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LIMA, Janirza Cavalcante da Rocha. "Espelho quebrado - Algafan e Desvio." Universidade Federal de Pernambuco, 1987. https://repositorio.ufpe.br/handle/123456789/17025.
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A farmacodependência é um fenômeno de todos os tempos e de todos os povos. É um fenômeno permanente, variando segundo o critério relativo das normas sócio-culturais de cada sociedade, numa dada época. Através dos tempos, o homem utilizou substâncias diversas no intuito de modificar sua percepção do mundo e transformar sua vivência subjetiva. Este estudo objetiva verificar, na prática, até que ponto a condição de desviante (usuário de Algafan) é sancionada e reforçada pelo aparelho institucional. O referencial empírico foi a divisão de Serviços técnicos da Secretaria da Segurança Pública de Pernambuco, onde se operacionaliza o disposto no Decreto –lei n. 6.368 e tendo dentre a clientela atendida, o dependente de Cloridrato de Destro-propoxifeno, conhecido comercialmente sob o nome de Algafan Composto. Apoiada em dados secundários, entrevistas e, sobretudo, na observação participante, a análise se desenvolve em três momentos: inicialmente, procura explicitar como se configura o usuário de Algafan; numa segunda etapa, tenta delinear os momentos marcantes da produção da identidade desviante onde as relações se estabelecem numa forma dialética entre acusados (dependentes de algafan) e acusadores (lei, família, agentes policiais e equipe terapêutica); finalmente, através de uma análise dos discursos dos dependentes, busca entender como eles percebem a situação em que vivem e os projetos que elaboram. Destacam-se, nas conclusões, os aspectos mais significativos dessa interpretação, face aos objetivos a que se propõe o estudo e o marco referencial teórico que o norteou. O estudo revela que a operacionalidade do Decreto-lei n.6.368 vem, antes, reforçar a condição de desviante, e não, ao contrário, recuperá-lo, tendo a Divisão de Serviçoes Técnicos um papel marcante nesse processo. Mostra também que, apesar de perceberem-se como outsiders, os dependentes ainda elaboram projetos de vida, na tentativa de superação de suas carências afetivas, econômicas e sociais. Eles anseiam pela existência de espaços sociais e psicológicos próprios onde possam se inserir e aos quais sintam pertencer.
La farmacodependencia es um hecho de todos los tiempos y todos los pueblos. Se trate de un fenómeno permanente, cuyas variaciones obedecen al criterio, relativo, de las normas sociocultureles de cada sociedad en determinada época. A través de los tiempos el hombre ha utilizado distintos tipos de drogas, con miras a cambiar su percepción del mundo y transformar sus experiencias subjetivas. El presente estudio se propone comprobar en la práctica, hasta que punto la condición de descarriado (adicto al Algafan) es sancionada y reforzada por el aparato institucional. El marco empirico ha sido la Division de Servicios Tecnicos de la Secretaria de Seguridad Pública del Estado de Pernambuco, donde se cumple dos dispuesto por el Decreto n. 6.368. Los clientes son los dependientes del Clorhidrato de destropropoxifeno, comercialmente conocido como “Algafan Composto”. Con base en datos secundarios, entrevistas y, sobre todo, en la observación participativa, el análisis se desarrolla en tres etapas: inicialmente trata de caracterizar el adicto al “Algafan”; en seguida intenta definir los momentos marcantes del proceso de surgimiento de la identidad discrepante, durante el cual se establecen las relaciones dialécticas entre acusados (dependientes de “Algafan”) y acusadores (ley, familia, agentes de la policía y equipo terapéutico); finalmente, a través del análisis de las declaraciones de los drogadictos, se trata de entender de que forma ellos captan la propia situación y los planos que hacen. En las conclusiones sobresalen los rasgos más significativos de esa interpretación, en relación a los objetivos de estudio y a su marco teorico. Este trabajo revela que la aplicación del Decreto n. 6.368 refuerza la condición del descarriado, en vez de recuperarlo; y la División de Servicios Técnicos juega un papel fundamental en ese proceso. Muestra, además, el estudio que, prese al hecho de reconocerse como “outsiders”, los dependientes siguen elaborando proyectos de vida, en el intento de superar sus necesidades afectivas, económicas e sociales. Ellos anhelar espacios sociales y sicológicos propios, en lo que se puedan incluir y a los cuales sientan pertenecer.
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Mouetsi, Souheil. "Contribution à l’étude du bruit basse fréquence dans des hétérostructures AlGaAs/GaAs/AlGaAs." Reims, 2010. http://theses.univ-reims.fr/sciences/2010REIMS023.pdf.
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Le travail présenté dans ce mémoire a pour objet la caractérisation d’un gaz bidimensionnel d’électrons dans une hétérostructure AlGaAs/GaAs/AlGaAs par la méthode de bruit basse fréquence à des différentes tensions de polarisation et à différentes températures (4 - 300K). Plusieurs sources de bruit contribuant au spectre total de bruit (bruit thermique, bruit de génération - recombinaison (G-R) et bruit en 1/f) ont été identifiés. Grâce au bruit thermique, nous avons montré qu’il est possible d’accéder aux résistances de contact. L’analyse du bruit de G-R a permis d’identifier des défauts sources de ce type de bruit. Pour ce faire, il a fallu déterminer les énergies d’activation thermiques et les sections efficaces de capture caractérisant ces défauts. L’étude du bruit en 1/f a été faite de deux manières ; d’abord l’application du modèle de Hooge a permis de montrer que ce bruit est causé essentiellement par la fluctuation de la mobilité du réseau. Puis, l’application du modèle modifié de Handel a permis de renforcer la proposition de la fluctuation de la mobilitéThe study presented in this manuscript is devoted to characterize a two dimensional electron gaz (2DEG) in a AlGaAs/GaAs/AlGaAs heterostructure by using the low frequency noise technique. The study was made for different bias voltages and at different temperatures (4 - 300 K). Several noise sources (thermal noise, generation-recombination noise (G-R) and 1/f noise) contributing to the total spectrum were identified. With thermal noise, we have shown that it was possible to access to the contact resistances. Analysis of the G-R noise has allowed identification of defects responsible of this noise. To do this, it was necessary to determine thermal activation energies and capture cross sections characterizing these defects. The study of 1/f noise was made in two ways: first, application of the Hooge model showed that this noise is mainly caused by the network mobility fluctuation. Then, applying the modified model of Handel has strengthened the proposal fluctuation of the mobility
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Ulman, Morrison. "Femtosecond carrier dynamics in AlGaAs." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/17396.
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Affandy, Gabriel, Donald Bridges, Quinn Daniels, Drew Janicek, Julia Martin, Edward Poling, Jordan Schmalz, et al. "HAWAII ALGAL BIOFUEL." Monterey, California. Naval Postgraduate School, 2013. http://hdl.handle.net/10945/32891.
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This report investigates the feasibility and affordability of producing algae-derived biofuel in Hawaii for military aviation. The authors evaluated methods for cultivation of algae, investigated the processes necessary to locally refine bio-oil into bio-kerosene, researched the environmental impacts of cultivation and refinement facilities in Hawaii, and studied the resultant cost per gallon of bio-kerosene production. Based on the current state of technology and the proposed system of systems architecture, this report estimates that bio-kerosene can be produced for $8.00 - 22.87/gal, indicating that although this system is technically feasible, it is unlikely to be affordable at current fuel prices without ongoing subsidy or further technical innovation.
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Lam, Hoi-yeung Ironside. "Marine microalgal dynamics at Crooked and Lamma Islands, Hong Kong." Click to view the E-thesis via HKUTO, 2002. http://sunzi.lib.hku.hk/hkuto/record/B43895323.
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Held, Lucas. "Implantation isolation in AlGaAs/GaAs structures." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32366.
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In this work the effect of implantation isolation in vertical cavity surface emitting laser (VCSEL) samples have been investigated cross sectional measurements using scanning spreading resistance microscopy (SSRM). The samples consist of two AlGaAs/GaAs Distributed Bragg Reflectors (DBR) structures with a GaAs quantum well region sandwiched in between them. The samples were implanted with 330 and 660 keV helium ions using doses from 7*1013 cm-2 to 1*1016 cm-2. Due to variations and uncertainties in the SSRM output quantitative values of resistivity in the highly resistive regions created by ion implantations were not attained. Relative differences, however, were notable for the different doses. It was found that the resistive regions were not located as deep inside the samples for the 660 keV implantations as for the 330 keV. This does not agree with the simulations performed. A correlation between implantation dose and the depth of the resistive region created was also found - higher doses caused resistive regions deeper inside the samples. Furthermore, as the implantation dose is increased the resistive region is confined to only about one AlGaAs/GaAs period of width at the same depth as the wide resistive region for lower doses, i.e. the structure is somehow regaining its conductive properties in the shallow areas only leaving a thin stripe of the resistive region at the deepest end for higher implantation doses. Samples implanted with low He doses were heated in a vacuum furnace at 300, 350 and 380 ˚C. The heated samples showed a tendency to regain the conductivity in the resistive region, similar to the samples implanted with high doses. This suggests that there may be some kind of annealing effect for higher doses, possibly due to the increased flux for higher doses.
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Brown, Robert James. "Electronic transport in GaAs/AlGaAs microstructures." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335681.
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Sharma, Adesh. "Electronic transport in GaAs-AlGaAs heterostructures." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239264.
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John, Gareth. "Spin relaxation phenomena in GaAs/AlGaAs." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433964.
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Chatterjee, Ritwik 1974. "Linearity of power AlGaAs/GaAs HBTs." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/47494.
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Schulz, Robert [Verfasser]. "Optische Spektroskopie an zweidimensionalen Lochsystemen in GaAs-AlGaAs-Quantenwells und an GaAs-AlGaAs-GaMnAs-Schichtstrukturen / Robert Schulz." Regensburg : Univ.-Verl. Regensburg, 2010. http://d-nb.info/1007748524/34.
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Li, Shuo. "Interactions of Toxic Metals with Algal Toxins Derived from Harmful Algal Blooms." FIU Digital Commons, 2011. http://digitalcommons.fiu.edu/etd/478.
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The purposes of this study were to characterize the complexation of toxic metals with algal toxins and to determine the effects of arsenic and copper on the growth of Karenia brevis under specific experimental conditions.
Microcystins, pahayokolides, brevetoxins and okadaic acid were used as representatives of algal toxins while arsenic, copper, cadmium, cobalt, iron, manganese and mercury were selected as typical toxic metals (including metalloids here) in the aquatic environment. The stabilities of the toxin-metal complexes were determined using equilibrium dialysis and/or centrifugal ultrafiltration technique. A direct exposure of arsenic and copper to the K. brevis was carried out to determine the effects of these metals to the growth of the algal cell.
The results indicated that Cu2+, Hg2+, Co2+, Cd2+ and Fe2+ were capable of complexing with the algal toxins. Moreover, the exposure experiments demonstrated that the high concentration of arsenic and copper could affect the growth of the K. brevis.
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Hetherington, C. "Transmission electron microscopy of GaAs/AlGaAs multilayers." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379967.
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Bristow, Alan Douglas. "Optical investigation of AlGaAs photonic crystal waveguides." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398692.
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Callebaut, Hans 1975. "GaAs/AlGaAs far-infrared quantum cascade laser." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/44513.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (p. 123-127).
In this thesis I investigated the feasibility of an optically pumped inter subband farinfrared (40-100[mu]m) laser, using GaAs/ AlxGal-xAs heterostructures. The proposed design aims to use LO-phonon-mediated depopulation of the lower THz laser level to aid the intersubband laser population inversion. Interband recombination occurs by means of stimulated emission, thus combining an interband (~1550 me V) and intersubband (~16-18 meV) laser. As the subband properties of both the valence band and the conduction band are important for this work, a numerical program code was developed for the valence band to supplement the available tools for the conduction band. The steady state rate equations for the proposed quantum well structure were solved self-consistently for several different carrier temperatures. The calculations indicate that a pump beam of moderate power (0.5-1 W) concentrated on a device of typical dimensions (104 cm2) can generate an intersuhb and gain of 20 cm-1 at 50 K for a THz emission linewidth of 2 meV. This gain level can suffice to obtain THz lasing action, provided that the cavity losses can be kept in check. The performance of the THz laser is predicted to be very dependent on electron temperature, mainly due to the opening of a parasitic LO-phonon channel between the THz laser levels. Interband lasing seems to be easier to obtain, as the calculated threshold pump intensity is lower than for the intersubband case.
by Hans Callebaut.
S.M.
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Williams, Benjamin S. (Benjamin Stanford) 1974. "GaAs/AlGaAs mid-infrared quantum cascade laser." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/49645.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.Includes bibliographical references (p. 111-115).
by Benjamin S. Williams.
M.S.
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Hultgren, Charles T. (Charles Timothy). "Femtosecond nonlinearities in AlGaAs diode laser amplifers." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/32621.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (leaves 141-148).
by Charles Timothy Hultgren.
Ph.D.
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Jin, Yan. "Evolution des parametres electriques dans les tegfet standards (algaas/gaas) et pseudomorphiques (algaas/ingaas/gaas)-a grille ultra courte." Paris 11, 1993. http://www.theses.fr/1993PA112037.
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L'evolution des proprietes dynamiques des transistors a heterojonction (tegfet) standards algaas/gaas et pseudomorphiques algaas/ingaas/gaas de longueur de grille ultra courte autour de 0,1 micron est analysee a partir de caracterisations electriques en regime statique et micro-onde (jusqu'a 50 ghz). Une methodologie de caracterisation micro-onde dont l'application aboutit a l'obtention des parametres electriques precis des tegfet de tres faible dimension a ete developpee. L'etude experimentale a permis de determiner, a partir d'un nombre eleve d'echantillons, les caracteristiques de transistors des deux technologies en fonction de la longueur de grille et des polarisations de grille et de drain. Ces resultats confrontes a ceux obtenus par des modelisations physiques effectuees dans une etude parallele conduisent a mieux comprendre le comportement de ces tegfet a grille ultra courte. L'analyse detaillee du fonctionnement des transistors met en evidence l'influence de certains choix de conception et de la technologie de fabrication sur les performances. Les resultats preliminaires de la caracterisation a tres basse temperature (70k) sont aussi presentes. Les caracteristiques des tegfet pseudomorphiques montrent un meilleur controle et un meilleur confinement des porteurs dans le canal. L'analyse de la variation des parametres electriques pour les deux types de structures fournit des informations quantitatives sur les ameliorations a apporter pour optimiser des tegfet de longueur de grille voisine de 0,1 micron
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Lizzul, A. M. "Integrated production of algal biomass." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1474169/.
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Applied research is increasingly defined within a context of sustainability and ecological modernisation. Within this remit, recent developments in algal biotechnology are considered to hold particular promise in integrating aspects of bioremediation and bioproduction. However, there are still a number of engineering and biological bottlenecks related to large scale production of algae; including requirements to reduce both capital expenditure (CAPEX) and operational expenditure (OPEX). One potential avenue to reduce these costs is via feedstock substitution and resource sharing; often described as industrial symbiosis. Such an approach has the benefit of providing both environmental and economic benefits as part of an 'eco-biorefinery'. This thesis set out to investigate and address how best to approach some of the cost related bottlenecks within the algal industry, through a process of industrial integration and novel system design. The doctorate focussed on applications within a Northern European context and was split into four research topics. The first and second parts identified a suitable algal strain and were followed by the characterisation of its growth on wastewater; with the findings showing Chlorella sorokiniana (UTEX1230) capable of robust growth and rapid inorganic nutrient removal. The third part detailed the design, construction and validation of a lower cost and fully scalable modular airlift (ALR) photobioreactor, suitable amongst other applications for use within wastewater treatment. This work concluded with a pilot scale deployment of a 50 L ALR system. The fourth research section detailed the costs of ALR construction and operation at a wastewater treatment works, with a particular focus on the benefits that can be derived by industrial symbiosis. The thesis concludes with an appraisal of the ALR design and considers the potential for the technology, particularly within a wastewater treatment role. A final consideration is given to the practicalities of developing the algal industry within the UK in the short to medium term.
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Shellcock, Carole. "Molecular aspects of algal biofuels." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=217886.
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The ability of micro–algae to respond to diverse and often rapidly changing habitats has been attributed to the versatility of their cellular lipids. Amongst these the energy rich triacylglycerols (TAG) have attracted considerable attention due to their potential use as feedstock for renewable biofuel. Although micro-algae have considerable advantages over other biofuel sources there are constraints to their utilisation. Improvements are required in certain areas including efficiencies in production and enhanced lipid yields if micro-algal biofuels are to become commercially feasible. To achieve this, genetic and metabolic manipulation will be essential and therefore a greater understanding of the lipid biosynthetic pathways is required. In this study the expression of genes putatively involved in TAG biosynthesis in the diatom Phaeodactylum tricornutum was investigated, for the first time, with CO2 supplementation and low pH stress over the entire growth cycle. This molecular analysis was combined with physiochemical examination of the lipid accumulation in the micro-algal model. The results indicated that TAG accumulation was enhanced by CO2 supplementation and occurred predominantly during the stationary growth phase. The molecular analysis revealed increased expression for three genes of interest, encoding enzymes involved in the acyl dependent pathway: Glycerol-3-phosphate acyl transferase (GPAT) -7198728 (Phatrdraft_50031), lysophosphatidic acyl transferase (LPAAT) -7196550 (Phatrdraft_42446) and phosphotidic acid phosphatase (PAP) -7195747 (Phatrdraft_40261) in cultures supplemented with CO2. Under the same conditions up-regulation of a gene involved in the first committed step of fatty acid biosynthesis, Acetyl CoA carboxylase (ACC) -7194806 (Phatrdraft_54926) was also observed. Overall, this study provides further insight on the specific genes linked with increased TAG production in P. tricornutum and the identification of references genes suitable for normalisation of qPCR data across the growth cycle and under CO2 supplementation, thus providing the tools needed for future molecular studies of P. tricornutum lipid production.
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Ross, Oliver N. "Algal motility in variable turbulence." Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/45995/.
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Wissinger, Joshua Clinton. "Hydrothermal Treatment of Algal Feedstocks." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1370954774.
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Provan, Anne. "Systematic chemical screening of mircroalgae." Thesis, University of Strathclyde, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366955.
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Gomes, Prova Christina. "AlGaAs Microring Resonators for All-Optical Signal Processing." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35592.
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Photonic integration and all-optical signal processing are promising solutions to the increasing demand for high-bandwidth and high-speed communication systems. III-V semiconductor materials, specially AlGaAs, have shown potentials for photonic integration and efficient nonlinear processes due to their low nonlinear absorption, flexibility at controlling the refractive index, and mature fabrication technology.
In this thesis, we report the designs of AlGaAs microring resonators optimized for efficient four-wave mixing. Four-wave mixing (FWM) is a nonlinear optical phenomenon which can be used to realize many optical signal processing operations such as optical wavelength conversion and optical time division multiplexing and demultiplexing. Our designed AlGaAs microring resonators are expected to have good optical confinement, transmission characteristics, and efficient coupling between the ring and waveguide.
Here we also present our fabrication efforts to fabricate the microring resonators device and the insights gained in the process. The microring resonators devices have a potential to be used in optical communication networks for all-optical signal processing operations.
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Ahmad, S. T. "Low dimensional hybrid ferromagnetic AlGaAs/GaAs semiconductor nanostructures." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595379.
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There has been a shift in focus towards systems that integrate “nanomagnetic” components with existing device technologies, particularly for the further miniaturisation of magnetic storage devices. This thesis presents results, analysis and conclusions of studies on novel hybrid magnetic/metallic (Au/Co/Au) compositions in conjunction with low dimensional structures AlGaAs/GaAs quantum point contacts (QPC) and quantum dots (QD). The Au/Co/Au gates are used as surface confinement gates and also to apply a local inhomogeneous magnetic strayfield. Magneto-transport measurements were performed in low temperature cryostats with a minimum temperature of 350mK. It was concluded that the gating properties of these magnetic/metallic structures was significantly poor to allow for accurate characterisation of the devices. In addition, the QPC and QD themselves showed inhomogeneous effects that were dependent on the fabrication processes and material impurities. Novel broadband microwave spectroscopy measurements were used to study the transport mechanisms of a QPC. A continuous frequency range of 1-20GHz was studied where there have been no previous investigations on such devices. The experimental setup utilizes a non-invasive microwave source via a coaxial transmission line, based on the Corbino approach. The response of the device was seen to be very sensitive to these microwaves and showed ‘aperiodic’ fluctuations in the source-drain current as a function of the frequency and the onset of negative current features. These fluctuations are determined to be a result of semi-classical chaotic trapped electrons states that can be modified by the electric field of the microwave at these frequencies.
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Carmmona, Humberto de Andrade. "Quantum magneto-transport in AlGaAs/GaAs nano-devices." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319672.
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Chen, Ye Huang. "AlGaInP/AlGaAs visible vertical cavity surface emitting lasers." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389670.
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Holder, Jonathan Paul. "Resonant tunnelling spectroscopy of vertical GaAs/AlGaAs structures." Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312281.
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Harrell, Ruth Helen. "Induced electron gases in undoped GaAs/AlGaAs heterostructures." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.625054.
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Seraide, Rodrigo Migotto. "Mobilidade eletrônica em poços quânticos parabólicos de AlGaAs." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-11112013-162344/.
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Neste trabalho estudamos as estruturas e as mobilidades eletrônicas em um sistema quase-bidimensional de poços quânticos parabólicos de AlxGa1-xAs dopados. Obtemos as auto-energias, as funções de onda e os perfis dos potencias de confinamento efetivo no sistema, através das soluções numéricas das equações de Schrödinger e de Poisson de forma autoconsistente. Em particular, estudamos as mobilidades quânticas e de transporte nestes sistemas. Devido a ocupação de várias subbandas nestes sistemas, as contribuições dos espalhamentos inter-subbandas para as mobilidades têm a mesma importância que os espalhamentos intra-subbandas. Obtemos as mobilidades de cada subbanda devido aos espalhamentos por impurezas doadoras e aceitadoras ionizadas e por potencial de liga. Analisamos os efeitos das distribuições de doadores dopados, de aceitadores de fundo e do potencial de gate externoIn this work we study the electronic structure and electron mobilities in doped wide parabolic quantum wells of AlxGa1-xAs. The subband energies, the wavefunctions, and the effective confining potential profile are obtained by studying selfconsistently the coupled Schrödinger and Poisson equations. Based on the numerical results of the electronic structure, we calculate the quantum and transport mobilities of the system. Usually several subbands are occupied in such systems and they are strongly coupled to each other, the intersubband interaction shows the same importance as the intrasubband one to the electronic transport. We study and analyze the electron mobility of each subband due to the ionized donor scattering and the alloy scattering. We also show the effect of ionized background acceptor impurity scattering
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Montanher, Valter César. "Propriedades Óticas de Poços Quânticos de GaAs/AlGaAs." Universidade de São Paulo, 1997. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-23102017-143621/.
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Neste trabalho investigamos as propriedades óticas de poços quânticos de GaAs/GaAlAs, crescidos no Laboratório de Novos Materiais Semicondutores (LNMS) do Instituto de Física da USP com a técnica de MBE (\"Molecular Beam Epitaxy\"), utilizando as técnicas experimentais de foto luminescência (PL) e fotoluminescência-excitação (PLE). Analisamos duas amostras de poços quânticos não dopados crescidas sob diferentes condições experimentais e com diferentes parâmetros estruturais. As amostras têm a mesma largura nominal de poço (Lw ~c I 00 Á) e diferem em outros parâmetros, sendo que os mais importantes destes são a largura nominal da barreira (L,,) e a interrupção do crescimento nas interfaces de GaAs/GaAlAs. A amostra #241 (#419) obtida com interrupção de crescimento (sem interrupção de crescimento) tem largura nominal da barreira L\"= 500 Á(Lh c\" 300 Á)In this work we investigated the optical properties of GaAs/GaAlAs quantum wells grown by MBE (Molecular Beam Epitaxy) at the Laboratório de Novos Materiais Semicondutores (LNMS) do Instituto de Física da USP, using photoluminescence and photoluminescence-excitation techniques. Two non-intentionally doped samples grown under difterent experimental conditions and with dift\'erent structural limit were analysed. The samples had the same nominal quantum well width (Lw = I 00 Â) but different nominal barrier width (Lb) and the growth-intenuption time at the interfaces. The sample #241 (#419) was grown with (without) growth-interruption at both interfaces of the quantum well and has nominal barrier width ~. = 500 Â (Lb = 300 Â)
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Sfigakis, François. "Electron transport in etched GaAs/AlGaAs quantum wires." Thesis, University of Cambridge, 2006. https://www.repository.cam.ac.uk/handle/1810/284060.
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Baratte, Hervé. "Technologie bipolaire hétérojonction AlGaAs/GaAs pour circuits intégrés." Paris 11, 1985. http://www.theses.fr/1985PA112012.
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Un modèle analytique proche de la réalité permet de réaliser une structure optimale et de corréler les performances et les paramètres. La séquence de croissance épitaxique est compliquée par la présence des deux hétérojonctions différentes algaas/gaas et gaas/algaas et de deux types de dopants, le silicium pour le type n et le béryllium pour le type p. Un recuit rapide assure un bon rendement d'activation tout en limitant la diffusion des dopants. La double hétérostructure à jonctions progressives obtenue par implantation d'ions convient aux circuits intègres. On prévoit une grande rapidité et une grande densité d'intégration pour les montages j**(2),l (à injection intégrée) et ecl (à émetteur commun). Le transistor bipolaire a hétérojonction convient également dans des applications linéairesThe good injection properties of the heterojunction bipolar transistor allow predicting very high frequency performance of the device. An ion-implanted double hétérostructure with graded junctions is well adapted for integrated circuits application. An analytic model, close to reality, helps calibrate an optimized structure. It is also a convenient tool to correlate observed performance to the device internal structure. The epitaxial growth sequence is rather complicated because of the presence of two different heterojunctions (AlGaAs/GaAs and GaAs/AlGaAs) and of two types of dopants (Silicium for n-type and Beryllium for p-type). Thanks to a GaAs none intentionally doped interfacial layer, recombination effects in the junctions are greatly reduced. Then, a rapid thermal annealing treatment of the implanted devices proves to be a suitable method to achieve good activation efficiency while limiting dopants diffusion inside the structure. Further integration of such a device is then analyzed. Very high speed and high density of integration are predicted for future I²L or ELC bipolar heterostructures. The HBT (Heterojunction Bipolar Transistor) is also well adapted for linear application
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Ozanam, Cécile. "Oscillateur paramétrique optique en guides d'ondes AlGaAs/A10x." Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC226.
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Ce travail de thèse porte sur la réalisation expérimentale d'un oscillateur paramétrique optique (OPO) en guides d'ondes AlGaAs/A10x. L'insertion de fines couches d'oxyde d'aluminium (A10x) dans un coeur guidant en GaAs à une échelle sub-longueur d'onde permet d'obtenir artificiellement la biréfringence nécessaire pour obtenir une interaction non linéaire efficace entre une onde de pompe TMOO à 1064 nm et des ondes signal et complémentaire TE00 autour de 2128 nm. Après définition d'une cavité optique résonnante pour les ondes signal et complémentaire grâce au dépôt de miroirs diélectriques sur les facettes du guide, le seuil d'oscillation est atteint pour une puissance de pompe de 210 mW. Ce résultat constitue la première démonstration d'un OPO en guide d'ondes semi-conducteur dans le proche infrarouge. Dans un second temps, nous avons cherché à améliorer les performances de ce dispositif en explorant trois pistes. La première a été la réduction des pertes de propagation par un meilleur contrôle de l'étape d'oxydation et par l'insertion de barrières de GaInP de part et d'autre des couches oxydées. Le deuxième axe de développement a été l'utilisation d'une cavité à double passage de la pompe qui a permis de réduire légèrement le seuil d'oscillation. La troisième piste explorée est la protection thermique de l'échantillon par une couche de verre déposée sur les guides d'ondes. Une partie de cette thèse a par ailleurs été consacrée à un dispositif similaire visant à obtenir une radiation cohérente autour de 2000 nm par génération de second harmonique d'un laser à cascade quantique émettant autour de 4500 nmThis PhD work is about the experimental demonstration of an optical parametric oscillator (OPO; in AlGaAs/A10x waveguides. Inserting thin aluminum oxide (A10x) layers in the GaAs guiding core of the waveguide at a sub-wavelength scale allows us to artificially reach the birefringence which is necessary to get an efficient nonlinear interaction between a TMOO pump at 1064 nm and TE00 signal and idler around 2128 nm. After defining an optical signal and idler-resonant cavity by the means of dielectric mirrors, the oscillation threshold is reached with an internai pump power of 210 mW. This result is the first demonstration of a guided-wave semiconductor OPO in the near infrared. In a second part, we tried to improve the performances of this device following three different paths. The first is the reduction of the propagation losses through a better control of the oxidation step and the insertion of GaInP barriers on each side of the oxidized layers. The second development path is a change in the optical cavity configuration : using a double pump pass cavity has enabled us to slightly reduce the oscillation threshold. The third explored path is the thermal protection of the sample with a glass layer deposited on the top of the waveguides. A part of this PhD work has also been devoted to a similar device for the emission of a coherent radiation around 2000 nm by second harmonic generation from a quantum cascade laser emitting around 4500 nm
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Allford, Craig. "Resonant tunnelling in GaAs/AlGaAs triple barrier heterostructures." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/91151/.
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This thesis describes experimental and theoretical research into triple barrier resonant tunnelling structures which are attractive as potential high frequency oscillators in the terahertz frequency range. A lack of practical and coherent radiation emitters in this frequency range has resulted in it being named the \terahertz gap". However resonant tunnelling structures are seen as potential sources for practical solid state emitters which operate in this frequency range at room temperature. A series of symmetric and asymmetric GaAs/Al0:33Ga0:67As triple barrier resonant tunnelling structures have been studied at low temperatures to investigate the tunnelling electrical behaviour and origin of the current resonances observed in the current-voltage characteristics of these structures. The e�ect of charge accumulation in the emitter quantum well has been investigated, and has been found to signi�cantly alter the behaviour of the electrical characteristics of the structures. These investigations have provided a thorough understanding of the behaviour of these structures and has allowed for optimisation of the triple barrier design with a view to being utilised as a high frequency emitter. The current-voltage characteristics have also been studied as a function of temperature and a novel temperature dependent resonant tunnelling mechanism has been observed. The magnitude of the observed current resonance, which is associated with the energetic alignment to the n = 1 quasi-bound subband states increases with increasing sample temperature which is rare behaviour in systems dominated by quantum mechanics. Finally, the maximum oscillation frequency and output power of these resonant tunnelling structures has been calculated and an optimised triple barrier structure in which charge accumulation in the emitter quantum well does not occur has been designed. Simulated current-voltage characteristics for this design shows it improves the maximum oscillation frequency and maximum output power reported in current state of the art double barrier resonant oscillator structures.
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Modi, Nihar Triplett Gregory Edward. "Thermal management in GaAs/AlGaAs laser diode structures." Diss., Columbia, Mo. : University of Missouri--Columbia, 2007. http://hdl.handle.net/10355/6262.
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Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 16, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis supervisor: Dr. Gregory Triplett. Includes bibliographical references.
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Feteha, Mohamed Yousef Mohamed. "Heterojunction AlGaAs-GaAs solar cells for space applications." Thesis, University of Central Lancashire, 1995. http://clok.uclan.ac.uk/18836/.
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Two types of solar cell AlGaAs-GaAs structures which are heteroface and triple heterojunction are investigated in this study. A complete theoretical study including optimisation for the optical properties ( transmission and reflection) of the heteroface Alo.sGao.2As- GaAs space solar cell is presented. The grid shadow and window layer effects, angle of incidence and the effects of the layer design parameters for AR-coating and window layer on the optical properties are considered in the calculations. A new structure for space solar cell which consists of double heterojunction AlGaAsGaAs structure with GaAs/AlGaAs heterojunction back surface field (triple heterojunction(TIIJ))-to enhance the performance of the existed double heterojunction solar cell- is proposed. The analytical model for this TIU cell is presented as a function of all the cell's design parameters ( such as _layers doping, thicknesses, etc). The calculated results for this structure is compared with the experimental results for the previous double heterojunction structure. The effects of the design parameters of all layers including the AR-coating on the cell's output performance and the optimisation conditions are studied as well. The techniques of the light trapping and the photon recycling( which are gocxl for space solar cells) are applied for the THJ thin film AlGaAs-GaAs structure to improve further the efficiency . The change of the optimisation conditions due to the usage of these two techniques is also discussed.
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SCACCABAROZZI, ANDREA. "GaAs/AlGaAs quantum dot intermediate band solar cells." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2013. http://hdl.handle.net/10281/40117.
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This thesis presents my Ph.D. work about quantum dot GaAs/AlGaAs solar cells grown by droplet epitaxy, exploring the potential of this materials system for the realization of intermediate band photovoltaic devices. In the first chapter a general introduction to the field of solar energy is given, outlining the reasons why this research has been performed. The physics of the photovoltaic cell is briefly explained in its most important points, to give the reader clear understanding of what is presented in the following chapters. Intermediate band devices are presented in the second chapter. The theoretical foundations presented do not aim at constituting an exhaustive explanation of the theory underlying intermediate band solar cells, but the scope is again to give clear understanding of the characterization of the quantum dot devices reported in the following chapters. A survey of the state of the art in the field is given, pointing out the differences with our technology. The initial part of my Ph.D. work was spent in developing the technology to design and grow (Al)GaAs photovoltaic devices, as well as the characterization techniques required to understand the behavior of such devices. In chapter 3 the method developed to design the solar cell structure is illustrated, and in chapter 5 the experimental setup used for characterization is presented, along with the measurements on the single junction devices realized during this work. Chapter 4 is dedicated to the description of the growth and fabrication methods used to grow the samples reported here. The development of the fabrication technology proceeded in close contact with the characterizations of the devices, in order to optimize the process. Finally in chapter 6 the results on quantum dot photovoltaic cells are reported: the key working principles of intermediate band devices have been demonstrated with our materials system, and this, to the knowledge of the author, is the first time that strain free quantum dot solar cells are reported of intermediate band behavior. The role of defects in the AlGaAs matrix is explained in connection with both the optical and electrical characterizations presented.
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Schmidt, Poul-Erik. "Transistor à effet de champ, à hétérojonction et grille isolée : fabrication et étude de SISFET GaAs-AlGaAs et GaAs-GaInAs-AlGaAs." Paris 11, 1989. http://www.theses.fr/1989PA112306.
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Ce travail est consacré à l'étude de transistors à effet de champ à grille isolée et à hétérojonction "SISFET". Ce dispositif est attrayant pour la réalisation de circuits intégrés rapides à haute densité, car une excellente uniformité des tensions de seuil peut être obtenue et des circuits complémentaires à faible consommation pourraient être aisément fabriqués. Nous avons pour la première fois réussi à fabriquer des SISFET "pseudomorphiques" GaAs/GalnAs/A1GaAs. La teneur en indium du canal contraint GaInAs a été déterminée à partir de mesures de photoluminescence à 4K. Des mesures électriques confrontées à un modèle classique de la structure nous ont permis de déduire la charge d'espace et la hauteur de barrière effective de la couche de A10. 6Ga0. 4As isolante. Une technologie auto-alignée a été mise au point avec pour l'objectif la réalisation de transistors de hautes performances. Le procédé de fabrication inclut une gravure sèche (RIE) de la grille GaAs; ensuite un espaceur en nitrure de silicium est déposé sur les flancs du mesa de grille par PECVD et RIE; les contacts de source et drain sont formés par implantation ionique et recuit flash. Pour des longueurs de grille de 1µm, des résultats au meilleur niveau mondial ont été obtenus avec des transconductances de 240 mS/mm et 273 mS/mm pour les SISFET conventionnels et pseudomorphiques respectivement. L'uniformité des tensions de seuil est excellente, avec un écart-type égal à seulement 11 mV pour les SISFET conventionnels. Des effets d'électrons chauds ont été observés et sont discutés en détail. Nous montrons que ces effets induisent un régime de résistance différentielle négative dans les caractéristiques I(V) de drainThis work is devoted to the study of Semiconductor Insulator Semiconductor Field Effect Transistors (SISFET), a promising device for integrated circuits, since very good threshold voltage control and uniformity can be obtained, and it should be possible to realize complementary circuits. During this work we have for the first time successfully grown and processed pseudomorphic GaAs/GalnAs/A1GaAs SISFET. From electrical measurements and modelling the residual doping level, and the effective barrier height of the A10. 4Ga0. 6As barrier layer has been deduced. Photoluminescense measurements have been performed on the pseudomorphic structures in order to determine the Indium content of the GainAs layer. A self-aligned technology has been established in order to fabricate high performance devices. The process includes first an anisotropic etch of the gate using Reactive Ion Etching. Next a silicon nitride sidewall is formed. A self-aligned ion implantation followed by rapid thermal annealing is used to form highly doped source and drain contacts. DC characterizations are presented. For 1µm SISFETs state-of-the-art results have been obtained, with a transconductance of 240 mS/mm. The transconductance of the pseudomorphic SISFET is even higher with a maximum value of 273 mS/mm. Our SISFET's have a source resistance of only 0. 16 Ωmm which is the lowest ever reported. A very good on-wafer threshold voltage uniformity has been obtained with a standard deviation of only 11mV for the conventional SISFETs. Hot electron effects have been observed and are discussed. We show that this induces a negative differential resistance regime in the the drain current characteristics
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Trinko, Tara Rae. "Bottom-Up and Top-Down Controls on Algal Bloom Frequency in Two Shallow Mesotrophic Lakes." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/TrinkoTR2008.pdf.
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Leeb, Tobias [Verfasser]. "MBE-Wachstum von ZnMnSe zur Spininjektion in GaAs-AlGaAs-Heterostrukturen = MBE-growth of ZnMnSe for spininjection into GaAs-AlGaAs-heterostructures / Tobias Leeb." Regensburg : Univ.-Verl. Regensburg, 2009. http://d-nb.info/999400762/34.
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Kuyucak, Nural. "Algal biosorbents for gold and cobalt." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75374.
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Different types of biomass samples including fungi and algae were treated for their gold and cobalt uptake capacity. The performance of activated carbon and ion-exchange resins were compared with the metal uptake capacity of the biosorbents. Sargassum natans, a brown seaweed, exhibited a high gold uptake capacity outperforming the ion-exchange resin and equalling activated carbon. Algal biomass of Ascophyllum nodosum proved to be a very potent biosorbent for cobalt. While the temperature, agitation and biomass particle size did not affect the metal uptake process, the effect of pH was significant for both gold and cobalt uptakes. The optimum pH for gold uptake was 2.5 and for cobalt, was 4-5. The kinetics of cobalt biosorption was relatively rapid (5 min) at the initial concentration of the metal in solution, 100 mg/L. The biosorptive uptake of gold required 2 h to reach equilibrium when the initial concentration of gold was 100 mg/L. None of the tested cations, such as K$ sp+$, Ca$ sp{2+}$, Fe$ sp{2+}$, Cr$ sp{3+}$, UO$ sbsp{2}{2+}$, Ni$ sp{2+}$, Zn$ sp{2+}$, Ag$ sp+$, affected the gold uptake capacity of S. natans biomass under the optimum conditions. Anions, such as NO$ sbsp{3}{-}$, SO$ sbsp{4}{2-}$, CO$ sbsp{3}{2-}$, PO$ sbsp{4}{3-}$, and Pb$ sp{2+}$ suppressed the gold uptake somewhat. Under the optimum process conditions cations, except K$ sp+$ and Fe$ sp{2+}$, and anions, NO$ sbsp{3}{-}$ in particular, exhibited a pronounced negative effect on the cobalt uptake by A. nodosum biomass.Sequestered gold was eluted with a mixture of thiourea and ferric ammonium sulphate solution. Approximately 98% of sequestered gold was eluted with 17 h in a batch contacting system at the optimum solids (biomass)-to-liquid ratio of 5 and pH of 5. At increased temperatures, the gold elution rate increased only slightly. Efficient desorption of cobalt was achieved using CaCl$ sb2$/HCL solution at pH 3. Cobalt elution time was quite short. Temperature affected neither desorption rate nor the equilibrium. The optimum solid-to-liquid ratio was 12 for desorption of cobalt from A. nodosum biomass.
The gold taken up by the biosorbent was deposited in its elemental form.
Available mathematical models, including the REDEQL2 chemical equilibrium model, were tested for theoretical predictions of co-ion competition in attempt to better understand the biosorption mechanism. (Abstract shortened with permission of author.)
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Martinez, Joaquin. "Molecular ecology of marine algal viruses." Thesis, University of Plymouth, 2006. http://hdl.handle.net/10026.1/2459.
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In this study phytoplankton viruses were investigated from a point of view of their genotypic richness, ecology and role in controlling two microalgae species: Emiliania huxleyi and Phaeocystis pouchetii. Host specificity determined for Emiliania huxleyi-virus (EhV) isolates revealed a highly variable host range suggesting a relation between virus specificity and genetic or phenotypic variations within E. huxleyi strains and EhVs. Subsequently the dynamics and genetic richness of Emiliania huxleyi and EhVs were monitored in mesocosm experiments and during the progression of a natural bloom in the sea. The results confirmed the role of virus infection in regulating the intraspecific succession of E. huxleyi in the ocean. Furthermore, they revealed significant differences in genotypic composition and dynamics among blooms. The mesocosm setup appeared to be a very robust experimental system, which allowed reproducibility. The most important factor determining the development of the blooms in the enclosures was the experimental manipulation (i.e. nutrient addition), whereas the effect of filling of the enclosures, delay in nutrient addition and position in the raft were of minor importance. Further laboratory experiments revealed differences in the genomic content of different EhVs. EhV isolates from the English Channel carry a putative phosphate permease gene (ehv117) while the only available EhV from a Norwegian fjord has replaced ehv117 with a putative endonuclease, suggesting different propagation strategies among closely related EhVs. Culture studies using one of the English Channel isolates and E. huxleyi CCMP 1516 showed that the lack of phosphate (P) reduced the growth rate of the host and inhibited the production of viral particles. Furthermore, P availability was shown to have an effect on the level of ehv117 expression. In addition, other mesocosm studies revealed that specific viruses (PpVs) play a significant role in the termination of induced Phaeocystis pouchetii blooms. However, the role of PpVs may be significant only for the flagellated stage of P. pouchetii. Phenotypic characteristics of PpVs isolated during these studies indicate that they are probably members of the Phycodnaviridae family.
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Curtis-Jackson, Phillippa Kate. "Characterisation of algal derived organic nitrogen." Thesis, University of Plymouth, 2006. http://hdl.handle.net/10026.1/2076.
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The molecular level characterisation of compounds comprising the dissolved organic nitrogen (DON) pool is an important task for chemical oceanographers wishing to understand its role in the marine N cycle. Low DON concentrations, problems with saline matrices and a lack of pre-concentration methods have all contributed to DON being ignored and disregarded, until recently. Sub units of DON have been analysed as bulk parameters within which the low molecular weight (LMW; < 1,500 Da) fraction has been proposed to drive regenerated production within the oceans. The largest producers of these compounds are phytoplankton. Dissolved combined amino acids (DCAAs) are proposed to be the largest identifiable component of the LMW fraction. Peptides were chosen as the starting point for this study on DON characterisation, due to their unrivalled detection when analysed via liquid chromatography/ mass spectrometry (LC/MS). A method was developed for the characterisation of low molecular weight peptides, released either actively or passively from the axenically-cultured phytoplankton Phaeodactylum tricornutum. Methods for the separation (high performance liquid chromatography; HPLC), detection (mass spectrometric; MS), de-salination and pre-concentration (solid phase extraction; SPE), of analytes present in the culture water sampled during the period of maximum DON, were developed. The successful chromatographic separation of LMW peptides was achieved using a Phenomenex® Gemini Gig column in conjunction with mobile phases of acidified MeOH and water. The SPE method was developed on a Hamilton PRP-1 column containing a polystyrene divinylbenzene stationary phase (PSDVB). During the extraction process the increased hydrophobicity of the PS-DVB phase was predicted to yield increased recoveries of peptides, when compared to analogous d g phase cartridges. The method was transferred to extraction cartridges (500 mg, StrataX). Further investigations were then carried out into the affects of salt and dissolved organic matter on the extraction process. Samples were prepared by applying the extraction method to 1 L supernatants of culture water samples. The HPLC protocol was used to separate the components of the complex sample prior to data acquisition in both full MS mode and in the data dependent mode (DDMS). Mass spectra and chromatograms of ions unique to the cultured waters were identified. Further instrument manipulation allowed interfering ions to be diverted away from the mass analyser and consequently multistage mass spectrometry (MS²) to be carried out on unique ions that exceeded the threshold intensity of 1 x 105. Unique ions identified in the axenic cultures were two amino acids TYR and a modified structure isomerically/isobarically related to TYR. Seven peptides were partially sequenced. These were H-(VAL, THR, Xxx)-OH, H-(GLN/LYS, ALA, ASN, Xxx)-OH, H-(ASN, ALA, GLU, Xxx)-OH, H-(VAL, GLU, Xxx)-OH, H-(SER, HIS, Xxx)-OH, H- (PRO, XLE,HIS, GLN/LYS, GLY, Xxx)-OH and H-(Xxx, XLE, GLN/LYS, XLE, GLU)- OH. One whole peptide was tentatively proposed as H-TRP-PHE-OH. A significant loss of data was observed between the unique peptide ions identified in the MS analysis and the ions that underwent CID during the DDMS analysis, because they were below the threshold ion count or co-eluted with a more dominant ion. The method development carried out through this study has enabled the successful analysis of samples previously considered incompatible with LC/MS instrumentation. The method can be applied to all aquatic environment samples for both contaminant removal and preconcentration requirements and can be seen as an initial step from which many different avenues of future work may be explored.
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Gates, Ruth D. "Seawater temperature and algal-cnidarian symbiosis." Thesis, University of Newcastle Upon Tyne, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.346445.
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Cassidy, Keelin Owen. "EVALUATING ALGAL GROWTH AT DIFFERENT TEMPERATURES." UKnowledge, 2011. http://uknowledge.uky.edu/bae_etds/3.
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In recent years, there has been a concern for the amount of carbon dioxide released into the atmosphere and how it will be captured. One way to capture carbon dioxide is with algae. In this study, algae's growth was measured at different temperatures. The first part of the study was to grow Scenedesmus and Chlorella with M8 or urea growth media at a temperature of 25, 30 or 35ºC. It was found that 30ºC had the best growth rates for both algae. The second part studied Scenedesmus growth with urea, more in-depth, and found the optimum growth temperature to be 27.5ºC with a growth rate of 0.29 1/hr. The last part of the study was a heat transfer model which predicted the temperature of a greenhouse and an outdoor unit. The model could also predict the growth rate of the algae and the temperature if flue gas is mixed in with the algae.
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Kemp, Ronelle. "The algal gardens of Patella cochlear." Thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/26450.
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Guo, Jiahua. "Impact of pharmaceuticals on algal species." Thesis, University of York, 2015. http://etheses.whiterose.ac.uk/12390/.
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Trace amounts of activated pharmaceutical ingredients (APIs) have been reported in aquatic environments worldwide, and their toxicity to non-target organisms is of increasing concern. Algae are primary producers in aquatic food chains, and as such are very sensitive to external disturbance. The understanding of the adverse effects on the algal species such as growth and physiological effects is vital to understand the risks of APIs in the aquatic environment. This thesis therefore describes desk-based studies and a series of laboratory experiments to characterise the risk of APIs, and to investigate the effects of APIs on a wide range of algal species. In the desk-study, a review summarising the available ecotoxicological data of APIs to algal species was initially performed, where differences in the sensitivity of the algal species towards API exposures were found. After that, an approach for prioritising APIs and associated metabolites in the UK environment was developed, where three major-use antibiotics lincomycin, tylosin and trimethoprim that pose a potential threat to algal species in the natural environment were identified for further experimental investigation. Laboratory experiments were then conducted to investigate the effects of three antibiotics on the growth and physiology of a range of algal species from chlorophytes, cyanobacteria and diatoms. Risk arising from the antibiotic mixture in the European surface waters was characterised In conclusion three major-use antibiotics could cause inhibitory effects on both algal growth and physiology. At environmentally relevant concentrations the antibiotic mixtures can pose potential risks in European surface waters.
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Achtnich, Thomas Martin. "Charakterisierung von Defekten in epitaktischem ALGaAs hergestellet mittels Molekularstrahlen /." Lausanne : EPFL, 1988. http://library.epfl.ch/theses/?nr=748.
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MAEZAWA, Koichi, Shigeru KISHIMOTO, Makoto YAMAMOTO, and Takashi MIZUTANI. "Low-Frequency Noise Characteristics of AlGaAs/InGaAs Pseudomorphic HEMTs." Institute of Electronics, Information and Communication Engineers, 2001. http://hdl.handle.net/2237/15005.
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