It's a 3-D printer, but not as we know it

3D printing techniques have quickly become some of the most widely used tools to rapidly design and build new components. A team of engineers at the University of Bristol has developed a new type of 3D printing that can print composite materials, which are used in many high performance products such as tennis rackets, golf clubs and aeroplanes. This technology will soon enable a much greater range of things to be 3D printed at home and at low-cost.

The study published in Smart Materials and Structures creates and demonstrates a novel method in which ultrasonic waves are used to carefully position millions of tiny reinforcement fibres as part of the 3D printing process. The fibres are formed into a microscopic reinforcement framework that gives the material strength. This microstructure is then set in place using a focused laser beam, which locally cures the epoxy resin and then prints the object.

To achieve this the research team mounted a switchable, focused laser module on the carriage of a standard three-axis 3D printing stage, above the new ultrasonic alignment apparatus.

Tom Llewellyn-Jones, a PhD student in advanced composites who developed the system, said: "We have demonstrated that our ultrasonic system can be added cheaply to an off-the-shelf 3D printer, which then turns it into a composite printer."

In the study, a print speed of 20mm/s was achieved, which is similar to conventional additive layer techniques. The researchers have now shown the ability to assemble a plane of fibres into a reinforcement framework. The precise orientation of the fibres can be controlled by switching the ultrasonic standing wave pattern mid-print.

This approach allows the realisation of complex fibrous architectures within a 3D printed object. The versatile nature of the ultrasonic manipulation technique also enables a wide-range of particle materials, shapes and sizes to be assembled, leading to the creation of a new generation of fibrous reinforced composites that can be 3D printed.

Bruce Drinkwater, Professor of Ultrasonics in the Department of Mechanical Engineering, said: "Our work has shown the first example of 3D printing with real-time control over the distribution of an internal microstructure and it demonstrates the potential to produce rapid prototypes with complex microstructural arrangements. This orientation control gives us the ability to produce printed parts with tailored material properties, all without compromising the printing."

Dr Richard Trask, Reader in Multifunctional Materials in the Department of Aerospace Engineering, added: "As well as offering reinforcement and improved strength, our method will be useful for a range of smart materials applications, such as printing resin-filled capsules for self-healing materials or piezoelectric particles for energy harvesting."

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Story Source:

The above post is reprinted from materials provided by University of Bristol. Note: Materials may be edited for content and length.

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Journal Reference:

1. Thomas M Llewellyn-Jones, Bruce W Drinkwater, Richard S Trask. 3D printed components with ultrasonically arranged microscale structure. Smart Materials and Structures, 2016; 25 (2): 02LT01 DOI:10.1088/0964-1726/25/2/02LT01

Watching electrons cool in 30 quadrillionths of a second

An illustration showing single layers of graphene with thin layers of insulating boron nitride that form a sandwich structure.

Two University of California, Riverside assistant professors of physics are among a team of researchers that have developed a new way of seeing electrons cool off in an extremely short time period.

The development could have applications in numerous places where heat management is important, including visual displays, next-generation solar cells and photodetectors for optical communications.

In visual displays, such as those used in cell phones and computer monitors, and photodetectors, which have a wide variety of applications including solar energy harvesting and fiber optic telecommunications, much of the energy of the electrons is wasted by heating the material. Controlling the flow of heat in the electrons, rather than wasting this energy by heating the material, could potentially increase the efficiency of such devices by converting excess energy into useful power.

The research is outlined in a paper, "Tuning ultrafast electron thermalization pathways in a van der Waals heterostructure," published online Monday (Jan. 18) in the journal Nature Physics. Nathan Gabor and Joshua C.H. Lui, assistant professors of physics at UC Riverside, are among the co-authors.

In electronic materials, such as those used in semiconductors, electrons can be rapidly heated by pulses of light. The time it takes for electrons to cool each other off is extremely short, typically less than 1 trillionth of a second.

To understand this behavior, researchers use highly specialized tools that utilize ultra-fast laser techniques. In the two-dimensional material graphene cooling excited electrons occurs even faster, taking only 30 quadrillionths of a second. Previous studies struggled to capture this remarkably fast behavior.

To solve that, the researchers used a completely different approach. They combined single layers of graphene with thin layers of insulating boron nitride to form a sandwich structure, known as a van der Waals heterostructure, which gives electrons two paths to choose from when cooling begins. Either the electrons stay in graphene and cool by bouncing off one another, or they get sucked out of graphene and move through the surrounding layer.

By tuning standard experimental knobs, such as voltage and optical pulse energy, the researchers found they can precisely control where the electrons travel and how long they take to cool off. The work provides new ways of seeing electrons cool off at extremely short time scales, and demonstrates novel devices for nanoscale optoelectronics.

This structure is one of the first in a new class of devices that are synthesized by mechanically stacking atomically thin membranes. By carefully choosing the materials that make up the device, the researchers developed a new type of optoelectronic photodetector that is only 10 nanometers thick. Such devices address the technological drive for ultra-dense, low-power, and ultra-efficient devices for integrated circuits.

The research follows advances made in 2011 Science article, in which the research team discovered the fundamental importance of hot electrons in the optoelectronic response of devices based on graphene.

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Story Source:

The above post is reprinted from materials provided by University of California - Riverside. Note: Materials may be edited for content and length.

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Journal Reference:

1. Qiong Ma, Trond I. Andersen, Nityan L. Nair, Nathaniel M. Gabor, Mathieu Massicotte, Chun Hung Lui, Andrea F. Young, Wenjing Fang, Kenji Watanabe, Takashi Taniguchi, Jing Kong, Nuh Gedik, Frank H. L. Koppens, Pablo Jarillo-Herrero. Tuning ultrafast electron thermalization pathways in a van der Waals heterostructure. Nature Physics, 2016; DOI: 10.1038/nphys3620

Astronomers Detect Signs of an Invisible Black Hole at the Center of the Milky Way

A team of astronomers led by Tomoharu Oka, a professor at Keio University in Japan, has found an enigmatic gas cloud, called CO-0.40-0.22, only 200 light years away from the center of the Milky Way. What makes CO-0.40-0.22 unusual is its surprisingly wide velocity dispersion: the cloud contains gas with a very wide range of speeds. The team found this mysterious feature with two radio telescopes, the Nobeyama 45-m Telescope in Japan and the ASTE Telescope in Chile, both operated by the National Astronomical Observatory of Japan.

To investigate the detailed structure, the team observed CO-0.40-0.22 with the Nobeyama 45-m Telescope again to obtain 21 emission lines from 18 molecules. The results show that the cloud has an elliptical shape and consists of two components: a compact but low density component with a very wide velocity dispersion of 100 km/s, and a dense component extending 10 light years with a narrow velocity dispersion.

What makes this velocity dispersion so wide? There are no holes inside of the cloud. Also, X-ray and infrared observations did not find any compact objects. These features indicate that the velocity dispersion is not caused by a local energy input, such as supernova explosions.

Figure. (a) The center of the Milky Way seen in the 115 and 346 GHz emission lines of carbon monoxide (CO). The white regions show the condensation of dense, warm gas. (b) Close-up intensity map around CO-0.40-0.22 seen in the 355 GHz emission line of HCN molecules. The ellipses indicate shell structures in the gas near C0-0.40-0.22. (c) Velocity dispersion diagram taken along the dotted line shown above. The wide velocity dispersion of 100 km/s in CO-0.40-0.22 stands out.

The team performed a simple simulation of gas clouds flung by a strong gravity source. In the simulation, the gas clouds are first attracted by the source and their speeds increase as they approach it, reaching maximum at the closest point to the object. After that the clouds continue past the object and their speeds decrease. The team found that a model using a gravity source with 100 thousand times the mass of the Sun inside an area with a radius of 0.3 light years provided the best fit to the observed data. “Considering the fact that no compact objects are seen in X-ray or infrared observations,” Oka, the lead author of the paper that appeared in the Astrophysical Journal Letters, explains “as far as we know, the best candidate for the compact massive object is a black hole.”

If that is the case, this is the first detection of an intermediate mass black hole. Astronomers already know about two sizes of black holes: stellar-mass black holes, formed after the gigantic explosions of very massive stars; and supermassive black holes (SMBH) often found at the centers of galaxies. The mass of SMBH ranges from several million to billions of times the mass of the Sun. A number of SMBHs have been found, but no one knows how the SMBHs are formed. One idea is that they are formed from mergers of many intermediate mass black holes. But this raises a problem because so far no firm observational evidence for intermediate mass black holes has been found. If the cloud CO-0.40-0.22, located only 200 light years away from Sgr A* (the 400 million solar mass SMBH at the center of the Milky Way), contains an intermediate mass black hole, it might support the intermediate mass black hole merger scenario of SMBH evolution.

(Left Top) CO-0.40-0.22 seen in the 87 GHz emission line of SiO molecules. (Left Bottom) Position-velocity diagram of CO-0.04-0.22 along the magenta line in the top panel. (Right Top) Simulation results for two moving clouds affected by a strong compact gravity source. The diagram shows changes in the positions and shapes of the clouds over a period of 900 thousand years (starting from t=0) at intervals of 100 thousand years. The axes are in parsecs (1 parsec = 3.26 light years). (Right Bottom) Comparison of observational results (in gray) and the simulation (red, magenta, and orange) in terms of the shape and velocity structure. The shapes and velocities of the clouds at 700 thousand years in the simulation match the observational results well.

These results open a new way to search for black holes with radio telescopes. Recent observations have revealed that there are a number of wide-velocity-dispersion compact clouds similar to CO-0.40-0.22. The team proposes that some of those clouds might contain black holes. A study suggested that there are 100 million black holes in the Milky Way Galaxy, but X-ray observations have only found dozens so far. Most of the black holes may be “dark” and very difficult to see directly at any wavelength. “Investigations of gas motion with radio telescopes may provide a complementary way to search for dark black holes” said Oka. “The on-going wide area survey observations of the Milky Way with the Nobeyama 45-m Telescope and high-resolution observations of nearby galaxies using the Atacama Large Millimeter/submillimeter Array (ALMA) have the potential to increase the number of black hole candidates dramatically.”

The observation results were published as Oka et al. “Signature of an Intermediate-Mass Black Hole in the Central Molecular Zone of Our Galaxy” in the Astrophysical Journal Letters issued on January 1, 2016. The research team members are Tomoharu Oka, Reiko Mizuno, Kodai Miura, Shunya Takekawa, all at Keio University.

This research is supported by the Japanese Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (C) No. 24540236.

PDF Copy of the Study: Signature of an Intermediate-Mass Black Hole in the Central Molecular Zone of Our Galaxy

UAE desert sand can store solar energy up to 1000°c

Desert sand from the UAE can now be considered a possible thermal energy storage (TES) material, say researchers. Its thermal stability, specific heat capacity, and tendency to agglomerate have been studied at high temperatures

The Masdar Institute of Science and Technology, an independent, research-driven graduate-level university focused on advanced energy and sustainable technologies, today announced that its researchers have successfully demonstrated that desert sand from the UAE could be used in concentrated solar power (CSP) facilities to store thermal energy up to 1000°C.

The research project called 'Sandstock' has been seeking to develop a sustainable and low-cost gravity-fed solar receiver and storage system, using sand particles as the heat collector, heat transfer and thermal energy storage media.

Desert sand from the UAE can now be considered a possible thermal energy storage (TES) material. Its thermal stability, specific heat capacity, and tendency to agglomerate have been studied at high temperatures.

Dr. Behjat Al Yousuf, Interim Provost, Masdar Institute, said, "The research success of the Sandstock project illustrates the strength of our research and its local relevance. With the launch of the MISP in November, we have further broadened the scope of our solar energy research and we believe more success will follow in the months ahead."

A research paper on the findings developed under the guidance of Dr. Nicolas Calvet, Assistant Professor, Department of Mechanical and Materials Engineering, was presented by PhD student Miguel Diago at the 21st Solar Power and Chemical Energy Systems (SolarPACES 2015) Conference in South Africa. The paper was co-authored by alumni Alberto Crespo Iniesta, Dr. Thomas Delclos, Dr. Tariq Shamim, Professor of Mechanical and Materials Engineering at Masdar Institute, and Dr. Audrey Soum-Glaude (French National Center for Scientific Research PROMES CNRS Laboratory).

Replacing the typical heat storage materials used in TES systems -- synthetic oil and molten salts -- with inexpensive sand can increase plant efficiency due to the increased working temperature of the storage material and therefore reduce costs. A TES system based on such a local and natural material like sand also represents a new sustainable energy approach that is relevant for the economic development of Abu Dhabi's future energy systems.

The analyses showed that it is possible to use desert sand as a TES material up to 800-1000 °C. The sand chemical composition has been analyzed with the X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques, which reveal the dominance of quartz and carbonate materials. The sand's radiant energy reflectiveness was also measured before and after a thermal cycle, as it may be possible to use the desert sand not only as a TES material but also as a direct solar absorber under concentrated solar flux.

Dr Nicolas Calvet said: "The availability of this material in desert environments such as the UAE allows for significant cost reductions in novel CSP plants, which may use it both as TES material and solar absorber. The success of the Sandstock project reflects that usability and practical benefits of the UAE desert sand."

In parallel to sand characterization, a laboratory scale prototype was tested with a small solar furnace at the laboratory of PROMES CNRS 1 MW solar furnace in Odeillo, France. Masdar Institute alumnus Alberto Crespo Iniesta was in charge of the design, construction, and experiment.

The next step of the project is to test an improved prototype at the pre-commercial scale at the Masdar Institute Solar Platform (MISP) using the beam down concentrator, potentially in collaboration with an industrial partner.

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Story Source:

The above post is reprinted from materials provided by Masdar Institute of Science and Technology. Note: Materials may be edited for content and length.

Single-chip laser delivers powerful result

A schematic of the new laser system.

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From their use in telecommunication to detecting hazardous chemicals, lasers play a major role in our everyday lives. They keep us connected, keep us safe, and allow us to explore the dark corners of the universe.

Now a Northwestern University team has made this ever-important tool even simpler and more versatile by integrating a mid-infrared tunable laser with an on-chip amplifier. This breakthrough allows adjustable wavelength output, modulators, and amplifiers to be held inside a single package.

With this architecture, the laser has demonstrated an order-of-magnitude more output power than its predecessors, and the tuning range has been enhanced by more than a factor of two.

"We have always been leaders in high-power and high-efficiency lasers," said Manijeh Razeghi, Walter P. Murphy Professor of Electrical Engineering and Computer Science at Northwestern's McCormick School of Engineering, who led the study. "Combining an electrically tunable wavelength with high power output was the next logical extension."

Supported by the Department of Homeland Security Science and Technology Directorate, National Science Foundation, Naval Air Systems Command, and NASA, the research is described in a paper published online on December 21, 2015 in the journal Applied Physics Letters.

With mid-infrared spectroscopy, a chemical can be identified through its unique absorption spectrum. This greatly interests government agencies that aim to detect hazardous chemicals or possible explosive threats. Because Razeghi's new system is highly directional, the high power can be used more efficiently, allowing for the greater ability to detect chemicals. It also allows for standoff application, which keeps personnel physically distant from potentially dangerous environments. The technology could also benefit free-space optical communications and aircraft protection.

This new research builds on Razeghi's many years of research with Northwestern's Center for Quantum Devices. In 2012, she developed a widely tunable, single chip, mid-infrared laser.

"We demonstrated the first continuously tunable, continuous operation, mid-infrared lasers with electrical tuning of the emission wavelength," Razeghi said. "This initial demonstration was very exciting, and continuing developing has led us to a number of new projects."

Story Source:

The above post is reprinted from materials provided by Northwestern University. The original item was written by Amanda Morris. Note: Materials may be edited for content and length.

Journal Reference:

1. S. Slivken, S. Sengupta, M. Razeghi. High power continuous operation of a widely tunable quantum cascade laser with an integrated amplifier. Applied Physics Letters, 2015; 107 (25): 251101 DOI: 10.1063/1.4938005

NuSTAR finds cosmic clumpy doughnut around black hole

Galaxy 1068 can be seen in close-up in this view from NASA's Hubble Space Telescope. NuSTAR's high-energy X-rays eyes were able to obtain the best view yet into the hidden lair of the galaxy's central, supermassive black hole.

The most massive black holes in the universe are often encircled by thick, doughnut-shaped disks of gas and dust. This deep-space doughnut material ultimately feeds and nourishes the growing black holes tucked inside.

Until recently, telescopes weren't able to penetrate some of these doughnuts, also known as tori.

"Originally, we thought that some black holes were hidden behind walls or screens of material that could not be seen through," said Andrea Marinucci of the Roma Tre University in Italy, lead author of a new Monthly Notices of the Royal Astronomical Society study describing results from NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, and the European Space Agency's XMM-Newton space observatory.

With its X-ray vision, NuSTAR recently peered inside one of the densest of these doughnuts known to surround a supermassive black hole. This black hole lies at the center of a well-studied spiral galaxy called NGC 1068, located 47 million light-years away in the Cetus constellation.

The observations revealed a clumpy, cosmic doughnut.

"The rotating material is not a simple, rounded doughnut as originally thought, but clumpy," said Marinucci.

Doughnut-shaped disks of gas and dust around supermassive black holes were first proposed in the mid-1980s to explain why some black holes are hidden behind gas and dust, while others are not. The idea is that the orientation of the doughnut relative to Earth affects the way we perceive a black hole and its intense radiation. If the doughnut is viewed edge-on, the black hole is blocked. If the doughnut is viewed face-on, the black hole and its surrounding, blazing materials can be detected. This idea is referred to as the unified model because it neatly joins together the different black hole types, based solely upon orientation.

In the past decade, astronomers have been finding hints that these doughnuts aren't as smoothly shaped as once thought. They are more like defective, lumpy doughnuts that a doughnut shop might throw away.

The new discovery is the first time this clumpiness has been observed in an ultra-thick doughnut, and supports the idea that this phenomenon may be common. The research is important for understanding the growth and evolution of massive black holes and their host galaxies.

"We don't fully understand why some supermassive black holes are so heavily obscured, or why the surrounding material is clumpy," said co-author Poshak Gandhi of the University of Southampton in the United Kingdom. "This is a subject of hot research."

Both NuSTAR and XMM-Newton observed the supermassive black hole in NGC 1068 simultaneously on two occasions between 2014 to 2015. On one of those occasions, in August 2014, NuSTAR observed a spike in brightness. NuSTAR observes X-rays in a higher-energy range than XMM-Newton, and those high-energy X-rays can uniquely pierce thick clouds around the black hole. The scientists say the spike in high-energy X-rays was due to a clearing in the thickness of the material entombing the supermassive black hole.

"It's like a cloudy day, when the clouds partially move away from the sun to let more light shine through," said Marinucci.

NGC 1068 is well known to astronomers as the first black hole to give birth to the unification idea. "But it is only with NuSTAR that we now have a direct glimpse of its black hole through such clouds, albeit fleeting, allowing a better test of the unification concept," said Marinucci.

The team says that future research will address the question of what causes the unevenness in doughnuts. The answer could come in many flavors. It's possible that a black hole generates turbulence as it chomps on nearby material. Or, the energy given off by young stars could stir up turbulence, which would then percolate outward through the doughnut. Another possibility is that the clumps may come from material falling onto the doughnut. As galaxies form, material migrates toward the center, where the density and gravity is greatest. The material tends to fall in clumps, almost like a falling stream of water condensing into droplets as it hits the ground.

"We'd like to figure out if the unevenness of the material is being generated from outside the doughnut, or within it," said Gandhi.

"These coordinated observations with NuSTAR and XMM-Newton show yet again the exciting science possible when these satellites work together," said Daniel Stern, NuSTAR project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.

For more information on NuSTAR, visit:

http://www.nasa.gov/nustar

http://www.nustar.caltech.edu/

Brain differences in compulsive video game players

A new study led by the University of Utah School of Medicine and Chung-Ang University provides evidence that several regions of the brain are hyperconnected in adolescent boys diagnosed with Internet gaming disorder (lines between colored areas, colored areas represent specific brain networks). Some of the changes may help game players respond to new information, others are associated with distractibility and poor impulse control.

Brain scans from nearly 200 adolescent boys provide evidence that the brains of compulsive video game players are wired differently. Chronic video game play is associated with hyperconnectivity between several pairs of brain networks. Some of the changes are predicted to help game players respond to new information. Other changes are associated with distractibility and poor impulse control. The research, a collaboration between the University of Utah School of Medicine, and Chung-Ang University in South Korea, was published online in Addiction Biology on Dec. 21, 2015.

"Most of the differences we see could be considered beneficial. However the good changes could be inseparable from problems that come with them," says senior author Jeffrey Anderson, M.D., Ph.D., associate professor of neuroradiology at the University of Utah School of Medicine.

Those with Internet gaming disorder are obsessed with video games, often to the extent that they give up eating and sleeping to play. This study reports that in adolescent boys with the disorder, certain brain networks that process vision or hearing are more likely to have enhanced coordination to the so-called salience network. The job of the salience network is to focus attention on important events, poising that person to take action. In a video game, the enhanced coordination could help a gamer to react more quickly to the rush of an oncoming fighter. And in life, to a ball darting in front of a car, or an unfamiliar voice in a crowded room.

"Hyperconnectivity between these brain networks could lead to a more robust ability to direct attention toward targets, and to recognize novel information in the environment," says Anderson. "The changes could essentially help someone to think more efficiently." Follow up studies will be needed to directly determine whether the boys with these brain differences do better on performance tests.

A more troublesome finding is a coordination between two brain regions, the dorsolateral prefrontal cortex and temporoparietal junction, that is more strong than in individuals who are not compulsive video game players. "Having these networks be too connected may increase distractibility," says Anderson. The same change is seen in patients with neuropsychiatric conditions such as schizophrenia, Down's syndrome, and autism, and in people with poor impulse control. At this point it's not known whether persistent video gaming causes rewiring of the brain, or whether people who are wired differently are drawn to video games.

This work is the largest, most comprehensive investigation of differences in the brains of compulsive video game players to date, says first author Doug Hyun Han, M.D., Ph.D., professor at Chung-Ang University School of Medicine and adjunct associate professor at the University of Utah School of Medicine. Study participants were screened in South Korea, where video game playing is a major social activity, much more than in the United States. The Korean government supports his research with the goal of finding ways to identify and treat addicts.

In this study, researchers performed magnetic resonance imaging on 106 boys between the ages of 10 to 19 who were seeking treatment for Internet gaming disorder, a psychological condition that the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) says warrants further research. The brain scans were compared to those from 80 boys without the disorder, and analyzed for regions that were activated simultaneously when participants were at rest. The more frequently two brain regions light up at the same time, the stronger the functional connectivity.

The team analyzed activity in 25 pairs of brain regions, 300 combinations in all. Specifically, boys with Internet gaming disorder had statistically significant, functional connections between the following pairs of brain regions:

• Auditory cortex (hearing) -- motor cortex (movement)
• Auditory cortex (hearing) -- supplementary motor cortices (movement)
• Auditory cortex (hearing) -- anterior cingulate (salience network)
• Frontal eye field (vision) -- anterior cingulate (salience network)
• Frontal eye field (vision) -- anterior insula (salience network)
• Dorsolateral prefrontal cortex -- temporoparietal junction

"Brain connectivity and psychiatric comorbidity in adolescents with Internet gaming disorder" was published in Addiction Biology online on December 21, 2015. In addition to Anderson and Han, the authors are Perry Renshaw from the University of Utah School of Medicine, and Sun Mi Kim and Sujin Bae from Chung-Ang University. The research was supported by a grant from the Korea Creative Content Agency

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Story Source:

The above post is reprinted from materials provided byUniversity of Utah Health Sciences. Note: Materials may be edited for content and length.

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Journal Reference:

1. Doug Hyun Han, Sun Mi Kim, Sujin Bae, Perry F. Renshaw, Jeffrey S. Anderson. Brain connectivity and psychiatric comorbidity in adolescents with Internet gaming disorder. Addiction Biology, 2015; DOI: 10.1111/adb.12347