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Alkali treatment was initially introduced by Kim to improve the bioactivity of Ti implants owing to a biologically active bone-like apatite layer on Ti surface .
 manufacturing process: Alkali treatment; machanical property: bioactivity; application: Ti implants; material: bone-like apatite layer; material: Ti; concept or principle: surface
Please list all entity words in the text that fit the category.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} 
Answer:
 manufacturing process: Alkali treatment; machanical property: bioactivity; application: Ti implants; material: bone-like apatite layer; material: Ti; concept or principle: surface