Hyaluronic acid-copper(II) complexes: Spectroscopic characterization

Hyaluronic acid-copper(II) complexes were studied by ultraviolet and electron spin resonance spectroscopy (ESR), as well as by rheological measurements. Spin-Hamiltonian parameters were obtained from experimental spectra measured at 200 K by non-linear optimization method. These showg _x g _y <g _z and indicate the ground electronic state of copper ion, which is characteristic for carboxylato-copper(II) complexes. The non-axial symmetry of theg-tensor suggest rhombic crystal field symmetry. Formation of HA-Cu(II) complex is realized through the interaction of copper ions with carboxyl groups of the HA macromolecule. This complex is characteristic of the network-like rheological properties of its aqueous solution.     

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Gas enrichment at liquid-wall interfaces

Molecular dynamics simulations of Lennard-Jones systems are performed to study the effects of dissolved gas on liquid-wall and liquid-gas interfaces. Gas enrichment at walls, which for hydrophobic walls can exceed more than 2 orders of magnitude when compared to the gas density in the bulk liquid, is observed. As a consequence, the liquid structure close to the wall is considerably modified, leading to an enhanced wall slip. At liquid-gas interfaces gas enrichment which reduces the surface tension is found.     

In-situ study of Ag nanoparticle hydrosol optical spectra evolution during laser ablation/fragmentation

The results of in-situ monitoring of a laser fragmentation process of a largely polydisperse and morphologically heterogeneous citrate-reduced Ag hydrosol containing a fraction of Ag nanowires are presented. The laser fragmentation was performed using several wavelengths of the incident laser pulses (1064, 532 and 355 nm). Surface plasmon extinction spectra monitoring the nanoparticle fragmentation process were acquired pulse by pulse and related to transmission electron microscopy (TEM) images and statistical TEM image analysis of Ag nanoparticles collected in selected stages of the fragmentation. It was found that, due to different interactions of the laser pulses of various wavelengths with a specific fraction of the Ag nanoparticles in the hydrosol, the course of the fragmentation process depends on the wavelength, leading to different size distributions of the nanoparticles in the resulting hydrosol. The laser pulses of 532 nm wavelength are the most effective for the fragmentation process of the citrate-reduced Ag hydrosol, yielding the narrowest size distribution and the smallest mean radius of the Ag nanoparticles. PACS 81.07.-b; 73.21.-b; 81.16.-c     

Automatic estimation of ring strain energies

A simple model has been developed which allows to estimate ring strain energies of monocyclic and bicyclic compounds. It can also be applied to polycyclic systems with reasonable accuracy. A computer program based on this model has been implemented which relies on a topological representation of molecular structures and performs the estimation of the effects of ring strain both on molecular energies and on reaction enthalpies.     

Simple Zeros of the Riemann Zeta-Function

Assuming the Riemann Hypothesis, Montgomery showed by meansof his pair correlation method that at least two-thirds of thezeros of Riemann's zeta-function are simple. Later he and Taylorimproved this to 67.25 percent and, more recently, Cheer andGoldston increased the percentage to 67.2753. Here we proveby a new method that if the Riemann and Generalized LindelöofHypotheses hold, then at least 70.3704 percent of the zerosare simple and at least 84.5679 percent are distinct. Our methoduses mean value estimates for various functions defined by Dirichletseries sampled at the zeros of the Riemann zeta-function. 1991Mathematics Subject Classification: 11M26.