612 research outputs found
Self-organization in turbulence as a route to order in plasma and fluids
Transitions from turbulence to order are studied experimentally in thin fluid
layers and magnetically confined toroidal plasma. It is shown that turbulence
self-organizes through the mechanism of spectral condensation. The spectral
redistribution of the turbulent energy leads to the reduction in the turbulence
level, generation of coherent flow, reduction in the particle diffusion and
increase in the system's energy. The higher order state is sustained via the
nonlocal spectral coupling of the linearly unstable spectral range to the
large-scale mean flow. The similarity of self-organization in two-dimensional
fluids and low-to-high confinement transitions in plasma suggests the
universality of the mechanism.Comment: 5 pages, 4 figure
Alpha-aminoisobutyric acid uptake in primary cultures of astrocytes
Homotypically pure cultures of rat brain astrocytes were used to examine some aspects of non-neuronal A-system (alanine preferring) amino acid uptake. The Asystem specific probe, alpha-aminoisobutyric acid is transported rapidly, and a steady state distribution ratio of 9â25 is reached after 30 minute incubations. Kinetic estimates derived from uptake progress curves indicated a K m of 1.35 mM and a V max of 133 nmol/min/mg protein. Uptake is reduced in the absence of either Na + or K + . Elevations in extracellular K + , a putative metabolic modulator of neuroglia, did not affect uptake.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45428/1/11064_2004_Article_BF00965086.pd
Strong "quantum" chaos in the global ballooning mode spectrum of three-dimensional plasmas
The spectrum of ideal magnetohydrodynamic (MHD) pressure-driven (ballooning)
modes in strongly nonaxisymmetric toroidal systems is difficult to analyze
numerically owing to the singular nature of ideal MHD caused by lack of an
inherent scale length. In this paper, ideal MHD is regularized by using a
-space cutoff, making the ray tracing for the WKB ballooning formalism a
chaotic Hamiltonian billiard problem. The minimum width of the toroidal Fourier
spectrum needed for resolving toroidally localized ballooning modes with a
global eigenvalue code is estimated from the Weyl formula. This
phase-space-volume estimation method is applied to two stellarator cases.Comment: 4 pages typeset, including 2 figures. Paper accepted for publication
in Phys. Rev. Letter
Enlargement of Submicron GasâBorne Particles by Heterogeneous Condensation for EnergyâEfficient Aerosol Separation
To improve the efficiency of aerosol separation, a process sequence for particle enlargement by condensation of water vapor on their surface is suggested. The presented method makes use of packed columns in non-equilibrium operation to achieve supersaturation, which is required for droplet growth. Although this method is known for several years, it is not widely used in industrial processes and still needs accurate investigations for consolidation and establishment. The simulation tool AerCoDe3.0 for predicting saturation and particle growth in packed columns allows investigating the thermal energy consumption under various operation conditions. Based on the results obtained in this study, optimized arrangements of columns, which are applicable as preconditioning step for existing particle separators, are proposed
Anderson localization of ballooning modes, quantum chaos and the stability of compact quasiaxially symmetric stellarators
The radially local magnetohydrodynamic(MHD) ballooning stability of a compact, quasiaxially symmetric stellarator (QAS), is examined just above the ballooning beta limit with a method that can lead to estimates of global stability. Here MHDstability is analyzed through the calculation and examination of the ballooning modeeigenvalue isosurfaces in the 3-space (s,α,Ξk); s is the edge normalized toroidal flux, α is the field linevariable, and Ξk is the perpendicular wave vector or ballooning parameter. Broken symmetry, i.e., deviations from axisymmetry, in the stellarator magnetic field geometry causes localization of the ballooning mode eigenfunction, and gives rise to new types of nonsymmetric eigenvalue isosurfaces in both the stable and unstable spectrum. For eigenvalues far above the marginal point, isosurfaces are topologically spherical, indicative of strong âquantum chaos.â The complexity of QAS marginal isosurfaces suggests that finite Larmor radius stabilization estimates will be difficult and that fully three-dimensional, high-nMHD computations are required to predict the beta limit.Research supported by U.S. DOE Contract No. DEAC02-76CH0373.
John Canik held a U.S. DOE National
Undergraduate Fellowship at Princeton Plasma Physics
Laboratory, during the summer of 2000
Magnetohydrodynamics and Plasma Cosmology
We study the linear magnetohydrodynamic (MHD) equations, both in the
Newtonian and the general-relativistic limit, as regards a viscous magnetized
fluid of finite conductivity and discuss instability criteria. In addition, we
explore the excitation of cosmological perturbations in anisotropic spacetimes,
in the presence of an ambient magnetic field. Acoustic, electromagnetic (e/m)
and fast-magnetosonic modes, propagating normal to the magnetic field, can be
excited, resulting in several implications of cosmological significance.Comment: 9 pages, RevTeX, To appear in the Proceedings of the Peyresq X
Meeting, IJTP Conference Serie
An examination of psychopathology among men who have suspended the use of violence in their intimate relationships
Heterologous expression of the isopimaric acid pathway in Nicotiana benthamiana and the effect of N-terminal modifications of the involved cytochrome P450 enzyme
The effects of stimulants and depressants on cocaine self-administration behavior in the Rhesus monkey
The effects of acute intramuscular pretreatment with several dosages of a variety of centrally acting compounds on intravenous cocaine self-administration behavior were ascertained. Pretreatment with morphine and pentobarbital produced no change in this behavior until dosages (2.0 mg/kg and 15.0 mg/kg respectively) were administered which grossly depressed grooming, exploratory, and locomotor activity behaviors, d -amphetamine (0.5â4.0 mg/kg) and phenmetrazine (2.0â12.0 mg/kg) pretreatment produced a dose-related decrease in cocaine self-administration. Trifluoperazine in dosages of 0.01â0.1 mg/kg increased the frequency of this behavior; whereas, higher dosages (0.2, 0.4 mg/kg) grossly depressed behavior. Imipramine (10â50 mg/kg) produced a dose-related decrease in cocaine self-administration. Potential mechanisms of these drugâbehavior and drugâdrug interactions are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46388/1/213_2004_Article_BF00421274.pd
Anderson localization of ballooning modes, quantum chaos and the stability of compact quasiaxially symmetric stellarators
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