Key principle of the efficient running, swimming, and flying

Empirical observations indicate striking similarities among locomotion in terrestrial animals, birds, and fish, but unifying physical grounds are lacking. When applied to efficient locomotion, the analytical mechanics principle of minimum action yields two patterns of mechanical similarity via two explicit spatiotemporal coherent states. In steady locomotory modes, the slow muscles determining maximal optimum speeds maintain universal intrinsic muscular pressure. Otherwise, maximal speeds are due to constant mass-dependent stiffness of fast muscles generating a uniform force field, exceeding gravitation. Being coherent in displacements, velocities and forces, the body appendages of animals are tuned to natural propagation frequency through the state-dependent elastic muscle moduli. Key words: variational principle of minimum action (04.20.Fy), locomotion (87.19.ru), biomechanics (87.85.G-).Comment: Submitted to the Europhysical Letter

Experimental research of neutron yield and spectrum from deuterium gas-puff z-pinch on the GIT-12 generator at current above 2 MA

The Z-pinch experiments with deuterium gas-puff surrounded by an outer plasma shell were carried out on the GIT-12 generator (Tomsk, Russia) at currents of 2 MA. The plasma shell consisting of hydrogen and carbon ions was formed by 48 plasma guns. The deuterium gas-puff was created by a fast electromagnetic valve. This configuration provides an efficient mode of the neutron production in DD reaction, and the neutron yield reaches a value above 1012 neutrons per shot. Neutron diagnostics included scintillation TOF detectors for determination of the neutron energy spectrum, bubble detectors BD-PND, a silver activation detector, and several activation samples for determination of the neutron yield analysed by a Sodium Iodide (NaI) and a high-purity Germanium (HPGe) detectors. Using this neutron diagnostic complex, we measured the total neutron yield and amount of high-energy neutrons

Cluster relaxation dynamics in liquids and solids near the glass-transformation temperature

The structural relaxation in glass forming materials is studied near the glass transformation temperature Tg indicated by the heat capacity maximum. The late-time asymptote of the Kohlrausch–Williams–Watts form of the relaxation function is rationalized via the mesoscopic-scale correlated regions in terms of the Debye-type clusters following the dynamic scaling law. It is repeatedly shown that regardless of underlying microscopic realizations in glass formers with site disorder the structural relaxation is driven by local random fields, described via the directed random walks model. The relaxation space dimension ds = 3 at Tg is suggested for relaxing units of fractal dimension d f = 5/2 for quadrupolar-glass clusters in ortho–para hydrogen mixtures, that is compared with entangled-chain clusters in polymers (d f = 1) and solid-like clusters relaxing in supercooled molecular liquids (with ds = 6 and d f = 3). The relaxation dynamics of orientational-glass clusters in plastic crystals is attributed to the model of continuos time random walks in space ds = 6. As a by-product, the expansivity in polymers, molecular liquids and networks is predicted

Orientational ordering in monolayers of ortho–para hydrogen

We discuss orientational ordering in monolayers of solid hydrogen in view of recent experimental findings in NMR studies of (\QTR{it}{ortho)}$_{c}$-(\QTR{it}{para)}$_{1-c}$-hydrogen mixtures on boron nitride substrate. Analysis of the temperature-concentration behavior for the observed NMR frequency splitting is given on the basis of a two-dimension ($J=1)_{c}$-($J=0)_{1-c}$-rotor model with the quadrupolar coupling constant $\Gamma_{0}=0.50\pm 0.03$ $K$ and the crystalline field amplitude $V_{0}=0.70\pm 0.10$ $K$ derived from experiment. The two distinct para-rotational (PR) short-range ordered structures are described in terms of the local alignment and orientation of the polar principal axis, and are shown to be due to the interplay between the positive and negative crystalline fields. It is shown that the observed below the 2D site percolation threshold $c_{p}=0.72$ local structures are rather different from the ferromagnetic-type PR ordering suggested earlier by Harris and Berlinsky.Comment: 2 figures, Keywords:monolayers, order-disorder transitions, solid-solid transformation