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Prior studies of the Caribbean-South American plate boundary have suffered from poor constraint on the structure of the crust and uppermost mantle. We use a recent wide-angle velocity model from the Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region project to constrain new seismic reflection data and previously published line drawing interpretations of the Caribbean-South American plate boundary at 64[degrees]W. Though commonly characterized as obliquely convergent, we determine that convergence is negligible in our study area. Previous estimates of Miocene to present north-south shortening onshore eastern Venezuela have commonly been 115 km or higher, but we constrain shortening to ~35 km onshore, with an additional ~30 km offshore. With such minor convergence, we conclude that uplift and basin subsidence in eastern Venezuela does not derive from typical collisional orogeny. Instead, the largely vertical tectonics likely result from mantle dynamics associated with an eastward propagating, near-vertical tear in the lithosphere along the former passive margin.

The AMP-activated protein kinase (AMPK) cascade has been linked to many of the acute effects of exercise on skeletal muscle substrate metabolism, as well as to some of the chronic training-induced adaptations. We determined the effect of 3 wk of intensified training (HIT; 7 sessions of 8 x 5 min at 85% V[O.sub.2 peak]) in skeletal muscle from well-trained athletes on AMPK responsiveness to exercise. Rates of whole body substrate oxidation were determined during a 90-min steady-state ride (SS) pre- and post-HIT. Muscle metabolites and AMPK signaling were determined from biopsies taken at rest and immediately after exercise during the first and seventh HIT sessions, performed at the same (absolute) pre-HIT work rate. HIT decreased rates of whole body carbohydrate oxidation (P < 0.05) and increased rates of fat oxidation (P < 0.05) during SS. Resting muscle glycogen and its utilization during intense exercise were unaffected by HIT. However, HIT induced a twofold decrease in muscle [lactate] (P < 0.05) and resulted in tighter metabolic regulation, i.e., attenuation of the decrease in the PCr/(PCr + Cr) ratio and of the increase in [AM[P.sub.free]]/ATP. Resting activities of AMPKal and -[alpha]2 were similar post-HIT, with the magnitude of the rise in response to exercise similar pre- and post-HIT. AMPK phosphorylation at [Thr.sup.172] on both the [alpha]1 and [alpha]2 subunits increased in response to exercise, with the magnitude of this rise being similar post-HIT. Acetyl-coenzyme A carboxylase-[beta] phosphorylation was similar at rest and, despite HIT-induced increases in whole body rates of fat oxidation, did not increase post-HIT. Our results indicate that, in well-trained individuals, short-term HIT improves metabolic control but does not blunt AMPK signaling in response to intense exercise. adenosine 5'-monophosphate-activated protein kinase; acetyl-coenzyme A carboxylase; glycogen; fat metabolism

Application of soft x-ray photoemission spectroscopy to the initial interface formation of In-In53Ga47As(100) for room and cryogenic temperatures indicated a predominantly three-dimensional mode of growth for room-temperature metallization, with accompanying As diffusion. Clustering and As outdiffusion is restricted for low temperature metallization. Interface geometry and bonding at low temperature variations conditioned surface state distribution and fermi level pinning position.

Admittance spectroscopic analyses of lattice-mismatched InAlAs InGaAs single-quantum-well semiconductors show that the temperature dependency of the space-charge region width governs the perpendicular conductivity of the semiconductor. A high density of deep electron traps in the layers near the quantum well controls the entire process, thus accounting for the strong influence of deep-level defects on the energy activation of the perpendicular conductivity. Thus, admittance measurements are incapable of yielding the value of the magnitude of band offset.

An analysis of the electrical and chemical characteristics of the room temperature interfaces between epitaxial n-type InAlAs diodes and Au, Ag, Cu and In metals by contact formation on the molecular beam epitaxy-grown InAlAs/InP(100) layer reveals that the Fermi levels are surfacial before metal deposition. This is due to variations in layer surface stoichiometry which causes forbidden gap-based metal-like states.

Capacitance-voltage, current-voltage-temperature, admittance spectroscopy calculations and deep level transient spectroscopy aid in defining the electrical properties of Al0.48In0.52As materials developed on n+-InP layers at various temperatures by using metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy. Reduction in growth temperature leads to reduction in Schottky barrier heights and rise in defect densities. Thermionic emission and reverse current due to electron-hole recombination are typical to forward biased current in the diodes fabricated on MOCVD-AlInAs.

The effect of layer thickness, mismatch and growth temperature on the fine speckle contrast in InGaAs/InP systems grown by molecular beam epitaxy on InP substrates was investigated. The results showed that fine contrast modulation was dependent on layer-substrate mismatch. There was a tendency of the modulation wavelength towards lower values when the growth temperature, layer thickness and mismatch increased.

InGaAs/Inp layers under compressive strain were studied using optical absorption spectra and transmission electron microscopy (TEM) to determine the source of strain inhomogeneities. By comparing the optical absorption quantified strain dispersion with TEM-determined dislocation density, two sources were determined. The first was local variations in the dislocation density in the layers and the second was a mechanism unrelated to plastic relaxation predominant in lattice-matched composition layers.

A combination of x-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) were used to study the interface formation between Ni and high quality low dislocation [Al.sub.0.2][Ga.sub.0.8]N. The results provide insight into preference of Ni to react with the contaminants at the surface rather than with the epilayer itself and the Schottky barrier formation.

Presents a study examining the physical and chemical reactions occurring during the formation of intimate In- and Au-InAlAs(100) interfaces at room temperature. Methodology used to conduct the study; Information on the Au-In0.52Al0.48As(100) interface formation; Details on photoemission experiments; Findings of the study.

A study was conducted, by using the x-ray photoemission spectroscopy (XPS), current-voltage measurement (I-V) and cross-section transmission electron microscopy (TEM), to investigate the influence of premetallization surface preparation on the structural, chemical, and electrical properties of Au-nGaN interfaces. The result shows a very important role of premetallization surface treatment in the structural and electrical properties of Au-nGaN contacts.

Modulation in composition and appearance of coarse quasiperiodic structure are observed in indium aluminum arsenide (InxAl1-xAs) layers grown by molecular beam epitaxy on indium phophoride (InP) substrates. Characterization of the InAlAs layers are done via transmission electron microscopy. Analysis of the layer composition and growth temperature showed compositional nonuniformities in strained layers. Formation of defects are observed in slightly mismatched layers of indium gallium arsenide with thickness of 0.5 microns. The quasiperiodic structure wavelength depends on the growth temperature, alloy composition and thickness of the layers.