Two minor diterpene glycosides from the leaves of Stevia rebaudiana

Two new new diterpene glycosides, 13-[(2-O-(6-O-beta-D-glucopyranosyl)-beta-D-glucopyranosyl-beta-D-glucopyranosyl)oxy] kaur-16-en-18-oic acid beta-D-glucopyranosyl ester (1) and 13-[(2-O-beta-D-glucopyranosyl-3-O-beta-D-fructofuranosyl-beta-D-glucopyranosyl)oxy] kaur-16-en-18-oic acid beta-D-glucopyranosyl ester (2) were isolated from the leaves of Stevia rebaudiana, along with the known steviol glycosides stevioside, rebaudiosides A-F and dulcoside A. The structures of the two new compounds were established on the basis of extensive 2D NMR (COSY, HSQC, and HMBC), MS and chemical studies.     

Dangling thiyl radical: stabilized in [PPh4]2[(bdt)W(VI)(O)(μ-S)2Cu(I)(SC6H4S•)

The synthesis, crystal structure, and spectroscopic characterization of [PPh(4)](2)[(bdt)W(O)(S(2))Cu(SC(6)H(4)S(?))] (3; bdt = benzenedithiolate) relevant to the active site of carbon monoxide dehydrogenase are presented. Curiously, in 3, the copper(I) benzenemonothiolate subcenter possesses a dangling thiyl radical that is stabilized by a disulfido-bridged oxo tungsten dithiolene core. The benzenedithiolate ligand, which is generally bidentate in nature, acts as a bidentate and also as a monodentate in 3. The formation of an unusual dangling thiyl radical has been magnetically and spectroscopically identified and has been supported by the density functional theory level of calculation.     

Kernel logistic regression using truncated Newton method

Kernel logistic regression (KLR) is a powerful nonlinear classifier. The combination of KLR and the truncated-regularized iteratively re-weighted least-squares (TR-IRLS) algorithm, has led to a powerful classification method using small-to-medium size data sets. This method (algorithm), is called truncated-regularized kernel logistic regression (TR-KLR). Compared to support vector machines (SVM) and TR-IRLS on twelve benchmark publicly available data sets, the proposed TR-KLR algorithm is as accurate as, and much faster than, SVM and more accurate than TR-IRLS. The TR-KLR algorithm also has the advantage of providing direct prediction probabilities.     

Embedding hypercubes into cylinders, snakes and caterpillars for minimizing wirelength

We consider the problem of embedding hypercubes into cylinders to minimize the wirelength. Further, we show that the edge isoperimetric problem solves the wirelength problem of regular graphs and, in particular, hypercubes into triangular snakes and caterpillars.     

Enhancement of dielectric constant in PVDF polymer using dendrite-shaped PbS nanostructures

Dendrite-shaped PbS has been successfully synthesized using hydrothermal method on a large scale. The formation of dendrite-shaped PbS was confirmed by scanning electron microscopy (SEM). A detailed study of variations in dielectric properties on frequency and temperature shows that composites of PVDF and dendrite-shaped PbS have significantly higher dielectric constant than PVDF/PbS nanoparticles (NP) nanocomposites due to low percolation threshold.     

Logical XOR gate response in a quantum interferometer: A spin dependent transport

We examine spin dependent transport in a quantum interferometer composed of magnetic atomic sites based on transfer matrix formalism. The interferometer, threaded by a magnetic flux ϕ, is symmetrically attached to two semi-infinite one-dimensional (1D) non-magnetic electrodes, namely, source and drain. A simple tight-binding model is used to describe the bridge system, and, here we address numerically the conductance-energy and current-voltage characteristics as functions of the interferometer-to-electrode coupling strength, magnetic flux and the orientation of local the magnetic moments associated with each atomic site. Quite interestingly it is observed that, for ϕ = ϕ ₀/2 (ϕ ₀ = ch/e, the elementary flux-quantum) a logical XOR gate like response is observed, depending on the orientation of the local magnetic moments associated with the magnetic atoms in the upper and lower arms of the interferometer, and it can be changed by an externally applied gate magnetic field. This aspect may be utilized in designing a spin based electronic logic gate.     

Photoacidic behavior of small phenolics in micellar media

The present work demonstrates the photophysical characterization of the interaction of two antibacterial and antimicrobial compounds, thymol and its isomer, carvacrol with different biomimetic micellar nanocavities having varying surface charge characteristics. These types of molecules are reported to be photoacids and this behavior is remarkably exhibited upon interaction with the macromolecular assemblies of micellar systems in the presence of inorganic and organic quencher molecules (silver nitrate and diethylamine) and is manifested through significant modulations of the bimolecular quenching constant values.     

Superconvergence results for linear second-kind Volterra integral equations

In this paper, Galerkin method is applied to approximate the solution of Volterra integral equations of second kind with a smooth kernel, using piecewise polynomial bases. We prove that the approximate solutions of the Galerkin method converge to the exact solution with the order \({\mathcal {O}}(h^{r}),\) whereas the iterated Galerkin solutions converge with the order \({\mathcal {O}}(h^{2r})\) in infinity norm, where h is the norm of the partition and r is the smoothness of the kernel. We also consider the multi-Galerkin method and its iterated version, and we prove that the iterated multi-Galerkin solution converges with the order \({\mathcal {O}}(h^{3r})\) in infinity norm. Numerical examples are given to illustrate the theoretical results.