Pressureless reaction sintering of yttrium aluminium garnet (YAG) from powder precursor in the hydroxyhydrogel form

Pressureless reaction sintering of YAG was carried out by using a precursor powder in the hydroxyhydrogel form synthesized by flash polycondensation technique. Reactive silica additive was used to modify Al-O-Y network where Si⁴⁺ was incorporated in the solvated form. The sintering experiments were carried out with the processed powder up to 1650 °C under ambient ambience. Densification indicated effective sintering with well-formed microstructure. Phase identification by XRD indicated only YAG in the sintered specimen.     

Peptide Induced Crystallization of Calcium Carbonate on Wrinkle Patterned Substrate: Implications for Chitin Formation in Molluscs

We here present the nucleation and growth of calcium carbonate under the influence of synthetic peptides on topographically patterned poly(dimethylsiloxane) (PDMS) substrates, which have a controlled density of defects between the wrinkles. Experiments with two lysine-rich peptides derived from the extracellular conserved domain E22 of the mollusc chitin synthase Ar-CS1, AKKKKKAS (AS8) and EEKKKKKES (ES9) on these substrates showed their influence on the calcium carbonate morphology. A transition from polycrystalline composites to single crystalline phases was achieved with the peptide AS8 by changing the pH of the buffer solution. We analyzed three different pH values as previous experiments showed that E22 interacts with aragonite biominerals more strongly at pH 7.75 than at pH 9.0. At any given pH, crystals appeared in characteristic morphologies only on wrinkled substrates, and did not occur on the flat, wrinkle-free PDMS substrate. These results suggest that these wrinkled substrates could be useful for controlling the morphologies of other mineral/peptide and mineral/protein composites. In nature, these templates are formed enzymatically by glycosyltransferases containing pH-sensitive epitopes, similar to the peptides investigated here. Our in vitro test systems may be useful to gain understanding of the formation of distinct 3D morphologies in mollusc shells in response to local pH shifts during the mineralization of organic templates.     

Biorefineries from the perspective of sustainability: Feedstocks, products, and processes

Today, sustainability is the buzzword in the developmental parlance. This has brought the issue of availability and utilization of energy into sharp focus. There is an urgent need to find viable alternative to fossils, mainly petroleum. It not only provides the major share of our present energy needs but also feeds the organic chemicals industry with vital raw materials. Among many alternative energy sources being explored biomass is the only one that has the potential for such dual application. Comprehensive yet judicious exploitation of biomass is, therefore crucial. The emerging concept of biorefineries is important in this context which advocates multiprocess and multiproduct biomass based industries. But everything green need not always be clean and sustainable as populism often makes it to be. Needless to say, the choices of feedstocks, processes as well as product mix are many. There is a need to critically examine them. This paper presents a status review of biorefineries from the stand point of feedstocks, products and processes.     

Design Formula for Sierpinski Gasket Pre-Fractal Planar-Monopole Antennas [Antenna Designer's Notebook]

An improved formula for determination of resonant frequencies in different Sierpinski modes is developed from other existing formulas, using physical and analytical reasoning. The superiority of the proposed formula over other existing formulas is verified by comparing the results with those from experiments and simulations. A design formula for the side length of the generating Sierpinski triangle is also proposed by algebraic rearrangement of the formula for the resonant frequency.     

ZnO nanocones: Solvothermal synthesis and photoluminescence properties

Ellipsoidal and prism shaped ZnO nanocrystals with hexagonal cross-sections have been synthesized by a simple solvothermal process. The ellipsoidal ZnO nanocrystals possessed a unique hexagonal cross-section having two sharp pointed ends and a flattened central part. The well faceted prism like particles resembled hexagonal cones in their shape. Dimensions of the nanocrystals increased systematically with the increase in the synthesis temperature. The synthesized nanocrystals exhibited near band edge UV emission centered at ～400 nm. An additional defect related green emission band at ～500 nm was observed from the samples synthesized at higher temperatures.     

Identification of a Novel Five-Gene Signature as a Prognostic and Diagnostic Biomarker in Colorectal Cancers

Colorectal cancer (CRC) is one of the leading causes of cancer-related mortality worldwide. The current TNM (Tumor, Node, and Metastasis) classification approach is suboptimal in determining the prognosis of CRC patients. The prognosis for CRC is affected by a variety of features that are present at the initial diagnosis. Herein, we performed a systematic exploration and established a novel five-panel gene signature as a prognostic and early diagnosis biomarker after performing differential gene expression analyses in five independent in silico CRCs cohort and independently validating it in one clinical cohort, using immunohistochemistry. Four genes (BDNF, PTGS2, GSK3B, and CTNNB1) were significantly upregulated and one gene (HPGD) was significantly downregulated in primary tumor tissues compared with adjacent normal tissues throughout all the five in silico datasets. The univariate CoxPH analysis yielded a five-gene signature that accurately predicted overall survival (OS) and recurrence-free survival (RFS) in the in silico training (AUC = 0.73 and 0.69, respectively) and one independent in silico validation cohort (AUC = 0.69 and 0.74, respectively). This five-gene signature demonstrated significant associations with poor OS in independent clinical validation cohorts of colon cancer (CC) patients (AUC = 0.82). Intriguingly, a risk stratification model comprising of the five-gene signature together with TNM stage and gender status achieved an even superior AUC of 0.89 in the clinical cohorts. On the other hand, the circulating mRNA expression of the upregulated four-gene signature achieved a robust AUC = 0.83 with high sensitivity and specificity as a diagnosis marker in plasma from CRC patients. We have identified a novel, five-gene signature as an independent predictor of OS, which in combination with TNM stage and gender offers an easy-to-translate and facile assay for the personalized risk-assessment in CRC patients.     

Modified Airy function method for the analysis of tunnelingproblems in optical waveguides and quantum-well structures

A simple method for the analysis of tunneling through an arbitrary one-dimensional potential barrier, based on the modified Airy function approach, is presented. Truncated step-linear, step-exponential, parabolic, and quartic potential barriers are considered. The results are compared with those obtained by the conventional WKBJ, modified WKBJ, and matrix methods. The effect of the truncation level on the tunneling coefficient is investigated. The tunneling coefficient is sensitive to the truncation level. For the step-linear potential, the tunneling coefficient is a monotonically decreasing function of the truncation level, while for the parabolic potential, it oscillates before saturating to a constant value     

Design of Sierpinski gasket fractal microstrip antenna using real coded genetic algorithm

A novel technique for designing Sierpinski gasket fractal microstrip antenna is proposed. In the absence of any available closed-form formulae, this scheme uses an evolutionary method, based on real coded genetic algorithm (RCGA) in conjunction with electromagnetic simulations. This method determines the side-length and the fractal iteration number of the antenna, for operation at 4.56, 7.51 and 11.78 GHz. The design simulation of the antenna uses two different RCGA implementation strategies. The Adewuya mating with Gaussian mutation is the basis for the first one, whereas the second one uses heuristic crossover in conjunction with non-uniform mutation. Converging results, from these two strategies to those obtained from experiments on fabricated prototypes, validate the proposed method.     

Effect of axial refractive-index dip on zero total dispersion wavelength in single-mode fibres

The effect of the axial refractive-index dip, which is a characteristic of c.v.d. high-silica optical fibres, on the dispersion characteristics of single-mode fibres is studied. In particular, the effect of a Gaussian dip on zero total dispersion wavelength ?0 in a single-mode fibre is investigated. The dip is found, in general, to shift ?0 to a wavelength shorter than that in the absence of the dip for the same fibre.