Parameter estimation for a morphochemical reaction-diffusion model of electrochemical pattern formation

The process of electrodeposition can be described in terms of a reaction-diffusion PDE system that models the dynamics of the morphology profile and the chemical composition. Here we fit such a model to the different patterns present in a range of electrodeposited and electrochemically modified alloys using PDE constrained optimization. Experiments with simulated data show how the parameter space of the model can be divided into zones corresponding to the different physical patterns by examining the structure of an appropriate cost function. We then use real data to demonstrate how numerical optimization of the cost function can allow the model to fit the rich variety of patterns arising in experiments. The computational technique developed provides a potential tool for tuning experimental parameters to produce desired patterns

Insight into the Cycling Behaviour of Metal Anodes, Enabled by X-ray Tomography and Mathematical Modelling

This work tackles the methodological challenge of rationalizing symmetric-cell cycling data from a materials-science perspective, through experiment replication, mathematical modelling, and tomographic imaging. Specifically, we address Zn electrode cycling in alkaline electrolyte with and without adding tetrabutylammonium bromide (TBAB). This additive is known from literature, but its practical impact is jeopardized by lack of in-depth understanding of its behaviour. Electrochemical testing was carried out at practically relevant current densities and the effect of variations of operating conditions was taken into account. The physical chemistry underlying cell potential profiles, has been modelled mathematically, accounting for: electrokinetics, mass-transport, electrode shape change and passivation. In particular, we disclosed an unexpected joint effect of TBAB and current density on passivation time: tomography allowed to rationalise this behaviour in terms of precipitate morphology

What Happens to MnO2 When It Comes in Contact with Zn2+? An Electrochemical Study in Aid of Zn/MnO2-Based Rechargeable Batteries

In the science and technology of electrochemical energy storage, different allotropes of MnO2, fabricated with a variety of methods, are assembled into electrodes, playing the role of cathode or oxygen reduction reaction (ORR) electrocatalyst. Often, MnO2-based cathodes are combined with Zn anodes into different types of batteries, resulting in contact between MnO2 and its electrochemical reaction products, and Zn2+. Awareness is growing that this interaction adversely affects the functional performance of MnO2, but no definitive understanding has been reached for this issue. This study contributes, through electrochemical measurements accompanied by microscopy and Raman spectroscopy, to a better understanding of the way the electrochemical behavior of two technologically representative types of manganese dioxide - hydrothermally grown α-MnO2 and electrodeposited γ-MnO2 (EDM) - is degraded when these materials are exposed to neutral and alkaline aqueous solutions, containing Zn2+. Specifically, we highlighted different types of irreversible changes in electrochemical response, which can be interpreted with phase-formation processes. Such changes result in the deactivation of α-MnO2 as ORR electrocatalyst, and of both α-MnO2 and EDM as zinc-ion battery (ZIB) cathodes. The electroactivity of EDM for ZIB operation can be restored if Mn2+ is added to the neutral electrolyte, because a phase, active in discharge, is electrodeposited during charging

A puzzling Mule Coin from the Parabita Hoard: a Material Characterisation

In this research, we report on the compositional, microstructural and crystallographic properties of a lead coin which has been regarded for many years as a genuine silver coin minted in the Southern Italy in the course of the 4th century BC. The material characterisation of this object allowed detecting an ancient forging technology, not previously reported, which was meant for the silvering of lead substrates The data collected have disclosed a contemporary counterfeiting procedure based on a metal coating process onto a Pb substrate. This coating has been identified as a bi-layer with a Cu innermost and an Ag outermost visible layer. As far as the coating application technique is concerned, the gathered evidence has clearly indicated that the original appearance of this artifact cannot be explained in terms of any of the established methods for the growth of an artificially silvered coating in classical antiquity. This technology is now being explained in terms of modern, fully non destructive scientific methods.Comment: 9 pages including 8 figures. To be presented at the Cavallino Archaeometry Workshop 2006, Cavallino (Lecce - Italy) - May 22-25, 200

new energy sources in situ characterisation of fuel cell and supercapacitor components complementary studies using transmission fluorescence and photoelectron microscopy and imaging

Fuel cells and supercapacitors are electrochemical devices providing efficient and pollution-free production and transformation of electricity. Notwithstanding their environmental appeal, a host of materials-science problems – chiefly related to the limited durability of crucial functional components – are hindering their widespread application. The present knowledge of the relevant materials-science notion is mostly at the macroscopic and empirical trial-and-error level and the answers to many questions require much deeper scientific understanding of the origin of degradation processes. In this regard, the development and the implementation of appropriate methods for in-situ characterization of cell components at the functionally relevant length scales is highly required. Soft X-ray spectroscopies, such as X-ray absorption spectroscopy, X-ray emission (fluorescence) spectroscopy, resonant inelastic X-ray spectroscopy and X-ray photoelectron spectroscopy have been extensively employed for ex-situ characterization of materials used in electrochemical systems. Furthermore, adding spatial resolution capabilities by implementing proper optical solutions has opened unique opportunities for monitoring material changes and mass transport events occurring at submicron length scales. The input from these methods is providing correlative information about the status of the electrode surface and of the electrode/electrolyte interface and also of the processes occurring under operation conditions

Chromosomal control of non-gliadin proteins from the 70% ethanol extract of wheat endosperm

The non-gliadin fraction of the 70% ethanol extracts of compensated nulli-tetrasomics and ditelosomics of Triticum aestivum cv. Chinese Spring has been analyzed by combined electrofocusing and electrophoresis. Seventeen of the 21 protein map components of the euploid have been ascribed to eight chromosomes: 4A, 3BS, 6BS, 7BS, 3D, 4D, 5D and 7DS. The relationship of the different map components with other proteins previously associated with the same chromosomes is discusse

Disposable versus reusable ureteroscopes. A prospective multicenter randomized comparison

Introduction: To compare reusable and disposable flexible ureteroscopes in terms of efficacy and safety for patients undergoing RIRS, with specific reference to post-operative complications and infection rates. Materials and methods: Patients with a renal stone eligible for RIRS were enrolled in this multicenter, randomized, clinical trial study. Patients were randomized into two groups: group A (90 patients) underwent RIRS with a reusable flexible ureteroscope and group B (90 patients) were treated with a disposable one. Results: The patients’ demographics, stones features and preoperative urine cultures were comparable between the groups. The SFRs were not significantly different (86,6% and 90,0% for group A and group B respectively, p = 0.11) and the mean cost for each procedure was comparable (2321 € in group A vs 2543 € in group B, p = 0.09). However, the days of hospitalization and of antibiotic therapy were higher in group A (p ≤ 0.05). The overall complication rate in group A was 8.8% whilst in group B it was 3.3% (p ≤ 0.05); in particular, group A exhibited a greater number of major complications (Clavien score IIIa-V). The overall postoperative infections rate was 16.6% in group A and 3.3% in group B (p ≤ 0.05). Furthermore, none of the patients in group B developed urosepsis or had a positive blood culture, while 3 patients in group A did (p < 0.05). Conclusions: The use of disposable ureteroscopes is characterized by significantly lower post-operative complications and infection rates, while having comparable costs and SFRs vis à vis reusable ureteroscopes

A prospective multicenter randomized comparison between Holmium Laser Enucleation of the Prostate (HoLEP) and Thulium Laser Enucleation of the Prostate (ThuLEP)

Purpose: To compare intra and perioperative parameters between HoLEP and ThuLEP in the treatment of benign prostatic hyperplasia and to evaluate clinical and functional outcomes of the two procedures with a 12-month follow-up. Methods: A prospective randomized study was performed on 236 consecutive patients who underwent ThuLEP (n = 115), or HoLEP (n = 121) in three different centers. Intra and perioperative parameters were analyzed: operative time, enucleated tissue weight, irrigation volume, blood loss, catheterization time, hospital stay and complications. Patients were evaluated preoperatively and 3 and 12 months postoperatively with the international prostate symptom score (IPSS), the quality of life (QoL) score, post-void residual volume (PVR), PSA and maximum flow rate (Qmax). Results: Preoperative variables in each study arm did not show any significant difference. Compared to HoLEP, ThuLEP showed similar operative time (63.69 vs 71.66 min, p = 0.245), enucleated tissue weight (48.84 vs 51.13 g, p = 0.321), catheterization time (1.9 vs 2.0 days, p = 0.450) and hospital stay (2.2 vs 2.8 days, p = 0.216), but resulted in less haemoglobin decrease (0.45 vs 2.77 g/dL, p = 0.005). HoLEP presented a significantly higher number of patients with postoperative acute urinary retention and stress incontinence. No significant differences were found in PSA, Qmax, PVR, IPSS and QoL score during follow-up. Conclusion: ThuLEP and HoLEP both relieved lower urinary tract symptoms equally, with high efficacy and safety. ThuLEP detemined reduced blood loss and early postoperative complications. Catheterization time, enucleated tissue, hospital stay, operative time and follow-up parameters did not show any significant difference

First Powering of the LHC Test String 2

String 2 is a full-size model of a regular cell in an LHC arc. In the first phase, three dipole magnets and two quadrupole magnets have been assembled in String 2 and commissioning started in April 2001. By the beginning of 2002 three pre-series dipole magnets will be added to complete the cell. As for its predecessor String 1, the facility was built to individually validate the LHC systems and to investigate their collective behaviour for normal operation with the magnets at a temperature of 1.9 K, during transients as well as during exceptional conditions. String 2 is a precious milestone before installation and commissioning of the first LHC sector (1/8 of the machine) in 2004, with respect to infrastructure, installation, tooling and assembly procedures, testing and commissioning of individual systems, as well as the global commissioning of the technical systems. This paper describes the commissioning, and retraces the first powering history