Terpenoids—XXV Structure of saussurea lactone

Saussurea lactone is identical with the product of pyrolysis of dihydrocostunolide. On cyclisation in the presence of p-nitrobenzoic acid followed by hydrogenation it gives santanolide C. Hence structure (V) is assigned to saussurea lactone.     

Theoretical study of the flowfield inside a hydrocyclone for higher Reynolds numbers

The axi-symmetric turbulent boundary layers formed on the conical surface and under the roof of different hydrocyclones have been studied for higher Reynolds numbers. Calculating the total flux through the boundary layers it has been found that the mathematical model for the flowfield, presented in a previous paper [2] for the 1/7th power law velocity distribution, holds even for higher Reynolds numbers and for different cyclones with vortex finder diameters greater than that of apex opening. Theoretical results agree well with previous experimental findings.A part of this work was performed in the Mining Engineering Department of Delft University of Technology, The Netherlands.     

Quasi-one dimensional graphite ribbon structures in the presence of a magnetic field and the on-site Coulomb correlation at half-filling

We have presented the role of the Coulomb interaction (U) and the magnetic field [(B)\vec]\vec{B} on the ground state properties of the quasi-one dimensional graphite ribbon structures at half-filling. Mean field Hartree-Fock Approximation is used to study the systems. To understand the boundary effects in graphite structures, we have compared the results of these systems with those of the square lattice ribbon structures. Studying the density of states, the Drude weight and the charge gap, we have drawn the U – B phase diagrams for the zigzag and the armchair graphite ribbons.     

Femtosecond study of partially folded states of cytochrome C by solvation dynamics

Using femtosecond time-resolved fluorescence spectroscopy, it is shown that the solvation dynamics in the two partially folded states (IS' and IS' ') of a protein, cytochrome C, are very different. In the case of IS' (formed by the addition of 2 mM sodium dodecyl sulfate, SDS) almost the entire dynamic solvent shift of coumarin 153 (C153) is captured in a picosecond setup and the contribution of the ultrafast component (0.5 ps) is very small (5%). Solvation dynamics of IS' ' (formed by 2 mM SDS and 5 M urea) displays a major component (47%) of 1.3 ps. This indicates that the structure of IS' ' is much more open and exposed compared to that of IS'. The difference in the dynamics of IS' and IS' ' is attributed to differences in their structure, particularly near the heme region, and the presence of urea in IS' '.     

A wavelet cross-spectral analysis of solar–ENSO–rainfall connections in the Indian monsoons

The possible connections between the El Nino-Southern Oscillation (ENSO) phenomenon and Indian monsoon rainfall have been widely discussed in the meteorological literature. We show strong statistical evidence here for connections of ENSO with solar activity. This is particularly evident in a comparison between the two contrasting test periods of 1878–1913 and 1933–1964, representing three complete cycles of lowest and highest solar activity respectively since 1850. Wavelet statistical analysis reveals that the link between solar activity and ENSO is generally stronger than that between ENSO and rainfall but only slightly weaker than that between solar activity and rainfall. Over the two test periods an increase in solar activity is associated with a decrease in ENSO indices and an increase in the monsoon rainfall in the 8–16 y period band. In the 2–7 y period band the effects vary with region. The net effect of solar processes on rainfall thus appears to be the result of counteracting or cooperating influences on shorter (about 5–6 y) and longer (about 11–12 y) time scales, the latter on the whole dominating over the former. The present analysis thus suggests that the influence of solar processes on Indian rainfall operates in part indirectly through ENSO, but on more than one time scale.     

Clusters of bound particles in the derivative δ-function Bose gas

In this paper we discuss a novel procedure for constructing clusters of bound particles in the case of a quantum integrable derivative δ-function Bose gas in one dimension. It is shown that clusters of bound particles can be constructed for this Bose gas for some special values of the coupling constant, by taking the quasi-momenta associated with the corresponding Bethe state to be equidistant points on a single circle in the complex momentum plane. We also establish a connection between these special values of the coupling constant and some fractions belonging to the Farey sequences in number theory. This connection leads to a classification of the clusters of bound particles associated with the derivative δ-function Bose gas and allows us to study various properties of these clusters like their size and their stability under the variation of the coupling constant.     

Heat transfer in boundary layer stagnation-point flow towards a shrinking sheet with non-uniform heat flux

In this paper, the effect of non-uniform heat flux on heat transfer in boundary layer stagnation-point flow over a shrinking sheet is studied. The variable boundary heat fluxes are considered of two types: direct power-law variation with the distance along the sheet and inverse power-law variation with the distance. The governing partial differential equations (PDEs) are transformed into non linear self-similar ordinary differential equations (ODEs) by similarity transformations, and then those are solved using very efficient shooting method. The direct variation and inverse variation of heat flux along the sheet have completely different effects on the temperature distribution. Moreover, the heat transfer characteristics in the presence of non-uniform heat flux for several values of physical parameters are also found to be interesting.     

When almost Cohen–Macaulay algebras map into big Cohen–Macaulay modules

In this article, we show that almost Cohen–Macaulay algebras are solid. Moreover, we seek for the conditions when (a) an almost Cohen–Macaulay algebra is a phantom extension and (b) when it maps into a balanced big Cohen–Macaulay module.     

Spectroscopic ellipsometric characterization of TiAlN/TiAlON/Si3N4 tandem absorber for solar selective applications

Sputter deposited TiAlN/TiAlON/Si₃N₄ tandem absorber has been characterized by spectroscopic ellipsometry in the wavelength range of 450-1200 nm. Each layer of the tandem absorber viz., TiAlN, TiAlON and Si₃N₄ has been deposited separately on copper substrate (Cu) and ellipsometric measurements have been carried out on each of these layers. The measured ellipsometric spectra were fitted with theoretically simulated spectra and the sample structure and wavelength dispersion of optical constants of each layers have been determined. The ellipsometric measurements have also been carried out on the three-layer tandem absorber deposited on Cu substrate. By analyzing the ellipsometric data, depth profiling of the tandem absorber has been carried out using the derived optical constants of the individual layers.