On the computation of two-dimensional compressible flow fields by the modified local stability scheme

The modified local stability scheme is applied to several two-dimensional problems—blunt body flow, regular reflection of a shock and lambda shock. The resolution of the flow features obtained by the modified local stability scheme is found to be better than that achieved by the other first order schemes and almost identical to that achieved by the second order schemes incorporating artificial viscosity. The scheme is easy for coding, consumes moderate amount of computer storage and time. The scheme can be advantageously used in place of second order schemes.

Light- and cytokinin-induced changes in the levels of leucine and tyrosine isoaccepting tRNA species and modified nucleotide contents of total tRNA in cucumber seedlings

We have determined relative levels of chloroplast leucine and tyrosine isoaccepting tRNAs and modified nucleotide contents from total tRNAs isolated from dark-grown, light-grown, N6-isopentenyladenine (i6A)-treated dark-grown and i6A-treated light-grown cucumber seedlings. Significant increases in the relative amounts of tRNA(Leu)2 and tRNA(Leu)3 were observed in the i6A-treated dark-grown seedlings compared to dark-grown, light-grown and i6A-treated light-grown seedlings. On the other hand, i6A-treated light-grown seedlings tRNA(Tyr)1 increased to 85% of total tRNAs(Tyr) from about 9% in light-grown seedlings and tRNA(Tyr)2 decreased to 15% compared with 91% in light-grown seedlings. Analysis of modified nucleotide of total tRNAs indicated that pT, pI, pm1A, pm5C, pGm, pm1G, pm2G and pm7G contents were significantly higher in the total tRNA of i6A-treated dark-grown seedlings than those from untreated dark-grown seedlings. Illumination of 8-day-old dark-grown seedlings for 12 h increased the contents of pT, pI, pGm and pm1G when compared to 8-day-old dark-grown seedlings with extended growth for 12 h in dark. On the contrary, i6A had no stimulatory effect in the contents of modified nucleotide in the light-grown seedlings.

Microstrip square ring antenna for dual-band operation

This paper presents a generalized approach to design an electromagnetically coupled microstrip ring antenna for dual-band operation. By widening two opposite sides of a square ring antenna, its fractional bandwidth at the primary resonance mode can be increased significantly so that it may be used for practical applications. By attaching a stub to the inner edge of the side opposite to the feed arm, some of the losses in electrical length caused by widening can be regained. More importantly, this addition also alters the current distribution on the antenna and directs radiations at the second resonant frequency towards boresight. It has also been observed that for the dual frequency configurations studied, the ratio of the resonant frequencies (center dot r(2)center dot center dot r(1)) can range between 1.55 and 2.01. This shows flexibility in designing dual frequency antennas with a desired pair of resonant frequencies.

Tendency to promote ferroelectric distortion in Pr-modified PbTiO3

Structural, microstructural, and dielectric studies have been carried out on Pr-modified PbTiO3. A comparative analysis with La-modified PbTiO3 suggests that for chemical modification by same amount, the Pr-modified system has larger tetragonal strain and Curie point. No clear feature of relaxor ferroelectric state is observed for Pr concentration as high as x=0.35, suggesting that Pr modification is less effective, as compared to La-modification, in inducing a relaxor ferroelectric state. Results suggest that inspite of increased chemical disorder, Pr modification partly tends to restore the ferroelectric distortion of the lattice through partial occupancy of the Pr4+ ions on the Ti4+ sites.

Observation of persistent photoconductivity in flower shaped PbS dendrite structures

We report the observation of persistent photoconductivity (PPC) in flower shaped PbS dendrites grown by the hydrothermal method. Potential fluctuations, due to the presence of various confinement regimes in the branches of dendrites, and surface traps, are likely responsible for the PPC observed here. We also observed photocurrent quenching and decreased dark current in the PPC below 40 K, due to the presence of a metastable state, whereas positive PPC was observed in the temperature region 40-220 K. Dark conductivity measurements, time constant parameters obtained from the stretched exponential fittings of PPC, also showed the metastable state related transition around 50 K.

Serum bilirubin concentration is modified by UGT1A1 Haplotypes and influences risk of type-2 diabetes in the Norfolk Island Genetic Isolate

Background Located in the Pacific Ocean between Australia and New Zealand, the unique population isolate of Norfolk Island has been shown to exhibit increased prevalence of metabolic disorders (type-2 diabetes, cardiovascular disease) compared to mainland Australia. We investigated this well-established genetic isolate, utilising its unique genomic structure to increase the ability to detect related genetic markers. A pedigree-based genome-wide association study of 16 routinely collected blood-based clinical traits in 382 Norfolk Island individuals was performed. Results A striking association peak was located at chromosome 2q37.1 for both total bilirubin and direct bilirubin, with 29 SNPs reaching statistical significance (P < 1.84 × 10−7). Strong linkage disequilibrium was observed across a 200 kb region spanning the UDP-glucuronosyltransferase family, including UGT1A1, an enzyme known to metabolise bilirubin. Given the epidemiological literature suggesting negative association between CVD-risk and serum bilirubin we further explored potential associations using stepwise multivariate regression, revealing significant association between direct bilirubin concentration and type-2 diabetes risk. In the Norfolk Island cohort increased direct bilirubin was associated with a 28 % reduction in type-2 diabetes risk (OR: 0.72, 95 % CI: 0.57-0.91, P = 0.005). When adjusted for genotypic effects the overall model was validated, with the adjusted model predicting a 30 % reduction in type-2 diabetes risk with increasing direct bilirubin concentrations (OR: 0.70, 95 % CI: 0.53-0.89, P = 0.0001). Conclusions In summary, a pedigree-based GWAS of blood-based clinical traits in the Norfolk Island population has identified variants within the UDPGT family directly associated with serum bilirubin levels, which is in turn implicated with reduced risk of developing type-2 diabetes within this population.

Automated inspection of aircraft parts using a modified ICP algorithm

The application of computer-aided inspection integrated with the coordinate measuring machine and laser scanners to inspect manufactured aircraft parts using robust registration of two-point datasets is a subject of active research in computational metrology. This paper presents a novel approach to automated inspection by matching shapes based on the modified iterative closest point (ICP) method to define a criterion for the acceptance or rejection of a part. This procedure improves upon existing methods by doing away with the following, viz., the need for constructing either a tessellated or smooth representation of the inspected part and requirements for an a priori knowledge of approximate registration and correspondence between the points representing the computer-aided design datasets and the part to be inspected. In addition, this procedure establishes a better measure for error between the two matched datasets. The use of localized region-based triangulation is proposed for tracking the error. The approach described improves the convergence of the ICP technique with a dramatic decrease in computational effort. Experimental results obtained by implementing this proposed approach using both synthetic and practical data show that the present method is efficient and robust. This method thereby validates the algorithm, and the examples demonstrate its potential to be used in engineering applications.

Differences in the levels of aminoacylation and contents of modified nucleotides between total tRNAs from N2- and NH4+-grown Azospirillum lipoferum cells

Total tRNAs isolated from N2- and NH4(+)-grown Azospirillum lipoferum cells were compared with respect to amino acid acceptance, isoacceptor tRNA species levels and extent of nucleotide modifications. Amino-acylation of these two tRNA preparations with ten different amino acids indicated differences in the relative acceptor activities. Comparison of aminoacyl-tRNA patterns by RPC-5 column chromatography revealed no qualitative differences in the elution profiles. However, quantitative differences in the relative amounts of some isoacceptors were observed. These results indicate that alterations of relative amounts of functional tRNA species occur to match cellular requirements of the bacterial cells using N2 or NH4+ as nitrogen source. In addition, the content of modified nucleotides in total tRNAs of N2- and NH4(+)-grown cells was determined. In the NH4(+)-grown cells, content of most of the modified nucleotides decreased significantly. Based upon these results, the relationship of chargeability of tRNAs to base modifications is discussed.

Improved photovoltaic performance of dye-sensitized solar cells with modified self-assembling highly ordered mesoporous TiO 2 photoanodes

Strategies for improving the photovoltaic performance of dye-sensitized solar cells (DSSCs) are proposed by modifying highly transparent and highly ordered multilayer mesoporous TiO 2 photoanodes through nitrogen-doping and top-coating with a light-scattering layer. The mesoporous TiO 2 photoanodes were fabricated by an evaporation-induced self-assembly method. In regard to the modification methods, the light-scattering layer as a top-coating was proved to be superior to nitrogen-doping in enhancing not only the power conversion efficiency but also the fill factor of DSSCs. The optimized bifunctional photoanode consisted of a 30-layer mesoporous TiO 2 thin film (4.15 μm) and a Degussa P25 light-scattering top-layer (4 μm), which gives rise to a ∼200% higher cell efficiency than for unmodified cells and a fill factor of 0.72. These advantages are attributed to its higher dye adsorption, better light scattering, and faster photon-electron transport. Such a photoanode configuration provides an efficient way to enhance the energy conversion efficiency of DSSCs.

Convective heat-transfer rate distributions over a missile shaped body flying at hypersonic speeds

Experiments are carried out with air as the test gas to obtain the surface convective heating rate on a missile shaped body flying at hypersonic speeds. The effect of fins on the surface heating rates of missile frustum is also investigated. The tests are performed in a hypersonic shock tunnel at stagnation enthalpy of 2 MJ/kg and zero degree angle of attack. The experiments are conducted at flow Mach number of 5.75 and 8 with an effective test time of 1 ms. The measured stagnation-point heat-transfer data compares well with the theoretical value estimated using Fay and Riddell expression. The measured heat-transfer rate with fin configuration is slightly higher than that of model without fin. The normalized values of experimentally measured heat transfer rate and Stanton number compare well with the numerically estimated results. (C) 2009 Elsevier Inc. All rights reserved.

Nafion and modified-Nafion membranes for polymer electrolyte fuel cells: An overview

Polymer electrolyte fuel cells (PEFCs) employ membrane electrolytes for proton transport during the cell reaction. The membrane forms a key component of the PEFC and its performance is controlled by several physical parameters, viz. water up-take, ion-exchange capacity, proton conductivity and humidity. The article presents an overview on Nafion membranes highlighting their merits and demerits with efforts on modified-Nafion membranes.

Design considerations and economics of different shaped surface aeration tanks

This paper deals with the design considerations of surface aeration tanks on two basic issues of oxygen transfer coefficient and power requirements for the surface aeration system. Earlier developed simulation equations for simulating the oxygen transfer coefficient with theoretical power per unit volume have been verified by conducting experiments in geometrically similar but differently shaped and sized square tanks, rectangular tanks of length to width ratio (L/W) of 1.5 and 2 as well as circular tanks. Based on the experimental investigations, new simulation criteria to simulate actual power per unit volume have been proposed. Based on such design considerations, it has been demonstrated that it is economical (in terms of energy saving) to use smaller tanks rather than using a bigger tank to aerate the same volume of water for any shape of tanks. Among the various shapes studied, it has been found that circular tanks are more energy efficient than any other shape.

DMT of Multi-hop Cooperative Networks-Part II: Layered and Multi-Antenna Networks

We consider single-source, single-sink (ss-ss) multi-hop relay networks, with slow-fading Rayleigh links. This two part paper aims at giving explicit protocols and codes to achieve the optimal diversity-multiplexing tradeoff (DMT) of two classes of multi-hop networks: K-parallel-path (KPP) networks and Layered networks. While single-antenna KPP networks were the focus of the first part, we consider layered and multi-antenna networks in this second part. We prove that a linear DMT between the maximum diversity d(max). and the maximum multiplexing gain of 1 is achievable for single-antenna fully-connected layered networks under the half-duplex constraint. This is shown to be equal to the optimal DMT if the number of relaying layers is less than 4. For the multiple-antenna case, we provide an achievable DMT, which is significantly better than known lower bounds for half duplex networks. Along the way, we compute the DMT of parallel MIMO channels in terms of the DMT of the component channel. For arbitrary ss-ss single-antenna directed acyclic networks with full-duplex relays, we prove that a linear tradeoff between maximum diversity and maximum multiplexing gain is achievable using an amplify-and-forward (AF) protocol. Explicit short-block-length codes are provided for all the proposed protocols. Two key implications of the results in the two-part paper are that the half-duplex constraint does not necessarily entail rate loss by a factor of two as previously believed and that simple AN protocols are often sufficient to attain the best possible DMT.