepts for the future.     

Conductivity of highly sulfonated polyphenylene sulfide in the powder form as a function of temperature and humidity

Block-copolymers with highly sulfonated ionomer blocks are considered as leading candidates for low-humidity high-temperature Polymer Electrolyte Fuel Cell membranes. We present a new approach that allows for faster measurement of conductivity of powdered ionomers in a wide range of temperature and humidity with a single 10–30 mg sample. Our method is exemplified by a case study of polyphenylenesufide with a degree of sulfonation 0.70. This material shows 0.12 S/cm conductivity at 127 °C and 50% relative humidity. At higher temperatures and lower humidities, this polymer undergoes irreversible cross-linking. Further routes to improving conductivity, chemical and mechanical properties of the polymer are discussed.     

Incipient motion of individual particles in horizontal particle-fluid systems: B. Theoretical analysis

This paper presents a theoretical analysis of the force and moment balance during incipient motion of a single particle. The analysis showed that large particles start their motion by rolling for spherical particles and by sliding for non-spherical particles. It also showed that fine spherical or near spherical powders start their motion by rolling. The theoretical analysis shown that the incipient motion velocity of individual particles for all fluid, system and particle properties might be presented as power relationships between the Reynolds and Archimedes numbers.     

Sounding Out Pharmaceutical Processes

High-resolution ultrasonic spectroscopy is a novel technique with enormous potential for analysis of a wide range of samples and processes. This technique is based on precision measurements of velocity and attenuation of acoustical waves at high frequencies propagating through materials. It allows fast at/on line measurements analysis of formulation consistency (composition, structure) of raw materials, ingredients and intermediates, process impurity analysis, particle sizing, batch to batch variation, stability assessment etc in pharmaceutical industry. The technology can be used for static fingerprint measurements or for dynamic analysis of systems. Optical transparency is not required as ultrasonic waves propagate through opaque samples. The analysis is fast and non-destructive. High-resolution ultrasonic spectrometers were developed, patented and brought to the market by Ultrasonic Scientific Ltd. and recognised with various international awards. These instruments require small sample volumes, down to 0.03 ml, and give excellent resolution. They can be used for the analysis of composition, aggregation, particle sizing, gelation, micellisation, crystallisation, sedimentation, enzymatic activity, conformational transitions in polymers, biopolymer-ligand binding and antigen-antibody interactions, etc. This article describes main features of High-Resolution Ultrasonic Spectroscopy and area of applications of new high-resolution HR-US series of ultrasonic spectrometers. Several applications are illustrated including the monitoring of denaturation and aggregation of proteins in antibody solution, the measurements of the particle size in emulsions, precipitation in synthetic blood substitutes and crystallisation