TASK DEFINITION: In this task, you are given a sentence from the research paper and your task is to classify the given sentence into the following categories: Background (Why is this problem important? What relevant works have been created before? What is still missing in the previous works? What are the high-level research questions? How might this help other research or researchers?), Purpose (What specific things do the researchers want to do? What specific knowledge do the researchers want to gain? What specific hypothesis do the researchers want to test?), Method (How did the researchers do the work or find what they sought? What are the procedures and steps of the research?), or Finding (What did the researchers find out? Did the proposed methods work? Did the thing behave as the researchers expected?). 
PROBLEM: it is important to recognize such findings in order to include infection with the H1N1 virus in the differential diagnosis of respiratory symptoms.

SOLUTION: finding

PROBLEM: It remains to be shown how such a restricted infection leads to demyelination.

SOLUTION: background

PROBLEM: Here , we first present the structure of the full-length Nsp13 helicase of SARS-CoV ( SARS-Nsp13 ) and investigate the structural coordination of its five domains and how these contribute to its translocation and unwinding activity.

SOLUTION:
purpose