Evidence for 2D precursors and interdiffusion in the evolution of self-assembled CdSe quantum dots on ZnSe

The evolution of self-assembled CdSe quantum dots deposited on (and subsequently capped by) ZnSe was investigated on a series of samples grown by molecular beam epitaxy, with CdSe coverages from 0.5 to 2.6 monolayers. The samples were investigated by cross-sectional scanning transmission electron microscopy, as well as macro- and microphotoluminescence. The results clearly indicated a coexistence of 2D ZnCdSe platelets and 3D islands, showing clearly that the platelets act as precursors for the formation of the 3D islands.     

Flames in narrow circular tubes

We examine an axi-symmetric deflagration located in a tube with thermally active walls. It is noted that the flame-in-tube configuration defines a classical edge-flame, a flame in a shear flow for which there is a water-shed solution for a critical value of the Damköhler number (D), ignition front solutions for larger values of D, and failure wave solutions for smaller values. We examine semi-infinite tubes with a heat flux imposed at the tube wall ends, to simulate experiments reported in the 30th Symposium. We identify parameters for which stable solutions are obtained at certain flow rates, but unstable solutions are generated at higher flow rates, followed by stable solutions at still higher flow rates. These solutions are consistent with the experimental record. Instability leads either to regular oscillations or to a violent process characterized by quenching and re-ignition.     

Kinetic Spectroelectrochemical Assay for Uric Acid in Human Urine

A spectroelectrochemical (SEC) assay for uric acid in human urine has been developed that is essentially reagent-free and involves relatively short analysis times of ∼12 min per specimen using a single-point standard addition approach. The SEC method was demonstrated to be selective for uric acid in human urine, avoiding interference through both the usual control parameters (electrolysis potential and measurement wavelength) and the relatively slow kinetics of a post-electrolysis reaction involving the oxidation product. Results from the SEC analysis of a split set of human urine specimens were well correlated to those obtained using a standard high-performance liquid chromatography method, suggesting the feasibility of clinical applications.     

Elektroanalyse

Ohne Zusammenfassung     

A Hybrid Genetic Algorithm with Boltzmann Convergence Properties

Stochastic global search algorithms such as genetic algorithms are used to attack difficult combinatorial optimization problems. However, genetic algorithms suffer from the lack of a convergence proof. This means that it is difficult to establish reliable algorithm braking criteria without extensive a priori knowledge of the solution space. The hybrid genetic algorithm presented here combines a genetic algorithm with simulated annealing in order to overcome the algorithm convergence problem. The genetic algorithm runs inside the simulated annealing algorithm and provides convergence via a Boltzmann cooling process. The hybrid algorithm was used successfully to solve a classical 30-city traveling salesman problem; it consistently outperformed both a conventional genetic algorithm and a conventional simulated annealing algorithm. This work was supported by the University of Colorado at Colorado Springs.     

Verschiedene Gasbrennerconstructionen

Ohne Zusammenfassung