Laser-induced acoustic wave generation/propagation/interaction in water in various internal channels

Short pulsed laser-induced single acoustic wave generation, propagation, interaction within a water-filled internal channel are experimentally and numerically studied. A large-area, short-duration, single-plane acoustic wave was generated by the thermoelastic interaction of a homogenized nanosecond pulsed laser beam with a liquid–solid interface and propagated at the speed of sound in water. Laser flash Schlieren photography was used to visualize the transient interaction of the plane acoustic wave in various internal channel structures ((a) sudden expansion and contraction channels, (b) bifurcating channels, (c) gradual contraction wall channels and (d) a cylinder). Fairly good agreement between the experimental results and numerical simulation is observed.     

Magnesium complexes incorporated by sulfonate phenoxide ligands as efficient catalysts for ring‐opening polymerization of ε‐caprolactone and trimethylene carbonate

Two novel sulfonate phenol ligands—3,3′‐di‐tert‐butyl‐2′‐hydroxy‐5,5′,6,6′‐tetramethyl‐biphenyl‐2‐yl 4‐X‐benzenesulfonate (X?CF₃, L^CF3 ‐H, and X?OCH₃, L^OMe ‐H)—were prepared through the sulfonylation of 3,3′‐di‐tert‐butyl‐5,5′,6,6′‐tetramethylbiphenyl‐2,2′‐diol with the corresponding 4‐substituted benzenesulfonyl chloride (1 equiv.) in the presence of excess triethylamine. Magnesium (Mg) complexes supported by sulfonate phenoxide ligands were synthesized and characterized structurally. The reaction of MgⁿBu₂ with L‐H (2 equiv.) produces the four‐coordinated monomeric complexes ( L^CF3 )₂Mg ( 1 ) and ( L^OMe )₂Mg ( 2 ). Complexes 1 and 2 are efficient catalysts for the ring‐opening polymerization of ε‐caprolactone (ε‐CL) and trimethylene carbonate (TMC) in the presence of 9‐anthracenemethanol; complex 1 catalyzes the polymerization of ε‐CL and TMC in a controlled manner, yielding polymers with the expected molecular weights and narrow polydispersity indices (PDIs). In ε‐CL polymerization, the activity of complex 1 is greater than that of complex 2 , likely because of the greater Lewis acidity of Mg²⁺ metal caused by the electron‐withdrawing substitute trifluoromethyl (? CF₃) at the 4‐position of the benzenesulfonate group. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3564–3572, 2010     

C-14 and H-3 contents in the groundwater around radioactive repository site in Korea

The contents of H-3 and C-14 in groundwater and surface waters around low and medium-level atomic waste repository site in Korea were determined. The concentrations of C-14 were in the range 0.186–0.287 Bq/L. The H-3 concentration of the groundwaters and surface waters were <0.06–5.75 and 1.22–4.74 Bq/L. The average H-3 contents of west, north and south direction were 1.18 ± 0.12, 1.11 ± 0.78 and 2.85 ± 2.66. H-3 and C-14 concentrations in the south direction were relatively higher than west and north direction samples. The surface waters sampled from catchment were four times higher than average H-3 concentration in precipitation. The concentrations of H-3 and C-14 within 5 km area samples were much higher than other samples.     

A multinomial tree model for pricing credit default swap options

Among the traded credit derivatives, the market interest in credit default swap options (CDSwaptions) is enormous. We propose a multinomial tree model to price Bermudan CDSwaptions. Our basic rationale is that we distribute the occurring probability for each node in a branch proportional to the probability density function of the assumed (normal) distribution. Through this approach, without the need of solving a large number of equations simultaneously, only the first four moments are required to build an arbitrarily large N-branches tree. We also demonstrate the detailed model implementation procedure including the valuation and the estimation of critical prices through an empirical example in Tucker and Wei (J Fixed Income 15(1):88–95, 2005). Numerical results show that, in the valuation, the proposed multinomial tree model is accurate and can significantly save pricing time under the same degree of accuracy as the binomial tree model. In the estimation of critical prices, the results are less accurate than those in the valuation, but the relative errors are acceptable.     

Defect Analysis of Ionically Compensated Quadruple and Quintuple Perovskite Layered Cuprates with Ti Blocking Layers

This work presents a modified defect model for pure and chemically substituted quadruple and quintuple pure perovskite layered cuprates, using data from the Jonker (thermopower vs ln conductivity) and Brouwer (log conductivity vs log pO₂) analyses. The closely matched in-plane bond lengths of the blocking and the active layers in these structures promote ionic compensation rather than electronic compensation upon aliovalent p-type doping. A comprehensive defect model that takes into account all the major defect species in an ionically compensated quadruple or quintuple perovskite provides a better means for understanding the electrical behavior of these novel materials. The presented model allows for the calculation of effective dopant and the oxygen interstitial concentrations in these materials.     

A high statistics measurement of the Lambda(+)(c) lifetime

A high statistics measurement of the Lambda(+)(c) lifetime from the Fermilab fixed-target FOCUS photoproduction experiment is presented. We describe the analysis technique with particular attention to the determination of the systematic uncertainty. The measured value of 204.6 +/- 3.4 (stat) +/- 2.5 (syst) fs from 8034 +/- 122 Lambda(+)(c)-->pK(-)pi(+) decays represents a significant improvement over the present world average.     

Dynamic aspects of phase decomposition in reactive blends of polycarbonate and syndiotactic polymethyl methacrylate

Dynamics of phase separation in bisphenol-A polycarbonate (PC)/syndiotactic polymethyl methacrylate (sPMMA) blends has been investigated by means of time-resolved light scattering. Solvent-cast films of the PC/sPMMA blends were transparent, suggestive of miscible character. Several temperature jumps were carried out at a 50/50 PC/sPMMA composition from a homogeneous state (room temperature) into a two-phase regime. The process of phase separation first occurred for some considerable period, then it was followed by phase dissolution driven by chemical reaction. The thermodegradative reaction of sPMMA triggered the dissolution process by probably forming PC/sPMMA graft or random copolymers at the interface, which eventually resulted in a single phase. However, annealing at elevated temperatures for an extended period could lead to cross-linking, and thus a two-phase structure could be fixed permanently. The early stage of spinodal decomposition was interpreted in terms of the linearized Cahn-Hilliard theory. In the late stages of spinodal decomposition, the relationship between scattering peak wavenumber and time was found to obey a power law, but the exponents showed a strong dependence on temperature jumps. The temporal universal scaling failed due to the influence of the chemical reaction. © 1995 John Wiley & Sons, Inc.