Leucosceptrine--a novel sesterterpene with prolylendopeptidase inhibitory activity from Leucosceptrum canum

A novel sesterterpene, leucosceptrine, was isolated from the medicinal plant Leucosceptrum canum from Nepal. The structure was determined by single-crystal X-ray diffraction and spectroscopic techniques. The biosynthesis of leucosceptrine (1) is proposed here. Leucosceptrine (1) exhibited prolylendopeptidase inhibitory activity.     

Low-temperature synthesis of hexagonal barium ferrite (BaFe<Subscript>12</Subscript>O<Subscript>19</Subscript>) nanoparticles by annealing at 450 °C followed by quenching

Citrate precursor method has been used to obtain nanosized particles of barium hexaferrite at low temperatures. Samples were annealed at 450 °C for 3 and 5 h. Quenching of the third sample was done by taking the crucible out from the muffle furnace after annealing it for 5 h and putting it abruptly into an ice bath. The saturation magnetization has been found to be 4.36 and 0.04 emu g^?1 for the samples obtained upon annealing at 450 °C for 3 and 5 h, respectively, while that of the quenched sample has been found to be 4.61 emu g^?1. In case of the sample obtained after 5-h annealing, the squareness value was found to be maximum indicating significance in memory and switching applications. For the quenched and the 3-h annealing products, the magnetic data values are similar. Creation of spin disorders on the surface upon prolonged annealing, due to disappearance of oxygen ions and subsequent breakage of superexchange interactions between cations, has been undone upon quenching. The XRD and TEM data indicate that the particle size (9–17 nm) gets lower in case of the quenched samples. Photoluminescence study of the quenched sample furnished prominent peaks in UV, visible and near-IR regions under 200-nm excitation. The TG–DSC data were analysed for the kinetic parameters, activation energy (E), pre-exponential factor (A) using the Kissinger isoconversion and the Ozawa–Flynn–Wall methods for the first-step decomposition of the quenched sample.     

Semi-infinite medium with a cylindrical inclusion twisted by an annular die

The problem considered is that of torsion of an elastic half-space consisting of two materials which are separated by a cylindrical surface. It is assumed that there is perfect bonding at the common cylindrical surface. The torque is applied to the half-space through an annular rigid disc which is bonded to both materials. By use of integral transforms and the theory of dual integral equations the problem is reduced to that of solving a pair of simultaneous Fredholm integral equations of the second kind. These simultaneous integral equations are solved numerically. The numerical results obtained are exhibited graphically.Research for this paper was partially supported by the Natural Sciences and Engineering Research Council of Canada through NSERC Grant No. A4177.     

On the explosive instability in a three‐species food chain model with modified Holling type IV functional response

In earlier literature, a version of a classical three‐species food chain model, with modified Holling type IV functional response, is proposed. Results on the global boundedness of solutions to the model system under certain parametric restrictions are derived, and chaotic dynamics is shown. We prove that in fact the model possesses explosive instability, and solutions can explode/blow up in finite time, for certain initial conditions, even under the parametric restrictions of the literature. Furthermore, we derive the Hopf bifurcation criterion, route to chaos, and Turing bifurcation in case of the spatially explicit model. Lastly, we propose, analyze, and simulate a version of the model, incorporating gestation effect, via an appropriate time delay. The delayed model is shown to possess globally bounded solutions, for any initial condition. Copyright © 2017 John Wiley & Sons, Ltd.     

CuO micro plates from a 3D metallo-organic framework (MOF) of a binary copper(II) complex of N,N-bis(2-hydroxyethyl)glycine

The crystal structure of [Cu(Bic)₂] (1) (Bic⁻ = N,N-bis(2-hydroxyethyl)glycinate), was determined by single-crystal X-ray diffraction techniques. [Cu(Bic)₂]: monoclinic system, space group P21/n. In the complex, the copper atom is tetra coordinated by two oxygen atoms of the carboxylato groups and two nitrogen atoms of the bicinate ligand, forming a distorted square planar coordination geometry. The molecular structure of the complex in solution is the same as that of the crystalline state, as supported by ESR and electronic spectra in solution. The blue complex 1 on heating at ∼500 °C for 6 h results in the formation of black CuO (Tenorite) micro plates.     

Multi-Step Synthesis of Miltefosine: Integration of Flow Chemistry with Continuous Mechanochemistry

Herein we report for the first time, an advanced continuous flow synthesis of the blockbuster Leishmaniasis drug miltefosine from simple starting materials by a sequence involving four steps of chemical transformation including a continuous mechanochemical step. First three reaction steps were performed in simple tubular reactors in a telescopic mode, while in the last step the product precipitated from the 3^rd step was used for a continuous mechanochemical synthesis of miltefosine. When compared to a typical batch protocol that takes 15 h, miltefosine was obtained in 58 % overall yield in flow synthesis mode at the laboratory scale in a total residence time 34 min at synthesis rate of 10 g/hr, which is sufficient to treat 4800 patients per day.     

Synthesis and Novel Crystal Structure Analysis of Anthracene-Based Chalcone Derivatives

Abstract

Four novel anthracene-based chalcone derivatives, (E)-1-(anthracen-9-yl)-3-(4-nitrophenyl)prop-2-en-1-one 1, (E)-1-(anthracen-9-yl)-3-(3-chlorophenyl)prop-2-en-1-one 2, (E)-1-(anthracen-9-yl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one 3, and (E)-1-(anthracen-9-yl)-3-(pyridin-4-yl)prop-2-en-1-one four were synthesized and their structures were solved by single crystal X-ray diffraction methods. The anthracenyl chalcone 1 crystallizes in the centrosymmetric monoclinic P2₁/c space group. The crystal structure analysis shows that the molecules of one form two dimensional (2D) corrugated layer structure. The anthracenyl chalcone 2 crystallizes in the centrosymmetric triclinic P-1 space group and forms one dimensional (1D) tape like structure in the crystal. Compound 3 crystallizes in the centrosymmetric monoclinic P2₁/n space group. Anthracenyl chalcone 4 crystallizes in the centrosymmetric triclinic P-1 space group.     

Dynamical consequences of predator interference in a tri-trophic model food chain

A model food chain involving a specialist and a generalist predator is proposed and studied. One of the salient features of this model food chain is that it combines both the schemes (Volterra and Leslie) of modeling predator–prey interaction in one system in such a way that the demerits of these individual formulations are suppressed and the resulting model system represents a common unit of real world food webs. The stability analysis of the proposed model is carried out. The Hopf bifurcation conditions of the positive equilibrium point are established. Our numerical computations show that chaotic dynamics is sensitive to changes in values of parameters measuring attributes of either interacting populations or their environments. Two dimensional parameter scans suggest that the model food chain displays short-term recurrent chaos. This can be regarded as a plausible explanation for why it has been so difficult to detect deterministic chaos in natural populations.