ABSTRACT
In order to test the application of the "nanoparticle" concept to viruses in terms of low-frequency dynamics, large viruses (140-190 nm) were compared to similar-sized polymer colloids using ultra-small-angle x-ray scattering and very-low-frequency Raman or Brillouin scattering. While both viruses and polymer colloids show comparable highly defined morphologies, with comparable abilities of forming self-assembled structures, their respective abilities to confine detectable acoustic vibrations, as expected for such monodisperse systems, differed. Possible reasons for these different behaviors are discussed.
Subject(s)
Colloids/chemistry , Nanoparticles/chemistry , Polymers/chemistry , Viruses/chemistry , Microscopy, Atomic Force , Microscopy, Electron, Transmission , Models, Theoretical , Scattering, Radiation , Vibration , Water/chemistry , X-RaysABSTRACT
We report on Brillouin and in situ small angle X-ray scattering (SAXS) analyses of topological heterogeneity in compressed sodium borosilicate glasses. SAXS intensity extrapolated to very low angular regimes, I(q = 0), is related to compressibility. From Brillouin scattering and analyses of the elastic properties of the glass, the Landau-Placzek ratio is determined and taken as a direct reflection of the amplitude of frozen-in density fluctuations. It is demonstrated that with increasing fictive pressure, topological (mid- and long-range) homogeneity of the glass increases significantly. Heating and cooling as well as isothermal scans were performed to follow the evolution of density fluctuations upon pressure recovery. For a sample with a fictive pressure p(f) of 470 MPa, complete recovery to p(f) = 0.1 MPa was observed to occur close to the glass transition temperature. The values of fictive and apparent fictive temperature, respectively, as obtained via the intersection method from plots of I(q = 0) vs. temperature were found in good agreement with previous calorimetric analyses. Isothermal scans suggest that mid- and long-range recovery govern macroscopic density relaxation.
ABSTRACT
The evolution of the boson peak with densification at medium densification rates (up to 2.3%) in silicate glasses was followed through heat capacity measurements and low frequency Raman scattering. It is shown that the decrease of the boson peak induced by densification does not conform to that expected from a continuous medium; rather it follows a two step behaviour. The comparison of the heat capacity data with the Raman data shows that the light-vibration coupling coefficient is almost unaffected in this densification regime. These results are discussed in relation to the inhomogeneity of the glass elastic network at the nanometre scale.
ABSTRACT
Forty-nine sourses of Russian and foreign literature dedicated to the role of endothelial dysfunction in the development of pulmonary hypertension and chronic cor pulmonale were analyzed. Data on endothelium-dependent vasoactive mediators are presented in the article.
Subject(s)
Endothelins/metabolism , Endothelium, Vascular/physiopathology , Pulmonary Heart Disease/metabolism , Vasoconstriction/physiology , Cell Proliferation , Endothelium, Vascular/metabolism , Endothelium-Dependent Relaxing Factors/metabolism , Humans , Pulmonary Artery/metabolism , Pulmonary Artery/physiopathology , Pulmonary Heart Disease/physiopathologySubject(s)
Electrocardiography/methods , Heart/physiology , Action Potentials , Atrial Function , Electrodes , HumansABSTRACT
For producing artificial cardiac valves possessing high antitrombogenic properties, two methods of their treatment were investigated: mechanical and electrochemical. It was found that electrochemical polishing reduced the possibility of thrombogenesis.
