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21.
The activation of zirconium nickel alloys with and without the addition of chromium and titanium is investigated through electrochemical
and optical techniques. Recent investigations in aqueous 1 M KOH indicate oxide layer growth and occlusion of hydrogen species
in the alloys during the application of different cathodic scan potential programmes currently used for the activation process.
In this research, several techniques, such as voltammetry, ellipsometry, energy dispersive analysis of X-rays and scanning
electron microscopy, are applied to three polished massive alloys, Zr1−x
Ni
x
, x = 0.36 and 0.43, and Zr0.9Ti0.1NiCr. Data analysis shows that the stability, compactness and structure of the passive layers are strongly dependent on the
applied potential programme. The alloy activation depends on the formation of deep crevices that remain after further polishing.
The microscopic observation shows an increase in crevice thickness after cathodic sweep potential cycling, which produces
fragmentation of the grains and oxide growth during the activation process. This indicates metal breaking and intergranular
alloy dissolution that take place together with oxide and hydride formation. In some cases, the resultant crevice thickness
is one or two orders higher than the growth of surface oxide indicating localised intergranular corrosion.
Dedicated to Prof. Dr. Teresa Iwasita on the occasion of her 65th birthday in recognition of her numerous contributions to
interfacial electrochemistry. 相似文献
22.
Enzymatic Oxygen Microsensor Based on Bilirubin Oxidase Applied to Microbial Fuel Cells Analysis 下载免费PDF全文
Matteo Grattieri Sofia Babanova Carlo Santoro Edoardo Guerrini Stefano PM Trasatti Pierangela Cristiani Massimiliano Bestetti Plamen Atanassov 《Electroanalysis》2015,27(2):327-335
A selective oxygen biosensor based on bilirubin oxidase (BOx) was developed. The sensor was used for determining oxygen profiles in a membraneless, single‐chamber microbial fuel cell (SCMFC), fed with raw wastewater. The linear response of the sensor was optimized by a diffusion layer of silica gel. A computer‐controlled stage was used to obtain accurate and precise measurements. Oxygen concentration in biofilms covering electrodes was measured, showing 3 mg L?1 of O2 in the bulk solution, decreasing to 0 mg L?1 in the cathodic biofilm. The MFC generated power in the range of 0–0.08 mW, associated to the oxygen content. 相似文献
23.
Augusto Visintin 《Calculus of Variations and Partial Differential Equations》2013,47(1-2):273-317
After Fitzpatrick’s seminal work [MR 1009594], it is known that in a real Banach space V any maximal monotone operator ${\alpha: V \to {\mathcal P}(V^{\prime})}$ may be given a variational representation. This is here illustrated on some examples. On this basis, De Giorgi’s notion of Γ-convergence is then applied to the analysis of monotone inclusions, like ${D_tu + \alpha(u)\ni h}$ . The compactness and the structural stability are studied, with respect to variations of the operator α and of the datum h. The possible onset of long memory in the limit is also discussed. 相似文献
24.
Eleonora Amante Eugenio Alladio Rebecca Rizzo Daniele Di Corcia Pierre Negri Lia Visintin Michela Guglielmotto Elena Tamagno Marco Vincenti Alberto Salomone 《Molecules (Basel, Switzerland)》2021,26(16)
The misuse of fentanyl, and novel synthetic opioids (NSO) in general, has become a public health emergency, especially in the United States. The detection of NSO is often challenged by the limited diagnostic time frame allowed by urine sampling and the wide range of chemically modified analogues, continuously introduced to the recreational drug market. In this study, an untargeted metabolomics approach was developed to obtain a comprehensive “fingerprint” of any anomalous and specific metabolic pattern potentially related to fentanyl exposure. In recent years, in vitro models of drug metabolism have emerged as important tools to overcome the limited access to positive urine samples and uncertainties related to the substances actually taken, the possible combined drug intake, and the ingested dose. In this study, an in vivo experiment was designed by incubating HepG2 cell lines with either fentanyl or common drugs of abuse, creating a cohort of 96 samples. These samples, together with 81 urine samples including negative controls and positive samples obtained from recent users of either fentanyl or “traditional” drugs, were subjected to untargeted analysis using both UHPLC reverse phase and HILIC chromatography combined with QTOF mass spectrometry. Data independent acquisition was performed by SWATH in order to obtain a comprehensive profile of the urinary metabolome. After extensive processing, the resulting datasets were initially subjected to unsupervised exploration by principal component analysis (PCA), yielding clear separation of the fentanyl positive samples with respect to both controls and samples positive to other drugs. The urine datasets were then systematically investigated by supervised classification models based on soft independent modeling by class analogy (SIMCA) algorithms, with the end goal of identifying fentanyl users. A final single-class SIMCA model based on an RP dataset and five PCs yielded 96% sensitivity and 74% specificity. The distinguishable metabolic patterns produced by fentanyl in comparison to other opioids opens up new perspectives in the interpretation of the biological activity of fentanyl. 相似文献
25.
Augusto Visintin 《Calculus of Variations and Partial Differential Equations》2002,15(1):115-132
A forward-backward parabolic problem is obtained by coupling the equation with a nonmonotone relation . In the framework of a two-scale model, we replace the latter condition by a relaxation dynamics which converges to a hysteresis
relation. We provide a suitable formulation of the hysteresis law, approximate it by the relaxation dynamics, couple it with
the P.D.E., derive uniform estimates via an -technique, and then pass to the limit as the relaxation parameter vanishes. This yields existence of a solution for the modified
problem. This procedure is also applied to other equations.
Received: 25 May 2000 / Accepted: 11 May 2001 / Published online: 19 October 2001 相似文献
26.
27.
Visintin PM Carbonell RG Schauer CK Desimone JM 《Langmuir : the ACS journal of surfaces and colloids》2005,21(11):4816-4823
The steric stabilization and flocculation of modified silica and alumina particle suspensions in condensed CO(2) were studied. Silica particles (average diameters of 7 and 12 nm) were functionalized using chlorosilanes of the form C(n)F(2n+1)CH(2)CH(2)Si(CH(3))(2)Cl (n = 8, 4, or 1) to give C(n)F(2n+1)-silica. Alumina particles (diameter of 8-14 nm) were grafted with C(8)F(17)CH(2)CH(2)Si(OEt)(3) and chemically modified with perfluorononanoic acid to yield C(8)F(17)-alumina and C(8)F(17)COOH-alumina, respectively. Elemental analysis and thermogravimetric analysis on the derivatized particles were carried out, and surface coverage was calculated. The stabilization of these modified particles in condensed CO(2) was quantified using turbidimetry. Particle stability was found to increase with increasing fluorinated tail length, temperature, and CO(2) density. Unmodified particles and those modified with only -CF(3) tails were unstable in condensed CO(2). Stabilization in supercritical CO(2) is continuous up to 24 h for the C(n)F(2n+1)-silica (n >/= 4) particles and 96 h for the C(8)F(17)-alumina particles. The C(8)F(17)COOH-alumina particles gave a significantly higher graft density than the C(8)F(17)-alumina particles but are not as stable in CO(2). The C(8)F(17)-alumina particles were stable at lower CO(2) densities than the modified silica particles. This stability difference may be attributed to the precursor organosilanes being monofunctional (modified silica) versus trifunctional (modified alumina), producing different structures on the surface. 相似文献
28.
29.
Augusto Visintin 《Calculus of Variations and Partial Differential Equations》2009,36(4):565-590
This work is devoted to scale transformations of stationary nonlinear problems. A class of coarse-scale problems is first derived by integrating a family of two-scale minimization problems (scale-integration), in presence of appropriate orthogonality conditions. The equivalence between the two formulations is established by showing that conversely any solution of the coarse-scale problem can be represented as the fine-scale average of a solution of the two-scale problem (scale-disintegration). This procedure may be applied to the homogenization of several quasilinear problems, and is related to De Giorgi’s notion of Γ-convergence. As an example the homogenization of a simple nonlinear model of magnetostatics is illustrated: a two-scale minimization problem is first derived via Nguetseng’s notion of two-scale convergence, and afterwards the equivalence with a coarse-scale problem is proved. 相似文献
30.
Alan Rigter Jan Priem Drophatie Timmers-Parohi Jan PM Langeveld Fred G van Zijderveld Alex Bossers 《BMC biochemistry》2009,10(1):29-16