Teses / dissertações sobre o tema "Cell-Less"

With the increased usage of electrical equipment for various applications, the demand for quality power apart from continuous power availability has increased and hence requires the development of appropriate power conditioning system. A major factor during development of these systems is the requirement that they remain environment-friendly. This cannot be realized using the conventional systems as they use batteries and/or engine generators. Among various viable technologies, fuel cells have emerged as one of the most promising sources for both portable and stationary applications. In this thesis, a new battery less UPS system configuration powered by fuel cell is discussed. The proposed topology utilizes a standard offline UPS module and the battery is replaced by a supercapacitor. The system operation is such that the supercapacitor bank is sized to support startup and load transients and steady state power is supplied by the fuel cell. Further, the fuel cell runs continuously to supply 10% power in steady state. In case of power outage, it is shown that the startup time for fuel cell is reduced and the supercapacitor bank supplies power till the fuel cell ramps up from supplying 10% load to 100% load. A detailed design example is presented for a 200W/350VA 1- phase UPS system to meet the requirements of a critical load. The equivalent circuit and hence the terminal behavior of the fuel cell and the supercapacitor are considered in the analysis and design of the system for a stable operation over a wide range. The steady state and transient state analysis were used for stability verification. Hence, from the tests such as step load changes and response time measurements, the non-linear model of supercapacitor was verified. Temperature rise and fuel consumption data were measured and the advantages of having a hybrid source (supercapacitor in parallel with fuel cell) over just a standalone fuel cell source were shown. Finally, the transfer times for the proposed UPS system and the battery based UPS system were measured and were found to be satisfactory. Overall, the proposed system was found to satisfy the required performance specifications.

Mechanisms of post-transcriptional control are critical to deploy RNAs and proteins asymmetrically to a discrete region of cytoplasm at the posterior of the Drosophila oocyte and embryo, called the pole plasm and thus allow differentiation of the germline. Research presented in this thesis investigates the post-transcriptional control of Drosophila pole plasm component germ cell-less (gcl ). Maternal gcl activity is required for germ cell specification and gcl RNA and protein accumulate asymmetrically in the pole plasm. gcl RNA, but not Gcl protein, is also detected in somatic regions of the embryo, and ectopic expression of Gcl in the soma causes repression of somatic patterning genes suggesting that gcl RNA is subject to translational control. I find that Gcl is expressed during oogenesis, where its expression is regulated by translational repressor Bruno (Bru). Increased levels of Gcl are observed in the oocyte when Bru is reduced (i.e., in an arrest heterozygote) and Bru overexpression reduces the amount of Gcl. Consistent with this, reduction of the maternal dosage of Bru leads to ectopic Gcl expression in the embryo, which, in turn, causes repression of anterior huckebein RNA expression. Bruno binds directly to the gcl3'UTR in vitro, but surprisingly, this binding is largely independent of a Bruno Response Element (BRE) in the gcl 3'UTR and depends upon a novel site. Furthermore, the gcl BRE-like region is not required to repress Gcl expression during oogenesis or embryogenesis. I concluded that Bru regulates gcl translation in a BRE-independent manner. In addition, I established the role of the gcl 3'UTR in gcl RNA localization and translation using transgenes that replace the endogenous 3'UTR with the alpha-tubulin 3'UTR or place it in tandem to the bicoid 3'UTR. I find that accumulation of gcl RNA in the embryonic pole plasm requires the gcl 3'UTR. Moreover, Gel is restricted to the pole plasm by translational repression mediated by the gcl 3'UTR and a limiting pool of trans-acting translational repressors. The phenotypic consequences of loss of this translational control are relatively mild, suggesting that gcl translation does not require stringent repression in the soma.

L’augmentation significative du nombre d’utilisateurs ayant des besoins toujours croissants, l’émergence de nouveaux services et de nouvelles applications ont amené les réseaux mobiles à évoluer. Les travaux de cette thèse ont pour objectif de répondre à ces enjeux. La première partie de cette thèse s’intéresse particulièrement à l’allocation des ressources classique et fournit quatre contributions : une analyse de la diversité multi-utilisateur, deux nouvelles solutions d’ordonnancement et une nouvelle solution de routage. Les résultats de ces travaux montrent que ces contributions apportent des solutions pour répondre aux enjeux des réseaux mobiles 5G de demain en augmentant par exemple l’efficacité spectrale et l’efficacité énergétique, la qualité de service tout en réduisant le délai global des utilisateurs. Fort de ces résultats et des analyses qui en découlent, la deuxième partie de cette thèse se concentre sur l’allocation des ressources dans un contexte "Cell-less". Cette approche innovante permet notamment d’avoir une prise de décision de manière logiquement centralisée. Cela sied tout particulièrement à la gestion des interférences inter-cellulaires, où deux nouvelles solutions sont présentées dans cette thèse. Les résultats montrent une augmentation de l’efficacité spectrale et une réduction du délai des utilisateurs, particulièrement pour ceux en bordure de cellule. De plus, les résultats obtenus via l’approche "Cell-less" sont accrus grâce à l’utilisation du Joint-Transmission Coordinated MultiPoint
The significant increase of the number of users with ever-growing needs, the emergence of new services and new applications have led mobile networks to evolve. The main objective of this thesis is to respond to these challenges. The first part of this thesis focuses on classical resource allocation and provides four contributions: a multi-user diversity analysis, two new scheduling solutions and a new routing solution. The results of this work show that these contributions provide solutions to meet the challenges of tomorrow’s 5G mobile network, by, for instance, increasing spectral and energy efficiencies, increasing the QoS while reducing the user delay. Based on these results and the ensuing analysis, the second part of this thesis focuses on resource allocation in a "Cell-less" context. This innovative approach enables logically centralized decision making. This is particularly efficient for inter-cell interference management, where two new solutions are presented in this thesis. The results show an increase in spectral efficiency and a reduction in user delay, particularly for those located at cell-edges. In addition, the results obtained with the "Cell-less" approach are enhanced by the use of Joint-Transmission Coordinated MultiPoint

Malkostrake Krebse zeigen im postnauplialen Keimstreif ein invariantes Zellteilungsmuster und eine Zelllinie. Embryonen eines Isopoden (Porcellio scaber) und eines Amphipoden (Orchestia cavimana) wurden bezüglich ihrer Zelllinie vergleichend Untersucht. Mittels immunhistochemischer Färbungen wurde das Expressionsmuster der Gene engrailed und Distal-less in Hinblick auf die Zelllinie und die Morphogenese der Segmente und der Beinentwicklung analysiert. Die Zelllinie wurde bei Porcellio scaber mit der Methode der 4D-Mikroskopie untersucht. Mit Zellablationsexperimenten wurden Abhängigkeiten der Zellen untereinander aufgezeigt. Die Ergebnisse dieser Untersuchungen zeigen: I. Die Genexpression von Distal-less und engrailed wird unabhängig von der Zelllinie reguliert. II. Die Bildung der konvergenten einästigen Beine im Thoraxbereich beider Krebse erfolgt durch unterschiedliche Regulation des Gens Distal-less - bei Orchestia cavimana wird die Expression des Gens in den lateralen Zellen abgeschaltet, während diese Zellen bei Porcellio scaber erst gar nicht Distal-less exprimieren. III. Die Anwendung des Systems der 4D-Mikroskopie zeigte unter anderem, dass in den vorderen Reihen nichtektoteloblastischen Ursprungs bei Porcellio scaber die Zelllinie variabel ist und eine Zellsortierung und Zellimmigration stattfindet. IV. Die Ähnlichkeit der Bildung dieser Reihen bei Porcellio scaber mit der der Tanaidaceen lässt auf ein Schwestergruppenverhältnis der Taxa Isopoda und Tanaidacea schliessen. Die Dissertation enthält fünf Videoaufnahmen als separate AVI-Dateien.
Malacostracan crustaceans show in their postnaupliar germ-band an invariant cleavage pattern and a cell-lineage. A comparative analysis of this cell-lineage in an Isopod (Porcellio scaber) and an amphipod (Orchestia cavimana) was done in this thesis. Immunohistochemical stainings of the gene products Distal-less and Engrailed were used, to show the relation of these genes to the morphogenesis of segments and legs. Further, the cell-lineage of Porcellio scaber was analyzed with a 4D-microscope system. Cell-ablation experiments were used to show regulational networks in the development of the germ-band. The results of this work show: I. The regulation of the genes Distal-less and engrailed is independent of the cell-lineage. II. The morphogenesis of the convergent monoramous limbs in the thorax is reflected by different expression patterns of the gene Distal-less - in Orchestia cavimana the expression of Distal-less is switched off in the lateral cells, in Porcellio scaber these cells do not start the Distal-less expression. III. The 4D-microscopy analysis show, that the cell-lineage in the cellrows wich have a non-ectoteloblastic origin is not invariant. In these rows of cells show cell sorting. IV. The formation of these rows in the isopod Porcellio scaber shows similarity to the formation in tanaidaceans. A sister group relationship of Tanaidacea and Isopoda is strongly supported. This dissertation contains five video recordings as separate AVI files.

Os fitoplasmas são organismos procariotos sem parede celular, que habitam as células do floema das plantas e são transmitidos, principalmente, por cigarrinhas sugadoras de floema. Este patógeno é responsável por causar doenças em diversas espécies vegetais, provocando a expressão de diversos sintomas, entre os quais podem ser destacados a redução do tamanho foliar, amarelecimento das folhas, superbrotamento de ramos e enfezamento da planta hospedeira. Entre os anos de 2013 e 2014, plantas de três espécies vegetais com sintomas característicos de infecção causada por fitoplasmas foram observadas no estado de São Paulo. O DNA total foi extraído a partir de plantas de couve-flor com sintomas de nanismo, malformação da inflorescência e necrose dos vasos do floema; de plantas da ornamental conhecida por árvore-da-felicidade com sintomas amarelecimento e redução do limbo foliar; e de plantas de Alho-poró com sintomas de enfezamento. Por meio do teste de PCR conduzido em sua maioria com os primers P1A/16S-SR foi possível detectar fitoplasmas nas três espécies vegetais testadas. Os fragmentos genômicos correspondentes ao 16S rRNA dos fitoplasmas foram sequenciados e identificados. Nas plantas de couve-flor e da árvore-da-felicidade foram identificados fitoplasmas afilados ao grupo 16SrVII-B, através da análise virtual de RFLP, cálculo do coeficientes de similaridade (F) e análise filogenética. Para ambas as espécies, este é o primeiro relato da ocorrência de representantes deste grupo, nas condições brasileiras. Nas plantas de Alho-poró foram identificados fitoplasmas afiliados ao subgrupo 16SrIII-J e ao grupo 16SrXIII, com base na análise dos genes 16S rRNA, SecY e proteína ribossomal, conduzidas através de análise virtual de RFLP, valores de coeficientes de similaridade e análise filogenética. Para o fitoplasma membro do grupo 16SrXIII foram identificadas quatro estirpes, uma delas afiliada ao subgrupo 16SrXIII-E e as demais como prováveis representantes de novos subgrupos. O presente estudo se constitui em uma contribuição ao conhecimento de novos patossistemas envolvendo fitoplasmas, bem como à caracterização molecular de fitoplasmas baseadas em diferentes genes marcadores, atualmente usados para a classificação de representantes deste grupo emergente de agentes causais de doenças de plantas.
The phytoplasmas are prokaryotic organisms without cell walls, which inhabit the phloem cells of plants and are transmitted mainly by leafhoppers sucking the phloem. This pathogen is responsible for causing diseases in various plant species, leading to expression of many symptoms, among which can be highlighted the reduction of leaf size, leaf yellowing, shoots proliferation and stunting of the plant host. Between the years 2013 and 2014, three plant species with characteristic symptoms of infection caused by phytoplasma were observed in São Paulo. Total DNA was extracted from cauliflower plants with symptoms of stunting, malformation of the inflorescence and necrosis of the phloem; ornamental plants known for Ming Aralia with symptoms yellowing and little leaves; and leek plants with symptoms of stunting. Through the PCR test conducted mostly with the primers P1A/16S-SR was possible to detect phytoplasmas in the three species of plants. The genomic fragments corresponding of 16S rRNA gene of the phytoplasma were sequenced and identified. In plants of cauliflower and Ming Aralia were identified phytoplasmas belonging to 16SrVII-B group through virtual RFLP analysis, calculation of similarity coefficients (F) and phylogenetic analysis. For both species, this is the first report of the occurrence of representatives of this group, in Brazilian conditions. In leek plants were identified phytoplasmas affiliated with 16SrIII-J subgroup, and the 16SrXIII group, based on the analysis of the 16S rRNA, SecY and ribosomal protein genes, conducted through virtual analysis of RFLP, similarity coefficient values and phylogenetic analysis. For the phytoplasma member of group 16SrXIII were identified four strains, one affiliated with 16SrXIII-E subgroup and the others as probable representatives of new subgroups. This study constitutes a contribution to knowledge of new pathosystems involving phytoplasmas and the molecular characterization of phytoplasma based on different marker genes, currently used for the classification of representatives of this emerging group of plant pathogens.

The submitted work deals with the methods for manufacturing and analysis of contacts on crystalline silicon solar cells. It is focused on selective processes for the production of solar cells metal contacts. The masking feature of silicon nitride is used for selective silicon etching, selective phosphorus diffusion and selective electro-less nickel deposition. Properties of metal contacts precursors are investigated using optical microscopy and their electrical properties using methods based on a four-point probe method. Results are used for the manufacturing of silicon, solar cell with an innovative type of the structure of the front side metallization: chemical nickel, conductive adhesive and copper wire. This approach allows to reduce shading of the front area of PV cells with the ability to avoid usage of busbars. The another advantage of this approach is in replacement of costly silver in at least 2/3 cross section of the front side metallization. Selective ablation of silicon nitride layer was conducted by means of IR laser beam.

L'épidermolyse bulleuse dystrophique récessive (EBDR) est une maladie génétique cutanée due à des mutations de perte de fonction du gène COL7A1 codant pour le collagène VII. Le collagène VII forme les fibres d'ancrage, structures essentielles pour l'adhésion de l'épiderme au derme sous-jacent. Les patients EBDR développent dès la naissance, des décollements bulleux de la peau et des muqueuses responsables de plaies chroniques et de graves complications locales et systémiques. La survenue de carcinomes épidermoïdes cutanés agressifs reste la première cause de décès. Il n'existe pas de traitement à ce jour. Les cellules stromales mésenchymateuses (CSM) sont des cellules multipotentes, isolées à partir de tissus adultes (moelle osseuse, tissu adipeux) ou de tissus périnataux (cordon ombilical). Des travaux antérieurs ont montré que les injections locales et systémiques de CSM issues de la moelle osseuse (CSM-MO) allogéniques ont un potentiel pour réduire l'inflammation cutanée et améliorer la cicatrisation des plaies chez les patients EBDR. Ces améliorations cliniques sont cependant transitoires et les mécanismes d'action des CSM-MO dans l'EBDR ainsi que leur durée de vie après injection sont mal connus. Les CSM-MO pourraient agir via leurs propriétés immunomodulatrices, anti-fibrotiques, pro-angiogéniques, par un effet paracrine permettant l'expression de collagène VII endogène et/ou la sécrétion de collagène VII par les CSM-MO injectées. L'objectif de cette thèse a été d'étudier le potentiel thérapeutique des CSM dans des modèles précliniques de l'EBDR. Nous avons tout d'abord montré que les CSM-MO expriment une quantité d'ARNm de COL7A1 et de collagène VII comparable aux fibroblastes dermiques sains en culture. Nous avons ensuite évalué la capacité des CSM-MO humaines à survivre et produire du collagène VII à la jonction dermo-épidermique (JDE) à long terme après une injection locale dans des peaux équivalentes humaines EBDR greffées sur souris nude. L'injection intradermique (ID) de CSM-MO in vivo a permis de restaurer l'expression du collagène VII ainsi que la formation de fibres d'ancrage à la JDE jusqu'à 6 mois après l'injection. Les CSM-MO sont retrouvées dans la peau équivalente jusqu'à 4 mois après l'injection. Ces résultats montrent qu'une injection ID unique de CSM-MO in vivo permet de rétablir une production prolongée de collagène VII synthétisé par les cellules injectées et d'améliorer l'adhésion dermo-épidermique de la peau équivalente EBDR. Nous avons ensuite comparé l'efficacité des CSM issues de la gelée de Wharton de cordon ombilicaux (CSM-CO) humains aux CSM-MO suivant la même méthodologie que précédemment. Les CSM-CO expriment en culture une quantité d'ARNm de COL7A1 et de collagène VII supérieures aux CSM-MO et fibroblastes dermiques sains. Une injection unique ID de CSM-CO dans la peau EBDR équivalente greffée permet de rétablir une faible expression de collagène VII jusqu'à 4 mois après l'injection. Les CSM-CO sont détectées dans la peau équivalente jusqu'à 2 mois après l'injection. Ces données montrent que les CSM-CO ont une capacité moindre à restaurer l'expression du collagène VII à la JDE comparativement aux CSM-MO injectées dans le même modèle de xénogreffes EBDR. Ces résultats ouvrent la perspective d'une thérapie génique ex vivo utilisant des CSM-MO murines Col7a1-/-. Les souris Col7a1-/- reproduisent les lésions cutanées et muqueuses observées chez les patients EBDR. L'espérance de vie de ces animaux est très réduite. Les CSM-MO murines Col7a1-/- transduites en culture à l'aide d'un vecteur rétroviral SIN exprimant COL7A1 produisent en moyenne 30 fois plus de collagène VII que les CSM-MO murines WT. Des expériences in vivo sont nécessaires pour déterminer si l'injection de CSM-MO génétiquement corrigées ont le potentiel de traiter des lésions cutanées et muqueuses, pour définir la dose optimale et la durée de l'effet chez l'animal. Ceci constituerait une étape importante vers la clinique
Recessive dystrophic epidermolysis bullosa (RDEB) is a severe skin disease caused by loss-of-function mutations in COL7A1 encoding type VII collagen. Type VII collagen forms anchoring fibrils which are essential structures for dermal-epidermal adherence. Patients with RDEB suffer since birth from skin and mucosal blistering and develop severe complications. The development of aggressive squamous cell carcinomas is the first cause of demise of these young patients. To date, there is no treatment. Mesenchymal stromal cells (MSC) are multipotent cells, isolated from adult tissue (bone marrow, adipose tissue) or perinatal tissue (umbilical cord). Previous works have shown that local and systemic injections of allogeneic bone marrow-derived MSC (BM-MSC) have a potential to reduce skin inflammation and to improve wound healing in RDEB patients. However, clinical improvement was transient and the mechanisms of action of BM-MSC in RDEB and also their survival after injection are still poorly understood. BM-MSC could act through immunomodulation, anti-fibrotic and angiogenic proprieties, paracrine effects leading to type VII collagen production in the host tissues and/or type VII collagen secretion by injected BM-MSC. The aim of our work was to study the therapeutic potential of MSC for RDEB in preclinical models. We first showed that BM-MSC produce COL7A1 mRNA and type VII collagen levels comparable to healthy dermal fibroblasts in culture. We then assessed the long-term capacity of human BM-MSC to survive, produce and deposit type VII collagen at the dermal-epidermal junction (DEJ) after local injection in human RDEB skin equivalents transplanted onto nude mice. In vivo intradermal (ID) injection of a single dose of human BM-MSC led to the production and deposition of human type VII collagen at the DEJ and allowed anchoring fibrils formation for at least six months post-injection. Injected human BM-MSC were found in the skin at least four months post-injection. These data show that intradermally injected human BM-MSC have the potential to improve dermal-epidermal adhesion of RDEB skin equivalents through sustained deposit of type VII collagen molecules and subsequent anchoring fibrils formation. We then compared the efficacy of human Umbilical Cord Wharton's Jelly-MSC (UC-MSC) with BM-MSC using the same methodology as previously described. UC-MSC showed in vitro a significantly higher amount of COL7A1 mRNA and type VII collagen compared to BM-MSC and healthy dermal fibroblasts in culture. ID injection of a single dose of UC-MSC in vivo led to the production and deposition of low levels of human type VII collagen at the DEJ for four months post-injection. Injected human UC-MSC were found in the skin two months post-injection. These data disclosed a lower efficacy of UC-MSC to restore collagen VII at the DEJ compared to BM-MSC injected in the same xenograft RDEB model. These data open the perspective of using gene-corrected BM-MSC from a Col7a1-/- RDEB murine model to restore normal dermal-epidermal adhesion. Col7a1-/- mice reproduce cutaneous and mucosal lesions observed in RDEB patients. The life expectancy of these animals is very short. We could show that transduction of Col7a1-/- murine BM-MSC in culture using a COL7A1-expressing SIN retroviral vector led to type VII collagen expression levels which were 30-fold higher on average than in BM-MSC from WT mice. In vivo data are required to determine whether the injection of gene-corrected BM-MSC has the potential to treat skin and mucosal lesions in RDEB mice and to define the optimal dose and duration of the effect in vivo. Restoration of type VII collagen expression and anchoring fibrils formation in Col7a1-/- mice would represent an important step towards clinical translation

Recent years have witnessed an explosion in the identification and understanding of stem cells, affording new cellular reagents for the study of regeneration in vitro. Traditionally, regeneration is studied in tissue culture in which the gaseous environment surrounding the cells contains about 20% oxygen. Cells in our bodies are never exposed to such high levels of oxygen, well out of normal physiologic range. In this work, stem cell regeneration in several systems was studied in traditional 20% oxygen culture and in oxygen levels more reflective of normal physiology. These lower oxygen-cultured progenitors behaved differently than those cultured in traditional environments. In several stem cell systems low oxygen significantly increased proliferation of progenitor populations, and in central nervous system stem cells, also decreased apoptotic death. More physiologic levels of oxygen in culture also led to regeneration of different daughter progeny populations with a distribution of phenotypes distinct from that generated in 20% oxygen. For example in CNS stem cells, a significantly greater yield of dopaminergic and serotonergic neurons was generated in low oxygen compared to 20% oxygen. Skeletal muscle satellite stem cells in high oxygen were significantly more likely to assume an adipocyte phenotype than those cultured in low oxygen. Furthermore, genes expressed during regeneration in physiologic vs. 20% oxygen were different from each other in timing and in abundance. These data suggest that oxygen manipulations will be useful to increase the survival and expansion of progenitor populations for research and possible transplantation, as well as for the survival and expansion of selected regenerated progeny. Furthermore, oxygen levels are a useful manipulation to help isolate and identify pathways used during regeneration and differentiation.

博士
國立臺灣大學
工程科學及海洋工程學研究所
97
This thesis presents a series of novel fuel sensor-less control schemes for a liquid feed fuel cell system that operate under various loading conditions and are suitable for portable power sources. The proposed techniques utilize the operating characteristics of a fuel cell, such as temperature, voltage, current and power to control the supply of fuel and regulate its concentration. A current integral technique with two different approaches has been developed for calculating the fuel quantity required at each monitoring cycle, which can be applied with the concentration regulating process to control the fuel supply for stable operation. As verified by systematic experiments, these schemes can control effectively and stably the supply of fuel with greatly reduced response time even when the MEA deteriorates gradually. The primary features and advantages of fuel sensor-less control scheme are as follows. When the fuel concentration sensor is excluded, the cost of a liquid feed fuel cell system is decreased and system volume as well as weight is reduced, thereby increasing specific energy density and design simplicity, and shortening system response time. Notably, temperature-compensation for measurement data is unnecessary. With a decreased number of components, this technology improves durability and reliability of a liquid feed fuel cell. That will help commercialization of liquid feed fuel cells and thus more adapt to portable and automotive power units like camcorder, PDA, laptops, E-Bikes and handicap cars.

碩士
國立臺灣海洋大學
河海工程學系
95
Electricity generation from membrane-less microbial fuel cells (ML-MFC) with the external resistance of 500 Ω was conducted in this study. The fuels for test include supernatant from primary sediment tank and the mixture of primary supernatant combined with glucose solution. Experimental works consist of three phases: hydraulic loading, organic loading, and aeration rate. As hydraulic retention time decreased from 48 to 6 hr, COD removal efficiency remained unchanged but coulomb efficiency and power density decreased. When fuel concentration increased from 150 to 1000 mg COD/L, COD removal exhibited a Monod-type Kinetics related to fuel concentration, the removal efficiency increased from 72 to 91 %, but coulomb efficiency and power density decreased. When aeration rate in cathode increased from 0 to 400 mL/min, COD removal efficiency exhibited a Monod-type Kinetics related to aeration rate, coulomb efficiency and power density increased. The Results indicated that, COD removal efficiency reached the level of wastewater treatment facilities currently employed, while electricity generation, and the maximum power output of the ML-MFC was quite low, implying that most organics degraded in a pathway without producing electricity.

New insights into biomedicine and related areas require the parallel development of new analytical methods. A technique for chemical analysis based on the use of acoustically levitated droplets, suitable for the study of intra and extracellular reactions at single or few cells level has been developed. Microenvironments suited for specific cell types and cell reactions can be created in levitated droplets to serve as biomimetic systems. The applicability of the Airborne System is broad and circumvents limitations associated with chip-based analytical systems, such as adsorption of the analytes or optical interferences at the walls of the sample containers. Furthermore, the low attomole detection limit highlights the potential of the method. Dysfunctional adipocytes and insulin-producing pancreatic β-cells are dynamic parts in the development of type 2 diabetes. The mechanisms involved are however not yet fully understood. With this project we aim to give our contribution for the understanding of the phenomena associated with the development of the disease and at the same time provide science with new tools which can be useful in the pursuit of new knowledge, as well as in the development of novel drugs, both in type 2 diabetes or in other metabolic diseases. The system was here applied in cellular studies at the single/few cell level. Reagents are added to the droplet using flow-through dispensers, with no physical contact with the droplet. After exposure of the cells to drugs, activators or inhibitors, the cell response (or lack of response) is monitored using fluorescence imaging detection and MALDI-TOF-MS. Adipocyte lipolysis was followed. Stimulation of lipolysis with isoprenaline resulted in a pH decrease detectable by this methodology. Moreover, the addition of insulin resulted in the inhibition of isoprenaline stimulated lipolysis in adipocytes in the levitated droplet. The addition of glycated insulin to an adipocyte containing droplet revealed not to be as effective to stop lipolysis as non-glycated insulin, which is na important finding in the search for new targets in type 2 diabetes related research. Additionally, we are now attempting to develop techniques which can interrogate and monitor analytes of interest in a levitated droplet, non-destructively, ondemand, and over extended periods of time and in real-time by MS. In current work droplet fission is induced by polarization in a containerless environment. Various electrode configurations are attempted varying parameters such as number and shape, voltage, pulse length and frequency for the applied electric field in order to get the proper droplet response. Miniaturization and single-cell analysis could ultimately result in a decreasing of the number of animal trials necessary in medical research.
Inovações em biomedicina e áreas relacionadas exigem o paralelo desenvolvimento de novos métodos analíticos. Assim, a técnica aqui apresentada é baseada na levitação acústica de pequenas amostras. O estudo de reacções intra e extracelulares utilizando apenas uma ou poucas células é, desta forma, possível. Microambientes adequados ao estudo the específicos tipos celulares e respectivas reacções podem assim ser criados, funcionando como sistemas biomiméticos. As aplicações do Airborne System são variadas. Com esta técnica algumas limitações, tais como a adsorção dos analitos e interferências ópticas devido à presença de superficies, associadas com outras técnicas de miniaturização incluindo as que se baseiam no uso de chips, são eliminadas. Além do mais, a possibilidade de detecção ao nível da attomole aumenta ainda mais o potencial desta técnica. Adipócitos disfuncionais bem como as células produtoras de insulina – células β - são factores importantes envolvidos no desenvolvimento da diabetes tipo 2. No entanto, estes mecanismos não são ainda totalmente conhecidos. Com este projecto pretendemos contribuir para a compreensão dos fenómenos associados com o desenvolvimento da doença e ao mesmo tempo equipar a ciência com novas ferramentas que poderão ser úteis, quer na descoberta quer no desenvolvimento de novas drogas para o tratamento, não só, da diabetes tipo 2, como de outras doenças metabólicas. O Airborne System foi aqui aplicado no estudo do metabolismo dos adipócitos ao nível de uma/poucas células. Os reagentes são adicionados à gota levitada usando flow-through dispensers, sem qualquer contacto físico. Depois de expostas tanto a drogas activadoras como inibitórias, a resposta das células (ou a falta dela) é monotorisada usando fluorescence imaging detection e MALDI-TOF-MS. A estimulação da lipólise em adipócitos é feita através da adição de isoprenalina. A resultante diminuição dos valores de pH do meio pode ser então detectada com o uso desta metodologia. A inibição da lipólise iniciada com a administração de isoprenalina foi conseguida através da adição de insulina. Em paralelo, a administração de insulina glicada, revelou não ser tão eficaz no objectivo de parar a lipólise, como foi a insulina não glicada. Este facto representa uma descoberta importante na procura de novos caminhos que levem ao total conhecimento dos mecanismos responsáveis pelo desenvolvimento da diabetes tipo 2. Ainda, estamos no momento a aplicar esforços no desenvolvimento the técnicas que nos permitam seguir a resposta das células de forma não destrutiva, por longos períodos de tempo e em tempo real utilizando MS. Actualmente, a fissão da gota levitada é induzida através da polarização de cargas num ambiente em que não existe qualquer contacto da gota com superficies externas. Eléctrodos com várias configurações são testados, fazendo variar parâmetros tais como o valor e o perfil da voltagem aplicada, frequência e comprimento dos pulsos aplicados no campo eléctrico, de forma a conseguir uma resposta apropriada por parte da gota em levitação. O desenvolvimento desta técnicas analítica poderá, em última análise levar a uma diminuição do número de animais sacrificados diáriamente em laboratório.

This thesis proposes to reduce the latency of MPI receive operations on cacheless architectures, by removing the delay of copying messages when they are first received. This is achieved by copying the messages directly into buffers in the lowest level of the memory hierarchy (e.g., scratchpad memory). The previously proposed solution introduced an Indirection Cache which would map between the receive variables and the buffered message payload locations. This proved somewhat beneficial, but the lookup penalty of the Indirection Cache limited its effectiveness. Therefore this thesis proposes that a most recently used buffer (i.e., an Indirection Buffer) be placed in front of the Indirection Cache to eliminate this penalty and speed up access. The tests conducted demonstrated that this method was indeed effective and improved over the original method by at least an order of magnitude. Finally, examination of implementation feasibility showed that this could be implemented with a small Cache, and that even with access times 6x slower than initially assumed, the approach with the Indirection Buffer would still be effective.
Graduate

BACKGROUND: Previous work has shown that follicular dendritic cells (FDCs) play an important role in selecting B cells such that antigens are responded to in a specific manner. FcγRΙΙB (CD32) is an antibody constant-region receptor found on FDCs and mutation of this receptor in humans is associated with Systemic Lupus Erythematosus (SLE). In addition, previous work has demonstrated that autoreactive germinal centers are the product of expression of interferon alpha (ΙFNα) by FDCs, so FcγRIIB signaling may involve modulation of IFNα signaling. OBJECTIVE: Because FcγRIIB mutation is associated with SLE and FDCs have been shown to be important in orchestrating B cell responses, understanding FcγRIIB on FDCs helps characterize B cell repertoire development in response to antigen—whether the antigen is foreign or self, as is the case in autoimmunity. Better characterization of the role of FcγRIIB could have consequences for autoimmune and cancer therapy. This study seeks to determine the role of FcγRΙΙB on FDCs in germinal center B cell selection dynamics within single, autoreactive germinal centers. METHODS: This study compares transplanted wild-type (B6) B cells—that are driven to be autoimmune by simultaneously transplanted autoimmune B cells—in two stromal cell settings: first, in germinal centers containing wild-type FDCs and second, in germinal centers containing FcγRIIB-knockout FDCs. Transplanted B6 B cell populations express photoactivatable protein, which allows for sorting of B cells from individual germinal centers. B cell sequences from single germinal centers were analyzed to determine how focused each germinal center response was and how the B cells differ in maturity and affinity for antigen. Finally, mice expressing a lineage-tracing system were treated with IFNα in order to observe the cytokine’s effect on B cell selection. RESULTS: Cells sorted from germinal centers containing FcγRIIB-knockout FDCs contain a distinguished population of less-developed B cells, as quantified by population-based analysis of their variable heavy chain genes. Overall, the IgM sequences from B cells sorted from germinal centers (GCs) containing FcγRIIB-knockout follicular dendritic cells displayed lower levels of somatic hypermutation (SHM) (p<.05) and shorter hypervariable regions (CDR3) (p<.05) compared to other B cell populations. Values computed to summarize how many different B cell lineages were present in a GC—its “clonality”—did not vary between the two mouse populations, although FcγRIIB-knockout FDC germinal centers displayed a correlation between clonality and immunoglobulin (Ig) isotype expression (R2= .85). Finally, lineage tracing mice receiving injections of interferon alpha (IFNα) displayed no difference in GC clonality compared to those receiving vehicle and assays of IFNα downstream signaling genes also displayed no change. CONCLUSIONS: FcγRIIB encourages more stringent selection of immature B cells in germinal centers as evidenced by survival of less developed B cells as defined by degree of somatic hypermutation and CDR3 length in GCs comprising FcγRIIB-knockout FDCs. In spite of this, sequence-based measures of germinal center clonality as completed here may fail to capture the functional results of B cell selection. In addition, the link between FcγRIIB and IFNα requires further investigation.
2019-07-03T00:00:00Z

碩士
國立中山大學
生物科學系研究所
95
Pluchea indica (L.) Less. is a shrub of the family Compositae and is widespread along the western coast in Taiwan. Previous studies indicated that the components of Pluchea indica have potent anti-inflammatory, anti-ulcer and antimicrobial activities. In the present study, the effects of aqueous extract of roots and leaves from P. indica on the cancer cell lines were investigated. Various experimental approaches including cell growth curves, MTT assay, MTS assay, focus formation assay and cell migration assay were performed on the aqueous extract-treated cancer cells. Our results demonstrate the aqueous extract of P. indica induced anti-proliferation activity on GBM8401 and HeLa cancer cell lines.

碩士
國立中山大學
生物科學系研究所
104
Pluchea indica (L.) Less. is a perennial plant known for its versatile uses in traditional oriental medicine. In our previous study, we demonstrate the in vitro anti-cancer activity of Pluchea indica root extract (PIRE) through induction of apoptotic cell death. However, one of the fractional extract, the hexane fraction of PIRE, despite showing the strongest potential of anti-cancer activity, the mechanism of cell death it induced remain unknown. In this study, we investigated the potential anticancer effect of the hexane fraction of Pluchea indica root extract (PIRE) on glioblastoma multiforme U87 cell lin. PIRE significantly suppressed the growth of cells in a dose-dependent manner. Propidium iodide staining result for cell cycle distributi28on shows cell cycle arrest at G1 phase. The result of Annexin V and propidium iodide staining following analysis with flow cytometry shows no significant induction of apoptosis. Fluorescent microscopy observation revealed the formations of acidic vesicular organelle (AVO) in PIRE-treated group. Expression of microtubule-associated protein light chain 3-II (LC3-II) protein also drastically increased, as well as the phosphorylation of JNK and p38 in response to PIRE treatment, suggesting the occurrence of autophagy. Our results provide evidence that through the induction of autophagic cell death, the hexane fraction of PIRE has the potential in its anti-brain cancer activity.

碩士
國立臺灣海洋大學
水產養殖學系
100
The purpose of this study was to investigate the gene expresstion of deleted in azoospermia-like (dazl) and germ cell-less (gcl) in the gonad of black porgy, Acanthopagrus schlegeli. dazl full length cDNA contains 2359 nucleotides encoding a putative 200 amino acid (aa) protein, and gcl contains 3415 nucleotides encoding a putative 503 aa protein. By RT-PCR, dazl is specificly expressed only in the gonad, and gcl has a high expression in the gonad and low expression level in brain, eyes, heart, liver, kidney and is not detectable in muscle. The gene expression of dazl and gcl are significantly increased at 120 dah. This suggests that dazl and gcl are closely related to sex differention in black porgy. E2 suppresses the expression of dazl and gcl at 120, 150, 180 dah. The expression of dazl in testicular tissues are higher than ovarian tissues from Aug to Dec in 1+-yr black porgy. This suggests that dazl may be related to spermatogenesis.The expression of gcl in January is significantly increased in the testis-excised gonads of 2+-yr black porgy, suggesting that gcl may be associated with oocyte maturation. By immunohistochemistry, Dazl and Gcl are expressed in oogonia, primary oocyte, vitellogenic oocytes, spermatogonia. Dazl is also expressed in the follicle cells surrounding the vitellogenic oocytes. By RNA in situ hybridization, dazl and gcl were co-expressed in the primary oocytes of the gonad in the first spawning season.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science. April, 2015
Microbial fuel cell (MFC) technology presents great potential for use as a dual system for industrial waste water remediation and electricity generation. The hurdle in up-scaling this technology has been identified as MFC-bioreactor architecture, both with regards to bioremediation and carbon source to electricity conversion rates. In addition to the latter’s limitations, the use of expensive mediators and membrane to enhance MFC performance renders the technology uneconomic to employ industrially. A 60mm high double chamber membrane and mediator-less MFC-bioreactor was designed, and constructed. The novel MFC-bioreactor made of transparent polyacrylic plastic had a total working volume of 8 litres with the anode chamber situated at the bottom and the cathode chamber at the top separated by a 10cm deep artificial membrane made up of glass wool, glass beads and marble balls. The MFC was operated under various operating parameters including; feeding modes (batch and continuous), with different substrate concentration at a range of external resistance (100-9000Ω) .The voltage produced during MFC operation was monitored and used to estimate the power density output of the MFC. The pseudo membrane was able to sufficiently separate the anode and cathode chambers allowing the development of potential difference and hence generation of current. The MFC demonstrated the potential for sustainable operation by producing and maintaining a stable power density of 2000mW/m2 when operated with an external resistance of 1000Ω. This power density was accompanied by a 73% remediation efficiency of the synthetic wastewater. It was concluded that the results of this research show proof of concept for a membrane-less MFC that can produce electrical energy in the absence of an electron shuffling mediator.

Objective: To develop a predictive model for preoperative differentiation between benign (B) and malignant (M) histology in patients with renal masses (RM) using recursive partitioning. Methods: We analyzed preoperative patient and tumour characteristics in 395 subjects who had surgery for RM suspicious for renal cell carcinoma. Results: The model predicted B vs. M histology with an overall accuracy of 89.6% (95% CI 86.2,92.5). It assigned patients with smaller tumours (<5.67cc) and a predominantly (>45%) exophytic component a high risk of B disease (52.6%). Patients with symptoms, larger tumours (>5.67cc) and larger endophytic component (>35%) have a 0% risk of B disease. Conclusion: B vs. M disease can be predicted accurately. This predictive accuracy is higher than that shown in renal biopsy series. It is hypothesized that for smaller and exophytic RMs, a biopsy is indicated. Symptomatic, larger and endophytic RMs should be removed without further investigations.

Microorganisms, mainly bacteria and fungi, are the producers of structurally diverse, complex organic compounds called as secondary metabolites. These metabolites include polyketides (PKs), non-ribosomal peptides (NRPs), and hybrid PKs/NRPs. The final products from these three classes display different characteristics like antibiotics, antiparasitic agents, antifungals, anticancer drugs, and immunosuppressants. As these products have wide range of potential application in pharmaceuticals, a number of biochemical studies have been carried out to elucidate of their biosynthetic pathways. The biosynthesis of these products is catalysed by large, multi-modular proteins including the NRPSs (non-ribosomal peptide synthases), the PKSs (polyketide synthases) and hybrid NRPS/PKS. Knowledge of the quaternary structure of PKS, NRPS and hybrid NRPS/PKS assembly line enzymes have been topic of interest since it helps not only in elucidating the crosstalk between different domains but also useful in modification of products. It has been demonstrated in the literature that FAS and PKS are homodimeric enzyme complexes, whereas the majority of NRPS are monomeric in nature. Whether NRPS is monomeric or homodimeric in the case of hybrid NRPS/PKS of a modular enzymatic manufacturing line has been questioned. To gain structural insights into the hybrid multidomain NRPS, we focused module-2 (Cy1-Cy2-A-PCP-Ox) of hybrid NRPS/PKS of leinamycin biosynthetic pathway. We performed cryo-EM of module 2 (Cy1-Cy2-A-PCP-Ox) which resulted in a low resolution cryo-EM map of this NRPS perhaps as a result of the linkers present in between the domains. However, to elucidate crucial interdomain interfaces and interactions that occur during different steps of the NRPS catalytic cycle, we undertook truncation studies including the domains (Cy1-Cy2) and (A-PCP-Ox) of the module2 of NRPS. We determined the structure of multidomain constructs (PCP-Cy1-Cy2) and (A-PCP-Ox) at overall resolutions of 5.2 Å and 7 Å respectively. The unravelling of architecture, organization, and mechanism of NRPS module 2 of leinamycin biosynthesis by cryo-EM will help design bioengineering approaches to understand the mechanistic insight into this novel pathway (swapping modules and domains). DNA-binding protein under starvation (Dps), is a miniature ferritin complex, which plays a vital role in protecting bacterial DNA during starvation for maintaining the integrity of bacteria from hostile conditions. Mycobacterium smegmatis is one such bacteria that express MsDps2, which binds DNA to protect it under oxidative and nutritional stress conditions. Several approaches, including cryo-electron tomography (Cryo-ET), were implemented to identify the structure of the Dps protein that is bound to DNA. However, none of the structures of the Dps-DNA complex was resolved to high resolution to be able to identify the DNA binding residues. In this study, we implemented various biochemical and biophysical studies to characterize the DNA protein interactions of Dps protein. We employed single-particle cryo-EM-based structural analysis of MsDps2-DNA and identify that the region close to N-terminal confers the DNA binding property. Based on cryo-EM data, we performed mutations of several arginine residues proximal to the DNA binding region, which dramatically reduced the MsDps2-DNA interaction. In addition, we propose a model for DNA compaction during lattice formation. We performed single-molecule imaging experiments of MsDps2-DNA interactions that corroborate well with our structural studies. Single molecule imaging also deciphers the mechanism of compaction required for DNA protection.

Alla luce del recente allarmante tasso di esaurimento delle riserve di combustibili fossili e al contemporaneo drastico aumento dei livelli di CO2 nell'atmosfera, principale gas serra responsabile del riscaldamento globale e di cambiamenti climatici molto gravi, una delle priorità assolute nella ricerca a livello mondiale è quella di sfruttare il più possibile le fonti di energia rinnovabile. Una possibilità molto interessante è quella di realizzare un processo di riduzione della CO2 a combustibili liquidi che sfrutti energie rinnovabili, quale quella solare, mediante dispositivi più comunemente noti come celle fotosintetiche artificiali o foglie artificiali o celle foto-elettro-catalitiche (PEC). L'obiettivo principale di questo lavoro, è stato pertanto quello di condurre uno studio approfondito su due diversi sistemi elettrocatalitici di riduzione della CO2 a prodotti liquidi con un più alto valore aggiunto, uno operante in fase gassosa (cioè in assenza di elettrolita al catodo) e uno operante in fase liquida. In particolare, è stata progettata e utilizzata nel processo di conversione della CO2, un’innovativa cella in fase liquida operante su scala di laboratorio, sulla falsariga della cella in fase gas precedentemente sviluppata all’Università di Messina. Il lavoro è stato svolto principalmente presso il laboratorio CASPE/INSTM dell’Università degli Studi di Messina (Dipartimento di Ingegneria Elettronica, Chimica e Ingegneria Industriale). Un periodo di sei mesi è stato svolto invece, nel corso del secondo anno di dottorato, presso l’École supérieure de chimie, physique, électronique de Lyon (CPE Lyon). In tale periodo sono stati sintetizzati, mediante innovative tecniche di sintesi organometallica, materiali compositi da utilizzare come elettrocatalizzatori nel processo di riduzione della CO2. Sono state effettuate molteplici prove sperimentali utilizzando svariate tipologie di catalizzatori, sia in fase gas che in fase liquida, al fine di indagare la differente selettività, produttività e varietà di prodotti ottenuti. Il processo in fase liquida è infatti quello maggiormente studiato in letteratura, ma esistono alcune problematiche che devono essere superate per consentire un successivo semplice scale up. quali ad esempio, la scarsa solubilità della CO2 e la tipologia di prodotti ottenuti (principalmente acido formico). Lo scopo principale di questo lavoro è stato quello di preparare nuovi materiali a base di carboni dopati con metalli, catalizzatori questi molto diversi da quelli comunemente utilizzati nel processo di riduzione della CO2 (generalmente metalli in bulk), e di testarli sia in fase gas (per sfruttare i vantaggi di questa condizione, quali ad esempio facile recupero dei prodotti e alta qualità dei prodotti stessi) sia in fase liquida (per avere un miglior confronto con i dati ampiamente presenti in letteratura). Per gli studi sulla riduzione elettrocatalitica della CO2 nella cella operante in fase gassosa, sono stati preparati una serie di elettrodi (basati su nano particelle –NP- di Cu, Fe, Pt e Cu/Fe depositate su nanotubi di carbonio o carbon black e successivamente poste all'interfaccia tra una membrana di Nafion e uno strato a diffusione di gas –GDL-). I risultati ottenuti sono stati molto promettenti, sia in termini di tipologia di prodotti formati che di produttività. In fase gas (senza elettrolita) è stata osservata la formazione di prodotti ≥C1 quali etanolo, acetone e isopropanolo, in particolare utilizzando il Fe (seguito dal Pt), evidenziando che anche metalli non nobili possono essere usati in maniera efficiente in questo processo. Per migliorare la produttività nella reazione di riduzione della CO2, sono stati preparati elettrodi differenti, basati su coating con sostituti zeolitici imidazolici (SIM-1) tipo MOF. In particolare, i catalizzatori testati sono stati MOF modificati con Fe-CNT, Pt-CNT, e CuFe-CNT. E’ stato osservato un cambiamento significativo in termini di produttività e anche di selettività verso i prodotti finali. Nel dettaglio, in particolare per il catalizzatore a base di MOF modificato con Pt, è stato osservato un aumento nei prodotti carboniosi e anche una selettività più alta verso prodotti con un più elevato numero di atomi di C. Per quanto riguarda lo studio del processo di riduzione elettrocatalitica della CO2 utilizzando la cella operante in fase liquida, sono state preparate tipologie di elettrodi simili ai precedenti. Inizialmente infatti, sono stati studiati elettrodi a base di nanoparticelle metalliche (Cu, Fe, Pt, Ru, Co) depositate su nanotubi di carbonio o carbon black. L'ordine relativo della produttività nella riduzione elettrocatalitica della CO2 in questa serie di elettrodi, è però risultato essere diverso rispetto alla fase gassosa, indicando quindi un differente percorso di reazione. In termini di produttività totale, gli elettrodi a base di Pt hanno consentito di ottenere le migliori performance, seguiti da Ru e Cu, mentre il Fe ha dato risultati peggiori. Sulla base dei risultati sperimentali ottenuti, è stato inoltre ipotizzato un possibile meccanismo di reazione. Successivamente, per cercare di migliorare ulteriormente le prestazioni nel processo di riduzione della CO2 in fase liquida, è stato effettuato uno studio approfondito, volto ad indagare la dipendenza di tale processo dalle dimensioni delle nanoparticelle metalliche. A tale scopo sono stati utilizzati elettrodi a base di nanoparticelle metalliche (Ru, Fe, Pt e Cu) su nanotubi di carbonio (CNT) depositati su GDL. Sono state sintetizzate nanoparticelle metalliche di diverse dimensioni utilizzando molteplici tecniche di sintesi: (i) impregnazione che ha consentito di ottenere NP di dimensioni comprese tra 10-50 nm; (ii) sintesi organometallica che ha consentito di ottenere NP uniformi e ultrafine con dimensioni comprese tra 1-5 nm. (ad esempio sono state sintetizzate NP di Fe di 1-3 P nm) (iii) sintesi mediante nanowires che ha consentito di ottenere NP di rame ultrafine con dimensioni comprese tra 2-3,8 nm. In particolare, la novità dell’approccio mediante nanowires sta nella possibilità di ottenere particelle di dimensioni molto piccole sintetizzando inizialmente i Cu NWs, mettendoli poi a contatto con il supporto carbonioso e facilitandone il suo trasferimento, ciò grazie alle forze intermolecolari di attrazione dei gruppi funzionali presenti sui CNT parzialmente ossidati. Inoltre, a differenza della sintesi organometallica, tale approccio permette di condurre le reazioni in aria e non in atmosfera inerte. I valori di produttività ottenuti sono stati 5-30 volte più alti utilizzando nanoparticelle metalliche più piccole (ottenute via nanowires o mediante sintesi organometallica) rispetto alle nanoparticelle metalliche più grandi (ottenute per impregnazione). I risultati sperimentali indicano pertanto che le NP di dimensioni più piccole hanno un ruolo fondamentale nelle performance catalitiche. Inoltre, il carico di NP metalliche è stato significativamente ridotto dal 10% al 1-2% in peso consentendo di ottenere, per le NP più piccole, una produttività equivalente o addirittura superiore rispetto alle nanoparticelle più grandi. In seguito, è stato effettuato anche uno studio sul possibile riutilizzo degli elettrodi di lavoro e sulla disattivazione per tempi di reazione più lunghi. E’ stata infine preparata una diversa tipologia di elettrodi a base di nano-foams su lastrine metalliche, al fine di ottenere un ulteriore miglioramento nel processo di riduzione elettrocatalitica della CO2. Le nano-foams o dendriti, sono state preparate mediante la tecnica di deposizione elettrochimica ed è stato effettuato uno studio preliminare di ottimizzazione, al fine di determinare le condizioni di sintesi più adatte. In aggiunta, è stato eseguito uno studio specifico per ottimizzare il valore di Voltaggio da utilizzare nelle prove catalitiche, mediante sia test di voltammetria ciclica che test completi di riduzione della CO2. Sono stati testati nano-foams a base di Cu e Fe depositati su fogli di Cu Fe, Al, di Inconel e su una griglia di Al. L’aumento nella produttività usando queste tipologie di elettrodi, è stata nell’ordine di 2-10 volte rispetto alla massima produttività ottenuta utilizzando NP metalliche su materiali carboniosi. Svariate tecniche analitiche sono state poi utilizzate per caratterizzare in modo approfondito i materiali preparati tra cui, microscopia elettronica a trasmissione (TEM), microscopia elettronica a scansione (SEM), spettroscopia ad assorbimento atomico (AAS), diffrazione a raggi X (XRD), spettroscopia fotoelettronica a raggi X (XPS), determinazione dell’area superficiale mediante metodo Brunauer-Emmett-Teller (BET). La determinazione dei prodotti di reazione è stata effettuata invece mediante cromatografia ionica (IC), gas cromatografia con rivelatore a spettrometria di massa (GC-MS), gas cromatografia (GC) con rivelatore a termo conducibilità (TCD).
In view of the recent alarming rate of depletion of fossil fuel reserves and the drastic rise in the CO2 levels in the atmosphere leading to global warming and severe climate changes, tapping into all kinds of renewable energy sources has been among the top priorities in the research fields across the globe. One of the many such pathways is CO2 reduction to fuels using renewable energies, more commonly referred as artificial photosynthetic cells or artificial leaves or photo-electro-catalytic (PEC) cells. The key objective of the present PhD work was to conduct in-depth studies on two different electro-catalytic CO2 reduction systems: electrolyte-less cell (gas phase) and electrolytic cell (liquid phase). In particular, a novel lab scale liquid phase cell, on the similar lines of the previously realized gas phase cell at the University of Messina, was developed and used to convert electro-catalytically CO2 to more value-added products. The work was carried out at the Laboratory CASPE/INSTM of the University of Messina (Department of Electronic Engineering, Industrial Chemistry and Engineering). During the second year, a six-month period was spent at the École supérieure de chimie, physique, électronique de Lyon (CPE Lyon), where organometallic routes were explored for the synthesis of novel composite materials to be used as electrocatalysts in the CO2 reduction process. Experimental tests were carried out on various types of catalysts in both the gas and liquid phase cells to understand the different selectivity, productivity and the reaction products obtained. Liquid phase, in fact, has been the most studied process in literature, but some issues mainly related to CO2 solubility and types of products formed (i.e. mainly formic acid), have never be allowed to pass the lab scale stage. The general aim of this PhD was to prepare novel metal doped nanocarbon substrates, which are very different with respect to the conventional metal bulk layers used as electrocatalysts in CO2 reduction, and test them both in gas phase (to take advantage of these conditions, i.e easy recovery and improved quality of the products) and in liquid phase (to have a better comparison with conditions typically adopted in literature). For the studies on the electro-catalytic reduction of CO2 in gas phase cell, a series of electrodes (based on Cu, Fe, Pt and Cu/Fe metal nanoparticles – NPs - deposited on carbon nanotubes – CNTs - or carbon black and then placed at the interface between a Nafion membrane and a gas diffusion-layer) were prepared. The results, evidencing the various types of products formed and their different productivities, are very promising. Under electrolyte-less conditions, the formation of ≥C1 products (such as ethanol, acetone and isopropanol) were observed, the highest being for Fe and closely followed by Pt, evidencing that also non-noble metals can be used as efficient catalysts under these conditions. To enhance the productivities of the CO2 reduction, a different set of electrodes were also prepared based on substituted Zeolitic Imidazolate (SIM-1) type MOF coatings during a stay at CPE Lyon and Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON). Particularly, the catalysts tested were MOF-based Fe-CNTs, Pt-CNTs and Cu/Fe-CNTs. There was a significant change in the reaction products and in the selectivity towards the end-products. Particularly, especially for the MOF modified Pt based catalyst, there was an increase in the C-products and also a better selectivity towards higher C-products. Moving to the studies on the electro-catalytic reduction of CO2 in liquid phase cell, a similar set of electrodes were prepared. Initially, electrodes based on metal NPs of Cu, Fe, Pt, Ru and Co deposited on CNTs or carbon black were studied for their CO2 reduction capability. The relative order of productivity in CO2 electro-catalytic reduction in these series of electrodes was found to be different between the gas and liquid phase cells indicating the different reaction pathways. For liquid phase conditions, in terms of net C-products, catalytic electrodes based on Pt topped the class, closely followed by Ru and Cu, while Fe got the lowest position. The probable underlying reaction mechanism was also provided. In order to improve further the performances of the CO2 reduction in liquid phase conditions, a metal NPs size dependant study on the electro-catalytic reduction of CO2 to fuels was carried out. This study was performed using electrodes based on metal NPs of Ru, Fe, Pt and Cu loaded on CNTs and then transferred on a gas diffusion layers (GDL). Varied sized metal NPs have been synthesized using different techniques: (i) impregnation route to achieve NPs in the size range of 10-50 nm; (ii) organometallic approach to synthesize uniform and ultrafine NPs in the size range of 1-5 nm (i.e., Fe NPs were synthesized through a novel synthesis route to attain 13 nm NPs);(iii) Nanowire (NW) top-down approach to obtain ultrafine copper metal NPs in the size range of 2-3.8 nm. Particularly, the novelty of nanowire approach is the ability to obtain very small metal NPs starting from the synthesis of Cu NWs and then transferring the Cu onto the carbon surface, taking advantage of the different inter-forces of between Cu NWs and the functional groups present on the partially oxidized CNT surface. Furthermore, unlike the case of organo-metallic approach, this approach allows a preparation under air avoiding the use of potentially demanding inert atmospheric conditions. The enhancements in the fuel productivity were found to be 5-30 times higher for the smaller metal NPs obtained via organo-metallic route or nanowire route as compared to the larger metal NPs obtained via impregnation route. The results signify that the smaller sized metal NPs loading on the CNTs have a prevailing role in the catalytic performance and the selectivity towards different products. Moreover, the percentage of metal NPs loading was significantly reduced from 10 to 1-2 wt. % producing higher or equivalent fuels for small NPs as compared to the larger NPs. The reusability of the working electrodes and long reaction times (until 24 hours) were also probed. A different set of electrodes based on nano-foams on metal foils, were also investigated to achieve further improvements in the electro-reduction of CO2 to fuels. These nano-foams or dendrites were prepared by electrochemical deposition technique. Optimization studies on the deposition of these foams were performed initially to fix the set of preparation conditions. Moreover, voltage optimization study was performed using cyclic voltammetry and full CO2 reduction tests to find the optimum voltage for the process. The nano-foam electrodes tested include Cu and Fe foams on Cu foil, Fe foil, Al foil, Inconel foil and Al grid/mesh. The enhancements in the fuel productivity for various foams were in the range of 2-10 times greater as compared to the highest net fuel productivity achieved using metal NPs doped carbon catalytic electrodes, from all the previous studies. Various characterizations and analysis tools were used to analyse the catalysts qualitatively and quantitatively, which include Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Atomic Absorption Spectroscopy (AAS), X-ray diffraction (XRD), X-ray Photo-electron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET). To determine the fuel productivities, Ion Chromatography (IC), Gas Chromatography-Mass Spectrometer (GC-MS), Gas Chromatography (GC) were used.
Compte tenu du récent taux alarmant d'épuisement des réserves de combustibles fossiles et de l'augmentation drastique des niveaux de CO2 dans l'atmosphère qui a conduit au réchauffement de la planète et à des changements climatiques sévères, l'exploitation de toutes sortes d'énergies renouvelables a été la Parmi les principales priorités de la recherche Champs à travers le monde. L'une des nombreuses voies de ce genre est la réduction du CO2 aux combustibles utilisant des énergies renouvelables, plus communément appelées cellules photosynthétiques artificielles ou feuilles artificielles ou cellules photoélectro-catalytiques (PEC). L'objectif principal de ce travail était de réaliser des études approfondies sur les différents systèmes de réduction électro-catalytique du CO2, à savoir les cellules sans électrolyte (phase gazeuse) et les cellules électrolytiques (phase liquide). Dans ce processus, nous avons conçu une nouvelle cellule en phase liquide à échelle de laboratoire sur les lignes similaires de la cellule de phase gazeuse de modèle précédemment modélisée. Des essais expérimentaux sur la réduction du CO2 ont été réalisés sur différents types de catalyseurs dans les deux cellules afin de comprendre la sélectivité, la productivité et les produits de réaction obtenus. L'obtention de résultats de test dans les deux cellules nous a permis d'effectuer une comparaison décente avec les résultats de réduction électro-catalytique de CO2 existants dans la littérature. Des essais expérimentaux ont été réalisés sur différents types de catalyseurs à la fois dans les cellules en phase gazeuse et en phase liquide pour comprendre la sélectivité, la productivité et les produits de réaction obtenus. La phase liquide, en fait, a été le processus le plus étudié dans la littérature, mais certaines questions liées principalement à la solubilité du CO2 et aux types de produits formés (c'est-à-dire principalement l'acide formique) n'ont jamais été autorisées à franchir le stade de l'échelle du laboratoire. L'objectif général de ce doctorat était de préparer de nouveaux substrats de nanocarbone dopés par des métaux, qui sont très différents par rapport aux couches en vrac métalliques conventionnelles utilisées comme électrocatalyseurs dans la réduction de CO2, et de les tester en phase gazeuse (pour profiter de ces conditions, Une récupération facile et une qualité améliorée des produits) et en phase liquide (pour une meilleure comparaison avec les conditions typiquement adoptées dans la littérature). Pour les études sur la réduction électro-catalytique du CO2 en phase gazeuse, une série d'électrodes (à base de nanoparticules de Cu, Fe, Pt et CuFe déposées sur des nanotubes de carbone ou de noir de carbone puis placées à l'interface entre une membrane Nafion et Une électrode à couche de diffusion de gaz). Les résultats démontrent le type divers de produits formés et leurs productivités. Dans des conditions sans électrolyte, la formation de produits ≥C1 tels que l'éthanol, l'acétone et l'isopropanol a été observée la plus élevée étant pour Fe et suivie de près par Pt. Pour améliorer les productivités de la réduction du CO2, un ensemble différent d'électrodes a été préparé sur la base de revêtements MOF de type imidazolate de type zéolitique substitué (SIM-1) lors d'un séjour au CPE Lyon et à l'Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON). Les catalyseurs testés étaient Fe-CNT, Pt-CNT et CuFe-CNT basés sur MOF. Il y a eu un changement significatif dans les produits de réaction et aussi, la sélectivité vis-à-vis des produits finaux. Pour le catalyseur à base de Pt modifié, MOF, il y avait une augmentation des produits C et également une sélectivité différente tandis que pour le catalyseur à base de Fe, il y avait une légère diminution des produits C. En se reportant aux études sur la réduction électro-catalytique du CO2 dans une cellule en phase liquide, un ensemble similaire d'électrodes a été préparé afin d'obtenir une bonne comparaison des résultats dans les expériences en phase gazeuse. Initialement, des électrodes à base de nanoparticules métalliques (Cu, Fe, Pt, Ru, Co) déposées sur des nanotubes de carbone ou du noir de carbone ont été étudiées pour leur capacité de réduction du CO2. L'ordre relatif de productivité dans la réduction électrocatalytique de CO2 dans ces séries d'électrodes a été trouvé différent entre les cellules en phase gazeuse et en phase liquide indiquant les différentes voies de réaction. Pour les conditions de phase liquide, en termes de produits C nets, les électrodes catalytiques à base de Pt sont en tête de la catégorie, suivies de près par Ru et Cu, tandis que Fe a obtenu la position la plus basse. Le mécanisme réactionnel sous-jacent probable a également été fourni. Afin d'améliorer encore les performances de la réduction du CO2 dans les conditions de phase liquide, une étude de la nanoparticules métalliques (NPs) dépendant de la taille de la réduction électro-catalytique du CO2 aux combustibles a été réalisée. Ceci a été réalisé à l'aide d'électrodes à base de nanoparticules métalliques (Ru, Fe, Pt et Cu) chargées sur les nanotubes de carbone (CNT) transférés sur les couches de diffusion gazeuse (GDL). On a synthétisé des nanoparticules de métal de différentes tailles en utilisant différentes techniques de synthèse: (i) l'itinéraire d'imprégnation pour obtenir des NP dans la plage de tailles de 10 à 50 nm; (Ii) Approche organométallique pour synthétiser des NPs uniformes et ultrafines dans la plage de tailles de 1-5 nm. Fe ont été synthétisés par une nouvelle voie de synthèse et des conditions pour atteindre des NP de 1 à 3 nm. (Iii) Approche de haut en bas de Nanowire pour obtenir des NP métalliques de cuivre ultrafin dans la plage de taille de 2-3,8 nm. En particulier, la nouveauté de l'aide de nanofils est la capacité à obtenir des particules de très petite taille d'abord la synthèse du Cu NFs, puis de les mettre en contact avec le support carboné et de faciliter son transfert, cela grâce à des forces d'attraction intermoléculaires des groupes fonctionnels présent sur le CNT partiellement oxydée. En outre, contrairement à la synthèse organométallique, cette approche permet d'effectuer les réactions dans l'air et non pas dans une atmosphère inerte. Les améliorations de la productivité du combustible ont été trouvées être au moins 5 à 30 fois plus élevées pour les NP métalliques de plus petite taille obtenus par voie organo-métallique ou par nanofil, par rapport aux NP métalliques plus grands obtenus par voie d'imprégnation. Les résultats indiquent que les NP métalliques de plus petite taille chargés sur les CNT jouent un rôle prédominant dans la performance catalytique et la sélectivité vis-à-vis de différents produits. En outre, le pourcentage de charge de NP métalliques a été réduit de façon significative de 10% à 1-2% en poids, produisant des carburants plus élevés ou équivalents pour de petites NP en comparaison avec les NP plus grandes. De plus, comme on a observé clairement la productivité en H2 qui a augmenté de nombreux facteurs pour les NP plus petits sur les plus grandes NP. La réutilisabilité des électrodes de travail et les longs temps de réaction ont également été sondés. Un ensemble différent d'électrodes à base de nano-mousses sur des feuilles métalliques a également été étudié afin d'obtenir des améliorations beaucoup plus importantes de l'électro-réduction de CO2 aux carburants. Ces nano-mousses ou dendrites ont été préparées par une technique de dépôt électrochimique. Des études d'optimisation sur le dépôt de ces mousses ont été effectuées initialement pour fixer l'ensemble des conditions de préparation. De plus, une étude d'optimisation de la tension a été réalisée en utilisant la voltamétrie cyclique et des tests de réduction de CO2 complets pour fixer une tension optimale pour les réactions. Les électrodes nano-mousses testées incluent (mousses Cu, Fe sur feuille Cu, feuille Fe, feuille Al, feuille Inconel et grille Al). Les améliorations de la productivité du combustible pour diverses mousses se situaient dans la plage de 2 à 10 fois par rapport à la productivité nette de combustible la plus élevée obtenue en utilisant des électrodes catalytiques en carbone dopé par des NP métalliques. Différentes caractérisations et outils d'analyse ont été utilisés pour analyser les catalyseurs qualitativement et quantitativement qui incluent la microscopie électronique à transmission (TEM), la microscopie électronique à balayage (SEM), la spectroscopie d'absorption atomique (AAS), la diffraction des rayons X (XRD) La spectroscopie électronique (XPS) et Brunauer-Emmett-Teller (BET) et pour déterminer les productivités des combustibles, chromatographie ionique (IC), chromatographie gazeuse-spectromètre de masse (GC-MS), chromatographie gazeuse.