Urban road networks -- Spatial networks with universal geometric features? A case study on Germany's largest cities

Urban road networks have distinct geometric properties that are partially determined by their (quasi-) two-dimensional structure. In this work, we study these properties for 20 of the largest German cities. We find that the small-scale geometry of all examined road networks is extremely similar. The object-size distributions of road segments and the resulting cellular structures are characterised by heavy tails. As a specific feature, a large degree of rectangularity is observed in all networks, with link angle distributions approximately described by stretched exponential functions. We present a rigorous statistical analysis of the main geometric characteristics and discuss their mutual interrelationships. Our results demonstrate the fundamental importance of cost-efficiency constraints for in time evolution of urban road networks.Comment: 16 pages; 8 figure

Assessment of Fibrin-Based Hydrogels Containing a Fibrin-Binding Peptide to Tune Mechanical Properties and Cell Responses

Fibrin-based hydrogels are used as scaffolds in tissue engineering and regenerative medicine due to their biocompatibility, low cell toxicity, autologous production, and relevance for wound healing and clot formation. The availability of fibrinogen as well as its unique mechanical behavior exhibiting nonlinear elasticity makes it suitable for the fabrication of hydrogels. However, the broad application of fibrin hydrogels in biomaterials still faces challenges in terms of gel shrinkage and degradation processes. This can be addressed through the modulation of the hydrogels'r chemical and mechanical properties. In the present work, it is demonstrated that fibrin-based hydrogels with adjustable mechanical properties and controllable degradation profiles can be fabricated through the addition of fibrin-binding peptides. The cyclic peptide X2CXYYGTCLX (Tn7) is used, binding to fibrin by noncovalent supramolecular interactions. These new hydrogels exhibit no toxicity and reduced degradation rate at the same time supporting cell proliferation. Tn7 peptides significantly increase the Young's Modulus and mechanical stiffness as well as fibrin fiber thickness and inter-fiber crosslinking in hydrogels. In conclusion, hydrogels with optimized mechanical properties and controllable degradation profiles that can be advantageous for further approaches in tissue regeneration, cell-based therapies, or clinical treatment options are produced