Effect of nanoparticle concentration on coagulation rate of colloidal suspensions.

Theoretically and with the help of numerical simulation the coagulation rate of nanoparticle suspensions is analyzed. Analytical expressions are proposed that describes the rate of stationary coagulation of the nanoparticles suspended in a solvent ( d n a / d t , where n a is the particle concentration) and the characteristic coagulation time θ = - n a / ( d n a / d t ) . In the contrast to traditionally used equations, the proposed expressions allow one to describe with high accuracy the rate of stationary coagulation of not only low concentrated suspensions, where the volume content of nanoparticles is ρ ≪ 1 %, but also rather highly concentrated ones, at ρ ∼ 1 % and more ( ρ = n a v a where v a is a particle volume), which are relevant for most of the industrial applications. Analytical expressions are written for both three-dimensional geometry, which is relevant for real colloids, and two-dimensional geometry, which is useful to compare results of the analytical solution and numerical simulation. Computer experiments are performed in the framework of the two-dimensional method of stochastic dynamics. Satisfactory agreement of the obtained analytical expressions with the results of numerical calculations is demonstrated. The dependences of the coagulation time on the height of the interparticle energy barrier and on the suspension concentration are analyzed. It is shown that, in contrast to the obtained theoretical expressions, the traditionally used formulas overestimate the characteristic coagulation time for highly concentrated suspensions by more than an order of magnitude.

Self-propagating high-temperature synthesis of (Ho1-xLax)2O3 nanopowders for magneto-optical ceramics.

Weakly agglomerated nanoparticles of (Ho1-xLax)2O3 solid solutions were synthesized with the help of a self-propagating high-temperature synthesis (SHS). The nanopowders were studied by a simultaneous thermal analysis (TG-DSC), X-ray diffraction (XRD), BET and FT-IR spectroscopy methods. Changes of the particles morphology after annealing at different temperatures and ball milling were investigated by a scanning electron microscopy (SEM) and a dynamic light scattering (DLS) method. It was found that annealing at a temperature of 900 °C in air and ball milling of the SHS nanopowders allow obtaining rounded shape particles with a mean diameter of about 20 nm and C-type cubic crystal structure. Up to 10 mol.% of the lanthana was shown to dissolve in the holmium oxide nanoparticles.

[Hyperbaric oxygenation in the intensive therapy of hypoconjugation neonatal jaundice]. / Giperbaricheskaia oksigenatsiia v intensivnoi terapii gipokon''iugatsionnykh zheltukh novorozhdennykh.

Sixty-three newborns aged 4 +/- 1 days with hypoconjugation icterus and bilirubinemia of 313 to 524 mumoles/liter, prematurity of the I-II degree, birth injuries to the CNS, hypothyrosis, maternal diabetes mellitus, and threatened encephalopathy were examined. All patients were divided in 2 identical groups: controls (n = 30) and main (n = 33). The only difference was addition of HBO sessions to the basic complex of intensive care. In contrast to the controls, in the main group the level of indirect bilirubin was decreased 40% more intensively, the conjugation function of the liver for direct bilirubin was reliably improved by days 3-4 of therapy, by day 5 the enzymatic function of the liver was reliably normalized, mixed acidosis was arrested during the first day of treatment in more than 90% of patients, adequate glycemia and serum albumin concentrations were attained sooner, and the need in extracorporeal detoxication decreased.