Alexey Volkov

Preparation of S-aryl xanthates via transition-metal-catalyzed or SNAr reactions is complicated by their further transformations under the utilized conditions. In contrast, S-arylation of potassium O-alkyl xanthates with diaryliodonium salts proceeds under mild conditions, enabling access to substituted S-aryl xanthates. The method exhibits good functional group tolerance and can be applied to the late-stage C-H functionalization of drug molecules. Divergent transformations of the resulting S-aryl xanthates provide rapid access to a range of medicinal chemistry-relevant organosulfur compounds.

Reactions of acceptor-substituted aryl iodides and bromides with potassium thiocarboxylates under white light irradiation allow for the preparation of S-aryl thioesters including synthetically versatile S-aryl thioacetates. This transition-metal and external photocatalyst-free method features extremely mild reaction conditions compared with those used in transition-metal-catalyzed protocols. Reactions proceed via the initial formation of an electron donor-acceptor (EDA) complex in the ground state, which was supported by UV-vis spectra. Electron paramagnetic resonance (EPR) spin-trapping experiments using phenyl-N-tert-butylnitrone (PBN) have revealed the radical nature of the reaction.

Abstract The visible‐light‐induced arylation of tertiary phosphines with aryl(mesityl)iodonium triflates to produce the quaternary phosphonium salts occurs under mild, metal, and catalyst‐free conditions. Photo‐excited EDA complexes between diaryliodonium salts and phosphines supposedly enable this transformation, which is difficult to achieve through the traditional ground‐state reactions. Demonstrating high functional group tolerance, broad scope, and complete selectivity of the aryl group transfer, the method is particularly compatible with sterically congested phosphines, which are challenging under metal‐based catalytic methods.

Abstract Visible‐light‐activated organic reactions unlock novel avenues for complex molecular transformations, impossible under standard “thermal” conditions, which makes them powerful tools in the arsenal of synthetic chemistry. However, transition metal‐based or organic photoredox catalysts are often used to ensure productive absorption of visible light, which might be not desirable to medicinal chemistry and industry due to toxicity, low sustainability, and high cost of most photocatalysts. A more environmentally and economically benign approach is based on the formation of transient electron donor‐acceptor (EDA) complexes between two reagents or a reagent and an additive, that readily absorb visible light, acting as internal photosensitizers. Within the EDA complex‐based arylation strategies, chemical transformations are mediated by noncovalent interaction between two molecules, namely between electron‐poor aryl halides or their synthetic equivalents and electron‐rich nucleophilic reagents or additives. Moreover, besides stoichiometric EDA complexes between two molecules, EDA complex based organocatalysis can be achieved in certain cases through regeneration of the donor molecules in the course of the reaction. Photoexcitation of the EDA complexes induces a single electron transfer (SET) process to generate aryl radical species for the arylation step. This Review will focus on the state‐of‐the‐art EDA complex‐based arylation strategies utilizing aryl halides, aryldiazonium, diaryliodonium, arylsulfonium and arylphosphonium salts as reactants, published mainly in the last five years.

Arylation methods based on the generation and use of aryl radicals have been a rapidly growing field of research in recent years and currently represent a powerful strategy for carbon – carbon and carbon – heteroatom bond formation. The progress in this field is related to advances in the methods for generation of aryl radicals. The currently used aryl radical precursors include aryl halides, aryldiazonium and diaryliodonium salts, arylcarboxylic acids and their derivatives, arylboronic acids, arylhydrazines, organosulfur(II, VI) compounds and some other compounds. Aryl radicals are generated under mild conditions by single electron reduction or oxidation of precursors induced by conventional reagents, visible light or electric current. A crucial role in the development of the radical arylation methodology belongs to photoredox processes either catalyzed by transition metal complexes or organic dyes or proceeding without catalysts. Unlike the conventional transition metal-catalyzed arylation methods, radical arylation reactions proceed very often at room temperature and have high functional group tolerance. Without claiming to be exhaustive, this review covers the most important advances of the current decade in the generation and synthetic applications of (het)aryl radicals. Examples of reactions are given and mechanistic insights are highlighted. The bibliography includes 341 references.

Results of a search for prompt neutrinos in a beam-dump experiment with 70 GeV protons are reported. The observed rate is νpr/π = (2.7 ± 2.2) × 10−5 for mean neutrino energy 〈Eν〉 ≈ 5 GeV. An estimation on charmed meson production as a possible source of prompt neutrinos is given. Production rate of the axion relative to π0 mesons is found to be less than 6 × 10−9 (95%C.L.).

We propose a new framework to rank image attractiveness using a novel pairwise deep network trained with a large set of side-by-side multi-labeled image pairs from a web image index. The judges only provide relative ranking between two images without the need to directly assign an absolute score, or rate any predefined image attribute, thus making the rating more intuitive and accurate. We investigate a deep attractiveness rank net (DARN), a combination of deep convolutional neural network and rank net, to directly learn an attractiveness score mean and variance for each image and the underlying criteria the judges use to label each pair. The extension of this model (DARN-V2) is able to adapt to individual judge's personal preference. We also show the attractiveness of search results are significantly improved by using this attractiveness information in a real commercial search engine. We evaluate our model against other state-of-the-art models on our side-by-side web test data and another public aesthetic data set. With much less judgments (1M vs 50M), our model outperforms on side-by-side labeled data, and is comparable on data labeled by absolute score.

Abstract An arylation of anions of active methylene compounds with aryl halides provides an access to synthetically versatile α‐arylated 1,3‐diketones, β‐keto esters, β‐keto nitriles, β‐cyano esters, etc. Previously, these C−C cross‐coupling reactions have been accomplished only using transition metal‐based catalysts. Herein, we demonstrate that these arylations can be successfully realized under catalyst‐free conditions employing the electron donor‐acceptor (EDA) complex photoactivation strategy. The protocol was further optimized for a semi‐one pot synthesis of indole derivatives via an intramolecular C−C coupling.

The design and main parameters of the completly redesigned DØ Forward Angle MUon System (FAMUS: 1.0<|η|<2.0) for the next high luminosity Tevatron Collider run are reported. Results of the studies of trigger scintillation counters based on fast scintillator Bicron 404A and WLS bars SOFZ-105 are presented. We report about results of test beam studies of prototype counters including minimum ionizing particles detection efficiency, time resolution and amplitude response. Radiation ageing of scintillating materials for the doses up to 1 Mrad, phototubes magnetic shielding in the fields of up to 700 G and ageing of phototubes are presented. Mini-Drift Tubes (MDTs) are chosen as FAMUS tracking detectors. The detector is a drift wire chamber with a metallic cathode. The detector operates in proportional mode with a fast freon–methane gas mixture to provide high drift velocity, adequate counting rate and low ageing. A description of the performance of the MDT is given. Studies of two prototypes in test beams were performed at FNAL and JINR. Obtained coordinate accuracy is around 0.5 mm r.m.s. All tests show robustness of MDT as tracking detector of the new muon system for a long period in high DØ background radiation conditions.

ВОЗДЕЙСТВИЕ КЛИМАТИЧЕСКИХ ФАКТОРОВ НА ЛИНЕЙНЫЙ ПРИРОСТ ЛЕСОКУЛЬТУР И ЕСТЕСТВЕННОГО ВОЗОБНОВЛЕНИЯ СОСНЫ ОБЫКНОВЕННОЙ В ПЕНЗЕНСКОЙ ОБЛАСТИ

Most existing methods for the synthesis of alkyl aryl thioethers require the use of mercaptans as the starting materials, which comes with practical limitations. Reactions of diaryliodonium salts with xanthate salts, easily prepared from the corresponding alcohols and CS2, under the developed conditions represent an operationally simple, thiol-free method for the synthesis of these valuable compounds. The protocol features high functional group tolerance and can be applied to the late-stage C–H functionalization and for the introduction of a CD3S group.

Temperature variation of RF-cavities leads to a change of their geometrical sizes that provides undesirable cavity modes and to excitation of phase oscillations. It leads to decrease in luminosity and a beam life time. Flowing water heaters with stabilization of temperature have been established for elimination of this disadvantage. Temperature probes LM335 were used with a sensitivity of 10 мV per degree centigrade. The power part is made on the controllable switches CPV240. The analysis of temperature of input and output temperatures of water is carried out by microcontroller ADAM connected to a computer by means of interface RS-485. The temperature variation have been reduced from 5 to 0.2 degrees centigrade. That has led to decrease in probability of occurrence of parasitical phase oscillations more than in 100 times.

The design and main parameters of the completely redesigned DO Forward Angle Muon System (FAMUS:1.0<|/spl eta/|<2.0) for the next high luminosity Tevatron Collider run are reported. Results of the studies of trigger scintillation counters based on fast scintillator Bicron 404 A and WLS bars SOFZ-105 are presented. We report about results of test beam studies of prototype counters including minimum ionizing particles detection efficiency, time resolution and amplitude response.

С целью исследования особенностей рентгеновских проявлений дистрофических изменений передней продольной связки у женщин в зависимости от величины минеральной плотности кости были изучены данные комплексного рентгенодиагностического и абсорбциометрического исследований 127 женщин в возрасте от 40 лет и старше (средний возраст 62,8 лет). По данным стандартной рентгенографии грудного и поясничного отделов позвоночного столба в боковой проекции проводилась полуколичественная оценка дистрофических изменений передней продольной связки в баллах с учетом степени их выраженности и распространенности характерных клювовидной формы костных разрастаний под передней продольной связкой с возможной оценкой от 0 до 6 баллов. Менее распространенные изменения (1-2 сегмента) характеризовались как проявления деформирующего спондилоза, изменения с большей распространенностью (3 сегмента и более) считались следствием болезни Форестье. Абсорбциометрия выполнялась в виде количественной рентгеновской компьютерной томографии с оценкой средней минеральной плотности кортикальной и губчатой кости с учетом возраста и ряда связанных с ними показателей, характеризующих качественное состояние кости (плотностный интервал и соотношение плотности кортикальной и губчатой костной ткани). Результаты.На первом этапе абсорбциометрические данные были проанализированы в зависимости от степени дистрофических изменений передней продольной связки в группах пациенток с оценками 1-2, 3-4 и 5-6 баллов. Была выявлена достоверная зависимость величины минеральной плотности кости от степени и распространенности дистрофических изменений. При увеличении оценки дистрофических изменений отмечено снижение минеральной плотности губчатой кости от 107,5 мг/мм3 при 1-2 баллах до 91,6 мг/мм3 при 5-6 баллах, и кортикальной кости от 305,7 мг/мм3 до 278,7 мг/мм3 соответственно. Отмечено также достоверное сокращение плотностного интервала губчатой костной ткани от 137,6 мг/мм3 до 95,8 мг/мм3 без существенного изменения соотношения костной массы кортикальной и губчатой кости. На второй стадии работы изучались дистрофические изменения передней продольной связки в зависимости от величины минеральной плотности кости в пяти группах пациенток с костной массой 125 мг/мм3 и более, 100-124, 75-99, 50-74 и менее 50 мг/мм3. При этом было определено существенное и достоверное снижение степени дистрофических изменений передней продольной связки по типу спондилеза от средней оценки 1,1 балла в группе с минеральной плотностью 125 мг/мм3 и более до 0,4 балла при костной массе 50 74 мг/мм3. Вместе с тем выявлено достоверное увеличение частоты наиболее распространенных изменений, характерных для болезни Форестье, от 0,3 балла при максимальной величине костной массы до 0,6 балла при наименьшем ее значении. Выводы. 1. Определяется закономерная взаимосвязь степени и распространенности дистрофических изменений передней продольной связки в зависимости от величины минеральной плотности кости. 2. Ограниченные дистрофические изменения передней продольной связки по типу деформирующего спондилёза связаны с увеличением минеральной плотности кости и не сопровождаются изменениями ее качества. 3. Распространенные изменения передней продольной связки дистрофической природы по типу болезни Форестье связаны с уменьшением минеральной плотности губчатой кости, сопровождающимся некоторым снижением ее качества.

The paper presents a novel approach to finding regional scopes (geotagging) of websites. It relies on a single binary classification model per region type to perform the multi-class classification and uses a variety of features of different nature that have not been yet used together for machine-learning based regional classification of websites. The evaluation demonstrates the advantage of our "one model per region type" method versus the traditional "one model per region" approach.

В статье представлена зависимость линейного прироста сосны обыкновенной (Pinus sylvestris L.), произрастающей в сухих, свежих и влажных биотопах на территории Кандалакшского Государственного природного Заповедника и Государственного заказника «полярный круг» Мурманской области от серии климатических факторов. Использовались стандартные дендрохронологические методы. Результаты показали, что для исследуемых древостоев не было выявлено общей зависимости линейного прироста от температуры. Таким образом температурный фактор не может рассматриваться в качестве лимитирующего для данных биотопов. Установлено, что лимитирующим фактором линейного прироста сосны обыкновенной для сухих и влажных биотопов является содержание влаги в почве. Лимитирующий фактор для свежих биотопов не был установлен, потому что это региональный оптимум для P. sylvestris.

The paper presents a novel approach to finding regional scopes (geotagging) of websites. It relies on a single binary classification model per region type to perform the multi-label classification and uses a variety of different features that have not been yet used together for machine-learning based regional classification of websites. The evaluation demonstrates the advantage of our one model per region type method versus the traditional one model per region approach.

The search for dimuon production in vN and v̄N interactions at the Serpukhov accelerator was started in December, 1974. Preliminary data after analysis of part of the statistics of the neutrino exposure showed no effect [1, 2]. In further measurements we changed the neutrino spectrum. Namely, we suppressed the low energy part and enriched the high energy part. It was done because similar experiments at Fermilab [3, 4] indicated predominant dimuon production at energies E v ≳ 30 GeV. Fig. 1 shows qualitatively the variation of the neutrino spectra from the first to the second run.

Bounds are calculated for the oscillation parameters of muon neutrinos, ..nu../sub ..mu../ ..-->.. ..nu../sub x/' from data on quasi-elastic scattering in the neutrino beams of the Institute of High-Energy Physics, Serpukhov. The experiment was carried out jointly by the Institute of High-Energy Physics and the Institute of Theoretical and Experimental Physics. At square-mass differences ..delta..m/sup 2/> or approx. =15 eV/sup 2/ the mixing ratio is sin/sup 2/ 2theta< or approx. =9 x 10/sup -2/ at a 90% confidence level.