To see the other types of publications on this topic, follow the link: Plasmid production.
Dissertations / Theses on the topic 'Plasmid production'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Plasmid production.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
O'Mahony, Kevin. "Large scale plasmid production /." [S.l.] : [s.n.], 2005. http://library.epfl.ch/theses/?nr=3320.
Full text
2
Yap, Wee Ching Melvyn. "Analysis of retroviral production in murine leukaemia virus." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325497.
Full text
3
Bower, Diana M. (Diana Morgan). "Development of new tools for the production of plasmid DNA biopharmaceuticals." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76475.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 96-104).
DNA vaccines and gene therapies that use plasmid DNA (pDNA) as a vector have gained attention in recent years for their good safety profile, ease of manufacturing, and potential to treat a host of diseases. With this interest comes increased demand for high-yield manufacturing processes. Overall, this thesis aims to develop new, innovative tools for the production of plasmid DNA biopharmaceuticals. As one part of this thesis, we designed a 1-mL fed-batch microbioreactor with online monitoring and control of dissolved oxygen, pH, and temperature, as well as continuous monitoring of cell density. We used the microbioreactors to scale down temperature-induced production of a pUC-based DNA vaccine vector, pVAX1-GFP. Scaled-down processes can facilitate high-thoughtput, low-cost bioprocess development. We found that the microbioreactors accurately reproduced the behavior of a bench-scale bioreactor as long as key process parameters, such as dissolved oxygen, were held constant across scales. The monitoring capabilities of the microbioreactors also provided enhanced process insight and helped identify conditions that favored plasmid amplification. A second aspect of this thesis involved construction and characterization of a new DNA vaccine vector based on a runaway replication mutant of the R1 replicon. Runaway replication plasmids typically show increased amplification after a temperature upshift. However, we found that our new vector, pDMB02-GFP, gave higher yields during constant temperature culture at 30"C, reaching a maximum of 19 mg pDNA/g DCW in shake flasks. We gained mechanistic insight into this behavior by measuring RNA and protein expression levels of RepA, a plasmid-encoded protein required for initiation of replication at the R1 origin. Through these studies we found that RepA levels may limit plasmid amplification at 42*C, and relieved this limitation by increasing RepA translation efficiency via a start codon mutation. We also scaled up production of pDMB02-GFP at 300C from 50-mL shake flasks to 2-L bioreactors. Initial scale up efforts resulted in increased growth rate compared to the shake flasks, accompanied by very low plasmid yields. Decreasing the growth rate by limiting dissolved oxygen increased plasmid specific yield and emerged as a viable strategy for maintaining productivity during scale up.
by Diana M. Bower.
Ph.D.
4
Hales, Barbara A. "Plasmid determined fimbrial production responsible for bacterial colonization of the urinary tract." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/23962.
Full text
5
Cheng, Chinyuan. "Engineering strategies to optimize plasmid stability and protein production in recombinant Saccharomyces cerevisiae fermentation /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487779914824623.
Full text
6
Chamsart, Saedthawat. "A cell lysis reactor for the production of plasmid DNA from recombinant E.coli for gene therapy." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366017.
Full text
7
Pensri, Charoensit. "Development of inhibition methods for pro-inflammatory cytokine production induced by cationic carrier/plasmid DNA complex." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/126605.
Full text
8
Robinson, Susan Clare. "Enhanced production of a recombinant, thermostable alpha-amylase in Streptomyces lividans : effects of plasmid construction and culture conditions." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393582.
Full text
9
García, Mark Megan Olga. "Production and validation of anti-HCV antibodies for viral neutralization." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278578.
Full textAbstract:
Hepatitis-C Virus (HCV) remains the leading cause of liver transplant in the US and the UK, and the World Health Organization (WHO) estimates that 71 million people are infected worldwide. A vaccine would drastically impact the healthcare-associated burdens that HCV causes globally. The objective of this master’s thesis project is to produce human antibody (IgG) against HCV. This project will focus on the monoclonal antibodies (mAbs) HEPC3, AR3C, HEPC74, and HCV1. These four antibodies have been isolated from patients who have successfully cleared the infection, and their sequences and structures are available in the public domain. These four antibodies have also shown to bind to E2, a glycoprotein on the surface HCV that is crucial for viral binding and entry. This interaction of the mABs with E2 has been implicated in viral neutralization, making them promising choices for this study. Overall, 3 out of 4 mAbs were successfully cloned and produced. The unsuccessful antibody, HEPC74, was discovered to have failed due to an error in the plasmid sequence. Just as the western blot to confirm secretion was ready to be run, the laboratory closed due the Covid-19 outbreak. Therefore, the data can officially declare a ¾ mAb production success, however it is safe to assume that the alternative clone for HEPC74 was also a success due to a perfect sequence match. Since the primary objective of this project was to successfully clone and produce these four antibodies, then this study is considered an overall success. Lastly, this study examined how the same protocol could be applied the SARS-CoV-2 outbreak, by the cloning and production of anti-RBD IgG and testing them for viral neutralization.Hepatit-C (HCV) är fortsatt den enskilt största orsaken till levertransplantationer med uppskattningsvis 71 miljoner infekterade globalt sett, enligt världshälsoorganisationen (WHO).Ett vaccin mot HCV skulle drastiskt minska trycket på global hälso- och sjukvård. Syftet med detta projekt är att producera antikroppar (igG) mot HCV. Projektet fokuserar på HEPC3, AR3C, HEPC74 och HCV1 som är monoklonala antikroppar (mAbs). Dessa antikroppsvarianter har isolerats från patienter som tillfrisknat från infektion. Både DNA-sekvenser och strukturer av antikropparna finns offentligt tillgängliga. Dessa fyra antikroppar har också visats kunna binda till E2 som är ett membranbundet glykoprotein hos HCV som är centralt för viral adhesion och fusion. Interaktionen mellan dessa mAbs och E2 har visat sig neutralisera virulens, vilket gör dem till lovande kandidater för denna studie. Tre av fyra mAbs kunde klonas och produceras framgångsrikt. Försöket med HEPC74 misslyckades på grund av ett fel i plasmidsekvensen och just som western blot skulle genomföras för att bekräfta sekretion av en alternativ klon avslutades the praktiska arbetet med anledning av Covid-19 utbrottet. Resultaten visar entydigt att tre av fyra mAb producerades framgångsrikt. Det går dock att anta att det andra försöket med HEPC74 sannolikt också lyckades pga perfekt sekventiell matchning. Då det huvudsakliga syftet med projektet var att framgångsrikt klona och producera dessa fyra antikroppar så kan studien anses vara framgångsrik. Slutligen så undersöktes huruvida samma förfarande kunde appliceras mot SARS-CoV-2 genom kloning och produktion av anti-RBD IgG och tester av viral neutralisering.
10
Andersson, Christin. "Production and delivery of recombinant subunit vaccines." Doctoral thesis, KTH, Biotechnology, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3027.
Full textAbstract:
Recombinant strategies are today dominating in thedevelopment of modern subunit vaccines. This thesis describesstrategies for the production and recovery of protein subunitimmunogens, and how genetic design of the expression vectorscan be used to adapt the immunogens for incorporation intoadjuvant systems. In addition, different strategies fordelivery of subunit vaccines by RNA or DNA immunization havebeen investigated.
Attempts to create general production strategies forrecombinant protein immunogens in such a way that these areadapted for association with an adjuvant formulation wereevaluated. Different hydrophobic amino acid sequences, beingeither theoretically designed or representing transmembraneregions of bacterial or viral origin, were fused on gene leveleither N-terminally or C-terminally to allow association withiscoms. In addition, affinity tags derived fromStaphylococcus aureusprotein A (SpA) or streptococcalprotein G (SpG), were incorporated to allow efficient recoveryby means of affinity chromatography. A malaria peptide, M5,derived from the central repeat region of thePlasmodium falciparumblood-stage antigen Pf155/RESA,served as model immunogen in these studies. Furthermore,strategies forin vivoorin vitrolipidation of recombinant immunogens for iscomincorporation were also investigated, with a model immunogendeltaSAG1 derived fromToxoplasma gondii. Both strategies were found to befunctional in that the produced and affinity purified fusionproteins indeed associated with iscoms. The iscoms werefurthermore capable of inducing antigen-specific antibodyresponses upon immunization of mice, and we thus believe thatthe presented strategies offer convenient methods for adjuvantassociation.
Recombinant production of a respiratory syncytial virus(RSV) candidate vaccine, BBG2Na, in baby hamster kidney(BHK-21) cells was investigated. Semliki Forest virus(SFV)-based expression vectors encoding both intracellular andsecreted forms of BBG2Na were constructed and found to befunctional. Efficient recovery of BBG2Na could be achieved bycombining serum-free production with a recovery strategy usinga product-specific affinity-column based on a combinatoriallyengineered SpA domain, with specific binding to the G proteinpart of the product.
Plasmid vectors encoding cytoplasmic or secreted variants ofBBG2Na, and employing the SFV replicase for self-amplification,was constructed and evaluated for DNA immunization against RSV.Both plasmid vectors were found to be functional in terms ofBBG2Na expression and localization. Upon intramuscularimmunization of mice, the plasmid vector encoding the secretedvariant of the antigen elicited significant anti-BBG2Na titersand demonstrated lung protective efficacy in mice. This studyclearly demonstrate that protective immune responses to RSV canbe elicited in mice by DNA immunization, and that differentialtargeting of the antigens expressed by nucleic acid vaccinationcould significantly influence the immunogenicity and protectiveefficacy.
We further evaluated DNA and RNA constructs based on the SFVreplicon in comparison with a conventional DNA plasmid forinduction of antibody responses against theP. falciparumPf332-derived antigen EB200. In general,the antibody responses induced were relatively low, the highestresponses surprisingly obtained with the conventional DNAplasmid. Also recombinant SFV suicide particles inducedEB200-reactive antibodies. Importantly, all immunogens inducedan immunological memory, which could be efficiently activatedby a booster injection with EB200 protein.
Keywords: Affibody, Affinity chromatography, Affinitypurification, DNA immunization, Expression plasmid, Fusionprotein, Hydrophobic tag, Iscoms, Lipid tagging, Malaria,Mammalian cell expression, Recombinant immunogen, RespiratorySyncytial Virus, Semliki Forest virus, Serum albumin,Staphylococcus aureusprotein A, Subunit vaccine,Toxoplasma gondii
11
Yau, S. Y. "An investigation on E. coli host strain influences and strategies to improve supercoiled plasmid DNA production for gene therapy and vaccination." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/668715/.
Full textAbstract:
The growing demand for quick and effective methods of producing large amounts of plasmid DNA for human therapy and vaccination has increased the practical challenges associated with process optimisation to improve supercoiled plasmid DNA yields obtained through current methods. The supercoiled isoform of DNA is the preferred form for use in gene therapy and vaccination as this isoform is known to produce higher levels of in vitro and in vivo transgene expression than other forms of plasmid DNA. This study was designed to investigate whether different strategies can be implemented early on in a process to improve supercoiled plasmid DNA yields obtained upstream, with the view to aid and/or ease further downstream stages. The main theme investigated is the influence of the host strain on supercoiled plasmid DNA production. Seventeen strains of Escherichia coli and three different plasmids were investigated at shake flask scale, before two strains were selected for scale up to 7L fermentation scale. The results obtained indicated that the host strain plasmid combination can heavily influence both the quantity and quality of plasmid DNA obtained and this behaviour cannot simply be determined by looking at the host strain genotype. Fermentation runs on the two strains selected for scale up (BL21 DE3 gWiz and HB101 gWiz) demonstrated that these two strains scale up very well, maintaining high specific pDNA yields (1.5mg/L/OD for BL21 DE3 gWiz) and high SC-DNA yields (98% for HB101 gWiz). Temperature amplification studies using strains harbouring pUC18 have shown that although most strain-plasmid combinations yielded more plasmid at a higher temperature of 40°C, the extent of this increase is highly influenced by the host strain. Indeed in some cases, such as for the strains ABLE K, W3110, W1485, a higher plasmid yield was obtained at 37°C. However, as the growth rates of these cultures were not measured, the extent of the accumulation of plasmid DNA due to the effects of the growth rate and/or temperature during the exponential phase of growth is unknown at this time. Similarities to what has been reported as temperature induced runaway plasmid replication have been observed in this study, although no experiments were conducted to confirm whether these observations were indeed as result of runaway replication as defined in the literature. Potential alternative strategies investigated included implementing anaerobiosis to test if these conditions can improve supercoiled plasmid DNA production at fermentation scale, and whether a ‘Quiescent cell expression system’ (a state where chromosomal replication and expression is temporarily shut down but residual proteins remain metabolically active) can be implemented to improve plasmid DNA yields by redirecting resources away from biomass production. The results suggest that under the conditions set in this study, these strategies do not increase plasmid DNA production or the percentage of supercoiled plasmid obtained. In conclusion, the results from this investigation have demonstrated that a highly effective and influential strategy for improving the quality and quantity of plasmid DNA obtained is the initial choice of the host strainplasmid combination. Further improvements can then be obtained through the application of other reported fermentation strategies.
12
Yoshida, Hiroyuki. "Analysis of production profiles of inflammatory cytokine and type I interferon induced by plasmid DNA in cultured cells and in mice." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124069.
Full text
13
Aune, Trond Erik Vee. "High level recombinant protein production in Escherichia coli by engineering broad-host-range plasmid vectors containing the Pm/xylS expression cassette." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bioteknologi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2096.
Full textAbstract:
The use of recombinant gene expression for industrial protein production has since the early 1970s become a multi-billion industry. Despite many years of intensive research, no universal expression system exists that can be used for high-level industrial production of any given recombinant gene. Because of this, much work must be done prior to production to identify the ideal production organism for the gene of interest, usually followed by optimization of an expression system useful in this organism. One of the most popular production organisms is the gram-negative bacterium Escherichia coli, which is regularly used for high-level production of both prokaryotic and eukaryotic proteins. Despite its popularity there are some well-known drawbacks of using E. coli for recombinant expression, including lack of some post-translational modifications of recombinant proteins, and few and inefficient systems for translocation and secretion. In the present work selected key processes in E. coli recombinant protein production has been studied with focus on exploring methods to improve protein production in this organism. The key processes include the use of signal peptides for efficient translocation of eukaryotic proteins to the periplasm, directed evolution of the transcription regulators for increased expression from their cognate promoters, and the use of codon-optimized synthetic genes. The use of signal peptides to achieve efficient translocation of recombinant genes is a well-known and common method. By testing the signal peptides sequences ompA, pelB and the novel, designed consensus signal peptide sequence CSP, in combination with the eukaryotic cDNA for the proteins hGM-CSF, scFv-phOx and hIFN-α2b, it was shown that the effect of signal peptides are gene-specific and, more importantly, that the presence of signal peptides not only directs the gene products to the periplasm but also increases the expression of the recombinant genes. Under high cell density culture (HCDC) expression production volumes of 2.3, 1.7 and 0.6 g/L of scFv-phOx, hGM-CSF and hIFN-α2b, respectively, were obtained.
14
Colina, Delacqua Ligia Maria. "Modélisation/diagnostic de production de poussières dans un plasma H₂au contact d’une cible C/W : Contribution à l’étude des interactions plasma/surface dans les machines de fusion thermonucléaire." Paris 13, 2012. http://scbd-sto.univ-paris13.fr/intranet/edgalilee_th_2012_colina_delacqua.pdf.
Full textAbstract:
Ce travail de thèse a porté sur la caractérisation expérimentale d’un plasma d’hydrogène au contact de cibles de carbone ou tungstène généré dans le réacteur microonde multi dipolaire CASIMIR II. Ce dernier, développé pendant ce projet de thèse, a pour objectif de simuler quelques des processus plasma/surface ayant lieu sous le dome du divertor et dans les régions à l’ombre du plasma (SOL) dans les tokamaks. CASIMIR II se compose de 16 sources dipolaires microondes disposées de manière circulaire le long du périmètre de l’enceinte à vide de manière à obtenir un plasma basse pression (10⁻³ à 10⁻² mbar), haute densité (10⁹ - 10¹¹ cm⁻³) homogène dans tout le volume du réacteur. Des cibles C/W ont été exposées à de tels plasmas. La mise en oeuvre de plusieurs diagnostics in situ spectroscopie optique d’émission, spectrométrie de masse et sonde de langmuir) ont permis d’identifier la nature de quelques produits d’érosion et de constater leur incidence sur les paramètres plasma (Vp' Tₑ‚ nₑ et nᵢ). Un premier modèle 1D collisionnel radial du plasma d’hydrogène généré par une source dipolaire microonde a été développé dans le but de valider et d’aider à l’interprétation des résultats expérimentauxThe work presented in the frame of this thesis dealt with the experimental characterization of a hydrogen plasma in contact with carbon or tungsten target generated in the microwave multidipolar plasma reactor CASIMIR II. This reactor, developed during this thesis project, is envisioned to simulate some plasma / surface processes occuring under the divertor dome and in the far Scrape-off Layer (SOL) regions of tokamaks. The CASIMIR II device is composed of 16 dipolar plasma sources close enough together to ensure large enough homogenous plasma density (10⁹ - 10¹¹ cm⁻³) at low presure (10⁻³ à 10⁻² mbar). Carbon/tungsten targets have been exposed to such plasma. The implementation of several in situ diagnostics (optical emission spectroscopy, mass spectrometry and Langmuir probe) provided us the possibility to identify the nature of some erosion products and observe their effect on plasma parameters (Vp' Tₑ‚ nₑ et nᵢ). A ID collisional radial model of the hydrogen plasma generated by a single microwave dipolar source was developed to validate and help understanding of the experimental results
15
Wadstein, Victor. "Circular Economy in Plastic Production : The recycling challenges and solutions in plastic production." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264551.
Full textAbstract:
The consequences of the linear economy of plastic production has started to show. Media reports of "plastic seas," beaches full of waste, and habitats and environments destroyed. The question on how to make plastic production more circular have been a hot topic. Every year 311 million tonnes of plastic gets produced around the world. The plastics that can be recycled are thermoplastics. 70% of all produced plastic is made from five different plastic materials, PVC, PET, EPS, PP, and HDPE. Of the total of 311 million tonnes 87 million tonnes of that plastic is plastic packages for household consumers. Of that 87 million tonnes 32% of that is never collected, ending up in the oceans. Sweden is doing well compared to most countries, 99% of all plastic in Sweden is collected. The number is much thanks to all the regulations, recycling organs, and producer requirements that are active in Sweden compared to many other countries. This report is going to point out some important challenges and its solutions to move towards a globally circular economy. Sweden still faces challenges. Of all plastic collected only 50% goes into recycling while the other 50% ends up for incineration to energy recovery, to warm up houses and give electricity to cities. There are four different methods of recycling in facilities today. Closed - loop Open - loop Chemical recycling Energy recovery through incineration Closed - loop recycling is when the recycled product ends up as the same product after the recycling process while open - loop is when something gets recycled to a plastic product with a lower value than the original product. Chemical recycling is when chemicals in the plastic are extracted and recycle these, usually for fuels. Energy recovery through incineration is when plastic waste is burnt down to recover the energy stored in the plastic. The most common recycling methods in Sweden are open-loop recycling and energy recovery through incineration. One plastic container differs from the rest. The PET - bottles. Of all plastic bottles 85% are collected and recycled in Sweden much thanks to the deposit-refund system available in Sweden. Plastic bottles often follow a process called URRC process, which is a full process from collecting plastic bottles to selling clean plastic flakes that can be renewed to new plastic bottles. Sweden is building the largest recycling facility in Europe, with a technology called "Near-echnology" which is a technology with Near-infrared light to efficiently sort out coloured and clear plastic as well as type of material and chemical compound. This technology will help the facility sort out more than 50% plastic waste compared to other facilities in Europe, an essential step toward a circular economy. Another meaningful action is in the form of global and international producer recommendations, where strict regulation regarding production, design, and materials are agreed upon that favours packaging improving its recycling abilities. These regulations come from the recycling companies such as Returpack and Plastkretsen.Konsekvenserna från en linjär ekonomi inom plastproduktion har börjat att visas. Media rapporterar om "plast hav", stränder fulla med avfall med habitat och miljöer förstörda. Frågan hur man kan göra plastproduktionen mer cirkulär har varit ett hett debatterat ämne. Varje år produceras 311 miljoner ton plast runt om i världen. Plasten som idag går att återvinna kallas Termoplaster. Av de plasterna består 70% av dessa olika plastmaterial, PVC, PET, EPS, PP och HDPE. Av all tillverkad plast är 78% miljoner ton plastförpackningar varav 32% av det som tillverkas hamnar i haven. Sverige sköter sig bättre än många andra länder när det gäller uppsamling av plast plockas 99% upp. Denna siffra är mycket tack vare de lagar, förordningar och återvinning organ som existerar i Sverige jämfört med andra länder. Detta arbete kommer att fokusera på de utmaningar som uppkommer när man ska röra sig mot en mer cirkulär ekonomi och de lösningar som finns för att klara av utmaningarna. Sverige står för ett antal utmaningar. Av all plast som samlas in i Sverige går 50% till återvinning av materialet medan 50% går till förbränning för att få ut energi, för att värma hus och generera energi till städerna. De fyra vanligaste metoderna som används i återvinning av plast idag är. Closed - loop Open - loop Kemisk återvinning Förbränning för energi Closed - loop är en återvinningsmetod som betyder att när en produkt återvinns kommer den komma ur cykeln som samma eller liknande produkt, detta kan jämföras med open - loop där produkten återvinns till ett material med sämre kvaliteter. I kemisk återvinning återvinner man kemikalierna i plasten. Vanligt är att utvinna kemikalier för att sedan använda som olika bränslen. Den sista vanligaste metoden är förbränning av plast för att få ut energin som finns lagrad i plasten. De vanligaste metoderna i Sverige är idag open - loop samt förbränning. En typ av plastförpackning skiljer sig dock mot mängden, PET - flaskor. Av alla flaskor återvinns 85% till en ny plastprodukt. Detta är mycket beroende på det välfungerande pantsystem som finns i Sverige. Insamlade plastflaskor följer i Sverige en process som heter URRC - processen. Denna process följer allt från insamling av plastflaskor till försäljning av klara plastflingor som kan återvinnas till bland annat flaskor. Sverige bygger även Europas största återvinningscentral för plastinsamling. Med en ny teknologi som de kallar "Near- Technology" som bygger på Near - infrarött ljus´ skall öka precisionen på sortering av plasten. Från material, färg och kemisk uppsättning. Potentialen är 50% mer sorterad plast än någon annan anläggning i Europa. Andra nödvändiga åtgärder för att skapa en cirkulär ekonomi är i form av strikta förordningar, skärpa lagar och att plastproducenter följer de rekommendationer som kommer från till exempel, Returpack och Plastkretsen.
16
Moussaoui, Roba. "Study of negative ions surface production in cesium-free H2 and D2 plasmas." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0328/document.
Full textAbstract:
Cette thèse porte sur l’étude de la production de surface des ions négatifs (IN) pour des applications dans la fusion thermonucléaire. Ce travail a été réalisé à l'aide d'une source plasma PHISIS. Les IN formés en surface de l'échantillon sont collectés et analysés avec un spectromètre de masse (SM). La fonction de la distribution en énergie des ions négatifs FDEIN est mesurée. Dans cette thèse, une technique de polarisation DC pulsée est introduite pour permettre l'étude de la production d'IN en surface sur des échantillons isolants comme le diamant. Un modèle qui calcule le taux de changement de la variation de la tension sur une surface isolante polarisée en mode pulsé est développé. De façon surprenante, la production d’IN en surface sur un diamant dopé au bore ou non dopé est beaucoup plus élevée en mode pulsé qu'en mode continu. Il est traité également la production d’IN en surface dans les conditions de faible tension de polarisation. Le meilleur rendement d’IN mesuré à faible polarisation est obtenu avec du diamant dopé au bore (BDD) et il est 2 fois plus élevé que celui mesuré sur HOPG (high oriented pyrolitic graphite). L'analyse de la production d’IN en surface à différents polarisations pour différents matériaux a été effectuée afin de corréler l'évolution du rendement d’IN aux changements d'état de surface. Une étude approfondie de la production en surface d'IN a été réalisée sur la surface de Nanoporous 12 CaO. 7Al2O3 electride surface. L'influence des conditions expérimentalles sur le rendement en IN a été étudiée. Dans cette contribution, nous montrons que ce matériau pourrait potentiellement être utilisé dans les sources d'ions négatifs sans césiumThis thesis deals with negative ions (NI) surface production for applications in thermonuclear fusion. This work was conducted using a plasma source PHISIS. NI formed on a negatively biased sample surfaceare collected and analyzed with energy mass spectrometer (MS). Negative ion distribution function NIEDF is measured. A SIMION calculation was done to have a complete idea about MS transmission effect on the NIEDF. In the course of this thesis, a DC pulsed bias technique is introduced to enable the study of negative ion surface production on insulating samples as non-doped diamond layers. A model that calculate the rate of change of bias on insulator surface biased in pulsed mode is developed. Surprisingly, negative-ion surface production on boron-doped or non-doped diamond is much higher in pulsed mode than in continuous mode. This thesis deals also with negative ion surface production in low bias condition. The best NI yield measured at low bias is obtained with Boron doped diamond (BDD) ant it is 2 times higher than the one measured on HOPG (highly oriented pyrolytic graphite) surface. Analysis of NI surface production at different surface bias for different material were performed in order to correlate the NI yield evolution to the surface state changes.An extensive study of NI surface production was performed on Nanoporous 12CaO.7Al2O3 electride surface. The influence of surface temperature, bias and plasma exposure time on negative-ion yield was investigated. In this contribution, we show that the electride material has potentials to be used as a production surface in negative ion sources devoted to nuclear fusion application
17
Aleiferis, Spyridon. "Étude expérimentale de la production d’ions négatifs H- par des plasmas à la résonance cyclotron électronique." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI032/document.
Full textAbstract:
Cette thèse porte sur l'étude expérimentale de la production d’ions négatifs (H-) par des sources multi-dipolaires microondes (2.45 GHz) fonctionnant à la Résonance Cyclotron des Electrons (RCE). Les sources H- sont nécessaires aux accélérateurs de haute énergie et surtout pour les systèmes d’injection de neutres à haute énergie pour le chauffage des plasmas de fusion. Pour cette étude, deux sources (Prometheus I et ROSAE III) ont été conçues, fabriquées et étudiées. Ces deux sources sont munies de réseaux 2D des sources multi-dipolaires. Il est prouvé que la formation des ions négatifs dans ces sources d'ions, est dû à un mécanisme de production en volume : l'attachement dissociatif des électrons de faible énergie sur des molécules ro-vibrationallement excitées. Contrairement aux sources impliquant des réactions de surface, la production en volume a l’avantage de fonctionner sans césium. Une étude détaillée des principes fondamentaux de la production de H- est réalisée, et les voies possibles pour d'optimisation sont explorées au moyen de : sondes électrostatiques, photodetachment laser, spectroscopie d'émission optique dans la région spectrale du visible et de l'ultraviolet du vide et finalement par spectroscopie d'absorption et de fluorescence induite dans la région spectral de l'ultraviolet du vide en utilisant radiation synchrotron dans un montage expérimental spécial (SCHEME). Analytiquement:La source "Prometheus I" est d'abord étudiée en détails, dans une large gamme de conditions expérimentales (par exemple, pression, puissance, position des zones RCE). Cette étude souligne l’efficacité de production des ions H- en volume, et dévoile une fenêtre de fonctionnement optimal et des voies d'optimisation pour atteindre de plus fortes densités d'ions H-. La contribution du processus d'attachement dissociatif et de l'ionisation résonnante des neutres, à la production H- pour cette source ont été évaluée et la prépondérance de la première finalement confirmée par un modèle rendant compte du bilan des créations et pertes d’espèces.En raison de l'importance des molécules ro-vibrationnallement excitées lors du processus d'attachement dissociatif, l'étude se concentre sur leurs réactions de formation. Deux réactions de formation sont étudiées par des expériences dédiées : la désorption recombinative des atomes d'hydrogène à la surface de divers matériaux ("ROSAE III" et "SCHEME") et l'excitation par impact d'électrons à travers les états singulets temporaires ("Prometheus I"). L'étude de la désorption recombinative a été appréhendée de deux façons différentes. Avec la source ROSAE III, l'impact indirect du processus pour la production d'ions négatifs, à travers la formation de molécules ro-vibrationnellement excitées, a été évaluée dans les plasmas RCE. Dans la deuxième approche, la source "SCHEME" a été conçue pour l'étude de la désorption recombinative des atomes en utilisant le rayonnement synchrotron. La formation des états vibrationnels suite à l’excitation des états singulets, dans la source "Prometheus I" a été étudiée par des mesures d'émission de l'ultraviolet du vide.Une étude qui combine la spectroscopie d'émission de l'ultraviolet du vide, le photodétachement et la caractérisation de la cinétique des électrons par sondes électrostatiques, a permis l'identification des facteurs qui limitent la production d'ions négatifs dans le plasma RCE de "Prometheus I". Des perspectives pour surmonter ces limitations sont finalement proposéesThe present PhD thesis is devoted to the experimental study of hydrogen negative ion (H-) production in microwave-driven (2.45 GHz) multi-dipolar Electron Cyclotron Resonance (ECR) plasma sources. H- sources are required in high-energy accelerators and more importantly in neutral beam injection systems for fusion plasma heating. Towards this directions, two sources (namely, "Prometheus I" and "ROSAE III") are designed, fabricated and studied. Both sources are driven by 2D networks of dipolar ECR elementary sources. It is proven that, negative ion formation in these ion sources is governed by the volume production mechanism, which mostly refers to the dissociative attachment of low energy electrons to vibrationally excited molecules. Contrary to the so called surface sources, volume production sources have the advantage of cesium-free operation. Extended experimental study on fundamental principles of H- production is realized, and possible ways for potential source optimization are tested by means of: electrostatic probes, laser photodetachment, optical emission spectroscopy, both in the visible and vacuum ultra-violet spectral range and finally, vacuum-ultraviolet absorption and induced fluorescence spectroscopy using synchrotron radiation in a specially designed setup ("SCHEME"). Analytically:The source "Prometheus I" is initially studied in detail (EEDF, H- density, optical emission spectra etc), under a wide range of experimental conditions (e.g., pressure, power, ECR-zone location), proving its efficiency for H- volume production, and unveiling optimum operational window and paths for obtaining higher H- densities. The contribution of the dissociative attachment process and neutral resonant ionization to H- production in this source, is evaluated, and the dominance of the former is finally confirmed by an equilibrium model.Due to the importance of the ro-vibrationally excited molecules to the dissociative attachment process, the study is focused on their formation reactions. Two formation reactions are considered by adequately adapted experiments: the recombinative desorption of hydrogen atoms on the surface of various materials (ROSAE III and SCHEME) and the electron impact excitation through temporary singlet states (Prometheus I). The study of recombinative desorption is approached in two different ways. With the source ROSAE III, the indirect impact of the process to the production of negative ions, through the formation of ro-vibrationally excited molecules, is evaluated in ECR plasmas. In the second approach, the source SCHEME is designed for the independent investigation of the recombinative desorption of unexcited atoms using synchrotron radiation based diagnostics. The formation of vibrational states through singlet excitation in the source "Prometheus I" is studied by vacuum-ultraviolet emission measurements.A study that combined vacuum-ultraviolet emission spectroscopy, photodetachment and the characterization of electron kinetics with electrostatic probes, allowed the identification of the factors that limit negative ion production in the ECR plasma of "Prometheus I". Perspectives for overcoming these limitations are finally proposed
18
O'Brien, Christopher J. (Christopher John). "Hydrogen production via plasma reformers." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38123.
Full text
19
Legault, Lawrence E. "The production of hot electrons by the two-plasmon decay instability in a CO2 laser plasma interaction." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26438.
Full textAbstract:
The generation of hot electrons characterizing the two-plasmon decay (TPD) instability is investigated experimentally both in and out of the plane of polarization of a CO₂ laser incident on an underdense gas target. The results presented here show that, for high intensities (I > ~ 3.5 x 10¹³ W/cm² for a helium target, 1 > ~ 5.5 x 10¹³ W/cm² for a nitrogen target), the electron plasma waves (EPW's) generated by the TPD instability are modified by the electron decay instability (EDI). The relatively short scale lengths at the onset of TPD for these high intensities
(<~0.125mm) cause the EPW's propagating towards the higher density regions of the plasma to undergo the EDI resulting in EPW's which contain a vector component perpendicular to the plane of polarization and accelerate electrons by nonlinear Landau damping up to 55° outside the plane of polarization.Science, Faculty of
Physics and Astronomy, Department of
Graduate
20
Ruban, Anna. "Life Cycle Assessment of Plastic Bag Production." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-179846.
Full textAbstract:
The main focus of this report is to establish a comparative study of traditional and biodegradable vest-plastic bag production through the utilization of a life cycle assessment (LCA) approach. The measurements were made for the Ukrainian limited liability company “Polymer”, as a representative manufacturer, in order to calculate the environmental impact of plastic bag manufacturing, and identify the more environmental friendly item. This research is based on a literature review of the special characteristics of life cycle assessment and its methods and methodologies, a field study, which included two semi-structure interviews, and measurements and comparison of the harmfulness of traditional and biodegradable bag production. The software SimaPro 7.3.2 and IMACT 2002+ method were chosen in order to accomplish the research purpose. The results of the study show that traditional vest-bags produced by the researched enterprise are less environmentally friendly. Their production process has a bigger impact on environment and human health than that of the biodegradable bags. Moreover, a list of recommendations for possible improvements was developed based on the results of the research. It was sent to the directors of LLC “Polymer” as a suggestion for creating a “green strategy” of further development.
21
Podestà, Mario. "Plasma production and transport in a simple magnetised toroidal plasma /." Lausanne : EPFL, 2007. http://library.epfl.ch/theses/?nr=3765.
Full textAbstract:
Thèse Ecole polytechnique fédérale de Lausanne EPFL, no 3765 (2007), Faculté des sciences de base SB, Section de physique, Centre de recherches en physique des plasmas CRPP (CRPP Association Euratom CRPP-AE). Dir.: Ambrogio Fasoli.
22
Covas, Jose A. C. G. "Processing of UPVC in single and twin screw extruders." Thesis, Loughborough University, 1985. https://dspace.lboro.ac.uk/2134/11942.
Full textAbstract:
The processing characteristics of PVC compounds play a major role on the ability of the equipment to control the final properties of the product. Therefore, information on the effect of processing conditions on such characteristics. and its influence on the final properties can lead to an optimization of the extrusion process. In this work. a statistically based experimental design was used in order to investigate the role of the operating conditions on the extrusion of a simple lead based PVC formulation. Both a single and a twin screw extruder were used - they were instrumented, and data collected by computer. A die was designed for the formulation used. with both shear and extensional flows being taken into account. These experiments produced both core samples along the screw(s) and final products with varying states of fusion. The fusion mechanism on processing was monitored with the help of electron and light microscopy techniques. thermal analysis and density measurements. In both types of extruders the primary particles were found to fuse well before the grains, but the overall mechanism differs for each type of machine. An experimental technique was developed for the study of the Residence Time (RT) and Residence Time Distribution (RTD) of the material in the processing equipment. These functions were related to the operating conditions and compared with the available models for extrusion. The degree of fusion of the processed products was assessed by rheology and thermal analysis. A range of mechanical properties, relevant to the general end - use of rigid PVC formulations. was analysed: flexural. tensile and impact properties were found to be directly related with fusion level. Hardness, measured using a newly developed apparatus. proved to be a potential technique for the degree of gelation of PVC formulations.
23
Lee, Yuk-ting, and 李玉婷. "Production of transgenic plant-derived vaccines via plastid transformation technology." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B3015943X.
Full text
24
Hislop, David John. "Strangeness production in a quark-gluon plasma." Doctoral thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/18382.
Full textAbstract:
This thesis is arranged as follows: Chapter 1 notes that the production of strangeness measured at CERN and Brookhaven has two possible explanations. One is that strange quarks, being relatively light, are easily produced, creating an abundance of strange particles in the experiment. On the other hand, hadron gas models use only thermodynamics, strangeness neutrality and baryon number conservation to predict the same ratios. Both models need a parameter, ϒs, reflecting the relative departure from equilibrium of strangeness. Chapter 2 discusses the Cutkosky rules and their thermal field theory counterparts, the Kobes-Semenoff rules. The influence of the medium is brought into consideration through Braaten-Pisarski resummation. In Chapter 3 we use the Cutkosky rules to calculate the standard QCD quark production mechanisms. The intention is to eventually generalise these calculations to finite temperature. We then derive the rate of plasmon decay (gluons pick up finite masses and widths due to interactions with the medium), which was proposed by Tanguy Altherr and David Seibert to be another important mechanism for the production of strangeness. In Chapter 4 we use Bjorken's framework of one-dimensional hydrodynamic flow to study the evolution of a gluon plasma, through the production of quarks to a later stage, by which times hadrons should be prevalent. Of critical importance is the thermal equilibration time. We derive some analytic expressions for the proper time dependence of the chemical potential and temperature of the quark-gluon plasma. Chapter 5 concludes this thesis and sets out a program to be continued. The Appendices summarise some useful data, notation and concepts with regard to make reading easier and to be used in continuing this research. Specifically the propagators and vertices of Thermal Field Theory (TFT) are listed as well as the cut propagators. Finally, at the end are listed acknowledgments and a bibliography.
25
Majeri, Nassim. "Production de rayons X par plasma ECR." Thesis, Orléans, 2009. http://www.theses.fr/2009ORLE2077/document.
Full textAbstract:
Durant cette thèse nous avons caractérisé et amélioré une nouvelle source de rayons X avec unplasma ECR (résonance cyclotronique électronique) permettant de générer des électronsénergétiques de 10 à 120 keV, qui vont ensuite produire le rayonnement X par freinage(bremsstrahlung). Les améliorations de l’installation ont permis d’obtenir une source stable, pouvantfonctionner une journée entière de travail (huit heures) sans arrêt. Dans la première partie de l’étudeexpérimentale on a étudié et déterminé les paramètres optimaux de la source : la pression, lapuissance micro-onde et la configuration magnétique sur le rayonnement X du plasma. Nous avonségalement confirmé la localisation des électrons énergétiques sur un anneau due à la configurationmagnétique. L’intensité trop faible et la zone d’émission non ponctuelle du rayonnement plasma, nepermettant pas l’utilisation de la source à plasma, une cible a été insérée sur la trajectoire desélectrons énergétique pour résoudre ces deux problèmes.Le principal avantage de notre source par rapport aux tubes X, est l’absence de haute tension (20 à400 kV). Pour chauffer les électrons, nous utilisons une onde de 2,45 GHz, qui est la fréquenceindustrielle autorisée dans les fours à micro-ondes, délivrée par un magnétron. Les éléments simplesqui composent notre source donne un coût plus faible qu’un système classique de tubes X, dûprincipalement au prix élevé du générateur HT pour les tubes X. De plus, nous n’avons pas besoind’un vide très poussé car, à la différence des tubes X, la source ECRX fonctionne avec une pressionrésiduelle de 0,1mPa. Et enfin notre source est compacte ce qui la rend facilement transportable. Lesapplications de cette source sont nombreuses comme la radiologie, la stérilisation et le contrôle nondestructif industrielDuring this thesis we have characterised and developed a new X-ray source with an ECR plasma(electron cyclotron resonance) generating energetic electrons from 10 to 120 keV, which will emit adeceleration radiation (the Bremsstrahlung). The improvements of the installation permit to obtain astable source, which can work during one day (eight hours) without stop. In first part of theexperimental study we have studied and determined the optimal parameters of the source: pressure,micro-wave power and the magnetic configuration on the X radiation of the plasma. We also confirmedthe localisation of the energetic electron on a ring due to the magnetic configuration. The low intensityand the non punctual emission size of the X radiation, don’t allow the use of the source, so a target isinserted in the trajectory of the energetic electron to solve these two weaknesses.The main advantage of our source compared with X-ray tubes, is the absence of high voltage (20 to400 kV). For heating the electron, we use a 2,45 GHz wave, that is the industrial frequency authorizedfor the micro-wave oven, delivered by the magnetron. The simple elements that compose our sourceare less expensive than the classical X-ray tubes, due to mainly the high cost of the X-ray generator.Moreover, we don’t need a high vacuum, mandatory for the X-ray tubes; an ECRX operates at aresidual pressure of 0,1 mPa. And finally, we have a compact source. Applications will be various frommedical, like radiological, sterilization, to non-destructive industrial control
26
Stellman, Jeffrey Taylor. "Production, development, and characterization of plastic hypodermic needles." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29748.
Full textAbstract:
Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Dr. Jonathan S. Colton; Committee Member: Dr. Mark R. Prausnitz; Committee Member: Dr. Rudolph L. Gleason. Part of the SMARTech Electronic Thesis and Dissertation Collection.
27
Stamouli, Konstantina. "Fuel production and optimisation from mixed plastic waste." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8268/.
Full textAbstract:
Increasing plastic consumption has created an alerting problem with waste disposal of the mixed waste plastics once the recyclable fractions have been recovered. The percentage sent to landfill of the generated mixed plastic waste amounts to one third of the total. Liquid fuel recovery from mixed plastic waste is possible using pyrolysis as a tertiary recycling process. The focus of this study was to obtain useful liquid product recovered from the pyrolysis of a variety of commercial mixed plastic waste utilising a pilot scale fluidised bed reactor of 1kg/hr processing capacity. The influence of residence time (1.78 to 2.74s), feedstock variation and reaction temperature (500 – 550oC) were investigated to optimise the quality of the wax products. Characterisation of the mixed plastic feedstocks through TGA, DSC and FTIR analysis was carried out to lay the foundation of the pyrolysis conditions. Understanding the fuel quality and product distribution was essential in assessing the key properties such as melting point and viscosity in the optimisation process. Key findings of the research concluded that increasing residence time has the strongest effect on reducing the melting point (up to 14oC) of the liquid product across all studied feedstocks although the magnitude of the effect greatly depends upon the initial feedstock composition. Changes is the average melting point correspond to a shift in the average carbon number distribution of the product. Feedstock and process parameters variability were also found to greatly affect the final product quality resulting in a versatile product composition as well as the product yields that varied between 27 and 60% w.t.
28
Rhodes, Peter. "Indices of nitric oxide production." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307982.
Full text
29
Petitpas, Guillaume. "Étude du reformage d'hydrocarbures liquides assisté par plasma hors-équilibre pour la production de gaz de synthèse." Paris, ENMP, 2008. https://pastel.archives-ouvertes.fr/tel-01138136.
Full textAbstract:
L’utilisation directe d’hydrogène comme vecteur énergétique pour des applications embarquées doit actuellement faire face à l’absence d’infrastructure de distribution et à des difficultés technologiques liées au problème du stockage de l’hydrogène. Une étape transitoire possible avant le passage à une économie «direct hydrogène» consiste à produire l’hydrogène à bord du véhicule à partir des carburants automobiles traditionnels. Le reformage assisté par plasma hors équilibre constitue une alternative au reformage catalytique qui, bien que largement utilisé à l’échelle industrielle, reste peu adapté aux contraintes des systèmes embarqués. Ce travail s’inscrit dans le cadre de recherches menées depuis une quinzaine d’années par le Centre Énergétique et Procédés, dans le domaine de la conversion d’hydrocarbures par plasma. L’objectif de ce travail a été la caractérisation précise du dispositif de reformage assisté par plasma, à travers différentes études paramétriques (influence de l’écoulement – géométrie de l’électrode cylindrique, régime de fonctionnement, pression, polarité – et influence des conditions chimiques – mélange initiale, débit total, puissance électrique, nature du carburant précurseur), conduites tant sur le plan expérimental que théorique. Une étude du comportement de la torche dans les conditions non-réactives (eau, air) a d'abord été effectuée. La réaction de reformage a ensuite été étudiée suivant des conditions variées (POx, SR, ATR) et à l'aide d'essence SP95, d'éthanol, d'E85 et de gazole ; prouvant le caractère versatile de la technologie. Un modèle simple d'arc a été développé dans le cas de l'air. La modélisation du réacteur a ensuite concerné différents aspects. L'étude de l'écoulement, tout d'abord, a permis de montrer que le mélange homogène entre les trois réactifs (air, eau, octane) était rapidement atteint lors de leur injection dans le réacteur, conférant au système une symétrie axiale. L'étude d'un modèle cinétique 1D a ensuite mis en évidence le rôle des radicaux dans l'activation de la réaction de reformage, et a donné lieu à une étude paramétrique poussée (mélange initial, débit total, puissance injectée, schéma cinétique utilisé). Un modèle couplé prenant en compte l'interaction entre l'écoulement 2D axisymétrique et les réactions de cinétique chimique a enfin été élaboré, mettant l'accent sur le déroulement de la réaction dans l'ensemble du réacteurThe direct use of hydrogen as an energy vector currently faces difficulties due to both the lack of a distribution infrastructure, and to technical limitations concerning hydrogen storage. Before the transition to a “direct hydrogen” economy, a possible intermediate step could be the onboard hydrogen production from conventional car fuels. Non-thermal, plasma-assisted reforming provides an alternative to conventional industrial catalytic reforming, since the latter has limitations when an onboard system. The objective of this work is the characterization of plasma assisted reforming technology, through various parametric studies (factors influencing flow – geometry of the cylindrical electrode, pattern of behaviour, pressure, polarity – and factors influencing chemical conditions – initial mixture, total flow rate, injected electrical power, nature of combustible components), on both experimental and theoretical fronts. A study of the behaviour of the torch in non-reactive conditions (steam water, air) was first performed. The reforming reaction was then studied under various conditions (POx, SR, ATR), using gasoline SP95, ethanol, E85 and diesel fuel; establishing the adaptability of the reactor. A simple physical model of the arc was also developed in the case of air. The modelling of the reactor focused then on different aspects. Firstly, the study of flow showed that the good mixing between the three reactive species (air, water, octane) was attained quickly during their injection in the reactor, conferring an axial symmetry on the system. The study of a 1D kinetic model then served to highlight the role of radicals in the activation of the reaction of reforming. This was followed by a sensitivity analysis. A coupled model taking into account correlation between flow (2D axisymetric) and the reactions of chemical kinetics was finally worked out, with emphasis placed on the sequence of reactions in the reactor as a whole
30
Blandin, Christopher. "Production of dielectric materials." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26568.
Full textAbstract:
Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Colton, Jonathan; Committee Member: Schultz, John; Committee Member: Zhou, Min. Part of the SMARTech Electronic Thesis and Dissertation Collection.
31
Devillers, Guillaume. "Instabilités paramétriques et production d'impuretés sur JET durant le chauffage à la résonance cyclotronique des ions." Grenoble 1, 1991. http://www.theses.fr/1991GRE10051.
Full textAbstract:
Les spectres en frequence, jusqu'a 100 mhz, du champ electrique toroidal et poloidal ont ete mesures dans le bord de jet durant le chauffage a la resonance cyclotronique des ions. Plusieurs scenarios d'instabilite parametrique etaient evidents. La decomposition de l'onde rapide (pompe) en onde lente a ete observee pour chaque gaz chauffe par resonance centrale de minorite. Le champ electrique seuil et le taux de croissance ont ete calcules dans une approximation froide avec une correction collisionnelle. Les seuils calcules etaient suffisamment bas pour autoriser leur excitation potentielle par les antennes de chauffage radio frequence de jet pour une large bande de parametre du plasma. Durant des experiences de chauffage particulieres, des decompositions non resonnantes en onde de bernstein ont probablement ete excitees. Aucune antenne donnee n'etait la source des instabilites mesurees par la sonde. Ces instabilites sont caracterisees par une faible puissance de chauffage seuil (<100 kw) et une rapide saturation au-dessus de 1 mw. Les modes propres avaient une forte influence sur le signal de la pompe et le niveau de saturation des modes decomposes. L'importante divergence entre le comportement de ces instabilites et celui des differents flux d'impuretes generees par le chauffage cyclotronique des ions suggere une faible correlation entre ces deux phenomenes
32
Pavlenko, O. P., and Burkhard Kämpfer. "Photon production in an expanding gluon-enriched plasma." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-32727.
Full textAbstract:
Photon production in an expanding gluon plasma with initially little quark admixture is considered. Photons are created by lowest order a, processes which include quarks. Chemical equilibration of the quarks in turn is followed by rate equations which rely on lowest order αsgg = qq processes. Expansion slows down the quark cooking. Compared with the standard local equilibrium estimates we find a drastic reduction of mediumenergy photons if the initial quark admixure is below 20% of the chemical saturation density. Higher initial temperatures increase significantly the high-energy photon yield and overcompensate this reduction.
33
Nell, Annalien. "Study of the plasma based production of tetrafluoroethylene." Thesis, Stellenbosch : Stellenbosch University, 1999. http://hdl.handle.net/10019.1/51440.
Full textAbstract:
Thesis (MIng) --Stellenbosch University, 1999.ENGLISH ABSTRACT: A method was developed at the Atomic Energy Corporation of South Africa (AEC) for the plasma based production of tetrafluoroethylene (TFE). The process involves the feeding of carbon particles into a direct-current CF4 plasma. The resultant plasma gas is quenched rapidly to obtain TFE and other fluorocarbons. The mixing of the particles with the plasma gas is very important in order to achieve a high C:F-ratio in the gas phase, which promotes the desired reactions. The gas enthalpy in the reactor is a governing factor in the TFE yields that are obtained. In this study research was done on particle mixing and the enthalpy distribution in the laboratory scale reactor. An enthalpy probe was used as the main diagnostic tool. Results indicated that particle mixing is quite uniform throughout the reactor. A basic one-dimensional mechanistic model of the reactor was also expanded to assist in· the scale-up of the process. In its present form the model is adequate for predicting trends in the reactor. The model could still be expanded further to include reaction kinetics and internal heat transfer in the particles. Considering the restrictions of the model, satisfactory agreement was obtained between the model and experimental results.
AFRIKAANSE OPSOMMING: 'n Proses vir die plasmagebaseerde produksie van tetrafluoroetileen (TFE) is deur die Atoomenergiekorporasie van Suid-Afrika (AEK) ontwikkel. Koolstofpartikels word in 'n gelykstroomCF4- plasma gevoer en die resulterende plasmagas word vinnig geblus ten einde TFE en ander fluoor-koolstofverbindings as produkte te verkry. Goeie vermenging van die koolstofpartikels met die plasmagas is van uiterste belang ten einde 'n hoe C:F-verhouding, wat die gewenste reaksies bevorder, in die gasfase te verkry. Die entalpie van die plasmagas in die reaktor is 'n bepalende faktor in die opbrengs TFE wat verkry word. Vir die doel van hierdie werkstuk is navorsing op laboratoriumskaal gedoen oor partikelvermenging en die entalpie-verspreiding in die reaktor. Die hoof diagnostiese apparaat wat vir die doel aangewend is, is die entalpiesonde. Resultate toon dat partikelvermenging naastenby uniform deur die reaktor voorkom. Verder is 'n basiese een-dimensionele meganistiese model van die reaktor uitgebrei ten einde van nut te wees in die opskaling van die proses. In sy huidige vorm is die model voldoende om algemene neigings in die reaktor te voorspel. Die model kan nog verder uitgebrei word om reaksie-kinetika en interne hitte-oordrag in die partikels in te sluit. Die beperkings van die model in ag genome, is ooreenstemming tussen die model en eksperimentele resultate egter bevredigend.
34
Pavlenko, O. P., and Burkhard Kämpfer. "Photon production in an expanding gluon-enriched plasma." Forschungszentrum Rossendorf, 1993. https://hzdr.qucosa.de/id/qucosa%3A22099.
Full textAbstract:
Photon production in an expanding gluon plasma with initially little quark admixture is considered. Photons are created by lowest order a, processes which include quarks. Chemical equilibration of the quarks in turn is followed by rate equations which rely on lowest order αsgg = qq processes. Expansion slows down the quark cooking. Compared with the standard local equilibrium estimates we find a drastic reduction of mediumenergy photons if the initial quark admixure is below 20% of the chemical saturation density. Higher initial temperatures increase significantly the high-energy photon yield and overcompensate this reduction.
35
Watson, T. L. "Accumulation and manipulation of positron plasmas for antihydrogen production." Thesis, Swansea University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639359.
Full textAbstract:
This thesis describes a buffer gas positron accumulator which has been used by the ATHENA collaboration to produce and detect the first cold antihydrogen atoms. In particular, the work presented is centred on the implementation of a so-called rotating wall electric field to compress a positron plasma in preparation for recombination with antiprotons, in addition to maximising the accumulation efficiency by the automatic optimisation of the trap applied potentials. Central results include successful compression of the positron plasma with an increase in central density by a factor of six. The use of a rotating wall during accumulation of a positron plasma has been investigated for the first time with interesting distinctions observed when compared to a typical accumulation without the use of a rotating wall. Results show that its application results in a greater number of positrons being accumulated at a given time, and that there appears to be an optimum, pressure dependent, time at which to apply the rotating wall. Results also indicate that the accumulation time at which the plasma is maximally compressed is also pressure dependent. A useful program has also been written, and successfully implemented that automatically optimises the electrode array applied potentials to maximise the trapping efficiency after the growth of new solid neon moderators.
36
Gunnarsson, Rickard. "Titanium oxide nanoparticle production using high power pulsed plasmas." Licentiate thesis, Linköpings universitet, Plasma och beläggningsfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-128622.
Full textAbstract:
This thesis covers fundamental aspects of process control when growing titanium oxide nanoparticles in a reactive sputtering process. It covers the influence of oxygen containing gas on the oxidation state of the cathode from which the growth material is ejected, as well as its influence on the particles oxidation state and their nucleation. It was found that a low degree of reactive gases was necessary for nanoparticles of titanium to nucleate. When the oxygen gas was slightly increased, the nanoparticle yield and particle oxygen content increased. A further increase caused a decrease in particle yield which was attributed to a slight oxidation of the cathode. By varying the oxygen flow to the process, it was possible to control the oxygen content of the nanoparticles without fully oxidizing the cathode. Because oxygen containing gases such as residual water vapour has a profound influence on nanoparticle yield and composition, the deposition source was re-engineered to allow for cleaner and thus more stable synthesis conditions. The size of the nanoparticles has been controlled by two means. The first is to change electrical potentials around the growth zone, which allows for nanoparticle size control in the order of 25-75 nm. This size control does not influence the oxygen content of the nanoparticles. The second means of size control investigated was by increasing the pressure. By doing this, the particle size can be increased from 50 – 250 nm, however the oxygen content also increases with pressure. Different particle morphologies were found by changing the pressure. At low pressures, mostly spherical particles with weak facets were produced. As the pressure increased, the particles got a cubic shape. At higher pressures the cubic particles started to get a fractured surface. At the highest pressure investigated, the fractured surface became poly-crystalline, giving a cauliflower shaped morphology.
37
Muppidi, Mahanand. "Toward libraries for increased bio plastic production in cyanobacteria." Thesis, KTH, Skolan för bioteknologi (BIO), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173649.
Full textAbstract:
Cyanobateria are promising cell factories due to their minimal nutrient requirements and utilization of asmospheric carbon di-oxide as its sole carbon source. In particular, polyhydroxybutyrate (PHB) is an industrially useful bio plastic that is produced naturally by some cyanobacteria. Furthermore, PHB biosynthetic pathway is a starting point for production of the biofuel, 1-butanol. There has been much genetic engineering effort toward increasing the production of PHB from cyanobacteria. These have been focused on increasing the pool of acetyl-CoA precursor, or increasing the amount of the reductant NADPH. The upstream process for increasing these reactants is complex and involves many genes. In this contect, cyanobacteria libraries will contribute to reveal genes or gene fragments that are responsible for production of PHB, alkanes and other high value compounds. In pursuit of finding these novel genes or genefragments, a transcription factor library is created in this study with 50 transcription factors. Furthermore, the process is optimized towards the creation of genomic fragment library and metagenomic fragment library with 26 diverse strains. Membersof the transcription factor library are over-expressed by a PHB - producing host Synechocystis PCC 6803 and the process towards creation of genomic and metagenomic libraries is optimized. The members of the metagenomic library can be screened for increased PHB, alkanes, lactate and other high value products and the potential members can be isolated and characterized.
38
Cowx, Peter M. "An evaluation of thermal plasmas in pyrometallurgy." Thesis, Aston University, 1988. http://publications.aston.ac.uk/11906/.
Full textAbstract:
The development of reliable, high powered plasma generators has resulted in many plasma processes being proposed as alternatives to existing pyrometallurgical technologies. This work evaluates the advantages and disadvantages of plasma systems by reviewing plasma generators, their integration with reactors and the process economics. Many plasma systems were shown to be technically and economically superior to existing technologies, but some of the plasma system advantages quoted in the literature were found to be impractical because of other system constraints. Process applications were limited by the power inputs available from plasma generators compared to AC electric furnaces. A series of trials were conducted where chromite and steelplant baghouse dusts were smelted in the Tetronics' 2.0 MW transferred arc/open bath reactor to confirm the operating characteristics of the plasma system and its economics. Chromite smelting was technical superior to submerged arc furnace technology, but the economics were unfavourable because of the limited power available from the water-cooled plasma torch and the high electrical energy consumption. A DC graphite electrode plasma furnace using preheated and prereduced chromite concentrates will compete economically with the submerged arc furnace. Ni, Cr and Mo were economically recovered from high alloy content steelplant dusts for recycling. Five Electric Arc Furnace dusts were smelted to produce a non-toxic residue and recover the contained zinc to an enriched zinc oxide product for recycling. It should be possible to condense the zinc vapour directly in a zinc splash condenser to increase the value of the product. Because of the limited power available from plasma generators, plasma processes will be most suitable for treating high and medium value materials such as Au, Pt, Mo, Ni, Ti, V, Cr etc at small production rates, heating metals in tundishes and ladles and remelting superalloy scrap. The treatment of environmentally hazardous waste materials is a particularly interesting application because of the additional financial incentives. Non-transferred arc plasma generators will be used for air and gas preheating in blast furnaces to reduce metallurgical coke consumptions.
39
Chikkala, Veera, and veera chikkala@rmit edu au. "Production and transformation of tobacco and Brassica containing macrochloroplasts." RMIT University. Applied Sciences, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091005.144005.
Full textAbstract:
Plastid division, sustained by the equilibrium expression and coordination of plastid division genes is vital for the maintenance of plastid populations in dividing plant cells. Macrochloroplasts (MCP), the occurrence of one or a few chloroplasts per cell is due to the imbalance in the expression of plastid division genes. Because of the MCP size and number it was proposed that they may provide better targets for the plastid transformation than the normal (WT) chloroplasts and result in better plastid transformation frequencies. The objective of this research was to produce transgenic plants containing macrochloroplasts by nuclear transformation and then to use these plants as a model for the development of plastid transformation of crop species. By using AtFtsZ1-1 and AtMinD1 as query sequences in the TIGR (U.S.A) and ASTRA (Australia) Brassica oleracea EST databases, this project resulted in the isolation of cauliflower FtsZ1-1 (EU684588) and MinD (EU684589) genes. In addition, AtFtsZ1-1 was used as a control gene for comparison to the cauliflower FtsZ1-1. Binary vectors were constructed to express these genes in tobacco and cauliflower either by Agrobacterium tumefaciens-mediated or PEG-mediated transformation methods. Transgenic tobacco and cauliflower plants with abnormal chloroplasts (MCP, minichloroplasts, honeycomb or doughnut shaped chloroplasts, uneven surface membrane chloroplasts) were developed. Furthermore, the transgenic tobacco and cauliflower plants were examined by PCR, RT-PCR and Southern blotting. In addition, th ese plants were also analysed for the different abnormal chloroplast phenotypes by fluorescence microscopy. This project also generated the first plastid transformants from macrochloroplast bearing tobacco plants via biolistics. After one round of regeneration homoplasmic plastid transformants were obtained from both WT chloroplast and MCP tobacco plants. The homoplasmic nature of plastid transformants were confirmed by PCR and Southern blotting. Plastid expression of GFP in WT and MCP was confirmed by fluorescence/confocal microscopy and western blot analysis. This project showed for the first time the characterisation of cauliflower FtsZ1-1 and MinD plastid division genes in homologous and heterologous systems (cauliflower and tobacco). Moreover, obtaining homoplasmic plastid transformant shoots from one round of regeneration from the MCP containing tobacco plants is reported for the first time in this study. In addition this study explored the effect of transgene expression level on the chloroplast abnormality, highlighting the importance of analysing transgenic tobacco and cauliflower plants at the protein lev el specifically with regard to plastid division genes. The maintenance of MCP phenotype in the regenerated shoots and the requirement of standardisation of MCP containing plants via biolistics for increasing the plastid transformation frequency were also examined.
40
Pratontep, Sirapat. "Production and characterisation of size-selected nanoclusters on surfaces." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289304.
Full text
41
Kuznetsova, Inga Vladimirovna. "Particle Production in Matter at Extreme Conditions." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/193745.
Full textAbstract:
We study particle production and its density evolution and equilibration in hot dense medium, such as hadronic gas after quark gluon plasma hadronization and relativistic electron positron photon plasma. For this study we use kinetic momentum integrated equations for particles density evolution with Lorentz invariant reaction rates. We extend these equations, used before for two-to-two particles reactions (1 + 2 ↔ 3 + 4), to the case of two-to-one and backward reactions (1 + 2 ↔ 3). One type of hot dense medium, which we study, is hadronic gas produced at quark gluon plasma hadronization in heavy ions collisions in SPS, RHIC and LHC experiments. We study hadron production at quark gluon plasma hadronization and their evolution in thermal hadronic gas phase. We consider non-equilibrium hadronization model, for which the yields of the light quark hadrons are defined by entropy conservation. Yields of hadrons containing heavier (strange, charm, bottom) quarks are mainly controlled by flavor conservation. We predict yields of charm and bottom hadrons within this non-equilibrium statistical hadronization model. Then we use this non-equilibrium hadronization as the initial condition in the study of hadronic kinetic phase. During this time period some hadronic resonances can be produced in lighter hadrons fusion. This reaction is opposite to resonance decay. Production of resonances is dominant over decay if there is non-equilibrium excess of decay products. Within this model we explain apparently contradictory experimental results reported in RHIC experiments: ∑(1385) yield is enhanced while ∧(1520) yield is suppressed compared to the statistical hadronization model expectation obtained without kinetic phase. We also predict Δ(1232) enhancement. The second type of plasma medium we consider is the relativistic electron position photon plasma (EP³) drop. This plasma is expected to be produced in decay of supercritical field created in ultrashort laser pulse. We study at what conditions this plasma drop is opaque for photons and therefore may reach thermal and chemical equilibrium. Further we consider muon and pion production in this plasma also as a diagnostic tool. Such heavy particles can be diagnostic tool to study the properties of EP³ plasma, similar to the role taken by heavy hadrons production in heavy ions collisions. Finally all these theoretical developments can be applied to begin a study of particles evolution in early universe in temperatures domain from QGP hadronization (160 MeV) to nucleosynthesis (0.1 MeV). The first results on pion equilibration are presented here.
42
Ouni, Fakhreddine. "Production d'hydrogène et valorisation des alcanes par plasma non thermique." Orléans, 2006. http://www.theses.fr/2006ORLE2055.
Full textAbstract:
Le travail de thèse a porté sur la valorisation des hydrocarbures par plasma non thermique. L'étude concerne plus particulièrement la production de gaz de synthèse (CO + H2) et d'hydrogène (H2) à partir des alcanes (CnH2n+2) par vaporeformage et/ou craquage dans une décharge glissante à la pression atmosphérique. Un réacteur plasma tri-anodes et un montage expérimental dédié ont été développés afin de contrôler et de réduire le coût de production de H2 à partir du méthane (CH4) et du propane (C3H8). L'efficacité du réacteur plasma a été étudié en fonction des paramètres expérimentaux tels que les débits de l'alcane et de la vapeur d'eau, la puissance électrique injectée et le rapport molaire eau/alcane. Malgré leurs comportements différents dans la décharge, les deux alcanes étudiés ont permis d'obtenir une concentration élevée en H2 (50%) en sortie du réacteur plasma. L'ajout d'oxygène (jusqu'à 20%) à un effet défavorable sur la production de H2. Dans tous les cas étudiés les taux de conversion de CH4 et de C3H8 restent faibles (< 45%). Les résultats expérimentaux ont été comparés à un modèle thermodynamique qui a permis de montrer que seulement 45 à 55% du gaz injecté est traité par la décharge. Un modèle physique basé sur l'équation de Potapov à deux températures a permis de décrire la décharge et calculer la température du gaz. Ces données ont ensuite été utilisées dans un modèle d'écoulement couplé à un modèle cinétique afin de comprendre les phénomènes mis en jeu dans le plasma.
43
Renou, Jean-Pierre. "Transformation génétique du chrysanthème (dendranthema grandiflora tzvelev) par agrobacterium." Angers, 1992. http://www.theses.fr/1992ANGE0009.
Full textAbstract:
La possibilité de transformation génétique du chrysanthème par agrobacterium a été étudiée. Des racines transformées ont pu être obtenues après inoculation avec a. Rhizogenes. Cependant la régénération de plantes transformées ne fut possible que dans de rares cas, après des temps de culture in vitro très longs. Des plantes transformées furent ensuite obtenues grâce à la souche d'agrobacterium. Eha 101 contenant un plasmide vecteur binaire qui comporte les gènes : npt ii, hpt et gus. Ces plantes ont été obtenues par sélection sur la résistance à la kanamycine. Différents protocoles ont conduit à l'obtention de plantes transformées, mais les conditions optimales furent l'inoculation de nuds immédiatement transférés sur un milieu sélectif contenant du cefotaxime. La transformation de plantes gus positives a été confirmée par hybridation moléculaire de l'ADN et amplification génique. Des plasmides vecteurs binaires contenant des gènes d'intérêt agronomiques ont été construits : les gènes rol a, b et c du ri tl-dna afin d'étudier leur effet sur le port de la plante, et le gène de la dihydroflavonol réductase de l'antirrhinum majus afin de permettre une modification de la couleur des fleurs de chrysanthème.
44
Cunningham, James Leo. "To develop a standard processing technique in order to maximise the bond strength between acrylic resin denture base material and polymer teeth." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359018.
Full text
45
Achkasov, Kostiantyn. "Study of negative ion surface production in cesium-free H2 and D2 plasmas : application to neutral beam injectors for ITER and DEMO." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4770.
Full textAbstract:
L'objectif de cette thèse était trouver des solutions pour produire de hauts rendements d’ions négatifs (IN) H–/D– sur des surfaces dans des plasmas de H2/D2 sans Cs pour des applications en fusion thermonucléaire. La modélisation des fonctions de distribution en énergie des ions négatifs (FDEIN) a montré un accord remarquable avec l'expérience pour les matériaux carbonés. Une méthode de reconstruction mis au point dans le cadre de cette thèse a permis de déterminer les distributions en énergie et en angle des IN émis de la surface. La méthode de reconstruction peut être appliquée à tout type de surface et/ou d’IN. Une étude de la production des IN en surface a été réalisée sur une grande variété de matériaux (des différents types de graphite, couches de diamant et métaux). L'influence sur le rendement des IN de la température de surface, de la tension de polarisation et du temps d'exposition au plasma a été étudiée. Une méthode de polarisation pulsée a été développée pour permettre l'étude de production des IN sur les surfaces de matériaux isolants tels que le diamant microcristallin non dopé. L'utilisation de diagnostics de surface ex situ tels que la désorption programmée en température (DPT) et la spectroscopie Raman ont permis de caractériser l'état de surface des matériaux carbonés. L’ensemble des études a permis de montrer que pour optimiser le rendement des IN sur le diamant, il faut travailler avec une surface moins dégradée. Celle ci peut être obtenu en augmentant la température de surface jusqu’à 400°C – 500°C ce qui permet de restaurer les propriétés intrinsèques des diamants ou en appliquant une polarisation pulséeThe objective of this thesis was to find solutions to produce high yields of H–/D– negative ions (NI) on surfaces in Cs-free H2/D2 plasmas for thermonuclear fusion applications. Modeling of the negative-ion energy distribution functions (NIEDF) has shown remarkable agreement with experiment for carbon materials. The reconstruction method developed in the course of this thesis has allowed to determine the distribution in energy and angle of NI emitted from the surface. The reconstruction method can be applied to any type of surface and/or NI. A study was performed on a large variety of materials: different types of graphite, diamond films and metals. The influence of surface temperature, bias and plasma exposure time on NI yield was investigated. The method of pulsed bias was developed to enable the study of NI production on surfaces of insulating materials such as microcrystalline non-doped diamond (MCD). The use of ex situ surface diagnostics such as temperature programmed desorption (TPD) and Raman spectroscopy has allowed to characterize the surface state of carbon materials. Basing on the performed studies, we demonstrated that to optimize the NI yield on diamond one has to work with a less degraded surface. This can be obtained rising the surface temperature to 400°C–500°C which allows restoring intrinsic properties of diamond. The less degraded surface state can also be obtained by applying the pulsed bias which gives the possibility to increase the H2/D2 surface coverage and diminish the defects induced by plasma exposure
46
Pristavita, Ramona. "Transferred arc production of fumed silica : rheological properties." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99787.
Full textAbstract:
The thermal plasma production of fumed silica in a transferred arc consists of the decomposition of quartz to SiO (g) and oxygen followed by an oxidizing quench back to SiO2. The particles formed have diameters of the order of 10 to 20 nm and are linked in a three dimensional branched chain aggregate. Previous work by Addona and Munz (1999) demonstrated the technical feasibility of producing fumed silica using this method, but was unable to demonstrate the special rheological properties of the powder. The most important characteristic of fumed silica is the presence of hydroxyls on the surface of the particles, in the form of isolated hydroxyl groups, hydrogen-bonded hydroxyl groups and siloxane groups.In the present work, we studied the changes in the powder quality by varying the quench conditions used for the production of the powder and by agglomerating the obtained particles. The fumed silica was agglomerated by conveying in a length of tubing with sharp bends. The powder was characterized using BET, Viscosity tests, FT-IR, TEM, SEM and XRD. The product was compared to both a commercial product (Aerosil 200) and the material previously produced by Addona. Tests were done before and after the agglomeration experiments.
The experimental results showed that the agglomeration had no effect on the powder's rheological properties. We concluded that the smaller viscosity values obtained for the plasma produced fumed silica were due to the lack of the free hydroxyl groups from the surface of the particles.
47
Santiago, Santiago Luz Mary. "Plastic Scintillation microspheres for radioactivity determination: synthesis, characterization and production." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/380546.
Full textAbstract:
Plastic scintillation microspheres (PSm) are a solid dispersion of one or more fluorescent solutes encapsulated within a polymeric matrix. PSm appear as an alternative to the use of liquid scintillation cocktails for radioactivity determination with the advantage of avoiding the mixed waste, for the measurement of salty samples, for performing measurements in continuous, or for employing them as a medium to join the measurement and separation steps. However, PSm are not completely available in the market, since only a few providers supply them at a high cost and with a limited range of sizes and compositions.
This thesis has been focused in two main objectives. The first one has been the evaluation of the feasibility of different methodologies to produce PSm, starting at laboratory scale and addressing their production at a higher scale. The second one has been to increase the knowledge about the energy transfer mechanism through the evaluation of different quenching agents and different organic scintillators.
The production of PSm was successfully performed through organic solvent extraction/evaporation methodology (E/E). Other techniques based on drying, the Spray Drying (SD) and the supercritical antisolvent (SAS) were also evaluated. The E/E allowed the production of PSm at laboratory and at large scale with features and radiometric performances comparable to those of the commercial ones, and also producing PSm with the ability for alpha/beta discrimination. On the other hand, SD and SAS proved to produce PSm and polystyrene based submicron particles, respectively, which enabled the measurement of radioactivity but involving a high associated operational cost and a low production yield.
Finally, the evaluation of the energy transfer mechanism was performed by conducting a systematic study of the interference of several quenching agents when different organic scintillators were employed. Moreover, the wide range of PSm diameters obtained allowed the study of the relationship between the size and the radiometric capacities, resulting in a better understanding of the energy transfer mechanism through the evaluation of the particle and optical quenching.Las microesferas de centelleador plastico (PSm) son una dispersión sólida de uno o más solutos fluorescentes disueltos y encapsulados en una matriz polimérica. Su diámetro puede variar desde los pocos hasta varios centenares de micrómetros. Las PSm han aparecido como una alternativa al uso de los cócteles de centelleador líquido para la mayoría de las deteminaciones de radionucleidos de media y alta energía, con la ventaja de que al estar polimerizadas se evita la producción del residuo mixto (mezcla de residuos orgánicos y radioactivos). Por otro lado, las PSm son de utilidad en las medidas de muestras salinas, de sistemas de medida en continuo y además sirven de soporte para la inmovilización de extractantes selectivos a determinados radionucleidos. Sin embargo, las PSm no están completamente disponibles en el mercado, ya que existen sólo un par de casas comerciales capaces de proveerlas a un alto coste y con un rango limitado de diámetros y composiciones. El presente trabajo ha sido enfocado en dos objetivos principales. El primero, ha sido evaluar diferentes metodologías que permitan la producción de PSm de diferentes diámetros y composiciones a escala de laboratorio para superar la dependencia sobre los proveedores comerciales y a su vez, ampliar su uso en nuevas aplicaciones. El segundo objetivo, ha sido explorar el mecanismo de transferencia de energía en las medidas de radionucleidos cuando se emplean las PSm. La síntesis de PSm se llevó a cabo por medio de diferentes técnicas. La primera, basada en la evaporación/extracción del disolvente orgánico. Dicha técnica permitió la producción de PSm con un alto rendimiento y con características físicas y capacidades radiométricas similares a las de las microesferas de centelleador plástico de origen comercial. También permitió la evaluación de la encapsulación de los solutos fluorescentes, la producción de microesferas con capacidad para discriminar partículas alfa y beta, la evaluación de los parámetros de síntesis para optimizar la producción y además se empleó para producir PSm a una mayor escala que la empleada en el laboratorio (prueba de concepto con equipos industriales). Por otro lado, la producción de PSm mediante las técnicas basadas en el secado del disolvente orgánico (Spray Drying y antidisolvente supercrítico). Dichas técnicas permitieron la producción de PSm y de partículas poliméricas centelleadoras de tamaño submicrométrico, respectivamente, capaces de medir la radioactividad. Sin embargo, resultaron en un alto coste operacional asociado y bajos rendimientos de producción. Finalmente, la evaluación del mecanismo de transferencia de energía se llevó a cabo mediante el estudio sistemático de diferentes interferentes (NaCl, BaCl2, glicerina, nitrometano y naranja de metilo) y distintos centelleadores orgánicos (PSm de diferentes diámetros, cóctel de centelleador líquido y cóctel de centelleador gel) para la medida de dos emisores beta de baja y alta energía, 3H y 36Cl, respectivamente. Adicionalmente, teniendo en cuenta el amplio rango de diámetros de PSm obtenidos mediante las diferentes metodologías, fue posible realizar algunas observaciones sobre la relación de las capacidades radiométricas de diferentes radionucleidos respecto al tamaño de diámetro de las PSm, basadas principalmente en los fenómenos de quenching de partícula y de quenching óptico.
48
McKee, Erik Scott. "Neutron Production from Z-pinch Plasmas at the 1 MA Zebra Generator." Thesis, University of Nevada, Reno, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10247687.
Full textAbstract:
Neutrons produced deuterium Z-pinch plasmas are widely acknowledged to be a consequence of highly accelerated deuterons undergoing nuclear fusion with relatively stationary deuterons. The acceleration is thought to occur in intense fields created in the MHD instabilities that punctuate the plasma column. Interestingly, the energies of the accelerated ions exceed the applied voltage across the electrode gap. We use the 1 MA Zebra pulsed-power generator at the Nevada Terawatt Facility (NTF) to explore this poorly understood fast neutron production mechanism by creating deuterium Z-pinches in three distinct types of target loads. The loads are a cylindrical shell of deuterium gas, the far less explored deuterided palladium wire arrays, and a deuterium-carbon ablated laser plume target, which is unique to the NTF.
The pinch dynamics vary considerably in these three targets and provide the opportunity to explore the ion acceleration mechanism. We infer the characteristics of the accelerating fields from a wide range of diagnostic data including the neutron yield, energy spectrum and angular distribution, and the properties of the matching electron beams that are accelerated in the same field, and the energetic X-rays they produce on stopping. The plasma and the instabilities were recorded on several high-speed imaging diagnostics along with time-integrated soft (<10 keV) X-ray pinhole images. The three load types produced total neutron yields in the 108–1010 n/pulse range. The synchronization we observe between the ion and electron beams and the development of instabilities leads us to conrm the acceleration hypothesis. We also present the characteristics of the fields and ion beams in these varied pinches.
49
Robert, Jean-Marie Paul. "Dileptons, spectral weights, and conductivity in the quark-gluon plasma." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101171.
Full textAbstract:
This thesis re-examines soft dilepton emission from a weakly coupled Quark-Gluon Plasma. It shows that Braaten, Pisarski, and Yuan's result, that the dilepton rate rises as 1/q40 (and the spectral weight scales as 1/q0) at small energy q0 ≪ gT is correct, but that the coefficient they found for this behavior is not correct, because their analysis was incomplete. At still smaller scales, the behavior moderates to ∝ 1/q20 for q0 ≲ g4T, consistent with a finite electrical conductivity. An evaluation of the spectral weight in the q0 ~ g4 T region by kinetic theory techniques is carried out. The spectral weight is then shown to satisfy a sum rule, which makes the determination of electrical conductivity from the Euclidean correlation function very challenging.
50
Liu, Fuming. "La production des particules dans le modèle Nexus." Nantes, 2002. http://www.theses.fr/2002NANT2033.
Full textAbstract:
Pour étudier la formation d'un plasma de quarks et de gluons, il est d'une importance capitale de comprendre en détails la dynamique des collisions hadroniques. La "Parton based Gribov-Regge Theory", dont la solution numérique est le modèle neXus, est une approche cohérente de la description de la diffusion hadron-hadron et des premiers instants des collisions noyau-noyau aux énergies ultra-relativistes. Les résultats des simulations permettent, par des comparaisons quantitatives avec les données expérimentales, une exploration efficace et systématique de certains domaines de la physique inaccessibles autrement. La connaissance de ces conditions initiales est fondamentale pour n'importe quel traitement théorique d'une possible transition de phase parton-hadron, que les expériences basées sur les ions lourds cherchent à décrire. .To study the formation of a quark gluon plasma, it is of crucial importance to understand in detail the collision dynamics. Parton based Gribov-Regge Theory, realized in the Monte Carlo code neXus, provides a consistent approach for hadron-hadron scattering and the initial stage of nucleus-nucleus collisions at ultra-relativistic energies