The capability of endophytic fungi for production of hemicellulases and related enzymes

Abstract Background There is an imperative necessity for alternative sources of energy able to reduce the world dependence of fossil oil. One of the most successful options is ethanol obtained mainly from sugarcane and corn fermentation. The foremost residue from sugarcane industry is the bagasse, a rich lignocellulosic raw material uses for the production of ethanol second generation (2G). New cellulolytic and hemicellulytic enzymes are needed, in order to optimize the degradation of bagasse and production of ethanol 2G. Results The ability to produce hemicellulases and related enzymes, suitable for lignocellulosic biomass deconstruction, was explored using 110 endophytic fungi and 9 fungi isolated from spoiled books in Brazil. Two initial selections were performed, one employing the esculin gel diffusion assay, and the other by culturing on agar plate media with beechwood xylan and liquor from the hydrothermal pretreatment of sugar cane bagasse. A total of 56 isolates were then grown at 29°C on steam-exploded delignified sugar cane bagasse (DEB) plus soybean bran (SB) (3:1), with measurement of the xylanase, pectinase, β-glucosidase, CMCase, and FPase activities. Twelve strains were selected, and their enzyme extracts were assessed using different substrates. Finally, the best six strains were grown under xylan and pectin, and several glycohydrolases activities were also assessed. These strains were identified morphologically and by sequencing the internal transcribed spacer (ITS) regions and the partial β-tubulin gene (BT2). The best six strains were identified as Aspergillus niger DR02, Trichoderma atroviride DR17 and DR19, Alternaria sp. DR45, Annulohypoxylon stigyum DR47 and Talaromyces wortmannii DR49. These strains produced glycohydrolases with different profiles, and production was highly influenced by the carbon sources in the media. Conclusions The selected endophytic fungi Aspergillus niger DR02, Trichoderma atroviride DR17 and DR19, Alternaria sp. DR45, Annulohypoxylon stigyum DR47 and Talaromyces wortmannii DR49 are excellent producers of hydrolytic enzymes to be used as part of blends to decompose sugarcane biomass at industrial level.

The capability of endophytic fungi for production of hemicellulases and related enzymes

Abstract BACKGROUND: There is an imperative necessity for alternative sources of energy able to reduce the world dependence of fossil oil. One of the most successful options is ethanol obtained mainly from sugarcane and corn fermentation. The foremost residue from sugarcane industry is the bagasse, a rich lignocellulosic raw material uses for the production of ethanol second generation (2G). New cellulolytic and hemicellulytic enzymes are needed, in order to optimize the degradation of bagasse and production of ethanol 2G. RESULTS: The ability to produce hemicellulases and related enzymes, suitable for lignocellulosic biomass deconstruction, was explored using 110 endophytic fungi and 9 fungi isolated from spoiled books in Brazil. Two initial selections were performed, one employing the esculin gel diffusion assay, and the other by culturing on agar plate media with beechwood xylan and liquor from the hydrothermal pretreatment of sugar cane bagasse. A total of 56 isolates were then grown at 29°C on steam-exploded delignified sugar cane bagasse (DEB) plus soybean bran (SB) (3:1), with measurement of the xylanase, pectinase, β-glucosidase, CMCase, and FPase activities. Twelve strains were selected, and their enzyme extracts were assessed using different substrates. Finally, the best six strains were grown under xylan and pectin, and several glycohydrolases activities were also assessed. These strains were identified morphologically and by sequencing the internal transcribed spacer (ITS) regions and the partial β-tubulin gene (BT2). The best six strains were identified as Aspergillus niger DR02, Trichoderma atroviride DR17 and DR19, Alternaria sp. DR45, Annulohypoxylon stigyum DR47 and Talaromyces wortmannii DR49. These strains produced glycohydrolases with different profiles, and production was highly influenced by the carbon sources in the media. CONCLUSIONS: The selected endophytic fungi Aspergillus niger DR02, Trichoderma atroviride DR17 and DR19, Alternaria sp. DR45, Annulohypoxylon stigyum DR47 and Talaromyces wortmannii DR49 are excellent producers of hydrolytic enzymes to be used as part of blends to decompose sugarcane biomass at industrial level.

Study of the antioxidant fraction in edible olive oils obtained from different technological systems and parameters

Questo lavoro di tesi è stato suddiviso in tre parti. L’argomento principale è stato lo “Studio della componente antiossidante di oli ottenuti da olive mediante l’utilizzo di diversi sistemi e parametri tecnologici”. E’ ben noto come la qualità ossidativa di un olio di oliva dipenda oltre che dalla sua composizione in acidi grassi, dalla presenza di composti caratterizzati da un elevata attività antiossidante, ovvero le sostanze fenoliche. I composti fenolici contribuiscono quindi in maniera preponderante alla shelf life dell’olio extravergine di oliva. Inoltre sono state riscontrate delle forti correlazione tra alcune di queste sostanze e gli attributi sensoriali positivi di amaro e piccante. E’ poi da sottolineare come il potere antiossidante dei composti fenolici degli oli vergini di oliva, sia stato negli ultimi anni oggetto di considerevole interesse, poiché correlato alla protezione da alcune patologie come ad esempio quelle vascolari, degenerative e tumorali. Il contenuto delle sostanze fenoliche negli oli di oliva dipende da diversi fattori: cultivar, metodo di coltivazione, grado di maturazione delle olive e ovviamente dalle operazioni tecnologiche poiché possono variare il quantitativo di questi composti estratto. Alla luce di quanto appena detto abbiamo valutato l’influenza dei fattori agronomici (metodi di agricoltura biologica, integrata e convenzionale) e tecnologici (riduzione della temperatura della materia prima, aggiunta di coadiuvanti in fase di frangitura e di gramolatura, confronto tra tre oli extravergini di oliva ottenuti mediante diversi sistemi tecnologici) sul contenuto in composti fenolici di oli edibili ottenuti da olive (paper 1-3-4). Oltre alle sostanze fenoliche, negli oli di oliva sono presenti altri composti caratterizzati da proprietà chimiche e nutrizionali, tra questi vi sono i fitosteroli, ovvero gli steroli tipici del mondo vegetale, che rappresentano la frazione dell’insaponificabile quantitativamente più importante dopo gli idrocarburi. La composizione quali-quantitativa degli steroli di un olio di oliva è una delle caratteristiche analitiche più importanti nella valutazione della sua genuinità; infatti la frazione sterolica è significativamente diversa in funzione dell’origine botanica e perciò viene utilizzata per distinguere tra di loro gli oli e le loro miscele. Il principale sterolo nell’olio di oliva è il β- sitosterolo, la presenza di questo composto in quantità inferiore al 90% è un indice approssimativo dell’aggiunta di un qualsiasi altro olio. Il β-sitosterolo è una sostanza importante dal punto di vista della salute, poiché si oppone all’assorbimento del colesterolo. Mentre in letteratura si trovano numerosi lavori relativi al potere antiossidante di una serie di composti presenti nell’olio vergine di oliva (i già citati polifenoli, ma anche carotenoidi e tocoferoli) e ricerche che dimostrano invece come altri composti possano promuovere l’ossidazione dei lipidi, per quanto riguarda il potere antiossidante degli steroli e dei 4- metilsteroli, vi sono ancora poche informazioni. Per questo è stata da noi valutata la composizione sterolica in oli extravergini di oliva ottenuti con diverse tecnologie di estrazione e l’influenza di questa sostanza sulla loro stabilità ossidativa (paper 2). E’ stato recentemente riportato in letteratura come lipidi cellulari evidenziati attraverso la spettroscopia di risonanza nucleare magnetica (NMR) rivestano una importanza strategica da un punto di vista funzionale e metabolico. Questi lipidi, da un lato un lato sono stati associati allo sviluppo di cellule neoplastiche maligne e alla morte cellulare, dall’altro sono risultati anche messaggeri di processi benigni quali l’attivazione e la proliferazione di un normale processo di crescita cellulare. Nell’ambito di questa ricerca è nata una collaborazione tra il Dipartimento di Biochimica “G. Moruzzi” ed il Dipartimento di Scienze degli Alimenti dell’Università di Bologna. Infatti, il gruppo di lipochimica del Dipartimento di Scienze degli Alimenti, a cui fa capo il Prof. Giovanni Lercker, da sempre si occupa dello studio delle frazioni lipidiche, mediante le principali tecniche cromatografiche. L’obiettivo di questa collaborazione è stato quello di caratterizzare la componente lipidica totale estratta dai tessuti renali umani sani e neoplastici, mediante l’utilizzo combinato di diverse tecniche analitiche: la risonanza magnetica nucleare (1H e 13C RMN), la cromatografia su strato sottile (TLC), la cromatografia liquida ad alta prestazione (HPLC) e la gas cromatografia (GC) (paper 5-6-7)

The use of remote sensing imagery for monitoring recovery in the aftermath of a natural disaster: the Hurricane Katrina Case

Although Recovery is often defined as the less studied and documented phase of the Emergency Management Cycle, a wide literature is available for describing characteristics and sub-phases of this process. Previous works do not allow to gain an overall perspective because of a lack of systematic consistent monitoring of recovery utilizing advanced technologies such as remote sensing and GIS technologies. Taking into consideration the key role of Remote Sensing in Response and Damage Assessment, this thesis is aimed to verify the appropriateness of such advanced monitoring techniques to detect recovery advancements over time, with close attention to the main characteristics of the study event: Hurricane Katrina storm surge. Based on multi-source, multi-sensor and multi-temporal data, the post-Katrina recovery was analysed using both a qualitative and a quantitative approach. The first phase was dedicated to the investigation of the relation between urban types, damage and recovery state, referring to geographical and technological parameters. Damage and recovery scales were proposed to review critical observations on remarkable surge- induced effects on various typologies of structures, analyzed at a per-building level. This wide-ranging investigation allowed a new understanding of the distinctive features of the recovery process. A quantitative analysis was employed to develop methodological procedures suited to recognize and monitor distribution, timing and characteristics of recovery activities in the study area. Promising results, gained by applying supervised classification algorithms to detect localization and distribution of blue tarp, have proved that this methodology may help the analyst in the detection and monitoring of recovery activities in areas that have been affected by medium damage. The study found that Mahalanobis Distance was the classifier which provided the most accurate results, in localising blue roofs with 93.7% of blue roof classified correctly and a producer accuracy of 70%. It was seen to be the classifier least sensitive to spectral signature alteration. The application of the dissimilarity textural classification to satellite imagery has demonstrated the suitability of this technique for the detection of debris distribution and for the monitoring of demolition and reconstruction activities in the study area. Linking these geographically extensive techniques with expert per-building interpretation of advanced-technology ground surveys provides a multi-faceted view of the physical recovery process. Remote sensing and GIS technologies combined to advanced ground survey approach provides extremely valuable capability in Recovery activities monitoring and may constitute a technical basis to lead aid organization and local government in the Recovery management.

Technological processes study for high value health ingredients and foods production

This PhD thesis describes set up of technological models for obtaining high health value foods and ingredients that preserve the final product characteristics as well as enrich with nutritional components. In particular, the main object of my research has been Virgin Olive Oil (VOO) and its important antioxidant compounds which differentiate it from all other vegetables oils. It is well known how the qualitative and quantitative presence of phenolic molecules extracted from olives during oil production is fundamental for its oxidative and nutritional quality. For this purpose, agronomic and technological conditions of its production have been investigated. It has also been examined how this fraction can be better preserved during storage. Moreover, its relation with VOO sensorial characteristics and its interaction with a protein in emulsion foods have also been studied. Finally, an experimental work was carried out to determine the antioxidative and heat resistance properties of a new antioxidant (EVS-OL) when used for high temperature frying such as is typically employed for the preparation of french fries. Results of the scientific research have been submitted for a publication and some data has already been published in national and international scientific journals.

Modulation Techniques for Multi-Phase Converters and Control Strategies for Multi-Phase Electric Drives

The ever-increasing spread of automation in industry puts the electrical engineer in a central role as a promoter of technological development in a sector such as the use of electricity, which is the basis of all the machinery and productive processes. Moreover the spread of drives for motor control and static converters with structures ever more complex, places the electrical engineer to face new challenges whose solution has as critical elements in the implementation of digital control techniques with the requirements of inexpensiveness and efficiency of the final product. The successfully application of solutions using non-conventional static converters awake an increasing interest in science and industry due to the promising opportunities. However, in the same time, new problems emerge whose solution is still under study and debate in the scientific community During the Ph.D. course several themes have been developed that, while obtaining the recent and growing interest of scientific community, have much space for the development of research activity and for industrial applications. The first area of research is related to the control of three phase induction motors with high dynamic performance and the sensorless control in the high speed range. The management of the operation of induction machine without position or speed sensors awakes interest in the industrial world due to the increased reliability and robustness of this solution combined with a lower cost of production and purchase of this technology compared to the others available in the market. During this dissertation control techniques will be proposed which are able to exploit the total dc link voltage and at the same time capable to exploit the maximum torque capability in whole speed range with good dynamic performance. The proposed solution preserves the simplicity of tuning of the regulators. Furthermore, in order to validate the effectiveness of presented solution, it is assessed in terms of performance and complexity and compared to two other algorithm presented in literature. The feasibility of the proposed algorithm is also tested on induction motor drive fed by a matrix converter. Another important research area is connected to the development of technology for vehicular applications. In this field the dynamic performances and the low power consumption is one of most important goals for an effective algorithm. Towards this direction, a control scheme for induction motor that integrates within a coherent solution some of the features that are commonly required to an electric vehicle drive is presented. The main features of the proposed control scheme are the capability to exploit the maximum torque in the whole speed range, a weak dependence on the motor parameters, a good robustness against the variations of the dc-link voltage and, whenever possible, the maximum efficiency. The second part of this dissertation is dedicated to the multi-phase systems. This technology, in fact, is characterized by a number of issues worthy of investigation that make it competitive with other technologies already on the market. Multiphase systems, allow to redistribute power at a higher number of phases, thus making possible the construction of electronic converters which otherwise would be very difficult to achieve due to the limits of present power electronics. Multiphase drives have an intrinsic reliability given by the possibility that a fault of a phase, caused by the possible failure of a component of the converter, can be solved without inefficiency of the machine or application of a pulsating torque. The control of the magnetic field spatial harmonics in the air-gap with order higher than one allows to reduce torque noise and to obtain high torque density motor and multi-motor applications. In one of the next chapters a control scheme able to increase the motor torque by adding a third harmonic component to the air-gap magnetic field will be presented. Above the base speed the control system reduces the motor flux in such a way to ensure the maximum torque capability. The presented analysis considers the drive constrains and shows how these limits modify the motor performance. The multi-motor applications are described by a well-defined number of multiphase machines, having series connected stator windings, with an opportune permutation of the phases these machines can be independently controlled with a single multi-phase inverter. In this dissertation this solution will be presented and an electric drive consisting of two five-phase PM tubular actuators fed by a single five-phase inverter will be presented. Finally the modulation strategies for a multi-phase inverter will be illustrated. The problem of the space vector modulation of multiphase inverters with an odd number of phases is solved in different way. An algorithmic approach and a look-up table solution will be proposed. The inverter output voltage capability will be investigated, showing that the proposed modulation strategy is able to fully exploit the dc input voltage either in sinusoidal or non-sinusoidal operating conditions. All this aspects are considered in the next chapters. In particular, Chapter 1 summarizes the mathematical model of induction motor. The Chapter 2 is a brief state of art on three-phase inverter. Chapter 3 proposes a stator flux vector control for a three- phase induction machine and compares this solution with two other algorithms presented in literature. Furthermore, in the same chapter, a complete electric drive based on matrix converter is presented. In Chapter 4 a control strategy suitable for electric vehicles is illustrated. Chapter 5 describes the mathematical model of multi-phase induction machines whereas chapter 6 analyzes the multi-phase inverter and its modulation strategies. Chapter 7 discusses the minimization of the power losses in IGBT multi-phase inverters with carrier-based pulse width modulation. In Chapter 8 an extended stator flux vector control for a seven-phase induction motor is presented. Chapter 9 concerns the high torque density applications and in Chapter 10 different fault tolerant control strategies are analyzed. Finally, the last chapter presents a positioning multi-motor drive consisting of two PM tubular five-phase actuators fed by a single five-phase inverter.

Entrepreneurial opportunities, capability development and the performance of new firms

This study aims at providing a theoretical framework encompassing the two approaches towards entrepreneurial opportunity (opportunity discovery and opportunity creation) by outlining a trajectory from firm creation to capability development, to firm performance in the short term (firm survival) and the medium/long term (growth rate). A set of empirically testable hypotheses is proposed and tested by performing qualitative analyses on interviews on a small sample of entrepreneurs and event history analysis on a large sample of firms founded in the United States in 2004.

Functional components and lipid quality assessment in vegetable foods: analytical and technological approaches

Lipids are important components that contribute very significantly to nutritional and technological quality of foods because they are the least stable macro-components in foods, due to high susceptibility to oxidation. When rancidity take place, it makes food unhealthy and unacceptable for consumers. Thus, the presence of antioxidants, naturally present of added to foods, is required to enhance shelf life of foods. Moreover, antioxidant like phenolic compounds play an important role in human health enhancing the functionality of foods. The aim of this PhD project was the study of lipid quality and lipid oxidation in different vegetable foods focusing on analytical and technological aspects in order to figure out the effects of lipid composition and bioactive compounds (phenolic compounds, omega-3 fatty acids and dietary fiber) addition on their shelf life. In addition, bioavailability and antioxidant effects of phenolic compounds in human and animals, respectively, were evaluated after consumption of vegetable foods. The first section of the work was focused on the evaluation of lipid quality impact on technological behaviour of vegetable foods. Because of that, cocoa butter with different melting point were evaluated by chromatographic techniques (GC, TLC) and the sample with the higher melting point showed the presence of fatty acids, triglycerides, 2-monoglycerides and FT-IR profile different from genuine cocoa butter, meaning an adding of foreign fat (lauric-fat) not allowed by the law. Looking at lipid quality of other vegetable foods, an accelerated shelf life test (OXITEST®), was used to evaluate of lipid stability to oxidation in tarallini snacks made up using different lipid matrices (sunflower oil, extravirgin olive oil and a blend of extravirgin olive oil and lard). The results showed a good ability of OXITEST® to discriminate between lipid unsaturation and different cooking times, without any samples fat extraction. In the second section, the role of bioactive compounds on cereal based food shelf life was studied in different bakeries by GC, spectrophotometric methods and capillary electrophoresis. It was examined the relationships between phenolic compounds, added with flour, and lipid oxidation of tarallini and frollini. Both products showed an increase in lipid oxidation during storage and antioxidant effects on lipid oxidation were not as expected. Furthermore, the influence of enrichment in polyunsaturated fatty acids on lipid oxidation of pasta was evaluated. The results proved that LC n-3 PUFA were not significantly implicated in the onset of oxidation in spaghetti stored under daylight and accelerated oxidation in a laboratory heater. The importance of phenolic compounds as antioxidant in humans and rats was also studied, by HPLC/MS in the latter section. For this purpose, apigenin and apigenin glycosides excretion was investigated in six women’s urine in a 24 hours study. After a single dose of steamed artichokes, both aglicone and glucuronide metabolites were recovered in 24 h urine. Moreover, the effect of whole grain durum wheat bread and whole grain Kamut® khorasan bread in rats were evaluated. Both cereals were good sources of antioxidants but Kamut® bread fed animals had a better response to stress than wheat durum fed, especially when a sourdough bread was supplied.

Organic heterostructure approach for multifunctional light-emitting field-effect transistors

The possibility of combining different functionalities in a single device is of great relevance for further development of organic electronics in integrated components and circuitry. Organic light-emitting transistors (OLETs) have been demonstrated to be able to combine in a single device the electrical switching functionality of a field-effect transistor and the capability of light generation. A novel strategy in OLET realization is the tri-layer vertical hetero-junction. This configuration is similar to the bi-layer except for the presence of a new middle layer between the two transport layers. This “recombination” layer presents high emission quantum efficiency and OLED-like (Organic Light-Emitting Diode) vertical bulk mobility value. The key idea of the vertical tri-layer hetero-junction approach in realizing OLETs is that each layer has to be optimized according to its specific function (charge transport, energy transfer, radiative exciton recombination). Clearly, matching the overall device characteristics with the functional properties of the single materials composing the active region of the OFET, is a great challenge that requires a deep investigation of the morphological, optical and electrical features of the system. As in the case of the bi-layer based OLETs, it is clear that the interfaces between the dielectric and the bottom transport layer and between the recombination and the top transport layer are crucial for guaranteeing good ambipolar field-effect electrical characteristics. Moreover interfaces between the bottom transport and the recombination layer and between the recombination and the top transport layer should provide the favourable conditions for the charge percolation to happen in the recombination layer and form excitons. Organic light emitting transistor based on the tri-layer approach with external quantum efficiency out-performing the OLED state of the art has been recently demonstrated [Capelli et al., Nat. Mater. 9 (2010) 496-503] widening the scientific and technological interest in this field of research.

Technological innovation in Emilia-Romagna: knowledge, practice, strategies

The present study aims at assessing the innovation strategies adopted within a regional economic system, the Italian region Emilia-Romagna, as it faced the challenges of a changing international scenario. As the strengthening of the regional innovative capabilities is regarded as a keystone to foster a new phase of economic growth, it is important also to understand how the local industrial, institutional, and academic actors have tackled the problem of innovation in the recent past. In this study we explore the approaches to innovation and the strategies adopted by the main regional actors through three different case studies. Chapter 1 provides a general survey of the innovative performance of the regional industries over the past two decades, as it emerges from statistical data and systematic comparisons at the national and European levels. The chapter also discusses the innovation policies that the regional government set up since 2001 in order to strengthen the collaboration among local economic actors, including universities and research centres. As mechanics is the most important regional industry, chapter 2 analyses the combination of knowledge and practices utilized in the period 1960s-1990s in the design of a particular kind of machinery produced by G.D S.p.A., a world-leader in the market of tobacco packaging machines. G.D is based in Bologna, the region’s capital, and is at the centre of the most important Italian packaging district. In chapter 3 the attention turns to the institutional level, focusing on how the local public administrations, and the local, publicly-owned utility companies have dealt with the creation of new telematic networks on the regional territory during the 1990s and 2000s. Finally, chapter 4 assesses the technology transfer carried out by the main university of the region – the University of Bologna – by focusing on the patenting activities involving its research personnel in the period 1960-2010.

Silicon-containing block copolymers with well-defined, branched architectures

In the past decade, block copolymers (BCPs) have attracted increasing scientific and technological interest because of their inherent capability to spontaneously self-assemble into ordered arrays of nanostructures. The importance of nanostructures in a number of applications has fostered the need for well-defined, complex macromolecular architectures. In this thesis, the influence of macromolecular architecture on the bulk morphologies of novel linear-hyperbranched and linear brush-like diblock copolymer structure is investigated. An innovative, generally applicable strategy for the preparation of these defined diblock copolymers, consisting of linear polystyrene and branched polycarbosilane blocks, is demonstrated. Furthermore, complete characterization and solid-state morphological studies are provided. Finally, the concept is extended to linear-hyperbrached and linear brush-like polyalkoxysilanes. A shift of the classical phase boundaries to higher PS weight fractions as well as the appearance of new morphologies confirms the dramatic effect that polymer topology has on the morphology of BCPs.

Determinants of child undernutrition in India. A micro-case study to operationalize the Capability Approach

The present research aims at shedding light on the demanding puzzle characterizing the issue of child undernutrition in India. Indeed, the so called ‘Indian development paradox’ identifies the phenomenon according to which higher level of income per capita is recorded alongside a lethargic reduction in the proportion of underweight children aged below three years. Thus, in the time period occurring from 2000 to 2005, real Gross Domestic Production per capita has annually grown at 5.4%, whereas the proportion of children who are underweight has declined from 47% to 46%, a mere one point percent. Such trend opens up the space for discussing the traditionally assumed linkage between income-poverty and undernutrition as well as food intervention as the main focus of policies designed to fight child hunger. Also, it unlocks doors for evaluating the role of an alternative economic approach aiming at explaining undernutrition, such as the Capability Approach. The Capability Approach argues for widening the informational basis to account not only for resources, but also for variables related to liberties, opportunities and autonomy in pursuing what individuals value.The econometric analysis highlights the relevance of including behavioral factors when explaining child undernutrition. In particular, the ability of the mother to move freely in the community without the need of asking permission to her husband or mother-in-law is statistically significant when included in the model, which accounts also for confounding traditional variables, such as economic wealth and food security. Also, focusing on agency, results indicates the necessity of measuring autonomy in different domains and the need of improving the measurement scale for agency data, especially with regards the domain of household duties. Finally, future research is required to investigate policy venues for increasing agency in women and in the communities they live in as viable strategy for reducing the plague of child undernutrition in India.

Investigation on laser shock peening capability by FE simulation

Laser shock peening is a technique similar to shot peening that imparts compressive residual stresses in materials for improving fatigue resistance. The ability to use a high energy laser pulse to generate shock waves, inducing a compressive residual stress field in metallic materials, has applications in multiple fields such as turbo-machinery, airframe structures, and medical appliances. The transient nature of the LSP phenomenon and the high rate of the laser's dynamic make real time in-situ measurement of laser/material interaction very challenging. For this reason and for the high cost of the experimental tests, reliable analytical methods for predicting detailed effects of LSP are needed to understand the potential of the process. Aim of this work has been the prediction of residual stress field after Laser Peening process by means of Finite Element Modeling. The work has been carried out in the Stress Methods department of Airbus Operations GmbH (Hamburg) and it includes investigation on compressive residual stresses induced by Laser Shock Peening, study on mesh sensitivity, optimization and tuning of the model by using physical and numerical parameters, validation of the model by comparing it with experimental results. The model has been realized with Abaqus/Explicit commercial software starting from considerations done on previous works. FE analyses are “Mesh Sensitive”: by increasing the number of elements and by decreasing their size, the software is able to probe even the details of the real phenomenon. However, these details, could be only an amplification of real phenomenon. For this reason it was necessary to optimize the mesh elements' size and number. A new model has been created with a more fine mesh in the trough thickness direction because it is the most involved in the process deformations. This increment of the global number of elements has been paid with an "in plane" size reduction of the elements far from the peened area in order to avoid too high computational costs. Efficiency and stability of the analyses has been improved by using bulk viscosity coefficients, a merely numerical parameter available in Abaqus/Explicit. A plastic rate sensitivity study has been also carried out and a new set of Johnson Cook's model coefficient has been chosen. These investigations led to a more controllable and reliable model, valid even for more complex geometries. Moreover the study about the material properties highlighted a gap of the model about the simulation of the surface conditions. Modeling of the ablative layer employed during the real process has been used to fill this gap. In the real process ablative layer is a super thin sheet of pure aluminum stuck on the masterpiece. In the simulation it has been simply reproduced as a 100µm layer made by a material with a yield point of 10MPa. All those new settings has been applied to a set of analyses made with different geometry models to verify the robustness of the model. The calibration of the model with the experimental results was based on stress and displacement measurements carried out on the surface and in depth as well. The good correlation between the simulation and experimental tests results proved this model to be reliable.

Design, synthesis and Chemical-physical characterization of photocatalytic inorganic nanocrystals for technological applications

This work was based on the synthesis and characterization of innovative crystals for biomedical and technological applications. Different types of syntheses were developed in order to obtain crystals with high photocatalytic properties. A hydrothermal synthesis was also processed to correlate the chemical-physical characteristics with synthesis parameters obtaining synthesis of nanoparticles of titanium dioxide with different morphology, size and crystalline phase depending on the variation of the synthesis parameters. Also a synthesis in water at 80 °C temperature and low pressure was developed from which anatase containing a small percentage of brookite nanoparticles were obtained, presenting a high photocatalytic activity. These particles have been used to obtain the microcrystals formed by an inorganic core of hydroxyapatite surface covered by TiO2 nanoparticles. Micrometer material with higher photocatalytic has been produced. The same nanoparticles have been functionalized with resorcinol oxidized in order to increase the photocatalytic efficiency. Photodegradation test results have confirmed this increase. Finally, synthetic nanoparticles with a waterless synthesis using formic acid and octanol, through esterification "in situ" were synthesized. Nanoparticles superficially covered by carboxylic residues able to bind a wide range of molecules to obtain further photocatalytic properties were obtained.

Skin tissue engineering: medical problems and technological solutions.

In questo elaborato si affrontano problematiche cliniche legate ai traumi gravi della cute in cui è necessario intervenire chirurgicamente per ripristinare una situazione normale: si approfondisce lo studio della fisiologia del tessuto, la classificazione dei gradi delle ustioni della pelle, la guarigione delle ferite e la meccanica della cute. Il trapianto di tessuto autologo costituisce la soluzione più efficace e con minori complicazioni. Tuttavia il paziente potrebbe non presentare una superficie di cute disponibile sufficientemente estesa, per cui si ricorre ad altri metodi. In primo luogo, si effettuano degli allotrapianti di tessuto di donatore cadavere prelevati secondo le normative vigenti e conservati attraverso le varie tecniche, il cui sviluppo ha consentito una durata di conservazione maggiore; mentre la glicerolizzazione abbatte al 100% il rischio di trasmissione di patologie e lo sviluppo di microorganismi, la crioconservazione preserva la vitalità del tessuto. La chirurgia utilizzata per queste operazioni si avvale di tecnologie innovative come la Tecnologia a Pressione Negativa. Un'alternativa necessaria per sopperire all'ingente richiesta di tessuto di donatore sono i sostituti cutanei, che presentano un grande potenziale per il futuro. Per eliminare totalmente il rischio di rigetto sarebbe necessario personalizzare il costrutto utilizzando cellule autologhe, ma la ricerca è stata rallentata da minori investimenti da parte dell'industria biomedica, che si è maggiormente focalizzata sulla realizzazione di prodotti utilizzabili da un più ampio raggio di pazienti. Per queste ragioni, l'ingegneria tissutale della cute ha trovato più ampio campo di applicazione nel sistema dei test in vitro. A tale scopo sono stati creati dei protocolli certificati per testare la corrosività, la irritabilità e la vitalità del tessuto cutaneo, quali EpiDerm, EpiSkin e SkinEthic che si avvalgono dell'uso del metodo MMT e della spettrofotometria, che è diventata un supporto fondamentale per le scienze biologiche.