Cryogenics Definition and Uses

Cryogenics Definition and Uses Cryogenics is defined as the scientific study of materials and their behavior at extremely low temperatures. The word comes from the Greek cryo, which means cold, and genic, which means producing. The term is usually encountered in the context of physics, materials science, and  medicine. A scientists who studies cryogenics is called a cryogenicist. A cryogenic material may be termed a cryogen. Although cold temperatures may be reported using any temperature scale, the Kelvin and Rankine scales are most common because they are absolute scales that have positive numbers. Exactly how cold a substance has to be to be considered cryogenic is a matter of some debate by the scientific community. The U.S. National Institute of Standards and Technology (NIST) considers cryogenics to include temperatures below  Ã¢Ë†â€™180  °C (93.15 K; −292.00  °F), which is a temperature above which common refrigerants (e.g., hydrogen sulfide, freon) are gases and below which permanent gases (e.g., air, nitrogen, oxygen, neon, hydrogen, helium) are liquids. There is also a field of study called high temperature cryogenics, which involves temperatures above the boiling point of liquid nitrogen at ordinary pressure (−195.79  °C (77.36 K; −320.42  °F), up to −50  °C (223.15 K; −58.00  °F). Measuring the temperature of cryogens requires special sensors. Resistance temperature detectors (RTDs) are used to take temperature measurements as low as 30 K. Below 30 K, silicon diodes are often used. Cryogenic particle detectors are sensors that operate a few degrees above absolute zero and are used to detect photons and elementary particles. Cryogenic liquids are typically stored in devices called Dewar flasks. These are double-walled containers that have a vacuum between the walls for insulation. Dewar flasks intended for use with extremely cold liquids (e.g., liquid helium) have an additional insulating container filled with liquid nitrogen. Dewar flasks are named for their inventor, James Dewar. The flasks allow gas to escape the container to prevent pressure buildup from boiling that could lead to an explosion. Cryogenic Fluids The following fluids are most often used in cryogenics: Fluid Boiling Point (K) Helium-3 3.19 Helium-4 4.214 Hydrogen 20.27 Neon 27.09 Nitrogen 77.36 Air 78.8 Fluorine 85.24 Argon 87.24 Oxygen 90.18 Methane 111.7 Uses of Cryogenics There are several applications of cryogenics. It is used to produce cryogenic fuels for rockets, including liquid hydrogen and liquid oxygen (LOX). The strong electromagnetic fields needed for nuclear magnetic resonance (NMR) are usually produced by supercooling electromagnets with cryogens. Magnetic resonance imaging (MRI) is an application of NMR that uses liquid helium. Infrared cameras frequently require cryogenic cooling. Cryogenic freezing of food is used to transport or store large quantities of food. Liquid nitrogen is used to produce fog for special effects and even specialty cocktails and food. Freezing materials using cryogens can make them brittle enough to be broken into small pieces for recycling. Cryogenic temperatures are used to store tissue and blood specimens and to preserve experimental samples. Cryogenic cooling of superconductors may be used to increase electric power transmission for big cities. Cryogenic processing is used as part of some alloy treatments and to facilitate low temperature chemical reactions (e.g., to make statin drugs). Cryomilling is used to mill materials that may be too soft or elastic to be milled at ordinary temperatures. Cooling of molecules (down to hundreds of nano Kelvins) may be used to form exotic states of matter. The Cold Atom Laboratory (CAL) is an instrument designed for use in microgravity to form Bose Einstein condensates (around 1 pico Kelvin temperature) and test laws of quantum mechanics and other physics principles. Cryogenic Disciplines Cryogenics is a broad field that encompasses several disciplines, including: Cryonics - Cryonics is the cryopreservation of animals and humans with the goal of reviving them in the future. Cryosurgery - This is a branch of surgery in which cryogenic temperatures are used to kill unwanted or malignant tissues, such as cancer cells or moles. Cryoelectronics - This is the study of superconductivity, variable-range hopping, and other electronic phenomena at low temperature. The practical application of cryoelectronics is called cryotronics. Cryobiology - This is the study of the effects of low temperatures on organisms, including the preservation of organisms, tissue, and genetic material using cryopreservation. Cryogenics Fun Fact While cryogenics usually involves temperature below the freezing point of liquid nitrogen yet above that of absolute zero, researchers have achieved temperatures below absolute zero (so-called negative Kelvin temperatures). In 2013 Ulrich Schneider at the University of Munich (Germany) cooled gas below absolute zero, which reportedly made it hotter instead of colder! Sources Braun, S., Ronzheimer, J. P., Schreiber, M., Hodgman, S. S., Rom, T., Bloch, I., Schneider, U. (2013) Negative Absolute Temperature for Motional Degrees of Freedom.  Science  339,  52–55.Gantz, Carroll (2015). Refrigeration: A History. Jefferson, North Carolina: McFarland Company, Inc. p. 227. ISBN 978-0-7864-7687-9.  Nash, J. M.  (1991) Vortex Expansion Devices for High Temperature Cryogenics. Proc. of the 26th Intersociety Energy Conversion Engineering Conference, Vol. 4, pp. 521–525.

Plot and Themes of J.R.R. Tolkiens Book The Hobbit

Plot and Themes of J.R.R. Tolkien's Book 'The Hobbit' The Hobbit: Or, There and Back Again was written by J.R.R. Tolkien as a childrens book and first published in Great Britain in 1937 by George Allen Unwin. It was published just before the outbreak of WWII in Europe, and the book acts as a prologue of sorts for the great trilogy, The Lord of the Rings. While it was originally conceived as a book for children, it has been accepted as a great work of literature in its own right. While The Hobbit was by no means the first fantasy novel, it was among the first to combine influences from multiple sources. Elements of the book draw from Norse mythology, classic fairy tales, Jewish literature, and the works of 19th century Victorian childrens authors such as George MacDonald (author The Princess and the Goblin, among others). The book also experiments with a variety of literary techniques including forms of epic poetry and song. Setting The novel takes place in the fictional land of Middle Earth, a complex fantasy world which Tolkien developed in detail. The book contains carefully drawn maps showing various parts of Middle Earth including the peaceful and fertile Shire, the Mines of Moria, the Lonely Mountain, and Mirkwood Forest. Each area of Middle Earth has its own history, characters, qualities, and significance. Main Characters The characters in The Hobbit include a wide range of fantasy creatures, most drawn from classical fairy tales and mythology. The hobbits themselves, however, are Tolkiens own creation. Small, home-loving people, hobbits are also called halflings. They are very similar to small human beings except for their very large feet. Some of the main characters in the book include: Bilbo Baggins, a quiet, unassuming Hobbit and the protagonist of the story.Gandalf, a wizard who initiates Bilbo’s journey with the dwarves. Gandalf causes Bilbo to set aside his reputation for cautious respectability and go on an adventure that will change the hobbit forever.Thorin Oakenshield, the leader of a group of 13 dwarves who wish to recover a treasure horde stolen by a dragon.Elrond, a wise leader of the elves.Gollum, a once-human creature who found and is governed by a great ring of power.Smaug, the dragon and antagonist of the story. Plot and Storyline The story of The Hobbit begins in the Shire, land of the hobbits. The Shire is similar to a pastoral English countryside, and the hobbits are represented as quiet, agricultural people who shun adventure and travel. Bilbo Baggins, the protagonist of the story, is surprised to find himself hosting a group of dwarves and the great wizard, Gandalf. The group has decided that now is the right time to journey to the Lonely Mountain, where they will retake the dwarves treasure from the dragon, Smaug. They have nominated Bilbo to join the expedition as their burglar. Though initially reluctant, Bilbo agrees to join the group, and they head off far from the Shire into the increasingly dangerous sections of Middle Earth. Along the journey, Bilbo and his company meet up with a wide range of creatures both beautiful and terrible. As he is tested, Bilbo discovers his own inner strength, loyalty, and cunning. Each chapter involves an interaction with a new set of characters and challenges: The group is captured by trolls and nearly eaten, but are saved when sunlight strikes the trolls and they are turned to stone.Gandalf leads the group to the Elven settlement of Rivendell where they meet the Elvish leader, Elrond.The group is caught by goblins and driven deep underground. Although Gandalf rescues them, Bilbo gets separated from the others as they flee the goblins. Lost in the goblin tunnels, he stumbles across a mysterious ring and then encounters Gollum, who engages him in a game of riddles. As a reward for solving all riddles Gollum will show him the path out of the tunnels, but if Bilbo fails, his life will be forfeit. With the help of the ring, which confers invisibility, Bilbo escapes and rejoins the dwarves, improving his reputation with them. The goblins and Wargs give chase, but the company is saved by eagles.The company enters the black forest of Mirkwood without Gandalf. In Mirkwood, Bilbo first saves the dwarves from giant spiders and then from the dungeons of the Wood-elves. Nearing the Lonely Mountain, the travelers are welcomed by the human inhabitants of Lake-town, who hope the dwarves will fulfill prophecies of Smaugs demise. The expedition travels to the Lonely Mountain and finds the secret door; Bilbo scouts the dragons lair, stealing a great cup and learning of a weakness in Smaugs armor. The enraged dragon, deducing that Lake-town has aided the intruder, sets out to destroy the town. A thrush has overheard Bilbos report of Smaugs vulnerability and reports it to Lake-town defender Bard. His arrow finds the chink and slays the dragon.When the dwarves take possession of the mountain, Bilbo finds the Arkenstone, an heirloom of Thorins dynasty, and hides it away. The Wood-elves and Lake-men besiege the mountain and request compensation for their aid, reparations for Lake-towns destruction, and settlement of old claims on the treasure. Thorin refuses and, having summoned his kin from the Iron Hills, reinforces his position. Bilbo tries to ransom the Arkenstone to head off a war, but Thorin is intransigent. He banishes Bilbo, and battle seems inevitable.Gandalf reappears to warn all of an approaching army of goblins and Wargs. The dwarves, men, and elves band together, but only with the timely arrival of the eagles and Beorn do they win the climactic Battle of Five Armies. Thorin is fatally wounded and reconciles with Bilbo before he dies. Bilbo accepts only a small portion of his share of the treasure, having no want or need for more, but still returns home a very wealthy hobbit. Themes The Hobbit is a simple tale when compared to Tolkiens masterpiece  The Lord of the Rings. It does, however, contain several themes: It explores the process by which an untested individual develops the insight and skills to become a leader;It guides the reader to question the value of wealth as opposed to peace and contentment;It builds on Tolkiens personal experience in World War I to consider the question of whether victory, though desirable, is worth the price of war.

Cultural diversity Research Paper Example | Topics and Well Written Essays - 250 words

Cultural diversity - Research Paper Example Whether in an organization or in a classroom, cultural diversity, if managed correctly, can bring cohesion, harmonious and synergistic efforts that would bring the highest productivity of performance , from ‘optimum’ to maximum, in achieving set goal(s). On account of the presence of cross-national perspective in a classroom, a recent research conducted by Konan, Paul N’Dri; Chatard, Armand; Selimbegovic, Leila; Mugny, Gabriel on Cultural diversity in the classroom and its effects on academic performance: A cross-national perspective indicated that the presence of immigrants in the classroom resulted to performance benefits for both locals and immigrant students (Konan, et.al, 2010). This is indicative that a class with diversified culture, talents, skills, interests of students must be ready with flexible learning tools and strategies that would address the different responsiveness and performance of each student without compromising the overall impact of learnin g of the whole class. REFERENCES Bhatia, (2007) Shruti. Diversity Management -The Challenges And Opportunities. Retrieved from   http://www.slideshare.net/shruti27bhatia/diversity-management-the-challenges-and-opportunities-presentation Cultural Diversity (n.d.) In Business Dictionary.