ABSTRACT
The oscillatory electrodissolution of nickel is one among several reactions utilized as a model-system to study the emergence of oscillations and pattern formation in electrochemical interfaces, in addition to frequently providing experimental proofs for theoretical predictions in synchronization engineering. The reaction was modeled in 1992 by Haim and co-workers [J. Phys. Chem. 1992, 96, 2676] and since then the model has been used with great success. Although some numerical studies have been done in this regard, there is apparently no detailed investigation of the effect of control parameters on the complex dynamics of nickel dissolution. Here, we provide a well-detailed and rigorous analysis of the effect of the external resistance and applied potential by simulating high-resolution phase diagrams based on the calculation of Lyapunov exponents and isospike diagrams. Our findings clearly indicate a strong dependence of the self-similar periodic islands, the so-called shrimps (i.e., periodic islands within chaotic domains in the parameter space), with the control parameters. Overall, we have observed a low density of periodic structures in the phase diagrams, being completely suppressed for large values of resistance and potential. The shrimp-like structures become gradually elongated with an increase of the control parameters to the point where only diagonally aligned periodic bands intertwined with chaotic domains are present. Interestingly, period-doubling cascades were observed not only on the shrimps but also on the periodic bands. The detailed distribution of chaos and periodicity of oscillatory electrodissolution reactions in resistance-potential phase diagrams can bring, for instance, important information to experimentalists to set a desired dynamic behavior and, therefore, to create novel nanostructured self-organized materials.
ABSTRACT
OBJECTIVE: To provide an overall estimate of the direct, indirect and total costs of irritable bowel syndrome (IBS) for the adult population of the European countries with universal healthcare coverage. MATERIALS AND METHODS: We searched MedLine and Scopus databases (up to September 2018) to identify the European studies that evaluated the economic impact of IBS. Mean annual direct, indirect and total per-capita IBS costs were estimated using random-effect single-group meta-analyses of continuous data. All analyses were stratified by payer category (governments, insurance, societal), and the results were expressed as summary mean and 95% CI. RESULTS: A total of 24 studies were included in the meta-analyses. Only two studies evaluated IBS costs in Italy. The pooled summary of direct IBS per-capita cost, obtained from 23 European datasets (n=15,157), was 1837/year (95% CI: 1480-2195), with large differences across payers (from 1183 to 3358, in countries with publicly-funded and insurance-based health systems, respectively). The mean indirect cost, extracted from 13 datasets (n=3978), was 2314/year (95% CI: 1811-2817), again with wide differences across payers. Finally, the meta-analysis estimating the total annual cost, based upon 11 European datasets (n=2757), yielded a summary estimate of 2889/year (95% CI: 2318-3460) per patient, ranging from 1602 (insurance-based health systems) to 3909 (studies adopting a societal perspective). CONCLUSIONS: Considering a conservative estimate of 2,736,700 Italian adults affected by the syndrome, the minimum costs due to IBS in Italy - likely underestimated - range from 6 to 8 billion euro per year. Given the substantial economic burden for patients, healthcare systems and society, IBS should be included among the priorities of the public health agenda.
