Secure information sharing on Decentralized Social Networks.

Decentralized Social Networks (DSNs) are web-based platforms built on distributed systems (federations) composed of multiple providers (pods) that run the same social networking service. DSNs have been presented as a valid alternative to Online Social Networks (OSNs), replacing the centralized paradigm of OSNs with a decentralized distribution of the features o\u21b5ered by the social networking platform. Similarly to commercial OSNs, DSNs o\u21b5er to their subscribed users a number of distinctive features, such as the possibility to share resources with other subscribed users or the possibility to establish virtual relationships with other DSN users. On the other hand, each DSN user takes part in the service, choosing to store personal data on his/her own trusted provider inside the federation or to deploy his/her own provider on a private machine. This, thus, gives each DSN user direct control of his/hers data and prevents the social network provider from performing data mining analysis over these information. Unfortunately, the deployment of a personal DSN pod is not as simple as it sounds. Indeed, each pod\u2019s owner has to maintain the security, integrity, and reliability of all the data stored in that provider. Furthermore, given the amount of data produced each day in a social network service, it is reasonable to assume that the majority of users cannot a\u21b5ord the upkeep of an hardware capable of handling such amount of information. As a result, it has been shown that most of DSN users prefer to subscribe to an existing provider despite setting up a new one, bringing to an indirect centralization of data that leads DSNs to su\u21b5er of the same issues as centralized social network services. In order to overcome this issue in this thesis we have investigated the possibility for DSN providers to lean on modern cloud-based storage services so as to o\u21b5er a cloudbased information sharing service. This has required to deal with many challenges. As such, we have investigated the definition of cryptographic protocols enabling DSN users to securely store their resources in the public cloud, along with the definition of communication protocols ensuring that decryption keys are distributed only to authorized users, that is users that satisfy at least one of the access control policies specified by data owner according to Relationship-based access control model (RelBAC) [20, 34]. In addition, it has emerged that even DSN users have the same difficulties as OSN users in defining RelBAC rules that properly express their attitude towards their own privacy. Indeed, it is nowadays well accepted that the definition of access control policies is an error-prone task. Then, since misconfigured RelBAC policies may lead to harmful data release and may expose the privacy of others as well, we believe that DSN users should be assisted in the RelBAC policy definition process. At this purpose, we have designed a RelBAC policy recommendation system such that it can learn from DSN users their own attitude towards privacy, and exploits all the learned data to assist DSN users in the definition of RelBAC policies by suggesting customized privacy rules. Nevertheless, despite the presence of the above mentioned policy recommender, it is reasonable to assume that misconfigured RelBAC rules may appear in the system. However, rather than considering all misconfigured policies as leading to potentially harmful situations, we have considered that they might even lead to an exacerbated data restriction that brings to a loss of utility to DSN users. As an example, assuming that a low resolution and an high resolution version of the same picture are uploaded in the network, we believe that the low-res version should be granted to all those users who are granted to access the hi-res version, even though, due to a misconfiurated system, no policy explicitly authorizes them on the low-res picture. As such, we have designed a technique capable of exploiting all the existing data dependencies (i.e., any correlation between data) as a mean for increasing the system utility, that is, the number of queries that can be safely answered. Then, we have defined a query rewriting technique capable of extending defined access control policy authorizations by exploiting data dependencies, in order to authorize unauthorized but inferable data. In this thesis we present a complete description of the above mentioned proposals, along with the experimental results of the tests that have been carried out so as to verify the feasibility of the presented techniques

Secure information sharing on Decentralized Social Networks.

Decentralized Social Networks (DSNs) are web-based platforms built on distributed systems (federations) composed of multiple providers (pods) that run the same social networking service. DSNs have been presented as a valid alternative to Online Social Networks (OSNs), replacing the centralized paradigm of OSNs with a decentralized distribution of the features o↵ered by the social networking platform. Similarly to commercial OSNs, DSNs o↵er to their subscribed users a number of distinctive features, such as the possibility to share resources with other subscribed users or the possibility to establish virtual relationships with other DSN users. On the other hand, each DSN user takes part in the service, choosing to store personal data on his/her own trusted provider inside the federation or to deploy his/her own provider on a private machine. This, thus, gives each DSN user direct control of his/hers data and prevents the social network provider from performing data mining analysis over these information. Unfortunately, the deployment of a personal DSN pod is not as simple as it sounds. Indeed, each pod’s owner has to maintain the security, integrity, and reliability of all the data stored in that provider. Furthermore, given the amount of data produced each day in a social network service, it is reasonable to assume that the majority of users cannot a↵ord the upkeep of an hardware capable of handling such amount of information. As a result, it has been shown that most of DSN users prefer to subscribe to an existing provider despite setting up a new one, bringing to an indirect centralization of data that leads DSNs to su↵er of the same issues as centralized social network services. In order to overcome this issue in this thesis we have investigated the possibility for DSN providers to lean on modern cloud-based storage services so as to o↵er a cloudbased information sharing service. This has required to deal with many challenges. As such, we have investigated the definition of cryptographic protocols enabling DSN users to securely store their resources in the public cloud, along with the definition of communication protocols ensuring that decryption keys are distributed only to authorized users, that is users that satisfy at least one of the access control policies specified by data owner according to Relationship-based access control model (RelBAC) [20, 34]. In addition, it has emerged that even DSN users have the same difficulties as OSN users in defining RelBAC rules that properly express their attitude towards their own privacy. Indeed, it is nowadays well accepted that the definition of access control policies is an error-prone task. Then, since misconfigured RelBAC policies may lead to harmful data release and may expose the privacy of others as well, we believe that DSN users should be assisted in the RelBAC policy definition process. At this purpose, we have designed a RelBAC policy recommendation system such that it can learn from DSN users their own attitude towards privacy, and exploits all the learned data to assist DSN users in the definition of RelBAC policies by suggesting customized privacy rules. Nevertheless, despite the presence of the above mentioned policy recommender, it is reasonable to assume that misconfigured RelBAC rules may appear in the system. However, rather than considering all misconfigured policies as leading to potentially harmful situations, we have considered that they might even lead to an exacerbated data restriction that brings to a loss of utility to DSN users. As an example, assuming that a low resolution and an high resolution version of the same picture are uploaded in the network, we believe that the low-res version should be granted to all those users who are granted to access the hi-res version, even though, due to a misconfiurated system, no policy explicitly authorizes them on the low-res picture. As such, we have designed a technique capable of exploiting all the existing data dependencies (i.e., any correlation between data) as a mean for increasing the system utility, that is, the number of queries that can be safely answered. Then, we have defined a query rewriting technique capable of extending defined access control policy authorizations by exploiting data dependencies, in order to authorize unauthorized but inferable data. In this thesis we present a complete description of the above mentioned proposals, along with the experimental results of the tests that have been carried out so as to verify the feasibility of the presented techniques

Exploiting magnetic properties of Fe doping in zirconia

In this study we explore, both from theoretical and experimental side, the effect of Fe doping in ZrO2 (ZrO2:Fe). By means of first principles simulation we study the magnetization density and the magnetic interaction between Fe atoms. We also consider how this is affected by the presence of oxygen vacancies and compare our findings with models based on impurity band and carrier mediated magnetic interaction. Experimentally thin films (~ 20 nm) of ZrO2:Fe at high doping concentration are grown by atomic layer deposition. We provide experimental evidence that Fe is uniformly distributed in the ZrO2 by transmission electron microscopy and energy dispersive X-ray mapping, while X-ray diffraction evidences the presence of the fluorite crystal structure. Alternating gradient force magnetometer measurements show magnetic signal at room temperature, however with low magnetic moment per atom. Results from experimental measures and theoretical simulations are compared.Comment: 8 pages, 9 figures. JEMS 201

Twenty years experience in oncologic surgery for primary cardiac tumors

Introduction. Primary cardiac tumors are uncommon in cardiac surgery. To investigate the clinical presentation, surgical results and long-term follow-up we retrospectively analyzed our experience in the treatment of primary cardiac tumors. Patients and methods. Ninety-one patients with primary cardiac tumors underwent surgery in our department in the last 20 years. Fifthy-one patients were female, the mean age was 62,2 years. Sixty-three had myxomas, 22 had papillary fibroelastoma, 4 had malignant neoformations and 2 had other benign tumors. Results. All myxomas, fibroelastomas and angiomyolipoma were radically removed. Only a palliative treatment was possible in malignant disease. In-hospital mortality was 1.2%. The mean follow-up time was 78.5 months. Three patients had recurrence of myxoma, all patients with malignant disease dead during the follow-up. Discussion. Primary benign cardiac tumors can be treated with low morbidity and mortality. The follow-up demonstrates that radical surgery is curative in case of benign tumors. The prognosis of malignant tumors is still poor. Palliative procedures have small impact on survival in these patients

Mechanism of ferritin iron uptake: activity of the H-chain and deletion mapping of the ferro-oxidase site. A study of iron uptake and ferro-oxidase activity of human liver, recombinant H-chain ferritins, and of two H-chain deletion mutants.

To study the functional differences between human ferritin H- and L-chains and the role of the protein shell in the formation and growth of the ferritin iron core, we have compared the kinetics of iron oxidation and uptake of ferritin purified from human liver (90% L) and of the H-chain homopolymer overproduced in Escherichia coli (100% H). As a control for iron autocatalytic activity, we analyzed the effect of Fe(III) on the iron uptake reaction. The results show that the H-chain homopolymer has faster rates of iron uptake and iron oxidation than liver ferritin in all the conditions analyzed and that the difference is reduced in the conditions in which iron autocatalysis in high: i.e. at pH 7 and in presence of iron core. We have also analyzed the properties of two engineered H-chains, one lacking the last 22 amino acids at the carboxyl terminus and the other missing the first 13 residues at the amino terminus. These mutant proteins assemble in ferritin-like proteins and maintain the ability to catalyze iron oxidation. The deletion at the carboxyl terminus, however, prevents the formation of a stable iron core. It is concluded that the ferritin H-chain has an iron oxidation site which is separated from the sites of iron transfer and hydrolysis and that either the integrity of the molecule or the presence of the amino acid sequences forming the hydrophobic channel is necessary for iron core formation

Accuracy Assessment of Virtual Surgical Planning Comparing 3D Virtual Surgical Planning and Post-Operative CBCTs in Surgical Skeletal Class III Cases: A Retrospective Study

Objective: To evaluate the accuracy of Virtual Surgical Planning (VSP) comparing VSPs and post-operative CBCT scans in patients undergoing bimaxillary orthognathic surgery of severe Skeletal Class III malocclusion. Material and Methods: Twenty-three patients (9 males and 14 females, mean age 24.1 ± 7.0 years) were selected and submitted to bimaxillary orthognathic surgery. Pre-operative VSPs and post-operative CBCTs were compared using both linear (taking into account four skeletal and six dental landmarks, each one described by the respective coordinates) and angular measures (seven planes in total). The threshold discrepancies for post-operative clinical acceptable results were set at ≤2 mm for liner and ≤4° for angular discrepancies. The mean difference values and its 95% confidence interval were identified, comparing which planned and which obtained in absolute value. Results: There were significant statistical differences for all absolute linear measures investigated, although only two overcome the linear threshold value of 2mm in both X and Y-linear dimensions. Linear deviations in Z-linear dimension do not reach statistical significance. All 12 angular measures reach the statistical significance, although none overcome the threshold angular value of 4°. Angular deviation for roll register the higher accuracy in contrast to pitch and yaw. Conclusion: Virtual surgical planning is a reliable planning method to be used in orthognathic surgery field; as a matter of fact, although some discrepancies between the planned on the obtained are evident, most of them meet the tolerability range

Human Mitochondrial Ferritin Expressed in HeLa Cells Incorporates Iron and Affects Cellular Iron Metabolism

Mitochondrial ferritin (MtF) is a newly identified ferritin encoded by an intronless gene on chromosome 5q23.1. The mature recombinant MtF has a ferroxidase center and binds iron in vitro similarly to H-ferritin. To explore the structural and functional aspects of MtF, we expressed the following forms in HeLa cells: the MtF precursor (approximately 28 kDa), a mutant MtF precursor with a mutated ferroxidase center, a truncated MtF lacking the approximately 6-kDa mitochondrial leader sequence, and a chimeric H-ferritin with this leader sequence. The experiments show that all constructs with the leader sequence were processed into approximately 22-kDa subunits that assembled into multimeric shells electrophoretically distinct from the cytosolic ferritins. Mature MtF was found in the matrix of mitochondria, where it is a homopolymer. The wild type MtF and the mitochondrially targeted H-ferritin both incorporated the (55)Fe label in vivo. The mutant MtF with an inactivated ferroxidase center did not take up iron, nor did the truncated MtF expressed transiently in cytoplasm. Increased levels of MtF both in transient and in stable transfectants resulted in a greater retention of iron as MtF in mitochondria, a decrease in the levels of cytosolic ferritins, and up-regulation of transferrin receptor. Neither effect occurred with the mutant MtF with the inactivated ferroxidase center. Our results indicate that exogenous iron is as available to mitochondrial ferritin as it is to cytosolic ferritins and that the level of MtF expression may have profound consequences for cellular iron homeostasis

Validation and Ecological Niche Investigation of a New Fungal Intraspecific Competitor as a Biocontrol Agent for the Sustainable Containment of Aflatoxins on Maize Fields

Crop yield and plant products quality are directly or indirectly affected by climate alterations. Adverse climatic conditions often promote the occurrence of different abiotic stresses, which can reduce or enhance the susceptibility to pests or pathogens. Aflatoxin producing fungi, in particular, whose diffusion and deleterious consequences on cereals commodities have been demonstrated to highly depend on the temperature and humidity conditions that threaten increasingly larger areas. Biological methods using intraspecific competitors to prevent fungal development and/or toxin production at the pre-harvest level are particularly promising, even if their efficacy could be affected by the ecological interaction within the resident microbial population. A previously characterized Aspergillus flavus atoxigenic strain was applied in two maize fields to validate its effectiveness as a biocontrol agent against aflatoxin contamination. At one month post-application, at the harvest stage, its persistence within the A. flavus population colonizing the maize kernels in the treated area was assessed, and its efficacy was compared in vitro with a representation of the isolated atoxigenic population. Results proved that our fungal competitor contained the aflatoxin level on maize grains as successfully as a traditional chemical strategy, even if representing less than 30% of the atoxigenic strains re-isolated, and achieved the best performance (in terms of bio-competitive potential) concerning endogenous atoxigenic isolates