University of Würzburg

One of the most important principles of J.-Y. Girard's Π 2 1 -logic is induction on dilators. In particular, Girard used this principle to construct his famous functor Λ. He claimed that the totality of Λ is equivalent to the set existence axiom of Π 1 1 -comprehension from reverse mathematics. While Girard provided a plausible description of a proof around 1980, it seems that the very technical details have not been worked out to this day. A few years ago, a loosely related approach led to an equivalence between Π 1 1 -comprehension and a certain Bachmann-Howard principle. The present paper closes the circle. We relate the Bachmann-Howard principle to induction on dilators. This allows us to show that Π 1 1 -comprehension is equivalent to the totality of a functor J due to P. Päppinghaus, which can be seen as a streamlined version of Λ.

The vasculature within the bone marrow plays a pivotal role in shaping the hematopoietic environment, significantly influencing the development and function of blood cells. However, the intricate shifts in vascular architecture, especially as the body ages or under physiological stress, remain largely uncharted territory. In this study, we explored these vascular dynamics using light sheet fluorescence microscopy paired with advanced image analysis, focusing on both large, CD31hi, and smaller, CD105+, vessels within murine femora. We compared young adult (aged 8 weeks) mice with moderately aged (52 weeks) mice, and assessed the impact of hematological stress induced by previous blood sampling. Our findings revealed an intriguing balance of resilience and adaptability: larger vessels show a remarkable structural stability across ages, whereas smaller vessels undergo pronounced age-associated remodeling. In aged mice, vascular branching complexity surges, with higher branch density and narrower vessel diameters in specific femur regions, clear hallmarks of vascular aging. Interestingly, even after previous blood sampling, the bone marrow vasculature maintains its integrity, hinting at a robust resilience to hematological stress. This resilience underscores the potential to streamline research models by reusing animals for both cell isolation and histology, supporting the 3R principles (replacement, reduction, and refinement) to minimize animal use. These insights into the stability, adaptability, and regional-specific remodeling of bone marrow vasculature, highlighting its remarkable resilience, provide a deeper understanding of age-related vascular remodeling, and offer valuable implications for experimental design in hematopoiesis research.

Reliable odometry in highly dynamic environments remains challenging when it relies on ICP-based registration: ICP assumes near-static scenes and degrades in repetitive or low-texture geometry. We introduce Dynamic-ICP, a Doppler-aware registration framework. The method (i) estimates ego translational velocity from per-point Doppler velocity via robust regression and builds a velocity filter, (ii) clusters dynamic objects and reconstructs object-wise translational velocities from ego-compensated radial measurements, (iii) predicts dynamic points with a constant-velocity model, and (iv) aligns scans using a compact objective that combines point-to-plane geometry residual with a translation-invariant, rotation-only Doppler residual. The approach requires no external sensors or sensor–vehicle calibration and operates directly on FMCW LiDAR range and Doppler velocities. We evaluate Dynamic-ICP on three real-world datasets-HeRCULES, HeLiPR, AevaScenes-focusing on highly dynamic scenes. Dynamic-ICP consistently improves rotational stability and translation accuracy over the state-of-the-art methods. To encourage further research, the code is available at: <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://github.com/JMUWRobotics/Dynamic-ICP</uri>.

Routine augmentation of pedicle screws in standard clinical practice is performed using polymethylmethacrylate (PMMA) cement. However, owing to its high compressive strength and high Young's modulus, this material acts more as a stiffener in the spine than as a suitable replacement for compressed cancellous bone. Adjacent fractures caused by this represent a common clinical problem. A new experimental magnesium phosphate cement seems more suitable for this purpose, as it shows promising biomechanical properties and has been proven to be injectable via long cannulated systems. However, the application of this material has not yet been explored or quantified. Fenestrated pedicle screws were inserted into polyurethane bone blocks of different densities and augmented with experimental magnesium phosphate cement. This was followed by biomechanical testing in a realistic loading scenario. In addition, the injection force required for augmentation was quantified depending on the syringe type. Cement augmentation was possible in all bone blocks used and consistently had a positive effect on the biomechanical stability of fenestrated pedicle screws. The size of this effect varied depending on the density of the bone blocks used. No cutoff value could be identified at which augmentation should be performed. The novel experimental ready-to-use formulation of magnesium phosphate cement reliably enabled cement augmentation of fenestrated pedicle screws and consistently resulted in improved biomechanical stability. These findings suggest that a biocompatible and degradable bone cement with suitable biomechanical properties may represent a future alternative for spinal augmentation.

Photon-recoil-based actuation enables maneuvering of micro- and nanoscale objects without beam steering or tight focusing, mitigating system complexity and photodamage. Recent light-driven microdrones achieved full control in two dimensions using multiple laser fields; however, for many applications, sacrificing degrees of freedom allows substantial miniaturization and improved propulsion efficiency. Here, we demonstrate sub-micrometer nanorobots actuated by a plasmonic directional antenna that simultaneously provides propulsion force and orientation control. The nanorobots reach propulsion speeds up to 50 μm/s, with their motion direction intrinsically locked perpendicular to the linear polarization axis. Circularly polarized light pulses lift the resulting twofold orientational degeneracy through spin-momentum transfer. Using opto-thermophoretic forces, nanorobots efficiently capture, transport, reversibly assemble, and release bacteria. By sequencing linear and circular polarization states, they execute complex, high-precision trajectories to systematically sweep defined regions, functioning as light-driven robotic cleaners. This work expands the capabilities of nanorobots for biological manipulation and high-speed, localized sensing.

Regulatory T (Treg) cells are central mediators of immune tolerance and are generally considered to rely predominantly on mitochondrial metabolism rather than glucose-driven glycolysis. To define the role of glucose metabolism in Treg cells, we investigated the contribution of the hexose transporters GLUT1 and GLUT3. Genetic ablation of GLUT1 in T cells or selectively in Treg cells had minimal impact on Treg cell numbers, phenotype or immune homeostasis, indicating that GLUT1 is largely dispensable in this lineage. By contrast, deletion of GLUT3 in T cells resulted in a marked reduction in Treg cell numbers. However, it remained unclear whether this reduction reflected diminished IL-2 production by GLUT3-deficient conventional T cells or a cell-intrinsic requirement for GLUT3 in Treg cells. To investigate this, we generated mice with Treg cell-specific deletion of GLUT3. These animals developed severe systemic inflammation accompanied by lethal cellular and humoral autoimmunity. Mechanistically, GLUT3-deficient Treg cells exhibited reduced glycolytic activity and mitochondrial respiration, leading to impaired suppressive function and defective effector and follicular Treg cell differentiation. Collectively, our findings demonstrate a non-redundant requirement for GLUT3 in Treg cell metabolic fitness and immune regulation, refining the prevailing view that Treg cells operate largely independently of glucose metabolism. Our data further suggest that therapeutic strategies targeting glucose uptake and glycolysis in autoimmune and inflammatory diseases should account for potential adverse effects on Treg cell-mediated immune tolerance.

Molecular crystals of apolar π-conjugated hydrocarbons exhibit pronounced solution-to-crystal spectral shifts, yet the interplay between band formation and exciton coupling remains unclear. Adamantylethynyl-pyrene derivatives were designed to adopt unidirectional crystal packing, providing a model system to disentangle these effects. Large redshifts of up to -203 meV are observed, which cannot be explained by exciton coupling alone but require a substantial contribution from band dispersion, identified here as a narrowing of frontier crystal orbital energy levels. The remaining discrepancies between experiment and the full-coherence limit correspond to coherence lengths of four to seven molecules, consistent with literature values. These results provide a basis for interpreting more complex organic crystalline materials and highlight the need for a more comprehensive understanding of the photophysical properties of molecular crystals.