Structure and dynamics of titania - poly(N-vinyl caprolactam) composite hydrogels.

The morphologies and dynamics of poly(N-vinyl caprolactam) (PVCL) based hydrogels with titania nanoparticles in different states (native, air-dried to a constant weight and swollen in H2O or D2O) are studied by a combination of complementary techniques: wide angle X-ray scattering, small angle neutron scattering, neutron spin echo spectroscopy, differential scanning calorimetry. The results suggest the presence of different structural types of water leading to different properties of the hydrogels. We propose a hierarchical structure of hydrogels spanning from the molecular to the microscopic scale consistent with both the static structure (polymer mesh size, association of the nodes of crosslinks and microchains of PVCL) and the dynamics (rate of relaxation of polymer chains, hydrodynamic polymer-polymer correlation length). The presence of nanoscale titania does not change the molecular structure and nanostructure due to its aggregation into meso-domains, but does affect the microstructure, changing the response rate to a temperature jump from 20 to 50 °C. Titania nanoparticles do not change the equilibrium swelling degree of hydrogels.

[Clinical implications of physicochemical examination of uroliths and urine].

We have examined composition of uroliths (qualitative and quantitative x-ray tests) and measured 24-h excretion of electrolytes (Cl-, NO2-, NO3-, SO4(2-), PO4(3-), cytrate, isocytrate and uric acid) using ion-exchange chromatography with a conductometric detector. We revealed correlations between ion characteristics, their concentration in the urine before and after treatment and composition of disintegrated uroliths and clinical data. This allowed us to identify some urinary ions which indicate activity of urolithogenesis, predisposition to urolithiasis, production of certain uroliths, reflect some processes running in patients with urolithiasis. We give concentrations of some urinary ions which can be considered normal and deviations which may indicate urolithogenesis.

[Urolithiasis: current aspects of diagnosis and treatment].

The aim of the study was clinicodiagnostic assessment of current methods of computer visualization (spiral computed tomography, multispiral computed tomography) and their role in specification of indications, contraindications and technical characteristics of current methods of urolithiasis treatment. The results of combined examination and therapy of 759 urolithiasis patients treated in the urological clinic of I.M. Sechenov Moscow Medical Academy in 1999-2003 are presented.