Physics principle explains order and disorder of swarms

Current experiments support the controversial hypothesis that a well-known concept in physics — a “critical point” — is behind the striking behaviour of collective animal systems. Physicists from the Cluster of Excellence “Centre for the Advanced Study of Collective Behaviour” at the University of Konstanz showed that light-controlled microswimming particles can be made to organize into different collective states such as swarms and swirls. By studying the particles fluctuating between these states, they provide evidence for critical behaviour — and support for a physical principle underlying the complex behaviour of collectives. The research results were published in the scientific journal Nature Communications.

Animal groups exhibit the seemingly contradictory characteristics of being both robust and flexible. Imagine a school of fish: hundreds of individuals in perfect order and alignment can suddenly transition to a convulsing tornado dodging an attack. Animal groups benefit if they can strike this delicate balance between being stable in the face of “noise” like eddies or gusts of wind, yet responsive to important changes like the approach of a predator.

Critical transition

How they achieve this is not yet understood. But in recent years, a possible explanation has emerged: criticality. In physics, criticality describes systems in which a transition between states — such as gas to liquid — occurs at a critical point. Criticality has been argued to provide biological systems with the necessary balance between robustness and flexibility. “The combination of stability and high responsiveness is exactly what characterizes a critical point,” says the study’s lead author Clemens Bechinger, Principal Investigator in the Centre for the Advanced Study of Collective Behaviour and Professor in the Department of Physics at the University of Konstanz, “and so it made sense to test if this could explain some of the patterns we see in collective behaviour.”

The hypothesis that collective states are hovering near critical points has been studied in the past largely through numerical simulations. In the new study published in Nature Communications, Bechinger and his colleagues have given rare experimental support to the mathematical prediction. “By demonstrating a close link between collectivity and critical behaviour, our findings not only add to our general understanding of collective states but also suggest that general physical concepts may apply to living systems,” says Bechinger.

Experimental evidence

In experiments, the researchers used glass beads coated on one side by a carbon cap and placed in a viscous liquid. When illuminated by light, they swim much like bacteria, but with an important difference: every aspect of how the particles interact with others — from how the individuals move to how many neighbours can be seen — can be controlled. These microswimming particles allow the researchers to eschew the challenges of working with living systems in which rules of interaction cannot be easily controlled. “We design the rules in the computer, put them in an experiment, and watch the result of the interaction game,” says Bechinger.

But to ensure that the physical system bore a resemblance to living systems, the researchers designed interactions that mirrored the behaviour of animals. For example, they controlled the direction that individuals moved in relation to their neighbours: particles were programmed either to swim straight towards others in the main group or to deviate away from them. Depending on this angle of movement, the particles organized into either swirls or disordered swarms. And incrementally adjusting this value elicited rapid transitions between a swirl and a disordered but still cohesive swarm. “What we observed is that the system can make sudden transitions from one state to the other, which demonstrates the flexibility needed to react to an external perturbation like a predator,” says Bechinger, “and provides clear evidence for a critical behaviour.”

“Similar behaviour to animal groups and neural systems”

This result is “key to understanding how animal collectives have evolved,” says Professor Iain Couzin, co-speaker of the Centre for the Advanced Study of Collective Behaviour and Director of the Department of Collective Behavior at the Konstanz Max Planck Institute of Animal Behavior. Although not involved with the study, Couzin has worked for decades to decipher how grouping may enhance sensing capabilities in animal collectives.

Says Couzin: “The particles in this study behave in a very similar way to what we see in animal groups, and even neural systems. We know that individuals in collectives benefit from being more responsive, but the big challenge in biology has been testing if criticality is what allows the individual to spontaneously become much more sensitive to their environment. This study has confirmed this can occur just via spontaneous emergent physical properties. Through very simple interactions they have shown that you can tune a physical system to a collective state — criticality — of balance between order and disorder.”

Application areas

By demonstrating the existence of a link between collectivity and critical behaviour in living systems, this study also hints at how the intelligence of collectives can be engineered into physical systems. Beyond just simple particles, the finding could assist with designing efficient strategies of autonomous microrobotics devices with on-board control units. “Similar to their living counterparts, these miniature agents should be able to spontaneously adapt to changing conditions and even cope with unforeseen situations which might be accomplished by their operation near a critical point,” says Bechinger.

Key facts:

  • Physicists from the University of Konstanz show a link between collective behaviour and a concept in physics known as criticality.
  • Through experiments using tiny glass particles, they create collective states of swarms and swirls.
  • Showing that the particles can make sudden transitions from one state to the other provides clear evidence for a critical behaviour
  • Original publication: Bäuerle, T., Löffler, R.C. & Bechinger, C. Formation of stable and responsive collective states in suspensions of active colloids. Nat Commun 11, 2547 (2020).
  • Authors include Tobias Bäuerle (lead author) and Robert Löffler, both doctoral students at the University of Konstanz. Senior author Clemens Bechinger is Professor of Physics at the University of Konstanz
  • Clemens Bechinger is also part of the University of Konstanz’s Cluster of Excellence “Centre for the Advanced Study of Collective Behaviour,” which has been funded in the Excellence Strategy of the German Federal and State Governments since 2019.
  • The research was supported by an ERC Advanced Grant ASCIR and the Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy — EXC 2117 — 42203798.
  • is the University of Konstanz’s online magazine. We use multimedia approaches to provide insights into our research and science, study and teaching as well as life on campus.

Story Source:

Materials provided by University of Konstanz. Original written by Carla Avolio. Note: Content may be edited for style and length.

Go to Source

3D Printing Industry

Co-founders of Uber and Tinder are backing a “3D printed” hotel start-up

Hospitality management group Habitas has raised $20m to expand their concept of “social” beach huts. The addition of an unspecified 3D printing technology has also raised eyebrows. A recent profile by the Financial Times reveals that backers of project include Travis Kalanick, co-founder of Uber and Justin Mateen, co-founder of Tinder and a “brains trust” […]

Go to Source
Author: Olivia Harangozó


Simple experiment explains magnetic resonance

Physicists at University of California, Riverside, have designed an experiment to explain the concept of magnetic resonance. The project was carried out by undergraduate students in collaboration with local high school teachers.

A versatile technique employed in chemistry, physics, and materials research, magnetic resonance describes a resonant excitation of electron or atomic nuclei spins residing in a magnetic field by means of electromagnetic waves. Magnetic resonance also provides the basis for magnetic resonance imaging, or MRI — the central noninvasive tool in diagnostic medicine and medical research.

“Two of my undergraduate students developed the demonstration experiment based on a compass, an object everybody can relate to,” said Igor Barsukov, an assistant professor in the UC Riverside Department of Physics and Astronomy, who supervised the project.

Barsukov explained the compass is placed in the middle of a wire coil that is fed with a small alternating voltage. A refrigerator magnet in the vicinity of the compass aligns its needle. When the fridge magnet is brought closer to the compass, the needle starts to oscillate at a “sweet spot.” When the magnet is moved away from the sweet spot, the oscillation stops. This oscillation corresponds to magnetic resonance of the compass needle in the magnetic field of the fridge magnet.

“During outreach events for the broader public, people often share with us their concerns about MRI procedures they need to undergo in a hospital,” Barsukov said. “They associate it with radiation. We wanted to design a hands-on, table-top experiment to alleviate their concerns and to provide a visual explanation for the underlying physics.”

Barsukov’s team initiated a collaboration with the Physics Teacher Academy, a UCR-based program providing training for local high school teachers, to ensure it is also suitable for a high-school classroom.

“Close interaction with the teachers changed our perspective on what a good demonstration experiment aimed at improving scientific literacy should be,” Barsukov said. “We decided to employ 3D-printing techniques for the experimental setup and smartphone-based voltage generators. It reduces the time burden for instructors and makes the presentation more accessible and appealing to students.”

The project was recently published in The Physics Teacher and presented in early November 2019 in the educational section of Magnetism and Magnetic Materials, a major conference in magnetism research.

“The project turned out to be truly synergistic,” Barsukov said. “We learned a lot from the high school teachers we worked with and were able to design an exciting tool for outreach, which I can also use in my classes at UCR. Working on this project was a great lab experience for my students.”

Story Source:

Materials provided by University of California – Riverside. Original written by Iqbal Pittalwala. Note: Content may be edited for style and length.

Go to Source

IEEE Spectrum

Register for Our Application Note “Tips and Tricks on How to Verify Control Loop Stability”

The Application Note explains the main measurement concept and will guide the user during the measurements and mention the main topics in a practical manner. Wherever possible, a hint is given where the user should pay attention. 


Understanding and Organizing Successful API Ecosystems

One of the most complex topics, especially for organizations that are new to the API economy, is the concept of an API ecosystem. This whitepaper was written to help you demystify what an ecosystem is and its role in your overall API strategy.

This is the second of our ongoing series of whitepapers that are written to help you to understand the essentials of a great API strategy. In the first part of this series (see Why a Holistically Conceived Digital Strategy is Key to Monetizing APIs), we covered the four major pillars of a great API strategy and talked about how a great API strategy can be a very natural by-product of a great business strategy. In this paper, we tackle a concept that remains an enigma for many API practitioners; the API ecosystem.

Compared to the early days of the API economy — more like an API gold rush — when there were only a handful of APIs, and Web developers had a nearly insatiable thirst for consuming them, API providers can no longer simply build their APIs and wait for developers to come. 

Instead, in outside-in fashion, API providers must carefully consider the types of customer experiences and business outcomes they’d like to enable. Then, they have to decide who they’ll be relying on to co-create those experiences and outcomes. Candidates include internal developers, third-party developers, independent software vendors (ISVs), and strategic business partners just to name a few. Your engagement with each of these constituencies may result in distinctly separate channels through which your ultimate customers do business with you. Adding to that complexity, each of those channels may involve different business models in order to produce winning outcomes for everyone involved; your customers, your partners, and most importantly your organization. 

We wrote this paper to help you to demystify this tricky but important topic so you can start to think about how best to organize your own API ecosystem for business success. It includes and explains examples and visualizations of real-world ecosystems that involve multiple business channels, multiple constituencies, and multiple business models, and how the various constituencies engage with the API ecosystem host (an organization like yours) while touching on the role of other ecosystem components such as developer tooling and marketplaces. 

Finally, after studying this paper, you’ll have a much better idea of the role that an ecosystem plays in your overall API strategy.  

Go to Source
Author: <a href="">david_berlind</a>


A new concept could make more environmentally friendly batteries possible

A new concept for an aluminium battery has twice the energy density as previous versions, is made of abundant materials, and could lead to reduced production costs and environmental impact. The idea has potential for large scale applications, including storage of solar and wind energy. Researchers from Chalmers University of Technology, Sweden, and the National Institute of Chemistry, Slovenia, are behind the idea.

Using aluminium battery technology could offer several advantages, including a high theoretical energy density, and the fact that there already exists an established industry for its manufacturing and recycling. Compared with today’s lithium-ion batteries, the researchers’ new concept could result in markedly lower production costs.

“The material costs and environmental impacts that we envisage from our new concept are much lower than what we see today, making them feasible for large scale usage, such as solar cell parks, or storage of wind energy, for example,” says Patrik Johansson, Professor at the Department of Physics at Chalmers.

“Additionally, our new battery concept has twice the energy density compared with the aluminium batteries that are ‘state of the art’ today.”

Previous designs for aluminium batteries have used the aluminium as the anode (the negative electrode) — and graphite as the cathode (the positive electrode). But graphite provides too low an energy content to create battery cells with enough performance to be useful.

But in the new concept, presented by Patrik Johansson and Chalmers, together with a research group in Ljubljana led by Robert Dominko, the graphite has been replaced by an organic, nanostructured cathode, made of the carbon-based molecule anthraquinone.

The anthraquinone cathode has been extensively developed by Jan Bitenc, previously a guest researcher at Chalmers from the group at the National Institute of Chemistry in Slovenia.

The advantage of this organic molecule in the cathode material is that it enables storage of positive charge-carriers from the electrolyte, the solution in which ions move between the electrodes, which make possible higher energy density in the battery.

“Because the new cathode material makes it possible to use a more appropriate charge-carrier, the batteries can make better usage of aluminium’s potential. Now, we are continuing the work by looking for an even better electrolyte. The current version contains chlorine — we want to get rid of that,” says Chalmers researcher Niklas Lindahl, who studies the internal mechanisms which govern energy storage.

So far, there are no commercially available aluminium batteries, and even in the research world they are relatively new. The question is if aluminium batteries could eventually replace lithium-ion batteries.

“Of course, we hope that they can. But above all, they can be complementary, ensuring that lithium-ion batteries are only used where strictly necessary. So far, aluminium batteries are only half as energy dense as lithium-ion batteries, but our long-term goal is to achieve the same energy density. There remains work to do with the electrolyte, and with developing better charging mechanisms, but aluminium is in principle a significantly better charge carrier than lithium, since it is multivalent — which means every ion ‘compensates’ for several electrons. Furthermore, the batteries have the potential to be significantly less environmentally harmful,” says Patrik Johansson.

Go to Source


Tidal barriers bring more benefits than producing clean energy

An ambitious new Mersey barrage concept shows how tidal energy projects can offer many benefits to society in addition to clean renewable energy.

When designed holistically, tidal barrage schemes can provide additional transport links for commuters, become tourism destinations, mitigate wildlife habitat loss, as well as provide opportunities to boost people’s health and wellbeing with additional options for cycling and walking, say researchers from Lancaster University and the University of Liverpool.

The academics have proposed an ambitious new design for a mooted tidal energy barrage on the Mersey Estuary, which has one of the largest tidal ranges in the UK. Their concept, which is based on the shape of a whale and includes buildings and platforms for recreation in the centre of the river, illustrates the additional benefits tidal schemes can bring.

The researchers developed their Mersey estuary design to illustrate how developers can apply a novel decision-making framework for tidal schemes called the ‘North West Hydro Resource Model’.

This model, which was developed by academics at Lancaster University’s Engineering Department, includes a range of factors that should be considered for tidal scheme designs, including: energy generation; land use; habitat; flood risk; transport; fisheries; cultural heritage; water supply; tourism and job creation.

George Aggidis, Professor of Energy Engineering at Lancaster University, lead researcher on the paper and creator of the North West Hydro Resource Model, said: “We need to view tidal energy projects holistically and recognise that they provide opportunities beyond energy generation, including environmental, societal and economic opportunities.

“The UK is uniquely positioned to benefit from tidal power, but so far no schemes have managed to get off the drawing board. By considering the needs of people, and the need to create compensatory habitats for wildlife, organic architectural designs like ours show how developers can enhance, rather than detract, from estuaries like the Mersey.

“Tidal barrages and lagoons can offer significant advantages over other sources of renewable power — we need to keep these additional opportunities in mind when comparing the costs and benefits of different forms of energy generation,” added Professor Aggidis.

The researchers say that with the right design a Mersey barrage has the potential to become a globally identifiable piece of architectural infrastructure — a ‘hydropower landmark’ boosting tourism to the region.

Their vision includes new transport and leisure links from Port Sunlight on the Wirral to the Festival Gardens on the Liverpool side of the estuary with new recreational walking and cycle paths and a monorail for commuters.

The concept includes a world-leading centre for hydropower research, which they argue would further enhance the region’s excellence in science and innovation and support education into the technology.

However, one of the main obstacles to tidal projects, in addition to relatively high initial capital costs, is the perceived impact on the habitat of existing wildlife within estuaries.

The researchers believe any Mersey tidal project would need to offer alternative habitat to compensate for losses to existing mud flats — which are a major feeding ground for migratory birds.

However, they argue that concerns about impact to existing wildlife needs to be balanced against future environmental challenges.

Professor Aggidis said: “As with hydropower dams, tidal barrages could have a major impact on local environments, with concerns over biodiversity. Steps would need to be taken to balance the negative environmental impact against the potential to protect against flooding from future sea-level rises caused by global warming.

“We recognise that the total area of intertidal mud-flats that would be lost cannot be replaced. To compensate for the negative ecological effects of the barrage, wildlife will be integrated into the core of the design, which provide habitats to encourage increases in the variety of biodiversity on the Mersey estuary.”

Go to Source

IEEE Spectrum

Water Jet Powered Drone Takes Off With Explosions

At ICRA 2015, the Aerial Robotics Lab at the Imperial College London presented a concept for a multimodal flying swimming robot called AquaMAV. The really difficult thing about a flying and swimming robot isn’t so much the transition from the first to the second, since you can manage that even if your robot is completely dead (thanks to gravity), but rather the other way: going from water to air, ideally in a stable and repetitive way. The AquaMAV concept solved this by basically just applying as much concentrated power as possible to the problem, using a jet thruster to hurl the robot out of the water with quite a bit of velocity to spare.

In a paper appearing in Science Robotics this week, the roboticists behind AquaMAV present a fully operational robot that uses a solid-fuel powered chemical reaction to generate an explosion that powers the robot into the air.


Machine Money Empowering Devices with Wallets

In this webinar, we’ll introduce the concept of a machine wallet and show how it can change the way devices will interact with each other in the future. A small demo will be presented as well as some code examples outlining how to build your own IOTA-powered machine.

IOTA is a distributed ledger technology (DLT) that allows computers in an IOTA network to transfer immutable data and value (IOTA tokens) among each other. IOTA aims to improve efficiency, increase production, and ensure data integrity in a machine-to-machine economy.


Scientists can now control thermal profiles at the nanoscale

At human scale, controlling temperature is a straightforward concept. Turtles sun themselves to keep warm. To cool a pie fresh from the oven, place it on a room-temperature countertop.

At the nanoscale — at distances less than 1/100th the width of the thinnest human hair — controlling temperature is much more difficult. Nanoscale distances are so small that objects easily become thermally coupled: If one object heats up to a certain temperature, so does its neighbor.

When scientists use a beam of light as that heat source, there is an additional challenge: Thanks to heat diffusion, materials in the beam path heat up to approximately the same temperature, making it difficult to manipulate the thermal profiles of objects within the beam. Scientists have never been able to use light alone to actively shape and control thermal landscapes at the nanoscale.

At least, not until now.

In a paper published online July 30 by the journal ACS Nano, a team of researchers reports that they have designed and tested an experimental system that uses a near-infrared laser to actively heat two gold nanorod antennae — metal rods designed and built at the nanoscale — to different temperatures. The nanorods are so close together that they are both electromagnetically and thermally coupled. Yet the team, led by researchers at the University of Washington, Rice University and Temple University, measured temperature differences between the rods as high as 20 degrees Celsius. By simply changing the wavelength of the laser, they could also change which nanorod was cooler and which was warmer, even though the rods were made of the same material.

“If you put two similar objects next to each other on a table, ordinarily you would expect them to be at the same temperature. The same is true at the nanoscale,” said lead corresponding author David Masiello, a UW professor of chemistry and faculty member in both the Molecular & Engineering Sciences Institute and the Institute for Nano-Engineered Systems. “Here, we can expose two coupled objects of the same material composition to the same beam, and one of those objects will be warmer than the other.”

Masiello’s team performed the theoretical modeling to design this system. He partnered with co-corresponding authors Stephan Link, a professor of both chemistry and electrical and computer engineering at Rice University, and Katherine Willets, an associate professor of chemistry at Temple University, to build and test it.

Their system consisted of two nanorods made of gold — one 150 nanometers long and the other 250 nanometers long, or about 100 times thinner than the thinnest human hair. The researchers placed the nanorods close together, end to end on a glass slide surrounded by glycerol.

They chose gold for a specific reason. In response to sources of energy like a near-infrared laser, electrons within gold can “oscillate” easily. These electronic oscillations, or surface plasmon resonances, efficiently convert light to heat. Though both nanorods were made of gold, their differing size-dependent plasmonic polarizations meant that they had different patterns of electron oscillations. Masiello’s team calculated that, if the nanorod plasmons oscillated with either the same or opposite phases, they could reach different temperatures — countering the effects of thermal diffusion.

Link’s and Willets’ groups designed the experimental system and tested it by shining a near-infrared laser on the nanorods. They studied the beam’s effect at two wavelengths — one for oscillating the nanorod plasmons with the same phase, another for the opposite phase.

The team could not directly measure the temperature of each nanorod at the nanoscale. Instead, they collected data on how the heated nanorods and surrounding glycerol scattered photons from a separate beam of green light. Masiello’s team analyzed those data and discovered that the nanorods refracted photons from the green beam differently due to nanoscale differences in temperature between the nanorods.

“This indirect measurement indicated that the nanorods had been heated to different temperatures, even though they were exposed to the same near-infrared beam and were close enough to be thermally coupled,” said co-lead author Claire West, a UW doctoral candidate in the Department of Chemistry.

The team also found that, by changing the wavelength of near-infrared light, they could change which nanorod — short or long — heated up more. The laser could essentially act as a tunable “switch,” changing the wavelength to alter which nanorod was hotter. The temperature differences between the nanorods also varied based on their distance apart, but reached as high as 20 degrees Celsius above room temperature.

The team’s findings have a range of applications based on controlling temperature at the nanoscale. For example, scientists could design materials that photo-thermally control chemical reactions with nanoscale precision, or temperature-triggered microfluidic channels for filtering tiny biological molecules.

The researchers are working to design and test more complex systems, such as clusters and arrays of nanorods. These require more intricate modeling and calculations. But given the progress to date, Masiello is optimistic that this unique partnership between theoretical and experimental research groups will continue to make progress.

“It was a team effort, and the results were years in the making, but it worked,” said Masiello.

Go to Source