Francesco Lo Iudice

Structural permeability of complex networks to control signals

Many biological, social and technological systems can be described as complex networks. The goal of affecting their behaviour has motivated recent work focusing on the relationship between the network structure and its propensity to be controlled. While this work has provided insight into several relevant problems, a comprehensive approach to address partial and complete controllability of networks is still lacking. Here, we bridge this gap by developing a framework to maximize the diffusion of the control signals through a network, while taking into account physical and economic constraints that inevitably arise in applications. This approach allows us to introduce the network permeability, a unified metric of the propensity of a network to be controllable. The analysis of the permeability of several synthetic and real networks enables us to extract some structural features that deepen our quantitative understanding of the ease with which specific controllability requirements can be met.

The evolving cobweb of relations among partially rational investors

To overcome the limitations of neoclassical economics, researchers have leveraged tools of statistical physics to build novel theories. The idea was to elucidate the macroscopic features of financial markets from the interaction of its microscopic constituents, the investors. In this framework, the model of the financial agents has been kept separate from that of their interaction. Here, instead, we explore the possibility of letting the interaction topology emerge from the model of the agents’ behavior. Then, we investigate how the emerging cobweb of relationship affects the overall market dynamics. To this aim, we leverage tools from complex systems analysis and nonlinear dynamics, and model the network of mutual influence as the output of a dynamical system describing the edge evolution. In this work, the driver of the link evolution is the relative reputation between possibly coupled agents. The reputation is built differently depending on the extent of rationality of the investors. The continuous edge activation or deactivation induces the emergence of leaders and of peculiar network structures, typical of real influence networks. The subsequent impact on the market dynamics is investigated through extensive numerical simulations in selected scenarios populated by partially rational investors.

Determinants of myocardial mechanics in top-level endurance athletes: three-dimensional speckle tracking evaluation

Aims The determinants of systolic function in the performing heart are not completely understood. Aim of the study was to assess the contributors of left ventricular (LV) strain components, using 3D speckle tracking echocardiography (STE) in endurance athletes. Methods and Results A total of 36 top-level male endurance athletes (AT) and 36 age-matched sedentary normal controls (NC) underwent standard and real-time 3D echocardiography. Global longitudinal strain (GLS), global circumferential strain (GCS), global area strain (GAS), and global radial strain (GRS) were assessed using 3D STE. AT had significantly higher GLS (-22.1 ± 4.4 vs. -18.4 ± 3.5%; P < 0.0001), GCS (-17.9 ± 2.4 vs. -16.0 ± 3.2; P = 0.006), and GAS (-35.5 ± 6.7 vs. -30.2 ± 4.9; P < 0.0001), while GRS did not differ significantly with NC. At separate multiple linear regression analyses, heart rate emerged as independent predictor of GLS (β = -0.37, P < 0.002), GCS (β = -0.32, P = 0.007), GAS (β = -0.37, P < 0.001), and GRS (β = -0.29, P = 0.019); LV mass was independently associated with GLS (β = 0.34, P = 0.009) and GAS (β = 0.41, P < 0.001) but not with GCS and GRS, while diastolic blood pressure predicted GCS (β = -0.46, P < 0.0001), GAS (β = -0.28; P = 0.006), and GRS (β = -0.42, P < 0.001). No independent correlation emerged for body surface area and stroke volume. By replacing LV mass with end-diastolic volume, the latter showed independent association with GCS (β = -0.65, P = 0.028) and with GRS (β = -0.60, P < 0.05). Conclusion AT have an increased myocardial function at rest when compared with NC, this being elicited mainly by subendocardial and mid-wall fibres. Sinus bradycardia, LV mass, and afterload are independent determinants of supernormal myocardial deformation at rest.

Overconfident agents and evolving financial networks

In this paper, we investigate the impact of agent personality on the complex dynamics taking place in financial markets. Leveraging recent findings, we model the artificial financial market as a complex evolving network: we consider discrete dynamics for the node state variables, which are updated at each trading session, while the edge state variables, which define a network of mutual influence, evolve continuously with time. This evolution depends on the way the agents rank their trading abilities in the network. By means of extensive numerical simulations in selected scenarios, we shed light on the role of overconfident agents in shaping the emerging network topology, thus impacting on the overall market dynamics.

Normal reference values of multilayer longitudinal strain according to age decades in a healthy population: A single-centre experience.

Aims Recent advancements in echocardiographic technology allow to analyse myocardial strain in multiple layers. Little is known about the impact of age on layer-specific longitudinal strain in healthy subjects. The aim of this study was to analyse the influence of age on multilayer longitudinal strain and establish normal reference values of layer-specific strain according to age decades in a healthy population referring to our echo laboratory using 2D speckle-tracking echocardiography with layer-specific software. Methods and results Two-hundred sixty-six healthy, consecutive subjects (mean age = 39.2 ± 17.5 years, women/men = 137/129), free of cardiovascular risk factors, were enrolled. Subjects were divided according to six age decades: 10-19, 20-29, 30-39, 40-49, 50-59, >60 years. All subjects underwent a complete echo Doppler examination including quantitation of 2D global longitudinal strain (GLS). Subendocardial longitudinal strain (LSsubendo), subepicardial longitudinal strain (LSsubepi), and strain gradient (LSsubendo - LSsubepi) were also determined. GLS (P < 0.001), LSsubendo, and LSsubepi (both P < 0.0001) were all progressively reduced with increasing age decades, but post hoc intra-group analyses demonstrated that the decline of GLS, LSsubendo, and LSsubepi was significant in the decades 50-60 and ≥60 years. In separate multiple linear regression analyses, the effect of age on GLS, LSsubendo, and LSsubepi remained significant even after adjusting for clinical and echocardiographic confounders. Strain gradient remained unchanged in age decades. Conclusion Ageing shows an independent effect on GLS, LSsubendo, and, particularly on, LSsubepi. Our data also provide normal reference values of layer-specific longitudinal strain for age decades.

The partial pinning control strategy for large complex networks

Abstract In large directed complex networks, it may result unfeasible to successfully pinning control the whole network. Indeed, when the pinner node can be connected only to a limited number of nodes, it may be impossible to guarantee pinning controllability of all the network nodes. In this paper, we introduce the partial pinning control problem, which consists in determining the optimal selection of the nodes to be pinned so as to maximize the fraction of nodes of the whole network that can be asymptotically controlled to the pinner’s trajectory. A suboptimal solution to this problem is provided for a class of nonlinear node dynamics, together with the bounds on the minimum coupling and control gains required to “partially control” the network. The theoretical analysis is translated into an integer linear program (ILP), which is solved on a testbed network of 688 nodes.

Myocardial deformation in pediatric patients with mucopolysaccharidoses: A two-dimensional speckle tracking echocardiography study

Mucopolysaccharidoses (MPS) are inherited lysosomal storage disorders caused by deficiency of required glycosaminoglycans breakdown enzymes, inducing cardiac involvement. Little is known about myocardial deformation involvement in MPS. Our aim was to assess biventricular structure and function in asymptomatic children with MPS using standard echo Doppler and 2D speckle tracking (STE).

Rationale and design of the EACVI AFib Echo Europe Registry for assessing relationships of echocardiographic parameters with clinical thrombo-embolic and bleeding risk profile in non-valvular atrial fibrillation

The European Society of Cardiology (ESC) guidelines for management of atrial fibrillation (AF) recommend the use of CHA2DS2VASc risk score for assessment of thromboembolic (TE) risk, whereas the stratification of bleeding risk should be obtained by HAS-Bleed to balance the most appropriate anticoagulation (OAC) therapy. However, men with CHA2DS2VASc score = 1 and women with CHA2DS2VASc = 2, who are at intermediate TE risk, represent a grey zone where guidelines do not provide a definite OAC indication. Accordingly, implementation of risk stratification with echocardiography could be extremely useful. Both prospective and cross-sectional studies on transthoracic echocardiography (TTE) prediction of TE events and studies utilizing transoesophageal echocardiographic parameters as surrogate markers of TE events makes sustainable the hypothesis that echocardiography could improve TE prediction in non-valvular AF. Moreover, considering the close association of AF and stroke, all echo-Doppler parameters that have shown to predict AF onset and recurrence could be useful also to predict TE events in this clinical setting. Accordingly, EACVI AFib Echo Europe Registry has been designed as an observational, cross-sectional study, with the aim of evaluating: (i) left atrial (LA) size and function together with left ventricular geometry, systolic and diastolic functions in paroxysmal, persistent, and permanent AF; (ii) relationships of structural/functional parameters with clinical TE and bleeding risk profile. By the AFib Echo Europe Registry, we expect to collect data on echocardiographic phenotype of patients with AF. The large data set accumulated will be useful to test the level of agreement of different echocardiographic measurements with the available risk scores.

Obstructive sleep apnoea and right ventricular function: A combined assessment by speckle tracking and three-dimensional echocardiography

BACKGROUND Little is known on right ventricular (RV) involvement in obstructive sleep apnoea (OSA). This study aimed at evaluating early RV dysfunction by standard and advanced echocardiography in OSA. METHODS Fifty-nine OSA patients without heart failure and 29 age-matched controls underwent standard, speckle tracking and real time 3D echocardiography of right ventricle. OSA patients performed lung function tests and overnight cardio-respiratory monitoring with evaluation of apnea-hypopnea index (AHI). RESULTS OSA had significantly higher body mass index and systolic blood pressure (BP) than controls. RV diameters and systolic pulmonary arterial pressure (sPAP) were significantly higher in OSA, in presence of comparable tricuspid annular plane systolic excursion (TAPSE). OSA showed marginally lower RV global longitudinal strain (GLS) (p<0.05) and RV lateral wall strain (RV LLS) (p=0.04). Three-dimensional RV ejection fraction did not differ between the two groups. By stratifying patients according to sPAP, 18 OSA patients with sPAP≥30mmHg had lower TAPSE (p<0.05), RV GLS and RV LLS (both p<0.001) than 37 patients with normal sPAP. By separate multivariate analyses, RV GLS and RV LLS were independently associated with sPAP (both p<0.0001), AHI (p=0.035 and p=0.015 respectively) and BMI (p<0.05 and p=0.034) but not with age and systolic BP in OSA. CONCLUSIONS A subclinical RV dysfunction is detectable by speckle tracking in OSA. The impairment of RV GLS and RV LLS is more prominent than that of TAPSE and is evident when RVEF is still normal. GLS is independently associated with sPAP and OSA severity.

Speckle tracking analysis in intensive care unit: A toy or a tool?

The use of conventional echocardiography in the intensive care unit (ICU) is today established to assess left and right ventricular systolic function, for preload determination and procedural guidance. Next step in ICU echocardiography could be the use of novel ultrasound techniques such as strain echocardiography to assist in the management of patients with acute coronary syndrome, heart failure, or pulmonary embolism. This review has gathered the available evidence supporting the incremental value of strain in the diagnostic workup of cardiac diseases treated in ICU.