The number of Alabamians signing up for the federally operated health insurance marketplace jumped significantly in the past month. The Department of Health and Human Services says more than 28,600 signed up through late December. Federal health officials said 58 percent of those who have signed up in Alabama are women. The biggest group signing up in Alabama is those 55 to 64 years old, in line with the national trend. In Alabama, 83 percent of those who signed up qualified for financial assistance. A recent report from the Kaiser Family Foundation says about 198,000 Alabamians are eligible for federal subsidies to purchase health insurance under the federal health care law.