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Implementation of solar UV and energetic particle precipitation within the LINOZ scheme in ICON-ART
No full textWe extended the Linearized ozone scheme – LINOZ in the ICON (ICOsahedral Nonhydrostatic) – ART (the extension for Aerosols and Reactive Trace gases) model system to include NOy formed by auroral and medium-energy electrons in the upper mesosphere and lower thermosphere, and the corresponding ozone loss, as well as changes in the rate of ozone formation due to the variability of the solar radiation in the ultraviolet wavelength range. This extension allows us to realistically represent variable solar and geomagnetic forcing in the middle atmosphere using a very simple ozone scheme. The LINOZ scheme is computationally very cheap compared to a full middle atmosphere chemistry scheme, yet provides realistic ozone fields consistent with the stratospheric circulation and temperatures, and can thus be used in climate models instead of prescribed ozone climatologies. To include the reactive nitrogen (NOy) produced by auroral and radiation belt electron precipitation in the upper mesosphere and lower thermosphere during polar winter, the so-called energetic particle precipitation indirect effect, an upper boundary condition for NOy has been implemented into the simplified parameterization scheme of the N2O/NOy reactions. This parameterization, which uses the geomagnetic Ap index, is also recommended for chemistry-climate models in the CMIP6 experiments. With this extension, the model simulates realistic “tongues” of NOy propagating downward in polar witner from the model top in the upper mesosphere into the mid-stratosphere with an amplitude that is modulated by geomagnetic activity. We then expanded the simplified ozone description used in the model by applying LINOZ version 3. The additional ozone tendency from NOy is included by applying the corresponding terms of the version 3 of LINOZ. This NOy, coupled as an additional term in the linearized ozone chemistry, led to significant ozone losses in the polar upper stratosphere in both hemispheres which is qualitatively in good agreement with ozone observations and model simulations with EPP-NOy and full stratospheric chemistry. In a subsequent step, the tabulated coefficients forming the basis of the LINOZ scheme were provided separately for solar maximum and solar minimum conditions. These coefficients were then interpolated to ICON-ART using the F10.7 index as a proxy for daily solar spectra (UV) variability to account for solar UV forcing. This solar UV forcing in the model led to changes in ozone in the tropical and mid-latitude stratosphere consistent with observed solar signals in stratospheric ozone
Effect of Silicon‐Based Electrolyte Additive on the Solid‐Electrolyte Interphase of Rechargeable Mg Batteries
No full textThe unstable solid-electrolyte interface (SEI) poses a major obstacle to the widespread use of rechargeable magnesium batteries (RMBs) as high-volumetric-capacity next-generation energy storage systems. This issue is effectively mitigated by adding 3 wt.% tris(trimethylsilyl) borate (TMSB, C9H27BO3Si3) to a state-of-the-art Cl-free magnesium tetrakis(hexafluoroisopropyloxy)borate in dimethoxyethane (Mg[B(hfip)(4)](2)/DME) non-aqueous electrolyte. The modified electrolyte enables stable Mg||Mo6S8 (Chevrel phase, CP) full cell operation for up to 1000 cycles at a 1C rate. Tip-enhanced Raman spectroscopy (TERS) reveals that TMSB scavenges degraded electrolyte components and facilitates the formation of a uniform and thin SEI on the magnesium anode. Reflection anisotropy spectroscopy (RAS) further demonstrates that TMSB transforms the interfacial structure, creating a more isotropic and robust SEI during the initial stripping and plating process, thereby extending electrochemical cycling stability. This approach presents a compelling pathway for practical RMB development by stabilizing the SEI and optimizing magnesium electrolyte formulations
Kinetic modeling and conceptual design of the OME synthesis from trioxane and dimethyl ether on H-ZSM-5
No full textThis work presents a new nine-parameter kinetic model for the synthesis of oxymethylene ethers (OME) from
dimethyl ether (DME) and trioxane (TRI) on the zeolite H-ZSM-5 (Si/Al = 40), which according to recent studies
is an active and selective catalyst for this reaction. To establish a database for model parametrization, experi-
ments covering a relevant operating window were performed in a batch reactor with periodic sampling (at
353–393 K and a TRI/DME molar ratio in feed of 0.25–0.70). In addition, the database was enlarged with ex-
periments from a previous work. The model accurately reproduced the data, and the simulations suggest that the
direct incorporation of TRI to form OME is the preferred reaction pathway for OME production. Furthermore, an
optimal operating window was identified considering the trade-off between catalyst activity and OME selectivity.
Finally, a conceptual process design for continuous OME production from DME and TRI is proposed
Elucidating decay pathways of bispidine–iron( iv )–tosylimido complexes: insights gained from decay products
No full textThis study investigates the degradation pathways of three iron(IV)–tosylimido complexes coordinated by tetra- and pentadentate bispidine ligands, a class of rigid nitrogen-donor frameworks based on the 3,7-diazabicyclo[3.3.1]nonane scaffold. Using a combination of spectroscopic (UV-vis-NIR, EPR, Mössbauer) and spectrometric techniques (HR ESI-MS/MS) it was revealed that two of the complexes, derived from a tetradentate bispidine ligand and a pentadentate bispidine ligand, follow a common degradation route. This involves initial reduction to a high-spin iron(III) species, followed by ligand demethylation at a nitrogen donor. The demethylation step is confirmed by the elimination of a CH2NTs (tosylaminomethyl) fragment, as detected by tandem mass spectrometry. This transformation is analogous to formaldehyde loss observed in the degradation of related bispidine-iron(IV)–oxido complexes. In contrast, an isomeric iron(IV)–tosylimido complex bearing a structurally similar pentadentate bispidine ligand follows a distinct pathway, forming a low-spin iron(III)–amido complex of the type [(L)Fe–NHTs]. Mössbauer parameters support this assignment and align with previously reported low-spin iron-amido species. We attribute the difference in reactivity to the orientation of the tosylimido group within the coordination sphere: axial in the isomeric pentadentate ligand, but equatorial in the other two. This spatial change influences both the electronic structure and the accessibility of the tosylimido moiety. Although direct observation of the transient iron(IV)–tosylimido intermediate remains elusive in the tetradentate system due to its high reactivity, analysis of its degradation products provides indirect but compelling evidence for its formation. All complexes mediate NTs transfer to styrene, supporting the presence of tosylimido intermediates and offering a platform for rational catalyst design through ligand and counter ion tuning
Of Issue Advocates and Honest Brokers: Participation of U.S. and German scientists in COVID-19 policy disputes
No full textThe study examines the intersection of science and politics by analyzing the involvement of N = 205 U.S. and N = 174 German scientists in policy disputes during the COVID-19 pandemic. I investigate how scientists integrate themselves into policy disputes. Through a survey, I identify four groups of scientists with specific self-images regarding their roles in policy disputes: Moderate Mainstreamers, Issue Advisors, Issue Advocates, and Honest Brokers. Furthermore, the findings reveal differences in how these groups of scientists perceive the importance of science in policy-making: Particularly U.S.-based Issue Advocates wish for science to direct policy-making. In addition, I find that pandemic researchers overwhelmingly do not support political causes by selectively communicating political advice. I present empirically evidence that pandemic researchers sought to clarify the relevance of research during the pandemic, but did not attempt to distort policy disputes dishonestly
AIDA Arctic transport experiment – Part 1: Simulation of northward transport and aging effect on fundamental black carbon properties
No full textValidierung der Synthesewege von ferroelektrischem Barium- Strontium-Titanat für potenzielle Anwendungen in der Mikrosystemtechnik Validation of Synthesis Routes for Ferroelectric Barium Strontium Titanate for Potential Applications in Microsystem Technology
No full textAls mögliche Alternative zum bleihaltigen Blei-Zirkonat-Titanat (PZT) kann Bariumtitanat (BaTiO3) als Ferro- und Piezoelektrikum
eingesetzt werden. Um den Einsatzbereich von BaTiO3 zu erweitern, können die physikalischen Eigenschaften
durch den Einbau anderer Elemente, wie beispielsweise Strontium, in die Kristallstruktur maßgeschneidert werden.
Dies erlaubt insbesondere die Variation der Curie-Temperatur (TC) in Abhängigkeit des Strontiumgehalts. Die hier
vorgestellte Arbeit vergleicht die Herstellung von Barium-Strontium-Titanat-Keramiken (BST, Ba1-xSrxTiO3) über die
einfach zu realisierende Festkörperreaktion (SSR: Solid State Reaction) mit dem material- und kostenaufwendigeren Sol-
Gel-Prozess (SGP) im Hinblick auf die erzielten Pulverpartikelgrößen, die Kristallstruktur sowie die dielektrischen Eigenschaften
für unterschiedliche Strontiumanteile. Aus den so hergestellten Pulvern gelang bereits die Herstellung dünner
Schichten durch elektrophoretische Abscheidung (EPD)
Experimentelle und numerische Untersuchung der Beanspruchungsvorgänge beim Trockenmischen von Kathodenmaterialien für Lithium-Ionen-Batterien
No full textSimulation-based optimization of the injection of ultrashort non-Gaussian electron beams into a storage ring
No full textThe compact STorage ring for Accelerator Research and Technology (cSTART) project at the Karlsruhe Institute of Technology (KIT, Germany) aims to explore non-equilibrium electron beam dynamics and injection of laser-plasma accelerator (LPA) bunches. The Very Large Acceptance compact Storage Ring (VLA-cSR) is also filled by a second injector that delivers ultra-short bunches from the Ferninfrarot Linac- Und Test-Experiment (FLUTE). Injection from FLUTE into the VLA-cSR is achieved via a complex 3D injection line featuring tilted deflections, negative dispersion, and extreme compression to femtosecond bunch lengths. From this transport, the bunch develops pronounced non-Gaussian tails; nevertheless, near the injection point, it is crucial to ensure matching to both the dynamic aperture and the periodic solutions of the storage ring dynamics. The 25 quadrupole magnets of the injection line make conventional optimization methods impractical. This contribution discusses the development of the magnet optics to meet these extreme requirements. The optimization task was divided into two parts: longitudinal compression was addressed using a surrogate model, while transverse matching is currently being pursued with Bayesian optimization
Beamline to inject laser plasma accelerated electrons to a quasi-isochronous compact storage ring
No full textLaser plasma accelerators (LPAs) can produce high-energy electron bunches from short distances. Successfully coupling these sources with dedicated compact storage rings tuned to quasi-isochronous conditions would demonstrate the capture and storage of ultra-short electron bunches in a circular accelerator. Electron bunches generated from LPAs can have a correlated distribution in longitudinal phase space: a chirp, as well as comparably large angular divergence and energy spread. We, therefore, design a flexible beamline that can transport ultrashort bunches with large angular and energy spread to a ring. We have used the accelerator design programs OPA and MAD8 to build up optical model of a beamline. The line is composed of focusing and dispersion matching sections. A set of small angle bending magnets counteracts the dispersion created by injection septum of the storage ring and provides quasi-isochronous bunch transfer with a flexible value of longitudinal dispersion (R56)