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.

How to Answer “Can I Contact Your Current Employer”

How to Answer â€Å"Can I Contact Your Current Employer† If anyone asks where you were today, you were at a dentist’s appointment. Right? The vague â€Å"appointment,† always in the middle of the day, is a classic tactic for interviewing for new jobs while you’re still at your current one. You just put up your â€Å"out of office† message and hope no one notices that you’re awfully dressed up for a Wednesday. However, your slick cover story could be blown if the interviewing company contacts your current one. How does one avoid this potential explosion of awkwardness?Look, everyone understands that the sneaky interview is kind of the dirty little secret of the working world. Everyone does it at some point, in hopes of trading up their current position, or pursuing a new opportunity. That doesn’t mean you want your intentions broadcast across your current company- especially if you don’t get the new gig. Ideally, the interviewer will accept your list of non-current-boss references without que stion. But there’s a chance he or she might ask you the dreaded question: â€Å"Hey, do you mind if I contact your current employer?†DO understand that they’re not trying to double-cross you.No one is snitching†¦the person interviewing you merely wants to get a sense of what you’re like as a current employee. He or she knows it’s awkward, but it’s a valid question. After all, your current boss might know you’re interviewing for a variety of reasons (like your job is ending due to a layoff, your job is temporary, etc.)- so it certainly can’t hurt to ask.DON’T panic, and assume that everyone will soon know about your secret interview.It’s definitely okay to say that you’d like to keep your job search under wraps for now.DO have some current colleagues in mind that you could include as a reference.If you have a trusted coworker who has a clear sense of your abilities as an employee, but who can also be tr usted with a secret (and who has been told ahead of time that you’re on the hunt), then offer them as an alternative reference. That way, you can say to the interviewer that you’re not comfortable if she talks to your current boss yet, but that you have another reference at your current company whom she could talk to in the meantime.DON’T act cagey, like you have something to hide.Be up-front that you’re not comfortable offering up your current boss as a reference at this time. Emphasize that your available references are well aware of your abilities as an employee, and let the interviewer know that they’re happy to talk to him or her in the meantime.DO leave the door open for the future.After you say that you’re not comfortable with the interviewer talking with your current manager, make sure they know that it’s not a final â€Å"no.† Let him or her know that when the timing is right, you’d be open to them contacting yo ur current company.If all goes well, you can sneak back into your office with a spring in your step, and secure in the knowledge that your secret is safe for now.