Static balance has a relevant influence on athletic performance as well as on reducing the risk of injury. The main goal of this study was to assess soccer athlete versus non-athlete balance performance via displacement and velocity parameters extracted from the center-of-pressure (COP) position time series. In order to accomplish our goal, we investigated standing balance in two male groups with unimpaired balance: non-athletes (n = 12) and collegiate varsity soccer athletes (n = 12). In order to make the standing balancing task more or less difficult, we altered participant base-of-support, as well as vision, yielding static (quiet stance) test conditions increasing in difficulty. From the COP position time series, displacement and velocity parameters were computed and plotted as a function of increasing test condition difficulty level. COP parameters showed steeper increases with increased test difficulty in non-athletes compared to athletes; this demonstrated athletes’ better ability to control their balance. We concluded that balance performance could be characterized via COP displacement and velocity response curves. This study lends new insights into how COP parameters can be utilized to determine and characterize improvements in balance between un-impaired subject populations (athletes versus non-athletes).

We derive a fully quantum-mechanical equation of motion for a vortex in a 2-dimensional Bose superfluid in the temperature regime where the normal fluid density ρn(T ) is small. The coupling between the vortex "zero mode" and the quasiparticles has no term linear in the quasiparticle variables -the lowest-order coupling is quadratic. We find that as a function of the dimensionless frequencyΩ = Ω/kBT , the standard Hall-Vinen-Iordanskii equations are valid whenΩ 1 (the "classical regime"), but elsewhere, the equations of motion become highly retarded, with significant experimental implications whenΩ 1. Remarkably, the fundamental question of how vortices and quasiparticles interact, and how vortices move is very controversial, notably for superfluids [5][6][7]. The argument is usually phrased in terms of forces acting on a vortex moving with respect to both the superfluid [having local velocity v s (r) and superfluid density ρ s ] and the normal fluid [with velocity v n (r) and density ρ n ]. Then, the classical equation of motion for the semiclassical vortex coordinate R v (t) (here taken to be a point in the plane -we discuss the 3D problem at the end) is usually written [8] aswhere F ac (t) is some driving force, M v is the vortex mass,Magnus force for a vortex with circulation κ =ẑh/m, and the quasiparticle force iswhereThese "HVI equations," due to Hall, Vinen, and Iordanskii [8,9], have been used to analyze thousands of experiments in superfluids and superconductors in the last 60 years [10]. However, there is no consensus on the value of either the mass M v (estimates in the literature range from zero to infinity [6,9,[11][12][13]. The resolution of these questions has become an important unsolved problem in physics. We briefly discuss the experimental situation below.Previous analyses have been restricted to a local (in space and time) description, derived from semiclassical or perturbative calculations of quasiparticle scattering off a static vortex, with no vortex recoil [6,9,[11][12][13]. This yields forces acting instantaneously on a quasiclassical vortex coordinate R v (t). There is no general agreement between these calculations (which are rendered difficult by the long-range vortex profile). Our tactic has been to formulate the problem fully quantum mechanically, in terms of an equation of motion for the vortex reduced density matrixρ(R, R ; t) which is obtained by integrating out all quasiparticle degrees of freedom. Here the vortex coordinate states |R , |R are defined by the position of the vortex node appearing in the many-body wave function. We then define a vortex "center of mass" coordinate R v = 1 2 (R + R ), and a "quantum fluctuation coordinate" ξ = R − R . Equations of motion are then found for these two quantum variables, with the vortex recoil automatically incorporated. Remarkably, in thermal equilibrium we find that the results largely depend on one key parameter, the ratioΩ = Ω/k B T , where Ω is the characteristic frequency of the vortex motion, and k B T is the thermal energy of ...

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Intravaginal rings (IVRs) are currently under investigation as devices for the delivery of agents to protect against the sexual transmission of HIV and STIs, as well as pregnancy. To assist product developers in creating highly acceptable rings, we sought to identify characteristics that intravaginal ring users consider when making decisions about ring use or non-use. We conducted four semi-structured focus groups with 21 women (aged 18–45) who reported using an IVR in the past 12 months. Participants manipulated four prototype rings in their hands, discussed ring materials, dimensionality, and “behavior,” and shared perceptions and appraisals. Five salient ring characteristics were identified: 1) appearance of the rings’ surfaces, 2) tactile sensations of the cylinder material, 3) materials properties, 4) diameter of the cylinder, and 5) ring circumference. Pliability (or flexibility) was generally considered the most important mechanical property. Several ring properties (e.g., porousness, dimensionality) were associated with perceptions of efficacy. Women also revealed user behaviors that may impact the effectiveness of certain drugs, such as removing, rinsing and re-inserting the ring while bathing, and removing the ring during sexual encounters. As product developers explore IVRs as prevention delivery systems, it is critical to balance product materials and dimensions with use parameters to optimize drug delivery and the user experience. It is also critical to consider how user behaviors (e.g., removing the ring) might impact drug delivery.

Women’s initial understandings and anticipated acceptability of long-acting vaginal gels as potential anti-HIV microbicides was investigated by exploring the perceptibility variables associated with prototype formulations. Four focus groups with 29 women, aged 18–45, were conducted to consider gel prototypes with varied physicochemical and rheological properties. Participants responded favorably to the concept of long-acting vaginal gels as microbicides. Distinctions in understandings and stated needs regarding product dosing, characteristics, and effectiveness offer valuable insights into product design. Long-acting vaginal gels capable of protecting against HIV/STIs will be a viable option among potential users, with dosing frequency being an important factor in willingness to use.