Characterisation and numerical modelling of the geometry of rock joints

This paper describes the measurement and analysis of the roughness of natural rock joints with the aim of proceeding to their characterisation and comparison. Eight rock joints (corresponding to sixteen surfaces) were scanned with a three-dimensional scanner. This was followed by the description and characterisation of the surface roughness, as well as its reproduction and generation using techniques such as fractal models and Fourier transforms. Shear tests under constant normal load were performed, the joint surfaces were again scanned, and the resulting roughness surfaces were compared allowing the evaluation of asperity breakage and surface wear. One of the joint specimens was tested under several normal stresses, which allowed the estimation of its mechanical characteristics, and was scanned after each test to evaluate the influence of the normal and shear load on the variation of roughness. The scans of the rock joints produced accurate numerical descriptions of their topologies, allowing countless possibilities of future studies, such as the study of the matching of rock joints by the numerical adjustment of bottom and top surfaces, the statistical and geostatistical characterisation of rock joints or the degradation of roughness after normal and shear tests. This paper presents an overview of the research work that is still under way.info:eu-repo/semantics/publishedVersio

Rock joint roughness characterization and numerical modelling

As descontinuidades dos maciços rochosos influenciam o seu comportamento mecânico e hidráulico e consequentemente as obras neles construídas. Este trabalho descreve o desenvolvimento e aplicação de uma técnica de digitalização das superfícies de descontinuidades rochosas que recorre a uma mesa digitalizadora, visando contribuir para a compreensão dos mecanismos de contacto e desgaste. As superfícies numéricas obtidas são analisadas usando parâmetros geo-estatísticos que podem ser comparados com parâmetros semi-empíricos, como o JRC, permitindo quantificar a evolução da rugosidade após ensaios mecânicos de compressão ou deslizamento. Os resultados deste trabalho permitiram ainda a geração de descontinuidades que poderão ser usadas futuramente em modelos micromecânicos de partículas para simular o comportamento mecânico e hidráulico de descontinuidades.info:eu-repo/semantics/publishedVersio

Estudo do contacto e fecho em descontinuidades rochosas através de digitalização tridimensional

As descontinuidades marcam de forma decisiva a deformabilidade e a resistência, mas também a condutividade hidráulica e a transmissão de vibrações em maciços rochosos. Se a medição de certas características do material rochoso é uma tarefa corrente, já a caracterização da topografia das superfícies é difícil de medir e quantificar de forma inequívoca. Trabalhos anteriores empregam métodos de digitalização com e sem contacto e são múltiplas as abordagens para a análise da topografia das paredes de descontinuidades. No entanto, a maioria foca a caracterização individual de cada superfície sem avaliar a interação entre as paredes. Este trabalho apresenta um equipamento facilmente disponível para a digitalização de superfícies rochosas em ambiente laboratorial e o tratamento e análise dos resultados através de algoritmos de ajuste das superfícies e de mapeamento e cálculo de áreas de contacto e volumes de vazio durante o fecho das juntas, tendo-se encontrado resultados interessantes para o estudo das propriedades mecânicas, estáticas e dinâmicas, e da condutibilidade hidráulica.info:eu-repo/semantics/acceptedVersio

Azulejo blues – An analytical study of the blue colours in portuguese azulejos

This communication reviews the main variants of the blue colour found on glazed tiles (mainly of Portuguese manufacture) used in Portugal from the 16th to the late 18th centuries and discusses the composition of the pigments from which they result

The origins of the Selden map of China: scientific analysis of the painting materials and techniques using a holistic approach

Since the 'rediscovery' of the Selden map of China, an early seventeenth century map of Asia, in the Bodleian Library in Oxford, the importance of the map in our understanding of globalisation in the early seventeenth century has been recognised. One of the unresolved questions is the origin of the map. This paper addresses the question through material evidence provided by a holistic approach using a suite of complementary analytical techniques. The map was examined in situ and non-invasively by a remote spectral imaging instrument (PRISMS) modified for close range imaging, which was followed by a range of complementary techniques applied to a number of detached fragments, though most of the techniques are non-invasive and can be applied to the map directly in the future. The binding medium was found to be a gum, almost certainly gum Arabic, rather than the animal glue commonly used in Chinese paintings. Some of the pigments and their usage were found to be at odds with the common practice in paintings from China. The detection of gum Arabic, a binding medium used by the Europeans, South and West Asians and the use of a mixture of orpiment and indigo, commonly found in European, South and West Asian paintings gives further evidence on the unusual origins of this map. The likely detection of a basic copper chloride, such as atacamite, in the green areas suggests an influence from the South and West Asian rather than the European tradition. Detailed analysis of the various spectral bands of the spectral image cube along with visual inspection of the large scale colour image showed that the map was not fully planned at the beginning but rather painted in stages, at times by trial and error and that it was unfinished. A new hypothesis for the origin of the Selden map in Aceh Sumatra is proposed based on the new evidences

Laparoscopy in management of appendicitis in high-, middle-, and low-income countries: a multicenter, prospective, cohort study.

BACKGROUND: Appendicitis is the most common abdominal surgical emergency worldwide. Differences between high- and low-income settings in the availability of laparoscopic appendectomy, alternative management choices, and outcomes are poorly described. The aim was to identify variation in surgical management and outcomes of appendicitis within low-, middle-, and high-Human Development Index (HDI) countries worldwide. METHODS: This is a multicenter, international prospective cohort study. Consecutive sampling of patients undergoing emergency appendectomy over 6 months was conducted. Follow-up lasted 30 days. RESULTS: 4546 patients from 52 countries underwent appendectomy (2499 high-, 1540 middle-, and 507 low-HDI groups). Surgical site infection (SSI) rates were higher in low-HDI (OR 2.57, 95% CI 1.33-4.99, p = 0.005) but not middle-HDI countries (OR 1.38, 95% CI 0.76-2.52, p = 0.291), compared with high-HDI countries after adjustment. A laparoscopic approach was common in high-HDI countries (1693/2499, 67.7%), but infrequent in low-HDI (41/507, 8.1%) and middle-HDI (132/1540, 8.6%) groups. After accounting for case-mix, laparoscopy was still associated with fewer overall complications (OR 0.55, 95% CI 0.42-0.71, p < 0.001) and SSIs (OR 0.22, 95% CI 0.14-0.33, p < 0.001). In propensity-score matched groups within low-/middle-HDI countries, laparoscopy was still associated with fewer overall complications (OR 0.23 95% CI 0.11-0.44) and SSI (OR 0.21 95% CI 0.09-0.45). CONCLUSION: A laparoscopic approach is associated with better outcomes and availability appears to differ by country HDI. Despite the profound clinical, operational, and financial barriers to its widespread introduction, laparoscopy could significantly improve outcomes for patients in low-resource environments. TRIAL REGISTRATION: NCT02179112

Global economic burden of unmet surgical need for appendicitis

Background: There is a substantial gap in provision of adequate surgical care in many low-and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods: Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results: Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion: For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe