An environment for sustainable research software in Germany and beyond: current state, open challenges, and call for action.

Research software has become a central asset in academic research. It optimizes existing and enables new research methods, implements and embeds research knowledge, and constitutes an essential research product in itself. Research software must be sustainable in order to understand, replicate, reproduce, and build upon existing research or conduct new research effectively. In other words, software must be available, discoverable, usable, and adaptable to new needs, both now and in the future. Research software therefore requires an environment that supports sustainability. Hence, a change is needed in the way research software development and maintenance are currently motivated, incentivized, funded, structurally and infrastructurally supported, and legally treated. Failing to do so will threaten the quality and validity of research. In this paper, we identify challenges for research software sustainability in Germany and beyond, in terms of motivation, selection, research software engineering personnel, funding, infrastructure, and legal aspects. Besides researchers, we specifically address political and academic decision-makers to increase awareness of the importance and needs of sustainable research software practices. In particular, we recommend strategies and measures to create an environment for sustainable research software, with the ultimate goal to ensure that software-driven research is valid, reproducible and sustainable, and that software is recognized as a first class citizen in research. This paper is the outcome of two workshops run in Germany in 2019, at deRSE19 - the first International Conference of Research Software Engineers in Germany - and a dedicated DFG-supported follow-up workshop in Berlin.

Surface Engineering of Graphene Oxide Shells Using Lamellar LDH Nanostructures.

The discovery of graphene oxide (GO) has made a profound impact on varied areas of research due to its excellent physicochemical properties. However, surface engineering of these nanostructures holds the key to enhanced surface properties. Here, we introduce surface engineering of reduced GO (rGO) shells by radially grafting Ni-Co layered double hydroxide (LDH) lamella on rGO shells to form Ni-Co LDH@rGO. The morphology of synthesized Ni-Co LDH@rGO mimics dendritic cell-like three-dimensional (3D) hierarchical morphologies. Silica nanospheres form self-sacrificial templates during the reduction of GO shells to form rGO shells during the template-assisted synthesis. The radial growth of LDH lamellae during hydrothermal process on GO shells provides access to a significantly larger number of additional active redox sites and overcompensates the loss of pseudocapacitive charge storage centers during the reduction of GO to form rGO shells. This enables in the synthesis of novel surface-engineered rGO nanoshells, which provide large surface area, enhanced redox sites, high porosity, and easy transport of ions. These synthesized 3D dendritic cell-like morphologies of Ni-Co LDH@rGO show a high capacitance of ∼2640 F g-1. A flexible hybrid device fabricated using this nanomaterial shows a high energy density of ∼35 Wh kg-1 and a power density of 750 W kg-1 at 1 A g-1. No appreciable compromise in device performance is observed under bending conditions. This synthesis strategy may be used in the development of functional materials useful for potential applications, including sensors, catalysts, and energy storage.

Rationally engineered 3D-dendritic cell-like morphologies of LDH nanostructures using graphene-based core-shell structures.

Functionalization of graphene-based materials using chemical moieties not only modify the electronic structure of the underlying graphene but also enable in limited enhancement of targeted properties. Surface modification of graphene-based materials using other nanostructures enhances the effective properties by minimally modifying the properties of pristine graphene backbone. In this pursuit, we have synthesized bio-inspired hierarchical nanostructures based on Ni-Co layered double hydroxide on reduced graphene oxide core-shells using template based wet chemical approach. The material synthesized have been characterized structurally and electrochemically. The fabricated dendritic morphology of the composite delivers a high specific capacity of 1056 Cg-1. A cost effective solid state hybrid supercapacitor device was also fabricated using the synthesized electrode material which shows excellent performance with high energy density and fast charging capability.

Identifying overlapping and hierarchical thematic structures in networks of scholarly papers: a comparison of three approaches.

The aim of this paper is to introduce and assess three algorithms for the identification of overlapping thematic structures in networks of papers. We implemented three recently proposed approaches to the identification of overlapping and hierarchical substructures in graphs and applied the corresponding algorithms to a network of 492 information-science papers coupled via their cited sources. The thematic substructures obtained and overlaps produced by the three hierarchical cluster algorithms were compared to a content-based categorisation, which we based on the interpretation of titles, abstracts, and keywords. We defined sets of papers dealing with three topics located on different levels of aggregation: h-index, webometrics, and bibliometrics. We identified these topics with branches in the dendrograms produced by the three cluster algorithms and compared the overlapping topics they detected with one another and with the three predefined paper sets. We discuss the advantages and drawbacks of applying the three approaches to paper networks in research fields.

Local density of states for individual energy levels in finite quantum wires.

The local density of states in finite quantum wires is calculated as a function of discrete energies and position along the wire. By using a combination of numerical density matrix renormalization group calculations and analytical bosonization techniques, it is possible to obtain a good understanding of the local spectral weights along the wire in terms of the underlying many-body excitations.

Electron correlations and single-particle physics in the integer quantum Hall effect.

The compressibility of a two-dimensional electron system with spin in a spatially correlated random potential and a quantizing magnetic field is investigated. Electron-electron interaction is treated with the Hartree-Fock method. Numerical results for the influences of interaction and disorder on the compressibility as a function of the particle density and the strength of the magnetic field are presented. Localization-delocalization transitions associated with a highly compressible region in the energy spectrum are found at half-integer filling factors. Coulomb blockade effects are found near integer fillings in the regions of low compressibility. Results are compared with recent experiments.