Academic literature on the topic 'Particules en cellule (PIC)'
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Journal articles on the topic "Particules en cellule (PIC)":
1
Poirson, Philippe. "Pic de particules fines et inertie des autorités." Revue Médicale Suisse 4, no. 146 (2008): 559a. http://dx.doi.org/10.53738/revmed.2008.4.146.559a.
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Gallinari, F., S. Elmaleh, and R. Ben Aïm. "Influence de la dissipation énergetique sur l'efficacité de la flottation à air dissous : analogie avec la floculation." Revue des sciences de l'eau 9, no. 4 (April 12, 2005): 485–98. http://dx.doi.org/10.7202/705263ar.
Abstract:
Les flottateurs à air dissous sont classiquement dimensionnés à partir de deux paramètres: le rapport mA/mS des masses d'air et de solides en présence et le temps de contact entre phases. Une série d'essais effectués sur cinq différentes unités continues ou discontinues montre que ces seules variables opératoires ne suffisent pas à déterminer l'efficacité. De plus, l'extrapolation des données obtenues sur un floculateur discontinu conduirait à des besoins en air dissous considérables pouvant limiter le développement industriel. La dissipation d'énergie, habituellement négligée, peut être quantifiée par le gradient de vitesse tel qu'il a été introduit en théorie de la floculation. De plus, une analogie entre la capture bulles-particules et le processus de floculation des particules primaires sur les flocs déjà formés permet d'étendre les équations de vitesse de la floculation et d'obtenir un modèle cinétique où interviennent seulement le gradient de vitesse et la concentration de particules; ce modèle remplace avantageusement l'approche classique qui considère la flottation comme un processus du premier ordre par rapport aux particules. L'efficacité d'une cellule discontinue ou d'un floculateur piston est alors fonction du seul nombre de Camp. Les résultats montrent l'existence d'un intervalle optimal pour le gradient de vitesse, 3000 à 4000 s-¹, et pour le nombre de Camp 105 à 106. Le modèle devra être amélioré par introduction de la tension critique de mouillage des particules.
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Hengé-Napoli, M. H., E. Ansoborlo, V. Chazel, R. Gibert, P. Houpert, F. Paquet, and L. Zhang. "Interaction uranium-cellule cible : exemple de la transformation de particules d'UO4dans le macrophage alvéolaire." Radioprotection 32, no. 5 (December 1997): 625–36. http://dx.doi.org/10.1051/radiopro:1997121.
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Fortin, JF, R. Cantin, and MJ Tremblay. "Présence des protéines de la cellule hôte sur les particules virales : influences sur le cycle de vie du VIH-1." médecine/sciences 17, no. 2 (2001): 186. http://dx.doi.org/10.4267/10608/1891.
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Krug, S. A., S. L. Eggers, and B. Matthiessen. "High nitrate to phosphorus ratio attenuates negative effects of rising <i>p</i>CO<sub>2</sub> on net population carbon accumulation." Biogeosciences Discussions 8, no. 4 (July 11, 2011): 6833–57. http://dx.doi.org/10.5194/bgd-8-6833-2011.
Abstract:
Abstract. The ongoing rise in atmospheric pCO2 and the consequent increase in ocean acidification have direct effects on marine calcifying phytoplankton which potentially translates into altered carbon export. To date it remains unclear first, how nutrient ratio, in particular from coccolithophores preferred phosphate limitation, interacts with pCO2 on particulate carbon accumulation. Second, how direct physiological responses on the cellular level translate into a net population response. In this study cultures of Emiliania huxleyi were full-factorially exposed to two different N:P ratios (Redfield and high N:P) and three different pCO2 levels. Effects on net population particulate inorganic and organic carbon (PIC, POC) were measured after E. huxleyi cultures reached stationary phase. Thereby cell sizes and total cell abundance were taken into account. Corresponding to literature results show a significant negative cellular PIC and POC response which, however, was strongest under high N:P ratio. In contrast, net population PIC and POC accumulation was significantly attenuated under high N:P ratio. We suggest that less cellular nutrient accumulation allowed for higher cell abundances which compensated for the strong negative cellular PIC and POC response to pCO2 on the population level. Moreover, the design of this study also allowed following natural alteration of carbon chemistry through changing DIC and alkalinity. Our results suggest that at high initial pCO2 natural alteration of pCO2 during the experimental runtime was regulated by algal biomass. In contrast, at low initial pCO2 the PIC/POC ratio was responsible for changes in pCO2. Our results point to the fact that the physiological (i.e. cellular) PIC and POC response to ocean acidification cannot be linearly extrapolated to total population response and thus carbon export. It is therefore recommended to consider effects of nutrient limitation on cell physiology and translate these to net population carbon accumulation when predicting the influence of coccolithophores on both, the atmospheric pCO2 feedback and their function in carbon export mechanisms.
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Brajkovic, S., D. Favre, G. Niederhäuser, R. Regazzi, G. Waeber, and A. Abderrahmani. "P241 L’induction du stress du réticulum endoplasmique contribue au dysfonctionnement de la cellule bêta provoquée par les particules de LDL oxydées." Diabetes & Metabolism 35 (March 2009): A84. http://dx.doi.org/10.1016/s1262-3636(09)72039-7.
7
Ito, Sayuri, Eisuke Gotoh, Shigeru Ozawa, and Kazuo Yanagi. "Epstein–Barr virus nuclear antigen-1 is highly colocalized with interphase chromatin and its newly replicated regions in particular." Journal of General Virology 83, no. 10 (October 1, 2002): 2377–83. http://dx.doi.org/10.1099/0022-1317-83-10-2377.
Abstract:
Epstein–Barr virus (EBV) nuclear antigen-1 (EBNA-1), which binds to both the EBV origin of replication (oriP) and metaphase chromosomes, is essential for the replication/retention and segregation/partition of oriP-containing plasmids. Here the chromosomal localization of EBNA-1 fused to green fluorescent protein (GFP–EBNA-1) is examined by confocal microscopy combined with a ‘premature chromosome condensation’ (PCC) procedure. Analyses show that GFP–EBNA-1 expressed in living cells that lack oriP plasmids is associated with cellular chromatin that has been condensed rapidly by the PCC procedure into identifiable forms that are unique to each phase of interphase as well as metaphase chromosomes. Studies of cellular chromosomal DNAs labelled with BrdU or Cy3-dUTP indicate that GFP–EBNA-1 colocalizes highly with the labelled, newly replicated regions of interphase chromatin in cells. These results suggest that EBNA-1 is associated not only with cellular metaphase chromosomes but also with condensing chromatin/chromosomes and probably with interphase chromatin, especially with its newly replicated regions.
8
Matthiessen, B., S. L. Eggers, and S. A. Krug. "High nitrate to phosphorus regime attenuates negative effects of rising <i>p</i>CO<sub>2</sub> on total population carbon accumulation." Biogeosciences 9, no. 3 (March 28, 2012): 1195–203. http://dx.doi.org/10.5194/bg-9-1195-2012.
Abstract:
Abstract. The ongoing rise in atmospheric pCO2 and consequent increase in ocean acidification have direct effects on marine calcifying phytoplankton, which potentially alters carbon export. To date it remains unclear, firstly, how nutrient regime, in particular by coccolithophores preferred phosphate limitation, interacts with pCO2 on particulate carbon accumulation; secondly, how direct physiological responses on the cellular level translate into total population response. In this study, cultures of Emiliania huxleyi were full-factorially exposed to two different N:P regimes and three different pCO2 levels. Cellular biovolume and PIC and POC content significantly declined in response to pCO2 in both nutrient regimes. Cellular PON content significantly increased in the Redfield treatment and decreased in the high N:P regime. Cell abundance significantly declined in the Redfield and remained constant in the high N:P regime. We hypothesise that in the high N:P regime severe phosphorous limitation could be compensated either by reduced inorganic phosphorous demand and/or by enzymatic uptake of organic phosphorous. In the Redfield regime we suggest that enzymatic phosphorous uptake to supplement enhanced phosphorous demand with pCO2 was not possible and thus cell abundance declined. These hypothesised different physiological responses of E. huxleyi among the nutrient regimes significantly altered population carrying capacities along the pCO2 gradient. This ultimately led to the attenuated total population response in POC and PIC content and biovolume to increased pCO2 in the high N:P regime. Our results point to the fact that the physiological (i.e. cellular) PIC and POC response to ocean acidification cannot be linearly extrapolated to total population response and thus carbon export. It is therefore necessary to consider both effects of nutrient limitation on cell physiology and their consequences for population size when predicting the influence of coccolithophores on atmospheric pCO2 feedback and their function in carbon export mechanisms.
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Lukaszuk, Bartlomiej, Agnieszka Miklosz, Adrian Chabowski, and Jan Górski. "Modest Decrease in Pgc1α Results in TAG Accumulation but not in Insulin Resistance in L6 Myotubes." Cellular Physiology and Biochemistry 35, no. 4 (2015): 1609–22. http://dx.doi.org/10.1159/000373975.
Abstract:
Background/Aims: PGC-1α is an important cellular protein (coactivator) regulating myocyte mitochondria number and function, and therefore whole cellular energy status. The aim of this work was to investigate the effects of modest, temporary PGC-1α knock-down on L6 myotubes insulin resistance in a light of cellular lipid metabolism. Methods: Gas liquid chromatography was applied for assessing FAs content and composition. For the expression of mitochondrial enzymes, as well as FA and glucose transporters, Western Blot technique was adopted. Additionally, radiolabelled glucose and palmitic acid uptake was performed to estimate the nutrients cellular influx. Results: Modest (-24%) PGC-1α protein ablation resulted in decreased mitochondrial activity in general (reduced Cyt C content) and FAs oxidation in particular (diminished β-HAD expression) without increased FAs cellular influx. The aforementioned intervention led to significantly increased TAG cellular level, but not DAG nor CER. Consequently, no changes in cellular insulin responsiveness were noticed. Conclusions: Modest (-24%) PGC-1α protein depletion results in lipid accumulation, without causing insulin resistance. Importantly, it seems that this TAG loading is a result of decreased mitochondrial oxidative capacity and/or possibly increased lipid biosynthesis but not fatty acid cellular influx.
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Lopez, Katherine C., Sridhar Kandala, Scott Marek, and Deanna M. Barch. "Development of Network Topology and Functional Connectivity of the Prefrontal Cortex." Cerebral Cortex 30, no. 4 (December 6, 2019): 2489–505. http://dx.doi.org/10.1093/cercor/bhz255.
Abstract:
Abstract The prefrontal cortex (PFC) comprises distinct regions and networks that vary in their trajectories across development. Further understanding these diverging trajectories may elucidate the neural mechanisms by which distinct PFC regions contribute to cognitive maturity. In particular, it remains unclear whether PFC regions of distinct network affiliations differ in topology and their relationship to cognition. We examined 615 individuals (8–21 years) to characterize age-related effects in participation coefficient of 28 PFC regions of distinct networks, evaluating connectivity profiles of each region to understand patterns influencing topological maturity. Findings revealed that PFC regions of attention, frontoparietal, and default mode networks (DMN) displayed varying rates of decline in participation coefficient with age, characterized by stronger connectivity with each PFC’s respective network; suggesting that PFC regions largely aid network segregation. Conversely, PFC regions of the cinguloopercular/salience network increased in participation coefficient with age, marked by stronger between-network connections, suggesting that some PFC regions feature a distinctive ability to facilitate network integration. PFC topology of the DMN, in particular, predicted improvements in global cognition, including motor speed and higher order abilities. Together, these findings elucidate systematic differences in topology across PFC regions of different network affiliation, representing important neural signatures of typical brain development.
Dissertations / Theses on the topic "Particules en cellule (PIC)":
1
Monel, Blandine. "Assemblage des particules virales et transmission du VIH de cellule à cellule." Paris 7, 2012. http://www.theses.fr/2012PA077170.
Abstract:
La transmission directe de cellule à cellule du VIH est un moyen de propagation plus puissant et plus efficace que l’infection par particules virales libres. Lors de la première étude de ma thèse nous avons montré que l'assemblage et le relargage de particules virales enveloppées sont nécessaires pour la transmission de cellule à cellule. Des cores viraux ne peuvent pas passer directement d'une cellule donneuse à une cellule cible à travers des pores de fusion induits par Env. ! L'augmentation de l'efficacité de cette voie de propagation du VIH doit donc être attribuée plutôt à une forte concentration locale de particules virales aux sites de contacts cellulaires plutôt qu'à une différence qualitative du processus de transmission, La troncation de la partie cytoplasmique de Envgp41 inhibe la réplication virale dans certains types cellulaires qui sont alors nommées cellules non-permissives. Dans d'autres cellules (cellules permissives), le VIH-1 peut encore se propager. L'objectif de la deuxième étude de ma thèse est de caractériser l'impact de cette troncation dans les deux types cellulaires. Nos résultats montrent que 1*effet de la troncation de Env s'exprime de façon significativernent plus intense quand les virus sont produits dans des cellules non permissives que dans les cellules permissives, et ceci pour les deux modes de transmission. Nos données préliminaires suggèrent que le défaut de réplication dans les cellules non permissives pourrait s'expliquer par une importante mortalité Env-dépendante des cellules "bystanders" non infectées en plus d'un défaut d'incorporation de Env dans les particules virales, comme suggéré dans la littératureDirect cell-to-cell transmission of human immunodeficiency virus (HIV) is a more potent and efficient means of virus propagation than infection by cell-free virus particles, During the first part of my thesis we show that HIV cell-to-cell transmission requires the assembly of enveloped virus particles. Nucleic acids with replication potential can not translocate directly from donor to target cells through envelope glycoprotein (Env)-induced fusion pores, The increased efficiency of this infection route may thus be attributed to the high local concentrations of virus particles at sites of cellular contacts rather than to a qualitatively different transmission process. The truncation of the cytopïasmic tail of Envgp41 inhibits HIV-1 propagation in some cells named non-permissive cells. In some other cell lines (permissive cells), HIV can still propagate. The aim of the second study of my thesis is to characterize the impact of this truncation in the two kinds of cell lines, both on HIV cell-free infectivity and on HTV cell-to-cell transmission. Our results show that, for both transmission modes, the gp41CT truncation of HIV-1 leads to a drastic decrease of infectivity when viruses are produced in non-permissive cells. The replication defect of the HIV-1 gp41CT truncated mutant in non-permissive cells could be explained by an important mortality of the non-infected "bystanders" cells, in addition to the previously shown reduction of Env incorporation into virus particles. Our preliminary results show that contacts established with a cell expressing the truncated Env rapidly induces cell-cell fusion and syncytia formation in non-permissive cells, leading to cell death
2
Betar, Homam. "Kinetic Effects in Magnetic Reconnection." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0043.
Abstract:
Les plasmas sont des systèmes gazeux d'ions et d'électrons qui interagissent avec les champs électromagnétiques et affichent des propriétés collectives. Parmi ceux-ci, il y a la notion de "connexion" de lignes magnétiques. Ceci exprime le fait que, dans des régimes dans lesquels les particules chargées s'enroulent suffisamment vite le long des lignes d'induction magnétique, ces dernières sont liées au mouvement du plasma massif et acquièrent une identité topologique qui leur interdit de se rompre, se croiser et se reconnecter. Cette identité topologique peut cependant être localement violée grâce à un certain nombre d'effets cinétiques, comme les collisions entre les particules, lorsque les courants dans le plasma sont suffisamment intenses : on parle de “reconnexion magnétique”. La reconnexion magnétique est un ingrédient important de l'auto-organisation du plasma et a une importance pour les plasmas spatiaux et de laboratoire, car elle est à la base de phénomènes naturels comme les éruptions solaires et les aurores polaires, ou de processus disruptifs dans les expériences de fusion thermonucléaire. Un problème de longue date dans l'étude des plasmas de laboratoire et astrophysiques est de comprendre les mécanismes d'accélération des électrons et des ions, lorsqu’un champ magnétique se reconnecte et libère de l'énergie. Dans ce travail, nous avons étudié les effets cinétiques sur les instabilités de reconnexion se développant spontanément dans les nappes de courant statique (modes de déchirement) et en combinaison avec une classe d'instabilités cinétiques (instabilités de Weibel) qui sont pertinentes à la fois pour les jets de plasma astrophysiques et pour les expériences d'interaction laser-plasma. Nous avons effectué cette étude en utilisant des modèles fluides réduits et cinétiques, et nous avons étudié la concurrence entre les modes de type déchirement et les instabilités de type Weibel au moyen de simulations cinétiques complètes avec codes semi-lagrangiennes Vlasov-Maxwell et de type “Particle-In-Cell“Plasmas are gaseous systems of ions and electrons which interact via electromagnetic fields and display collective properties. Among these, is the notion of the magnetic line "connection". This expresses the fact that, in regimes in which charged particles spiral sufficiently fast along lines of magnetic induction, the latter is linked to the bulk plasma motion and acquire a topological identity which forbids them to break, intersect and reconnect. This topological identity, however, can be locally violated thanks to a number of kinetic effects, such as particle collisions, when the currents in the plasma are sufficiently intense: one speaks of "magnetic reconnection". Magnetic reconnection is an important ingredient of the plasma self-organization and has significance for both space and laboratory plasmas since it is at the basis of natural phenomena like solar flares and polar lights, or of disruptive processes in thermonuclear fusion experiments. A long-standing problem in the study of laboratory and astrophysical plasmas is to understand the mechanisms of acceleration of electrons and ions, as a magnetic field reconnect and release energy. In this work, we studied kinetic effects on reconnection instabilities developing spontaneously in static current sheets (tearing modes) and in combination with a class of kinetic instabilities (Weibel instabilities) that are relevant both to astrophysical plasma jets and to laser-plasma interaction experiments. We performed this study using reduced-fluid and kinetic models and we investigated the competition between tearing-type modes and Weibel-type instabilities by means of both semi-lagrangian full kinetic Vlasov-Maxwell simulations and particles in cell simulations
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Malbec, Marine. "La transmission de cellule à cellule du VIH-1 : rôle de la protéine Nef et effet inhibiteur des anticorps neutralisants à large spectre." Paris 7, 2013. http://www.theses.fr/2013PA077191.
Abstract:
Nous avons étudié deux aspects de la transmission du VIH-1 de cellule à cellule. Nous avons d'une part examiné le rôle de la protéine virale Nef dans la réplication et le transfert viral et nous sommes intéressés d'autre part aux effets et mécanismes d'action d'un panel d'anticorps neutralisants à large spectre (bNAbs) anti-VIH. Nef est une protéine accessoire du VIH-1, indispensable à la réplication virale et à la pathogénicité in vivo. Nef augmente l'infectivité des virions, diminue les taux d'expression membranaire de différentes protéines de surface et affecte la mobilité cellulaire. Nous avons montré que Nef favorisait la transmission virale de cellule à cellule, augmentait la concentration cellulaire de la protéine de structure Gag et favorisait sa localisation à la membrane plasmique. En l'absence de Nef, les virions transférés aux cellules cibles présentent des défauts de maturation. Les bNAbs inhibent la réplication d'une majorité de souches et sous types viraux. Leur efficacité est déterminée par leur capacité à bloquer l'infection par virus libre mais leur impact sur la transmission intercellulaire du VIH a été peu évalué. Nous avons testé l'activité de 15 bNAbs en collaboration avec l'équipe de Michel Nussenzweig et montré que seul un petit nombre inhibait efficacement l'infection par contact cellulaire. Ces bNAbs s'accumulent à la synapse virologique et bloquent la formation de conjugués et le transfert de matériel viral aux cellules cibles. La transmission cellule-cellule constitue certainement le mode principal de dissémination dans l'organisme; ces bNAbs représentent donc des candidats de choix pour les stratégies thérapeutiques et prophylactiquesWe have studied two aspects of HIV-1 cell-to-cell transmission. First, we have investigated the role of Nef in HIV-1 replication and cell transfer. Second, we have examined the effect of a panel of broad neutralizing antibodies (bNAbs) on cell-to-cell transmission and studied the mechanisms involved. Nef is an HIV regulatory protein indispensable for replication and pathogenicity in vivo. Nef is known to down-regulate the surface expression of various cellular molecules, to increase virions infectivity and to affect cellular motility. We have shown that Nef facilitates HIV cell-to-cell transmission and that this function is conserved among lentiviruses. Nef increases levels of the virus structural Gag protein in the cell and promotes Gag localization to the plasma membrane. In the absence of Nef, viral material transferred to target cells is mostly immature. BNAbs are defined by their potency and their breadth, neutralizing a wide'panel of circulating viral strains from a variety of clades. The antiviral activity of these bNAbs is typically measured in cell free infection assay but little is know about their ability to block cell-associated transmission. By examining 15 bNAbs in collaboration with Michel Nussenzweig's group, we demonstrate that only a small subset efficiently prevent HIV cell-to-cell transmission. These bNAbs accumulate at the virological synapse, block the formation of conjugates and inhibit the transfer of viral material to target cells. Infection by cellular contact is likely the main mode of virus dissemination in vivo and the bNAbs identified in our study may represent candidates for therapeutic or prophylactic strategies
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Lemercier, Nicolas. "CEMOVIS, développements méthodologiques et étude ultrastructurale de la cellule HT29 : De la cellule aux nucléosomes." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00685425.
Abstract:
Nous avons utilisé la méthode de CEMOVIS (Cryo-Electron Microscopy Of Vitreous Sections) pour étudier l'ultrastructure des cellules HT29 (lignée cancéreuse colique humaine) et plus particulièrement l'organisation de la chromatine au sein du noyau. Pour améliorer la méthode, nous avons développé un micromanipulateur qui facilite la collecte des coupes et leur transfert sur la grille. Nous avons également cherché à préparer de nouveaux films métalliques (en remplacement du carbone) permettant une meilleure adhésion des coupes sur le support Au vu des premiers tests réalisés, les films de TiO2 que nous avons fabriqués au laboratoire et caractérisés par microscopie électronique (HR, spectroscopie et cartographie EELS) semblent offrir des perspectives intéressantes que nous attribuons à leur propriétés de conducteur électrique à basse température (ce qui reste à démontrer). Les organites cellulaires (noyaux, réseaux de filaments du cytosquelette, systèmes multilamellaires) ont été identifiés in situ. Les conditions d'imagerie choisies nous ont permis d'obtenir une résolution permettant d'identifier les deux feuillets des bicouches membranaires. Dans le noyau, nous avons observé des motifs striés, distants de 2.7 à 3.5 nm que nous attribuons à la molécule d'ADN enroulée autour du cœur d'histones. Comparées aux images de phases denses de nucléosomes, ces images suggèrent que les nucléosomes (jamais identifiés in situ jusqu'à présent) présentent un ordre très local au sein de la chromatine, que nous discutons à la lumières des modèles polymériques actuels.
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Boudhib, Mohamed. "Analyse d’aérosols par méthodes LIBS sans étalonnage et LIBS couplée à une cellule radiofréquence utilisée comme piège à particules." Thesis, Orléans, 2017. http://www.theses.fr/2017ORLE2011/document.
Abstract:
Pour répondre aux besoins des nouvelles techniques de caractérisation sur site in-situ et temps réel, l’unité NOVA de l’INERIS en partenariat avec les laboratoires LP3 et GREMI, a entamé des travaux pour étudier deux approches afin d’améliorer les performances de la technique Laser-Induced Breakdown Spectroscopy (LIBS) pour l’analyse des aérosols. LIBS est une technique optique de spectroscopie atomique. Elle consiste à focaliser un faisceau laser impulsionnel sur un échantillon à analyser créant ainsi un plasma. L’émission optique du plasma contient alors la signature des éléments chimiques présents dans l’échantillon. La première approche concerne la détermination de la composition chimique relative (stoechiométrique) d’aérosols sans étalonnage. En effet, l’étalonnage présente des problèmes pratiques. Pour ce faire, les spectres expérimentaux enregistrés lors de l’analyse des particules d’alumine (Al2O3) suspendues dans de l’hélium (He) ont été comparés à des spectres théoriques calculés pour un plasma contenant les mêmes éléments, à l’Équilibre Thermodynamique Local (ETL). L’ajustement des spectres simulés sur les spectres expérimentaux nous a permis de déterminer correctement la composition chimique relative des éléments présents dans le plasma. L’évolution temporelle du plasma a permis de valider l’ETL, et ainsi estimer la meilleure plage temporelle permettant la détermination de la composition relative de l’aérosol. La deuxième approche utilise une cellule radiofréquence (RF) à pression réduite comme piège à particules pour analyser des aérosols contenant des nanoparticules. Un tel piège permet d’améliorer la détection en concentrant spatialement les particules. Les paramètres optimaux d’utilisation de ce système ont été étudiés. Cette étude a permis d’établir que l’émission continue du plasma est fortement réduite dès ses premiers instants de vie. Le volume d’échantillonnage de ce système a été évalué et la limite de détection a été estimée de manière théoriqueNew issues related to process control and workplace surveillance accompany the emergence of nanotechnology industry. This involves the development of new real-time and in-situ characterization techniques. In this context, the NOVA unit from the INERIS institute collaborated with LP3 and GREMI laboratories to study two approaches aiming to enhance the LIBS technic performances. The first approach used a flow cell to determine the relative elemental composition of an aerosol with a calibration-free procedure. The recorded spectra were compared to theoretical spectra calculated for a plasma in the Local Thermodynamic Equilibrium LTE. The best agreement between recorded and computed spectra allowed the determination of the relative composition with a good agreement with the reference value, for an alumina aerosol. The study of the temporal evolution of the plasma allowed the estimation of a temporal range within which the LTE hypothesis was verified. The second approach used a low-pressure radiofrequency plasma generated in an inert gas as a particle trap to analyse aerosols and nanoparticles. The use of such a system allowed the enhancement of particles detection by concentrating them spatially. We determined the optimal parameters for the LIBS analysis using this system. Furthermore, we established the plasma continuum was attenuated even at very low time delays. We evaluated the sampling volume of this new system and compared it to case of LIBS analysis on air. Finally, we estimated the detection limits of this system when analysing nanoparticles
6
DOORNAERT, BLANDINE. "Impact des particules diesel et des acariens sur les cellules epitheliales bronchiques humaines : alteration des interactions cellule-matrice extracellulaire." Paris 12, 2001. http://www.theses.fr/2001PA120016.
Abstract:
L'objectif de cette etude fut d'evaluer l'impact des particules diesel (pds) et des acariens sur l'interaction des cellules epitheliales bronchiques humaines (cebhs) avec leur microenvironnement matriciel et cellulaire. Cette interaction fut etudiee sur les cebhs en culture, en termes d'interaction cellulaire et matricielle via les integrines et le cd44 (cytometrie en flux), de rigidite du cytosquelette (csq) d'actine (magnetocytometrie) et de remaniement matriciel via les metalloproteinases (mmps) et leurs inhibiteurs tissulaires les timps (zymographie et elisa). La proliferation cellulaire fut evaluee par incorporation de brdu, la capacite de reparation cellulaire par la vitesse de fermeture d'une blessure mecanique et la capacite de de-adherence cellulaire par la vitesse de detachement cellulaire. La 1 e r e partie de l'etude montre que : 1) l'augmentation de la rigidite du csq d'actine, de l'ensemencement a la confluence, est correlee a l'organisation progressive d'une actine hautement polymerisee et a la sur-expression des sous-unites d'integrines 5, v et 1 ; 2) le niveau de rigidite du csq d'actine est optimal sur collagene de type iv par comparaison aux types i et iii, suggerant une dependance matricielle. La 2 e m e partie de l'etude montre que l'exposition aux pds induit une perte dose-dependante de la rigidite du csq d'actine, associee a une redistribution des filaments d'actine autour des particules lors de la phagocytose et a la reduction de l'expression des sous-unites d'integrines 3 et 1 et de cd44. Ces donnees sont coherentes avec l'augmentation de la capacite de de-adherence cellulaire et avec la moindre capacite de reparation cellulaire elle-meme liee a un defaut de proliferation cellulaire et a une perte
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Khelifi, Sadjia. "Étude du comportement hydrodynamique de suspensions concentrées de particules d’hématite : sédimentation, comportement rhéologique et écoulement forcé dans une cellule inclinée." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0036.
Abstract:
Cette thèse s’inscrit dans le projet ASCoPE qui vise à développer les connaissances scientifiques et technologiques nécessaires à la conception et à la réalisation d’un pilote de production d’acier par réduction électrochimique de particules d’hématite en suspension dans un milieu alcalin à 110°C, en vue de proposer un procédé industriel fiable et écologique, comme alternative au procédé classique reposant sur le charbon. Le mélange considéré contient une suspension d’hématite à 12% en volume dans une solution aqueuse de soude à 50% en masse. Cette thèse a pour objectif l’étude de la sédimentation et de la rhéologie des suspensions d’hématite et le comportement hydrodynamique des particules d’hématite dans une cellule inclinée et de quantifier l’éventuel phénomène d’impact sur la cathodeThis thesis aims to develop scientific and technological knowledge needed to design a pilot production of steel by electrochemical reduction of hematite particles suspended in an alkaline medium at 110°C in order to provide a reliable and environmentally friendly industrial process, as an alternative to the conventional process based on coal. The mixture considered contains a suspension of hematite of 12% by volume in an aqueous sodium hydroxide solution of 50% by weight. This thesis seeks to study the sedimentation and rheology of hematite suspensions and the hydrodynamic behavior of hematite particles in inclined cell and to quantify the possible phenomeno impact on the cathode
8
Turkcan, Silvan. "Interaction toxine-cellule étudiée par imagerie de nanoémetteurs individuels." Phd thesis, Ecole Polytechnique X, 2010. http://tel.archives-ouvertes.fr/tel-00608124.
Abstract:
La membrane cellulaire est une partie vitale de la cellule dont l'architecture joue un rˆole crucial dans de nombreux processus cellulaires, comme la signalisation et le trafic, et dans diverses pathologies. Cette th'ese vise 'a sonder l'architecture membranaire via le mouvement de deux r'ecepteurs membranaires qui sont exploit'es par des toxines bact'eriennes. Les progr'es r'ecents des techniques de microscopie optique ont montr'e que certains r'ecepteurs membranaires ne diffusent pas librement dans la membrane, mais sont confin'es ou diffusent de fa¸con anomale. Actuellement, plusieurs mod'eles con- courent pour expliquer le confinement des r'ecepteurs, tel que le mod'e le Picket-Fence, les radeaux lipidiques et les agr'egats de prot'eines. Pour sonder la membrane, des nanoparticules (Y0.6Eu0.4VO4) dop'ees avec des lan- thanides sont coupl'ees 'a deux toxines peptidiques diff'erentes formant des pores dans la membrane, la toxine α de C. septicum et la toxine ǫ de C. perfingens. Le suivi de r'ecepteurs individuels sur lesquels sont fix'ees des toxines marqu'ees dans la mem- brane apicale de cellules MDCK avec un microscope 'a champ large permet de d'etecter le mouvement du r'ecepteur avec une r'esolution meilleure que la limite de diffrac- tion. Les r'ecepteurs de la toxine α et ǫ montrent une diffusion confin'ee avec des coefficients de diffusion similaires de 0.16 ± 0.14 µm2/s dans des domaines stables de 0.5 µm2. Pour analyser les trajectoires des r'ecepteurs, nous avons mis en oeuvre une nouvelle technique bas'ee sur une m'ethode d'inf'erence. Notre seule hypoth'ese est que le r'ecepteur se d'eplace selon l''equation de Langevin. Cette m'ethode exploite l'ensemble de l'information stock'ee dans la trajectoire et la qualit'e des valeurs extraites est v'erifi'ee par des simulations. Les deux r'ecepteurs sont confin'es dans un potentiel de type ressort avec une raideur de 0.45 pN/µm. Des exp'eriences apr'es d'epl'etion du cholest'erol par la cholest'erol oxydase et apr'es la d'epolym'erisation du cytosquelette par latrunculin B montrent que le confinement des r'ecepteurs individuels d'epend du taux de cholest'erol et que la d'epolym'erisation de l'actine n'influence pas le confinement. En utilisant la nanoparticule coupl'ee aux toxines comme un amplificateur de la force hydrodynamique applique'e par un flux liquide, nous avons mesur'e la r'eponse du r'ecepteur 'a une force ext'erieure. Les r'esultats indiquent une fixation des domaines de confinement sur le cy- tosquelette. Enfin, un mod'ele pour le confinement du r'ecepteur est propos'e, bas'e sur le couplage hydrophobe entre le r'ecepteur et la bicouche lipidique qui l'entoure. Ce mod'ele permet d'expliquer le potentiel de type ressort 'a l'int'erieur du domaine de confinement.
9
Saias, Laure. "Laboratoires-sur-puce pour l'analyse cellulaire : tri de cellules tumorales circulantes et culture de neurones." Paris 6, 2009. http://www.theses.fr/2009PA066684.
Abstract:
Nous présentons deux dispositifs microfluidiques dédiés à l’analyse cellulaire. Le premier système est dédié à la caractérisation de Cellules Tumorales Circulantes (CTC) dans l’objectif de permettre une meilleure prise en charge d’un patient ayant développé un cancer (pronostic, orientation du traitement le plus adapté). Afin de permettre l’analyse d’un prélèvement sanguin à haut débit, l’architecture des canaux d’un nouveau système microfluidique a été optimisée grâce à des simulations fluidiques avec le logiciel COMSOL. Les cellules sont capturées dans le microsystème par un réseau de colonnes constituées de billes magnétiques fonctionnalisées avec des anticorps dirigés spécifiquement contre une protéine membranaire exprimée par les CTC (en particulier dans les cas de cancer du sein), EpCAM (Epithelial Cell Adhesion Molecule). Ce réseau de colonnes a été stabilisé en réalisant un ancrage magnétique par assemblage capillaire. Les capacités de capture du système ont été évaluées grâce à des échantillons cellulaires modèles (lignées cellulaires, sang de donneurs sains). Une fois les cellules immobilisées sur les colonnes, l’expression de protéines spécifiques (cytokératine, CD45) peut être caractérisée par marquages immunofluorescents en imagerie confocale haute résolution. Le deuxième système microfluidique a été développé afin de pouvoir reconstruire des réseaux neuronaux dirigés. Une géométrie innovante de microcanaux a permis l’élaboration de diodes axonales. L’aptitude du système à structurer les connexions entre neurones a été évaluée avec des neurones primaires. Plusieurs types de réseaux ont ainsi été reconstruits et maintenus en culture sur 12 jours.
10
Lyu, Jinming. "Modélisation numérique de la dynamique de particules molles en microcanaux." Thesis, Ecole centrale de Marseille, 2019. http://www.theses.fr/2019ECDM0002.
Abstract:
Une vésicule est un système modèle utilisé pour comprendre le comportement dynamique en écoulement d’une particule molle fermée telle qu’un globule rouge. La membrane bicouche lipidique inextensible d’une vésicule admet une résistance d’élasticité en flexion. Lorsque dégonflée, c’est-à-dire pour un grand rapport surface sur volume, une vésicule présente des changements de formes remarquables. Des progrès significatifs ont été réalisés au cours des dernières décennies dans la compréhension de leur dynamique en milieu infini. Ce manuscrit s’intéresse à la transition de formes et à la migration latérale d’une vésicule dans des écoulements confinés. L’approche est numérique, basée sur une méthode aux éléments finis de frontière (BEM) isogéométrique. Partant d’une version existante pour les écoulements de Stokes non confiné, un code original est développé pour prendre en compte les parois de microcanaux de section transversale arbitraire. L’essentiel des études porte sur la dynamique d’une vésicule transportée par un écoulement de Poiseuille dans une conduite de section circulaire. Tout d’abord, nous examinons les formes typiques des vésicules, les différents modes de migration latérale et la structure de l’écoulement des lipides dans la membrane, en fonction des trois paramètres sans dimension caractéristiques : le volume réduit, le confinement et le nombre capillaire (de flexion). Les transitions de forme et le diagramme de phase de formes stables pour plusieurs volumes réduits sont obtenus dans l’espace (confinement, nombre capillaire). Ils montrent une extension de l’ensemble des morphologies de la vésicule. L’interaction complexe entre la paroi du tube, les contraintes hydrodynamiques et l’élasticité de flexion de la membrane conduit à une dynamique bien plus riche. Nous étudions ensuite, via une version axisymétrique du modèle, le comportement de la vésicule lorsque des conditions de confinement deviennent sévères et imposent des formes de vésicule axisymétriques. Un accent particulier est mis sur la prédiction de la mobilité de la vésicule et de la perte de charge additionnelle induite par la présence de la vésicule. Cette dernière est importante pour comprendre la rhéologie d’une suspension diluée. De plus, sur la base des résultats numériques du comportement proche du confinement maximal, nous établissons plusieurs lois d’échelle portant sur la vitesse de la vésicule et sa longueur, ainsi que sur l’épaisseur du film de lubrification. Enfin, nous présentons un modèle hybride BEM–coarse-graining permettant d’adjoindre un cytosquelette à une vésicule pour étendre nos études au cas des globules rouges. La modélisation coarse-graining du cytosquelette repose sur un réseau de ressorts identifié à l’ensemble des arêtes du maillage d’éléments finis de la membrane de la vésicule. Les résultats numériques montrent que ce modèle à deux composants vésicule–cytosquelette est capable d’extraire les propriétés mécaniques des globules rouges et de prédire sa dynamique dans les écoulements de fluideVesicles are a model system for understanding the dynamical behavior of a closed soft particle such as red blood cells (RBCs) in flows. The inextensible lipid bilayer membrane of a vesicle admits resistance to the bending elasticity, and its large surface-area-to-volume ratio allows the vesicle to exhibit remarkable shape changes in the dynamics even in a simple flow. Significant progress has been made over the past decades in understanding vesicle dynamics in unbounded Stokes flows. This manuscript deals with the numerical investigation of shape transition and lateral migration of 3D vesicles in wall-bounded Stokes flows by means of an isogeometric finite-element method (FEM) and boundary-element method (BEM). Starting from a previously reported isogeometric FEM-BEM simulations of the dynamics of soft particles (drops, capsule, and vesicle) in Stokes flows in free space, the original code is developed to account for microchannel walls of arbitrary cross-section. The present work focuses on the dynamics of a vesicle that is transported through a circular tube in a pressure-driven flow. First, we investigate typical vesicle shapes, different lateral migration modes, and flow structure onto vesicle membrane versus three independent dimensionless parameters, namely, the reduced volume, the confinement, and the (bending) capillary number. Shape transitions and the phase diagram of stable shapes for several reduced volumes are obtained in the (confinement, capillary number) space, showing an extension of the set of vesicle morphologies and rich vesicle dynamics owing to the intricate interplay among the tube wall, hydrodynamic stresses, and membrane bending. Secondly, we study, via an axisymmetric BEM, the hydrodynamics under high confinements in which the shape of the vesicle is expected to maintain axisymmetry. A particular emphasis is given to the prediction of the vesicle mobility and the extra pressure drop caused due to the presence of the vesicle, the latter having implications in the rheology of a dilute suspension. In addition, based on the numerical results of limiting behavior of quantities of interest near maximal confinement, we give various scaling laws to infer, for example, the vesicle velocity, its length, and the thickness of lubrication film. Finally, we present a coupled, hybrid continuum–coarse-grained model for the study of RBCs in fluid flows. This model is based on a combination of the vesicle model with a network of springs with fixed connectivity, representing the cytoskeleton. Numerical results show that this two-component vesicle–cytoskeleton model isable to extract the mechanical properties of RBCs and predict its dynamics in fluid flows
Book chapters on the topic "Particules en cellule (PIC)":
1
Williams, Barbara A., and Michael J. Gidley. "The use of dietary fibre to optimize microbial gut function in pigs, with particular consideration of dietary cereal grains and legumes." In Understanding gut microbiomes as targets for improving pig gut health, 239–84. Burleigh Dodds Science Publishing, 2022. http://dx.doi.org/10.19103/as.2021.0089.10.
Abstract:
This chapter examines interactions of dietary fibre components of pig diets with GIT microbiota, emphasizing cereals and legumes fed to pigs. Carbohydrate composition of these feedstuffs are described, and their relationship to metabolic activity of the porcine intestinal microbiota and interactions with the host. Fermentable carbohydrates which act as substrates for microbial metabolism are described, followed by an assessment of cereals and legumes as potential modulators of intestinal microbiota. Past work focussed on purified extracts, but attention is now focussing on whole grains or their fractions such as brans, in terms of effects on microbial populations. Such studies are showing the positive consequences of mixtures of DF in the form of complex plant cellular structures, rather than single refined ingredients, to achieve beneficial health outcomes. Further work is also needed to define appropriate quantities and types of DF to achieve desired effects whilst minimising negative outcomes.
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Becker, Richard C., and Frederick A. Spencer. "Factor Xa Inhibitors." In Fibrinolytic and Antithrombotic Therapy. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195155648.003.0021.
Abstract:
The importance of factor Xa in the initiation and propagation of coagulation, as well as its pluripotential cellular properties, has been discussed previously. Considered collectively, the effects exhibited by this particular protease make it an attractive target for pharmacologic inhibition. Factor Xa inhibition can be classified and subcategorized as follows: indirect (antithrombin [AT]-dependent), nonselective (e.g., unfractionated heparin); indirect, semi-selective (e.g., low-molecular-weight heparin); indirect, selective (e.g., fondaparinux); and direct, selective (e.g., DX-9065a [in early stage of development]). Oral factor Xa inhibitors are in phase II testing. Fondaparinux (Arixtra) is a synthetic pentasaccharide that requires AT for selective fXa binding (Petitou et al., 1991). Unlike heparin compounds, fondaparinux does not inhibit thrombin directly nor does it interact with platelets (or platelet-derived proteins). After subcutaneous administration in healthy volunteers, fondaparinux was nearly 100% bioavailable, and absorption was rapid (Cmax within 2 hours) (Donat et al., 2002). Clearance is through renal mechanisms with a terminal halflife of 17 ± 3 hours (slightly longer in elderly volunteers). Overall, drug clearance is 25% lower in patients with mild renal impairment (creatinine clearance [CrCl] 50–80 mL/min), approximately 40% lower in patients with moderate renal impairment (CrCl 30–50 mL/min), and 55% lower in patients with severe renal impairment (CrCl <30 mL/min). OASIS-5, the largest trial performed to date in non-ST segment elevation acute coronary syndromes (ACS), randomized 20,078 patients to fondaparinux (2.5 mg subcuaneous once daily) or enoxaparin (1 mg/kg twice daily) for 2 to 8 days. The primary outcome (composite of death, MI, and refractory ischemia on day 9) was 5.9% and 5.8%, respectively. Major bleeding rates were 2.1% and 4.0%, respectively (hazard ratio 0.53; p<.001). By 6-month follow-up, the endpoints of death, death/MI, stroke, and composite of death/MI/stroke were significantly reduced in those receiving fondaparinux. Catheter thrombosis (during PCI) was 3-fold higher in fondaparinux-treated patients compared to those receiving enoxaparin (1.3% vs. 0.5%, respectively) (European Society of Cardiology presentation, September 2005). The clinical use of fondaparinux for venous thromboembolism prophylaxis will be discussed in Chapter 22.
Conference papers on the topic "Particules en cellule (PIC)":
1
FERRANDON, Erwan, Mathis COURANT, Camélia POPESCU, Yann LAUNAY, Sophie ALAIN, and Claire LEFORT. "Un pipeline instrumental et computationnel pour visualiser des particules virales de SARS-CoV-2 en suspension." In Les journées de l'interdisciplinarité 2022. Limoges: Université de Limoges, 2022. http://dx.doi.org/10.25965/lji.684.
Abstract:
La compréhension des modes d’actions biologiques des virus dans une cellule hôte est un sujet complexe pour lequel nous pensons que les solutions optiques pourraient apporter des éléments de réponse nouveaux. Cependant, les dimensions des particules virales sont environ 3 fois plus petites que la résolution d’un microscope optique. Nous proposons de tester une nouvelle stratégie instrumentale et computationnelle, reposant sur la microscopie multiphotonique, pour visualiser des objets dont les dimensions sont de l’ordre de quelques centaines de nanomètres. Cette stratégie repose sur la prise en compte de la réponse impulsionnelle de l’instrument (PSF pour Point Spread Function) in situ, modélisée mathématiquement. A partir de ce modèle qui prend en compte les distorsions optiques locales, un post-traitement numérique des images est appliqué en vue d’optimiser la qualité visuelle des images. Nous faisons des tests sur deux populations de virus : les Cytomégalovirus (CMV) et le SARS-CoV-2.
2
Pontecorvo, Michael E., Silvestro Barbarino, and Farhan S. Gandhi. "Cellular Honeycomb-Like Structures With Internal Inclusions in the Unit-Cell." In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8075.
Abstract:
Cellular structures with hexagonal unit cells show a high degree of flexibility in design. Based on the geometry of the unit cells, highly orthotropic structures, structures with negative Poisson’s ratios, structures with high strain capability in a particular direction, or other desirable characteristics may be designed. Much of the prior work on cellular structures is based on hexagonal honeycomb-like unit cells, without any inclusions. The present paper envisages extending conventional cellular honeycomb-like structures to have inclusions or internal features within the unit cells. Various types of internal features such as contact elements, buckling beams, bi-stable/snap-through elements or viscous dashpots can result in unit cells which display stiffening, softening, negative stiffness, or dissipative behavior. A structure can be assembled using a specific element type, or different types of elements in specific arrangements, to provide desired system level behavior. The ability to so optimally and flexibly design cellular structures could potentially lead to their replacing conventional structures made from bulk materials. As a first step, this paper presents work on hexagonal unit cells with linear springs as the simplest of inclusions. The hexagonal cell itself is comprised of rigid links and pin-joints. Since such a cell has no stiffness of its own, the behavior of any internal feature is emphasized. However, for kinematic stability purposes, three springs are required, and the significance of these constraints within the cell will be discussed. For different spring arrangements, closed-form analytical expressions are derived for the in-plane modulus and Poisson’s ratio. The analytical expressions are validated using NASTRAN finite element simulations, as well as against experimental tensile/compressive tests of fabricated unit cells with internal springs. When the spring stiffness exceeds certain values, the rigid cell wall assumption is no longer valid, and these bounds are established. The validated analysis is used to conduct design studies on how the cell modulus would vary with geometric parameters such as cell angle and cell wall length ratio.
3
Barbarino, Silvestro, Michael E. Pontecorvo, and Farhan S. Gandhi. "Cellular Honeycomb-Like Structures With Internal Buckling and Viscous Elements for Simultaneous Load-Bearing and Dissipative Capability." In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8080.
Abstract:
Cellular structures with hexagonal unit cells show a high degree of flexibility in design. Based on the geometry of the unit cells, highly orthotropic structures, structures with negative Poisson’s ratios, structures with high strain capability in a particular direction, or other desirable characteristics may be designed. Much of the prior work on cellular structures is based on hexagonal honeycomb-like unit cells, without any inclusions. A companion paper to the current paper presented a vision of cellular honeycomb-like structures with diverse inclusions or internal features within the unit cells (such as contact elements resulting in stiffening behavior, buckling beams resulting in softening behavior, bi-stable elements producing negative stiffness or viscous dashpots producing dissipative behavior). That paper further went into details on linear springs as the most fundamental of inclusions. In the present paper, a buckling beam and viscous dashpots are used as inclusions in the basic pin-jointed rigid-walled hexagonal unit cell. The buckling beam provides the cell with a high initial stiffness and load carrying capability. At loads beyond the critical buckling load, the unit cell softens (while still retaining the ability to carry a “design” load), and undergoes large deformation under incremental load. The viscous dampers undergo a correspondingly large stroke resulting in high dissipative capability and loss factor under harmonic or transient disturbance beyond the design load. In the paper, an analysis and design study of the cell behavior with variation in unit cell geometric parameters, buckling beam parameters and viscous dashpot parameters is presented. The analytical results in the paper are validated against ANSYS Finite Element results. Further, a prototype unit cell with an aluminum internal buckling beam and viscous dashpots is fabricated and tested under static and dynamic loads in an Instron machine. Good correlation is observed between the tests, the FE results and the analytical simulations when accounting for the non-linear behavior of the viscous dashpot used in the tests.
4
Zhang, Zhenyu, Jhon Diaz, and Nejat Olgac. "Adaptive Hybrid Control for Rotationally Oscillating Drill (Ros-Drill©), Using a Low-Resolution Sensor." In ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control. ASMEDC, 2011. http://dx.doi.org/10.1115/dscc2011-6065.
Abstract:
A novel hybrid (i.e., discrete/continuous) control system is studied on a cellular microinjector technology called the Ros-Drill© (Rotationally Oscillating Drill). Ros-Drill© is developed primarily for ICSI (Intra-Cytoplasmic Sperm Injection). It is an inexpensive set-up, which creates high-frequency rotational oscillations at the tip of an injection pipette tracking a harmonic motion profile. These rotational oscillations enable the pipette to drill into cell membranes with minimum biological damage. Such a motion control procedure presents no particular difficulty when it uses sufficiently precise motion sensors. However, size, costs and accessibility of technology on hardware components may severely constrain the sensory capabilities. Then the trajectory tracking is adversely affected. In this paper we handle such a practical case, and present a novel adaptive-hybrid control logic to overcome the hurdles. The control is implemented using a commonly available microcontroller and extremely low-resolution position measurements. First, the continuous control system is analyzed and designed. Then, an adaptive, robust and optimal PID (proportional-integral-derivative) control strategy is performed. We demonstrate via simulations and experiments that the tracking of the harmonic rotational motion is achieved with desirable fidelity.
Reports on the topic "Particules en cellule (PIC)":
1
Morrison, Mark, and Joshuah Miron. Molecular-Based Analysis of Cellulose Binding Proteins Involved with Adherence to Cellulose by Ruminococcus albus. United States Department of Agriculture, November 2000. http://dx.doi.org/10.32747/2000.7695844.bard.
Abstract:
At the beginning of this project, it was clear that R. albus adhered tightly to cellulose and its efficient degradation of this polysaccharide was dependent on micromolar concentrations of phenylacetic acid (PAA) and phenylpropionic acid (PPA). The objectives for our research were: i) to identify how many different kinds of cellulose binding proteins are produced by Ruminococcus albus; ii) to isolate and clone the genes encoding some of these proteins from the same bacterium; iii) to determine where these various proteins were located and; iv) quantify the relative importance of these proteins in affecting the rate and extent to which the bacterium becomes attached to cellulose. BARD support has facilitated a number of breakthroughs relevant to our fundamental understanding of the adhesion process. First, R. albus possesses multiple mechanisms for adhesion to cellulose. The P.I.'s laboratory has discovered a novel cellulose-binding protein (CbpC) that belongs to the Pil-protein family, and in particular, the type 4 fimbrial proteins. We have also obtained genetic and biochemical evidence demonstrating that, in addition to CbpC-mediated adhesion, R. albus also produces a cellulosome-like complex for adhesion. These breakthroughs resulted from the isolation (in Israel and the US) of spontaneously arising mutants of R. albus strains SY3 and 8, which were completely or partially defective in adhesion to cellulose, respectively. While the SY3 mutant strain was incapable of growth with cellulose as the sole carbon source, the strain 8 mutants showed varying abilities to degrade and grow with cellulose. Biochemical and gene cloning experiments have been used in Israel and the US, respectively, to identify what are believed to be key components of a cellulosome. This combination of cellulose adhesion mechanisms has not been identified previously in any bacterium. Second, differential display, reverse transcription polymerase chain reaction (DD RT-PCR) has been developed for use with R. albus. A major limitation to cellulose research has been the intractability of cellulolytic bacteria to genetic manipulation by techniques such as transposon mutagenesis and gene displacement. The P.I.'s successfully developed DD RT- PCR, which expanded the scope of our research beyond the original objectives of the project, and a subset of the transcripts conditionally expressed in response to PAA and PPA have been identified and characterized. Third, proteins immunochemically related to the CbpC protein of R. albus 8 are present in other R. albus strains and F. intestinalis, Western immunoblots have been used to examine additional strains of R. albus, as well as other cellulolytic bacteria of ruminant origin, for production of proteins immunochemically related to the CbpC protein. The results of these experiments showed that R. albus strains SY3, 7 and B199 all possess a protein of ~25 kDa which cross-reacts with polyclonal anti-CbpC antiserum. Several strains of Butyrivibrio fibrisolvens, Ruminococcus flavefaciens strains C- 94 and FD-1, and Fibrobacter succinogenes S85 produced no proteins that cross-react with the same antiserum. Surprisingly though, F. intestinalis strain DR7 does possess a protein(s) of relatively large molecular mass (~200 kDa) that was strongly cross-reactive with the anti- CbpC antiserum. Scientifically, our studies have helped expand the scope of our fundamental understanding of adhesion mechanisms in cellulose-degrading bacteria, and validated the use of RNA-based techniques to examine physiological responses in bacteria that are nor amenable to genetic manipulations. Because efficient fiber hydrolysis by many anaerobic bacteria requires both tight adhesion to substrate and a stable cellulosome, we believe our findings are also the first step in providing the resources needed to achieve our long-term goal of increasing fiber digestibility in animals.
2
Blumwald, Eduardo, and Avi Sadka. Citric acid metabolism and mobilization in citrus fruit. United States Department of Agriculture, October 2007. http://dx.doi.org/10.32747/2007.7587732.bard.
Abstract:
Accumulation of citric acid is a major determinant of maturity and fruit quality in citrus. Many citrus varieties accumulate citric acid in concentrations that exceed market desires, reducing grower income and consumer satisfaction. Citrate is accumulated in the vacuole of the juice sac cell, a process that requires both metabolic changes and transport across cellular membranes, in particular, the mitochondrial and the vacuolar (tonoplast) membranes. Although the accumulation of citrate in the vacuoles of juice cells has been clearly demonstrated, the mechanisms for vacuolar citrate homeostasis and the components controlling citrate metabolism and transport are still unknown. Previous results in the PIs’ laboratories have indicated that the expression of a large number of a large number of proteins is enhanced during fruit development, and that the regulation of sugar and acid content in fruits is correlated with the differential expression of a large number of proteins that could play significant roles in fruit acid accumulation and/or regulation of acid content. The objectives of this proposal are: i) the characterization of transporters that mediate the transport of citrate and determine their role in uptake/retrieval in juice sac cells; ii) the study of citric acid metabolism, in particular the effect of arsenical compounds affecting citric acid levels and mobilization; and iii) the development of a citrus fruit proteomics platform to identify and characterize key processes associated with fruit development in general and sugar and acid accumulation in particular. The understanding of the cellular processes that determine the citrate content in citrus fruits will contribute to the development of tools aimed at the enhancement of citrus fruit quality. Our efforts resulted in the identification, cloning and characterization of CsCit1 (Citrus sinensis citrate transporter 1) from Navel oranges (Citrus sinesins cv Washington). Higher levels of CsCit1 transcripts were detected at later stages of fruit development that coincided with the decrease in the juice cell citrate concentrations (Shimada et al., 2006). Our functional analysis revealed that CsCit1 mediates the vacuolar efflux of citrate and that the CsCit1 operates as an electroneutral 1CitrateH2-/2H+ symporter. Our results supported the notion that it is the low permeable citrateH2 - the anion that establishes the buffer capacity of the fruit and determines its overall acidity. On the other hand, it is the more permeable form, CitrateH2-, which is being exported into the cytosol during maturation and controls the citrate catabolism in the juice cells. Our Mass-Spectrometry-based proteomics efforts (using MALDI-TOF-TOF and LC2- MS-MS) identified a large number of fruit juice sac cell proteins and established comparisons of protein synthesis patterns during fruit development. So far, we have identified over 1,500 fruit specific proteins that play roles in sugar metabolism, citric acid cycle, signaling, transport, processing, etc., and organized these proteins into 84 known biosynthetic pathways (Katz et al. 2007). This data is now being integrated in a public database and will serve as a valuable tool for the scientific community in general and fruit scientists in particular. Using molecular, biochemical and physiological approaches we have identified factors affecting the activity of aconitase, which catalyze the first step of citrate catabolism (Shlizerman et al., 2007). Iron limitation specifically reduced the activity of the cytosolic, but not the mitochondrial, aconitase, increasing the acid level in the fruit. Citramalate (a natural compound in the juice) also inhibits the activity of aconitase, and it plays a major role in acid accumulation during the first half of fruit development. On the other hand, arsenite induced increased levels of aconitase, decreasing fruit acidity. We have initiated studies aimed at the identification of the citramalate biosynthetic pathway and the role(s) of isopropylmalate synthase in this pathway. These studies, especially those involved aconitase inhibition by citramalate, are aimed at the development of tools to control fruit acidity, particularly in those cases where acid level declines below the desired threshold. Our work has significant implications both scientifically and practically and is directly aimed at the improvement of fruit quality through the improvement of existing pre- and post-harvest fruit treatments.
3
Funkenstein, Bruria, and Cunming Duan. GH-IGF Axis in Sparus aurata: Possible Applications to Genetic Selection. United States Department of Agriculture, November 2000. http://dx.doi.org/10.32747/2000.7580665.bard.
Abstract:
Many factors affect growth rate in fish: environmental, nutritional, genetics and endogenous (physiological) factors. Endogenous control of growth is very complex and many hormone systems are involved. Nevertheless, it is well accepted that growth hormone (GH) plays a major role in stimulating somatic growth. Although it is now clear that most, if not all, components of the GH-IGF axis exist in fish, we are still far from understanding how fish grow. In our project we used as the experimental system a marine fish, the gilthead sea bream (Sparus aurata), which inhabits lagoons along the Mediterranean and Atlantic coasts of Europe, and represents one of the most important fish species used in the mariculture industry in the Mediterranean region, including Israel. Production of Sparus is rapidly growing, however, in order for this production to stay competitive, the farming of this fish species has to intensify and become more efficient. One drawback, still, in Sparus extensive culture is that it grows relatively slow. In addition, it is now clear that growth and reproduction are physiological interrelated processes that affect each other. In particular sexual maturation (puberty) is known to be closely related to growth rate in fish as it is in mammals, indicating interactions between the somatotropic and gonadotropic axes. The goal of our project was to try to identify the rate-limiting components(s) in Sparus aurata GH-IGF system which might explain its slow growth by studying the ontogeny of growth-related genes: GH, GH receptor, IGF-I, IGF-II, IGF receptor, IGF-binding proteins (IGFBPs) and Pit-1 during early stages of development of Sparus aurata larvae from slow and fast growing lines. Our project was a continuation of a previous BARD project and could be divided into five major parts: i) obtaining additional tools to those obtained in the previous project that are necessary to carry out the developmental study; ii) the developmental expression of growth-related genes and their cellular localization; iii) tissue-specific expression and effect of GH on expression of growth-related genes; iv) possible relationship between GH gene structure, growth rate and genetic selection; v) the possible role of the IGF system in gonadal development. The major findings of our research can be summarized as follows: 1) The cDNAs (complete or partial) coding for Sparus IGFBP-2, GH receptor and Pit-1 were cloned. Sequence comparison reveals that the primary structure of IGFBP-2 protein is 43-49% identical to that of zebrafish and other vertebrates. Intensive efforts resulted in cloning a fragment of 138 nucleotides, coding for 46 amino acids in the proximal end of the intracellular domain of GH receptor. This is the first fish GH receptor cDNA that had been cloned to date. The cloned fragment will enable us to complete the GH - receptor cloning. 2) IGF-I, IGF-II, IGFBP-2, and IGF receptor transcripts were detected by RT-PCR method throughout development in unfertilized eggs, embryos, and larvae suggesting that these mRNAs are products of both the maternal and the embryonic genomes. Preliminary RT-PCR analysis suggest that GH receptor transcript is present in post-hatching larvae already on day 1. 3) IGF-1R transcripts were detected in all tissues tested by RT-PCR with highest levels in gill cartilage, skin, kidney, heart, pyloric caeca, and brain. Northern blot analysis detected IGF receptor only in gonads, brain and gill cartilage but not in muscle; GH increased slightly brain and gill cartilage IGF-1R mRNA levels. 4) IGFBP-2 transcript were detected only in liver and gonads, when analyzed by Northern blots; RT-PCR analysis revealed expression in all tissues studied, with the highest levels found in liver, skin, gonad and pyloric caeca. 5) Expression of IGF-I, IGF-II, IGF-1R and IGFBP-2 was analyzed during gonadal development. High levels of IGF-I and IGFBP-2 expression were found in bisexual young gonads, which decreased during gonadal development. Regardless of maturational stage, IGF-II levels were higher than those of IGF-L 6) The GH gene was cloned and its structure was characterized. It contains minisatellites of tandem repeats in the first and third introns that result in high level of genetic polymorphism. 7) Analysis of the presence of IGF-I and two types of IGF receptor by immunohistochemistry revealed tissue- and stage-specific expression during larval development. Immunohistochemistry also showed that IGF-I and its receptors are present in both testicular and ovarian cells. Although at this stage we are not able to pinpoint which is the rate-limiting step causing the slow growth of Sparus aurata, our project (together with the previous BARD) yielded a great number of experimental tools both DNA probes and antibodies that will enable further studies on the factors regulating growth in Sparus aurata. Our expression studies and cellular localization shed new light on the tissue and developmental expression of growth-related genes in fish.