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Investigation of the CO₂ Activation and Regeneration of Reduced VOₓ/CeO₂ Catalysts Using Multiple In Situ Spectroscopies
No full textCeria‐supported vanadium oxide (VOₓ/CeO₂) is an important catalyst for various oxidation reactions. Recently, vanadia has emerged again as a less toxic alternative to CrOₓ‐based catalysts for the CO₂‐assisted oxidative dehydrogenation (ODH) of alkanes. To establish a mechanistic understanding of catalyst regeneration during CO₂ exposure, often described as the rate‐limiting step of these reactions, we investigated the regeneration of VOₓ/CeO₂ catalysts with different vanadia loadings using multiple in situ spectroscopies, that is, multi‐wavelength Raman, UV‐Vis, IR and X‐ray photoelectron spectroscopy. Time‐dependent analysis reveals that ceria is only partially regenerated in the bulk but fully regenerated in the subsurface. At the surface, stable carbonates form at vacancies, which are able to regenerate the lattice and deactivate ceria surface oxygen. The VOₓ/CeO₂ samples show a loading‐dependent behavior, with low‐loaded samples regenerating vanadia only partially, due to the high concentration of monomers, while at higher loadings, vanadia can be almost fully regenerated due to the higher nuclearities being thermodynamically more stable. Ceria is regenerated faster than vanadia, indicating that vanadia regenerates by oxygen spill‐over from the ceria lattice. Our results provide important mechanistic insight into CO₂ activation over supported vanadia catalysts, which is of great relevance for CO₂‐assisted ODH reactions
Enantioselective Hydroaminations Catalyzed by Yttrium(III)‐Bis(sulfoximine) Complexes
No full textBis(sulfoximine) yttrium complexes as catalysts for enantioselective intramolecular hydroaminations were prepared for the first time and characterized by a multinuclear NMR study including the nuclei ¹H, ¹³C, ¹⁵N and ⁸⁹Y. The stoichiometries of the complexes were confirmed by a Job plot. In addition to the experimental results, the ⁸⁹Y NMR shifts and the complex structures were elucidated by DFT calculations
Aptamers Binding to c-Met Inhibiting Tumor Cell Migration
No full textThe human receptor tyrosine kinase c-Met plays an important role in the control of critical cellular processes. Since c-Met is frequently over expressed or deregulated in human malignancies, blocking its activation is of special interest for therapy. In normal conditions, the c-Met receptor is activated by its bivalent ligand hepatocyte growth factor (HGF). Also bivalent antibodies can activate the receptor by cross linking, limiting therapeutic applications. We report the generation of the RNA aptamer CLN64 containing 2’-fluoro pyrimidine modifications by systematic evolution of ligands by exponential enrichment (SELEX). CLN64 and a previously described single-stranded DNA (ssDNA) aptamer CLN3 exhibited high specificities and affinities to recombinant and cellular expressed c-Met. Both aptamers effectively inhibited HGF-dependent c-Met activation, signaling and cell migration. We showed that these aptamers did not induce c-Met activation, revealing an advantage over bivalent therapeutic molecules. Both aptamers were shown to bind overlapping epitopes but only CLN3 competed with HGF binding to cMet. In addition to their therapeutic and diagnostic potential, CLN3 and CLN64 aptamers exhibit valuable tools to further understand the structural and functional basis for c-Met activation or inhibition by synthetic ligands and their interplay with HGF binding
Betty’s (Re)Search Engine : A client-based search engine for research software stored in repositories
No full textPromoting research, without providing the source code that was used to conduct
the research, means a greater effort for every researcher down the line. Existing solutions
that aim to make research software FAIR [1], fail to provide a wholesome solution, for they do
not sufficiently consider already existing research software stored on platforms like GitHub
or organizational GitLabs. We therefore present Betty’s research engine, a client-based
implementation of a cascading search process, that first finds research software stored on
platforms like GitHub and then links them to corresponding publications or entries in third
party databases. We evaluated 400 random search results from the domain of ecology and
found that 345 out of 400 repositories made a reference to a corresponding publication /
entry in third party database and therefore clearly indicating the potential of the cascading
search. Betty’s research engine is live and openly available under this URL: http://nfdi4ing.rzhousing.tu-clausthal.de
Multifunctionality of single‐atom‐thick 2D magnetic atoms in nanolaminated M₂AX: toward permanent magnets and topological properties
No full textM(ₙ₊₁)AXₙ (MAX) phases' nanolaminated ternary carbides or nitrides possess a unique crystal structure in which single‐atom‐thick A sublayers are interleaved by alternative stacking of an M(ₙ₊₁)Xₙ sublayer; these materials have been investigated as promising functional materials for industrial applications because of their laminated structure, as well as their metallic and ceramic properties. Based on high‐throughput density functional theory calculations, the stabilities and magnetic properties of M₂AX phases with A as magnetic elements (A = V, Cr, Mn, Fe, Co, and Ni) are investigated, aiming for designing new multifunctional magnets. The thermodynamical stabilities and the relative stability trend are first evaluated, resulting in 139 unreported metastable compounds, 39 of which are carbon‐based M₂AX compounds. After this, the mechanical stability and properties of metastable phases are analyzed. To determine the magnetic ground states of the newly predicted compounds, the magnetic exchange coupling parameters are further calculated, with the critical magnetic transition temperature evaluated based on the mean‐field theory. Particularly, several compounds such as Be₂FeN, Be₂CoN, and Fe₂FeN show high Curie temperature over 1000 K. Subsequently, the absolute value of magneto‐crystalline anisotropy energy (MAE) is calculated, and 20 compounds are found with a uniaxial anisotropy greater than 0.4 MJ m⁻³, which are potential gap magnets. Finally, the transport properties of the predicted ferromagnetic (FM) M₂AX compounds are evaluated. Notably, Y₂FeN possesses an anomalous Hall conductivity (AHC) and anomalous Nernst conductivity (ANC) (at 300 K) of around –1158 S cm⁻¹ and –4.59 A mK⁻¹. Particularly, when considering carbon doping in Ta₂FeN, the AHC and ANC are significantly enhanced, which also offers an effective tuning strategy for spintronics applications
Surface charge density and induced currents by self-charging sliding drops
No full textSpontaneous charge separation in drops sliding over a hydrophobized insulator surface is a well-known phenomenon and lots of efforts have been made to utilize this effect for energy harvesting. For maximizing the efficiency of such devices, a comprehensive understanding of the dewetted surface charge would be required to quantitatively predict the electric current signals, in particular for drop sequences. Here, we use a method based on mirror charge detection to locally measure the surface charge density after drops move over a hydrophobic surface. For this purpose, we position a metal electrode beneath the hydrophobic substrate to measure the capacitive current induced by the moving drop. Furthermore, we investigate drop-induced charging on different dielectric surfaces together with the surface neutralization processes. The surface neutralizes over a characteristic time, which is influenced by the substrate and the surrounding environment. We present an analytical model that describes the slide electrification using measurable parameters such as the surface charge density and its neutralization time. Understanding the model parameters and refining them will enable a targeted optimization of the efficiency in solid–liquid charge separation
Fluorescence-based pH-shift assay with wide application scope for high-throughput determination of enzymatic activity in enzyme mining and engineering
No full textA number of enzymes important for biocatalyst development or as drug targets are associated with a pH shift during their catalytic reaction, owing to the concommitant release or uptake of protons. Here, we show that an enzyme assay developed using the fluorescent pH indicator HPTS can be adapted for reliable and continuous activity determination of representative enzymes from multiple EC classes that operate in the viable pH range 5.5–8.5, using ratiometric measurement (F₄₈₅/F₄₀₅). Kinetic measurements obtained with this method closely match literature values determined using other assay types. Further, the assay was employed to screen variants of transketolase from Geobacillus stearothermophilus (TKgst) aimed at engineering substrate promiscuity and remote enantioselectivity for 3-hydroxyaldehydes. The fluorescence-based assay displayed 70-fold improved sensitivity in comparison to an absorption-based assay for transketolase screening, with a limit of detection of 0.044 mM and Z-factor of 0.52. Double-site mutagenesis at the G264 and S385 positions yielded variants with 5–15-fold increased activity on the tested 3-hydroxyaldehydes compared to the TKgst (L382F) base variant. Although the directed evolution engineering strategy did not achieve significant remote enantioselectivity in this first round of mutagenesis, the simple fluorescence-based pH-shift assay was shown to be useful as a versatile primary high-throughput screen for in vitro enzyme engineering
Parawasserstoff Induzierte Hyperpolarisation an Peptiden und Miniproteinen
No full textDie Kernspinmagnetresonanzspektroskopie (NMR-Spektroskopie) ist eine bedeutende Technik in der modernen Analytik, vor allem in der Chemie. Darüber hinaus besitzt die NMR eine medizinische Relevanz in Form der Magnetresonanztomographie (MRT). Beide Techniken besitzen allerdings nur eine geringe Sensitivität bedingt durch die niedrigen Energieunterschiede der Kernspinniveaus und der daraus resultierenden geringen Polarisation. Verschiedene Hyperpolarisationstechniken ermöglichen die Verstärkung von NMR-Signalen in der Spektroskopie und der MRT. Die Parawasserstoffinduzierte Polarisation (PHIP) ist eine besonders einfach anwendbare, schnelle und vergleichsweise günstige Methode der Hyperpolarisation. Die Anwendung von PHIP an biologischen Molekülen ermöglicht einfachere und schnellere Untersuchungen von biologischen Prozessen und die Entwicklung neuartiger Kontrastmittel für die Medizin. Während bisher vor allem kleine Moleküle des Stoffwechsels hierfür untersucht wurden, widmet sich diese Arbeit größeren Molekülen wie Peptiden und Miniproteinen. In dieser Arbeit wird PHIP an dem Octapeptid Octreotid und dem Miniprotein MCoTI angewendet. Es wird zunächst die Synthese und der Einbau der speziellen Marker in die Biomoleküle durchgeführt und optimiert. Anschließend wird der Einfluss unterschiedlicher Positionen der Marker in den Biomolekülen auf die Effektivität von PHIP untersucht, diskutiert und ein Bezug zur biologischen Aktivität hergestellt
Exploring the evolving landscape of human-centred crisis informatics: current challenges and future trends
No full textModern Information and Communication Technology (ICT) has been used in safety-critical situations for over twenty years. Rooted in Human-Computer Interaction (HCI) and related disciplines, the field of crisis informatics made considerable efforts to investigate social media use and role patterns in crises, facilitate the collection, processing and refinement of social media data, design and evaluate supportive ICT, and provide cumulative and longitudinal research. This narrative review examines contemporary challenges of human-centred crisis informatics and envision trends for the following decade, including (I) a broadening scope of crisis informatics, (II) the professionalisation of cross-platform collaboration of citizen communities and emergency services, (III) expert interfaces for explainable and multimodal artificial intelligence for user-generated content assessment, (IV) internet of things and mobile apps for bidirectional communication and warnings in disruption-tolerant networks, as well as (V) digital twins and virtual reality for the effective training of multi-agency collaboration in hybrid hazards
Juliane Schröter. 2021. Linguistische Argumentationsanalyse. (KEGLI 26). Heidelberg: Winter Verlag. 100 S.
No full textJuliane Schröter hat es unternommen, eine Einführung in die linguistische Analyse von Argumentationen zu schreiben, und zwar als 26. Band der KEGLI-Reihe („Kurze Einführungen in die germanistische Linguistik“). Damit ist stilistisch, quantitativ und funktional ein enger Rahmen abgesteckt. KEGLI-Bücher sind „leicht verständliche und klar geschriebene Einführungen in alle Gebiete der Sprachwissenschaft. Sie wecken Freude an der Beschäftigung mit der deutschen Sprache und befähigen dazu, eigene Sprachanalysen herzustellen“ (Meibauer & Steinbach, o. J.) Um es vorwegzunehmen: Diesen Anspruch löst die Autorin vollumfänglich ein. Nicht nur gehört es zu den anspruchsvollen Schreibaufgaben, ein akademisches Gebiet leicht verständlich, kurz und mit praktischem Bezug darzustellen; im Falle der Argumentationsforschung kommt hinzu, dass man sich einem gut 2300-jährigen Forschungsdiskurs zu stellen hat, an dem ungezählte Gelehrte und Forschende aus allen Bereichen der Text-, Geistes- und Gesellschaftswissenschaften, aus Praxis und Theorie, mit edlen und sinisteren Absichten beteiligt waren und sind. Das geht nur mit Mut zur Lücke und dem Willen zur Gestaltung. Beides hat die Autorin: „Das Buch betrachtet Argumentation aus der Perspektive der Linguistik, nicht etwa der Logik, Rhetorik, Pädagogik oder einer anderen Disziplin“ (Vorwort). Diese Abgrenzung klingt allerdings eindeutiger, als sie sein kann, wenn man bedenkt, dass insbesondere die linguistische Pragmatik, die das Dach der linguistischen Argumentationsforschung bildet, ihrerseits auf diversen Disziplinen fußt, von denen die Logik und die Rhetorik nicht die unbedeutendsten sind