On Lie Algebras Generated by Few Extremal Elements

We give an overview of some properties of Lie algebras generated by at most 5 extremal elements. In particular, for any finite graph {\Gamma} and any field K of characteristic not 2, we consider an algebraic variety X over K whose K-points parametrize Lie algebras generated by extremal elements. Here the generators correspond to the vertices of the graph, and we prescribe commutation relations corresponding to the nonedges of {\Gamma}. We show that, for all connected undirected finite graphs on at most 5 vertices, X is a finite-dimensional affine space. Furthermore, we show that for maximal-dimensional Lie algebras generated by 5 extremal elements, X is a point. The latter result implies that the bilinear map describing extremality must be identically zero, so that all extremal elements are sandwich elements and the only Lie algebra of this dimension that occurs is nilpotent. These results were obtained by extensive computations with the Magma computational algebra system. The algorithms developed can be applied to arbitrary {\Gamma} (i.e., without restriction on the number of vertices), and may be of independent interest.Comment: 19 page

Cross-layer Optimization for Video Delivery over Wireless Networks

As video streaming is becoming the most popular application of Internet mo- bile, the design and the optimization of video communications over wireless networks is attracting increasingly attention from both academia and indus- try. The main challenges are to enhance the quality of service support, and to dynamically adapt the transmitted video streams to the network condition. The cross-layer methods, i.e., the exchange of information among different layers of the system, is one of the key concepts to be exploited to achieve this goals. In this thesis we propose novel cross-layer optimization frameworks for scalable video coding (SVC) delivery and for HTTP adaptive streaming (HAS) application over the downlink and the uplink of Long Term Evolution (LTE) wireless networks. They jointly address optimized content-aware rate adaptation and radio resource allocation (RRA) with the aim of maximiz- ing the sum of the achievable rates while minimizing the quality difference among multiple videos. For multi-user SVC delivery over downlink wireless systems, where IP/TV is the most representative application, we decompose the optimization problem and we propose the novel iterative local approxi- mation algorithm to derive the optimal solution, by also presenting optimal algorithms to solve the resulting two sub-problems. For multiple SVC de- livery over uplink wireless systems, where healt-care services are the most attractive and challenging application, we propose joint video adaptation and aggregation directly performed at the application layer of the transmit- ting equipment, which exploits the guaranteed bit-rate (GBR) provided by the low-complexity sub-optimal RRA solutions proposed. Finally, we pro- pose a quality-fair adaptive streaming solution to deliver fair video quality to HAS clients in a LTE cell by adaptively selecting the prescribed (GBR) of each user according to the video content in addition to the channel condi- tion. Extensive numerical evaluations show the significant enhancements of the proposed strategies with respect to other state-of-the-art frameworks

Sugli spazi pubblici: discorsi sulla sfera pubblica della città contemporanea

The purpose of this research is to single out new requisites for the public space project, that are suitable to promote acknowledgment of the public dimension of urban space and to reveal the unexpressed potential of the marginal spaces of contemporary city. New interpretations of urban dynamics might suggest fresh resources for the city project and stimulate a renewal of project-work which could give back to public space its political and relational dimension. The aim of this PhD Thesis is to explore the “publicness” of contemporary city. Several scholars argue that most discourses about urban public sphere are focused on the inner city and on the decline of public space, but few attention has been paid on the vitality of alternative and marginal spaces in the urban field. Starting from the recognition of the crucial concept of public and its different meanings, this research analyses the concept of decline of public space and the contemporary need to rethinking public space. This thesis suggests some ways of thinking contemporary public space, its perception and transformation processes. Relationship between public sphere and public space will be discussed by means of the main approaches provided by the scientific literature: the decline of the public sphere, the illusion of the public life, the renaissance of the public space and the utopia of the public space project. Analysing the main discourses on the urban public sphere it will be possible to identify weakness and strengths into the literature on this topic on which to focalize next research activities

The relativity experiment of MORE: global full-cycle simulation and results

BepiColombo is a joint ESA/JAXA mission to Mercury with challenging objectives regarding geophysics, geodesy and fundamental physics. In particular, the Mercury Orbiter Radioscience Experiment (MORE) intends, as one of its goals, to perform a test of General Relativity. This can be done by measuring and constraing the post-Newtonian (PN) parameters to an accuracy significantly better than current one. In this work we perform a global full-cycle simulation of the BepiColombo Radio Science Experiments (RSE) in a realistic scenario, focussing on the relativity experiment but solving simultaneously for all the parameters of interest for RSE in a global least squares fit within a constrained multiarc strategy. The results on the achievable accuracy for each PN parameter will be presented and discussed

La Storia della Facoltà di Architettura

La Facoltà di Architettura di Alghero, istituita con decreto del rettore Alessandro Maida il 24 maggio 2001, nasce con l’obiettivo di attivare un centro studi sull’urbanesimo mediterraneo originato dall’alleanza delle università dell’area del Mediterraneo occidentale (Università di Sassari e Cagliari per la Sardegna, Università di Corte per la Corsica, Università di Maiorca per le Isole Baleari). In un decennio di attività, la Facoltà è già divenuta un polo di eccellenza per l’alta formazione, al servizio delle comunità locali e in funzione del loro sviluppo, mentre il CENSIS la valuta come migliore Facoltà di Architettura d’Italia per produttività, didattica, ricerca e rapporti con l’estero

A Prospective Cohort Analysis of the Prevalence and Predictive Factors of Delayed Discharge After Laparoscopic Cholecystectomy in Italy: The DeDiLaCo Study

Background: the concept of early discharge ≤24 hours after laparoscopic cholecystectomy (LC) is still doubted in italy. this prospective multicentre study aims to analyze the prevalence of patients undergoing elective LC who experienced a delayed discharge >24 hours in an extensive Italian national database and identify potential limiting factors of early discharge after LC. methods: this is a prospective observational multicentre study performed from january 1, 2021 to december 31, 2021 by 90 Italian surgical units. results: a total of 4664 patients were included in the study. clinical reasons were found only for 850 patients (37.7%) discharged >24 hours after LC. after excluding patients with nonclinical reasons for delayed discharge >24 hours, 2 groups based on the length of hospitalization were created: the early group (≤24 h; 2414 patients, 73.9%) and the delayed group (>24 h; 850 patients, 26.1%). at the multivariate analysis, ASA III class (P<0.0001), charlson's comorbidity index (P=0.001), history of choledocholithiasis (P=0.03), presence of peritoneal adhesions (P<0.0001), operative time >60 min (P<0.0001), drain placement (P<0.0001), pain (P=0.001), postoperative vomiting (P=0.001) and complications (P<0.0001) were independent predictors of delayed discharge >24 hours. conclusions: the majority of delayed discharges >24 hours after LC in our study were unrelated to the surgery itself. ASA class >II, advanced comorbidity, the presence of peritoneal adhesions, prolonged operative time, and placement of abdominal drainage were intraoperative variables independently associated with failure of early discharge

Factors influencing delayed discharge after day-surgery laparoscopic cholecystectomy: the DeDiLaCo study protocol

OBJECTIVE: Laparoscopic cholecystectomy (LC) is the gold standard for most benign gallbladder diseases. Early discharge (<24 hours) has the same outcomes as longer (>24 hours) hospital stay. Nevertheless, the rate of delayed discharge >24 hours range from 4.6% to 37%. The primary endpoint of this Italian nationwide study is to analyze the prevalence of patients undergoing elective LC who experienced a delayed discharge >24 hours and identify potential limiting factors of early discharge. Results from these analyses will be used to select patients who can be safely discharged on the same day after surgery. Secondary endpoints will be to evaluate the patient’s quality of life (QoL), assess the direct health costs associated with late discharge, and quantify the patient’s involvement in the treatment process. PATIENTS AND METHODS: This prospective, observational study was conducted following a resident-led model and the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) guidelines. All patients were treated according to the local hospital protocol and received routine care as standard therapy. RESULTS: We expected to obtain the enrollment of at least 500 patients based on an assumed difference in discharge delay between the reference and the recruitable population of 6% and the identification of factors related to discharge failure within 24 h. Early discharge after LC leads to advantages both in terms of clinical outcomes and quality of life of the patient, and it is highly effective in terms of health costs and shortening the waiting list. However, clinical reality differs from the results of randomized studies by a complex series of non-objectionable real-world data influencing treatment plans. Therefore, we expected to identify independent predictors and factors of failure of early discharge. CONCLUSIONS: Clinical reality often differs from randomized trial results. In Italy, the vast majority of delayed discharges after LC may not be related to surgery and can be prevented both with logistical reorganization and with a readjustment of the trust reimbursement policies

Neoplasie neuroendocrine del pancreas serotonina positive: correlazione imaging – anatomia patologica

Analisi delle caratteristiche radiologiche delle neoplasie neuroendocrine pancreatiche serotonina positive

A Prospective Cohort Analysis of the Prevalence and Predictive Factors of Delayed Discharge After Laparoscopic Cholecystectomy in Italy: The DeDiLaCo Study

Background: The concept of early discharge ≤24 hours after Laparoscopic Cholecystectomy (LC) is still doubted in Italy. This prospective multicentre study aims to analyze the prevalence of patients undergoing elective LC who experienced a delayed discharge >24 hours in an extensive Italian national database and identify potential limiting factors of early discharge after LC. Methods: This is a prospective observational multicentre study performed from January 1, 2021 to December 31, 2021 by 90 Italian surgical units. Results: A total of 4664 patients were included in the study. Clinical reasons were found only for 850 patients (37.7%) discharged >24 hours after LC. After excluding patients with nonclinical reasons for delayed discharge >24 hours, 2 groups based on the length of hospitalization were created: the Early group (≤24 h; 2414 patients, 73.9%) and the Delayed group (>24 h; 850 patients, 26.1%). At the multivariate analysis, ASA III class ( P <0.0001), Charlson's Comorbidity Index (P=0.001), history of choledocholithiasis (P=0.03), presence of peritoneal adhesions (P<0.0001), operative time >60 min (P<0.0001), drain placement (P<0.0001), pain ( P =0.001), postoperative vomiting (P=0.001) and complications (P<0.0001) were independent predictors of delayed discharge >24 hours. Conclusions: The majority of delayed discharges >24 hours after LC in our study were unrelated to the surgery itself. ASA class >II, advanced comorbidity, the presence of peritoneal adhesions, prolonged operative time, and placement of abdominal drainage were intraoperative variables independently associated with failure of early discharge