Publications

Abstract Diblock star polymers were synthesized via atom transfer radical polymerization from a palladium porphyrin macroinitiator. The arms of the star polymers had an amphiphilic design, with the central Pd‐porphyrin surrounded by a relatively hydrophobic block of poly(butyl acrylate) and terminated by a hydrophilic block of poly(oligoethyleneglycol monomethylether monomethacrylate). The size of both the interior and exterior blocks of the polymer arms were tuned over a wide range of molecular weights with the exterior block used to solubilize the stars in polar media. The star polymers showed enhanced reactivity in the oxidation of 2‐furaldehyde relative to a small molecule porphyrin, suggesting that the polymer backbone aids with catalytic turnover. Oxygen diffusion studies indicate that the polymer backbone shields the porphyrin excited state from oxygen quenching. Shielding is independent of molecular weight and polymer composition, but it is not pronounced enough to retard the rate of singlet oxygen generation under preparative photooxidation conditions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4939–4951, 2006

Abstract The great majority of models that have been developed to predict localized corrosion damage are empirical in nature. As such, they lack the ability to effectively predict damage outside of their immediate realm of calibration and generally can only “predict” what is already known. Furthermore, empirical models generally cannot predict new phenomena or relationships. It is shown that it is possible to describe propagation of corrosion damage deterministically, i.e. to describe how the systems evolves from the present state to the future state on the basis of natural laws [conservation of charge, mass-energy, and mass-charge equivalence (Faraday's law), etc. ], subject to constraint by the natural laws. It is clear that deterministic models have much more predictive power than do empirical models. However, in the general case, it is possible to describe the development of localized corrosion damage in terms of the propagation of an ensemble of corrosion events, rather than as individual cavities. Accordingly, the prediction can be made in terms of statistical terms, for example, probability that the deepest pit will exceed the critical dimension that defines failure ( e.g. , thickness of a pipe wall). In doing so, the statistical parameters (mean depth of the deepest pit with its standard deviation, etc. ) can be calculated deterministically. In order to perform such calculations, we must possess deterministic models for every stage of cavity development (pit nucleation, propagation and repassivation, transition pit into crack, crack propagation, and so forth). Some of these models are outlined in the current review. The deterministic theory outlined here has been applied for the predation of localized corrosion damage in important, practical systems, including pitting in oil field components, in low pressure steam turbine blades and discs, and in condensing heat exchangers, to name but a few of the current and past applications, some of which are reviewed in this paper.

The relationship between the peak deformations of inelastic and corresponding linear single-degree-of-freedom (SDF) systems is investigated. Presented are the median of the inelastic deformation ratio for 214 ground motions organized into 11 ensembles of ground motions, representing large or small earthquake magnitude and distance, and National Earthquake Hazards Reduction Program (NEHRP) site classes B, C, and D; near-fault ground motions are also included. Two sets of results are presented for bilinear nondegrading systems over the complete range of elastic vibration period, Tn:Cμ for systems with known ductility factor, μ, and CR for systems with known yield-strength reduction factor, Ry. The influence of postyield stiffness on the inelastic deformation ratios Cμ and CR is investigated comprehensively. All data are interpreted in the context of acceleration-sensitive, velocity-sensitive, and displacement-sensitive regions of the spectrum for broad applications. The median Cμ versus Tn and CR versus Tn plots are demonstrated to be essentially independent of the earthquake magnitude and distance (over their ranges considered), and of site class. In the acceleration-sensitive spectral region, the median inelastic deformation ratio for near-fault ground motions is systematically different when plotted against Tn; however, when plotted against normalized period Tn/Tc (where Tc is the period separating the acceleration- and velocity-sensitive regions) they become very similar in all spectral regions. Determined by regression analysis of the data, two equations—one for Cμ and the other for CR—have been developed as a function of Tn/Tc, and μ or Ry, respectively, and are valid for all ground motion ensembles considered. These equations for Cμ and CR should be useful in estimating the inelastic deformation of new or rehabilitated structures—where the global ductility capacity can be estimated—and existing structures with known lateral strength.

We report highly enantioselective intramolecular, silylations of unactivated, primary C(sp³)-H bonds. The reactions form dihydrobenzosiloles in high yields with excellent enantioselectivities by functionalization of enantiotopic methyl groups under mild conditions. The reaction is catalyzed by an iridium complex generated from [Ir(COD)OMe]₂ and chiral dinitrogen ligands that we recently disclosed. The C-Si bonds in the enantioenriched dihydrobenzosiloles were further transformed to C-Cl, C-Br, C-I, and C-O bonds in final products. The potential of this reaction was illustrated by sequential C(sp³)-H and C(sp²)-H silylations and functionalizations, as well as diastereoselective C-H silylations of a chiral, natural-product derivative containing multiple types of C-H bonds. Preliminary mechanistic studies suggest that C-H cleavage is the rate-determining step.

Abstract In 2000, a regional rule governing maximum individual cancer risk from stationary facilities in Southern California was dramatically altered, reducing allowable risk levels by 75%. This article uses a case study approach to explore the role of a community‐based participatory research (CBPR) partnership, the Southern California Environmental Justice Collaborative, in producing research and helping spearhead policy advocacy leading to this policy change. It also highlights the role of the collaborative in helping to change the framing of the issue from individual to cumulative risk assessment, so that the regulatory agencies began to reflect this broader thinking in their policymaking. The collaborative's structure and methodology, regional focus, relationships with key decision makers, and its reputation as an important source of both credible science and “people power” were seen as contributing to its effectiveness. The role of contextual factors including a recovering and more regulation‐friendly economy also is highlighted, as are key barriers faced. Implications for other community–academic partnerships working to address regional and statewide public policy are discussed.

Intermolecular acceptorless dehydrogenative coupling of silanes with arene C−H bonds and intramolecular coupling of silanes with aryl and alkyl C−H bonds occur in good yield in the presence of 5 mol % of Tp<sup>Me</sup><sub><sup>2</sup></sub>PtMe<sub>2</sub>H (Tp<sup>Me</sup><sub><sup>2</sup></sub> = hydridotris(3,5-dimethylpyrazolyl)borate) and related platinum(IV) complexes. The intermolecular reactions of arenes occurred with both trialkyl and dialkylaryl silanes. Intramolecular reactions of dialkylsilylalkylarenes occurred at aryl C−H bonds, and reactions of tributylsilane or dibutylphenylsilane occurred intramolecularly at the aliphatic, primary C−H bond. The reactions of arenes occurred preferentially at the least sterically hindered C−H bonds and preferentially with more electron-poor arenes. Crossover experiments and the lack of reactivity of the arylsilanes with H<sub>2</sub> imply that the dehydrogenative silylation of arenes can be irreversible, even in a closed reaction vessel.