04 Fakultät Energie-, Verfahrens- und Biotechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/5
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Item Open Access 2-Methoxyestradiol damages DNA in glioblastoma cells by regulating nNOS and heat shock proteins(2022) Bastian, Paulina Emilia; Daca, Agnieszka; Płoska, Agata; Kuban-Jankowska, Alicja; Kalinowski, Leszek; Gorska-Ponikowska, MagdalenaGliomas are the most prevalent primary tumors of the central nervous system (CNS), accounting for over fifty percent of all primary intracranial neoplasms. Glioblastoma (GBM) is the most prevalent form of malignant glioma and is often incurable. The main distinguishing trait of GBM is the presence of hypoxic regions accompanied by enhanced angiogenesis. 2-Methoxyestradiol (2-ME) is a well-established antiangiogenic and antiproliferative drug. In current clinical studies, 2-ME, known as Panzem, was examined for breast, ovarian, prostate, and multiple myeloma. The SW1088 grade III glioma cell line was treated with pharmacological and physiological doses of 2-ME. The induction of apoptosis and necrosis, oxidative stress, cell cycle arrest, and mitochondrial membrane potential were established by flow cytometry. Confocal microscopy was used to detect DNA damage. The Western blot technique determined the level of nitric oxide synthase and heat shock proteins. Here, for the first time, 2-ME is shown to induce nitro-oxidative stress with the concomitant modulation of heat shock proteins (HSPs) in the SW1088 grade III glioma cell line. Crucial therapeutic strategies for GMB should address both cell proliferation and angiogenesis, and due to the above, 2-ME seems to be a perfect candidate for GBM therapy.Item Open Access 20000 Jahre Klimawandel und Kulturgeschichte – von der Eiszeit in die Gegenwart(2002) Blümel, Wolf DieterVerunsichert durch Meldungen über zunehmende Sturmtätigkeit, Hochwasserbedrohung oder Dürre bangt die Menschheit einer ,Klimakatastrophe‘ entgegen. Der Geist ist aus der Flasche, und er ist so schnell nicht wieder hineinzuzwingen: Gemeint sind die noch nicht zu bestimmenden Ausmaße und Folgen eines eskalierenden Einsatzes fossiler Kohlenwasserstoffe (= über lange Zeiträume gespeicherte Sonnenenergie) und eines radikalen Landschaftsverbrauchs in geologisch kürzesten Zeiträumen. Damit verbunden ist eine mögliche Temperaturerhöhung, die in ihrer synergetischen Wirkung auf das globale Klimasystem und seine Dynamik nur schwer zu fassen ist.Item Open Access (+)-4-Carboxymethyl-2,4-dimethylbut-2-en-4-olide as dead-end metabolite of 2,4-dimethylphenoxyacetic acid or 2,4-dimethylphenol by alcaligenes eutrophus JMP 134(1990) Pieper, Dietmar H.; Engesser, Karl-Heinrich; Knackmuss, Hans-Joachim2,4-Dimethylphenoxyacetic acid and 2,4-dimethylphenol are not growth substrates for Alcaligenes eutrophus JMP 134 although being cooxidized by 2,4-dichlorophenoxyacetate grown cells. None of the relevant catabolic pathways were induced by the dimethylphenoxyacetate, 3,5-Dimethylcatechol is not subject to metacleavage. The alternative ortho-eleavage is also unproductive and gives rise to (+)-4-carboxymethyl-2,4-dimethylbut-2-en-4-olide as a dead-end metabolite. High yields of this metabolite were obtained with the mutant Alcaligenes eutrophys JMP 134-1 which constitutively expresses the genes of 2,4-dichlorophenoxyacetic acid metabolism.Item Open Access 6-Hydroxydopamine lesion of the rat prefrontal cortex impairs motor initiation but not motor execution(1994) Hauber, Wolfgang; Bubser, Michael; Schmidt, Werner J.We examined the effects of bilateral 6-hydroxydopamine (6-OHDA) lesions of the medial prefrontal cortex (PFC) in rats on motor initiation and execution in a simple reaction time task. Reaction times (RT) and movement times (MT) were measured in trained rats on four preand postoperative days. Animals with 6-OHDA lesions were selectively impaired on motor initiation as measured by a significant increase in RT on each postoperative day. Motor execution was intact postoperatively, since MT was not altered. Neurochemical analysis revealed a significant depletion of prefrontal dopamine (DA) and noradrenaline (NA) in lesioned animals. It was concluded that DA and, to a lesser extent, NA in the rat PFC were involved in monitoring RT performance.Item Open Access β-galactosidase activity in transfected Ltk- cells is differentially regulated in monolayer and in spheroid cultures(1993) Klünder, Irene; Hülser, Dieter F.We have investigated whether three-dimensional cultivation of cells to multicell spheroids influences the expression of a transfected gene. Ltk- cells (mouse fibroblasts. thymidine kinase negative) have been transfected with a bacterial lacZ gene which was coupled to a β-actin promoter. The transfected cells synthesize β-galactosidase, a cytoplasmic enzyme which can easily be stained for histology with 5-bromo-4-chloro-3-indoxyl β-D-galactoside and for cytometry with fluorescein di(β-D-galactopyranoside). As we have shown with monolayer cells, β-galactosidase is produced independently of cell density, medium condition, and cell cycle. In multicell spheroids, however, the portion of producing cells was reduced from ~98% to ~2% within a week. This reduction is also independent of cell density, medium condition, and cell cycle. Nonproducing multicell spheroid cells, however, regained their ability to synthesize β-galactosidase within a few days when the cells were recultivated as monolayers. Since the lacZ gene was not lost, its expression might have been regulated by its β-actin promoter. We, therefore, investigated whether the endogenous synthesis of β-actin was similarly regulated. A correlation between the distinct reduction in β-galactosidase-producing cells and filamentous or total actin concentration was not unequivocally observed.Item Open Access A systematic selection process of machine learning cloud services for manufacturing SMEs(2022) Kaymakci, Can; Wenninger, Simon; Pelger, Philipp; Sauer, AlexanderSmall and medium-sized enterprises (SMEs) in manufacturing are increasingly facing challenges of digital transformation and a shift towards cloud-based solutions to leveraging artificial intelligence (AI) or, more specifically, machine learning (ML) services. Although literature covers a variety of frameworks related to the adaptation of cloud solutions, cloud-based ML solutions in SMEs are not yet widespread, and an end-to-end process for ML cloud service selection is lacking. The purpose of this paper is to present a systematic selection process of ML cloud services for manufacturing SMEs. Following a design science research approach, including a literature review and qualitative expert interviews, as well as a case study of a German manufacturing SME, this paper presents a four-step process to select ML cloud services for SMEs based on an analytic hierarchy process. We identified 24 evaluation criteria for ML cloud services relevant for SMEs by merging knowledge from manufacturing, cloud computing, and ML with practical aspects. The paper provides an interdisciplinary, hands-on, and easy-to-understand decision support system that lowers the barriers to the adoption of ML cloud services and supports digital transformation in manufacturing SMEs. The application in other practical use cases to support SMEs and simultaneously further development is advocated.Item Open Access Abluftoxidation in Monolith-Katalysatoren mit periodischem Wechsel der Strömungsrichtung(1988) Eigenberger, Gerhart; Nieken, UlrichMit steigenden gesetzlichen Anforderungen zur Reduzierung des Schadstoffgehalts gewinnen Verfahren zur oxidativen Umwandlung von Schadstoffen in Abluft zunehmend an Bedeutung. Typische Aufgaben der Abluftreinigung sind gekennzeichnet durch hohe Luftdurchsätze und niedrige Schadstoffkonzentrationen; die adiabate Temperaturerhöhung der Totaloxidation beträgt häufig weniger als 100°C. Das bedeutet, daß der Druckverlust in der Reinigungsanlage niedrig und der Warmerücktausch zwischen Zu- und Ablauf hoch sein muß, um die Betriebskosten niedrig zu halten. Im folgenden wird eine neuartige Betriebsweise der katalytischen Oxidation untersucht, die sich durch effektiven Warmerücktausch, niedrigen Druckverlust und geringes Bauvolumen auszeichnet. Sie beruht auf der Benutzung von Monolith-Katalysatoren in Verbindung mit der von Macros und Mitarb. entwickelten Prozeßführung mit periodischem Wechsel der Strömungsrichtung. Dabei wirkt jeweils der vordere und der hintere Teil des Katalysatorbettes als Regenerator-Wärmeaustauscher.Item Open Access Acclimation to elevated CO2 affects the C/N balance by reducing de novo N‐assimilation(2021) Krämer, Konrad; Kepp, Gabi; Brock, Judith; Stutz, Simon; Heyer, Arnd G.Plants exposed to elevated atmospheric CO2 concentrations show an increased photosynthetic activity. However, after prolonged exposure, the activity declines. This acclimation to elevated CO2 is accompanied by a rise in the carbon‐to‐nitrogen ratio of the biomass. Hence, increased sugar accumulation and sequential downregulation of photosynthetic genes, as well as nitrogen depletion and reduced protein content, have been hypothesized as the cause of low photosynthetic performance. However, the reason for reduced nitrogen content in plants at high CO2 is unclear. Here, we show that reduced photorespiration at increased CO2‐to‐O2 ratio leads to reduced de novo assimilation of nitrate, thus shifting the C/N balance. Metabolic modeling of acclimated and non‐acclimated plants revealed the photorespiratory pathway to function as a sink for already assimilated nitrogen during the light period, providing carbon skeletons for de novo assimilation. At high CO2, low photorespiratory activity resulted in diminished nitrogen assimilation and eventually resulted in reduced carbon assimilation. For the hpr1‐1 mutant, defective in reduction of hydroxy‐pyruvate, metabolic simulations show that turnover of photorespiratory metabolites is expanded into the night. Comparison of simulations for hpr1‐1 with those for the wild type allowed investigating the effect of a perturbed photorespiration on N‐assimilation.Item Open Access Acid catalyzed cross‐linking of polyvinyl alcohol for humidifier membranes(2021) Michele, Andre; Paschkowski, Patrick; Hänel, Christopher; Tovar, Günter E. M.; Schiestel, Thomas; Southan, AlexanderPolyvinyl alcohol (PVA) is a hydrophilic polymer well known for good film forming properties, high water vapor permeance JW, and low nitrogen permeance. However, depending on molar mass and temperature, PVA swells strongly in water until complete dissolution. This behavior affects the usability of PVA in aqueous environments and makes cross‐linking necessary if higher structural integrity is envisaged. In this work, PVA networks are formed by thermal cross‐linking in the presence of p‐toluenesulfonic acid (TSA) and investigated in a design of experiments approach. Experimental parameters are the cross‐linking period tc, temperature ϑ and the TSA mass fraction wTSA. Cross‐linking is found to proceed via ether bond formation at all reaction conditions. Degradation is promoted especially by a combination of high wTSA, tc and ϑ. Thermal stability of the networks after preparation is strongly improved by neutralizing residual TSA. Humidification membranes with a JW of 6423 ± 63.0 gas permeation units (GPU) are fabricated by coating PVA on polyvinyliden fluoride hollow fibers and cross‐linking with TSA. Summarizing, the present study contributes to a clearer insight into the cross‐linking of PVA in presence of TSA, the thermal stability of the resulting networks and the applicability as selective membrane layers for water vapor transfer.Item Open Access Acid-base flow battery, based on reverse electrodialysis with bi-polar membranes : stack experiments(2020) Xia, Jiabing; Eigenberger, Gerhart; Strathmann, Heinrich; Nieken, UlrichNeutralization of acid and base to produce electricity in the process of reverse electrodialysis with bipolar membranes (REDBP) presents an interesting but until now fairly overlooked flow battery concept. Previously, we presented single-cell experiments, which explain the principle and discuss the potential of this process. In this contribution, we discuss experiments with REDBP stacks at lab scale, consisting of 5 to 20 repeating cell units. They demonstrate that the single-cell results can be extrapolated to respective stacks, although additional losses have to be considered. As in other flow battery stacks, losses by shunt currents through the parallel electrolyte feed/exit lines increases with the number of connected cell units, whereas the relative importance of electrode losses decreases with increasing cell number. Experimental results are presented with 1 mole L^-1 acid (HCl) and base (NaOH) for open circuit as well as for charge and discharge with up to 18 mA/cm2 current density. Measures to further increase the effciency of this novel flow battery concept are discussed.Item Open Access Acoustic streaming‐induced multimodal locomotion of bubble‐based microrobots(2023) Mahkam, Nima; Aghakhani, Amirreza; Sheehan, Devin; Gardi, Gaurav; Katzschmann, Robert; Sitti, MetinAcoustically‐driven bubbles at the micron scale can generate strong microstreaming flows in its surrounding fluidic medium. The tunable acoustic streaming strength of oscillating microbubbles and the diversity of the generated flow patterns enable the design of fast‐moving microrobots with multimodal locomotion suitable for biomedical applications. The acoustic microrobots holding two coupled microbubbles inside a rigid body are presented; trapped bubbles inside the L‐shaped structure with different orifices generate various streaming flows, thus allowing multiple degrees of freedom in locomotion. The streaming pattern and mean streaming speed depend on the intensity and frequency of the acoustic wave, which can trigger four dominant locomotion modes in the microrobot, denoted as translational and rotational, spinning, rotational, and translational modes. Next, the effect of various geometrical and actuation parameters on the control and navigation of the microrobot is investigated. Furthermore, the surface‐slipping multimodal locomotion, flow mixing, particle manipulation capabilities, the effective interaction of high flow rates with cells, and subsequent cancerous cell lysing abilities of the proposed microrobot are demonstrated. Overall, these results introduce a design toolbox for the next generation of acoustic microrobots with higher degrees of freedom with multimodal locomotion in biomedical applications.Item Open Access Active ester containing surfmer for one-stage polymer nanoparticle surface functionalization in mini-emulsion polymerization(2018) Albernaz, Vanessa L.; Bach, Monika; Weber, Achim; Southan, Alexander; Tovar, Günter E. M.Functional surface active monomers (surfmers) are molecules that combine the functionalities of surface activity, polymerizability and reactive groups. This study presents an improved pathway for the synthesis of the active ester containing surfmer p-(11-acrylamido)undecanoyloxyphenyl dimethylsulfonium methyl sulfate (AUPDS). Further, the preparation of poly(methyl methacrylate) and polystyrene nanoparticles (NPs) by miniemulsion polymerization using AUPDS is investigated, leading to NPs with active ester groups on their surface. By systematically varying reaction parameters and reagent concentrations, it was found that AUPDS feed concentrations between 2-4 mol-% yielded narrowly distributed and stable spherical particles with average sizes between 83 nm and 134 nm for non-cross-linked NPs, and up to 163 nm for cross-linked NPs. By basic hydrolysis of the active ester groups in aqueous dispersion, the positive ζ-potential (ZP) was converted into a negative ZP and charge quantities determined by polyelectrolyte titrations before and after hydrolysis were in the same range, indicating that the active ester groups were indeed accessible in aqueous suspension. Increasing cross-linker amounts over 10 mol-% also led to a decrease of ZP of NPs, probably due to internalization of the AUPDS during polymerization. In conclusion, by using optimized reaction conditions, it is possible to prepare active ester functionalized NPs in one stage using AUPDS as a surfmer in miniemulsion polymerization.Item Open Access Adaptive winding pin and hooking capacity model for coreless filament winding(2023) Mindermann, Pascal; Gresser, Götz TCoreless filament winding is a manufacturing process used for fiber-reinforced composites, resulting in high-performance lightweight lattice structures. Load transmission elements, which are assembled from commercially available standardized parts, often restrict the component design. A novel adaptive winding pin was developed, which is made by additive manufacturing and can therefore be adjusted to specific load conditions resulting from its position within the component. This allows to decouple the fiber arrangement from the winding pin orientation, which allows a fully volumetric framework design of components. A predictive model for the pin capacity was derived and experimentality validated. The hooking conditions, pin capacity, and occupancy were considered in the creation of a digital design tool.Item Open Access Adsorption on inkjet-printable polyelectrolyte hydrogels allows refractive index sensing of diclofenac and metoprolol in aqueous solution(2024) Southan, Alexander; Tan, Jennifer; Schuster, Fabian; Rotenberger, Julia; Tovar, Günter E. M.Polyelectrolyte hydrogels containing negatively charged sulfonate groups or positively charged ammonium groups are characterized by their adsorption behavior toward the pharmaceuticals metoprolol (cationic) and diclofenac (anionic) in an aqueous solution. Additionally, the change in the hydrogel refractive index with metoprolol and diclofenac concentrations inside the hydrogel is investigated. Both metoprolol adsorption on sulfonate group containing hydrogels as well as diclofenac adsorption on the ammonium group containing hydrogels can be described using a modified Langmuir-type adsorption isotherm with Ks values around 0.1 and 10 mL μmol-1, respectively. In both cases, the adsorption capacities are close to the concentration of charged groups in the hydrogels. Thus, diclofenac concentrations inside the hydrogels are enhanced by a factor of approximately 1000 and metoprolol concentrations by a factor of approximately 10 compared to their concentrations in solution. In contrast, metoprolol was completely excluded from the ammonium group containing hydrogels, and diclofenac showed weak adsorption on the poly(ethylene glycol) fraction of the sulfonate group containing hydrogels, resulting in lower concentration enhancements. Hydrogel refractive indices increased linearly with the concentration of metoprolol and diclofenac inside the hydrogels. Thus, monitoring the refractive index of sulfonate group containing hydrogels is shown to be efficient in measuring the solution concentrations of metoprolol up to 10 μmol mL-1 and of ammonium group containing hydrogels for diclofenac concentrations up to 0.1 μmol mL-1, both values corresponding to the reciprocal of the Ks values. In the case of Langmuir-type adsorption, maximizing Ks values therefore leads to the best refractive index sensor sensitivities at low analyte concentrations, whereas lower Ks values lead to lower sensitivities at low concentrations but to superior sensitivities at rather high analyte concentrations. Inkjet printing of the hydrogel formulations is demonstrated to facilitate their future use as spatially resolved coatings on sensor surfaces.Item Open Access Advanced impedance analysis for performance degradation during low-temperature CO2 electroreduction(2024) Chen, Qinhao; Kube, Alexander; Kopljar, Dennis; Friedrich, Kaspar AndreasElectrochemical impedance spectroscopy (EIS) is a powerful tool commonly used to study electrochemical systems. Nevertheless, its application in CO2 electroreduction has been so far limited due to its complex reaction mechanism and environment. Although initial findings have demonstrated the viability of applying EIS analysis in CO2 electrolyzers, the assignment of individual processes in the impedance spectra remains ambiguous. Therefore, a more detailed investigation, especially focused on its application in evaluating degradation mechanisms, is essential. In this study, a stable gas diffusion electrode (GDE) system was developed for a comprehensive EIS and distribution of relaxation time (DRT) evaluation to assess key degradation mechanisms under accelerated stress conditions such as high current density and low operating temperature. Validated by post-mortem analysis and complementary methods, we demonstrate the viability of this approach for operando monitoring of CO2 electroreduction by assigning individual mechanistic processes in the GDE and linking them to performance degradation over time.Item Open Access Advancement of segmented cell technology in low temperature hydrogen technologies(2020) Biswas, Indro; Sánchez, Daniel G.; Schulze, Mathias; Mitzel, Jens; Kimmel, Benjamin; Gago, Aldo Saul; Gazdzicki, Pawel; Friedrich, K. AndreasThe durability and performance of electrochemical energy converters, such as fuel cells and electrolysers, are not only dependent on the properties and the quality of the used materials. They strongly depend on the operational conditions. Variations in external parameters, such as flow, pressure, temperature and, obviously, load, can lead to significant local changes in current density, even local transients. Segmented cell technology was developed with the purpose to gain insight into the local operational conditions in electrochemical cells during operation. The operando measurement of the local current density and temperature distribution allows effective improvement of operation conditions, mitigation of potentially critical events and assessment of the performance of new materials. The segmented cell, which can replace a regular bipolar plate in the current state of the technology, can be used as a monitoring tool and for targeted developments. This article gives an overview of the development and applications of this technology, such as for water management or fault recognition. Recent advancements towards locally resolved monitoring of humidity and to current distributions in electrolysers are outlined.Item Open Access The AMPA antagonist GYKI 52466 reverses the anticataleptic effects of the competitive NMDA antagonist CGP 37849(1994) Hauber, Wolfgang; Waldenmeier, Marc T.The effects of the AMPA receptor antagonist GYKI 52466 (1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine HCl) on haloperidol-induced catalepsy were tested in drug-naive rats and in rats pretreated with the competitive NMDA receptor antagonist CGP 37849 (DL-(E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid). CGP 37849 (4 mg/kg i.p.) given alone significantly reversed haloperidol-induced catalepsy (0.5 mg/kg i.p.) while GYKI 52466 (4.8 mg/kg i.p.) given alone was without effect. Administration of GYKI 52466 to rats pretreated with CGP 37849 abolished the anticataleptic effects of the competitive NMDA receptor antagonist seen following single administration. Thus the AMPA receptor antagonist prevents behavioural effects induced by a NMDA receptor antagonist in this behavioral model.Item Open Access Analyse von Stoffwechselprozessen mit der Fermentationskalorimetrie(1993) Meier-Schneiders, Martin; Grosshans, Ulrich; Busch, Claudia; Eigenberger, GerhartBiologische Aktivität ist mit der Freisetzung von Wärmeenergie verbunden. Die Wärmeproduktion ist dabei proportional zur gesamten Stoffwechselaktivität. Da Wärme kontinuierlich entsteht, eignet sie sich zur Nutzung als On-Iine-Signal. Kalorimetrische Methoden werden in den Biowissenschaften bereits seit Jahrzehnten verwendet. Fermentationskalorimetrie ist eine neu entwickelte Meßtechnik, die insbesondere für die kalorimetrische Vermessung biotechnisch relevanter Fermentationen im Labormaßstab gedacht ist.Item Open Access Analysis and prediction of electromobility and energy supply by the example of Stuttgart(2021) Wörner, Ralf; Morozova, Inna; Cao, Danting; Schneider, Daniela; Neuburger, Martin; Mayer, Daniel; Körner, Christian; Kagerbauer, Martin; Kostorz, Nadine; Blesl, Markus; Jochem, Patrick; Märtz, AlexandraThis paper seeks to identify bottlenecks in the energy grid supply regarding different market penetration of battery electric vehicles in Stuttgart, Germany. First, medium-term forecasts of electric and hybrid vehicles and the corresponding charging infrastructure are issued from 2017 to 2030, resulting in a share of 27% electric vehicles by 2030 in the Stuttgart region. Next, interactions between electric vehicles and the local energy system in Stuttgart were examined, comparing different development scenarios in the mobility sector. Further, a travel demand model was used to generate charging profiles of electric vehicles under consideration of mobility patterns. The charging demand was combined with standard household load profiles and a load flow analysis of the peak hour was carried out for a quarter comprising 349 households. The simulation shows that a higher charging capacity can lead to a lower transformer utilization, as charging and household peak load may fall temporally apart. Finally, it was examined whether the existing infrastructure is suitable to meet future demand focusing on the transformer reserve capacity. Overall, the need for action is limited; only 10% of the approximately 560 sub-grids were identified as potential weak points.Item Open Access Analysis of cooling technologies in the data center sector on the basis of patent applications(2024) Ott, Benjamin; Wenzel, Paula M.; Radgen, PeterThe cooling of server components has been developed over the past few years in order to meet increasing cooling requirements. The growth in performance and power density increases the cooling demand. To gain a better understanding of the evolution and possible future technology developments in the field of data center cooling, a patent analysis method was used with a focus on the server and computer room levels. After the patent extraction from the European patent database for the period 2000-2023, the search results were classified and analyzed. Most of the patents deal with air or liquid cooling. Since 2015, a technological shift from air to liquid cooling can be identified on the level of patent activities. In conclusion, from the patent analysis, it can be derived that liquid cooling will continue to gain in importance in the future and could also be combined with other approaches in the form of hybrid cooling. However, air cooling may still be relevant, even if the main cooling load is handled by liquid-based approaches. At the same time, the optimization potential for air cooling seems to have been largely exploited in comparison to liquid cooling, as can be seen from the falling number of the patent applications.