DIFFERENT SCHEMES FOR OBTAINING FRACTAL RELIEF OF NANOSIZED PLATINUM FILMS

В работе исследуется морфология рельефа наноразмерных пленок платины на поверхности слюды с помощью сканирующего зондового (в режиме атомного-силового) и туннельного микроскопов. Пленки платины исследовались непосредственно после их получения на установке магнетронного напыления, а также после отжига в муфельной печи в воздушной атмосфере. Отжиг позволял установить возможные диапазоны изменения фрактальной размерности и высотных параметров, соответствующие деградации нанорельефа. Получены значения фрактальной размерности для пленок разной толщины при двух альтернативных методах исследования на разных исходных масштабах образцов: на основе данных атомносилового микроскопа - D̅=2,17÷2,38 и сканирующего туннельного микроскопа - D̅=2,28÷2,50 в зависимости от последовательности напыления слоев и отжига пленок. Выбор последовательности операций магнетронного напыления и отжига и внешних условий позволяют формулировать рекомендации по развитию технологии «выращивания» структур с заданной морфологией поверхности. The morphology of the relief of nanosized platinum films on the mica surface is investigated using the scanning probe (in the atomic force mode) and tunneling microscopy. Platinum films were investigated immediately after their preparation in a magnetron sputtering facility, as well as after annealing in a muffle furnace in an air atmosphere. Annealing made it possible to establish the possible ranges of variation of the fractal dimension and the altitude parameters corresponding to degradation of the nanorelief. The values of the fractal dimension were obtained for films of different thicknesses using two alternative methods of investigation at different initial scales of samples: based on the data of an atomic force microscope - D̅ = 2,17÷2,38 and a scanning tunneling microscope - D̅ = 2,28÷2,50 depending on the sequence of deposition of layers and annealing of films. For comparison, experimental data of other authors are presented. The choice of the sequence of operations for magnetron sputtering and annealing, and external conditions makes it possible to formulate recommendations for development of the technology for «growing» structures with a given surface morphology.

Interfacial Friction Anisotropy in Few-Layer Van der Waals Crystals

Friction anisotropy is one of the important friction behaviors for two-dimensional (2D) van der Waals (vdW) crystals. The effects of normal pressure and thickness on the interfacial friction anisotropy in few-layer graphene, h-BN, and MoSe2 under constant normal force mode have been extensively investigated by first-principle calculations. The increase of normal pressure and layer number enhances the interfacial friction anisotropy for graphene and h-BN but weakens that for MoSe2. Such significant deviations in the interfacial friction anisotropy of few-layer graphene, h-BN and MoSe2 can be mainly attributed to the opposite contributions of electron kinetic energies and electrostatic energies to the sliding energy barriers and different interlayer charge exchanges. Our results deepen the understanding of the influence of external loading and thickness on the friction properties of 2D vdW crystals.

Designing a kinematic module with rounding to model the processes of combined radial-longitudinal extrusion involving a tool whose configuration is complex

It is advisable that parts whose shape is complex and which are made from solid or hollow blanks should be made by means of transverse and combined radial-longitudinal extrusion. The variation of manufacturing modes, tool configurations (in the form of chambers and rounding of the transitional sections of matrices) requires an adequate preliminary assessment of the force regime and the features of part shape formation. This paper has proposed a curvilinear kinematic module of the trapezoidal form for modeling radial-longitudinal extrusion processes in the presence of matrix rounding. Given the impossibility of using a quarter-circle boundary for the kinematically assigned possible velocity field, it has been proposed to use approximate curves in the form of z1(r) and z2(r). Taking into account the slightest deviation in the length of the arc of the approximate curve z1(r) and the area of the curvilinear trapezoid bounded by it relative to a quarter of the circle (not exceeding 0.8 % for any ratio), it has been recommended using this particular replacement. We have performed calculations of the value of the reduced deformation pressure inside the kinematic module with rounding taking into consideration the power of cutting forces at the border with adjacent kinematic modules. As an example, the devised module with rounding embedded in the estimation scheme of radial extrusion was analyzed. A significant impact of friction conditions on the force mode and the corresponding optimal value of the rounding radius have been identified. The resulting kinematic module makes it possible to expand the capabilities of the energy method for modeling cold extrusion processes involving the tools of complex form according to new deformation schemes. That could contribute to preparing recommendations on the optimal tool configuration and more active industrial implementation of these processes

Atomi c-force microscopy of viruses and bacteria

The article is devoted to the study of viruses and bacteria using a scanning probe microscope in atomic force mode, in particular, to the features of sample preparation, interpretation of the data obtained, and image processing.

Error sources in the force mode of the “PB2” Planck-Balance

The PB2 Planck-Balance is a table-top Kibble balance, that is designed for the calibration of class E₂ weights in a range of 1 mg up to 100 g. This work presents typical systematic errors which have to be considered during the calibration and will show results for measurements with small masses.

Control of Shrinkage Porosity and Spot Segregation in Ø195 mm Continuously Cast Round Bloom of Oil Pipe Steel by Soft Reduction

Based on the Ø195 mm round bloom continuous casting of oil pipe steel, a two dimensional thermal-mechanical coupled model has been developed to investigate the deformation behavior of round bloom during soft reduction (SR) in the reduction force mode. Good agreement was achieved in surface temperature, shell thickness and contact zone width from modeling and measurement. Under the same reduction force, the reduction amount of round bloom at the front unit is much larger than back unit. Moreover, due to its higher temperature and lower center solid fraction, the deformation penetration before solidification is much stronger than that after solidification. Considering the limitation of the round bloom ovality, the maximum allowable force in reduction unit is calculated. According to the simulation results, a multi-unit soft reduction plan was proposed and carried out on the Ø195 mm round bloom. After the reduction process of No.1 to No.3 withdrawal units, the shrinkage porosity in the center of the round bloom was almost vanished, while the number and size of spot segregation were significantly reduced. Moreover, the oil pipe produced by the round bloom with SR got a better resistance to sulfide stress corrosion (SSC). It indicates that SR is an effective technology for the round bloom to control the shrinkage porosity and spot segregation in the continuous casting.

OBTAINING NANOSIZED PLATINUM FILMS WITH FRACTAL PROPERTIES

Проведено комплексное исследование морфологии рельефа наноразмерных пленок платины на поверхности слюды с помощью сканирующего зондового (в режиме атомного-силового) и туннельного микроскопов, а также оптического интерференционного профилометра. Описаны характерные особенности нанорельефа поверхности пленок платины различной толщины, включая фрактальные свойства. Получены значения фрактальной размерности для пленок разной толщины при двух альтернативных методах исследования на разных исходных масштабах образцов: на основе данных атомного-силового микроскопа - ̅D = 2,28÷2,35 и сканирующего туннельного микроскопа - ̅D = 2,12÷2,26. Для сравнения приведены экспериментальные данные других авторов. Предложены рекомендации по развитию технологии «выращивания» структур с заданной морфологией поверхности. A comprehensive study of the morphology of the relief of nanosized platinum films on the mica surface was carried out using a scanning probe (in the atomic force mode) and tunneling microscopes, as well as an optical interference profilometer. Characteristic features of the surface nanorelief of platinum films of various thicknesses, including fractal properties, are described. The values of the fractal dimension were obtained for films of different thicknesses using two alternative methods of investigation at different initial scales of samples: based on the data of an atomic force microscope - ̅D = 2,28÷2,35 and a scanning tunneling microscope - ̅D = 2,12÷2,26. For comparison, experimental data of other authors are presented. Recommendations for development of the technology for «growing» structures with a given surface morphology are proposed.

Stress fiber anisotropy contributes to force-mode dependent chromatin stretching and gene upregulation in living cells

Living cells and tissues experience various complex modes of forces that are important in physiology and disease. However, how different force modes impact gene expression is elusive. Here we apply local forces of different modes via a magnetic bead bound to the integrins on a cell and quantified cell stiffness, chromatin deformation, and DHFR (dihydrofolate reductase) gene transcription. In-plane stresses result in lower cell stiffness than out-of-plane stresses that lead to bead rolling along the cell long axis (i.e., alignment of actin stress fibers) or at different angles (90° or 45°). However, chromatin stretching and ensuing DHFR gene upregulation by the in-plane mode are similar to those induced by the 45° stress mode. Disrupting stress fibers abolishes differences in cell stiffness, chromatin stretching, and DHFR gene upregulation under different force modes and inhibiting myosin II decreases cell stiffness, chromatin deformation, and gene upregulation. Theoretical modeling using discrete anisotropic stress fibers recapitulates experimental results and reveals underlying mechanisms of force-mode dependence. Our findings suggest that forces impact biological responses of living cells such as gene transcription via previously underappreciated means.

High-Temperature Distillation Using N-Parallel Evacuated Tube Collector Integrated With Double Slope Solar Still in Force Mode

In the present communication, a performance investigation of a double-slope solar still augmented with parallel evacuated tubes under forced mode is carried out for a modified geometry. A comprehensive mathematical model is used for the numerical simulation using the experimental data and incorporating the effect of variable flowrate, water depth, and the number of tubes. An optimum flowrate range ∼0.006–0.007 kg/s/tube is found irrespective of the number of tubes and basin water depth to extract optimal energy. The flowrate is validated with other experiments, carried out by various authors. At optimal flowrate with ten tubes and 0.005 m basin water depth, the system yields 6.644 kg, while overall energetic and exergetic efficiencies are observed as ∼33.8% and 4.9%, respectively. With an increase in the tubes as 20 and 30, the respective yields are found to be increased by ∼2.64% and ∼6.62% for nearly the same collector output temperature attainable (≈98.5°C), while the energy and exergy efficiencies decreased significantly by ∼24.6% and ∼38.6%, compared with ten tubes arrangement. Daily yield and overall exergy efficiency are increased by 13.3% and 19.3%, respectively, using a diffused reflector.