THEORETICAL AND NUMERICAL STUDY OF HYDROGEN DIFFUSION IN Zr-NbALLOYS

Within the framework of the delayed hydride cracking phenomena reported for the pressure tubes of CANDU-typenuclear reactors, we study the influence of the Zr-β(∼20 %Nb -∼80 %Zr) continuous phase on the hydrogen diffusion coefficient,DH, through the Zr-α/ Zr-βbiphasic alloy. We propose an improved phenomenological model forDHwithrespect to those found in the literature. Furthermore, we study the influence of the Nb content onDHfor the cubic phase Zr-β, employing the transition state theory furnished with ab-initio parameters provided by the SIESTA code. In particular, 9 ordered alloys are considered with different Nb content and effective activation energies are computed by Arrhenius fits for each alloy. We find that activation energies vary in a non-monotonic way as Nb content increases, reaching a maximum value at about Zr-50 %Nb. Finally, we observe that the predicted and measured larger diffusivity along the tube axis vs. the radial direction, is consistent with the material texture. Moreover, we conclude that the loss of continuity of the Zr-βsheets present in the tube microstructure, is consistent with the decrease ofDHin time at a given temperature

Centri ecclesiastici e dinamiche di popolamento: la fondazione dei borghi nuovi subalpini e l’eredità romanica

Le testimonianze di architettura dell’XI e del XII secolo costituiscono non solo documenti utili allo studio della cultura artistica e tecnica, ma sono indicatori significativi per lo studio della storia delle dinamiche insediative. Il processo di patrimonializzazione delle architetture romaniche ha seguito infatti percorsi strettamente legati alle sorti del popolamento nelle aree loro circostanti: nei casi in cui i villaggi si siano riallocati o ri-concentrati nel basso medioevo, si è verificato il fenomeno della ‘ruralizzazione’ delle architetture romaniche, associato a una sostanziale conservazione ‘fossile’ della loro facies originaria; ove invece l’insediamento abbia avuto fortuna demica e politica presso la chiesa, l’edificio medievale è stato conservato in maniera parziale o selettiva, subendo ordinariamente interventi di adeguamento liturgico e di gusto. Il fenomeno è stato studiato attraverso alcuni casi-studio relativi al dinamismo insediativo della fondazione di borghi nuovi tra XII e XIV secolo. The architectural examples dating to 11th and 12th centuries are not only important to studying artistic and technical culture, but they are also meaningful indicators about history of settlement dynamics. In fact, the process of patrimonialization of Romanesque architectures followed ways closely linked to the destiny of the population in the nearby areas. When villages were re-positioned or re-focused during the late Middle Ages, Romanesque architectures experienced phenomenon of ‘ruralisation’, in association with a significant conservation of their original appearance as a ‘fossil’. Instead, when settlements had demographic and political successful outcomes beside the church, the medieval buildings have been partially or selectively preserved, routinely undergoing interventions of liturgical and style adaptation. The phenomenon is studied through case studies related to the dynamism of the foundation of new villages between 12th and 14th centuries

Performance characterization and near-realtime monitoring of MUSE adaptive optics modes at Paranal

The Multi Unit Spectroscopic Explorer (MUSE) is an integral field spectrograph on the Very Large Telescope Unit Telescope 4, capable of laser guide star assisted and tomographic adaptive optics using the GALACSI module. Its observing capabilities include a wide field (1 square arcmin), ground layer AO mode (WFM-AO) and a narrow field (7.5"x7.5"), laser tomography AO mode (NFM-AO). The latter has had several upgrades in the 4 years since commissioning, including an optimisation of the control matrices for the AO system and a new sub-electron noise detector for its infra-red low order wavefront sensor. We set out to quantify the NFM-AO system performance by analysing $\sim$230 spectrophotometric standard star observations taken over the last 3 years. To this end we expand upon previous work, designed to facilitate analysis of the WFM-AO system performance. We briefly describe the framework that will provide a user friendly, semi-automated way for system performance monitoring during science operations. We provide the results of our performance analysis, chiefly through the measured Strehl ratio and full width at half maximum (FWHM) of the core of the point spread function (PSF) using two PSF models, and correlations with atmospheric conditions. These results will feed into a range of applications, including providing a more accurate prediction of the system performance as implemented in the exposure time calculator, and the associated optimization of the scientific output for a given set of limiting atmospheric conditions.Comment: SPIE proceedings (2022), Observatory Operations: Strategies, Processes, and Systems I

Pharmacokinetics of high-dose oral thiamine hydrochloride in healthy subjects

Background: High dose oral thiamine may have a role in treating diabetes, heart failure, and hypermetabolic states. The purpose of this study was to determine the pharmacokinetic profile of oral thiamine hydrochloride at 100 mg, 500 mg and 1500 mg doses in healthy subjects. Methods: This was a randomized, double-blind, single-dose, 4-way crossover study. Pharmacokinetic measures were calculated. Results: The $AUC_{0-10 hr}$ and $C_{max}$ values increased nonlinearly between 100 mg and 1500 mg. The slope of the $AUC_{0-10 hr}$ vs dose, as well as the $C_{max}$ vs dose, plots are steepest at the lowest thiamine doses. Conclusion: Our study demonstrates that high blood levels of thiamine can be achieved rapidly with oral thiamine hydrochloride. Thiamine is absorbed by both an active and nonsaturable passive process

Electro-oxidation of cyanide on active and non-active anodes: Designing the electrocatalytic response of cobalt spinels

[EN] The feasibility of the electrochemical technologies for wastewater treatment greatly relies on the design of efficient but inexpensive electrocatalysts. It is generally accepted that the so-called ¿non-active¿ anodes (like the boron-doped diamond (BDD) or SnO2-based anodes), producing highly oxidizing hydroxyl radicals, are the most promising candidates for pollutants abatement. In this work, the electrocatalytic performance of various cobalt oxides, pure and doped with Cu or Au, for CN¿ oxidation has been studied and compared with that of conventional graphite, BDD, SnO2-Sb and SnO2-Sb-Pt. The metal oxide electrodes were prepared by thermal decomposition of the salt precursors onto Ti. For the M-doped Co3O4 electrodes, the nominal M/Co ratios were Cu/ Co=0.07¿1.00; and Au/Co=0.05¿0.20. The electrodes were characterized by different techniques (XRD, SEM, EDX, XPS) and their electrocatalytic response was studied by cyclic voltammetry and galvanostatic electrolysis in a H-type cell in aqueous 0.1M NaOH. The obtained results show that the nature of the dopant plays a key role on the electrocatalytic behavior of cobalt spinels. Thus, while Cu catalyzes the CN¿ electro-oxidation, Au declines it. This is explained by the fact that, unlike Au (which segregates as Au-rich particles), Cu is effectively incorporated into the spinel structure by forming a solid solution (CuxCo3-xO4). In this solid solution, atomic scale Cu(spinel)-CN¿ specific interactions occur to catalyze the reaction, whereas in segregated Au particles the oxidation is hindered probably by a too-strong adsorption of cyanide and/or its inaccessibility to oxide active sites. Electrolysis runs have revealed that ¿active¿ over-saturated Cu-doped spinels (Cu/Co=1.00) exhibit higher current efficiencies than conventional graphite and ¿non-active¿ BDD and SnO2-based anodes. Hence, we hereby demonstrate that an inexpensive ¿active¿ electrocatalyst can show even higher efficiency than the most powerful BDD anode. These results highlight the significance of anode design in the application of the electrochemical technique for wastewater treatment.Financial support from the Spanish Ministerio de Economia y Competitividad and FEDER funds (MAT2016-76595-R, IJCI-2014-20012) is gratefully acknowledgedBerenguer, R.; Quijada, C.; La Rosa-Toro, A.; Morallón, E. (2019). Electro-oxidation of cyanide on active and non-active anodes: Designing the electrocatalytic response of cobalt spinels. Separation and Purification Technology. 208:42-50. https://doi.org/10.1016/j.seppur.2018.05.024S425020