Phenology is the study of recurring plant and animal life cycle stages, or phenophases, such as leafing and flowering of plants, maturation of agricultural crops, emergence of insects, and migration of birds. Many of these events are sensitive to climatic variation and change, and are simple to observe and record.
Polychlorinated biphenyls (PCBs) are a group of manmade chemicals. They are oily liquids or solids, clear to yellow in color, with no smell or taste. PCBs are very stable mixtures that are resistant to extreme temperature and pressure.
Ibb is a city in Yemen, the capital of Ibb Governorate, located about 117 kilometres northeast of Mocha and 194 kilometres south of Sana'a. A market town and administrative centre developed during the Ottoman occupation, it is one of the most important medium-sized cities in the country. It is situated on a mountain ridge, surrounded by fertile land. As of 2005, it had a population of 160,000.