4072
Co-axial measurements of infrared radiation emitted from the melt pool showed correlation to the presence of O2 or CO2 in the gas mixture .
 concept or principle: infrared; material: melt pool; material: CO2; concept or principle: gas
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: infrared, melt pool, CO2, gas 
Answer:
 concept or principle: infrared; material: melt pool; material: CO2; concept or principle: gas