To see the other types of publications on this topic, follow the link: Pbci.
Dissertations / Theses on the topic 'Pbci'
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 'Pbci.'
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
Hinss, Marcel. "Interaction humain/système de drones et facteurs humains : Prise en compte de l'estimation de l'état de fatigue d'un opérateur dans le design d'interactions adaptatives pour le contrôle de drones longue endurance." Electronic Thesis or Diss., Toulouse, ISAE, 2024. http://www.theses.fr/2024ESAE0035.
Full textAbstract:
L’utilisation de drones est fréquente dans de nombreuses industries et dans les activités militaires modernes. Toutefois les drones militaires à longue endurance souffrent encore d’un taux élevé d’accidents liés à des erreurs humaines, en particulier lorsque les opérateurs ressentent de la fatigue mentale (FM).En particulier, la flexibilité cognitive exigée des opérateurs offre une possibilité d’amélioration. Cependant, peu de recherches ont été menées sur celle-ci lors de tâches complexes tel que le contrôle d’un drone.Dans cette thèse, nous remédions à cette lacune, et la possibilité d’atténuer les effets négatifs de la FM sur la flexibilité cognitive a également été explorée. Pour ce faire, des alertes visuelles ont été développées pour informer les participants lorsqu’ils devaient passer d’une tâche à l’autre. Pour accroître l’efficacité des alertes visuelles, leur utilisation devrait être limitée aux périodes de faible performance (par exemple, en raison de la FM), au cours desquelles l’impact positif des alertes visuelles peut être maximisé.Les interfaces cerveau-ordinateur passives (pBCI) et les systèmes informatiques physiologiques utilisant l’électroencéphalographie (EEG), l’électrocardiographie (ECG) et l’oculométrie peuvent détecter des états sub-optimaux comme la FM. Dans ce cas, les alertes visuelles sont susceptibles d’avoir un impact positif plus important. La détection d’ états mentaux pose plusieurs problèmes : Un état mental n’est pas nécessairement un bon indicateur de performance. D’autre part, l’estimation peut s’avérer difficile, notamment parce que la performance peut être définie de différentes manières.À la suite de plusieurs entretiens avec des opérateurs, cinq expériences ont été conçues.(i) La première expérience, appelée expérience Double Task Switching (DTS), teste un nouveau protocole comportemental pour étudier la flexibilité cognitive. Les résultats ont montré que le passage d’une tâche similaire à une autre impacte significativement la performance.(ii) Cette expérience est suivie d’un second paradigme visant à déterminer si la simple présence d’alertes visuelles peut améliorer les performances. Les résultats de cette étude montrent que les alertes visuelles sans explication préalable ne semblent pas améliorer les performances. Deux autres expériences explorent la possibilité d’utiliser l’EEG, l’ECG et le suivi des yeux pour détecter la FM lors de simulations réalistes de drone.(iii) La première expérience se concentre sur une tâche de recherche et constitue une première étude des différences entre l’estimation de la FM basée sur le temps passé sur la tâche (TOT) et celle basée sur la performance.(iv) L’expérience suivante combine ensuite les deux expériences précédentes en ajoutant une tâche de navigation pour recréer certains aspects de l’opération de drones. Les résultats mettent en évidence la différence dans l’utilisation de définitions différentes de la FM pour le design de systèmes informatiques physiologiques. Notamment, le TOT et la performance de la tâche sont comparés.(v) Enfin, nous étudions si les alertes visuelles peuvent être utilisées pour adapter une interface adaptative dans les simulations de drones afin d’améliorer les performances. Pour ce faire, des alertes visuelles ont été ajoutées à l’expérience précédente. Les résultats préliminaires mettent en évidence l’impact d’une simple adaptation basée sur le comportement dans un environnement de travail complexe.Les travaux présentés dans ce manuscrit montrent que la flexibilité cognitive devrait être considérée comme une priorité dans la recherche sur les facteurs humains et que des adaptations simples peuvent améliorer la performance. Ils soulignent également l’importance de la FM et la manière dont différentes définitions de ce concept peuvent entraîner des différences de performance majeures pour les pBCI et les systèmes d’informatique physiologiqueUncrewed Aerial Systems (UAS) are common in many industries and an important pillar ofmany modern militaries. While technology advances rapidly, military long-endurance UASstill suffer from high rates of human error-related mishaps, especially when operators experience mental fatigue.In particular, the frequent switching between tasks required by operators presents an opportunity for improvement. Cognitive flexibility, the mental ability to switch between tasks or responses, is an important executive function. However, little research has investigated cognitive flexibility during complex tasks such as UAS control. In this thesis we address this lack, and the possibility of mitigating the adverse effects of fatigue on cognitive flexibility was also explored. For this, visual alerts were developed to inform participants when they had to switch between tasks. To increase the effectiveness of visual alerts, their use should be restricted to periods of poor performance (e.g. due to mental fatigue), during which the positive impact ofvisual alerts may be maximized.Passive Brain-Computer Interfaces (pBCI) and physiological computing systems using electroencephalography (EEG), electrocardiography (ECG) and eye-tracking may detect sub-optimal states, such as mental fatigue. Detecting mental states poses several theoretical issues. Most notably, a mental state is not necessarily a good performance indicator. Directly estimating performance, on the other hand, has proven to be more challenging for BCIs and Physiological Computing, partially because performance can be defined in many ways.Following several interviews with operators, 5 experiments were designed. (i) The firstexperiment, the Double Task Switching (DTS) experiment, tests a novel behaviouralprotocol to investigate cognitive flexibility and the effects of similarity on task-switching costs.Results showed that switching between similar and dissimilar tasks significantly differs in accuracy and reaction time. This experiment is followed by (ii) a second behavioural paradigm investigating whether the mere presence of visual alerts can improve performance. It builds on the DTS protocol and is called the DTS-II experiment. The results of this study show that visual alerts without any prior explanation do not appear to improve performance when switching between tasks.Two further experiments explore the possibility of using EEG, ECG and eye-tracking to detect mental fatigue during realistic UAS simulations. (iii) The Remot3e experiment (Remote search, 3 Es for EEG, ECG & Eye-Tracking) focuses on a search task. It constitutes a primary investigation into the differences between Time-on-Task (TOT) and performance-based mental fatigue estimation. Then, (iv) the UASOS (UAS Operator Simulation) experiment combines the DTS protocol and the Remot3e Task, adding a navigation task to recreate some of the fundamental aspects of UAS operations. Both experiments highlight the difference in using different definitions of mental fatigue for constructing and training physiological computing systems.Notably, Time-On-Task (TOT, the time a participant has been performing a task) and task performance are compared.Finally, (v) we investigate if visual alerts can be used to adapt an adaptive interface inUAS simulations to improve performance. For this, Visual Alerts were added to the UASOSexperiment. The preliminary results highlight the impact of a simple adaptation on behaviour within a complex work environment.The work in this manuscript shows that cognitive flexibility should be considered a priorityin human factor research and that simple adaptations, such as visual alerts, can improve cognitive flexibility. It also highlights the importance of mental fatigue and how different definitions of the construct (based on performance or TOT) can result in major performance differences when researching pBCIs and Physiological Computing systems
2
Cuba, B. Elmer. "Estimación del PBI potencial y de la brecha del PBI: Perú 1970-1995." Economía, 2012. http://repositorio.pucp.edu.pe/index/handle/123456789/117258.
Full text
3
Bøe, Andreas Gagnat. "Degradation and Stability of PBCA and POCA Nanoparticles." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22417.
Full textAbstract:
Nanoparticles represent promising carriers for controlled drug delivery. In this project threedifferent intruments: Zetasizer, Nanosight and Gas Chromatography, have been used to detect and analyse degradation of monodisperse poly butylcyanoacrylate (PBCA) and polyoctylcyanoacrylate (POCA) nanoparticles with a mean size diameter of 145 and 155 nm,respectively. It was found that the Nanosight and Gas Chromatography are valuable instrumentsfor detecting and analysing degradation, whereas the Zetasizer turned out to giveunreliable results because of increasing polydispersity in the samples. PBCA and POCAparticles were tested in two different setups. One including a dialysis setup in room temperature,in which the solvent was regularly exchanged. The other consisted of reagent bottlesheld in an oven at 37C. In the dialysis method the influence of buffers with pH 4.0, pH5.5 and pH 7.4 were tested. In the reagent bottles different mediums were tested, like cellmedium, blood serum and buffer pH 7.4 with and without the enzyme esterase. From theseexperiments it became clear that PBCA particles degraded significantly faster than POCAparticles in all tested mediums. Degradation of PBCA particles were also strongly affectedby the pH. At pH 4.0 there was little (10%) or no degradation still after 30 days. The concentration of PBCA particles in pH 7.4 decayed as a 1/x -function, in which 53\% of the PBCA particles in buffer pH 7.4 have been degraded after 8.5 hours.The degradation-rate for PBCA and POCA in blood serum was approximately similar as in buffer pH 7.4, whereas in cell medium it was slightly slower.
4
Van, Staden Wynand Fourie. "The fabrication of PBCO buffered step-edge Josephson junctions." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019.1/1597.
Full text
5
Lee, Jeong Kyu. "Direct Methanol Fuel Cell Membranes from Polymer Blends." Case Western Reserve University School of Graduate Studies / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1134316195.
Full text
6
Kovalenko, E. N., O. N. Yunakova, and N. N. Yunakov. "Absorption Spectra of Thin Films Compounds in the PbCl-CuCl System." Thesis, Eskisehir Technical University, 2021. https://openarchive.nure.ua/handle/document/18639.
Full text
7
Kreisz, Aurélien. "Membranes PBI pour pile à combustible haute température." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT224.
Full textAbstract:
Cette thèse débute par une courte introduction traitant des principes et de l'état de l'art des PEMFC dans le but de situer le contexte des travaux. Le but des travaux présentés dans ce manuscrit est de développer une nouvelle méthode de préparation de membrane pour les piles à combustible haute température (> 120 °C). Le polybenzimidazole dopé à l'acide phosphorique est devenu la référence des PEM haute température. Un degré de dopage élevé est essentiel pour minimiser les pertes ohmiques dans la cellule. Malheureusement un degré de dopage élevé entraine aussi une plastification de la membrane détériorant aussi sa résistance mécanique. Il est donc essentiel d'atteindre un compromis entre conductivité protonique élevée et résistance mécanique en contrôlant le degré de dopage. Dans ce travail, nous avons développé une nouvelle méthode de préparation de membrane, basée sur la gélation thermoréversible d'une solution de PBI dans l'acide phosphorique ou polyphosphorique, dans le but d'obtenir des degrés de dopage élevés. Une modification chimique a été réalisée dans l'état dopé afin d'induire une réticulation du polymère. De plus, les résistances mécaniques ont été améliorées en introduisant dans la membrane un mat de PBI réticulé obtenu par filage électrostatique. La faisabilité des approches suivies dans ces travaux a été démontrée par des tests en cellule de pile à combustible jusqu'à une température de 180 °C. Les AMEs élaborés à partir de ces membranes ont montré une stabilité satisfaisante durant 900 - 1000 heures de fonctionnement sous conditions statiques (opération continue à 0.2 A.cm-2) et sous conditions dynamiques (cyclage en tension et courant) avec une décroissance de la tension de la cellule au cours du temps de 0.7 - 0.8 µV.h-1 à 0.2 A.cm-2. Les caractéristiques I-V de ces AMEs ont été comparées à des assemblages de référence PBI/H3PO4 commerciaux et ont présenté des performances améliorées par rapport aux assemblages commerciauxThe thesis begins with a short overview of the principles and the current state at the art of the PEMFC in order to give a background on the specific subject of high temperature PEM fuel cell. The aim of the work presented in this thesis is to develop a new method of preparation of membrane for high temperature fuel cell (T > 120 °C). Phosphoric acid doped PBI has become the reference for high temperature PEM. A high phosphoric acid content is essential to minimize the ohmic voltage loss in the fuel cell for high current density. Unfortunately high phosphoric acid content exerts a strong plasticizing effect resulting in poor mechanical properties of the membrane. Consequently the doping level of the membrane should be a compromise between the highest proton conductivity and mechanical strength. In this work we have presented a new method of preparation of membrane based on the thermoreversible gelation of a PBI solution in phosphoric or polyphosphoric acid in order to obtain high acid doping. The chemical modification of the membrane has been performed in the doped state in order to induce a chemical crosslinking. The mechanical strength of the membrane has been further improved by the introduction of PBI electrospun mat as reinforcement. The feasibility of the approaches followed in this work was demonstrated in fuel cell tests at temperature up to 180 °C. The MEA based on those membranes have shown a stability up to 900 - 1000 hours either under static (continuous operation at 0.2 A.cm-2) or dynamic (voltage and current cycling) operation with a small voltage decay of 0.7 - 0.8 µV.h-1 at 0.2 A.cm-2. The I-V characteristics of these MEA have been compared with reference commercial PBI/H3PO4 MEAs and shown improved performances
8
Monteiro, João Frederico Haas Leandro. "Análise da transição de fase normal-supercondutora dos compósitos [{Y,Gd}Ba2Cu3O7-]1-y-[PrBa2Cu3O7-]y e {[YBa2Cu3O7-]0,95-[PrBa2Cu3O7-]0,05}1-x-{Ag}x." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2015. http://tede2.uepg.br/jspui/handle/prefix/850.
Full textAbstract:
Made available in DSpace on 2017-07-21T19:25:49Z (GMT). No. of bitstreams: 1
joao frederico Monteiro.pdf: 4579056 bytes, checksum: fa083a32b5c935e6fb6513dea178d562 (MD5)
Previous issue date: 2015-09-22Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná
In this work we analyzed the superconductor-normal transition of the composites [YBa2Cu3O7-]1-y-[PrBa2Cu3O7-]y with 0
9
Suarez, Matthew. "The Effect of Membrane Thickness on the Performance of PBI-Based High-Temperature Direct Methanol Fuel Cells." Digital WPI, 2013. https://digitalcommons.wpi.edu/etd-theses/1131.
Full textAbstract:
"This project investigates the effect of membrane thickness on the performance and durability of a Direct Methanol Fuel Cell (DMFC) using a commercially available Celtec®P-1000 PBI-based membrane electrode assembly (MEA). The PBI-based membranes tested were the 100µm, the standard thickness, 200µm and 250µm thick. With various methanol feed concentrations and cathode feeds, oxygen and air, the PBI-based MEAs were operated between 160 and 180°C with vaporized methanol feed. Results showed that the DMFC performance increased with temperature and with PBI membrane thickness. The optimal concentration for the 100µm membrane was at 5M while the best performance with the 200µm membrane was obtained at 3M. The 250µm membrane looked like it could have had better performance than the 200µm, but unfortunately experimental issues didn’t allow completion of these results."
10
Knox, Daniel. "Performance Characteristics of PBI-based High Temperature Direct Methanol Fuel Cells." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/956.
Full textAbstract:
"This thesis investigates the effect of temperature, methanol concentration, and oxidant type on the performance of a Direct Methanol Fuel Cell (DMFC) using two versions of a commercially available polybenzimidazole (PBI)-based membrane electrode assembly (MEA): the Celtec®-P 1000 MEA of original thickness and double thickness. The PBI-based MEA’s were tested under the vapor-phase methanol concentrations of 1M, 2M, 3M, 5M, 7.5M, and 10M, temperatures of 160-180°C, and oxidants of oxygen and air. It was found that performance increased with temperature and that oxygen outperformed air as methanol concentrations increased. The double thickness PBI-based MEA, was more resistant to methanol crossover and performed better with increasing methanol concentrations. Thus, these commercial MEAs may be suitable for developing higher temperature DMFCs."
11
Ahmed, Fahad. "Invasive and non-invasive detection of bias temperature instability." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52227.
Full textAbstract:
Invasive and non-invasive methods of BTI monitoring and wearout preemption have been proposed. We propose a novel, simple to use, test structure for NBTI /PBTI monitoring. The proposed structure has an AC and a DC stress mode. Although during stress mode, both PMOS and NMOS devices are stressed, the proposed structure isolates the PBTI and NBTI degradation during test mode. A methodology of converting any data-path into ring oscillator (DPRO) is also presented. To avoid the performance overhead of attaching monitoring circuitry to functional block, a non-invasive scheme for BTI monitoring is presented for sleep transistor based logic families. Since, BTI is a critical issue for memories, a scheme for BTI monitoring of 6T SRAM cell based memories is also presented. We make use of the concept of a DPRO and show how a memory system can be made to oscillate in test mode. The frequency of oscillation is a function of the devices in the cell. After validation of the proposed schemes using extensive simulations, we have also validated the results on silicon. We also introduce the concept of wearout mitigation at the compiler level. Using an example of a register file, we present a preemptive method of wearout mitigation using a compiler directed scheme.
12
Basdemir, Merve. "Development Of Pbi Based Membranes For H2/co2 Separation." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615473/index.pdf.
Full textAbstract:
Recent developments have confirmed that in the future hydrogen demand in industrial applications will arise because of the growing requirements for H2 in chemical manufacturing, petroleum refining, and the newly emerging clean energy concepts. Hydrogen is mainly produced from the steam reforming of natural gas and water gas shift reactions. The major products of these processes are hydrogen and carbon dioxide. The selective removal of CO2 from the product gas is important because it poisons catalysts in the reactor and it is highly corrosive. Membrane separation processes for hydrogen purification may be employed as alternative for conventional methods such as adsorption, cryogenic distillation.
Mixed matrix membranes (MMMs) are composed of an insoluble phase dispersed homogeneously in a continuous polymer matrix. They have potential in gas separation applications by combining the advantageous properties of both phases. The objective of this study is to produce neat polybenzimidazole (PBI) membranes and PBI based mixed matrix membranes for separation of H2/CO2. Furthermore, to test the gas permeation performance of the prepared membranes at permeation temperatures of 35oC to 90oC.
Commercial PBI supplied from both Celanese and FumaTech were used as polymer matrix. PBI was selected based on its thermal, chemical stabilities and mechanical properties and its performance as a fuel-cell membrane produced by PBI.
Micro-sized Zeolite 3A and nano-sized SAPO-34 are zeolites with 0.30 nm and 0.38 nm pore size respectively have attracted considerable interest and employed as fillers in this study. Commercial Zeolite 3A and synthesized SAPO-34 by our group was used throughout the study. Membranes were prepared using N,N-dimethylacetamide as the solvent. Prepared membranes were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The effect of annealing procedure and operating temperature on gas separation performance of resultant neat PBI, PBI/Zeolite 3A and PBI/SAPO-34 membranes were investigated by gas permeation tests. Hydrogen and carbon dioxide gases were used for single gas permeation measurements. Two different annealing strategies were utilized namely in-line annealing and in-oven annealing. In-oven annealing was performed in an oven in nitrogen atmosphere at 120oC, 0.7 atm while in-line annealing was performed in the gas permeation set-up by feeding helium as permeating gas at 90oC and 3 bar.
Neat PBI and PBI/ Zeolite 3A membranes were in-oven annealed. The in-oven annealed membranes showed better selectivities with lower permeabilities, but the performance results of these membranes had low repeatability. On the other hand, in-line annealed membranes showed much higher permeabilities and lower selectivities with stable performance. By changing the annealing method hydrogen permeability increased from 5.16 Barrer to almost 7.77 barrer for neat membranes and for PBI/Zeolite 3A mixed matrix membranes increased from 5.55 to to 7.69 Barrer at 35oC. The selectivities were decreased from 6.21 to 2.31 for neat membranes and for PBI/Zeolite 3A from 5.55 to 2.63.
Effect of increasing operating temperature was investigated by using in-line annealed membranes. Increasing temperature from 35oC to 90o improved the performance of the both types of membranes and repeatable results were obtained. Besides neat PBI and PBI/Zeolite 3A, PBI/SAPO-34 membranes were prepared only via in-line annealing. The addition of nano-sized filer to the membranes provided homogeneous distribution in polymer matrix for PBI/SAPO-34 membranes. For this type of membrane hydrogen permeability increased from 8.01 to 26.73 Barrer and with no change in H2/CO2 selectivities via rising temperature. Consequently, it is better to study hydrogen and carbon dioxide separation at high temperature.
For all types of membranes hydrogen showed higher activation energies. In between all membranes magnitude of activation energies were the highest for PBI/SAPO-34 membrane which is an indication of good interaction between polymer and zeolite interface. In-line annealed membranes gave the best gas permeation results by providing repeatability of measurements. Among all studied membranes in-line annealed PBI/SAPO-34 membrane exhibited the best gas permeation results.
13
(UPC), Universidad Peruana de Ciencias Aplicadas. "Macroeconomía (AP26 U1 MTA1): macroeconomía, PBI y crecimiento económico." Universidad Peruana de Ciencias Aplicadas (UPC), 2012. http://hdl.handle.net/10757/274038.
Full text
14
Pontes, Debora da Silva Lima [UNESP]. "Filmes finos ferroelétricos do tipo PBCT, PBST e PCST: estudo experimental e teórico." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/106648.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:35:45Z (GMT). No. of bitstreams: 0
Previous issue date: 2012-02-24Bitstream added on 2014-06-13T19:25:22Z : No. of bitstreams: 1
pontes_dsl_dr_bauru.pdf: 4536733 bytes, checksum: 0e0e50403b6e1c3dfec710c1dc43dff6 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Perovisquita é a estrutura mais comum vista nos materiais ferroelétricos, a qual tem sido amplamente utilizado na indústria de dispositivos nas últimas décadas. Dentre essa classe de materiais o PbTiO3 é um dos materiais extensamente estudado devido a sua ampla faixa de aplicações como, por exemplo, capacitores, sensores piroelétrico e piezelétricos, memórias ferroelétricas. A substituição do Pb2+ pelos íons Ba2+/Ca2+, Ba2+/Sr2+ e Ca2+/Sr2+ no siste ma PbtiO3, a qual conduziu a formação de sistemas PBCT, PBST e PCST, produziu varias mudanças nas propriedades elétricas e estruturais desses materiais. No entanto, poucos trabalhos têm sido dedicados a esses sistemas baseado numa incorporação complexa de dois diferentes íons no sítio A, com relação a um profundo estudo teórico e experimental. A caracterização experimental por difração de raios X, espectroscopia micro-Raman e FT-IR mostram uma diminuição no grau de tetragonalidade para esses materiais. Essa alteração estrutural em função dos substituintes foi também responsável pela diminuição do grau de polarização. Nesta tese, foi aplicado também o método computacional dos primeiros princípios para estudar esta importante classe de materiais. A estrutura eletrônica, energia do banc gap, a densidade e estados (DOS) nos cristais ferroelétricos PBCT, PBST e PCST foram estudadas usando a teoria do funcional de densidade combinada com B3LYP. Os resultados teóricos foram correlacionados com os resultados experimentais para investigar e interpretar melhor a influência dos pares de íons Ba/Ca, Ba/Sr e Ca/Sr na ferroeletricidade do sistema PT. Pela análise teórica o grau de polarização bem como de tetragonalidade diminuiu no sistema PCST comparado ao PBCT e PBST, devido à presença agora de um forte caráter de ligações iônicas dentro...
Perovskites are the most commonly seen ferroelectrics, which have been widely used in the industry of devices in the last few decades. In addition, Lead titanate (PbTiO3) is an extensively studied material wich a wide range of application, for intance as capacitors, piezoeletric and pyroelectric sensors and ferroelectric memories. The substitution of Pb2+ ions Ba2+/Ca2+, Ba2+/Sr2+ e Ca2+/Sr2+ ions in the PbTiO3 system, which leads to the formation of the PBCT, PBST e PCST systems, induces several change in the electric and structural properties of these materials. However, PBCT, PBST and PCST systems based on the complex incorporation of two different ions at site A have not been thoroughly investigated and the literature contains few reports concerning their experimental and theoretical study of these materials. The characterization with X-ray diffraction, Raman spectroscopy and spectroscopy techniques on the infrared region of these samples showed a decrease of the tetragonality degree. These structural modifications were also responsible by the decrease in the polarization degree of these samples. In this thesis, we also have applied first-principles computational methods to the study this important class of materials. The electronic structure, energy band structure, and density of states (DOS) in ferroelectric crystal PBCT and PCST are studied by using density functional theory (DFT) combined with the B3LYP. The theoretical results were correlated with experimentals results to investigate and interpret better the influence of pairs of ions Ba/Ca, Ba/Sr and Ca/Sr on the ferroelectricity of the system PT. By theoretical analysis the degree of polarization as well as ferroelectricity in the PCST decreased compared with the systems PBCT and PBST, due to the presence of strong ionic character in this crystal... (Complete abstract click electronic access below)
15
Pontes, Debora da Silva Lima. "Filmes finos ferroelétricos do tipo PBCT, PBST e PCST : estudo experimental e teórico /." Bauru : [s.n.], 2012. http://hdl.handle.net/11449/106648.
Full textAbstract:
Orientador: Elson Longo da SilvaBanca: Alberthmeiry Teixeira de Figueiredo
Banca: Alejandra Hortencia Miranda Gonzáles
Banca: Marcia Tsuyama Escote
Banca: Maria Fernanda do Carmo Gurgel
O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caracter institucional e integra as atividades de pesquisa em materiais de diversos campi
Resumo: Perovisquita é a estrutura mais comum vista nos materiais ferroelétricos, a qual tem sido amplamente utilizado na indústria de dispositivos nas últimas décadas. Dentre essa classe de materiais o PbTiO3 é um dos materiais extensamente estudado devido a sua ampla faixa de aplicações como, por exemplo, capacitores, sensores piroelétrico e piezelétricos, memórias ferroelétricas. A substituição do Pb2+ pelos íons Ba2+/Ca2+, Ba2+/Sr2+ e Ca2+/Sr2+ no siste ma PbtiO3, a qual conduziu a formação de sistemas PBCT, PBST e PCST, produziu varias mudanças nas propriedades elétricas e estruturais desses materiais. No entanto, poucos trabalhos têm sido dedicados a esses sistemas baseado numa incorporação complexa de dois diferentes íons no sítio A, com relação a um profundo estudo teórico e experimental. A caracterização experimental por difração de raios X, espectroscopia micro-Raman e FT-IR mostram uma diminuição no grau de tetragonalidade para esses materiais. Essa alteração estrutural em função dos substituintes foi também responsável pela diminuição do grau de polarização. Nesta tese, foi aplicado também o método computacional dos primeiros princípios para estudar esta importante classe de materiais. A estrutura eletrônica, energia do banc gap, a densidade e estados (DOS) nos cristais ferroelétricos PBCT, PBST e PCST foram estudadas usando a teoria do funcional de densidade combinada com B3LYP. Os resultados teóricos foram correlacionados com os resultados experimentais para investigar e interpretar melhor a influência dos pares de íons Ba/Ca, Ba/Sr e Ca/Sr na ferroeletricidade do sistema PT. Pela análise teórica o grau de polarização bem como de tetragonalidade diminuiu no sistema PCST comparado ao PBCT e PBST, devido à presença agora de um forte caráter de ligações iônicas dentro... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Perovskites are the most commonly seen ferroelectrics, which have been widely used in the industry of devices in the last few decades. In addition, Lead titanate (PbTiO3) is an extensively studied material wich a wide range of application, for intance as capacitors, piezoeletric and pyroelectric sensors and ferroelectric memories. The substitution of Pb2+ ions Ba2+/Ca2+, Ba2+/Sr2+ e Ca2+/Sr2+ ions in the PbTiO3 system, which leads to the formation of the PBCT, PBST e PCST systems, induces several change in the electric and structural properties of these materials. However, PBCT, PBST and PCST systems based on the complex incorporation of two different ions at site A have not been thoroughly investigated and the literature contains few reports concerning their experimental and theoretical study of these materials. The characterization with X-ray diffraction, Raman spectroscopy and spectroscopy techniques on the infrared region of these samples showed a decrease of the tetragonality degree. These structural modifications were also responsible by the decrease in the polarization degree of these samples. In this thesis, we also have applied first-principles computational methods to the study this important class of materials. The electronic structure, energy band structure, and density of states (DOS) in ferroelectric crystal PBCT and PCST are studied by using density functional theory (DFT) combined with the B3LYP. The theoretical results were correlated with experimentals results to investigate and interpret better the influence of pairs of ions Ba/Ca, Ba/Sr and Ca/Sr on the ferroelectricity of the system PT. By theoretical analysis the degree of polarization as well as ferroelectricity in the PCST decreased compared with the systems PBCT and PBST, due to the presence of strong ionic character in this crystal... (Complete abstract click electronic access below)
Doutor
16
Felix, Daniel André. "PBC and MEIS class genes in the planarian Schmidtea mediterranea." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.575479.
Full textAbstract:
Planarians have outstanding regenerative capabilities which depend on the presence of a pool of somatic stem cells. In addition planarians keep perfect proportion of the body while degrowing during starvation. While the establishment and maintenance of the anteroposterior (AlP) axis has been shown to depend on Wnt and Hedgehog signalling, not much is known about the subsequent patterning events. PBC and MEIS class genes are evolutionary conserved TALE homeobox genes with important functions in patteming and cell differentiation. They are well known co-factors of the Hox genes however they also have other Hox-independent functions. The aim of this study was to identify the planarian orthologs of the PBC and MEIS class genes and to examine their putative role in anteroposterior patteming. Here one PBC class gene, Smed-pbx, and the three MEIS class genes Smed-meis I , Smed-meis2 and Smed-prep were identified and orthology established through phylogenetic analyses. Smed-prep was found to define the cephalic area in which the anterior structures are formed, most prominently the brain. In anterior regenerating Smed-prep(RNAi) worms a reduction or even complete absence of the brain and anterior markers was observed. Importantly, the differentiation of stem cells into nerve cells was shown not to be dependent on Smed-prep. In step with its function the Smed-prep gene was found to have an anteroposterior bias in expression, being highly expressed in the head. While both Smed-meis genes were found to be important for regeneration and maintenance of the eyes and for the adaptation of the body to the new size of the animal after amputation, Smed-pbx was found to have pleiotropic functions, phenocopying aspects of all three MEIS class genes upon RNAi interference, and also producing additional phenotypes. This study has found that the four planarian orthologs of PBC and MEIS class genes are important players in regeneration. Two genes, Smed-pbx and especially Smed-prep, have been found to be necessary for anteroposterior patterning. This is the first time that a homeobox transcription factor has been directly implicated in anteroposterior patterning in planarians.
17
Padenko, Eugen [Verfasser], and Ulf [Akademischer Betreuer] Breuer. "PBI-Hochleistungsbeschichtungen für verschleißbeanspruchte Funktionsflächen / Eugen Padenko ; Betreuer: Ulf Breuer." Kaiserslautern : Technische Universität Kaiserslautern, 2019. http://d-nb.info/1203624697/34.
Full text
18
Jebbari, Saïda. "Contribution à l'étude structurale des halogénures de plomb par diffraction des rayons X. Système PBCL::(2X)BR::(2(1-X)) : Comportement de la structure de PBCL::(2) en fonction de la température." Nancy 1, 1988. http://www.theses.fr/1988NAN10159.
Full textAbstract:
Évolution des paramètres de maille du système PBCL::(2X)BR::(2(1-X)) en fonction de X et apport d'une preuve irréfutable de l'existence d'une substitution ordonnée au niveau des sites halogènes X et Y. Étude de l'enthalpie et de l'entropie de fusion des solutions solides PBCL::(2X)BR::(2(1-X)) en fonction de X. Amélioration de la structure de PBCL::(2) à la température ordinaire, et comparaison avec la structure à T = 473K, 523K ET 573K. Étude de la densité électronique résiduelle par le modèle de vibrations anharmoniques de Gram. Charlier jusqu'à l'ordre 6 A T = 293K et T = 473K
19
Wulfmeyer, Timo [Verfasser], Gerhard [Akademischer Betreuer] Thiel, and Felicitas [Akademischer Betreuer] Pfeifer. "Strukturelle Organisation der DNA in PBCV-1 / Timo Wulfmeyer. Betreuer: Gerhard Thiel ; Felicitas Pfeifer." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2012. http://d-nb.info/1106257146/34.
Full text
20
Souza, Alexandre Pereira de. "Analisando conteúdos e mapeando informação em periódicos eletrônicos: um estudo do periódico secundário PBCIB." Universidade Federal da Paraíba, 2011. http://tede.biblioteca.ufpb.br:8080/handle/tede/3915.
Full textAbstract:
Made available in DSpace on 2015-04-16T15:23:17Z (GMT). No. of bitstreams: 1
arquivototal.pdf: 2979296 bytes, checksum: f1c1b1357760a3c7a74c0967129c5426 (MD5)
Previous issue date: 2011-10-11Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Abstract: Examines the regular secondary PBCIB considering the processes of indexing and retrieval of light for Information Management. Describes the structure of regular secondary PBCIB, and evaluate the recovery of the articles indexed in line with your keywords by examining which journals in the areas of Library and Information Science are indexed by the magazine. Search to verify that management information can be used as a strategy for optimizing the processes of indexing and retrieval of abstracts of articles published, tracing a map of its themes, in order to create a controlled vocabulary in order to prevent the dispersion of articles indexed by magazine. To systematize our theoretical axis consistently and provide better understanding of the present study explored theories on scientific topics, journals, electronic journals, scholarly communication, open access journals, open archives movement and free access to scientific information, information management and indexing the Internet. It is characterized as to their goals as a research-type exploratory descriptive, quantitative and qualitative. Bibliometrics uses for statistical analysis and content associated with the concept maps, in order to better understand the relationship between the themes of the journal and its indexing terms, the key words. In his concluding remarks the study states that PBCIB is inserted in the list of journals that provide a fundamental contribution to the dissemination of scientific articles in the field of information science, perfectly fulfilling its role as a secondary or periodic summaries in line with the philosophy of open access and OAI. In order to optimize the activities of recovery and indexing of the articles recommended the adoption of information management processes of the magazine publishing, and maintenance of links that are down.
Resumo: Analisa o periódico secundário PBCIB, considerando os processos de indexação e recuperação a luz da Gestão da Informação. Descreve a estrutura do periódico secundário PBCIB, além de avaliar a recuperação dos artigos indexados de acordo com suas palavraschave, averiguando quais periódicos nas áreas de Biblioteconomia e Ciência da Informação são indexados pela revista. Busca verificar se a gestão da informação pode ser utilizada como estratégia de otimização nos processos de indexação e recuperação dos resumos de artigos publicados, traçando um mapa de suas temáticas, no intuito de criar um vocabulário controlado com vistas a evitar a dispersão dos artigos indexados pela revista. Para sistematizar nosso eixo teórico de forma consistente e proporcionar melhor compreensão do estudo apresentado exploramos teorias acerca de temas sobre produção científica, periódicos científicos, periódicos eletrônicos, comunicação científica, acesso livre aos periódicos científicos, open archives e movimento de acesso livre a informação científica, gestão da informação e indexação na internet. Caracteriza-se quanto aos seus objetivos como uma pesquisa do tipo exploratório-descritiva, com abordagem quanti-qualitativa. Utiliza a bibliometria como método estatístico e a análise de conteúdo associada aos mapas conceituais, com vistas a melhor compreender a relação entre as temáticas do periódico e seus termos indexadores, as palavras-chave. Em suas considerações finais o estudo estabelece que a PBCIB se insere no rol de periódicos científicos que oferecem uma contribuição fundamental para a disseminação de artigos científicos no campo da Ciência da informação, cumprindo perfeitamente o seu papel de periódico secundário ou de resumos em consonância com a filosofia do livre acesso e a OAI. No intuito de otimizar as atividades de recuperação e indexação dos seus artigos recomenda-se a adoção da gestão da informação aos processos editoriais da revista, e a manutenção dos links que se encontram fora do ar.
21
Meneses, Valdez Sergio Roberto. "Estudio de la relación entre el crecimiento económico y pobreza en el Perú durante el periodo 2001 -2016." Escuela de Postgrado Neumann Business School (Perú), 2017. http://hdl.handle.net/10757/622525.
Full textAbstract:
The present study defines the concepts of Economic Growth and Poverty. The main objective of the study is to identify the relationship between these macroeconomic variables in Peru during the period 2001-2016. During the process of analysis of the variables, the evolution of Economic Growth and Poverty is described. The methodology used is descriptive and correlational, the source of data for the study was obtained from the INEI, the variables used were PBI. PBI pc and Poverty. Product of the study carried out determines the significant link that economic growth has in the reduction of poverty. Finally, it is determined that sustained economic growth in the country is a necessary but not sufficient condition for the eradication of poverty.
22
Schmiech, Peter [Verfasser]. "Zur Vorhersage des Kristallhabitus unter Fremdstoffeinfluss mittels PBC-Vektoren / Peter Schmiech." Aachen : Shaker, 2005. http://d-nb.info/1181614430/34.
Full text
23
Schoeman, Johannes Gerhardus. "H2SO4 stability of PBI–blend membranes for SO2 electrolysis Schoeman / H." Thesis, North-West University, 2011. http://hdl.handle.net/10394/7567.
Full textAbstract:
Alternative energy sources are needed if the current use of energy is to be sustained while
reducing global warming. A possible alternative energy source that has significant potential
is hydrogen. For hydrogen to become a serious contender for replacing fossil fuels, the
production thereof has to be further investigated. One such process, the membrane–based
Hybrid Sulphur (HyS) process, where hydrogen is produced from the electrolysis of SO2, has
received considerable interest recently.
Since H2SO4 is formed during SO2 electrolysis, H2SO4 stability is a prerequisite for any
membrane to be used in this process. In this study, pure as well as high and low
temperature blended polybenzimidazole (PBI), partially fluorinated poly(arylene ether) (sFS)
and nonfluorinated poly(arylene ethersulphone) (sPSU) membranes were investigated in
terms of their acid stability as a function of acid concentration by treating them in H2SO4 (30,
60 and 90wt%) for 120h at 1bar pressure. The high temperature blend membranes contain
the basic polymer in excess (70 wt% basic PBI and 30wt% acid sPSU/sFS polymer) and
require acid doping in order to conduct protons. In the doped state they are able to conduct
protons up to 200°C. The low temperature blend membranes are also composed of the
same PBI polymer used in the high temperature membranes, as well as the same acidic
polymers with one of the membranes containing a fluorinated polymer and the other a nonfluorinated
polymer (sFS or sPSU) in excess. These membranes do not require any acid
doping to conduct protons but they are only stable at temperatures below 80°C.
High temperature blend membranes were characterised using through–plane conductivity,
GPC and IEC, whilst low temperature membranes were characterised using in–plane and
through–plane proton conductivity, weight change, TGA, GPC, SEM, EDX and IEC
techniques. The conductivity determination techniques (especially the in–plane technique)
proved to be cumbersome, whilst all the other analysis techniques were deemed
appropriate.
H2SO4 exposure had a destabilising effect on the PBI membrane which presented as weight
gain at the 30 and 60wt% H2SO4 concentrations due to salt formation and dissolution at the
90wt% acid treatment due to sulphonation. In the sFS membrane dissolution was observed
at 30 and 60wt% as a result of oligomer loss that occurred during the post treatment
washing process and partial dissolution, as a result of sulphonation, at the 90wt% treated membrane. The sPSU membrane showed great stability at 30 and 60wt%, though
dissolution was observed at 90wt% because of membrane sulphonation due to a lack of
fluorination. The sFS–PBI membrane blend proved to be stable with only slight degradation
taking place at 90wt% treatment due to sulphonation. Similarly the sPSU–PBI blend
membrane showed great stability at the 30 and 60wt% H2SO4 treatment concentrations
however total dissolution occurred at 90wt% treatment again due to a lack of fluorination.
Although both the low temperature blended membranes showed superb stability to H2SO4
concentrations expected in the SO2 electrolyser (30–40wt%), the low temperature blended
sFS–PBI membrane seemed slightly more stable over the H2SO4 treatment concentration
range (30–90wt%), due to the protective role of the fluorinated polymer. The superior acid
stability of this membrane could prove vital for proper SO2 electrolysis, especially for
prolonged periods of operationThesis (M.Sc. (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2012.
24
Popayán, Avila Jhossep Augusto. "Contributions to ida-pbc with adaptive control for underactuated mechanical systems." Master's thesis, Pontificia Universidad Católica del Perú, 2018. http://tesis.pucp.edu.pe/repositorio/handle/123456789/12894.
Full textAbstract:
This master thesis is devoted to developing an adaptive control scheme for the well-
known Interconnection and Damping Assignment Passivity-Based Control (IDA-PBC) technique. The main
objective of this adaptive scheme is to asymptotically stabilize a class of Underactuated
Mechanical Systems (UMSs) in the presence of uncertainties (not necessarily matched). This class of
UMSs is characterized by the solvability of the Partial Differential Equation (PDE) resulting from
the IDA-PBC technique. Two propositions are stated in this work to design the adaptive IDA-PBC. One
of the main properties of these propositions is that even though the parameter estimation conver-
gence is not guaranteed, the adaptive IDA-PBC achieves asymptotic stabilization. To illustrate the
effectiveness of these propositions, this work performs simulations of the Inertia Wheel Inverted
Pendulum (IWIP) system, considering a time-dependent input disturbance, a type of physical damping,
i.e., friction (not considered in the standard
IDA-PBC methodology), and parameter uncertainties in the system (e.g., inertia).Tesis
25
Vidal, Sandoval Jesus Enrique. "Implicit IDA-PBC Design and Implementation for a Portal Crane System." Master's thesis, Pontificia Universidad Católica del Perú, 2019. http://hdl.handle.net/20.500.12404/15353.
Full textAbstract:
Interconnection and damping assignment passivity-based control (IDA-PBC) is a wellknown technique which regulates the behavior of nonlinear systems, assigning a target port-Hamiltonian (pH) structure to the closed-loop. In underactuated mechanical systems (UMSs) its application requires the satisfaction of matching conditions, which in many cases demands to solve partial differential equations (PDEs). Only recently, the IDA-PBC has been extended to UMSs modeled implicitly, where the system dynamics
in pH representation are described by a set of differential-algebraic equations (DAEs). In some system classes this implicit approach allows to circumvent the PDE problem and also to design an output-feedback law. The present thesis deals with the design and implementation of the total energy shaping
implicit IDA-PBC on a portal crane system located at the laboratory of the Control Engineering Group at TU-Ilmenau. The implicit controller is additionally compared with a simplified (explicit) IDA-PBC [1]. This algorithm shapes the total energy and avoids the PDE problem. However, this thesis reveales a significant implementation flaw in the algorithm, which then could be solved.Interconnection and damping assignment passivity-based control (IDA-PBC) ist eine wohlbekannte Methode zur Regelung von nichtlinearen Systemen, die im geschlossenen Regelkreis eine gewünschte Port-Hamiltonian-Struktur (pH) haben. Die Anwendung auf unteraktuierte mechanische Systeme (UMS) erfordert die Erfüllung von sogenannten Matching Conditions, die meistens die Lösung partieller Differentialgleichungen (PDE) benötigt. Erst kürzlich wurde die IDA-PBC auf implizit modellierte UMS erweitert, bei denen die Systemdynamik in pH-Darstellungen durch Differentialalgebraische Gleichungen (DAE) beschrieben wird. Dieser implizite Ansatz ermöglicht bei einigen Systemklassen, das PDE-Problem zu umgehen und auch eine Ausgangsrückführung zu entwerfen. Die vorliegende Masterarbeit beschäftigt sich mit dem Entwurf und der Implementierung des impliziten IDA-PBC zur Gesamtenergievorgabe auf einem Portalkransystem im Labor des Fachgebiets Regelungstechnik der TU-Ilmenau. Der implizite Regler wird mit einem vereinfachten (expliziten) IDA-PBC verglichen [1]. Dieser Algorithmus gibt ebenso die Gesamtenergie vor und vermeidet das PDE-Problem. In der Masterarbeit wird in diesem Algorithmus ein wesentlicher Implementierungsfehler offengelegt und behoben.
Tesis
26
Wei, Yuping. "Characterization of two Bacillus subtilis penicillin-binding protein-coding genes, ykuA (pbpH) and yrrR (pbpI)." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/34900.
Full textAbstract:
Penicillin-binding proteins (PBPs) are required in the synthesis of the cell wall of bacteria. In Bacillus subtilis, PBPs play important roles in the life cycle, including both vegetative growth and sporulation, and contribute to the formation of the different structures of vegetative cell wall and spore cortex. The B. subtilis genome sequencing project revealed there were two uncharacterized genes, ykuA and yrrR, with extensive sequence similarity to class B PBPs. These two genes are renamed and referred to henceforth as pbpH and pbpI, respectively.
A sequence alignment of the predicted product of pbpH against the microbial protein database demonstrated that the most similar protein in B. subtilis is PBP2A and in E. coli is PBP2. This suggested that PbpH belongs to a group of the genes required for maintaining the rod shape of the cell. Study of a pbpH-lacZ fusion showed that pbpH was expressed weakly during vegetative growth and the expression reached the highest level at the transition from exponential phase to stationary phase. The combination of a pbpA deletion and the pbpH deletion was lethal and double mutant strains lacking pbpH and pbpC or pbpI (also named yrrR) were viable. The viable mutants were indistinguishable from the wild-type except that the vegetative PG of the pbpC pbpH strain had a slightly slightly lower amount of disaccharide tetrapeptide with 1 amidation and higher amount of disaccharide tripeptide tetrapeptide with 2 amidations when compared to others strains. This suggests that PbpC (PBP3) is involved in vegetative PG synthesis but only affects the PG structure with a very low efficiency.
A pbpA pbpH double mutant containing a xylose-regulated pbpH gene inserted into the chromosome at the amyE locus was constructed. Depletion of PbpH resulted in an arrest in cell growth and a dramatic morphological change in both vegetative cells and outgrowing spores. Vegetative cells lacking pbpA and pbpH expression swelled and cell elongation was arrested, leading to the formation of pleiomorphic spherical cells and eventual lysis. In these cells, cell septations were randomly localized, cell walls and septa were thicker than those seen in wild type cells, and the average cell width and volume were larger than those of cells expressing pbpA or pbpH. The vegetative PG had an increased abundance of one unidentified muropeptide. Spores produced by the pbpA pbpH double mutant were able to initiate germination but the transition of the oval-shaped spores to rod-shape cells was blocked. The outgrowing cells were spherical, gradually enlarged, and eventually lysed. Outgrowth of these spores in the presence of xylose led to the formation of helical cells. Thus, PbpH is apparently required for maintenance of cell shape, specifically for cell elongation. PbpH and PBP2a play a redundant role homologous to that of PBP2 in E. coli.
A sequence alignment of the predicted product of pbpI against the microbial protein database demonstrated that the most similar protein in B. subtilis is SpoVD and in E. coli is PBP3. This suggested that PbpI belongs to the group of the genes required for synthesis of the spore or septum PG. PbpI was identified using radio-labeled penicillin and found to run underneath PBP4 on SDS-PAGE. PbpI is therefore renamed PBP4b. Study of a pbpI-lacZ fusion showed that pbpI was expressed predominantly during early sporulation. A putative sigma F recognition site is present in the region upstream of pbpI and studies using mutant strains lacking sporulation-specific sigma factors demonstrated that the expression of pbpI is mainly dependent on sigma factor F. A pbpI single mutant, a pbpI pbpG double mutant, and a pbpI pbpF double mutant were indistinguishable from the wild-type. The sporulation defect of a pbpI pbpF pbpG triple mutant was indistinguishable from that of a pbpF pbpG double mutant. Structure parameters of the forespore PG in a pbpI spoVD strain are similar to that of a spoVD strain. These results indicate that PBP4b plays a unknown redundant role.
Master of Science
27
Uhl, Juli D. "Hox Specificity: Constrained vs. Flexible Requirements for the PBC and MEIS Cofactors." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1397234792.
Full text
28
FRANCESCO, M. L. DI. "ANALYSIS OF INHERENT PROPERTIES OF ION CHANNELS FROM PBCV-1 CHLORELLA VIRUS AND INFLUENZA A VIRUS." Doctoral thesis, Università degli Studi di Milano, 2011. http://hdl.handle.net/2434/150556.
Full textAbstract:
Kcv from the chlorella virus PBCV-1 is a viral protein that forms a tetrameric, functional K+ channel in heterologous
systems. Kcv can serve as a model system to study and manipulate basic properties of the K+ channel pore because
its minimalistic structure (94 amino acids) produces basic features of ion channels, such as selectivity, gating,
and sensitivity to blockers. We present a characterization of Kcv properties at the single-channel level. In symmetric
100 mM K+, single-channel conductance is 114 ± 11 pS. Two different voltage-dependent mechanisms are responsible
for the gating of Kcv. “Fast” gating, analyzed by distributions, is responsible for the negative slope conductance
in the single-channel current–voltage curve at extreme potentials, like in MaxiK potassium channels, and can
be explained by depletion-aggravated instability of the filter region. The presence of a “slow” gating is revealed by
the very low (in the order of 1–4%) mean open probability that is voltage dependent and underlies the time-dependent
component of the macroscopic current.
29
Cisneros, Montoya Rafael. "Commande PI basée sur la passivité : application aux systèmes physiques." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS187/document.
Full textAbstract:
Le régulateur PID (Proportionnel-Intégral-Dérivée) est la commande par retour d'état la plus connue. Elle permet d'aborder un bon nombre de problèmes de commande, particulièrement pour des systèmes faiblement non linéaire et dont la performance requise est relativement modeste. En plus, en raison de sa simplicité, la commande PID est largement utilisée en l'industrie. Étant donnés que les méthodes de réglage de la commande PID sont basées sur la linéarisation, la synthèse d'un contrôleur autour d'un point d'équilibre est relativement simple, néanmoins, la performance sera faible dans des modes de fonctionnement loin du point d'équilibre. Pour surmonter ce désavantage, une pratique courante consiste en adapter les gains du PID, procédure connue sous le nom de séquencement de gain (ou gain-scheduling en anglais). Il y a plusieurs désavantages à cette procédure, comme la commutation des gains de la commande et la définition -non triviale- des régions de l'espace d'état dans lesquelles cette commutation aura lieu. Ces deux problèmes se compliquent quand la dynamique est fortement non linéaire. Dans d'autres méthodes, la synthèse de la commande utilise des schémas empiriques, ce qui ne permet pas l'analyse de la stabilité globale du processus. Dans ce contexte, ce travail de thèse a pour objectif de synthétiser des contrôleurs PI, basés sur la passivité, de telle sorte que la stabilité globale du système en boucle fermé soit garantie. L'un des avantages à utiliser la passivité est son attrait intuitif, qui exploite les propriétés physique des systèmes. L'idée centrale dans un système passive est que l'écoulement d'énergie entrante au système provenant de l'extérieur n'est pas inférieur à l'incrément de son énergie de stockage. Par conséquence, ces systèmes ne peuvent pas stocker plus d'énergie que celle fournie, dont la différence correspond à l'énergie dissipée. En introduisant le concept d'énergie, cette méthodologie nous permet de formuler le problème de commande en celui de trouver un système dynamique dont la fonction de stockage d'énergie prend la forme désirée. En incorporant le concept d'énergie cette méthode devient accessible à la communauté de praticiens et permets de fournir des interprétations physique de l'action de commande. Dans cette thèse, une méthodologie constructive de commande PI basée sur la passivité est présentée et motivée par des applications à des systèmes physiquesOne of the best known forms of feeding back a system is through a three-term control law called PID (Proportional-Integral-Derivative) controller. PID controllers are sufficient for many control problems, particularly when process dynamics are not highly nonlinear and the performance requirements are modest. Besides, because of its simple structure, the PID controller is the most adopted control scheme by industry and practitioners, beeing the PI the form mostly employed. Since the PI tuning methods are based on the linearization, commissioning a PI to operate around a single operating point is relatively easy, however, the performance will be below par in wide operating regimes. To overcome this drawback the current practice is to re-tune the gains of the PI controllers based on a linear model of the plant evaluated at various operating points, a procedure known as gain-scheduling. There are several disadvantages of gain-scheduling including the need to switch (or interpolate) the controller gains and the non-trivial definition of the regions in the plants state space where the switching takes place - both problems are exacerbated if the dynamics of the plant is highly nonlinear. In other common scenarios, a little information about the process dynamics or only a "good" linear approximation is taken into account when designing the control design. This impedes to analyse the global stability of the system. In this context, the current thesis work is aimed at the designing of PI controllers, based on the passivity theory, such that the stability of the closed-loop system is guarantied. One of the main advantages of passivity concepts is that they offer a physical and intuitive appeal. The primary idea in passive systems is that the power flowing into the system is not less that the increase of storage. Thus, they cannot store more energy than is supplied to it from the outside, with the difference being the dissipated energy. Thus, introducing the concept of energy, this methodology allows to recast the control problem as finding a dynamical system such that system energy function takes the desired form. Also, with this formulation, the communication between practitioners and control theorists is facilitated, incorporating prior knowledge of the system and providing physical interpretations of the control action. In this thesis, a constructive methodology for deriving PI passivity-based controllers is presented and motivated by the application to physical systems
30
Mells, George Frank Gannaway. "Investigation of the genetic basis of primary biliary cirrhosis : the PBC genetics study." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648610.
Full text
31
Foos, Nicolas. "Etudes structurales d'un complexe HOX-PBC de drosophile. : Un exemple de régulateur transcriptionnel." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4075.
Full textAbstract:
Les protéines Hox sont des protéines à homéodomaine. Elles sont très conservées et impliquées dans l'identité cellulaire selon les axes antéropostérieur, dorsoventral et proximodistal. Elles reconnaissent l'ADN pour réguler l’expression des gènes. La coopérativité avec des partenaires de la famille PBC est un modèle pour l'amélioration de la spécificité. Cette étude utilise Ubx (Hox) et Exd (PBC) de D. melanogaster comme modèles. Deux modes d'interaction entre Ubx et Exd : un par le motif « hexapeptide » d'Ubx et un autre par le motif UbdA objet de ce travail. UbdA se situe en C-terminal de l'hélice de reconnaissance de l'ADN d'Ubx. Nous avons résolu différentes structures de complexes Ubx-Exd-ADN avec deux types de séquences d'ADN. Ces structures montrent que le motif UbdA peut adopter différentes conformations permettant différents rôles : surface d'interaction avec Exd ou charnière entre l'HD et les domaines C-terminaux. En plus des motifs d'Ubx important pour la fonction de régulation, Ubx et Exd comportent des motifs intrinsèquement désordonnés appelés linker et bras N-terminal de l'homéodomaine, respectivement. Ces motifs interagissent avec l'ADN au niveau du sillon mineur et ont la capacité d'explorer l’environnement. Nous avons étudié l'extrémité en C-terminale d'Exd. Ce motif forme une quatrième hélice dont le repliement peut influer sur les contacts établis avec Ubx et avec l'ADN. L'ensemble de ces observations nous a permis d'apporter des éléments supplémentaires pour la compréhension de la spécificité de fonctions et de contribuer à alimenter les modèles de scannage de l'ADN de type monkey bar et d'« interface glissante »Hox proteins are homeodomain proteins belonging to the Transcription Factors superfamilly. These proteins are necessary for the determination of the cellular identity along the anteroposterior, dorsoventral and proximodistal axes. It's essential to recognize DNA targets with high specificity. One possible mechanism to acquire specificity implies the cooperativity between Hox and their PBC partners. Ubx (Hox) and Exd (PBC) proteins from D. melanogaster are the object of this work. One mechanisme of coopertivity involves the “hexapeptide” motif in Ubx and another one that involves its UbdA motif. The UbdA motif is located C-terminal to the recognition helix. We have solved seven different structures of Ubx-Exd-DNA complexes. Thanks to these structures, we show that UbdA can have a multipurpose role : it can provide an interaction surface to contact Exd and it can also act like a hinge between the C-terminal regions of Ubx and its homeodomain. UbdA and HX motifs from Ubx are not the only regions involved in the control of these proteins functions. Ubx and Exd also contain intrinsically disordered regions which are the linker region and the homeodomain N-terminal arm, for Ubx and Exd respectively. They interact with the DNA in the minor groove and can explore the space around. We studied the Exd 's C-terminal motif and determined that it has a flexible, helical fold. The folding of this fourth helix could modify the contacts established with Ubx and with the DNA. All these observations allow us to add supplementary information for the understanding of functional specificity and provide new arguments for the monkey-bar and for the « gliding interface » DNA- scanning models
32
Jeanniard, Adrien. "A la redécouverte des Chlorovirus : Contribution à l'étude des virus géants à ADN." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4028/document.
Full textAbstract:
Les virus du genre Chlorovirus (phycoDNAviridae) sont des virus à ADN double-brin de grande taille, qui infectent des algues vertes eucaryotes unicellulaires vivant en eau douce nommées les chlorelles (Trebouxiophyceae). A l'aide d'approches bioinformatiques, j'ai consacré mon travail de thèse à l'étude de la diversité génomique des chlorovirus et de leur histoire évolutive, ainsi qu'à l'étude transcriptomique de l'infection virale chez son hôte.Dans le premier volet de ma thèse, j'ai procédé à l'assemblage et à l'annotation de 50 nouveaux génomes de chlorovirus récemment séquencés (Roche-454). J'ai ainsi été en mesure de mieux caractériser les différences de structure du génome et de contenu en gène des différents chlorovirus en fonction de leurs hôtes. J'ai également mis en évidence l'existence d'un quatrième sous-groupe de chlorovirus, repoussant les limites connues de la diversité de ces virus. Enfin j'ai montré que les Chlorovirus ne suivent pas le même schéma évolutif des autres NCLDV et que l'origine de leurs gènes est encore inconnue, bien que probablement virale.Dans un autre projet, j'ai également étudié les variations de la transcription des gènes de la chlorelle (C. varabilis NC64A) induites par l'infection par un chlorovirus (PBCV-1) grâce au séquençage profond (Illumina) des ARNm polyadénylés présent dans la cellule saine, puis après infection. J'ai ainsi pu montrer que les différentes fonctions cellulaires sont impactées de façon préférentielle par l'infectionGiant viruses in the genus Chlorovirus (Phycodnaviridae) infect eukaryotic green microalgae known as Chlorella (Trebouxiophyceae). Using bioinformatic approaches, I dedicated my thesis on the study of the genomic diversity and evolutionnary history of the chlorovirus at the genus level, and the transcriptomic of the viral infection.In the first part on my work, I conducted the assembly and annotation of 50 new chlorovirus genomes recently sequenced (Roche-454). I was able to refine the known differences between chloroviruses, both in genome structure and gene content terms. Clues for the existence of a fourth subgroup of chloroviruses were also found. I was also able to show that the chlorovirus does not follow the same evolutionnary pattern as the other NCLDV, and that the origin of their genes is still largely unknown, but presumably of viral origin.In a second project, I studied the variation in the transcription of chlorella's genes (C. variabilis NC64A) during the infection by a chlorovirus (PBCV-1) using the deep-sequencing (Illumina) of all polyadenylated messenger RNA in the healthy or infected cell. This way, I was able to show that the various cellular functions are preferentially impacted by the infection
33
Westerlund, Jörgen. "HUMINT - En begreppsanalys." Thesis, Swedish National Defence College, War Studies Division, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:fhs:diva-714.
Full textAbstract:
Under det senaste 10-15 åren finns ett ökande inslag av särskilda förband och enheter för inhämtning av information och underrättelser från mänskliga källor i de insatsområden som Sverige skickar trupp till. Dessa förband kan vara av typen Field Humint Teams (FHT) eller National Intelligence Cells (NIC). Ökningen av denna typ av förband samt ökningen av det militära behovet av att agera i miljöer som präglas av kontakter med människor har skapat en ökad användning av det engelska uttrycket HUMINT (Human Intelligence) i den svenska militära vokabulären. HUMINT och Personbaserad inhämtning (PBI) är det två begrepp som i Sverige används för att beskriva inhämtningen av information och underrättelser från mänskliga källor. I Försvarsmaktens Underrättelsehandbok - Förhandsutgåva (FM UndH Fu) från 2006 används begreppet HUMINT trots sitt engelska ursprung och ingen tydlig svensk översättning är där gjord. De övriga underrättelsedisciplinerna är dock översatta till en svensk benämning. Begreppet personbaserad inhämtning nämns inte en enda gång i boken.
Inom Försvarsmakten finns det dessutom olika uppfattningar om vad som är HUMINT och PBI eller vad det inte är. Dessa två begrepp används ibland lite slarvigt och jämställs ibland med varandra.
Det övergripande syftet med denna uppsats är att pröva hypotesen att de i Sverige vedertagna begreppen HUMINT och PBI uppfattas och värderas olika av individer och organisationer. Dessutom syftar uppsatsen till att jämföra de svenska definitionerna med andra försvarsmakter, organisationer och enskilda författares tolkningar av begreppen i syfte att utröna om dessa skiljer sig åt. Avslutningsvis syftar uppsatsen till att diskutera huruvida det har någon betydelse att begreppen tolkas olika.
34
ABANS, Mariângela de Oliveira. "Parametrização de redes neurais artificiais em problemas de séries temporais não lineares empregando PBCA (Plackett-burman correlation analysis)." reponame:Repositório Institucional da UNIFEI, 2018. http://repositorio.unifei.edu.br/xmlui/handle/123456789/1429.
Full textAbstract:
Submitted by repositorio repositorio (repositorio@unifei.edu.br) on 2018-06-29T17:53:27Z
No. of bitstreams: 1
tese_2018016.pdf: 7348957 bytes, checksum: 39237c89c95bdb2055e4b91fe2b855c3 (MD5)Made available in DSpace on 2018-06-29T17:53:27Z (GMT). No. of bitstreams: 1 tese_2018016.pdf: 7348957 bytes, checksum: 39237c89c95bdb2055e4b91fe2b855c3 (MD5) Previous issue date: 2018-04-20
Séries temporais são encontradas em fenômenos naturais, mercadológicos e financeiros, e em processos de manufatura, entre outros, o que as torna importantes objetos de pesquisa. Quando não são lineares, sua modelagem é complexa devido ao grande número de parâmetros, à existência de fatores exógenos, à alta volatilidade e à presença de sazonalidade. Tem sido demonstrado que, nesses casos, RNAs apresentam bom desempenho tanto na apreensão do comportamento dos dados como na sua previsão dentro dos limites de exatidão requeridos. Apesar do grande número de parâmetros de uma RNA, delineamentos têm sido usados com sucesso, porém a alta demanda de recursos humanos, computacionais, financeiros e de tempo são obstáculos para sua total exploração. Neste trabalho, implantou-se uma nova metodologia denominada Análise de Correlação em Plackett_Burman (Plackett_Burman Correlation Analysis ̶ PBCA) na parametrização de Redes Neurais Artificiais ̶ RNAs, com o propósito de modelar e prever Séries Temporais Univariadas Não Lineares. Esta é uma metodologia de seleção de variáveis significativas baseada no Delineamento de Experimentos (DOE) de Plackett_Burman com rebatimento e que propõe a análise de correlação entre as séries de resíduos, consideradas como sinais. Sua vantagem é requerer um número de experimentos menor que o Delineamento Fatorial Completo e ser capaz de identificar as significativas interações de segunda ordem entre todas as variáveis. Nesta tese, implementou-se esta nova metodologia PBCA na construção de RNAs previsoras para auxiliar os profissionais responsáveis por decisões tático-estratégicas baseadas em séries temporais. A metodologia foi aplicada a dois casos: (i) número de horas disponíveis para pesquisa em um observatório astronômico profissional de classe mundial e (ii) distribuição de carga elétrica fornecida a uma empresa brasileira, com o objetivo de fornecer previsões de curtíssimo e curto prazos para a tomada de decisões sobre o melhor uso das infraestruturas envolvidas. Ambas as séries foram primeiramente estudadas através da aplicação de técnicas e modelos ditos “clássicos” a fim de estabelecer benchmarking para comparação. Os resultados deste trabalho sugerem a adequação apenas parcial da metodologia para estes fins. Não é possível aplicar a PBCA totalmente devido (i) à maneira de definir as RNAs, (ii) ao fato do processo não ser modelável, afinal e (iii) à impossibilidade de uso das interações de ordem dois entre as variáveis significativas no software Statistica®. São também apresentados possíveis desdobramentos da pesquisa e aplicações em outras áreas do conhecimento.
35
FERREIRA, Joana Braga de Moraes Marques. "Screening of genes related to inorganic phosphate in families with primary brain calcifications (PBC)." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/26882.
Full textAbstract:
Submitted by Pedro Barros (pedro.silvabarros@ufpe.br) on 2018-09-21T22:13:13Z
No. of bitstreams: 2
license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5)
TESE Joana Braga de Moraes Marques Ferreira.pdf: 5193351 bytes, checksum: 0e24ea46d41e7220625b8f65daf73891 (MD5)Approved for entry into archive by Alice Araujo (alice.caraujo@ufpe.br) on 2018-09-24T17:34:42Z (GMT) No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) TESE Joana Braga de Moraes Marques Ferreira.pdf: 5193351 bytes, checksum: 0e24ea46d41e7220625b8f65daf73891 (MD5)
Made available in DSpace on 2018-09-24T17:34:42Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) TESE Joana Braga de Moraes Marques Ferreira.pdf: 5193351 bytes, checksum: 0e24ea46d41e7220625b8f65daf73891 (MD5) Previous issue date: 2016-03-10
FACEPE
Primary brain calcification (PBC), also known as idiopathic brain calcification or Fahr's disease, is a rare neurological condition that is characterized by calcium phosphate deposits in the basal ganglia and adjacent areas, movement disorders, headache and neuropsychiatric symptoms. It presents autosomic dominant inheritance and it is associated with two inorganic phosphate transporter coding genes: SLC20A2 and XPR1. Two other genes related to the blood-brain barrier maintenance and integrity are also linked to PBC, the platelet-derived growth factor-β and its receptor (PDGFB and PDGFRB), although their roles in the formation mechanism of the calcifications is not clear yet. For this study, besides the four genes above mentioned, other members of the platelet-derived grown factor family (PDGFA, PDGFRA, PDGFC and PDGFD) have also been selected as candidate genes, for which new primer pairs were designed. All genes above were screened for new variants by Sanger sequencing in fifteen Brazilian unrelated patients with brain calcifications. Sequence in silico analysis was performed using CLC Main Workbench 6.9 software and online tools available in NCBI and GOLDENPATH platforms, resulting in the identification of the first de novo SLC20A2 mutation in a patient diagnosed with PBC (NM_006749.4:c.1158C>G; NP_006740.1:p.Y386*). SLC20A2 is to-date the main gene associated with PBC, with affecting-variants observed in ~50% cases. In order to find SLC20A2 deletions and/or duplications not detected by sequencing, all Brazilian probands were screened by QMPSF (Quantitative Multiplex PCR of Short fluorescent Fragments) and a duplication of the terminal exon was found in a patient with brain calcifications and hyperparatiroidism. Simultaneously, twenty-four French unrelated patients with PBC were also analyzed by QMPSF and partial SLC20A2 deletions were detected in four patients: two with deletion of the exon 2, where the start codon is located; one with deletion of the exon 4; and one with deletion of exons 4 and 5. These results reinforce SLC20A2 role as the main gene associated to PBC, as well as demonstrate that copy number variation analyses, even when revealing only partial deletions or duplications of a gene, are complementary to sequencing and work side by side in the search of genetic variations involved in this disease.
Introdução: A calcificação cerebral primária (CCP), também conhecida como calcificação idiopática dos núcleos da base ou doença de Fahr, é uma condição neurológica caracterizada por depósitos de fosfato de cálcio dos núcleos da base e região de entorno, parkinsonismo e sintomas neuropsiquiátricos. Apresenta herança autossômica dominante e é associada a dois genes codificantes de transportadores de fosfato inorgânico: o SLC20A2 e o XPR1. Dois outros genes relacionados à manutenção e à integridade da barreira hemato-encefálica, o fator de crescimento plaquetário B e seu receptor (PDGFB e PDGFRB), também foram associados à CCP, embora seus papeis no mecanismo de formação das calcificações ainda não estejam claros. Materiais e Métodos: Além dos quatro genes acima, foram selecionados como candidatos outros genes da família dos fatores de crescimento plaquetário (PDGFA, PDGFRA, PDGFC e PDGFD) e das protocaderinas (PCDH12), para os quais foram confeccionados pares de primers utilizados no seu sequenciamento e para análise de variação de número de cópia. Resultados e Discussão: Quinze famílias brasileiras com CCP foram triadas para novas variantes nos genes candidatos por sequenciamento. A análise in silico do sequenciamento foi feita através do software CLC Combined Workbench versão 6.9 e das ferramentas disponíveis nas plataformas online do NCBI e do GOLDENPATH. A partir dessa análise, foi identificada em um probando a primeira mutação de novo do SLC20A2, o principal gene associado a CCP (NM_006749.4:c.1158C>G; NP_006740.1:p.Y386*). A fim de encontrar deleções e/ou duplicações do SLC20A2 não detectadas por sequenciamento, todos os probandos brasileiros com calcificações cerebrais foram triados através da técnica de QMPSF (do inglês, Quantitative Multiplex PCR of Short fluorescent Fragments). Foi encontrada uma duplicação do exon terminal do mesmo gene em um paciente brasileiro com calcificações cerebrais e hiperparatireoidismo. Simultaneamente, foram identificadas deleções parciais no mesmo gene em quatro famílias francesas com CCP. Conclusões: Esses resultados reafirmam o SLC20A2 como o principal gene associado a CCP, bem como demonstram que análises de variação de número de cópia (CNV), ainda que parciais, são complementares ao sequenciamento na busca por variantes genéticas relacionadas a esta doença.
36
Cipro, Caio Vinicius Zecchin. "Ocorrência de compostos organoclorados em Euphausia superba e em ovos gorados de pingüins do gênero Pygoscelis." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/21/21133/tde-19072007-110620/.
Full textAbstract:
Bifenilos policlorados (PCBs) e pesticidas organoclorados são compostos que não ocorrem naturalmente no ambiente e não são facilmente degradados química ou microbiologicamente. Seu estudo no ambiente é importante devido à sua persistência, toxicidade, lipossolubilidade e conseqüente biomagnificação. Por isso, representam a maioria dos poluentes orgânicos persistentes (POPs) considerados prioritários pela UNEP (United Nations Environmental Programme) e banidos ou restritos pela Convenção de Estocolmo, de maio de 2001. Tais poluentes podem ser facilmente emitidos para a atmosfera, atingindo áreas remotas como a Antártida, integrando um processo cíclico de contaminação conhecido como destilação global. No presente trabalho otimizou-se uma metodologia analítica capaz de detectá-los em ovos gorados de pingüins e indivíduos de krill coletados na Baía do Almirantado, Ilha Rei Jorge, Antártida. Tal metodologia foi avaliada e enquadrou-se em critérios internacionais de controle de qualidade. Os compostos mais presentes foram, de um modo geral, os PCBs, DDTs e o HCB e a ocorrência pareceu ser espécie-específica dentro do gênero Pygoscelis. Em todos os casos, o teor dos compostos não foi superior ao de aves árticas em nível trófico semelhante. A análise do krill permitiu estimar a biomagnificação dos compostos encontrados nos ovos, cuja única fonte de contaminação é a transferência fêmea-filhote.Polychlorinated biphenyls (PCBs) and organochlorine pesticides are compounds that do not occur naturally in the environment and are not easily degraded by chemical or microbiological action. Their study in the environment is important due to persistence, toxicity, liposolubility and consequent biomagnification. For these reasons, they represent the majority of the persistent organic pollutants (POPs), considered to have priority by the UNEP (United Nations Environmental Programme) and banished and/or restricted by the Stockholm Convention of May, 2001. Such pollutants can be easily ejected into the atmosphere and reach areas as remote as Antarctica, integrating a cyclical contamination process known as ?global distillation?. In the present work an analytical methodology capable of detecting such compounds in unhatched penguin eggs and whole krill was optimized. The samples were collected in Admiralty Bay, King George Island, Antarctica. This methodology was evaluated and fitted international quality control criteria. The compounds found in higher levels were, in most of the samples, the PCBs, DDTs and HCB and the occurrence seemed to be species-specific for the Pygoscelis genus. In all of the cases, the levels found were not higher than the ones in arctic birds in a similar trophic level.The krill samples analysis made it possible to estimate the biomagnification of the compounds found in eggs, whose only source of contamination is the female-offspring transfer.
37
Arredondo, Rosas Marcial. "Diseño y eficacia de un programa de entrenamiento en mindfulness y compasión basado en prácticas breves integradas." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/454897.
Full textAbstract:
La presente tesis pretende demostrar que un programa de entrenamiento basado en prácticas breves de mindfulness, respiración coherente y compasión (como prácticas principales) y así como también, acceder a un estado “mindful” de consciencia a través de “prácticas informales” en la vida cotidiana, produce cambios significativos en la disminución de síntomas de ansiedad, depresión estrés y burnout y en el aumento de las capacidades de mindfulness, descentramiento y autocompasión, así como también produce un incremento de la HRV en los participantes. Para demostrar esto, se presenta el diseño del protocolo M-PBI y dos estudios: En el protocolo se describe el programa y las diferentes prácticas que se realizan, en el primer estudio piloto (pre-post) no controlado, con una muestra de 74 participantes, se pudieron observar las diferencias estadísticamente significativas del efecto del programa M-PBI entre las medidas previas a la intervención y una vez finalizado el programa, en cuanto a ansiedad, depresión, estrés y capacidades de mindfulness y descentramiento, tanto para personas que estaban en tratamiento psicológico al momento de iniciar el programa 25% de la muestra), como en población no clínica (75% de la muestra); el segundo estudio se realizó en un entorno laboral, con una muestra de 40 sujetos, y consistió en un estudio intervencionista, aleatorizado y controlado con un grupo en lista de espera, evaluando el efecto del programa M-PBI sobre el estrés, burnout, HRV, mindfulness, descentramiento y autocompasión.
Se pudo concluir que el Programa de entrenamiento en Mindfulness y Compasión basado en Prácticas Breves Integradas (M-PBI) se ha mostrado eficaz en la reducción de síntomas de estrés y burnout, y en el aumento de la capacidad de mindfulness, descentramiento y autocompasión. Se ha observado también un aumento de la HRV de los participantes, así como también, cambios significativos en la disminución de síntomas de ansiedad y depresión (pre vs. post entrenamiento). Se requieren estudios posteriores, con un tamaño muestral más grande, para confirmar estos resultados.The present thesis aims to demonstrate that a training program based on brief practices of mindfulness, coherent breathing and compassion (as main practices) and also, access to a "mindful" state of consciousness through "informal practices" in life produces significant changes in the reduction of symptoms of anxiety, depression, stress and burnout and in the increase of the abilities of mindfulness, decentralization and self-compassion, as well as also an increase of the HRV in the participants. To demonstrate this, the design of the M-PBI protocol and two studies are presented: The protocol describes the program and the different practices that are performed in the first uncontrolled (pre-post) pilot study with a sample of 74 Participants, it was possible to observe the statistically significant differences in the effect of the M-PBI program between the measures prior to the intervention and at the end of the program, in terms of anxiety, depression, stress and mindfulness and decentralization capacities, both for people who were In psychological treatment at the time of starting the program 25% of the sample), as in non-clinical population (75% of the sample); The second study was performed in a work environment with a sample of 40 subjects, and consisted of an interventionist, randomized and controlled study with a waiting list group, evaluating the effect of the M-PBI program on stress, burnout, HRV , Mindfulness, decentering and self-compassion. It was concluded that the Mindfulness and Compassion Training Program based on Integrated Brief Practices (M-PBI) has been shown to be effective in reducing symptoms of stress and burnout, and in increasing the capacity for mindfulness, decentration and self-pity. An increase in participants' HRV has also been observed, as well as significant changes in the decrease in anxiety and depression symptoms (pre vs. post training). Further studies, with a larger sample size, are required to confirm these results.
38
Cottle, Jake R. "The Political Business Cycle: Endogenous Election Timing & Hyperbolic Memory Discounting." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7606.
Full textAbstract:
In the models analyzed in this paper, there exists an incumbent politician with one objective, two choices, and voters who remember the past differently. The politician's primary goal is to get reelected, which is done by maximizing the number of votes on the day of election. The politician can increase their chances of reelection if they influence the state of the economy over time and ensure the economy is in its 'best' state on the days leading up to the election.
In conducting this research, I wanted to study how different rates of memory decay influences the choices the politician makes during the course of their term. Also, I wanted to explore how long a politician would wait to have an election if that were a choice they could make. I found that voters who remember more of the past place a greater constraint on the incumbent leading to moderate fluctuations in the economy and frequent elections.
39
Aucher, Christophe. "Amélioration de l'électrode positive des systèmes PbC® : propriétés anticorrosives de la polyaniline appliquées aux batteries plomb-acide." Nantes, 2011. https://archive.bu.univ-nantes.fr/pollux/show/show?id=83fa1b26-5df4-4ae1-b0af-7960f1d0c050.
Full textAbstract:
La batterie hybride PbC est constituée d'une électrode faradique dont la matière active est le dioxyde de plomb et d'une électrode capacitive de carbone activé identique à celle utilisée dans les supercondensateurs. L'association de composants d'un accumulateur classique au plomb et d'un supercondensateur permet d'obtenir des performances intermédiaires entre un supercondensateur et un accumulateur. Le supercondensateur possède une puissance spécifique très élévée et une durée de vie de plusieurs millions de cycles tandis que la batterie peut être assimilée à un réservoir énergétique ayant une très grande densité d'énergie avec des temps de décharge de plusieurs heures. L'étude présentée dans ce manuscrit porte essentiellement sur l'amélioration des performances de l'électrode positive de la batterie. Les travaux sont divisés en deux parties, la première porte sur l'élaboration d'un collecteur de courant composite plomb/polyanyline résistant à la corrosion en mileu acide sulfurique 1,5 M, qui conduit à une diminution de la densité de courant de corrosion de 95 % comparé au métal nu. Le second volet concerne l'amélioration de la cyclabilité et de la capacité de l'électrode positive par l'élaboration de PbO2 avec des tailles et des morphologies de particules différentesThe hybrid battery PbC consists of a faradaic electrode whose active material is lead dioxide and a capacitive electrode of activated carbon similar to that used in capacitors. The association of components of a conventional lead-acid battery and components from a capacitor enable to achieve performances that are intermediate between those of a capacitor and a battery. The capacitor has a high specific power with a lifespan of several million cycles while the battery can be considered to an energy tank, with a high energy density, with energy discharge time of several hours. The study presented in this manuscript focuses on improving the performance of the positive electrode of the battery. The work is divided into two parts, the first concerns the development of a composite lead/polyanyline current collector resistant to corrosion in 1. 5 M sulfuric acid, which leads to a 95 % decrease of the corrosion current density compared to a bare metal without polyaniline. The second part concerns the improvement of cyclability and capacity of the positive electrode through the development of the PbO2 with sizes and morphologies of different particles
40
Silva, Fábio Molina da. "Estratégias para a programação da produção em ambientes com capacidade flexível controlados pelo sistema PBC." Universidade Federal de São Carlos, 2014. https://repositorio.ufscar.br/handle/ufscar/3452.
Full textAbstract:
Made available in DSpace on 2016-06-02T19:50:25Z (GMT). No. of bitstreams: 1
6422.pdf: 2110662 bytes, checksum: eb693b2b653ba32626459f3fd72fa98b (MD5)
Previous issue date: 2014-12-05The PBC System is a well-known Ordering System that periodically syncronizes the material flow of the shop floor. The PBC has the property of constant and planned production lead-time, a policy of minimal lot sizing and a constant frequency on order releasing. An exhaustive literature review presented in this thesis has shown that work uses PBC when the production capacity is not constant. This is a reality presented in companies where compensatory times off allows the capacity be tranfer between time stamps and employees that can work on diferente positions, allowing the capacity to be managed from one working center to another. This work formally defines those issues using mathematical programming, and defines a set of heuristics to solve it. After the application of the models and heuristics to a set of instances, one can note that the heuristics are eficiente to solve the problem, and the strategy of using PBC is very successful in the studied environment (production system with variable capacity).
O sistema PBC é conhecido como um sistema de controle da produção que sincroniza periodicamente o fluxo de materiais no chão de fábrica. O PBC tem a característica de possuir lead-time de produção constante e planejado, política de dimensionamento de lote conforme o mínimo necessário e frequência estável na liberação de ordens. Uma revisão exaustiva da literatura, apresentada neste trabalho, mostrou que não existem relatos do uso do PBC em ambientes onde a capacidade produtiva não é constante, uma realidade que se apresenta às empresas com a adoção de políticas de banco de horas (que permitem a transferência de capacidade produtiva entre diferentes períodos) e funcionários polivantes (que permitem a transferência de capacidade produtiva entre diferentes centros de trabalho). O presente trabalho define formalmente esse problema, usando técnicas de programação matemática, e propõe um conjunto de heurísticas para resolvê-lo. Após a aplicação dos modelos e heurísticas em um conjunto de casos de teste, mostra-se que as heurísticas propostas são eficazes para a resolução do problema, sendo estratégias viáveis para a implementação do PBC em ambientes de manufatura com capacidade variável.
41
Casimiro, Soriano Enzo Martin. "Síntesis y caracterización del complejo: 2-(2-piridil)bencimidazol sacarinato plata (I), [Ag(pbi)(sac)]." Bachelor's thesis, Universidad Nacional Mayor de San Marcos, 2018. https://hdl.handle.net/20.500.12672/7943.
Full textAbstract:
Publicación a texto completo no autorizada por el autorDesarrolla una nueva ruta de síntesis del complejo polimérico sacarinato plata (I), [Ag(sac)]n, y la síntesis del complejo 2-(2-piridil)bencimidazol sacarinato plata(I), [Ag(pbi)(sac)]. La caracterización de ambos compuestos se realiza a través de los métodos de amperometría, análisis elemental, análisis por XPS, espectroscopía de IR, UV-Visible, 1H-RMN y 13C-RMN.
Tesis
42
Morales, Bueno Patricia. "How Is the Evaluation Process in a Course Following the PBI (Problems-Based Learning) Methodology?" En Blanco y Negro, 2013. http://repositorio.pucp.edu.pe/index/handle/123456789/117352.
Full textAbstract:
This article focuses on the different ways in which the concepts of teaching and learning are conceived. It also defines the conception on which the educational view of the PBL is based, and how it determines its learning goals. Likewise, it shows how evaluation strategies are bonded to each of the stages in the PBL process, noting their features and the relation with learning goals of the methodology.El artículo discute las diferentes concepciones acerca de la enseñanza y el aprendizaje, caracterizando aquellas que constituyen el fundamento de la visión educativa del ABP y que condicionan sus metas de aprendizaje. De acuerdo a ello, las estrategias de evaluación se plantean vinculadas con cada una de las etapas del proceso ABP, destacando sus características y su relación con las metas de aprendizaje de la metodología
43
Freitas, Mauricio Azevedo de. "Poli(indeno) fosfonado : síntese, propriedades e uso como eletrólito em membranas a base de PBI." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/181807.
Full textAbstract:
Neste trabalho, um polímero eletrólito derivado do poli(indeno) (PInd) foi desenvolvido como componente de membranas poliméricas a base de polibenzimidazol (PBI) para célula a combustível de média temperatura. Foi investigado o método de síntese, envolvendo a reação de fosfonação pelo método de Friedel-Crafts assistido por catalisador ácido de Lewis AlCl3. O polímero poli(indeno) fosfonado (PPInd) foi comparado com seu análogo sulfonado, o poli(indeno) sulfonado (SPInd), e usados nas blendas com 5, 7,5 e 10% em peso com o PBI. Os polímeros precursores foram caracterizados por espectroscopia de infravermelho, espectroscopia de ressonância magnética nuclear, espectroscopia de energia dispersiva, espectrometria de espalhamento Rutherford, análise termogravimétrica acoplada com espectrometria de massas e calorimetria exploratória diferencial. As blendas PPInd/PBI e SPInd/PBI foram caracterizadas por análise termogravimétrica, grau de dopagem e espectroscopia de impedância eletroquímica. A modificação realizada pelo método de Friedel-Crafts permitiu a obtenção do poli(indeno) fosfonado parcialmente solúvel em solventes orgânicos e água, com grau de modificação de 81%. Houve convergência dos teores de modificação encontrados pelas análises termogravimétrica, espectrometria de espalhamento Rutherford e espectroscopia de energia dispersiva. O polímero PPInd apresentou estabilidade química na temperatura de operação da célula a combustível de média temperatura, passando por processos de degradação típicos de sua estrutura aromática fosfonada. A degradação dos polímeros PInd, PPInd e SPInd ocorreu majoritariamente com cisão de unidades monoméricas de indeno não funcionalizado. A inserção dos polímeros modificados PPInd e SPInd no PBI resultou no aumento da condutividade iônica, tendo a blenda com 10% de PPInd apresentado o maior valor de condutividade protônica (0,015 S.cm-1), a 25 oC. O uso do poli(indeno) modificado com grupos ácido fosfônico visa aumentar a gama de eletrólitos para células a combustível de média temperatura.In this work a polymer electrolyte derivated from the poly(indene) (PInd) was developed to be used as polymer electrolyte membrane in medium-temperature fuel cells. The modification method, based on the AlCl3 assisted Friedel-Crafts reaction, was investigated as fosfonation strategy. The phosphonated poly(indene) was compared to its similar sulphonated poly(indene) and they were used in blends of 5, 7.5 and 10wt% in polybenzimidazole (PBI). Pristine polymers were characterized by infrared spectroscopy, nuclear magnetic resonance spectroscopy, energy dispersive spectroscopy, Rutherford backscattering spectrometry, thermogravimetric analysis coupled with mass spectrometry and differential scanning calometry. The PPInd/PBI and SPInd/PBI blends were characterized by thermogravimetric analysis, doping level and electrochemical impedance spectroscopy. The modification by Friedel-Crafts reaction produced phophonated poly(indene) with degree of phosphonation of 81%, partially soluble in organic solvent and water. It was found convergence on the results for degree of phosphonation calculated by thermogravimetric analysis, Rutherford backscattering spectrometry and energy dispersive spectroscopy. PPInd presented chemical and thermal stabilities within the fuel cell operating temperature, passing by typical degradation processes of macromolecules made of phosphonated aromatic structures. The degradation of PPInd and SPInd occurred mainly by cleavage of monomeric units of non-funcionalized indene. Addition of modified polymers PPInd and SPInd resulted in increase of PBI’s ionic conductivity. 10PPInd/PBI blend presented the highest ionic conductivity (0.015 S.cm-1) at 25 oC. The use of phosphonated poly(indene) on PBI membranes enlarges the variety of available polymer electrolyte membranes for medium-temperature fuel cells.
44
Alwan, Mohamad. "Contribution à l’étude de l’impact des dégradations d’origines électriques et thermiques sur les performances du transistor VDMOS de puissance." Rouen, 2007. http://www.theses.fr/2007ROUES027.
Full textAbstract:
Les modules d’électronique de puissance sont appelés à être fortement intégrés et poussés aux limites de leurs capacités de fonctionnement. D’autre part, ces modules sont souvent soumis à des environnements thermiques sévères qui peuvent altérer profondément les propriétés des semi-conducteurs, voire même les détruire. La température peut jouer un rôle essentiel dans les mécanismes de dégradation. Ce travail a pour objectif la prise en compte des mécanismes de dégradation dans les composants microélectroniques, de type VDMOS de puissance, sur leurs performances électriques. Une analyse numérique de l’effet de la contrainte thermique sur les caractéristiques statiques et dynamiques du transistor VDMOSFET de puissance a été effectuée. Sous les conditions de la contrainte thermique, nous observons quelques modifications des propriétés physiques et électriques du VDMOS. Nous analysons théoriquement et numériquement, les paramètres responsables de ces modifications. Une expression approximative du coefficient d’ionisation en fonction de la température a été proposée. La tension de claquage et l’extension maximale de la charge d’espace en fonction du dopage et de la température ont été calculées pour une jonction plane abrupte P+N dissymétrique. L’effet de la contrainte thermique sur les caractéristiques dynamiques C(V) a été observé et analysé. Dans un champ étendu de conditions expérimentales, ce travail consiste, par des analyses physiques approfondies et des simulations 2D (Silvaco), à mettre en évidence ces phénomènes de dégradation pouvant causer des défaillances des dispositifs et systèmes microélectroniques à base de VDMOS. Nous avons étudié les contraintes à forts champs électriques (HEFS), à la température en fonctionnement opérationnel, à haute température sous polarisation (BTI) et à cyclage thermique sous polarisation sur la tension de seuil et sur le transfert de charge du VDMOSFET de puissance à canal n. Les caractéristiques du transfert de charge et C-V ont été étudiées durant les contraintes. Nous expliquons les causes principales dues à la dégradation dans le VDMOSFET qui sont les piégeages de charges dans l’oxyde et à l’interface oxyde-silicium induits par des porteurs libres qui ont l’énergie suffisante pour traverser la barrière SiO2/SiThe power electronics modules are required to be strongly integrated and led to their capacity limits of operation. In addition, these modules are often subjected to several thermal environments which can deteriorate the semiconductors properties, and even to destroy them. The temperature can play an essential part in the degradation mechanisms. This work consists to take into account the degradation mechanisms in microelectronics components, like Power VDMOS, on their electric performances. A numerical analysis has been performed to evaluate the thermal stress effect on static and dynamic characteristics of VDMOS power FET’s. Under thermal stress conditions, some modifications of physical and electrical VDMOS properties are observed. We analyse, theoretically and numerically, parameters responsible of these modifications. Approximate expressions of the ionization coefficients and breakdown voltage in terms of temperature are proposed. Non-punch-throughjunction theory is used to express the breakdown voltage and the space charge extension with respect to the impurity concentration and the temperature. The capacitances of the device have been also studied. The effect of the stress on C-V characteristics is observed and analyzed. We notice that the drain-gate, drain-source and gate-source capacitances are shifted due to the degradation of device physical properties versus thermal stress. In a wide field of experimental conditions, we propose, by deepened physical analyses and 2D simulations (Silvaco), to highlight these phenomena of degradation being able to cause failures of the devices and microelectronics systems containing VDMOS. We have studied the effects of High Electric Field Stress (HEFS), thermal operating, Bias Temperature Instability (BTI) and Bias thermal cycling in threshold voltage and gate charge of n-channel Power VDMOSFETs. The gate charge characteristics and C-V capacitance have been investigated during stress. It is shown that the main degradation issues in the Si Power VDMOSFETs are the charge trapping and the trap creation at the interface of the gate dielectric induced by energetic free carriers which have sufficient energy to cross the SiO2/Si barrier
45
Astier, Florence. "Le canal du PBPI : une analyse théorique et empirique d'un canal de transmission particulier de la politique monétaire au Japon." Lyon 2, 2000. http://www.theses.fr/2000LYO22008.
Full textAbstract:
L'objectif de cette thèse est de décrire, analyser et vérifier théoriquement et empiriquement un canal de transmission de la politique monétaire spécifique au système financier japonais : le canal du programme de prêts et d'investissements publics au Japon (PBPI). Le PBPI consiste en un ensemble de flux de financement et un ensemble d'institutions. Le taux d'épargne des ménages japonais est élevé et la part de l'épargne postale dans le patrimoine financier des ménages est supérieur à 20 %. Cette épargne collectée est centralisée au Trust Fund Bureau (TFB), une institution financière qui joue à peu près le rôle de la Caisse des dépôts et consignation française. Le TFB transforme cette épargne en prêts à des taux bonifiés ayant une orientation politique et sociale. Les institutions financières gouvernementales forment le réseau de distribution de ces prêts. La particularité du PBPI autorise l'existence de canaux spécifiques de transmission de la politique monétaire supplémentaire aux canaux "classiques". Nous confortons cette théorie par une analyse empirique qui établit des relations de cointégration entre les variables qui composent ce système et par des simulations dynamiques entre les relations instantanées qui s'établissent entre les variables. Nous constatons empiriquement que le canal du PBPI est largement actif durant les périodes de difficulté économique et n'était pas ou peu actif durant la période de la bulle finanière confirmant bien son rôle de "béquille" de l'économieThe aim of this study is to analyze how monetary policy impulses are propagating through the FILP system and to show that the Japanese Fiscal Investment and Loan Program (FILP) system allows the existence of a new monetary policy channel : the FILP channel. .
46
Huang, Wenting. "Immunology and Genetics of Autoimmune Biliary Disease." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447691320.
Full text
47
Vannozzi, Valerio. "Effetto della lunghezza di ramificazione sulle proprietà finali di copolimeri statistici ottenuti da fonte rinnovabile." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15808/.
Full textAbstract:
La gestione dei rifiuti plastici, in particolare degli imballaggi primari, risulta un problema fortemente sentito sia dalla società civile che dalle istituzioni, date le ingenti quantità prodotte e il difficile riciclo, che in molti casi non è praticabile a causa della contaminazione con materia organica e comunque non economicamente conveniente. In questo scenario quanto mai complesso e articolato, si inserisce il presente lavoro di Tesi avente come obiettivo il design di nuovi materiali biobased e biodegradabili da utilizzare nell’imballaggio alimentare primario e dunque caratterizzati da buone proprietà meccaniche per la realizzazione di film sottili e da idonee performance barriera. Tali materiali sono stati pensati come risultato della modifica chimica di poli(butilene succinato) (PBS) e poli(butilene trans-1,4-cicloesanoato) (PBCE).
Il PBS è una bioplastica già prodotta a livello industriale mentre il PBCE, le cui proprietà sono estremamente interessanti, non è ancora disponibile in commercio. Entrambi i materiali sono però troppi rigidi per la realizzazione di film flessibili e trasparenti. In particolare, sono stati sintetizzati copolimeri statistici a diversa composizione contenenti catene laterali alifatiche di diversa lunghezza. Nel caso del PBCE, si è ritenuto interessante valutare anche l’effetto dell’isomeria cis/trans dell’anello cicloesano sulle proprietà finali del materiale. I polimeri ottenuti sono stati caratterizzati dal punto di vista delle proprietà termiche, meccaniche e barriera e i risultati ottenuti messi in relazione con la lunghezza delle catene laterali e la composizione.
48
"Economía para la Gestión.MTA11. PBI nominal y PBI real." Universidad Peruana de Ciencias Aplicadas - UPC, 2014. http://hdl.handle.net/10757/336660.
Full text
49
Wulfmeyer, Timo. "Strukturelle Organisation der DNA in PBCV-1." Phd thesis, 2012. http://tuprints.ulb.tu-darmstadt.de/3199/1/Wulfmeyer.PDF.
Full textAbstract:
Der Prozess der DNA-Kondensation stellt in allen lebenden Organismen einen komplizierten Prozess dar. Der Größenunterschied zwischen DNA-Molekül und Zelle bzw. Viruskapsid, sowie die negative Ladung des Phosphatrückgrates der DNA sind die größte Schwierigkeit einer erfolgreichen DNA-Aggregation.
Im Laufe der Evolution haben sich unterschiedliche Prozesse entwickelt, um diese Aufgabe erfolgreich durchzuführen. So kodieren z.B. eukaryotische Zellen für Proteine, so genannte Histone, die wie in einer Spule von der DNA eng umschlungen werden. Dadurch ist es möglich die DNA zu kondensieren und eng zu packen. Dieser Prozess kann ebenfalls von positiv geladenen Molekülen, Polyaminen oder Kationen durchgeführt werden. Ebenso wurden Prozesse etabliert, die es ermöglichen Geninformation auf geringem Raum zu kodieren, die so genannten overlapping genes, um die Größe des Genoms zu reduzieren. Chlorellaviren sind ein positives Beispiel für eine erfolgreiche DNA-Kondensation wie am Prototyp dieser Familie, PBCV-1 zu erkennen ist. Die Herausforderung für diese Virengruppe besteht darin, ein Genom in ihrem Kapisd zu verpacken, welches 1000 mal länger ist.
In topographischen Atomic force microscopy - und fluoreszenzmikroskopischen Messungen wurde festgestellt, dass die isolierte, virale DNA repetitive Strukturen aufweist. Des Weiteren zeigen Sequenzanalysen, dass eine periodische Verteilung GC-reicher Sequenzen vorliegt, die mögliche Bindungsstellen für basische Proteine sein können. Biochemische Experimente zeigen, dass keine signifikanten Konzentrationen an Polyaminen vorliegen und diese Menge lediglich 0.02 % der DNA kondensieren könnte. Ebenso liegt keine höhere Konzentration eines einzelnen Kations, z.B. Mg2+, vor, wie Energy dispersive X-ray spectroscopy und Inductively coupled plasma-mass spectrometry belegen. Es ist allerdings möglich, dass die Summe aller Kationen für die Kondensierung teilweise verantwortlich ist, da bereits 58 % der DNA neutralisiert werden könnte. Diese Erkenntnis steht im Gegensatz zu den Ergebnissen der Phage λ, die ausschließlich Kationen und Polyamine zur Aggregation nutzt.
PBCV-1 kodiert für ein Protein, A278L, welches Kinaseaktivität aufweist. Des Weiteren ähnelt A278L in den physikalischen Eigenschaften Histonen und ist somit ein wichtiger Kandidat für die Aggregation der viralen DNA.
Das rekombinante Protein zeigt in topographischen AFM-Messungen, im Vergleich zum neutralen Protein BSA, eine Verdopplung der Aggregation der viralen DNA.
Kraftspektroskopische Messungen zeigen, dass das rekombinante Protein A278L (25 nN) eine ähnliche Bindungskraft zur DNA aufweist wie die an der DNA assoziierten Partikel (64 nN).
Dieses Protein könnte, neben Kationen, für das Aggregieren der DNA verantwortlich sein, so dass eine Metastruktur und eine Organisation der viralen DNA gewährleistet werden kann.
50
Hsieh, Yi-Shan, and 謝依珊. "Preparations and Performance Studies of PBI/PTFE andPBI/PBI-BS/PTFE Composite Membranes." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/11078163668215140178.
Full textAbstract:
碩士元智大學
化學工程與材料科學學系
97
In this study, we synthesized polybenzimidazole (PBI) and its derivative butyl sulfonated polybenzimidazle (PBI-BS).The porous poly tetra fluoro ethylene (PTFE) was used as supporting membranes to reinforce PBI and PBI/PBI-BS (8/2 g/g) blend to prepare PBI/PTFE and PBI/PBI-BS/PTFE composite membranes. These two composite membranes were used to prepare membrane electrode assemblies (MEA). We performed 400 hr H2/O2 life test on PBI/PTFE MEA and 100 hr test on PBI/PBI-BS/PTFE MEA at 160 ℃ with a current density i = 200 mA/cm2. During long time life test, the i-V curve and AC-impedance measurements of MEAs were performed every 12 hr.