Periodic Orbits and Escapes in Dynamical Systems

We study the periodic orbits and the escapes in two different dynamical systems, namely (1) a classical system of two coupled oscillators, and (2) the Manko-Novikov metric (1992) which is a perturbation of the Kerr metric (a general relativistic system). We find their simple periodic orbits, their characteristics and their stability. Then we find their ordered and chaotic domains. As the energy goes beyond the escape energy, most chaotic orbits escape. In the first case we consider escapes to infinity, while in the second case we emphasize escapes to the central "bumpy" black hole. When the energy reaches its escape value a particular family of periodic orbits reaches an infinite period and then the family disappears (the orbit escapes). As this family approaches termination it undergoes an infinity of equal period and double period bifurcations at transitions from stability to instability and vice versa. The bifurcating families continue to exist beyond the escape energy. We study the forms of the phase space for various energies, and the statistics of the chaotic and escaping orbits. The proportion of these orbits increases abruptly as the energy goes beyond the escape energy.Comment: 28 pages, 23 figures, accepted in "Celestial Mechanics and Dynamical Astronomy

The emerging prevalence of obesity within families in europe and its associations with family socio-demographic characteristics and lifestyle factors; a cross-sectional analysis of baseline data from the feel4diabetes study

The Feel4Diabetes study is a type 2 diabetes prevention program that recruited 12,193 children [age: 8.20 (±1.01) years] and their parents from six European countries. The current work used pre-intervention data collected from 9576 children–parents pairs, to develop a novel family obesity variable and to examine its associations with family sociodemographic and lifestyle characteristics. Family obesity, defined as the presence of obesity in at least two family members, had a prevalence of 6.6%. Countries under austerity measures (Greece and Spain) displayed higher prevalence (7.6%), compared to low-income (Bulgaria and Hungary: 7%) and high-income countries (Belgium and Finland: 4.5%). Family obesity odds were significantly lower when mothers (OR: 0.42 [95% CI: 0.32, 0.55]) or fathers (0.72 [95% CI: 0.57, 0.92]) had higher education, mothers were fully (0.67 [95% CI: 0.56, 0.81]) or partially employed (0.60 [95% CI: 0.45, 0.81]), families consumed breakfast more often (0.94 [95% CI: 0.91 0.96]), more portions of vegetables (0.90 [95% CI: 0.86, 0.95]), fruits (0.96 [95% CI: 0.92, 0.99]) and wholegrain cereals (0.72 [95% CI: 0.62, 0.83]), and for more physically active families (0.96 [95% CI: 0.93, 0.98]). Family obesity odds increased when mothers were older (1.50 [95% CI: 1.18, 1.91]), with the consumption of savoury snacks (1.11 [95% CI: 1.05, 1.17]), and increased screen time (1.05 [95% CI: 1.01, 1.09]). Clinicians should familiarise themselves with the risk factors for family obesity and choose interventions that target the whole family. Future research should explore the causal basis of the reported associations to facilitate devising tailored family-based interventions for obesity prevention

Cost effectiveness review of text messaging, smartphone application, and website interventions targeting T2DM or hypertension

Digital health interventions have been shown to be clinically-effective for type 2 diabetes mellitus (T2DM) and hypertension prevention and treatment. This study synthesizes and compares the cost-effectiveness of text-messaging, smartphone application, and websites by searching CINAHL, Cochrane Central, Embase, Medline and PsycInfo for full economic or cost-minimisation studies of digital health interventions in adults with or at risk of T2DM and/or hypertension. Costs and health effects are synthesised narratively. Study quality appraisal using the Consensus on Health Economic Criteria (CHEC) list results in recommendations for future health economic evaluations of digital health interventions. Of 3056 records identified, 14 studies are included (7 studies applied text-messaging, 4 employed smartphone applications, and 5 used websites). Ten studies are cost-utility analyses: incremental cost-utility ratios (ICUR) vary from dominant to €75,233/quality-adjusted life year (QALY), with a median of €3840/QALY (interquartile range €16,179). One study finds no QALY difference. None of the three digital health intervention modes is associated with substantially better cost-effectiveness. Interventions are consistently cost-effective in populations with (pre)T2DM but not in populations with hypertension. Mean quality score is 63.0% (standard deviation 13.7%). Substandard application of time horizon, sensitivity analysis, and subgroup analysis next to transparency concerns (regarding competing alternatives, perspective, and costing) downgrades quality of evidence. In conclusion, smartphone application, text-messaging, and website-based interventions are cost-effective without substantial differences between the different delivery modes. Future health economic studies should increase transparency, conduct sufficient sensitivity analyses, and appraise the ICUR more critically in light of a reasoned willingness-to-pay threshold

The need to improve access to dietetic services for people with type 2 diabetes

The need to improve access to dietetic services for people with type 2 diabete

Access To And Effectiveness Of Dietetic Services For People With Type 2 Diabetes

Nutrition therapy is central to the management of type 2 diabetes and Accredited Practising Dietitians have the expertise to best deliver this type of health care. Yet, some people with type 2 diabetes never consult with a dietitian. This research used a mixed-methods approach to assess the effectiveness of dietetic services and to elucidate the enablers and the barriers to access to these services for people with type 2 diabetes. Chapter 1 provides the context for this research by introducing the problem of type 2 diabetes mellitus and the strategies for its management with emphasis on diet. Chapter 2 summarises the methods. Chapters 3 and 4 respectively present the clinical- and cost-effectiveness evidence of dietetic interventions for type 2 diabetes. Nutrition interventions led by dietitians improve glycaemia more than when led by other healthcare professionals and are cost-effective, reducing hospitalisation costs and sick days at work and at home. Chapter 5 describes the inequitable access to dietetic services in Australia, with rural, remote and areas of lower socioeconomic status having higher prevalence of type 2 diabetes but less dietitians. The next chapters discuss the experiences and perspectives of people with type 2 diabetes (Chapter 7) and of dietitians (Chapter 6) and doctors (Chapter 8) that treat them, in regard to the access to and delivery of dietetic services for these people. Patients report that dietitians, social support and health literacy facilitate their dietary change. Although dietitians report a lack of referrals from doctors, doctors report preferring to refer their patients to a dietitian, but often not doing so due to lack of available services, inability to afford services or lack of motivation by patients. Chapter 9 reports on the utilisation of dietetic services in Australia. Chapter 10 collates the evidence from this research into recommendations for policy-makers. Finally, Chapter 11 highlights areas for future research

Elite athletes maintain peak performance after testing positive for SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has to date resulted in more than 200 million cases and more than four million deaths. Following a few months of hiatus, as part of the initial response to the pandemic, professional sporting activities resumed throughout the world. To ensure a safe return-to-play, the effects of SARS-CoV-2 infections on elite athletes were carefully monitored. Several elite professional athletes tested positive for SARS-CoV-2. A few reports of persistent and residual symptoms of infections emerged. However, peak athletic performance in elite athletes did not seem to be affected, with some athletes recording historical performances both in the weeks following as well as several months after contracting the novel coronavirus. This manuscript presents these data along with a discussion on the potential protective mechanisms in athletes. These findings raise further awareness about the importance of performing regular physical activity and maintaining a favourable body composition and overall fitness, and emphasise the need for public health initiatives and actions to promote a healthy lifestyle on a population level. Given that SARS-CoV-2, with its mutations, will be a chronic public health issue, preventive medicine measures such as advocacy and incentives to lead a healthy lifestyle are warranted as another shield, along with vaccines, in the arsenal against SARS-CoV-2