Osmosedimentation: Approach To Sedimentation Equilibrium Under Gravity

Aqueous dextran solutions contained within tall (20 cm) dialysis cells reach a state of sedimentation equilibrium in less than 10 hr, under gravity. Experiments were performed in which the solute was transported downward or upward, giving always the same final result. Calculation of molecular weights (M̄w) of two well-defined dextran samples and of bovine thyroglobulin, using the vertical concentration gradients measured in the equilibrated solution columns, gives results in agreement with other methods. The well-known kinetic limitations to solute transport under gravity are thus effectively removed by coupling solvent osmotic currents to solute sedimentation. © 1984.982489493Schachman, (1959) Ultracentrifugation in Biochemistry, , Academic Press, New YorkBovey, Winslow, (1979) Macromolecules, p. 305. , Academic Press, New YorkVan Holde, Baldwin, (1958) J. Phys. Chem., 62, p. 734Morawetz, (1975) Macromolecules in Solution, p. 82. , Wiley, New YorkMason, Weaver, (1924) Phys. Rev., 23, p. 412Galembeck, Robilotta, Pinheiro, Joekes, Bernardes, (1980) J. Phys. Chem., 84, p. 112Edelhoch, (1960) J. Biol. Chem., 235, p. 1326Nunes, Galembeck, (1983) J. Polym. Sci. Polym. Lett. Ed., 21, p. 49Williams, Van Holde, Baldwin, Fujita, (1958) Chem. Rev., 58, p. 715Edmond, Farquhar, Dunstone, Ogston, (1968) Biochem. J., 108, p. 77

Ceramics Derived From Hybrid Polymer And Multiwall Carbon Nanotubes

Ceramic samples (labelled NT and CS) were obtained from a hybrid polymeric precursor derived from poly(methylsiloxane) and divinylbenzene with and without carbon nanotubes (MWCNT), respectively, as an additional C-source. The precursor was pyrolysed under Ar atmosphere at 1500 °C for different pyrolysis times. XRD patterns of CS ceramics showed broad diffractions of β-SiC, C-graphitic and opaline-SiO2 phases. For NT ceramics, besides the diffractions observed for CS ceramics, an intense diffraction peak of cristobalite was observed. The introduction of MWCNT changed the morphology of the resulting ceramics and decreased the solubility of SiO2 in the matrix, promoting the formation of relatively large cristobalite crystals.Schiavon, M.A., Redondo, S.U.A., Pina, S.R.O., Yoshida, I.V.P., Investigation on kinetics of thermal decomposition in polysiloxane networks used as precursors of silicon oxycarbide glasses (2002) Journal of Non-Crystalline Solids, 304, pp. 92-100Kleebe, H.-J., Gregori, G., Babonneau, F., Blum, Y.D., MacQueen, D.B., Masse, S., Evolution of c-rich sioc ceramics. Part I. Characterization by integral spectroscopic techniques: Solid-state nmr and raman spectroscopy (2006) International Journal of Materials Research, 97, pp. 699-709Pinho, R.O., Radovanovic, E., Torriani, I.L., Yoshida, I.V.P., V, P.I., Hybrid materials derived from divinylbenzene and cyclic siloxane (2004) European Polymer Journal, 40, pp. 615-622Tuinstra, F., Koenig, J.L., Raman spectrum of graphite (1970) Journal of Chemical Physics, 53, pp. 1126-1130Li, F., Wen, G., Song, L., Growth of nanowires from annealing sibonc nanopowders (2006) Journal of Crystal Growth, 290, pp. 466-472Graetsch, H., Gies, H., Topalovié, I., Nmr, xrd and ir study on microcrystalline opals (1994) Physics and Chemistry of Minerals, 21, pp. 166-175Bois, L., Maquet, J.J., Babonneau, F., Structural characterization of sol-gel derived oxycarbide glasses 2. study of the thermal stability of the silicon oxycarbide phase (1995) Chemistry of Materials, 7, pp. 975-98