Studies of silver iodide ice-forming activity. i. influence of the aerosol particle size on the ice-forming activity at —20°C

Silver iodide ice-forming activity has been studied at the supercooled fog temperature —20°C. The number of ice crystals calculated per gram reagent depends greatly on the aerosol particle mean cubed radius. The analysis of published data shows that this is the principal cause of a considerable divergence in the data on silver iodide ice-forming activity obtained by various authors.     

Theory of chromatography of complex cyclic polymers: eight-shaped and daisy-like macromolecules

A theory of chromatography of eight-shaped, trefoil-shaped and daisy-like polymers is developed. For a model of an ideal chain in a slit-like pore exact equations and a number of approximate formulae for the distribution coefficient K of these polymers are derived. All modes of chromatography of complex macrocycles of arbitrary molar mass in both narrow and wide pores are covered by the theory. It is shown that complex macrocycles always elute after linear polymers and rings of the same contour length. The effective chromatographic radius of eight-shaped and daisy-like macromolecules, which determines retention in size-exclusion chromatography are calculated. The increase in the retention with molar mass is predicted for all types of macrocycles at the critical interaction condition. Non-monotonous molar mass dependences of K are found at pre-critical interaction. We simulate separation of complex cyclic polymers from linear and ring precursors, discuss possibilities to separate symmetric and asymmetric eights, and speculates on the use of chromatography for separating knotted and unknotted polymer rings. According to the theory, the chromatography under the critical and pre-critical interaction conditions is expected to be especially efficient in these and similar problems. Boundary conditions for the theory and its applicability to real systems are discussed.     

Influence of the composition and structure of epoxy siloxane matrix on the spectral behavior of the nile red dye: II. Sol-gel system based on tetraethoxysilane and glycidoxypropyltrimethoxysilane

The organic-inorganic materials with fluorescence properties are synthesized in the form of gels and xerogels from tetraethoxysilane and glycidoxypropyltrimethoxysilane by the sol-gel method. The concentration of the introduced Nile Red dye is 2.2 × 10^?6 M. The fluorescence spectra of the prepared materials are measured and analyzed as a function of the ratio between the initial components forming the sol-gel epoxy siloxane matrices. The assumption regarding the structure of the synthesized hybrids is made invoking the data obtained by Fourier-transform IR spectroscopy and atomic-force microscopy.     

Analysis of molecular scale roughness effect on contact of solids based on computer modeling

The real contact between solids is modeled at the molecular scale, and the results are presented. Adhesion, real contact area, and approach of the surfaces are evaluated with the help of scanning, tunneling, and atomic force microscope imaging of the surfaces.