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Sample records for peak jumping mode

  1. Different Modes of Feedback and Peak Vertical Ground Reaction Force During Jump Landing: A Systematic Review

    PubMed Central

    Ericksen, Hayley M.; Gribble, Phillip A.; Pfile, Kate R.; Pietrosimone, Brian G.

    2013-01-01

    Context: Excessive ground reaction force when landing from a jump may result in lower extremity injuries. It is important to better understand how feedback can influence ground reaction force (GRF) and potentially reduce injury risk. Objective: To determine the effect of expert-provided (EP), self-analysis (SA), and combination EP and SA (combo) feedback on reducing peak vertical GRF during a jump-landing task. Data Sources: We searched the Web of Science database on July 1, 2011; using the search terms ground reaction force, landing biomechanics, and feedback elicited 731 initial hits. Study Selection: Of the 731 initial hits, our final analysis included 7 studies that incorporated 32 separate data comparisons. Data Extraction: Standardized effect sizes and 95% confidence intervals (CIs) were calculated between pretest and posttest scores for each feedback condition. Data Synthesis: We found a homogeneous beneficial effect for combo feedback, indicating a reduction in GRF with no CIs crossing zero. We also found a homogeneous beneficial effect for EP feedback, but the CIs from 4 of the 10 data comparisons crossed zero. The SA feedback showed strong, definitive effects when the intervention included a videotape SA, with no CIs crossing zero. Conclusions: Of the 7 studies reviewed, combo feedback seemed to produce the greatest decrease in peak vertical GRF during a jump-landing task. PMID:24067153

  2. Noise Induced Jumping Dynamics Between Synchronized Modes

    NASA Astrophysics Data System (ADS)

    Algar, Shannon D.; Stemler, Thomas; de Saedeleer, Bernard

    Synchronization is a common phenomenon whereby a dynamical system follows the pacemaker provided by an external forcing. Often, such systems have multiple synchronization modes, which are equivalent solutions. We investigate the specific case of two to one synchronization produced by the periodic forcing of a van der Pol oscillator where two possible modes, shifted by one period of the modulation, exist. By studying the flow and the local Lyapunov exponents along the orbit we give an explanation of the noise induced jumps observed in a stochastic forced oscillator. While this investigation gives results that are specific to this system, the framework presented is more general and can be applied to any system showing similar jumping dynamics.

  3. Transsonic accretion modes with density jumps

    NASA Astrophysics Data System (ADS)

    Adarchenko, V. A.; Voronin, S. M.

    2015-08-01

    In this study, a class of steady-state solutions of the problem of matter incidence on a gravitating center (accretion), in which the matter jump through a sound barrier is performed at the discontinuity (density jump), is proposed. Substantiation of such solutions is given based on the theory of fast—slow systems. Certain partial solutions are presented as an example.

  4. Relationship between jump landing kinematics and peak ACL force during a jump in downhill skiing: a simulation study.

    PubMed

    Heinrich, D; van den Bogert, A J; Nachbauer, W

    2014-06-01

    Recent data highlight that competitive skiers face a high risk of injuries especially during off-balance jump landing maneuvers in downhill skiing. The purpose of the present study was to develop a musculo-skeletal modeling and simulation approach to investigate the cause-and-effect relationship between a perturbed landing position, i.e., joint angles and trunk orientation, and the peak force in the anterior cruciate ligament (ACL) during jump landing. A two-dimensional musculo-skeletal model was developed and a baseline simulation was obtained reproducing measurement data of a reference landing movement. Based on the baseline simulation, a series of perturbed landing simulations (n = 1000) was generated. Multiple linear regression was performed to determine a relationship between peak ACL force and the perturbed landing posture. Increased backward lean, hip flexion, knee extension, and ankle dorsiflexion as well as an asymmetric position were related to higher peak ACL forces during jump landing. The orientation of the trunk of the skier was identified as the most important predictor accounting for 60% of the variance of the peak ACL force in the simulations. Teaching of tactical decisions and the inclusion of exercise regimens in ACL injury prevention programs to improve trunk control during landing motions in downhill skiing was concluded.

  5. Peak versus mean propulsive power outputs: which is more closely related to jump squat performance?

    PubMed

    Loturco, Irineu; Pereira, Lucas A; Kobal, Ronaldo; Kitamura, Katia; Cal Abad, Cesar C; Nakamura, Fábio Y; Pai, Chi N

    2017-11-01

    This study aimed to compare the predictive value of muscle power (peak power, mean power until the peak-velocity or mean propulsive power) in relation to the jump height achieved during the jump squat performed at different loads. One hundred and ninety-four elite athletes performed jump squats against loads corresponding to 40%, 60%, and 80% of their respective body mass. A linear regression analysis was performed to establish the relationship between muscle power expressions and jump squat height. The coefficient of determination (R2) in the different linear regression models between muscle power-related variables and jump squat height, for the different load ranges, varied from 0.50 to 0.57 (for absolute power values) and from 0.72 to 0.78 (for relative power values [W/kg]). The mean propulsive power presented similar capacity to predict the jump squat height as the peak power-related values. For all analyzed variables, this prediction power was increased when the absolute power values were normalized by the individuals' body mass. Selection of the values related to the mean propulsive phase to assess top-level athletes might be considered as an advantageous alternative, due to its adequacy to properly reflect the neuromuscular potential of the subjects in both ballistic and traditional exercises.

  6. Peak effect and giant flux jumps in hard superconductors: the problem of “islands” jumps on H-T diagram

    NASA Astrophysics Data System (ADS)

    Chabanenko, V. V.; Rusakov, V. F.; D'yachenko, A. I.; Piechota, S.; Nabialek, A.; Szymczak, H.

    2000-11-01

    Magnetic properties of superconductors with peak effect were investigated both experimentally and theoretically in frames of the critical state model which incorporates the flux jump instability criterion. Theoretical analyses show some “forbidden” band for flux jumps on the magnetic field axis. Features of H-T diagrams of instability of superconductors with peak effect are discussed.

  7. Optimal loading range for the development of peak power output in the hexagonal barbell jump squat.

    PubMed

    Turner, Thomas S; Tobin, Daniel P; Delahunt, Eamonn

    2015-06-01

    Recent studies indicate that the utilization of the hexagonal barbell jump squat (HBJS) compared with the traditional barbell jump squat may offer a superior method of developing peak power. The notion that a single optimal load may be prescribed in training programs aiming to develop peak power is subject to debate. The purpose of this study was to identify the optimal load corresponding with peak power output during the HBJS in professional rugby union players. Seventeen professional rugby union players participated in this study. Participants performed 3 unloaded countermovement jumps on a force plate and 3 HBJS at each of the following randomized loads: 10, 20, 30, and 40% of box squat 1 repetition maximum (1RM). Peak power output was the dependent variable of interest. A one-way repeated measures analysis of variance was conducted to compare peak power output across each load. Peak power output was the dependent variable of interest. A significant main effect for load was observed (Wilk's Lambda = 0.11, F(4,13) = 18.07, p < 0.01, partial η2 = 0.88). Results of the Bonferroni-adjusted pairwise comparisons indicated that peak power output in the HBJS is optimized at a load range between 10 and 20% of box squat 1RM. The results of this study indicate that the use of the HBJS with a training load between 10 and 20% of box squat 1RM optimizes peak power output in professional rugby union players.

  8. Sample distribution in peak mode isotachophoresis

    SciTech Connect

    Rubin, Shimon; Schwartz, Ortal; Bercovici, Moran

    2014-01-15

    We present an analytical study of peak mode isotachophoresis (ITP), and provide closed form solutions for sample distribution and electric field, as well as for leading-, trailing-, and counter-ion concentration profiles. Importantly, the solution we present is valid not only for the case of fully ionized species, but also for systems of weak electrolytes which better represent real buffer systems and for multivalent analytes such as proteins and DNA. The model reveals two major scales which govern the electric field and buffer distributions, and an additional length scale governing analyte distribution. Using well-controlled experiments, and numerical simulations, we verify and validate the model and highlight its key merits as well as its limitations. We demonstrate the use of the model for determining the peak concentration of focused sample based on known buffer and analyte properties, and show it differs significantly from commonly used approximations based on the interface width alone. We further apply our model for studying reactions between multiple species having different effective mobilities yet co-focused at a single ITP interface. We find a closed form expression for an effective-on rate which depends on reactants distributions, and derive the conditions for optimizing such reactions. Interestingly, the model reveals that maximum reaction rate is not necessarily obtained when the concentration profiles of the reacting species perfectly overlap. In addition to the exact solutions, we derive throughout several closed form engineering approximations which are based on elementary functions and are simple to implement, yet maintain the interplay between the important scales. Both the exact and approximate solutions provide insight into sample focusing and can be used to design and optimize ITP-based assays.

  9. Peak Vertical Jump Power as a Marker of Bone Health in Children.

    PubMed

    Baptista, F; Mil-Homens, P; Carita, A I; Janz, K; Sardinha, L B

    2016-07-01

    The objective of this investigation was to evaluate the accuracy of peak vertical jump power (VJP) to identify children with bone mineral density (BMD) below average, defined as BMD measured by DXA and adjusted for body height at the whole body less head≤- 1.0 standard deviation (SD). The sample included 114 boys and girls aged 8.5±0.4 years old. VJP was estimated from a countermovement jump performed on a contact mat using the measured flight time to calculate the height of rise of the center of gravity. Logistic regression analysis revealed that the odds ratio of having BMD≤1.0 SD decreased 1.2% per watt of power and the probability of BMD below average was 75.6% higher in boys than in girls with the same peak power jump. Receiver operating characteristic analysis showed that the best trade-off between sensitivity and specificity to identify children with BMD<- 1.0 SD was 635 watts in boys (sensitivity=63.3%; specificity=69.2%; AUC=0.816, 95% CI: 0.681-0.95; p<0.001) and 515 watts in girls (sensitivity=75.0%; specificity=77.0%; AUC=0.849, 95% CI: 0.698-0.999; p=0.002). These cut-off values correspond to a vertical jump of 19.9 cm and 20.5 cm in 8-year-old boys and girls, respectively. The VJP showed a reasonable sensitivity and specificity as well good discriminant ability to identify children with BMD below average.

  10. Changes in Sprint and Jump Performances After Traditional, Plyometric, and Combined Resistance Training in Male Youth Pre- and Post-Peak Height Velocity.

    PubMed

    Lloyd, Rhodri S; Radnor, John M; De Ste Croix, Mark B A; Cronin, John B; Oliver, Jon L

    2016-05-01

    The purpose of this study was to compare the effectiveness of 6-week training interventions using different modes of resistance (traditional strength, plyometric, and combined training) on sprinting and jumping performances in boys before and after peak height velocity (PHV). Eighty school-aged boys were categorized into 2 maturity groups (pre- or post-PHV) and then randomly assigned to (a) plyometric training, (b) traditional strength training, (c) combined training, or (d) a control group. Experimental groups participated in twice-weekly training programs for 6 weeks. Acceleration, maximal running velocity, squat jump height, and reactive strength index data were collected pre- and postintervention. All training groups made significant gains in measures of sprinting and jumping irrespective of the mode of resistance training and maturity. Plyometric training elicited the greatest gains across all performance variables in pre-PHV children, whereas combined training was the most effective in eliciting change in all performance variables for the post-PHV cohort. Statistical analysis indicated that plyometric training produced greater changes in squat jump and acceleration performances in the pre-PHV group compared with the post-PHV cohort. All other training responses between pre- and post-PHV cohorts were not significant and not clinically meaningful. The study indicates that plyometric training might be more effective in eliciting short-term gains in jumping and sprinting in boys who are pre-PHV, whereas those who are post-PHV may benefit from the additive stimulus of combined training.

  11. Countermovement jump peak force relative to body weight and jump height as predictors for sprint running performances: (in)homogeneity of track and field athletes?

    PubMed

    Markström, Jonas L; Olsson, Carl-Johan

    2013-04-01

    The purpose of this study was to investigate: (a) If variables from 1-leg drop jump (DJ), DJ, squat jump (SJ), and countermovement jump (CMJ) tests can predict sprint performances for sprinters. (b) If sprinters and jumpers can be distinguished based on variables from 1-leg DJ, DJ, SJ, and CMJ tests, also if sprinters and throwers can be distinguished based on variables from stiff leg jump (SLJ), SJ, and CMJ tests. A single linear regression and multiple linear regression analysis approach with models including 2 or 3 variables were used when predicting sprint performances. Five elite sprinters (1 woman) participated in the first subexamination and 5 sprinters (1 woman) vs. 5 jumpers and 6 sprinters vs. 6 throwers (4 women) participated in the second. The force variable CMJ peak force (PF) relative to body weight significantly predicted the sprint performances maximal running velocity through 10-m (V[Combining Dot Above]O2max10m) and 60-m time. The Vmax10m was also predicted by CMJ height. Jump heights from SJ and DJ did not predict sprint performances. The between-group analysis of the athletes showed a nonsignificant group difference with respect to the jump variables. However, planned comparisons between sprinters and throwers showed significant differences in a number of SLJ variables. When constructing training programs for sprinters, the aim should be to improve CMJ PF and CMJ height because of the prediction of Vmax10-m and 60-m time, presumably because of velocity specificity components.

  12. Peak power, force, and velocity during jump squats in professional rugby players.

    PubMed

    Turner, Anthony P; Unholz, Cedric N; Potts, Neill; Coleman, Simon G S

    2012-06-01

    Training at the optimal load for peak power output (PPO) has been proposed as a method for enhancing power output, although others argue that the force, velocity, and PPO are of interest across the full range of loads. The aim of this study was to examine the influence of load on PPO, peak barbell velocity (BV), and peak vertical ground reaction force (VGRF) during the jump squat (JS) in a group of professional rugby players. Eleven male professional rugby players (age, 26 ± 3 years; height, 1.83 ± 6.12 m; mass, 97.3 ± 11.6 kg) performed loaded JS at loads of 20-100% of 1 repetition maximum (1RM) JS. A force plate and linear position transducer, with a mechanical braking unit, were used to measure PPO, VGRF, and BV. Load had very large significant effects on PPO (p < 0.001, partial η² = 0.915); peak VGRF (p < 0.001, partial η² = 0.854); and peak BV (p < 0.001, partial η² = 0.973). The PPO and peak BV were the highest at 20% 1RM, though PPO was not significantly greater than that at 30% 1RM. The peak VGRF was significantly greater at 1RM than all other loads, with no significant difference between 20 and 60% 1RM. In resistance trained professional rugby players, the optimal load for eliciting PPO during the loaded JS in the range measured occurs at 20% 1RM JS, with decreases in PPO and BV, and increases in VGRF, as the load is increased, although greater PPO likely occurs without any additional load.

  13. Leg and calf press training modes and their impact on jump performance adaptations.

    PubMed

    Caruso, John F; Coday, Michael A; Ramsey, Charles A; Griswold, Shawn H; Polanski, David W; Drummond, Jan L; Walker, Ron H

    2008-05-01

    To examine the effects of resistance exercise (REX) mode on jump performance, subjects were assigned to one of three groups over a 6-week period with no cross-over. Subjects were assigned to leg and calf press REX on either a standard (n = 10) or ergometer (n = 9) device while a third group (n = 9) served as controls (CTRL). REX subjects worked out twice per week, which consisted of a three-set, 10-repetition paradigm for leg and calf press exercises. Immediately before and after the 6-week period, subjects performed tests that assessed jump (standing vertical jump, four-jump test protocol, depth jump) ability, while a fourth estimated knee extensor fast-twitch percentage (FT%) from fatigue incurred through a 50-repetition isokinetic protocol. Data analyses utilized 3 x 2 (group x time) repeated-measures ANCOVAs. Several dependent variables showed effects by group (standard REX, ergometer REX > CTRL) and time (post > pre). An interaction occurred for explosive leg power factor, a four-jump test variable, with standard REX post-test values as the interaction source. A trend for an interaction occurred for depth jump hang time, as ergometer REX values improved over time. Results suggest that mode-specific adaptations occur with REX training. Thus, athletes are best served with the selection of a REX device that is most specific to the demands of their jump performance task.

  14. Functional knee brace use effect on peak vertical ground reaction forces during drop jump landing.

    PubMed

    Rishiraj, Neetu; Taunton, Jack E; Lloyd-Smith, Robert; Regan, William; Niven, Brian; Woollard, Robert

    2012-12-01

    The aim of the study was to investigate the landing strategies used by non-injured athletes while wearing functional knee braces (FKB, BR condition) during a drop jump task compared with non-injured, non-braced (NBR condition) subjects and also to ascertain whether accommodation to a FKB was possible by non-injured BR subjects. Twenty-three healthy male provincial and national basketball and field hockey athletes (age, 19.4 ± 3.0 years) were tested. Each subject was provided with a custom-fitted FKB. Five NBR testing sessions were performed over 3 days followed by five BR testing sessions also over 3 days, for a total of 17.5 h of testing per condition. Each subject performed eight trials of the drop jump task during each testing session per condition. Single-leg peak vertical ground reaction forces (PVGRF) and the time to PVGRF were recorded for each NBR and BR trail. The BR group mean PVGRF at landing was significantly lower (1,628 ± 405 N, 2.1 ± 0.5 BW versus 1,715 ± 403 N, 2.2 ± 0.5 BW, F (1,22) = 6.83, P = 0.01) compared with NBR subjects, respectively. The group mean time to PVGRF was not statistically longer during the BR condition (F (1,22) = 0.967, P = 0.3). Further, an accommodation trend was noted as percent performance difference decreased with continued FKB use. The significantly lower group mean PVGRF while using a FKB could keep traumatic forces from reaching the ACL until the active neuromuscular restraints are activated to provide protection to the knee joint ligaments. Also, accommodation to FKB is possible after approximately 14.0 h of brace use. The results of this paper will assist clinicians in providing information to their patients regarding a FKB ability to offer protection to an ACL-deficient knee or to address concerns about early muscle fatigue, energy expenditure, heart rate, and decrease in performance level. Prospective study, Level I.

  15. Mode-independent robust stabilization for uncertain Markovian jump nonlinear systems via fuzzy control.

    PubMed

    Wu, Huai-Ning; Cai, Kai-Yuan

    2006-06-01

    This paper is concerned with the robust-stabilization problem of uncertain Markovian jump nonlinear systems (MJNSs) without mode observations via a fuzzy-control approach. The Takagi and Sugeno (T-S) fuzzy model is employed to represent a nonlinear system with norm-bounded parameter uncertainties and Markovian jump parameters. The aim is to design a mode-independent fuzzy controller such that the closed-loop Markovian jump fuzzy system (MJFS) is robustly stochastically stable. Based on a stochastic Lyapunov function, a robust-stabilization condition using a mode-independent fuzzy controller is derived for the uncertain MJFS in terms of linear matrix inequalities (LMIs). A new improved LMI formulation is used to alleviate the interrelation between the stochastic Lyapunov matrix and the system matrices containing controller variables in the derivation process. Finally, a simulation example is presented to illustrate the effectiveness of the proposed design method.

  16. Peaked density profile circular limiter H-modes on TFTR

    SciTech Connect

    Bush, C.E. ); Goldston, R.J.; Scott, S.D.; Fredrickson, E.D.; McGuire, K.; Schivell, J.; Taylor, G.; Bell, M.G.; Boivin, R.L.; Bretz, N.; Cavallo, A.; Efthimion, P.C.; Grek, B.; Hawryluk, R.; Hill, K.; Hulse, R.A.; Janos, A.; Johnson, D.W.; Kilpatrick, S.; Manos, D.M.; Mansfield, D.K.; Meade, D.M.; Park, H.; Ramsey, A.T.; Stratton, B.; Synakowski, E.J.; Towner, H.H.; Wieland, R.M.; Zarnstor

    1990-06-01

    Circular limiter H-modes are obtained on TFTR during high power neutral beam heating. The transition is usually from the supershot to the H-mode rather than the usual L- to H- transition, and thus is obtained in a low recycling environment with core fueling mainly from the heating beams. As a result, the density and pressure profiles are highly peaked at the center. Global confinement time, {tau}{sub E}, is enhanced over L-mode scaling by up to {approx} 2.5 times. The onset of ELMs shortly after the H-mode transition appears to limit {tau}{sub E}. Limiter H-modes of up to 1.5 sec duration have been realized. 18 refs., 4 figs.

  17. The effect of gender and fatigue on the biomechanics of bilateral landings from a jump: peak values.

    PubMed

    Pappas, Evangelos; Sheikhzadeh, Ali; Hagins, Marshall; Nordin, Margareta

    2007-01-01

    Female athletes are substantially more susceptible than males to suffer acute non-contact anterior cruciate ligament injury. A limited number of studies have identified possible biomechanical risk factors that differ between genders. The effect of fatigue on the biomechanics of landing has also been inadequately investigated. The objective of the study was to examine the effect of gender and fatigue on peak values of biomechanical variables during landing from a jump. Thirty-two recreational athletes performed bilateral drop jump landings from a 40 cm platform. Kinetic, kinematic and electromyographic data were collected before and after a functional fatigue protocol. Females landed with 9° greater peak knee valgus (p = 0.001) and 140% greater maximum vertical ground reaction forces (p = 0.003) normalized to body weight compared to males. Fatigue increased peak foot abduction by 1.7° (p = 0.042), peak rectus femoris activity by 27% (p = 0.018), and peak vertical ground reaction force (p = 0.038) by 20%. The results of the study suggest that landing with increased peak knee valgus and vertical ground reaction force may contribute to increased risk for knee injury in females. Fatigue caused significant but small changes on some biomechanical variables. Anterior cruciate ligament injury prevention programs should focus on implementing strategies to effectively teach females to control knee valgus and ground reaction force. Key pointsFemale athletes landed with increased knee valgus and VGRF which may predispose them to ACL injury.Fatigue elicited a similar response in male and female athletes.The effectiveness of sports injury prevention programs may improve by focusing on teaching females to land softer and with less knee valgus.

  18. Dynamic analysis of modal shifting and mode jumping in thermally buckled plates

    NASA Astrophysics Data System (ADS)

    Chen, H.; Virgin, L. N.

    2004-11-01

    Both analytical and finite element investigations are performed for the various static and dynamic aspects of the mode jumping phenomenon of a simply-supported rectangular plate heated deeply into the post-buckling regime. For the analytical method, the von Kármán plate equation is reduced to a system of non-linear ODEs by expressing the transverse deflection as a series of linear buckling modes. The ODEs, combined with the non-linear algebraic constraint equations obtained from in-plane boundary conditions, are then solved numerically under the parametric variation of the temperature. The results are checked by the finite element method, where a hybrid static-dynamic scheme is implemented. The contribution of each assumed (buckling) mode component is studied systematically. Characterized by the strong geometrical non-linearity, the secondary bifurcation point of the thermally loaded plate with fixed in-plane boundary conditions occurs far beyond the primary buckling point, and the jump behavior cannot be predicted correctly without sufficient assumed modes. Stationary bifurcation analysis indicates that while the post-buckling deflection before mode jumping is composed of pure symmetric modes, additional pure antisymmetric modes will appear after the occurrence of the snapping and they play the role of destabilizing the equilibrium. Furthermore, by monitoring natural frequencies and modal shapes, we find that a mode shifting phenomenon (the exchanging of vibration modes) exists in the primary post-buckling regime. Breaking of the symmetry of the dynamic modes is also found. By introducing a linear temperature sweeping scheme, transient analysis is performed to capture the snapping phenomenon dynamically, which occurs with moderate heating ratio. Comparison between the analytic and finite element results shows good agreement.

  19. Dropout dynamics in pulsed quantum dot lasers due to mode jumping

    SciTech Connect

    Sokolovskii, G. S.; Dudelev, V. V.; Deryagin, A. G.; Novikov, I. I.; Maximov, M. V.; Ustinov, V. M.; Kuchinskii, V. I.; Viktorov, E. A.; Abusaa, M.; Danckaert, J.; Kolykhalova, E. D.; Soboleva, K. K.; Zhukov, A. E.; Sibbett, W.; Rafailov, E. U.; Erneux, T.

    2015-06-29

    We examine the response of a pulse pumped quantum dot laser both experimentally and numerically. As the maximum of the pump pulse comes closer to the excited-state threshold, the output pulse shape becomes unstable and leads to dropouts. We conjecture that these instabilities result from an increase of the linewidth enhancement factor α as the pump parameter comes close to the excitated state threshold. In order to analyze the dynamical mechanism of the dropout, we consider two cases for which the laser exhibits either a jump to a different single mode or a jump to fast intensity oscillations. The origin of these two instabilities is clarified by a combined analytical and numerical bifurcation diagram of the steady state intensity modes.

  20. Mode Jumping of an Isogrid Panel Under Quasi-Static Compression

    NASA Technical Reports Server (NTRS)

    Muheim, Danniella M.; Johnson, Eric R.

    2003-01-01

    A wide column test of a composite isogrid panel subjected to quasi-static, axial compression is modeled with a hybrid-static dynamic computational method. The data from the test panel exhibited discontinuous responses in the compressive load for slowly increased end-shortening. The computational model was developed to corroborate these discontinuities with the phenomenon of mode jumping. Mode jumping refers to the transient response of the panel from an unstable bifurcation point on a postbuckled equilibrium path to a second stable equilibrium state on a new equilibrium path. On the new equilibrium path, both the analysis and test show that the panel can resist increased endshortening beyond that of the unstable critical point. Fair agreement is achieved between the analysis and test.

  1. Minimizing tip-sample forces in jumping mode atomic force microscopy in liquid.

    PubMed

    Ortega-Esteban, A; Horcas, I; Hernando-Pérez, M; Ares, P; Pérez-Berná, A J; San Martín, C; Carrascosa, J L; de Pablo, P J; Gómez-Herrero, J

    2012-03-01

    Control and minimization of tip-sample interaction forces are imperative tasks to maximize the performance of atomic force microscopy. In particular, when imaging soft biological matter in liquids, the cantilever dragging force prevents identification of the tip-sample mechanical contact, resulting in deleterious interaction with the specimen. In this work we present an improved jumping mode procedure that allows detecting the tip-sample contact with high accuracy, thus minimizing the scanning forces (-100 pN) during the approach cycles. To illustrate this method we report images of human adenovirus and T7 bacteriophage particles which are prone to uncontrolled modifications when using conventional jumping mode. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Transit time instabilities in an inverted fireball. II. Mode jumping and nonlinearities

    SciTech Connect

    Stenzel, R. L.; Gruenwald, J.; Fonda, B.; Ionita, C.; Schrittwieser, R.

    2011-01-15

    A fireball is formed inside a highly transparent spherical grid immersed in a dc discharge plasma. The ambient plasma acts as a cathode and the positively biased grid as an anode. A strong nearly current-free double layer separates the two plasmas. Electrons are accelerated into the fireball, ionize, and establish a discharge plasma with plasma potential near the grid potential. Ions are ejected from the fireball. Since electrons are lost at the same rate as ions, most electrons accelerated into the fireball just pass through it. Thus, the electron distribution contains radially counterstreaming electrons. High-frequency oscillations are excited with rf period given by the electron transit time through the fireball. Since the frequency is well below the electron plasma frequency, no eigenmodes other than a beam space-charge wave exists. The instability is an inertial transit-time instability similar to the sheath-plasma instability or the reflex vircator instability. In contrast to vircators, there is no electron reflection from a space-charge layer but counterstreaming arises from spherical convergence and divergence of electrons. While the basic instability properties have been presented in a companion paper [R. L. Stenzel et al., Phys. Plasmas 18, 012104 (2011)], the present paper focuses on observed mode jumping and nonlinear effects. The former produce frequency jumps and different potential profiles, the latter produce harmonics associated with electron bunching at large amplitudes. In situ probe measurements are presented and interpreted.

  3. Nonlinear mode interactions and frequency-jump effects in a doubly tuned oscillator configuration

    NASA Astrophysics Data System (ADS)

    Grun, J.; Lashinsky, H.

    1980-05-01

    Frequency-jump effects associated with nonlinear mode competition are investigated in an oscillator configuration consisting of a passive linear resonance system coupled to an active nonlinear resonance system. These effects give rise to a hysteresis pattern whose height and width can be related to system parameters such as the resonance frequencies, dissipation, coupling coefficient, etc. It is noted that these effects offer a novel means of determining these parameters in cases in which conventional techniques may not be desirable or as advantageous. The analysis provides an qualitative explanation of empirical observations in a recent nuclear magnetic resonance experiment (Timsit and Daniels, 1976). The results also apply to other nonlinear resonance systems such as lasers, microwave generators, and electronic oscillators.

  4. Mode jumping of split-ring resonator metamaterials controlled by high-permittivity BST and incident electric fields

    NASA Astrophysics Data System (ADS)

    Fu, Xiaojian; Zeng, Xinxi; Cui, Tie Jun; Lan, Chuwen; Guo, Yunsheng; Zhang, Hao Chi; Zhang, Qian

    2016-08-01

    We investigate the resonant modes of split-ring resonator (SRR) metamaterials that contain high-permittivity BST block numerically and experimentally. We observe interesting mode-jumping phenomena from the BST-included SRR absorber structure as the excitation wave is incident perpendicularly to the SRR plane. Specifically, when the electric field is parallel to the SRR gap, the BST block in the gap will induce a mode jumping from the LC resonance to plasmonic resonance (horizontal electric-dipole mode), because the displacement current excited by the Mie resonance in the dielectric block acts as a current channel in the gap. When the electric field is perpendicular to the gap side, the plasmonic resonance mode (vertical electric-dipole mode) in SRR changes to two joint modes contributed simultaneously by the back layer, SRR and BST block, as a result of connected back layer and SRR layer by the displacement current in the BST dielectric block. Based on the mode jumping effect as well as temperature and electric-field dependent dielectric constant, the BST-included SRR metamaterials may have great potentials for the applications in electromagnetic switches and widely tunable metamaterial devices.

  5. Mode jumping of split-ring resonator metamaterials controlled by high-permittivity BST and incident electric fields

    PubMed Central

    Fu, Xiaojian; Zeng, Xinxi; Cui, Tie Jun; Lan, Chuwen; Guo, Yunsheng; Zhang, Hao Chi; Zhang, Qian

    2016-01-01

    We investigate the resonant modes of split-ring resonator (SRR) metamaterials that contain high-permittivity BST block numerically and experimentally. We observe interesting mode-jumping phenomena from the BST-included SRR absorber structure as the excitation wave is incident perpendicularly to the SRR plane. Specifically, when the electric field is parallel to the SRR gap, the BST block in the gap will induce a mode jumping from the LC resonance to plasmonic resonance (horizontal electric-dipole mode), because the displacement current excited by the Mie resonance in the dielectric block acts as a current channel in the gap. When the electric field is perpendicular to the gap side, the plasmonic resonance mode (vertical electric-dipole mode) in SRR changes to two joint modes contributed simultaneously by the back layer, SRR and BST block, as a result of connected back layer and SRR layer by the displacement current in the BST dielectric block. Based on the mode jumping effect as well as temperature and electric-field dependent dielectric constant, the BST-included SRR metamaterials may have great potentials for the applications in electromagnetic switches and widely tunable metamaterial devices. PMID:27502844

  6. Frequency jump phenomena of e-fishbone mode during high-power ECRH on HL-2A

    NASA Astrophysics Data System (ADS)

    Yu, L. M.; Ding, X. T.; Chen, W.; Chen, S. Y.; Dong, Y. B.; Ji, X. Q.; Zhang, Y. P.; Shi, Z. B.; Liu, Yi.; Li, J. X.; Li, Y. G.; Zhou, Y.; Huang, Y.; Zhou, J.; Huan, M.; Rao, J.; Cao, J. Y.; Lei, G. J.; Zhong, W. L.; Cui, Z. Y.; Dong, J. Q.; Yang, Q. W.; Duan, X. R.; the HL-2A Team

    2013-05-01

    Fishbone instability excited by energetic electrons during electron cyclotron resonant heating (ECRH) is identified on HL-2A. With high-power ECRH, periodic frequency jump phenomena are observed by soft x-ray arrays. Soft x-ray tomography shows that the poloidal and toroidal mode numbers are 1/1 and 2/2 with the frequency jump. There is an ECRH power threshold for the frequency jump phenomena, which is generally about 0.9 MW. The frequencies of the two modes increase with the ECRH power. Experiments show that trapped particles are dominant in the low-density high-power ECRH plasma. The precessional frequency of the energetic trapped electrons is calculated with different discharge parameters. The results indicate that the energy of resonant electrons is in agreement with the hard x-ray measurement.

  7. Water-Based Concurrent Training Improves Peak Oxygen Uptake, Rate of Force Development, Jump Height, and Neuromuscular Economy in Young Women.

    PubMed

    Pinto, Stephanie S; Alberton, Cristine L; Cadore, Eduardo L; Zaffari, Paula; Baroni, Bruno M; Lanferdini, Fábio J; Radaelli, Régis; Pantoja, Patrícia D; Peyré-Tartaruga, Leonardo A; Wolf Schoenell, Maira C; Vaz, Marco A; Kruel, Luiz F M

    2015-07-01

    The study investigated the effects of different intrasession exercise sequences on the cardiorespiratory and neuromuscular adaptations induced by water-based concurrent training in young subjects. Twenty-six healthy young women (25.1 ± 2.9 years) were placed into 2 water-based concurrent training groups: resistance before (RA, n = 13) or after (AR, n = 13) aerobic training. Subjects trained resistance and aerobic training during 12 weeks, 2 times per week performing both exercise types in the same training session. Peak oxygen uptake (V[Combining Dot Above]O2peak), rate of force development (RFD) obtained during an isometric peak torque knee extension protocol, jump height, and neuromuscular economy (normalized electromyography at 80% of pretraining knee extension isometric peak torque) in young women were determined. After training, there was a significant increase (p < 0.001) in both RA and AR in the V[Combining Dot Above]O2peak, with no differences between groups (7 vs. 5%). The maximal isometric knee extension RFD showed significant increases (p = 0.003) after training (RA: 19 vs. AR: 30%), and both groups presented similar gains. In addition, the countermovement jump height also increased (p = 0.034) after training (RA: 5% vs. AR: 6%), with no difference between groups. After training, there were significant improvements on vastus lateralis (p < 0.001) (RA: -13% vs. AR: -20%) and rectus femoris (p = 0.025) (RA: -17% vs. AR: -7%) neuromuscular economy, with no difference between groups. In conclusion, 12 weeks of water-based concurrent training improved the peak oxygen uptake, RFD, jump height, and neuromuscular economy in young women independent from the intrasession exercise sequence.

  8. Frequency synchronization of Fourier domain harmonically mode locked fiber laser by monitoring the supermode noise peaks.

    PubMed

    Li, Feng; Zhang, Aiqin; Feng, Xinhuan; Wai, P K A

    2013-12-16

    In a harmonically mode locked laser, the supermode noise peaks in the RF spectrum can be observed directly because they are separated from the driving frequency and its harmonics of the active mode locker. Using a simple theoretical model, we showed that the intensities of the supermode noise peaks will decrease if the coherence of the laser output decreases. We harmonically mode locked a Fourier domain mode locked (FDML) fiber laser to the third order. We observed that the supermode noise peak intensities decrease significantly when the detune between the sweeping frequency of the tunable filter and the cavity resonant frequency increases. It is therefore possible to use the supermode noise peaks to monitor the frequency detune of the tunable filter for auto-calibration of FDML fiber lasers.

  9. Electron heating and the potential jump across fast mode shocks. [in interplanetary space

    NASA Technical Reports Server (NTRS)

    Schwartz, Steven J.; Thomsen, Michelle F.; Bame, S. J.; Stansberry, John

    1988-01-01

    Two different methods were applied to determine the cross-shock potential jump in the de Hoffmann-Teller reference frame, using a data set that represented 66 crossings of the terrestrial bow shock and 14 interplanetary shocks observed by various ISEE spacecraft, and one crossing each of the Jovian bow shock and the Uranian bow shock made by the Voyager spacecraft. Results for estimates of the electrostatic potential based on an estimate of the jump in electron enthalpy correlated well with estimates based on Liouville's theorem, although the Liouville-determined values were systematically the higher of the two, suggesting that significant irreversible processes contribute to the shape of the downstream distribution. The potential jump corresponds to approximately 12-15 percent of the incident ion ram kinetic energy, and was found not to be controlled by the Mach number, plasma beta, shock geometry, or electron to ion temperature ratios.

  10. Electron heating and the potential jump across fast mode shocks. [in interplanetary space

    NASA Technical Reports Server (NTRS)

    Schwartz, Steven J.; Thomsen, Michelle F.; Bame, S. J.; Stansberry, John

    1988-01-01

    Two different methods were applied to determine the cross-shock potential jump in the de Hoffmann-Teller reference frame, using a data set that represented 66 crossings of the terrestrial bow shock and 14 interplanetary shocks observed by various ISEE spacecraft, and one crossing each of the Jovian bow shock and the Uranian bow shock made by the Voyager spacecraft. Results for estimates of the electrostatic potential based on an estimate of the jump in electron enthalpy correlated well with estimates based on Liouville's theorem, although the Liouville-determined values were systematically the higher of the two, suggesting that significant irreversible processes contribute to the shape of the downstream distribution. The potential jump corresponds to approximately 12-15 percent of the incident ion ram kinetic energy, and was found not to be controlled by the Mach number, plasma beta, shock geometry, or electron to ion temperature ratios.

  11. When does jumping-to-conclusions reach its peak? The interaction of vulnerability and situation-characteristics in social reasoning.

    PubMed

    Lincoln, Tania M; Salzmann, Stefan; Ziegler, Michael; Westermann, Stefan

    2011-06-01

    Persons with delusions tend to display a jumping-to-conclusions (JTC) bias which is considered relevant to delusion formation. However, its contribution in real life social scenarios is unknown. This study investigates whether JTC increases when decisions have to be made in delusion-relevant situations and whether the increase is uniquely moderated by delusion-proneness. JTC was assessed by a social reasoning paradigm in 92 healthy participants that were classified as high, medium or low in paranoid ideation and social anxiety. Decisions had to be made for emotionally salient scenarios without direct self-relevance, self-relevant scenarios and delusion-relevant scenarios, by successively drawing pieces of information. All participants drew less information in the scenarios that were self-relevant and delusion-relevant compared to non-self-relevant scenarios. Participants with higher paranoid ideation generally drew less information than persons with medium or low levels of paranoid ideation. However, the hypothesized interaction of delusion-proneness and type of scenario was not significant. Social anxiety had no effect on draws to decision in any of the task types. The description of social encounters in the task does still not capture the full perceptual experience in real life encounters. The data support the assumption that the formation of persecutory delusions might arise as a function of a delusion-specific JTC-bias in combination with a normal and functional tendency to collect less information in self-relevant situations. Copyright © 2010 Elsevier Ltd. All rights reserved.

  12. Stability of the n{=}1 Internal Kink Mode in Plasmas with Centrally Peaked Pressure

    NASA Astrophysics Data System (ADS)

    Ozeki, Takahisa; Azumi, Masafumi

    1990-12-01

    The stability of the n{=}1 internal kink mode in a tokamak is numerically analyzed for plasmas with a centrally peaked pressure profile. The effect of pressure profile is studied by the comparison of a strongly peaked pressure inside the q{=}1 surface with a parabolic pressure profile. The effects of shaping, i.e., elongation and triangularity, are also studied for the both pressure profiles. The plasma with the strongly peaked pressure profile has higher limiting value of poloidal beta defined within the q{=}1 surface than that of the parabolic pressure profile. Though the beta limit reduces with the increase of the elongation, the plasma with the peaked pressure profile has larger improvement due to the triangularity than that with the parabolic pressure profile. However, to enter the second stability region of the n{=}1 internal kink mode, the plasma with a flat pressure profile and the large minor radius of the q{=}1 surface is effective.

  13. Coherent Enhancement of 10 s Burst-Mode Ultraviolet Pulses at Megawatt Peak Power

    SciTech Connect

    Abudureyimu, Reheman; Liu, Yun

    2017-01-01

    A doubly-resonant optical cavity and its locking technique have been developed to achieve coherent enhancement of 402.5-MHz, 50-ps, megawatt peak power ultraviolet (355 nm) laser pulses operating at a 10- s/10-Hz burst mode.

  14. Direct link between boson-peak modes and dielectric α -relaxation in glasses

    NASA Astrophysics Data System (ADS)

    Cui, Bingyu; Milkus, Rico; Zaccone, Alessio

    2017-02-01

    We compute the dielectric response of glasses starting from a microscopic system-bath Hamiltonian of the Zwanzig-Caldeira-Leggett type and using an ansatz from kinetic theory for the memory function in the resulting generalized Langevin equation. The resulting framework requires the knowledge of the vibrational density of states (DOS) as input, which we take from numerical evaluation of a marginally stable harmonic disordered lattice, featuring a strong boson peak (excess of soft modes over Debye ˜ωp2 law). The dielectric function calculated based on this ansatz is compared with experimental data for the paradigmatic case of glycerol at T ≲Tg . Good agreement is found for both the reactive (real) part of the response and for the α -relaxation peak in the imaginary part, with a significant improvement over earlier theoretical approaches. On the low-frequency side of the α peak, the fitting supports the presence of ˜ωp4 modes at vanishing eigenfrequency as recently shown [E. Lerner, G. During, and E. Bouchbinder, Phys. Rev. Lett. 117, 035501 (2016), 10.1103/PhysRevLett.117.035501]. α -wing asymmetry and stretched-exponential behavior are recovered by our framework, which shows that these features are, to a large extent, caused by the soft boson-peak modes in the DOS.

  15. Gyrokinetic modeling of impurity peaking in JET H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Manas, P.; Camenen, Y.; Benkadda, S.; Weisen, H.; Angioni, C.; Casson, F. J.; Giroud, C.; Gelfusa, M.; Maslov, M.

    2017-06-01

    Quantitative comparisons are presented between gyrokinetic simulations and experimental values of the carbon impurity peaking factor in a database of JET H-modes during the carbon wall era. These plasmas feature strong NBI heating and hence high values of toroidal rotation and corresponding gradient. Furthermore, the carbon profiles present particularly interesting shapes for fusion devices, i.e., hollow in the core and peaked near the edge. Dependencies of the experimental carbon peaking factor ( R / L nC ) on plasma parameters are investigated via multilinear regressions. A marked correlation between R / L nC and the normalised toroidal rotation gradient is observed in the core, which suggests an important role of the rotation in establishing hollow carbon profiles. The carbon peaking factor is then computed with the gyrokinetic code GKW, using a quasi-linear approach, supported by a few non-linear simulations. The comparison of the quasi-linear predictions to the experimental values at mid-radius reveals two main regimes. At low normalised collisionality, ν * , and T e / T i < 1 , the gyrokinetic simulations quantitatively recover experimental carbon density profiles, provided that rotodiffusion is taken into account. In contrast, at higher ν * and T e / T i > 1 , the very hollow experimental carbon density profiles are never predicted by the simulations and the carbon density peaking is systematically over estimated. This points to a possible missing ingredient in this regime.

  16. Mode shape analysis using a commercially available peak store video frame buffer

    NASA Technical Reports Server (NTRS)

    Snow, Walter L.; Childers, Brooks A.

    1994-01-01

    Time exposure photography, sometimes coupled with strobe illumination, is an accepted method for motion analysis that bypasses frame by frame analysis and resynthesis of data. Garden variety video cameras can now exploit this technique using a unique frame buffer that is a non-integrating memory that compares incoming data with that already stored. The device continuously outputs an analog video signal of the stored contents which can then be redigitized and analyzed using conventional equipment. Historically, photographic time exposures have been used to record the displacement envelope of harmonically oscillating structures to show mode shape. Mode shape analysis is crucial, for example, in aeroelastic testing of wind tunnel models. Aerodynamic, inertial, and elastic forces can couple together leading to catastrophic failure of a poorly designed aircraft. This paper will explore the usefulness of the peak store device as a videometric tool and in particular discuss methods for analyzing a targeted vibrating plate using the 'peak store' in conjunction with calibration methods familiar to the close-range videometry community. Results for the first three normal modes will be presented.

  17. Dynamics and stabilization of peak current-mode controlled buck converter with constant current load

    NASA Astrophysics Data System (ADS)

    Leng, Min-Rui; Zhou, Guo-Hua; Zhang, Kai-Tun; Li, Zhen-Hua

    2015-10-01

    The discrete iterative map model of peak current-mode controlled buck converter with constant current load (CCL), containing the output voltage feedback and ramp compensation, is established in this paper. Based on this model the complex dynamics of this converter is investigated by analyzing bifurcation diagrams and the Lyapunov exponent spectrum. The effects of ramp compensation and output voltage feedback on the stability of the converter are investigated. Experimental results verify the simulation and theoretical analysis. The stability boundary and chaos boundary are obtained under the theoretical conditions of period-doubling bifurcation and border collision. It is found that there are four operation regions in the peak current-mode controlled buck converter with CCL due to period-doubling bifurcation and border-collision bifurcation. Research results indicate that ramp compensation can extend the stable operation range and transfer the operating mode, and output voltage feedback can eventually eliminate the coexisting fast-slow scale instability. Project supported by the National Natural Science Foundation of China (Grant No. 61371033), the Fok Ying-Tung Education Foundation for Young Teachers in the Higher Education Institutions of China (Grant No. 142027), the Sichuan Provincial Youth Science and Technology Fund, China (Grant Nos. 2014JQ0015 and 2013JQ0033), and the Fundamental Research Funds for the Central Universities, China (Grant No. SWJTU11CX029).

  18. Single-mode single-frequency high peak power all-fiber MOPA at 1550 nm

    NASA Astrophysics Data System (ADS)

    Kotov, L. V.; Likhachev, M. E.; Bubnov, M. M.; Paramonov, V. M.; Belovolov, M. I.; Lipatov, D. S.; Guryanov, A. N.

    2014-10-01

    In this Report, we present a record-high-peak-power single-frequency master oscillator power amplifier (MOPA) system based on a newly developed double-clad large-mode-area Yb-free Er-doped fiber (DC-LMA-EDF). A fiber Bragg grating wavelength-stabilized fiber-coupled diode laser at λ=1551 nm with ~2 MHz spectral width was used as the master oscillator. Its radiation was externally modulated with a 5 kHz repetition rate and 92 ns pulse duration and then amplified in a core-pumped Er-doped fiber amplifier up to an average power of 4 mW. The amplified spontaneous emission (ASE) generated at the last preamplifier stage was suppressed by a narrow-band (0.7 nm) DWDM filter. The last MOPA stage was based on the recently developed single-mode DC-LMA-EDF with a mode field diameter of 25 microns and pump clad-absorption of 3 dB/m at λ=980 nm. The pump and the signal were launched into this fiber through a commercial pump combiner in a co-propagating amplifier scheme. At first, we used a 3-m long DC-LMAEDF. In such configuration, a peak power of 800 W was achieved at the output of the amplifier together with a ~ 12 % pump conversion slope efficiency. Further power scaling was limited by SBS. After that we shortened the fiber length to 1 m. As a result, owing to large unabsorbed pump power, the efficiency decreased to ~5 %. However, a peak power of more than 3.5 kW was obtained before the SBS threshold. In this case, the pulse shape changed and its duration decreased to ~60 ns owing to inversion depletion after propagation of the forward front of the pulse. To the best of our knowledge, the peak power of more than 3.5 kW reported here is the highest value ever published for a single-frequency single-mode silica-based fiber laser system operating near λ=1550 nm.

  19. Osteological postcranial traits in hylid anurans indicate a morphological continuum between swimming and jumping locomotor modes.

    PubMed

    Soliz, Mónica; Tulli, Maria J; Abdala, Virginia

    2017-03-01

    Anurans exhibit a particularly wide range of locomotor modes that result in wide variations in their skeletal structure. This article investigates the possible correlation between morphological aspects of the hylid postcranial skeleton and their different locomotor modes and habitat use. To do so, we analyzed 18 morphometric postcranial variables in 19 different anuran species representative of a variety of locomotor modes (jumper, hopper, walker, and swimmer) and habitat uses (arboreal, bush, terrestrial, and aquatic). Our results show that the evolution of the postcranial hylid skeleton cannot be explained by one single model, as for example, the girdles suggest modular evolution while the vertebral column suggests other evolutionary modules. In conjunction with data from several other studies, we were able to show a relationship between hylid morphology and habitat use; offering further evidence that the jumper/swimmer and walker/hopper locomotor modes exhibit quite similar morphological architecture. This allowed us to infer that new locomotor modalities are, in fact, generated along a morphological continuum. J. Morphol. 278:403-417, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  20. Effects of carbon dioxide on peak mode isotachophoresis: simultaneous preconcentration and separation.

    PubMed

    Khurana, Tarun K; Santiago, Juan G

    2009-05-21

    We present a method that achieves simultaneous preconcentration and separation of analytes using peak-mode isotachophoresis with a single step injection in simple, off-the-shelf microchannels or capillaries. We leverage ions resulting from dissolved atmospheric carbon dioxide to weakly disrupt isotachophoretic preconcentration and induce separation of analyte species. We experimentally study the region between the leading and trailing electrolytes, and individually identify the carbonate and carbamate zones that result from the hydration and carbamation reaction of dissolved atmospheric carbon dioxide, respectively. The width of these zones and the gradient regions between them grow with time and create an electric field gradient that causes analytes to separate. Using this assay, we achieve focusing and separation of a 25 bp DNA ladder in a straight, 34 microm wide microchannel in a single loading step. As a demonstration of the fractionation capabilities of the assay, we show simultaneous preconcentration and separation of a DNA ladder from two proteins, GFP and allophycocyanin.

  1. Boson peak in supercooled liquids: Time domain observations and mode coupling theory

    NASA Astrophysics Data System (ADS)

    Cang, Hu; Li, Jie; Andersen, Hans C.; Fayer, M. D.

    2005-08-01

    Optical heterodyne-detected optical Kerr effect (OHD-OKE) experiments are presented for the supercooled liquid acetylsalicylic acid (aspirin - ASP). The ASP data and previously published OHD-OKE data on supercooled dibutylphthalate (DBP) display highly damped oscillations with a periods of ˜2ps as the temperature is reduced to and below the mode coupling theory (MCT) temperature TC. The oscillations become more pronounced below TC. The oscillations can be interpreted as the time domain signature of the boson peak. Recently a schematic MCT model, the Sjögren model, was used to describe the OHD-OKE data for a number of supercooled liquids by Götze and Sperl [W. Götze and M. Sperl, Phys. Rev. E 92, 105701 (2004)], but the short-time and low-temperature behaviors were not addressed. Franosch et al. [T. Franosch, W. Gotze, M. R. Mayr, and A. P. Singh, Phys. Rev. E 55, 3183 (1997)] found that the Sjögren model could describe the boson peak observed by depolarized light-scattering (DLS) experiments on glycerol. The OHD-OKE experiment measures a susceptibility that is a time domain equivalent of the spectrum measured in DLS. Here we present a detailed analysis of the ASP and DBP data over a broad range of times and temperatures using the Sjögren model. The MCT schematic model is able to describe the data very well at all temperatures and relevant time scales. The trajectory of MCT parameters that fit the high-temperature data (no short-time oscillations) when continued below TC results in calculations that reproduce the oscillations seen in the data. The results indicate that increasing translational-rotational coupling is responsible for the appearance of the boson peak as the temperature approaches and drops below TC.

  2. Bifurcation and chaos in high-frequency peak current mode Buck converter

    NASA Astrophysics Data System (ADS)

    Chang-Yuan, Chang; Xin, Zhao; Fan, Yang; Cheng-En, Wu

    2016-07-01

    Bifurcation and chaos in high-frequency peak current mode Buck converter working in continuous conduction mode (CCM) are studied in this paper. First of all, the two-dimensional discrete mapping model is established. Next, reference current at the period-doubling point and the border of inductor current are derived. Then, the bifurcation diagrams are drawn with the aid of MATLAB. Meanwhile, circuit simulations are executed with PSIM, and time domain waveforms as well as phase portraits in i L-v C plane are plotted with MATLAB on the basis of simulation data. After that, we construct the Jacobian matrix and analyze the stability of the system based on the roots of characteristic equations. Finally, the validity of theoretical analysis has been verified by circuit testing. The simulation and experimental results show that, with the increase of reference current I ref, the corresponding switching frequency f is approaching to low-frequency stage continuously when the period-doubling bifurcation happens, leading to the converter tending to be unstable. With the increase of f, the corresponding I ref decreases when the period-doubling bifurcation occurs, indicating the stable working range of the system becomes smaller. Project supported by the National Natural Science Foundation of China (Grant No. 61376029), the Fundamental Research Funds for the Central Universities, China, and the College Graduate Research and Innovation Program of Jiangsu Province, China (Grant No. SJLX15_0092).

  3. Real-time bilinear rotation decoupling in absorptive mode J-spectroscopy: Detecting low-intensity metabolite peak close to high-intensity metabolite peak with convenience

    NASA Astrophysics Data System (ADS)

    Verma, Ajay; Baishya, Bikash

    2016-05-01

    "Pure shift" NMR spectra display singlet peak per chemical site. Thus, high resolution is offered at the cost of valuable J-coupling information. In the present work, real-time BIRD (BIlinear Rotation Decoupling) is applied to the absorptive-mode 2D J-spectroscopy to provide pure shift spectrum in the direct dimension and J-coupling information in the indirect dimension. Quite often in metabolomics, proton NMR spectra from complex bio-fluids display tremendous signal overlap. Although conventional J-spectroscopy in principle overcomes this problem by separating the multiplet information from chemical shift information, however, only magnitude mode of the experiment is practical, sacrificing much of the potential high resolution that could be achieved. Few J-spectroscopy methods have been reported so far that produce high-resolution pure shift spectrum along with J-coupling information for crowded spectral regions. In the present work, high-quality J-resolved spectrum from important metabolomic mixture such as tissue extract from rat cortex is demonstrated. Many low-intensity metabolite peaks which are obscured by the broad dispersive tails from high-intensity metabolite peaks in regular magnitude mode J-spectrum can be clearly identified in real-time BIRD J-resolved spectrum. The general practice of removing such spectral overlap is tedious and time-consuming as it involves repeated sample preparation to change the pH of the tissue extract sample and subsequent spectra recording.

  4. Real-time bilinear rotation decoupling in absorptive mode J-spectroscopy: Detecting low-intensity metabolite peak close to high-intensity metabolite peak with convenience.

    PubMed

    Verma, Ajay; Baishya, Bikash

    2016-05-01

    "Pure shift" NMR spectra display singlet peak per chemical site. Thus, high resolution is offered at the cost of valuable J-coupling information. In the present work, real-time BIRD (BIlinear Rotation Decoupling) is applied to the absorptive-mode 2D J-spectroscopy to provide pure shift spectrum in the direct dimension and J-coupling information in the indirect dimension. Quite often in metabolomics, proton NMR spectra from complex bio-fluids display tremendous signal overlap. Although conventional J-spectroscopy in principle overcomes this problem by separating the multiplet information from chemical shift information, however, only magnitude mode of the experiment is practical, sacrificing much of the potential high resolution that could be achieved. Few J-spectroscopy methods have been reported so far that produce high-resolution pure shift spectrum along with J-coupling information for crowded spectral regions. In the present work, high-quality J-resolved spectrum from important metabolomic mixture such as tissue extract from rat cortex is demonstrated. Many low-intensity metabolite peaks which are obscured by the broad dispersive tails from high-intensity metabolite peaks in regular magnitude mode J-spectrum can be clearly identified in real-time BIRD J-resolved spectrum. The general practice of removing such spectral overlap is tedious and time-consuming as it involves repeated sample preparation to change the pH of the tissue extract sample and subsequent spectra recording.

  5. AFM in peak force mode applied to worn siloxane-hydrogel contact lenses.

    PubMed

    Abadías, Clara; Serés, Carme; Torrent-Burgués, Juan

    2015-04-01

    The objective of this work is to apply Atomic Force Microscopy in Peak Force mode to obtain topographic characteristics (mean roughness, root-mean-square roughness, skewness and kurtosis) and mechanical characteristics (adhesion, elastic modulus) of Siloxane-Hydrogel Soft Contact Lenses (CLs) of two different materials, Lotrafilcon B of Air Optix (AO) and Asmofilcon A of PremiO (P), after use (worn CLs). Thus, the results obtained with both materials will be compared, as well as the changes produced by the wear at a nanoscopic level. The results show significant changes in the topographic and mechanical characteristics of the CLs, at a nanoscopic level, due to wear. The AO CL show values of the topographic parameters lower than those of the P CL after wear, which correlates with a better comfort qualification given to the former by the wearers. A significant correlation has also been obtained between the adhesion values found after the use of the CLs with tear quality tests, both break-up-time and Schirmer.

  6. Influence of photo- and thermal bleaching on pre-irradiation low water peak single mode fibers

    NASA Astrophysics Data System (ADS)

    Yin, Jianchong; Wen, Jianxiang; Luo, Wenyun; Xiao, Zhongyin; Chen, Zhenyi; Wang, Tingyun

    2011-12-01

    Reducing the radiation-induced transmission loss in low water peak single mode fiber (LWP SMF) has been investigated by using photo-bleaching method with 980nm pump light source and using thermal-bleaching method with temperature control system. The results show that the radiation-induced loss of pre-irradiation optical fiber can be reduced effectively with the help of photo-bleaching or thermal-bleaching. Although the effort of photo-bleaching is not as significant as thermal-bleaching, by using photo-bleaching method, the loss of fiber caused by radiation-induced defects can be reduced best up to 49% at 1310nm and 28% at 1550nm in low pre-irradiation condition, the coating of the fiber are not destroyed, and the rehabilitating time is just several hours, while self-annealing usually costs months' time. What's more, the typical high power LASER for photo-bleaching can be 980nm pump Laser Diode, which is very accessible.

  7. AFM in mode Peak Force applied to the study of un-worn contact lenses.

    PubMed

    Torrent-Burgués, J; Sanz, F

    2014-09-01

    Contact lenses (CLs) are of common use and the biocompatibility, topography and mechanical properties of the used materials are of major importance. The objective of this contribution is to apply the AFM in mode Peak Force to obtain surface topography and mechanical characteristics of un-worn CLs of different materials. One material of hydrogel, two of siloxane-hydrogel and one of rigid gas-permeable were used in the study. The results obtained with different materials have been compared, at a nanoscopic level, and the conclusions are diverse. There is no significant influence of the two environments used to measure the characteristics of the CLs, either water or saline solution. The pHEMA hydrogel CL (Polymacon of Soflens) shows the highest values of roughness, adhesion and elastic modulus. The siloxane-hydrogel CL named Asmofilcon A of PremiO presents the lowest values of mean roughness (Ra), root-mean-square roughness (RMS or Rq), adhesion (Adh) and elastic modulus (Ym), meanwhile the siloxane-hydrogel CL named Lotrafilcon B of Air Optix presents the lowest value of skewness (Rsk) and the rigid gas-permeable CL, named RXD, presents the lowest values of kurtosis (Rku) and maximum roughness (Rmax).

  8. Multi-peak accumulation and coarse modes observed from AERONET retrieved aerosol volume size distribution in Beijing

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Li, Zhengqiang; Zhang, Yuhuan; Chen, Yu; Cuesta, Juan; Ma, Yan

    2016-08-01

    We present characteristic peaks of atmospheric columnar aerosol volume size distribution retrieved from the AErosol RObotic NETwork (AERONET) ground-based Sun-sky radiometer observation, and their correlations with aerosol optical properties and meteorological conditions in Beijing over 2013. The results show that the aerosol volume particle size distribution (VPSD) can be decomposed into up to four characteristic peaks, located in accumulation and coarse modes, respectively. The mean center radii of extra peaks in accumulation and coarse modes locate around 0.28 (±0.09) to 0.38 (±0.11) and 1.25 (±0.56) to 1.47 (±0.30) μm, respectively. The multi-peak size distributions are found in different aerosol loading conditions, with the mean aerosol optical depth (440 nm) of 0.58, 0.49, 1.18 and 1.04 for 2-, 3-I/II and 4-peak VPSD types, while the correspondingly mean relative humidity values are 58, 54, 72 and 67 %, respectively. The results also show the significant increase (from 0.25 to 0.40 μm) of the mean extra peak median radius in the accumulation mode for the 3-peak-II cases, which agrees with aerosol hygroscopic growth related to relative humidity and/or cloud or fog processing.

  9. Scaling law to determine peak forces in tapping-mode AFM experiments on finite elastic soft matter systems

    PubMed Central

    2017-01-01

    Analytical equations to estimate the peak force will facilitate the interpretation and the planning of amplitude-modulation force microscopy (tapping mode) experiments. A closed-form analytical equation to estimate the tip–sample peak forces while imaging soft materials in liquid environment and within an elastic deformation regime has been deduced. We have combined a multivariate regression method with input from the virial–dissipation equations and Tatara’s bidimensional deformation contact mechanics model. The equation enables to estimate the peak force based on the tapping mode observables, probe characteristics and the material properties of the sample. The accuracy of the equation has been verified by comparing it to numerical simulations for the archetypical operating conditions to image soft matter with high spatial resolution in tapping-mode AFM. PMID:28546891

  10. Scaling law to determine peak forces in tapping-mode AFM experiments on finite elastic soft matter systems.

    PubMed

    Guzman, Horacio V

    2017-01-01

    Analytical equations to estimate the peak force will facilitate the interpretation and the planning of amplitude-modulation force microscopy (tapping mode) experiments. A closed-form analytical equation to estimate the tip-sample peak forces while imaging soft materials in liquid environment and within an elastic deformation regime has been deduced. We have combined a multivariate regression method with input from the virial-dissipation equations and Tatara's bidimensional deformation contact mechanics model. The equation enables to estimate the peak force based on the tapping mode observables, probe characteristics and the material properties of the sample. The accuracy of the equation has been verified by comparing it to numerical simulations for the archetypical operating conditions to image soft matter with high spatial resolution in tapping-mode AFM.

  11. 1400, +/- 900V PEAK PULSE SWITCH MODE POWER SUPPLIES FOR SNS INJECTION KICKERS.

    SciTech Connect

    LAMBIASE,R.ENG,W.SANDBERG,J.DEWAN,S.HOLMES,R.RUST,K.ZENG,J.

    2004-03-10

    This paper describes simulation and experimental results for a 1400A, {+-} 900V peak rated, switch mode power supply for SNS Injection Kicker Magnets. For each magnet (13 m{Omega}, 160{micro}H), the power supply must supply controlled pulses at 60 Hz repetition rate. The pulse current must rise from zero to maximum in less than 1 millisec in a controlled manner, flat top for up to 2 millisec, and should fall in a controlled manner to less than 4A within 500{micro}s. The low current performance during fall time is the biggest challenge in this power supply. The simulation results show that to meet the controlled fall of the current and the current ripple requirements, voltage loop bandwidth of at least 10 kHz and switching frequency of at least 100 kHz are required. To achieve high power high frequency switching with IGBT switches, a series connected topology with three phase shifted (O{sup o}, 60{sup o} & 120{sup o}) converters each with 40 kHz switching frequency (IGBT at 20kHz), has been achieved. In this paper, the circuit topology, relevant system specifications and experimental results that meet the requirements of the power supply are described in detail. A unique six pulse SCR rectifier circuit with capacitor storage has been implemented to achieve minimum pulse width to meet required performance during current fall time below 50A due to the very narrow pulse width and non-linearity from IGBT turn-on/off times.

  12. Quantitative mapping of the elastic modulus of soft materials with HarmoniX and PeakForce QNM AFM modes.

    PubMed

    Dokukin, Maxim E; Sokolov, Igor

    2012-11-20

    The modulus of elasticity of soft materials on the nanoscale is of interest when studying thin films, nanocomposites, and biomaterials. Two novel modes of atomic force microscopy (AFM) have been introduced recently: HarmoniX and PeakForce QNM. Both modes produce distribution maps of the elastic modulus over the sample surface. Here we investigate the question of how quantitative these maps are when studying soft materials. Three different polymers with a macroscopic Young's modulus of 0.6-0.7 GPa (polyurethanes) and 2.7 GPa (polystyrene) are analyzed using these new modes. The moduli obtained are compared to the data measured with the other commonly used techniques, dynamic mechanical analyzer (DMA), regular AFM, and nanoindenter. We show that the elastic modulus is overestimated in both the HarmoniX and PeakForce QNM modes when using regular sharp probes because of excessively overstressed material in the samples. We further demonstrate that both AFM modes can work in the linear stress-strain regime when using a relatively dull indentation probe (starting from ~210 nm). The analysis of the elasticity models to be used shows that the JKR model should be used for the samples considered here instead of the DMT model, which is currently implemented in HarmoniX and PeakForce QNM modes. Using the JKR model and ~240 nm AFM probe in the PeakForce QNM mode, we demonstrate that a quantitative mapping of the elastic modulus of polymeric materials is possible. A spatial resolution of ~50 nm and a minimum 2 to 3 nm indentation depth are achieved.

  13. Evolution of habitat preference and nutrition mode in a cosmopolitan fungal genus with evidence of interkingdom host jumps and major shifts in ecology.

    PubMed

    Chaverri, Priscila; Samuels, Gary J

    2013-10-01

    Host jumps by microbial symbionts are often associated with bursts of species diversification driven by the exploitation of new adaptive zones. The objective of this study was to infer the evolution of habitat preference (decaying plants, soil, living fungi, and living plants), and nutrition mode (saprotrophy and mycoparasitism) in the fungal genus Trichoderma to elucidate possible interkingdom host jumps and shifts in ecology. Host and ecological role shifts were inferred by phylogenetic analyses and ancestral character reconstructions. The results support several interkingdom host jumps and also show that the preference for a particular habitat was gained or lost multiple times. Diversification analysis revealed that mycoparasitism is associated with accelerated speciation rates, which then suggests that this trait may be linked to the high number of species in Trichoderma. In this study it was also possible to infer the cryptic roles that endophytes or soil inhabitants play in their hosts by evaluating their closest relatives and determining their most recent ancestors. Findings from this study may have implications for understanding certain evolutionary processes such as species radiations in some hyperdiverse groups of fungi, and for more applied fields such as the discovery and development of novel biological control strategies.

  14. Finite-time H∞ control for a class of Markovian jump systems with mode-dependent time-varying delays via new Lyapunov functionals.

    PubMed

    Cheng, Jun; Zhu, Hong; Zhong, Shouming; Zeng, Yong; Dong, Xiucheng

    2013-11-01

    This paper is concerned with the problem of finite-time H∞ control for a class of Markovian jump systems with mode-dependent time-varying delays via new Lyapunov functionals. In order to reduce conservatism, a new Lyapunov-Krasovskii functional is constructed. Based on the derived condition, the reliable H∞ control problem is solved, and the system trajectory stays within a prescribed bound during a specified time interval. Finally, numerical examples are given to demonstrate the proposed approach is more effective than some existing ones.

  15. Relationship between height and width of resonance peaks in a whispering gallery mode resonator immersed in water and sucrose solutions

    NASA Astrophysics Data System (ADS)

    Teraoka, Iwao; Yao, Haibei; Huiyi Luo, Natalie

    2017-06-01

    We employed a recently developed whispering gallery mode (WGM) dip sensor made of silica to obtain spectra for many resonance peaks in water and solutions of sucrose at different concentrations and thus having different refractive indices (RI). The apparent Q factor was estimated by fitting each peak profile in the busy resonance spectrum by a Lorentzian or a sum of Lorentzians. A plot of the Q factor as a function the peak height for all the peaks analyzed indicates a straight line with a negative slope as the upper limit, for each of water and the solutions. A coupling model for a resonator and a pair of fiber tapers to feed and pick up light, developed here, supports the presence of the upper limit. We also found that the round-trip attenuation of WGM was greater than the one estimated from light absorption by water, and the difference increased with the concentration of sucrose.

  16. Concentric and impact forces of single-leg jumps in an aquatic environment versus on land.

    PubMed

    Triplett, N Travis; Colado, Juan C; Benavent, Juan; Alakhdar, Yasser; Madera, Joaquin; Gonzalez, Luis M; Tella, Victor

    2009-09-01

    This study investigated the kinetic and the kinematic differences in female athletes in single-leg static jumps in an aquatic environment compared with those performed on dry land. Twelve healthy, junior national team handball players participated. Subjects completed a familiarization and a testing session. The subjects performed a series of single-leg jumps, dry land and aquatic with and without devices, which were randomized to avoid fatigue effects. Peak concentric force, rate of force development, impact force, and time of the jumps were determined using a force plate. Peak concentric force and rate of force development were significantly (P < 0.05) higher in the aquatic jumps, whereas impact force was significantly (P < 0.05) lower. There was a shorter total jump time (P < 0.05) for the aquatic jump without devices, whereas the time required to reach peak force was not significantly different between the two environments, despite the greater resistance to movement in the aquatic medium. Aquatic jump exercises result in greater force production and rate of force development in the same amount of time with less impact and can thus offer a viable alternative to traditional dry-land jump exercises, which may also be beneficial for rehabilitating or aging populations. The benefits of this type of exercise include an exercise mode that can be performed without compromising speed while reducing the potential for joint injury.

  17. Twin peak high-frequency quasi-periodic oscillations as a spectral imprint of dual oscillation modes of accretion tori

    NASA Astrophysics Data System (ADS)

    Bakala, P.; Goluchová, K.; Török, G.; Šrámková, E.; Abramowicz, M. A.; Vincent, F. H.; Mazur, G. P.

    2015-09-01

    Context. High-frequency (millisecond) quasi-periodic oscillations (HF QPOs) are observed in the X-ray power-density spectra of several microquasars and low-mass X-ray binaries. Two distinct QPO peaks, so-called twin peak QPOs, are often detected simultaneously exhibiting their frequency ratio close or equal to 3:2. A widely discussed class of proposed QPOs models is based on oscillations of accretion toroidal structures orbiting in the close vicinity of black holes or neutron stars. Aims: Following the analytic theory and previous studies of observable spectral signatures, we aim to model the twin peak QPOs as a spectral imprint of specific dual oscillation regime defined by a combination of the lowest radial and vertical oscillation mode of slender tori. We consider the model of an optically thick slender accretion torus with constant specific angular momentum. We examined power spectra and fluorescent Kα iron line profiles for two different simulation setups with the mode frequency relations corresponding to the epicyclic resonance HF QPOs model and modified relativistic precession QPOs model. Methods: We used relativistic ray-tracing implemented in the parallel simulation code LSDplus. In the background of the Kerr spacetime geometry, we analyzed the influence of the distant observer inclination and the spin of the central compact object. Relativistic optical projection of the oscillating slender torus is illustrated by images in false colours related to the frequency shift. Results: We show that performed simulations yield power spectra with the pair of dominant peaks that correspond to the frequencies of radial and vertical oscillation modes and with the peak frequency ratio equal to the proper value 3:2 on a wide range of inclinations and spin values. We also discuss exceptional cases of a very low and very high inclination, as well as unstable high spin relativistic precession-like configurations that predict a constant frequency ratio equal to 1:2. We

  18. Burst-mode gain switched technique for high peak and average optical energy extraction.

    PubMed

    Nikumb, S K; Seguin, H J; Seguin, V A; Willis, R J; Cheng, Z; Reshef, H

    1989-05-01

    The optical performance of a cw PIE CO(2) laser has been substantially improved through the adoption of a burst-mode gain switching technique. The approach has provided a doubling of the average beam power extractable from the device. With appropriate optimization, the process could possibly permit the attainment of pulsed energy extraction in the kilohertz range, and with average optical powers within the several tens of kilowatt category.

  19. Peaked-density profile mode and improved confinement in helical systems

    NASA Astrophysics Data System (ADS)

    Itoh, K.; Itoh, Sanae

    1990-10-01

    The difference in the effect of the peaked density profile on the improved transport between tokamaks and toroidal-helical systems is discussed. Based on the theory that the rotational shear causes the inward pinch in tokamaks, the magnitude of the possible inward pinch is estimated. Owing to the strong damping of the rotation due to the helical ripple, the anomalous inward pinch would be small. This may be consistent with recent observation in the Heliotron E device that the density peakedness of n(0)/(n) = 5 does not correspond to the improved confinement.

  20. Jumping hoops

    NASA Astrophysics Data System (ADS)

    Yang, Eunjin; Kim, Ho-Young

    2012-01-01

    We investigate the dynamics of an elastic hoop as a model of the jumps of small insects. During a jump the initial elastic strain energy is converted to translational, gravitational, and vibrational energy, and is dissipated by interaction with the floor and the ambient air. We show that the strain energy is initially divided into translational, vibrational, and dissipation energies with a ratio that is constant regardless of the dimension, initial deflection, and the properties of a hoop. This novel result enables us to accurately predict the maximum jump height of a hoop with known initial conditions and drag coefficient without resorting to a numerical computation. Our model reduces the optimization of the hoop geometry for maximizing the jump height to a simple algebraic problem.

  1. 4.35 kW peak power femtosecond pulse mode-locked VECSEL for supercontinuum generation.

    PubMed

    Wilcox, Keith G; Tropper, Anne C; Beere, Harvey E; Ritchie, David A; Kunert, Bernardette; Heinen, Bernd; Stolz, Wolfgang

    2013-01-28

    We report a passively mode-locked vertical external cavity surface emitting laser (VECSEL) producing 400 fs pulses with 4.35 kW peak power. The average output power was 3.3 W and the VECSEL had a repetition rate of 1.67 GHz at a center wavelength of 1013 nm. A near-antiresonant, substrate-removed, 10 quantum well (QW) gain structure designed to enable femtosecond pulse operation is used. A SESAM which uses fast carrier recombination at the semiconductor surface and the optical Stark effect enables passive mode-locking. When 1 W of the VECSEL output is launched into a 2 m long photonic crystal fiber (PCF) with a 2.2 µm core, a supercontinuum spanning 175 nm, with average power 0.5 W is produced.

  2. Twin-Peak Quasi Periodic Oscillations and Tri-dimen-sional Spiral Modes of Disks Around Black Holes*

    NASA Astrophysics Data System (ADS)

    Rebusco, P.; Coppi, B.

    2008-11-01

    Existing explanations of high frequency Quasi Periodic Oscillations (QPOs) from compact objects have shortcomings [1] that a theory based on the excitation of tri-dimensional spiral modes [2] co-rotating with the plasma near a black hole can avoid. The modes that are likely to prevail, with the largest growth rates, are localized relatively close to the last stable orbit (a.k.a. ISCO). The modulation of the radiation due to the rotating plasma density enhancements associated with the spirals and reaching the observer, is evaluated by an appropriate extension of existing analyses [3] developed for a rotating ``hot spot'' model. As a result of relevant non-linear decays, the lowest harmonics mφ=2 and mφ=3 of the considered spiral modes (where mφ is the toroidal mode number) are envisioned to acquire the largest amplitudes justifing the observed 3/2 ratios of the two peaks of the frequency spectra of high frequency QPOs. *Sponsored in part by the U.S. D.O.E and the Pappalardo Fellowship. [1] B. Coppi and P. Rebusco, Paper P5.154, E.P.S. Inter. Conf. (Crete, Greece, 2008).[2] B. Coppi, Paper P1.177, E.P.S. Inter. Conf. (Crete, Greece, 2008).[3] J. D. Schmittman and E. Bertschinger, Ap. J. 606, 1098 (2004).

  3. [The Study of Characteristics of Cladding-Reduced Coated Long-Period Fiber Grating Based on Mode Transition and Dual Peak Resonance].

    PubMed

    Lan, Jin-long; Gu, Zheng-tian

    2015-11-01

    Based on coupled-mode theory, the mode transition of the high-order cladding modes in a coated long-period tiber grating (LPFG) has been studied firstly; the mode transition region and non-mode transition region of high-order cladding modes are divided. The response characteristic of cladding mode effective index with increasing the overlay thickness is analyzed; the shift of resonant wavelength in the mode transition region will be larger than that in the non-mode transition region. Further, the changes of the resonant wavelength of some high-order cladding modes with grating period are investigated when the cladding radius are different, the shift between two resonant wavelengths of dual peak in the mode transition region is bigger than that in non-mode transition region when the cladding radius are uniform. And the shift between two resonant wavelengths of dual peak will be increased by the decrease of the cladding radius in both mode transition and non-mode transition regions. Finally, the response characteristics of film refractive index of coated LPFG are investigated for a high-order cladding mode while the cladding radius are different and the overlay thickness is located in mode transition region and non-transition mode region, then the optimized design scheme is come up with. The higher sensitivity dual-peak sensor of coated LPFG than the traditional dual-peak sensor will be obtained when the overlay thickness and refractive index is located in the mode transition region and the grating period close to the phase matching turning points. Further, the resolution power of coated LPFG sensor will further be improved by the appropriate reducing of the cladding radius.

  4. Symmetrical dynamics of peak current-mode and valley current-mode controlled switching dc-dc converters with ramp compensation

    NASA Astrophysics Data System (ADS)

    Zhou, Guo-Hua; Xu, Jian-Ping; Bao, Bo-Cheng; Jin, Yan-Yan

    2010-06-01

    The discrete iterative map models of peak current-mode (PCM) and valley current-mode (VCM) controlled buck converters, boost converters, and buck-boost converters with ramp compensation are established and their dynamical behaviours are investigated by using the operation region, parameter space map, bifurcation diagram, and Lyapunov exponent spectrum. The research results indicate that ramp compensation extends the stable operation range of the PCM controlled switching dc-dc converter to D > 0.5 and that of the VCM controlled switching dc-dc converter to D < 0.5. Compared with PCM controlled switching dc-dc converters with ramp compensation, VCM controlled switching dc-dc converters with ramp compensation exhibit interesting symmetrical dynamics. Experimental results are given to verify the analysis results in this paper.

  5. Finite-time stability and stabilization for stochastic markov jump systems with mode-dependent time delays.

    PubMed

    Yan, Zhiguo; Song, Yunxia; Park, Ju H

    2017-05-01

    This paper is concerned with the problems of finite-time stability and stabilization for stochastic Markov systems with mode-dependent time-delays. In order to reduce conservatism, a mode-dependent approach is utilized. Based on the derived stability conditions, state-feedback controller and observer-based controller are designed, respectively. A new N-mode algorithm is given to obtain the maximum value of time-delay. Finally, an example is used to show the merit of the proposed results. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  6. High-peak-power, high-repetition-rate LD end-pumped Nd:YVO4 burst mode laser

    NASA Astrophysics Data System (ADS)

    Pan, Hu; Yan, Renpeng; Fa, Xin; Yu, Xin; Ma, Yufei; Fan, Rongwei; Li, Xudong; Chen, Deying; Zhou, Zhongxiang

    2016-06-01

    A compact high-peak-power, high-repetition-rate burst mode laser is achieved by an acousto-optical Q-switched Nd:YVO4 1064 nm laser directly pumped at 878.6 nm. Pulse trains with 10-100 pulses are obtained using acousto-optical Q-switch at repetition rates of 10-100 kHz under a pulsed pumping with a 1 ms duration. At the maximum pump energy of 108.5 mJ, the pulse energy of 10 kHz burst mode laser reaches 44 mJ corresponding to a single pulse energy of 4.4 mJ and an optical-to-optical efficiency of 40.5 %.The maximum peak power of ~468.1 kW at 10 kHz is obtained with a pulse width of 9.4 ns. The beam quality factor is measured to be M 2 ~1.5 and the pulse jitter is estimated to be less than 1 % in both amplitude and time region.

  7. a1(1420 ) peak as the π f0(980 ) decay mode of the a1(1260 )

    NASA Astrophysics Data System (ADS)

    Aceti, F.; Dai, L. R.; Oset, E.

    2016-11-01

    We study the decay mode of the a1(1260 ) into a π+ in p wave and the f0(980 ) that decays into π+π- in s wave. The mechanism proceeds via a triangular mechanism where the a1(1260 ) decays into K*K ¯, the K* decays to an external π+ and an internal K that fuses with the K ¯ producing the f0(980 ) resonance. The mechanism develops a singularity at a mass of the a1(1260 ) around 1420 MeV, producing a peak in the cross section of the π p reaction, used to generate the mesonic final state, which provides a natural explanation of all the features observed in the COMPASS experiment, where a peak observed at this energy is tentatively associated to a new resonance called a1(1420 ). On the other hand, the triangular singularity studied here gives rise to a remarkable feature, where a peak is seen for a certain decay channel of a resonance at an energy about 200 MeV higher than its nominal mass.

  8. Phenomenology of the soft gap, zero-bias peak, and zero-mode splitting in ideal Majorana nanowires

    NASA Astrophysics Data System (ADS)

    Liu, Chun-Xiao; Setiawan, F.; Sau, Jay D.; Das Sarma, S.

    2017-08-01

    We theoretically consider the observed soft gap in the proximity-induced superconducting state of semiconductor nanowires in the presence of spin-orbit coupling, Zeeman spin splitting, and tunneling leads, but in the absence of any extrinsic disorder (i.e., an ideal system). We critically consider the effects of three distinct intrinsic physical mechanisms (tunnel barrier to normal leads, temperature, and dissipation) on the phenomenology of the gap softness in the differential conductance spectroscopy of the normal-superconductor junction as a function of spin splitting and chemical potential. We find that all three mechanisms individually can produce a soft gap, leading to calculated conductance spectra qualitatively mimicking experimental results. We also show through extensive numerical simulations that the phenomenology of the soft gap is intrinsically tied to the broadening and the height of the Majorana zero-mode-induced differential conductance peak above the topological quantum phase transition point with both the soft gap and the quality of the Majorana zero mode being simultaneously affected by tunnel barrier, temperature, and dissipation. We establish that the Majorana zero-mode splitting oscillations can be suppressed by temperature or dissipation (in a similar manner) but not by the tunnel barrier. Since all three mechanisms (plus disorder, not considered in the current work) are likely to be present in any realistic nanowires, discerning the effects of various mechanisms is difficult, necessitating detailed experimental data as a function of all the system parameters, some of which (e.g., dissipation, chemical potential, tunnel barrier) may not be known experimentally. While the tunneling-induced soft-gap behavior is benign with no direct adverse effect on the Majorana topological properties with the zero-bias peak remaining quantized at 2 e2/h , the soft gap induced by finite temperature and/or finite dissipation is detrimental to topological

  9. Vertical jump coordination: fatigue effects.

    PubMed

    Rodacki, André Luiz Felix; Fowler, Neil E; Bennett, Simon J

    2002-01-01

    The aim of this study was to investigate the segmental coordination of vertical jumps under fatigue of the knee extensor and flexor muscles. Eleven healthy and active subjects performed maximal vertical jumps with and without fatigue, which was imposed by requesting the subjects to extend/flex their knees continuously in a weight machine, until they could not lift a load corresponding to approximately 50% of their body weight. Knee extensor and flexor isokinetic peak torques were also measured before and after fatigue. Video, ground reaction forces, and electromyographic data were collected simultaneously and used to provide several variables of the jumps. Fatiguing the knee flexor muscles did not reduce the height of the jumps or induce changes in the kinematic, kinetic, and electromyographic profiles. Knee extensor fatigue caused the subjects to adjust several variables of the movement, in which the peak joint angular velocity, peak joint net moment, and power around the knee were reduced and occurred earlier in comparison with the nonfatigued jumps. The electromyographic data analyses indicated that the countermovement jumps were performed similarly, i.e., a single strategy was used, irrespective of which muscle group (extensor or flexors) or the changes imposed on the muscle force-generating characteristics (fatigue or nonfatigue). The subjects executed the movements as if they scaled a robust template motor program, which guided the movement execution in all jump conditions. It was speculated that training programs designed to improve jump height performance should avoid severe fatigue levels, which may cause the subjects to learn and adopt a nonoptimal and nonspecific coordination solution. It was suggested that the neural input used in the fatigued condition did not constitute an optimal solution and may have played a role in decreasing maximal jump height achievement.

  10. Supersonic Jump

    ERIC Educational Resources Information Center

    Muller, Andreas

    2013-01-01

    On October 14,2012, Felix Baumgartner, an Austrian sky-diver, set some new world records for his discipline. Jumping from a height of about 39 km, he reached a top speed of 1342 km/h, becoming the first human being to break the sound barrier in free fall. In order to understand some essential physics aspects of this remarkable feat, we wonder why…

  11. Supersonic Jump

    ERIC Educational Resources Information Center

    Muller, Andreas

    2013-01-01

    On October 14,2012, Felix Baumgartner, an Austrian sky-diver, set some new world records for his discipline. Jumping from a height of about 39 km, he reached a top speed of 1342 km/h, becoming the first human being to break the sound barrier in free fall. In order to understand some essential physics aspects of this remarkable feat, we wonder why…

  12. Internal Hydraulic Jumps in Shallow Flows over Topography

    NASA Astrophysics Data System (ADS)

    Ogden, Kelly

    2016-11-01

    A barotropically forced stratified flow over topography can generate an internal hydraulic jump with upstream shear. The structure and mixing of these jumps are investigated theoretically and numerically. The effect of upstream shear on simplified jumps in two-layer flows without topography results in jump types such as undular bores, smooth front turbulent jumps, and fully turbulent jumps (Ogden and Helfrich, 2016). Increased shear results in entrainment across the jump with jump structures that resemble expanding shear layers. The addition of topography increases the number of qualitative jump types. Idealized simulations are conducted to characterize the types of jumps that can occur under various parameter regimes. The effect of parameters such as the volume flow rate and topographic height are considered. Flow structures including first-mode jumps with wave overturning and higher-mode jumps with wedges of homogeneous stagnant fluid are found. The degree of mixing and the mass budget of the developing stagnant wedge illuminate the important physical characteristics of each jump type. Existing hydraulic jumps in the environment are compared to the parameter regimes the identified jump types. The applicability of two-layered theories for studying these jumps is also considered.

  13. Comparison of V[Combining Dot Above]O2peak and Achievement of V[Combining Dot Above]O2peak Criteria in Three Modes of Exercise in Female Triathletes.

    PubMed

    Snoza, Colleen T; Berg, Kris E; Slivka, Dustin R

    2016-10-01

    Snoza, CT, Berg, KE, and Slivka, DR. Comparison of V[Combining Dot Above]O2peak and achievement of V[Combining Dot Above]O2peak criteria in three modes of exercise in female triathletes. J Strength Cond Res 30(10): 2816-2822, 2016-The purpose of this study was to compare peak aerobic capacity in female triathletes in 3 modes of exercise: treadmill, cycle, and arm ergometer. A second purpose was to determine the extent that physiologic criteria for achieving V[Combining Dot Above]O2peak were reached in each mode of exercise. Six criteria were examined: V[Combining Dot Above]O2 plateau, heart rate (HR), blood lactate concentration (BLC), respiratory exchange ratio, oxygen saturation, and rating of perceived exertion (RPE). Twelve recreational level female triathletes completed maximal tests on the treadmill, stationary bike, and arm ergometer. Results indicated V[Combining Dot Above]O2peak (ml·kg·min) is highest on a treadmill (46.8 ± 2.1), intermediate in cycling (40.7 ± 5.0), and lowest in arm ergometry (28.2 ± 3.3) with mean differences being significant (p ≤ 0.05). Blood lactate concentration and RPE criteria were met by the highest number of subjects across the 3 modes of testing while the HR criterion was not achieved in any participant in arm ergometry and only 2 in cycling. It was concluded that in moderately trained recreational level triathletes, V[Combining Dot Above]O2peak is highest in running and lowest in arm ergometry. Criteria for achieving V[Combining Dot Above]O2peak most frequently were blood lactate level and RPE. Coaches and researchers should appreciate that V[Combining Dot Above]O2peak values of moderately trained triathletes differ considerably in contrast to elite triathletes and tend to be highest on the treadmill and lowest in arm ergometry. Also, criteria used to determine achievement of V[Combining Dot Above]O2peak should be carefully selected and seem to be best achieved using BLC and RPE.

  14. Asymmetric-shell ignition capsule design to tune the low-mode asymmetry during the peak drive

    NASA Astrophysics Data System (ADS)

    Gu, Jianfa; Dai, Zhensheng; Song, Peng; Zou, Shiyang; Ye, Wenhua; Zheng, Wudi; Gu, Peijun; Wang, Jianguo; Zhu, Shaoping

    2016-08-01

    The low-mode radiation flux asymmetry in the hohlraum is a main source of performance degradation in the National Ignition Facility (NIF) implosion experiments. To counteract the deleterious effects of the large positive P2 flux asymmetry during the peak drive, this paper develops a new tuning method called asymmetric-shell ignition capsule design which adopts the intentionally asymmetric CH ablator layer or deuterium-tritium (DT) ice layer. A series of two-dimensional implosion simulations have been performed, and the results show that the intentionally asymmetric DT ice layer can significantly improve the fuel ρR symmetry, hot spot shape, hot spot internal energy, and the final neutron yield compared to the spherical capsule. This indicates that the DT asymmetric-shell capsule design is an effective tuning method, while the CH ablator asymmetric-shell capsule could not correct the fuel ρR asymmetry, and it is not as effective as the DT asymmetric-shell capsule design.

  15. Asymmetric-shell ignition capsule design to tune the low-mode asymmetry during the peak drive

    SciTech Connect

    Gu, Jianfa Dai, Zhensheng Song, Peng; Zou, Shiyang; Ye, Wenhua; Zheng, Wudi; Gu, Peijun; Wang, Jianguo; Zhu, Shaoping

    2016-08-15

    The low-mode radiation flux asymmetry in the hohlraum is a main source of performance degradation in the National Ignition Facility (NIF) implosion experiments. To counteract the deleterious effects of the large positive P2 flux asymmetry during the peak drive, this paper develops a new tuning method called asymmetric-shell ignition capsule design which adopts the intentionally asymmetric CH ablator layer or deuterium-tritium (DT) ice layer. A series of two-dimensional implosion simulations have been performed, and the results show that the intentionally asymmetric DT ice layer can significantly improve the fuel ρR symmetry, hot spot shape, hot spot internal energy, and the final neutron yield compared to the spherical capsule. This indicates that the DT asymmetric-shell capsule design is an effective tuning method, while the CH ablator asymmetric-shell capsule could not correct the fuel ρR asymmetry, and it is not as effective as the DT asymmetric-shell capsule design.

  16. Formation and conversion of defect centers in low water peak single mode optical fiber induced by gamma rays irradiation

    SciTech Connect

    Wen, J. X.; Luo, W. Y.; Xiao, Z. Y.; Wang, T. Y.; Chen, Z. Y.; Zeng, X. L.

    2010-02-15

    The formation and conversion processes of defect centers in low water peak single mode optical (LWPSM) fiber irradiated with gamma rays were investigated at room temperature using electron spin resonance. Germanium electron center (GEC) and self-trapped hole center (STH) occur when the fibers are irradiated with 1 and 5 kGy cumulative doses, respectively. With the increase in irradiation doses, the GEC defect centers disappear, and new defect centers such as E{sup '} centers (Si and Ge) and nonbridge oxygen hole centers (NBOHCs) generate. The generation of GEC and STH is attributed to the electron transfer, which is completely balanced. This is the main reason that radiation-induced attenuation (RIA) of the LWPSM fiber is only 10 dB/km at communication window. The new defect centers come from the conversion of GEC and STH to E{sup '} centers and NBOHC, and the conversion processes cause bond cleavage, which is the root cause that the RIA of the LWPSM fiber significantly increases up to 180 dB/km at working window. Furthermore, the concentration of new defect centers is saturated easily even by increasing cumulative doses.

  17. Effects of Fusion Zone Size and Failure Mode on Peak Load and Energy Absorption of Advanced High Strength Steel Spot Welds under Lap Shear Loading Conditions

    SciTech Connect

    Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2008-06-01

    This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS) under lap shear loading condition. DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. Static weld strength tests using lap shear samples were performed on the joint populations with various fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied for all the weld populations using statistical data analysis tools. The results in this study show that AHSS spot welds with conventionally required fusion zone size of can not produce nugget pullout mode for both the DP800 and TRIP800 welds under lap shear loading. Moreover, failure mode has strong influence on weld peak load and energy absorption for all the DP800 welds and the TRIP800 small welds: welds failed in pullout mode have statistically higher strength and energy absorption than those failed in interfacial fracture mode. For TRIP800 welds above the critical fusion zone level, the influence of weld failure modes on peak load and energy absorption diminishes. Scatter plots of peak load and energy absorption versus weld fusion zone size were then constructed, and the results indicate that fusion zone size is the most critical factor in weld quality in terms of peak load and energy absorption for both DP800 and TRIP800 spot welds.

  18. Puddle Jumping

    NASA Astrophysics Data System (ADS)

    Wollman, Andrew; Snyder, Trevor; Weislogel, Mark

    2014-11-01

    Rebounding droplets from superhydrophobic surfaces have attracted significant public and scientific attention because they are both enjoyable as well as industrially relevant. Demonstrations of bouncing droplets with volumes between 0.003 and 0.03 ml are common in the literature and limited primarily by gravity. In this presentation we demonstrate large droplet ``rebounds'' made possible by low-gravity testing in a drop tower. The up to 300 ml drops are best described as puddles that launch in a nearly identical manner to rebounding drops 4 orders of magnitude smaller in volume. A variety of jumping liquid and gas puddles are shown including puddles of highly specified and unusual initial geometry. The large length sales of the capillary fluidic surfaces ~ O (10 cm) enable 3D printing of all superhydrophobic surface topologies demonstrated. In addition, we demonstrate such puddle jumping as a passive drop-on-demand technique for large low-gravity drop dynamics investigations; such as collisions, rebounds, heat and mass transfer, and containerless possessing.

  19. Polarization dependence of Brillouin linewidth and peak frequency due to fiber inhomogeneity in single mode fiber and its impact on distributed fiber Brillouin sensing.

    PubMed

    Xie, Shangran; Pang, Meng; Bao, Xiaoyi; Chen, Liang

    2012-03-12

    The dependence of Brillouin linewidth and peak frequency on lightwave state of polarization (SOP) due to fiber inhomogeneity in single mode fiber (SMF) is investigated by using Brillouin optical time domain analysis (BOTDA) system. Theoretical analysis shows fiber inhomogeneity leads to fiber birefringence and sound velocity variation, both of which can cause the broadening and asymmetry of the Brillouin gain spectrum (BGS) and thus contribute to the variation of Brillouin linewidth and peak frequency with lightwave SOP. Due to fiber inhomogeneity both in lateral profile and longitudinal direction, the measured BGS is the superposition of several spectrum components with different peak frequencies within the interaction length. When pump or probe SOP changes, both the peak Brillouin gain and the overlapping area of the optical and acoustic mode profile that determine the peak efficiency of each spectrum component vary within the interaction length, which further changes the linewidth and peak frequency of the superimposed BGS. The SOP dependence of Brillouin linewidth and peak frequency was experimentally demonstrated and quantified by measuring the spectrum asymmetric factor and fitting obtained effective peak frequency respectively via BOTDA system on standard step-index SMF-28 fiber. Experimental results show that on this fiber the Brillouin spectrum asymmetric factor and effective peak frequency vary in the range of 2% and 0.06MHz respectively over distance with orthogonal probe input SOPs. Experimental results also show that in distributed fiber Brillouin sensing, polarization scrambler (PS) can be used to reduce the SOP dependence of Brillouin linewidth and peak frequency caused by fiber inhomogeneity in lateral profile, however it maintains the effects caused by fiber inhomogeneity in longitudinal direction. In the case of non-ideal polarization scrambling using practical PS, the fluctuation of effective Brillouin peak frequency caused by fiber inhomogeneity

  20. Supersonic Jump

    NASA Astrophysics Data System (ADS)

    Müller, Andreas

    2013-01-01

    On October 14,2012, Felix Baumgartner, an Austrian sky-diver, set some new world records for his discipline. Jumping from a height of about 39 km, he reached a top speed of 1342 km/h, becoming the first human being to break the sound barrier in free fall. In order to understand some essential physics aspects of this remarkable feat, we wonder why his start height had to be that high (when the tremendous effort that was necessary for leaping from such a height required 50 million, as reported in the press). More precisely, can you give an estimate for the minimal start height—which we will call the Baumgartner limit, zB—of a sky diver who wants to break the sound barrier in free fall?

  1. Nonwork and off-peak trips by transit, walk and bicycle modes: An understanding of existing and potential markets. Final report, 1 August 1996--28 February 1998

    SciTech Connect

    Soeoet, S.; Sen, A.; Yang, D.; Dirks, L.; Sternberg, T.

    1999-03-01

    The study identifies the characteristics of neighborhoods that contribute to off-peak transit, walk or bike use. The emphasis is on off-peak and nonwork trips and how to promote modes other than the automobile. By producing thirty maps illustrating socioeconomic and travel behavior patterns in the Chicago area, the potential for stabilizing and then increasing the utilization of these modes is examined. Substantial amounts of data were processed and reported. For example, off-peak trips, accounting for 48% of daily travel, are shorter than trips during the peak (in miles and minutes) for travel by both public transit and by private vehicle. Regionally, walking trips vary from 42% of all trips made by Chicago CBD residents (mainly to shop and work), 17% in the rest of the city and less than 5% in suburban Chicago. Bicycle ownership is related to the number of vehicles in the household, household income, household size and distance from the Chicago CBD. These data and field observations of three case-study neighborhoods revealed that differences in modes used are related to the land-use patterns and the socioeconomic characteristics of the resident population. While areas with low automobile ownership rates might suggest walking and bicycling, these nonmotorized modes are more common in affluent neighborhoods with a large number of nearby commercial and recreational destinations.

  2. Quantum-dot saturable absorber and Kerr-lens mode-locked Yb:KGW laser with >450  kW of peak power.

    PubMed

    Akbari, R; Zhao, H; Fedorova, K A; Rafailov, E U; Major, A

    2016-08-15

    The hybrid action of quantum-dot saturable absorber and Kerr-lens mode locking in a diode-pumped Yb:KGW laser was demonstrated. Using a quantum-dot saturable absorber with a 0.7% (0.5%) modulation depth, the mode-locked laser delivered 90 fs (93 fs) pulses with 3.2 W (2.9 W) of average power at the repetition rate of 77 MHz, corresponding to 462 kW (406 kW) of peak power and 41 nJ (38 nJ) of pulse energy. To the best of our knowledge, this represents the highest average and peak powers generated to date from quantum-dot saturable absorber-based mode-locked lasers.

  3. Potential for Non-Contact ACL Injury Between Step-Close-Jump and Hop-Jump Tasks

    PubMed Central

    Wang, Li-I; Gu, Chin-Yi; Chen, Wei-Ling; Chang, Mu-San

    2010-01-01

    This study aimed to compare the kinematics and kinetics during the landing of hop-jump and step-close-jump movements in order to provide further inferring that the potential risk of ACL injuries. Eleven elite male volleyball players were recruited to perform hop-jump and step-close-jump tasks. Lower extremity kinematics and ground reaction forces during landing in stop-jump tasks were recorded. Lower extremity kinetics was calculated by using an inverse dynamic process. Step-close-jump tasks demonstrated smaller peak proximal tibia anterior shear forces during the landing phase. In step-close-jump tasks, increasing hip joint angular velocity during initial foot-ground contact decreased peak posterior ground reaction force during the landing phase, which theoretically could reduce the risk of ACL injury. Key points The different landing techniques required for these two stop-jump tasks do not necessarily affect the jump height. Hop-jump decreased the hip joint angular velocity at initial foot contact with ground, which could lead to an increasing peak posterior GRF during the landing phase. Hop-jump decreased hip and knee joint angular flexion displacement during the landing, which could increase the peak vertical loading rate during the landing phase. PMID:24149397

  4. Potential for Non-Contact ACL Injury Between Step-Close-Jump and Hop-Jump Tasks.

    PubMed

    Wang, Li-I; Gu, Chin-Yi; Chen, Wei-Ling; Chang, Mu-San

    2010-01-01

    This study aimed to compare the kinematics and kinetics during the landing of hop-jump and step-close-jump movements in order to provide further inferring that the potential risk of ACL injuries. Eleven elite male volleyball players were recruited to perform hop-jump and step-close-jump tasks. Lower extremity kinematics and ground reaction forces during landing in stop-jump tasks were recorded. Lower extremity kinetics was calculated by using an inverse dynamic process. Step-close-jump tasks demonstrated smaller peak proximal tibia anterior shear forces during the landing phase. In step-close-jump tasks, increasing hip joint angular velocity during initial foot-ground contact decreased peak posterior ground reaction force during the landing phase, which theoretically could reduce the risk of ACL injury. Key pointsThe different landing techniques required for these two stop-jump tasks do not necessarily affect the jump height.Hop-jump decreased the hip joint angular velocity at initial foot contact with ground, which could lead to an increasing peak posterior GRF during the landing phase.Hop-jump decreased hip and knee joint angular flexion displacement during the landing, which could increase the peak vertical loading rate during the landing phase.

  5. Influence of dorsiflexion shoes on jump performance.

    PubMed

    Salinero, Juan J; González-Millán, Cristina; Abián-Vicén, Javier; Del Coso Garrigós, Juan

    2014-04-01

    The goal of dorsiflexion sports shoes is to increase jumping capacity by means of a lower position of the heel in relation to the forefoot which results in additional stretching of the ankle plantar flexors. The aim of this study was to compare a dorsiflexion sports shoe model with two conventional sports shoe models in a countermovement jump test. The sample consisted of 35 participants who performed a countermovement jump test on a force platform wearing the three models of shoes. There were significant differences in the way force was manifested (P<0.05) in the countermovement jump test, with a decrease in the velocity of the center of gravity and an increase in force at peak power and mean force in the concentric phase. Moreover, peak power was reached earlier with the dorsiflexion sports shoe model. The drop of the center of gravity was increased in CS1 in contrast to the dorsiflexion sports shoe model (P<.05). However, the dorsiflexion sports shoes were not effective for improving either peak power or jump height (P>.05). Although force manifestation and jump kinetics differ between dorsiflexion shoes and conventional sports shoes, jump performance was similar.

  6. Possible enhancement of SASE FEL output field intensity induced by local phase jump

    NASA Astrophysics Data System (ADS)

    Varfolomeev, A. A.; Yarovoi, T. V.; Bousine, P. V.

    1998-02-01

    A possible influence on the FEL dynamics of a locally induced phase jump between the FEL radiation and electron beam is considered. A numerical study has been made for the SASE mode FEL supposing that the phase jumps are introduced at different depths inside the undulator. The FEL evolution starting from a small input signal was studied in 1D high gain approach. It was shown that the FEL radiation output is sensitive to the phase jump value if it is introduced at the depth where saturation of output power takes places. In the steady state regime, the phase displacement of order ˜π provides enhancement of the peak output power up to 50%. Some kind of optical tapering is also possible giving further FEL efficiency enhancement.

  7. Chasing maximal performance: a cautionary tale from the celebrated jumping frogs of Calaveras County.

    PubMed

    Astley, H C; Abbott, E M; Azizi, E; Marsh, R L; Roberts, T J

    2013-11-01

    Maximal performance is an essential metric for understanding many aspects of an organism's biology, but it can be difficult to determine because a measured maximum may reflect only a peak level of effort, not a physiological limit. We used a unique opportunity provided by a frog jumping contest to evaluate the validity of existing laboratory estimates of maximum jumping performance in bullfrogs (Rana catesbeiana). We recorded video of 3124 bullfrog jumps over the course of the 4-day contest at the Calaveras County Jumping Frog Jubilee, and determined jump distance from these images and a calibration of the jump arena. Frogs were divided into two groups: 'rental' frogs collected by fair organizers and jumped by the general public, and frogs collected and jumped by experienced, 'professional' teams. A total of 58% of recorded jumps surpassed the maximum jump distance in the literature (1.295 m), and the longest jump was 2.2 m. Compared with rental frogs, professionally jumped frogs jumped farther, and the distribution of jump distances for this group was skewed towards long jumps. Calculated muscular work, historical records and the skewed distribution of jump distances all suggest that the longest jumps represent the true performance limit for this species. Using resampling, we estimated the probability of observing a given jump distance for various sample sizes, showing that large sample sizes are required to detect rare maximal jumps. These results show the importance of sample size, animal motivation and physiological conditions for accurate maximal performance estimates.

  8. Characterisation of tissue factor-bearing extracellular vesicles with AFM: comparison of air-tapping-mode AFM and liquid Peak Force AFM.

    PubMed

    Hardij, Julie; Cecchet, Francesca; Berquand, Alexandre; Gheldof, Damien; Chatelain, Christian; Mullier, François; Chatelain, Bernard; Dogné, Jean-Michel

    2013-01-01

    Extracellular vesicles (EVs) are shed from cells and carry markers of the parent cells. Vesicles derived from cancer cells reach the bloodstream and locally influence important physiological processes. It has been previously shown that procoagulant vesicles are circulating in patients' fluids. These EVs are therefore considered as promising biomarkers for the thrombotic risk. Because of their small size, classical methods such as flow cytometry suffer from limitation for their characterisation. Atomic force microscopy (AFM) has been proposed as a promising complementary method for the characterisation of EVs. THE OBJECTIVES OF THIS STUDY ARE: (a) to develop and validate AFM with specific antibodies (anti-TF) and (b) to compare air and liquid modes for EVs' size and number determination as potential biomarkers of the prothrombotic risk. AFM multimode nanoscope III was used for air tapping mode (TM). AFM catalyst was used for liquid Peak Force Tapping (PFT) mode. Vesicles are generated according to Davila et al.'s protocol. Substrates are coated with various concentrations of antibodies, thanks to ethanolamine and glutaraldehyde. Vesicles were immobilised on antibody-coated surfaces to select tissue factor (TF)-positive vesicles. The size range of vesicles observed in liquid PFT mode is 6-10 times higher than in air mode. This corresponds to the data found in the literature. We recommend liquid PFT mode to analyse vesicles on 5 µg/ml antibody-coated substrates.

  9. Peak locations and relative phase of different decay modes of the a1 axial vector resonance in diffractive production

    SciTech Connect

    Basdevant, Jean-Louis; Berger, Edmond L.

    2015-05-12

    We show that a single I = 1 spin-parity J(PC) = 1(++) a(1) resonance can manifest itself as two separated mass peaks, one decaying into an S-wave rho pi system and the second decaying into a P-wave f(0)(980)pi system, with a rapid increase of the phase difference between their amplitudes arising mainly from the structure of the diffractive production process. This study clarifies questions related to the mass, width, and decay rates of the a(1) resonance raised by the recent high statistics data of the COMPASS Collaboration on a 1 production in pi N -> pi pi pi N at high energies.

  10. Lift-Off Dynamics in a Simple Jumping Robot

    NASA Astrophysics Data System (ADS)

    Aguilar, Jeffrey; Lesov, Alex; Wiesenfeld, Kurt; Goldman, Daniel I.

    2012-10-01

    We study vertical jumping in a simple robot comprising an actuated mass-spring arrangement. The actuator frequency and phase are systematically varied to find optimal performance. Optimal jumps occur above and below (but not at) the robot’s resonant frequency f0. Two distinct jumping modes emerge: a simple jump, which is optimal above f0, is achievable with a squat maneuver, and a peculiar stutter jump, which is optimal below f0, is generated with a countermovement. A simple dynamical model reveals how optimal lift-off results from nonresonant transient dynamics.

  11. Effects of Fusion Zone Size and Failure Mode on Peak Load and Energy Absorption of Advanced High Strength Steel Spot Welds

    SciTech Connect

    Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2007-01-01

    This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using limit load based analytical model and micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on the joint populations with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied for all the weld populations using statistical data analysis tools. The results in this study show that AHSS spot welds with fusion zone size of can not produce nugget pullout mode for both the DP800 and TRIP800 materials examined. The critical fusion zone size for nugget pullout shall be derived for individual materials based on different base metal properties as well as different heat affected zone (HAZ) and weld properties resulted from different welding parameters.

  12. Biomechanical Analysis of the Jump Shot in Basketball

    PubMed Central

    Struzik, Artur; Pietraszewski, Bogdan; Zawadzki, Jerzy

    2014-01-01

    Basketball players usually score points during the game using the jump shot. For this reason, the jump shot is considered to be the most important element of technique in basketball and requires a high level of performance. The aim of this study was to compare the biomechanical characteristics of the lower limbs during a jump shot without the ball and a countermovement jump without an arm swing. The differences between variables provide information about the potential that an athlete can utilise during a game when performing a jump shot. The study was conducted among 20 second-league basketball players by means of a Kistler force plate and the BTS SMART system for motion analysis. The variables measured included the take-off time, mean power, peak power, relative mean power, jump height, maximum landing force and calculated impact ratio. Surprisingly, more advantageous variables were found for the jump shot. This finding suggests a very high performance level in the jump shot in the studied group and a maximum utilisation of their motor abilities. Both types of jumps were characterised by high mean and peak power values and average heights. The high forces at landing, which result in considerable impact ratios, may have prompted the studied group to land softly. Use of the countermovement jump without an arm swing is recommended to assess and predict the progression of player’s jumping ability. PMID:25414741

  13. Direct measurement of elastic modulus of InP nanowires with Scanning Probe Microscopy in PeakForce QNM mode

    NASA Astrophysics Data System (ADS)

    Geydt, P.; Dunaevskiy, M.; Alekseev, P.; Kakko, J.-P.; Haggrén, T.; Lähderanta, E.; Lipsanen, H.

    2016-11-01

    In this manuscript, we present the study of elastic properties of InP nanowires with help of scanning probe microscope in advanced PeakForce Tapping® regime. The measuring method was developed in order to investigate the Young's modulus of these cone-shaped structures with significant accuracy. The difference in InP elasticity for wurtzite phase and zinc- blende phase was revealed. It was shown that elastic modulus of InP nanowires significantly increases from 60 GPa to more than 100 GPa when diameter of a nanowire is reduced below 50 nm. The core-shell model for InP nanowire was used for the explanation of this effect.

  14. High average/peak power linearly polarized all-fiber picosecond MOPA seeded by mode-locked noise-like pulses

    NASA Astrophysics Data System (ADS)

    Yu, H. L.; Ma, P. F.; Tao, R. M.; Wang, X. L.; Zhou, P.; Chen, J. B.

    2015-06-01

    The characteristics of mode-locked noise-like pulses generated from a passively mode-locked fiber oscillator are experimentally investigated. By carefully adjusting the two polarization controllers, stable mode-locked noise-like pulse emission with a high radio frequency signal/noise ratio of  >55 dB is successfully achieved, ensuring the safety and possibility of high power amplification. To investigate the amplification characteristics of such pulses, one all-fiber master oscillator power amplifier (MOPA) is built to boost the power and energy of such pulses. Amplified noise-like pulses with average output power of 423 W, repetition rate of 18.71 MHz, pulse energy of 22.61 μJ, pulse duration of 72.1 ps and peak power of 314 kW are obtained. Near diffraction-limited beam is also demonstrated with M2 factor measured at full power operation of ~1.2 in the X and Y directions. The polarization extinction ratio at output power of 183 W is measured to be ~13 dB. To the best of our knowledge, this is the first demonstration of high-power amplification of noise-like pulses and the highest peak power ever reported in all-fiber picosecond MOPAs. The temporal self-compression process of such pulses and high peak power when amplified make it an ideal pump source for generation of high-power supercontinuum. Other potential applications, such as material processing and optical coherent tomography, could also be foreseen.

  15. Majorana modes in InSb nanowires (I): zero bias peaks in hybrid devices with low-disorder and hard induced superconducting gap

    NASA Astrophysics Data System (ADS)

    Gül, Ö.; Zhang, H.; de Moor, M. W. A.; de Vries, F.; van Veen, J.; van Woerkom, D. J.; Zuo, K.; Mourik, V.; Cassidy, M.; Geresdi, A.; Car, D.; Bakkers, E. P. A. M.; Goswami, S.; Watanabe, K.; Taniguchi, T.; Kouwenhoven, L. P.

    Majorana modes in hybrid superconductor-semiconductor nanowire devices can be probed via tunnelling spectroscopy which shows a zero bias peak (ZBP) in differential conductance (1). However, alternative mechanisms such as disorder or formation of quantum dots can also give rise to ZBPs, and obscure experimental studies of Majoranas. Further, a soft induced superconducting gap commonly observed in experiments presents an outstanding challenge for the demonstration of their topological protection. In this talk we show that with device improvements, we reach low-disorder transport regime with clear quantized conductance plateaus and Andreev enhancement approaching the theoretical limit. Tunnelling spectroscopy shows a hard induced superconducting gap and no formation of quantum dots. Together with extremely stable ZBPs observed in large gate voltage and magnetic field ranges, we exclude various alternative theories besides the formation of localized Majorana modes for our observations.

  16. Effects of unilateral and bilateral plyometric training on power and jumping ability in women.

    PubMed

    Makaruk, Hubert; Winchester, Jason B; Sadowski, Jerzy; Czaplicki, Adam; Sacewicz, Tomasz

    2011-12-01

    Makaruk, H, Winchester, JB, Sadowski, J, Czaplicki, A, and Sacewicz, T. Effects of unilateral and bilateral plyometric training on power and jumping ability in women. J Strength Cond Res 25(12): 3311-3318, 2011-The purpose of this study was to examine the effects of unilateral and bilateral plyometric exercise on peak power and jumping performance during different stages of a 12-week training and detraining in women. Forty-nine untrained but physically active female college students were randomly assigned to 1 of 3 groups: unilateral plyometric group (n = 16), bilateral plyometric group (BLE; n = 18), and a control group (n = 15). Peak power and jumping ability were assessed by means of the alternate leg tests (10-second Wingate test and 5 alternate leg bounds), bilateral leg test (countermovement jump [CMJ]) and unilateral leg test (unilateral CMJ). Performance indicators were measured pretraining, midtraining, posttraining, and detraining. Differences between dependent variables were assessed with a 3 × 4 (group × time) repeated analysis of variance with Tukey's post hoc test applied where appropriate. Effect size was calculated to determine the magnitude of significant differences between the researched parameters. Only the unilateral plyometric training produced significant (p < 0.05) improvement in all tests from pretraining to midtraining, but there was no significant (p < 0.05) increase in performance indicators from midtraining to posttraining. The BLE group significantly (p < 0.05) improved in all tests from pretraining to posttraining and did not significantly (p > 0.05) decrease power and jumping ability in all tests during detraining. These results suggest that unilateral plyometric exercises produce power and jumping performance during a shorter period when compared to bilateral plyometric exercises but achieved performance gains last longer after bilateral plyometric training. Practitioners should consider the inclusion of both unilateral and

  17. BIOMECHANICS. Jumping on water: Surface tension-dominated jumping of water striders and robotic insects.

    PubMed

    Koh, Je-Sung; Yang, Eunjin; Jung, Gwang-Pil; Jung, Sun-Pill; Son, Jae Hak; Lee, Sang-Im; Jablonski, Piotr G; Wood, Robert J; Kim, Ho-Young; Cho, Kyu-Jin

    2015-07-31

    Jumping on water is a unique locomotion mode found in semi-aquatic arthropods, such as water striders. To reproduce this feat in a surface tension-dominant jumping robot, we elucidated the hydrodynamics involved and applied them to develop a bio-inspired impulsive mechanism that maximizes momentum transfer to water. We found that water striders rotate the curved tips of their legs inward at a relatively low descending velocity with a force just below that required to break the water surface (144 millinewtons/meter). We built a 68-milligram at-scale jumping robotic insect and verified that it jumps on water with maximum momentum transfer. The results suggest an understanding of the hydrodynamic phenomena used by semi-aquatic arthropods during water jumping and prescribe a method for reproducing these capabilities in artificial systems. Copyright © 2015, American Association for the Advancement of Science.

  18. A biomechanical comparison of the vertical jump, power clean, and jump squat.

    PubMed

    MacKenzie, Sasho James; Lavers, Robert J; Wallace, Brendan B

    2014-01-01

    The purpose of this study was to compare the kinetics, kinematics, and muscle activation patterns of the countermovement jump, the power clean, and the jump squat with the expectation of gaining a better understanding of the mechanism of transfer from the power clean to the vertical jump. Ground reaction forces, electromyography, and joint angle data were collected from 20 trained participants while they performed the three movements. Relative to the power clean, the kinematics of the jump squat were more similar to those of the countermovement jump. The order in which the ankle, knee, and hip began extending, as well as the subsequent pattern of extension, was different between the power clean and countermovement jump. The electromyography data demonstrated significant differences in the relative timing of peak activations in all muscles, the maximum activation of the rectus femoris and biceps femoris, and in the activation/deactivation patterns of the vastus medialis and rectus femoris. The greatest rate of force development during the upward phase of these exercises was generated during the power clean (17,254 [Formula: see text]), which was significantly greater than both the countermovement jump (3836 [Formula: see text]) and jump squat (3517 [Formula: see text]) conditions (P < .001, [Formula: see text]).

  19. Jumping Good Fun

    ERIC Educational Resources Information Center

    Nye, Susan B.

    2010-01-01

    Jumping rope is an activity that can be fun and enjoyable for all students. It requires minimal activity space, can be performed individually or in small groups, and is an inexpensive way to engage students in a lifelong physical activity. Jumping rope is commonly used by coaches and athletes for training purposes to improve aerobic endurance,…

  20. Optimal Ski Jump

    ERIC Educational Resources Information Center

    Rebilas, Krzysztof

    2013-01-01

    Consider a skier who goes down a takeoff ramp, attains a speed "V", and jumps, attempting to land as far as possible down the hill below (Fig. 1). At the moment of takeoff the angle between the skier's velocity and the horizontal is [alpha]. What is the optimal angle [alpha] that makes the jump the longest possible for the fixed magnitude of the…

  1. Optimal Ski Jump

    ERIC Educational Resources Information Center

    Rebilas, Krzysztof

    2013-01-01

    Consider a skier who goes down a takeoff ramp, attains a speed "V", and jumps, attempting to land as far as possible down the hill below (Fig. 1). At the moment of takeoff the angle between the skier's velocity and the horizontal is [alpha]. What is the optimal angle [alpha] that makes the jump the longest possible for the fixed magnitude of the…

  2. Jumping for Joy.

    ERIC Educational Resources Information Center

    Whiting, Donna L.

    1996-01-01

    Presents an activity from the track and field unit of the Science of Sporting Events program in which teachers and students experiment with four broad jump techniques in order to determine which method will allow them to jump the farthest. Enables students to use a variety of math and science skills including observing, predicting, measuring, and…

  3. Jumping Good Fun

    ERIC Educational Resources Information Center

    Nye, Susan B.

    2010-01-01

    Jumping rope is an activity that can be fun and enjoyable for all students. It requires minimal activity space, can be performed individually or in small groups, and is an inexpensive way to engage students in a lifelong physical activity. Jumping rope is commonly used by coaches and athletes for training purposes to improve aerobic endurance,…

  4. Correlation between toe flexor strength and ankle dorsiflexion ROM during the countermovement jump

    PubMed Central

    Yun, Sung Joon; Kim, Moon-Hwan; Weon, Jong-Hyuck; Kim, Young; Jung, Sung-Hoon; Kwon, Oh-Yun

    2016-01-01

    [Purpose] This study assessed the relationships between peak toe flexor muscle strength, ankle dorsiflexion range of motion, and countermovement jump height. [Subjects and Methods] Eighteen healthy volunteers participated in the study. Each participant completed tests for peak toe flexor muscle strength, ankle dorsiflexion range of motion, and countermovement jump height. [Results] The results showed (1) a moderate correlation between ankle dorsiflexion range of motion and countermovement jump height and (2) a high correlation between peak first toe flexor muscle strength and countermovement jump height. Peak first toe flexor muscle strength and ankle dorsiflexion range of motion are the main contributors to countermovement jump performance. [Conclusion] These findings indicate that the measurement of peak first toe flexor muscle strength and ankle dorsiflexion range of motion may be useful in clinical practice for improving jump performance in athletes training for sports such as volleyball and basketball. PMID:27630405

  5. Temporal and kinetic analysis of unilateral jumping in the vertical, horizontal, and lateral directions.

    PubMed

    Meylan, Cesar M P; Nosaka, Kazunori; Green, Jonathon; Cronin, John B

    2010-03-01

    The aims of this study were to: (1) assess the reliability of various kinetic and temporal variables for unilateral vertical, horizontal, and lateral countermovement jumps; (2) determine whether there are differences in vertical ground reaction force production between the three types of jumps; (3) quantify the magnitude of asymmetry between limbs for variables that were established as reliable in a healthy population and whether asymmetries were consistent across jumps of different direction; and (4) establish the best kinetic predictor(s) of jump performance in the vertical, horizontal, and lateral planes of motion. Thirty team sport athletes performed three trials of the various countermovement jumps on both legs on two separate occasions. Eccentric and concentric peak force and concentric peak power were the only variables with acceptable reliability (coefficient of variation = 3.3-15.1%; intra-class correlation coefficient = 0.70-0.96). Eccentric and concentric peak vertical ground reaction force (14-16%) and concentric peak power (45-51%) were significantly (P < 0.01) greater in the vertical countermovement jump than in the horizontal countermovement jump and lateral countermovement jump, but no significant difference was found between the latter two jumps. No significant leg asymmetries (-2.1% to 9.3%) were found in any of the kinetic variables but significant differences were observed in jump height and distance. The best single predictors of vertical countermovement jump, horizontal countermovement jump, and lateral countermovement jump performance were concentric peak vertical power/body weight (79%), horizontal concentric peak power/body weight (42.6%), and eccentric peak vertical ground reaction force/body weight (14.9%) respectively. These findings are discussed in relation to monitoring and developing direction-specific jump performance.

  6. Relationship between sprint ability and loaded/unloaded jump tests in elite sprinters.

    PubMed

    Loturco, Irineu; DʼAngelo, Ricardo A; Fernandes, Victor; Gil, Saulo; Kobal, Ronaldo; Cal Abad, Cesar C; Kitamura, Katia; Nakamura, Fabio Y

    2015-03-01

    The neuromechanical determinants of sprint running performance have been investigated in team sports athletes and non-elite sprinters. The aim of this study was to quantify the relationships between kinetic and performance parameters, obtained in loaded and unloaded vertical and horizontal jumps, and sprinting in elite athletes. Twenty-two sprinters performed squat jumps, countermovement jumps, horizontal jumps, and jump squats with different loads on a force platform, in addition to a 50-m sprint. Results indicated that jumping height and distance in vertical and horizontal jumps are more strongly correlated (R ≈ 0.81) to sprinting speed than the respective peak forces (R ≈ 0.36). Furthermore, the optimum load generating the maximum power in the jump squat is also highly correlated to sprint performance (R ≈ 0.72). These results reveal that vertical and horizontal jump tests may be used by coaches for assessing and monitoring qualities related to sprinting performance in elite sprinters.

  7. Explanation of the bilateral deficit in human vertical squat jumping.

    PubMed

    Bobbert, Maarten F; de Graaf, Wendy W; Jonk, Jan N; Casius, L J Richard

    2006-02-01

    In the literature, it has been reported that the mechanical output per leg is less in two-leg jumps than in one-leg jumps. This so-called bilateral deficit has been attributed to a reduced neural drive to muscles in two-leg jumps. The purpose of the present study was to investigate the possible contribution of nonneural factors to the bilateral deficit in jumping. We collected kinematics, ground reaction forces, and electromyograms of eight human subjects performing two-leg and one-leg (right leg) squat jumps and calculated mechanical output per leg. We also used a model of the human musculoskeletal system to simulate two-leg and one-leg jumps, starting from the initial position observed in the subjects. The model had muscle stimulation as input, which was optimized using jump height as performance criterion. The model did not incorporate a reduced maximal neural drive in the two-leg jump. Both in the subjects and in the model, the work of the right leg was more than 20% less in the two-leg jump than in the one-leg jump. Peak electromyogram levels in the two-leg jump were reduced on average by 5%, but the reduction was only statistically significant in m. rectus femoris. In the model, approximately 75% of the bilateral deficit in work per leg was explained by higher shortening velocities in the two-leg jump, and the remainder was explained by lower active state of muscles. It was concluded that the bilateral deficit in jumping is primarily caused by the force-velocity relationship rather than by a reduction of neural drive.

  8. Jump for the Moon

    NASA Image and Video Library

    Increase bone strength and improve heart and other muscle endurance by performing jump training with a rope, both while stationary and moving. The Train Like an Astronaut project uses the excitemen...

  9. A Noise Reduction Method for Dual-Mass Micro-Electromechanical Gyroscopes Based on Sample Entropy Empirical Mode Decomposition and Time-Frequency Peak Filtering

    PubMed Central

    Shen, Chong; Li, Jie; Zhang, Xiaoming; Shi, Yunbo; Tang, Jun; Cao, Huiliang; Liu, Jun

    2016-01-01

    The different noise components in a dual-mass micro-electromechanical system (MEMS) gyroscope structure is analyzed in this paper, including mechanical-thermal noise (MTN), electronic-thermal noise (ETN), flicker noise (FN) and Coriolis signal in-phase noise (IPN). The structure equivalent electronic model is established, and an improved white Gaussian noise reduction method for dual-mass MEMS gyroscopes is proposed which is based on sample entropy empirical mode decomposition (SEEMD) and time-frequency peak filtering (TFPF). There is a contradiction in TFPS, i.e., selecting a short window length may lead to good preservation of signal amplitude but bad random noise reduction, whereas selecting a long window length may lead to serious attenuation of the signal amplitude but effective random noise reduction. In order to achieve a good tradeoff between valid signal amplitude preservation and random noise reduction, SEEMD is adopted to improve TFPF. Firstly, the original signal is decomposed into intrinsic mode functions (IMFs) by EMD, and the SE of each IMF is calculated in order to classify the numerous IMFs into three different components; then short window TFPF is employed for low frequency component of IMFs, and long window TFPF is employed for high frequency component of IMFs, and the noise component of IMFs is wiped off directly; at last the final signal is obtained after reconstruction. Rotation experimental and temperature experimental are carried out to verify the proposed SEEMD-TFPF algorithm, the verification and comparison results show that the de-noising performance of SEEMD-TFPF is better than that achievable with the traditional wavelet, Kalman filter and fixed window length TFPF methods. PMID:27258276

  10. A Noise Reduction Method for Dual-Mass Micro-Electromechanical Gyroscopes Based on Sample Entropy Empirical Mode Decomposition and Time-Frequency Peak Filtering.

    PubMed

    Shen, Chong; Li, Jie; Zhang, Xiaoming; Shi, Yunbo; Tang, Jun; Cao, Huiliang; Liu, Jun

    2016-05-31

    The different noise components in a dual-mass micro-electromechanical system (MEMS) gyroscope structure is analyzed in this paper, including mechanical-thermal noise (MTN), electronic-thermal noise (ETN), flicker noise (FN) and Coriolis signal in-phase noise (IPN). The structure equivalent electronic model is established, and an improved white Gaussian noise reduction method for dual-mass MEMS gyroscopes is proposed which is based on sample entropy empirical mode decomposition (SEEMD) and time-frequency peak filtering (TFPF). There is a contradiction in TFPS, i.e., selecting a short window length may lead to good preservation of signal amplitude but bad random noise reduction, whereas selecting a long window length may lead to serious attenuation of the signal amplitude but effective random noise reduction. In order to achieve a good tradeoff between valid signal amplitude preservation and random noise reduction, SEEMD is adopted to improve TFPF. Firstly, the original signal is decomposed into intrinsic mode functions (IMFs) by EMD, and the SE of each IMF is calculated in order to classify the numerous IMFs into three different components; then short window TFPF is employed for low frequency component of IMFs, and long window TFPF is employed for high frequency component of IMFs, and the noise component of IMFs is wiped off directly; at last the final signal is obtained after reconstruction. Rotation experimental and temperature experimental are carried out to verify the proposed SEEMD-TFPF algorithm, the verification and comparison results show that the de-noising performance of SEEMD-TFPF is better than that achievable with the traditional wavelet, Kalman filter and fixed window length TFPF methods.

  11. Suicide by jumping.

    PubMed

    Gunnell, D; Nowers, M

    1997-07-01

    This review summarizes the published literature on suicide by jumping, in particular focusing on the social and psychological characteristics of people who have chosen this method of suicide, and the opportunities for prevention. Suicide by jumping accounts for 5% of suicides in England and Wales, and there are marked variations in the use of this method world-wide. A number of locations have gained notoriety as popular places from which to jump. Such sites include The Golden Gate Bridge and Niagara Falls in the USA, and Beachy Head and the Clifton Suspension Bridge in the UK. There is no consistent evidence that those who commit suicide by jumping differ sociodemographically or in their psychopathology from those who use other methods of suicide, although this method is more often used for in-patient suicides, possibly due to lack of access to other means. Survivors of suicidal jumps experience higher subsequent rates of suicide and mental ill health, but the majority do not go on to kill themselves, suggesting that preventive efforts may be worthwhile. This view is supported by other evidence that restricting access to the means of suicide may prevent some would-be suicides. Such measures may also reduce the emotional trauma suffered by those who witness these acts. Health authorities and coroners should consider reviewing local patterns of suicide by jumping, and if necessary institute preventive measures.

  12. Jumping on water

    NASA Astrophysics Data System (ADS)

    Kim, Ho-Young

    2016-11-01

    Water striders can jump on water as high as they can jump on land. Quick jumps allow them to avoid sudden dangers such as predators' attacks, and therefore understanding how they make such a dramatic motion for survival can shed light on the ultimate level of semi-aquatic motility achievable through evolution. However, the mechanism of their vertical jumping from a water surface has eluded hydrodynamic explanations so far. By observing movements of water strider legs and theoretically analyzing their dynamic interactions with deforming liquid-air interface, we have recently found that different species of jumping striders always tune their leg rotation speed with a force just below that required to break the water surface to reach the maximum take-off velocity. Here, we start with discussing the fundamental theories of dynamics of floating and sinking of small objects. The theories then enable us to analyze forces acting on a water strider while it presses down the water surface to fully exploit the capillary force. We further introduce a 68-milligram at-scale robotic insect capable of jumping on water without splash, strikingly similar to the real strider, by utilizing the water surface just as a trampoline.

  13. Manipulation of polystyrene nanoparticles on a silicon wafer in the peak force tapping mode in water: pH-dependent friction and adhesion force

    SciTech Connect

    Schiwek, Simon; Stark, Robert W. E-mail: dietz@csi.tu-darmstadt.de; Dietz, Christian E-mail: dietz@csi.tu-darmstadt.de; Heim, Lars-Oliver

    2015-03-14

    The friction force between nanoparticles and a silicon wafer is a crucial parameter for cleaning processes in the semiconductor industry. However, little is known about the pH-dependency of the friction forces and the shear strength at the interface. Here, we push polystyrene nanoparticles, 100 nm in diameter, with the tip of an atomic force microscope and measure the pH-dependency of the friction, adhesion, and normal forces on a silicon substrate covered with a native silicon dioxide layer. The peak force tapping mode was applied to control the vertical force on these particles. We successively increased the applied load until the particles started to move. The main advantage of this technique over single manipulation processes is the achievement of a large number of manipulation events in short time and in a straightforward manner. Geometrical considerations of the interaction forces at the tip-particle interface allowed us to calculate the friction force and shear strength from the applied normal force depending on the pH of an aqueous solution. The results clearly demonstrated that particle removal should be performed with a basic solution at pH 9 because of the low interaction forces between particle and substrate.

  14. Appropriate Loads for Peak-Power During Resisted Sprinting on a Non-Motorized Treadmill

    PubMed Central

    Andre, Matthew J.; Fry, Andrew C.; Lane, Michael T.

    2013-01-01

    The purpose of this study was to determine the load which allows the highest peak power for resisted sprinting on a non-motorized treadmill and to determine if other variables are related to individual differences. Thirty college students were tested for vertical jump, vertical jump peak and mean power, 10 m sprint, 20 m sprint, leg press 1 RM, leg press 1 RM relative to body weight, leg press 1 RM relative to lean body mass, leg press 1 RM power, and leg press power at 80% of 1 RM. Participants performed eight resisted sprints on a non-motorized treadmill, with increasing relative loads expressed as percent of body weight. Sprint peak power was measured for each load. Pearson correlations were used to determine if relationships between the sprint peak power load and the other variables were significant. The sprint peak power load had a mode of 35% with 73% of all participants having a relative sprint peak power load between 25–35%. Significant correlations occurred between sprint peak power load and body weight, lean body mass, vertical jump peak and mean power, leg press 1 RM, leg press 1 RM relative to lean body mass, leg press 1 RM power, and leg press power at 80% of 1 RM (r = 0.44, 0.43, 0.39, 0.37, 0.47, 0.39, 0.46, and 0.47, respectively). Larger, stronger, more powerful athletes produced peak power at a higher relative load during resisted sprinting on a non-motorized treadmill. PMID:24233103

  15. Jumping of water striders on water

    NASA Astrophysics Data System (ADS)

    Yang, Eunjin; Son, Jaehak; Jablonski, Piotr; Kim, Ho-Young

    2012-11-01

    Small insects such as water striders, springtails, fishing spiders freely move on water by adopting various modes of locomotion, such as rowing, galloping, jumping and meniscus-climbing. As the physics of jumping have not yet been fully understood among those ways of semi-aquatic propulsion, here we present the results of a combined experimental and theoretical investigation of the dynamics of water striders leaping off water. We first image and analyze the trajectories of the legs and body of jumping water striders of three different species with a high-speed camera. We then theoretically compute the forces acting on the body by considering the capillary interaction between the flexible legs and deforming water meniscus. Our theory enables us to predict the maximum take-off speed for given leg lengths. The experimental measurements suggest that the water striders drive their legs near the optimal speed to gain the maximum take-off speed.

  16. Lift-off dynamics in a simple jumping robot

    NASA Astrophysics Data System (ADS)

    Aguilar, Jeffrey; Lesov, Alex; Wiesenfeld, Kurt; Goldman, Daniel I.

    2013-03-01

    Jumping is an important behavior utilized by animals to escape predation, hunt, reach higher ground, and as a primary mode of locomotion. Many mathematical and physical robot models use numerous parameters and multi-link legs to accurately model jumping dynamics. However, a simple robot model can reveal important principles of high performance jumping. We study vertical jumping in a simple robot comprising an actuated mass-spring arrangement. The actuator frequency and phase are systematically varied to find optimal performance. Optimal jumps occur above and below (but not at) the robot's resonant frequency f0. Two distinct jumping modes emerge: a simple jump which is optimal above f0 is achievable with a squat maneuver, and a peculiar stutter jump which is optimal below f0 is generated with a counter-movement. A simple dynamical model reveals how optimal lift-off results from non-resonant transient dynamics. An expanded explanation of this work is provided at http://crablab.gatech.edu/pages/jumpingrobot/index.html This work was supported by the GEM Consortium, Burroughs Wellcome Fund, ARL MAST CTA, and NSF PoLS.

  17. Effect of Instructions on Selected Jump Squat Variables.

    PubMed

    Talpey, Scott W; Young, Warren B; Beseler, Bradley

    2016-09-01

    Talpey, SW, Young, WB, and Beseler, B. Effect of instructions on selected jump squat variables. J Strength Cond Res 30(9): 2508-2513, 2016-The purpose of this study was to compare 2 instructions on the performance of selected variables in a jump squat (JS) exercise. The second purpose was to determine the relationships between JS variables and sprint performance. Eighteen male subjects with resistance training experience performed 2 sets of 4 JS with no extra load with the instructions to concentrate on (a) jumping for maximum height and (b) extending the legs as fast as possible to maximize explosive force. Sprint performance was assessed at 0- to 10-m and 10- to 20-m distances. From the JS jump height, peak power, relative peak power, peak force, peak velocity, and countermovement distance were measured from a force platform and position transducer system. The JS variables under the 2 instructions were compared with paired t-tests, and the relationships between these variables and sprint performance were determined with Pearson's correlations. The jump height instruction produced greater mean jump height and peak velocity (p < 0.05), but the fast leg extension instruction produced greater (p < 0.05) peak force (3.7%). There was a trivial difference between the instructions for peak power output (p > 0.05). Jump height was the variable that correlated most strongly with 10-m time and 10- to 20-m time under both instructions. The height instruction produced a stronger correlation with 10-m time (r = -0.455), but the fast leg extension JS produced a greater correlation with 10-20 time (r = -0.545). The results indicate that instructions have a meaningful influence on JS variables and therefore need to be taken into consideration when assessing or training athletes.

  18. Spinning hydraulic jump

    NASA Astrophysics Data System (ADS)

    Abderrahmane, Hamid; Kasimov, Aslan

    2013-11-01

    We report an experimental observation of a new symmetry breaking of circular hydraulic jump into a self-organized structure that consists of a spinning polygonal jump and logarithmic-spiral waves of fluid elevation downstream. The waves are strikingly similar to spiral density waves in galaxies. The fluid flow exhibits counterparts of salient morphological features of galactic flows, in particular the outflow from the center, jets, circum-nuclear rings, gas inflows toward the galactic center, and vortices. The hydrodynamic instability revealed here may have a counterpart that plays a role in the formation and sustainability of spiral arms in galaxies.

  19. Predicting lower body power from vertical jump prediction equations for loaded jump squats at different intensities in men and women.

    PubMed

    Wright, Glenn A; Pustina, Andrew A; Mikat, Richard P; Kernozek, Thomas W

    2012-03-01

    The purpose of this study was to determine the efficacy of estimating peak lower body power from a maximal jump squat using 3 different vertical jump prediction equations. Sixty physically active college students (30 men, 30 women) performed jump squats with a weighted bar's applied load of 20, 40, and 60% of body mass across the shoulders. Each jump squat was simultaneously monitored using a force plate and a contact mat. Peak power (PP) was calculated using vertical ground reaction force from the force plate data. Commonly used equations requiring body mass and vertical jump height to estimate PP were applied such that the system mass (mass of body + applied load) was substituted for body mass. Jump height was determined from flight time as measured with a contact mat during a maximal jump squat. Estimations of PP (PP(est)) for each load and for each prediction equation were compared with criterion PP values from a force plate (PP(FP)). The PP(est) values had high test-retest reliability and were strongly correlated to PP(FP) in both men and women at all relative loads. However, only the Harman equation accurately predicted PP(FP) at all relative loads. It can therefore be concluded that the Harman equation may be used to estimate PP of a loaded jump squat knowing the system mass and peak jump height when more precise (and expensive) measurement equipment is unavailable. Further, high reliability and correlation with criterion values suggest that serial assessment of power production across training periods could be used for relative assessment of change by either of the prediction equations used in this study.

  20. Correlation between ground reaction force and tibial acceleration in vertical jumping.

    PubMed

    Elvin, Niell G; Elvin, Alex A; Arnoczky, Steven P

    2007-08-01

    Modern electronics allow for the unobtrusive measurement of accelerations outside the laboratory using wireless sensor nodes. The ability to accurately measure joint accelerations under unrestricted conditions, and to correlate them with jump height and landing force, could provide important data to better understand joint mechanics subject to real-life conditions. This study investigates the correlation between peak vertical ground reaction forces, as measured by a force plate, and tibial axial accelerations during free vertical jumping. The jump heights calculated from force-plate data and accelerometer measurements are also compared. For six male subjects participating in this study, the average coefficient of determination between peak ground reaction force and peak tibial axial acceleration is found to be 0.81. The coefficient of determination between jump height calculated using force plate and accelerometer data is 0.88. Data show that the landing forces could be as high as 8 body weights of the jumper. The measured peak tibial accelerations ranged up to 42 g. Jump heights calculated from force plate and accelerometer sensors data differed by less than 2.5 cm. It is found that both impact accelerations and landing forces are only weakly correlated with jump height (the average coefficient of determination is 0.12). This study shows that unobtrusive accelerometers can be used to determine the ground reaction forces experienced in a jump landing. Whereas the device also permitted an accurate determination of jump height, there was no correlation between peak ground reaction force and jump height.

  1. Jump into Action

    ERIC Educational Resources Information Center

    Ball, Stephen; Cohen, Ann; Meyer, Margaret

    2012-01-01

    Jump Into Action (JIA) is a school-based team-taught program to help fifth-grade students make healthy food choices and be more active. The JIA team (physical education teacher, classroom teacher, school nurse, and parent) work together to provide a supportive environment as students set goals to improve food choices and increase activity.…

  2. Jump with Jill

    ERIC Educational Resources Information Center

    Henderson, Nancy

    2010-01-01

    This article profiles Jill Jayne, who was working as a registered nutritionist in the New York City public school system when she was assigned to a group of 25 urban students in an after-school program in East Harlem. In the spring of 2006, Jayne took her "Jump With Jill" show to the streets outside Central Park, collected tips in a tin…

  3. Egg Bungee Jump!

    ERIC Educational Resources Information Center

    Fitzgerald, Mike; Brand, Lance

    2004-01-01

    In this article, the authors present an egg bungee jumping activity. This activity introduces students to ways that engineers might apply calculations of failure to meet a challenge. Students are required to use common, everyday materials such as rubber bands, string, plastic bags, and eggs. They will apply technological problem solving, material…

  4. The Jumping Ring Experiment

    ERIC Educational Resources Information Center

    Baylie, M.; Ford, P. J.; Mathlin, G. P.; Palmer, C.

    2009-01-01

    The jumping ring experiment has become central to liquid nitrogen shows given as part of the outreach and open day activities carried out within the University of Bath. The basic principles of the experiment are described as well as the effect of changing the geometry of the rings and their metallurgical state. In general, aluminium rings are…

  5. Viscous Puddle Jump

    NASA Astrophysics Data System (ADS)

    Al Jubaree, Taif; Weislogel, Mark; Hua, Tan

    2016-11-01

    The phenomena of spontaneous droplet jump from hydrophobic surfaces during low-g drop tower tests was recently reviewed. Such drops may be over 10,000 times larger than typical terrestrial drops and are more akin to puddles than drops. In this work we investigate the effect of viscosity on the puddle jump process for drop/puddle volumes up to 100 mL and dynamic viscosities up to 950 cSt. The large low-cost hydrophobic surfaces are created using PTFE-coated 320 grit sand paper. We adopt a scaling approach to evaluate the relevant terms of the momentum equation before performing an energy balance for both driving and dissipation terms. A scaling law is corroborated by the experimental data for viscous puddle jump time and puddle recoil velocity. Numerical solutions are also conducted for comparisons. We demonstrate highly damped puddle jumps which may be exploited in turn to study further drop dynamics phenomena such as vanishingly small Weber number drop-wall impacts, over-damped oblique impacts and rebounds, and viscous wall-bound droplet boiling in low-gravity environments.

  6. The Jumping Ring Experiment

    ERIC Educational Resources Information Center

    Baylie, M.; Ford, P. J.; Mathlin, G. P.; Palmer, C.

    2009-01-01

    The jumping ring experiment has become central to liquid nitrogen shows given as part of the outreach and open day activities carried out within the University of Bath. The basic principles of the experiment are described as well as the effect of changing the geometry of the rings and their metallurgical state. In general, aluminium rings are…

  7. Jump into Action

    ERIC Educational Resources Information Center

    Ball, Stephen; Cohen, Ann; Meyer, Margaret

    2012-01-01

    Jump Into Action (JIA) is a school-based team-taught program to help fifth-grade students make healthy food choices and be more active. The JIA team (physical education teacher, classroom teacher, school nurse, and parent) work together to provide a supportive environment as students set goals to improve food choices and increase activity.…

  8. Jump with Jill

    ERIC Educational Resources Information Center

    Henderson, Nancy

    2010-01-01

    This article profiles Jill Jayne, who was working as a registered nutritionist in the New York City public school system when she was assigned to a group of 25 urban students in an after-school program in East Harlem. In the spring of 2006, Jayne took her "Jump With Jill" show to the streets outside Central Park, collected tips in a tin…

  9. Egg Bungee Jump!

    ERIC Educational Resources Information Center

    Fitzgerald, Mike; Brand, Lance

    2004-01-01

    In this article, the authors present an egg bungee jumping activity. This activity introduces students to ways that engineers might apply calculations of failure to meet a challenge. Students are required to use common, everyday materials such as rubber bands, string, plastic bags, and eggs. They will apply technological problem solving, material…

  10. Comparison of the Hang High-Pull and Loaded Jump Squat for the Development of Vertical Jump and Isometric Force-Time Characteristics.

    PubMed

    Oranchuk, Dustin J; Robinson, Tracey L; Switaj, Zachary J; Drinkwater, Eric J

    2017-04-15

    Weightlifting movements have high skill demands and require expert coaching. Loaded jumps have a comparably lower skill demand, but may be similarly effective for improving explosive performance. The purpose of this study was to compare vertical jump performance, isometric force, and rate of force development (RFD) following a ten-week intervention employing the hang high-pull (hang-pull) or trap-bar jump squat (jump-squat). Eighteen NCAA Division II swimmers (8 males, 10 females) with at least one year of resistance training experience volunteered to participate. Testing included the squat jump (SJ), countermovement jump (CMJ) and the isometric mid-thigh pull (IMTP). Vertical ground reaction forces were analyzed to obtain jump height and relative peak power. Relative peak force, peak RFD and relative force at five time bands were obtained from the IMTP. Subjects were randomly assigned to either a hang-pull (n = 9) or jump-squat (n = 9) training group and completed a ten-week, volume-equated, periodized training program. While there was a significant main effect of training for both groups, no statistically significant between-group differences were found (p ≥ 0.17) for any of the dependent variables. However, medium effect sizes in favor of the jump-squat training group were seen in SJ height (d = 0.56) and SJ peak power (d = 0.69). Loaded jumps seem equally effective as weightlifting derivatives for improving lower-body power in experienced athletes. Since loaded jumps require less skill and less coaching expertise than weightlifting, loaded jumps should be considered where coaching complex movements is difficult.

  11. DC-Powered Jumping Ring

    ERIC Educational Resources Information Center

    Jeffery, Rondo N.; Farhang, Amiri

    2016-01-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant…

  12. DC-Powered Jumping Ring

    ERIC Educational Resources Information Center

    Jeffery, Rondo N.; Farhang, Amiri

    2016-01-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant…

  13. Effects of assisted jumping on vertical jump parameters.

    PubMed

    Tran, Tai T; Brown, Lee E; Coburn, Jared W; Lynn, Scott K; Dabbs, Nicole C

    2012-01-01

    Vertical jumping ability is a critical skill for success in many sports. Previous studies have reported conflicting results on the effects of heavy-load, light-load, contrast, or plyometric training to improve vertical jump height. A novel jump training method, using assistance via elastic cords or an absolute weight, has received little attention. These studies, using an overspeed paradigm, support assistance as an effective training method compared with free or overload jump training. However, there is a lack of investigation and standardization related to the critical assisted jump training variables of frequency, intensity (assistance level), volume, and rest. Therefore, the purpose of this review was to provide an overview of assisted jump training, associated variables, and potential benefits to enhance vertical jump height.

  14. Inter-segmental moment analysis characterises the partial correspondence of jumping and jerking

    PubMed Central

    Cleather, Daniel J; Goodwin, Jon E; Bull, Anthony MJ

    2014-01-01

    The aim of this study was to quantify internal joint moments of the lower limb during vertical jumping and the weightlifting jerk in order to improve awareness of the control strategies and correspondence between these activities, and to facilitate understanding of the likely transfer of training effects. Athletic males completed maximal unloaded vertical jumps (n=12) and explosive push jerks at 40 kg (n=9). Kinematic data were collected using optical motion tracking and kinetic data via a force plate, both at 200 Hz. Joint moments were calculated using a previously described biomechanical model of the right lower limb. Peak moment results highlighted that sagittal plane control strategies differed between jumping and jerking (p<0.05) with jerking being a knee dominant task in terms of peak moments as opposed to a more balanced knee and hip strategy in jumping and landing. Jumping and jerking exhibited proximal to distal joint involvement and landing was typically reversed. High variability was seen in non-sagittal moments at the hip and knee. Significant correlations were seen between jump height and hip and knee moments in jumping (p<0.05). Whilst hip and knee moments were correlated between jumping and jerking (p<0.05), joint moments in the jerk were not significantly correlated to jump height (p>0.05) possibly indicating a limit to the direct transferability of jerk performance to jumping. Ankle joint moments were poorly related to jump performance (p>0.05). Peak knee and hip moment generating capacity are important to vertical jump performance. The jerk appears to offer an effective strategy to overload joint moment generation in the knee relative to jumping. However, an absence of hip involvement would appear to make it a general, rather than specific, training modality in relation to jumping. PMID:22362089

  15. Drop jumping as a training method for jumping ability.

    PubMed

    Bobbert, M F

    1990-01-01

    Vertical jumping ability is of importance for good performance in sports such as basketball and volleyball. Coaches are in need of exercises that consume only little time and still help to improve their players' jumping ability, without involving a high risk of injury. Drop jumping is assumed to satisfy these requirements. This assumption is supported by a review of results of training studies. However, it appears that regular jumping exercises can be just as helpful. The same holds for exercises with weights, provided the subjects have no weight-training history. In fact, for unskilled jumpers who have no weight-training history, the effects of training programmes utilising these different exercises are additive. The most effective, efficient and safe way for a coach to improve the jumping achievement of his athletes may well be to submit them first to a training programme utilising regular jumps, then to a weight-training programme and finally to a drop jump training programme. In drop jump training programmes themselves, the improvement in jumping height varies greatly among studies. This variation cannot be explained satisfactorily with the information available on subjects and training programmes. Given the current state of knowledge, coaches seem to have no other option than to strictly copy a programme which has proved to be very effective. Obviously there is a need for more systematic research of the relationship between design and effect of drop jump training programmes. The most important variable to be controlled is drop jumping technique. From a review of biomechanical studies of drop jumping, it becomes clear that jumping technique strongly affects the mechanical output of muscles. The biomechanics of 2 techniques are discussed. In the bounce drop jump the downward movement after the drop is reversed as soon as possible into an upward push-off, while in the countermovement drop jump this is done more gradually by increasing the amplitude of the

  16. The Lower Extremity Biomechanics of Single- and Double-Leg Stop-Jump Tasks

    PubMed Central

    2011-01-01

    The anterior cruciate ligament (ACL) injury is a common occurrence in sports requiring stop-jump tasks. Single- and double-leg stop-jump techniques are frequently executed in sports. The higher risk of ACL injury in single-leg drop landing task compared to a double-leg drop landing task has been identified. However the injury bias between single- and double-leg landing techniques has not been investigated for stop-jump tasks. The purpose of this study was to determine the differences between single- and double-leg stop-jump tasks in knee kinetics that were influenced by the lower extremity kinematics during the landing phase. Ground reaction force, lower extremity kinematics, and knee kinetics data during the landing phase were obtained from 10 subjects performing single- and double-leg stop-jump tasks, using motion-capture system and force palates. Greater peak posterior and vertical ground reaction forces, and peak proximal tibia anterior and lateral shear forces (p < 0.05) during landing phase were observed of single-leg stop-jump. Single-leg stop-jump exhibited smaller hip and knee flexion angle, and knee flexion angular velocity at initial foot contact with the ground (p < 0.05). We found smaller peak hip and knee flexion angles (p < 0.05) during the landing phase of single-leg stop-jump. These results indicate that single-leg landing may have higher ACL injury risk than double-leg landing in stop-jump tasks that may be influenced by the lower extremity kinematics during the landing phase. Key points Non-contact ACL injuries are more likely to occur during the single-leg stop-jump task than during the double-leg stop-jump task. Single-leg stop-jump exhibited greater peak proximal tibia anterior and lateral shear forces, and peak posterior and vertical ground reaction forces during the landing phase than the double-leg stop-jump task. Single-leg stop-jump exhibited smaller hip flexion angle, knee flexion angle, and knee flexion angular velocity at initial foot

  17. Injuries and bungee jumping.

    PubMed

    Vanderford, L; Meyers, M

    1995-12-01

    Bungee jumping is a recreational sport that has gained world-wide popularity since its inception in 1955. Over 2 million individuals have performed bungee jumps since that time. The injuries and deaths which have occurred have made safety an integral issue in the practice of the sport. Although early reports of significant injuries are infrequent, more recent investigations have indicated severe sequelae, including ocular haemorrhage, peroneal nerve palsy and quadriplegia. Reports of minor trauma have also been numerous. Aetiology includes natural forces, impact, technician error, equipment failure and repetitive stress. Free-falling approximately 60 to 120m (200 to 400ft) and then being jerked to safety at the last minute creates a certain amount of unavoidable, and almost desired risk. A reduction in acute trauma may be possible with immediate changes in equipment, technique and regulations. Further studies are warranted to determine the future direction and safety of this recreational sport.

  18. Optimal Ski Jump

    NASA Astrophysics Data System (ADS)

    Rebilas, Krzysztof

    2013-02-01

    Consider a skier who goes down a takeoff ramp, attains a speed V, and jumps, attempting to land as far as possible down the hill below (Fig. 1). At the moment of takeoff the angle between the skier's velocity and the horizontal is α. What is the optimal angle α that makes the jump the longest possible for the fixed magnitude of the velocity V? Of course, in practice, this is a very sophisticated problem; the skier's range depends on a variety of complex factors in addition to V and α. However, if we ignore these and assume the jumper is in free fall between the takeoff ramp and the landing point below, the problem becomes an exercise in kinematics that is suitable for introductory-level students. The solution is presented here.

  19. Jumping number in the droplet jumping by resonant AC electrowetting

    NASA Astrophysics Data System (ADS)

    Lee, Sanghyun; Lee, Seung Jun; Kang, Kwang Hyoung

    2010-11-01

    The droplet jumping by resonant AC electrowetting (DJ-RACE) is recently introduced to transport droplets to vertical direction, whereby three-dimensional digital microfluidics are envisioned. In DJ-RACE, the central mechanism of the droplet jumping is the conversion of the surface energy stored by resonant AC electrowetting to the kinetic energy for jumping. Here, we newly introduce the jumping number (Ju=γ/ρgR^2), measuring the energy conversion in the jumping process and, thus, the feasibility of droplet jumping. Ju interprets that droplets having higher Ju can make higher and easier jumping, and smaller and lighter droplets with higher surface tension can have higher Ju. Practically, Ju should be greater than 1.5 for the droplet jumping, and active jumping was observed when Ju is greater than 5. In addition, Ju can predict the effect of diverse physicochemical changes in a system such as enzymatic additives or impurities on jumping, where it can also provide diverse strategies to compensate these changes. The newly introduced Ju could be the fundamental and useful parameter in the three-dimensional digital microfluidic devices based on DJ-RACE.

  20. Effects of jump training with negative versus positive loading on jumping mechanics.

    PubMed

    Markovic, G; Vuk, S; Jaric, S

    2011-05-01

    We examined the effects of jump training with negative (-30% of the subject's body weight (BW)) VS. positive loading (+30% BW) on the mechanical behaviour of leg extensor muscles. 32 men were divided into control (CG), negative loading (NLG), or positive loading training group (PLG). Both training groups performed maximal effort countermovement jumps (CMJ) over a 7-week training period. The impact of training on the mechanical behaviour of leg extensor muscles was assessed through CMJ performed with external loads ranging from -30% BW to +30% BW. Both training groups showed significant ( P≤0.013) increase in BW CMJ height (NLG: 9%, effect size (ES)=0.85, VS. PLG: 3.4%, ES=0.31), peak jumping velocity ( V(peak); NLG: 4.1%; ES=0.80, P=0.011, VS. PLG: 1.4%, ES=0.24; P=0.017), and depth of the countermovement (Δ H(ecc); NLG: 20%; ES=-1.64, P=0.004, VS. PLG: 11.4%; ES=-0.86, P=0.015). Although the increase in both the V(peak) and Δ H(ecc) were expected to reduce the recorded ground reaction force, the indices of force- and power-production characteristics of CMJ remained unchanged. Finally, NLG (but not PLG) suggested load-specific improvement in the movement kinematic and kinetic patterns. Overall, the observed results revealed a rather novel finding regarding the effectiveness of negative loading in enhancing CMJ performance which could be of potential importance for further development of routine training protocols. Although the involved biomechanical and neuromuscular mechanisms need further exploration, the improved performance could be partly based on an altered jumping pattern that utilizes an enhanced ability of leg extensors to provide kinetic and power output during the concentric jump phase. © Georg Thieme Verlag KG Stuttgart · New York.

  1. Jumping phase control in interband photonic transition.

    PubMed

    Liu, Ye; Zhu, Jiang; Gao, Zhuoyang; Zhu, Haibin; Jiang, Chun

    2014-03-10

    Indirect interband photonic transition provides a nonmagnetic and linear scheme to achieve optical isolation in integrated photonics. In this paper, we demonstrate that the nonreciprocal transition can be induced through two pathways respectively by different modulation designs. At the end of those pathways, the two final modes have π phaseshift. We call this phenomenon jumping phase control since this approach provides a method to control the mode phase after the conversion. This approach also yields a novel way to generate nonreciprocal phaseshift and may contribute to chip-scale optoelectronic applications.

  2. Jumping hoops on water

    NASA Astrophysics Data System (ADS)

    Yang, Eunjin; Kim, Ho-Young

    2015-11-01

    Small aquatic arthropods, such as water striders and fishing spiders, are able to jump off water to a height several times their body length. Inspired by the unique biological motility on water, we study a simple model using a flexible hoop to provide fundamental understanding and a mimicking principle of small jumpers on water. Behavior of a hoop on water, which is coated with superhydrophobic particles and initially bent into an ellipse from an equilibrium circular shape, is visualized with a high speed camera upon launching it into air by releasing its initial elastic strain energy. We observe that jumping of our hoops is dominated by the dynamic pressure of water rather than surface tension, and thus it corresponds to the dynamic condition experienced by fishing spiders. We calculate the reaction forces provided by water adopting the unsteady Bernoulli equation as well as the momentum loss into liquid inertia and viscous friction. Our analysis allows us to predict the jumping efficiency of the hoop on water in comparison to that on ground, and to discuss the evolutionary pressure rendering fishing spiders select such dynamic behavior.

  3. Jumping mechanisms and strategies in moths (Lepidoptera).

    PubMed

    Burrows, Malcolm; Dorosenko, Marina

    2015-06-01

    To test whether jumping launches moths into the air, take-off by 58 species, ranging in mass from 0.1 to 220 mg, was captured in videos at 1000 frames s(-1). Three strategies for jumping were identified. First, rapid movements of both middle and hind legs provided propulsion while the wings remained closed. Second, middle and hind legs again provided propulsion but the wings now opened and flapped after take-off. Third, wing and leg movements both began before take-off and led to an earlier transition to powered flight. The middle and hind legs were of similar lengths and were between 10 and 130% longer than the front legs. The rapid depression of the trochantera and extension of the middle tibiae began some 3 ms before similar movements of the hind legs, but their tarsi lost contact with the ground before take-off. Acceleration times ranged from 10 ms in the lightest moths to 25 ms in the heaviest ones. Peak take-off velocities varied from 0.6 to 0.9 m s(-1) in all moths, with the fastest jump achieving a velocity of 1.2 m s(-1). The energy required to generate the fastest jumps was 1.1 µJ in lighter moths but rose to 62.1 µJ in heavier ones. Mean accelerations ranged from 26 to 90 m s(-2) and a maximum force of 9 G: was experienced. The highest power output was within the capability of normal muscle so that jumps were powered by direct contractions of muscles without catapult mechanisms or energy storage. © 2015. Published by The Company of Biologists Ltd.

  4. Twin Peaks

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The two hills in the distance, approximately one to two kilometers away, have been dubbed the 'Twin Peaks' and are of great interest to Pathfinder scientists as objects of future study. The white areas on the left hill, called the 'Ski Run' by scientists, may have been formed by hydrologic processes.

    The image was taken by the Imager for Mars Pathfinder (IMP) after its deployment on Sol 3. Mars Pathfinder was developed and managed by the Jet Propulsion Laboratory (JPL) for the National Aeronautics and Space Administration. The IMP was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

  5. Muscular strength and jumping performance relationships in young women athletes.

    PubMed

    Rousanoglou, Elissavet N; Georgiadis, Georgios V; Boudolos, Konstantinos D

    2008-07-01

    The relationships between muscular strength and vertical jumping performance were examined in young women (14-19 years) track and field jumpers (n = 20) and volleyball players (n = 21). The knee extensor muscular strength measured at 9 knee angles was correlated with jumping height and peak power at the squat (SJ) and the countermovement (CMJ) vertical jump tests. Pearson product coefficient of correlation was used to test the significance of these relationships (p 0.80). Specifically, in the volleyball players, the strong relationships were noted for muscular strength at the knee angle range of 40 degrees to 90 degrees and CMJ jumping height as well as SJ peak power. Results indicate the dissimilarity in the relationships between the knee extensor muscular strength and jumping performance in the young female track and field jumpers and volleyball players. In addition, it appears that the measure selected to evaluate jumping performance alters the correlational results.

  6. Factors influencing spike jump height in female college volleyball players.

    PubMed

    Ikeda, Yusuke; Sasaki, Yusuke; Sorimachi, Shingo; Hamano, Rena

    2017-09-06

    The purpose of this study was to examine factors influencing spike jump (SPJ) performance by female competitive volleyball players through comparisons of the kinematic data of SPJ with those of the standing long jump (SLJ) and vertical jump (VJ). Seventeen female competitive volleyball players were asked to perform SPJ, SLJ, and VJ. Motion data of SPJ including the approach phase were recorded. Regarding SLJ and VJ, jumping motion and ground reaction force were recorded during each performance. The results obtained showed that SPJ height correlated with vertical velocity at take-off, horizontal velocity at third step contact, and the deceleration of horizontal velocity from third step contact to take-off. Regarding the relationship among SPJ, SLJ, and VJ, the relationship between SPJ and SLJ was stronger than that with VJ. The contributions of the hip, knee, and ankle muscles to the propulsive phase of SLJ were 39.7%, 21.1%, and 39.2%, respectively, whereas their contributions to VJ were 36.2%, 30.2%, and 33.6%, respectively. The vertical velocity of SPJ at take-off correlated with hip work and ankle peak power in SLJ and knee peak power in VJ. These results suggest the importance of enhancing horizontal and vertical jumping abilities separately to improve the height of SPJ because the primary generator for power production appears to depend on jump direction.

  7. The fluid dynamics of swimming by jumping in copepods

    PubMed Central

    Jiang, Houshuo; Kiørboe, Thomas

    2011-01-01

    Copepods swim either continuously by vibrating their feeding appendages or erratically by repeatedly beating their swimming legs, resulting in a series of small jumps. The two swimming modes generate different hydrodynamic disturbances and therefore expose the swimmers differently to rheotactic predators. We developed an impulsive stresslet model to quantify the jump-imposed flow disturbance. The predicted flow consists of two counter-rotating viscous vortex rings of similar intensity, one in the wake and one around the body of the copepod. We showed that the entire jumping flow is spatially limited and temporally ephemeral owing to jump-impulsiveness and viscous decay. In contrast, continuous steady swimming generates two well-extended long-lasting momentum jets both in front of and behind the swimmer, as suggested by the well-known steady stresslet model. Based on the observed jump-swimming kinematics of a small copepod Oithona davisae, we further showed that jump-swimming produces a hydrodynamic disturbance with much smaller spatial extension and shorter temporal duration than that produced by a same-size copepod cruising steadily at the same average translating velocity. Hence, small copepods in jump-swimming are in general much less detectable by rheotactic predators. The present impulsive stresslet model improves a previously published impulsive Stokeslet model that applies only to the wake vortex. PMID:21208972

  8. Application of a tri-axial accelerometer to estimate jump frequency in volleyball.

    PubMed

    Jarning, Jon M; Mok, Kam-Ming; Hansen, Bjørge H; Bahr, Roald

    2015-03-01

    Patellar tendinopathy is prevalent among athletes, and most likely associated with a high jumping load. If methods for estimating jump frequency were available, this could potentially assist in understanding and preventing this condition. The objective of this study was to explore the possibility of using peak vertical acceleration (PVA) or peak resultant acceleration (PRA) measured by an accelerometer to estimate jump frequency. Twelve male elite volleyball players (22.5 ± 1.6 yrs) performed a training protocol consisting of seven typical motion patterns, including jumping and non-jumping movements. Accelerometer data from the trial were obtained using a tri-axial accelerometer. In addition, we collected video data from the trial. Jump-float serving and spike jumping could not be distinguished from non-jumping movements using differences in PVA or PRA. Furthermore, there were substantial inter-participant differences in both the PVA and the PRA within and across movement types (p < 0.05). These findings suggest that neither PVA nor PRA measured by a tri-axial accelerometer is an applicable method for estimating jump frequency in volleyball. A method for acquiring real-time estimates of jump frequency remains to be verified. However, there are several alternative approaches, and further investigations are needed.

  9. Relationship between vertical and horizontal jump variables and muscular performance in athletes.

    PubMed

    Dobbs, Caleb W; Gill, Nicholas D; Smart, Daniel J; McGuigan, Michael R

    2015-03-01

    This study investigated the relationship between vertical and horizontal measures in bilateral and unilateral countermovement jump, drop jump and squat jump (SJ), and sprinting speed and muscle architecture of both the vastus lateralis and gastrocnemius. Subjects (n = 17) completed a 30-m sprint test, muscle stiffness test; ultrasound measures, and a jump testing session. Measures of horizontal peak and mean force, in both bilateral and unilateral jumps, tended to have greater relationships to sprint speeds (R = 0.132-0.576) than peak and mean force in the vertical plane (R = 0.008-0.504). Vertical velocity variables also showed some large and very large correlations to sprint speed (R = 0.062-0.635). Unilateral measures of velocity tended to have larger correlations to sprint performance than their bilateral counterparts across all jump types and peak and mean velocity in SJ showed large and very large correlations to sprint speed (bilateral R = 0.227-0.635; unilateral 0.393-0.574). Few large correlations were shown between muscle stiffness measures of muscle architecture and kinetic and kinematic variables in either vertical or horizontal jumps. The present findings suggest that sport scientists and strength and conditioning practitioners concerned with the prognostic value of kinetic variables to functional movements such as sprint speed should also use horizontal jumps in addition to vertical jumps in testing and training.

  10. Kinematics of the long jump

    NASA Astrophysics Data System (ADS)

    Tan, Ajun; Zumerchik, John

    2000-03-01

    The long jump is one of the most natural events in track and field athletics. The jumper is allowed to run a 40-m runway at top speed and jump as far as possible from a takeoff board. It is an event in which the natural ability of the athlete plays a large role and technique is of secondary importance. The two most important factors in the long jump are speed and elevation.

  11. High peak-power picosecond pulse generation at 1.26 µm using a quantum-dot-based external-cavity mode-locked laser and tapered optical amplifier.

    PubMed

    Ding, Y; Aviles-Espinosa, R; Cataluna, M A; Nikitichev, D; Ruiz, M; Tran, M; Robert, Y; Kapsalis, A; Simos, H; Mesaritakis, C; Xu, T; Bardella, P; Rossetti, M; Krestnikov, I; Livshits, D; Montrosset, Ivo; Syvridis, D; Krakowski, M; Loza-Alvarez, P; Rafailov, E

    2012-06-18

    In this paper, we present the generation of high peak-power picosecond optical pulses in the 1.26 μm spectral band from a repetition-rate-tunable quantum-dot external-cavity passively mode-locked laser (QD-ECMLL), amplified by a tapered quantum-dot semiconductor optical amplifier (QD-SOA). The laser emission wavelength was controlled through a chirped volume Bragg grating which was used as an external cavity output coupler. An average power of 208.2 mW, pulse energy of 321 pJ, and peak power of 30.3 W were achieved. Preliminary nonlinear imaging investigations indicate that this system is promising as a high peak-power pulsed light source for nonlinear bio-imaging applications across the 1.0 μm - 1.3 μm spectral range.

  12. Aeromechanics of the Spider Cricket Jump: How to Jump 60+ Times Your Body Length and Still Land on Your Feet

    NASA Astrophysics Data System (ADS)

    Palmer, Emily; Deshler, Nicolas; Gorman, David; Neves, Catarina; Mittal, Rajat

    2015-11-01

    Flapping, gliding, running, crawling and swimming have all been studied extensively in the past and have served as a source of inspiration for engineering designs. In the current project, we explore a mode of locomotion that straddles ground and air: jumping. The subject of our study is among the most proficient of long-jumpers in Nature: the spider cricket of the family Rhaphidophoridae, which can jump more than 60 times its body length. Despite jumping this immense distance, these crickets usually land on their feet, indicating an ability to control their posture during ``flight.'' We employ high-speed videogrammetry, to examine the jumps and to track the crickets' posture and appendage orientation throughout their jumps. Simple aerodynamic models are developed to predict the aerodynamic forces and moment on the crickets during `flight`. The analysis shows that these wingless insects employ carefully controlled and coordinated positioning of the limbs during flight so as to increase jump distance and to stabilize body posture during flight. The principles distilled from this study could serve as an inspiration for small jumping robots that can traverse complex terrains.

  13. The relationship between vertical jump power estimates and weightlifting ability: a field-test approach.

    PubMed

    Carlock, Jon M; Smith, Sarah L; Hartman, Michael J; Morris, Robert T; Ciroslan, Dragomir A; Pierce, Kyle C; Newton, Robert U; Harman, Everett A; Sands, William A; Stone, Michael H

    2004-08-01

    The purpose of this study was to assess the usefulness of the vertical jump and estimated vertical-jump power as a field test for weightlifting. Estimated PP output from the vertical jump was correlated with lifting ability among 64 USA national-level weightlifters (junior and senior men and women). Vertical jump was measured using the Kinematic Measurement System, consisting of a switch mat interfaced with a laptop computer. Vertical jumps were measured using a hands-on-hips method. A counter-movement vertical jump (CMJ) and a static vertical jump (SJ, 90 degrees knee angle) were measured. Two trials were given for each condition. Test-retest reliability for jump height was intra-class correlation (ICC) = 0.98 (CMJ) and ICC = 0.96 (SJ). Athletes warmed up on their own for 2-3 minutes, followed by 2 practice jumps at each condition. Peak power (PP) was estimated using the equations developed by Sayers et al. (24). The athletes' current lifting capabilities were assessed by a questionnaire, and USA national coaches checked the listed values. Differences between groups (i.e., men versus women, juniors versus resident lifters) were determined using t-tests (p < or = 0.05). Correlations were determined using Pearson's r. Results indicate that vertical jumping PP is strongly associated with weightlifting ability. Thus, these results indicate that PP derived from the vertical jump (CMJ or SJ) can be a valuable tool in assessing weightlifting performance.

  14. Effects of footwear condition on maximal jumping performance.

    PubMed

    Harry, John R; Paquette, Max R; Caia, Johnpaul; Townsend, Robert J; Weiss, Lawrence W; Schilling, Brian K

    2015-06-01

    The purpose of this investigation was to examine the effects of footwear on kinetics and lower extremity electromyographic (EMG) activity during the vertical jump (VJ) and standing long jump. Fifteen men performed the 2 jump types in 3 footwear conditions: barefoot, minimal shoes, and cross-training shoes. Jump displacement and kinetic data were collected, along with EMG activity of the biceps femoris, medial gastrocnemius, peroneus longus, semitendinosus/semimembranosus, soleus (SOL), tibialis anterior, vastus lateralis, and vastus medialis. Subjective footwear performance and comfort were also assessed with a custom survey. No differences were found in jump displacement, peak ground reaction forces (GRF), countermovement and propulsive phase durations, vertical impulse, peak countermovement, or average propulsive EMG activity. Significant differences in peak propulsive root mean square EMG were found between barefoot and minimal shoes (p = 0.030) and minimal shoes and shod (p = 0.031) conditions for the SOL during the VJ, and for average countermovement EMG of the semitendinosus/semimembranosus during the VJ between barefoot and shod (p = 0.039). Moderate-to-large effect sizes (>0.59) were found between conditions for horizontal GRF, propulsive phase duration, average EMG amplitude, and duration of EMG activity during the countermovement. Participants reported higher comfort ratings when shod compared with barefoot and minimal shoes for both jumps. Participants also perceived better performance when shod compared with barefoot and minimal shoes for the VJ only. No acute differences in displacement were observed between barefoot, minimal shoes, and cross-trainer shoes during vertical and horizontal jumps. Some differences in muscle activation and timing seem to be present, and thus, training effects between footwear conditions should be examined. Footwear familiarization may prove beneficial, as acute increases in comfort seem unrelated to performance improvements.

  15. Influence of a Horizontal Approach on the Mechanical Output during Drop Jumps

    ERIC Educational Resources Information Center

    Ruan, Mianfang; Li, Li

    2008-01-01

    This study investigated the influence of a horizontal approach to mechanical output during drop jumps. Participants performed drop jumps from heights of 15, 30, 45, and 60 cm with zero, one, two, and three approach steps. The peak summed power during the push-off phase changed quadratically across heights (6.2 [plus or minus] 0.3, 6.7 [plus or…

  16. Influence of a Horizontal Approach on the Mechanical Output during Drop Jumps

    ERIC Educational Resources Information Center

    Ruan, Mianfang; Li, Li

    2008-01-01

    This study investigated the influence of a horizontal approach to mechanical output during drop jumps. Participants performed drop jumps from heights of 15, 30, 45, and 60 cm with zero, one, two, and three approach steps. The peak summed power during the push-off phase changed quadratically across heights (6.2 [plus or minus] 0.3, 6.7 [plus or…

  17. More Puddle Jumping

    NASA Astrophysics Data System (ADS)

    Attari, Babak; Weislogel, Mark; Wollman, Andrew; Chen, Yongkang; Snyder, Trevor

    2016-11-01

    Large droplets and puddles jump spontaneously from sufficiently hydrophobic surfaces during routine drop tower tests. The simple low-cost passive mechanism can in turn be used as an experimental device to investigate dynamic droplet phenomena for drops up to 10,000 times larger than their normal terrestrial counterparts. We provide or confirm quick and qualitative design guides for such 'drop shooters' as employed in drop tower tests including relationships to predict droplet ejection durations and velocities as functions of drop volume, surface texture, surface contour, wettability pattern, drop volume, and fluid properties including contact angle. The latter are determined via profile image comparisons with numerical equilibrium interface computations. Water drop volumes of 0.04 to 400 mL at ejection speeds of -0.007 to 0.12 m/s are demonstrated. An example application of the puddle jump method is made to the classic problem of regime mapping for low-gravity phase change heat transfer for large impinging drops. Many other candidate problems might be identified.

  18. Exploring Lightning Jump Characteristics

    NASA Technical Reports Server (NTRS)

    Chronis, Themis; Carey, Larry D.; Schultz, Christopher J.; Schultz, Elise; Calhoun, Kristin; Goodman, Steven J.

    2014-01-01

    This study is concerned with the characteristics of storms exhibiting an abrupt temporal increase in the total lightning flash rate (i.e., lightning jump, LJ). An automated storm tracking method is used to identify storm "clusters" and total lightning activity from three different lightning detection systems over Oklahoma, northern Alabama and Washington, D.C. On average and for different employed thresholds, the clusters that encompass at least one LJ (LJ1) last longer, relate to higher Maximum Expected Size of Hail, Vertical Integrated Liquid and lightning flash rates (area-normalized) than the clusters that did not exhibit any LJ (LJ0). The respective mean values for LJ1 (LJ0) clusters are 80 min (35 min), 14 mm (8 mm), 25 kg per square meter (18 kg per square meter) and 0.05 flash per min per square kilometer (0.01 flash per min per square kilometer). Furthermore, the LJ1 clusters are also characterized by slower decaying autocorrelation functions, a result that implies a less "random" behavior in the temporal flash rate evolution. In addition, the temporal occurrence of the last LJ provides an estimate of the time remaining to the storm's dissipation. Depending of the LJ strength (i.e., varying thresholds), these values typically range between 20-60 min, with stronger jumps indicating more time until storm decay. This study's results support the hypothesis that the LJ is a proxy for the storm's kinematic and microphysical state rather than a coincidental value.

  19. Are there quantum jumps

    NASA Astrophysics Data System (ADS)

    Ferry, D. K.

    2014-09-01

    Generally, one thinks of a “quantum jump” as the process in which an electron “jumps” between a pair of quantum states, even as the process is treated within perturbation theory. This jump of an electron has remained a key point of conservative (i.e., traditional) quantum mechanics. But, the question of the time dependence of such a transition, e.g. the time for an atom to be ionized by radiation, is somewhat different than this view. A detailed approach in which an incoming wave first polarizes the quantum states and then completes the transition has allowed for a detailed discussion of the smooth transition of the electron from one state to the next. Here, we will discuss the history of the process, and illustrate the approach with the question of “how long does it take for an electron to emit a phonon?” The entire process arises from the proper application of wave mechanics and obviates the need to even consider a discussion of quantum jumps.

  20. Comparing jumping ability among athletes of various sports: vertical drop jumping from 60 centimeters.

    PubMed

    Kollias, Iraklis; Panoutsakopoulos, Vassilios; Papaiakovou, Georgios

    2004-08-01

    Drop jumping performance (DJP) is of high importance in order to achieve sporting performance in both team and individual sports. The purpose of the present study was to compare DJP among athletes from various sports. One hundred thirty-eight male athletes (age: 22.3 +/- 3.6 years, body height: 1.87 +/- 0.08 m, body mass: 81.8 +/- 10.8 kg) from 6 different sports performed drop jumps from 60 cm (DJ60) on a force plate. Results revealed that volleyball players jumped higher (p < 0.001) than other athletes. However, track and field athletes produced higher peak force and higher power output using a shorter upward phase (p < 0.001). Further examination using principal components analysis (PCA) revealed that team sport athletes and single scull rowers exhibited DJP utilizing force and time parameters differently than track and field athletes. Conclusively, DJP was different among athletes of various sports. Furthermore, PCA can be a useful method for evaluating the above mentioned differences and for monitoring drop jumping training programs.

  1. Physics and the Vertical Jump

    ERIC Educational Resources Information Center

    Offenbacher, Elmer L.

    1970-01-01

    The physics of vertical jumping is described as an interesting illustration for motivating students in a general physics course to master the kinematics and dynamics of one dimensional motion. The author suggests that mastery of the physical principles of the jump may promote understanding of certain biological phenomena, aspects of physical…

  2. Evaluation of Metabolic Stress between Jumping at Different Cadences on the Digi-Jump Machine.

    PubMed

    Lyons, Thomas S; Navalta, James W; Callahan, Zachary J

    The American College of Sports Medicine (ACSM) recommends that healthy adults achieve a minimum of thirty minutes of moderate intensity aerobic exercise five days per week. While cycling, walking, and jogging are commonly observed methods of achieving these recommendations, another option may be repetitive jumping. The purpose of this study was to examine the metabolic responses between repetitive jumping at a cadence of 120 jumps per minute (JPMs) vs. 100 JPMs when utilizing the Digi-Jump machine. Twenty-eight subjects completed two jumping trials, one at 120 JPMs and one at 100 JPMs. Subjects jumped until volitional exhaustion, or for a maximum of fifteen minutes. Oxygen uptake (VO2), heart rate (HR), respiratory exchange ratio (RER), and rating of perceived exertion (RPE) were assessed each minute of each exercise trial. RPE was differentiated, in that subjects reported perceived exertion of their total body, their upper-leg, and their lower leg. Results of this study indicated that there was no significant difference between the two trials for VO2, HR, or total body RPE. Differences were reported between trials for peak and average RER, with the 120 JPM trial eliciting a lower RER for both (peak: 1.08 ± .087 vs. 1.17 ± .1 p=.000; average: .99 ± .076 vs. 1.04 ± .098 p=.002), peak upper leg RPE (120: 15.29 ± 3.89 vs. 100: 16.75 ± 2.52 p=.022), and average lower leg RPE (120: 15.04 ± 2.55 vs. 100: 13.94 ± 2.02 p=.019). Also, there was a significant difference in exercise duration between the trials, with subjects able to exercise longer during the 120 JPM trial (12.4 ± 3.42 mins vs. 9.68 ± 4.31 mins p=.000). These data indicate that while the physiological stress may not be different between the two trials as indicated by VO2 and HR, the 120 JPM trial appears less strenuous as evidenced by RER values and by subjects' ability to exercise longer at that cadence.

  3. Evaluation of Metabolic Stress between Jumping at Different Cadences on the Digi-Jump Machine

    PubMed Central

    LYONS, THOMAS S.; NAVALTA, JAMES W.; CALLAHAN, ZACHARY J.

    2010-01-01

    The American College of Sports Medicine (ACSM) recommends that healthy adults achieve a minimum of thirty minutes of moderate intensity aerobic exercise five days per week. While cycling, walking, and jogging are commonly observed methods of achieving these recommendations, another option may be repetitive jumping. The purpose of this study was to examine the metabolic responses between repetitive jumping at a cadence of 120 jumps per minute (JPMs) vs. 100 JPMs when utilizing the Digi-Jump machine. Twenty-eight subjects completed two jumping trials, one at 120 JPMs and one at 100 JPMs. Subjects jumped until volitional exhaustion, or for a maximum of fifteen minutes. Oxygen uptake (VO2), heart rate (HR), respiratory exchange ratio (RER), and rating of perceived exertion (RPE) were assessed each minute of each exercise trial. RPE was differentiated, in that subjects reported perceived exertion of their total body, their upper-leg, and their lower leg. Results of this study indicated that there was no significant difference between the two trials for VO2, HR, or total body RPE. Differences were reported between trials for peak and average RER, with the 120 JPM trial eliciting a lower RER for both (peak: 1.08 ± .087 vs. 1.17 ± .1 p=.000; average: .99 ± .076 vs. 1.04 ± .098 p=.002), peak upper leg RPE (120: 15.29 ± 3.89 vs. 100: 16.75 ± 2.52 p=.022), and average lower leg RPE (120: 15.04 ± 2.55 vs. 100: 13.94 ± 2.02 p=.019). Also, there was a significant difference in exercise duration between the trials, with subjects able to exercise longer during the 120 JPM trial (12.4 ± 3.42 mins vs. 9.68 ± 4.31 mins p=.000). These data indicate that while the physiological stress may not be different between the two trials as indicated by VO2 and HR, the 120 JPM trial appears less strenuous as evidenced by RER values and by subjects’ ability to exercise longer at that cadence. PMID:27182351

  4. DC-Powered Jumping Ring

    NASA Astrophysics Data System (ADS)

    Jeffery, Rondo N.; Amiri, Farhang

    2016-02-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant differences from the AC case. In particular, the ring does not fly off the core but rises a short distance and then falls back. If the ring jumps high enough, the rising and the falling motion of the ring does not follow simple vertical motion of a projectile. This indicates that there are additional forces on the ring in each part of its motion. Four possible stages of the motion of the ring with DC are identified, which result from the ring current changing directions during the jump in response to a changing magnetic flux through the moving ring.

  5. [Anxiety associated with parachute jumping].

    PubMed

    Kowalczyk, Edward; Kura, Marcin; Ciećwierz, Julita

    2012-08-01

    The aim of the study was to estimate an influence of parachute jumps on anxiety among professional soldiers from air-borne forces. The investigation was carried out on 46 professional soldiers from 16 Air-Borne Battalion, patients of outpatient department of 4495 Military Unit, men at 20 to 45 age, healthy--admitted to parachute jumping in air-borne forces. They were divided on groups according to a knowledge and an experience in parachuting. In order to estimate the level of nervous tension and mental stress, personal questionnaires in accordance with STAI were carried out on free day, day of parachute jump and 24h after jump. The results show the influence of parachute jumps on the parameters of psychological stress.

  6. [Pneumothorax after "reversed" bungee jump].

    PubMed

    Pedersen, M N; Jensen, B N

    1999-10-04

    We here present a case of pneumothorax in a 24 year-old previously healthy man who had performed an uncomplicated "reversed" bungee jump a few hours before. A high resolution CT scan of the thorax taken three weeks later was normal. The high energy produced during a "reversed" bungee jump, up to 7-8 g corresponds to the threshold value for NASA astronauts, and can cause injuries in healthy persons. In this case we believe that there is a correlation between the pneumothorax and the high energy jump. Bungee jumping is a very popular amusement, millions of jumps have been carried out since 1979, when the sport was introduced. No register and therefore no ratio of risk exists.

  7. Electrostatic charging of jumping droplets

    NASA Astrophysics Data System (ADS)

    Miljkovic, Nenad; Preston, Daniel J.; Enright, Ryan; Wang, Evelyn N.

    2013-09-01

    With the broad interest in and development of superhydrophobic surfaces for self-cleaning, condensation heat transfer enhancement and anti-icing applications, more detailed insights on droplet interactions on these surfaces have emerged. Specifically, when two droplets coalesce, they can spontaneously jump away from a superhydrophobic surface due to the release of excess surface energy. Here we show that jumping droplets gain a net positive charge that causes them to repel each other mid-flight. We used electric fields to quantify the charge on the droplets and identified the mechanism for the charge accumulation, which is associated with the formation of the electric double layer at the droplet-surface interface. The observation of droplet charge accumulation provides insight into jumping droplet physics as well as processes involving charged liquid droplets. Furthermore, this work is a starting point for more advanced approaches for enhancing jumping droplet surface performance by using external electric fields to control droplet jumping.

  8. Electrostatic charging of jumping droplets.

    PubMed

    Miljkovic, Nenad; Preston, Daniel J; Enright, Ryan; Wang, Evelyn N

    2013-01-01

    With the broad interest in and development of superhydrophobic surfaces for self-cleaning, condensation heat transfer enhancement and anti-icing applications, more detailed insights on droplet interactions on these surfaces have emerged. Specifically, when two droplets coalesce, they can spontaneously jump away from a superhydrophobic surface due to the release of excess surface energy. Here we show that jumping droplets gain a net positive charge that causes them to repel each other mid-flight. We used electric fields to quantify the charge on the droplets and identified the mechanism for the charge accumulation, which is associated with the formation of the electric double layer at the droplet-surface interface. The observation of droplet charge accumulation provides insight into jumping droplet physics as well as processes involving charged liquid droplets. Furthermore, this work is a starting point for more advanced approaches for enhancing jumping droplet surface performance by using external electric fields to control droplet jumping.

  9. Jumping From a Chair is a More Sensitive Measure of Power Performance In Older Adults Than Chair Rising.

    PubMed

    Zemková, Erika; Jeleň, Michal; Schickhofer, Peter; Hamar, Dušan

    2016-01-01

    Background/Study Context: The study estimates the reliability of peak velocity and peak power during chair rising and chair jumping tests and their ability to discriminate between different age and physical activity level groups. Physically active and sedentary individuals (N = 262) of different ages (young: 22.9 ± 2.0 years, range: 21-25 years; older: 63.1 ± 1.8 years, range: 61-65 years) performed, in random order, chair rising and chair jumping tests on a force plate. Randomly selected young subjects performed both tests repeatedly on two different occasions separated by 1 week. From the sitting position with the arms crossed on the chest, they either stand up completely (chair rising test), or jump as high as possible (chair jumping test). The test-retest reliability of peak power and peak velocity during chair rising as well as chair jumping was excellent, with high intraclass correlation coefficients (ICCs; .90-.98) and low standard error of measurement (SEM; 7.0-9.1%). Post hoc analysis revealed significant differences in peak power and peak velocity between the sedentary and physically active young and older subjects. However, greater coefficients of variation for both parameters were found for chair jumping than chair rising (21.1-40.2% vs. 11.0-15.2%). Additionaly, there were moderate correlations of peak power and peak velocity between chair rising and chair jumping (r = .42-.49). There were greater within- and between-group differences in peak force and peak power and a steeper increase in their values during the initial phase of chair jumping than chair rising. Both chair rising and chair jumping tests provide reliable data and are valid indicators of lower body power in young and older adults. However, jumping from a chair is a more sensitive measure of strength and power performance than chair rising.

  10. Thersites: a `jumping' Trojan?

    NASA Astrophysics Data System (ADS)

    Tsiganis, K.; Dvorak, R.; Pilat-Lohinger, E.

    2000-02-01

    In this paper, we examine the dynamical evolution of the asteroid (1868) Thersites, a member of the Trojan belt. Thersites is librating around the Lagrangian point L_4, following, however, a chaotic orbit. The equations of motion for Thersites as well as for a distribution of neighboring initial conditions are integrated numerically for 50 million years in the Outer Solar System model (OSS), which consists of the Sun and the four giant planets. Our results indicate that the probability that this asteroid will eventually escape from the Trojan swarm is rather high. In fact, 20% from our initial distribution escaped within the integration time. Many of the remaining ones also show characteristic `jumps' in the orbital elements, especially the inclination. Secular resonances involving the nodes of the outer planets are found to be responsible for this chaotic behavior. The width of libration and eccentricity values that lead to grossly unstable orbits are calculated and compared with previously known results on the stability of the Trojans. Finally, a very interesting behavior has been observed for one of the escaping asteroids as he `jumped' from L_4 to L_5 where he remained performing a highly inclined libration for ~ 2 Myrs before escaping from the Trojan swarm. According to Homer, Thersites was not only the ugliest of all Greeks that took part in the Trojan war, but also had the most intolerable personality. His nasty habit of making fun of everybody cost him his life, as the last person for whom he spoke ironically about was Achilles, the mightiest warrior of all Greeks, who killed Thersites with just one punch!

  11. Effect of ankle kinesio taping on vertical jump with run-up and countermovement jump in athletes with ankle functional instability.

    PubMed

    Ho, Yi-Hung; Lin, Cheng-Feng; Chang, Chih-Han; Wu, Hong-Wen

    2015-07-01

    [Purpose] Limited research has been performed in spite of biomechanical evaluation of jump landing with kinesio taping. Therefore, the main objective of this study was to evaluate the effect of kinesio taping applied to athletes. In this study, the authors wished to investigate the effect of kinesio taping during a vertical jump with run-up and countermovement jump on ankle functional instability. [Subjects and Methods] Ten male athletes with ankle functional instability (FI) were recruited in this study from a college volleyball team. Each participant was requested to perform two tasks, the countermovement jump and vertical jump with run-up. Infrared high-speed cameras and force plates were used to assess the effect of ankle taping. [Results] The results showed that the peak ground reaction force in the sagittal plane during a vertical jump with run-up slowed down after kinesio taping and that the peak ankle plantar flexion moment in both types of jump also decreased. [Conclusion] In conclusion, this study proved the effect of kinesio taping on ankle functional instability, which was evaluated by measuring the vertical ground reaction force and peak plantar flexion moment. Its finding may allow us to provide some recommendations for athletes and trainers.

  12. Effect of ankle kinesio taping on vertical jump with run-up and countermovement jump in athletes with ankle functional instability

    PubMed Central

    Ho, Yi-Hung; Lin, Cheng-Feng; Chang, Chih-Han; Wu, Hong-Wen

    2015-01-01

    [Purpose] Limited research has been performed in spite of biomechanical evaluation of jump landing with kinesio taping. Therefore, the main objective of this study was to evaluate the effect of kinesio taping applied to athletes. In this study, the authors wished to investigate the effect of kinesio taping during a vertical jump with run-up and countermovement jump on ankle functional instability. [Subjects and Methods] Ten male athletes with ankle functional instability (FI) were recruited in this study from a college volleyball team. Each participant was requested to perform two tasks, the countermovement jump and vertical jump with run-up. Infrared high-speed cameras and force plates were used to assess the effect of ankle taping. [Results] The results showed that the peak ground reaction force in the sagittal plane during a vertical jump with run-up slowed down after kinesio taping and that the peak ankle plantar flexion moment in both types of jump also decreased. [Conclusion] In conclusion, this study proved the effect of kinesio taping on ankle functional instability, which was evaluated by measuring the vertical ground reaction force and peak plantar flexion moment. Its finding may allow us to provide some recommendations for athletes and trainers. PMID:26311931

  13. Aerial Rotation Effects on Vertical Jump Performance Among Highly Skilled Collegiate Soccer Players.

    PubMed

    Barker, Leland A; Harry, John R; Dufek, Janet S; Mercer, John A

    2016-07-07

    In soccer matches, jumps involving rotations occur when attempting to head the ball for a shot or pass from set pieces such as corner kicks, goal kicks, and lob passes. However, the 3-dimensional ground reaction forces used to perform rotational jumping tasks are currently unknown. Therefore, the purpose of this study was to compare bilateral, 3-dimensional, ground reaction forces of a standard countermovement jump (CMJ0) to a countermovement jump with a 180° rotation (CMJ180) among Division 1 soccer players. Twenty-four participants from the university's soccer team performed 3 trials of the CMJ0 and the CMJ180. Dependent variables included jump height, downward and upward phase times, vertical (Fz) peak force and net impulse relative to mass, and medial-lateral (ML) and anterior-posterior (AP) force couple values. Statistical significance was set a priori at α = 0.05. CMJ180 reduced jump height, increased the AP force couple in the downward and upward phases, and increased upward peak Fz (p<0.05). All other variables were not significantly different between groups (p>0.05). However, we did recognize downward peak Fz trended lower in the CMJ0 condition (p=0.059), and upward net impulse trended higher in the CMJ0 condition (p=0.071). It was concluded jump height was reduced during the rotational jumping task, and rotation occurred primarily via AP ground reaction forces through the entire countermovement jump. Coaches and athletes may consider additional rotational jumping in their training programs to mediate performance decrements during rotational jump tasks.

  14. Effects of a Low-Load Gluteal Warm-Up on Explosive Jump Performance

    PubMed Central

    Comyns, Thomas; Kenny, Ian; Scales, Gerard

    2015-01-01

    The purpose of this study was to investigate the effects of a low-load gluteal warm-up protocol on countermovement and squat jump performance. Research by Crow et al. (2012) found that a low-load gluteal warm-up could be effective in enhancing peak power output during a countermovement jump. Eleven subjects performed countermovement and squat jumps before and after the gluteal warm-up protocol. Both jumps were examined in separate testing sessions and performed 30 seconds, and 2, 4, 6 & 8 minutes post warm-up. Height jumped and peak ground reaction force were the dependent variables examined in both jumps, with 6 additional variables related to fast force production being examined in the squat jump only. All jumps were performed on a force platform (AMTI OR6-5). Repeated measures analysis of variance found a number of significant differences (p ≤ 0.05) between baseline and post warm-up scores. Height jumped decreased significantly in both jumps at all rest intervals excluding 8 minutes. Improvement was seen in 7 of the 8 recorded SJ variables at the 8 minute interval. Five of these improvements were deemed statistically significant, namely time to peak GRF (43.0%), and time to the maximum rate of force development (65.7%) significantly decreased, while starting strength (63.4%), change of force in first 100 ms of contraction (49.1%) and speed strength (43.6%) significantly increased. The results indicate that a gluteal warm-up can enhance force production in squat jumps performed after 8 minutes recovery. Future research in this area should include additional warm-up intervention groups for comparative reasons. PMID:26240661

  15. Effects of a Low-Load Gluteal Warm-Up on Explosive Jump Performance.

    PubMed

    Comyns, Thomas; Kenny, Ian; Scales, Gerard

    2015-06-27

    The purpose of this study was to investigate the effects of a low-load gluteal warm-up protocol on countermovement and squat jump performance. Research by Crow et al. (2012) found that a low-load gluteal warm-up could be effective in enhancing peak power output during a countermovement jump. Eleven subjects performed countermovement and squat jumps before and after the gluteal warm-up protocol. Both jumps were examined in separate testing sessions and performed 30 seconds, and 2, 4, 6 & 8 minutes post warm-up. Height jumped and peak ground reaction force were the dependent variables examined in both jumps, with 6 additional variables related to fast force production being examined in the squat jump only. All jumps were performed on a force platform (AMTI OR6-5). Repeated measures analysis of variance found a number of significant differences (p ≤ 0.05) between baseline and post warm-up scores. Height jumped decreased significantly in both jumps at all rest intervals excluding 8 minutes. Improvement was seen in 7 of the 8 recorded SJ variables at the 8 minute interval. Five of these improvements were deemed statistically significant, namely time to peak GRF (43.0%), and time to the maximum rate of force development (65.7%) significantly decreased, while starting strength (63.4%), change of force in first 100 ms of contraction (49.1%) and speed strength (43.6%) significantly increased. The results indicate that a gluteal warm-up can enhance force production in squat jumps performed after 8 minutes recovery. Future research in this area should include additional warm-up intervention groups for comparative reasons.

  16. Energy jump during bond breaking

    NASA Astrophysics Data System (ADS)

    Miyazawa, Naoki; Hakamada, Masataka; Mabuchi, Mamoru

    2017-07-01

    In current fracture theory, the fracture stress is related to the surface energy on the basis of linear elastic theory. However, the fracture stress does not necessarily exceed the stress required to break atomic bonds. Here, we show that a jump in the inelastic separation energy is generated by fracture, where the inelastic separation energy is the energy between the separation planes measured by excluding the contribution of elastic relaxation, and the stress at the onset of the energy jump is the fracture stress. Analysis of the electronic states of β -SiC (cubic SiC), Ge, and Cu by first-principles tensile tests shows that the electrons redistribute during surface formation in the transition from the onset to the end of the energy jump. Therefore, it is suggested that the inelastic separation energy at the end of the energy jump can be identified with the fracture energy. Also, first-principles shear tests show that an energy jump occurs during shearing for β -SiC , but not for Ge and Cu. Thus, an energy jump is a sign of fracture (bond breaking), and an energy jump during shearing is a good indicator estimating the ductile and brittle character. These principles can hold for any solid and will therefore be beneficial for the fundamental understanding of the mechanical properties of solids and for their industrial applications.

  17. Hydraulic jumps in inhomogeneous strongly coupled toroidal dust flows

    NASA Astrophysics Data System (ADS)

    Piel, Alexander; Wilms, Jochen

    2016-07-01

    The inhomogeneous flow of strongly coupled dust particles in a toroidal particle trap with harmonic radial confinement is analyzed in the incompressible fluid limit. It is shown that the flow can spontaneously generate shock-like events, which are similar to the hydraulic jump in open channel flows. A definition of the Froude number for this model is given and the critical speed is recovered as the group velocity of surface waves. This hydraulic model is compared with molecular-dynamics simulations, which show that a sudden bifurcation of the flow lines and a localized temperature peak appear just at the point where the critical condition for the hydraulic jump is located.

  18. Hydraulic jumps in inhomogeneous strongly coupled toroidal dust flows

    SciTech Connect

    Piel, Alexander Wilms, Jochen

    2016-07-15

    The inhomogeneous flow of strongly coupled dust particles in a toroidal particle trap with harmonic radial confinement is analyzed in the incompressible fluid limit. It is shown that the flow can spontaneously generate shock-like events, which are similar to the hydraulic jump in open channel flows. A definition of the Froude number for this model is given and the critical speed is recovered as the group velocity of surface waves. This hydraulic model is compared with molecular-dynamics simulations, which show that a sudden bifurcation of the flow lines and a localized temperature peak appear just at the point where the critical condition for the hydraulic jump is located.

  19. Lift-off performance of a jumping robot on hard and soft ground

    NASA Astrophysics Data System (ADS)

    Aguilar, Jeffrey; Lesov, Alex; Wiesenfeld, Kurt; Goldman, Daniel

    2012-11-01

    We study lift-off during jumping on hard ground and granular media in a simple robot composed of a linear actuator in series with a spring. On hard ground, the robot jumps from a metallic base. On granular media (GM) composed of 0 . 3 mm glass particles, a circular foot is attached to the spring and an air-fluidized bed sets the initial volume fraction, φ. The actuator frequency and phase are systematically varied to find optimal performance. On both substrates, optimal jump height does not occur at the robot's resonant frequency f0. Two distinct jumping modes emerge: a simple jump which is optimal above f0 is achievable with a squat maneuver, and a ``stutter'' jump which is optimal below f0 is generated with a counter-movement. For hard ground, both modes exhibit similar performance. On closely packed GM (φ = 0 . 62), the simple jump becomes the favored mode. On loosely packed GM (φ = 0 . 58), jump height performance is significantly reduced due to greater yielding in the material. A dynamical model reveals how optimal lift-off results from non-resonant transient dynamics.

  20. Redistribution of suprathermal electrons due to fishbone frequency jumps.

    PubMed

    Macor, A; Goniche, M; Artaud, J F; Decker, J; Elbeze, D; Garbet, X; Giruzzi, G; Hoang, G T; Maget, P; Mazon, D; Molina, D; Nguyen, C; Peysson, Y; Sabot, R; Ségui, J L

    2009-04-17

    MHD instabilities driven by fast electrons identified as fishbonelike modes have been detected on Tore Supra during lower hybrid current drive discharges. Direct experimental evidence is reported of a novel feature: the regular redistribution of suprathermal electrons toward external tokamak regions which are correlated to periodic mode frequency jumps. Sharp drops of the electron temperature time trace are factually linked to the cyclical deterioration of the fast electron confinement.

  1. Redistribution of Suprathermal Electrons due to Fishbone Frequency Jumps

    SciTech Connect

    Macor, A.; Goniche, M.; Artaud, J. F.; Decker, J.; Elbeze, D.; Garbet, X.; Giruzzi, G.; Hoang, G. T.; Maget, P.; Mazon, D.; Molina, D.; Nguyen, C.; Peysson, Y.; Sabot, R.; Segui, J. L.

    2009-04-17

    MHD instabilities driven by fast electrons identified as fishbonelike modes have been detected on Tore Supra during lower hybrid current drive discharges. Direct experimental evidence is reported of a novel feature: the regular redistribution of suprathermal electrons toward external tokamak regions which are correlated to periodic mode frequency jumps. Sharp drops of the electron temperature time trace are factually linked to the cyclical deterioration of the fast electron confinement.

  2. Gender bias in the effects of arms and countermovement on jumping performance.

    PubMed

    Walsh, Mark S; Böhm, Harald; Butterfield, Michelle M; Santhosam, Jabakar

    2007-05-01

    The ability to jump high is considered important in a number of sports. It is commonly accepted that the use of the arms and a counter movement increase jump height. In some sport situations (e.g., volley ball block, basketball rebound), athletes may not be able to utilize a counter movement or arm swing. The purpose of this study is to examine gender differences in the contribution of the arm swing and counter movement to vertical jump height. Fifty college students, 25 men (age = 21.4 +/- 1.7 years, height = 182.2 +/- 8 cm, weight = 83.7 +/- 12.4 kg) and 25 women (age = 20.7 +/- 1.6 years, height = 166.7 +/- 6.3 cm, weight = 61.5 +/- 7.0 kg), performed 4 jumping movements: squat jumps with hands on hips (SNA), counter movement jump with hands on hips (CMNA), squat jump with arm swing (SA), and counter movement with arm swing (CMA). Significant differences were found between men's and women's performance, as well as between each type of jump within each gender. A mixed-model analysis of variance detected gender differences with respect to changes in the jumping movement. For both sexes the jumps in order from worst to best were SNA, CMNA, SA, and CMA. Peak power values for men were 4,057, 4,020, 4,644, and 4,747 W, respectively, for the 4 jumps. The female power values were 2,543, 2,445, 2,842, and 2,788 W, respectively, for the 4 jumps. Arms increased jump height more than a counter movement for both genders, with jump heights for men at 29.6, 31, 36, and 38 cm, respectively, and those of women 21, 22, 26, and 27 cm, respectively. Use of the arms was found to increase the jump height of the men significantly more than that of women. Changes in jumping movements affect men and women differently. The greater increase in jump height for the men when using the arm swing could be because of greater upper body strength of men compared with women. This could have applications to training and upper body strength and also to modeling of jumping movements.

  3. The Jumps: Contemporary Theory, Technique and Training.

    ERIC Educational Resources Information Center

    Wilt, Fred, Ed.

    This collection of essays offers a cross section of modern theory and progress in the training of the four "jumping" events in track and field athletics--pole vault, high jump, long jump, and triple jump. It is written for athletic coaches in these specialties. Articles range from general and historical reviews of technique and training…

  4. Gas Transfer in Hydraulic Jumps.

    DTIC Science & Technology

    1981-07-01

    gas transfer based on measurements made in a hydraulic model. 5. Hydraulic jumps are flow phenomena that are part of the energy dissipation design at...gas transfer to energy dissipation. In a hydraulic jump, the energy loss is related to the Froude number of incoming flow. Fig- ures 15, 16, and 17...number in a similar manner for each of the unit discharges tested. As energy dissipation and Froude number in- creased, gas loss increased for a

  5. The Effect of Depth Jumps and Weight Training on Leg Strength and Vertical Jump.

    ERIC Educational Resources Information Center

    Clutch, David; And Others

    1983-01-01

    Two experiments examined the results of depth jumping programs to determine: (1) whether certain depth jumping routines, when combined with weight training, are better than others; and (2) the effect of depth jumping on athletes already in training. Results indicated that depth jumping is effective, but no more so than regular jumping routines.…

  6. Localized topological states in Bragg multihelicoidal fibers with combined pitch-jump and twist defects

    NASA Astrophysics Data System (ADS)

    Alexeyev, C. N.; Lapin, B. P.; Yavorsky, M. A.

    2017-04-01

    We have studied the influence of pitch-jump defects on the existence of defect-localized states in multihelicoidal Bragg fibers with twist defects. We have shown that the total electromagnetic field energy stored in the defect-localized topologically charged modes essentially depends on the pitch jump and rapidly tends to zero as this increases. This can be used to make the defect mode radiate the stored energy. We have also shown that by tuning the magnitude of the pitch mismatch one can control the wavelength at which the maximal localization takes place. Such fine tuning of the pitch jump can in principle be achieved by piezoelectric modulation.

  7. A Comparison of Pairs Figure Skaters in Repeated Jumps

    PubMed Central

    Sands, William A.; Kimmel, Wendy L.; McNeal, Jeni R.; Murray, Steven Ross; Stone, Michael H.

    2012-01-01

    Trends in pairs figure skating have shown that increasingly difficult jumps have become an essential aspect of high-level performance, especially in the latter part of a competitive program. We compared a repeated jump power index in a 60 s repeated jump test to determine the relationship of repeated jump test to competitive rank and to measure 2D hip, knee, and ankle angles and angular velocities at 0, 20, 40, and 60 s. Eighteen National Team Pairs Figure Skaters performed a 60 s repeated jump test on a large switch-mat with timing of flight and ground durations and digital video recording. Each 60-s period was divided into 6, 10-s intervals, with power indexes (W/kg) calculated for each 10-s interval. Power index by 10-s interval repeated measures ANOVAs (RMANOVA) showed that males exceeded females at all intervals, and the highest power index interval was during 10 to 20 s for both sexes. RMANOVAs of angles and angular velocities showed main effects for time only. Power index and jumping techniques among figure skaters showed rapid and steady declines over the test duration. Power index can predict approximately 50% of competitive rank variance, and sex differences in jumping technique were rare. Key pointsThe repeated jumps test can account for about 50% of the variance in pairs ranks.Changes in technique are largely due to fatigue, but the athletes were able to maintain a maximum flexion knee angle very close to the desired 90 degrees. Changes in angular velocity and jump heights occurred as expected, again probably due to fatigue.As expected from metabolic information, the athletes' power indexes peak around 20s and decline thereafter. Coaches should be aware of this time as a boundary beyond which fatigue becomes more manifest, and use careful choreographic choices to provide rest periods that are disguised as less demanding skating elements to afford recovery.The repeated jumps test may be a helpful off-ice test of power-endurance for figure skaters. PMID

  8. A comparison of pairs figure skaters in repeated jumps.

    PubMed

    Sands, William A; Kimmel, Wendy L; McNeal, Jeni R; Murray, Steven Ross; Stone, Michael H

    2012-01-01

    Trends in pairs figure skating have shown that increasingly difficult jumps have become an essential aspect of high-level performance, especially in the latter part of a competitive program. We compared a repeated jump power index in a 60 s repeated jump test to determine the relationship of repeated jump test to competitive rank and to measure 2D hip, knee, and ankle angles and angular velocities at 0, 20, 40, and 60 s. Eighteen National Team Pairs Figure Skaters performed a 60 s repeated jump test on a large switch-mat with timing of flight and ground durations and digital video recording. Each 60-s period was divided into 6, 10-s intervals, with power indexes (W/kg) calculated for each 10-s interval. Power index by 10-s interval repeated measures ANOVAs (RMANOVA) showed that males exceeded females at all intervals, and the highest power index interval was during 10 to 20 s for both sexes. RMANOVAs of angles and angular velocities showed main effects for time only. Power index and jumping techniques among figure skaters showed rapid and steady declines over the test duration. Power index can predict approximately 50% of competitive rank variance, and sex differences in jumping technique were rare. Key pointsThe repeated jumps test can account for about 50% of the variance in pairs ranks.Changes in technique are largely due to fatigue, but the athletes were able to maintain a maximum flexion knee angle very close to the desired 90 degrees. Changes in angular velocity and jump heights occurred as expected, again probably due to fatigue.As expected from metabolic information, the athletes' power indexes peak around 20s and decline thereafter. Coaches should be aware of this time as a boundary beyond which fatigue becomes more manifest, and use careful choreographic choices to provide rest periods that are disguised as less demanding skating elements to afford recovery.The repeated jumps test may be a helpful off-ice test of power-endurance for figure skaters.

  9. Archer fish jumping prey capture: kinematics and hydrodynamics.

    PubMed

    Shih, Anna M; Mendelson, Leah; Techet, Alexandra H

    2017-04-15

    Smallscale archer fish, Toxotes microlepis, are best known for spitting jets of water to capture prey, but also hunt by jumping out of the water to heights of up to 2.5 body lengths. In this study, high-speed imaging and particle image velocimetry were used to characterize the kinematics and hydrodynamics of this jumping behavior. Jumping used a set of kinematics distinct from those of in-water feeding strikes and was segmented into three phases: (1) hovering to sight prey at the surface, (2) rapid upward thrust production and (3) gliding to the prey once out of the water. The number of propulsive tail strokes positively correlated with the height of the bait, as did the peak body velocity observed during a jump. During the gliding stage, the fish traveled ballistically; the kinetic energy when the fish left the water balanced with the change in potential energy from water exit to the maximum jump height. The ballistic estimate of the mechanical energy required to jump was comparable with the estimated mechanical energy requirements of spitting a jet with sufficient momentum to down prey and subsequently pursuing the prey in water. Particle image velocimetry showed that, in addition to the caudal fin, the wakes of the anal, pectoral and dorsal fins were of nontrivial strength, especially at the onset of thrust production. During jump initiation, these fins were used to produce as much vertical acceleration as possible given the spatial constraint of starting directly at the water's surface to aim. © 2017. Published by The Company of Biologists Ltd.

  10. Changes in biomechanical properties during drop jumps of incremental height.

    PubMed

    Peng, Hsien-Te

    2011-09-01

    The purpose of this study was to investigate changing biomechanical properties with increasing drop jump height. Sixteen physically active college students participated in this study and performed drop jumps from heights of 20, 30, 40, 50, and 60 cm (DJ20-DJ60). Kinematic and kinetic data were collected using 11 Eagle cameras and 2 force platforms. Data pertaining to the dominant leg for each of 3 trials for each drop height were recorded and analyzed. Statistical comparisons of vertical ground reaction force (vGRF), impulse, moment, power, work, and stiffness were made between different drop jump heights. The peak vGRF of the dominant leg exceeded 3 times the body weight during DJ50 and DJ60; these values were significantly greater than those for DJ20, DJ30, and DJ40 (all p < 0.004). The height jumped during DJ60 was significantly less than that during DJ20 and DJ30 (both p = 0.010). Both the landing impulse and total impulse during the contact phase were significantly different between each drop height (all p < 0.036) and significantly increased with drop height. There were no significant differences in the takeoff impulse. Peak and mean power absorption and negative work at the knee and ankle joints during DJ40, DJ50, and DJ60 were significantly greater than those during DJ20 and DJ30 (all p < 0.049). Leg, knee, and ankle stiffness during DJ60 were significantly less than during DJ20, DJ30, and DJ40 (all p < 0.037). The results demonstrated that drop jumps from heights >40 cm offered no advantages in terms of mechanical efficiency (SSC power output) and stiffness. Drop jumps from heights in excess of 60 cm are not recommended because of the lack of biomechanical efficiency and the potentially increased risk of injury.

  11. The correlation of segment accelerations and impact forces with knee angle in jump landing.

    PubMed

    Elvin, Niell G; Elvin, Alex A; Arnoczky, Steven P; Torry, Michael R

    2007-08-01

    Impact forces and shock deceleration during jumping and running have been associated with various knee injury etiologies. This study investigates the influence of jump height and knee contact angle on peak ground reaction force and segment axial accelerations. Ground reaction force, segment axial acceleration, and knee angles were measured for 6 male subjects during vertical jumping. A simple spring-mass model is used to predict the landing stiffness at impact as a function of (1) jump height, (2) peak impact force, (3) peak tibial axial acceleration, (4) peak thigh axial acceleration, and (5) peak trunk axial acceleration. Using a nonlinear least square fit, a strong (r = 0.86) and significant (p < or = 0.05) correlation was found between knee contact angle and stiffness calculated using the peak impact force and jump height. The same model also showed that the correlation was strong (r = 0.81) and significant (p < or = 0.05) between knee contact angle and stiffness calculated from the peak trunk axial accelerations. The correlation was weaker for the peak thigh (r = 0.71) and tibial (r = 0.45) axial accelerations. Using the peak force but neglecting jump height in the model, produces significantly worse correlation (r = 0.58). It was concluded that knee contact angle significantly influences both peak ground reaction forces and segment accelerations. However, owing to the nonlinear relationship, peak forces and segment accelerations change more rapidly at smaller knee flexion angles (i.e., close to full extension) than at greater knee flexion angles.

  12. The Effects of Caffeine on Vertical Jump Height and Execution in Collegiate Athletes.

    PubMed

    Bloms, Lucas P; Fitzgerald, John S; Short, Martin W; Whitehead, James R

    2016-07-01

    Bloms, LP, Fitzgerald, JS, Short, MW, and Whitehead, JR. The effects of caffeine on vertical jump height and execution in collegiate athletes. J Strength Cond Res 30(7): 1855-1861, 2016-Caffeine ingestion elicits a variety of physiological effects that may be beneficial to maximal-intensity exercise performance, although its effectiveness and physical mechanism of action enhancing ballistic task performance are unclear. The purpose of this study was to examine the effects of caffeine ingestion on vertical jump height and jump execution in Division I collegiate athletes. The study used a single-blind, randomized, crossover design. Athletes (n = 25) consumed either caffeine (5 mg·kg) or placebo. After a 60-minute waiting period, athletes performed 3 squat jumps (SJ) and 3 countermovement jumps (CMJ) while standing on a force platform. Jump height and execution variables were calculated from mechanography data. In comparison with placebo, caffeine increased SJ height (32.8 ± 6.2 vs. 34.5 ± 6.7 cm; p = 0.001) and CMJ height (36.4 ± 6.9 vs. 37.9 ± 7.4 cm; p = 0.001). Peak force (p = 0.032) and average rate of force development (p = 0.037) were increased during the CMJ in the caffeine trail compared with the control. Time to half peak force was the only execution variable improved with caffeine (p = 0.019) during the SJ. It seems that caffeine affects both height and execution of jumping. Our data indicate that the physical mechanism of jump enhancement is increased peak force production or rate of force development during jumping depending on technique. The physical mechanism of jump enhancement suggests that the ergogenic effects of caffeine may transfer to other ballistic tasks involving the lower-body musculature in collegiate athletes.

  13. Kinetic analysis of complex training rest interval effect on vertical jump performance.

    PubMed

    Jensen, Randall L; Ebben, William P

    2003-05-01

    Complex training has been recommended as a method of incorporating plyometrics with strength training. Some research suggests that plyometric performance is enhanced when performed 3-4 minutes after the strength training set, whereas other studies have failed to find any complex training advantage when plyometrics are performed immediately after the strength training portion of the complex. The purpose of this study was to determine if there is an ergogenic advantage associated with complex training and if there is an optimal time for performing plyometrics after the strength training set. Subjects were 21 NCAA Division I athletes who performed a countermovement vertical jump, a set of 5 repetitions maximum (5 RM) squats, and 5 trials of countermovement vertical jump at intervals of 10 seconds and 1, 2, 3, and 4 minutes after the squat. Jump height and peak ground reaction forces were acquired via a force platform. The pre-squat jump performance was compared with the post-squat jumps. Repeated measures ANOVA determined a difference (p jump performance immediately following the squat exercise was hindered (0.66 m), but no effect (p > 0.05) was found comparing subsequent jumps (0.72-0.76 m) to the pre-squat condition (0.74 m). When comparing high to low strength individuals, there was no effect on jump performance following the squat (p > 0.05). In conclusion, complex training does not appear to enhance jumping performance significantly and actually decreases it when the jump is performed immediately following the strength training set; however, a nonsignificant trend toward improvement seemed to be present. Therefore to optimize jump performance it appears that athletes should not perform jumps immediately following resistance training. It may be possible that beyond 4 minutes of recovery performance could be enhanced; however, that was not within the scope of the current study.

  14. Test-retest reliability of jump execution variables using mechanography: A comparison of jump protocols

    USDA-ARS?s Scientific Manuscript database

    Mechanography during the vertical jump test allows for evaluation of force-time variables reflecting jump execution, which may enhance screening for functional deficits that reduce physical performance and determining mechanistic causes underlying performance changes. However, utility of jump mechan...

  15. In-Situ Study of the Tensile Deformation and Fracture Modes in Peak-Aged Cast Mg-11Y-5Gd-2Zn-0.5Zr (Weight Percent)

    NASA Astrophysics Data System (ADS)

    Yin, D. D.; Wang, Q. D.; Boehlert, C. J.; Chen, Z.; Li, H. M.; Mishra, R. K.; Chakkedath, A.

    2016-12-01

    Tensile deformation and fracture modes in peak-aged cast Mg-11Y-5Gd-2Zn-0.5Zr (wt pct) (WGZ1152) samples at temperatures between 298 K [25 °C, room temperature (RT)] and 623 K (350 °C) (0.33 to 0.69 T m) were studied in situ inside a scanning electron microscope (SEM) using electron backscatter diffraction (EBSD) and slip trace analysis. The ultimate tensile strength (UTS) (265 MPa) and yield strength (YS) (193 MPa) at 523 K (250 °C) were 91 and 80 pct of those at RT, respectively. The observed dominant slip mode transitioned from basal slip (100 pct) to basal slip (81 pct) combined with prismatic slip (12 pct) from RT to 473 K (200 °C). As the temperature increased to 623 K (350 °C), basal slip (67 pct) and pyramidal slip (25 pct) became the dominant slip modes. The estimated critical resolved shear stress (CRSS) ratio of pyramidal slip/basal slip (7.3) was lower than that of prismatic slip/basal slip (12.7) at temperatures above 573 K (300 °C). Prismatic slip and pyramidal slip were more active at higher strains for moderate temperatures [473 K to 523 K (200 °C to 250 °C)] and at high temperatures [573 K to 623 K (300 °C to 350 °C)], respectively. A transition in the dominant fracture mode occurred from transgranular cracking (40 pct) combined with intergranular cracking (60 pct) to intergranular cracking as temperatures increased from RT to 623 K (350 °C). The intergranular crack nucleation sites tended to be located at grain boundaries and the interface between the Mg matrix and the large intermetallic grain boundary X phase. Slip bands were associated with transgranular crack nucleation.

  16. Mechanical output in jumps of marmosets (Callithrix jacchus).

    PubMed

    Bobbert, Maarten F; Plas, Rogier L C; Weide, Guido; Clairbois, H E Bert; Hofman, Sam O; Jaspers, Richard T; Philippens, Ingrid H C H M

    2014-02-15

    In this study we determined the mechanical output of common marmosets (Callithrix jacchus) during jumping. Vertical ground reaction forces were measured in 18 animals while they jumped from an instrumented crossbar to a crossbar located 70 cm higher. From the vertical force time histories, we calculated the rate of change of mechanical energy of the centre of mass (dE/dt). The mean value of dE/dt during the push-off amounted to 51.8±6.2 W kg(-1) body mass, and the peak value to 116.4±17.6 W kg(-1) body mass. We used these values in combination with masses of leg muscles, determined in two specimens, to estimate mean and peak values of dE/dt of 430 and 970 W kg(-1) muscle, respectively. These values are higher than values reported in the literature for jumps of humans and bonobos, but smaller than those of jumps of bushbabies. Surprisingly, the mean value of dE/dt of 430 W kg(-1) muscle was close to the maximal power output of 516 W kg(-1) muscle reported in the literature for isokinetic contractions of rat medial gastrocnemius, one of the fastest mammalian muscles. Further study of the force-velocity relationship of muscle tissue of small primates is indicated.

  17. Coalescence-induced nanodroplet jumping

    NASA Astrophysics Data System (ADS)

    Cha, Hyeongyun; Xu, Chenyu; Sotelo, Jesus; Chun, Jae Min; Yokoyama, Yukihiro; Enright, Ryan; Miljkovic, Nenad

    2016-10-01

    Water vapor condensation on superhydrophobic surfaces has received much attention in recent years due to the ability of such surfaces to shed microscale water droplets via coalescence-induced droplet jumping, resulting in heat transfer, anti-icing, and self-cleaning performance enhancement. Here we report the coalescence-induced removal of water nanodroplets (R ≈500 nm ) from superhydrophobic carbon nanotube (CNT) surfaces. The two-droplet coalescence time is measured for varying droplet Ohnesorge numbers, confirming that coalescence prior to jumping is governed by capillary-inertial dynamics. By varying the conformal hydrophobic coating thickness on the CNT surface, the minimum jumping droplet radius is shown to increase with increasing solid fraction and decreasing apparent advancing contact angle, allowing us to explore both hydrodynamic limitations stemming from viscous dissipation and surface adhesion limitations. We find that, even for the smallest nanostructure length scale (≤100 nm) and lowest surface adhesions, nonideal surface interactions and the evolved droplet morphology play defining roles in limiting the minimum size for jumping on real surfaces. The outcomes of this work demonstrate the ability to passively shed nanometric water droplets, which has the potential to further increase the efficiency of systems that can harness jumping droplets for a wide range of energy and water applications.

  18. Gravity current jump conditions, revisited

    NASA Astrophysics Data System (ADS)

    Ungarish, Marius; Hogg, Andrew J.

    2016-11-01

    Consider the flow of a high-Reynolds-number gravity current of density ρc in an ambient fluid of density ρa in a horizontal channel z ∈ [ 0 , H ] , with gravity in - z direction. The motion is often modeled by a two-layer formulation which displays jumps (shocks) in the height of the interface, in particular at the leading front of the dense layer. Various theoretical models have been advanced to predict the dimensionless speed of the jump, Fr = U /√{g' h } ; g' , h are reduced gravity and jump height. We revisit this problem and using the Navier-Stokes equations, integrated over a control volume embedding the jump, derive balances of mass and momentum fluxes. We focus on understanding the closures needed to complete this model and we show the vital need to understand the pressure head losses over the jump, which we show can be related to the vorticity fluxes at the boundaries of the control volume. Our formulation leads to two governing equations for three dimensionless quantities. Closure requires one further assumption, depending on which we demonstrate that previous models for gravity current fronts and internal bores can be recovered. This analysis yield new insights into existing results, and also provides constraints for potential new formulae.

  19. Body acceleration distribution and O2 uptake in humans during running and jumping

    NASA Technical Reports Server (NTRS)

    Bhattacharya, A.; Mccutcheon, E. P.; Shvartz, E.; Greenleaf, J. E.

    1980-01-01

    The distribution of body acceleration and associated oxygen uptake and heart rate responses are investigated in treadmill running and trampoline jumping. Accelerations in the +Gz direction were measured at the lateral ankle, lumbosacral region and forehead of eight young men during level treadmill walking and running at four speeds and trampoline jumping at four heights, together with corresponding oxygen uptake and heart rate. With increasing treadmill speed, peak acceleration at the ankle is found always to exceed that at the back and forehead, and acceleration profiles with higher frequency components than those observed during jumping are observed. Acceleration levels are found to be more uniformly distributed with increasing height in jumping, although comparable oxygen uptake and heat rates are obtained. Results indicate that the magnitude of the biomechanical stimuli is greater in trampoline jumping than in running, which finding could be of use in the design of procedures to avert deconditioning in persons exposed to weightlessness.

  20. Body acceleration distribution and O2 uptake in humans during running and jumping

    NASA Technical Reports Server (NTRS)

    Bhattacharya, A.; Mccutcheon, E. P.; Shvartz, E.; Greenleaf, J. E.

    1980-01-01

    The distribution of body acceleration and associated oxygen uptake and heart rate responses are investigated in treadmill running and trampoline jumping. Accelerations in the +Gz direction were measured at the lateral ankle, lumbosacral region and forehead of eight young men during level treadmill walking and running at four speeds and trampoline jumping at four heights, together with corresponding oxygen uptake and heart rate. With increasing treadmill speed, peak acceleration at the ankle is found always to exceed that at the back and forehead, and acceleration profiles with higher frequency components than those observed during jumping are observed. Acceleration levels are found to be more uniformly distributed with increasing height in jumping, although comparable oxygen uptake and heat rates are obtained. Results indicate that the magnitude of the biomechanical stimuli is greater in trampoline jumping than in running, which finding could be of use in the design of procedures to avert deconditioning in persons exposed to weightlessness.

  1. How far can Tarzan jump?

    NASA Astrophysics Data System (ADS)

    Shima, Hiroyuki

    2012-11-01

    The tree-based rope swing is a popular recreational facility, often installed in outdoor areas. Hanging from a rope, users drop from a high platform and then swing at great speed like ‘Tarzan’, finally jumping ahead to land on the ground. The question naturally arises, how far can Tarzan jump using the swing? In this paper, I present an introductory analysis of the mechanics of the Tarzan swing, a large pendulum-like swing with Tarzan himself attached as weight. This enables determination of how much further forward Tarzan can jump using a given swing apparatus. The discussion is based on elementary mechanics and is, therefore, expected to provide rich opportunities for investigations using analytic and numerical methods.

  2. The Kinematics of Swimming and Relocation Jumps in Copepod Nauplii

    PubMed Central

    Andersen Borg, Christian Marc; Bruno, Eleonora; Kiørboe, Thomas

    2012-01-01

    Copepod nauplii move in a world dominated by viscosity. Their swimming-by-jumping propulsion mode, with alternating power and recovery strokes of three pairs of cephalic appendages, is fundamentally different from the way other microplankters move. Protozoans move using cilia or flagella, and copepodites are equipped with highly specialized swimming legs. In some species the nauplius may also propel itself more slowly through the water by beating and rotating the appendages in a different, more complex pattern. We use high-speed video to describe jumping and swimming in nauplii of three species of pelagic copepods: Temora longicornis, Oithona davisae and Acartia tonsa. The kinematics of jumping is similar between the three species. Jumps result in a very erratic translation with no phase of passive coasting and the nauplii move backwards during recovery strokes. This is due to poorly synchronized recovery strokes and a low beat frequency relative to the coasting time scale. For the same reason, the propulsion efficiency of the nauplii is low. Given the universality of the nauplius body plan, it is surprising that they seem to be inefficient when jumping, which is different from the very efficient larger copepodites. A slow-swimming mode is only displayed by T. longicornis. In this mode, beating of the appendages results in the creation of a strong feeding current that is about 10 times faster than the average translation speed of the nauplius. The nauplius is thus essentially hovering when feeding, which results in a higher feeding efficiency than that of a nauplius cruising through the water. PMID:23115647

  3. Comparison of weighted jump squat training with and without eccentric braking.

    PubMed

    Hori, Naruhiro; Newton, Robert U; Kawamori, Naoki; McGuigan, Michael R; Andrews, Warren A; Chapman, Dale W; Nosaka, Kazunori

    2008-01-01

    The purpose of this study was to investigate the effect of weighted jump squat training with and without eccentric braking. Twenty male subjects were divided into two groups (n = 10 per group), Non-Braking Group and Braking Group. The subjects were physically active, but not highly trained. The program for Non-Braking Group consisted of 6 sets of 6 repetitions of weighted jump squats without reduction of eccentric load for 8 weeks. The training program for the Braking Group consisted of the same sets and repetitions, but eccentric load was reduced by using an electromagnetic braking mechanism. Jump and reach, countermovement jump, static jump, drop jump, one repetition maximum half squat, weighted jump squat, and isometric/isokinetic knee extension/flexion at several different positions/angular velocities were tested pre- and posttraining intervention. The Non-Braking Group exhibited greater improvement in peak torque during isokinetic concentric knee flexion at 300 degrees/s [Non-Braking Group: (mean +/- SD) 124.0 +/- 22.6 Nm at pre- and 134.1 +/- 18.4 Nm at posttraining, and Braking Group: 118.5 +/- 32.7 Nm at pre- and 113.2 +/- 26.7 Nm at posttraining]. Braking Group exhibited superior adaptations in peak power relative to body mass during weighted jump squat [Non-Braking Group: (mean +/- SD) 49.1 +/- 8.6 W/kg at pre- and 50.9 +/- 6.2 W/kg at posttraining, and Braking Group: 47.9 +/- 6.9 W/kg at pre- and 53.7 +/- 7.3 W/kg at posttraining]. It appears that power output in relatively slow movement (weighted jump squat) was improved more in the Braking Group, however strength in high velocity movements (isokinetic knee flexion at 300 degrees/s) was improved more in Non-Braking Group. This study supports load and velocity specific effects of weighted jump squat training.

  4. [Hearing disorders after Bungee jumping?].

    PubMed

    Mees, K

    1994-03-01

    Acceleration forces in bungee jumping acting on the head are different in nature and extent from those in merry-go-round, looping and scooter rides. They act mainly in the vertical plane, horizontal accelerations may develop only during uncontrollable vibrations in different directions after slowing down. According to our present knowledge the risks for injuries of the cervical spine and functional disorders of the inner ear in bungee jumping are lower than in merry-go-round, looping and scooter rides. They seem to be enhanced, however, in individuals suffering from diseases of the cervical spine and disorders of the heart and the blood circulation.

  5. Diode-pumped ultrafast Yb:KGW laser with 56 fs pulses and multi-100 kW peak power based on SESAM and Kerr-lens mode locking

    NASA Astrophysics Data System (ADS)

    Akbari, R.; Fedorova, K. A.; Rafailov, E. U.; Major, A.

    2017-04-01

    A high-power sub-60 fs mode-locked diode-pumped Yb:KGW laser based on hybrid action of an InGaAs quantum-dot saturable absorber mirror and Kerr-lens mode locking was demonstrated. The laser delivered 56 fs pulses with 1.95 W of average power corresponding to 450 kW of peak power. The width of the generated laser spectrum was 20.5 nm, which was near the gain bandwidth limit of the Yb:KGW crystal. To the best of our knowledge, these are the shortest pulses generated from the monoclinic double tungstate crystals (and Yb:KGW laser crystal in particular) and the most powerful in the sub-60 fs regime. At the same time, they are also the shortest pulses produced to date with the help of a quantum-dot-based saturable absorber. High-power operation with a pulse duration of 90 fs and 2.85 W of average output power was also demonstrated.

  6. Influence of lumbar spine extension on vertical jump height during maximal squat jumping.

    PubMed

    Blache, Yoann; Monteil, Karine

    2014-01-01

    The purpose of this study was to determine the influence of lumbar spine extension and erector spinae muscle activation on vertical jump height during maximal squat jumping. Eight male athletes performed maximal squat jumps. Electromyograms of the erector spinae were recorded during these jumps. A simulation model of the musculoskeletal system was used to simulate maximal squat jumping with and without spine extension. The effect on vertical jump height of changing erector spinae strength was also tested through the simulated jumps. Concerning the participant jumps, the kinematics indicated a spine extension and erector spinae activation. Concerning the simulated jumps, vertical jump height was about 5.4 cm lower during squat jump without trunk extension compared to squat jump. These results were explained by greater total muscle work during squat jump, more especially by the erector spinae work (+119.5 J). The erector spinae may contribute to spine extension during maximal squat jumping. The simulated jumps confirmed this hypothesis showing that vertical jumping was decreased if this muscle was not taken into consideration in the model. Therefore it is concluded that the erector spinae should be considered as a trunk extensor, which enables to enhance total muscle work and consequently vertical jump height.

  7. Intra-task variability of trunk coordination during a rate-controlled bipedal dance jump.

    PubMed

    Smith, Jo Armour; Siemienski, Adam; Popovich, John M; Kulig, Kornelia

    2012-01-01

    In this study, we investigated trunk coordination during rate-controlled bipedal vertical dance jumps. The aims of the study were to investigate the pattern of coordination and the magnitude of coordination variability within jump phases and relative to phase-defining events during the jump. Lumbar and thoracic kinematics were collected from seven dancers during a series of jumps at 95 beats per minute. The vector coding technique was used to quantify the pattern and variability of trunk coordination. Coordination was predominantly anti-phase during propulsion and landing. Mean coordination variability peaked just before the landing phase and at the transition from landing to propulsion phases, and was lowest during the propulsion phase just before toe-off. The results indicate that peaks in variability could be explained by task and phase-specific biomechanical demands.

  8. Neuromuscular adaptations to 4 weeks of intensive drop jump training in well-trained athletes.

    PubMed

    Alkjaer, Tine; Meyland, Jacob; Raffalt, Peter C; Lundbye-Jensen, Jesper; Simonsen, Erik B

    2013-10-01

    This study examined the effects of 4 weeks of intensive drop jump training in well-trained athletes on jumping performance and underlying changes in biomechanics and neuromuscular adaptations. Nine well-trained athletes at high national competition level within sprinting and jumping disciplines participated in the study. The training was supervised and augmented feedback on performance was used to ensure maximal training intensity. The drop jumps were performed with minimal contact time and maximal jumping height. Assessment of performance during training showed effects of motor learning. Before and after the training intervention maximal isometric muscle strength, the biomechanics, muscle activity pattern of the lower extremities and the soleus H-reflex and V-wave during drop jumping were measured. Maximal jump height and performance index (PI) defined as jumping height divided by contact time improved significantly by 11.9% (P = 0.024) and 16.2% (P = 0.009), respectively. Combined ankle and knee joint peak power was significantly increased by 7% after training (P = 0.047). The preactivity in the soleus muscle decreased 16% (P = 0.015). The soleus H-reflex was unchanged after training, while the soleus V-wave increased significantly at 45 msec after touchdown. This may indicate an increased drive to the α-motor neuron pool following training. Muscle strength parameters were unaffected by the training. The results demonstrate that 4 weeks of intensive drop jump training can improve jumping performance also in well-trained athletes without concomitant changes in muscle strength. It is suggested that the behavioral improvement is primarily due to neural factors regulating the activation pattern controlling the drop jump movement.

  9. Neuromuscular adaptations to 4 weeks of intensive drop jump training in well-trained athletes

    PubMed Central

    Alkjaer, Tine; Meyland, Jacob; Raffalt, Peter C; Lundbye-Jensen, Jesper; Simonsen, Erik B

    2013-01-01

    This study examined the effects of 4 weeks of intensive drop jump training in well-trained athletes on jumping performance and underlying changes in biomechanics and neuromuscular adaptations. Nine well-trained athletes at high national competition level within sprinting and jumping disciplines participated in the study. The training was supervised and augmented feedback on performance was used to ensure maximal training intensity. The drop jumps were performed with minimal contact time and maximal jumping height. Assessment of performance during training showed effects of motor learning. Before and after the training intervention maximal isometric muscle strength, the biomechanics, muscle activity pattern of the lower extremities and the soleus H-reflex and V-wave during drop jumping were measured. Maximal jump height and performance index (PI) defined as jumping height divided by contact time improved significantly by 11.9% (P = 0.024) and 16.2% (P = 0.009), respectively. Combined ankle and knee joint peak power was significantly increased by 7% after training (P = 0.047). The preactivity in the soleus muscle decreased 16% (P = 0.015). The soleus H-reflex was unchanged after training, while the soleus V-wave increased significantly at 45 msec after touchdown. This may indicate an increased drive to the α-motor neuron pool following training. Muscle strength parameters were unaffected by the training. The results demonstrate that 4 weeks of intensive drop jump training can improve jumping performance also in well-trained athletes without concomitant changes in muscle strength. It is suggested that the behavioral improvement is primarily due to neural factors regulating the activation pattern controlling the drop jump movement. PMID:24303171

  10. Combined Effects of Fatigue and Surface Instability on Jump Biomechanics in Elite Athletes.

    PubMed

    Prieske, Olaf; Demps, Marie; Lesinski, Melanie; Granacher, Urs

    2017-09-01

    The present study aimed to examine the effects of fatigue and surface instability on kinetic and kinematic jump performance measures. Ten female and 10 male elite volleyball players (18±2 years) performed repetitive vertical double-leg box jumps until failure. Pre and post fatigue, jump height/performance index, ground reaction force and knee flexion/valgus angles were assessed during drop and countermovement jumps on stable and unstable surfaces. Fatigue, surface condition, and sex resulted in significantly lower drop jump performance and ground reaction force (p≤0.031, 1.1≤d≤3.5). Additionally, drop jump knee flexion angles were significantly lower following fatigue (p=0.006, d=1.5). A significant fatigue×surface×sex interaction (p=0.020, d=1.2) revealed fatigue-related decrements in drop jump peak knee flexion angles under unstable conditions and in men only. Knee valgus angles were higher on unstable compared to stable surfaces during drop jumps and in females compared to males during drop and countermovement jumps (p≤0.054, 1.0≤d≤1.1). Significant surface×sex interactions during countermovement jumps (p=0.002, d=1.9) indicated that knee valgus angles at onset of ground contact were significantly lower on unstable compared to stable surfaces in males but higher in females. Our findings revealed that fatigue and surface instability resulted in sex-specific knee motion strategies during jumping in elite volleyball players. © Georg Thieme Verlag KG Stuttgart · New York.

  11. Kinesiology tape does not promote vertical jumping performance: A deceptive crossover trial.

    PubMed

    Cheung, R T H; Yau, Q K C; Wong, K; Lau, P; So, A; Chan, N; Kwok, C; Poon, K Y; Yung, P S H

    2016-02-01

    Kinesiology tape (KINTAPE) is one of the most common adhesive therapeutic tapes. Apart from clinical applications, KINTAPE claims to be able to enhance functional performance by muscle activity facilitation. However, emerging evidence suggests that the isokinetic muscle strength remains similar when the placebo effect is eliminated. In view of the weak relationship between functional performance and isokinetic muscle strength, this study investigated the true effects of KINTAPE on functional performance. Deceptive, randomized, and crossover trial. Sixty four experienced volleyball players performed vertical jumping test under three taping conditions: true facilitative KINTAPE, sham KINTAPE, and no KINTAPE. Under the pretense of applying adhesive muscle sensors, KINTAPE was applied to their quadriceps and gastrocnemius in the first two conditions. Mean maximum jump height and peak jump power were averaged from three attempts. Within-subject comparisons were conducted by repeated measure ANOVA. Out of 64 participants, 30 of them were successfully deceived and they were ignorant about KINTAPE. No significant differences were found in both maximum jump height (η(2) = 0.001; p = 0.241) and peak jump power (η(2) = 0.001; p = 0.134) between three taping conditions. The results showed that KINTAPE did not facilitate muscle performance by generating higher jumping power or yielding a better jumping performance. These findings reinforce that previously reported muscle facilitatory effects or functional enhancement using KINTAPE may be attributed to placebo effects. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Effect of different knee starting angles on intersegmental coordination and performance in vertical jumps.

    PubMed

    Gheller, Rodrigo G; Dal Pupo, Juliano; Ache-Dias, Jonathan; Detanico, Daniele; Padulo, Johnny; dos Santos, Saray G

    2015-08-01

    This study aimed to analyze the effect of different knee starting angles on jump performance, kinetic parameters, and intersegmental coupling coordination during a squat jump (SJ) and a countermovement jump (CMJ). Twenty male volleyball and basketball players volunteered to participate in this study. The CMJ was performed with knee flexion at the end of the countermovement phase smaller than 90° (CMJ(<90)), greater than 90° (CMJ(>90)), and in a preferred position (CMJ(PREF)), while the SJ was performed from a knee angle of 70° (SJ(70)), 90° (SJ(90)), 110° (SJ(110)), and in a preferred position (SJ(PREF)). The best jump performance was observed in jumps that started from a higher squat depth (CMJ(<90)-SJ(70)) and in the preferred positions (CMJ and SJ), while peak power was observed in the SJ(110) and CMJ(>90). Analysis of continuous relative phase showed that thigh-trunk coupling was more in-phase in the jumps (CMJ and SJ) performed with a higher squat depth, while the leg-thigh coupling was more in-phase in the CMJ(>90) and SJ(PREF). Jumping from a position with knees more flexed seems to be the best strategy to achieve the best performance. Intersegmental coordination and jump performance (CMJ and SJ) were affected by different knee starting angles. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. International Toys in Space: Jump Rope

    NASA Image and Video Library

    Cosmonaut Valery Korzun attempts jumping rope in microgravity. He decides to adapt the activity by taking out the "jumping part," but the act of spinning the rope around him still proves difficult....

  14. Alzheimer's Deaths Jump 55 Percent: CDC

    MedlinePlus

    ... page: https://medlineplus.gov/news/fullstory_165941.html Alzheimer's Deaths Jump 55 Percent: CDC More patients also ... News) -- As more baby boomers age, deaths from Alzheimer's disease have jumped 55 percent, and in a ...

  15. Effect of jumping interval training on neuromuscular and physiological parameters: a randomized controlled study.

    PubMed

    Ache-Dias, Jonathan; Dellagrana, Rodolfo A; Teixeira, Anderson S; Dal Pupo, Juliano; Moro, Antônio R P

    2016-01-01

    This study analyzed the effect of 4 weeks of jumping interval training (JIT), included in endurance training, on neuromuscular and physiological parameters. Eighteen recreational runners, randomized in control and experimental groups, performed 40 min of running at 70% of velocity at peak oxygen uptake, for 3 times per week. Additionally, the experimental group performed the JIT twice per week, which consisted of 4 to 6 bouts of continuous vertical jumps (30 s) with 5-min intervals. Three days before and after the training period, the countermovement (CMJ) and continuous jump (CJ30), isokinetic and isometric evaluation of knee extensors/flexors, progressive maximal exercise, and submaximal constant-load exercise were performed. The JIT provoked improvement in neuromuscular performance, indicated by (i) increased jump height (4.7%; effect size (ES) = 0.99) and power output (≈ 3.7%; ES ≈ 0.82) of CMJ and rate of torque development of knee extensors in isometric contraction (29.5%; ES = 1.02); (ii) anaerobic power and capacity, represented by the mean of jump height (7.4%; ES = 0.8), and peak power output (PPO) (5.6%; ES = 0.73) of the first jumps of CJ30 and the mean of jump height (10.2%, ES = 1.04) and PPO (9.5%, ES = 1.1), considering all jumps of CJ30; and (iii) aerobic power and capacity, represented by peak oxygen uptake (9.1%, ES = 1.28), velocity at peak oxygen uptake (2.7%, ES = 1.11), and velocity corresponding to the onset of blood lactate accumulation (9.7%, ES = 1.23). These results suggest that the JIT included in traditional endurance training induces moderate to large effects on neuromuscular and physiological parameters.

  16. Revival of the Jumping Disc

    ERIC Educational Resources Information Center

    Ucke, C.; Schlichting, H-J.

    2009-01-01

    Snap discs made of bimetal have many technical applications as thermostats. Jumping discs are a toy version of such snap discs. Besides giving technical information, we describe physical investigations. We show especially how, through simple measurements and calculations, you can determine the initial speed ([approximately equal to]3.5 m…

  17. Revival of the Jumping Disc

    ERIC Educational Resources Information Center

    Ucke, C.; Schlichting, H-J.

    2009-01-01

    Snap discs made of bimetal have many technical applications as thermostats. Jumping discs are a toy version of such snap discs. Besides giving technical information, we describe physical investigations. We show especially how, through simple measurements and calculations, you can determine the initial speed ([approximately equal to]3.5 m…

  18. Peaking Into the Dark

    NASA Image and Video Library

    2017-09-28

    In this dramatic scene, an unnamed crater in Mercury's northern volcanic plains is bathed in darkness as the sun sits low on the horizon. Rising from the floor of the crater is its central peak, a small mountain resulting from the crater's formation. A central peak is a type of crater morphology that lies between "simple" and "peak ring" in the range of crater morphology on Mercury. This image was acquired as a high-resolution targeted observation. Targeted observations are images of a small area on Mercury's surface at resolutions much higher than the 200-meter/pixel morphology base map. It is not possible to cover all of Mercury's surface at this high resolution, but typically several areas of high scientific interest are imaged in this mode each week. The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft's seven scientific instruments and radio science investigation are unraveling the history and evolution of the Solar System's innermost planet. During the first two years of orbital operations, MESSENGER acquired over 150,000 images and extensive other data sets. MESSENGER is capable of continuing orbital operations until early 2015. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  19. Jumping performance in the highly aquatic frog, Xenopus tropicalis: sex-specific relationships between morphology and performance

    PubMed Central

    Vasilopoulou-Kampitsi, Menelia; Bonneaud, Camille

    2014-01-01

    Frogs are characterized by a morphology that has been suggested to be related to their unique jumping specialization. Yet, the functional demands associated with jumping and swimming may not be that different as suggested by studies with semi-aquatic frogs. Here, we explore whether features previously identified as indicative of good burst swimming performance also predict jumping performance in a highly aquatic frog, Xenopus tropicalis. Moreover, we test whether the morphological determinants of jumping performance are similar in the two sexes and whether jumping performance differs in the two sexes. Finally we test whether jumping capacity is positively associated with burst swimming and terrestrial endurance capacity in both sexes. Our results show sex-specific differences in jumping performance when correcting for differences in body size. Moreover, the features determining jumping performance are different in the two sexes. Finally, the relationships between different performance traits are sex-dependent as well with females, but not males, showing a trade-off between peak jumping force and the time jumped to exhaustion. This suggests that different selective pressures operate on the two sexes, with females being subjected to constraints on locomotion due to their greater body mass and investment in reproductive capacity. In contrast, males appear to invest more in locomotor capacity giving them higher performance for a given body size compared to females. PMID:25392760

  20. Strawberry Shortcake and Other Jumping Rope Ideas.

    ERIC Educational Resources Information Center

    Adams, Polly K.; Taylor, Michaell K.

    Information, guidelines, and activities for jumping rope are given. A short history of jumping rope explains how it evolved from a spring ritual for men to a play activity involving mostly young girls. Physical and cultural reasons are given as to why jumping rope has been more a sport for girls than for boys. Research studies are noted which show…

  1. The Physics of Equestrian Show Jumping

    ERIC Educational Resources Information Center

    Stinner, Art

    2014-01-01

    This article discusses the kinematics and dynamics of equestrian show jumping. For some time I have attended a series of show jumping events at Spruce Meadows, an international equestrian center near Calgary, Alberta, often referred to as the "Wimbledon of equestrian jumping." I have always had a desire to write an article such as this…

  2. Strawberry Shortcake and Other Jumping Rope Ideas.

    ERIC Educational Resources Information Center

    Adams, Polly K.; Taylor, Michaell K.

    Information, guidelines, and activities for jumping rope are given. A short history of jumping rope explains how it evolved from a spring ritual for men to a play activity involving mostly young girls. Physical and cultural reasons are given as to why jumping rope has been more a sport for girls than for boys. Research studies are noted which show…

  3. The Physics of Equestrian Show Jumping

    ERIC Educational Resources Information Center

    Stinner, Art

    2014-01-01

    This article discusses the kinematics and dynamics of equestrian show jumping. For some time I have attended a series of show jumping events at Spruce Meadows, an international equestrian center near Calgary, Alberta, often referred to as the "Wimbledon of equestrian jumping." I have always had a desire to write an article such as this…

  4. Mesopause jumps at Antarctic latitudes

    NASA Astrophysics Data System (ADS)

    Lübken, Franz-Josef; Höffner, Josef; Becker, Erich; Latteck, Ralph; Murphy, Damian

    2016-04-01

    Recent high resolution temperature measurements by resonance lidar at Davis (69°S) occasionally showed a sudden mesopause altitude increase by ˜5 km and an associated mesopause temperature decrease by ˜10 K. We present further observations which are closely related to this 'mesopause jump', namely the increase of mean height of polar mesospheric summer echoes (PMSE) observed by a VHF radar, very strong westward winds in the upper mesosphere measured by an MF radar, and relatively large eastward winds in the stratosphere taken from reanalysis. We compare to similar observations in the Northern Hemisphere, namely at ALOMAR (69°N) where such mesopause jumps have never been observed. We present a detailed explanation of mesopause jumps. They occur only when stratospheric winds are moderately eastward and mesospheric winds are very large (westward). Under these conditions, gravity waves with comparatively large eastward phase Speeds can pass the stratosphere and propagate to the lower thermosphere because their vertical wavelengths in the mesosphere are rather large which implies reduced dynamical stability. When finally breaking in the lower thermosphere, these waves drive an enhanced residual circulation that causes a cold and high-altitude mesopause. The conditions for a mesopause jump occur only in the Southern Hemisphere (SH) and are associated with the late breakdown of the polar vortex. Mesopause jumps are primarily, but not only, observed prior and close to solstice. We also show that during the onset of PMSE in the SH, stratospheric zonal winds are still eastward (up to 30 m/s), and that the onset is not closely related to the Transition of the stratospheric circulation.

  5. A geometric approach to H∞ control of nonlinear Markovian jump systems

    NASA Astrophysics Data System (ADS)

    Lin, Zhongwei; Liu, Jizhen; Zhang, Weihai; Niu, Yuguang

    2014-09-01

    This paper first discusses the H∞ control problem for a class of general nonlinear Markovian jump systems from the viewpoint of geometric control theory. Following with the updating of the Markovian jump mode, the appropriate diffeomorphism can be adopted to transform the system into special structures, which establishes the basis for the geometric control of nonlinear Markovian jump systems. Through discussing the strongly minimum-phase property or the strongly γ-dissipativity of the zero-output dynamics, the H∞ control can be designed directly without solving the traditional coupled Hamilton-Jacobi inequalities. A numerical example is presented to illustrate the effectiveness of our results.

  6. Peakompactons: Peaked compact nonlinear waves

    DOE PAGES

    Christov, Ivan C.; Kress, Tyler; Saxena, Avadh

    2017-04-20

    This paper is meant as an accessible introduction to/tutorial on the analytical construction and numerical simulation of a class of nonstandard solitary waves termed peakompactons. We present that these peaked compactly supported waves arise as solutions to nonlinear evolution equations from a hierarchy of nonlinearly dispersive Korteweg–de Vries-type models. Peakompactons, like the now-well-known compactons and unlike the soliton solutions of the Korteweg–de Vries equation, have finite support, i.e., they are of finite wavelength. However, unlike compactons, peakompactons are also peaked, i.e., a higher spatial derivative suffers a jump discontinuity at the wave’s crest. Here, we construct such solutions exactly bymore » reducing the governing partial differential equation to a nonlinear ordinary differential equation and employing a phase-plane analysis. Lastly, a simple, but reliable, finite-difference scheme is also designed and tested for the simulation of collisions of peakompactons. In addition to the peakompacton class of solutions, the general physical features of the so-called K#(n,m) hierarchy of nonlinearly dispersive Korteweg–de Vries-type models are discussed as well.« less

  7. Peakompactons: Peaked compact nonlinear waves

    NASA Astrophysics Data System (ADS)

    Christov, Ivan C.; Kress, Tyler; Saxena, Avadh

    2017-04-01

    This paper is meant as an accessible introduction to/tutorial on the analytical construction and numerical simulation of a class of nonstandard solitary waves termed peakompactons. These peaked compactly supported waves arise as solutions to nonlinear evolution equations from a hierarchy of nonlinearly dispersive Korteweg-de Vries-type models. Peakompactons, like the now-well-known compactons and unlike the soliton solutions of the Korteweg-de Vries equation, have finite support, i.e., they are of finite wavelength. However, unlike compactons, peakompactons are also peaked, i.e., a higher spatial derivative suffers a jump discontinuity at the wave’s crest. Here, we construct such solutions exactly by reducing the governing partial differential equation to a nonlinear ordinary differential equation and employing a phase-plane analysis. A simple, but reliable, finite-difference scheme is also designed and tested for the simulation of collisions of peakompactons. In addition to the peakompacton class of solutions, the general physical features of the so-called K#(n,m) hierarchy of nonlinearly dispersive Korteweg-de Vries-type models are discussed as well.

  8. Effects of fatigue of plantarflexors on control and performance in vertical jumping.

    PubMed

    Bobbert, Maarten F; van der Krogt, Marjolein M; van Doorn, Hemke; de Ruiter, Cornelis J

    2011-04-01

    We investigated the effects of a mismatch between control and musculoskeletal properties on performance in vertical jumping. Six subjects performed maximum-effort vertical squat jumps before (REF) and after the plantarflexors of the right leg had been fatigued (FAT) while kinematic data, ground reaction forces, and EMG of leg muscles were collected. Inverse dynamics was used to calculate the net work at joints, and EMG was rectified and smoothed to obtain the smoothed rectified EMG (SREMG). The jumps of the subjects were also simulated with a musculoskeletal model comprising seven body segments and 12 Hill-type muscles, and having as only input muscle stimulation. Jump height was approximately 6 cm less in FAT jumps than in REF jumps. In FAT jumps, peak SREMG level was reduced by more than 35% in the right plantarflexors and by approximately 20% in the right hamstrings but not in any other muscles. In FAT jumps, the net joint work was reduced not only at the right ankle (by 70%) but also at the right hip (by 40%). Because the right hip was not spanned by fatigued muscles and the reduction in SREMG of the right hamstrings was relatively small, this indicated that the reduction in performance was partly due to a mismatch between control and musculoskeletal properties. The differences between REF and FAT jumps of the subjects were confirmed and explained by the simulation model. Reoptimization of control for the FAT model caused performance to be partly restored by approximately 2.5 cm. The reduction in performance in FAT jumps was partly due to a mismatch between control and musculoskeletal properties.

  9. The Hydraulic Jump in Liquid Helium

    SciTech Connect

    Rolley, Etienne; Guthmann, Claude; Chevallier, Christophe; Pettersen, Michael S.

    2006-09-07

    We present the results of some experiments on the circular hydraulic jump in normal and superfluid liquid helium. The radius of the jump and the depth of the liquid outside the jump are measured through optical means. Although the scale of the apparatus is rather small, the location of the jump is found to be consistent with the assumption that the jump can be treated as a shock, if the surface tension is taken into account. The radius of the jump does not change when going down in temperature through the lambda point; we think that the flow is supercritical. A remarkable feature of the experiment is the observation of stationary ripples within the jump when the liquid is superfluid.

  10. Retinal complications after bungee jumping.

    PubMed

    Filipe, J A; Pinto, A M; Rosas, V; Castro-Correia, J

    Bungee jumping is becoming a popular sport in the Western world with some cases of ophthalmic complications being reported in recent literature. The authors reported a case of a 23-year-old healthy female who presented retinal complications following a bungee jumping. Her fundi showed superficial retinal hemorrhages in the right eye and a sub-internal limiting membrane hemorrhage affecting the left eye. A general examination, including a full neurological examination, was normal and laboratorial investigations were all within normal values. More studies are necessary to identify risk factors and the true incidence of related ocular lesions, but until then, we think this sport activity should be desencouraged, especially to those that are not psychological and physically fit.

  11. Relationship between tibial acceleration and proximal anterior tibia shear force across increasing jump distance.

    PubMed

    Sell, Timothy C; Akins, Jonathan S; Opp, Alexis R; Lephart, Scott M

    2014-02-01

    Proximal anterior tibia shear force is a direct loading mechanism of the anterior cruciate ligament (ACL) and is a contributor to ACL strain during injury. Measurement of this force during competition may provide insight into risk factors for ACL injury. Accelerometers may be capable of measuring tibial acceleration during competition. The purpose of this study was to examine the relationship between acceleration measured by a tibia-mounted accelerometer and proximal anterior tibia shear force as measured through inverse dynamics and peak posterior ground reaction forces during two leg stop-jump tasks. Nineteen healthy male subjects performed stop-jump tasks across increasing jump distances. Correlation coefficients were calculated to determine if a relationship exists between accelerometer data and proximal anterior tibia shear force and peak posterior ground reaction force. An analysis of variance was performed to compare these variables across jump distance. Significant correlations were observed between accelerometer data and peak posterior ground reaction force, but none between accelerometer data and proximal anterior tibia shear force. All variables except peak proximal anterior tibia shear force increased significantly as jump distance increased. Overall, results of this study provide initial, positive support for the use of accelerometers as a useful tool for future injury prevention research.

  12. The perils of bungee jumping.

    PubMed

    Shapiro, M J; Marts, B; Berni, A; Keegan, M J

    1995-01-01

    Bungee jumping is a relatively new recreational sport. Most emergency physicians and trauma surgeons have limited experience with its associated injuries. We report the case of a bungee cord attachment apparatus malfunctioning, resulting in a free fall of the jumper of approximately 240 feet. The presence of an air cushion on the ground prevented significant injury. Knowledge of the potential injuries of this new sport is crucial for effective management.

  13. Model for polygonal hydraulic jumps.

    PubMed

    Martens, Erik A; Watanabe, Shinya; Bohr, Tomas

    2012-03-01

    We propose a phenomenological model for the polygonal hydraulic jumps discovered by Ellegaard and co-workers [Nature (London) 392, 767 (1998); Nonlinearity 12, 1 (1999); Physica B 228, 1 (1996)], based on the known flow structure for the type-II hydraulic jumps with a "roller" (separation eddy) near the free surface in the jump region. The model consists of mass conservation and radial force balance between hydrostatic pressure and viscous stresses on the roller surface. In addition, we consider the azimuthal force balance, primarily between pressure and viscosity, but also including nonhydrostatic pressure contributions from surface tension in light of recent observations by Bush and co-workers [J. Fluid Mech. 558, 33 (2006); Phys. Fluids 16, S4 (2004)]. The model can be analyzed by linearization around the circular state, resulting in a parameter relationship for nearly circular polygonal states. A truncated but fully nonlinear version of the model can be solved analytically. This simpler model gives rise to polygonal shapes that are very similar to those observed in experiments, even though surface tension is neglected, and the condition for the existence of a polygon with N corners depends only on a single dimensionless number φ. Finally, we include time-dependent terms in the model and study linear stability of the circular state. Instability occurs for sufficiently small Bond number and the most unstable wavelength is expected to be roughly proportional to the width of the roller as in the Rayleigh-Plateau instability.

  14. Diagnostic studies of ensemble forecast "jumps"

    NASA Astrophysics Data System (ADS)

    Magnusson, Linus; Hewson, Tim; Ferranti, Laura; Rodwell, Mark

    2016-04-01

    During 2015 we saw exceptional consistency in successive seasonal forecasts produced at ECMWF, for the winter period 2015/16, right across the globe. This winter was characterised by a well-predicted and unusually strong El Nino, and some have ascribed the consistency to that. For most of December this consistency was mirrored in the (separate) ECMWF monthly forecast system, which correctly predicted anomalously strong (mild) zonal flow, over the North Atlantic and western Eurasia, even in forecasts for weeks 3 and 4. In monthly forecasts in general these weeks are often devoid of strong signals. However in late December and early January strong signals, even in week 2, proved to be incorrect, most notably over the North Atlantic and Eurasian sectors. Indeed on at least two occasions the outcome was beyond the ensemble forecast range over Scandinavia. In one of these conditions flipped from extreme mild to extreme cold as a high latitude block developed. Temperature prediction is very important to many customers, notably those dealing with renewable energy, because cold weather causes increased demand but also tends to coincide with reduced wind power production. So understandably jumps can cause consternation amongst some customer groups, and are very difficult to handle operationally. This presentation will discuss the results of initial diagnostic investigations into what caused the "ensemble jumps", particularly at the week two lead, though reference will also be made to a related shorter range (day 3) jump that was important for flooding over the UK. Initial results suggest that an inability of the ECMWF model to correctly represent convective outbreaks over North America (that for winter-time were quite extreme) played an important role. Significantly, during this period, an unusually large amount of upper air data over North America was rejected or ascribed low weight. These results bear similarities to previous diagnostic studies at ECMWF, wherein major

  15. Lack of association between postactivation potentiation and subsequent jump performance.

    PubMed

    Pearson, Stephen John; Hussain, Syed Robiul

    2014-01-01

    Postactivation potentiation (PAP) is a strategy that has been used to acutely enhance the performance of explosive activities. Although, isometric maximal voluntary contractions (MVCs) have previously been shown to enhance subsequent explosive performance, no information currently exists regarding (1) the optimal variables (intensity/volume) of a MVC that best elicits a PAP response, and (2) the utilisation of evoked isometric twitch contractions in combination with performance measures to directly ascertain the presence of PAP following a MVC, and its relationship to performance. Thus, the purpose of this study was to (1) investigate the influence of isometric contraction duration on the PAP response, and (2) to determine the relationship between PAP, indicated as potentiation of muscle twitch force and subsequent jump performance following different-duration MVCs. Eight males (age: 21 ± 0.99) were assessed using performance measures [countermovement jumps] and evoked twitch contractions, before and 4 minutes after three different conditioning contractions (CCs), (1) a 3-second MVC (MVC3), (2) a 5-second MVC (MVC5) and (3) a 7-second MVC (MVC7). Following all CCs, peak twitch torque of the knee extensor muscles was found to increase (MVC3, + 3.9%; MVC5, + 9.6%; MVC7, + 5.2%), although not significantly (P > 0.05). No significant increases in jump height, jump power, rate of force development or takeoff velocity were observed following any of the CCs (P > 0.05). There was also a lack of association between the changes in PAP (twitch torque) and jump height following all CCs (MVC3, r = 0.25; MVC5, r = 0.28; MVC7, r = -0.47). These data indicate that PAP as assessed via twitch contractions is not associated with performance measures subsequent to single-set isometric CCs of varying durations.

  16. The fluid dynamics of the ciliate Pseudotontonia sp. jumping by ``tail'' contraction

    NASA Astrophysics Data System (ADS)

    Jiang, Houshuo; Gemmell, Brad; Buskey, Edward

    2015-11-01

    The marine planktonic ciliate Pseudotontonia sp. (~ 80 μm in cell size) possesses two sets of propulsive machinery: (1) an anteriorly located ciliary band that beats to let the cell swim backward, and (2) a long, contractile appendage (i.e. the `tail') that at times contracts rapidly to pull the cell body backward, resulting in the tail contraction and body jumping motion being oppositely directed inwards towards the same location. We use high-speed microscale imaging and micro-particle image velocimetry techniques to measure the ciliate swimming and jumping kinematics and imposed flow fields. We show that the cilia-propelled swimming achieves a sustained swimming speed ~ 10 mm s-1 that can last more than 100 ms. The swimming imposed flow conforms to the steady stresslet flow field that decays spatially at r-2. On the other hand, the tail contraction causes the cell to jump at a peak speed ~ 55 mm s-1 and cover a jumping distance 2-4 cell lengths within ~ 12 ms jumping time. The jumping imposed flow fits quite well to the unsteady impulsive stokeslet flow field that decays spatially at r-3. Based on the measured jumping kinematics, we develop a fluid dynamics model to explain the thrust generation due to the tail contraction.

  17. Transcutaneous spinal direct current stimulation induces lasting fatigue resistance and enhances explosive vertical jump performance.

    PubMed

    Berry, Helen R; Tate, Rothwelle J; Conway, Bernard A

    2017-01-01

    Transcutaneous spinal direct current stimulation (tsDCS) is a non-invasive neuromodulatory intervention that has been shown to modify excitability in spinal and supraspinal circuits in animals and humans. Our objective in this study was to explore the functional neuromodulatory potential of tsDCS by examining its immediate and lasting effects over the repeated performance of a whole body maximal exercise in healthy volunteers. Using a double-blind, randomized, crossover, sham-controlled design we investigated the effects of 15 min of anodal tsDCS on repeated vertical countermovement jump (VCJ) performance at 0, 20, 60, and 180 minutes post-stimulation. Measurements of peak and take-off velocity, vertical displacement, peak power and work done during countermovement and push-off VCJ phases were derived from changes in vertical ground reaction force (12 performance parameters) in 12 healthy participants. The magnitude and direction of change in VCJ performance from pre- to post-stimulation differed significantly between sham and active tsDCS for 7 of the 12 VCJ performance measures (P < 0.05). These differences comprised of a post-sham fatigue in VCJ displacement/work done, peak to peak power and take-off velocity, and a resilience to this fatigue effect post-active tsDCS. In addition there was also an enhancement of countermovement performance and total work done (P < 0.05). These changes did not vary across repeated VCJ performances over time post-tsDCS (P > 0.05). Our original findings demonstrate that one single session of anodal tsDCS in healthy subjects can prevent fatigue and maintain or enhance different aspects of whole body explosive motor power over repeated sets of VCJs performed over a period of three hours. The observed effects are discussed in relation to alterations in central fatigue mechanisms, muscle contraction mode during jump execution and changes in spinal cord excitability. These findings have important implications for power endurance sport

  18. Relationship between anaerobic power and jumping of selected male volleyball players of different ages.

    PubMed

    Kasabalis, Athanasios; Douda, Helen; Tokmakidis, Savvas P

    2005-06-01

    The aim of the present study was to evaluate the anaerobic power of elite male volleyball players, using the Wingate Anaerobic Test to examine the relationship between anaerobic power and jumping performance. Athletes (n=56) and Nonathletes (n=53) were divided into three age groups: Adults (18-25 yr.), Juniors (15-16 yr.), and Youth (10-11 yr.). Measurements of height, body mass, vertical jump and Wingate scores indicated higher values for athletes. The specific training effects of anaerobic power were more pronounced at the age of 10-11 years than for Nonathletes. A significant correlation coefficient between peak power and vertical jump was found for Athletes (r=.86) and for the total group (r=.82). These results indicated that vertical jump may predict the maximal anaerobic power and could be used by coaches as a practical and easy-to-apply field screening test for evaluation in volleyball training.

  19. Repetitive hops induce postactivation potentiation in triceps surae as well as an increase in the jump height of subsequent maximal drop jumps.

    PubMed

    Bergmann, Julian; Kramer, Andreas; Gruber, Markus

    2013-01-01

    Postactivation potentiation (PAP) has been defined as the increase in twitch torque after a conditioning contraction. The present study aimed to investigate the effectiveness of hops as conditioning contractions to induce PAP and increase performance in subsequent maximal drop jumps. In addition, we wanted to test if and how PAP can contribute to increases in drop jump rebound height. Twelve participants performed 10 maximal two-legged hops as conditioning contractions. Twitch peak torques of triceps surae muscles were recorded before and after the conditioning hops. Then, subjects performed drop jumps with and without 10 conditioning hops before each drop jump. Recordings included ground reaction forces, ankle and knee angles and electromyographic activity in five leg muscles. In addition, efferent motoneuronal output during ground contact was estimated with V-wave stimulation. The analyses showed that after the conditioning hops, twitch peak torques of triceps surae muscles were 32% higher compared to baseline values (P < 0.01). Drop jumps performed after conditioning hops were significantly higher (12%, P < 0.05), but V-waves and EMG activity remained unchanged. The amount of PAP and the change in drop jump rebound height were positively correlated (r(2) = 0.26, P < 0.05). These results provide evidence for PAP in triceps surae muscles induced by a bout of hops and indicate that PAP can contribute to the observed performance enhancements in subsequent drop jumps. The lack of change in EMG activity and V-wave amplitude suggests that the underlying mechanisms are more likely intramuscular than neural in origin.

  20. Effect of Ankle Joint Contact Angle and Ground Contact Time on Depth Jump Performance.

    PubMed

    Phillips, Joshua H; Flanagan, Sean P

    2015-11-01

    Athletes often need to both jump high and get off the ground quickly, but getting off the ground quickly can decrease the vertical ground reaction force (VGRF) impulse, impeding jump height. Energy stored in the muscle-tendon complex during the stretch-shortening cycle (SSC) may mitigate the effects of short ground contact times (GCTs). To take advantage of the SSC, several coaches recommend "attacking" the ground with the foot in a dorsiflexed (DF) position at contact. However, the efficacy of this technique has not been tested. This investigation tested the hypotheses that shorter GCTs would lead to smaller vertical depth jump heights (VDJH), and that this difference could be mitigated by instructing the athletes to land in a DF as opposed to a plantar flexed (PF) foot position. Eighteen healthy junior college athletes performed depth jumps from a 45-cm box onto force platforms under instruction to achieve one of the 2 objectives (maximum jump height [hmax] or minimal GCT [tmin]), with one of the 2 foot conditions (DF or PF). These variations created 4 distinct jump conditions: DF-hmax, DF-tmin, PF-hmax, and PF-tmin. For all variables examined, there were no significant interactions. For all 4 conditions, the ankle was PF during landing, but the DF condition was 28.87% less PF than the PF condition. The tmin conditions had a 23.48% shorter GCT than hmax. There were no significant main effects for jump height. The peak impact force for tmin was 22.14% greater than hmax and 19.11% greater for DF compared with PF conditions. A shorter GCT did not necessitate a smaller jump height, and a less PF foot did not lead to improvements in jump height or contact time during a depth jump from a 45-cm box. The same jump height was attained in less PF and shorter GCT conditions by larger impact forces. To decrease contact time while maintaining jump height, athletes should be instructed to "get off the ground as fast as possible." This cue seems to be more important than foot

  1. Spatially constrained propulsion in jumping archer fish

    NASA Astrophysics Data System (ADS)

    Mendelson, Leah; Techet, Alexandra

    2016-11-01

    Archer fish jump multiple body lengths out of the water for prey capture with impressive accuracy. Their remarkable aim is facilitated by jumping from a stationary position directly below the free surface. As a result of this starting position, rapid acceleration to a velocity sufficient for reaching the target occurs with only a body length to travel before the fish leaves the water. Three-dimensional measurements of jumping kinematics and volumetric velocimetry using Synthetic Aperture PIV highlight multiple strategies for such spatially constrained acceleration. Archer fish rapidly extend fins at jump onset to increase added mass forces and modulate their swimming kinematics to minimize wasted energy when the body is partially out of the water. Volumetric measurements also enable assessment of efficiency during a jump, which is crucial to understanding jumping's role as an energetically viable hunting strategy for the fish.

  2. Plyometric Long Jump Training With Progressive Loading Improves Kinetic and Kinematic Swimming Start Parameters.

    PubMed

    Rebutini, Vanessa Z; Pereira, Gleber; Bohrer, Roberta C D; Ugrinowitsch, Carlos; Rodacki, André L F

    2016-09-01

    Rebutini, VZ, Pereira, G, Bohrer, RCD, Ugrinowitsch, C, and Rodacki, ALF. Plyometric long jump training with progressive loading improves kinetic and kinematic swimming start parameters. J Strength Cond Res 30(9): 2392-2398, 2016-This study was aimed to determine the effects of a plyometric long jump training program on torque around the lower limb joints and kinetic and kinematics parameters during the swimming jump start. Ten swimmers performed 3 identical assessment sessions, measuring hip and knee muscle extensors during maximal voluntary isometric contraction and kinetic and kinematics parameters during the swimming jump start, at 3 instants: INI (2 weeks before the training program, control period), PRE (2 weeks after INI measurements), and POST (24-48 hours after 9 weeks of training). There were no significant changes from INI to PRE measurements. However, the peak torque and rate of torque development increased significantly from PRE to POST measurements for both hip (47 and 108%) and knee (24 and 41%) joints. There were significant improvements to the horizontal force (7%), impulse (9%), and angle of resultant force (19%). In addition, there were significant improvements to the center of mass displacement (5%), horizontal takeoff velocity (16%), horizontal velocity at water entrance (22%), and peak angle velocity for the knee (15%) and hip joints (16%). Therefore, the plyometric long jump training protocol was effective to enhance torque around the lower limb joints and to control the resultant vector direction, to increase the swimming jump start performance. These findings suggest that coaches should use long jump training instead of vertical jump training to improve swimming start performance.

  3. Ocular injury due to bungee jumping.

    PubMed

    Curtis, Edward B; Collin, H Barry

    1999-01-01

    BACKGROUND: Bungee jumping is a well-established recreational activity in New Zealand and Australia which may be associated with injuries to the eyes and other tissues. CASE HISTORY: A patient with a retinal haemorrhage which resulted from bungee jumping is reported and the clinical characteristics described. DISCUSSION: There have been several reports of injury due to bungee jumping. The types of ocular injury are reviewed and the aetiological theories discussed.

  4. PeakWorks

    SciTech Connect

    2016-11-30

    The PeakWorks software is designed to assist in the quantitative analysis of atom probe tomography (APT) generated mass spectra. Specifically, through an interactive user interface, mass peaks can be identified automatically (defined by a threshold) and/or identified manually. The software then provides a means to assign specific elemental isotopes (including more than one) to each peak. The software also provides a means for the user to choose background subtraction of each peak based on background fitting functions, the choice of which is left to the users discretion. Peak ranging (the mass range over which peaks are integrated) is also automated allowing the user to chose a quantitative range (e.g. full-widthhalf- maximum). The software then integrates all identified peaks, providing a background-subtracted composition, which also includes the deconvolution of peaks (i.e. those peaks that happen to have overlapping isotopic masses). The software is also able to output a 'range file' that can be used in other software packages, such as within IVAS. A range file lists the peak identities, the mass range of each identified peak, and a color code for the peak. The software is also able to generate 'dummy' peak ranges within an outputted range file that can be used within IVAS to provide a means for background subtracted proximity histogram analysis.

  5. Psychophysiological response in parachute jumps, the effect of experience and type of jump.

    PubMed

    Clemente-Suárez, Vicente Javier; Robles-Pérez, José Juan; Fernández-Lucas, Jesús

    2017-10-01

    We aimed to analyse the effect of experience and type of parachute jump on the psychophysiological responses of jumpers. We analysed blood oxygen saturation, heart rate, blood glucose, lactate and creatinkinase, leg strength, isometric hand strength, cortical arousal, specific fine motor skills, self-confidence and cognition, and somatic and state anxiety, before and after four different parachute jumps: a sport parachute jump, a manual tactical parachute jump, tandem pilots, and tandem passengers. Independently of the parachute jump, the psychophysiological responses of experienced paratroopers were not affected by the jumps, except for an increase in anaerobic metabolism. Novice parachute jumpers presented a higher psychophysiological stress response than the experienced jumpers, together with a large anticipatory anxiety response before the jump; however, this decreased after the jump, although the high physiological activation was maintained. This information could be used by civil and military paratroopers' instructors to improve their training programmes. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Fluidodynamical Representation and Quantum Jumps

    NASA Astrophysics Data System (ADS)

    Chiatti, Leonardo; Licata, Ignazio

    The sophistication of recent experimental procedures has made it possible to detect experimentally the so-called Quantum Jumps (QJ), i.e. the stop and restart of the wave function as a real phenomenon. In this work, we connect this experimental evidence to a foundational interpretation of QM, based on an a-temporal vacuum. In that picture, the QJ is a localization process, defined as the time-symmetric action of a self-conjugate projection operator. The compatibility of these discontinuous processes with the Theory of Relativity is demonstrated using the Bohm representation of quantum mechanics.

  7. Vertical jumping and signaled avoidance

    PubMed Central

    Cándido, Antonio; Maldonado, Antonio; Vila, Jaime

    1988-01-01

    This paper reports an experiment intended to demonstrate that the vertical jumping response can be learned using a signaled-avoidance technique. A photoelectric cell system was used to record the response. Twenty female rats, divided equally into two groups, were exposed to intertrial intervals of either 15 or 40 s. Subjects had to achieve three successive criteria of acquisition: 3, 5, and 10 consecutive avoidance responses. Results showed that both groups learned the avoidance response, requiring increasingly larger numbers of trials as the acquisition criteria increased. No significant effect of intertrial interval was observed. PMID:16812559

  8. Ocular complications of bungee jumping

    PubMed Central

    Hassan, H Mohammed J; Mariatos, Georgios; Papanikolaou, Theocharis; Ranganath, Akshatha; Hassan, Hala

    2012-01-01

    Aim In this paper, we will try to highlight the importance of various investigations and their crucial role in identifying whether the defect is structural or functional. Case history A 24-year-old woman presented with ocular complications after bungee jumping. Subsequently, although all ophthalmic signs resolved, she complained of decreased vision in her left eye. Conclusion Initial ophthalmic injury was detected by optical coherence tomography scan showing a neurosensory detachment of the fovea. This was not initially detected on slit-lamp examination or fluorescein angiography. On later examination, although the optical coherence tomography scan showed no structural damage, electrodiagnostic tests showed a functional defect at the fovea. PMID:23055687

  9. The aerodynamics of jumping rope

    NASA Astrophysics Data System (ADS)

    Aristoff, Jeffrey; Stone, Howard

    2010-11-01

    We present the results of a combined theoretical and experimental investigation of the motion of a rotating string that is held at both ends (i.e. a jump rope). In particular, we determine how the surrounding fluid affects the shape of the string at high Reynolds numbers. We derive a pair of coupled non-linear differential equations that describe the shape, the numerical solution of which compares well with asymptotic approximations and experiments. Implications for successful skipping will be discussed, and a demonstration is possible.

  10. The aerodynamics of jumping rope

    NASA Astrophysics Data System (ADS)

    Aristoff, Jeffrey; Stone, Howard

    2011-03-01

    We present the results of a combined theoretical and experimental investigation of the motion of a rotating string that is held at both ends (i.e. a jump rope). In particular, we determine how the surrounding fluid affects the shape of the string at high Reynolds numbers: the string bends toward the axis of rotation, thereby reducing its total drag. We derive a pair of coupled non-linear differential equations that describe the shape, the numerical solution of which compares well with asymptotic approximations and experiments. Implications for successful skipping will be discussed.

  11. Blunt facial trauma from a bungee jump.

    PubMed

    Kmucha, S T

    1996-05-01

    A 28-year-old man was brought to the emergency department for severe facial swelling the morning after a bungee jumping accident. The patient had been making jumps nearly every weekend for the past 3 years without injury. This time, he had performed a nighttime jump from a railroad trestle over the gorge of a small river. The height of the bridge at the center of the gorge was about 200 ft, and the river was about 12 ft deep. When the patient jumped, he hit the water face first, plunging under the surface to his waist. The cause of the accident was thought to be a miscalculation of the bridge height.

  12. Neuromechanical simulation of the locust jump

    PubMed Central

    Cofer, D.; Cymbalyuk, G.; Heitler, W. J.; Edwards, D. H.

    2010-01-01

    The neural circuitry and biomechanics of kicking in locusts have been studied to understand their roles in the control of both kicking and jumping. It has been hypothesized that the same neural circuit and biomechanics governed both behaviors but this hypothesis was not testable with current technology. We built a neuromechanical model to test this and to gain a better understanding of the role of the semi-lunar process (SLP) in jump dynamics. The jumping and kicking behaviors of the model were tested by comparing them with a variety of published data, and were found to reproduce the results from live animals. This confirmed that the kick neural circuitry can produce the jump behavior. The SLP is a set of highly sclerotized bands of cuticle that can be bent to store energy for use during kicking and jumping. It has not been possible to directly test the effects of the SLP on jump performance because it is an integral part of the joint, and attempts to remove its influence prevent the locust from being able to jump. Simulations demonstrated that the SLP can significantly increase jump distance, power, total energy and duration of the jump impulse. In addition, the geometry of the joint enables the SLP force to assist leg flexion when the leg is flexed, and to assist extension once the leg has begun to extend. PMID:20228342

  13. Peak flow meter (image)

    MedlinePlus

    A peak flow meter is commonly used by a person with asthma to measure the amount of air that can be ... become narrow or blocked due to asthma, peak flow values will drop because the person cannot blow ...

  14. The effect of assisted jumping on vertical jump height in high-performance volleyball players.

    PubMed

    Sheppard, Jeremy M; Dingley, Andrew A; Janssen, Ina; Spratford, Wayne; Chapman, Dale W; Newton, Robert U

    2011-01-01

    Assisted jumping may be useful in training higher concentric movement speed in jumping, thereby potentially increasing the jumping abilities of athletes. The purpose of this study was to evaluate the effects of assisted jump training on counter-movement vertical jump (CMVJ) and spike jump (SPJ) ability in a group of elite male volleyball players. Seven junior national team volleyball players (18.0±1.0 yrs, 200.4±6.7 cm, and 84.0±7.2 kg) participated in this within-subjects cross-over counter-balanced training study. Assisted training involved 3 sessions per week of CMVJ training with 10 kg of assistance, applied through use of a bungee system, whilst normal jump training involved equated volume of unassisted counter-movement vertical jumps. Training periods were 5 weeks duration, with a 3-week wash-out separating them. Prior to and at the conclusion of each training period jump testing for CMVJ and SPJ height was conducted. Assisted jump training resulted in gains of 2.7±0.7 cm (p<0.01, ES=0.21) and 4.6±2.6 cm (p<0.01, ES=0.32) for the CMVJ and SPJ respectively, whilst normal jump training did not result in significant gains for either CMVJ or SPJ (p=0.09 and p=0.51 respectively). The changes associated with normal jump training and assisted jump training revealed significant differences in both CMVJ and SPJ (p=<0.03) in favour of the assisted jump condition, with large effect (CMVJ, ES=1.22; SPJ, ES=1.31). Assisted jumping may promote the leg extensor musculature to undergo a more rapid rate of shortening, and chronic exposure appears to improve jumping ability. Copyright © 2010 Sports Medicine Australia. All rights reserved.

  15. Kinematics and Kinetics of Squats, Drop Jumps and Imitation Jumps of Ski Jumpers.

    PubMed

    Pauli, Carole A; Keller, Melanie; Ammann, Fabian; Hübner, Klaus; Lindorfer, Julia; Taylor, William R; Lorenzetti, Silvio

    2016-03-01

    Squats, drop jumps, and imitation jumps are commonly used training exercises in ski jumping to enhance maximum force, explosive force, and sport-specific skills. The purpose of this study was to evaluate the kinetics and kinematics of training exercises in ski jumping and to find objective parameters in training exercises that most correlate with the competition performance of ski jumpers. To this end, barbell squats, drop jumps, and imitation jumps were measured in a laboratory environment for 10 elite ski jumpers. Force and motion data were captured, and the influence of maximum vertical force, force difference, vertical take-off velocity, knee moments, knee joint power, and a knee valgus/varus index was evaluated and correlated with their season jump performance. The results indicate that, especially for the imitation jumps, a good correlation exists between the vertical take-off velocity and the personal jump performance on the hill (R = 0.718). Importantly, however, the more the athletes tended toward a valgus knee alignment during the measured movements, the worse their performance (R = 0.729 imitation jumps; R = 0.685 squats). Although an evaluation of the athletes' lower limb alignment during competitive jumping on the hill is still required, these preliminary data suggest that performance training should additionally concentrate on improving knee alignment to increase ski jumping performance.

  16. Leg stiffness and expertise in men jumping.

    PubMed

    Laffaye, Guillaume; Bardy, Benoît G; Durey, Alain

    2005-04-01

    The aim of the present study is to investigate: a) the leg spring behavior in the one-leg vertical jump, b) the contribution of impulse parameters to this behavior, and c) the effect of jumping expertise on leg stiffness. Four categories of experts (handball, basketball, volleyball players, and Fosbury athletes), as well as novice subjects performed a run-and-jump test to touch a ball with the head. Five experimental conditions were tested from 55 to 95% of the maximum jump height. Kinematic and kinetic data were collected using six cameras and a force plate. The mechanical behavior of the musculoskeleton component of the human body can be modeled as a simple mass-spring system, from which leg stiffness values can be extracted to better understand energy transfer during running or jumping. The results indicate that leg stiffness (mean value of 11.5 kN.m) decreased with jumping height. Leg shortening at takeoff also increased with jumping height, whereas contact time decreased (-18%). No difference was found between experts and novices for leg stiffness. However, a principal components analysis (PCA) indicated the contribution of two main factors to the performance. The first factor emerged out of vertical force, stiffness, and duration of impulse. The second factor included leg shortening and jumping height. Differences between experts and novices were observed in terms of the contribution of leg stiffness to jump height, and more importantly, clear differences existed between experts in jumping parameters. The analysis performed on the sport categories indeed revealed different jumping profiles, characterized by specific, sport-related impulse parameters.

  17. Alterations of Vertical Jump Mechanics after a Half-Marathon Mountain Running Race

    PubMed Central

    Rousanoglou, Elissavet N.; Noutsos, Konstantinos; Pappas, Achilleas; Bogdanis, Gregory; Vagenas, Georgios; Bayios, Ioannis A.; Boudolos, Konstantinos D.

    2016-01-01

    The fatiguing effect of long-distance running has been examined in the context of a variety of parameters. However, there is scarcity of data regarding its effect on the vertical jump mechanics. The purpose of this study was to investigate the alterations of countermovement jump (CMJ) mechanics after a half-marathon mountain race. Twenty-seven runners performed CMJs before the race (Pre), immediately after the race (Post 1) and five minutes after Post 1 (Post 2). Instantaneous and ensemble-average analysis focused on jump height and, the maximum peaks and time-to-maximum peaks of: Displacement, vertical force (Fz), anterior-posterior force (Fx), Velocity and Power, in the eccentric (tECC) and concentric (tCON) phase of the jump, respectively. Repeated measures ANOVAs were used for statistical analysis (p ≤ 0.05). The jump height decrease was significant in Post 2 (-7.9%) but not in Post 1 (-4.1%). Fx and Velocity decreased significantly in both Post 1 (only in tECC) and Post 2 (both tECC and tCON). Α timing shift of the Fz peaks (earlier during tECC and later during tCON) and altered relative peak times (only in tECC) were also observed. Ensemble-average analysis revealed several time intervals of significant post-race alterations and a timing shift in the Fz-Velocity loop. An overall trend of lowered post-race jump output and mechanics was characterised by altered jump timing, restricted anterior-posterior movement and altered force-velocity relations. The specificity of mountain running fatigue to eccentric muscle work, appears to be reflected in the different time order of the post-race reductions, with the eccentric phase reductions preceding those of the concentric one. Thus, those who engage in mountain running should particularly consider downhill training to optimise eccentric muscular action. Key points The 4.1% reduction of jump height immediately after the race is not statistically significant The eccentric phase alterations of jump mechanics precede

  18. Alterations of Vertical Jump Mechanics after a Half-Marathon Mountain Running Race.

    PubMed

    Rousanoglou, Elissavet N; Noutsos, Konstantinos; Pappas, Achilleas; Bogdanis, Gregory; Vagenas, Georgios; Bayios, Ioannis A; Boudolos, Konstantinos D

    2016-06-01

    The fatiguing effect of long-distance running has been examined in the context of a variety of parameters. However, there is scarcity of data regarding its effect on the vertical jump mechanics. The purpose of this study was to investigate the alterations of countermovement jump (CMJ) mechanics after a half-marathon mountain race. Twenty-seven runners performed CMJs before the race (Pre), immediately after the race (Post 1) and five minutes after Post 1 (Post 2). Instantaneous and ensemble-average analysis focused on jump height and, the maximum peaks and time-to-maximum peaks of: Displacement, vertical force (Fz), anterior-posterior force (Fx), Velocity and Power, in the eccentric (tECC) and concentric (tCON) phase of the jump, respectively. Repeated measures ANOVAs were used for statistical analysis (p ≤ 0.05). The jump height decrease was significant in Post 2 (-7.9%) but not in Post 1 (-4.1%). Fx and Velocity decreased significantly in both Post 1 (only in tECC) and Post 2 (both tECC and tCON). Α timing shift of the Fz peaks (earlier during tECC and later during tCON) and altered relative peak times (only in tECC) were also observed. Ensemble-average analysis revealed several time intervals of significant post-race alterations and a timing shift in the Fz-Velocity loop. An overall trend of lowered post-race jump output and mechanics was characterised by altered jump timing, restricted anterior-posterior movement and altered force-velocity relations. The specificity of mountain running fatigue to eccentric muscle work, appears to be reflected in the different time order of the post-race reductions, with the eccentric phase reductions preceding those of the concentric one. Thus, those who engage in mountain running should particularly consider downhill training to optimise eccentric muscular action. Key pointsThe 4.1% reduction of jump height immediately after the race is not statistically significantThe eccentric phase alterations of jump mechanics precede

  19. Instruction and Jump-Landing Kinematics in College-Aged Female Athletes Over Time

    PubMed Central

    Etnoyer, Jena; Cortes, Nelson; Ringleb, Stacie I.; Van Lunen, Bonnie L.; Onate, James A.

    2013-01-01

    Context: Instruction can be used to alter the biomechanical movement patterns associated with anterior cruciate ligament (ACL) injuries. Objective: To determine the effects of instruction through combination (self and expert) feedback or self-feedback on lower extremity kinematics during the box–drop-jump task, running–stop-jump task, and sidestep-cutting maneuver over time in college-aged female athletes. Design: Randomized controlled clinical trial. Setting: Laboratory. Patients or Other Participants: Forty-three physically active women (age = 21.47 ± 1.55 years, height = 1.65 ± 0.08 m, mass = 63.78 ± 12.00 kg) with no history of ACL or lower extremity injuries or surgery in the 2 months before the study were assigned randomly to 3 groups: self-feedback (SE), combination feedback (CB), or control (CT). Intervention(s): Participants performed a box–drop-jump task for the pretest and then received feedback about their landing mechanics. After the intervention, they performed an immediate posttest of the box–drop-jump task and a running–stop-jump transfer test. Participants returned 1 month later for a retention test of each task and a sidestep-cutting maneuver. Kinematic data were collected with an 8-camera system sampled at 500 Hz. Main Outcome Measure(s): The independent variables were feedback group (3), test time (3), and task (3). The dependent variables were knee- and hip-flexion, knee-valgus, and hip- abduction kinematics at initial contact and at peak knee flexion. Results: For the box–drop-jump task, knee- and hip-flexion angles at initial contact were greater at the posttest than at the retention test (P < .001). At peak knee flexion, hip flexion was greater at the posttest than at the pretest (P = .003) and was greater at the retention test than at the pretest (P = .04); knee valgus was greater at the retention test than at the pretest (P = .03) and posttest (P = .02). Peak knee flexion was greater for the CB than the SE group (P = .03

  20. Relationship between traditional and ballistic squat exercise with vertical jumping and maximal sprinting.

    PubMed

    Requena, Bernardo; García, Inmaculada; Requena, Francisco; de Villarreal, Eduardo Sáez-Sáez; Cronin, John B

    2011-08-01

    The purpose of this study was to quantify the magnitude of the relationship between vertical jumping and maximal sprinting at different distances with performance in the traditional and ballistic concentric squat exercise in well-trained sprinters. Twenty-one men performed 2 types of barbell squats (ballistic and traditional) across different loads with the aim of determining the maximal peak and average power outputs and 1 repetition maximum (1RM) values. Moreover, vertical jumping (countermovement jump test [CMJ]) and maximal sprints over 10, 20, 30, 40, 60, and 80 m were also assessed. In respect to 1RM in traditional squat, (a) no significant correlation was found with CMJ performance; (b) positive strong relationships (p < 0.01) were obtained with all the power measures obtained during both ballistic and traditional squat exercises (r = 0.53-0.90); (c) negative significant correlations (r = -0.49 to -0.59, p < 0.05) were found with sprint times in all the sprint distances measured when squat strength was expressed as a relative value; however, in the absolute mode, no significant relationships were observed with 10- and 20-m sprint times. No significant relationship was found between 10-m sprint time and relative or absolute power outputs using either ballistic or traditional squat exercises. Sprint time at 20 m was only related to ballistic and traditional squat performance when power values were expressed in relative terms. Moderate significant correlations (r = -0.39 to -0.56, p < 0.05) were observed between sprint times at 30 and 40 m and the absolute/relative power measures attained in both ballistic and traditional squat exercises. Sprint times at 60 and 80 m were mainly related to ballistic squat power outputs. Although correlations can only give insights into associations and not into cause and effect, from this investigation, it can be seen that traditional squat strength has little in common with CMJ performance and that relative 1RM and power

  1. Electroencephalographic recordings during parachute jump sessions.

    PubMed

    Gauthier, P; Jouffray, L; Rodi, M; Gottesmann, C

    1980-04-01

    Electroencephalographic (EEG) recordings of experienced parachutists were done by means of telemetry before, during, and after jumps of up to 3500m. During free-fall and after stabilization, alpha rhythm was recorded from several alpha reactive subjects when they closed their eyes. No pathological EEG recordings were obtained during the different phases of the jump.

  2. The Phase Shift in the Jumping Ring

    ERIC Educational Resources Information Center

    Jeffery, Rondo N.; Amiri, Farhang

    2008-01-01

    The popular physics demonstration experiment known as Thomson's Jumping Ring (JR) has been variously explained as a simple example of Lenz's law, or as the result of a phase shift of the ring current relative to the induced emf. The failure of the first-quadrant Lenz's law explanation is shown by the time the ring takes to jump and by levitation.…

  3. Natural and systematic polar motion jumps

    NASA Astrophysics Data System (ADS)

    Chapanov, Y.; Vondrak, J.; Ron, C.; Pachalieva, R.

    2014-12-01

    Polar motion consists mainly of two harmonic oscillations with variable phases and amplitudes and small irregular variations. The small irregular variations may be due to various geophysical excitations and observation inaccuracy (mostly in the first half of the last century). A part of irregular polar motion variations consists of fast jumps of the mean values of polar motion coordinates. The direct determination of the polar motion jumps is difficult, because the jump values are very small relative to the seasonal and Chandler amplitudes. A useful high sensitive method of data jumps determination is proposed. The method consists of data integration and piecewise linear or parabolic trends determina- tion. This method is applied to determine the natural and systematic polar motion jumps existing in pole coordinates from the solutions OA10 for the period 1899.7ñ1962.0 and C04 for the period 1962.0- 2013.5. Only a few of the determined polar motion jumps can be interpreted as systematic biases due to observational errors. The major part of the detected polar motion jumps occurs almost regularly near the epochs of minimum amplitude (due to the beat of seasonal and Chandler wobbles), so the natural origin of these jumps is supposed.

  4. Orientation Dependence of Jumping Droplet Condensation

    NASA Astrophysics Data System (ADS)

    Berrier, Austin; Boreyko, Jonathan; Nature-Inspired Fluids; Interfaces Team

    2015-11-01

    On nanostructured superhydrophobic surfaces, microscopic condensate exhibits out-of-plane jumping that minimizes the average droplet size for maximal phase-change heat transfer. This jumping-droplet phenomenon occurs independently of gravity and is due to surface energy being partially converted to kinetic energy upon coalescence events. Although the initial departure of the jumping droplets is independent of gravity, the subsequent trajectories exhibit a dependence upon the orientation of the substrate. The drop size distribution of jumping-droplet condensation growing on a superhydrophobic substrate was characterized for both horizontal and vertical surface orientations. With the horizontal orientation, jumping condensate returns to the substrate by gravity. While this can result in chain reactions with other droplets to trigger further jumping events, eventually the rebounding droplets become too large to jump and are stuck on the surface. In contrast, droplets jumping off a vertically oriented surface do not return to the substrate. For this reason, the maximum droplet diameters during condensation growth were found to be significantly larger on the horizontally oriented superhydrophobic surface than on the vertical orientation.

  5. Internal hydraulic jumps with large upstream shear

    NASA Astrophysics Data System (ADS)

    Ogden, Kelly; Helfrich, Karl

    2015-11-01

    Internal hydraulic jumps in approximately two-layered flows with large upstream shear are investigated using numerical simulations. The simulations allow continuous density and velocity profiles, and a jump is forced to develop by downstream topography, similar to the experiments conducted by Wilkinson and Wood (1971). High shear jumps are found to exhibit significantly more entrainment than low shear jumps. Furthermore, the downstream structure of the flow has an important effect on the jump properties. Jumps with a slow upper (inactive) layer exhibit a velocity minimum downstream of the jump, resulting in a sub-critical downstream state, while flows with the same upstream vertical shear and a larger barotropic velocity remain super-critical downstream of the jump. A two-layer theory is modified to account for the vertical structure of the downstream density and velocity profiles and entrainment is allowed through a modification of the approach of Holland et al. (2002). The resulting theory can be matched reasonably well with the numerical simulations. However, the results are very sensitive to how the downstream vertical profiles of velocity and density are incorporated into the layered model, highlighting the difficulty of the two layer approximation when the shear is large.

  6. The Locust Jump: An Integrated Laboratory Investigation

    ERIC Educational Resources Information Center

    Scott, Jon

    2005-01-01

    The locust is well known for its ability to jump large distances to avoid predation. This class sets out a series of investigations into the mechanisms underlying the jump enabling students to bring together information from biomechanics, muscle physiology, and anatomy. The nature of the investigation allows it to be undertaken at a number of…

  7. A subdural haematoma following 'reverse' bungee jumping.

    PubMed

    FitzGerald, J J; Bassi, S; White, B D

    2002-06-01

    Bungee jumping has been exploited commercially for 13 years and proprietors claim a good safety record. However, published case reports document a wide variety of possible injuries. To this list, we add a report of a subdural haematoma sustained during a variant of the sport, the 'reverse' bungee jump.

  8. The Phase Shift in the Jumping Ring

    ERIC Educational Resources Information Center

    Jeffery, Rondo N.; Amiri, Farhang

    2008-01-01

    The popular physics demonstration experiment known as Thomson's Jumping Ring (JR) has been variously explained as a simple example of Lenz's law, or as the result of a phase shift of the ring current relative to the induced emf. The failure of the first-quadrant Lenz's law explanation is shown by the time the ring takes to jump and by levitation.…

  9. JumpStart III Final Report.

    ERIC Educational Resources Information Center

    Cohen, Arthur M.; Brawer, Florence B.; Kozeracki, Carol A.

    This final report for the JumpStart III program presents a summary of the entrepreneurship training programs developed by each of the four JumpStart III partners selected in March 1997. Grants for the colleges totaled $354,546 over 2 years. The Jumpstart funding has been only a starting point for these and the other 12 Jumpstart partners in…

  10. The Locust Jump: An Integrated Laboratory Investigation

    ERIC Educational Resources Information Center

    Scott, Jon

    2005-01-01

    The locust is well known for its ability to jump large distances to avoid predation. This class sets out a series of investigations into the mechanisms underlying the jump enabling students to bring together information from biomechanics, muscle physiology, and anatomy. The nature of the investigation allows it to be undertaken at a number of…

  11. Rope Jumping: A Preliminary Developmental Study.

    ERIC Educational Resources Information Center

    Wickstrom, Ralph L.

    The basic movement pattern used in skilled individual rope jumping performance was determined and used as a model against which to evaluate the rope jumping form used by children at various levels of skills development. The techniques of adults and nursery school children were filmed and analyzed. The specific causes of unsuccessful attempts were…

  12. A Comparison of Mechanical Parameters Between the Counter Movement Jump and Drop Jump in Biathletes

    PubMed Central

    Król, Henryk; Mynarski, Władysław

    2012-01-01

    The main objective of the study was to determine to what degree higher muscular activity, achieved by increased load in the extension phase (eccentric muscle action) of the vertical jump, affects the efficiency of the vertical jump. Sixteen elite biathletes participated in this investigation. The biathletes performed tests that consisted of five, single “maximal” vertical jumps (counter movement jump – CMJ) and five, single vertical jumps, in which the task was to touch a bar placed over the jumping biathletes (specific task counter movement jump – SCMJ). Then, they performed five, single drop jumps from an elevation of 0.4m (DJ). Ground reaction forces were registered using the KISTLER 9182C force platform. MVJ software was used for signal processing (Król, 1999) and enabling calculations for kinematic and kinetic parameters of the subject’s jump movements (on-line system). The results indicate that only height of the jump (h) and mean power (Pmean) during the takeoff are statistically significant. Both h and Pmean are higher in the DJ. The results of this study may indicate that elite biathletes are well adapted to eccentric work of the lower limbs, thus reaching greater values of power during the drop jump. These neuromuscular adaptive changes may allow for a more dynamic and efficient running technique. PMID:23487157

  13. Effects of Short-Term Isokinetic Training on Standing Long-Jump Performance in Untrained Men.

    ERIC Educational Resources Information Center

    Morriss, Calvin J.; Tolfrey, Keith; Coppack, Russell J.

    2001-01-01

    Evaluated the effects of a brief isokinetic training program on quadriceps and hamstring peak torque (PT) and standing long-jump performance. Tests on 12 untrained men indicated that the brief training program was at least as effective in improving quadriceps isokinetic (but not hamstring) PT. PT gains subsequent to isokinetic resistance training…

  14. Effects of Short-Term Isokinetic Training on Standing Long-Jump Performance in Untrained Men.

    ERIC Educational Resources Information Center

    Morriss, Calvin J.; Tolfrey, Keith; Coppack, Russell J.

    2001-01-01

    Evaluated the effects of a brief isokinetic training program on quadriceps and hamstring peak torque (PT) and standing long-jump performance. Tests on 12 untrained men indicated that the brief training program was at least as effective in improving quadriceps isokinetic (but not hamstring) PT. PT gains subsequent to isokinetic resistance training…

  15. Stochastic stability properties of jump linear systems

    NASA Technical Reports Server (NTRS)

    Feng, Xiangbo; Loparo, Kenneth A.; Ji, Yuandong; Chizeck, Howard J.

    1992-01-01

    Jump linear systems are defined as a family of linear systems with randomly jumping parameters (usually governed by a Markov jump process) and are used to model systems subject to failures or changes in structure. The authors study stochastic stability properties in jump linear systems and the relationship among various moment and sample path stability properties. It is shown that all second moment stability properties are equivalent and are sufficient for almost sure sample path stability, and a testable necessary and sufficient condition for second moment stability is derived. The Lyapunov exponent method for the study of almost sure sample stability is discussed, and a theorem which characterizes the Lyapunov exponents of jump linear systems is presented.

  16. Vertical jumping performance of bonobo (Pan paniscus) suggests superior muscle properties

    PubMed Central

    Scholz, Melanie N; D'Août, Kristiaan; Bobbert, Maarten F; Aerts, Peter

    2006-01-01

    Vertical jumping was used to assess muscle mechanical output in bonobos and comparisons were drawn to human jumping. Jump height, defined as the vertical displacement of the body centre of mass during the airborne phase, was determined for three bonobos of varying age and sex. All bonobos reached jump heights above 0.7 m, which greatly exceeds typical human maximal performance (0.3–0.4 m). Jumps by one male bonobo (34 kg) and one human male (61.5 kg) were analysed using an inverse dynamics approach. Despite the difference in size, the mechanical output delivered by the bonobo and the human jumper during the push-off was similar: about 450 J, with a peak power output close to 3000 W. In the bonobo, most of the mechanical output was generated at the hips. To account for the mechanical output, the muscles actuating the bonobo's hips (directly and indirectly) must deliver muscle-mass-specific power and work output of 615 W kg−1 and 92 J kg−1, respectively. This was twice the output expected on the basis of muscle mass specific work and power in other jumping animals but seems physiologically possible. We suggest that the difference is due to a higher specific force (force per unit of cross-sectional area) in the bonobo. PMID:16901837

  17. Breast Support Garments are Ineffective at Reducing Breast Motion During an Aqua Aerobics Jumping Exercise

    PubMed Central

    Mills, Chris; Ayres, Bessie; Scurr, Joanna

    2015-01-01

    The buoyant forces of water during aquatic exercise may provide a form of ‘natural’ breast support and help to minimise breast motion and alleviate exercise induced breast pain. Six larger-breasted females performed standing vertical land and water-based jumps, whilst wearing three breast support conditions. Underwater video cameras recorded the motion of the trunk and right breast. Trunk and relative breast kinematics were calculated as well as exercised induced breast pain scores. Key results showed that the swimsuit and sports bra were able to significantly reduce the superioinferior breast range of motion by 0.04 and 0.05 m, respectively, and peak velocity by 0.23 and 0.33 m/s, respectively, during land-based jumping when compared to the bare-breasted condition, but were ineffective at reducing breast kinematics during water-based jumping. Furthermore, the magnitude of the swimsuit superioinferior breast range of motion during water-based jumping was significantly greater than land-based jumping (0.13 m and 0.06 m), yet there were no significant differences in exercise induced breast pain, thus contradicting previously published relationships between these parameters on land. Furthermore, the addition of an external breast support garment was able to reduce breast kinematics on land but not in water, suggesting the swimsuit and sports bras were ineffective and improvements in swimwear breast support garments may help to reduce excessive breast motion during aqua aerobic jumping exercises. PMID:26240648

  18. Parachute Jumping Induces More Sympathetic Activation Than Cortisol Secretion in First-Time Parachutists.

    PubMed

    Messina, Giovanni; Chieffi, Sergio; Viggiano, Andrea; Tafuri, Domenico; Cibelli, Giuseppe; Valenzano, Anna; Triggiani, Antonio Ivano; Messina, Antonietta; De Luca, Vincenzo; Monda, Marcellino

    2016-03-01

    The word "stress" describes the status of the body affected by external or internal forces, or "stressors", threatening to alter its dynamic balance or homeostasis. The adaptive changes which occur in reply to stressors are either behavioral or physical. Once a given threshold is surpassed, a systemic reaction takes place involving the "stress system" in the brain together with its peripheral components, the hypothalamic-pituitary-adrenal axis and autonomic sympathetic. Stress induces an activation of the sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis. The purpose of this study was to investigate whether the SNS and the HPA axis would show parallel or divergent stress response patterns in a session of first parachute jump. Activation of the SNS was evaluated by dosage of salivary alpha-amylase, galvanic skin responses, and heart rate in seven male novice parachutists. Activation of HPA axis was tested by dosage of cortisol. These variables were measured before and 1 minute and 90 minute after the jump. All variables reached a peak at 1 minute post-jump. Salivary alpha-amylase, galvanic skin responses and heart rate did not return to basal value at 90 minutes post-jump, while cortisol returned to basal value at 90 minutes post-jump. This evidence indicates that parachute jumping is accompanied by a dissociation of SNS and HPA response patterns in novice parachutists, showing a slower recovery in sympathetic activity than in cortisol secretion.

  19. Vertical jumping performance of bonobo (Pan paniscus) suggests superior muscle properties.

    PubMed

    Scholz, Melanie N; D'Août, Kristiaan; Bobbert, Maarten F; Aerts, Peter

    2006-09-07

    Vertical jumping was used to assess muscle mechanical output in bonobos and comparisons were drawn to human jumping. Jump height, defined as the vertical displacement of the body centre of mass during the airborne phase, was determined for three bonobos of varying age and sex. All bonobos reached jump heights above 0.7 m, which greatly exceeds typical human maximal performance (0.3-0.4m). Jumps by one male bonobo (34 kg) and one human male (61.5 kg) were analysed using an inverse dynamics approach. Despite the difference in size, the mechanical output delivered by the bonobo and the human jumper during the push-off was similar: about 450 J, with a peak power output close to 3000 W. In the bonobo, most of the mechanical output was generated at the hips. To account for the mechanical output, the muscles actuating the bonobo's hips (directly and indirectly) must deliver muscle-mass-specific power and work output of 615 Wkg-1 and 92 Jkg-1, respectively. This was twice the output expected on the basis of muscle mass specific work and power in other jumping animals but seems physiologically possible. We suggest that the difference is due to a higher specific force (force per unit of cross-sectional area) in the bonobo.

  20. The dynamics of flight-initiating jumps in the common vampire bat Desmodus rotundus.

    PubMed

    Schutt, W A; Altenbach, J S; Chang, Y H; Cullinane, D M; Hermanson, J W; Muradali, F; Bertram, J E

    1997-12-01

    Desmodus rotundus, the common vampire bat (Phyllostomidae: Desmodontinae), exhibits complex and variable terrestrial movements that include flight-initiating vertical jumps. This ability is unique among bats and is related to their unusual feeding behavior. As a consequence of this behavior, the wing is expected to have design features that allow both powered flight and the generation of violent jumps. In this study, high-speed cine images were synchronized with ground reaction force recordings to evaluate the dynamics of jumping behavior in D. rotundus and to explore the functional characteristics of a wing operating under competing mechanical constraints. The pectoral limbs are responsible for generating upward thrust during the jump. The hindlimbs stabilize and orient the body over the pectoral limbs. The thumbs (pollices) stabilize the pectoral limb and contribute to extending the time over which vertical force is exerted. Peak vertical force can reach 9.5 times body weight in approximately 30 ms. Mean impulse is 0.0580+/-0.007 N s (mean +/- s.d., N=12), which accelerates the animal to a mean take-off velocity of 2.38+/-0.24 m s-1. A model of the muscular activity during jumping is described that accounts for the characteristic force output shown by these animals during flight-initiating jumps.

  1. The Application of Nonstandard Analysis to the Study of Inviscid Shock Wave Jump Conditions

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Baty, R. S.

    1998-01-01

    The use of conservation laws in nonconservative form for deriving shock jump conditions by Schwartz distribution theory leads to ambiguous products of generalized functions. Nonstandard analysis is used to define a class of Heaviside functions where the jump from zero to one occurs on an infinitesimal interval. These Heaviside functions differ by their microstructure near x = 0, i.e., by the nature of the rise within the infinitesimal interval it is shown that the conservation laws in nonconservative form can relate the different Heaviside functions used to define jumps in different flow parameters. There are no mathematical or logical ambiguities in the derivation of the jump conditions. An important result is that the microstructure of the Heaviside function of the jump in entropy has a positive peak greater than one within the infinitesimal interval where the jump occurs. This phenomena is known from more sophisticated studies of the structure of shock waves using viscous fluid assumption. However, the present analysis is simpler and more direct.

  2. Usefulness of the jump-and-reach test in assessment of vertical jump performance.

    PubMed

    Menzel, Hans-Joachim; Chagas, Mauro H; Szmuchrowski, Leszek A; Araujo, Silvia R; Campos, Carlos E; Giannetti, Marcus R

    2010-02-01

    The objective was to estimate the reliability and criterion-related validity of the Jump-and-Reach Test for the assessment of squat, countermovement, and drop jump performance of 32 male Brazilian professional volleyball players. Performance of squat, countermovement, and drop jumps with different dropping heights was assessed on the Jump-and-Reach Test and the measurement of flight time, then compared across different jump trials. The very high reliability coefficients of both assessment methods and the lower correlation coefficients between scores on the assessments indicate a very high consistency of each method but only moderate covariation, which means that they measure partly different items. As a consequence, the Jump-and-Reach Test has good ecological validity in situations when reaching height during the flight phase is critical for performance (e.g., basketball and volleyball) but only limited accuracy for the assessment of vertical impulse production with different jump techniques and conditions.

  3. Are Bragg Peaks Gaussian?

    PubMed Central

    Hammouda, Boualem

    2014-01-01

    It is common practice to assume that Bragg scattering peaks have Gaussian shape. The Gaussian shape function is used to perform most instrumental smearing corrections. Using Monte Carlo ray tracing simulation, the resolution of a realistic small-angle neutron scattering (SANS) instrument is generated reliably. Including a single-crystal sample with large d-spacing, Bragg peaks are produced. Bragg peaks contain contributions from the resolution function and from spread in the sample structure. Results show that Bragg peaks are Gaussian in the resolution-limited condition (with negligible sample spread) while this is not the case when spread in the sample structure is non-negligible. When sample spread contributes, the exponentially modified Gaussian function is a better account of the Bragg peak shape. This function is characterized by a non-zero third moment (skewness) which makes Bragg peaks asymmetric for broad neutron wavelength spreads. PMID:26601025

  4. Kinematics and Kinetics of Squats, Drop Jumps and Imitation Jumps of Ski Jumpers

    PubMed Central

    Pauli, Carole A.; Keller, Melanie; Ammann, Fabian; Hübner, Klaus; Lindorfer, Julia; Taylor, William R.

    2016-01-01

    Abstract Pauli, CA, Keller, M, Ammann, F, Hübner, K, Lindorfer, J, Taylor, WR, and Lorenzetti, S. Kinematics and kinetics of squats, drop jumps and imitation jumps of ski jumpers. J Strength Cond Res 30(3): 643–652, 2016—Squats, drop jumps, and imitation jumps are commonly used training exercises in ski jumping to enhance maximum force, explosive force, and sport-specific skills. The purpose of this study was to evaluate the kinetics and kinematics of training exercises in ski jumping and to find objective parameters in training exercises that most correlate with the competition performance of ski jumpers. To this end, barbell squats, drop jumps, and imitation jumps were measured in a laboratory environment for 10 elite ski jumpers. Force and motion data were captured, and the influence of maximum vertical force, force difference, vertical take-off velocity, knee moments, knee joint power, and a knee valgus/varus index was evaluated and correlated with their season jump performance. The results indicate that, especially for the imitation jumps, a good correlation exists between the vertical take-off velocity and the personal jump performance on the hill (R = 0.718). Importantly, however, the more the athletes tended toward a valgus knee alignment during the measured movements, the worse their performance (R = 0.729 imitation jumps; R = 0.685 squats). Although an evaluation of the athletes' lower limb alignment during competitive jumping on the hill is still required, these preliminary data suggest that performance training should additionally concentrate on improving knee alignment to increase ski jumping performance. PMID:26418370

  5. Jumping from the Brooklyn Bridge.

    PubMed

    Kurtz, R J; Pizzi, W F; Richman, H; Tiefenbrun, J

    1987-07-01

    In an attempt to identify factors contributing to survival of free fall and impact, we evaluated the records of four patients who survived a jump from the Brooklyn Bridge into the East River in New York Harbor between 1977 and 1985. All four patients were male and ranged in age from 22 to 67 years. They had free falls of between 41.0 and 48.8 meters. All of the patients were brought to the hospital within 24 minutes of entering the water. Three of the four had emergency surgical treatment and the fourth patient had only minor injuries. All four patients survived the suicide attempts. The length of the hospital stay ranged from two to 26 days.

  6. Mobile Jump Assessment (mJump): A Descriptive and Inferential Study.

    PubMed

    Mateos-Angulo, Alvaro; Galán-Mercant, Alejandro; Cuesta-Vargas, Antonio

    2015-08-26

    Vertical jump tests are used in athletics and rehabilitation to measure physical performance in people of different age ranges and fitness. Jumping ability can be analyzed through different variables, and the most commonly used are fly time and jump height. They can be obtained by a variety of measuring devices, but most are limited to laboratory use only. The current generation of smartphones contains inertial sensors that are able to record kinematic variables for human motion analysis, since they are tools for easy access and portability for clinical use. The aim of this study was to describe and analyze the kinematics characteristics using the inertial sensor incorporated in the iPhone 4S, the lower limbs strength through a manual dynamometer, and the jump variables obtained with a contact mat in the squat jump and countermovement jump tests (fly time and jump height) from a cohort of healthy people. A cross sectional study was conducted on a population of healthy young adults. Twenty-seven participants performed three trials (n=81 jumps) of squat jump and countermovement jump tests. Acceleration variables were measured through a smartphone's inertial sensor. Additionally, jump variables from a contact mat and lower limbs dynamometry were collected. In the present study, the kinematic variables derived from acceleration through the inertial sensor of a smartphone iPhone 4S, dynamometry of lower limbs with a handheld dynamometer, and the height and flight time with a contact mat have been described in vertical jump tests from a cohort of young healthy subjects. The development of the execution has been described, examined and identified in a squat jump test and countermovement jump test under acceleration variables that were obtained with the smartphone. The built-in iPhone 4S inertial sensor is able to measure acceleration variables while performing vertical jump tests for the squat jump and countermovement jump in healthy young adults. The acceleration

  7. Vertical jumping in Galago senegalensis: the quest for an obligate mechanical power amplifier

    PubMed Central

    Aerts, P.

    1998-01-01

    Bushbabies (Galago senegalensis) are renowned for their phenomenal jumping capacity. It was postulated that mechanical power amplification must be involved. Dynamic analysis of the vertical jumps performed by two bushbabies confirms the need for a power amplifier. Inverse dynamics coupled to a geometric musculo-skeletal model were used to elucidate the precise nature of the mechanism powering maximal vertical jumps. Most of the power required for jumping is delivered by the vastus muscle-tendon systems (knee extensor). Comparison with the external joint-powers revealed, however, an important power transport from this extensor (about 65%) to the ankle and the midfoot via the bi-articular calf muscles. Peak power output likely implies elastic recoil of the complex aponeurotic system of the vastus muscle. Patterns of changes in length and tension of the muscle-tendon complex during different phases of the jump were found which provide strong evidence for substantial power amplification (times 15). It is argued here that the multiple internal connective tissue sheets and attachment structures of the well-developed bundles of the vastus muscle become increasingly stretched during preparatory crouching and throughout the extension phase, except for the last 13 ms of the push-off (i.e. when power requirements peak). Then, tension in the knee extensors abruptly falls from its maximum, allowing the necessary fast recoil of the tensed tendon structures to occur.

  8. Relationships between explosive and maximal triple extensor muscle performance and vertical jump height.

    PubMed

    Chang, Eunwook; Norcross, Marc F; Johnson, Sam T; Kitagawa, Taichi; Hoffman, Mark

    2015-02-01

    The purpose of this study was to examine the relationships between maximum vertical jump height and (a) rate of torque development (RTD) calculated during 2 time intervals, 0-50 milliseconds (RTD50) and 0-200 milliseconds (RTD200) after torque onset and (b) peak torque (PT) for each of the triple extensor muscle groups. Thirty recreationally active individuals performed maximal isometric voluntary contractions (MVIC) of the hip, knee and ankle extensors, and a countermovement vertical jump. Rate of torque development was calculated from 0 to 50 (RTD50) and 0 to 200 (RTD200) milliseconds after the onset of joint torque. Peak torque was identified and defined as the maximum torque value during each MVIC trial. Greater vertical jump height was associated with greater knee and ankle extension RTD50, RTD200, and PT (p ≤ 0.05). However, hip extension RTD50, RTD200, and PT were not significantly related to maximal vertical jump height (p > 0.05). The results indicate that 47.6 and 32.5% of the variability in vertical jump height was explained by knee and ankle extensor RTD50, respectively. Knee and ankle extensor RTD50 also seemed to be more closely related to vertical jump performance than RTD200 (knee extensor: 28.1% and ankle extensor: 28.1%) and PT (knee extensor: 31.4% and ankle extensor: 13.7%). Overall, these results suggest that training specifically targeted to improve knee and ankle extension RTD, especially during the early phases of muscle contraction, may be effective for increasing maximal vertical jump performance.

  9. Dynamic control of muscle stiffness and H reflex modulation during hopping and jumping in man.

    PubMed Central

    Dyhre-Poulsen, P; Simonsen, E B; Voigt, M

    1991-01-01

    1. The objective of the study was to evaluate the functional effects of reflexes on muscle mechanics during natural voluntary movements. The excitability of the H (Hoffmann) reflex was used as a measure of the excitability of the central component of the stretch reflex. 2. We recorded EMG, ground reaction forces and the H reflex in the soleus muscle in humans while landing from a downward jump, during drop jumping and during hopping. The movements were also recorded by high-speed cinematography. 3. The EMG pattern was adapted to the motor task. When landing the EMG in the soleus muscle and in the anterior tibial muscle showed preinnervation and alternating activity after touch down. When hopping there was little preinnervation in the soleus muscle, and the activity was initiated about 45 ms after touch down by a peak and continued unbroken until lift off. In the drop jumps the EMG pattern depended on the jumping style used by the subject. 4. The H reflex in the soleus muscle was strongly modulated in a manner appropriate to the requirements of the motor task. During landing from a downward jump the H reflex was low at touch down whereas while hopping it was high at touch down. During drop jumping it was variable and influenced by the jumping technique. 5. Muscle stiffness in the ankle joint was negative after touch down when landing, but always positive when hopping. 6. It is suggested that during landing the alternating EMG pattern after touch down was programmed and little influenced by reflexes. During hopping reflexes could contribute to the initial peak and the EMG during lift off. 7. The programmed EMG activity and the suppression of the H reflex while landing probably contribute to the development of the negative stiffness and change the muscles from a spring to a damping unit. PMID:1890636

  10. Reliability, usefulness, and validity of a repeated sprint and jump ability test.

    PubMed

    Buchheit, Martin; Spencer, Matt; Ahmaidi, Said

    2010-03-01

    Two studies involving 122 handball players were conducted to assess the reliability, usefulness, and validity of a repeated shuttle-sprint and jump ability (RSSJA) test. The test consisted of 6x(2x12.5-m) sprints departing on 25 s, with a countermovement jump performed during recovery between sprints. For the reliability and usefulness study, 14 well-trained male handball players performed the RSSJA test 7 d apart. Reliability of the test variables was assessed by the typical error of measurement, expressed as a coefficient of variation (CV). The minimal changes likely to be "real" in sprint time and jump power were also calculated. For the validity study, players of seven teams (national to international levels, women and men) performed the RSSJA test. CV values for best and mean sprint time were 1.0% (90% CL, 0.7 to 1.6) and 1.0% (90% CL, 0.7 to 1.4). CV values for best and mean jump peak power were 1.7% (90% CL, 1.2 to 2.7) and 1.5% (90% CL, 1.1 to 2.5). The percent sprint and jump decrements were less reliable, with CVs of 22.3% (90% CL, 15.7 to 38.3) and 34.8% (90% CL, 24.2 to 61.8). Minimal changes likely to be "real" for mean sprint time and jumping peak power were -2.6% and 4.8%. Qualitative analysis revealed that the majority of between-team differences were rated as "almost certain" (ie, 100% probability that the true differences were meaningful) for mean sprint and jump performances. The RSSJA test is reliable and valid to assess repeated explosive effort sequences in team sports such as handball. Test results are likely to be representative of gender and competition level; thus the test could be used to discriminate across playing standards and monitor fitness levels.

  11. Power output in the jump squat in adolescent male athletes.

    PubMed

    Dayne, Andrea M; McBride, Jeffrey M; Nuzzo, James L; Triplett, N Travis; Skinner, Jared; Burr, Alan

    2011-03-01

    The load that maximizes power output in the jump squat (JS) in college-aged athletic males has been reported to be 0% of 1 repetition maximum [1RM] squat strength) or in other words body mass. No data exist concerning adolescent athletic males. In addition, strength levels have been theorized to possibly affect the load that maximizes power output in the JS. The purpose of this investigation was to identify the load that maximizes power output in the JS in adolescent athletic men, and concurrently describe their strength level and its effect on the load that maximizes power output. Eleven high-school male athletes were tested on 2 occasions, first determining their 1RM in the squat (1RM = 141.14 ± 28.08 kg; squat 1RM-to-body mass ratio = 1.76 ± 0.15) and then performing JS testing at loads equal to 0% (body mass), 20, 40, 60, and 80% of squat 1RM. Peak power (PP), peak force, peak velocity (PV), and peak displacement were measured at each load. Jump squat at the 0% load produced significantly (p ≤ 0.05) higher PP, PV, and peak displacement in comparison with the 40, 60, and 80% loading conditions. It was concluded that the load that maximizes power output in the JS is 0% of 1RM in adolescent athletic men, the same as found in college-aged athletic men. In addition, strength level relative to body mass did not affect the load that maximized power output. Practically, when devising a training program to increase PP, it is important to include JSs at body mass along with traditional strength training at heavier loads to increase power output across the entire loading spectrum.

  12. Asynchronous Dissipative Control for Fuzzy Markov Jump Systems.

    PubMed

    Wu, Zheng-Guang; Dong, Shanling; Su, Hongye; Li, Chuandong

    2017-08-25

    The problem of asynchronous dissipative control is investigated for Takagi-Sugeno fuzzy systems with Markov jump in this paper. Hidden Markov model is introduced to represent the nonsynchronization between the designed controller and the original system. By the fuzzy-basis-dependent and mode-dependent Lyapunov function, a sufficient condition is achieved such that the resulting closed-loop system is stochastically stable with a strictly (Q, S, R)-α-dissipative performance. The controller parameter is derived by applying MATLAB to solve a set of linear matrix inequalities. Finally, we present two examples to confirm the validity and correctness of our developed approach.

  13. Acute kinematic and kinetic augmentation in horizontal jump performance using haltere type handheld loading.

    PubMed

    Cronin, John B; Brughelli, Matt; Gamble, Paul; Brown, Scott R; Mckenzie, Chloe

    2014-06-01

    The purposes of this study were to investigate the effects of haltere/handheld loading on the kinematics and kinetics of horizontal jumping and to determine if an optimum relative load (% body mass [BM]) exists to maximize jump distance. A repeated measures analysis of variance with post hoc contrasts was used to determine the effects of haltere loading (no external loading, 6, 8, 12, and 16 kg) on the horizontal jump performance of 16 sportsmen as quantified by an in-ground force plate. The haltere loads of 6 and 8 kg elicited significant (p < 0.05) increases in jump distance (effect size [ES] = 0.22-0.37). The incremental loads also resulted in significant increases in jump duration (ES = 1.22-1.83), peak vertical ground reaction force (GRF) (ES = 0.20-0.37), and vertical (ES = 0.69-1.22) and horizontal (ES = 0.70-0.88) impulse. There was a significant reduction in jump distance with the 16 kg load (ES = 0.45). Significant decreases in mean horizontal GRF were likewise observed with the 12 and 16 kg loads. The optimum relative load for enhancing jump distance was 9.2 ± 3.4% of BM, which resulted in a predicted augmented horizontal jump of 13.6 ± 7.7 cm (ES = 0.56). The findings clearly indicate that haltere/handheld loading augments vertical and horizontal force and impulses. This could have a number of interesting training implications if the strength profiling of athletes identify horizontal and/or vertical deficits in force production. Further longitudinal investigation is warranted to establish what chronic adaptations result with repeated application of this type of training.

  14. Potentiation: Effect of Ballistic and Heavy Exercise on Vertical Jump Performance.

    PubMed

    Hester, Garrett M; Pope, Zachary K; Sellers, John H; Thiele, Ryan M; DeFreitas, Jason M

    2017-03-01

    Hester, GM, Pope, ZK, Sellers, JH, Thiele, RM, and DeFreitas, JM. Potentiation: Effect of ballistic and heavy exercise on vertical jump performance. J Strength Cond Res 31(3): 660-666, 2017-The purpose of this study was to compare the acute effects of heavy and ballistic conditioning protocols on vertical jump performance in resistance-trained men. Fourteen resistance-trained men (mean ± SD: age = 22 ± 2.1 years, body mass = 86.29 ± 9.95 kg, and height = 175.39 ± 9.34 cm) with an average relative full squat of 2.02 ± 0.28 times their body mass participated in this study. In randomized, counterbalanced order, subjects performed two countermovement vertical jumps before and 1, 3, 5, and 10 minutes after either performing 10 rapid jump squats or 5 heavy back squats. The back squat protocol consisted of 5 repetitions at 80% one repetition maximum (1RM), whereas the jump squat protocol consisted of 10 repetitions at 20% 1RM. Peak jump height (in centimeters) using a jump mat, along with power output (in Watts) and velocity (in meters per second) through a linear transducer, was recorded for each time interval. There was no significant condition × time interaction for any of the dependent variables (p = 0.066-0.127). In addition, there was no main effect for condition for any of the dependent variables (p = 0.457-0.899). Neither the ballistic nor heavy protocol used in this study enhanced vertical jump performance at any recovery interval. The use of these protocols in resistance-trained men to produce postactivation potentiation is not recommended.

  15. Peak Experience Project

    ERIC Educational Resources Information Center

    Scott, Daniel G.; Evans, Jessica

    2010-01-01

    This paper emerges from the continued analysis of data collected in a series of international studies concerning Childhood Peak Experiences (CPEs) based on developments in understanding peak experiences in Maslow's hierarchy of needs initiated by Dr Edward Hoffman. Bridging from the series of studies, Canadian researchers explore collected…

  16. Peak Experience Project

    ERIC Educational Resources Information Center

    Scott, Daniel G.; Evans, Jessica

    2010-01-01

    This paper emerges from the continued analysis of data collected in a series of international studies concerning Childhood Peak Experiences (CPEs) based on developments in understanding peak experiences in Maslow's hierarchy of needs initiated by Dr Edward Hoffman. Bridging from the series of studies, Canadian researchers explore collected…

  17. Seasonal changes of jumping performance and knee muscle strength in under-19 women volleyball players.

    PubMed

    Rousanoglou, Elissavet N; Barzouka, Karolina G; Boudolos, Konstantinos D

    2013-04-01

    The purpose of the study was to compare the seasonal changes (preparation period [PP] and competition period [CP]) of vertical jumping performance and knee muscle strength in a team of under-19 women volleyball players (N = 12, 16.2 ± 1.5 years). The countermovement jump was used to evaluate jumping performance. The isometric knee extension moment at 150 ms from the onset of contraction (T150) and at a maximum of contraction (TMAX) were determined at 9 knee angles (from 10° to 90°, full knee extension = 0°). The peak isokinetic knee extension (TISOK-EXT) and flexion (TISOK-FLEX) moment were determined at 60, 180, and 240°·s. Repeated-measures analysis of variance was applied to the differences between PP and CP (p ≤ 0.05). Significant increases in jumping performance were found for jump height, peak impulse, total impulse, peak power, and takeoff velocity (p ≤ 0.05). At the knee flexion angles from 40° to 90°, T150 was significantly increased (p ≤ 0.05), whereas the increase was not significant at the rather extended knee angles of 10°, 20°, and 30° (p > 0.05). Only at 90° of knee flexion (p ≤ 0.05), TMAX was significantly increased. With the exception of TISOK-FLEX at 60°·s (p ≤ 0.05), the increases of TISOK-EXT and TISOK-FLEX were not significant (p > 0.05). The TISOK-EXT/TISOK-FLEX ratios were not significantly changed (p > 0.05). The main application of the study is that it provides performance standards and potential criteria for variable selection for jumping performance and knee muscle strength seasonal evaluation.

  18. Jump-landing biomechanics following a 4-week real-time feedback intervention and retention.

    PubMed

    Ericksen, Hayley M; Thomas, Abbey C; Gribble, Phillip A; Armstrong, Charles; Rice, Martin; Pietrosimone, Brian

    2016-02-01

    Poor neuromuscular control can increase the risk of anterior cruciate ligament (ACL) injury. Landing with decreased knee and hip flexion may increase the risk of lower extremity injury. Feedback interventions have demonstrated changes in jump-landing biomechanics. Traditional feedback (TF), provided after task completion, includes critical factors to focus on during jump-landing. Real-time feedback (RTF), provided while completing the task, may be superior for improving jump-landing biomechanics. This investigation evaluated the effect of RTF+TF compared to TF and a control group in changing lower extremity jump-landing biomechanics following a 4-week feedback intervention and a 1-week no feedback retention. Participants completed 12 feedback sessions over 4 weeks. At each session, participants performed 6 sets of 6 jumps off a 30 cm box. Participants were provided TF or RTF+TF following each set of jumps. Participants were tested at baseline, immediately following the 4-week intervention and following a 1-week retention. The control group was tested at two time points 4 weeks apart. Acquisition analysis: RTF+TF and TF groups demonstrated greater change in peak hip flexion angles and peak knee flexion angles compared to the control group following the intervention. TF and RTF+TF groups demonstrated a greater decrease in peak vertical ground reaction force compared to the control group. No significant differences were observed between groups in the retention analysis. This study provides evidence of acquisition of biomechanical changes following a 4-week feedback intervention. Future research should further investigate the retention of biomechanical changes, the optimal length of feedback interventions and transfer of learned biomechanics to similar athletic tasks. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Achilles tendon material properties are greater in the jump leg of jumping athletes

    PubMed Central

    Bayliss, A.J.; Weatherholt, A.M.; Crandall, T.T.; Farmer, D.L.; McConnell, J.C.; Crossley, K.M.; Warden, S.J.

    2016-01-01

    Purpose: The Achilles tendon (AT) must adapt to meet changes in demands. This study explored AT adaptation by comparing properties within the jump and non-jump legs of jumping athletes. Non-jumping control athletes were included to control limb dominance effects. Methods: AT properties were assessed in the preferred (jump) and non-preferred (lead) jumping legs of male collegiate-level long and/or high jump (jumpers; n=10) and cross-country (controls; n=10) athletes. Cross-sectional area (CSA), elongation, and force during isometric contractions were used to estimate the morphological, mechanical and material properties of the ATs bilaterally. Results: Jumpers exposed their ATs to more force and stress than controls (all p≤0.03). AT force and stress were also greater in the jump leg of both jumpers and controls than in the lead leg (all p<0.05). Jumpers had 17.8% greater AT stiffness and 24.4% greater Young’s modulus in their jump leg compared to lead leg (all p<0.05). There were no jump versus lead leg differences in AT stiffness or Young’s modulus within controls (all p>0.05). Conclusion: ATs chronically exposed to elevated mechanical loading were found to exhibit greater mechanical (stiffness) and material (Young’s modulus) properties. PMID:27282454

  20. Motor Control of Landing from a Jump in Simulated Hypergravity.

    PubMed

    Gambelli, Clément N; Theisen, Daniel; Willems, Patrick A; Schepens, Bénédicte

    2015-01-01

    On Earth, when landing from a counter-movement jump, muscles contract before touchdown to anticipate imminent collision with the ground and place the limbs in a proper position. This study assesses how the control of landing is modified when gravity is increased above 1 g. Hypergravity was simulated in two different ways: (1) by generating centrifugal forces during turns of an aircraft (A300) and (2) by pulling the subject downwards in the laboratory with a Subject Loading System (SLS). Eight subjects were asked to perform counter-movement jumps at 1 g on Earth and at 3 hypergravity levels (1.2, 1.4 and 1.6 g) both in A300 and with SLS. External forces applied to the body, movements of the lower limb segments and muscular activity of 6 lower limb muscles were recorded. Our results show that both in A300 and with SLS, as in 1 g: (1) the anticipation phase is present; (2) during the loading phase (from touchdown until the peak of vertical ground reaction force), lower limb muscles act like a stiff spring, whereas during the second part (from the peak of vertical ground reaction force until the return to the standing position), they act like a compliant spring associated with a damper. (3) With increasing gravity, the preparatory adjustments and the loading phase are modified whereas the second part does not change drastically. (4) The modifications are similar in A300 and with SLS, however the effect of hypergravity is accentuated in A300, probably due to altered sensory inputs. This observation suggests that otolithic information plays an important role in the control of the landing from a jump.

  1. Motor Control of Landing from a Jump in Simulated Hypergravity

    PubMed Central

    Gambelli, Clément N.; Theisen, Daniel; Willems, Patrick A.; Schepens, Bénédicte

    2015-01-01

    On Earth, when landing from a counter-movement jump, muscles contract before touchdown to anticipate imminent collision with the ground and place the limbs in a proper position. This study assesses how the control of landing is modified when gravity is increased above 1 g. Hypergravity was simulated in two different ways: (1) by generating centrifugal forces during turns of an aircraft (A300) and (2) by pulling the subject downwards in the laboratory with a Subject Loading System (SLS). Eight subjects were asked to perform counter-movement jumps at 1 g on Earth and at 3 hypergravity levels (1.2, 1.4 and 1.6 g) both in A300 and with SLS. External forces applied to the body, movements of the lower limb segments and muscular activity of 6 lower limb muscles were recorded. Our results show that both in A300 and with SLS, as in 1 g: (1) the anticipation phase is present; (2) during the loading phase (from touchdown until the peak of vertical ground reaction force), lower limb muscles act like a stiff spring, whereas during the second part (from the peak of vertical ground reaction force until the return to the standing position), they act like a compliant spring associated with a damper. (3) With increasing gravity, the preparatory adjustments and the loading phase are modified whereas the second part does not change drastically. (4) The modifications are similar in A300 and with SLS, however the effect of hypergravity is accentuated in A300, probably due to altered sensory inputs. This observation suggests that otolithic information plays an important role in the control of the landing from a jump. PMID:26505472

  2. Gender Differences and Biomechanics in the 3000M Steeplechase Water Jump

    PubMed Central

    Hunter, Ian; Lindsay, Bryan K.; Andersen, Kassi R.

    2008-01-01

    Since 1996, women have been competing in the 3000m steeplechase race internationally. Whenever women and men both compete in similar events with different equipment (the barriers are lower for women) consideration should be given as to how techniques should be coached differently. This study investigated the differences in water-jump technique between men and women after accounting for differences in running speed and which techniques led to maintenance of race pace through the water-jump. Eighteen men and 18 women were filmed at two major track and field meets during the 2004 season. Peak Motus 8.2 was used to digitize all seven jumps from each athlete. Various characteristics of water-jump technique were measured or calculated and compared using two multiple linear regressions (one for men and one for women) to determine which characteristics led to maintaining race pace speeds through the water jump obstacle. Repeated measures ANOVA was used to determine any differences between men and women in the measured characteristics of technique.Velocity through the jump divided by race pace was predicted very well by approach velocity and landing distance for men and women. Other characteristics of the movement were non-significant. Differences between genders were found in: approach velocity, take-off distance, landing distance, push-off angle, velocity through jump, and exit velocity. Men and women steeplechasers must focus on approach velocity and landing distance to complete the water-jump close to their race pace. Coaches need to consider many characteristics of technique that differ between men and women. Key pointsWomen may need to be coached differently than men in the steeplechase water jump due to different techniques required.Men and women must focus on a high approach velocity to complete the steeplechase water jump successfully.Men and women must generate a relatively long landing distance to maintain velocity and keep from having to use extra energy exiting

  3. Condensation-induced jumping water drops

    NASA Astrophysics Data System (ADS)

    Narhe, R. D.; Khandkar, M. D.; Shelke, P. B.; Limaye, A. V.; Beysens, D. A.

    2009-09-01

    Water droplets can jump during vapor condensation on solid benzene near its melting point. This phenomenon, which can be viewed as a kind of micro scale steam engine, is studied experimentally and numerically. The latent heat of condensation transferred at the drop three phase contact line melts the substrate during a time proportional to R (the drop radius). The wetting conditions change and a spontaneous jump of the drop results in random direction over length ˜1.5R , a phenomenon that increases the coalescence events and accelerates the growth. Once properly rescaled by the jump length scale, the growth dynamics is, however, similar to that on a solid surface.

  4. Condensation-induced jumping water drops.

    PubMed

    Narhe, R D; Khandkar, M D; Shelke, P B; Limaye, A V; Beysens, D A

    2009-09-01

    Water droplets can jump during vapor condensation on solid benzene near its melting point. This phenomenon, which can be viewed as a kind of micro scale steam engine, is studied experimentally and numerically. The latent heat of condensation transferred at the drop three phase contact line melts the substrate during a time proportional to R (the drop radius). The wetting conditions change and a spontaneous jump of the drop results in random direction over length approximately 1.5R , a phenomenon that increases the coalescence events and accelerates the growth. Once properly rescaled by the jump length scale, the growth dynamics is, however, similar to that on a solid surface.

  5. Predicting vertical jump height from bar velocity.

    PubMed

    García-Ramos, Amador; Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Strojnik, Vojko; Feriche, Belén

    2015-06-01

    The objective of the study was to assess the use of maximum (Vmax) and final propulsive phase (FPV) bar velocity to predict jump height in the weighted jump squat. FPV was defined as the velocity reached just before bar acceleration was lower than gravity (-9.81 m·s(-2)). Vertical jump height was calculated from the take-off velocity (Vtake-off) provided by a force platform. Thirty swimmers belonging to the National Slovenian swimming team performed a jump squat incremental loading test, lifting 25%, 50%, 75% and 100% of body weight in a Smith machine. Jump performance was simultaneously monitored using an AMTI portable force platform and a linear velocity transducer attached to the barbell. Simple linear regression was used to estimate jump height from the Vmax and FPV recorded by the linear velocity transducer. Vmax (y = 16.577x - 16.384) was able to explain 93% of jump height variance with a standard error of the estimate of 1.47 cm. FPV (y = 12.828x - 6.504) was able to explain 91% of jump height variance with a standard error of the estimate of 1.66 cm. Despite that both variables resulted to be good predictors, heteroscedasticity in the differences between FPV and Vtake-off was observed (r(2) = 0.307), while the differences between Vmax and Vtake-off were homogenously distributed (r(2) = 0.071). These results suggest that Vmax is a valid tool for estimating vertical jump height in a loaded jump squat test performed in a Smith machine. Key pointsVertical jump height in the loaded jump squat can be estimated with acceptable precision from the maximum bar velocity recorded by a linear velocity transducer.The relationship between the point at which bar acceleration is less than -9.81 m·s(-2) and the real take-off is affected by the velocity of movement.Mean propulsive velocity recorded by a linear velocity transducer does not appear to be optimal to monitor ballistic exercise performance.

  6. Predicting Vertical Jump Height from Bar Velocity

    PubMed Central

    García-Ramos, Amador; Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Strojnik, Vojko; Feriche, Belén

    2015-01-01

    The objective of the study was to assess the use of maximum (Vmax) and final propulsive phase (FPV) bar velocity to predict jump height in the weighted jump squat. FPV was defined as the velocity reached just before bar acceleration was lower than gravity (-9.81 m·s-2). Vertical jump height was calculated from the take-off velocity (Vtake-off) provided by a force platform. Thirty swimmers belonging to the National Slovenian swimming team performed a jump squat incremental loading test, lifting 25%, 50%, 75% and 100% of body weight in a Smith machine. Jump performance was simultaneously monitored using an AMTI portable force platform and a linear velocity transducer attached to the barbell. Simple linear regression was used to estimate jump height from the Vmax and FPV recorded by the linear velocity transducer. Vmax (y = 16.577x - 16.384) was able to explain 93% of jump height variance with a standard error of the estimate of 1.47 cm. FPV (y = 12.828x - 6.504) was able to explain 91% of jump height variance with a standard error of the estimate of 1.66 cm. Despite that both variables resulted to be good predictors, heteroscedasticity in the differences between FPV and Vtake-off was observed (r2 = 0.307), while the differences between Vmax and Vtake-off were homogenously distributed (r2 = 0.071). These results suggest that Vmax is a valid tool for estimating vertical jump height in a loaded jump squat test performed in a Smith machine. Key points Vertical jump height in the loaded jump squat can be estimated with acceptable precision from the maximum bar velocity recorded by a linear velocity transducer. The relationship between the point at which bar acceleration is less than -9.81 m·s-2 and the real take-off is affected by the velocity of movement. Mean propulsive velocity recorded by a linear velocity transducer does not appear to be optimal to monitor ballistic exercise performance. PMID:25983572

  7. Female recreational athletes demonstrate different knee biomechanics from male counterparts during jumping rope and turning activities.

    PubMed

    Tanikawa, Hidenori; Matsumoto, Hideo; Harato, Kengo; Kiriyama, Yoshimori; Suda, Yasunori; Toyama, Yoshiaki; Nagura, Takeo

    2014-01-01

    A variety of athletic exercises are performed in sports training or rehabilitation after knee injuries. However, it remains unclear whether males and females exhibit similar joint loading during the various athletic motions. The purpose of this study was to identify gender differences in knee biomechanics during the athletic motions. Three-dimensional knee kinematics and kinetics were investigated in 20 recreational athletes (10 males and 10 females) while jumping rope, backward running, side running, side-to-side running, side-to-forward running, inside turning, and outside turning. The strengths of the quadriceps and hamstring muscles, the knee joint force, the knee joint angle, and the knee joint moment were compared between males and females using one-tailed t tests. Peak knee anterior force was greater in female recreational athletes than in their male counterparts during jumping rope, side-to-forward running, inside turning, and outside turning. Female subjects displayed greater peak knee abduction angles and greater peak knee flexion moments while jumping rope compared to their male counterparts. There were no significant differences between the sexes in knee kinematics and kinetics in the frontal and transverse planes during running and turning motions. Female recreational athletes exhibited significantly different knee biomechanics compared with male counterparts during jumping rope and turning motions.

  8. Power output in vertical jumps: does optimum loading depend on activity profiles?

    PubMed

    Pazin, Nemanja; Berjan, Bobana; Nedeljkovic, Aleksandar; Markovic, Goran; Jaric, Slobodan

    2013-03-01

    The previously proposed maximum dynamic output hypothesis (MDO: i.e. the optimum load for maximizing the power output during jumping is one's own body) was tested on individuals of various activity profiles. Forty males (10 strength-trained athletes, 10 speed-trained athletes, 10 physically active non-athletes, and 10 sedentary individuals) performed different vertical jumps on a force plate while a pulley system was used to either reduce or increase the subject's body weight by 10-30 %. As expected, an increase in external loading resulted in a significant increase (p < 0.001) in force output and a concomitant decrease of peak jumping velocity in all groups of participants. The main finding, however, was that all groups revealed the maximum peak and mean power output at approximately the subjects' own body weight although their weight represented prominently different percentage of their maximum dynamic strength. While a significant (p < 0.05), albeit moderate, 'group × load' interaction in one jump was observed for the peak power output, the individual optimum load for maximizing the power output number did not differ among the groups. Although apparently further research on various types of movements is needed, the present results provide, so far, the strongest support of the MDO hypothesis.

  9. Altered astronaut lower limb and mass center kinematics in downward jumping following space flight

    NASA Technical Reports Server (NTRS)

    Newman, D. J.; Jackson, D. K.; Bloomberg, J. J.

    1997-01-01

    Astronauts exposed to the microgravity conditions encountered during space flight exhibit postural and gait instabilities upon return to earth that could impair critical postflight performance. The aim of the present study was to determine the effects of microgravity exposure on astronauts' performance of two-footed jump landings. Nine astronauts from several Space Shuttle missions were tested both preflight and postflight with a series of voluntary, two-footed downward hops from a 30-cm-high step. A video-based, three-dimensional motion-analysis system permitted calculation of body segment positions and joint angular displacements. Phase-plane plots of knee, hip, and ankle angular velocities compared with the corresponding joint angles were used to describe the lower limb kinematics during jump landings. The position of the whole-body center of mass (COM) was also estimated in the sagittal plane using an eight-segment body model. Four of nine subjects exhibited expanded phase-plane portraits postflight, with significant increases in peak joint flexion angles and flexion rates following space flight. In contrast, two subjects showed significant contractions of their phase-plane portraits postflight and three subjects showed insignificant overall changes after space flight. Analysis of the vertical COM motion generally supported the joint angle results. Subjects with expanded joint angle phase-plane portraits postflight exhibited larger downward deviations of the COM and longer times from impact to peak deflection, as well as lower upward recovery velocities. Subjects with postflight joint angle phase-plane contraction demonstrated opposite effects in the COM motion. The joint kinematics results indicated the existence of two contrasting response modes due to microgravity exposure. Most subjects exhibited "compliant" impact absorption postflight, consistent with decreased limb stiffness and damping, and a reduction in the bandwidth of the postural control system

  10. Controller design for nonlinear quadratic Markov jumping systems with input saturation

    NASA Astrophysics Data System (ADS)

    Chen, Fu; Xu, Shengyuan; Zou, Yun; Xu, Huiling

    2014-01-01

    This paper deals with the controller design problem of nonlinear quadratic Markov jumping systems with input saturation. Both mode-dependent and mode-independent state feedback controllers are designed. By using the concept of domain of attraction in mean square sense, sufficient conditions for stochastic stabilisation for nonlinear quadratic systems are derived in terms of linear matrix inequalities. Certain existing results are improved. Simulation examples are presented to illustrate the effectiveness of the proposed technique.

  11. Isokinetic knee strength qualities as predictors of jumping performance in high-level volleyball athletes: multiple regression approach.

    PubMed

    Sattler, Tine; Sekulic, Damir; Spasic, Miodrag; Osmankac, Nedzad; Vicente João, Paulo; Dervisevic, Edvin; Hadzic, Vedran

    2016-01-01

    Previous investigations noted potential importance of isokinetic strength in rapid muscular performances, such as jumping. This study aimed to identify the influence of isokinetic-knee-strength on specific jumping performance in volleyball. The secondary aim of the study was to evaluate reliability and validity of the two volleyball-specific jumping tests. The sample comprised 67 female (21.96±3.79 years; 68.26±8.52 kg; 174.43±6.85 cm) and 99 male (23.62±5.27 years; 84.83±10.37 kg; 189.01±7.21 cm) high- volleyball players who competed in 1st and 2nd National Division. Subjects were randomly divided into validation (N.=55 and 33 for males and females, respectively) and cross-validation subsamples (N.=54 and 34 for males and females, respectively). Set of predictors included isokinetic tests, to evaluate the eccentric and concentric strength capacities of the knee extensors, and flexors for dominant and non-dominant leg. The main outcome measure for the isokinetic testing was peak torque (PT) which was later normalized for body mass and expressed as PT/Kg. Block-jump and spike-jump performances were measured over three trials, and observed as criteria. Forward stepwise multiple regressions were calculated for validation subsamples and then cross-validated. Cross validation included correlations between and t-test differences between observed and predicted scores; and Bland Altman graphics. Jumping tests were found to be reliable (spike jump: ICC of 0.79 and 0.86; block-jump: ICC of 0.86 and 0.90; for males and females, respectively), and their validity was confirmed by significant t-test differences between 1st vs. 2nd division players. Isokinetic variables were found to be significant predictors of jumping performance in females, but not among males. In females, the isokinetic-knee measures were shown to be stronger and more valid predictors of the block-jump (42% and 64% of the explained variance for validation and cross-validation subsample, respectively

  12. Peak power ratio generator

    DOEpatents

    Moyer, Robert D.

    1985-01-01

    A peak power ratio generator is described for measuring, in combination with a conventional power meter, the peak power level of extremely narrow pulses in the gigahertz radio frequency bands. The present invention in a preferred embodiment utilizes a tunnel diode and a back diode combination in a detector circuit as the only high speed elements. The high speed tunnel diode provides a bistable signal and serves as a memory device of the input pulses for the remaining, slower components. A hybrid digital and analog loop maintains the peak power level of a reference channel at a known amount. Thus, by measuring the average power levels of the reference signal and the source signal, the peak power level of the source signal can be determined.

  13. Significance of periodogram peaks

    NASA Astrophysics Data System (ADS)

    Süveges, Maria; Guy, Leanne; Zucker, Shay

    2016-10-01

    Three versions of significance measures or False Alarm Probabilities (FAPs) for periodogram peaks are presented and compared for sinusoidal and box-like signals, with specific application on large-scale surveys in mind.

  14. Peak power ratio generator

    DOEpatents

    Moyer, R.D.

    A peak power ratio generator is described for measuring, in combination with a conventional power meter, the peak power level of extremely narrow pulses in the gigahertz radio frequency bands. The present invention in a preferred embodiment utilizes a tunnel diode and a back diode combination in a detector circuit as the only high speed elements. The high speed tunnel diode provides a bistable signal and serves as a memory device of the input pulses for the remaining, slower components. A hybrid digital and analog loop maintains the peak power level of a reference channel at a known amount. Thus, by measuring the average power levels of the reference signal and the source signal, the peak power level of the source signal can be determined.

  15. Pikes Peak, Colorado

    USGS Publications Warehouse

    Brunstein, Craig; Quesenberry, Carol; Davis, John; Jackson, Gene; Scott, Glenn R.; D'Erchia, Terry D.; Swibas, Ed; Carter, Lorna; McKinney, Kevin; Cole, Jim

    2006-01-01

    For 200 years, Pikes Peak has been a symbol of America's Western Frontier--a beacon that drew prospectors during the great 1859-60 Gold Rush to the 'Pikes Peak country,' the scenic destination for hundreds of thousands of visitors each year, and an enduring source of pride for cities in the region, the State of Colorado, and the Nation. November 2006 marks the 200th anniversary of the Zebulon M. Pike expedition's first sighting of what has become one of the world's most famous mountains--Pikes Peak. In the decades following that sighting, Pikes Peak became symbolic of America's Western Frontier, embodying the spirit of Native Americans, early explorers, trappers, and traders who traversed the vast uncharted wilderness of the Western Great Plains and the Southern Rocky Mountains. High-quality printed paper copies of this poster are available at no cost from Information Services, U.S. Geological Survey (1-888-ASK-USGS).

  16. Central Peak Crater

    NASA Image and Video Library

    2010-10-07

    As crater size increases, craters become more complex. This moderate size crater contains a central peak, created by rebound of molten material just following the impact. This image was captured by NASA Mars Odyssey on Sept. 8, 2010.

  17. Frontal plane comparison between drop jump and vertical jump: implications for the assessment of ACL risk of injury.

    PubMed

    Cesar, Guilherme M; Tomasevicz, Curtis L; Burnfield, Judith M

    2016-11-01

    The potential to use the vertical jump (VJ) to assess both athletic performance and risk of anterior cruciate ligament (ACL) injury could have widespread clinical implications since VJ is broadly used in high school, university, and professional sport settings. Although drop jump (DJ) and VJ observationally exhibit similar lower extremity mechanics, the extent to which VJ can also be used as screening tool for ACL injury risk has not been assessed. This study evaluated whether individuals exhibit similar knee joint frontal plane kinematic and kinetic patterns when performing VJs compared with DJs. Twenty-eight female collegiate athletes performed DJs and VJs. Paired t-tests indicated that peak knee valgus angles did not differ significantly between tasks (p = 0.419); however, peak knee internal adductor moments were significantly larger during the DJ vs. VJ (p < 0.001). Pearson correlations between the DJ and VJ revealed strong correlations for knee valgus angles (r = 0.93, p < 0.001) and for internal knee adductor moments (r = 0.82, p < 0.001). Our results provide grounds for investigating whether frontal plane knee mechanics during VJ can predict ACL injuries and thus can be used as an effective tool for the assessment of risk of ACL injury in female athletes.

  18. Peak Oil, Peak Coal and Climate Change

    NASA Astrophysics Data System (ADS)

    Murray, J. W.

    2009-05-01

    Research on future climate change is driven by the family of scenarios developed for the IPCC assessment reports. These scenarios create projections of future energy demand using different story lines consisting of government policies, population projections, and economic models. None of these scenarios consider resources to be limiting. In many of these scenarios oil production is still increasing to 2100. Resource limitation (in a geological sense) is a real possibility that needs more serious consideration. The concept of 'Peak Oil' has been discussed since M. King Hubbert proposed in 1956 that US oil production would peak in 1970. His prediction was accurate. This concept is about production rate not reserves. For many oil producing countries (and all OPEC countries) reserves are closely guarded state secrets and appear to be overstated. Claims that the reserves are 'proven' cannot be independently verified. Hubbert's Linearization Model can be used to predict when half the ultimate oil will be produced and what the ultimate total cumulative production (Qt) will be. US oil production can be used as an example. This conceptual model shows that 90% of the ultimate US oil production (Qt = 225 billion barrels) will have occurred by 2011. This approach can then be used to suggest that total global production will be about 2200 billion barrels and that the half way point will be reached by about 2010. This amount is about 5 to 7 times less than assumed by the IPCC scenarios. The decline of Non-OPEC oil production appears to have started in 2004. Of the OPEC countries, only Saudi Arabia may have spare capacity, but even that is uncertain, because of lack of data transparency. The concept of 'Peak Coal' is more controversial, but even the US National Academy Report in 2007 concluded only a small fraction of previously estimated reserves in the US are actually minable reserves and that US reserves should be reassessed using modern methods. British coal production can be

  19. The Crown Bite Jumping Herbst.

    PubMed

    Owen, Reuel

    2003-01-01

    The Crown Bite Jumping Herbst Appliance is evaluated and combined with Straight Wire Arch Fixed Orthodontics in treatment of Class II, Division I malocclusions. This article will evaluate a combined orthodontic approach of "straightening teeth" and an orthognathic approach of "moving jaws or making skeletal changes." Orthodontic treatment cannot be accomplished well without establishing a healthy temporomandibular joint. This is defined by Keller as a joint that is "noiseless, painless and has a normal range of motion without deviation and deflection." It is not prudent to separate orthodontic treatment as its own entity without being aware of the changes in the temporomandibular joint before, during and after treatment. In other words, "If you're doing orthodontics you're doing TMJ treatment." One should treat toward a healthy, beautiful face asking, "Will proposed treatment achieve this goal?" Treatment should be able to be carried out in an efficient manner, minimizing treatment time, be comfortable and affordable for the patient, and profitable for the dentist. The finished treatment should meet Andrews' Six Keys of Occlusion, or Loudon's Twelve Commandments. Above all, do no harm to the patient. We think that a specific treatment plan can embrace these tenets. The focus will be to show Class II treatment using a modified Herbst Appliance and fixed straight wire orthodontics.

  20. Mechanical jumping power in athletes.

    PubMed

    Kirkendall, D T; Street, G M

    1986-12-01

    The Wingate cycle ergometer test is a widely used test of sustained muscular power. A limitation of the test is the lack of development and retrieval of stored elastic energy due to a lack of an eccentric phase. To measure mechanical power output of the entire stretch-shortening cycle, the test of Bosco et al (1983) was administered to 119 male athletes in 7 different activities during their pre-participation evaluations. The sports tested were indoor soccer, American football and ballet (professionals), outdoor soccer, basketball and wrestling (collegiate) and amateur bobsled. Results showed the overall average power output to be 20.37 W.kg-1 for the 60s reciprocal jumping test. Ballet dancers generated significantly less mechanical power than indoor soccer, basketball and bobsled athletes, while wrestlers generated significantly less power than indoor soccer and basketball athletes (all p less than 0.05). No other between-sport differences were seen. A subset of indoor soccer players (n = 10) were retested after 4 months of training. Power improved from 20.8 to 24.3 W.kg-1 (p less than 0.05). While between sport differences were limited, training differences in one subset of athletes were readily identified.

  1. Jumping to conclusions in schizophrenia

    PubMed Central

    Evans, Simon L; Averbeck, Bruno B; Furl, Nicholas

    2015-01-01

    Schizophrenia is a mental disorder associated with a variety of symptoms, including hallucinations, delusions, social withdrawal, and cognitive dysfunction. Impairments on decision-making tasks are routinely reported: evidence points to a particular deficit in learning from and revising behavior following feedback. In addition, patients tend to make hasty decisions when probabilistic judgments are required. This is known as “jumping to conclusions” (JTC) and has typically been demonstrated by presenting participants with colored beads drawn from one of two “urns” until they claim to be sure which urn the beads are being drawn from (the proportions of colors vary in each urn). Patients tend to make early decisions on this task, and there is evidence to suggest that a hasty decision-making style might be linked to delusion formation and thus be of clinical relevance. Various accounts have been proposed regarding what underlies this behavior. In this review, we briefly introduce the disorder and the decision-making deficits associated with it. We then explore the evidence for each account of JTC in the context of a wider decision-making deficit and then go on to summarize work exploring JTC in healthy controls using pharmacological manipulations and functional imaging. Finally, we assess whether JTC might have a role in therapy. PMID:26170674

  2. PERFORMANCE OF THE AGS TRANSITION JUMP SYSTEM.

    SciTech Connect

    AHRENS,L.A.; BRENNAN,J.M.; GLENN,J.W.; ROSER,T.; VAN ASSELT,W.K.

    1999-03-29

    The transition jump system has been indispensable to the high intensity proton operation of the AGS complex. Nevertheless, transition crossing remains one of the major hurdles as the accelerator complex intensity is pushed upward. To enhance the performance of the system ''quadrupole pumping'' in the Booster is used to minimize the necessary longitudinal dilution of the beam on the AGS injection porch. During the transition jump sextupole correctors at strategic locations are pulsed to minimize the effects of the chromatic non-linearity of the jump system. The available instrumentation for diagnosing the performance of the system will be described, along with installed hardware to counter the non-linear effects of the transition jump system.

  3. Knee biomechanics during a jump-cut maneuver: Effects of gender & ACL surgery

    PubMed Central

    Miranda, Daniel L.; Fadale, Paul D.; Hulstyn, Michael J.; Shalvoy, Robert M.; Machan, Jason T.; Fleming, Braden C.

    2012-01-01

    Purpose The purpose of this study was to compare kinetic and knee kinematic measurements from male and female ACL-intact (ACLINT) and ACL-reconstructed (ACLREC) subjects during a jump-cut maneuver using biplanar videoradiography. Methods Twenty subjects were recruited; 10 ACLINT (5 males, 5 females) and 10 ACLREC (4 males, 6 females; five years post surgery). Each subject performed a jump-cut maneuver by landing on a single leg and performing a 45° side-step cut. Ground reaction force was measured by a force plate and expressed relative to body weight. Six-degree-of-freedom knee kinematics were determined from a biplanar videoradiography system and an optical motion capture system. Results ACLINT female subjects landed with a larger peak vertical GRF (p<0.001) compared to ACLINT male subjects. ACLINT subjects landed with a larger peak vertical GRF (p≤0.036) compared to ACLREC subjects. Regardless of ACL reconstruction status, female subjects underwent less knee flexion angle excursion (p=0.002) and had an increased average rate of anterior tibial translation (0.05±0.01%/millisecond; p=0.037) after contact compared to male subjects. Furthermore, ACLREC subjects had a lower rate of anterior tibial translation compared to ACLINT subjects (0.05±0.01%/millisecond; p=0.035). Finally, no striking differences were observed in other knee motion parameters. Conclusion Women permit a smaller amount of knee flexion angle excursion during a jump-cut maneuver, resulting in a larger peak vertical GRF and increased rate of anterior tibial translation. Notably, ACLREC subjects also perform the jump cut maneuver with lower GRF than ACLINT subjects five years post surgery. This study proposes a causal sequence whereby increased landing stiffness (larger peak vertical GRF combined with less knee flexion angle excursion) leads to an increased rate of anterior tibial translation while performing a jump-cut maneuver. PMID:23190595

  4. An Investigation Into the Relationship Between Maximum Isometric Strength and Vertical Jump Performance.

    PubMed

    Thomas, Christopher; Jones, Paul A; Rothwell, James; Chiang, Chieh Y; Comfort, Paul

    2015-08-01

    Research has demonstrated a clear relationship between dynamic strength and vertical jump (VJ) performance; however, the relationship of isometric strength and VJ performance has been studied less extensively. The aim of this study was to determine the relationship between isometric strength and performance during the squat jump (SJ) and countermovement jump (CMJ). Twenty-two male collegiate athletes (mean ± SD; age = 21.3 ± 2.9 years; height = 175.63 ± 8.23 cm; body mass = 78.06 ± 10.77 kg) performed isometric midthigh pulls (IMTPs) to assess isometric peak force (IPF), maximum rate of force development, and impulse (IMP) (I100, I200, and I300). Force-time data, collected during the VJs, were used to calculate peak velocity, peak force (PF), peak power (PP), and jump height. Absolute IMTP measures of IMP showed the strongest correlations with VJ PF (r = 0.43-0.64; p ≤ 0.05) and VJ PP (r = 0.38-0.60; p ≤ 0.05). No statistical difference was observed in CMJ height (0.33 ± 0.05 m vs. 0.36 ± 0.05 m; p = 0.19; ES = -0.29) and SJ height performance (0.29 ± 0.06 m vs. 0.33 ± 0.05 m; p = 0.14; ES = -0.34) when comparing stronger to weaker athletes. The results of this study illustrate that absolute IPF and IMP are related to VJ PF and PP but not VJ height. Because stronger athletes did not jump higher than weaker athletes, dynamic strength tests may be more practical methods of assessing the relationships between relative strength levels and dynamic performance in collegiate athletes.

  5. Jump Horse Safety: Reconciling Public Debate and Australian Thoroughbred Jump Racing Data, 2012-2014.

    PubMed

    Ruse, Karen; Davison, Aidan; Bridle, Kerry

    2015-10-22

    Thoroughbred jump racing sits in the spotlight of contemporary welfare and ethical debates about horse racing. In Australia, jump racing comprises hurdle and steeplechase races and has ceased in all but two states, Victoria and South Australia. This paper documents the size, geography, composition, and dynamics of Australian jump racing for the 2012, 2013, and 2014 seasons with a focus on debate about risks to horses. We found that the majority of Australian jump racing is regional, based in Victoria, and involves a small group of experienced trainers and jockeys. Australian jump horses are on average 6.4 years of age. The jump career of the majority of horses involves participating in three or less hurdle races and over one season. Almost one quarter of Australian jump horses race only once. There were ten horse fatalities in races over the study period, with an overall fatality rate of 5.1 fatalities per 1000 horses starting in a jump race (0.51%). There was significant disparity between the fatality rate for hurdles, 0.75 fatalities per 1000 starts (0.075%) and steeplechases, 14 fatalities per 1000 starts (1.4%). Safety initiatives introduced by regulators in 2010 appear to have significantly decreased risks to horses in hurdles but have had little or no effect in steeplechases. Our discussion considers these Animals 2015, 5 1073 data in light of public controversy, political debate, and industry regulation related to jump horse safety.

  6. Jumping mechanisms in dictyopharid planthoppers (Hemiptera, Dicytyopharidae).

    PubMed

    Burrows, Malcolm

    2014-02-01

    The jumping performance of four species of hemipterans belonging to the family Dictyopharidae, from Europe, South Africa and Australia, were analysed from high-speed images. The body shape in all was characterised by an elongated and tapering head that gave a streamlined appearance. The body size ranged from 6 to 9 mm in length and from 6 to 23 mg in mass. The hind legs were 80-90% of body length and 30-50% longer than the front legs, except in one species in which the front legs were particularly large so that all legs were of similar length. Jumping was propelled by rapid and simultaneous depression of the trochantera of both hind legs, powered by large muscles in the thorax, and was accompanied by extension of the tibiae. In the best jumps, defined as those with the fastest take-off velocity, Engela minuta accelerated in 1.2 ms to a take-off velocity of 5.8 m s(-1), which is the fastest achieved by any insect described to date. During such a jump, E. minuta experienced an acceleration of 4830 m s(-2) or 490 g, while other species in the same family experienced 225-375 g. The best jumps in all species required an energy expenditure of 76-225 μJ, a power output of 12-80 mW and exerted a force of 12-29 mN. The required power output per mass of jumping muscle ranged from 28,000 to 140,200 W kg(-1) muscle and thus greatly exceeded the maximum active contractile limit of normal muscle. To achieve such a jumping performance, these insects must be using a power amplification mechanism in a catapult-like action. It is suggested that their streamlined body shape improves jumping performance by reducing drag, which, for a small insect, can substantially affect forward momentum.

  7. Pulmonary hemorrhage resulting from bungee jumping.

    PubMed

    Manos, Daria; Hamer, Okka; Müller, Nestor L

    2007-11-01

    Pulmonary hemorrhage is a relatively common complication of blunt chest trauma. Occasionally, it may result from pulmonary barotrauma after scuba diving or from sports activities not associated with barotrauma such as long breath-hold diving. We report a case of symmetric diffuse upper lobe hemorrhage resulting from a bungee jump in a previously healthy man. Bungee jumping is an increasingly popular sport with relatively few reported injuries. To our knowledge pulmonary hemorrhage in this setting has not yet been described.

  8. Dissipativity-Based Reliable Control for Fuzzy Markov Jump Systems With Actuator Faults.

    PubMed

    Tao, Jie; Lu, Renquan; Shi, Peng; Su, Hongye; Wu, Zheng-Guang

    2017-09-01

    This paper is concerned with the problem of reliable dissipative control for Takagi-Sugeno fuzzy systems with Markov jumping parameters. Considering the influence of actuator faults, a sufficient condition is developed to ensure that the resultant closed-loop system is stochastically stable and strictly ( Q, S,R )-dissipative based on a relaxed approach in which mode-dependent and fuzzy-basis-dependent Lyapunov functions are employed. Then a reliable dissipative control for fuzzy Markov jump systems is designed, with sufficient condition proposed for the existence of guaranteed stability and dissipativity controller. The effectiveness and potential of the obtained design method is verified by two simulation examples.

  9. Dynamical approach to displacement jumps in nanoindentation experiments

    NASA Astrophysics Data System (ADS)

    K, Srikanth; Ananthakrishna, G.

    2017-01-01

    The load-controlled mode is routinely used in nanoindentation experiments. Yet there are no simulations or models that predict the generic features of force-displacement F -z curves, in particular, the existence of several displacement jumps of decreasing magnitude. Here, we show that the recently developed dislocation dynamical model predicts all the generic features when the model is appropriately coupled to an equation defining the load rate. Since jumps in the indentation depth result from the plastic deformation occurring inside the sample, we devise a method for calculating this contribution by setting up a system of coupled nonlinear time evolution equations for the mobile and forest dislocation densities. The equations are then coupled to the force rate equation. We include nucleation, multiplication, and propagation threshold mechanisms for the mobile dislocations apart from other well known dislocation transformation mechanisms between the mobile and forest dislocations. The commonly used Berkovitch indenter is considered. The ability of the approach is illustrated by adopting experimental parameters such as the indentation rate, the geometrical quantities defining the Berkovitch indenter including the nominal tip radius, and other parameters. We identify specific dislocation mechanisms contributing to different regions of the F -z curve as a first step for obtaining a good fit to a given experimental F -z curve. This is done by studying the influence of the parameters on the model F -z curves. In addition, the study demonstrates that the model predicts all the generic features of nanoindentation such as the existence of an initial elastic branch followed by several displacement jumps of decreasing magnitude, and residual plasticity after unloading for a range of model parameter values. Further, an optimized set of parameter values can be easily determined that gives a good fit to the experimental force-displacement curve for Al single crystals of (110

  10. Decentralised ? - filtering of networked control systems: a jump system approach

    NASA Astrophysics Data System (ADS)

    Al-Radhawi, Muhammad Ali; Bettayeb, Maamar

    2014-10-01

    We consider the problem of decentralised estimation of discrete-time interconnected systems with local estimators communicating with their subsystems over lossy communication channels. Assuming that the packet losses follow the Gilbert-Elliot model, the networked estimation problem can be formulated into a Markovian jump linear system framework. Modelling subsystem interactions as sum quadratic constrained uncertainties, we design mode-dependent decentralised ?-estimators that robustly stabilise the estimator system and guarantee a given disturbance attenuation level. The estimation gains are derived with necessary and sufficient rank-constrained linear matrix inequality conditions. Results are also provided for local mode-dependent estimators. Estimator synthesis is done using a cone-complementarity linearisation algorithm for the rank-constraints. The results are illustrated via an example.

  11. Velocity-jump models with crowding effects

    NASA Astrophysics Data System (ADS)

    Treloar, Katrina K.; Simpson, Matthew J.; McCue, Scott W.

    2011-12-01

    Velocity-jump processes are discrete random-walk models that have many applications including the study of biological and ecological collective motion. In particular, velocity-jump models are often used to represent a type of persistent motion, known as a run and tumble, that is exhibited by some isolated bacteria cells. All previous velocity-jump processes are noninteracting, which means that crowding effects and agent-to-agent interactions are neglected. By neglecting these agent-to-agent interactions, traditional velocity-jump models are only applicable to very dilute systems. Our work is motivated by the fact that many applications in cell biology, such as wound healing, cancer invasion, and development, often involve tissues that are densely packed with cells where cell-to-cell contact and crowding effects can be important. To describe these kinds of high-cell-density problems using a velocity-jump process we introduce three different classes of crowding interactions into a one-dimensional model. Simulation data and averaging arguments lead to a suite of continuum descriptions of the interacting velocity-jump processes. We show that the resulting systems of hyperbolic partial differential equations predict the mean behavior of the stochastic simulations very well.

  12. Velocity-jump models with crowding effects.

    PubMed

    Treloar, Katrina K; Simpson, Matthew J; McCue, Scott W

    2011-12-01

    Velocity-jump processes are discrete random-walk models that have many applications including the study of biological and ecological collective motion. In particular, velocity-jump models are often used to represent a type of persistent motion, known as a run and tumble, that is exhibited by some isolated bacteria cells. All previous velocity-jump processes are noninteracting, which means that crowding effects and agent-to-agent interactions are neglected. By neglecting these agent-to-agent interactions, traditional velocity-jump models are only applicable to very dilute systems. Our work is motivated by the fact that many applications in cell biology, such as wound healing, cancer invasion, and development, often involve tissues that are densely packed with cells where cell-to-cell contact and crowding effects can be important. To describe these kinds of high-cell-density problems using a velocity-jump process we introduce three different classes of crowding interactions into a one-dimensional model. Simulation data and averaging arguments lead to a suite of continuum descriptions of the interacting velocity-jump processes. We show that the resulting systems of hyperbolic partial differential equations predict the mean behavior of the stochastic simulations very well.

  13. Stochastic approach to modelling of near-periodic jumping loads

    NASA Astrophysics Data System (ADS)

    Racic, V.; Pavic, A.

    2010-11-01

    A mathematical model has been developed to generate stochastic synthetic vertical force signals induced by a single person jumping. The model is based on a unique database of experimentally measured individual jumping loads which has the most extensive range of possible jumping frequencies. The ability to replicate many of the temporal and spectral features of real jumping loads gives this model a definite advantage over the conventional half-sine models coupled with Fourier series analysis. This includes modelling of the omnipresent lack of symmetry of individual jumping pulses and jump-by-jump variations in amplitudes and timing. The model therefore belongs to a new generation of synthetic narrow band jumping loads which simulate reality better. The proposed mathematical concept for characterisation of near-periodic jumping pulses may be utilised in vibration serviceability assessment of civil engineering assembly structures, such as grandstands, spectator galleries, footbridges and concert or gym floors, to estimate more realistically dynamic structural response due to people jumping.

  14. Standing jumps in shallow granular flows down smooth inclines

    NASA Astrophysics Data System (ADS)

    Faug, Thierry; Childs, Philippa; Wyburn, Edward; Einav, Itai

    2015-07-01

    The shapes of standing jumps formed in shallow granular flows down an inclined smooth-based chute are analysed in detail, by varying both the slope and mass discharge. Laboratory tests and analytic jump solutions highlight two important transitions. First, for dense flows at high mass discharge, we observe a transition between steep jumps and more diffuse jumps. The traditional shallow-water equation offers a valid prediction for the thickness of the steep water-like jumps. Diffuse frictional jumps require a more general equation accounting for the forces acting inside the jump volume. Second, moving from dense to dilute flows produces another transition between incompressible and compressible jumps. The observed jump height decrease may be reproduced for a more dilute incoming flow by including experimentally measured density variation in the jump equation. Finally, we briefly discuss the likely relevance to avalanche protection dam design that currently utilises traditional shock equations for incompressible frictionless fluids.

  15. Humans adjust control to initial squat depth in vertical squat jumping.

    PubMed

    Bobbert, Maarten F; Casius, L J Richard; Sijpkens, Igor W T; Jaspers, Richard T

    2008-11-01

    The purpose of this study was to gain insight into the control strategy that humans use in jumping. Eight male gymnasts performed vertical squat jumps from five initial postures that differed in squat depth (P1-P5) while kinematic data, ground reaction forces, and electromyograms (EMGs) of leg muscles were collected; the latter were rectified and smoothed to obtain SREMGs. P3 was the preferred initial posture; in P1, P2, P4, and P5 height of the mass center was +13, +7, -7 and -14 cm, respectively, relative to that in P3. Furthermore, maximum-height jumps from the initial postures observed in the subjects were simulated with a model comprising four body segments and six Hill-type muscles. The only input was the onset of stimulation of each of the muscles (Stim). The subjects were able to perform well-coordinated squat jumps from all postures. Peak SREMG levels did not vary among P1-P5, but SREMG onset of plantarflexors occurred before that of gluteus maximus in P1 and > 90 ms after that in P5 (P < 0.05). In the simulation study, similar systematic shifts occurred in Stim onsets across the optimal control solutions for jumps from P1-P5. Because the adjustments in SREMG onsets to initial posture observed in the subjects were very similar to the adjustments in optimal Stim onsets of the model, it was concluded that the SREMG adjustments were functional, in the sense that they contributed to achieving the greatest jump height possible from each initial posture. For the model, we were able to develop a mapping from initial posture to Stim onsets that generated successful jumps from P1-P5. It appears that to explain how subjects adjust their control to initial posture there is no need to assume that the brain contains an internal dynamics model of the musculoskeletal system.

  16. The Effects of Arms and Countermovement on Vertical Jumping

    DTIC Science & Technology

    1989-04-28

    Vertical jumping is an integral part of the high jump track-and-field event and sports such as volleyball , diving and basketball. Some form of...countermovement. Often, in basketball, volleyball , or other team sport in which jumping plays a major part, it is well worth sacrificing 2 cm in jump height in...is)(is not) attached. Title The Effects of Arms and Countermovement on Vertical Jumping Author(s) Everett A. Harman, Michael T. Rosenstein, Peter N

  17. Performance analysis of jump-gliding locomotion for miniature robotics.

    PubMed

    Vidyasagar, A; Zufferey, Jean-Christohphe; Floreano, Dario; Kovač, M

    2015-03-26

    Recent work suggests that jumping locomotion in combination with a gliding phase can be used as an effective mobility principle in robotics. Compared to pure jumping without a gliding phase, the potential benefits of hybrid jump-gliding locomotion includes the ability to extend the distance travelled and reduce the potentially damaging impact forces upon landing. This publication evaluates the performance of jump-gliding locomotion and provides models for the analysis of the relevant dynamics of flight. It also defines a jump-gliding envelope that encompasses the range that can be achieved with jump-gliding robots and that can be used to evaluate the performance and improvement potential of jump-gliding robots. We present first a planar dynamic model and then a simplified closed form model, which allow for quantification of the distance travelled and the impact energy on landing. In order to validate the prediction of these models, we validate the model with experiments using a novel jump-gliding robot, named the 'EPFL jump-glider'. It has a mass of 16.5 g and is able to perform jumps from elevated positions, perform steered gliding flight, land safely and traverse on the ground by repetitive jumping. The experiments indicate that the developed jump-gliding model fits very well with the measured flight data using the EPFL jump-glider, confirming the benefits of jump-gliding locomotion to mobile robotics. The jump-glide envelope considerations indicate that the EPFL jump-glider, when traversing from a 2 m height, reaches 74.3% of optimal jump-gliding distance compared to pure jumping without a gliding phase which only reaches 33.4% of the optimal jump-gliding distance. Methods of further improving flight performance based on the models and inspiration from biological systems are presented providing mechanical design pathways to future jump-gliding robot designs.

  18. The effects of passive leg press training on jumping performance, speed, and muscle power.

    PubMed

    Liu, Chiang; Chen, Chuan-Shou; Ho, Wei-Hua; Füle, Róbert János; Chung, Pao-Hung; Shiang, Tzyy-Yuang

    2013-06-01

    Passive leg press (PLP) training was developed based on the concepts of the stretch-shortening cycle (SSC) and the benefits of high muscle contraction velocity. Passive leg press training enables lower limb muscle groups to apply a maximum downward force against a platform moved up and down at high frequency by an electric motor. Thus, these muscle groups accomplished both concentric and eccentric isokinetic contractions in a passive, rapid, and repetitive manner. This study investigates the effects of 10 weeks of PLP training at high and low movement frequencies have on jumping performance, speed, and muscle power. The authors selected 30 college students who had not performed systematic resistance training in the previous 6 months, including traditional resistance training at a squat frequency of 0.5 Hz, PLP training at a low frequency of 0.5 Hz, and PLP training at a high frequency of 2.5 Hz, and randomly divided them into 3 groups (n = 10). The participants' vertical jump, drop jump, 30-m sprint performance, explosive force, and SSC efficiency were tested under the same experimental procedures at pre- and post-training. Results reveal that high-frequency PLP training significantly increased participants' vertical jump, drop jump, 30-m sprint performance, instantaneous force, peak power, and SSC efficiency (p < 0.05). Additionally, their change rate abilities were substantially superior to those of the traditional resistance training (p < 0.05). The low-frequency PLP training significantly increased participants' vertical jump, 30-m sprint performance, instantaneous force, and peak power (p < 0.05). However, traditional resistance training only increased participants' 30-m sprint performance and peak power (p < 0.05). The findings suggest that jump performance, speed, and muscle power significantly improved after 10 weeks of PLP training at high movement frequency. A PLP training machine powered by an electrical motor enables muscles of the lower extremities to

  19. Ten minutes of dynamic stretching is sufficient to potentiate vertical jump performance characteristics.

    PubMed

    Turki, Olfa; Chaouachi, Anis; Drinkwater, Eric J; Chtara, Moktar; Chamari, Karim; Amri, Mohamed; Behm, David G

    2011-09-01

    The current literature recommends dynamic rather than static stretching for the athletic warm-up. Dynamic stretching and various conditioning stimuli are used to induce potentiation in subsequent athletic performance. However, it is unknown as to which type of activity in conjunction with dynamic stretching within a warm-up provides the optimal potentiation of vertical jump performance. It was the objective of the study to examine the possible potentiating effect of various types of conditioning stimuli with dynamic stretching. Twenty athletes participated in 6 protocols. All the experimental protocols included 10 minutes of dynamic stretching. After the dynamic stretching, the subjects performed a (a) concentric (DS/CON): 3 sets of 3 repetition maximum deadlift exercise; (b) isometric (DS/ISOM): 3 sets of 3-second maximum voluntary contraction back squats; (c) plyometric (DS/PLYO): 3 sets of 3 tuck jumps; (d) eccentric (DS/ECC): 3 modified drop jumps; (e) dynamic stretching only (DS), and (f) control protocol (CON). Before the intervention and at recovery periods of 15 seconds, 4, 8, 12, 16, and 20 minutes, the participants performed 1-2 maximal countermovement jumps. The DS and DS/CON protocols generally had a 95-99% likelihood of exceeding the smallest worthwhile change for vertical jump height, peak power, velocity and force. However, the addition of the deadlift to the DS did not augment the potentiating effect. Time-to-peak potentiation was variable between individuals but was most consistent between 3 and 5 minutes. Thus, the volume and the intensity associated with 10 minutes of dynamic stretching were sufficient to provide the potentiation of vertical jump characteristics. Additional conditioning activities may promote fatigue processes, which do not permit further potentiation.

  20. Effect of acute fatigue and training adaptation on countermovement jump performance in elite snowboard cross athletes.

    PubMed

    Gathercole, Rob J; Stellingwerff, Trent; Sporer, Ben C

    2015-01-01

    Countermovement jump performance was examined in response to acute neuromuscular (NM) fatigue (study I) and chronic training (study II) in elite snowboard cross (SBX) athletes, through both typical (countermovement jump [CMJ]-TYP) and alternative (CMJ-ALT) CMJ variables. Seven (4 men and 3 women) elite (Olympic-level) SBX athletes participated in study I, and 5 of the same athletes (2 men and 3 women) participated in study II. Countermovement jump variables relating to force, velocity, power, and time were measured during both eccentric and concentric jump phases, with CMJ-TYP variables reflecting CMJ output and CMJ-ALT variables reflecting CMJ mechanics. In study I, CMJ performance was assessed before and after a fatiguing lower-body exercise protocol, and in study II, CMJ performance was examined before and after a 19-week structured training block. Meaningful differences in CMJ performance were examined using the magnitude of change (effect sizes [ES]) for group and individual changes. Acute fatigue decreased peak force and eccentric function, while the duration of the jump increased. The structured training block increased peak force and eccentric function, while jump duration markedly decreased. In both study I and study II, the largest ES were associated with CMJ-ALT variables. The CMJ test seems a suitable monitoring tool in elite SBX athletes for the detection of both acute fatigue and training-adaptation. Compared with CMJ output, CMJ mechanics exhibits more marked and divergent changes after both acute NM fatigue and a structured training block. CMJ-ALT variables should therefore be incorporated into CMJ analysis.

  1. Jump Horse Safety: Reconciling Public Debate and Australian Thoroughbred Jump Racing Data, 2012–2014

    PubMed Central

    Ruse, Karen; Davison, Aidan; Bridle, Kerry

    2015-01-01

    Simple Summary This paper documents the dynamics of Australian thoroughbred jump racing in the 2012, 2013, and 2014 seasons with the aim of informing debate about risks to horses and the future of this activity. We conclude that the safety of Australian jump racing has improved in recent years but that steeplechases are considerably riskier for horses than hurdle races. Abstract Thoroughbred jump racing sits in the spotlight of contemporary welfare and ethical debates about horse racing. In Australia, jump racing comprises hurdle and steeplechase races and has ceased in all but two states, Victoria and South Australia. This paper documents the size, geography, composition, and dynamics of Australian jump racing for the 2012, 2013, and 2014 seasons with a focus on debate about risks to horses. We found that the majority of Australian jump racing is regional, based in Victoria, and involves a small group of experienced trainers and jockeys. Australian jump horses are on average 6.4 years of age. The jump career of the majority of horses involves participating in three or less hurdle races and over one season. Almost one quarter of Australian jump horses race only once. There were ten horse fatalities in races over the study period, with an overall fatality rate of 5.1 fatalities per 1000 horses starting in a jump race (0.51%). There was significant disparity between the fatality rate for hurdles, 0.75 fatalities per 1000 starts (0.075%) and steeplechases, 14 fatalities per 1000 starts (1.4%). Safety initiatives introduced by regulators in 2010 appear to have significantly decreased risks to horses in hurdles but have had little or no effect in steeplechases. Our discussion considers these data in light of public controversy, political debate, and industry regulation related to jump horse safety. PMID:26506396

  2. Correlation-Peak Imaging

    NASA Astrophysics Data System (ADS)

    Ziegler, A.; Metzler, A.; Köckenberger, W.; Izquierdo, M.; Komor, E.; Haase, A.; Décorps, M.; von Kienlin, M.

    1996-08-01

    Identification and quantitation in conventional1H spectroscopic imagingin vivois often hampered by the small chemical-shift range. To improve the spectral resolution of spectroscopic imaging, homonuclear two-dimensional correlation spectroscopy has been combined with phase encoding of the spatial dimensions. From the theoretical description of the coherence-transfer signal in the Fourier-transform domain, a comprehensive acquisition and processing strategy is presented that includes optimization of the width and the position of the acquisition windows, matched filtering of the signal envelope, and graphical presentation of the cross peak of interest. The procedure has been applied to image the spatial distribution of the correlation peaks from specific spin systems in the hypocotyl of castor bean (Ricinus communis) seedlings. Despite the overlap of many resonances, correlation-peak imaging made it possible to observe a number of proton resonances, such as those of sucrose, β-glucose, glutamine/glutamate, lysine, and arginine.

  3. Sex differences in kinetic and neuromuscular control during jumping and landing

    PubMed Central

    Márquez, G.; Alegre, L.M.; Jaén, D.; Martin-Casado, L.; Aguado, X.

    2017-01-01

    In the present study, we analysed the kinetic profile together with the lower limb EMG activation pattern during a countermovement jump and its respective landing phase in males and females. Twenty subjects (10 males and 10 females) took part in the study. One experimental session was conducted in order to record kinetic and electromyographic (EMG) parameters during a countermovement jump (CMJ) and the subsequent landing phase. During the CMJ, males recorded a higher (p<0.001) performance than females in terms of jump height and power production. Stiffness values were lower in males than females due to greater centre of mass displacement during the countermovement (p<0.01). According to the EMG activity, males demonstrated greater (p<0.05) activation during the concentric phase of the jump. However, females revealed a higher co-contraction ratio in the plantar flexors during the push-off phase. During landings males showed higher (p<0.01) peak ground reaction forces (Fpeak), greater (p<0.05) stiffness and a higher maximal displacement of the CoM (p<0.05) than females. EMG analysis revealed greater EMG activity in the tibialis anterior (p<0.05) and rectus femoris (p=0.05) muscles in males. Higher plantar flexor co-activation during landing has also been found in males. Our findings demonstrated different neuromuscular control in males and females during jumping and landing. PMID:28250245

  4. Biomechanical comparison in different jumping tasks between untrained boys and men.

    PubMed

    Lazaridis, Savvas N; Bassa, Eleni I; Patikas, Dimitrios; Hatzikotoulas, Konstantinos; Lazaridis, Filippos K; Kotzamanidis, Christos M

    2013-02-01

    This study examines the biomechanical differences during different vertical jump tasks in 12 prepubescent and 12 adult males. The sagittal knee kinematics, vertical ground reaction force (vGRF) and electromyographic (EMG) activity of 5 lower extremity muscles were recorded. Compared with boys, men presented higher peak vGRF during the propulsive phase in all examined jumps, but lower values during the braking phase, even when related to body mass. Normalized EMG agonist activity in all phases was higher in men (p < .05), while antagonist coactivation was enhanced in boys (p < .05). The knee joint was on average 9 degrees more flexed at touchdown in men during drop jump tasks, but boys exhibited 12 degrees and 17 degrees higher knee flexion at the deepest point when performing drop jump from 20 and 40 cm, respectively. In conclusion, the performance deficit observed in boys in all jump types is a reflection of their immature technique, which could be partly attributed to the less efficient stiffness regulation and activation of their neuromuscular system.

  5. Hale Central Peak

    NASA Technical Reports Server (NTRS)

    2004-01-01

    19 September 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the mountains that make up the central peak region of Hale Crater, located near 35.8oS, 36.5oW. Dark, smooth-surfaced sand dunes are seen to be climbing up the mountainous slopes. The central peak of a crater consists of rock brought up during the impact from below the crater floor. This autumn image is illuminated from the upper left and covers an area approximately 3 km (1.9 mi) across.

  6. Make peak flow a habit!

    MedlinePlus

    Asthma - make peak flow a habit; Reactive airway disease - peak flow; Bronchial asthma - peak flow ... your airways are narrowed and blocked due to asthma, your peak flow values drop. You can check ...

  7. The role of human ankle plantar flexor muscle-tendon interaction and architecture in maximal vertical jumping examined in vivo.

    PubMed

    Farris, Dominic James; Lichtwark, Glen A; Brown, Nicholas A T; Cresswell, Andrew G

    2016-02-01

    Humans utilise elastic tendons of lower limb muscles to store and return energy during walking, running and jumping. Anuran and insect species use skeletal structures and/or dynamics in conjunction with similarly compliant structures to amplify muscle power output during jumping. We sought to examine whether human jumpers use similar mechanisms to aid elastic energy usage in the plantar flexor muscles during maximal vertical jumping. Ten male athletes performed maximal vertical squat jumps. Three-dimensional motion capture and a musculoskeletal model were used to determine lower limb kinematics that were combined with ground reaction force data in an inverse dynamics analysis. B-mode ultrasound imaging of the lateral gastrocnemius (GAS) and soleus (SOL) muscles was used to measure muscle fascicle lengths and pennation angles during jumping. Our results highlighted that both GAS and SOL utilised stretch and recoil of their series elastic elements (SEEs) in a catapult-like fashion, which likely serves to maximise ankle joint power. The resistance of supporting of body weight allowed initial stretch of both GAS and SOL SEEs. A proximal-to-distal sequence of joint moments and decreasing effective mechanical advantage early in the extension phase of the jumping movement were observed. This facilitated a further stretch of the SEE of the biarticular GAS and delayed recoil of the SOL SEE. However, effective mechanical advantage did not increase late in the jump to aid recoil of elastic tissues. © 2016. Published by The Company of Biologists Ltd.

  8. Network-based event-triggered filtering for Markovian jump systems

    NASA Astrophysics Data System (ADS)

    Wang, Huijiao; Shi, Peng; Agarwal, Ramesh K.

    2016-06-01

    The problem of event-triggered H∞ filtering for networked Markovian jump system is studied in this paper. A dynamic discrete event-triggered scheme is designed to choose the transmitted data for different Markovian jumping modes. The time-delay modelling method is employed to describe the event-triggered scheme and the network-related behaviour, such as transmission delay, data package dropout and disorder, into a networked Markovian time-delay jump system. Furthermore, a sufficient condition is derived to guarantee that the resulting filtering error system is stochastically stable with a prescribed performance index. A co-design method for the H∞ filter and the event-triggered scheme is then proposed. The effectiveness and potential of the theoretic results obtained are illustrated by a simulation example.

  9. Jump rates for surface diffusion of large molecules from first principles

    SciTech Connect

    Shea, Patrick Kreuzer, Hans Jürgen

    2015-04-21

    We apply a recently developed stochastic model for the surface diffusion of large molecules to calculate jump rates for 9,10-dithioanthracene on a Cu(111) surface. The necessary input parameters for the stochastic model are calculated from first principles using density functional theory (DFT). We find that the inclusion of van der Waals corrections to the DFT energies is critical to obtain good agreement with experimental results for the adsorption geometry and energy barrier for diffusion. The predictions for jump rates in our model are in excellent agreement with measured values and show a marked improvement over transition state theory (TST). We find that the jump rate prefactor is reduced by an order of magnitude from the TST estimate due to frictional damping resulting from energy exchange with surface phonons, as well as a rotational mode of the diffusing molecule.

  10. High-peak-power single-oscillator actively Q-switched mode-locked Tm3+-doped fiber laser and its application for high-average output power mid-IR supercontinuum generation in a ZBLAN fiber.

    PubMed

    Kneis, Christian; Donelan, Brenda; Manek-Hönninger, Inka; Robin, Thierry; Cadier, Benoît; Eichhorn, Marc; Kieleck, Christelle

    2016-06-01

    A single-oscillator actively Q-switched mode-locked (QML) thulium-doped silica fiber laser is presented and used to pump a ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber for mid-infrared (mid-IR) supercontinuum (SC) generation. The fiber laser provided high-peak-power levels directly from the oscillator delivering single mode-locked pulse energies up to 48 μJ, being 2-4 orders of magnitude higher than conventional continuous wave mode-locked lasers. By pumping a ZBLAN fiber specially designed for high-output-power SC generation, 7.8 W have been achieved in all spectral bands with a spectrum extending to 4.2 μm.

  11. The Boson peak in supercooled water

    PubMed Central

    Kumar, Pradeep; Wikfeldt, K. Thor; Schlesinger, Daniel; Pettersson, Lars G. M.; Stanley, H. Eugene

    2013-01-01

    We perform extensive molecular dynamics simulations of the TIP4P/2005 model of water to investigate the origin of the Boson peak reported in experiments on supercooled water in nanoconfined pores, and in hydration water around proteins. We find that the onset of the Boson peak in supercooled bulk water coincides with the crossover to a predominantly low-density-like liquid below the Widom line TW. The frequency and onset temperature of the Boson peak in our simulations of bulk water agree well with the results from experiments on nanoconfined water. Our results suggest that the Boson peak in water is not an exclusive effect of confinement. We further find that, similar to other glass-forming liquids, the vibrational modes corresponding to the Boson peak are spatially extended and are related to transverse phonons found in the parent crystal, here ice Ih. PMID:23771033

  12. Understanding Vertical Jump Potentiation: A Deterministic Model.

    PubMed

    Suchomel, Timothy J; Lamont, Hugh S; Moir, Gavin L

    2016-06-01

    This review article discusses previous postactivation potentiation (PAP) literature and provides a deterministic model for vertical jump (i.e., squat jump, countermovement jump, and drop/depth jump) potentiation. There are a number of factors that must be considered when designing an effective strength-power potentiation complex (SPPC) focused on vertical jump potentiation. Sport scientists and practitioners must consider the characteristics of the subject being tested and the design of the SPPC itself. Subject characteristics that must be considered when designing an SPPC focused on vertical jump potentiation include the individual's relative strength, sex, muscle characteristics, neuromuscular characteristics, current fatigue state, and training background. Aspects of the SPPC that must be considered for vertical jump potentiation include the potentiating exercise, level and rate of muscle activation, volume load completed, the ballistic or non-ballistic nature of the potentiating exercise, and the rest interval(s) used following the potentiating exercise. Sport scientists and practitioners should design and seek SPPCs that are practical in nature regarding the equipment needed and the rest interval required for a potentiated performance. If practitioners would like to incorporate PAP as a training tool, they must take the athlete training time restrictions into account as a number of previous SPPCs have been shown to require long rest periods before potentiation can be realized. Thus, practitioners should seek SPPCs that may be effectively implemented in training and that do not require excessive rest intervals that may take away from valuable training time. Practitioners may decrease the necessary time needed to realize potentiation by improving their subject's relative strength.

  13. Jump locations of jump-diffusion processes with state-dependent rates

    NASA Astrophysics Data System (ADS)

    Miles, Christopher E.; Keener, James P.

    2017-10-01

    We propose a general framework for studying statistics of jump-diffusion systems driven by both Brownian noise (diffusion) and a jump process with state-dependent intensity. Of particular natural interest in many physical systems are the jump locations: the system evaluated at the jump times. As an example, this could be the voltage at which a neuron fires, or the so-called ‘threshold voltage’. However, the state-dependence of the jump rate provides direct coupling between the diffusion and jump components, making it difficult to disentangle the two to study individually. In this work, we provide an iterative map formulation of the sequence of distributions of jump locations. The distributions computed by this map can be used to elucidate other interesting quantities about the process, including statistics of the interjump times. Ultimately, the limit of the map reveals that knowledge of the stationary distribution of the full process is sufficient to recover (but not necessarily equal to) the distribution of jump locations. We propose two biophysical examples to illustrate the use of this framework to provide insight about a system. We find that a sharp threshold voltage emerges robustly in a simple stochastic integrate-and-fire neuronal model. The interplay between the two sources of noise is also investigated in a stepping model of molecular motor in intracellular transport pulling a diffusive cargo.

  14. Increase in Jumping Height Associated with Maximal Effort Vertical Depth Jumps.

    ERIC Educational Resources Information Center

    Bedi, John F.; And Others

    1987-01-01

    In order to assess if there existed a statistically significant increase in jumping performance when dropping from different heights, 32 males, aged 19 to 26, performed a series of maximal effort vertical jumps after dropping from eight heights onto a force plate. Results are analyzed. (Author/MT)

  15. Comparing Fast Pressure Jump and Temperature Jump Protein Folding Experiments and Simulations

    PubMed Central

    Prigozhin, Maxim B.; Schulten, Klaus; Gruebele, Martin

    2016-01-01

    The unimolecular folding reaction of small proteins is now amenable to a very direct mechanistic comparison between experiment and simulation. We present such a comparison of microsecond pressure and temperature jump refolding kinetics of the engineered WW domain FiP35, a model system for beta sheet folding. Both perturbations produce experimentally a faster and a slower kinetic phase, the “slow” microsecond phase being activated. The fast phase shows differences between perturbation methods and is closer to the downhill limit by temperature jump, but closer to the transiently populated intermediate limit by pressure jump. These observations make more demands on simulations of the folding process than just a rough comparison of time scales. To complement experiments, we calculated several pressure jump and temperature jump all-atom molecular dynamics trajectories in explicit solvent, where FiP35 folded in five of the six simulations. We analyzed our pressure jump simulations by kinetic modeling and found that the pressure jump experiments and MD simulations are most consistent with a 4-state kinetic mechanism. Together, our experimental and computational data highlight FiP35’s position at the boundary where activated intermediates and downhill folding meet, and we show that this model protein is an excellent candidate for further pressure jump molecular dynamics studies to compare experiment and modeling at the folding mechanism level. PMID:25988868

  16. Increase in Jumping Height Associated with Maximal Effort Vertical Depth Jumps.

    ERIC Educational Resources Information Center

    Bedi, John F.; And Others

    1987-01-01

    In order to assess if there existed a statistically significant increase in jumping performance when dropping from different heights, 32 males, aged 19 to 26, performed a series of maximal effort vertical jumps after dropping from eight heights onto a force plate. Results are analyzed. (Author/MT)

  17. Determination of the Best Pre-Jump Height for Improvement of Two-Legged Vertical Jump

    PubMed Central

    Jafari, Mahsa; Zolaktaf, Vahid; Marandi, Sayyed M

    2013-01-01

    Background: Athletic performance in many sports depends on two-legged vertical jump. The objective of this study was to examine the effect of different pre-jump height exercises on two-legged vertical jump and to determine the best pre-jump height(s). Methods: Subjects included 35 females and 42 males. By matched randomized sampling, subjects of each sex were assigned into four groups, namely, control, 10-cm hurdle, 20-cm hurdle, and 30-cm hurdle. They participated in the same training program for 6 weeks. Statistical analyses were based on one-way and repeated-measure analysis of variance (ANOVA). Results: Analysis of the data showed that practice over hurdles of 10 cm was better than no hurdle and hurdles of >10 cm. Also, jump attempts over hurdles were efficient for trained athletes, but not for untrained athletes. For both sexes, the rate of spike improvement was much better in the experimental groups than in the control groups; it was independent from the rate of progress in jump, which was relatively less evident. Conclusions: It is likely that rather than increasing jump height, training over hurdle enabled the players to use a higher percent of their jump potentials. PMID:23717758

  18. The ingestion of a caffeinated energy drink improves jump performance and activity patterns in elite badminton players.

    PubMed

    Abian, Pablo; Del Coso, Juan; Salinero, Juan José; Gallo-Salazar, Cesar; Areces, Francisco; Ruiz-Vicente, Diana; Lara, Beatriz; Soriano, Lidon; Muñoz, Victor; Abian-Vicen, Javier

    2015-01-01

    The aim of this study was to investigate the effectiveness of a caffeine-containing energy drink to enhance physical and match performance in elite badminton players. Sixteen male and elite badminton players (25.4 ± 7.3 year; 71.8 ± 7.9 kg) participated in a double-blind, placebo-controlled and randomised experiment. On two different sessions, badminton players ingested 3 mg of caffeine per kg of body mass in the form of an energy drink or the same drink without caffeine (placebo). After 60 min, participants performed the following tests: handgrip maximal force production, smash jump without and with shuttlecock, squat jump, countermovement jump and the agility T-test. Later, a 45-min simulated badminton match was played. Players' number of impacts and heart rate was measured during the match. The ingestion of the caffeinated energy drink increased squat jump height (34.5 ± 4.7 vs. 36.4 ± 4.3 cm; P < 0.05), squat jump peak power (P < 0.05), countermovement jump height (37.7 ± 4.5 vs. 39.5 ± 5.1 cm; P < 0.05) and countermovement jump peak power (P < 0.05). In addition, an increased number of total impacts was found during the badminton match (7395 ± 1594 vs. 7707 ± 2033 impacts; P < 0.05). In conclusion, the results show that the use of caffeine-containing energy drink may be an effective nutritional aid to increase jump performance and activity patterns during game in elite badminton players.

  19. Kitt Peak Observes Comet

    NASA Image and Video Library

    2005-05-16

    he Kitt Peak National Observatory 2.1-meter telescope observed comet Tempel 1 on April 11, 2005, when the comet was near its closest approach to the Earth. A pinkish dust jet is visible to the southwest, with the broader neutral gas coma surrounding it.

  20. Mantises exchange angular momentum between three rotating body parts to jump precisely to targets.

    PubMed

    Burrows, Malcolm; Cullen, Darron A; Dorosenko, Marina; Sutton, Gregory P

    2015-03-16

    Flightless animals have evolved diverse mechanisms to control their movements in air, whether falling with gravity or propelling against it. Many insects jump as a primary mode of locomotion and must therefore precisely control the large torques generated during takeoff. For example, to minimize spin (angular momentum of the body) at takeoff, plant-sucking bugs apply large equal and opposite torques from two propulsive legs [1]. Interacting gear wheels have evolved in some to give precise synchronization of these legs [2, 3]. Once airborne, as a result of either jumping or falling, further adjustments may be needed to control trajectory and orient the body for landing. Tails are used by geckos to control pitch [4, 5] and by Anolis lizards to alter direction [6, 7]. When falling, cats rotate their body [8], while aphids [9] and ants [10, 11] manipulate wind resistance against their legs and thorax. Falling is always downward, but targeted jumping must achieve many possible desired trajectories. We show that when making targeted jumps, juvenile wingless mantises first rotated their abdomen about the thorax to adjust the center of mass and thus regulate spin at takeoff. Once airborne, they then smoothly and sequentially transferred angular momentum in four stages between the jointed abdomen, the two raptorial front legs, and the two propulsive hind legs to produce a controlled jump with a precise landing. Experimentally impairing abdominal movements reduced the overall rotation so that the mantis either failed to grasp the target or crashed into it head first.

  1. Custom-Made Foot Orthoses Decrease Medial Foot Loading During Drop Jump in Individuals With Patellofemoral Pain.

    PubMed

    Rathleff, Michael S; Richter, Camilla; Brushøj, Christoffer; Bencke, Jesper; Bandholm, Thomas; Holmich, Per; Thorborg, Kristian

    2016-07-01

    To investigate the effect of foot orthoses on medial-to-lateral plantar forces during drop jump and single leg squat, and second, to explore the self-reported change in symptoms after 12 weeks of wearing the orthoses in individuals with patellofemoral pain (PFP). Cohort study with 12 weeks of follow-up. Hospital setting. 23 adults with PFP. Custom-made foot orthoses. Foot loading (plantar pressure) was collected from the most painful side during drop jump and single leg squat using pressure sensitive Pedar insoles. Primary outcome was the medial-to-lateral peak force under the forefoot during drop jump. The PFP syndrome severity score was used to measure self-reported improvement from baseline to follow-up. Orthoses were associated with a significant 2.9%-point (95% confidence intervals: 0.7-5.1) reduction in peak medial-to-lateral force during drop jump. Individuals with a self-reported improvement after 12 weeks had a significant 4.2%-point larger reduction in medial-to-lateral foot loading during drop jump. This preliminary study showed that foot orthoses were associated with a decrease in medially directed foot loading among individuals with PFP. Individuals, who have an immediate decrease in the medial-to-lateral peak force after fitting the orthoses, were more likely to report improvements after 12 weeks of use.

  2. Impact Crater with Peak

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 14 June 2002) The Science This THEMIS visible image shows a classic example of a martian impact crater with a central peak. Central peaks are common in large, fresh craters on both Mars and the Moon. This peak formed during the extremely high-energy impact cratering event. In many martian craters the central peak has been either eroded or buried by later sedimentary processes, so the presence of a peak in this crater indicates that the crater is relatively young and has experienced little degradation. Observations of large craters on the Earth and the Moon, as well as computer modeling of the impact process, show that the central peak contains material brought from deep beneath the surface. The material exposed in these peaks will provide an excellent opportunity to study the composition of the martian interior using THEMIS multi-spectral infrared observations. The ejecta material around the crater can is well preserved, again indicating relatively little modification of this landform since its initial creation. The inner walls of this approximately 18 km diameter crater show complex slumping that likely occurred during the impact event. Since that time there has been some downslope movement of material to form the small chutes and gullies that can be seen on the inner crater wall. Small (50-100 m) mega-ripples composed of mobile material can be seen on the floor of the crater. Much of this material may have come from the walls of the crater itself, or may have been blown into the crater by the wind. The Story When a meteor smacked into the surface of Mars with extremely high energy, pow! Not only did it punch an 11-mile-wide crater in the smoother terrain, it created a central peak in the middle of the crater. This peak forms kind of on the 'rebound.' You can see this same effect if you drop a single drop of milk into a glass of milk. With craters, in the heat and fury of the impact, some of the land material can even liquefy. Central peaks like the one

  3. Impact Crater with Peak

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 14 June 2002) The Science This THEMIS visible image shows a classic example of a martian impact crater with a central peak. Central peaks are common in large, fresh craters on both Mars and the Moon. This peak formed during the extremely high-energy impact cratering event. In many martian craters the central peak has been either eroded or buried by later sedimentary processes, so the presence of a peak in this crater indicates that the crater is relatively young and has experienced little degradation. Observations of large craters on the Earth and the Moon, as well as computer modeling of the impact process, show that the central peak contains material brought from deep beneath the surface. The material exposed in these peaks will provide an excellent opportunity to study the composition of the martian interior using THEMIS multi-spectral infrared observations. The ejecta material around the crater can is well preserved, again indicating relatively little modification of this landform since its initial creation. The inner walls of this approximately 18 km diameter crater show complex slumping that likely occurred during the impact event. Since that time there has been some downslope movement of material to form the small chutes and gullies that can be seen on the inner crater wall. Small (50-100 m) mega-ripples composed of mobile material can be seen on the floor of the crater. Much of this material may have come from the walls of the crater itself, or may have been blown into the crater by the wind. The Story When a meteor smacked into the surface of Mars with extremely high energy, pow! Not only did it punch an 11-mile-wide crater in the smoother terrain, it created a central peak in the middle of the crater. This peak forms kind of on the 'rebound.' You can see this same effect if you drop a single drop of milk into a glass of milk. With craters, in the heat and fury of the impact, some of the land material can even liquefy. Central peaks like the one

  4. Mixed quantum-classical Liouville molecular dynamics without momentum jump

    NASA Astrophysics Data System (ADS)

    Ando, Koji; Santer, Mark

    2003-06-01

    An alternative Liouville formulation of mixed quantum-classical dynamics outlined recently [K. Ando, Chem. Phys. Lett. 360, 240 (2002)] is expanded in detail by taking an explicit account of the parametric dependence of the electronic (adiabatic) basis on the nuclear coordinates. As a consequence of the different operational order of the partial Wigner transformation for the nuclear coordinates and the calculation of the matrix elements in the adiabatic electronic basis, the present formula differs from the previously proposed one, slightly in the appearance but significantly in the treatment of nonadiabatic transitions in the trajectory implementation in that the former does not contain the "off-diagonal Hellmann-Feynman forces" representing the so-called "momentum-jump" associated with the nonadiabatic transitions. Because of this, the present formula is free from the numerical instability intrinsically coming from the momentum-jump operation at around the classical turning points of the nuclear motion. It is also shown that the density matrices from the two approaches coincide when the electronic basis is independent of the nuclear coordinates (R), and hence the momentum-jump approximation stems from the R-dependence of the adiabatic electronic basis. Improved stability and comparable to better reproduction of the quantum reference calculations are demonstrated by applications to one and three dimensional spin-boson models and a two-state three-mode model of the S2→S1 internal conversion of pyrazine. Also discussed is the importance of electronic coherence for the proper treatment of nonadiabatic transition rates which is naturally described by the Liouville methods compared to the conventional independent trajectory approaches.

  5. Mechanical jumping power in young athletes.

    PubMed

    Viitasalo, J T; Osterback, L; Alen, M; Rahkila, P; Havas, E

    1987-09-01

    Mechanical jumping power was determined for 286 young male athletes representing six sports events and ranging in calendar and skeletal ages from 8.8 to 17.1 and from 7.8 to 18.1 years, respectively. The subjects performed successive maximal vertical jumps on a contact mat for 30 s. The number of jumps and their cumulative flight time after 15 and 30 s were used for calculations of mechanical power. The jumping performances of the young athletes were found to be reproducible from the age of 10-12 years in respect to the angular displacement of the knee and duration of contact. Absolute mechanical power, as well as power related to body weight, increased with calendar and skeletal ages. Of the anthropometric characteristics, the circumference of the thigh and body weight showed the highest correlation with mechanical power; subjects with the greatest thigh circumference and body weight having the lowest mechanical power. The subjects were divided into 'power' (track and field, gymnastics) and 'endurance' (skiing, orienteering) groups. The former reached higher mechanical power values than the latter. Mechanical power for the second 15-s jumping period was on average 4.7% lower than for the first. The events did not differ from each other in respect of the decrease in power.

  6. A locust-inspired miniature jumping robot.

    PubMed

    Zaitsev, Valentin; Gvirsman, Omer; Ben Hanan, Uri; Weiss, Avi; Ayali, Amir; Kosa, Gabor

    2015-11-25

    Unmanned ground vehicles are mostly wheeled, tracked, or legged. These locomotion mechanisms have a limited ability to traverse rough terrain and obstacles that are higher than the robot's center of mass. In order to improve the mobility of small robots it is necessary to expand the variety of their motion gaits. Jumping is one of nature's solutions to the challenge of mobility in difficult terrain. The desert locust is the model for the presented bio-inspired design of a jumping mechanism for a small mobile robot. The basic mechanism is similar to that of the semilunar process in the hind legs of the locust, and is based on the cocking of a torsional spring by wrapping a tendon-like wire around the shaft of a miniature motor. In this study we present the jumping mechanism design, and the manufacturing and performance analysis of two demonstrator prototypes. The most advanced jumping robot demonstrator is power autonomous, weighs 23 gr, and is capable of jumping to a height of 3.35 m, covering a distance of 1.37 m.

  7. PEAK LIMITING AMPLIFIER

    DOEpatents

    Goldsworthy, W.W.; Robinson, J.B.

    1959-03-31

    A peak voltage amplitude limiting system adapted for use with a cascade type amplifier is described. In its detailed aspects, the invention includes an amplifier having at least a first triode tube and a second triode tube, the cathode of the second tube being connected to the anode of the first tube. A peak limiter triode tube has its control grid coupled to thc anode of the second tube and its anode connected to the cathode of the second tube. The operation of the limiter is controlled by a bias voltage source connected to the control grid of the limiter tube and the output of the system is taken from the anode of the second tube.

  8. INDIAN PEAKS WILDERNESS, COLORADO.

    USGS Publications Warehouse

    Pearson, Robert C.; Speltz, Charles N.

    1984-01-01

    The Indian Peaks Wilderness northwest of Denver is partly within the Colorado Mineral Belt, and the southeast part of it contains all the geologic characteristics associated with the several nearby mining districts. Two deposits have demonstrated mineral resources, one of copper and the other of uranium; both are surrounded by areas with probable potential. Two other areas have probable resource potential for copper, gold, and possibly molydenum. Detailed gravity and magnetic studies in the southeast part of the Indian Peaks Wilderness might detect in the subsurface igneous bodies that may be mineralized. Physical exploration such as drilling would be necessary to determine more precisely the copper resources at the Roaring Fork locality and uranium resources at Wheeler Basin.

  9. PEAK READING VOLTMETER

    DOEpatents

    Dyer, A.L.

    1958-07-29

    An improvement in peak reading voltmeters is described, which provides for storing an electrical charge representative of the magnitude of a transient voltage pulse and thereafter measuring the stored charge, drawing oniy negligible energy from the storage element. The incoming voltage is rectified and stored in a condenser. The voltage of the capacitor is applied across a piezoelectric crystal between two parallel plates. Amy change in the voltage of the capacitor is reflected in a change in the dielectric constant of the crystal and the capacitance between a second pair of plates affixed to the crystal is altered. The latter capacitor forms part of the frequency determlning circuit of an oscillator and means is provided for indicating the frequency deviation which is a measure of the peak voltage applied to the voltmeter.

  10. Popcorn: critical temperature, jump and sound.

    PubMed

    Virot, Emmanuel; Ponomarenko, Alexandre

    2015-03-06

    Popcorn bursts open, jumps and emits a 'pop' sound in some hundredths of a second. The physical origin of these three observations remains unclear in the literature. We show that the critical temperature 180°C at which almost all of popcorn pops is consistent with an elementary pressure vessel scenario. We observe that popcorn jumps with a 'leg' of starch which is compressed on the ground. As a result, popcorn is midway between two categories of moving systems: explosive plants using fracture mechanisms and jumping animals using muscles. By synchronizing video recordings with acoustic recordings, we propose that the familiar 'pop' sound of the popcorn is caused by the release of water vapour.

  11. Friction through reversible jumps of surface atoms.

    PubMed

    Fajardo, O Y; Barel, Itay; Urbakh, Michael

    2014-08-06

    We propose a microscopic model that incorporates the effect of thermally activated motion of surface atoms on nanoscopic friction. Our calculations demonstrate that the stick-slip motion of the tip is governed by two competing processes: (i) jumps of the surface atoms to the tip which tend to inhibit sliding, and (ii) jumps back to the sample which give rise to sliding. The energy dissipated during the reversible jumps of the surface atoms between the sample and tip contributes significantly to the friction force, and leads to a nonmonotonic dependence of friction on temperature, which has been observed in recent friction force microscopy experiments for different material classes. The proposed model elucidates the physical origin of microscopic instabilities introduced in phenomenological models for the interpretation of the experimental results.

  12. Popcorn: critical temperature, jump and sound

    PubMed Central

    Virot, Emmanuel; Ponomarenko, Alexandre

    2015-01-01

    Popcorn bursts open, jumps and emits a ‘pop’ sound in some hundredths of a second. The physical origin of these three observations remains unclear in the literature. We show that the critical temperature 180°C at which almost all of popcorn pops is consistent with an elementary pressure vessel scenario. We observe that popcorn jumps with a ‘leg’ of starch which is compressed on the ground. As a result, popcorn is midway between two categories of moving systems: explosive plants using fracture mechanisms and jumping animals using muscles. By synchronizing video recordings with acoustic recordings, we propose that the familiar ‘pop’ sound of the popcorn is caused by the release of water vapour. PMID:25673298

  13. Nonlinear regimes on polygonal hydraulic jumps

    NASA Astrophysics Data System (ADS)

    Rojas, Nicolas

    2016-11-01

    This work extends previous leading and higher order results on the polygonal hydraulic jump in the framework of inertial lubrication theory. The rotation of steady polygonal jumps is observed in the transition from one wavenumber to the next one, induced by a change in height of an external obstacle near the outer edge. In a previous publication, the study of stationary polygons is considered under the assumption that the reference frame rotates with the polygons when the number of corners change, in order to preserve their orientation. In this research work I provide a Hamiltonian approach and the stability analysis of the nonlinear oscillator that describe the polygonal structures at the jump interface, in addition to a perturbation method that enables to explain, for instance, the diversity of patterns found in experiments. GRASP, Institute of Physics, University of Liege, Belgium.

  14. Dynamics of 'jumping' Trojans: Perturbative treatment

    NASA Astrophysics Data System (ADS)

    Sidorenko, V.

    2014-07-01

    The term ''jumping'' Trojan was introduced by Tsiganis et al. (2000) in their studies of long-term dynamics exhibited by the asteroid (1868) Thersites: as it turned out, this asteroid may pass from the librations around L4 to the librations around L5. One more example of a ''jumping'' Trojan was found by Connors et al. (2011): librations of the asteroid 2010 TK_7 around Earth's libration point L4 preceded by its librations around L5. We explore the dynamics of ''jumping'' Trojans under the scope of the restricted planar elliptical three-body problem. Via double numerical averaging, we construct evolutionary equations which describe the long-term behavior of the orbital elements of these asteroids.

  15. Kinematic control of extreme jump angles in the red leg running frog (Kassina maculata).

    PubMed

    Richards, Christopher Thomas; Porro, Laura Beatriz; Collings, Amber Jade

    2017-03-08

    The kinematic flexibility of frog hindlimbs enables multiple locomotor modes within a single species. Prior work has extensively explored maximum performance capacity in frogs; however, the mechanisms by which anurans modulate performance within locomotor modes remain unclear. We explored how Kassina maculata, a species known for both running and jumping abilities, modulates takeoff angle from horizontal to nearly vertical. Specifically, how do 3D motions of leg segments coordinate to move the center of mass (COM) upwards and forwards? How do joint rotations modulate jump angle? High-speed video was used to quantify 3D joint angles and their respective rotation axis vectors. Inverse kinematics was used to determine how hip, knee and ankle rotations contribute to components of COM motion. Independent of takeoff angle, leg segment retraction (rearward rotation) was twofold greater than adduction (downward rotation). Additionally, the joint rotation axis vectors reoriented through time suggesting dynamic shifts in relative roles of joints. We found two hypothetical mechanisms for increasing takeoff angle: Firstly, greater knee and ankle excursion increased shank adduction, elevating the COM. Secondly, during the steepest jumps the body rotated rapidly backwards to redirect the COM velocity. This rotation was not caused by pelvic angle extension, but rather by kinematic transmission from leg segments via reorientation of the joint rotation axes. We propose that K. maculata uses proximal leg retraction as the principal kinematic drive while dynamically tuning jump trajectory by knee and ankle joint modulation.

  16. Hydrodynamics and energetics of jumping copepod nauplii and copepodids.

    PubMed

    Wadhwa, Navish; Andersen, Anders; Kiørboe, Thomas

    2014-09-01

    Within its life cycle, a copepod goes through drastic changes in size, shape and swimming mode. In particular, there is a stark difference between the early (nauplius) and later (copepodid) stages. Copepods inhabit an intermediate Reynolds number regime (between ~1 and 100) where both viscosity and inertia are potentially important, and the Reynolds number changes by an order of magnitude during growth. Thus we expect the life stage related changes experienced by a copepod to result in hydrodynamic and energetic differences, ultimately affecting the fitness. To quantify these differences, we measured the swimming kinematics and fluid flow around jumping Acartia tonsa at different stages of its life cycle, using particle image velocimetry and particle tracking velocimetry. We found that the flow structures around nauplii and copepodids are topologically different, with one and two vortex rings, respectively. Our measurements suggest that copepodids cover a larger distance compared to their body size in each jump and are also hydrodynamically quieter, as the flow disturbance they create attenuates faster with distance. Also, copepodids are energetically more efficient than nauplii, presumably due to the change in hydrodynamic regime accompanied with a well-adapted body form and swimming stroke.

  17. Recent Advancements in Lightning Jump Algorithm Work

    NASA Technical Reports Server (NTRS)

    Schultz, Christopher J.; Petersen, Walter A.; Carey, Lawrence D.

    2010-01-01

    In the past year, the primary objectives were to show the usefulness of total lightning as compared to traditional cloud-to-ground (CG) networks, test the lightning jump algorithm configurations in other regions of the country, increase the number of thunderstorms within our thunderstorm database, and to pinpoint environments that could prove difficult for any lightning jump configuration. A total of 561 thunderstorms have been examined in the past year (409 non-severe, 152 severe) from four regions of the country (North Alabama, Washington D.C., High Plains of CO/KS, and Oklahoma). Results continue to indicate that the 2 lightning jump algorithm configuration holds the most promise in terms of prospective operational lightning jump algorithms, with a probability of detection (POD) at 81%, a false alarm rate (FAR) of 45%, a critical success index (CSI) of 49% and a Heidke Skill Score (HSS) of 0.66. The second best performing algorithm configuration was the Threshold 4 algorithm, which had a POD of 72%, FAR of 51%, a CSI of 41% and an HSS of 0.58. Because a more complex algorithm configuration shows the most promise in terms of prospective operational lightning jump algorithms, accurate thunderstorm cell tracking work must be undertaken to track lightning trends on an individual thunderstorm basis over time. While these numbers for the 2 configuration are impressive, the algorithm does have its weaknesses. Specifically, low-topped and tropical cyclone thunderstorm environments are present issues for the 2 lightning jump algorithm, because of the suppressed vertical depth impact on overall flash counts (i.e., a relative dearth in lightning). For example, in a sample of 120 thunderstorms from northern Alabama that contained 72 missed events by the 2 algorithm 36% of the misses were associated with these two environments (17 storms).

  18. Differences in Lateral Drop Jumps From an Unknown Height Among Individuals With Functional Ankle Instability

    PubMed Central

    Rosen, Adam; Swanik, Charles; Thomas, Stephen; Glutting, Joseph; Knight, Christopher; Kaminski, Thomas W.

    2013-01-01

    Context: Functional ankle instability (FAI) is a debilitating condition that has been reported to occur after 20% to 50% of all ankle sprains. Landing from a jump is one common mechanism of ankle injury, yet few researchers have explored the role of visual cues and anticipatory muscle contractions, which may influence ankle stability, in lateral jumping maneuvers. Objective: To examine muscle-activation strategies between FAI and stable ankles under a lateral load and to evaluate the differences in muscle activation in participants with FAI and participants with stable ankles when they were unable to anticipate the onset of lateral loads during eyes-open versus eyes-closed conditions. Design: Case-control study. Setting: Controlled laboratory setting. Patients or Other Participants: A total of 40 people participated: 20 with FAI and 20 healthy, uninjured, sex- and age-matched persons (control group). Intervention(s): Participants performed a 2-legged lateral jump off a platform onto a force plate set to heights of 35 cm or 50 cm and then immediately jumped for maximal height. They performed jumps in 2 conditions (eyes open, eyes closed) and were unaware of the jump height when their eyes were closed. Main Outcome Measure(s): Amplitude normalized electromyographic (EMG) area (%), peak (%), and time to peak in the tibialis anterior (TA), peroneus longus (PL), and lateral gastrocnemius (LG) muscles were measured. Results: Regardless of the eyes-open or eyes-closed condition, participants with FAI had less preparatory TA (t158 = 2.22, P = .03) and PL (t158 = 2.09, P = .04) EMG area and TA (t158 = 2.45, P = .02) and PL (t158 = 2.17, P = .03) peak EMG than control-group participants. Conclusions: By removing visual cues, unanticipated lateral joint loads occurred simultaneously with decreased muscle activity, which may reduce dynamic restraint capabilities in persons with FAI. Regardless of visual impairment and jump height, participants with FAI exhibited PL and TA

  19. The epidemiology of injury in bungee jumping, BASE jumping, and skydiving.

    PubMed

    Søreide, Kjetil

    2012-01-01

    Knowledge regarding epidemiology of injury is of benefit to injury prevention of activities associated with high risk. As relatively 'young' activities, the investigation of injuries and deaths related in extreme sports such as bungee jumping and BASE jumping is relatively sparse. Studies evaluating risk in civilian and military skydiving activities have been reported over the past decades, but technique and equipment has changed. Risk with bungee jumping is only sporadically reported in the literature, most often in connection with eye injuries, but also rare events of serious, life-threatening injuries and even death. BASE is an acronym for Building, Antenna, Span, Earth, which represents the fixed objects from which jumps are made. Estimated risk in BASE jumping for any injury (independent of severity grade) is 0.4-0.5%, which as 5- to 8-fold higher than skydiving. Typically, men outnumber women in a ratio of 10:1 in both injuries and case fatality rates. Age is frequently reported to range from 30 to 40 years. Notably, differences in training and environmental locations exist between recreational skydiving and BASE jumping. As BASE jumps are made from lower altitudes than skydives, jumpers generally fall at lower speeds, have far less aerodynamic control, and may lose flying stability. Yet, typical injuries include a bruised or sprained ankle during landing. Protective gear including helmet and pads may help to prevent such injuries, while more complex knowledge of human factors, environment and training are needed to prevent fatal injuries.

  20. Jumping in a winged stick insect.

    PubMed

    Burrows, Malcolm; Morris, Oliver

    2002-08-01

    The Thailand winged stick insect (Sipyloidea sp.) flees rapidly from a disturbance by jumping forwards when stimulated on the abdomen and backwards when stimulated on the head. The mechanisms underlying these fast movements were analysed by measuring movements of the body and legs from images captured at 250 Hz. A forward jump of both adults and nymphs involves movements of the abdomen and the middle and hind pairs of legs. The abdomen is raised and swung forwards by flexion at the joint with the metathorax and at the joint between the meso- and metathorax. At the same time, the tibiae of the hind and middle legs are extended and their femora depressed. The femoro-tibial joints of the legs are not fully flexed before a jump, and no structures in these joints appear to store muscular energy. The whole jumping sequence takes approximately 100 ms and results in take-off angles of 10-35 degrees at velocities of 0.6-0.8 m s(-1) and with an acceleration of 10 m s(-2). The abdominal angular velocity was 2000 degrees s(-1) and the tip of the abdomen moved at linear velocities of some 1 m s(-1), while the maximum rate of tibial extension was 4000 degrees s(-1). Rapid backward movements result either in the collapse of the body onto the ground, with a displacement away from the stimulus of approximately half a body length, or in the propulsion of the insect off its perch. Neither movement involves curling of the abdomen. From a horizontal posture, the forward jumps result in a displacement of a few body lengths. More lift can be generated in adults by elevating the hind wings as the abdomen is swung forwards and depressing them as the legs lose contact with the ground. In this way, jumps can lead directly to flapping flight. Take-off into flight can, however, be achieved without the abdominal movements seen during jumping. From a vertical posture, a forward jump propels the insect upwards and backwards before it falls to the ground horizontally displaced from its perch

  1. Correlations between sagittal plane kinematics and landing impact force during single-leg lateral jump-landings.

    PubMed

    Aizawa, Junya; Ohji, Shunsuke; Koga, Hideyuki; Masuda, Tadashi; Yagishita, Kazuyoshi

    2016-08-01

    [Purpose] The correlations of peak vertical ground reaction force and sagittal angles during single-leg lateral jump-landing with noncontact anterior cruciate ligament injury remain unknown. This study aimed to clarify the correlations between kinematics and impact force during lateral jump-landing. [Subjects and Methods] Twenty active males were included in the analysis. A sagittal-view movie camera and force plate were time synchronized. Trunk and lower extremity sagittal angles were measured 100 ms before initial contact and at peak vertical ground reaction force. Peak vertical ground reaction force, time between initial contact and peak vertical ground reaction force, and loading rate were calculated. [Results] The mean sagittal angle was 40.7° ± 7.7° for knee flexion during the flight phase and 16.4° ± 6.3° for pelvic anterior inclination during the landing phase. The mean peak vertical ground reaction force was four times the body weight. The median time to peak vertical ground reaction force was 63.8 ms. The knee flexion during the flight phase and pelvic anterior inclination angles during the landing phase were related to the peak vertical ground reaction force. [Conclusion] Increasing knee flexion and decreasing pelvic anterior inclination might reduce the impact during single-leg lateral jump-landing.

  2. Correlations between sagittal plane kinematics and landing impact force during single-leg lateral jump-landings

    PubMed Central

    Aizawa, Junya; Ohji, Shunsuke; Koga, Hideyuki; Masuda, Tadashi; Yagishita, Kazuyoshi

    2016-01-01

    [Purpose] The correlations of peak vertical ground reaction force and sagittal angles during single-leg lateral jump-landing with noncontact anterior cruciate ligament injury remain unknown. This study aimed to clarify the correlations between kinematics and impact force during lateral jump-landing. [Subjects and Methods] Twenty active males were included in the analysis. A sagittal-view movie camera and force plate were time synchronized. Trunk and lower extremity sagittal angles were measured 100 ms before initial contact and at peak vertical ground reaction force. Peak vertical ground reaction force, time between initial contact and peak vertical ground reaction force, and loading rate were calculated. [Results] The mean sagittal angle was 40.7° ± 7.7° for knee flexion during the flight phase and 16.4° ± 6.3° for pelvic anterior inclination during the landing phase. The mean peak vertical ground reaction force was four times the body weight. The median time to peak vertical ground reaction force was 63.8 ms. The knee flexion during the flight phase and pelvic anterior inclination angles during the landing phase were related to the peak vertical ground reaction force. [Conclusion] Increasing knee flexion and decreasing pelvic anterior inclination might reduce the impact during single-leg lateral jump-landing. PMID:27630422

  3. Relationship between countermovement jump performance and multijoint isometric and dynamic tests of strength.

    PubMed

    Nuzzo, James L; McBride, Jeffrey M; Cormie, Prue; McCaulley, Grant O

    2008-05-01

    The purpose of this investigation was to determine the relationship between countermovement vertical jump (CMJ) performance and various methods used to assess isometric and dynamic multijoint strength. Twelve NCAA Division I-AA male football and track and field athletes (age, 19.83 +/- 1.40 years; height, 179.10 +/- 4.56 cm; mass, 90.08 +/- 14.81 kg; percentage of body fat, 11.85 +/- 5.47%) participated in 2 testing sessions. The first session involved 1 repetition maximum (1RM) (kg) testing in the squat and power clean. During the second session, peak force (N), relative peak force (N x kg(-1)), peak power (W), relative peak power (W x kg(-1)), peak velocity (m x s(-1)), and jump height (meters) in a CMJ, and peak force and rate of force development (RFD) (N x s(-1)) in a maximal isometric squat (ISO squat) and maximal isometric mid-thigh pull (ISO mid-thigh) were assessed. Significant correlations (P < or = 0.05) were found when comparing relative 1RMs (1RM/body mass), in both the squat and power clean, to relative CMJ peak power, CMJ peak velocity, and CMJ height. No significant correlations existed between the 4 measures of absolute strength, which did not account for body mass (squat 1RM, power clean 1RM, ISO squat peak force, and ISO mid-thigh peak force) when compared to CMJ peak velocity and CMJ height. In conclusion, multijoint dynamic tests of strength (squat 1RM and power clean 1RM), expressed relative to body mass, are most closely correlated with CMJ performance. These results suggest that increasing maximal strength relative to body mass can improve performance in explosive lower body movements. The squat and power clean, used in a concurrent strength and power training program, are recommended for optimizing lower body power.

  4. Influence of Knee-to-Feet Jump Training on Vertical Jump and Hang Clean Performance.

    PubMed

    Stark, Laura; Pickett, Karla; Bird, Michael; King, Adam C

    2016-11-01

    Stark, L, Pickett, K, Bird, M, and King, AC. Influence of knee-to-feet jump training on vertical jump and hang clean performance. J Strength Cond Res 30(11): 3084-3089, 2016-From a motor learning perspective, the practice/training environment can result in positive, negative, or neutral transfer to the testing conditions. The purpose of this study was to examine the training effect of a novel movement (knee-to-feet [K2F] jumps) and whether a 6-week training program induced a positive transfer effect to other power-related movements (vertical jump and hang clean [HC]). Twenty-six intercollegiate athletes from power-emphasized sports were paired and counter-balanced into a control (i.e., maintained their respective sport-specific lifting regimen) or an experimental group (i.e., completed a 6-week progressive training program of K2F jumps in addition to respective lifting regimen). A pre- and posttest design was used to investigate the effect of training on K2F jump height and transfer effect to vertical jump height (VJH) and 2-repetition maximum (RM) HC performance. A significant increase in K2F jump height was found for the experimental group. Vertical jump height significantly increased from pre- to posttest but no group or interaction (group × time) effect was found, and there were nonsignificant differences for HC. Posttest data showed significant correlations between all pairs of the selected exercises with the highest correlation between K2F jump height and VJ H (R = 0.40) followed by VJH and 2RM HC (R = 0.38) and 2RM HC and K2F jump height (R = 0.23). The results suggest that K2F jump training induced the desired learning effect but was specific to the movement in that no effect of transfer occurred to the other power-related movements. This finding is value for strength and condition professionals who design training programs to enhance athletic performance.

  5. Kitt Peak speckle camera

    NASA Technical Reports Server (NTRS)

    Breckinridge, J. B.; Mcalister, H. A.; Robinson, W. G.

    1979-01-01

    The speckle camera in regular use at Kitt Peak National Observatory since 1974 is described in detail. The design of the atmospheric dispersion compensation prisms, the use of film as a recording medium, the accuracy of double star measurements, and the next generation speckle camera are discussed. Photographs of double star speckle patterns with separations from 1.4 sec of arc to 4.7 sec of arc are shown to illustrate the quality of image formation with this camera, the effects of seeing on the patterns, and to illustrate the isoplanatic patch of the atmosphere.

  6. Kitt Peak speckle camera

    NASA Technical Reports Server (NTRS)

    Breckinridge, J. B.; Mcalister, H. A.; Robinson, W. G.

    1979-01-01

    The speckle camera in regular use at Kitt Peak National Observatory since 1974 is described in detail. The design of the atmospheric dispersion compensation prisms, the use of film as a recording medium, the accuracy of double star measurements, and the next generation speckle camera are discussed. Photographs of double star speckle patterns with separations from 1.4 sec of arc to 4.7 sec of arc are shown to illustrate the quality of image formation with this camera, the effects of seeing on the patterns, and to illustrate the isoplanatic patch of the atmosphere.

  7. Peak-Finding Algorithms.

    PubMed

    Hung, Jui-Hung; Weng, Zhiping

    2017-03-01

    Microarray and next-generation sequencing technologies have greatly expedited the discovery of genomic DNA that can be enriched using various biochemical methods. Chromatin immunoprecipitation (ChIP) is a general method for enriching chromatin fragments that are specifically recognized by an antibody. The resulting DNA fragments can be assayed by microarray (ChIP-chip) or sequencing (ChIP-seq). This introduction focuses on ChIP-seq data analysis. The first step of analyzing ChIP-seq data is identifying regions in the genome that are enriched in a ChIP sample; these regions are called peaks.

  8. Twin Peaks - 3D

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The two hills in the distance, approximately one to two kilometers away, have been dubbed the 'Twin Peaks' and are of great interest to Pathfinder scientists as objects of future study. 3D glasses are necessary to identify surface detail. The white areas on the left hill, called the 'Ski Run' by scientists, may have been formed by hydrologic processes.

    The IMP is a stereo imaging system with color capability provided by 24 selectable filters -- twelve filters per 'eye.

    Click below to see the left and right views individually. [figure removed for brevity, see original site] Left [figure removed for brevity, see original site] Right

  9. Sunset over "Twin Peaks"

    NASA Image and Video Library

    1997-08-06

    This image was taken by the Imager for Mars Pathfinder (IMP) about one minute after sunset on Mars on Sol 21. The prominent hills dubbed "Twin Peaks" form a dark silhouette at the horizon, while the setting sun casts a pink glow over the darkening sky. The image was taken as part of a twilight study which indicates how the brightness of the sky fades with time after sunset. Scientists found that the sky stays bright for up to two hours after sunset, indicating that Martian dust extends very high into the atmosphere. http://photojournal.jpl.nasa.gov/catalog/PIA00783

  10. Economic and safety analysis of unconventional peak regulation on power unit of peak shifting start-stop

    NASA Astrophysics Data System (ADS)

    Cao, X.; Zhao, J. F.; Duan, X. Q.; Jin, Y. A.

    2017-01-01

    Tthe capacity difference of peak regulation between the power gird and the actual demand has become a serious problem considering the growth in the difference between electricity supply and demand. Therefore, peak regulation of power grid needs to be deeply studied. Unconventional peak regulation on unit of peak shifting start-stop is a way that can broaden the range of power regulation, as well as benefit safe operation of the power grid. However, it requires frequent and fast unit start-stop, complex operation, and more staff labor. By carrying out unconventional thermal power unit load test, the start-stop mode of peak auxiliary equipment is studied in this paper, indicating that it has a positive effect on safety and economic of load-peaking operation. The best working conditions of the peak units is found by analysing consumption cost, safety specifications, and life lost of the start-stop peak regulation mode.

  11. The role of rate of force development on vertical jump performance.

    PubMed

    McLellan, Christopher P; Lovell, Dale I; Gass, Gregory C

    2011-02-01

    The purpose of this study was to examine a) the relationship between rate of force development (RFD) and vertical jump (VJ) performance during a counter movement jump (CMJ), and b) the reliability of RFD recorded during the CMJ and squat jump (SJ) forms of the VJ. Twenty-three physically active men aged 23 ± 3.9 years participated in the study. Subjects completed 3 unloaded CMJ and 3 unloaded SJ in random order on a force plate. The RFD was measured during CMJ and SJ movements with vertical jump displacement (VJD) measured simultaneously during the CMJ only. Subjects incorporated arm swing to their CMJ technique to reach up as high as possible, and VJD was measured. All SJ were executed with both hands on the hips throughout the full range of movement. Peak rate of force development (PRFD), peak force (PF), and time to peak force (TPF) were significantly correlated to VJD during the CMJ (r = 0.68, r = 0.51, and r = -0.48, respectively). The RFD and TPF during the CMJ and SJ were associated with low test-retest reliability (coefficient of variation [CV]: 11.8-7.9%). Peak and average power, PF, and VJD produced high test-retest reliability (CV: 2.8-5.1%) during both the CMJ and SJ movements. Our results indicate that PRFD, a measure of explosive strength, and PF, a measure of maximal strength, are the primary contributors to VJD during the CMJ in physically active men. However, caution must be used when interpreting data using PRFD because of its low retest reliability.

  12. Effect of unloading and loading on power in simulated countermovement and squat jumps.

    PubMed

    Bobbert, Maarten F

    2014-06-01

    In the literature, substantial decreases in power output in jumping have been described for both unloading and loading, and these have been attributed to the intrinsic force-velocity-power relationship of muscle. The purpose of this study was to gain a solid understanding of how and why unloading and loading affect power output during jumping. Vertical jumps were simulated with a model of the musculoskeletal system, consisting of four rigid segments actuated by six muscles. Muscle stimulation over time was optimized to ensure maximal performance in each loading condition. It was found that, in contrast to what is reported in the literature, unloading by an extra vertical force of -60% of body weight caused a small increase in the peak of the rate of change of the effective energy of the center of mass (dEeff/dt). Loading by an extra vertical force of +60% of body weight caused a decrease in peak dEeff/dt, but this decrease was much smaller than that described in the literature. The small variations in peak dEeff/dt among loading conditions in the simulated jumps were only in part due to the intrinsic force-velocity-power relationship of muscle. Why did the effects of unloading and loading in the simulation model deviate from effects reported in subjects? One possible explanation is that subjects tend to make a smaller countermovement when loaded; in the simulation model, making a smaller countermovement caused a major reduction in peak dEeff/dt. A second possible explanation is that subjects cannot quickly optimize their control and therefore produce submaximal power output in unfamiliar loading conditions. The effects of unloading and loading are due only in part to the intrinsic force-velocity-power relationship of muscle.

  13. Parachute Jumping Induces More Sympathetic Activation Than Cortisol Secretion in First-Time Parachutists

    PubMed Central

    Messina, Giovanni; Chieffi, Sergio; Viggiano, Andrea; Tafuri, Domenico; Cibelli, Giuseppe; Valenzano, Anna; Triggiani, Antonio Ivano; Messina, Antonietta; De Luca, Vincenzo; Monda, Marcellino

    2016-01-01

    Background: The word “stress” describes the status of the body affected by external or internal forces, or “stressors”, threatening to alter its dynamic balance or homeostasis. The adaptive changes which occur in reply to stressors are either behavioral or physical. Once a given threshold is surpassed, a systemic reaction takes place involving the “stress system” in the brain together with its peripheral components, the hypothalamic-pituitary-adrenal axis and autonomic sympathetic. Objectives: Stress induces an activation of the sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis. The purpose of this study was to investigate whether the SNS and the HPA axis would show parallel or divergent stress response patterns in a session of first parachute jump. Patients and Methods: Activation of the SNS was evaluated by dosage of salivary alpha-amylase, galvanic skin responses, and heart rate in seven male novice parachutists. Activation of HPA axis was tested by dosage of cortisol. These variables were measured before and 1 minute and 90 minute after the jump. Results: All variables reached a peak at 1 minute post-jump. Salivary alpha-amylase, galvanic skin responses and heart rate did not return to basal value at 90 minutes post-jump, while cortisol returned to basal value at 90 minutes post-jump. Conclusions: This evidence indicates that parachute jumping is accompanied by a dissociation of SNS and HPA response patterns in novice parachutists, showing a slower recovery in sympathetic activity than in cortisol secretion. PMID:27217924

  14. Reproducibility of jumping mechanography and traditional measures of physical and muscle function in older adults.

    PubMed

    Buehring, B; Krueger, D; Fidler, E; Gangnon, R; Heiderscheit, B; Binkley, N

    2015-02-01

    Improved approaches to assess functional change over time are needed to optimally reduce fall/fracture risk; jumping mechanography (JM) may be one such methodology. In this study, JM parameters were more reproducible than traditional functional tests. JM may be better able to demonstrate efficacy of interventions to mitigate sarcopenia. Jumping mechanography (JM), a tool using maximal countermovement jumps performed on a force plate, may more reliably assess muscle function than traditional methods. The purpose of this study was to examine JM retest reliability in older adults compared with commonly used muscle and physical function assessments. Community-dwelling individuals age≥70 years performed physical and muscle function assessments including the short physical performance battery (SPPB), grip strength, and JM on multiple occasions over 3 months. JM parameters included body weight-corrected peak power and jump height. Appendicular lean mass was measured by dual energy x-ray (DXA). Mixed effects linear regression models were used to estimate between- and within-person variability summarized as intra-class correlation coefficients (ICC). Ninety-seven individuals (49 females, 48 males, mean age 80.7 years) participated. All testing was well tolerated; no participant sustained injury. Jump power, height, and grip strength were greater (p<0.0001) in men than women. Grip strength, jump power, and height had excellent ICCs (0.95, 0.93, and 0.88, respectively); chair rise, SPPB score, and gait speed had lower ICCs (0.81, 0.77, and 0.76, respectively). In older adults, JM has excellent retest reliability, is stable over time, and can be performed safely. JM retest reliability was comparable to grip strength and possibly better than SPPB and gait speed. JM is a promising tool for muscle function assessment in older adults. Comparison of this approach with traditional assessment tools in longitudinal interventional studies is needed.

  15. Seasonal changes in leg strength and vertical jump ability in internationally competing ski jumpers.

    PubMed

    Rønnestad, Bent R

    2013-07-01

    The aim of the present study was to investigate the effects of the seasonal changes in heavy strength training on maximal strength and vertical jump ability in internationally competing ski jumpers. A repeated-measures design was used to follow-up the changes in strength, vertical jump capacity, and neuromuscular efficiency (expressed as the ratio between squat jump height and the relative isometric force) in the ski jumpers. Measurements were performed in November (pre), January (middle of the competition season), and in March (end of the competition season). The weekly number of strength training sessions, absolute, and relative peak isometric squat force was significantly reduced during the competition period (p < 0.05). The body mass was reduced from pre-season to the middle of the competition season and remained at this level at the end of the competition season (p < 0.05). Squat jump height remained unchanged from pre-season until the end of the competition season (p < 0.05). Neuromuscular efficiency increased from pre-season until the end of the competition season (p < 0.05). The present study shows that maximal strength and body weight is reduced from pre-season to the end of the competitive season in internationally competing ski jumpers. The vertical jump ability did not change from pre-season to the end of the competitive season, while the neuromuscular efficiency increased during the competitive season. These findings indicate that coaches and athletes should emphasize adequate nutritional strategies and to apply a larger focus on strength maintenance training during the competitive season to maximize ski jump performance.

  16. Jumping Jupiter Can Explain Mercury’s Orbit

    NASA Astrophysics Data System (ADS)

    Roig, Fernando; Nesvorný, David; DeSouza, Sandro Ricardo

    2016-04-01

    The orbit of Mercury has large values of eccentricity and inclination that cannot be easily explained if this planet formed on a circular and coplanar orbit. Here, we study the evolution of Mercury’s orbit during the instability related to the migration of the giant planets in the framework of the jumping-Jupiter model. We found that some instability models are able to produce the correct values of Mercury’s eccentricity and inclination, provided that relativistic effects are included in the precession of Mercury’s perihelion. The orbital excitation is driven by the fast change of the normal oscillation modes of the system corresponding to the perihelion precession of Jupiter (for the eccentricity) and the nodal regression of Uranus (for the inclination).

  17. The Effect of Patellar Taping on Some Landing Characteristics During Counter Movement Jumps in Healthy Subjects

    PubMed Central

    Cámara, Jesús; Díaz, Francisco; Anza, María Soledad; Mejuto, Gaizka; Puente, Asier; Iturriaga, Gorka; Fernández, Juan-Ramón

    2011-01-01

    The aim of the present study was to determine the effect of patellar taping (PT) on landing characteristics of the vertical ground reaction force (VGRF) and on flight time during a counter movement jump (CMJ). Eleven healthy male subjects (age: 31.1 ± 4.2 years) volunteered for the study. Each subject performed six CMJs under two different jumping conditions: with PT and without PT (WPT). The order of the two conditions was randomized. All of the measured variables had fair-to-good reliability (intra-class correlation coefficient > 0.75). When we compared the PT and WPT groups, we did not find a significant difference in the magnitude of the first (F1) and second (F2) peaks of the VGRF. We also did not find a significant difference in the time to production of these peaks (T1 and T2), and the time to stabilization (TTS) (p < 0. 05). Furthermore, the flight time was similar in the two groups (0.475 ± 0.046 and 0.474 ± 0.056 s, respectively, for PT and WPT). These results suggest that PT does not jeopardize performance during CMJ. Furthermore, it also does not soften the VGRF generated during the landing, indicating that PT may be of limited utility in preventing injuries associated with this type of movement. Key points We investigated whether patellar taping interferes with athletic performance, as has been suggested by previous studies. We also explored the effect of patellar taping on the forces generated during the landing phase of counter movement jumps. Patellar taping had no effect on the flight time during counter movement jumps. Patellar taping also had no effect on the vertical ground reaction force variables measured during the landing phase of counter movement jumps. This information may be relevant to athletes and trainers who are concerned about the effects of patellar taping on performance. PMID:24149562

  18. Occurrence of fatigue during sets of static squat jumps performed at a variety of loads.

    PubMed

    Thomasson, Michael L; Comfort, Paul

    2012-03-01

    Research has identified that the optimal power load for static squat jumps (with no countermovement) is lower than the loads usually recommended for power training. Lower loads may permit the performance of additional repetitions before the onset of fatigue compared with heavier loads; therefore, the aim of this study was to determine the point of fatigue during squat jumps at various loads (0, 20, 40, 60% 1-repetition maximum [1RM]). Seventeen professional rugby league players performed sets of 6 squat jumps (with no countermovement), using 4 loading conditions (0, 20, 40, and 60% of 1RM back squat). Repeated measures analysis of variance revealed no significant differences (p > 0.05) in force, velocity, power, and displacement between repetitions, for the 0, 20, and 40% loading conditions. The 60% condition showed no significant difference (p > 0.05) in peak force between repetitions; however, velocity (1.12 + 0.10 and 1.18 + 0.11 m·s(-1)), power (3,385 + 343 and 3,617 + 396 W) and displacement (11.13 + 2.31 and 11.85 + 2.16 cm) were significantly (p < 0.02) lower during repetition 6 compared with repetition 2. These findings indicate that when performing squat jumps (with no countermovement) with a load <40% 1RM back squat, up to >6 repetitions can be completed without inducing fatigue and a minimum of 4-6 repetitions should be performed to achieve peak power output. When performing squat jumps (with no countermovement) with a load equal to the 60% 1RM only, 5 repetitions should be performed to minimize fatigue and ensure maintenance of velocity and power.

  19. The importance of maximal leg strength for female athletes when performing drop jumps.

    PubMed

    Barr, Matthew J; Nolte, Volker W

    2014-02-01

    A common suggestion is that a predetermined level of maximal leg strength is required before drop jump (DJ) training can begin. This study sought to examine the relationship between maximal squat strength (1 repetition maximum [RM]) and DJ performance in 15 female rugby players (n = 15). The subjects were tested for 1RM, countermovement jump, squat jump, and DJs from 0.24, 0.36, 0.48, 0.60, 0.72, and 0.84 m. Jump height (JH) was calculated for all jumps and relative peak eccentric force, relative peak concentric force, ground contact time (GCT), and reactive strength index were also calculated for DJs. Pearson correlations were used to examine the relationship between 1RM relative to body mass (BM) (1RM/BM) and JHs, reactive strength index, and GCT during DJs. The subjects were placed in a high strength (HS) or low strength (LS) group depending on whether or not their 1RM/BM was >1 or <1. The T-tests and 2-way analysis of variance (ANOVA) were used to compare the groups. A Fishers post hoc test was used for the ANOVA with significance set at p < 0.05. A large correlation between JH and 1RM/BM was shown at the 0.84-m dropping height (r = 0.56). A significant overall difference was found between the HS and LS groups for DJ JH with a post hoc analysis revealing a significant difference at the 0.84-m drop height (p = 0.029). It is likely beneficial for female athletes to achieve high levels of maximal leg strength if they are going to use high (>0.8-m) drop heights when performing DJs.

  20. Knee Control and Jump-Landing Technique in Young Basketball and Floorball Players.

    PubMed

    Leppänen, M; Pasanen, K; Kulmala, J-P; Kujala, U M; Krosshaug, T; Kannus, P; Perttunen, J; Vasankari, T; Parkkari, J

    2016-04-01

    Poor knee alignment is associated with increased loading of the joints, ligaments and tendons, and may increase the risk of injury. The study purpose was to compare differences in knee kinematics between basketball and floorball players during a vertical drop jump (VDJ) task. We wanted to investigate whether basketball players, whose sport includes frequent jump-landings, exhibited better knee control compared with floorball players, whose sport involves less jumping. Complete data was obtained from 173 basketball and 141 floorball players. Peak knee valgus and flexion angles during the VDJ were analyzed by 3D motion analysis.Larger knee valgus angles were observed among basketball players (- 3.2°, 95%CI -4.5 to - 2.0) compared with floorball players (- 0.9°, 95%CI -2.3 to 0.6) (P=0.022). Basketball players landed with a decreased peak knee flexion angle (83.1°, 95%CI 81.4 to 84.8) compared with floorball players (86.5°, 95%CI 84.6 to 88.4) (P=0.016). There were no significant differences in height, weight or BMI between basketball and floorball players. Female athletes exhibited significantly greater valgus angles than males. This study revealed that proper knee control during jump-landing does not seem to develop in young athletes simply by playing the sport, despite the fact that jump-landings occur frequently in practice and games. © Georg Thieme Verlag KG Stuttgart · New York.

  1. Peak distortion effects in analytical ion chromatography.

    PubMed

    Wahab, M Farooq; Anderson, Jordan K; Abdelrady, Mohamed; Lucy, Charles A

    2014-01-07

    The elution profile of chromatographic peaks provides fundamental understanding of the processes that occur in the mobile phase and the stationary phase. Major advances have been made in the column chemistry and suppressor technology in ion chromatography (IC) to handle a variety of sample matrices and ions. However, if the samples contain high concentrations of matrix ions, the overloaded peak elution profile is distorted. Consequently, the trace peaks shift their positions in the chromatogram in a manner that depends on the peak shape of the overloading analyte. In this work, the peak shapes in IC are examined from a fundamental perspective. Three commercial IC columns AS16, AS18, and AS23 were studied with borate, hydroxide and carbonate as suppressible eluents. Monovalent ions (chloride, bromide, and nitrate) are used as model analytes under analytical (0.1 mM) to overload conditions (10-500 mM). Both peak fronting and tailing are observed. On the basis of competitive Langmuir isotherms, if the eluent anion is more strongly retained than the analyte ion on an ion exchanger, the analyte peak is fronting. If the eluent is more weakly retained on the stationary phase, the analyte peak always tails under overload conditions regardless of the stationary phase capacity. If the charge of the analyte and eluent anions are different (e.g., Br(-) vs CO3(2-)), the analyte peak shapes depend on the eluent concentration in a more complex pattern. It was shown that there are interesting similarities with peak distortions due to strongly retained mobile phase components in other modes of liquid chromatography.

  2. Jumping on the Social Media Bandwagon

    ERIC Educational Resources Information Center

    Blakeslee, Lori

    2012-01-01

    Should a school district jump on the social media bandwagon? Yes! Social media provide a low-cost way to communicate school district priorities, influence decision makers, and tell its story without filters. Equally important, social media are where constituents are spending a lot of their time. With more than 800 million members, Facebook is an…

  3. Kinematic analysis of volleyball spike jump.

    PubMed

    Wagner, H; Tilp, M; von Duvillard, S P; Mueller, E

    2009-10-01

    The purpose of this study was to determine the influence of upper and lower extremity movements on the volleyball spike jump (SJ) and how this movement may differ from the standing vertical jumps due to its asymmetry. The 3-D kinematics of body segments were measured in 16 experienced volleyball players with a VICON motion capture system. The jump heights (JH) of counter-movement (CM) and SJ were determined utilizing a force platform. A significant correlation was found between the JH during the SPJ and the maximal horizontal velocity of the center of mass (CoM) (r=0.71, p=0.002), the minimum height of the CoM (r=-0.68, p=0.004), the JH during CMJ (r=0.66, p=0.006) and SJ (r=0.74, p=0.001), the range of movement of right knee flexion-extension (r=0.76, p=0.001) and the angular velocity of left shoulder hyperextension (r=0.72, p=0.002). The asymmetry of the SJ revealed differences in angles, angular velocities of the right and left legs and arms, and a significant difference (p=0.001) between the distances of the left and right foot center to the CoM. Results of our study suggest the importance of optimal approach technique to reach a maximal JH in the volleyball SJ. The SJ movement is influenced by general jumping ability. Georg Thieme Verlag KG Stuttgart New York.

  4. Jumping Rope at Day of Play

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Sarah Dastugue, 11, leaps in the air as Libby Knox, 9, swings a jump rope. The children were participants in Nickelodeon's Worldwide Day of Play celebration at Stennis Space Center (SSC) on Oct. 1. On the day of the event, children all over the world participate in physical activities as part of the celebration.

  5. Jumping the Alligators in the Ditch.

    ERIC Educational Resources Information Center

    Barber, Rims

    Poor black young people in rural Mississippi contemplate their schooling with the same feelings as their friends who dare to jump the local ditches filled with alligators: the odds are against escaping the alligators, and the advantages of getting to the far side are not very apparent. Living in conditions of extreme poverty, these young people…

  6. Jumping Genes: The Transposable DNAs of Bacteria.

    ERIC Educational Resources Information Center

    Berg, Claire M.; Berg, Douglas E.

    1984-01-01

    Transposons are transposable elements that carry genes for antibiotic resistance. Provides background information on the structure and organization of these "jumping genes" in bacteria. Also describes the use of transposons in tagging genes and lists pertinent references and resource materials. (DH)

  7. Injuries resulting from bungee-cord jumping.

    PubMed

    Hite, P R; Greene, K A; Levy, D I; Jackimczyk, K

    1993-06-01

    A 19-year-old woman sustained a nonfatal hanging injury and a 28-year-old man sustained a unilateral locked facet with resultant quadriplegia as a result of bungee jumping. Injuries due to this sport have not been reported previously.

  8. Jumping-droplet electrostatic energy harvesting

    NASA Astrophysics Data System (ADS)

    Miljkovic, Nenad; Preston, Daniel J.; Enright, Ryan; Wang, Evelyn N.

    2014-07-01

    Micro- and nanoscale wetting phenomena have been an active area of research due to its potential for improving engineered system performance involving phase change. With the recent advancements in micro/nanofabrication techniques, structured surfaces can now be designed to allow condensing coalesced droplets to spontaneously jump off the surface due to the conversion of excess surface energy into kinetic energy. In addition to being removed at micrometric length scales (˜10 μm), jumping water droplets also attain a positive electrostatic charge (˜10-100 fC) from the hydrophobic coating/condensate interaction. In this work, we take advantage of this droplet charging to demonstrate jumping-droplet electrostatic energy harvesting. The charged droplets jump between superhydrophobic copper oxide and hydrophilic copper surfaces to create an electrostatic potential and generate power during formation of atmospheric dew. We demonstrated power densities of ˜15 pW/cm2, which, in the near term, can be improved to ˜1 μW/cm2. This work demonstrates a surface engineered platform that promises to be low cost and scalable for atmospheric energy harvesting and electric power generation.

  9. Understanding the Physics of Bungee Jumping

    ERIC Educational Resources Information Center

    Heck, Andre; Uylings, Peter; Kedzierska, Ewa

    2010-01-01

    Changing mass phenomena like the motion of a falling chain, the behaviour of a falling elastic bar or spring, and the motion of a bungee jumper surprise many a physicist. In this article we discuss the first phase of bungee jumping, when the bungee jumper falls, but the bungee rope is still slack. In instructional material this phase is often…

  10. Jumping Rope at Day of Play

    NASA Image and Video Library

    2005-10-05

    Sarah Dastugue, 11, leaps in the air as Libby Knox, 9, swings a jump rope. The children were participants in Nickelodeon's Worldwide Day of Play celebration at Stennis Space Center (SSC) on Oct. 1. On the day of the event, children all over the world participate in physical activities as part of the celebration.

  11. Jumping Genes: The Transposable DNAs of Bacteria.

    ERIC Educational Resources Information Center

    Berg, Claire M.; Berg, Douglas E.

    1984-01-01

    Transposons are transposable elements that carry genes for antibiotic resistance. Provides background information on the structure and organization of these "jumping genes" in bacteria. Also describes the use of transposons in tagging genes and lists pertinent references and resource materials. (DH)

  12. Project Broad Jump: A Leap Into Learning

    ERIC Educational Resources Information Center

    Fleming, Douglas

    1972-01-01

    Project Broad Jump is a New York-based education program for some 600 youngsters from urban areas, in the third through tenth grades. The basic concept of the program is that academic opportunities are not accessible to many inner-city youth, whereas Head Start and Follow Through help pre-third graders, and Upward Bound helps high school students.…

  13. Jumping Rope at Day of Play

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Sarah Dastugue, 11, leaps in the air as Libby Knox, 9, swings a jump rope. The children were participants in Nickelodeon's Worldwide Day of Play celebration at Stennis Space Center (SSC) on Oct. 1. On the day of the event, children all over the world participate in physical activities as part of the celebration.

  14. Understanding the Physics of Bungee Jumping

    ERIC Educational Resources Information Center

    Heck, Andre; Uylings, Peter; Kedzierska, Ewa

    2010-01-01

    Changing mass phenomena like the motion of a falling chain, the behaviour of a falling elastic bar or spring, and the motion of a bungee jumper surprise many a physicist. In this article we discuss the first phase of bungee jumping, when the bungee jumper falls, but the bungee rope is still slack. In instructional material this phase is often…

  15. Jumping on the Social Media Bandwagon

    ERIC Educational Resources Information Center

    Blakeslee, Lori

    2012-01-01

    Should a school district jump on the social media bandwagon? Yes! Social media provide a low-cost way to communicate school district priorities, influence decision makers, and tell its story without filters. Equally important, social media are where constituents are spending a lot of their time. With more than 800 million members, Facebook is an…

  16. Safety assessment of jumps in ski racing.

    PubMed

    Schindelwig, K; Reichl, W; Kaps, P; Mössner, M; Nachbauer, W

    2015-12-01

    The influence of important parameters on the flight trajectory for jumps in downhill World Cup races was investigated. To quantify the impact injury risk at landing, the parameter equivalent landing height (ELH) was introduced, which considered a variable slope inclination during the landing movement. Altogether, 145 runs at four different jumps in World Cup races and trainings were recorded and analyzed. A simulation model was developed to predict the flight phase of the skier. Drag and lift areas were selected by parameter identification to fit the simulation trajectory to the two-dimensional data from the video analysis. The maximum values of the ELH which can be absorbed with muscle force was taken from the study of Minetti et al. for elite female and male ski racers. A sensitivity analysis based on the four jumps showed that ELH is mainly influenced by takeoff angle, takeoff speed, and the steepness of the landing surface. With the help of the developed simulation software, it should be possible to predict the ELH for jumps in advance. In case of an excessive ELH, improvements can be made by changing the takeoff inclination or the approach speed.

  17. Hypohydration Reduces Vertical Ground Reaction Impulse But Not Jump Height

    DTIC Science & Technology

    2010-01-01

    jumping plays a major role, such as basketball and volleyball (Hoffman et al. 1995). The precise balance between losses in body mass and losses in strength...code) 2010 Journal Article-Eur. Journal of Applied Physiology Hypohydration Reduces Vertical Ground Reaction Impulse But Not Jump Height S.N...study examined vertical jump performance using a force platform and weighted vest to determine why hypohydration (~4% body mass) does not improve jump

  18. Dual time-resolved temperature-jump fluorescence and infrared spectroscopy for the study of fast protein dynamics

    NASA Astrophysics Data System (ADS)

    Davis, Caitlin M.; Reddish, Michael J.; Dyer, R. Brian

    2017-05-01

    Time-resolved temperature-jump (T-jump) coupled with fluorescence and infrared (IR) spectroscopy is a powerful technique for monitoring protein dynamics. Although IR spectroscopy of the polypeptide amide I mode is more technically challenging, it offers complementary information because it directly probes changes in the protein backbone, whereas, fluorescence spectroscopy is sensitive to the environment of specific side chains. With the advent of widely tunable quantum cascade lasers (QCL) it is possible to efficiently probe multiple IR frequencies with high sensitivity and reproducibility. Here we describe a dual time-resolved T-jump fluorescence and IR spectrometer and its application to study protein folding dynamics. A Q-switched Ho:YAG laser provides the T-jump source for both time-resolved IR and fluorescence spectroscopy, which are probed by a QCL and Ti:Sapphire laser, respectively. The Ho:YAG laser simultaneously pumps the time-resolved IR and fluorescence spectrometers. The instrument has high sensitivity, with an IR absorbance detection limit of < 0.2 mOD and a fluorescence sensitivity of 2% of the overall fluorescence intensity. Using a computer controlled QCL to rapidly tune the IR frequency it is possible to create a T-jump induced difference spectrum from 50 ns to 0.5 ms. This study demonstrates the power of the dual time-resolved T-jump fluorescence and IR spectroscopy to resolve complex folding mechanisms by complementary IR absorbance and fluorescence measurements of protein dynamics.

  19. Finite dispersal of a separative nepheloid plume by an internal hydraulic jump in a tropical mountainous river estuary

    NASA Astrophysics Data System (ADS)

    Wu, Jiaxue; Ametistova, Lioudmila; Heron, Malcolm; Lemckert, Charles J.; Kalangi, Patrice

    2006-11-01

    This paper investigates the dynamics of an internal hydraulic jump in a river plume and associated suspended sediment dispersal. Field investigations were undertaken into the river plume generated by the Herbert River, Australia, following a moderate flood event induced by Cyclone Fritz in 2004. The forced plume experiences an abrupt transition from supercritical to subcritical via an internal hydraulic jump, as defined by a mode-1 internal Froude number computed using the phase speeds from the Taylor-Goldstein equation. The hydraulic theory of a two-layer stratified flow was used to identify the plume shape and the mechanical energy loss within the jump. The hydraulic jump energy loss is primarily transferred to the buoyancy-driven potential energy, uplifting the river plume. Intense stratification decreases the bottom stress, damping the resuspension. Therefore, a separative nepheloid dispersal system occurs at the jump section. Both the upper and lower nepheloid flows are confined to the inner shelf, but have different dispersal behaviors and mechanisms. The upper nepheloid flow, which is primarily controlled by advection and settling, satisfies an exponential decay law of the total suspended sediment concentrations versus the offshore distance. The lower nepheloid flow dominated by deposition is detached seaward near the lift-off point of the river plume. A turbidity front associated with the jump may accumulate a large quantity of suspended sediments, enhancing sediment release from the river plume. These findings will promote in-depth understanding of both the cross-shelf sediment dispersal and muddy deposit on the shelf.

  20. Vertical Jump and Leg Power Norms for Young Adults

    ERIC Educational Resources Information Center

    Patterson, David D.; Peterson, D. Fred

    2004-01-01

    Medical students and their spouses (N = 724) served as participants to create norm-referenced vertical jump values for active, healthy people ages 21-30. All tests were conducted and measured by the same individual during a campus fitness evaluation using a Vertec[TM] apparatus. Jump height was measured to the nearest 0.5 in. Mean jump height was…

  1. Costs and benefits of larval jumping behaviour of Bathyplectes anurus

    NASA Astrophysics Data System (ADS)

    Saeki, Yoriko; Tani, Soichiro; Fukuda, Katsuto; Iwase, Shun-ichiro; Sugawara, Yuma; Tuda, Midori; Takagi, Masami

    2016-02-01

    Bathyplectes anurus, a parasitoid of the alfalfa weevils, forms a cocoon in the late larval stage and exhibits jumping behaviour. Adaptive significance and costs of the cocoon jumping have not been thoroughly studied. We hypothesised that jumping has the fitness benefits of enabling habitat selection by avoiding unfavourable environments. We conducted laboratory experiments, which demonstrated that jumping frequencies increased in the presence of light, with greater magnitudes of temperature increase and at lower relative humidity. In addition, when B. anurus individuals were allowed to freely jump in an arena with a light gradient, more cocoons were found in the shady area, suggesting microhabitat selection. In a field experiment, mortality of cocoons placed in the sun was significantly higher than for cocoons placed in the shade. B. anurus cocoons respond to environmental stress by jumping, resulting in habitat selection. In the presence of potential predators (ants), jumping frequencies were higher than in the control (no ant) arenas, though jumping frequencies decreased after direct contact with the predators. Body mass of B. anurus cocoons induced to jump significantly decreased over time than cocoons that did not jump, suggesting a cost to jumping. We discuss the benefits and costs of jumping behaviour and potential evolutionary advantages of this peculiar trait, which is present in a limited number of species.

  2. Instruction of jump-landing technique using videotape feedback: altering lower extremity motion patterns.

    PubMed

    Oñate, James A; Guskiewicz, Kevin M; Marshall, Stephen W; Giuliani, Carol; Yu, Bing; Garrett, William E

    2005-06-01

    Anterior cruciate ligament injury prevention programs have used videotapes of jump-landing technique as a key instructional component to improve landing performance. All videotape feedback model groups will increase knee flexion angles at initial contact and overall knee flexion motion and decrease peak vertical ground reaction forces and peak proximal anterior tibial shear forces to a greater extent than will a nonfeedback group. The secondary hypothesis is that the videotape feedback using the combination of the expert and self models will create the greatest change in each variable. Controlled laboratory study. Knee kinematics and kinetics of college-aged recreational athletes randomly placed in 3 different videotape feedback model groups (expert only, self only, combination of expert and self) and a nonfeedback group were collected while participants performed a basketball jump-landing task on 3 testing occasions. All feedback groups significantly increased knee angular displacement flexion angles [F(6,70) = 8.03, P = .001] and decreased peak vertical ground reaction forces [F(6,78) = 2.68, P = .021] during performance and retention tests. The self and combination groups significantly increased knee angular displacement flexion angles more than the control group did; the expert model group did not change significantly more than the control group did. All feedback groups and the nonfeedback group significantly reduced peak vertical forces across performance and retention tests. There were no statistically significant changes in knee flexion angle at initial ground contact (P = .111) and peak proximal anterior tibial shear forces (P = .509) for both testing sessions for each group. The use of self or combination videotape feedback is most useful for increasing knee angular displacement flexion angles and reducing peak vertical forces during landing. The use of self or combination modeling is more effective than is expert-only modeling for the implementation of

  3. The Effects of Aquatic Plyometric Training on Repeated Jumps, Drop Jumps and Muscle Damage.

    PubMed

    Jurado-Lavanant, A; Alvero-Cruz, J R; Pareja-Blanco, F; Melero-Romero, C; Rodríguez-Rosell, D; Fernandez-Garcia, J C

    2015-09-22

    The purpose of this study was to compare the effects of land- vs. aquatic based plyometric training programs on the drop jump, repeated jump performance and muscle damage. Sixty-five male students were randomly assigned to one of 3 groups: aquatic plyometric training group (APT), plyometric training group (PT) and control group (CG). Both experimental groups trained twice a week for 10 weeks performing the same number of sets and total jumps. The following variables were measured prior to, halfway through and after the training programs: creatine kinase (CK) concentration, maximal height during a drop jump from the height of 30 (DJ30) and 50 cm (DJ50), and mean height during a repeated vertical jump test (RJ). The training program resulted in a significant increase (P<0.01-0.001) in RJ, DJ30, and DJ50 for PT, whereas neither APT nor CG reached any significant improvement APT showed likely/possibly improvements on DJ30 and DJ50, respectively. Greater intra-group Effect Size in CK was found for PT when compared to APT. In conclusion, although APT seems to be a safe alternative method for reducing the stress produced on the musculoskeletal system by plyometric training, PT produced greater gains on reactive jumps performance than APT.

  4. Functional evolution of jumping in frogs: Interspecific differences in take-off and landing.

    PubMed

    Reilly, Stephen M; Montuelle, Stephane J; Schmidt, André; Krause, Cornelia; Naylor, Emily; Essner, Richard L

    2016-03-01

    Ancestral frogs underwent anatomical shifts including elongation of the hindlimbs and pelvis and reduction of the tail and vertebral column that heralded the transition to jumping as a primary mode of locomotion. Jumping has been hypothesized to have evolved in a step-wise fashion with basal frogs taking-off with synchronous hindlimb extension and crash-landing on their bodies, and then their limbs move forward. Subsequently, frogs began to recycle the forelimbs forward earlier in the jump to control landing. Frogs with forelimb landing radiated into many forms, locomotor modes, habitats, and niches with controlled landing thought to improve escape behavior. While the biology of take-off behavior has seen considerable study, interspecific comparisons of take-off and landing behavior are limited. In order to understand the evolution of jumping and controlled landing in frogs, data are needed on the movements of the limbs and body across an array of taxa. Here, we present the first description and comparison of kinematics of the hindlimbs, forelimbs and body during take-off and landing in relation to ground reaction forces in four frog species spanning the frog phylogeny. The goal of this study is to understand what interspecific differences reveal about the evolution of take-off and controlled landing in frogs. We provide the first comparative description of the entire process of jumping in frogs. Statistical comparisons identify both homologous behaviors and significant differences among species that are used to map patterns of trait evolution and generate hypotheses regarding the functional evolution of take-off and landing in frogs.

  5. Charmonium's K2 Peak

    SciTech Connect

    Llanes-Estrada, Felipe J.; /Madrid U.

    2005-07-11

    The newly reported Y(4260) becomes the second most massive state in the charmonium family. We argue that it displaces the {psi}(4415) as the (largely) 4s vector charmonium state, recall s-d wave interference to explain the lack of a signal in e{sup -}e{sup +} {yields} hadrons and suggest some further study avenues that can exclude exotic meson assignments. The absence of a J/{psi} KK mode can be understood, beyond phase space suppression, to be a consequence of chiral symmetry. We also provide a model calculation in this sector showing that, although forcing the fit somewhat (which suggests a small sea quark wavefunction component), the state can be incorporated in a standard scheme.

  6. Changes in Indirect Markers of Muscle Damage and Tendons After Daily Drop Jumping Exercise with Rapid Load Increase

    PubMed Central

    Paleckis, Vidas; Mickevičius, Mantas; Snieckus, Audrius; Streckis, Vytautas; Pääsuke, Mati; Rutkauskas, Saulius; Steponavičiūtė, Rasa; Skurvydas, Albertas; Kamandulis, Sigitas

    2015-01-01

    The aim of this study was to assess changes in indirect markers of muscle damage and type I collagen degradation, as well as, patellar and Achilles tendon morphological differences during nine daily drop-jumps sessions with constant load alternated with rapid increases in load to test the hypothesis that frequent drop-jump training results in negative muscular and tendon adaptation. Young men (n = 9) performed daily drop jump workouts with progression every 3 days in terms of number of jumps, platform height and squat amplitude. Voluntary and electrically evoked knee extensor torque, muscle soreness, blood plasma creatine kinase (CK) activity and carboxyterminal cross-linked telopeptide (ICTP), patellar and Achilles tendon thickness and cross-sectional area (CSA) were assessed at different time points during the training period and again on days 1, 3, 10 and 17 after the training. The findings were as follows: (1) steady decline in maximal muscle strength with major recovery within 24 hours after the first six daily training sessions; (2) larger decline in electrically induced muscle torque and prolonged recovery during last three training sessions; (3) increase in patellar and Achilles tendons CSA without change in thickness towards the end of training period; (4) increase in jump height but not in muscle strength after whole training period. Our findings suggest that frequent drop-jump sessions with constant load alternated with rapid increases in load do not induce severe muscle damage or major changes in tendons, nonetheless, this type of loading is not advisable for muscle strength improvement. Key points Frequent drop jump training induces activation mode dependent muscle torque depression late in the training period. No significant changes in the thickness of patellar and Achilles tendons are observed during frequent training, while CSA increases towards the end of training period. Longitudinal effect for jump height but not for muscle strength is evident

  7. Changes in Indirect Markers of Muscle Damage and Tendons After Daily Drop Jumping Exercise with Rapid Load Increase.

    PubMed

    Paleckis, Vidas; Mickevičius, Mantas; Snieckus, Audrius; Streckis, Vytautas; Pääsuke, Mati; Rutkauskas, Saulius; Steponavičiūtė, Rasa; Skurvydas, Albertas; Kamandulis, Sigitas

    2015-12-01

    The aim of this study was to assess changes in indirect markers of muscle damage and type I collagen degradation, as well as, patellar and Achilles tendon morphological differences during nine daily drop-jumps sessions with constant load alternated with rapid increases in load to test the hypothesis that frequent drop-jump training results in negative muscular and tendon adaptation. Young men (n = 9) performed daily drop jump workouts with progression every 3 days in terms of number of jumps, platform height and squat amplitude. Voluntary and electrically evoked knee extensor torque, muscle soreness, blood plasma creatine kinase (CK) activity and carboxyterminal cross-linked telopeptide (ICTP), patellar and Achilles tendon thickness and cross-sectional area (CSA) were assessed at different time points during the training period and again on days 1, 3, 10 and 17 after the training. The findings were as follows: (1) steady decline in maximal muscle strength with major recovery within 24 hours after the first six daily training sessions; (2) larger decline in electrically induced muscle torque and prolonged recovery during last three training sessions; (3) increase in patellar and Achilles tendons CSA without change in thickness towards the end of training period; (4) increase in jump height but not in muscle strength after whole training period. Our findings suggest that frequent drop-jump sessions with constant load alternated with rapid increases in load do not induce severe muscle damage or major changes in tendons, nonetheless, this type of loading is not advisable for muscle strength improvement. Key pointsFrequent drop jump training induces activation mode dependent muscle torque depression late in the training period.No significant changes in the thickness of patellar and Achilles tendons are observed during frequent training, while CSA increases towards the end of training period.Longitudinal effect for jump height but not for muscle strength is evident after

  8. High-Intensity Jump Training Is Tolerated during 60 Days of Bed Rest and Is Very Effective in Preserving Leg Power and Lean Body Mass: An Overview of the Cologne RSL Study

    PubMed Central

    Kümmel, Jakob; Mulder, Edwin; Gollhofer, Albert; Frings-Meuthen, Petra; Gruber, Markus

    2017-01-01

    Purpose Space agencies are looking for effective and efficient countermeasures for the degrading effects of weightlessness on the human body. The aim of this study was to assess the effects of a novel jump exercise countermeasure during bed rest on vitals, body mass, body composition, and jump performance. Methods 23 male participants (29±6 years, 181±6 cm, 77±7 kg) were confined to a bed rest facility for 90 days: a 15-day ambulatory measurement phase, a 60-day six-degree head-down-tilt bed rest phase (HDT), and a 15-day ambulatory recovery phase. Participants were randomly allocated to the jump training group (JUMP, n = 12) or the control group (CTRL, n = 11). A typical training session consisted of 4x10 countermovement jumps and 2x10 hops in a sledge jump system. The training group had to complete 5–6 sessions per week. Results Peak force for the reactive hops (3.6±0.4 kN) as well as jump height (35±4 cm) and peak power (3.1±0.2 kW) for the countermovement jumps could be maintained over the 60 days of HDT. Lean body mass decreased in CTRL but not in JUMP (-1.6±1.9 kg and 0±1.0 kg, respectively, interaction effect p = 0.03). Resting heart rate during recovery was significantly increased for CTRL but not for JUMP (interaction effect p<0.001). Conclusion Participants tolerated the near-daily high-intensity jump training and maintained high peak forces and high power output during 60 days of bed rest. The countermeasure was effective in preserving lean body mass and partly preventing cardiac deconditioning with only several minutes of training per day. PMID:28081223

  9. The Effect of an Altitude Training Camp on Swimming Start Time and Loaded Squat Jump Performance.

    PubMed

    García-Ramos, Amador; Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Calderón, Carmen; Bonitch-Góngora, Juan; Tomazin, Katja; Strumbelj, Boro; Strojnik, Vojko; Feriche, Belén

    2016-01-01

    This study evaluated the influence of an altitude training (AT) camp on swimming start time and loaded squat jump performance. To accomplish this goal, 13 international swimmers (8 women, 5 men) were allocated to both the control (Sea Level Training, SLT) and experimental conditions (AT, 2320 m above sea level) that were separated by a one year period. All tests (15 m freestyle swimming start and loaded squat jumps with additional loads of 25%, 50%, 75%, and 100% of swimmers' body weight) were performed before and after a concurrent 3-week strength and endurance training program prescribed by the national coach. Following the SLT camp, significant impairments in swimming start times to 10 (+3.1%) and 15 m (+4.0%) were observed (P < 0.05), whereas no significant changes for the same distances were detected following the AT camp (-0.89%; P > 0.05). Trivial changes in peak velocity were obtained during the loaded squat jump after both training periods (effect sizes: < 0.20). Based on these results we can conclude that a traditional training high-living high strategy concurrent training of 3 weeks does not adversely affect swimming start time and loaded squat jump performance in high level swimmers, but further studies are necessary to assess the effectiveness of power-oriented resistance training in the development of explosive actions.

  10. Effects of the rider on the linear kinematics of jumping horses.

    PubMed

    Powers, Pippa; Harrison, Andrew

    2002-07-01

    This study examined the effects of the rider on the linear projectile kinematics of show-jumping horses. SVHS video recordings (50 Hz) of eight horses jumping a vertical fence 1 m high were used for the study. Horses jumped the fence under two conditions: loose (no rider or tack) and ridden. Recordings were digitised using Peak Motus. After digitising the sequences, each rider's digitised data were removed from the ridden horse data so that three conditions were examined: loose, ridden (including the rider's data) and riderless (rider's data removed). Repeated measures ANOVA revealed significant differences between ridden and loose conditions for CG height at take-off (p < 0.001), CG distance to the fence at take-off (p = 0.001), maximum CG during the suspension phase (p < 0.001), CG position over the centre of the fence (p < 0.001), CG height at landing (p < 0.001), and vertical velocity at take-off (p < 0.001). The results indicated that the rider's effect on jumping horses was primarily due to behavioural changes in the horses motion (resulting from the rider's instruction), rather than inertial effects (due to the positioning of the rider on the horse). These findings have implications for the coaching of riders and horses.

  11. Throwing velocity and jump height in female water polo players: performance predictors.

    PubMed

    McCluskey, Lisa; Lynskey, Sharon; Leung, Chak Kei; Woodhouse, Danielle; Briffa, Kathy; Hopper, Diana

    2010-03-01

    Throwing velocity and vertical jumping ability are essential components for shooting and passing in water polo. The purpose of this study was to determine whether there is a relationship between throwing velocity and water jump height in highly skilled female water polo players. Throwing velocity and head height at ball release were measured in twenty-two female players (age 20.41 years (6.16); weight 68.28 kg (8.87)) with two 50 frames per second cameras while shooting at goal. Water jump height was also measured with a modified Yardstick device. Multiple regression analyses showed that peak lower limb power was the most significant predictor of maximal velocity. Power alone accounted for 62% of the variance in maximum velocity (p<0.001). Once power was entered into the model none of the other physical characteristics (lean mass, fat mass, land jump height and anthropometry) made a significant contribution to throwing velocity. After controlling for the effect of power, head height at ball release accounted for an additional significant proportion of the variance in maximal velocity (R(2) change 7%; p=0.049). Lower body power was a significant predictor of higher throwing velocity in highly skilled female water polo players. Players with relatively higher underlying levels of lower limb power who are able to generate greater elevation out of the water are able to throw the ball faster.

  12. The Effect of an Altitude Training Camp on Swimming Start Time and Loaded Squat Jump Performance

    PubMed Central

    Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Calderón, Carmen; Bonitch-Góngora, Juan; Tomazin, Katja; Strumbelj, Boro; Strojnik, Vojko; Feriche, Belén

    2016-01-01

    This study evaluated the influence of an altitude training (AT) camp on swimming start time and loaded squat jump performance. To accomplish this goal, 13 international swimmers (8 women, 5 men) were allocated to both the control (Sea Level Training, SLT) and experimental conditions (AT, 2320 m above sea level) that were separated by a one year period. All tests (15 m freestyle swimming start and loaded squat jumps with additional loads of 25%, 50%, 75%, and 100% of swimmers’ body weight) were performed before and after a concurrent 3-week strength and endurance training program prescribed by the national coach. Following the SLT camp, significant impairments in swimming start times to 10 (+3.1%) and 15 m (+4.0%) were observed (P < 0.05), whereas no significant changes for the same distances were detected following the AT camp (-0.89%; P > 0.05). Trivial changes in peak velocity were obtained during the loaded squat jump after both training periods (effect sizes: < 0.20). Based on these results we can conclude that a traditional training high—living high strategy concurrent training of 3 weeks does not adversely affect swimming start time and loaded squat jump performance in high level swimmers, but further studies are necessary to assess the effectiveness of power-oriented resistance training in the development of explosive actions. PMID:27467760

  13. In vivo muscle force and muscle power during near-maximal frog jumps.

    PubMed

    Moo, Eng Kuan; Peterson, Daniel R; Leonard, Timothy R; Kaya, Motoshi; Herzog, Walter

    2017-01-01

    Frogs' outstanding jumping ability has been associated with a high power output from the leg extensor muscles. Two main theories have emerged to explain the high power output of the frog leg extensor muscles, either (i) the contractile conditions of all leg extensor muscles are optimized in terms of muscle length and speed of shortening, or (ii) maximal power is achieved through a dynamic catch mechanism that uncouples fibre shortening from the corresponding muscle-tendon unit shortening. As in vivo instantaneous power generation in frog hind limb muscles during jumping has never been measured directly, it is hard to distinguish between the two theories. In this study, we determined the instantaneous variable power output of the plantaris longus (PL) of Lithobates pipiens (also known as Rana pipiens), by directly measuring the in vivo force, length change, and speed of muscle and fibre shortening in near maximal jumps. Fifteen near maximal jumps (> 50cm in horizontal distance) were analyzed. High instantaneous peak power in PL (536 ± 47 W/kg) was achieved by optimizing the contractile conditions in terms of the force-length but not the force-velocity relationship, and by a dynamic catch mechanism that decouples fascicle shortening from muscle-tendon unit shortening. We also found that the extra-muscular free tendon likely amplifies the peak power output of the PL by modulating fascicle shortening length and shortening velocity for optimum power output, but not by releasing stored energy through recoiling as the tendon only started recoiling after peak PL power had been achieved.

  14. In vivo muscle force and muscle power during near-maximal frog jumps

    PubMed Central

    Leonard, Timothy R.; Kaya, Motoshi; Herzog, Walter

    2017-01-01

    Frogs’ outstanding jumping ability has been associated with a high power output from the leg extensor muscles. Two main theories have emerged to explain the high power output of the frog leg extensor muscles, either (i) the contractile conditions of all leg extensor muscles are optimized in terms of muscle length and speed of shortening, or (ii) maximal power is achieved through a dynamic catch mechanism that uncouples fibre shortening from the corresponding muscle-tendon unit shortening. As in vivo instantaneous power generation in frog hind limb muscles during jumping has never been measured directly, it is hard to distinguish between the two theories. In this study, we determined the instantaneous variable power output of the plantaris longus (PL) of Lithobates pipiens (also known as Rana pipiens), by directly measuring the in vivo force, length change, and speed of muscle and fibre shortening in near maximal jumps. Fifteen near maximal jumps (> 50cm in horizontal distance) were analyzed. High instantaneous peak power in PL (536 ± 47 W/kg) was achieved by optimizing the contractile conditions in terms of the force-length but not the force-velocity relationship, and by a dynamic catch mechanism that decouples fascicle shortening from muscle-tendon unit shortening. We also found that the extra-muscular free tendon likely amplifies the peak power output of the PL by modulating fascicle shortening length and shortening velocity for optimum power output, but not by releasing stored energy through recoiling as the tendon only started recoiling after peak PL power had been achieved. PMID:28282405

  15. Fatigue Alters Landing Shock Attenuation During a Single-Leg Vertical Drop Jump

    PubMed Central

    Tamura, Akihiro; Akasaka, Kiyokazu; Otsudo, Takahiro; Sawada, Yutaka; Okubo, Yu; Shiozawa, Jyunya; Toda, Yuka; Yamada, Kaori

    2016-01-01

    Background: Landings in fatigue conditions are considered to be one of the factors that cause noncontact anterior cruciate ligament (ACL) injury. Additionally, it is known that fatigue alters lower extremity landing strategies and decreases the ability to attenuate shock during landing. Purpose: To determine characteristics of knee kinematics and shock attenuation during the landing phase of a single-leg vertical drop jump in a fatigued condition. The hypothesis was that knee kinematics during the landing phase of a single-leg vertical drop jump would demonstrate a significant difference between before and after fatigue. Study Design: Controlled laboratory study. Methods: Thirty-four college females participated in this experiment. They were randomly assigned to either the fatigue (n = 17) or control group (n = 17). The fatigue group performed the single-leg vertical drop jump before and after the fatigue protocol, which was performed on a bike ergometer. Knee kinematics data were obtained from the 3-dimensional motion analysis system. The ratio of each variable (%) was calculated, comparing the pre- to postfatigue protocol. Unpaired t tests were used to compare changes in kinematic variables between the fatigue-induced group and control group. Results: Peak knee flexion angular velocity increased significantly in the fatigue group (106.1% ± 8.0%) in comparison with the control group (100.7% ± 6.6%) (P < .05). However, peak knee flexion angle and acceleration had no differences between each group. Peak knee adduction/abduction angle, velocity, and acceleration also had no differences between each group. Conclusion: Fatigue decreased the ability to attenuate shock by increasing angular velocity in the direction of knee flexion during single-leg drop jump landing. These findings indicate the need to evaluate the ability to attenuate shock by measuring knee flexion angular velocity when fatigue is considered. Clinical Relevance: Measuring knee angular velocity

  16. DESIGN OF A FAST CHROMATICITY JUMP IN RHIC.

    SciTech Connect

    MONTAG,C.KEWISCH,J.BRUNO,D.GANETIS,G.LOUIE, W.

    2003-05-12

    During transition crossing in the .Relativistic Heavy Ion Collider (RHIC), chromaticities have to change sign. This sign change is partially accomplished by the {gamma}{sub t} quadrupole jump; however, the resulting chromaticity jump is only {Delta}{xi}{sub x} = 2.1 in the horizontal and {Delta}{xi}{sub y} = 2.4 in the vertical plane. To increase the jump height, a dedicated chromaticity jump scheme has been designed, consisting of fast power supplies connected to six sextupoles per ring, which is capable of providing a chromaticity jump of {Delta}{xi} = 6.

  17. Jump conditions for Maxwell equations and their consequences

    NASA Astrophysics Data System (ADS)

    Satapathy, Sikhanda; Hsieh, Kuota

    2013-01-01

    We derived the jump conditions for Faraday's induction law at the interface of two contacting bodies in both Eulerian and Lagrangian descriptions. An algorithm to implement the jump conditions in the potential formulation of Maxwell equation is presented. Calculations show that the use of the correct jump conditions leads to good agreement with experimental data, whereas the use of incorrect jump conditions can lead to severe inaccuracies in the computational results. Our derivation resolves the jump condition discrepancy found in the literature and is validated with experimental results.

  18. Simple jumping process with memory: Transport equation and diffusion

    NASA Astrophysics Data System (ADS)

    Kamińska, A.; Srokowski, T.

    2004-06-01

    We present a stochastic jumping process, defined in terms of jump-size probability density and jumping rate, which is a generalization of the well-known kangaroo process. The definition takes into account two process values: after and before the jump. Therefore, the process is able to preserve memory about its previous values. It possesses a simple stationary limit. Its master equation is interpreted as the kinetic equation with variable collision rate. The process can be easily applied to model systems which relax to distributions other than Maxwellian. The case of a constant jumping rate corresponds to the diffusion process, either normal or ballistic.

  19. Kitt Peak Observes Comet

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The Kitt Peak National Observatory's 2.1-meter telescope observed comet Tempel 1 on April 11, 2005, when the comet was near its closest approach to the Earth. A pinkish dust jet is visible to the southwest, with the broader neutral gas coma surrounding it. North is up, East is to the left, and the field of view is about 80,000 km (50,000 miles) wide. The Sun was almost directly behind the observer at this time. The red, green and blue bars in the background are stars that moved between the individual images.

    This pseudo-color picture was created by combining three black and white images obtained with different filters. The images were obtained with the HB Narrowband Comet Filters, using CN (3870 A - shown in blue), C2 (5140 A - shown in green) and RC (7128 A - shown in red). The CN and C2 filters capture different gas species (along with the underlying dust) while the RC filter captures just the dust.

  20. Reductions in Sprint Paddling Ability and Countermovement Jump Performance After Surfing Training.

    PubMed

    Secomb, Josh L; Sheppard, Jeremy M; Dascombe, Ben J

    2015-07-01

    The present study aimed to determine whether any meaningful change in a surfer's sprint paddling ability and countermovement jump (CMJ) performance developed after a 2-hour surfing training session and also whether any physical demands of the surfing session were related to the resultant changes in the capacities. Fifteen competitive male surfing athletes (age, 22.1 ± 3.9 years; height, 175.4 ± 6.4 cm; body mass, 72.5 ± 7.7 kg) performed a 2-hour surfing training session, with 15-m sprint paddle and CMJ trials performed both before and after the surfing session. Pre- to posttesting measures were analyzed using magnitude-based inferences. Likely declines were observed in the velocity achieved at the 5-, 10-, and 15-m splits of the 15-m sprint paddle, as well as peak velocity. Similarly, likely declines were calculated for CMJ peak force, relative peak force, and jump height. Furthermore, large correlations were calculated between presurfing session peak velocity and the change in 5, 10, 15 m, and peak velocity of the 15-m sprint paddle and total distance covered, wave riding bouts, and success rate. Surfing athletes and coaches may need to consider implementing shorter duration training sessions to reduce the decline in sprint paddling ability and CMJ performance. Furthermore, surfing athletes should possess highly developed sprint paddling ability because this may allow them to undertake a greater workload and catch more waves, which will increase the opportunity for technical refinement of maneuvers and skill acquisition.

  1. Force-velocity relationship and maximal power on a cycle ergometer. Correlation with the height of a vertical jump.

    PubMed

    Vandewalle, H; Peres, G; Heller, J; Panel, J; Monod, H

    1987-01-01

    The force-velocity relationship on a Monark ergometer and the vertical jump height have been studied in 152 subjects practicing different athletic activities (sprint and endurance running, cycling on track and/or road, soccer, rugby, tennis and hockey) at an average or an elite level. There was an approximately linear relationship between braking force and peak velocity for velocities between 100 and 200 rev.min-1. The highest indices of force P0, velocity V0 and maximal anaerobic power (Wmax) were observed in the power athletes. There was a significant relationship between vertical jump height and Wmax related to body mass.

  2. The acute effect of whole-body low-frequency vibration on countermovement vertical jump performance in college-aged men.

    PubMed

    Lamont, Hugh S; Cramer, Joel T; Bemben, Debra A; Shehab, Randa L; Anderson, Mark A; Bemben, Michael G

    2010-12-01

    The purpose of this study was to examine the acute effects of whole-body vibration on jump performance. A total of 21 college-aged men, 18-30 years, recreationally resistance trained, were exposed to a total of 4 different acute whole-body low-frequency vibration (WBLFV) protocols (conditions 1-4), performing 2 protocols per testing session in random order. Exposures were all performed using high-amplitude (peak-peak 4-6 mm) and either 30 or 50 Hz for 30 continuous seconds, or 3 exposures of 10 seconds with 1 minute between exposures. Three countermovement vertical jumps (CMVJs) were performed before vibration (testing phase 1 or Tp1 and J1 the highest of 3 attempts) and at 3 separate time points postvibration (Tp2-4). Jump height (cm), peak power (Pmax), peak power per kilogram of body mass (Pmax kg), mean power (Pav), and mean velocity (Vav) were recorded. Repeated measures analysis of variance and analysis of covariance revealed no significant condition (C) or jump (J) differences for CMVJ height (cm) (p > 0.05). Analysis of percent change (Δ%) for CMVJ height (cm) revealed a significant Condition × Jump interaction, C4, J3 > C1, J3 (p = 0.009, mean diff 4.12%). Analysis of Pmax and Pmax kg revealed no significant Condition, Jump, or Condition × Jump interaction for the raw data or percent change (p > 0.05). Analysis of Pav (W) revealed significant differences for Condition (p = 0.031) but not for Jump (p = 0.226). There was a strong trend toward significance for Condition × Jump interaction (p = 0.059). C4 > C3 (p = 0.043, mean diff 23.78 W) and C1 (p = 0.038, mean diff 32.03 W). Analysis of Vav (m·s) revealed no significant main effects for Condition or Jump (p > 0.05) but found a significant Condition × Jump interaction (p = 0.007). C4, J6 > C2, J6 (p = 0.014, mean diff 0.05 m·s), and C3, J6 (p = 0.020, 0.05 m·s). WBLFV applied intermittently using 50 Hz appears to be more effective than other protocols using 30 and 50 Hz in facilitating select

  3. Effect of early training on the jumping technique of horses.

    PubMed

    Santamaría, Susana; Bobbert, Maarten F; Back, Willem; Barneveld, Ab; van Weeren, P Rene

    2005-03-01

    To investigate the effects of early training for jumping by comparing the jumping technique of horses that had received early training with that of horses raised conventionally. 40 Dutch Warmblood horses. The horses were analyzed kinematically during free jumping at 6 months of age. Subsequently, they were allocated into a control group that was raised conventionally and an experimental group that received 30 months of early training starting at 6 months of age. At 4 years of age, after a period of rest in pasture and a short period of training with a rider, both groups were analyzed kinematically during free jumping. Subsequently, both groups started a 1-year intensive training for jumping, and at 5 years of age, they were again analyzed kinematically during free jumping. In addition, the horses competed in a puissance competition to test maximal performance. Whereas there were no differences in jumping technique between experimental and control horses at 6 months of age, at 4 years, the experimental horses jumped in a more effective manner than the control horses; they raised their center of gravity less yet cleared more fences successfully than the control horses. However, at 5 years of age, these differences were not detected. Furthermore, the experimental horses did not perform better than the control horses in the puissance competition. Specific training for jumping of horses at an early age is unnecessary because the effects on jumping technique and jumping capacity are not permanent.

  4. Real-time measurement of rectus femoris muscle kinematics during drop jump using ultrasound imaging: a preliminary study.

    PubMed

    Eranki, Avinash; Cortes, Nelson; Ferencek Gregurić, Zrinka; Kim, John J; Sikdar, Siddhartha

    2012-01-01

    We have developed an office based vector tissue Doppler imaging (vTDI) that can be used to quantitatively measure muscle kinematics using ultrasound. The goal of this preliminary study was to investigate if vTDI measures are repeatable and can be used robustly to measure and understand the kinematics of the rectus femoris muscle during a drop jump task. Data were collected from 8 healthy volunteers. Vector TDI along with a high speed camera video was used to better understand the dynamics of the drop jump. Our results indicate that the peak resultant vector velocity of the rectus femoris immediately following landing was repeatable across trials (intraclass correlation coefficient=0.9).The peak velocity had a relatively narrow range in 6 out of 8 subjects (48-62 cm/s), while in the remaining two subjects it exceeded 70 cm/s. The entire drop jump lasted for 1.45 0.27 seconds. The waveform of muscle velocity could be used to identify different phases of the jump. Also, the movement of the ultrasound transducer holder was minimal with peak deflection of 0.91 0.54 degrees over all trials. Vector TDI can be implemented in a clinical setting using an ultrasound system with a research interface to better understand the muscle kinematics in patients with ACL injuries.

  5. Scaled Jump in Gravity-Reduced Virtual Environments.

    PubMed

    Kim, MyoungGon; Cho, Sunglk; Tran, Tanh Quang; Kim, Seong-Pil; Kwon, Ohung; Han, JungHyun

    2017-04-01

    The reduced gravity experienced in lunar or Martian surfaces can be simulated on the earth using a cable-driven system, where the cable lifts a person to reduce his or her weight. This paper presents a novel cable-driven system designed for the purpose. It is integrated with a head-mounted display and a motion capture system. Focusing on jump motion within the system, this paper proposes to scale the jump and reports the experiments made for quantifying the extent to which a jump can be scaled without the discrepancy between physical and virtual jumps being noticed by the user. With the tolerable range of scaling computed from these experiments, an application named retargeted jump is developed, where a user can jump up onto virtual objects while physically jumping in the real-world flat floor. The core techniques presented in this paper can be extended to develop extreme-sport simulators such as parasailing and skydiving.

  6. Effects of different footwear on vertical jump and landing parameters.

    PubMed

    LaPorta, Joe W; Brown, Lee E; Coburn, Jared W; Galpin, Andrew J; Tufano, James J; Cazas, Vanessa L; Tan, Jeremy G

    2013-03-01

    Little is known about the effects of different footwear on anaerobic performance variables. The purpose of this study was to investigate the effect of different footwear on vertical jumping and landing parameters. Ten men and 10 women participated. After a dynamic warm-up, subjects performed a vertical jump (VJ), depth drop (DD), and Bosco test on a force plate in 3 different conditions, on 3 separate days: bare feet (BF), minimalist footwear (MF), and tennis shoes (TS). Bare feet had greater relative peak power (relPP) in the VJ (men: BF, 59.87 ± 5.09 W⋅kg(-1); MF, 58.39 ± 5.69 W·kg(-1); TS, 57.70 ± 6.54 W·kg(-1); women: BF, 45.26 ± 4.10 W·kg(-1); MF, 45.06 ± 3.53 W·kg(-1); TS, 44.77 ± 4.55 W·kg(-1)), while for men, jump height (JH) was also greater in BF and MF (BF, 44.5 ± 4.46 cm; MF, 43.47 ± 5.5 cm; TS, 41.47 ± 14.45 cm). Results of the Bosco test revealed average relPP was greatest in BF compared with MF and TS (men: BF, 19.70 ± 3.01 W·kg(-1); MF, 19.28 ± 3.00 W·kg(-1); TS, 18.93 ± 3.33 W·kg(-1); women: BF, 14.68 ± 1.41 W·kg(-1); MF, 13.97 ± 1.56 W·kg(-1); TS 13.62 ± 1.67 W·kg(-1)), while for JH, BF and MF were greater than TS (men: BF, 28.62 ± 5.0 cm; MF, 27.78 ± 5.09 cm; TS, 26.54 ± 5.1 cm; women: BF, 18.60 ± 1.97 cm; MF, 17.86 ± 6.35 cm; TS, 17.35 ± 2.47 cm). No differences in relative impact force were seen during the DD between conditions. Therefore, athletes and coaches interested in enhancing single and multiple VJs might consider either BF or minimalist shoes.

  7. Optimal estimation for discrete time jump processes

    NASA Technical Reports Server (NTRS)

    Vaca, M. V.; Tretter, S. A.

    1978-01-01

    Optimum estimates of nonobservable random variables or random processes which influence the rate functions of a discrete time jump process (DTJP) are derived. The approach used is based on the a posteriori probability of a nonobservable event expressed in terms of the a priori probability of that event and of the sample function probability of the DTJP. Thus a general representation is obtained for optimum estimates, and recursive equations are derived for minimum mean-squared error (MMSE) estimates. In general, MMSE estimates are nonlinear functions of the observations. The problem is considered of estimating the rate of a DTJP when the rate is a random variable with a beta probability density function and the jump amplitudes are binomially distributed. It is shown that the MMSE estimates are linear. The class of beta density functions is rather rich and explains why there are insignificant differences between optimum unconstrained and linear MMSE estimates in a variety of problems.

  8. Highly sensitive microwave temperature-jump apparatus.

    PubMed

    Aubard, J; Nozeran, J M; Levoir, P; Meyer, J J; Dubois, J E

    1979-01-01

    A temperature-jump apparatus with repetitive microwave heating and spectrophotometric detection is described. Temperature jumps of 1.5 degrees C are achieved in a flow microcell within 1.5 mus (two shorter heating times of 0.5 and 0.25 mus are also available) at a repetition rate up to 50 Hz. On-line accumulation of the relaxation signals is performed with a PDP 11 processor, leading to very short recording times (more than 1000 signals accumulated in less than 50 s) and to a sensitivity better than 10(-4) optical density (OD) units. Nonlinear identification treatment permits processing the summed signal even when it is strongly blurred by noise. To demonstrate the capabilities of our apparatus, highly shifted fast prototropic equilibria in aqueous solutions of pyrimidine base have been studied.

  9. Ehrenfest model with large jumps in finance

    NASA Astrophysics Data System (ADS)

    Takahashi, Hisanao

    2004-02-01

    Changes (returns) in stock index prices and exchange rates for currencies are argued, based on empirical data, to obey a stable distribution with characteristic exponent α<2 for short sampling intervals and a Gaussian distribution for long sampling intervals. In order to explain this phenomenon, an Ehrenfest model with large jumps (ELJ) is introduced to explain the empirical density function of price changes for both short and long sampling intervals.

  10. Entropy jump across an inviscid shock wave

    NASA Technical Reports Server (NTRS)

    Salas, Manuel D.; Iollo, Angelo

    1995-01-01

    The shock jump conditions for the Euler equations in their primitive form are derived by using generalized functions. The shock profiles for specific volume, speed, and pressure are shown to be the same, however density has a different shock profile. Careful study of the equations that govern the entropy shows that the inviscid entropy profile has a local maximum within the shock layer. We demonstrate that because of this phenomenon, the entropy, propagation equation cannot be used as a conservation law.

  11. Looking Back on Operation Jump Start

    DTIC Science & Technology

    2009-01-01

    Operation Jump Start Major David M. Church, USARNG, is Plans Officer for the Unmanned Aircraft Systems Training Battalion at Fort Huachuca, Arizona. He...SUPPLEMENTARY NOTES 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Same as Report (SAR) 18... system would have contributed to a more sound unity of effort by reducing organizational uncertainty. Another measure that could have reduced this

  12. The effects of jumping distance on the landing mechanics after a volleyball spike.

    PubMed

    Marquez, Walter Quispe; Masumura, Masanao; Ae, Michiyoshi

    2009-06-01

    The purpose of this study was to assess the effects of jumping distance on the landing mechanics after a volleyball spike, to help in injury prevention and training for safer landing. Ground reaction forces and three-dimensional kinematic data were collected from six male university right-handed volleyball players under "Normal" and "Long" jumping distance conditions of landing after a spike. The results revealed that the landings under the Long jumping distance condition produced significantly greater centre of gravity velocities and larger mean loading rates. Although data were collected for bilateral landings with the two feet contacting the force platform at the same time, landing motion was asymmetric and the left leg was considered to play a more critical role in the absorption of the landing impact. The trunk and hip positions at the initial contact with the floor and the range of motions of the knee and ankle were key kinematic parameters for reducing the vertical peak ground reaction forces and extending the time from the initial contact to the occurrence of this peak force, which consequently reduced the mean loading rate upon landing.

  13. Field measurements in unwadeable natural hydraulic jumps

    NASA Astrophysics Data System (ADS)

    Valle, B.; Pasternack, G.

    2003-04-01

    Recent research in fluvial geomorphology has emphasized the development and application of digital terrain models to better understand process-form relations. However, field measurements in mountain channels have largely been restricted to low velocity or ephemeral flow conditions. To address this problem, a new high-resolution mechanical surveying system was developed at UC Davis and used to measure the 3D bed and water surface topographies of an unwadeable plunging hydraulic jump in the Cache Creek basin, CA. Labeled as the River Truss, the system is capable of making high-resolution form and process measurements over a 30 to 115 m2 area. Bed and water surface DTMs were derived from the field data using AutoCAD. River Truss precision was assessed by DTM differencing the hydraulic jump bed surface topography with a DTM developed from tacheometric survey at low base flows. Bed surface DTMs indicate significant spatial complexity of the underlying bed step in the supercritical flow region and significant downstream bed scour. Water surface DTMs indicate 3D complexity of the plunging flow surface and divergence from 1D free-fall theory. Further study will emphasize the development and deployment of process-based instrumentation such that the complex turbulent air-water flow dynamics associated with natural hydraulic jumps may be better understood. Also, a second generation River Truss that has a larger coverage area and automated data collection has been designed and is now being built.

  14. Quantum jumps of a fluxonium qubit

    NASA Astrophysics Data System (ADS)

    Vool, U.; Pop, I. M.; Sliwa, K.; Abdo, B.; Brecht, T.; Shankar, S.; Hatridge, M.; Schoelkopf, R. J.; Mirrahimi, M.; Glazman, L.; Devoret, M. H.

    2014-03-01

    The fluxonium qubit has recently been shown to have energy relaxation time (T1) of the order of 1 ms, limited by quasiparticle dissipation. With the addition of a Josephson Parametric Converter (JPC) to the experiment, trajectories corresponding to quantum jumps between the ground and 1st excited state can be measured, thus allowing the observation of the qubit decay in real time instead of that of an ensemble average. Our measurement fidelity with the JPC is in excess of 98% for an acquisition time of 5 us and we can thus continuously monitor the quantum jumps of the qubit in equilibrium with its environment in a time much shorter than its average relaxation time. We observe in our sample a jump statistics that varies from being completely Poissonian with a long (500 us) mean time in the ground state to being highly non-Poissonian with short (100 us) mean time in the ground state. The changes between these regimes occur on time scales of seconds, minutes and even hours. We have studied this effect and its relation to quasiparticle dynamics by injecting quasiparticles with a short intense microwave pulse and by seeding quasiparticle-trapping vortices with magnetic field. Work supported by: IARPA, ARO, and NSF.

  15. Peak resolution by semiderivative voltammetry

    SciTech Connect

    Toman, Jeffrey J.; Brown, Steven D.

    1981-08-01

    One of the limitations of dynamic electrochemistry, when used as a quantitative analytical technique, is the resolution of overlapping waves. Approaches used in the past have been either time intensive methods using many blanks, or have relied on many empirical peak parameters. Using an approach based on semidifferential voltammetry, two new techniques have been developed for rapid peak deconvolution. The first technique, NIFITl, is an iterative stripping routine, while the second, BIMFIT, is based on sequential simplex optimization. Both approaches were characterized by deconvolution of synthetic fused peak systems. Subsequently, both were applied to semi-differentiated linear scan voltammograms of Cd2+, Pb2+ and In3+ and to semi-differentiated linear scan anodic stripping voltammograms of Cd2+, ln3+ and Tl+. Deconvolutions were directly characterized by peak height, peak potential and peak halfwidth, in addition to the total squared deviation of the fit peaks from the real fused peaks. Studies of individual peaks as well as of standard additions to fused peaks showed both methods worked well, with excellent deconvolution efficiencies. Synthetic data were totally deconvoluted with peak separation as small as 25 mv, while real systems were deconvoluted with separations below 40 mv. Peak parameters obtained from these deconvolutions allow observations of electrode processes, even in systems containing overlapping peaks.

  16. Jump Squat is More Related to Sprinting and Jumping Abilities than Olympic Push Press.

    PubMed

    Loturco, I; Kobal, R; Maldonado, T; Piazzi, A F; Bottino, A; Kitamura, K; Abad, C C C; Pereira, L A; Nakamura, F Y

    2015-12-14

    The aim of this study was to test the relationships between jump squat (JS) and Olympic push press (OPP) power outputs and performance in sprint, squat jump (SJ), countermovement jump (CMJ) and change of direction (COD) speed tests in elite soccer players. 27 athletes performed a maximum power load test to determine their bar mean propulsive power (MPP) and bar mean propulsive velocity (MPV) in the JS and OPP exercises. Magnitude-based inference was used to compare the exercises. The MPV was almost certainly higher in the OPP than in the JS. The MPP relative to body mass (MPP REL) was possibly higher in the OPP. Only the JS MPP REL presented very large correlations with linear speed (r>0.7, for speed in 5, 10, 20 and 30 m) and vertical jumping abilities (r>0.8, for SJ and CMJ), and moderate correlation with COD speed (r=0.45). Although significant (except for COD), the associations between OPP outcomes and field-based measurements (speed, SJ and CMJ) were all moderate, ranging from 0.40 to 0.48. In a group composed of elite soccer players, the JS exercise is more associated with jumping and sprinting abilities than the OPP. Longitudinal studies are needed to confirm if these strong relationships imply superior training effects in favor of the JS exercise.

  17. An efficient interpolation technique for jump proposals in reversible-jump Markov chain Monte Carlo calculations

    PubMed Central

    Farr, W. M.; Mandel, I.; Stevens, D.

    2015-01-01

    Selection among alternative theoretical models given an observed dataset is an important challenge in many areas of physics and astronomy. Reversible-jump Markov chain Monte Carlo (RJMCMC) is an extremely powerful technique for performing Bayesian model selection, but it suffers from a fundamental difficulty and it requires jumps between model parameter spaces, but cannot efficiently explore both parameter spaces at once. Thus, a naive jump between parameter spaces is unlikely to be accepted in the Markov chain Monte Carlo (MCMC) algorithm and convergence is correspondingly slow. Here, we demonstrate an interpolation technique that uses samples from single-model MCMCs to propose intermodel jumps from an approximation to the single-model posterior of the target parameter space. The interpolation technique, based on a kD-tree data structure, is adaptive and efficient in modest dimensionality. We show that our technique leads to improved convergence over naive jumps in an RJMCMC, and compare it to other proposals in the literature to improve the convergence of RJMCMCs. We also demonstrate the use of the same interpolation technique as a way to construct efficient ‘global’ proposal distributions for single-model MCMCs without prior knowledge of the structure of the posterior distribution, and discuss improvements that permit the method to be used in higher dimensional spaces efficiently. PMID:26543580

  18. Stepwise advancement versus maximum jumping with headgear activator.

    PubMed

    Wey, Mang Chek; Bendeus, Margareta; Peng, Li; Hägg, Urban; Rabie, A Bakr M; Robinson, Wayne

    2007-06-01

    The aim of this study was to compare the effects of stepwise mandibular advancement versus maximum jumping and extended treatment versus early retention. The material was obtained prospectively and consisted of lateral cephalograms taken at the start (T0), after initial (T1), and at the end (T2) of treatment, from two groups of consecutively treated skeletal Class II patients who had undergone therapy with headgear activators. The first headgear activator group, HGA-S (n=24; mean age 11.9 +/- 1.2 years), was treated for 13 months and had 4-mm mandibular advancement every 3 months. The second headgear activator group, HGA-M (n=31; mean age 11.2 +/- 1.5 years), had maximum jumping, 6-8 mm interincisal opening, for a total of 15.4 months, and with reduced wear for the last 6.9 months. The dropout over 12 months was 41 and 46 per cent, respectively. Pre-treatment growth changes were obtained as a reference. An independent t-test was used to determine differences in baseline dentofacial morphology between the groups, a paired t-test for intra-group comparisons, and an independent t-test to evaluate differences between the groups. The results, in both groups, showed enhanced mandibular prognathism during the initial phase (T0-T1), followed by normal growth (T1-T2), and lower face height enhancement throughout treatment (T0-T2). For both groups, the mandibular plane and occlusal angle increased, possibly enhanced by 'extrusion' of the lower molars. For both groups, maxillary forward growth was restrained only during the initial phase, but the effect remained significant at T2 for the HGA-S group. In the HGA-M group, the lower incisors were protruded, while in the HGA-S group, they were unaffected. The findings indicate that both modes of mandibular jumping resulted in skeletal and dental effects. The length of active treatment seemed to be decisive in maintaining the treatment effects; stepwise advancement had less dental effects.

  19. Differences in End Range of Motion Vertical Jump Kinetic and Kinematic Strategies Between Trained Weightlifters and Elite Short Track Speed Skaters.

    PubMed

    Haug, William B; Spratford, Wayne; Williams, Kym J; Chapman, Dale W; Drinkwater, Eric J

    2015-09-01

    The purpose of this investigation was to identify differences in end range of motion (ROM) kinetic and kinematic strategies between highly resistance and vertical jump-trained athletes and controls. Weightlifters (WL: n = 4), short track speed skaters (STSS: n = 5), and nonresistance-trained controls (C: n = 6) performed 6 standing vertical squat jumps (SJ) and countermovement jumps (CMJ) without external resistance. Jump testing was performed using 3-dimensional marker trajectories captured with a 15-camera motion analysis system synchronized with 2 in-ground force plates. During SJ, there were large effects for the difference in time before toe off of peak vertical velocity between WL to STSS and C (ES: -1.43; ES: -1.73, respectively) and for the decrease between peak and toe off vertical velocity (ES: -1.28; ES: -1.71, respectively). During CMJ, there were large effects for the difference in time before toe off of peak vertical velocity between WL to STSS and C (ES: -1.28; ES: -1.53, respectively) and for decrease between peak and toe off vertical velocity (ES: -1.03; ES: -1.59, respectively). Accompanying these differences for both jump types were large effects for time of joint deceleration before toe off for all lower body joints between WL compared with C with large effects between WL and STSS at the hip and between STSS and C at the ankle. These findings suggest that the end ROM kinetic and kinematic strategy used during jumping is group-specific in power-trained athletes, with WL exhibiting superior strategies as compared with resistance- and jump-trained STSS.

  20. Jumping Performance is Preserved, but not Muscle Thickness in Collegiate Volleyball Players After a Taper.

    PubMed

    Bazyler, Caleb D; Mizuguchi, Satoshi; Sole, Christopher J; Suchomel, Timothy J; Sato, Kimitake; Kavanaugh, Ashley A; DeWeese, Brad H; Stone, Michael H

    2017-05-25

    The purpose of this study was to examine changes in muscle architecture and jumping performance in NCAA Division I women's volleyball players throughout a competitive season and in preparation for conference championships. Ten women's volleyball players were tested at pre-season (T1), pre-taper (T2), and post-taper (T3) on measures of vastus lateralis muscle thickness (MT), pennation angle (PA) and fascicle length (FL) using ultrasonography, and unloaded and loaded squat jump height (SJH) and peak power allometrically scaled to body mass (SJPPa) on a force platform. Rating of perceived exertion training load and strength training volume-load were monitored weekly. Player's MT (p<0.001, Glass's Δ=2.8) and PA increased (p=0.02, Δ=3.9) following in-season training. However, MT decreased following the taper (p=0.01, Δ=0.6), but remained elevated above pre-season values (p<0.001, Δ=1.7). There were no statistical changes in FL, SJH or SJPPa. Large to very large, negative relationships (r=-0.51 to -0.81) were observed between pre-season relative maximal strength and changes in SJH and SJPPa with various loads over the season. These findings demonstrate that relatively low volumes of strength training and concurrent sport training during a tapering period are capable of preserving jumping performance, but not MT in women's volleyball players; however, jumping performance changes appear to be related to the player's strength level. Stronger players may benefit from an overreaching microcycle prior to the taper to preserve previously accrued muscular adaptations and jumping performance.

  1. Peak flow meter use - slideshow

    MedlinePlus

    ... medlineplus.gov/ency/presentations/100202.htm Peak flow meter use - Series—Peak flow meter use - part one To use the sharing features ... 7 out of 7 Overview A peak flow meter helps you check how well your asthma is ...

  2. Preliminary Development and Evaluation of Lightning Jump Algorithms for the Real-Time Detection of Severe Weather

    NASA Technical Reports Server (NTRS)

    Schultz, Christopher J.; Petersen, Walter A.; Carey, Lawrence D.

    2009-01-01

    Previous studies have demonstrated that rapid increases in total lightning activity (intracloud + cloud-to-ground) are often observed tens of minutes in advance of the occurrence of severe weather at the ground. These rapid increases in lightning activity have been termed "lightning jumps." Herein, we document a positive correlation between lightning jumps and the manifestation of severe weather in thunderstorms occurring across the Tennessee Valley and Washington D.C. A total of 107 thunderstorms were examined in this study, with 69 of the 107 thunderstorms falling into the category of non-severe, and 38 into the category of severe. From the dataset of 69 isolated non-severe thunderstorms, an average peak 1 minute flash rate of 10 flashes/min was determined. A variety of severe thunderstorm types were examined for this study including an MCS, MCV, tornadic outer rainbands of tropical remnants, supercells, and pulse severe thunderstorms. Of the 107 thunderstorms, 85 thunderstorms (47 non-severe, 38 severe) from the Tennessee Valley and Washington D.C tested 6 lightning jump algorithm configurations (Gatlin, Gatlin 45, 2(sigma), 3(sigma), Threshold 10, and Threshold 8). Performance metrics for each algorithm were then calculated, yielding encouraging results from the limited sample of 85 thunderstorms. The 2(sigma) lightning jump algorithm had a high probability of detection (POD; 87%), a modest false alarm rate (FAR; 33%), and a solid Heidke Skill Score (HSS; 0.75). A second and more simplistic lightning jump algorithm named the Threshold 8 lightning jump algorithm also shows promise, with a POD of 81% and a FAR of 41%. Average lead times to severe weather occurrence for these two algorithms were 23 minutes and 20 minutes, respectively. The overall goal of this study is to advance the development of an operationally-applicable jump algorithm that can be used with either total lightning observations made from the ground, or in the near future from space using the

  3. Influence of dorsiflexion shoes on neuromuscular fatigue of the plantar flexors after combined tapping-jumping exercises in volleyball players.

    PubMed

    Lapole, Thomas; Ahmaidi, Said; Gaillien, Benjamin; Leprêtre, Pierre-Marie

    2013-07-01

    Dorsiflexion shoes could be useful to increase jumping performance. The aim of the present study was to investigate the impact of wearing shoes inducing moderate dorsiflexion (2°) on neuromuscular fatigue induced by volleyball exercises involving multiple stretch-shortening cycles. Squat jump (SJ) and countermovement jump (CMJ) performance, and plantar flexors isometric voluntary and evoked contractile properties were assessed in 10 unfamiliarized trained volleyball players before and after a 10-minute intensive combined tapping-jumping volleyball exercise performed, in blinded randomized conditions, with neutral (0°) or moderate dorsiflexion (2°). No significant difference was observed on SJ performance in neutral and moderate dorsiflexion conditions. However, CMJ height was initially lower with 2° dorsiflexion compared with 0° (p < 0.05). Height in CMJ was increased after exercise with 2° dorsiflexion shoes and remained unchanged in neutral 0° condition. Combined tapping-jumping volleyball exercise also induced a significant decrease in maximal voluntary contraction (p < 0.001), peak-twitch torque (p = 0.009), contraction time (p < 0.001) and twitch relaxation rate (p = 0.001) values without any significant difference between neutral and dorsiflexion conditions. Voluntary activation level (p = 0.014) and rate of force development (p = 0.05) were also decreased in both conditions. In conclusion, acute moderate dorsiflexion had no effect on jumping performance and neuromuscular fatigue in unfamiliarized trained subjects and altered the elastic energy store in plyometric condition (CMJ). Future studies are necessary to investigate the chronic effect of moderate dorsiflexion on jumping performance and neuromuscular fatigue in trained volleyball players.

  4. Long memory behavior of returns after intraday financial jumps

    NASA Astrophysics Data System (ADS)

    Behfar, Stefan Kambiz

    2016-11-01

    In this paper, characterization of intraday financial jumps and time dynamics of returns after jumps is investigated, and will be analytically and empirically shown that intraday jumps are power-law distributed with the exponent 1 < μ < 2; in addition, returns after jumps show long-memory behavior. In the theory of finance, it is important to be able to distinguish between jumps and continuous sample path price movements, and this can be achieved by introducing a statistical test via calculating sums of products of returns over small period of time. In the case of having jump, the null hypothesis for normality test is rejected; this is based on the idea that returns are composed of mixture of normally-distributed and power-law distributed data (∼ 1 /r 1 + μ). Probability of rejection of null hypothesis is a function of μ, which is equal to one for 1 < μ < 2 within large intraday sample size M. To test this idea empirically, we downloaded S&P500 index data for both periods of 1997-1998 and 2014-2015, and showed that the Complementary Cumulative Distribution Function of jump return is power-law distributed with the exponent 1 < μ < 2. There are far more jumps in 1997-1998 as compared to 2015-2016; and it represents a power law exponent in 2015-2016 greater than one in 1997-1998. Assuming that i.i.d returns generally follow Poisson distribution, if the jump is a causal factor, high returns after jumps are the effect; we show that returns caused by jump decay as power-law distribution. To test this idea empirically, we average over the time dynamics of all days; therefore the superposed time dynamics after jump represent a power-law, which indicates that there is a long memory with a power-law distribution of return after jump.

  5. Structure and Dynamics of Katabatic Flow Jumps: Idealised Simulations

    NASA Astrophysics Data System (ADS)

    Yu, Ye; Cai, Xiao-Ming

    2006-03-01

    For the first time, results from a high-resolution numerical simulation (with horizontal grid spacing of 35m) were used to reveal the detailed structure near an atmospheric katabatic jump over an idealized slope. The simulation represents flow over the slopes of Coats Land, Antarctica for austral winter conditions. The katabatic jump is characterised by an updraft with vertical velocities of order 1ms-1 and serves as a possible forcing mechanism for the gravity waves frequently observed over the ice shelves around the Antarctic. Results also indicate that strong turbulence is generally confined within a mixing zone near the top of the katabatic layer upstream of the jump and extends downstream through the top of the strong updraft associated with the jump. Detailed analyses of momentum and heat budgets across the katabatic jump indicate that, upstream of the jump, turbulent mixing is important in decelerating the upper part of the katabatic layer, while within the jump the upslope pressure gradient force associated with the pool of cold air plays a role in decelerating the flow near the surface. The heat budget near the jump reveals a simple two-term balance: the turbulent heat flux divergence is balanced by the advection. A comparison of model results with available theories indicates that mixing between layers of different potential temperature structure indeed plays some role in the development of katabatic flow jumps, especially for strong jumps. Theories used to study katabatic jumps should include this mixing process, of which the amount depends on the intensity of the jump. A conceptual model of a katabatic jump, including the main dynamical processes, is constructed from these detailed analyses.

  6. Analysis of the Vertical Ground Reaction Forces and Temporal Factors in the Landing Phase of a Countermovement Jump

    PubMed Central

    Ortega, Daniel Rojano; Rodríguez Bíes, Elisabeth C.; Berral de la Rosa, Francisco J.

    2010-01-01

    In most common bilateral landings of vertical jumps, there are two peak forces (F1 and F2) in the force-time curve. The combination of these peak forces and the high frequency of jumps during sports produce a large amount of stress in the joints of the lower limbs which can be determinant of injury. The aim of this study was to find possible relationships between the jump height and F1 and F2, between F1 and F2 themselves, and between F1, F2, the time they appear (T1 and T2, respectively) and the length of the impact absorption phase (T). Thirty semi-professional football players made five countermovement jumps and the highest jump of each player was analyzed. They were instructed to perform the jumps with maximum effort and to land first with the balls of their feet and then with their heels. All the data were collected using a Kistler Quattro Jump force plate with a sample rate of 500 Hz. Quattro Jump Software, v.1.0.9.0., was used. There was neither significant correlation between T1 and F1 nor between T1 and F2. There was a significant positive correlation between flight height (FH) and F1 (r = 0.584, p = 0.01) but no significant correlation between FH and F2. A significant positive correlation between F1 and T2 (r = 0.418, p < 0.05) and a significant negative correlation between F2 and T2 (r = -0.406, p < 0.05) were also found. There is a significant negative correlation between T2 and T (r = -0. 443, p < 0.05). T1 has a little effect in the impact absorption process. F1 increases with increasing T2 but F2 decreases with increasing T2. Besides, increasing T2, with the objective of decreasing F2, makes the whole impact absorption shorter and the jump landing faster. Key points In the landing phase of a jump there are always sev-eral peak forces. The combination of these peaks forces and the high frequency of jumps during sports produces a large amount of stress in the joints of the lower limbs which can be determinant of injury. In the most common two

  7. The effect of 8-week plyometric training on leg power, jump and sprint performance in female soccer players.

    PubMed

    Ozbar, Nurper; Ates, Seda; Agopyan, Ani

    2014-10-01

    The aim of this study was to determine the effect of 8-week plyometric training (PT) on the leg power and jump and sprint performance in female soccer players. Eighteen female soccer players from Women Second League (age = 18.2 ± 2.3 years, height = 161.3 ± 5.4 cm, body mass = 56.6 ± 7.2 kg) were randomly assigned to control (n = 9) and plyometric (n = 9) groups. Both groups continued together with regular technical and tactical soccer training for 4 days a week. Additionally, the plyometric group underwent PT for 8 weeks, 1 day per week, 60-minute session duration. During the 8-week period, the control group was hindered from any additional conditioning training. All players' jumps (triple hop, countermovement jump, and standing broad jump), running speed (20 m), and peak power were evaluated before and after 8 weeks. No significant difference was found between the groups at pretest variables (p > 0.05). Significant improvements were found in the posttest of both the groups (p ≤ 0.05), except for 20-m sprint test in the control group (p > 0.05). Triple hop distance, countermovement jump, standing broad jump, peak power, and 20-m sprint test values were all significantly improved in the plyometric group, compared with the control group (p ≤ 0.05). We concluded that short duration PT is an improved important component of athletic performance in female soccer players. The results indicate that safe, effective, and alternative PT can be useful to strength and conditioning coaches, especially during competition season where less time is available for training.

  8. The effects of rope or weighted rope jump training on strength, coordination and proprioception in adolescent female volleyball players.

    PubMed

    Ozer, D; Duzgun, I; Baltaci, G; Karacan, S; Colakoglu, F

    2011-06-01

    The aim was to assess the effects of a 12-week "rope jumping" and "weighted rope jumping" training programs on functional parameters including multi-joint coordination and proprioception, strength, endurance in adolescent female volleyball players. Pretest posttest experimental design. Weighted Rope Training group (N.=9; 15±1 years), Rope Training group (N.=9; 14.1±1.3 years) and Controls (N.=7; 14.4±1.3 years). Motor coordination, proprioception, strength and endurance of the lower extremities with concentric and eccentric performances in closed kinetic chain on multi joint system assessed by the Monitorized Squat system. Absolute average error (cm) and the standard deviation for coordination and proprioception, Peak Force (N), Total Work (Nm), Average Power (Nm/s), Maximal Speed for strength and endurance tests were calculated. Kruskal-Wallis and Mann Whitney U test were utilized. Weighted rope jump group had significant decrease for the deviation results of coordination on the concentric and eccentric phases for both legs (P<0.05). Rope jump and weighted rope jump groups had significantly lower results on non visible second movement deviation (P<0.05). In strength tests, the difference was found for total work that there was difference on the post assessment within groups in favour of Weighted Rope Training group in comparison to controls (P<0.05). Weighted Rope Training and control groups improved in concentric maximal speed (P<0.05). Most significant changes occured on eccentric phaese of the endurance tests that peak force increased in Weighted Rope Training group (P<0.05). Adding rope jump to training programs improves joint repositioning and coordination. Weighted Rope Training group got greater gains for coordination and eccentric endurance parameters for lower extremities in a closed kinetic chain.

  9. Reliability of the Tuck Jump Injury Risk Screening Assessment in Elite Male Youth Soccer Players.

    PubMed

    Read, Paul J; Oliver, Jon L; de Ste Croix, Mark B A; Myer, Gregory D; Lloyd, Rhodri S

    2016-06-01

    Read, PJ, Oliver, JL, de Ste Croix, MBA, Myer, GD, and Lloyd, RS. Reliability of the tuck jump injury risk screening assessment in elite male youth soccer players. J Strength Cond Res 30(6): 1510-1516, 2016-Altered neuromuscular control has been suggested as a mechanism for injury in soccer players. Ligamentous injuries most often occur during dynamic movements, such as decelerations from jump-landing maneuvers where high-risk movement patterns are present. The assessment of kinematic variables during jump-landing tasks as part of a preparticipation screen is useful in the identification of injury risk. An example of a field-based screening tool is the repeated tuck jump assessment. The purpose of this study was to analyze the within-subject variation of the tuck jump screening assessment in elite male youth soccer players. Twenty-five pre-peak height velocity (PHV) and 25 post-PHV elite male youth soccer players from the academy of a professional English soccer club completed the assessment. A test-retest design was used to explore the within-subject intersession reliability. Technique was graded retrospectively against the 10-point criteria set out in the screening protocol using two-dimensional video cameras. The typical error range reported for tuck jump total score (0.90-1.01 in pre-PHV and post-PHV players respectively) was considered acceptable. When each criteria was analyzed individually, kappa coefficient determined that knee valgus was the only criterion to reach substantial agreement across the two test sessions for both groups. The results of this study suggest that although tuck jump total score may be reliably assessed in elite male youth soccer players, caution should be applied in solely interpreting the composite score due to the high within-subject variation in a number of the individual criteria. Knee valgus may be reliably used to screen elite youth male soccer players for this plyometric technique error and for test-retest comparison.

  10. Association between traditional standing vertical jumps and a soccer-specific vertical jump.

    PubMed

    Requena, Bernardo; Garcia, Inmaculada; Requena, Francisco; Bressel, Eadric; Saez-Saez de Villarreal, Eduardo; Cronin, John

    2014-01-01

    The present study aimed to determine the relationships between a soccer-specific vertical jump (ssVJ) test, that included common elements of a soccer VJ (e.g. run-up and intention to head), and three traditional VJ tests using elite soccer players. A secondary purpose of this study was to determine the reliability of the VJs used in the analysis. A randomised order and counterbalanced design was used to assess the relationships between these VJs [countermovement jump (CMJ), drop jump for height (DJh), drop jump for maximum height and minimum ground contact time (DJh/t) and the ssVJ]. Take-off velocity, contact time and flight time were the dependent variables of interest and compared between jumps. Intra-class correlation coefficient (ICC) and coefficient of variation (CV) were used as measures of inter-session reliability. All VJ tests were found to have high ICCs (0.89-0.99) and acceptable within-subject CVs (<7.5%). All the ssVJ dependent variables were not significantly related (r<0.44) with similar variables from the CMJ and DJh tests and only moderately related (r=~0.49) with the DJh/t test variables. In addition, the DJh/t variables were not significantly correlated (r<0.47) with DJh and CMJ test variables. In conclusion, it would seem that the proposed ssVJ test and CMJ or DJh tests assess different leg qualities and thought should be given before using them interchangeably to assess or develop the same performance measures (i.e. velocity at take-off or jump height).

  11. Does performing drop jumps with additional eccentric loading improve jump performance?

    PubMed

    Aboodarda, Saied J; Byrne, Jeannette M; Samson, Michael; Wilson, Barry D; Mokhtar, Abdul H; Behm, David G

    2014-08-01

    Previous investigators have speculated that applying additional external load throughout the eccentric phase of the jumping movement could amplify the stretch-shortening cycle mechanism and modulate jumping performance and jump exercise intensity. The aims of this study, therefore, were to determine the effect of increased eccentric phase loading, as delivered using an elastic device, on drop jumps (DJs) performed from different drop heights. Of specific interest were changes in (a) the kinetics; eccentric and concentric impulse, rate of force development (RFD), concentric velocity and (b) the electromyographic (EMG) activity of leg muscles. In a randomized repeated-measure study, 15 highly resistance trained male subjects performed DJs from 3 heights (20, 35, and 50 cm) under 3 different conditions: body weight only (free DJ) and with elastic bands providing downward force equivalent to 20% (+20% DJ) and 30% (+30% DJ) of body mass. All DJs were recorded using video and force plate data that were synchronized with EMG data. Results demonstrated that using additional tensile load during the airborne and eccentric phases of the DJ could enhance eccentric impulse (p = 0.042) and RFD (p < 0.001) and resulted in small to moderate effect size (ES) increases in quadriceps intergrated EMG across the eccentric phase (0.23 > ES > 0.51). The observed greater eccentric loading, however, did not immediately alter concentric kinetics and jump height nor did it alter muscle activation levels during this phase. The findings indicated that, in addition to the conventional technique of increasing drop height, using a tensile load during the airborne and eccentric phases of the DJ could further improve eccentric loading of DJs. As it has been suggested that eccentric impulse and RFD are indicators of DJ exercise intensity, these findings suggest that the loaded DJs, using additional elastic load, may be an effective technique for improving DJ exercise intensity without acute effects

  12. Fatigue Effects on Knee Joint Stability During Two Jump Tasks in Women

    PubMed Central

    Ortiz, Alexis; Olson, Sharon L.; Etnyre, Bruce; Trudelle-Jackson, Elaine E.; Bartlett, William; Venegas-Rios, Heidi L.

    2010-01-01

    Dynamic knee joint stability may be affected by the onset of metabolic fatigue during sports participation that could increase the risk for knee injury. The purpose of this investigation was to determine the effects of metabolic fatigue on knee muscle activation, peak knee joint angles, and peak knee internal moments in young women during 2 jumping tasks. Fifteen women (mean age: 24.6 ± 2.6 years) participated in one nonfatigued session and one fatigued session. During both sessions, peak knee landing flexion and valgus joint angles, peak knee extension and varus/valgus internal moments, electromyographic (EMG) muscle activity of the quadriceps and hamstrings, and quadriceps/hamstring EMG cocontraction ratio were measured. The tasks consisted of a single-legged drop jump from a 40-cm box and a 20-cm, up-down, repeated hop task. The fatigued session included a Wingate anaerobic protocol followed by performance of the 2 tasks. Although participants exhibited greater knee injury–predisposing factors during the fatigued session, such as lesser knee flexion joint angles, greater knee valgus joint angles, and greater varus/valgus internal joint moments for both tasks, only knee flexion during the up-down task was statistically significant (p = 0.028). Metabolic fatigue may perhaps predispose young women to knee injuries by impairing dynamic knee joint stability. Training strength-endurance components and the ability to maintain control of body movements in either rested or fatigued situations might help reduce injuries in young women athletes. PMID:20300024

  13. Fatigue effects on knee joint stability during two jump tasks in women.

    PubMed

    Ortiz, Alexis; Olson, Sharon L; Etnyre, Bruce; Trudelle-Jackson, Elaine E; Bartlett, William; Venegas-Rios, Heidi L

    2010-04-01

    Dynamic knee joint stability may be affected by the onset of metabolic fatigue during sports participation that could increase the risk for knee injury. The purpose of this investigation was to determine the effects of metabolic fatigue on knee muscle activation, peak knee joint angles, and peak knee internal moments in young women during 2 jumping tasks. Fifteen women (mean age: 24.6 +/- 2.6 years) participated in one nonfatigued session and one fatigued session. During both sessions, peak knee landing flexion and valgus joint angles, peak knee extension and varus/valgus internal moments, electromyographic (EMG) muscle activity of the quadriceps and hamstrings, and quadriceps/hamstring EMG cocontraction ratio were measured. The tasks consisted of a single-legged drop jump from a 40-cm box and a 20-cm, up-down, repeated hop task. The fatigued session included a Wingate anaerobic protocol followed by performance of the 2 tasks. Although participants exhibited greater knee injury-predisposing factors during the fatigued session, such as lesser knee flexion joint angles, greater knee valgus joint angles, and greater varus/valgus internal joint moments for both tasks, only knee flexion during the up-down task was statistically significant (p = 0.028). Metabolic fatigue may perhaps predispose young women to knee injuries by impairing dynamic knee joint stability. Training strength-endurance components and the ability to maintain control of body movements in either rested or fatigued situations might help reduce injuries in young women athletes.

  14. Jump Kinetic Determinants of Sprint Acceleration Performance from Starting Blocks in Male Sprinters

    PubMed Central

    Maulder, Peter S.; Bradshaw, Elizabeth J.; Keogh, Justin

    2006-01-01

    The purpose of this research was to identify the jump kinetic determinants of sprint acceleration performance from a block start. Ten male (mean ± SD: age 20 ± 3 years; height 1.82 ± 0.06 m; weight 76.7 ± 7.9 kg; 100 m personal best: 10.87 + 0.36 s {10.37 - 11.42}) track sprinters at a national and regional competitive level performed 10 m sprints from a block start. Anthropometric dimensions along with squat jump (SJ), countermovement jump (CMJ), continuous straight legged jump (SLJ), single leg hop for distance, and single leg triple hop for distance measures of power were also tested. Stepwise multiple regression analysis identified CMJ average power (W/kg) as a predictor of 10 m sprint performance from a block start (r = 0.79, r2 = 0.63, p<0.01, SEE = 0.04 (s), %SEE = 2.0). Pearson correlation analysis revealed CMJ force and power (r = -0.70 to -0.79; p = 0.011 - 0.035) and SJ power (r = -0.72 to -0.73; p = 0.026 - 0.028) generating capabilities to be strongly related to sprint performance. Further linear regression analysis predicted an increase in CMJ average and peak take-off power of 1 W/kg (3% & 1.5% respectively) to both result in a decrease of 0.01 s (0.5%) in 10 m sprint performance. Further, an increase in SJ average and peak take-off power of 1 W/kg (3.5% & 1.5% respectively) was predicted to result in a 0.01 s (0.5%) reduction in 10 m sprint time. The results of this study seem to suggest that the ability to generate power both elastically during a CMJ and concentrically during a SJ to be good indicators of predicting sprint performance over 10 m from a block start. Key Points The relative explosive ability of the hip and knee extensors during a countermovement jump can predict 10 m sprint performance from a block start. The relative power outputs of male competitive sprinters during a squat jump can predict 10 m sprint performance from a block start. PMID:24260010

  15. Biomechanical differences of arm swing countermovement jumps on sand and rigid surface performed by elite beach volleyball players.

    PubMed

    Giatsis, George; Panoutsakopoulos, Vassilios; Kollias, Iraklis A

    2017-07-04

    The purpose of this study was to investigate the possible arm swing effect on the biomechanical parameters of vertical counter movement jump due to differences of the compliance of the take-off surface. Fifteen elite male beach-volleyball players (26.2 ± 5.9 years; 1.87 ± 0.05 m; 83.4 ± 6.0 kg; mean ± standard deviation, respectively) performed counter movement jumps on sand and on a rigid surface with and without an arm swing. Results showed significant (p < .05) surface effects on the jump height, the ankle joint angle at the lowest height of the body center of mass and the ankle angular velocity. Also, significant arm swing effects were found on jump height, maximum power output, temporal parameters, range of motion and angular velocity of the hip. These findings could be attributed to the instability of the sand, which resulted in reduced peak power output due to the differences of body configuration at the lowest body position and lower limb joints' range of motion. The combined effect of the backward arm swing and the recoil of the sand that resulted in decreased resistance at ankle plantar flexion should be controlled at the preparation of selected jumping tasks in beach-volleyball.

  16. Assessment of isokinetic knee strength in elite young female basketball players: correlation with vertical jump.

    PubMed

    Rouis, M; Coudrat, L; Jaafar, H; Filliard, J-R; Vandewalle, H; Barthelemy, Y; Driss, T

    2015-12-01

    To explore the isokinetic concentric strength of the knee muscle groups, and the relationship between the isokinetic knee extensors strength and the vertical jump performance in young elite female basketball players. Eighteen elite female basketball players performed a countermovement jump, and an isokinetic knee test using a Biodex dynamometer. The maximal isokinetic peak torque of the knee extensor and flexor muscles was recorded at four angular velocities (90°/s, 180°/s, 240°/s and 300°/s) for the dominant and non-dominant legs. The conventional hamstring/quadriceps ratio (H/Q) was assessed at each angular velocity for both legs. There was no significant difference between dominant and non-dominant leg whatever the angular velocity (all P>0.05). However, the H/Q ratio enhanced as the velocity increased from 180°/s to 300°/s (P<0.05). Furthermore, low to high significant positive correlations were detected between the isokinetic measures of the knee extensors and the vertical jump height. The highest one was found for the knee extensors peak torque at a velocity of 240°/s (r=0.88, P<0.001). The results accounted for an optimal velocity at which a strong relationship could be obtained between isokinetic knee extensors strength and vertical jump height. Interestingly, the H/Q ratio of the young elite female basketball players in the present study was unusual as it was close to that generally observed in regular sportsmen.

  17. Measurement of in vivo anterior cruciate ligament strain during dynamic jump landing.

    PubMed

    Taylor, K A; Terry, M E; Utturkar, G M; Spritzer, C E; Queen, R M; Irribarra, L A; Garrett, W E; DeFrate, L E

    2011-02-03

    Despite recent attention in the literature, anterior cruciate ligament (ACL) injury mechanisms are controversial and incidence rates remain high. One explanation is limited data on in vivo ACL strain during high-risk, dynamic movements. The objective of this study was to quantify ACL strain during jump landing. Marker-based motion analysis techniques were integrated with fluoroscopic and magnetic resonance (MR) imaging techniques to measure dynamic ACL strain non-invasively. First, eight subjects' knees were imaged using MR. From these images, the cortical bone and ACL attachment sites of the tibia and femur were outlined to create 3D models. Subjects underwent motion analysis while jump landing using reflective markers placed directly on the skin around the knee. Next, biplanar fluoroscopic images were taken with the markers in place so that the relative positions of each marker to the underlying bone could be quantified. Numerical optimization allowed jumping kinematics to be superimposed on the knee model, thus reproducing the dynamic in vivo joint motion. ACL length, knee flexion, and ground reaction force were measured. During jump landing, average ACL strain peaked 55±14 ms (mean and 95% confidence interval) prior to ground impact, when knee flexion angles were lowest. The peak ACL strain, measured relative to its length during MR imaging, was 12±7%. The observed trends were consistent with previously described neuromuscular patterns. Unrestricted by field of view or low sampling rate, this novel approach provides a means to measure kinematic patterns that elevate ACL strains and that provide new insights into ACL injury mechanisms. Copyright © 2010 Elsevier Ltd. All rights reserved.

  18. Measurement of in vivo anterior cruciate ligament strain during dynamic jump landing

    PubMed Central

    Taylor, K.A.; Terry, M.E.; Utturkar, G.M.; Spritzer, C.E.; Queen, R.M.; Irribarra, L.A.; Garrett, W.E.; DeFrate, L.E.

    2011-01-01

    Despite recent attention in the literature, anterior cruciate ligament (ACL) injury mechanisms are controversial and incidence rates remain high. One explanation is limited data on in vivo ACL strain during high-risk, dynamic movements. The objective of this study was to quantify ACL strain during jump landing. Marker-based motion analysis techniques were integrated with fluoroscopic and magnetic resonance (MR) imaging techniques to measure dynamic ACL strain non-invasively. First, eight subjects’ knees were imaged using MR. From these images, the cortical bone and ACL attachment sites of the tibia and femur were outlined to create 3D models. Subjects underwent motion analysis while jump landing using reflective markers placed directly on the skin around the knee. Next, biplanar fluoroscopic images were taken with the markers in place so that the relative positions of each marker to the underlying bone could be quantified. Numerical optimization allowed jumping kinematics to be superimposed on the knee model, thus reproducing the dynamic in vivo joint motion. ACL length, knee flexion, and ground reaction force were measured. During jump landing, average ACL strain peaked 55 ± 14 ms (mean and 95% confidence interval) prior to ground impact, when knee flexion angles were lowest. The peak ACL strain, measured relative to its length during MR imaging, was 12 ± 7%. The observed trends were consistent with previously described neuromuscular patterns. Unrestricted by field of view or low sampling rate, this novel approach provides a means to measure kinematic patterns that elevate ACL strains and that provide new insights into ACL injury mechanisms. PMID:21092960

  19. CO and H2O vibrational emission toward Orion Peak 1 and Peak 2

    NASA Astrophysics Data System (ADS)

    González-Alfonso, E.; Wright, C. M.; Cernicharo, J.; Rosenthal, D.; Boonman, A. M. S.; van Dishoeck, E. F.

    2002-05-01

    ISO/SWS observations of Orion Peak 1 and Peak 2 show strong emission in the ro-vibrational lines of CO v=1-0 at 4.45-4.95 μm and of H2O ν2=1-0 at 6.3-7.0 μm. Toward Peak 1 the total flux in both bands is, assuming isotropic emission, ≈2.4 and ≈0.53 Lsun, respectively. This corresponds to ≈14 and ≈3% of the total H2 luminosity in the same beam. Two temperature components are found to contribute to the CO emission from Peak 1/2: a warm component, with TK=200-400 K, and a hot component with Tk~3×103 K. At Peak 2 the CO flux from the warm component is similar to that observed at Peak 1, but the hot component is a factor of ≈2 weaker. The H2O band is ≈25% stronger toward Peak 2, and seems to arise only in the warm component. The P-branch emission of both bands from the warm component is significantly stronger than the R-branch, indicating that the line emission is optically thick. Neither thermal collisions with H2 nor with H I seem capable of explaining the strong emission from the warm component. Although the emission arises in the postshock gas, radiation from the most prominent mid-infrared sources in Orion BN/KL is most likely pumping the excited vibrational states of CO and H2O. CO column densities along the line of sight of N{(CO)}=5-10×1018 cm-2 are required to explain the band shape, the flux, and the P-R-asymmetry, and beam-filling is invoked to reconcile this high N(CO) with the upper limit inferred from the H2 emission. CO is more abundant than H2O by a factor of at least 2. The density of the warm component is estimated from the H2O emission to be ~ 2×107 cm-3. The CO emission from the hot component is neither satisfactorily explained in terms of non-thermal (streaming) collisions, nor by resonant scattering. Vibrational excitation through collisions with H2 for densities of ~3×108 cm-3 or, alternatively, with atomic hydrogen, with a density of at least 107 cm-3, are invoked to explain simultaneously the emission from the hot component

  20. Asymmetrical loading demands associated with vertical jump landings in people with unilateral transtibial amputation.

    PubMed

    Schoeman, Marlene; Diss, Ceri E; Strike, Siobhan C

    2013-01-01

    Loading symmetry during vertical jump landings between a person with amputation's intact and prosthetic limbs was assessed to determine the role of each limb in controlling the downward momentum of the center of mass during landing. Six participants with unilateral transtibial amputation (TTA) and ten nondisabled participants completed 10 maximal vertical jumps, of which the highest jump was analyzed. Contralateral symmetry was assessed through the Symmetry Index (SI), while symmetry at the group level was assessed through a Mann-Whitney U test. Participants with TTA performed quasi-unilateral landings onto the intact limbs, resulting from either the incapability of the prosthetic ankle to plantar flex or increased residual-limb knee and hip flexion. In the loading phase, the participants with TTA displayed reduced prosthetic-side peak vertical forces (p = 0.04) along with reduced prosthetic-side ankle range of motion (p < 0.001), extensor moments (p = 0.03), and negative work generated (p = 0.00). Individual asymmetries were evident in the peak vertical force magnitudes (SI = 51%-140%), duration from touchdown to peak vertical force (SI = 52%-157%), ankle joint angles at touchdown (SI = 100%-538%), ranges of motion (SI = 147%-200%), knee (SI = 66%-179%) and hip (SI = 87%-132%) extensor moments, and work done at the ankle (SI = 155%-199%) and hip (SI = 83%-204%). High peak forces (25.25 +/- 4.89 N·kg(-1) intact limb and 14.61 +/- 8.28 N·kg(-1) prosthetic limb) from significantly lower (p < 0.001) landing heights than the nondisabled participants indicate a potential injury risk associated with landing for people with TTA.

  1. Validity and intra-rater reliability of MyJump app on iPhone 6s in jump performance.

    PubMed

    Stanton, Robert; Wintour, Sally-Anne; Kean, Crystal O

    2017-05-01

    Smartphone applications are increasingly used by researchers, coaches, athletes and clinicians. The aim of this study was to examine the concurrent validity and intra-rater reliability of the smartphone-based application, MyJump, against laboratory-based force plate measurements. Cross sectional study. Participants completed counter-movement jumps (CMJ) (n=29) and 30cm drop jumps (DJ) (n=27) on a force plate which were simultaneously recorded using MyJump. To assess concurrent validity, jump height, derived from flight time acquired from each device, was compared for each jump type. Intra-rater reliability was determined by replicating data analysis of MyJump recordings on two occasions separated by seven days. CMJ and DJ heights derived from MyJump showed excellent agreement with the force plate (ICC values range from 0.991 for CMJ to 0.993) However mean DJ height from the force plate was significantly higher than MyJump (mean difference: 0.87cm, 95% CI: 0.69-1.04cm). Intra-rater reliability of MyJump for both CMJ and DJ was almost perfect (ICC values range from 0.997 for CMJ to 0.998 for DJ); however, mean CMJ and DJ jump height for Day 1 was significantly higher than Day 2 (CMJ: 0.43cm, 95% CI: 0.23-0.62cm); (DJ: 0.38cm, 95% CI: 0.23-0.53cm). The present study finds MyJump to be a valid and highly reliable tool for researchers, coaches, athletes and clinicians; however, systematic bias should be considered when comparing MyJump outputs to other testing devices. Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  2. Predator Mimicry: Metalmark Moths Mimic Their Jumping Spider Predators

    PubMed Central

    Rota, Jadranka; Wagner, David L.

    2006-01-01

    Cases of mimicry provide many of the nature's most convincing examples of natural selection. Here we report evidence for a case of predator mimicry in which metalmark moths in the genus Brenthia mimic jumping spiders, one of their predators. In controlled trials, Brenthia had higher survival rates than other similarly sized moths in the presence of jumping spiders and jumping spiders responded to Brenthia with territorial displays, indicating that Brenthia were sometimes mistaken for jumping spiders, and not recognized as prey. Our experimental results and a review of wing patterns of other insects indicate that jumping spider mimicry is more widespread than heretofore appreciated, and that jumping spiders are probably an important selective pressure shaping the evolution of diurnal insects that perch on vegetation. PMID:17183674

  3. Orbital emphysema as a complication of bungee jumping.

    PubMed

    Krott, R; Mietz, H; Krieglstein, G K

    1997-07-01

    Bungee jumping is a dangerous sport with increasing popularity in the western world. We report the case of a 28-yr-old man who sustained an orbital emphysema as a result of bungee jumping. He jumped head first from a 160-ft high bridge over a river. At the end of the jump he dived into the water with his head in a reclined position. The sudden dive into the water caused an increase of the air pressure in the nose and paranasal sinuses, which led to an emphysema of the right orbit resulting from a skull fracture not detectable by x-ray. The patient was treated with oral antibiotics. Five days later, he had no clinical complaints and the ophthalmologic examination was normal. This variation of bungee jumping may bear severe risk factors for health in addition to those known from the classic jumps.

  4. Robust Filtering for Nonlinear Nonhomogeneous Markov Jump Systems by Fuzzy Approximation Approach.

    PubMed

    Yin, Yanyan; Shi, Peng; Liu, Fei; Teo, Kok Lay; Lim, Cheng-Chew

    2015-09-01

    This paper addresses the problem of robust fuzzy L2-L∞ filtering for a class of uncertain nonlinear discrete-time Markov jump systems (MJSs) with nonhomogeneous jump processes. The Takagi-Sugeno fuzzy model is employed to represent such nonlinear nonhomogeneous MJS with norm-bounded parameter uncertainties. In order to decrease conservation, a polytope Lyapunov function which evolves as a convex function is employed, and then, under the designed mode-dependent and variation-dependent fuzzy filter which includes the membership functions, a sufficient condition is presented to ensure that the filtering error dynamic system is stochastically stable and that it has a prescribed L2-L∞ performance index. Two simulated examples are given to demonstrate the effectiveness and advantages of the proposed techniques.

  5. Vibrational dynamics and boson peak in a supercooled polydisperse liquid.

    PubMed

    Abraham, Sneha Elizabeth; Bagchi, Biman

    2010-03-01

    Vibrational density of states (VDOS) in a supercooled polydisperse liquid is computed by diagonalizing the Hessian matrix evaluated at the potential energy minima for systems with different values of polydispersity. An increase in polydispersity leads to an increase in the relative population of localized high-frequency modes. At low frequencies, the density of states shows an excess compared to the Debye squared-frequency law, which has been identified with the boson peak. The height of the boson peak increases with polydispersity and shows a rather narrow sensitivity to changes in temperature. While the modes comprising the boson peak appear to be largely delocalized, there is a sharp drop in the participation ratio of the modes that exist just below the boson peak indicative of the quasilocalized nature of the low-frequency vibrations. Study of the difference spectrum at two different polydispersity reveals that the increase in the height of boson peak is due to a population shift from modes with frequencies above the maximum in the VDOS to that below the maximum, indicating an increase in the fraction of the unstable modes in the system. The latter is further supported by the facilitation of the observed dynamics by polydispersity. Since the strength of the liquid increases with polydispersity, the present result provides an evidence that the intensity of boson peak correlates positively with the strength of the liquid, as observed earlier in many experimental systems.

  6. Correlation Between Local Structure and Boson Peak in Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Ahmad, Azkar Saeed; Zhao, Xiangnan; Xu, Mingxiang; Zhang, Dongxian; Hu, Junwen; Fecht, Hans J.; Wang, Xiaodong; Cao, Qingping; Jiang, J. Z.

    2017-01-01

    We made a systematic study of the boson peak for six different Zr-based metallic glasses and found a universal correlation between average local atomic structure and boson peak. It is found that the boson peak can be decomposed into six characteristic vibratory modes, i.e., Debye's vibratory mode and five Einstein's vibratory modes. By using the Ioffe-Regel condition over all studied Zr-based metallic glasses, we reveal that atomic pair correlation function exactly maps on the low-temperature dynamics and the origin of the boson peak, which is the sum of vibrations of local density fluctuation domains in the glasses. In addition, it is found that the Debye's type oscillators are the major contributors to the low-temperature specific heat capacities. This study opens a new way of understanding the relationship of the physical properties with the atomic arrangements in glasses.

  7. The influence of resting period length on jumping performance.

    PubMed

    Pereira, Gleber; Almeida, Alexandre G; Rodacki, André L F; Ugrinowitsch, Carlos; Fowler, Neil E; Kokubun, Eduardo

    2008-07-01

    The purpose of this study was to determine a resting interval between countermovement jumps (i.e., volleyball spikes) that allows the maintenance of maximal jumping performance. Ten male volleyball players (1.85 +/- 0.05 m, 77.2 +/- 10.6 kg, 21.6 +/- 5.3 years) performed 6 experimental jumping sessions. In the first and sixth sessions, maximal countermovement jump height was measured, followed by submaximal countermovement jumps to the point of volitional fatigue. The number of countermovement jumps was used as a reference to test the effect of rest period between volleyball spikes. From the second to fifth experimental sessions, 30 maximal volleyball spikes were performed with different resting periods (i.e., 8, 14, 17, and 20 seconds) followed by countermovement jumps. Between the 15th and 30th spikes, the blood lactate concentration and heart rate were measured. Because the performance on the first and sixth sessions was the same, no training effects were noticed. During the 8-second resting interval set, the lactate concentration increased significantly between the 15th and 30th spikes (i.e., from 3.37 +/- 1.16 mmol to 4.94 +/- 1.49 mmol); the number of countermovement jumps decreased significantly after spikes compared to those performed without a previous effort (i.e., from 23 +/- 7 jumps to 17 +/- 9 jumps); and these variables were significantly correlated (r = -0.7). On the other hand, the lactate concentration and number of countermovement jumps were stable across the other resting intervals, without a heart rate steady state. The results indicate that an adequate resting period between spikes allowed participants to achieve a lactate steady state in which the performance was maintained during the exercise. These findings show that resting intervals between 14 and 17 seconds, typical during volleyball matches, are indicated to use in volleyball spike drills due to their capacity to maintain maximal jumping performance.

  8. Manifestations of Proprioception During Vertical Jumps to Specific Heights

    PubMed Central

    Struzik, Artur; Pietraszewski, Bogdan; Winiarski, Sławomir; Juras, Grzegorz; Rokita, Andrzej

    2017-01-01

    Abstract Artur, S, Bogdan, P, Kawczyński, A, Winiarski, S, Grzegorz, J, and Andrzej, R. Manifestations of proprioception during vertical jumps to specific heights. J Strength Cond Res 31(6): 1694–1701, 2017—Jumping and proprioception are important abilities in many sports. The efficiency of the proprioceptive system is indirectly related to jumps performed at specified heights. Therefore, this study recorded the ability of young athletes who play team sports to jump to a specific height compared with their maximum ability. A total of 154 male (age: 14.8 ± 0.9 years, body height: 181.8 ± 8.9 cm, body weight: 69.8 ± 11.8 kg, training experience: 3.8 ± 1.7 years) and 151 female (age: 14.1 ± 0.8 years, body height: 170.5 ± 6.5 cm, body weight: 60.3 ± 9.4 kg, training experience: 3.7 ± 1.4 years) team games players were recruited for this study. Each participant performed 2 countermovement jumps with arm swing to 25, 50, 75, and 100% of the maximum height. Measurements were performed using a force plate. Jump height and its accuracy with respect to a specified height were calculated. The results revealed no significant differences in jump height and its accuracy to the specified heights between the groups (stratified by age, sex, and sport). Individuals with a higher jumping accuracy also exhibited greater maximum jump heights. Jumps to 25% of the maximum height were approximately 2 times higher than the target height. The decreased jump accuracy to a specific height when attempting to jump to lower heights should be reduced with training, particularly among athletes who play team sports. These findings provide useful information regarding the proprioceptive system for team sport coaches and may shape guidelines for training routines by working with submaximal loads. PMID:28538322

  9. Data reliability from an instrumented vertical jump platform.

    PubMed

    Caruso, John F; Daily, Jeremy S; McLagan, Jessica R; Shepherd, Catherine M; Olson, Nathan M; Marshall, Mallory R; Taylor, Skyler T

    2010-10-01

    A Vertec jump measurement and training system measures vertical jump heights but not additional variables that would reveal how the performance was achieved. Technology advances to equipment now include additional variables that elucidate how jump performance is achieved. However, acceptance of new jump-related equipment is predicated on the reliability of the vertical heights it measures in relation to those assessed by the Vertec. Thus, our study compared vertical jump height reliability data from a newly created instrumented platform to those concurrently derived from the Vertec. Methods required subjects (n = 105) to perform 2 jump trials separated by at least 2 days of rest. Trials began with a warm-up, followed by 3 to 5 maximal-effort jumps. The Vertec was placed directly over the platform so, as jumps occurred, subjects took off and landed on the instrumented device. At the jump apex subjects contacted the highest Vertec slapstick possible to assess maximum height attained. Four height measurements were derived from each jump: 3 platform-based calculations (from subject's take-off, hang time, and landing) and 1 Vertec. The platform-based calculations were compared to Vertec data to assess the reliability of the instrumented device. Intraclass correlation coefficient (0.90), coefficient of variation (17.3%), standard error of measurement (0.9 cm), and smallest real difference (3.7 cm) results showed heights calculated from platform take-offs were most reliable to Vertec values. It was concluded take-off from the platform yielded jump heights that are a viable alternative to those derived from the Vertec. Practical applications suggest coaches may use the platform to derive reliable vertical jump data in addition to other variables to better understand the performance of their athletes.

  10. Hydrodynamics of jumping for prey capture in Archer fish

    NASA Astrophysics Data System (ADS)

    Techet, A. H.; Shih, A. M.

    2010-11-01

    The prey capture behavior by jumping Archer fish (Toxotes microlepisis) was investigated using high speed imaging and particle imaging velocimetry (PIV). Archer fish are renowned for their ability to spit jets of water at insects and also to jump out of the water to capture their prey. Our investigations reveal that the fish typically fail to reach their prey by jumping when the bait is placed at a height above 3.5 body lengths. After jumping and failing, the fish do not typically jump again, only spit. For our experiments bait was placed between 0.5 and 3.5 body lengths (BL) above the free surface, within reach of jumping, and thus the fish rarely spit unless they missed first by jumping. It is observed that the fish typically position their bodies under the bait with a slight angle, hover momentarily, snap in their pectoral fins, and then flap their tail in an "S-start"-type maneuver with a fixed number of cycles, which increases as a function of bait height. High speed imaging, including time-resolved PIV, was used to capture the kinematics of the jumping behavior and compare the fluid impulse generated during the fast start, jump maneuver with the total change in momentum of the fish body. Maximum acceleration was observed in the early stages of the jump maneuver and was often on the order of 5 to 15 times gravity. Correlations between the maximum energy, power in, number of tail beats, jump height and overall jumping kinematics will be discussed.

  11. Jump to contact of hcp nanowires

    NASA Astrophysics Data System (ADS)

    Wakasugi, Shinsaku; Kurokawa, Shu; Sakai, Akira

    2016-12-01

    Exploiting molecular dynamics simulations, we have investigated jump to contact (JC) at the recontact of broken Mg and Cd nanowires. We observed frequent JCs for junctions of these soft hcp metals, as previously reported for soft fcc metals [C. Untiedt et al., Phys. Rev. Lett. 98, 206801 (2007)]. Thus, the crystal structure matters little for JC, and the high rate of JC should be a common characteristic of soft metal junctions. Recontacts of broken nanowires also lead to the frequent formation of single-atom contacts (SACs). For comparison, we have also studied JC and the SAC formation for tip-sample junctions of Pb.

  12. Katabatic jumps over Martian polar terrains

    NASA Astrophysics Data System (ADS)

    Spiga, Aymeric; Smith, Isaac; Holt, Jack

    2015-04-01

    Recent observational and modeling studies have shed light on the key role of mesoscale phenomena in driving the Martian climate and giving rise to remarkable signatures in the temperature, wind, pressure, and aerosol fields of the Martian atmosphere. At the mesoscale, Mars appears as an intense and exotic counterpart to the Earth, mainly as a result of pronounced diurnal and regional contrasts of surface temperature, and the much thinner atmosphere. While observations of clear-cut katabatic events are difficult on Earth, except over vast ice sheets, those intense downslope circulations are widespread on Mars owing to near-surface radiative cooling and uneven topography. Their intensity and regularity can be witnessed through numerous aeolian signatures on the surface, and distinctive thermal signatures in the steepest craters and volcanoes. Several observations (radar observations, frost streaks, spectral analysis of ices, ...) concur to show that aeolian processes play a key role in glacial processes in Martian polar regions over geological timescales. A spectacular manifestation of this resides in elongated clouds that forms at the bottom of polar spiral troughs, which dominates the polar landscape both in the North and South. An analogy with the terrestrial "wall-of-snow" over e.g. Antarctica slopes or coastlines posits that those clouds are caused by local katabatic jumps, also named Loewe phenomena, which can be deemed similar to first order to hydraulic jumps in open channel flow. With mesoscale modeling in polar regions using 5 nested domains operating a model downscaling from horizontal resolutions of about twenty kilometers to 200 meters, we were able 1. to predict the near-surface wind structure over the whole Martian polar caps, with interactions between katabatic acceleration, Coriolis deflection, transient phenomena, and thermally-forced circulations by the ice / bare soil contrast and 2. to show that katabatic jumps form at the bottom of polar troughs

  13. On the jump behavior of distributions and logarithmic averages

    NASA Astrophysics Data System (ADS)

    Vindas, Jasson; Estrada, Ricardo

    2008-11-01

    The jump behavior and symmetric jump behavior of distributions are studied. We give several formulas for the jump of distributions in terms of logarithmic averages, this is done in terms of Cesàro-logarithmic means of decompositions of the Fourier transform and in terms of logarithmic radial and angular local asymptotic behaviors of harmonic conjugate functions. Application to Fourier series are analyzed. In particular, we give formulas for jumps of periodic distributions in terms of Cesàro-Riesz logarithmic means and Abel-Poisson logarithmic means of conjugate Fourier series.

  14. Patterns of injury in a fatal BASE jumping accident.

    PubMed

    Wolf, Barbara C; Harding, Brett E

    2008-12-01

    Skydiving is a popular and relatively safe sport. The patterns of injury and mechanisms of death in the rare fatalities resulting from skydiving accidents have been well-documented. In contrast, BASE jumping, that is, jumping from a fixed object using a parachute, is a more dangerous and unregulated sport practiced by few individuals. There are no reports in forensic literature documenting the injuries found in deaths occurring in the practice of BASE jumping. We report the case of the death of an experienced BASE jumper who died after jumping from the antenna of a radio broadcast tower in southwest Florida to illustrate the unique hazards inherent in this sport.

  15. Tuning Superhydrophobic Nanostructures To Enhance Jumping-Droplet Condensation.

    PubMed

    Mulroe, Megan D; Srijanto, Bernadeta R; Ahmadi, S Farzad; Collier, C Patrick; Boreyko, Jonathan B

    2017-08-22

    It was recently discovered that condensation growing on a nanostructured superhydrophobic surface can spontaneously jump off the surface, triggered by naturally occurring coalescence events. Many reports have observed that droplets must grow to a size of order 10 μm before jumping is enabled upon coalescence; however, it remains unknown how the critical jumping size relates to the topography of the underlying nanostructure. Here, we characterize the dynamic behavior of condensation growing on six different superhydrophobic nanostructures, where the topography of the nanopillars was systematically varied. The critical jumping diameter was observed to be highly dependent upon the height, diameter, and pitch of the nanopillars: tall and slender nanopillars promoted 2 μm jumping droplets, whereas short and stout nanopillars increased the critical size to over 20 μm. The topology of each surface is successfully correlated to the critical jumping diameter by constructing an energetic model that predicts how large a nucleating embryo needs to grow before it can inflate into the air with an apparent contact angle large enough for jumping. By extending our model to consider any possible surface, it is revealed that properly designed nanostructures should enable nanometric jumping droplets, which would further enhance jumping-droplet condensers for heat transfer, antifogging, and antifrosting applications.

  16. Theory of spacecraft potential jump in geosynchronous plasma

    NASA Astrophysics Data System (ADS)

    Huang, Jianguo; Liu, Guoqing; Jiang, Lixiang

    2015-12-01

    For disturbed geosynchronous plasma, the onset of spacecraft charging and its evolution become more complex than quiet environment. A sudden jump of spacecraft potential can occur in specific environment conditions which can be detrimental to onboard electronics. In this paper, the potential jump for geosynchronous spacecraft charging is theoretically modeled and comprehensively characterized. Two types of potential jump in opposite directions are elucidated, and the threshold conditions for both types of jump are determined. At both thresholds, the spacecraft potentials are semisteady, but in opposite directions, with the possibility of a jump to a stable potential. The polarity of movement across the thresholds from different plasma will cause a spacecraft to experience irreversible charging histories which result in significant hysteresis. Generally, the jump to negative potential occurs with greater magnitude as compared to a potential jump in positive direction. Ion distribution has negligible influence to the threshold condition for jump to negative potential. However, ion distribution significantly affects the threshold for jump to positive potential and subsequently modifies the parametric domains of spacecraft charging.

  17. Distance perception in the spiny mouse Acomys cahirinus: vertical jumping.

    PubMed

    Goldman, M; Skolnick, A J; Hernandez, T P; Tobach, E

    1992-12-01

    Acomys cahirinus, a precocial muroid, that has shown precise jumping in the natural habitat, did not jump from 25 cm in a laboratory situation. To investigate this further, A. cahirinus were observed jumping from platforms at two different heights, onto different sized checkered substrates and from a visual cliff. Adult animals discriminated between platforms that were 6.4 cm and 25.4 cm above the substrate and between small and large checkered patterns on the floor. Most adult animals and neonates jumped down on the shallow side of the visual cliff. Animals developed individual patterns of jumping over a series of trials, with some jumping often, some rarely, and others jumping only from the low platform. Good distance perception was indicated when they did not jump from heights, and by their making appropriate postural adjustment when they did jump from heights and landed without mishap. Different spacing of trials indicated that height was a more effective stimulus for animals which had all four conditions on the same day, while floor pattern was more effective for animals with each of the four conditions on a separate day.

  18. Effect of drop jump technique on the reactive strength index

    PubMed Central

    Juras, Grzegorz; Pietraszewski, Bogdan; Rokita, Andrzej

    2016-01-01

    Abstract The basic drill of plyometric training aimed at improving lower limb power and jump height is a drop jump. This exercise can be performed using different techniques, which substantially affects jump variables. Therefore, the aim of this study was to compare the values of the reactive strength index (RSI) for countermovement drop jumps (CDJs) and bounce drop jumps (BDJs). The study was carried out in a group of 8 male youth basketball players. The tests were conducted using the AMTI BP600900 force plate to measure ground reaction forces and the Noraxon MyoMotion system to record kinematic data. Each player performed two CDJs and two BDJs from the height of 15, 30, 45 and 60 cm. The RSI was calculated as a ratio of jump height and contact time. Moreover, the RSI was determined for the amortization and take-off phases separately. Significant differences (p < 0.05) between RSI values for CDJs and BDJs were recorded for jumps from 30, 45 and 60 cm. Differences in RSI values for jumps from 15 cm were not significant. Furthermore, CDJ height values were significantly higher (p < 0.05) than the values recorded for BDJs. Times of contact, amortization and take-off during BDJs were significantly shorter (p < 0.05) than the respective values obtained for CDJs. Therefore, the use of the RSI to monitor plyometric training should be based on the drop jump technique that is commonly performed by basketball players. PMID:28149403

  19. Tuning Superhydrophobic Nanostructures To Enhance Jumping-Droplet Condensation

    DOE PAGES

    Mulroe, Megan D.; Srijanto, Bernadeta R.; Ahmadi, S. Farzad; ...

    2017-07-18

    It was recently discovered that condensation growing on a nanostructured superhydrophobic surface can spontaneously jump off the surface, triggered by naturally occurring coalescence events. Many reports have observed that droplets must grow to a size of order 10 μm before jumping is enabled upon coalescence; however, it remains unknown how the critical jumping size relates to the topography of the underlying nanostructure. Here, we characterize the dynamic behavior of condensation growing on six different superhydrophobic nanostructures, where the topography of the nanopillars was systematically varied. The critical jumping diameter was observed to be highly dependent upon the height, diameter, andmore » pitch of the nanopillars: tall and slender nanopillars promoted 2 μm jumping droplets while short and stout nanopillars increased the critical size to over 20 μm. The topology of each surface is successfully correlated to the critical jumping diameter by constructing an energetic model that predicts how large a nucleating embryo needs to grow before it can inflate into the air with an apparent contact angle large enough for jumping. Furthermore, by extending our model to consider any possible surface, it is revealed that properly designed nanostructures should enable nanometric jumping droplets, which would further enhance jumping droplet condensers for heat transfer, anti-fogging, and anti-frosting applications.« less

  20. Effect of drop jump technique on the reactive strength index.

    PubMed

    Struzik, Artur; Juras,