THREE DIMENSIONAL KINEMATICS AND KINETICS OF THE BODY CENTER OF GRAVITY IN RUNNING

The present study was designed t o investigate the methodology of the running kinematics derived from kinetic measurement. From theoretical point of view, external forces acting on the body center of gravity (C/G) could determine acceleration , velocity , and displacement of t h e c /G . These kinematic parameters of the C/G were mathematically derived from the ground reaction forces recorded by a set of forceplates . Integral computing, however, to obtain the velocity and displacement must be carried out with much difficulties because of low frequency errors included in force signals . The present study was composed of three parts ; 1 ) how to reduce the errors in integrations of force signals using either analogue or digital computer system, 2) choice of transducers such as strain gauges or quartz to record the reaction forces in jumping, stepping, knee bending, running and walking, and 3) continuous recording of the triaxial force acting on the C/G during treadmill running. , 1 ) Low frequency errors was multiplied . essentially in the integration . The DC ( direct current ) component included in the force signals , even if a little, was considerably grown up in both velocity and displacement curves. These errors could be reduced by a mathematical filter in a digital computer system, o r by a band-pass analogue filter . In general, the former was more advantageous t o obtain an optimal compensation of integral errors than the latter. whose usage was limited within relatively prolonged and periodical data. 2) Recently the strain gauge was competant for biomechanical analysis of human motions, as well as the quartz. The primary problem was not transducer itself but design of mechanical setup of it. If the peak value of impulsive reaction force was not necessary and/or if the triaxial measurement was not necessary, the choice of transducers was dependent upon economical problems. 3) A motor-driven treadmill (250 kg in mass) was fixed upon a set of two force plates (Kistler; 60x40 cm2). Head and tail parts of the treadmill were supported by each forceplate respectively . I The sum of outputs from both plates showed the external force acting upon the C/G, because both plates could detect changes of mass distributions of a system of human body and treadmill . Motion equations of the system showed the acceleration of the body C/G during walk or run on the treadmill , where the C/G of the treadmill was not moved even a t work. The velocity and displacement curves of the C/G were calculated continuously in each triaxial direction by the digital computer system. The growth of the DC error in integration was approximated by a linear regression line related to time, and then it could be compensated numerically. On the other hand, the force signal was mixed with high frequency noise composed of mechanical vibrations of treadmill and motor at work. However, the high frequency noise did have little effect on the integrations . The present method had some advantages in biomechanical analysis of running as well as walking

Maternal lineages in polyploid wheat species inferred from organeller DNA fingerprinting

Contains fulltext : 134958.pdf (publisher's version ) (Closed access)Health promoting messages can be framed in terms of the gains that are associated with healthy behaviour, or the losses that are associated with unhealthy behaviour. In this study, we examined the influence of self-efficacy to quit smoking on the effects of gain framed and loss framed anti-smoking messages in a randomized controlled trial among 539 adult smokers. Participants with a high self-efficacy to quit smoking reported higher levels of motivation to quit smoking after receiving a loss framed message than after receiving a gain framed message or no message. For these participants receiving a gain framed message did not result in a higher motivation to quit smoking than receiving no message. For participants with a low self-efficacy to quit smoking there were no differences in motivation to quit smoking between the gain framed message condition, loss framed message condition and control condition. Our results suggest that self-efficacy can moderate the effects of message framing on persuasion

Temperature dependence of the upper critical field of an anisotropic singlet superconductivity in a square lattice tight-binding model in parallel magnetic fields

Upper critical field parallel to the conducting layer is studied in anisotropic type-II superconductors on square lattices. We assume enough separation of the adjacent layers, for which the orbital pair-breaking effect is suppressed for exactly aligned parallel magnetic field. In particular, we examine the temperature dependence of the critical field H_c(T) of the superconductivity including the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO or LOFF) state, in which the Cooper pairs have non-zero center-of-mass momentum q. In the system with the cylindrically symmetric Fermi-surface, it is known that H_c(T) of the d-wave FFLO state exhibits a kink at a low temperature due to a change of the direction of q in contrast to observations in organic superconductors. It is shown that the kink disappears when the Fermi-surface is anisotropic to some extent, since the direction of q is locked in an optimum direction independent of the temperature.Comment: 5 pages, 5 figures, revtex.sty, submitted to J.Phys.Soc.Jp

Unrestricted Hartree-Fock Analysis of Sr3−x_{3-x}Cax_xRu2_2O7_7

We investigated the electronic and magnetic structure of Sr$_{3-x}$Ca$_x$Ru$_2$O$_7$ ($0 \leq x \leq 3$) on the basis of the double-layered three-dimensional multiband Hubbard model with spin-orbit interaction. In our model, lattice distortion is implemented as the modulation of transfer integrals or a crystal field. The most stable states are estimated within the unrestricted Hartree-Fock approximation, in which the colinear spin configurations with five different spin-quantization axes are adopted as candidates. The obtained spin structures for some particular lattice distortions are consistent with the neutron diffraction results for Ca$_3$Ru$_2$O$_7$. Also, some magnetic phase transitions can occur due to changes in lattice distortion. These results facilitate the comprehensive understanding of the phase diagram of Sr$_{3-x}$Ca$_x$Ru$_2$O$_7$.Comment: 16 pages, 7 figure

Cyclotron effective masses in layered metals

Many layered metals such as quasi-two-dimensional organic molecular crystals show properties consistent with a Fermi liquid description at low temperatures. The effective masses extracted from the temperature dependence of the magnetic oscillations observed in these materials are in the range, m^*_c/m_e \sim 1-7, suggesting that these systems are strongly correlated. However, the ratio m^*_c/m_e contains both the renormalization due to the electron-electron interaction and the periodic potential of the lattice. We show that for any quasi-two-dimensional band structure, the cyclotron mass is proportional to the density of states at the Fermi energy. Due to Luttinger's theorem, this result is also valid in the presence of interactions. We then evaluate m_c for several model band structures for the \beta, \kappa, and \theta families of (BEDT-TTF)_2X, where BEDT-TTF is bis-(ethylenedithia-tetrathiafulvalene) and X is an anion. We find that for \kappa-(BEDT-TTF)_2X, the cyclotron mass of the \beta-orbit, m^{*\beta}_c, is close to 2 m^{*\alpha}_c, where m^{*\alpha}_c is the effective mass of the \alpha- orbit. This result is fairly insensitive to the band structure details. For a wide range of materials we compare values of the cyclotron mass deduced from band structure calculations to values deduced from measurements of magnetic oscillations and the specific heat coefficient.Comment: 12 pages, 3 eps figure

Field-Orientation Dependent Heat Capacity Measurements at Low Temperatures with a Vector Magnet System

We describe a heat capacity measurement system for the study of the field-orientation dependence for temperatures down to 50 mK. A "Vector Magnet" combined with a mechanical rotator for the dewar enables the rotation of the magnetic field without mechanical heating in the cryostat by friction. High reproducibility of the field direction, as well as an angular resolution of better than 0.01 degree, is obtained. This system is applicable to other kinds of measurements which require a large sample space or an adiabatic sample environment, and can also be used with multiple refrigerator inserts interchangeably.Comment: 7 pages, 8 figure

Cyclotron resonance in the layered perovskite superconductor Sr2RuO4

We report a detailed study of the magnetic-field-orientation dependence of the millimetre-wave magnetoconductivity of the superconductor Sr2RuO4 We find two harmonic series of cyclotron resonances. We assign the first, corresponding to a quasiparticle mass of $4.29 \pm 0.05 m_{\rm e}$, where $m_{\rm e}$ is the free-electron mass, to the $\beta$ Fermi-surface section. We assign the second series, which contains only odd harmonics, to cyclotron resonance of the $\gamma$ Fermi-surface section, yielding a quasiparticle mass of $12.35 \pm 0.20 m_{\rm e}$. A third, single cyclotron resonance, corresponding to a quasiparticle mass of $5.60 \pm 0.03 m_{\rm e}$, is attributed to the $\alpha$ Fermi-surface section. In addition, we find a very strong absorption mode in the presence of a magnetic field component parallel to the quasi-two-dimensional planes of the sample. Its dependence on the orientation of the magnetic field cannot be described in the context of conventional cyclotron resonance, and the origin of this mode is not yet clear.Comment: Submitted to J. Phys. Cond. Ma

Indication for the coexistence of closed orbit and quantum interferometer with the same cross section in the organic metal (ET)4(H3O)[Fe(C2O4)3].C6H4Cl2: Persistence of SdH oscillations above 30 K

Shubnikov-de Haas (SdH) and de Haas-van Alphen (dHvA) oscillations spectra of the quasi-two dimensional charge transfer salt $\beta$"-(ET)$_4$(H$_3$O)[Fe(C$_2$O$_4$)$_3$]$\cdot$C$_6$H$_4$Cl$_2$ have been investigated in pulsed magnetic fields up to 54 T. The data reveal three basic frequencies F$_a$, F$_b$ and F$_{b - a}$, which can be interpreted on the basis of three compensated closed orbits at low temperature. However a very weak thermal damping of the Fourier component F$_b$, with the highest amplitude, is evidenced for SdH spectra above about 6 K. As a result, magnetoresistance oscillations are observed at temperatures higher than 30 K. This feature, which is not observed for dHvA oscillations, is in line with quantum interference, pointing to a Fermi surface reconstruction in this compound.Comment: published in Eur. Phys. J. B 71 203 (2009

The effect of an in-plane magnetic field on the interlayer transport of quasiparticles in layered superconductors

We consider the quasiparticle c-axis conductivity in highly anisotropic layered compounds in the presence of the magnetic field parallel to the layers. We show that at low temperatures the quasiparticle interlayer conductivity depends strongly on the orientation of the in-plane magnetic field if the excitation gap has nodes on the Fermi surface. Thus measurements of the angle-dependent c-axis (out-of-plane) magnetoresistance, as a function of the orientation of the magnetic field in the layers, provide information on the momentum dependence of the superconducting gap (or pseudogap) on the Fermi surface. Clean and highly anisotropic layered superconductors seem to be the best candidates for probing the existence and location of the nodes on the Fermi surface.Comment: 4 pages RevTeX, including 2 PostScript figures, to appear in Phys. Rev. Let