The Experts below are selected from a list of 2706 Experts worldwide ranked by ideXlab platform
Richard C Willson - One of the best experts on this subject based on the ideXlab platform.
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characterization of escherichia coli mg1655 grown in a low shear modeled microgravity environment
BMC Microbiology, 2007Co-Authors: Don L Tucker, Stephen Huff, Yuriy Fofanov, Duane L Pierson, Richard C WillsonAbstract:Background Extra-cellular shear force is an important environmental parameter that is significant both medically and in the space environment. Escherichia coli cells grown in a low-shear modeled microgravity (LSMMG) environment produced in a high aspect Rotating Vessel (HARV) were subjected to transcriptional and physiological analysis.
B Veyssiere - One of the best experts on this subject based on the ideXlab platform.
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combustion mechanism of flame propagation and extinction in a Rotating cylindrical Vessel
Combustion and Flame, 2000Co-Authors: Andrzej Gorczakowski, Andrzej Zawadzki, Jozef Jarosinski, B VeyssiereAbstract:Abstract The effect of radial acceleration in a Rotating Vessel on flame propagation has been investigated experimentally. Methane–air mixture compositions between the lean flammability limit and stoichiometric were studied. The behavior of flame propagation and the extinction mechanism were examined in detail. The flame propagating in a Rotating Vessel is axisymmetric. Initially it propagates axially from the ignition point at one end of the cylindrical Vessel to the opposite end. After touching the side wall of the cylindrical Vessel the flame starts to propagate radially and is locally quenched at the contact surface with the walls. The axial propagation velocity of the flame under all conditions increases with the rotation rate. When local quenching occurs, the radial flame propagation velocity decreases and the extinction rate increases with increasing rotation rate. The extinction mechanism is a multistep process. The most probable stages in that mechanism are as follows. First, heat loss causes the cylindrical flame to extinguish locally near the walls. Once this happens, the combustion gases, which are in contact with the walls, are cooled and displaced radially under the action of centrifugal forces. They flow towards the region of the fresh mixture, which remains in contact with the previously extinguished flame. Differential buoyancy forces the cool gases to move ahead of the flame, which is then extinguished because it is now propagating into a partially diluted nonflammable mixture. The extinction wave propagates along the cylindrical surface of the flame to complete extinction.
Don L Tucker - One of the best experts on this subject based on the ideXlab platform.
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characterization of escherichia coli mg1655 grown in a low shear modeled microgravity environment
BMC Microbiology, 2007Co-Authors: Don L Tucker, Stephen Huff, Yuriy Fofanov, Duane L Pierson, Richard C WillsonAbstract:Background Extra-cellular shear force is an important environmental parameter that is significant both medically and in the space environment. Escherichia coli cells grown in a low-shear modeled microgravity (LSMMG) environment produced in a high aspect Rotating Vessel (HARV) were subjected to transcriptional and physiological analysis.
Peter I Lelkes - One of the best experts on this subject based on the ideXlab platform.
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real time assessment of three dimensional cell aggregation in Rotating wall Vessel bioreactors in vitro
Nature Protocols, 2006Co-Authors: Gregory P Botta, Prakash Manley, Steven Miller, Peter I LelkesAbstract:Until now, tissue engineering and regenerative medicine have lacked non-invasive techniques for monitoring and manipulating three-dimensional (3D) tissue assembly from specific cell sources. We have set out to create an intelligent system that automatically diagnoses and monitors cell-cell aggregation as well as controls 3D growth of tissue-like constructs (organoids) in real time. The capability to assess, in real time, the kinetics of aggregation and organoid assembly in Rotating wall Vessel (RWV) bioreactors could yield information regarding the biological mechanics of tissue formation. Through prototype iterations, we have developed a versatile high-resolution 'horizontal microscope' that assesses cell-cell aggregation and tissue-growth parameters in a bioreactor and have begun steps to intelligently control the development of these organoids in vitro. The first generation system was composed of an argon-ion laser that excited fluorescent beads at 457 nm and fluorescent cells at 488 nm while each was suspended in a high-aspect Rotating Vessel (HARV) type RWV bioreactor. An optimized system, which we introduce here, is based on a diode pumped solid state (DPSS) green laser that emits a wavelength at 532 nm. By exciting both calibration beads and stained cells with laser energy and viewing them in real time with a charge-coupled device (CCD) video camera, we have captured the motion of individual cells, observed their trajectories, and analyzed their aggregate formation. Future development will focus on intelligent feedback mechanisms in silico to control organoid formation and differentiation in bioreactors. As to the duration of this entire multistep protocol, the laser system will take about 1 h to set up, followed by 1 h of staining either beads or cells. Inoculating the bioreactors with beads or cells and starting the system will take approximately 1 h, and the video-capture segments, depending on the aims of the experiment, can take from 30 s to 5 min each. The total duration of a specific experimental protocol will also depend on the specific cell type used and on its population-doubling times so that the required numbers of cells are obtained.
P. L. Read - One of the best experts on this subject based on the ideXlab platform.
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wave interactions and the transition to chaos of baroclinic waves in a thermally driven Rotating annulus
Philosophical Transactions of the Royal Society A, 1997Co-Authors: Wolf-gerrit Fruh, P. L. ReadAbstract:A series of laboratory experiments is presented investigating regular and chaotic baroclinic waves in a high–Prandtl number fluid contained in a Rotating Vessel and subjected to a horizontal temperature gradient. The study focuses on nonlinear aspects of mixed–mode states at moderate values of the forcing parameters within the regular wave regime. Frequency entrainment and phase locking of resonant triads and sidebands were found to be widespread. Cases were analysed in phase space reconstructions through a singular value decomposition of multi–variate time series. Four forms of mixed–mode states were found, each in well–defined regions of parameter space: (1) a nonlinear interference vacillation associated with strong phase locking through higher harmonics; (2) a modulated amplitude vacillation showing strong phase coherence in triads involving the long wave; (3) an intermittent bursting of secondary modes; (4) an attractor switching flow, where the dominant wave number switched at irregular intervals between two possible wave numbers. Many of the mixed–mode states are suggested to arise from homoclinic bifurcations, whereas no secondary Hopf bifurcations were found. One of the postulated homoclinic bifurcations was consistent with a bifurcation through intermittency. The bifurcation sequences, however, were strongly affected by phase locking between different wave number components and frequency locking between drift and modulation frequencies. When all free frequencies were locked, the flow reduced to a limit cycle which subsequently became unstable through an incomplete period–doubling cascade. The only observed case of torus–doubling was also associated with strong phase locking. Most of the observed regimes were consistent with low–dimensional dynamics involving a limited number of domain–filling modes, which can be represented in phase space reconstructions and characterized by invariants such as attractor dimensions and the Lyapunov exponents. Some flows associated with a weak structural vacillation, however, were not consistent with low–dimensional dynamics. It appeared rather that they were the result of spatially localized instabilities consistent with high–dimensional dynamics, which can be parametrized as stochastic dynamics.
