Kinematics of the South Atlantic rift

The South Atlantic rift basin evolved as branch of a large Jurassic-Cretaceous intraplate rift zone between the African and South American plates during the final breakup of western Gondwana. By quantitatively accounting for crustal deformation in the Central and West African rift zone, we indirectly construct the kinematic history of the pre-breakup evolution of the conjugate West African-Brazilian margins. Our model suggests a causal link between changes in extension direction and velocity during continental extension and the generation of marginal structures such as the enigmatic Pre-salt sag basin and the S\~ao Paulo High. We model an initial E-W directed extension between South America and Africa (fixed in present-day position) at very low extensional velocities until Upper Hauterivian times ($\approx$126 Ma) when rift activity along in the equatorial Atlantic domain started to increase significantly. During this initial $\approx$17 Myr-long stretching episode the Pre-salt basin width on the conjugate Brazilian and West African margins is generated. An intermediate stage between 126.57 Ma and Base Aptian is characterised by strain localisation, rapid lithospheric weakening in the equatorial Atlantic domain, resulting in both progressively increasing extensional velocities as well as a significant rotation of the extension direction to NE-SW. Final breakup between South America and Africa occurred in the conjugate Santos--Benguela margin segment at around 113 Ma and in the Equatorial Atlantic domain between the Ghanaian Ridge and the Piau\'i-Cear\'a margin at 103 Ma. We conclude that such a multi-velocity, multi-directional rift history exerts primary control on the evolution of this conjugate passive margins systems and can explain the first order tectonic structures along the South Atlantic and possibly other passive margins.Comment: 46 Pages, 22 figures. Submitted to Solid Earth (http://www.solid-earth.net). Abstract shortened due to arXiv restrictions. New version contains revisions and amendments as per reviewers requests. Supplementary data is available at http://datahub.io/en/dataset/southatlanticrif

From Geometry to Activity: A Quantitative Analysis of WO3/Si Micropillar Arrays for Photoelectrochemical Water Splitting

The photoelectrochemical (PEC) activity of microstructured electrodes remains low despite the highly enlarged surface area and enhanced light harvesting. To obtain a deeper understanding of the effect of 3D geometry on the PEC performance, well‐defined WO3/n‐Si and WO3/pn‐Si micropillar arrays are fabricated and subjected to a quantitative analysis of the relationship between the geometry of the micropillars (length, pitch) and their PEC activity. For WO3/n‐Si micropillars, it is found that the photocurrent increases for WO3/n‐Si pillars, but not in proportion to the increase in surface area that results from increased pillar length or reduced pillar pitch. Optical simulations show that a reduced pillar pitch results in areas of low light intensity due to a shadowing effect. For WO3/pn‐Si micropillar photoelectrodes, the p–n junction enhances the photocurrent density up to a factor of 4 at low applied bias potential (0.8 V vs RHE) compared to the WO3/n‐Si. However, the enhancement in photocurrent density increases first and then decreases with reduced pillar pitch, which scales with the photovoltage generated by the p–n junction. This is related to an increased dead layer of the p–n junction Si surface, which results in a decreased photovoltage even though the total surface area increases.</p

Surface and sub-surface thermal oxidation of thin ruthenium films

A mixed 2D (film) and 3D (nano-column) growth of ruthenium oxide has been experimentally observed for thermally oxidized polycrystalline ruthenium thin films. Furthermore, in situ x-ray reflectivity upon annealing allowed the detection of 2D film growth as two separate layers consisting of low density and high density oxides. Nano-columns grow at the surface of the low density oxide layer, with the growth rate being limited by diffusion of ruthenium through the formed oxide film. Simultaneously, with the growth of the columns, sub-surface high density oxide continues to grow limited by diffusion of oxygen or ruthenium through the oxide fil

Effect of strain on surface diffusion in semiconductor heteroepitaxy

We present a first-principles analysis of the strain renormalization of the cation diffusivity on the GaAs(001) surface. For the example of In/GaAs(001)-c(4x4) it is shown that the binding of In is increased when the substrate lattice is expanded. The diffusion barrier \Delta E(e) has a non-monotonic strain dependence with a maximum at compressive strain values (e 0) studied. We discuss the consequences of spatial variations of both the binding energy and the diffusion barrier of an adatom caused by the strain field around a heteroepitaxial island. For a simplified geometry, we evaluate the speed of growth of two coherently strained islands on the GaAs(001) surface and identify a growth regime where island sizes tend to equalize during growth due to the strain dependence of surface diffusion.Comment: 10 pages, 8 figures, LaTeX2e, to appear in Phys. Rev. B (2001). Other related publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm

Charge carrier dynamics and photocatalytic activity of 111 and 100 faceted Ag3PO4 particles

Silver orthophosphate is a highly promising visible light photocatalyst with high quantum yield for solar driven water oxidation. Recently, the performance of this material has been further enhanced using facet controlled synthesis. The tetrahedral particles with 111 exposed facets demonstrate higher photocatalytic performance than the cubic particles with 100 exposed facets. However, the reason behind this large difference in photocatalytic performance is still not understood. In this work, we study the free charge carrier dynamics, such as mobility, lifetime, and diffusion lengths, for the 111 faceted tetrahedral and the 100 faceted cubic particles using time resolved microwave conductivity measurements. An order of magnitude higher charge carrier mobility and diffusion length are found for the tetrahedral particles as compared to the cubic particles. The differences in crystal structure, surface composition, and optical properties are investigated in order to understand how these properties impact the charge carrier dynamics and the photocatalytic performance of differently faceted particle

Acute effects of MDMA (3,4-methylenedioxymethamphetamine) on EEG oscillations: alone and in combination with ethanol or THC (delta-9-tetrahydrocannabinol)

Item does not contain fulltextRATIONALE: Typical users of 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") are polydrug users, combining MDMA with alcohol or cannabis [most active compound: delta-9-tetrahydrocannabinol (THC)]. OBJECTIVES: The aim of the present study was to investigate whether co-administration of alcohol or THC with MDMA differentially affects ongoing electroencephalogram (EEG) oscillations compared to the administration of each drug alone. METHODS: In two separate experiments, 16 volunteers received four different drug conditions: (1) MDMA (100 mg); (2) alcohol clamp (blood alcohol concentration = 0.6 per thousand) or THC (inhalation of 4, 6 and 6 mg, interval of 1.5 h); (3) MDMA in combination with alcohol or THC; and (4) placebo. Before and after drug administration, electroencephalography was recorded during an eyes closed resting state. RESULTS: Theta and alpha power increased after alcohol intake compared to placebo and reduced after MDMA intake. No interaction between alcohol and MDMA was found. Significant MDMA x THC effects for theta and lower-1-alpha power indicated that the power attenuation after the combined intake of MDMA and THC was less than the sum of each drug alone. For the lower-2-alpha band, the intake of MDMA or THC alone did not significantly affect power, but the intake of combined MDMA and THC significantly decreased lower-2-alpha power. CONCLUSIONS: The present findings indicate that the combined intake of MDMA and THC, but not of MDMA and alcohol, affects ongoing EEG oscillations differently than the sum of either one drug alone. Changes in ongoing EEG oscillations may be related to the impaired task performance that has often been reported after drug intake

First-principles calculation of the effect of strain on the diffusion of Ge adatoms on Si and Ge (001) surfaces

First-principles calculations are used to calculate the strain dependencies of the binding and diffusion-activation energies for Ge adatoms on both Si(001) and Ge(001) surfaces. Our calculations reveal that the binding and activation energies on a strained Ge(001) surface increase and decrease, respectively, by 0.21 eV and 0.12 eV per percent compressive strain. For a growth temperature of 600 degrees C, these strain-dependencies give rise to a 16-fold increase in adatom density and a 5-fold decrease in adatom diffusivity in the region of compressive strain surrounding a Ge island with a characteristic size of 10 nm.Comment: 4 pages, 4 figure

The Joint Influence of Intra- and Inter-Team Learning Processes on Team Performance: A Constructive or Destructive Combination?

In order for teams to build a shared conception of their task, team learning is crucial. Benefits of intra-team learning have been demonstrated in numerous studies. However, teams do not operate in a vacuum, and interact with their environment to execute their tasks. Our knowledge of the added value of inter-team learning (team learning with external parties) is limited. Do both types of team learning compete over limited resources, or do they form a synergistic combination? We aim to shed light on the interplay between intra- and inter-team learning in relation to team performance, by including adaptive and transformative sub-processes of intra-team learning. A quantitative field study was conducted among 108 university teacher teams. The joint influence of intra- and inter-team learning as well as structural (task interdependence) and cultural (team efficacy) team characteristics on self-perceived and externally rated team performance were explored in a path model. The results showed that adaptive intra-team learning positively influenced self-perceived team performance, while transformative intra-team learning positively influenced externally rated team performance. Moreover, intra-team and inter-team learning were found to be both a constructive and a destructive combination. Adaptive intra-team learning combined with inter-team learning led to increased team performance, while transformative intra-team learning combined with inter-team learning hurt team performance. The findings demonstrate the importance of distinguishing between both the scope (intra- vs. inter-team) and the level (adaptive vs. transformative) of team learning in understanding team performance