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Berg B.,Complesso Universitario | Berg B.,University of Helsinki | Davey M.P.,University of Cambridge | de Marco A.,Complesso Universitario | And 10 more authors.
Biogeochemistry | Year: 2010

We synthesized available data for decomposition of pine (Pinus) needle litter in pine forests to determine the litter chemical characteristics and climate factors that explained variation in the limit value, i. e. the level of accumulated mass loss at which the decomposition process either continues at a very low rate or possibly stops. Our data base included 56 separate studies on decomposition of pine needle litter, spanning Scots pine, lodgepole pine, Aleppo pine, stone pine and white pine, mainly incubated at the site of collection. Studies had 5 to 19 samplings, on average 10, and the decomposition was followed to a mass loss ranging from 47 to 83%, on average 67%. The periods from 3.0 to 5.4 years, on average 3.9 years, were of sufficient duration to allow estimates of limit values of decomposition. We used a linear mixed model with regression effects to relate limit values to potential explanatory variables, namely the sites' long-term mean annual temperature (MAT) and mean annual precipitation (MAP) and to substrate-chemistry factors. Regarding the latter, we explored two models; one that included initial concentrations of water solubles, lignin, N, P, K, Ca, Mg, and Mn and one that included only lignin, N, Ca, and Mn to focus on those nutrients known to influence lignin degradation. Using backward elimination significant explanatory variables were determined. For litter decomposed in its site of origin we found the limit value to depend mainly on the initial concentration of Mn, with higher Mn concentrations resulting in higher accumulated mass loss. Thus, litter with higher Mn reached a higher limit value and left a smaller stable fraction. This is likely due to the fact that Mn is an essential component of ligninolytic enzymes important for degrading litter in the later stages of decomposition. Manganese has received little attention in decomposition studies to date. Given its significance in this synthesis, the role of Mn in influencing variation in the late stages of decomposition among ecosystems and among litters of other genera besides Pinus deserves further attention. © 2010 Springer Science+Business Media B.V.


Sanna R.,Complesso Universitario | Scorciapino A.M.,Complesso Universitario | Floris C.,Complesso Universitario | Casu M.,Complesso Universitario
American Mineralogist | Year: 2013

To better understand lattice disorder in hydrozincite, natural hydrozincite samples and synthetic analogues were investigated by XRD, FTIR, 13C MAS, and 13C CPMAS NMR. The size of coherent diffraction domains ranges between ∼10 nm (Synth1) and ∼30 nm (Synth2). FTIR peaks from the antisymmetric CO3 2- stretching n3 mode were observed at 1383 and 1515 cm-1 in all samples. Peaks due to OH vibrations were observed for all the samples at 3234, 3303, and 3363 cm-1, and were sharp only for the samples having larger crystal domains. The 13C MAS and CPMAS NMR spectra showed a main carbon signal at 164 ppm in the Synth2 sample, while two main signals were observed at ∼164 and ∼168 ppm in the Synth1 sample. The intensity ratio of the latter signals were found to be independent of contact time, in the investigated range between 0.2 and 30 ms. In addition, 13C CPMAS dynamics indicates that the Synth1 sample has shorter T1ρ with respect to Synth2. This indicates a more effective process of spin diffusion of proton magnetization in the former due to different structural properties of Synth1 and Synth2 samples. In addition, chemical shift anisotropy analysis was attributed to a structural change in the carbonate group or hydrogen bonding for Synth1 and Synth2. This was interpreted as a deviation from the ideal structure generated by linear and planar lattice defects and/or grain boundaries.


Ambrosone G.,CNR Institute of Neuroscience | Ambrosone G.,University of Naples Federico II | Basa D.K.,Utkal University | Coscia U.,University of Naples Federico II | And 2 more authors.
Thin Solid Films | Year: 2010

Hydrogenated amorphous silicon carbon alloy films of different carbon content were prepared by Plasma Enhanced Chemical Vapor Deposition using silane and methane with helium dilution and were characterized to study their opto-electronic, structural and defective properties. A linear correlation between micro structural disorder and overall disorder has been demonstrated. Further, it has been shown that the increase in the intrinsic disorder leads to an increase in the defect density while the increase in voids results in the decrease in the mass density for the studied films. © 2010 Elsevier B.V. All rights reserved.


Kang H.,Shanghai JiaoTong University | Xin Z.,Shanghai JiaoTong University | Xin Z.,Hubei University | Berg B.,Complesso Universitario | And 7 more authors.
Annals of Forest Science | Year: 2010

Forest ecosystems exert an important influence on global biogeochemical cycles. A global dataset of nitrogen (N) and phosphorus (P) concentrations in leaf-litter of woody plants was compiled from the literature. Among the 677 data sets, 482 included P concentrations and the N:P ratio. At a global scale, the mean leaf-litter N and P and N:P ratio were 10.9 mg g -1, 0.85 mg g -1 and 18.3, respectively. Leaf-litter N and P were significantly correlated. When the data was grouped by continents, the highest mean N was found in Africa (19.5 mg g -1), and the lowest in North America (8.18 mg g -1). P was significantly smaller in the Asian Islands (Japan and Malaysia, 0.44 mg g -1) than on the Asian mainland. For the global dataset, leaf-litter N increased linearly with mean annual temperature and annual precipitation and decreased with latitude. Although leaf-litter P showed no significant relationship with temperature, it declined linearly with precipitation and there was a convex quadratic relationship with latitude. For the global dataset and also for different functional groups (e.g. shrubs, evergreen broadleaf, deciduous broadleaf, and conifers) the leaf-litter N:P ratio generally followed a positive linear relationship with temperature and precipitation, and showed a concave quadratic response with latitude. The differences in leaf-litter N:P ratio among functional groups and among continents should be taken into account when modeling biogeochemical cycles in different regions as well as on a global scale. © 2010 INRA, EDP Sciences.


Coscia U.,University of Naples Federico II | Coscia U.,Complesso Universitario | Ambrosone G.,University of Naples Federico II | Ambrosone G.,CNR Institute of Neuroscience | And 4 more authors.
Thin Solid Films | Year: 2013

Nanostructured silicon carbon thin films, composed of Si nanocrystallites embedded in hydrogenated amorphous silicon carbon matrix, have been prepared by varying rf power in ultra high vacuum plasma enhanced chemical vapour deposition system using silane and methane gas mixtures diluted in hydrogen. In this paper we have studied the compositional, structural and electrical properties of these films as a function of rf power. It is shown that with increasing rf power the atomic densities of carbon and hydrogen increase while the atomic density of silicon decreases, resulting in a reduction in the mass density. Further, it is demonstrated that carbon is incorporated into amorphous matrix and it is mainly bonded to silicon. The study has also revealed that the crystalline volume fraction decreases with increase in rf power and that the films deposited with low rf power have a size distribution of large and small crystallites while the films deposited with relatively high power have only small crystallites. Finally, the enhanced transport properties of the nanostructured silicon carbon films, as compared to amorphous counterpart, have been attributed to the presence of Si nanocrystallites. © 2013 Elsevier B.V.


Zucca P.,Consortium University of Oristano | Zucca P.,Complesso Universitario | Rescigno A.,Complesso Universitario | Rinaldi A.C.,Complesso Universitario | Sanjust E.,Complesso Universitario
Journal of Molecular Catalysis A: Chemical | Year: 2014

Lignin is a recalcitrant polymer arising from addition polymerization of phenylpropanoid units via an oxidative, enzyme-catalyzed radical mechanism. Lignin removal is a serious technological challenge in wood-related industries such as pulping for paper production. In this review, some outstanding aspects in lignin biosynthesis and structure are depicted; also the commonly used industrial protocols for pulp delignification are described, with special emphasis on their molecular aspects. A discussion is presented concerning the known chemical mechanisms of enzyme-catalyzed delignification by white-rot fungi. Biomimetic and bioinspired synthetic metalloporphines show monooxygenase/peroxygenase-like catalytic activity, being quite more versatile catalysts than ligninolytic enzymes (being capable only of one-electron oxidations). The advantages of this behavior are encompassed with an in-depth discussion about the molecular aspects of their action mechanisms, the possible oxygen donors, and the known oxidizable substrates. Limitations and perspectives about their practical use at an industrial scale in delignification processes are discussed. © 2013 Elsevier B.V.


Iacovacci M.,University of Naples Federico II | Iacovacci M.,Complesso Universitario | Di Girolamo T.,University of Naples Federico II | Di Girolamo T.,Complesso Universitario | And 2 more authors.
Nuclear Physics B - Proceedings Supplements | Year: 2013

Following recently proposed approaches on gamma/hadron separation, spatial correlations among secondary charged particles in extensive air showers have been studied for the case of the ARGO-YBJ experiment, which represents a particularly suited detector in this respect because of its "continuous- carpet" geometry. Two different types of statistics have been considered, namely the nearest-neighbor spacing distribution (NNSD) and the variance of the number of secondary particles at given distance. The results of this preliminary investigation are reported. © 2013 Elsevier B.V.


Basa D.K.,Utkal University | Abbate G.,University of Naples Federico II | Abbate G.,CNR Institute of Neuroscience | Ambrosone G.,University of Naples Federico II | And 5 more authors.
Journal of Applied Physics | Year: 2010

The optical properties of the hydrogenated amorphous silicon carbon alloy films, prepared by plasma enhanced chemical vapor deposition technique from silane and methane gas mixture diluted in helium, have been investigated using variable angle spectroscopic ellipsometry in the photon energy range from 0.73 to 4.59 eV. Tauc-Lorentz model has been employed for the analysis of the optical spectra and it has been demonstrated that the model parameters are correlated with the carbon content as well as to the structural properties of the studied films. © 2010 American Institute of Physics.


Zucca P.,Consorzio University Oristano | Zucca P.,Complesso Universitario | Cocco G.,Complesso Universitario | Pintus M.,Complesso Universitario | And 2 more authors.
Journal of Chemistry | Year: 2013

This paper describes the oxidation of inorganic sulfide to sulfate, minimizing the formation of elemental sulfur. The described catalytic reaction uses dilute hydrogen peroxide at nearly neutral pH values in the presence of a bioinspired, heterogenized, and commercial ferriporphin. A substantial increase of the percentage of sulfide converted to sulfate is obtained in comparison with the yields obtained when working with hydrogen peroxide alone. The biomimetic catalyst also proved to be a much more efficient catalyst than horseradish peroxidase. Accordingly, it could be suitable for large-scale applications. Further studies are in progress to drive sulfate yields up to nearly quantitative. © 2013 Paolo Zucca et al.


Ambrosone G.,CNR Institute of Neuroscience | Ambrosone G.,University of Naples Federico II | Basa D.K.,Utkal University | Coscia U.,University of Naples Federico II | And 2 more authors.
Thin Solid Films | Year: 2012

Nanostructured silicon carbon films composed of silicon nanocrystallites embedded in hydrogenated amorphous silicon carbon matrix have been deposited by plasma enhanced chemical vapour deposition technique using silane and methane gas mixture highly diluted in hydrogen. The structural and optical properties of the films have been investigated by X-ray diffraction, Raman, Fourier transform infrared, ultra violet-visible-near infrared and photoluminescence spectroscopies while the composition of the films has been obtained from nuclear techniques. The study has demonstrated that the structure of the films evolves from microcrystalline to nanocrystalline phase with the increase in radio frequency (rf) power. Further, it is shown that with increasing the rf power the size of silicon nanocrystallites decreases while the optical gap increases and a blueshift of visible room temperature photoluminescence peak can be observed. © 2012 Elsevier B.V. All rights reserved.

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