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Sandstone Consolidation III Year End Report
Two areas of cap rock occurrence have been mapped, one in the upper Texas Coast and the other in South Texas. These may be related to ancient delta systems. Two high-resistivity zones have been identified in Brazoria County. The nature of the high-resistivity intervals remains enigmatic. Most of the carbonate they contain is microscopically and isotopically skeletal in origin. Few authigenic components have been identified. Isotopic data suggest minimal recycling of pore waters between shale and sandstone.
Hydrolysis reactions and reactions between key pairs of minerals have been written. The goal is to plot formation waters on stability diagrams for these reaction pairs and to correlate log activity ratios with the presence or absence of cap rock and deep secondary porosity. Mineral compositions are based on microprobe data from earlier Sandstone Consolidation projects and new data collected in this project. Methods have been developed to estimate thermodynamic functions for most of these minerals at elevated temperatures. Methods differ depending on the mineral class and availability of published thermodynamic data.Bureau of Economic Geolog
Design Considerations for Efficient and Effective Microarray Studies
This paper describes the theoretical and practical issues in experimental design for gene expression microarrays. Specifically, this paper (1) discusses the basic principles of design (randomization, replication, and blocking) as they pertain to microarrays, and (2) provides some general guidelines for statisticians designing microarray studies
Nonuniversal behavior of scattering between fractional quantum Hall edges
Among the predicted properties of fractional quantum Hall states are
fractionally charged quasiparticles and conducting edge-states described as
chiral Luttinger liquids. In a system with a narrow constriction, tunneling of
quasi-particles between states at different edges can lead to resistance and to
shot noise. The ratio of the shot noise to the backscattered current, in the
weak scattering regime, measures the fractional charge of the quasi-particle,
which has been confirmed in several experiments. However, the non-linearity of
the resistance predicted by the chiral Luttinger liquid theory was apparently
not observed in some of these cases. As a possible explanation for these
discrepancies, we consider a model where a smooth edge profile leads to
formation of additional edge states. Coupling between the current carrying edge
mode and the additional phonon like mode can lead to {\it nonuniversal}
exponents in the current-voltage characteristic, while preserving the ratio
between shot noise and the back-scattered current, for weak backscattering. For
special values of the coupling, one may obtain a linear I-V behavior.Comment: 10 pages, 3 figure
Série Negra black quartzites - Tomar Cordoba Shear Zone, E Portugal: mineralogy and cathodoluminescence studies
The Evolution of Quasiparticle Charge in the Fractional Quantum Hall Regime
The charge of quasiparticles in a fractional quantum Hall (FQH) liquid,
tunneling through a partly reflecting constriction with transmission t, was
determined via shot noise measurements. In the nu=1/3 FQH state, a charge
smoothly evolving from e*=e/3 for t=1 to e*=e for t<<1 was determined, agreeing
with chiral Luttinger liquid theory. In the nu=2/5 FQH state the quasiparticle
charge evolves smoothly from e*=e/5 at t=1 to a maximum charge less than e*=e/3
at t<<1. Thus it appears that quasiparticles with an approximate charge e/5
pass a barrier they see as almost opaque.Comment: 4 pages, Correct figure 3 and caption include
Anomalous Exponent of the Spin Correlation Function of a Quantum Hall Edge
The charge and spin correlation functions of partially spin-polarized edge
electrons of a quantum Hall bar are studied using effective Hamiltonian and
bosonization techniques. In the presence of the Coulomb interaction between the
edges with opposite chirality we find a different crossover behavior in spin
and charge correlation functions. The crossover of the spin correlation
function in the Coulomb dominated regime is characterized by an anomalous
exponent, which originates from the finite value of the effective interaction
for the spin degree of freedom in the long wavelength limit. The anomalous
exponent may be determined by measuring nuclear spin relaxation rates in a
narrow quantum Hall bar or in a quantum wire in strong magnetic fields.Comment: 4 pages, Revtex file, no figures. To appear in Physical Revews B,
Rapid communication
Role of soil texture, clay mineralogy, location, and temperature in coarse wood decomposition—a mesocosm experiment
Of all the major pools of terrestrial carbon (C), the dynamics of coarse woody debris (CWD) are the least understood. In contrast to soils and living vegetation, the study of CWD has rarely relied on ex situ methods for elaborating controls on decomposition rates. In this study, we report on a mesocosm incubation experiment examining how clay amount (8%, 16%, and 24% clay), clay type (soil reconstructed with kaolinite vs. montmorillonite), wood placement (on litter layer surface, at the litter layer–soil interface, buried in the mineral soil), and laboratory incubation temperature (10°, 20°, or 30°C) control decomposition rates of highly standardized stakes and blocks of coarse aspen wood. Clay type effect was pronounced, with wood decomposing more quickly in kaolinite- than in montmorillonite-amended soils, perhaps due to a combined effect of moisture and microbial access to the substrate. Clay amount had only very limited effect on wood decomposition, which was a function of contact with the mineral soil (Surface \u3c Interface \u3c Mineral), perhaps due to greater contact with the decomposer community. Temperature effects were significant and dependent on interactions with clay type and wood placement. Effects of temperature on wood decomposition declined as the effects of soil variables increased, suggesting a hierarchy of controls on wood decomposition rates. Both water content and temperature had a strong effect on wood decomposition. Our results highlight that multiple interacting factors likely regulate wood decomposition processes. Multifactorial field experiments are needed to examine the physical, chemical, and biological factors controlling wood decompositio
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