Science, Art, Litt, Science based Art & Science Communication

Q: What is low temperature science called as? What is it used for?

Krishna: Cryogenics is the scientific study of materials and their behaviour at extremely low temperatures.

The term is usually encountered in the context of physics, materials science, and medicine. Scientists who study cryogenics is called a cryogenicists. A cryogenic material may be termed a cryogen.

Cryogenic Disciplines:

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.

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 −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).

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 speciality 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.


Human hibernation (Art work based on this theme by Dr. Krishna Kumari Challa)

Hibernation is a state of inactivity and metabolic depression in living beings. It is characterized by lower body temperature, slower breathing and lower metabolic rate.
There are many research projects currently investigating how to achieve "induced hibernation" in humans. The ability for humans to hibernate would be useful for a number of reasons, such as saving the lives of seriously ill or injured people by temporarily putting them in a state of hibernation to escape death until treatment can be given or until the body heals and recovers fully. In addition, hibernation would be useful for humans during various proposed plans for space travel in the future.


Doctors have placed humans in suspended animation for the first time recently (in Nov., 2019), as part of a trial in the US that aims to make it possible to fix traumatic injuries that would otherwise cause death.

Samuel Tisherman, at the University of Maryland School of Medicine and his team of medics had placed at least one patient in suspended animation, calling it “a little surreal” when they first did it. He wouldn’t reveal how many people had survived as a result.

The technique, officially called emergency preservation and resuscitation (EPR), is being carried out on people who arrive at the University of Maryland Medical Centre in Baltimore with an acute trauma – such as a gunshot or stab wound – and have had a cardiac arrest. Their heart will have stopped beating and they will have lost more than half their blood. There are only minutes to operate, with a less than 5 per cent chance that they would normally survive.

EPR involves rapidly cooling a person to around 10 to 15°C by replacing all of their blood with ice-cold saline. The patient’s brain activity almost completely stops. They are then disconnected from the cooling system and their body – which would otherwise be classified as dead – is moved to the operating theatre.

A surgical team then has 2 hours to fix the person’s injuries before they are warmed up and their heart restarted.  Tisherman says he hopes to be able to announce the full results of the trial by the end of 2020.

At normal body temperature – about 37°C – our cells need a constant supply of oxygen to produce energy. When our heart stops beating, blood no longer carries oxygen to cells. Without oxygen, our brain can only survive for about 5 minutes before irreversible damage occurs. However, lowering the temperature of the body and brain slows or stops all the chemical reactions in our cells, which need less oxygen as a consequence.

Tisherman’s plan for the trial was that 10 people who receive EPR will be compared with 10 people who would have been eligible for the treatment but for the fact that the correct team wasn’t in the hospital at the time of admittance.

The trial was given the go-ahead by the US Food and Drug Administration. The FDA made it exempt from needing patient consent as the participants’ injuries are likely to be fatal and there is no alternative treatment. The team had discussions with the local community and placed ads in newspapers describing the trial, pointing people to a website where they can opt out.

Tisherman’s interest in trauma research was ignited by an early incident in his career in which a young man was stabbed in the heart after an altercation over bowling shoes. “He was a healthy young man just minutes before, then suddenly he was dead. We could have saved him if we’d had enough time,” he says. This led him to start investigating ways in which cooling might allow surgeons more time to do their job.

Animal studies showed that pigs with acute trauma could be cooled for 3 hours, stitched up and resuscitated.  The doctors are only trying to buy time to save patients. 

In fact, how long you can extend the time in which someone is in suspended animation isn’t clear. When a person’s cells are warmed up, they can experience reperfusion injuries, in which a series of chemical reactions damage the cell – and the longer they are without oxygen, the more damage occurs.

It may be possible to give people a cocktail of drugs to help minimise these injuries and extend the time in which they are suspended, says Tisherman, “but we haven’t identified all the causes of reperfusion injuries yet”.

Tisherman described the team’s progress in Nov. 2019 at a symposium at the New York Academy of Sciences.

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