Geometric Integration of Hamiltonian Systems Perturbed by Rayleigh Damping

Explicit and semi-explicit geometric integration schemes for dissipative perturbations of Hamiltonian systems are analyzed. The dissipation is characterized by a small parameter $\epsilon$, and the schemes under study preserve the symplectic structure in the case $\epsilon=0$. In the case $0<\epsilon\ll 1$ the energy dissipation rate is shown to be asymptotically correct by backward error analysis. Theoretical results on monotone decrease of the modified Hamiltonian function for small enough step sizes are given. Further, an analysis proving near conservation of relative equilibria for small enough step sizes is conducted. Numerical examples, verifying the analyses, are given for a planar pendulum and an elastic 3--D pendulum. The results are superior in comparison with a conventional explicit Runge-Kutta method of the same order

Diffeomorphic random sampling using optimal information transport

In this article we explore an algorithm for diffeomorphic random sampling of nonuniform probability distributions on Riemannian manifolds. The algorithm is based on optimal information transport (OIT)---an analogue of optimal mass transport (OMT). Our framework uses the deep geometric connections between the Fisher-Rao metric on the space of probability densities and the right-invariant information metric on the group of diffeomorphisms. The resulting sampling algorithm is a promising alternative to OMT, in particular as our formulation is semi-explicit, free of the nonlinear Monge--Ampere equation. Compared to Markov Chain Monte Carlo methods, we expect our algorithm to stand up well when a large number of samples from a low dimensional nonuniform distribution is needed.Comment: 8 pages, 3 figure

Middleborns disadvantaged? testing birth-order effects on fitness in pre-industrial finns

Parental investment is a limited resource for which offspring compete in order to increase their own survival and reproductive success. However, parents might be selected to influence the outcome of sibling competition through differential investment. While evidence for this is widespread in egg-laying species, whether or not this may also be the case in viviparous species is more difficult to determine. We use pre-industrial Finns as our model system and an equal investment model as our null hypothesis, which predicts that (all else being equal) middleborns should be disadvantaged through competition. We found no overall evidence to suggest that middleborns in a family are disadvantaged in terms of their survival, age at first reproduction or lifetime reproductive success. However, when considering birth-order only among same-sexed siblings, first-, middle-and lastborn sons significantly differed in the number of offspring they were able to rear to adulthood, although there was no similar effect among females. Middleborn sons appeared to produce significantly less offspring than first-or lastborn sons, but they did not significantly differ from lastborn sons in the number of offspring reared to adulthood. Our results thus show that taking sex differences into account is important when modelling birth-order effects. We found clear evidence of firstborn sons being advantaged over other sons in the family, and over firstborn daughters. Therefore, our results suggest that parents invest differentially in their offspring in order to both preferentially favour particular offspring or reduce offspring inequalities arising from sibling competition

‘‘Beet-ing’’ the Mountain: A Review of the Physiological and Performance Effects of Dietary Nitrate Supplementation at Simulated and Terrestrial Altitude

Exposure to altitude results in multiple physiological consequences. These include, but are not limited to, a reduced maximal oxygen consumption, drop in arterial oxygen saturation, and increase in muscle metabolic perturbations at a fixed sub-maximal work rate. Exercise capacity during fixed work rate or incremental exercise and time-trial performance are also impaired at altitude relative to sea-level. Recently, dietary nitrate (NO3-) supplementation has attracted considerable interest as a nutritional aid during altitude exposure. In this review, we summarise and critically evaluate the physiological and performance effects of dietary NO3- supplementation during exposure to simulated and terrestrial altitude. Previous investigations at simulated altitude indicate that NO3- supplementation may reduce the oxygen cost of exercise, elevate arterial and tissue oxygen saturation, improve muscle metabolic function, and enhance exercise capacity/ performance. Conversely, current evidence suggests that NO3- supplementation does not augment the training response at simulated altitude. Few studies have evaluated the effects of NO3- at terrestrial altitude. Current evidence indicates potential improvements in endothelial function at terrestrial altitude following NO3- supplementation. No effects of NO3- supplementation have been observed on oxygen consumption or arterial oxygen saturation at terrestrial altitude, although further research is warranted. Limitations of the present body of literature are discussed, and directions for future research are provided

Family physicians' effort to stay in charge of the medical treatment when patients have home care by district nurses. A grounded theory study

<p>Abstract</p> <p>Background</p> <p>District nurses (DNs) provide home care for old persons with a mixture of chronic diseases, symptoms and reduced functional ability. Family physicians (FPs) have been criticised for their lack of involvement in this care. The aim of this study was to obtain increased knowledge concerning the FP's experience of providing medical treatment for patients with home care provided by DNs by developing a theoretical model that elucidates how FPs handle the problems they encounter regarding the individual patients and their conditions.</p> <p>Methods</p> <p>Semi-structured interviews were conducted with 13 Swedish FPs concerning one of their registered patients with home care by a DN, and the treatment of this patient. Grounded theory methodology (GTM) was used in the analyses.</p> <p>Results</p> <p>The core category was the effort to stay in charge of the medical treatment. This involved three types of problems: gaining sufficient insight, making adequate decisions, and maintaining appropriate medical treatment. For three categories of patients, the FPs had problems staying in charge. Patients with reduced functional ability had problems providing information and maintaining treatment. Patients who were "fixed in their ways" did not provide information and did not comply with recommendations, and for patients with complex conditions, making adequate decisions could be problematic. To overcome the problems, four different strategies were used: relying on information from others, supporting close observation and follow-up by others, being constantly ready to change the goal of the treatment, and relying on others to provide treatment.</p> <p>Conclusion</p> <p>The patients in this study differed from most other patients seen at the healthcare centre as the consultation with the patient could not provide the usual foundation for decisions concerning medical treatment. Information from and collaboration with the DN and other home care providers was essential for the FP's effort to stay in charge of the medical treatment. The complexity of the situation made it problematic for the FP to make adequate decisions about the goal of the medical treatment. The goal of the treatment had to be constantly evaluated based on information from the DN and other care providers, and thus this information was absolutely crucial.</p

Beetroot juice supplementation speeds O2 uptake kinetics and improves exercise tolerance during severe-intensity exercise initiated from an elevated metabolic rate

Recent research has suggested that dietary nitrate (NO3-) supplementation might alter the physiological responses to exercise via specific effects on type II muscle. Severe-intensity exercise initiated from an elevated metabolic rate would be expected to enhance the proportional activation of higher-order (type II) muscle fibers. The purpose of this study was therefore to test the hypothesis that, compared to placebo (PL), NO3--rich beetroot juice (BR) supplementation would speed the phase II o2 kinetics (τp) and enhance exercise tolerance during severe-intensity exercise initiated from a baseline of moderate-intensity exercise. Nine healthy, physically-active subjects were assigned in a randomized, double-blind, crossover design to receive BR (140 mL/day, containing ~8 mmol of NO3-) and PL (140 mL/day, containing ~0.003 mmol of NO3-) for 6 days. On days 4, 5 and 6 of the supplementation periods, subjects completed a double-step exercise protocol that included transitions from unloaded-to-moderate intensity exercise (U→M) followed immediately by moderate-to-severe-intensity exercise (M→S). Compared to PL, BR elevated resting plasma nitrite concentration (PL: 65 ± 32 vs. BR: 348 ± 170 nM, P0.05). During M→S exercise, the faster o2 kinetics coincided with faster NIRS-derived muscle [deoxyhemoglobin] kinetics (τ; PL: 20 ± 9 vs. BR: 10 ± 3 s, P<0.05) and a 22% greater time-to-task failure (PL: 521 ± 158 vs. BR: 635 ± 258 s, P<0.05). Dietary supplementation with NO3--rich BR juice speeds o2 kinetics and enhances exercise tolerance during severe-intensity exercise when initiated from an elevated metabolic rate

HLA-A Confers an HLA-DRB1 Independent Influence on the Risk of Multiple Sclerosis

A recent high-density linkage screen confirmed that the HLA complex contains the strongest genetic factor for the risk of multiple sclerosis (MS). In parallel, a linkage disequilibrium analysis using 650 single nucleotide polymorphisms (SNP) markers of the HLA complex mapped the entire genetic effect to the HLA-DR-DQ subregion, reflected by the well-established risk haplotype HLA-DRB1*15,DQB1*06. Contrary to this, in a cohort of 1,084 MS patients and 1,347 controls, we show that the HLA-A gene confers an HLA-DRB1 independent influence on the risk of MS (P = 8.4×10−10). This supports the opposing view, that genes in the HLA class I region indeed exert an additional influence on the risk of MS, and confirms that the class I allele HLA-A*02 is negatively associated with the risk of MS (OR = 0.63, P = 7×10−12) not explained by linkage disequilibrium with class II. The combination of HLA-A and HLA-DRB1 alleles, as represented by HLA-A*02 and HLA-DRB1*15, was found to influence the risk of MS 23-fold. These findings imply complex autoimmune mechanisms involving both the regulatory and the effector arms of the immune system in the triggering of MS

Effects of high-dose versus standard-dose quadrivalent influenza vaccine among patients with diabetes: a post-hoc analysis of the DANFLU-1 trial

Aim: High-dose quadrivalent influenza vaccine (QIV-HD) has been shown to be more effective than standard-dose (QIV-SD) in reducing influenza infection, but whether diabetes status affects relative vaccine effectiveness (rVE) is unknown. We aimed to assess rVE on change in glycated haemoglobin [HbA1c (∆HbA1c)], incident diabetes, total all-cause hospitalizations (first + recurrent), and a composite of all-cause mortality and hospitalization for pneumonia or influenza. Methods: DANFLU-1 was a pragmatic, open-label trial randomizing adults (65-79 years) 1:1 to QIV-HD or QIV-SD during the 2021/22 influenza season. Cox proportional hazards regression was used to estimate rVE against incident diabetes and the composite endpoint, negative binomial regression to estimate rVE against all-cause hospitalizations, and ANCOVA when assessing rVE against ∆HbA1c. Results: Of the 12 477 participants, 1162 (9.3%) had diabetes at baseline. QIV-HD, compared with QIV-SD, was associated with a reduction in the rate of all-cause hospitalizations irrespective of diabetes [overall: 647 vs. 742 events, incidence rate ratio (IRR): 0.87, 95% CI (0.76-0.99); diabetes: 93 vs. 118 events, IRR: 0.80, 95% CI (0.55-1.15); without diabetes: 554 vs. 624 events, IRR: 0.88, 95% CI (0.76-1.01), pinteraction = 0.62]. Among those with diabetes, QIV-HD was associated with a lower risk of the composite outcome [2 vs. 11 events, HR: 0.18, 95% CI (0.04-0.83)] but had no effect on ∆HbA1c; QIV-HD adjusted mean difference: ∆ + 0.2 mmol/mol, 95% CI (−0.9 to 1.2). QIV-HD did not affect the risk of incident diabetes [HR 1.18, 95% CI (0.94-1.47)]. Conclusions: In this post-hoc analysis, QIV-HD versus QIV-SD was associated with an increased rVE against the composite of all-cause death and hospitalization for pneumonia/influenza, and the all-cause hospitalization rate irrespective of diabetes status

Effectiveness of high-dose versus standard-dose quadrivalent influenza vaccine against recurrent hospitalizations and mortality in relation to influenza circulation: a post-hoc analysis of the DANFLU-1 randomized clinical trial

Objectives: To evaluate the relative effectiveness of high-dose quadrivalent influenza vaccine (QIV-HD) versus standard-dose quadrivalent influenza vaccine (QIV-SD) against recurrent hospitalizations and its potential variation in relation to influenza circulation. Methods: We did a post-hoc analysis of a pragmatic, open-label, randomized trial of QIV-HD versus QIV-SD performed during the 2021–2022 influenza season among adults aged 65–79 years. Participants were enrolled in October 2021–November, 2021 and followed for outcomes from 14 days postvaccination until 31 May, 2022. We investigated the following outcomes: Hospitalizations for pneumonia or influenza, respiratory hospitalizations, cardio-respiratory hospitalizations, cardiovascular hospitalizations, all-cause hospitalizations, and all-cause death. Outcomes were analysed as recurrent events. Cumulative numbers of events were assessed weekly. Cumulative relative effectiveness estimates were calculated and descriptively compared with influenza circulation. The trial is registered at Clinicaltrials.gov: NCT05048589. Results: Among 12,477 randomly assigned participants, receiving QIV-HD was associated with lower incidence rates of hospitalizations for pneumonia or influenza (10 vs. 33 events, incidence rate ratio [IRR] 0.30 [95% CI, 0.14–0.64]; p 0.002) and all-cause hospitalizations (647 vs. 742 events, IRR 0.87 [95% CI, 0.76–0.99]; p 0.032) compared with QIV-SD. Trends favouring QIV-HD were consistently observed over time including in the period before active influenza transmission; i.e. while the first week with a ≥10% influenza test positivity rate was calendar week 10, 2022, the first statistically significant reduction in hospitalizations for pneumonia or influenza was already observed by calendar week 3, 2022 (5 vs. 15 events, IRR 0.33 [95% CI, 0.11–0.94]; p 0.037). Discussion: In a post-hoc analysis, QIV-HD was associated with lower incidence rates of hospitalizations for pneumonia or influenza and all-cause hospitalizations compared with QIV-SD, with trends evident independent of influenza circulation levels. Our exploratory results correspond to a number needed to treat of 65 (95% CI 35–840) persons vaccinated with QIV-HD compared with QIV-SD to prevent one additional all-cause hospitalization per season. Further research is needed to confirm these hypothesis-generating findings