Negative refraction of a three-dimensional metallic photonic crystal

A metamaterial with a negative effective index of refraction is made from a three-dimensional hexagonal lattice photonic crystal with a metallic basis embedded in foam. It has been simulated with Ansoft HFSSTM in a frequency range from 7.0 to 12.0 GHz. Simulated results tested experimentally and negative refraction verified in some frequencies. Experimental results are in excellent agreement with simulations

Low density polyurethane microcellular elastomer

The present invention is concerned with a process for producing polyurethane foam moldings having a density of200 to 500 g/dm3, wherein (a) polyisocyanate prepolymer obtainable by reacting at least one organic polyisocyanate (al), at least one first polyesterol (a2) and at least one polyetherol (a3) obtained from the alkoylation of a starter molecule with alkylenoxide compris­ ing ethylene oxide wherein the polyetherol (a3) has a hydroxyl number in the range of20 to 65 mg KOH/g, a number average mo­ lecular weight of 2000 to 6000, a functionality of I.7 to 3.0 and a content of ethylenoxide units in the range of 13 to 30 % by weight based on the total weight of the polyetherol (a3) and wherein the content of the polyetherol (a3), based on the total weight of the or­ ganic polyisocyanate prepolymer (a), is in the range of 3 to 15 % by weight, is mixed with (b) at least one second polyesterol, (c) blowing agent and optionally (d) chain extender and/or crosslinker, (e) catalyst and (f) other auxiliaries and/or additives to form a re­ action mixture, the latter is introduced into a mold and allowed to react to form a polyurethane foam molding. The present invention further concerns a polyurethane foam moldings obtained from a process according to the invention and the use of a polyurethane foam moldings according to the invention as shoe sole