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George, Mariam M. B. S. "Zinc regulates tolerogenic dendritic cell phenotype and skews regulatory T cell- Th17 balance." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439305564.
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Sidoli, Fabio. "Systematic development of a coupled population-balance-single-cell model for mammalian cell cultures." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428151.
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Sharma, Rohit M. "Water balance considerations in modeling of PEM fuel cell systems." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011866.
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Liu, Feng. "Defense of Endothelial Cells Against Tumor Cell Adhesion-Crucial Role of Nitric Oxide and Peroxynitrite Balance." View abstract, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3293013.
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Lax, Stephanie J. "Interdisciplinary investigation of the balance between T cell subsets throughout life." Thesis, University of Nottingham, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.718990.
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To understand how immune balance is affected in immunoscnescencc and discover opportunities for correction with immunotherapy, a cross-sectional study of pro- and anti-inflammatory CD4+ T cell subsets in the peripheral blood of donors of different, ages was conducted. A whole blood assay using extra- and intracellular flow cytometry was designed to enumerate anti-inflammatory natural CD127lowCD25highFoxp3+ T regulatory cells (nTreg) and inducible IL-10+IFNy- T regulatory cells (iTreg) versus proinflammatory T helper 17 cells (Thl7) and T helper 1 cells (Thl), both IL-10+ and IL-10- . The frequency of these cell types was also linked to functional measurements of IL-17, IL-10 and IFN7 in whole blood supernatants after an overnight stimulation. We tested the hypothesis that the balance between these subsets changes with older age. This work shows for the first time that iTreg increase relative to nTreg and Thl7, but not Thl, with healthy ageing in man. We also identify that the previously reported increases in IL-10 levels relate to changes in the iTreg population. However, they did not increase relative to the Thl subset. During this project, scope for improvement in multicolour flow cytometry data analysis was identified, in order to minimise subjectivity and maximise efficiency of nTreg enumeration. The hypothesis that automating nTreg analysis with the SamSPECTRAL algorithm is superior to baseline C means clustering and traditional manual gating was investigated. SamSPECTRAL was qualitatively better than /c-means in clustering nTreg from flow cytometry data containing overlapping, non-spherical clusters with different densities, and was more objective than traditional manual gating. However, across 90 data files, an optimal solution was not always achieved, and statistical measures of cluster validity did not support the visual evidence that SamSPECTRAL better captured the natural structure of the data. A novel extension of SamSPECTRAL to include an automated elliptical gating step allowed for comparison of test and control datasets to correct nTreg frequency measurements for false positive events. As manual inspection of each solution was required, however, the ability to entirely automate nTreg analysis was prevented. We hope that this work will encourage further collaboration between the disciplines of immunology and computer science to advance the study of cancer and ageing.
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Oberdanner, Christian. "ROS and antioxidant systems in apoptosis oxidant balance in cell death and cancer therapy." Saarbrücken VDM Verlag Dr. Müller, 2007. http://d-nb.info/988931672/04.
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Schulz, Kerstin Ingrid. "Modulation of Th1 and Th2 type immune responses." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390690.
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Grangeray-Vilmint, Anais. "Modulation of cerebellar Purkinje cell discharge by subthreshold granule cell inputs." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAJ023/document.
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La décharge des cellules de Purkinje (CP), neurone de sortie du cortex cérébelleux, joue un rôle majeur dans le contrôle moteur. Les CP reçoivent des entrées excitatrices provenant des cellules des grains (CG), lesquelles génèrent également une inhibition antérograde sur les CP via l’activation d’interneurones de la couche moléculaire (IN). Lors de ma thèse, j’ai étudié l’influence simultanée de la balance excitation-inhibition (E/I) et des plasticités à court terme aux synapses CG-IN-CP sur la décharge des CP, par des techniques d’électrophysiologie, d’optogénétique et de simulation. Ces travaux démontrent l’existence d’une hétérogénéité d’E/I dans le cortex cérébelleux ainsi qu’une grande diversité de modulation des CP en réponse à la stimulation de CG. Le nombre de stimulation des CG influence fortement la direction et l’intensité de la modulation observée. Enfin, la combinaison de plasticités à court terme et d’E/I génère dans la décharge des CP des motifs de réponses complexes mais reproductibles, ayant sans doute un rôle essentiel dans l’encodage sensorielRate and temporal coding in Purkinje cells (PC), the sole output of the cerebellar cortex, play a major role in motor control. PC receives excitatory inputs from granule cells (GC) which also provide feedforward inhibition on PC through the activation of molecular layer interneurons (MLI). In this thesis, I studied the influence of the combined action of excitation/inhibition (E/I) balance and short-term plasticity of GC-MLI-PC synapses on PC discharge, by using electrophysiological recordings, optogenetic stimulation and modelling. This work demonstrates that E/I balances are not equalized in the cerebellar cortex and showed a wide distribution of PC discharge modulation in response to GC inputs, from an increase to a shut down of the discharge. The number of stims in GC bursts strongly controls the strength and sign of PC modulation. Lastly, the interplay between short-term plasticity and E/I balance implements complex but reproducible output patterns of PC responses to GC inputs that should play a key role in stimulus encoding by the cerebellar cortex
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Douglas, Mary Elizabeth. "Cost analysis and balance-of-plant of a solid oxide fuel cell/gas turbine combined cycle." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/17960.
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Khama, Mopeli. "Numerical simulation of bubble columns by integration of bubble cell model into the population balance framework." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9118.
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Includes bibliographical references.Bubble column reactors are widely used in the chemicals industry including pharmaceuticals, waste water treatment, flotation etc. The reason for their wide application can be attributed to the excellent rates of heat and mass transfer that are achieved between the dispersed and continuous phases in such reactors. Although these types of contactors possess the properties that make them attractive for many applications, there still remain significant challenges pertaining to their design, scale-up and optimization. These challenges are due to the hydrodynamics being complex to simulate. In most cases the current models fail to capture the dynamic features of a multiphase flow. In addition, since most of the developed models are empirical, and thus beyond the operating conditions in which they were developed, their accuracy can no longer be retained. As a result there is a necessity to develop eneric models which can predict hydrodynamics, heat and mass transfer over a wide range of operating conditions. With regard to simulating these systems, Computational Fluid Dynamics (CFD) has been used in various studies to predict mass and heat transfer characteristics, velocity gradients etc (Martín et al., 2009; Guha et al., 2008; Olmos et al., 2001; Sanyal et al., 1999; Sokolichin et al., 1997).The efficient means for solving CFD are needed to allow for investigation of more complex systems. In addition, most models report constant bubble particle size which is a limitation as this can only be applicable in the homogenous flow regime where there is no complex interaction between the continuous and dispersed phase (Krishna et al., 2000; Sokolichin & Eigenberger., 1994). The efficient means for solving CFD intimated above is addressed in the current study by using Bubble Cell Model (BCM). BCM is an algebraic model that predicts velocity, concentration and thermal gradients in the vicinity of a single bubble and is a computationally efficient approach The objective of this study is to integrate the BCM into the Population Balance Model (PBM) framework and thus predict overall mass transfer rate, overall intrinsic heat transfer coefficient, bubble size distribution and overall gas hold-up. The experimental determination of heat transfer coefficient is normally a difficult task, and in the current study the mass transfer results were used to predict heat transfer coefficient by applying the analogy that exists between heat and mass transfer. In applying the analogy, the need to determine the heat transfer coefficient experimentally or numerically was obviated. The findings indicate that at the BCM Renumbers (Max Re= 270), there is less bubble-bubble and eddy-bubble interactions and thus there is no difference between the inlet and final size distributions. However upon increasing Re number to higher values, there is a pronounced difference between the inlet and final size distributions and therefore it is important to extend BCM to higher Re numbers. The integration of BCM into the PBM framework was validated against experimental correlations reported in the literature. In the model validation, the predicted parameters showed a close agreement to the correlations with overall gas hold-up having an error of ±0.6 %, interfacial area ±3.36 % and heat transfer coefficient ±15.4 %. A speed test was also performed to evaluate whether the current model is quicker as compared to other models. Using MATLAB 2011, it took 15.82 seconds for the current model to predict the parameters of interest by integration of BCM into the PBM framework. When using the same grid points in CFD to get the converged numerical solutions for the prediction of mass transfer coefficient, the computational time was found to be 1.46 minutes. It is now possible to predict the intrinsic mass transfer coefficient using this method and the added advantage is that it allows for the decoupling of mass transfer mechanisms, thus allowing for more detailed designs.The decoupling of mass transfer mechanisms in this context refers to the separate determination of the intrinsic mass transfer coefficient and interfacial area.
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Sullivan, Gary V. "An investigation into acid-base balance at the gills of rainbow trout (Oncorhynchus mykiss) using in situ hybridization and immunocytochemistry for proton-ATPase and band 3." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/9654.
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This thesis examines changes that occur in the epithelial cells of rainbow trout (Oncorhynchus mykiss) gills with respect to the expression of Na$\sp+$ and Cl$\sp-$ ion-transporting proteins during periods of acid-base disturbance. In the first part of the study, the expression of the V-type proton ATP-ase (H$\sp+$-ATPase) was examined in the gill of trout to provide direct evidence for its existence, determine its cellular distribution, and assess its response to acid-base disturbance. Gill epithelial cells demonstrated specific immunoreactivity, the intensity of which was increased markedly after 18 h of exposure to hypercapnia (1% CO$\sb2$ in air). The specificity of the antiserum for the 31-kDa subunit of the H$\sp+$-ATPase was supported by Western blotting with the presence of an immunoreactive band at 31-kDa. The increased H$\sp+$-ATPase immunoreactivity in the epithelial cells of hypercapnic fish demonstrates an "up-regulation" of this protein in response to respiratory acidosis. Oligonucleotide probes, complementary to the mRNA of the 31- and 56-kDa subunits of the bovine renal H$\sp+$-ATPase were constructed. The H$\sp+$-ATPase mRNA expression was increased markedly in the gills of acidotic fish and was accompanied by a pronounced elevation in branchial H$\sp+$ excretion. The probe for the Band 3 mRNA also demonstrated a specific hybridization signal in gill epithelial cells which was greatly increased in the gills of alkalotic fish, which were excreting large amounts of HCO$\sb3\sp-$. The results of this thesis provide direct evidence for the presence of an electrogenic H$\sp+$ pump located on the apical surface of the pavement cell which is actively up-regulated during periods of acidosis through increased transcription and translation of the protein as well as increased membrane association. Further evidence is provided for the presence of Band 3 or a Band 3-like protein which is responsible for Cl$\sp-$/HCO$\sb3\sp-$ exchange across the gill. (Abstract shortened by UMI.)
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Jacquemin, Clément. "Modulation de la balance lymphocytaire T régulatrice et effectrice dans deux modèles de maladies auto-immunes." Thesis, Bordeaux 2, 2013. http://www.theses.fr/2013BOR22050.
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Le respect de l’équilibre entre lymphocytes T effecteurs auto-réactifs et lymphocytes T régulateurs (LTreg) est primordial dans le maintien de la tolérance aux antigènes du soi. Les partenaires cellulaires et les mécanismes moléculaires impliqués dans la rupture de l’équilibre de cette balance ne sont pas ou peu connus dans les maladies auto-immunes. Ainsi, les travaux décrits dans cette thèse portent sur le dérèglement de la balance T effecteurs/ Treg dans deux modèles de maladies auto-immunes chez l’homme: le lupus érythémateux systémique et l’anémie hémolytique auto-immune (AHAI). Nous montrons une augmentation de l’expression de la molécule de costimulation OX40L (CD252, TNFSF4) à la surface des cellules présentatrices d’antigène circulantes et infiltrant les tissus chez les patients lupiques. Cette augmentation est corrélée à l’activité de la maladie chez l’adulte comme chez l’enfant. Elle a pour conséquence l’induction de lymphocytes T effecteurs de type Tfh (T follicular helper) et le blocage des fonctions suppressives des Treg, deux acteurs majeurs dans la physiopathologie du lupus. Dans le second projet, nous montrons une augmentation de la proportion de T8reg circulants chez les patients affectés d’une AHAI à anticorps chauds en phase de rémission. Ces Treg expriment le CD25, le FoxP3 et exercent leur fonction suppressive par un mécanisme faisant intervenir l’IL10. De faibles doses d’IL-2 permettent l’expansion de cette population cellulaire in vitro. Ces résultats apportent de nouvelles connaissances dans la physiopathologie de ces deux maladies et offrent des perspectives thérapeutiques potentiellesRespect of the balance between autoreactive T cells and regulatory T cells (LTreg) is important to maintain tolerance to self-antigens. Cellular partners and molecular mechanisms involved in the disruption of this balance are not or little known in autoimmune diseases.Thus, the work described in this thesis focuses on the disruption of the T effector/ Treg balance in two models of human autoimmune diseases: systemic lupus erythematosus and autoimmune hemolytic anemia (AIHA). We show an increased expression of the OX40L (CD252, TNFSF4) costimulatory molecule at the surface of both circulating and tissues-infiltrating antigen presenting cells in SLE patients. OX40L expression is correlated with disease activity in adults and in children and results in Tfh (follicular helper T) effector cells induction and Treg suppressive functions inhibition, two key mechanisms in the pathogenesis of lupus. In the second project, we show an increase of the circulating T8reg proportion in patients with a warm AIHA in a non-active state. These Treg express CD25, FoxP3 and exert their suppressive function by a mechanism involving IL-10. Low-dose IL-2 allows the expansion of this cell population in vitro. These results provide new insights into the pathophysiology of these diseases and offer potential therapeutic perspectives
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Sawyer, Frederick Emile. "Coupled mixing-cell and mass balance flow path models of the White River Flow System, Nevada, USA." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1467765.
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Bomber, Kristin. "Work/Life Balance and Smartphones: Can a Smartphone make a difference?" Thesis, Linnaeus University, Linnaeus School of Business and Economics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-6848.
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This thesis examines the relationship between work/life balance and Smartphones (Blackberry, iPhone, Android etc.)
Academic research has areas where not much research has been done previously including the qualitative research on work/life balance, positive crossover of work/life balance, newness of Smartphone technology, and consequences of constant connectivity. This study hopes to eliminate some of the gaps in these areas of research and proposes two research questions: So what does owning a Smartphone mean for work life and home life? Most importantly can this phone help people towards or assist with the balance they are so looking for or do the phones not impact this balance and just assist in the work life and home life realms separately?
A qualitative approach using constructionist and interpretivist views were used to conduct the research. Empirical material was collected during phone interviews with participants in the USA, while supporting material was gathered from conference papers, academic articles, websites, and textbooks.
There are two major themes within this paper, work/life balance and Smartphone technology. For work/life balance a common understanding was reached that work and personal life should be kept happy but that doesn’t mean equal. Also discussed is research about people that put up boundaries in their lives to try and separate things, one group of people likes to have work and personal separate but one group likes them combined. Research also presents that there are consequences for setting up boundaries but that having the ability to choose where these boundaries are makes for a much happier situation. On the technology side of research there is support for these devices being used to manage people’s different selves through communication from being more connected to people to feeling left out when the technology is not there. Also mentioned is how people adapt the devices to fit new and unique situations that the devices may not have been intended to be used for.
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Bergin, Stephen Michael. "Hypothalamic brain-derived neurotrophic factor regulates lymphocyte immunity, energy balance, and cancer progression." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487669797216355.
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Jayat, Maximilien. "Rôle des cellules ß - intercalaires dans le maintien de la balance du sodium et de la pression artérielle." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066553/document.
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L'hypertension est l'une des maladies humaines les plus courantes. Aujourd'hui, de nombreuses études confirment l'hypothèse selon laquelle l'hypertension implique nécessairement un transport anormal de sel (NaCl) par les reins.Le néphron, l'unité fonctionnelle du rein, est composé de plusieurs segments présentant différents systèmes de transport de NaCl. Notre équipe a récemment démontré que les cellules intercalaires du canal collecteur (CD) étaient capables de réabsorber du NaCl. Ce transport est possible grâce au couplage fonctionnel de deux échangeurs : la pendrine et NDCBE. L'objectif de cette thèse est de caractériser ce transport et de montrer que les cellules intercalaires ( IC) jouent un rôle important dans le maintien de la balance sodée et de la pression artérielle. Grâce à plusieurs modèles de souris transgéniques nous avons pu montrer que la délétion de NDCBE provoque une hypotension et la mise en place d'une compensation par un autre transporteur du néphron : le cotransporteur NCC. A partir d'un autre modèle murin knock-out pour la pompe à proton H+-ATPase spécifiquement dans les cellules intercalaires et nécessaire à la réabsorption de NaCl par les ICs, nous avons montré que les ICs étaient capables de moduler le transport de sodium des cellules principales du CD par la sécrétion de facteurs paracrines. Enfin, chez des souris possédant une mutation de kinase WNK4, connue pour provoquer le syndrôme de Gordon, une maladie caractérisée entre autre par une hypertension artérielle et une hyperkaliémie, le transport de NaCl par les ICs est suractivée et cette suractivation contribue probablement à la mise en place de la maladieHypertension is one of the most common human diseases. Today, many studies support the hypothesis that hypertension necessarily involve abnormal transport of salt (NaCl) by the kidneys. The nephron, the functional unit of the kidney, is composed of several segments with different NaCl transport systems. Our team has recently demonstrated that β-intercalated cells of the collecting duct (CD) were able to reabsorb NaCl. This transport is possible through functional coupling of two exchangers : pendrin and NDCBE. The objective of this thesis is to characterize the transport and show that β-intercalated cells (β-IC) play an important role in maintaining of sodium balance and blood pressure. Through several transgenic mouse models, we have shown that deletion of NDCBE causes hypotension and induces a compensation by another transporter of NaCl : the NCC cotransporter. With another mouse model, knockout for the proton pump H+- ATPase specifically in the intercalated cells and necessary for the reabsorption of NaCI in the β-ICs, we have shown that the β-ICs were capable of modulating the sodium transport of the principal cell of the CD through the secretion of paracrine factors.Otherwise, in mice with a mutated form of the WNK4 kinase, known to cause the Gordon syndrome, a disease characterized by hypertension and hyperkalemia, the NaCl transport by β-ICs is overactive and this overactivation probably contributes to the establishment of the disease
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Abele, Julia Verfasser], and Daniela C. [Gutachter] [Dieterich. "Ageing in a dish : strategies ro rejuvenate neuronal cell cultures and balance protein homoeostasis / Julia Abele ; Gutachter: Daniela C. Dieterich." Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2019. http://d-nb.info/1219965723/34.
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Veligodskiy, Alexey. "The mechanisms of epithelial morphogenesis and de novo lumen formation : a balance of cell division, cellular tension, and vectorial fluid transport /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17870.
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Hofmann, Saskia Gabriele [Verfasser]. "Establishment of a perfusion cell culture system for bovine granulosa cells to investigate the relation between negative energy balance and declining fertility in dairy cattle / Saskia Gabriele Hofmann." Gießen : Universitätsbibliothek, 2013. http://d-nb.info/1065065361/34.
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El, Missiry M. A. "Membrane sulphydryl groups in the control of water and ion balance in the red blood cell of the eel Anguilla anguilla L." Thesis, University of Bath, 1986. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374600.
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Gunnarson, Eli. "Studies on aquaporin 4, a molecular determinant of brain water homeostasis /." Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-829-0/.
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Peters, Dorothea Maren [Verfasser]. "TGF-beta mediates alveolar fluid balance by regulating the cell-surface stability of the epithelial sodium channel in the lung / Dorothea Maren Peters." Gießen : Universitätsbibliothek, 2011. http://d-nb.info/1063110807/34.
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Chen, Helen. "The non-motor protein RHAMM locates TPX2 to coordinate spindle assembly and balance motor forces needed to segregate chromosomes and complete cell division." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/60235.
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Cell division requires the assembly and organization of a microtubule-based mitotic spindle. Microtubule assembly at multiple sites is dependent on Aurora kinase A activity, which is promoted through a complex with TPX2 (targeting protein for XKlp2). Subsequent organization of these microtubules and progression into anaphase requires balance between forces orchestrated by antagonistic motor complexes. My studies show that the non-motor protein RHAMM (receptor for hyaluronan mediated motility) integrates structural and biochemical pathways to ensure the fidelity of cell division. Silencing RHAMM in HeLa cells delayed the kinetics of spindle assembly. I located RHAMM to centrosomes and non-centrosome sites for microtubule nucleation and found it necessary for TPX2 localization and Aurora A activity at kinetochores. The RHAMM-TPX2 complex requires a conserved leucine zipper motif in RHAMM and a domain that includes the nuclear localization signal in TPX2. These findings indicate RHAMM is needed for spatially-regulated activation of Aurora A by TPX2, which coordinates spindle assembly. I monitored mouse embryonic fibroblasts deficient for RHAMM through division and identified defects progressing through the spindle checkpoint. In RHAMM-silenced HeLa cells, I identified sustained activation of the checkpoint with unfocused spindles and unattached kinetochores, implicating unbalanced motor activities mediated by kinesins. In metaphase-delayed cells, the abundance or location of checkpoint proteins was not altered. Moreover, aberrant spindle orientation could not account for each delayed division. In RHAMM-silenced cells, I found that the reciprocal immunoprecipitation of Eg5-TPX2, an inhibitory complex, was reduced and that the concurrent inhibition of Eg5-generated force recovered division kinetics. I also observed a prolonged metaphase delay in a proportion of RHAMM-silenced cells, which resolved through cohesion fatigue. Together, my findings indicate that RHAMM-mediated attenuation of Eg5-dependent outward forces is needed to align chromosomes and progress through division. Lastly, I identified defects in spindle structure and function in redundant models for RHAMM over-expression. Collectively, my studies demonstrate that RHAMM coordinates Aurora A signaling and balances motor forces that are needed for cell division. These findings provide novel insights into processes that are essential for mammalian cell division and the maintenance of genome stability.Medicine, Faculty of
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Blank, Beatrix Johanna [Verfasser], Uwe [Akademischer Betreuer] Rau, and Carsten [Akademischer Betreuer] Deibel. "Towards a generalized framework for the analysis of solar cell performance based on the principle of detailed balance / Beatrix Johanna Blank ; Uwe Rau, Carsten Deibel." Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1227056443/34.
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Niazi, Erfan. "A Mesoscopic Model for Blood Flow Prediction Based on Experimental Observation of Red Blood Cell Interaction." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38078.
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In some species, including humans, red blood cells (RBCs) under low shear stress tend to clump together and form into regular stacks called rouleaux. These stacks are not static, and constantly move and break apart. This phenomenon is referred to as red blood cell aggregation and disaggregation. When modelled as a single liquid, blood behaves as a non-Newtonian fluid. Its viscosity varies, mainly due to the aggregation of RBCs. The aim of this research is to develop a mesoscale computational model for the simulation of RBCs in plasma. This model considers RBC interaction and aggregation to predict blood-flow characteristics such as viscosity, rouleaux size and velocity distribution.
In this work, the population-balance modelling (PBM) approach is utilized to model the RBC aggregation process. The PBM approach is a known method that is used for modelling agglomeration and breakage in two-phase flow fluid mechanics to find aggregate size. The PBM model is coupled to the incompressible Navier-Stokes equations for the plasma. Both models are numerically solved simultaneously. The population-balance equation has been used previously in a more restricted form, the Smoluchowski equation, to model blood viscosity, but it has never been fully coupled with the Navier-Stokes equation directly for the numerical modelling of blood flow. This approach results in a comprehensive model which aims to predict RBC aggregate size and their velocities for different flow configurations, as well as their effects on the apparent macro-scale viscosity.
The PBM approach does not treat the microscopic physics of aggregation directly but rather uses experimental correlations for aggregation and disaggregation rates to account for the effects of aggregation on the bulk. To find the aggregation rate, a series of experiments on RBC sedimentation due to gravity is designed. In these tests, aggregated RBCs (rouleaux) tend to settle faster than single RBCs and, due to low shear stresses, disaggregation is very low and can be neglected. A high-speed camera is used to acquire video-microscopic pictures of the process. The size of the aggregates and their velocities are extracted using image processing techniques. For image processing, a general Matlab program is developed which can analyze all the images and report the velocity and size distribution of rouleaux.
An experimental correlation for disaggregation rate is found using results from a previous steady-state Couette flow experiment. Aggregation and disaggregation rates from these experiments are used to complete the PBM model. Pressure-driven channel flow experiments are then used for the final validation of the model. Comparisons of the apparent viscosity of whole blood in previous experiments show reasonable agreement with the developed model. This model fills a gap between micro-scale and macro-scale treatments and should be more accurate than traditional macro-scale models while being cheaper than direct treatment of RBCs at the micro-scale.
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Zhang, Hong. "Energy-efficient strategies with base station power management for green wireless networks." IEEE Publishing, 2013. http://hdl.handle.net/1993/31307.
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In this thesis, our objective is to improve the energy efficiency and load balance for wireless networks. We first study the relationships between the base station (BS) on/off operation and traffic distribution. A cooperative power saving method called clustering BS-off (CBSO) scheme is proposed. Instead of adopting a unified and consistent BS-off scheme in the whole network, the proposed centralized and distributed CBSO schemes can adaptively group BSs in several clusters based on the traffic fluctuations with space and time. Second, to further improve the network load balance and energy efficiency in distributed manner, we propose a power efficient self-organized virtual small networking (VSN) protocol. A heuristic firefly algorithm is applied to arrange the BSs' operation in small groups based on the traffic level. By jointly considering the load balance, the effectiveness of the proposed algorithm is demonstrated based on the average and min-max traffic levels of BSs' groups. Finally, the importance of detailed BS operation between active and sleep modes is considered. The operating procedure of femtocell base station, i.e., HeNB, is modeled as an MAP/PH/1/k queueing system. Such queueing analysis particularly focuses on the HeNB vacation process with user priorities. The HeNB's power on/off scheme is modeled as alternative service and vacation periods. The hybrid access is regarded as high and low priority users in the queuing system. We further propose the adaptive service rate and vacation length (ASV) method, so that the HeNB can work in a more energy-efficient way while satisfying QoS requirements such as blocking probability and users waiting time.
Simulation results show the effectiveness of the proposed strategies and the overall network energy efficiency can be improved significantly.October 2016
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Ometto, Francesco. "Microalgae to energy : biomass recovery and pre-treatments optimisation for biogas production integrated with wastewater nutrients removal." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/8403.
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The increasing concern about water quality and energy demand promotes the development of innovative and low-cost processes to improve the nutrient uptake and energy efficiency of existing wastewater treatments (WWT). In this context, the inclusion of a microalgae system (MAS) in the flowsheet of a WWT plant represents a sustainable alternative to conventional technologies, as it combines a low-cost nutrient uptake system with the production of biomass suitable for biofuel production. However, at present, the energy required to cultivate and process the algae cells is often too high to justify their use. The adoption of a low energy harvesting system and an efficient energy conversion process are the sine qua non requirements to guarantee the sustainability of the process. In this thesis, current and innovative harvesting technologies for large scale applications have been reviewed to identify the optimal working conditions of each system and their link to the main characteristics of the algae suspension. In particular, the performance of the Ballasted Dissolved Air Flotation (BDAF) system was investigated using different algae and compared to the conventional Dissolved Air Flotation (DAF). BDAF was demonstrably a very viable harvesting method where the use of floating microspheres as ballasting agents allowed significant coagulant savings, reduced the level of energy dissipation within the flotation chamber, and lowered the overall carbon emissions and the process costs. Cont/d.
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Areny, naves Cel. "Identification and characterization of the RIG-I helicase partners involved in the balance proliferation / cell differentiation. Characterization of G-quadruplex resolving by the helicase Pif1 in Bacteroides sp 3_1_23." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLN002/document.
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Les hélicases sont des protéines qui utilisent l'énergie fournie par l'hydrolyse de l'ATP ou du GTP pour catalyser la disjonction des doubles hélices d'ADN ou d'ARN. Cette activité de déroulement de double brin leur confère un rôle essentiel dans le métabolisme des acides nucléiques, le maintien de la stabilité du génome et les processus de signalisation cellulaire. En conséquence, ils sont impliqués dans des processus aussi divers que le vieillissement, l'apparition de cancers, l'immunité innée. Cette thèse est axée sur la compréhension de la fonction et des mécanismes moléculaires de deux hélicases différentes et le manuscrit est donc divisé en deux parties. Le premier est dédié à l'hélicase RIG-I, une hélicase à ARN, exprimée lorsque les cellules leucémiques cessent de proliférer et sont induites à se différencier en granulocytes, indispensables à la reconnaissance de l'ARN double brin des virus, initiant la protection des cellules contre la réplication des génomes viraux. Le mécanisme d'action de RIG-I est bien décrit dans le contexte d'une infection virale. Mais dans le cas de la différenciation des cellules myéloïdes, l'intervention de RIG-I et son rôle dans la balance la prolifération / différenciation restent incomplets. En effet, les interactions RIG-I en particulier avec les ligands cellulaires ne sont pas totalement comprises. La première partie de mon travail consistait à tenter d'isoler et de caractériser les partenaires de RIG-I lors de la différenciation des cellules leucémiques NB4. La seconde est consacrée à l'étude des mécanismes sous-jacents aux G-quadruplexes résolus par les hélicases. Plusieurs questions subsistent quant aux interactions entre la structure particulière des G-quadruplexes et ces enzymes. Une hélicase de Bacteroides sp 3_1_23, BsPif1, a été choisie pour comparer et caractériser l'interaction entre les G-quadruplexes et l'ADN canonique de Watson-Crick. Dans les deux parties du travail, les interactions ont été étudiées par des techniques biochimiques utilisant soit une lignée cellulaire ou une protéine purifiée et des acides nucléiques synthétiquesHelicases are proteins that utilize the energy provided by the hydrolysis of ATP or GTP to catalyse the disjunction of double DNA or RNA helices. This double strand unwinding activity gives them an essential role in the metabolism of nucleic acids, the maintenance of the genome stability and cell signalling processes. As a result, they are involved in processes as diverse as aging, the appearance of cancers, innate immunity. This thesis is focused on the understanding of the function and the molecular mechanisms of two different helicases and the manuscript is therefore divided in two parts. The first one is dedicated to the RIG-I helicase, an RNA helicase, expressed when leukemic cells stop proliferate and are induced to differentiate in granulocytes, which are essential in the recognition of double-stranded RNA of viruses, initiating the protection of the cells against the replication of the viral genomes. The mechanism of action of RIG-I is well described in the context of viral infection. But in the case of the differentiation of myeloid cells, the intervention of RIG-I and its influence on the equilibrium proliferation / differentiation remains incomplete. Indeed, RIG-I interactions in particular with cellular ligands are not fully understood. The first part of my work consisted in an attempt to isolate and characterize RIG-I partners during differentiation of NB4 leukemic cells. The second one is devoted to the study of mechanisms underlying G-quadruplexes resolving by helicases. Several questions remain about the interactions between the particular structure of G-quadruplexes and these enzymes. A Bacteroides sp 3_1_23 helicase, BsPif1, was chosen to compare and characterize the interaction between G-quadruplexes and canonical Watson-Crick DNA. In the two parts of the work, the interactions were investigated by biochemical techniques using either a cell line or purified protein and synthetic nucleic acids
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Soubeyrand, Eric. "Etude de la régulation par l’azote de la biosynthèse des anthocyanes dans les cellules de vigne, par une approche intégrative." Thesis, Bordeaux 2, 2013. http://www.theses.fr/2013BOR22118/document.
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Les anthocyanes sont une famille de polyphénols très répandus chez les végétaux. Chez la vigne, elles sont responsables de la coloration des baies des cépages rouges, et sont impliquées dans les propriétés organoleptiques des vins. Une nutrition azotée faible induit la production des anthocyanes dans les cellules de la pellicule de raisin des cépages rouges via des mécanismes de régulation qui ne sont pas encore totalement élucidés. Dans ce contexte, nous avons étudié les mécanismes moléculaires impliqués dans la réponse de l’accumulation des anthocyanes pour différents niveaux d’apports azotés. Deux matériels biologiques complémentaires ont été utilisés : des suspensions cellulaires de vigne (lignée GT3) et des plants de Cabernet-Sauvignon, cultivés au vignoble.L’augmentation de la synthèse d’anthocyanes en réponse à la diminution de la nutrition azotée a été confirmée dans les baies et les cellules de vigne en culture. Les analyses transcriptomiques globales (génome complet) et ciblées (qPCR) ont mis en lumière des modifications de l’expression génique, notamment de gènes liés au métabolisme des flavonoïdes, en réponse à la nutrition azotée. L’expression de nombreux gènes structuraux impliqués dans la voie de biosynthèse des anthocyanes est induite par une faible nutrition azotée. La variation de l’apport azoté influence également de façon coordonnée l’expression des gènes régulateurs positifs (facteurs de transcription de type MYB) et négatifs (protéine de type Lateral organ Boundary Domain (LBD)) des gènes de la biosynthèse des flavonoïdes chez la Vigne. L’expression de gènes liés à la production d’énergie (NADH, NADPH), est également affectée.En parallèle, une approche intégrative a été développée sur les suspensions cellulaires, en combinant des mesures d’activités enzymatiques, des dosages de métabolites primaires et secondaires, avec un modèle de balance de flux (Flux Balance Analysis, FBA). Les cartes de flux obtenues prédisent que la diminution de l’apport azoté entraîne une augmentation des flux métaboliques dans la voie du shikimate et des phénylpropanoïdes ; ainsi qu’une répression de la majorité des flux dans les différentes voies du métabolisme primaire, à l’exception de la voie des pentoses phosphates, dont le flux est maintenu, et de la voie de synthèse de l’amidon qui est accrue. Les résultats obtenus plaident en faveur d’un lien fort entre synthèse des anthocyanes et statut énergétique (ATP, NADPH) des cellules vigneAnthocyanins are polyphenol compounds very abundant in most of the plants. In grapevine, they give color to red berries and they improve red wine quality and increase the organoleptic properties of the wine. Low nitrogen supply stimulates anthocyanin production in berry skin cells of red grape varieties through regulation mechanisms that are far from being fully understood. In this context, we worked on the molecular mechanisms involved in anthocyanin biosynthesis response to nitrogen supply. Two complementary biological materials were used: grapevine cell suspensions (GT3 line) that originate from a teinturier cultivar and produce anthocyanins under normal conditions; and red grape berries of cv. Cabernet-Sauvignon cultivated in a commercial vineyard. Increases of anthocyanins synthesis in response to low nitrogen levels were confirmed in the field-grown berries and the cells suspensions. Both comparative global (microarrays) and targeted (qPCR) transcriptomic analysis showed different regulations on the expression of the genes involved in the secondary (especially the anthocyanin) and nitrogen metabolisms. The expression of most structural genes of the anthocyanin biosynthesis pathway was induced by a low nitrogen supply. Nitrogen controls also the expression of the positive (MYB transcription factors) and negative (Lateral organ Boundary Domain family protein LBD39) regulatory genes of the flavonoid pathway in grapevine. Furthermore, some genes improved in energy production (ATP, NADPH) were affected. In parallel, an integrative approach combining enzymatic activities and primary and secondary metabolites measurements with developing a Flux Balance Analysis (FBA) modeling approach was used on cells suspensions GT3. The flux maps deciphered that low nitrogen increases metabolic fluxes in shikimate and phenylpropanoid pathways and represses the majority metabolic fluxes in different pathways of primary metabolism. The two exceptions included the pentose phosphate pathway, which the flux metabolism was maintained, and the starch synthesis pathway, which was enhanced. The results obtained showed a strong link between anthocyanin synthesis and energy status (ATP, NADPH) in the berry cell suspensions
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Breitkopf, Daniel Maximilian [Verfasser], Ute Akademischer Betreuer] Raffetseder, and Ralph [Akademischer Betreuer] [Panstruga. "Notch-3 and a posttranslational modification of Y-box binding protein 1 alter the immune cell balance and the pathophysiology in systemic lupus erythematosus / Daniel Breitkopf ; Ute Raffetseder, Ralph Panstruga." Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1217789650/34.
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Crotti, Andrea. "The balance between latency and productive human immunodeficiency virus type I infection : contribution of the viral accessory gene nef and of the JAK-STAT signal transduction pathway of cell activation." Thesis, Open University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487160.
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The balance between latent and productive human immunodeficiency virus (HIV) infection is the result of a complex interplay of viral and host factors. In the first part of this study I investigated a group of 6 HIV+ haemophilic long term nonprogressor~ (LTNP) for maintenance of functional defects of their HIV-I nefgene. Our results showed that Nef alleles from these nonprogressor hemophiliacs are defective in enhancing virus replication and CD4 down-regulation. This was not predictive of disease outcome as 3 out of the 6 individuals studied progressed later to full HIV disease. The primary viral isolates from these the 3 'late progressors' showed an extension of gpl20 Env dependent entry co-receptor use from CCR5 only to CCR5/CXCR4, a known correlate of disease progression, while the non I f progressors maintained monotropic CCR5 use. In addition to viral genes, several pro-inflammatory cytokines upregulated in HIV infection influence HIV latency and replication via activation of cellular transcription factors. Peripheral blood mononuclear cells from HIV+ individuals frequently show a constitutive activation of the cytokine-related Janus kinase/Signal Transducer and Activator of Transcription (JAKISTAT) pathway, and particularly of a C-terminally truncated isoform of STAT5 (STAT5 ). I investigated whether STAT5 and STAT5~ could affect HIV transcription and replication. STAT5 induced HIV transcription driven by the long terminal repeats (LTR). Chromatin immunoprecipitation and related molecular assays showed that STAT5~ actually bound to the HIV LTR and suppressed viral transcription and expression. Thus, a key finding from the present thesis is that the constitutiveIy activated STAT5~ present in the leukocytes of most HIV-positive individuals acts as a negative regulator of HIV expression. Thus, both viral factors, such as the evolution of gp120 Env coreceptor use towards CXCR4 in individuals maintaining functional nef mutations, and host transcription factors, including STAT5/STAT58, regulate HIV- I replication in vitro and, likely, its pathogenicity in infected individuals.
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Safa, Mohamad. "Modélisation réduite de la pile à combustible en vue de la surveillance et du diagnostic par spectroscopie d'impédance." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00855160.
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Cette thèse porte sur la modélisation des piles à combustible à membrane d'échange de protons (PEMFC), en vue de leur surveillance et de leur diagnostic par spectroscopie d'impédance. La première partie du document présente le principe de fonctionnement de ces piles, ainsi que l'état de l'art de la modélisation et des méthodes de surveillance et diagnostic. Le modèle physique multi échelle particulièrement détaillé publié en 2005 par A.A. Franco sert de point de départ. Il est simplifié de façon à aboutir à un système d'équations aux dérivées partielles en une unique dimension spatiale. L'objectif principal de la seconde partie est l'analyse harmonique du fonctionnement de la pile. En s'inspirant de travaux classiques sur l'analyse géométrique de réseaux de réactions électrochimiques, un modèle réduit compatible avec la thermodynamique est obtenu. Cette classe de systèmes dynamiques permet de déterminer, pour un tel réseau, une formule analytique de l'impédance de l'anode et de la cathode d'une pile PEMFC. Un modèle complet de la pile est obtenu en connectant ces éléments à des éléments représentant la membrane, les couches diffuses et les couches de diffusion des gaz. Les modèles précédents supposent la pile représentée par une cellule unique et homogène. Afin de permettre d'en décrire les hétérogénéités spatiales, nous proposons finalement un résultat de modélisation réduite d'un réseau de cellules représentées par leur impédance. Ce modèle approxime l'impédance globale du réseau par une "cellule moyenne", connectée à deux cellules "série" et "parallèle" représentatives d'écart par rapport à la moyenne.
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Ali, Qasim. "Contribution to the mathematical modeling of immune response." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2013. http://tel.archives-ouvertes.fr/tel-00905603.
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The early steps of activation are crucial in deciding the fate of T-cells leading to the proliferation. These steps strongly depend on the initial conditions, especially the avidity of the T-cell receptor for the specific ligand and the concentration of this ligand. The recognition induces a rapid decrease of membrane TCR-CD3 complexes inside the T-cell, then the up-regulation of CD25 and then CD25-IL2 binding which down-regulates into the T-cell. This process can be monitored by flow cytometry technique. We propose several models based on the level of complexity by using population balance modeling technique to study the dynamics of T-cells population density during the activation process. These models provide us a relation between the population of T-cells with their intracellular and extracellular components. Moreover, the hypotheses are proposed for the activation process of daughter T-cells after proliferation. The corresponding population balance equations (PBEs) include reaction term (i.e. assimilated as growth term) and activation term (i.e. assimilated as nucleation term). Further the PBEs are solved by newly developed method that is validated against analytical method wherever possible and various approximate techniques available in the literature.
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Firmin, Stéphane. "Efficacité de détoxication de l'aflatoxine B1 et de l'ochratoxine A par un adsorbant organique : évaluation par la balance d'excrétion et les paramètres toxicocinétiques chez le rat et la brebis laitière." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2011. http://tel.archives-ouvertes.fr/tel-00673423.
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L'aflatoxine B1 (AFB1) et l'ochratoxine A (OTA) sont des mycotoxines pouvant contaminer une large variété de denrées alimentaires. L'ingestion d'aliments contaminés par des animaux d'élevage peut entraîner l'altération de leur santé et de leurs performances zootechniques ainsi qu'un problème de sécurité alimentaire lié à la présence de résidus de mycotoxines dans les produits animaux, notamment le lait. Des traitements de détoxication basés sur l'addition d'adsorbants organiques ont été développés pour fixer les mycotoxines dans le tube digestif et ainsi réduire l'exposition des animaux. L'objectif de ce travail de thèse était d'évaluer l'efficacité d'un adsorbant à base d'extraits de parois modifiées de levures (Mycosorb®) sur deux modèles animaux, le rat et la brebis. L'efficacité a été déterminée en réalisant un suivi des mycotoxines et/ou de leurs métabolites dans 3 matrices : l'excrétion urinaire et fécale et la cinétique sanguine. Sur les 2 modèles animaux, nous avons ainsi étudié les effets de l'apport en Mycosorb sur l'excrétion urinaire et fécale et la cinétique sanguine des 2 mycotoxines (AFB1 et OTA). Chez le rat, le suivi de la radioactivité a montré que les fèces d'animaux supplémentés en parois de levures contiennent significativement plus de mycotoxines. Cette augmentation de la radioactivité dans les fèces s'est accompagnée d'une diminution marquée de la radioactivité dans le sang et dans les urines. Chez la brebis laitière, en plus de ces paramètres, nous avons évalué l'effet de l'adsorbant sur les paramètres de production de l'animal et l'excrétion des mycotoxines dans le lait. L'addition de la paroi de levure a entraîné une augmentation significative de l'excrétion de l'AFB1 et de son métabolite, l'aflatoxine M1(AFM1) dans les fèces du ruminant. Cette augmentation de l'excrétion fécale s'accompagne de la réduction du taux d'AFM1 excrété dans l'urine mais pas dans le lait. Les effets observés chez les deux modèles expérimentaux semblent être liés à la séquestration des mycotoxines dans le tractus digestif des animaux et permettent de conclure à la capacité de l'adsorbant organique à réduire la biodisponibilité des mycotoxines testées. L'ajout de la paroi de levure pourrait, par conséquent, réduire les risques sanitaires chez les animaux d'élevage exposés à une alimentation contaminée par les mycotoxines. Cependant, nous n'avons pas observé d'effet sur la santé et les paramètres zootechniques des animaux dans les conditions expérimentales utilisées.
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Guo, Weihua. "Computational Modeling of Planktonic and Biofilm Metabolism." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/79669.
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Most of microorganisms are ubiquitously able to live in both planktonic and biofilm states, which can be applied to dissolve the energy and environmental issues (e.g., producing biofuels and purifying waste water), but can also lead to serious public health problems. To better harness microorganisms, plenty of studies have been implemented to investigate the metabolism of planktonic and/or biofilm cells via multi-omics approaches (e.g., transcriptomics and proteomics analysis). However, these approaches are limited to provide the direct description of intracellular metabolism (e.g., metabolic fluxes) of microorganisms.
Therefore, in this study, I have applied computational modeling approaches (i.e., 13C assisted pathway and flux analysis, flux balance analysis, and machine learning) to both planktonic and biofilm cells for better understanding intracellular metabolisms and providing valuable biological insights. First, I have summarized recent advances in synergizing 13C assisted pathway and flux analysis and metabolic engineering. Second, I have applied 13C assisted pathway and flux analysis to investigate the intracellular metabolisms of planktonic and biofilm cells. Various biological insights have been elucidated, including the metabolic responses under mixed stresses in the planktonic states, the metabolic rewiring in homogenous and heterologous chemical biosynthesis, key pathways of biofilm cells for electricity generation, and mechanisms behind the electricity generation. Third, I have developed a novel platform (i.e., omFBA) to integrate multi-omics data with flux balance analysis for accurate prediction of biological insights (e.g., key flux ratios) of both planktonic and biofilm cells. Fourth, I have designed a computational tool (i.e., CRISTINES) for the advanced genome editing tool (i.e., CRISPR-dCas9 system) to facilitate the sequence designs of guide RNA for programmable control of metabolic fluxes. Lastly, I have also accomplished several outreaches in metabolic engineering.
In summary, during my Ph.D. training, I have systematically applied computational modeling approaches to investigate the microbial metabolisms in both planktonic and biofilm states. The biological findings and computational tools can be utilized to guide the scientists and engineers to derive more productive microorganisms via metabolic engineering and synthetic biology. In the future, I will apply 13C assisted pathway analysis to investigate the metabolism of pathogenic biofilm cells for reducing their antibiotic resistance.Ph. D.
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Murphy, Julian. "Standard cell and full custom power-balanced logic : ASIC implementation." Thesis, University of Newcastle Upon Tyne, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533690.
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Kotb, Iman. "The balance between regulatory and effector T cells in psoriasis." Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=225790.
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Güell, Riera Oriol. "A network-based approach to cell metabolism: from structure to flux balances." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/292364.
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The thesis called “A network-based approach to cell metabolism: from structure to flux balances” shows how the vision of cell metabolism as a whole allows to unveil new mechanisms and responses impossible to reach by traditional reductionist approaches. Different lines of research have been used, and each one has allowed extracting new insights about the properties of cell metabolism of three organisms, Mycoplasma pneumoniae, Escherichia coli, and Staphylococcus aureus. To do so, tools that belong to the complex network science and Systems Biology have been used.
The first line of study analyzes how the structure of the metabolic networks of the three mentioned organisms respond when their metabolic networks are affected by perturbations, i.e., when a reaction or a set of them are forced to be non-operative. To do this, the applied algorithm spreads a structural cascade when an initial reaction is forced to be non-operative. This study determines that evolutionary pressure favors the ability of efficient metabolic regulation at the expense of losing robustness to reaction failures.
The second line of study focuses on the application of the technique called Flux Balance Analysis (FBA), which is able to compute the fluxes of all reactions composing a metabolic network, assuming that the biological target of the organism is to maximize maximizes the growth rate. The study of synthetic lethal pairs in E. coli and M. pneumoniae with FBA allows identifying two protection mechanisms called plasticity and redundancy. Plasticity sets up as a backup mechanism that is able to reorganize metabolic fluxes turning on inactive reactions when coessential counterparts are removed in order to maintain viability in a specific medium. Redundancy corresponds to a simultaneous use of different flux channels that ensures viability and besides increases growth.
The third part combines FBA and the technique called Disparity Filter in E. coli and M. pneumoniae to obtain metabolic backbones, which are reduced versions of metabolic networks composed by the most relevant connections, this relevancy being determined by the importance of the chemical fluxes. One finds that the disparity filter recognizes metabolic connections that are important for long-term evolution, these connections being related to ancestral pathways. In addition, the disparity filter identifies metabolic connections that are important for short-term adaptation. These connections are related to pathways whose reactions quickly adapt to external stimuli.
The last line of study studies whether the assumption of maximizing the growth rate leads to a representative solution or not. Although FBA gives a single solution, there exist a number of other possible solutions that are chemically feasible but that do not maximize growth, and that form part of the whole flux space. In this way, the third line of study computes all the possible solutions, obtaining in this way the whole space of flux solutions of E. coli. The information content in the whole space of solutions provides with an entire map of phenotypes to evaluate behavior and capabilities of metabolism. Therefore, it is found that the FBA solution is eccentric compared to the mean of solutions. In addition, the whole flux solution map can be used to calibrate the deviation of FBA from experimental observations. To finish, in the map it is possible to find solutions that perform aerobic fermentation, a process which is impossible to recover with FBA computations unless extra constraints are used.
The obtained results could be applied in medical applications, for example to study the metabolism of cancer cells. Thus, it could be a way to study how to force that these cells do not proliferate in the human body, a fact that causes many problems in humans.La visió completa del metabolisme cel·lular, és a dir, tenint en compte totes les reaccions que el componen, permet descobrir nous mecanismes i respostes que són impossibles d’obtenir amb els mètodes reduccionistes tradicionals. L’estudi d’una xarxa metabòlica completa requereix eines que pertanyen a la Biologia de Sistemes i a la Ciència de les Xarxes Complexes. La present tesi mostra com la combinació de les eines que pertanyen a aquests dos camps es pot aplicar per a descobrir noves propietats de les xarxes metabòliques. D'aquesta manera, s’han estudiat les xarxes metabòliques de tres bacteris amb les següents eines: (1) algoritme de cascada, que es pot usar per estudiar si les xarxes metabòliques poden sobreviure a inactivacions de determinades reaccions, (2) Flux Balance Analysis, que s’usa per a calcular els fluxos a través de les reaccions que composen la xarxa metabòlica suposant que l’objectiu biològic de l’organisme a estudiar és maximitzar la velocitat de creixement, (3) Disparity Filter, que permet obtenir versions reduïdes de xarxes metabòliques, cosa que facilita el seu estudi i anàlisi, i (4) Hit-And-Run, que permet obtenir totes les solucions metabòliques independentment de que maximitzin el creixement de l’organisme. En aquesta tesi es demostra que el metabolisme de les cèl·lules dels organismes vius ha evolucionat de forma que aconsegueix sobreviure a les inactivacions de les reaccions que el componen. Addicionalment, s’identifiquen les rutes metabòliques responsables dels processos evolutius i adaptatius que es donen en les xarxes metabòliques. A més, també es demostra que la tècnica Flux Balance Analysis dóna una solució de fluxos que no es representativa de totes les possibles solucions. Cal remarcar que això no invalida la tècnica, sinó que les assumpcions que usa donen una solució concreta que té sentit biològic però que és molt diferent de la resta de solucions. És important recalcar que els resultats obtinguts en aquesta tesi podrien emprar-se en aplicacions mèdiques, per exemple estudiar el metabolisme de les cèl·lules cancerígenes, que podia utilitzar-se per a que aquestes cèl·lules no proliferin en el cos dels humans, un fet que causa moltes problemes en l'ésser humà.
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Ioannides, Andreas. "Characterisation of monolithic tandem solar cells containing strain balanced quantum well sub-cells." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/30625.
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This thesis presents the milestone efficiency of 30.6% under 54x concentration achieved by a monolithic tandem solar cell containing strain balanced quantum well sub-cells. This is the first demonstration of tandem cells containing quantum well sub-cells. Characterisation and modelling of the quantum efficiency and dark currents of monolithic tandem cells containing quantum well sub-cells are also presented for the first time. Predictions performed by a simulation program indicate that 32.3% efficiency at 500x concentration can be achieved and in combination with an active Ge substrate efficiencies of 37.5% are possible. The model created in the simulation program is presented which makes possible the accurate fitting of quantum efficiency and prediction of dark current. The procedure developed to process tandem solar cells into concentrator devices is presented. A detailed account of the characterisation methods used for tandem solar cells are also described. Going further, a new optical concept for building integrated PV design was examined in this thesis. The design is based on a Buffon lens as an alternative to convex and Fresnel lens designs. The low cost design presented can be accommodated in the space of a double glazing window for glass facades.
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Adams, Jessica G. J. "Photonic properties of strain-balanced quantum well solar cells." Thesis, Imperial College London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540681.
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Johnson, David C. "Photon Recycling in strain-balanced quantum well solar cells." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501136.
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Tupin, Emmanuel. "Immunomodulation of atherosclerosis : impact of Th balance and CD1d-restricted NKT cells." Stockholm, 2004. http://diss.kib.ki.se/2004/91-7140-128-8/.
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Kranjac, Tanja. "Balanced chromosomal translocations and chromosome 13 rearrangements in human breast cancer cell lines." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615205.
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Cano, Noel. "Modifications du métabolisme hépato-splanchnique des nutriments au cours de l'insuffisance rénale chronique expérimentale." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10043.
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L'insuffisance renale chronique se caracterise par la frequence de la denutrition et la presence d'anomalies metaboliques affectant les trois classes de macronutriments. Celles-ci ont ete peu etudiees au niveau du secteur hepatosplanchnique. Ce travail, effectue chez des rats insuffisants renaux et temoins, a eu pour buts 1) d'evaluer le statut acide-base splanchnique et son retentissement sur l'ureogenese induite par la perfusion enterale in situ d'un melange nutritif, 2) d'etudier les principales voies metaboliques sur hepatocytes isoles. Les resultats suivants ont ete obtenus. 1) au cours de l'insuffisance renale, une acidose portale liee a une diminution de la production intestinale de hco#3#-, ainsi qu'une reduction de la synthese d'uree induite par la nutrition enterale ont ete observees. Ces resultats suggerent la responsabilite des troubles du statut acide-base splanchnique dans les anomalies de l'utilisation des acides amines rapportees au cours de l'uremie. 2) l'etude du metabolisme hepatocytaire au cours de l'insuffisance renale a montre une baisse d'environ 30% de l'ureogenese (en presence de: alanine, glutamine, ammoniaque, ammoniaque-ornithine) et de la gluconeogenese (en presence de: alanine, glutamine, lactate-pyruvate, glycerol, dihydroxyacetone, fructose). La cetogenese a partir de l'oleate et de l'octanoate etait normale. En presence d'oleate, d'oleate-ammoniaque, d'oleate-lactate-pyruvate et d'oleate-lactate-pyruvate-ammoniaque, le rapport atp/adp mitochondrial etait diminue, alors que la consommation d'oxygene etait normale. Le mecanisme par lequel l'insuffisance renale altere ces voies metaboliques n'est pas univoque. Dans ce travail, la suppression de l'acidose par l'administration orale de nahco#3 corrigeait le metabolisme des acides amines mais n'avait pas d'effet substantiel sur la gluconeogenese induite par les autres substrats. Une reduction de l'activite de la phosphoenolpyruvate carboxykinase, permettant d'expliquer la reduction de la gluconeogenese a partir du lactate, a ete mise en evidence. Le role de l'acidose peut egalement etre discute a propos des modifications du statut energetique cellulaire et d'une eventuelle augmentation de la demande energetique au cours de l'insuffisance renale chronique
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Chap, Christna. "Sprouty4 regulates the balance between pluripotency and trophectoderm differentiation in mouse embryonic stem cells." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16816.
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Unbegrentzte Selbsterneuerungkapazität und Pluripotenz sind charakteristische Merkmale von embryonalen Stammzellen (ES-Zellen). Dennoch sind die molekularen und zellulären Mechanismen, die für das Schicksal der ES-Zellen zuständig sind, noch nicht genau definiert. Um regulierende Faktoren des undifferenzierten Zustands von ES-Zellen zu identifizieren, wurden undifferenzierte ES Zellen, "Embryoid Bodies", spontan differenzierte und mit Retinsäure differenzierte ES Zellen mittels Microarray-Analysen verglichen. Neben bereits etablierten Pluripotenz-Markern, wurde Sprouty4 als eines der am stärksten degerulierten Transkripte unter diesen Bedingungen identifiziert. Sprouty4 ist als Inhibitor des ERK (Extracellular signal-regulated protein kinase)-Signalweges bekannt, aber seine Rolle in ES-Zellen wurde noch nicht definiert. Mittels Genexpression und Western BlotAnalysen konnte gezeigt werden, dass Sprouty4 in undifferenzierten ES-Zellen stark exprimiert ist und im Verlauf der Differenzierung schnell herunterreguliert wird. In vivo war Sprouty4 auf die innere Zellmasse (ICM) der Mausblastozyste beschränkt. Außerdem wurde gezeigt, dass der Sprouty4 Promotor durch direkte Bindung der PluripotenzMarkern Nanog, Klf4 und Stat3 reguliert wird. ES-Zellen, die Sprouty4 konstitutiv exprimieren, waren resistent gegen Differenzierung durch Zugabe von Retinsäure oder Bildung von Embryoid Bodies. Hingegen führte die Expression einer dominant-negativen Mutante von Sprouty4 zu einer erhörten Sensitivierung von ES-Zellen gegenüber der Differenzierung und zur Bildung extraembryonaler Gewebe begleitet von Endoreduplikation. Zusammenfassend konnten unsere Ergebnisse zeigen, dass die enge Regulation des ERK-Signalweges und warscheinlich anderer Signalwege durch Sprouty4 notwendig ist, um die Balance zwichen Pluripotenz und Differenzierung embryonaler Stammzellen zu kontrollieren.A hallmark feature of embryonic stem (ES) cells is the ability to self-renew indefinitely while maintaining pluripotency. However, the molecular and cellular mechanisms underlying ES cell fate are poorly understood. To identify signaling pathway molecules that maintain the uncommitted state of ES cells, a microarray analysis was performed comparing undifferentiated ES cells, mature embryoid bodies, spontaneously differentiated and retinoic acid-induced differentiated ES cells. Among several well-validated pluripotency markers, Sprouty4 was identified as one of the most highly deregulated transcripts under these conditions. Sprouty4 is known as an inhibitor of the extracellular signal-regulated protein kinase (ERK/MAPK) pathway however its role in ES cells has not yet been defined. Gene expression and western-blot analyses have shown that Sprouty4 is highly expressed in ES cells and strongly downregulated upon differentiation whilst in vivo, Sprouty4 is confined to the founder population of ES cells, the inner cell mass of mouse blastocysts. Moreover, the Sprouty4 promoter was found to be regulated via the direct binding of the intrinsic pluripotency-associated factors Nanog, Klf4 and Stat3. ES cells engineered to constitutively express a wild-type version of Sprouty4 were found to be resistant to differentiation induced by retinoic acid or embryoid bodies formation. Conversely, expression of a dominant negative Sprouty4 mutant activating the ERK/MAPK pathway in a sustained manner sensitized ES cells to differentiation and triggered endoreduplication leading to the formation of extraembryonic tissue. Taken together, these results highlight the essential role of Sprouty4 in the tight regulation of the ERK/MAPK pathway- and probably others- for the balance between pluripotency and lineage commitment in mouse embryonic stem cells.
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Zedník, Roman. "Příprava experimentálního měření aerodynamických charakteristik na zmenšeném modelu automobilu v aerodynamickém tunelu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417795.
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This master thesis focuses on designing of an external six-component balance. This universal concept would provide access of results from different models of wings, aircraft and automobiles with relatively small scales. This work also includes theoretical background needed in aerodynamic testing, analysis of 1D beam element model of scale and explanation of components used in scale. Lastly methods of calibration and measurement in aerodynamic tunnel are described, which can be adopted for this design to achieve the adequate level of accuracy.
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Chadha, Kush. "Improvement of water management in PEM fuel cells using water balance and electrochemical noise analysis." Thesis, Poitiers, 2021. http://www.theses.fr/2021POIT2251.
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Cette thèse s’inscrit dans une démarche d’optimisation des performances des piles à combustibles PEMFC, à travers le développement de nouveaux designs de plaque d’alimentation. Des outils tel que le bilan hydrique et l’analyse des bruits électrochimiques ont été utilisés comme diagnostic de la gestion de l’eau au sein d’un mono-cellule PEMFC. Une gestion optimale du transport d’eau permet une augmentation des performances et de la durée de vie des piles à combustible. Le bilan hydrique a été utilisé pour mesurer et encadrer la valeur du coefficient de diffusion effectif de l’eau au sein des membranes de piles à combustibles. De nouvelles géométries de plaque d’alimentation ont été développées et caractériser par des mesures classiques de courbes de performance et des mesures de pression. La technique du bruit électrochimique a été utilisée pour détecter des phénomènes liés au comportement de l’eau lors du fonctionnement de la pile pour chaque géométrie développée. Le bruit électrochimique enregistré pendant ces expériences a été associé à des mécanismes sources grâce à une démarche expérimentale et à un traitement de signal approprié basé sur l’analyse fréquentielle et temporelle. Les résultats des descripteurs obtenus par l’analyse temporel et fréquentiel ont permis de d’obtenir la signature dans un fonctionnement normal de pile à combustible utilisant une géométrie classique de canaux en serpentin. Cette signature a été comparée aux nouveaux designs développés permettant de caractériser l’influence de ces nouvelles géométries sur le transport d’eau. Enfin, de manière à compléter l’approche expérimental effectuée sur le coefficient de diffusion de l’eau au sein des membranes de piles à combustibles PEMFC, une modélisation de la courbe de polarisation prenant en compte ce coefficient a été développé et comparé aux courbes de performances expérimentales. En termes d’ouverture, l’impact des nouvelles géométries développées a été étendu à leur utilisation en stack et un modèle de pronostic basé sur les réseaux de neurones artificiels a été proposéThis thesis deals to optimize the performance of PEMFC fuel cells, through the development of new flow-field plate designs. Tools such as water balance and electrochemical noise analysis have been used to diagnose water management within a PEMFC single cell. Optimal management of the water transport enables an increase of the performance and durability of fuel cells. Water balance method was used to measure and frame the value of the effective water diffusion coefficient within the membranes of fuel cells. New flow-flied plate geometries have been developed and characterized by conventional polarization curve and pressure measurements. The electrochemical noise technique was used to detect phenomena related to the behavior of water during fuel cell operation for each geometry developed. Electrochemical noise measurements have been associated with source mechanisms through an experimental approach and an appropriate signal processing based on frequency and time analysis. The descriptors obtained by time and frequency analysis shows that it possible to obtain the signature in normal operation of a fuel cell using a classical serpentine. This signature was compared to the new developed designs allowing to characterize the influence of these new geometries on the water transport. Finally, to complete the experimental approach carried out on the water diffusion coefficient within the membranes of PEMFC fuel cells, a model based on polarization curve, considering this coefficient, was developed and compared to the experimental curves of performances. In perspective, the impact of the new developed geometries has been extended in a stack utilization and a prognosis model based on artificial neural networks has been proposed
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Lynch, Marianne Catherine. "Modelling and optimisation of single junction strain balanced quantum well solar cells." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/8479.
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In an attempt to find the optimum number of wells for maximum conversion efficiency a pair of otherwise identical strain balanced samples, one containing 50 wells and the other 65 wells have been characterised. The 65 well sample is found to possess a lower predicted efficiency than the 50 well sample, suggesting that the optimum well number lies between these values. Devices grown using tertiary butyl arsine (TBAs) are found to possess comparable conversion efficiencies to the control cells grown using arsine and slightly superior dark IV characteristics, indicating that TBAs may be substituted for arsine without loss of device efficiency and may even be beneficial to cell performance. Several fundamental refinements to the existing quantum efficiency model of are explored. Firstly, expressions for the strained band gaps are derived. A value for the conduction band offset is determined using the difference in energy between the heavy and light hole exciton peaks in low temperature photo current scans and found to be 0.55±0.03. The magnitude of the el-hhl exciton binding energy is also estimated from these scans and found to be in excellent agreement with the value obtained from a simple, parameterized expression for the exciton binding energy. Finally, an absolute calculation for the absorption coefficient is incorporated into the quantum efficiency model and values for the heavy and light hole in-planes masses are obtained. The model is found to underestimate the level of absorption in the intrinsic region by an amount consistent with estimates of the magnitude of the reflection from the back surface. The conversion efficiency of a sample predicted using SOL is compared to an independently obtained value. Good agreement is observed between the two results (25.3% and 25.7% for 317 suns AM1.5D). Additionally, an optimum structure for illumination by the AM1.5D spectrum was found to be a 120A well ofIno.lGaAs.
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Jobin, Lucas. "Stimulation et maitrise électrochimique de la bioremédiation des eaux." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1080.
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Notre étude porte sur la preuve de concept de contrôle électrochimique de la méthanogénèse, métabolisme clé de la digestion anaérobie et de la bioremédiation des eaux, en exploitant le principe des piles à combustible microbiennes. Une première partie bibliographique vise à décrire les mécanismes de la méthanogénèse dans le contexte de l'auto-épuration des eaux et de production naturelle de gaz à effet de serre (GES). Les technologies de pile à combustibles microbiennes y sont traitées. Une analyse critique des études sur le contrôle électrochimique de la méthanogénèse permet de dimensionner un montage expérimental dédié à la quantification des GES en cultures biologiques électro-stimulées. Sa conception, sa validation ainsi que les méthodes de mise en culture sont décrites dans une seconde partie. Une série de cultures préliminaires sur des boues digérées anaérobies de station d'épuration permettent d'identifier et fixer les paramètres expérimentaux. Dans une troisième partie, une étude expérimentale fait la preuve de concept de contrôle électrochimique de la méthanogénèse avec une diminution significative de 33% en CH4 (tension de +300 mV vs Ag/AgCl) par rapport à la méthanogénèse naturelle non stimulée. Toutefois, la stimulation contribue à multiplier par 10 la production de CO2. Ce constat amène la problématique supplémentaire d'impact sur l'effet de serre des cultures étudiées. Nous allons donc plus loin que l'objectif initial en nous intéressant à l'empreinte carbone générée par l'ensemble des GES. Le traitement électrochimique, outre la diminution du CH4 produit, permet de diminuer la contribution à l'effet de serre de 15% des cultures électro-stimuléesOur study focuses on the proof of concept of electrochemical control of methanogenesis, key metabolism of anaerobic digestion and water bioremediation, using the principle of microbial fuel cells. A first bibliographic section aims to describe the mechanisms of methanogenesis in the context of self-purification of water and natural production of greenhouse gases (GHG). Microbial fuel cell technologies are addressed. A critical analysis of the studies dealing with electrochemical control of methanogenesis makes it possible to size an experimental setup dedicated to quantification of GHGs in electro-stimulated biological cultures. Its design, validation and methods of cultivation are described in a second part. A series of preliminary cultures on anaerobic digested sewage sludge make it possible to identify and set the experimental parameters. In a third part, an experimental study proves the concept of electrochemical control of methanogenesis with a significant decrease of 33% in CH4 (voltage of +300 mV vs Ag/AgCl) compared to natural unstimulated methanogenesis. However, stimulation contributes to a 10-fold increase in CO2 production. This observation leads to the additional problem of impact on the greenhouse effect of the cultures studied. We go further than the initial objective by looking at the carbon footprint generated by all GHGs. The electrochemical treatment, in addition to the reduction of CH4 produced, makes it possible to reduce the contribution to the greenhouse effect of 15% of electro-stimulated cultures
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Pelletier, François. "Mise au point d'observateurs d'état pour le suivi de cultures de cellules animales." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL135N.
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L’objectif de ce travail est l'élaboration d'outils d'estimation d'état simples d'emploi pour l'évaluation de la composition des milieux de culture cellulaires. La première partie concerne le développement d'un nouvel estimateur appelé observateur à base de bilans de matière construit sur le principe de l'observateur asymptotique. Il peut être appliqué à n'importe quel type de culture. Il ne nécessite aucun réglage. La possibilité de prendre en compte certaines lois cinétiques connues permet de le faire fonctionner avec un nombre restreint de mesures. La seconde partie traite de la mise au point d'une nouvelle variante du filtre de Kalman, le filtre de Kalman auto-ajustable. Le réglage du filtre de Kalman est délicat et peut conduire à des problèmes de stabilité de l'erreur d'estimation et de convergence des valeurs estimées vers les valeurs réelles. Le filtre de Kalman auto-ajustable assura la stabilité des erreurs d'estimations avec un nombre réduit de réglages. Les deux nouveaux observateurs ont été appliqués à trois cultures d'hybridomes productrices d'anticorps monoclonaux. À partir de deux mesures expérimentales (glucose et lactate déshydrogénase ou ammoniaque et lactate déshydrogénase), la composition du milieu de culture est évaluée par les deux techniques. L’observateur à base de bilans de matière a donné de bons résultats et ceux obtenus avec le filtre de Kalman auto-ajustable sont acceptables tant que l'on ne sort pas du domaine de validité du modèle