Monte Carlo optimization

Monte Carlo optimization techniques for solving mathematical programming problems have been the focus of some debate. This note reviews the debate and puts these stochastic methods in their proper perspective.     

Theory of the NO+CO surface-reaction model

We derive a pair approximation (PA) for the NO+CO model with instantaneous reactions. For both the triangular and square lattices, the PA, derived here using a simpler approach, yields a phase diagram with an active state for CO-fractions y in the interval y(1)相似文献   

Dynamic mechanical relaxation of compressed rubber cylinders

TMTD-vulcanised natural rubber cylinders (diameter = height = 20 mm) were compressed to 20%. Sinusoidal strains of 2·5, 5 and 10%, respectively, were superimposed on the static compression and the decrease of the maximum and minimum values of the stress recorded. A large difference between the curves representing the maximum and minimum values was obtained. This difference increased with increasing dynamic amplitude. The maximum values showed no dependence on the amplitude and the curves asymptotically reached the same relaxation value at long ageing times. The difference between the maximum and minimum values increased with increasing temperature.     

Effects of sequence and structure in the separation of nucleic acids using ion pair reverse phase liquid chromatography

Ion pair reverse phase high performance liquid chromatography on non-porous alkylated poly(styrene-divinylbenzene) particles enables the high resolution separation of double stranded DNA fragments. To further understand the separation mechanisms involved in ion pair reverse phase liquid chromatography we have analysed the effects of curved or "bent" DNA fragments with respect to their separation using both gel electrophoresis and ion pair reverse phase liquid chromatography. Size dependent separations of curved DNA fragments that migrate anomalously during gel electrophoresis were observed using ion pair reverse phase liquid chromatography. To further study the sequence effect and resulting changes in hydrophobicity of the duplex DNA, PCR fragments were generated that contain uracil in place of thymine. The resulting fragments were shown to elute with shorter retention times, demonstrating that sequence-specific effects can alter the retention of duplex DNA. The study was extended to the investigation of non-canonical B-DNA structures (Holliday junctions) under various chromatographic conditions, demonstrating that the coaxial stacking of the helices in such structures, in the presence of magnesium causes a change in retention.