Engineered Robot Interacts With Live FishEngineered Robot Interacts With Live Fish

Engineered Robot Interacts With Live FishEngineered Robot Interacts With Live Fish

  3:22:00 PM    Science Lover

---

A bioinspired robot has provided the first experimental evidence that live zebrafish can be influenced by engineered robots.

A robotic zebrafish. 
(Credit: Image courtesy of Institute of Physics)

Results published 8 June in IOP Publishing's journal Bioinspiration and Biomimetics, provide a stepping stone on the path to using autonomous robots in an open environment to monitor and control fish behaviour.

In the future, water-based robots could potentially contribute to the protection of endangered animals and the control of pest species.

The robot, created by researchers from Polytechnic Institute of New York University and Instituto Superiore di Sanitá, Italy, was 15 centimetres long and spray-painted with the characteristic blue stripes of the zebrafish. The tail of the robot was mechanically controlled by the researchers to mimic the action of the zebrafish itself.

When placed in a 65 litre fish tank, the movements of the robot's tail attracted both individual and shoals of zebrafish; the researchers believe that such capability was influenced by its bioinspired features which were optimised to increase attraction.

For example, the robot was given a rounder shape to mimic a fertile female, which is preferred by both male and female zebrafish, and its colour pattern -- a magnified stripe width and saturated yellow pigment -- emphasized distinctive biologically relevant features.

The robot was in a fixed position in the tank so that the tail movements could be controlled, recorded and, most importantly, associated with the behaviour of the zebrafish.

The fish tank where the experiments took place was divided into one large middle section and two smaller sections at either end, separated by transparent Plexiglas. A total of 16 experiments were performed in which individual, and then shoals of, zebrafish were placed in the middle compartment of the tank and two stimuli were placed at either end behind the Plexiglass.

The combinations of stimuli were: one fish versus an empty space; ten fish versus an empty space; ten fish versus one fish; the robot versus an empty space, and the robot versus one fish.

A camera was placed above the tank to monitor the movements of the zebrafish, and statistical tests were performed to calculate whether the robot acted as an attractive, neutral or aversive stimulus and whether this relationship depends on the fish being isolated or in a shoal.

Although the live zebrafish tended to prefer each other to the robot, when given the choice to spend time next to the robotic fish or an empty space, both the individual fish and shoal of fish preferred the robot. While the noise of the robot's motor was shown to decrease its attraction, the actual beating of the tail emphasized its attractiveness.

The corresponding author, Dr Maurizio Porfiri, said: "These findings provide practical evidence that a species' preference for conspecifics may be used to inspire the design of robots which can actively engage their source of inspiration.

"New studies are currently underway in our lab investigating the interactions between fish and robotic fish when they are free to swim together under controlled and ecologically complex conditions."

Read More

Metal Discovered To Become Transparent Under High Pressure

Metal Discovered To Become Transparent Under High Pressure

  8:46:00 AM    Science Lover

---

Sodium, a white metal at pressures below 1.5 Mbar (left -- picture at 1.1 Mbar, 1 Mbar = 1 million atmospheres), turns black at 1.5 Mbar (center -- picture at 1.56 Mbar) and becomes red transparent at 1.9 Mbar (right -- picture at 1.99 Mbar). It is predicted to become colorless and transparent like glass at ~3 Mbar. (Credit: Image courtesy of Stony Brook University)

An international team of scientists have discovered a transparent form of the element sodium (Na). The team, led by Artem Oganov, Professor of Theoretical Crystallography at Stony Brook University, and Yanming Ma, the lead author and professor of physics at Jilin University in China, was able to demonstrate that sodium defies normal physical expectations by going transparent under pressure.

“It is well known that at sufficiently high compression all materials must go metallic,” said Oganov. “This is seen in the metallization of hydrogen at high pressures and temperatures inside planets Jupiter and Saturn.”

However, as the researchers found, element sodium does just the opposite. A perfect white metal at atmospheric pressure, on increasing pressure sodium first turns black, then (at the pressure of 2 million atmospheres) red transparent, and eventually becomes a colorless transparent material – just like glass.

“This fundamental result is important for understanding properties of highly compressed matter, particularly within stars and giant planets,” said Oganov.

The unexpected transformation was first predicted by Professor Ma. His sophisticated calculations clearly indicated that sodium adopts unusual crystal structures and becomes an insulator at high pressures. Together with Professor Oganov, Ma was able to demonstrate that, at very high compressions, overlapping sodium atoms force their outer electrons into the “holes” between the atoms.

“In these holes electrons demonstrate an extremely localized behavior, responsible for the collapse of the metallic state,” said Ma. “These electrons behave as ‘fake atoms,’ just like in electrides - ionic compounds where the role of the anion is played by localized electrons.”

To test this unexpected prediction, Ma and Oganov contacted Mikhail Eremets, the leader of an experimental group at Max Planck Institute of Chemistry, Mainz (Germany). Eremets was initially skeptical of the Ma-Oganov predictions, yet he was undeterred by extreme technical challenges of reaching pressures of over 2 million atmospheres. Eremets and his group initiated a cohort of several extremely difficult experiments, using a tiny micrometer-size sample. Through these experiments, the group was able to confirm the predictions of a new structure and transparency of sodium.

“What fascinated us most is that the pressures at which this transformation was predicted were experimentally reachable,” Oganov said, “and that at these conditions such a remarkable change of chemistry occurs”.

The results are published in the March 12 edition of the journal Nature.

Adapted from materials provided by Stony Brook University, via Newswise.

Source : www.sciencedaily.com

If you like this post, buy me a beer at $3!

Read More