20 research outputs found
Developing surface ionisation charge-transfer dynamics of hydrogen Rydberg atoms into an energy-resolved probe of surfaces
No full textAs a Rydberg atom approaches a surface, it will eventually undergo ionisation by charge transfer into the surface at a distance of about
100nm (for principal quantum numbers n > 20). The dynamics of this process are sensitive to the electronic and geometric structure
of the surface and can display signature characteristics. As such, Rydberg atoms can be used to probe image-charge effects or to measure small
superficial electric stray or patch fields. The charge-transfer process can be in resonance between the Rydberg energies and the energetically
discrete surface states (image states) in a bandgap. Surface ionisation of Rydberg atoms is investigated for graphene, which is a zero-bandgap
semiconductor and can behave either as a metal or a semiconductor. The charge-transfer dynamics observed here exhibit the characteristics of a metal
with enlarged ion detection efficiency compared to a copper sample -- in accordance with other properties of graphene, such as conductivity, that are
enlarged compared with a regular metal. For hydrogen Rydberg atoms, surface ionisation is detected for distances up to 10 µm, with a
double series of high-lying image states extending far from the graphene film possibly creating a quasi-continuum at large atom-surface separations
with a density of states beyond the resolution of the Rydberg states from n=20 to 40. The resonance behaviour for graphene is explored with a
range of Rydberg H-atom collisional velocities whose effect on the charge transfer process introduces an additional handle on the probing of
electronically discrete features of a surface. A wave-packet propagation study of a hydrogen atom incident at a free-metal surface up to n=20
displays shifts in ionisation towards greater distances and over a narrower range when acceleration of the ion core is not included. The thereby
significantly reduced effect of the collisional velocity of Rydberg surface ionisation is also observed in an experimental study with a limited
velocity range available from supersonic expansion directed at a gold sample. This either suggests that the range of Rydberg projectile velocities is
to narrow to have observable effects or that a pronounced velocity dependency is merely detected for distinct electronic resonances. With the aim to
further elucidate the velocity dependence and to prospectively remove ambiguities that arise from the nature of the experiment, a chip-based
decelerator is constructed and integrated into the experimental apparatus for the first time. Within the constraints of the design and the existing
apparatus, the chip device is not able to produce sufficient densities of decelerated particles to be employed in surface-ionisation experiments.
Extensive modelling of the deceleration process indicates that modifications to the existing design and the experimental apparatus could achieve a
tunable-velocity source of hydrogen Rydberg atoms with greatly enhanced densities for future investigations.</p
Datengetriebene Verknüpfung von virtuellen und realen Tests für die szenariobasierte Validierung von automatisierten Fahrzeugen
No full textValidating the safety of automated vehicles (AVs) is paramount due to the risks associated with their deployment. Scenario-based testing has emerged as an approach to decompose the overall validation of AVs into smaller components represented by individual driving scenarios. However, identifying critical scenarios and selecting suitable test setups for scenario execution remain open challenges. Real-world tests involving AVs and their environment are considered the trustworthy gold standard. However, within economic constraints, it is impossible to collect sufficient data to prove a positive risk balance compared to manual driving. Conversely, virtual tests provide enormous amounts of data, but as they use models of AVs and their environment, conclusions about the real AVs are limited.
This thesis proposes a methodology that links different test setups and harmonizes scenario descriptions for virtual and real tests. Through active learning, scalable virtual test setups provide a broad coverage of scenarios, and probabilistic models characterize the outcomes of these tests. Leveraging transfer learning, the models enable the targeted parameterization of tests in other test setups. Utilizing importance sampling, this transfer can accelerate quantitative risk estimation in more trustworthy test setups with more real components or more detailed models of the AVs and their environment.
The results show that linking a scalable test setup with a trustworthy test setup can accelerate the risk estimation process while preserving the accuracy of the trustworthy test setup. Thus, linked test setups achieve a better tradeoff between efficiency and accuracy than each test setup individually. Increased similarity of the behaviors in the different test setups leads to higher efficiency gains. Large discrepancies may prevent direct efficiency gains. However, the developed methodology also allows for identifying scenarios with large discrepancies, which can then be used to determine the causes of the discrepancies and ultimately improve the AVs and test setups.
By linking diverse data, the techniques presented leverage synergies across scenarios and test setups. This enables accelerated validation that is more data-efficient than considering individual scenarios in isolation. The proposed methods aid the transition from virtual testing to real-world deployment and a continuous assessment of the risks of AVs, which enables decisions in the development process.Die Validierung der Sicherheit automatisierter Fahrzeuge ist aufgrund der mit ihrer Nutzung verbundenen Risiken essenziell. Im szenario-basierten Testen wird die Gesamtvalidierung der Fahrzeuge in kleinere Komponenten in Form von Fahrszenarien unterteilt, jedoch ist die Identifikation relevanter Szenarien und die Auswahl geeigneter Testaufbauten herausfordernd. Realtests sind zuverlässig, da sie Fahrzeuge und Umgebung uneingeschränkt abbilden, jedoch können im ökonomisch tragbaren Rahmen nicht genügend Daten gesammelt werden, um eine positive Risikobilanz gegenüber manuellem Fahren nachzuweisen. Virtuelle Tests können enorme Datenmengen liefern, aber da sie Modelle der Fahrzeuge und deren Umgebung verwenden, sind Rückschlüsse auf die realen Fahrzeuge nur mit Einschränkungen möglich.
Diese Arbeit präsentiert eine Methodik, die verschiedene Testaufbauten verknüpft und Szenariobeschreibungen für virtuelle und reale Tests harmonisiert. Durch Active Learning liefern skalierbare virtuelle Testaufbauten eine breite Abdeckung an Szenarien; probabilistische Modelle charakterisieren deren Ergebnisse. Mittels Transfer Learning erlauben die Modelle eine gezielte Parametrisierung von Tests in anderen Testaufbauten. Durch Importance Sampling kann dieser Transfer die quantitative Risikoschätzung in zuverlässigeren Testaufbauten mit mehr realen Komponenten oder detaillierteren Fahrzeug- und Umgebungsmodellen beschleunigen.
Die Ergebnisse zeigen, dass die Verknüpfung eines skalierbaren mit einem zuverlässigen Testaufbau die Risikoschätzung beschleunigt und die Genauigkeit des zuverlässigen Testaufbaus erhält. Verknüpft erzielen Testaufbauten somit einen besseren Kompromiss aus Effizienz und Genauigkeit als separat. Je ähnlicher das Verhalten in den Testaufbauten, desto höher die Effizienzgewinne. Große Diskrepanzen können direkte Effizienzgewinne verhindern. Doch die Methodik ermöglicht auch die Identifikation von Szenarien mit großen Diskrepanzen, deren Ursachen dann ermittelt und zur Verbesserung der Fahrzeuge und Testaufbauten verwendet werden können.
Durch die Verknüpfung von Daten heben die vorgestellten Techniken Synergien über Szenarien und Testaufbauten hinweg und erlauben eine im Vergleich zur Betrachtung einzelner Szenarien dateneffizientere, beschleunigte Validierung. Der Übergang von virtuellen Tests zum realen Einsatz wird begünstigt; Risiken der Fahrzeuge werden laufend bewertet und ermöglichen Entscheidungen im Entwicklungsprozess
McCall crew portrait, 1964
No full textA group portrait of the crew for the McCall Smokejumper base.
1. Ed Guy, 2. Carl Rosselli, 3. John Blackwell, 4. Gordon Dickinson, 5. John Cramer, 6. Gerry McCray, 7. Jack Seagraves, 8. Dave Hemry, 9. Frank Odom, 10. Ray Roark, 11. Ron Maki, 12. Dick Bradshaw, 13. Steve Marshall, 14. Bill Strawn, 15. Reid Shinn, 16. Mike Kohlhoff, 17. Jerry Blattner, 18. Dave Austin, 19. Bill Yensen, 20. Dale Schmaljohn, 21. Terry Lewton, 22. Lester Rosenkrance, 23. Larry Moore, 24. Jim Swartley, 25. Stan Ramsay, 26. Bruce Yergenson, 27. Gary Watts, 28. Wayne Webb, 29. Del Catlin, 30. Bill Donnelley, 31. Vaughn Heinrich, 32. Dennis Symes, 33. Bob Tomlinson, 34. Dale Carlson, 35. Mike McCracken, 36. John Mowery, 37. Bill Bull, 38. Layton Smith, 39. Charles Hay, 40. Allen Graham, 41. Dick Lynch, 42. Jon Petterson, 43. Bob Moloney.
Missing Max Allen, Ray Beasley, Julio Bilbao, Steve Carlson, Pat Carney, Tom Chiprany, Harry Clark, Jim Crockett, Tom Decker, Thad Duel, Pete Fallini, Dick Graham, Clarence Greet, Gene Hobbs, Marion Horton, Nick Kennedy, Jim Lafferty, Jim Lancaster, Jim Lindell, Ben McBride, Francis Mohr, Bob Montoya, Dave Nani, Benny Ortiz, Bill Rember, Ken Salyer, Ken Smith, James (Smokey) Stover, Clarence Teichert, Darell Weaver.https://dc.ewu.edu/nsa_crewpics/1289/thumbnail.jp
McCall crew portrait, 1965
No full textA group portrait of the crew for the McCall Smokejumper base.
1. Paul Bradley, 2. Tom Decker, 3. Clarence Teichert, 4. Thad Duel, 5. Horace Cordova, 6. Del Catlin, 7. Dale Carlson, 8. Neil Satterwhite, 9. Clarence Greet, 10. Carl Brown, 11. Marion Horton, 12. Bruce Montgomery, 13. Frank Odom, 14. Jon Petterson, 15. Bill Bull, 16. Ray Roark, 17. Bruce Yergenson, 18. James (Smokey) Stover, 19. Jim Tracy, 20. Dick Lynch, 21. Ron Berkey, 22. Ron Maki, 23. Bill Rember, 24. Tom Chiprany, 25. Julio Bilbao, 26. Mike Kohlhoff, 27. Bill Strawn, 28. Bill Yensen, 29. Jim Swartley, 30. Jim Rush, 31. Gary Watts, 32. Sam Defler, 33. Jim Weaver, 34. Wayne Sugg, 35. Howard Koskello, 36. Bruce Granquist, 37. Nick Kennedy, 38. Ben McBride, 39. Pete Fallini, 40. Gene Hobbs, 41. Vaughn Heinrich, 42. Jim Lafferty, 43. John Mowery, 44. Dale Schmaljohn, 45. Dave Austin, 46. Les Rosenkrance, 47. Dick Graham, 48. C.J. Horner, 49. Stan Ramsey, 50. Gerry McCray, 51. Jerry Blattner, 52. Jim Lindell, 53. Ken Smith, 54. Ken Salyer, 55. Wayne Webb.
Missing: Max Allen, Harry Clark, John Cramer, Jim Crockett, Craig DeSilvia, Gordon Dickinson, Bill Donnelley, Allan Graham, Ed Guy, Charles Hay, Dave Hemry, Terry Lewton, Larry Looney, Bob Moloney, John Seagraves, Layton Smith.https://dc.ewu.edu/nsa_crewpics/1290/thumbnail.jp
Probabilistic Metamodels for an Efficient Characterization of Complex Driving Scenarios
No full textTo validate the safety of automated vehicles (AV), scenario-based testing
aims to systematically describe driving scenarios an AV might encounter. In
this process, continuous inputs such as velocities result in an infinite number
of possible variations of a scenario. Thus, metamodels are used to perform
analyses or to select specific variations for examination. However, despite the
safety criticality of AV testing, metamodels are usually seen as a part of an
overall approach, and their predictions are not questioned. This paper analyzes
the predictive performance of Gaussian processes (GP), deep Gaussian processes,
extra-trees, and Bayesian neural networks (BNN), considering four scenarios
with 5 to 20 inputs. Building on this, an iterative approach is introduced and
evaluated, which allows to efficiently select test cases for common analysis
tasks. The results show that regarding predictive performance, the appropriate
selection of test cases is more important than the choice of metamodels.
However, the choice of metamodels remains crucial: Their great flexibility
allows BNNs to benefit from large amounts of data and to model even the most
complex scenarios. In contrast, less flexible models like GPs convince with
higher reliability. Hence, relevant test cases are best explored using scalable
virtual test setups and flexible models. Subsequently, more realistic test
setups and more reliable models can be used for targeted testing and
validation.Comment: 10 pages, 14 figures, 1 table, associated dataset at
https://github.com/wnklmx/DSIO
The effect of vitamin D supplementation on markers of insulin resistance in women with polycystic ovarian syndrome: a systematic review
No full textThe version of record of this article, first published in [European Journal of Nutrition], is available online at Publisher’s website: http://dx.doi.org/10.1007/s00394-024-03489-6Insulin resistance (IR) is a common pathology in women with polycystic ovarian syndrome (PCOS) involved in increased rates of cardiometabolic disease such as diabetes and cardiovascular disease. Low serum vitamin D is often associated with insulin resistance but there is no consensus on whether vitamin D supplementation can ameliorate markers of IR in PCOS. We assessed evidence on the effects of vitamin D supplementation (≥ 1000 IU/day), without the use of additional supplements or other pharmacological treatments known to affect IR, on markers of IR and glycemic control in women with PCOS. A systematic search was conducted using PubMed, Medline and Web of Science databases from January 2000 up to November 2023. Randomized controlled trials that assessed the effects of vitamin D supplementation in women with PCOS, on fasting glucose, fasting insulin, glycated haemoglobin (HbA1c) or homeostatic model assessment for insulin resistance (HOMA-IR) were included. 9 studies were identified. Study populations ranged from 28 to 180 participants, with mean ages ranging from 22 to 30 years. Daily vitamin D doses ranged from 1714-12,000 IU. Of the included studies, 3 reported statistically significant reductions in fasting glucose, 2 reported reductions in fasting insulin, 2 reported reductions in HOMA-IR, none reported reductions in HbA1c and 5 reported no differences in any of the relevant outcomes. In conclusion, in RCTs of vitamin D supplementation in women with PCOS, the majority of studies do not report statistically significant improvements in fasting glucose, fasting insulin, HbA1c or HOMA-IR. However, as a minority of studies report some statistically significant results, further investigation may be warranted. PROSPERO ID: CRD42023486144. [Abstract copyright: © 2024. The Author(s).]UnfundedVoR added 30/09/2024
in situ tracking of redox transitions and mode of catalysis
No full textWater oxidation by amorphous oxides is of high interest in artificial
photosynthesis and other routes towards non-fossil fuels, but the mode of
catalysis in these materials is insufficiently understood. We tracked
mechanistically relevant oxidation-state and structural changes of an
amorphous Co-based catalyst film by in situ experiments combining directly
synchrotron-based X-ray absorption spectroscopy (XAS) with electrocatalysis.
Unlike a classical solid-state material, the bulk material is found to undergo
chemical changes. Two redox transitions at midpoint potentials of about 1.0 V
(CoII0.4CoIII0.6 ↔ all-CoIII) and 1.2 V (all-CoIII ↔ CoIII0.8CoIV0.2) vs. NHE
at pH 7 are coupled to structural changes. These redox transitions can be
induced by variation of either electric potential or pH; they are broader than
predicted by a simple Nernstian model, suggesting interacting bridged cobalt
ions. Tracking reaction kinetics by UV-Vis-absorption and time-resolved mass
spectroscopy reveals that accumulated oxidizing equivalents facilitate
dioxygen formation. On these grounds, a new framework model of catalysis in an
amorphous, hydrated and volume-active oxide is proposed: Within the oxide
film, cobalt ions at the margins of Co-oxo fragments undergo CoII ↔ CoIII ↔
CoIV oxidation-state changes coupled to structural modification and
deprotonation of Co-oxo bridges. By the encounter of two (or more) CoIV ions,
an active site is formed at which the O–O bond-formation step can take place.
The Tafel slope is determined by both the interaction between cobalt ions
(width of the redox transition) and their encounter probability. Our results
represent a first step toward the development of new concepts that address the
solid-molecular Janus nature of the amorphous oxide. Insights and concepts
described herein for the Co-based catalyst film may be of general relevance
also for other amorphous oxides with water-oxidation activity
Electrosynthesis, functional, and structural characterization of a water oxidizing manganese oxide
No full textDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.In the sustainable production of non-fossil fuels, water oxidation is pivotal. Development of efficient catalysts based on manganese is desirable because this element is earth-abundant, inexpensive, and largely non-toxic. We report an electrodeposited Mn oxide (MnCat) that catalyzes electrochemical water oxidation at neutral pH at rates that approach the level needed for direct coupling to photoactive materials. By choice of the voltage protocol we could switch between electrodeposition of inactive Mn oxides (deposition at constant anodic potentials) and synthesis of the active MnCat (deposition by voltage-cycling protocols). Electron microscopy reveals that the MnCat consists of nanoparticles (100 nm) with complex fine-structure. X-ray spectroscopy reveals that the amorphous MnCat resembles the biological paragon, the water-splitting Mn4Ca complex of photosynthesis, with respect to mean Mn oxidation state (ca. +3.8 in the MnCat) and central structural motifs. Yet the MnCat functions without calcium or other bivalent ions. Comparing the MnCat with electrodeposited Mn oxides inactive in water oxidation, we identify characteristics that likely are crucial for catalytic activity. In both inactive Mn oxides and active ones (MnCat), extensive di-μ-oxo bridging between Mn ions is observed. However in the MnCat, the voltage-cycling protocol resulted in formation of MnIII sites and prevented formation of well-ordered and unreactive MnIVO2. Structure–function relations in Mn-based water-oxidation catalysts and strategies to design catalytically active Mn-based materials are discussed. Knowledge-guided performance optimization of the MnCat could pave the road for its technological use.DFG, EXC 314, Unifying Concepts in CatalysisEC/FP7/212508/EU/European Solar-Fuel Initiative - Renewable Hydrogen from Sun and Water. Science Linking Molecular Biomimetics and Genetics/SOLARH
A β-Amino-Ketone that Disrupts the Fungal Plasma Membrane Exhibits Potent Activity Against Pathogenic Trichophyton Species.
No full textSuperficial fungal infections, mainly caused by dermatophytes, are a global public health issue. We evaluated the antifungal activity of six β-amino-ketones against Trichophyton rubrum, a leading agent of superficial mycoses. Among them, 3-(morpholin-4-yl)-1-phenylpropan-1-one (AB1) showed the most potent effect, with a minimum inhibitory concentration (MIC) of 7.81 µg/ml against the T. rubrum reference strain and fungicidal activity against clinical isolates, as demonstrated by minimum fungicidal concentration (MFC) assays. AB1 was effective against both conidia and hyphae of T. rubrum, while showing limited activity against Candida albicans and the bacteria Escherichia coli and Staphylococcus aureus. Mechanistic studies suggest AB1 targets the fungal plasma membrane, possibly via ergosterol interactions, supported by increased MICs in ergosterol-rich conditions and membrane integrity assays. Confocal microscopy revealed morphological alterations in AB1-treated hyphae, indicative of membrane damage. Transmission electron microscopy confirmed cytoplasmic disorganization and membrane disruption at subinhibitory concentrations. Toxicological assays showed moderate cytotoxicity in human fibroblasts (IC₅₀ = 37.75 µg/ml) and no toxicity in Galleria mellonella larvae at high doses. These findings highlight AB1 as a promising antifungal candidate against Trichophyton spp., with the potential benefit of reduced impact on the host microbiota compared to broad-spectrum antimicrobials.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
