24 resultados para topologia, superfici, teorema di Seifert van Kampen.
em AMS Tesi di Dottorato - Alm@DL - Università di Bologna
Resumo:
L’attività di ricerca contenuta in questa tesi si è concentrata nello sviluppo e nell’implementazione di tecniche per la co-simulazione e il co-progetto non lineare/elettromagnetico di sistemi wireless non convenzionali. Questo lavoro presenta un metodo rigoroso per considerare le interazioni tra due sistemi posti sia in condizioni di campo vicino che in condizioni di campo lontano. In sostanza, gli effetti del sistema trasmittente sono rappresentati da un generatore equivalente di Norton posto in parallelo all’antenna del sistema ricevente, calcolato per mezzo del teorema di reciprocità e del teorema di equivalenza. La correttezza del metodo è stata verificata per mezzo di simulazioni e misure, concordi tra loro. La stessa teoria, ampliata con l’introduzione degli effetti di scattering, è stata usata per valutare una condizione analoga, dove l’elemento trasmittente coincide con quello ricevente (DIE) contenuto all’interno di una struttura metallica (package). I risultati sono stati confrontati con i medesimi ottenibili tramite tecniche FEM e FDTD/FIT, che richiedono tempi di simulazione maggiori di un ordine di grandezza. Grazie ai metodi di co-simulazione non lineari/EM sopra esposti, è stato progettato e verificato un sistema di localizzazione e identificazione di oggetti taggati posti in ambiente indoor. Questo è stato ottenuto dotando il sistema di lettura, denominato RID (Remotely Identify and Detect), di funzioni di scansione angolare e della tecnica di RADAR mono-pulse. Il sistema sperimentale, creato con dispositivi low cost, opera a 2.5 GHz ed ha le dimensioni paragonabili ad un normale PDA. E’ stato sperimentata la capacità del RID di localizzare, in scenari indoor, oggetti statici e in movimento.
Resumo:
In a context of technological innovation, the aim of this thesis is to develop a technology that has gained interest in both scientific and industrial realms. This technology serves as a viable alternative to outdated and energy-consuming industrial systems. Electro-adhesive devices (EADs) leverage electrostatic forces for grasping objects or adhering to surfaces. The advantage of employing electrostatics lies in its adaptability to various materials without compromising the structure or chemistry of the object or surface. These benefits have led the industry to explore this technology as a replacement for costly vacuum systems and suction cups currently used for handling most products. Furthermore, the broad applicability of this technology extends to extreme environments, such as space with ultra-high vacuum conditions. Unfortunately, research in this area has yet to yield practical results for industrially effective gripper prototyping. This is primarily due to the inherent complexity of electro-adhesive technology, which operates on basic capacitive principles that does not find satisfying physical descriptions. This thesis aims to address these challenges through a series of studies, starting with the manufacturing process and testing of an EAD that has become the standard in our laboratory. It then delves into material and electrode geometry studies to enhance system performance, ultimately presenting potential industrial applications of the technology. All the presented results are encouraging, as they have yielded shear force values three times higher than those previously reported in the literature. The various applications have demonstrated the significant effectiveness of EADs as brakes or, more broadly, in exerting shear forces. This opens up the possibility of utilizing cutting-edge technologies to push the boundaries of technology to the fullest.
Resumo:
This research, carried out during the PhD in Materials Engineering, deals with the creation of layers, with different functionality, deposited on a ceramic substrate, to obtain photovoltaic cells for electricity production. The research activities are included in the project PRRIITT, Measure 4 (Development of Networks), Action A (Research and Technology Transfer Laboratories), Thematic reference 3 (Advanced materials applications development), co-financed by the Emilia Romagna Region, for the creation of CECERBENCH laboratory, which aims to develop "Tiles with a functionalised surface”. The innovation lies in the study of materials and in the development of technologies to achieve a "photovoltaic surface", directly in the tiles production process. The goal is to preserve the technical characteristics, and to make available new surfaces, exploiting renewable energy sources. The realization of Building Integrated PhotoVoltaic (BIPV) is nowadays a more and more spread tendency. The aims of the research are essentially linked to the need to diversify the actual ceramic tile production (which is strongly present in the Emilia Romagna Region ), and to provide a higher added value to the tiles. Solar energy production is the primary objective of the functionalization, and has a relevant ecological impact, taking into account the overwhelming global energy demand. The specific activities of the PhD were carried out according to the achievement of scientific and technological objectives of CECERBENCH laboratory, and involved the collaboration in design solutions, to obtain the cells directly on the tiles surface. The author has managed personally a part of the research project. Layers with different features were made: - Electrically conductive layers, directly on the ceramic tiles surface; - Layers to obtain the photovoltaic functionality; - Electrically insulating, protective layers (double function). For each layer, the most suitable materials have been selected. Among the technical application, the screen printing was used. This technique, widely used in ceramics, has many application areas, including the electronics and photovoltaic industries. It is an inexpensive technique, easy to use in industrial production lines. The screen printing technique was therefore studied in depth by theoretical considerations, and through the use of rheological measurements.
Sviluppo di biosensori: modifiche di superfici elettrodiche e sistemi di immobilizzazione enzimatica
Resumo:
An amperometric glucose biosensor was developed using an anionic clay matrix (LDH) as enzyme support. The enzyme glucose oxidase (GOx) was immobilized on a layered double hydroxide Ni/Al-NO3 LDH during the electrosynthesis, which was followed by crosslinking with glutaraldehyde (GA) vapours or with GA and bovine serum albumin (GABSA) to avoid the enzyme release. The electrochemical reaction was carried out potentiostatically, at -0.9V vs. SCE, using a rotating disc Pt electrode to assure homogeneity of the electrodeposition suspension, containing GOx, Ni(NO3)2 and Al(NO3)3 in 0.3 M KNO3. The mechanism responsible of the LDH electrodeposition involves the precipitation of the LDH due to the increase of pH at the surface of the electrode, following the cathodic reduction of nitrates. The Pt surface modified with the Ni/Al-NO3 LDH shows a much reduced noise, giving rise to a better signal to noise ratio for the currents relative to H2O2 oxidation, and a linear range for H2O2 determination wider than the one observed for bare Pt electrodes. We pointed out the performances of the biosensor in terms of sensitivity to glucose, calculated from the slope of the linear part of the calibration curve for enzimatically produced H2O2; the sensitivity was dependent on parameters related to the electrodeposition in addition to working conditions. In order to optimise the glucose biosensor performances, with a reduced number of experimental runs, we applied an experimental design. A first screening was performed considering the following variables: deposition time (30 - 120 s), enzyme concentration (0.5 - 3.0 mg/mL), Ni/Al molar ratio (3:1 or 2:1) of the electrodeposition solution at a total metals concentration of 0.03 M and pH of the working buffer solution (5.5-7.0). On the basis of the results from this screening, a full factorial design was carried out, taking into account only enzyme concentration and Ni/Al molar ratio of the electrosynthesis solution. A full factorial design was performed to study linear interactions between factors and their quadratic effects and the optimal setup was evaluated by the isoresponse curves. The significant factors were: enzyme concentration (linear and quadratic terms) and the interaction between enzyme concentration and Ni/Al molar ratio. Since the major obstacle for application of amperometric glucose biosensors is the interference signal resulting from other electro-oxidizable species present in the real matrices, such as ascorbate (AA), the use of different permselective membranes on Pt-LDHGOx modified electrode was discussed with the aim of improving biosensor selectivity and stability. Conventional membranes obtained using Nafion, glutaraldehyde (GA) vapours, GA-BSA were tested together with more innovative materials like palladium hexacyanoferrate (PdHCF) and titania hydrogels. Particular attention has been devoted to hydrogels, because they possess some attractive features, which are generally considered to favour biosensor materials biocompatibility and, consequently, the functional enzyme stability. The Pt-LDH-GOx-PdHCF hydrogel biosensor presented an anti-interferant ability so that to be applied for an accurate glucose analysis in blood. To further improve the biosensor selectivity, protective membranes containing horseradish peroxidase (HRP) were also investigated with the aim of oxidising the interferants before they reach the electrode surface. In such a case glucose determination was also accomplished in real matrices with high AA content. Furthermore, the application of a LDH containing nickel in the oxidised state was performed not only as a support for the enzyme, but also as anti-interferant sistem. The result is very promising and it could be the starting point for further applications in the field of amperometric biosensors; the study could be extended to other oxidase enzymes.
Resumo:
Questo lavoro di tesi nasce da un progetto di ricerca promosso nel 2001 dal Prof. Leonardo Seccia (Seconda Facoltà di Ingegneria, sede di Forlì, e C.I.R.A.M., Università di Bologna), dal Prof. Nicola Santopuoli (Facoltà di Architettura Valle Giulia, Sapienza Università di Roma), dal Prof. Ingo Muller e dal Dott. André Musolff (Technical University Berlin, Facultat III, Thermodynamics). Tale progetto ha avuto come obiettivo lo studio, la progettazione e la realizzazione di un dispositivo di ancoraggio in lega a memoria di forma per il restauro di affreschi e mosaici parietali, che presentino distacchi più o meno evidenti fra gli strati di intonaco di supporto, proponendosi come mezzo efficace per la salvaguardia strutturale di tali zone variamente ammalorate. In particolare, è stata programmata una serie di prove di laboratorio per caratterizzare in modo preciso il comportamento del materiale prescelto, al fine di realizzare un prototipo rispondente alle caratteristiche di progetto ed anche per implementare un modello numerico sufficientemente realistico. A questo proposito, è stato anche approfondito il problema della scelta del modello costitutivo più adeguato. Successivamente, i risultati ottenuti sono stati impiegati nella progettazione e realizzazione di nuovi dispositivi in lega a memoria di forma da impiegare nel campo dei beni culturali, fra cui sistemi reversibili per il ricongiungimento di parti fratturate e sistemi di movimentazione intelligenti sia per lastre di protezione di superfici affrescate, sia per finestre da inserire in contesti museali per il controllo del microclima.
Resumo:
The conversion coefficients from air kerma to ICRU operational dose equivalent quantities for ENEA’s realization of the X-radiation qualities L10-L35 of the ISO “Low Air Kerma rate” series (L), N10-N40 of the ISO “Narrow spectrum” series (N) and H10-H60 of the ISO “High Air-kerma rate” (H) series and two beams at 5 kV and 7.5 kV were determined by utilising X-ray spectrum measurements. The pulse-height spectra were measured using a planar high-purity germanium spectrometer (HPGe) and unfolded to fluence spectra using a stripping procedure then validate with using Monte Carlo generated data of the spectrometer response. HPGe portable detector has a diameter of 8.5 mm and a thickness of 5 mm. The entrance window of the crystal is collimated by a 0.5 mm thick Aluminum ring to an open diameter of 6.5 mm. The crystal is mounted at a distance of 5 mm from the Berillium window (thickness 25.4 micron). The Monte Carlo method (MCNP-4C) was used to calculate the efficiency, escape and Compton curves of a planar high-purity germanium detector (HPGe) in the 5-60 keV energy. These curves were used for the determination of photon spectra produced by the X-ray machine SEIFERT ISOVOLT 160 kV in order to allow a precise characterization of photon beams in the low energy range, according to the ISO 4037. The detector was modelled with the MCNP computer code and validated with experimental data. To verify the measuring and the stripping procedure, the first and the second half-value layers and the air kerma rate were calculated from the counts spectra and compared with the values measured using an a free-air ionization chamber. For each radiation quality, the spectrum was characterized by the parameters given in ISO 4037-1. The conversion coefficients from the air kerma to the ICRU operational quantities Hp(10), Hp(0.07), H’(0.07) and H*(10) were calculated using monoenergetic conversion coefficients. The results are discussed with respect to ISO 4037-4, and compared with published results for low-energy X-ray spectra. The main motivation for this work was the lack of a treatment of the low photon energy region (from a few keV up to about 60 keV).
Resumo:
The aim of this work is to investigate whether the actual position of a stimulus is more relevant than intuitive knowledge about the direction of an object's movement and the participants’ intention (Michaels 1988; Hommel, 1993; Proctor, Van Zandt, Lu and Weeks, 1993; Ansorge, 2000). To investigate this we used a spatial compatibility task in 4 experiments replicating what had be done by Hommel (1993) and Micheals (1988), but changing a single aspect of the procedure: neither the movement nor the effects of the action were visible to the participant. The experimental task asked them to simply imagine an action in movement.
Resumo:
The recent default of important Italian agri-business companies provides a challenging issue to be investigated through an appropriate scientific approach. The events involving CIRIO, FERRUZZI or PARMALAT rise an important research question: what are the determinants of performance for Italian companies in the Italian agri – food sector? My aim is not to investigate all the factors that are relevant in explaining performance. Performance depends on a wide set of political, social, economic variables that are strongly interconnected and that are often very difficult to express by formal or mathematical tools. Rather, in my thesis I mainly focus on those aspects that are strictly related to the governance and ownership structure of agri – food companies representing a strand of research that has been quite neglected by previous scholars. The conceptual framework from which I move to justify the existence of a relationship between the ownership structure of a company, governance and performance is the model set up by Airoldi and Zattoni (2005). In particular the authors investigate the existence of complex relationships arising within the company and between the company and the environment that can bring different strategies and performances. They do not try to find the “best” ownership structure, rather they outline what variables are connected and how they could vary endogenously within the whole economic system. In spite of the fact that the Airoldi and Zattoni’s model highlights the existence of a relationship between ownership and structure that is crucial for the set up of the thesis the authors fail to apply quantitative analyses in order to verify the magnitude, sign and the causal direction of the impact. In order to fill this gap we start from the literature trying to investigate the determinants of performance. Even in this strand of research studies analysing the relationship between different forms of ownership and performance are still lacking. In this thesis, after a brief description of the Italian agri – food sector and after an introduction including a short explanation of the definitions of performance and ownership structure, I implement a model in which the performance level (interpreted here as Return on Investments and Return on Sales) is related to variables that have been previously identified by the literature as important such as the financial variables (cash and leverage indices), the firm location (North Italy, Centre Italy, South Italy), the power concentration (lower than 25%, between 25% and 50% and between 50% and 100% of ownership control) and the specific agri – food sector (agriculture, food and beverage). Moreover we add a categorical variable representing different forms of ownership structure (public limited company, limited liability company, cooperative) that is the core of our study. All those variables are fully analysed by a preliminary descriptive analysis. As in many previous contributions we apply a panel least squares analysis for 199 Italian firms in the period 1998 – 2007 with data taken from the Bureau Van Dijck Dataset. We apply two different models in which the dependant variables are respectively the Return on Investments (ROI) and the Return on Sales (ROS) indicators. Not surprisingly we find that companies located in the North Italy representing the richest area in Italy perform better than the ones located in the Centre and South of Italy. In contrast with the Modigliani - Miller theorem financial variables could be significant and the specific sector within the agri – food market could play a relevant role. As the power concentration, we find that a strong property control (higher than 50%) or a fragmented concentration (lower than 25%) perform better. This result apparently could suggest that “hybrid” forms of concentrations could create bad functioning in the decision process. As our key variables representing the ownership structure we find that public limited companies and limited liability companies perform better than cooperatives. This is easily explainable by the fact that law establishes that cooperatives are less profit – oriented. Beyond cooperatives public limited companies perform better than limited liability companies and show a more stable path over time. Results are quite consistent when we consider both ROI and ROS as dependant variables. These results should not lead us to claim that public limited company is the “best” among all possible governance structures. First, every governance solution should be considered according to specific situations. Second more robustness analyses are needed to confirm our results. At this stage we deem these findings, the model set up and our approach represent original contributions that could stimulate fruitful future studies aimed at investigating the intriguing issue concerning the effect of ownership structure on the performance levels.
Resumo:
Calcolo della superficie curvilinea di scorrimento di un getto di litio in maniera che la pressione lungo il getto vari in maniera lineare. Formulazione di un codice di calcolo per la determinazione delle diverse possibili superfici. Studio termofluidodinamico del getto con codici CFD. Accoppiamento tra codici di sistema e codici CFD. Valutazioni delle condizioni di Incipient Boiling per il litio.
Resumo:
Il concetto di "core training" è ampiamente diffuso nelle moderne metodologie di allenamento, nonostante sia spesso collegato a pratiche da campo non pienamente supportate dalla ricerca scientifica. Il termine "core" identifica il "centro funzionale del corpo" in grado di garantire una "adeguata stabilità prossimale al fine di ottimizzare la mobilità distale", sostenendo il complesso lombo-pelvico e permettendo la connessione funzionale tra arti e tronco. La muscolatura del core, cositutita principalmente dalla regione addominale e paraspinale, è ben condizionabile dall'utilizzo di superfici instabili quali Bosu e Fitball, strumenti comuni nel settore sportivo e rieducativo ma sui quali esistono teorie e conoscenze altamente eterogenee. Obiettivo della presente tesi è, dunque, da un lato quello di confrontare una varietà di esercizi eseguibili su entrambe le superfici instabili precedentemente citate al fine di determinare le attivazioni muscolari a livello del "core", dall'altro quello di valutare gli effetti indotti da un "core training" di 8 settimane su parametri performance-specifici. Lo studio, effettuato su atleti aventi una elevata esperienza in tale settore, evidenzia valori elettromiografici superiori nella Fitball e Bosu rispetto al tappeto, seppure in maniera non significativa; circa il legame con aspetti prestativi, emerge invece come un allenamento specifico ad alto impatto nervoso, modulato secondo un target razionale, consenta di incrementare l'endurance della muscolatura addominale, l'equilibrio funzionale dinamico e la capacità di trasmissione di forze arti-tronco, giustificandone un utilizzo in vari settori dell'attività motoria.
Resumo:
My project explores and compares different forms of gender performance in contemporary art and visual culture according to a perspective centered on photography. Thanks to its attesting power this medium can work as a ready-made. In fact during the 20th century it played a key role in the cultural emancipation of the body which (using a Michel Foucault’s expression) has now become «the zero point of the world». Through performance the body proves to be a living material of expression and communication while photography ensures the recording of any ephemeral event that happens in time and space. My questioning approach considers the gender constructed imagery from the 1990s to the present in order to investigate how photography’s strong aura of realism promotes and allows fantasies of transformation. The contemporary fascination with gender (especially for art and fashion) represents a crucial issue in the global context of postmodernity and is manifested in a variety of visual media, from photography to video and film. Moreover the internet along with its digital transmission of images has deeply affected our world (from culture to everyday life) leading to a postmodern preference for performativity over the more traditional and linear forms of narrativity. As a consequence individual borders get redefined by the skin itself which (dissected through instant vision) turns into a ductile material of mutation and hybridation in the service of identity. My critical assumptions are taken from the most relevant changes occurred in philosophy during the last two decades as a result of the contributions by Jacques Lacan, Michel Foucault, Jacques Derrida, Gilles Deleuze who developed a cross-disciplinary and comparative approach to interpret the crisis of modernity. They have profoundly influenced feminist studies so that the category of gender has been reassessed in contrast with sex (as a biological connotation) and in relation to history, culture, society. The ideal starting point of my research is the year 1990. I chose it as the approximate historical moment when the intersection of race, class and gender were placed at the forefront of international artistic production concerned with identity, diversity and globalization. Such issues had been explored throughout the 1970s but it was only from the mid-1980s onward that they began to be articulated more consistently. Published in 1990, the book "Gender trouble: feminism and the subversion of identity" by Judith Butler marked an important breakthrough by linking gender to performance as well as investigating the intricate connections between theory and practice, embodiment and representation. It inspired subsequent research in a variety of disciplines, art history included. In the same year Teresa de Lauretis launched the definition of queer theory to challenge the academic perspective in gay and lesbian studies. In the meantime the rise of Third Wave Feminism in the US introduced a racially and sexually inclusive vision over the global situation in order to reflect on subjectivity, new technologies and popular culture in connection with gender representation. These conceptual tools have enabled prolific readings of contemporary cultural production whether fine arts or mass media. After discussing the appropriate framework of my project and taking into account the postmodern globalization of the visual, I have turned to photography to map gender representation both in art and in fashion. Therefore I have been creating an archive of images around specific topics. I decided to include fashion photography because in the 1990s this genre moved away from the paradigm of an idealized and classical beauty toward a new vernacular allied with lifestyles, art practices, pop and youth culture; as one might expect the dominant narrative modes in fashion photography are now mainly influenced by cinema and snapshot. These strategies originate story lines and interrupted narratives using models’ performance to convey a particular imagery where identity issues emerge as an essential part of fashion spectacle. Focusing on the intersections of gender identities with socially and culturally produced identities, my approach intends to underline how the fashion world has turned to current trends in art photography and in some case turned to the artists themselves. The growing fluidity of the categories that distinguish art from fashion photography represents a particularly fruitful moment of visual exchange. Varying over time the dialogue between these two fields has always been vital; nowadays it can be studied as a result of this close relationship between contemporary art world and consumer culture. Due to the saturation of postmodern imagery the feedback between art and fashion has become much more immediate and then increasingly significant for anyone who wants to investigate the construction of gender identity through performance. In addition to that a lot of magazines founded in the 1990s bridged the worlds of art and fashion because some of their designers and even editors were art-school graduates encouraging innovation. The inclusion of art within such magazines aimed at validating them as a form of art in themselves supporting a dynamic intersection for music, fashion, design and youth culture: an intersection that also contributed to create and spread different gender stereotypes. This general interest in fashion produced many exhibitions of and about fashion itself at major international venues such as the Victoria and Albert Museum in London, the Metropolitan Museum of Art and the Solomon R. Guggenheim Museum in New York. Since then this celebrated success of fashion has been regarded as a typical element of postmodern culture. Owing to that I have also based my analysis on some important exhibitions dealing with gender performance like "Féminin-Masculin" at the Centre Pompidou of Paris (1995), "Rrose is a Rrose is a Rrose. Gender performance in photography" at the Solomon R. Guggenheim Museum of New York (1997), "Global Feminisms" at the Brooklyn Museum (2007), "Female Trouble" at the Pinakothek der Moderne in München together with the workshops dedicated to "Performance: gender and identity" in June 2005 at the Tate Modern of London. Since 2003 in Italy we have had Gender Bender - an international festival held annually in Bologna - to explore the gender imagery stemming from contemporary culture. In few days this festival offers a series of events ranging from visual arts, performance, cinema, literature to conferences and music. Being aware that any method of research is neither race nor gender neutral I have traced these critical paths to question gender identity in a multicultural perspective taking account of the political implications too. In fact, if visibility may be equated with exposure, we can also read these images as points of intersection of visibility with social power. Since gender assignations rely so heavily on the visual, the postmodern dismantling of gender certainty through performance has wide-ranging effects that need to be analyzed. In some sense this practice can even contest the dominance of visual within postmodernism. My visual map in contemporary art and fashion photography includes artists like Nan Goldin, Cindy Sherman, Hellen van Meene, Rineke Dijkstra, Ed Templeton, Ryan McGinley, Anne Daems, Miwa Yanagi, Tracey Moffat, Catherine Opie, Tomoko Sawada, Vanessa Beecroft, Yasumasa Morimura, Collier Schorr among others.
Resumo:
Questa ricerca presenta i risultati di una indagine volta a verificare la reale efficacia di rinforzo corticale su rocce carbonatiche di differenti caratteristiche mineralogiche, utilizzando consolidanti inorganici in soluzione acquosa quali l’Ossalato Ammonico (AmOX) e il Diammonio Fosfato Acido (DAHP). Le matrici carbonatiche scelte sono quelle del marmo invecchiato e una biomicrite. Sui campioni sono state effettuate indagini (SEM,MIP,XRD,MO,TG-DTA) di caratterizzazione prima e dopo i trattamenti volte a valutare eventuali effetti di rinforzo e misure fisiche di suscettività all’acqua. L’efficacia dei consolidanti inorganici è stata comparata con diversi consolidanti organici e ibridi presenti in commercio ed utilizzati in ambito conservativo. L'efficacia si è mostrata fortemente legata al fabric del materiale e alle modalità di strutturazione del prodotto di neomineralizzazione all’interno della compagine deteriorata. Nel caso del trattamento con AmOx il soluzione acquosa al 4%, la whewellite è l’unica fase di neoformazione riscontrata; la sua crescita avviene con un meccanismo essenzialmente topochimico. Nei materiali carbonatici compatti si possono ottenere solo modesti spessori di coating di neoformazione; per le rocce porose, contenenti difetti come lesioni, pori o micro-fratture, l’efficacia del trattamento può risultare più incisiva. Questo trattamento presenta lo svantaggio legato alla rapidissima formazione dei cristalli di whewellite che tendono a passivare le superfici impedendo la progressione della reazione; il vantaggio è connesso alla facile applicazione in cantiere. Nel caso del DAHP sulla matrice carbonatica trattata, si formano cluster cristallini contenenti specie più o meno stabili alcune riconducibili all’idrossiapatite. La quantità e qualità delle fasi, varia fortemente in funzione della temperatura, pH, pressione con conseguenze interferenza nelle modalità di accrescimento dei cristalli. Il trattamento alla stato attuale appare comunque di notevole interesse ma allo stesso tempo difficilmente applicabile e controllabile nelle reali condizioni operative di un cantiere di restauro.