Unambiguous determination of gravitational waveforms from binary black hole mergers

Gravitational radiation is properly defined only at future null infinity (\scri), but in practice it is estimated from data calculated at a finite radius. We have used characteristic extraction to calculate gravitational radiation at \scri for the inspiral and merger of two equal mass non-spinning black holes. Thus we have determined the first unambiguous merger waveforms for this problem. The implementation is general purpose, and can be applied to calculate the gravitational radiation, at \scri, given data at a finite radius calculated in another computation.Comment: 4 pages, 3 figures, published versio

Discrete Breathers in a Nonlinear Polarizability Model of Ferroelectrics

We present a family of discrete breathers, which exists in a nonlinear polarizability model of ferroelectric materials. The core-shell model is set up in its non-dimensionalized Hamiltonian form and its linear spectrum is examined. Subsequently, seeking localized solutions in the gap of the linear spectrum, we establish that numerically exact and potentially stable discrete breathers exist for a wide range of frequencies therein. In addition, we present nonlinear normal mode, extended spatial profile solutions from which the breathers bifurcate, as well as other associated phenomena such as the formation of phantom breathers within the model. The full bifurcation picture of the emergence and disappearance of the breathers is complemented by direct numerical simulations of their dynamical instability, when the latter arises.Comment: 9 pages, 7 figures, 1 tabl

Intra- and inter-limb strength asymmetry in soccer: a comparison of professional and under-18 players

(1) Background: the present study examined the isokinetic peak torque exerted by both knee extensors and flexors, anterior–posterior imbalance and the magnitude and direction of inter-limb asymmetry in professional and academy soccer players. (2) Methods: one hundred soccer players (professional = 50, elite academy = 50) volunteered to take part in this investigation. An isokinetic dynamometer was used to measure the knee extensor (quadriceps) and flexors muscle (hamstrings) torques of the limbs as well as inter-limb asymmetries—using a standard percentage difference equation. (3) Results: professional players exhibited significantly greater (effect size [ES] = large) strength levels in the quadriceps and hamstrings under both testing conditions, significantly higher (small to moderate) intra-limb ratio values for 60°·s−1 but not for the 300°·s−1 test condition, significantly (small to moderate) lower inter-limb asymmetry values for all test conditions, with the exception of the hamstrings at 60°·s−1 and the direction of asymmetry was poor to slight, indicating that limb dominance was rarely the same between groups. (4) Conclusions: this study shows that isokinetic assessments, i.e., peak torque exerted by both knee extensors and flexors and intra-limb ratio, and the subsequent inter-limb asymmetry, i.e., magnitude and direction, can differentiate between professional and academy soccer players

Integrity static analysis of COTS/SOUP

This paper describes the integrity static analysis approach developed to support the justification of commercial off-the-shelf software (COTS) used in a safety-related system. The static analysis was part of an overall software qualification programme, which also included the work reported in our paper presented at Safecomp 2002. Integrity static analysis focuses on unsafe language constructs and “covert” flows, where one thread can affect the data or control flow of another thread. The analysis addressed two main aspects: the internal integrity of the code (especially for the more critical functions), and the intra-component integrity, checking for covert channels. The analysis process was supported by an aggregation of tools, combined and engineered to support the checks done and to scale as necessary. Integrity static analysis is feasible for industrial scale software, did not require unreasonable resources and we provide data that illustrates its contribution to the software qualification programme

Comment on "Can one predict DNA Transcription Start Sites by Studying Bubbles?"

Comment on T.S. van Erp, S. Cuesta-Lopez, J.-G. Hagmann, and M. Peyrard, Phys. Rev. Lett. 95, 218104 (2005) [arXiv: physics/0508094]

Initial data transients in binary black hole evolutions

We describe a method for initializing characteristic evolutions of the Einstein equations using a linearized solution corresponding to purely outgoing radiation. This allows for a more consistent application of the characteristic (null cone) techniques for invariantly determining the gravitational radiation content of numerical simulations. In addition, we are able to identify the {\em ingoing} radiation contained in the characteristic initial data, as well as in the initial data of the 3+1 simulation. We find that each component leads to a small but long lasting (several hundred mass scales) transient in the measured outgoing gravitational waves.Comment: 18 pages, 4 figure

Inter-limb strength asymmetry in adolescent distance runners: test-retest reliability and relationships with performance and running economy

The purpose of this investigation was, firstly, to quantify the test-retest reliability of strength measures in adolescent distance runners; and secondly, to explore the relationships between inter-limb strength asymmetry and performance and running economy (RE) in a similar cohort of young runners. For the reliability study, twelve (n=6 female) post-pubertal adolescent distance runners performed an isometric quarter-squat on a dual force plate and unilateral isometric hip extension and hip abduction tests on two occasions. For the correlation study, participants (n=31) performed the strength tests plus a submaximal incremental running assessment and a maximal running test. Running economy was expressed as the average energy cost of running for all speeds below lactate turnpoint and was scaled for body mass using a previously calculated power exponent. Allometrically scaled peak force during the quarter-squat and peak torque in the hip strength tasks showed acceptable levels of reproducibility (typical error ≤6.3%). Relationships between strength asymmetry and performance and RE were low or negligible (r0.05), except for hip abduction strength asymmetry and RE in the female participants (r=0.85, p<0.001, n=16). Practitioners should consider inter-limb hip abduction strength asymmetry on an individual level, and attempting to reduce this asymmetry in females may positively impact RE

Optimal training sequences to develop lower body force, velocity, power, and jump height: a systematic review with meta-analysis

Background: Resistance training has been used to enhance a range of athletic abilities through correct manipulation of several variables such as training load, training volume, set configuration, and rest period. Objective: The aim of this systematic review and meta-analysis was to compare the acute and chronic responses of lower body cluster, contrast, complex, and traditional training across a range of athletic performance outcomes (1-repetition maximum squat strength, jump height, peak power, peak force, peak velocity, and sprint time). Methods: A database search was completed (SPORTDiscus, Medline and CINAHL) followed by a quality scoring system, which concluded with 41 studies being used in the meta-analysis. Effect sizes were calculated for acute and training intervention changes compared to baseline. For acute cluster training, effect sizes were used to represent differences between equated traditional and cluster sets. Results: Acutely, contrast and cluster training can be implemented to enhance and maintain velocity. Complex training does not acutely show a performance-enhancing effect on jump performance. Conclusion: When looking to develop exercise-specific force, the exercise should be completed closer to set failure with fewer repetitions still able to be completed, which can be achieved using complex or high-volume contrast training to pre-fatigue the lighter exercise. When the objective is to improve velocity for the target exercise, it can be combined with a heavier contrast pair to create a postactivation performance enhancing effect. Alternatively, cluster set designs can be used to maintain high velocities and reduce drop-off. Finally, traditional training is most effective for increasing squat 1-repetition maximum

A systematic review of kinematic models used in foot & ankle biomechanics

Over the past decade our understanding of foot function has increased significantly. Our understanding of foot and ankle biomechanics appears to be directly correlated to advances in models used to assess and quantify kinematic parameters in gait. These advances in models in turn lead to greater detail in the data. However, we must consider that the level of complexity is determined by the question or task being analysed. This systematic review aims to provide a critical appraisal of commonly used marker sets and foot models to assess foot and ankle kinematics in a wide variety of clinical and research purposes