4-Hy­droxy-N′-[1-(2-hy­droxy­phen­yl)ethyl­idene]benzohydrazide

In the title compound, C15H14N2O3, there is an intra­molecular O—H⋯N hydrogen bond and the dihedral angle between the two aromatic rings is 13.9 (3)°. In the crystal structure, mol­ecules are stabilized by inter­molecular O—H⋯O and N—H⋯O hydrogen bonds

One-way cloak based on nonreciprocal photonic crystal

We propose a physical concept of non-reciprocal transformation optics, by which a one-way invisible cloak is designed. The one-way invisible cloak is made of a coordinate-transformed nonreciprocal photonic crystal, showing a perfect cloaking for wave incident from one direction but acting as a perfect reflector for wave from the counter direction. The proposed design shows a high promise of applications in military, as protecting the own information to be detected but efficiently grabbing the information from the “enemy” side