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Dissertations / Theses on the topic 'Cell packing'
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1
Classen, Anne-Kathrin. "Hexagonal packing of Drosophila wing epithelial cells by the Planar Cell Polarity pathway." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1157034530833-40169.
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The mechanisms that order cellular packing geometry are critical for the functioning of many tissues, but are poorly understood. Here we investigate this problem in the developing wing of Drosophila. The surface of the wing is decorated by hexagonally packed hairs that are uniformly oriented towards the distal wing tip. They are constructed by a hexagonal array of wing epithelial cells. We find that wing epithelial cells are irregularly arranged throughout most of development but become hexagonally packed shortly before hair formation. During the process, individual cell junctions grow and shrink, resulting in local neighbor exchanges. These dynamic changes mediate hexagonal packing and require the efficient delivery of E-cadherin to remodeling junctions; a process that depends on both the large GTPase Dynamin and the function of Rab11 recycling endosomes. We suggest that E-cadherin is actively internalized and recycled as wing epithelial cells pack into a regular hexagonal array. Hexagonal packing furthermore depends on the activity of the Planar Cell Polarity proteins. The Planar Cell Polarity group of proteins coordinates complex and polarized cell behavior in many contexts. No common cell biological mechanism has yet been identified to explain their functions in different tissues. A genetic interaction between Dynamin and the Planar Cell Polarity mutants suggests that the planar cell polarity proteins may modulate Dynamin-dependent trafficking of E-cadherin to enable the dynamic remodeling of junctions. We furthermore show that the Planar Cell Polarity protein Flamingo can recruit the exocyst component Sec5. Sec5 vesicles also co-localizes with E-cadherin and Flamingo. Based on these observations we propose that during the hexagonal repacking of the wing epithelium these proteins polarize the trafficking of E-cadherin-containing exocyst vesicles to remodeling junctions. The work presented in this thesis shows that one of the basic cellular functions of planar cell polarity signaling may be the regulation of dynamic cell adhesion. In doing so, the planar cell polarity pathway mediates the acquisition of a regular packing geometry of Drosophila wing epithelial cells. We identify polarized exocyst-dependent membrane traffic as the first basic cellular mechanism that can explain the role of PCP proteins in different developmental systems.
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Farhadifar, Reza. "Dynamics of Cell Packing and Polar Order in Developing Epithelia." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244035271841-50183.
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During development, organs with different shape and functionality form from a single fertilized egg cell. Mechanisms that control shape, size and morphology of tissues pose challenges for developmental biology. These mechanisms are tightly controlled by an underlying signaling system by which cells communicate to each other. However, these signaling networks can affect tissue size and morphology through limited processes such as cell proliferation, cell death and cell shape changes,which are controlled by cell mechanics and cell adhesion. One example of such a signaling system is the network of interacting proteins that control planar polarization of cells. These proteins distribute asymmetrically within cells and their distribution in each cell determines of the polarity of the neighboring cells. These proteins control the pattern of hairs in the adult Drosophila wing as well as hexagonal repacking of wing cells during development. Planar polarity proteins also control developmental processes such as convergent-extension. We present a theoretical study of cell packing geometry in developing epithelia. We use a vertex model to describe the packing geometry of tissues, for which forces are balanced throughout the tissue. We introduce a cell division algorithm and show that repeated cell division results in the formation of a distinct pattern of cells, which is controlled by cell mechanics and cell-cell interactions. We compare the vertex model with experimental measurements in the wing disc of Drosophila and quantify for the first time cell adhesion and perimeter contractility of cells. We also present a simple model for the dynamics of polarity order in tissues. We identify a basic mechanism by which long-range polarity order throughout the tissue can be established. In particular we study the role of shear deformations on polarity pattern and show that the polarity of the tissue reorients during shear flow. Our simple mechanisms for ordering can account for the processes observed during development of the Drosophila wing.
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Farhadifar, Reza. "Dynamics of Cell Packing and Polar Order in Developing Epithelia." Doctoral thesis, Technische Universität Dresden, 2009. https://tud.qucosa.de/id/qucosa%3A23750.
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During development, organs with different shape and functionality form from a single fertilized egg cell. Mechanisms that control shape, size and morphology of tissues pose challenges for developmental biology. These mechanisms are tightly controlled by an underlying signaling system by which cells communicate to each other. However, these signaling networks can affect tissue size and morphology through limited processes such as cell proliferation, cell death and cell shape changes,which are controlled by cell mechanics and cell adhesion. One example of such a signaling system is the network of interacting proteins that control planar polarization of cells. These proteins distribute asymmetrically within cells and their distribution in each cell determines of the polarity of the neighboring cells. These proteins control the pattern of hairs in the adult Drosophila wing as well as hexagonal repacking of wing cells during development. Planar polarity proteins also control developmental processes such as convergent-extension. We present a theoretical study of cell packing geometry in developing epithelia. We use a vertex model to describe the packing geometry of tissues, for which forces are balanced throughout the tissue. We introduce a cell division algorithm and show that repeated cell division results in the formation of a distinct pattern of cells, which is controlled by cell mechanics and cell-cell interactions. We compare the vertex model with experimental measurements in the wing disc of Drosophila and quantify for the first time cell adhesion and perimeter contractility of cells. We also present a simple model for the dynamics of polarity order in tissues. We identify a basic mechanism by which long-range polarity order throughout the tissue can be established. In particular we study the role of shear deformations on polarity pattern and show that the polarity of the tissue reorients during shear flow. Our simple mechanisms for ordering can account for the processes observed during development of the Drosophila wing.
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Curran, S. A. "The changing role of junctional actomyosin in epithelial cell packing during Drosophila notum development." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1472489/.
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Dramatic changes in tissue architecture can be produced by the cumulative action of individual cell movements within epithelia. During rapid developmental processes polarised recruitment of Myosin-II has previously been shown to drive changes in cell shape and direct neighbour exchange. It is important to ask whether similar mechanisms facilitate junction movement in stable epithelia, that are more prevalent in nature, and whether seemingly noisy fluctuations in junction length contribute to homeostatic tissue packing under ordinary growth conditions. By using the Drosophila notum, I have taken advantage of a model system that remains constant in overall size and shape, whilst it orders, as a result of changes in cells packing. Confocal live imaging enabled quantitative junction fluctuation measurements of control and RNAi expressing nota, before and after periods of cell division, delamination and bristle cell differentiation. Through a reduction in Myosin II (Myo II) activity, I established that junctional actomyosin was not required to drive neighbour exchange events in this tissue. Conversely, an increase in active Myo II levels was sufficient to inhibit junction fluctuations, cell intercalation and midline live cell delamination events. These results suggest a model in which Myo II independent junction length fluctuations fluidize the tissue, thereby enabling cells to move in order to relieve tissue stresses and crowding. Furthermore, over the course of pupal development a systematic re-localisation of medioapical actomyosin to the junction correlated with a rise in line tension and an increase in tissue order. Thus, changes to actomyosin levels appear to tune neighbour exchange in a process akin to annealing, as the tissue moves from a state of disorder to hexagonal packing prior to the completion of development.
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Moussaoui, Hamza. "Microstructural optimization of Solid Oxide Cells : a coupled stochastic geometrical and electrochemical modeling approach applied to LSCF-CGO electrode." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI028/document.
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Ce travail porte sur la compréhension de l’impact de la microstructure sur les performances des Cellules à Oxyde Solide (SOC), avec une illustration sur l’électrode à oxygène en LSCF-CGO. Une approche couplant de la modélisation géométrique et électrochimique a été adoptée pour cet effet. Le modèle des champs aléatoires plurigaussiens et un autre basé sur des empilements de sphères ont été développés et adaptés pour les microstructures des SOCs. Ces modèles 3D de géométrie stochastique ont été ensuite validés sur différentes électrodes reconstruites par nano-holotomographie aux rayons X au synchrotron ou par tomographie avec un microscope électronique à balayage couplé à une sonde ionique focalisée. Ensuite, des corrélations semi-analytiques ont été proposées et validées sur une large base de microstructures synthétiques. Ces relations permettent de relier les paramètres ‘primaires’ de l’électrode (la composition, la porosité et les diamètres des phases) aux paramètres qui pilotent les réactions électrochimiques (la densité de points triples, les surfaces spécifiques interphases) et sont particulièrement pertinents pour les équipes de mise-en-forme des électrodes qui ont plus de contrôle sur ce premier ensemble de paramètres. Concernant la partie portant sur l’électrochimie, des tests sur une cellule symétrique en LSCF-CGO ont permis de valider un modèle déjà développé au sein du laboratoire, et qui permet de simuler la réponse électrochimique d’une électrode à oxygène à partir des données thermodynamiques et de microstructure. Finalement, le couplage des deux modèles validés a permis d’étudier l’impact de la composition des électrodes, leur porosité ou encore taille des grains sur leurs performances. Ces résultats pourront guider les équipes de mise-en-forme des électrodes vers des électrodes plus optimiséesThis work aims at better understanding the impact of Solid Oxide Cells (SOC) microstructure on their performance, with an illustration on an LSCF-CGO electrode. A coupled 3D stochastic geometrical and electrochemical modeling approach has been adopted. In this frame, a plurigaussian random field model and an in-house sphere packing algorithm have been adapted to simulate the microstructure of SOCs. The geometrical models have been validated on different electrodes reconstructed by synchrotron X-ray nano-holotomography or focused ion-beam tomography. Afterwards, semi-analytical microstructural correlations have been proposed and validated on a large dataset of representative synthetic microstructures. These relationships allow establishing the link between the electrode ‘basic’ parameters (composition, porosity and grain size), to the ‘key’ electrochemical parameters (Triple Phase Boundary length density and Specific surface areas), and are particularly useful for cell manufacturers who can easily control the first set of parameters. Concerning the electrochemical part, a reference symmetrical cell made of LSCF-CGO has been tested in a three-electrode setup. This enabled the validation of an oxygen electrode model that links the electrode morphological parameters to its polarization resistance, taking into account the thermodynamic data. Finally, the coupling of the validated models has enabled the investigation of the impact of electrode composition, porosity and grain size on the cell electrochemical performance, and thus providing useful insights to cell manufacturers
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Mekkaoui, Leila. "Lentiviral vector purification using genetically encoded biotin mimic in packaging cell." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10053191/.
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Lentiviral vectors (LVs) are powerful tools in gene therapy that have recently witnessed an increasing demand in both research and clinical applications. Current LVs purification represents the main bottle neck in their application as several methods are employed which are time consuming, cumbersome and yield low recoveries. The aim of this project was to develop a one-step method to specifically and efficiently purify LVs, with high vector yields and reduced levels of impurities, using the biotin-streptavidin system. Herein, packaging 293T cells were genetically engineered with biotin mimicking synthetic peptides and different cell membrane anchoring strategies for optimal streptavidin binding were tested. We have identified a flanked disulphide-constrained peptide, termed Ctag (ECHPQGPPCIEGRK), displayed on a CD8α stalk to be the most promising. LVs were modified with Ctag by its random incorporation onto viral surfaces during budding, without viral protein engineering or hindrance on infectivity. The expression of Ctag on LVs allowed complete capture of infectious particles by streptavidin magnetic beads. As Ctag binds streptavidin in the nanomolar range, we hypothesised that gentle elution from streptavidin matrix should occur by biotin’s competitive binding. Accordingly, addition of micromolar concentrations of biotin to captured LVs resulted in an overall yield of ≥60%. Analysis of eluted LVs revealed high purity levels, with a ≤3-log and 2-log reduction of DNA contamination and host cell proteins, respectively. This one-step purification was also tested for scalable vector processing using streptavidin monolith affinity chromatography and preliminary results were encouraging with 20% overall yield. In conclusion, we developed a single-step affinity chromatography which allows specific purification and concentration of infectious vectors modified with a biotin mimic. Based on intended usage, efficient LV purification can be achieved using both magnetic beads and column chromatography. This method will be of valuable use for both research and clinical applications of LVs.
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Coulberson, Arlena. "Packaging DNA for delivery to cells by electroporation." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/11178.
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Pizzato, Massimo. "Retroviral vectors for gene therapy : characterisation of vector particle-cell interaction and development of novel packaging cell lines." Thesis, Institute of Cancer Research (University Of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313365.
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Penaud, Magalie. "Characterization of rAAV vectors packaging in baculovirusinfected insect cells." Thesis, Nantes, 2018. http://www.theses.fr/2018NANT1003.
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Les vecteurs dérivés du virus adéno-associé (AAVr) constituent des outils de choix pour le transfert de gène in vivo. Leur innocuité a notamment contribué à leur attractivité et leur utilisation dans des essais cliniques de thérapie génique. Afin d'étendre le champ de leur application au traitement de maladies systémiques, un défi majeur reste à relever : leur production à grande échelle. Le système d'infection de cellules d'insecte par des baculovirus peut répondre à ce challenge, pourtant la biologie de l'AAV dans ces cellules reste méconnue. Ceci se répercute par la présence de particules vides ou par une perte d'infectiosité des vecteurs viraux produits. Le travail présenté dans ce manuscrit a pour objectifs de 1) déterminer l'efficacité et la spécificité d'encapsidation du gène d'intérêt dans les capsides d'AAVr 2) étudier le lien entre ces paramètres et l'expression des protéines Rep et 3) définir le rôle de la protéine AAP (assembly-activating protein) en cellules d'insecte. De façon inédite, nous avons montré que moins de 30% des particules générées contenaient le transgène et que l'ADN baculoviral représentait jusqu'à 2,1% du contenu des capsides d'AAV, avec une prédominance pour les séquences proches des ITR (inverted terminal repeats). Enfin, nous avons démontré que l'AAP était essentielle pour l'assemblage des particules d'AAV2 dans les cellules Sf9. Ce projet participe non seulement à l'élucidation des mécanismes· d'encapsidation des AAV dans les cellules d'insecte mais répond également aux exigences des organismes réglementaires en proposant une technique d' avant-garde d'évaluation des contaminants ADN présents dans les stocks de vecteurs AAVDue to their efficiency and safety, recombinant adenoassociated virus (rAAV) vectors have been widely used for gene therapy. ln the past few years, there have been a large number of positive clinical outputs using AAVbased products spanning broad therapeutic areas. However, the generation of rAAV at sufficient quantity and quality appears as a bottleneck on the path to commercialization. The baculovirus-infected insect cell platform has proven to tackle this challenge, yet, surprisingly, the biology of rAAV in insect cells remains largely unknown. As a result, current vectors suffer from quality problems such as generation of empty particles or reduced infectivity. The objectives of the present work are 1) to determine the rAAV packaging efficiency and specificity in insect cells 2) to investigate the link between packaging and Rep proteins expression, and 3) to decipher the role of the assembly-activating protein (AAP). First, we showed that less than 30% of rAAV particles contained the gene of interest in S19 cells cleared lysate. Second, we found that baculoviral DNA contamination is below 2.1% of encapsidated DNA, with a higher representativity for sequences close to the inverted terminal repeats. Finally, we demonstrated that functional AAP is strictly required for rAAV2 particles assembly in insect cells. Altogether, our data provide novel insights into the biological mechanism of rAAV genome packaging in insect cells and suggest that there is still room for improvement in order to increase vector quality. From a safety perspective, this project has allowed the development of an accurate quality control method to assess DNA contamination in viral vector stocks
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Liu, Yan. "Superhydrophobic surfaces for electronic packaging and energy applications." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52164.
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Superhydrophobic surfaces, which display water contact angles of larger than 150°, have attracted more and more attention due to their importance in both fundamental research and practical applications. This dissertation is mainly focused on the fundamental understanding and exploring applications of superhydrophobic surfaces. First, some specific examples of superhydrophobic surface fabrication were given, which include superoleophobic Si surface, robust superhydrophobic SiC surface, and reversible wettability nanocomposite films. Based on the study of superhydrophobic surfaces, the application of superhydrophobic surfaces in electronic packaging were explored. Superhydrophobic silica/epoxy nanocomposite coating serves as an encapsulant to improve the electronic device reliability. Such superhydrophobic coating showed good stability under humidity at elevated temperatures and was applied on the triple track resistors test coupons. In addition, the applications of superhydrophobic surfaces in solar cells were studied. Two multi-functional hierarchical structure solar cells with self-cleaning, low reflection and high efficiency properties were built up by coating or etching methods.
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Curran, Alan J. "Reliability of Commercially Relevant Photovoltaic Cell and Packaging Combinations in Accelerated and Outdoor Environments." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1626783783924982.
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Sanber, K. S. R. "Production of self-inactivating lentiviral vectors by constitutive packaging cell lines for gene therapy clinical applications." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1472300/.
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Lentiviral vectors (LVs) are useful experimental tools for stable gene delivery and have been used to treat human inherited genetic disorders and hematologic malignancies with promising results. Because some of the LV components are cytotoxic, transient plasmid transfection has been used to produce the large batches needed for clinical trials. However, this method is costly, poorly reproducible and hard to scale up. Generation of stable packaging cell lines (PCLs) that continuously produce LVs can potentially overcome these limitations. The WinPac-RDpro cell line was developed between Collins and Takeuchi laboratories in Division of Infection and Immunity, UCL by inserting a codon-optimized HIV-1 Gag-Pol expression cassette in a continuously expressed locus in 293FT cells using Cre recombinase-mediated cassette exchange (RMCE). Subsequently HIV-1 Rev and RDpro envelope expression cassettes were serially transfected. In this thesis, WinPac-RDpro cells were used to generate model producer cells by stably transfecting a plasmid expressing a SIN GFP-encoding LV. Vector titers in excess of 106 293T transducing units (TU)/ml could be repeatedly harvested from the final producer clones in a volume of >0.5 L even under reduced serum conditions. Titers could be increased to around 1 x 10^8 293T TU/ml by concentration using scalable tangential flow filtration (TFF). Additionally, these LVs efficiently transduced human T cells and CD34+ cells at low multiplicities of infection (MOI). Titers in excess of 10^6 TU/ml were achieved using an RMCE-based strategy that was aimed at introducing a SIN LV expression cassette at a pre-selected locus. Similar titers were also achieved by using a promoterless selectable marker cloned in cis to the vector genome expression cassette. Furthermore, the Cocal Virus G protein (COCV-G) was stably expressed in WinPac cells to generate WinPac-CVG cells. These packaging cells were able to support the production of COCV-G pseudotyped SIN LVs at high titers (up to 106 TU/ml) following transient supplementation of a SIN LV expression plasmid. The efficient and stable expression of SIN LV genomes in these cells is expected to facilitate high-titer production of vectors with favorable characteristics. In conclusion, the work presented here provides significant improvements to available LV production methods. This will be of use to all basic and clinical investigators who wish to produce large batches of LVs, and addresses an important issue that has hindered large-scale LV clinical testing and application.
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Jewell, Nancy Ann. "Studies of deltaretrovirus RNA packaging, infectivity and drug susceptibility." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1080001210.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xiii, 111 p.; also includes graphics Includes bibliographical references (p. 102-111). Available online via OhioLINK's ETD Center
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Williams, Eva Christabel. "Smart Packaging: A Novel Technique For Localized Drug Delivery For Ovarian Cancer." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4257.
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Localized drug delivery is emerging as an effective technique due to its ability to administer therapeutic concentrations and controlled release of drugs to cancer sites in the body. It also prevents the contact of harsh chemotherapy drugs to healthy regions in the body that otherwise would become exposed to current treatments.
This study reports on a model chemotherapy drug delivery system comprising non-ionic surfactant vesicles (niosomes) packaged within a temperature-sensitive chitosan network. This smart packaging, or package-within-a package system, provides two distinct advantages. First, the gel prevents circulation of the niosomes and maintains delivery in the vicinity of a tumor. Secondly, the chitosan network protects the niosomes against fluctuations in tonicity, which affects delivery rates. Tonicity is the sum of the concentrations of the solutes which have the capacity to exert an osmotic force across the membrane. Release rates were monitored from both bare niosomes alone and niosome-embedded, chitosan networks. It was observed that chitosan networks prolonged delivery from 100 hours to 55 days in low ionic strength environment and pH conditions similar to a tumor site. The primary effect of chitosan is to add control on release time and dosage, and stabilize the niosomes through a high ionic strength surrounding that prevents uncontrolled bursting of the niosomes. Secondary factors include cross-link density of the chitosan network, molecular weight of the individual chitosan polymers, dye concentration within the niosomes, and the number density of niosomes packaged within the chitosan network. Each of these factors can be altered to fine-tune release rates. Release rate experiments were conducted with 5,6-carboxyfluorescein, a fluorescent dye and chemotherapeutics paclitaxel and carboplatin. In vitro studies showed a preferential affinity of the smart packaged system to ovarian carcinoma cell line OV2008 as compared to normal epithelial cell lines of Ilow and MCC3. Further, feasibility of the drug delivery system was evaluated in vivo. Toxicity studies revealed that the system was non-toxic and feasible in vivo. The final outcome of this study includes tuning of the variables mentioned above that will contribute to the development of low cost and improved methods for drug delivery with application to intracavitary ovarian cancer treatment and other types of cancer
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Shu, Ying. "NOVEL SOLUTION PROCESSABLE ACCEPTORS FOR ORGANIC PHOTOVOLTAIC APPLICATIONS." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/135.
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The field of organic electronics has become an increasingly important field of research in recent years. Organic based semiconductors have the potential for creating inexpensive, solution processed devices on flexible substrates. Some of the applications of organic semiconductors include organic field effect transistors, organic light emitting diodes and organic photovoltaics.
Functionalized pentacenes have been proven to be viable donor materials for use in organic photovoltaic devices. The goal of this research is to synthesize and test the viability of novel electron deficient pentacenes and pentacene based materials as acceptors to be used as drop-in replacements for PCBM in bulk-heterojunction organic solar cells.
Our goal was to tune and improve the efficiencies of these solar cells in a two pronged approach. First we tuned the open circuit voltage of these devices by determining the optimal energy levels of these acceptors by varying the number of electron withdrawing substituents on the acene core. We also tuned the short circuit current by chemically altering the solid state packing and optimizing device processing conditions. A preliminary structure-property relationship of these small molecule acceptors and photovoltaic device efficiency was established as a result.
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Shelton, Kerri. "NEW PHOTOVOLTAIC ACCEPTORS: SYNTHESIS AND CHARACTERIZATION OF FUNCTIONALIZED C-FUSED ANTHRADITHIOPHENE QUINONES." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/92.
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Stable organic semiconductors are critical to produce inexpensive, efficient and flexible thin film organic solar cells. A current chemical focus is the synthesis of stable, electron-accepting materials to be utilized as an acceptor layer in photovoltaics.1 The Anthony group has shown that the functionalization of pentacene with suitable electron withdrawing groups provides a catalog of suitable acceptors for this purpose.2 These pentacenes can be further modified to pack in a unique 1-dimensional "sandwich herringbone" crystal packing, leading to improved device current.3 To improve the stability of acene acceptors, we have taken two hetero-atom themed approaches. First, we have studied the acenequinone as an electron-accepting chromophore.4 Further, we replaced the terminal aromatic rings with heterocycles, such as furan or thiophene. In order to enhance the crystal engineering versatility of the chromophore, we utilize c-fused heterocycles (rather than the more commonly used b-fused cycles seen in e.g. anthradithiophenes). The c-fused acenequinones can be tetra-functionalized with silylethynyl groups to influence crystal packing and increase solubility.5 The silylethyne groups are known to increase the photostability and lower the energy gap (Eg) of pentacenes.5 The functionalization of the silylethyne groups also aids in lowering the lowest unoccupied orbital (LUMO) of acene structures.5
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Farley, Daniel Colin. "Identification of novel adenovirus late gene regulatory components and the engineering of cell lines towards gene therapy vector packaging." Thesis, University of Warwick, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409785.
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Molina, Gil Alberto. "Lentiviral vector packaging cell line development using genome editing to target optimal loci discovered by high throughput DNA barcoding." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1573558/.
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Lentiviral vectors are increasingly used as delivery methods in gene therapy clinical trials due to their high efficiency transducing cells and stability of transgene expression. The development of packaging and producer cell lines for the production of lentiviral vectors has always been a labour-intensive and lengthy process. Sequential introduction of vector components, adaptability to suspension cultures, autotransduction and genetic, transcriptional or cell line growth instability are some of the limitations that cause significant drops in productivity. Improved transcription of self-inactivating vectors leading to high titers has been attempted in different ways with the intent to find a high stable producer clone. In this project, we studied the use of lentiviral vectors as a tool to target and identify high-transcribing loci in the genome of our host cells for lentiviral packaging cell line development. Third generation lentiviral vectors carrying eGFP under the control of an endogenous clinically-tested promoter (short EF1α) were produced, containing a variable DNA sequence tag (barcode) in their long terminal repeat (LTR). The aim of the barcode is to uniquely tag, identify and track a particular clone within the heterologous expressing population. Human embryonic kidney cell lines (HEK-293) were transduced with a barcoded lentiviral library at a low multiplicity of infection. We demonstrated that integration site analysis and next-generation sequencing of lentiviral barcoded vector junctions by ligation-mediated PCR (LM-PCR) coupled with RNA-Seq allows for quantification of the relative abundance of each barcode variant in each specific genomic position. Expression cassettes containing lentiviral vector components were then site-specifically integrated into these genomes sites using the CRISPR-Cas9 technology. The barcoding lentiviral system allows for rapid and high-resolution high-throughput screening of gene expression in a large number of genomic positions naturally targeted for optimal vector expression but also of lower expressing sites in order to meet lentiviral cytotoxicity and stoichiometric constraints.
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Subramanian, Sankar. "SYNTHESIS AND DEVICE CHARACTERIZATION OF FUNCTIONALIZED PENTACENES AND ANTHRADITHIOPHENES." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/588.
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Research on pi-conjugated organic materials in the recent past has produced enormous developments in the field of organic electronics and it is mainly due to their applications in electronic devices such as organic field effect transistors (OFETs), organic light emitting diodes (OLEDs) and organic photovoltaic cells (OPVs). The primary goal of this research work is to design and synthesize high performing charge transport organic semiconductors. One of the criteria for better performance of the organic thin film transistor (OTFT) is to have high uniform thin film morphology of the organic semiconductor layer on the substrate. The first project in this dissertation has been directed towards improving the thin film morphology of the functionalized pentacenes through liquid crystalline behaviour. The results have suggested the possibility of thermotropic liquid crystalline phases in 6,13-bis(diisopropylhexylsilylethynyl) pentacene which has no pi-stacking in its solid state and the presence of silyl group at the peri-position is crucial for the stability of the functionalized pentacenes. In the second project, i have investigated the effect of alkyl groups with varying chain length on the anthradithiophene chromophore on the performance of the charge transporting devices. Organic blend cell based on solution processable 2,8-diethyl-5,12-bis(triethylsilylethynyl) anthradithiophene has showed 1% power conversion efficiency and the performance is mainly attributed to the large crystalline phase segregation of the functionalized anthradithiophene from the amorphous soluble fullerene derivative matrix. OTFT study on alkyl substituted functionalized anthradithiophenes suggested the need of delegate balance between thin film morphology and the crystal packing. Third project has been directed towards synthesizing halogen substituted functionalized anthradithiophenes and their influence in the performance of OFETs. OTFT made of 2,8-difluoro-5,12-bis(triethylsilylethynyl) anthradithiophene produced devices with thin film hole mobilities greater than 1 cm2/Vs. The result suggested that the device is not contact limited rather this high performance OTFTs are due to the contact induced crystallinity of the organic semiconductor.
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Cho, Eunkyung. "Determination via computational modeling of the structure-properties relationships in intercalated polymer:fullerene blends found in bulk-heterojunction solar cells." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45902.
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In bulk-heterojunction solar cells, device performance is influenced by both the intrinsic properties of the individual components - typically conjugated polymers and fullerene derivatives - and how they assemble and interact at their interface. The ability of fullerene to intercalate within the side-chains of a conjugated polymer can significantly affect the microstructure and overall device performance. Here, a series of computational chemistry approaches are applied to investigate the relationships between structure and property in intercalated polymer:fullerene blend. Using a combination of molecular mechanics (MM) calculation and simulations of 2D grazing incidence X-ray diffraction (GIXD) patterns, we have determined the molecular packing configuration of poly (2,5-bis (3-tetradecyl thiophene-2-yl) thieno[3,2-b]thiophene) (PBTTT-C₁₄) and a blend of PBTTT-C₁₄ and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM). Based on the confirmed packing structures, the electronic properties and morphological disorder were examined using density functional theory (DFT) and molecular dynamics (MD) calculations, respectively; we also investigated the intermolecular interaction energies behind the structure formation. Finally, we examined the vibrational, redox, and optical properties of the pristine polymer and a series of fullerene derivatives to understand the characteristic modes related to the various charged states of the systems.
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Saravia, Fernando. "Cryopreservation of boar semen : impact of the use of specific ejaculate portions, concentrated packaging, and simplified freezing procedures on sperm cryosurvival and potential fertilising capacity /." Uppsala : Department of Clinical Sciences, Swedish University of Agricultural Sciences, 2008. http://epsilon.slu.se/200898.pdf.
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Vargas, Carolina Galarza. "Caracterização e utilização de arroz vermelho (Oryza glaberrima) e preto (Oryza sativa) e seus subprodutos para a produção de filmes biodegradáveis." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/178778.
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O crescente interesse científico relacionado ao estudo das propriedades dos grãos de arroz vermelho (Oryza glaberrima) e preto (Oryza sativa) está atrelado ao elevado teor nutricional desses grãos. Quando submetidos ao processo de beneficiamento, eles geram subprodutos, entre os quais a quirera e o farelo, ricos em amido e compostos fenólicos, respectivamente. Uma vez consideradas as diferenças varietais dos grãos e o potencial uso dos seus subprodutos, os objetivos deste trabalho foram, primeiramente, determinar a composição química e o perfil de compostos bioativos desses grãos e, sequencialmente, avaliar sua atividade antioxidante por meio da análise do efeito protetor de células SH- SY5Y. Posteriormente, esses grãos e seus subprodutos foram utilizados como material para o desenvolvimento de filmes biodegradáveis. A identificação e quantificação de compostos fenólicos foi avaliada em extratos da fração farelo de ambos os grãos, por ser essa a fração que contém sua maior concentração. Os resultados evidenciaram que o ácido ferúlico foi o principal composto fenólico encontrado em ambas as amostras. Enquanto no farelo de arroz preto a cianidina-3-glicosídeo foi a antocianina majoritária, no farelo de arroz vermelho foi identificada a presença de proantocianidinas Com relação à atividade antioxidante, o ensaio realizado em cultura de células SH-SY5Y, demonstrou que os extratos de ambos os farelos de arroz, nas duas concentrações testadas (10 and 50 μg/mL), apresentam um efeito protetor contra as espécies reativas geradas pelo H2O2 (ensaio DCFH-DA) e, esse resultado foi relacionado à presença de compostos bioativos, especialmente ácidos fenólicos e antocianinas. Devido às propriedades físico-químicas e antioxidantes, amido e farinha de arroz vermelho foram utilizados para o desenvolvimento de filmes biodegradáveis. Foram desenvolvidas formulações contendo diferentes proporções de farinha e amido (10:0, 9:1, 7:3, 5:5 e 0:10, p/p). A incorporação de amido nos filmes de farinha promoveu melhora das propriedades mecânicas e estruturais e, redução da permeabilidade ao vapor de água. Baseado na excelente atividade de sequestro do radical DPPH. e no menor custo de produção, a formulação 9:1 foi escolhida para ser aplicada na forma de sachê para análise da estabilidade de óleo de girassol armazenado sob condições de oxidação acelerada. Os resultados demonstraram que os filmes foram eficazes como embalagem protetora impedindo a formação de produtos de degradação primários (peróxidos e dienos conjugados) e secundários (trienos conjugados) durante o armazenamento. A partir dos resultados obtidos neste trabalho, fica evidenciada a possibilidade de utilização dos grãos de arroz vermelho e preto e seus subprodutos como matérias-primas promissoras para o desenvolvimento de embalagens biodegradáveis fonte de compostos antioxidantes.The increase scientific interest related to the study of the properties of red (Oryza glaberrima) and black rice (Oryza sativa) grains is related to the high nutritional content of these grains. When submitted to the polishing process, they generate by-products, among them broken grains and bran, rich in starch and phenolic compounds, respectively. Once considered varietal differences of the grains, and the potential use of their by-products, the goals of this work were, firstly, to determine the chemical composition and the bioactive compounds profile of these grains and, sequentially evaluate their antioxidant activity by analyzing the protective effect of SH-SY5Y cells. Subsequently, these grains and their by-products were used as material for the development of biodegradable films. The identification and quantification of phenolic compounds was evaluated in extracts of the bran fraction of both grains, since this is the fraction that contains the highest concentration of them. The results showed that ferulic acid was the main phenolic compound found in both samples. While in the black rice bran cyanidin-3-glycoside was the major anthocyanin, in the red rice bran the presence of proanthocyanidins was identified. In relation to the antioxidant activity, the SHSY5Y cell culture assay showed that the extracts from both rice bran, at both concentrations tested (10 and 50 μg/ mL), had a protective effect against the reactive species generated by H2O2 (DCFH-DA assay) and this result was related to the presence of bioactive compounds, especially phenolic acids and anthocyanins. Due to the physicochemical and antioxidant properties, starch and red rice flour were used for the development of biodegradable films Formulations containing different ratios of flour and starch (10:0, 9:1, 7:3, 5:5 and 0:10, w/w) were developed. The incorporation of starch in the flour films promoted improved mechanical and structural properties, and reduced permeability to water vapor. Based on excellent scavenging activity of DPPH radical and lowest production cost, the 9: 1 formulation was chosen to be applied in the form of sachets to analyze the stability of sunflower oil stored under accelerated oxidation conditions. The results demonstrated that the films were effective as protective packaging preventing the formation of primary degradation products (peroxides and conjugated dienes) and secondary (conjugated trienes) during the storage. Based on the results obtained in this work, it was confirmed the possibility of using red and black rice grains and their by-products as promising raw materials for the development of biodegradable packaging source of antioxidant compounds.
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Francis, Laurent A. "Thin film acoustic waveguides and resonators for gravimetric sensing applications in liquid." Université catholique de Louvain, 2006. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-01272006-113333/.
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The fields of health care and environment control have an increasing demand for sensors able to detect low concentrations of specific molecules in gaseous or liquid samples. The recent introduction of microfabricated devices in these fields gave rise to sensors with attractive properties. A cutting edge technology is based on guided acoustic waves, which are perturbed by events occurring at the nanometer scale. A first part of the thesis investigates the Love mode waveguide, a versatile structure in which a thin film is guiding the acoustic wave generated in a piezoelectric substrate. A systematic analysis of its sensitivity was obtained using a transmission line model generalized to discriminate the rigid or viscous nature of the probed layers. We developed a novel integrated combination of the Love mode device with a Surface Plasmon Resonance optical sensor to quantify the thickness and the composition of soft layers. The electromagnetic interferences in the recorded signal were modeled to determine the phase velocity in the sensing area and to provide new mechanisms for an enhanced sensitivity. The experimental aspects of this work deal with the fabrication, the important issue of the packaging and the sensitivity calibration of the Love mode biosensor. A second part of the thesis investigates nanocrystalline diamond under the form of a thin film membrane suspended to a rigid silicon frame. The high mechanical and chemical resistance of nanocrystalline diamond, close to single-crystal diamond, open ways to membrane based acoustic sensors such as Flexural Plate Wave and thin Film Bulk Acoustic Resonators (FBAR). A novel dynamic characterization of the thin film is reported and the properties of composite FBAR devices including a diamond thin film membrane and a piezoelectric aluminum nitride layer are assessed using the perturbation theory. This study is applied to evaluate the high sensing potential of the first prototype of an actual diamond-based composite FBAR.
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Dubreil, Chloé. "Nanoparticules tolérogènes pour l’administration d’un auto-antigène des cellules bêta dans le diabète auto-immun Tolerogenic iron oxide nanoparticles in type 1 diabetes: biodistribution and pharmacokinetics studies in nonobese diabetic mice Tolerogenic nanoparticles boost regulatory B cells to reverse autoimmune diabetes." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCB141.
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Les maladies auto-immunes chroniques sont la conséquence de la reconnaissance par le système immunitaire d'auto-antigènes comme élément étranger, entraînant une destruction des tissus et organes cibles. Le diabète de type 1 (DT1), la maladie auto-immunes chronique la plus courante, est caractérisé par un insuffisance en insuline due à la destruction sélective des cellules bêta productrices d'insuline. Lors de l'apparition des signes cliniques, plus de 70% de la masse des cellules bêta peut être détruite. Par conséquent, le diagnostic précoce est un objectif majeur afin de limiter l'agression auto-immune, et de créer une fenêtre thérapeutique pour améliorer la survie ou la régénération des cellules bêta. Les approches spécifiques d'antigène (Ag) sont attrayantes du fait de la spécificité de leur mécanisme limité à l'organe cible. Cependant, bien que la prévention du développement du diabète via l'utilisation d'autoantigènes chez la souris non obèse diabétique (NOD) ait été étudiée, les essais cliniques chez l'homme ont produit des résultats décevants. Par conséquent, des approches combinant deux stratégies thérapeutiques pourraient être envisagées. Une stratégie potentielle consiste à co-administrer des auto-antigènes à un traitement antiinflammatoire afin que les deux traitements soient présentés au même moment dans l'environnement des cellules immunitaires auto-réactives. La première partie de ce travail consiste à caractériser physico-chimiquement le vecteur transportant les deux traitements afin d'optimiser la charge médicamenteuse tout en maintenant la biocompatibilité et la stabilité du véhicule de délivrance. Ainsi, des nanoparticules (NPs) d'oxydes de fer superparamagnétiques (USPIO) ont été fonctionnalisées en surface avec des polymères de phosphonate polyéthylène glycol (USPIO-PEG). Les fonctions acide carboxylique ont été utilisées pour lier par covalence un autoantigène DT1. Une molécule antiinflammatoire est piégée par interactions hydrophobes dans les chaines de polymères. Après avoir mis en évidence l'internalisation cellulaire et la non toxicité sur des cellules dendritiques dérivées de la moelle osseuse murine (BMDCs), nous avons entrepris des études de biodistribution et de pharmacocinétique en utilisant le modèle NOD qui partage de nombreuses caractéristiques avec la pathologie humaine. Différentes techniques ont été utilisées à savoir l'IRM, l'histologie et de la magnétométrie sur organe isolé. Les NPs s'accumulent préférentiellement dans le pancréas des souris NOD via un effet de perméabilité et de rétention accrue (EPR effect). Cette bioaccumulation pourrait être exploitée pour la délivrance ciblée du traitement. La deuxième partie du travail consiste à évaluer l'effet thérapeutique de telles nanoparticules tolérogènes sur des souris diabétiques NOD. Des souris diabétiques ont été injectées par voie intraveineuse. Les souris contrôles traitées avec des nanoparticules « nues » ont atteint un niveau de glucose sanguin de 600 mg/dL, considéré comme point limite de l'expérience, en 4-6 jours. Les nanoparticules portant soit la molécule tolérogène soit l'autoantigène ont retardé la progression du diabète jusqu'à 40 jours. Les NP complètes quant à elles, ont montré des effets synergiques. En effet, 50% des souris traitées étaient encore en vie 65 jours après l'apparition de la maladie, et deux souris montrèrent une normoglycémie stable plus de 300 jours après l'apparition de la pathologie. Les nanoparticules tolérogènes induisent une splénomégalie principalement due à la prolifération des lymphocytes B. Les cellules B stimulées par des nanoparticules sécrètent des cytokines anti-inflammatoires, à savoir IL-10 et TGF-bêta. Des cellules B similaires sont également produites in vitro lors de l'incubation avec des nanoparticules. Notre stratégie au potentiel thérapeutique prometteur pourrait être appliquée, en utilisant des antigènes appropriés, à un plus large éventail de maladies auto-immunesChronic autoimmune diseases are the consequence of self-antigens recognition as foreign by the adaptive immune system, resulting in inflammation and potential destruction of targeted tissues and organs. Type 1 diabetes (T1D) is one of the most common chronic autoimmune diseases. It is characterized by insulin deficiency due to selective destruction of insulin-producing beta-cells. At clinical onset, more than 70% of beta-cell mass can be destroyed. Consequently, early diagnosis is a major objective in order to avoid, limit or reverse autoimmune aggression, and to create opportunities for strategies enhancing beta-cell survival or regeneration. Antigen (Ag)-specific approaches are appealing because their effects are expected to be limited to cells expressing the chosen antigen, ideally the target organ. However, while treatment with beta -cell Ags can prevent disease in the model of the Non-Obese Diabetic (NOD) mouse, clinical trials in humans have produced disappointing results. Consequently, combinatorial approaches may be required for reversal and prevention of T1D. A potential strategy is to associate self-antigens with signals inducing a tolerogenic phenotype. Co-delivery ensures that both compounds get delivered at the same time and presented in the same cellular environment to auto-reactive immune cells. The first part of this work consisted in undertaking a thorough physicochemical characterization of a new drug vector, aiming to establish quantitative methods to optimize drug loading while maintaining biocompatibility and stability of the delivery vehicle. In this work, 9nm Ultra-small superparamagnetic iron-oxide (USPIO) nanoparticles were surface functionalized with phosphonate polyethylene glycol molecules (USPIO-PEG). Carboxylic acid functions were used to covalently bind a T1D autoantigen. PEG brush allows for the co-packaging of hydrophobic tolerogenic drug molecules, trapped between PEG chains through hydrophobic interactions. We carefully characterized protein and tolerogenic drug loading, and studied cell labeling, toxicity, integrity of loaded protein and tolerogenic drug, and activity of our nanoplatform on murine Bone Marrow Derived Dendritic Cells (BMDCs). We undertook biodistribution and pharmacokinetics studies using the NOD model that shares numerous features with human T1D. Biokinetic studies were performed both qualitatively using MRI 7T and histological Perls staining analyses and quantitatively using magnetometry for NP quantification. USPIO accumulate preferentially in NOD mice pancreas via Enhanced Permeability retention (EPR) effect thus, allowing us to distinguish pre-diabetic mice from non-diabetic controls. This result suggests that vascular leakage could be exploited for NP bioaccumulation, for therapeutic agent delivery and for imaging using MRI agents to monitor treatment. The second part of the work consisted in evaluating the therapeutic effect of such tolerogenic nanoparticles (NPS) on NOD diabetic mice. Diabetic mice were injected intravenously at diabetes onset. USPIO-PEG and vehicle treated mice reached 600mg/dL blood glucose level, considered limit for sacrificing mice, within a couple of days. NPs carrying either the tolerogenic drug or the autoantigen delayed diabetes progression up to 40 days. Complete NPs showed synergistic effects. In fact, 50% of treated mice were still alive 65 days after disease onset, and two mice reverted to stable normoglycemia for more than 300 days. To identify the underlying mechanism, the immune response to NPs in lymphoid organs was investigated. It was found that tolerogenic NPs induce splenomegaly mainly due to B cell proliferation. NP-stimulated B cells secrete anti-inflammatory cytokines namely IL-10 and TGF-beta. Similar B cells could be produced in vitro upon incubation of with NPs. Our strategy has promising therapeutic potential and could be applied, using relevant antigens, to a wider range of autoimmune diseases
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Claßen, Anne-Kathrin [Verfasser]. "Hexagonal packing of Drosophila wing epithelial cells by the planar cell polarity pathway / von Anne-Kathrin Claßen." 2006. http://d-nb.info/981291023/34.
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Farhadifar, Reza [Verfasser]. "Dynamics of cell packing and polar order in developing epithelia / vorgelegt von Reza Farhadifar." 2009. http://d-nb.info/1006682694/34.
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TING, WU YING, and 吳英霆. "Rearch of Solar Cell Efficiency with Packaging Material." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/28331997531764507946.
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碩士南開科技大學
電子工程研究所
101
Abstract Under consideration for the energy going to run-down on our planet, people start to search for alternative energy. Solar energy is one of the solution. This study is discussing different packaging material would change the efficiency of solar modules. In experiment 1, we add additive in packaging material to test the efficiency would be higher or contrary. Experiment 2, we try to improve the high temperature causing lower efficiency situation. Experiment 1, using fluorescent agent as additive in EPOXY, both are commercially available, in specific ratio, then measuring electrical characteristics by multimeter under daylight and solar simulator, to see how the additive change the efficiency. Experiment 2, under high temperature, efficiency would decrease dramatically, we use aluminum plate to replace print circuit board as the module’s base, trying to ease the efficiency decreasing by temperature. We use EPOXY as packaging material for our solar modules, and make few packaging cubes by add different amount of fluorescent agents in EPOXY with specific ratios. Use light source going through these cubes to see how the efficiency change. After completing our test, this fluorescent agent only decreased light absorbing in solar modules which means lower the efficiency. After done experiment 2, efficiency of using aluminum plate was better than using general base obviously. There are two commercially available fluorescent agents, direct fluorescent type and night fluorescent type, in this study we use the direct fluorescent agent and knew it had no help to gain solar module’s efficiency. But about how efficiency changing with other types of fluorescent agent need more tests to confirm that. Radiating character of aluminum makes great improvement of high temperature causing voltage decreasing problem by aluminum plate. SIC got good radiate as aluminum, and the cost of SIC plate was way cheaper than A grade aluminum plate. The purpose of our study wants to help the application of solar energy under extreme weather condition.
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(10189067), Luping Xu. "Mammalian Cell-based Biosensors for Foodborne Pathogen Detection." Thesis, 2021.
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Rapid detection of live pathogens is of paramount importance to ensure food safety. At present, nucleic acid-based polymerase chain reaction and antibody-based lateral flow assays are the primary methods of choice for rapid detection, but these are prone to interference from inhibitors, and resident microbes. Moreover, the positive results may neither assure virulence potential nor viability of the analyte. In contrast, the mammalian cell-based assay detects pathogen interaction with the host cells and is responsive to only live pathogens, but the short shelf-life of the mammalian cells is the major impediment for its widespread application. An innovative approach to prolong the shelf-life of mammalian cells by using formalin was undertaken. Formalin (4% formaldehyde)-fixed human ileocecal adenocarcinoma cell line, HCT-8 on 24-well tissue culture plates was used for the capture of viable pathogens while an antibody was used for specific detection. The specificity of the Mammalian Cell-based ImmunoAssay (MaCIA) was validated with Salmonella enterica serovar Enteritidis and Typhimurium as model pathogens and further confirmed against a panel of 15 S. Enteritidis strains, 8 S. Typhimurium,11 other Salmonella serovars, and 14 non-Salmonella spp. The total detection time (sample-to-result) of MaCIA with artificially inoculated ground chicken, eggs, milk, and cake mix at 1-10 CFU/25 g was 16-21 h using a traditional enrichment set up but the detection time was shortened to 10-12 h using direct on-cell (MaCIA) enrichment. Formalin-fixed stable cell monolayers in MaCIA provide longer shelf-life (at least 14 weeks) for possible point-of-need deployment and multi-sample testing on a single plate.
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Li, Shengnan. "Packaging Design of IGBT Power Module Using Novel Switching Cells." 2011. http://trace.tennessee.edu/utk_graddiss/1205.
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Parasitic inductance in power modules generates voltage spikes and current ringing during switching which cause extra stress in power electronic devices, increase electromagnetic interference (EMI), and degrade the performance of the power converter system. As newer power devices have faster switching speeds and higher power ratings, the effect of the parasitic inductance of the power module is more pronounced. This dissertation proposes a novel packaging method for power electronics modules based on the concepts of novel switching cells: P-cell and N-cell. It can reduce the stray inductance in the current commutation path in a phase-leg module and hence improve the switching behavior.
Taking an insulated gate bipolar transistor (IGBT) as an example, two phase-leg modules, specifically a conventional module and a P-cell and N-cell based module were designed. Using Ansoft Q3D Extractor, electromagnetic simulation was carried out to extract the stray inductance from the two modules. An ABB 1200 V / 75 A IGBT model and a diode model were built for simulation study. Circuit parasitics were extracted and modeled. Switching behavior with different package parasitics was studied based on the Saber simulation.
Two prototype phase-leg modules were fabricated. The parasitics were measured using a precision impedance analyzer. The measurement results agree with the simulation very well. A double pulse tester was built in laboratory. Several approaches were used to reduce the circuit and measuring parasitics. From the switching characteristics of the two modules, it was verified that the larger stray inductance in the layout causes higher voltage overshoot during turn off, which in turn increases the turn off losses.
Multichip (two in parallel) IGBT modules applying novel switching cells was also designed. The parasitics were extracted and compared to a conventional design. The overall loop inductance was reduced in the proposed module. However, the mismatch of the paralleled branches was larger.
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Yang, Ming-Fu, and 楊明輔. "Study of Taguchi-Grey Relational Analysis on Optimization Process for Solar Cell Module Packaging." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/z8d793.
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碩士國立臺灣科技大學
自動化及控制研究所
99
An optical Epoxy (EPO-TEK 301-2FL) may be used to replace the Ethylene Vinyl Acetate (EVA) for a solar cell module packaging. Firstly, this study explores the effect of different processing parameters for the Epoxy-based solar cell module. The main parameters include Epoxy thickness, curing temperature and curing time. The Taguchi method L9(33) and Grey Relational Analysis (GRA) are employed to obtain the best processing parameters for Epoxy-based solar cell module. Both output power (W) and fill factor (FF) are concerned as the multiple qualities of optimization to obtain the best processing parameters for Epoxy-based solar cell module.From the experimental results, the best combinations for Epoxy-based solar cell module are Epoxy thickness of 0.3mm, curing temperature of 80 ℃, and curing time of 2.5hr. It has the best output power of 4.14 W, which is better than the maximum output power of 4.10W from the original nine experiments. The output power is improved about 0.98%. Therefore, the results demonstrate that it is efficiently confirmed to obtain the best parameters for multiple qualities optimization by using such a Taguchi-Gray Relational Analysis method.
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Huang, Chen Yu, and 黃陳昱. "Thermal Deformation and Stresses of Multilayered Structures in Electronic Packaging and Solar Cells: Measurement and Analylsis." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/09464853768346876418.
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博士長庚大學
機械工程學系
100
Thermal/residual deformations and stresses in electronic packages and silicon solar cells would significantly impact on production yield rate and their reliabilities during product designs, fabrications and services. The purpose of this study is to investigate the parameters such as thermal loads, material properties, cure shrinkage, and moisture, affecting the deformations and stresses of electronic packages and silicon solar cells. The methodologies, including experimental measurements, theoretical and finite element analyses, are applied for measuring deformation and further calculating thermal-, or process-induced strains and stresses in bi- or multi-layered structures in this study. In the theoretical analysis, the formulas developed for estimating bending curvature and interfacial stresses in bi- or multi-layered plates are employed. In the experiments, the out-of-plane deformations are obtained using Twyman-Green interferometry and shadow moiré. The dissertation mainly consists of three cases of study: (1) chip on glass (COG) packaging for liquid crystal display (LCD) driver IC, (2) ball grid array (BGA) packages with epoxy molding compound (EMC) for IC packaging, and (3) silicon solar cells in photovoltaic (PV) industry. In the first part, some parameters such as bonding conditions, thermal loads, adhesive material properties, fillet effect, bump materials, and moisture, affecting the warpage and bump-joint stresses of the COG packages, are investigated. The results show that the warpage simulations are compared well with experimental observations. Moreover, the effects on warpage and bump-joint stresses of COG packages have been discussed in detail in terms of adhesives fillet size, elastic modulus, and coefficient of thermal expansion (CTE). In the second part, for the BGA packages under thermal loading, the solution to quantifying the residual strains of the EMC is proposed. Furthermore, the key material and geometric parameters affecting the coplanarity of these packages are resolved. For wBGA packages, the material results indicate that the residual strain of the EMC with 72% volume fraction of fillers after post-mold curing was found to be 0.15%. The package results show that chip thickness can significantly affect the warpage of wBGA by taking into account the residual strain of the EMC. In the last part, the deformation mechanism and stress development of silicon solar cells subject to thermal loadings are investigated. The warpage of conventional cells and Al/Si bi-layer plates have been measured and simulated, and the nonlinear deformation behaviors have been found in their experimental and finite element results. Furthermore, the curvature variation and residual stresses for Al/Si bi-layered plates in geometric nonlinear deformation have been presented and discussed in detail. Key words: warpage, stress, Chip on Glass (COG), wBGA, residual strain, silicon solar cells, geometric nonlinear deformation
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CHU, CHUN-WEI, and 朱駿維. "Studies and Synthesis of 2D and 3D Perovskite Material as a New Type of Solar Cell and Parylene C packaging under atmosphere." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/84m5ua.
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碩士國立臺北科技大學
分子科學與工程系有機高分子碩士班
106
The MAPbX3(MA= CH3NH3) layer was prepared as follows: PbX2 and CH3NH3X (X=Cl, Br, I,SCN) were dissolved in solvent to fabricate Perovskite solar cells(PSCs) light absorbing layer materials{3D MAPbX3 and 2D [ MA2Pb(SCN)2Br2 and (Butyl-1,4-diammonium) PbI4]. Previous research use reflectance to test the stability of perovskites in the air, and we observe the rate of degradation of the absorbing layer. In this research, we assemble it to the PSCs to measure efficiency. Our laboratory also hopes to remove the process of glove box then spin-coated Perovskite under the atmosphere (relative humidity 50 ~ 65％), and we furtherly observe the relationship between time and efficiency(relative humidity 60 ~ 80％). We find two-dimensional materials [MA2Pb (SCN )2Br2 and (Butyl-1,4-diammonium)PbI4] have higher stability than three-dimensional materials(MAPbI3). In addition, we use the waterproof properties of Parylene C to package MAPbI3(160-500 nm). The result shows that under atmospheric conditions (relative humidity 60 to 80％), Parylene C with a thickness of 300 nm will make the efficiency reduce to zero after 24.5 days. We also find there is still 80％efficiency (η=6.88％) under relative humidity of 40％ after 18 days and the efficiency reduce to zero after 68 days, which thus exhibits a much better stability. And in unpackaged condition, the efficiency is reduce to zero after 2 days.
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Lin, Yi Ming, and 林宜明. "Application of Automation Systems to Improve the Process of Packaging Quality Control-A Case Study of N Company for the Solar Cell Industry." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/hjxezq.
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碩士國立清華大學
工業工程與工程管理學系碩士在職專班
104
To solve energy crisis and environmental issues, people are actively looking for alternative energy sources, including Biomass Energy, Wind Energy, Geothermal Energy, Marine Energy and Solar Energy, to replace fossil fuels in recent years. Among them, Solar Energy is the most anticipated. Solar industry is highly growing, and it may become a competitive industry in Taiwan after Two Trillion and Twin Star industries. In solar cell industry, the automation of manufacturing process is becoming mature. Now all of the automation systems are still focused on the process of solar cell manufacturing, but the process of Packaging Quality Control (PQC), including packing, conveyance and inspection, are still operated manually. Therefore, these processes could cause problems such as low operating efficiency and Miss-Operation (MO). In this study, we examined the whole process of case study by Value Stream Mapping (VSM) and identified which activities were value-added (VA), non-value added (NVA) and necessary non-value added (NNVA) through controlling material flow and information flow. After constructing automation systems and continuing improving processes, we could eliminate what we define as waste. From the result, we found that constructing automation systems could not only effectively eliminate or reduce waste in the process but also reduce human cost and miss-operation. Ultimately, we could meet customer’s requirements, and reduce cycle time so that improve company’s competitiveness.
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簡煒哲. "Application of heparinized cellulose matrices to adsorb unpurified rAAV2 from the crude lysate of packaging cells for binding and transduction." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/84381664686373388370.
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碩士國立清華大學
化學工程學系
95
The microporous affinity membrane based on cellulose matrices offers minimal mass-transfer effects in membrane chromatography with low nonspecific adsorption. In this research, we tested a novel application of the microporous, heparinized cellulose matrices (H-CM) for their affinity toward recombinant adeno-associated virus serotype 2 (rAAV2, which uses heparan sulfate proteoglycans as the primary cellular receptor) to develop a controlled, substrate-mediated viral vector delivery. We adsorb rAAV2 from the crude lysate of packaging cells to an epoxy-crosslinked heparin cellulose membrane, which led to vector transduction upon cellular adhesion. When adhered, the human HT-1080 fibroblasts exhibited proliferation kinetics similar to those on the standard polystyrene tissue-culture surface. Using green fluorescent protein and beta-galactosidase as reporters, we showed that the heparin-bound rAAV2 particles remained active and that the rAAV2-heparin binding was reversible and capable of mediating transgene delivery in cell culture. This method avoids the use of conventional ultracentrifugation or chromatography in preparation of infectious rAAV2 for transduction. Our work explores a new application of affinity cellulose matrices in substrate-mediated viral vector delivery, which can be a useful tool in developing protocols for localized gene transfer.
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Teixeira, Alexandra Isabel Lopes. "Evidence for BCR-ABL oncoprotein packaging into extracellular vesicles released by BCR-ABL+ leukemia cells: possible implications on cellular response to STI571." Dissertação, 2017. https://repositorio-aberto.up.pt/handle/10216/109232.
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Teixeira, Alexandra Isabel Lopes. "Evidence for BCR-ABL oncoprotein packaging into extracellular vesicles released by BCR-ABL+ leukemia cells: possible implications on cellular response to STI571." Master's thesis, 2017. https://repositorio-aberto.up.pt/handle/10216/109232.
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Koldej, Rachel Marie. "The development of HIV-1 derived gene transfer technology: optimisation of vector safety, processing and production." 2008. http://hdl.handle.net/2440/42907.
Full textAbstract:
Vectors derived from Human Immunodeficiency Virus type 1 (HIV-1) are being widely developed for gene therapy applications, principally because they are able to transduce both dividing and non-dividing cells and result in stable, long term gene expression. However, these vectors are difficult to produce in high titres and sufficient volumes for large scale experiments and clinical application. Therefore, an investigation into methods to improve the production of HIV-1 derived gene transfer vectors was undertaken. One factor that limits the production of recombinant virus is the amount of viral genomic RNA available for packaging into virions. Therefore, a transfer vector was modified with the aim of increasing the amount of genomic RNA produced. Substitution of the polyadenylation (pA) signal, mutation splice donor sites and removal of unnecessary sequences were all examined. pA signal readthrough was quantified to determine the effect of these modifications on the rate of pA signal readthrough. Insertional mutagenesis and vector mobilisation are recognised risk factors with all integrating vectors. Self inactivating (SIN) vectors, which contain a deletion of U3 sequences in the 3’ LTR, demonstrate a reduced rate of mobilisation. Transduction with these vectors results in a provirus containing no viral promoter elements, with transcription of the transgene being controlled from an internal promoter. However, LTR repair of SIN vectors occurs at an appreciable frequency. Therefore, the extent of this deletion was maximised and the effect on the frequency of the repair examined. The production of lentiviral gene therapy vectors by large-scale transient transfection is both time consuming and technically difficult. Therefore, methods to increase the scale of production without compromising virus titre were developed. This resulted in fewer transfections and less handling of the cells when making virus on a large scale (3-4 L). In order to process the virus on this scale in a single day (i.e. 8 hours), new concentration and purification methods were established. The protocol consisted of low speed centrifugation, 0.45 μm filtration, 750 kDa ultrafiltration, 0.8 μm filtration and ultracentrifugation. However, the use of ultracentrifugation means that this protocol is not amenable to further scale up. Therefore, the replacement of the ultracentrifugation step with anion exchange was investigated. A number of different resins and anion exchange devices were investigated, two of which show promise for large scale purification of HIV-1 derived gene transfer vectors. In an ideal world, HIV-1 derived gene transfer vectors would be produced using stable packaging cell lines engineered to produce the desired virus. However, previous attempts to produce such a cell line with the desired properties have had limited success and have generally used outdated helper systems. Therefore, in an attempt to combine the efficiency advantages of having a single helper plasmid with the safety advantages of expressing each protein separately, a single packaging construct that contained separate transcription units for each of the required proteins was produced. Transcription of cyotoxic proteins was controlled by inducible promoters. Initial results suggest that such a system is technically feasible but that further work is required to optimise the expression of helper functions.http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1309550
Thesis (Ph.D.) -- School of Paediatrics and Reproductive Health, 2008
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Barker, Megan. "Structural Investigation of Processing α-Glucosidase I from Saccharomyces cerevisiae." Thesis, 2010. http://hdl.handle.net/1807/32660.
Full textAbstract:
N-glycosylation is the most common eukaryotic post-translational modification, impacting on protein stability, folding, and protein-protein interactions. More broadly, N-glycans play biological roles in reaction kinetics modulation, intracellular protein trafficking, and cell-cell communications.
The machinery responsible for the initial stages of N-glycan assembly and processing is found on the membrane of the endoplasmic reticulum. Following N-glycan transfer to a nascent glycoprotein, the enzyme Processing α-Glucosidase I (GluI) catalyzes the selective removal of the terminal glucose residue. GluI is a highly substrate-specific enzyme, requiring a minimum glucotriose for catalysis; this glycan is uniquely found in biology in this pathway. The structural basis of the high substrate selectivity and the details of the mechanism of hydrolysis of this reaction have not been characterized. Understanding the structural foundation of this unique relationship forms the major aim of this work.
To approach this goal, the S. cerevisiae homolog soluble protein, Cwht1p, was investigated. Cwht1p was expressed and purified in the methyltrophic yeast P. pastoris, improving protein yield to be sufficient for crystallization screens. From Cwht1p crystals, the structure was solved using mercury SAD phasing at a resolution of 2 Å, and two catalytic residues were proposed based upon structural similarity with characterized enzymes. Subsequently, computational methods using a glucotriose ligand were applied to predict the mode of substrate binding. From these results, a proposed model of substrate binding has been formulated, which may be conserved in eukaryotic GluI homologs.
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(9226604), Amin Joodaky. "MECHANICS AND DESIGN OF POLYMERIC METAMATERIAL STRUCTURES FOR SHOCK ABSORPTION APPLICATIONS." Thesis, 2020.
Find full textAbstract:
This body of work examines analytical and numerical models to simulate the response of structures in shock absorption applications. Specifically, the work examines the prediction of cushion curves of polymer foams, and a topological examination of a $\chi$ shape unit cell found in architected mechanical elastomeric metamaterials. The $\chi$ unit cell exhibits the same effective stress-strain relationship as a closed cell polymer foam. Polymer foams are commonly used in the protective packaging of fragile products. Cushion curves are used within the packaging industry to characterize a foam's impact performance. These curves are two-dimensional representations of the deceleration of an impacting mass versus static stress. The main drawback with cushion curves is that they are currently generated from an exhaustive set of experimental test data. This work examines modeling the shock response using a continuous rod approximation with a given impact velocity in order to generate cushion curves without the need of extensive testing. In examining the $\chi$ unit cell, this work focuses on the effects of topological changes on constitutive behavior and shock absorbing performance. Particular emphasis is placed on developing models to predict the onset of regions of quasi-zero-modulus (QZM), the length of the QZM region and the cushion curve produced by impacting the unit cell. The unit cell's topology is reduced to examining a characteristic angle, defining the internal geometry with the cell, and examining the effects of changing this angle.
However, the characteristic angle cannot be increased without tradeoffs; the cell's effective constitutive behavior evolves from long regions to shortened regions of quasi-zero modulus. Finally, this work shows that the basic $\chi$ unit cell can be tessellated to produce a nearly equivalent force deflection relationship in two directions. The analysis and results in this work can be viewed as new framework in analyzing programmable elastomeric metamaterials that exhibit this type of nonlinear behavior for shock absorption.