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Lundskog, Anders. "Characterization of AlGaN HEMT structures." Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9729.
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During the last decade, AlGaN High Electron Mobility Transistors (HEMTs) have been intensively studied because their fundamental electrical properties make them attractive for highpower microwave device applications. Despite much progress, AlGaN HEMTs are far from fully understood and judged by the number of published papers the understanding of advanced structures is even poorer. This work is an exploration of the electrical and structural properties of advanced HEMT structure containing AlN exclusionlayer and double heterojunctions. These small modifications had great impact on the electrical properties.
In this work, AlGaN HEMT structures grown on SiC substrates by a hot-wall MOCVD have been characterized for their properties using optical microscopy, scanning electron microscopy, transmission electron microscopy, capacitance/voltage, eddy-current resistivity, and by homebuilt epi-thickness mapping equipment.
A high electron mobility of 1700 [cm2/Vs] was achieved in an AlN exclusion-layer HEMT. A similar electron mobility of 1650 [cm2/Vs] was achieved in a combination of a double heterojunction and exclusion-layer structure. The samples had approximately the same electron mobility but with a great difference: the exclusion-layer version gave a sheet carrier density of 1.58*1013 [electrons/cm2] while the combination of double heterojunction and exclusion-layer gave 1.07*1013 [electrons/cm2]. A second 2DEG was observed in most structures, but not all, but was not stable with time.
The structures we grew during this work were also simulated using a one-dimensional Poisson-Schrödinger solver and the simulated electron densities were in fairly good agreement with the experimentally obtained. III-nitride materials, the CVD concept, and the onedimensional solver are shortly explained.
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Rajasingam, Srikaran. "Applications of Raman spectroscopy to AlxGaâ‚-xN technology : AlN substrates, high temperature annealing and HEMT devices." Thesis, University of Bristol, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407018.
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Said, Nasri. "Evaluation de la robustesse des technologies HEMTs GaN à barrière AlN ultrafine pour l'amplification de puissance au-delà de la bande Ka." Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0425.
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La filière GaN est stratégique pour l'Union Européenne car elle permet d'améliorer la puissance et le rendement des systèmes radar et de télécommunication, notamment dans les bandes S à Ka (jusqu'à 30 GHz). Pour répondre aux besoins des futures applications, telles que la 5G et les systèmes militaires, le développement des technologies GaN vise à augmenter les fréquences jusqu'aux ondes millimétriques. Cela nécessite d'optimiser l'épitaxie et la réduction de la longueur de grille à moins de 150 nm, ainsi que l'utilisation de barrières ultrafines (<10 nm) pour éviter les effets de canaux courts. La substitution de la barrière AlGaN par du AlN représente une solution pour maintenir de bonnes performances tout en miniaturisant les composants. Dans ces travaux de thèse, plusieurs variantes technologiques à barrière AlN ultrafine (3 nm) sur des canaux GaN non-dopés de différentes épaisseurs, développées par le laboratoire IEMN sont étudiés. L'évaluation des performances et de la robustesse de ces technologies, cruciale pour leur qualification et utilisation dans des missions à long-terme, sont ainsi menées en mode DC et RF afin de définir les zones de sécurité de fonctionnement (SOA) et d’identifier les mécanismes de dégradation.La campagne de caractérisation DC et pulsée a révélé une faible dispersion des composants après leur stabilisation électrique, reflétant une bonne maîtrise technologique : ceci permet par ailleurs des études statistiques et des analyses génériques plus pertinentes sur l’ensemble des lots de composants étudiés. L'analyse de la sensibilité des dispositifs à des températures allant jusqu'à 200°C a prouvé la forte stabilité thermique des performances en mode diode et transistor, en suivant les indicateurs paramétriques représentatifs des modèles électriques des composants (courants de saturation et courants de fuite, tension de seuil, taux de retard aux commandes entrée sortie, …). L’ajout d’une barrière arrière AlGaN sur une couche tampon moyennement dopée C a réglé le compromis entre confinement des électrons et densités de pièges. Les tests de vieillissement accéléré en mode DC à différents points de polarisation et en mode RF par paliers de puissance d’entrée ont montré que la barrière arrière AlGaN confère une meilleure stabilité des courants de fuite et des courbes I(V) statiques, une réduction des effets de piégeage et d'auto-échauffement, ainsi qu'une extension de la SOA-DC opérationnelle. Les tests de vieillissement accéléré en mode dynamique à 10 GHz sur des HEMTs avec différents espacements grille-drain ont montré que la SOA-RF ne dépend pas de cet espacement, mais plutôt de la capacité de la grille à supporter des signaux RF élevés, avant dégradation brutale de cette dernière. En utilisant une méthode de modélisation non linéaire originale, prenant en compte le phénomène d'auto-polarisation, les dispositifs avec barrière AlGaN se sont révélés plus robustes également en RF. Cela se traduit par leur compression plus tardive de gain, allant jusqu’à +10dB et sans dégradation électrique ainsi que structurelle apparente (observée par photoluminescence). Indépendamment de la variante AlN/GaN, le mécanisme de dégradation en stress RF correspond au claquage abrupt de la grille Schottky conduisant à sa défaillance. Ces résultats prouvent que les composants sont plus sensibles aux conditions de polarisation DC qu’au niveau de signal RF injecté [...]The GaN industry is strategic for the European Union because it enhances the power and efficiency of radar and telecommunication systems, especially in the S to Ka bands (up to 30 GHz). To meet the needs of future applications such as 5G and military systems, GaN technology development aims to increase frequencies to the millimeter-wave range. This requires optimizing epitaxy and reducing the gate length to less than 150 nm, as well as using ultrathin barriers (<10 nm) to avoid short-channel effects. Replacing the AlGaN barrier with AlN is a solution to maintain good performance while miniaturizing devices. In this thesis, several technological variants with an ultrathin AlN barrier (3 nm) on undoped GaN channels of various thicknesses, developed by the IEMN laboratory, are studied. The evaluation of the performance and robustness of these technologies, crucial for their qualification and use in long-term profil missions, is conducted in both DC and RF modes to define the safe operating areas (SOA) and identify degradation mechanisms.The DC and pulsed characterization campaign revealed low component dispersion after electrical stabilization, reflecting good technological control. This also allows for more relevant statistical studies and generic analyses across all component batches studied. The sensitivity analysis of the devices at temperatures up to 200°C demonstrated strong thermal stability in diode and transistor modes, following parametric indicators representative of the electrical models of the components (saturation currents and leakage currents, threshold voltage, gate and drain lags rates, ...). The addition of a AlGaN back-barrier on a moderately C-doped buffer layer resolved the trade-off between electron confinement and trap densities. Accelerated aging tests in DC mode at various biasing conditions and in RF mode by input power steps showed that the AlGaN back-barrier provides better stability in leakage currents and static I(V) curves, reduces trapping and self-heating effects, and extends the operational DC-SOA.Dynamic accelerated aging tests at 10 GHz on HEMTs with different gate-drain spacings showed that the RF-SOA does not depend on this spacing but rather on the gate's ability to withstand high RF signals before abrupt degradation occurs. Using an original nonlinear modeling method that considers the self-biasing phenomenon, devices with the AlGaN back-barrier proved to be more robust in RF as well. This is reflected in their later gain compression, up to +10 dB, without apparent electrical or structural degradation (as observed by photoluminescence). Regardless of the AlN/GaN variant, the RF stress degradation mechanism corresponds to the abrupt breakdown of the Schottky gate, leading to its failure. These results indicate that the components are more sensitive to DC bias conditions than to the level of injected RF signals [...]
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Bradley, Shawn Todd. "Investigation of AlGaN films and nickel/AlGaN Schottky diodes using depth-dependent cathodoluminescence spectroscopy and secondary ion mass spectrometry." Columbus, Ohio : Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1078329692.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xxii, 182 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Leonard J. Brillson, Dept. of Electrical Engineering. Includes bibliographical references (p. 173-182).
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Taking, Sanna. "AlN/GaN MOS-HEMTs technology." Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3356/.
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The ever increasing demand for higher power devices at higher frequencies has prompted much research recently into the aluminium nitride/gallium nitride high electron mobility transistors (AlN/GaN HEMTs) in response to theoretical predictions of higher performance devices. Despite having superior material properties such as higher two-dimensional electron gas (2DEG) densities and larger breakdown field as compared to the conventional aluminium gallium nitride (AlGaN)/GaN HEMTs, the AlN/GaN devices suffer from surface sensitivity, high leakage currents and high Ohmic contact resistances. Having very thin AlN barrier layer of ∼ 3 nm makes the epilayers very sensitive to liquids coming in contact with the surface. Exposure to any chemical solutions during device processing degrades the surface properties, resulting in poor device performance. To overcome the problems, a protective layer is employed during fabrication of AlN/GaN-based devices. However, in the presence of the protective/passivation layers, formation of low Ohmic resistance source and drain contact becomes even more difficult. In this work, thermally grown aluminium oxide (Al2O3) was used as a gate di- electric and surface passivation for AlN/GaN metal-oxide-semiconductor (MOS)-HEMTs. Most importantly, the Al2O3 acts as a protection layer during device processing. The developed technique allows for a simple and effective wet etching optimisation using 16H3PO4:HNO3:2H2O solution to remove Al from the Ohmic contact regions prior to the formation of Al2O3 and Ohmic metallisation. Low Ohmic contact resistance (0.76Ω.mm) as well as low sheet resistance (318Ω/square) were obtained after optimisation. Significant reduction in the gate leakage currents was observed when employing an additional layer of thermally grown Al2O3 on the mesa sidewalls, particularly in the region where the gate metallisation overlaps with the exposed channel edge. A high peak current ∼1.5 A/mm at VGS=+3 V and a current-gain cutoff frequency, fT , and maximum oscillation frequency, fMAX , of 50 GHz and 40 GHz, respectively, were obtained for a device with 0.2 μm gate length and 100 μm gate width. The measured breakdown voltage, VBR, of a two-finger MOS-HEMT with 0.5μm gate length and 100 μm gate width was 58 V. Additionally, an approach based on an accurate estimate of all the small-signal equivalent circuit elements followed by optimisation of these to get the actual element values was also developed for AlN/GaN MOS-HEMTs. The extracted element values provide feedback for further device process optimisation. The achieved results indicate the suitability of thermally grown Al2O3 for AlN/GaN-based MOS-HEMT technology for future high frequency power applications.
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Xiao, Xiao Mr. "Purification and Characterization of Rhodobacter sphaeroides Polyhistidine-tagged HemA and Comparison with Purified Polyhistidine-tagged HemT." Bowling Green State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1371650467.
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John, Dylan Boone. "Atomistic Modeling of AlN/GaN HEMTs for Applications in Harsh Environments." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/572.
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AlN/GaN high-electron mobility transistors (HEMT) are subject to internal structural and electrostatic fields originating mainly from: (i) the fundamental crystal atomicity and the interface discontinuity between dissimilar materials, (ii) atomistic strain, (iii) piezoelectricity, and (iv) spontaneous polarization (pyroelectricity). In this thesis, through numerical simulations, we have studied the origin and effects of these competing internal fields on the electrostatics and the I-V characteristic of scaled nitride HEMT structures. It is shown that strain in these devices is asymmetric and long-ranged (demanding simulations using millions of atoms). The resulting piezoelectric polarization is arge and atomistic in nature. However, the pyroelectric potential is significantly larger than the piezoelectric counterpart and opposes the latter at the InN/GaN interface as opposed to AlGas which only produces a piezoelectric potential. The polarization induced charge density is computed using a three-dimensional Poisson solver and shown to be strongly dependent on the thickness of the AlN barrier layer. This finding has been validated using available experimental data. We have also demonstrated that the olarization fields alone can induce channel carriers at zero external bias and lead to a significant increase in the ON current.
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Coulianos, Natalie N. G. "A comparison of ALA synthase gene transcription in three wild type strains of Rhodobacter sphaeroides." Bowling Green State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1308169087.
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Tilstra, Liesbeth. "Grenzen aan het stakingsrecht : het Nederlandse rechtsoordeel over collectieve actie van werknemers getoetst aan het Europees Sociaal Handvest /." Deventer : Kluwer, 1994. http://www.gbv.de/dms/spk/sbb/recht/toc/272312207.pdf.
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Libkind, Marianna. "SiaA: A Heme Protein." Digital Archive @ GSU, 2007. http://digitalarchive.gsu.edu/chemistry_hontheses/2.
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The protein SiaA (Streptococcal iron acquisition) is involved in heme uptake in the bacterium Streptococcus pyogenes. It is difficult to obtain this protein in its fully holo form (completely loaded with heme). To increase the concentration of heme in the growing cell, we added ä-aminolevulinic acid (ALA) and ferrous sulfate (FeSO4), precursors of heme, to the growth media. Neither increasing the concentration of heme in vivo, nor growth at lower temperature for longer times, increased the production of holoprotein. The classical method of measuring the concentration of heme in a newly discovered heme protein is cumbersome. We have developed an improved method, which gives a solution that is more stable and has a cleaner spectrum. With further development, this new technique may replace the classical assay. Background information on S. pyogenes, SiaA, ABC transporters, heme biosynthesis, and the pyridine hemochrome assay are described.
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Nelissen-de, Vos Yolande Catharina Magdalena. "Slaapklachten in de periode voorafgaande aan het hartinfarct." Maastricht : Maastricht : Universitaire Pers Maastricht ; University Library, Maastricht University [Host], 1994. http://arno.unimaas.nl/show.cgi?fid=6958.
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Urk, H. van. "Even stilstaan bij het werk aan de weg." [S.l.] : Rotterdam : [de auteur] ; Erasmus University [Host], 1992. http://hdl.handle.net/1765/7406.
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Inaugurale rede Erasmus Universiteit Rotterdam.Rede uitgesproken op 3 april 1992 bij de aanvaarding van het ambt van bijzonder hoogleraar in de Vaatchirurgie aan de Erasmus Universiteit Rotterdam.
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Coulianos, Natalie N. G. "Regulation of hemT expression in Rhodobacter sphaeroides wild type strain 2.4.9." Bowling Green State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1522070574933425.
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Vaughan, Haydn. "Accelerated Corrosion Test with Operation Simulation of All-Aluminum Microchannel Heat Exchangers." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849775/.
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The HVAC&R industry is looking to transition from copper-aluminum heat exchangers to all-aluminum microchannel technology. The want for the transition stemmed from seeing the performance improvement of all-aluminum microchannel radiators in the automotive industry. Applications differ between the two industries; therefore, applying this technology for HVAC&R use must be validated. Research towards operating modes of an all-aluminum heat exchanger in a defined corrosive environment will provide the industry with a better understanding of heat exchanger design and heat exchanger material selection. The worth in this is preventing overdesign and producing more efficient heat exchangers. Furthermore, ASHRAE members and the corrosion community will find value in a defined corrosion system and corrosion test procedure. The information gained through past research has progressed assessment of material performance; however, the methods improperly simulate and expedite natural weathering. The most common method being used is the ASTM (American Society of Testing Materials) Sea Water Acetic Acid Test. The research discussed in this paper was focused on improving a standard corrosion system by implementing system modifications to simulate heat exchanger operation while performing a modified wet-dry cyclic test (e.g. ASTM G85 Annex 5). The goal is to produce results that are more representative of natural corrosion behavior and its forms. Current results were gathered from five of ten samples that underwent initial testing. Finally, possible improvements towards the chamber system and the test method, including the salt solution, are discussed.
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Abou, Daher Mahmoud. "Réalisation et optimisation de transistors HEMT GaN forte puissance et haute fréquence par technologie de transfert de couches sur substrat hôte." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30046.
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Le marché des télécommunications tire profit des nouvelles technologies Nitrures qui sont en véritable rupture de performances par rapport aux technologies traditionnellement utilisées. Les recherches actuelles ouvrent de nombreuses pistes et solutions alternatives afin de couvrir des contraintes parfois antagonistes de coût, de performances et/ou de fiabilité. La plupart des HEMTs AlGaN / GaN est fabriquée sur un substrat de silicium hautement résistif à faible coût ou sur substrat SiC beaucoup plus onéreux et sensible du point de vue approvisionnement. Les contraintes de performances électriques requises lors de l'intégration de ces technologies dans les systèmes radars, les satellites et en télécommunication rendent les HEMTs très dépendants au paramètre de température de fonctionnement, essentiellement liée à la forte puissance dissipée lors du transfert d'énergie statique/dynamique. En effet, ces composants sont capables de générer des densités de puissance élevées dans le domaine des hyperfréquences. Aussi, l'augmentation de la fréquence de fonctionnement s'accompagne d'une augmentation de la puissance dissipée engendrant le phénomène d'auto-échauffement qui influe sur les performances des composants (ID,max,ft,fmax...). Dans ce contexte, plusieurs solutions ont déjà été proposées dans la littérature (utilisations des substrats composites, passivation des composants, etc...). De plus, la technologie de transfert des HEMTs d'un substrat de croissance initial vers un substrat hôte de bonne conductivité thermique (tel que le substrat de diamant) est une solution prometteuse, encore peu détaillée à ce jour. L'objectif de ce travail de thèse est d'améliorer la dissipation thermique et donc les performances et la fiabilité des transistors HEMT hautes fréquences en utilisant la technologie de transfert de couche. Les hétérostructures AlGaN/GaN sont développées sur substrat de silicium par MOCVD au CHREA. Après la fabrication des HEMTs sur substrat de silicium au sein du laboratoire IEMN, les composants (pour lesquels le substrat silicium a été retiré) sont transférés sur un substrat de diamant. Ce transfert est obtenu grâce à un collage par thermocompression de couche d'AlN pulvérisées sur chaque surface à assembler (face arrière des transistors et substrat diamant). Le procédé de transfert développé n'a pas endommagé la fonctionnalité des transistors HEMTs AlGaN/GaN à faible longueur de grille (Lg = 80 nm). Les transistors de développement 2x35 µm transférés sur diamant présentent un courant ID,max = 710 mA.mm-1, une fréquence de coupure ft de 85GHz et une fréquence d'oscillation fmax de 144GHz. Toutefois, la technique de transfert mérite des phases d'optimisations (notamment pour diminuer l'épaisseur et améliorer la qualité cristalline et la conductivité thermique des couches d'AlN) afin de mieux satisfaire aux contraintes de réduction de résistance thermique de cette couche d'assemblage et ainsi limiter le phénomène d'auto-échauffement relevé à l'issue de ces travaux de thèseWireless telecommunication market largely benefits from new nitride technologies, which reach outstanding performance compared with traditional technologies. Current research is opening up many new strategies and alternative solutions to address simultaneously antagonist considerations such as cost, performances and/or reliability. Most AlGaN / GaN HEMTs are fabricated on a low cost, highly resistive silicon substrate or on a much more expensive and supply sensitive SiC substrate. However, the electrical performance constraints required when these technologies are integrating into radar systems, satellites and in telecommunications systems make them dependent to the operating temperature parameter, mainly linked to the high power dissipation during static/dynamic energy transfer. Indeed, these components are capable of generating high power densities in the microwave range. However, the operating frequency increase leads an increase of the power dissipation, generating the self-heating phenomenon which influences the devices performance (ID,max,ft,fmax...). In this context, several solutions were already proposed in the literature (use of composite substrates, passivation of devices, etc.). Furthermore, the layer transfer technology to report HEMTs from growth substrate onto a host substrate with a good thermal conductivity (such as diamond substrate) is a promising solution, still poorly detailed to date. The objective of this thesis work is to improve the heat dissipation and thus the performance and reliability of high-frequency HEMT transistors by using a layer transfer technology. AlGaN / GaN heterostructures are grown on a silicon substrate by MOCVD at CHREA. After the fabrication of HEMTs on a silicon substrate, AlGaN / GaN devices (for which the silicon substrate has been removed) are transferred onto a CVD diamond substrate. This transfer is obtained by thermocompression bonding of sputtered AlN layers on each surface to be assembled (backside of the transistors and diamond substrate). This transfer process has not damaged the functionality of the transistors with short gate length (Lg = 80 nm). The AlGaN/GaN HEMTs with a 2x35 µm development transferred onto diamond of feature a current ID,max = 710 mA.mm-1, a cutoff frequency ft of 85GHz and an oscillation frequency fmax of 144GHz. However, this transfer technique requires optimization phases (especially to reduce thickness and improve the crystalline quality and thermal conductivity of AlN layers) in order to reduce the thermal resistance of this adhesion layer and to limit the self-heating phenomenon noted at the end of this thesis work
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Simon, Henk. "Publiekrecht of privaatrecht? : Een geschiktheidsonderzoek aan de hand van het nutsmaximalisatiebeginsel toegespitst op het gebruik van het privaatrecht door het bestuur /." Zwolle : Tjeenk Willink, 1993. http://www.gbv.de/dms/spk/sbb/recht/toc/277912245.pdf.
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Meershoek, Agnes Maria. "Weer aan het werk verzekeringsgeneeskundige verzuimbegeleiding als onderhandeling over verantwoordelijkheden /." [Amsterdam : Maastricht : Thela Thesis] ; University Library, Maastricht University [Host], 1999. http://arno.unimaas.nl/show.cgi?fid=6867.
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Weij, Jan-Willem van der. "Beweging en bewogenheid : het prozagedicht in de Nederlandse literatuur aan het einde van de negentiende eeuw /." Amsterdam : Thesis publ, 1997. http://catalogue.bnf.fr/ark:/12148/cb391376807.
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Hudson, P. T. W. "Neurale netwerken en het symbolisch paradigma bouwen aan de zesde generatie /." Maastricht : Maastricht : Rijksuniversiteit Limburg ; University Library, Maastricht University [Host], 1991. http://arno.unimaas.nl/show.cgi?fid=12952.
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Hung, Ting-Hsiang. "Novel High-k Dielectric Enhanced III-Nitride Devices." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437684419.
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Boorsma, Miranda. "Kunstmarketing : hoe marketing kan bijdragen aan het maatschappelijk functioneren van kunst, in het bijzonder van toneelkunst in Nederland /." Groningen : Rijksuniversiteit Groningen, 1998. http://bibpurl.oclc.org/web/31615.
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Gerards, Janneke Hilligje. "Rechterlijke toetsing aan het gelijkheidsbeginsel : een rechtsvergelijkend onderzoek naar een algemeen toetsingsmodel /." Den Haag : Maastricht : Sdu Uitgevers ; University Library, Maastricht University [Host], 2002. http://arno.unimaas.nl/show.cgi?fid=7521.
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De, Lange Hanine. "Didaktiese hulpverlening aan leerders met 'n kogleêre inplanting wat taalagerstande ontwikkel het." Thesis, Cape Peninsula University of Technology, 2009. http://hdl.handle.net/20.500.11838/1888.
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Thesis (MTech(Education))--Cape Peninsula University of Technology, 2009When a child enters formal education a certain level of development and experience is expected. If there is a language deficit or shortfall upon entering formal schooling, a negative perception of schooling can develop, resulting in a low level of success in the classroom. Research has clearly shown that learners with a hearing deficit, and who received very little stimulation at an early age, tended to develop a language deficit which hampered their entrance into, as well as their performance in mainstream education. The ideal is thus that a child should experience success in the learning process at the earliest possible stage. Hereupon he can develop and realise his full potential as a human being. Children who experience early success should be more capable of coping with the challenges that schooling and learning present. If these learners receive early intervention to support their language development it could lead to being more successful in mainstream education. Learners with a cochlear implant must receive intensive hearing and communicative training. They are taught how to effectively interpret the sound relayed by the implant, and thereafter, if possible, be able to use this "hearing ability" to enter into interactive spoken language. Motivation and support from parents, family and friends is a determining factor in the successful use of the implant. This should lead to a learner being able to reach his full potential. From the research conducted it has become evident that the language deficit retrogression of the child leads to under-achievement when formal schooling begins.This is because of different hearing difficulties. However, if such a pre-school child is assisted and supported at an early stage through effective intervention strategies, language deficit can be decreased or even completely cured. In this study a learner who had received a cochlear implant, was closely observed. A significant improvement in his language ability was evinced. The action research study was an individualised teaching and learning situation with a learner who had a cochlear implant and with a language deficit. Over a period of 19 months different intervention strategies were used to improve the learner's language ability. The intervention strategies which were successful can be used as a possible point of departure for further research and study to give educators and parents a better insight into this problem. Through intensive research these findings can be developed as a possible support system or methodolgy for educators in the inclusive classroom.
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Brinkman, Herman. "Dichten uit liefde : literatuur in Leiden aan het einde van de Middeleeuwen /." Hilversum : Verloren, 1997. http://catalogue.bnf.fr/ark:/12148/cb376363875.
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Barnes, Javier. "Application of Cyclic Polarization of Aluminum 3003 Used in All-Aluminum Microchannel Heat Exchangers." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc801930/.
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All-aluminum microchannel heat exchangers are designed to significantly reduce refrigerant charge requirements, weight, reduced brazed joints, and decreased potential for leakage by increasing reliability. Al 3003 alloy is corrosion resistant and can be formed, welded, and brazed but the issue with all-aluminum heat exchangers is localized corrosion (pitting) in corrosive environments. Currently, there is no universally accepted corrosion test that all coil manufacturers use to characterize their products. Electrochemical testing method of cyclic polarization was employed in this investigation and relevant parameters including electrolyte corrosive agent and its concentration, electrolyte pH, and applied potential scan rate was varied to find an optimal set of parameters. Results of cyclic polarization of Al 3003 in electrolytes containing various concentrations of NaCl were compared with those of the tests in Sea Water Acidified Accelerated Test (SWAAT) electrolyte and it is shown the SWAAT electrolyte (4.2% sea salt acidified to pH of 2.9) is by far stronger (in terms of corrosivity) than typical 3.5% NaCl solution used in most corrosion testing. Corrosion rates (g/m2yr) of Al 3003 measured in this investigation were comparable to those provided by ISO 9223 standard corresponding to C1 through CX categories. Duration of cyclic polarization test is much shorter than that of SWAAT and results obtained in this test is more reproducible compared to those of SWAAT. Scanning electron microscopy micrographs show typical pit depths of about 50 μm.
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Kolluri, Sridevi. "Upregulation of Heme Pathway Enzyme ALA Synthase-1 by Glutethimide and 4,6-Dioxoheptanoic Acid and Downregulation by Glucose and Heme: A Dissertation." eScholarship@UMMS, 2004. https://escholarship.umassmed.edu/gsbs_diss/121.
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5-Aminolevulinic acid synthase-1 (ALAS-1) is the first and normally rate-controlling enzyme for hepatic heme biosynthesis. ALAS-1 is highly inducible, especially in liver, in response to changes in nutritional status, and to drugs that induce cytochrome P-450. The critical biochemical abnormality of the acute porphyrias, a group of disorders of heme synthesis, is an uncontrolled up-regulation of ALAS-1. High intakes of glucose or other metabolizable sugars and intravenous heme are the cornerstones of therapy for acute attacks of porphyrias and both repress the over-expression ALAS-1, although their mechanisms of action have not been fully characterized.
In this work, the chick hepatoma cell line, LMH, was characterized with respect to its usefulness in studies of heme biosynthesis and compared with chick embryo liver cells (CELCs), a widely used model for studies of heme metabolism. The inducibility of ALAS-1 mRNA and enzyme activity and accumulation of porphyrins by chemicals were used to evaluate heme biosynthesis in LMH cells. Repression of ALAS-1 mRNA and induced activity by exogenous heme (20 μM) was shown to occur in LMH cells as in CELCs. In addition, a synergistic induction of ALAS-1 enzyme activity was observed in LMH cells, as shown previously in CELCs, by treatment with a barbiturate-like chemical, Glutethimide (Glut), in combination with an inhibitor of heme synthesis, 4,6-dioxoheptanoic acid (DHA). This induction of ALAS-1 enzyme activity is analogous to what occurs in patients with acute hepatic porphyrias and LMH cells were used to further characterize effects of Glut, DHA, glucose, and heme on ALAS-1.
A "glucose effect" to decrease Glut and DHA-induced ALAS-1 enzyme activity was obtained in LMH cells and CELCs in the absence of serum or hormones. This "glucose effect" was further characterized in LMH cells using a construct containing approximately 9.1 kb of chick ALAS-1 5'- flanking and 5' -UTR region attached to a luciferase/reporter gene (pGcALAS9.1-Luc). Glut (50 μM) and DHA (250 μM) synergistically induced luciferase activity (5-fold) in LMH cells transiently transfected with pGcALAS9.l-Luc. Addition of glucose (11 or 33 mM), in a dose-dependent manner, decreased the Glut+DHA up-regulation of pGcALAS9.1-Luc activity. Gluconeogenic or glycolytic substrates such as fructose, galactose, glycerol and lactate, but not the non-metabolizable sugar sorbitol, also down-regulated pGcALAS9.1-Luc in LMH cells. The cAMP analog 8-CPT-cAMP, augmented Glut induction of ALAS-1, indicating that the glucose effect may be partly mediated by changes in cAMP levels.
The remaining studies focused on delineating the synergistic effect of Glut and DHA, and heme-dependent repression of ALAS-1. The 9.1 kb construct was compared with a construct containing the first 3.5 kb (pGcALAS3.5-Luc). The drug and heme effects were shown to be separate as drug induction was present in -3.4 to +0.082 kb region while the heme responsiveness was present in the -9.1 to -3.4 kb region. Using computer sequence analysis, several consensus activator protein-1 (AP-1) sites were found in the 9.1 kb ALAS-1 sequence but no consensus direct repeat (DR)-4 or DR-5 type recognition sequences for nuclear receptors were identified in the drug-responsive 3.5 kb region. Deletion constructs containing +0.082 to -7.6 kb (pGcALAS7.6-Luc) and +0.082 to -6.2 kb (pGcALAS6.3-Luc) cALAS 5'- flanking and 5' - UTR region were generated and tested and pGcALAS6.3-Luc was shown to have heme-dependent repression of basal and Glut and DHA-induced activity.
A recently identified 167 bp chick ALAS-1 drug responsive enhancer (DRE) was PCR amplified and inserted upstream of the 9.1 kb (pGcALAS9.1+DRE), a 0.399 kb (+0.082 to -0.317) (pGcALAS0.3+DRE), and pGL3SV40 construct (pGL3SV40+DRE). DRE mediated the up-regulation of pGL3SV40+DRE construct by Glut was ~ 15-30 fold but interestingly only 3.2 and 3.7-fold for pGcALAS9.l +DRE and pGcALAS0.3+DRE constructs, respectively.
In summary, in LMH cells drugs up-regulate ALAS-1 through non-DRE element(s) in the first 3.5 kb of ALAS-1 5'-flanking and 5'-UTR region and heme down-regulates ALAS-1 and determines the extent of the drug response through element(s) in the -6.3 to -3.5 kb region of ALAS-1 5'- flanking region.
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Heijs, Eric. "Van vreemdeling tot Nederlander : de verlening van het Nederlanderschap aan vreemdelingen 1813-1992 /." Amsterdam : Het Spinhuis, 1995. http://catalogue.bnf.fr/ark:/12148/cb392015713.
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Kawazoe, Yoshinori. "Proteasome inhibition leads to the activation of all members of the heat shock factor family." Kyoto University, 1999. http://hdl.handle.net/2433/181719.
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Kraan-Jetten, Andrea. "Effectiviteit van overheidsbeleid : systematisering van inzichten getoetst aan het beleid ter bevordering van het eigen-woningbezit = Effectiveness of public policy /." [S.l. : s.n.], 1991. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=003422846&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Kamp, Hendrik Rijk van de. "Israël in openbaring : een ondeerzoek naar de plaats van het joodse volk in het toekomstbeeld van de Openbaring aan Johannes /." Kampen : J. H. Kok, 1990. http://catalogue.bnf.fr/ark:/12148/cb392897926.
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Rezaie, Navaie Ali [Verfasser], George [Akademischer Betreuer] Tsatsaronis, George [Gutachter] Tsatsaronis, and Udo [Gutachter] Hellwig. "Thermal design and optimization of heat recovery steam generators and waste heat boilers / Ali Rezaie Navaie ; Gutachter: George Tsatsaronis, Udo Hellwig ; Betreuer: George Tsatsaronis." Berlin : Technische Universität Berlin, 2017. http://d-nb.info/1156187052/34.
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Blom, Sarah. "Intellectuele vorming in Nederland en Frankrijk : een vergelijkend onderzoek naar deelname aan intellectuele vorming in het Franse en het Nederlandse voortgezet onderwijs /." Groningen : Wolters-Noordhoff, 1995. http://catalogue.bnf.fr/ark:/12148/cb401662524.
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Li, Letian. "Microstructural evolution in 9 wt.% Cr power plant steels." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/11980.
Full textAbstract:
High chromium ferritic steels such as Grade 91 and Grade 92 are extensively used in the power plant industry. Components made from these types of steels, including headers, steam pipes and tubes, are required to provide reliable service at high pressures (20-30 MPa) and temperatures (550-610°C) for several decades. However, in order to further improve the thermal efficiency of the power plant, the future operation temperature for the ferritic steels needs to be elevated to 650°C. Therefore, the current research project focuses on the examination of recently developed MarBN type steels (Martensitic steel strengthened by Boron and Nitrides) and four Grade 92 derivatives in order to evaluate their suitability for 650°C application, and also to assess their creep strength from a microstructural point of view.
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Crippa, V. "MISFOLDING PROTEICO E NEURODEGENERAZIONE : STUDIO DEL COINVOLGIMENTO DELLA PROTEINA CHAPERONE HEAT SHOCK PROTEIN B8." Doctoral thesis, Università degli Studi di Milano, 2008. http://hdl.handle.net/2434/58000.
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Coppens, Herman. "De financiën van de centrale regering van de Zuidelijke Nederlanden aan het einde van het Spaanse en onder Oostenrijks bewind (ca. 1680-1788) /." Brussel : AWLSK, 1992. http://catalogue.bnf.fr/ark:/12148/cb35615030f.
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Hartog, Anita den. "Artikel 6 EVRM : grenzen aan het streven de straf eerder op de daad te doen volgen /." Antwerpen [u.a.] : Maklu Uitg, 1992. http://www.gbv.de/dms/spk/sbb/recht/toc/27796718X.pdf.
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Pouwelse, Willemina Johanna. "Haar verstand dienstbaar aan het hart : middelbaar onderwijs voor meisjes : debatten, acties en beleid, 1860-1917 /." Tilburg, 1993. http://catalogue.bnf.fr/ark:/12148/cb401238976.
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Berger, Claire. "Propriétés électroniques des alliages quasicristallins AlMn." Grenoble 1, 1987. http://www.theses.fr/1987GRE10067.
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Miró, Jané Arnau. "Flow and heat transfer of impinging synthetic jets." Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/667300.
Full textAbstract:
Synthetic jets are produced by the oscillatory movement of a membrane inside a cavity, causing fluid to enter and leave through a small orifice. This results in a net jet that is able to transfer kinetic energy and momentum to a fluid medium without the need of an external fluid source. This is why synthetic jets are interesting and will have key roles in a wide range of relevant applications such as active flow control, thermal cooling or fuel mixing. From the phenomenological point of view, synthetic jets are formed by elaborate flow patterns given their non-linear nature and, under certain conditions, unstable complex flows can be observed.
The present dissertation is focused on the investigation of the fluid flow and thermal performance of synthetic jets. Two different synthetic jet actuator geometries (i.e., slotted and circular) are studied. The jets in both configurations are confined by two parallel isothermal plates with an imposed temperature difference, and impinge into a heated plate located at a certain distance from the actuator orifice. The unsteady three-dimensional Navier-Stokes equations are solved for a range of Reynolds numbers using time-accurate numerical simulations. Moreover, a detailed model of the actuator that uses Arbitrary Lagrangian-Eulerian (ALE) formulation to account for the movement of the actuator membrane is developed. This model, based on the governing numbers of the flow, is used to conduct the numerical analyses.
The flows obtained in both configurations are noticeably different and three-dimensional for almost all the Reynolds numbers considered. The jet in the slotted configuration is formed by a pair of vortices that undergo turbulent transition and eventually coalesce into the jet. The external flow is dominated by two major recirculation structures that find their counterparts inside the actuator cavity. A new vortical structure, observed in confined slotted jets, appears as an interaction of the synthetic jet flow with the bottom wall and results in a change on the jet’s heat transfer mechanisms. On the other hand, the jet in the circular configuration presents three different flow regions that have been identified according to the literature: the main vortex ring, the trailing jet and the potential core. In this case, the external flow is dominated by the main vortex ring and the trailing jet, thus presenting a different morphology and heat transfer behavior than the slotted configuration. A detailed analysis of the vortex trajectories has shown that the advected vortices on the circular configuration reach the impingement before their slotted counterparts. Distributions of turbulent kinetic energy at the expulsion and vortex swirl and shear strength have revealed that the flow on the circular jet is mostly concentrated near the jet centerline, while it is more spread for the slotted configuration. For these reasons, at the same jet ejection velocity and actuator geometry, synthetic jet formation on the circular configuration can occur at higher frequencies than on the slotted configuration.
The analysis of the synthetic jet outlet temperature has shown that assuming a uniform profile is reasonable if the Reynolds number is high enough. Moreover, the outlet jet temperature is significantly higher than the cold plate temperature. The two configurations present different impinging behaviors due to the differences on the flow. Heat transfer analysis on the hot wall has revealed that the circular configuration reaches a higher heat transfer peak than the slotted configuration, however, heat transfer decays faster in the circular configuration when moving away from the jet centerline. Eventually, correlations for the heat transfer at the hot wall and the outlet temperature with the Reynolds number are proposed. They can be useful to include the cavity effects when using simplified models that do not account for actuator cavity.Els jets sintètics (SJ) són produïts pel moviment oscil·latori d'una membrana a l'interior d'una cavitat, cosa que fa que el líquid entri i surti per un petit orifici. Això es tradueix en un jet que és capaç de transferir energia cinètica i impuls a un medi fluid sense la necessitat d'una font externa. És per això que els SJ són interessants i tindran un paper clau en una àmplia gamma d'aplicacions rellevants, com ara el control actiu de flux, el refredament tèrmic o la barreja de combustible. Des del punt de vista fenomenològic, els SJ estan formats per patrons de flux elaborats per la seva naturalesa no lineal i, sota certes condicions, es poden observar fluxos complexos i inestables. Aquesta tesis està centrada en la investigació del flux de fluids i el rendiment tèrmic dels jets sintètics. S'estudien dues geometries diferents d’actuadors de SJ (és a dir, ranurats i circulars). Els jets en ambdues configuracions estan confinats per dues plaques isotèrmiques paral·leles amb una diferència de temperatura imposada i afecten a una placa escalfada situada a una certa distància de l'orifici de l'actuador. Les equacions tridimensionals inestables de Navier-Stokes es resolen per un nombre de Reynolds utilitzant simulacions numèriques precises en el temps. A més, es desenvolupa un model detallat de l'actuador que utilitza la formulació arbitrària lagrangiana-euleriana (ALE) per explicar el moviment de la membrana de l'actuador. Aquest model, basat en els números de govern del flux, s'utilitza per realitzar els anàlisis numèrics. Els fluxos obtinguts en ambdues configuracions són notablement diferents i tridimensionals per a gairebé tots els números de Reynolds considerats. El jet en la configuració ranurada està format per un parell de vòrtexs que experimenten una transició turbulenta que finalment formen el jet. El flux extern està dominat per dues recirculacions principals amb els seus homòlegs dins de la cavitat de l'actuador. Una nova estructura, observada en els jets ranurats confinats, apareix com una interacció del flux amb la paret inferior i provoca un canvi en els mecanismes de transferència de calor del jet. D'altra banda, el jet en la configuració circular presenta tres regions de flux diferents que s'han identificat segons la literatura: l'anell de vòrtex principal, el jet final i el nucli potencial. En aquest cas, el flux extern està dominat per l'anell de vòrtex principal i el jet de sortida, presentant així un comportament diferent de morfologia i transferència de calor que la configuració ranurada. Un anàlisi detallat de les trajectòries de vòrtex ha demostrat que els vòrtexs de la configuració circular arriben a la paret superior abans que els seus homòlegs ranurats. Les distribucions d'energia cinètica turbulenta a l'expulsió, entre altres, han revelat que el flux del jet circular es concentra majoritàriament a prop de la línia central del jet, mentre que és més estès per a la configuració ranurada. Per aquestes raons, a la mateixa velocitat d'ejecció del jet i geometria de l'actuador, la formació de SJ en la configuració circular pot produir-se a freqüències més altes que a la configuració ranurada. L'anàlisi de la temperatura de sortida dels SJ ha demostrat que assumir un perfil uniforme és raonable si el nombre de Reynolds és prou elevat. A més, la temperatura del jet de sortida és significativament superior a la temperatura de la placa freda. Les dues configuracions presenten diferents comportaments a causa de les diferències en el flux. L’anàlisi de la transferència de calor a la paret calenta ha revelat que la configuració circular arriba a un màxim de transferència de calor més gran que la configuració ranurada, però, la transferència de calor es desaccelera més ràpidament en la configuració circular quan s’allunya de la línia central. Finalment, es proposen correlacions per a la transferència de calor a la paret calenta i la temperatura de sortida amb el nombre de Reynolds. Poden ser útils per incloure els efectes de la cavitat quan s’utilitzen models simplificats que no tenen en compte la cavitat de l’actuador.
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Lench, Martyn John. "Direct contact heat transfer between an evaporating fluid and an immiscible liquid." Thesis, University of South Wales, 1991. https://pure.southwales.ac.uk/en/studentthesis/direct-contact-heat-transfer-between-an-evaporating-fluid-and-an-immiscible-liquid(972548ab-c177-40e4-8800-4c24d6021f67).html.
Full textAbstract:
An investigation has been conducted into the process of cooling water by the evaporation of droplets of isopentane in direct contact. The research has potential industrial application to a pickling acid recovery crystalliser. In order to minimise industrial equipment size a counter current flowing apparatus was developed and studied. Studies of optimum column height were carried out over a wide range of flow and drop size values. Several computer-based models have been developed to predict optimum column height. The results of initial models were used to modify experimental work and gave rise to the measurement of initial drop size using a high speed video camera technique. A more sophisticated version of the computer based model has been developed and is the major product of this research. This included the development of a dimensionless correlation for instantaneous heat transfer to an evaporating droplet. This is based on existing correlations which are compared and modified empirically. The correlation produced is: Nu= 2 + 0.76 Re 1/3 Pr 1/2 The computer model with this correlation is accurate to within 22%. The model assumes an average vapour half opening angle (β) of 135° based on published work. Drop velocities are based on terminal values and rigid sphere behaviour of 2-phase droplets is assumed. The final model assumes that the vapour and liquid dispersed phase remain attached as they rise through the column. Reynolds number of the continuous phase is found to have no independent effect on minimum evaporative height. The pinch temperature difference in the temperature profiles through the evaporative column is found to be significant in determination of minimum evaporative height. An approximate relationship of the form: Minimum evaporative height α ΔTpinch-0.5 is proposed.
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Benevides, Matos Najla. "Rôle des protéines paralogues TonB et HasB dans le transport de l'hème par le récepteur de membrane externe HemR de Serratia marcescens." Paris 7, 2008. http://www.theses.fr/2008PA077163.
Full textAbstract:
Chez les bactéries à Gram négatif, les ferri-sidérophores, le fer de ferri-protéines, Thème ou la vitamine B12 sont transportés à travers la membrane externe par des récepteurs spécifiques. Cette activité de transport a besoin de l'énergie produite par le complexe de la membrane interne TonB/ExbB/ExbD. La protéine TonB interagit avec ces récepteurs de membrane externe par l'intermédiaire d'une séquence peptidique localisée près de leur extrémité N-terminale. Cette séquence consensus DTLWTA, bien conservée, est appelée TonB box. Serratia marcescens possède 2 paralogues de TonB fonctionnels, TonB et HasB. TonB est capable de transmettre l'énergie du complexe TonB /exbB/ExbD à des récepteurs impliqués dans le transport du fer ou de Thème chez Serratia marcescens ou chez Escherichia coll. Par contre HasB, dont le gène est situé dans un opéron impliqué dans l'acquisition de Thème (opéron has), est fonctionnel pour l'acquisition de Thème via le récepteur HasR mais ne peut pas se substituer à TonB pour les transporteurs de ferri-sidérophores d3Escherichia coli ou de Serratia marcescens. Ceci pose la question du niveau de spécificité de HasB: est-ce une spécificité vis-à-vis des différents systèmes système de transport de Thème de Serratia marcescens ou bien une spécificité stricte vis-à-vis de HasR ? Pour répondre à cette question, le deuxième récepteur à hème (HemR) de S. Marcescens a été clone et son activité caractérisée chez Escherichia coli. HemR est actif en présence de TonB, mais pas de HasB. Cette étude démontre ainsi que HasB et HasR forment une paire spécifique. A l'aide de mutants nous avons étudié, la contribution des différents systèmes au processus de transport de Thème chez Serratia marcescens. Les systèmes Has et Hem sont les. Seuls transporteurs de Thème fonctionnels. Le système Has est plus efficace mais nécessite une carence en fer plus importante. En absence de HasA, le système Has est inopérant. L'activité du système Has est presque complètement abolie en absence de HasB. La quantité de récepteur HasR est fortement diminuée dans des mutants hasA ou hasB de Serratia marcescens. A l'aide d'une fusion entre le promoteur de Topéron has et le gène lacZ, nous avons montré que le niveau d'expression de Topéron has est fortement diminué dans un mutant hasB. L'absence d'activité de transport de Thème par le système dans les mutants hasA et hasB, est donc corrélée à une forte diminution de Topéron has. Nous proposons le scénario suivant pour le transport de Thème chez Serratia marcescens. Dans un milieu non carence en fer, les gènes de structure des opérons has et hem ne sont pas exprimés. En cas de carence en fer le système Hem peu transporter Thème. En cas de carence en fer, et quand la concentration en hème est très faible, le système Has, prend le relais grâce à l'activité de Thèmophore HasAIn Gram-negative bacteria, molecules, including ferri-siderophores, iron, vitamin B 12 or heme, are transported through the outer membrane by specific receptor. This transportation activity requires the energy provided by the inner membrane complex TonB/ExbB/ExbD. Two components, ExbB, and ExbD use the proton motive force to produce energy. The third component, TonB, which transmit energy, interacts with the outer membrane receptors by peptide sequence located near their N-terminus end. This preserved consensus sequence DTLWTA, is named TonB box. Serratia marcescens has 2 functional TonB paralogs, TonB and HasB. TonB is able to transmit the energy of the complex TonB/ExbB/ExbD to receptors involved in the transport of iron or heme in Serratia marcescens or Escherichia coll. On the other hand HasB, whose gene is located in an operon encoding for the component of the Has heme uptake System (has operon), is functional for the heme acquisition via the HasR receptor but cannot substitute TonB for the transporter the ferrisiderophores in Escherichia coli and Serratia marcescens. This raises the question of the level of the HasB specificity: is this a specificity with respect to the various heme transport Systems of Serratia marcescens or a strict specificity with respect to HasR? To answer this question, the second heme receptor (HemR) of S. Marcescens, was cloned and its activity characterized in Escherichia coli. HemR was shown to be active in the presence of TonB, but not with HasB. This result shows that HasB and HasR form a specific pair. Using mutants we studied, the contribution of the various Systems to the heme uptake process in Serratia marcescens. The Has and Hem Systems are the only functional heme transporter in Serratia marcescens. The Has System is more efficient but requires a higher iron deficiency. In absence its cognate hemophore, the heme uptake activity of the HasA System is dramatically, decreased. The Has System activity is almost completely abolished in absence of HasB. The quantity of HasR receptor in Serratia marcescens is strongly decreased in hasB mutant similarly with a hasA mutant. Using a transcriptional fusion between the has operon promoter and the lacZ gene, we showed that the has operon expression level is strongly decreased in a hasB mutant. The absence of activity of heme transport activity of the Has System in hasA and hasB mutants, is correlated with a sharp decrease of the has operon expression level. We propose the following scénario for the heme transport in Serratia marcescens. In an iron containing medium has, and hem operons are not expressed. In the presence of iron depletion, the Hem System can transport heme. In the presence of iron deficiency, and when the heme concentration is very low, the Has System transports heme thanks to thé activity of the hemophore HasA
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Grönkvist, Stefan. "All CO2 molecules are equal, but some CO2 molecules are more equal than others." Doctoral thesis, KTH, Energiprocesser, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-452.
Full textAbstract:
This thesis deals with some challenges related to the mitigation of climate change and the overall aim is to present and assess different possibilities for the mitigation of climate change by: • Suggesting some measures with a potential to abate net greenhouse gas (GHG) emissions, • Discussing ideas for how decision-makers could tackle some of the encountered obstacles linked to these measures, and • Pointing at some problems with the current Kyoto framework and suggesting modifications of it. The quantification of the net CO2 effect from a specific project, frequently referred to as emissions accounting, is an important tool to evaluate projects and strategies for mitigating climate change. This thesis discusses different emissions accounting methods. It is concluded that no single method ought to be used for generalisation purposes, as many factors may affect the real outcome for different projects. The estimated outcome is extremely dependent on the method chosen and, thus, the suggested approach is to apply a broader perspective than the use of a particular method for strategic decisions. The risk of losing the integrity of the Kyoto Protocol when over-simplified emissions accounting methods are applied for the quantification of emission credits that can be obtained by a country with binding emissions targets for projects executed in a country without binding emission targets is also discussed. Driving forces and obstacles with regard to energy-related co-operations between industries and district heating companies have been studied since they may potentially reduce net GHG emissions. The main conclusion is that favourable techno-economic circumstances are not sufficient for the implementation of a co-operation; other factors like people with the true ambition to co-operate are also necessary. How oxy-fuel combustion for CO2 capture and storage (CCS) purposes may be much more efficiently utilised together with some industrial processes than with power production processes is also discussed. As cost efficiency is relevant for the Kyoto framework, this thesis suggests that CCS performed on CO2 from biomass should be allowed to play on a level playing field with CCS from fossil sources, as the outcome for the atmosphere is independent of the origin of the CO2.QC 20101015
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Zorzi, Elisa. "Heat Shock Protein 70 nel linfoma anaplastico a grandi cellule: ruolo, espressione e correlazione con la tirosin chinasi NPM-ALK." Doctoral thesis, Università degli studi di Padova, 2009. http://hdl.handle.net/11577/3426040.
Full textAbstract:
Anaplastic Large Cell Lymphoma (ALCL) belongs to the group of high grade non Hodgkin
Lymphomas, described as a T- or null-cells origin large-cell lymphoma. More than 90% of all
ALCL are characterized by the chromosomal translocation t(2;5)(p23;q35), which fuses the
ALK tyrosine kinase receptor with the nuclear NPM (nucleophosmin) genes. The resulting
constitutively activated kinase NPM-ALK, leads to activation of signaling pathways involved
in survival and cell proliferation through activation of PI3K/Akt and STAT3. More recently
NPM-ALK has been shown to regulate the activation of MEK, ERK1/2 and p38-MAPK, as
well. Previously we have demonstrated that treatment of NPM-ALK+ ALCL cells with
proteasome inhibitor Bortezomib (BZ) causes the induction of Hsp70, a heat shock protein
relevant for the maintenance of the cellular homeostasis through the conservation and correct
folding of newly synthesized and/or denatured proteins. This is also helpful for several tumor
models, in which drug-induced protein misfolding and degradation is preceded by cell cycle
arrest and apoptosis. In this study we evaluated the expression and functional role of Hsp70 in
ALCL cell lines and in lymph nodal biopsies, assessing its anti-apoptotic activity after drug
treatment (Bortezomib) or cellular stress (heat shock, HS). Our results demonstrate that
Hsp70 is over-expressed in NPM-ALK+ ALCL cell lines following activation of the hsp
transcription factor, HSF1, most likely through a positive feedback mechanism.
Furthermore, when assessing the anti-apoptotic activity of over-expressed Hsp70 after
Bortezomib (BZ) treatment in NPM-ALK+ cells, we demonstrated that Hsp70 prevents the
loss of mitochondrial membrane permeabilization by binding and sequestering pro-apoptotic
protein Bax into the cytoplasm, lowering drug sensitivity compared to NPM-ALK- cells.
Hsp70 expression analysis was extended to 23 biopsies of ALCL, 20 NPM-ALK+ and 3
NPM-ALK-. Tissue array analysis demonstrated that 20/20 NPM-ALK+ ALCL biopsies were
Hsp70 positive compared to 1/3 NPM-ALK- ALCL biopsies. Such a difference was also
statistically significant, whereas, due to the small number of cases, a statistical correlation
between Hsp70 expression and patient outcome could not be demonstrated. However it is
worth of noting that 4/6 (67%) patients with an Hsp70 expression value of 3 (in a range
between 0 and 3) relapsed or died compared to only 3/12 (25%) of the patients with a protein
expression value ranging between 0 and 2, regardless NPM-ALK status and activity.
Finally transcription of Hsp70 was evaluated by RQ-PCR in 4 healthy control lymph nodes
and 10 NPM-ALK+ ALCL lymph node biopsies, demonstrating that in NPM-ALK+ ALCL
lymph nodes over-expression of Hsp70 reflect increased gene promoter activity, respect to
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healthy lymphonodes as verified also through a statistical analysis. To test if NPM-ALK
plays a role in Hsp70 induction via HSF1 activity, we treated ALCL cell lines with WHIP154,
an ATP-competitive small molecule inhibitor of ALK kinase, before exposing cells to
BZ o HS, and showed HSF1 retention in the cytoplasm and Hsp70 mRNA and protein
expression downregulation.
We further observed a marked down regulation of the MAPK p38, among the downstream
NPM-ALK effector proteins, along with the HSF1 inhibition described above. Notably,
inhibition of p38 reduced significantly Hsp70 expression in NPM-ALK+ ALCL cells,
supporting a role of the NPM-ALK/p38 axis in the regulation of the HSF1/hsp70 pathway in
these cells, but also encouraging future investigations. This kinase may have some effect on
HSF1, but this hypothesis warrants further investigation. Indeed citostatic concentrations of
Bortezomib and WHI-P154 given together induced cell death in NPM-ALK+ ALCL cell lines,
at least in part because of Hsp70 downregulation.I linfomi anaplastici a grandi cellule (ALCL) pediatrici sono caratterizzati, per più dell’90%, dalla presenza della caratteristica traslocazione cromosomica t(2;5) da cui origina il trascritto codificante per NPM-ALK, chinasi oncogena essenziale per la trasformazione della cellula linfoide normale e per la sopravvivenza della cellula neoplastica. Oltre al suo potenziale promitogenico e antiapoptotico mediato dall’attivazione dei pathway di PI3K/Akt e STAT3, studi recenti hanno dimostrato il ruolo di NPM-ALK nell’attivazione di MEK, ERK1/2 e p38- MAPK. Tuttavia, nonostante le numerose conoscenze sull’attività trasformante di NPM-ALK sia in vivo che in vitro, poco è noto sui meccanismi di chemioresistenza indotti dalla stessa chinasi, anche se forte rimane l’interesse per lo sviluppo di strategie terapeutiche mirate per la cura dell’ALCL. In un nostro studio precedente abbiamo dimostrato che in linee cellulari di ALCL NPM-ALK positive (NPM-ALK+) l’inibitore proteosomale Bortezomib (BZ) provoca l’induzione di Hsp70, una heat shock protein normalmente coinvolta nella maturazione e nella preservazione della conformazione della maggioranza delle proteine cellulari ma che induce anche fenomeni di chemioresistenza in molti modelli sperimentali tumorali. In questo studio abbiamo quindi valutato lo stato e la funzione di Hsp70 in linee cellulari e in preparati istologici di pazienti pediatrici affetti da ALCL, e i possibili meccanismi di resistenza al trattamento farmacologico (BZ) o allo stress cellulare (heat shock, HS) che favorirebbero la sopravvivenza delle cellule NPM-ALK+. Abbiamo dimostrato che Hsp70 risulta espressa ad alti livelli nelle linee cellulari NPM-ALK+ grazie alla capacità di queste cellule di attivare efficacemente il fattore di trascrizione delle hsp, HSF1. Dalle nostre analisi è emerso inoltre che Hsp70 interagisce con HSF1 nella sua forma fosforilata e attiva, ma solo nelle linee cellulari NPM-ALK+. Ciò lascia supporre che Hsp70 possa regolare positivamente la trascrizione delle hsp mediante un meccanismo a feed-back. Inoltre abbiamo dimostrato che, quando indotta dopo trattamento con BZ o shock termico, in linee cellulari NPM-ALK+ Hsp70 previene la perdita dell’omeostasi mitocondriale e il rilascio transmembrana di fattori apoptogenici, attraverso l’inibizione della proteina pro-apoptotica mitocondriale Bax. Questo giustificherebbe la resistenza al trattamento farmacologico evidenziata nelle linee cellulari NPM-ALK+ rispetto alla linea di ALCL che non esprime NPM-ALK. L’analisi dell’espressione di Hsp70 e’ stata quindi estesa a 23 preparati istologici di pazienti pediatrici affetti da ALCL, 20 NPM-ALK+ e 3 NPM-ALK-. Mediante analisi 2 immunoistochimica, abbiamo verificato che la totalità delle biopsie NPM-ALK+ è risultata positiva ad Hsp70, rispetto a solo uno su tre dei casi NPM-ALK-, confermando statisticamente (p=0.019) una correlazione tra la presenza di NPM-ALK e Hsp70. Data la limitata numerosità dei campioni non è stato possibile correlare in maniera statistica l’espressione di Hsp70 con l’andamento della malattia, ma è da sottolineare come il 67% dei casi (4/6) con elevata espressione di Hsp70 (valore attribuito pari a 3, in una scala di espressione crescente da 0 a 3) siano recidivati o deceduti, contro solo il 25% (3/12) dei casi con espressione della proteina assente o intermedia (compresa tra 0 e 2, nella stessa scala). Abbiamo verificato poi, che l’espressione del trascritto Hsp70 in biopsie linfonodali di bambini affetti da ALCL NPM-ALK+, è significativamente più elevata rispetto a quella riscontrata nei linfonodi reattivi non patologici (p=0.049). Per valutare il possibile ruolo di NPM-ALK nell’induzione di Hsp70, prima di esporre le cellule di ALCL in studio a trattamento con BZ o a calore (HS), la sua attività chinasica è stata inibita farmacologicamente (WHI-P154). I nostri studi dimostrano che nelle cellule trattate con WHI-P154, sia singolarmente che in combinazione con BZ o HS, HSF1 rimane localizzato nel citoplasma con conseguente calo del trascritto e dell’espressione di Hsp70. Infine abbiamo dimostrato che la combinazione di dosi singolarmente non citotossiche, o al più citostatiche di BZ e WHI-P154, inibisce la proliferazione cellulare e induce apoptosi nelle linee cellulari che esprimono NPM-ALK, effetto al quale concorre l’inibizione della trascrizione e dell’espressione di Hsp70, oltre ad altri numerosi fattori dipendenti dall’attività della chinasi.
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Romo, Vladimir Canudas. "Decomposition methods in demography : proefschrift ter verkrijging van het doctoraat in de Ruimtelijke Wetenschappen aan de Rijksuniversiteit Groningen." Amsterdam : Rozenberg Publishers, 2003. http://dissertations.ub.rug.nl/faculties/rw/2003/v.canudas.romo/.
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Elbanhawy, Amr Yehia Hussein. "On numerical investigations of flow-induced vibration and heat transfer for flow around cylinders." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/on-numerical-investigations-of-flowinduced-vibration-and-heat-transfer-for-flow-around-cylinders(6722ba6d-80de-47f4-a14d-191d4e9ed7fb).html.
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Vortex shedding is an important mechanism, by which the flow around bluff bodies create forces that excite vibratory motion. Vortex-induced vibration (VIV) is studied for a single circular cylinder by means of Computational Fluid Dynamics (CFD) simulations. An arbitrary Lagrangian Eulerian (ALE) formulation is used to achieve the grid deformation needed for VIV. In this thesis, a multifaceted approach is undertaken by which response dynamics and wake interaction are addressed. Four major aspects are considered in the study: the Reynolds number (Re); the mass and damping; the degree-of-freedom for VIV; and the mutual effect between VIV and heat transfer.As attention is paid towards high pre-critical Re flow, the turbulent flow around the cylinder is treated by two turbulence modelling approaches: unsteady Reynolds Averaged Navier Stokes (uRANS), and Large Eddy Simulation (LES). The wake-VIV interaction is analyzed by looking at mean velocities and Reynolds stresses, where decomposition of flow scales is undertaken to explore the evolution of coherent eddy structures, downstream of the cylinder. Conversely, the VIV response is analyzed by considering oscillation amplitude and frequency, in addition to the excitation and inertial dynamics.High turbulence in the separated shear layers disorders the cylinder's VIV response and induces higher amplitudes. The sensitivity for Re is found more pronounced in cylinders with low mass and damping. Meanwhile, VIV is found to enhance wake mixing, and to significantly change the near wake Reynolds stresses. It is suggested that the increase in Re brings a change to the wake patterns, which are known in VIV at lower Re. The kinetic energy production, of near wake eddy structures, is qualitatively altered with the presence of VIV. Furthermore, the surface heat flux is found to cause a noticeable increase in VIV amplitude, as long as it does not disorder the wake correlation. The cylinder's oscillation increases the average value of the Nusselt number (Nu), while the local variance of Nu rises markedly post-separation.
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Zenclussen, Maria Laura [Verfasser], Hans-Dieter [Gutachter] Volk, Alf [Gutachter] Hamann, and Barbara [Gutachter] Tzschentke. "Role of Heme oxygenase-1 in the feto-maternal tolerance / Maria Laura Zenclussen ; Gutachter: Hans-Dieter Volk, Alf Hamann, Barbara Tzschentke." Berlin : Humboldt-Universität zu Berlin, 2009. http://d-nb.info/1208078771/34.
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Apitz, Janina. "Charakterisierung von Arabidopsis HEMA-Mutanten und in vivo-Analyse funktioneller Domänen der pflanzlichen Glutamyl-tRNA-Reduktasen." Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17527.
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Die Tetrapyrrolbiosynthese (TBS) führt zu wichtigen Endprodukten wie Häm und Chlorophyll. Das gemeinsame Vorstufenmolekül aller Tetrapyrrole ist die 5-Aminolävulinsäure (ALA), die in Pflanzen über den C5-Weg aus Glutamat synthetisiert wird. Das erste spezifische Enzym der ALA-Synthese und somit auch der TBS ist die Glutamyl-tRNA Reduktase (GluTR). Sie unterliegt als Schlüsselenzym einer strengen Regulation. Aufgrund der unterschiedlichen Expression der HEMA-Gene in Arabidopsis wird ein differenzieller Beitrag der GluTR-Isoformen zu den Endprodukten der TBS vermutet. Analysen von knockout-Mutanten gaben Aufschluss darüber, inwiefern die Isoformen den Verlust des jeweils anderen kompensieren können. Die knockout-Mutante von HEMA1 zeigte einen blassgrünen Phänotyp, war nicht mehr in der Lage photoautotroph zu wachsen und demonstrierte eine essentielle Rolle der GluTR1 gegenüber GluTR2, wohingegen hema2-Mutanten einen wildtypartigen Phänotyp aufzeigten. Die Bedeutung der N-terminalen GluTR-Domäne in der posttranslationalen Regulation der ALA-Synthese wurde durch BiFC-Analysen und Komplementationsversuche aufgeklärt. BiFC-Analysen zeigten eine Interaktion der N-terminalen Domäne der GluTR1 mit Proteinen der Clp Proteasen und dem GluTR-Bindeprotein (GBP). Veränderte GluTR-Stabilitäten in gbp-Mutanten lassen eine schützende Funktion des GBP gegenüber dem Abbau des Proteins postulieren. Die Expression einer N-terminal verkürzten GluTR1 komplementierte hema1-Mutanten vollständig. Die in diesen Pflanzen und in clp-Mutanten beobachteten erhöhten GluTR1-Proteinstabilitäten im Dunkeln lassen einen Abbau der GluTR durch Clp Proteasen vermuten, bei dem der N-Terminus des Enzyms für die Substraterkennung notwendig zu sein scheint. Die Detektion von erhöhten Pchlid-Mengen als Folge der erhöhten Proteinstabilität in Linien, die die verkürzte GluTR1 exprimierten, demonstriert erstmals die Bedeutung einer kontrollierten Proteolyse der GluTR in der Regulation der ALA-Synthese.In plants 5-aminolevulinic acid (ALA) is the common precursor of all tetrapyrrols and formed from glutamate via the C5 pathway. Glutamyl-tRNA reductase (GluTR) is the initial enzyme of ALA synthesis and thus tetrapyrrole biosynthesis (TBS). The most important control point of the TBS is the synthesis of ALA and GluTR is the key enzyme, that is tightly regulated. Due to the different expression of HEMA genes in Arabidopsis, a differential contribution to endproducts of the TBS is proposed for GluTR isoforms. Analysis of knockout mutants gave some indications of how the isoforms can compensate each other. I introduced a new knockout mutant of HEMA1 that was pale-green and not able to grow photoautotrophically, indicating that the remaining GluTR2 does not sufficiently compensate ALA synthesis for the extensive needs of chlorophyll. In contrast, hema2 mutants were wild-type-like. The function of the N-terminal region of GluTR1 in posttranslational regulation has been analyzed by BiFC analysis and complementation experiments of hema1. BiFC analysis showed an interaction of the N-terminal region of GluTR1 with the GluTR binding protein (GBP) and with proteins of the Clp proteases. Mutants of GBP revealed a decreased GluTR1 stability during the dark period, indicating a protective role of GBP against proteolysis of GluTR1 in darkness. The expression of a GluTR1 lacking the N-terminal amino acid residues successfully complemented hema1. These plants as well as clp mutants revealed an increased GluTR1 stability in darkness, suggesting a degradation of the protein through Clp proteases. Thereby, the N-terminal region of GluTR1 seems to be necessary for the recognition by Clp proteins. The observed high amount of truncated GluTR1 in transformed hema1 mutants was caused by the increased GluTR1 stability and lead to an accumulation of Pchlide in prolonged dark periods, demonstrating the importance of a controlled proteolysis of GluTR in the regulation of ALA synthesis.
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Geloven, Anna Adriana Wilhelmina van. "Spoedeisende hulp bij buikklachten evaluatie van het functioneren van de spoedeisende hulpafdeling aan de hand van patiënten met buikklachten /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/84086.
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Beukes, Wynand J. "Dorpsondernaam : 'n kultuurhistoriese ondersoek na die dambouersgemeenskap wat aan die einde van die 19de eeu op Tafelberg ontstaan het." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6665.
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Thesis (MA)--University of Stellenbosch, 2011.ENGLISH ABSTRACT: Table Mountain is one of the world’s most well-known natural landmarks. For more than a half million years the mountain played a role in human cultural activities. The water flowing off Table Mountain resulted in the establishment of Cape Town in 1652. During the first 240 years of the city’s existence until 1891, everything possible was employed to make the most of the water cascading down the northern slopes of the mountain. In 1891, the city commenced with the utilising of the mountain’s water running southwards to waste. This course of action to maximise the supply of water from Table Mountain to the city, extended over a period of more than seven decades and included the construction of dams, tunnels and pipelines. Towards the end of the nineteenth century and at the beginning of the twentieth century, two dams were built in the Disa Stream to the east of Kasteels Poort’s upper end. The construction work on the Woodhead Dam commenced in 1892 and continued until 1897. Building operations on the Hely-Hutchinson Dam started shortly after the completion of the Woodhead Dam and was concluded in 1904. The dam builders were settled as a community in the vicinity of the construction sites. The housing comprised permanent as well as temporary structures. The dwellings did not form a unit, but were scattered in the proximity of the construction terrains. The majority of the structures were demolished after the completion of the work. Only four dwellings still exist today. A feature of the accommodation was the separate housing for the white and black workers. The dam builders’ backgrounds were very diverse. Some of them were highly skilled artisans from Britain whereas the majority of the untrained labourers were black people from the Eastern Cape. Also included in the work force, were people from Cape Town and environs. The number of workers on the mountain varied to a high degree. The largest number at any stage totaled 470. Information on the mountain dwellers’ material culture, for example their clothing, foodstuffs and compensation, and spiritual life, for example religion, communication and leisure-time activities, is analysed in this study. Fragments of the dam builders’ cultural heritage is preserved in the Waterworks Museum next to the wall of the Hely-Hutchinson Dam. The exhibition of implements and equipment is disorganised and neglected. The transfer of the museum to another more efficient building in the area is vitally important in order that proper justice can be done to the dam builders who rendered an essential service to Cape Town in difficult circumstances.
AFRIKAANSE OPSOMMING: Tafelberg is een van die wêreld se bekendste natuurbakens. Die berg speel al langer as ‘n halfmiljoen jaar ‘n rol in menslike kultuurbedrywighede. Die water wat vanaf Tafelberg vloei, het in 1652 tot die ontstaan van Kaapstad gelei. In die eerste 240 jaar van die stad se bestaan tot 1891 is alles moontlik gedoen om die water wat aan die noordekant teen die berg afvloei, ten beste te benut. In 1891 is begin om ook die berg se water wat onbenut suidwaarts vloei vir die stad se gebruik aan te wend. Dié proses om Tafelberg se water maksimaal tot die beskikking van die stad te stel, het oor ‘n tydperk van meer as sewe dekades gestrek en het die konstruksie van damme, tonnels en pypleidings ingesluit. Twee damme is aan die einde van die negentiende eeu en die begin van die twintigste eeu in die Disastroom ten ooste van die bo-punt van Kasteelspoort gebou. Die bouwerk aan die Woodhead-dam het in 1892 begin en het tot 1897 geduur. Die konstruksie aan die Hely-Hutchinson-dam is net ná die voltooiing van die Woodhead-dam van stapel gestuur en is in 1904 voltooi. Die dambouers is as ‘n gemeenskap in die omgewing van die dambouterreine gevestig. Die akkommodasie het uit stewige en tydelike wonings bestaan. Die wonings het nie ‘n eenheid gevorm nie, maar is verspreid in die nabyheid van die konstruksiewerk opgerig. Die meeste van die geboue is na afhandeling van die bouwerk gesloop en net vier wonings bestaan vandag nog. ‘n Kenmerk van die akkommodasie was dat die blanke en swart werkers apart gehuisves is. Die dambouers se agtergrond was baie uiteenlopend. Sommige van hulle was hoogs geskoolde vakmanne van Brittanje, terwyl die meeste ongeskoolde arbeiders swart mense van die Oos-Kaap was. Die res van die werkspan het uit mense van Kaapstad en die omgewing bestaan. Die getal werkers op die berg het baie gewissel. Die grootste getal werkers wat op een tydstip betrokke was, het 470 beloop. Inligting oor die bergbewoners se materiële kultuur, byvoorbeeld hul kleredrag, lewensmiddele en vergoeding, en geestelike kultuur, onder meer godsdiens, kommunikasie en vryetydsbesteding, word in dié ondersoek ontleed. Fragmente van die dambouers se kulturele nalatenskap word in die Waterwerke Museum by die wal van die Hely-Hutchinson-dam bewaar. Dié uitstalling van implemente en toerusting is baie ongeorden en verwaarloos. Dit is noodsaaklik dat die museum na ‘n doeltreffender gebou in die omgewing skuif sodat behoorlik eer betoon kan word aan die mense wat in moeilike omstandighede ‘n onontbeerlike diens aan Kaapstad gelewer het.
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Balabani, Stavroula. "An experimental investigation of the crossflow over tube bundles." Thesis, King's College London (University of London), 1996. https://kclpure.kcl.ac.uk/portal/en/theses/an-experimental-investigation-of-the-crossflow-over-tube-bundles(27c20ab8-798a-4a07-b1cd-b31fbd77578e).html.
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