1,721,246 research outputs found
Cava muracci: A new middle-upper palaeolithic site in west-central Italy
No full textComprehensive studies of Palaeolithic sites and the application of modern analytical techniques are still incredibly rare in coastal central Italy. In this paper, we present the Middle-Upper Palaeolithic cave deposits excavated in the travertine quarry of Cava Muracci (Cisterna di Latina, central Italy) and summary describe the multidisciplinary approach carried out on findings discovered therein. A large faunal assemblage, fossil faeces (coprolites) and a small lithic collection have been examined along with reliable dating analyses for the interpretation of the context. The site proved to be extensively frequented by cave hyena (Crocuta crocuta spelaea) between 34–44 ka BP, with a marginal human presence also attested. This study demonstrates that a holistic approach is crucial for enhancing our understanding of the archaeological context of the area, previously interpreted using studies of fauna or lithic industries alone. The evidence gathered from Cava Muracci and the results from their study provide a valuable reference database from which to draw upon for future investigations
ELECTRODEPOSITION AND CHARACTERIZATION OF NICKEL-COPPER ALLOY FILMS AS ELECTRODE MATERIAL IN ALKALINE MEDIA.
No full textA new and simple electrochemical procedure of anodic codeposition of nickel and copper oxide-hydroxide species on the gold electrode substrate from alkaline solutions is described. The electrodeposited alloy film, with an average composition Ni: Cu of 0.67 (i.e., Ni40Cu60) was investigated by electrochemical, scanning electron microscopy, and X-ray photoelectron spectroscopy techniques. The resulting deposited alloys appear uniform, smooth, adherent to the gold substrate, and homogeneous, independently of the electrochemical procedure adopted for the preparation (i.e., potentiostatic or potentiodynamic conditions). The presence of copper oxyhydroxide species in deposited film imparts an extensive stabilization of the beta/beta crystallographic forms of the nickel oxyhydroxide under prolonged repetitive potential cycling in alkaline medium. The electrocatalytic activity of the resulting composite Ni-Cu film was investigated toward the oxidation of carbohydrates using glucose as a model compound
ELECTROCATALYSIS AND DETECTION OF CARBOHYDRATES BY ANION-EXCHANGE CHROMATOGRAPHY AT A GOLD SUBSTRATE ELECTRODE MODIFIED WITH NICKEL CYANIDE IONS.
No full textChemically modified electrodes obtained by direct interaction between gold substrate and tetracyanonickelate(II) ions in alkaline medium were characterized by cyclic voltammetry toward the electrooxidation of carbohydrates. Satisfactory performance with respect to catalytic stability, background current stability and lowering of detection limit was obtained for the analysis of ten oligosaccharides contained in a synthetic sample by anion-exchange chromatography in alkaline solutions. Under constant applied potential of 0.55V (vs. Ag/AgCl), the detection limits (S/N=3) for all investigated compounds ranged between 3 and 6 pmol injected for melezitose and turanose, respectively. The dynamic linear ranges spanned generally three orders of magnitude above the limit of detection. The effects of the concentration of tetracyanonickelate(II) ion on the catalytic activity, amperometric stability and chromatographic separations were examined
ANODIC ELECTRODEPOSITION OF COPPER OXIDE/HYDROXIDE FILMS BY ALKALINE SOLUTIONS CONTAINING CUPROUS CYANIDE IONS.
No full textA novel procedure of anodic electrodeposition of copper oxides and hydroxides on glassy carbon and noble metals electrodes in an alkaline medium is described. The deposited films have been investigated by electrochemical and by X-ray photoelectron spectroscopy (\XPS) techniques. The copper films are deposited on the electrode surface as Cu(OH)(2) and CuO after the dissociation of the Cu(CN)(n)(1-n) complex caused probably by the formation of Cu-III species at relatively high applied potentials (i.e. 0.5 V). The resulting active copper films, independently of the electrochemical procedure adopted (i.e. potentiostatic or potentiodynamic conditions), appear to be uniform, smooth and with a good degree of adhesion on the electrode surface The electrocatalytic properties of the copper deposited films were investigated in an alkaline medium for the electrooxidation of several classes of organic compounds
STUDY OF THE ELECTROCHEMICAL DEPOSITION AND PROPERTIES OF COBALT OXIDE SPECIES IN CITRATE ALKALINE SOLUTIONS.
No full textGlassy carbon electrode substrates coated with thin films of cobalt oxyhydroxide were investigated in moderately alkaline medium by cyclic voltammetry. The cobalt oxide formation process was accomplished in alkaline solution (30 mM NaOH) containing millimolar concentrations of CoCl2 and ligand species such as sodium citrate. The cobalt oxide/hydroxide films were obtained either by voltage cycling between 0.4 and 1.1 V versus SCE or under potentiostatic conditions at moderate positive potentials (i.e. 0.5 V). The resulting electrodeposited film was characterized electrochemically in alkaline solutions by cyclic voltammetry and, independently of the electrodeposition procedure adopted, reveals three well-defined sets of redox waves related to the Co(OH)(2)/Co(2)o(3), Co(2)o(3)/CoOOH and CoOOH/CoO2 electrochemical transitions. The charge/discharge processes and the oxygen evolution reaction during continuous potential cycling were severely inhibited in the presence of increasing concentrations of electroinactive electrolytes (i.e. NaNO3, K2SO4, Na3PO4, etc.). The electrochemical behaviour of the electrodeposited cobalt oxide/hydroxide film in alkaline solution and in the presence of various organic molecules was also investigated
ELECTROCHEMICAL AND XPS CHARACTERIZATION OF COMPOSITE MODIFIED ELECTRODES OBTAINED BY NICKEL DEPOSITION ON METALS.
No full textA chemically modified electrode composed of nickel oxyhydroxide film deposited on noble metals (i.e., gold or platinum) was characterized in an alkaline medium by cyclic voltammetry and XPS (X-ray photoelectron spectroscopy) techniques. The nickel was deposited on the gold substrate in an alkaline medium by various strategies: cycling the potential between -0.1 and 0.65 V vs SCE, in potentiostatic conditions at potentials comprised between 0.0 and 0.55 V and by simple immersion of the electrode in non-deaerated 0.2 M NaOH solutions containing 3 mM K2Ni(CN)(4). The effects of several experimental parameters such as applied potentials, pH, tetra-cyanonickelate concentration, electrode substrate, etc., on the nickel film formation and growth were evaluated. The electroactivity of the resulting composite gold-nickel electrode was investigated in an alkaline medium toward the oxidation of carbohydrates using arabinose as a model compound
ELECTROCATALYTIC REDUCTION OF NO3- AND NO2- ON COMPOSITE COPPER-THALLIUM ELECTRODE IN ALKALINE SOLUTIONS.
No full textThe electrochemical behaviour of the copper-thallium composite film has been investigated in 10 mM NaOH solutions towards the electroreduction of nitrate and nitrite ions in the range of potentials between 0.0 and -1.4 V vs. SCE. The Cu45Tl55 binary films exhibited a higher electrocatalytic activity for the reduction of NO3- and NO2- than pure copper and thallium electrodeposited films. The presence of thallium species in the composite film causes a marked increase of the roughness factor with subsequent increase of the catalytic response due to the nitrate and nitrite reduction. Alternatively, thallium particles act as promoters of NO3- and NO2- adsorption on the electrode surface with their subsequent accumulation on the surface catalytic centres and increase of the cathodic currents
DETERMINATION OF ALIPHATIC ORGANIC ACIDS BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY WITH PULSED ELECTROCHEMICAL DETECTION.
No full textA new ion exclusion HPLC procedure accomplished with a pulsed electrochemical detection for the determination of several common aliphatic acids is described. A triple-step waveform of the applied potentials, based on the formation/inhibition of PtOH species on the electrode surface, is successfully used for sensitive detection of several aliphatic acids in flowing systems avoiding pre- or postcolumn derivatization and/or cleanup procedures. Under optimal chromatographic conditions (i.e., 50 mM HCIO4) the proposed method allowed detection limits between 0.5 and 7 muM for all investigated acids, and the dynamic linear range spanned generally over 1 or 2 orders of magnitude. Determination of citric, malic, tartaric, lactic, formic, and acetic acids in several foods and beverages was performed, in similar to15 min, without the necessity of any sample pretreatment
DETERMINATION OF ELECTROACTIVE ORGANIC ACIDS BY ANION-EXCHANGE CHROMATOGRAPHY USING A COPPER MODIFIED ELECTRODE.
No full textAn ion-chromatographic method combined with electrochemical detection at a copper-based chemically modified glassy carbon electrode (Cu-GC) has been shown to provide a simple analytical approach for the determination of some common organic acids in alkaline medium. Under the optimized isocratic chromatographic conditions (i.e. 0.1 M NaOH plus 80 mM CH3COONa), organic acids such as gallic, ascorbic, gluconic, lactobionic, galacturonic and glucuronic acid could be separated in less than 20 min. Under constant potential amperometric detection (i.e. 0.55 V vs. Ag-AgCl) the Cu-GC modified electrode allowed detection limits between 2 and 5 pmol for all investigated organic acids while the linear dynamic range spanned generally over three orders of magnitude. Examples of applications included the separation and quantitation of some common organic acids in vinegar, honey and tea samples, are given
- …
