58 research outputs found
Condition numbers for singular integral equations in weighted L2 spaces
No full textAbstractThe convergence and stability of a discrete collocation method for Cauchy singular integral equations in some weighted Besov spaces are studied. This numerical method results in solving a linear system in order to determine the unknown coefficients of the approximate solution. The author proves that this linear system is well conditioned
Geochronological study of zircons from continental crust rocks in the Frido Unit (southern Apennines)
No full textZircon crystals have been separated from gneisses and metagranitoids of the Pollino area (southern Apennines) in order to unravel the origin of these crustal slices within the ophiolite-bearing Frido Unit. The morphology of the zircon has been investigated by SEM, and the internal structure was revealed by cathodoluminescence. Data obtained by U/Pb dating have been used to deduce the age and significance of the different crystallization stages of zircon, connected to the evolutionary stages of the continental crust (Late Paleozoic–Early Mesozoic). Zircons in gneisses are characterized by inherited cores of magmatic origin, bordered by metamorphic rims. Inherited zircons generally show Paleoproterozoic to Ordovician ages, indicating the provenance of the sedimentary protolith from different sources. The exclusive presence of Late Neoproterozoic zircon cores in leucocratic gneisses may suggest a different magmatic source possibly connected to Pan-African events. Late Carboniferous–Early Permian ages are found mainly in zircon rims of metamorphic origin. These are similar to the emplacement ages of protolith of the metagranites in the middle crust portion. Late Carboniferous–Early Permian metamorphism and magmatism testify the extensional collapse of the Hercynian belt, recorded in European, particularly, in the Corsica–Sardinia block and in Calabria. Late Permian–Triassic ages have been detected in zircon rims from gneisses and metagranitoids. These younger ages appear related to deformation and emplacement of albite–quartz veins in both lithologies, and are related to an extensional episode predating the Middle Triassic to Middle Jurassic rifting in the Tethyan domain, followed by Middle to Late Jurassic spreading
Improved separation and size characterization of gold nanoparticles through a novel capillary zone electrophoresis method using poly(sodium4-styrenesulfonate) as stabiliser and a stepwise field strength gradient
No full textA novel capillary zone electrophoresis (CZE) method was developed for an improved separation and size characterization of pristine gold nanoparticles (AuNP) using uncoated fused-silica capillaries with UV-Vis detection at 520 nm. To avoid colloid aggregation and/or adsorption during runs, poly(sodium 4-styrenesulfonate) (PSS) was added (1%, w/v) in the running buffer (CAPS 10 mM, pH 11). This polyelectrolyte conferred an enhanced stabilization to AuNP, both steric and electrostatic, exalting at the same time their differences in electrophoretic mobility. Resolution was further and successfully improved through a stepwise field strength gradient by the application of 25 kV for the first 5 min and then 10 kV. Migration times varied linearly with particles diameters showing relative standard deviations better than 1% for daily experiments and 3% for interday experiments. A comparison with the size distribution obtained by transmission electron microscopy (TEM) allowed assessing that the electrophoretic profile can reasonably be considered as representative of the effective size heterogeneity of each colloid. Finally, the practical utility of the proposed method was demonstrated by measuring the core diameter of a gold colloid sample produced by chemical synthesis which was in good agreement with the value obtained by TEM measurements
Flexible Biphenyls as Probes for the Determination of Absolute Configuration of 1,2- and 1,3-Diols by CD Spectroscopy
No full textFunghi ipogei della Basilicata. III Contributo
No full textViene segnalata la presenza in Basilicata dei seguenti funghi ipogei: Balsamia vulgaris, Genea fragrans, G. hispidula, Pachyphloeus citrinus, P.ligericus;
Hymenogaster lycoperdineus. Con questi 6 nuovi ritrovamenti, sale a 35 il n. degli ipogei segnalati fino all'aprile 2004 nella regione
Sistemi Bifenillici Flessibili come Sonde per la Determinazione della Configurazione Assoluta di 1,2- e 1,3-Dioli Mediante Spettroscopia DC
No full textStudies on Volatile Organic Compounds of Tuber borchii and T. asa-foetida.
No full textAscomata of two truffle species, Tuber borchii and T. asa-foetida, both naturally growing in woodlands of the Basilicata region (southern Italy), were identified on the basis of ascospore morphology and compared under a volatile organic compound profile to determine the particular volatile organic compounds that characterize each taxon. Solid-phase microextraction-gas chromatography-mass spectrometry analysis of the samples showed the presence of 1-methyl-1,3-butadiene as a primary component in both truffles. T. asa-foetida showed a compound, toluene, not present in T. borchii, which creates the penetrating "solvent" smell of the truffle
Flexible Biphenyls as Probes for Configurational Assignment of 1,2- and 1,3-Diols by CD Spectroscopy
No full text
Pulsed electrochemical deposition of nickel oxides on multi-walled carbon nanotubes from EDTA alkaline solutions: a SEM, XPS, and voltammetric characterization
Get PDFA study regarding the electrodeposition of nickel oxide particles on the activated multi-walled carbon nanotubes from 2 M NaOH solution containing Ni(NO3)2 and EDTA was carried out. The electrodeposition process was carried out using an optimized double-pulse sequence of potentials: E1 = â0.2 V vs. SCE (t1 = 0.3 s) and E2 = 0.7 V vs. SCE (t2 = 0.03 s). Spectroscopic XPS investigations and SEM analysis were used in order to characterize the surface and morphology of the studied modified electrode. Cyclic voltammetry and chronoamperometry were used in order to evaluate the electrochemical/amperometric performance of the GC/MWCNT-Ni electrode toward the oxidation of some aliphatic alcohols in strong alkaline medium
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