Time-resolved amplified spontaneous emission in quantum dots

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 97, 251106 (2010) and may be found at https://doi.org/10.1063/1.3529447.In time-resolved experiments at InGaAs/GaAs quantum-dots-in-a-well (DWELL) semiconductor optical amplifiers, pump-probe of the ground state (GS) population, and complementary measurement of the amplified spontaneous emission of the excited state (ES) population, we are able to separate the early subpicosecond dephasing dynamics from the later picosecond population relaxation dynamics. We observe a 10 ps delay between the nonlinear GS pulse amplification and the subsequent ES population drop-off that supports the dominance of a direct two dimensional reservoir-GS capture relaxation path in electrically pumped quantum-dot-DWELL structures.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement

СТРУКТУРНЫЕ ОСОБЕННОСТИ ПРИРОДНЫХ И ОБОГАЩЕННЫХ КАОЛИНОВ МЕСТОРОЖДЕНИЙ РЕСПУБЛИКИ БЕЛАРУСЬ

IR-spectroscopic results of study of primary kaolins of the Belarusian deposits «Sitnica» and «Dedovka» in a natural state and enriched by hydraulic sieve method are presented. The structural features of Belarusian kaolins as compared with known high-quality kaolin of Ukrainian deposits «Prosyanovskoe» are revealed, the values of crystallinity index are determined. Analysis of IR-spectra in the high-frequency region allowed us to establish the water connection forms in natural and enriched kaolins, the presence of OH-groups in the interlayer space, inside and on the surface of the octahedral layer and adsorbed water molecules, which can affect the rheology of kaolin suspensions. Silicate absorption band of kaolin, as well as intense peaks of deformation vibrations of quartz, typical for unenriched natural kaolin of Belarusian deposits, are in the lowfrequency region. Investigation using IR-spectroscopy made it possible to establish the structural features of natural kaolins related to the presence in the primary kaolin of the «Sitnitsa» and «Dedovka» deposits of the mineral of the kaolinite group of dikkite. The crystallinity index values (according to Hinckley) are established for natural and enriched kaolins «Sitnica» (0.94 and 1.11) and «Dedovka» (0.98 and 1.04) in comparison with kaolins of Prosyanovskoye deposit (1.31). Представлены результаты ИК-спектроскопического исследования первичных каолинов белорусских месторождений «Ситница» и «Дедовка» в природном состоянии и обогащенном гидравлическим ситовым способом. Выявлены структурные особенности каолинов Республики Беларусь по сравнению с известным высококачественным каолином украинского месторождения «Просяновское», определены значения индекса кристалличности. Анализ ИК-спектров в высокочастотной области позволил установить формы связи воды в природном и обогащенном каолинах, наличие ОН-групп в межслоевом пространстве, внутри и на поверхности октаэдрического слоя, а также адсорбированных молекул воды, что может оказать влияние на реологические свойства каолиновых суспензий. В низкочастотной области сосредоточены полосы поглощения силикатных структур каолинов, а также интенсивные пики деформацинных колебаний кварца, характерные для природных необогащенных каолинов белорусских месторождений. Исследование с помощью ИК-спектроскопии позволило установить структурные особенности природных каолинов, связанные с присутствием в первичных каолинах месторождений «Ситница» и «Дедовка» минерала каолинитовой группы диккита. Определены значения показателя индекса кристалличности (по Хинкли) для природных и обогащенных каолинов «Ситница» (0,94 и 1,11) и «Дедовка» (0,98 и 1,04) в сравнении с известным просяновским каолином (1,31).

Применение самораспространяющегося высокотемпературного синтеза для получения защитно-упрочняющих алюмосиликатных покрытий

This article shows the possibility of using the method of self-propagating high-temperature synthesis to obtain protective and hardening coatings for the lining of various thermal installations. The development of compositions of ceramic masses for the production of SHS coatings was carried out on the basis of aluminum powder, clay raw materials, exhausting and fluxing components as well as mineralizing additives. The prepared suspension including pre-prepared and thoroughly mixed raw materials was applied with a brush or a spray gun onto the previously cleaned and moistened surface of an aluminosilicate refractory. The firing of the coating was carried out in accordance with the mode of removing the thermal unit at the operating temperature. The temperature of the initiation of the SHS process, previously established using differential thermal analysis, was in the range of 570–720 °C and depended on the chemical composition of the charge. It has been established that the presence of crystalline phases of silica, corundum, hematite and a number of solid solutions (mainly calcium and sodium aluminosilicates) in the coating structure provides the necessary combination of the thermomechanical and thermophysical characteristics of the coatings. On the basis of the conducted research, the expediency of applying the technology of self-propagating high-temperature synthesis for the production of protective and hardening coatings on the lining of thermal units is demonstrated, which is confirmed by industrial tests in the conditions of the Minsk Ceramic Factory OJSC «Keramin».Показана возможность использования метода самораспространяющегося высокотемпературного синтеза для получения защитно-упрочняющих покрытий по футеровке различных тепловых установок. Разработка составов керамических композиций для получения СВС-покрытий осуществлялась на основе алюминиевой пудры, глинистого сырья, отощающих и флюсующих компонентов, а также минерализующих добавок. Приготовленную суспензию, включающую предварительно подготовленные и тщательно перемешанные сырьевые компоненты, с помощью кисти или пульверизатора наносили на предварительно очищенную и увлажненную поверхность алюмосиликатного огнеупора. Обжиг покрытия осуществляли в соответствии с режимом выведения теплового агрегата на рабочую температуру. Температура инициирования процесса СВС, предварительно установленная с помощью дифференциально-термического анализа, находилась в интервале 570–720 °С и зависела от химического состав шихты. Установлено, что наличие в структуре покрытий кристаллических фаз кремнезема, корунда, гематита, а также ряда твердых растворов (преимущественно алюмосиликаты кальция и натрия) обеспечивает необходимое сочетание термомеханических и теплофизических характеристик покрытий. На основании проведенных исследований показана целесообразность применения технологии СВС для получения защитно-упрочняющих покрытий по футеровке тепловых агрегатов, что подтверждено промышленными испытаниями в условиях Минского керамического завода ОАО «Керамин»

Quality of life of patients of the physiathritic profile.

The article emphasizes the relevance of studying the indicators of the quality of life of patients with a phthisiological profile. The results of the study of the quality of life structure in patients with pulmonary tuberculosis and extrapulmonary tuberculosis, namely tuberculosis of the osteo-articular system, without HIV infection and with HIV infection are presented.В статье подчеркивается актуальность изучения показателей качества жизни пациентов фтизиатрического профиля. Представлены результаты исследования структуры качества жизни у пациентов с легочной и внелегочной формой туберкулеза, а именно туберкулезное поражение костно-суставной системы у ВИЧ больных и у пациентов без сопутствующей ВИЧ инфекции соответственно

nnovative Seasonal Migrations and Subsistence System of the Mobile Pastoralists of the Desert-Steppe Zone of Eurasia:role of social groups

The study of the economic system of the earliest nomads which inhabited the Eurasian desert-steppe belt in 5000-2000 is a relevant task of contemporary studies. The data on the organization of living space and the role of social groups of early prehistoric pastoralists in the exploitation of open steppe resources are scarce. The paper presents a new methodological approach to searching camps of the earliest pastoralists. The application of this approach enabled the archaeologists to discover numerous seasonal camps in the Sal-Manych Ridge located in the western part of the Eurasian steppes, including Eneolithic camps dated to 4200-3600 BC. The study of the occupation layers at the sites, evaluation of the productivity of pasture systems made it possible to categorize such sites as short-term seasonal camps occupied by pastoralists, evaluate the role of social groups in the organization of innovative seasonal migrations and reconstruct their subsistence system. The camps emerged as a result of developing pastoral economic strategy in the Lower Don region and the abutting areas reflecting the role of special social groups of pastoralists who managed to organize seasonal moves and address the issue of exploiting pastures located beyond the permanently occupied area

Origin of Axial and Radial Expansions in Carbon Nanotubes Revealed by Ultrafast Diffraction and Spectroscopy

The coupling between electronic and nuclear degrees of freedom in low-dimensional, nanoscale systems plays a fundamental role in shaping many of their properties. Here, we report the disentanglement of axial and radial expansions of carbon nanotubes, and the direct role of electronic and vibrational excitations in determining such expansions. With subpicosecond and subpicometer resolutions, structural dynamics were explored by monitoring changes of the electron diffraction following an ultrafast optical excitation, whereas the transient behavior of the charge distribution was probed by time-resolved, electron-energy-loss spectroscopy. Our experimental results, and supporting density functional theory calculations, indicate that a population of the excited carriers in the antibonding orbitals of the nanotube walls drives a transient axial deformation in ∼1 ps; this deformation relaxes on a much longer time scale, 17 ps, by nonradiative decay. The electron-driven expansion is distinct from the phonon-driven dynamics observed along the radial direction, using the characteristic Bragg reflections; it occurs in 5 ps. These findings reveal the nonequilibrium distortion of the unit cell at early times and the role of the electron(phonon)-induced stress in the lattice dynamics of one-dimensional nanostructures

Records and peculiarities of distribution of the European mole (Talpa europaea) in the Lower Dniester area

The occurrence of a new mammals species, the European mole, was revealed for the Lower Dnister area based on own observations and analysis of materials deposited in the National Museum of Natural History, NAS of Ukraine (Kyiv). In the Lower Dniester area, the species occurs on floodplain meadows, floodplain forests, agrocenoses, and homestead lands. We recorded the species’ migration across the Dnister river during flood in 2008. The present materials are not sufficient to make any conclusions on terms and ways of the species settlement in the region. The authors assume that the species occurred in the Lower Dniester floodplain area earlier