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Bounds on the fixed effects estimand in the presence of heterogeneous assignment propensities
No full textFixed effects estimation, with linear controls for stratum membership, is often used to estimate treatment effects when assignment propensities differ across strata. In the presence of heterogeneity in treatment effects across strata, this estimator does not target the average treatment effect, however. Indeed, the implied estimand can range anywhere from the lowest to the highest stratum-level average effect. To facilitate the interpretation of results using this approach, I establish that if stratum-level average effects are monotonic in the shares assigned to treatment, then the fixed effects estimand lies between the average treatment effect for the treated and the average treatment effect for the controls.Peer Reviewe
Saccade-induced temporal distortion: opposing effects of time expansion and compression
No full textSaccadic eye movements, or saccades, can distort our perception of time, as evidenced by the phenomenon of Chronostasis, where the first event after a saccade appears to last longer than it actually does. However, the impact of saccades on events following the first has never been explored. Here, we compared how participants perceived durations of first and second intervals after a saccade with their perceived durations during fixation, where no saccades occurred. We found that saccades lengthened the perceived duration of the first event, confirming Chronostasis. Moreover, when the second event occurred right after the first, its duration was perceived as shorter. Interestingly, when the second event was used as a reference, the Chronostasis effect was even stronger. Notably, this shortening of the second event persisted even when we ruled out processes like the “attentional blink” that might interfere with the timing between the two events. Our findings suggest that saccades induce a brief, uneven distribution of attentional processing in time, leading to an overestimation of the first and an underestimation of the second interval when the two intervals occur close together.Open Access funding enabled and organized by Projekt DEAL.Ludwig-Maximilians-Universität München (1024)Peer Reviewe
Pre-service mathematics teachers’ experiences and insights into the benefits and challenges of using explanatory videos in flipped modelling education
No full textExplanatory videos play an important role in the flipped classroom (FC) approach, which has become highly important especially since the COVID-19 crisis. In this qualitative study, we explore the potential of using explanatory videos (EVs) in mathematical modelling education as important component of FC and assess its merits and deficiencies. We focus on the perspectives and experiences of 44 preservice mathematics teachers (PSTs) attending a German university in their master phase. Considering EVs in an interactive FC context, we employed a multifaceted approach to data collection that included interviews, online surveys with open-ended questions, EVs generated by the PSTs, and written documents resulting from collaborative group activities. The findings show that the EVs used in FCs in modelling can enhance understanding and simplifying modelling content and real-world situations. Moreover, PSTs report that using EVs in flipped modelling seminars can offer personalized learning, optimize teaching hours, decrease anxiety, and increase learners’ attention. PSTs also improved their skills in developing EVs on modelling and evaluating their quality in terms of structure, content, and focus. The experienced challenges include time-consuming content development, workload, technical hurdles, and feasibility of FC implementations. Although these challenges are important, they are not content-specific issues, and we conclude that the notable benefits of using EVs in FCs have the potential to promote technology-enhanced modelling education.Open Access funding enabled and organized by Projekt DEAL.Humboldt-Universität zu Berlin (1034)Peer Reviewe
Erstes und Zweites Fach, Überfachlicher Wahlpflichtbereich für andere Masterstudiengänge
No full textModelling the potential of autumn tree leaves for energy production – A case study of the city of Berlin
No full textDie Gesellschaft ist auf Energie für Alltag und Wirtschaft angewiesen. Fossile Brennstoffe dominieren historisch den Energiemix, verursachen jedoch durch ihre Verbrennung erhebliche Treibhausgasemissionen (THG). Erneuerbare Quellen wie Biomasse bieten Alternativen. Restbiomasse, etwa Herbstlaub, hat Potenzial für nachhaltige Energie. In Berlin werden jährlich ca. 36.000 Tonnen Laub gesammelt und kompostiert – ein Prozess, der THG freisetzt. Alternativen wie Vergärung, Vergasung und Mitverbrennung zeigen Potenzial, wurden aber selten szenariobasiert und wirtschaftlich bewertet. Diese Arbeit bewertet THG-Emissionen und die Wirtschaftlichkeit der Umwandlung von Berliner Herbstlaub in Energie mittels Biogas, Vergasung und Mitverbrennung. Sie untersucht: Emissionen und Rentabilität der Technologien - Energiepotenzial von Herbstlaub - Schlüsselfaktoren für die Machbarkeit. Mit Lebenszyklusanalyse (LCA) und Kapitalwertmethode (NPV) simuliert das Python-basierte BIORIM-Modell Umwelt- und Wirtschaftseffekte. LCA fokussiert auf 100-jährige THG-Wirkung, NPV berücksichtigt Kosten, Erlöse und Diskontierung. Drei Szenarien (Biogas, Vergasung, Mitverbrennung) werden mit Kompostierung verglichen. Alle Energieszenarien schnitten besser ab als Kompostierung. In 10 Jahren wurden 144.000–252.000 t CO₂eq eingespart, bei einem Kapitalwert von 10,3–12,1 Mio. €. In 20 Jahren lagen die Einsparungen bei 127.000–204.000 t CO₂eq und die NPVs bei 2,3–9,8 Mio. €. Mitverbrennung lieferte am meisten Energie. Wirtschaftlichkeit hing stark von Energieausbeute, Einspeisevergütung, Laubtyp, Feuchtegehalt und Logistik ab. Mitverbrennung ist effizient, aber durch den Kohleausstieg begrenzt. Vergasung bietet zusätzlich chemische Nutzungsmöglichkeiten. Biogas liefert weniger Energie, könnte aber durch Technik oder Kombination verbessert werden. Alle Optionen sind ökologisch und ökonomisch vorteilhaft. Zukünftige Forschung sollte BIORIM erweitern und partizipative Modellierung (ComMod) einbeziehen.Society depends on energy for daily life and economic activity. Historically, fossil fuels have dominated the energy mix, but their combustion emits greenhouse gases (GHGs), harming the environment. To reduce this impact, renewable sources like biomass are being explored. Residual biomass, such as autumn tree leaves, offers potential for sustainable energy. In Berlin, ~36,000 tonnes of leaves are annually collected and composted, contributing to GHG emissions. Alternatives like anaerobic digestion, gasification, and co-firing show energy potential but lack scenario-level and economic assessments. This thesis assesses the GHG emissions and economic performance of converting Berlin’s autumn leaves into energy using biogas, gasification, and co-firing. It aims to evaluate: GHG emissions and profitability of these technologies
- The energy potential of leaves - Key factors influencing feasibility. Using Life Cycle Assessment (LCA) and Net Present Value (NPV), the BIORIM model simulates the environmental and economic outcomes. LCA focuses on 100-year GHG impacts, and NPV includes costs, revenues, and discount rates. Three scenarios—biogas, gasification, and co-firing—are compared with composting. All energy scenarios outperformed composting. Over 10 years, GHG savings ranged from 144,000–252,000 t CO2eq, and NPVs reached €10.3–€12.1M. Gasification and biogas saved 127,000–204,000 t CO2eq in 20 years, with NPVs of €2.3–€9.8M. Co-firing showed the highest energy output. Economic outcomes were sensitive to energy recovery rates, feed-in tariffs, leaf type, moisture, and logistics. Co-firing is efficient but limited by coal phase-out. Gasification offers fuel and chemical production potential. Biogas yields less energy but may improve with new tech or hybrid approaches. All alternatives reduce GHGs and offer profits compared to composting. Future work should expand BIORIM and explore stakeholder-based scenario building using Companion Modelling (ComMod)
Farmers' tolerance for crop damage caused by wildlife: the role of compensation
No full textCompensation is a common strategy to alleviate financial losses caused by wildlife, but its effects on farmers' tolerance towards damage to crops caused by wildlife are poorly understood. To address this knowledge gap, we conducted semi‐structured interviews in three areas in and around biosphere reserves in Sweden and Germany to examine farmers' appraisals of wildlife‐related crop damage and their evaluation of financial compensation in relation to crop damage prevention measures. We found that tolerated yield loss was higher and more variable with compensation compared to a scenario without compensation. Yet, also under a scenario of full financial compensation, farmers tolerated a median of less than 10% yield loss. Using an environmental stress model, our analysis revealed that farmers' perception of crop damage risk was influenced by their experience with wildlife and crop damage, their coping appraisals (e.g. accessibility of prevention measures and compensation), and individual motivations. Our results indicate that while compensation can be effective, its success to increase tolerance to crop damage varies most likely based on farmers' values and how they perceive administrative challenges. Effective management of wildlife‐related crop damage near and within protected areas should thus combine compensation schemes with tailored communication and crop damage prevention strategies involving governmental authorities, farmers, and other stakeholders.Peer Reviewe
Coordinated cpSRP43 and cpSRP54 Abundance Is Essential for Tetrapyrrole Biosynthesis While cpSRP43 Is Independent of Retrograde Signaling
No full textThe chloroplast signal recognition particle (cpSRP) components cpSRP43 and cpSRP54 not only form a complex with light-harvesting chlorophyll (Chl)-binding proteins to direct them to the thylakoid membrane, but also serve other functions. cpSRP43 independently acts as a chaperone for some tetrapyrrole biosynthesis (TBS) enzymes, while cpSRP54 participates in the co-translational targeting of plastid-encoded proteins. However, it remains unclear to what extent the two cpSRP components are coregulated—despite their distinct functions—and whether both participate in genomes-uncoupled (GUN)-mediated retrograde signaling. Here, we demonstrate that cpSRP43 and cpSRP54 accumulation is strongly interdependently controlled: overexpression of one protein increases the level of the other, while a deficiency in one of the two proteins leads to a simultaneous decrease in the other component. Disruption of this balance, e.g., by combining the overexpression of one component with a knockout of the other, results in severe chlorosis, stunted growth, and reduced levels of Chl and tetrapyrrole intermediates. Moreover, cpSRP43 deficiency exacerbates the pale-green phenotype of gun4 and gun5 mutants, highlighting a synergistic impact on TBS; however, cpSRP43 overexpression fails to rescue these defects. Remarkably, loss of cpSRP43 does not affect the expression of nuclear-encoded photosynthetic genes under intrinsic plastid stress, clearly demonstrating that cpSRP43 is not involved in plastid-to-nucleus retrograde signaling. Overall, our findings underscore that the fine-tuned expression of cpSRP43 and cpSRP54 is crucial for proper chloroplast function and pigment biosynthesis, while cpSRP43 alone does not participate in the retrograde signaling pathway.This work was financially supported by China Postdoctoral Science Foundation (2023M731247, 2024T170319) and by the self-determined research funds of CCNU from the colleges’ basic research and operation of MOE (CCNU23XJ010).China Postdoctoral Science Foundationself-determined research funds of CCNU from the colleges’ basic research and operation of MOEPeer Reviewe
Development of Plasmonic Nano-Antenna-Waveguide Systems for Routing and Sensing
No full textChiralität beschreibt die Asymmetrie von Objekten. Die Eigenschaft, nicht mit dem Spiegelbild deckungsgleich zu sein, ist wesentlich für die molekularen Bausteine der belebten Natur. Auch propagierende, elliptisch polarisierte Lichtstrahlen sind chiral. Im aufstrebenden Bereich der Nanophotonik wird jedoch die Nutzung chiraler Phänomene durch schwache Licht-Materie-Wechselwirkung und Grenzen der Fokussierung erschwert. In dieser Arbeit wird experimentell ein metallisches Nano-Antennen-Wellenleiter-System entwickelt, welches die Elliptizität eines Lichtfeldes konzentriert, verstärkt und in geführte Oberflächenplasmonen umwandelt und damit eine wichtige Funktionalität für die Detektion von Chiralität bereitstellt. Der schrittweise Ansatz umfasst die Verwendung von 80 Nanometer breiten siliziumdioxidbeschichteten Silber-Nanodrähten als Plasmonenwellenleiter, die Farbstoffdotierung der Nanodrähte zur Nutzung als Frequenzwandler sowie die Kopplung mit Nanoantennen zur Erzeugung chiralitätssensitiver Plasmonenverteiler. Einzelsysteme wurden durch Korrelation von Hellfeld-, Dunkelfeld- und Photolumineszenzmikroskopie in Form von Rastermikroskopie, Weitfeld-Bildgebung und Spektroskopie untersucht. Als Ergebnis wurde eine gerichtete Photonen-zu-Plasmonen-Konversion in verschiedenen Nano-Antennen-Wellenleiter-Systemen beobachtet, die empfindlich auf die Chiralität des einfallenden Lichts reagiert. Die Robustheit des Effekts wird durch die Asymmetrie der Systeme bestimmt und bietet Potenzial für weitere Optimierungen. Basierend auf diesen Ergebnissen sind nicht nur Plasmonenverteiler in zukünftigen nanophotonischen Schaltungen denkbar, sondern auch hybride Sensoren. So könnte die Elliptizität eines fokussierten Lichtstrahls bis in den Milligradbereich nachgewiesen werden. Dies könnte genutzt werden, um zirkularen Dichroismus – ein charakteristisches Merkmal chiraler Substanzen – einer winzigen Probenmenge im nanovolumetrischen Hotspot der Nanoantennen-Drahtsysteme zu messen.Chirality refers to the asymmetry of objects, meaning that they cannot be superimposed on their mirror image. This is a fundamental geometrical property of the molecular building blocks of living nature. A propagating elliptically polarised light beam also has handedness, i.e., chirality. However, the exploitation of chiral phenomena in the emerging field of nanophotonics suffers from both the generally weak light-matter interaction and the lack of confinement due to the diffraction limit of light. In this work, a metallic nano-antenna-waveguide system is experimentally developed that confines, enhances and converts ellipticity of light fields into routed surface plasmon polaritons, providing an important functionality for detecting chirality. The step-by-step approach consists of the utilisation of 80 nanometre wide silica-coated silver nanowires as plasmon waveguides, the utilisation of dye-doped nanowires as plasmon frequency converters, and the assembly of nanowires and nanoantennas to achieve polarisation-sensitive plasmon routers. The optical studies of individual systems are based on a correlation of bright-field, dark-field and photoluminescence scanning, imaging and spectroscopy. As a result, directional photon-to-plasmon conversion was observed in a variety of nano-antenna-waveguide systems as a sensitive function of the chirality of the incident light. The robustness of the effect is driven by the asymmetry of the systems and gives rise to further optimisation. Based on these results, not only plasmon routers are envisaged in future nanophotonic circuits but also prospect hybrid sensors. Ellipticity could be detected of a focused light beam down to the milli-degree range. This could be exploited to measure circular dichroism - a characteristic feature of chiral substances - of a tiny amount of sample locally introduced into the nanovolumetric hot spot in the nano-antenna-wire systems
Activation of perfluoro(methyl vinyl ether) at Rh(i) complexes: metal-centered versus phosphine-mediated decarbonylation†
No full textThis study investigates the reactivity of perfluoro(methyl vinyl ether) [PMVE, CF2[double bond, length as m-dash]CF(OCF3)] towards rhodium(I) phosphine complexes. The reaction pathways are characterized by C–O and C–F bond cleavage reactions and decarbonylation steps. On using the complex [Rh(H)(PEt3)3] (1), unprecedented reactivity pathways were observed that are distinct from those found for previously studied fluoroolefins. Reactivity of an excess PMVE at Rh is initiated by coordination to the Rh center in 1, followed by its insertion into the Rh–H bond and a β-OCF3 elimination. This process ultimately results in OCF3 ligand transformation to give trans-[Rh(F)(CO)(PEt3)3] (4) and Et3PF2. Reactions of stoichiometric amounts of PMVE with [Rh(H)(PEt3)3] (1) or an excess amount of it with [Rh(F)(PEt3)3] (6) led to olefin complex formation to yield trans-[Rh(F)(η2-CF2CFH)(PEt3)2] (7) and trans-[Rh(F)(CF(OCF3)CF2)(PEt3)2] (8), respectively. In contrast, a remarkable insertion into the Rh–F bond at [Rh(F)(CO)(PEt3)2] (4) was observed leading to the formation of trans-[Rh(CO)(CF(OCF3)CF3)(PEt3)2] (5). Decarbonylation of PMVE proceeds not only at Rh, but also via a metal-free, phosphine-mediated process. The latter is characterized by oxidative addition of PMVE at PEt3 to form the fluorophosphoranes E/Z-(F3CO)CF[double bond, length as m-dash]CF(PFEt3), which subsequently convert into Et3PF2, CO and presumably tetrafluoroethene.Deutsche Forschungsgemeinschaft 10.13039/501100001659Peer Reviewe
