Tesi: "Chemical engineers"

1

Gissing, Philip School of Science &amp Technology Studies UNSW. "Sir Philip Baxter, Engineer: The Fabric of a Conservative Style of Thought". Awarded by:University of New South Wales. School of Science and Technology Studies, 1999. http://handle.unsw.edu.au/1959.4/17017.

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This thesis is concerned with the life and career of Sir Philip Baxter (1905-1989), particularly during the period following his arrival in Australia from England in 1950. But the thesis is not a conventional biographical study in terms of either the sources used or its guiding themes. Instead, my subject's values and attitudes are portrayed as reflections of a 'conservative style of thought', a concept developed by Karl Mannheim. This approach, centred on close readings of key texts, permits a deeper understanding of a figure who polarised opinion over a long career as Chairman of the Australian Atomic Energy Commission, and as Vice-Chancellor of the University of NSW. My picture of Baxter draws significantly on the Archives of the University of NSW, which provided the bulk of my primary sources, such as correspondence files, typescripts of articles and talks, newspaper clippings, official documents and personal memorabilia. This material is a substantial but curiously unrevealing source for Baxter's life. Although I rely largely on written material, on several important occasions I refer to discussions I had with Baxter's children, colleagues and students. Insights thereby gained into Baxter's childhood reading, and the circumstances of the composition of his play, The Day the Sun Rose in the West, profoundly influenced my portrayal of Baxter. Throughout, I argue for an appreciation of the significance of such material, even though in a more conventional study of an engineer/administrator it would be thought of only marginal interest. In Baxter's case, certainly, careful interpretation of such material enables the construction of a compelling portrait of the man despite the unrevealing primary records and the still often fervently partisan personal recollections of those who knew him. My major conclusion is that previous characterisations of Baxter as a cold war warrior of the post-war period in Australia have failed to appreciate the complexity and coherence of his attitudes and philosophy. Secondly, I demonstrate that the notion of a 'conservative style of thought' captures that complexity as evidenced in the many facets of Baxter's career and interests.

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2

Merchant, Shamel Sarfaraz. "Molecules to engines : combustion chemistry of alcohols and their application to advanced engines". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98711.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 237-266).
A major challenge in energy is the identification of viable liquid fuels as alternatives to petroleum-based fuels. There are a wide variety of candidate fuels to select from and assessing each new fuel is far from trivial. Small variations in chemical structure can cause large changes in a fuel's performance. Simultaneously, engine designs are also changing rapidly. Accurately predicting how new fuels will perform in future engines are in many ways more valuable than knowing which fuels perform well in today's engines. Predictive theoretical modeling is required to efficiently screen candidates. The selection of a good candidate fuel requires the development of detailed kinetic models capable of accurately predicting fuel behavior over the entire range of engine operating conditions. Despite the fact that most literature models succeed to accurately predict primary combustion products and high temperature ignition delay, two areas require further scientific understanding: peroxy chemistry and polycyclic aromatic hydrocarbon (PAH) formation. The first section of this thesis describes significant contributions to both these areas. Peroxy chemistry is important for accurately predicting ignition in future engine designs based on the concept of low temperature combustion (LTC). This thesis provides a clear explanation of how peroxy chemistry affects low temperature ignition behavior. Simple analytical expressions are provided for the time constant for radical growth and first-stage ignition delay. To improve the understanding of PAH formation, abintio calculations to indene and naphthalene from cyclopentadiene and cyclopentadienyl radical were performed. The calculated gas phase rate constants and thermochemistry were used to develop the first elementary micro-kinetic model for the formation of indene and naphthalene from cyclopentadiene. The model is validated against cyclopentadiene pyrolysis data in flow reactors. The second section of this thesis presents a combined computational-experimental approach to rapidly construct accurate combustion chemistry simulations for alcohol fuels. In this approach experiments and quantum chemical calculations are carried out in parallel, informing an evolving chemical kinetic model. This approach was used to understand and predictively model the combustion chemistry of iso-butanol and pentanol isomers. Detailed kinetic models for iso-butanol and pentanol isomers are presented which are validated against a large number of datasets spanning the entire range of operating conditions seen during real engine operation. We see that for many performance parameters, the model predictions are as accurate as experiment and help provide mechanistic insight into differing reactivity of a fuel's isomers. Lastly, we show how detailed kinetic model can be applied in multi-dimensional CFD simulations of a new type of engine, the reactivity controlled compression ignition engine (RCCI), in order to make predictions of how iso-butanol will affect the engine efficiency and emissions. This thesis covers the entire process of predictively accessing a fuel by taking a new fuel molecule, developing a detailed model, and evaluating it in a new engine design in order to make informed decisions.
by Shamel Sarfaraz Merchant.
Ph. D.

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3

Brunelli, Andrea <1984&gt. "Advanced physico-chemical characterization of engineered nanomaterials in nanotoxicology". Doctoral thesis, Università Ca' Foscari Venezia, 2013. http://hdl.handle.net/10579/4656.

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L'ampio utilizzo di nanomateriali ingegnerizzati (ENM) in svariati prodotti sta suscitando una crescente attenzione sull potenziale rischio di ENM nei confronti della salute umana e l'ambiente. Nonostante le indagini tossicologiche fin qui condotte, solo in poche di esse è stata condotta la caratterizzazione di ENM prima, durante e dopo i test tossicologici. In questa tesi, all’interno del progetto europeo EU-FP7 (ENPRA) e nazionale (PRIN 2009), è stata effettuata una caratterizzazione completa di alcuni più diffusi ENM (i.e. n-TiO2, n-ZnO, n-Ag e MWCNT). In primo luogo, sono stati aggiornati i dati di caratterizzazione primaria con ulteriori analisi; inoltre, è stata effettuata la caratterizzazione secondaria di ENM, indagando il loro comportamento in matrici ambientali. I risultati ottenuti mostrano che la stabilità di ENM è stata principalmente influenzata da agenti stabilizzanti (in mezzi biologici) e dalla concentrazione iniziale di ENM (in acque sia artificiali e reali). Inoltre, la biodistribuzione di ENM negli organi studiati è stata maggiormente influenzata dalla composizione chimica e dimensione delle particelle indagate. Sono discussi sia l'approccio di caratterizzazione proposto che l'implicazione dei risultati ottenuti.
The extensive use of engineered nanomaterials (ENM) in both industrial and consumer products is triggering a growing attention on the potential risk of ENM posed to human health and the environment. Despite the intensive toxicological investigations, both in vitro and in vivo, only few of them have embedded a solid characterization approach, including the study of ENM before, during and after toxicological testing. Within EU-FP7 (ENPRA) and national (Toxicological and environmental behaviour of nano-sized titanium dioxide) projects activities, a comprehensive characterization of both inorganic (n-TiO2, n-ZnO, n-Ag) and organic (multiwalled carbon nanotubes, MWCNT) ENM was carried out, updating and adding primary characterization data, investigating particle size, shape, crystallite size, crystalline phases, specific surface area, pore volume as well as inorganic impurities of concern. Electron microscopy, X-ray diffraction, BET method and Inductively coupled plasma- mass spectrometry or optical spectroscopy were the employed techniques. With regard to the secondary characterization of ENM, the study was divided in: (a) assessing the engineered nanoparticles (ENP) behavior in biological (0.256 mg ENP/ml) as well as in real and synthetic waters (environmentally realistic concentrations: 0.01, 0.1, 1 and 10 mg n-TiO2 P25/l) over different time interval (24 h in biological media instead of 50 h in water media) to mimic duration of toxicological tests, by means of Dynamic Light Scattering (DLS), analytical centrifugation and nephelometry; (b) evaluating the ENM biodistribution in a secondary target organ (i.e. mice brain) after intratracheally instillation of ENM (0, 1, 4, 8, 16, 32, 64 and 128 ug ENM/animal tested), achieved by a microwave-assisted digestion method, followed by ICP-MS analysis, after selecting inorganic elements (i.e. Ti, Zn, Ag, Al and Co) as tracers of ENM presence in biological tissues. To investigate the ENP behavior in biological media and ENM biodistribution in mice, both dispersion protocols of the selected ENP and analytical protocols for ENM detection after toxicological testing were provided. The study of ENP stability in biological media highlighted that the fetal bovine serum (FBS) is the main parameter affected the ENP behavior. Among biological media tested, the largest size distributions, immediately after sample preparation, were irecorded for n-TiO2 NRCWE-003 dispersions. n-ZnO NM-111 dispersions were the most stable (12% average demixing, simulating 24 h of real sedimentation), except for Ag NM-300, originally received as dispersion (<1% average demixing). As expected, the ENP sedimentation rates investigated in the biological medium without any stabilizer (i.e. RPMI), were the highest for the whole set of ENP tested. In general, the highest sedimentation rates were recorded for n-TiO2 NM-101 and n-Ag 47MN-03 dispersions (51% average demixing, simulating 24 h of real sedimentation). The study of the n-TiO2 P25 stability in waters showed that agglomeration and sedimentation of n-TiO2 were mainly affected by the initial concentration. Sedimentation data fitted satisfactorily (R2 average: 0.90; 0.740.98) with a first- order kinetic equation. The settling rate constant, k, increased by approx. one order of magnitude by moving from the lowest to the highest concentration, resulting very similar especially for all dispersions at 1 (k = 8•10-6 s-1) and 10 mg/l (k = 2•10-5 s-1) n- TiO2, regardless the ionic strength and composition of dispersions. The results from ENM biodistribution underlined that the chemical composition and the particle size were the main parameters that influenced the ENM partitioning into organs. Ti from n-TiO2 samples with the smallest particle size distribution tested (80-400 nm and 4-100 nm) and Al from MWCNT samples were the only inorganic tracers detected in mice brain. The whole characterization approach and the implication of these results are discussed.

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4

Kuforiji, Folashade. "The investigation of surface chemical and nanotopographical cues to engineer biointerfaces". Thesis, Keele University, 2015. http://eprints.keele.ac.uk/2351/.

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This thesis is focused on understanding the fundamental physical interaction occurring, when a material interacts with a biological fluid containing protein molecules and cells. The interaction of proteins with defined surface chemistry and nanotopography is of major interest in the field of biomaterials. Despite the degree of research undertaken to study this interface, there is still a lack of understanding of how the protein layer evolves with respect to surface parameters, and further how cells condition the surface. By understanding these processes, advanced biomaterial coatings may be developed that allow control over specific cell responses to direct healing processes. Colourimetric and fluorometric assays were carried out to assess protein-surface affinity and amount of protein adsorption. Infrared spectroscopy was used to quantify protein conformational changes incurred upon adsorption on defined nanoscale surfaces presenting a range of chemical functional groups. Model experiments were performed using bovine albumin and fibrinogen adsorbing onto surfaces presenting defined surface chemistry: OH, COOH, NH2, and CH3. Surface curvature on the nanoscale was used to model topography on the same length scale as protein molecules. Silica colloidal dispersions were prepared in batches,11-215 nm diameters allowing chemical modification whilst keeping nanotopography constant. 3T3 fibroblasts were cultured over a library of surfaces presenting a spectrum of batches chemical functionality and nanostructure. Changes in cell attachment, morphology, migration and proliferation were examined. Media was removed at two different time points of 30 minutes and 24 hours, and examined to identify changes in fibroblast secreted proteins. Liquid chromatography was used to separate the cell culture media after incubation with cells over various chemically functionalised surfaces. Electrospray ionisation (ESI) and matrix assisted laser desorption (MALDI) mass spectrometry were used to identify changes in media with respect to the varying surfaces used and over time. The studies presented in this thesis give a better understanding of the interaction between silica nanoparticles and protein molecules, including conformational changes that occur when protein adsorbs on the nanoparticle; the effect of surface nanotopography and defined chemistry on protein adsorption is examined with respect to both chemical functionality and nanotopography. Clear differences were observed in the amount of protein adsorbed and its structural presentation when bound. The strength of the interaction, described through isotherm fitting, gave insight into the mechanism of competitive protein binding. Surface curvature on the nanoscale was also found to act synergistically with surface chemistry to dictate the dynamic accumulation of protein at the surface interface. In the later chapter discussion is given in terms of cell-surface interaction. Experimental evidence is shown for different mass spectroscopic analysis of reduced complexity media following initial cell-surface interaction and that after 24 hours. From this it is postulated that cell secretions are effected through interaction with the surface, with these changes being significant even after 30 minutes of cell culture with the defined surfaces. These changes are specific to the presented surface as they do not alter with respect to longer culture periods, but media are clearly different collected from cells cultured on different surfaces. This research will help solve challenges facing materials science, understand biological responses to surroundings and help in the development and advance of medical devices, drug delivery, therapeutics and diagnostics.

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5

Miller, Shannon L. "Theory and implementation of low-irreversibility chemical engines /". May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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6

Tseng, Hsien-Chung Ph D. Massachusetts Institute of Technology. "Production of pentanol in metabolically engineered Escherichia coli". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65767.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 149-160).
Public concerns about global warming and energy security contribute to an ever-increasing focus on biologically-derived fuels, leading to significant interest in several candidate molecules capable of complementing petroleum-derived fuel resources. Ethanol, one of the most developed biofuels, is used extensively as a gasoline additive. However, the high water miscibility of ethanol creates corrosion problems when transporting the fuel by pipelines. Furthermore, the low energy density of ethanol limits its fuel efficiency. Thus, it is important to explore alternative biofuels with properties that are more similar to conventional gasoline. With a higher energy density, enhanced physical properties that would allow better integration with current infrastructure, pentanol represents an excellent alternative, and has the potential to be a replacement for gasoline. The primary objective of my thesis work is to construct pentanol biosynthetic pathways in Escherichia coli, offering the possibility of producing pentanol from renewable carbon sources through microbial fermentations. We used butanol synthesis as a platform from which microbial synthesis of pentanol can be obtained. To explore the possibility of employing the butanol pathway enzymes for pentanol biosynthesis, we implemented a bypass/feeding strategy to thoroughly evaluate the ability of those enzymes to act on five-carbon substrates. Additionally, by boosting the intracellular NADH availability, we achieved up to 85 mg/L pentanol from glucose and propionate, providing an initial proof-of-concept of a functional and feasible pentanol biosynthetic pathway in E. coli. Furthermore, a platform pathway was established for synthesis of value-added chiral 3-hydroxyalkanoic acids with applications ranging from chiral building blocks to high-value pharmaceuticals. Of significance, such pathway was constructed as one portion of the pentanol pathway, illustrating versatility of our pentanol pathway as it can be modularized for synthesis of various valuable chemicals. Altogether, our results suggest that direct microbial synthesis of pentanol solely from glucose or glycerol can be realized once an efficient redox balancing within the recombinant strains is ensured. As construction of desired biosynthetic pathways is just the first step toward economically viable pentanol production, increasing the titer, yield, and productivity will ultimately determine the feasibility of such pathways.
by Hsien-Chung Tseng.
Ph.D.

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7

Algharrawi, Khalid Hussein Rheima. "Production of methlxanthines by metabolically engineered E. coli". Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5904.

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Methylxanthines are natural and synthetic compounds found in many foods, drinks, pharmaceuticals, and cosmetics. Aside from caffeine, production of many methylxanthines is currently performed by chemical synthesis. This process utilizes many chemicals, multiple reactions, and different reaction conditions, making it complicated, environmentally dissatisfactory, and expensive, especially for monomethylxanthines and paraxanthine. In this work, we developed a novel biocatalytic platform for the production of methylxanthines from economic feedstocks; bench scale production of three different methlxanthines, theobromine, 3 and 7-methylxanthines has been demonstrated. The biocatalytic process used in this work operates at 30 OC and atmospheric pressure, and is environmentally friendly. The biocatalyst was E. coli BL21(DE3) engineered with ndmA/D or ndmB/D genes combinations. These modifications enabled specific N1 and N3- demethylation of caffeine, theophylline and theobromine to theobromine & paraxanthine, 3-methylxanthine and 7-methylxanthine respectively. This common production platform consists of uniform fermentation conditions with a specific metabolically engineered strain, uniform induction of specific enzymes for methylxanthine production, uniform recovery and preparation of biocatalyst for reaction and uniform recovery of pure products. Many E. coli BL21(DE3) strains metabolically engineered with single and/or multiple ndmA/D or ndmB/D genes were tested for catalytic activity, and the best strains which had the higher activity were chosen to carry out the N-demethylation reaction to produce the higher value methylxanthines. Strain pDdA had the highest activity for the production of 3-methylxanthine from theophylline; strain pAD1dDD had the highest activity for the production of theobromine from caffeine, and strain pBD2dDB had the highest activity for the production of 7-methylxanthine from theobromine. Each of these strains were used to find the optimum amount of cells required to achieve complete conversion of substrates to product(s) within two hours. It was found that 15 mg/mL resting cells concentration of pDdA strain was required to completely N-demethylate 1 mM theophylline to 3-methylxanthine (81% conversion) and 1-methylxanthine (13%). Also, 15 mg/mL resting cells concentration of pAD1dDD strain was required to completely convert 1 mM caffeine to theobromine (98.5% conversion) and paraxanthine (1.5%). The optimum concentration of pBD2dDB strain to achieve 100% conversion of 0.5 mM theobromine to 7-methylxanthine was 5 mg/mL. Moreover, coffee post -brew waste was used as a source of caffeine, which was completely utilized by 25 mg/mL resting cells pAD1dDD strain to theobromine by a conversion of 97%. The cell growth of each specific strain was studied using different growth media, including Luria-Bertani Broth, Terrific Broth, and Super Broth. In all cases, super broth was found to be the best medium to produce the highest amount of cell paste. The amount of cell paste produced from 100 mL Super broth medium after 14-16 hour of growth was found to be 0.9, 0.9, and 1.5 g for pDdA, pAD1dDD, and pBD2dDB strains respectively. Subsequently, each reaction was scaled up to produce 100-300 mg pure methylxanthines products, and therefore cell growth was also scaled up (1-4 L) to produce adequate amount of biocatalyst to carry out these larger scale reactions. 1.3 L reaction volume was used to produce 3-methylxanthine (81%conversion) from 1 mM theophylline catalyzed by 15 mg/mL pDdA strain. 2 L reaction volume was used to produce theobromine (98.5% conversion) from 1 mM caffeine catalyzed by 15 mg/mL pAd1dDD strain. 2 L reaction volume was used to produce 7-methylxanthine (100% conversion) from 0.5 mM theobromine catalyzed by pBD2dDB strain. All reactions were carried out at 30 oC and 250 rpm shaker speed, and the reaction medium was 50 mM potassium phosphate buffer (pH=7). All methylxanthines products were separated by preparative chromatography with high recovery, and each product solution was collected in bottles. Products were purified by drying at 120-140 C for 4 hours and 100, 255, and 127 mg 3-methylxanthine, theobromine, and 7-methylxanthine were recovered. Also, 178 mg theobromine was produced form post brew coffee waste from 1.16 L reaction catalyzed by 25 mg/mL pAD1dDD strain. Purity of the isolated methylxanthine products was comparable to authentic commercially standards with no contaminant peaks, as observed by HPLC, LC-MS and NMR.

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8

Domagalski, Jakub. "Electrochemically engineered anodic alumina Nanotubes: physico-chemical properties and Applications". Doctoral thesis, Universitat Rovira i Virgili, 2021. http://hdl.handle.net/10803/671688.

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Des del seu descobriment, l'alúmina anòdica porosa s’ha utilitzat com a recobriment protector. El descobriment de la seva estructura porosa va animar els investigadors a desenvolupar nous mètodes de fabricació d'alúmina, obtenint així geometries complexes de propietats diverses. En aquesta tesi es desenvolupen nanotubs d'alúmina anòdica (AANTs) mitjançant un procés d’anodització que es coneix com anodització per polsos. El procés consisteix a entrellaçar polsos de corrent de baixa (~6 mA/cm2) i alta (~290-390 mA/cm2) densitat. Un flux de corrent prou alt produeix un estrenyiment vertical dels porus i unions entre cel·les més febles. L'atac electroquímic selectiu i la sonicació en aigua de l'estructura resultant permeten produir col·loides de nanotubs. El primer objectiu d'aquesta tesi és una anàlisi exhaustiva del procés per comprendre millor el mecanisme de formació dels AANTs i relacionar les condicions d’anodització amb la seva geometria resultant. El segon objectiu és avaluar i optimitzar el seu postprocessat, investigant nous mètodes d'alteració de les seves propietats fisicoquímiques. L'últim objectiu és dissenyar i fabricar nanotubs i proposar les seves aplicacions. Aquest treball investiga l'evolució del perfil de l'alúmina en funció dels paràmetres d’anodització. A més, el corrent i el potencial del procés s'associen amb la geometria i les propietats dels nanotubs obtinguts: longitud, diàmetre intern i extern, potencial Z i tamany. En resum, un corrent més alt condueix a nanotubs més llargs i estrets amb menor càrrega superficial. S'avaluen i optimitzen les condicions de sonicació. Es demostra que el recuit a alta temperatura dels nanotubs té un impacte en la seva estructura cristal·lina i composició elemental. Posteriorment, els nanotubs es decoren electrostàticament amb nanopartícules magnètiques i es modifica el seu interior amb una proteïna marcada amb fluoròfor. Aquests col·loides magnètics han demostrat ser útils per a la detecció de la catepsina B, el que demostra la seva utilitat com a sensors.
La anodización del aluminio tiene casi un siglo de historia. La alúmina anódica se utilizó inicialmente como recubrimiento protector, pero el desarrollo de la microscopía electrónica reveló la morfología porosa de este óxido. Este descubrimiento animó a los investigadores a desarrollar nuevos métodos de fabricación de la alúmina porosa, obteniendo así geometrías complejas con diversas propiedades. En esta tesis se desarrollan nanotubos de alúmina anódica (AANTs) a través de un proceso de anodización que se conoce como anodización por pulsos. El proceso consiste en entrelazar pulsos de corriente de baja (~ 6 mA / cm2) y alta (~ 290-390 mA / cm2) densidad. Un flujo de corriente suficientemente alto afecta a la formación de la estructura, resultando en un estrechamiento vertical de los poros y uniones entre celdas más débiles. El ataque electroquímico selectivo y la sonicación en agua de la estructura resultante permiten producir coloides de nanotubos. El primer objetivo de esta tesis es un análisis exhaustivo del proceso para comprender mejor el mecanismo de formación de los AANTs y conectar con precisión las condiciones de anodización con la geometría resultante de la estructura. El segundo objetivo es evaluar y optimizar su posprocesado, investigando nuevas posibilidades de alterar las propiedades fisicoquímicas de los AANT. El último objetivo es diseñar y fabricar nanotubos funcionales y proponer sus aplicaciones. Este trabajo investiga la evolución del perfil de anodización en función de las condiciones del proceso de anodización. Además, la corriente y el potencial del proceso se asocian con la geometría y las propiedades de los nanotubos obtenidos: longitud, diámetro interno y externo, potencial Z y dispersión de tamaño. En resumen, una corriente más alta conduce a nanotubos más largos y estrechos con una carga superficial más baja. Se evalúan las condiciones de sonicación proponiendo un conjunto de parámetros más óptimo. Se demuestra que el recocido a alta temperatura de los nanotubos tiene un impacto en su estructura cristalina y composición elemental: el aumento de temperatura produce una fracción cristalina más alta y disminuye su contenido de azufre. Posteriormente, los nanotubos se decoran electrostáticamente con nanopartículas de maghemita y se modifica su interior con una proteína marcada con
Most of the time since its discovery, nanoporous anodic alumina was used as a protective coating. The intrinsic property revealed by the electron microscope – porosity – encouraged researchers to investigate new methods of porous alumina fabrication, obtaining complex geometries with various properties. In this thesis, anodic alumina nanotubes (AANTs) are developed through a carefully adjusted anodization process defined as pulse anodization. The process consists of interlacing current pulses of low (~6 mA/cm2) and high (~290-390 mA/cm2) density. Sufficiently high current flow affects the formation of the structure, resulting in vertical pore narrowings and weaker cell junctions. Selective acid etching and sonication in water enables to yield colloids of nanotubes. First aim of this thesis is a thorough analysis of the process to better understand the formation mechanism of AANTs and precisely connect anodization conditions with the resultant geometry of the structure. Second goal is to evaluate and optimize post-processing investigating further possibilities to alter physio-chemical properties of AANTs. Last objective is to design and fabricate functional nanotubes and propose their applications. This work reports the evolution of the anodization profile depending on the process conditions. Further, current and potential of the process are associated with the geometry and the properties of the obtained nanotubes: length, inner and outer diameter, z-potential and size dispersity. In brief, higher current leads to longer and narrower nanotubes with lower surface charge. Sonication conditions are evaluated leading to the proposal of a more optimal set of parameters. Annealing of the nanotubes is demonstrated to impact on their crystalline structure and elemental composition: temperature increase leads to higher crystalline fraction and decrease their sulfur content. Nanotubes are later electrostatically-decorated with maghemite nanoparticles and modified inside with a fluorophore labelled protein. These magnetically responsive colloids demonstrate stimuli-responsive detection of cathepsin B, supporting its utility as a sensor.

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9

Basim, Gul Bahar. "Formulation of engineered particulate systems for chemical mechanical polishing applications". [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001115.

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10

Khan, Ahmed Faraz. "Chemical kinetics modelling of combustion processes in SI engines". Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/7554/.

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The need for improving the efficiency and reducing emissions is a constant challenge in combustion engine design. For spark ignition engines, these challenges have been targeted in the past decade or so, through ‘engine downsizing’ which refers to a reduction in engine displacement accompanied by turbocharging. Besides the benefits of this, it is expected to aggravate the already serious issue of engine knock owing to increased cylinder pressure. Engine knock which is a consequence of an abnormal mode of combustion in SI engines, is a performance limiting phenomenon and potentially damaging to the engine parts. It is therefore of great interest to develop capability to predict autoignition which leads to engine knock. Traditionally, rather rudimentary skeletal chemical kinetics models have been used for autoignition modelling, however, they either produce incorrect predictions or are only limited to certain fuels. In this work, realistic chemical kinetics of gasoline surrogate oxidation has been employed to address these issues. A holistic modelling approach has been employed to predict combustion, cyclic variability, end gas autoignition and knock propensity of a turbocharged SI engine. This was achieved by first developing a Fortran code for chemical kinetics calculations which was then coupled with a quasi-dimensional thermodynamic combustion modelling code called LUSIE and the commercial package, GT-Power. The resulting code allowed fast and appreciably accurate predictions of the effects of operating condition on autoignition. Modelling was validated through comparisons with engine experimental data at all stages. Constant volume chemical kinetics modelling of the autoignition of various gasoline surrogate components, i.e. iso-octane, n-heptane, toluene and ethanol, by using three reduced mechanisms revealed how the conversion rate of relatively less reactive blend components, toluene and ethanol, is accelerated as they scavenge active radical formed during the oxidation of n-heptane and iso-octane. Autoignition modelling in engines offered an insight into the fuel-engine interactions and that how the composition of a gasoline surrogate should be selected. The simulations also demonstrated the reduced relevance of research and motor octane numbers to the determination of gasoline surrogates and that it is crucial for a gasoline surrogate to reflect the composition of the target gasoline and that optimising its physicochemical properties and octane numbers to match those of the gasoline does not guarantee that the surrogate will mimic the autoignition behaviour of gasoline. During combustion modelling, possible deficiencies in in-cylinder turbulence predictions and possible inaccuracies in turbulent entrainment velocity model required an optimisation of the turbulent length scale in the eddy burn-up model to achieve the correct combustion rate. After the prediction of a correct mean cycle at a certain engine speed, effects of variation in intake air temperature and spark timing were studied without the need for any model adjustment. Autoignition predictions at various conditions of a downsized, turbocharged engine agreed remarkably well with experimental values. When coupled with a simple cyclic variability model, the autoignition predictions for the full spectrum of cylinder pressures allowed determination of a percentage of the severely autoigniting cycles at any given spark timing or intake temperature. Based on that, a knock-limited spark advance was predicted within an accuracy of 2° of crank angle.

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11

Li, Cheri Yingjie. "Engineered microtissue platforms for modeling human pathophysiology and drug metabolism". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81683.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 139-160).
Over 50% of all drug candidates entering clinical trials are abandoned due to insufficient efficacy or unexpected safety issues despite extensive pre-clinical testing. Liver metabolites that cause toxicity or other side effects cannot always be predicted in animals, in part because of human-specific drug metabolism. Furthermore, while the clinical need for cancer drugs is increasing, anti-tumor activity in animals often leads to a disappointing lack of efficacy in real patients. In vitro models that can better predict human responses to drugs would mitigate the overall costs of development and help bring new therapies to market. In order to improve the predictive power of in vitro tissue models, various features of the microenvironment that modulate cell behavior have been investigated, such as cell-cell interactions, cell-matrix interactions, soluble signals, 3-dimensional (3D) architecture, and mechanical stiffness. Synthetic hydrogels offer a versatile platform within which these cues can be precisely perturbed in a 3D context; however, the throughput of these methods is quite limited. In this thesis, we explore the potential of high-throughput manufacturing and monitoring of populations of miniaturized 3D tissues, termed 'microtissues,' for modeling healthy and diseased tissues in both static and perfused systems. First, we developed a flow-based platform to test tumor proliferation in defined microenvironmental settings with large numbers of replicates (n > 1000). A microfluidic droplet generator was designed to encapsulate tumor cells with stromal cells and extracellular matrix in 100 pm-diameter poly(ethylene glycol) (PEG) microtissues (6000 microtissues/min). Upon screening a small panel of soluble stimuli, TGF-p and the TGF-pR1/2 inhibitor LY2157299 were found to have opposing effects on the proliferation of lung adenocarcinoma cells in microtissues vs. in 2-dimensional culture, affirming a potential role for 3D models in the investigation of cancer therapies. Next, we extend these techniques to the analysis of drug-induced liver injury. Phenotypic maintenance of primary hepatocytes was achieved by controlled pre-aggregation (-50 tm units) with J2-3T3 fibroblasts to establish cell-cell contacts prior to encapsulation into microtissues. Retention of both constitutive and inducible Phase I drug metabolism activity allowed detection of prototypical hepatotoxins through generation of toxic metabolites and emergence of drug-drug interactions, thereby demonstrating the suitability of hepatic microtissues for 3D, high-throughput toxicity screening. Finally, we describe efforts to bridge the gap between multi-organ models and human drug metabolism. Modular human hepatocyte microtissues were entrapped by semi-circular microsieves in a microfluidic perfusion chamber for over 3 weeks. In contrast to immortalized hepatic cell lines, primary hepatocytes stabilized in microtissues exhibited human-specific induction profiles, reflected donor hetereogeneity in CYP2D6 and CYP2C19 enzyme activity levels, and performed xenobiotic detoxification on circulating drugs, establishing the ability to incorporate hepatic functions in 'human-on-a-chip' devices. Collectively, these three applications of cell-laden microtissues demonstrate their versatility and potential impact in both drug development and fundamental studies of the cellular microenvironment.
by Cheri Yingjie Li.
Ph.D.

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12

Tam, Brooke Elizabeth. "DNA methylation detection using an engineered methyl-CpG-binding protein". Thesis, Massachusetts Institute of Technology, 2018. https://hdl.handle.net/1721.1/121898.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2018
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 96-103).
DNA methylation, specifically the methylation of cytosine bases, is an important biomarker, as abnormal DNA methylation patterns are found in many different types of cancer. Currently, a small number of cancer hospitals evaluate the methylation status of the MGMT gene promoter to determine the best course of treatment for patients with glioblastoma. However, improved methylation detection techniques are required in order to expand the availability of such testing to more patients. Methyl-CpG-binding domain (MBD) proteins bind specifically to methylated DNA sequences, and many assays have been developed that use these proteins in methylation profiling of DNA. The wild-type proteins in the MBD family bind specifically to symmetrically methylated CpG dinucleotides. Here, I have engineered a new MBD variant that binds to hemi-methylated DNA but not unmethylated DNA, allowing for the detection of a methylated target sequence hybridized to a simple, unmethylated DNA probe.
With four amino acid substitutions, a protein that did not show any binding to hemi-methylated DNA at concentrations up to 100 nM was altered to bind hemi-methylated DNA with high affinity. Based on equilibrium binding titrations, this engineered variant binds a DNA sequence with a single hemi-methylated CpG dinucleotide with a dissociation constant of 5.6 ± 1.4 nM. After engineering a protein to bind hemi-methylated CpG dinucleotides, I developed a simple, hybridization-based assay to determine the methylation status of the MGMT promoter using this protein variant and magnetic microparticles. The target DNA molecules are captured on the surface of magnetic microparticles and an MBD-GFP fusion protein is added to bind if the captured target is methylated. Therefore, MBD binding can be detected directly based on fluorescence of the microparticles after the binding step without requiring any chemical conversion or additional labeling steps.
In addition to simplifying the assay and eliminating the need for methylated capture probes, I was able to improve the sensitivity of the assay to 5 pM target DNA. Finally, I also studied the DNA capture and MBD binding events to identify the key parameters and guide future efforts to develop clinically relevant diagnostics.
by Brooke Elizabeth Tam.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering

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13

De, almeida Tania. "Impact d’une espèce ingénieure de l’écosystème et son utilisation en restauration écologique : Le cas de Messor barbarus (L.) dans les pelouses méditerranéennes Above- and below-ground effects of an ecosystem engineer ant in Mediterranean dry grasslands Harvester ants as ecological engineers for Mediterranean grassland restoration: impacts on soil and vegetation A trait-based approach to promote ants in restoration ecology". Thesis, Avignon, 2020. http://www.theses.fr/2020AVIG0358.

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L’objectif principal de cette thèse était double : (i) mesurer l’impact d’une espèce de fourmi sur son écosystème, afin (ii) d’en déduire des applications potentielles dans le domaine de la restauration écologique.Les fourmis sont parmi les organismes les plus abondants des écosystèmes terrestres et occupent des zones géographiques très variées. Elles jouent des rôles écologiques clés dans de nombreux écosystèmes comme ingénieurs du sol, prédateurs ou régulateurs de la croissance et de la reproduction des plantes. Cependant les données collectées localement sont souvent parcellaires et ne permettent pas d’avoir une vision complète de l’impact d’une espèce sur son milieu.Messor barbarus (L.), connue pour redistribuer les graines et pour modifier les propriétés physico-chimiques du sol, est largement répandue dans le Sud-Ouest de l’Europe notamment au sein des pelouses méditerranéennes. Elle pourrait donc jouer un rôle majeur dans la composition et structuration de ces pelouses caractérisées par une forte biodiversité mais dont le nombre et la superficie ont drastiquement diminué ces dernières décennies.Dans un premier temps, par une étude multi-compartiments, nous avons confirmé l’hypothèse selon laquelle M. barbarus est une ingénieure de l’écosystème au sein des pelouses méditerranéennes. Elle transforme cet habitat en modifiant, comme attendu, les propriétés physico-chimiques du sol. Ces modifications sont associées à une augmentation de la biomasse et de l’hétérogénéité des communautés végétales ainsi qu’à des changements dans les faunes épigée et endogée (abondance, occurrence et structure des communautés). De plus, M. barbarus modifie profondément les relations trophiques et non trophiques interspécifiques et entre les espèces et leur habitat. L’hétérogénéité créée à l’échelle locale par l’activité de cette fourmi, entraine une diversification des niches écologiques au sein de ces pelouses.Malgré leur rôle souvent majeur sur le fonctionnement des écosystèmes, les fourmis ne sont que très rarement considérées en restauration écologique. Sur notre site d’étude, un chantier de réhabilitation d’une pelouse sèche après une fuite d’hydrocarbures et un transfert de sol, M. barbarus a permis d’accélérer la restauration des propriétés physico-chimiques du sol mais aussi de la banque de graines à moyen terme - sept ans après la réhabilitation du site. Ces résultats font donc de cette espèce une bonne candidate en ingénierie écologique.Afin de généraliser l’utilisation des fourmis en restauration écologique, nous proposons une méthodologie à destination des gestionnaires basée sur l’utilisation de traits fonctionnels et d’histoire de vie. Pour cela nous avons évalué le potentiel des fourmis en écologie de la restauration, puis nous avons listé l’ensemble des traits connus pour affecter les compartiments abiotiques et biotiques et/ou pertinent pour effectuer un suivi du succès de la phase de restauration. La méthodologie proposée permet une première sélection des espèces potentiellement utilisables en fonction des objectifs de restauration
The main objective of this thesis was double: (i) to assess the impact of an ant species on its ecosystem, in order to (ii) deduce potential applications in the field of ecological restoration.Ants are among the most abundant organisms in terrestrial ecosystems and occupy a wide range of geographical areas. They play key ecological roles in many ecosystems as soil engineers, predators or regulators of plant growth and reproduction. However, the information collected locally is often fragmented and does not provide a complete overview of the impact of a species on its environment.Messor barbarus (L.), known to redistribute seeds and to modify the soil physico-chemical properties, is widespread in South-Western Europe, particularly in Mediterranean grasslands. Therefore, it may play a major role in the composition and structuring of these ecosystems, which are characterised by high biodiversity but whose abundance and surface area have decreased drastically in recent decades.Through a multi-compartment study, we confirmed the hypothesis that M. barbarus is an ecological engineer in Mediterranean grasslands. This species changes this habitat by modifying, as expected, soil physico-chemical properties. These modifications are associated with an increase in both biomass and heterogeneity of plant communities, as well as changes in above- and belowground fauna (abundance, occurrence and structure of communities). Messor barbarus profoundly changes trophic and non-trophic relationships within and between species and their habitat. The heterogeneity created locally by the activity of M. barbarus leads to a diversification of ecological niches within these grasslands.Despite their major role in the functioning of ecosystems, ants are rarely considered in restoration ecology. In our study site, corresponding to a dry grassland rehabilited after an oil leak and a soil transfer, M. barbarus contributed to accelerate the restoration of the soil physico-chemical properties but also of the seed bank in the medium term - seven years after the rehabilitation. These results make this species a good candidate for ecological engineering.In order to generalise the use of ants in restoration ecology, we propose a trait-based methodology for stakeholders. We evaluated the potential of ants in restoration ecology, then listed all the traits known to affect abiotic and biotic compartments and/or relevant to monitor the success of the restoration phase. The proposed methodology provides a first selection of potentially relevant species according to the restoration objectives

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Rafique, Nasir. "Engineered functional films for photo-electro-chemical sensing of environmental matters". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2023. https://ro.ecu.edu.au/theses/2672.

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The identification and detection of harmful substances in various matrices has gained significant attention due to the negative impacts they have on human health and aquatic life. To address this issue, various analytical techniques have been developed and utilized by monitoring agencies and regulatory bodies. However, many of these techniques are complex, costly and require specialized equipment and trained personnel to operate. Furthermore, the large and cumbersome nature of these techniques makes it difficult to conduct measurements in the field. Additionally, some of these techniques may not be sensitive enough or selective enough and require time-consuming sample preparation procedures. Electrochemical (EC) and Photoelectrochemical (PEC) techniques are gaining significant attention in the field of environmental monitoring and clinical analysis due to their sensitivity, cost-effectiveness, simplicity, rapid operation, flexibility, and device miniaturization. The adaptability of electrochemical and photoelectrochemical techniques, combined with the emergence of novel materials and technology, has facilitated the creation of various methodologies for identifying environmental contaminants and clinical pollutants with heightened sensitivity and specificity. To this end, nanocomposites of transition metals and their oxide (Ni, Co, Fe), along with carbonaceous materials (g-C3N4) were redesigned with engineered approaches to improve the efficiency of EC and PEC sensors. In this thesis, novel strategies for the preparation and modification of these nanocomposites are presented to improve the performance of the EC and PEC technologies. The physical, electronic, and chemical properties of these nanocomposite materials were carefully manipulated and adjusted to produce core shell nanoarrays, layered double hydroxide, and heterostructures morphology for highly promising electroactive and photoactive sensing platform for detecting 4-chlorophenol, nitrite, and glucose. Different synthesis techniques, including electrodeposition, electroreduction, chemical reduction, and template-assisted synthesis were used to attain the desired fine-tuned morphology. Advanced characterization techniques such as SEM, TEM, XRD, XPS, BET, PL, and UV-Vis were then utilized to determine the materials' architectural and structural composition. Subsequently, the use of a binder-free current collector, such as a 3 dimensional (3D) porous metal foam, instead of traditional Indium Tin Oxide (ITO) and Fluorine-doped Tin Oxide (FTO) was systematically explored to make it more attractive option for use in EC and PEC applications. The influence of operation parameters such as solution pH, applied voltage, and catalyst loading was comprehensively investigated and optimized for practical application, highlighting the significance of the work in advancing electrochemical and photoelectrochemical sensing. This study aimed to contribute to the successful implementation of proof-of-concept experiments that utilize nanocomposite materials with rational design and cutting-edge technology in the field of EC and PEC sensing. These developments have the potential to significantly enhance the capabilities and precision of these sensors for the development of more efficient and cost-effective devices in the future.

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Єрмак, Аліна Володимирівна. "Education and personal skills of a chemical technology engineer in the 21st century". Thesis, Київський національний університет технологій та дизайну, 2020. https://er.knutd.edu.ua/handle/123456789/15295.

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16

Angelos, John P. (John Phillip). "Fuel effects in homogeneous charge compression ignition (HCCI) engines". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/50615.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009.
Includes bibliographical references (p. 209-217).
Homogenous-charge, compression-ignition (HCCI) combustion is a new method of burning fuel in internal combustion (IC) engines. In an HCCI engine, the fuel and air are premixed prior to combustion, like in a spark-ignition (SI) engine. However, rather than using a spark to initiate combustion, the mixture is ignited through compression only, as in a compression-ignition (CI) engine; this makes combustion in HCCI engines much more sensitive to fuel chemistry than in traditional IC engines. The union of SI- and CI-technologies gives HCCI engines substantial efficiency and emissions advantages. However, one major challenge preventing significant commercialization of HCCI technology is its small operating range compared to traditional IC engines. This project examined the effects of fuel chemistry on the size of the HCCI operating region, with an emphasis on the low-load limit (LLL) of HCCI operability. If commercialized, HCCI engines will have to operate using standard commercial fuels. Therefore investigating the impact of fuel chemistry variations in commercial gasolines on the HCCI operability limits is critical to determining the fate of HCCI commercialization. To examine these effects, the operating ranges of 12 gasolines were mapped in a naturally-aspirated, single-cylinder HCCI engine, which used negative valve overlap to induce HCCI combustion. The fuels were blended from commercial refinery streams to span the range of market-typical variability in aromatic, ethanol, and olefin concentrations, RON, and volatility. The results indicated that all fuels achieved nearly equal operating ranges. The LLL of HCCI operability was completely insensitive to fuel chemistry, within experimental measurement error. The high-load limit showed minor fuel effects, but the trends in fuel performance were not consistent across all the speeds studied. These results suggest that fuel sensitivity is not an obstacle to auto-makers and/or fuel companies to introducing HCCI technology.
(cont.) Developing an understanding of what causes an HCCI engine to misfire allows for estimation of how fuel chemistry and engine operating conditions affect the LLL. The underlying physics of a misfire were studied with an HCCI simulation tool (MITES), which used detailed chemical kinetics to model the combustion process. MITES was used to establish the minimum ignition temperature (Tmisfire) and full-cycle, steady-state temperature (Tss) for a fuel as a function of residual fraction. Comparison of Tmisfire and Tss near the misfire limit showed that Tss approaches Tmisfire quite closely (to within ~ 14 K), suggesting that the primary cause of a misfire is insufficient thermal energy needed to sustain combustion for multiple cycles. With this relationship, the effects of engine speed and fuel chemistry on the LLL were examined. Reducing the engine speed caused a reduction in T, which allowed fuel chemistry effects to be more apparent. This effect was also observed experimentally with 2 primary reference fuels (PRFs): PRF60 and PRF90. At 1000 RPM, PRF60 obtained a substantially lower (~30%) LLL than PRF90, but at speeds >/= 1500 RPM, fuel ignitability had no effect on the LLL. Fuel chemistry was shown to influence the LLL by increasing both Tmisfire and Tss for more auto-ignition resistant fuels. However, the extent to which fuel chemistry affects these temperatures may not be equivalent. Therefore, the relative movement of each temperature determines the extent to which fuel chemistry impacts the LLL.
by John P. Angelos.
Ph.D.

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Tsekenis, Stylianos-Alexios. "High speed chemical species tomography for advanced fuels and engines". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/high-speed-chemical-species-tomography-for-advanced-fuels-and-engines(2ea2e7eb-c3e7-4fe9-96c1-a01d7e4c4a04).html.

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Current research in CI combustion aims to reduce PM and NOx emissions by controlling mixture homogeneity. Low CN fuels are suitable due to their auto-ignition resistance, but the in-cylinder mixture stratification level must be carefully visualised and controlled. Numerous diagnostic techniques exist for imaging the in-cylinder hydrocarbon species concentration. Tomographic techniques based on spectroscopic modalities are minimally-intrusive and able to target species of interest even in multi-component fuel blends. The high-speed CST technique applied in this work is based on the NIRAT modality. A number of collimated LASER beams at 1700nm traverse the optically accessible engine combustion chamber and are spectroscopically absorbed by the first overtone of the C-H stretch bond. Non species-specific attenuation mechanisms are suppressed by a DWR scheme utilising a reference wavelength at 1651nm. Ratiometric data is used to tomographically reconstruct the spatially-varying fuel concentration. In this work the first application of NIRAT on a commercial CI engine is presented, using instrumentation capable of imaging 13 frames/CAD at 1200rpm using a 31-beam array. A novel method was developed to experimentally quantify the tomography system’s non-uniform spatial resolution. The method was applied in laboratory experiments involving free-space propane plumes and a map of the spatial resolution was created. The spatial resolution varies between 4mm and 14mm. The mean of 9mm is 72% better than previous estimates in the literature. Regions of poor performance correlated with non-uniformities in the sensitivity matrix, indicating that a regular beam array may contribute towards more accurate and objective reconstructions of unknown concentrations. The characterised tomography system was installed on an optically-accessible Volvo D5 CI engine. The optically-inaccessible CAD region achieved was ±18CAD, a reduction of ±12° from previous works. The vibration-tolerance of the optical access system was verified, concluding that the initial alignment of the beams is the dominant factor that determines beam integrity after prolonged engine operation. The behavior of individual beams was studied, finding strong cycle-to-cycle correlation of the anomalies present. This was exploited to develop a novel, robust analysis algorithm to process the engine data. The algorithm achieved a standard deviation of <10% of the maximum pk-pk magnitude of the transmission signal in the fuel vapour phase. The system was applied to qualitatively visualise the mixing of a 50/50% blend of iso-/n-dodecane in a motored, nitrogen-aspirated engine under a range of operating conditions. A study by simulation of the decomposition of n-dodecane concluded that only 0.492% of the quantity injected is pyrolytically converted during a compression stroke. Spray-phase imaging was not possible due to severe reduction of the optical throughput, lasting for 8-15 CAD for a lean mixture and for 15-30 CAD for a rich mixture. Vapour-phase reconstructions using the enhanced iterative Landweber algorithm were successful in resolving rich fuel pockets consistent with the injection pattern. It was shown that the degree of mixture homogeneity at TDC is dependent upon the initial intake temperature. PLIF was used to cross-validate the NIRAT reconstructions. Localisation of the features reconstructed with NIRAT was excellent, with a maximum angular deviation of ±10°. A swirl motion of the mixture by 1°/CAD was observed using both techniques, confirming the features previously observed in the NIRAT reconstructions. In conclusion, NIRAT has been, for the first time, successfully applied for in-cylinder fuel distribution imaging in a CI engine. The results, created using an original data analysis algorithm, were successfully cross-validated using PLIF. A novel spatial resolution quantification method was formulated and used to characterise the tomography system. The numerous findings and learning points from the individual stages of this work will be used to advance the field of combustion diagnostics as well as contribute towards the development of advanced in-cylinder tomographic imaging systems.

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Prevo, Brian Geoffrey. "ENGINEERED DEPOSITION OF FUNCTIONAL COATINGS FROM MICRO- AND NANOPARTICLES USING CONVECTIVE ASSEMBLY". NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-11202005-150427/.

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The potential technological applications of micro- and nanoparticle coatings necessitate the development of rapid, inexpensive and easily controlled deposition procedures. We have developed a technique for making structured thin films from micro- and nanoparticles by dragging on a substrate a liquid meniscus at constant velocity. The advantages of this technique are improved process speed, efficiency and reduced material consumption relative to standard dip coating techniques. The governing mechanism of the deposition process was found to be convective assembly at high volume fractions. Uniform, large area coatings (square centimeters in area) can be deposited in minutes at rates approaching 100 microns per second from microliters of suspension. Operational ?phase? diagrams were constructed from coating data, relating the coating layer thickness and particle packing symmetry to the process parameters: deposition speed, particle volume fraction, and solvent evaporation rate. Varying these parameters provided the means to control and tune nanocoating structure and properties. We found the most potent parameter to be the deposition speed. The deposition process was well modeled by a simple macroscopic species balance taken around the thin film drying site. We have successfully applied this deposition technique to a wide variety of colloidal systems including: latex and silica microspheres, gold nanoparticles, ferritin proteins, and living yeast cells. Conductive coatings from metal nanoparticles exhibited tunable optical and electronic properties simply by virtue of the adjusting deposition speed. The antireflective (AR) capabilities of silica nanoparticle coatings on glass and silicon substrates can also be facilely tuned using this deposition process. These AR coatings demonstrably improved the photovoltaic efficiency of solar cells. We have also investigated the use of compressed carbon dioxide as a replacement solvent for colloidal coating deposition. We achieved rapid sedimentation of uniform, conformal nanoparticle coatings using liquid and supercritical carbon dioxide (primarily as an antisolvent). These results show potential for fabricating conformal coatings of self cleaning, technologically relevant materials by simple self-assembly techniques.

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Augustine, Chad R. "Hydrothermal spallation drilling and advanced energy conversion technologies for Engineered Geothermal Systems". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51671.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references.
The purpose of this research was to study the various factors affecting the economic and technical feasibility of Engineered Geothermal Systems, with a special emphasis on advanced drilling technologies. The first part of the thesis was devoted to modeling and analysis of the technologies used to develop EGS projects. Since the cost of completing wells is a major factor in determining the economic feasibility of EGS projects, it is vital to be able to accurately predict in determining the economic feasibility of EGS projects, it is vital to be able to accurately predict their costs. Historic well cost data was analyzed to identify trends, and a drilling cost index for updating historic geothermal well costs to present day costs was developed. The effects of different advanced drilling technologies on drilling costs were estimated and incorporated into a techno-economic model to estimate their impact, as well as the impact of advanced reservoir stimulation technologies, on EGS levelized electricity costs. A technical analysis of geothermal binary Rankine cycle surface power plants was also performed to determine the effect of novel working fluids on plant efficiency for both sub- and supercritical binary cycles. The objective of the second part of the thesis was the application of thermal spallation drilling to deep boreholes. Thermal spallation is the fragmentation of a brittle solid into small, disc-like flakes by rapidly heating a confined fraction of the rock. It was proposed that the necessary temperatures and heat fluxes needed to induce thermal spallation in the high pressure, high density deep borehole environment could be achieved using hydrothermal flame technologies. An autoclave reaction system was designed and constructed to create flame jets in water at a pressure of 250 bar. The temperatures of these flames were measured, and attempts were made to use the flames to spall small rock samples. The experimental system was modified to study the centerline temperature decay of supercritical water jets injected at temperatures up to 525 °C into ambient temperature water. A device for measuring the heat flux from these jets was designed, constructed, and used to determine the heat transfer coefficients of the jets impinging against a flat surface. Together, these studies indicate that the necessary temperatures and heat fluxes required to induce thermal spallation in rocks can be achieved in a deep borehole.
by Chad R. Augustine.
Ph.D.

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20

Rickard, Jonathan James Stanley. "Advanced micro-engineered platforms for novel device technologies". Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8303/.

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The objectives of this thesis are to explore, design, fabricate and implement the use of advanced micro-engineered platforms to be exploited as versatile, novel device technologies. An increasing number of technologies require the fabrication of conductive structures on a broad range of scales and large areas. Here, we introduce advanced yet simple electrohydrodynamic lithography for patterning conductive polymers directly on a substrate with high-fidelity. We illustrate the generality of this robust, low-cost method by structuring thin films via electric-field-induced instabilities, yielding well-defined conductive structures with a broad range of feature sizes. We show the feasibility of the polypyrrole-based structures for field-effect transistors, which might herald a route towards submicron device applications. We also demonstrate a miniaturised platform technology for timely, sensitive and rapid point-of-care diagnostics of disease-indicative biomarkers. Our micro-engineered device technology (MEDTech) is based on reproducible electrohydrodynamically fabricated platforms for surface enhanced Raman scattering enabling tuneable, high-throughput nanostructures yielding high-signal enhancements. These, integrated within a microfluidic-chip provide cost-effective, portable devices for detection of miniscule biomarker concentrations from biofluids, offering clinical tests that are simple, rapid and minimally invasive. Using MEDTech to analyse clinical blood-plasma, we deliver a prognostic tool for long-term outcomes, in the hospital or at the point-of-care.

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21

Pitukmanorom, Pemakorn 1976. "Nanocomposites for nitrogen oxide emissions control in lean-burn engines". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28848.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2004.
Includes bibliographical references.
(cont.) reducing agent than propane in the SCR of NO. Pt-Rh/CuO/A1₂O₃ nanocomposites capable of adsorbing SO₂ in oxygen-rich environment as metal sulfates and releasing SO₂ in reducing atmosphere were synthesized with sequential precipitation technique. These CuO-based sorbents possessed excellent SO₂ adsorption capacity and superior regenerability by CO compared to those produced by the impregnation method due to higher surface area and dispersion of Cu species. A gram of sorbent with 30 wt% Cu could adsorb over 50 mg of SO2 before SO₂ breakthrough was observed. The rate of SO₂ desorption from the CuO/A1₂O₃ sorbents could be enhanced through the incorporation of noble metals. With the use of 0.1 wt% Pt, the CuO/A1₂O₃ sorbent with 30 wt% Cu could be regenerated twice as quickly. Also, on average only 8 ppm of SO₂ were detected downstream of this sorbent over each adsorption cycle at 400⁰C. The excellent sorbent regeneration was attributed to better CO adsorption and lower sulfate decomposition temperature as a result of Pt addition. The nature of sulfur deactivation of these sorbents was highly dependent on the composition of noble metals used. By employing both Rh and Pt, sorbent regeneration rate and stability could be optimized. Rh/CuO-MgO/A1₂O₃ nanocomposites capable of adsorbing NOx and SO₂ in oxygen-rich environment and releasing N₂ and SO₂ in reducing atmosphere were successfully prepared by sequential precipitation ...
Over the past few years, increase in environmental concern has led to a demand for more effective pollution control strategies that would satisfy the new EPA standards regarding automotive emissions of nitrogen oxides (NOx). In particular, the removal of NOx from lean-burn and diesel engines operating under an oxygen-rich atmosphere presents a significant challenge as conventional three-way catalysts are ineffective in this environment. Moreover, the presence of water vapor and sulfur oxides (SOx) in the exhaust stream both inhibits catalyst activity and results in long-term catalyst instability. Thus, it is necessary to develop novel technologies for the removal of NOx from the exhaust of lean-bum engines. This thesis examined three metal oxide nanocomposite systems to serve as (i) catalysts for the selective catalytic reduction (SCR) of NOx by propene, (ii) sorbents for SO₂ storage, and (iii) catalysts for NOx storage-reduction (NSR). In₂O₃-Ga₂O₃/A1₂O₃ nanocomposite catalysts have been synthesized using the sequential precipitation technique. These alumina-based catalysts exhibited superior NO reduction activity to those produced by the impregnation and sol-gel methods due to their higher surface area and dispersion of active components. In fact, an excellent N2 yield of 80% was achieved at 450⁰C over the In₂O₃-Ga₂O₃/A1₂O₃ nanocomposite with 2 wt% In and 8 wt% Ga. The high catalytic activity was attributed to better propene activation by In and improved NOx adsorption on the high surface area Ga₂O₃/A1₂O₃. The In₂O₃-Ga₂O₃/A1₂O₃ nanocomposite remained active even in the presence of SO2. The NO reduction activity of this catalyst system depended on the hydrocarbons that were used as the reducing agents. Propene was found to be a more effective
by Pemakorn Pitukmanorom.
Ph.D.

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22

Park, Kyoo Chul. "Physico-chemical hydrodynamics of droplets on textured surfaces with engineered micro/nanostructures". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81704.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Understanding physico-chemical hydrodynamics of droplets on textured surfaces is of fundamental and practical significance for designing a diverse range of engineered surfaces such as low-reflective, self-cleaning or anti-fogging glass, easy-cleaning robust inkjet printer heads, or efficient fog-harvesting surfaces. Developing such functional surfaces requires interdisciplinary considerations that have not been broadly explored and which integrate principles from capillarity, optics, nanofabrication, hydrodynamics of complex fluids, and even aerodynamics. The primary contribution of this thesis is to integrate consideration of wetting phenomena coupled with reflection of light, mechanical failure of slender structures, energy dissipation in non-Newtonian fluids, and aerodynamics of airborne droplets impacting onto permeable structures. Based on this integrative understanding, we construct design frameworks for both quantifying the performance of the desired functionalities for each application and for developing optimal functional surfaces. The first part of this thesis is focused on the development of superhydrophobic and superphotophilic surfaces that can be used for improving light-harvesting efficiency of photovoltaic cells. A design framework that combines wetting phenomena and adiabatic refractive index-matching together with a novel nanofabrication method is introduced to select slender tapered nanostructures that fulfill the multiple functionalities. The resulting nanoconetextured glass substrate exhibits highly robust superhydrophobicity and omnidirectional broadband anti-reflectivity as well as self-cleaning or anti-fogging property when conformally coated with a suitable chemical layer. Extending the nonwettability of textured surfaces to low surface tension oils is more difficult because oleophobic surfaces require a re-entrant topography. Deep reactive ion etching is used to fabricate square arrays of silicon nanopillars with wavy sidewalls that help support the superoleophobic state. The effect of the re-entrant nanotexture on the apparent contact angle, contact angle hysteresis, and sliding angle of water and hexadecane droplets is studied. We discuss numerical predictions for the critical pressure differences that cause failure of the Cassie- Baxter state that characterizes the super-repellent state for water and hexadecane droplets on the textured surfaces. In addition, dimensionless design parameters for quantifying the resistance to bending or buckling of the slender nanostructures are derived to design robust superoleophobic inkjet printer heads. Because of the natural repellency of many leaf surfaces to water, non-Newtonian fluids such as dilute polymer solutions are widely used to maximize the deposition rate of aqueous droplets sprayed onto textured liquid-repellent target surfaces. The drop impact dynamics of complex liquids on such surfaces is studied to develop a systematic understanding of the coupled effects of fluid viscoelasticity and the resulting dynamic wetting characteristics. We use hydrophobically-coated flat glass substrates, microtextured pillar surfaces, and nanocone surfaces as well as natural lotus leaves in conjunction with impacting droplets of dilute polyethylene oxide solutions to construct a drop impact dynamics diagram that can be used for understanding deposition of complex fluids on a wide range of hydrophobic textured surfaces. Lastly, the fundamental principles underlying the collection of fog droplets impacting permeable and textured structures such as woven meshes are studied. A design map predicting the theoretical collection efficiency is constructed based on two important dimensionless ratios that characterize the mesh geometry and the impacting droplet stream. Two physical limitations associated with clogging and re-entrainment are identified and potential solutions utilizing surface wettability are discussed. We use a family of physico-chemically patterned meshes with a directed stream of fog droplets to simulate a natural foggy environment and demonstrate a fivefold enhancement in the fog-collecting efficiency of a conventional polyolefin mesh. The design rules developed in this thesis can be applied to select a mesh surface with optimal topography and wetting characteristics to harvest enhanced water fluxes over a wide range of natural convected fog environments. In summary, by developing an integrative understanding of the physico-chemical hydrodynamics of droplets on textured substrates, we have been able to realize a number of novel functionalities using textured surfaces and have constructed design frameworks that can be applied for optimizing the performance of each multi-functional surface. For future work, initial steps for commercializing several of these multi-functional surfaces developed in this thesis are briefly discussed.
by Kyoo Chul Park.
Ph.D.

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Moon, Tae Seok. "Retrobiosynthesis of D-glucaric acid in a metabolically engineered strain of Escherichia coli". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/57868.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 173-181).
Synthetic biology is an evolving field that emphasizes synthesis more than observation which has been and is the scientific method for traditional biology. With powerful synthetic tools, synthetic biologists seek to reproduce natural behaviors (and eventually to create artificial life) from unnatural molecules or try to construct unnatural systems from interchangeable parts. Accompanied with this recent movement, metabolic engineers started to utilize these interchangeable parts (enzymes in this case) to create novel pathways. In addition, engineering biological parts including enzymes, promoters, and protein-protein interaction domains has led to productivity improvement. However, understanding behaviors of a synthetic pathway in an engineered chassis is still a daunting task, requiring global optimization. As the first step to understand pathway design rules and behaviors of synthetic pathways, a synthetic pathway for the production of D-glucaric acid has been designed and constructed in E. coli. To this end, three disparate enzymes were recruited from three different organisms, and the system perturbed by this introduction of heterologous genes was analyzed. Limiting flux through the pathway is the second recombinant step, catalyzed by myo-inositol oxygenase (MIOX), whose activity is strongly influenced by the concentration of the myo-inositol substrate. To increase the effective concentration of myo-inositol, synthetic scaffold devices were built from protein-protein interaction domains to co-recruit all three pathway enzymes in a designable complex.
(cont.) This colocalization led to enhancement of MIOX activity with concomitant productivity improvement, achieving 2.7 g/L of D-glucaric acid production from 10 g/L of D-glucose input. Secondly, retrobiosynthetic approach, a product-targeted design of biological pathways, has been proposed as an alternative strategy to exploit the diversity of enzymecatalyzed reactions. The first step in a glucaric acid pathway designed retrosynthetically involves oxidation of the C-6 hydroxyl group on glucose, but no glucose oxidase in nature has been found to act on this hydroxyl group on glucose. To create glucose 6- oxidase, a computational design and experimental selection was combined with the help of DNA synthesis technology. To this end, the sequence space of candidate mutations was computationally searched, the selected sequences were combinatorially assembled, and the created library was experimentally screened and characterized. Furthermore, the structure-activity relationship of the newly created glucose oxidases was elucidated, and the kinetic model mechanism for these mutants was proposed and analyzed. Collectively, parts, devices, and chassis engineering were applied to a synthetic pathway for the production of D-glucaric acid, and this synthetic biology approach was proven to be effective for new pathway design and improvement.
by Tae Seok Moon.
Ph.D.

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24

Kalezi, Artemis. "Tissue-engineered liver microreactor as an in vitro surrogate assay for gene delivery". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38981.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007.
Includes bibliographical references.
The lack of correlation between in vitro and in vivo gene delivery experiments presents a significant obstacle in the progress of gene therapy studies by preventing the extrapolation of successful cell culture results into animals. This phenomenon has also been documented in the specific case of liver where standard hepatocyte culture systems fail to reliably predict the in vivo performance of gene delivery vectors. This is possibly a consequence of the loss of differentiated phenotype that these cells undergo when they are dissociated from their in vivo environment and cultured in vitro. This problem underscores the necessity for better in vitro models that can mimic the physiological environment and responses of in vivo liver tissue. This thesis aimed at developing an alternative in vitro gene delivery assay based on the Tissue-Engineered Liver Microreactor, a culture system designed to facilitate the morphogenesis of three-dimensional tissue-like structures from isolated liver cells under continuous perfusion, maintain cell viability and hepatic functionality for long-term culture periods and enable repeated in situ observation with microscopy. We developed experimental assays to non-invasively detect and quantify gene delivery efficiency in the 3D environment of the microreactor culture based on the application of 2-photon microscopy and spectroscopy.
(cont.) These techniques provide a convenient platform for comparative analysis of different vectors. Our main objective was to compare the gene delivery efficiency of an adenoviral vector (Ad5-CMV-EGFP) in the microreactor system and 2D hepatocyte monolayer culture. Quantitative assays were developed based on Real-Time PCR and RT-PCR to measure the levels of Ad vector uptake and transgene expression. The Ad mass transport in both systems was mathematically modeled to estimate the Ad uptake constant as a basis for comparison of delivery efficiency. This parameter was found to be significantly higher in the microreactor system, suggesting a more efficient mechanism of Ad internalization. Moreover, gene expression was measured in terms of transgene mRNA levels; the ratio of gene expression relative to Ad uptake was estimated as the basis for comparison of vector transcription efficiency. No significant difference was found between the 2 systems. These results provide some evidence that a more physiological culture system can yield different information (potentially more relevant to the in vivo situation) compared to standard in vitro culture.
by Artemis Kalezi.
Ph.D.

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25

Hsieh, Vivian Ph D. Massachusetts Institute of Technology. "High relaxivity biomolecule based contrast agents engineered for molecular functional magnetic resonance imaging". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104206.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 71-84).
Magnetic resonance imaging (MRI) is a powerful neuroimaging tool that allows non-invasive visualization of the brain with high spatial and temporal resolution. Research on MRI contrast agents and their application to problems in neuroscience is burgeoning, and there is particular interest in developing MRI agents that are sensitive to time varying components of neurophysiology. Relatively recent advances in biomolecular probes has demonstrated the potential and versatility of bioengineered MRI sensors for molecular imaging. However, a major limitation of these probes is the high concentration needed for imaging, which can lead to issues such as analyte buffering and toxicity, and restrict the applicability of the sensors. In this work, we explore two approaches for developing high relaxivity protein-based contrast agents to address the issues of low detectability. First, we coupled monoamine sensing with the disaggregation of superparamagnetic iron oxide nanoparticles (SPIOs). Ligand detection was imparted by integration of a monoamine sensing protein-based contrast agent derived from P450- BM3h (BM3). We demonstrated that this mechanism can produce robust signal changes of approximately 2-fold, while reducing the concentration of BM3 needed by 100-fold compared to the amount needed when only the protein is used for imaging. The second method demonstrated the feasibility of using semi-rational protein design to engineer a high relaxivity metalloprotein by tuning phenylalanine hydroxylase to bind gadolinium at high affinity. Mutations were found that increased the protein affinity by two orders of magnitude and enhanced relaxivity. The results of this thesis advance approaches for creating high relaxivity contrast agents which can be applied to the development of probes for other analytes, ultimately advancing and broadening the applicability of bioengineered probes in molecular functional neuroimaging.
by Vivian Hsieh.
Ph. D.

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26

Liu, Zhen. "Chemical kinetics modelling study on fuel autoignition in internal combustion engines". Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6533.

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Chemical kinetics has been widely acknowledged as a fundamental theory in analysis of chemical processes and the corresponding reaction outputs and rates. The study and application of chemical kinetics thus provide a simulation tool to predict many characteristics a chemical process. Oxidation of hydrocarbon fuels applied in internal combustion engines is a complex chemical process involving a great number of a series of chained reaction steps and intermediate and simultaneous species. Symbolic and Numerical description of such a chemical process leads to the development and application of chemical kinetics models. The up-to-date application of chemical kinetics models is to the simulation of autoignition process in internal combustion engines. Multi-zone thermodynamic combustion modelling has been regarded as a functional simulation approach to studying combustion process in IC engines as a decent compromise between computation accuracy and efficiency. Integration of chemical kinetics models into multi-zone models is therefore a potential modelling method to investigate the chemical and physical processes of autoignition in engine combustion. This research work has been therefore concerned with the development, validation and application of multi-zone chemical kinetic engine models in the simulation of autoignition driven combustion in SI and HCCI engines. The contribution of this work is primarily made to establish a mathematical model based on the underlying physical and chemical principles of autoignition of the fuel-air mixture in SI and HCCI engines. Then, a computer code package has been developed to numerically solve the model. The derived model aims at improving the understanding of autoignition behaviour under engine-like conditions and providing an investigative tool to autoignition characteristics. Furthermore, as part of the ongoing program in the research of free piston engines, the results of this work will significantly aid in the investigation and simulation of the constant volume autoignition applied in free piston engines.

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27

Sidhu, J. S. "The acceptability of alcohol fuels for automobile engines". Thesis, Aston University, 1988. http://publications.aston.ac.uk/9714/.

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The aim of this project was to carry out an investigastion into suitable alternatives to gasoline for use in modern automobiles. The fuel would provide the western world with a means of extending the natural gasoline resources and the third world a way of cutting down their dependence on the oil producing countries for their energy supply. Alcohols, namely methanol and ethanol, provide this solution. They can be used as gasoline extenders or as fuels on their own.In order to fulfil the aims of the project a literature study was carried out to investigate methods and costs of producing these fuels. An experimental programme was then set up in which the performance of the alcohols was studied on a conventional engine. The engine used for this purpose was the Fiat 127 930cc four cylinder engine. This engine was used because of its popularity in the European countries. The Weber fixed jet carburettor, since it was designed to be used with gasoline, was adapted so that the alcohol fuels and the blends could be used in the most efficient way. This was mainly to take account of the lower heat content of the alcohols. The adaptation of the carburettor was in the form of enlarging the main metering jet. Allowances for the alcohol's lower specfic gravity were made during fuel metering.Owing to the low front end volatility of methanol and ethanol, it was expected that `start up' problems would occur. An experimental programme was set up to determine the temperature range for a minimum required percentage `take off' that would ease start-up since it was determined that a `take off' of about 5% v/v liquid in the vapour phase would be sufficient for starting. Additions such as iso-pentane and n-pentane were used to improve the front end volatility. This proved to be successful.The lower heat content of the alcohol fuels also meant that a greater charge of fuel would be required. This was seen to pose further problems with fuel distribution from the carburettor to the individual cylinders on a multicylinder engine. Since it was not possible to modify the existing manifold on the Fiat 127 engine, experimental tests on manifold geometry were carried out using the Ricardo E6 single cylinder variable compression engine. Results from these tests showed that the length, shape and cross-sectional area of the manifold play an important part in the distribution of the fuel entering the cylinder, ie. vapour phase, vapour/small liquid droplet/liquid film phase, vapour/large liquid droplet/liquid film phase etc.The solvent properties of the alcohols and their greater electrical conductivity suggested that the materials used on the engine would be prone to chemical attack. In order to determine the type and rate of chemical attack, an experimental programme was set up whereby carburettor and other components were immersed in the alcohols and in blends of alcohol with gasoline. The test fuels were aerated and in some instances kept at temperatures ranging from 50oC to 90oC. Results from these tests suggest that not all materials used in the conventional engine are equally suitable for use with alcohols and alcohol/gasoline blends. Aluminium for instance was severely attacked by methanol causing pitting and pin-holing in the surface.In general this whole experimental programme gave valuable information on the acceptability of substitute fuels. While the long term effects of alcohol use merit further study, it is clear that methanol and ethanol will be increasingly used in place of gasoline.

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Gibson, Gillian Hutton. "The development of chemically engineered pullulan for drug delivery". Thesis, University of Greenwich, 2007. http://gala.gre.ac.uk/6174/.

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Pullulan has been chemically modified by the incorporation of various hydrophobic molecules, to produce two types of derivatives (hydrophobically modified carboxymethyl pullulans (HMCMPs), and crosslinked carboxymethyl pullulan). The foregoing modifications were performed in two steps from the parent pullulan. The first step involved carboxylation of pullulan with sodium chloroacetate yielding carboxymethyl pullulan (CMP). The second step involved the medication of CMP by coupling different amine functionalized molecules onto the carboxylic groups of CMP, using the coupling agent dicyclohexylcarbodiimide. The amines used in this modification step were: hexadecylamine, decylamine, cadaverine (1-5 diaminopentane), and three jeffamine® (polyoxypropylenediamine) compounds of differing molecular weights (230, 400 and 2000). Results concluded that all six pullulan derivatives show an increase in reduced viscosity to varying degrees, compared to the parent pullulan. Characterization of pullulan and the derivatives concluded that the correct structures have been synthesised. Gel permeation chromatography confirmed that four pullulan derivatives had been crosslinked (due to doubled molecular weight terms), and a further two have increased in molecular weights, with no increase in polydispersity indices. Isothermal titration calorimetry experiments were initially performed on model systems (two different ß-cyclodextrins, and benzoic acid and eletriptan hydrobromide), and then on pullulan and the derivatives with eletriptan hydrobromide. These experiments probed the nature and extent of drug binding interactions. Results concluded that pullulan derivatives showed exothermic drug binding interactions with the named drug, with the exception of jeffamine 2000 crosslinked CMP, which exhibited endothermic interactions with the titrated drug. Pullulans excellent film forming capabilities may lead these polymers to a novel oral dosage form containing active (dissolving films).

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Wudebwe, Uchena Nomusa Geraldine. "Factors influencing the development of a tissue engineered bone to bone ligament". Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5719/.

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This thesis aimed to quantify the effect of anabolic agents ascorbic acid (AA)/ proline (P) on the rates of contraction of the fibrin hydrogel scaffold as well as develop a process for increasing construct collagen content, tensile strength and widths. Supplementation with AA/ P, in combination or individually, revealed contrasting effects on the rates of fibrin gel contraction dependent on concentration and culture duration. There appeared to be strong correlations between the extents of contraction and construct collagen content. Enhancing the stiffness of the fibrin hydrogel augmented widths of the constructs but did not improve construct collagen content or tensile strength. The results further demonstrated that increasing the volume fraction of fibrin fibres present, either by increasing the total volume of reagents or by adjusting the ratio of thrombin to fibrinogen used could be utilised to modify sinew widths. Constructs prepared using a stiffer fibrin gel formulation, supplemented with AA+P, resulted in enhanced collagen content, sinew tensile strength and improved interface tensile attachment. The results also demonstrated variation in fibrin gel contraction rates and collagen production due to different cell sources, growth medium employed or the use of metal ion cofactors Zn$^{2+}$/ Mn$^{2+}$, thereby suggesting areas that could be investigated further and optimized.

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CODAZZI, VERA. "Breaking phylogenetic barriers for fine and bulk chemical products in engineered Saccharomyces cerevisiae". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2011. http://hdl.handle.net/10281/19692.

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Industrial biotechnologies allow today to obtain both fine and bulk chemicals and yeasts as cell factories can produce many products belonging to both field (Branduardi et al., 2008, Porro and Branduardi, 2009). Among yeasts, Saccharomyces cerevisiae still represents the microorganism of election to develop such cell factories. As regard bioethanol production, yeasts utilization is well established for its natural fermentation ability, but new generation biofuels require the development of strain more and more robust, able to face conditions imposed by the process that should be as cheaper and more profitable as possible. In this direction, processes that use lignocellulosic feedstock for bioethanol production (the so called second generation biofuels) are still in development (NEMO project-Novel high performance Enzymes and Micro-Organisms for conversion of lignocellulosic biomass to ethanol, seventh framework program). This means that the cell factory has to be deeper and deeper investigated in structures and pathways trying to find good targets for improving the robustness. Among the many different functions, cell cytoplasmic membrane plays a key role in cell homeostasis and is deeply involved in facing and reacting to stressing conditions, so it can represent a good target for direct improvements of laboratory as well as industrial strains. Fishing in Arabidopsis thaliana genome, a potentially interesting gene was found, codifying for a Temperature Induced Lipocalin, named TIL. As it has positive effects in plants in unfavourable situations (Charron et al., 2008), TIL was expressed in S. cerevisiae and the recombinant strains compared with the parental counterpart under some of the stresses typical of industrial processes. The recombinant yeasts show an increased tolerance towards heat shock and to the presence of hydrogen peroxide and organic acids. In detail TIL expressing strain generate lower levels of ROS and accumulate less amounts of reactive electrophile species generated after membrane lipids fragmentation. Another industrial field that is gaining more and more importance is represented by bioplastics not coming from petrochemical sources. Vegetable oils derived fatty acids are interesting as bulk compounds for the synthesis of biopolymers, even if they have to be previously modified to possess two chemically reactive groups at molecules extremities. High catalytic activity and stability together with high versatility in reaction of performed by bacteria cytochromes answered to this need. The heterologous expressed B. subtilis cytochrome CYP102A2 in S. cerevisiae showed some activity, measured in terms of NADPH consumption towards fatty acids of different chain length, interestingly also towards short chain fatty acids. However as CYP is able to catalyze different type of reaction involving NADPH consumption (hydroxylation, oxidation and epooxidation as example), the products will be further characterized to understand what kind of modifications are carried out on the tested substrates. Considering the valuable reactions that cytochromes P450 are able to catalyze on a vast variety of substrates (fatty acids, steroids and a multitude of non natural compounds such as drugs, organic solvents and hydrocarbon products), their successful expression in yeast could open the possibility to develop sustainable processes in alternative to classical chemical synthesis. Because of the nice and positive results, S. cereviasiae potential as cell factory was deeper exploited for the expression of a whole plant biosynthetic pathway. In detail, yeast was engineered to express the pathway leadind to the formation of glucobrassicin, a nutraceutical indicated as a potential cancer chemoprotective agent. In this work we describe the construction of a recombinant S. cerevisiae strain able to produce glucobrassicin. Despite some investigation about possible strain optimization through the employment of multicopy plasmids, the final producer will exploit only integrative vectors and the described findings and the process of production were deposited as patent application [Mauro Magnani, E. Bartolucci, Danilo Porro, Paola Branduardi, Vera Codazzi, Umberto Benatti, Gianluca Damonte, Giovanni Schippa e Stefano Bianchini Sviluppo di una cell factory ricombinante per la produzione di Glucobrassicina]. Specific analysis on biosynthetic intermediates suggest steps on which focusing the attention to further improve the glucobrassicin production levels. Despite the number of biotechnological processes based on engineered microorganisms for the production of metabolites is still limited in comparison with the potentiality expressed at lab scale, the studies about strain robustness and heterologous pathway optimization are going to change that situation very soon.

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Wu, Kuo-chʻun 1968. "Chemical kinetic modeling of oxidation of hydrocarbon emissions in spark ignition engines". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/35377.

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32

Du, Yinming. "High-Yield and High-Titer n-Butanol Production from Lignocellulosic Feedstocks by Metabolically Engineered Clostridium tyrobutyricum". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1374193011.

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33

Kotta, Linda Thokozile. "Structural conditioning and mediation by student agency : a case study of success in chemical engineerng design". Doctoral thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11475.

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Ncongwane, Mpendulo S. "Assessment of the potential carbon footprint of engineered processes for the mineral carbonation of PGM tailings". Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20951.

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Mineral carbonation is a carbon sequestration technology that entails the reaction of CO2 with oxides or silicates of magnesium, calcium or iron to produce stable carbonate compounds. Magnesium-rich tailings from the platinum industry in South Africa have been identified as a potentially viable and attractive feedstock for CO2 sequestration through mineral carbonation. Many of the strategies proposed to enhance the dissolution kinetics of silicate minerals, such as the use of elevated temperatures and pressures and chemical additives, as well as pretreatment through mechanical and thermal activation, are energy intensive and will thus reduce the net CO2 sequestration capacity of the overall mineral carbonation process. As a result, there is growing recognition of the need to evaluate the processes using life-cycle based approaches and tools to ensure they result in net CO2 reduction. However, to date, research and development has focused primarily on the optimisation of extraction and/or carbonation efficiencies, with specific emphasis on the relatively reactive silicate minerals, such as olivine and serpentine. This project seeks to investigate the viability of using pyroxene-rich PGM tailings for the sequestration of CO2, with specific emphasis on net carbon neutrality. Promising mineral carbonation processes have been identified on the basis of an extensive literature review, and include the: ammonium salts pH swing, Lackner's HCl multi-stage, gas-solid Abo Akademi University process, direct aqueous process, and mineral acid pH swing. Material and energy balances were then conducted for these processes on the basis of the sequestration of 1 ton of carbon dioxide, using Aspen Plus v8 simulation software package. The material and energy data were then used to determine the total carbon footprint contributions, through the use of SimaPro v 7.7.3. life cycle assessment software.

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Chang, Wei-Lun. "Acetone-Butanol-Ethanol Fermentation by Engineered Clostridium beijerinckii and Clostridium tyrobutyricum". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1282108408.

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36

Asghari, Adib Ali. "Interactions of Engineered Silica Nanoparticles with Cell Membrane Models". Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1501764587639053.

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Timar, Maria Cristina. "Chemically modified wood for thermally formed composites". Thesis, Bucks New University, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.714440.

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Zhou, Zilan. "Engineered Nanoparticle for Targeted and Controlled Drug Delivery". University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1505831582487098.

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Jabbarzadeh, Ehsan Abrams Cameron F. Laurencin Cato T. "Theoretical and experimental approaches to control blood vessel growth into tissue engineered scaffolds /". Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1794.

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40

Li, Xin. "Kinetic study and modelling of ethanol production from glucosexylose mixtures using the genetically-engineered strain Escherichia coli KO11". Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/27800.

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Kinetics of ethanol fermentation on different synthetic glucose/xylose mixtures using Escherichia coli KO11 was studied. No substrate inhibition was observed in both glucose-only and xylose-only experiments. In single substrate fermentations, results show that glucose was the preferred substrate and its ethanol conversion rate was 1.5 times higher than the one obtained with xylose. In mixed-sugar fermentations, glucose was fully consumed significantly earlier than xylose, indicating an initial inhibition on xylose fermentation. The xylose consumption rate after the depletion of glucose significantly decreased with an increase in the initial glucose content. An unstructured kinetic model for ethanol production from glucose, xylose, and their mixtures using Escherichia coli KO11 was developed based on metabolic analysis. Ethanol inhibition and effect of pH were taken into account in the proposed model. Terms related to the inhibition on xylose metabolism by glucose were also included. Good agreement between model predictions and experimental data was obtained.

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Sivaraman, Anand 1977. "A microfabricated 3D tissue engineered "Liver on a Chip" : information content assays for in vitro drug metabolism studies". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28661.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2004.
Includes bibliographical references (p. 180-195).
(cont.) approaches to improving hepatocyte function in culture have been described, not all of the important functions--specifically the biotransformation functions of the liver--can as yet be replicated at desired in ivo levels, especially in culture formats amenable to routine use in drug development. The in vivo microenvironment of hepatocytes in the liver capillary bed includes signaling mechanisms mediated by cell-cell and cell-matrix interactions, soluble factors, and mechanical forces. This thesis focuses on the design, fabrication, modeling and characterization of a microfabricated bioreactor system that attempts to mimic the in vivo microenvironment by allowing for the three dimensional morphogenesis of liver tissue under continuous perfusion conditions. A key feature of the bioreactor that was designed is the distribution of cells into many tiny ([approximately]0.001 cm³) tissue units that are uniformly perfused with culture medium. The total mass of tissue in the system is readily adjusted for applications requiring only a few thousand cells to those requiring over a million cells by keeping the microenvironment the same and scaling the total number of tissue units in the reactor. Using a computational fluid dynamic model in ADINA® and a species conservation mass transfer model in FEMLAB®, the design of the bioreactor and the fluidic circuit was optimized to mimic physiological shear stress rates ...
Recent reports indicate that it takes nearly $800 million dollars and 10-15 years of development time to bring a drug to market. The pre-clinical stage of the drug development process includes a panel of screens with in vitro models followed by comprehensive studies in animals to make quantitative and qualitative predictions of the main pharmacodynamic, pharmacokinetic, and toxicological properties of the candidate drug. Nearly 90% of the lead candidates identified by current in vitro screens fail to become drugs. Among lead compounds that progress to Phase I clinical trials, more than 50% fail due to unforeseen human liver toxicity and bioavailability issues. Clearly, better methods are needed to predict human responses to drugs. The liver is the most important site of drug metabolism and a variety of ex vivo and in vitro model systems have therefore been developed to mimic key aspects of the in vivo biotransformation pathways of human liver-- a pre-requisite for a good, predictive pharmacologically relevant screen. Drug metabolism or biotransformation in the liver involves a set of Phase I (or p450 mediated) and Phase II enzyme reactions that affect the overall therapeutic and toxic profile of a drug. The liver is also a key site of drug toxicity following biotransformation, a response that is desirable but difficult to mimic in vitro. A major barrier to predictive liver metabolism and toxicology is the rapid (hours) loss of liver-specific functions in isolated hepatocytes when maintained under standard in itrom cell culture condition. This loss of function may be especially important in predicting toxicology, where the time scale for toxic response may greatly exceed the time scale for loss of hepatocyte function in culture. Although a wide variety of
by Anand Sivaraman.
Ph.D.

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Scanferlato, Vjera Sostarec. "Environment risk assessment for toxic chemicals and genetically-engineered microorganisms : a microcosm approach /". Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-07282008-135357/.

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Mantri, Shiksha. "Engineered α-hemolysin pores with chemically and genetically-fused functional proteins". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:55450bd3-b93f-410f-b795-0110449c0da9.

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Abstract (sommario):

Protein engineering could be used to bring two proteins together, which don't normally interact, in an oriented configuration. Using computer modelling and experimental work involving mutagenesis, a new dimer complex, (α7)2, was engineered with two α-hemolysin (αHL) heptamers (α7) units linked via disulfide bridges in a cap-to-cap orientation. The structure of (α7)2 was confirmed by biochemical analysis, transmission electron microscopy (TEM) and single-channel electrical recording. Importantly, it was shown that the one of two transmembrane  barrels of (α7)2 can insert into an attoliter liposome, while the other spans a planar lipid bilayer. (α7)2 pores spanning two bilayers were also observed by TEM. In potential, (α7)2 could be used for small molecule transfer between micron-sized vesicles (minimal cells) and would have applications in forming proto-tissues from minimal cells. Another target has been to couple a highly processive exonuclease, λ-exonuclease (λ-exo), which functions as a trimer, with the α7 pore for DNA sequencing and single molecule studies of λ-exo. Several genetic fusion constructs of λ-exo and αHL were screened and optimized for activity. By linking the N-terminus of λ-exo monomer to the C-terminus of the αHL monomer (α1), a new kind of processive exonuclease (AE) was synthesized that can form pores in bilayers. AE and wild-type α1 could be integrated into hetero-heptamers with different number of AE subunits. To achieve a hetero-heptamer with only one λ-exo trimer molecule mounted on the αHL cap, a concatemer of 2 λ-exo (exo3) was made by genetically linking the monomers of λ-exo with 15 and 17 amino acid linkers. The immediate next step is to link exo3 to α1 and then to co-assemble the exo3-α1 fusion construct with α1 to make the λ-exo-αHL pore complex. Using similar strategies as described in this thesis, other proteins could be linked to αHL increasing the scope of the nanopore technology.

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Hammerstein, Anne Friederike. "Single-molecule chemistry studies with engineered alpha-hemolysin pores". Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:1dd1f11d-2b20-42e9-9dfc-c30498822b77.

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Abstract (sommario):

Engineered protein nanopores can be used to investigate a wide range of dynamic processes in real time and at the single-molecule level, for example covalent bond making and breaking or the interaction of ligands with their cognate binding sites. The detection of such processes is accomplished by monitoring the current carried by ions through the pore in an applied potential, which is modulated as molecules of interest interact with engineered binding sites within the pore. In contrast to ensemble measurements, where the behaviour of individual molecules is obscured by averaging, single-channel recordings can identify short-lived intermediates and rare reaction pathways, thereby adding to our understanding of fundamental processes in chemistry and biology. The goal of my thesis work was to engineer alpha-hemolysin (αHL) pores to gain insight into such processes. Chapter 1 provides an overview of common techniques used to study single- molecule processes, in particular single channel recordings. General techniques to engineer ion channels and pores are presented, followed by examples of how the alpha-HL pore has been engineered to monitor dynamic processes at the single- molecule level. Chapter 2 describes how alpha-HL pores can be chemically modifeed with a tridentate "half-chelator" ligand. Single channel recordings show that this modifeed pore can be used to determine rates of chelation and the stability of divalent metal ion complexes. The modifeed pore can also be used as a stochastic sensor for the detection of different divalent metal ions in solution. Chapter 3 investigates the chelate-cooperativity between two half-chelator ligands installed in close proximity in the alpha-HL pore, as they form a full complex with a single Zn²⁺ ion. The single channel recordings reveal a two step process, in which the Zn²⁺ ion must fiferst bind to one of the two half-chelators, before the second one completes the complex. The rate constants for all the major steps of the process are determined and the extent of cooperativity between the half-chelators is quantifeed. Chapter 4 demonstrates that genetically encoded subunit dimers of alpha-HL can be used to control the subunit arrangement in the heptameric pore. Although techniques exist to prepare heteroheptameric pores, pores containing more than one type of modifeed subunit are not commonly used because it is impossible to distinguish between the permutations of the pore. By using subunit dimers, heptamers in which two defefined subunits are adjacent to each other can be formed, which increases the range of structures that can be obtained from engineered protein nanopores. Chapter 5 explores the possibility of following the nuclease activity of a metal complex in the alpha-HL pore at the single-molecule level. The Rh(III) complex [Rh(bpy)2phzi]²⁺ binds strongly to CC mismatches in dsDNA, and on activation with UV light promotes the cleavage of one of the two strands. To follow this reaction by single channel recording, a piece of dsDNA with the bound Rh-complex was immobilised in the HL pore and the single current changes under UV irradiation were monitored. The preliminary data indicate that the rate of the photocleavage reaction can be measured.

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Nazemidashtarjandi, Saeed. "Interactions of Engineered Nanomaterials with the Cell Plasma Membrane". Ohio University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1617363923755762.

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Shim, Min Suk. "Molecularly Engineered Acid-Responsive Polymers for Nucleic Acid Delivery". Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1291412851.

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47

Peng, Yucheng. "EFFECT OF HIGH TEMPERATURES ON ADHESIVE BOND DURABILITY AND TOXIC CHEMICAL PRODUCTION FOR ENGINEERED WOOD PRODUCTS". MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07082008-153319/.

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Abstract (sommario):

The objectives of this research were to investigate the heat resistant performance of a structural adhesive and to analyze the contribution of the adhesive to the chemical emissions from the glued wood products affected by the elevated temperatures. Phenol-resorcinol-formaldehyde (PRF) and two wood species, southern pine (Pinus palustris) and Douglas-fir (Pseudotsuga menziesii), were investigated. The dynamic mechanical analysis (DMA) test results showed that the heat durability performance of cured PRF resin was better than that of the two wood species used in this study. The results indicated that the fire safety of PRF bonded wood products should be comparable to solid wood products. The pyroysis products obtained from pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) system showed that most of the pyrolysis products of glued wood samples were same as those of wood and adhesive samples at the same temperature level except a few compounds, such as carbon disulfide, Cyclopropyl carbinol, acetaldehyde, furfural and others.

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Tyrologou, Pavlos. "A structural and physico-chemical investigation of mineral/organic composites as novel components of engineered fill". Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424391.

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Gothard, David. "Enhanced osteogenic differentiation via chemically engineered aggregation of mouse embryonic stem cells". Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10826/.

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Abstract (sommario):

The formation of embryoid bodies has long been utilized to initiate differentiation of embryonic stem cells in vitro. The embryoid body provides an effective means of recapitulating early stages during embryogenesis and formation of the three germ layers. Current methodology for embryoid formation is extensive but exhibits a lack of standardisation and coherence. Here is shown a 3D culure system for controlled embryonic stem cell aggregation via a non-cytotoxic cell surface modification and cell-cell cross-linking. Embryoid body formation was found to be a complex relationship between embryonic stem cell aggregation, proliferation, death, cluster agglomeration, extracellular matrix deposition and structural reorganisation. Engineered embryoid bodies formed more rapidly and were significantly larger than those in control samples. Embryoid body characterisation revealed a layered internal structure resulting from poor nutrient and gaseous diffusion and consequent core necrosis after ≥ 5 days in suspension culture. Immuno-labelling and PCR amplification analysis of Brachyury, Nestin, Gata-4 and Oct-4 showed differentiation of mesoderm, ectoderm and endoderm on the embryoid body surface and internal undifferentiated cells, respectively. Engineering appeared to enhance mesoderm differentiation, a progenitor of the osteogenic lineage. Embryoid bodies in settled culture spread outwards to form a plateau of collagen matrix which was later mineralized through differentiated osteoblast function. Quantification through Alizarin Red stained bone nodules and alkaline phosphatase activity demonstrated osteogenic differentiation enhancement within engineered samples. Dex-loaded poly-(lactic co-glycolic) acid polymer microparticles were found to be an effective method for delivery of osteo-inductive factors to internal undifferentiated embryonic stem cells within the embryoid bodies. These findings show that the proposed 3D culture system provides reliable and repeatable methodology for the controlled formation of embryoid bodies which exhibit enhanced osteogenic differentiation. It is hoped that these engineered embryoid bodies could be used to efficiently generate homogeneous bone tissue for clinical application.

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Chandran, Davannendran. "Experimental investigation into the physico-chemical properties changes of palm biodiesel under common rail diesel engine operation for the elucidation of metal corrosion and elastomer degradation in fuel delivery system". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/35228/.

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Abstract (sommario):

Compatibility of fuel delivery materials (FDM) with biodiesel fuel in the fuel delivery system (FDS) under real-life common rail diesel engine (CRDE) operation poses a challenge to researchers and engine manufacturers alike. Although standard methods such as ASTM G31 and ASTM D471 for metals and elastomers, respectively, are deemed suitable for evaluating the effects of water content, total acid number (TAN) and oxidation products in biodiesel on FDM degradation, they do not resemble the actual engine operation conditions such as varying fuel pressure/temperature as well as the presence of a wide range of materials in the FDS of a diesel engine. Hence, the current allowable maximum 20 vol% of biodiesel with 80 vol% of diesel (B20) for use in diesel engines to date is debatable. Additionally, biodiesel utilization beyond B20 is essential to combat declining air quality and to reduce the dependence on fuel imports. This thesis aims to elucidate the actual compatibility present between FDM and biodiesel in the FDS under real-life CRDE operation. This was achieved through multi-faceted experimentations which commenced with analyses on the deteriorated palm biodiesel samples collected during and after CRDE operation. Next, the fuel properties which should be emphasized based on the deteriorated fuel were determined. This was then followed by ascertaining the effects of the emphasized fuel properties towards FDM degradation. Ultimately, the actual compatibility of FDM with biodiesel under engine operation through modified immersion investigations was determined. FDM degradation acceleration factors such as oxidized biodiesel, TAN and water content were eliminated since these factors were not affected based on the analysed fuel samples collected after engine operation. No oxidation products such as aldehydes, ketones and carboxylic acids were detected while the TAN and water content were within 0.446% and 0.625% of their initial values, respectively. Instead, the biodiesel’s dissolved oxygen (DO) concentration and conductivity value were not only found to have changed during and after engine operation by -93% and 293%, respectively, but were also found to have influenced biodiesel deterioration under engine operation. These two properties were subsequently discovered to have adversely affected FDM degradation independently. The copper corrosion rate and nitrile rubber (NBR) volume change increased by 9% and 13%, respectively, due to 22% increase in the conductivity value. In contrast, the copper corrosion rate and NBR volume swelling reduced by 91% and 27%, respectively, due to 96% reduction in the DO concentration. Ultimately, copper corrosion and NBR degradation were determined to be lowered by up to 92% and 73%, respectively, under modified immersion as compared to typical immersion condition. These outcomes distinctly show that acceptable to good compatibility is present between FDM and biodiesel under CRDE operation. The good compatibility is strongly supported since only a maximum lifespan reduction of 1.5 years is predicted for metal exposed to biodiesel as compared to diesel for a typical component lifespan of 15 years. For the elastomers, acceptable compatibility is found present between elastomer and biodiesel based on the determined 11% volume change which conforms to the tolerance level of elastomer degradation as stated by the elastomer manufacturers. These are especially true for the evaluated metals and elastomers investigated under the modified laboratory immersion which replicates similar conditions to a real-life CRDE. Overall, this work has contributed to the advancement of knowledge and application of biodiesel use in diesel engines.

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Tesi sul tema "Chemical engineers"

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