Nuclear reaction rate in Debye-Hückel electrolytic plasma in stellar interiors

The transmission probability of charged particle reactions in a stellar plasma is examined by considering the effective potential between the interacting charges as having an exponential factor in the Coulomb term arising out of the spherical distribution of electrons with its uniform background of positive charges (Debye-Hückel electrolyte). The expression for the ratio of this transmission probability to that due to pure Coulomb field, called the enhancement factor, is then obtained. Thermonuclear reactions of astrophysical interest such as¹²C(α, γ)¹⁶O and¹⁶O(α, γ)²⁰ Ne are then considered. Our enhancement factor in the¹²C(α, γ)¹⁶O reaction rate is found to agree reasonably well with those calculated from the expression given by Alastuey and Jancovici.     

De novo asymmetric syntheses of D- and L-talose via an iterative dihydroxylation of dienoates

[reaction: see text] A short and highly efficient route to D- and L-talo-gamma-lactones has been developed. The key transformation was the sequential osmium-catalyzed bis-dihydroxylation reaction of substituted 2,4-dienoates. When the first dihydroxylation reaction is performed on (2Z,4E)-dienoates with use of the Sharpless AD-mix procedure, a regio- and enantioselective dihydroxylation resulted along with an in situ lactonization. A subsequent dihydroxylation, using OsO4/NMO in MeOH conditions, resulted in an exceedingly diastereo- and enantioselective synthesis of talo-gamma-lactone.     

Ab initio quantum chemical investigation of intramolecular magnetic interaction in some diradical derivatives of imino nitroxide and nitronyl nitroxide

The magnetic properties of the monoradicals 2-(4-phenyl acetylene)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidozolyl-oxyl (1) and 2-(4-phenyl acetylene)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl-3-oxide (2) and the diradicals 2,2'-(1,2-ethynediyldi-4,1-phenylene)bis[4,4,5,5-tetramethyl-4,5-dihydro-1H-imidozolyl-oxyl] (3), 2,2'-(1,2-ethynediyldi-4,1 3,1-phenylene)bis[4,4,5,5-tetramethyl-4,5-dihydro-1H-imidozolyl-oxyl] (4), and 2,2'-(1,2-ethynediyldi-4,1 3,1-phenylene)bis[4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl-3-oxide] (5) are investigated by ab initio quantum chemical methods. The rule of spin alternation in the unrestricted Hartree-Fock (UHF) method clearly shows that the radical sites are antiferromagnetically coupled in 3 and ferromagnetically coupled in 4 and 5, which is consistent with a previous experiment. The molecular geometries are optimized at Hartree-Fock levels. This is followed by single-point calculations using the density functional (UB3LYP) treatment and the multiconfigurational complete active space self-consistent field (CASSCF) methodology. Magnetic exchange coupling constants are determined from the broken-symmetry approach. The calculated J values, -3.60 cm(-1) for 3, 0.16 cm(-1) for 4, and 0.67 cm(-1) for 5, are in excellent agreement with the observed values. Because of the very large size of the diradicals 3-5, the CASSCF (10,10) calculations cannot yield realistic J values. Nevertheless, the CASSCF calculations support the antiferromagnetic nature of the magnetic coupling in 3 and the ferromagnetic nature of the coupling in 4 and 5. The existence of an intramolecular magnetic coupling in 3-5 is also confirmed through computations of the isotropic hyperfine coupling constants for monoradicals 1 and 2 as well as diradicals 3-5.     

Solvent effect on the photochemical properties of symmetrically substituted trans-3,3',5,5'-tetramethoxystilbene

Photochemical properties of trans-3,3',5,5'-tetramethoxystilbene (TMST) have been studied in various polar solvents. The Stokes shift of trans-TMST was found to be increased with increasing solvent polarity. The fluorescence lifetime of trans-TMST experienced a large solvent effect changing from 2.3 ns in cyclohexane to 16.6 ns in acetonitrile. These results indicate that the excited singlet state of trans-TMST has a charge-transfer (CT) character. On the basis of the obtained results, the interior polar environment of a water-soluble TMST dendrimer is discussed.     

Bifurcations and chaos control in a discrete-time predator-prey system of Leslie type

We investigate the dynamics of a discrete-time predator-prey system of Leslie type. We show algebraically that the system passes through a flip bifurcation and a Neimark-Sacker bifurcation in the interior of $\R^{2}_+$ using center manifold theorem and bifurcation theory. Numerical simulations are implimented not only to validate theoretical analysis but also exhibits chaotic behaviors, including phase portraits, period-11 orbits, invariant closed circle, and attracting chaotic sets. Furthermore, we compute Lyapunov exponents and fractal dimension numerically to justify the chaotic behaviors of the system. Finally, a state feedback control method is applied to stabilize the chaotic orbits at an unstable fixed point.     

Impact of farming awareness based roguing,insecticide spraying and optimal control on the dynamics of mosaic disease

Control interventions and farming knowledge are equally important for plant disease control. In this article, a mathematical model has been derived using saturated response functions (nonlinear infection rate) for studying the dynamics of mosaic disease with farming awareness based roguing (removal of infected plants) and insecticide spraying . It is assumed that the use of roguing and spraying depend on the level of awareness about the disease. The model possesses three equilibria namely the trivial, which is always unstable, the disease-free equilibrium which is stable if the basic reproduction number is below unity and the coexisting which may be stable or can exhibit Hopf-bifurcation under certain condition. Finally, we have opted an optimal control problem introducing three control parameters for determining the optimal level of roguing, spraying and cost regarding media awareness for cost-effective control of mosaic disease. Numerical simulations establish the main results suggesting that the awareness campaigns through radio, TV advertisement are important for eradication of the disease. Also, awareness campaign, roguing and spraying should be incorporated with optimal level for cost effective control of mosaic disease.

     

Dynamics of mosaic disease with roguing and delay in <Emphasis Type="Italic">Jatropha curcas</Emphasis> plantations

In this paper, we consider the multi-Galerkin and multi-collocation methods for solving the Urysohn integral equation with a smooth kernel, using Legendre polynomial basis functions. Superconvergence results for the approximate and iterated approximate solutions of the proposed methods are obtained in both infinity and \(L^2\)-norm. Numerical examples are presented to illustrate the theoretical results.     

Computational Homogenization of Piezoelectric Materials using FE2

Due to the growing interest in determining the macroscopic material response of inhomogeneous materials, computational methods are becoming increasingly concerned with the application of homogenization techniques. In this work, two-scale classical (first-order) homogenization of electro-mechanically coupled problems using a FE²-approach is discussed. We explicitly formulated the homogenized coefficients of the elastic, piezoelectric and dielectric tensors for small strain as well as the homogenized remanent strain and remanent polarization. The homogenization of the coupled problem is done using different representative volume elements (RVEs), which capture the microstructure of the inhomogeneous material, to represent the macro material response. Later this technique is used to determine the macroscopic and microscopic configurational forces on certain defects. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bioactive Abietane-Type Diterpenoid Glycosides from Leaves of Clerodendrum infortunatum (Lamiaceae)

In this study, two previously undescribed diterpenoids, (5R,10S,16R)-11,16,19-trihydroxy-12-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl-17(15→16),18(4→3)-diabeo-3,8,11,13-abietatetraene-7-one (1) and (5R,10S,16R)-11,16-dihydroxy-12-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl-17(15→16),18(4→3)-diabeo-4-carboxy-3,8,11,13-abietatetraene-7-one (2), and one known compound, the C₁₃-nor-isoprenoid glycoside byzantionoside B (3), were isolated from the leaves of Clerodendrum infortunatum L. (Lamiaceae). Structures were established based on spectroscopic and spectrometric data and by comparison with literature data. The three terpenoids, along with five phenylpropanoids: 6′-O-caffeoyl-12-glucopyranosyloxyjasmonic acid (4), jionoside C (5), jionoside D (6), brachynoside (7), and incanoside C (8), previously isolated from the same source, were tested for their in vitro antidiabetic (α-amylase and α-glucosidase), anticancer (Hs578T and MDA-MB-231), and anticholinesterase activities. In an in vitro test against carbohydrate digestion enzymes, compound 6 showed the most potent effect against mammalian α-amylase (IC₅₀ 3.4 ± 0.2 μM) compared to the reference standard acarbose (IC₅₀ 5.9 ± 0.1 μM). As yeast α-glucosidase inhibitors, compounds 1, 2, 5, and 6 displayed moderate inhibitory activities, ranging from 24.6 to 96.0 μM, compared to acarbose (IC₅₀ 665 ± 42 μM). All of the tested compounds demonstrated negligible anticholinesterase effects. In an anticancer test, compounds 3 and 5 exhibited moderate antiproliferative properties with IC₅₀ of 94.7 ± 1.3 and 85.3 ± 2.4 μM, respectively, against Hs578T cell, while the rest of the compounds did not show significant activity (IC₅₀ > 100 μM).     

Optical switching in a Ξ system: A comparative study on DROP and EIT

Liquid Lennard-Jones clusters with magic number of atoms N = 55, 147, 309, 561 and 923 were cooled down in Monte Carlo simulations until freezing. Structural properties of the clusters, including the radial dependence of atomic concentration/density and the local regular structure in arrangement of atoms, just before freezing were analysed. Existence of spherical layers in atomic density around the centre of mass of liquid LJ clusters was confirmed. Formation of layers is explained by central net forces acting on every cluster atom and leading to positioning an atom close to the cluster centre of mass. The strong layering in small clusters of N = 55 and 147 affects atomic diffusion in radial and tangential directions inside the cluster, leading to easier movement of atoms on the layer surface. Analysis of radial profiles of four types of structural units detected in liquid clusters reveals that icosahedral units are the most numerous and are located mainly near cluster surface of all clusters and also in the centre of small clusters.