20,429 research outputs found
A Peak Point Theorem for Uniform Algebras on Real-Analytic Varieties
It was once conjectured that if is a uniform algebra on its maximal ideal
space , and if each point of is a peak point for , then .
This peak-point conjecture was disproved by Brian Cole in 1968. Here we
establish a peak-point theorem for uniform algebras generated by real-analytic
functions on real-analytic varieties, generalizing previous results of the
authors and John Wermer
Balancing Efficiency, Equity, and Voice in Workplace Resolution Procedures
Systems for resolving workplace disputes are very important to workers and firms, and have been the subject of much debate. In the United States, traditional unionized grievance procedures, emerging nonunion dispute resolution systems, and the court-based system for resolving employment law disputes have all been criticized. Much of the existing debate on workplace dispute resolution, however, has been atheoretical, with a focus on techniques of dispute resolution rather than the goals of the system. What is missing from the debate are fundamental standards for comparing and evaluating dispute resolutions systems. In this paper, we develop efficiency, equity, and voice as these standards. Unionized, nonunion, and employment law procedures are then evaluated against these three standards.
Homogeneous CO Hydrogenation: Ligand Effects on the Lewis Acid-Assisted Reductive Coupling of Carbon Monoxide
Structure-function studies on the role of pendent Lewis acids in the reductive coupling of CO are reported. Cationic rhenium carbonyl complexes containing zero, one, or two phosphinoborane ligands (Ph_2P(CH_2)_nB(C_8H_(14)), n=1-3) react with the nucleophilic hydride [HPt(dmpe)_2]^+
to reduce [M-CO]^+ to M-CHO; this step is relatively insensitive to the Lewis acid, as both pendent
(internal) and external boranes of appropriate acid strength can be used. In contrast, whether a
second hydride transfer and C-C bond forming steps occur depends strongly on the number of carbon atoms between P and B in the phosphinoborane ligands, as well as the number of pendent acids in the complex: shorter linker chain lengths favor such reductive coupling, whereas longer
chains and external boranes are ineffective. A number of different species containing partially reduced CO groups, whose exact structures vary considerably with the nature and
number of phosphinoborane ligands, have been crystallographically characterized. The reaction of [(Ph -2P(CH_2)_2B(C_8H_(14)))_2Re(CO)4]^+ with [HPt(dmpe)_2]^+
takes place via a âhydride shuttleâ mechanism, in which hydride is transferred from Pt to a pendent borane and thence to CO, rather than by direct hydride attack at CO. Addition of a second hydride in C_6D_5Cl at -40 ÂșC affords an unusual anionic bis(carbene) complex, which converts to a C-C bonded product on warming. These results support a working model for Lewis acid-assisted reductive coupling of CO, in which B (pendent or external) shuttles hydride from Pt to coordinated CO, followed by formation of an
intramolecular B-O bond, which facilitates reductive coupling
Homogeneous CO Hydrogenation: Dihydrogen Activation Involves a Frustrated Lewis Pair Instead of a Platinum Complex
During a search for conditions appropriate for Pt-catalyzed CO reduction using dihydrogen directly, metal-free conditions were discovered instead. A bulky, strong phosphazene base forms a âfrustratedâ Lewis pair (FLP) with a trialkylborane in the secondary coordination sphere of a rhenium carbonyl. Treatment of the FLP with dihydrogen cleanly affords multiple hydride transfers and CâC bond formation
Trialkylborane-Assisted CO_2 Reduction by Late Transition Metal Hydrides
Trialkylborane additives promote reduction of CO_2 to formate by bis(diphosphine) Ni(II) and Rh(III) hydride complexes. The late transition metal hydrides, which can be formed from dihydrogen, transfer hydride to CO_2 to give a formateborane adduct. The borane must be of appropriate Lewis acidity: weaker acids do not show significant hydride transfer enhancement, while stronger acids abstract hydride without CO_2 reduction. The mechanism likely involves a pre-equilibrium hydride transfer followed by formation of a stabilizing formateborane adduct
Thermodynamic simulation of deoxyoligonucleotide hybridization, polymerization, and ligation
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 54-55).by Alexander J. Hartemink.M.S
Prospects for non-immunological molecular therapeutics in melanoma
In 2006 there were 60,000 new cases of cutaneous melanoma in the European Union and 13,000 deaths (www.europeancancerleagues.org). Currently available systemic treatment options for metastatic melanoma, including both cytotoxic and immunologic therapies, produce low rates of response and have modest survival impact. Therefore, there is an urgent need for effective novel therapies. Molecularly targeted treatments have demonstrated efficacy in certain cancers e.g. in HER2-positive breast cancer and in chronic myeloid leukaemia.
Several pathways are currently being investigated as potential molecular targets in melanoma. The best studied is BRAF which is frequently mutated in melanoma. A multi tyrosine kinase inhibitor, sorafenib, which targets BRAF, has shown promising activity in preclinical studies and is currently being tested in combination with chemotherapy in patients with metastatic disease.
In addition to BRAF, therapies which target other components of the Raf/Ras/MAPK pathway are being investigated. Other novel targets currently being investigated include the PI3/AKT pathway, tyrosine kinases, angiogenesis, poly (ADP ribose) polymerases, survivin and heat shock protein 90. Progress on preclinical and clinical evaluation of these novel targets in melanoma will be reviewed
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Asymmetric phase-transfer-catalyzed synthesis of five-membered cyclic gamma-Amino acid precursors
The first example of an intramolecular enantioselective Michael addition of nitronates onto conjugated systems utilizing a chiral phase-transfer catalyst is described. A range of five-membered gamma-nitro esters with up to three stereocentres have been prepared and the relative and absolute configurations proven by chemical and crystallographic methods. The products are rapidly obtained and are precursors to five-membered cyclic gamma-amino acids
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