1,927 research outputs found
Factors associated with injuries among first-division Rwandan female soccer players
Background: Female soccer has grown tremendously in the last decade. Studies have suggested that female soccer players are more susceptible to injuries than their male counterparts, and their vulnerability is due mainly to intrinsic factors such as their anatomical and physiological structure. Objectives: To establish factors associated with soccer injuries among first-division Rwandan female soccer players. Methods: In a descriptive cross-sectional study, self-administered questionnaires were used to investigate factors associated with injuries among soccer players. Results: Almost half of the 300 participants (45%) indicated having been injured in the three seasons prior to the study. More than half (52.6%) were recurrent injuries. The ankle was the most common body part injured. Intrinsic factors associated with injuries were age, excessive ankle range of motion, pre-menstrual symptoms, and previous injury (p-value < 0.05). Extrinsic factors associated with injuries were use of oral contraceptive pills, (OCP), competition level, use of protective equipment, and playerâs position. Conclusions: The large number of recurring injuries was notable, emphasizing the importance of prevention strategies and access to adequately trained medical personnel as research has shown a significant reduction in the prevalence of recurring injuries after the introduction of effective prevention programmes
Gamma Ray Fresnel lenses - why not?
Fresnel lenses offer the possibility of concentrating the flux of X-rays or
gamma-rays flux falling on a geometric area of many square metres onto a focal
point which need only be a millimetre or so in diameter (and which may even be
very much smaller). They can do so with an efficiency that can approach 100%,
and yet they are easily fabricated and have no special alignment requirements.
Fresnel lenses can offer diffraction-limited angular resolution, even in a
domain where that limit corresponds to less than a micro second of arc.
Given all these highly desirable attributes, it is natural to ask why Fresnel
gamma ray lenses are not already being used, or at least why there is not yet
any mission that plans to use the technology. Possible reasons (apart from the
obvious one that nobody thought of doing so) include the narrow bandwidth of
simple Fresnel lenses, their very long focal length, and the problems of target
finding. It is argued that none of these is a "show stopper" and that this
technique should be seriously considered for nuclear astrophysics.Comment: Presented at "Gamma Wave 2005", Bonifacio, September 2005. To be
published in "Experimental Astronomy
Assessing system reliability through binary decision diagrams using bayesian techniques.
Binary Decision Diagrams (BDDs) have been shown to be efficient for the numerical
evaluation of the reliability of complex systems. They achieve exact results where
Fault Tree Analysis could generally produce only bounds. In this paper the approach
to systems evaluation using a Bayesian method in conjunction with BDDs is explored.
The advantages of the approach are discussed with respect to both efficiency and the
ability to deal with dependency within the system in a natural manner. As an
illustration a simple pump configuration is considered which features a dependency.
The results demonstrate both the flexibility of the approach and the ease of dealing
with the additional complexity of dependency
The impact of aging on the neural networks involved in gaze and emotional processing.
Normal adult aging is associated with difficulties in processing social cues to emotions such as anger and also altered motivation to focus more on positive than negative information. Gaze direction is an important modifier of the social signals conveyed by an emotion, for example, an angry face looking directly at you is considerably more threatening than an angry face looking away. In the present study we tested the hypothesis that older adults would show less neural differentiation to angry faces with direct and avert gaze compared to younger people, with the opposite prediction for happy faces. Healthy older (65-75 years; mean = 69.75) and younger (17-27 years; mean = 20.65) adults completed a functional magnetic resonance imaging experiment in which they were asked to identify happy and angry expressions displayed either with direct or averted gaze. While younger adults showed neural sensitivity to eye-gaze direction during recognition of angry expressions, older adults showed no effect of eye-gaze direction on neural response. In contrast, older adults showed sensitivity to eye-gaze direction during recognition of happy expressions but younger adults did not. Additionally, brain-behavior correlations were conducted to investigate the relationships between emotion recognition and mentalizing brain network in both age groups. Younger (but not older) adults' social cognitive performance was differentially correlated with activation in 2 brain networks when looking at angry faces with direct compared to averted gaze. These novel findings provide evidence for age-related differences in the neural substrates underlying the capacity to integrate facial affect and eye-gaze cues. The results of this study suggest that age-related differences in integrating facial cues may be related to engagement of the mentalizing network, with potentially important implications for social cognitive functioning in late adulthood
The Shortest Scale of Quantum Field Theory
It is suggested that the Minkowski vacuum of quantum field theories of a
large number of fields N would be gravitationally unstable due to strong vacuum
energy fluctuations unless an N dependent sub-Planckian ultraviolet momentum
cutoff is introduced. We estimate this implied cutoff using an effective
quantum theory of massless fields that couple to semi-classical gravity and
find it (assuming that the cosmological constant vanishes) to be bounded by
. Our bound can be made consistent with entropy bounds and
holography, but does not seem to be equivalent to either, and it relaxes but
does not eliminate the implied bound on N inherent in entropy bounds.Comment: 8 pages. One author added, additional clarifcations and discussions.
Figure removed. Version published in PR
Testing a Grassroots Citizen Science Venture Using Open Design, âthe Bee Lab Projectâ
The Bee Lab project applies Citizen Science and Open Design to beekeeping, enabling participants to construct monitoring devices gathering reciprocal data, motivating participants and third parties. The presented approach uses design workshops to provide insight into the design of kits, user motivations, promoting reciprocal interests and address community problems. This paper signposts issues and opportunities in the process of designing Citizen Science tools for communities using Open Design to solve individual problems, including: downloadable design for social/local change, laypeople creating technology and repairable kits
Transformation of in-plane in at fixed oxygen content
This paper reveals the origin of variation in the magnitude and temperature
dependence of the normal state resistivity frequently observed in different
YBCO single crystal or thin film samples with the same . We investigated
temperature dependence of resistivity in thin films
with 7- and 6.90, which were subjected to annealing in argon at
400-420 K (). Before annealing these films exhibited a non-linear
, with a flattening below 230 K, similar to and
observed in untwinned and twinned YBCO crystals, respectively.
For all films the annealing causes an increase of resistivity and a
transformation of from a non-linear dependence towards a more
linear one (less flattening). In films with 7- the increase of
resistivity is also associated with an increase in . We proposed the
model that provides an explanation of these phenomena in terms of thermally
activated redistribution of residual O(5) oxygens in the chain-layer of YBCO.
Good agreement between the experimental data for , where t is
the annealing time, and numerical calculations was obtained.Comment: 8 pages, 9 figures, submitted to PR
Tensile Forces and Shape Entropy Explain Observed Crista Structure in Mitochondria
A model is presented from which the observed morphology of the inner
mitochondrial membrane can be inferred as minimizing the system's free energy.
Besides the usual energetic terms for bending, surface area, and pressure
difference, our free energy includes terms for tension that we believe to be
exerted by proteins and for an entropic contribution due to many dimensions
worth of shapes available at a given energy.
In order to test the model, we measured the structural features of
mitochondria in HeLa cells and mouse embryonic fibroblasts using 3D electron
tomography. Such tomograms reveal that the inner membrane self-assembles into a
complex structure that contains both tubular and flat lamellar crista
components. This structure, which contains one matrix compartment, is believed
to be essential to the proper functioning of mitochondria as the powerhouse of
the cell. We find that tensile forces of the order of 10 pN are required to
stabilize a stress-induced coexistence of tubular and flat lamellar cristae
phases. The model also predicts \Deltap = -0.036 \pm 0.004 atm and \sigma=0.09
\pm 0.04 pN/nm
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