Simulation von Tunnelstrukturen - Experimentelle und theoretische Untersuchungen an Systemen mit anomaler Dispersion

Die vorliegende Arbeit gliedert sich in zwei aufeinander aufbauende Teilgebiete: Zunächst wurden die verschiedenen physikalischen Mechanismen, die zum Tunnelverhalten führen, analysiert und in numerischen Simulationen im Zeit- und Frequenzbereich nachgebildet. Anschließend wurden die entwickelten Simulationsroutinen genutzt, um die Planung und die Optimierung von Messungen im Vorfeld zu unterstützen. Dabei wurden neue Eigenschaften des Tunnelprozesses aufgedeckt. Außerdem konnten die gemessenen Daten mit den simulierten Werten verglichen werden, wenn keine analytische Lösung bereitstand. Mit entsprechenden Zeitbereichssimulationen konnten die Freiraummessungen an periodischen und resonanten Strukturen nachvollzogen werden. Es konnte gezeigt werden, daß eine Signalfront den Tunnelprozess zwar störend überlagern kann, die überlichtschnelle Übertragung der Modulation aber nicht verhindert. Zusätzlich zu den bereits bekannten Anwendungen und Experimenten, die amplitudenmodulierte Signale verwenden, wurde ein frequenzmoduliertes Signal mit überlichtschneller Gruppengeschwindigkeit übertragen. Es wurde gezeigt, wie eine ideale mathematische Signalfolge durch Tiefpassfilterung und Modulation auf einen hochfrequenten Träger überlichtschnell übertragen werden kann. Mit der kombinierten Zeit- und Frequenzbereichsanalyse konnten die Tunnelzeitergebnisse reproduziert werden, die bisher nur auf indirektem Wege mit Hilfe einer Streuparametermessung möglich waren. Zusätzlich zu den Tunnelzeiten wurden auch die Reflexionszeiten untersucht. Dabei wurde gezeigt, daß bei unsymmetrischen Gitterstrukturen außerhalb der Bandlücke sogar negative Reflexionszeiten auftreten. Es wurde erklärt, daß die überlichtgeschwindigkeitseffekte von Bessel-Wellen rein geometrischer Natur sind und nichts mit überlichtschneller Signalausbreitung zu tun haben. Die Tunnelzeit-Hypothese wurde überprüft, ihre Gültigkeit konnte über viele Frequenzdekaden bestätigt werden, noch bevor eine analytische Lösung zu diesem Problem zur Verfügung stand. Die theoretische Vorhersage einer negativen Transmissionszeit durch einen Quantentopf konnte mit Hilfe der Simulationen auf ein Analogie-Experiment mit Mikrowellen übertragen und durch Messungen bestätigt werden. Eine Untersuchung der Resonanzen und Streuzustände des Quantentopfs ergab einen Mechanismus zur Entstehung negativer Phasenzeiten

Could the GSI Oscillations be Observed in a Standard Electron Capture Decay Experiment?

The electron-capture decay of 180Re has been investigated to search for oscillations in the decay probability as reported from a recent measurement at GSI, Darmstadt. The production period was kept short compared to the reported oscillation period. No such oscillation was observed, indicating that the reported oscillations would not have been observable in a conventional experiment with radioactive atoms in a solid environment but must have to do with the unique conditions in the GSI experiment where hydrogen-like ions are moving independently in a storage ring and decaying directly by a true two-body decay to a long-lived (ground-) state. Our finding could restrict possible theoretical interpretations of the oscillations.Comment: 6 pages, 4 figure

A RAS-Independent Biomarker Panel to Reliably Predict Response to MEK Inhibition in Colorectal Cancer

Background: In colorectal cancer (CRC), mutations of genes associated with the TGF-β/BMP signaling pathway, particularly affecting SMAD4, are known to correlate with decreased overall survival and it is assumed that this signaling axis plays a key role in chemoresistance. Methods: Using CRISPR technology on syngeneic patient-derived organoids (PDOs), we investigated the role of a loss-of-function of SMAD4 in sensitivity to MEK-inhibitors. CRISPR-engineered SMAD4R361H PDOs were subjected to drug screening, RNA-Sequencing, and multiplex protein profiling (DigiWest®). Initial observations were validated on an additional set of 62 PDOs with known mutational status. Results: We show that loss-of-function of SMAD4 renders PDOs sensitive to MEK-inhibitors. Multiomics analyses indicate that disruption of the BMP branch within the TGF-β/BMP pathway is the pivotal mechanism of increased drug sensitivity. Further investigation led to the identification of the SFAB-signature (SMAD4, FBXW7, ARID1A, or BMPR2), coherently predicting sensitivity towards MEK-inhibitors, independent of both RAS and BRAF status. Conclusion: We identified a novel mutational signature that reliably predicts sensitivity towards MEK-inhibitors, regardless of the RAS and BRAF status. This finding poses a significant step towards better-tailored cancer therapies guided by the use of molecular biomarkers

Building the Policy Ecosystem in Europe for Cultivation and Use of Perennial Biomass Crops

Perennial biomass crops (PBCs) can potentially contribute to all ten Common Agricultural Policy (2023-27) objectives and up to eleven of the seventeen UN Sustainable Development Goals. This paper discusses interlinked issues that must be considered in the expansion of PBC production: i) available land; ii) yield potential; iii) integration into farming systems; iv) research and development requirements; v) utilisation options; and vi) market systems and the socio-economic environment. The challenge to create development pathways that are acceptable for all actors, relies on measurement, reporting and verification of greenhouse gas emissions reduction in combination with other environmental, economic and social aspects. This paper makes the following policy recommendations to enable greater PBC deployment: 1) incentivise farmers and land managers through specific policy measures, including carbon pricing, to allocate their less productive and less profitable land for uses which deliver demonstrable greenhouse gas reductions; 2) enable greenhouse gas mitigation markets to develop and offer secure contracts for commercial developers of verifiable low carbon bioenergy and bio-products; 3) support innovation in biomass utilisation value chains; and 4) continue long-term, strategic research and development and education for positive environmental, economic and social sustainability impacts. © 2023 ETA-Florence Renewable Energies

Beneficial cardiovascular effects of endothelin ET(A) receptor blockade in established long-term heart failure after myocardial infarction

Although experimental prevention studies have suggested therapeutic potential of endothelin (ET) antagonists for the treatment of heart failure, the results of clinical trials using ET antagonists on top of standard heart failure medications have been largely disappointing. This experimental study investigated the effects of chronic ET(A) receptor blockade in long-term survivors of myocardial infarction who had developed stable chronic heart failure in the absence of other treatments. Systolic blood pressure, heart rate, organ weights of the right atrium and ventricle, and the lungs were determined, and tissue ET-1 peptide levels were measured in cardiac tissue, lung, and aorta. The results show that chronic blockade of ET(A) receptors stabilizes systolic blood pressure and reverses the heart failure-induced weight increases of right heart chambers and lung. The changes observed occurred independently of tissue ET-1 concentrations and heart rate, suggesting mechanisms independent of local cardiac or pulmonary ET-1 synthesis, which are yet to be identified

Oxide ceramic fibers via dry spinning process - from lab to fab

Oxide fibers preparation and manufacturing capabilities at Fraunhofer-Center HTL are introduced, showing the development and preparation of oxide ceramic fibers from lab scale to pilot scale up to near production scale. As a specific example, the development of an aluminosilicate fiber with mullite composition is discussed in more detail. Fiber development started from nonaqueous sol-gel precursors in the early lab scale. With increasing fiber spinning volume, precursors were switched to water-soluble systems. Transformation from green fiber to ceramic fiber was monitored by thermogravimetric and differential thermal analysis, X-ray diffraction, and scanning electron microscopy. The evolution of ceramic phases, microstructure formation, and the effects on tensile strength and Young's modulus were investigated. Weibull statistics and fracture analysis helped to understand the results. Next step will be the transition from large lab scale to pilot scale, demonstrating manufacturing capability