Quaternized and Unmodified Chitosans: Hydrodynamic Properties

Molecular properties of N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan (modified chitosan) series with the averaged quaternization degree 90% have been studied in comparison with the unmodified chitosan series by the method of translation isothermal diffusion, viscometry and static light scattering in dilute solutions in 0.33M CH3COOH+0.2M.CH3COONa at pH 3.54. Molecular mass, translation diffusion coefficient, and hydrodynamic size of the homologues samples in the modified/unnmodified series have been determined as well as their chain rigidity and Mark-Kuhn-Houwink equations at acidic pH. It was established that the size of modified chitosan molecules might be smaller than the initial polysaccharide of an equal polymerization degree in the same solvent, which was explained by the change of thermodynamic conditions and the change of the ratio of thermodynamic/electrostatic contributions to the total chain rigidity. Quaternized chitosan molecules displayed the different hydrodynamic behavior in 0.33M CH3COOH+0.2M.CH3COONa and in 0.2M NaCl (neutral pH). Solution properties of quaternized chitosan at neutral pH had been identified as the concentration dependent. The threshold influence of the secondary amino group protonation on the hydrodynamic properties of modified chitosan molecules was detected in 0.2M NaCl at the solute concentration range 0.001-0.004 g/cm3

Studies of Particle Acceleration by an Active Microwave Medium

The PASER is potentially a very attractive method for particle acceleration, in which energy from an active medium is transferred to a charged particle beam. The effect is similar to the action of a maser or laser with the stimulated emission of radiation being produced by the virtual photons in the electromagnetic field of the beam. We have been investigating the possibility of developing a demonstration PASER operating at X-band. The less restrictive beam transport and device dimensional tolerances required for working at X-band rather than optical frequencies as well as the widespread application of X-band hardware in accelerator technology all contribute to the attractiveness of performing a PASER demonstration experiment in this frequency range. Key to this approach is the availability of a new class of active materials that exhibit photoinduced electron spin polarization. We will report on the status of active material development and measurements, numerical simulations, and progress towards a planned microwave PASER acceleration experiment at the Argonne Wakefield Accelerator facility.Comment: 9 pages, 3 figures, submitted to Proceedings of the 2006 Advanced Accelerator Concepts Worksho

Adducts AnC60Hn: Electro-optical properties and quantum chemical calculation data

Experimental studies of electro-optical Kerr effect in solution detect variations in the molecular behavior of adducts AnC 60Hn (n=1, 2...6) synthesized by fullerene reactions with the charged (lithium precursor) and neutral (primary amine) nucleophiles. Theoretical analysis of two corresponding structure compounds (adducts A1 and A2) performed by quantum chemical semi-empirical method AM1 shows a difference in the charge distribution for A1 and A2 and a significant difference in polarity of adducts A1 and A2 with the same addend numbers, which may be responsible for the observed peculiarities in electro-optical behavior of styrene-fullerene and amine-fullerene derivatives