Ultra-high vacuum compatible induction-heated rod casting furnace

We report the design of a radio-frequency induction-heated rod casting furnace that permits the preparation of polycrystalline ingots of intermetallic compounds under ultra-high vacuum compatible conditions. The central part of the system is a bespoke water-cooled Hukin crucible supporting a casting mold. Depending on the choice of mold, typical rods have a diameter between 6 mm and 10 mm and a length up to 90 mm, suitable for single-crystal growth by means of float-zoning. The setup is all-metal sealed and may be baked out. We find that the resulting ultra-high vacuum represents an important precondition for processing compounds with high vapor pressures under a high-purity argon atmosphere up to 3 bar. Using the rod casting furnace, we succeeded to prepare large high-quality single crystals of two half-Heusler compounds, namely the itinerant antiferromagnet CuMnSb and the half-metallic ferromagnet NiMnSb.Comment: 5 pages, 4 figure

Einfluss mechanischer Umgebungseffekte auf Messungen in Modenverwirbelungskammern

Modenverwirbelungskammern (MVK) bieten eine Messumgebung, die sich besonders für Störfestigkeitsuntersuchungen eignet, da auch mit geringer Leistung hohe Prüffeldstärken erreicht werden können, indem Veränderungen geometrischer Randbedingungen zu Feldüberhöhung führen. Diese können statistisch als homogen verteilt im Prüfvolumen angesehen werden. Zunehmend finden MVK auch für die Messung von Antennen oder Transferpfaden Anwendung. Dies geschieht auch bei Frequenzen, die Größenordnungen über der Mindestfrequenz von beispielsweise 30 MHz liegen, wobei die Randbedingungen der MVK grundsätzlich immer als statisch angenommen werden [1]. Bei deutlich höheren Frequenzen, z.B. über 10 GHz, können schon kleine Änderungen der Geometrie die konstruktiven und destruktiven Überlagerungen ändern, weil sie im Bereich/der Größenordnung der Wellenlänge liegen. In [2] wird gezeigt, dass bereits Vibrationen des Tuners oder der Wände Einfluss auf die Feldverteilung in der MVK haben. Diese Vibrationen können einerseits für beabsichtigte Feldveränderungen genutzt werden, andererseits können diese auch von Umgebungseinflüssen kommen und so die Qualität einer Messung in einer vermeintlich als statisch angenommenen MVK beeinträchtigen. Dies zeigen die im vorliegenden Beitrag präsentierten Messungen

In-Line Monitoring of Polyhydroxyalkanoate (PHA) Production during High-Cell-Density Plant Oil Cultivations Using Photon Density Wave Spectroscopy

Polyhydroxyalkanoates (PHAs) are biodegradable plastic-like materials with versatile properties. Plant oils are excellent carbon sources for a cost-effective PHA production, due to their high carbon content, large availability, and comparatively low prices. Additionally, efficient process development and control is required for competitive PHA production, which can be facilitated by on-line or in-line monitoring devices. To this end, we have evaluated photon density wave (PDW) spectroscopy as a new process analytical technology for Ralstonia eutropha (Cupriavidus necator) H16 plant oil cultivations producing polyhydroxybutyrate (PHB) as an intracellular polymer. PDW spectroscopy was used for in-line recording of the reduced scattering coefficient µs’ and the absorption coefficient µa at 638 nm. A correlation of µs’ with the cell dry weight (CDW) and µa with the residual cell dry weight (RCDW) was observed during growth, PHB accumulation, and PHB degradation phases in batch and pulse feed cultivations. The correlation was used to predict CDW, RCDW, and PHB formation in a high-cell-density fed-batch cultivation with a productivity of 1.65 gPHB·L−1·h−1 and a final biomass of 106 g·L−1 containing 73 wt% PHB. The new method applied in this study allows in-line monitoring of CDW, RCDW, and PHA formation.BMBF, 03Z22AN12, Zentrum für Innovationskompetenz innoFSPEC, Nachwuchsgruppe Angewandte Analytische Photonik (AAP

Mehrwegeausbreitung bei Navigationssystemen - ein universeller Ansatz zur EMV-Analyse mit skalierten Messungen

Dieser Beitrag beschreibt einen universellen, messtechnisch verifizierten Ansatz, mit dem EMV-Analysen für oben genannte bzw. sogar beliebige Navigationssysteme in einer verkleinerten Messumgebung mit nahezu uneingeschränkter Flexibilität durchgeführt werden können. Die Skalierung beinhaltet dabei nicht nur das Verkleinern der Reflexionsobjekte selbst, sondern vielmehr die Nachbildung der betroffenen Navigationssysteme bei entsprechend höherer Frequenz; im hier beschriebenen Ansatz für das ILS und das Drehfunkfeuer bei 16 GHz. Die ingenieurtechnische Schwierigkeit besteht in der getreuen Nachbildung der Abstrahlcharakteristik und der eigentlichen Navigationsinformation des Originalsystems

High-cell-density fed-batch cultivations of Vibrio natriegens

Objectives: With generation times of less than 10 min under optimal conditions, the halophilic Vibrio natriegens is the fastest growing non-pathogenic bacterium isolated so far. The availability of the full genome and genetic engineering tools and its ability to utilize a wide range of carbon sources make V. natriegens an attractive host for biotechnological production processes. However, high-cell-density cultivations, which are desired at industrial-scale have not been described so far. Results: In this study we report fed-batch cultivations of V. natriegens in deep-well plates and lab-scale bioreactor cultivations at different temperatures in mineral salt medium (MSM). Upon switching from exponential glucose to constant glucose-feeding cell death was induced. Initial NaCl concentrations of 15–18 g L −1 and a temperature reduction from 37 to 30 °C had a positive effect on cell growth. The maximal growth rate in MSM with glucose was 1.36 h −1 with a specific oxygen uptake rate of 22 mmol g CDW −1 h −1 . High biomass yields of up to 55 g L −1 after only 12 h were reached. Conclusions: The shown fed-batch strategies demonstrate the potential of V. natriegens as a strong producer in industrial biotechnology.TU Berlin, Open-Access-Mittel – 202

Recovery of the PHA Copolymer P(HB-co-HHx) With Non-halogenated Solvents: Influences on Molecular Weight and HHx-Content

Biodegradable and biocompatible polyhydroxyalkanoates (PHAs) are promising alternatives to conventional plastics. Based on the chain length of their monomers they are classified as short chain length (scl-) or medium chain length (mcl-) PHA polymers. The type of monomers, the composition and the molecular weight (MW) define the polymer properties. To accelerate the use of PHA as a bulk material, the downstream associated costs need to be minimized. This study focuses on the evaluation of non-halogenated solvents, especially acetone as a scl-PHA non-solvent, for the recovery of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) – P(HB-co-HHx) – with an mcl-HHx content >15 mol% and a MW average (Mw) < 2 × 105 Da. Solvents and precipitants were chosen regarding zeotrope formation, boiling point differences, and toxicity. Non-halogenated solvent-precipitant pairs were evaluated regarding the MW characteristics (MWCs) of the extracted polymer. Acetone and 2-propanol as a low toxic and zeotropic solvent-precipitant pair was evaluated at different extraction temperatures and multiple extraction times. The extraction process was further evaluated by using impure acetone for the extraction and implementing a multi-stage extraction process. Additionally, P(HB-co-HHx) extracted with three different solvents was characterized by 1H and 13C-APT NMR. The screening of precipitants resulted in a negative influence on the MWCs by ethanol precipitation for extractions with acetone and ethyl acetate, respectively. It was observed, that extractions with acetone at 70°C extracted a higher fraction of PHA from the cells compared to extractions at RT, but the Mw was decreased by 9% in average. Acetone with a 2-propanol fraction of up to 30% was still able to extract the polymer 95% as efficient as pure acetone. Additionally, when acetone and ethyl acetate were used in a multi-stage extraction process, a two-stage process was sufficient to extract 98–99% of the polymer from the cells. 1H and 13C-APT NMR analysis confirmed the monomer fraction and structure of the extracted polymers and revealed a random copolymer structure. The presented strategy can be further developed to an ecological and economically feasible PHA downstream process and thus contributes to the commercialization of low-cost PHAs.TU Berlin, Open-Access-Mittel – 2020BMBF, 031B0001C, Bioökonomie International 2014: PHABIO APP - Polyhydroxyalkanoate Biopolymere aus tierischen Abfallfetten für die Produktion von wertschöpfendem, biobasierten und abbauendem Plastik; Teilprojekt CBMBF, 031B0001B, Bioökonomie International 2014: PHABIO APP - Polyhydroxyalkanoate Biopolymere aus tierischen Abfallfetten für die Produktion von wertschöpfendem, biobasierten und abbauendem Plastik; Teilprojekt BBMBF, 031B0798C, Bioökonomie International 2017: PHABio-up - Polyhydroxyalkanoate Biopolymere aus tierischen Abfallfetten: Scale-up zur Realisierung einer industriellen Produktion - Teilvorhaben: Feedstock und Produktextraktio

Deep drilling reveals massive shifts in evolutionary dynamics after formation of ancient ecosystem

The scarcity of high-resolution empirical data directly tracking diversity over time limits our understanding of speciation and extinction dynamics and the drivers of rate changes. Here, we analyze a continuous species-level fossil record of endemic diatoms from ancient Lake Ohrid, along with environmental and climate indicator time series since lake formation 1.36 million years (Ma) ago. We show that speciation and extinction rates nearly simultaneously decreased in the environmentally dynamic phase after ecosystem formation and stabilized after deep-water conditions established in Lake Ohrid. As the lake deepens, we also see a switch in the macroevolutionary trade-off, resulting in a transition from a volatile assemblage of short-lived endemic species to a stable community of long-lived species. Our results emphasize the importance of the interplay between environmental/climate change, ecosystem stability, and environmental limits to diversity for diversification processes. The study also provides a new understanding of evolutionary dynamics in long-lived ecosystems

Cerebral Blood Flow during Rest Associates with General Intelligence and Creativity

Recently, much scientific attention has been focused on resting brain activity and its investigation through such methods as the analysis of functional connectivity during rest (the temporal correlation of brain activities in different regions). However, investigation of the magnitude of brain activity during rest has focused on the relative decrease of brain activity during a task, rather than on the absolute resting brain activity. It is thus necessary to investigate the association between cognitive factors and measures of absolute resting brain activity, such as cerebral blood flow (CBF), during rest (rest-CBF). In this study, we examined this association using multiple regression analyses. Rest-CBF was the dependent variable and the independent variables included two essential components of cognitive functions, psychometric general intelligence and creativity. CBF was measured using arterial spin labeling and there were three analyses for rest-CBF; namely mean gray matter rest-CBF, mean white matter rest-CBF, and regional rest-CBF. The results showed that mean gray and white matter rest-CBF were significantly and positively correlated with individual psychometric intelligence. Furthermore, mean white matter rest-CBF was significantly and positively correlated with creativity. After correcting the effect of mean gray matter rest-CBF the significant and positive correlation between regional rest-CBF in the perisylvian anatomical cluster that includes the left superior temporal gyrus and insula and individual psychometric intelligence was found. Also, regional rest-CBF in the precuneus was significantly and negatively correlated with individual creativity. Significance of these results of regional rest-CBF did not change when the effect of regional gray matter density was corrected. The findings showed mean and regional rest-CBF in healthy young subjects to be correlated with cognitive functions. The findings also suggest that, even in young cognitively intact subjects, resting brain activity (possibly underlain by default cognitive activity or metabolic demand from developed brain structures) is associated with cognitive functions