Mathematical modelling of the spatial network of bone implants obtained by 3D-prototyping

In this paper, the mathematical model suitable for bone implants 3D-prototyping is proposed. The composite material with the spatial configuration of reinforcement with matrix of hydroxyapatite and titanium alloys fibers is considered. An octahedral cell is chosen as an elementary volume. The distribution of reinforcing fibers is described by textural parameters. Textural parameters are integrated characteristics that summarize information on the direction of reinforcing fibers and their volume fractions. Textural parameters, properties of matrix and reinforcing fibers allow calculating effective physical and mechanical properties of the composite material. The impact of height and width of the octahedral reinforcement cells on textural parameters of the composite material is investigated in this work. The impact of radius of fibers is also analyzed. It is shown that the composite becomes quasi-isotropic under certain geometrical parameters of cell. © 2016 Author(s)

Steam turbines produced by the Ural Turbine Works for combined-cycle plants

The most interesting and innovative solutions adopted in the projects of steam turbines for combined-cycle plants with capacities from 115 to 900 MW are pointed out. The development of some ideas and components from the first projects to subsequent ones is shown. © 2013 Pleiades Publishing, Ltd

ИССЛЕДОВАНИЕ ПРОБЛЕМ БЕЗОПАСНОСТИ ИСПОЛЬЗОВАНИЯ КОРОТКИХ ССЫЛОК

В работе рассмотрены сферы применения коротких ссылок, указаны их преимущества и недостатки. Описаны возможные уязвимости и атаки, а также методы защиты от них. Проанализирован общий уровень безопасности использования коротких ссылок

A new approach to use of oral mucosa in reconstructive urethral surgery: micrografts

Introduction. Treatment of patients with complex urethral strictures is an actual problem of reconstructive urology. After multi-staged urethral surgery with multiple revisions the new reconstruction is limited by paucity of plastic material (for grafts and flaps). In-thing, new materials for urethral reconstruction (various auto, allo and xenografts) are still being developed in reconstructive urethral surgery.Purpose of the study. To study the possibility of using oral mucosa micrografts to form the urethral plate in the multi-stage surgery for patients with extended urethral strictures.Materials and methods. In the experimental study, male Wistar rats (22 individuals) weighing 300 – 400 g underwent a full-thickness skin wound after intramuscular sedation. We used the wound chamber (12 mm diameter) to exclude the wound contraction. The oral mucosa graft was harvested (6 mm in diameter). After pre-fabrication, the graft was minced to fragments < 1 mm2. Micrografts with fibrin-thrombin glue were applied to the wound. By day 45, the epithelial plate was excised for histological examination. In the clinical study, 4 patients with recurrent penile urethral strictures were treated with staged urethroplasty with urethral plate formation using oral mucosa micrografts. The average length of the stricture was 7.5 ± 1.2 cm (with extremely narrow and obliteration sites). The urethral plate was formed as the first stage. The preparation of the graft bed and oral mucosa grafts harvesting was carried out according to the standard procedure. Micrografts preparation and implantation was carried out as in experimental part of this study. After 6 months, neourethra tubularization was performed. The patients were evaluated every 3 months after the final stage of urethroplasty (uroflowmetry, ultrasound, X-ray, PROM-USS). The median follow-up was 9 months (3 – 18 months).Results. On day 15, in the experimental study, in 16 of 22 (72.7%) rats, the wound chambers had focal growth of the oral mucosa epithelium. On day 45, the wounds healed completely healed with oral mucosa. The final area of the plate was 78 ± 12 mm2. In the clinical study, 6 months after the first stage, all patients (n = 4) had a urethral plate covered with an oral mucosa epithelium without scar formation and sufficient for neurethra tubularization. All patients underwent urethral tubularization. After catheter removal, all men urinated. After 9 months (median follow-up, n = 3), the Qmax was 22.7 ± 4.2 ml/s, the post-void residual urine was 34.8 ± 2.2 ml, the total PROM-USS score was 7.4 ± 1.2, urethral lumen is preserved. All patients showed high satisfaction with the treatment.Conclusion. The oral mucosa micrografts showed good take in heterotopic transplantation (72.7%) with the formation of an epithelial layer on the wound surface. The final mucosal plate area 3 times exceeded the initial micrografts area. This initial clinical experience of using oral mucosa micrografts shows the new possibility of this technology in reconstructive urethral surgery, especially in patients with complex urethral strictures

Soft elasticity in biaxial smectic and smectic-C elastomers

Ideal (monodomain) smectic-$A$ elastomers crosslinked in the smectic-$A$ phase are simply uniaxial rubbers, provided deformations are small. From these materials smectic-$C$ elastomers are produced by a cooling through the smectic-$A$ to smectic-$C$ phase transition. At least in principle, biaxial smectic elastomers could also be produced via cooling from the smectic-$A$ to a biaxial smectic phase. These phase transitions, respectively from $D_{\infty h}$ to $C_{2h}$ and from $D_{\infty h}$ to $D_{2h}$ symmetry, spontaneously break the rotational symmetry in the smectic planes. We study the above transitions and the elasticity of the smectic-$C$ and biaxial phases in three different but related models: Landau-like phenomenological models as functions of the Cauchy--Saint-Laurent strain tensor for both the biaxial and the smectic-$C$ phases and a detailed model, including contributions from the elastic network, smectic layer compression, and smectic-$C$ tilt for the smectic-$C$ phase as a function of both strain and the $c$-director. We show that the emergent phases exhibit soft elasticity characterized by the vanishing of certain elastic moduli. We analyze in some detail the role of spontaneous symmetry breaking as the origin of soft elasticity and we discuss different manifestations of softness like the absence of restoring forces under certain shears and extensional strains.Comment: 26 pages, 6 figure

Evolution of climate, glaciation and subglacial environments of Antarctica from the deep ice core and Lake Vostok water sample studies (Key results of implementation of the Russian Science Foundation project, 2014–2016)

Work on the project focused on the following five areas: 1)  field works in Antarctica at Vostok and Concordia stations; 2)  experimental and theoretical studies in the field of ice core and paleoclimate research; 3) experimental and theoretical works related to the exploration of subglacial Lake Vostok; 4) development of technology and drilling equipment for deep ice coring and exploration of subglacial lakes; 5) upgrading the analytical instrumentation in the Climate and Environmental Research Laboratory (CERL) of the Arctic and Antarctic Research Institute. The main achievements in the field of ice core and paleoclimate research include 1) further elaboration of a new method of ice core dating, which is based on the link between air content of ice and local insolation, 2) investigation of the possible applications of the 17O-excess measurements in ice core to the paleoclimate research, 3)  a better understanding of the mechanisms of the formation of relief-related variations in the isotopic content of an ice core drilled in the area of Antarctic megadunes, and 4) obtaining the first reliable data set on the variations of the 17O-excess in the Vostok core corresponding to marine isotope stage 11. As part of our studies of subglacial Lake Vostok, we have obtained a large body of new experimental data from the new ice core recovered from the 5G-3 borehole to the surface of the subglacial lake. Stacked profiles of isotopic composition, gas content and the size and orientation of the ice crystals in the lake ice have been composed from the data of three replicate cores from boreholes 5G-1, 5G-2 and 5G-3. The study reveals that the concentration of gases in the lake water beneath Vostok is unexpectedly low. A clear signature of the melt water in the surface layer of the lake, which is subject to refreezing on the icy ceiling of Lake Vostok, has been discerned in the three different properties of the accreted ice (the ice texture, the isotopic and gas content of the ice). These sets of data indicate in concert that poor mixing of the melt (and hydrothermal) water with the resident lake water and pronounced spatial and/or temporal variability of local hydrological conditions are likely to be the characteristics of the southern end of the lake. A considerable part of the funding allocated by the RSF to this project was used for upgrading the analytical instrumentation for ice core studies in the CERL of AARI. Using this grant, we purchased and started working with the Picarro L-2140i, a new-generation laser mass analyzer, and set the upgraded mass spectrometer Delta V Plus into operation. The new equipment was used to carry out research planned as part of the project, including the setting up and carrying out of new measurements of 17О in ice cores

BUILDING A TOMOGRAPHIC VELOCITY MODEL FOR SAMOYLOV ISLAND AREA (LENA DELTA) FROM LOCAL SEISMOLOGICAL DATA FOR THE PERIOD OF 2019–2021

In our paper we present the results of seismotomographic inversion for the local seismological monitoring data obtained in the area of the Samoylov Island (Lena River delta) in 2019–2021. Tomographic velocity model was used for refining hypocenter locations of local earthquakes and for geological interpretation. The results are shown as maps of anomalies of seismic waves and Vp /Vs ratios for the 5 and 10 km depths. The velocity anomalies structure made it possible to interpret low Vp /Vs ratio as rocks related to the Siberian platform, and to compare between the boundary of the low Vp /Vs area and the trace of the known geological fault running along the Olenekskaya Channel

Aerodynamic investigations of ventilated brake discs.

The heat dissipation and performance of a ventilated brake disc strongly depends on the aerodynamic characteristics of the flow through the rotor passages. The aim of this investigation was to provide an improved understanding of ventilated brake rotor flow phenomena, with a view to improving heat dissipation, as well as providing a measurement data set for validation of computational fluid dynamics methods. The flow fields at the exit of four different brake rotor geometries, rotated in free air, were measured using a five-hole pressure probe and a hot-wire anemometry system. The principal measurements were taken using two-component hot-wire techniques and were used to determine mean and unsteady flow characteristics at the exit of the brake rotors. Using phase-locked data processing, it was possible to reveal the spatial and temporal flow variation within individual rotor passages. The effects of disc geometry and rotational speed on the mean flow, passage turbulence intensity, and mass flow were determined. The rotor exit jet and wake flow were clearly observed as characterized by the passage geometry as well as definite regions of high and low turbulence. The aerodynamic flow characteristics were found to be reasonably independent of rotational speed but highly dependent upon rotor geometry

The Effects of Fourth Generation on the double Lepton Polarization in B \rar K \ell^+ \ell^- decay

This study investigates the influence of the fourth generation quarks on the double lepton polarizations in B \rar K \ell^+ \ell^- decay. Taking |V_{t's}V_{t'b}|\sim \{0.01-0.03\} with phase about 100^\circ, which is consistent with the b\to s\ell^+\ell^- rate and the B_s mixing parameter Delta m_{B_s}$, we obtain that the double lepton(muon and tau) polarizations are quite sensitive to the existence of fourth generation. It can serve as a good tool to search for new physics effects, precisely, to indirect search for the fourth generation quarks(t', b').Comment: 30 pages, 27 figure