Local Geometry of the Fermi Surface and Magnetoacoustic Responce of Two-Dimensional Electron Systems in Strong Magnetic Fields

A semiclassical theory for magnetotrasport in a quantum Hall system near filling factor $\nu = 1/2$ based on the Composite Fermions physical picture is used to analyze the effect of local flattening of the Composite Fermion Fermi surface (CF-FS) upon magnetoacoustic oscllations. We report on calculations of the velocity shift and attenuation of a surface acoustic wave (SAW) which travels above the two-dimensional electron system, and we show that local geometry of the CF-FS could give rise to noticeable changes in the magnitude and phase of the oscillations. We predict these changes to be revealed in experiments, and to be used in further studies of the shape and symmetries of the CF-FS. Main conclusions reported here could be applied to analyze magnetotransport in quantum Hall systems at higher filling factors $\nu = 3/2, 5/2$ provided the Fermi-liquid-like state of the system.Comment: 7 pages, 2 figure

Plasmonic Hot Spots in Triangular Tapered Graphene Microcrystals

Recently, plasmons in graphene have been observed experimentally using scattering scanning near-field optical microscopy. In this paper, we develop a simplified analytical approach to describe the behavior in triangular samples. Replacing Coulomb interaction by a short-range one reduces the problem to a Helmholtz equation, amenable to analytical treatment. We demonstrate that even with our simplifications, the system still exhibits the key features seen in the experiment.Comment: 4 pages, 3 figure

Ground state phase diagram of 2D electrons in a high Landau level: - DMRG study

The ground state phase diagram of 2D electrons in a high Landau level (index N=2) is studied by the density matrix renormalization group method. Pair correlation functions are systematically calculated for various filling factors from v=1/8 to 1/2. It is shown that the ground state phase diagram consists of three different CDW states called stripe-phase, bubble-phase, and Wigner crystal. The boundary between the stripe and the bubble phases is determined to be v_c = 0.38, and that for the bubble phase and Wigner crystal is v_c = 0.24. Each transition is of first order.Comment: 4 pages, 6 figure

Dissolution of powdered minerals: The effect of polydispersity

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37407/1/690350520_ftp.pd

Emulsion stability: Delineation of different particle loss mechanisms

The kinetics of the emulsion-breaking process are governed by three different particle loss mechanisms: Brownian flocculation, sedimentation flocculation, and creaming. Various particle loss mechanisms have been delineated and the relative importance of Brownian flocculation and sedimentation flocculation compared. A general map presenting regimes of dominant particle loss mechanisms has been developed from which one can determine the dominant particle loss mechanism for a given particle size and density difference. In addition, the relative importance of flocculation and creaming has been delineated for a monodispersed system. The effects of particle size, surface potential, concentration, density difference, temperature, and ionic strength on the relative importance of flocculation and creaming have been analyzed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24511/1/0000789.pd

Population balance modeling of the dissolution of polydisperse solids: Rate limiting regimes

Significant errors can result in modeling dissolution processes if the polydispersity of the solid particles is ignored and the sample is treated as a collection of monodisperse spheres having the average size of the mixture. Population balance modeling provides an effective analytical means of predicting the effect of polydispersity on a wide variety of heterogeneous reaction systems including dissolution processes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37395/1/690330108_ftp.pd

The role of conduction/valence bands and redox potential in accelerated mineral dissolution

The dissolution kinetics of a number of manganese oxides in acidic solutions were studied. Using a slurry reactor, rate laws were determined for each of the manganese oxides in the hydrohalogen acids. Significant variations in the reaction rates (up to five orders of magnitude over the HCl base rate) were obtained with different acids. The addition of anions as neutral salts to acidic solutions is shown to produce the same rate-accelerating effect as acids containing that anion. The effect of the different acids on the oxide dissolution rates is explained using semiconductor band theory and energy diagrams.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37394/1/690321013_ftp.pd

Emulsion stability--experimental studies on simultaneous flocculation and creaming

An experimental technique has been developed to study the emulsion stability with simultaneous flocculation and creaming. Experiments were carried out by using different ionic strengths, two different dispersants in water (C36H74 and C28H58) and different particle size distributions. Cyclic changes in particle size distributions (PSD) are observed when flocculation and creaming occur simultaneously. Initially, the PSD shifts to the right toward larger particle sizes and then reverses and shifts to the left toward smaller particle sizes. This reverse shift in PSD had been observed both in theory and experiment. There are no adjustable parameters in the theory and the agreement between the theoretically predicted changes in PSD and those observed experimentally is excellent.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24324/1/0000591.pd

A note on capillary model of developments for sandstone acidization

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23048/1/0000620.pd

Emulsion stability: Determination from turbidity

A novel technique for studying the stability of emulsions has been developed. Owing to the fact that emulsion turbidity is a function of particle concentration and size, the stability of emulsions can be determined by measuring the change in turbidity with time. The relationship between turbidity and particle size and concentration is derived for a polydispersed emulsion. The stability of acoustically prepared emulsions determined by measuring the initial mean particle size and changes in emulsion turbidity is compared with the stability determined from scanning electron microscope measurements of the particle growth rate. The agreement between the two methods is excellent.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24510/1/0000787.pd