169,825 research outputs found
I beni ecclesiastici nel diritto dello Stato: diritto comune e diritto speciale, diritto unilaterale e diritto pattizio
No full textEnergy Production and Storage from Renewable Sources through Electrocatalysis
No full textThe energy transition from fossil fuels to renewables will be a long and difficult process but it is not avoidable since fossil sources depletion, pollution and geopolitical situations are becoming worrisome. There are different challenges for researchers in the field of energy. From renewable energy production data it is clear the remarkable growth of solar electricity technologies, that crystalline silicon photovoltaics (PV) and wind turbines are the workhorses of the first wave of renewable energy deployment around the globe. Anyway these renewable energy are not equally distributed and, for their natural discontinuity, cannot sustain the requirements of our society. In this perspective the energy storage will play a fundamental role in the development of an energy system based on renewable sources.
The storage of hydrogen as gas in pressured tanks poses many problems, in particular for transport safety concerns. The alternative is the production on demand of this gas by using storing hydrogen materials. These materials can help developing mobility systems based on hydrogen as fuel, since the reserve of hydrogen would be stored as a solution, for example of sodium borohydride.
The interconversion between electricity and hydrogen and biofuels, like bioethanol, could be the keystone of a new sustainable energy economy. The development of two electrochemical devices can serve to this energy system, fuel cells and electrolyzers. Fuel cells are devices that can convert cleanly chemical energy stored in hydrogen or bioalcohols into electrical energy, while electrolyzers use electrical energy to produce molecules, which can be energy vectors such as hydrogen.
The electrical energy surplus could be used in another kind of electrolyzers, for example for the reduction of CO2. In these devices it’s possible to obtain different products but the performance of electrocatalysts at the moment are not so good to make this electroreduction particularly appealing due to high energy costs, low activity and stability of the catalysts.
The focus on this thesis is to face the energy problems by different points of view: 1) the production of electrical energy from renewable resources with Direct Liquid Fuel Cells (DLFCs), 2) the production of hydrogen from storage materials and from electrolysis, 3) the storage of electrical energy producing useful molecules in electrolyzers.
During the three years catalysts have been synthesized and characterized for their morphology and activity, both in electrochemical half-cell and complete cell systems or in properly designed reactors.
In Chapter 1 a description of the state of the art of fuel cells and electrolyzers is provided and describes the advantages in replacing the traditional proton exchange membrane electrolytes with anion exchange membranes. In Chapter 2 an introduction of the electrochemical reduction of CO2 is given, focusing on copper and palladium as electrode for this reaction.
The discussion of the results will be divided in three main Chapters,(3,4,5).
The first one, Chapter 3, is on Direct Liquid Fuel Cells. The electrocatalysts employed are nanostructured Pd at the anode and Fe-Co at the cathode. The performance of microscale direct ethanol fuel cells (DEFCs) was studied with an equipment of a membrane electrode assembly (MEA) of 1 cm2 size with four anion exchange membranes. A fuel concentration of 6 M ethanol+6 M KOH was chosen to test the stability at a constant current density of 1 mA cm−2. The cell ran for 87 days with a potential drop of 3 mV day−1, and the energy delivered was 1.08 Wh. Furthermore, in order to explore functioning in conditions that maximize delivered energy density, a direct formate fuel cell (DFFC) operating at different formate and alkali concentrations has been investigated. The active DFFC at 60 °C with 4 M HCOOK + 4 M KOH as anode fuel and O2fed to the cathode produces a maximum power density of 258 mA cm−2.
In Chapter 4, for the production of hydrogen the design and construction of a reactor for sodium borohydride (SBH) hydrolysis and the performance of palladium and rhodium based electrocatalysts in a electrochemical reformer are presented. For SBH hydrolysis a cobalt boride (CoxB) catalyst supported on a commercial Cordierite Honeycomb Monolith (CHM) was used. The electrooxidation performances of Pd/C and Rh/C catalysts were studied at different temperature with different organic molecules as substrates. In particular, Pd/C with formate, exhibits an onset of 200 mV and a specific activity of 2100 A g−1Pd; while Rh/C has an excellent activity for methanol oxidation, showing an onset potential 200 mV lower than Pd/C and a specific activity almost double reaching the value of 2600 A g−1Rh. In addition examples of electrooxidation of biomass-derived alcohols such as EtOH, EG, G and 1,2-P have been studied in an electroreformer containing Rh nanoparticles supported on carbon as the anode electrocatalyst, equipped with an anion exchange membrane and a Pt/C on carbon cloth cathode. The oxidation of alcohols was investigated in electrochemical half-cells at room temperature and at 60–80 °C in alkaline media. The results highlighted the excellent activity of Rh/C in terms of peak current densities (as high as 5700 A gRh-1 for EG at 80 °C) and low onset of potentials.
Copper and Palladium based catalysts, studied for the electroreduction of CO2, are reported in Chapter 5. To enhance the activity of these two metals for CO2RR, two different paths were followed: 1) copper surface and morphology were modified to vary the products compositions and enhance activity; 2) palladium was alloyed with a different metal, gold, to improve performance and stability. The surface modification on copper resulted in an enhancement of the surface area of a copper foil and influenced the selectivity of the reduction reaction products. The Au-Pd alloy nanoparticles have shown high activity and selectivity for the electroreduction of CO2, where CO was the only product of the electrocatalysis.
In the Chapter 6 there are conclusions and considerations on the whole work during the three years. The importance of the nanostructured catalyst is evident in every application described in this work. These materials showed improved performance and their applications can really represent a turning point in the energy field
Comportamento delle lepri allevate in harem e in coppia fissa.
No full textHare behaviour was video recorded during two years. The hares were reared in cage in fixed couples and in harem. The presence in display zone, rest, feeding, drinking, locomotion, reproduction, comfort and stereotypes were observed. Results showed that presence in display zone decreased February through June; rest and comfort behaviour were observed during the whole season. repeated activities (stereotypes) were observed in couples bred hares during the whole season while in harem bred hares were observed mainly during the starting of the reproductive season
Effetto della tecnica di allevamento sul comportamento antipredatorio della starna (Perdix perdix L.).
No full textAllevamento delle lepri in gabbie harem o in gabbie con coppie fisse
No full textHare behaviour was video recorded during two years. In the first yearr the hares were video recorded during the whole day; in the second year the hares were video recorded February thriugh March, April through May, and June through July, from 8:00 AM to 10:30 AM, and from 4:00 PM to 6:30 PM (peaks of activity observed during daylight) Presence in display zone of the cages, rest, feeding, drinking, locomotion, reproduction, comfort and stereotypes were video recorded. Results showed that: presence in display zone decreased February through June. Repeated activities (stereotypes) were observed, in couple bred hares during the whole season while in harem bred hares mainly during the starting of the reproductive season. Aggressivness was mainly related to refuse of mating in couple-bred hares, and to feeding competitivity in harem.bred hares
L’impiego della paglia di avena come alimento complementare nella lepre
No full textThe aim of this study was to evaluate the digestibility in the hare of two commercial feeds with or without oat straw fed ad libitum. Four couples bred hares were fed ad libitum with two commercial pellet (first pellet: crude protein 17% and crude fibre 21%; second pellet: crude protein 15% and crude fibre 23%) with or without oat straw. Feed intake was not significantly influenced by the addition of oat straw, although the hares decreased the pellet intake in presence of oat straw. The coefficients of digestibility were higher in 15% p - 23% f .pellet than in 17% p - 21% f. pellet. The oat straw did not decrease the digestibility of the organic matter, probably in relationship to a best production and utilization of soft faeces
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
L’impiego della paglia di avena e dell’acqua clorata nell’allevamento della lepre
No full textThe aim of this study was to evaluate the effect of oat straw and drinking water chlorination on the performance and total bacteria counts in faeces and drinking water of young hares. 25 days old hares were reared in cages, fed ad libitum with commercial diet and monitored for 50 days. 39 animals were divided into four groups factorial design: the first group with straw and without chlorine, the second with straw and with chlorine, the third wiyhout straw and wiyhout chlorine, the fourth without straw and with chlorine. The presence of chlorine in the drinking water was about 1 p.p.m. Young hares fed with oat straw and watered with chlorinated water showed the best performance. Young hares fed with straw and without chlorine showed the highest results of total bacterial counts. Regression exponential analysis showed low negative correlation between bacterial counts and water chlorine levels
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