A two-stage framework for optical coherence tomography angiography image quality improvement

IntroductionOptical Coherence Tomography Angiography (OCTA) is a new non-invasive imaging modality that gains increasing popularity for the observation of the microvasculatures in the retina and the conjunctiva, assisting clinical diagnosis and treatment planning. However, poor imaging quality, such as stripe artifacts and low contrast, is common in the acquired OCTA and in particular Anterior Segment OCTA (AS-OCTA) due to eye microtremor and poor illumination conditions. These issues lead to incomplete vasculature maps that in turn makes it hard to make accurate interpretation and subsequent diagnosis.MethodsIn this work, we propose a two-stage framework that comprises a de-striping stage and a re-enhancing stage, with aims to remove stripe noise and to enhance blood vessel structure from the background. We introduce a new de-striping objective function in a Stripe Removal Net (SR-Net) to suppress the stripe noise in the original image. The vasculatures in acquired AS-OCTA images usually exhibit poor contrast, so we use a Perceptual Structure Generative Adversarial Network (PS-GAN) to enhance the de-striped AS-OCTA image in the re-enhancing stage, which combined cyclic perceptual loss with structure loss to achieve further image quality improvement.Results and discussionTo evaluate the effectiveness of the proposed method, we apply the proposed framework to two synthetic OCTA datasets and a real AS-OCTA dataset. Our results show that the proposed framework yields a promising enhancement performance, which enables both conventional and deep learning-based vessel segmentation methods to produce improved results after enhancement of both retina and AS-OCTA modalities

Tuning the Computational Effort: An Adaptive Accuracy-aware Approach Across System Layers

This thesis introduces a novel methodology to realize accuracy-aware systems, which will help designers integrate accuracy awareness into their systems. It proposes an adaptive accuracy-aware approach across system layers that addresses current challenges in that domain, combining and tuning accuracy-aware methods on different system layers. To widen the scope of accuracy-aware computing including approximate computing for other domains, this thesis presents innovative accuracy-aware methods and techniques for different system layers. The required tuning of the accuracy-aware methods is integrated into a configuration layer that tunes the available knobs of the accuracy-aware methods integrated into a system

Extraction of Bio-based Organic Acids using Supported Liquid Membranes with Novel Solvents

A thesis submitted to The University of Manchester for the degree of Doctor of Philosophy in the Faculty of Science and Engineering.Novel green solvents and supported liquid membranes were studied for the recovery of bio-based organic acids from model fermentation broths. As fundamental building blocks for the chemical industry, the production of organic acids from renewable feedstock have been broadly developed. Among them, succinic acid, levulinic acid, and fumaric acid have been highlighted as leading representatives. Nevertheless, their downstream separation and purification still require further research to build a suitable green production route. This turns the development of environmentally-friendly extractants as well as efficient separation methods into priority key research areas for bio-separations. The growing number of available green solvents, such as ionic liquids, eutectic solvents, and bio-based solvents, makes unbearable the experimental screening process to find the most appropriate extractant. In this work, the molecular interactions driving the overall extraction performance for the organic acids were systematically analysed. Experimental measurements of the liquid-liquid extraction and solid-liquid equilibria, as well as thermodynamic modelling using the quantum chemistry-based COSMO-RS method, were carried out. Organic acids extraction yields and solubilities, systems excess energies, activity coefficients, and energies of solutions are reported. The combination of structurally different acids and extraction solvents arise complex interactions; however, hydrogen bonding showed to determine the overall behaviour. As a result, a straightforward selection guide was developed based on the organic acids partition coefficients in the extractant/water system, ln(K), system's water affinity, ln(y), and separation process spontaneity, G. Furthermore, the dissolution process of the organic acids in green solvents displayed an endothermic and spontaneous process with an enthalpy-entropy compensation effect. The separation is driven by the new and stronger interactions formed, increasing the order of the systems. The state-of-the-art on sustainable applications of liquid membrane technology was thoroughly reviewed. Despite its high potential to replace conventional liquid-liquid extraction processes, some operational issues must be overcome and better predictive models developed. The feasibility of green-supported liquid membranes for succinic acid recovery was explored. As suggested by previous results, the solvent-phase affinities became key in the extraction performance. Experimental extractions were carried out to assess the effect of the green solvents and receiving phase. Commercial polyvinylidene fluoride (PVDF) porous membranes were impregnated with four different green solvents: the eutectic solvents DL-menthol:OctA and N4444Cl:OctA, the bio-based solvents eucalyptol, and the ionic liquid [C4pyrr][Tf2N]. The acid recovery for all liquid membranes was 50%, 51% and 59% with pure water and alkaline aqueous solutions of 0.1M and 0.5M NaOH in the stripping phase, respectively. It was found that extraction yield indeed depends on the pH of the stripping phase and that the solute permeation rate depends on the extraction solvent. For the first time, a permeability model based on experimental data and activity coefficients computed using the COSMO-RS method was developed. Moreover, the novel Permeability Activity-Based Linear Operation (PABLO) method was developed and proposed to determine the theoretical stages number and mass transfer area in a countercurrent cascade extraction system. Overall, this thesis comprehensively covers two research needs for the bioseparations of key building blocks. The contributions will certainly enhance the development and design of green production routes, boosting the next generation of sustainable chemicals and biorefinery industries.This work was funded by the CONICYT PFCHA/ DOCTORADO BECAS CHILE/2017−72180306.Peer reviewe

A differentiated proposal of three dimension i/o performance characterization model focusing on storage environments

The I/O bottleneck remains a central issue in high-performance environments. Cloud computing, high-performance computing (HPC) and big data environments share many underneath difficulties to deliver data at a desirable time rate requested by high-performance applications. This increases the possibility of creating bottlenecks throughout the application feeding process by bottom hardware devices located in the storage system layer. In the last years, many researchers have been proposed solutions to improve the I/O architecture considering different approaches. Some of them take advantage of hardware devices while others focus on a sophisticated software approach. However, due to the complexity of dealing with high-performance environments, creating solutions to improve I/O performance in both software and hardware is challenging and gives researchers many opportunities. Classifying these improvements in different dimensions allows researchers to understand how these improvements have been built over the years and how it progresses. In addition, it also allows future efforts to be directed to research topics that have developed at a lower rate, balancing the general development process. This research present a three-dimension characterization model for classifying research works on I/O performance improvements for large scale storage computing facilities. This classification model can also be used as a guideline framework to summarize researches providing an overview of the actual scenario. We also used the proposed model to perform a systematic literature mapping that covered ten years of research on I/O performance improvements in storage environments. This study classified hundreds of distinct researches identifying which were the hardware, software, and storage systems that received more attention over the years, which were the most researches proposals elements and where these elements were evaluated. In order to justify the importance of this model and the development of solutions that targets I/O performance improvements, we evaluated a subset of these improvements using a a real and complete experimentation environment, the Grid5000. Analysis over different scenarios using a synthetic I/O benchmark demonstrates how the throughput and latency parameters behaves when performing different I/O operations using distinct storage technologies and approaches.O gargalo de E/S continua sendo um problema central em ambientes de alto desempenho. Os ambientes de computação em nuvem, computação de alto desempenho (HPC) e big data compartilham muitas dificuldades para fornecer dados em uma taxa de tempo desejável solicitada por aplicações de alto desempenho. Isso aumenta a possibilidade de criar gargalos em todo o processo de alimentação de aplicativos pelos dispositivos de hardware inferiores localizados na camada do sistema de armazenamento. Nos últimos anos, muitos pesquisadores propuseram soluções para melhorar a arquitetura de E/S considerando diferentes abordagens. Alguns deles aproveitam os dispositivos de hardware, enquanto outros se concentram em uma abordagem sofisticada de software. No entanto, devido à complexidade de lidar com ambientes de alto desempenho, criar soluções para melhorar o desempenho de E/S em software e hardware é um desafio e oferece aos pesquisadores muitas oportunidades. A classificação dessas melhorias em diferentes dimensões permite que os pesquisadores entendam como essas melhorias foram construídas ao longo dos anos e como elas progridem. Além disso, também permite que futuros esforços sejam direcionados para tópicos de pesquisa que se desenvolveram em menor proporção, equilibrando o processo geral de desenvolvimento. Esta pesquisa apresenta um modelo de caracterização tridimensional para classificar trabalhos de pesquisa sobre melhorias de desempenho de E/S para instalações de computação de armazenamento em larga escala. Esse modelo de classificação também pode ser usado como uma estrutura de diretrizes para resumir as pesquisas, fornecendo uma visão geral do cenário real. Também usamos o modelo proposto para realizar um mapeamento sistemático da literatura que abrangeu dez anos de pesquisa sobre melhorias no desempenho de E/S em ambientes de armazenamento. Este estudo classificou centenas de pesquisas distintas, identificando quais eram os dispositivos de hardware, software e sistemas de armazenamento que receberam mais atenção ao longo dos anos, quais foram os elementos de proposta mais pesquisados e onde esses elementos foram avaliados. Para justificar a importância desse modelo e o desenvolvimento de soluções que visam melhorias no desempenho de E/S, avaliamos um subconjunto dessas melhorias usando um ambiente de experimentação real e completo, o Grid5000. Análises em cenários diferentes usando um benchmark de E/S sintética demonstra como os parâmetros de vazão e latência se comportam ao executar diferentes operações de E/S usando tecnologias e abordagens distintas de armazenamento

Development of an optical fiber probe for mercury detection

El mercurio presenta una alta toxicidad, pudiendo causar adversos efectos en la salud humana. Los procedimientos recomendados para la detección analítica de metales pesados no son apropiados para aquellas aplicaciones donde se requiere un bajo coste y equipos ligeros que permitan realizar medidas de campo. Por el contrario, los sensores opto-químicos son una tecnología con un alto potencial para el desarrollo de dispositivos detectores de bajo coste y dimensiones reducidas. Esta Tesis describe los aspectos más relevantes en el desarrollo de una sonda opto-química basada en fibra óptica para la determinación de mercurio en agua. La investigación se plantea a partir de un compuesto de rutenio(II) descubierto recientemente que presenta un cambio de color desde un rojo púrpura oscuro hasta el naranja en solución orgánica ante la exposición a iones de mercurio(II). Otro factor importante es la capacidad de anclaje de la molécula a finas capas de óxidos metálicos como puede ser el TiO2. Los logros principales alcanzados en este trabajo de investigación son: (1) un software de análisis espectral multi-variable que reduce notablemente las interferencias principales del reactivo en fase líquida. El modelo matemático se basa en la regresión lineal por mínimos cuadrados parciales (PLS), y además se ha optimizado el resultado mediante una comparativa entre diferentes modelos PLS que incluyen un tratamiento previo de los datos mediante wavelet, corrección ortogonal de la señal, algoritmos genéticos, y selección de características estadísticas. (2) Una mejora de la estabilidad acuosa de la molécula al soportarla sobre una matriz de nanopartículas de Al2O3. Algunos trabajos preliminares con el complejo de Ru(II) se centraron en la inmovilización de la molécula sobre capas finas mesoporosas de TiO2. No obstante, pérdidas del colorante son apreciables cuando se analizan muestras acuosas. Resultados de la presente investigación garantizan la estabilidad acuosa de la molécula soportada sobre películas de Al2O3 y tratadas con ácido sulfúrico, con pérdidas por debajo del 2% (durante 3 horas). (3) La construcción del transductor basado en fibra óptica consiste en la sustitución de un trozo de cubrimiento (2 cm) del núcleo de la fibra óptica por el material sensibilizado compuesto por las nanopartículas de Al2O3. El principio de funcionamiento se basa en los cambios ópticos del material reactivo ante la exposición a iones de Hg2+, modulando así la intensidad de luz que se transmite a través del núcleo óptico. Se intuye a priori que la configuración del dispositivo conlleva a admitir que la propagación de la luz en la interfase núcleo y película de alumina tratada es mediante la aparición del campo evanescente. Sin embargo, al tener la cubierta de alumina un mayor índice de refracción que el núcleo, la condición de reflexión interna total no se satisface completamente, y como resultado se tiene una respuesta de la sonda óptica a la que contribuye tanto el campo evanescente como el modo de radiación generado por la porción de luz que se refracta a través de la cubierta de alumina-molécula. Finalmente, si tenemos en cuenta que la respuesta de este tipo de sondas ópticas varía significativamente de sonda a sonda, la cuantificación de mercurio ha sido posible a través de una calibración multivariable. Se ha logrado un error en la predicción de mercurio de un 11.5 por ciento, considerando un rango de 0 a 6 mg L-1 de iones de Hg2+. De este modo, se ha conseguido una sonda opto-química basada en fibra óptica cuyo modo de funcionamiento no es muy habitual en la literatura. La originalidad del presente trabajo se fundamenta en los pocos ejemplos de dispositivos ópticos de estas características que existen para la detección de metales pesados. En lo referente al autor, este es el primer dispositivo con configuración de fibra óptica evanescente destinado a la determinación de mercurio en medio acuoso.The organic form of mercury (methylmercury) is highly toxic, affecting the nervous system and even causing death. In the last years, human activities on coal combustion, waste incineration, gold mining and other industrial processes have raised the level of mercury in the atmosphere, rivers and other sources. Several public bodies have demonstrated that the direct detection of inorganic mercury (the precursor of mehtylmercury) will be beneficial in order to prevent mercury contamination. The detection of inorganic mercury through simple and low cost systems is possible by using colorimetric chemical sensors.Thus, several research groups worldwide have shown that the use of molecular probes, which change their optical properties upon the binding of inorganic mercury, is a promising topic for the development of detector devices for pollutant species.This Thesis describes the most remarkable aspects in the development of an optical fiber probe designed for mercury determination in aqueous samples. The research arises from the discovery of a novel molecule (IUPAC name bis(2,2'-bipyridyl-4,4'-dicarboxylato) ruthenium(II) bistetrabutylammonium bis-thiocyanate) that upon mercury binding induces a color change from dark red-purple to orange in solution. The selectivity towards mercury of this ruthenium complex is high when compared to other known chemical reagents. Yet, in this work, we have been able to increase the selectivity through a fully multivariate calibration of the absorbance measurements. We have analyzed the mercury-containing solutions under the co-existence of higher concentrations (19.5 mg L-1) of other potential competitors such as Cd2+, Pb2+, Cu2+ and Zn2+ ions. Our experimental model is based on partial least squares (PLS) linear regression and other general techniques as wavelet, orthogonal signal correction, genetic algorithm and statistical feature selection that have been used to refine, a priori, the analytical data. In summary, we have demonstrated that the root mean square error of mercury prediction with statistical feature selection, as compared to the absence of pre-treatment, can be reduced from 10.5 to 5.2 percent, which improves the prediction ability of the calibration model by a factor of 2.On the other hand, the possibility of working in solid-liquid phase increases the integration ability of the molecule in a device, making easier the measurement process. Nevertheless, the immobilization of the molecule onto a surface constitutes one of the challenges of this Thesis.Some preliminary works with the Ru(II) complex focussed on the immobilization of the molecule onto TiO2 mesoporous thin films.However, some leaching problems were apparent when aqueous samples were analysed. Accordingly, we have improved the water stability of the molecule by anchoring the dye onto Al2O3 nanoparticles thin films treated with sulphuric acid. Moreover, the good optical properties of the alumina support allow a better transparency of the films, which translates in a higher amount of available spectral absorbance information.A compact mercury read-out system has been achieved by coating an unclad optical fiber piece with Al2O3 paste. The proof-of-principle is based on the optical changes of the reagent upon Hg2+ ions exposure, which modulates the light intensity transmitted through the optical core.There are many theoretical studies that explore a particular research case of the evanescent optical fibers. As the alumina cladding has higher refractive index than the core, both evanescent field and radiative mode may appear in the modified cladding. This Thesis exposes a brief explanation of this behavior in order to understand the mechanisms of the response of our mercury optical fiber probe. Moreover, several experiments have been carried out in mercury aqueous samples so as to find the proper working conditions, such as the optimum dye concentration adsorbed onto the alumina cladding, which has a great effect on the device performance. Finally, mercury quantification has been possible through multivariate calibration, direct partial least squares being the most robust procedure if we take into account the fact that the response of this kind of optical probes varies significantly from one to another. A root mean square error for mercury predictions of 11.5 percent has been achieved within a range from 0 to 6 mg L-1 of Hg2+ ions.Overall, this thesis work has illustrated all the steps that come into play in the design of an optical fiber chemical-based probe, providing a simplified measurement process and a lower cost if it is compared to traditional analysis equipment. As far as the author is concerned, an optical fiber probe for mercury determination is presented for the first time

Transcutaneous subunit vaccine delivery. A combined approach of vesicle formulations and microneedle arrays

Traditional vaccination is performed via subcutaneous or intramuscular injections, which is painful, causes stress, especially in children and requires trained personnel. Vaccination via the skin provides effective, easy-to-use, painless, and needle-free vaccination with fewer side effects and safer handling. It has the potential to dramatically improve current vaccination practice in developing countries and in cases of mass vaccination campaigns. The main challenge is to delivery antigen molecules across the skin barrier in proper formulations in sufficient amounts. The aim of the work described in this thesis was to improve the efficiency of transcutaneous vaccination (vaccine application on intact or pretreated skin) by using microneedle arrays, adjuvants, and antigen-containing vesicle formulations. In this study, we observed that application of free antigens (diphtheria toxoid and influenza vaccine) and diphtheria toxoid-containing vesicle formulations onto intact skin does not induce significant antibody responses. Transcutaneous immunization with influenza antigen is significantly improved by co-administration of adjuvants, independent of microneedle pretreatment. For diphtheria vaccination, microneedle pretreatment and the use of adjuvant, but not antigen association to vesicles, enhances the immunogenicity. The potency and quality of the immune response can be further optimized by the use of adjuvants.UBL - phd migration 201

Nuclear Power - Control, Reliability and Human Factors

Advances in reactor designs, materials and human-machine interfaces guarantee safety and reliability of emerging reactor technologies, eliminating possibilities for high-consequence human errors as those which have occurred in the past. New instrumentation and control technologies based in digital systems, novel sensors and measurement approaches facilitate safety, reliability and economic competitiveness of nuclear power options. Autonomous operation scenarios are becoming increasingly popular to consider for small modular systems. This book belongs to a series of books on nuclear power published by InTech. It consists of four major sections and contains twenty-one chapters on topics from key subject areas pertinent to instrumentation and control, operation reliability, system aging and human-machine interfaces. The book targets a broad potential readership group - students, researchers and specialists in the field - who are interested in learning about nuclear power

Halide Perovskite and Perovskite-Inspired Nanocrystals for Optoelectronic Applications

Optoelectronic applications, such as photovoltaics (PVs) and light-emitting diodes (LEDs), play a key role in addressing the global energy crisis. Yet, they demand new semiconductors with high stability, low environmental impact, and low cost. One of the attractive ways of synthesizing semiconductor materials is their colloidal synthesis at the nanoscale, leading to nanocrystals (NCs). This thesis focuses on a promising family of NCs extensively investigated during the last decade, namely NCs based on halide perovskites and their derivatives. Halide perovskite nanocrystals (PNCs) display appealing optoelectronic properties due to high defect tolerance, tunable crystal structures and dimensions, and versatile synthesis. However, a comprehensive optimization of these PNCs synthesis to enhance their stability and optical properties is lacking. Furthermore, the understanding of the fundamental structure-property relationships in emerging PNCs is still very limited. At the same time, the toxicity of lead (Pb) present in the most efficient PNC compositions demands the development of eco-friendly lead-free PNCs for optoelectronic applications. In this dissertation, we have identified the relationships between the synthesis and the key properties of emerging or novel PNCs, starting from the popular CsPbI3 and then moving towards Pb-free compositions. In particular, we have (i) enhanced the phase stability of CsPbI3 PNCs by tailoring the reaction temperature, (ii) achieved highly luminescent CsMnCl3 PNCs by tailoring the synthesis of the emissive crystalline phase, and (iii) proposed the first-ever syntheses of Cs2TiX6 (X = Br and Cl) PNCs and phase-pure AgBiI4 perovskite-inspired NCs with enhanced stabilities for potential nonlinear optical applications. We believe that the results of this thesis will encourage other researchers and practitioners in the field to further investigate the promising perovskites and perovskite-inspired NCs that we have identified and eventually enable their usage in real-life optoelectronics applications