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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
231

Navigation in Wheeled Mobile Robots Using Kalman Filter Augmented with Parallel Cascade Identification to Model Azimuth Error

Rahman, ATIF 13 June 2013 (has links)
Unmanned ground mobile robots are land-based robots which do not have a human passenger on board. They can be either autonomous, or controlled via telecommunication. For navigational purposes, GPS is often used. However, the GPS signal can be distorted in obstructive environments such as tunnels, urban canyons, and dense forests. IMUs can be used to provide an internal navigational solution, free from external input. However, low cost IMUs are prone to various intrinsic sources of error, which leads to large errors in the long run. Using the short term accuracy of the IMU, and the long term accuracy of the GPS, these two technologies are often integrated to combine the aforementioned aspects of the two systems. For integration of the two, various methods are implemented. Such integration methods include Particle Filters, and Kalman Filters. Kalman Filters are commonly used due to their simplicity in calculations. However, the Kalman Filter linearizes the nonlinear error estimates which are inherent with low cost IMUs. The Kalman Filter also does not account for IMU measurement drift, which is present when the measurement unit is used for a long period of time. In this thesis, a Parallel Cascade Identification (PCI) algorithm is augmented with the Kalman Filter (KF) to model the nonlinear errors which are intrinsic to the low cost IMU. The method of integration used was 2D GPS/RISS loosely coupled integration using a Kalman Filter. The PCI algorithm modelled the nonlinear error for the z-axis gyroscope while the GPS signal was available. During a GPS outage, the PCI nonlinear error model was combined with the KF estimated error and the mechanization error, to provide a corrected azimuth. The KFPCI algorithm showed an improvement over the KF algorithm in RMS position error, maximum position error, RMS azimuth error, and maximum azimuth error by an average of 30.76%, 34.71%, 66.76%, and 53.58% in each of the respective areas. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2013-06-11 18:13:12.625
232

One-pot nitro-Mannich cascade reactions : new methodologies and synthetic applications

Pelletier, Sophie Marie-Clémentine January 2011 (has links)
Pyrrolidine and pyrrolidinone rings are common motifs found in many biologically active natural products and drugs. Accordingly, our work focuses on the development of new methodologies for their one-pot synthesis. An efficient diastereoselective nitro-Mannich / lactamisation reaction cascade of methyl 3-nitropropanoate with cyclic and acyclic imines for the direct preparation of trans-monocyclic and fused tricyclic pyrrolidinone derivatives was developed. The reaction is easy to perform, broad in scope and tolerates a wide variety of functional groups. For the monocyclic methodology, 28 examples with a very good average yield of 72% and excellent diastereocontrol (typical dr >98:2) were obtained using optimized conditions and varying the amine and the aldehyde reagents. The methodology has been extended to the synthesis of 1,3,5-trisubstituted 4-nitropyrrolidinone derivatives using α-substituted 3-nitropropanoate. Using a one-pot protocol, 22 derivatives were synthesised in good yields (65% average) and diastereomeric ratios ranging from 3:1 to 30:1 in favor of the trans/trans diastereoisomer. In addition, the nitro-Mannich / lactamisation cascade of methyl 3-nitropropanoate was developed further to allow the rapid synthesis of 5-isopropyl-4-nitropyrrolidin-2-one from reaction with ammonium acetate and 1-butyl-4-nitropyrrolidin-2-one from reaction with formaldehyde. Also, the synthetic utility of the nitro-pyrrolidinones formed was exemplified through various functional group modifications: the selective reduction of the lactam carbonyl, the reduction of the nitro group in the presence or absence of a carbonyl group and the reductive removal of the nitro group. The development of an enantioselective version of the cascade under chiral Brönsted acid catalysis provided promising results (up to 90% ee). Moreover, various studies were undertaken to understand the mechanism of the reaction and the nitro-Mannich / latamisation cascade is now well understood. Furthermore, a formal synthesis of rac-Slaframine in 8 steps and 15% overall yield was achieved and it inspired additional work towards a nitro-Mannich / epoxide ring opening cascade.
233

High speed very thin films with reverse roll coatings : an experimental investigation of reverse roll coating of fluids using rigid and deformable rolls at high speeds

Shibata, Yusuke January 2012 (has links)
The objective of a coating operation is to transfer a defect free liquid film onto a continuous substrate in order to meet the requirements of the final products. Mainly two concerns govern the process. The first concern is the economics of the process and the second concern is the quality of the coated film. The economics of the process are dictated by the speed of coating and the film thickness. Clearly, higher speeds mean better productivity hence less cost of operation and thinner films are desirable because less material is being used. Quality is governed by film uniformity and integrity, indicating that the film will perform as designed. Film defects such as streaks or tiny air bubbles are indication that the film properties are not uniform rendering it unacceptable to customers. One of the most versatile coating systems to achieve thin films at high speeds is reverse roll coating which has been used for a long time all over the world. At low speed, typically 1m/s, this coating operation is inherently stable and with small gaps of order 100 microns can ii lead to film thickness of order 30-50 microns. Much research, theoretical and experimental, has been devoted to this coating flow but only at low speeds and for large gaps (>100 microns). There are no comprehensive data how very thin films, 20 microns and less (particularly lower limits in the region of 5 microns) can be achieved at high speeds, of 2 or more metres per second. This study is concerned precisely with this aim, that of investigating the effect of large speeds and small roller gaps (rollers nearly touching or in elastohydrodynamic contact) to achieve the very thin films desired by modern applications (electronics, medical and others). In order to achieve this aim, a rig was designed and built to enable to understand the effect of various coating conditions and liquid properties on the metered film thickness and coating instability. To achieve thin films at high speeds, small roll gap and low viscosity are needed, however flow instabilities will develop under these conditions. To achieve stable coating window at high speeds high surface tension is needed. It was found that the roll gap and the viscosity have complicated effect on the coating window. In the case of low viscosity liquid (7mPa.s), small roll gaps are needed, whereas in the case of high viscosity liquid (more than 30mPa.s), large gaps are needed. It was found that Weber number is better describer for ribbing instability in rigid reverse roll coating unlike in rigid forward roll coating in which capillary number is the one. In addition the potential of reverse deformable roll coating (rolls in elastohydrodynamic contact) was investigated in order to achieve much thinner films at higher speeds. As a result of the investigation of reverse deformable roll coating, it was found that there is a possibility to get much thinner stable films at much higher speeds compared to reverse rigid roll coating. The liquid transfer from an applicator roller to a PET film was investigated in this study. It was found that air stagnation at downstream meniscus and air entrainment at upstream meniscus depend on the liquid properties such as viscosity and surface tension and coating conditions such as web tension and wrap angle of web. As a result, wet film instability also depends on liquid properties and coating conditions. It was found that air stagnation causes streaks on the wet film and air entrainment caused bubbles on the wet film. To get a stable wet film, it was found that suitable viscosity and high surface tension were needed.
234

INFLUENCE OF ELECTROSTATIC CHARGE UPON THE DEPOSITION BEHAVIOR OF PHARMACEUTICAL AEROSOLS WITHIN CASCADE IMPACTORS

Mohan, Megha 16 August 2012 (has links)
Cascade impactors, routinely used for in vitro particle size characterization of pharmaceutical aerosols, are calibrated using dilute, charge-neutralized, monodisperse aerosols. But pharmaceutical aerosols are known to generate concentrated, inherently charged, polydisperse aerosol clouds. A computational model of the Andersen Cascade Impactor (ACI) suggested that the presence of charge on aerosol particles may influence their deposition within the ACI, but experimental validation of the model is warranted. This dissertation investigates the influence of electrostatic charge upon the deposition behavior of aerosols within cascade impactors, to address the impact of charge on particle size characterization. The influence of applied charge upon the deposition pattern and aerodynamic particle size distribution (APSD) of commercially available pressurized metered dose inhalers (pMDIs) within the Electrical Low Pressure Impactor (ELPI) was examined. Electrostatic properties were modified using an external voltage source in conjunction with the ELPI corona charger and observed to be dependent on the formulation and device packaging. Induced artificial charge on the aerosol particles influenced the deposition pattern within the impactor, but did not result in a significant change in the apparent APSD. An experimental apparatus capable of producing charge neutralized and charged aerosol, with targeted deposition on the CFD predicted ‘charge sensitive’ ACI stages, was developed. In vitro results were observed to be in partial agreement with the CFD predictions. While charge influenced the deposition pattern in the ACI with increased deposition observed in the charger and on the upper stages of the ACI, it did not influence the apparent APSD of the aerosol. Electrostatic charge effects on deposition behavior within cascade impactors were delineated with respect to space charge and image charge effects by investigating the influence of impactor grounding, particle size, stage coating and loading. While the deposition pattern within the ACI was influenced by charge, only stage coating and stage loading resulted in a small, significant difference in the apparent APSD, which may not be practically relevant due to the variability associated with in vitro aerosol testing. Similar trends were observed in the deposition behavior of charge neutralized and charged aerosol within an abbreviated ACI system compared to the full resolution ACI.
235

Optimal control of clarifier-thickeners

Teerikoski, Sakari January 2017 (has links)
A computer model for a general clarifier-thickener has been made and used for comparing different strategies for control of such dewatering units through simulations. The model builds on widely acknowledged theory for modelling clarifier-thickeners - discretizing the settling PDE into a set of ODEs so that concentrations of solids at discrete depths inside the unit become the states of the numerical model - and it was written in the Modelica language using the modelling and simulation environment Dymola. The work of estimating model parameters for themodel and comparing different control strategies was made looking at one particular clarifier-thickener at the company Boliden's mineral processing plant in Garpenberg. Among the control strategies that were compared in simulations were simple PID control and cascade control as well as more advanced control schemes. The simulations showed that the optimal control strategy to use is cascade control using rake torque as a secondary variable, which makes sense in particular for large thickeners such as the one mainly considered in this work.
236

An asymmetric pericyclic cascade approach to oxindoles

Richmond, Edward January 2014 (has links)
The research in this thesis describes an asymmetric pericyclic cascade approach to the synthesis of a range of enantioenriched oxindoles using enantiopure oxazolidine derived nitrones and disubstituted ketenes. Chapter 1 aims to place this work in the context of the literature, describing other commonly employed or state-of-the-art asymmetric approaches to oxindoles and related compounds. Examples of where these approaches have been used successfully in the total synthesis of related indole alkaloids are also presented. The conception of this project within the group is also described alongside initial attempts to develop the first enantioselective variant of the same reaction using nitrone chiral auxiliaries. Chapter 2 details the optimisation of this asymmetric oxindole forming reaction by structural variation of the nitrone component, culminating in the preparation of an N-TIPBS nitrone based on an oxazolidine framework, which proved to be optimal for this process. Also detailed are attempts to gain insight towards the mechanism of this transformation and to understand the mode of chirality transfer. Chapter 3 details the use of the N-TIPBS nitrone scaffold as a transmitter of chiral information in the synthesis of 3-alkyl-3-aryloxindoles and spirocyclic oxindoles. Chapter 4 delineates the mechanism of this transformation as a pericyclic cascade process. The key stereo-determining features are discussed including the conformational preferences of such chiral oxazolidine derived nitrones and the influence of the N-protecting group on the stereochemical outcome. Synthetic endeavours to provide evidence as to the validity of this computational mechanistic rationale are also presented. Chapter 5 describes regioselectivity studies, and tolerance of both the racemic and asymmetric reactions to varying substitution on the nitrone N-aryl ring. Initial studies were undertaken using achiral nitrones before the interplay between regio- and stereoselectivity was explored, initially with enantiopure N-Boc Garner's aldehyde derived nitrones, and further with N-TIPBS nitrones. Chapter 6 initially describes attempts to transform this chiral auxiliary methodology into a catalytic asymmetric protocol, by investigating in situ ketene formation via various strategies including activation of carboxylic acids. Also described are investigations into related nitrone-ketenimine cycloadditions, and related [3+2] nitrone cycloadditions. Chapter 7 describes the application of this methodology toward the synthesis of compounds with biological relevance. The concise asymmetric synthesis of a Roche anti-cancer agent is outlined, as is the extension of this methodology to the synthesis of indole alkaloid-like species. Finally, the attempted application of this methodology toward the asymmetric synthesis of (+)-gliocladin C is outlined.
237

Identificação de proteases de Leptospira envolvidas na degradação de proteínas da matriz extracelular e do plasma humano / Identification of Leptospira proteases involved in the degradation of extracellular matrix and plasma proteins

Silva, Ludmila Bezerra da 06 September 2017 (has links)
Leptospiras são bactérias espiroquetas altamente móveis dotadas de estratégias que possibilitam grande eficiência nos processos de invasão e disseminação no hospedeiro. Nosso grupo demonstrou previamente que leptospiras patogênicas secretam proteases capazes de clivar e inativar moléculas-chave do sistema complemento humano, o que confere a essas bactérias a capacidade de driblar os mecanismos de defesa do sistema imune inato. Dada a rápida disseminação das leptospiras durante o processo de infecção, aventou-se a hipótese de que essas proteases secretadas pudessem alvejar uma gama maior de moléculas do hospedeiro. No presente estudo, a atividade proteolítica de proteínas secretadas por leptospiras sobre um painel de moléculas da matriz extracelular e do plasma foi avaliada. O sobrenadante de cultura da estirpe virulenta L. interrogans sorovar Kennewicki Fromm degradou fibrinogênio humano, fibronectina plasmática, colágeno Tipo I, e as proteoglicanas decorina, biglicam e lumicam. A atividade proteolítica foi inibida por 1,10-fenantrolina, sugerindo o envolvimento de metaloproteases. Laminina, matrigel, plasminogênio e trombina não foram clivados por proteases presentes nos sobrenadantes. Ainda, os dados indicam que a produção de proteases deve ser um determinante de virulência importante, uma vez que os sobrenadantes de estirpes saprófitas ou patogênicas atenuadas em cultura não apresentaram atividade proteolítica sobre componentes da matriz ou do plasma. A análise dos genomas de leptospiras disponíveis nos levou à identificação de quatro termolisinas, metaloproteases presentes apenas nas espécies patogênicas. Uma delas, codificada pele LIC13322, foi produzida na forma recombinante e apresentou atividade proteolítica sobre fibrinogênio, biglicam e decorina. Em paralelo, foram também realizadas análises comparativas dos exoproteomas das estirpes Fromm e Patoc I. Algumas metaloproteases que podem estar envolvidas na degradação de moléculas do hospedeiro foram identificadas. A capacidade de clivar moléculas do tecido conjuntivo e proteínas da cascata de coagulação pode certamente contribuir para a invasão e a destruição tecidual observadas durante a infecção por Leptospira. / Leptospires are highly motile spirochetes equipped with strategies for efficient invasion and dissemination within the host. Our group previously demonstrated that pathogenic leptospires secrete proteases capable of cleaving and inactivating key molecules of the human complement system, allowing these bacteria to circumvent host´s innate immune defense mechanisms. Given the successful dissemination of leptospires during infection, we wondered if such proteases would target a broader range of host molecules. In the present study, the proteolytic activity of secreted leptospiral proteases against a panel of extracellular matrix and plasma proteins was assessed. The culture supernatant of the virulent L. interrogans serovar Kennewicki strain Fromm degraded human fibrinogen, plasma fibronectin, collagen Type 1, and the proteoglycans decorin, biglycan, and lumican. Proteolytic activity was inhibited by 1,10-phenanthroline, suggesting the participation of metalloproteases. Laminin, matrigel, plasminogen and thrombin were not cleaved by proteases present in the supernatants. Moreover, production of proteases might be an important virulence determinant since culture-attenuated or saprophytic Leptospira did not display proteolytic acticity against ECM or plasma components. A search against Leptospira genomes allowed identification of four thermolysins, which are metalloproteases found exclusively in pathogenic species. One of them, encoded by LIC13322, was produced in the recombinant form and displayed proteolytic activity against fibrinogen, biglycan and decorin. Comparative exoproteomic analyses using Fromm and Patoc I strains were also performed and allowed identification of a few metalloproteases that could be involved in the degradation of host components. The ability to cleave connective tissue molecules and coagulation cascade proteins may certainly contribute to invasion and tissue destruction observed upon infection with Leptospira.
238

Biocatálise aplicada à síntese de núcleos β-hidroxi-1,2,3-triazólicos e síntese multienzimática do alcaloide diidropinidina / Biocatalysis applied to the synthesis of β-hydroxy-1,2,3-triazole nucleus and multi-enzymatic synthesis of the alkaloid dihydropinidine.

Silva, Natália Alvarenga da 12 May 2017 (has links)
O capítulo 1 descreve o estudo da biorredução do grupo carbonílico de cetoazidas e β-ceto-1,2,3-triazois para a produção de β-hidroxi-1,2,3-triazois enantiomericamente puros ou enriquecidos. Cinco linhagens de fungos de origem marinha foram avaliadas para a redução da 2-azido-1-feniletanona 1 e duas linhagens, A. sydowii CBMAI 935 e M. racemosus CBMAI 847, foram selecionadas também para a biorredução das 2-azido-1-feniletanonas 2-4 para a produção dos (R)- e (S)-2-azido-1-feniletanois 2a-4a. Os azidoálcoois enantiomericamente enriquecidos obtidos 1a-4a das reações biocatalíticas foram empregados como material de partida para a síntese dos β-hidroxi-1,2,3-triazois 7a-10a enantiomericamente enriquecidos através da click reaction entre a azida terminal e o alcino, fenilacetileno. Uma segunda abordagem para a obtenção de β-hidroxi-1,2,3-triazois enantiomericamente enriquecidos foi o estudo da biorredução de β-ceto-1,2,3-triazois, que são cetonas contendo dois substituintes volumosos. Uma triagem inicial para a biorredução do β-ceto-1,2,3-triazol 7 foi realizada com seis linhagens de fungos de origem marinha, na qual a linhagem do fungo P. citrinum CBMAI 1186 foi selecionada para estudos de otimização da reação biocatalítica. Estudos com variação do meio reacional, utilização de co-solvente e efeito do pH mostraram que as condições ótimas de reação foram utilizando-se tampão fosfato (Na2HPO4/KH2PO4, 0,07 M) em pH 5 e metanol 5% (v/v) como co-solvente. O fungo P. citrinum CBMAI 1186 foi empregado na biorredução dos β-ceto-1,2,3-triazois 8-12 com excelentes resultados de rendimento e seletividade para a produção dos (S)-β-hidroxi-1,2,3-triazois 8a-12a. O Capítulo 2 apresenta a síntese multienzimática da diidropinidina, um alcaloide de origem natural. A nonano-2,6-diona utilizada como material de partida foi obtida através da descarboxilação do dicetoéster, 2-butiril-5-oxo-hexanoato de etila. Estudos para a otimização tanto da síntese do dicetoéster quanto da etapa de descarboxilação foram realizados. Condições ótimas de produção do 2-butiril-5-oxo-hexanoato de etila foram obtidas através da reação da but-3-em-2-ona com o 3-oxo-hexanoato de metila catalisada por CeCl3/NaI. A descarboxilação do dicetoéster foi avaliada através do método de Krapcho empregando-se sais de cloro e água em altas temperaturas, entretanto, a elevada formação de subprodutos estimulou a busca por uma diferente metodologia para a obtenção da nonano-2,6-diona. Foram avaliadas diferentes lipases e esterases para a hidrólise enzimática do dicetoéster seguida por descarboxilação por HCl, na qual a esterase de fígado de porco foi selecionada e promoveu a hidrólise de até 1,6 M de dicetoéster para a produção da nonano-2,6-diona. Diferentes transaminases (TAs) foram estudadas para a aminação redutiva assimétrica da nonano-2,6-diona e duas linhagens foram selecionadas para a produção da (R)- e (S)-2-metil-6-propil-2,3,4,5-tetra-hidropiridina, as TAs de Arthrobacter sp. e Arthrobacter citreus, respectivamente empregando-se isopropilamina como amino doador. As (R)- e (S)-2-metil-6-propil-2,3,4,5-tetra-hidropiridina foram avaliadas pela redução assimétrica para a síntese da diidropinidina por imina redutases (IREDs) e duas linhagens foram selecionadas, a IRED de Mesorhizobium sp. e Norcardiopsis alba, respectivamente. TAs e IREDs foram acopladas em um sistema one-pot multienzimático utilizando como material de partida a nonano2,6-diona (100 mM) para a obtenção dos isômeros cis da diidropinidina com excelentes excessos diastereoisoméricos. / The Chapter 1 describes the bioreduction of the carbonyl group of ketoazides and β-keto-1,2,3-triazoles to produce enantiomerically pure or enriched β-hydroxy-1,2,3-triazoles. Five marine-derived fungi strains were screened to perform the reduction of 2-azido-1-phenylethanone 1. The strains from A.sydowii CBMAI 935 and M. racemosus CBMAI 847 were selected for the bioreduction of the 2-azido-1-phenylethanones 2-4 to yield the (R)- and (S)-2-azido-1-phenylethanols 2a-4a. The enantiomerically enriched azidoalcohols 1a-4a obtained from biocatalytical reactions were used as starting materials for the synthesis of enantiomerically enriched β-hydroxy-1,2,3-triazoles 7a-10a through the click reaction between the terminal azide and phenylacetylene. A second approach for obtaining enantiomerically enriched β-hydroxy-1,2,3-triazoles was the bioreduction of β-keto-1,2,3-triazoles, which are ketones with two bulky substituents. The screening for the bioreduction of the β-keto-1,2,3-triazol 7 was performed with six marine-derived fungi strains and P. citrinum CBMAI 1186 was selected for the optimization studies for the biocatalytic reduction of β-keto-1,2,3-triazoles 8-12.Studies about the composition of reaction medium, use of cosolvent and pH effect showed that the optimal conditions was in phosphate buffer (Na2HPO4/KH2PO4, 0.07 M) at pH 5 and methanol 5% (v/v) as cosolvent. P. citrinum CBMAI 1186 was applied to the bioreduction of β-keto-1,2,3-triazoles 8-12 and good yields and selectivities were obtained for the (S)-β-hydroxy-1,2,3-triazoles 8a-12a. The Chapter 2 describes the multienzymatic synthesis of dihydropinidine, a natural alkaloid. The nonane-2,6-dione used as starting material was obtained through the reduction of the diketoester, methyl butyryl-5-oxohexanoate, and the optimization studies for both diketoester synthesis and decarboxylation reaction were performed. Optimal conditions for the synthesis of methyl butyryl-5-oxohexanoate were obtained by the reaction between but-3-en-2-one and 3-oxohexanoate catalyzed by CeCl3/NaI. The diketoester decarboxylation step was evaluated by the Krapcho method using chlorine and water at high temperatures. However, because of the production of side products by this method, a different procedure for the synthesis of nonane-2,6-dione was studied. Different enzymes (lipases and esterases) were evaluated for the diketoester hydrolysis followed by decarboxylation by HCl. The porcine liver esterase was selected to promote the diketoester hydrolysis up to 1.6 M, yielding nonane-2,6-dione. Different transaminases (TAs) were applied to the asymmetric reductive amination of the nonane-2,6-dione and TAs from Arthrobacter sp. e Arthrobacter citreus were selected for the production of (R)- and (S)-2-methyl-6-propyl-2,3,4,5-tetrahydropyridine, respectively, using isopropylamine as the amine donor. The asymmetric reduction of (R)- and (S)-2-methyl-6-propyl-2,3,4,5-tetrahydropyridine by imine reductases (IREDs) was evaluated and the IREDs from Mesorhizobium sp. and Norcardiopsis alba were selected. TAs and IREDs were coupled in multienzymatic one-pot system using nonane-2,6-dione (100 mM) as starting material for the syntheses of cis isomers of dihydropinidine in excellent diastereoisomeric excess.
239

Acoustic detection of ultra-high energy cascades in ice

Böser, Sebastian 03 August 2007 (has links)
Existierende Neutrinoteleskope sind für den Nachweis von Neutrinos aus astrophysikalischen Quellen mit Energien im TeV Bereich optimiert. Aufgrund der geringen Flüsse und Wirkungsquerschnitte wurden bislang keine extraterrestrischen hochenergetischen Neutrinos beobachtet. Erst die im Bau befindlichen kubikkilometer-großen Cherenkov-Neutrinodetektoren werden das notwendige Volumen haben, um diese nachzuweisen. Für Neutrinos aus Wechselwirkungen der kosmischen Strahlung im EeV-Bereich mit dem kosmischen Mikrowellenhintergrund wird dennoch nicht mehr als ein Ereignis im Jahr erwartet. Nachweisvolumen in der Größenordnung von 100 km^3 sind notwendig, um den Fluß dieser Neutrinos zu bestimmen und die vorhergesagten Wirkungsquerschnitte zu überprüfen. Alternative Meßtechniken sind erforderlich, um einen Detektor dieses Ausmaßes zu realisieren. Eine vielversprechende Idee ist die Erfassung akustischer Wellen aus den in der Neutrinowechselwirkung erzeugten hadronischen Kaskaden. Aufgrund der höheren Signalstärke und der großen Schalldämpfungslängen ist die Eisdecke des Südpols dem Wasser der Ozeane als Medium vorzuziehen. Zunächst sind jedoch geeignete Sensoren, eine Überprüfung der thermo-akustischen Schallerzeugung und Kenntnisse der akustischen Eigenschaften des Eises von Nöten. In einer theoretischen Ableitung konnte die Äquivalenz der Mechanismen der Erzeugung akustischer Wellen durch thermo-elastische Anregung in Flüßigkeiten und isotropen Festkörpern gezeigt werden. Einer Analyse des existierenden Wissensstandes folgte die Simulation eines kombinierten Cherenkov-Radiowellen-Ultraschall-Detektors. Für den Einsatz im Eis wurden spezielle akustische Sensoren entwickelt und zur Erfassung der Schallemission von intensiven Protonen- und Laserstrahlen eingesetzt. Darauf aufbauend wurde ein akustische Sender- und Empfänger-Aufbau entwickelt, mit dem Ziel, die Ultraschalleigenschaften des südpolaren Eises in-situ zu untersuchen. Die Ergebnisse dieser ersten Bemühungen werden in dieser Arbeit vorgestellt. / Current neutrino telescopes are designed to detect neutrinos with energies in the TeV range. Due to the low fluxes and small cross sections, no high energy neutrinos of extraterrestrial origin have been observed so far. Only the Cherenkov neutrino detectors on the km^3 scale that are currently under construction will have the necessary volume to observe these rare interactions. Yet, for neutrinos from interactions of the ultra-high energy cosmic at EeV energies rays with the ambient cosmic microwave background, event rates of only one per year are expected. To measure the flux and verify the predicted cross sections of these cosmogenic neutrinos, an observed volume of around 100 km^3 will be necessary, that will not be feasible with existing detection techniques. Alternative methods are required to build a detector on these scales. One promising idea is to record the acoustic waves generated in cascades following the neutrino interaction. Higher amplitudes of the sonic signal and the large absorption length of sound favour South Polar ice instead of sea water as a medium. For an estimate of the potential of such a detector, suitable acoustic sensors, a verification of the model of thermo-acoustic sound generation and a determination of the acoustic properties of the ice are necessary. In a theoretical derivation the mechanism of thermo-elastic excitation of acoustic waves was shown to be equivalent for isotropic solids and liquids. A detailed analysis of the existing knowledge and a simulation study of a hybrid optical-radio-acoustic detector have been performed. Ultrasonic sensors dedicated to in-ice application were developed and have been used to record acoustic signals from intense proton and laser beams. Based on this, the hitherto largest array of acoustic sensors and transmitters was devised and implemented, with the aim to study the ultrasonic properties of the South Polar ice in-situ. Results from all of these first efforts are presented.
240

Estudo experimental de biomanipulação: análise dos impactos ambientais de duas espécies de predadores no controle de Tilápia, no lago Paranoá (Brasília - DF) / Experimental study of biomanipulation: analysis of environmental impact of two species of predators in the control of Tilápia, in Paranoá lake (Brasília, DF)

Ribeiro Filho, Rinaldo Antonio 26 July 2002 (has links)
O gerenciamento dos estoques pesqueiros, um dos instrumentos da biomanipulação, deve ter início com a classificação das espécies existentes e sua diversidade, a estrutura da rede alimentar e as relações reguladoras, como a relação predador-presa. O lago Paranoá (Brasília - DF) é um reservatório urbano que sofre pressões antrópicas devido a seus usos múltiplos. Após a construção enchimento, sucessivas introduções de espécies ictíicas exóticas causaram um desequilíbrio que, associado às pressões descritas acima, geraram uma aceleração no processo de eutrofização deste ambiente. Desta forma, os objetivos deste trabalho foram: avaliar os impactos ambientais da introdução das espécies predadoras sobre a cadeia trófica e a qualidade da água do reservatório; determinar a eficiência das diferentes espécies de predadores no controle das presas nas áreas marginais da represa, discutindo possíveis estratégias de manejo pesqueiro baseadas na estocagem de peixes predadores. Para tanto foram construídos 10 limnocurrais com lonas impermeáveis numa baía localizada no ETE-Norte (Estação de tratamento de esgotos - Norte). Em seu interior, após a retirada de todos os peixes, foram estocadas por um período de 28 dias, duas espécies de predadores (Cichla ocellaris e Pseudoplatytoma fasciatum) e uma comunidade simplificada de presas (Tilapia rendalli e Oreochromis niloticus), acima da capacidade do suporte do sistema, definida em 4 classes de tamanho. As biomassas de estocagem foram determinadas a partir da aplicação de retenona em uma área com dimensões conhecidas, e extrapoladas para as áreas dos limnocurrais. As variáveis físicas e químicos da água foram acompanhados semanalmente durante o experimento. Não houve diferenças significativas entre os tratamentos, em relação às variáveis limnológicas. Quanto ao controle das presas, o tucunaré mostrou-se um predador eficiente em relação às classes de tamanhos menores ) (2 - 6,9 cm e 7 - 12,9 cm), fato não observado para o tratamento com surubim. De acordo com os resultados obtidos, não foi comprovada a hipótese de cascata trófica devido à complexidade das interações entre os organismos em ambientes tropicais. / The managing of the fish stocks, one of the tools of the biomanipulation, must begin with the classification of the present species and their diversity, of the structure of the food web and of the regulation relations (as the relation predator-prey).The Paranoá Lake (Brasília, DF) is an urban reservoir that suffers human pressures as a result of its multiple uses. After its construction and filling, the successive introduction of many fish exotic species resulted in an unbalance that, associated with the pressures described above, generated an acceleration in the eutrophication process of the ambient. In this way, the objectives of this work were: evaluate the environmental impacts from the introduction of the species predators in food web and quality from the reservoir\'s water; decide the efficiency of the species of predators in the prey\'s control in the marginal areas from dam, discussing possible fishing strategies of management based in the Stocking of fish predators. Them, 10 limnocorrals were built with waterproof canvases in a bay located in ETE-NORTE (sewers handling Station - North). In its interior, after retreat of all fishes, by a period of 28 days, two species of predators were stocked (Cichla ocellaris and Pseudoplatystoma coruscans), and a community simplified of prey (Tilapia rendalli and Oreochromis niloticus), above from the capacity of the system, defined in 4 classes of size. The biomasses of stocking were determined from application of rotenona in an area with known dimensions, and overstepped for the areas of the limnocorrals. The physical-chemists parameters from the water were accompanied weekly during the experiment. It had no significant differences between the handlings, regarding the variables limnological. As regards the control of prey, C. ocellaris showed itself an efficient predator regarding the smallest classes of sizes (2 - 6,9 cm and 7 - 12,9 cm), fact do not observe for the handling with P. coruscans. Agreement with the results obtained, was not verified to hypothesis of trophic cascade due to the complexity of the interactions between the agencies in tropical environments.

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