Studio e sviluppo di algoritmi per la segmentazione e la caratterizzazione di fegato e lesioni epatiche da immagini TC multifase in ambiente java

Il presente lavoro è stato svolto in collaborazione con il Reparto di Diagnostica per Immagini della Fondazione Toscana G. Monasterio dell’ Ospedale del Cuore di Massa. Tale lavoro ha come scopo la realizzazione di un software di elaborazione di immagini TC multifase per la segmentazione del fegato e delle lesioni epatiche. E' stato implementato un algoritmo semi-automatico per la segmentazione sia del fegato che delle lesioni epatiche in ambiente java. Tale algoritmo è in grado di individuare le lesioni ed estrarre le loro caratteristiche in tutte e tre le fasi contrastografiche. In questo modo è possibile discriminare i vari tipi di lesioni presenti, osservandone il comportamento nelle tre fasi contrastografiche

A Structural Analysis of the Internet AS-level topology

The study of the structural characteristics of the Internet topology at the Autonomous System (AS) level of abstraction is an important and interesting subject that has attracted significant interest over the last few years. Above all, a deep knowledge of the Internet underlying structure helps researchers in designing a more accurate model of the network; as a result, engineers can design applications and protocols that can take into account the underlying structure and test their projects on synthetic graphs, thereby developing more efficient algorithms. A significant challenge for researchers analyzing the Internet is how to interpret the global organization of the graph as the coexistence of its structural blocks associated with more highly interconnected parts, namely communities. While a huge number of papers have already been published on the issue of community detection, very little attention has so far been devoted to the discovery and interpretation of Internet communities. The contribution of this work is twofold. First, we study the evolution of the Internet AS-level topology over the last 9 years by means of two innovative approaches: the k-dense method and the dK-analysis. Second, we focus on substructures that play a key role in the Internet connectivity, and we investigate the classes of the ASes and the nature of the connections that create such communities. We find that as the Internet grows over time, some of its structural properties remain unchanged. Although the size of the network, as well as the kMAX -dense index (an index of the maximum level of density reached in a network), has doubled over the last 9 years, we show that after proper normalizations the k-dense decomposition has remained stable. Besides, we provided a clear evidence that the formation of denser and denser sub-graphs over time has been triggered by the proliferation of Internet eXchange Points (IXP) and public peering connections. We found that ASes within most densely-connected substructures are usually Network Service Providers, Content Providers, or Content Delivery Networks; in addition, all of them participate to at least one IXP

k-dense Communities in the Internet AS-Level Topology

Extracting a set of well connected subgraphs as com- munities from the Internet AS-level topology graph is crucially important for assessing the performance of protocols and routing algorithms, for designing ecient networks, and for evaluating the impact of failures. A huge number of community extraction methods have been proposed in the literature, among which the k-core decomposition and the k-clique community extraction methods. The former method is computationally e- cient, but it only discovers coarse-grained and loosely connected communities. On the other hand, k-clique can extract ne-grained and tightly connected communities, but is NP hard and therefore useless for analyzing the Internet AS-level topology graph. In the paper we inves- tigate the Internet structure by exploiting an ecient algorithm for extracting k-dense communities, where a k-clique community implies a k-dense community, which in turn implies a k-core community. The paper provides two innovative contributions. The rst is the application of the k-dense method to the Internet AS-level topology graph - obtained from the CAIDA, DIMES and IRL datasets - to identify well- connected communities and to analyze how these are connected to the rest of the graph. The second contribution relates to the study of the most well-connected communities with the support of two additional datasets: a geographical dataset (which lists, for each AS, the countries in which it has at least one geographical location) and the IXP dataset (which maintains, for each IXP, its geographical position and the list of its participants). We found that the k-max- dense community holds a central position in the Internet AS-level topology graph structure since its 101 ASs (less than the 0.3% of Internet ASs) are involved in more than 39% of all Internet connections. We also found that those ASs are connected to at least one IXP and have at least one geographical location in Europe (only 70.3% of them have at least one additional geographical location outside Europe)

k-clique Communities in the Internet AS-level

A signicant challenge for researchers analysing the Internet AS-level topology graph is how to interpret the global organization of the graph as the coexistence of its structural blocks (communities) associated with more highly interconnected parts. While a huge number of papers have already been published on the issue of community detection, very little attention has so far been devoted to the discovery and interpretation of Internet communities at the various levels of abstractions. We believe that by discovering and interpreting a priori these unknown building blocks (i.e. communities), this will then pave the way for new types of analysis which are crucial in understanding of the structural and functional properties of the Internet at least at the AS level of abstraction. We thus propose a novel type of analysis of the Internet AS-level topology graph by exploiting the k-clique community denition. First, we show that detected communities can be described by a tree representation. Then we show the presence of two classes of k-clique communities: those that are strictly aected by the nesting process which is embedded in the k-clique community denition, and, on the other hand, those that appear as branches in the tree. We conclude our analysis by highlighting the properties that characterize k-clique communities with dierent k values by exploiting both geographical data and information related to IXPs

Essays on Informal and Formal Care for the Elderly

This dissertation consists of two essays. In the first one I exploit geographic variation in the Medicare Home Health Care reimbursement rate that arose as a result of legislation passed in 1997 to identify the impact of government coverage of home health care visits on the living arrangements of older Medicare beneficiaries. I find that less generous reimbursement policies lead to a greater fraction of elderly living in shared living arrangements. My estimates imply that the law change had a large effect on shared living arrangements. One way to see this is to consider how the reimbursement change differentially affected living arrangements in the state that was most impacted by the law relative to the median state. My results imply that the law change caused the fraction of the elderly living in shared living arrangements to increase by 8 percent more in the most impacted state relative to the increase in the median state. In the second essay of this dissertation I use the imposition of limits in reimbursement for Medicare Home Health Care introduced in 1997 to study changes in exit patterns of home health care agencies in California between 1994 and 2000. When using piece-wise-constant Exponential hazard models estimated on the entire sample of providers, I find that the imposition of limits in reimbursement had a statistically significant effect on exit of home health care agencies in California. When conducting the analysis separately for for-profit and not-for-profit providers, results obtained with the piece-wise-constant Exponential model indicate that the imposition of limits in reimbursement had a statistically significant effect on exit for for-profit agencies, but had no statistically significant effect on not-for-profit agencies

k-Dense communities in the Internet AS-level topology graph

In this paper we investigate the structure of the Internet by exploiting an efficient algorithm for extracting k-dense communities from the Internet AS-level topology graph. The analyses showed that the most well-connected communities consist of a small number of ASs characterized by a high level of clusterization, although they tend to direct a lot of their connections to ASs outside the community. In addition these communities are mainly composed of ASs that participate at the Internet Exchange Points (IXPs) and have a worldwide geographical scope. Regarding k-max-dense ASs we found that they play a primary role in the Internet connectivity since they are involved in a huge number of Internet connections (42% of Internet connections). We also investigated the properties of three classes of k-max-dense ASs: Content Delivery Networks, Internet Backbone Providers and Tier-1s. Specifically, we showed that CDNs and IBPs heavily exploit IXPs by participating in many of them and connecting to many IXP participant ASs. On the other hand, we found that a high percentage of connections originated by Tier-1 ASs are likely to involve national ASs which do not participate at IXPs

Go beyond financial and performance information to reach donors: Designing‐effective online disclosure in the perception of European Community foundations

Building perceptions of trustworthiness that encourage donors to give is critical for no.nprofit organizations that depend on charitable giving. Several studies focused on the disclosure of financial and performance information to foster public trust and help donors to make giving decisions. Drawing from stewardship theory, this study explores how additional content dimensions of a more relational nature—including appreciation for the support received and willingness to dialog with donors—might be combined with financial and performance dimensions to design effective online disclosure in the view of nonprofits. By focusing on the viewpoint of European community foundations and using the configurational approach of qualitative comparative analysis, we found that information about fundraising campaigns is deemed must-have content to discharge online. However, this information alone is not considered to be enough; to retain current donors or attract new ones, it must be combined properly with disclosures demonstrating gratitude to and engagement with donors alongside organizational finances and performance

Circular economy in the water and wastewater sector: Tariff impact and financial performance of SMARTechs

This paper proposes a financial evaluation of the investment in SMARTechs in wastewater companies. SMAR Techs are innovative technologies that enable companies to work toward the circular economy approach, thanks to allowing the development of by-products from wastewater. A simulation of the financial impact of the SMARTech introduction was conducted based on the Italian tariff system. It is performed assuming two different scenarios. These relate to a market’s presence (or absence) for the by-products resulting from the application of SMARTechs. The results show that investing in these technologies provides both financial and environmental benefits