Variation of long periodicity in blends of styrene butadiene,styrene copolymer/polyaniline using small angle X-ray scattering data

Small angle X-ray scattering data have been recorded for the blends of styrene butadiene, styrene copolymer/polyaniline using the beamline of the LNLS (Laboratorio Nacional de Luz sincroton-Campinas, Brazil). Employing one-dimensional Hosemann’s paracrystalline model, we have simulated the meridional reflections of these blends in order to compute the long periodicity and hence to find the variation with concentrations of the blends. Within the region of available experimental data we observe that there is a linear relationship between long periodicity and concentration of blends. These parameters are compared with physical measurements like tensile strength to find the structure-property relation in these blends.      

Fibrillar aggregation in cotton cellulose subjected to multiple swelling treatments with alkali

The role of aqueous alkali solutions as swelling agents of cotton cellulose has been studied by various workers and these reagents have been invariably considered to cause lattice disorder in cellulose. The effect of multiple swelling treatments on the cotton cellulose structure has not been studied hitherto. The present study on cotton demonstrates that is the concentration of the swelling agents and the conditions at the time of treatment which determine the resultant order in the final product. The resultant lattice order so attained is shown to be far in excess of any observed in either native or regenerated celluloses or even their hydrolyzed products, with complete retention of their fibrous form. X-ray diffraction and electron microscopy data show conclusively that fibrillar “aggregation” or their “dispersion” can be effectively controlled and are the results of the soda cellulose complexes which form upon alkali treatments. The role of water vis-á-vis the formation of cellulose II is extensively discussed. Studies on sorption and tensile properties of the treated samples lend support to the phenomenon of fibrillar aggregation in cellulosic fibers.     

Microwave synthesis of 1-aryl-1H-pyrazole-5-amines

A microwave-mediated synthesis of 1H-pyrazole-5-amines utilizing 1?M HCl at 150?°C was developed in order to provide products in a matter of minutes with minimal purification. Most reactions are complete in only 10?min and can be isolated via a simple filtration without the need for further purification by column chromatography or recrystallization. This method tolerates a range of functional groups and can be performed on milligram to gram scales.     

Autofluorescence of oral tissue for optical pathology in oral malignancy

Pulsed laser-induced-fluorescence studies of pathologically certified oral tissues are carried out at different excitations and time delays. Among the several excitations used, 325 nm produced noticeably different spectral profile for normal and malignant tissues. Extensive curve analysis was carried out in order to understand changes in biochemical composition of tissue based on spectral profiles. Curve resolution and principal component analysis (PCA) show that the fluorescence intensity changes from normal to malignant tissue samples are not completely explained in terms of simple collagen and NAD(P)H intensity changes. The spectra require at least five components to be fully accounted for. Several discrimination methodologies based on PCA and intensity differences between different emission peaks (resultant peaks of curve analysis) were also evaluated. The results obtained indicate PCA using Mahalanobis distance and spectral residual as discrimination parameters provides best discrimination and can be used for matching unknown samples to standard calibration sets. Intensity ratio of bound NAD(P)H to collagen seems to be more suitable for discrimination between normal and malignant oral tissue, compared to ratio of collagen to total intensity of all the other components together.     

Total Synthesis of Myceliothermophins C,D, and E

The total synthesis of cytotoxic polyketides myceliothermophins E ( 1 ), C ( 2 ), and D ( 3 ) through a cascade‐based cyclization to form the trans‐fused decalin system is described. The convergent synthesis delivered all three natural products through late‐stage divergence and facilitated unambiguous C21 structural assignments for 2 and 3 through X‐ray crystallographic analysis, which revealed an interesting dimeric structure between its enantiomeric forms.     

Progressive addition of GO to TiO2 nanowires for remarkable changes in photochemical hydrogen production

Addition of 2D GO to the TiO₂ nanowires brings about progressive changes in the optical properties and photochemical hydrogen production. The composition with progressive addition of GO played a dramatic role in making the material blue shift. The blue shift may happen due to transition from O²⁻ anti-bonding orbital to the Ti⁴⁺ lowest empty orbital and also the process of band shifting towards lower wavelength is attributed to quantum confinement effect which occurs due to the transformation of bulk titanate to nanostructure titanate. In this article, we present the results of TiO₂ nanowires and its rGO composites. TiO₂ with 30 mg rGO nanocomposite exhibits good UV-light induced hydrogen production unlike bare TiO₂. Current studies explain how rGO addition can be employed for better hydrogen production.

     

Persistence probabilities in centered,stationary, Gaussian processes in discrete time

Lower bounds for persistence probabilities of stationary Gaussian processes in discrete time are obtained under various conditions on the spectral measure of the process. Examples are given to show that the persistence probability can decay faster than exponentially. It is shown that if the spectral measure is not singular, then the exponent in the persistence probability cannot grow faster than quadratically. An example that appears (from numerical evidence) to achieve this lower bound is presented.