Simultaneously-Measured Mid-Infrared Refractive Indices of GaAs/AlGaAs

We present our results for a simultaneous measurement of the refractive indices of Gallium Arsenide (GaAs) and Aluminum Gallium Arsenide (Al$_\mathrm{x}$Ga$_\mathrm{1-x}$As) in the spectral region from $2.0$ to $7.1\,\mathrm{\mu}\mathrm{m}$ ($5000$ to $1400\,\mathrm{cm^{-1}}$). These values are obtained from a monocrystalline thin-film multilayer Bragg mirror of excellent purity (background doping $\leq 1 \times 10^{-14}\,\mathrm{cm^{-3}}$), grown via molecular beam epitaxy. To recover the refractive indices over such a broad wavelength range, we fit a dispersion model for each material. For that, we measure both a photometrically accurate transmittance spectrum of the Bragg mirror via Fourier-transform infrared spectrometry and the individual physical layer thicknesses of the structure via scanning electron microscopy. To infer the uncertainty of the refractive index values, we estimate relevant measurement uncertainties and propagate them via a Monte-Carlo-type method. This method conclusively yields propagated relative uncertainties on the order of $10^{-4}$ over the measured spectral range for both GaAs and Al$_{0.929}$Ga$_{0.071}$As. The fitted model can also approximate the refractive index for MBE-grown Al$_\mathrm{x}$Ga$_\mathrm{1-x}$As for $0 \leq x \leq 1$. These updated values will be essential in the design and fabrication of next-generation active and passive optical devices in a spectral region which is of high interest in many fields, e.g., laser design and cavity-enhanced spectroscopy.Comment: 20 pages, 5 figures, submitted to PR

Maximilian types of S.A. birds

p. 199-202 ; 24 cm.Includes bibliographical references

Skull of Rhinoceros sondaicus in the American Museum of Natural History

3 p. : ill. ; 24 cm.Includes bibliographical references

OpenLB User Guide: Associated with Release 1.6 of the Code

OpenLB is an object-oriented implementation of LBM. It is the first implementation of a generic platform for LBM programming, which is shared with the open source community (GPLv2). Since the first release in 2007, the code has been continuously improved and extended which is documented by thirteen releases as well as the corresponding release notes which are available on the OpenLB website (https://www.openlb.net). The OpenLB code is written in C++ and is used by application programmers as well as developers, with the ability to implement custom models OpenLB supports complex data structures that allow simulations in complex geometries and parallel execution using MPI, OpenMP and CUDA on high-performance computers. The source code uses the concepts of interfaces and templates, so that efficient, direct and intuitive implementations of the LBM become possible. The efficiency and scalability has been checked and proved by code reviews. This user manual and a source code documentation by DoxyGen are available on the OpenLB project website

de.NBI Cloud federation through ELIXIR AAI

Belmann P, Fischer B, Krüger J, et al. de.NBI Cloud federation through ELIXIR AAI. F1000Research. 2019;8: 842.The academic de.NBI Cloud offers compute resources for life science research in Germany.  At the beginning of 2017, de.NBI Cloud started to implement a federated cloud consisting of five compute centers, with the aim of acting as one resource to their users. A federated cloud introduces multiple challenges, such as a central access and project management point, a unified account across all cloud sites and an interchangeable project setup across the federation. In order to implement the federation concept, de.NBI Cloud integrated with the ELIXIR authentication and authorization infrastructure system (ELIXIR AAI) and in particular Perun, the identity and access management system of ELIXIR. The integration solves the mentioned challenges and represents a backbone, connecting five compute centers which are based on OpenStack and a web portal for accessing the federation.This article explains the steps taken and software components implemented for setting up a federated cloud based on the collaboration between de.NBI Cloud and ELIXIR AAI. Furthermore, the setup and components that are described are generic and can therefore be used for other upcoming or existing federated OpenStack clouds in Europe

Myelin insulation as a risk factor for axonal degeneration in autoimmune demyelinating disease

Axonal degeneration determines the clinical outcome of multiple sclerosis and is thought to result from exposure of denuded axons to immune-mediated damage. Therefore, myelin is widely considered to be a protective structure for axons in multiple sclerosis. Myelinated axons also depend on oligodendrocytes, which provide metabolic and structural support to the axonal compartment. Given that axonal pathology in multiple sclerosis is already visible at early disease stages, before overt demyelination, we reasoned that autoimmune inflammation may disrupt oligodendroglial support mechanisms and hence primarily affect axons insulated by myelin. Here, we studied axonal pathology as a function of myelination in human multiple sclerosis and mouse models of autoimmune encephalomyelitis with genetically altered myelination. We demonstrate that myelin ensheathment itself becomes detrimental for axonal survival and increases the risk of axons degenerating in an autoimmune environment. This challenges the view of myelin as a solely protective structure and suggests that axonal dependence on oligodendroglial support can become fatal when myelin is under inflammatory attack

26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 - Meeting Abstracts - Antwerp, Belgium. 15–20 July 2017

This work was produced as part of the activities of FAPESP Research,\ud Disseminations and Innovation Center for Neuromathematics (grant\ud 2013/07699-0, S. Paulo Research Foundation). NLK is supported by a\ud FAPESP postdoctoral fellowship (grant 2016/03855-5). ACR is partially\ud supported by a CNPq fellowship (grant 306251/2014-0)