fixed typo in Deff = Dab e / tau

examples/applications/effective_diffusivity_and_tortuosity.ipynb

@@ -16,7 +16,7 @@
     "In this example we show how to find the effective diffusivity and tortuosity of a cubic network. A similar procedure can be used on more complicated extracted networks from Porespy. The effective diffusivity is defined as the diffusion coefficient multiplied by the porosity and divided by the tortuosity. \n",
     "\n",
     "$$\n",
-    "D_{AB} = D_{eff}\\frac{\\epsilon}{\\tau}\\\\\n",
+    "D_{eff} = D_{AB}\\frac{\\epsilon}{\\tau}\\\\\n",
     "$$\n",
     "\n",
     "The tortuosity is an attempt to correct for the windy path of matter moving through a porous substance. The classical definition is the actual length divided by the direct length.  In reality, there are many actual pathways that matter could move through. This means that the actual length should more precisely be thought of as the average path length.\n",