A Newtown man, Donald S. Hammalian Jr., pleaded not guilty to child exploitation charges in Hartford on Monday. Hammalian, a registered sex offender, faces multiple counts, including receiving child pornography and coercing a minor into sending explicit material. Federal authorities say he used social media to communicate with minors while managing several accounts, some with over 100,000 followers. Hammalian’s criminal history includes prior convictions for child pornography, with the current charges carrying mandatory prison sentences