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1
Wang, Baoyong. "Fractionation Statistics." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31001.
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Paralog reduction, the loss of duplicate genes after whole genome duplication (WGD)
is a pervasive process. Whether this loss proceeds gene by gene or through deletion
of multi-gene DNA segments is controversial, as is the question of fractionation bias,
namely whether one homeologous chromosome is more vulnerable to gene deletion
than the other. As a null hypothesis, we first assume deletion events, on one homeolog
only, excise a geometrically distributed number of genes with unknown mean mu, and
these events combine to produce deleted runs of length l, distributed approximately
as a negative binomial with unknown parameter r; itself a random variable with
distribution pi(.). A biologically more realistic model requires deletion events on both
homeologs distributed as a truncated geometric. We simulate the distribution of run
lengths l in both models, as well as the underlying pi(r), as a function of mu, and
show how sampling l allows us to estimate mu. We apply this to data on a total of 15
genomes descended from 6 distinct WGD events and show how to correct the bias
towards shorter runs caused by genome rearrangements. Because of the difficulty in
deriving pi(.) analytically, we develop a deterministic recurrence to calculate each pi(r)
as a function of mu and the proportion of unreduced paralog pairs. This is based on a
computing formula containing nested sums. The parameter mu can be estimated based
on run lengths of single-copy regions. We then reduce the computing formulae, at least
in the one-sided case, to closed form. This virtually eliminates computing time due
to highly nested summations. We formulate a continuous version of the fractionation
process, deleting line segments of exponentially distributed lengths in analogy to
geometric distributed numbers of genes. We derive nested integrals and discover that
the number of previously deleted regions to be skipped by a new deletion event is
exactly geometrically distributed. We undertook a large simulation experiment to
show how to discriminate between the gene-by-gene duplicate deletion model and the
deletion of a geometrically distributed number of genes. This revealed the importance
of the effects of genome size N, the mean of the geometric distribution, the progress
towards completion of the fractionation process, and whether the data are based on
runs of deleted genes or undeleted genes.
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Chen, Xiaocai Joyce. "Fractionation of nylon fibres." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/MQ28927.pdf.
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Ghosh, Raja. "Protein fractionation using ultrafiltration." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302133.
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Rajah, Kanes K. "Fractionation of milk fat." Thesis, University of Reading, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233844.
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Al-Jabari, Maher. "Particle fractionation by elutriation-spouting." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28409.
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Pulp fibers can be spouted in a conical vessel if the inlet Reynolds number is above a critical value which varies linearly with mass of pulp in the vessel. Continuous pulp spouting is also feasible in a wedge-like vessel within certain limits of flow rate and inlet pulp consistency. Spouting hydrodynamics and particle separation behavior in both vessels were investigated for pulp fibers and recycled pulp suspensions.The minimum spouting velocity (MSV), spouting stability and the pressure drop-flow rate relationship were determined for liquid spouting of pulp fibers and of rigid particles. Liquid spouting of rigid particles is similar to gaseous spouting; pulp spouting is different. The liquid flow field in a conical spouted bed of pulp fibers is of a jet expansion type. A model for predicting the MSV for spouting pulp fibers was developed based on visual observation of the transition of the jet flow patterns in the conical vessel.
Small particles including both ink and pulp fines can be elutriated from a spouted bed of a recycled pulp suspension, with little fiber loss, in both semi-batch and continuous modes using conical and wedge-like vessels, respectively. Both processes were studied using on-line measurement of the exit particle concentration.
For the semi-batch process, the first order elutriation coefficient increased with the flow rate, but was about the same for all pulps. Based on the analysis of the flow field around a porous spherical particle in a shear flow, an elutriation model was developed for fine particle removal from a suspension of porous coarse particles. For the continuous operation, the particle separation mechanism and the fractional particle removal were investigated. Separation occurs by excluding fibers from the top stream, while fines are split according to the ratio of top to bottom flow rates.
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Wehmeier, Silvia. "Antimony isotope fractionation through biomethylation." Thesis, University of Aberdeen, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401160.
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Fermenter cultures with anaerobe bacteria communities (sewage sludge medium) were analysed for volatile and non-volatile methylantimony species. Gas-samples were analysed by GC-ICP-MS, and fermenter sludge medium and cytosol by HG-GC-ICP-MS. Trimethylstibine was the sole volatile species, and non-volatile methylantimony species were found in the fermenter sludge medium, but higher levels were found in sludge cytosol. Antimony isotopic fractionation values were determined as high as d 123Sb + 150 in one fermenter experiment. Additionally, the species-specific isotope ratio ‘fingerprint’ from the methylantimony species confirmed the mechanism proposed by Challenger for the biomethylation process. It showed the formation of partially methylated antimony species as intermediates. However, other stimulated bacteria cultures did not show any antimony isotope fractionation through biomethylation. Further investigation into the biomethylation process was studied to determine whether antimonate, Sb(V), is methylated by anaerobe bacteria communities. For this purpose, isotopically enriched 123Sb(V) was used to monitor the antimony isotope ratio of the methylantimony metabolite species. The antimonate was stepwise methylated. Environmental gas samples from a landfill site and a digester plant, showed trimethylstibine as the prominent organometal(loid)-species. Moreover, the biovolatilisation species trimethylstibine was determined to have an antimony isotope fractionation value of d 123Sb + 10. Antimony-glutathione complexes were identified in both in vivo and in vitro studies of antimony interactions with biomolecules. The molecular structures of these Sb-GS complexes were determined using FI-ESI-MS. The glutathione influence was then further investigated in a non-enzymatic methylation of antimony with methylcobalamin. The prominent species produces in vivo was monomethylantimony, with small amount of dimethylantimony.
7
Katz, David P. "The Fractionation of Working Memory." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1559732086225506.
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Dean, Lauren Rachael. "Neural pathways of movement fractionation." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/2812.
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Stroke is a common neurological event which often results in motor deficits of the hand and arm. The reticulospinal tract (RST) may partly underlie residual hand and arm movement ability after a stroke but remains poorly characterised. A greater understanding of the RST could inform work to improve motor recovery. Additionally, the development of non-invasive methods of probing the RST in humans should allow comparison of the characteristics of the RST across species. It has been suggested that the RST is involved in mediating muscle responses to auditory startle, experimentally known as the StartReact paradigm. However, it was not clear how this pathway was involved. A human experiment presented here suggests that the RST comprises the final pathway in the StartReact effect, confirming it as a technique to probe the RST in humans. Other factors such as habituation and the validity of a marker of the StartReact effect were also further explored; these findings may inform future use of the technique. The output divergence, co-activation patterns, level of fractionation and synergies produced by the RST were further characterised in macaques and baboons; these factors had previously been mostly unexplored. In macaques, two subdivisions of primary motor cortex (M1) were also characterised in order to compare to the RST. These subdivisions are based upon the presence of corticomotoneuronal (CM) cells, and consist of ‘old’ (CM cells absent) and ‘new’ (CM cells present) M1. Stimulation of new M1 produced a higher level of fractionation of movement than stimulation of old M1 and the reticular formation (RF). The RF is suggested to produce slightly more fractionated behaviour than old M1, though the baboon RF responses may be less fractionated than those from macaque old M1. Output divergence of the RF as well as old and new M1 was also explored. However, methodological limitations may have biased the results towards muscles with more excitable motoneurons, or monosynaptic connections. Abstract ii In baboons, threshold stimulation elicited responses in upper limb and axial muscles only, with higher stimulation intensities or trains of pulses required to activate leg muscles. In contrast to long-held beliefs about RST output, distal upper limb muscles were more commonly activated than proximal ones. Previously reported attempts to record natural electromyography (EMG) data from macaques were limited to controlled experimental settings, and hence may have differed from EMG observed during truly natural behaviours. Here, EMG was recorded from 18 muscles in one macaque over several hours of natural, untrained activity in her home cage. Two matrix decomposition algorithms extracted three to four dominant synergies from the data. This number is comparable to that previously described for ‘natural’ behaviour in more controlled conditions, suggesting that it accurately reflects the dominant synergies used across both conditions. Future work should aim to delineate the respective contributions of the RST and corticospinal tract to natural movement and to develop approaches to manipulate RST projections in humans to improve post-stroke motor outcomes.
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Chen, Zhi. "Separation with electrical field-flow fractionation." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013788.
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Chand, Amita. "On-farm fractionation of milk components." The University of Waikato, 2006. http://hdl.handle.net/10289/2669.
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Methods for on-farm extraction of low-concentration (minor) proteins from raw whole bovine milk directly after milking were explored. These minor proteins have high commercial value. Lactoferrin (LF) and lactoperoxidase (LP) were used as model proteins for extraction using cation exchange chromatography. Laboratory fractionations showed that milk could be processed by conventional column chromatography without excessive column backpressures if resin with large particles sizes were used and the temperature was high enough so fat in the milk was malleable; ideally the milk should be near the secretion temperature of 37oC. Processing parameters such as equilibrium and dynamic capacities were determined for SP Sepharose ™ (GE Healthcare Technologies) and Bio Rex 70 (BioRad Laboratories) resins. SP Sepharose Big Beads (SP BB) were found to be more suitable than BR 70, for raw whole milk processing due to the larger size (200 um). Design considerations showed that column chromatography was not the most practical method for on-farm processing of fresh, raw whole milk. Trials with a single-stage stirred tank showed that SP BB resin could extract up to 65% of LF (initial LF concentration of 0.5 mg/mL) with a 10-minute adsorption time. The composite non-linear (CNL) model of Rowe et al. (1999) was used to describe LF uptake by SP BB resin in raw whole milk with initial LF concentrations of 0 to 1.0 mg/mL and resin:milk volume ratios of 0.010, 0.012, 0.017 and 0.024 over 45-minute contact times. The CNL model could be used to predict LF yields if initial feed concentration, milk and resin volumes, and contact times were known. Laboratory extractions showed that processing did not significantly affect bulk milk composition (fat, protein, lactose and total solids), indicating that the milk could be used for conventional processing after the minor proteins had been extracted. Resin cleaning and regeneration studies, using a procedure similar to that recommended by the resin supplier, showed that the Sepharose resin had not degraded and there was no significant decrease in binding capacity after 50 extraction cycles. A Protein Fractionation Robot (PFR) prototype based on a single-stage stirred tank and the operating parameters obtained from the laboratory trials was designed, assembled and coupled to an Automated Milking System (AMS) to process fresh, raw whole milk from individual cows immediately after milking. The LF and LP extracted from the milk from 16 individual cows were 19.7 - 55.2% (35.6 10.2%) and 21.2 - 99.5% (87.1 12.0%) respectively. Generally, higher extraction levels were obtained at higher resin:milk ratios. The amount of LF extracted on-farm agreed within 14.1 9.8% of those predicted by the CNL model, with predicted values generally being higher. The experimental on-farm adsorption values were calculated using data of LF recovered after elution, so differences between actual and predicted values may be due to losses during post-adsorption processing. Economic feasibility studies, based on experimental data from the PFR and realistic wholesale prices for LF and LP ($400 and $150/kg respectively) showed that PFR-based processing is economically viable if the farmer is paid for the LF and LP produced as well as the bulk milk. This system would have a payback period of approximately five years and an internal rate of return of 14.5%. Further case studies determined the sensitivity of the economics to various operating parameters and value/cost assumptions, including producing recombinant human protein from transgenic bovine milk. These studies showed that the higher the value of the processed raw milk, the higher the absorptive capacity of the resin, and the higher the value of the extracted protein, the more favourable the economics. In the extreme case of producing a very high value therapeutic protein (e.g. $20 000), the payback period could be as low as 0.3 years, with an internal rate of return of 818%.
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Wararatananurak, Puchong. "Fractionation of chromium toxicity in water." Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327394.
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Radebe, Nonhlanhla Mtandi. "Multidimensional fractionation of wood-based tannins." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6621.
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Thesis (MSc)--University of Stellenbosch, 2011.ENGLISH ABSTRACT: High molar mass tannin extracts are complex mixtures which are distributed in both molar mass and chemical composition. Condensed tannins from quebracho and mimosa and hydrolysable tannins of tara, chestnut wood and turkey gall were studied. Application of a single analytical technique is not sufficient to elucidate the complete structures present in the extracts. 13C Nuclear Magnetic Resonance (NMR) spectroscopy and Matrix Assisted Laser Desorption/Ionisation Time-of-Flight (MALDI-TOF) mass spectrometry were applied in order to determine the chemical composition and molar mass, respectively. A new mass spectrometric method that can uniquely determine the oligomer microstructure was developed using Collision Induced Dissociation (CID) experiments. Bulk analysis only showed the average composition of the extracts, in order to obtain specific information on the molar mass and chemical composition distributions. Hydrophilic Interaction Liquid Chromatography (HILIC) was used for analysis of the condensed tannins and for the hydrolysable tannins Normal Phase Liquid Chromatography (NP-LC) was utilised. The HILIC separation was up-scaled and the fractions were collected and analysed by MALDI-TOF, and this coupling revealed that separation occurs by molar and chemical composition. For separation of the molecules only by size, Size Exclusion Chromatography (SEC) analyses were carried out; this allowed for relative comparison of the tannin molecules. In conclusion, for characterisation of high molar mass tannins a multi-dimensional approach was necessary since the various distributions present in these extracts are superimposed.
AFRIKAANSE OPSOMMING: Hoë molekulêre massa tannienekstrakte is komplekse mengsels, in terme van beide molekulêre massa en chemiese samestelling. Gekondenseerde tanniene vanaf quebracho en mimosa, en hidroliseerbare tanniene vanaf tara, kastaaiinghout en Turksegal is bestudeer. Die gebruik van ‘n enkele analitiese tegniek is nie voldoende om die volledige struktuur van komponente teenwoordig in die ekstrakte te analiseer nie. 13C KMR-spektroskopie en MALDI-TOF-massaspektroskopie is gebruik om die chemiese samestelling en molekulêre massa, onderskeidelik, te bepaal. ‘n Nuwe metode is ontwikkel vir die bepaling van die oligomeer-mikrostruktuur deur gebruik te maak van botsings-geïnduseerde dissosiasie eksperimente. Grootmaat analise het net die gemiddelde samestelling van die ekstrak bepaal. Hidrofiliese-interaksie-vloeistofchromatografie (HILIC) is gebruik vir die analise van gekondenseerde tanniene en gewone fase-vloeistofchromatografie is gebruik vir die hidroliseerbare tanniene. Die HILIC-skeiding is op groter skaal uitgevoer en die fraksies is versamel en gebruik vir MALDI-TOF analise. Hierdie koppeling het getoon dat skeiding plaasvind op grond van molekulêre massa en chemiese samestelling. Grootte-uitsluitingschromatografie is gebruik vir die skeiding van molekules alleenlik op grootte. Hierdeur kon ‘n relatiewe vergelyking van die tannienmolekules gemaak word. Vir die karakterisering van hoë molekulêre massa tanniene is ‘n multi-dimensionele benadering nodig aangesien die verskeie verspreidings teenwoording in hierdie ekstrakte supergeponeerd is.
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Molinari, Michael B. "Mechanical fractionation of the intervertebral disc." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:7385c54f-a3d0-4467-aca4-c7a9b8686982.
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Chronic lower back pain is a major public health problem, with direct and indirect economic costs comparable to those of heart disease, depression and diabetes. In many cases this pain derives from degeneration of the intervertebral disc (IVD), a fibrous, avascular tissue that sits between the vertebrae in the spinal column. A novel treatment approach for this ‘discogenic’ pain is the injection of a hydrogel that hybridises in situ and restores the normal biomechanical function of the disc. While a number of promising materials are currently under development, existing approaches to removing degenerate material from the disc prior to injection are invasive and compromise the structural integrity of the disc. Mechanical fractionation of the tissue using acoustic cavitation generated by high intensity focussed ultrasound (HIFU) has the potential to be non-invasive, and to enhance the effectiveness of the procedure by preserving the outer regions of the disc. The primary goal of this thesis is to investigate the feasibility of this approach. The acoustic properties of the disc were first measured using a modified scanning acoustic microscope. The outer region of the disc, the annulus fibrosus (AF) was found to be highly attenuative compared to the central nucleus pulposus (NP). These measured properties were then used in a simplified two-dimensional model to simulate the shape of the acoustic pressure field within the disc. A configuration using two confocal spherically focussed 0.5 MHz single-element transducers was able to produce a tightly focused field suitable for use in the IVD. As preliminary experiments suggested that high pressure amplitudes were required to initiate cavitation inside the disc, the use of exogenous nuclei to lower this threshold was investigated. A novel class of solid sonosensitive nanoparticles (SNPs) suitable for use in the IVD were developed and characterised. These SNPs comprise a layer of hydrophobic silica particles deposited onto a polystyrene core, and are thought to trap small gas pockets in surface crevices. Coated particles were found to reduce the cavitation threshold significantly in both water and blood, from some 2.0 - 2.5 MPa at 1.067 MHz to below 1.0 MPa. The particles were also found to provide repeatable initiation of cavitation activity during prolonged or repeated exposures, and to exhibit good storage stability, suggesting that they they may be appropriate for use within the IVD. Finally, a combined therapy and monitoring system was designed, built and validated. The system comprised two confocal 0.5 MHz spherically focussed HIFU transducers with central openings, each co-axially aligned with either a single element passive cavitation detector or a 64-element array that could be used for both active and passive imaging. The system was found to be capable of initiating inertial cavitation in the disc at pressures as low as 2.5MPa in the presence of sonosensitive nanoparticles. Use of the array in active mode enables creation of a B-mode image that provides anatomical information on the boundaries of the IVD, whist the same array could be used for passive mapping of acoustic emissions arising fromthe HIFU focus during therapy. Two different exposure regimes were found to be capable of producing sizeable perforations within the NP without significantly damaging the AF, and preliminary investigations were carried out into themechanism of damage. The location and extent of cavitation as seen on passive maps acquired during treatment was found to coincide with the regions of NP fractionation. This confirms that passive acoustic mapping can provide the real-time treatment monitoring necessary to ensure both safety and efficacy of ultrasonic IVD fractionation. Prior to clinical application, a significant amount of further development is required to further validate non-invasive disc fractionation by HIFU and the subsequent steps for minimally invasive disc replacement using injectable hydrogels. The present work has nonetheless demonstrated for the first time that minimally invasive removal of degenerate disc tissue is feasible trough the combined use of sonosensitive nanoparticles and a relatively low-cost therapeutic ultrasound system that provides simultaneous anatomical imaging and real-time treatment monitoring by passive acoustic mapping.
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Bhambra, Kalwant S. "The fractionation of dextran using ethanol." Thesis, Aston University, 1985. http://publications.aston.ac.uk/10231/.
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Kamalanathan, Ishara Dedunu. "Foam fractionation of surfactant-protein mixtures." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/foam-fractionation-of-surfactantprotein-mixtures(a6484b1a-d796-45ff-bc5c-420ef9130363).html.
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Foam fractionation is an adsorptive bubble separation technology that has shown potential as a replacement to the more costly and non-sustainable traditional downstream processing methods such as solvent extraction and chromatography for biological systems. However biological systems mostly tend to be a mixture of surface active species that complicates the foam fractionation separation. In this thesis a detailed experimental study on the application of foam fractionation to separate a well-defined surfactant-protein mixture was performed with emphasis on the competitive adsorption behaviour and transport processes of surfactant-protein mixtures in a foam fractionation process. Surface tension and nuclear magnetic resonance (NMR) measurements showed that nonionic surfactant Triton X−100 maximum surface pressure, surface affinity and diffusivity were a factor of 2.05, 67.0 and 19.6 respectively greater than that of BSA. Thus Triton X−100 dominated the surface adsorption at an air-water surface by diffusing to the surface and adsorbing at the surface faster than BSA. This competitive adsorption behaviour was observed in foam fractionation experiments performed for Triton X−100/BSA mixtures for different feed concentration ratios and air flow rates. The recovery and enrichment of Triton X−100 were found to increase and decrease respectively with increasing air flow rate for all foam fractionation experiments as expected for a single component system. However the recovery and enrichment of BSA were both found to increase with increasing air flow rate for high feed concentrations of Triton X−100.Bubble size measurements of the foamate produced from foam fractionation experiments showed that at steady state conditions the bubbles rising from the liquid pool were stabilised by BSA. However at the top of the column the recovery of Triton X−100 in the foamate (75% to 100%) was always greater than the recovery of BSA (13% to 76%) for all foam fractionation experiments. In addition, for high feed concentrations of both components and at low air flow rates, the enrichment of BSA remained at almost unity for most experiments and only increased when the recovery of Triton X−100 reached 100%. Thus it was concluded that Triton X-100 displaced the adsorbed BSA from the surface. The foam drainage properties of Triton X−100/BSA mixtures were characterised using two methods; forced foam drainage and from pressure profiles of steady state foam fractionation experiments (pressure method). The drainage data from the forced foam drainage was found not to be compatible with experimental foam fractionation results, by indicating that stable foam was not produced during the foam fractionation experiments. However stable foam was repeatedly produced during foam fractionation experiments. The drainage data from the pressure method was found to be in close agreement to experimental foam fractionation experiments. The work in this thesis takes a significant step beyond the literature experimental foam fractionation studies for multicomponent systems. In addition to investigating the effect of foam fractionation process parameters on the separation of mixed systems, the results from the characterisation studies of surface adsorption and foam properties provided insight and deeper understanding of the competitive adsorption behaviour of surfactants and proteins in a foam fractionation process.
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Safi, Carl. "Microalgae biorefinery : proposition of a fractionation process." Phd thesis, Toulouse, INPT, 2013. http://oatao.univ-toulouse.fr/11469/1/safi.pdf.
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A primary algorefinery, concept that deals with the main components of microalgae (lipids, proteins, carbohydrates and pigments), has been studied. A sequence of unit operations has been implemented in order to obtain separated enriched fractions of these biomolecules by conserving their integrity in the downstream process. The study was mainly centred on Chlorella vulgaris, a species known for its rigid cell wall. Most of the lipophilic fraction (lipids and pigments) was recovered using supercritical carbon dioxide with ethanol as a co-solvent, without a preliminary unit operation of cell disruption. The hydrophilic fraction (proteins and polysaccharides) was recovered in the aqueous phase after bed milling as cell disruption method. Subsequently, the aqueous phase was fractionated into three fractions by means of a process of two-stage ultrafiltration. Thus, starches, pigments, proteins and sugars were successfully separated from each other. A life cycle assessment will be necessary to estimate the cost and the sustainability of the fractionation process.
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Vega, R. "Fractionation and concentration of fish protein hydrolysates." Thesis, University of Reading, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378685.
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The extraction of nitrogenous compounds from cod (Cadus morhua) offal by enzymic hydrolysis with papain, the membrane separation of the peptides in the soluble fraction and their freeze and membrane concentration were investigated with the aim of obtaining a high yield of functional products. The following aspects were covered: kinetics of the hydrolysis and of the enzyme inactivation, separation of insoluble solids and yield of nitrogen under different operating conditions (water to fish offal ratio, temperature and particle size of the raw material). Three of the processing options -the hydrolyses, without and with added water, and the water extraction of the minced fish offal followed by hydrolysis of the residue- gave nitrogen yields of 51%, 62% and 69% of the total nitrogen in the fish offal, and required water: fish offal ratios of 0,1 and 1.86 respectively. The peptides in the hydrolysate supernatants were not amenable to membrane separation but those in the water extract supernatant could be split by pH precipitation and ultrafiltration. Eight functional properties of the potential products were evaluated. The hydrolysate supernatants lacked most of them except for high solubility but their low ash content and the particular molecular weight distribution of their peptides may be useful in special feeding diets. The pH precipitate and the concentrate from the ultrafiltration of the supernatant from the pH precipitation exhibited all the functional properties tested to some extent. The precipitate exhibited low solubility and high buffering capacity, high viscosity and good foaming properties. The concentrate had good solubility, gel strength and emulsifying properties.
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Kirk, Charles A. C. "Geochemical fractionation of heavy metals in soils." Thesis, University of Bristol, 1995. http://hdl.handle.net/1983/2153b6ab-75d5-4b4f-b648-f3ff6795b4d9.
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Chroona, Gustaf. "Fractionation of textile fibres from denim jeans." Thesis, KTH, Skolan för kemivetenskap (CHE), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209012.
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The structure and composition of denim jeans is complex. In addition to cotton, which is the dominating type of textile fibre, there may be up to about 20 % synthetic fibres. The synthetic fibres are found in the sewing thread and in the elastic yarns that are used to make stretch denim jeans. In total it was found that up to six different types of textile fibres may be present in the material. To be able to recycle cotton in jeans by producing regenerated cellulose fibres a very high purity with respect to cotton is required. The purpose with this project was to investigate the possibility to fractionate the textile material found in denim jeans to obtain a pure cotton fraction that can be used in the viscose process to produce regenerated cellulose fibres, which then can be used to manufacture new clothes. In this project traditional wet mechanical separation equipment found in the pulp and paper industry, in the form of a laboratory screen (used as a model for a pressure screen) and hydrocyclone, was used to fractionate the textile material from cut and shredded denim jeans. The degree of separation of synthetic fibres from cotton fibres was quantitatively evaluated by measuring the glucose content after acid hydrolysis. The results from the experimental work showed that there were runnability problems both regarding disintegration and fractionation. Regarding the fractionation, plugging was found to be a problem and no significant separation of synthetic fibres from cotton fibres was obtained with the conditions of the experiment.Strukturen och sammansättningen i denimjeans är komplex. Utöver bomull, vilken är den dominerande typen av textilfiber, kan de innehålla upp till 20 % syntetiska fibrer i tyget. De syntetiska fibrerna finns i sytråden och i elastiska garner som används för att tillverka stretchdenimjeans. Den här studien visade att upp till sex olika typer av textilfibrer kan förekomma i materialet. För att kunna återvinna bomull i denimjeans genom att producera regenererade cellulosafibrer krävs en mycket hög renhet med avseende på bomull. Syftet med projektet var att undersöka möjligheten att fraktionera textilmaterialet i denimjeans för att erhålla en ren bomullsfraktion som kan användas i viskosprocessen för att tillverka regenererade textilfibrer, vilka sedan kan användas för att tillverka nya kläder. I projektet användes, inom massa och pappersindustrin traditionell våtmekanisk separationsutrustning i form av en laboratoriesil (här använd som en modell av en trycksil) och en hydrocyklon, för att fraktionera textilmaterialet från klippta och sönderslitna denimjeans. Separationsgraden av syntetiska fibrer från bomullsfibrer bestämdes kvantitativt genom att mäta glukoshalten efter sur hydrolys. Resultatet från det experimentella arbetet visade att det finns körbarhetsproblem både gällande uppslagning och fraktionering. För fraktioneringen visade sig pluggning vara ett problem och ingen signifikant separation av syntetiska fibrer från bomullsfibrer erhölls med förhållandena i experimentet.
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Xu, Xianping. "Mass independent isotopic fractionation in solid phase /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9820888.
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Edwards, Thayne Lowell. "Microfrabricated Acoustic and Thermal Field-Flow Fractionation Systems." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/6981.
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Arguments for miniaturization of a thermal field-flow fractionation system ( and #956;-ThFFF) and fabrication of a micro-scale acoustic field-flow fractionation system ( and #956;-AcFFF) using similar methods was presented. Motivation for miniaturization of ThFFF systems was established by examining the geometrical scaling of the fundamental ThFFF theory. Miniaturization of conventional macro-scale ThFFF systems was made possible through utilization of micromachining technologies. Fabrication of the and #956;-ThFFF system was discussed in detail. The and #956;-ThFFF system was characterized for plate height versus flow rate, single component polystyrene retention, and multi-component polystyrene separations. Retention, thermal diffusion coefficients, and maximum diameter-based selectivity values were extracted from separation data and found comparable with macro-scale ThFFF system results. Retention values ranged from 0.33 to 0.46. Thermal diffusion coefficients were between 3.0ױ0-8 and 5.4ױ0-8 cm2/sec?? The maximum diameter-based selectivity was 1.40.
While the concept of an acoustic FFF sub-technique has been around for decades, the fabrication methods have not been available until recently. The theory was developed in full including relating sample physical properties to retention time in the FFF system. In addition to the theory, the design and fabrication of the and #956;-AcFFF was presented. Design results from an acoustic modeling program were presented with the determination of the acoustic resonant frequency. The acoustic-based systems was designed around the model results and characterized by electrical input impedance, fluidic, plate height, polystyrene suspension retention, and polystyrene mixture separation studies.
The and #956;-AcFFF system was able to retain a series of nanometer scale polystyrene samples. However, the retention data did not follow normal mode retention but did reveal the location of the steric inversion point for the power level used, around 200 nm. The results of the multiple component separation confirmed this results as the sample, which contained 110, 210, and 300 nm diameter samples, was not resolved but only broadened.
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Fraunhofer, Wolfgang. "Asymmetrical flow field-flow-fractionation in pharmaceutical analytics." Diss., lmu, 2003. http://nbn-resolving.de/urn:nbn:de:bvb:19-84503.
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Bergström, Jonas. "Flow Field and Fibre Fractionation Studies in Hydrocyclones." Doctoral thesis, KTH, Fiber- och polymerteknik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4175.
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Hydrocyclones can be used to fractionate fibres according to their papermaking potential. The obtained fractions typically differ in fibre wall thickness and/or degree of fibre treatment. Despite a multitude of potential application scenarios, the process has so far had little commercial success. This is largely explained by the low fractionation efficiency and unfavourable operating characteristics of the process. The fractionation efficiency of a hydrocyclone is closely related to its flow field. The influence of pulp concentration on the tangential velocity field was therefore studied, by using a self-cleaning pitometer. It was found that the pulp concentration had a strong influence on the tangential velocity. At a feed pulp concentration above 7.5 g/l, the suspension rotated almost as a solid body. As a consequence, the magnitude of radial acceleration and shear stresses decreased dramatically. It is suggested that this is detrimental to the fractionation efficiency. The radial velocity field was measured using an Ultrasonic Velocity Profiler. The measurements showed that the rotational centre of the flow field did not correspond with the geometrical centre of the hydrocyclone. This displacement caused the tangential velocity component of the vortex to contribute substantially to the measurement result of the radial velocity component. Based on the findings in respect to the flow field studies, a novel design for a fibre fractionation hydrocyclone was proposed. The flow field inside this hydrocyclone was compared to that in a conventional hydrocyclone. It was found, that high radial acceleration and shear stresses could be maintained in the novel design even at high fibre concentration. The fractionation efficiency of the novel hydrocyclone was characterised in terms of surface roughness difference between fine and coarse fraction. When operated with refined bleached softwood kraft pulp, the novel hydrocyclone could produce fractions with a substantial surface roughness difference without deteriorating the dewatering characteristics of the fine fraction. A low thickening of the reject is proposed to be the explanation for that. When fractionating TMP, the best efficiency occurred at a concentration of 10 g/l.QC 20100804
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Fang, Yi. "Fractionation of organic liquid mixtures by reverse osmosis." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5890.
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A systematic investigation has been conducted to demonstrate the general applicability of reverse osmosis (RO) fractionation of organic liquid mixtures by laboratory prepared cellulose acetate butyrate (CAB) and aromatic polyamide (PA) membranes. Surface excess values have been determined by liquid chromatography (LC) technique for the four model organic liquid mixtures for CAB and PA materials. The principal findings of this study are: (i) separations take place in all the four model organic liquid mixtures, and PA membranes given separations higher than CAB membranes under same experimental conditions; (ii) preferential sorption exists in all the four model systems for CAB and PA materials, (iii) the RO results are explained by the combined consideration of surface excess data determined from LC, and Stokes' Law radius calculated from literature data.
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Babcsanyi, Izabella. "Copper transport and isotope fractionation in an agrosystem." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAH006/document.
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Depuis la fin du 19ème siècle, le traitement des vignes par des fongicides cupriques a engendré une augmentation de la teneur en cuivre (Cu) dans les sols viticoles, ainsi que dans les écosystèmes aquatiques en aval. Cette thèse vise à mieux comprendre le devenir de ce Cu dans un agrosystème basé sur l’étude du fractionnement isotopique du 65Cu/63Cu. Les résultats montrent que durant 4 à 5 décennies de culture de vignes, les sols en surface se sont enrichis en Cu de 9 à 28 fois par rapport au fond géochimique et que les minéraux argileux jouent un rôle important dans l’accumulation du Cu. Lors des événements pluvieux, ~1% du Cu appliqué est mobilisé, essentiellement lié à des argiles. Le bassin d’orage récoltant les lames ruisselantes retient en moyenne 68% du Cu dissous et plus de 92% du Cu particulaire. Les ratios isotopiques du Cu dans le bassin indiqueraient la sorption du Cu dissous dans les sédiments, ainsi que la réduction du Cu(II) in situ due à des processus biogéochimiquesSince the end of the 19th century, the use of copper (Cu)-based fungicides has resulted in increased Cu concentrations in vineyard soils, but also in downstream aquatic ecosystems. The aim of the thesis was to better understand the fate of this Cu in an agrosystem based on assessing Cu isotope fractionation (65Cu/63Cu). The results have shown that the surface vineyard soils have become enriched in Cu from 9 to 28 times compared to the background level during 4 to 5 decades of vine-growing and that clay minerals were the major Cu sorbing phases in the soils. During rainfall, runoff mobilized ~1% of the applied Cu during the, mainly associated with clays. The stormwater wetland collecting the runoff retained in average 68% of the dissolved and more than 92% of particulate Cu. Cu isotope ratios measured in the wetland suggested dissolved Cu sorption to the sediments and in situ reduction of Cu(II) due to biogeochemical processes
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Bergström, Jonas. "Flow field and fibre fractionation studies in hydrocyclones /." Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4175.
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Sumual, Maria Fransisca. "Fractionation and characterization of proteins from coconut milk." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22813.
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Centrifugation of coconut milk resulted in cream, skim milk, and insoluble solids. Proteins were isolated from skim milk by the addition of acid, with or without heating. The separation and isolation gave the following coconut protein preparations: coconut milk, coconut skim milk, insoluble solids, acid precipitate, and acid-heat precipitate.Trypsin inhibitory activity (TIA) of the coconut protein preparations was relatively low while tryptic digestibility of the isolated proteins was considerably lower than those of the coconut milk and skim milk, the digestibility of coconut protein preparations was lower than that of casein. In general, the emulsifying and farming properties of coconut protein preparations were lower than casein. The insoluble solids showed the highest viscosity when compared with the coconut protein preparations. In contrast to the whey protein concentrate (WPC), the apparent strain of gels from the acid precipitate increased as the pH increased. The gelation properties at pH 3 of the insoluble solids were better than WPC.
The estimated molecular weight by size-exclusion chromatography of coconut protein preparations gave 3 fractions with MW ranging from 6850 Da to 229402 Da. In native PAGE, coconut proteins were separated into at least 3 subunits and under SDS-denatured conditions, the major protein subunits showed MW of 54531 Da and 25008 Da, respectively. RP-HPLC separation of coconut milk, acid precipitate, and acid-heat precipitate gave 3 fractions containing several species of MW ranging between 35574 Da to 51209 Da when analyzed by mass spectometry.
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Morin, Pierre. "On the fractionation of buttermilk by microfiltration membranes." Thesis, Université Laval, 2006. http://www.theses.ulaval.ca/2006/23852/23852.pdf.
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Ramadhan, Omar M. "Biomass derived oil : production, fractionation and structural investigation." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326043.
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Hill, David M. "Size fractionation of metals in rivers by ultrafiltration." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307892.
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Osman, Mohamed Elmubarak. "Fractionation and characterisation of gum from Acacia senegal." Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336168.
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Al-Rabiah, Hassan. "Fractionation of petroleum crude oil using superheated water." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399875.
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Bennett, Sarah Louise. "High field strength element fractionation in the mantle." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409322.
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Manning, Harriet. "The fractionation of gum arabic using synthetic membranes." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687326.
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Gum arabic is a natural product used widely in the food industry as an emulsifier and stabilising agent. The gum contains 3 main fractions: an arabinogalactan (~80 wt%; AG) fraction, a glycoprotein (~ 2 wt%; GP) fraction and an arabinogalactan-protein complex (~18 wt%; AGP). This AGP fraction is largely responsible for the functional properties of gum arabic and, due to natural variation, the proportion of AGP within a gum arabic batch varies enormously. There is industrial interest, therefore, in fractionating the gum arabic to allow creation of a more homogenous product, as well as new products for the food industry. The aim of this work was to investigate the feasibility of using membrane technology to fractionate gum arabic. Polymeric membranes were used initially and showed success at rejection of AGP by size exclusion. Polysulfone membranes of 0.1, 0.5 and 0.8 μm nominal pore size were employed and the rejection of AGP was seen to decrease with increasing pore size, but the overall transmission of solids was seen to increase. Beneficial fouling was observed with the larger two pore sizes, which allowed greater fractionation after a fouling layer had developed. It was hypothesised that the 0.1 μm PS membrane was fouled by mainly cake formation, whereas the 0.5 and 0.8 μm PS membranes were subject to more in pore fouling. The critical flux of gum arabic was measured for these three pore sized membranes and was found to be highest (27 L m-2 h-1) for the 0.1 μm PS membrane. This was attributed to the lack of in pore fouling, which the 0.5 and 0.8 μm membranes suffered and resulted in fouling occurring at lower fluxes for these membranes; the critical fluxes for these membranes was found to be 15 and 22 L m-2 h-1, respectively Increasing the crossflow velocity (CFV) from 0.18 to 0.67 m s-1 was found to increase the critical flux. Filtration experiments above and below the critical flux for each pore size demonstrated the efficiency of operating below the critical flux, as operation could be sustained for much longer periods (up to 4h was tested) without the need for cleaning cycles. It also demonstrated the beneficial effect of the fouling layer with the 0.5 iii and 0.8 μm membranes, which showed little or no fractionation during operation below the critical flux. Finally, filtration studies were carried out with 3 different membrane materials and detailed surface analysis was performed to explain the differences in performance observed. Both polysulfone and fluoropolymer membranes were fairly hydrophobic, with contact angles of between 70 and 90º, and showed very high overall rejection of solids. High transmission of solids is required together with good rejection of AGP for an effective fractionation process. Hydrophilic cellulose acetate, however, showed very high transmission of gum arabic (~ 75%), but no rejection of AGP. Overall, the work has shown that fractionation of gum arabic with membranes is feasible using polysulfone membranes, but that further work is needed to optimise the separation. Higher transmission of the GP and AG are required whilst maintaining rejection of the AGP.
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Ramakrishnan, Jagdish. "Dynamic optimization of fractionation schedules in radiation therapy." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82181.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 145-156).
In this thesis, we investigate the improvement in treatment effectiveness when dynamically optimizing the fractionation scheme in radiation therapy. In the first part of the thesis, we consider delivering a different dose each day depending on the observed patient anatomy. Given that a fixed prescribed dose must be delivered to the tumor over the course of the treatment, such an approach results in a lower cumulative dose to a radio-sensitive organ-at-risk when compared to that resulting from standard fractionation. We use the dynamic programming algorithm to solve the problem exactly. Next, we suggest an approach which optimizes the fraction size and selects a treatment plan from a plan library. Computational results from patient datasets indicate this approach is beneficial. In the second part of the thesis, we analyze the effect of repopulation on the optimal fractionation scheme. A dynamic programming framework is developed to determine an optimal fractionation scheme based on a model of cell kill due to radiation and tumor growth in between treatment days. We prove that the optimal dose fractions are increasing over time. We find that the presence of accelerated tumor repopulation suggests larger dose fractions later in the treatment to compensate for the increased tumor proliferation.
by Jagdish Ramakrishnan.
Ph.D.
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Bose, Suman. "Affinity Flow Fractionation for label-free cell sorting." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87961.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages [107]-118).
Capture and isolation of flowing cells from body fluids such as peripheral blood, bone marrow or pleural effusion has enormous implications in diagnosis, disease monitoring, and drug testing. However, in many situations the conventional methods of cell sorting are of limited use due to complex sample preparation steps, high costs, or low sensitivity. Drawing inspiration from nature, a novel platform technology for cell separation known as Affinity Flow Fractionation (AFF) was developed. AFF relies on interaction of cells with asymmetric patterns of weak adhesive molecules allowing for continuous sorting of cells with high purity without irreversible capture of cells. Cells are sorted in a single step, which is a significant advance over conventional immunocapture methods, especially for point-of-care and point-of-use applications. In this work, first, the interaction of cells under shear flow with asymmetric patterns of weak adhesive molecules was studied systematically to highlight the underlying mechanism of AFF at a phenomenological level. Next, an optimized separation device was fabricated and its performance was characterized using model cell lines. A detailed predictive mathematical model, which accounts for the major transport processes involved in cell separation by AFF, was developed and the results validated using experiments. Finally, AFF was applied for rapid isolation of neutrophils from blood, which is important for several applications where conventional procedures involve multiple steps and time-intense manual skills. It was demonstrated that asymmetric patterns of Pselectin, a weak adhesive molecule involved in cell trafficking, can directly draw neutrophils out of a continuously flowing stream of blood, with high purity (92%). As cells exhibiting non-specific adhesion are not drawn out of the flowing stream, an ultrahigh 400,000-fold enrichment of leukocytes over erythrocytes is achieved. Moreover, the sorted neutrophils remain viable, unaltered, and functionally intact. The lack of background erythrocytes enabled direct enumeration of neutrophils by a downstream detector, which could distinguish the activation state of neutrophils in blood. This method is compatible with capillary microfluidics and may find use in isolation of neutrophils for diagnosis of sepsis, genetic analysis, HLA typing, assessment of chemoreadiness, and other applications. Weak molecular interactions govern a large number of important physiological processes such as stem cell homing, inflammation, immune modulation and cancer metastasis. Yet, currently there are no effective technologies that can separate cells based on weak interactions alone. We believe, AFF would fulfill this un-met need in the area of cell sorting and enabling new discoveries. Keywords: Microfluidics, Cell sorting, cell rolling, selectin, blood, point-of-care, neutrophils.
by Suman Bose.
Ph. D.
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Andersson, Rasmus. "Evaluation of two hydrocyclone designs for pulp fractionation." Licentiate thesis, KTH, Träkemi och massateknologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-25272.
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The process conditions and fractionation efficiency of two hydrocyclone designs, a novel and a conventional conical design, were evaluated. The novel design comprised a modified inlet section, where the pulp suspension had to pass a narrow ring-shaped opening, and a very compact fractionation zone. The influence of feed concentration and fine fraction mass ratio was studied. The trials were performed with never-dried, unrefined bleached chemical softwood pulp. Fractionation efficiency was evaluated in terms of change of surface roughness of handsheets made out of the fractions and the feed pulp respectively. The fractionation efficiency increased considerably with decreasing fine fraction mass ratio, especially at higher feed concentrations. This finding prompted a hypothesis on the existence of a radial gradient in the composition of the suspension inside the novel hydrocyclone. Using the novel hydrocyclone in a feed-forward fractionation system would therefore prove to be more favourable as a larger total fine fraction of better properties can be obtained. A three-stage feed-forward fractionation system was evaluated in laboratory scale. Here, it was indeed possible to extract fine fractions with improved surface properties in each of the three consecutive stages. All three fine fractions had about the same surface roughness. The fractionation performance of the novel design was benchmarked against that of a conventional, best available technology (BAT) design. In terms of fractionation efficiency, the BAT design performed better. However, the fractions produced with the novel hydrocyclone had a much smaller difference in concentration, implying a much less pronounced enrichment of fines in the fine fraction. It is unclear, to what extent the lower share of latewood fibres and the increased fines content, respectively, contributed to the improved surface roughness of the fine fractions. However, it is clear that the lower enrichment of fines in the novel hydrocyclone makes it easier to install it in industrial applications without a need for auxiliary equipment to redistribute large water flows.QC 20101014
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Ibrahim, Mazlan. "Clean Fractionation of Biomass - Steam Explosion and Extraction." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36583.
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The fractionation of two biomass resources, red oak (Quercus rubra) chips and oil palm (Elaeis guineensis) trunk solids, into constitutive chemical components, cellulose, hemicelluloses (called "other carbohydrates") and non-carbohydrates (includes lignin, tannins, etc.), was studied quantitatively in terms of relative cleanness. Red oak chips were steam exploded using a batch reactor at five different treatment severities, Ro 5,000, 10,000, 15,000, 20,000 and 35,000. Steam exploded fibers (SEF) of each severity were extracted with water and alkali. Mass fractionation and summative analysis data of all solid biomass fractions were determined. These data were interpreted in term of a unifying clean fractionation concept designed to evaluate the effectiveness of the fractionation processes. Within a series of severities applied to a single biomass resource, the quantitative clean fractionation can be used to choose an optimum severity for the isolation of any particular component fraction. The red oak results revealed that 25 % (on average) of biomass solids were lost during steam explosion. Cellulose remained almost unaffected (retained in fibers form) by water and alkali extraction. About 35-55 % of the hemicelluloses can be recovered in the water extracted liquor fraction (WEL). The remaining non-cellulosic carbohydrates were lost during steam explosion, especially at high severity. At Ro 10,000 and above, alkali extracted fibers (AEF) consists almost entirely of cellulose and non-carbohydrates. The majority of the non-carbohydrates component (> 50 %) can be isolated by alkali extraction. The non-carbohydrate component harvested increased with severity to 67% at Ro 35,000.Master of Science
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Rhim, Jeemin Hannah. "Experimental investigations of isotopologue fractionation during microbial methanogenesis." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129057.
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Thesis: Ph. D. in Geobiology, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2020Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 150-160).
The work described in this thesis explores and develops different culturing methods to test the following hypothesis: hydrogen concentration and redox potential are important controlling factors of carbon (¹³C/¹²C) and hydrogen (D/H) isotope ratios as well as the abundance of methane clumped isotopologues ([delta]¹³CH₃D) during microbial methanogenesis. Chapter 2 uses batch and fed-batch culturing systems to investigate the effects of H₂ concentrations on isotopologue fractionation. The results from fed-batch experiments confirmed the previous observation of decoupled ¹³C/¹²C and D/H systematics and provide experimental support for the hypothesis linking D/H and [delta]¹³CH₃D systematics.
Results from a mathematical model indicated that the dissolved H₂ concentration, [H₂], at the cell surface can be up to an order of magnitude lower than [H₂] expected in equilibrium with the headspace mixing ratio, highlighting the importance and challenge in controlling [H₂] during fed-batch experiments. Chapter 3 and Chapter 4 present the application of bioelectrochemical system (BES) as a means to control methane production. In Chapter 3, mixed culture BESs were used to enrich for methanogenic microbial communities. Distinct molecular and morphological characterized the anodic and cathodic communities. Within the tested range, methane production and the D/H values of methane showed general correlations with applied potentials, indicating a promising application of this system in isotope studies. Chapter 4 introduces a new design of a pure culture BES to directly test the effects of cathode potentials on methane production and isotope signatures.
Methane production decreased exponentially with increasing cathode potentials, up to 80 mV within the thermodynamic limit under our experimental conditions. Theoretical predictions indicate that the decrease in methane production rate is expected to be much more extreme at higher cathode potentials (<30 mV within the limit, for our system), while isotope data indicated a negative correlation between methane production rate and D/H values. This demonstrates the potential application of pure culture BESs to elucidate the origin of equilibrium isotope signatures in energy-limited environments often found in marine sediments. Limitations and future directions in the application of each experimental system explored in this thesis work are discussed at the end of each chapter.
by Jeemin Hannah Rhim.
Ph. D. in Geobiology
Ph.D.inGeobiology Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences
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Niamke, Justine N'guessan. "Fractionation of poly(ethylene glycol) between liquid phases." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1875.
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Thesis (M.S.) -- University of Maryland, College Park, 2004.Thesis research directed by: Dept. of Chemical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Kinneer, Krista L. "Size fractionation of bacterial functional diversity within soils." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1095.
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Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains x, 68 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 47-48).
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Sin, E. H. K. "The extraction and fractionation of waxes from biomass." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3123/.
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The aim of this project was to extract and fractionate waxes from abundant and low-cost under-utilised renewable resources using a green alternative technology. Through a review of the literature, the waxes covering agricultural by-products such as straw were identified as a potential source of high value chemicals for a wide range of applications. Wheat straw waxes were extracted using organic solvents to demonstrate that straw contained high value wax compounds including free fatty acids, fatty alcohols, alkanes, wax esters, sterols, aldehydes and β-diketones. The solvent properties did not affect the composition of the extracts but changed the relative abundance of the different compounds. Linear solvation energy relationship (LSER) was used to model the extraction selectivity relating to total extraction yield and the various wax compounds. Lipophilic and aqueous fractions were separated and LSER results identified that the solvent properties affect only on the quantity of aqueous fraction recovered indicating the selectivity of the solvent. Extraction of wheat straw wax was carried out using a more environmentally friendly supercritical CO2 extraction. The compositional profiles can be tuned by the manipulation of temperature and pressure and compared with the organic solvent extractions. Optimisation of temperature and pressure was carried out and the total crude yields and wax chemical group yields were modelled using the Chrastil equation to gain a better understanding of conditions required to achieve optimum extraction. The optimisation was used as part of the industrial collaboration scale up with Sundown Products Limited and Evonik Industries where a total of three tonnes of wheat, barley and oat straws were extracted using supercritical CO2 which yielded approximately 60 kg of wax. The three cereal straws were selected based on yield and composition as raw materials for the scale up from the biomass screen of seven different straws using hexane and ethanol extractions. Economical assessment was carried out based on the scale up trial and it was concluded that currently the cereal straw wax would cost £12 per kg which is about 2 – 3 times higher than commercial waxes. The straw waxes were characterised and physical properties such as melting point were determined and found to be similar to commercial waxes such as beeswax. Fractionation by scCO2, GPC and saponification were used to further separate the wax products for formulation trials and product tests with the project sponsor, Croda. The crude wax products were deeply coloured and highly hydrophobic with no emulsification properties therefore applications such as coatings and polishes were suggested.
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Nilsson, Mikael. "Ribosomes and subunits from Escherichia coli studied by asymmetrical flow field-flow fractionation." Lund : Technical Analytical Chemistry, Lund University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/39761331.html.
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Lake, Donna L. "Fractionation and characterisation of heavy metals in sewage sludges." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38078.
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Richter, Andreas. "Structure formation and fractionation in systems of colloidal rods." Phd thesis, Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2007/1309/.
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Dilts, Mark David. "Application of the rollermill and hammermill for biomass fractionation." [Ames, Iowa : Iowa State University], 2007.
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Merz, Juliane [Verfasser]. "A contribution to design foam fractionation processes / Juliane Merz." München : Verlag Dr. Hut, 2012. http://d-nb.info/1028785623/34.
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Chang, Veronica Tzu-Chun. "Mg and Ca isotope fractionation during CaCO₃ biomineralisation." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269953.
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Coward, Thea. "Foam fractionation : an effective technology for harvesting microalgae biomass." Thesis, University of Newcastle Upon Tyne, 2012. http://hdl.handle.net/10443/1753.
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Harvesting and dewatering can account for up to 30% of the overall cost of production of usable microalgae biomass for the biotechnology and bioenergy sectors. Harvesting is particularly challenging due to the small amount of algal biomass produced relative to water volume. This process exacts high energy and cost demands and therefore limits further expansion in the microalgae biomass industry. Foam fractionation has potential to deliver a low cost, low energy harvesting solution. Microalgae cells adsorb to the surface of a stream of fine air bubbles, which then rise up a closed column, discharging the concentrated product at the top. Foam fractionation significantly reduces construction, maintenance, and energy costs compared to other harvesting technologies. In this research, a fractional factorial design of experiments followed by a central composite design were used to determine the optimal levels of major variables influencing the harvest of the freshwater microalga Chlorella sp. The effects of bubble size within the liquid pool and foam phase of the harvesting unit were determined, a high concentration factor of 427 as achieved using fluidic oscillation for microbubble generation. The influence of microalgal growth phase on harvest efficiency was investigated to gain insight into the optimal time to harvest during cell cultivation. The effect of surfactant, used to induce foaming, on lipid recovery was examined through methods including total lipid recovery, gas chromatography, energy dispersive x-ray spectrometry and solid phase extraction. The results indicate that the surfactant had the additional benefit of significantly increasing the overall lipid recovery. These encouraging results suggest foam fractionation offers considerable potential as an efficient, low cost, and scalable microalgae biomass harvesting technology.
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Yunos, Khairul Faezah Md. "Separation and fractionation of proteins using sandwich membrane untrifiltration." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531982.
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