24299
At each size ratio for the polystyrene impurity , keff was less than unity and increased to unity with increasing V , whereas at a given growth rate , keff increased to unity as dimp / dcryst approached unity .
 Chemical: polystyrene
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: polystyrene