Depletion-induced seismicity in NW-Germany: lessons from comprehensive investigations

Evaluating various investigations for north-German gas fields, we discuss past and actual evolutions of the rock fabric in the light of dilatant driven and spontaneous contractant critical phenomena. Features of the latter were discovered by multi-stage triaxial tests with water-saturated sandstone samples and were similarly observed around the gas fields. A Mohr–Coulomb condition with quasi-local stress components (${\hat{\sigma }}\u27_1$ and ${\hat{\sigma }}\u27_3$), and variable parameters ϕ’ and ${{\hat{c}}}\u27$, can capture successive critical states of the solid fabric. The implied driven dilatation up to a collapse with contraction is captured by a stress-dilatancy relation. Fractal patterns of shear bands (faults) dominate if the smallest principal stress ${\hat{\sigma }}\u27_3$ exceeds ${{\hat{c}}}\u27$, otherwise cracks dominate and can lead to a rockburst. Triaxial tests with X-ray attenuation, seismometry including the splitting of shear waves and/or neutron beam diffraction contribute to clarification and validation. Seismic early warning and calculation models for various geotechnical operations with dominating faults can thus be improved, but the task is more difficult for rockbursts

In situ strain detection of stress-strain relationships and their controls on progressive damage in marble and quartzite by neutron diffraction experiments

The application of data derived from rock mechanical experiments to large spatial and temporal scales required to assess rock slope stability and landscape evolution is complicated, as these processes of rocks are affected by its lithology, tectonic heritage and rheological behavior under the contemporary stress field. Interpretations of experiments and field sites are restricted to surficial, pre and post state observations of deformations, under almost always subcritical near surface stress fields. We set up an novel experiment to quantify a) the level of inherited residual elastic strains, b) the effect of subcritical low magnitude load steps, c) load magnitudes at which deformation become permanent and further strains are induced and d) differences of rheological behavior due to lithology. In order to gain greater insight into the stress-strain relationships and their control on progressive damage we employed in situ neutron diffraction techniques to observe crystal lattice strains in pure marble (Carrara marble, > 98 vol% CaCO3) and quartzite (Dalsland quartzite, > 98 vol% SiO2) samples during stepped Brazilian tests. We measure a gauge volume of ∼42mm3 in the center of cylindrical samples (Ø= 30 mm, l = 22 mm quartzite, l = 26 mm marble) using the EPSILON neutron time-of-flight (TOF) strain diffractometer in Dubna, Russia. Surface-mounted strain gauges provide macroscopic strain data, and acoustic emission sensors are used to detect microcrack initiation. Initial states are measured without load to determine the load-free lattice parameters. Load is increased in three to four stages of approximately 15%, 33%, 66%, and 75-80% of the ultimate intact rock strength (σ1 max), and maintained during diffraction measurements (up to 12 hours each). Each load step is followed by a load-free state. Deviatoric strain in both major principal compressive (σ1) and minor principal in plane (σ3) direction, as well as residual strain, with reference to a strain-free state of powdered samples are calculated for whole diffraction patterns. We obtained initial residual contractional strains of ∼-150 μstrain for Carrara marble and of ∼-50 μstrain for the Dalsland quartzite samples. Already during the first load step of ∼10-15% σ1 max superposition of the residual strain state is observed and strains partially remain during unloading step. Increased stress magnitudes of the load steps enable us to identify strains as a function of external load and subsequent unloading, indicating, in both rocks, that upon unloading from former loads to less than 75% σ1 max, the material remains partially extensionally strained

Exclusive diffractive processes and the quark substructure of mesons

Exclusive diffractive processes on the nucleon are investigated within a model in which the quark-nucleon interaction is mediated by Pomeron exchange and the quark substructure of mesons is described within a framework based on the Dyson-Schwinger equations of QCD. The model quark-nucleon interaction has four parameters which are completely determined by high-energy $\pi N$ and $K N$ elastic scattering data. The model is then used to predict vector-meson electroproduction observables. The obtained $\rho$- and $\phi$-meson electroproduction cross sections are in excellent agreement with experimental data. The predicted $q^2$ dependence of $J/\psi$-meson electroproduction also agrees with experimental data. It is shown that confined-quark dynamics play a central role in determining the behavior of the diffractive, vector-meson electroproduction cross section. In particular, the onset of the asymptotic $1/q^4$ behavior of the cross section is determined by a momentum scale that is set by the current-quark masses of the quark and antiquark inside the vector meson. This is the origin of the striking differences between the $q^2$ dependence of $\rho$-, $\phi$- and $J/\psi$-meson electroproduction cross sections observed in recent experiments.Comment: 53 pages, 23 figures, revtex and epsfig. Minor additions to tex

The influence of threading dislocations propagating through an AlGaN UVC LED

During the epitaxy of AlGaN on sapphire for deep UV emitters, significant lattice mismatch leads to highly strained heterojunctions and the formation of threading dislocations. Combining cathodoluminescence, electron beam induced current and x-ray microanalysis reveal that dislocations with a screw component permeate through a state-of-the-art UVC LED heterostructure into the active region and perturb their local environment in each layer as growth progresses. In addition to acting as non-radiative recombination centers, these dislocations encourage high point defect densities and three-dimensional growth within their vicinity. We find that these point defects can add parasitic recombination pathways and compensate intentional dopants

New measures to capture end of life concerns in Huntington disease: Meaning and Purpose and Concern with Death and Dying from HDQLIFE (a patient-reported outcomes measurement system).

PURPOSE: Huntington disease (HD) is an incurable terminal disease. Thus, end of life (EOL) concerns are common in these individuals. A quantitative measure of EOL concerns in HD would enable a better understanding of how these concerns impact health-related quality of life. Therefore, we developed new measures of EOL for use in HD. METHODS: An EOL item pool of 45 items was field tested in 507 individuals with prodromal or manifest HD. Exploratory and confirmatory factor analyses (EFA and CFA, respectively) were conducted to establish unidimensional item pools. Item response theory (IRT) and differential item functioning analyses were applied to the identified unidimensional item pools to select the final items. RESULTS: EFA and CFA supported two separate unidimensional sets of items: Concern with Death and Dying (16 items), and Meaning and Purpose (14 items). IRT and DIF supported the retention of 12 Concern with Death and Dying items and 4 Meaning and Purpose items. IRT data supported the development of both a computer adaptive test (CAT) and a 6-item, static short form for Concern with Death and Dying. CONCLUSION: The HDQLIFE Concern with Death and Dying CAT and corresponding 6-item short form, and the 4-item calibrated HDQLIFE Meaning and Purpose scale demonstrate excellent psychometric properties. These new measures have the potential to provide clinically meaningful information about end-of-life preferences and concerns to clinicians and researchers working with individuals with HD. In addition, these measures may also be relevant and useful for other terminal conditions

Top Quark Physics at the LHC: A Review of the First Two Years

This review summarizes the highlights in the area of top quark physics obtained with the two general purpose detectors ATLAS and CMS during the first two years of operation of the Large Hadron Collider LHC. It covers the 2010 and 2011 data taking periods, where the LHC provided pp collisions at a center-of-mass energy of sqrt(s)=7 TeV. Measurements are presented of the total and differential top quark pair production cross section in many different channels, the top quark mass and various other properties of the top quark and its interactions, for instance the charge asymmetry. Measurements of single top quark production and various searches for new physics involving top quarks are also discussed. The already very precise experimental data are in good agreement with the standard model.Comment: 107 pages, invited review for Int. J. Mod. Phys. A, v2 is identical to v1 except for the addition of the table of content

Structure and kinetics in the freezing of nearly hard spheres

We consider homogeneous crystallisation rates in confocal microscopy experiments on colloidal nearly hard spheres at the single particle level. These we compare with Brownian dynamics simuations by carefully modelling the softness in the interactions with a Yukawa potential, which takes account of the electrostatic charges present in the experimental system. Both structure and dynamics of the colloidal fluid are very well matched between experiment and simulation, so we have confidence that the system simulated is close to that in the experiment. In the regimes we can access, we find reasonable agreement in crystallisation rates between experiment and simulations, noting that the larger system size in experiments enables the formation of critical nuclei and hence crystallisation at lower supersaturations than the simulations. We further examine the structure of the metastable fluid with a novel structural analysis, the topological cluster classification. We find that at densities where the hard sphere fluid becomes metastable, the dominant structure is a cluster of m=10 particles with five-fold symmetry. At a particle level, we find three regimes for the crystallisation process: metastable fluid (dominated by m=10 clusters), crystal and a transition region of frequent hopping between crystal-like environments and other (m\neq10) structuresComment: 10 page