7 research outputs found
Alkali Activated Systems: Understanding the Influence of Curing Conditions and Activator Type/Chemistry on the Mechanical Strength and Chemical Structure of Fly Ash/Slag Systems
No full textabstract: The alkali activation of aluminosilicate materials as binder systems derived from industrial byproducts have been extensively studied due to the advantages they offer in terms enhanced material properties, while increasing sustainability by the reuse of industrial waste and byproducts and reducing the adverse impacts of OPC production. Fly ash and ground granulated blast furnace slag are commonly used for their content of soluble silica and aluminate species that can undergo dissolution, polymerization with the alkali, condensation on particle surfaces and solidification. The following topics are the focus of this thesis: (i) the use of microwave assisted thermal processing, in addition to heat-curing as a means of alkali activation and (ii) the relative effects of alkali cations (K or Na) in the activator (powder activators) on the mechanical properties and chemical structure of these systems. Unsuitable curing conditions instigate carbonation, which in turn lowers the pH of the system causing significant reductions in the rate of fly ash activation and mechanical strength development. This study explores the effects of sealing the samples during the curing process, which effectively traps the free water in the system, and allows for increased aluminosilicate activation. The use of microwave-curing in lieu of thermal-curing is also studied in order to reduce energy consumption and for its ability to provide fast volumetric heating. Potassium-based powder activators dry blended into the slag binder system is shown to be effective in obtaining very high compressive strengths under moist curing conditions (greater than 70 MPa), whereas sodium-based powder activation is much weaker (around 25 MPa). Compressive strength decreases when fly ash is introduced into the system. Isothermal calorimetry is used to evaluate the early hydration process, and to understand the reaction kinetics of the alkali powder activated systems. A qualitative evidence of the alkali-hydroxide concentration of the paste pore solution through the use of electrical conductivity measurements is also presented, with the results indicating the ion concentration of alkali is more prevalent in the pore solution of potassium-based systems. The use of advanced spectroscopic and thermal analysis techniques to distinguish the influence of studied parameters is also discussed.Dissertation/ThesisM.S. Engineering 201
Finite Element Based Microstructural Modeling of Cementitious Composites
No full textabstract: This study employs a finite element method based modeling of cementitious composite microstructure to study the effect of presence of inclusions on the stress distribution and the constitutive response of the composite. A randomized periodic microstructure combined with periodic boundary conditions forms the base of the finite element models. Inclusion properties of quartz and light weight aggregates of size 600μm obtained from literature were made use of to study the effect of their material (including inclusion stiffness, stiffness of interfacial transition zone and matrix stiffening) and geometric properties (volume fraction of inclusion, particle size distribution of inclusion and thickness of the interfacial transition zone) on the composite. Traction-separation relationship was used to incorporate the effect of debonding at the interface of the matrix and the inclusion to study the effect on stress distribution in the microstructure. The stress distributions observed upon conducting a finite element analysis are caused due to the stiffness mismatch in both the quartz and the light weight aggregates as expected. The constitutive response of the composite microstructure is found to be in good conformance with semi-analytical models as well as experimental values. The effect of debonding throws up certain important observations on the stress distributions in the microstructure based on the stress concentrations and relaxations caused by the stiffness of the individual components of the microstructure. The study presented discusses the different micromechanical models employed, their applicability and suitability to correctly predict the composite constitutive response.Dissertation/ThesisMasters Thesis Civil Engineering 201
The regulation of commercial banks in Zambia and their role in development
No full textThis work analyses the regulation of commercial banks in
Zambia and its impact on the role that these institutions are
playing in national development. The background to this
analysis is -the conviction that as these institutions control
enormous amounts of resources, or are capable of doing so, then
they need certain incentives to make them available for
investment. These institutions are not using their own money.
Such incentives or inducements therefore must ensure that those
resources are safely invested. The incentives envisaged include
regulations both of the institutions themselves as well as the
economic system. It is these aspects that this work examines.
The work is divided into six basic chapters. The first
chapter is the introduction which makes the case for a role to
be played by commercial banks in development, under proper
regulation. The second chapter gives a historical origin of
banks in Zambia, including the circumstances of existing
commercial banks. Chapter three deals with the regulations
affecting commercial banking. This is basically an outline of
the various statutes enacted in the country since the colonial
days. Chapter four makes the case for the actual relevance or
need for commercial bank involvement in Zambia's economic
development. It sketches out the historical shortage of
resources in investment. Chapter five deals with the actual
role played by banks in Zambia's development, while chapter six
appraises the effect of the regulations on that performance.
The seventh chapter is a summary of the study and the
conclusions reached. The law is stated as it stood in 1985,
although recent developments and laws known to the author are
included
How well do India's social service programs serve the poor?
No full textReaching India's poor calls for greatly improved social service delivery systems, better targeting of the poor, more coordination between agencies, policies aimed at income generation, and more involvement of the poor and of nongovernmental organizations. The authors of this paper found that India's social services were used relatively little by the poor. The health and education of the poor has improved but not as much for the population as a whole. The reasons that all social service programs did so little to alleviate poverty are similar. Physical access to education and health services has improved but inequalities exist because of biases in locating facilities. The access of the poor to housing, social security, and social welfare services has been limited because these services were inadequate relative to needs and because services leak to the nonpoor. Social service policies are not comprehensive enough and the quality of services is low. Issues common to the social sector delivery systems are weak management, ineffective targeting, and inflexible service delivery systems that result in a mismatch between perceived needs and services delivered. The bureaucracy is inadequate to reach the poor. Existing capacity and resources are inadequate, particularly for education and health.Health Monitoring&Evaluation,Health Economics&Finance,Poverty Assessment,Safety Nets and Transfers,Rural Poverty Reduction
The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy
No full textBackground: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p < 0.001), with the proportions of operations lasting > 90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care.</p
Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy
No full textBackground:
A reliable system for grading operative difficulty of laparoscopic cholecystectomy would standardise description of findings and reporting of outcomes. The aim of this study was to validate a difficulty grading system (Nassar scale), testing its applicability and consistency in two large prospective datasets.
Methods:
Patient and disease-related variables and 30-day outcomes were identified in two prospective cholecystectomy databases: the multi-centre prospective cohort of 8820 patients from the recent CholeS Study and the single-surgeon series containing 4089 patients. Operative data and patient outcomes were correlated with Nassar operative difficultly scale, using Kendall’s tau for dichotomous variables, or Jonckheere–Terpstra tests for continuous variables. A ROC curve analysis was performed, to quantify the predictive accuracy of the scale for each outcome, with continuous outcomes dichotomised, prior to analysis.
Results:
A higher operative difficulty grade was consistently associated with worse outcomes for the patients in both the reference and CholeS cohorts. The median length of stay increased from 0 to 4 days, and the 30-day complication rate from 7.6 to 24.4% as the difficulty grade increased from 1 to 4/5 (both p < 0.001). In the CholeS cohort, a higher difficulty grade was found to be most strongly associated with conversion to open and 30-day mortality (AUROC = 0.903, 0.822, respectively). On multivariable analysis, the Nassar operative difficultly scale was found to be a significant independent predictor of operative duration, conversion to open surgery, 30-day complications and 30-day reintervention (all p < 0.001).
Conclusion:
We have shown that an operative difficulty scale can standardise the description of operative findings by multiple grades of surgeons to facilitate audit, training assessment and research. It provides a tool for reporting operative findings, disease severity and technical difficulty and can be utilised in future research to reliably compare outcomes according to case mix and intra-operative difficulty
Análisis de rutas biológicas y estudio de asociación amplia del genoma identificaron factores genéticos del cromosoma 10 asociados con la variación de antocianinas en papa
No full textilustraciones, gráficas, tablasPotato is considered a basic crop worldwide and is the third source of antioxidants in the human diet, due to its per capita consumption. Some of the most relevant antioxidant compounds in potatoes within dietary polyphenols are anthocyanin pigments. The anthocyanin compounds’ synthesis implies a chain of potentially superimposed regulatory signals. Since their synthesis cannot be seen exclusively from the transcription of the genes included in the synthesis of the enzymes involved in the biosynthetic pathway but it is important to consider different allelic variants not associated in the pathway and / or transcription factors that may be playing an important role in the regulation of the synthesis of the enzymes and, therefore, in the production and accumulation of these bioactive compounds in different plant tissues. To approach the understanding of the genetic architecture that controls complex traits such as nutritional quality, specifically the dietary polyphenols compounds. In different species and also in potato, the genome wide association mapping strategy (GWAS) has been implemented, in order to identify genes and sequences that control different traits of agronomic interest, especially quantitative traits to apply in genetic breeding programs. Thus, since regulation and accumulation of bioactive compounds in plants is governed by multiple genes organized within complex biological networks, the genome-wide association study approach presents a limitation does not offer direct evidence about the biological process that link the variant associated with the trait. In this way, the integration of the biological pathway approach is considered in the study of the genetic association of anthocyanin compounds in potatoes. The objective of this research was the integration of allelic variants / genes obtained by a study of wide genome association and allelic variants of genes putatively related in the biosynthetic pathway of anthocyanin compounds. The approach integrating the genetic participation of each associated genomic regions, allowing a biological interpretation of each association. An association panel of 109 Phureja Group diploid potato genotypes was used. which phenotyping for the five-anthocyanin content by means of High Performance Liquid Chromatography (HPLC) and genotyping under the genotyping by sequencing (GBS) methodology with a matrix of 87,657 single nucleotide polymorphic markers. Promising biosinthetic pathway models were established that integrated the gene participation of each associated gene. Promising biosynthetic pathway models were established that integrated the gene involvement of each associated gene. As a result, a region of interest on chromosome 10 was identified, identifying genes associated with the anthocyanin biosynthetic pathway in a 4Mpb region on the final arm of chromosome 10; a marker linked to the phenylalanine ammonia lyase gene, which encodes the first enzyme in the phenylpropanoid biosynthetic pathway, was associated with the five anthocyanin compounds evaluated, explaining the greater phenotypic variation of the trait. The L-methionine biosynthetic pathway was identified as being important for the late anthocyanin pathway. This investigation confirmed genomic regions whose allelic variability is associated with the analyzed compounds and which had previously been detected. It also allowed the identification of other new genomic regions in a “biological pathways” approach complementing existing knowledge. The results contribute to the understanding of anthocyanin regulation in potatoes and can be used in future studies for integration into potato improvement programs.La papa es considerada un cultivo básico a nivel mundial y constituye la tercera fuente de antioxidantes en la dieta humana, debido a su consumo per cápita. Algunos de los compuestos antioxidantes más relevantes en papa dentro de los polifenoles dietarios son los pigmentos antociánicos. La síntesis de los compuestos antociánicos implica una matriz de señales reguladoras potencialmente superpuestas, por lo que, no se puede ver su síntesis exclusivamente a partir de la transcripción de los genes incluidos en la síntesis de las enzimas involucradas en la ruta biosintética, sino que, es importante considerar diferentes variantes alélicas no asociadas en las rutas y/o factores de transcripción que pueden estar desempeñando un papel importante en la regulación y acumulación de estos compuestos en diferentes tejidos vegetales. Para entender la arquitectura genética que gobierna rasgos complejos relacionados con la composición nutricional de los alimentos, como es la composición de antocianinas en diferentes especies y en papa; se han implementado estrategias como los estudios de mapeo de asociación amplia del genoma (GWAS), en programas de mejoramiento genético, con el fin de identificar loci de caracteres cuantitativos asociados al rasgo, para luego aplicar en programas de mejoramiento genético. En el caso de polifenoles dietarios, debido a que su síntesis y acumulación en plantas está regulada por múltiples genes que se organizan dentro de redes biológicas complejas, la metodología de GWAS presenta una limitante y es que no ofrece evidencia directa acerca del proceso biológico que liga la variante asociada con el rasgo. Esta investigación plantea la integración de la aproximación de rutas biológicas “biological pathway” en un estudio de asociación genética de compuestos de antocianinas en papa. El objetivo de esta investigación fue la integración de variantes alélicas/genes obtenidos por un estudio de asociación amplia del genoma y variantes alélicas de genes putativamente relacionados en la ruta biosintética de los compuestos antociánicos, integrando la participación génica de cada una de las regiones genómicas asociadas, permitiendo una interpretación biológica de cada asociación. Para lo cual, se empleó un panel de asociación de 109 genotipos de papa diploide Grupo Phureja, fenotipado para el rasgo del contenido de cinco antocianindinas por medio de cromatografía liquida de alta precisión (HPLC) y, genotipado bajo la metodología de “genotyping by sequencing” con una matriz de 87,657 marcadores polimórficos de un solo nucleótido. Se establecieron modelos de rutas biosintéticas promisorias que integraron la participación génica de cada gen asociado. Como resultado se identificó una región de interés en el cromosoma 10, identificando genes asociados a la ruta biosintética de las antocianinas en una región de 4Mpb en el brazo final del cromosoma 10; un marcador ligado al gen de fenilalanina amoniaco-liasa, que codifica la primera enzima en la ruta biosintética de fenilpropanoides, se asoció a los cinco compuestos antociánicos evaluados explicando la mayor variación fenotípica del rasgo. Se identificó que la ruta biosintética de la L-metionina es importante para la ruta tardía de las antocianinas. Esta investigación confirmó regiones genómicas cuya variabilidad alélica está asociada con los compuestos analizados y que ya previamente habían sido detectadas. También permitió la identificación de otras nuevas regiones genómicas en un enfoque de “rutas biológicas” complementando el conocimiento existente. Los resultados contribuyen a la comprensión de la regulación de las antocianinas en la papa y pueden usarse en futuros estudios para la integración en programas de mejoramiento de papa. (Texto tomado de la fuente).MaestríaMagíster en Ciencias AgrariasGenética y fitomejoramientoCiencias Agronómica
