The Jabal Akhdar Dome in the Oman Mountains : evolution of a dynamic fracture system

Acknowledgments: This study was carried out within the framework of DGMK (German Society for Petroleum and Coal Science and Technology) research project 718 “Mineral Vein Dynamics Modelling,” which is funded by the companies ExxonMobil Production Deutschland GmbH, GDF SUEZ E&P Deutschland GmbH, RWE Dea AG and Wintershall Holding GmbH, within the basic research program of the WEG Wirtschaftsverband Erdo¨l- und Erdgasgewinnung e.V. We thank the companies for their financial support and their permission to publish these results. The German University of Technology in Oman (GU-Tech) is acknowledged for its logistic support. We gratefully acknowledge the reviewers Andrea Billi and Jean-Paul Breton, whose constructive reviews greatly improved the manuscriptPeer reviewedPreprin

Solid-state-concentration effects on the optical absorption and emission of poly(p-phenylene vinylene)-related materials

We present measurements of the optical absorption and emission properties of poly(p-phenylene vinylene) (PPV)-related materials focusing on the differences between molecules isolated by dispersion in an inert host and concentrated molecular films. Optical absorption spectra, photoluminescence (PL) spectra, PL efficiency, and time-resolved PL spectra of dilute blends of PPV oligomers with 2-5 phenylene-phenyl rings are compared with those of dense oligomer and polymer films. In dilute oligomer-poly(methyl methacrylate) (PMMA) blends with high PL efficiency, the PL decay is exponential, independent of both temperature and oligomer length. This implies that the fundamental radiative lifetime of PPV oligomers is essentially independent of oligomer length. Concentrated spin-cast oligomer films and polymers have a faster and strongly temperature-dependent PL decay that approaches that of the dilute oligomer results at low temperature. The differences in PL decay correspond to changes in PL efficiency. The efficiency of the oligomer-PMMA blend is high and only weakly temperature dependent, whereas that of concentrated films is lower and strongly temperature dependent, decreasing by more than a factor of 3 from 10 to 350 K. The quenching of the PL efficiency in concentrated films is due to migration to extrinsic, impurity related centers as opposed to an intrinsic intermolecular recombination process. The PL spectrum of a dilute oligomer blend redshifts substantially, both as the excitation energy is decreased and as the emission time increases. This spectral redshift is due to disorder-induced site-to-site variation and not to diffusion to lower-energy sites. In contrast, no spectral shift with excitation energy or emission time was observed for dense oligomer films

Heterostructures for High Performance Devices

Contains an introduction and reports on ten research projects.Charles S. Draper Laboratory, Contract DL-H-315251Joint Services Electronics Program, Contract DAAL03-89-C-0001National Science Foundation Grant, Grant EET 87-03404MIT FundsInternational Business Machines CorporationNational Science Foundation Grant ECS 84-1317

Heterostructures for Optical Devices

Contains research objectives and reports on eight research projects.Joint Services Electronics Program (Contract DAAL03-86-K-0002)Joint Services Electronics Program (Contract DAALO3-89-C-0001)National Science Foundation (Grant EET 87-03404)Charles Stark Draper Laboratory (Contract DL-H-315251)Xerox Corporation FellowshipMIT Fund

Deformation mechanisms and evolution of the microstructure of gouge in the Main Fault in Opalinus Clay in the Mont Terri rock laboratory (CH)

We studied gouge from an upper-crustal, low-offset reverse fault in slightly overconsolidated claystone in the Mont Terri rock laboratory (Switzerland). The laboratory is designed to evaluate the suitability of the Opalinus Clay formation (OPA) to host a repository for radioactive waste. The gouge occurs in thin bands and lenses in the fault zone; it is darker in color and less fissile than the surrounding rock. It shows a matrix-based, P-foliated microfabric bordered and truncated by micrometer-thin shear zones consisting of aligned clay grains, as shown with broad-ion-beam scanning electron microscopy (BIB-SEM) and optical microscopy. Selected area electron diffraction based on transmission electron microscopy (TEM) shows evidence for randomly oriented nanometer-sized clay particles in the gouge matrix, surrounding larger elongated phyllosilicates with a strict P foliation. For the first time for the OPA, we report the occurrence of amorphous SiO2 grains within the gouge. Gouge has lower SEM-visible porosity and almost no calcite grains compared to the undeformed OPA. We present two hypotheses to explain the origin of gouge in the Main Fault: (i) authigenic generation consisting of fluid-mediated removal of calcite from the deforming OPA during shearing and (ii) clay smear consisting of mechanical smearing of calcite-poor (yet to be identified) source layers into the fault zone. Based on our data we prefer the first or a combination of both, but more work is needed to resolve this. Microstructures indicate a range of deformation mechanisms including solution–precipitation processes and a gouge that is weaker than the OPA because of the lower fraction of hard grains. For gouge, we infer a more rate-dependent frictional rheology than suggested from laboratory experiments on the undeformed OPA

LUMINESCENCE STUDY OF NON-EQUILIBRIUM EFFECTS IN LASER GENERATED PLASMA

The properties of surface generated electron-hole plasma in Silicon are studied using luminescence spectroscopy. By detailed line shape analysis we determine plasma densities up to 2 · 1019cm-3 for 300K and (ns-)pulse energies of 0.08 J/cm2. We demonstrate that drift effects are essential for the description of the luminescence. Typical plasma drift velocities are about 4 · 106cm/s

Porosity generated during the fluid-mediated replacement of calcite by fluorite

© 2016 The Royal Society of Chemistry.Mineral replacement reactions are common phenomena in natural and laboratory environments where solids have re-equilibrated with aqueous solutions and are characterized by the generation or destruction of porosity in the product phase(s). Here, the evolution of porosity during the replacement of calcite by fluorite is used as a model system to characterize the kinetics of volume variations. Non-porous single crystals of calcite were reacted with sodium fluoride solutions for different reaction times. The crystals were pseudomorphically replaced by highly porous fluorite. Complementary use of porosimetry techniques, high resolution imaging, and mass-balance calculations revealed the total, open, and closed porosity in the samples. The infiltration of aqueous fluids in the Earth depends on the evolution of porosity and hence porosity variations are important in various geological processes such as, rock weathering and soil formation, fluid-controlled metamorphism, mineral ore emplacement, or oil and gas reservoir compaction. Such mechanisms can also be used to develop geo-inspired materials designed for industrial and medical applications

Polymers for integrated optical interconnects

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The recent discovery of electroluminescent polymers opens up, for the first time, the possibility of using optical interconnects for conventional silicon integrated circuits (ICs). If this capability can be realized, it will have a tremendous impact on the architecture and performance of complex computing and communication systems. The primary objective of this project was to understand the light-emission mechanism of electroluminescent polymers and to use this knowledge to make efficient light-emitting-polymer diodes (LEPDs). These devices are the critical missing element for a polymer-based integrated-optical interconnect technology. The authors studied and obtained experimental results in several areas including the energetic position of fundamental excitation, the degradation of the polymer caused by oxygen, and the luminescence efficiency of polymer and oligomers. Parallel to the experimental effort, theoretical calculations were performed on the microscopic scale and on the device scale