Massiv-parallele und großskalige Phasenfeldsimulationen zur Untersuchung der Mikrostrukturentwicklung

The development of tailored materials with defined properties requires a deep understanding of the microstructure evolution. In the first part, the microstructure evolution during the directional solidification of ternary eutectics with a highly optimized phase-field solver in the waLBerla-framework is studied. In the second part, the microstructure evolution under the influence of pores at the grain boundaries in the final sintering stage is analyzed with the PACE3D solver

Massiv-parallele und großskalige Phasenfeldsimulationen zur Untersuchung der Mikrostrukturentwicklung

Für maßgeschneiderte Bauteile mit definierten Eigenschaften ist ein detailliertes Verständnis der Mikrostrukturentwicklung notwendig. Im ersten Teil wird die Mikrostrukturentwicklung bei der ternären eutektischen gerichteten Erstarrung mit einem optimierten Phasenfeldlöser im massiv-parallelen waLBerla-Framework untersucht. Im zweiten Teil wird die Mikrostrukturentwicklung unter dem Einfluss von Poren an Korngrenzen während des Endstadiums des Sinterprozesses mit dem PACE3D-Löser analysiert

Compound droplets on fibers

Droplets on fibers have been extensively studied in the recent years. Although the equilibrium shapes of simple droplets on fibers are well established, the situation becomes more complex for compound fluidic systems. Through experimental and numerical investigations, we show herein that compound droplets can be formed on fibers and that they adopt specific geometries. We focus on the various contact lines formed at the meeting of the different phases and we study their equilibrium state. It appears that, depending on the surface tensions, the triple contact lines can remain separate or merge together and form quadruple lines. The nature of the contact lines influences the behavior of the compound droplets on fibers. Indeed, both experimental and numerical results show that, during the detachment process, depending on whether the contact lines are triple or quadruple, the characteristic length is the inner droplet radius or the fiber radius

Data workflow to incorporate thermodynamic energies from Calphad databases into grand-potential-based phase-field models

In order to approximate Gibbs energy functions, a semi-automated framework is introduced for binary and ternary material systems, using CALPHAD databases. To generate Gibbs energy formulations by means of second-order polynomials, the framework includes a precise approach. Furthermore, an optional extensional step enables the modeling of systems in which a direct generation leads to the unsatisfactory results in the representation of the thermodynamics. Furthermore, an optional extensional step enables the modeling of systems, in which a direct generation leads to the unsatisfactory results, when representing the thermodynamics. Within this extension, the commonly generated functions are modified to satisfy the equilibrium conditions in the observed material systems, leading to a better correlation with thermodynamic databases. The generated Gibbs energy formulations are verified by recalculating the equilibrium concentrations of the phases and rebuilding the phase diagrams in the considered concentration and temperature ranges, prior to the simulation studies. For all comparisons, a close match is achieved between the results and the CALPHAD databases. As practical examples of the method, phase-field simulation studies for the directional solidification of the binary Ni–35Mo and the ternary NiAl–10Mo eutectic systems are performed. Good agreements between the simulation results and the reported theoretical and experimental studies from literature are found, which indicates the applicability of the presented approaches

Быть марксистом: крест советского историка

Semiconductor quantum dot nanocrystals (QDs) for optical biosensing applications often contain thick polyethylene glycol (PEG)-based coatings in order to retain the advantageous QD properties in biological media such as blood, serum or plasma. On the other hand, the application of QDs in Förster resonance energy transfer (FRET) immunoassays, one of the most sensitive and most common fl uorescence-based techniques for non-competitive homogeneous biomarker diagnostics, is limited by such thick coatings due to the increased donor-acceptor distance. In particular, the combination with large IgG antibodies usually leads to distances well beyond the common FRET range of approximately 1 to 10 nm. Herein, time-gated detection of Tb-to-QD FRET for background suppression and an increased FRET range is combined with single domain antibodies (or nanobodies) for a reduced distance in order to realize highly sensitive QD-based FRET immunoassays. The “(nano) 2 ” immunoassay (combination of nanocrystals and nanobodies) is performed on a commercial clinical fl uorescence plate reader and provides sub-nanomolar (few ng/mL) detection limits of soluble epidermal growth factor receptor (EGFR) in 50 μ L buffer or serum samples. Apart from the fi rst demonstration of using nanobodies for FRET-based immunoassays, the extremely low and clinically relevant detection limits of EGFR demonstrate the direct applicability of the (nano) 2− assay to fast and sensitive biomarker detection in clinical diagnostics

Molecularly imprinted polymer based on MWCNTs-QDs as fluorescent biomimetic sensor for specific recognition of target protein

A novel molecularly imprinted optosensing material based on multi-walled carbon nanotube-quantum dots (MWCNT-QDs) has been designed and synthesized for its high selectivity, sensitivity and specificity in the recognition of a target protein bovine serum albumin (BSA). Molecularly imprinted polymer coated MWCNT-QDs using BSA as the template (BMIP-coated MWCNT-QDs) exhibits a fast mass-transfer speed with a response time of 25 min. It is found that the BSA as a target protein can significantly quench the luminescence of BMIP-coated MWCNT-QDs in a concentration-dependent manner that is best described by a Stem-Volmer equation. The K-SV for BSA is much higher than bovine hemoglobin and lysozyme, implying a highly selective recognition of the BMIP-coated MWCNT-QDs to BSA. Under optimal conditions, the relative fluorescence intensity of BMIP-coated MWCNT-QDs decreases linearly with the increasing target protein BSA in the concentration range of 5.0 x 10(-7)-35.0 x 10(-7) M with a detection limit of 80 nM