Copper-catalyzed aerobic oxidative C-H functionalizations: trends and mechanistic insights

The selective oxidation of C-H bonds and the use of O(2) as a stoichiometric oxidant represent two prominent challenges in organic chemistry. Copper(II) is a versatile oxidant, capable of promoting a wide range of oxidative coupling reactions initiated by single-electron transfer (SET) from electron-rich organic molecules. Many of these reactions can be rendered catalytic in Cu by employing molecular oxygen as a stoichiometric oxidant to regenerate the active copper(II) catalyst. Meanwhile, numerous other recently reported Cu-catalyzed C-H oxidation reactions feature substrates that are electron-deficient or appear unlikely to undergo single-electron transfer to copper(II). In some of these cases, evidence has been obtained for the involvement of organocopper(III) intermediates in the reaction mechanism. Organometallic C-H oxidation reactions of this type represent important new opportunities for the field of Cu-catalyzed aerobic oxidations.     

Strain-hardening modulus of cross-linked glassy poly(methyl methacrylate)

The strain hardening modulus, defined as the slope of the increasing stress with strain during large strain uniaxial plastic deformation, was extracted from a recently proposed constitutive model for the finite nonlinear viscoelastic deformation of polymer glasses, and compared to previously published experimental compressive true stress versus true strain data of glassy crosslinked poly(methyl methacrylate) (PMMA). The model, which treats strain hardening predominantly as a viscous process, with only a minor elastic contribution, agrees well with the experimentally observed dependence of the strain hardening modulus on strain rate and crosslink density in PMMA, and, in addition, predicts the well-known decrease of the strain hardening modulus in polymer glasses with temperature. General scaling aspects of continuum modeling of strain hardening behavior in polymer materials are also presented. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1464–1472, 2010     

Über die Inhaltsstoffe der Wurzel von Pimpinella saxifraga II

Ohne Zusammenfassung     

An apparatus for simultaneous gas evolution analysis and mass spectrometric analysis

An apparatus is described which enables the gas evolution analysis(GEA) and mass spectrometric analysis(MSA) curves of a sample to be recorded simultaneously. The sample is pyrolyzed in a chamber in a dynamic helium atmosphere.The evolved products are detected in the helium gas by a thermal conductivity cell which results in the (GEA) curve. An inexpensive mass spectrometer is used to moniter the helium gas stream which gives the (MSA)curve. The advantages of the appparatus over other recent techniques are given.     

Thermolysis of thorium precipitates : Salts of organic acids

The thermal decomposition of the thorium salts of tannic (digallic), 5-bromosalicyclic, 5-nitrosali cyclic, 1-hydroxy-2-naphthoic, phenylglycine-o-carbocylic, phenylpropionic, acetyl-o-salicylic, phenoxyacetic, 2,4,5-trichlorophenoxyacetic and 2,2'-diphenic acids was investigated on the thermobalance. Most of the precipitated compounds were of a basic composition, correspoding to the general formula, Th(OH)4-n(A)n, where A - is the organic acid ligand The first weight losses were found from 35 to 200° with minimum oxide level temperatures occuring in the 475 to 665° temperature range.     

Knowledge-based proteome profiling: considering identified proteins to evaluate separation efficiency by 2-D PAGE

Proteome profiling techniques rely on the separation of proteins or peptides and their subsequent quantification. The reliability of this technique is still limited because a proteome profiling result does not necessarily represent the true protein composition of the analysed sample, thus seriously hampering proper data interpretation. Many experimentally observed proteome alterations are biologically not significant. It was the aim of this study to use the knowledge of the biological context of proteins in order to establish optimised proteome profiling protocols. While 2-D spot patterns of total cell protein fractions were found to poorly represent the true protein composition, purified subcellular protein fractions were found to better represent the protein composition of the analysed sample. The application of a standardised protocol to different kinds of cells revealed several striking observations. Firstly, the protein composition of cultured cells of various origins is very similar. Secondly, proteome alterations observed with the described protocols do make sense from a biologic point of view and may thus be considered as truly representative for the analysed samples. Thirdly, primary white blood cells isolated from different donors were found to show minor, but reproducible and significant individual differences. We designate the consideration of known properties of identified proteins in proteome profiles as a knowledge-based approach. The present data suggest that this approach may tremendously help to improve the applied techniques and assess the results. We demonstrate that the fulfilment of well-defined criteria of proteome profiles eventually results in reliable and biologically relevant data.     

Thermodilatometkic analysis: some chemical applications

Some applications of thermodilatometric analysis are discussed. The technique may be used for the determination of solid-solid phase transitions and decomposition reactions. An inexpensive recording dilatometer is described.     

The shape of CUSUM — an indicator for tendencies in a time series

Summary CUSUM (cumulative sum) can be seen as integral of the attached time series. Therefore the shape of CUSUM allows conclusions as to the type of an instationarity inherent in the time series to be made. This indirect way is advantageous for the evaluation of time series with high random fluctuations. The theoretical background for the information to be derived from the shape of CUSUM as well as examples for application (time series, distribution analysis) are shown in this paper.