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The hierarchical microstructure includes the melt pools and slightly elongated columnar grains at the micron scale , cellular structures decorated with a high density of dislocations at the sub-micron scale and oxides at the nanoscale .
 concept or principle: microstructure; material: melt pools; machanical property: columnar grains; engineering feature: micron; engineering feature: cellular structures; machanical property: density; concept or principle: dislocations; engineering feature: sub-micron; material: oxides
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
 Entities: microstructure, melt pools, columnar grains, micron, cellular structures, density, dislocations, sub-micron, oxides 
Answer:
 concept or principle: microstructure; material: melt pools; machanical property: columnar grains; engineering feature: micron; engineering feature: cellular structures; machanical property: density; concept or principle: dislocations; engineering feature: sub-micron; material: oxides