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Tseitlin, Musii, and Valentina Raiko. "Ratio between heat and mass transfer when concentrating the solution in a cooling tower." Thesis, Lviv Polytechnic National University, 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/42106.
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The ratio between the intensity of the mass transfer in gas and the heat transfer in liquid during the evaporative solution concentration has been studied. It was determined that the share of liquid resistance in the total resistance to enthalpy transfer increases in the temperature range from 30 to 50°C by almost 2 times, and reaches 40 %. The technique has been developed for the separate determination of the mass transfer coefficients in gas and heat transfer in liquid.<br>Досліджено співвідношення між інтенсивністю масопереносу в газі та передачею тепла в рідині під час концентрації випарного розчину. Встановлено, що частка опору рідини в загальному опорі переносу ентальпії зростає в діапазоні температур від 30 до 50 ° С майже в 2 рази, досягає 40%. Розроблена методика для окремого визначення коефіцієнтів масопереносу в газі і теплопередачі в рідині.
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Jeong, Dahai. "Laboratory Measurements of the Moist Enthalpy Transfer Coefficient." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_theses/145.
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The enthalpy (sensible and latent heat) exchange processes within the surface layers at an air-water interface have been examined in 15-m wind-wave tunnel at the University of Miami. Measurements yielded 72 mean values of fluxes and bulk variables in the wind speed (referred to 10 m) range form 0.6 to 39 m/s, covering a full range of aerodynamic conditions from smooth to fully rough. Meteorological variables and bulk enthalpy transfer coefficients, measured at 0.2-m height, were adjusted to neutral stratification and 10-m height following the Monin-Obukhov similarity approach. The ratio of the bulk coefficients of enthalpy and momentum was estimated to evaluate Emanuel's (1995) hypothesis. Indirect "Calorimetric" measurements gave reliable estimates of enthalpy flux from the air-water interface, but the moisture gained in the lower air from evaporation of spray over the rough water remained uncertain, stressing the need for flux measurements along with simultaneous spray data to quantify spray's contribution to the turbulent air-water enthalpy fluxes.
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Staton, JoAnna Christen II. "Heat and Mass Transfer Characteristics of Desiccant Polymers." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/9785.
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Desiccant-enhanced air conditioning equipment has exhibited both the capability to improve humidity control and the potential to save energy costs by lowering the latent energy requirement of the supply air stream. The resulting increasing popularity of desiccant-enhanced air conditioning systems has sparked new interest in the search for a better, more efficient desiccant material. The ultimate goal of this research was to develop a material that, when applied to an existing air-to-air heat exchanger, would achieve the necessary heat and mass transfer in a single process, thus transforming a sensible heat exchanger into a total enthalpy exchanger.
This study focuses on the development and determination of appropriate polymeric desiccant materials for use in different heat and mass transfer applications. Various candidate materials were initially studied. It was decided that polyvinyl alcohol best met the pre-determined selection criteria. After the focus material was chosen, numerical models representing two heat and mass transfer applications were created. One-dimensional numerical models were developed for the performance studies of a rotary wheel total enthalpy exchanger. A two-dimensional numerical model was developed for the performance studies of a fixed plate total enthalpy exchanger as well. Material characterization tests were performed to collect material property information required by the numerical models.
Sensible, latent, and total efficiencies gathered from both the rotary wheel total enthalpy exchanger and the fixed plate total enthalpy exchanger models indicate potential uses for some candidate polyvinyl alcohol materials.<br>Master of Science
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Maza, William Antonio. "Reaction Enthalpy and Volume Profiles for Excited State Reactions Involving Electron Transfer and Proton-Coupled Electron Transfer." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4539.
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Electron transfer, ET, and proton-coupled electron transfer, PCET, reactions are central to biological reactions involving catalysis, energy conversion and energy storage. The movement of electrons and protons in either a sequential or concerted manner are coupled in a series of elementary reaction steps in respiration and photosynthesis to harvest and convert energy consumed in foodstuffs or by absorption of light into high energy chemi-cal bonds in the form of ATP. These electron transfer processes may be modulated by conformational dynamics within the protein matrix or at the protein-protein interface, the energetics of which are still not well understood. Photoacoustic calorimetry is an estab-lished method of obtaining time-resolved reaction enthalpy and volume changes on the nanosecond to microsecond timescale. Photoacoustic calorimetry is used here to probe 1) the energetics and volume changes for ET between the self-assembled anionic uroporphy-rin:cytochrome c complex and the role of the observed volume changes in modulating ET within the complex, 2) the enthalpy and volume change for the excited state PCET reac-tion of a tyramine functionalized ruthenium(II) bis-(2,2'-bipyridine)(4-carboxy-4'-methyl-2,2'-bipyrine) meant to be a model for the tyrosine PCET chemistry carried out by cyto-chrome c oxidase and photosystem II, 3) the enthalpy and volume changes related to car-bon monoxide and tryptophan migration in heme tryptophan catabolic enzyme indoleam-ine 2,3-dioxygenase.
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Mondragon, Camacho Ricardo. "Non-physical enthalpy method for phase change modelling in the solidification process." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/nonphysical-enthalpy-method-for-phase-change-modelling-in-the-solidification-process(2ab7597c-eaaa-44d8-abb8-0bf49e413c76).html.
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This research is concerned with the development of a mathematical approach for energy and mass transport in solidification modelling involving a control volume (CV) technique and finite element method (FEM) and incorporating non-physical variables in its solution. The former technique is used to determine an equivalent capacitance to describe energy transport whilst the latter technique provides temperatures over the material domain. The numerical solution of the transport equations is achieved by the introduction of two concepts, i.e. weighted transport equations and non-physical variables. The main aim is to establish equivalent transport equations that allow exact temporal integration and describe the behaviour of non-physical variables to replace the original governing transport equations. The variables defined are non-physical in the sense that they are dependent on the velocity of the moving CV. This dependence is a consequence of constructing transport equations that do not include flux integrals. The form of the transport equations facilitate the construction of a FEM formulation that is applicable to heat and mass transport problems and caters for singularities arising from phase-change, which can prove difficult to model. However, applying the non-physical enthalpy method (NEM) any singularity involved in the solidification process is precisely identified and annihilated.
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Alamaro, Moshe 1948. "Wind wave tank for experimental investigation of momentum and enthalpy transfer from the ocean surface at high wind speed." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/51587.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2001.<br>Includes bibliographical references (leaves 77-79).<br>Thermodynamic analysis and numerical modeling of hurricane intensity has shown that its is controlled by the enthalpy transfer from the ocean surface and by drag. Direct measurements of drag, evaporation, and sensible heat transfer are not easily performed on the high seas. Therefore, a wind wave tank has been constructed in which a few aspects of a tropical storm are simulated. The air velocity inside the annular tank is comparable to that of hurricane. However, the three dimensionality of the tank obscures the quantitative comparison between experiments and actual conditions over the surface of the ocean at high wind speeds. The design of the wind wave tank and the initial experiments create a foundation for future and more comprehensive experimental programs. This thesis focuses mainly on the design and engineering of the tank, and on the fluid mechanics of the rotational flow in the tank. It also provides preliminary experimental data on the drag at high wind speeds obtained by using spindown experiments.<br>by Moshe Alamaro.<br>S.M.
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Stanczak-Mrozek, Kinga Izabela. "Antimicrobial resistance gene transfer between MRSA from colonized patients." Thesis, St George's, University of London, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687072.
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Methicillin-resistant Staphylococcus aureus (MRSA) are opportunistic commensal bacteria that are evolving to become increasingly resistant to antimicrobial agents. Resistance is due to acquisition of resistance genes encoded by mobile genetic elements (MGEs) but little is known about the gene transfer and conditions influencing this process in clinically important MRSA isolates. In this thesis I showed that populations of MRSA colonizing isolates vary phenotypically in antimicrobial resistance (AMR) and genotypically in MGE profiles. A potential mechanism of horizontal gene transfer (HGT) in colonized patients is generalized transducing bacteriophage and we detected free bacteriophage in nasal swabs. AMR and genetic variability have implications for diagnostics, epidemiology, antimicrobial stewardship and selective pressures driving evolution of MRSA populations. All clinical strains harbour at least one prophage which are potentially capable of HGT. Bacteriophage are thought to be induced by environmental conditions including exposure to antibiotics, and 30% of hospitalized patients who are carriers are prescribed antibiotics. Exposure of clinical MRSA isolates to sub-inhibitory concentration of range of anti microbials resulted in increased phage induction and resistance gene transfer, however the ratio of virulent particles to transducing particles differed for each antimicrobial using the new technology of droplet digital peR. Exposure of colonizing MRSA strains to specific antimicrobials may lead to enhanced horizontal transfer of antimicrobial resistance potentially leading to fully resistant MRSA. MRSA isolates collected from patient admitted to St Georges NHS Healthcare Trust between 1999-2003 versus 2012-2013 showed that the recent isolates more easily induced phages and transferred resistance genes more effectively, especially upon induction with ciprofloxacin, suggesting that MRSA is evolving over time to transfer AMR genes more effectively. I developed a new in vitro model mimicking in vivo colonization conditions in the human host by co-culturing two distinct isolates from MRSA carriers in human plasma. Transfer of DNA via HGT occurred at high frequency in plasmas from all 8 donors. However, the presence of certain resistance genes had a fitness cost in some plasma but not others. Frequent horizontal transfer of antimicrobial resistance and other genes between isolates during colonization may play an important role in host-pathogen adaptation and evolution.
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Wang, Lin. "Mass Transfer and GDL Electric Resistance in PEM Fuel Cells." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/486.
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Many modeling studies have been carried out to simulate the current distribution across the channel and shoulder direction in a proton exchange membrane (PEM) fuel cell. However the modeling results do not show agreement on the current density distribution. At the same time, no experimental measurement result of current density distribution across the channel and the shoulder direction is available to testify the modeling studies. Hence in this work, an experiment was conducted to separately measure the current densities under the channel and the shoulder in a PEM fuel cell by using the specially designed membrane electrode assemblies. The experimental results show that the current density under the channel is lower than that under the shoulder except when the fuel cell load is high. Afterwards two more experiments were carried out to find out the reason causing the higher current density under the shoulder. The effects of the electric resistance of gas diffusion layer (GDL) in the lateral and through-plane directions on the current density distribution were studied respectively. The experimental results show that it is the through-plane electric resistance that leads to the higher current density under the shoulder. Moreover, a three-dimensional fuel cell model is developed using FORTRAN. A new method of combining the thin-film model and homogeneous model is utilized to model the catalyst layer. The model is validated by the experimental data. The distribution of current density, oxygen concentration, membrane phase potential, solid phase potential and overpotential in a PEM fuel cell have been studied by the model. The modeling results show that the new modeling method provides better simulations to the actual transport processes and chemical reaction in the catalyst layer of a PEM fuel cell.
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Barbosa, Teresa Maria Leite Martins. "Tetracycline resistance transfer among obligate anaerobes from the ruminant gut." Thesis, University of Aberdeen, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286850.
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The main aim of this work was to investigate the nature, distribution and transmissibility of tetracycline resistance (Tc<sup>R</sup>) genes among ruminant anaerobic bacteria. Two Tc<sup>R</sup> rumen strains of <I>Butyrivibrio fibrisolvens,</I> 1.230 and 1.23, were able to transfer the resistance phenotype to the type strain, 2221<sup>R</sup> although a third Tc<sup>R</sup> strain, 1.210, could not. PCR amplification of 16S rDNA sequences showed that the three isolates were phylogenetically distinct from the recipient strain, but related to each other. Hybridisation work suggested the presence of two chromosomal Tc<sup>R</sup> determinants among the <I>B. fibrisolvens </I>isolates. All three strains contained a non-transferable <I>tet</I>(O) gene, 100% identical at the nucleotide level with <I>tet</I>(O) from <I>S. pneumoniae. </I>The mobile Tc<sup>R</sup> determinant present in strains 1.230 and 1.23, proved to be a novel ribosome protection <I>tet </I>gene, <I>tet</I>(V), whose gene product shares only 68% amino acid identity with its closest relatives, TetO/TetM and has G+C content considerably higher than that of other <I>B. fibrisolvens </I>genes. <I>tet</I>(V) was also identified in two Australian rumen <I>B. fibrisolvens </I>strains, in the rumen anaerobes <I>Selenomonas ruminantium </I>and <I>Mitsuokella multiacidus, </I>and in a pig isolate of <I>M. multiacidus. </I>These results provide evidence for gene transfer between obligate and facultative anaerobes from different gut ecosystems and different geographical locations. PFGE demonstrated that mobile chromosomal elements 40-50 kb in size, Tn<I>B1230 </I>and Tn<I>B123, </I>with preferred insertion sites in the recipient genome mediated the transfer of <I>tet</I>(V) in <I>B. fibrisolvens. </I>No homology was found between Tn<I>B1230</I> and regions from Tn<I>916</I> and Tn<I>5253. </I>Tn<I>B1230</I> is not associated with <I>tet</I>(V) in the other bacterial strains, suggesting that a diverse range of elements carry the gene in different bacteria. Although <I>tet</I>(V) is chromosomally encoded in the majority of the strains examined, there is some evidence that the gene may be located in a plasmid in <I>S. ruminantium </I>FB32 and FB34.
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Barnard, Danielle. "Conjugative Transfer Pathways of High-Level Mupirocin Resistance and Conjugative Transfer Genes in Staphylococcus." Digital Commons @ East Tennessee State University, 2006. https://dc.etsu.edu/etd/2188.
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To combat widespread infections caused by Staphylococcus aureus, mupirocin was introduced at the Veterans Affairs Medical Center, Mountain Home, Tennessee. Soon after introduction, high-level mupirocin-resistance emerged. The rapid emergence was hypothesized to be due to conjugative transfer of the mupA resistance gene from S. epidermidis to S. aureus. Results have shown that transfer of high-level mupirocin-resistance from S. aureus donors commonly occurs. However, transfer from naturally-occurring S. epidermidis donors was not attainable. Staphylococcus epidermidis transconjugants, however, were capable of serving as donors. Further examination of non-transmissibility included PCR analysis of conjugative transfer genes (tra genes) in capable and non-capable donors. Results confirmed that capable donors possess full-length copies of selected transfer genes. Non-capable donors varied in the presence/absence of full-length copies of transfer genes, but none had all three genes. The genetic differences among non-capable donors suggest that non-transmissibility has arisen independently in different strains via gene deletions and recombinations.
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Hart, Erin F. "Using the Abraham Solvation Parameter Model to Predict Solute Transfer into Various Mono- and Multi-Functional Organic Solvents." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157615/.
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The Abraham Solvation Parameter Model (ASPM) is a linear, free-energy relationship that can be used to predict various solute properties based on solute-solvent interactions. The ASPM has been used to predict log (K or Cs,organic/Cs,gas) values, as well as log (P or Cs,organic/Cs,water) values for solute transfer into the following organic solvents: 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-isopropoxyethanol and 2-butoxyethanol. The derived log (K or Cs,organic/Cs,gas) correlations describe the experimental data to within 0.14 log units (or less). The derived log (P or Cs,organic/Cs,water) correlations describe the experimental data to within 0.16 log units (or less). The ASPM has also been used to predict the enthalpies of solvation of organic solutes dissolved in the following solvents: acetic acid, dimethyl carbonate, diethyl carbonate, 1-butanol, 1-pentanol, 1-hexanol. The derived enthalpy of solvation correlations, using the L solute descriptor, describe the experimental data to within 2.50 log units (or less). The derived enthalpy of solvation correlations, using the V solute descriptor, describe the experimental data to within 3.10 log units (or less). Validation analyses have been performed on several of the correlations; and, as long as the solute descriptors fall within the given ranges as reported, the original correlations show good predictive ability for determining 1) solute transfer into, and 2) enthalpy of solvation for the aforementioned solvents.
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Seward, Rebecca Joanne. "Molecular and epidemiological analysis of antibiotic resistance in Acinetobacter spp." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262787.
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Seaman, Paul F. "Development and horizontal gene transfer of triclosan resistance in Staphylococcus aureus." Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/54591/.
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<italic>Staphylococcus aureus</italic> is a major cause of hospital-acquired infections that are becoming increasingly difficult to treat because of the organism's ability to acquire resistance to current antimicrobial agents. Particular attention has been focussed on the evolution of methicillin-resistant <italic> S. aureus</italic> (MRSA) - strains of <italic>S. aureus</italic> that are, in some cases, resistant to almost all known antibiotic classes. One method used to control the spread of MRSA has been the use of topical washes that include triclosan, a potent antimicrobial with particular activity against Gram-positive organisms. Triclosan has traditionally been classed as a biocide and is also used in a broad spectrum of consumer healthcare products, including toothpastes and deodorants. It has also been used to prevent bacterial growth through incorporation into plastics used during food preparation or sutures used to close wounds following surgery. However, in 1991 resistance to triclosan was reported and was described to transfer in association with mupirocin resistance. This was followed by reports that resistance was present in 7.5% of <italic> S. aureus</italic> isolates and that MRSA was less susceptible to triclosan than methicillin- sensitive <italic>S. aureus</italic> (MSSA). It later emerged that, contrary to previous thinking, triclosan targets a specific bacterial protein, Fabl. We aimed to characterize the development of reduced susceptibility to triclosan in MSSA and MRSA and to identify whether triclosan does have a single, specific target. We also set out to elucidate the potential for triclosan resistance to be disseminated by horizontal gene transfer (HGT). By using extensive microbiological and genetic techniques we found that <italic> S. aureus</italic> can evolve reduced susceptibility to triclosan through spontaneous mutation. MICs of 1-4 mg/L were achieved by a C284T mutation offabl, compared to wild-type MICs of -0.03 mg/L. However, reduced susceptibility was also observed in non-fabl mutants, implying that other mechanisms of resistance are available (and that triclosan has targets other than Fabl). We have shown that triclosan induces the leakage of potassium ions from cells, an indication that triclosan targets the cytoplasmic membrane. However, whilst reduced susceptibility to triclosan did confer reduced susceptibility to the lethal effects of 7.5 mg/L triclosan, this effect was ameliorated by higher concentrations of triclosan. Indeed, in-use concentrations of the commercial preparation of triclosan, Irgacide LP 10, are equally active against reduced susceptibility <italic> S. aureus</italic> and wild-type. Therefore, the evolution of reduced-susceptibility to triclosan is of ambiguous clinical significance. We found that spontaneous mutation to reduced susceptibility was not associated with a significant fitness cost, augmenting its potential for emergence in nature. Evolution of reduced susceptibility did not confer co-resistance to other antimicrobials and MRSA and MSSA strains were equally susceptible. An assessment of commensal <italic> S. aureus</italic> carried amongst the student population of Cardiff revealed that reduced susceptibility to triclosan is rare in this population. However, coagulase-negative staphylococci (CoNS) showed consistently higher MICs for triclosan and may represent an amenable reservoir of resistance. There was no indication that mupirocin and triclosan resistance have co-transferred in the past. Indeed, there appeared to be no relationship between resistance to either of these compounds in <italic>S. aureus</italic>. Reduced susceptibility to triclosan could not be disseminated amongst 5". aureus, or related Gram-positive bacteria by transduction, conjugation or transformation. Importantly, during the course of this work we discovered that triclosan could select for <italic> S. aureus</italic> small-colony variants (SCVs) that were coincidently resistant to gentamicin and penicillin. These were slow growing and illustrated the typical SCV phenotype. SCVs were more readily transformable than wild-type cells and may represent an enduring reservoir of resistance determinants. In conclusion, we found that <italic>S. aureus</italic> could develop reduced susceptibility to triclosan by spontaneous mutation or the evolution of SCVs. However, the level of resistance is of ambiguous significance. We propose that triclosan does target Fabl, but also has other cellular targets, particularly at higher concentrations. Whilst the evolution of reduced susceptibility and the occurrence of SCVs should be monitored these should not preclude the use of triclosan as part of infection control procedures. However, to reduce the opportunities for resistance, infection control procedures should not rely upon a single antimicrobial to provide the panacea for nosocomial infections.
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Inzoli, Isabella, Jean Marc Simon, and Signe Kjelstrup. "Surface resistance to heat and mass transfer in a silicalite membrane." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-193396.
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Tao, Hongbin. "Transfer of Fusarium Head Blight Resistance to Hard Red Winter Wheat." Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/29730.
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Fusarium head blight (FHB; caused by Fusarium graminearum Schwabe) is a serious disease of hard red winter wheat (HRWW) in North Dakota. Current varieties are lacking in resistance. Many resistance quantitative trait loci (QTL) were discovered in spring wheat that can be employed in HRWW. The North Dakota State University breeding program aims to acquire and pyramid useful FHB resistance QTL into its breeding population. Therefore, hybrid populations derived from CM82036 (Fhb1 and Qfhs.ifa-5A), PI277012 (Qfhb.rwg-5A.1 and Qfhb.rwg-5A.2), Frontana (Qfhs.ifa-3A), and TA5660 (Fhb6) were tested for type II resistance to: derive new FHB resistant HRWW lines with pyramided QTL (Fhb1+) using molecular marker-assisted selection; evaluate the ability of the different QTL to complement Fhb1. A second project objective was to assess FHB resistance in Thinopyrum distichum (wheat wild relative), random Thinopyrum single chromosome additions to wheat and triticale, and a triticale-Th. distichum secondary hybrid population segregating for a small translocation from Th. distichum.
Useful winter wheat lines carrying Fhb1 with 1-2 additional resistance QTL were developed; however, transfer of Qfhb.rwg-5A.2 was not completed as it was not in the spring wheat intermediate, RWG21. Loci Qfhs.ifa-5A and Qfhb.rwg-5A.1 are probably alleles of the same locus with similar additive effects relative to Fhb1 on the overall resistance. Addition of Qfhs.ifa-3A to Fhb1 plants resulted in no convincing improvement in type II resistance. Combining either Qfhs.ifa-5A or Fhb6 with Fhb1 improved type II resistance; however, pyramiding of three QTL did not give further symptom reduction. No associated, detrimental phenotypic and yield effects were detected in a greenhouse assessment of the alien-derived Fhb6 resistance. The pyramids will be used in crosses to initiate full integration of the new QTL in the breeding germplasm. A select group of pyramids will be evaluated in field trials to better assess the full resistance. Strong FHB resistance was found in triticale-Th. distichum addition lines and secondary hybrid population (W1423). However, the W1423 lineage showed a high incidence of aneuploidy ascribable to aberrant segregation of chromosome 7A and an unknown chromosome. It was not possible to select a translocation homozygote or to identify the translocation chromosome.<br>USDA National Institute of Food and Agriculture, Hatch project number: 1011140; US Wheat and Barley Scab Initiative (allocation number FAR0026888)
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Gorgy, Evraam I. "Pool boiling of R-134a and R-123 on smooth and enhanced tubes." Thesis, Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/804.
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Govik, Alexander. "Modelling of the Resistance Spot Welding Process." Thesis, Linköping University, Linköping University, Department of Management and Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-17835.
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<p>A literature survey on modelling of the resistance spot welding process has been carried out and some of the more interesting models on this subject have been reviewed in this work. The underlying physics has been studied and a brief explanation of Heat transfer, electrokinetics and metallurgy in a resistance spot welding context have been presented.\nl\hsLastly a state of the art model and a simplified model, with implementation in the FEM software LS-DYNA in mind, have been presented.</p>
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Laskey, Alexander. "Horizontal Transfer of β-Lactam Resistance in the Mouse Gut Microbiota Under Antibiotic Treatment". Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41404.
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The rise of β-lactam-resistant bacteria from agricultural settings, including food-producing animals and their related food products has become a significant public health concern. Consumption of food contaminated by such bacteria may cause infection as well as the transmission of resistance genes. Here we used a mouse model to assess the impact of different antibiotic treatments on the composition of the gut microbiota and any impact on the transfer of β-lactam resistance genes between donor and recipient bacteria. Mice were inoculated with β-lactam resistant Escherichia coli and an antibiotic-susceptible Salmonella Heidelberg strain. The mice were treated with either streptomycin, ampicillin or both antibiotics. Mouse feces were collected at regular intervals and processed using selective culture techniques to capture potential transfer of resistance genes. Gene transfer was confirmed by whole genome sequencing. DNA extracted from the feces was used for monitoring changes in microbial profiles by 16S rDNA sequencing. In the absence of antibiotic treatment, the inoculated bacteria were only transiently detected and no transconjugants were recovered from the mouse feces. In comparison, antibiotic treatment changed microbial profiles in the mouse gut, enhanced colonization of the bacterial isolates, and facilitated the transfer of the resistance genes into both S. Heidelberg and commensal E. coli recipient strains. The results of this study indicated that the use of multiple antibiotics may enhance infection of opportunistic β-lactam resistant bacterial pathogens relative to single antibiotics and pose a greater risk in terms of antibiotic resistance gene transfer. Such process might occur in clinical settings where patients are under prolonged antibiotic treatments. Information gained through this study together with future work will inform the development of new policies guiding the prudent use of antibiotics.
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Lai, Chan Ji. "Flow resistance, discharge capacity and momentum transfer in smooth compound closed ducts." Thesis, University of Birmingham, 1986. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.749571.
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RIVA, FRANCESCO. "ANTIBIOTIC RESISTANCE SPREAD MEDIATED BY HORIZONTAL GENE TRANSFER IN THE AGRI-FOOD ECOSYSTEM." Doctoral thesis, Università degli Studi di Milano, 2022. http://hdl.handle.net/2434/914666.
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Antibiotic resistance (AR) is a public problem for human health and food safety. Globalization has contributed to create an intense connection among human and animal health and the environment, allowing bacteria and their genes to move among all these compartments, making a “one-health approach” necessary to counteract this phenomenon. Horizontal gene transfer (HGT), which contributes to AR determinants diffusion, is mediated by three main mechanisms: i) conjugation, ii) transduction, and ii) natural transformation. Several environments linked to the agri-food system are both sources of AR determinants and hot spots of HGT.
One of the main routes of AR spread in the agri-food system could be represented by the use of treated wastewater as irrigation source: the reuse of water is indeed a common practice in several countries, including Europe, to fight the water crisis exacerbated by global warming. Wastewater treatment plants (WWTPs) could be one of the main sources of free antibiotic resistance genes (ARGs) which could be released in freshwater bodies. AR determinants present in the treated wastewater would thus enter in the food production through irrigation and could be acquired by pathogenic strains, potentially posing a risk to human health. Even if the presence and the related issues about AR determinants in the environment are well known, there are many aspects which have to be understood e.g. the relative contributions of different sources of AR determinants in the environment, also considering HGT events.
Since information about the relationship between environmental HGT and spread of AR determinants is limited, the aim of this PhD thesis was to evaluate the diffusion of ARGs through natural transformation and conjugation in environment or in environmental-like conditions to describe several possible routes of AR spread in the agri-food system.
Zooplankton plays a crucial role in waterbodies, being closely linked to bacteria inhabiting aquatic environments in several ecological function, and it establishes a connection with bacterial communities that are inhabitant of the environment in which it lives. Due to the interaction between bacteria and zooplankton, together with the presence of Escherichia coli in waterbodies, derived from human and animal faecal waste, I first evaluated the relationship established between zooplankton, with the model Daphnia obtusa, and E. coli, isolated from it, suggesting that Daphnia could help the bacterium to adapt to the harsh condition that could be found in the freshwater bodies, highlighting the possible role of zooplankton in the diffusion of antibiotic resistant bacteria (ARB) in the agri-food system.
The interaction observed between Daphnia and E. coli in the first part of this thesis, together with the knowledge of the presence of ARGs in aquatic environment and the moderate ability to E. coli to acquire DNA through natural transformation, have thus led to the study of natural transformation in zooplankton-associated bacteria, also in terms to unveil the animal influence. Indeed, I studied the natural transformation of the environmental E. coli strain ED1, isolated from D. obtusa, mimicking environmental conditions which could be found in the agri-food system. ED1 ability to acquire exogenous DNA, with a higher frequency than the one of a laboratory strain, together with its ability to thrive in lettuce rhizosphere, underlined the importance to investigate the spread of AR determinants in the agri-food system, especially in the rhizosphere of plants which are usually raw-consumed. Moreover, the possible influence of the zooplankton on natural transformation was investigated through the use of D. obtusa and Acinetobacter baylyi BD413, known to be naturally competent to acquire DNA. A decrease of transformation frequency was observed in presence of Daphnia, due to the degradation of exogenous DNA, highlighting the need of further investigations on zooplankton involvement in ARGs diffusion in aquatic environments.
Considering possible routes of diffusion of AR determinants in the agri-food system, i.e. from WWTPs to freshwater bodies and their inhabitant community, to crops and plants, I then devoted my attention on HGT by conjugation in rhizosphere of lettuce, used as model of raw-eaten vegetables. The aim of this work was the construction of a donor strain belonging to the Enterobacteriaceae family and isolated from treated wastewater. Specifically, Klebsiella variicola subsp. variicola was genetically manipulated through the chromosomal tagging with a mCherry gene and a constitutively expressed LacIq gene, and the insertion of the broad host range plasmid pKJK5::gfp::KanR, carrying a green fluorescent protein gene (Gfp) under the control of laclq repressible promoter, and thus resulting in the absence of gfp expression in the donor. The gfp was expressed only in recipient strains, following the mobilization of the plasmid through conjugation. The strain ability to donate the plasmid within the bacterial community of lettuce rhizosphere and its ability to colonize the plant root system were verified, making K. variicola subsp. variicola EEF15::lacIq-pLppmCherry-GmR with plasmid pKJK5::gfp a perfect candidate for the study of conjugation in plants microniches.
Finally, I contributed to prepare a critical review on microbial assisted phytodepuration and the use of plant growth promoting bacteria in Constructed Wetland (CW) systems, with a focus on HGT events and the possible spread of AR determinants in the rhizosphere of plants used in phytodepuration.
Data collected in this PhD project underline the importance to study the diffusion of AR determinants trough HGT events in the agri-food system, in order to create a rank risk and a risk assessment map to mitigate the diffusion of AR.
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Pathak, Sayali V. "Enhanced Heat Transfer in Composite Materials." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1368105955.
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Horn, Marizanne. "Transfer of genetic resistance to the Russian wheat aphid from rye to wheat." Thesis, Stellenbosch : Stellenbosch University, 1997. http://hdl.handle.net/10019.1/55770.
Full textAbstract:
Thesis (MSc.) -- Stellenbosch University, 1997.<br>ENGLISH ABSTRACT: An octoploid triticale was derived from the F1 of a Russian wheat aphid
resistant rye, 'Turkey 77', and 'Chinese Spring' wheat. The alloploid was
crossed (a) to common wheat, and (b) to the 'Imperial' rye to 'Chinese Spring'
disomic addition lines. F2 progeny from these crosses were tested for
Russian wheat aphid resistance and C-banded. Resistance was found to be
associated with chromosome arm 1RS of the 'Turkey 77' rye genome. This
initial work was done by MARAIS (1991) who made a RWA resistant,
monotelosomic 1RS ('Turkey 77') addition plant available for the study. The
F3 progeny of this monotelosomic addition plant was used to confirm the
RWA resistance on chromosome 1RS. The monotelosomic addition plant
was then crossed with the wheat cultivar 'Gamtoos', which has the 1BL.1 RS
'Veery' translocation. Unlike the 1RS segment in 'Gamtoos', the 'Turkey 77'-
derived 1RS telosome did not express the rust resistance genes 5r31 and
Lr26 which could then be used as markers. From the F1 a monotelosomic
1RS addition plant that was also heterozygous for the 1BL.1 RS translocation,
was selected and testcrossed with an aphid susceptible common wheat, 'Inia
66'. Meiotic pairing between the .rye arms resulted in the recovery of five
euploid, Russian wheat aphid resistant plants out of a progeny of 99
euploids. One recombinant also retained 5r31 and Lr26 and was allowed to
self pollinate. With the aid of SOS-PAGE profiles, Russian wheat aphid
resistant 1BL.1 RS translocation homozygotes were identified and it was
possible to confirm that the Russian wheat aphid resistance gene was in fact
transferred to the 1BL.1RS ('Veery') translocation.
Two attempts were made to map the Russiar, wheat aphid locus or loci.
(1) Telosomic mapping was attempted. For this purpose a plant with 2n =
40 + 1BL.1 RS + 1RS was obtained, and testcrossed with a Russian wheat
aphid susceptible wheat. (2) A disomic, recombined 1BL.1 RS translocation
line with Russian wheat aphid resistance but lacking the Lr26 and Sr31 alleles was crossed with 'Gamtoos' and the F1 testcrossed. The testcross in
both strategies were done with 'Chinese Spring'. In the first experiment the
Sr31 locus was located 10.42 map units from the Lr26 locus. The rust
resistance data implied that the genetic distance estimates may be unreliable
and therefore the laborious Russian wheat aphid resistance tests were not
done. In the second experiment a Russian wheat aphid resistance gene was
located 14.5 map units from the Lr26 locus. In the latter cross nonmendel
ian segregation of the Russian wheat aphid resistance evidently
occurred which implied that the estimated map distance may be inaccurate.
It was also not possible to determine the number of genes involved from the
data.<br>Digitized at 300 dpi Colour & b/W PDF format (OCR), using ,KODAK i 1220 PLUS scanner. Digitised, Ricardo Davids on request from ILL 25 April 2013<br>AFRIKAANSE OPSOMMING: 'n Oktaplo"lede triticale is gemaak vanaf die F1 van 'n kruising tussen 'n
Russiese koringluis-weerstandbiedende rog, 'Turkey 77', en die
koringkultivar 'Chinese Spring'. Die alloplo"led is gekruis met gewone
broodkoring en met 'Imperial' rog/'Chinese Spring' disomiese addissielyne.
Die F2 nageslag vanaf hierdie kruisings is getoets vir Russiese koringluisweerstandbiedendheid
en C-bande is ook gedoen. Weerstand is gevind wat
geassosieer is met die 1RS chromosoomarm van 'Turkey 77'. Hierdie
oorspronklike werk is deur MARAIS (1991) gedoen en uit sy materiaal is 'n
monotelosomiese 1RS ('Turkey 77') addissieplant beskikbaar gestel vir die
huidige studie. Die F3 nageslag van hierdie monotelosomiese addissieplant
is gebruik om die weerstand teen die Russiese koringluis op chromosoom
1RS te bevestig. Die monotelosomiese addissieplant is ook gekruis met die
koringkultivar 'Gamtoos' wat die 1BL.1 RS-translokasie dra. Hoewel die 1RS
segment van 'Gamtoos' die roesweerstandsgene, Sr31 en Lr26 uitdruk, is dit
nie die geval met die 'Turkey 77' 1RS telosoom nie. Hierdie gene kon dus as
merkergene gebruik word. Vanuit die F1 is 'n monotelosomiese 1RS
addissieplant geselekteer wat ook heterosigoties was vir die 1BL.1 RStranslokasie.
Hierdie plant is getoetskruis met 'n luisvatbare gewone
broodkoring, 'Inia 66'. Meiotiese paring tussen die rogarms het daartoe gelei
dat vyf euplo"lede Russiese koringluis-weerstandbiedende nageslag uit 99
euplo"lede nageslag geselekteer kon word. Een rekombinant het ook Sr31
en Lr26 behou en is toegelaat om self te bestuif. Met behulp van SDSPAGE
profiele is Russiese koringluis-weerstandbiedende 1BL.1 RStranslokasie
homosigote ge"ldentifiseer en kon bevestig word dat die
weerstandsgeen vir die Russiese koringluis oorgedra is na die 1BL.1 RS
('Veery') -translokasie.
Twee strategies is gevolg om die Russiese koringluislokus of -loci te karteer:
(1) 'n Telosomiese analise is gedoen. 'n Plant met 2n = 40 + 1BL.1 RS +
1RS is verkry en met 'n luisvatbare koring bestuif. (2) 'n Gerekombineerde, disomiese plant met Russiese koringluis-weerstandbiedendheid maar sonder
die Lr26 en Sr31 allele is gekruis met 'Gamtoos' en die F1 getoetskruis. Die
toetskruisouer in beide die strategiee was 'Chinese Spring'. In die eerste
eksperiment is die Sr31-lokus 10.42 kaarteenhede vanaf die Lr26-lokus
gelokaliseer. Die raesdata het ge"impliseer dat onbetraubare genetiese
kaarteenhede geskat sou word en daarom is die omslagtige Russiese
koringluis weerstandsbepalings nie gedoen nie. In die tweede eksperiment
is die Russiese koringluis-weerstandsgeen op 14.5 kaarteenhede vanaf die
Lr26-lokus gelokaliseer. Nie-Mendeliese segregasie van die Russiese
koringluis-weerstand in hierdie karteringseksperiment het ge'impliseer dat die
berekende kaartafstand onakkuraat mag wees. Dit was ook nie moontlik om
op grand van die data die aantal gene betrakke af te lei nie.
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Ray, Melissa D. "CHARACTERIZATION OF TRANSFER OF THE MOBILE GENOMIC ISLAND ENCODING METHICILLIN RESISTANCE AMONG STAPHYLOCOCCI." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3946.
Full textAbstract:
The gene encoding methicillin resistance in Staphylococcus aureus (MRSA) is carried in the chromosome on a large genomic island called SCCmec and is always inserted at the att site within orfX. SCCmec has been designated a mobile genetic element but a mechanism by which it moves among different strains and species of staphylococci has never been demonstrated. This work shows that bacteriophage 80α is capable of transducing SCCmec into a recipient cell, after which it can integrate into the bacterial chromosome via homologous recombination. More importantly, this work characterizes a conjugative mechanism of SCCmec transfer. Results demonstrate the capture of a 30.8 kb SCCmec element on a conjugative plasmid for the first time, its transfer into both S. aureus and S. epidermidis recipients, and its excision from the plasmid with insertion in the orfX att site in recipients. The element was integrated into the plasmid by recombination between IS elements invariably present on all SCCmec types and pGO1/pSK41-like conjugative plasmids. These data explain the movement of SCCmec from reservoirs in commensal coagulase-negative staphylococci into different Staphylococcus aureus lineages using a ubiquitous conjugative plasmid that can transfer among staphylococci of different species and, thus, describes a mechanism for the environmental dissemination of methicillin resistance in nature.
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Gorgy, Evraam. "Experimental evaluation of heat transfer impacts of tube pitch on highly enhanced surface tube bundle." Diss., Kansas State University, 2011. http://hdl.handle.net/2097/11995.
Full textAbstract:
Doctor of Philosophy<br>Department of Mechanical and Nuclear Engineering<br>Steven J. Eckels<br>The current research presents the experimental investigation of the effect of tube pitch on enhanced tube bundles’ performance. The typical application of this research is flooded refrigerant evaporators. Boosting evaporator’s performance through optimizing tube spacing reduces cost and energy consumption. R-134a with the enhanced tube Turbo BII-HP and R-123 with Turbo BII-LP were used in this study. Three tube pitches were tested P/D 1.167, P/D 1.33, and P/D 1.5. Each tube bundle includes 20 tubes (19.05 mm outer diameter and 1 m long each) constructed in four passes. The test facility’s design allows controlling three variables, heat flux, mass flux, and inlet quality.
The type of analysis used is local to one location in the bundle. This was accomplished by measuring the water temperature drop in the four passes. The water-side pressure drop is included in the data analysis. A new method called the EBHT (Enthalpy Based Heat Transfer) was introduced, which uses the water-side pressure drop in performing the heat transfer analysis.
The input variables ranges are: 15-55 kg/m².s for mass flux, 5-60 kW/m² for heat flux, and 10-70% for inlet quality. The effect of local heat flux, local quality, and mass flux on the local heat transfer coefficient was investigated. The comparison between the bundle performance and single tube performance was included in the results of each tube bundle. The smallest tube pitch has the lowest performance in both refrigerants, with a significantly lower performance in the case of R-134a. However, the two bigger tube pitches have very similar performance at low heat flux. Moreover, the largest tube pitch performance approaches that of the single tube at medium and high heat fluxes.
For the R-123 study, the smallest tube bundle experienced quick decease in performance at high qualities, exhibiting tube enhancement dry-out at certain flow rates and high qualities. The flow pattern effect was demonstrated by the dry-out phenomena. At medium and high heat fluxes, as the tube pitch increases, the performance approaches that of the single tube. All tube bundles experience quick decrease in performance at high qualities. Evidently, P/D 1.33 is the optimum tube pitch for the studied refrigerants and enhanced tubes combinations.
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Kamali-Moghaddam, Masood. "Co-operative recombination mechanisms promoting gene clustering and lateral transfer of antibacterial drug resistance." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-4936-0/.
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Byrne-Bailey, Kathryne Greta. "Bacterial antibiotic resistance and horizontal gene transfer in slurries and slurry amended agricultural soils." Thesis, University of Warwick, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439746.
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To, Pui-chi Amanda, and 杜佩芝. "Molecular epidemiology of erythromycin resistance in Streptococcus bovis and lancefield group G beta-hemolytic streptococci andhorizontal gene transfer of antibiotic resistance genes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29387401.
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Vessabutr, Suyanee. "Transfer of chlorsulfuron resistance from tobacco to birdsfoot trefoil (Lotus corniculatus) by asymmetric somatic hybridization." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41010.
Full textAbstract:
A method was developed for rapid plant regeneration from protoplasts of birdsfoot trefoil (Lotus corniculatus cv. Leo) using in vitro cotyledons and a new enzyme formula. Protoplasts of a transgenic Nicotiana tabacum cv. Xanthi line KCR were isolated from leaves, in vitro shoots, and calli by an enzyme formula consisting of 0.5 % Cellulase R-10 and 0.05 % Pectolyase Y23 with either 0.4 M sucrose or 0.5 M mannitol as the osmoticum. Nine asymmetric fusion experiments were conducted between iodoacetate inactivated birdsfoot trefoil and irradiated transgenic tobacco protoplasts. The fusion products underwent several divisions but no visible colonies were obtained. Resistance analyses revealed the inactivation of the herbicide resistant gene in the transgenic tobacco calli. A putative chlorsulfuron resistant line has been obtained by in vitro selection from birdsfoot trefoil cotyledonous protoplasts. Their regenerants had normal ploidy, and expressed improved tolerance when sprayed with chlorsulfuron at the rate of 30 g/ha.
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Robinson, Esther Rhiannon. "Conjugative transfer and phylogeny of an antibiotic resistant haemophilus element, ICEHin1056." Thesis, University of Oxford, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.572683.
Full textAbstract:
Antibiotic resistance in bacteria is a growing threat to global health. Many of the genes responsible for resistance are carried on mobile genetic elements which can be transferred laterally between strains and species. The most important of these are conjugative and mobilisable elements including plasmids and integrating and conjugating elements, ICEs. Haemophi/us influenzae is an important human pathogen, which was first identified as carrying antibiotic resistance genes in the 1970s. Much of this resistance is encoded by ICEHin1056, which is present in H. influenzae strains worldwide. The aims of this study were to describe features of the biology of ICEHin1056, with particular reference to the genetic site and control mechanisms responsible for instigating conjugative transfer. The origin of transfer has been localised to a sequence on ICEHin1056 and an environmental stressor initiating conjugative transfer, oxidative stress, has been identified. In addition, detailed phylogenetic analysis has demonstrated ICEHin1056 to be part of a much larger family of mobile genetic elements, widely distributed in proteobacteria and carrying accessory genes responsible for survival in adverse environments, virulence and antibiotic resistance. The ICEs in the family have conserved homology of gene content and synteny of gene arrangement over deep evolutionary time, challenging the accepted paradigm of modular mosaicism of mobile genetic elements. A key event in increasing dissemination of the ICE, acquisition of a phage type integrase gene has also been identified. The findings presented provide significant insight into the behaviour of ICEs and may in future allow predictions about the spread of virulence factors and antibiotic resistance genes, with important implications for human and animal health.
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Woloszczuk, Kyra. "pCF10 MEDIATES INTERSPECIES DISSEMINATION OF ANTIBIOTIC RESISTANCE DETERMINANTS IN MIXED SPECIES BIOFILMS." Master's thesis, Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/390993.
Full textAbstract:
Biomedical Sciences<br>M.S.<br>Enterococcus faecalis is a commensal bacterium, which upon acquisition of virulence factors on mobile genetic elements can cause sepsis, urinary tract infections and endocarditis. E. faecalis isolates can be multi-drug resistant and have been implicated in the dissemination of antibiotic resistance genes to other genera. Although the host range of pheromone inducible conjugative plasmids is restricted to Enterococci, they often carry transposons, which are capable of transposing into the chromosome of other genera. The plasmid pCF10 contains the antibiotic resistance gene tetM on a conjugative transposon Tn925. Tn925 is a Tn916-like plasmid and is capable of pCF10-independent conjugative transfer to multiple bacterial species at low levels. Biofilms are communities of bacteria growing within a matrix. In biofilms, bacteria are more difficult to kill because of their lower susceptibility to antibiotics. In hospital settings, biofilms can grow on medically implanted devices, catheters or even human tissue. In mixed species biofilms, antibiotic resistances are able to be transferred through horizontal gene transfer from E. faecalis to other bacterial species. In mixed species biofilms, it has been show that Tn925 can transpose into S. aureus at rates of 10-8 by Ella Massie Schuh. Using static mixed species biofilms, the transfer of tetM from E. faecalis to S. aureus was studied, hoping to better understand the underlying mechanisms. The goal of these studies was to determine if residence on pCF10 increased the transfer frequency of Tn925 in mixed species biofilms. Mixed species biofilms containing E. faecalis (pCF10) and S. aureus (pALC2073aPSM) were established and pCF10 conjugation was induced with pheromone cCF10. Transfer of Tn925::tetM to S. aureus was detected at a rate of approx. 10-8. No transfer was detected when Tn925 was present in the E. faecalis chromosome (lower limit of approx. 10-10). The increased transfer frequency was dependent on induction with cCF10. These results suggest that pCF10 can disseminate Tn925::tetM to S. aureus and the presence of the conjugative transposon on the plasmid increases its transfer rate. Previous observations in the laboratory show that in some circumstances, E. faecalis would be erythromycin resistant. To understand how this resistance was occurring, we investigated whether retrotransfer was occurring in mixed species biofilms. Retrotransfer is the transfer of genes from the recipient cell, back into the donor cell. For this experimental design, mixed species biofilms were forms erythromycin resistant E. faecalis transconjugants were selected for. While we successfully selected erythromycin resistant E. faecalis, upon gene sequencing it was shown that retrotransfer of the ermC gene was not occurring. Instead, these erythromycin resistant E. faecalis were spontaneous mutants. While transfer was not detected, this model leads to the hypothesis that induction of conjugation may increase the rates of spontaneous mutations of E. faecalis in biofilms.<br>Temple University--Theses
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Arsenyeva, O. P. "The hydraulic resistance in the small-scale pillow-plate heat exchangers." Thesis, Національний університет "Львівська політехніка", 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/48523.
Full textAbstract:
The Pillow-Plate Heat Exchangers (PPHEs) are rated as innovative type of heat transfer equipment. The present paper gives the information about the research made in Paderborn University aimed to investigate the heat transfer and pressure drop in the channels of the small-scale PPHE.
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Alvarez-Narvaez, Sonsiray. "Conjugal transfer of host-adaptive determinants in the pathogenic actinobacterium Rhodococcus equi." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/31487.
Full textAbstract:
The soil-dwelling gram-positive coccobacillus Rhodococcus equi is a well-known veterinary pathogen and emerging human pathogen. Although Rhodococcus infection is primarily associated with pyogranulomatous pneumonia in foals, these bacteria can also infect other animal species including humans. R. equi pathogenicity is mediated by the conjugative virulence plasmid (pVAP) which promotes intracellular proliferation in host macrophages. Currently R. equi is endemic in horse breeding farms worldwide. No R. equi vaccine is available and both treatment and prophylaxis rely on the administration of a prolonged course with a combination of macrolide antibiotics (typically erythromycin) and rifampicin. These antimicrobials were introduced in the therapy against R. equi in the 1980s and multiresistance has now emerged among foal isolates, increasing the risk of zoonotic transmission. In this thesis, the role of conjugal extrachromosomal replicons in the host adaptation of R. equi was explored. A previous epidemiological study indicated that different variants of the pVAP virulence plasmid are associated with different animal hosts. This PhD project provides experimental confirmation of a R. equi plasmid-driven host tropism. In vivo and in vitro competition assays were performed using a set of isogenic strains only different in the virulence plasmid type, in adapted (horse) and non-adapted (mouse) model species. The data obtained in the horse model provides clear evidence of a significant negative selection of the non-equine virulence plasmids both at a cell and at the animal level, while no selection was observed in the non-adapted mouse model. Furthermore, this project characterized the determinant responsible for macrolide resistance in R. equi, a novel erm methylase gene, erm(46). The erm(46) determinant was shown to be transferable between strains by conjugation and herein the underlying mechanism and how erm(46) becomes stabilized in R. equi is described. PacBio SMRT-sequencing based analysis revealed that the erm(46) gene is carried in a self-replicating conjugative plasmid of about 80 kb, that we designated pRErm46. The conjugation machinery of pRErm46 was hypothesized to be responsible for bringing the erm(46) determinant into R. equi. However, some erythromycin resistant isolates lack pRErm46 but erm(46) transfer is still observed. This reflects the observation that erm(46) is present in a mobile element that, upon acquisition with the pRErm46 replicon, transposes at a high frequency and to multiple locations of the host genome. If the erm(46) mobile element transposes to the chromosome, no further transfer of the resistance is observed at a detectable frequency in the absence of pRErm46. On the other hand, if the erm(46) element transposes to the R. equi virulence plasmid, the erm(46) determinant co-opts the pVAPA conjugal transfer machinery and gets transferred at the same high frequency as the virulence plasmid (10-2). This constitutes a unique example of efficient co-transfer, in the same genetic vehicle, of virulence and antimicrobial determinants, two key niche-adaptive traits required for within-host survival of bacterial pathogen.
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Tasker, Jacqueline Ruth. "The investigation of a novel proteinase inhibitor as a means to transfer insect resistance to plants." Master's thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/21413.
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Bibliography: pages 124-148.<br>A viable IPM programme involves a clear understanding of and the use of a number of components, the most important being the bionomics of insect pests; monitoring systems to establish the prevalence and seasonal occurrence of insect pests; calculation of economic thresholds; the biology of parasites and predators; utilisation of insect resistant plant varieties; and methods to maximise the advantages of pesticides and minimise their disadvantages. Insect-resistant crop varieties form an important part of IPM. There is usually no extra cost to the farmer once the resistant variety has been obtained and it is easily available to him thereafter. In the context of an IPM strategy, plant resistance should improve the impact on a pest population when both biological and chemical control methods are used.
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Jahan, Musarrat. "Virulence characteristics of enterococci from cured meat and potential for inter-genetic transfer of antibiotic resistance determinants." Elsevier Limited, 2015. http://hdl.handle.net/1993/30656.
Full textAbstract:
The genus Enterococcus has an exceptional ability to acquire and transmit antibiotic resistance genes and is considered to be a major vector in their dissemination. Enterococci are part of the normal gut microbiota of humans and animals and are frequently encountered in food products including dry fermented sausage. Since fermented sausages are not heat-treated before consumption they might be a vehicle for transmitting resistance and virulence traits of enterococci by conjugation with commensal bacteria present in the human gut and pathogenic bacteria that might be present, such as Listeria species. A PCR-based assay was developed to detect enterococci in dry fermented sausage meat at the generic level by targeting a 16S rRNA sequence and a total of 29 Enterococccus strains (15 E. faecalis, 13 E. faecium, and one E. gallinarum) were identified. The susceptibility of these enterococci to antibiotics was tested and it was found that 27/29 were resistant to more than one antibiotic and possessed antibiotic resistance determinants. All strains were positive for at least one virulence gene. Strong biofilm formation occurred at lower than optimum temperature in all three species of enterococci and probably contributed to their survival in the harsh conditions experienced during dry sausage fermentation and drying. SmaI pulsed-field gel electrophoresis (PFGE) patterns exhibited genomic heterogeneity within and between the two larger groups of isolates. In spite of this heterogeneity, the phenotypic similarities observed suggested that food could still be a vehicle for distribution of antibiotic resistant bacteria among humans. In vitro conjugation experiments demonstrated transfer of the tetracycline resistant determinant, tet(M), from E. faecium S27 isolated from fermented sausage to clinical isolates of both E. faecium and E. faecalis. The streptomycin resistance of E. faecium S27 was also transferred to a clinical strain, E. faecalis 82916, which was confirmed by the presence of the streptomycin resistance gene, aadA, in the donor and transconjugant strains. E. faecium S27 also transferred tet(M) and streptomycin resistance to Listeria monocytogenes GLM-2 by in vitro mating. Evidence suggests that enterococci in fermented meats may contribute to the spread of resistance determinants.<br>October 2015
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Chandrasekhar, Nambiar Shyam. "Design of a Wireless Power Transfer System using Electrically Coupled Loop Antennas." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/54003.
Full textAbstract:
Wireless Power Transfer (WPT) has become quite popular over the recent years. This thesis
presents some design challenges while developing a WPT system and describes a system-level methodology for designing an end-to-end system. A critical analysis of contemporary research is performed in the form of a literature survey of both academic and commercial research to understand their benefits and demerits. Some theoretical notes are presented on coupled-mode theory and coupled filter theory and the problems concerning WPT analyzed using these models. The need for higher power transfer efficiency (PTE) and power delivered to load (PDL) is studied using these models. The case for using magnetic antennas over electric antennas when surrounded by lossy media (specifically for the case of human body tissues at various frequencies) is made using some theoretical models and simulation results. An Electrically Coupled Loop Antenna (ECLA) is introduced, studied and designed for two main WPT applications, viz. free space transmission and that of powering implanted devices. An equivalent circuit is proposed to better understand the coupling effects of the antennas on a circuit level and to study the effect of various environmental and structural factors on the coupling coefficient. Some prototypes were created and measured for the two use cases of free space and implanted applications. In order to complete the system design, a negative resistance-based oscillator is designed and fabricated, that incorporates the antennas as a load and oscillates at the required frequency. Some changes in load conditions and power handling are studied by the use of two circuits for free-space (high-power) and implanted (low-power) applications. Finally, the salient points of the thesis are re-iterated and some future work outlined in the concluding chapter.<br>Master of Science
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Kim, Joo-Sung. "NATURAL TRANSFORMATION-MEDIATED TRANSFER OF ERYTHROMYCIN RESISTANCE IN Campylobacter coli AND Campylobacter jejuni." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-10272005-170447/unrestricted/etd.pdf.
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Numan, Zuhair. "The stability and transfer of antibiotic resistance plasmids in Escherichia coli in homogeneous and heterogeneous culture systems." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329689.
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Inzoli, Isabella, Jean Marc Simon, and Signe Kjelstrup. "Surface resistance to heat and mass transfer in a silicalite membrane: a non-equilibrium molecular dynamics study." Diffusion fundamentals 6 (2007) 22, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14196.
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Bowers, DeJuana Sue. "The effect of flexibility and resistance exercise on selected balance tasks and gait transfer in elderly subjects." Thesis, This resource online, 1997. http://scholar.lib.vt.edu/theses/available/etd-08222008-063017/.
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Ehsanpour, Ali Akbar. "Cell biological manipulations for transfer of the Mi root-knot nematode resistance gene from tomato to potato." Thesis, Ehsanpour, Ali Akbar (1995) Cell biological manipulations for transfer of the Mi root-knot nematode resistance gene from tomato to potato. PhD thesis, Murdoch University, 1995. https://researchrepository.murdoch.edu.au/id/eprint/41580/.
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Improvement of potato (Solanum tuberosum), an important crop for food consumption and biomass has until recently been confined to conventional breeding approaches. Root-knot nematodes (Meloidogyne spp) are serious pests of crop and horticultural plants, including potato, in tropical and sub-tropical regions of the world. The Mi resistance gene derived from Lycopersicon peruvianum has been introduced into cultivated tomato. This gene confers resistance to three major species of root-knot nematodes. Tomato lines containing the Mi gene have been obtained and were tested for functional resistance to root-knot nematodes by infection with nematode juveniles in glasshouse tests. The presence of the Mi gene in resistant tomato lines was also confirmed using two biochemical methods: (1) by staining of specific bands on polyacrylamide gels (PAGE) for an acid phosphatase-I I enzyme linked to the Mi gene, and (2) the presence of an amplified DNA fragment of 570 hp using specific PCR primers (REX-Fl and REX-F2) which amplify a DNA sequence closely linked to the Mi gene. For tissue culture experiments, potato and tomato shoot cultures were established, and larger potato leaves were induced by treatment with silver thiosulfate (STS) to inhibit ethylene production. Potato and tomato protoplasts were isolated from these shoots and a protoplast-to-plant regeneration system for potato cv. Delaware was established. Conditions required to induce electrofusion between potato and tomato protoplasts were optimised. However, the Mi resistant tomato genotypes were not responsive in culture, and hybrid plants were not generated. As a result, procedures for direct gene transfer of the Mi gene were studied. Optimum conditions for direct gene transfer ( electroporation) of potato cv. Delaware were established and calli were obtained from Delaware protoplasts after electroporation with tomato DNA (line BTN815). These were analysed by PCR. To improve the frequency of transformants that might contain Mi DNA, DNA enriched with low copy repetitive sequences was obtained by passage through a hydroxyapatite column. This work forms the basis for further experiments to transfer DNA fragments, which include the Mi gene, into potato by direct gene transfer. In further cell biological studies, transgenic plants containing a Parasponia promoter-glucuronidase insert were analysed for expression of the reporter gene when infected with root-knot nematodes. The reporter gene was down-regulated in early stages of giant cell development, but strongly up-regulated in mature giant cells.
The results of the research were discussed in relation to various options available to introduce resistance to root-knot nematodes into potato, using cell biological transfer or genetic engineering of natural or synthetic resistance genes.
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Akande, Sodiq. "Investigating different modeling techniques for quantifying heat transfer through building envelopes." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/asrf/2018/schedule/58.
Full textAbstract:
There is interest concerning the energy performance of buildings in the United States. Buildings, whether residential, commercial or institutional, generally underperform in terms of energy efficiency when compared to buildings that are constructed following sustainably and energy efficiency standards. A substantial percentage of energy loss in these buildings is associated with the thermal efficiency of its envelope (exterior walls, windows roof, floors and doors). The objective of this study will evaluate the results of three energy modeling techniques developed to investigate the energy transfer through the envelope of existing campus buildings. The techniques employed are solving the heat transfer calculations using spreadsheets, using a stand-alone modeling software (OpenStudio) and using an integrated building energy modeling software (eQuest) employed in Autodesk Revit. The first technique is somewhat different from the other two because it does not require a 3D representation of the building to be generated as the first step in the modeling process. It is the application of a mathematical methodology employing heat transfer algorithms entered into the spreadsheet’s cells to estimate the heat transfer through the building envelope. Data needed for this technique are weather data of the buildings location, surface area of the building envelope, and the overall heat transfer coefficient (U-value) of each component of the building envelope. The OpenStudio technique involves a 3D representation of the building. The building is drawn on a 3D modeling computer program called SketchupPro, which communicates directly to the OpenStudio energy modelling interface. The building operations as well as the building characteristics, such as the composition and type of the elements that made up the building envelop, the thermal zone, occupancy schedule and the space type was inputted in the OpenStudio engine. The OpenStudio engine runs the simulation and generates a detail result about the energy usage and energy transfer in the building. The third method that employs AutoCAD Revit software is a standalone technique that does not require an external software for sketching the building model. Revit the ability to draw the model as well as perform the energy analysis at the same time with the aid of inbuilt eQuest modeling engine. The model in Revit is generated with the right building envelope characteristics as the existing building and the weather file. The process is somewhat similar to the OpenStudio technique; the main difference is the level of detail and limitation provided by both the energy modeling engine (eQuest and EnergyPlus). At the end of the simulation, the building energy modeling using Autodesk Revit presents a detailed result of the energy usage and energy flow in the building. The underlying reason of the comparison of three techniques is to understand the simplest, most efficient, accurate method to quantify heat transfer through the building envelope. By the end of this study, the most efficient technique for investigating the building envelope will be expected to be the EnergyPlus technique because of the usage simplicity, ability to take in a lot of details required for simulation and the periodical software updates.
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Ma, Fuhao. "Progressive Collapse Resistance of RC Flat Plate Substructures under Single- and Double-Column Removal Scenarios." Thesis, Griffith University, 2020. http://hdl.handle.net/10072/392383.
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Progressive collapse is defined as the spread of an initial local failure of a critical load bearing structural element to the remaining structure, ultimately leading to the collapse of the entire building or of a large portion of it. After the partial collapse of the Ronan Point apartment tower in 1968, when a localised gas explosion ultimately led to the collapse of the whole corner of the building, progressive collapse firstly drew public attention due to its catastrophic consequences on human casualties and economic losses. Other recent collapse events, such as those of the Murrah Federal Building in 1995, Sampoong department store in 1995 and World Trade Centre towers in 2001, have further highlighted the importance of this topic and made engineering communities aware of the necessity to prevent the occurrence of progressive collapse in building structures. In the past decades, considerable research has been devoted to investigate progressive collapse of building structures. These research typically followed an alternate load path approach. This approach allows an initial failure to occur, while the remaining structure needs to seek alternate load paths to dissipate damage and prevent progressive collapse.
In practice, the progressive collapse resistance of building structures is generally evaluated by notionally removing one or more load bearing structural elements, representing the initial failure. Despite all research efforts made, they have predominately focused on frame systems. Relevant investigations on reinforced concrete (RC) flat plate structures, a commonly used structural system, are still scarce. The flat plate system contains slabs, of uniform thickness, directly supported by columns without using beams, drop panels and column capitals. This provides structures with increased storey height, architectural convenience and significant savings in construction costs. Nevertheless, the slab-column connection is prone to punching shear failure, which may propagate to the vicinity of connections, potentially leading to progressive collapse. The present study aims at filling some of the current knowledge gap with comprehensive experimental, analytical and numerical investigations on RC flat plate structures.
The experimental program consists of four quasi-static large-deformation tests performed on three 1/3-scale, 2×2-bay RC flat plate substructures subjected to critical column removal scenarios. The test specimens included one specimen tested under two consecutive corner column removal scenarios, one specimen under an edge column removal and one specimen under the scenario of concurrently removing both an edge and an interior column. For the loading scheme, a multi-point loading system was specially designed to simulate an increasing uniformly distributed load (UDL). The loading points of this system were equally positioned on the bays adjacent to the removed column(s) to apply the load until failure of the slab. Throughout each test, the structural behaviour of the slab was monitored by extensive apparatuses mounted to the slab both internally and externally. Failure and post-failure behaviours, failure modes, and collapse resisting mechanisms were observed and analysed. Additionally, a complement of analytical studies to the experimental tests, based on the observed yield lines, was carried out to estimate the flexural capacity of the test specimens.
To numerically investigate the progressive collapse behaviour of RC flat plate structures, a set of 3D nonlinear finite element modelling approaches, using LS-DYNA software, was established. A total of five numerical models were explicitly created based on the four experimental tests in present research and one from the literature. The proposed modelling approach was basically composed of appropriate definitions of element types, bond-slip relationships, loadings and boundary conditions, and more importantly development of the material models for concrete and reinforcements and calibration of failure criteria for element erosion. A quasi-static loading scheme in displacement control in the numerical models was adopted, the same as that in the conducted tests, through explicitly modelling the multi-point loading system in order to replicate the true test conditions. The numerical models were respectively validated by comparing the load displacement responses, failure modes, crack patterns, and displacement and strain results against the experimental ones, which confirmed the appropriateness and reliability of the proposed models. The validated modelling techniques could be applied to further perform parametric studies of the progressive collapse resistance of RC flat plate substructures and prototype structures.
In summary, the significant and original contribution of this research is to (1) obtain a solid understanding of the collapse behaviour of RC flat plate structures under critical column removal scenarios, (2) examine the analytical solution using the yield line theory to predict the flexural capacity of RC flat plate structures, (3) establish a set of numerical modelling techniques which can reasonably replicate the experimental process and provide valuable references of numerically analysing progressive collapse of RC flat plate structures, and (4) give design insights into Australian and international Standards in mitigating progressive collapse of RC flat plate structures.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Eng & Built Env<br>Science, Environment, Engineering and Technology<br>Full Text
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Zetterström, Sebastian. "Evaluation of a suction pyrometer : By heat and mass transfer methods." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-36450.
Full textAbstract:
Sebastian Zetterström, Master of Science in energy systems, Mälardalens University in Västerås. Abstract of Master’s thesis, submitted 16th of August. Evaluation of a suction pyrometer by heat and mass transfer methods. The aim of the thesis is to evaluate the cooling of a specific suction pyrometer which is designed by Jan Skvaril, doctorate at Mälardalens University. First part is explained how the balances and correlations are performed before being implemented in MATLAB, after this a ANSYS Fluent model is constructed and explained, which is used for the comparison of results. The cooling is performed by using water at an inlet temperature of 10°C and an assumed flue gas temperature of 810°C. Sensitivity analysis are performed to test the stability of the models which yield good results for stability, done by adjusting both flue gas temperature and inlet cooling water temperature which are as well presented for observation. From doing further MATLAB sensitivity analysis which show that the model still performs well and is stable. The resulting cooling water is heated to approximately 24, 8°C and the flue gas is cooled to 22, 4°C, in ANSYS Fluent the answer differs approximately 2°C and results in 20, 4°C which can be considered by looking at the flue gas inlet temperature of 810°C that this can be deemed an insignificant change and can therefore conclude that the comparison between the two platforms match each other good and that calculations can be considered accurate. Keywords: Suction pyrometer, cooling, heat transfer, thermal resistance network, MATLAB, ANSYS Fluent, simulation
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Cheng, Wui-wai Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Enhancing the heat transfer performance of compact heat exchangers by minimizing the contact resistance between fins and tubes." Awarded by:University of New South Wales. School of Mechanical and Manufacturing Engineering, 2006. http://handle.unsw.edu.au/1959.4/24952.
Full textAbstract:
Thermal contact resistance or, its reciprocal, thermal contact conductance is an important parameter in a wide range of thermal phenomena. It plays a significant role in heat transfer applications such as electronic packaging and nuclear reactors. This parameter also appears in fin-tube heat exchangers; however, it is often neglected in the performance calculations of heat exchangers. This thesis project explores the means by which the heat transfer performance of a finned tube heat exchanger may be enhanced. It includes experimental studies and finite element analysis investigating the effects of expansion bullets and coatings on the thermal contact conductance. An apparatus has been designed and fabricated for the experimental part of the work. A finite element model established the fintube configuration to be used in the design and manufacture of the apparatus. The apparatus was specially made for measuring thermal contact conductance directly in a finned-tube heat exchanger both in vacuum and in gaseous environment. The experiments were done on hexagon shaped specimens with a single fin connecting seven tubes. Sixteen type-T thermocouples have been used to measure temperatures at several locations on the specimen. A full-scale quarter-fin model was chosen for a second finite element analysis. The model simulates the actual specimen and predicts the temperatures. The finite element analyses have been used to validate the experimental results. The experimental results from the bare contact specimens, assembled with different sizes of expansion bullet, show that while higher expansions enhance the thermal contact conductance, the effect of interstitial gas such as nitrogen is beneficial for all specimens expanded with the 9.42 mm size bullet. Applying a coating material with high thermal conductivity is also an effective way to enhance the thermal contact conductance. The results show that the highly conductive plating materials, such as zinc, tin, silver and gold, enhance the thermal contact conductance. The presence of interstitial gas such as nitrogen also results in higher heat transfer rates and higher thermal contact conductance compared to those obtained in vacuum.
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Melville, Claire Margaret. "Molecular analysis of novel tetracycline resistance genes and the elements involved in their transfer between diverse gut bacteria." Thesis, University of Aberdeen, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367364.
Full textAbstract:
A previously undescribed tetracycline resistance gene, <I>tet</I>(W), was isolated by our group from the rumen anaerobe <I>Butyrivibrio fibrisolvens. tet</I>(W) is less than 65% homologous to <I>tet</I>(M) and in the <I>B. fibrisolvens </I>strain 1.230, is carried on a 50 kb mobile chromosomal element, Tn<I>B1230</I>, which is unrelated to known conjugative transposons. This thesis has identified a gene >99% homologous to <I>tet</I>(W) from two groups of human faecal bacteria, a low % G+C Gram Positive human colonic bacteria, Strain K10 and <I>Bifidobacterium longum</I>. In each isolate <I>tet</I>(W) was identified by Southern blot on differently sized chromosomal fragments which are unrelated to Tn<I>B1230</I>. Sequence analysis of 13 kb of Tn<I>B1230</I> from a cosmoid library clone identified several open reading frames with identity to transfer functions encoded by conjugative elements from important human pathogens. The DNA% G+C of <I>tet</I>(W) is considerably higher than the flanking <I>orf's</I> in Tn<I>B1230</I> and also the <I>Butyrivibrio</I> host itself, suggesting that it may have originated in a higher % G+C bacterium. The tetracycline resistance (Tc<sup>R</sup>) was transmissible from Strain K10 to the rumen anaerobe <I>B. fibrisolvens</I> 2221<I>R</I> by filter mating, however <I>tet</I>(W) was not detected in the transconjugants by PCR with the <I>tet</I>(W) specific primers. Instead a second novel Tc<sup>R</sup> gene designated <I>tet</I>(32) was shown to be responsible for transmissible resistance in K10. This novel ribosome protection gene has also been sequenced and characterised and is most related to <I>tet</I>(O), expresses a higher level of Tc<sup>R</sup> than other ribosome protection proteins and is abundant in the ovine rumen, human and porcine gut.
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Lubbers, Brian Vincent. "The impact of oxytetracycline dosing on bacterial populations and transfer of resistance elements in vitro and in vivo." Diss., Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/2284.
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Arosemena, Arturo. "Numerical Model of MeltingProblems." Thesis, KTH, Mekanik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-221141.
Full textAbstract:
In the present study, a finite volume method is employed to modelthe advection-diffusion phenomenon during a pure substance meltingprocess. The exercise is limited to a benchmark problem consisting ofthe 2D melting from a vertical wall of a PCM driven by natural convectionin the melt. Numerical results, mainly the temporal evolutionof average Nusselt number at the hot wall and the average liquid fraction,are validated by available literature data and the effect of thermalinertia in the heat transfer is considered as well. Finally, motivatedby recent publications and the model presented here, possible new researchtopics are proposed.
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Lantto, Jonas. "Analytical model of mass transfer through supported liquid membranes." Thesis, KTH, Skolan för kemivetenskap (CHE), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176912.
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This report details the development and validation of a model for the simulation of supported liquid membrane processes, as applied to the extraction of lanthanides. Supported liquid membranes are systems where two phases, usually aqueous, are separated by a third phase, typically organic, which acts as a membrane, in order to separate solutes from one phase to the other. The model employs an analytical solution to the diffusion equation for the organic phase and linear approximations of the resistances to mass transfer in the aqueous phase boundary layers. The goal of this model is to underline the importance of taking these boundary layer resistances into account.<br>Detta arbete introducerar, deriverar och evaluerar en matematisk modell för simulering av vätskemembranprocesser, tillämpat på vätskeextraktion av lantanider. Immobiliserade vätskemembran betecknar system där två faser oftast vatten, separeras av en tredje organisk fas som agerar membran för att separera och transportera lösta komponenter från den ena vattenfasen till den andra. Modellen utnyttjar sig av en analytisk lösning till diffusionsekvationen för den organiska fasen och linjära approximationer för motstånden mot masstransport i de båda vattenfasernas gränsskikt. Målet med modellen är att understryka vikten av att inkludera dessa gränsskikt i beräkningarna.
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Babenko, Maksims. "A Study of Heat Transfer at the Cavity-Polymer Interface in Microinjection Moulding. The effects of processing conditions, cavity surface roughness and polymer physical properties on the heat transfer coefficient." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14745.
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This thesis investigates the cooling behaviour of polymers during the microinjection moulding process. The work included bespoke experimental mould design and manufacturing, material characterisation, infra-red temperature measurements, cooling analysis and cooling prediction using commercial simulation software. To measure surface temperature of the polymers, compounding of polypropylene and polystyrene with carbon black masterbatch was performed to make materials opaque for the IR camera. The effects of addition of carbon black masterbatch were analysed using differential scanning calorimetry and Fourier transform infrared spectroscopy. Sapphire windows formed part of the mould wall and allowed thermal measurements using an IR camera. They were laser machined on their inside surfaces to generate a range of finishes and structures. Their topographies were analysed using laser confocal microscope. The surface energy of sapphire windows was measured and compared to typical mould steel, employing a contact angle measurement technique and calculated using Owens-Wendt theory. A heating chamber was designed and manufactured to study spreading of polymer melts on sapphire and steel substrates. A design of experiments approach was taken to investigate the influence of surface finish and the main processing parameters on polymer cooling during microinjection moulding. Cooling curves were obtained over an area of 1.92 by 1.92 mm of the sapphire window. These experiments were conducted on the Battenfeld Microsystem 50 microinjection moulding machine. A simulation study of polymer cooling during the microinjection moulding process was performed using Moldflow software. Particular interest was paid to the effect of the values of the interfacial heat transfer coefficient (HTC) on the simulated cooling predictions. Predicted temperature curves were compared to experimentally obtained temperature distributions, to obtain HTC values valid for the material and processing parameters.
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Bancarzewski, Maciej Albert. "Japanese foreign direct investment : varieties of capitalism, employment practices and worker resistance in Poland." Thesis, University of Hertfordshire, 2015. http://hdl.handle.net/2299/17112.
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This research contributes to an understanding of Japanese Foreign Investment (JFDI) in Poland, by using a Variety of Capitalism approach and drawing on literature from employment relations. It examines firstly, the extent to which Japanese production and managerial institutions and practices can be transplanted to different economic and cultural environments; and secondly, the character of workers' response towards these practices, in the context of JFDI in Poland. It draws on primary data drawn from interviews conducted with the managers and workers in five firms in a Japanese electronics manufacturing cluster in Toruń, Northern Poland, as well as the policy makers, researchers and journalists on a regional level. First, the transfer of Japanese management 'style' is considered in terms of recruitment, training practices, issues of monitoring and discipline and quality assurance policies. This study reveals that the transfer of Japanese typical practices is of minor importance to Japanese corporations based in Poland, and the character of these practices in the Polish workplace is peripheral. However, the subordination of labour is brought by the precarisation of employment, rather than the implementation of Japanese quality policies. Second, the focus of the research is on the response of workers and finds that they did not remain passive actors in this process and resisted the adapted form of Japanisation in Poland. Although the role of formal trade unions was limited, the data pointed to other forms of resistance, both conventional and novel, from sabotage, absenteeism, humour to insubordination and the use of blogging sites. In the context of the researched labour process, the empirical findings point to markers of collectivism in all forms of worker resistance and hence identified that the collective worker not only has not disappeared from both the labour process debate and the workplace itself, but, even if not evidently, is present through the resistance to management practices and control.