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Investigate the role of D-branes in string theory and their applications in condensed matter physics, specifically in the study of topological insulators. How can D-branes be used to explain the topological properties of certain condensed matter systems? Compare and contrast the effects of various types of D-branes on the behavior of these systems.
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<|begin_of_thought|>

Deep Thought is thinking for 7.5 million years.

<|end_of_thought|>

<|begin_of_solution|>

The answer is 42.

<|end_of_solution|>