Eldorado - Repositorium der TU Dortmund

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Bei diesem Service handelt es sich um das Institutionelle Repositorium der Technischen Universität Dortmund. Hier werden Ressourcen aus und für Lehre, Studium und Forschung gespeichert, erschlossen und der Öffentlichkeit zugänglich gemacht.

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Aktuellste Veröffentlichungen

Glycerol-mediated improvement of heterologous aurachin D production in E. coli
(Springer Science and Business Media LLC, 2026-05-30) Korb, Jonas; Demir, Büsra; Graw, Kai; Nett, Markus
Neglected tropical diseases and the increasing prevalence of antibiotic resistance in nosocomial infections represent a major challenge in medicine. Intensive research into bioactive compounds has identified the myxobacterial natural product aurachin D as promising drug candidate due to its potent antibiotic and antiprotozoal properties. The biosynthesis of aurachin D from 2-methyl-1H-quinolin-4-one (MQO) is catalyzed by the membrane-bound farnesyltransferase AuaA. Recently, this enzymatic conversion was reconstructed in the heterologous host Escherichia coli, yielding an aurachin D titer of 17 mg L−1. In this study, we investigated the influence of the medium on aurachin D biosynthesis in E. coli in order to improve the product titer. Our analyses revealed that the glycerol concentration has a major impact on both the growth of the production host and the biocatalytic formation of aurachin D. After switching to a glycerol-based minimal medium and adjustment of the MQO precursor concentration, an aurachin D titer of 124 mg L−1 was achieved in a microbioreactor system, highlighting the superior performance of minimal over complex medium as well as the beneficial effect of glycerol compared to glucose. Further studies were conducted to elucidate the mechanism underlying glycerol’s effects. While improved growth and substrate solubilization were found to be insignificant for increasing the product titer, it was demonstrated that glycerol supplementation positively influenced the expression of the enzyme AuaA. Using a folding reporter, we were able to show that the availability of correctly folded AuaA increased until growth defects of the host, presumably resulting from osmotic stress, began to appear. Key points • Product toxicity is negligible in the production of aurachin D using E. coli • The media supplement glycerol improves the availability of the enzyme AuaA • Aurachin D titers increase after switching to a minimal medium
In situ observation of the pore formation during laser-based reactive air brazing of alumina
(Springer Science and Business Media LLC, 2024-03-16) Wojarski, Lukas; Ulitzka, Henrik; Geldmacher, Anna; Ulitzka, Tim; Tillmann, Wolfgang
Reactive air brazing (RAB) is a low-cost process for joining ceramic composites in air. However, due to the comparably low strength values that can be achieved by RAB, the process is only used in special applications like solid oxide fuel cells as a sealant. The limited strength values are the result of a severe pore formation during the brazing operation that remain in the brazing fillet after the solidification of the brazing filler. In this work, the formation of the pores during RAB brazing of alumina using a paste containing Ag4CuO powder and various binders was investigated. The formation and evolution of the pores were observed and quantified in in situ X-ray measurements. It could be observed that during debinding, pores have developed in the filler metal. The pore structure depends on the binder and the heating rate in the debinding stage. With the melting of the filler metal, many pores are closed by the melt flow. But it seems that the wetting of the alumina was hindered by the pores. The change of porosity during cooling is comparatively low.
Integer optimal control with fractional perimeter regularization
(Springer Science and Business Media LLC, 2024-07-01) Antil, Harbir; Manns, Paul
Motivated by many applications, optimal control problems with integer controls have recently received a significant attention. Some state-of-the-art work uses perimeter-regularization to derive stationarity conditions and trust-region algorithms. However, the discretization is difficult in this case because the perimeter is concentrated on a set of dimension d - 1 for a domain of dimension d. This article proposes a potential way to overcome this challenge by using the fractional nonlocal perimeter with fractional exponent 0 < α < 1 . In this way, the boundary integrals in the perimeter regularization are replaced by volume integrals. Besides establishing some non-trivial properties associated with this perimeter, a Γ-convergence result is derived. This result establishes convergence of minimizers of fractional perimeter-regularized problem, to the standard one, as the exponent α tends to 1. In addition, the stationarity results are derived and algorithmic convergence analysis is carried out for α ∈ (0.5, 1) under an additional assumption on the gradient of the reduced objective. The theoretical results are supplemented by a preliminary computational experiment. We observe that the isotropy of the total variation may be approximated by means of the fractional perimeter functional.
Non-local synchronization of continuous time crystals in a semiconductor
(Springer Science and Business Media LLC, 2026-07-22) Greilich, Alex; Kopteva, Nataliia E.; Korenev, Vladimir L.; Haude, Philipp A.; Kunze, Linus; Grobecker, Ben W.; Anghel, Sergiu; Betz, Markus; Bayer, Manfred
Synchronization resulting in unified collective behavior of the individual elements of a system that are weakly coupled to each other has long fascinated scientists. Examples range from the periodic oscillation of coupled pendulum clocks to the rhythmic behavior in biological systems. Here we demonstrate this effect in a solid-state platform: spatially remote, auto-oscillating electron-nuclear spin systems in a semiconductor. When two such oscillators separated by up to 40 μm are optically pumped, their individually different frequencies lock to a common value, revealing long-range coupling. For larger separations, the synchronization breaks. The interaction distance matches the electron spin diffusion length, identifying spin transport as the coupling-mediating mechanism and maintaining correlated behavior over mesoscopic distances. As a consequence, a wide-area optical pump drives all oscillators within the illuminated spot into a single synchronized state, despite their inhomogeneity. This synchronization accounts for the exceptional stability of the resulting auto-oscillations, enabling collective motion in distributed spin systems and paving the way toward spin networks in spintronics.
The association between employment and family histories and caregiving in later life. European findings based on SHARE and ELSA
(Springer Science and Business Media LLC, 2026-04-29) Deindl, Christian; Di Gessa, Giorgio; Wahrendorf, Morten; van Damme, Maike; Spijker, Jeroen; Lacey, Rebecca; Xue, Baowen; King, Markus; McMunn, Anne
Caregiving can be time-consuming, and it can be challenging for caregivers to combine caregiving tasks with other obligations. While we know a lot about the problems of combining informal care with employment and family obligations, past employment and family histories are seldom discussed. This study tries to fill this gap by examining the association between employment and family histories and caregiving in later life. We used pooled data from the Survey of Health, Ageing and Retirement in Europe (SHARE, waves 1 and 2) and the English Longitudinal Study of Ageing (ELSA, waves 2 and 3) and combined them with the life history interviews from both surveys conducted in wave 3. First, we used sequence analysis and cluster analysis to analyze employment, partnership, and children histories between 25 and 50 years of age, separately for men and women. Then, we used logistic regression analysis to examine the relationships between these clusters and informal caregiving at ages 50 and above. Results indicate that women who stayed home (homemakers) and those who were self-employed were more likely to provide informal care in later life. Partnership histories matter only for men. Men who were separated were less involved in in-household caregiving and more in care provision outside of the household. Furthermore, childless men and women were more likely to be caregivers. Finally, differences in long-term care policies across countries significantly affected the likelihood of informal caregiving for men and women.