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Design and synthesis of novel biobased polyamines for non- isocyanate polyurethanes (NIPUs) = Conception et synthèse de nouvelles polyamines biosourcées pour les polyuréthanes sans isocyanate (NIPUs) = Entwicklung und Synthese neuartiger biobasierter Polyamine für Nicht-Isocyanat-Polyurethane (NIPUs)
Get PDFDie Erschöpfung der Erdölvorkommen sowie die erheblichen menschlichen und ökologischen Kosten,
die mit der Herstellung fossiler Derivate verbunden sind, stellen heutzutage große Herausforderungen
dar. In diesem Zusammenhang konzentrierte sich diese Forschungsarbeit auf die Untersuchung
nachhaltigerer Monomere und Polymere. Sie wurde im Rahmen des europäischen Projekts NIPU-EJD
durchgeführt, das darauf abzielt, die Entwicklung von nicht-isocyanat Polyurethanen (NIPUs)
voranzutreiben. Der erste Teil der Arbeit konzentrierte sich auf die Entwicklung effizienter und weniger
gefährlicher Synthesestrategien zur Herstellung neuartiger biobasierter Polyamine und zyklischer
Carbonate als Monomere. Dabei wurde besonderes Augenmerk daraufgelegt, die Prinzipien der Grünen
Chemie so weit wie möglich einzuhalten. Im Anschluss kamen die synthetisierten Polyamine in der
Entwicklung von vinylogischen Urethanen (VUs), Epoxidharzen und Poly(hydroxyurethane)s (PHUs)
zum Einsatz, mit dem Ziel, sowohl teilweise als auch vollständig biobasierte Materialien zu schaffen.
Die resultierenden Polymere wurden umfassend charakterisiert, wobei ihre chemischen und
physikalischen Eigenschaften analysiert und miteinander verglichen wurden
Toward High-Efficiency Solar Cells: Insights into AsNCa Antiperovskite as an Active Layer
Get PDFAdvances in photovoltaic technology are a viable route for contributing to cleaner and more sustainable energy solutions, placing perovskite-based materials among the best candidates for solar energy conversion. However, some challenges must be addressed to enhance their performance and stability. Herein, we report an investigation of the AsNCa3 antiperovskite system for its potential in photovoltaic devices, using the density functional theory with semilocal and hybrid exchange-correlation functionals. We consider eight distinct crystalline phases, their structural parameters, dynamical stability, and electronic and optical properties. Furthermore, we consider each structural phase\u27s contributions to solar harvesting efficiency by calculating the power conversion efficiency (PCE) using the spectroscopic limited maximum efficiency formalism, which in this case reaches a maximum of 31.2%. All dynamically stable phases exhibit a band gap around similar to 1.3 eV, which lies within the optimal range for single-junction solar cells and yields PCE values comparable to the theoretical maximum PCE for silicon. These results place AsNCa3 antiperovskite as promising candidate for high-efficiency photovoltaic applications. Notably, the PCE is only slightly changed by structural phase modification, suggesting that phase transitions induced by environmental conditions during device operation might not compromise the device performance
Development and Expert Evaluation of an Informative Video Concerning Verifiable Internet Voting
Get PDFAs digitalization advances, online elections are becoming increasingly prevalent. State-of-the-art internet voting systems implement verifiability, which allows to observe the election result to be correct, while safeguarding the secrecy of the election. However, the continued use of unverifiable ‘black-box’ systems suggests that election organizers may be unaware of the security challenges in internet voting and the mitigation strategies that have been developed.
To address this gap, we developed an informative video on the topic for election organizers who are non-experts in internet voting. To ensure that the simplifications made for our target audience do not lead to misunderstandings, 19 German-speaking internet voting experts evaluated the video. Based on their feedback, we consider improvements to the video to enhance its correctness, clarity, and completeness. Further, developing the video and then performing the expert evaluation provided valuable experiences and lessons learned we want to share with similar endeavours trying to simplify complex topics for non-expert audiences
Optimized Machine Learning for Autonomous Enzymatic Reaction Intensification in a Self‐Driving Lab
Get PDFPhosphinoamine coinage metal complexes with a coumarin fluorophore: synthesis, characterization, and in vitro (photo)cytotoxicity
Get PDFHerein, we report the synthesis and characterization of coinage metal complexes coordinated to a coumarin-functionalized (bis(4-(tert-butyl)phenyl)) phosphinoamine ligand (L1). Treatment of the ligand with CuCl led to the formation of an unexpected tetranuclear compound [L1CuCl]4, while reaction with [Au(tht)2SbF6] or [Au(tht)Cl] (tht = tetrahydrothiophene) in an equimolar ratio resulted in [L12Au]SbF6 or [L1AuCl]. Reaction of the latter compound with 1-thio-beta-d-glucose tetraacetate (Glc) led to [L1Au(Glc)]. Owing to the presence of the fluorophore, the resulting metal complexes exhibited strong emissive properties, with the AuI complexes demonstrating quantum yields exceeding 80%. The emission is mainly contributed by the coumarin moiety. As a result, we further investigated these compounds for their cytotoxicity, photocytotoxicity, and potential in cellular imaging applications. Despite the known general cytotoxicity of CuI, the new coinage metal complexes show low cytotoxicity and are useful for cell imaging
Enantiomer selectivity and energy transfer in imperfect chiral cavities
Get PDFChiral polaritonics offers promising opportunities to selectively manipulate molecular species based on their handedness by harnessing unique interaction pathways offered by strong coupling in cavity QED. While significant progress has been made in understanding the fundamental mechanisms of enantiomer selectivity, many existing studies focus on perfectly chiral cavities that contain only one type of enantiomer. Here, we investigate a scenario of imperfect cavities containing varying mixtures of enantiomers. Using a generalized Hopfield-type model, we systematically explore how the degree of enantiomeric mixing and cavity imperfections affect chiral selectivity. Our analysis includes both an examination of the cavity\u27s eigenmode structure and a quantitative assessment of differential energy transfer into specific enantiomeric species. We demonstrate that both cavity imperfections and the presence of enantiomer mixtures profoundly modify the polaritonic dispersion. We also highlight that pushing the system into the deep strong coupling regime-by increasing molecular concentration-can decrease the efficiency of energy transfer to matter modes. These findings emphasize that precise cavity design and detailed consideration of enantiomeric composition are essential for achieving optimal chiral selectivity in practical cavity QED systems
Existence and stability of soliton-based frequency combs in the Lugiato–Lefever equation
Get PDFKerr frequency combs are optical signals consisting of a multitude of equally spaced excited modes in frequency space. They are generated in optical microresonators pumped by a continuous-wave laser. It has been experimentally observed that the interplay of Kerr nonlinearity and dispersion in the microresonator can lead to a stable optical signal consisting of a periodic sequence of highly localized ultra-short pulses, resulting in broad frequency spectrum. The discovery that stable broadband frequency combs can be generated in microresonators has unlocked a wide range of promising applications, particularly in optical communications, spectroscopy and frequency metrology. In its simplest form, the physics in the microresonator is modeled by the Lugiato–Lefever equation, a damped nonlinear Schrödinger equation with forcing. In this paper, we rigorously demonstrate that the Lugiato–Lefever equation indeed supports arbitrarily broad Kerr frequency combs by proving the first existence and stability results of periodic solutions consisting of any number of well-separated, strongly localized and highly nonlinear pulses on a single periodicity interval. We realize these periodic multi-soliton solutions as concatenations of individual bright cavity solitons by phrasing the problem as a reversible dynamical system and employing results from homoclinic bifurcation theory. The spatial dynamics formulation enables us to harness general results, based on Evans-function techniques and Lin’s method, to rigorously establish diffusive spectral stability. This, in turn, yields nonlinear stability of the periodic multi-soliton solutions against localized and subharmonic perturbations
Body Composition and Its Correlates in Children and Adolescents Living in Germany: A Cross-Sectional Study
Get PDFBody composition is an important health parameter during childhood and adolescence. In this study, we investigate the associations between body composition and age, physical activity, side jump, standing long jump, physical working capacity at 170 beats per minute pulse, screen time, and socioeconomic status in a nationwide German sample. A total of 2.869 children and adolescents (1.456 girls) aged 6–17 years from the Motorik-Modul study (2014–2017) were stratified by sex and three age groups (6–10, 11–13, 14–17 years). Physical activity was quantified by accelerometers, while physical fitness parameters were measured as part of the Motorik-Modul field-based fitness test battery. Body composition analysis (BIA 2000-S; Data Input, Frankfurt, Germany) included phase angle as well as height-adjusted indices for fat mass and fat-free mass. Potential correlates of body composition were examined by testing 18 preregistered hypotheses via multiple regression analyses. We found a general increase in fat mass index, fat-free mass index, and phase angle during childhood with sex-dependent changes in these trajectories occurring between the ages of 10 and 14 and persisting up to age 17. Besides age, the most important correlates were standing long jump and physical working capacity. Higher screen time and lower socioeconomic status accompany higher fat mass index but do not predict a lower fat-free mass index. Physical activity correlates negatively with fat mass index only among 6 to 13-year-olds. These findings emphasize the complex interplay between body composition, physical fitness parameters, lifestyle factors, and socioeconomic background in childhood and adolescence
Roton dispersion and displacement oscillatory for a nonlocal mechanical system
Get PDFRecently, we revealed anomalous static response in metamaterials with strong beyond-nearest-neighbor interactions or nonlocal interactions. Therein, the displacement field of a metamaterial beam when stretched is not simply linear in space like for ordinary materials, but rather exhibits pronounced spatial oscillations. The unusual behavior originates from evanescent Bloch modes at zero frequency, or frozen evanescent modes, with large decaying length. Here, we start from a discrete nonlocal mass-and-spring model and adopt an effective-medium approach based on higher-order differential equation to describe the anomalous behaviors. We demonstrate that the theory well captures the frozen evanescent modes and predicates the exact spatial oscillations of the displacement field. The strong dependence of the displacement field on the beam length is also revealed. The feasibility of the effective-medium approach is validated by comparison with the uniaxial tensile test results of metamaterials designed to support the anomalous frozen evanescent phonons. This theory can potentially be used for exploring other intriguing phenomena in nonlocal materials