10,000 publications from this institution
Abstract The design and performance of reference electrodes for use in high subcritical and supercritical aqueous systems are reviewed. Particular attention is paid to the stability of the electrochemically active elements, to the contribution of the two irreversible thermodynamic potentials (the isothermal liquid junction potential and the thermal liquid junction potential) to the measured potential, to calibration of the reference electrode on to the standard hydrogen scale, and to the application of the electrodes in pH measurements and in potentiometry. Methods for estimating and suppressing the thermal diffusion potential and the isothermal liquid junction potential are also discussed. While significant progress has been made over the past several decades in developing viable reference electrodes for use in high temperature aqueous systems, particularly for potential monitoring in subcritical systems, no universally accepted reference electrode has emerged for potential monitoring in supercritical aqueous systems.
The performance of medical groups is receiving increased attention. Relatively little conceptual or empirical work exists that examines the various dimensions of medical group performance. Using a national database of 693 medical groups, this article develops a scorecard approach to assessing group performance and presents a theory-driven framework for differentiating between high-performing versus low-performingmedical groups. The clinical quality of care, financial performance, and organizational learning capability of medical groups are assessed in relation to environmental forces, resource acquisition and resource deployment factors, and a quality-centered culture. Findings support the utility of the performance scorecard approach and identification of a number of key factors differentiating high-performing from low-performing groups including, in particular, the importance of a quality-centered culture and the requirement of outside reporting from third party organizations. The findings hold a number of important implications for policy and practice, and the framework presented provides a foundation for future research.
Generalized synchronization (GS) of two chaotic systems is a generalization of identical synchronization. Usually, the manifold of GS is much more complex than the driven system and the driving system. In this paper, we study a special case of GS in which the synchronization manifold is linear (linear GS for short). In a theorem, we present the necessary and sufficient conditions under which a linear GS can be achieved between two chaotic systems. In particular, we study the linear GS of two Chua's circuits.
Abstract Political polarization, meaning sharp differences in the political ideologies and preferences of the partisans of different parties, implies that members of one party are more likely to dismiss the policies and recommendations of spokesmen and appointees of the other party on the grounds that those policies and recommendations are informed by value systems inimical to their own. In the US, this means that when spokesmen for one party endorse masks, members of the other party reject them instinctively and automatically.
Abstract : The thermal analysis system and tube furnace have been used to conduct initial studies on the conversion of alkoxysiloxy derivatives to metal silicate solid state materials. These results, pertaining titanium, zirconium, and hafnium, are described. Interest in low-temperature chemical routes to ceramic materials is based largely on the potential for generating metastable structures with unusual properties, or on development of improved processing methods. The sol-gel method in particular has attracted attention as a low temperature route to oxides. This method can be extended to the synthesis of mixed metal oxides, however the formation of homogeneous materials can be complicated by differences in hydrolysis rates for the starting metal compounds. Sol-gel processes have been utilized to produce titanium oxides or zirconium oxides containing silicates in the form of thin films, fibers, or monoliths. Materials of this type find applications that take advantage of their optical properties, chemical inertness, high melting points, insulating properties, and fracture toughness.
The kinetics of the amine catalyzed intramolecular imidization of alkyl and phenyl phthalamates with a variety of amines were measured in deuteriated chloroform at 40.1 °C. An overall second-order kinetic rate law, rate =koverall[amine][phthalamate], was obtained from our experiments. Although pre-association between the amides and the amines through hydrogen-bonding interaction was suggested by proton NMR spectroscopy, the catalytic ability of amines was found to be related to their basicity rather than to their hydrogen-bonding ability or nucleophilicity. This observation implies the involvement of proton transfer from the amide to the amine in the critical transition state. In addition, by changing the leaving group from phenoxy to butoxy group, the reaction rate constants decrease by a factor of 30 to 70. On the basis of these kinetic results, we propose that the intramolecular imidization proceeds through an amine assisted cyclization to a zwitterionic intermediate, followed by the expulsion of the alkoxy or phenoxy group to provide phthalimide and the corresponding alcohol.
