It is associated with the production of eggs and preparing the uterus for the implantation of fertilised eggs. The menstrual cycle occurs over a period of about 28 days. The changes during the cycle are due to four hormones, progesterone, oestrogen, FSH (follicle stimulating hormone) and LH (luteinising hormone).
Examples include wood and paper. Combustible liquids have a flashpoint at or above 100 degrees F but below 200 degrees F. This definition does not include mixtures containing one or more components with a flashpoint at or above 200 degrees F. This group of liquids can also be identified by class.
acidity is one of the most important causes of damage in paper as it weakens and eventually destroys the fibres that make up the paper as a result paper made from groundwood pulp breaks down rapidly from within the first sign of this is that the paper becomes yellow then brown and increasingly brittle for example newspapers are made from groundwood pulp and the acids in the paper cause it to discolour and become brittle breakdown of the newspaper from within speeds up with exposure to light and or high humidity