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Rettangoli grigliati. Riflessioni tra isoperimetrie in diversi contesti di apprendimento
No full textThe “grilled rectangles”, namely brectangles drawn in a grid, have a perfect coincidence with the rectangles obtained by moving a tight string between the thumb and forefinger of the two hands proposed by Emma Castelnuovo. From this movement, which has been reproduced on squared paper during the workshop, many questions arise: how many of them are there? Do the perimeter and area of these rectangles vary? What unit of measurement do we choose? For the perimeter it is unique. Instead, for the area we have more choices. What does this fact entail? The rectangles drawn in grids of different sizes are then analyzed. The various data are calculated, tabulated and compared. Why is the perimeter always an even number? Why is the area not always an even number? When does the square form? In conclusion we look for a regularity and we try to find a formula that generalizes it. The activity is exciting at any age and allows you to introduce, or consolidate, the concepts of isoperimetry and equivalence.I “rettangoli grigliati” ovvero disegnati in una griglia, hanno una perfetta corrispondenza con i rettangoli proposti da Emma Castelnuovo ottenuti muovendo uno spago ben teso tra il pollice e l’indice delle due mani. Da questo movimento riprodotto su carta quadrettata, possono nascere molte domande durante un laboratorio di matematica: quanti rettangoli si sono ottenuti? Perimetro e area di questi rettangoli variano? Quale sarà l’unità di misura adatta? Perché il perimetro è sempre espresso da un numero pari? Perché l’area non sempre è un numero pari? Quando si forma il quadrato? Esiste una regolarità per griglie di lato n che si può esprimere tramite una formula matematica? L’attività appassiona a qualunque età e permette di introdurre o di consolidare i concetti di isoperimetria e di equivalenza
Photoelectrochemical hydrogen production from aqueous solution employing nanostructured semiconductors
No full textThe focus of this thesis is the exploitation of various types of photoelectrodes based on nanostructured materials to be employed in photoassisted electrolysis schemes, aimed to convert solar energy into chemical energy. Since the world demand of energy is projected to increase in the next years, environmental issues like global warming and climate change impose a change in our way of producing and storing energy, currently and mainly based on the combustion of fossil fuels. Both a stable improvement of the quality of life for an increasing world population and the preservation the environment will require the use of progressively larger amounts of new energy sources which must be carbon neutral, renewable and low cost. This defines a grand scientific and technological challenge for the XXI century. Sunlight provides by far the largest of all carbon-neutral energy sources. More energy from sunlight strikes the Earth in one hour (4.3 x 1020 ) than all the energy consumed on the planet in a year (4.1 x 1020 J). Yet solar electricity provides only approximately 1 millionth of the total electricity supply, and renewable biomass provides less than 0.1% of the total energy consumed. There is a huge gap between our present use of solar energy and its enormous undeveloped potential. Hydrogen production from solar water splitting is regarded by many as the “holy grail” of photochemistry, providing a practically inexhaustible fuel source and, since the experiment of Fujishima and Honda, the use of semiconductor photoelectrodes capable of operating with a virtually unitary quantum yield has appeared as a convenient mean to realize water splitting in a photoelectrochemical cell. In particular, a large part of this thesis work has been devoted to the development of efficient WO3 photoelectrodes which is a promising material for water splitting, coupling favourable energetics for oxygen evolution, high photochemical stability in aqueous media and visible photon absorption up to 500 nm. . At first, different synthetic approaches for obtaining nanostructured WO3 on transparent conductive oxides have been explored by keeping the Santato-Augustynski recipe as a main guideline. In general the preparation of nanostructured photoelectrodes involves the formation of stabilized H2WO4 colloidal precursors in the presence of different organic dispersing agents which control both nanoparticle size and film porosity. The relationships between crystallite size, film porosity, electrochemically active surface and photoelectrochemical behavior under simulated solar illumination have been studied. The work has then focused on the preparation of WO3 films by potentiostatic anodization of metallic tungsten in different solvent/electrolyte compositions with the aim of improving the charge transfer and charge transport kinetics by creating tightly interconnected porous oxide structures directly bound to a metal collector. In the NMF/H2O/NH4F solvent mixture the anodization leads to highly efficient WO3 photoanodes, which, combining spectral sensitivity, high electrochemically active surface and improved charge transfer kinetics, outperform, under simulated solar illumination, most of the reported nanocrystalline substrates produced by anodization in aqueous electrolytes and by sol gel methods. The use of such electrodes results in high water electrolysis yield, of the order of 70% in 1 M H2SO4 under a potential bias of 1 V vs SCE and close to 100% in the presence of methanol acting as a hole scavenger. The requirement to harvest large part of the solar spectrum and photooxidize small molecules like H2S (largely present as a contaminant of hydrocarbon sources) has led us to the study of heterointerfaces between TiO2 and group VI semiconductors like CdS, CdSe, CdTe and Bi2S3, which are characterized by a relatively narrow band gap (from 2.4 eV for CdS to 1.4 eV for Bi2S3). The use of colloidal and nanotubular TiO2 as a substrate for growing sensitizing semiconductors by chemical and electrochemical means was instrumental in reducing significantly degradative self photoxidation and recombination leading to good photon to electron quantum yields, ranging from 20% (Bi2S3) to 60% (CdS) The photoelectrochemical behavior of TiO2 photoanodes sensitized by water stable molecular Ru(II) dyes was finally explored in the context of photoinduced hydrogen generation. The photoanodes sustained 240 h of irradiation without undergoing appreciable hydrolysis and decomposition in an aqueous environment at pH 3. Despite a favourable driving force for direct water oxidation, the performances in pure water were far from an applicative interest. However, the use of organic sacrificial donors, like isoprapanol and ascorbic acid considerably enhanced their photoanodic response and, interestingly, the exploitation of iodide, a well known electron donor in photoelectrchemical cells, was more problematic because the adsorption of photogenerated I3 - from aqueous media favored charge recombination with conduction band electrons, thus limiting the efficiency of the photoelectrosynthetic device. However, experiments performed in a three-compartment cell, where the photolectrode was in contact with an organic solvent preventing triiodide adsorption, revealed a remarkable photocurrent, with an electrolysis yield close to 87%. Although the problem of finding the ideal system for photoassisted electrolysis has not been entirely solved, this thesis work suggests some feasible approaches for obtaining high photon to electron conversion efficiencies, pointing out that the basis of an efficient photoelectrochemical system reside in the combination of an high electroactive area with fast interfacial charge transfer kinetics, necessary to overcome losses arising from recombination.The focus of this thesis is the exploitation of various types of photoelectrodes based on nanostructured materials to be employed in photoassisted electrolysis schemes, aimed to convert solar energy into chemical energy. Since the world demand of energy is projected to increase in the next years, environmental issues like global warming and climate change impose a change in our way of producing and storing energy, currently and mainly based on the combustion of fossil fuels. Both a stable improvement of the quality of life for an increasing world population and the preservation the environment will require the use of progressively larger amounts of new energy sources which must be carbon neutral, renewable and low cost. This defines a grand scientific and technological challenge for the XXI century. Sunlight provides by far the largest of all carbon-neutral energy sources. More energy from sunlight strikes the Earth in one hour (4.3 x 1020 ) than all the energy consumed on the planet in a year (4.1 x 1020 J). Yet solar electricity provides only approximately 1 millionth of the total electricity supply, and renewable biomass provides less than 0.1% of the total energy consumed. There is a huge gap between our present use of solar energy and its enormous undeveloped potential. Hydrogen production from solar water splitting is regarded by many as the “holy grail” of photochemistry, providing a practically inexhaustible fuel source and, since the experiment of Fujishima and Honda, the use of semiconductor photoelectrodes capable of operating with a virtually unitary quantum yield has appeared as a convenient mean to realize water splitting in a photoelectrochemical cell. In particular, a large part of this thesis work has been devoted to the development of efficient WO3 photoelectrodes which is a promising material for water splitting, coupling favourable energetics for oxygen evolution, high photochemical stability in aqueous media and visible photon absorption up to 500 nm. . At first, different synthetic approaches for obtaining nanostructured WO3 on transparent conductive oxides have been explored by keeping the Santato-Augustynski recipe as a main guideline. In general the preparation of nanostructured photoelectrodes involves the formation of stabilized H2WO4 colloidal precursors in the presence of different organic dispersing agents which control both nanoparticle size and film porosity. The relationships between crystallite size, film porosity, electrochemically active surface and photoelectrochemical behavior under simulated solar illumination have been studied. The work has then focused on the preparation of WO3 films by potentiostatic anodization of metallic tungsten in different solvent/electrolyte compositions with the aim of improving the charge transfer and charge transport kinetics by creating tightly interconnected porous oxide structures directly bound to a metal collector. In the NMF/H2O/NH4F solvent mixture the anodization leads to highly efficient WO3 photoanodes, which, combining spectral sensitivity, high electrochemically active surface and improved charge transfer kinetics, outperform, under simulated solar illumination, most of the reported nanocrystalline substrates produced by anodization in aqueous electrolytes and by sol gel methods. The use of such electrodes results in high water electrolysis yield, of the order of 70% in 1 M H2SO4 under a potential bias of 1 V vs SCE and close to 100% in the presence of methanol acting as a hole scavenger. The requirement to harvest large part of the solar spectrum and photooxidize small molecules like H2S (largely present as a contaminant of hydrocarbon sources) has led us to the study of heterointerfaces between TiO2 and group VI semiconductors like CdS, CdSe, CdTe and Bi2S3, which are characterized by a relatively narrow band gap (from 2.4 eV for CdS to 1.4 eV for Bi2S3). The use of colloidal and nanotubular TiO2 as a substrate for growing sensitizing semiconductors by chemical and electrochemical means was instrumental in reducing significantly degradative self photoxidation and recombination leading to good photon to electron quantum yields, ranging from 20% (Bi2S3) to 60% (CdS) The photoelectrochemical behavior of TiO2 photoanodes sensitized by water stable molecular Ru(II) dyes was finally explored in the context of photoinduced hydrogen generation. The photoanodes sustained 240 h of irradiation without undergoing appreciable hydrolysis and decomposition in an aqueous environment at pH 3. Despite a favourable driving force for direct water oxidation, the performances in pure water were far from an applicative interest. However, the use of organic sacrificial donors, like isoprapanol and ascorbic acid considerably enhanced their photoanodic response and, interestingly, the exploitation of iodide, a well known electron donor in photoelectrchemical cells, was more problematic because the adsorption of photogenerated I3 - from aqueous media favored charge recombination with conduction band electrons, thus limiting the efficiency of the photoelectrosynthetic device. However, experiments performed in a three-compartment cell, where the photolectrode was in contact with an organic solvent preventing triiodide adsorption, revealed a remarkable photocurrent, with an electrolysis yield close to 87%. Although the problem of finding the ideal system for photoassisted electrolysis has not been entirely solved, this thesis work suggests some feasible approaches for obtaining high photon to electron conversion efficiencies, pointing out that the basis of an efficient photoelectrochemical system reside in the combination of an high electroactive area with fast interfacial charge transfer kinetics, necessary to overcome losses arising from recombination
La Vittima nel Sistema Penale
No full textThe present work is based on the assumption that the victim of the offence, notwithstanding a longstanding obsolescence, plays a crucial role in criminal sciences. On this base, the investigation focuses on the role and the protection of the victim under national and supranational criminal laws, which still displays remarkable discrepancies. As a matter of fact, while the latter grant the victim with a central role, the former are still far from such perspective. With regard to internal acts, different approaches are put in place towards the objectives of the prevention of victimization and the victim’s protection. As for the first objective, which is still pursued by means of punitive measures, i. e. criminal law., some contradictions shall by underlined: from one side, some recent criminal policy options, concerning behaviour causing high social alarm, displays certain attention to victimology, even though they are also influenced by a social-defence approach; from the other side, other legislative responses are not keen at all on the victimological side, even though they concern behaviour rather frequent and harmful, but not perceived as such in the community, also because of a misinformation campaign by the mass media. As for the second objective, the situation does not seem much better. It is true that the role and the protection of the offended person in the criminal proceeding has been strengthened – even though what has been done is not sufficient yet to meet the obligations under supranational acts – and it is also true that certain restorative justice mechanisms have been introduced with the aim to develop such role. However, the legal framework is not at all satisfactory with regard to the tools for the assistance to the victim and for the reparation with public resources, the latter being extremely limited to the victim of certain types of offences only, in spite of a EU infringement procedure.The present work is based on the assumption that the victim of the offence, notwithstanding a longstanding obsolescence, plays a crucial role in criminal sciences. On this base, the investigation focuses on the role and the protection of the victim under national and supranational criminal laws, which still displays remarkable discrepancies. As a matter of fact, while the latter grant the victim with a central role, the former are still far from such perspective. With regard to internal acts, different approaches are put in place towards the objectives of the prevention of victimization and the victim’s protection. As for the first objective, which is still pursued by means of punitive measures, i. e. criminal law., some contradictions shall by underlined: from one side, some recent criminal policy options, concerning behaviour causing high social alarm, displays certain attention to victimology, even though they are also influenced by a social-defence approach; from the other side, other legislative responses are not keen at all on the victimological side, even though they concern behaviour rather frequent and harmful, but not perceived as such in the community, also because of a misinformation campaign by the mass media. As for the second objective, the situation does not seem much better. It is true that the role and the protection of the offended person in the criminal proceeding has been strengthened – even though what has been done is not sufficient yet to meet the obligations under supranational acts – and it is also true that certain restorative justice mechanisms have been introduced with the aim to develop such role. However, the legal framework is not at all satisfactory with regard to the tools for the assistance to the victim and for the reparation with public resources, the latter being extremely limited to the victim of certain types of offences only, in spite of a EU infringement procedure
Measurement of Collins asymmetries in inclusive production of pion pairs at BABAR
No full textTransversity Distribution, which describes the quark transverse polarization inside a transversely polarized nucleon, is the last leading-twist missing piece of the QCD description of the partonic structure of the nucleon. Transversity can be extracted from Semi-Inclusive Deep Inelastic Scattering (SIDIS) data, where, due to its chiralodd nature, it couples to a new, unknown fragmentation function, called Collins function. Independent information on the Collins function can be obtained in e+e- -> qq annihilation processes, where q = u, d, s. In the cross section formula, the Collins effect introduces a term that depends on the polarization of the quark q (antiquark q), which produces an asymmetry in the azimuthal distribution of the fragmenting products. For unpolarized beams we do not know the spin of the quarks arising from the e+e- annihilation process, and hence we cannot measure the spin effects due to the Collins function analyzing the hadron distributions generated in only one jet, which come from the fragmentation of a single quark. The Collins spin effect can instead be studied in inclusive production of two hadrons detected in opposite jets, produced by the fragmentation of a correlated qq pair: e+e- -> qq -> h1h2X. This correlation results in an observable azimuthal asymmetry distribution of the two hadrons. In this thesis, we present the measurement of the Collins asymmetries in the pions system (h1; h2 = π), using a sample of about 468 fb^(-1) of data collected at a center of mass energy of 10.54 and 10.58 GeV, with the BABAR detector at the e+e- collider PEPII at the SLAC National Accelerator Laboratory of Stanford. The Collins asymmetries are calculated in two different frames called thrust reference frame (RF12), and second hadron momentum frame (RF0), and the final results are shown as a function of the fractional energy and, for the first time in e+e- annihilation, as a function of the transverse momenta of the two pions. These results can be used in combination with Belle, HERMES, and COMPASS data in order to improve the extraction of the Transversity function, and Collins fragmentation function.Transversity Distribution, which describes the quark transverse polarization inside a transversely polarized nucleon, is the last leading-twist missing piece of the QCD description of the partonic structure of the nucleon. Transversity can be extracted from Semi-Inclusive Deep Inelastic Scattering (SIDIS) data, where, due to its chiralodd nature, it couples to a new, unknown fragmentation function, called Collins function. Independent information on the Collins function can be obtained in e+e- -> qq annihilation processes, where q = u, d, s. In the cross section formula, the Collins effect introduces a term that depends on the polarization of the quark q (antiquark q), which produces an asymmetry in the azimuthal distribution of the fragmenting products. For unpolarized beams we do not know the spin of the quarks arising from the e+e- annihilation process, and hence we cannot measure the spin effects due to the Collins function analyzing the hadron distributions generated in only one jet, which come from the fragmentation of a single quark. The Collins spin effect can instead be studied in inclusive production of two hadrons detected in opposite jets, produced by the fragmentation of a correlated qq pair: e+e- -> qq -> h1h2X. This correlation results in an observable azimuthal asymmetry distribution of the two hadrons. In this thesis, we present the measurement of the Collins asymmetries in the pions system (h1; h2 = π), using a sample of about 468 fb^(-1) of data collected at a center of mass energy of 10.54 and 10.58 GeV, with the BABAR detector at the e+e- collider PEPII at the SLAC National Accelerator Laboratory of Stanford. The Collins asymmetries are calculated in two different frames called thrust reference frame (RF12), and second hadron momentum frame (RF0), and the final results are shown as a function of the fractional energy and, for the first time in e+e- annihilation, as a function of the transverse momenta of the two pions. These results can be used in combination with Belle, HERMES, and COMPASS data in order to improve the extraction of the Transversity function, and Collins fragmentation function
Per la biblioteca di Santa Croce: i manoscritti di autori classici ‘ad usum’ di Sebastiano Bucelli
No full textThis article focuses on the figure of Sebastiano Bucelli, keeper of the Santa Croce library in the first half of the 15th century; specifically the manuscripts including works by authors of the classical period used by Bucelli and further donated to the florentine convent of Santa Croce represent the objective of the study. The essay shows which classical authors and literary genres circulated and were studied in the Franciscan settings in Florence during the 1400s, in the light of the decisive turning point from the late Middle Ages to Humanism. These manuscripts were also analyzed according to a catalographic perspective in which all major codicological and paleographical elements were rendered in the form of a codex description.Questo articolo si concentra sulla figura di Sebastiano Bucelli, custode della biblioteca di Santa Croce nella prima metà del XV secolo; nello specifico, i manoscritti comprendenti opere di autori del periodo classico utilizzati da Bucelli e successivamente donati al convento fiorentino di Santa Croce rappresentano l\u27obiettivo dello studio. Il saggio mostra quali autori classici e quali generi letterari circolavano e venivano studiati negli ambienti francescani di Firenze durante il Quattrocento, alla luce della svolta decisiva dal tardo Medioevo all\u27Umanesimo. Questi manoscritti sono stati analizzati anche secondo una prospettiva catalografica in cui tutti i principali elementi codicologici e paleografici sono stati resi sotto forma di descrizione del codice
A Cosmogram of Its Time - A Conceptual Analysis of the Catalan Atlas
No full textThis article aims to evaluate the role of maps in the Middle Ages and to assess whether they should be understood uniquely as antique geographical tools or, rather, as important historic records of a certain-time culture. Thus, the concept of cosmogram is applied to a specific case-study, the medieval portolan chart known as Catalan Atlas. The paper challenges what makes a map a complete and tangible representation of the understanding of the world at a specific moment, as opposed to a “simple” instrument to navigate the physical environment. In addition, the whole concept of medieval maps being just orientational aids will be put under pressure, comparing the Catalan Atlas with another medieval map, the Peutinger Tabula. Ultimately, it demonstrates that any map, even a contemporary one, always presents a degree of interpretation in the way it may mirror the historic context in which it was produced.L’articolo si propone di valutare il ruolo delle carte geografiche nel Medioevo e di stabilire se esse debbano essere intese unicamente come strumenti geografici antichi o, piuttosto, come importanti documenti storici di una certa cultura del tempo. Il concetto di cosmogramma viene quindi applicato a un caso di studio specifico, la carta portolana medievale nota come Atlante catalano. Il documento mette in discussione ciò che rende una mappa una rappresentazione completa e tangibile della comprensione del mondo in un momento specifico, rispetto a un "semplice" strumento per navigare nell\u27ambiente fisico. Inoltre, l\u27intero concetto di mappe medievali come semplici ausili all\u27orientamento sarà messo in discussione, confrontando l\u27Atlante catalano con un\u27altra mappa medievale, la Tabula Peutinger. In definitiva, si dimostra che qualsiasi mappa, anche contemporanea, presenta sempre un grado di interpretazione nel modo in cui può rispecchiare il contesto storico in cui è stata prodotta
Carlo Goldoni, il suo interesse per l’antico e la Galleria della villa Arconati Visconti del Castellazzo di Bollate
No full textIn the study of Carlo Goldoni’s relationship with the Ancient and antiquarian speculation, and in particular the role that the playwright played in the eighteenth-century satire of the figure of the anticomaniac, the written examines the Venetian’s attention to the collection of sculptures ancient ones that Count Giuseppe Antonio Arconati Visconti had collected in the Gallery of the Villa del Castellazzo di Bollate near Milan, about which the Venetian mentions in the letter of dedication from La Putta onorata.Nello studio del rapporto di Carlo Goldoni con l\u27Antico e la speculazione antiquaria, e in particolare del ruolo che il drammaturgo ebbe nella satira settecentesca della figura dell\u27anticomane, lo scritto esamina l\u27attenzione del veneziano per la collezione di sculture antiche che il conte Giuseppe Antonio Arconati Visconti aveva raccolto nella Galleria della Villa del Castellazzo di Bollate presso Milano, di cui il veneziano parla nella lettera di dedica de La Putta onorata
