Phase diagram of Pb(Zr,Ti)O3 solid solutions from first principles

A first-principles-derived scheme, that incorporates ferroelectric and antiferrodistortive degrees of freedom, is developed to study finite-temperature properties of PbZr1-xTixO3 solid solutions near its morphotropic phase boundary. The use of this numerical technique (i) resolves controversies about the monoclinic ground-state for some Ti compositions, (ii) leads to the discovery of an overlooked phase, and (iii) yields three multiphase points, that are each associated with four phases. Additional neutron diffraction measurements strongly support some of these predictions.Comment: 10 pages, 2 figure

A combined theoretical and experimental study of the low temperature properties of BaZrO3

Low temperature properties of BaZrO3 are revealed by combining experimental techniques (X-ray diffraction, neutron scattering and dielectric measurements) with theoretical first-principles-based methods (total energy and linear response calculations within density functional theory, and effective Hamiltonian approaches incorporating/neglecting zero-point phonon vibrations). Unlike most of the perovskite systems, BaZrO3 does not undergo any (long-range-order) structural phase transition and thus remains cubic and paraelectric down to 2 K, even when neglecting zero-point phonon vibrations. On the other hand, these latter pure quantum effects lead to a negligible thermal dependency of the cubic lattice parameter below ~ 40 K. They also affect the dielectricity of BaZrO3 by inducing an overall saturation of the real part of the dielectric response, for temperatures below ~ 40 K. Two fine structures in the real part, as well as in the imaginary part, of dielectric response are further observed around 50-65 K and 15 K, respectively. Microscopic origins (e.g., unavoidable defects and oxygen octahedra rotation occurring at a local scale) of such anomalies are suggested. Finally, possible reasons for the facts that some of these dielectric anomalies have not been previously reported in the better studied KTaO3 and SrTiO3 incipient ferroelectrics are also discussed.Comment: 8 pages, 5 figures, submitted to Physical Review

High pressure phases in highly piezoelectric Pb(Zr0.52Ti0.48)O3

Two novel room-temperature phase transitions are observed, via synchrotron x-ray diffraction and Raman spectroscopy, in the Pb(Zr0.52Ti0.48)O3 alloy under hydrostatic pressures up to 16 GPa. A monoclinic (M)-to-rhombohedral (R1) phase transition takes place around 2-3 GPa, while this R1 phase transforms into another rhombohedral phase, R2, at about 6-7 GPa. First-principles calculations assign the R3m and R3c symmetry to R1 and R2, respectively, and reveal that R2 acts as a pressure-induced structural bridge between the polar R3m and a predicted antiferrodistortive R-3c phase.Comment: REVTeX, 4 pages with 3 figures embedded. Figs 1 and 3 in colo

Atomic excitation during recollision-free ultrafast multi-electron tunnel ionization

Modern intense ultrafast pulsed lasers generate an electric field of sufficient strength to permit tunnel ionization of the valence electrons in atoms. This process is usually treated as a rapid succession of isolated events, in which the states of the remaining electrons are neglected. Such electronic interactions are predicted to be weak, the exception being recollision excitation and ionization caused by linearly-polarized radiation. In contrast, it has recently been suggested that intense field ionization may be accompanied by a two-stage `shake-up' reaction. Here we report a unique combination of experimental techniques that enables us to accurately measure the tunnel ionization probability for argon exposed to 50 femtosecond laser pulses. Most significantly for the current study, this measurement is independent of the optical focal geometry, equivalent to a homogenous electric field. Furthermore, circularly-polarized radiation negates recollision. The present measurements indicate that tunnel ionization results in simultaneous excitation of one or more remaining electrons through shake-up. From an atomic physics standpoint, it may be possible to induce ionization from specific states, and will influence the development of coherent attosecond XUV radiation sources. Such pulses have vital scientific and economic potential in areas such as high-resolution imaging of in-vivo cells and nanoscale XUV lithography.Comment: 17 pages, 4 figures, original format as accepted by Nature Physic

Conceptual Justification of Research of Structural Development of Economic Systems

In the article, a theoretical and methodological substantiation of the strategy of structural development based on the statics and dynamics, qualitative and quantitative, vertical and horizontal interrelationships of the processes of structuring economic systems in the current and long-term perspective is developed on the basis of the synthesis of domestic and foreign research. Clarification of scientific definitions enabled the authors to give a definition of the concept of “structural development” as a guided progressive evolutionary and procedural transformation that forms new potential for economic growth through systemic convergence and the balance of quantitative and qualitative processes that qualitatively transform a certain economic system. The concept of the strategy of structural development takes into account objective economic laws and laws governing the speed and intensity of effective changes in the economic mechanism of managing the national economy at all levels – from the enterprise and the industry to the country as a whole. To analyze the structural dynamics, we propose a system-process approach in which, along with individual ones, aggregated indices are recommended, which makes it possible to study cumulative-dynamic states of transformation simultaneously as a result and as a prerequisite for structural development. Among all extractive industries, the coal industry holds one of the leading places that determines the priorities for sustainable development of the country. The testing of the proposed methods for diagnosing structural development was carried out with reference to the analysis and evaluation of indicators of the dynamics of structural transformations at enterprises of the Russian coal industry, where prolonged structural reorganization is observed. Analysis of the dynamics of indicators of Russia’s structural development for 2006-2016 illustrates the quantitative and qualitative characteristics of crisis situations during periods of structural transformations with the predominance of inertial components that form economic growth. This brings about the need to search for new scientific approaches that allow the modeling of the vector and the pace of optimal changes, taking into account more complex horizontal and vertical relationships, trends and specific evolution that determine disproportions of different structures. The purpose of the study is determined by the urgency and growing theoretical and practical importance of the problem of developing a scientifically based strategy for the structural development of economic systems at various hierarchical levels of national economic management. The solution to this problem calls for the identification of structural adjustment priorities using appropriate indicators and methods for assessing optimization changes based on the transition from extensive to intensive growth in order to achieve sustainable economic dynamics in the long term.В статье на основе обобщения отечественных и зарубежных исследований разаботано теоретико-методологическое обоснование стратегии структурного развития с учетом статики и динамики, качественных и количественных, вертикальных и горизонтальных взаимосвязей процессов структуризации экономических систем в современных условиях и долгосрочной перспективе. Уточнение научных определений позволило дать авторское определение понятию «структурное развитие» как управляемой прогрессивной эволюционно-процессуальной трансформации, формирующей новый потенциал экономического роста за счет системной конвергенции и сбалансированности квантитативных и квалитативных процессов, качественно преобразующих определенную экономическую систему. В концепции стратегии структурного развития учтены объективные экономические законы и закономерности, регулирующие скорость и интенсивность эффективных преобразований хозяйственного механизма управления народным хозяйством на всех уровнях – от предприятия и отрасли до страны в целом. Для анализа структурной динамики предлагается системно-процессный подход, в котором, наряду с индивидуальными, рекомендуются агрегированные индексы, что позволяет исследовать кумулятивно-динамические состояния трансформации одновременно как результат и как предпосылку структурного развития. Среди всех добывающих отраслей угольная промышленность занимает одно из ведущих мест, определяющих приоритеты устойчивого развития страны. Апробация предложенных методов диагностики структурного развития выполнена применительно к решению задач анализа и оценки показателей динамики структурных трансформаций на предприятиях угольной промышленности России, где наблюдается длительная структурная перестройка. Анализ динамики показателей структурного развития России за 2006–2016 гг. иллюстрирует количественные и качественные характеристики кризисных ситуаций в периоды структурных трансформаций с преобладанием инерционных компонент, формирующих экономический рост, что приводит к необходимости поиска новых научных подходов, позволяющих моделировать вектор и темпы оптимальных изменений с учетом усложняющихся горизонтальных и вертикальных взаимосвязей, тенденций и специфики эволюции, обусловливающих диспропорции различных структурах. Цель исследования обусловлена актуальностью и все возрастающим теоретическим и практическим значением проблемы разработки научно обоснованной стратегии структурного развития экономических систем на различных иерархических уровнях управления народным хозяйством. Решение данной проблемы вызывает необходимость определения приоритетов структурной перестройки с применением соответствующих показателей и методов оценки оптимизационных изменений на основе перехода от экстенсивного к интенсивному росту для достижения устойчивой экономической динамики в долгосрочной перспективе

Resonant raman scattering in complexes of nc-Si/SiO₂ quantum dots and oligonucleotides

We report on the functionalization of nanocrystalline nc-Si/SiO2 semiconductor quantum dots (QDs) by short d(20G, 20T) oligonucleotides. The obtained complexes have been studied by Raman spectroscopy techniques with high spectral and spatial resolution. A new phenomenon of multiband resonant light scattering on single oligonucleotide molecules has been discovered, and peculiarities of this effect related to the nonradiative transfer of photoexcitation from nc-Si/SiO2 quantum dots to d(20G, 20T) oligonucleotide molecules have been revealed

Conformal mapping methods for interfacial dynamics

The article provides a pedagogical review aimed at graduate students in materials science, physics, and applied mathematics, focusing on recent developments in the subject. Following a brief summary of concepts from complex analysis, the article begins with an overview of continuous conformal-map dynamics. This includes problems of interfacial motion driven by harmonic fields (such as viscous fingering and void electromigration), bi-harmonic fields (such as viscous sintering and elastic pore evolution), and non-harmonic, conformally invariant fields (such as growth by advection-diffusion and electro-deposition). The second part of the article is devoted to iterated conformal maps for analogous problems in stochastic interfacial dynamics (such as diffusion-limited aggregation, dielectric breakdown, brittle fracture, and advection-diffusion-limited aggregation). The third part notes that all of these models can be extended to curved surfaces by an auxilliary conformal mapping from the complex plane, such as stereographic projection to a sphere. The article concludes with an outlook for further research.Comment: 37 pages, 12 (mostly color) figure

Патогенетическое и клиническое обоснование применения N-ацетилцистеина (Флуимуцила) при идиопатическом фиброзирующем альвеолите

The aim of this study was to investigate free radical and lipid disorders in idiopathic pulmonary fibrosis (IPF), to assess clinical efficacy of Fluimucil and to substantiate its administration in different stages of the disease. We observed 127 IPF patients, of them 59 were treated typically with prednisolone, colchicines, or azathioprin, 68 ones received immunosuppressors and Fluimucil. The diagnosis of IPF was verified morphologically in open lung biopsy samples. The patients’ age was 25 to 74 yrs, the mean age, 46.7 ± 9.8 yrs. A control group included 20 healthy donors, the mean age, 41.2 ± 1.2 yrs. N-acetylcysteine (Fluimucil, Zambon group) was administered initially IV 1800 mg a day for 14 days, then orally 1 800 mg a day for a month, then 600 mg a day for 3 months. Clinical and free radical conditions were monitored before the treatment and 3, 6 and 12 months starting the therapy. Fluimucil improved thrombocyte antioxidant activity and plasma antioxidant activity, reduced CT signs of IPF, provided a stable growth in FEV1 and FVC (by 10 % and 12 % respectively) and DLco. Fluimucil was well-tolerated, adverse effects (nausea, stomach ache) were noted in 7 patients (10.2 %). Thus, the results confirmed antioxidant efficacy of Fluimucil in IPF. The long-term administration of Fluimucil combined with the immunosuppressive drugs in IPF patients was safe and reasonable as this inhibited progression of the disease.Цель нашего исследования — уточнить особенности свободнорадикальных и липидных нарушений при идиопатическом фиброзирующем альвеолите (ИФА), определить клиническую эффективность флуимуцила и патогенетически обосновать его применение на различных стадиях заболевания. Обследованы 127 больных с ИФА, из них 59 получали традиционную терапию (преднизолон, колхицин, азатиоприн), 68 — иммуносупрессивные препараты в сочетании с Флуимуцилом. Морфологическая верификация диагноза проводилась по материалу открытых легочных биопсий. Возраст больных варьировался от 25 до 74 лет, в среднем — 46,7 ± 9,8 лет. Контрольную группу составили 20 практически здоровых доноров, средний возраст — 41,2 ± 1,2 года. N-ацетилцистеин (Флуимуцил, «Zambon») назначался по двухэтапной схеме: внутривенно в дозе 1 800 мг в течение 14 дней, затем — реr os по 1 800 мг в сутки в течение месяца и по 600 мг в сутки в последующие 3 мес. Клиническое обследование и исследование свободнорадикальных процессов проводили до лечения, через 3, 6 и 12 мес. от начала терапии. Флуимуцил оказывал положительный эффект на антиоксидантную активность тромбоцитов, коэффициенты их ингибирующего влияния на генерацию АФК лейкоцитами и антиперекисную активность плазмы. Также Флуимуцил положительно влиял на компьютерно-томографические показатели активности альвеолита. У больных, получавших Флуимуцил, к концу наблюдения отмечен стойкий прирост ЖЕЛ и ФЖЕЛ (на 10 % и 12 % соответственно) и DLсо. Флуимуцил хорошо переносился больными, побочные эффекты в виде тошноты, болей в эпигастрии наблюдались только у 7 (10,2 %) больных. Таким образом, результаты исследования подтверждают эффективность Флуимуцила как антиоксиданта при ИФА. Длительное применение высоких доз Флуимуцила в сочетании с иммунносупрессивной терапией при ИФА безопасно и патогенетически обоснованно, т. к. препятствует прогрессированию заболевания

Исследование свойств эластомерных материалов, наполненных модифицированным техническим углеродом в сочетании со связующим агентом

Possibility of interaction between modified by proposed method carbon black and silane coupling agent is shown. It allows to optimize hysteresis properties of elastomer composites, while modified carbon black leads to increasing in its hardness at impact load.Показана возможность взаимодействия связующего агента (силана) с модифи-цированным предложенным способом техническим углеродом, что позволяет оптимизировать гистерезисные свойства эластомерных композитов, в то время как модифицированный технический углерод позволяет улучшить их упруго-прочностные свойства