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Why Hot Water Freezes Faster than Cold Water

The fact that preheated liquids freeze faster than those that are already cold was observed for the first time by Aristotle in the 4th century AD.

A team of researchers from Universidad Carlos III de Madrid, the Universidad de Extremadura and the Universidad de Sevilla have defined a theoretical framework that could explain the Mpemba effect, a counterintuitive physical phenomenon revealed when hot water freezes faster than cold water.

The researchers, who have recently published the findings in Physical Review Letters, have confirmed how this phenomenon occurs in granular fluids, that is, those composed of particles that are very small and interact among those that lose part of their kinetic energy. Thanks to this theoretical characterization, “we can simulate on a computer and make analytical calculations to know how and when the Mpemba effect will occur,” said Antonio Lasanta. Lasanta is from the UC3M Gregorio Millán Barbany University Institute for Modeling and Simulation on Fluid Dynamics, Nanoscience and Industrial Mathematics. “In fact,” he said, “we find not only that the hottest can cool faster but also the opposite effect: the coldest can heat faster, which would be called the inverse Mpemba effect.

The fact that preheated liquids freeze faster than those that are already cold was observed for the first time by Aristotle in the 4th century AD. Francis Bacon, the father of scientific empiricism, and René Descartes, the French philosopher, were also interested in the phenomenon, which became a theory when, in 1960, a Tanzanian student named Erasto Mpemba explained to his teacher in a class that the hottest mixture of ice cream froze faster than the cold one. This anecdote inspired a technical document about the subject, and the effect began to be analyzed in educational and science magazines. However, its causes and effects have hardly been studied until now.

“It is an effect that, historically, has not been addressed in a rigorous manner but merely as an anomaly and a didactic curiosity,” said Antonio Prados, one of the researchers from the Universidad de Sevilla Department of Theoretical Physics. “From our perspective, it was important to study it in a system with the minimum ingredients to be able to control and understand its behavior,” he said. This has enabled them to understand what scenarios it is easier to occur in, which is one of the main contributions of this scientific study. “Thanks to this, we have identified some of the ingredients so that the effect occurs in some physical systems that we can describe well theoretically,” stated researcher Francisco Vega Reyes and Andrés Santos, from the Universidad de Extremadura Instituto de Computación Científica Avanzada (Institute of Advanced Scientific Computation).

“The scenario that the effect will most easily occur in is when the velocities of the particles before heating or cooling have a specific disposition — for example, with a high dispersion around the mean value,” he said. This way, the evolution of the temperature of the fluid can be significantly affected if the state of the particles is prepared before the cooling.

This research of “basic science,” in addition to contributing to improving fundamental knowledge, might have other applications in the mid or long term. In fact, this group of researchers is planning to carry out an experiment that verifies the theory. Learning to emulate and use this effect might have applications in our daily life, according to scientists. For example, it could be used to make electronic devices which we want to cool faster.

Video (Spanish with English subtitles):

Journal Reference:
Antonio Lasanta, Francisco Vega Reyes, Antonio Prados, Andrés Santos. When the Hotter Cools More Quickly: Mpemba Effect in Granular Fluids. Physical Review Letters, 2017; 119 (14)

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NTP nuclear rocket engine will take humans to Mars in just three months

Although the romance of the peaceful atom has subsided since the mid-1960s, the idea of ​​using nuclear reactors for “civilian” purposes is still regularly returned. The new nuclear rocket engine (NRM) will deliver a man to Mars much faster than is possible now.

The danger of cosmic radiation is much more serious than the risk of infection from an accident with such an engine. The most dangerous of all the constraining vectors for projects of sending people to other bodies in the solar system is cosmic radiation. Radiation from our star and galactic rays can seriously damage the health of the mission crew. Therefore, when planning flights to Mars, engineers and scientists try to reduce travel time as much as possible.

One promising way to get to the Red Planet in just three months could be a new NTP engine. Its concept was developed and submitted to NASA by Ultra Safe Nuclear Technologies ( USNC-Tech ) from Seattle, USA. The name of the unit is simply deciphered – Nuclear Thermal Propulsion ( NTP ), that is, “thermal nuclear power plant”. The novelty differs from its previously created or invented counterparts in the most secure design.

A key component of USNC’s development is mid – grade uranium fuel “pellets”. They contain 5% to 20% of the highly reactive isotope U- 235 coated with zirconium carbide ceramics. This degree of enrichment lies roughly halfway between the “civilian” nuclear power plants and the military. The proprietary ceramic coating technology makes the tablets incredibly resistant to mechanical damage and extreme temperatures.

Schematic diagram of a thermal nuclear rocket engine / © Wikipedia |  Tokono
Schematic diagram of a thermal nuclear rocket engine / © Wikipedia | Tokono

The company promises that their fuel elements are significantly superior in these parameters to those currently used at nuclear power plants. As a result, the engine will have a higher specific impulse with a lower degree of uranium enrichment than in earlier versions of NRE. In addition to the flight to Mars, among the goals of the ambitious project are other missions within the solar system. The perspectives of the concept will soon be considered by specialists from NASA and the US Department of Defense ( DoD ). Perhaps departments will even allow its commercial use by private companies.

Theoretically, NRE based on modern technologies can have a specific impulse (SR) seven times higher than that of chemical jet engines. And this is one of the key performance parameters. At the same time, unlike electric and plasma ones, the ID of a nuclear rocket engine is combined with high thrust. One of the limiting factors in the use of NRE, in addition to safety issues, are extremely high temperatures in the reactor core.

The higher the temperature of the gases flowing out of the engine, the more energy they have. And accordingly, they create traction. However, mankind has not yet come up with relatively inexpensive and safe materials that can withstand more than three thousand degrees Celsius without destruction. The solution created by USNC will operate at the limit of modern materials science (3000 ° C) and have a specific impulse twice that of the best liquid-propellant engines.

Tests of the first nuclear jet engine in 1967 / © NASA
Tests of the first nuclear jet engine in 1967 / © NASA

The official press release does not specify which working body will be used in NTP . Usually, in all NRE projects, the reactor core heats hydrogen, less often ammonia. But, since we are talking about a long-term mission, the creators could have chosen some other gas. Keeping liquid hydrogen on board for three months is no easy task. But you still need to invent something for the way back.

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Scientist Peter Scott-Morgan is set to become “the world’s first complete cyborg”

Scientist and roboticist Peter Scott Morgan, who is using an advanced version of Stephen Hawking's communication system, built by Intel. INTEL

Two years ago scientist Peter Scott-Morgan was diagnosed with motor neuron disease, also known as Lou Gehrig’s disease, and today he is still fighting for a new life, not just for survival.

This October, Dr. Scott-Morgan is on track to become the world’s first full-fledged cyborg, potentially giving him more years of life.

The world’s first complete cyborg

It was in 2017 that Dr. Peter Scott-Morgan (a brilliant robotics writer, scientific writer, and talented speaker) was diagnosed with degenerative motor neuron disease that ultimately paralyzed his entire body except his eyes.

The diagnosis is understandably grim, especially considering that he has only two years to live, but he has not given up the fight.

Teaming up with world-class organizations with expertise in artificial intelligence, Dr. Scott-Morgan is transforming himself into what he calls “the world’s first fully fledged cyborg.”

“And when I say ‘Cyborg’, I mean not just that some kind of payment will be implanted in me, I mean that I will become the most advanced human cybernetic organism ever created on Earth for 13.8 billion years. My body and brain will be irreversibly changed, ”says Dr. Scott-Morgan.

What does it mean to be human

According to Dr. Scott-Morgan, he will become part robot and part living organism. Moreover, the change will not be one-time, but with subsequent updates.

“I have more updates in the process than Microsoft ,” says Dr. Scott-Morgan.

AI-powered creative expression

The cyborg artist is a great example of the power of human-AI collaboration. AI uses the data that make up Peter’s digital portrait ( articles, videos, images, and social media ) and is trained to recognize key ideas, experiences, and images.

Peter will introduce a theme, AI will suggest composition, and Peter will apply images to suggest style and mood. Peter will direct the AI ​​to render a new digital image that none of them could create alone.

A unique blend of AI and human, reflects Peter’s creative and emotional self – a critical aspect of what it means to be human.

Peter 2.0

This October, Dr. Scott-Morgan will undergo what he calls the latest procedure that will transform him into “Complete Cyborg”.

October 9 he tweeted a photo of himself, writing the following:

“This is my last post as Peter 1.0. Tomorrow I will trade my vote for potentially decades of life as we complete the last medical procedure for my transition to Full Cyborg, in the month that I was told statistically I would be dead. I am not dying, I am transforming. ! Oh, how I LOVE science !!! “.

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Japan has developed an inflatable scooter that weighs practically nothing

The University of Tokyo engineers have developed the Poimo inflatable electric scooter, which is created individually for each owner. It is enough to send your photo to the manufacturers – and a personal optimized model will be assembled for you.

The scooter is designed with a special program for the body size of a particular user and his specific fit. Moreover, each owner is free to make any changes to this model. If he makes any changes to the drawing, the program will automatically redesign the electric bike to maintain its strength, stability and controllability. When the model is finished and approved, it is handed over to the manufacturer.

Scooter Poimo

The scooter consists of seven separate inflatable sections that are constructed from durable fabric and sewn with straight stitch. It remains to add electronic components – in particular, a brushless motor and a lithium-ion battery. 

The finished electric scooter weighs about 9 kg and can travel at speeds up to 6 km / h (that is, slightly faster than a pedestrian). It can work for an hour on one charge.

This is how the current version of Poimo looks like in action:

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