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Sarkar, Aniruddh. "Microfluidic concentration-enhanced single cell enzyme activity assay." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79325.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references.
Cells sense stimuli, process information and respond using signaling networks regulated by enzymatic activity of various proteins. Aberrations in signaling are associated with diseases such as cancer. Most current methods lack the sensitivity to measure enzymatic activity in single cells and instead measure the average of large cell populations. Cellular heterogeneity, overlooked in these methods, is widespread and relevant. Microfabricated tools are uniquely suited to single cell analysis due to the match in size scale which enables high sensitivity, high throughput measurements. In this thesis we develop a microfluidic platform for the direct measurement of enzyme activities from selected single cells without disrupting their extracellular context. We develop modules to: enhance enzyme assay sensitivity by microfluidic confinement, interface microfluidic devices with selected single cells, enable multiplexing and then integrate these modules to perform single cell assays. We first investigate electrokinetic trapping of charged biomolecules in a nanofluidic concentrator for enhancing enzyme assay sensitivity by simultaneously accumulating enzyme and substrate into a reaction plug. Non-linear enhancement of reaction kinetics in this device is predicted by a mathematical model and experimentally verified. A linear enhancement mode is developed where only the enzyme is accumulated and is reacted with substrate later in an enclosed volume defined by integrated pneumatic valves or by micro-droplets formed using an integrated droplet generator. This device is then used to perform high-throughput measurement of secreted cellular proteases. We then develop a nicrofluidic probe for lysis and capture of the contents of selected single adherent cells from standard tissue culture platforms by creating a small lysis zone at its tip using hydrodynamic confinement. The single cell lysate is then divided and mixed with different substrates and confined in small chambers for fluorimetric assays. An integrated nanofluidic concentrator enables further concentration-enhancement. We demonstrate the ability to measure, from selected single cells, the activity of kinases: Akt, MAPKAPK2, PKA and a metabolic enzyme, GAPDH - separately or simultaneously. This assay platform can correlate single cell phenotype or extracellular context to intracellular biochemical state. We present preliminary explorations of the correlation of cell morphology or local cell population density to kinase activity.
by Aniruddh Sarkar.
Ph.D.
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Haas, Kathleen. "Modeling Blood Cell Concentration in a Dialysis Cartridge." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-theses/425.
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Healthy kidneys are able to filter toxins from one's blood and remove excess fluid from one's body. Kidney dialysis is a process that performs the work of kidneys that cannot function normally. During the process of hemodialysis, blood from the patient's body is run through a dialysis cartridge through very thin hollow fibers made of a semi- permeable membrane. Waste and water travel from the blood, through the pores of the membrane, and into a fluid called dialysate. We attempt to model the velocities and pressures of blood plasma and dialysate in a dialysis cartridge, as well as to model the concentration of blood cells. We find that varying the pressure in the dialysate moves the location at which the maximum blood cell concentration occurs. We also find that the maximum blood cell concentration is directly proportional to the product of the blood cell Peclet number and the permeability of the membrane.
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Andrews, Arcadio Garcia de Castro. "Growth inhibitors and promoters from high concentration animal cell cultures." Thesis, University of Surrey, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259568.
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Bajpayee, Anurag. "Concentration of Cryoprotectant in water-in-oil microdroplets for single cell vitrificaton." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/46055.
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Includes bibliographical references (leaves 50-51).Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
"September 2008."
(cont.) Droplets with an initial concentration of IM were found to be concentrated to about 3-4M in 90s while droplets starting at 2M were concentrated to 6M in about the same time. The entire process takes place over a time scale of about one minute, fast enough to minimize exposure times but slow enough to be precisely controllable. This phenomenon is demonstrated to dynamically concentrate cryoprotectants within single cell-containing droplets. These droplets of sizes of about 30 micron diameter were concentrated to 3-4M from a starting concentration of IM in about 300s. The cells are tolerant to this concentration process and do not die when subjected to it. The process may be used in practice to innocuously concentrate cell encapsulating droplets which may then be vitrified before they are exposed to high temperatures for fatally long time scales. With appropriate characterization, the controllability of the process will allow for choosing exact cryoprotectant concentration levels used for vitrification. The demonstrated phenomenon has several other applications in cryobiology. Its controllability and speed may be used to dynamically modulate cryoprotectant concentrations in preservation protocols that require stepwise concentration or dilution. In addition, the process was found to be reversible and may thus be used for unloading cryoprotectants by controlled cooling as opposed to heating.
Among the several challenges associated with vitrification of cells, a major roadblock is the requirement of high concentrations of cryoprotectant chemicals and the damages caused by exposure of cells to these high concentrations at physiological temperatures. It is thus desirable to minimize the time of exposure of cells with high concentrations of cryoprotectants to physiological temperatures. In addition, vitrification requires very rapid cooling rates. As cooling rates of a sample are limited by its size, it becomes ideal to use the minimum sizes of the sample to be preserved. Certain organic oils, such as soybean oil, are made of triacylglycerols and are capable of dissolving small amounts of water due to the presence of ester groups, a property which enhances significantly with increasing temperature. This phenomenon was exploited to accomplish temperature controlled concentration of cryoprotectants in single water droplets with and without cells dispersed in the organic phase. The organic phase used in the present work is soybean oil while glycerol is used as the cryoprotectant. Glycerol was found to be comparatively insoluble in soybean oil at 35 'C for up to 10 minutes. The present work employed heating on a temperature controlling stage and temperature increases of about 10K. Solutions of glycerol in DI Water were mixed with soybean oil and emulsions made by vigorous agitation. The water to oil concentration was kept at 0.1% v/v to simulate an infinite dissolution medium and to prevent different droplets from affecting each other. To prevent premature dissolution, the oil is saturated with water at room temperature by incubating for 48 hours. Micro-liter-sized droplets of the emulsion are placed on a heating/ cooling stage and droplets of 15-20 micron diameter are visually selected from polydisperse emulsion for observation under a microscope. Upon increasing temperature, water dissolves into the oil rendering the droplet highly concentrated with the oil-insoluble cryoprotectant. The experiment involved heating to 35 °C from room temperature, so that all water eventually dissolved into the oil.
by Anurag Bajpayee.
S.M.
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Barrett, E., and Phillip R. Scheuerman. "The Effect of Cell Inoculum Level and Substrate Concentration on p- cresol Degradation." Digital Commons @ East Tennessee State University, 1998. https://dc.etsu.edu/etsu-works/2914.
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Norcio, Lawrence P. "Effects of microcarrier concentration, agitation rate, and serum concentration on the specific growth rate of mouse L cells in batch cultures." Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1179949129.
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McQuinn, Chris. "Design of a mechanical device for fabricating protein concentration gradients to study cell adhesion." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18728.
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The binding interaction between specialized proteins within the extracellular matrix (ECM) and specific membrane receptors in cells are pivotal for regulating cell adhesion and migration. Current methods used to generate patterned ECM substrates for the study of migration involve technically complicated devices that are expensive and demand specialized training. Some are also not applicable to the microscopic scale relevant for cells or provide inadequate substrates for growing sensitive cells such as neurons. This Masters thesis introduces an effective method to pattern proteins with micron scale precision at a reasonable financial cost and requires minimal training. The method is based on a device called the squeegee that uses a PDMS (polydimethyl siloxane) barrier to precisely control exposure of protein from solution onto specific areas of a glass surface to regulate adsorption time. The patterns may be produced with a range of proteins on a multitude of glass surfaces. The squeegee method recreated an ECM in the form of graded protein patterns, including continuous gradients and stepped gradients. Mammalian epithelial cells (CHO-K1) were cultured on a surface comprised of a fibronectin stepped gradient and shown to increase in cell spreading with increasing fibronectin surface density. Other proteins were successfully pattered including netrin-1, an important guidance cue in the developing mammalian spinal cord.L'interaction entre les protéines spécialisées qui sont dans la matrice extracellulaire (MEC) et les récepteurs à la limite de la membrane d'un organisme cellulaire est essentielle à la migration des cellules. Les méthodes actuelles pour étudier la migration impliquent l'utilisation d'appareils techniquement complexes, dispendieux et requérant une formation spécifique. De plus, ces méthodes ne sont pas applicables à l'échelle microscopique des organismes cellulaires ou sont inadéquates pour cultiver des cellules spécialisées. Ce mémoire de maîtrise introduit une méthode ayant un faible rapport coût-efficacité pour modeler les protéines avec une précision micrométrique et qui requiert peu de connaissances techniques. Il est possible de produire ces modèles avec une gamme de protéines et sur une multitude de surfaces de verre. La base de cette méthode est un appareil qui est nommé « la racle » qui utilise une barrière de polydimethyl siloxane (PDMS) pour contrôler précisément l'adsorption de protéine d'une solution sur une surface de verre. La méthode qui utilise la racle a permis de recréer des MEC sous forme de gradients de protéines, comprenant aussi bien des pentes continues que des marches d'escalier. Des cellules épithéliales de mammifères (CHO-K1) ont été cultivées sur une surface ayant un gradient de fibronectine en marche d'escalier, les cellules ont montré une augmentation dans leur étalement proportionnelle à la densité de surface de fibronectine.
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Gordon, Christopher, and res cand@acu edu au. "Hydrostatic and thermal influences on intravascular volume determination during immersion: quantification of the f-cell ratio." Australian Catholic University. School of Exercise Science, 2001. http://dlibrary.acu.edu.au/digitaltheses/public/adt-acuvp4.14072005.
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Previous data have shown that the most prevalent, indirect plasma volume (PV) measurement technique, which utilises changes in haematocrit (Hct) and haemoglobin concentration ([Hb]), underestimates actual PV changes during immersion, when compared to a direct tracer-dilution method. An increase in the F-cell ratio (whole-body haematocrit (Hctw) to large-vessel haematocrit (Hctv) ratio) has been purported as a possible explanation, probably due to hydrostatic and thermally-mediated changes during water immersion. Previous investigators have not quantified the F-cell ratio during immersion. Therefore, this study sought to determine the effect of the F-cell ratio on the indirect method during both, thermoneutral and cold-water immersions. Seven healthy males were tested three times, seated upright in air (control: 21.2°C SD ±1.1), and during thermoneutral (34.5oC SD ±0.2) and cold-water immersion (18.6oC SD ±0.2), immersed to the third intercostal space for 60 min. Measurements during the immersion tests included PV (Evans blue dye column elution, Evans blue dye computer programme, and Hct [Hb]), red cell volume (RCV; sodium radiochromate), cardiac frequency (fc) and rectal temperature (Tre). Plasma volume during the control trial remained stable, and equivalent across the three tests. There was a hydrostatically-induced increase in PV during thermoneutral immersion, when determined by the Evans blue dye method (16.2%). However, the Hct/[Hb] calculation did not adequately reflect this change, and underestimated the relative PV change by 43%. In contrast, PV decreased during cold immersion when determined using the Evans blue dye method by 17.9% and the Hct/[Hb] calculation by 8.0%, respectively, representing a 52% underestimation by the latter method. There was a non-significant decline in RCV during both immersions. Furthermore, an increase (8.6%) and decrease (-14.4%) in blood volume (BV) was observed during thermoneutral and cold-water immersions, respectively. The decline in RCV during thermoneutral immersion attenuated the BV expansion. Despite the disparity between the PV methods, there was no increase in the F-cell ratio during either immersion. In contrast, there was a significant decline in the F-cell ratio during the control: air and thermoneutral immersion, which may indicate that other, undefined variables may impact on the stability of the red cell compartment. The current study is the first to show that the Hct/[Hb] method clearly underestimates PV changes during both thermoneutral and cold-water immersion. Furthermore, RCV was shown, for the first time, to decline during both immersions. However, the changes in the F-cell ratio during this study, did not account for the underestimation of PV change using the Hct/[Hb] method.
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Tunggal, Jonathan Kurniadi. "Cell concentration and drug penetration, implications for the reversal of multidrug resistance in solid tumours." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0017/NQ45743.pdf.
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Chornewich, Cristina. "Bacterial transport in granular porous media: the effects of cell concentration and media pre-coating." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=67039.
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Column transport experiments were conducted under saturated conditions to examine the effects of cell concentration and media pre-coating. Two strains of E. coli were used in the study; the commonly studied laboratory organism E. coli K12 D21 and a mutant of the waterborne pathogen E. coli O157:H7. Column experiments were conducted with both clean sand and sand that was pre-coated with bacteria. The influent concentration of the E. coli strains was varied over several orders of magnitude to examine the effect of cell concentration. Concentration dependent removal rates were observed for both organisms in both the clean and media pre-coated sand columns. It was also found that the media pre-coating either does not influence the transport behavior or it decreases the attachment efficiency. Although differences in transport are observed, these differences are not large enough to have a significant influence on the predicted travel distances.Des expériences de transport par colonne ont été menées afin d'examiner les effets de la concentration des cellules et du pré-revêtement de média. Deux souches de bactéries ont été utilisées: E. coli K12 D12 et une souche mutante E. coli O157:H7. Les expériences par colonne ont été menées avec du sable propre et du sable qui a été préalablement enduit de bactéries. La concentration de l'influent en bactérie a été variée sur plusieurs ordres de grandeur pour examiner l'effet de la concentration cellulaire. Une dépendance du taux d'élimination à la concentration a été observée pour les deux souches de bactéries dans les deux types de sable. De plus, le pré-revêtement de média n'influence d'aucune façon le comportement du transport ni en réduit l'efficacité d'adhésion. Bien que des différences dans le transport ont été observées, celles-ci n'ont eu aucun effet significatif sur la prédiction de la distance à parcourir.
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Fuska, Jana. "The effect of ammonium chloride and leupeptin on the concentration of prosaposin in endosomes and lysosomes of Marshall cells." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0025/MQ50770.pdf.
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Liu, Guansheng, Hua Zhong, Yongbing Jiang, Mark L. Brusseau, Jiesheng Huang, Liangsheng Shi, Zhifeng Liu, Yang Liu, and Guangming Zeng. "Effect of low-concentration rhamnolipid biosurfactant on P seudomonas aeruginosa transport in natural porous media." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/623109.
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Enhanced transport of microbes in subsurface is a focus in bioaugmentation applications for remediation of groundwater. In this study, the effect of low-concentration monorhamnolipid biosurfactant on transport of Pseudomonas aeruginosa ATCC 9027 in natural porous media (silica sand and a sandy soil) with or without hexadecane as the nonaqueous phase liquids (NAPLs) was studied with miscible-displacement experiments using artificial groundwater as the background solution. Transport of two types of cells was investigated, glucose-grown and hexadecane-grown cells with lower and higher cell surface hydrophobicity (CSH), respectively. A clean-bed colloid deposition model was used to calculate deposition rate coefficients (k) for quantitative assessment on the effect of the rhamnolipid on the transport. In the absence of NAPLs, significant cell retention was observed in the sand (81% and 82% for glucose-grown and hexadecane-grown cells, respectively). Addition of low-concentration rhamnolipid enhanced cell transport, with 40 mg/L of rhamnolipid reducing retention to 50% and 60% for glucose-grown and hexadecane-grown cells, respectively. The k values for both glucose-grown and hexadecane-grown cells correlated linearly with rhamnolipid-dependent CSH quantitatively measured using a bacterial-adhesion-to-hydrocarbon method. Retention of cells by the soil was nearly complete (>99%). Forty milligrams per liter of rhamnolipid reduced the retention to 95%. The presence of NAPLs in the sand enhanced the retention of hexadecane-grown cells with higher CSH. Transport of cells in the presence of NAPLs was enhanced by rhamnolipid at all concentrations tested, and the relative enhancement was greater than in the absence of NAPLs. This study shows the importance of hydrophobic interaction on bacterial transport in natural porous media and the potential of using low-concentration rhamnolipid for facilitating cell transport in subsurface for bioaugmentation efforts.
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Vinnakota, Kalyan Chakravarthy. "pH dynamics, glycogenolysis and phosphoenergetics in isolated cell free reconstituted systems and in mouse skeletal muscle /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/8034.
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Heyes, Colin D. "Effects of pH, cations and lipids on the structure, stability and function of bacteriorhodopsin." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/30754.
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Hamilton, Cynthia Louise. "The relationship between red blood cell concentration and inflammation, studies in runners and rheumatoid arthritis patients." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24312.pdf.
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Campoli, Paolo. "Concentration of antifungal agents within host cell membranes: a new paradigm governing the efficacy of prophylaxis." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114373.
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PCZ prophylaxis has proven highly effective in preventing invasive fungal infections, despite relatively low serum drug concentrations. However, high tissue levels of this agent have been reported in treated patients. Therefore, we hypothesized that intracellular levels of antifungal agents are an important factor in determining the success of fungal prophylaxis. To examine the effect of host cell-associated antifungals on the growth of medically important molds, we exposed lung epithelial cells to antifungal agents and removed extracellular drug prior to in vitro infection. Epithelial cells exposed to PCZ and its parent molecule itraconazole, but not other antifungals, were able to inhibit fungal growth for at least 48 hours and were protected from damage caused by infection. Cell-associated PCZ levels were 40 to 50-fold higher than extracellular levels and the drug was predominantly detected in cellular membranes. Fungistatic levels of PCZ persisted within epithelial cells for up to 48 hours. Further co-localization studies using fluorophore conjugated PCZ determined that PCZ concentrates within the endoplasmic reticulum of both host and fungal cells and persists long after drug exposure. Finally, during in vitro infection of PCZ loaded cells, there is a rapid transfer of PCZ from host membrane to fungal membranes. We propose a mechanism where PCZ transfers from host membranes to fungal membranes including the endoplasmic reticulum (ER), where it accumulates to inhibit the ER membrane bound target enzyme CYP51a. Therefore, the concentration of PCZ in mammalian host cell membranes mediates its efficacy in prophylactic regimens and likely explains the observed discrepancy between serum antifungal levels and efficacy.La prophylaxie à l'aide de PCZ est éfficace pour prévenir les infections fongiques invasives, malgré les faibles concentrations sériques. Cependant, des fortes concentrations de PCZ sont trouvés dans les tissus des patients. Nous formulons donc l'hypothése que les concentrations intracellulaires d'antifongiques sont une facteur important pour déterminer le succès des régimes prophylactiques. Pour éxaminer l'effet des concentrations intracellulaires sur des champignons médicale, on a exposé des cellules épithéliales à des concentrations difféerents d'antifongiques pour quelques heures, et qu'on a ensuite enlevé avant d'infecter les cellules avec des spores. Les cellules exposées au PCZ ou à l'itraconazole, mais pas les autres antifongiques, étaient capables d'inhiber la croissance des fongique et prevenir le dommage cellulaires. Les concentrations intracellulaires de PCZ étaient 40 à 50 fois plus élevés que les concentrations extracellulaires, et le PCZ était concentré dans les membranes cellulaires. Des concentrations fongistatiques de PCZ ont persisté dans les cellules pour plus que 48 heures. Par ailleurs, des études de localiaation ont démontré que le PCZ se concentre dans le réticulum endoplasmique des fongi et des cellules épitheliales. Finalement, au cours de l'infection, PCZ est transferé des membranes cellulaires aux fongi, où il s'accumule pour inhiber sa cible, le CYP51a. Donc, l'éfficacité de PCZ pourrait s'éxpliquer par son accumulation dans les membranes cellulaires, expliquant ainsi la descordance entre les niveaux sérumiques et l'éfficacité contre les champignons.
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Heuser, Florian [Verfasser]. "Increasing the Productivity of Whole Cell Biotransformation by Enhancing the intracellular NAD(H) Concentration / Florian Heuser." München : GRIN Verlag, 2009. http://d-nb.info/1188018965/34.
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Verma, Darpan. "Hybrid Solar Energy System with integrated Concentration Photovoltaic Cells and Thermoelectric Devices." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1553613351859182.
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Junior, Roberto Janny Teixeira. "On governing equations and closure relations for the multiscale modeling of concentration polarization in solid-oxide fuel cells: mass transfer and concentration-induced voltage losses." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-07112017-075939/.
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The aim of this dissertation is to appraise and critically reflect on the physical pertinence of governing equations and closure relations often used for the modeling of gas-phase transport phenomena in high-temperature solid-oxide fuel cells (SOFCs). More precisely, this work conducts a critical literature review on the concentration-induced voltage losses (i.e., concentration polarization) resulting from mass transfer limitations. Thus, the overall object of this work was to stress awareness of the limits of mathematical models studied and developed in the SOFC literature to date, and which are specifically related to concentration polarization processes. To a great extent, the design of SOFC porous layers is likened to that of optimizing the transport of multicomponent gas mixtures in structured porous catalysts, for which diffusional and flow limitations are of cardinal importance. In both cases, severe inconsistencies in mass transport models cannot be simply ignored and the main uncertainties in utilizing such models should be clarified. It is hoped that the information herein will serve usefully to support future developments of more consistent theoretical frameworks, thereby improving the confidence on the results of numerical simulations. The critical literature review has been carried out so to identify a number of physical inconsistences, ill-defined approximations, and misleading mathematical derivations. Along the review, it is argued that the choice (or, more properly, the lack of conceptual refinement) of a particular mathematical model can significantly impair the \"prediction\" of transport processes relevant to concentration-induced power losses in SOFCs. One of the keystones of this work was therefore to re-interpret and thus to reassess the frequently contradictory literature related to certain classes of gas-phase transport models pertinent to the evaluation of concentration polarization. With this revisionary approach, it is expected that one could reduce confusion, clear up apparent contradictions, and improve the possibility of gaining new insights.Esta dissertação tem o objetivo de avaliar e refletir criticamente sobre a pertinência física de equações de conservação e de relações de fechamento, frequentemente utilizadas na modelagem multiescala de fenômenos de transporte em células a combustível de óxido-sólido (SOFC). Dêu-se atenção especial ao escoamento em \"microescala\" de misturas gasosas multicomponentes, dentro de meios porosos quimicamente reativos. Em outras palavras, esta monografia busca ressaltar quais os limites para aplicação de certas classes de modelos matemáticos, os quais têm sido desenvolvidos e utilizados na literatura de SOFCs até o presente momento. O projeto de camadas porosas de SOFCs assemelha-se à tarefa de otimizar processos de transporte em catalisadores estruturados, para os quais a existência de limitações de transporte por difusão e por escoamento tem importância primordial. Por esta razão, inconsistências originadas em modelos de fenômenos de transporte não podem ser, simplesmente, negligenciadas e, portanto, as principais incertezas ao se utilizar tais modelos devem ser devidamente esclarecidas. Espera-se, com efeito, que as informações contidas neste trabalho sejam úteis para futuros desenvolvimentos teóricos mais consistentes, de forma a aumentar a confiabilidade no uso de resultados obtidos por simulações numéricas.
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Bagdonaitė, Ernesta. "Metanolio kuro elemento statinių charakteristikų tyrimas." Bachelor's thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2010~D_20100902_233011-07391.
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Bakalauro darbą „Metanolio kuro elemento statinių charakteristikų tyrimas“ sudaro įvadas, keturi skyriai, išvados bei rekomendacijos. Darbo apimtis 33 lapai. Likusioji dalis pateikiami priedai (eksperimento rezultatai). Darbe išanalizuotos metanolio kuro elemento voltamperinės bei galių charakteristikos, esant skirtingoms metanolio koncentracijos tirpalams. Įvadinėje dalyje iškeliamas darbo tikslas, uždaviniai, problematika bei tematikos aktualumas. Pirmame skyriuje aptariami kuro elementai, jų veikimo principai, panaudojimas. Antrame skyriuje aptariamas tiesioginio veikimo metanolio kuro elementas. Sekantis skyrius skirtas eksperimento matavimo metodikai, o ketvirtame skyriuje pateikiami eksperimento metu gauti rezultatai naudojant metanolio kuro elementą, esat skirtingoms metanolio koncentracijos tirpalams.The bachelor’s thesis “Methanol fuel cell static characteristic and power characteristic research” consists of the introduction, 3 sections, conclusions and recommendations. The thesis comprises 33 pages. The rest of the accessories (experimental results). At the thesis is presented analysis methanol fuel cell power characteristic and performance at different methanol concentration solutions. The introduction sets the problem, the aims, the goals of the study and relevance of the topic. The first chapter is devoted to fuel cells, their operating principles to use. The second section deals with the direct methanol fuel cell operation. Next chapter for the experimental measurement methods, and the fourth section presents the experimental results obtained using methanol fuel cell, you are a different concentration of methanol solutions.
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Ritou, Arnaud. "Développement, fabrication et caractérisation de modules photovoltaïques à concentration à ultra haut rendement à base de micro-concentrateurs." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY059/document.
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Les modules photovoltaïques à concentration (CPV) ont tendance à se miniaturiser. D’une part, la distance focale plus courte des optiques de concentration permet de réduire le besoin en matériaux pour l’assemblage du module ; et d’autre part, le rendement des modules est sensiblement meilleurs que ceux des modules CPV de taille normale. L’étude de chaque élément de la chaine de pertes dans la littérature des micro-concentrateurs a permis de confirmer cette tendance. Cette thèse aborde les problématiques de coût et de rendement à travers la conception optique d’un concentrateur à deux étages de lentilles, sa fabrication puis une étude approfondie de ses performances.La méthode de conception, développée à partir de lois d’optique géométrique et non-imageante, définit le profil des lentilles à λ=589nm en premiers lieux. Ensuite, une simulation par tracé de rayons permet d’optimiser ces lentilles pour l’ensemble du spectre solaire puis d’étudier l’impact de leur désalignement lors de la mise en module. Les limites des déplacements des éléments du module ainsi déterminées conditionnent la précision de sa fabrication. Dans notre cas, l’alignement est réalisé automatiquement par un jeu de repères mécaniques lors du moulage simultané des optiques primaires (POE) et des optiques secondaires (SOE). Contrairement aux procédés habituels, ce procédé de moulage innovant permet d’assembler un module en seulement trois étapes au lieu de cinq.Pour caractériser les micro-concentrateurs réalisés, une méthode de mesure du rapport module à cellule (CTM) est développée. Pour cela, le rendement des cellules est mesuré en simulateur solaire avant et après leur mise en module. Les cellules multi-jonctions mises en œuvre étant sensibles aux variations spectrales et spatiales de l’éclairement, la validation préalable de ces mesures est primordiale. En complément du CTM qui quantifie la somme des pertes introduites lors de la mise en module, d’autres mesures sont développées pour comprendre la chaine de perte plus en détails.Le dispositif étudié au cours de cette thèse utilise des cellules triple-jonction de 0,6 x 0,6mm² avec une concentration de 1000X et atteint un rendement de 29%. Le CTM est de 70% et l’analyse de la chaine de perte montre que le procédé inventé n’impacte pas ou peu les performances du module. De plus, la détermination de la chaine de perte montre que les pertes par réflexion et par absorption sont prédominantes, au même titre que les pertes dues à la diffusion des lentilles ainsi que les pertes dues aux non-uniformités d’éclairement sur la celluleThe actual trend of CPV is the micro-scaling of modules. A bibliographic study shows that shorter focal length of optics implies less material consumption in manufacturing and an enhanced efficiency of the modules. In this thesis, a double stage refractive micro-concentrator is designed, manufactured and characterized. First, the optical design of the concentrator is based on non-imaging technics. Thus, the profile of the lenses is generated for a single wavelength. Then, a ray tracing simulator is used to optimize the lens profile for the overall solar spectrum and study the concentrator element misalignment effect on the performances.Secondly, a three steps self-assembly process is developed instead of the usual five steps one. Both POE and SOE lenses of our device are molded simultaneously and a mechanical guidance system in the mold ensures the alignment of the micro-concentrator elements (POE, SOE and Cell).Finally, the performances measurements of the manufactured modules are managed in solar simulators in which the lightening condition are previously studied and validated. Comparing the bare cells efficiency with the module efficiency, the cell-to-module ratio (CTM) represents the overall losses in the module. Further experiments are managed to quantify each loss of the module. The manufactured and characterized micro-concentrator is a 1000X concentrating ratio with 0.6 x 0.6mm² triple junction cells. It efficiency is 29% with a 70% CTM. Finally, the loss chain study reveals that the three steps self-assembly process is reliable
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Awwad, Yousef Ahmad. "The Effect of Interleukin-1 (IL-1) Concentration on Single Cell NF-kappaB Activation in a Gradient-Generating Microfluidic Device." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/35315.
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Interleukin-1 (IL-1) is a multifunctional cytokine produced primarily by activated monocytes/macrophages and by a variety of other cell types. IL-1 plays an integral role in the immuno-inflammatory response of the body to a variety of stimuli including infection, trauma and other bodily injuries. Once IL-1 is released from the synthesizing cell, it acts as a hormone, initializing a variety of responses in different cells and tissues. These responses are believed to be crucial to survival and are termed acute-phase responses. NF-κB is a family of dimeric transcription factors that control the expression of hundreds of genes which regulate cellular stress responses, cell division, apoptosis, and inflammation. NF-κB dwells in the cytoplasm of the cell until activation in response to a wide range of extracellular stimuli including signaling molecules such as cytokines. NF-κB regulates transcription and gene expression through nucleocytoplasmic transport. Most previous studies on NF-κB activation have been performed using bulk assays to look at populations of cells. Determining cell variance at a single-cell level is crucial in understanding the full mechanisms of drug response. The goal of this study is to analyze the effects of variant concentrations of IL-1β on the activation of NF-κB in individual cells through use of a microfluidic gradient generator.
The gradient generator was adopted from Jeon et al and used principles of diffusive mixing and splitting of flows in order create a solute concentration gradient. A soft lithography procedure was used. Briefly, the design was printed on a transparency using a high resolution printer. A master of the design is then created using an SU-8 photoresist and UV light to imprint the design on a silicon wafer. The master is then used to create a Polydimethylsiloxane (PDMS) mold of the design which can be irreversibly attached to a glass slide through oxidation in order to close off the microfluidic channels.
FITC-conjugated β-Casein (a protein with similar molecular weight to IL-1β) was used in order to verify the gradient generated by the design. The concentration gradient was analyzed by measuring fluorescent intensity of images taken under a UV light microscope and found to agree with microfluidic simulations run on COMSOL. A procedure for culturing cells in a microfluidic device was then adapted from Jeon that is explained in detail in Chapter 3.
Two main trends were revealed; firstly, as IL-1β concentration decreased, the percent of cells activated also decreased. Secondly, as IL-1β concentration decreased, the activation time of the responding cells increased. Cells were observed to act in a single-cell manner; in which multiple cells subjected to the same concentration would not all respond in the same fashion. No major activation threshold was observed but two minor thresholds were; the first at 0.02 ng/mL IL-1β where activation levels drop from 20% to around 5%. The second around 1 ng/mL, in which all greater concentrations show nearly complete activation of all cells exposed.
Of the cells that activated, the activation times were recorded and analyzed as well. In general, a decrease in IL-1β concentration caused cells to take longer to activate. Concentrations greater than 5 ng/mL responded on average in 30 minutes with a significant amount of variation. Between 5 ng/mL and 0.1 ng/mL, activation time increased as IL-1β concentration decreased in a linear fashion when concentration was plotted on a base-10 log scale. Below 0.1 ng/mL, the trend disappears and an average activation time of around 95 minutes is observed that no longer depended on concentration. This is interesting because fewer and fewer cells are activating in this concentration range but activation time follows no trend and remains partially stochastic with times ranging from 80 to 105 minutes.
The previous results were all observed with a continuous flow and stimulation of the cells. Experiments were also run by only exposing the cells to the IL-1β for 10 minutes and then replacing the flow with a buffer. These studies yielded interesting results; the fraction of activated cells reported the same trends and values as those that were continuously stimulated. The activation times, however, were delayed between 10 and 20 minutes but otherwise followed the same trend as the continuous stimulation. These results suggest that a brief exposure to an external stimulant is all it takes for the cascade of intercellular events to take place and cause NF-κB translocation.Master of Science
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Ma, Yanrui. "Facile Fabrication of One- and Two-Dimensional Orthogonal Peptide Concentration Gradient Surfaces for Directed Stem Cell Differentiation." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1405936934.
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Taylor, Leander III. "Determination of the Mechanical Properties of Electrospun Gelatin Based on Polymer Concentration and Fiber Alignment." VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd/1287.
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The process of electrospinning has given the field of tissue engineering insight into many aspects of tissue engineered scaffolds, including how factors such as fiber diameter and porosity are affected by polymer concentration. However, the affects of fiber alignment upon the material properties of electrospun scaffolds remains unclear. The purpose of this study is to determine how the material properties of electrospun gelatin scaffolds are affected by changes in fiber alignment and starting gelatin concentration. Gelatin scaffolds, with starting concentrations of 80, 100, and 130mg/m1, were electrospun onto a target mandrel rotating at various speeds. Samples of each scaffold were taken parallel and perpendicular to the axis of mandrel rotation. Fast Fourier Transform (FFT) analysis was performed on these samples, to determine how fiber alignment is affected by starting polymer concentration and the rotational speed of the target mandrel. Mechanical tests were aiso performed on these samples. Results were analyzed by Three-way ANOVA. It was determined that starting gelatin concentration, mandrel speed, and direction of fiber alignment interact together to produce effects on the mechanical properties of electrospun gelatin scaffolds.
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Jantakananuruk, Nattikarn. "Performance, Temperature and Concentration Profiles in a Non-Isothermal Ammonia-Fueled Tubular SOFC." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-theses/1295.
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Ammonia has emerged as an attractive potential hydrogen carrier due to its extremely high energy density (hydrogen density), ease of storage and transportation as a liquid, and carbon-free nature. Direct utilization of ammonia in high-temperature solid oxide fuel cells (SOFCs) has been demonstrated over the past decade. Concurrence of in situ endothermic ammonia decomposition and exothermic electrochemical hydrogen oxidation permit efficient heat integration. In this study, the experimental analyses of axial temperature and concentration profiles along the tubular SOFC (t-SOFC) fed directly with ammonia are performed to investigate the coupled ammonia decomposition and hydrogen oxidation reactions as well as the effect of polarization. Fast ammonia decomposition over the Ni catalyst is evident at the inlet of t-SOFC and complete ammonia conversion is confirmed above 600ºC. It is found that direct ammonia-fueled t-SOFC and an equivalent hydrogen-nitrogen fueled t-SOFC provide identical performances. With 100 SCCM of ammonia fuel feed, a maximum power of 12.2 W and fuel utilization of 81% are obtained at 800ºC in a t-SOFC with active area of 32 cm2. The temperature and concentration profiles validate that the efficient heat integration inside ammonia-fueled t-SOFC is feasible if t-SOFC is operated at the temperature of 700ºC and below. The 23-hour performance test and SEM-EDS images of the fresh and used Ni-YSZ cermet surfaces confirm uniform performance and good durability of ammonia t-SOFC.
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Ahlman, Justin Robert. "Concentration of specific biogenic amines in ventricular CSF of type A and B Parkinson's disease patients on Sinemet." CSUSB ScholarWorks, 2001. https://scholarworks.lib.csusb.edu/etd-project/1912.
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Wang, Zhaowei. "Two Approaches for Cell Retention in Perfusion Culture Systems." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1274106674.
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Ye, Xuemin. "The effect of water pH on swimming performance, blood pH, red cell pH, ion concentrations and catecholamine concentrations in plasma, and gill potential in rainbow trout (Salmo gairdneri)." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26676.
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The effect of transferring fish from water at pH 7.0 to either more acid or more alkaline conditions was to reduce the maximum critical velocity of the fish. In water of pH 4.0, 5.0, and 10.0, the maximum critical velocity was only 54.5%, 66.5%, and 61% respectively of that recorded for fish in the water of pH 7.0. Thus, both acid and alkaline conditions in the water reduce the aerobic swimming capacity of trout.
Exposure to acid conditions increased mucus secretion and this was associated with an increase in coughing and breathing frequency in resting fish. Coughing rate increased from 41/hr to 592/hr; and respiration frequency increased from 81/min to 104/min when fish were transferred from water at pH 7.0 to water at pH 4.0.
In comparing fish exposed to acid and alkaline waters, the results indicates that fish have a greater capacity to regulate blood pH in acid than in alkaline conditions.
The gill potential was strongly dependent on water pH, being negative in neutral water, but positive in acid water and more negative in alkaline solution. Catecholamine levels increased significantly during acid exposure, but were not altered during alkaline exposure. The increasing catecholamine levels appeared at different time periods in different fish during acid exposure and seemed to be associated with the death of the fish.
Na⁺ and C1⁻ ion concentrations in plasma decreased significantly after 24hrs of acid exposure, but did not change significantly in alkaline water. This may indicate that ionoregulatory disturbance in plasma is one of the reasons for the decrease in the maximum critical velocity in acid water, but not in alkaline water.Science, Faculty of
Zoology, Department of
Graduate
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Moore, Gareth James. "Methane conversion over nickel/zirconia solid oxide fuel cell anodes : influence of dopant materials, methane/oxidant ratio and sulphur concentration." Thesis, Keele University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545749.
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Behan, John. "The utilisation of artificial insemination in swine at reduced sperm cell concentration, and the subsequent effect upon fertility and fecundity." Thesis, Royal Veterinary College (University of London), 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618281.
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Linhares, Boakari Yatta. "EFFECTS OF A SYSTEMIC HIGH UREA CONCENTRATION ON THE ENDOMETRIAL AND EMBRYONIC TRANSCRIPTOMES OF THE MARE." UKnowledge, 2019. https://uknowledge.uky.edu/gluck_etds/42.
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Pregnancy loss remains a major source of economic cost to the equine industry. Frequently, the exact causes of pregnancy loss remain unknown. It has been shown, in other species, that increased dietary protein leading to elevated blood urea nitrogen concentrations (BUN) can be a factor in decreased survival of the early embryo. Our studies provided novel information regarding the effects of elevated BUN on endometrium and embryos from mares as well as insights on changes in their gene expression. Our first objective was to develop an experimental model to elevate BUN during diestrus using intravenous urea infusion. We analyzed the effects of an acute elevation in BUN on uterine and vaginal pH along with changes in the endometrial transcriptome of mares with RNA sequencing. There was a significant increase in BUN and a decrease in uterine pH in the urea group compared to the control group. A total of 193 genes were differentially expressed (DEG) between the urea and control groups. The DEG were predicted to be related to cell pH, ion homeostasis, changes in epithelial tissue, fatty acid metabolism, and solute carriers. Our second objective was to evaluate the effects of elevated BUN in the endometrium of mares using a chronic oral urea administration to elevate BUN in mares. Uterine and vaginal pH were evaluated and RNA sequencing of the endometrium was again performed. There was an increase in BUN in the urea-fed mares, but no significant change in uterine or vaginal pH between the groups. A total of 60 DEG were characterized, with prediction of transcriptomic changes in the endometrium of mares related to cell death (necrosis) and cellular movement (invasion of cells). Our third objective was to determine the effects of a high BUN on the transcriptome of day-14 embryos. There was a positive correlation between plasma BUN and blastocoele fluid urea nitrogen concentration. Changes in embryo transcriptome were related to survival of organism, angiogenesis, adhesion, and quantity of cells. Our final objective was to evaluate the correlation between BUN and follicular fluid urea nitrogen and evaluate the survival of embryos collected from donor mares with high BUN concentrations. Urea nitrogen concentration was positively correlated between the plasma and follicular fluid of mares. Additionally, there was a higher pregnancy rate when embryos were collected from mares with lower BUN. Overall, these results further elucidate the mechanisms through which urea affects endometrial and embryonic transcriptome of mares with high BUN, serving to identify effects of a high BUN in the reproductive tract of mares that might lead to decreased fertility.
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Walls, A., and Phillip R. Scheuerman. "The Effects of Substrate Concentration and Cell Density on the Rate of Degradation of o-cresol Using a Freeze-Dried Consortium." Digital Commons @ East Tennessee State University, 1998. https://dc.etsu.edu/etsu-works/2917.
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Tsurumi, Fumitoshi. "The intracellular Ca²⁺ concentration is elevated in cardiomyocytes differentiated from hiPSCs derived from a Duchenne muscular dystrophy patient." Kyoto University, 2020. http://hdl.handle.net/2433/253462.
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Rassie, Candice. "Optimisation of a microfluidic device for the pre-concentration and size separation of cell free foetal DNA from maternal plasma by capillary electrophoresis." University of the Western Cape, 2012. http://hdl.handle.net/11394/4589.
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>Magister Scientiae - MScThe discovery of cell free foetal DNA (cffDNA) in 1997 allows for the combination of accuracy as well as non-invasiveness for prenatal diagnosis. This non-invasive genetic test requires only a maternal blood sample from which the cffDNA can be isolated and analysed. In this work cffDNA was isolated from a maternal blood sample using a micro-fluidic device which was fabricated using hot embossing and laser ablation techniques. The DNA sample was first pre-concentration by electrokinetic trapping (EKT) and then isotachophoresis (ITP). The concentrated sample was then separated by size using capillary electrophoresis (CE), all in a single device. All parameters and processes concerned with the micro-fluidic device were optimised sequentially. These parameters include both the chemical components as well as the physical processes which occur. The DNA used for the optimisation protocol was analysed using fluorescence spectroscopy, agarose gel electrophoresis as well as an Agilent Bioanalyser. The optimised protocol included a 9% acrylamide/pDMA matrix, 3 M N,N-dimethylurea as a denaturing agent, with tris based buffers for pre-concentration steps and 1X TBE (tris/borate/EDTA) buffer for capillary electrophoresis. The applied voltage of ITP was 300 V and CE was carried out at 180 V. The timing at which DNA was extracted from the device was kept at time = 60 s intervals. The optimised protocol was then used for real sample analysis and these samples were obtained from mothers pregnant with male foetuses. The DNA extracted from the micro-fluidic device was then analysed using real time PCR (RT-PCR) in order to distinguish which was maternal and which was foetal. This was carried out by amplification of male and general (present in male and female) genes respectively. RT-PCR results confirmed that only the male specific gene was amplified in initial samples exiting the device and it was thus successful in isolating cffDNA from a maternal plasma sample.
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Svensson, Johanna. "Methodological aspects within the FMCA-method : do incubation time and the amount of tumor cells influence the antitumoral effect?" Thesis, Uppsala University, Department of Medical Biochemistry and Microbiology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9235.
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ABSTRACT
Chemotherapy is a common method used for cancer treatment. Especially when it concerns cancers that have grown invasively it seems to be the only efficient treatment due to the substances ability to reach and affect almost the entire body. One major obstacle regarding chemotherapy is that the patients often develop resistance to the cytotoxic substances used. Fluorometric microculture cytotoxicity assay (FMCA) is a method developed to measure sensitivity of tumor cells to different cytotoxic substances in vitro. The assay is based on hydrolysis of fluorescein diacetate to fluorescein by cells with intact cell membranes after incubation with drugs for 72 hours. This study investigated the impact of two methodological factors that may cause errors in the achieved results; namely the possible occurrence of drug decay during incubation and the use of an inappropriate amount of cells. These factors were tested by exposing the cytotoxic drugs to pre-incubation in absence of tumor cells for different times and to use suspensions with different concentrations of cells. The results indicated occurrence of drug decay in 3 of the 18 substances tested and that the amount of cells affected the results for most of the drugs tested but to different extent.
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Besson, Pierre. "Compréhension des comportements électrique et optique des modules photovoltaïques à haute concentration, et développement d’outils de caractérisations adaptés." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI013/document.
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Le travail de thèse effectué a pour objectif d'amener vers une meilleure compréhension des comportements électrique et optique des modules CPV, dans des conditions environnantes variables. La première partie est consacrée à l’étude de la performance des modules en conditions réelles de fonctionnement. Quatre technologies de module, toutes équipées de cellules triple-jonctions, mais de concentrateurs optiques différents, ont été testées en extérieur sur des périodes de un mois à deux ans. Les résultats montrent que la sensibilité à la température de lentille, la température de cellule et au spectre incident varie selon le type d'architecture optique. La sensibilité la plus importante à la température de lentille a été obtenue pour un dispositif sans optique secondaire. Le coefficient en température de la tension Voc a été calculé et varie entre les technologies. Enfin, les variations importantes de facteur de forme avec le spectre incident observées pour une technologie, mettent en évidence la nécessité d'étudier les phénomènes de non-uniformités d'irradiance sur la cellule. Dans une deuxième partie, le développement d’un banc de test en intérieur permettant de mesurer les performances électriques et optiques est présenté. Ce banc a pour objectif de permettre la reproduction des conditions réelles de fonctionnement des modules de façon contrôlée en intérieur. Un système d’imagerie est utilisé pour déterminer la distribution spatiale et spectrale d’irradiance sur la cellule. Associé à un traceur de courbes IV, il vise à caractériser les effets de flux non-uniformes sur la cellule. Le banc de mesure a pour avantage de découpler les paramètres d’études, telles que la température de la lentille et la température de la cellule, et permet ainsi de décorréler leurs effets respectifs sur l'ensemble optique-cellule, ce qui n’est que difficilement possible sur des mesures en extérieur. Le procédé de calibration et la validation du dispositif sont détaillés dans le manuscrit. Enfin, dans une dernière partie, le banc développé est utilisé pour caractériser trois différents dispositifs CPV : un sans optique secondaire, et deux avec des optiques secondaires différentes. Les impacts de la distance lentille-cellule et de la température de lentille sur les performances de la cellule sont quantifiés optiquement et électriquement. Les résultats montrent comment ces paramètres modifient la distribution de densités de courant des sous-cellules, et donc le comportement électrique du dispositif. Ils soulignent plus spécifiquement comment les non-uniformités spectrales et spatiales affectent les performances de la cellule pour les différents concentrateurs. Le dispositif sans optique secondaire montre une sensibilité importante à la température de la lentille et la distance optique primaire-cellule, qui se traduit par une perte de production d'énergie dans des conditions réelles de fonctionnementThe goal of this doctoral thesis is to bring answers to a better understanding of the electrical and optical behavior of CPV modules, under different operating conditions. In the first part, a study on module performance under real conditions is presented. Using an outdoor automated test bench, the sensitivity of four different CPV module technologies to most operating conditions relevant to CPV systems has been studied, namely DNI, spectrum, cell and lens temperature and clearness of the sky. In order to isolate the influence of a single operation parameter, the analysis of outdoor monitoring data from one month to two years is performed. The results show how the optical design influences the sensitivity of the electrical parameters to the mentionned operating conditions. The effect of lens temperature on cell current has been found to be maximum for the CPV module without Secondary Optical Element. Also the $V_{oc}$ thermal coefficient was found to vary between module technologies. Finally, the important variations of the fill factor for one technology underlines the need of studying non-uniformities effects on the cell performance. According to the results observed outdoors, an indoor tool was developed in order to uncorrelate outdoor parameters. A test bench that measures multi-spectral irradiance profiles, through CMOS imaging and bandpass filters in conjunction with electrical $IV$ curves, is used as a mean to visualize and characterize the effects of chromatic aberrations and nonuniform flux profiles under controllable testing conditions. The bench allows decoupling the temperatures of the Primary Optical Element and cell allowing the analyze of their respective effects on optical and electrical performance. In varying the temperature of the Primary Optical Element, the effects on electrical efficiency, focal distance, spectral sensitivity, acceptance angle, or multi-junction current matching profiles can be quantified. Calibration procedures and validation process are detailed. Finally, the developed testbench is used for analyzing the behvaior of three different CPV devices : one without Secondary Optical Element, and two with different Secondary Optical Elements. The impacts of cell position and lens temperature on the cell performance are quantified optically and electrically. The results show how these parameters modify the current density distribution of the subcells, and hence the electrical behavior of the device. They underline more specifically how spectral and spatial non-uniformities affect the cell performance for the different devices. The device without SOE shows a strong sensitivity to lens temperature and POE-cell distance, that will correspond to a decrease of energy production under real conditions of operation
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Aziz, Seemal. "Antibiotic Susceptibility Testing: Effects Of Variability In Technical Factors On Minimum Inhibitory Concentration Using Broth Microdilution." Thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-454819.
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Background Broth microdilution (BMD) is a gold-standard reference method to determine minimum inhibitory concentration (MIC) of antibiotics. For this, a standardized concentration of bacterial inoculum (2e5–8e5 colony-forming units, CFU/ml) is added to progressively higher concentrations of antibiotics. Bacteria stop growing at a particular antibiotic concentration termed MIC. Like other assays, various biological and/or technical factors can affect BMD results. Aims To investigate the effects of inoculum concentration (5e4–5e6 CFU/ml), growth-medium concentration (cation-adjusted Mueller-Hinton Broth (CAMHB)), ranging 0.5x to 2x (1x as standard)) and age (<6-months or >1-year old) of fastidious medium on MIC results. And to compare BMD results using 5 different brands of CAMHBs and 1 cation-non-adjusted MH-broth (non-CAMHB). Methods 12 isolates of bacteria (gram-positive (n=3), gram-negative(n=5), fastidious isolates (n=7)) and custom-made antibiotics-containing plates for gram-positive (11 antibiotics) or gram-negative bacteria (10 antibiotics) were used. Overnight-grown colonies were used to prepare BMD solutions (MH-broth + inoculum +/- fastidious) which were plated on antibiotic-plates as well as diluted prior to plating on agar-plates. Antibiotic- and agar-plates were incubated (18–20hr, 35°C) and used to determine MICs (following European Committee on Antimicrobial Susceptibility Testing instructions) and actual number of viable bacteria in BMD solutions, respectively. Results Increasing inoculum concentration increased MICs of all antibiotics except cefoxitin. Piperacillin–tazobactam, levofloxacin, benzylpenicillin and ampicillin were especially sensitive to increase in inoculum and showed a 4-fold increase in >50% isolates. MICs for tobramycin, tigecycline and gentamicin increased by 2-fold in >50% isolates every time MH-broth concentration increased. Age of fastidious medium had no decipherable pattern of effects on MIC. All MH-broths gave similar results except when testing daptomycin which gave higher MICs with non-CAMHB compared to CAMHB. Conclusion This research reveals some technical factors affecting MIC results. These results could help define parameters for automated BMD-performing-systems. However, this research shows only trends as more replicates are needed to determine statistically significant results.
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Diehl, Jeremy Howard. "CHANGES IN SERUM ICAM-1, SERUM VCAM-1, AND SERUM E-SELECTIN CONCENTRATION FOLLOWING PERIODONTAL SCALING AND ROOT PLANING." VCU Scholars Compass, 2007. http://scholarscompass.vcu.edu/etd_retro/133.
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Cellular adhesion molecules (CAMs) and selectins are cell-surface proteins involved in the binding of cells to the vascular endothelium. Elevated levels of sCAMs and soluble E-selectin (sE-selectin) have been reported in patients with periodontitis. The aim of this study was to determine if periodontal scaling and root planing would influence the serum concentration of sICAM-1, sVCAM-1, and sE-selectin. Twenty-one subjects with chronic periodontitis received scaling and root planing in conjunction with blood serum sample analysis using enzyme-linked immunosorbent assay (ELISA), to determine if periodontal instrumentation results in changes in serum concentrations of sICAM-1, sVCAM-1, and sE-selectin. No change was observed in serum concentration of sICAM-1 or sVCAM-1. However, in a subset of 17 patients a statistically significant change in serum sE-selectin was observed (P < 0.05). This suggests that there is a decrease in endothelial activation following periodontal treatment.
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Pinkerton, Thad Marshall. "Sensitivity of Half-Cell Potential Measurements to Properties of Concrete Bridge Decks." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1258.
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Half-cell potential testing has been recommended as a non-destructive method for assessing the corrosion potential of reinforcing steel in concrete bridge decks. The technique is particularly useful because it can be utilized to evaluate the probability of corrosion before damage is evident at the surface of a bridge deck. The specific objective of this research was to quantify the effects of age, chloride concentration, concrete cover thickness, spatial position, temperature, and presence or condition of epoxy coating on half-cell potential measurements of concrete bridge decks typical of those in Utah. The laboratory testing associated with this research followed a full-factorial experimental design. Nine rectangular concrete slab specimens were prepared, each containing three black reinforcing steel bars at three different concrete cover depths and four epoxy-coated bars each having different coating conditions. Three replicate slabs were created at each of three different chloride concentrations. Three repeated measurements were made at each of three locations along each of the seven bars in all nine of the slabs at three ages, with testing performed at three temperatures per age. In addition, compressive strengths of the concrete cylinders were measured at 7 and 28 days. Statistical analyses of the half-cell potentials were performed using analysis of variation and Tukey's method for multiple comparisons. Although American Society for Testing and Materials C 876 only specifies the measuring of half-cell potentials of uncoated reinforcing steel, credible half-cell potentials were also obtained for epoxy-coated rebar in this research. The results of the testing indicated that all of the factors except for cover thickness and spatial position have important impacts on half-cell potentials over the ranges of levels investigated in this research. Half-cell potential measurements became consistently less negative with increasing age and consistently more negative with increasing chloride concentrations and increasing temperature. With regard to the factor of treatment, the uncoated rebar had the most negative half-cell potential, followed by epoxy-coated rebar with rib scrapes, pliers strikes, end cuts, and full epoxy coatings, in that order. While these data indicate that a coating, even damaged, reduces the probability of corrosion when compared to uncoated rebar, the data also suggest that both the amount and distribution of the coating damage over the affected rebar influence corrosion. Given these research findings, bridge engineers and managers should have confidence in using half-cell potential testing for assessing the corrosion probability of reinforcing steel in concrete bridge decks. In decks with properties similar to those investigated in this research, variations in age, chloride concentration, temperature, and presence or condition of epoxy coating cause variation in half-cell potential readings consistent with the effects of these factors on corrosion. Therefore, the half-cell potential technique is recommended for assessing the probability of corrosion of reinforcing steel on bridge decks. Although the use of epoxy-coated reinforcement, even when damaged, reduces the probability of corrosion, care should still be taken to minimize any damage to the coating during shipping and field handling. Owners and contractors alike should establish appropriate inspection protocols and repair methods for epoxy-coated reinforcing steel used on bridge decks to ensure maximum service life.
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Macalintal, Lizza M. "IN OVO SELENIUM (SE) INJECTION OF INCUBATING CHICKEN EGGS: EFFECTS ON EMBRYO VIABILITY, TISSUE SE CONCENTRATION, LIPID PEROXIDATION, IMMUNE RESPONSE AND POST HATCH DEVELOPMENT." UKnowledge, 2012. http://uknowledge.uky.edu/animalsci_etds/4.
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Studies were conducted to investigate the effects of in ovo injection of selenium (Se) either as seleno-methionine (Se-Met) or sodium selenite (Na2SeO3) into the yolk of incubating eggs on tissue Se concentration, embryo livability, lipid peroxidation, immune response and growth performance. When white-shelled eggs were injected with 0.1ml of solutions providing 0, 2.5, 5, 10 or 20 μg Se/egg, no detrimental effects on embryo viability at 20 days of incubation were noted. The effects on tissue Se concentrations suggested that Se-Met and Na2SeO3 were metabolized differently by the chick embryo. In a subsequent study using injection doses up to 60 μg/egg, a greater linear response in tissue Se was obtained with Se-Met, compared with Na2SeO3 (P < 0.01). Minimal changes in heart and breast muscle Se concentrations were noted above the 40 μg dose when Na2SeO3 was used (P > 0.05). In a study with broiler eggs, injection doses of 0, 2.5, 5, 10, 20 and 40 μg Se/egg were used. Se-Met or Na2SeO3 at doses up to 40 μg Se/egg had little effect on embryo viability. Injecting Se-Met resulted in greater tissue Se accumulation than Na2SeO3 at 20 days of incubation. In another study with broiler eggs using injection doses up to 40 μg Se/egg, Se-Met injection resulted in higher hatchability, reduced lipid peroxidation in the lung and heart muscle of the embryos after 20 days incubation and higher Se concentrations in heart and breast muscle of hatched chicks through 7 days and in lung through 21 days of growth. In a feeding trial with broiler breeder hens, adding 0.3 mg/kg of Se as Se yeast or Na2SeO3 to the diet improved tissue Se status at hatching of progeny chicks. Taken together, these results indicate that injection of Se into the yolk of incubating eggs may be useful for enhancing Se status during embryonic and early post-hatch development. Therefore, the improvement in Se status using this method in conjunction with dietary Se supplementation of breeder hens would be much greater than with only using dietary supplementation.
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Coyne, Jeffrey Michael. "Flow Induced Failures of Copper Drinking Water Tube." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/32765.
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Excessive water flow velocities can contribute to rapid failures of copper premise plumbing systems. This is the first fundamental study to scientifically isolate mechanistic impacts from distinct flow induced failure mechanisms that include concentration cell corrosion, cavitation, particle/bubble impingement and high velocity impingement. Concentration cell effects resulting from exposing different copper surfaces to different flow regimes created a strong electrochemical cell that caused rapid corrosion that persisted for periods lasting from hours to days in certain waters. Free chlorine appeared to inhibit this effect in a range of waters. Under typical water chemistries the resulting non-uniform attack diminished, presumably due to formation of a protective scale or rust layer. Consequently, concentration cell corrosion would not be a major contributor to damage from high flow rates in the range of fresh waters investigated.
In experiments using an ultrasonic processor, implosion of vaporous cavitation bubbles against a copper surface caused dramatic pitting, considerable copper weight loss, and, in some cases, the development of pinhole leaks. Changes in water chemistry and the existence of a pre-existing protective scale layer had nearly no mitigating effects on copper cavitation damage. An exponential relationship was found between the initial copper pipe wall thickness and the time necessary to cause a leak via vaporous cavitation. On the basis of this relationship, a Type M tube would be expected to last 23 and 3000 times less than a Type K and L tube, respectively, when facing continual cavitation attack. However, it was not possible to re-create cavitation damage in any practical circumstance that was tested in copper pipes, even though it is strongly believed that cavitation can play a practical role in service failures.
On the basis of the above results, it was hypothesized that brief intervals of cavitation could remove protective scale from portions of the copper pipe surface exposed to high turbulence. In this case, even if minimal damage from cavitation occurred directly, it could allow concentration cell corrosion to become a significant contributor to non-uniform corrosion damage. On the basis of preliminary testing, it appears that this idea has considerable merit. A combination of brief cavitation and waters that create strong concentration cell effects is expected to cause serious damage to copper pipe. These potential synergies are deserving of additional research.
In experiments testing the effect of high velocity jets (17.5 ft/sec) impinging against submerged copper plates perpendicularly and longitudinally, plates in heated sea water were aggressively gouged and penetrated. It is believed that the copper plate damage resulted from a combination of mechanisms including concentration cell corrosion, cavitation implosion, and high velocity impingement.
Impingement of sand on the surface of copper tube created very little damage. This was surprising given prior reports in the literature.Master of Science
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Stuart, Mark R. "Influence of Carbohydrate Starvation on the Culturability and Amino Acid Utilization of Lactococcus lactis." DigitalCommons@USU, 1999. https://digitalcommons.usu.edu/etd/5461.
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Lactococci are widely used in the cheese industry as a starter culture. Starter cultures face carbohydrate starvation due to the absence of a fermentable carbohydrate in the cheese curd after pressing. Starvation leads to a decreased ability to synthesize ATP, generate a proton motive force, and accumulate nutrients necessary to maintain viability. The aim of this work was to investigate the culturability of lactococci grown with and without lactose in a chemically defined medium, and to define the metabolic changes that occur during carbohydrate starvation.
Lactose metabolism provided energy for logarithmic phase growth and greater cell density in L. lactis ssp. lactis ML3 and L. lactis ssp. cremoris S2. However, the rate of lactose metabolism was strain dependent in that L. lactis ssp. lactis 11454 did not metabolize lactose as rapidly as did ML3 and S2. In the absence of lactose the cells became nonculturable on agar.
In addition to becoming nonculturable, the aminopeptidase and lipase/ esterase activity became nonmeasurable after 21 d, and cellular metabolism was altered because of carbohydrate starvation. Nevertheless, the cells remained viable for up to 42 d in spent media as measured by fluorescent viability stains and intracellular ATP content. Fluorescent viability staining demonstrated that the cells maintained an intact cell membrane to contain their DNA, as well as to contain enzymes and ATP necessary to maintain viability and metabolic activity.
With the addition of arginine to the basal medium, the survival time, cell number, and ATP concentration increased. Amino acids, including arginine, provided energy after carbohydrate exhaustion. At the onset of lactose exhaustion, the extracellular concentrations of arginine, glycine/valine, glutamate, and glutamine decreased in the media when energy was present for their transport. There was a significant increase in serine and methionine concentrations in the spent media over the same time period.
These data indicated lactococci remained viable and metabolically active, but were nonculturable in response to carbohydrate starvation. Additionally, amino acids are in a dynamic state during carbohydrate starvation, and utilization of amino acids, such as arginine and serine, could facilitate lactococcal cells in maintaining viability in harsh environments such as ripening cheese.
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Schreiber, Jadwiga [Verfasser]. "The cell adhesion molecule coxsackie virus and adenovirus receptor (CAR) modulates intracellular Ca2+ concentration and Cl- conductance in cultivated mouse cortical neurons / Jadwiga Schreiber." Berlin : Freie Universität Berlin, 2010. http://d-nb.info/1023958511/34.
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Couderc, Romain. "Etude du comportement thermique et électrique des cellules photovoltaïques en silicium cristallin sous concentration." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0054/document.
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Le silicium est très utilisé dans la production de cellules photovoltaïques mais très peu pour les applications sous concentration. Il possède pourtant un fort potentiel sous concentration grâce à son faible coût et la maturité de sa filière industrielle. De plus, il est possible d'avoir recours à la cogénération pour augmenter fortement les rendements énergétiques du système. La concentration et la cogénération impliquent un fonctionnement de la cellule à une température plus élevée que les conditions standards de test des cellules photovoltaïques. Cela engendre le besoin de connaître le comportement thermique et électrique de la cellule en fonction de sa température de fonctionnement. La variation de celle-ci, en conditions réelles, est pourtant souvent ignorée. Pour remédier à cette lacune, nous présentons un modèle électro-thermo-radiatif pour les cellules photovoltaïques en silicium cristallin. Il réalise le couplage de l'ensemble des phénomènes physiques prenant place dans une cellule photovoltaïque sous éclairement. Grâce à de nombreuses analyses effectuées dans le cadre des travaux de cette thèse, l'importance du comportement thermique d'une cellule photovoltaïque pour sa conception est mise en évidence. Entre autres, la variation de la température de la cellule avec sa tension que nous avons confirmé expérimentalement grâce à des mesures de température différentes de 2°C entre le Mpp et le Voc. Un des paramètres majeurs influençant le comportement électrique et thermique d’une cellule photovoltaïque en silicium est la densité de porteurs de charge intrinsèque du silicium, ni. Le développement du modèle électro-thermo-radiatif nous a amené à proposer une nouvelle expression semi-empirique de sa variation en fonction de la température. En complément de ces avancées théoriques, la réalisation de cellules photovoltaïques à contacts arrière interdigités implantées ioniquement (3IBC) a été menée. Nous avons diminué le nombre d'étapes nécessaires à sa réalisation et amélioré sa métallisation grâce à un empilement Si/Ti/Ag permettant d'espérer un gain absolu pour le Jsc de 0.72 mA.cm-2. Un rendement de 14.6% a été obtenu sous 1 soleil avec une cellule 3IBC dont la résistance série est de seulement 0.4 Ω.cm2 ce qui confirme le potentiel des cellules 3IBC pour la concentration linéaireSilicon is largely used to produce solar cells but not for applications under concentration. Nevertheless, it has a great potential under concentration thanks to its low cost and the maturity of its industry. Moreover, it is possible to cogenerate electric and thermal power in order to increase the energy output. Cogeneration and concentration imply a higher operating temperature than under standard conditions. Thus, it is interesting to understand the thermal and électrical behavior of the cell as a functiton of its temperature. However the variation of the operating temperature is often ignored. In order to change this, we propose an electro-thermo-radiative model for crystalline silicon solar cells. It couples all phenomenon taking place in an illuminated solar cell. Thanks to this thesis, the importance of the thermal behavior is outlined. For example, the temperature variation as a function of the voltage that we confirmed experimentaly thanks to mesures of the cell temperature at Mpp and at Voc. One of the most important parameters in a silicon solar cell is the intrinsic carrier density, ni. The work on the electro-thermo-radiative model led us to propose a new semi-empirical temperature variation of ni. In addition to these theoretical analysis, we realized ionically implanted interdigitated back contacts solar cells (3IBC). Thanks to this work fewer process steps are needed and the improved metallization (Si/Ti/Ag) possibly lead an absolute Jsc gain of 0.72 mA.cm-2. The efficiency of the best 3IBC cell is 14.6% under 1 sun illumination with a particularly low series resistance (0.4 Ω.cm2) which confirm the potential of such cells for linear concentration
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Li, Xiaoji. "Understanding Liquid-Air Interface Corrosion of Steel in Simplified Liquid Nuclear Waste Solutions." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1365506823.
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Symonds, Paul James. "The investigation of the characterisation of flotation froths and design of a machine vision system for monitoring the operation of a flotation cell ore concentration." Master's thesis, University of Cape Town, 1992. http://hdl.handle.net/11427/8352.
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Electrical and Electronic EngineeringThis dissertation investigates the application of digital image processing techniques in the development of a machine vision system that is capable of characterising the froth structures prevalent on the surface of industrial flotation cells. At present, there is no instrument available that has the ability to measure the size and shape of the bubbles that constitute the surface froth. For this reason, research into a vision based system for surface froth characterisation has been undertaken. Being able to measure bubble size and shape would have far reaching consequences, not only in enhancing the understanding of the flotation process but also in the control and optimization of flotation cells.
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Albarazanchi, Abbas Kamal Hasan. "Composant diffractif numérique multispectral pour la concentration multifonctionnelle pour des dispositifs photovoltaïque de troisième génération." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAD029/document.
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La lumière du soleil est un bon candidat comme source propre et abondante d'énergie renouvelable. Cette source d'énergie écocompatible peut être exploitée pour répondre aux besoins croissants en énergie du monde. Plusieurs générations de cellules photovoltaïques ont été utilisées pour convertir directement la lumière solaire en énergie électrique. La troisième génération de type multijonction des cellules photovoltaïques est caractérisée par un niveau d'efficacité plus élevé que celui de tous les autres types de cellules photovoltaïques. Des dispositifs optiques, tels que des concentrateurs optiques, des séparateurs optiques et des dispositifs optiques réalisant simultanément la séparation du spectre et la concentration du faisceau ont été utilisés dans des systèmes de cellules solaires. Récemment, les Eléments Optiques Diffractifs (EOD) font l'objet d'un intérêt soutenu en vue de leur utilisation dans la conception de systèmes optiques appliqués aux cellules photovoltaïques. Cette thèse est consacrée à la conception d'un EOD qui peut réaliser simultanément la séparation du spectre et la concentration du faisceau pour des cellules photovoltaïques de type multijonction latéral ou similaire. Les EOD qui ont été conçus ont une structure sous-longueur d'onde et fonctionnent en espace lointain pour implanter la double fonction séparation du spectre et concentration du faisceau. Pour cette raison, des outils de simulation ont été développés pour simuler le comportement du champ magnétique à l'intérieur de l'EOD à structure sous-longueur d'onde. De plus, un propagateur hybride rigoureux a aussi été développé, il est basé sur les deux théories de la diffraction, à savoir la théorie scalaire et la théorie rigoureuse. La méthode FDTD (Finite Difference Time Domain) ou méthode de différences finies dans le domaine temporel a été utilisée pour modéliser la propagation du champ magnétique en champ proche c'est-à-dire à l'intérieur et autour de l'EOD. La méthode ASM (Angular Spectrum Method) ou méthode à spectre angulaire a été utilisée pour modéliser de façon rigoureuse la propagation libre en champ lointain. Deux EOD différents ont été développés permettant d'implanter les fonctions souhaitées (séparation du spectre et concentration du faisceau) ; il s'agit d'une part d'un composant diffractif intitulé G-Fresnel (Grating and Fresnel lens) qui combine un réseau avec une lentille de Fresnel et d'autre part d'une lentille hors-axe. Les composants proposés réalisent la séparation du spectre en deux bandes pour une plage visible-proche infrarouge du spectre solaire. Ces deux bandes peuvent être absorbées et converties en énergie électrique par deux cellules photovoltaïques différentes et disposées latéralement par rapport à l'axe du système. Ces dispositifs permettent d'obtenir un faible facteur de concentration et une efficacité de diffraction théorique d'environ 70 % pour les deux bandes séparées. Grâce à une distance de focalisation faible, ces composants peuvent être intégrés dans des systèmes compacts de cellules solaires. La validation expérimentale du prototype fabriqué montre une bonne correspondance entre les performances expérimentales et le modèle théoriqueSunlight represents a good candidate for an abundant and clean source of renewable energy. This environmentally friendly energy source can be exploited to provide an answer to the increasing requirement of energy from the world. Several generations of photovoltaic cells have been successively used to convert sunlight directly into electrical energy. Third generation multijunction PV cells are characterized by the highest level of efficiency between all types of PV cells. Optical devices have been used in solar cell systems such as optical concentrators, optical splitters, and hybrid optical devices that achieve Spectrum Splitting and Beam Concentration (SSBC) simultaneously. Recently, diffractive optical elements (DOE’s) have attracted more attention for their smart use it in the design of optical devices for PV cells applications.This thesis was allocated to design a DOE that can achieve the SSBC functions for the benefit of the lateral multijunction PV cells or similar. The desired design DOE's have a subwavelength structure and operate in the far field to implement the target functions (i.e. SSBC). Therefore, some modelling tools have been developed which can be used to simulate the electromagnetic field behavior inside a specific DOE structure, in the range of subwavelength features. Furthermore, a rigorous hybrid propagator is developed that is based on both major diffraction theories (i.e. rigorous and scalar diffraction theory). The FDTD method was used to model the propagation of the electromagnetic field in the near field, i.e. inside and around a DOE, and the ASM method was used to model rigorously propagation in the free space far field.The proposed device required to implement the intended functions is based on two different DOE’s components; a G-Fresnel (i.e. Grating and Fresnel lens), and an off-axis lens. The proposed devices achieve the spectrum splitting for a Vis-NIR range of the solar spectrum into two bands. These two bands can be absorbed and converted into electrical energy by two different PV cells, which are laterally arranged. These devices are able to implement a low concentration factor of “concentrator PV cell systems”. These devices also allow achieving theoretically around 70 % of optical diffraction efficiency for the both separated bands. The impact distance is very small for the devices proposed, which allows the possibility to integrate these devices into compact solar cell systems. The experimental validation of the fabricated prototype appears to provide a good matching of the experimental performance with the theoretical model
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Han, Xiangmin. "CONTINUOUS PRODUCTION OF MICROCELLULAR FOAMS." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1041275301.
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Lin, Hsiu Chen, and 林秀珍. "The relationship between cell death and intracellular calcium concentration." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/86356583922073899641.
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碩士國防醫學院
生物化學研究所
90
In neuroblastoma x glioma NG108-15 cells, depletion of Ca2+ stores by thapsigargin caused an increase of the cytosolic Ca2+ concentration ([Ca2+]i), activation of caspase-3 and cell death. To characterize the relationship among [Ca2+]i increase, caspase-3 activation and cell death, we determine the effect of caspase-3 inhibitor (DEVD-CHO) and Ca2+ chelator (BAPTA) on thapsigargin-induced cell death in NG108-15 cells. Cell death was quantified by counting the percent of cells with DNA fragmentation. The dose of BAPTA and DEVD-CHO used were efficient to inhibited thapsigargin-induced [Ca2+]i increase and caspase-3 activation, respectively, while having no effect on caspase-3 activity and [Ca2+]i increase, respectively. In the presence of DEVD-CHO, cells were protected from thapsigargin-induced cell death regardless of the presence of BAPTA or not, while thapsigargin-induced cell death remained the same when [Ca2+]i increase was chelated. Our data indicate that depletion of Ca2+ stores is required for cell death, but not sufficient. It further depends on the activation of caspase-3, while being insensitive to the increase of [Ca2+]i in NG108-15 cells. Similar experiments were undertaken in cultured porcine aortic smooth muscle cells. Addition of ZVAD-fmk alone (broad caspases inhibitor) partially attenuated thapsigargin-induced cell death determined by trypan blue exclusion, while BAPTA enhanced cell death. The effect of BAPTA on the enhancement of thapsigargin-induced cell death is not relieved by the addition of ZVAD-fmk. Thus, in porcine aortic smooth muscle cells, thapsigargin-induced cell death partly attributed to the activation of caspases. Translocation of cytochrome C from mitochondria fraction to cytosol was observed after treatment of porcine aortic smooth muscle cells with thapsigargin for one hr. The translocation of cytochrome C was further enhanced when BAPTA and ZVAD-fmk were present. This is consistent with thapsigargin-induced cell death indicating that cell death is partly attributed to the translocation of cytochrome C. Thapsigargin-induced cytochrome C translocation was not correlated reduced as observed in cell death when BAPTA was applied simultaneously. BAPTA may remove the Ca2+ that holds cytochrome C with mitochondrial inner membrane as a peripheral membrane protein. Ca2+ uptake within mitochondria and the collapse of mitochondrial membrane potential were evoked by thapsigargin and the former preceded the latter. Both could be inhibited by cyclosporin A. Cyclosporin A also blocked the translocation of cytochrome C and cell death induced by thapsigargin. In conclusion, in porcine aortic smooth muscle cells, after Ca2+ stores depletion induced by thapsigargin, activation of caspases and translocation of cytochrome C via the opening of permeability transition pores occur. Activation of caspases and translocation of cytochrome C additively cause cell death.
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Chen, Chien-Hsien, and 陳建憲. "Study of Cell Optimizing Glucose Concentration by Using Concentration Gradient Microfluidic Chips and Micro-imprinting Technology." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/76381224357559215160.
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碩士國立成功大學
工程科學系碩博士班
97
In this study, the Polydimethylsilcoxane (PDMS) concentration gradient microfluidic chip and PDMS stamp are fabricated by MEMS, casting molding, and microimprinting technology. The chip is used to research optimizing concentration of endothelial cells on glucose concentration gradient. The experiment strategy is based on a microfluidic network to generate a concentration gradient in solution, and observes the effect of concentration gradient in different flow rates. Besides, it combines micropatterns that cell adhesion space width with 300 μm and gap with 200 μm to discuss the optimizing glucose concentration (0~10%, 0~20%, 5~15%, 6~17%) of endothelial cells. Through the experiment data, we can prove that the concentration gradients are all stable under different flow rates (20, 30, 40, 50 μL/min), however, when flow rates are over 20 μL/min, cell leaves substrate surface. The result shows that the glucose concentration gradient in the 7~15% is the optimizing concentration of endothelial cells, nevertheless, too high and low concentration will lead cell to leave or die. This study can solve the problems of the different drug concentrations prepare and test. It will apply drug concentration test and hypersensitive test in the future.