VictorJuiz/thesis huggingface dataset:
Prevention of Iron-Polyphenol Complex Formation in Iron Fortified Tea
Keywords: chelation
EDTA
fortification
iron
polyphenol
tea

The fortification of black tea with iron has the potential to reduce the prevalence of iron deficiency in the developing world. Tea is an ideal vehicle for food fortification because it is centrally processed, is the most consumed beverage globally, aside from water, and is consumed in regular quantities by those of all socioeconomic strata in many regions. Unfortunately polyphenolic compounds present in tea, which are responsible for colour and flavour, form complexes with iron which reduce the bioavailability of both compounds and cause strong unattractive colour development. The objective of this study was to develop a technique for the fortification of tea with iron such that these complexes do not form. A spectrophotometric method was developed and validated for the quantification of iron-polyphenol complex formation. Iron-polyphenol complex formation was further investigated with a variety of iron sources, temperatures, and polyphenol concentrations using a gallic acid model system and tea extract. Analysis and modeling of iron-polyphenol complex formation prompted the investigation of predicted inhibitors, specifically reducing and chelating agents. Reducing agents were able to hinder iron complex formation at pH 5 (the pH of brewed tea) but not at pH 7 (an approximation of the small intestineâ s pH). Chelating agents were successful at preventing iron-polyphenol complex formation at both pH 5 and pH 7. Due to its superior performance, disodium ethylenediaminetetraacetate (EDTA) was optimized for use in black tea. In summary, a technique has been developed for producing iron fortified tea based on a comprehensive framework for understanding the formation and inhibition of iron-polyphenol complexes in the presence of black tea polyphenols. This tea maintains its visual acceptability while providing iron in a bioavailable form. A process for effective iron fortification based on our laboratory technique is ready for in-vivo evaluation of its effectiveness and pilot scale testing.
Development of Passive Samplers for Measuring Indoor Air Concentrations, and Measurement of Physical and Chemical Properties of Semi-Volatile Organic Compounds
Keywords: Passive air sampling
Polydimethylsiloxane
Polyurethane Foam
SVOCs
Vapour pressure

Human exposure to semi-volatile organic compounds (SVOCs) including flame retardants (FRs) and plasticizers used in consumer products from indoor sources is a serious concern. These compounds are then advected to the outdoor environment which leads to regional and long-range transport and exposure to the ecosystem. This thesis aims to improve our understanding of exposure to selected SVOCs by developing tools, methods and providing data to facilitate exposure assessment particularly regarding indoor air. Three new passive air samplers (PAS), namely silicone rubber (polydimethylsiloxane, PDMS), styrene-divinylbenzene copolymer (XAD)-Pocket and XAD-PDMS were calibrated against an active air sampler and compared to the more popular polyurethane foam (PUF) PAS. Although the indoor sampling rates vary, we recommend from these studies a generic sampling rate of 1.7 m3 day-1dm-2 and 0.94 m3 day-1dm-2 for PDMS and PUF, respectively. The active air sampler was also used to assess the gas-particle distribution of the target compounds. The particle-phase partitioning fractions of SVOCs is a key determinant of their environmental behaviour and potential for exposure thus toxicity. A key finding here, is that some relatively volatile organophosphate ester FRs are present in the gas-phase where most published studies of active air sampling report them largely in the particle phase, indicating a sampling artifact. To improve chemical screening and modelling of the transport and fate, this thesis provides experimentally determined values of vapour pressures and octanol-air partition coefficients for over 50 SVOCs measured here using the well-established gas chromatography retention time method. Deployment of PDMS and PUF in residential homes gave comparable estimates of air concentrations for SVOCs in the gas-phase, although PUF was more able to capture compounds with higher fractions in the particulate phase. PDMS shows promise as a tool for estimating exposure to a wide range of SVOCs indoors, although its particle sampling efficiency warrants further work.
Oxygen Bubble Propagation in Polymer Electrolyte Membrane Electrolyzer Porous Transport Layers
Keywords: Bubble
Computational
Electrolysis
Fuel Cell
Multiphase
Porous

Identifying the physical properties related to the primary functions of the porous transport layer (PTL) (thermal, electrical, and mass transport) is necessary for understanding the impact of PTL design choices on electrolyzer performance. In this thesis, two-dimensional (2D) representations of three common PTLs were fabricated on microfluidic chips in order to study the impact of PTL microstructure on multiphase transport via visualization of air bubble transport in liquid-saturated porous networks. Air bubble patterns and breakthrough gas saturation were used to characterize the impact of porosity and average throat size on displacement patterns and oxygen saturation values. Next, a multiphase computational fluid dynamics (CFD) simulation tool was developed and validated with experimental results to simulate the dynamic displacement process of oxygen gas injection into liquid water saturated porous media. Using this CFD tool, a comprehensive phase diagram was developed through a parametric characterization of the porous media in terms of material hydrophobicity and gas flow rates. In addition to calculating the saturation of the invading gas, gas pressure variations were calculated and used to identify the locations of the phase diagram boundaries. The proposed phase diagram serves to inform the design of efficient PTL for improved polymer electrolyte membrane (PEM) electrolyzer performance.
The Problem of Political Authority in the Philosophy of Plato and Hegel
Keywords: German Idealism
Hegel
Plato
Political Authority
Rhetoric
Sophistry

This dissertation examines the problem of political authority in Plato and Hegel. It is animated by an interest in the disavowal of authority characteristic of political culture today, and serves to fill gaps in the existing literature on German and Greek political philosophy. Contemporary scholarship on German Idealism follows Hegel in comparing 19th century critical philosophy to Greek philosophy, which it claims to surpass on account of its emphasis on subjective freedom. At the same time, contemporary reappraisals of Greek political thought hold up Plato and the classical teachings on rhetoric as promising alternatives to philosophy from Kant to Hegel, which is found to be overly rationalistic and insufficient in its treatment of political passion. Due to the division of scholarly labor, an adequate confrontation between classical political thought and German idealism remains wanting. Through a rigorous textual analysis of the Philosophy of Right and Gorgias, the dissertation expounds the Platonic and Hegelian approaches to the problem of political authority, and supplies the grounds for a dialogue between the two thinkers. On the basis of this preparatory work, it proceeds to take up the consolidation of political authority, or the production of obedience by the regime, insofar as Plato and Hegel disagree profoundly on that subject and its significance to political right. The dissertation presents the political philosophy of Plato and Hegel as robust and contesting alternatives, and concludes by returning to the challenge of political authority as it faces us today.
FRAMEWORK FOR MANAGING INTEGRATION CHALLENGES OF PRODUCTION PLANNING AND CONTROL IN INTERNATIONAL CONSTRUCTION MEGA-PROJECTS
Keywords: Delphi
international mega projects
Last Planner System ( LPS )
Lean Construction
Nominal Group Technique (NGT)
Production Planning and Control

The public often associates mega-projects with poor performance due to delays and budget overruns. International mega-projects (IMPs) comprise multiple subprojects across widely spread areas, often with independent resources and individual plans. Such decentralization into clusters increases the integration planning and execution challenges. Changes to the schedule, budget, and scope, as well as poor design, are critical integration challenges within and across subprojects of mega-projects. International characteristics of project delivery compound additional complexity on integration aspects. It is essential for the production planning system in IMPs to be robust in addressing integration challenges to achieve necessary interface and realistic reporting. This study aimed to reveal the significance of operational gaps and resolve the integration challenges in IMPs. To achieve its goal, the study was divided to three phases. They are: 1) synthesize literature and practice with respect to production planning and control systems; 2) evaluate the performance of the production planning and control system at a mega-scale in a case study; 3) develop a framework to provide workable solutions to address the unique and complex integration challenges of IMPs. The Last Planner速 System (LPS速) was found to be an emerging production planning and control system with a promising potential. Fostered to complement, not to replace, the existing LPS速 model, the proposed IMPact framework is a roadmap aiming to improve the operations of IMPs, keeping them on track, and potentially replacing the negative image of IMPs with positive impressions. The validated framework provided a conceptual practical solution, based in LPS速, to address the challenges that project teams on IMPs have within and across subprojects. It is intended to be an adaptive system in an effort to improve delivery and performance of IMPs.
Modifications to Laboratory Test Methods to Evaluate the Beneficial Effects of Low-Alkali Binders on the Alkali-Silica Reaction
Keywords: Accelerated Mortar Bar Test
Alkali-Silica Reaction
Concrete
Concrete Prism Test
Laboratory Test Methods

Since alkali-silica reaction (ASR) was identified in the 1940â s by Thomas Stanton, thousands of research papers have been published on identification and mitigation of the reaction. Laboratory test methods have been created, modified, and their results compared to the performance of concrete in the field. Current standardized test methods do not allow for testing of low-alkali cements, due to their storage conditions. This has been found to be a severe limitation on assessment of ASR mitigation options. The objective of this research is to adapt current standardized test methods (the concrete prism test and the accelerated mortar bar test) so they can detect the beneficial effects of low-alkali cementing systems, with or without supplementary cementing materials. The alkali leaching and the alkali boosting in the concrete prism test make it unable to evaluate concrete mixtures with low-alkali cement. The effect of cement alkali content and binder combination on the expansion and leaching was investigated, as well as ways to minimize the alkali leaching. Leaching from concrete prisms ranged from 25-50% but covering each prism with a plastic bag reduced the leaching to only about 10%, without reducing the expansion measured. By modifying the alkali boosting procedure, and with the use of improved storage conditions to minimize alkali leaching, it is possible to use the concrete prism test for evaluating the benefits of concrete mixtures made with low-alkali cements. The storage solution for the accelerated mortar bar test provides an abundance of alkali ions to cause ASR, making it unfit to evaluate low-alkali cement mixtures. Therefore, samples were also tested in a storage solution with alkalinity similar to the pore solution of the samples tested. Lowering the concentration of the storage solution to 0.7 times the alkali content of the cement used, greatly improves the correlation between the two test methods.
The Anaerobic Digestion of Organic Solid Wastes of Variable Composition
Keywords: anaerobic digestion
co-digestion
methane
solid waste

Abstract Every year in Canada approximately 8 million tonnes of organic solid waste is placed in landfills where it decomposes anaerobically over decades, produces large volumes of leachate requiring treatment, and releases 20 million tonnes of greenhouse gas emissions as CO2eq. Anaerobically digesting this waste prior to landfill would obviously be beneficial, but this is difficult to achieve because solid waste is a complex, heterogeneous and variable mixture, making any form of processing much more expensive than landfill. This thesis investigates the capabilities of a new approach to the anaerobic digestion of solid waste designed to overcome these obstacles. Most of the costly separation and pretreatment steps common in European anaerobic digesters are eliminated. The waste remains stationary, the leachate is recirculated through it, and the resulting digestate is aerobically cured. The biogas generated is recovered for the generation of electricity or the production of renewable natural gas. A laboratory scale system comprising six sequentially batch fed leach beds and an upflow anaerobic sludge blanket reactor was constructed, and operated continuously for 616 days. The feedstock consisted of a mixture of cardboard, boxboard, newsprint, and fine paper, to which varying amounts of food waste were added (from 0% to 29% on a COD basis). The digester accommodated these and other changes without any signs of process upset or instability. It was found that the addition of food waste increased biogas production from the fibre mixture from 101 L.kg-1CODfibreadded to 330 L. kg-1CODfibreadded an increase of 225%. A substrate destruction efficiency of 65% (on a COD basis) and a methane yield of 225 L.kg-1 CODadded were achieved, at a solids retention time of 42 days. This performance was similar to that of a CSTR digesting similar wastes. A financial analysis showed that the technology can be competitive with landfill.
Evaluating Stem Cell Transplantation in Novel Models of Bilateral Cervical Spinal Cord Injury
Keywords: Animal model
Cell transplantation
Functional recovery
Neural stem cell
Neurophysiology
Spinal cord injury

The majority of spinal cord injuries (SCI) occur at the cervical level, which results in significant impairment. Severity and neurologic level of injury are primary endpoints in clinical trials; however, showing level-dependence in experimental models has proven difficult. Stem cell transplantation for SCI has been explored in preclinical models; however, the specific mechanisms, such as remyelination, environmental modification or synaptic integration, are incompletely understood. Despite these knowledge gaps, stem cell transplantation for SCI has entered human clinical trials. We sought to establish level-dependent models of cervical SCI that could subsequently be used to examine efficacy and mechanism of neural precursor cell (NPC) transplantation. First, we examined whether ascending level of injury leads to progressive loss of tissue and specific neuron pools, causing worsening forelimb motor performance. We directly compared injury at the C5, C6, C7 and T7 vertebral levels caused by severe bilateral clip compression injury. Animals were assessed for 10 weeks post-injury with numerous (42) outcome measures of neuroanatomy, physiology, and sensorimotor function. The cervical enlargement (C5-T2) showed progressive ventral horn atrophy and loss of motor columns with ascending injury, resulting in progressive and reciprocal changes forelimb function and gait. Multivariate statistics revealed a robust dataset and allowed prediction of injury level with single-level discrimination using forelimb function, gait performance, and neuron counts. Injury at C5 and C6 were categorically distinct to other injuries. We then examined whether NPCs would ameliorate C6-level SCI and return function through remyelination and synaptic integration. Long-term survival of NPCs was evident to 16 weeks. Despite improving axonal conduction and close physical apposition to host motor neurons, NPC-derived cells did not form synapses with forelimb circuitry. Graft-derived cells deposited myelin around endogenous axons, causing reduced astrogliosis, preserved motor neuron pools, and improved motor function in a dose-dependent manner. Level-dependent models were generated using clip-compression SCI, with marked differences in forelimb performance and neuron atrophy. Transplantation of NPCs in the injured cervical spinal cord resulted in significantly improved tissue integrity and forelimb function, warranting further study in level-dependent preclinical cervical models to improve this treatment paradigm for clinical translation.
Fast and Scalable Physics-Based Electromigration Checking for Power Grids in Integrated Circuits
Keywords: Electromigration
Partial Differential Equations
Power Grids in ICs
Probability
Reliability

Electromigration (EM) is a key reliability concern in chip power/ ground (p/g) grids, which has been exacerbated by the high current levels and narrow metal lines in modern grids. EM checking is expensive due to the large sizes of modern p/g grids and is also inherently difficult due to the complex nature of the EM phenomenon. Traditional EM checking is based on empirical models, but better models are needed for accurate prediction due to the very small margins between the allowed failure rates (spec) and the failure rates at which the chips actually operate in the field. Thus, recent more accurate physics-based EM models have been proposed, which remain computationally expensive because they require solution of a system of partial differential equations (PDEs). In this work, we extend the existing physics-based models for EM in metal branches to track EM degradation in multi-branch interconnect trees and propose a fast and scalable methodology for power grid EM verification. We speed up our implementation by using filtering schemes (that focus the computation only on the most EM susceptible trees) and by developing optimized numerical methods to solve the PDE system arising out of the physics-based EM models. The lifetimes found using our physics-based approach are on average 2.35x longer than those based on a (calibrated) Blackâ s model, as extended to handle mesh power grids. With a runtime of only 10 minutes for a 4.1M node grid, our approach is extremely fast and should scale well for large integrated circuits.
Lessons Learned from the Reactivity of Mandelylthiamin and Derivatives
Keywords: Breslow
carbene
decarboxylation
mandelylthiamin
MTh
thiamin

Mandelylthiamin (MTh) is an accurate model of the pre-decarboxylation intermediate formed on benzoylformate decarboxylase (BFDC). In solution, it decarboxylates to the Breslow intermediate 108 times slower than on the enzyme. Earlier studies proposed that the Câ C bond-breaking step in the decarboxylation of MTh is highly reversible, and thus possibly impeding the overall reaction rate. More recently, it was observed that the decarboxylation of MTh could be more effective through formation of HCO3-, suggesting the enzyme could be applying a similar strategy to maximize its catalytic efficiency. This thesis investigates in detail the decarboxylation of MTh and related analogs in solution phase, and proposes possible enzymic strategies for catalysis. Research on MTh had suffered from a low yield synthesis and ineffective purification. The work in this thesis was made possible because lithium ions were discovered to greatly promote formation of the MTh ester and its analogs. Using the new synthetic methodology I could synthesize previously unattainable MTh variants. This thesis can be divided into three main sections: 1) the study of MTh analogs and other compounds to understand molecular features responsible for decarboxylation by formation of HCO3-. This was probed through observation of base catalysis and a solvent kinetic isotope effect (SKIE), which are indications of a decarboxylation by formation of HCO3-. Based on the collected results, it was concluded that a base catalyzed decarboxylation is a unique phenomenon. A coincidental outcome of this study was the discovery of intramolecular cyclization reactions of the Breslow intermediate. 2) the study of substituent effects on the decarboxylation of MTh to probe the nature of the BF-derived Breslow intermediate in solution and comparison of results to the enzymic decarboxylation. This revealed that certain enzymes likely enforce an unnatural geometry of the Breslow intermediate to achieve catalytic perfection. 3) the study of the fragmentation of the BF-derived Breslow intermediate from a radicalsâ formation perspective. This was done after recent reports that radicals are involved in related transformations. My results lead to a conclusion that radicals are unlikely to be involved, and instead a simple polar alternative that is consistent with experimental observations was proposed.
Frequency Domain Method for Resolution of Two Overlapping Ultrasonic Echoes
Keywords: Frequency Domain
Non Destructive Testing
Signal Processing
Ultrasonics

The ability to identify and resolve overlapping echoes is crucial to the enhancement of axial scan resolution in ultrasonic testing. Overlapping echoes are frequently encountered in the inspection of shallow and/or short cracks in Time-of-Flight Diffraction and normal incidence reflection inspection of near surface flaws. Dictionary-based parametric representation (DBPR) has been proposed as a powerful framework to separate overlapping echoes of different shapes. However, the large solution space in DBPR renders the optimization process difficult. We propose a new echo separation method named Trigonometric Echo Identification (TEI) that exploits the consistent frequency domain amplitude and phase relationships of two overlapping ultrasonic echoes to reduce the number of optimization parameters. In TEI, frequency amplitude profiles are entered as inputs and the corresponding set of frequency phase profiles are reconstructed as outputs. The optimality of the output phase profiles is then used as a metric to determine the accuracy of the trial amplitude inputs. By reconstructing the phase information instead of explicitly specifying the phase profiles, we can reduce the number of unknowns in the problem of identifying two overlapping ultrasonic echoes. Compared to DBPR, TEI can describe more complex ultrasonic echoes using the same number of optimization parameters. In addition, since the phase profiles are reconstructed using the acquired data, TEI would perform more reliably in the presence of noise. Simulation tests were conducted to assess the relative performance of TEI and DBPR. Echo parameters including center frequency, phase shift and relative amplitudes were systematically varied to yield different test configurations. The standard deviation of timing errors obtained from TEI were 50% lower compared to DBPR. The difference in algorithm performance is especially evident in low SNR signals and signals containing echoes of complex shapes. The TEI algorithm was also verified on experimental ultrasound testing data containing overlapping echoes. The echo arrival times extracted using TEI agree with the values obtained using geometric calculations.