Сравнительный анализ биомеханических показателей в системах маркерного и безмаркерного видеозахвата движений

Motion capture systems are a key tool for performing quantitative analysis and evaluation of complex in movements sports. The prospect of the development and practical application of markerless motion capture tecnology in applied biomechanics increases research interest regarding the features of using such systems, as well as evaluat ing their accuracy and reliability in comparison with marker-based motion capture systems, which are the gold standard nowadays. Markerless motion capture systems have incomparable advantages over marker-based ones.In particular, significantly reduced time costs for the registration and data processing procedures, since registration is represented by filming a video from different angles, and processing is accompanied by the use of software algorithms for tracking the silhouette of an athlete using a presetted computer avatar. However, there is still no clear answer regarding the accuracy and reliability of the data recorded using markerless motion capture systems in relation to specific sports movements. Thus, the purpose of the presented work is to assess the statistical relationship of the data based on the correlation analysis of biomechanical variables on the example of a golf swing recorded using the Qualisys motion capture system and Simi Reality Motion markerless motion capture system.Системы захвата движений являются ключевым инструментом анализа и оценки техники движений в сложнокоординационных видах спорта. Перспектива развития и внедрения в практику прикладной биомеханики технологии безмаркерного захвата движений повышает научно-исследовательский интерес к особенностям использования подобных систем, а также к оценке их точности и достоверности в сравнении с маркерными системами захвата движений, которые сегодня являются золотым стандартом. Системы безмаркерного захвата движений обладают несравненными преимуществами перед маркерными. В частности, существенно уменьшены временные затраты на регистрацию и обработку данных, поскольку регистрация представляет собой съемку видео с разных ракурсов, а обработка сопровождается применением программных алгоритмов отслеживания силуэта спортсмена посредством компьютерного аватара. Однако до сих пор нет однозначного ответа относительно точности и достоверности данных, регистрируемых с использованием систем безмаркерного захвата движений применительно к конкретным видам спорта и спортивным движениям. В статье приведена оценка статистической взаимосвязи данных на основе корреляционного анализа биомеханических показателей на примере выполнения удара в гольфе, зарегистрированных с использованием маркерной системы оптического захвата движений Qualisys и безмаркерной системы захвата движений Simi Reality Motion

Excitonic instability and electric-field-induced phase transition towards a two dimensional exciton condensate

We present an InAs-GaSb-based system in which the electric-field tunability of its 2D energy gap implies a transition towards a thermodynamically stable excitonic condensed phase. Detailed calculations show a 3 meV BCS-like gap appearing in a second-order phase transition with electric field. We find this transition to be very sharp, solely due to exchange interaction, and so, the exciton binding energy is greatly renormalized even at small condensate densities. This density gradually increases with external field, thus enabling the direct probe of the Bose-Einstein to BCS crossover.Comment: LaTex, 11 pages, 3 ps figures, To appear in PR

High-pressure x-ray diffraction study on the structure and phase transitions of the defect-stannite ZnGa2Se4 and defect-chalcopyrite CdGa2S4

X-ray diffraction measurements on the sphalerite-derivatives ZnGa2Se4 and CdGa2S4 have been performed upon compression up to 23 GPa in a diamond-anvil cell. ZnGa2Se4 exhibits a defect tetragonal stannite-type structure (I-42m) up to 15.5 GPa and in the range from 15.5 GPa to 18.5 GPa the low-pressure phase coexists with a high-pressure phase, which remains stable up to 23 GPa. In CdGa2S4, we find the defect tetragonal chalcopyrite-type structure (I-4) is stable up to 17 GPa. Beyond this pressure a pressure-induced phase transition takes place. In both materials, the high-pressure phase has been characterized as a defect-cubic NaCl-type structure (Fm-3m). The occurrence of the pressure induced phase transitions is apparently related with an increase of the cation disorder on the semiconductors investigated. In addition, the results allow the evaluation of the axial compressibility and the determination of the equation of state for each compound. The obtained results are compared with those previously reported for isomorphic digallium sellenides. Finally, a systematic study of the pressure-induced phase transition in twenty-three different sphalerite-related ABX2 and AB2X4 compounds indicates that the transition pressure increases as the ratio of the cationic radii and anionic radii of the compounds increases.Comment: 34 pages, 3 tables, 6 figure

Technologies for measuring the dynamic parameters of rowing based on strain gauge systems

One of the criteria for the effectiveness of flatwater rowing biomechanics is the interaction of the athlete with the surface of the water by an oar, as well as the effectiveness of transferring the efforts developed by the athlete to the boat for its advancement. The quality of an athlete's move-ments with a paddle in rowing locomotives depends on the level of development of power abilities and can be quantified using strain gauge systems. However, the lack of recommendations describ-ing the specifics of the preparation and use of such systems in training process significantly reduce the degree of their use. The article discusses the technical features and methodological founda-tions of the use of strain gauge systems to measure the efforts of an athlete when interacting with an oar in flatwater kayaking and canoeing. To substantiate the choice of the scheme of loading and securing the paddle when graduating the strain gauge system, as well as the place of its direct attachment to the forearm, the authors carried out mathematical modeling of diagrams of bending moments arising on the paddle in response to external forces, as a result of which three options for the support and orientation of the paddle are presented, depending on the location of key sup-port points. To substantiate the method of attaching the strain gauge system to the forearm, a series of tests with paddle loading was carried out, as a result of which the presence of a linear relationship between the values of the external load and the readings of the strain gauge system was assessed, as well as the repeatability of the recorded data. Based on the results of the as-sessment, recommendations are presented for the practical application of the results of the study in assessing the speed and strength training of rowers on kayaks and canoes.Одним из критериев эффективности биомеханики гребли на плоской воде является взаимодействие спортсмена с поверхностью воды при помощи весла, а также эффективность передачи усилий, развиваемых спортсменом, на лодку для ее продвижения. Качество движений спортсмена с веслом в гребных тренажерах зависит от уровня развития силовых способностей и может быть количественно оценено с помощью тензометрических систем. Однако отсутствие рекомендаций, описывающих специфику подготовки и использования таких систем в тренировочном процессе, существенно снижает степень их использования. В статье рассматриваются технические особенности и методологические основы использования тензометрических систем для измерения усилий спортсмена при взаимодействии с веслом в плавании на плоских байдарках и каноэ. Для обоснования выбора схемы нагружения и закрепления лопатки при градуировке тензометрической системы, а также места ее непосредственного крепления к цевью, авторами было проведено математическое моделирование диаграмм изгибающих моментов, возникающих на лопатке в ответ на воздействие внешних сил, в результате которого были получены три представлены варианты крепления и ориентации лопасти в зависимости от расположения ключевых точек опоры. Для обоснования способа крепления тензометрической системы к предплечью была проведена серия испытаний с лопастной нагрузкой, в результате которых было оценено наличие линейной зависимости между значениями внешней нагрузки и показаниями тензометрической системы, а также повторяемость записанные данные. По результатам оценки представлены рекомендации по практическому применению результатов исследования при оценке скоростно-силовой подготовки гребцов на байдарках и каноэ

Charged vortices in superfluid systems with pairing of spatially separated carriers

It is shown that in a magnetic field the vortices in superfluid electron-hole systems carry a real electrical charge. The charge value depends on the relation between the magnetic length and the Bohr radiuses of electrons and holes. In double layer systems at equal electron and hole filling factors in the case of the electron and hole Bohr radiuses much larger than the magnetic length the vortex charge is equal to the universal value (electron charge times the filling factor).Comment: 4 page

Bilateral percutaneous mininephrolithotripsy: simultaneous or staged approach?

Introduction. Patients with bilateral nephrolithiasis are a challenge for the treating physician. Therefore, such patients traditionally are subject to phased surgery to reduce the rate of complications. At the same time, the enhancement of endoscopic technologies and anesthesia makes it possible to perform surgical treatment of bilateral nephrolithiasis simultaneously.Objective. To evaluate the effectiveness and safety of performing simultaneous bilateral percutaneous nephrolithotripsy (PCNL).Materials & methods. The main group comprises 19 patients (avg age 45.0 ± 2.25 years) suffering from bilateral nephrolithiasis (13 men and 6 women). The control group include 20 patients (avg age 45.80 ± 2.29 years) suffering from bilateral nephrolithiasis. Main group patients underwent simultaneous bilateral mini-PCNL, control group patients — staged PCNL within two hospitalisations. The visual analogue scale (VAS) was used to assess the pain severity. Patients noted subjective pain sensations on post-op days 1 and 3. QoL indicators were assessed using the SF-36 general questionnaire, as well as the Russian-language validated version of the WISQoL questionnaire.Results. There were no statistically significant differences between the parameters (the difference between the hemoglobin before and after mini-PCNL was 12 g/l; between the serum creatinine was 18 µmol/l). There was a decrease in total surgery time (121.0 ± 6.1 min) for main group patients compared to (147.0 ± 7.3 min) control group patients (total surgery time during the first and second hospitalisations) and a reduction in hospital stay (4.50 ± 0.23 days) for main group patients compared to control group patients (10.0 ± 0.5 days). Complications observed by us in the two groups were comparable. The valuesobtained on the SF, RE and MH scales in main group patients were higher both on post-op day 1 (67.9 ± 3.39; 56.90 ± 2.85 and 63.80 ± 3.19, respectively) and post-op day 3 (86.80 ± 4.34; 83.70 ± 4.19 and 82.50 ± 4.13, respectively) compared to control group patients during the first and second hospitalizations. Statistically significant differences were also recorded according to the grades "Social functioning" and "Emotional influence" in main group patients (80.90 ± 0.26 and 82.6 ± 0.19, respectively).Conclusion. Simultaneous bilateral mini-PCNL is safe and effective in well-selected patients

Models of coherent exciton condensation

That excitons in solids might condense into a phase-coherent ground state was proposed about 40 years ago, and has been attracting experimental and theoretical attention ever since. Although experimental confirmation has been hard to come by, the concepts released by this phenomenon have been widely influential. This tutorial review discusses general aspects of the theory of exciton and polariton condensates, focussing on the reasons for coherence in the ground state wavefunction, the BCS to Bose crossover(s) for excitons and for polaritons, and the relationship of the coherent condensates to standard lasers.Comment: 27 pages, 6 figures. Submitted for a special issue of J. Phys. Cond. Matt. associated with the EU network "Photon-mediated phenomena in semiconductor nanostructures

Mimicking diffuse supernova antineutrinos with the Sun as a source

Measuring the electron antineutrino component of the cosmic diffuse supernova neutrino background (DSNB) is the next ambitious goal for low-energy neutrino astronomy. The largest flux is expected in the lowest accessible energy bin. However, for E < 15 MeV a possible signal can be mimicked by a solar electron antineutrino flux that originates from the usual 8B neutrinos by spin-flavor oscillations. We show that such an interpretation is possible within the allowed range of neutrino electromagnetic transition moments and solar turbulent field strengths and distributions. Therefore, an unambiguous detection of the DSNB requires a significant number of events at E > 15 MeV.Comment: 4 pages, 1 figur

The Relation Between the Surface Brightness and the Diameter for Galactic Supernova Remnants

In this work, we have constructed a relation between the surface brightness ($\Sigma$) and diameter (D) of Galactic C- and S-type supernova remnants (SNRs). In order to calibrate the $\Sigma$-D dependence, we have carefully examined some intrinsic (e.g. explosion energy) and extrinsic (e.g. density of the ambient medium) properties of the remnants and, taking into account also the distance values given in the literature, we have adopted distances for some of the SNRs which have relatively more reliable distance values. These calibrator SNRs are all C- and S-type SNRs, i.e. F-type SNRs (and S-type SNR Cas A which has an exceptionally high surface brightness) are excluded. The Sigma-D relation has 2 slopes with a turning point at D=36.5 pc: $\Sigma$(at 1 GHz)=8.4$^{+19.5}_{-6.3}$$\times10^{-12}$ D$^{{-5.99}^{+0.38}_{-0.33}}$ Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ (for $\Sigma$$\le3.7\times10^{-21}$ Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ and D$\ge$36.5 pc) and $\Sigma$(at 1 GHz)=2.7$^{+2.1}_{-1.4}$$\times$ 10$^{-17}$ D$^{{-2.47}^{+0.20}_{-0.16}}$ Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ (for $\Sigma$$>3.7\times10^{-21}$ Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ and D$<$36.5 pc). We discussed the theoretical basis for the $\Sigma$-D dependence and particularly the reasons for the change in slope of the relation were stated. Added to this, we have shown the dependence between the radio luminosity and the diameter which seems to have a slope close to zero up to about D=36.5 pc. We have also adopted distance and diameter values for all of the observed Galactic SNRs by examining all the available distance values presented in the literature together with the distances found from our $\Sigma$-D relation.Comment: 45 pages, 2 figures, accepted for publication in Astronomical and Astrophysical Transaction