Forschungszentrum Jülich
  • Jülich, NRW, Germany
Recent publications
LiNi1/3Mn1/3Co1/3O2 (NMC-111) is one of the most popular cathode materials in Li-ion batteries. However, chemical and structural instabilities of the cathode/electrolyte interface at high charge cutoff voltages cause capacity fading. Surface modifications using metal oxides are promising candidates to suppress capacity fading. Here a systematic study on the degradation mechanism of an uncoated NMC-111 powder electrode is presented. Moreover, the effect of an Al-doped ZnO (Al:ZnO) coating layer on the structural and chemical stabilities of NMC-111 electrode cycled at high charge cutoff voltages is analyzed using X-ray photoelectron spectroscopy, scanning electron microscopy and analytical transmission electron microscopy as well as electrochemical testing. The coating is applied to commercial NMC-111 powder using a microwave-assisted sol-gel synthesis method. In the case of uncoated NMC-111 electrodes, pitting corrosion due to hydrofluoric acid attacking the electrode surface, cation mixing, and an irreversible phase transformation from a trigonal layered to a rock-salt phase occurs, causing capacity fading. While, in the case of Al:ZnO-coated NMC-111 electrodes, pitting corrosion, cation mixing, and the irreversible phase transformation are mitigated. Therefore, the capacity retention and rate capability are improved as the coating layer protects the electrode surface from the direct electrolyte exposure.
Heterogeneous chemical cycles of pyrogenic nitrogen and halides influence tropospheric ozone and affect the stratosphere during extreme pyrocumulonimbus (PyroCB) events. We report field-derived N2O5 uptake coefficients, γ(N2O5), and ClNO2 yields, φ(ClNO2), from two aircraft campaigns observing fresh smoke in the lower and mid troposphere and processed/aged smoke in the upper troposphere and lower stratosphere (UTLS). Derived φ(ClNO2) varied across the full 0–1 range but was typically < 0.5 and smallest in a PyroCB (< 0.05). Derived γ(N2O5) was low in agricultural smoke (0.2–3.6 ×10-3), extremely low in mid-tropospheric wildfire smoke (0.1 × 10-3), but larger in PyroCB processed smoke (0.7–5.0 × 10–3). Aged BB aerosol in the UTLS had a higher median γ(N2O5) of 17 × 10–3 that increased with sulfate and liquid water, but that was nevertheless 1–2 orders of magnitude lower than values for aqueous sulfuric aerosol used in stratospheric models.
Electrochemical recovery of succinic acid is an electricity intensive process with storable feeds and products, making its flexible operation promising for fluctuating electricity prices. We perform experiments of an electrolysis cell and use these to identify a data-driven model. We apply global dynamic optimization using discrete-time Hammerstein–Wiener models to solve the nonconvex offline scheduling problem to global optimality. We detect the method’s high computational cost and propose an adaptive grid refinement algorithm for global optimization (AGRAGO), which uses a wavelet transform of the control time series and a refinement criterion based on Lagrangian multipliers. AGRAGO is used for the automatic optimal allocation of the control variables in the grid to provide a globally optimal schedule within a given time frame. We demonstrate the applicability of AGRAGO while maintaining the high computational expenses of the solution method and detect superior results to uniform grid sampling indicating economic savings of 14.1%.
Mechanical stimulation is a promising means to non-invasively excite and modulate neuronal networks with a high spatial resolution. Despite the thorough characterization of the initiation mechanism, whether or how mechanical responses disperse into non-target areas remains to be discovered. Our in vitro study demonstrates that a single-neuron deformation evokes responses that propagate to about a third of the untouched neighbors. The responses develop via calcium influx through mechanosensitive channels and regeneratively propagate through the neuronal ensemble via gap junctions. Although independent of action potentials and synapses, mechanical responses reliably evoke membrane depolarizations capable of inducing action potentials both in the target and neighbors. Finally, we show that mechanical stimulation transiently potentiates the responding assembly for further inputs, as both gain and excitability are transiently increased exclusively in neurons that respond to a neighbor’s mechanical stimulation. The findings indicate a biological component affecting the spatial resolution of mechanostimulation and point to a cross-talk in broad-network mechanical stimulations. Since giga-seal formation in patch-clamp produces a similar mechanical stimulus on the neuron, our findings inform which neuroscientific questions could be reliably tackled with patch-clamp and what recovery post-gigaseal formation is necessary.
Herein, we report the fabrication of amphibious polymer materials with outstanding mechanical performances, both underwater and in the air. A polyvinyl alcohol/poly(2‐methoxyethylacrylate) (PVA/PMEA) composite with multiscale nanostructures was prepared by combining solvent exchange and thermal annealing strategies, which contributed to nanophase separation with rigid PVA‐rich and soft PMEA‐rich phases and high‐density crystalline domains of PVA chains, respectively. Benefiting from the multiscale nanostructure, the PVA/PMEA hydrogel demonstrated excellent stability in harsh (such as acidic, alkaline, and saline) aqueous solutions, as well as superior mechanical behavior with a breaking strength of up to 34.8 MPa and toughness of up to 214.2 MJ m−3. Dehydrating the PVA/PMEA hydrogel resulted in an extremely robust plastic with a breaking strength of 65.4 MPa and toughness of 430.9 MJ m−3. This study provides a promising phase–structure engineering route for constructing high‐performance polymer materials for complex load‐bearing environments. This article is protected by copyright. All rights reserved
Despite the need for quantitative measurements of light intensity across many scientific disciplines, existing technologies for measuring light dose at the sample of a fluorescence microscope cannot simultaneously retrieve light intensity along with spatial distribution over a wide range of wavelengths and intensities. To address this limitation, we developed two rapid and straightforward protocols that use organic dyes and fluorescent proteins as actinometers. The first protocol relies on molecular systems whose fluorescence intensity decays and/or rises in a monoexponential fashion when constant light is applied. The second protocol relies on a broad-absorbing photochemically inert fluorophore to back-calculate the light intensity from one wavelength to another. As a demonstration of their use, the protocols are applied to quantitatively characterize the spatial distribution of light of various fluorescence imaging systems, and to calibrate illumination of commercially available instruments and light sources.
Magnetic skyrmions and hopfions are topological solitons¹—well-localized field configurations that have gained considerable attention over the past decade owing to their unique particle-like properties, which make them promising objects for spintronic applications. Skyrmions2,3 are two-dimensional solitons resembling vortex-like string structures that can penetrate an entire sample. Hopfions4–9 are three-dimensional solitons confined within a magnetic sample volume and can be considered as closed twisted skyrmion strings that take the shape of a ring in the simplest case. Despite extensive research on magnetic skyrmions, the direct observation of magnetic hopfions is challenging¹⁰ and has only been reported in a synthetic material¹¹. Here we present direct observations of hopfions in crystals. In our experiment, we use transmission electron microscopy to observe hopfions forming coupled states with skyrmion strings in B20-type FeGe plates. We provide a protocol for nucleating such hopfion rings, which we verify using Lorentz imaging and electron holography. Our results are highly reproducible and in full agreement with micromagnetic simulations. We provide a unified skyrmion–hopfion homotopy classification and offer insight into the diversity of topological solitons in three-dimensional chiral magnets.
Impranil ® DLN‐SD is a poly(ester‐urethane) (PEU) that is widely used as coating material for textiles to fine‐tune and improve their properties. Since coatings increase the complexity of such plastic materials, they can pose a hindrance for sustainable end‐of‐life solutions of plastics using enzymes or microorganisms. In this study, we isolated Halopseudomonas formosensis FZJ due to its ability to grow on Impranil DLN‐SD and other PEUs as sole carbon sources. The isolated strain was exceptionally thermotolerant as it could degrade Impranil DLN‐SD at up to 50°C. We identified several putative extracellular hydrolases of which the polyester hydrolase Hfor _PE‐H showed substrate degradation of Impranil DLN‐SD and thus was purified and characterized in detail. Hfor _PE‐H showed moderate temperature stability (T m = 53.9°C) and exhibited activity towards Impranil DLN‐SD as well as polyethylene terephthalate. Moreover, we revealed the enzymatic release of monomers from Impranil DLN‐SD by Hfor_ PE‐H using GC‐ToF‐MS and could decipher the associated metabolic pathways in H . formosensis FZJ. Overall, this study provides detailed insights into the microbial and enzymatic degradation of PEU coatings, thereby deepening our understanding of microbial coating degradation in both contained and natural environments. Moreover, the study highlights the relevance of the genus Halopseudomonas and especially the novel isolate and its enzymes for future bio‐upcycling processes of coated plastic materials.
Electrochemiluminescence (ECL) is the generation of light induced by an electrochemical reaction, driven by electricity. Here, an all‐optical ECL (AO–ECL) system is developped, which triggers ECL by the illumination of electrically autonomous “integrated” photoelectrochemical devices immersed in the electrolyte. Because these systems are made using small and cheap devices, they can be easily prepared and readily used by any laboratories. They are based on commercially available p‐i‐n Si photodiodes (≈1 € unit ⁻¹ ), coupled with well‐established ECL‐active and catalytic materials, directly coated onto the component leads by simple and fast wet processes. Here, a Pt coating (known for its high activity for reduction reactions) and carbon paint (known for its optimal ECL emission properties) are deposited at cathode and anode leads, respectively. In addition to its optimized light absorption properties, using the commercial p‐i‐n Si photodiode eliminates the need for a complicated manufacturing process. It is shown that the device can emit AO–ECL by illumination with polychromatic (simulated sunlight) or monochromatic (near IR) light sources to produce visible photons (425 nm) that can be easily observed by the naked eye or recorded with a smartphone camera. These low‐cost off‐grid AO‐ECL devices open broad opportunities for remote photodetection and portable bioanalytical tools.
The rather few cases of humans infected by HIV-1 N, O, or P raise the question of their incomplete adaptation to humans. We hypothesized that early postentry restrictions may be relevant for the impaired spread of these HIVs. One of the best-characterized species-specific restriction factors is TRIM5α. HIV-1 M can escape human (hu) TRIM5α restriction by binding cyclophilin A (CYPA, also known as PPIA, peptidylprolyl isomerase A) to the so-called CYPA-binding loop of its capsid protein. How non-M HIV-1s interact with huTRIM5α is ill-defined. By testing full-length reporter viruses (Δ env ) of HIV-1 N, O, P, and SIVgor (simian IV of gorillas), we found that in contrast to HIV-1 M, the nonpandemic HIVs and SIVgor showed restriction by huTRIM5α. Work to identify capsid residues that mediate susceptibility to huTRIM5α revealed that residue 88 in the capsid CYPA-binding loop was important for such differences. There, HIV-1 M uses alanine to resist, while non-M HIV-1s have either valine or methionine, which avail them for huTRIM5α. Capsid residue 88 determines the sensitivity to TRIM5α in an unknown way. Molecular simulations indicated that capsid residue 88 can affect trans -to- cis isomerization patterns on the capsids of the viruses we tested. These differential CYPA usages by pandemic and nonpandemic HIV-1 suggest that the enzymatic activity of CYPA on the viral core might be important for its protective function against huTRIM5α.
The investigation of uncertainties in high-dimensional and computationally expensive engineering applications requires Uncertainty Quantification (UQ) methods that efficiently provide reliable High-Dimensional Model Representations (HDMR) of stochastic results with a justifiable number of calculation runs.
A human respiratory system consists of phonation components that are coupled in a complex manner in order to ensure various vital functions, in particular voice generation. The interdisciplinary nature of the processes controlling sound generation complicates the analysis. Analytical studies are limited and can only be used to characterize the main acoustic sources in connection to various types of fluid motion. Numerical investigations of sound generation require an accurate simulation of the flow field with a proper representation of the respiratory pathways and process conditions in order to get the acoustic source terms. Furthermore, voice formation is closely related to the resonance of acoustic modes in and around the mouth cavity; in order to be able to model this properly, it is essential to identify first the sound sources excited within the vocal tract.
Understanding mineral precipitation induced porosity clogging and being able to quantify its non‐linear feedback on transport properties is fundamental for predicting the long‐term evolution of energy‐related subsurface systems. Commonly applied porosity‐diffusivity relations used in numerical simulations on the continuum‐scale predict the case of clogging as a final state. However, recent experiments and pore‐scale modeling investigations suggest dissolution‐recrystallization processes causing a non‐negligible inherent diffusivity of newly formed precipitates. To verify these processes, we present a novel microfluidic reactor design that combines time‐lapse optical microscopy and confocal Raman spectroscopy, providing real‐time insights of mineral precipitation induced porosity clogging under purely diffusive transport conditions. Based on 2D optical images, the effective diffusivity was determined as a function of the evolving porous media, using pore‐scale modeling. At the clogged state, Raman isotopic tracer experiments were conducted to visualize the transport of deuterium through the evolving microporosity of the precipitates, demonstrating the non‐final state of clogging. The evolution of the porosity‐diffusivity relationship in response to precipitation reactions shows a behavior deviating from Archie's law. The application of an extended power law improved the description of the evolving porosity‐diffusivity, but still neglected post‐clogging features. Our innovative combination of microfluidic experiments and pore‐scale modeling opens new possibilities to validate and identify relevant pore‐scale processes, providing data for upscaling approaches to derive key relationships for continuum‐scale reactive transport simulations.
The understanding and prediction of mineral precipitation processes in porous media are relevant for various energy-related subsurface applications. While it is well known that thermodynamic effects can inhibit crystallization in pores with sizes <0.1 µm, the retarded observation of mineral precipitation as function of pore size is less explored. Using barite as an example and based on a series of microfluidic experiments with well-defined pore sizes and shapes, we show that retardation of observation of barite crystallite can already start in pores of 1 µm size, with the probability of nucleation scaling with the pore volume. In general, it can be expected that mineralization occurs preferentially in larger pores in rock matrices, but other parameters such as the exchange of the fluids with respect to reaction time, as well as shape, roughness, and surface functional properties of the pores may affect the crystal-lization process which can reverse this trend.
The use of transgenic mice displaying amyloid-β (Aβ) brain pathology has been essential for the preclinical assessment of new treatment strategies for Alzheimer’s disease. However, the properties of Aβ in such mice have not been systematically compared to Aβ in the brains of patients with Alzheimer’s disease. Here, we determined the structures of nine ex vivo Aβ fibrils from six different mouse models by cryogenic-electron microscopy. We found novel Aβ fibril structures in the APP/PS1, ARTE10 and tg-SwDI models, whereas the human type II filament fold was found in the ARTE10, tg-APPSwe and APP23 models. The tg-APPArcSwe mice showed an Aβ fibril whose structure resembles the human type I filament found in patients with sporadic Alzheimer’s disease. A detailed assessment of the Aβ fibril structure is key to the selection of adequate mouse models for the preclinical development of novel plaque-targeting therapeutics and positron emission tomography imaging tracers in Alzheimer’s disease.
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2,860 members
Uli Schurr
  • Plant Sciences (IBG-2)
Andreas Wilden
  • Institute of Energy and Climate Research (IEK)
Martina Reske
  • Computational and Systems Neuroscience (INM-6)
Alexandros Katranidis
  • Institute of Biological Information Processing IBI-6
Leo-Brandt-Str., 52428, Jülich, NRW, Germany
Head of institution
Prof. Dr.-Ing. Wolfgang Marquardt (Chairman of the Board of Directors)
02461 61 0