Reaction nanoscopy

Die Wechselwirkung zwischen Licht und Nanoteilchen führt zu einer lokalen Verstärkung des elektromagnetischen Feldes auf der Teilchenoberfläche. Im Regime der Starkfeld-Physik verursacht diese Feldlokalisierung eine räumlich begrenzte Emission von Ionen von der Oberfläche von sphärischen Nanopartikeln, die mit der kürzlich eingeführten Reaktionsnanoskopietechnik abgebildet werden kann. Die Technik erlaubt die massenaufgelöste Messung der Energie- und Winkelverteilungen von Ionen, die durch die Starkfeld-Ionisation einzelner Nanopartikel im Vakuum erzeugt werden. In der vorliegenden Arbeit wurden Reaktionsnanoskpie-Experimente für einen breiten Bereich experimenteller Parameter durchgeführt und die Ergebnisse weitgehend durch ein Monte-Carlo-Modell reproduziert, das auf der Nahfeld-getriebenen Erzeugung von Ladungen und ihrer klassischen Propagation beruht. Im ersten Teil der Arbeit werden Experimente an SiO2-Nanoteilchen mit hohen Probenkonzentrationen und niedrigen Laserintensitäten behandelt. Mit Hilfe des Monte-Carlo-Modells wurden charakteristische Signaturen in den Daten auf die Ionenemission von Nanopartikel-Clustern zurückgeführt. Auf der Grundlage dieser Ergebnisse wurden verschiedene Methoden vorgeschlagen, die eine Trennung der Messdaten in die Beiträge einzelner Nanopartikel und Clusterbeiträge ermöglichen. Diese Signaltrennung und der Nachweis von Nanopartikel-Clustern im Allgemeinen war in früheren Studien zur Starkfeld-Elektronen-Emission von Nanopartikeloberflächen nicht möglich. Die dort beobachteten Abweichungen zwischen Theorie und Experiment könnten daher durch einen nicht berücksichtigten Beitrag von Elektronen aus Nanopartikel-Clustern erklärt werden. Der zweite Teil der Arbeit enthält eine Parameterstudie an einzelnen SiO2-Nanopartikeln bei verschiedenen Laserpolarisationen und -intensitäten. Außerdem werden Isotopenaustauschexperimente vorgestellt, die die molekulare Oberflächenzusammensetzung von SiO2-Nanoteilchen in typischen Reaktionsnanoskopie-Experimenten klären. Die Analyse der entsprechenden Ergebnisse wurde genutzt, um die Gültigkeit des Monte-Carlo-Modells zu prüfen und die Grenzen seiner Anwendbarkeit zu ermitteln. Die hier gewonnenen Erkenntnisse bilden die Grundlage für die zukünftige Entwicklung einer theoretischen Beschreibung von Reaktionsnanoskopie-Experimenten, die auf der molekularen Beschaffenheit der Nanopartikeloberfläche basiert. Der letzte Teil der Arbeit befasst sich mit der ersten Studie zur Reaktionsnanoskopie an starkfeld-ionisierten Nanotröpfchen. Anhand von Propandiol-Tröpfchen wurde gezeigt, dass der an festen Nanoteilchen beobachtete enge Zusammenhang zwischen der Nahfeldverteilung und der Winkelverteilung der Ionenausbeute auch für Nanotröpfchen beobachtet wird. Diese Übereinstimmung wurde für eine in-situ-Charakterisierung der häufigsten Tröpfchengröße in der Verteilung und für die Bewertung der Tröpfchenstabilität genutzt. Schließlich wird ein Vergleich der Ionenspektren von Tröpfchen aus zwei verschiedenen Propandiol-Isomeren durchgeführt. Ergebnisse aus Dichtefunktionaltheorie-Rechnungen deuten darauf hin, dass ein Teil der beobachteten Unterschiede in den Spektren auf die isomerspezifische Molekülstruktur auf der Tröpfchenoberfläche zurückzuführen ist. Die Ergebnisse dieser Arbeit belegen das enorme Potenzial der Anwendung der Reaktionsnanoskopie auf Problemstellungen der Oberflächenchemie. Die Technik legt den Grundstein für die Verfolgung der Entstehung von Reaktionsprodukten auf den Größenordnungen von Femtosekunden und Nanometern.The interaction between light and nanoparticles leads to a local enhancement of the electromagnetic field on the particle surface. In the regime of strong-field physics, this field localization causes a spatially confined emission of ions from the surface of spherical nanoparticles, which can be imaged using the recently introduced reaction nanoscopy technique. The technique facilitates the mass-resolved measurement of energy and angular distributions of ions produced by the strong-field ionization of individual nanoparticles in a vacuum. In this work, reaction nanoscopy experiments were performed for a wide range of experimental parameters. The results were largely reproduced by a Monte Carlo model based on the near-field driven generation of charges and their classical propagation. The first part of this work describes experiments employing silica nanoparticles with high sample concentrations and low laser intensities. Using the Monte-Carlo model, characteristic signatures in the data are attributed to ion emission from nanoparticle clusters. Based on these results, several methods are proposed to separate reaction nanoscopy data into single nanoparticle and cluster contributions. This signal separation and the detection of nanoparticle clusters has not been possible in previous studies on strong-field electron emission from nanoparticles. The deviations between theory and experiment observed there are consistent with an unaccounted contribution of nanoparticle clusters. The second part contains a parametric study of different laser polarizations and intensities incident on single silica nanoparticles. Isotope exchange experiments are presented, which are used to investigate the molecular surface composition of silica particles in typical reaction nanoscopy experiments. The results are used to evaluate the applicability of the Monte-Carlo model and explore its limitations. The insights gained here form the foundation for future developments toward a theoretical description of reaction nanoscopy experiments based on the molecular details of the nanoparticle surface. The final part of this thesis covers the first reaction nanoscopy study on strong-field ionized nanodroplets. Using propanediol droplets, it is demonstrated that a close correspondence between the near-field distribution and the angular distribution of the ion yield is observed for droplets similar to that of solid particles. This correspondence is used for an in situ characterization of the mean droplet size and for evaluating droplet stability. Finally, a comparison of the ion spectra for droplets from two different propanediol isomers is carried out. Density functional theory results suggest that parts of the observed differences can be attributed to the isomer-specific molecular structure on the droplet surface. The findings of this thesis demonstrate the great potential of the application of reaction nanoscopy to surface chemistry. The technique paves the way toward spatiotemporal tracing of reaction products on the femtosecond and nanometer scales

Metrics for Specification, Validation, and Uncertainty Prediction for Credibility in Simulation of Active Perception Sensor Systems

The immense effort required for the safety validation of an automated driving system of SAE level 3 or higher is known not to be feasible by real test drives alone. Therefore, simulation is key even for limited operational design domains for homologation of automated driving functions. Consequently, all simulation models used as tools for this purpose must be qualified beforehand. For this, in addition to their verification and validation, uncertainty quantification (VV&UQ) and prediction for the application domain are required for the credibility of the simulation model. To enable such VV&UQ, a particularly developed lidar sensor system simulation is utilized to present new metrics that can be used holistically to demonstrate the model credibility and -maturity for simulation models of active perception sensor systems. The holistic process towards model credibility starts with the formulation of the requirements for the models. In this context, the threshold values of the metrics as acceptance criteria are quantifiable by the relevance analysis of the cause-effect chains prevailing in different scenarios, and should intuitively be in the same unit as the simulated metric for this purpose. These relationships can be inferred via the presented aligned methods “Perception Sensor Collaborative Effect and Cause Tree” (PerCollECT) and “Cause, Effect, and Phenomenon Relevance Analysis” (CEPRA). For sample validation, each experiment must be accompanied by reference measurements, as these then serve as simulation input. Since the reference data collection is subject to epistemic as well as aleatory uncertainty, which are both propagated through the simulation in the form of input data variation, this leads to several slightly different simulation results. In the simulation of measured signals and data over time considered here, this combination of uncertainties is best expressed as superimposed cumulative distribution functions. The metric must therefore be able to handle such so-called p-boxes as a result of the large set of simulations. In the present work, the area validation metric (AVM) is selected by a detailed analysis as the best of the metrics already used and extended to be able to fulfill all the requirements. This results in the corrected AVM (CAVM), which quantifies the model scattering error with respect to the real scatter. Finally, the double validation metric (DVM) is elaborated as a double-vector of the former metric with the estimate for the model bias. The novel metric is exemplarily applied to the empirical cumulative distribution functions of lidar measurements and the p-boxes from their re-simulations. In this regard, aleatory and epistemic uncertainties are taken into account for the first time and the novel metrics are successfully established. The quantification of the uncertainties and error prediction of a sensor model based on the sample validation is also demonstrated for the first time

Phosphorylation of Vasodilator-Stimulated Phosphoprotein (VASP) dampens hepatic ischemia-reperfusion injury

Recent work has demonstrated that the formation of platelet neutrophil complexes (PNCs) affects inflammatory tissue injury. Vasodilator-stimulated phosphoprotein (VASP) is crucially involved into the control of PNC formation and myocardial reperfusion injury. Given the clinical importance of hepatic IR injury we pursued the role of VASP during hepatic ischemia followed by reperfusion. We report here that VASP−/− animals demonstrate reduced hepatic IR injury compared to wildtype (WT) controls. This correlated with serum levels of lactate dehydrogenase (LDH), aspartate (AST) and alanine (ALT) aminotransferase and the presence of PNCs within ischemic hepatic tissue and could be confirmed using repression of VASP through siRNA. In studies employing bone marrow chimeric mice we identified hematopoietic VASP to be of crucial importance for the extent of hepatic injury. Phosphorylation of VASP on Ser153 through Prostaglandin E1 or on Ser235 through atrial natriuretic peptide resulted in a significant reduction of hepatic IR injury. This was associated with a reduced presence of PNCs in ischemic hepatic tissue. Taken together, these studies identified VASP and VASP phosphorylation as crucial target for future hepatoprotective strategies

SceML - A Graphical Modeling Framework for Scenario-based Testing of Autonomous Vehicles

Ensuring the functional correctness and safety of autonomous vehicles is a major challenge for the automotive industry. However, exhaustive physical test drives are not feasible, as billions of driven kilometers would be required to obtain reliable results. Scenariobased testing is an approach to tackle this problem and reduce necessary test drives by replacing driven kilometers with simulations of relevant or interesting scenarios. These scenarios can be generated or extracted from recorded data with machine learning algorithms or created by experts. In this paper, we propose a novel graphical scenario modeling language. The graphical framework allows experts to create new scenarios or review ones designed by other experts or generated by machine learning algorithms. The scenario description is modeled as a graph and based on behavior trees. It supports different abstraction levels of scenario description during software and test development. Additionally, the graphbased structure provides modularity and reusable sub-scenarios, an important use case in scenario modeling. A graphical visualization of the scenario enhances comprehensibility for different users. The presented approach eases the scenario creation process and increases the usage of scenarios within development and testing processes.Comment: In ACM/IEEE 23rd International Conference on Model Driven Engineering Languages and Systems (MODELS 20), October 18to23, 2020, Virtual Event, Canada. ACM, New York, NY, USA, 7 page

Few-cycle laser driven reaction nanoscopy on aerosolized silica nanoparticles

Nanoparticles offer unique properties as photocatalysts with large surface areas. Under irradiation with light, the associated near-fields can induce, enhance, and control molecular adsorbate reactions on the nanoscale. So far, however, there is no simple method available to spatially resolve the near-field induced reaction yield on the surface of nanoparticles. Here we close this gap by introducing reaction nanoscopy based on three-dimensional momentum-resolved photoionization. The technique is demonstrated for the spatially selective proton generation in few-cycle laser-induced dissociative ionization of ethanol and water on SiO2 nanoparticles, resolving a pronounced variation across the particle surface. The results are modeled and reproduced qualitatively by electrostatic and quasi-classical mean-field Mie Monte-Carlo (M3C) calculations. Reaction nanoscopy is suited for a wide range of isolated nanosystems and can provide spatially resolved ultrafast reaction dynamics on nanoparticles, clusters, and droplets

Feasibility and suitability of a graded exercise test in patients with aggressive hemato-oncological disease

Purpose Physical activity promises to reduce disease-related symptoms and therapy-related side effects in patients suffering from aggressive lymphoma (L) or acute leukemia (AL). For an efficient training program, determination of patients’ physical capacity with a purposive exercise test is crucial. Here, we evaluated the feasibility and suitability of a graded exercise test (GXT) frequently applied in patients suffering from solid tumors by assessing whether patients achieved criteria for maximal exercise testing according to the American College of Sports Medicine (ACSM). Methods The GXT was performed by 51 patients with an aggressive L or AL prior to the start or in the earliest possible phase of high-dose chemotherapy, following a recommended protocol for cancer patients, starting at 20 Watts (W), with an increase of 10 W/min until volitional exhaustion. Subsequently, we investigated whether the following ACSM criteria were fulfilled: (1) failure of heart rate to increase despite increasing workload, (2) post-exercise capillary lactate concentration ≥ 8.0 mmol L−1, (3) rating of perceived exertion at exercise cessation > 17 on the 6–20 Borg Scale. Results Out of 51 patients, two, six, and 35 participants met the first, second, and third criterion, respectively. No relevant relationships between the completion of the criteria and patients’ characteristics (e.g., gender, age) were found. Conclusion Although results of this study suggest a general feasibility of the applied GXT, the ACSM criteria were not met by the majority of the participants. Therefore, this study raises doubts about the suitability of the GXT protocol and the ACSM criteria for this group of patients

Data-driven Derivation of Requirements for a Lidar Sensor Model

Safety assurance in virtual driving simulation environments requires accurate sensor models. However, generally accepted quality criteria for sensor models do not yet exist. In this work, we investigate the model quality needed for a Lidar sensor model for virtual validation. We seek to answer the question, whether neglecting sensor effects in a simplified sensor model might lead to a measurable difference in performance of the sensor model compared to a real sensor. A data-driven approach has been chosen to identify relevant features for object classification in Lidar pointclouds which need to be accurately represented in simulations. The contribution of our work is two-fold: Firstly, we identify important features for object detection in point clouds from Lidar data. For this, we apply object classification algorithms to pointcloud segments, for which a variety of geometric, stochastic, and sensor-specific features have been calculated. Using filter models, principal component analysis (PCA), and embedded models, each feature is assessed and ranked on an individual basis. Secondly, we derive implications for Lidar sensor models based on our findings. We investigate variations in classification quality by succesively removing groups of features from our feature set. Our results show, that to make sensor models suitable for the validation of object detection algorithms, the accurate representation of simple geometric features in synthetic pointclouds is sufficient in many cases. Our method can also be used to support the derivation of requirements and validation criteria for sensor models

Reaction Nanoscopy of Ion Emission from Sub-wavelength Propanediol Droplets

Droplets provide unique opportunities for the investigation of laser-induced surface chemistry. Chemical reactions on the surface of charged droplets are ubiquitous in nature and can provide critical insight into more efficient processes for industrial chemical production. Here, we demonstrate the application of the reaction nanoscopy technique to strong-field ionized nanodroplets of propanediol (PDO). The technique's sensitivity to the near-field around the droplet allows for the in-situ characterization of the average droplet size and charge. The use of ultrashort laser pulses enables control of the amount of surface charge by the laser intensity. Moreover, we demonstrate the surface chemical sensitivity of reaction nanoscopy by comparing droplets of the isomers 1,2-PDO and 1,3-PDO in their ion emission and fragmentation channels. Referencing the ion yields to gas-phase data, we find an enhanced production of methyl cations from droplets of the 1,2-PDO isomer. Density functional theory simulations support that this enhancement is due to the alignment of 1,2-PDO molecules on the surface. The results pave the way towards spatio-temporal observations of charge dynamics and surface reactions on droplets in pump-probe studies

Microresonator solitons for massively parallel coherent optical communications

Optical solitons are waveforms that preserve their shape while propagating, relying on a balance of dispersion and nonlinearity. Soliton-based data transmission schemes were investigated in the 1980s, promising to overcome the limitations imposed by dispersion of optical fibers. These approaches, however, were eventually abandoned in favor of wavelength-division multiplexing (WDM) schemes that are easier to implement and offer improved scalability to higher data rates. Here, we show that solitons may experience a comeback in optical communications, this time not as a competitor, but as a key element of massively parallel WDM. Instead of encoding data on the soliton itself, we exploit continuously circulating dissipative Kerr solitons (DKS) in a microresonator. DKS are generated in an integrated silicon nitride microresonator by four-photon interactions mediated by Kerr nonlinearity, leading to low-noise, spectrally smooth and broadband optical frequency combs. In our experiments, we use two interleaved soliton Kerr combs to transmit a data stream of more than 50Tbit/s on a total of 179 individual optical carriers that span the entire telecommunication C and L bands. Equally important, we demonstrate coherent detection of a WDM data stream by using a pair of microresonator Kerr soliton combs - one as a multi-wavelength light source at the transmitter, and another one as a corresponding local oscillator (LO) at the receiver. This approach exploits the scalability advantages of microresonator soliton comb sources for massively parallel optical communications both at the transmitter and receiver side. Taken together, the results prove the significant potential of these sources to replace arrays of continuous-wave lasers in high-speed communications.Comment: 10 pages, 3 figure