Isoflavonoid glycosides from the rhizomes of Iris germanica

Four isoflavone glycosides were isolated from the rhizomes of Iris germanica. Compounds 1 and 2 are new, while compounds 3 and 4 are known isoflavone glycosides. These compounds were identified as iriskashmirianin 4'-O-beta-D-glucoside (1), nigricin 4'-O-beta-D-glucoside (2), irilone 4'-O-beta-D-glucoside (3) and iridin (4). Their structures were determined with the help of spectroscopic methods.     

Separation of radioindium (N.C.A.) from neutron irradiated tin and cadmium on hydrated antimony pentoxide

Hydrated antimony pentoxide (HAP) as an absorbent for column operation has been prepared by hydrolysis of SbCl₅ with deionized water. Sorption behavior of Sn, Cd, Sb and In was studied on HAP in HCl medium. Radiochemical separation of no-carrier added^113mIn from¹¹³Sn/¹²⁵Sb and^115mIn from¹¹⁵Cd wa achieved over a HAPO column. The separated products were of high radionuclidic purity.     

Crown ether molecular complexes with urea and thiourea

Crystalline complexes of urea and thiourea with crown ethers, have been prepared, viz., 18-crown-6 (18C6), benzo-18-crown-6 (B18C6), dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6 (DC 18C6) and dibenzo-24-crown-8 (DB24C8). While the complexes of the large ring size crown ether, DB24C8, have high ether to (thio)urea ratios, the stoichiometry of the others lies between one molecule of crown ether and from one to six molecules of (thio)urea. An IR spectral study of the urea and thiourea complexes showed that the behavior of thiourea in these complexes is clearly different from that of urea, indicating the role of sulphur in the interaction of thiourea with crown ethers. The urea and thiourea complexes were classified according to their stoichiometries and their IR spectral behavior into three classes for which credible structures were proposed.     

Finite difference technique for solving obstacle problems

In this paper, we use the variational inequality theory coupled with finite difference technique to obtain an approximate solution for a class of obstacle problems in elasticity, like those describing the equilibrium configuration of an elastic string stretched over an elastic obstacle. The variational inequality formulation is used to discuss the problem of uniqueness and existence of the solution of the obstacle problems.     

Absorption intensities for the 4-0 through 7-0 overtone bands of HCl

We have measured the absorption intesities for a number of rotation-vibration lines in the 4-0 through 7-0 overtone bands of HCl utilizing a Fourier transform spectrometer and a 409.6 m path length White cell. Individual line strengths, band strengths, dipole matrix elements, and Herman-Wallis factors are presented.     

Localization of elastic waves in heterogeneous media with off-diagonal disorder and long-range correlations

Using the Martin-Siggia-Rose method, we study propagation of acoustic waves in strongly heterogeneous media which are characterized by a broad distribution of the elastic constants. Gaussian-white distributed elastic constants, as well as those with long-range correlations with nondecaying power-law correlation functions, are considered. The study is motivated in part by a recent discovery that the elastic moduli of rock at large length scales may be characterized by long-range power-law correlation functions. Depending on the disorder, the renormalization group (RG) flows exhibit a transition to localized regime in any dimension. We have numerically checked the RG results using the transfer-matrix method and direct numerical simulations for one- and two-dimensional systems, respectively.     

Scanning tunneling microscopy and surface simulation of zinc-blende GaN(001) intrinsic 4x reconstruction: linear gallium tetramers?

Scanning tunneling microscopy images confirm electron diffraction studies that the zinc-blende GaN(001)-4x reconstruction consists of rows aligned along [110] with a spacing along [110] of 4a. Dual-bias imaging shows a 180 degree shift of the corrugation maximum position between the profiles of empty and occupied states, in agreement with surface simulations based on the 4 x 1 linear tetramer model of Neugebauer et al. [Phys. Rev. Lett. 80, 3097 (1998)]. Electronic structure calculations predict a surface band gap of 1.1 eV, close to the measured value of 1.14 eV and the previously predicted value (1.2 eV). Despite the successes of this model, high-resolution images reveal an unexpected 3x periodicity (not seen in diffraction) along the [110] row direction, indicating the need for a 4 x 3 model, and putting into question the existence of linear Ga tetramers.     

A new 9-methoxyyohimbine-type indole alkaloid from Mitragyna africanus

A new yohimbine-type indole alkaloid (1). was isolated from the stem bark of Mitragyna africanus (WILLD.) collected in Nigeria, along with known seven Corynanthe-type oxindole alkaloids, two secoiridoids, three lignans, and a quinovic acid derivative. Their structures were elucidated by spectroscopic analyses.     

Determining the strengths of hydrogen bonds in solid-state ammonia and urea: insight from periodic DFT calculations

Plane-wave density functional theory has been applied to determine the strengths of hydrogen bonds in the phase I crystal structures of ammonia and urea. For ammonia, each component of the trifurcated hydrogen bond has been found to be almost as strong as a standard N-H.N interaction, and for urea the strengths of the two different N-H.O interactions have been determined by a quantum mechanical technique for the first time.     

Paeonins A and B,lipoxygenase inhibiting monoterpene galactosides from Paeonia emodi

Paeonins A and B, new monoterpene galactosides have been isolated from the chloroform-soluble fraction of the roots of Paeonia emodi and showed potent lipoxygenase inhibitory activity. The structures of 1 and 2 have been assigned on the basis of spectral analysis including one- and two-dimensional NMR techniques.