Carbon clusters: From ring structures to nanographene

The lowest energy configurations of Cn(n =< 55) clusters are obtained using the energy mini- mization technique with the conjugate gradient (CG) method where a modified Brenner potential is invoked to describe the carbon and hydrocarbon interaction. We found that the ground state configuration consists of a single ring for small number of C atoms and multi-ring structures are found with increasing n, which can be in planar, bowl-like or cap-like form. Contrary to previous predictions, the binding energy Eb does not show even-odd oscillations and only small jumps are found in the Eb(n) curve as a consequence of specific types of edges or equivalently the number of secondary atoms. We found that hydrogenation of the edge atoms may change the ground state configuration of the nanocluster. In both cases we determined the magic clusters. Special attention is paid to trigonal and hexagonal shaped carbon clusters and to clusters having a graphene-like configuration. Trigonal clusters are never the ground state, while hexagonal shaped clusters are only the ground state when they have zigzag edges.Comment: Accepted for publication in Phys. Rev.

Theoretical study of the stable states of small carbon clusters Cn (n = 2-10)

Both even- and odd-numbered neutral carbon clusters Cn (n = 2-10) are systematically studied using the energy minimization method and the modified Brenner potential for the carbon-carbon interactions. Many stable configurations were found and several new isomers are predicted. For the lowest energy stable configurations we obtained their binding energies and bond lengths. We found that for n < 6 the linear isomer is the most stable one while for n > 5 the monocyclic isomer becomes the most stable. The latter was found to be regular for all studied clusters. The dependence of the binding energy for linear and cyclic clusters versus the cluster size n (n = 2-10) is found to be in good agreement with several previous calculations, in particular with ab initio calculations as well as with experimental data for n = 2-5.Comment: Submitted to Phys. Rev.

First-principles modeling of the polycyclic aromatic hydrocarbons reduction

Density functional theory modelling of the reduction of realistic nanographene molecules (C42H18, C48H18 and C60H24) by molecular hydrogen evidences for the presence of limits in the hydrogenation process. These limits caused the contentions between three-fold symmetry of polycyclic aromatic hydrocarbon molecules and two-fold symmetry of adsorbed hydrogen pairs. Increase of the binding energy between nanographenes during reduction is also discussed as possible cause of the experimentally observed limited hydrogenation of studied nanographenes.Comment: 18 pages, 7 figures, accepted to J. Phys. Chem.

BIOGAS PRODUCTION IN LABORATORY AND HOME CONDITIONS

From cattle manure and various household waste and farm waste, biogas was obtained using anaerobic digestion in the laboratory as well as in the field in the summer months. For this work, a laboratory 5-liter digester was used. and installed a 200 liter biogas plant. The so-called bioreactor is installed in the safest place in the plot

К вопросу о метрической однородности текстов на славянских языках

In the studies of R. Gray and K. Atkinson by the statistical analysis of related words, W. Chang, C. Cathcart, D. Hall and A. Garrett using statistical modeling and A. S. Kasyan and A. V. Dybo on the basis of lexicostatistical classification, in addition to discussing historical issues, geneological trees are presented, reflecting both kinship and divergence of modern Slavic languages. There are a lot of such trees, they are similar in general terms and differ in small details, see, for example. The area of the formerly common language is now divided into three groups - the eastern one, consisting of the Belarusian, Russian and Ukrainian languages, the western one from the Czech, Slovak, Polish, Kashubian and Lusatian languages, and the southern one, consisting of the Bulgarian, Macedonian, Serbo-Croatian and Slovenian languages. Using the example of a randomly generated model collection of 26 texts in 13 languages (2 works from each language), the article establishes the applicability of the γ-classifier for automatic recognition of the belongingof texts to a particular group of Slavic languages based on the frequency of a set of Latin characters that is universal for all languages. The mathematical model of the γ-classifier is presented in the form of a triad composed of a digital portrait (DP) of the text - the distribution of the frequency of Latin symbolic unigrams in the text; formulas for calculating the distances between DP texts and a machine learning algorithm that implements the hypothesis of “homogeneity” of works from one language group and “heterogeneity” of works belonging to different groups of languages. The tuning of the algorithm using a table of paired distances between all products of the model collection was carried out by selecting the optimal value of the real parameter γ, which minimizes the number of errors in violation of tho “homogeneity” hypothesis. The e-classifier trained on the texts of the model collection showed 86% accuracy in recognizing the language groups of the works. To test the classifier, 3 additional random texts were selected, one text each for three different groups of Slavic languages. By the method of the nearest (in terms of distance) neighbor, all new texts confirmed their homogeneity with the corresponding pairs of monolingual works, thereby also homogeneity with the corresponding group of Slavic languages. В исследованиях Р. Грея и К. Аткинсона посредством статистического анализа родственных слов, У. Чанга, Ч. Кэткарта, Д. Холла и А. Гарретта с помощью статистического моделирования и А. С. Касьяна и А. В. Дыбона основе лексикостатистической классификации помимо обсуждения исторических вопросов представлены генеологические деревья, отражающие как родство, так и дивергенцию современных славянских языков. Таких деревьев достаточно много, они сходны в общих чертах и различны в небольших деталях, см. например. Ареал прежде единого языка ныне разделился на три группы – восточную в составе белорусского, русского и украинского языков, западную - из чешского, словацкого, польского, кашубского и лужицкихязыков и южную, состоящую из болгарского, македонского, сербо-хорватского и словенского языков. В статье на примере случайно сформированной модельной коллекции из 26 текстов на 13 языках (по 2 произведения от каждого языка) устанавливается применимость γ-классификатора для автоматического распознавания принадлежности текстов той или иной группе славянских языков на основе частотности универсального для все языков набора латинских символов. Математическая модель -классификатора представляется в виде триады, составленной из цифрового портрета (ЦП) текста - распределения в тексте частотности латинских символьных униграмм; формулы для вычисления расстояний между ЦП текстами и алгоритма машинного обучения, реализующего гипотезу “однородности” произведений из одной группы языков и “неоднородности” произведений, при- надлежащих разным группам языков. Настройка алгоритма, использующего таблицу парных расстояний между всеми произведениями модельной коллекции, осуществлялась путем подбора оптимального значения вещественного параметра γ, минимизирующего число ошибок нарушения гипотезы “однородности”. Обученный на текстах модельной коллекции γ-классификатор показал 86%- ю точность в распознавании языков произведений. Для тестирования классификатора были выбраны 3 дополнительных случайных текста, по одному тексту для трёх разных групп славянских языков. Методом ближайшего (по расстоянию) соседа все новые тексты подтвердили свою однородность с соответствующими парами одноязычных произведений, тем самым и однородность с соответствующей группой славянских языков

Influence of hydrochemical indicators on the age and density of bivalve molluscs, spread in the lower reaches of the Zarafshan river

Hydrochemical parameters of water in ecosystems of Gijdivan district of Bukhara region: O2 content 4,9 ± 0,5 mg / l, Cl2 312 ± 14 mg / l, mineralization - 992-1402 mg / l and oil products about 0,6-0,8 mg / l, it turned out that the amount of these elements in the water exceeds the permissible norm. The following conclusions were made on the basis of the study of the status of the species listed in the “Red Book” in aquatic ecosystems of the lower reaches of the Zarafshan river. We found that the population of the species Colletopterum and Corbicula in the village of Sultanabad in the Navoi region is a growing population, while the population of the species Colletopterum and Corbicula in the Gijduvan region of the Bukhara region is decreasing