Hexakis(dimethylformamide)bis(hexaphenylcyclohexasiloxanehexaolato)hexacopper(II) Dimethylformamide Solvate

The sandwich-like title complex, hexakis(dimethylformamide)-1O,2O,3O,4O,5O,6O-bis[2,4,6,8,10,12-hexaphenylsiloxane-2,4,6,8,10,12-hexaolato(6-)-1:22O1,2:32O2,3:42O3,- 4:52O4,5:62O5,1:62O6]hexacopper(II) tetrakis(dimethylformamide) solvate, [Cu6(C3H7NO)6{(C6H5)6O12Si6}2].4C3H7NO, is comprised of two regular crown-shaped macrocyclic hexadentate organosiloxanolate ligands chelating a flat Cu6 hexagon, as in the ethanol-solvated analogue investigated previously. The title complex has a more distorted shape than the trigonal ethanol-solvated analogue, being slightly side-oblated, but still contains a large empty inner channel accessible by small molecules (the diameter of the free cross-section being about 2.5 Å). Each CuII ion has square-pyramidal coordination with four basal siloxanolate O atoms and an apical dimethylformamide (DMFA) molecule (coordinated through its carbonyl group). The average bond lengths are: Cu-O(Si) 1.964 (11) Å and Cu-O(DMFA) 2.215 (10) Å. The structure contains four additional DMFA molecules per complex unit, linked by weak C-HO hydrogen bonds. Unexpectedly, the C=O bond length is longer [1.248 (10) and 1.255 (9) Å] in the uncoordinated DMFA molecules than in the coordinated [1.214-1.227 (7) Å]

Synthesis and Characterization of Large Stereoregular Organosiloxane Cycles

The large stereoregular phenyltrimethylsiloxysiloxane macrocycles of general formula [PhSi(OSiMe3)O]n (n=6 and 12) have been selectively obtained with high yields by trimethylsilylation of cage-like oligophenylmetallasiloxanes (OPMS) which we described earlier. The compounds 3 (n=6) and 4 (n=12) have been characterized by NMR-spectroscopy method and by single crystal X-ray analysis. This investigation showed unambiguously that the siloxane macrocycles keep their size and configuration (the same as in the initial OPMS) during the trimethylsilylation. Thus a synthetic route for obtaining large stereoregular siloxane macrocycles has been developed

One-step synthesis of γ-Fe₂ O₃/Fe₃ O₄ nanocomposite for sensitive electrochemical detection of hydrogen peroxide

Maghemite/magnetite nanocomposite ( γ-Fe₂ O₃/Fe₃ O₄ ) was prepared via an electrochemical method using pulse alternating current and applied for electrocatalytic reduction and sensing of hydrogen peroxide. The structural and compositional analysis of the γ-Fe₂ O₃/Fe₃ O₄ was characterized by XRD, SEM, TEM and XPS. Its thermal decomposition behavior was studied using TG/DSC. The mechanism for γ- Fe₂ O₃/Fe₃ O₄ nanocomposite formation was propose

2D/3D Metallic Nano-objects Self-Organized in an Organic Molecular Thin Film

We present the fabrication and investigation of the properties of nanocomposite structures consisting of two-dimensional (2D) and three-dimensional (3D) metallic nano-objects self-organized on the surface and inside of organic molecular thin-film copper tetrafluorophthalocyanine (CuPcF4). Metallic atoms, deposited under ultrahigh vacuum (UHV) conditions onto the organic ultrathin film, diffuse along the surface and self-assemble into a system of 2D metallic overlayers. At the same time, the majority of the metal atoms diffuse into the organic matrix and self-organize into 3D nanoparticles (NPs) in a well-defined manner. The evolution of the morphology and electronic properties of such structures as a function of nominal metal content is studied under UHV conditions using transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), and photoelectron spectroscopy (PES) techniques. Using HR-TEM, we have observed the periodicity of atomic planes of individual silver NPs. The steady formation of agglomerates from individual single nanocrystallites with intercrystallite boundaries is observed as well. PES reveals generally weak chemical interactions between silver and the organic matrix and n-doping of CuPcF4 at the initial stages of silver deposition, which is associated with charge transfer from the 2D wetting layer on the basis of core-level spectra shift analysis. Copyright © 2020 American Chemical Society

Atomic and electronic structure of nanostructured few-layer graphene with self-aligned boundaries synthesized on SiC/Si(001) wafers

This work was partially supported by the Russian Academy of Sciences, Russian Foundation for Basic Research (grant № 17-02-01139, 17-02-01291), Beijing Institute of Technology Research Fund Program for Young Scholars, and Science Foundation Ireland

Swarmodroid 1.0: A Modular Bristle-Bot Platform for Robotic Active Matter Studies

Large swarms of extremely simple robots (i.e., capable just of basic motion activities, like propelling forward or self-rotating) are widely applied to study collective task performance based on self-organization or local algorithms instead of sophisticated programming and global swarm coordination. Moreover, they represent a versatile yet affordable platform for experimental studies in physics, particularly in active matter - non-equilibrium assemblies of particles converting their energy to a directed motion. However, a large set of robotics platforms is being used in different studies, while the universal design is still lacking. Despite such platforms possess advantages in certain application scenarios, their large number sufficiently limits further development of results in the field, as advancing some study requires to buy or manually produce the corresponding robots. To address this issue, we develop an open-source Swarmodroid 1.0 platform based on bristle-bots with reconfigurable 3D-printed bodies, external control of motion velocity, and basic capabilities of velocity profile programming. In addition, we introduce AMPy software package in Python featuring OpenCV-based extraction of robotic swarm kinematics accompanied by the evaluation of key physical quantities describing the collective dynamics. We perform a detailed analysis of individual Swarmodroids' motion characteristics and address their use cases with two examples: a cargo transport performed by self-rotating robots and a velocity-dependent jam formation in a bottleneck by self-propelling robots. Finally, we provide a comparison of existing centimeter-scale robotic platforms, a review of key quantities describing collective dynamics of many-particle systems, and a comprehensive outlook considering potential applications as well as further directions for fundamental studies and Swarmodroid 1.0 platform development.Comment: 18 pages, 7 figures, 1 table + Supplementary Information. Comments are welcom

Systematic study of niobium thermal treatments for superconducting radio frequency cavities employing x ray photoelectron spectroscopy

The structural and chemical composition of the surface layer 100 140 nm of niobium radiofrequency cavities operating at cryogenic temperature has enormous impact on their superconducting characteristics. During the last years, cavities treated with a new thermal processing recipe, so called nitrogen infusion, have demonstrated an increased efficiency and high accelerating gradients. The role and importance of nitrogen gas has been a topic of many debates. In the present work we employ variable energy synchrotron x ray photoelectron spectroscopy XPS , to study the niobium surface subjected to the following treatments vacuum annealing at 800 C, nitrogen infusion, and vacuum heat treatment as for the infusion process but without nitrogen supply. Careful analysis of XPS energy distribution curves revealed a slightly increased thickness of the native oxide Nb2O5 for the infused samples amp; 8764;3.8 nm as compared to the annealed one amp; 8764;3.5 nm which indicates insignificant oxygen incorporation into niobium during 120 C baking and no effect of nitrogen on the formation of oxides or other niobium phases. By conducting an additional in situ annealing experiment and analyzing the niobium after the failed infusion process, we conclude that the vacuum furnace hygiene particularly during the high temperature stage is the prerequisite for success of any treatment recip

ИССЛЕДОВАНИЕ СТРУКТУРЫ КРУПНОГАБАРИТНЫХ МОНОКРИСТАЛЛОВ АНТИМОНИДА ГАЛЛИЯ, ВЫРАЩЕННЫХ МЕТОДОМ ЧОХРАЛЬСКОГО В КРИСТАЛЛОГРАФИЧЕСКОМ НАПРАВЛЕНИИ [100]

The properties of Chochralski grown [100] undoped GaSb crystals with diameters > 60 mm have been studied. We found that the dislocation density reduction in large undoped crystals can be achieved both by the well known technological approaches and by isovalent impurity (indium) doping. We show that the introduction of two additional annealing stages, one being close to the moment the crystal reaches the target diameter (the length of this stage is 1 hour, the temperature being close to the melting point) and the other being 3 h long post−growth annealing at 650 °C, reduces the dislocation density in ~60 mm diameter crystals to (3—5) · 103 cm−2. We found that dislocations in large GaSb crystals form in two distinct temperature ranges as evidenced by the difference in the morphology of the dislocation traces. The dislocation critical stresses were identified in the 420—690 °C temperature range. It is demonstrated that isovalent doping (In, concentration in the range (2—4) · 1018 cm−3 leads to a significant incr ase in dislocation critical stresses and, accordingly, to a drastic decrease in the average dislocation density to (4—5) · 102 cm−2. This opens new prospects for obtaining large low dislocation density GaSb crystals.Проведено исследование свойств нелегированных монокристаллов антимонида галлия  диаметром более 60 мм, выращенных методом Чохральского в кристаллографическом направлении [100].  Установлено, что снижение плотности дислокаций в крупногабаритных нелегированных монокристаллах антимонида галлия может быть достигнуто как с использованием известных технологических приемов в процессе выращивания, так и с помощью легирования изовалентной примесью (индием). Показано, что введение в технологический процесс выдержки при температуре, близкой к температуре кристаллизации, на стадии выхода  кристалла на диаметр в течение 1 ч и термообработки в посткристаллизационном состоянии при температуре 650 оС в течение 3 ч позволяет достичь в нелегированных монокристаллах антимонида галлия диаметром ~60 мм значения плотности дислокаций (3—5) ⋅ 103  см−2. Установлено,  что образование дислокаций в крупногабаритных монокристаллах антимонида галлия  обусловлено двумя температурными диапазонами, о чем свидетельствует различная морфоло- гия следов дислокаций. Определены значения критических напряжений образования дислокаций в интервале температур 420—690 оС. Показано, что легирование изовалентной примесью (In до концентраций  (2—4)⋅ 1018 ат/см3) приводит к существенному увеличению критических напряжений образования дислокаций и, следовательно, снижению их средней плотности до (4—5) ⋅ 102  см−2, что открывает перспективу получения крупногабаритных малодислокационных монокристаллов антимонида галлия.  

Рецидивирующий респираторный папилломатоз с вовлечением легких и малигнизацией

Recurrent respiratory papillomatosis (RP) is one of the most challenging benign tumors of the upper and lower respiratory tract. Dissemination of the tumor process and damage to the lung tissue not only increase the likelihood of malignancy, but also complicate the choice of treatment tactics, largely limit the surgical options, and necessitate a multidisciplinary approach.Methods. The enrolled patients with RP have been treated (n = 190) in the Federal State Budgetary Educational Institution of Higher Education “Academician I.P.Pavlov First St. Petersburg State Medical University”, Ministry of Healthcare of Russian Federation, from 2000 to the present. Changes in the lung tissue were detected in 5 (2.6%) patients (2 men and 3 women) with aggressive course of the disease.Results. The clinical characteristics of patients and the outcomes of lung damage in RP are presented. Four patients had malignant transformation of the tumor into verrucous carcinoma of the upper third of the trachea with invasion into the soft tissues of the neck (n = 1) or malignant degeneration of the lesion in the lung parenchyma (n = 3).Conclusion. The presented rare observations suggest polymorphism of clinical and radiological symptoms of papillomatous damage to the tracheobronchial system and lungs.Рецидивирующий респираторный папилломатоз (РРП) является одной из сложнейших проблем среди доброкачественных опухолей верхних и нижних дыхательных путей. Диссеминация опухолевого процесса и поражение легочной ткани не только создают вероятность малигнизации, но и усложняют выбор тактики лечения и во многом ограничивают хирургические возможности, обусловливая необходимость мультидисциплинарного подхода. Материалы и методы. С 2000 г. по настоящее время пациенты с РРП (n = 190) получали лечение в Федеральном государственном бюджетном образовательном учреждении высшего образования «Первый СанктПетербургский государственный медицинский университет имени академика И.П.Павлова» Министерства здравоохранения Российской Федерации. У 5 (2,6 %) больных (2 мужчин и 3 женщины) с агрессивным течением заболевания выявлены изменения в легочной ткани. Результаты. Представлена клиническая характеристика пациентов и исходы течения поражения легких при РРП. У 4 пациентов установлена малигнизация опухоли в виде веррукозной карциномы верхней трети трахеи с прорастанием в мягкие ткани шеи (n = 1) и злокачественное перерождение очага в паренхиме легких (n = 3). Заключение. По данным представленных редких наблюдений продемонстрирован полиморфизм клинической и рентгенологической симптоматики поражения трахеобронхиальной системы и легких папилломатозным процессом

Transport properties of copper phthalocyanine based organic electronic devices

Ambipolar charge carrier transport in Copper phthalocyanine (CuPc) is studied experimentally in field-effect transistors and metal-insulator-semiconductor diodes at various temperatures. The electronic structure and the transport properties of CuPc attached to leads are calculated using density functional theory and scattering theory at the non-equilibrium Green's function level. We discuss, in particular, the electronic structure of CuPc molecules attached to gold chains in different geometries to mimic the different experimental setups. The combined experimental and theoretical analysis explains the dependence of the mobilityand the transmission coefficient on the charge carrier type (electrons or holes) and on the contact geometry. We demonstrate the correspondence between our experimental results on thick films and our theoretical studies of single molecule contacts. Preliminary results for fluorinated CuPc are discussed.Comment: 18 pages, 16 figures; to be published in Eur. Phys. J. Special Topic