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Production of Ultraviolet A protectant C50 carotenoid decaprenoxanthin by metabolically engineered Corynebacterium glutamicum
No full textCarotenoids play roles as active compounds in cosmetics, food, and feed applications, for which C40 carotenoids are most common. In recent years, Corynebacterium glutamicum, a Gram-positive bacterium renowned for largescale amino acid processes, has been engineered to produce various C40 carotenoids such as the high value astaxanthin. In contrast, the native glucosylated C50 carotenoid decaprenoxanthin of C. glutamicum remained rather unexplored. Here, by using genome editing and plasmid-based overexpression of carotenogenic genes, 230 mg L-1 decaprenoxanthin was produced in shake flasks. Transfer to a 2 L fed-batch fermentation yielded 1450 mg L-1, the highest C50 carotenoid titer reported to date. Production on alternative carbon sources, solubility, glucosylation impact and antioxidative activity were investigated. The antioxidative activity of glucosylated decaprenoxanthin was higher than that of unglucosylated decaprenoxanthin. This work lays a foundation for the access to rare C50 carotenoids from C. glutamicum fermentation broth with a perspective towards higher production scales
Molecular‐Metallic Binding Characteristics of the Intermetalloid f‐/p‐Block Cluster [(La@InBi)Bi]
No full textMain goals of contemporary research in chemistry are to create new materials with unique properties and to understand the chemical bonding in them, especially between metal atoms in larger structures. The isolation of a single lanthanide atom in a In/Bi cage offers a non-standard bonding situation, which deserves thorough exploration. In this study, the bonding behavior of La, In, and Bi atoms in the ternary cluster [(La@In2Bi11)2Bi2]6− and the complex [La(C5Me4H)3] used for its synthesis are characterized and compared by applying high energy resolution X-ray spectroscopy and computations. A clearly detectable covalent La(5d)─Bi(6p) interaction, induced in a highly electron-rich environment, is illustrated. The electronic structure of the La atom can be described as having the character of an ion being trapped and bonded in a heterometallic Bi/In cage. The advanced X-ray spectroscopic experimental tools applied here enable comparative studies of binding properties, focusing on different metals within the intermetalloid cluster. These tools can be employed iteratively to support the development of synthetic strategies that aim at tuning bond characteristics at the boundary of covalent and metallic bonding, thereby advancing the chemical and physical properties of novel multinary cluster compounds. The results were corroborated by GW and Bethe–Salpeter-equation (GW-BSE) calculations
A Study on the Synthesis and Properties of NaSICON Solid Electrolyte
No full textIn recent years, there has been a growing interest in developing solid electrolytes due to safety considerations, high energy density, relatively long lifetime, and wide operating range, all of which make them a key to the future of battery technology. However, the availability of cost-effective synthesis routes is a prerequisite to driving progress in the manufacturing and use of such electrolytes. The sodium superionic conductor Na3Zr2Si2PO12 a so-called NaSICON structure, is a promising solid-state sodium electrolyte with high ionic conductivity and good thermal, chemical, and electrochemical stability. However, the reported synthesis methods for this material are time-consuming and energy-intensive. To address this issue, this work aims to develop a simple, time-efficient alternative processing route for the synthesis of solid-state sodium electrolytes. A comparative study was carried out between the developed alternative and commonly reported methods to understand the NaSICON structure\u27s formation mechanism better. The results showed that using precursors with a large surface area together with high-energy milling (HEM) improved the conversion process, and the required processing time and energy was reduced. Subsequently, the synthesis conditions of the High Energy Mill (HEM) precursors were determined. Stable cycling of the obtained solid-state electrolyte was observed with Na vs. Na at 1 mA/cm2 and a room temperature conductivity of 1.8 mS/cm was achieved at a reduced total processing time and energy. This marks a new alternative route for the syn-thesis of NaSICON solid-state sodium electrolytes.
Furthermore, to pursue process simplification, the processing was optimized, combined (with-out an intermediate grinding and re-pelletizing step between calcination and sintering) two-step heat treatment were studied. The effect of varying process parameters on microstructural evolution, ionic conductivity, doping, and cycling was investigated. Varying the heat-ing/cooling rate, sintering environment, quenching, and particle size were found to affect the microstructure. The most promising microstructure-property correlation was observed by reducing the chemical potential gradient of the HEM powder by sieving, leading to improved sintering and normal grain growth with good conductivities. The effect of Mg and Mo on the structure, microstructure and conductivity was evaluated, Mg went into a secondary Na3PO4 phase while Mo led to grain growth it has limited solubility in the NaSICON structure, and marginally increased the conductivity.
Finally, the study explores the effects of processing route/composition on the structure and dynamics of Na3Zr2Si2PO12 and Na3.4Zr2Si2.4P0.6O12. High temperature x-ray diffraction (HT-XRD), nuclear magnetic resonance (NMR), and electrochemical impedance spectroscopy (EIS) were employed to investigate the structure and ion dynamics. Two monoclinic NaSICON models with 3Na and 4Na sodium position sub-lattices and a 3Na sodium sublattice rhombo-hedral model were used for the FullProf Rietveld refinement of the high-temperature structure. An attempt was made to determine a correlation between the refinement data and observed motions using NMR. Two migration paths were identified, slow hopping motion observed by NMR was attributed to the slow motion of Na at sites other than the Na3(8f) site in the mono-clinic phase and the difference in lattice potential energy due to the forces governing the distri-bution of P and Si in the lattice, as well as local compositional variation
Global-in-time well-posedness of the compressible Navier–Stokes equations with striated density
No full textWe first show local-in-time well-posedness of the compressible Navier- Stokes equations, assuming striated regularity while no other smoothness or smallness conditions on the initial density. With these local-in-time solutions served as blocks, for less regular initial data where the vacuum is permitted, the global-in-time well-posedness follows from the energy estimates and the propagated striated regularity of the density function, if the bulk viscosity coefficient is large enough in the two-dimensional case. The global-in-time well-posedness holds also true in the three-dimensional case, provided with large bulk viscosity coefficient together with small initial energy. This solves the density-patch problem in the exterior domain for the compressible model with W-2;p-interfaces. Finally, the singular incompressible limit toward the inhomogeneous incompressible model when the bulk viscosity coefficient tends to infinity is obtained
Early state of Li₇La₃Zr₂O₁₂/Li heterointerface in all-solid-state battery: causality dilemma between crack formation and Li-rich nanodendrites
Get PDFIt has been argued that the Li7La3Zr2O12/Li hetero-interface in all-solid-state batteries is prone to decomposition and degradation during synthesis and cycling, leading to the formation of Li dendrites and their propagation inside the Li7La3Zr2O12 bulk. However, the exact formation mechanism of these dendrites, as well as their chemical composition, remains not fully understood until now due to the difficulty of quantifying the Li concentration within the battery materials.
Therefore, in this work, we employed atom probe tomography in conjunction with advanced transmission electron microscopy to investigate the Li7La3Zr2O12 bulk in the vicinity of the Li7La3Zr2O12/Li heterointerface, a region prone to crack formation and propagation. We discovered that numerous Li-nanodendrites are present inside the LLZO bulk close to the Li/LLZO interface and that these nanodendrites appear similar to cracks being filled by Li. Therefore, this study raises a possible dilemma of causality between the crack formation and Li segregation in LLZO grains.
Interestingly, advanced microscopy investigations prove the existence of a high density of dislocations within LLZO for some grains. Moreover, the finite element modeling suggests that the dislocations’ cores can act as nucleation sites for strong Li segregation, leading to an increase in hydrostatic stress. This implies that this strong Li segregation at the dislocation cores and the resultant high hydrostatic stress might be the cause for the crack formation. Subsequently, Li can be further accumulated at the cracks, forming the Li-nanodendrites.
It is without doubt that the presence of such microscopic Li-rich nanodendrites in the as-deposited state will lead to the growth and propagation of the well-known macroscopic Li dendrites during cycling
Influence of the Manufacturing Process and Dynamic Testing on the Residual Stress State of Additively Manufactured Ti-6Al-4V Lattice Structure Specimens
Get PDFA hypothesis-based method for building specific design knowledge for robust design
Get PDFRobust Design (RD) is crucial in product development to ensure that products maintain reliable performance under varying conditions. Design knowledge is fundamental to RD. However, current methods lack a systematic approach to support design engineers in building design knowledge for RD. This paper addresses this gap by introducing a hypothesis-based method for systematically building design knowledge for RD. RD hypotheses are specifically developed for this purpose and are tested through a five-step method. The application of this method is demonstrated in a case study involving a hand-operated coining machine. The results show that the proposed method supports building specific design knowledge through two RD hypotheses. By employing this method, design engineers are systematically supported in making design decisions, leading to more robust product concepts
Personalized and Demand-Based Education Concept: Practical Tools for Control Engineers
Get PDFThis paper presents a personalized lecture concept using educational blocks and its demonstrative application in a new university lecture. Higher education faces daily challenges: deep and specialized knowledge is available from everywhere and accessible to almost everyone. University lecturers of specialized master courses confront the problem that their lectures are either too boring or too complex for the attending students. Additionally, curricula are changing more rapidly than they have in the past 10–30 years. The German education system comprises different educational forms, with universities providing less practical content. Consequently, many university students do not obtain the practical skills they should ideally gain through university lectures. Therefore, in this work, a new lecture concept is proposed based on the extension of the just-in-time teaching paradigm: Personalized and Demand-Based Education. This concept includes: 1) an initial assessment of students’ backgrounds, 2) selecting the appropriate educational blocks, and 3) collecting ongoing feedback during the semester. The feedback was gathered via Pingo, ensuring anonymity for the students. Our concept was exemplarily tested in the new lecture ”Practical Tools for Control Engineers” at the Karlsruhe Institute of Technology. The initial results indicate that our proposed concept could be beneficial in addressing the current challenges in higher education
Modellierung reaktiver Partikelsysteme am Beispiel von Thermitreaktionen
Get PDFReaktive Partikelsysteme, oder speziell pyrotechnische Mischungen wie Thermite, haben eine Vielzahl technischer Anwendungen bei der Anzündung, Erzeugung von Leucht- oder Schallerscheinungen oder der Verzögerung eines Effekts. Zu den genannten gehört die Anzündung von Festtreibstoffen oder ein Feuerwerk. Die bekannteste Anwendung kommt allerdings aus der Verbindungstechnik, nämlich das Schweißen von Eisenbahnschienen.
Die Abbrandgeschwindigkeit und die bei der Reaktion entstehende Temperatur einer solchen Mischung sind sicherlich die wichtigsten Größen für deren Einsatz in einer technischen Applikation. Dabei reagieren die Systeme stark exotherm, ohne externen Sauerstoff, in einer sich selbst-erhaltenden Reaktion, in einem Abbrand oder in einer Deflagration. Die Reaktion findet meist in der festen Phase statt und erzeugt wenig Gas. Die Mischungen bestehen aus Komponenten, die in getrennten Partikeln vorliegen und miteinander vermischt wurden. Der partikuläre Charakter der Systeme, die auftretende chemische Reaktion und der treibende Energie- und Stofftransport machen die Beschreibung solcher Reaktionen auf einer mesoskopischen Ebene äußerst komplex.
In der vorliegenden Arbeit wird ein einfaches Modell entwickelt, das versucht, die wichtigsten physikalischen und chemischen Effekte, die bei der Reaktion solcher Systeme auftreten, zu berücksichtigen und eine Vorhersage für das Reaktionsverhalten, insbesondere den Reaktionsfortschritt zu machen. Bei den ausgesuchten Modellsystemen aus Thermitmischungen sind dies das Abbrandverhalten und die Abbrandgeschwindigkeit. In dem Modell werden Energie- und Stofftransport für die beteiligten Komponenten über eine chemische Reaktionskinetik gekoppelt. Die dabei auftretenden parabolischen partiellen Differentialgleichungen werden mittels Fundamentallösung, dann unter Randbedingungen mit den Greenschen Funktionen, gelöst. Die für das Modell notwendigen Eingangsparameter, Partikel- und Mischungseigenschaften, thermophysikalische und reaktionskinetische Eigenschaften, werden wiederum durch Modelle berechnet oder durch Modellbildung und Anpassung an experimentelle Daten von vier ausgesuchten Thermitmischungen ermittelt. Die Thermitmischungen, bestehend aus den Brennstoff/Oxidator-Kombinationen, Aluminium/Mangan(IV)-oxid, Aluminium/Kupfer(II)-oxid, Titan/Mangan(IV)-oxid und Titan/Kupfer(II)-oxid, werden in einer Konzentrationsreihe experimentell hinsichtlich ihrer Abbrandgeschwindigkeit untersucht. Deren Ergebnis ist die Abbrandgeschwindigkeit als Funktion der Brennstoffkonzentration. Das gleiche Ergebnis erhält man aus den Modellrechnungen, die dann mit den experimentellen Ergebnissen verglichen werden.
Man erhält für alle untersuchten Modellsysteme eine sehr gute Übereinstimmung von experimentell bestimmten Abbrandgeschwindigkeiten mit den aus Modellrechnungen ermittelten. Das Modell eignet sich also sehr gut zur Beschreibung des Reaktionsverhaltens reaktiver Partikelsysteme, deren Reaktion in der festen Phase stattfindet und für die die Gasdynamik nur eine untergeordnete Rolle spielt. Damit wurde ein Modell implementiert, das hilft das Reaktionsverhalten solcher Systeme besser zu verstehen, Vorhersagen über deren Verhalten zu machen und die Entwicklung neuer Systeme zu beschleunigen