Modelling Head Impact Safety Performance of Polymer-based Foam Protective Devices

The aim of this paper is to investigate an iterative statistical procedure, based on a small and censored sample of impact test experiments, useful for interval estimation of head impact safety parameter as critical fall height of protective devices. An adaptive testing routine was developed that was mainly constituted by a series of at least four impact test experiments, followed by the comparison of at least two parameter estimates based on incremental exponential regression fittings and a final confirmation experiment. A total number of 23 protective devices, mainly made of polyethylene foam, were investigated in order to validate the adaptive routine. The routine, applied to critical fall height of protective devices, was 19 times convergent within a maximum of 6 impact test experiments. 4 times the sample was censored because the iterative procedure has exceeded the available number of specimens. Confidence intervals at the 90 % level were always less than 0.18 m. The applicability of the adaptive routine was satisfactory demonstrated with reference to devices made of PE-foam and safety threshold of peak acceleration a-max equal to 200 g. The target of a confidence interval below the state-of-art was achieved

Dam breach modelling: influence on downstream water levels and a proposal of a physically based module for flood propagation software

The influence exerted by the method used for computing the dam breach hydrograph on the simulated maximum water levels throughout the downstream valley is essential for selecting a specific computing module to be implemented in the numerical codes used by practitioners. This module should be able to balance the need for a reasonable physical description of the phenomenon and, at the same time, limit as much as possible the maximum number of parameters. In order to feed a debate on this field, in this paper the performances of some parametric models used for the dam breach module implemented in the popular HEC-RAS software, and a simplified but physically based model have been analysed. The performances of the dam breach models have been assessed with reference to the historical event of the Big Bay dam, using both one-dimensional and two-dimensional (1-D and 2-D) flood propagation modelling. The results show that the physically based model considered here, without any operations of ad hoc calibration, has provided the best results in predicting computation of that event. Therefore, it may be proposed as a valid alternative to parametric models, which need the estimation of some parameters that can add further uncertainties in studies like these

Pricing exotic derivatives exploiting structure

In this paper we introduce a new fast and accurate numerical method for pricing exotic derivatives when discrete monitoring occurs, and the underlying evolves according to a Markov one-dimensional stochastic processes. The approach exploits the structure of the matrix arising from the numerical quadrature of the pricing backward formulas to devise a convenient factorization that helps greatly in the speed-up of the recursion. The algorithm is general and is examined in detail with reference to the CEV (Constant Elasticity of Variance) process for pricing different exotic derivatives, such as Asian, barrier, Bermudan, lookback and step options for which up to date no efficient procedures are available. Extensive numerical experiments confirm the theoretical results. The MATLAB code used to perform the computation is available online at http://www1.mate.polimi.it/∼marazzina/BP.htm. © 2013 Elsevier B.V. All rights reserved

A machine-learning based bio-psycho-social model for the prediction of non-obstructive and obstructive coronary artery disease

Background: Mechanisms of myocardial ischemia in obstructive and non-obstructive coronary artery disease (CAD), and the interplay between clinical, functional, biological and psycho-social features, are still far to be fully elucidated. Objectives: To develop a machine-learning (ML) model for the supervised prediction of obstructive versus non-obstructive CAD. Methods: From the EVA study, we analysed adults hospitalized for IHD undergoing conventional coronary angiography (CCA). Non-obstructive CAD was defined by a stenosis < 50% in one or more vessels. Baseline clinical and psycho-socio-cultural characteristics were used for computing a Rockwood and Mitnitski frailty index, and a gender score according to GENESIS-PRAXY methodology. Serum concentration of inflammatory cytokines was measured with a multiplex flow cytometry assay. Through an XGBoost classifier combined with an explainable artificial intelligence tool (SHAP), we identified the most influential features in discriminating obstructive versus non-obstructive CAD. Results: Among the overall EVA cohort (n = 509), 311 individuals (mean age 67 ± 11 years, 38% females; 67% obstructive CAD) with complete data were analysed. The ML-based model (83% accuracy and 87% precision) showed that while obstructive CAD was associated with higher frailty index, older age and a cytokine signature characterized by IL-1β, IL-12p70 and IL-33, non-obstructive CAD was associated with a higher gender score (i.e., social characteristics traditionally ascribed to women) and with a cytokine signature characterized by IL-18, IL-8, IL-23. Conclusions: Integrating clinical, biological, and psycho-social features, we have optimized a sex- and gender-unbiased model that discriminates obstructive and non-obstructive CAD. Further mechanistic studies will shed light on the biological plausibility of these associations. Clinical trial registration: NCT02737982

The Sex-Specific Detrimental Effect of Diabetes and Gender-Related Factors on Pre-admission Medication Adherence Among Patients Hospitalized for Ischemic Heart Disease: Insights From EVA Study

Background: Sex and gender-related factors have been under-investigated as relevant determinants of health outcomes across non-communicable chronic diseases. Poor medication adherence results in adverse clinical outcomes and sex differences have been reported among patients at high cardiovascular risk, such as diabetics. The effect of diabetes and gender-related factors on medication adherence among women and men at high risk for ischemic heart disease (IHD) has not yet been fully investigated.Aim: To explore the role of sex, gender-related factors, and diabetes in pre-admission medication adherence among patients hospitalized for IHD.Materials and Methods: Data were obtained from the Endocrine Vascular disease Approach (EVA) (ClinicalTrials.gov Identifier: NCT02737982), a prospective cohort of patients admitted for IHD. We selected patients with baseline information regarding the presence of diabetes, cardiovascular risk factors, and gender-related variables (i.e., gender identity, gender role, gender relations, institutionalized gender). Our primary outcome was the proportion of pre-admission medication adherence defined through a self-reported questionnaire. We performed a sex-stratified analysis of clinical and gender-related factors associated with pre-admission medication adherence.Results: Two-hundred eighty patients admitted for IHD (35% women, mean age 70), were included. Around one-fourth of the patients were low-adherent to therapy before hospitalization, regardless of sex. Low-adherent patients were more likely diabetic (40%) and employed (40%). Sex-stratified analysis showed that low-adherent men were more likely to be employed (58 vs. 33%) and not primary earners (73 vs. 54%), with more masculine traits of personality, as compared with medium-high adherent men. Interestingly, women reporting medication low-adherence were similar for clinical and gender-related factors to those with medium-high adherence, except for diabetes (42 vs. 20%, p = 0.004). In a multivariate adjusted model only employed status was associated with poor medication adherence (OR 0.55, 95%CI 0.31–0.97). However, in the sex-stratified analysis, diabetes was independently associated with medication adherence only in women (OR 0.36; 95%CI 0.13–0.96), whereas a higher masculine BSRI was the only factor associated with medication adherence in men (OR 0.59, 95%CI 0.35–0.99).Conclusion: Pre-admission medication adherence is common in patients hospitalized for IHD, regardless of sex. However, patient-related factors such as diabetes, employment, and personality traits are associated with adherence in a sex-specific manner

Sustainable Design for Passive Safety of Sports Equipment

This thesis project concerned passive safety and sustainable assessment of protective polymer-based foam devices, actually installed in Sports Area, and it aimed to investigate regulations, severity of injuries, material absorption properties and testing procedures, in order to propose a new approach. Thus, a focus on international Sports injury statistics it has been done and mostly frequent accident mechanisms, falls and head collisions, highlighted. It has been also possible, through a study on Biomechanical issues, to comprehend evaluation methods of concussion thresholds and brain trauma degree. From product design process point of view, Ecodesign principles were studied in order to minimize consumptions and emissions in a product life-cycle vision and Robust Design methods were applied in order to maximize product performances through a proper evaluation of design parameters. Sports area standards, provided by international organizations, were compared in order to extract testing procedures and related technical requirements. Therefore, a flexible impact testing apparatus was designed and built in Sports Equipment and Technology department of Chemnitz University of Technology: by replacing the falling striker, in fact, it has been possible to comply with the American ASTM F1292, the European EN 1177 and EN 913 specifications, and then realize the so-called, in scientific literature, “Low-velocity” impact experiments. Afterwards, three experimental program phases were followed and a huge number of Polyethylene foam architectures were tested according to the previous American and European testing protocols. Due to lacks in EN 913 and EN 1177 specifications, a new testing method was proposed by considering friction influences in guidance system of the apparatus; by adopting an ergonomic missile; by a joint monitoring on the characteristic parameters during impact tests, that are acceleration peak, Head Injury Criterion (HIC) and critical fall height. Main goals achieved during this research could allow sports area technicians and responsible in making proper evaluation concerns the selection of several protective devices, and could improve the safety level of sports participants during their practice

Toward a New Approach for Passive Safety Assessment of Gymnastic Equipment

Purpose: Aim of the paper is to propose a new approach for the assessment of passive safety of gymnastic equipment that allows technicians to optimize the choice of protection devices. Design/methodology/approach: According to different standard procedures, EN 913 and EN 1177 with an additional control on the acceleration parameter, experimental tests on polymer foam materials were performed using cylindrical and hemispherical missiles connected to a flexible impact testing apparatus realized at Chemnitz University of Technology. Findings: Impact tests carried out using cylindrical and hemispherical missiles have shown, for the same impact energy, different acceleration peak values, always greater for hemispherical missile than cylindrical one. So considering EN 913 procedure, the severity of head impacts, in term of acceleration peak can be underestimated when a cylindrical missile is used. For this reason to correctly assess the head injuries is necessary to take into account in addition to the acceleration peak value, also HIC parameter. Research limitations/implications: The research described in the paper was carried out taking into account only the human head impacts (the most severe injuries) and not other parts of the human body. Practical implications: The new approach proposed in the paper can be useful for the choice of the protective devices to improve the passive safety of gymnastic equipment. It represents a starting point to define new standards. Originality/value: On the base of experimental tests, the authors show that the safety threshold of peak acceleration defined in the EN913 standard is poor. For this reason it is necessary to modify the current standards, in order to guarantee an adequate passive safety and to allow the technicians to optimize the choice of protection devices on the base of impact absorption properties, that are evaluated using all together the parameters: acceleration peak, drop height and Head Injury Criterion (HIC)