Do even the smallest clouds simply drift with the wind? Vast areas of our oceans and land are covered with shallow cumulus clouds. These low-level clouds are receiving increased attention as uncertainties in their representation in global climate models lead to a spread in predictions of future climate. This attention emphasizes radiative and thermodynamic impacts of clouds, which are thought to energize the large-scale Hadley circulation. But broadly overlooked is the impact of shallow cumuli on the trade-winds that drive this circulation. Reasons for this negligence are a lack of observations of vertical wind structure and the wide range of scales involved. My project will test the hypothesis that shallow cumuli can also slow down the Hadley circulation by vertical transport of momentum. First, observations of clouds and winds will be explicitly connected and the causality of their relationship will be exposed using ground-based and airborne measurements and high-resolution modeling. Second, new lidar techniques aboard aircraft are exploited to validate low-level winds measured by the space-borne Aeolus wind lidar and collect high-resolution wind and turbulence data. Third, different models of momentum transport by shallow convection will be developed to represent its impact on winds. Last, evidence of global relationships between winds and shallow cumulus are traced in Aeolus and additional satellite data and the impact of momentum transport on circulations in a control and warmer climate is tested in a general circulation model. This project exploits my expertise in observing and modeling clouds and convection focused on a hypothesis which, if true, will strongly influence our understanding of the sensitivity of circulations and the sensitivity of climate. It will increase the predictability of low-level winds and convergence patterns, which are important to many disciplines, including climate studies, numerical weather prediction and wind-energy research.

My goal is to overcome the two-most pressing theoretical challenges necessary to build large-scale quantum communication networks: routing and designing protocols that use them to solve useful tasks. In two interconnected projects, I will devise entirely new concepts, models and mathematical methods that take into account the intricacies of real world quantum devices that can operate on only very few quantum bits at a time. (1) Security: I will prove the security of quantum cryptographic protocols under realistic conditions, and implement them in collaboration with experimentalists. I will develop a general theory and practical tests for the security of multi-party cryptographic primitives using untrusted quantum devices. This is mathematically challenging due to the possibility of entanglement between the devices. (2) Routing: I will initiate the systematic study of effective routing in a quantum communication network. This is necessary for quantum networks to grow in scale. Quantum entanglement offers very different means of routing messages than is possible in classical networks, and poses genuinely new challenges to computer science. I will design routing protocols in a multi-node quantum network of potentially different physical implementations, i.e., hybrid networks, that will establish a new line of research in my field. Quantum networks are still in their infancy, even though quantum communication offers unparalleled advantages that are provably impossible using classical communication. Building a quantum network is an interdisciplinary effort bringing together computer science, physics, and engineering. I am in a unique position in computer science, since I have recently joined QuTech where I have direct access to small quantum devices - bringing me tantalizingly close to seeing such networks realized. As with early classical networks, it is difficult to predict where our journey will end, but my research will join theory and experiment to move forward.

The research proposed in BioAqua aims at breaking new ground in the area of catalysis by enabling water-driven biocatalytic redox reactions. Oxidoreductases are a class of enzymes with a very high potential for preparative organic synthesis, which is why they are increasingly used also on industrial scale. The current state-of-the-art, however, utilises valuable high-energy cosubstrates (such as glucose and alcohols) to promote oxidoreductases. Thereby valuable (and edible) building blocks are wasted as sacrificial electron donors which will have significant ethical (food for chemistry), economic and environmental consequences once redox biocatalysis is applied at scale. I envision utilizing water as sacrificial electron donor. Hence, a simple and abundant cosubstrate will be used instead of the valuable cosubstrates mentioned above. This will be a completely new approach in (bio)catalysis. However, activating water for this purpose water is extremely difficult due to its kinetic and thermodynamic inertness. To solve this problem, I propose using visible light as external energy source and advanced chemical catalysts to facilitate water oxidation. The electrons liberated in this process will be made available (for the first time) to promote oxidoreductases-catalysed transformations. BioAqua represents an entirely new paradigm in catalysis as I will bridge the gap between photocatalysis and biocatalysis enabling cleaner and more efficient reaction schemes.

The target of climate-neutral aviation has led to a strong increase in the size of new propulsion systems, resulting in their lowered distance to the airframe components. This causes new aerodynamic interactions with heavy distortion of the turbulent flow, determining unpredictable sources of noise. Mitigating this interaction noise would allow to deploy radically new aircraft configurations capable of reducing up to 20% of the current aviation emissions. While studies from literature have tried to correct discrepancies larger than 10 dB from acoustic predictions by a-posteriori tuning the models to very specific flow patterns, recent results from my team have shed light on the physics behind the unpredictability of these noise sources. Results hinted that the geometrical deformation of the turbulent flow from its original pattern might explain the origin of interaction noise. To solve this puzzle, with MORASINA I aim at first understanding how the flow and the turbulence are distorted in archetypal interactions between rotating and stationary aerodynamic objects. My objective is to discover the unknown mathematical formulation to model this distortion mechanism and to use it to create the first holistic acoustic model for predictions of interaction noise. By innovatively describing the interaction mechanisms with mathematical functions related to the geometrical distortion of the flow, I will find an answer to whether different flow fields can be assimilated in a unique fundamental flow pattern. With this knowledge, I will create the first acoustic model based on a mathematical “flow twin” to accurately predict interaction noise. For maximum impact on the society, I will extend the model to equipollent interaction mechanisms with a neural network approach trained on the results, allowing the use of the prediction framework for reducing interaction noise in the design of the next generation of zero-emission and silent aircraft.

Our immune system provides a formidable barrier to the many microbial pathogens that we encounter every day. Yet, many pathogens have the ability to avert this barrier by invading the host cell and seeking shelter inside a phagosome whose membrane physically prevents the pathogen from being recognized and eliminated. Cell-autonomous immunity is a part of the innate immune system that fights off such pathogens. Among the antimicrobial effectors mobilized by this immune response are the Guanylate-Binding Proteins (GBPs). GBPs form dynamic supramolecular assemblies that promote lysis of phagosomes and, thus, killing of pathogens. Despite their central importance, we know very little about the molecular mechanisms of GBPs. Two fundamental questions are: (1) What is the structure and composition of GBP assemblies on membranes?, and (2) Once assembled, how do the GBPs structurally rearrange to reshape and rupture the phagosome's membrane? These questions remain unanswered because structural biology has been lacking methods for determining dynamically changing structures of proteins that are assembled in complex environments such as phagosomes. Here, I propose to take a two-pronged approach to address these questions: first, I will use cryo-EM and (single-molecule) fluorescence microscopy to elucidate the interactions and conformational changes involved in GBP oligomerization on model membranes. Second, I will visualize this pathway on native phagosomes using a recently developed ex vivo reconstitution system unique to my laboratory. By determining how GBP assemblies form on phagosome membranes, how they reshape the membrane so that it ruptures, and how these processes can be regulated and inhibited, I will derive a mechanistic model of a key effector function that cells employ to combat disease-causing pathogens. More broadly, my study will establish a novel approach for integrative imaging that will be applicable to a wide range of dynamic molecular assemblies in cells.