Monthly Archives: October 2014

This artist’s impression depicts the formation of a galaxy cluster in the early Universe. The galaxies are vigorously forming new stars and interacting with each other. Such a scene closely resembles the Spiderweb Galaxy (formally known as MRC 1138-262) and its surroundings, which is one of the best-studied protoclusters.

Credit:

ESO/M. Kornmesser

Universe may face a darker future

Since the discovery of the accelerated expansion of the universe in 1997 by High-Z Supernova Team led by Prof. Brian Schmidt and Adam Rees, and by Supernova Cosmology Project Team led by Prof. Saul Perlmutter, the question of the nature of this expansion and the role of the mysterious dark energy has puzzled the minds of many theoretical and observational physicists/astrophysicists.

Another puzzling question in astronomy comes from the unusual behavior of the stars revolving around the galaxies with higher velocities than expected if we consider the apparent baryonic matter in the galaxy.This has led to many new questions related to something we called the dark matter, another unexplained phenomenon.

 


 

New research offers a novel insight into the nature of dark matter and dark energy and what the future of our Universe might be.

Researchers in Portsmouth and Rome have found hints that dark matter, the cosmic scaffolding on which our Universe is built, is being slowly erased, swallowed up by dark energy.

The findings appear in the journal Physical Review Letters, published by the American Physical Society. In the journal cosmologists at the Universities of Portsmouth and Rome, argue that the latest astronomical data favours a dark energy that grows as it interacts with dark matter, and this appears to be slowing the growth of structure in the cosmos.

Professor David Wands, Director of Portsmouth’sInstitute of Cosmology and Gravitation, is one of the research team.

He said: “This study is about the fundamental properties of space-time. On a cosmic scale, this is about our Universe and its fate.

“If the dark energy is growing and dark matter is evaporating we will end up with a big, empty, boring Universe with almost nothing in it.

 

“Dark matter provides a framework for structures to grow in the Universe. The galaxies we see are built on that scaffolding and what we are seeing here, in these findings, suggests that dark matter is evaporating, slowing that growth of structure.”

Cosmology underwent a paradigm shift in 1998 when researchers announced that the rate at which the Universe was expanding was accelerating. The idea of a constant dark energy throughout space-time (the “cosmological constant”) became the standard model of cosmology, but now the Portsmouth and Rome researchers believe they have found a better description, including energy transfer between dark energy and dark matter.

Research students Valentina Salvatelli and Najla Said from the University of Rome worked in Portsmouth with Dr Marco Bruni and Professor Wands, and with Professor Alessandro Melchiorri in Rome. They examined data from a number of astronomical surveys, including the Sloan Digital Sky Survey, and used the growth of structure revealed by these surveys to test different models of dark energy.

Professor Wands said: “Valentina and Najla spent several months here over the summer looking at the consequences of the latest observations. Much more data is available now than was available in 1998 and it appears that the standard model is no longer sufficient to describe all of the data. We think we’ve found a better model of dark energy.

“Since the late 1990s astronomers have been convinced that something is causing the expansion of our Universe to accelerate. The simplest explanation was that empty space – the vacuum – had an energy density that was a cosmological constant. However there is growing evidence that this simple model cannot explain the full range of astronomical data researchers now have access to; in particular the growth of cosmic structure, galaxies and clusters of galaxies, seems to be slower than expected.”

Professor Dragan Huterer,of the University of Michigan, has read the research and said scientists need to take notice of the findings.

He said: “The paper does look very interesting. Any time there is a new development in the dark energy sector we need to take notice since so little is understood about it. I would not say, however, that I am surprised at the results, that they come out different than in the simplest model with no interactions. We’ve known for some months now that there is some problem in all data fitting perfectly to the standard simplest model.”

Source: Materials taken from Uop News

ambitious

ESA enters into the sci-fi realm with ‘Ambitious’

European Space Agency has entered the area of science fiction in an unusual and innovative way of doing public outreach. This new experimental work was done in the form of a short film ‘Ambitious’, premiered on Friday in London.

ambitious

Ambition is a collaboration between Platige Image and ESA. Directed by Tomek Bagiński and starring Aiden Gillen and Aisling Franciosi, Ambition was shot on location in Iceland, and screened on 24 October 2014 during the British Film Institute’s celebration of Sci-Fi: Days of Fear and Wonder, at the Southbank, London. 

Source: ESA

Projecting a robot’s intentions

A new spin on virtual reality helps engineers read robots’ minds.  

By Jennifer Chu


Video/release: http://newsoffice.mit.edu/2014/system-shows-robot-intentions-1029

MIT Video release for the news

[MIT researchers explain their new visualization system that can project a robot's "thoughts." Video: Melanie Gonick/MIT]

CAMBRIDGE, Mass. – In a darkened, hangar-like space inside MIT’s Building 41, a small, Roomba-like robot is trying to make up its mind.

Standing in its path is an obstacle — a human pedestrian who’s pacing back and forth. To get to the other side of the room, the robot has to first determine where the pedestrian is, then choose the optimal route to avoid a close encounter.

As the robot considers its options, its “thoughts” are projected on the ground: A large pink dot appears to follow the pedestrian — a symbol of the robot’s perception of the pedestrian’s position in space. Lines, each representing a possible route for the robot to take, radiate across the room in meandering patterns and colors, with a green line signifying the optimal route. The lines and dots shift and adjust as the pedestrian and the robot move.

This new visualization system combines ceiling-mounted projectors with motion-capture technology and animation software to project a robot’s intentions in real time. The researchers have dubbed the system “measurable virtual reality (MVR) — a spin on conventional virtual reality that’s designed to visualize a robot’s “perceptions and understanding of the world,” says Ali-akbar Agha-mohammadi, a postdoc in MIT’s Aerospace Controls Lab..

“Normally, a robot may make some decision, but you can’t quite tell what’s going on in its mind — why it’s choosing a particular path,” Agha-mohammadi says. “But if you can see the robot’s plan projected on the ground, you can connect what it perceives with what it does to make sense of its actions.”

Agha-mohammadi says the system may help speed up the development of self-driving cars, package-delivering drones, and other autonomous, route-planning vehicles.

“As designers, when we can compare the robot’s perceptions with how it acts, we can find bugs in our code much faster,” Agha-mohammadi says. “For example, if we fly a quadrotor, and see something go wrong in its mind, we can terminate the code before it hits the wall, or breaks.”

The system was developed by Shayegan Omidshafiei, a graduate student, and Agha-mohammadi. They and their colleagues, including Jonathan How, a professor of aeronautics and astronautics, will present details of the visualization system at the American Institute of Aeronautics and Astronautics’ SciTech conference in January.

Seeing into the mind of a robot

The researchers initially conceived of the visualization system in response to feedback from visitors to their lab. During demonstrations of robotic missions, it was often difficult for people to understand why robots chose certain actions.

“Some of the decisions almost seemed random,” Omidshafiei recalls.

The team developed the system as a way to visually represent the robots’ decision-making process. The engineers mounted 18 motion-capture cameras on the ceiling to track multiple robotic vehicles simultaneously. They then developed computer software that visually renders “hidden” information, such as a robot’s possible routes, and its perception of an obstacle’s position. They projected this information on the ground in real time, as physical robots operated.

The researchers soon found that by projecting the robots’ intentions, they were able to spot problems in the underlying algorithms, and make improvements much faster than before.

“There are a lot of problems that pop up because of uncertainty in the real world, or hardware issues, and that’s where our system can significantly reduce the amount of effort spent by researchers to pinpoint the causes,” Omidshafiei says. “Traditionally, physical and simulation systems were disjointed. You would have to go to the lowest level of your code, break it down, and try to figure out where the issues were coming from. Now we have the capability to show low-level information in a physical manner, so you don’t have to go deep into your code, or restructure your vision of how your algorithm works. You could see applications where you might cut down a whole month of work into a few days.”

Bringing the outdoors in

The group has explored a few such applications using the visualization system. In one scenario, the team is looking into the role of drones in fighting forest fires. Such drones may one day be used both to survey and to squelch fires — first observing a fire’s effect on various types of vegetation, then identifying and putting out those fires that are most likely to spread.

To make fire-fighting drones a reality, the team is first testing the possibility virtually. In addition to projecting a drone’s intentions, the researchers can also project landscapes to simulate an outdoor environment. In test scenarios, the group has flown physical quadrotors over projections of forests, shown from an aerial perspective to simulate a drone’s view, as if it were flying over treetops. The researchers projected fire on various parts of the landscape, and directed quadrotors to take images of the terrain — images that could eventually be used to “teach” the robots to recognize signs of a particularly dangerous fire.

Going forward, Agha-mohammadi says, the team plans to use the system to test drone performance in package-delivery scenarios. Toward this end, the researchers will simulate urban environments by creating street-view projections of cities, similar to zoomed-in perspectives on Google Maps.

“Imagine we can project a bunch of apartments in Cambridge,” Agha-mohammadi says. “Depending on where the vehicle is, you can look at the environment from different angles, and what it sees will be quite similar to what it would see if it were flying in reality.”

Because the Federal Aviation Administration has placed restrictions on outdoor testing of quadrotors and other autonomous flying vehicles, Omidshafiei points out that testing such robots in a virtual environment may be the next best thing. In fact, the sky’s the limit as far as the types of virtual environments that the new system may project.

“With this system, you can design any environment you want, and can test and prototype your vehicles as if they’re fully outdoors, before you deploy them in the real world,” Omidshafiei says.

This work was supported by Boeing.

Source: MIT News

This artist’s impression shows the dust and gas around the double star system GG Tauri-A. Researchers using ALMA have detected gas in the region between two discs in this binary system. This may allow planets to form in the gravitationally perturbed environment of the binary. Half of Sun-like stars are born in binary systems, meaning that these findings will have major consequences for the hunt for exoplanets.

Credit:

ESO/L. Calçada

Planet-forming Lifeline Discovered in a Binary Star System

ALMA Examines Ezekiel-like “Wheel in a Wheel” of Dust and Gas


For the first time, researchers using ALMA have detected a streamer of gas flowing from a massive outer disc toward the inner reaches of a binary star system. This never-before-seen feature may be responsible for sustaining a second, smaller disc of planet-forming material that otherwise would have disappeared long ago. Half of Sun-like stars are born in binary systems, meaning that these findings will have major consequences for the hunt for exoplanets. The results are published in the journal Nature on 30 October 2014.

A research group led by Anne Dutrey from the Laboratory of Astrophysics of Bordeaux, France and CNRS used theAtacama Large Millimeter/submillimeter Array (ALMA) to observe the distribution of dust and gas in a multiple-star system called GG Tau-A [1]. This object is only a few million years old and lies about 450 light-years from Earth in the constellation of Taurus (The Bull).

This artist’s impression shows the dust and gas around the double star system GG Tauri-A. Researchers using ALMA have detected gas in the region between two discs in this binary system. This may allow planets to form in the gravitationally perturbed environment of the binary. Half of Sun-like stars are born in binary systems, meaning that these findings will have major consequences for the hunt for exoplanets. Credit: ESO/L. Calçada
This artist’s impression shows the dust and gas around the double star system GG Tauri-A. Researchers using ALMA have detected gas in the region between two discs in this binary system. This may allow planets to form in the gravitationally perturbed environment of the binary. Half of Sun-like stars are born in binary systems, meaning that these findings will have major consequences for the hunt for exoplanets.
Credit:
ESO/L. Calçada

Like a wheel in a wheel, GG Tau-A contains a large, outer disc encircling the entire system as well as an inner disc around the main central star. This second inner disc has a mass roughly equivalent to that of Jupiter. Its presence has been an intriguing mystery for astronomers since it is losing material to its central star at a rate that should have depleted it long ago.

While observing these structures with ALMA, the team made the exciting discovery of gas clumps in the region between the two discs. The new observations suggest that material is being transferred from the outer to the inner disc, creating a sustaining lifeline between the two [2].

Material flowing through the cavity was predicted by computer simulations but has not been imaged before. Detecting these clumps indicates that material is moving between the discs, allowing one to feed off the other,” explains Dutrey. “These observations demonstrate that material from the outer disc can sustain the inner disc for a long time. This has major consequences for potential planet formation.”

Planets are born from the material left over from star birth. This is a slow process, meaning that an enduring disc is a prerequisite for planet formation. If the feeding process into the inner disc now seen with ALMA occurs in other multiple-star systems the findings introduce a vast number of new potential locations to find exoplanets in the future.

The first phase of exoplanet searches was directed at single-host stars like the Sun [3]. More recently it has been shown that a large fraction of giant planets orbit binary-star systems. Now, researchers have begun to take an even closer look and investigate the possibility of planets orbiting the individual stars of multiple-star systems. The new discovery supports the possible existence of such planets, giving exoplanet discoverers new happy hunting grounds.

Emmanuel Di Folco, co-author of the paper, concludes: “Almost half the Sun-like stars were born in binary systems. This means that we have found a mechanism to sustain planet formation that applies to a significant number of stars in the Milky Way. Our observations are a big step forward in truly understanding planet formation.

Notes

[1] GG Tau-A is part of a more complex multiple-star system called GG Tauri. Recent observations of GG Tau-A using the VLTI have revealed that one of the stars — GG Tau Ab, the one not surrounded by a disc — is itself a close binary, consisting of GG Tau-Ab1 and GG Tau-Ab2. This introduced a fifth component to the GG Tau system.

[2] An earlier result with ALMA showed an example of a single star with material flowing inwards from the outer part of its disc.

[3] Because orbits in binary stars are more complex and less stable, it was believed that forming planets in these systems would be more challenging than around single stars.

Source: ESO

Discrete bands of superconductivity
A diagram depicts unpaired spin up electrons congregating in discrete bands. Credit: Brown University

New evidence for exotic, predicted superconducting state

A research team led by a Brown University physicist has produced new evidence for an exotic superconducting state, first predicted a half-century ago, that can arise when a superconductor is exposed to a strong magnetic field.

PROVIDENCE, R.I. [Brown University] — Superconductors and magnetic fields do not usually get along. But a research team led by a Brown University physicist has produced new evidence for an exotic superconducting state, first predicted a half-century ago, that can indeed arise when a superconductor is exposed to a strong magnetic field.

“It took 50 years to show that this phenomenon indeed happens,” said Vesna Mitrovic, associate professor of physics at Brown University, who led the work. “We have identified the microscopic nature of this exotic quantum state of matter.”

The research is published in Nature Physics.

Superconductivity — the ability to conduct electric current without resistance — depends on the formation of electron twosomes known as Cooper pairs (named for Leon Cooper, a Brown University physicist who shared the Nobel Prize for identifying the phenomenon). In a normal conductor, electrons rattle around in the structure of the material, which creates resistance. But Cooper pairs move in concert in a way that keeps them from rattling around, enabling them to travel without resistance.

Magnetic fields are the enemy of Cooper pairs. In order to form a pair, electrons must be opposites in a property that physicists refer to as spin. Normally, a superconducting material has a roughly equal number of electrons with each spin, so nearly all electrons have a dance partner. But strong magnetic fields can flip “spin-down” electrons to “spin-up”, making the spin population in the material unequal.

“The question is what happens when we have more electrons with one spin than the other,” Mitrovic said. “What happens with the ones that don’t have pairs? Can we actually form superconducting states that way, and what would that state look like?”

In 1964, physicists predicted that superconductivity could indeed persist in certain kinds of materials amid a magnetic field. The prediction was that the unpaired electrons would gather together in discrete bands or stripes across the superconducting material. Those bands would conduct normally, while the rest of the material would be superconducting. This modulated superconductive state came to be known as the FFLO phase, named for theorists Peter Fulde, Richard Ferrell, Anatoly Larkin, and Yuri Ovchinniko, who predicted its existence.

To investigate the phenomenon, Mitrovic and her team used an organic superconductor with the catchy name κ-(BEDT-TTF)2Cu(NCS)2. The material consists of ultra-thin sheets stacked on top of each other and is exactly the kind of material predicted to exhibit the FFLO state.

Discrete bands of superconductivity A diagram depicts unpaired spin up electrons congregating in discrete bands. Credit: Brown University
Discrete bands of superconductivity
A diagram depicts unpaired spin up electrons congregating in discrete bands. Credit: Brown University

After applying an intense magnetic field to the material, Mitrovic and her collaborators from the French National High Magnetic Field Laboratory in Grenoble probed its properties using nuclear magnetic resonance (NMR).

What they found were regions across the material where unpaired, spin-up electrons had congregated. These “polarized” electrons behave, “like little particles constrained in a box,” Mitrovic said, and they form what are known as Andreev bound states.

“What is remarkable about these bound states is that they enable transport of supercurrents through non-superconducting regions,” Mitrovic said. “Thus, the current can travel without resistance throughout the entire material in this special superconducting state.”

Experimentalists have been trying for years to provide solid evidence that the FFLO state exists, but to little avail. Mitrovic and her colleagues took some counterintuitive measures to arrive at their findings. Specifically, they probed their material at a much higher temperature than might be expected for quantum experiments.

“Normally to observe quantum states you want to be as cold as possible, to limit thermal motion,” Mitrovic said. “But by raising the temperature we increased the energy window of our NMR probe to detect the states we were looking for. That was a breakthrough.”

This new understanding of what happens when electron spin populations become unequal could have implications beyond superconductivity, according to Mitrovic.

It might help astrophysicists to understand pulsars — densely packed neutron stars believed to harbor both superconductivity and strong magnetic fields. It could also be relevant to the field of spintronics, devices that operate based on electron spin rather than charge, made of layered ferromagnetic-superconducting structures.

“This really goes beyond the problem of superconductivity,” Mitrovic said. “It has implications for explaining many other things in the universe, such as behavior of dense quarks, particles that make up atomic nuclei.”

This research was  supported  by the French ANR (grant:06-BLAN-0111), the Euro-MagNET II network (EU Contract No. 228043), and the visiting faculty program of Université Joseph Fourier, Grenoble.

Source: Brown University

This artist’s impression depicts the formation of a galaxy cluster in the early Universe. The galaxies are vigorously forming new stars and interacting with each other. Such a scene closely resembles the Spiderweb Galaxy (formally known as MRC 1138-262) and its surroundings, which is one of the best-studied protoclusters.

Credit:

ESO/M. Kornmesser

Syracuse Physicists Closer to Understanding Balance of Matter, Antimatter

Physicists in the College of Arts and Sciences have made important discoveries regarding Bs meson particles—something that may explain why the universe contains more matter than antimatter. Distinguished Professor Sheldon Stone and his colleagues recently announced their findings at a workshop at CERN in Geneva, Switzerland. Titled “Implications of LHCb Measurements and Their Future Prospects,” the workshop enabled him and other members of the Large Hadron Collider beauty (LHCb) Collaboration to share recent data results. The LHCb Collaboration is a multinational experiment that seeks to explore what happened after the Big Bang, causing matter to survive and flourish in the Universe. LHCb is an international experiment, based at CERN, involving more than 800 scientists and engineers from all over the world. At CERN, Stone heads up a team of 15 physicists from Syracuse. “Many international experiments are interested in the Bs meson because it oscillates between a matter particle and an antimatter particle,” says Stone, who heads up Syracuse’s High-Energy Physics Group. “Understanding its properties may shed light on charge-parity [CP] violation, which refers to the balance of matter and antimatter in the universe and is one of the biggest challenges of particle physics.” Scientists believe that, 14 billion years ago, energy coalesced to form equal quantities of matter and antimatter. As the universe cooled and expanded, its composition changed. Antimatter all but disappeared after the Big Bang (approximately 3.8 billion years ago), leaving behind matter to create everything from stars and galaxies to life on Earth. “Something must have happened to cause extra CP violation and, thus, form the universe as we know it,” Stone says. He thinks part of the answer lies in the Bs meson, which contains an antiquark and a strange quark and is bound together by a strong interaction. (A quark is a hard, point-like object found inside a proton and neutron that forms the nucleus of an atom.) Enter CERN, a European research organization that operates the world’s largest particle physics laboratory. In Geneva, Stone and his research team—which includes Liming Zhang, a former Syracuse research associate who is now a professor at Tsinghua University in Beijing, China—have studied two landmark experiments that took place at Fermilab, a high-energy physics laboratory near Chicago, in 2009. The experiments involved the Collider Detector at Fermilab (CDF) and the DZero (D0), four-story detectors that were part of Fermilab’s now-defunct Tevatron, then one of the world’s highest-energy particle accelerators. “Results from D0 and CDF showed that the matter-antimatter oscillations of the Bs meson deviated from the standard model of physics, but the uncertainties of their results were too high to make any solid conclusions,” Stone says. He and Zhang had no choice but to devise a technique allowing for more precise measurements of Bs mesons. Their new result shows that the difference in oscillations between the Bs and anti-Bs meson is just as the standard model has predicted. Stone says the new measurement dramatically restricts the realms where new physics could be hiding, forcing physicists to expand their searches into other areas. “Everyone knows there is new physics. We just need to perform more sensitive analyses to sniff it out,” he adds.

Source: Syracuse University

nil_28

Tropical Cyclone – 04A (NILOFAR) in Arabian Sea:MET Pakistan Advisory

Just when the Southern Pakistani province of Sindh and especially the coastal city of Karachi is facing some serious political crisis due to some rift between the two ruling parties of Sindh (PPP and MQM), the nature is busy in doing some serious stuff in the neighboring Arabian Sea.

Meteorological Department of Pakistan has issued an advisory to fishermen of Sindh and Baluchistan provinces of Pakistan to avoid going in the sea due to NILOFAR storm.

Very Severe Tropical Cyclone (Nilofar) in Arabian Sea is now located at Lat. 16.0°N and Long. 61.6°E, about 1120 km in southwest of Karachi and 1010 Km south of Gawadar. The Cyclone is likely to move northward in next 24 hours with a speed of 05 Km/hour. The TC would re-curve northeastwards (towards adjoining coastal areas of Lower Sindh and Indian Gujrat) on Wednesday. At present the estimated central pressure of Cyclone is 990 hpa and the average sustained wind speed around is 90-100 gusting up to 110 Knots.

Under the influence of this Cyclone, widespread rain/thundershowers with isolated heavy/very heavy falls accompanied by strong gusty winds are expected in Lower Sindh including Karachi and Coastal Areas of Balochistan during Wednesday (night) to Friday.

The sea conditions along Pakistan coast have become rough and likely to become very rough from tomorrow. The fishermen of Sindh and Balochistan are advised not to venture in open sea from Wednesday to Friday.

Note: Latest Satellite Image of 28th Oct 2014 at 1700 PST and predicted track are as follows:

Images released by MET Pakistan office on 28th October 2014 showing the NILOFAR storm near Pakistani and Indian coastal areas.
Images released by MET Pakistan office on 28th October 2014
showing the NILOFAR storm near Pakistani and Indian coastal areas.

nil_28

Earlier 27th October 2014 images released by MET Pakistan showing the path of NILOFAR.image001

 

 

Microscopic “walkers” find their way across cell surfaces

Technology could provide a way to deliver probes or drugs to cell structures without outside guidance.

By David Chandler


 

CAMBRIDGE, Mass–Nature has developed a wide variety of methods for guiding particular cells, enzymes, and molecules to specific structures inside the body: White blood cells can find their way to the site of an infection, while scar-forming cells migrate to the site of a wound. But finding ways of guiding artificial materials within the body has proven more difficult.

Now a team of researchers at MIT led by Alfredo Alexander-Katz, the Walter Henry Gale Associate Professor of Materials Science and Engineering, has demonstrated a new target-finding mechanism. The new system allows microscopic devices to autonomously find their way to areas of a cell surface, for example, just by detecting an increase in surface friction in places where more cell receptors are concentrated.

The finding is described this week in a paper in the journal Physical Review Letters, written by Alexander-Katz, graduate student Joshua Steimel, and postdoc Juan Aragones.

“The idea was to find out if we could create a synthetic, active system that could sense gradients in biological receptors,” Alexander-Katz explains. “Currently, we don’t know of anything that can do that.”

Cells have a way of locating areas that bear a specific kind of chemical signature — a process called chemotaxis. That’s the method used by white blood cells, for example, to locate regions where pathogens are attacking body cells.

“Our system is very simple,” Alexander-Katz says — similar to the way in which bacteria locate nutrients they need. The system, without guidance, samples areas on a surface and migrates toward those where friction is greater — which also correspond to areas where receptors are concentrated.

The system uses a pair of linked particles with magnetic properties. In the presence of a magnetic field, the paired particles begin to tumble across a surface, with first one particle and then the other making contact — in effect, “walking” across the surface.

So far, the work has been carried out on a model cell surface, on a functionalized microscope slide, but the effect should work similarly with living cells, Alexander-Katz says. The team’s goal now is to demonstrate the ability of the microscopic walkers to find their way toward concentrations of receptors in actual living tissue.

The method could potentially have a variety of applications, Alexander-Katz says. For example, it could be developed as a method of locating tumor cells within the body by identifying their surface texture, perhaps in combination with other characteristics.

Such magnetic microwalkers, he adds, could be unleashed to locate areas of interest on various kinds of surfaces, based solely on differences in friction. The particles naturally migrate toward high-friction regions, where they could then be induced to interact with a surface by active molecules attached to them.

“It’s a very versatile system,” Alexander-Katz says, that can be functionalized by attaching other kinds of receptors or binding agents to affect or monitor the target area in different ways.

The next step is to test the approach in more complex settings. The initial work was done with flat surfaces; the team now aims to conduct studies in complex 3-D settings to make sure the process works effectively in situations that more closely resemble a real cellular environment.

The research was supported by the U.S. Department of Energy, the MIT Energy Initiative, and the Chang family.

Turning today’s composite materials innovations into tomorrow’s reality

By Meres J. Weche


As sustainability has increasingly become a central focus in many sectors of the global economy, manufacturers are constantly striving to increase efficiency in terms of energy, weight, emissions and generally reducing their environmental footprint. Those requirements are the primary drivers behind the widespread adoption of composite materials.

Composite “materials” are created when two or more different materials are arranged together according to a microstructure (i.e. the way these materials are arranged together in space). The properties at large scale are intimately related to this microstructure. In other words, starting from the same raw materials but engineering different microstructures can result in completely different behaviors.

That makes this field full of opportunities for optimizing and tailoring the material to the application. When not only the mechanical behavior is considered, but multiple physics together (thermal, electrical) as well as the coupling between them, such materials can be engineered to obtain the complex behaviors needed for achieving multifunctional structures.

Composites are found in sports equipment, buildings, aircraft manufacturing, and the energy sector to name a few. Latest generation composite aircraft, for instance, can have a gain of around 25% efficiency compared to the same metallic design. Composites pipes can be used to make water or oil transportation infrastructures insensitive to corrosion and to reduce the pollution of the conveyed product.

As most common composites make use of carbon, they are often referred as “black metal”. They have of course nothing to do with more classical metallic materials, but this expression well stresses the potential of these materials to become the most popular candidates for large-scale engineering. Yet, we are only at the beginning of the “black metal” revolution.

“Today we are very good at making composite structures; the main problem is how they are going to evolve in time,” says Gilles Lubineau, Associate Professor of Mechanical Engineering at KAUST and Principal Investigator of the Composite and Heterogeneous Materials Analysis and Simulation Laboratory (COHMAS). That means it’s possible to employ innovative composite structure technology to manufacture versatile aircrafts, windmill blades, and industrial pipes — but the big question is ensuring their “stability and service lifetime.”

Prof. Lubineau and his group’s research thrust essentially focuses on computational modeling and experimental developments to tackle complex problems related to composite engineering. In the group, new materials are developed to meet new challenging operational conditions, techniques are being developed to understand their behavior, monitor their integrity, and computational approaches are being put in place to make possible the prediction of the relations between microstructure, functionality and durability.

Optimizing the microstructure to achieve the best performance

Successfully capturing the structural properties and optimal functionality of composite and heterogeneous materials requires a multi-faceted set of skills. The COHMAS team is split 50 percent with experts in computational mechanics while the other 50 percent has an expertise in experimental mechanics.

One of the particularities of Professor Lubineau’s team, part of the mechanical engineering program and specializing in a wide variety of composite materials, is to bring together people with very different backgrounds, ranging from mechanical engineering, applied mathematics, and theoretical mechanics to material science and chemical engineering.

“This wide variety of background makes the team able to tackle real composite problems that are necessarily multiphysics and multiscale problems. This also makes the team capable of theoretically designing the microstructure to reach the best performance, and then to synthesize it and explore it from the experimental point of view; this ability is quite rare in a single group,” Prof. Lubineau says.

The background of the team being primarily Mechanical Engineering and not Material Science, “we look at the material more from a structural point of view and this completely changes the approach” as Lubineau explains. The COHMAS team sees the material as a structure or as something that is part of a structure.

For illustration purposes, Prof. Lubineau takes the example of an aircraft: “The stresses, strains and everything is very heterogeneous. So it becomes necessary to accommodate the gradients in order to optimize materials at the critical locations in the aircraft’s structure.”

Doing so, Prof. Lubineau’s group has recently design highly conductive polymer fibers with controlled conductivity and piezoresistivity. “Such fibers will help in creating new self sensing and multifunctional structures and fast-response heating components in wearable textiles. They are the building blocks for better functional integration which serves cost reduction, energy efficiency and improved conductivity in service,” said Prof. Lubineau. “This has been made possible only by people with very different backgrounds working together towards a common goal”.

Prof. Lubineau’s group also works on composite materials destined for large industrial pipes, five or six meters in diameter, used for oil or water transportation. Particularly in arid regions like in Saudi Arabia, these pipes can experience high levels of degradation and specific aging conditions due to the extreme environmental conditions. Here again, understanding how the microstructure drives the final performance is key to process and design optimization.

Predicting and monitoring integrity

Material design is important, but understanding how the material is going to evolve in time is at least as crucial. A material might have tremendous properties, and be totally useless if these cannot be sustained at long term in a real working environment.

Among the multitude of factors that need to be considered are: mechanical degradation, aging, coupling with environments.

“You need to be able to predict what will happen in thirty years based on experiments that cannot last for more than a few weeks or a few months. What we want to achieve is more than a classical phenomenological model. We need models that can be use for making predictions with trust, models that can be use for design and exploration of new solutions,” Lubineau said.

Predictive science, with a physics based description of experimental observations later formalized in rigorous models, is then essential to Prof. Lubineau’s group. They have been engaged in designing models for many advanced structures while at Kaust, ranging from composite fuselage integrity to pipes integrity in sour environment.

Prof. Lubineau stresses that the objective is not to replace accelerated testing that is usually the preferred choice in industry (that means subjecting the structure to harsher condition during a shorter time to predict long term degradation).

“The objective of predictive testing is first, to design relevant accelerated testing conditions that are actually representative of what will happen at long term, and to understand the physics well enough to develop techniques for structural health monitoring (SHM),” said Prof. Lubineau.

“Monitoring composites is a real challenge today. Practical technologies are investigated to provide the most efficient and reliable real time monitoring such as optical fiber sensing (with Fiber Bragg Gratings) or electrical impedance/resistivity tomography (EIT/ERT). Thanks to these detection methods more challenging engineering may be envisaged through the design of preventive maintenance strategies.” His team is then investigating how such reliable models can be used for better SHM techniques. Successes have already been met for impedance based monitoring for example.

Computational techniques for better design of Composite structures

A last axis of Prof. Lubineau’s group is the design of adequate computational techniques to predict the integrity of complex structures such as composite made structures.

Prediction of crack propagation in such complex media is particularly challenging. Yet, this is a real industrial need.

“A crack is first of all a discontinuity, and continuum mechanics does not like discontinuities. It makes simulations much more complex and sometimes intractable with current technologies when many of them are involved,” said Prof. Lubineau.

He developed with Boeing a successful technique called “morphing”, published in Journal of the Mechanics and Physics of Solids, in which non-local continuum mechanics can be efficiently glued with classical continuum mechanics. “This provides a natural framework for computing crack nucleation and extension. This is still in its infancy, but we believe a promising technique in the future” adds Prof. Lubineau

Collaborations with Industry

Most of Prof. Lubineau’s research at COHMAS is done in close collaboration with major industrial partners such as Boeing, Sabic, Aramco or Amiantit. The applied research and advanced theoretical concepts are directly tested and applied to concrete problems.

Despite the variety of these projects, they are all related to the application of advanced composite material to some real application such as composite fuselage, composite pipes, composites for civil engineering or the automotive industry. The team helps in bridging the gap between theoretical knowledge and the real application of these materials.

Saudi Arabia is already a major player as a provider of the raw products. But Prof. Lubineau foresees an expanded future role for the Kingdom where, instead of just selling the raw material, Saudi Arabia could directly sell technologies with the more advanced derived material at a much higher added value. “This can really play a role in developing the local economy.”

Source: KAUST

Artist’s impression of exocomets around Beta Pictoris. Credit: ESO

Two Families of Comets Found Around Nearby Star

Two Families of Comets Found Around Nearby Star


The HARPS instrument at ESO’s La Silla Observatory in Chile has been used to make the most complete census of comets around another star ever created. A French team of astronomers has studied nearly 500 individual comets orbiting the star Beta Pictoris and has discovered that they belong to two distinct families of exocomets: old exocomets that have made multiple passages near the star, and younger exocomets that probably came from the recent breakup of one or more larger objects. The new results will appear in the journal Nature on 23 October 2014.

Beta Pictoris is a young star located about 63 light-years from the Sun. It is only about 20 million years old and is surrounded by a huge disc of material — a very active young planetary system where gas and dust are produced by the evaporation of comets and the collisions of asteroids.

Artist’s impression of exocomets around Beta Pictoris. Credit: ESO
Artist’s impression of exocomets around Beta Pictoris. Credit: ESO

Flavien Kiefer (IAP/CNRS/UPMC), lead author of the new study sets the scene: “Beta Pictoris is a very exciting target! The detailed observations of its exocomets give us clues to help understand what processes occur in this kind of young planetary system.”

For almost 30 years astronomers have seen subtle changes in the light from Beta Pictoris that were thought to be caused by the passage of comets in front of the star itself. Comets are small bodies of a few kilometres in size, but they are rich in ices, which evaporate when they approach their star, producing gigantic tails of gas and dust that can absorb some of the light passing through them. The dim light from the exocomets is swamped by the light of the brilliant star so they cannot be imaged directly from Earth.

To study the Beta Pictoris exocomets, the team analysed more than 1000 observations obtained between 2003 and 2011 with the HARPS instrument on the ESO 3.6-metre telescope at the La Silla Observatory in Chile.

The researchers selected a sample of 493 different exocomets. Some exocomets were observed several times and for a few hours. Careful analysis provided measurements of the speed and the size of the gas clouds. Some of the orbital properties of each of these exocomets, such as the shape and the orientation of the orbit and the distance to the star, could also be deduced.

This analysis of several hundreds of exocomets in a single exo-planetary system is unique. It revealed the presence of two distinct families of exocomets: one family of old exocomets whose orbits are controlled by a massive planet [1], and another family, probably arising from the recent breakdown of one or a few bigger objects. Different families of comets also exist in the Solar System.

The exocomets of the first family have a variety of orbits and show a rather weak activity with low production rates of gas and dust. This suggests that these comets have exhausted their supplies of ices during their multiple passages close to Beta Pictoris [2].

The exocomets of the second family are much more active and are also on nearly identical orbits [3]. This suggests that the members of the second family all arise from the same origin: probably the breakdown of a larger object whose fragments are on an orbit grazing the star Beta Pictoris.

Flavien Kiefer concludes: “For the first time a statistical study has determined the physics and orbits for a large number of exocomets. This work provides a remarkable look at the mechanisms that were at work in the Solar System just after its formation 4.5 billion years ago.”

Notes

[1] A giant planet, Beta Pictoris b, has also been discovered in orbit at about a billion kilometres from the star and studied using high resolution images obtained with adaptive optics.

[2] Moreover, the orbits of these comets (eccentricity and orientation) are exactly as predicted for comets trapped inorbital resonance with a massive planet. The properties of the comets of the first family show that this planet in resonance must be at about 700 million kilometres from the star  — close to where the planet Beta Pictoris b was discovered.

[3] This makes them similar to the comets of the Kreutz family in the Solar System, or the fragments of Comet Shoemaker-Levy 9, which impacted Jupiter in July 1994.

Source: ESO