Russia and Turkey refuse to back down in row over jet downing

By Nick Tattersall and Vladimir Soldatkin ISTANBUL/NIZHNY TAGIL, Russia (Reuters) - Russia sent an advanced missile system to Syria on Wednesday to protect its jets operating there and pledged its air force would keep flying missions near Turkish air space, sounding a defiant note after Turkey shot down a Russian fighter jet. The downing of the jet on Tuesday was one of the most serious publicly acknowledged clashes between a NATO member and Russia for half a century, and further complicated int