Recent Submissions
Second‐order computational homogenization of nonlinear fluid flow through porous media
(2026) Polukhov, Elten; Keip, Marc‐André
We present a second‐order computational multiscale model for heterogeneous porous media, which allows for the scale bridging of transient fluid‐flow processes through porous materials with non‐separated scales. The formulation connects a homogenized macroscopic scale described by a local theory of grade two with heterogeneous microstructures described by a local theory of grade one. At the macroscale, this leads to C1‐continuity requirements on the macroscopic solution field; at the microscale, we need to take account of constraints on fluctuation fields that require H(div)∩H(grad)‐conformity of microscopic solutions. Both these challenges are addressed through the development of mixed Hu-Washizu formulations that result in a variationally consistent homogenization framework with minimization structure across scales. We validate the second‐order multiscale model by means of fully resolved, direct numerical simulations and provide comparisons with results of first‐order FE 2 simulations. By considering linear Darcy and nonlinear Darcy-Forchheimer flow through two‐ and three‐dimensional porous microstructures, we provide further insights into the framework and associated length‐scale effects.
Oxygen diffusion in a functionally graded material with cracks using a novel probability distribution for varying parameters
(2025) Lammert, Robert; Petrova, Vera E.; Weihe, Stefan
The elastic modulus profile of a functionally graded material (FGM) is additionally affected by oxygen diffusion. In contrast to earlier work, the reacting material is decreasing in concentration toward the oxygen‐exposed surface, so the rule used to model the elastic modulus is adjusted accordingly. Furthermore, the original distribution function is replaced by a smoother one with similar properties. The resulting oxidation model, including an appropriate fracture toughness rule, is used to calculate critical loads for a set of three parallel edge cracks in the half plane. These loads are then checked against the model without oxygen diffusion.
Advances and applications of spatial proteomics : from organellar maps to clinical translation
(2026) Bernardini, Chiara; Däther, Maike; Traube, Franziska R.
Spatial proteomics has emerged as a powerful approach to systematically map the subcellular localization of thousands of proteins in parallel, providing insights into organelle composition, protein trafficking, and context‐dependent relocalization events. Building on advances in mass spectrometry sensitivity, and acquisition as well as quantification strategies, organelle‐resolved protein maps can now be generated with unprecedented depth and resolution, and recent workflows have expanded the applicability of spatial proteomics to diverse experimental and challenging contexts. Complementary bioinformatic pipelines enable the assignment of proteins to compartments, the detection of distribution shifts, and the integration of spatial data with other omics layers. Beyond fundamental cell biology, the technology holds great potential for clinical research, where limited input material and the complexity of primary samples pose specific challenges. Emerging low‐input preparation methods, antibody‐based organelle enrichment, and microscopy‐guided approaches offer promising solutions, while robust, marker‐independent data analysis will be essential to handle the biological variability of patient‐derived samples. As protocols become more automated, low‐input compatible, and bioinformatically standardized, spatial proteomics is poised to become a valuable tool for mechanistic disease research, biomarker discovery, and therapeutic target identification.
Bio‐based amphiphilic farnesyl glycidyl ether block copolymers : aqueous self‐assembly and solubilization boosting
(2025) Krappel, Maximilian; Schüttner, Sandra; Schneider, Ingo; Schiffmann, Pascal; Schweins, Ralf; Frey, Holger; Sottmann, Thomas
Sustainability has become essential in addressing the substitution of depleting fossil‐based resources with bio‐renewable alternatives, including products active at interfaces, such as surfactants. Enhancing their efficiency reduces both ecological and economic impact. Here, we present amphiphilic poly(ethylene glycol)‐b‐poly(terpenyl glycidyl ether) diblock copolymers synthesized via anionic ring‐opening polymerization from two terpenyl glycidyl ethers (TGE) based on the naturally occurring terpenoid farnesol, farnesyl glycidyl ether (FarGE), and its hydrogenated derivative hexahydrofarnesyl glycidyl ether (HHFarGE). Using poly(ethylene glycol) monomethyl ether (mPEG114) as a macroinitiator resulted in controlled molecular weights (5600 - 8400 g·mol-1) with low dispersities Đ (1.04-1.07). Fluorescence spectroscopy and light scattering revealed low critical micelle concentrations with a systematic decrease with increasing TGE block size due to the hydrophobic effect. The addition of small amounts of mPEG114‐b‐PTGEm to microemulsions leads to a significant increase of the solubilization efficiency not limited to conventional H2O/NaCl - n‐decane - tetraethylene glycol monodecyl ether microemulsions, but also in sustainable H2O - isopropyl myristate - n‐octyl β‐D‐glucopyranoside - farnesol formulations, serving as model systems for cosmetic applications. Using SANS, we observed that adsorption of the copolymer at the amphiphilic film leads to an increased structural order of bicontinuous microemulsions due to a higher film bending rigidity.
Regelungstechnische Aspekte der regelzonenübergreifenden Erbringung von Regelleistung im kontinentaleuropäischen Verbundnetz
(2025) Maucher, Philipp; Lens, Hendrik (Univ.-Prof. Dr.-Ing.)
Durch die Liberalisierung der Strommärkte in Europa wurden diese auch für den internationalen Handel geöffnet. Nachdem zunächst die Öffnung der Strommärkte priorisiert wurde, wird in den nächsten Schritten auch eine regelzonenübergreifende Leistungs-Frequenz-Regelung angestrebt. Innerhalb dieser Arbeit werden hierzu Aspekte, die mit der Erbringung der Regelleistung zusammenhängen und bislang nicht abschließend geklärt sind, betrachtet.
In Deutschland konnte eine solche Kooperation im Netzregelverbund aufgrund der einheitlichen Regularien und der homogenen Struktur der Regelleistungserbringer für zwei Produkte bereits umgesetzt werden. Im gesamteuropäischen Kontext waren die Regularien aufgrund der unterschiedlichen Erzeugungstechnologien unterschiedlich, wodurch ein fairer Wettbewerb nicht gewährleistet werden konnte. Die Harmonisierung der Regularien wurde bzw. wird bereits umgesetzt. Bei der Analyse dieser ergeben sich jedoch einige Unklarheiten im Bezug auf die Erbringungsanforderungen bei Teilabrufen. Hierzu werden in dieser Arbeit zwei mögliche Interpretationen der Erbringungsanforderungen analysiert und hieraus Schlussfolgerungen gezogen.
Zusätzlich zu den harmonisierten Regularien ist auch ein einheitliches Monitoring im Betrieb notwendig, um diese Regularien anzuwenden. Ursprünglich wurde die Regelleistung durch wenige konventionelle Kraftwerke erbracht, wodurch eine manuelle Prüfung der Regelleistungserbringung durch den jeweiligen Übertragungsnetzbetreiber möglich war. Da die Anzahl der Teilnehmer durch die neuen Technologien bereits deutlich gestiegen ist und zukünftig weiter steigen wird, sollte das Monitoringkonzept nicht nur einheitlich sondern auch automatisiert die Erbringungsqualität prüfen. In dieser Arbeit wird ein solches Monitoringverfahren vorgestellt. In diesem wird aus dem Sollwert des jeweiligen Regelleistungsprodukts ein Toleranzkanal, welcher den Bereich einer konformen Erbringung definiert, bestimmt. Hierzu werden die Erkenntnisse aus der Analyse der zwei Interpretationen verwendet. Anschließend erfolgt eine Auswertung der Ergebnisse über einen längeren Zeitraum anhand von Kennzahlen und der Darstellung in einem Schaubild. Da die Regelleistungsanbieter dem Übertragungsnetzbetreiber nur ihre Gesamtleistung übermitteln müssen, für das Monitoring jedoch die Leistung für das jeweilige Produkt notwendig ist, wird eine Methodik zur Aufteilung der Gesamtleistung auf die Produkte vorgestellt.
Der dritte Hauptaspekt dieser Arbeit ist das Regelkonzept für die Erbringung von automatic Frequency Restoration Reserves (aFRR). Da hierzu in jeder Regelzone ein PI-Regler zur Bestimmung des Sollwerts verwendet wird, muss das Regelkonzept für diese Kooperation auf seine Stabilität geprüft werden, um den Netzbetrieb nicht zu gefährden. Hierfür kommen derzeit zwei Regelkonzepte in Frage. Die detaillierte Struktur von einem dieser Konzepte wird dabei in dieser Arbeit definiert. Für beide Konzepte wird analysiert unter welchen Randbedingungen diese stabil betrieben werden können. Zusätzlich wird mit ausgewählten Szenarien die Performance der beiden Konzepte verglichen.
A cryogenic buffer gas beam source for cold barium monofluoride molecules
(2025) Albrecht, Ralf; Pfau, Tilman (Prof. Dr.)
Mini bubble columns for miniaturizing scale‐down
(2024) Wild, Moritz; Takors, Ralf
The successful scale‐up of biotechnological processes from laboratory to industrial scale is crucial for translating innovation to practice. Scale‐down simulators have emerged as indispensable tools in this endeavor, enabling the evaluation of potential hosts’ adaptability to the dynamic conditions encountered in large‐scale fermenters. By simulating these real‐world scenarios, scale‐down simulators facilitate more accurate estimations of host productivity, thereby improving the process of selecting optimal strains for industrial production. Conventional scale‐down systems for detailed intracellular analysis necessitate an elaborate setup comprising interconnected lab‐scale reactors such as stirred tank reactors (STRs) and plug‐flow reactors (PFRs), often proving time‐consuming and resource‐intensive. This work introduces a miniaturized bubble column reactor setup (60 mL working volume), enabling individual and parallel carbon‐limited chemostat fermentations, offering a more efficient and streamlined approach. The industrially relevant organism Escherichia coli , chosen as a model organism, is continuously grown and subjected to carbon starvation for 150 s, followed by a return to carbon excess for another 150 s. The cellular response is characterized by the accumulation of the alarmone guanosine pentaphosphate (ppGpp) accompanied by a significant reduction in energy charge, from 0.8 to 0.7, which is rapidly replenished upon reintroduction of carbon availability. Transcriptomic analysis reveals a two‐phase response pattern, with over 200 genes upregulated and downregulated. The initial phase is dominated by the CRP-cAMP‐ and ppGpp‐mediated response to carbon limitation, followed by a shift to stationary phase‐inducing gene expression under the control of stress sigma factors. The system's validity is confirmed through a thorough comparison with a conventional STR/PFR setup. The analysis reveals the potential of the system to effectively reproduce data gathered from conventional STR/PFR setups, showcasing its potential use as a scale‐down simulator integrated in the process of strain development.
Upconversion nanoparticle‐covalent organic framework core-shell particles as therapeutic microrobots trackable with optoacoustic imaging
(2025) Kim, Dong Wook; Wrede, Paul; Rodríguez‐Camargo, Andrés; Chen, Yi; Dogan, Nihal Olcay; Glück, Chaim; Lotsch, Bettina V.; Razansky, Daniel; Sitti, Metin
Despite the development of various medical imaging contrast agents, integrating contrast signal generation with therapeutic and microrobotic functions remains challenging without complicated fabrication processes. In this study, upconversion nanoparticle‐covalent organic framework (UCNP‐COF) core-shell sub‐micron particles are developed that function as therapeutic microrobots trackable with multi‐spectral optoacoustic tomography (MSOT) imaging and can be loaded with desired therapeutic molecular agents in a customizable manner. The mechanism of optoacoustic signal generation in UCNP‐COF particles is attributed to the quenching of upconversion luminescence emitted by the UCNPs, which is absorbed by the encapsulating COF and subsequently converted into acoustic waves. Unlike other microparticulate agents previously imaged with MSOT, UCNP‐COF particles do not pose concerns about their stability and biocompatibility. Simultaneously, the mesoporous texture of the COF provides a large surface area, allowing for the efficient loading of various drug molecules, which can be released at target sites. Furthermore, the magnetic UCNP‐COF Janus particles can be magnetically navigated through in vivo vasculature while being visualized in real‐time with volumetric MSOT. This study proposes an approach to design photonic materials with multifunctionality, enabling high‐performance medical imaging, drug delivery, and microrobotic manipulation toward their future potential clinical use.
Equilibration‐based a posteriori error estimates for solid mechanics
(2025) Brodbeck, Maximilian; Grünfelder, Nicolas; Bertrand, Fleurianne; Ricken, Tim
A posteriori error estimates and the corresponding adaptive finite element methods enable the computation of solutions with a prescribed accuracy while ensuring optimal convergence rates. An important class of reliable and fully computable error estimates relies on the concept of equilibration. This contribution compares the computational efficiency of different adaptive finite element methods for linear elasticity, all relying on equilibrated stresses. A main aspect of the presented analysis is the influence of the initial mesh quality on the convergence behaviour, as initial meshes for adaptive calculations are typically coarse and therefore prone to skew cells.
Toward carbon‐free cathodes for fluoride ion batteries : deconvoluting effects of active material and conductive additive on charging and cyclic stability
(2025) Aalto, Tommi Hendrik; Talei, Roham; Küster, Kathrin; Schmitz, Guido; Clemens, Oliver
In this study, conductive, fluorine and antimony codoped tin oxide nanoparticles (FATO‐NPs) are highlighted as a possible alternative for conductive carbon additives in fluoride ion batteries, successfully circumventing oxidative side reactions. Since good cyclability with high and stable discharge capacities is achieved with both types of conductive additive at a high stack pressure of 180 MPa, it is concluded that conductive carbon is well‐suited for high‐voltage fluoride ion batteries, contrary to prior assumptions. However, FATO‐NP‐based cathodes outperform those based on conductive carbon at lower stack pressures of 50 MPa, emphasizing the importance of avoiding carbon fluorination at low stack pressures.