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81.
The electrochemical determination of aqueous Hg(II) by anodic stripping voltammetry (ASV) at a solid gold electrode is described. The aim of this work is to optimise all factors that can influence this determination. Potential wave forms (linear sweep, differential pulse, square wave), potential scan parameters, deposition time, deposition potential and surface cleaning procedures were examined for their effect on the mercury peak shape and intensity. Five supporting electrolytes were tested. The best responses were obtained with square wave potential wave form and diluted HCl as supporting electrolyte. Electrochemical and mechanical surface cleaning, aimed at removing the amount of mercury deposited onto the gold surface, were necessary for obtaining a good performance of the electrode. Response linearity, repeatability, accuracy and detection limit were also evaluated. 相似文献
82.
83.
Federica Olivero Ornella Robutti 《International Journal of Computers for Mathematical Learning》2007,12(2):135-156
This paper sits within the research on the affordances of new technologies in the mathematics classroom and focuses on a specific
feature that is available in dynamic geometry environments, i.e. measuring tools, within the context of conjecturing and proving
in open geometry problems. We develop a classification of different modalities of measuring, based on our previous work on
dragging. The modalities are illustrated through the analysis of 15–16 year-old students’ proving processes, which focuses
on how these modalities relate to the moves between the spatio-graphical field and the theoretical field and may either support
or hinder the proving process. The classification of the modalities of measuring enables researchers to access students’ cognitive
processes and teachers to be aware of the different possible uses and interpretation of measuring, giving them tools to support
students when difficulties arise.
相似文献
Ornella RobuttiEmail: |
84.
de Petris G Troiani A Angelini G Ursini O Bottoni A Calvaresi M 《Journal of the American Society for Mass Spectrometry》2007,18(9):1664-1671
A hitherto unknown, isotope-exchange reaction is studied in ionized gaseous mixtures containing disulfur monoxide and water. The kinetics, mechanism, and intermediate of the reaction are investigated by experimental and theoretical methods. The reactivity of the S(2)O(*+) cation with water is investigated under a wide range of pressures ranging from 10(-7) to 10(-4) Torr, by FT-ICR, TQ, and high-resolution CAD mass spectrometry. In the high-pressure limit the reaction proves to be a route to strongly bound sulfur-containing species. 相似文献
85.
Mangiapia G Frielinghaus H D'Errico G Ortona O Sartorio R Paduano L 《Physical chemistry chemical physics : PCCP》2007,9(46):6150-6158
The structure of chemically-crosslinked chitosan and chitosan-poly(vinylpyrrolidone) (PVP) hydrogels is investigated by means of the combined use of small-angle neutron scattering (SANS), electron paramagnetic resonance spectroscopy (EPR), intradiffusion, and swelling degree measurements. These hydrogels may be described in terms of an inhomogeneous structure composed by polymer-rich and polymer-poor regions. The polymer-rich regions, whose correlation distance zeta is ranged between approximately 600 and approximately 850 A, are, in turn, characterized by the presence of a network formed by the chemical crosslinks, with a mean correlation distance xi approximately 90 A. The structures of chitosan and chitosan-PVP hydrogels have also been analyzed in the presence of sodium decylsulfate micelles that could provide a multidomain system useful, in principle, for drug delivery applications. Both SANS and EPR measurements show that sodium decylsulfate micelles do not significantly interact with both the gels. Finally, intradiffusion and swelling degree measurements show an improved hydrophilicity of chitosan-PVP gels, even further magnified by the presence of C10OS surfactant. 相似文献
86.
Cristina Cherubini Ornella Ursini Franco Cataldo Susana Iglesias-Groth Maria Elisa Crestoni 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(3):1061-1073
A selection of amino acids, namely arginine, proline and tyrosine previously irradiated to 3.2 mega-Gray in the solid state and analyzed by differential scanning calorimetry (DSC) and optical rotatory dispersion (ORD) were analyzed in the present work by mass spectrometry with the purpose to identify the radiolysis products and validate the results obtained previously with DSC and ORD. The radiolysis of amino acids is a top-down approach of a research program designed to assess the radiolysis resistance of these molecules for 4.6 × 109 years once buried in primitive bodies of the Solar System. 相似文献
87.
Paolo Stabile Alessandro Lamonica Damiano Castoldi Ornella Curcuruto 《Tetrahedron letters》2010,51(37):4801-4805
A mild, general, convenient, and efficient one-pot synthesis of 2-phenyl-5-substituted-1,3,4-oxadiazoles is described. Both (hetero)aryl and alkyl carboxylic acids were efficiently condensed with benzohydrazide in the presence of TBTU to give diacylhydrazine intermediates. The latter underwent a smooth TsCl-mediated cyclodehydration reaction to afford 2-phenyl-5-substituted-1,3,4-oxadiazoles in good to very good yields. 相似文献
88.
Dr. Fabio Pirro Dr. Salvatore La Gatta Dr. Federica Arrigoni Dr. Antonino Famulari Dr. Ornella Maglio Prof. Pompea Del Vecchio Prof. Mario Chiesa Prof. Luca De Gioia Prof. Luca Bertini Dr. Marco Chino Prof. Flavia Nastri Prof. Angela Lombardi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(1):e202211552
De novo metalloprotein design is a remarkable approach to shape protein scaffolds toward specific functions. Here, we report the design and characterization of Due Rame 1 (DR1), a de novo designed protein housing a di-copper site and mimicking the Type 3 (T3) copper-containing polyphenol oxidases (PPOs). To achieve this goal, we hierarchically designed the first and the second di-metal coordination spheres to engineer the di-copper site into a simple four-helix bundle scaffold. Spectroscopic, thermodynamic, and functional characterization revealed that DR1 recapitulates the T3 copper site, supporting different copper redox states, and being active in the O2-dependent oxidation of catechols to o-quinones. Careful design of the residues lining the substrate access site endows DR1 with substrate recognition, as revealed by Hammet analysis and computational studies on substituted catechols. This study represents a premier example in the construction of a functional T3 copper site into a designed four-helix bundle protein. 相似文献
89.
Nastri F Lista L Ringhieri P Vitale R Faiella M Andreozzi C Travascio P Maglio O Lombardi A Pavone V 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(16):4444-4453
Mimicking enzymes with alternative molecules represents an important objective in synthetic biology, aimed to obtain new chemical entities for specific applications. This objective is hampered by the large size and complexity of enzymes. The manipulation of their structures often leads to a reduction of enzyme activity. Herein, we describe the spectroscopic and functional characterization of Fe(III)-mimochrome VI, a 3.5 kDa synthetic heme-protein model, which displays a peroxidase-like catalytic activity. By the use of hydrogen peroxide, Fe(III)-mimochrome VI efficiently catalyzes the oxidation of several substrates, with a typical Michaelis-Menten mechanism and with several multiple turnovers. The catalytic efficiency of Fe(III)-mimochrome VI in the oxidation of 2,2'-azino-di(3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) and guaiacol (k(cat)/K(m)=4417 and 870 mM(-1) s(-1), respectively) is comparable to that of native horseradish peroxidase (HRP, k(cat)/K(m)=5125 and 500 mM(-1) s(-1), respectively). Fe(III)-mimochrome VI also converts phenol to 4- and 2-nitrophenol in the presence of NO(2) (-) and H(2) O(2) in high yields. These results demonstrate that small synthetic peptides can impart high enzyme activities to metal cofactors, and anticipate the possibility of constructing new biocatalysts tailored to specific functions. 相似文献
90.
Mehiddin Al-Baali Lucio Grandinetti Ornella Pisacane 《Journal of Optimization Theory and Applications》2014,161(2):688-699
This paper is aimed to extend a certain damped technique, suitable for the Broyden–Fletcher–Goldfarb–Shanno (BFGS) method, to the limited memory BFGS method in the case of the large-scale unconstrained optimization. It is shown that the proposed technique maintains the global convergence property on uniformly convex functions for the limited memory BFGS method. Some numerical results are described to illustrate the important role of the damped technique. Since this technique enforces safely the positive definiteness property of the BFGS update for any value of the steplength, we also consider only the first Wolfe–Powell condition on the steplength. Then, as for the backtracking framework, only one gradient evaluation is performed on each iteration. It is reported that the proposed damped methods work much better than the limited memory BFGS method in several cases. 相似文献