Epidemic processes in complex networks

In recent years the research community has accumulated overwhelming evidence for the emergence of complex and heterogeneous connectivity patterns in a wide range of biological and sociotechnical systems. The complex properties of real-world networks have a profound impact on the behavior of equilibrium and nonequilibrium phenomena occurring in various systems, and the study of epidemic spreading is central to our understanding of the unfolding of dynamical processes in complex networks. The theoretical analysis of epidemic spreading in heterogeneous networks requires the development of novel analytical frameworks, and it has produced results of conceptual and practical relevance. A coherent and comprehensive review of the vast research activity concerning epidemic processes is presented, detailing the successful theoretical approaches as well as making their limits and assumptions clear. Physicists, mathematicians, epidemiologists, computer, and social scientists share a common interest in studying epidemic spreading and rely on similar models for the description of the diffusion of pathogens, knowledge, and innovation. For this reason, while focusing on the main results and the paradigmatic models in infectious disease modeling, the major results concerning generalized social contagion processes are also presented. Finally, the research activity at the forefront in the study of epidemic spreading in coevolving, coupled, and time-varying networks is reported.Comment: 62 pages, 15 figures, final versio

Multi-Layer Cyber-Physical Security and Resilience for Smart Grid

The smart grid is a large-scale complex system that integrates communication technologies with the physical layer operation of the energy systems. Security and resilience mechanisms by design are important to provide guarantee operations for the system. This chapter provides a layered perspective of the smart grid security and discusses game and decision theory as a tool to model the interactions among system components and the interaction between attackers and the system. We discuss game-theoretic applications and challenges in the design of cross-layer robust and resilient controller, secure network routing protocol at the data communication and networking layers, and the challenges of the information security at the management layer of the grid. The chapter will discuss the future directions of using game-theoretic tools in addressing multi-layer security issues in the smart grid.Comment: 16 page

COMPARE LAAO: Rationale and design of the randomized controlled trial "COMPARing Effectiveness and safety of Left Atrial Appendage Occlusion to standard of care for atrial fibrillation patients at high stroke risk and ineligible to use oral anticoagulation therapy"

Contains fulltext : 252137.pdf (Publisher’s version ) (Open Access)BACKGROUND: Left atrial appendage occlusion (LAAO) provides an alternative to oral anticoagulation (OAC) for stroke prevention in patients with atrial fibrillation (AF). In patients with a long-term or permanent contraindication for OAC randomized controlled trial (RCT) data is lacking. STUDY OBJECTIVES: To assess the efficacy and safety of LAAO in AF patients who are ineligible to use OAC. The co-primary efficacy endpoint is (1) time to first occurrence of stroke (ischemic, hemorrhagic, or undetermined) and (2) time to first occurrence of the composite of stroke, transient ischemic attack (TIA), and systemic embolism (SE). The primary safety endpoint is the 30-day rate of peri-procedural complications. STUDY DESIGN: This is a multicenter, investigator-initiated, open-label, blinded endpoint (PROBE), superiority-driven RCT. Patients with AF, a CHA₂DS₂-VASc score ≥2 for men and ≥3 for women and a long-term or permanent contraindication for OAC will be randomized in a 2:1 fashion to the device- or control arm. Patients in the device arm will undergo percutaneous LAAO and will receive post-procedural dual antiplatelet therapy (DAPT) per protocol, while those in the control arm will continue their current treatment consisting of no antithrombotic therapy or (D)APT as deemed appropriate by the primary responsible physician. In this endpoint-driven trial design, assuming a 50% lower stroke risk of LAAO compared to conservative treatment, 609 patients will be followed for a minimum of 1 and a maximum of 5 years. Cost-effectiveness and budget impact analyses will be performed to allow decision-making on reimbursement of LAAO for the target population in the Netherlands. SUMMARY: The COMPARE LAAO trial will investigate the clinical superiority in preventing thromboembolic events and cost-effectiveness of LAAO in AF patients with a high thromboembolic risk and a contraindication for OAC use. NCT TRIAL NUMBER: NCT04676880

Towards designing robust coupled networks

Natural and technological interdependent systems have been shown to be highly vulnerable due to cascading failures and an abrupt collapse of global connectivity under initial failure. Mitigating the risk by partial disconnection endangers their functionality. Here we propose a systematic strategy of selecting a minimum number of autonomous nodes that guarantee a smooth transition in robustness. Our method which is based on betweenness is tested on various examples including the famous 2003 electrical blackout of Italy. We show that, with this strategy, the necessary number of autonomous nodes can be reduced by a factor of five compared to a random choice. We also find that the transition to abrupt collapse follows tricritical scaling characterized by a set of exponents which is independent on the protection strategy

Direct Stenting versus Conventional Stenting in Patients with ST-Segment Elevation Myocardial Infarction—A COMPARE CRUSH Sub-Study

Background: Direct stenting (DS) compared with conventional stenting (CS) after balloon predilatation may reduce distal embolization during percutaneous coronary intervention (PCI), thereby improving tissue reperfusion. In contrast, DS may increase the risk of stent underexpansion and target lesion failure. Methods:In this sub-study of the randomized COMPARE CRUSH trial (NCT03296540), we reviewed the efficacy of DS versus CS in a cohort of contemporary, pretreated ST-segment elevation myocardial infarction (STEMI) patients undergoing primary PCI. We compared DS versus CS, assessing (1) stent diameter in the culprit lesion, (2) thrombolysis in myocardial infarction (TIMI) flow in the infarct-related artery post-PCI and complete ST-segment resolution (STR) one-hour post-PCI, and (3) target lesion failure at one year. For proportional variables, propensity score weighting was applied to account for potential treatment selection bias. Results: This prespecified sub-study included 446 patients, of whom 189 (42%) were treated with DS. Stent diameters were comparable between groups (3.2 ± 0.5 vs. 3.2 ± 0.5 mm, p = 0.17). Post-PCI TIMI 3 flow and complete STR post-PCI rates were similar between groups (DS 93% vs. CS 90%, adjusted OR 1.16 [95% CI, 0.56–2.39], p = 0.69, and DS 72% vs. CS 58%, adjusted OR 1.29 [95% CI 0.77–2.16], p = 0.34, respectively). Moreover, target lesion failure rates at one year were comparable (DS 2% vs. 1%, adjusted OR 2.93 [95% CI 0.52–16.49], p = 0.22). Conclusion:In this contemporary pretreated STEMI cohort, we found no difference in early myocardial reperfusion outcomes between DS and CS. Moreover, DS seemed comparable to CS in terms of stent diameter and one-year vessel patency.</p

Learning curves of open and endoscopic fetal spina bifida closure: a systematic review and meta-analysis

OBJECTIVES: The Management Of Myelomeningocele Study (MOMS) trial demonstrated the safety and efficacy of open fetal surgery for spina bifida (SB). Recently developed alternative techniques may reduce maternal risks yet should do without compromising on fetal neuroprotective effects. We aimed to assess the learning curve of different fetal SB closure techniques. METHODS: We searched Medline, Web of Science, Embase, Scopus and Cochrane databases and the grey literature to identify relevant articles without language restriction from January 1980 until October 2018. We systematically reviewed and selected studies reporting all consecutive procedures and with a postnatal follow-up ≥12 months. They also had to report outcome variables necessary to measure the learning curve defined by fetal safety and efficacy. Two independent authors retrieved the data, assessed the quality of the studies and categorized observations into blocks of 30 patients. For meta-analysis, data were pooled using a random-effect model when heterogeneous. To measure the learning curve, we used two complementary methods. With the group splitting method, competency was defined when the procedure provided comparable results to the MOMS trial for 12 outcome variables representative for (1) the immediate surgical outcome, (2) short-term neonatal neuroprotection and (3) long-term neuroprotection at ≥12 months. Then, when the patients' raw data were available, we performed cumulative sum (CUSUM) analysis based on a composite binary outcome defining a successful surgery. It combined four clinically relevant variables for safety (fetal death within 7 days) and for efficacy (neuroprotection at birth). RESULTS: We included 17/6024 (0.3%) studies with low and moderate risks of bias. Fetal SB closure was performed via standard-hysterotomy (n=11), mini-hysterotomy (n=1) or fetoscopy [exteriorized-uterus single-layer (n=1), percutaneous single-layer (n=3) or percutaneous two-layer closure (n=1)]. Only outcomes for the standard-hysterotomy could be meta-analyzed. Overall, outcomes significantly improved with experience. Competency was reached after 35 consecutive cases for standard-hysterotomy and was predicted to be achieved after ≥57 cases for mini-hysterotomy and ≥56 for percutaneous two-layer fetoscopy. For percutaneous and uterus-exteriorized single-layer fetoscopy, competency was not respectively reached by cases 81 and 28 available for analysis. CONCLUSIONS: The number of cases operated correlates with the outcome of SB fetal closure and ranges from 35 cases for standard-hysterotomy to ≥56-57 cases for minimally invasive modifications. Our observations provide important information for institutions eager to establish a new fetal center, develop a new technique or train their team, and inform referring clinicians, potential patients and third-parties

Correlation between centrality metrics and their application to the opinion model

In recent decades, a number of centrality metrics describing network properties of nodes have been proposed to rank the importance of nodes. In order to understand the correlations between centrality metrics and to approximate a high-complexity centrality metric by a strongly correlated low-complexity metric, we first study the correlation between centrality metrics in terms of their Pearson correlation coefficient and their similarity in ranking of nodes. In addition to considering the widely used centrality metrics, we introduce a new centrality measure, the degree mass. The m order degree mass of a node is the sum of the weighted degree of the node and its neighbors no further than m hops away. We find that the B_{n}, the closeness, and the components of x_{1} are strongly correlated with the degree, the 1st-order degree mass and the 2nd-order degree mass, respectively, in both network models and real-world networks. We then theoretically prove that the Pearson correlation coefficient between x_{1} and the 2nd-order degree mass is larger than that between x_{1} and a lower order degree mass. Finally, we investigate the effect of the inflexible antagonists selected based on different centrality metrics in helping one opinion to compete with another in the inflexible antagonists opinion model. Interestingly, we find that selecting the inflexible antagonists based on the leverage, the B_{n}, or the degree is more effective in opinion-competition than using other centrality metrics in all types of networks. This observation is supported by our previous observations, i.e., that there is a strong linear correlation between the degree and the B_{n}, as well as a high centrality similarity between the leverage and the degree.Comment: 20 page

Two different charge-separation pathways in photosystem II

Charge separation is an essential step in the conversion of solar energy into chemical energy in photosynthesis. To investigate this process, we performed transient absorption experiments at 77 K with various excitation conditions on the isolated Photosystem II reaction center preparations from spinach. The results have been analyzed by global and target analysis and demonstrate that at least two different excited states, (Ch

Increased accuracy in computed tomography coronary angiography; a new body surface area adapted protocol

Vascular Biology and Interventio