Effect of change in the physical properties of water at its peculiar temperature points on the dielectric behavior of sodium polyacrylate

The behavior of sodium polyacrylate is studied via broadband dielectric spectroscopy. The non-Debye response in the frequency range 0.1 Hz–1.0 MHz, the non-Markovian dispersion in the infralow-frequency range, and the anomalies of dielectric permittivity and ac conductivity near “peculiar” temperatures of water (20, 35, 50, and 75°C) are ascertained experimentally. These facts make it possible to assign sodium polyacrylate to disordered media, in which the temperature behavior of dielectric parameters is described by the Kohlrausch–Williams–Watts relaxation function.     

One-Step Synthesis of Magnetic Nanocomposite with Embedded Biologically Active Substance

Magnetic nanocomposites based on hydroxyapatite were prepared by a one-step process using the hydrothermal coprecipitation method to sinter iron oxides (Fe₃O₄ and γ-Fe₂O₃). The possibility of expanding the proposed technique for the synthesis of magnetic composite with embedded biologically active substance (BAS) of the 2-arylaminopyrimidine group was shown. The composition, morphology, structural features, and magnetic characteristics of the nanocomposites synthesized with and without BAS were studied. The introduction of BAS into the composite synthesis resulted in minor changes in the structural and physical properties. The specificity of the chemical bonds between BAS and the hydroxyapatite-magnetite core was revealed. The kinetics of the BAS release in a solution simulating the stomach environment was studied. The cytotoxicity of (HAP)FexOy and (HAP)FexOy + BAS composites was studied in vitro using the primary culture of human liver carcinoma cells HepG2. The synthesized magnetic composites with BAS have a high potential for use in the biomedical field, for example, as carriers for magnetically controlled drug delivery and materials for bone tissue engineering.     

Some Features of the Energetics of Structure Formation in Mixtures of Solvents Differing in Nature and Polarity

Some regularities of the energetics of structure formation in mixtures of polar organic solvents not forming layered structures with liquid hydrocarbons and in mixtures of inert and low-polar diluents at 20 were established. In most cases, the deviation of the methylene group increments from additivity, defining the energy stability of a liquid structure, was distinctly negative. In particular, the increment decreases dramatically from individual higher alcohols to mixtures of propanol and n-octane which model the former in the concentration of functional groups per unit volume, and the structure of mixture is weakened. Solvents of close polarity, in turn, form mixtures whose methylene group increments are well approximated by the additivity law.     

Recombining-plasma spectroscopy in the LTE-PLTE transition region

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 49, No. 3, pp. 400–407, September, 1988.     

A Centrally Symmetric Version of the Cyclic Polytope

We define a centrally symmetric analogue of the cyclic polytope and study its facial structure. We conjecture that our polytopes provide asymptotically the largest number of faces in all dimensions among all centrally symmetric polytopes with n vertices of a given even dimension d=2k when d is fixed and n grows. For a fixed even dimension d=2k and an integer 1≤j<k we prove that the maximum possible number of j-dimensional faces of a centrally symmetric d-dimensional polytope with n vertices is at least for some c _j (d)>0 and at most as n grows. We show that c ₁(d)≥1−(d−1)⁻¹ and conjecture that the bound is best possible. Research of A. Barvinok partially supported by NSF grant DMS 0400617. Research of I. Novik partially supported by Alfred P. Sloan Research Fellowship and NSF grant DMS-0500748.     

Dielectric dispersion as an indication of the formation of a polar phase in ferroelectrics

The regularity of the appearance of dispersion in the rf range immediately at the Curie point upon transition to the polar phase is demonstrated using the three-dimensional dependences of the permittivity ε ₂₂ ^′ (f, T) for a triglycine sulfate single crystal as an example. This regularity is common to all ferroelectrics and can be used for the direct objective determination of the phase transition temperature.     

Socles of Buchsbaum modules, complexes and posets

The socle of a graded Buchsbaum module is studied and is related to its local cohomology modules. This algebraic result is then applied to face enumeration of Buchsbaum simplicial complexes and posets. In particular, new necessary conditions on face numbers and Betti numbers of such complexes and posets are established. These conditions are used to settle in the affirmative Kühnel's conjecture for the maximum value of the Euler characteristic of a 2k-dimensional simplicial manifold on n vertices as well as Kalai's conjecture providing a lower bound on the number of edges of a simplicial manifold in terms of its dimension, number of vertices, and the first Betti number.