Search

A new task-level adaptive controller is presented for the hybrid dynamic control of constrained motion systems. Using a hybrid dynamic model of the process, velocity constraints are derived from which satisfactory velocity commands are obtained. Due to modeling errors and parametric uncertainties, the velocity commands may be erroneous and may result in suboptimal performance. A task-level adaptive control scheme, based on the occurrence of discrete events, is used to change the model parameters from which the velocity commands are determined. Automated control of an assembly task is given as an example, and simulations and experiments for this task are presented. These results demonstrate the applicability of the method and also indicate properties for rapid convergence. Index Terms - Adaptive control, constrained motion, hybrid dynamic system, Lyapunov.

The influence of bridging ligand substituents in rhodium(II) catalysts on the chemoselectivity of cyclization-cycloaddition reactions was investigated. Specifically, 3-allyl-2,5-diazopentanedione was reacted with 3-butenyl-2,5-diazopentanedione under the catalysis of rhodium(II) in methylene chloride. The results showed that the ligands affected the product ratio and regiochemical control of the intramolecular cycloaddition process.

The chemoselectivity in competitive metal carbene transformations of diazo compounds is regulated by the carboxylate and carboxamide ligands of dirhodium(II) catalysts. Dirhodium(II) perfluorobutyrate (Rh2(pfb)4) offers only the aromatic substitution product, and dirhodium(II) caprolactamate (Rh2 (cap)4) offers only the cyclopropanation product, though the products from both transformations result in almost equal quantities from the use of Rh (OAc)4 for competitive intramolecular cyclopropanation versus intramolecular aromatic substitution with 1-diazo-3-aryl-5-hexen-2-ones.

The production of cycloalkenone carbenoids using rhodium(II) catalyzed reactions with alpha-diazo alkynyl substituted ketones is reported. The process provides a new cyclization strategy for generating polycyclic ring systems. Treatment of alpha-diazo ketone with rhodium-(II) acetate in the presence of ethyl vinyl ether produced cyclopropanes in 90% chemical yields and more than 95% isomeric purity. The metallo-carbenoid complexes were more selective than related carbene intermediates, resulting in the chemoselectivity.

A study of the rhodium-catalyzed cycloaddition of alpha-diazo ketones with pyridines in the presence of dimethyl acetylenedicarboxylate (DMAD) probes into the effect of reduced N-lone pair nucleophilicity on ylide formation. The trapping experiments, such as that of the ylide from the reaction of alpha-diazoacetophenone with 2-(methylthio)pyridine, shows a mechanism whereby the ylide undergoes dipolar cycloaddition with DMAD at the less substituted carbon, followed by a 1,5-hydride shift, forming an indolizine in high yields. Results and analyses of related reactions are also presented.

The reaction of 1-(phenylsulfonyl)-1,2-propadiene with either bromine or iodine results in the formation of a highly reactive 2,3-dihalo-1-(phenylsulfonyl)-1-propene which features allyl halide, vinyl halide and vinyl sulfone functionalities at a three-carbon array. The nature and condition of the nucleophilic reactions determine the reactivity of the dihalo propene. Amines, thiophenols, sodium hydrides and ambident nucleophiles such as beta-dicarbonyls, silyl enol ethers and thioamides react with the dihalo propene to efficiently synthesize different arylsulfonyl-substituted heterocycles and furans.

Research has been conducted on the gunosine, inosine, uridine and cytidine. The modification of these nucleosides has been carried out and the the experimental description and characterization of the produced nucleosides compounds are reported.

Changing the dirhodium ligand can alter the product distribution in reactions where intramolecular cyclopropanation and aromatic substitution are competitive. The course of the reaction can be changed by replacing the dirhodium(II) ligand from perfluorobutyrate to acetamide (acam) or caprolactam (cap). Cyclopropanation is the favored reaction path in using Rh2(cap)4 while aromatic substitution is the major route from Rh2(pfb)4- catalyzed reactions.

The in vitro identification and biochemical confirmation of a phosphorylation-dependent interaction between the Src activation loop phosphotyrosine and the N-terminal SH2 domain of the p85 regulatory subunit of phosphatidyl inositol-3 kinase (PI3K) is reported. It is found that the Src/P13K interaction is indeed dependent on both the phosphorylation state of the Src activation loop and an available N-terminal SH2 domain on P13K.

The use of a randomized phosphotyrosine (pTyr) peptide probe along with human cDNA phage display libraries, for both the isolation and binding evaluation of multiple SH2 domains, is described. A rapid on-phage binding assay that is compatible with any biotinylated probe is reported.

A non-preorganized acyclic bromide receptor has been discovered. The receptor was characterized to have a strong halide binding activity which appeared to be attributable to the strong N-H---Hal- hydrogen bonding as demonstrated by FT-IR, 1H-NMR and X-ray diffraction studies. It was also found that the crystals of 1.((PPh4)Br)2 assumes an unusual twisted syn-syn conformation that makes the formation of two N-H---Br hydrogen bonds with one bromide ion possible.

The choice of solvent influences the chemoselectivity in the rhodium(II)- catalyzed alkyne-insertion reactions on alpha-diazo ketones. With Rh2(oct)4 as the catalyst, the use of pentane as solvent leads to a 1:1 E/Z mix of cyclopropenylidenenones while dichloromethane yields a 2:3 mixture of cylclopropene and indenone. With Rh2(OAc)4 as catalyst, pentane exclusively forms cyclopropene while dichloromethane yields a 2:1 mix of cis- and trans- alkenyl substituted indenones. A mechanistic rationalization of the chemoselective solvent effect is presented.