Quark-diquark model for p(\bar p)-p elastic scattering at high energies

A model for elastic scattering of protons at high energies based on the quark-diquark representation of the proton is discussed. The predictions of the model are compared with experimental data for the differential elastic cross-sections from available databasesComment: 4 pages, 5 figure

An Alternative Approach to Aldol Reactions: Gold-Catalyzed Formation of Boron Enolates from Alkynes

A new method for enolate generation via the gold-catalyzed addition of boronic acids to alkynes is reported. The formation of boron enolates from readily accessible ortho-alkynylbenzeneboronic acids proceeds rapidly with 2 mol % PPh3AuNTf2 at ambient temperature. The enolates undergo aldol reaction with an aldehyde present in the reaction mixture to give cyclic boronate esters, which can be subsequently transformed into phenols, biaryls, or dihydrobenzofurans via oxidation, Suzuki-Miyaura, or intramolecular Chan-Lam coupling, respectively. A combined gold/boronic acid catalyzed aldol condensation reaction of an alkynyl aldehyde was also successfully achieved

Direct Synthesis of Amides from Carboxylic Acids and Amines Using B(OCH2CF3)3

B(OCH2CF3)3, prepared from readily available B2O3 and 2,2,2-trifluoroethanol, is as an effective reagent for the direct amidation of a variety of carboxylic acids with a broad range of amines. In most cases, the amide products can be purified by a simple filtration procedure using commercially available resins, with no need for aqueous workup or chromatography. The amidation of N-protected amino acids with both primary and secondary amines proceeds effectively, with very low levels of racemization. B(OCH2CF3)3 can also be used for the formylation of a range of amines in good to excellent yield, via transamidation of dimethylformamide

Diffractive photoproduction of meson pairs in the S\"oding model

We consider the diffractive photoproduction of $\pi^+\pi^- , K^+K^- , D^+D^-$ meson pairs with high masses and transverse momenta in the framework of the S\"oding model. The total and differential cross sections are calculated for these processes. The role of the form factors is stressed.Comment: 7 pages, 7 figures, latex; Talk at DIS 97 Workshop (Chicago, 1997

Catalytic electrophilic halogenation of silyl-protected and terminal alkynes: trapping gold(I) acetylides vs. a bronsted acid-promoted reaction

In the presence of a cationic gold(I) catalyst and N-halosuccinimide, both trimethylsilyl-protected and terminal alkynes are converted into alkynyl halides. Further experiments showed that silyl-protected alkynes undergo electrophilic iodination and bromination under Brønsted acid catalysis, whilst terminal alkynes require a cationic gold catalyst. The former reactions probably proceed via activation of the electrophile, whilst the latter reactions proceed via a gold(I) acetylide intermediate. Gold-catalysed halogenation was further combined with gold-catalysed hydration and subsequent annulation to provide convenient routes to iodomethyl ketones and five-membered aromatic heterocycles

High protonic potential actuates a mechanism of production of reactive oxygen species in mitochondria

AbstractFormation of H2O2 has been studied in rat heart mitochondria, pretreated with H2O2 and aminotriazole to lower their antioxidant capacity. It is shown that the rate of H2O2 formation by mitochondria oxidizing 6 mM succinate is inhibited by a protonophorous uncoupler, ADP and phosphate, malonate, rotenone and myxothiazol, and is stimulated by antimycin A. The effect of ADP is abolished by carboxyatractylate and oligomycin. Addition of uncoupler after rotenone induces further inhibition of H2O2 production. Inhibition of H2O2 formation by uncoupler, malonate and ADP+Pi is shown to be proportional to the ΔΨ decrease by these compounds. A threshold ΔΨ value is found, above which a very strong increase in H2O2 production takes place. This threshold slightly exceeds the state 3 ΔΨ level. The data obtained are in line with the concept [Skulachev, V.P., Q. Rev. Biophys. 29 (1996), 169–202] that a high proton motive force in state 4 is potentially dangerous for the cell due to an increase in the probability of superoxide formation

Исследование возможности разрядно-импульсной дезинтеграции стеклоподобного сырья до микронной фракции

A literature review of various methods of breaking and grinding of materials was performed, based on which a method of electric discharge disintegration (EDD) was chosen. It allows achieving of micron values fractional composition of the processed material. Mechanisms of material destruction under the influence of high-voltage electric discharge in water were considered. Used glassware (UG) was selected as raw material for disintegration due to economic and environmental reasons. Methodologies of UG preliminary preparation for disintegration and further grain-size analysis were developed. Calculation of compression wave (CW) parameters at different distances from the discharge channel for given discharge circuit initial parameters was performed. Maximum distance at which CW has required destructive effect was determined based on the comparison of physical and mechanical properties of glass and results of performed calculations. Appropriate discharge circuit properties (e.g., useful power) necessary for EDD grinding of UG to micron fraction was determined based on the parameters of the discharge circuit and practically achievable switch frequency. The results of previous processing which was carried out with set circuit parameters in the chamber providing the required maximum radius of destruction in pure water and in water with the addition of surfactants, were obtained to evaluate the possibilities (primarily, achievable dispersion) of UG EDD. The grain-size analysis of dispersion composition showed the possibility of disintegration of the glass into the micron fraction (with grains of size ranging from 5 to 7 microns – up to 30 weight percentage).Проведен литературный обзор различных методов дробления и измельчения материалов, на основе которого был выбран метод разрядно-импульсной дезинтеграции, который позволяет достичь микронных значений фракционного состава обрабатываемого материала. Рассмотрены механизмы разрушения материалов под воздействием высоковольтного электрического разряда в воде. В качестве сырья для дезинтеграции по экономическим и экологическим соображениям была выбрана стеклянная тара (СТ). Разработаны методики подготовки СТ к дезинтеграции и последующего гранулометрического анализа дисперсии. Проведен расчет параметров волны давления (ВД) на различных расстояниях от канала разряда для заданных начальных параметров разрядного контура. На основании сопоставления физико-механических свойств стекла и результатов проведенных расчетов определено максимальное расстояние, на котором ВД оказывает разрушительное воздействие. По параметрам разрядной цепи и практически достижимой частоты по условиям работы коммутатора выбраны необ- ходимые для разрядно-импульсной дезинтеграции характеристики разрядного контура (в первую очередь, полезная мощность) для измельчения СТ до микронных размеров. Получены результаты предыдущих обработок для оценки возможностей (в первую очередь, по дисперсности) разрядно-импульсной дезинтеграции СТ проведенные для заданных параметров цепи в камере, обеспечивающей необходимый максимальный радиус разрушения в чистой воде и в воде с добавлением поверхностно-активных веществ. Анализ гранулометрического состава дисперсии показал возможность дезинтеграции стекла в микронной фракции (от 5 до 7 мкм – 30 %)

Borate esters as convenient reagents for direct amidation of carboxylic acids and transamidation of primary amides

Simple borates serve as effective promoters for amide bond formation with a variety of carboxylic acids and amines. With trimethyl or tris(2,2,2-trifluoroethyl) borate, amides are obtained in good to excellent yield and high purity after a simple work-up procedure. Tris(2,2,2-trifluoroethyl) borate can also be used for the straightforward conversion of primary amides to secondary amides via transamidation

On auroral dynamics observed by HF radar: 1. Equatorward edge of the afternoon-evening diffuse luminosity belt

International audienceObservations and modelling are presented which illustrate the ability of the Finland CUTLASS HF radar to monitor the afternoon-evening equatorward auroral boundary during weak geomagnetic activity. The subsequent substorm growth phase development was also observed in the late evening sector as a natural continuation of the preceding auroral oval dynamics. Over an 8 h period the CUTLASS Finland radar observed a narrow (in range) and persistent region of auroral F- and (later) E-layer echoes which gradually moved equatorward, consistent with the auroral oval diurnal rotation. This echo region corresponds to the subvisual equatorward edge of the diffuse luminosity belt (SEEL) and the ionospheric footprint of the inner boundary of the electron plasma sheet. The capability of the Finland CUTLASS radar to monitor the E-layer SEEL-echoes is a consequence of the nearly zero E-layer rectilinear aspect angles in a region 5?10° poleward of the radar site. The F-layer echoes are probably the boundary blob echoes. The UHF EISCAT radar was in operation and observed a similar subvisual auroral arc and an F-layer electron density enhancement when it appeared in its antenna beam.Key words: Ionsophere (ionospheric irregularities) · Magnetospheric physics (auroral phenomena; magnetosphere?ionosphere interactions