The follicular phase begins with an increase in follicle-stimulation hormone (FSH), which causes increases in luteinizing hormone (LH) and gonadotropin-releasing hormone (GnRH). Concurrent increases in estrogen levels cause increases in progesterone, stimulating proliferation of the endometrium.
Examples of insulators include plastics, Styrofoam, paper, rubber, glass and dry air. The division of materials into the categories of conductors and insulators is a somewhat artificial division. It is more appropriate to think of materials as being placed somewhere along a continuum.
Chemicals are used to separate lignin from the cellulose fibers, leaving a pulp mixture that can make stronger papers. Depending on what type of paper is desired, the pulp mixture might need to be bleached to create whiter paper. Papermakers use a variety of chemicals to bleach pulp to the color they want.