Radioactive Tracer Definition

Radioactive Tracer Definition A radioactive tracer is a radioactive element or compound added to material to monitor the materials distribution as it progresses through a system. The use of a radioactive tracer is called radiolabeling, which is one form of isotopic labeling. Radioactive Tracer Uses Radioactive tracers form the basis of some medical imaging systems, such as PET scans. Radiolabeling is used in research to trace the path of elements in biochemical reactions and cells. Radioisotopes are also used to track the flow of fluids, particularly in the petroleum and natural gas industry. Examples of Radioactive Tracers Usually, the isotopes chosen for use as radioactive tracers have a short half life. Thus, they are produced via nuclear reactions. Examples of commonly used radioactive tracers include tritium, carbon-11, carbon-14, oxygen-15, fluorine-18, phosphorus-32, sulfur-35, technetium-99, iodine-123, and gallium-67. Sources Fowler, J. S.; Wolf, A. P. (1982). The synthesis of carbon-11, fluorine-18 and nitrogen-13 labeled radiotracers for biomedical applications. Nucl. Sci. Ser. Natl Acad. Sci. Natl Res. Council Monogr. 1982.Rennie, M. (1999). An introduction to the use of tracers in nutrition and metabolism. Proc Nutr Soc. 58 (4): 935–44. doi:10.1017/S002966519900124X

Chalchiuhtlicue - Aztec Goddess of Rivers and Oceans

Chalchiuhtlicue - Aztec Goddess of Rivers and Oceans Chalchiuhtlicue (Chal-CHEE-ooh-tlee-quay), whose name means She of the Jade Skirt, was the Aztec goddess of water as it collects on the earth, such as rivers and oceans, and so was considered by the Aztecs the patroness of navigation. She was one of the most important deities, as protector of childbirth and newborns. Chalchiuhtlicue was linked to the rain god Tlaloc, in some sources as his wife and feminine counterpart. In others, she is Tlalocs sister and some scholars suggest she was Tlaloc himself in a separate guise. She was also associated with the Tlaloques, Tlalocs brothers or perhaps their children. In some sources, she is described as the wife of the Aztec god of fire god Huehueteotl-Xiuhtecuhtli. She is also associated with different mountains in different Aztec communities. All rivers come from the mountains in the Aztec universe, and the mountains are like jars (ollas) filled with water, that spring from the womb of the mountain and wash down to water and protect the people. A Watery Rule According to the Spanish conquistador and priest Fray Diego Duran, Chalchiuhtlicue was universally revered by the Aztecs. She governed the waters of the oceans, springs, and lakes, and as such she appeared in both positive and negative guises. She was seen as a positive source who brought full irrigation canals for growing maize  when she was associated with the corn goddess Xilonen. When displeased, she brought empty canals and drought and was paired with the dangerous snake goddess Chicomecoatl. She was also known for creating whirlpools and big storms making water navigation tricky. She was also the goddess who ruled over and destroyed the previous world, known in the Aztec mythology as the Fourth Sun, the Mexica version of the Deluge Myth. The Aztec universe was based on the Legend of the Five Suns, which said that before the current world (the Fifth Sun), the various gods and goddesses made four attempts to create versions of the world and then destroyed them in order. The fourth sun (called Nahui Atl Tonatiuh or 4 Water) was ruled by Chalchiutlicue as a world of water, where fish species were marvelous and abundant. After 676 years, Chalchiutlicue destroyed the world in a cataclysmic flood, transforming all the humans into fish. Chalchiuhtlicues Festivals As the partner of Tlaloc, Chalchiuhtlicue pertained to the Aztec group of gods supervising water and fertility. To these deities was dedicated a series of ceremonies called Atlcahualo, which lasted the entire month of February. During these ceremonies, the Aztecs performed many rituals, usually on the mountain tops, where they sacrificed children. For the Aztec religion, the tears of children were considered good omens for abundant rain. The festival month of February dedicated to Chalchiuhtlicue was the sixth month of the Aztec year called Etzalcualiztli. It took place during the rainy season when the fields were beginning to ripen. The festival was conducted in and around the lagoons, with some objects ritually deposited within the lagoons. The festival involved fasting, feasting, and auto-sacrifice on the part of the priests, and the human sacrifice of war captives, women, and children some of which were dressed in the costume of Chalchiuhtlicue and Tlaloc. Offerings included maize, the blood of quail birds and resins made of copal and latex. Children were also sacrificed to Chalchiuhtlicue at the height of the dry season just before the rains were due; during the festivals dedicated to Chalchiuhtlicue and Tlaloc, a young boy would be sacrificed to Tlaloc on a mountaintop outside of Tenochtitlan, and a young girl would be drowned in Lake Texcoco at Pantitlan, where whirlpools were known to occur. Chalchiuhtlicues Images The goddess Chalchiuhtlicue is often illustrated in the pre-Columbian and colonial period books called codices as wearing a blue-green skirt, as her name illustrates, from which flows a long and abundant stream of water. Sometimes new-born children are portrayed floating in this water flow. She has black lines on her face and usually wears a jade nose-plug. In Aztec sculpture and portraits, her statues and images are often carved out of jade or other green stones. She is occasionally shown wearing Tlalocs mask. The allied Nahuatl word chalchihuitl means drop of water and sometimes refers to jade. The word is also used in connection with Tlalocs goggles, which may themselves be a symbol of water. In the Codex Borgia, Chalchiuhtlicue is wearing a serpent headdress and dress ornaments with the same markings as Tlaloc, and her half-moon nose ornament is the serpent itself, marked with stripes and dots. Sources Edited and updated by K. Kris Hirst. Almere Read K, and Gonzalez JJ. 2000. Mesoamerican Mythology: A Guide ot the Gods, Heroes, Rituals, and Beliefs of Mexico and Central America. Oxford: Oxford University Press.Berdan FF. 2014. Aztec Archaeology and Ethnohistory. New York: Cambridge University Press.Brundage BC. 1983. The Fifth Sun: Aztec Gods, Aztec Worlds. Austin: University of Texas Press.Carlson JB. 2015. The Maya Deluge Myth and Dresden Codex Page 74. In: Dowd AS, and Milbrath S, editors. Cosmology, Calendars, and Horizon-Based Astronomy in Ancient Mesoamerica. Boulder: University Press of Colorado. p 197-226.Garza Gà ³mez I. 2009. De Calchiuhtlicue, Diosa de rà ­os, lagunas y manantiales. El Tlacuache: Patrimonio de Morelos 2009:1-4.Heyden D. 1983. Water symbols and eye rings in the Mexican codices. Indiana 8:41-56.Leon-Portilla M, and Davis JE. 1963. Aztec Thought and Culture: A Study of the Ancient Nahuatl Mind. Norman: University of Oklahoma Press.Taube K. 1993. Aztec and Maya Myths. Fourth Edition. Universi ty of Texas Press, Austin, Texa.s Van Tuerenhout DR. 2005. The Aztecs. New Perspectives, ABC-CLIO Inc. Santa Barbara, CA; Denver, CO and Oxford, England.