Silicotungstic acid catalysed Claisen Schmidt condensation reaction: an efficient protocol for synthesis of 1,3-diaryl-2-propenones

An efficient and clean synthesis of 1,3-diaryl-2-propenones has been carried out by Claisen Schmidt condensation reaction of aryl methyl ketones with a series of aromatic aldehydes at room temperature in the presence of the catalyst silicotungstic acid (STA). This method provides an ecofriendly, chemoselective, efficient and green synthesis of 1,3-diaryl-2-propenones in excellent yields.     

Amelioration of H4[W12SiO40] by nanomagnetic heterogenization: For the synthesis of 1H–pyrazolo[1,2‐b]phthalazinedione derivatives

We conveniently coated silicotungstic acid (STA, H₄[W₁₂SiO₄₀]) on amino‐functionalized Si–magnetite nanoparticles, as surface functionalization of magnetic nanoparticles is an excellent way for green and efficient catalysis. The nanoparticles were structurally characterized using various techniques. The catalytic activity and recyclability of the STA–amine–Si–magnetite nanoparticles were probed through synthesis of 1H–pyrazolo[1,2‐b]phthalazinedione derivatives. The reaction proceeds smoothly to provide products in excellent yields and short reaction times. The catalyst could be readily recovered using a simple external magnet and reused several times without any significant loss in activity. Herein, we report a comparison of the activity of H₄[W₁₂SiO₄₀] as a homogeneous and heterogeneous catalyst, the latter being found to be more efficient. The findings offer effective methods for environmentally friendly synthesis of pyrazolo[1,2‐b]phthalazinedione derivatives.     

Essential oil yield and chemical composition changes during leaf ontogeny of palmarosa (Cymbopogon martinii var. motia)

Changes in leaf biomass yield, essential oil yield, and chemical composition were investigated during leaf ontogeny of palmarosa {Cymbopogon martinii (Roxb.) Wats. var. motia Burk., family Poaceae}. Eleven leaves representing different developmental stages, serially numbered from the apex to the base of the plant were utilized for the study. Leaf biomass yield increased up to the eighth leaf. Essential oil recovery increased up to the third leaf; thereafter it decreased. Minimum essential oil recovery was observed in the eleventh leaf. Essential oil yield/leaf increased up to the sixth leaf. Essential oil yield and concentrations of linalool, alpha-terpineol, geranyl isobutyrate and geraniol were relatively higher in the essential oils of mature, older leaves. Essential oil recovery, and percentages of myrcene, beta-caryophyllene, geranyl acetate, (E,Z) farnesol and geranyl hexanoate were higher in the essential oils of young, expanding leaves.     

Effects of ambient and humidity exposure on the MgB2 superconductor

Exposure effect of ambient (up to a period of 465 days) and humid atmosphere on stability and the physical properties of bulk samples of MgB₂ has been carried out based on ac-susceptibility and X-ray diffraction measurements performed at different times during the aging. The motivation of this study came from the device application potential of MgB₂ superconductor. It has been observed that on initial exposure to ambient for a period of about 2 months, the MgB₂ samples neither show any sign of phase decomposition nor any significant degradation of superconducting parameters. However, on further exposure to ambient for a period greater than 4 months duration, the samples progressively exhibited the partial conversion of MgB₂ phase into Mg-deficient phases, viz., MgB₆ and MgB₁₂ and also leading to formation of Mg(OH)₂ which is accompanied by decrease in the T_C and poor connectivity of the superconducting grains. When exposed to humid environment for a period of 30 days, a significant degradation was observed in the superconducting properties of MgB₂. In sharp contrast to the case of ambient exposure, the exposure of MgB₂ to humid atmosphere (for 30 days) did not result in any noticeable phase decomposition. A comparison of the magnetically inferred critical current density behavior before and after the humidity exposure of MgB₂ is also presented.     

Study of nano-scale diffusion in thin films and multilayers

It is shown that x-ray reflectivity and x-ray fluorescence under standing wave conditions can be used to study atomic diffusion with an accuracy of a fraction of a nanometer. Both the techniques can be made isotope selective by making use of nuclear resonance scattering from a Mössbauer active isotope. The techniques have been used to study self-diffusion of Fe in amorphous and nano-crystalline alloys of FeZr and FeN. The observed correlation of the activation energy E with pre-exponent factor D₀ confirms that in amorphous FeZr alloy diffusion takes place via collective motion of a group of atoms. Even in nanocrystalline alloys it is found that atomic diffusion occurs mainly through grain boundaries which are amorphous or highly disordered in nature.     

A representation of the characteristic function of a stable probability measure on certain TV spaces

In this paper, a Lévy-Khintchine type representation of the characteristic function of a K-regular stable probability measure on real locally convex topological vector spaces, satisfying certain conditions, is presented.     

Characterization of nucleobases in sea buckthorn leaves: An HPTLC approach

The present study aims to establish a high-performance thin layer chromatography (HPTLC)-based comparative analysis, directed toward characterization of nucleobases in aqueous and alcoholic extracts of sea buckthorn leaves from three different varieties: Hippophae salicifolia, Hippophae rhamnoides mongolica, and Hippophae rhamnoides turkestanica. The alcoholic and aqueous leaf extracts from these sea buckthorn varieties were prepared using accelerated solvent extraction technique. A novel HPTLC method for separating and identifying six nucleobases, namely, guanosine, guanine, cytosine, adenine, uracil, and thymine were adopted. HPTLC analysis indicated the presence of one or more of these nucleobases in a total of six leaf extracts evaluated, their quantities varying from 0.23 to 7.76?µg nucleobase per mg of extract. Though a typical trend could not be observed in the values obtained, the extracts were found to be considerably rich with respect to nucleobase contents. The results acquired from HPTLC were subsequently validated by hyphenation with mass spectrometry and also by applying chemometric tools in form of heat maps, hierarchical cluster dendrograms, and principal component analysis. The presence of nucleobases in the leaf extracts was confirmed by HPLC as well but HPTLC proved to be a better approach for characterization of nucleobases in plant extracts, than high performance liquid chromatography (HPLC).     

Uniform Comparison of Tails of (Non-Symmetric) Probability Measures and Their Symmetrized Counterparts with Applications

Let (, ) be a separable Banach space and let be a class of probability measures on , and let denote the symmetrization of . We provide two sufficient conditions (one in terms of certain quantiles and the other in terms of certain moments of relative to μ and , ) for the “uniform comparison” of the μ and measure of the complements of the closed balls of centered at zero, for every . As a corollary to these “tail comparison inequalities,” we show that three classical results (the Lévy-type Inequalities, the Kwapień-Contraction Inequality, and a part of the It?–Nisio Theorem) that are valid for the symmetric (but not for the general non-symmetric) independent -valued random vectors do indeed hold for the independent random vectors whose laws belong to any which satisfies one of the two noted conditions and which is closed under convolution. We further point out that these three results (respectively, the tail comparison inequalities) are valid for the centered log-concave, as well as, for the strictly α-stable (or the more general strictly (r, α) -semistable) α ≠ 1 random vectors (respectively, probability measures). We also present several examples which we believe form a valuable part of the paper.