Mechanism of oxidation at a copper–polyethylene interface. II. Penetration of copper ions in the polyethylene matrix

Two surface analysis techniques (Rutherford backscattering and surface composition by analysis of neutral and ion impact radiation) have been applied to the study of interfacial copper transport in the oxidation of polyethylene films over copper surfaces. Analysis of films oxidized several thousand hours at 40, 57, and 87°C shows maximum concentrations of copper species in the polymer matrix of ～0.1M extending to depths of several thousand angstroms. These results, together with previous infrared spectroscopic studies, allow some significant conclusions and hypotheses to be drawn as regards the roles of heterogeneous and homogeneous catalytic processes which occur in the thermal-oxidative degradation of polyethylene–copper systems.     

Structural aspects of decisional power

The concept of decisional power introduced by Hoede and Bakker is investigated. The one‐dictator system is proven to give the minimum value for the index of democracy. Next to results on power in structures with representation there is a discussion of the effect of vote binding.     

Enantioselective Synthesis of Functionalized Arenes by Nickel-Catalyzed Site-Selective Hydroarylation of 1,3-Dienes with Aryl Boronates

A catalytic method for the site-selective and enantioselective synthesis of functionalized arenes by the intermolecular hydroarylation of terminal and internal 1,3-dienes with aryl pinacolato boronates is reported. The reactions are promoted by 5.0 mol % of a readily available monodentate phosphoramidite-Ni complex in ethanol, affording a variety of enantioenriched products in up to 96 % yield and 99:1 er. Mechanistic studies indicate that Ni–allyl formation is irreversible and related to the nature of the arylboronate.     

Cu‐Catalyzed Diastereo‐ and Enantioselective Reactions of γ,γ‐Disubstituted Allyldiboron Compounds with Ketones

A catalytic diastereo‐ and enantioselective method for the preparation of complex tertiary homoallylic alcohols containing a vicinal quaternary carbon stereogenic center and a versatile alkenylboronic ester is disclosed. Transformations are promoted by 5 mol % of a readily available copper catalyst bearing a bulky monodentate phosphoramidite ligand, which is essential for attaining both high dr and er. Reactions proceed with a wide variety of ketones and allylic 1,1‐diboronate reagents, which enables the efficient preparation of diverse array of molecular scaffolds.     

Fluxional five-coordinate platinum(II) complexes containing chelating triphosphine ligands

Platinum(II) dimethyl complexes of the three triphosphines PhP(CH₂CH₂CH₂PPh₂)₂, PhP(CH₂CH₂PPh₂)₂, and PhP(CH₂CH₂PMe₂)₂ have been shown by ³¹P NMR to undergo exchange of the terminal phosphino groups. An exchange route involving a five-coordinate platinum(II) complex is proposed.     

Highly diastereoselective Simmons-Smith cyclopropanation of allylic amines

[reaction: see text] Cyclopropanation of allylic tertiary amines using the Simmons-Smith reagent has been achieved by employing chelating groups in close proximity to the amine. The chelating groups promote cyclopropanation at the expense of N-ylide formation. Using pseudoephedrine as the chelating group, high diastereoselectivity is observed.     

A phase I, randomized study of combined IL-2 and therapeutic immunisation with antiretroviral therapy

Background  

Fully functional HIV-1-specific CD8 and CD4 effector T-cell responses are vital to the containment of viral activity and disease progression. These responses are lacking in HIV-1-infected patients with progressive disease. We attempted to augment fully functional HIV-1-specific CD8 and CD4 effector T-cell responses in patients with advanced chronic HIV-1 infection.     

A note on finding clothoids

The clothoid is a spiral that is used as transition curve in highway and railway route design. Although its defining formulas are transcendental functions, recent work has shown that it can be used fairly easily on small computers. A single nonlinear equation must be solved in each of four common arrangements of the clothoid. The purpose of this work is to give starting intervals for which Newton's root finding method applied to those equations is guaranteed to converge.