FH Aachen University of Applied Sciences
Recent publications
Concentrating solar thermal systems are widely used for industrial heat production. The state-of-the-art methods use different concepts among which tracking Fresnel mirrors or parabolic troughs. In the market however there are very few devices operating at intermediate to medium temperatures. In order to fill this gap, an innovative concentrating solar thermal system is studied in the frame of the Hellenic — German cooperation project “SCoSCo”. The proposed device concentrates the solar radiation to the receiver using a micro-mirror array. The scope of this paper is to present the optical simulation results of this innovative reflector, and compare the results obtained by different software packages. The optical performance assessed using Solstice ray-tracing software, yields a theoretical optical efficiency from 0.7 to 0.9. In order to evaluate the annual energy yield of the prototype, solar radiation data measurements in Patras, Greece for 2016 and were used as input. A three dimensional thermal model is developed in the COMSOL software to estimate the temperature distribution at the receiver. It was found that temperatures , ranged from 115 to 225 °C. The annual energy yield, calculated using the CARNOT toolbox ranges from 683 to 729 kWh.
Nuclear magnetic resonance (NMR) spectrometric methods for the quantitative analysis of pure heparin in crude heparin is proposed. For quantification, a two-step routine was developed using a USP heparin reference sample for calibration and benzoic acid as an internal standard. The method was successfully validated for its accuracy, reproducibility, and precision. The methodology was used to analyze 20 authentic porcine heparinoid samples having heparin content between 4.25 w/w % and 64.4 w/w %. The characterization of crude heparin products was further extended to a simultaneous analysis of these common ions: sodium, calcium, acetate and chloride. A significant, linear dependence was found between anticoagulant activity and assayed heparin content for thirteen heparinoids samples, for which reference data were available. A Diffused-ordered NMR experiment (DOSY) can be used for qualitative analysis of specific glycosaminoglycans (GAGs) in heparinoid matrices and, potentially, for quantitative prediction of molecular weight of GAGs. NMR spectrometry therefore represents a unique analytical method suitable for the simultaneous quantitative control of organic and inorganic composition of crude heparin samples (especially heparin content) as well as an estimation of other physical and quality parameters (molecular weight, animal origin and activity).
Bacterial cellulose (BC) is a biopolymer produced by different microorganisms, but in biotechnological practice, Komagataeibacter xylinus is used. The micro- and nanofibrillar structure of BC, which forms many different-sized pores, creates prerequisites for the introduction of other polymers into it, including those synthesized by other microorganisms. The study aims to develop a cocultivation system of BC and prebiotic producers to obtain BC-based composite material with prebiotic activity. In this study, pullulan (PUL) was found to stimulate the growth of the probiotic strain Lactobacillus rhamnosus GG better than the other microbial polysaccharides gellan and xanthan. BC/PUL biocomposite with prebiotic properties was obtained by cocultivation of Komagataeibacter xylinus and Aureobasidium pullulans, BC and PUL producers respectively, on molasses medium. The inclusion of PUL in BC is proved gravimetrically by scanning electron microscopy and by Fourier transformed infrared spectroscopy. Cocultivation demonstrated a composite effect on the aggregation and binding of BC fibers, which led to a significant improvement in mechanical properties. The developed approach for “grafting” of prebiotic activity on BC allows preparation of environmentally friendly composites of better quality.
Carbon nanofiber nonwovens represent a powerful class of materials with prospective application in filtration technology or as electrodes with high surface area in batteries, fuel cells, and supercapacitors. While new precursor‐to‐carbon conversion processes have been explored to overcome productivity restrictions for carbon fiber tows, alternatives for the two‐step thermal conversion of polyacrylonitrile precursors into carbon fiber nonwovens are absent. In this work, we develop a continuous roll‐to‐roll stabilization process using an atmospheric pressure microwave plasma jet. We explore the influence of various plasma‐jet parameters on the morphology of the nonwoven and compare the stabilized nonwoven to thermally stabilized samples using scanning electron microscopy, differential scanning calorimetry, and infrared spectroscopy. We show that stabilization with a non‐equilibrium plasma‐jet can be twice as productive as the conventional thermal stabilization in a convection furnace, while producing electrodes of comparable electrochemical performance.
Despite the importance of cell characterization and identification for diagnostic and therapeutic applications, developing fast and label‐free methods without (bio)‐chemical markers or surface‐engineered receptors remains challenging. Here, we exploit the natural cellular response to mild thermal stimuli and propose a label‐ and receptor‐free method for fast and facile cell characterization. Cell suspensions in a dedicated sensor are exposed to a temperature gradient, which stimulates synchronized and spontaneous cell‐detachment with sharply defined time‐patterns, a phenomenon unknown from literature. These patterns depend on metabolic activity (controlled through temperature, nutrients, and drugs) and provide a library of cell‐type‐specific indicators, allowing to distinguish several yeast strains as well as cancer cells. Under specific conditions, synchronized glycolytic‐type oscillations are observed during detachment of mammalian and yeast‐cell ensembles, providing additional cell‐specific signatures. These findings suggest potential applications for cell viability analysis and for assessing the collective response of cancer cells to drugs.
An improved and convenient ninhydrin assay for aminoacylase activity measurements was developed using the commercial EZ Nin™ reagent. Alternative reagents from literature were also evaluated and compared. The addition of DMSO to the reagent enhanced the solubility of Ruhemann's purple (RP). Furthermore, we found that the use of a basic, aqueous buffer enhances stability of RP. An acidic protocol for the quantification of lysine was developed by addition of glacial acetic acid. The assay allows for parallel processing in a 96-well format with measurements microtiter plates.
Health disparity across layers of society involves reasons beyond the healthcare system. Socioeconomic status (SES) shapes people’s daily interaction with their social environment, and is known to impact various health outcomes. Using generative probabilistic modelling, we investigated health satisfaction and complementary indicators of socioeconomic lifestyle in the human social brain. In a population cohort of ~10,000 UK Biobank participants, our first analysis probed the relationship between health status and subjective social standing (i.e., financial satisfaction). We identified volume effects in participants unhappy with their health in regions of the higher associative cortex, especially the dorsomedial prefrontal cortex (dmPFC) and bilateral temporo-parietal junction (TPJ). Specifically, participants in poor subjective health showed deviations in dmPFC and TPJ volume as a function of financial satisfaction. The second analysis on health status and objective social standing (i.e., household income) revealed volume deviations in regions of the limbic system for individuals feeling unhealthy. In particular, low-SES participants dissatisfied with their health showed deviations in volume distributions in the amygdala and hippocampus bilaterally. Thus, our population-level evidence speaks to the possibility that health status and socioeconomic position have characteristic imprints in social brain differentiation.
Using gamification approaches in Higher Education is an appropriate way to increase student’s engagement especially during the time of the COVID-19 pandemic. Escape Games which could be either used as physical experience of a group in a room, or - more virtually - as several puzzles that need to be solved with the target to solve one overarching mystery, are well known tools that can be used in an educational environment as well. However, despite of existing frameworks and manifold examples it remains difficult to set up a Virtual Educational Escape Game (VEEG) with the proven positive effect on successful learning. This study presents some factors that support successful learning when using a VEEG and compares cost-benefit-ratios for manually versus automatically run VEEGs.
CLIL teachers, particularly in tertiary “hard” CLIL settings, tend to underestimate the role of language for developing conceptual understanding of new content. Nevertheless, they consistently engage with English outside the classroom and even report a variety of activities that they carry out in English with the explicit hope that this will improve their language skills. However, they do not seem to develop transfer strategies that would allow them to benefit from this language engagement in their teaching. The results of a nation-wide study on CLIL teacher wellbeing in Austria confirmed this disconnect, prompting our present follow-up study, which aims to combine teacher training and research and to raise tertiary CLIL teachers’ levels of Teacher Language Awareness (TLA). By means of an online questionnaire, class observations and stimulated recall interviews, we explored teachers’ conceptualization of language, specifically their awareness of the language needed for effective content teaching. Results suggest that research-based TLA coaching must be part of CLIL teacher training to resolve the disconnect between the general communicative functions of language, on the one hand, and the pedagogical functions of language, on the other hand. This can help teachers unlock the potential of their existing language engagement for improving their classroom discourse and practices.
Acetoin and diacetyl have a major impact on the flavor of alcoholic beverages such as wine or beer. Therefore, their measurement is important during the fermentation process. Until now, gas chromatographic techniques have typically been applied; however, these require expensive laboratory equipment and trained staff, and do not allow for online monitoring. In this work, a capacitive electrolyte–insulator–semiconductor sensor modified with tobacco mosaic virus (TMV) particles as enzyme nanocarriers for the detection of acetoin and diacetyl is presented. The enzyme acetoin reductase from Alkalihalobacillus clausii DSM 8716T is immobilized via biotin–streptavidin affinity, binding to the surface of the TMV particles. The TMV-assisted biosensor is electrochemically characterized by means of leakage–current, capacitance–voltage, and constant capacitance measurements. In this paper, the novel biosensor is studied regarding its sensitivity and long-term stability in buffer solution. Moreover, the TMV-assisted capacitive field-effect sensor is applied for the detection of diacetyl for the first time. The measurement of acetoin and diacetyl with the same sensor setup is demonstrated. Finally, the successive detection of acetoin and diacetyl in buffer and in diluted beer is studied by tuning the sensitivity of the biosensor using the pH value of the measurement solution.
Das kanonische Ensemble ist charakterisiert durch festes Volumen V, feste Teilchenzahl N und feste Temperatur T. Wie lassen sich makroskopische Variablen wie die Energie des Systems oder der Druck aus diesen Angaben berechnen? Gemäß des 1. Postulats der statistischen Thermodynamik müssen wir das Ensemblemittel berechnen. Dies wiederum bedeutet, dass wir diese gesuchten Variablen auch für einen bestimmten Mikrozustand kennen müssen, denn wir wollen gerade über alle Ensemble-Mitglieder mitteln. Wir gehen von einem unendlich großen Wärmebad aus, in welchem sich die Ensemble-Mitglieder befinden. Das unendlich große Wärmebad garantiert, dass alle Ensemble-Mitglieder die konstante, fest vorgegebene Temperatur T besitzen. Damit haben alle Ensemble-Mitglieder die identische Temperatur T und nach Voraussetzung gleiches Volumen V und gleiche Teilchenzahl N. Die Wände aller Teilsysteme sind wärmedurchlässig, Teilchen können die Wände nicht passieren.
Anhand der Übungsaufgaben wird aufgezeigt, welche Art Berechnungen mithilfe der kinetischen Gastheorie durchgeführt werden können.
Wir betrachten im Folgenden ein isoliertes System, das heißt ein System mit festem N, V und T. Ein solches Ensemble nennt man mikrokanonisches Ensemble . Im Fall des kanonischen und des großkanonischen Ensembles haben wir die Variation in der Energie E benutzt, um die beiden Postulate der statistischen Thermodynamik anwenden zu können. Dies ist aber bei festem E nicht mehr möglich! Um das Problem zu umgehen, kann man ein weiteres Postulat einführen, indem man festlegt: S = kB · ln Ω Dies ist aber nicht unbedingt erforderlich! Die Eigenschaften des mikrokanonischen Ensembles lassen sich auch auf anderem Weg ableiten. Dazu betrachten wir noch einmal das kanonische Ensemble. Wir suchen uns aus dem kanonischen Ensemble gerade die Ensemble-Mitglieder aus, welche exakt die richtige Energie E haben. Diese speziell ausgewählten Ensemble-Mitglieder umgeben wir dann mit einer Isolationshülle und trennen sie vom Rest der Ensemble-Mitglieder ab. Auf diese Weise haben wir eine Menge isolierter Teilsysteme gewonnen, die alle gleiches N, V und T besitzen; wir haben ein mikrokanonisches Ensemble!
Wir sind nun in der Lage, bei einfachen Systemen die Richtung eines spontan ablaufenden Prozesses vorherzusagen, zum Beispiel im Fall des Wärmeübergangs oder der Durchmischung. Grundsätzlich gilt in diesen Fällen, dass die Reaktion von selbst abläuft, wenn S > 0 gilt. Können wir damit auch bei chemischen Reaktionen die Richtung eines spontan ablaufenden Prozesses vorhersagen? Woran lässt sich erkennen, in welche Richtung eine chemische Reaktion abläuft? Welche thermodynamischen Funktionen kann ich zu Hilfe nehmen, um solche Fragen zu beantworten? Die Beschreibung der Richtung von freiwillig ablaufenden Prozessen ist das Thema dieses Kapitels.
Bei Veränderung der Systembedingungen können alle Substanzen unterschiedliche Phasen durchlaufen. Abgesehen von verschiedenen Festkörperphasen, die sich durch die jeweilige Kristallstruktur unterscheiden, oder auch verschiedenen elektronischen Zuständen, zum Beispiel supraleitenden Zuständen, sind es vor allem die Phasen fest, flüssig und gasförmig, die auch Laien bekannt sind. Die Systembedingungen legen die Stabilitätsbereiche dieser Phasen fest, und der Übergang von einer Phase in die andere kann kinetisch gehemmt sein, wie wir es bereits bei der Besprechung der van der Waals-Gleichung gesehen haben. In der Thermodynamik interessieren wir uns nur für die Gleichgewichtszustände, also auch im Fall der Phasengleichgewichte für diejenigen Zustände, die abhängig von den äußeren Bedingungen jeweils stabil sind, in denen das System somit vorliegen würde, wenn keinerlei kinetische Hemmungen existieren. Wir beginnen mit den einfachsten Fällen und betrachten zunächst Einkomponentensysteme, das heißt Systeme, die aus nur einer reinen Substanz bestehen. Ein Beispiel für ein solches System ist Wasser–Eis, bei dem die feste Phase im Gleichgewicht mit der flüssigen steht, oder auch das System Wasser–Dampf, bei dem die Flüssigkeit im Gleichgewicht mit ihrem Dampf steht. Möglich ist auch das System fest–dampfförmig, bei dem der Feststoff im Gleichgewicht mit dem Dampf ist. Bei der Behandlung dieser Systeme müssen wir uns zudem die Frage stellen: Wenn die Phasen nicht miteinander im Gleichgewicht sind, in welche Richtung läuft dann die jeweilige Reaktion ab?
View Video Presentation: https://doi.org/10.2514/6.2022-4118.vid The development and operation of hybrid or purely electrically powered aircraft in regional air mobility is a significant challenge for the entire aviation sector. This technology is expected to lead to substantial advances in flight performance, energy efficiency, reliability, safety, noise reduction, and exhaust emissions. Nevertheless, any consumed energy results in heat or carbon dioxide emissions and limited electric energy storage capabilities suppress commercial use. Therefore, the significant challenges to achieving eco-efficient aviation are increased aircraft efficiency, the development of new energy storage technologies, and the optimization of flight operations. Two major approaches for higher eco-efficiency are identified: The first one, is to take horizontal and vertical atmospheric motion phenomena into account. Where, in particular, atmospheric waves hold exciting potential. The second one is the use of the regeneration ability of electric aircraft. The fusion of both strategies is expected to improve efficiency. The objective is to reduce energy consumption during flight while not neglecting commercial usability and convenient flight characteristics. Therefore, an optimized control problem based on a general aviation class aircraft has to be developed and validated by flight experiments. The formulated approach enables a development of detailed knowledge of the potential and limitations of optimizing flight missions, considering the capability of regeneration and atmospheric influences to increase efficiency and range.
Halophilic and halotolerant microorganisms represent a promising source of salt‐tolerant enzymes suitable for various biotechnological applications where high salt concentrations would otherwise limit enzymatic activity. Considering the current growing enzyme market and the need for more efficient and new biocatalysts, the present study aimed at the characterization of a high‐alkaline subtilisin from Alkalihalobacillus okhensis Kh10‐101T. The protease gene was cloned and expressed in Bacillus subtilis DB104. The recombinant protease SPAO with 269 amino acids belongs to the subfamily of high‐alkaline subtilisins. The biochemical characteristics of purified SPAO were analysed in comparison to subtilisin Carlsberg, Savinase, and BPN’. SPAO, a monomer with a molecular mass of 27.1 kDa was active over a wide range of pH 6.0 ‐ 12.0 and temperature 20 ‐ 80 °C, optimally at pH 9.0‐9.5 and 55 °C. The protease is highly oxidatively stable to hydrogen peroxide and retained 58 % of residual activity when incubated at 10 °C with 5 % (v/v) H2O2 for 1 h while stimulated at 1 % (v/v) H2O2. Furthermore, SPAO was very stable and active at NaCl concentrations up to 5.0 M. This study demonstrates the potential of SPAO for biotechnological applications in the future.
Biocompatibility, flexibility and durability make polydimethylsiloxane (PDMS) membranes top candidates in biomedical applications. CellDrum technology uses large area, <10 µm thin membranes as mechanical stress sensors of thin cell layers. For this to be successful, the properties (thickness, temperature, dust, wrinkles, etc.) must be precisely controlled. The following parameters of membrane fabrication by means of the Floating-on-Water (FoW) method were investigated: (1) PDMS volume, (2) ambient temperature, (3) membrane deflection and (4) membrane mechanical compliance. Significant differences were found between all PDMS volumes and thicknesses tested (p < 0.01). They also differed from the calculated values. At room temperatures between 22 and 26 °C, significant differences in average thickness values were found, as well as a continuous decrease in thicknesses within a 4 °C temperature elevation. No correlation was found between the membrane thickness groups (between 3–4 µm) in terms of deflection and compliance. We successfully present a fabrication method for thin bio-functionalized membranes in conjunction with a four-step quality management system. The results highlight the importance of tight regulation of production parameters through quality control. The use of membranes described here could also become the basis for material testing on thin, viscous layers such as polymers, dyes and adhesives, which goes far beyond biological applications.
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2,506 members
Bernd Dachwald
  • Faculty of Aerospace Technology
Frank Hartung
  • Faculty of Electrical Engineering and Information Technology
Manfred Staat
  • Institut für Bioengineering(IfB)
Aysegül Temiz Artmann
  • Institut für Bioengineering(IfB)
Bernhard Hoffschmidt
  • Solar-Institut Jülich (SIJ)
Bayernallee 11, 52066, Aachen, NRW, Germany
Head of institution
Prof. Dr. rer. nat. Marcus Baumann