211,806 research outputs found
Urban sustainability: the role of ecosystem services provided by an italian green infrastructure
No full textCurrent population growth, climate change and the increase in derived pollution represent a significant threat to the delicate balance that governs the exploitation of resources on Earth. In recent decades, this balance has been undermined, coming to an over-exploitation condition, or a growing demand for natural raw materials that the planet is no longer able to satisfy, with impacting consequences on human well-being and the health of natural ecosystems. Cities represent the main collectors of such reactions: it is necessary to analyze which mitigation actions can be the best in order to counter their uncontrolled development. This work focuses on a specific tool aimed at achieving the goal: green infrastructures constitute a valid source of sustainability in the urban environment, slowing down the processes derived from climate change and intensifying the recovery of ecological functions. Specifically, the role of the "Le Vallere" park was analyzed, a green area of about 35 hectares that is part of the metropolitan context of the Municipality of Turin, in collaboration with the related management institution ("Ente di gestione delle Aree Protette del Po piemontese", ex "Ente di gestione delle aree del Po torinese"). The main purpose was to quantify the ecosystem services offered by the green infrastructure to the surrounding urban area, through the use of i-Tree, a specific software suite able to evaluate benefits offered by vegetation. Reduction of atmospheric pollutants, carbon storage and sequestration, avoided surface water runoff, improvement of water quality are the main aspects investigated, obtaining an estimate of these parameters also from a monetary point of view. The survey carried out has, therefore, made it possible to obtain an assessment of the sustainability produced by the infrastructure, providing essential information to the related management institution, in view of a future territorial planning
Surface and Structure Characterization of Some Perovskite-type Powders To Be Used As Combustion Catalysts
No full textSome perovskite-type transition-metal mixed oxide powders active in the combustion catalysis, with formulas LaMO(3) (M = Fe, Cr, Co, and Mn), have been prepared by different methods. Similarly, potential supports for combustion catalysts nearly isostructural with the above ones have been prepared, with compositions SrZrO3 and LaAlO3. Mixed phases with formulas Sr1-xLaxZr1-xMnxO3 have also been investigated. The bulk properties have been studied by XRD, far-IR spectroscopy, and DTA-TG analyses. Morphological properties have been determined by XRD, SEM, and surface area measurements. These phases crystallize after heating at 970 K (except LaFeO3, which is already crystalline after calcination at 770 K) with surface area ranging 10-20 m(2)/g. The solubility of LaMnO3 into SrZrO3 is limited to near 10%. Their surface properties have been investigated by IR spectroscopy that showed a predominantly basic surface character of all these solids
Characterization of silica-containing aluminum hydroxide and oxide aerogels
No full textPure and silica-containing Al hydroxide aerogels were prepared by the supercritical drying method. The samples were later calcined, giving rise to alumina and Si-Al mixed oxides. The materials were characterized from the points of view of their bulk and surface structures. The Si-free material before calcination is well-crystallized boehmite that converts to gamma-alumina by calcination. The silica-containing hydroxides are composed of boehmite layers with silicates in the interlayer region. The resulting mixed oxides present silica essentially in the bulk. The surface structure of alumina seems poorly sensitive to silica addition. Surface silanol groups appear only for SiO2 more than 4%. No Bronsted acidity appears. Silica addition allows mixed oxides with higher surface areas to be obtained. (C) 1997 Academic Press
Fluoride modification of Mo/Al2O3 catalysts characterization of the changes induced in support and Mo phases
No full textThe characterization of fluoride-modified Mo/Al2O3 catalysts was performed in order to investigate on the effect that low levels of fluoridation of the alumina support (0-2.0 wt.%) cause on the support itself and on the supported Mo oxide and sulfide phases. Fluoride-modified Al-2-O-3 supports and Mo/Al-2-O-3 catalysts where characterized by nitrogen physisorption, scanning electronic microscopy (SEM-EDX), isoelectric point (IEP), Fourier transform infrared spectroscopy (FT-IR), infrared spectroscopy of adsorbed CO2 (IR-CO2) and temperature programmed reduction (TPR). The dispersion of the sulfided catalysts was estimated by dynamic NO chemisorption. The results indicate that the different hydroxyl types present on the alumina surface react to a different extent with fluoride and that it is the most basic hydroxyl groups that are titrated first. The consumption of the alumina OH by F-, inhibits, during the deposition of Mo, the formation of tetrahedral molybdenum oxide species in strong interaction with the support, leading to an increased number of polymeric octahedral Mo surface species. The NO adsorption results put in evidence a drop in the dispersion of the MOS2 phase present in the sulfided samples. (C) 2003 Elsevier Science B.V. All rights reserved
Preparation and Characterization of Magnesium Chromite and Magnesium Ferrite Aerogels
No full textA supercritical drying process has been used to prepare MgO-Cr2O3 and MgO-Fe2O3 powders from a mixture of magnesium acetate and the metallic acetylacetonates hydrolyzed in a methanolic solvent. The resultant aerogels have small particle sizes in the range of 10 to 20 nm and high surface areas in the range of 50 to 250 m2/g. After removal from the autoclave, characterization by X-ray diffraction (XRD) showed that the MgO-Cr2O3 was amorphous and that the MgO-Fe2O3 was readily in the form of a spinel structure for magnesioferrite (MgFe2O4). Fourier transform infrared spectroscopy (FTIR) and thermogravimetric and differential thermal analyses (TG-DTG-DTA) showed a high level of retained surface methoxy and carboxylate species for the MgO-Cr2O3 aerogel (over 40% by weight). The MgFe2O4, on the otherhand, had less than 10% organic matter. The differences observed between MgO-Cr2O3 and MgFe2O4 have been attributed to the formation of Cr+6 in the former case. After heating in air at 970K. MgO-Cr2O3 crystallized to the spinel structure MgCr2O4. The IR transmittance of pressed disks of MgFe2O4 aerogel showed behavior typical for a n-type semiconductor. The MgCr2O4, however, was a p-type semiconductor due to mainly Cr+6 present on the surface. Lewis acid centers were prevalent on both materials. The acid strength was found to be higher on the MgFe2O4 compare to the MgCr2O4
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Skeletal Vibrations of Cuprate Superconductor-like Phases - A Comparison of the Ft-fir Spectra of La2-xSrxCuO4, Nd2-xCexCuO4 and RBa(2)Cu(3)O(7-x) (r=ln Or Y) Powders
No full textThe FT-IR/FT-FIR spectra of powders of Nd2-xCexCuO4 and La2-xSrxCuO4 solid solutions and of RBa(2)Cu(3)O(7-x) with R = Y, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm and Yb, have been recorded at room temperature. A comparison with the published single-crystal IR data is done. An empirical assignment of the observed bands is proposed on the basis of the factor group analysis and of a discussion of the internal vibrational structure of the CuOx sheets and chains
New Pd/Pt on Mg/Al basic mixed oxides for vapor phase hydrogenation and hydrogenolysis of naphthalene
No full textNew Pd/Pt catalysts supported on a basicMg/Al mixed oxide obtained by calcination of a commercial hydrotalcite (SASOL, D) have been fully characterized by XRD, SEM, and FTIR and investigated in the vapor-phase hydrogenation of naphthalene in order to put in evidence
the role of the Pd/Pt active phase and the acidity of the support on the hydrogenolysis/ring-opening reaction as well as the thio-tolerance of the catalysts. After calcination the hydrotalcite support (HT) gave rise to a Mg/Al mixed oxide with high surface area and a “brain-like” surface morphology. The IR spectra after adsorption of CO over the reduced samples showed the interaction between bimetallic particles and Mg–Al(O) basic support. The main band in the range 2080–2070 cm−1 is due to on-top CO adsorbed over Pd0 or Pt0, while the complex absorption below 2000 cm−1 is due to CO species bridging over Pd0. All the samples showed mainly a hydrogenation activity, highlighting the role of the support acidity in the ring-opening reactions to high molecular weight (HMW) products, having a boosting effect on the cetane number of the fraction obtained. A significant increase in the amount of HMWproducts was obtained by decreasing the Pd/Pt ratio, showing also the role of hydrogenolysis reactions attributable mainly to Pt, thus suggesting a hydrogenolysis/ring-opening mechanism. Furthermore, the Pd/Pt on basic oxide catalysts did not give rise to useless low molecular weight (LMW) cracking compounds, which thus formed only on
highly acid sites. Finally, these catalysts, investigated by feeding increasing amounts of dibenzothiophene (DBT), showed an almost constant activity up to 3000 wt ppm of DBT. This surprising result pointed out the intrinsic thio-resistance of the Pd/Pt pair, regardless of a possible
contribution of the acid sites of the support, and is mainly attributed to its high hydrodesulfurization (HDS) activity
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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