Buckman Laboratories (United States)

Background: Ablation of complex fractionated atrial electrograms (CFAEs) is controversial, primarily because of difficulty in visually distinguishing CFAEs representing an active site of driver activity from a passive site of double potentials, wave break, and/or slow conduction. We hypothesized that CFAEs within rotors in atrial fibrillation (AF) would exhibit highly recurrent behavior compared with CFAEs remote from these driver regions. Methods: Active and passive mechanisms of CFAE formation were simulated in several 2D 7.5 x 7.5 cm modified Luo-Rudy 1 models. CFAEs within areas of rotors were considered active, while those caused by wave break, slow conduction or double potentials remote from rotors were considered passive. Clinical signals were also collected during catheter ablation of paroxysmal AF (n=8 patients). An active driver CFAE site was defined by termination of AF with ablation followed by non-inducibility. A passive site was defined as CFAE occurring remotely. Detection of CFAEs was based on mean cycle length (MCL) calculated from 4 second windows using -dV/dt for detection (40ms refractory period/10ms maximum EGM width for simulations; 45ms/15ms respectively for clinical signals). Recurrence quantification analysis (RQA) was performed on discrete time series of simulated and clinical CFAE activations. Results: RQA was performed on 20 simulated EGMs. MCL was similar in both active and passive CFAEs (74±11ms and 78±6ms respectively, p=NS), but recurrence was significantly higher in active compared to passive sites (%recurrence: 61±22% active, 4±6% passive, p<0.01). In patients with AF, the driver sites were all located within the pulmonary vein antra while passive CFAEs were remote. The MCL of CFAEs at active driver sites was similar to that of passive sites (100±13ms active, 98±17ms passive, p=NS), but recurrence was significantly higher in the active driver sites (%recurrence: 18±15% active, 2±1% passive, p=0.02). Conclusion: CFAEs may occur due to either active or passive mechanisms. Sites within rotors or focal drivers of AF are more likely to exhibit recurrent patterns. RQA may be a powerful tool to differentiate driver from bystander CFAEs enabling more efficient targeting for ablation.

The root cause of corrosion of a pump impeller in a cooling water system is investigated. The impeller material was made of ductile cast iron. The pump failure was encountered after eight months of operation. A detailed visual examination, microstructure examination, and water analysis were carried out to ascertain the probable cause of failure. Finally, the obtained results infer that the solid-particle containing fluid flow was responsible for erosion–corrosion in the impeller failure.

This article proposes a new procedure to compute solid-liquid equilibrium in electrolyte systems that may form pure solid phases at a given temperature, pressure, and global composition. The procedure combines three sub-procedures: phase stability test, minimization of the Gibbs free energy with a stoichiometric formulation of the salt-forming reactions to compute phase splitting, and a phase elimination test. After the phase splitting calculation for a system configuration that has a certain number of phases, the phase stability test establishes whether including an additional phase will reduce the Gibbs free energy further. The criteria used for phase stability may lead, in some cases, to the premature inclusion of phases that should be absent from the final solution but, if this happens, the phase elimination sub-procedure removes them. It is possible to use the procedure with several excess Gibbs free energy models for liquid phase behavior. The procedure has proven to be reliable and fast and the results are in good agreement with literature data.

Abstract Low levels of inorganic phosphate are very effective at corrosion inhibition however, using this type of program under inappropriate water and plant conditions can result in severe scaling. This paper will discuss the basic selection / application criteria that need to be applied to avoid deposition problems. A number of case histories will be used to illustrate why this type of program can fail in industrial settings.

Synthetic approaches to novel 4,8-dimethyl-4'-halomethyl-4',5'-dihydropsoralens as synthetic precursors to 4,8-dimethyl-4'-(N-pyridiniummethyl)-4',5'-dihydropsoralens are described. The compounds are potential therapeutic agents for improved psoralen ultraviolet radiation therapy with reduced mutagenicity.

Agrochemicals continue to be the prime method for controlling insects, plant diseases, and weeds throughout the world and will continue as such for the foreseeable future. The increasing world population will require increased crop production and this will require the use of new environmentally safe and efficacious agrochemicals. Increasing costs of registration and re-registration are causing organizations to reevaluate their products and to discontinue those which are less profitable or have safety difficulties. Increasing pressures for greater product safety provide opportunities for new materials which are safer and more effective. Increasing knowledge about vital enzyme structures are providing greater understanding of interactions with control agents. This is being used in the design of new materials for agriculture. Resistance to agrochemicals by plants, insects, fungi, etc. continues to be a challenge to scientists. More is being learned about the molecular causes of this resistance and in the case of plants this is being used to prepare crop plants which are resistant to certain herbicides. These forces and how they present challenges for those working in the development of new agrochemicals are discussed in this chapter.

ADVERTISEMENT RETURN TO BOOKPREVPrefaceNEXTPrefaceDON R. BAKERDON R. BAKERICI Americas Inc. Richmond, CA 94804More by DON R. BAKER, JOSEPH G. FENYESJOSEPH G. FENYESBuckman Laboratories International, Inc. Memphis, TN 38108More by JOSEPH G. FENYES, and JAMES J. STEFFENSJAMES J. STEFFENSE. I. du Pont de Nemours and Company Stine-Haskell Research Center Newark, DE 19714More by JAMES J. STEFFENSDOI: 10.1021/bk-1992-0504.pr001 This publication is free to access through this site. Learn MorePublication Date (Print):September 22, 1992Publication History Published online23 July 2009Published inprint 22 September 1992Request reuse permissions Copyright © 1992 American Chemical Society. This publication is available under these Terms of Use. Synthesis and Chemistry of Agrochemicals IIIpp xi-xiiACS Symposium SeriesVol. 504ISBN13: 9780841224735eISBN: 9780841213609Chapter Views114Citations-LEARN ABOUT THESE METRICSChapter Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (152 KB) Get e-Alerts