Pineapple Upside-Down Muffins

2 tablespoons chopped walnuts or pecans

1 10-ounce can pineapple slices

3/4 cup whole-wheat flour

3/4 cup all-purpose flour

2 teaspoons baking powder

1/2 teaspoon baking soda

1/4 teaspoon salt

1 tablespoon ground cinnamon

2 large eggs

1/2 cup packed light brown sugar

1/4 cup canola oil

2 tablespoons pineapple juice or orange juice

1 teaspoon vanilla extract

1 8-ounce can crushed pineapple (not drained)

1 cup grated carrot (1 large)

1/2 cup old-fashioned oats

3/4 cup raisins, preferably baking raisins (see Ingredient note)

1/4 cup chopped walnuts or pecans