Logic learning and optimized drawing: two hard combinatorial problems

Nowadays, information extraction from large datasets is a recurring operation in countless fields of applications. The purpose leading this thesis is to ideally follow the data flow along its journey, describing some hard combinatorial problems that arise from two key processes, one consecutive to the other: information extraction and representation. The approaches here considered will focus mainly on metaheuristic algorithms, to address the need for fast and effective optimization methods. The problems studied include data extraction instances, as Supervised Learning in Logic Domains and the Max Cut-Clique Problem, as well as two different Graph Drawing Problems. Moreover, stemming from these main topics, other additional themes will be discussed, namely two different approaches to handle Information Variability in Combinatorial Optimization Problems (COPs), and Topology Optimization of lightweight concrete structures

Contractual networks: an organizational model to reduce the competitive disadvantage of small and medium enterprises (SMEs) in Europe's less developed regions. A survey in southern Italy

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The influence of process parameters on mechanical properties and corrosion behaviour of friction stir welded aluminum joints

Aim of this study is to analyse how the process parameters affect the mechanical properties and the corrosion behaviour of butt joints obtained by friction stir welding (FSW). The experimental study was performed by the friction stir welding of sheets having a thickness equal to 4 mm and made of three aluminum alloys, namely AA7075, AA6060 and AA2024, considering all the combinations among the three materials and varying the process parameters, namely rotational speed and feed rate. Tensile tests were performed orthogonally to the welding direction on specimens having the welding nugget placed in the middle of gage length, while micro-Vickers tests were carried out on each specimen moving from the joint axis until the hardness of the base material was reached. The best conditions in terms of mechanical strength were obtained using the "intermediate" values of rotational speed, and, in general, when the process parameters result in low values feed rate per unit revolution (F/S), that corresponds to the higher thermal contribution to the joint region. Since in many industrial applications the mechanical resistance is not sufficient for completely describing the joint reliability, further local corrosion potential measurements and four-point bending tests were performed to evaluate the corrosion behaviour and stress corrosion cracking susceptibility of FSW Joints. The tests were carried out on prismatic specimens obtained by FSW joints of the same alloy (7075-7075 and 2024-2024) and mixed joints (7075-2024). No specimens failed during the test. It was observed that the lower the hardness, the more anodic the corrosion potential. In these zones an intense localized attack takes place in the HAZ due to the presence of precipitates. No systematic correlations between the parameters and the resistance to corrosion were observed. The presence of preferential corrosion sites was confirmed also by means of long time immersion tests

Hydrogen Embrittlement and Diffusion in High Strength Low Alloyed Steels with Different Microstructures

The paper deals with the effect of microstructure on the hydrogen diffusion in traditional ferritic-pearlitic HSLA steels and new high strength steels, with tempered martensite microstructures or banded ferritic-bainitic-martensitic microstructures. Diffusivity was correlated to the hydrogen embrittlement resistance of steels, evaluated by means of slow strain rate tests. </p

The Market Reaction to the Appointment of Women on Corporate Boards: Evidence from the Italian Listed Companies

During the 2012-2016 period, a large number of Italian companies appointed women directors in their boards, an unusual and unpredictable fact in the Italian industrial system. This paper investigates if any significant reaction has consequently occurred in the Italian stock market. It assumes that a significant market reaction would indicate the investors view the female board members as a strategic value added at the decision making level. To achieve the objective, it was collected a database consisting of 76 appointments of women directors in 67 Italian listed companies over the period 2012-2016 and then it was investigated the stock price performance of those companies in that five years span. The research hypothesis is examined empirically through the event study methodology in order to check the existence of abnormal returns on the appointment of women directors. Findings suggest that investors do not strongly believe that the simple appointment of women directors would have a positive effect on the future performance of firms

Eu( iii )-doped calcium molybdate nano- and microstructures: microfluidic synthesis and morphology tuning via solvent dielectric constant and viscosity control

A novel and green microfluidic approach was employed for the synthesis of undoped and Eu(III)-doped calcium molybdate at room and low temperatures. The controlled formation of nano- and microstructures was successfully achieved by tuning the nucleation and growth stages of particle formation through a systematic variation of the viscosity and dielectric constant of the reaction medium, i.e. water and ethanol in different weight ratios and at different temperatures. Thanks to the inherent advantages of the microfluidic approach in terms of mass transport, mixing and heat exchange, it was possible to carry out the reaction at low temperature (-4 degrees C) in an effective manner and to further control the reaction conditions to achieve the formation of small and monodisperse nanoparticles. The synthesised nano- and microstructures, displaying different morphologies depending on reaction conditions, were investigated from a structural (XRD), dimensional and morphological (TEM, SEM), compositional (ICP-MS), and functional (photoluminescence) point of view. The remarkable photoluminescence properties of pure and Eu(III)-doped calcium molybdate structures proved that they are promising materials to be employed as phosphors

Risk factors and outcome among a large patient cohort with community-acquired acute hepatitis C in Italy

BACKGROUND: The epidemiology of acute hepatitis C has changed during the past decade in Western countries. Acute HCV infection has a high rate of chronicity, but it is unclear when patients with acute infection should be treated. METHODS: To evaluate current sources of hepatitis C virus (HCV) transmission in Italy and to assess the rate of and factors associated with chronic infection, we enrolled 214 consecutive patients with newly acquired hepatitis C during 1999-2004. The patients were from 12 health care centers throughout the country, and they were followed up for a mean (+/- SD) period of 14+/-15.8 months. Biochemical liver tests were performed, and HCV RNA levels were monitored. RESULTS: A total of 146 patients (68%) had symptomatic disease. The most common risk factors for acquiring hepatitis C that were reported were intravenous drug use and medical procedures. The proportion of subjects with spontaneous resolution of infection was 36%. The average timespan from disease onset to HCV RNA clearance was 71 days (range, 27-173 days). In fact, 58 (80%) of 73 patients with self-limiting hepatitis experienced HCV RNA clearance within 3 months of disease onset. Multiple logistic regression analyses showed that none of the variables considered (including asymptomatic disease) were associated with increased risk of developing chronic hepatitis C. CONCLUSIONS: These findings underscore the importance of medical procedures as risk factors in the current spread of HCV infection in Italy. Because nearly all patients with acute, self-limiting hepatitis C - both symptomatic and asymptomatic - have spontaneous viral clearance within 3 months of disease onset, it seems reasonable to start treatment after this time period ends to avoid costly and useless treatment

Environmentally assisted cracking of pipeline steels in CO2 containing environment at near-neutral pH

The paper summarizes the results obtained by authors concerning near-neutral stress corrosion cracking (SCC) phenomena on buried pipelines. Stress corrosion tests according to different methodologies and fatigue propagation tests were executed on traditional steel grades. Tests were performed also on specimens precorroded according to a procedure developed to produce localized attacks similar to those observed during failure analysis on pipelines, acting as preferential sites for crack nucleation. Electrochemical tests were carried out in order to evaluate the influence of environmental parameter on pit formation. The main role of continuous plastic deformations on near-neutral SCC is confirmed. The effect of pH, CO2, and bicarbonate concentrations on pitting formation is discussed

An efficient synthesis of bio-based Poly(urethane-acrylate) by SiO2-Supported CeCl3·7H2O–NaI as recyclable Catalyst

Poly(urethane-acrylates) (PUAs) are UV-curable resins used for biomedical applications, coatings, adhesives, and many others. Their syntheses usually involve the use of aromatic diisocyanates and polyols coming from fossil-based resources, in the presence of tin-based catalysts, which present a very well-known toxicity. In the last years the increase of environmental and economic issues related to the depletion of limited sources, the increase of greenhouse gas emissions, the release of toxic degradation compounds and the catalyst contamination has shifted the attention toward more sustainable solutions. In this study a low-impact, sustainable and efficient procedure for the synthesis of bio-based PUA promoted by solid supported CeCl3·7H2O–NaI/SiO2 was developed. This catalytic system provides the target compounds with good monomer conversion and molecular weights and allow the synthesis under heterogeneous conditions as main advantage, with the final recovery of the catalyst. We also confirmed its rapid separation, stability, and efficient recycling of the catalyst, obtaining comparable results over a seven reactions cycles. The goodness of the polymerization process under heterogeneous condition was confirmed by chemical and thermal characterizations

Angiotensin receptor I stimulates osteoprogenitor proliferation through TGFβ-mediated signaling:AT1R SIGNALING IN OSTEOBLAST DIFFERENTIATION

Clinical studies of large human populations and pharmacological interventions in rodent models have recently suggested that anti-hypertensive drugs that target angiotensin II (Ang II) activity may also reduce loss of bone mineral density. Here, we identified in a genetic screening the Ang II type I receptor (AT1R) as a potential determinant of osteogenic differentiation and, implicitly, bone formation. Silencing of AT1R expression by RNA interference severely impaired the maturation of a multipotent mesenchymal cell line (W20-17) along the osteoblastic lineage. The same effect was also observed after the addition of the AT1R antagonist losartan but not the AT2R inhibitor PD123,319. Additional cell culture assays traced the time of greatest losartan action to the early stages of W20-17 differentiation, namely during cell proliferation. Indeed, addition of Ang II increased proliferation of differentiating W20-17 and primary mesenchymal stem cells and this stimulation was reversed by losartan treatment. Cells treated with losartan also displayed an appreciable decrease of activated (phosphorylated)-Smad2/3 proteins. Moreover, Ang II treatment elevated endogenous transforming growth factor β (TGFβ) expression considerably and in an AT1R-dependent manner. Finally, exogenous TGFβ was able to restore high proliferative activity to W20-17 cells that were treated with both Ang II and losartan. Collectively, these results suggest a novel mechanism of Ang II action in bone metabolism that is mediated by TGFβ and targets proliferation of osteoblast progenitors