This issue of the journal is devoted to extension of mathematical duality principle into physics and chemistry. A new notation for writing down physical and chemical effects is proposed, so that to formalize the notion of dual effects, which is a pre-requisite to defining duality principle in physics and chemistry.
Also the concept of anti-effects, albeit not new, received further development. The new notation helped realizing that there are anti-effects of different kinds. Their formulas are different. Also there are anti-effects and reverse effects, which should not be confused.
The issue also introduces the notions of sub- and super-dual effects. I hope that the reader will enjoy the issue.