Chemical etching method helps transistors stand tall

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An array fin transistors made by the MacEtch method. The fins are tall and thin, with a higher aspect ratio and smoother sides than other methods can produce.

Smaller and faster has been the trend for electronic devices since the inception of the computer chip, but flat transistors have gotten about as small as physically possible. For researchers pushing for even faster speeds and higher performance, the only way to go is up.

University of Illinois researchers have developed a way to etch very tall, narrow finFETs, a type of transistor that forms a tall semiconductor "fin" for the current to travel over. The etching technique addresses many problems in trying to create 3-D devices, typically done now by stacking layers or carving out structures from a thicker semiconductor wafer.

"We are exploring the electronic device roadmap beyond silicon," said Xiuling Li, a U. of I. professor of electrical and computer engineering and the leader of the study. "With this technology, we are pushing the limit of the vertical space, so we can put more transistors on a chip and get faster speeds. We are making the structures very tall and smooth, with aspect ratios that are impossible for other existing methods to reach, and using a material with better performance than silicon."

The team published the results in the journal Electron Device Letters.

Typically, finFETs are made by bombarding a semiconductor wafer with beams of high-energy ions. This technique has a number of challenges, Li said. For one, the sides of the fins are sloped instead of straight up and down, making them look more like tiny mountain ranges than fins. This shape means that only the tops of the fins can perform reliably. But an even bigger problem for high-performance applications is how the ion beam damages the surface of the semiconductor, which can lead to current leakage.

The Illinois technique, called metal-assisted chemical etching or MacEtch, is a liquid-based method, which is simpler and lower-cost than using ion beams, Li said. A metal template is applied to the surface, then a chemical bath etches away the areas around the template, leaving the sides of the fins vertical and smooth.

"We use a MacEtch technique that gives a much higher aspect ratio, and the sidewalls are nearly 90 degrees, so we can use the whole volume as the conducting channel," said graduate student Yi Song, the first author of the paper. "One very tall fin channel can achieve the same conduction as several short fin channels, so we save a lot of area by improving the aspect ratio."

The smoothness of the sides is important, since the semiconductor fins must be overlaid with insulators and metals that touch the tiny wires that interconnect the transistors on a chip. To have consistently high performance, the interface between the semiconductor and the insulator needs to be smooth and even, Song said.

Right now, the researchers use the compound semiconductor indium phosphide with gold as the metal template. However, they are working to develop a MacEtch method that does not use gold, which is incompatible with silicon.

"Compound semiconductors are the future beyond silicon, but silicon is still the industry standard. So it is important to make it compatible with silicon and existing manufacturing processes," Li said.

The researchers said the MacEtch technique could apply to many types of devices or applications that use 3-D semiconductor structures, such as computing memory, batteries, solar cells and LEDs.

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Story Source:

The above post is reprinted from materials provided by University of Illinois at Urbana-Champaign. Note: Materials may be edited for content and length.

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Journal Reference:

1. Yi Song, Parsian K. Mohseni, Seung Hyun Kim, Jae Cheol Shin, Tatsumi Ishihara, Ilesanmi Adesida, Xiuling Li. Ultra-high Aspect Ratio InP Junctionless FinFETs by a Novel Wet Etching Method. IEEE Electron Device Letters, 2016; 1 DOI: 10.1109/LED.2016.2577046

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Cite This Page:

University of Illinois at Urbana-Champaign. "Chemical etching method helps transistors stand tall." ScienceDaily. ScienceDaily, 26 July 2016. <www.sciencedaily.com/releases/2016/07/160726094115.htm>.

DNA analyses reveal genetic identities of world's first farmers

Research reshapes understanding of genetic heritage of modern West Eurasians

Source:

Harvard Medical School

Summary:

Conducting the first large-scale, genome-wide analyses of ancient human remains from the Near East, an international team of scientists has illuminated the genetic identities and population dynamics of the world's first farmers.

FULL STORY

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This study reveals three genetically distinct farming populations living in the Near East at the dawn of agriculture 12,000 to 8,000 years ago: two newly described groups in Iran and the Levant and a previously reported group in Anatolia, in what is now Turkey.

Credit: © MG / Fotolia

Conducting the first large-scale, genome-wide analyses of ancient human remains from the Near East, an international team led by Harvard Medical School has illuminated the genetic identities and population dynamics of the world's first farmers.

The study reveals three genetically distinct farming populations living in the Near East at the dawn of agriculture 12,000 to 8,000 years ago: two newly described groups in Iran and the Levant and a previously reported group in Anatolia, in what is now Turkey.

The findings, published in Nature on July 25, also suggest that agriculture spread in the Near East at least in part because existing groups invented or adopted farming technologies, rather than because one population replaced another.

"Some of the earliest farming was practiced in the Levant, including Israel and Jordan, and in the Zagros mountains of Iran--two edges of the Fertile Crescent," said Ron Pinhasi, associate professor of archaeology at University College Dublin and co-senior author of the study. "We wanted to find out whether these early farmers were genetically similar to one another or to the hunter-gatherers who lived there before so we could learn more about how the world's first agricultural transition occurred."

The team's analyses alter what is known about the genetic heritage of present-day people in western Eurasia. They now appear to have descended from four major groups: hunter-gatherers in what is now western Europe, hunter-gatherers in eastern Europe and the Russian steppe, the Iran farming group and the Levant farming group.

"We found that the relatively homogeneous population seen across western Eurasia today, including Europe and the Near East, used to be a highly substructured collection of people who were as different from one another as present-day Europeans are from East Asians," said David Reich, professor of genetics at Harvard Medical School and co-senior author of the study.

"Near East populations mixed with one another over time and migrated into surrounding regions to mix with the people living there until those initially quite diverse groups became genetically very similar," added Iosif Lazaridis, HMS research fellow in genetics and first author of the study.

Early adopters

Even as advances in ancient-DNA technology have made it possible to probe population mixing and large-scale migrations that occurred thousands of years ago, researchers have had trouble studying the genetic history of the Near East because the region's warm climate has degraded much of the DNA in unearthed bones.

The team overcame the problem of poor-quality DNA in part by extracting genetic material from ear bones that can yield up to 100 times more DNA than other bones in the body. The team also used a technique called in-solution hybridization to enrich for human DNA and filter out contaminant DNA from microbes.

The combined techniques allowed the researchers to gather high quality genomic information from 44 ancient Near Easterners who lived between 14,000 and 3,400 years ago: hunter-gatherers from before the invention of farming, the first farmers themselves and their successors.

By comparing the genomes to one another as well as to those of nearly 240 previously studied ancient people from nearby regions and about 2,600 present-day people, the researchers learned that the first farming cultures in the Levant, Iran and Anatolia were all genetically distinct. Farmers in the Levant and Iran were genetically similar, however, to earlier hunter-gatherers who had lived in the same areas.

"Maybe one group domesticated goats and another began growing wheat, and the practices were shared in some way," said Lazaridis. "These different populations all invented or adopted some facets of the farming revolution, and they all flourished."

The findings tell a different story from what researchers believe happened later in Europe, when the first farmers moved in from Anatolia and largely replaced the hunter-gatherer populations who'd been living there.

Mix and match

Over the following 5,000 years, the Near East farming groups mixed with one another and with hunter-gatherers in Europe.

"All this extraordinary diversity collapsed," said Reich. "By the Bronze Age, populations had ancestry from many sources and broadly resembled present-day ones."

The researchers also learned how descendants of each early farming group, even as they began to intermingle, contributed to the genetic ancestry of people in different parts of the world: Farmers related to the Anatolian group spread west into Europe, people related to the Levant group moved south into East Africa, people related to those in Iran or the Caucasus went north into the Russian steppe, and people related to both the farmers in Iran and hunter-gatherers from the steppe spread into South Asia.

"The Near East was the missing link to understanding many human migrations," said Pinhasi.

Finally, the study provides a few more clues about a hypothetical, even more ancient, population called the Basal Eurasians, an early diverging branch of the family tree of humans living outside Africa, whose existence Lazaridis has inferred from DNA analyses but whose physical remains have not yet been found.

"Every single group from the ancient Near East appears to have Basal Eurasian ancestry--up to around fifty percent in the earliest groups," said Lazaridis.

To the researchers' surprise, statistical analyses suggested that the Basal Eurasians may have had no Neanderthal DNA. Other non-African groups have at least 2 percent Neanderthal DNA.

The team believes this finding could help explain why West Eurasians have less Neanderthal DNA than East Asians, even though Neanderthals are known to have lived in west Eurasia.

"Admixture with Basal Eurasians may have diluted the Neanderthal ancestry in West Eurasians who have ancient Near Eastern farmer ancestry," said Reich. "Basal Eurasians may have lived in parts of the Near East that did not come into contact with the Neanderthals."

Going forward, said Pinhasi, "We're eager to study remains from the world's first civilizations, who succeeded the samples analyzed in the study. The people everyone reads about in history books are now within the reach of our genetic technology."

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Story Source:

The above post is reprinted from materials provided by Harvard Medical School. Note: Materials may be edited for content and length.

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Journal Reference:

1. Iosif Lazaridis et al. Genomic insights into the origin of farming in the ancient Near East. Nature, July 2016 DOI: 10.1038/nature19310

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Cite This Page:

Harvard Medical School. "DNA analyses reveal genetic identities of world's first farmers: Research reshapes understanding of genetic heritage of modern West Eurasians." ScienceDaily. ScienceDaily, 25 July 2016. <www.sciencedaily.com/releases/2016/07/160725133733.htm>

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Hey robot, shimmy like a centipede

Devices mimic creature's surprising unstable advantage

FULL STORY

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What makes centipedes move with such agility? Researchers at Kyoto University have used simulations and robotics to find the answer -- and a surprising truth.

Credit: Kyoto University

Centipedes move quickly. And when one is coming directly at you, you might not care to spend a moment pondering its agility.

So perhaps our lack of understanding about just why centipedes move with such dexterity, even over obstacles, has been related to fear. But undeterred, researchers at Kyoto University have asked precisely this question, and have turned to computer simulations and ultimately robotics to find an answer.

What they have uncovered is a surprising insight into the mechanics of locomotion itself, namely that taming instability -- a factor that might be a disadvantage -- is a key to the centipede's success.

"During their locomotion, many legs are in contact with the ground to support the body against gravity and produce propulsive and decelerating forces," explains lead scientist Shinya Aoi. "These many legs are physically constrained on the ground, and this constraint can impede their locomotion maneuverability."

Centipedes overcome these constraints by harnessing instability, producing the creature's characteristic undulating movement.

"Our group developed a mathematical model of centipedes and found that the straight walk becomes unstable and body undulations appear through a supercritical Hopf bifurcation by changing the locomotion speed and body axis flexibility," continues Aoi, referring to a mathematical description of the walking system's tipping point from stable to unstable.

First with computer models and then with segmented, multi-legged robots, the team was able to replicate the centipede's movement, including the wave-like body motion, as described in a paper in the online journal Scientific Reports.

But Aoi and his colleagues are not satisfied with merely taming creepy crawlies.

"This study provides clues to unresolved issues of intelligent motor functions of animals, and meaningful insight for biological sciences," he says, pointing out that much remains unknown about the exact mechanics of animal locomotion.

And further down the line, such knowledge could lead to better motion for robots -- no matter how many legs they may have.

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Story Source:

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

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Journal Reference:

1. Shinya Aoi, Takahiro Tanaka, Soichiro Fujiki, Tetsuro Funato, Kei Senda, Kazuo Tsuchiya. Advantage of straight walk instability in turning maneuver of multilegged locomotion: a robotics approach. Scientific Reports, 2016; 6: 30199 DOI: 10.1038/srep30199

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Cite This Page:

Kyoto University. "Hey robot, shimmy like a centipede: Devices mimic creature's surprising unstable advantage." ScienceDaily. ScienceDaily, 22 July 2016. <www.sciencedaily.com/releases/2016/07/160722092944.htm>.

New remote-controlled microrobots for medical operations

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Scientists at EPFL and ETHZ have developed a new method for building microrobots that could be used in the body to deliver drugs and perform other medical operations.

For the past few years, scientists around the world have been studying ways to use miniature robots to better treat a variety of diseases. The robots are designed to enter the human body, where they can deliver drugs at specific locations or perform precise operations like clearing clogged-up arteries. By replacing invasive, often complicated surgery, they could optimize medicine.

EPFL scientist Selman Sakar teamed up with Hen-Wei Huang and Bradley Nelson at ETHZ to develop a simple and versatile method for building such bio-inspired robots and equipping them with advanced features. They also created a platform for testing several robot designs and studying different modes of locomotion. Their work, published in Nature Communications, produced complex reconfigurable microrobots that can be manufactured with high throughput. They built an integrated manipulation platform that can remotely control the robots' mobility with electromagnetic fields, and cause them to shape-shift using heat.

A robot that looks and moves like a bacterium

Unlike conventional robots, these microrobots are soft, flexible, and motor-less. They are made of a biocompatible hydrogel and magnetic nanoparticles. These nanoparticles have two functions. They give the microrobots their shape during the manufacturing process, and make them move and swim when an electromagnetic field is applied.

Building one of these microrobots involves several steps. First, the nanoparticles are placed inside layers of a biocompatible hydrogel. Then an electromagnetic field is applied to orientate the nanoparticles at different parts of the robot, followed by a polymerization step to "solidify" the hydrogel. After this, the robot is placed in water where it folds in specific ways depending on the orientation of the nanoparticles inside the gel, to form the final overall 3D architecture of the microrobot.

Once the final shape is achieved, an electromagnetic field is used to make the robot swim. Then, when heated, the robot changes shape and "unfolds." This fabrication approach allowed the researchers to build microrobots that mimic the bacterium that causes African trypanosomiasis, otherwise known as sleeping sickness. This particular bacterium uses a flagellum for propulsion, but hides it away once inside a person's bloodstream as a survival mechanism.

The researchers tested different microrobot designs to come up with one that imitates this behavior. The prototype robot presented in this work has a bacterium-like flagellum that enables it to swim. When heated with a laser, the flagellum wraps around the robot's body and is "hidden."

A better understanding of how bacteria behave

"We show that both a bacterium's body and its flagellum play an important role in its movement," said Sakar. "Our new production method lets us test an array of shapes and combinations to obtain the best motion capability for a given task. Our research also provides valuable insight into how bacteria move inside the human body and adapt to changes in their microenvironment."

For now, the microrobots are still in development. "There are still many factors we have to take into account," says Sakar. "For instance, we have to make sure that the microrobots won't cause any side-effects in patients."

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Story Source:

The above post is reprinted from materials provided by Ecole Polytechnique Fédérale de Lausanne. Note: Materials may be edited for content and length.

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Journal Reference:

1. Hen-Wei Huang, Mahmut Selman Sakar, Andrew J. Petruska, Salvador Pané, Bradley J. Nelson. Soft micromachines with programmable motility and morphology. Nature Communications, 2016; 7: 12263 DOI: 10.1038/ncomms12263

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Cite This Page:

Ecole Polytechnique Fédérale de Lausanne. "New remote-controlled microrobots for medical operations." ScienceDaily. ScienceDaily, 22 July 2016. <www.sciencedaily.com/releases/2016/07/160722104129.htm>

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Thinking inside the box: How our brain puts the world in order

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Neuroscientists have found the sorting center in the brain.

The world around is complex and changing constantly. To put it in order, we devise categories into which we sort new concepts. To do this we apply different strategies. A team of researchers at the Ruhr University Bochum (RUB) led by Prof. Dr. Boris Suchan, department of neuropsychology, and Prof. Dr. Onur Güntürkün, department of biopsychology, wanted to find our which areas of the brain regulate these strategies.

The results of their study using magnetic resonance imaging (MRI) show that there are indeed particular brain areas, which become active when a certain strategy of categorisation is applied.

When we categorise objects by comparing it to a prototype, the left fusiform gyrus is activated. This is an area, which is responsible for recognising abstract images. On the other hand, when we compare things to particular examples of a category, there is an activation of the left hippocampus. This field plays an important role for the storage or retrieval of memories.

Categories reduce information load

Thinking in categories or pigeonholing helps our brain in bringing order into a constantly changing world and it reduces the information load. Cognitive scientists differentiate between two main strategies which achieve this: the exemplar strategy and the prototype strategy.

When we want to find out, whether a certain animal fits into the category "bird" we would at first apply the prototype strategy and compare it to an abstract general "bird." This prototype has the defining features of the class, like a beak, feathers or the ability to fly. But when we encounter outliers or exceptions like an emu or a penguin, this strategy may be of no use. Then we apply the exemplar strategy and compare the animal to many different known examples of the category. This helps us find the right category, even for "distant relations."

Complex interaction

To find out where our brain is activated, when it is ordering the world, the neuroscientists in Bochum performed an MRI scan, while volunteers were completing a categorisation task. The functional imaging data showed that both strategies are triggered by different areas of the brain.

The scientists believe that there is a complex interaction between both learning patterns. "The results implicate that both strategies originate from distinct brain areas. We also observed that, during the learning process, the rhythm of activation in the two areas synchronised. This shows that both cognitive processes cannot be neatly separated," explains Boris Suchan. Further modelling and research must now clarify this interaction.

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Story Source:

The above post is reprinted from materials provided by Ruhr-Universitaet-Bochum. Note: Materials may be edited for content and length.

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Journal Reference:

1. Robert K. Lech, Onur Güntürkün, Boris Suchan. An interplay of fusiform gyrus and hippocampus enables prototype- and exemplar-based category learning. Behavioural Brain Research, 2016; 311: 239 DOI: 10.1016/j.bbr.2016.05.049

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Cite This Page:

Ruhr-Universitaet-Bochum. "Thinking inside the box: How our brain puts the world in order." ScienceDaily. ScienceDaily, 20 July 2016. <www.sciencedaily.com/releases/2016/07/160720094600.htm>

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New detector overcomes key challenge in using light for wireless communications

With data rates of more than 2 gigabits per second, new approach in photodetection could simplify free-space optical communication

Researchers developed a new way to capture and concentrate light for free-space optical communication. The fluorescent optical fibers absorb blue light coming from any direction over a large area and emit green light that travels inside the optical fiber until it reaches a very fast photodetector.

Today's high-speed wired communication networks use lasers to carry information through optical fibers, but wireless networks are currently based on radio frequencies or microwaves. In an advance that could one day make light-based wireless communications ubiquitous, researchers from Facebook Inc.'s Connectivity Lab have demonstrated a conceptually new approach for detecting optical communication signals traveling through the air.

The team described the new technology, which could pave the way for fast optical wireless networks capable of delivering internet service to far-flung places, in Optica, The Optical Society's journal for high impact research.

Bridging the Digital Divide

Facebook's Connectivity Lab develops technologies aimed at providing affordable internet services to the approximately 4 billion people in the world who cannot currently access it. "A large fraction of people don't connect to the internet because the wireless communications infrastructure is not available were they live, mostly in very rural areas of the world," said Tobias Tiecke, who leads the research team. "We are developing communication technologies that are optimized for areas where people live far apart from each other."

Light-based wireless communication, also called free-space optical communications, offers a promising way to bring the internet to areas where optical fibers and cell towers can be challenging to deploy in a cost-effective way. Using laser light to carry information across the atmosphere can potentially offer very high bandwidths and data capacity, but one of the primary challenges has been how to precisely point a very small laser beam carrying the data at a tiny light detector that is some distance away.

In the new study, Facebook researchers demonstrate a method for using fluorescent materials instead of traditional optics to collect light and concentrate it onto a small photodetector. They combined this light collector, which features 126 square centimeters of surface that can collect light from any direction, with existing telecommunications technology to achieve data rates of more than 2 gigabits-per-second (Gbps).

"We demonstrated the use of fluorescent optical fibers that absorb one color of light and emit another color," said Tiecke. "The optical fibers absorb light coming from any direction over a large area, and the emitted light travels inside the optical fiber, which funnels the light to a small, very fast photodetector."

Fast Communication Needs Fast Detectors

A high-speed free-space optical network requires very fast detectors to receive the laser light carrying information. But speed must be balanced against size; although larger detectors make an easier target to hit with a beam of laser light that's traveling through the air, increasing the size of a detector makes it slower.

A combination of optics and mechanical systems can be used to track the position of the detector and point it to the laser, but these approaches add quite a bit of complexity. The new light collector uses plastic optical fibers containing organic dye molecules that absorb blue light and emit green light. This setup replaces the classical optics and motion platform typically required to point the light to the collection area.

"The fact that these fluorescent optical fibers emit a different color than they absorb makes it possible to increase the brightness of the light entering the system," said Tiecke. "This approach has been used in luminescent concentrators for solar light harvesting, where the speed of the color conversion doesn't matter. We showed that the same concept can be used for communication to circumvent pointing and tracking problems while accomplishing very high speeds."

The fast speeds are possible because less than 2 nanoseconds lapse between the blue light absorption and the green light emission. In addition, by incorporating a signal modulation method called orthogonal frequency division multiplexing, or OFDM, the researchers transmitted more than 2 Gbps despite the system's bandwidth of 100 MHz. OFDM is a method of encoding digital data so that multiple data streams can be transmitted at once. Although it is commonly used for wired and wireless communication, it is not typically used with laser communication.

"We achieved such high data rates using commercially available materials that are not designed for communications applications," said Tiecke. "We want to get other groups interested in developing materials that are tailored for communications applications."

If materials were developed that operate in the infrared part of the spectrum, which would be invisible to people, and were even faster than the blue/green light system, the new approach could theoretically allow free-space optical data rates of more than 10 Gbps, Tiecke said.

Gathering Light from all Directions

In the Optica paper, the researchers demonstrate a light-bulb shaped light collector made from a bundle of fluorescent optical fibers. Although many shapes are possible, the light-bulb shape offers a very large bandwidth and omnidirectional sensitivity, which means it would work with mobile devices that move around with respect to the transmitter. The researchers also demonstrated that this geometry can gather light from an area as large as 126 square centimeters, making it less sensitive to alignment.

"Our detector absorbs the same amount of power and gets the same communication signal through independently of the alignment," said Tiecke.

In addition to working with partners to develop new materials, the research team is also planning to move this technology out of the lab by developing a prototype that could be tested in a real-world situation. "We are investigating the feasibility of a commercial product," said Tiecke. "This is a very new system, and there is a lot of room for future development."

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Story Source:

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

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Journal Reference:

1. T. Peyronel, K. J. Quirk, S. C. Wang, T. G. Tiecke. Luminescent detector for free-space optical communication. Optica, 2016; 3 (7): 787 DOI: 10.1364/optica.3.000787

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Cite This Page:

The Optical Society. "New detector overcomes key challenge in using light for wireless communications: With data rates of more than 2 gigabits per second, new approach in photodetection could simplify free-space optical communication." ScienceDaily. ScienceDaily, 19 July 2016. <www.sciencedaily.com/releases/2016/07/160719105404.htm>.

NASA's Kepler confirms 100+ exoplanets during its K2 mission

NASA's Kepler confirms 100+ exoplanets during its K2 mission

 

 

Image montage showing the Maunakea Observatories, Kepler Space Telescope, and night sky with K2 Fields and discovered planetary systems (dots) overlaid. An international team of scientists discovered more than 100 planets based on images from Kepler operating in the 'K2 Mission'. The team confirmed and characterized the planets using a suite of telescopes worldwide, including four on Maunakea (the twin telescopes of Keck Observatory, the Gemini­North Telescope, and the Infrared Telescope Facility). The planet image on the right is an artist's impression of a representative planet.

 

 Karen Teramura (UHIfA) based on night sky image of the ecliptic plane by Miloslav Druckmüller and Shadia Habbal, and Kepler Telescope and planet images by NASA.

 

An international team of astronomers led by the University of Arizona has discovered and confirmed a treasure trove of new worlds using NASA's Kepler spacecraft on its K2 mission. Among the findings tallying 197 initial planet candidates, scientists have confirmed 104 planets outside our solar system. Among the confirmed is a planetary system comprising four promising planets that could be rocky.

The planets, all between 20 and 50 percent larger than Earth by diameter, are orbiting the M dwarf star K2-72, found 181 light years away in the direction of the Aquarius constellation. The star is less than half the size of the sun and less bright. The planets' orbital periods range from five and a half to 24 days, and two of them may experience irradiation levels from their star comparable to those on Earth. Despite their tight orbits -- closer than Mercury's orbit around the sun -- the possibility that life could arise on a planet around such a star cannot be ruled out, according to lead author Ian Crossfield, a Sagan Fellow at the University of Arizona's Lunar and Planetary Laboratory.

The researchers achieved this extraordinary "roundup" of exoplanets by combining data with follow-up observations by earth-based telescopes including the North Gemini telescope and the W. M. Keck Observatory in Hawaii, the Automated Planet Finder of the University of California Observatories, and the Large Binocular Telescope operated by the University of Arizona. The discoveries are published online in the Astrophysical Journal Supplement Series.

Both Kepler and its K2 mission discover new planets by measuring the subtle dip in a star's brightness caused by a planet passing in front of its star. In its initial mission, Kepler surveyed just one patch of sky in the northern hemisphere, measuring the frequency of planets whose size and temperature might be similar to Earth orbiting stars similar to our sun. In the spacecraft's extended mission in 2013, it lost its ability to precisely stare at its original target area, but a brilliant fix created a second life for the telescope that is proving scientifically fruitful.

After the fix, Kepler started its K2 mission, which has provided an ecliptic field of view with greater opportunities for Earth-based observatories in both the northern and southern hemispheres. Additionally, the K2 mission is entirely community-driven with all targets proposed for by the scientific community.

Because it covers more of the sky, the K2 mission is capable of observing a larger fraction of cooler, smaller, red-dwarf type stars, and because such stars are much more common in the Milky Way than sun-like stars, nearby stars will predominantly be red dwarfs.

"An analogy would be to say that Kepler performed a demographic study, while the K2 mission focuses on the bright and nearby stars with different types of planets," said Ian Crossfield. "The K2 mission allows us to increase the number of small, red stars by a factor of 20, significantly increasing the number of astronomical 'movie stars' that make the best systems for further study."

To validate candidate planets identified by K2, the researchers obtained high-resolution images of the planet-hosting stars as well as high-resolution optical spectroscopy data. By dispersing the starlight as through a prism, the spectrographs allowed the researchers to infer the physical properties of a star -- such as mass, radius and temperature -- from which the properties of any planets orbiting it can be inferred.

These observations represent a natural stepping stone from the K2 mission to NASA's other upcoming exoplanet missions such as the Transiting Exoplanet Survey Satellite and James Webb Space Telescope.

"This bountiful list of validated exoplanets from the K2 mission highlights the fact that the targeted examination of bright stars and nearby stars along the ecliptic is providing many interesting new planets," said Steve Howell, project scientist for Kepler and K2 at NASA's Ames Research Center in Moffett Field, California. "This allows the astronomical community ease of follow-up and characterization, and picks out a few gems for first study by the James Webb Space Telescope, which could perhaps provide information about their atmospheres."

Story Source:
The above post is reprinted from materials provided by University of Arizona. The original item was written by Daniel Stolte. Note: Materials may be edited for content and length.

Journal Reference:

1. Ian J. M. Crossfield;, David R. Ciardi, Erik A. Petigura;, Evan Sinukoff;, Joshua E. Schlieder;, Andrew W. Howard, Charles A. Beichman, Howard Isaacson, Courtney D. Dressing;, Jessie L. Christiansen, Benjamin J. Fulton;, Sébastien Lépine, Lauren Weiss, Lea Hirsch, John Livingston, Christoph Baranec, Nicholas M. Law, Reed Riddle, Carlziegler, Steve B. Howell, Elliott Horch, Mark Everett, Johanna Teske, Arturo O. Martinez, Christian Obermeier, Björn Benneke, Nic Scott, Niall Deacon, Kimberly M. Aller, Brad M. S. Hansen, Luigi Mancini, Simona Ciceri;, Rafael Brahm;, Andrésjordán;, Heather A. Knutson, Thomas Henning, Michaël Bonnefoy, Michael C. Liu, Justin R. Crepp, Joshua Lothringer, Phil Hinz, Vanessa Bailey;, Andrew Skemer; Denis Defrere. 197 Candidates and 104 Validated Planets in K2’s First Five Fields. Astrophysical Journal Supplement Series, 2016

Cite This Page

 

University of Arizona. "NASA's Kepler confirms 100+ exoplanets during its K2 mission." ScienceDaily. ScienceDaily, 18 July 2016. <www.sciencedaily.com/releases/2016/07/160718142200.htm>.

 

'Green' electronic materials produced with synthetic biology

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Synthetic biowire are making an electrical connection between two electrodes. Researchers led by microbiologist Derek Lovely at UMass Amherst say the wires, which rival the thinnest wires known to man, are produced from renewable, inexpensive feedstocks and avoid the harsh chemical processes typically used to produce nanoelectronic materials.

Scientists at the University of Massachusetts Amherst report in the current issue of Small that they have genetically designed a new strain of bacteria that spins out extremely thin and highly conductive wires made up of solely of non-toxic, natural amino acids.

Researchers led by microbiologist Derek Lovely say the wires, which rival the thinnest wires known to man, are produced from renewable, inexpensive feedstocks and avoid the harsh chemical processes typically used to produce nanoelectronic materials.

Lovley says, "New sources of electronic materials are needed to meet the increasing demand for making smaller, more powerful electronic devices in a sustainable way." The ability to mass-produce such thin conductive wires with this sustainable technology has many potential applications in electronic devices, functioning not only as wires, but also transistors and capacitors. Proposed applications include biocompatible sensors, computing devices, and as components of solar panels.

This advance began a decade ago, when Lovley and colleagues discovered that Geobacter, a common soil microorganism, could produce "microbial nanowires," electrically conductive protein filaments that help the microbe grow on the iron minerals abundant in soil. These microbial nanowires were conductive enough to meet the bacterium's needs, but their conductivity was well below the conductivities of organic wires that chemists could synthesize.

"As we learned more about how the microbial nanowires worked we realized that it might be possible to improve on Nature's design," says Lovley. "We knew that one class of amino acids was important for the conductivity, so we rearranged these amino acids to produce a synthetic nanowire that we thought might be more conductive."

The trick they discovered to accomplish this was to introduce tryptophan, an amino acid not present in the natural nanowires. Tryptophan is a common aromatic amino acid notorious for causing drowsiness after eating Thanksgiving turkey. However, it is also highly effective at the nanoscale in transporting electrons.

"We designed a synthetic nanowire in which a tryptophan was inserted where nature had used a phenylalanine and put in another tryptophan for one of the tyrosines. We hoped to get lucky and that Geobacter might still form nanowires from this synthetic peptide and maybe double the nanowire conductivity," says Lovley.

The results greatly exceeded the scientists' expectations. They genetically engineered a strain of Geobacter and manufactured large quantities of the synthetic nanowires 2000 times more conductive than the natural biological product. An added bonus is that the synthetic nanowires, which Lovley refers to as "biowire," had a diameter only half that of the natural product.

"We were blown away by this result," says Lovley. The conductivity of biowire exceeds that of many types of chemically produced organic nanowires with similar diameters. The extremely thin diameter of 1.5 nanometers (over 60,000 times thinner than a human hair) means that thousands of the wires can easily be packed into a very small space.

The added benefit is that making biowire does not require any of the dangerous chemicals that are needed for synthesis of other nanowires. Also, biowire contains no toxic components. "Geobacter can be grown on cheap renewable organic feedstocks so it is a very 'green' process," he notes. And, although the biowire is made out of protein, it is extremely durable. In fact, Lovley's lab had to work for months to establish a method to break it down.

"It's quite an unusual protein," Lovley says. "This may be just the beginning" he adds. Researchers in his lab recently produced more than 20 other Geobacter strains, each producing a distinct biowire variant with new amino acid combinations. He notes, "I am hoping that our initial success will attract more funding to accelerate the discovery process. We are hoping that we can modify biowire in other ways to expand its potential applications."

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Story Source:

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

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Journal Reference:

1. Yang Tan, Ramesh Y. Adhikari, Nikhil S. Malvankar, Shuang Pi, Joy E. Ward, Trevor L. Woodard, Kelly P. Nevin, Qiangfei Xia, Mark T. Tuominen, Derek R. Lovley. Synthetic Biological Protein Nanowires with High Conductivity. Small, 2016; DOI: 10.1002/smll.201601112

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Cite This Page:

University of Massachusetts at Amherst. "'Green' electronic materials produced with synthetic biology." ScienceDaily. ScienceDaily, 14 July 2016. <www.sciencedaily.com/releases/2016/07/160714110749.htm>

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