Ergodic directions for billiards in a strip with periodically located obstacles

We study the size of the set of ergodic directions for the directional billiard flows on the infinite band $\R\times [0,h]$ with periodically placed linear barriers of length $0<\lambda<h$. We prove that the set of ergodic directions is always uncountable. Moreover, if $\lambda/h\in(0,1)$ is rational the Hausdorff dimension of the set of ergodic directions is greater than 1/2. In both cases (rational and irrational) we construct explicitly some sets of ergodic directions.Comment: The article is complementary to arXiv:1109.458

The Effects of Varying Doses of Caffeine on Sports Skill Related Performance and Reaction Time

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Identifying experiences of supportive care of children and young people affected by kidney failure: a qualitative systematic review.

Children and young people affected by kidney failure experience complexities in their care. Little is known about the unique needs of this young patient population group living with a long-term condition. A meta-aggregation of all qualitative studies was conducted to identify experiences of supportive care among children and young people living with kidney failure. A systematic review of qualitative studies was conducted following the Joanna Briggs Institute meta-aggregation method. This review has been reported according to the PRISMA statement guidelines. Six electronic databases (CINAHL, Cochrane Library, MEDLINE, Proquest, PsycINFO, and Scopus) were comprehensively searched by an expert systematic review librarian using keywords and subject headings, from inception to September 2022. All studies were accessed using a predetermined inclusion and exclusion criteria. Methodological quality assessment and data extraction performed. Qualitative findings accompanied by illustrative quotes from included studies were extracted and grouped into categories which created the overall synthesised findings. A total of 34 studies were included in this review representing a total of 613 children and young people affected by kidney failure. There was a total of 190 findings which created 13 categories representing experiences of supportive care. The meta-aggregation developed five synthesised findings namely: 'physical needs', 'information and technology', 'treatment and healthcare', 'social needs' and 'psychological impacts'. This systematic review identified that children and young people affected by kidney failure can experience a range of unmet supportive care needs in routine clinical services. Kidney failure impacted children and young people's self-identify, social and peer networks, introduced daily practical needs because of inherent physical and psychological burden due to the failure and associated treatments. Despite improvements in the medical management of kidney failure in children and young people, further attention is needed to optimise supported self-management in this young patient group

Elastic Scattering and Direct Detection of Kaluza-Klein Dark Matter

Recently a new dark matter candidate has been proposed as a consequence of universal compact extra dimensions. It was found that to account for cosmological observations, the masses of the first Kaluza-Klein modes (and thus the approximate size of the extra dimension) should be in the range 600-1200 GeV when the lightest Kaluza-Klein particle (LKP) corresponds to the hypercharge boson and in the range 1 - 1.8 TeV when it corresponds to a neutrino. In this article, we compute the elastic scattering cross sections between Kaluza-Klein dark matter and nuclei both when the lightest Kaluza-Klein particle is a KK mode of a weak gauge boson, and when it is a neutrino. We include nuclear form factor effects which are important to take into account due to the large LKP masses favored by estimates of the relic density. We present both differential and integrated rates for present and proposed Germanium, NaI and Xenon detectors. Observable rates at current detectors are typically less than one event per year, but the next generation of detectors can probe a significant fraction of the relevant parameter space.Comment: 23 pages, 11 figures; v2,v3: Ref. added, discussion improved, conclusions unchanged. v4: Introduction was expanded to be more appropriate for non experts. Various clarifications added in the text. Version to be published in New Journal of Physic

Should psychiatrists 'Google' their patients?

Since its beginnings in the 1980s the internet has come to shape our everyday lives, but doctors still seem rather afraid of it. This anxiety may be explained by the fact that researchers and regulatory bodies focus less on the way that the internet can be used to enhance clinical work and more on the potential and perceived risks that this technology poses in terms of boundary violations and accidental breaches of confidentiality. Some aspects of the internet’s impact on medicine have been better researched than others, for example, whether email communication, social media and teleconferencing psychotherapy could be used to improve the delivery of care. However, few authors have considered the specific issue of searching online for information about patients and much of the guidance published by regulatory organisations eludes this issue. In this article we provide clinical examples where the question ‘should I Google the patient?’ may arise and present questions for future research

The Isotropic Radio Background and Annihilating Dark Matter

Observations by ARCADE-2 and other telescopes sensitive to low frequency radiation have revealed the presence of an isotropic radio background with a hard spectral index. The intensity of this observed background is found to exceed the flux predicted from astrophysical sources by a factor of approximately 5-6. In this article, we consider the possibility that annihilating dark matter particles provide the primary contribution to the observed isotropic radio background through the emission of synchrotron radiation from electron and positron annihilation products. For reasonable estimates of the magnetic fields present in clusters and galaxies, we find that dark matter could potentially account for the observed radio excess, but only if it annihilates mostly to electrons and/or muons, and only if it possesses a mass in the range of approximately 5-50 GeV. For such models, the annihilation cross section required to normalize the synchrotron signal to the observed excess is sigma v ~ (0.4-30) x 10^-26 cm^3/s, similar to the value predicted for a simple thermal relic (sigma v ~ 3 x 10^-26 cm^3/s). We find that in any scenario in which dark matter annihilations are responsible for the observed excess radio emission, a significant fraction of the isotropic gamma ray background observed by Fermi must result from dark matter as well.Comment: 11 pages, 6 figure

The acute response of tendon to loading: implications for rehabilitation

Achilles tendinopathy is a common disorder involving physically active and sedentary individuals alike. Although the processes underlying its development are poorly understood, tendinopathy is widely regarded as an ‘overuse’ injury in which the tendon fails to adapt to prevalent loading conditions. Paradoxically, there is emerging evidence that heavy eccentric loading of the Achilles tendon may be an effective conservative approach for treatment of tendinopathy, with success rates of 60–80% reported. Interestingly, loading exercises involving other forms of muscle action, such as concentric activation, have been shown to be less effective treatment options. However, little is known about the acute response of tendon to exercise at present, and there are few plausible explanatory mechanisms for the observed beneficial effects of eccentric exercise, as opposed to other forms of strain stimuli. This paper presents the findings from a series of experiments undertaken to evaluate the effect of various strain stimuli on the time-dependent response of human Achilles tendon in vivo. It was shown for the first time, that heavy resistive ankle plantarflexion/ dorsiflexion exercises induced an immediate and significant decrease in Achilles tendon thickness (~15%). While thickness returned to pre-exercise levels within 24 hours, the recovery was exponential, with primary recovery occurring in less than 6 hours post-exercise. We proposed that such a diametral strain response with tensile loading reflects collagen realignment, Poison’s effects and radial extrusion of water from the tendon core. With unloading, the recovery of tendon dimensions likely reflects the re-diffusion of water via osmotic and/or inflammatory driven processes. Interestingly, prolonged walking was found to induce a similar diametral strain response. In subsequent studies, we demonstrated that eccentric exercise resulted in a greater reduction (-21%) in Achilles tendon thickness than isolated concentric exercise alone (-5%), despite a similar loading impulse. These novel findings, coupled with observations of a reduced diametral strain response with tendon pathology, highlight the importance of fluid movement to tendon function, nutrition and health. They also provide new insights into potential mechanisms underlying Achilles tendinopathy that impact rehabilitation strategies