Hervé This, the famous French scientist who coined the term “molecular gastronomy,” yesterday made a rare New York appearance, lecturing first at the Institute of Culinary Education, then at NYU before the Experimental Cuisine Collective, and finally before the Culinary Historians of America at the soon-to-open Astor Center downtown. We were fascinated by This’s PowerPoint presentation, which featured food images, mathematical formulas, Venn diagrams, and images of classical artwork, all accompanied by gnomic, rambling commentary on the nature of things edible. (There seemed to be a lot of stuff about emulsification in there as well.) The truth is that we could make neither head nor tail of the talk, which apparently was totally different at each of the three appearances.