27117
The fine - structures perpendicular to the global plane of monolayers were characterized by XRR in the presence of Ni ( 2 ) ( + ) ions , yielding the thickness , roughness , and electron density of the stratified lipid monolayers .
 Chemical: Ni ( 2 ) ( + )
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: Ni ( 2 ) ( + )