We prove that the characteristic flow of a K-contact form has at least n+1 closed leaves on a closed 2n+1-dimensional manifold. We also show that the first Betti number of a closed sasakian manifold with finitely many closed characteristics is zero.

International research consistently finds gender differences in depression, but do women genuinely experience more complaints or are the findings contaminated by group-specific elements unrelated to depression but affecting its measurement? The study of gender differences in depression depends on the measurement quality of the instrument used to evaluate depression. In the present study we test...

The State-Dependant Riccati Equation method has been frequently used to design suboptimal controllers applied to nonlinear dynamic systems. Different methods for local stability analysis of SDRE controlled systems of order greater than two such as the attitude dynamics of a general rigid body have been extended in literature; however, it is still difficult to show global stability properties of...

In this article, let Σ ⊂ R be a compact convex hypersurface which is symmetric with respect to the origin. We prove that if Σ carries finitely many geometrically distinct closed characteristics, then at least n − 1 of them must be non-hyperbolic; if Σ carries exactly n geometrically distinct closed characteristics, then at least two of them must be elliptic.

In this article, let Σ ⊂ R be a compact convex hypersurface which is (r,R)-pinched with R r < √ 3 2 . Then Σ carries at least two strictly elliptic closed characteristics; moreover, Σ carries at least 2[ 4 ] non-hyperbolic closed characteristics.

Parental investment theory predicts differences in risk-taking for females and males as a consequence of reproductive context, with females attempting to reduce risks in relation to their own offspring (here called the baby effect) and males taking more risks in competition with one another (young male syndrome). The experiment we report tests these predictions in a cooperative context by intro...

This study investigated the changes in performance and sex difference in performance of the world best triathletes at the ITU (International Triathlon Union) World Triathlon Series (i.e. 1.5 km swimming, 40 km cycling and 10 km running) during the 2009-2012 period including the 2012 London Olympic Games. Changes in overall race times, split times and sex difference in performance of the top ten...

The function of mate retention tactics is to prevent a long-term partner from defecting from the relationship and to ward off potential mate poachers. These tactics include Concealment of Mate, Appearance Enhancement, and Violence against Rivals. The current research is the first to investigate the performance of husband’s and wife’s mate retention tactics over time. We assessed 49 husbands and...