Extension, disruption, and translation of an orogenic wedge by exhumation of large ultrahigh-pressure terranes: Examples from the Norwegian Caledonides

Far-traveled allochthons (greater than 100 km) within collisional orogenic wedges may have undergone significant lateral movement by passive transport (in addition to thrusting) where they lie tectonically above large, exhumed, high-pressure/ultrahigh-pressure (HP/UHP) metamorphic terranes. Continental collision results in the subduction of one craton beneath another into the mantle. The subducted craton undergoes HP/UHP metamorphism, while an accretionary orogenic wedge develops simultaneously at its junction with the overlying craton. The subsequent exhumation of a large HP/UHP terrane by either far-field extension or buoyancy-driven extrusion, or both, reverses the shear traction along its upper boundary from foreland-directed thrust motion to hinterland-directed normal displacement. This normal-sense shear can stretch, thin, and fragment the overlying wedge and even carry a detached frontal fragment passively toward the foreland on top of the exhuming plate. The total “piggyback” displacement would be a function of the amount of exhumation of the HP/UHP terrane and the timing of its breakoff from the hinterland portion of the wedge. This model is applied to the Trondheim and Jotun nappe complexes of the Caledonides of southern Scandinavia, which were translated greater than 300 km to the E and SE, respectively, during the 430–385 Ma Scandian orogeny. Their hinterland boundaries rest on top of the HP/UHP Western Gneiss Complex. Kinematic indicators along their basal décollements indicate a change in shear sense from top-E/SE to top-W/NW at the same time (ca. 405 Ma) that radiometric ages indicate the Western Gneiss Complex began to exhume from the mantle. Displacements of tens of kilometers along these décollements stretched and thinned the Trondheim nappe complex and fragmented the Jotun nappe complex. Ultimately, this basal traction led to the breakaway of the frontal segments of the allochthons, allowing them to be carried passively to the E/SE as the Western Gneiss Complex continued to exhume. Top-W/NW shear continued between the Western Gneiss Complex and the stranded rearward segments of the allochthons, resulting in the opening up of the Western Gneiss Region tectonic window between the E/SE-translating nappes and their relatively “fixed” equivalents in the W/NW. The total displacement of the traveled frontal allochthons could have been considerably farther than that accomplished by thrusting alone

Clinical Experience with the PillCam Patency Capsule prior to Video Capsule Endoscopy: A Real-World Experience

Background. In patients with known or suspected risk factors for gastrointestinal stenosis, the PillCam patency capsule (PC) is given before a video capsule endoscopy (VCE) in order to minimize the risk of capsule retention (CR). CR is considered unlikely upon excretion of the PC within 30 hours, excretion in an undamaged state after 30 hours, or radiological projection to the colon. Methods. We performed a retrospective analysis of 38 patients with risk factors for CR, who received a PC from 02/2013 to 04/2015 at Klinikum Augsburg. Results. Sixteen of our 38 patients observed a natural excretion after a mean time of 34 hours past ingestion. However, only 8 patients observed excretion within 30 hours, as recommended by the company. In 20 patients passage of the PC into the colon was shown via RFID-scan or radiological imaging (after 33 and 45 hours, resp.). Only 2 patients showed a pathologic PC result. In consequence, 32 patients received the VCE; no CR was observed. Conclusion. Our data indicates that a VCE could safely be performed even if the PC excretion time is longer than 30 hours and the excreted PC was not screened for damage

Dirac-Brueckner Hartree-Fock Approach: from Infinite Matter to Effective Lagrangians for Finite Systems

One of the open problems in nuclear structure is how to predict properties of finite nuclei from the knowledge of a bare nucleon-nucleon interaction of the meson-exchange type. We point out that a promising starting point consists in Dirac-Brueckner-Hartree-Fock (DBHF) calculations us- ing realistic nucleon-nucleon interactions like the Bonn potentials, which are able to reproduce satisfactorily the properties of symmetric nuclear matter without the need for 3-body forces, as is necessary in non-relativistic BHF calculations. However, the DBHF formalism is still too com- plicated to be used directly for finite nuclei. We argue that a possible route is to define effective Lagrangians with density-dependent nucleon-meson coupling vertices, which can be used in the Relativistic Hartree (or Relativistic Mean Field (RMF)) or preferrably in the Relativistic Hartree- Fock (RHF) approach. The density-dependence is matched to the nuclear matter DBHF results. We review the present status of nuclear matter DBHF calculations and discuss the various schemes to construct the self-energy, which lead to differences in the predictions. We also discuss how effective Lagrangians have been constructed and are used in actual calculations. We point out that completely consistent calculations in this scheme still have to be performed.Comment: 16 pages, to be published in Journal of Physics G: Nuclear and Particle Physics, special issue

Simple approximation for the starting-energy-independent two-body effective interaction with applications to 6Li

We apply the Lee-Suzuki iteration method to calculate the linked-folded diagram series for a new Nijmegen local NN potential. We obtain an exact starting-energy-independent effective two-body interaction for a multi-shell, no-core, harmonic-oscillator model space. It is found that the resulting effective-interaction matrix elements can be well approximated by the Brueckner G-matrix elements evaluated at starting energies selected in a simple way. These starting energies are closely related to the energies of the initial two-particle states in the ladder diagrams. The ``exact'' and approximate effective interactions are used to calculate the energy spectrum of 6Li in order to test the utility of the approximate form.Comment: 15 text pages and 2 PostScript figures (available upon request). University of Arizona preprint, Number unassigne

Auxiliary potential in no-core shell-model calculations

The Lee-Suzuki iteration method is used to include the folded diagrams in the calculation of the two-body effective interaction $v^{(2)}_{\rm eff}$ between two nucleons in a no-core model space. This effective interaction still depends upon the choice of single-particle basis utilized in the shell-model calculation. Using a harmonic-oscillator single-particle basis and the Reid-soft-core {\it NN} potential, we find that $v^{(2)}_{\rm eff}$ overbinds ^4\mbox{He} in 0, 2, and $4\hbar\Omega$ model spaces. As the size of the model space increases, the amount of overbinding decreases significantly. This problem of overbinding in small model spaces is due to neglecting effective three- and four-body forces. Contributions of effective many-body forces are suppressed by using the Brueckner-Hartree-Fock single-particle Hamiltonian.Comment: 14 text pages and 4 figures (in postscript, available upon request). AZ-PH-TH/94-2

Ground State Energy of the Low Density Bose Gas

Now that the properties of low temperature Bose gases at low density, $\rho$, can be examined experimentally it is appropriate to revisit some of the formulas deduced by many authors 4-5 decades ago. One of these is that the leading term in the energy/particle is $2\pi \hbar^2 \rho a/m$, where $a$ is the scattering length. Owing to the delicate and peculiar nature of bosonic correlations, four decades of research have failed to establish this plausible formula rigorously. The only known lower bound for the energy was found by Dyson in 1957, but it was 14 times too small. The correct bound is proved here.Comment: 4 pages, Revtex, reference 12 change

Correspondence between solar fine-scale structures in the corona, transition region, and lower atmosphere from collaborative observations

The Soft X-Ray Imaging Payload and the High Resolution Telescope and Spectrograph (HRTS) instrument were launched from White Sands on 11 December 1987 in coordinated sounding rocket flights to investigate the correspondence of coronal and transition region structures, especially the relationship between X-ray bright points (XBPs) and transition region small spatial scale energetic events. The coaligned data from X-ray images are presented along with maps of sites of transition region energetic events observed in C IV (100,000 K), HRTS 1600 A spectroheliograms of the T sub min region and ground based magnetogram and He I 10830 A images

Nuclear shell-model calculations for 6Li and 14N with different NN potentials

Two ``phase-shift equivalent'' local NN potentials with different parametrizations, Reid93 and NijmII, which were found to give nearly identical results for the triton by Friar et al, are shown to yield remarkably similar results for 6Li and 14N in a (0+2)hw no-core space shell-model calculation. The results are compared with those for the widely used Hamada-Johnson hard-core and the original Reid soft-core potentials, which have larger deuteron D-state percentages. The strong correlation between the tensor strength and the nuclear binding energy is confirmed. However, many nuclear-structure properties seem to be rather insensitive to the details of the NN potential and, therefore, cannot be used to test various NN potentials. (Submitted to Phys. Rev. C on Nov. 9, 1993 as a Brief Report.)Comment: 12 text pages and 1 figure (Figure available upon request), University of Arizona Physics Preprint (Number not yet assigned

Mean-Field Description of Fusion Barriers with Skyrme's Interaction

Fusion barriers are determined in the framework of the Skyrme energy-density functional together with the semi-classical approach known as the Extended Thomas-Fermi method. The barriers obtained in this way with the Skyrme interaction SkM* turn out to be close to those generated by phenomenological models like those using the proximity potentials. It is also shown that the location and the structure of the fusion barrier in the vicinity of its maximum and beyond can be quite accurately described by a simple analytical form depending only on the masses and the relative isospin of target and projectile nucleus.Comment: 7 pages, latex, 5 figure