Progress and prospects of group-III nitride semiconductors

We review recent progress in the group-III nitride and related materials, and electronic and optical devices based on them. Blue and UV (e.g. ultra violet) emitters and detectors, and high temperature/high power electronics which has long been coveted are beginning to be realized either in the laboratory or in the commercial arena, due in part to the breathtaking progress made in the last few years in the art and science of GaN, InN, AlN and their salloys. With brief references to the historical aspect of the relevant developments, this review concerns itself primarily with the current status of wide bandgap gallium nitride and related semiconductors from both the materials and devices points of view. Following a discussion of the structural properties of these materials, their electrical and optical properties are described in detail. The available data on metal contacts, the properties of which are indeed very conducive for the devices mentioned, from the points of view of ohmic contacts and Schottky barriers, are elaborated on. Recent progress on processing issues such as etching are reviewed. The review then embarks on an indash;depth discussion and analysis of field effect transistors, bipolar transistors, light emitting diodes, laser and photo detectors.     

Purification and renaturation of recombinant human lymphotoxin (tumour necrosis factor beta) expressed in Escherichia coli as inclusion bodies

High level expression of recombinant human tumour necrosis factor β (rh TNF-β) in Escherichia coli results in the formation of two portions of protein, namely soluble active protein and insoluble protein which is inactive and aggregates in the form of inclusion bodies (IBs). In this study, a procedure for purification and renaturation of rh TNF-β from inclusion bodies has been designed and verified experimentally with a product purity of more than 90% and a recovery of about 30%. The procedure includes washing of IBs with specific wash buffer (Triton X-100/EDTA/lysozyme/PMSF), their solubilization with 8 mol dm^?3 alkaline urea, purification with ion-exchange columns, refolding with renaturation buffer and finally concentration and desalination with an ultrafiltration membrane. The characteristics of the renatured protein were identical with those of purified protein from the soluble fraction as demonstrated by (1) SDS-PAGE, (2) cytotoxic activity on mouse L929 cells, (3) N-terminal amino acid sequence, and (4) gel filtration chromatography.     

Proposal for st-Routing Protocol

A routing protocol chooses one of the several paths (routes) from a source node to a destination node in the computer network, to send a packet of information. In this paper, we propose a new routing protocol, which we call st-routing protocol, based on st-numbering of a graph. The protocol fits well in noisy environments where robustness of routing using alternative paths is a major issue. The proposed routing protocol provides a systematic way to retry alternative paths without generating any duplicate packets. The protocol works for only those networks that can be represented by biconnected graphs.     

Simulating program disturb faults in flash memories using SPICE compatible electrical model

Electrical simulation is an important tool that enables designers to evaluate different design alternatives and assess their performance. In memory technology, these tools are used to study the performance of different cell structures and implementations. In this paper we use such simulations to study the impact of defects on the performance of flash memory bitcells. In particular, using a device level simulator, we develop a SPICE compatible model to simulate the operation of a 1T flash bitcell. We then describe a fault injection technique that can be used, in conjunction with the model, to simulate faulty cell behavior. The model is used to simulate different defects in the oxide layer of the flash core memory element. The impact of defects on bitcell behavior under disturb and normal operations is investigated and evaluated. The model is demonstrated to be valuable to evaluate the appropriateness of the logic tests and stress tests used to detect such defects in flash memories.     

基于不同爆轰产物的格尼速度估算新方法（英）

A new method for prediction of Gurney velocity of explosives is introduced in which energy output is correlated with the heat of detonation, the number of moles of gaseous products of detonation per gram of explosive and the average molecular weight of gaseous products. It is assumed that the CHNO explosive reacts to form products composed of N2 , CO, H2O, CO2, H2,O2 and C（s） as determined by the oxygen balance of the unreacted compound. Good agreement is obtained between measured and calculated values of Gurney velocity as compared to previous correlations which assumed the reaction products to consist of N2 , H2O, CO2 and either C（s） or O2.     

The sinuous antenna-A dual polarized feed for reflector-based searching systems

The sinuous antennas have a numerous applications in military and civil systems such as direction finding systems and reflector feeds due to their superior broadband characteristics and simultaneous polarization capability. In this paper, design, construction and measurements of planar sinuous antennas are investigated for 1–5 GHz frequency range. Feeding sections of this antenna are realized by using microstrip tapered baluns. We have determined the microstrip tapered balun dimensions using Ansoft HFSS-simulation program. The performances of the manufactured antenna are measured using HP vector network analyzer. Polarization patterns and return loss characteristics of the designed antenna that have been measured in anechoic chamber, are presented.     

Effect of carbon surface oxidation on platinum supported carbon particles on the performance of gas diffusion electrodes for the oxygen reduction reaction

The effect of carbon surface oxidation on platinum supported carbon particles (Pt/C) with nitric acid was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, polarization experiments and chronoamperometry. Cyclic voltammograms, polarization curves and electrochemical impedance spectra showed that the treated catalyst had much larger active surface area and higher ionic conductivity than the untreated catalyst, and provided enhanced performance for oxygen reduction. The formation of acidic groups was examined by IR spectra. The Pt/C surface oxidation had a large effect on the performance of a gas diffusion electrode for oxygen reduction reaction.     

Synthesis of poly(methyl methacrylate)/silica nanocomposite through emulsion polymerization using dimethylaminoethyl methacrylate

Polymer/Silica nanocomposite latex particles were prepared by emulsion polymerization of methyl methacrylate (MMA) with dimethylaminoethyl methacrylate (DM). The reaction was performed using a nonionic surfactant and in the presence of silica nanoparticles as the seed. The polymer‐coated silica nanoparticles with polymer content and number average particle sizes ranged from 32 to 93 wt % and 114–310 nm, respectively, were obtained depending on reaction conditions. Influences of some synthetic conditions such as MMA, DM, surfactant concentration, and the nature of initiator on the coating of the silica nanoparticles were studied. Electrostatic attraction between anionic surface of silica beads and cationic amino groups of DM is the main driving force for the formation of the nanocomposites. It was demonstrated that the ratio of DM/MMA is important factor in stability of the system. The particle size, polymer content, efficiency of the coating reaction, and morphology of resulted nanocomposite particles showed a dependence on the amount of the surfactant. Zeta potential measurements confirmed that the DM was located at the surface of the nanocomposites particles. Thermogravimeteric analysis indicated a relationship between the composition of polymer shell and polymer content of the nanocomposites. The nanocomposites were also characterized by FTIR and differential scanning calorimetry techniques. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008