Mode competition in a system of two parametrically driven pendulums with nonlinear coupling

This paper is part three in a series on the dynamics of two coupled, parametrically driven pendulums. In the previous parts Banning and van der Weele (1995) and Banning et al. (1997) studied the case of linear coupling; the present paper deals with the changes brought on by the inclusion of a nonlinear (third-order) term in the coupling. Special attention will be given to the phenomenon of mode competition.\ud \ud The nonlinear coupling is seen to introduce a new kind of threshold into the system, namely a lower limit to the frequency at which certain motions can exist. Another consequence is that the mode interaction between 1¿ and 2ß (two of the normal motions of the system) is less degenerate, causing the intermediary mixed motion known as MP to manifest itself more strongly

Mode competition in a system of two parametrically driven pendulums: the role of symmetry

This paper is the final part in a series of four on the dynamics of two coupled, parametrically driven pendulums. In the previous three parts (Banning and van der Weele, Mode competition in a system of two parametrically driven pendulums; the Hamiltonian case, Physica A 220 (1995) 485¿533; Banning et al., Mode competition in a system of two parametrically driven pendulums; the dissipative case, Physica A 245 (1997) 11¿48; Banning et al., Mode competition in a system of two parametrically driven pendulums with nonlinear coupling, Physica A 245 (1997) 49¿98) we have given a detailed survey of the different oscillations in the system, with particular emphasis on mode interaction. In the present paper we use group theory to highlight the role of symmetry. It is shown how certain symmetries can obstruct period doubling and Hopf bifurcations; the associated routes to chaos cannot proceed until these symmetries have been broken. The symmetry approach also reveals the general mechanism of mode interaction and enables a useful comparison with other systems

Plagen en ziekten bij oesters en mosselen

O.a. mosselparasiet en infectieziekten bij mosselen, en schelpziekte, putziekte en de Polydora worm bij oester

Mode competition in a system of two coupled, parametrically driven pendulums: the Hamiltonian case

We study the mode competition in a Hamiltonian system of two parametrically driven pendulums, linearly coupled by a torsion spring. First we make a classification of all the periodic motions in four main types: the trivial motion, two `normal modes¿, and a mixed motion. Next we determine the stability regions of these motions, i.e., we calculate for which choices of the driving parameters (angular frequency ¿ and amplitude A) the respective types of motion are stable. To this end we take the (relatively simple) uncoupled case as our starting point and treat the coupling K as a control parameter. Thus we are able to predict the behaviour of the pendulums for small coupling, and find that increasing the coupling does not qualitatively change the situation anymore. One interesting result is that we find stable (and also Hopf bifurcated) mixed motions outside the stability regions of the other motions. Another remarkable feature is that there are regions in the (A, ¿)-plane where all four motion types are stable, as well as regions where all four are unstable. As a third result we mention the fact that the coupling (i.e. the torsion spring) tends to destabilize the normal mode in which the pendulums swing in parallel fashion. The effects of the torsion spring on the stability region of this mode is, suprisingly enough, not unlike the effect of dissipation

A Bleeding Kiss: intramural haematoma secondary to balloon angioplasty

<p>Abstract</p> <p>Background</p> <p>Intramural coronary haematoma following percutaneous coronary intervention in the absence of coronary dissection is a rare phenomenon.</p> <p>Case presentation</p> <p>A 69 year old lady with previous prosthetic aortic valve replacement underwent percutaneous coronary intervention (PCI) from the left mainstem to the left anterior descending artery (LAD) and kissing balloon inflations to the LAD and circumflex (Cx) arteries. Although intravascular ultrasound examination (IVUS) of both the LAD and Cx showed both vessels to be widely patent at the end of the procedure, she developed ischaemic chest pain six hours later. Repeat coronary angiography revealed a significant stenosis in the proximal Cx vessel, which was confirmed on IVUS to be intramural haematoma.</p> <p>Conclusion</p> <p>In patients taking warfarin in addition to standard antiplatelet therapy, kissing balloon inflations should be carried out with caution.</p

Gender Disparities in Authorships and Citations in Transplantation Research

Background: Over the past decades, there has been a rapid change in the gender ratio of medical doctors, whereas gender differences in academia remain apparent. In transplantation research, a field already understaffed with female doctors and researchers, there is little published data on the development in proportion, citations, and funding of female researchers over the past years. Methods: To evaluate the academic impact of female doctors in transplantation research, we conducted a bibliometric analysis (01 January 1999 to 31 December 2018) of high-impact scientific publications, subsequent citations, and funding in this field. Web of Science data was used in combination with software R-Package "Gender," to predict gender by first names. Results: For this study, 15 498 (36.2% female; 63.8% male) first and 13 345 (30.2% female; 69.8% male) last author gender matches were identified. An increase in the percentage of female first and last authors is seen in the period 1999-2018, with clear differences between countries (55.1% female authors in The Netherlands versus 13.1% in Japan, for example). When stratifying publications based on the number of citations, a decline was seen in the percentage of female authors, from 34.6%-30.7% in the first group (≤10 citations) to 20.8%-23.2% in the fifth group (>200 citations), for first (P < 0.001) and last (P = 0.014) authors, respectively. From all first author name-gender matches, 6574 (41.6% female; 58.4% male, P < 0.001) publications reported external funding, with 823 (35.5% female; 64.5% male, P = 0.701) reported funding by pharmaceutical companies and 1266 (36.6% female; 63.4% male, P < 0.001) reporting funding by the National Institutes of Health. Conclusions: This is the first analysis of gender bias in scientific publications, subsequent citations, and funding in transplantation research. We show ongoing differences between male and female authors in citation rates and rewarded funding in this field. This requires an active approach to increase female representation in research reporting and funding rewarding

Risk Factors for Delirium after Vascular Surgery:A Systematic Review and Meta-Analysis

Background: Vascular surgery is considered a risk factor for the development of postoperative delirium (POD). In this systematic review we provide a report on the incidence and risk-factors of POD after vascular surgery. Methods: A systematic literature search was conducted using Pubmed with the MeSH terms and key words "delirium" or "confusion", "vascular surgery procedures" and "risk factors or "risk assessment". Studies were selected for review after meeting the following inclusion cr iter ia: vascular surgery, POD diagnosed using validated screening tools, and DSM-derived criteria to assess delirium. A meta-analysis was performed for each endpoint if at least two studies could be combined. Results: Sixteen articles met the abovementioned cr iter ia. The incidence of delir ium ranged from 5% to 39%. Various preoperative risk factors were identified that is, age (Random MD 3.96, CI 2.57-5.35), hypertension (Fixed OR 1.30, CI 1.05-1.59), diabetes mellitus (Random OR 2.15, CI 1.30-3.56), hearing impairment (Fixed OR 1.89, CI 1.28-2.81), history of cerebrovascular incident or transient ischemic attack (Fixed OR 2.20, CI 1.68-2.88), renal failure (Fixed OR 1.61, CI 1.19-2.17), and pre-operative low haemoglobin level (fixed MD-0.76, CI-1.04 to-0.47). Intra-operative risk factors were duration of surgery (Random MD 15.68; CI 2.79-28.57), open aneurysm repair (Fixed OR 4.99, CI 3.10-8.03), aortic cross clamping time (fixed MD 7.99, CI 2.56-13.42), amputation surgery (random OR 3.77, CI 2.13-6.67), emergency surgery (Fixed OR 4.84, CI 2.81-8.32) and total blood loss (Random MD 496.5, CI 84.51-908.44) and need for blood transfusion (Random OR 3.72, CI 1.57-8.80). Regional anesthesia on the other hand, had a protective effect. Delirium was associated with longer ICU and hospital length of stay, and more frequent discharge to a care facility. Conclusions: POD after vascular surgery is a frequent complication and effect-size pooling supports the concept that delirium is a heterogeneous disorder. The risk factors identified can be used to either design a validated risk factor model or individual preventive strategies for high-risk patients