Nanocomposite polymer layers for molecular tribology

We discuss a novel strategy for the formation of elastomeric boundary lubrication coatings from block copolymers grafted to a reactive interface of a silicon substrate. We demonstrate molecularly thick thermoplastic elastomeric films with promising microtribological properties. These films are composed of an elastomeric rubber phase reinforced by the net of glassy nanodomains. These elastomeric layers are extremely wear resistant under shear stresses due to the unique combination of a chemically grafted elastic matrix capable of tremendous reversible deformation (500–1000%) stabilized by a chemically interconnected nanodomain net.     

Synthesis and application of triazinyl-2,2,6,6-tetramethyl-piperidine derivatives as stabilizers for polymeric materials

Two new unsaturated compounds, i. e. triazinyl-2,2,6,6-tetramethylpiperidine derivatives (TTMP), were synthesized under conditions of phase-transfer catalysis and their copolymers with styrene (St) were prepared. The participation of TTMP in the polymerization did not affect the rate of copolymerization, molecular weight and polydispersity of the St polymers. At low concentrations (0.1 wt.-%) a significant stabilizing effect against photodegradation was determined.     

A variational method for analysis of laminates with parallel arrays of intralaminar cracks

This paper presents a robust variational method for prediction of the effective thermoelastic properties of laminates with parallel, but not necessarily coplanar intralaminar cracks. Arbitrary laminate layup, crack patterns, and any in-plane forces and bending moments, and temperature change can be treated simultaneously. The method is based on the principle of minimum complementary energy. The admissible in-plane stress components are assumed to be linear through the ply thickness. Simple matrix expressions are derived for the effective compliance matrix, thermal expansions and curvatures, and specific heat of a cracked laminate. Predictions for the Young's modulus, Poisson's ratio, shear modulus, flexural rigidity, and thermal expansion as functions of crack density for various laminates of symmetric and nonsymmetric layups demonstrated excellent agreement with experimental results of seven independently published studies. Accuracy and robustness of the method are complemented by the fact that no experimentally fitted parameters are required. It is shown that the same formalism can be applied to analysis of closed intralaminar cracks, as well as nonuniform and nonsymmetrical distributions of cracks.     

Formation of a Corrosion-Resistant Layer on Steel by Reaction with a Si3N 4 ― Al2O3 Composite under the Conditions of Light-Thermal Treatment

The formation of a surface layer on low-alloyed steel during light-thermal treatment with a composite material based on Si₃N₄ Al₂O₃ was investigated. The working surfaces were studied using metallographic, x-ray diffraction, and electron-probe microanalysis. It was found that the corrosion-resistant phases Al₂SiO₅, (Fe, Cr)₂O₃, (Cr, Al) ₂O₃, and NiCrO₄ formed in the alloyed layer, increasing its microhardness by 2-5 times and its corrosion resistance in sea water by more than two orders of magnitude.     

Fabrication and AFM investigation of the temperature-dependent surface morphology of Au (100) single crystal ultramicroelectrodes

A previously reported method for preparation of gold (111) single-crystal utramicroelectrodes (scumes) has been used to fabricate gold (100) scumes with effective diameters from 20 to 50 microm. Cyclic voltammograms for these ultramicroelectrodes obtained in perchloric acid show similar features to gold (100) single-crystal electrodes of more conventional sizes, but with differences that are a result of different surface preparation methods used before the measurement. The gold crystals used to prepare Au (100) scumes were grown at room temperature so that the cyclic voltammetric characteristics reflect the unique properties of a room temperature-ordered surface. The AFM images of the (100) facets of these crystals are also presented. The effects of annealing Au (100) at 800 degrees C for a short time were studied both electrochemically and using AFM and are discussed with respect to the data obtained for crystals grown at room temperature.     

Design criteria and optical characteristics of one-dimensional photonic crystals based on periodically grooved silicon

Photonic bandgap (PBG) regions have been calculated for periodically grooved Si structures, acting as a one-dimensional photonic crystal. The wavelength range of the PBG as a function of the ratio (DSi/A) is presented, where DSi is the width of the Si walls and A is the grooved silicon lattice constant. The influence of the parameter DSi, the refractive index of the space between the Si walls and the number of structure periods, m, on the forming of PBG regions is discussed. A good correlation between the calculated and the experimentally observed PBG regions is obtained.     

Approximation algorithm for coloring of dotted interval graphs

Dotted interval graphs were introduced by Aumann et al. [Y. Aumann, M. Lewenstein, O. Melamud, R. Pinter, Z. Yakhini, Dotted interval graphs and high throughput genotyping, in: ACM-SIAM Symposium on Discrete Algorithms, SODA 2005, pp. 339-348] as a generalization of interval graphs. The problem of coloring these graphs found application in high-throughput genotyping. Jiang [M. Jiang, Approximating minimum coloring and maximum independent set in dotted interval graphs, Information Processing Letters 98 (2006) 29-33] improves the approximation ratio of Aumann et al. [Y. Aumann, M. Lewenstein, O. Melamud, R. Pinter, Z. Yakhini, Dotted interval graphs and high throughput genotyping, in: ACM-SIAM Symposium on Discrete Algorithms, SODA 2005, pp. 339-348]. In this work we improve the approximation ratio of Jiang [M. Jiang, Approximating minimum coloring and maximum independent set in dotted interval graphs, Information Processing Letters 98 (2006) 29-33] and Aumann et al. [Y. Aumann, M. Lewenstein, O. Melamud, R. Pinter, Z. Yakhini, Dotted interval graphs and high throughput genotyping, in: ACM-SIAM Symposium on Discrete Algorithms, SODA 2005, pp. 339-348]. In the exposition we develop a generalization of the problem of finding the maximum number of non-attacking queens on a triangle.     

A type of couple sexual dysfunction: A frequently overlooked contributor.

A frequently overlooked type of couple sexual dysfunction is presented. It requires a man with a passive symbiotic tie to his mother, a woman who needs a sexually dysfunctional man, and an intimate relationship between the 2. Four vignettes are presented to illustrate this syndrome. Clinical implications of this constellation are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)