Non-Dirac topological surface states in (SnTe)n≥2_{n\geq2}(Bi2_2Te3_3)m=1_{m=1}

A new type of topological spin-helical surface states was discovered in layered van der Waals bonded (SnTe)$_{n=2,3}$(Bi$_2$Te$_3$)$_{m=1}$ compounds which comprise two covalently bonded band inverted subsystems, SnTe and Bi$_2$Te$_3$, within a building block. This novel topological states demonstrate non-Dirac dispersion within the band gap. The dispersion of the surface state has two linear sections of different slope with shoulder feature between them. Such a dispersion of the topological surface state enables effective switch of the velocity of topological carriers by means of applying an external electric field

Pressure effects on crystal and electronic structure of bismuth tellurohalides

We study the possibility of pressure-induced transitions from a normal semiconductor to a topological insulator (TI) in bismuth tellurohalides using density functional theory and tight-binding method. In BiTeI this transition is realized through the formation of an intermediate phase, a Weyl semimetal, that leads to modification of surface state dispersions. In the topologically trivial phase, the surface states exhibit a Bychkov-Rashba type dispersion. The Weyl semimetal phase exists in a narrow pressure interval of 0.2 GPa. After the Weyl semimetal--TI transition occurs, the surface electronic structure is characterized by gapless states with linear dispersion. The peculiarities of the surface states modification under pressure depend on the band-bending effect. We have also calculated the frequencies of Raman active modes for BiTeI in the proposed high-pressure crystal phases in order to compare them with available experimental data. Unlike BiTeI, in BiTeBr and BiTeCl the topological phase transition does not occur. In BiTeBr, the crystal structure changes with pressure but the phase remains a trivial one. However, the transition appears to be possible if the low-pressure crystal structure is retained. In BiTeCl under pressure, the topological phase does not appear up to 18 GPa due to a relatively large band gap width in this compound

Pressure effects on crystal and electronic structure of bismuth tellurohalides

Westudy the possibility of pressure-induced transitions from a normal semiconductor to a topological insulator (TI) in bismuth tellurohalides using density functional theory and tight-binding method. In BiTeI this transition is realized through the formation of an intermediate phase, a Weyl semimetal, that leads to modification of surface state dispersions. In the topologically trivial phase, the surface states exhibit a Bychkov–Rashba type dispersion. The Weyl semimetal phase exists in a narrow pressure interval of 0.2 GPa. After the Weyl semimetal–TI transition occurs, the surface electronic structure is characterized by gapless states with linear dispersion. The peculiarities of the surface states modification under pressure depend on the band-bending effect.Wehave also calculated the frequencies of Raman active modes for BiTeI in the proposed high-pressure crystal phases in order to compare them with available experimental data. Unlike BiTeI, in BiTeBr and BiTeCl the topological phase transition does not occur. In BiTeBr, the crystal structure changes with pressure but the phase remains a trivial one. However, the transition appears to be possible if the low-pressure crystal structure is retained. In BiTeCl under pressure, the topological phase does not appear up to 18 GPa due to a relatively large band gap width in this compound

Unoccupied Topological States on Bismuth Chalcogenides

The unoccupied part of the band structure of topological insulators Bi$_2$Te$_{x}$Se$_{3-x}$ ($x=0,2,3$) is studied by angle-resolved two-photon photoemission and density functional theory. For all surfaces linearly-dispersing surface states are found at the center of the surface Brillouin zone at energies around 1.3 eV above the Fermi level. Theoretical analysis shows that this feature appears in a spin-orbit-interaction induced and inverted local energy gap. This inversion is insensitive to variation of electronic and structural parameters in Bi$_2$Se$_3$ and Bi$_2$Te$_2$Se. In Bi$_2$Te$_3$ small structural variations can change the character of the local energy gap depending on which an unoccupied Dirac state does or does not exist. Circular dichroism measurements confirm the expected spin texture. From these findings we assign the observed state to an unoccupied topological surface state

History of biomechanical research at the Ilizarov Centre (to the 100th anniversary of Academician G.A. Ilizarov)

Background. Biomechanical studies of both the Ilizarov apparatus itself and the physiological system “apparatus – limb” occupy a significant place in the history of the formation and elaboration of the Ilizarov method, developed in the middle of the last century at the Kurgan Research Institute of Experimental Traumatology and Orthopaedics (nowadays – the world-famous Centre named after its creator). The analysis of the history of biomechanical research in the formation of Ilizarov method is not without interest.The aim. To analyze the history and stages of development of biomechanical research in order to substantiate the effectiveness of the Ilizarov method of transosseous osteosynthesis.Results. The national medical industry did not produce the appropriate equipment for biomechanical research in the early 1970s. That is why a group of engineers was included into the Laboratory of Clinical Physiology and Biomechanics (established in 1971) of the Ilizarov Centre, which created equipment for studying the processes in the tissues of the limbs and in the structure of the Ilizarov apparatus itself during its traction and compression impact on biological structures. The community of physicians, scientists and engineers made it possible to overcome a number of difficulties and problems. In their scientific publications and dissertations, the laboratory staff paid great attention to biomechanical research during transosseous osteosynthesis with the Ilizarov apparatus. At present, the staff of the Ilizarov Centre continues the traditions established by G.A. Ilizarov. For the first time in our country, a computer 3D video analysis of the kinematics and kinetics of orthopedic patients gait was introduced; it was supplemented with embedded software for the preparation of a clinical report of human gait biomechanics.Conclusions. The initial stage of the biomechanical research at the Ilizarov Centre included the creation of the research equipment. Subsequently, the biomechanical studies carried out by the staff of the Centre for almost half a century have shown an applied and functional result of the realization of general biological regularities of the Ilizarov’s discovery. At present, the biomechanical research continues at a higher level with the use of modern high-tech equipment

Observation of a Highly Spin Polarized Topological Surface State in GeBi2_{2}Te4_{4}

Spin polarization of a topological surface state for GeBi$_2$Te$_4$, the newly discovered three-dimensional topological insulator, has been studied by means of the state of the art spin- and angle-resolved photoemission spectroscopy. It has been revealed that the disorder in the crystal has a minor effect on the surface state spin polarization and it exceeds 75% near the Dirac point in the bulk energy gap region ($\sim$180 meV). This new finding for GeBi$_{2}$Te$_{4}$ promises not only to realize a highly spin polarized surface isolated transport but to add new functionality to its thermoelectric and thermomagnetic properties.Comment: 5 pages, 4 figure

Experimental verification of PbBi2_{2}Te4_{4} as a 3D topological insulator

The first experimental evidence is presented of the topological insulator state in PbBi$_{2}$Te$_{4}$. A single surface Dirac cone is observed by angle-resolved photoemission spectroscopy (ARPES) with synchrotron radiation. Topological invariants $\mathbb{Z}_2$ are calculated from the {\it ab initio} band structure to be 1; (111). The observed two-dimensional iso-energy contours in the bulk energy gap are found to be the largest among the known three-dimensional topological insulators. This opens a pathway to achieving a sufficiently large spin current density in future spintronic devices.Comment: 5 pages, 5 figures, accepted for publication in Phys. Rev. Let

The Flight of Time by Anna Akhmatova: Through Personal Signature to Generational Emblem

Поступила в редакцию 18.05.2019. Принята к печати 21.06.2019.Submitted on 18 May, 2019. Accepted on 21 June, 2019.Логика статьи подчинена исследованию сложного «скрещения судеб» творческого пути Анны Ахматовой и жизни трех поколений, участником и свидетелем которой она была. Показано, что преломление трех эпох в биографии и творчестве поэта, обеспечившее образу Ахматовой эмблематичность, обусловлено историзмом как доминантной чертой ее поэтического мировидения. Выделены и описаны три личные сигнатуры поэта, востребованные временем: лунная дева, колдунья, пророчица Серебряного века; плакальщица, мать, жена, взявшая на себя миссию поминовения погибших в тюрьмах, лагерях, во время войны — в 1930–1940-е гг.; классик русской поэзии, ставший подлинным воплощением связи времен для молодого поколения поэтов в 1960-е гг., что отразилось в множественности и разнообразии «царских» сигнатур-инсигний Ахматовой, создаваемых ею на страницах «Записных книжек», моделируемых ее современниками в мемуарах (зачастую при известном участии поэта), а также — в визуальном коде: от портретов до фотографий, относящихся к разным десятилетиям. Важно, что образ поэта, преломившись в зеркалах каждой из непохожих друг на друга эпох, позволяет и самому времени отразиться в «ахматовских зеркалах». Наиболее драматичные моменты «некалендарного двадцатого века» во многом связаны с ее личной и поэтической судьбой, ставшей одним из воплощений судьбы — «трагической симфонии» ее поколения. Особое внимание уделяется самообозначению сакрального характера, которое предназначено Ахматовой не для времени, но для вечности, является своеобразным тайным кодом, могущим быть расшифрованным только поэзией и поэтами.The logic of this article comes from the research of the intricate “crossing of destinies” in the life and creative journey of Anna Akhmatova and in the life of three generations which she witnessed and shared. The study demonstrates that the deflection of the three epochs in Akhmatova’s biography and creative work, which made her image emblematical, is integral to historicism as a dominant feature of her poetical world perception. The authors distinguish and characterise three personal signatures of the poet demanded by the time: a lunar maiden, sorceress, and prophetess of the Silver Age; a mourner, mother, and wife who took up the mission of praying for those who died in prisons and camps during the war between the 1930s and 1940s; a classic of Russian poetry, who became an authentic incarnation of the link of times for the young generation of poets in the 1960s. It is represented in the multiplicity of Akhmatova’s “imperial” signaturesinsignias, which she created in her Notebooks, and her contemporaries reflected in their memoirs (sometimes with the participation of the poet). Additionally, they were realised in the visual code, namely portraits and photographs, dating back to different decades. It is important that having been reflected in the mirrors of various epochs, the poet’s image lets time itself be reflected in “Akhmatova’s mirrors”. The most dramatic moments of “not what the calendars say, but the real Twentieth Century” are mostly the parts of her private and poetic life, as her destiny was the embodiment of the “tragic symphony” of her generation. Special attention is paid in the article to the self-designation of sacral nature, which Akhmatova intends not for time, but for eternity, it is a unique secret code, which can be decoded only by poets and poetry itself.Работа выполнена при поддержке гранта РФФИ № 19-512-23003 «Самосознание и диалог поколений в русской и венгерской литературной практике XX–XXI веков».The work was supported by Russian Foundation for Basic Research, grant 19-512-23003 “Self-Awareness and Dialogue of Generations in Russian and Hungarian Literary Practice of the 20th–21st Centuries”

“A Flash of Consciousness in the Unconsciousness of Days”: Anna Akhmatova’s Prophetic Gift

The article was submitted on 13.01.2024.В центре исследования – малоизвестное стихотворение Анны Ахматовой позднего периода творчества «Из набросков» (1959), до настоящего момента не получившее литературоведческого комментария. В ходе исследования фрагмент вписывается в ряд достаточно известных поэтических и прозаических предсказаний поэта, а также соотнесен с образом Кассандры, сопровождавшим Ахматову на протяжении всей ее творческой судьбы. Обращение к массиву мемуаров, связанных с образом поэта, а также к автобиографической прозе и материалам записных книжек автора позволяет обнаружить пересечения, указывающие, с одной стороны, на последовательную стратегию пишущего (от предсказания как такового до страшной способности накликания несчастий), с другой – на целостность образа времени / конца времен, который складывается в записях Ахматовой и в работе над вариантами стихотворных строк, и в тайнописи записных книжек. На сегодняшний день доступно несколько вариантов стихотворения с разными датировками, поставленным или отсутствующим названием, существенными или небольшими разночтениями. Текстологический сопоставительный анализ поэтических вариаций свидетельствует о поисках поэтом все более сильных и точных средств изображения приближающейся апокалиптической катастрофы. Несмотря на интонационную близость «Бегу времени», рассматриваемый набросок, по всей видимости, так и не был включен поэтом в цикл или более крупный текст в качестве отдельных строф. Исследование показало, что стихотворение, подсвеченное поэтическим и прозаическим контекстом, являет одну из ключевых черт поэтики незавершенного, столь свойственных художественному мышлению поздней Ахматовой. Диалогичность, «смысловая валентность» поэзии Ахматовой, возникновение новых смыслов стимулируются «бегом времени», актуализируются при свершении катастроф и бед, что каждый раз позволяет обнаруживать ее скрытые провидческие пласты.This study focuses on From Sketches (1959), a little-known poem of Anna Akhmatova’s later work that has received no literary commentary. The fragment fits into some of the poet’s known poetic and prose predictions and is also correlated with the image of Cassandra that accompanied Akhmatova throughout her creative life. Referring to some of the poet’s memoirs and autobiographical prose, as well as to materials from the author’s notebooks, it is possible to discover some overlaps that indicate, on the one hand, the writer’s consistent strategy (from prediction to the terrible ability to draw upon misfortune), and, on the other hand, the integrity of the image of time / the end of time that is formed in Akhmatova’s notes: both in the work on variants of poetic lines, and in the secret writing of notebooks. At present, there are several versions of the poem, written at different times, some of which have a title and some of which do not, and are characterised by major and minor discrepancies. A comparative textual analysis of the poetic variations testifies to the poet’s search for increasingly powerful and precise means of describing the approach of an apocalyptic catastrophe. Despite the intonational similarity of The Running of Time, the ‘sketch’ in question appears never to have been incorporated by the poet as a separate stanza into a cycle or larger text. The study shows that the poem, highlighted by a poetic and prosaic context, reveals one of the key features of the poetics of the unfinished, typical of A. Akhmatova’s later artistic thinking. The dialogical nature and ‘semantic valence’ of Akhmatova’s poetry, and the emergence of new meanings, are stimulated by the ‘passage of time’ and are actualised when disasters and difficulties occur, each time helping to uncover the hidden visionary layers of Akhmatova’s poetry.Исследование А. Меньщиковой выполнено при финансовой поддержке Министерства науки и высшего образования Российской Федерации в рамках Программы развития Уральского федерального университета имени первого Президента России Б. Н. Ельцина в соответствии с Программой стратегического академического лидерства «Приоритет – 2030»