Metals, Rare Earth: A group of elements that include SCANDIUM; YTTRIUM; and the LANTHANOID SERIES ELEMENTS. Historically, the rare earth metals got their name from the fact that they were never found in their pure elemental form, but as an oxide. In addition they were very difficult to purify. They are not truly rare and comprise about 25% of the metals in the earth's crust.Neodymium: Neodymium. An element of the rare earth family of metals. It has the atomic symbol Nd, atomic number 60, and atomic weight 144.24, and is used in industrial applications.Ytterbium: Ytterbium. An element of the rare earth family of metals. It has the atomic symbol Yb, atomic number 70, and atomic weight 173. Ytterbium has been used in lasers and as a portable x-ray source.Dysprosium: Dysprosium. An element of the rare earth family that has the atomic symbol Dy, atomic number 66, and atomic weight 162.50. Dysprosium is a silvery metal used primarily in the form of various salts.Samarium: Samarium. An element of the rare earth family of metals. It has the atomic symbol Sm, atomic number 62, and atomic weight 150.36. The oxide is used in the control rods of some nuclear reactors.Scandium: Scandium. An element of the rare earth family of metals. It has the atomic symbol Sc, atomic number 21, and atomic weight 45.Metals: Electropositive chemical elements characterized by ductility, malleability, luster, and conductance of heat and electricity. They can replace the hydrogen of an acid and form bases with hydroxyl radicals. (Grant & Hackh's Chemical Dictionary, 5th ed)Cerium: An element of the rare earth family of metals. It has the atomic symbol Ce, atomic number 58, and atomic weight 140.12. Cerium is a malleable metal used in industrial applications.Yttrium: An element of the rare earth family of metals. It has the atomic symbol Y, atomic number 39, and atomic weight 88.91. In conjunction with other rare earths, yttrium is used as a phosphor in television receivers and is a component of the yttrium-aluminum garnet (YAG) lasers.Europium: Europium. An element of the rare earth family of metals. It has the atomic symbol Eu, atomic number 63, and atomic weight 152. Europium is used in the form of its salts as coatings for cathode ray tubes and in the form of its organic derivatives as shift reagents in NMR spectroscopy.Silica Gel: A non-crystalline form of silicon oxide that has absorptive properties. It is commonly used as a desiccating agent and as a stationary phase for CHROMATOGRAPHY. The fully hydrated form of silica gel has distinct properties and is referred to as SILICIC ACID.Digestive System Physiological Phenomena: Properties and processes of the DIGESTIVE SYSTEM as a whole or of any of its parts.Lanthanum: Lanthanum. The prototypical element in the rare earth family of metals. It has the atomic symbol La, atomic number 57, and atomic weight 138.91. Lanthanide ion is used in experimental biology as a calcium antagonist; lanthanum oxide improves the optical properties of glass.Magnets: Objects that produce a magnetic field.Cottonseed Oil: Oil obtained from the seeds of Gossypium herbaceum L., the cotton plant. It is used in dietary products such as oleomargarine and many cooking oils. Cottonseed oil is commonly used in soaps and cosmetics.Iron Isotopes: Stable iron atoms that have the same atomic number as the element iron, but differ in atomic weight. Fe-54, 57, and 58 are stable iron isotopes.Gastrointestinal Transit: Passage of food (sometimes in the form of a test meal) through the gastrointestinal tract as measured in minutes or hours. The rate of passage through the intestine is an indicator of small bowel function.Oxides: Binary compounds of oxygen containing the anion O(2-). The anion combines with metals to form alkaline oxides and non-metals to form acidic oxides.Soil: The unconsolidated mineral or organic matter on the surface of the earth that serves as a natural medium for the growth of land plants.Metals, Alkaline Earth: Metals that constitute the group 2 (formerly group IIa) of the periodic table.Evolution, Planetary: Creation and development of bodies within solar systems, includes study of early planetary geology.Exobiology: The interdisciplinary science that studies evolutionary biology, including the origin and evolution of the major elements required for life, their processing in the interstellar medium and in protostellar systems. This field also includes the study of chemical evolution and the subsequent interactions between evolving biota and planetary evolution as well as the field of biology that deals with the study of extraterrestrial life.Evolution, Chemical: Chemical and physical transformation of the biogenic elements from their nucleosynthesis in stars to their incorporation and subsequent modification in planetary bodies and terrestrial biochemistry. It includes the mechanism of incorporation of biogenic elements into complex molecules and molecular systems, leading up to the origin of life.