Activity

© 2020 The Author(s).We study the optimal design of numerical integrators for dissipative systems, for which there exists an underlying thermodynamic structure known as GENERIC (general equation for the nonequilibrium reversible-irreversible coupling). We present a frame-work to construct structure-preserving integrators by splitting the system into reversible and irreversible dynamics. The reversible part, which is often degenerate and reduces to a Hamiltonian form on its symplectic leaves, is solved by using a symplectic method (e.g. Verlet) with degenerate variables being left unchanged, for which an associated modified Hamiltonian (and subsequently a modified energy) in the form of a series expansion can be obtained by using backward error analysis. The modified energy is then used to construct a modified friction matrix associated with the irreversible part in such a way that a modified degeneracy condition is satisfied. The modified irreversible dynamics can be further solved by an explicit midpoint method if not exactly solvable. Our findings are verified by various numerical experiments, demonstrating the superiority of structure-preserving integrators over alternative schemes in terms of not only the accuracy control of both energy conservation and entropy production but also the preservation of the conformal symplectic structure in the case of linearly damped systems. © 2020 The Authors.Retinal haemorrhage is often observed following brain injury. The retinal circulation is supplied (drained) by the central retinal artery (vein) which enters (leaves) the eye through the optic nerve at the optic disc; these vessels penetrate the nerve immediately after passing through a region of cerebrospinal fluid (CSF). We consider a theoretical model for the blood flow in the central retinal vessels, treating each as multi-region collapsible tubes, where we examine how a sudden change in CSF pressure (mimicking an injury) drives a large amplitude pressure perturbation towards the eye. In some cases, this wave can steepen to form a shock. K03861 We show that the region immediately proximal to the eye (within the optic nerve where the vessels are strongly confined by the nerve fibres) can significantly reduce the amplitude of the pressure wave transmitted into the eye. When the length of this region is consistent with clinical measurements, the CSF pressure perturbation generates a wave of significantly lower amplitude than the input, protecting the eye from damage. We construct an analytical framework to explain this observation, showing that repeated rapid propagation and reflection of waves along the confined section of the vessel distributes the perturbation over a longer lengthscale. © 2020 The Author(s).The first record of the non-indigenous, alien amphipod Grandidierella gilesi in the Lam Ta Khong River is presented. Previously, this Indo-Pacific amphipod had only been reported in the Indian Ocean, the Andaman Sea, the Gulf of Thailand, the South China Sea and Australia. In Thailand, G. gilesi was previously reported in an isolated pond in Bangkok. The present study constitutes another record of this species in inland water. The characteristics and variation of G. gilesi, observed in this study, are also discussed. All the specimens described here are preserved at the Princess Maha Chakri Sirindhorn Natural History Museum, Prince of Songkla University, Songkla, Thailand. Koraon Wongkamhaeng, Pongrat Dumrongrojwattana, Myung-Hwa Shin, Chaichat Boonyanusith.Victoria Island in Canada’s western Arctic is the eighth largest island in the world and the second largest in Canada. Here, we report the results of a floristic study of vascular plant diversity of Victoria Island. The study is based on a specimen-based dataset comprising 7031 unique collections from the island, including some 2870 new collections gathered between 2008 and 2019 by the authors and nearly 1000 specimens variously gathered by N. Polunin (in 1947), M. Oldenburg (1940s-1950s) and S. Edlund (1980s) that, until recently, were part of the unprocessed backlog of the National Herbarium of Canada and unavailable to researchers. Results are presented in an annotated checklist, including keys and distribution maps for all taxa, citation of specimens, comments on taxonomy, distribution and the history of documentation of taxa across the island, and photographs for a subset of taxa. The vascular plant flora of Victoria Island comprises 38 families, 108 genera, 272 species, and 17 additional taxa. Of the 28d or poorly explored botanically – will build. Jeffery M. Saarela, Paul C. Sokoloff, Lynn J. Gillespie, Roger D. Bull, Bruce A. Bennett, Sergei Ponomarenko.Background The aim of this study was to evaluate early and long-term clinical and laboratory findings in patients with resistant hypertension secondary to aldosterone-producing adenoma (APA) treated with radiofrequency ablation (RFA). Methods From July 2009 to September 2017, eight adult patients underwent percutaneous computed tomography (CT)-guided RFA for APA. The safety, efficacy and complications of the procedure were determined. Blood pressure (BP), number of antihypertensive agents, serum potassium, plasma aldosterone and aldosterone-to-renin ratio (ARR) were analyzed before RFA and immediately, short-term and long-term after RFA. Results The technical success rate was 100%. Two patients developed minor complications but there were no major complications. Clinical improvement was achieved immediately and short-term after RFA. In the long-term (mean follow-up duration of 6.7 ± 2.1 years) there were significant improvements in systolic (from 162.3 mmHg ± 18.6 to 125 mmHg ± 16.1, p = 0.02) and diastolic (from 96.3 mmHg ± 12.7 to 68.5 mmHg ± 6.3, p = 0.02) BP, with a significant reduction in the number of antihypertensive agents (from 3.33 ± 0.82 to 1.33 ± 1.21, p = 0.02). Hypokalemia improved significantly (serum potassium from 2.16 meq/L ± 0.22 to 4.34 meq/L ± 0.54, p = 0.04). Although the plasma aldosterone level decreased significantly, ARR did not (from 100.7 ± 124.4 to 28.7 ± 30.7 ng/dL-per-ng/mL/h, p = 0.13). Hypertension was cured in 33.3% of the patients, and the BP of all patients was more easily controlled regardless of the plasma aldosterone and renin status. Conclusions CT-guided percutaneous RFA appears to be effective and safe to treat patients with APA, with clinical improvements in BP, reduced number of antihypertensive agents, and normalization of serum potassium level. These favorable outcomes persisted in short-term and long-term follow-up.