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Classifying Single-thread Rivers: A European perspective
No full textThis thesis develops and tests a classification of ‘near-natural’ European single-thread rivers, which are free to adjust to fluvial processes. The research involves subdividing rivers along a continuum of geomorphological characteristics to assign river reaches to geomorphologically-meaningful classes according to their channel dimensions and forms, and floodplain characteristics. The classification was developed and tested through three research components. First, a preliminary classification was developed using information entirely derived from a new information system containing remotely-sensed imagery and digital terrain data: Google Earth. This research stage required the development of rules for identifying, extracting and standardising information from this source for a large sample of river reaches. 221 single-thread river reaches distributed across 75 European rivers were investigated. Analysis of the derived information resulted in the development of a classification comprising six classes of European single thread river.
Second, the robustness of the classification was explored including assessments of (i) the degree to which the classes were interpretable in relation to the geomorphic features they displayed; (ii) the degree to which sub-divisions of the six classes could be identified and justified; (iii) the accuracy of some specific types of information extracted from Google Earth; and (iv) the degree to which the six classes corresponded to expected gradients in two controlling variables: stream power and bed sediment calibre. Thirdly, bar theory was applied to a sample of rivers representative of the six classes. Since bars are an important contributor to river channel form and dynamics, the correspondence of the bars in the six river classes to their expected distribution as indicated by bar theory, provided further confirmation of the robustness of the classification. The outputs of the research are (i) a fully-tested classification of European single-thread rivers; and (ii) a demonstration of how Google Earth can provide valuable information for research in fluvial geomorphology. Some additional future research stages are proposed that could turn the classification into an operational tool in the context of river assessment and management
Experimental investigations on seismic Behaviour of Light Timber framed Buildings and log-house traditional constructive System
No full textThis document presents a part of the wide research carried out on modern timber buildings by the timber research group of the University of Trento. In the last five years several experimental and numerical analysis have been performed on crucial structural topics about multistorey timber construction. The efforts have been focused on the traditional light timber framed system (LTF) and on the log-house system (LH). Concerning the LTF, different aspects of the structural behaviour to the lateral load bearing structure such as walls and connection devices were investigated through experimental tests from the single component up to the full-scale building tested on shake table. The goals of these capstone tests, carried out on three-storey buildings, were the investigation of peculiar aspects which especially for the European constructive tradition were not sufficiently discussed.
The same layout was follow for the traditional log-house system. In a first step of the research campaign the behaviour of single components (joints, reinforce elements) was tested and analysed in order to form the basis of the second part that was dedicated to the full scale shear walls tests and analysis. The thesis is organized in two main parts. In the opening chapters, after a brief introduction to the constructive system, the seismic behaviour of light timber framed constructions is analysed. The validation of the predictive models and the mechanical characterization of the gypsum fibreboard sheathing material are presented. Different steps of the S.E.R.I.E.S. project are summarized (tests on connection and real scale walls - shake table tests). The aim of the discussion is the deeper understanding of the boundary condition and the reliability of the tests on the single component on the real scale model. In the second part, the mechanical characterization of modern timber log-house building through experimental tests is presented. The strong cooperation among Rubner Haus Company and the timber research group of the University of Trento made possible a detailed experimental campaign organized on two steps. The first is focused on the evaluation of the corner joints proprieties by means of analysis of small portion of walls. The second part deals with the behaviour of full-scale walls with vertical loads in different geometries (corner joints types, length and presence of openings). The two innovative test setup were designed to reproduce the boundary condition of the structural elements of the building, and to minimize the effects of the test pparatus on the results. The outcomes of the tests show a complex interaction between contributions provided by different mechanisms. In the last chapters, a simplified model suitable to predict the overall load displacement curves of the wall is introduced
Para una estética del fragmento en José Ángel Valente
No full textEl trabajo presenta un análisis sistemático y exhaustivo de la obra lírica en castellano del poeta gallego José Ángel Valente (1929-2000). A través de una lectura hermenéutica de una selección de poesías, el trabajo destaca los elementos de una estética que participa en una concepción fragmentaria tanto de la experiencia lírica como de la escritura misma
Una congiuntura del "progresso". La modernizzazione italiana e Lombroso (1876-1880)
No full textThe study seeks to provide a non-teleological overview of a meaningful turning point of the "progress" in late nineteenth century Italy: the period from 1876 to 1880, when the Left wing party started to rule the country. The Italian case is set against the influential background of Europe at the dawn of the "Age of Empires". The study is based on primary sources. It provides a textual analysis of parliamentary reports, governmental documents, political newspapers and magazines. It also investigates the debates involving medical, social and criminal sciences, which were closely related to politics. It thus considers the mainstream-culture of the new "bourgeois" Italy: positivism. Specific attention is devoted to a key player of positivism, Cesare Lombroso, whose "discovery" of the "criminal man" - a sort of dangerous sub-man, that had to be neutralized as such – were about to become world famous. The study seeks to provide a multifaceted and comprehensive analysis. It deals with structures and agency, by refusing both deterministic and subjectivist approaches. The research therefore focuses on the interaction between structures and agency, looking into both the impact of social processes and the cultural-political shaping of these processes. The study hopefully provides a “view from the inside” of the risky capitalistic and democratic modernization in liberal Italy. Source analysis suggests that political elites and the rising bourgeoisie experienced a paradox: a) on the one hand, a need for a "progressive" change, in order to turn that late-comer into a competitive "nation" able to cope with social problems; b) on the other hand, a fear of the "progress" itself, whose tangible implications, i.e. the politicization of social conflict, were dangerous to this weak country. That paradox might shed some light on the later centrist political agenda of “trasformismo”. Moreover, it might support a view that liberal democratic and authoritarian trends, which paired up in liberal Italy, were the two sides of the same coin. As for the cultural developments, it might be argued that the biological theory of "crime" was a safe and nonetheless painful representation of the unbearable dark side ofthe "progress": the anti-illuministic features of that increasingly influential representation were dictated by "progressive" feelings
Capturing Complex Microenvironments for Directed Stem Cell Differentiation
No full textLoss of vascular function associated with cardiovascular disease, such as arthrosclerosis, represents the leading medical epidemic in the United States and typically requires surgical intervention through synthetic or autologous vascular grafts. To overcome the limitations associated with adult cell sources, which are often restricted by supply or compromised by disease, mesenchymal stem cells (MSCs) have emerged as potential candidates for vascular tissue engineering. While evidence suggests the roles of several factors influencing MSC differentiation into vascular phenotypes, including matrix rigidity, geometry and chemistry, the phenomena associated with these events are still largely unknown. Further, the development of mature vascular phenotypes, such as vascular smooth muscle cells (vSMCs), with functional behavior remains elusive to the research community. This thesis proposed to engineer and direct specific and mature vascular differentiation from MSCs by way of highly tailored matrices mimicking the vascular niche environment. Taking inspiration from natural organization, we contend that a biomimetic design approach to tissue scaffolds that display features of the natural cellular microenvironment whilst mimicking the bulk tissue properties may elicit highly specific differentiation of MSCs to vascular phenotypes. To validate our hypothesis, we employed a systemic approach incorporating physical and chemical microenvironmental cues, i.e. stiffness, biological ligands and chemical factors, with the aim to augment vascular phenotype expression, functionality, and final incorporation into a tailored biomaterial scaffolds.
First, we present a novel technique for the preparation of silk hydrogels directly from high pressure CO2 environments without the need for crosslinking agents or additional additives such as surfactants or co-solvents. Through this novel method, we demonstrate the utility of CO2 as a volatile electrolyte, capable of sufficiently influencing the sol-gel transition of silk proteins, resulting in the formation of stable hydrogels with properties suitable for biomedical applications. Second, we hypothesized that suitable soluble factor regimen and matrix rigidity can instruct MSC differentiation towards more mature, functional vSMCs. To address this, we investigated cellular differentiation on tunable SF hydrogels prepared using a solvent-free CO2 processing method. The focus of this portion of the thesis is on exploiting the combined use of substrate stiffness and growth factor (TGF- β1) on SF matrices, with the aim of correlating the effects on the vascular commitment of human mesenchymal stem cells (hMSCs). Our data reveal that hMSC differentiation into mature SMCs can be achieved within modest culture periods (72 h) by combining appropriate SF hydrogel stiffness (33 kPa) with growth factor (TGF-β1). These findings advance our understanding of how complex multicomponent biomaterials, whereby mimicking the intricacy of natural tissue environments, can play a significant role in developing optimal stem cell differentiation protocols.
Third, we postulated that the presentation of ECM proteins on 3D matrices with tunable stiffness will augment the differentiation of MSCs to vascular lineages. To address this, we established a high-throughput ECM platform based on soft, fibrous PEG hydrogels meanwhile highly-tunable in stiffness and 3-dimensional geometry. Using this technique, we identified several microenvironments supporting MSC adhesion, spreading and differentiation toward early vascular lineages. This portion of the thesis supports the hypothesis that a complex milieu exists coupling protein functional behavior with substrate rigidity and that this phenomenon may potentially be exploited through proper application of high-throughput screening methodologies.
In the final work of this thesis, we explored the integration of ECM-derived small engineered peptides with 3D soft matrices to refine the differentiation of MSCs to vascular phenotypes, and further successfully recapitulate the complex vascular niche necessary for specific and efficient MSC differentiation into vascular lineages. In line with this, we report the development of a microarray platform based on electrospun nanofibrous hydrogels of photoclickable thiol-ene poly(ethylene glycol) (PEG) hydrogels. Here, we demonstrate the ability to control primary cell adhesion to soft, fibrous hydrogels functionalized with RGD peptide. However, future work will be focused on designing combinatorial peptide studies, whereby, the integration of several biological ligands of interest with tunable physical properties can instruct stem cell differentiation in a highly specific manner. This thesis has provided fundamental insights into the effects of physiological stimuli on vascular differentiation of MSC in terms of the specificity and maturity of the final differentiated cells. Better understanding of such mechanisms will prove paramount in the sequential stages of MSC differentiation to mature vascular cells. Additionally, the findings of this thesis will help to better define the process of regenerating functional healthy vascular tissue from MSCs. Altogether, a combinatorial approach investigating the effects of matrix elasticity, biological ligands and growth factors on MSC differentiation in a 3D nanofiber culture will be critical towards understanding and recapitulating MSC differentiation in the in vivo vascular environment
Distributed Computing for Large-scale Graphs
No full textThe last decade has seen an increased attention on large-scale data analysis, caused mainly by the availability of new sources of data and the development of programming
model that allowed their analysis. Since many of these sources can be modeled as graphs, many large-scale graph processing frameworks have been developed, from vertex-centric models such as pregel to more complex programming models that allow asynchronous computation, can tackle dynamism in the data and permit the usage of different amount of resources. This thesis presents theoretical and practical results in the area of distributed large-
scale graph analysis by giving an overview of the entire pipeline. Data must first be pre-processed to obtain a graph, which is then partitioned into subgraphs of similar size. To analyze this graph the user must choose a system and a programming model that matches her available resources, the type of data and the class of algorithm to execute. Aside from an overview of all these different steps, this research presents three novel approaches to those steps. The first main contribution is dfep, a novel distributed partitioning algorithm that divides the edge set into similar sized partition. dfep can obtain partitions with good quality in only a few iterations. The output of dfep can then be used by etsch, a graph processing framework that uses partitions of edges as the focus of its programming model. etsch’s programming model is shown to be flexible and can easily reuse sequential classical graph algorithms as part of its workflow. Implementations
of etsch in hadoop, spark and akka allow for a comparison of those systems and the discussion of their advantages and disadvantages. The implementation of etsch in akka
is by far the fastest and is able to process billion-edges graphs faster that competitors such as gps, blogel and giraph++, while using only a few computing nodes. A final
contribution is an application study of graph-centric approaches to word sense induction and disambiguation: from a large set of documents a word graph is constructed and then processed by a graph clustering algorithm, to find documents that refer to the same entities. A novel graph clustering algorithm, named tovel, uses a diffusion-based approach inspired by the cycle of water
Optimization of a PVD Deposition System for the Realization of Dichroic Filters used in CPV spectral Separation System for the Energy Production
No full textPhotovoltaic technology in the field of renewable energy has reached a high commercial interest over the past decade.
The traditional silicon photovoltaic systems that is currently the most widespread, mainly due to government subsidies, have a low energy production. The wide use of material and the low efficiency of the silicon modules required the research and development of photovoltaic systems more efficient. The most promising technology is the photovoltaic concentration that increases the efficiency of the modules by reducing the area of the PV cell.
The concentration photovoltaic has had considerable technological progress related to the development of multi-junction PV cells with high efficiency. Another approach is the technology of photovoltaic concentration with the spectral separation, so using the interference filters the solar spectrum is splitted into different optical bands.
In this research was designed and built a CPV prototype system with spectral separation. The interference filters such as anti-reflection and dichroic mirror are made up of silicon dioxide and titanium dioxide. These oxides have been realized by means of physical vapor deposition reactive magnetron sputtering technique. The PVD technique allows to deposit thin films with a homogeneous process reproducible and reliable. In the first part of the work, the characterization of individual layers of oxide materials have allowed to extrapolate the optical constants. This is necessary for the design of the optical multilayer.
The characterization has nvolved various analyzes such as atomic force microscopy (AFM) to determine the thickness and the roughness, compositional analysis Rutherforf backscattering spectrometry (RBS), and optical analysis UV-Vis-NIR. These analyzes were necesary to calibrate the deposition system in order to subsequently to realize the multilayer optics. The as deposited optical multilayers not confirm the optical design, and it was necessary to carry out an annealing at 350°C. In the second part of the work, there were also micro structural characterizations for evaluating the phase variation of the titanium dioxide with the annealing treatment. The Fourier transform infrared (FT-IR) analysis has checked the absorption peak of the Ti-O-Ti of the crystalline phase. In addition, X-ray diffraction (XRD) analysis verified the phase variation of titanium dioxide from purely amorphous phase with a slight presence of rutile to the anatase phase. Through the optical analysis it was possible to extrapolate the new optical constants corresponding to the phase of anatase. In the third part of the work, the ray tracing design of optical splitting of the CPV prototype was carry out. The CPV system is designed by coupling a concentration Fresnel a dichroic mirror. The focus of the radiation on the PV cell, is simulated by two ideal detector. The optical optimization as function of the f-number of the lens has allowed to define the layout for the prototyping phase. A further optimization is to insert a secondary optics element (SOE) of homogenization. The secondary optics will also limits the optical losses due to a misalignment of the CPV prototype. In the last part of this thesis is devoted to the preparation and the characterization of the CPV prototype. Were performed measures of solar radiation, which combined with the characteristic I-V-P curves of the solar cells have enable to evaluate the efficiency of the prototype system. The efficiency of the spectral separation system was compared with concentration multi-junction PV cells. Daily measurement were performed to compare the spectral separation technology than to the multi-junction technology. The results show that the separation system maintains a more constant performance during the day. Finally, thermal measurements were conducted on the component of the CPV prototype separation system. The experimental results allows to guarantee that the spectral separation is also a selective filter of temperature. This allows the solar cells to maximize the photovoltaic conversion and to reduce the overheating
Provenance in Open Data Entity-Centric Aggregation
No full textAn increasing number of web services these days require combining data from several data providers into an aggregated database. Usually this aggregation is based on the linked data approach. On the other hand, the entity-centric model is a promising data model that outperforms the linked data approach because it solves the lack of explicit semantics and the semantic heterogeneity problems. However, current open data which is available on the web as raw datasets can not be used in the entity-centric model before processing them with an import process to extract the data elements and insert them correctly in the aggregated entity-centric database. It is essential to certify the quality of these imported data elements, especially the background knowledge part which acts as input to semantic computations, because the quality of this part affects directly the quality of the web services which are built on top of it. Furthermore, the aggregation of entities and their attribute values from different sources raises three problems: the need to trace the source of each element, the need to trace the links between entities which can be considered equivalent and the need to handle possible conflicts between different values when they are imported from various data sources. In this thesis, we introduce a new model to certify the quality of a back ground knowledge base which separates linguistic and language independent elements. We also present a pipeline to import entities from open data repositories to add the missing implicit semantics and to eliminate the semantic heterogeneity. Finally, we show how to trace the source of attribute values coming from different data providers; how to choose a strategy for handling possible conflicts between these values; and how to keep the links between identical entities which represent the same real world entity
Advanced Characterization of Nanocrystalline Materials by Synchrotron Radiation Xâray Diffraction
No full textSynchrotron Radiation (SR) is one of the most powerful and versatile tools in the study nanomaterials, supporting a variety of analytical techniques. Among the possible spectroscopies, X-ray Diffraction (XRD) is especially suited to investigate materials at the nanoscale. However, to benefit of the full potential of SR XRD, a complete control of the diffracted signal is necessary, including the optics and general setâup of the beamline, which contribute to the Instrumental Profile Function (IPF). Exploring and characterizing the optical components for powder diffraction beamlines is the bottom line of the present Thesis, with the purpose of properly calibrating and adjusting all components in order to deliver the beam under the best possible conditions. Main benefits of this novel approach appear in the study of relatively large crystalline domains, toward the upper limit of the nanoscale (â hundreds of nm), a critical range between nano- and micro-crystalline, where the IPF is the main feature appearing in the experimental data. Thanks to this investigation it was possible to develop solutions and tools to improve knowledge and enhance the capability of handling the IPF along the life-cycle of a powder diffraction experiment. This result was achieved by studying and characterizing a new possible reference material for Line Profile Analysis (of size and strain effects), and by developing an original simulation/modelling software, based on rayâtracing algorithms, capable to predict and analyse the instrumental behaviour of a beamline. As such the results of this work, and in a more general sense the emerging paradigm, will be of interest to many other beamlines currently employed for X-ray spectroscopies
Innovative Electromagnetic Field Manipulating Devices Based on Transformation Electromagnetics
No full textQuasiconformal Transformation Optics (QCTO) has been investigated and applied for the design of innovative electromagnetic field manipulating devises. The design is focused on enhancing radiation performance of antenna arrays. Towards this end, the QCTO approach has been utilized for the application of compressing dimension of linear array at the same time keeping its radiation performance equivalent to the original array. The basic QCTO is then generalized to allow an arbitrary physical arrangement coated with a suitable lens to exhibit the same radiating features of an arbitrary reference virtual array in free space. This removed the limitation on the state-of-the-art QCTO method to handle transformation between arbitrarily shaped geometries. A representative numerical example, concerned with a two-dimensional layout, is presented to assess the effectiveness of the proposed method as well as the enhanced features of the resulting metamaterial-coated arrays with respect to standard conformal arrangements. In addition, the capability to achieve significantly simplified structures by means of tile discretization approximation of the synthesized lens is investigated. Selected numerical examples are reported to illustrate the effectiveness of tile-discretized lenses versus ideal QCTO arrangements. The metamaterial lens that resulted from the extended QCTO was found to be significantly anisotropic posing implementation challenge. To address this issue, an innovative approach, based on the System-by-Design (SbD) paradigm, is proposed for the synthesis of isotropic non-magnetic metamaterial lenses. Selected numerical results, concerned with an application of the SbD-QCTO approach, are reported to give some insights on its advantages and current limitations in terms of computational efficiency, effectiveness, and flexibility