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Erlangen, Germany

Hesselmann A.,University Erlangen Nrnberg
Journal of Chemical Physics | Year: 2011

Several random-phase approximation (RPA) correlation methods were compared in third order of perturbation theory. While all of the considered approaches are exact in second order of perturbation theory, it is found that their corresponding third-order correlation energy contributions strongly differ from the exact third-order correlation energy contribution due to missing interactions of the particle-particle-hole-hole type. Thus a simple correction method is derived which makes the different RPA methods also exact to third-order of perturbation theory. By studying the reaction energies of 16 chemical reactions for 21 small organic molecules and intermolecular interaction energies of 23 intermolecular complexes comprising weakly bound and hydrogen-bridged systems, it is found that the third-order correlation energy correction considerably improves the accuracy of RPA methods if compared to coupled-cluster singles doubles with perturbative triples as a reference. © 2011 American Institute of Physics.

Moulton B.J.A.,University of Toronto | Henderson G.S.,University of Toronto | Sonneville C.,Ecole Normale Superieure de Cachan | O'Shaughnessy C.,University of Toronto | And 3 more authors.
Chemical Geology | Year: 2016

X-ray absorption near-edge structure (XANES) spectroscopy has been used to investigate the local structural environments around each of the elements within the haplobasaltic system. The XANES results reveal both, linear changes in Ca, O and Si whereas non-linear changes are also observed for Si as well as Al and Mg. Unexpectedly, both Si and Al spectra show complex edge structure that varies non-linearly across the join. The Si L2,3-edge results suggest that the Si environment in An100 is very similar to that in crystalline anorthite whereas the Di100 and diopside spectra show large offsets. The L3 and L2 peaks display a linear behavior whereas peak B of the Si L2,3 spectra displays a non-linear behavior displaying a maximum position at the Di40 and Di100 compositions and decreasing in between. We estimate the SiO bond length from shift in the peak B position which suggests a change in bond length between 1.58 and 1.66Å across the join. The Al K-edge spectra suggests that there is a constant decrease in the inter-tetrahedral angle as Al is added. The local Mg environment displays non-linear changes in intensity and for compositions with An content greater than Di40 it appears that [4]Mg plays an important role whereas [5]Mg is dominant in diopside-rich melts, though octahedral coordinated Mg cannot be ruled out. The oxygen environment appears similar to crystalline anorthite in the haplobasaltic system. Calcium is present in highly distorted sites that are dominantly [7]Ca in anorthite-rich glasses whereas [8]Ca is more important in diopside-rich glasses. These results provide additional independent constraints on the atomic structure of haplobasaltic silicate melts and highlight the need for further investigation into the relationships between network formers, modifiers and the oxygen to which they are bound. © 2015 Elsevier B.V.

Turner S.,Macquarie University | Beier C.,University Erlangen Nrnberg | Niu Y.,Durham University | Cook C.,University of Waikato
Geochemistry, Geophysics, Geosystems | Year: 2011

There is widespread interest in the distance that mid-ocean ridge magmatism extends beyond the neovolcanic zone. Off-axis magmas also provide a means to map out variations across the melting zone. We present 238U- 230Th-226Ra data for 35 well-characterized samples that extend up to 50 km away from the ridge axis across the East Pacific Rise at 9°30′N, 10°30′N, and 11°20′N. The ( 230Th/238U) ratios range from 1.00 to 1.19, and the ( 226Ra/230Th) ratios range from 1 to 2.78. The samples have a bimodal (230Th/238U) distribution with approximately half overlying published axial data on the U-Th diagram and the remainder lying close to the equiline. The U series disequilibria in the majority of the samples can be explained by aging subsequent to eruption in a zone ∼8 km wide about the neovolcanic zone, consistent with visual evidence for sample age. Nevertheless, seven of the samples lie above calculated (230Th/ 238U) axial decay curves and/or have 226Ra excesses implying eruption tens of kilometers off axis. These are consistent with evidence from seamounts and seismic interpretations that magmatism can extend up to 20 km off axis. The implication is that magma is not as efficiently focused beneath the ridge axis as has generally been believed. There is a decrease in initial (230Th/238U) in both these and published samples inferred to have formed off axis, but there is no compelling evidence that this reflects source heterogeneity. Simple modeling suggests that this could be explained by a decrease in fertility and melt column length as the overlying lithosphere thickens with age and the solidus shallows. Copyright 2011 by the American Geophysical Union.

Kopper C.,University Erlangen Nrnberg
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

Up to now, most of the simulation work for the KM3NeT neutrino telescope has been performed using software tools adapted from the ANTARES project, which have originally neither been set up for a km3-scale detector nor for long-term maintenance on a modern computer system. New Monte-Carlo tools, including a Geant4-based muon propagator, a photon propagation tool including a full light scattering simulation and a new optical module acceptance and readout simulator have been developed and implemented in a simulation chain using a modular software framework. An overview of the new software tools and simulation results for a possible detector configuration will be presented. © 2010 Elsevier B.V. All rights reserved.

Jonas J.B.,University of Heidelberg | Jonas S.B.,Dietrich Bonhoeffer Gymnasium Weinheim | Jonas R.A.,Dietrich Bonhoeffer Gymnasium Weinheim | Holbach L.,University Erlangen Nrnberg | Panda-Jonas S.,University of Heidelberg
American Journal of Ophthalmology | Year: 2011

Purpose: To examine histomorphometrically the parapapillary region in highly myopic eyes. Design: Retrospective laboratory investigation. Methods: We examined a highly myopic glaucomatous group (36 human globes; axial length >26.5 mm) and a nonhighly myopic group (28 globes with secondary angle-closure glaucoma; 17 eyes with malignant choroidal melanoma). Using light microscopy, pupil-optic nerve sections were assessed. Results: The length of the scleral flange (sclera between optic nerve border and optic nerve dura mater) increased with axial length (P <.001; correlation coefficient r = 0.70) and decreased with its thickness (P <.001; r = 0.75). In all highly myopic eyes (n = 15) with a distance of >0.5 mm between optic nerve border and beginning of Bruch membrane, the parapapillary region consisted of an elongated parapapillary scleral flange associated with a scleral flange thinning and a retrobulbar cerebrospinal fluid space extended into the retroparapapillary region. The parapapillary retina was composed of retinal nerve fiber layer (or its remnants) only, without elements of any other retinal layer, without underlying Bruch membrane or choroid. These histologic features were not detected in any of the nonhighly myopic eyes. Conclusions: Since parapapillary scleral thickness influences the lamina cribrosa biomechanics, the findings may partially explain the increased glaucoma susceptibility in highly myopic eyes. The implications of an absence of Bruch membrane and choroid in the highly myopic parapapillary region, and the implications of the retrobulbar parapapillary extension of the cerebrospinal spinal fluid space for the pathophysiology of the optic nerve head, have to be elucidated. © 2011 Elsevier Inc.

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