Subcritical fatigue in fuse networks

We obtain the Paris law of fatigue crack propagation in a fuse network model where the accumulated damage in each resistor increases with time as a power law of the local current amplitude. When a resistor reaches its fatigue threshold, it burns irreversibly. Over time, this drives cracks to grow until the system is fractured into two parts. We study the relation between the macroscopic exponent of the crack-growth rate -entering the phenomenological Paris law-and the microscopic damage accumulation exponent, gamma, under the influence of disorder. The way the jumps of the growing crack, Delta a, and the waiting time between successive breaks, Delta t, depend on the type of material, via gamma, are also investigated. We find that the averages of these quantities, <Delta a > and <Delta t >/< t(r)>, scale as power laws of the crack length a, <Delta a > proportional to a(alpha) and <Delta t >/< t(r)> proportional to a(-beta), where < t(r)> is the average rupture time. Strikingly, our results show, for small values of gamma, a decrease in the exponent of the Paris law in comparison with the homogeneous case, leading to an increase in the lifetime of breaking materials. For the particular case of gamma = 0, when fatigue is exclusively ruled by disorder, an analytical treatment confirms the results obtained by simulation. Copyright (C) EPLA, 2012

Speed Neuro-fuzzy Estimator Applied To Sensorless Induction Motor Control

This work proposes the development of an Adaptive Neuro-fuzzy Inference System (ANFIS) estimator applied to speed control in a three-phase induction motor sensorless drive. Usually, ANFIS is used to replace the traditional PI controller in induction motor drives. The evaluation of the estimation capability of the ANFIS in a sensorless drive is one of the contributions of this work. The ANFIS speed estimator is validated in a magnetizing flux oriented control scheme, consisting in one more contribution. As an open-loop estimator, it is applied to moderate performance drives and it is not the proposal of this work to solve the low and zero speed estimation problems. Simulations to evaluate the performance of the estimator considering the vector drive system were done from the Matlab/Simulink(R) software. To determine the benefits of the proposed model, a practical system was implemented using a voltage source inverter (VSI) to drive the motor and the vector control including the ANFIS estimator, which is carried out by the Real Time Toolbox from Matlab/Simulink(R) software and a data acquisition card from National Instruments.

Trypanosoma cruzi invades host cells through the activation of endothelin and bradykinin receptors: a converging pathway leading to chagasic vasculopathy

BACKGROUND AND PURPOSE Independent studies in experimental models of Trypanosoma cruzi appointed different roles for endothelin-1 (ET-1) and bradykinin (BK) in the immunopathogenesis of Chagas disease. Here, we addressed the hypothesis that pathogenic outcome is influenced by functional interplay between endothelin receptors (ETAR and ETBR) and bradykinin B2 receptors (B2R). EXPERIMENTAL APPROACH Intravital microscopy was used to determine whether ETR/B2R drives the accumulation of rhodamine-labelled leucocytes in the hamster cheek pouch (HCP). Inflammatory oedema was measured in the infected BALB/c paw of mice. Parasite invasion was assessed in CHO over-expressing ETRs, mouse cardiomyocytes, endothelium (human umbilical vein endothelial cells) or smooth muscle cells (HSMCs), in the presence/absence of antagonists of B2R (HOE-140), ETAR (BQ-123) and ETBR (BQ-788), specific IgG antibodies to each GPCRs; cholesterol or calcium-depleting drugs. RNA interference (ETAR or ETBR genes) in parasite infectivity was investigated in HSMCs. KEY RESULTS BQ-123, BQ-788 and HOE-140 reduced leucocyte accumulation in HCP topically exposed to trypomastigotes and blocked inflammatory oedema in infected mice. Acting synergistically, ETAR and ETBR antagonists reduced parasite invasion of HSMCs to the same extent as HOE-140. Exogenous ET-1 potentiated T. cruzi uptake by HSMCs via ETRs/B2R, whereas RNA interference of ETAR and ETBR genes conversely reduced parasite internalization. ETRs/B2R-driven infection in HSMCs was reduced in HSMC pretreated with methyl-beta-cyclodextrin, a cholesterol-depleting drug, or in thapsigargin-or verapamil-treated target cells. CONCLUSIONS AND IMPLICATIONS Our findings suggest that plasma leakage, a neutrophil-driven inflammatory response evoked by trypomastigotes via the kinin/endothelin pathways, may offer a window of opportunity for enhanced parasite invasion of cardiovascular cells.

Advanced Glycation in macrophages induces intracellular accumulation of 7-ketocholesterol and total sterols by decreasing the expression of ABCA-1 and ABCG-1

Abstract Background Advanced glycation end products (AGE) alter lipid metabolism and reduce the macrophage expression of ABCA-1 and ABCG-1 which impairs the reverse cholesterol transport, a system that drives cholesterol from arterial wall macrophages to the liver, allowing its excretion into the bile and feces. Oxysterols favors lipid homeostasis in macrophages and drive the reverse cholesterol transport, although the accumulation of 7-ketocholesterol, 7alpha- hydroxycholesterol and 7beta- hydroxycholesterol is related to atherogenesis and cell death. We evaluated the effect of glycolaldehyde treatment (GAD; oxoaldehyde that induces a fast formation of intracellular AGE) in macrophages overloaded with oxidized LDL and incubated with HDL alone or HDL plus LXR agonist (T0901317) in: 1) the intracellular content of oxysterols and total sterols and 2) the contents of ABCA-1 and ABCG-1. Methods Total cholesterol and oxysterol subspecies were determined by gas chromatography/mass spectrometry and HDL receptors content by immunoblot. Results In control macrophages (C), incubation with HDL or HDL + T0901317 reduced the intracellular content of total sterols (total cholesterol + oxysterols), cholesterol and 7-ketocholesterol, which was not observed in GAD macrophages. In all experimental conditions no changes were found in the intracellular content of other oxysterol subspecies comparing C and GAD macrophages. GAD macrophages presented a 45% reduction in ABCA-1 protein level as compared to C cells, even after the addition of HDL or HDL + T0901317. The content of ABCG-1 was 36.6% reduced in GAD macrophages in the presence of HDL as compared to C macrophages. Conclusion In macrophages overloaded with oxidized LDL, glycolaldehyde treatment reduces the HDL-mediated cholesterol and 7-ketocholesterol efflux which is ascribed to the reduction in ABCA-1 and ABCG-1 protein level. This may contribute to atherosclerosis in diabetes mellitus.

Proline dehydrogenase regulates redox state and respiratory metabolism in Trypanosoma Cruzi

Over the past three decades, L-proline has become recognized as an important metabolite for trypanosomatids. It is involved in a number of key processes, including energy metabolism, resistance to oxidative and nutritional stress and osmoregulation. In addition, this amino acid supports critical parasite life cycle processes by acting as an energy source, thus enabling host-cell invasion by the parasite and subsequent parasite differentiation. In this paper, we demonstrate that L-proline is oxidized to Δ(1)-pyrroline-5-carboxylate (P5C) by the enzyme proline dehydrogenase (TcPRODH, E.C. 1.5.99.8) localized in Trypanosoma cruzi mitochondria. When expressed in its active form in Escherichia coli, TcPRODH exhibits a Km of 16.58±1.69 µM and a Vmax of 66±2 nmol/min mg. Furthermore, we demonstrate that TcPRODH is a FAD-dependent dimeric state protein. TcPRODH mRNA and protein expression are strongly upregulated in the intracellular epimastigote, a stage which requires an external supply of proline. In addition, when Saccharomyces cerevisiae null mutants for this gene (PUT1) were complemented with the TcPRODH gene, diminished free intracellular proline levels and an enhanced sensitivity to oxidative stress in comparison to the null mutant were observed, supporting the hypothesis that free proline accumulation constitutes a defense against oxidative imbalance. Finally, we show that proline oxidation increases cytochrome c oxidase activity in mitochondrial vesicles. Overall, these results demonstrate that TcPRODH is involved in proline-dependant cytoprotection during periods of oxidative imbalance and also shed light on the participation of proline in energy metabolism, which drives critical processes of the T. cruzi life cycle.

A control and automation system for wave basins

This paper presents the new active absorption wave basin, named Hydrodynamic Calibrator (HC), constructed at the University of São Paulo (USP), in the Laboratory facilities of the Numerical Offshore Tank (TPN). The square (14 m 14 m) tank is able to generate and absorb waves from 0.5 Hz to 2.0 Hz, by means of 148 active hinged flap wave makers. An independent mechanical system drives each flap by means of a 1HP servo-motor and a ball-screw based transmission system. A customized ultrasonic wave probe is installed in each flap, and is responsible for measuring wave elevation in the flap. A complex automation architecture was implemented, with three Programmable Logic Computers (PLCs), and a low-level software is responsible for all the interlocks and maintenance functions of the tank. Furthermore, all the control algorithms for the generation and absorption are implemented using higher level software (MATLAB /Simulink block diagrams). These algorithms calculate the motions of the wave makers both to generate and absorb the required wave field by taking into account the layout of the flaps and the limits of wave generation. The experimental transfer function that relates the flap amplitude to the wave elevation amplitude is used for the calculation of the motion of each flap. This paper describes the main features of the tank, followed by a detailed presentation of the whole automation system. It includes the measuring devices, signal conditioning, PLC and network architecture, real-time and synchronizing software and motor control loop. Finally, a validation of the whole automation system is presented, by means of the experimental analysis of the transfer function of the waves generated and the calculation of all the delays introduced by the automation system.

M-protein is down-regulated in cardiac hypertrophy driven by thyroid hormone in rats

Although it is well known that the thyroid hormone (T3) is an important positive regulator of cardiac function over a short term and that it also promotes deleterious effects over a long term, the molecular mechanisms for such effects are not yet well understood. Because most alterations in cardiac function are associated with changes in sarcomeric machinery, the present work was undertaken to find novel sarcomeric hot spots driven by T3 in the heart. A microarray analysis indicated that the M-band is a major hot spot, and the structural sarcomeric gene coding for the M-protein is severely down-regulated by T3. Real-time quantitative PCR-based measurements confirmed that T3 (1, 5, 50, and 100 physiological doses for 2 days) sharply decreased the M-protein gene and protein expression in vivo in a dose-dependent manner. Furthermore, the M-protein gene expression was elevated 3.4-fold in hypothyroid rats. Accordingly, T3 was able to rapidly and strongly reduce the M-protein gene expression in neonatal cardiomyocytes. Deletions at the M-protein promoter and bioinformatics approach suggested an area responsive to T3, which was confirmed by chromatin immunoprecipitation assay. Functional assays in cultured neonatal cardiomyocytes revealed that depletion of M-protein (by small interfering RNA) drives a severe decrease in speed of contraction. Interestingly, mRNA and protein levels of other M-band components, myomesin and embryonic-heart myomesin, were not altered by T3. We concluded that the M-protein expression is strongly and rapidly repressed by T3 in cardiomyocytes, which represents an important aspect for the basis of T3-dependent sarcomeric deleterious effects in the heart.

Polyphase drive systems configuration aiming EMI mitigation

Topologies of motor drive systems are studied, aiming the reduction of common-mode (CM) currents. Initially, the aspects concerning the CM currents circulation are analysed. The reason of common-mode voltages generation, the circulating paths for the resulting CM currents and their effects are discussed. Then, a non-conventional drive system configuration is proposed in order to reduce the CM currents and their effects. This configuration comprehends a non-conventional inverter module wired to a motor with an unusual connection. The cables arrangement differs from the standard solution, too. The proposed topology is compared with other ones, like the active circuit for common-mode voltages compensation. The contribution of the configuration to the reduction of CM voltages and currents and their related interferences are evaluated, based on numerical simulations. Some results are presented and discussed regarding the suitability of the proposed configuration as a potential solution to reduce the CM currents effects, when the state of art and implementation cost of drives are taken into account.

Type Ia Supernovae : Homogeneity and Diversity

The use of type Ia supernovae as distance estimators has shown that about 75% of the energy content of the universe has a negative equation of state parameter and thus, drives the acceleration of the universe. Constraining the exact nature of this energy is one of the main goals in cosmology. As the statistics of observed high-redshift supernovae increases, systematic effects become the limiting factor to pursue such investigations, thus deeper understanding of the physical properties of SNe is of great importance. In this thesis we investigate spectral homogeneity and diversity of local and high redshift supernovae. Special emphasis has been given to the analysis of optical spectra of local peculiar supernovae 1999aa and 1999ac. The study of the spectra of SN 1999aa pointed out that this SN could be a link between the extreme peculiar SN 1991T and normal SNe. Moreover, the identification of a high velocity component of Ca II and possibly of a low velocity component of C III suggests some degree of asphericity in the ejecta of this supernova. Evidence for a deflagration of a C+O white dwarf was found in the early spectra of SN 1999ac. The spectral proprieties of a vast sample of local SNe are also studied by means of newly introduced spectral indicators. These were used to possibly improve the intrinsic spread of SN peak magnitudes to 0.15 mag, independently of light curve parameters. The first quantitative comparison between local and high redshift supernova is carried out. No evidence for extreme peculiar sub-luminous SNe was found in our data set including 13 SNe with redshift range z=0.279-0.912. Furthermore, SN2002fd (z=0.279) was found to show spectral characteristics similar to SN 1991T/SN 1999aa-like supernovae. We also present a feasibility study of the Hubble diagram in rest frame I-band up to z~0.5, and show the possibility to probe the presence of intergalactic dust, which could possibly mimic the effect of dark energy in the Hubble diagram.

A dynamic model of oceanic sulfur (DMOS) applied to the Sargasso Sea: Simulating the dimethylsulfide (DMS) summer paradox

[EN]A new one-dimensional model of DMSP/DMS dynamics (DMOS) is developed and applied to the Sargasso Sea in order to explain what drives the observed dimethylsulfide (DMS) summer paradox: a summer DMS concentration maximum concurrent with a minimum in the biomass of phytoplankton, the producers of the DMS precursor dimethylsulfoniopropionate (DMSP). Several mechanisms have been postulated to explain this mismatch: a succession in phytoplankton species composition towards higher relative abundances of DMSP producers in summer; inhibition of bacterial DMS consumption by ultraviolet radiation (UVR); and direct DMS production by phytoplankton due to UVR-induced oxidative stress. None of these hypothetical mechanisms, except for the first one, has been tested with a dynamic model. We have coupled a new sulfur cycle model that incorporates the latest knowledge on DMSP/DMS dynamics to a preexisting nitrogen/carbon-based ecological model that explicitly simulates the microbial-loop. This allows the role of bacteria in DMS production and consumption to be represented and quantified. The main improvements of DMOS with respect to previous DMSP/DMS models are the explicit inclusion of: solar-radiation inhibition of bacterial sulfur uptakes; DMS exudation by phytoplankton caused by solar-radiation-induced stress; and uptake of dissolved DMSP by phytoplankton. We have conducted a series of modeling experiments where some of the DMOS sulfur paths are turned “off” or “on,” and the results on chlorophyll-a, bacteria, DMS, and DMSP (particulate and dissolved) concentrations have been compared with climatological data of these same variables. The simulated rate of sulfur cycling processes are also compared with the scarce data available from previous works. All processes seem to play a role in driving DMS seasonality. Among them, however, solar-radiation-induced DMS exudation by phytoplankton stands out as the process without which the model is unable to produce realistic DMS simulations and reproduce the DMS summer paradox.

Metodi numerici per lo studio di centri di lavoro ad alta velocità

A Machining Centre is nowadays a complex mechanical, electronic, electrical system that needs integrated design capabilities which very often require a high time-consuming effort. Numerical techniques for designing and dimensioning the machine structure and components usually requires different knowledge according to the system that have to be designed. This Ph. D Thesis is related about the efforts of the Authors to develop a system that allows to perform the complete project of a new machine optimized in its dynamic behaviour. An integration of the different systems developed, each of which respond to specific necessities of designer, is here presented. In particular a dynamic analysis system, based on a lumped mass approach, that rapidly allows to setup the drives of the machine and an Integrated Dynamic Simulation System, based on a FEM approach, that permit a dynamic optimization, are shown. A multilevel Data Base, and an operator interface module provide to complete the designing platform. The proposed approach represents a significant step toward the virtual machining for the prediction of the quality of the worked surface.

Spectrum shaping and its application: spread-spectrum clock generator and circuits for ultra wide band

Electromagnetic spectrum can be identified as a resource for the designer, as well as for the manufacturer, from two complementary points of view: first, because it is a good in great demand by many different kind of applications; second, because despite its scarce availability, it may be advantageous to use more spectrum than necessary. This is the case of Spread-Spectrum Systems, those systems in which the transmitted signal is spread over a wide frequency band, much wider, in fact, than the minimum bandwidth required to transmit the information being sent. Part I of this dissertation deals with Spread-Spectrum Clock Generators (SSCG) aiming at reducing Electro Magnetic Interference (EMI) of clock signals in integrated circuits (IC) design. In particular, the modulation of the clock and the consequent spreading of its spectrum are obtained through a random modulating signal outputted by a chaotic map, i.e. a discrete-time dynamical system showing chaotic behavior. The advantages offered by this kind of modulation are highlighted. Three different prototypes of chaos-based SSCG are presented in all their aspects: design, simulation, and post-fabrication measurements. The third one, operating at a frequency equal to 3GHz, aims at being applied to Serial ATA, standard de facto for fast data transmission to and from Hard Disk Drives. The most extreme example of spread-spectrum signalling is the emerging ultra-wideband (UWB) technology, which proposes the use of large sections of the radio spectrum at low amplitudes to transmit high-bandwidth digital data. In part II of the dissertation, two UWB applications are presented, both dealing with the advantages as well as with the challenges of a wide-band system, namely: a chaos-based sequence generation method for reducing Multiple Access Interference (MAI) in Direct Sequence UWB Wireless-Sensor-Networks (WSNs), and design and simulations of a Low-Noise Amplifier (LNA) for impulse radio UWB. This latter topic was studied during a study-abroad period in collaboration with Delft University of Technology, Delft, Netherlands.

La costruzione razionale della casa. Scritti e progetti di Giuseppe Pagano

The rational construction of the house. The writings and projects of Giuseppe Pagano Description, themes and research objectives The research aims at analysing the architecture of Giuseppe Pagano, which focuses on the theme of dwelling, through the reading of 3 of his house projects. On the one hand, these projects represent “minor” works not thoroughly known by Pagano’s contemporary critics; on the other they emphasise a particular methodological approach, which serves the author to explore a theme closely linked to his theoretical thought. The house project is a key to Pagano’s research, given its ties to the socio-cultural and political conditions in which the architect was working, so that it becomes a mirror of one of his specific and theoretical path, always in a state of becoming. Pagano understands architecture as a “servant of the human being”, subject to a “utilitarian slavery” since it is a clear, essential and “modest” answer to specific human needs, free from aprioristic aesthetic and formal choices. It is a rational architecture in sensu stricto; it constitutes a perfect synthesis between cause and effect and between function and form. The house needs to accommodate these principles because it is closely intertwined with human needs and intimately linked to a specific place, climatic conditions and technical and economical possibilities. Besides, differently from his public and common masterpieces such as the Palazzo Gualino, the Istituto di Fisica and the Università Commerciale Bocconi, the house projects are representative of a precise project will, which is expressed in a more authentic way, partially freed from political influences and dogmatic preoccupations and, therefore, far from the attempt to research a specific expressive language. I believe that the house project better represents that “ingenuity”, freshness and “sincerity” that Pagano identifies with the minor architecture, thereby revealing a more authentic expression of his understanding of a project. Therefore, the thesis, by tracing the theoretical research of Pagano through the analysis of some of his designed and built works, attempts to identify a specific methodological approach to Pagano’s project, which, developed through time, achieves a certain clarity in the 1930s. In fact, this methodological approach becomes more evident in his last projects, mainly regarding the house and the urban space. These reflect the attempt to respond to the new social needs and, at the same time, they also are an expression of a freer idea of built architecture, closely linked with the place and with the human being who dwells it. The three chosen projects (Villa Colli, La Casa a struttura d’acciaio and Villa Caraccio) make Pagano facing different places, different customers and different economic and technical conditions, which, given the author’s biography, correspond to important historical and political conditions. This is the reason why the projects become apparently distant works, both linguistically and conceptually, to the point that one can define them as ”eclectic”. However, I argue that this eclecticism is actually an added value to the architectural work of Pagano, steaming from the use of a method which, having as a basis the postulate of a rational architecture as essence and logic of building, finds specific variations depending on the multiple variables to be addressed by the project. This is the methodological heritage that Pagano learns from the tradition, especially that of the rural residential architecture, defined by Pagano as a “dictionary of the building logic of man”, as an “a-stylistic background”. For Pagano this traditional architecture is a clear expression of the relationships between a theme and its development, an architectural “fact” that is resolved with purely technical and utilitarian aims and with a spontaneous development far from any aprioristic theoretical principle. Architecture, therefore, cannot be an invention for Pagano and the personal contribution of each architect has to consider his/her close relationship with the specific historical context, place and new building methods. These are basic principles in the methodological approach that drives a great deal of his research and that also permits his thought to be modern. I argue that both ongoing and new collaborations with younger protagonists of the culture and architecture of the period are significant for the development of his methodology. These encounters represent the will to spread his own understanding of the “new architecture” as well as a way of self-renewal by confronting the self with new themes and realities and by learning from his collaborators. Thesis’ outline The thesis is divided in two principal parts, each articulated in four chapters attempting to offer a new reading of the theory and work of Pagano by emphasising the central themes of the research. The first chapter is an introduction to the thesis and to the theme of the rational house, as understood and developed in its typological and technical aspects by Pagano and by other protagonists of the Italian rationalism of the 1930s. Here the attention is on two different aspects defining, according to Pagano, the house project: on the one hand, the typological renewal, aimed at defining a “standard form” as a clear and essential answer to certain needs and variables of the project leading to different formal expressions. On the other, it focuses on the building, understood as a technique to “produce” architecture, where new technologies and new materials are not merely tools but also essential elements of the architectural work. In this way the villa becomes different from the theme of the common house or from that of the minimalist house, by using rules in the choice of material and in the techniques that are every time different depending on the theme under exploration and on the contingency of place. It is also visible the rigorous rationalism that distinguishes the author's appropriation of certain themes of rural architecture. The pages of “Casabella” and the events of the contemporary Triennali form the preliminary material for the writing of this chapter given that they are primary sources to individuate projects and writings produced by Pagano and contemporary architects on this theme. These writings and projects, when compared, reconstruct the evolution of the idea of the rational house and, specifically, of the personal research of Pagano. The second part regards the reading of three of Pagano’s projects of houses as a built verification of his theories. This section constitutes the central part of the thesis since it is aimed at detecting a specific methodological approach showing a theoretical and ideological evolution expressed in the vast edited literature. The three projects that have been chosen explore the theme of the house, looking at various research themes that the author proposes and that find continuity in the affirmation of a specific rationalism, focussed on concepts such as essentiality, utility, functionality and building honesty. These concepts guide the thought and the activities of Pagano, also reflecting a social and cultural period. The projects span from the theme of the villa moderna, Villa Colli, which, inspired by the architecture of North Europe, anticipates a specific rationalism of Pagano based on rigour, simplicity and essentiality, to the theme of the common house, Casa a struttura d’acciaio, la casa del domani, which ponders on the definition of new living spaces and, moreover, on new concepts of standardisation, economical efficiency and new materials responding to the changing needs of the modern society. Finally, the third project returns to the theme of the, Villa Caraccio, revisiting it with new perspectives. These perspectives find in the solution of the open plant, in the openness to nature and landscape and in the revisiting of materials and local building systems that idea of the freed house, which express clearly a new theoretical thought. Methodology It needs to be noted that due to the lack of an official Archive of Pagano’s work, the analysis of his work has been difficult and this explains the necessity to read the articles and the drawings published in the pages of «Casabella» and «Domus». As for the projects of Villa Colli and Casa a struttura d’acciaio, parts of the original drawings have been consulted. These drawings are not published and are kept in private archives of the collaborators of Pagano. The consultation of these documents has permitted the analysis of the cited works, which have been subject to a more complete reading following the different proposed solutions, which have permitted to understand the project path. The projects are analysed thought the method of comparison and critical reading which, specifically, means graphical elaborations and analytical schemes, mostly reconstructed on the basis of original projects but, where possible, also on a photographic investigation. The focus is on the project theme which, beginning with a specific living (dwelling) typology, finds variations because of the historico-political context in which Pagano is embedded and which partially shapes his research and theoretical thought, then translated in the built work. The analysis of the work follows, beginning, where possible, from a reconstruction of the evolution of the project as elaborated on the basis of the original documents and ending on an analysis of the constructive principles and composition. This second phase employs a methodology proposed by Pagano in his article Piante di ville, which, as expected, focuses on the plant as essential tool to identify the “true practical and poetic qualities of the construction”(Pagano, «Costruzioni-Casabella», 1940, p. 2). The reading of the project is integrated with the constructive analyses related to the technical aspects of the house which, in the case of Casa a struttura d’acciaio, play an important role in the project, while in Villa Colli and in Villa Caraccio are principally linked to the choice of materials for the construction of the different architectural elements. These are nonetheless key factors in the composition of the work. Future work could extend this reading to other house projects to deepen the research that could be completed with the consultation of Archival materials, which are missing at present. Finally, in the appendix I present a critical selection of the Pagano’s writings, which recall the themes discussed and embodied by the three projects. The texts have been selected among the articles published in Casabella and in other journals, completing the reading of the project work which cannot be detached from his theoretical thought. Moving from theory to project, we follow a path that brings us to define and deepen the central theme of the thesis: rational building as the principal feature of the architectural research of Pagano, which is paraphrased in multiple ways in his designed and built works.

Biofuels Sustainability Certification Schemes: Challenges, Feasibility and Possible Approaches

The focus of this research is to develop and apply an analytical framework for evaluating the effectiveness and practicability of sustainability certification schemes for biofuels, especially in a developing country’s perspective. The main question that drives the research analysis is “Which are the main elements of and how to develop sustainability certification schemes that would be effective and practicable in certifying the contribution of biofuels in meeting the goals Governments and other stakeholders have set up?”. Biofuels have been identified as a promising tool to reach a variety of goals: climate change protection, energy security, agriculture development, and, especially in developing countries, economic development. Once the goals have been identified, and ambitious mandatory targets for biofuels use agreed at national level, concerns have been raised by the scientific community on the negative externalities that biofuels production and use can have at environment, social and economic level. Therefore certification schemes have been recognized as necessary processes to measure these externalities, and examples of such schemes are in effect, or are in a negotiating phase, both at mandatory and voluntary levels. The research focus has emerged by the concern that the ongoing examples are very demanding in terms of compliance, both for those that are subject to certification and those that have to certify, on the quantity and quality of information to be reported. A certification system, for reasons linked to costs, lack of expertise, inadequate infrastructure, absence of an administrative and legislative support, can represent an intensive burden and can act as a serious impediment for the industrial and agriculture development of developing countries, going against the principle of equity and level playing field. While this research recognizes the importance of comprehensiveness and ambition in designing an important tool for the measurement of sustainability effects of biofuels production and use, it stresses the need to focus on the effectiveness and practicability of this tool in measuring the compliance with the goal. This research that falls under the rationale of the Sustainability Science Program housed at Harvard Kennedy School, has as main objective to close the gap between the research and policy makers worlds in the field of sustainability certification schemes for biofuels.

Spin polarized transport in manganese oxide double-perovskite thin films

Gegenstand dieser Arbeit war die Untersuchung von metallischen gemischtvalenten Manganaten und magnetischen Doppelperowskiten. Aufgrund ihres großen negativen Magnetowiderstandes (MW) sind diese halbmetallischen Oxide interessant für mögliche technische Anwendungen, z.B. als Leseköpfe in Festplatten. Es wurden die kristallographischen, elektronischen und magnetischen Eigenschaften von epitaktischen Dünnschichten und polykristallinen Pulverproben bestimmt.Epitaktische Dünnschichten der Verbindungen La_0.67Ca_0.33MnO₃ und La_0.67Sr_0.33MnO₃ wurdenmit Kaltkathodenzerstäubung und Laserablation auf einkristallinen Substraten wie SrTiO₃abgeschieden. Mit Hall-Effekt Messungen wurde ein Zusammenbruch der Ladungsträgerdichte bei der Curie-Temperatur T_C beobachtet.Mit dem Wechsel des Dotierungsatoms A von Ca (T_C=232 K) zu Sr (T_C=345 K)in La_0.67A_0.33MnO₃ konnte die Feldsensitivität des Widerstandes bei Raumtemperatur gesteigert werden. Um die Sensitivität weiter zu erhöhen wurde die hohe Spinpolarisation von nahezu 100% in Tunnelexperimenten ausgenutzt. Dazu wurden biepitaktische La_0.67Ca_0.33MnO₃ Schichten auf SrTiO₃ Bikristallsubstraten hergestellt. Die Abhängigkeit des Tunnelmagnetowiderstandes (TMW) vom magnetischen Feld, Temperatur und Strum war ein Schwerpunkt der Untersuchung. Mittels spinpolarisierten Tunnelns durch die künstliche Korngrenze konnte ein hysteretischer TMW von 70% bei 4 K in kleinen Magnetfeldern von 120 Oe gemessen werden. Eine weitere magnetische Oxidverbindung, der Doppelperowskit Sr₂FeMoO₆ miteine Curie-Temperatur oberhalb 400 K und einem großen MW wurde mittels Laserablation hergestellt. Die Proben zeigten erstmals das Sättigunsmoment, welches von einer idealen ferrimagnetischen Anordnung der Fe und Mo Ionen erwartet wird. Mit Hilfe von Magnetotransportmessungen und Röntgendiffraktometrie konnte eine Abhängigkeit zwischen Kristallstruktur (Ordnung oder Unordnung im Fe, Mo Untergitter) und elektronischem Transport (metallisch oder halbleitend) aufgedeckt werden.Eine zweiter Doppelperowskit Ca₂FeReO₆ wurde im Detail als Pulverprobe untersucht. Diese Verbindung besitzt die höchste Curie-Temperatur von 540 K, die bis jetzt in magnetischen Perowskiten gefunden wurde. Mit Neutronenstreuung wurde eine verzerrte monoklinische Struktur und eine Phasenseparation aufgedeckt.