Some Developments in Flexible Regression Modelling

In this thesis we focus on the exible regression modelling with several applications to the insurance eld. We give our contribution to the exible regression modelling by the introduction and validation of some new models. As our aim was to give a contribution useful from the point of view of an insurance company, we did not focus only on theoretical aspects, but we also took care of practical ones. We rst introduce the class of exible regression models, highlighting strengths and drawbacks arising in their practical use, with the aim of pro- vide the tools necessary to the sequent steps. We then introduced GeDS model, a non-parametric approach that is based on a geometrical interpretation of the placement of the knots of a polynomial spline. We show that this model, in some cases, is able to out- perform other exible models. Some properties of the estimates obtained via GeDS regression are then studied, by setting the framework to obtain asymptotically correct con - dence intervals and a consistent version of the likelihood ratio test. Some e orts were also spent in order implement in statistical software this regression model. Hence we explain the features of the software devel- oped. In this thesis we present also an application of exible regression models in non-life ratemaking. We developed some models that can be applied in this framework, returning estimates as accurate as possible, but, at the same time, simple and understandable. We introduce some models that combine together other more simple ones and we show their performances through simulation studies based rst on a theoretical example and then on a more realistic one. We found that they perform better than other models adopted in common practice. Simulation studies are applied also for this purposeopenDottorato di ricerca in Scienze manageriali e atturialiopenLattuada, Andre

Shared Arrangements: practical inter-query sharing for streaming dataflows

Current systems for data-parallel, incremental processing and view maintenance over high-rate streams isolate the execution of independent queries. This creates unwanted redundancy and overhead in the presence of concurrent incrementally maintained queries: each query must independently maintain the same indexed state over the same input streams, and new queries must build this state from scratch before they can begin to emit their first results. This paper introduces shared arrangements: indexed views of maintained state that allow concurrent queries to reuse the same in-memory state without compromising data-parallel performance and scaling. We implement shared arrangements in a modern stream processor and show order-of-magnitude improvements in query response time and resource consumption for interactive queries against high-throughput streams, while also significantly improving performance in other domains including business analytics, graph processing, and program analysis

Verus: Verifying Rust Programs using Linear Ghost Types (extended version)

The Rust programming language provides a powerful type system that checks linearity and borrowing, allowing code to safely manipulate memory without garbage collection and making Rust ideal for developing low-level, high-assurance systems. For such systems, formal verification can be useful to prove functional correctness properties beyond type safety. This paper presents Verus, an SMT-based tool for formally verifying Rust programs. With Verus, programmers express proofs and specifications using the Rust language, allowing proofs to take advantage of Rust's linear types and borrow checking. We show how this allows proofs to manipulate linearly typed permissions that let Rust code safely manipulate memory, pointers, and concurrent resources. Verus organizes proofs and specifications using a novel mode system that distinguishes specifications, which are not checked for linearity and borrowing, from executable code and proofs, which are checked for linearity and borrowing. We formalize Verus' linearity, borrowing, and modes in a small lambda calculus, for which we prove type safety and termination of specifications and proofs. We demonstrate Verus on a series of examples, including pointer-manipulating code (an xor-based doubly linked list), code with interior mutability, and concurrent code

Protective effects of Vitamin D3 on fimbrial cells exposed to catalytic iron damage

BACKGROUND: Recently, vitamin D3 (1alpha, 25-dihydroxyvitamin D) has shown its capability to take part in many extraskeletal functions and its serum levels have been related to patient survival rate and malignancy of many types of neoplasms, including ovarian cancers. Catalytic iron is a free circulating form of iron that is able to generate reactive oxygen species and consequently to promote a number of cellular and tissutal dysfunctions including tumorigenesis. In fertile women an important source of catalytic iron is derived from retrograde menstruation. Epithelial secretory cells from fimbriae of fallopian tubes are greatly exposed to catalytic iron derived from menstrual reflux and so represent the site of origin for most serous ovarian cancers. The aim of this study was to assess whether vitamin D3 can play a role in counteracting catalytic iron-induced oxidative stress in cells from fimbriae of fallopian tubes. METHODS: The cells, isolated from women undergoing isteroannessiectomy, were treated with catalytic iron 50-75-100 mM and vitamin D3 at a concentration ranging from 0.01 to 10 nM to study cell viability, radical oxygen species production, p53, pan-Ras, Ki67 and c-Myc protein expressions through Western Blot, and immunocytochemistry or immunofluorescence analysis. RESULTS: The pre-treatment with vitamin D3 1 nM showed its beneficial effects that consists in a significant decrease in ROS production. In addition a novel finding is represented by the demonstration that pre-treatment with vitamin D3 is also able to significantly counteract tumoral biomarkers activation, such as p53, pan-Ras, Ki67 and c-Myc, and consequently the catalytic iron-induced cellular injury. CONCLUSIONS: This study demonstrates for the first time that vitamin D3 plays an important role in preventing catalytic iron-dependent oxidative stress in cultured fimbrial cells. These results support the hypothesis that vitamin D3 could counteract carcinogenic changes induced by catalytic iron

Effects of Prone Position and Positive End-Expiratory Pressure on Noninvasive Estimators of ICP: A Pilot Study.

BACKGROUND: Prone positioning and positive end-expiratory pressure can improve pulmonary gas exchange and respiratory mechanics. However, they may be associated with the development of intracranial hypertension. Intracranial pressure (ICP) can be noninvasively estimated from the sonographic measurement of the optic nerve sheath diameter (ONSD) and from the transcranial Doppler analysis of the pulsatility (ICPPI) and the diastolic component (ICPFVd) of the velocity waveform. METHODS: The effect of the prone positioning and positive end-expiratory pressure on ONSD, ICPFVd, and ICPPI was assessed in a prospective study of 30 patients undergoing spine surgery. One-way repeated measures analysis of variance, fixed-effect multivariate regression models, and receiver operating characteristic analyses were used to analyze numerical data. RESULTS: The mean values of ONSD, ICPFVd, and ICPPI significantly increased after change from supine to prone position. Receiver operating characteristic analyses demonstrated that, among the noninvasive methods, the mean ONSD measure had the greatest area under the curve signifying it is the most effective in distinguishing a hypothetical change in ICP between supine and prone positioning (0.86±0.034 [0.79 to 0.92]). A cutoff of 0.43 cm was found to be a best separator of ONSD value between supine and prone with a specificity of 75.0 and a sensitivity of 86.7. CONCLUSIONS: Noninvasive ICP estimation may be useful in patients at risk of developing intracranial hypertension who require prone positioning.DC and MC are partially supported by NIHR Brain Injury Healthcare Technology Co-operative, Cambridge, UK. JD is supported by a Woolf Fisher Scholarship (NZ)

Colorectal cancer after bariatric surgery (Cric-Abs 2020): Sicob (Italian society of obesity surgery) endorsed national survey

Background The published colorectal cancer (CRC) outcomes after bariatric surgery (BS) are conflicting, with some anecdotal studies reporting increased risks. The present nationwide survey CRIC-ABS 2020 (Colo-Rectal Cancer Incidence-After Bariatric Surgery-2020), endorsed by the Italian Society of Obesity Surgery (SICOB), aims to report its incidence in Italy after BS, comparing the two commonest laparoscopic procedures-Sleeve Gastrectomy (SG) and Roux-en-Y gastric bypass (GBP). Methods Two online questionnaires-first having 11 questions on SG/GBP frequency with a follow-up of 5-10 years, and the second containing 15 questions on CRC incidence and management, were administered to 53 referral bariatric, high volume centers. A standardized incidence ratio (SIR-a ratio of the observed number of cases to the expected number) with 95% confidence intervals (CI) was calculated along with CRC incidence risk computation for baseline characteristics. Results Data for 20,571 patients from 34 (63%) centers between 2010 and 2015 were collected, of which 14,431 had SG (70%) and 6140 GBP (30%). 22 patients (0.10%, mean age = 53 +/- 12 years, 13 males), SG: 12 and GBP: 10, developed CRC after 4.3 +/- 2.3 years. Overall incidence was higher among males for both groups (SG: 0.15% vs 0.05%; GBP: 0.35% vs 0.09%) and the GBP cohort having slightly older patients. The right colon was most affected (n = 13) and SIR categorized/sex had fewer values < 1, except for GBP males (SIR = 1.07). Conclusion Low CRC incidence after BS at 10 years (0.10%), and no difference between procedures was seen, suggesting that BS does not trigger the neoplasm development