Метод трехмерной триангуляции в задачах кластерного анализа

Представлен метод многомерного шкалирования на основе трехмерной триангуляции. Рассмотрена возможность качественного сохранения геометрической структуры множества объектов при отображении многомерного пространства в трехмерное. Приведены результаты применения метода для решения задачи кластеризации на примере периодической системы элементов Д.И. Менделеева. Экспериментально показано, что по критериям качества кластеризации предложенный метод более эффективен в сравнении с методами k-средних и нейронной сети Кохонена.Представлено метод багатовимірного шкалювання на основі тривимірної тріангуляції. Розглянуто можливість якісного збереження геометричної структури множини об’єктів при відображенні багатовимірного простору в тривимірне. Наведено результати застосування методу для вирішення задачі кластеризації на прикладі періодичної системи елементів Д.І. Менделєєва. Експериментально показано, що за критеріями якості кластеризації запропонований метод більш ефективний у порівнянні з методами k-середніх та нейронної мережі Кохонена.The method of multidimensional scaling on the basis of the 3-D triangulation is presented. The qualitative preservation possibility of geometrical structure of objects by multidimensional space mapping to three- dimensional space is considered. The results of application of the method for clustering problem of the Mendeleyev periodic table are presented. It is experimentally shown, that the presented method is more effective by criteria of clustering quality in comparison with the methods of k-averages and the Kohonen neural network

Near-infrared Emitting CulnSe2/CulnS2 Dot Core/Rod Shell Heteronanorods by Sequential Cation Exchange

The direct synthesis of heteronanocrystals (HNCs) combining different ternary semiconductors is challenging and has not yet been successful. Here, we report a sequential topotactic cation exchange (CE) pathway that yields CuInSe2/CuInS2 dot core/rod shell nanorods with near-infrared luminescence. In our approach, the Cu+ extraction rate is coupled to the In3+ incorporation rate by the use of a stoichiometric trioctylphosphine-InCl3 complex, which fulfills the roles of both In-source and Cu-extracting agent. In this way, Cu+ ions can be extracted by trioctylphosphine ligands only when the In–P bond is broken. This results in readily available In3+ ions at the same surface site from which the Cu+ is extracted, making the process a direct place exchange reaction and shifting the overall energy balance in favor of the CE. Consequently, controlled cation exchange can occur even in large and anisotropic heterostructured nanocrystals with preservation of the size, shape, and heterostructuring of the template NCs into the product NCs. The cation exchange is self-limited, stopping when the ternary core/shell CuInSe2/CuInS2 composition is reached. The method is very versatile, successfully yielding a variety of luminescent CuInX2 (X = S, Se, and Te) quantum dots, nanorods, and HNCs, by using Cd-chalcogenide NCs and HNCs as templates. The approach reported here thus opens up routes toward materials with unprecedented properties, which would otherwise remain inaccessible

Зимостойкость некоторых видов рода Sorbus L. в Донбассе

Изучены анатомические особенности годичных побегов Sorbus persica Hedl., S. domestica L. и S. aucuparia L. Определены толщина тканей и степень лигнификации ксилемы. Наиболее развиты покровные и механические ткани у S. aucuparia, годичные побеги полностью вызревшие. У S. persica наблюдается отставание в развитии тканей и степени одревеснения побегов по сравнению с S. aucuparia. Отмечена высокая зимостойкость S. domestica и S. aucuparia и более низкая – S. persica. К перспективным видам отнесены S. domestica и S. aucuparia. Вид – S. persica нецелесообразно вводить в ассортимент декоративных растений юго-востока Украины.The anatomical peculiarities of annual spears of Sorbus persica Hedl., S. domestica L. and S. aucuparia L. were studied. The tissue depth and xylem lignification rate were defined. The tissues of S. aucuparia are most developed and annual spears are fully mature for vegetative period. S. persica lags in terms of tissue development and spear lignification rate compared to S. aucuparia. S. domestica and S. aucuparia revealed winter resistance at high level, whereas S. persica demonstrated it at low level. S. domestica and S. aucuparia are treated as perspective, while S. persica is unreasonable for introduction to the assortment of decorative plants of south-east of Ukraine

Reducing nonideal to ideal coupling in random matrix description of chaotic scattering: Application to the time-delay problem

We write explicitly a transformation of the scattering phases reducing the problem of quantum chaotic scattering for systems with M statistically equivalent channels at nonideal coupling to that for ideal coupling. Unfolding the phases by their local density leads to universality of their local fluctuations for large M. A relation between the partial time delays and diagonal matrix elements of the Wigner-Smith matrix is revealed for ideal coupling. This helped us in deriving the joint probability distribution of partial time delays and the distribution of the Wigner time delay.Comment: 4 pages, revtex, no figures; published versio

Seagrass and submerged aquatic vegetation (VAS) habitats off the Coast of Brazil: state of knowledge, conservation and main threats

Seagrass meadows are among the most threatened ecosystems on earth, raising concerns about the equilibrium of coastal ecosystems and the sustainability of local fisheries. The present review evaluated the current status of the research on seagrasses and submerged aquatic vegetation (SAV) habitats off the coast of Brazil in terms of plant responses to environmental conditions, changes in distribution and abundance, and the possible role of climate change and variability. Despite an increase in the number of studies, the communication of the results is still relatively limited and is mainly addressed to a national or regional public; thus, South American seagrasses are rarely included or cited in global reviews and models. The scarcity of large-scale and long-term studies allowing the detection of changes in the structure, abundance and composition of seagrass habitats and associated species still hinders the investigation of such communities with respect to the potential effects of climate change. Seagrass meadows and SAV occur all along the Brazilian coast, with species distribution and abundance being strongly influenced by regional oceanography, coastal water masses, river runoff and coastal geomorphology. Based on these geomorphological, hydrological and ecological features, we characterised the distribution of seagrass habitats and abundances within the major coastal compartments. The current conservation status of Brazilian seagrasses and SAV is critical. The unsustainable exploitation and occupation of coastal areas and the multifold anthropogenic footprints left during the last 100 years led to the loss and degradation of shoreline habitats potentially suitable for seagrass occupation. Knowledge of the prevailing patterns and processes governing seagrass structure and functioning along the Brazilian coast is necessary for the global discussion on climate change. Our review is a first and much-needed step toward a more integrated and inclusive approach to understanding the diversity of coastal plant formations along the Southwestern Atlantic coast as well as a regional alert the projected or predicted effects of global changes on the goods and services provided by regional seagrasses and SAV