排序方式: 共有12条查询结果,搜索用时 93 毫秒
1.
High-throughput approaches for the discovery and optimization of new olefin polymerization catalysts
Murphy V Bei X Boussie TR Brümmer O Diamond GM Goh C Hall KA Lapointe AM Leclerc M Longmire JM Shoemaker JA Turner H Weinberg WH 《Chemical record (New York, N.Y.)》2002,2(4):278-289
The discovery of new olefin polymerization catalysts is currently a time-intensive trial-and-error process with no guarantee of success. A fully integrated high-throughput screening workflow for the discovery of new catalysts for polyolefin production has been implemented at Symyx Technologies. The workflow includes the design of the metal-ligand libraries using custom-made computer software, automated delivery of metal precursors and ligands into the reactors using a liquid-handling robot, and a rapid primary screen that serves to assess the potential of each metalligand-activator combination as an olefin polymerization catalyst. "Hits" from the primary screen are subjected to secondary screens using a 48-cell parallel polymerization reactor. Individual polymerization reactions are monitored in real time under conditions that provide meaningful information about the performance capabilities of each catalyst. Rapid polymer characterization techniques support the primary and secondary screens. We have discovered many new and interesting catalyst classes using this technology. 相似文献
2.
Thomas R. Boussie Carla Coutard Howard Turner Vince Murphy Timothy S. Powers 《Angewandte Chemie (International ed. in English)》1998,37(23):3272-3275
Active polymerization catalysts , novel resin-bound diimine complexes of nickel(II ) and palladium(II ) are obtained by combinatorial synthesis and combined in a catalyst library. By tagging with fluorescent markers, the catalysts can be coded. Therefore, after cleavage of the tag from the polymer-coated resin, HPLC can be used to determine the pathway along which the products were formed. 相似文献
3.
Boussie TR Diamond GM Goh C Hall KA LaPointe AM Leclerc M Lund C Murphy V Shoemaker JA Tracht U Turner H Zhang J Uno T Rosen RK Stevens JC 《Journal of the American Chemical Society》2003,125(14):4306-4317
For the first time, new catalysts for olefin polymerization have been discovered through the application of fully integrated high-throughput primary and secondary screening techniques supported by rapid polymer characterization methods. Microscale 1-octene primary screening polymerization experiments combining arrays of ligands with reactive metal complexes M(CH(2)Ph)(4) (M = Zr, Hf) and multiple activation conditions represent a new high-throughput technique for discovering novel group (IV) polymerization catalysts. The primary screening methods described here have been validated using a commercially relevant polyolefin catalyst, and implemented rapidly to discover the new amide-ether based hafnium catalyst [eta(2)-(N,O)[bond](2-MeO[bond]C(6)H(4))(2,4,6-Me(3)C(6)H(2))N]Hf(CH(2)Ph)(3) (1), which is capable of polymerizing 1-octene to high conversion. The molecular structure of 1 has been determined by X-ray diffraction. Larger scale secondary screening experiments performed on a focused 96-member amine-ether library demonstrated the versatile high temperature ethylene-1-octene copolymerization capabilities of this catalyst class, and led to significant performance improvements over the initial primary screening discovery. Conventional one gallon batch reactor copolymerizations performed using selected amide-ether hafnium compounds confirmed the performance features of this new catalyst class, serving to fully validate the experimental results from the high-throughput approaches described herein. 相似文献
4.
5.
Thomas R. Boussie Gary M. Diamond Christopher Goh Keith A. Hall Anne M. LaPointe Margarete K. Leclerc Vince Murphy James A. W. Shoemaker Howard Turner Robert K. Rosen James C. Stevens Francesca Alfano Vincenzo Busico Roberta Cipullo Giovanni Talarico 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2006,118(20):3356-3361
6.
The microwave heating of two-dimensional slabs in a long rectangularwaveguide propagating the TE10 mode is examined. The temperaturedependency of the electrical conductivity and the thermal absorptivityis assumed to be governed by the Arrhenius law, while both theelectrical permittivity and the magnetic permeability are assumedconstant. The governing equations are the forced heat equationand the steady-state version of Maxwell's equation while theboundary conditions take into account both convective and radiativeheat loss. Approximate analytical solutions, valid for smallthermal absorptivity, are found for the temperature and theelectric-field amplitude using the Galerkin method. As the Arrheniuslaw is not amenable analytically, it is approximated by a rational-cubicfunction. At the steady state the temperature versus power relationshipis found to be multivalued; at the critical power level thermalrunaway occurs when the temperature jumps from the lower (cool)temperature branch to the upper (hot) temperature branch ofthe solution. In the steady-state limit the approximate analyticalsolutions are compared with the numerical solutions of the governingequations for various special cases. These are the limits ofsmall and large heat loss and an intermediate case involvingradiative heat loss. Results are also presented for a case wheredifferential cooling occurs on the different sides on the slab.An alternative heating scenario, where one end of the waveguideis blocked by a short, is also considered. The approximate solutionsare found for this geometry and compared in the small Biot-numberlimit to Kriegsmann (1997). Also, a control process is presented,which allows thermal runaway to be avoided and the desired finalsteady state to be reached. Various special cases of the feedbackparameters associated with the control process are examined. 相似文献
7.
Andreas?Lüthi Martin?A?Wikstr?m Mary?J?Palmer Paul?Matthews Tim?A?Benke John?TR?Isaac Graham?L?CollingridgeEmail author 《BMC neuroscience》2004,5(1):44
Background
Knowledge of how synapses alter their efficiency of communication is central to the understanding of learning and memory. The most extensively studied forms of synaptic plasticity are long-term potentiation (LTP) and its counterpart long-term depression (LTD) of AMPA receptor-mediated synaptic transmission. In the CA1 region of the hippocampus, it has been shown that LTP often involves a rapid increase in the unitary conductance of AMPA receptor channels. However, LTP can also occur in the absence of any alteration in AMPA receptor unitary conductance. In the present study we have used whole-cell dendritic recording, failures analysis and non-stationary fluctuation analysis to investigate the mechanism of depotentiation of LTP. 相似文献8.
9.
Over the past 10 years a number of new techniques have emerged that allow the manipulation of single DNA molecules and other biopolymers (RNA, proteins, etc.). These experiments have permitted the measurement of the DNA stretching and twisting elasticity and have consequently revealed the essential role played by the DNA mechanical properties in its interactions with proteins. We shall first describe the different methods used to stretch and twist single DNA molecules. We will then focus on its behaviour under torsion, especially by discussing the different methods used to estimate its torsional modulus. 相似文献
10.
F. TRÄNKLE M. ZEITZ M. GINKEL E.D. GILLES 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(3):283-307
The novel process modeling tool PROMOT supports the object-oriented modeling of chemical processes for the simulation environment DIVA. In PROMOT, differential-algebraic process models can be built by aggregating structural and behavioral modeling entities that represent the topological structure or the dynamic and steady-state behavior, respectively, of the investigated chemical processes. Process models and their modeling entities may be defined either in an object-oriented modeling language or with a graphical user interface. This paper discusses the modeling concept, the modeling language, the knowledge representation aspects, and the implementation of PROMOT. 相似文献