Q: the average life expectancy of an aortic valve bioprostheses is 10 to 15 years. bioprostheses rapidly calcify, degenerate and narrow in young patients.
A: The average life expectancy of an aortic valve bioprostheses is 10 to 15 years. Bioprostheses rapidly calcify, degenerate and narrow in young patients.

Q: for those with continued severe symptoms, surgery can help alleviate the leg symptoms by creating more space for the nerve roots.
A: For those with continued severe symptoms, surgery can help alleviate the leg symptoms by creating more space for the nerve roots.

Q: lots of small improvements and bug fixes
A: Lots of small improvements and bug fixes

Q: by this time, however, he was in dorpat having been appointed to the chair of geography, ethnology and statistics in 1874.
A:
By this time, however, he was in Dorpat having been appointed to the chair of geography, ethnology and statistics in 1874.