Solvent Effects on Aza‐anionic Cycloaromatization of 2‐(2‐Substituted‐ethynyl)benzonitriles

The methanolysis of 2‐(2‐aryl ethynyl)benzonitriles is accelerated when the polar aprotic solvents are added, which could enhance the 6‐endo pathway and give isoquinolones, though the 5‐exo pathway is occupied mostly. The yields of products would also be in creased.     

Thermal degradation kinetics of biodegradable poly(3‐hydroxybutyrate)/layered double hydroxide nanocomposites

The thermal degradation behaviors of biodegradable poly(3‐hydroxybutyrate) (PHB) and PHB/poly(ethylene glycol) phosphonates (PEOPAs)‐modified layered double hydroxide (PMLDH) nanocomposites have been investigated using thermogravimetric analysis. Effects of PMLDH contents on the isothermal degradation kinetics of PHB were explored. These experimental results show that the degradation kinetics of PHB/PMLDH nanocomposites is the chain‐scission process of cyclic β‐elimination reaction with the following autocatalytic reactions, which is very similar to that of pure PHB matrix. Further calculated data based on the autocatalytic model can fit very well with the experimental data. The E_a value of PHB/PMLDH nanocomposites is increased as the content of PMLDH increases. This can be attributed to the incorporation of more PMLDH loading to PHB induced a decrease in the degradation rate and an increase in the residual weight for PHB/PMLDH nanocomposites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1207–1213, 2008     

A Note on Exact Moment Computation for Normal Lead Times in the Two-Supplier Case

In the stochastic lead time inventory model with two suppliers and different normal lead times, the mean and variance of the lead-time demand distribution are traditionally computed using numerical integration. Tables are made available to help practitioners determine the minimum size of replenishments when orders to the suppliers are placed at the same time. This paper presents closed-form solutions to evaluate the required quantities of interest and tries to correct some mistakes in the existing tables. The expressions given here may also provide insight into the choice of sole versus dual suppliers.     

A Discrete Lagrangian-Based Global-Search Method for Solving Satisfiability Problems

Satisfiability is a class of NP-complete problems that model a wide range of real-world applications. These problems are difficult to solve because they have many local minima in their search space, often trapping greedy search methods that utilize some form of descent. In this paper, we propose a new discrete Lagrange-multiplier-based global-search method (DLM) for solving satisfiability problems. We derive new approaches for applying Lagrangian methods in discrete space, we show that an equilibrium is reached when a feasible assignment to the original problem is found and present heuristic algorithms to look for equilibrium points. Our method and analysis provides a theoretical foundation and generalization of local search schemes that optimize the objective alone and penalty-based schemes that optimize the constraints alone. In contrast to local search methods that restart from a new starting point when a search reaches a local trap, the Lagrange multipliers in DLM provide a force to lead the search out of a local minimum and move it in the direction provided by the Lagrange multipliers. In contrast to penalty-based schemes that rely only on the weights of violated constraints to escape from local minima, DLM also uses the value of an objective function (in this case the number of violated constraints) to provide further guidance. The dynamic shift in emphasis between the objective and the constraints, depending on their relative values, is the key of Lagrangian methods. One of the major advantages of DLM is that it has very few algorithmic parameters to be tuned by users. Besides the search procedure can be made deterministic and the results reproducible. We demonstrate our method by applying it to solve an extensive set of benchmark problems archived in DIMACS of Rutgers University. DLM often performs better than the best existing methods and can achieve an order-of-magnitude speed-up for some problems.     

Effect of intra- and extra-liposomal distribution of sodium chloride on the stability of large unilamellar vesicles

Three groups of 1,2-dipalmitoyl-rac-glycero-3-phosphocholine (DPPC) large unilamellar vesicle (LUV) dispersions were studied: LUV (A) dispersions with only extraliposomal sodium chloride (NaCl), LUV (B) dispersions with intra- and extraliposomal NaCl, and LUV (C) dispersions with only intraliposomal NaCl. The NaCl concentrations ranged from 0 to 150 mM. An abrupt increase in leakage was observed around -10 degree C for all the three groups of LUV, which coincided with the temperature of extraliposomal ice formation. Within the three groups, leakage of LUV (C) was significantly higher than the other groups. Extraliposomal ice formation and the resulting freeze-concentration of LUV may be the major cause of the leakage. Intraliposomal ice formation observed at -43 degree C seemed to stop leakage of LUV when LUV were frozen below -43 degree C. An exotherm of eutectic crystallization of NaCl was occasionally observed at -37 degree C, with a higher probability of formation at 150 mM extraliposomal NaCl than at 50 mM. The eutectic crystals were thought to cause additional leakage from the LUV (B).     

Reconstruction of large coherent structures from SPIV measurements in a forced turbulent mixing layer

A procedure is suggested here for reconstructing the time variation of a three-dimensional (3D) coherent velocity field, based on applying Least Square Method to a very limited number of phase-locked measurements. The measurements are performed in a spanwise plane of a forced turbulent mixing layer by employing the stereo particle image velocimetry system. The forcing is produced by oscillating two- and three-dimensional (3D) flappers placed at the edge of the splitter plate. The feasibility and validity of the procedure for velocity field reconstruction are checked by using Hot Wire Measurements. Very clear patterns are observed of two types of coherent structures: spanwise K-H billows (rolls) and streamwise vortices. These are due to primary and secondary instabilities and their time evolution is presented.     

Measurements of two- and three-dimensional waves in a channel,including the vicinity of cut-off frequencies

Measurements of water wave profiles were performed in a rectangular flume equipped with a modular wavemaker. This particular wavemaker could generate both two- and three-dimensional waves. A method is proposed to evaluate quantitatively the deviations of a spacial flow field from the two-dimensional one. Plane propagating waves, as well as pure sloshing waves with their crests parallel to the walls, were generated in the flume. In all cases the measured amplitudes were compared against linear theory predictions.