Dispersion relations and wave operators in self-similar quasicontinuous linear chains

We construct self-similar functions and linear operators to deduce a self-similar variant of the Laplacian operator and of the D'Alembertian wave operator. The exigence of self-similarity as a symmetry property requires the introduction of nonlocal particle-particle interactions. We derive a self-similar linear wave operator describing the dynamics of a quasicontinuous linear chain of infinite length with a spatially self-similar distribution of nonlocal interparticle springs. The self-similarity of the nonlocal harmonic particle-particle interactions results in a dispersion relation of the form of a Weierstrass-Mandelbrot function that exhibits self-similar and fractal features. We also derive a continuum approximation, which relates the self-similar Laplacian to fractional integrals, and yields in the low-frequency regime a power-law frequency-dependence of the oscillator density

Oesophageal cancer surgery : predictors of health-related quality of life and survival

Oesophageal cancer is a devastating disease with a bleak prognosis. Only 25% of patients are eligible for surgery which is afflicted with 15% postoperative complications an overall 5-year survival of 30-50%. In the short term patients’ health- related quality of life (HRQOL) is highly deteriorated and postoperative complications contribute to this impairment. This thesis aims at shedding light on the recovery of HRQOL in the longer term and indicators of HRQOL and survival. Study I and II were based on a prospective nationwide cohort of oesophageal cancer patients operated on between 2001-2005 and followed up postoperatively with the HRQOL questionnaires EORTC QLQ-C30 and the oesophageal-specific module EORTC QLQ-OES18 and included 5-year survivors. Study I investigated postoperative HRQOL changes over time and compared to the general population. HRQOL outcomes seemed to recover; however, a subgroup of patients still suffered poor HRQOL in the longer term. Study II examined the effect of major postoperative complications on long-term HRQOL and found that the negative impact of these complications is long-standing. Study III and IV were retrospective nationwide cohort studies of oesophageal cancer patients who underwent surgery between1987-2005. Study III investigated whether the experience of the hospital or surgeon with oesophageal cancer influenced prognosis. The amount of operations performed by the hospital was not associated with mortality in the short or long term. Patients who were operated on by a surgeon who had performed more such operations over time and operated frequently had the lowest short-term mortality. Study IV examined the determinants of splenic injury and unintended splenectomy during surgery and its influence on prognosis and severe infections. Experienced surgeons (described above) had less risk of both injuring the spleen and conducting unintended splenectomy. Accidental splenectomy was followed by an increased risk of overall mortality and of sepsis or meningitis. In conclusion, for each HRQOL outcome some oesophageal cancer surgery survivors do not recover and postoperative complications exert a long-lasting negative effect in HRQOL. Patients operated on by experienced surgeons have an increased risk of survival and a decreased risk of splenic injury and accidental splenectomy. Accidental splenectomy confers an increased risk of mortality and severe infections

Investigating the governing factors influencing the pozzolanic activity through a database approach for the development of sustainable cementitious materials

Pozzolans, known to possess high pozzolanic activity, enhances the long-term engineering properties of concrete due to the consumption of calcium hydroxide and the consequent formation of the calcium-silicate-hydrate gels within the cementitious matrix. Although the key factors that affect the pozzolanic activity such as the chemical composition, amorphousness, and fineness are commonly addressed in literature, there is a growing need to further gain an insight into the factors that govern this activity in a more comprehensive approach. The aim of this empirical study is to develop concrete models comprising optimal replacement of pozzolans based on the governing factors affecting the activity through the database approach. The database, consisting of 631 number of data points harvested from the literature, is established to determine the optimum replacement levels of the designated pozzolans in concrete. The governing factors therefore played a key role in establishing the boundary conditions that enabled the potential concrete models to be generated particularly for the sustainability assessment of concrete incorporating pozzolans. The study shows that the optimum replacement levels in con- crete mixtures are 15–50% for GGBS, 10–35% for fly ash, and 5–15% for silica fume. The study furthermore demonstrated that the utilisation of these substitutions leaded a considerable reduction in carbon emissions that ranged from 13% to 43% for GGBS, 9–31% for fly ash, and 4–13% for silica fume. The study significantly contributes to the generation of greener construction materials, and offers a cleaner disposal route for the pozzolans principally compared to the traditional waste management alternatives

The long-term engineering properties and sustainability indices of dewatering hydrated lime mortars through Jacaranda seed pods

The progressive increase in the industrialisation, consequently the energy consumption and carbon footprint reacquaint the sustainable and environmental credentials of hydrated lime mortars and re-congregate the implications of such binders in masonry construction. The low water retaining characteristics of hydrated lime mortars that often results in insufficient bond development with the subsequent substrate, were manipulated through the incorporation of powdered Jacaranda seed pods and silica fume to establish mortar-masonry optimisation in practice. Although there are numerous studies addressing the agricultural waste incorporation in cement-based materials, the incorporation of Jacaranda seed pods on construction materials have not been reported in the literature. Characterisation study comprising the elemental composition and physical properties of Jacaranda seed pods were essential in assessing the compatibility of pods utilisation in hydrated lime mortars. The paper reports authentic experimental research results on the utilisation of Jacaranda seed pods as a binder substitute in hydrated lime mortars concerning the effect of dewatering on the long-term engineering properties and sustainability indices. The utilisation of powdered Jacaranda seed pods and silica fume demonstrated the eligibility of manipulating the strong water retaining characteristics of hydrated lime mortars to attain improved mortar-substrate optimisation in masonry construction. It is essentially shown in the paper that the degree of dewatering, governed by the incorporation of powdered Jacaranda seed pods and silica fume herein, could not be underestimated as this phenomenon yields approximately 18% increase in the compressive strength of hydrated lime mortars comprising both at short- and long-terms. Although the incorporation of both the powdered Jacaranda seed pods and silica fume decreased the water penetration depth and porosity of mortars by ~11% and 17% respectively, dewatering, an inevitable incident that occurs as soon as the freshly mixed mortars are placed on dry absorbent substrates, further yields a greater decrease in these physical measurements at 1 year. Incorporation of powdered Jacaranda seed pods and silica fume generated a crucial improvement on cost efficiency and eco-strength efficiency of mortars both at 91 days and 1 year. The results have shown that more than 30% reduction on the carbon footprint could be established through this practice. It is essentially established in the paper that the degree of dewatering, experienced at freshly-mixed stage, determines the authentic performance of hydrated lime mortars in masonry construction and governs the veritable sustainability analysis to be performed. The results reported in this paper does not only encourage the re-introduction of the hydrated lime binder in construction practice but also assert a cleaner alternative waste management route for the agricultural wastes

Factors affecting the CO2 emissions, cost efficiency and eco-strength efficiency of concrete containing rice husk ash: A database study

The agriculture industry has grown dramatically by about three times over the last 50 years due to the rapid population growth, improvements in green production technology and agricultural land development. Rice is the second most-consumed agricultural product globally. The rice husk ash (RHA), attained by burning the husk that is removed in the process of rice production, possesses high pozzolanic activity and therefore is a promising supplementary cementitious material. Despite the numerous studies on the successful incorporation of RHA in concrete in the literature, a comprehensive assessment on the sustainability aspects of these practices has not yet been solely and exclusively addressed. The paper reports findings from the analysis of a large database on the RHA incorporation in concrete. Principal sustainability components such as CO2 emissions, cost efficiency and eco-strength efficiency are described. The database, comprising over 1000 data points has been utilized to assess the key factors that have significant influences on the mechanical properties of concrete comprising RHA using the established set of criteria. Independent determination of the boundary conditions played a vital role in the sustainability assessment. The results showed that the use of RHA along with the other pozzolanic materials can yield a 25% diminution in the CO2 emissions generated during the concrete production in conjunction with a 65% rise in the cost efficiency of such practices. The findings reported in this study demonstrate improved sustainability for construction practice and highlight greener waste management routes that can be established for RHA

Utilisation of waste marble dust for improved durability and cost efficiency of pozzolanic concrete

This study demonstrates that the incorporation of waste marble dust to pozzolanic concrete improves the long-term mechanical properties and durability characteristics. A comprehensive study utilising specimens containing a cement and silica fume binder were manufactured with incremental levels of marble dust fine aggregate. Important physical properties including compressive strength, water penetration depth, porosity, resistance to sulphate attack and resistance to freeze/thaw cycling were evaluated over a period of 1 year. Microstructural development attributed to cement hydration and pozzolanic reaction was imaged at 28 days and 1 year using scanning electron microscopy. The inclusion of marble dust greatly improved the salt crystallization and freeze and thaw resistance of the concrete over the long-term with only a small decrease in compressive strength observed. Importantly this highlights the beneficial properties of marble dust on durability. Additional advantages were shown through cost efficiency analysis which revealed that utilisation of marble dust and silica fume in concrete can reduce the embodied CO2 emissions improving the economic credentials and environmental impact. Marble dust not only improves the physical characteristics but also provides an environmentally friendly route for waste disposal and creation of a more sustainable concrete

Properties, durability and cost efficiency of cement and hydrated lime mortars reusing copper mine tailings of Lefke-Xeros in Cyprus

The unexpected closure of the mine processing area of Lefke-Xeros generated the largest environmental disaster in the recent history of Northern Cyprus. The mining area, formed the biggest industry on the island in 1950s, was unpredictably closed and left all mine tailings and equipment behind without any preservation towards the environmental remediation nor sustainable rehabilitation for the locality. Substantial increase in the cost of energy supply, determination to decrease CO2 emissions and to reduce the consumption of natural materials on the other hand, are the major challenges in construction practice. The paper is investigating the consequences of dewatering by means of recycling copper mine tailings in mortars both for the sustainable development of construction materials and for the socio-economic recovery of Lefke-Xeros area of Cyprus. The degree of dewatering as a consequence of the substrate/mortar interaction on the mechanical and physical properties of cement and lime mortars containing copper tailings are reported in the paper. Physical measurements provided an insight into the actual effect of dewatering on the resistance of freezing and thawing action of mortars containing copper tailings. The use of copper tailings and therefore the degree of dewatering have shown to play a substantial role in the decrease in thermal conductivity and increase in cost efficiency of these mortars in construction practice. The results reported in this paper significantly contribute in the sustainable development of construction materials through the use of mine tailings to support environmental sustainability and socio-economic development of Lefke-Xeros area of Cyprus