With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Istanbul is thought of as an important node in the global economic system.
text_B: Lo-Ex is an aluminium alloy with a very small thermal expansion co-efficient .. aluminium alloy. aluminium alloy. It contains approximately 14 per cent silicon , 2 per cent nickel , and 1 per cent each of copper and magnesium .. silicon. silicon. nickel. nickel. copper. copper. magnesium. magnesium
not_related.