Volume discharge in a gas, excited by an electron beam under conditions of nonuniform ionization

Volume discharge in gases excited by electron beams is discussed. The steady state electric field distribution is derived. The voltage-current and energy characteristics are described

Reduction Techniques for Graph Isomorphism in the Context of Width Parameters

We study the parameterized complexity of the graph isomorphism problem when parameterized by width parameters related to tree decompositions. We apply the following technique to obtain fixed-parameter tractability for such parameters. We first compute an isomorphism invariant set of potential bags for a decomposition and then apply a restricted version of the Weisfeiler-Lehman algorithm to solve isomorphism. With this we show fixed-parameter tractability for several parameters and provide a unified explanation for various isomorphism results concerned with parameters related to tree decompositions. As a possibly first step towards intractability results for parameterized graph isomorphism we develop an fpt Turing-reduction from strong tree width to the a priori unrelated parameter maximum degree.Comment: 23 pages, 4 figure

ICP-AES analysis of high-purity arsenic

В настоящее время практически отсутствуют экспрессные многоэлементные методики анализа мышьяка, позволяющие определять широкий круг примесей на уровне 10⁻⁷-10⁻⁵ % мас. (в соответствии с современными требованиями), включая близкие по летучести к матрице элементы: P, S, Sb, Se и Te. Это связано с тем, что искровая масс-спектрометрия и нейтронно-активационный анализ сейчас труднодоступны, а атомно-эмиссионная спектрометрия с дуговым разрядом в сочетании с предварительным концентрированием примесей, позволяющая определять примеси до уровня 10⁻⁸-10⁻⁴ % мас., сокращает число определяемых примесей (например, P, S, Sb, Se, Te теряются при концентрировании отгонкой матрицы), отличается повышенной трудоёмкостью и длительностью анализа. В данной работе оценены возможности анализа высокочистого мышьяка доступным и широко распространённым методом атомно-эмиссионной спектрометрии с индуктивно связанной плазмой. Исследованы матричные помехи при распылении в индуктивно связанную плазму растворов с концентрацией мышьяка до 150 мг/мл. Установлено, что для достижения низких пределов определения примесей целесообразно анализировать растворы проб с концентрацией мышьяка ~100 мг/мл, что не вызывает технических трудностей. Проведение пробоподготовки в химически стойкой посуде из PFA (PerFluoroAlkoxy polymer) и использование доочищенных реактивов (вода, азотная кислота) позволило снизить влияние загрязнений на пределы определения большинства примесей. Разработана методика определения 39 элементов-примесей в высокочистом мышьяке, включая наиболее распространённые металлы (Al, Ca, Cu, Mg, Fe) и Si, и обычно теряемые при концентрировании отгонкой матрицы элементы (B, P, S, Sb, Se, Te). Пределы определения примесей в мышьяке составили ~10⁻⁷-10⁻⁵ % мас. При необходимости круг определяемых примесей может быть расширен, исходя из возможностей определения конкретных элементов методом атомно-эмиссионной спектрометрии с индуктивно связанной плазмой с учётом предложенной методики пробоподготовки и наличия соответствующих стандартных растворов солей определяемых элементов.The arc discharge atomic emission spectrometry method with pre-concentration of impurities is mainly used for multi-element analysis of high-purity arsenic. Spark ionization mass-spectrometry and neutron activation analysis are applied less often. The use of spark ionization mass-spectrometry and neutron activation analysis is quite problematic at the present time. Arc discharge atomic emission spectrometry in combination with pre-concentration of impurities makes it possible to determine the impurities at the level of 10⁻⁸-10⁻⁴ % mass. At the same time the number of the determined impurities is reduced (e.g., P, S, Sb, Se, Te are getting lost during concentration by matrix sublimation) with the increase in the duration of the analysis. Thus, at the present time the express multi-element techniques of analysis of arsenic which can provide the determination of wide range of impurities at the level of 10⁻⁷-10⁻⁵ % mass. (according to the modern requirements), including the elements P, S, Sb, Se and Te (with volatility close to that of the matrix) are actually absent. In the present paper the capabilities of available and widely used method of inductively-coupled plasma atomic emission spectrometry are estimated for analysis of high-purity arsenic. The matrix interference was investigated in the process of spraying the solutions with arsenic concentration up to 150 mg/mL into inductively-coupled plasma. It was found that in order to attain low limits of quantification of impurities it is expedient to analyze sample solutions with arsenic concentration ~100 mg/mL. It does not present a problem technically. Preparation of samples in chemically resistant vials of PFA (PerFluoroAlkoxy polymer) and the use of additionally purified reagents (water, nitric acid) made it possible to decrease the effect of contaminations on the limits of quantification of most impurities. A technique for determination of 39 elements in high-purity arsenic has been developed. The diapason of determined impurities includes the most abundant metals (Al, Ca, Cu, Mg, Fe) and Si, as well as the elements usually getting lost during concentration by matrix sublimation (B, P, S, Sb, Se, Te). The limits of quantification (as well as the limits of detection) of impurities in arsenic are equal ~10⁻⁷-10⁻⁵ % mass. If necessary, the range of impurities can be widened in view of the possibilities of inductively-coupled plasma atomic emission spectrometry, the possibilities of the suggested sample preparation technique and the availability of the corresponding standard solutions of the determined elements

Fixed Effect Estimation of Large T Panel Data Models

This article reviews recent advances in fixed effect estimation of panel data models for long panels, where the number of time periods is relatively large. We focus on semiparametric models with unobserved individual and time effects, where the distribution of the outcome variable conditional on covariates and unobserved effects is specified parametrically, while the distribution of the unobserved effects is left unrestricted. Compared to existing reviews on long panels (Arellano and Hahn 2007; a section in Arellano and Bonhomme 2011) we discuss models with both individual and time effects, split-panel Jackknife bias corrections, unbalanced panels, distribution and quantile effects, and other extensions. Understanding and correcting the incidental parameter bias caused by the estimation of many fixed effects is our main focus, and the unifying theme is that the order of this bias is given by the simple formula p/n for all models discussed, with p the number of estimated parameters and n the total sample size.Comment: 40 pages, 1 tabl

ОПРЕДЕЛЕНИЕ МАТРИЧНОГО СОСТАВА ХАЛЬКОГЕНИДНЫХ СТЕКОЛ СИСТЕМЫ GE-SE-TE МЕТОДОМ АЭС-ИСП

One of the most important stages of the high-purity chalcogenide glasses’ analytical control is the determination of matrix elements’ content with the uncertainty at the levels of 0.1–0.2 mol.%.  The content of the macro-components may differ from the composition of the initial charge; therefore, an important task is the macro-composition determination of the final materials. This article describes the development of the technique for determining the matrix elements of high-purity Ge-Se-Te glasses in the range of germanium content from 10 to 35 mol. %, selenium and tellurium content from 20 to 50 mol. % with the expanded uncertainty within 0.01–0.2 mol. % (P = 0.95) using the inductively coupled plasma atomic emission spectrometry (ICP-AES). A simple technique for the preparation of primary calibration solutions from pure elementary Ge, Se and Te is proposed. The correctness of the analysis results is confirmed by comparing the calculated matrix composition of model glass samples, prepared by direct synthesis from high-purity simple substances in the sealed quartz glass ampoule, with the analysis results.  The main advantage of the proposed analysis technique is the absence of the need for the reference samples identical to the analyzed material, which is especially important for determination of new materials’ matrix composition. The minimum sample mass for the determination of matrix elements is about 1 mg, which makes it possible to analyze not only bulk glass samples, but also fibers and expensive materials.Key words: Ge-Se-Te chalcogenide glasses, determination of matrix elements, high accuracy, inductively coupled plasma atomic emission spectrometry.DOI: http://dx.doi.org/10.15826/analitika.2020.24.4.002 D.A. Fadeeva, I.I. Evdokimov, V.G. PimenovG.G. Devyatykh Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences, Box-75, 49 Tropinin Str., Nizhny Novgorod, 603951, Russian FederationОдин из важнейших этапов аналитического контроля высокочистых халькогенидных стекол, используемых для изготовления оптоволоконных устройств, является установление содержания матричных элементов с неопределенностью на уровне 0.1–0.2 % мол. Необходимость данного этапа аналитического контроля возникает из-за сложности получения высокочистых халькогенидных стекол с необходимой точностью задания матричного состава, что связано, отчасти, с возможными потерями матричных элементов на многочисленных стадиях синтеза и очистки. Методик определения матричных элементов стекол системы Ge-Se-Te с необходимыми метрологическими характеристиками найти не удалось. В статье описана разработка методики определения матричных элементов высокочистых стекол вышеуказанной системы в диапазоне содержания германия от 10 до 35 % мол., селена и теллура – от 20 до 50 % мол. с расширенной неопределенностью результатов анализа на уровне 0.01–0.2 % мол. (P = 0.95) с использованием атомно-эмиссионной спектрометрии с индуктивно связанной плазмой. Предложен способ приготовления первичных градуировочных растворов, необходимых для достижения заявленного уровня неопределенности, с использованием германия, селена и теллура в форме чистых простых веществ. Корректность оценки точности результатов анализа подтверждена сопоставлением расчетного матричного состава модельных образцов стекол, изготовленных прямым синтезом из высокочистых простых веществ в запаянной ампуле из кварцевого стекла, с результатами анализа. Главное достоинство предложенной методики анализа – отсутствие потребности в образцах сравнения, идентичных анализируемому материалу, что особенно важно при установлении матричного состава новых материалов (т.е. когда образцы сравнения, и даже способы их изготовления отсутствуют в принципе). Минимальная для определения матричных элементов масса пробы составляет около 1 мг, что позволяет проводить анализ не только массивных образцов стекол, но и изготавливаемых из них волокон, а также дорогостоящих материалов.Ключевые слова: халькогенидные стекла Ge-Se-Te, определение матричных элементов, высокая точность, атомно-эмиссионная спектрометрия с индуктивно связанной плазмой.DOI: http://dx.doi.org/10.15826/analitika.2020.24.4.00

Studies of the Response of the Prototype CMS Hadron Calorimeter, Including Magnetic Field Effects, to Pion, Electron, and Muon Beams

We report on the response of a prototype CMS hadron calorimeter module to charged particle beams of pions, muons, and electrons with momenta up to 375 GeV/c. The data were taken at the H2 and H4 beamlines at CERN in 1995 and 1996. The prototype sampling calorimeter used copper absorber plates and scintillator tiles with wavelength shifting fibers for readout. The effects of a magnetic field of up to 3 Tesla on the response of the calorimeter to muons, electrons, and pions are presented, and the effects of an upstream lead tungstate crystal electromagnetic calorimeter on the linearity and energy resolution of the combined calorimetric system to hadrons are evaluated. The results are compared with Monte Carlo simulations and are used to optimize the choice of total absorber depth, sampling frequency, and longitudinal readout segmentation.Comment: 89 pages, 41 figures, to be published in NIM, corresponding author: P de Barbaro, [email protected]

First Observation of the Doubly Charmed Baryon Xi_cc^+

We observe a signal for the doubly charmed baryon Xi_cc^+ in the charged decay mode Xi_cc^+ --> Lambda_c^+ K- pi+ in data from SELEX, the charm hadro-production experiment at Fermilab. We observe an excess of 15.9 events over an expected background of 6.1 +/- 0.5 events, a statistical significance of 6.3sigma. The observed mass of this state is (3519 +/- 1) MeV/c^2. The Gaussian mass width of this state is 3MeV/c^2, consistent with resolution; its lifetime is less than 33fsec at 90% confidence.Comment: 5 pages, 3 figures, accepted for publication in Physical Review Letter

Drought tolerance gene pool in developing adaptive varieties of durum wheat identified in study nurseries under the Kazakhstan-Siberian program

Drought during the wheat vegetative period happens often in West Siberia and Kazakhstan condition. For this reason, varieties with adaptation to climatic zones, drought tolerance and high stability have high importance. The breeding efficiency and rates depend on the amount of information on genotypes in every study cycle. The aim of this study was to screen breeding material in Siberian and Kazakhstan research institutes from KASIB nurseries for drought tolerance and to develop a drought tolerant pool. For the evaluation of genotypes, it is necessary to study them in diverse condition. The basic purpose of the present work is to study breading material of durum wheat from KASIB institutions at different ecological sites. In 2000–2015, durum wheat entries in the Kazakhstan-Siberian program were studied. Progress in durum wheat breeding was tested in Russian and Kazakhstan institutes. Entries were screened for drought tolerance, yield and yield stability. They have value for including in hybridization for developing varieties with adaptation to Siberian and Kazakhstan conditions. The following varieties and lines are recommended for breading for drought tolerance: 383-МС, 452-МС, Каrgala 303, Каrgala 447, Каrgalа 24, Каrgala 1515/06, Каrgala 1516/06, Каrgala 69, Каrgala 1538, Каrgalа 1540, Каrgalа 1539, Kargalа 1671, Каrgalа 1411 (Акtubinsk Agricultural Experimental Station), Hordeiforme 91-25-5, Hordeiforme 91-22-2, Jemthujina Sibiri, Hordeiforme 94-94-13, Hordeiforme 98-42-1, Hordeiforme 01-121-3, Hordeiforme 02-156-1 (Siberian Research Agricultural Institute), Аltin schigis, Аltin dala, Line Г1549 (Каrabalyk Experimental Station), Hordeiforme 373, Hordeiforme 627 (Altai Research Agricultural Institute), 17394, 18053, Nauriz-6 (Кazakh Research-Production Center of Agriculture and Plant Growing), Коllektivnaya 2, ТС-15 (Kurgan Research Agricultural Institute), Line 653d-4 (Sаmara Research Agricultural Institute)

Development of spring durum wheat cultivars resistant to stem rust in Western Siberia

Background. Stem rust of wheat, caused by the biotrophic fungus Puccinia graminis Pers. f. sp. tritici Eriks. et Henn., is a dangerous disease that afflicts serious economic damage to the cultivation of durum wheat.Materials and methods. Cultivars and promising materials developed at the Spring Durum Wheat Breeding Laboratory, Omsk Agrarian Scientific Center (OASC), lines obtained under the CIMMYT and KASIB programs, and accessions from the VIR collection were the objects of research. Field experiments, phenological observations, and assessment of stem rust resistance were carried out from 1990 through 2019 in the OASC experimental fields using conventional methods. Resistance to the Ug99 race was evaluated under natural infection pressure at the Kenya Agricultural and Livestock Research Organization (KALRO).Results. Promising source material was identified and included in the Laboratory’s breeding program. The ways were shown to develop stable cultivars of spring durum wheat for the environments of Western Siberia. A strategy was proposed for the selection of genotypes in hybrid combinations of spring durum wheat: it would include early selection (starting from F2 ) for disease resistance with simultaneous screening for quantitative traits and pasta-making qualities. The description and advantages of cv. ‘Omsky korall’, submitted to the State Variety Trials in 2018, are presented. This cultivar combines high yield, adaptability, resistance to the local population and the Ug99 race of the stem rust pathogen, and excellent pasta-making qualities.Conclusion. As a result of these studies under heavy stem rust pressure in Western Siberia, all breeding nurseries obtained source material resistant to the Omsk population of P. graminis. The released cultivars ‘Omskaya yantarnaya’ and ‘Omsky izumrud’ demonstrate resistance to the Omsk population of the stem rust causative agent