Interdependence of magnetism and superconductivity in the borocarbide TmNi2B2C

We have discovered a new antiferromagnetic phase in TmNi2B2C by neutron diffraction. The ordering vector is Q_A = (0.48,0,0) and the phase appears above a critical in-plane magnetic field of 0.9 T. The field was applied in order to test the assumption that the zero-field magnetic structure at Q_F = (0.094,0.094,0) would change into a c-axis ferromagnet if superconductivity were destroyed. We present theoretical calculations which show that two effects are important: A suppression of the ferromagnetic component of the RKKY exchange interaction in the superconducting phase, and a reduction of the superconducting condensation energy due to the periodic modulation of the moments at the wave vector Q_A

The influence of altitude on the anaerobic and aerobic capacities of men in work Final scientific report

Altitude influence on anaerobic and aerobic capacities of working me

KINETICS AND ELECTROMYOGRAPHY OF THE MARTIAL ARTS HIGH FRONT KICK

INTRODUCTION Fast unloaded movements like striking, throwing and kicking are typically performed in a proximo-distal sequence: Initially proximal segments accelerate while distal segments lag behind, then proximal segments deceler- ate while distal segments accelerate. In kicking, for instance, it is observed that the movement starts with forward angular acceleration of the thigh while the shank lags behind. Then the thigh decelerates while simultaneously the shank accelerates and the foot reaches its maximal velocity. This raises two questions: Is the thigh actively decelerated by the glutei and/or hamstring muscles, or passively decelerated by joint reaction forces from the accelerating shank7 Is acceleration of the shank enhanced by the thigh's deceleration? From a kinematic perspective this movement coordination seems disadvantageous, considering that the resulting linear velocity of the foot relative to the ground equals the vector sum of the resulting linear velocity of the knee relative to the ground and the foot relative to the knee. However, from a kinetic perspective it can be argued that thigh deceleration enhances shah acceleration to a degree where toss of knee velocity is more than accounted for in gain of foot velocity. The theory is that the angularly decelerating thigh exerts a knee joint force which causes angular acceleration of the shank, i.e. a %hip-lash" action. To obtain knowledge regarding how these kinds of movements are performed we decided to examine the martial arts high front kick. Similar to previous kicking studies we did so by kinematic measurements but in addition recorded the electrical activity of selected muscles in order to asses their temporal activation during the kick. METHODS Seventeen skilled taekwondo practitioners (14 males. 3 females) volunteered to take part in this study. Each subject performed three high front kicks aiming at a tennis ball suspended from the ceiling and adjusted to chin level. The fastest kick from each subject was selected for further analysis. The subjects were high speed filmed (200 f.p.s.) from their right side while kicking. Contrasting markers on selected anatomical landmarks enabled subsequent automatic digitisation. Displacement data were lowpass filtered with optimal cut-off frequencies (6-1 0 Hz) determined by use of residual analysis/ Jackson Knee method. Velocities and accelerations were derived from the displacement data by finite difference calculation. During kicking the electtomyographic activity (EMG) from five selected leg muscles were measured with surface electrodes. Kinetic data were obtained through inverse dynamics calculation using a two-segment link-segment model of the kicking leg and the movement equations developed by Putnam (1983). These equations enable division of the resulting moment acting on a segment into muscular components and motion de- pendant components arising from movement of adjacent segments. RESULTS Data for the thigh indicated that deceleration was caused by motion dependant moments arising from shank motion and not by active hip extensor muscles. Shank acceleration was caused partly by a knee extensor muscle moment and partly by a motion dependant moment arising from thigh angular velocity. Both thigh and shank kinetics were supported by EMG recordings. CONCLUSION As part of the accelerating moment acting on the shank was due to thigh angular velocity we suggest that the observed thigh deceleration should be considered unwanted but unavoidable due to shank acceleration. This implies that even though knee extensor muscles are important for shank acceleration the hip flexor muscles must not be neglected

DIFFERENCES IN JUMPING PERFORMANCE OF CHILDREN FROM DIFFERENT SPORTS

The ability of high rate of force development is crucial in many high power sports. The aim of this study was to examine the possible differences in jumping skills of children participating in sports with different demands of leg strength, in order to investigate if specific training influenced different jump performances. 175 children from four different sports participated. The subjects performed squat jumps; counter movement jumps and drop jumps from 0.2 m and 0.4 m. The study showed that the nature of the sport has influence on the performance of drop jumping ability on children, though natural selection may also have an influence

JUMPING STRATEGIES IN A VOLLEYBALL AND A BALLET SPECIFIC JUMP

INTRODUCTION The performance of a maximal vertical jump fram a static preparatory position (SQJ) or starting with a counter movement (CMJ) implies transformation of rotation about the hip, knee and ankle joints to a maximal translatory movement. Different strategies have been proposed for this transformation. Previously both sequential and simullaneous strategies have been proposed as optimal for maximal vertical jumping (1 & 2). The purpose of this study was to analyze ]umping strategies in a sport and dance specific maximal vertical jump. The hypothesis was that the technical demands of the Jumps would preset the strategy. Six male subjects participated in the study three professional ballet dancers and three elite volleyball players. In the ballet specific jump (BSJ) the legs were outward rotated, one foot was placed in front of and close to the other foot and the upper body kept upright. Three elite volleyball players performed the jump used for the smash (VSJ) including a three step preliminary run up and a farcefull arm swing. Afterwards all six subjects performed SQJ and CMJ. The ]umps were recorded on high speed film (500Hz) combined with registrations trom an AMTI force platform and EMG recordings from the major lower extremity muscles Net joint moments and joint work ware calculated by inverse dynamics. The strategy of the jumps was determined on the basis of angular kinematics and the pattern of nel joint moments of the two dominant joints RESULTS For BSJ the jumping height (h) was 0.22O.28m.The war!< contribution from the knee and ankle joint were 50-70% and 47-63% of the total work respectively while the work at the hip joint showed a negative contribution of 13-17% caused by a net hip flexor moment. Because of the specific ballet position the hip extension took place in the frontal plane and mgluteus maximus could not contribute to the extension. The concentric activity in mrectus femoris could partly explain the hip flexor moment. The knee and ankle joint initiated the extension phase simultaneously and the net joint moments peaked also simultaneously Therefore, the strategy could be defined as simultaneous. For VSJ h was 0.310.45m. The work contribution fram the knee and hip joints were 22-60% and 35-62% of the total work respectively. The hip joint began the extension phase before the body center of mass had reached its lowest position (sn The knee extension began 40-100ms after s.j. The peaks of the net joint moments of the hip and knee showed a similar pattern. Accordingly, the strategy could be defined as sequentiaL The sequential joint extension could partly be explained by the forcefull armswing pressing down and giving negative momentum in the downward phase and by this delaying the knee extension. In SQJ and CMJ h was 0.22-0.36m and 0.33-0AOm. The work contribution from the knee was 64.5%(SE 5.9) and 76.0% (SE 9.2) and from the hip 18.8% (SE 5.8) and 133% (SE 8.7). One ballet dancer and one volleyball player performed SQJ and CMJ with a simultaneous strategy while the otller four subjects used a sequential strategy. CONCLUSION In a maximal vertical jump fram ballet and from volleyball the technical demands preset the jumping strategy. When the subjects were asked to perform SQJ and CMJ the choice of strategy seemed individual and not connected to the training background. REFERENCES (1) Hudson, J.L. (1986). Med Sci. Sports Exerc, 18,242-251 (2) Babbert, M.F. & van lngen Schenau, G.J. (1986). J Biomechanics, 21, 249•26

Investigative Pattern Detection Framework for Counterterrorism

Law-enforcement investigations aimed at preventing attacks by violent extremists have become increasingly important for public safety. The problem is exacerbated by the massive data volumes that need to be scanned to identify complex behaviors of extremists and groups. Automated tools are required to extract information to respond queries from analysts, continually scan new information, integrate them with past events, and then alert about emerging threats. We address challenges in investigative pattern detection and develop an Investigative Pattern Detection Framework for Counterterrorism (INSPECT). The framework integrates numerous computing tools that include machine learning techniques to identify behavioral indicators and graph pattern matching techniques to detect risk profiles/groups. INSPECT also automates multiple tasks for large-scale mining of detailed forensic biographies, forming knowledge networks, and querying for behavioral indicators and radicalization trajectories. INSPECT targets human-in-the-loop mode of investigative search and has been validated and evaluated using an evolving dataset on domestic jihadism.Comment: 9 pages, 4 figure

Mermin-Ho vortex in ferromagnetic spinor Bose-Einstein condensates

The Mermin-Ho and Anderson-Toulouse coreless non-singular vortices are demonstrated to be thermodynamically stable in ferromagnetic spinor Bose-Einstein condensates with the hyperfine state F=1. The phase diagram is established in a plane of the rotation drive vs the total magnetization by comparing the energies for other competing non-axis-symmetric or singular vortices. Their stability is also checked by evaluating collective modes.Comment: 4 pages, 4 figure

Dyke swarms and associated lava formations in the northern Lebombo monocline, Karoo Large Igneous Province, South Africa

As one of the early classical examples of plume-generated Large Igneous Provinces (LIPs), the Karoo is characterized by a bulls-eye distribution of High-Ti basalts, picrites, and earliest nephelinites onto a conspicuous triple rift junction (i.e., Okavango dyke swarm and the two Mwenezi and Lebombo monoclines), surrounded by Low-Ti basalts. It is noted that this regional distribution between high-and low-Ti basalts within the Jurassic Karoo LIP differs from that of the Permian Emeishan LIP; thereby undermining the use of this particular feature as evidence for mantle plume involvement

Formation of atomic tritium clusters and condensates

We present an extensive study of the static and dynamic properties of systems of spin-polarized tritium atoms. In particular, we calculate the two-body |F,m_F>=|0,0> s-wave scattering length and show that it can be manipulated via a Feshbach resonance at a field strength of about 870G. Such a resonance might be exploited to make and control a Bose-Einstein condensate of tritium in the |0,0> state. It is further shown that the quartet tritium trimer is the only bound hydrogen isotope and that its single vibrational bound state is a Borromean state. The ground state properties of larger spin-polarized tritium clusters are also presented and compared with those of helium clusters.Comment: 5 pages, 3 figure