VH spectra from liquid and supercooled salol

VH spectra of light scattered by salol have been measured over a wide temperature range. A hydrodynamic model using two relaxing processes fits accurately the line shapes in the full viscosity range.     

Structural and energy properties study using the AM1 calculations of aza-azulenes in their ground state

AM1 calculations with complete optimization have been carried out on the azulene molecule and its derivatives such as 1-aza-azulene and 1,3-diaza-azulene. We show that AM1 is an appropriate method for predicting the structure and energy properties of azulene. Experimental values are found with good accuracy and computer results are analogous to those obtained by sophisticated methods such as the ab initio method (6-31G^*). We describe a complete theoretical study of the structural and energy properties of 1-aza-azulene and 1,3-diaza-azulene in their ground states using the same method with full geometry optimization. From the theoretical finding, the most stable conformations are proposed. Otherwise, these geometrical conformations are preserved in order to determine some spectroscopic values of these compounds using the CNDO/M method. Our results are in qualitative agreement with the experimental data.     

Dual fluorescence of 4-N,N-dimethylaminopyridine. Role of hydrogen-bonded complex in the ground state

A correlation is shown between the appearance of the dual fluorescence of 4-N,N-dimethylaminopyridine (DMAP) solutions and the formation of hydrogen-bonded of complexes in the ground state. A comparative absorption study between pyridine, N,N-dimethylaniline and DMAP shows that the hydrogen-bonded complex is situated on the amino nitrogen of DMAP. A “pretwisted” conformation of DMAP in the ground state isassumed due to this hydrogen-bonded complex. Simulations by intermolecular interaction calculations and spectroscopic calculations (CNDO/s) confrim the “twisting” influence of water molecules (and/or any other hydrogen bonding) on the amine in the ground state. This “pretwisting” in the ground state by hydrogen bonding is common in many other aromatic amines. Moreover, the deforming role of hydrogen bonding in the ground state seems to be a general phenomenon in flexible aromatic molecules.     

An integrated strategy by absorbed component characterization,pharmacokinetics, and activity evaluation for identification of potential nephroprotective substances in Zhu-Ling decoction

An efficient strategy for the identification of potential nephroprotective substances in Zhu-Ling decoction has been established with the integration of absorbed components characterization, pharmacokinetics, and activity evaluation. A qualitative method was developed to characterize the chemical constituents absorbed components in vivo of Zhu-Ling decoction by using ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. A quantitative method was established and validated for the simultaneous determination of eight compounds in rat plasma by using ultra-performance liquid chromatography-triple quadruple tandem mass spectrometry. Finally, the nephroprotective activities of absorbed components with high exposure were assessed by cell survival rate, superoxide dismutase, and malondialdehyde activities in hydrogen peroxide–induced Vero cells. As a result, 111 compounds in Zhu-Ling decoction and 36 absorbed components were identified in rat plasma and urine, and poricoic acid A, poricoic acid B, alisol A, 16-oxo-alisol A, and dehydro-tumulosic acid had high exposure levels in rat plasma. Finally, poricoic acid B, poricoic acid A, 16-oxo-alisol A, and dehydro-tumulosic acid showed remarkable nephroprotective activity against Vero cells damage induced by hydrogen peroxide. Besides, superoxide dismutase and malondialdehyde activities were obviously regulated in hydrogen peroxide–induced Vero cells by treatment with the four compounds mentioned above. Therefore, these four compounds were considered to be effective substances of Zhu-Ling decoction due to their relatively high exposure in vivo and biological activity. This study provided a chemical basis for the action mechanism of Zhu-Ling decoction in the treatment of chronic kidney diseases.     

Tacticity, molecular weight, and molecular-weight-distribution relationships in stereoregular polyacrylonitrile prepared by electron beam irradiation canal polymerization

The preparation and characterization of stereoregular isotactic polyacrylonitrile (PAN) by electron beam (EB) irradiation on a urea canal complex are described. The EB method has several advantages over the ordinary γ-ray irradiation method: a very short polymerization time is needed (within a few seconds) and EB irradiation is carried out intermittently, and so all the polymer properties can be studied as a function of the EB irradiation dose. The structure–properties relationships of PAN, such as intrinsic viscosity versus the number-average molecular weight and the viscosity versus the isotacticity range were clarified. Significant information for the optimization of the tacticity of PAN was extracted. Received: 23 August 1999 Accepted : 10 January 2000     

High-order dispersion-managed solitons for dense wavelength-division multiplexed transmissions

Optimal dense wavelength-division multiplexed transmission is obtained based on high-order periodic dispersion-managed solitons in a dispersion-slope-compensated fiber link.     

Analytical solution of polarization mode dispersion for triangular spun fibers

An analytical solution for the differential group delay of a fiber spun according to a triangular function is derived from concatenation of Jones matrices for a fiber length equal to N x T, where T is the spinning period and N is an integer. This solution holds for any value of linear deterministic birefringence delta beta of amplitude A and period T of the triangular spinning function. We use the solution to emphasize the effect of birefringence on the efficiency of the spinning function.     

Ring of C60 polymers formed by electron or hole injection from a scanning tunneling microscope tip

Carrier (electron or hole) injection from a scanning tunneling microscope tip causes various surface modifications on the molecular scale. We report that injection into C60 close-packed layers forms a ring-shaped distribution of C60 polymers. This can be explained on the basis of the radial propagation and energy dissipation of carriers. Subsequent electron or hole injections enlarge the ring, showing that both carriers can induce both polymerization and depolymerization. Furthermore, we demonstrate visualization of carrier scattering by injecting carriers into C60 layers with grain boundaries.     

Dielectric relaxation of water adsorbed on cellulose

Water is an essential part of the structure of biological materials. To estimate how the physical state of water adsorbed on cellulose affects various properties, the dielectric properties of moist cellulose were investigated. Three dielectric relaxations were obtained. The relaxation with the lowest frequency was due to electrode polarization. The direct-current conduction calculated from the dielectric loss leaving out the relaxations appearing in mid and high frequencies increased rapidly from 7% or more moisture content (MC). Free water, which can dissolve electrolytes, was increased in the adsorbed water of materials with 7% or more MC. The relaxation appearing in the mid-frequency range was due to interfacial polarization in the heterogeneous structure which consists of adsorbed water with large electrical conductivity within the insulating cellulose. The relaxation appearing at higher frequencies was due to the motion of adsorbed water in cellulose. The relaxation was investigated from relationships between activation enthalpy and entropy in the relaxation. The relationships in low MC cellulose were close to those of sugar, while the relationships in high MC cellulose were close to the relationships extrapolated from bulk water.     

Soft magnetization of a semi-hard/soft magnetic bilayer produced by oblique-incidence evaporation

The possibility of achieving soft magnetization in semi-hard magnetic films such as Fe, Fe_93.5Si_6.5, Fe₅₀Co₅₀ and Fe₇₀Co₃₀ is investigated by depositing films on an Fe₂₀Ni₈₀ underlayer by oblique-incidence evaporation. The magnetic anisotropy of the underlayer is strengthened to a depth of several lattice parameters by vapor deposition of the film at an oblique angle to the substrate surface. This method also allows magnetic anisotropy to be induced in strongly isotropic semi-hard magnetic overlayers to a thickness of a few thousands Angstroms. The coercive force of bilayer films measured along the hard-axis is reduced remarkably by this process, and the strength of the anisotropy field is demonstrated to be readily controllable. When magnetic anisotropy exists in both magnetic layers, a significant change is observed in the magnetization processes of the semi-hard magnetic layer and the coercive forces in the hard magnetization direction is dramatically reduced. Soft magnetization of the semi-hard magnetic layer cannot be achieved when magnetic anisotropy exists in only one of the magnetic layers.