Sunspot numbers: Data analysis, predictions and economic impacts

We analyze the monthly sunspot number (SSN) data from January 1749 to June 2013. We use the Average Mutual Information and the False Nearest Neighbors methods to estimate the suitable embedding parameters. We calculate the correlation dimension to compute the dimension of the system's attractor. The convergence of the correlation dimension to its true value, the positive largest Lyapunov exponent and the Recurrence Quantitative Analysis results provide evidences that the monthly SSN data exhibit deterministic chaotic behavior. The future prediction of monthly SSN is examined by using a neural network-type core algorithm. We perform ex-post predictions comparing them with the observed SSN values and the predictions published by the Solar Influences Data Analysis Center. It is shown that our technique is a better candidate for the prediction of the maximum monthly SSN value. We perform future predictions trying to forecast the maximum SSN value from July 2013 to June 2014. We show that the present cycle 24 is yet to peak. Finally, the negative economic impacts of maximum solar activity are discussed. © 2015 Kavala Institute of Technology

Bifurcations and chaos in discrete-time gonorrhea model

A deterministic epidemic model for the spread of gonorrhea is investigated in discrete-time by taking into account the interval between successive clinical cases. It is shown that the discrete-time dynamical system exhibits far more complex dynamics than its continuous analogues. Stability analysis is obtained in order to investigate the local stability properties of the fixed points; it is verified that there are phenomena of Fold and Flip bifurcations. Numerical simulation tools are used in order to illustrate the stability analysis results and find some new qualitative dynamics. We come across the phenomenon of “intermittency route to chaos”. The density of infected individuals goes through quasi-periodicity and a strange attractor appears in the system. Chaos control is obtained in order to see how the male latex condom use during sexual intercourse affects the incidence of gonorrhea. It is shown that male latex condom use stabilizes the chaotic vibrations of the system to a point where the number of infected individuals remains stable and is significantly small or zero, leading to the control of disease. © 2014 ISAS

Nonlinear supply and demand model with two interrelated markets

Our target in this paper is to observe how the presence of nonlinear terms in the supply and demand model changes the price behavior of the system. The dynamical analysis refers, mainly, to discrete dynamical systems. We start with a simple linear supply and demand model with two markets interacting with each other. The stability conditions for the linear model are presented. Afterwards we add nonlinear terms and try to observe, if the presence of nonlinearity in the supply and demand model with two interrelated markets exhibits chaotic price behavior. Chaos bursts in the system via period-doubling bifurcations, and all orbits converge to a strange attractor. © 2011 Kavala Institute of Technology

Re-evaluation of Predictive Models in Light of New Data: Sunspot Number Version 2.0

The original version of the Zürich sunspot number (Sunspot Number Version 1.0) has been revised by an entirely new series (Sunspot Number Version 2.0). We re-evaluate the performance of our previously proposed models for predicting solar activity in the light of the revised data. We perform new monthly and yearly predictions using the Sunspot Number Version 2.0 as input data and compare them with our original predictions (using the Sunspot Number Version 1.0 series as input data). We show that our previously proposed models are still able to produce quite accurate solar-activity predictions despite the full revision of the Zürich Sunspot Number, indicating that there is no significant degradation in their performance. Extending our new monthly predictions (July 2013 – August 2015) by 50 time-steps (months) ahead in time (from September 2015 to October 2019), we provide evidence that we are heading into a period of dramatically low solar activity. Finally, our new future long-term predictions endorse our previous claim that a prolonged solar activity minimum is expected to occur, lasting up to the year ≈ 2100. © 2016, Springer Science+Business Media Dordrecht

Complex Dynamics in Non-linear Real Estate Models

In the present paper we study the complex dynamics of non-linear cobweb models of real estate markets in discrete time. Our model incorporates two sub-markets, land and housing, interacting with each other. We start by outlining the basic model, which assumes that land prices determine housing supply. This provides the foundations for the development of the more refined and complicated models that follow. These explore the dynamics of the real estate system, when land supply is affected by housing prices. Two forms of this relation are examined: linear and quotient, in order to investigate the dynamics of the system and the qualities and behaviour of the solutions. Stability analysis is obtained in order to investigate the stability properties of the fixed points. Various numerical simulation tools are used in order to study the complex dynamics of the systems. Finally, a global bifurcation occurring in the nonlinear case (quotient) is investigated, which changes the asymptotic behaviour of the system leading from a situation of bistability (cycle of period 2) to chaotic behaviour

Outcome of Endovascular Thrombectomy in Pre-stroke Dependent Patients With Acute Ischemic Stroke: A Systematic Review and Meta-Analysis

Introduction: Endovascular thrombectomy (EVT) is a well-established and effective therapeutic option for patients that meet certain criteria. However, this modality is not well studied in patients with pre-existing disability. The aim of the present study was to investigate the impact of mechanical thrombectomy in patients with acute onset ischemic stroke and pre-stroke dependency (PSD) in regard to their clinical outcome and mortality. Materials and Methods: The MEDLINE, Scopus, and Cochrane Library databases were comprehensively searched with a cut-off date of December 11th, 2021. We performed meta-analysis to investigate the 90-day clinical outcome, the 90-day mortality, and the rate of symptomatic intracerebral hemorrhage (sICH) between the PSD (modified Rankin Scale score ≥ 3) and non-PSD (modified Rankin Scale score = 0–2) groups who underwent EVT for acute onset ischemic stroke. Results: Six studies were included in the meta-analysis involving 4,543 cases with no PSD and 591 cases with PSD. The non-PSD group showed a statistically significant better clinical outcome at 90 days compared to the PSD group [RR (95% CI) = 1.44 (1.06, 1.85); pz = 0.02]. The non-PSD group demonstrated a statistically significant lower risk of death at 90 days in comparison to the PSD group [RR (95% CI) = 0.45 (0.41, 0.50); pz < 0.01]. Lastly, the rate of sICH was comparable between the two groups [RR (95% CI) = 0.89 (0.64, 1.24); pz = 0.48]. Discussion: We report a higher rate of unfavorable clinical outcome and a higher mortality rate in patients with PSD undergoing EVT compared to those with no previous disability. However, there was a significant proportion of PSD cases who fared well post-procedurally, indicating that PSD patients should not be routinely excluded from mechanical thrombectomy. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021284181, identifier: CRD42021284181. Copyright © 2022 Adamou, Gkana, Mavrovounis, Beltsios, Kastrup and Papanagiotou

Contemporary Biomarkers in Pulmonary Embolism Diagnosis: Moving beyond D-Dimers

Pulmonary embolism (PE) is a rather common cardiovascular disorder constituting one of the major manifestations of venous thromboembolism (VTE). It is associated with high mortality and substantial recurrence rates, and its diagnosis may be challenging, especially in patients with respiratory comorbidities. Therefore, providing a prompt and accurate diagnosis for PE through developing highly sensitive and specific diagnostic algorithms would be of paramount importance. There is sound evidence supporting the use of biomarkers to enhance the diagnosis and predict the recurrence risk in patients with PE. Therefore, several novel biomarkers, such as factor VIII, Ischemia Modified Albumin, and fibrinogen, as well as several MicroRNAs and microparticles, have been investigated for the diagnosis of this clinical entity. The present review targets to comprehensively present the literature regarding the novel diagnostic biomarkers for PE, as well as to discuss the evidence for their use in daily routine. © 2022 by the authors

On the Verge of a Grand Solar Minimum: A Second Maunder Minimum?

We analyze the yearly mean sunspot-number data covering the period 1700 to 2012. We show that the yearly sunspot number is a low-dimensional deterministic chaotic system. We perform future predictions trying to forecast the solar activity during the next five years (2013 -aEuro parts per thousand 2017). We provide evidence that the yearly sunspot-number data can be used for long-term predictions. To test and prove that our model is able to predict the Maunder Minimum period (1645 -aEuro parts per thousand 1715), we perform long-term post-facto predictions comparing them with the observed sunspot-number values. We also perform long-term future predictions trying to forecast the solar activity up to 2102. Our predictions indicate that the present Cycle 24 is expected to be a low-peak cycle. We conclude that the level of solar activity is likely to be reduced significantly during the next 90 years, somewhat resembling the Maunder Minimum period