Analytical CPG model driven by limb velocity input generates accurate temporal locomotor dynamics

The ability of vertebrates to generate rhythm within their spinal neural networks is essential for walking, running, and other rhythmic behaviors. The central pattern generator (CPG) network responsible for these behaviors is well-characterized with experimental and theoretical studies, and it can be formulated as a nonlinear dynam- ical system. The underlying mechanism responsible for locomotor behavior can be expressed as the process of leaky integration with resetting states generating appropriate phases for changing body velocity. The low-dimensional input to the CPG model generates the bilateral pattern of swing and stance modulation for each limb and is consistent with the desired limb speed as the input command. To test the minimal configuration of required parameters for this model, we reduced the system of equations representing CPG for a single limb and provided the analytical solution with two complementary methods. The analytical and empirical cycle durations were similar (R2 = 0.99) for the full range of walking speeds. The structure of solution is consistent with the use of limb speed as the input domain for the CPG network. Moreover, the reciprocal interaction between two leaky integration processes representing a CPG for two limbs was sufficient to capture fundamental experimental dynamics associated with the control of heading direction. This analysis provides further support for the embedded velocity or limb speed representation within spinal neural pathways involved in rhythm generation

Emergent nanoscale superparamagnetism at oxide interfaces

Atomically sharp oxide heterostructures exhibit a range of novel physical phenomena that do not occur in the parent bulk compounds. The most prominent example is the appearance of highly conducting and superconducting states at the interface between the band insulators LaAlO3 and SrTiO3. Here we report a new emergent phenomenon at the LaMnO3/SrTiO3 interface in which an antiferromagnetic insulator abruptly transforms into a magnetic state that exhibits unexpected nanoscale superparamagnetic dynamics. Upon increasing the thickness of LaMnO3 above five unit cells, our scanning nanoSQUID-on-tip microscopy shows spontaneous formation of isolated magnetic islands of 10 to 50 nm diameter, which display random moment reversals by thermal activation or in response to an in-plane magnetic field. Our charge reconstruction model of the polar LaMnO3/SrTiO3 heterostructure describes the sharp emergence of thermodynamic phase separation leading to nucleation of metallic ferromagnetic islands in an insulating antiferromagnetic matrix. The model further suggests that the nearby superparamagnetic-ferromagnetic transition can be gate tuned, holding potential for applications in magnetic storage and spintronics

Probing dynamics and pinning of single vortices in superconductors at nanometer scales

The dynamics of quantized magnetic vortices and their pinning by materials defects determine electromagnetic properties of superconductors, particularly their ability to carry non-dissipative currents. Despite recent advances in the understanding of the complex physics of vortex matter, the behavior of vortices driven by current through a multi-scale potential of the actual materials defects is still not well understood, mostly due to the scarcity of appropriate experimental tools capable of tracing vortex trajectories on nanometer scales. Using a novel scanning superconducting quantum interference microscope we report here an investigation of controlled dynamics of vortices in lead films with sub-Angstrom spatial resolution and unprecedented sensitivity. We measured, for the first time, the fundamental dependence of the elementary pinning force of multiple defects on the vortex displacement, revealing a far more complex behavior than has previously been recognized, including striking spring softening and broken-spring depinning, as well as spontaneous hysteretic switching between cellular vortex trajectories. Our results indicate the importance of thermal fluctuations even at 4.2 K and of the vital role of ripples in the pinning potential, giving new insights into the mechanisms of magnetic relaxation and electromagnetic response of superconductors.Comment: 15 pages and 5 figures (main text) + 15 pages and 11 figures (supplementary material

Influence of the substrate type on the surface morphology of Cu2ZnSnSe4 thin films

Investigations into the influence of the substrate type (a glass substrate with a molybdenum sublayer, tantalum and molybdenum foils) on the surface morphology of Cu2ZnSnSe4 thin films obtained by selenization of electrochemically deposited and preliminary annealed metallic precursors are presented. Исследования влияния типа подложки (стеклянная подложка с подслоем молибдена, фольги тантала и молибдена) на морфологию поверхности тонких пленок Cu2ZnSnSe4, полученных методом Представлена селенизация электрохимически осажденных и предварительно отожженных металлических прекурсоров

ANTARES: the first undersea neutrino telescope

The ANTARES Neutrino Telescope was completed in May 2008 and is the first operational Neutrino Telescope in the Mediterranean Sea. The main purpose of the detector is to perform neutrino astronomy and the apparatus also offers facilities for marine and Earth sciences. This paper describes the design, the construction and the installation of the telescope in the deep sea, offshore from Toulon in France. An illustration of the detector performance is given

A novel method of identifying motor primitives using wavelet decomposition

This study reports a new technique for extracting muscle synergies using continuous wavelet transform. The method allows to quantify coincident activation of muscle groups caused by the physiological processes of fixed duration, thus enabling the extraction of wavelet modules of arbitrary groups of muscles. Hierarchical clustering and identification of the repeating wavelet modules across subjects and across movements, was used to identify consistent muscle synergies. Results indicate that the most frequently repeated wavelet modules comprised combinations of two muscles that are not traditional agonists and span different joints. We have also found that these wavelet modules were flexibly combined across different movement directions in a pattern resembling directional tuning. This method is extendable to multiple frequency domains and signal modalities

Розробка моделі процесу обстрілу рухомої броньованої цілі осколково-пучковими снарядами направленої дії у вигляді дискретно-неперервної стохастичної системи

This paper describes the process of shooting a mobile armored combat vehicle with directed fragmentation-beam shells as a discrete-continuous random process. Based on this approach, a stochastic model has been proposed in the form of a system of Kolmogorov-Chapman differential equations. A universal model of the process of defeating a moving armored target with directed fragmentation-beam shells has been built, which would provide preconditions for experimental studies into the effectiveness of various variants of the components of the artillery system for three-shot firing. The execution of an artillery task is considered as a set of certain procedures characterized by the average value of its duration. They are dependent on the firing phases involving a prospective automatic gun and the explosive destruction of fragmentation-beam shells while the explosive destruction of each shell case is characterized by the self-propagation of the reaction of explosive transformations based on tabular data on the target. An indicator of the functionality of various design options for fragmentation-beam shells is the probability of causing damage by «useful fragments» in the vulnerable compartments of a combat armored vehicle. Devising universal models for the process of shooting a moving armored vehicle forms preconditions for further full-time experiments in accordance with the design solutions defined as a result of modeling. It is possible to use the developed discrete-continuous stochastic model in other modeling tasks to determine the optimal value of defeat. As regards the practical application of discrete-continuous stochastic models, one can argue about the possibility of reducing the cost of performing design tasks related to weapons by 25 % and decreasing the likelihood of making mistakes at the stage of system engineering designПредставлен процесс обстрела подвижной боевой бронированной машины направленными осколочно-пучковыми снарядами в виде дискретно-непрерывного случайного процесса. На основе этого подхода была предложена стохастическая модель в виде системы дифференциальных уравнений Колмогорова-Чепмена. Разработана универсальная модель процесса поражения подвижной бронированной цели осколочно-пучковыми снарядами направленного действия, что создаст предпосылки для проведения экспериментальных исследований эффективности различных вариантов составляющих артиллерийского комплекса для стрельбы из трех выстрелов. Выполнение огневой задачи рассматривается как набор определенных процедур, характеризующихся средним значением ее продолжительности. Они зависят от фаз стрельбы перспективной автоматической пушкой и взрывного разрушения оболочек осколочно-пучковых снарядов, а взрывное разрушение корпуса каждого снаряда характеризуется самораспространения реакции взрывчатых превращений на основе табличных данных о цели. Показателем функциональности различных вариантов конструкции осколочно-пучковых снарядов вероятность нанесения ущерба "полезными осколками" в уязвимые отсеки боевой бронированной машины. Разработка универсальных моделей процесса обстрела подвижной бронированной машин создает предпосылки для проведения дальнейших натурных экспериментов в соответствии с определенными в результате моделирования конструктивных решений. Возможно применение разработанной дискретно-непрерывного стохастической модели в других задачах моделирования для определения оптимального значения поражения. В практическом применении дискретно-непрерывных стохастических моделей возможно говорить о возможности сокращения затрат на выполнение проектных задач вооружения на 25 % и уменьшает вероятность внесения ошибок на этапе системотехнического проектированияПредставлено процес обстрілу рухомої бойової броньованої машини з спрямованими осколково-пучковими снарядами у вигляді дискретно-неперервного випадкового процесу. На основі цього підходу була запропонована стохастична модель у вигляді системи диференціальних рівнянь Колмогорова-Чепмена. Розроблено універсальну модель процесу ураження рухомої броньованої цілі осколково-пучковими снарядами спрямованої дії, що створить передумови для проведення експериментальних досліджень ефективності різних варіантів складових артилерійського комплексу для стрільби з трьох пострілів. Виконання вогневого завдання розглядається як набір певних процедур, що характеризуються середнім значенням її тривалості. Вони є залежними від фаз стрільби перспективною автоматичною гарматою та вибухового руйнування оболонок осколково-пучкових снарядів, а вибухове руйнування корпусу кожного снаряду характеризується саморозповсюдженням реакції вибухових перетворень на основі табличних даних про ціль. Показником функціональності різних варіантів конструкції осколково-пучкових снарядів є ймовірність нанесення збитків “корисними осколками” в уразливі відсіки бойової броньованої машини. Розроблення універсальних моделей процесу обстрілу рухомої броньованої машин створює передумови для проведення подальших натурних експериментів відповідно до визначених в результаті моделювання конструктивних рішень. Можливе застосування розробленої дискретно-неперервної стохастичної моделі в інших задачах моделювання для визначення оптимального значення ураження. У практичному застосуванні дискретно-неперервних стохастичних моделей можливо вести мову про можливість скорочення витрат на виконання проектних завдань озброєння на 25 % та зменшує ймовірність внесення помилок на етапі системотехнічного проектуванн

Cardiovascular system parameters in participants of Arctic expeditions

ObjectivesA method of continuous heart rate (HR) and blood pressure (BP) recording was used for the evaluation of the cardiovascular system parameters in participants of short-term (<1 month) high-latitude expeditions, in comparison with the parameters of residents of Central Russia and the Arctic region.Material and MethodsA dynamic examination of participants of Arctic expeditions (30 men, residents of middle-latitude regions, aged 46.7±1.7 years), workers permanently living in Central Russia (the Moscow region, 44 men, aged 46.7±1.0 years) and residents of the North (the Murmansk region, 35 men, aged 46.6±1.3 years) was performed. The authors used a spiroartheriocardiorythmograph allowing the parallel recording of HR, BP, spectral characteristics of HR variability (HRV) and the variability of systolic BP (sBP) and diastolic BP (dBP), cardiac performance parameters, and spontaneous baroreflex sensitivity (BRS). The parameters were recorded at rest, in a sitting position, over 2 min.ResultsThe basic clinical parameters (HR, BP and cardiac performance) did not differ in the workers living in different climatic zones. However, the residents of the North demonstrated a lower total power (TP) of the dBP variability spectrum and a lower relative power of the high-frequency (HF) range in both the sBP and dBP variability spectra. The participants of expeditions to the North had a lower TP of the HRV spectrum (in comparison with both control groups) that did not change during the expeditions; BRS was reduced, while the TP of the sBP spectrum was increased in comparison with the corresponding parameters obtained from the residents of circumpolar regions, and decreased during the expedition in parallel with a decrease in the sBP values. The TP of both the sBP and dBP variability spectra, as well as the power of the HF range in these spectra, were similar in the participants of expeditions to those obtained from the residents of Central Russia, and they considerably surpassed the corresponding parameters in the northerners surveyed.ConclusionsThe revealed peculiarities of the cardiovascular system in the participants of high-latitude expeditions can be considered as correlates of positive, and adequate in terms of the physiological value, adaptive shifts in the autonomous regulation of the cardiovascular system