Rhodium‐Catalyzed (5+1) Annulations Between 2‐Alkenylphenols and Allenes: A Practical Entry to 2,2‐Disubstituted 2H‐Chromenes

Readily available alkenylphenols react with allenes under rhodium catalysis to provide valuable 2,2‐disubstituted 2H‐chromenes. The whole process, which involves the cleavage of one C? H bond of the alkenyl moiety and the participation of the allene as a one‐carbon cycloaddition partner, can be considered a simple, versatile, and atom‐economical (5+1) heteroannulation. The reaction tolerates a broad range of substituents both in the alkenylphenol and in the allene, and most probably proceeds through a mechanism involving a rhodium‐catalyzed C? C coupling followed by two sequential pericyclic processes.     

Paraffin deposition in crude oil production and depressor additives for paraffin inhibition

Paraffin deposition on cold metallic surfaces in crude oil production, collection, and transportation is studied. Comparative analysis is made of the efficiencies of various paraffin inhibitors in West-Siberian paraffin oils. The mechanism of action of the additives is analyzed in relation to the phase and structural transitions in them in model systems.     

Peculiarities of the mechanism of electroreduction of cinnamic acid in DMF and DMF-H<Subscript>2</Subscript>O mixture

The electrochemical behavior of cinnamic acid (CA) on the cathodes with a high hydrogen overpotential (Hg, glassy carbon, and carbositall) in the aprotic solvent (DMF) and in DMF with additions of H₂O or Et₄NOH is studied by the methods of polarography, preparative electrolysis, cyclic voltammetry (CVA), coulometry, and chronoammetry. It is found that the mechanism of CA electroreduction is in conflict with the classical notion of the mechanism of electroreduction of α,β-unsaturated carboxyl compounds. It is shown that in the aprotic solution, in contrast to similar carbonyl compounds or ethers, which are the derivatives of organic acids, the products of double-bond hydrogenation, rather than the dimeric compounds, are the only products of CA electroreduction, i.e the presence of carboxyl group changes essentially the direction of electrochemical process. From the data of CVA, it is concluded that stable dimeric associates are present in the DMF solutions in the equilibrium with nondissociated CA.     

IC-100 accelerator complex for scientific and applied research

Industrial production of nuclear filters has been implemented at the IC-100 cyclotron complex of the Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research. After the complete upgrade, the cyclotron was equipped with the superconducting ECR ion source and the system of external axial beam injection. The implantation complex was equipped with the special transportation channel with the beam scanning system and the setup for irradiation of polymer films. Intense beams of heavy ions Ne, Ar, Fe, Kr, Xe, I, and W with an energy of ～1 MeV/nucleon were obtained. the properties of irradiated crystals were studied, different polymer films were irradiated, and several thousands of square meters of track membranes with pore densities varying in a wide range were produced. Other scientific and applied problems can be solved at the cyclotron complex.     

Analysis of ores by simple grinding and circular thin-layer chromatography and the nichrome wire ring chamber

Summary A method for the preparation of ore solutions by grinding the ore with distilled water is developed for the analysis of minerals and ores in the field by the circular thin-layer Chromatographic technique.

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Zusammenfassung Die Herstellung von Erzlösungen durch Mahlen des Erzes mit dest. Wasser zur Feldanalyse von Mineralen und Erzen durch Ring-Dünnschichtchromatographie wird empfohlen.

     

Specific laws of polymer fracture

The results of an experimental verification of the activation concept of strength, first proposed by the author in 1952, are described. The theoretical conclusions are confirmed by tests on various vulcanizates, polystyrene, polymethyl methacrylate, cellophane, and polypropylene, New means of improving the strength of polymers are suggested.Mekhanika Polimerov, Vol. 4, No. 3, pp. 474–482, 1968     

Synthesis of non-symmetrical 3,5-diamidobenzyl amines, ethers and sulfides

A straightforward synthesis of non-symmetrical 3,5-diamidobenzyl amines, ethers and sulfides starting from 3,5-dinitrobenzoic acid is reported. Functionalization of the benzylic position is only achieved after formation of the two amides, otherwise benzylic hydrogenolysis occurs during nitro group reduction.     

Ensemble of a subset of <Emphasis Type="Italic">k</Emphasis>NN classifiers

Combining multiple classifiers, known as ensemble methods, can give substantial improvement in prediction performance of learning algorithms especially in the presence of non-informative features in the data sets. We propose an ensemble of subset of kNN classifiers, ESkNN, for classification task in two steps. Firstly, we choose classifiers based upon their individual performance using the out-of-sample accuracy. The selected classifiers are then combined sequentially starting from the best model and assessed for collective performance on a validation data set. We use bench mark data sets with their original and some added non-informative features for the evaluation of our method. The results are compared with usual kNN, bagged kNN, random kNN, multiple feature subset method, random forest and support vector machines. Our experimental comparisons on benchmark classification problems and simulated data sets reveal that the proposed ensemble gives better classification performance than the usual kNN and its ensembles, and performs comparable to random forest and support vector machines.