Reperfusion Injury Field 2D: Diffusion-Limited Reoxygenation

This is the 2D companion to the 3D organ-transplant reperfusion sim: the same xanthine-oxidase free-radical kinetics, computed on a genuine 2D reaction-diffusion grid instead of a cloud of independently reperfused cells. Oxygen enters only at the vascular surface and must diffuse inward across the tissue cross-section before the free-radical burst can run at each patch, so a real reoxygenation front sweeps from the surface toward the avascular core — visibly slower and more damaging deep in the tissue, exactly the watershed-zone effect seen in real grafts. Reactive oxygen species also spread a short paracrine distance between neighboring patches. Tune cold ischemia time, antioxidant defense and the xanthine-oxidase inhibitor to see how they reshape both the reaction and how far the injury front reaches before it stalls.