The relation between cholesterol and haemorrhagic or ischaemic stroke in the Renfrew/Paisley study

Studies have found little association between cholesterol and overall stroke risk, but this could be attributable to different relations for haemorrhagic and ischaemic stroke. Stroke mortality data from prospective studies cannot usually be divided into stroke subtypes. We have therefore analysed stroke based on hospital admissions, obtained by computerised linkage with acute hospital discharges in Scotland for a large prospective cohort study

Interpretation of vaccine associated neurological adverse events:a methodological and historical review

As a result of significant recent scientific investment, the range of vaccines available for COVID-19 prevention continues to expand and uptake is increasing globally. Although initial trial safety data have been generally reassuring, a number of adverse events, including vaccine induced thrombosis and thrombocytopenia (VITT), have come to light which have the potential to undermine the success of the vaccination program. However, it can be difficult to interpret available data and put these into context and to communicate this effectively. In this review, we discuss contemporary methodologies employed to investigate possible associations between vaccination and adverse neurological outcomes and why determining causality can be challenging. We demonstrate these issues by discussing relevant historical exemplars and explore the relevance for the current pandemic and vaccination program. We also discuss challenges in understanding and communicating such risks to clinicians and the general population within the context of the ‘infodemic’ facilitated by the Internet and other media

Fractal and Transfractal Recursive Scale-Free Nets

We explore the concepts of self-similarity, dimensionality, and (multi)scaling in a new family of recursive scale-free nets that yield themselves to exact analysis through renormalization techniques. All nets in this family are self-similar and some are fractals - possessing a finite fractal dimension - while others are small world (their diameter grows logarithmically with their size) and are infinite-dimensional. We show how a useful measure of "transfinite" dimension may be defined and applied to the small world nets. Concerning multiscaling, we show how first-passage time for diffusion and resistance between hub (the most connected nodes) scale differently than for other nodes. Despite the different scalings, the Einstein relation between diffusion and conductivity holds separately for hubs and nodes. The transfinite exponents of small world nets obey Einstein relations analogous to those in fractal nets.Comment: Includes small revisions and references added as result of readers' feedbac

Critical behavior of cascading failures in overloaded networks

In recent years, research on spatial networks has become of widespread interest, with the focus on analyzing critical phenomena that can dramatically affect real systems via cascading failures and abrupt collapses. Here, we study the breakdown of a spatial network having a characteristic link-length due to overloads and the cascading failures that are triggered by failures of a fraction of links. While such breakdowns have been studied extensively, the critical exponents and the universality class of this phase transition have not been found. Here, we show indications that this transition has features and critical exponents which are the same as those of interdependent network systems, suggesting that both systems are in the same universality class. We find different abrupt transitions at the steady state, for different spatial embedding strength. For the weakly embedded systems (i.e., link-lengths of the order of the system size) we observe a mixed-order transition where the order parameter collapses with time in a long plateau shape. On the other hand, in strongly embedded systems (relatively short links), we find a pure first order transition which involves nucleation and growth of damage. System behavior in both limits is analogous to that observed in interdependent networks.Comment: 7 pages, 6 figure

Scale-Free Networks are Ultrasmall

We study the diameter, or the mean distance between sites, in a scale-free network, having N sites and degree distribution p(k) ~ k^-a, i.e. the probability of having k links outgoing from a site. In contrast to the diameter of regular random networks or small world networks which is known to be d ~ lnN, we show, using analytical arguments, that scale free networks with 2<a<3 have a much smaller diameter, behaving as d ~ lnlnN. For a=3, our analysis yields d ~ lnN/lnlnN, as obtained by Bollobas and Riordan, while for a>3, d ~ lnN. We also show that, for any a>2, one can construct a deterministic scale free network with d ~ lnlnN, and this construction yields the lowest possible diameter.Comment: Latex, 4 pages, 2 eps figures, small corrections, added explanation

Prediction of immediate ventricular arrhythmias after coronary artery ligation

AbstractObjectives. Our aim was to test the hypothesis that increased beat to beat morphologic variations in the body surface electrocardiogram (ECG) are associated with fragmented diastolic electrical activity that appears after coronary artery ligation and to correlate the appearance of spontaneous ventricular fibrillation after coronary ligation with the magnitude of the ECG beat to beat variability.Background. Unstable and variably delayed electrical activation precedes the development of ventricular fibrillation in dogs with acute ischemia. Detection of these highly variable low amplitude signals from the body surface is currently impossible. We have developed a system designed to measure the degree of beat to beat variability of the ECG.Methods. With high fidelity electrocardiography, subtle beat to beat ECG morphologic variations were detected in epicardial and body surface electrograms and quantified as the variance of the ECG voltage at specific points of the cardiac cycle. The ratio of the variance at the QRS offset to that of the QRS onset (beat to beat variability index) was then calculated.Results. Ventricular fibrillation developed in 12 of 27 dogs after left anterior descending coronary artery ligation. In 7 of the 12 dogs it occurred immediately (<15 min) after ligation; in the other 5 it developed late (15 min) after ligation. Dogs with subsequently immediate ventricular fibrillation had a significantly higher beat to beat variability index than that of dogs with late or no ventricular fibrillation both before coronary ligation (4.7 ± 1.4 vs. 1.1 ± 0.2 and 0.8 ± 0.1, respectively, p < 0.001) and after ligation (6.4 ± 2.6, 1.0 ± 0.6 and 1.2 ± 0.6, respectively, p < 0.001). In dogs that developed ventricular fibrillation immediately after coronary ligation, the arrhythmia was preceded by fragmented diastolic electrical activity on the epicardial electrogram and a simultaneous increase in the beat to beat morphologic variability of the terminal portion of the body surface ECG QRS complex.Conclusions. Beat to beat QRS offset morphologic variations appear to be increased before and further increased after coronary artery ligation in dogs that develop ventricular fibrillation immediately after ligation. Increased beat to beat variability index may be associated with the presence of electrophysiologic instability and can predict early ventricular fibrillation