Six New York-based community hospitals and five independent pediatrician groups have agreed to participate in a planned regional network offering low-cost preventive health services to the uninsured. Niagara Falls Memorial Medical Center, Medina Memorial Health Care System and MedFirst Urgent Care have signed long-term agreements to participate in the new Health Transaction Network. Bertrand Chaffee Hospital also gave a verbal commitment, officials said. The Health Transaction Network is aimed at the uninsured, the underinsured, college students, young adults aged 23 to 35, and those who must meet high deductibles before regular insurance kicks in.