Majid Shahriyari became an Iranian martyr while he was driving to work on an autumn day in Tehran. As he made his way along Artesh Boulevard, an explosive device ripped through his car. The 45-year-old was a devout man: Iranians would describe him as a Hizbollahi, a person fiercely loyal to the country’s Islamic system and easily identified by his unshaven face and simple clothes. But Shahriyari also stood out for another reason. He was one of Iran’s leading atomic scientists, an expert on nuclear chain reactions.