@incollection{DeutschmannGieseJacobetal., author = {Deutschmann, Bj{\"o}rn and Giese, Malte and Jacob, Arne F. and Lofti, Nima and Gerfers, Friedel and Vehring, S{\"o}nke and B{\"o}ck, Georg}, title = {PolyData/DataRace : polymer-integrated CMOS-based high-speed communication systems at W-band}, series = {Wireless 100 Gbps and beyond : architectures, approaches and findings of German Research Foundation (DFG) Priority Programme SPP1655}, booktitle = {Wireless 100 Gbps and beyond : architectures, approaches and findings of German Research Foundation (DFG) Priority Programme SPP1655}, doi = {10.26127/BTUOpen-5917}, publisher = {BTU Cottbus - Senftenberg}, pages = {397 -- 444}, abstract = {In 2012 a group of researchers proposed a basic research initiative to the German Research Foundation (DFG) as a special priority project (SPP) with the name: Wireless 100 Gbps and beyond. The main goal of this initiative was the investigation of architectures, technologies and methods to go well beyond the state of the art. The target of 100 Gbps was set far away from the (at that time) achievable 1 Gbps such that it was not possible to achieve promising results just by tuning some parameters. We wanted to find breakthrough solutions. When we started the work on the proposal we discussed the challenges to be addressed in order to advancing the wireless communication speed significantly. Having the fundamental Shannon boundary in mind we discussed how to achieve the 100 Gbps speed.}, subject = {100 Gbps; Wireless; Drahtlos; PolyData; DataRace; W-band; W-Band; Drahtloses Sensorsystem; Hochfrequenztechnik; Antenne; Terahertzbereich; Energieffizienz}, language = {en} } @article{HanReiterSchlipfetal.2023, author = {Han, Weijia and Reiter, Sebastian and Schlipf, Jon and Mai, Christian and Spirito, Davide and Jose, Josmy and Wenger, Christian and Fischer, Inga A.}, title = {Strongly enhanced sensitivities of CMOS compatible plasmonic titanium nitride nanohole arrays for refractive index sensing under oblique incidence}, series = {Optics Express}, volume = {31}, journal = {Optics Express}, number = {11}, publisher = {Optica Publishing Group}, address = {Washington, DC}, issn = {1094-4087}, doi = {10.1364/OE.481993}, pages = {17389 -- 17407}, year = {2023}, abstract = {Titanium nitride (TiN) is a complementary metal-oxide-semiconductor (CMOS) compatible material with large potential for the fabrication of plasmonic structures suited for device integration. However, the comparatively large optical losses can be detrimental for application. This work reports a CMOS compatible TiN nanohole array (NHA) on top of a multilayer stack for potential use in integrated refractive index sensing with high sensitivities at wavelengths between 800 and 1500 nm. The stack, consisting of the TiN NHA on a silicon dioxide (SiO2) layer with Si as substrate (TiN NHA/SiO2/Si), is prepared using an industrial CMOS compatible process. The TiN NHA/SiO2/Si shows Fano resonances in reflectance spectra under oblique excitation, which are well reproduced by simulation using both finite difference time domain (FDTD) and rigorous coupled-wave analysis (RCWA) methods. The sensitivities derived from spectroscopic characterizations increase with the increasing incident angle and match well with the simulated sensitivities. Our systematic simulation-based investigation of the sensitivity of the TiN NHA/SiO2/Si stack under varied conditions reveals that very large sensitivities up to 2305 nm per refractive index unit (nm RIU-1) are predicted when the refractive index of superstrate is similar to that of the SiO2 layer. We analyze in detail how the interplay between plasmonic and photonic resonances such as surface plasmon polaritons (SPPs), localized surface plasmon resonances (LSPRs), Rayleigh Anomalies (RAs), and photonic microcavity modes (Fabry-P{\´e}rot resonances) contributes to this result. This work not only reveals the tunability of TiN nanostructures for plasmonic applications but also paves the way to explore efficient devices for sensing in broad conditions.}, subject = {TiN; Plasmonics; Plasmonik; Plasmonik; Photonik; Titannitrid; Plasmonics; Photonics}, language = {en} } @article{TomasMarinGalanDiazRodriguezCalcerradeetal.2023, author = {Tom{\´a}s Mar{\´i}n, Sergio de and Gal{\´a}n D{\´i}az, Javier and Rodr{\´i}guez-Calcerrade, J{\´e}sus and Prieto, Iv{\´a}n and Riva, Enrique G. de la}, title = {Linking functional composition moments of the sub-mediterranean ecotone with environmental drivers}, series = {Frontiers in Plant Science}, volume = {14}, journal = {Frontiers in Plant Science}, publisher = {Frontiers}, address = {Lausanne}, issn = {1664-462X}, doi = {10.3389/fpls.2023.1303022}, year = {2023}, abstract = {Functional trait-based approaches are extensively applied to the study of mechanisms governing community assembly along environmental gradients. These approaches have been classically based on studying differences in mean values among species, but there is increasing recognition that alternative metrics of trait distributions should be considered to decipher the mechanisms determining community assembly and species coexistence. Under this framework, the main aim of this study is to unravel the effects of environmental conditions as drivers of plant community assembly in sub-Mediterranean ecotones. We set 60 plots in six plant communities of a sub-Mediterranean forest in Central Spain, and measured key above- and belowground functional traits in 411 individuals belonging to 19 species, along with abiotic variables. We calculated community-weighted mean (CWM), skewness (CWS) and kurtosis (CWK) of three plant dimensions, and used maximum likelihood techniques to analyze how variation in these functional community traits was driven by abiotic factors. Additionally, we estimated the relative contribution of intraspecific trait variability and species turnover to variation in CWM. The first three axes of variation of the principal component analyses were related to three main plant ecological dimensions: Leaf Economics Spectrum, Root Economics Spectrum and plant hydraulic architecture, respectively. Type of community was the most important factor determining differences in the functional structure among communities, as compared to the role of abiotic variables. We found strong differences among communities in their CWMs in line with their biogeographic origin (Eurosiberian vs Mediterranean), while differences in CWS and CWK indicate different trends in the functional structure among communities and the coexistence of different functional strategies, respectively. Moreover, changes in functional composition were primarily due to intraspecific variability. We observed a high number of strategies in the forest with the different communities spreading along the acquisitive-conservative axis of resource-use, partly matching their Eurosiberian-Mediterranean nature, respectively. Intraspecific trait variability, rather than species turnover, stood as the most relevant factor when analyzing functional changes and assembly patterns among communities. Altogether, our data support the notion that ecotones are ecosystems where relatively minor environmental shifts may result in changes in plant and functional composition.}, subject = {Mixed-species forest; Sub-mediterranean; Ecotone; Functional structure; Intraspecific variability; {\"O}koton; Funktionelle Struktur; Intraspezifische Variabilit{\"a}t; Artengemischter Wald; Submediterran; Spanien; Meseta; {\"O}koton; Wald; Pflanzengesellschaft; Umweltver{\"a}nderung; Maximum-Likelihood-Technik}, language = {en} } @article{BoellmannMartienssen2024, author = {B{\"o}llmann, J{\"o}rg and Martienssen, Marion}, title = {Seasonal variability of cultivable nitrate-reducing and denitrifying bacteria and functional gene copy number in fresh water lake}, series = {microorganisms}, volume = {12}, journal = {microorganisms}, number = {3}, publisher = {MDPI}, address = {Basel}, issn = {2076-2607}, doi = {10.3390/microorganisms12030511}, year = {2024}, abstract = {This study describes the seasonal course of denitrifying and nitrate-reducing bacteria in a dimictic mesotrophic lake (Lake Scharm{\"u}tzelsee, Brandenburg, Germany) within a three-year period from 2011 to 2013. The bacterial cell numbers were quantified by the fluorescence microscopy, most probable number (MPN) and PCR-dependent quantification of the chromosomal 16S rDNA and of the nirS and nirK gene copy number. The highest seasonal differences (up to three orders of magnitudes) have been measured usingMPNin the epilimnion. This variation was not reflected by PCR-dependent approaches or direct microscopical enumeration. At adverse conditions (low temperature and/or low nitrate concentrations), the differences between MPN and gene copy numbers increased by up to five orders of magnitudes and decreased to one magnitude at favourable environmental conditions. These results can be explained best by an increasing ratio of viable but not cultivable (VBNC) cells or dead cells at impairing conditions. In the hypolimnion, the courses of MPN and nir gene copy numbers were similar. This can be explained by a higher feeding pressure and therefore smaller amounts of dormant cells. In the pelagial in general, the total cell numbers enumerated by either microscopical or molecular approaches were similar. In the sediment, more than 99\% of the DNA was obviously not related to viable bacteria but was rather DNA in dead cells or adsorbed to particle surfaces.}, subject = {Denitrification; Nitrite reductase; Microscopical cell number; Hypolimnion; Dimictic lake; Denitrifikation; Nitrit-Reduktase; Mikroskopische Zellzahl; Dimiktischer See}, language = {en} } @article{FrimpongKorantengOpoku2023, author = {Frimpong, Bernard Fosu and Koranteng, Addo and Opoku, Fosu Senior}, title = {Analysis of urban expansion and its impact on temperature utilising remote sensing and GIS techniques in the Accra metropolis in Ghana (1986-2022)}, doi = {10.1007/s42452-023-05439-z}, year = {2023}, abstract = {The Accra Metropolis of Ghana has experienced rapid urban expansion over the past decades. Agricultural and forest-lands have been transformed into urban/built-up areas. This study analysed urban expansion and its relationship with the temperature of Accra from 1986 to 2022. Multi-source datasets such as remote sensing (RS) and other ancillary data were utilised. Land use land cover (LULC) maps were produced employing the random forests classifier. Land surface temperature (LST) and selected d(RS) Indices were extracted. Regression techniques assessed the interplay between LST and remote sensing indices. The LULC maps revealed increasing trends in the urban/built-up areas at the expense of the other LULC types. The analysis from the LST and the RS indices revealed a direct relationship between temperature and urban/built-up areas and an inverse relationship between temperature and vegetation. Thus, spatial urban expansion has modified the urban temperature of Accra. The integrated utilisation of RS and GIS demonstrated to be an efficient approach for analysing and monitoring urban expansion and its relationship with temperature.}, subject = {Urban expansion; Change detection; Land use land cover; Regression; Remote sensing; St{\"a}dtische Expansion; Erkennung von Ver{\"a}nderungen; Landnutzung Landbedeckung; Temperatur; Fernerkundung; Accra; Stadt; Expansion; Landnutzung; Temperatur; Fernerkundung}, language = {en} } @article{KhanSidorczukBeckeretal.2024, author = {Khan, Muhammad Moman and Sidorczuk, Katarzyna and Becker, Juliane and Aleksandrowicz, Adrianna and Baraniewicz, Karolina and Ludwig, Christina and Ali, Aamir and Kingsley, Robert A. and Schierack, Peter and Kolenda, Rafał}, title = {Characterization of clumpy adhesion of Escherichia coli to human cells and associated factors influencing antibiotic sensitivity}, series = {Microbiology Spectrum}, volume = {12}, journal = {Microbiology Spectrum}, number = {5}, publisher = {American Society for Microbiology (ASM)}, address = {Washington, DC}, issn = {2165-0497}, doi = {10.1128/spectrum.02606-23}, year = {2024}, abstract = {Escherichia coli intestinal infection pathotypes are characterized by distinct adhesion patterns, including the recently described clumpy adhesion phenotype. Here, we identify and characterize the genetic factors contributing to the clumpy adhesion of E. coli strain 4972. In this strain, the transcriptome and proteome of adhered bacteria were found to be distinct from planktonic bacteria in the supernatant. A total of 622 genes in the transcriptome were differentially expressed in bacteria present in clumps relative to the planktonic bacteria. Seven genes targeted for disruption had variable distribution in different pathotypes and non-pathogenic E. coli, with the pilV and spnT genes being the least frequent or absent from most groups. Deletion (Δ) of five differentially expressed genes, flgH, ffp, pilV, spnT, and yggT, affected motility, adhesion, or antibiotic stress. ΔflgH exhibited 80\% decrease and ΔyggT depicted 184\% increase in adhesion, and upon complementation, adhesion was significantly reduced to 13\%. ΔflgH lost motility and was regenerated when complemented, whereas Δffp had significantly increased motility, and reintroduction of the same gene reduced it to the wild-type level. The clumps produced by Δffp and ΔspnT were more resistant and protected the bacteria, with ΔspnT showing the best clump formation in terms of ampicillin stress protection. ΔyggT had the lowest tolerance to gentamicin, where the antibiotic stress completely eliminated the bacteria. Overall, we were able to investigate the influence of clump formation on cell surface adhesion and antimicrobial tolerance, with the contribution of several factors crucial to clump formation on susceptibility to the selected antibiotics.}, subject = {Escherichia coli; Clumpy adhesion; Motility; Antibiotic tolerance; Stress; Escherichia coli; Zelladh{\"a}sion; Ph{\"a}notyp; Genanalyse}, language = {en} } @article{LangnerSieberRietigetal.2023, author = {Langner, Thomas and Sieber, Tim and Rietig, Anja and Acker, J{\"o}rg}, title = {A phenomenological and quantitative view on the degradation of positive electrodes from spent lithium-ion batteries in humid atmosphere}, doi = {10.1038/s41598-023-32688-0}, year = {2023}, abstract = {The present study deals with the phenomenological observation of the corrosion of the positive electrode foil of lithium-ion batteries containing LiNi0.6Co0.2Mn0.2O2 (NMC) as cathode material. Due to the presence of moisture, localized water accumulation is formed on the NMC surface. The water absorbed by the electrolyte reacts with the NMC under Li+/H+ exchange and the resulting pH increase leads to dissolution of the carrier foil and characteristic salt-like blooms on the NMC surface. With the increase in the relative area occupied by the holes in the aluminum foil per time, a sufficiently suitable parameter was found with which to quantitatively determine the extent of corrosion. The degree of degradation depends on time and ambient humidity. It was shown that functional recycling with the water jet method is no longer applicable for degraded foils, since the mechanical stability of the foils decreases as corrosion progresses. Lithium, aluminum, sulfur and oxygen were detected in the blooms using SEM-EDX and Laser-Induced-Breakdown-Spectroscopy (LIBS). The underlying NMC layer was found to contain mainly aluminum and significantly lower lithium content than the non-degraded material. SEM and Raman microscopy analyses also showed that the active material is also locally degraded and therefore no longer suitable for functional recycling.}, subject = {Analytical chemistry Surface chemistry; Inorganic chemistry; Materials chemistry; Process chemistry; Materials science; Analytische Chemie; Anorganische Chemie; Werkstoffchemie; Werkstoffkunde; Chemische Technik; Analytische Chemie; Lithiumbatterie; Elektrodenfolie; Korrosion; Recycling}, language = {en} } @article{SchneidereitBreuss2023, author = {Schneidereit, Toni and Breuß, Michael}, title = {Adaptive neural-domain refinement for solving time-dependent differential equations}, doi = {10.1186/s13662-023-03789-x}, year = {2023}, abstract = {A classic approach for solving differential equations with neural networks builds upon neural forms, which employ the differential equation with a discretisation of the solution domain. Making use of neural forms for time-dependent differential equations, one can apply the recently developed method of domain segmentation. That is, the domain may be split into several subdomains, on which the optimisation problem is solved. In classic adaptive numerical methods, the mesh as well as the domain may be refined or decomposed, in order to improve the accuracy. Also, the degree of approximation accuracy may be adapted. Therefore, it is desirable to transfer such important and successful strategies to the field of neural-network-based solutions. In the presented work, we propose a novel adaptive neural approach to meet this aim for solving time-dependent problems. To this end, each subdomain is reduced in size until the optimisation is resolved up to a predefined training accuracy. In addition, while the neural networks employed are by default small, we propose a means to adjust also the number of neurons in an adaptive way. We introduce conditions to automatically confirm the solution reliability and optimise computational parameters whenever it is necessary. Results are provided for several initial-value problems that illustrate important computational properties of the method.}, subject = {Neural forms; Differential equations; Physics-informed neural networks; Adaptive neural refinement; Domain decomposition; Neuronale Formen; Differentialgleichungen; Physikalisch informierte neuronale Netze; Adaptive neuronale Verfeinerung; Gebietszerlegung; Differentialgleichung; Neuronales Netz}, language = {en} } @article{AfitiriAfrifa2024, author = {Afitiri, Abdul-Rahaman and Afrifa, Ernest Kofi Amankwa}, title = {Households' willingness to use water from a solar water disinfection treatment system for household purposes}, series = {World}, volume = {5}, journal = {World}, number = {4}, publisher = {MDPI}, address = {Basel}, issn = {2673-4060}, doi = {10.3390/world5040060}, pages = {1181 -- 1193}, year = {2024}, abstract = {The consumption of contaminated water contributes to the global burden of diarrhea and other water-borne diseases, especially among young children. While decentralized solar water disinfection treatment systems (hereafter SODIS) remain a viable option to have safe drinking water, our understanding of the effects of household water treatment before use on willingness to accept and adopt a SODIS is limited. In this study, a complementary log-log regression analysis of the compositional and contextual factors that systematically vary with willingness to accept and adopt a SODIS in the Sawla-Tuna-Kalba (STK) district of Ghana was carried out. Based on our findings, a greater proportion of households (97\%) are willing to accept and adopt a SODIS. Compositional and contextual factors such as age, marital status, education, religion, and geographical location significantly contribute to households' willingness to accept and adopt a SODIS in the STK district of Ghana. Households that treat their water before use (66\%, p < 0.05) are more likely to accept and adopt a SODIS compared to those that do not treat their water before use. The findings, therefore, suggest that scaling up SODIS in the STK district is sacrosanct and highlight the necessity to analyse compositional and contextual factors influencing willingness to accept and adopt SODIS. Our findings will inform policies and programs aimed at implementing SODIS in the study area to improve the health of communities that rely on poor-quality drinking water sources.}, subject = {SODIS; Disinfection; Willingness to accept; Adoption; Sawla-Tuna-Kalba district}, language = {en} } @article{ZschechLechowskiKuturkovaetal.2024, author = {Zschech, Ehrenfried and Lechowski, Bartlomiej and Kuturkova, Kristina and Panchenko, Luliana and Kr{\"u}ger, Peter and Clausner, Andr{\´e}}, title = {Laboratory X-ray microscopy of 3D nanostructures in the hard X-ray regime enabled by a combination of multilayer X-ray optics}, series = {Nanomaterials}, volume = {14}, journal = {Nanomaterials}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {2079-4991}, doi = {10.3390/nano14020233}, year = {2024}, abstract = {High-resolution imaging of buried metal interconnect structures in advanced microelectronic products with full-field X-ray microscopy is demonstrated in the hard X-ray regime, i.e., at photon energies > 10 keV. The combination of two multilayer optics—a side-by-side Montel (or nested Kirkpatrick-Baez) condenser optic and a high aspect-ratio multilayer Laue lens—results in an asymmetric optical path in the transmission X-ray microscope. This optics arrangement allows the imaging of 3D nanostructures in opaque objects at a photon energy of 24.2 keV (In-Kα X-ray line). Using a Siemens star test pattern with a minimal feature size of 150 nm, it was proven that features < 150 nm can be resolved. In-Kα radiation is generated from a Ga-In alloy target using a laboratory X-ray source that employs the liquid-metal-jet technology. Since the penetration depth of X-rays into the samples is significantly larger compared to 8 keV photons used in state-of-the-art laboratory X-ray microscopes (Cu-Kα radiation), 3D-nanopattered materials and structures can be imaged nondestructively in mm to cm thick samples. This means that destructive de-processing, thinning or cross-sectioning of the samples are not needed for the visualization of interconnect structures in microelectronic products manufactured using advanced packaging technologies. The application of laboratory transmission X-ray microscopy in the hard X-ray regime is demonstrated for Cu/Cu6Sn5/Cu microbump interconnects fabricated using solid-liquid interdiffusion (SLID) bonding.}, subject = {X-ray microscopy; High-resolution radiography; Nanostructure; Advanced packaging; R{\"o}ntgenmikroskopie; Hochaufl{\"o}sende Radiographie; Nanostruktur; Erweiterte Verpackung; Nanostruktur; R{\"o}ntgenmikroskopie; Radiographie}, language = {en} } @article{LiedtkeWartmannShietal.2025, author = {Liedtke, Victoria and Wartmann, Thomas and Shi, Wenjie and Kahlert, Ulf D.}, title = {Linking LEDGF/p75 overexpression with microsatellite instability and KRAS mutations : a small-scale study in colorectal cancer}, series = {Cancer Control}, volume = {32}, journal = {Cancer Control}, publisher = {Sage}, address = {London}, doi = {10.1177/10732748251313499}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-69673}, pages = {1 -- 9}, year = {2025}, abstract = {Colorectal cancer (CRC) ranks third in men and second in women, with 153,020 new cases and 52,550 deaths in 2023, and with a projected incidence of 2.2 million new cases by 2030 due to lifestyle changes and enhanced diagnostic capabilities. Identification and analysis of new biomarkers, like lens epithelium-derived growth factor splice variant of 75 kDa (LEDGF/p75), which is known to play a crucial role as stress-related oncogene, can make a significant contribution in facilitating early CRC detection. This study analyzed the expression of LEDGF/p75 and the ubiquitin E2 conjugating enzyme UBC13 in 15 CRC tissue samples and adjacent non-tumor tissues. All patient samples underwent NGS-based mutation analysis beforehand. The western blot technique was used for protein analysis, and the results were further validated using mRNA expression data from 521 patient samples from the TCGA database. LEDGF/p75 expression was significantly elevated in nearly all tumor tissue samples compared to adjacent tissue (11/15, 73.3\%). Additionally, the UBC13 enzyme, a key regulator in the degradation of signaling molecules, was also increased in most tumor tissue samples (9/15, 60.0\%). Co-overexpression of LEDGF/p75 and UBC13 was evident in 6/6 patients. Patients with KRAS and MSH2 mutations showed a 75\% and 100\% correlation with LEDGF/p75 overexpression, respectively. This study confirms the upregulation of LEDGF/p75 in CRC and shows its correlation with KRAS and MSH2 mutations. The interaction of LEDGF/p75 with DNA damage response proteins may contribute to drug resistance and increased tumor aggressiveness. LEDGF/p75's potential as a prognostic biomarker independent of lymph node involvement or CEA levels highlights its potential in personalized therapy, and warrants further research into its therapeutic targeting.}, subject = {LEDGF/p75; Colorectal cancer; Biomarker; Personalized therapy; DNA repair}, language = {en} } @book{Kuennemann2022, author = {K{\"u}nnemann, Andreas}, title = {Existenz- und Regularit{\"a}tstheorie der zweidimensionalen Variationsrechnung mit Anwendungen auf das Plateausche Problem f{\"u}r Fl{\"a}chen vorgeschriebener mittlerer Kr{\"u}mmung}, publisher = {Springer}, address = {Heidelberg}, isbn = {978-3-658-41640-9}, doi = {10.1007/978-3-658-41641-6}, publisher = {BTU Cottbus - Senftenberg}, pages = {247}, year = {2022}, abstract = {Die vorliegende Arbeit behandelt f{\"u}r eine breite Klasse zweidimensionaler Variationsprobleme eine Existenz- und Regularit{\"a}tstheorie, die der L{\"o}sung von Randwertproblemen partieller Differentialgleichungssysteme dient. Dabei werden bekannte Ergebnisse gr{\"u}ndlich untersucht und umfassend aufgearbeitet. Teilweise wird eine geeignete Anpassung der Voraussetzungen einiger Resultate vorgenommen. Speziell wird die Theorie auf das Plateausche Problem f{\"u}r Fl{\"a}chen vorgeschriebener mittlerer Kr{\"u}mmung im R3 angewendet. Eingangs wird das Konzept der direkten Methoden der Variationsrechnung erl{\"a}utert. {\"U}ber einen fundamentalen Satz zur schwachen Unterhalbstetigkeit von Funktionalen wird die Existenz eines Minimierers f{\"u}r eine breite Klasse von Variationsproblemen nachgewiesen. Da die Existenztheorie in Sobolev-R{\"a}umen agiert, sind Untersuchungen zur Regularit{\"a}t eines Minimierers notwendig. Im Rahmen der Regularit{\"a}tstheorie wird das Dirichletsche Wachstumstheorem von Morrey gezeigt, welches ein hinreichendes Kriterium f{\"u}r die H{\"o}lder-Stetigkeit einer Funktion X ∈ W1,2(G) liefert. Zum Nachweis der Anwendbarkeit des Dirichletschen Wachstumstheorems auf einen Minimierer wird ein Wachstumslemma verwendet. Dabei werden eine Verkn{\"u}pfung des Dirichlet-Integrals mit Fourierreihen sowie das Dirichlet- Integral der harmonischen Ersetzung einer Funktion mit L2-Randwerten genutzt. Infolgedessen ergibt sich die H{\"o}lder-Stetigkeit im Inneren f{\"u}r einen Minimierer. Zudem wird die Stetigkeit des Minimierers bis zum Rand gezeigt, sodass die Existenz eines stetigen Minimierers f{\"u}r eine breite Klasse von Variationsproblemen gesichert ist. Anschließend erfolgt die Berechnung der ersten Variation sowie die damit verbundene Herleitung der schwachen Euler-Lagrange-Gleichung, welche eine Beziehung zur L{\"o}sungstheorie von Differentialgleichungen im Sinne des Dirichletschen Prinzips herstellt. Ausgehend von der schwachen Euler-Lagrange-Gleichung wird die H{\"o}lder-Stetigkeit der ersten Ableitungen eines Minimierers bewiesen. F{\"u}r die L{\"o}sung von Randwertproblemen mit partiellen Differentialgleichungen zweiter Ordnung mithilfe der Variationsrechnung ist der Nachweis stetiger zweiter Ableitungen des Minimierers notwendig. Dabei wird der Fokus auf sogenannte Minimierer vom Poissonschen Typ gelegt. Eine C2,σ-Rekonstruktion, die auf der Schaudertheorie basiert, liefert in diesem Fall die gew{\"u}nschte Regularit{\"a}t. In Anwendung dessen werden das Randwertproblem harmonischer Abbildungen in Riemannschen R{\"a}umen sowie das Dirichletproblem des H-Fl{\"a}chen-Systems behandelt, indem jeweils ein geeignetes Variationsproblem aufgestellt wird. Als Erweiterung des Dirichletproblems des H-Fl{\"a}chen-Systems wird das allgemeine Plateausche Problem f{\"u}r Fl{\"a}chen vorgeschriebener mittlerer Kr{\"u}mmung mit den erarbeiteten Methoden der Variationsrechnung untersucht. Zudem wird das Plateausche Problem f{\"u}r Fl{\"a}chen vorgeschriebener mittlerer Kr{\"u}mmung in Kugeln, in Zylindern sowie insbesondere im Einheitskegel gel{\"o}st. Insgesamt wird eine ausf{\"u}hrliche, in sich geschlossene und gut verst{\"a}ndliche Existenzund Regularit{\"a}tstheorie der zweidimensionalen Variationsrechnung zur Behandlung von Randwertproblemen partieller Differentialgleichungssysteme dargestellt, welche sich in besonderer Weise bei der L{\"o}sung des Plateauschen Problems f{\"u}r Fl{\"a}chen vorgeschriebener mittlerer Kr{\"u}mmung entfaltet.}, subject = {Variationsrechnung; Variationsrechnung; Dimension 2; Mittlere Kr{\"u}mmung; Plateau-Problem; Partielle Differentialgleichungen; Plateausches Problem; Regularit{\"a}tstheorie; Morrey; Variation calculation; Partial differential equations; Plateau problem; Regularity theory}, language = {de} } @article{RichterRachowIsraeletal.2023, author = {Richter, Jana and Rachow, Fabian and Israel, Johannes and Roth, Norbert and Charlafti, Evgenia and G{\"u}nther, Vivien and Flege, Jan Ingo and Mauss, Fabian}, title = {Reaction mechanism development for methane steam reforming on a Ni/Al2O3 catalyst}, doi = {10.3390/catal13050884}, year = {2023}, abstract = {In this work, a reliable kinetic reaction mechanism was revised to accurately reproduce the detailed reaction paths of steam reforming of methane over a Ni/Al2O3 catalyst. A steadystate fixed-bed reactor experiment and a 1D reactor catalyst model were utilized for this task. The distinctive feature of this experiment is the possibility to measure the axially resolved temperature profile of the catalyst bed, which makes the reaction kinetics inside the reactor visible. This allows for understanding the actual influence of the reaction kinetics on the system; while pure gas concentration measurements at the catalytic reactor outlet show near-equilibrium conditions, the inhere presented temperature profile shows that it is insufficient to base a reaction mechanism development on close equilibrium data. The new experimental data allow for achieving much higher quality in the modeling efforts. Additionally, by carefully controlling the available active surface via dilution in the experiment, it was possible to slow down the catalyst conversion rate, which helped during the adjustment of the reaction kinetics. To assess the accuracy of the revised mechanism, a monolith experiment from the literature was simulated. The results show that the fitted reaction mechanism was able to accurately predict the experimental outcomes for various inlet mass flows, temperatures, and steam-to-carbon ratios.}, subject = {1D modeling; Reaction rates; Methane steam reforming; Fixed-bed reactor experiments; Nickel catalyst; 1D-Modellierung; Reaktionsgeschwindigkeiten; Methan-Dampfreformierung; Festbettreaktor-Experimente; Nickel-Katalysator; Katalysator; Reaktionsmechanismus; Festbettreaktor; Steamreforming; Reaktionsgeschwindigkeit}, language = {en} } @article{AsliMhgoubKlaus2025, author = {Asli, Majid and Mhgoub, Mosaab and Klaus, H{\"o}schler}, title = {Numerical investigation of a turbine working with a highly unsteady exhaust flow of a hydrogen-driven rotating detonation combustion}, series = {International Journal of Thermofluids}, volume = {29}, journal = {International Journal of Thermofluids}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2666-2027}, doi = {10.1016/j.ijft.2025.101356}, year = {2025}, abstract = {Traditionally, turbomachines are designed for steady-state operations around which they achieve optimal performance and efficiency. However, in novel applications, a turbomachine may be exposed to unsteady flow forcing the machine to operate under fluctuating off design conditions. Pressure Gain Combustion (PGC) through detonation can be an extreme example of unsteady flow which affects the turbine performance adversely. The efficient way of energy extraction from PGCs is still an open question which needs extensive turbine design optimizations for such unsteady flow. Any flow field optimization problem in such applications needs a multitude of simulations, which can be too computationally expensive to be utilized as it is realized as an unsteady 3D-CFD problem. In this regard, the current study aims at proposing and evaluating an approach for optimizing a turbine working under highly unsteady exhaust flow of a Rotating Detonation Combustion (RDC). A two stage turbine is placed downstream an RDC and the turbine inlet condition is calculated by a 2D-Euler simulation tool. A turbine optimization problem is defined and three optimization processes with an objective of minimizing entropy are performed using steady-state 3D-CFD simulation as the objective function evaluator. The turbine inlet boundary conditions in the three optimization efforts include peak, mean and trough values of the RDC outlet pulsating flow condition. Finally, detailed unsteady simulations are carried out for the three new geometries and compared with the baseline turbine. The results showed that the steady-state Reynolds Averaged Navier Stocks (RANS) simulations can be utilized using either mean or trough values of the pulsating boundary condition in iterating a design optimization problem, instead of full unsteady RANS simulations applying time and circumferential location dependent boundary conditions. Given the specific RDC boundary condition and the turbine geometry in this study, the optimized turbine exhibited up to 7.71\% less entropy generation and up to 7\% higher output power compared to the baseline counterpart in unsteady operation. This approach enables a more efficient design optimization process while accounting for the complex dynamics of the RDC exhaust flow. Overall, the approach presented in this paper is practical for optimizing highly unsteady turbomachines specifically for the case of RDCs during any early design optimization procedure, addressing the computational challenges associated with simulating unsteady flows while ensuring the turbine's effectiveness under real operating conditions.}, subject = {Unsteady turbine; Entropy generation; Rotating detonation; Optimization; Computational fluid dynamic}, language = {en} } @article{ErtugrulEmdadiHaertel2025, author = {Ertugrul, G{\"o}khan and Emdadi, Aliakbar and H{\"a}rtel, Sebastian}, title = {Powder production and additive manufacturing of iron aluminide alloys using plasma ultrasonic atomization and laser-directed energy deposition}, series = {Additive Manufacturing Letters}, volume = {14}, journal = {Additive Manufacturing Letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2772-3690}, doi = {10.1016/j.addlet.2025.100313}, year = {2025}, abstract = {With a combination of desirable properties such as low density, high specific yield strength, low material cost, and excellent oxidation and corrosion resistance, iron aluminide (Fe-Al) has shown considerable potential to be an alternative to high-alloy chromium steels, and in some cases even nickel-based superalloys, in hightemperature applications. Due to these features, it is especially suitable for the aerospace and automotive industries. Recent advancements indicate an increasing interest in Fe-Al within the additive manufacturing industry, particularly in directed energy deposition (DED) processes. Despite this progress, processing of Fe-Al materials using the laser directed energy deposition (L-DED) has not been sufficiently investigated. In this study, Fe-Al powder material was produced from a commercial Al rod encased in a commercial low alloy-steel tube by a plasma-based ultrasonic atomization eliminating the need to cast an alloy ingot in advance. Subsequently, the produced powder was used in a L-DED process to fabricate an additively manufactured sample. The sample was investigated in terms of mechanical property, microstructure, chemical composition, and phase structure by scanning electron microscope (SEM) / energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and microhardness analyses.}, subject = {Iron aluminides (Fe-Al); Laser directed energy deposition (L-DED); Plasma ultrasonic atomization; Powder; Intermetallic phase}, language = {en} } @article{RimHezilFellahetal.2025, author = {Rim, Imen and Hezil, Naouel and Fellah, Mamoun and Saoudi, Adel and Aleksei, Obrosov and El-Hiti, Gamal A.}, title = {Enhancing kaolin performance through organic molecule modification and assessing its efficiency for lead and copper adsorption}, series = {Environmental Technology \& Innovation}, volume = {36}, journal = {Environmental Technology \& Innovation}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2352-1864}, doi = {10.1016/j.eti.2024.103904}, year = {2025}, abstract = {The research aimed to enhance the efficacy of kaolin in water treatment by incorporating diphenylamine (DPA) and to evaluate its effectiveness in adsorbing lead and copper in wastewater in comparison to natural kaolin (Nat-kaolin). This entailed modifying kaolin with DPA to create DPA-kaolin and conducting comprehensive characterization utilizing a range of techniques, including X-ray diffraction analysis (XRD), scanning electron microscope (SEM), energy dispersion X-ray (EDX), thermogravimetric analysis (TGA), differential thermal analysis (DTA), Fourier-transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis. The results demonstrated the successful modification of DPA, as evidenced by an increase in BET-specific surface area of about 25 \% (from 66.69 m².g⁻¹ to 71.35 m².g⁻¹), indicating enhanced adsorption capacity. XRD analysis confirmed the composition of the samples, while TGA/DTA indicated changes in water adsorption and dehydroxylation. SEM and EDX illustrated the tubular nature of the clay with a decrease in the amount of Al, about 10.76 \%, and the amount of Si, about 10.38 \%, on the DPA-kaolin. Notably, the FTIR spectrum of DPA-kaolin showed the presence of new vibration bands at 1248 cm⁻¹, indicating the presence of DPA. In terms of adsorption, the DPA-kaolin exhibited significantly higher maximum adsorption capacities for Pb(II) and Cu(II) compared to the nat-kaolin, with values of 151 μmol/g and 134 μmol/g, respectively.These values were significantly higher than those observed for Nat-kaolin, which demonstrated adsorption capacities of 103 μmol/g for Pb(II) and 91 μmol/g for Cu(II). The adsorption kinetics indicated that the pseudo-second-order kinetic model described the sorption mechanism for both Pb(II) and Cu(II). This was evidenced by the values of R², which were 0.999 and 0.996, respectively. The study provides clear evidence that DPA-kaolin is more effective than Nat-kaolin in removing lead (Pb(II)) and copper (Cu(II)) from wastewater. Through rigorous experimentation, it was observed that DPA-kaolin exhibited notably enhanced adsorption capabilities for both Pb(II) and Cu(II) compared to Nat-kaolin. These findings serve to emphasize the practical importance and potential.}, subject = {Kaolin clay; Water treatment; DPA-Kaolin; Chemical treatment; Adsorption; Isotherms}, language = {en} } @article{FrankenNetzerMaussetal., author = {Franken, Tim and Netzer, Corinna and Mauss, Fabian and Pasternak, Michal and Seidel, Lars and Borg, Anders and Lehtiniemi, Harry and Matrisciano, Andrea and Kulzer, Andre Casal}, title = {Multi-objective optimization of water injection in spark-ignition engines using the stochastic reactor model with tabulated chemistry}, publisher = {SAGE Publications}, address = {London, England}, issn = {1468-0874}, doi = {10.1177/1468087419857602}, abstract = {Water injection is investigated for turbocharged spark-ignition engines to reduce knock probability and enable higher engine efficiency. The novel approach of this work is the development of a simulation-based optimization process combining the advantages of detailed chemistry, the stochastic reactor model and genetic optimization to assess water injection. The fast running quasi-dimensional stochastic reactor model with tabulated chemistry accounts for water effects on laminar flame speed and combustion chemistry. The stochastic reactor model is coupled with the Non-dominated Sorting Genetic Algorithm to find an optimum set of operating conditions for high engine efficiency. Subsequently, the feasibility of the simulation-based optimization process is tested for a three-dimensional computational fluid dynamic numerical test case. The newly proposed optimization method predicts a trade-off between fuel efficiency and low knock probability, which highlights the present target conflict for spark-ignition engine development. Overall, the optimization shows that water injection is beneficial to decrease fuel consumption and knock probability at the same time. The application of the fast running quasi-dimensional stochastic reactor model allows to run large optimization problems with low computational costs. The incorporation with the Non-dominated Sorting Genetic Algorithm shows a well-performing multi-objective optimization and an optimized set of engine operating parameters with water injection and high compression ratio is found.}, subject = {Ottomotor; Water injection; Genetic optimization; Spark-ignition engine; Stochastic reactor model; Detailed chemistry; Wassereinspritzung; Prozessoptimierung; Stochastisches Modell}, language = {en} } @article{AliKhanKolendaetal.2023, author = {Ali, Aamir and Khan, Muhammad Moman and Kolenda, Rafal and Olowe, Olugbenga Adekunie and Weinreich, J{\"o}rg and Li, Ganwu and Schierack, Peter}, title = {The role of AJB35136 and fdtA genes in biofilm formation by avian pathogenic Escherichia coli}, doi = {10.1186/s12917-023-03672-7}, year = {2023}, abstract = {Background Infections caused by avian pathogenic Escherichia coli (APEC) result in significant economic losses in poultry industry. APEC strains are known to form biofilms in various conditions allowing them to thrive even under harsh and nutrient-deficient conditions on different surfaces, and this ability enables them to evade chemical and biological eradication methods. Despite knowing the whole genome sequences of various APEC isolates, little has been reported regarding their biofilm-associated genes. A random transposon mutant library of the wild-type APEC IMT 5155 comprising 1,300 mutants was analyzed for biofilm formation under nutrient deprived conditions using Videoscan technology coupled with fluorescence microscopy. Seven transposon mutants were found to have reproducibly and significantly altered biofilm formation and their mutated genes were identified by arbitrary PCR and DNA sequencing. The intact genes were acquired from the wild-type strain, cloned in pACYC177 plasmid and transformed into the respective altered biofilm forming transposon mutants, and the biofilm formation was checked in comparison to the wild type and mutant strains under the same conditions. Results In this study, we report seven genes i.e., nhaA, fdeC, yjhB, lysU, ecpR, AJB35136 and fdtA of APEC with significant contribution to biofilm formation. Reintroduction of AJB35136 and fdtA, reversed the altered phenotype proving that a significant role being played by these two O-antigen related genes in APEC biofilm formation. Presence of these seven genes across nonpathogenic E. coli and APEC genomes was also analyzed showing that they are more prevalent in the latter.}, subject = {APEC; Biofilm; Gene; Complementation; Transposon mutant; VideoScan; Genkomplementierung; Transposon-Mutanten; Gefl{\"u}gelkrankheit; Escherichia coli; Biofilm; Komplementation; Transponson; Mutant}, language = {en} } @article{RakhiMauss2024, author = {Rakhi, and Mauss, Fabian}, title = {Numerical investigation of equilibrium and kinetic aspects for hydrogenation of CO₂}, series = {Catalysts}, volume = {14}, journal = {Catalysts}, number = {9}, publisher = {MDPI}, address = {Basel}, issn = {2073-4344}, doi = {10.3390/catal14090562}, year = {2024}, abstract = {Even if huge efforts are made to push alternative mobility concepts, such as electric cars and fuel-cell-powered cars, the significance and use of liquid fuels is anticipated to stay high during the 2030s. Biomethane and synthetic natural gas (SNG) might play a major role in this context, as they are raw material for chemical industry that is easy to be stored and distribute via existing infrastructure, and are a versatile energy carrier for power generation and mobile applications. Since biomethane and synthetic natural gas are suitable for power generation and for mobile applications, they can therefore replace natural gas without any infrastructure changes, thus playing a major role. In this paper, we aim to comprehend the direct production of synthetic natural gas from CO₂ and H₂ in a Sabatier process based on a thermodynamic analysis as well as a multi-step kinetic approach. For this purpose, we thoroughly discuss CO₂ methanation to control emissions in order to maximize the methane formation along with minimizing the CO formation and to understand the complex methanation process. We consider an equilibrium and kinetic modeling study on the NiO-SiO₂catalyst for methanation focusing on CO₂-derived SNG. The thermodynamic analysis of CO₂ hydrogenation is preformed to define the optimal process parameters followed by the kinetic simulations for catalyst development. The investigation presented in this paper can also be used for developing machine learning algorithms for methanation processes.}, subject = {Equilibrium calculations; Thermodynamic analysis; Kinetic modeling; CO₂ Methanation; Gibbs free energy minimization}, language = {en} } @article{ShafieeDorneanuArellanoGarcia2025, author = {Shafiee, Parisa and Dorneanu, Bogdan and Arellano-Garcia, Harvey}, title = {Improving catalysts and operating conditions using machine learning in Fischer-Tropsch synthesis of jet fuels (C8-C16)}, series = {Chemical Engineering Journal Advances}, volume = {21}, journal = {Chemical Engineering Journal Advances}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2666-8211}, doi = {10.1016/j.ceja.2024.100702}, year = {2025}, abstract = {Fischer-Tropsch synthesis (FTS) offers a promising route for producing sustainable jet fuels from syngas. However, optimizing catalyst design and operating conditions for the ideal C8-C16 jet fuel range is challenging. Thus, this work introduces a machine learning (ML) framework to enhance Co/Fe-supported FTS catalysts and optimize their operating conditions for a better jet fuel selectivity. For this purpose, a dataset was implemented with 21 features, including catalyst structure, preparation method, activation procedure, and FTS operating parameters. Moreover, various machine-learning models (Random Forest (RF), Gradient Boosted, CatBoost, and artificial neural networks (ANN)) were evaluated to predict CO conversion and C8-C16 selectivity. Among these, the CatBoost model achieved the highest accuracy (R2 = 0.99). Feature analysis revealed that FTS operational conditions mainly affect CO conversion (37.9 \%), while catalyst properties were primarily crucial for C8-C16 selectivity (40.6 \%). The proposed ML framework provides a first powerful tool for the rational design of FTS catalysts and operating conditions to maximize jet fuel productivity. .}, subject = {Jet fuels (C8-C16); Machine learning (ML); Fischer-Tropsch synthesis (FTS); Operational conditions; Catalyst preparation}, language = {en} }