Conversão para Why3 de formalizações em Coq

Dissertação de mestrado integrado em Informatics EngineeringO presente documento consiste no relatório da dissertação que descreve todo o trabalho desenvolvido no âmbito do projeto “Conversão para Why3 de Formalizações em Coq”. Este trabalho tem como objetivo principal a conversão das definições de alguns algoritmos funcionais, bem como as suas provas, desenvolvidas em Coq, para Why3. Ou seja, utilizar as duas linguagens do Why3 para perceber até que ponto é possível formalizar algoritmos definidos em Coq. Estas formalizações pertencem ao livro da “Software Foundations” sobre algoritmos funcionais. Este demonstra como uma variedade de algoritmos fundamentais podem ser especificados e verificados mecanicamente. Através da conversão de três algoritmos diferentes foi possível perceber que o Why3 apresenta uma linguagem bastante versátil. Este revela ser possível sem grandes dificuldades a conversão das formalizações Coq para a sua linguagem, principalmente utilizando a sua linguagem de programas, WhyML. A intenção, para além da definição, é também explorar o tipo de provas que as duas linguagens (lógica e de programas) do Why3 permitem realizar. Na linguagem de programas, as provas são extremamente simples, conseguidas, na sua grande maioria, através apenas dos solvers automáticos. Na linguagem lógica do Why3 é possível realizar algumas provas indutivas recorrendo às transformações de prova. No entanto, estas ficam restritas apenas às provas que utilizem a indução estrutural. O mais natural é utilizar a linguagem de programas, pois nesta a prova indutiva é automática e segue a estrutura da definição da função, não sendo necessário a definição de princípios de indução. Comparando as duas linguagens do Why3, a linguagem de programas é efetivamente mais interessante que a linguagem lógica.The present document is the dissertation report that describes all the work developed in the scope of the project "Conversion of Coq Formalizations to Why3". This work has as main objective the conversion of the definitions of some functional algorithms, as well as their proofs, developed in Coq, to Why3. That is, to use the two languages of Why3 to realize to what extent it is possible to formalize algorithms defined in Coq. These formalizations belong to the "Software Foundations"book on functional algorithms. This demonstrates how a variety of fundamental algorithms can be specified and verified mechanically. Through the conversion of three different algorithms it was possible to see that Why3 is a very versatile language. It shows that it is possible to convert Coq formalizations to its language without too much difficulty, especially using its program language, WhyML. The intention, beyond the definition, is also to explore the kind of proofs that the two languages (logical and program) of Why3 allow one to perform. In the program language, proofs are extremely simple, achieved, for the most part, through just the automatic solvers. In the Why3 logic language it is possible to perform some inductive proofs using proof transformations. However, these are restricted only to proofs that use structural induction. It is more natural to use the program language, because in this language the inductive proof is automatic and follows the structure of the function definition, without the need to define induction principles. Comparing the two Why3 languages, the program language is actually more interesting than the logical language

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved

Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries

© 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods: This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov, NCT03471494. Findings: Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation: Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding: National Institute for Health Research Global Health Research Unit

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

© 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licenseBackground: Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide. Methods: A multimethods analysis was performed as part of the GlobalSurg 3 study—a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital. Findings: Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3·85 [95% CI 2·58–5·75]; p<0·0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63·0% vs 82·7%; OR 0·35 [0·23–0·53]; p<0·0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer. Interpretation: Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised. Funding: National Institute for Health and Care Research