Synthesis of polymer microsphere-supported chiral pyrrolidine catalysts by precipitation polymerization and their application to asymmetric Michael addition reactions

Polymer microsphere-supported chiral pyrrolidine catalysts were successfully synthesized by a precipitation polymerization incorporating a methacrylate monomer bearing chiral N-Boc-pyrrolidine moiety, followed by removal of the N-Boc groups. The resulting polymeric catalysts were applied to the asymmetric Michael addition reactions of aldehydes with alkyl vinyl ketones. The effects of the comonomer, the molar ratios within the catalyst, the catalyst loading, the temperature, and the solvent on the catalytic performance were investigated in detail. The reactions were found to proceed smoothly in the absence of a solvent. A hydrophobic polystyrene-based chiral pyrrolidine catalyst exhibited high reactivity (up to 97% yield) and enantioselectivity (up to 95% ee) during these reactions. The catalyst could also be recovered and reused up to five times without significant loss of activity.     

Quality evaluation and quantification of cucurbitacin E in different cultivars of Cucumis sativus L. fruit by a validated high-performance thin-layer chromatography method

Cucumis sativus L. of the Cucurbitaceae family, commonly known as cucumber, is commercially cultivated worldwide. The major phytoconstituents present in the Cucurbitaceae family are different curcurbitacins, principally cucurbitacin E. The content of cucurbitacin E differs within the species or cultivars due to factors like genetic variation and geographical location. The present study reports a simple and rapid quantitative analysis of cucurbitacin E in 5 different C. sativus cultivars by a validated high-performance thin-layer chromatography (HPTLC) method. The mobile phase contained petroleum ether, ethyl acetate and formic acid in the ratio of 40:60:0.5 (V/V). Cucurbitacin E was analyzed densitometrically and the absorbance wavelength was 254 nm. The method showed R_F spot = 0.79 ± 0.06, corresponding to cucurbitacin E in various samples. The calibration curve of standard cucurbitacin E showed good linear relationship in the concentration range of 2‒10 µg/spot with a correlation coefficient (r) > 0.99. The HPTLC method was validated in terms of sensitivity, linearity, accuracy, precision, and specificity as per the International Conference on Harmonization (ICH) guidelines. The present study revealed that the content of cucurbitacin E differs among the C. sativus cultivars. This method may be beneficial for addressing the quality-related aspects of C. sativus for food and pharmaceutical preparation.

     

Analysing Hessence Intermediate and Logamediate Universe in Loop Quantum Cosmological Background

We have discussed here Hessence inflation in Loop Quantum Cosmological background. In this work, we have emphasized on late times, taking into account various slow-roll conditions. This model has been constructed taking intermediate and logamediate scale factors. In both cases the forms of hessence field, potential, number of e-folds, slow-roll parameters are manipulated by taking the dissipative co-efficient Γ =Γ₀, where Γ₀ > 0 is a constant, in accordance with second law of thermodynamics.     

Quasi-Spherical Gravitational Collapse in Any Dimension

We study the occurrence and nature of naked singularities for a dust model with non-zero cosmological constant in (n+2)-dimensional Szekeres space-times (which possess no Killing vectors) for n 2. We find that central shell-focusing singularities may be locally naked in higher dimensions but depend sensitively on the choice of initial data. In fact, the nature of the initial density determines the possibility of naked singularity in space-times with more than five dimensions. The results are similar to the collapse in spherically symmetric Tolman-Bondi-Lemaître space-times.     

Amide linkage in novel three-ring bent-core molecular assemblies: polar mesophases and importance of H-bonding

Here, we report the first examples of achiral unsymmetrical three-ring bent-shaped liquid crystals comprising amide and imine linkages with transverse substituents of methyl and chloro moieties on the central phenyl ring in the core, exhibiting polar banana phases. The extensive intra and inter molecular H-bonding induced novel banana mesomorphic phases. One-dimensional stacking in the mesomorphic phase as well as ferroelectric polar order promoted by intermolecular H-bonding of amide linkage is demonstrated. The compounds exhibit multifunctional properties viz., the enantiotropic liquid crystalline (LC) phase at ambient temperatures, electro-optical response, spontaneous polarisation, emission characteristics with large Stokes shift, and even charge distribution with large voltage holding ratio (VHR) values. The smectic type phase was confirmed by XRD studies and polar order was established by switching current and dielectric investigations. DFT studies revealed the importance of their suitability for display applications.     

An asymptotic treatment of the transient development of axisymmetric surface waves

A linearized theory is developed for the derivation of an asymptotic solution of the initial value problem of axisymmetric surface waves in an infinitely deep fluid produced by an arbitrary oscillating pressure distribution. An asymptotic treatment of the problem is presented in detail to obtain the solution for the surface elevation for sufficiently large time. Finally, the main prediction of this analysis for some particular pressure distributions of physical interest is exhibited.Nomenclature R, , Y cylindrical polar coordinates - frequency - g acceleration due to gravity - density of fluid - T time - (R, Y; T) velocity potential - E(R, T) vertical surface elevation - P(R, T) applied surface pressure - r, y nondimensional cylindrical polar coordinates, - p(r, t) nondimensional surface pressure - t nondimensional time, T - (r, y; t) nondimensional velocity potential, - (r, t) nondimensional vertical surface elevation, - (k) Hankel transform of a function p(r) with respect to r - I ₁ transient wave integral - I ₂ steady state wave integral     

Phi-pseudo-monotonicity and approximation-solvability of nonlinear equations

We generalize the results on the approximation-solvability of nonlinear functional equations to the case of Φ-pseudo-monotone mappings—a new and rather general class of mappings. An application is considered.     

Atmospheric-Pressure Plasma Reduction of Metal Cation-Containing Polymer Films to Produce Electrically Conductive Nanocomposites by an Electrodiffusion Mechanism

We describe an atmospheric-pressure plasma process for the reduction of metal cation-containing polymer films to form electrically conductive patterns. Thin films of poly(acrylic) acid (PAA) containing silver ions (Ag⁺) were prepared by mixing the polymer with silver nitrate (AgNO₃) in solution to produce a cross-linked precipitate, homogenizing, and depositing onto a substrate by doctor’s blade. Exposing the Ag–PAA films to a scanning microplasma resulted in reduction of the bulk dispersed Ag⁺ in a desired pattern at the film surface. The processed films were characterized by scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, and current–voltage measurements. The resistances of the patterned features were found to depend on the thickness of the films, the microplasma scan rate, residual solvent in the film, and electric field created between the microplasma and the substrate. Together these results show that the formation of conductive features occurs via an electrodiffusion process where Ag⁺ diffuses from the film bulk to the surface to be reduced by the microplasma.