Login with your Social Account

Discovery in gallium nitride a key enabler of energy efficient electronics

Discovery in gallium nitride a key enabler of energy efficient electronics

Gallium nitride, a semiconductor that revolutionized energy-efficient LED lighting, could also transform electronics and wireless communication, thanks to a discovery made by Cornell researchers.

Their paper, “A Polarization-Induced 2D Hole Gas in Undoped Gallium Nitride Quantum Wells,” was published Sept. 26 in Science.

Silicon has long been the king of semiconductors, but it has had a little help. The pure material is often augmented, or “doped,” with impurities like phosphorus or boron to enhance current flow by providing negative charges (electrons) or positive charges (“holes,” the absence of electrons) as needed.

In recent years, a newer, sturdier family of lab-grown compound semiconductor materials has emerged: group III-nitrides. Gallium nitride (GaN) and aluminum nitride (AlN) and their alloys have a wider bandgap, allowing them to withstand greater voltages and higher frequencies for faster, more efficient energy transmission.

“Silicon is very good at switching off and on and controlling electrical energy flow, but when you take it to high voltages it doesn’t operate very well because silicon has a weak electric strength, whereas GaN can sustain much higher electric fields,” said co-senior author Debdeep Jena, the David E. Burr Professorin Electrical and Computer Engineering and in Materials Science and Engineering. “If you’re doing very large amounts of energy conversion, then wide-bandgap semiconductors such as GaN and silicon carbide are the solutions.”

Since the 1990s, researchers have doped GaN by adding magnesium impurities to create holes, but the process is highly inefficient. For every hundred magnesium atoms introduced into the crystal, only three or four holes might appear at room temperature, and even fewer at low temperatures.

Rather than using impurities, Ph.D. student Reet Chaudhuri stacked a thin GaN crystal layer – called a quantum well – atop an AlN crystal, and the difference in their crystal structures was found to generate a high density of mobile holes. Compared with magnesium-doping, the researchers discovered that the resulting 2D hole gas makes the GaN structures almost 10 times more conductive.

“In 1992, researchers discovered that when aluminum nitride is deposited on top of gallium nitride, you get free electrons at the interface. Having electrons conduct inside GaN makes what we call n-type electronic devices,” said Chaudhuri, the paper’s lead author. “The polarization theory that explains why we get mobile electrons in this structure, which in fact was conceptualized and validated by Cornell researchers in late ’90s, also predicts that we should expect holes when the structure is flipped. But to date, there had not been any report of holes in an undoped III-nitride semiconductor structure. And that’s what we have found in this work.”

Using the new material structure created by Reet, co-author and Ph.D. student Samuel James Bader recently demonstrated some of the most efficient p-type GaN transistors in a collaborative project with Intel. Now that the team has the capability to make hole-channel transistors – which are called p-type – they plan to pair them with n-type transistors to form more complex circuits, opening up new possibilities in high-power switching, 5G cellular technology and energy efficient electronics, including phone and laptop chargers.

“It’s very difficult to simultaneously achieve n-type and p-type in a wide bandgap semiconductor. Right now, silicon carbide is the only other one that has both besides GaN. But the mobile electrons in silicon carbide are more sluggish than those in GaN,” said co-senior author Huili Grace Xing, the William L. Quackenbush Professor in electrical and computer engineering and in materials science and engineering. “Using these complementary operations enabled by both n-type and p-type devices, much more energy efficient architecture can be built.”

Another advantage of the 2D hole gas is that its conductivity improves as the temperature is lowered, meaning that researchers will now be able to study fundamental GaN properties in ways that haven’t been previously possible. Equally important is its ability to retain energy that would otherwise be lost in less efficient power systems.

“Gallium nitride caused a revolution in the lighting industry,” Jena said. “It enabled the white lighting that is in our cellphones, laptops, and LED bulbs that are replacing the incandescent bulbs in our homes. With a regular 100W incandescent light bulb, which is about 4% energy efficient, you might get 4 watts of light and the rest is heat. You know this very well if you touch the bulb when it is on. LEDs on the other hand can be almost 80% efficient, and only 20% is heat. A similar change in energy-efficiency of electronics has not yet happened. And maybe this finding is a step in that direction.”

A patent application has been filed through the Center for Technology Licensing for the discovery. Other contributors included David Muller, the Samuel B. Eckert Professor in Applied and Engineering physics; and Zhen Chen, a postdoctoral researcher in Muller’s lab.

The research was supported in part by Intel, the Air Force Office of Scientific Research, the National Science Foundation and the Cornell Center for Materials Research.

Materials provided by Cornell University

Discovery could mitigate fertilizer pollution in waterways

Discovery could mitigate fertilizer pollution in waterways

Excess fertilization of agricultural fields is a huge environmental problem. Phosphorus from fertilized cropland frequently finds its way into rivers and lakes, and the resulting boom of aquatic plant growth can cause oxygen levels in the water to plunge, leading to fish die-offs and other harmful

Researchers from Boyce Thompson Institute have uncovered the function of a pair of plant genes that could help farmers improve phosphate capture, potentially reducing the environmental harm associated with fertilization.

Maria Harrison, the William H. Crocker Professor at BTI and adjunct professor in the School of Integrative Plant Science in Cornell’s College of Agriculture and Life Sciences, is senior author of “A CLE–SUNN Module Regulates Strigolactone Content and Fungal Colonization in Arbuscular Mycorrhiza,” which published Sept. 2 in Nature Plants.

The discovery stems from Harrison’s focus on plants’ symbiotic relationships with arbuscular mycorrhizal (AM) fungi, which colonize plant roots to create an interface through which the plant trades fatty acids for phosphate and nitrogen. The fungi also can help plants recover from stressful conditions, such as periods of drought.

But feeding the AM fungi with fatty acids is costly, so plants don’t let this colonization go unchecked.

To discover how plants control the amount of fungal colonization, Harrison and lead author Lena Müller, a postdoctoral scientist in the Harrison lab, looked at genes that encode short proteins called CLE peptides in the plants Medicago truncatula (barrel clover) and Brachypodium distachyon (purple false brome).

CLE peptides are involved in cellular development and response to stress, and are present in plants ranging from green algae to flowering plants.

The researchers found that two of these CLE genes are key modulators of AM fungal symbiosis. One gene, CLE53, reduces colonization rates once the roots have been colonized. Another gene, CLE33, reduces colonization rates when there is plenty of phosphate available to the plant.

“Being able to control fungal colonization levels in plant roots and maintain the symbiosis even in higher phosphate conditions might be useful to a farmer,” Harrison said. “For example, you may want the other beneficial effects of AM fungi, like nitrogen uptake and recovery from drought, as well as further uptake of phosphate. You might be able to achieve these benefits by altering the levels of these CLE peptides in the plants.”

Müller found that the CLE peptides act through a receptor protein called SUNN. In collaboration with researchers from the University of Amsterdam, she found that the two CLE peptides modulate the plant’s synthesis of a compound called strigolactone.

Plant roots exude strigolactone into the soil, and the compound stimulates AM fungi to grow and colonize the root. Once the roots are colonized, or when there is plenty of phosphate, the CLE genes suppress the synthesis of strigolactone, thus reducing any further colonization by the fungi.

“In the early 2000s, researchers found that plants had a way to measure and then reduce colonization,” Müller said. “But until now, nobody really understood the molecular mechanism of that dynamic.”

The researchers’ next steps will include figuring out the molecules that turn on the CLE genes in response to colonization and high phosphate levels.

Müller also plans to compare the two CLE peptides from this study with additional CLE peptides that have different functions.

“The CLE peptides are all so similar but they have completely different functions,” Müller said. “It will be very interesting to see why that is.”

Other co-authors included Zhangjun Fei, adjunct professor in SIPS and a BTI faculty member; Xuepeng Sun of BTI; and researchers from Clemson University.

Materials provided by Cornell University

Want the money now or later? It may depend on your age

Want the money now or later? It may depend on your age

Imagine winning the lottery and having it payout over a scheduled period of time. Would you want the largest payments right away? Or would you rather start small and save the biggest windfall for later?

Your choice may depend on how old you are, according to new research from Corinna Loeckenhoff, associate professor of human development in the College of Human Ecology. The finding could have real-life implications.

“Retirement income is shifting from defined monthly pensions to flexible payouts from 401(k)s and other retirement savings plans,” Loeckenhoff said. “This means that retirees now have more control over when they spend their money, and spending too much of one’s nest egg in early retirement could, of course, spell trouble down the line.”

Fortunately, older adults do not appear to pursue immediate gratification at all cost.

Loeckenhoff’s paper, “Age Differences in Intertemporal Choice: The Role of Task Type, Outcome Characteristics, and Covariates,” published Aug. 14 in the Journal of Gerontology: Psychological Sciences. Her co-author was Gregory Samanez-Larkin, assistant professor of psychology and neuroscience at Duke University.

In their study, the researchers asked nearly 300 people of different ages how they would distribute a series of monetary gains and losses over time. Confirming prior findings by the researchers as well as from peers within the field, most participants preferred to get their winnings sooner rather than later and were more likely to postpone their losses. However, preferences for payment schedules differed by age. Older adults were more likely than younger adults to schedule the largest payouts first, the researchers say.

The study included a second task that asked participants to make trade-offs between a smaller payout available immediately and a delayed larger payout. In this setting, where asking for an earlier payout was costly, no differences based on age were found.

According to Loeckenhoff, this suggests that “retirement advisers can help older adults to make responsible choices by clearly spelling out the hidden costs of spending down one’s savings too early.”

More research is needed to understand underlying mechanisms, Loeckenhoff said. Although the present study examined a range of potential contributors – from subjective health to perceived time left in life – none of them could account for the observed age effects. Also, the amount of money at stake ($150 vs. $1,500) and the length of the delay (i.e., months vs. years) did not affect the pattern of findings.

In future work, the authors hope to examine a wider range of potential explanations and extend their findings beyond laboratory studies to real-life retirement savings scenarios.

Materials provided by Cornell University

New tools help detect digital domestic abuse

New tools help detect digital domestic abuse

Carol is locked in a custody battle with her abusive ex-husband. She has an order of protection against him, but he’s somehow able to access her private photos and post them on Facebook.

He hacks into her online accounts, where he poses as her to insult her friends and family. He locks her out of her own Gmail account, devastating her sales career.

Carol – a composite invented by researchers who have heard many similar stories – is vulnerable to digital harassment because her ex-husband bought two of her devices, knows or can guess her passwords and has access to their children’s phones.

A new clinical model developed by Cornell Tech researchers aims to respond systematically and effectively to the growing array of digital threats against victims of intimate partner violence. Working with the New York City Mayor’s Office to End Domestic and Gender-Based Violence, the researchers created and piloted a questionnaire, a spyware scanning tool and a diagram for assessing clients’ digital footprints.

The first-of-its-kind model can help counselors without tech expertise pinpoint online abuse – and protect the safety of abuse victims and their advisers. Using this strategy, researchers found potential spyware, compromised accounts or exploitable misconfigurations for 23 of the 44 clients they advised.

“Prior to this work, people were reporting that the abusers were very sophisticated hackers, and clients were receiving inconsistent advice,” said Diana Freed, Cornell Tech doctoral student in the field of information science and co-lead author of “Clinical Computer Security for Victims of Intimate Partner Violence,” presented Aug. 14 at the USENIX Security Symposium in Santa Clara, California.

“Some people were saying, ‘Throw your device out.’ Other people were saying, ‘Delete the app.’ But there wasn’t a clear understanding of how this abuse was happening and why it was happening,” Freed said. “We felt that a methodical approach through a uniform, data-driven consultation would yield better results so we can help other advocates do this type of work at the level it’s needed.”

Co-first author of the paper is Sam Havron, Cornell Tech doctoral student in computer science. Senior authors are Nicola Dell, assistant professor at the Jacobs Technion-Cornell Institute at Cornell Tech, and Thomas Ristenpart, associate professor at Cornell Tech.

The authors are among the researchers from Cornell Tech, Cornell in Ithaca and New York University collaborating to improve technological safety and security for survivors of intimate partner violence. Dell and Ristenpart were recently awarded a $1.2 million grant from the National Science Foundation to continue their research examining the role of tech in intimate partner abuse.

Abusers use a range of digital tools to stalk or harass their victims, from traditional spyware to tracking apps intended for more benign purposes, like finding one’s phone. It can be extremely challenging to detect vulnerabilities amid the sheer number of apps, digital devices and online accounts most people use daily – particularly for counselors without tech skills.

“They were making their best efforts, but there was no uniform way to address this,” Havron said. “They were using Google to try to help clients with their abuse situations.”

At the same time, tech experts don’t have the background to advise clients how to fix problems in ways that won’t endanger them, such as angering an abuser who just noticed a deleted app or a changed password.

The researchers run a weekly tech clinic in New York City’s Family Justice Centers, which provide a full range of services for intimate partner abuse victims. Through this work, the team developed and piloted its Technology Assessment Questionnaire, which includes such questions as, “Does the abuser show up unexpectedly or know things they shouldn’t know?” and “Is there a chance the abuser knows (or could guess) the answers to your password reset questions?”

They also created the “technograph,” a diagram which helps summarize clients’ digital assets; and ISDi (IPV Spyware Discovery), a spyware scanning tool. ISDi scans devices for known spyware apps through a USB cable, rather than a downloadable app, making it impossible for an abuser to detect.

“This sort of tool doesn’t exist anywhere else,” Havron said. “In earlier work, we did a comprehensive scrape of the Google Play Store and eventually compiled a list of thousands of apps across marketplaces, and that’s what the ISDi is based on.”

The questionnaire, technograph and ISDi are all freely available on the project team’s website.

Though the paper focused on intimate partner abuse, this method could be useful for any victims of online abuse, such as activists, dissidents or journalists, the researchers said.

“It’s consistent, it’s data-driven and it takes into account at each phase what the abuser will know if the client makes changes,” Freed said. “This is giving people a more accurate way to make decisions and providing them with a comprehensive understanding of how things are happening.”

The paper is co-authored by Rahul Chatterjee, Ph.D. ’19, and Damon McCoy of NYU. The research was funded by the National Science Foundation and gifts from Comcast and Google.

Materials provided by Cornell University

Fluorescent glow may reveal hidden life in the cosmos

Fluorescent glow may reveal hidden life in the cosmos

Astronomers seeking life on distant planets may want to go for the glow.

Harsh ultraviolet radiation flares from red suns, once thought to destroy surface life on planets, might help uncover hidden biospheres. Their radiation could trigger a protective glow from life on exoplanets called biofluorescence, according to new Cornell research.

Biofluorescent Worlds II: Biological Fluorescence Induced by Stellar UV Flares, a New Temporal Biosignature” was published Aug. 13 in Monthly Notices of the Royal Astronomical Society.

“This is a completely novel way to search for life in the universe. Just imagine an alien world glowing softly in a powerful telescope,” said lead author Jack O’Malley-James, a researcher at Cornell’s Carl Sagan Institute.

“On Earth, there are some undersea coral that use biofluorescence to render the sun’s harmful ultraviolet radiation into harmless visible wavelengths, creating a beautiful radiance. Maybe such life forms can exist on other worlds too, leaving us a telltale sign to spot them,” said co-author Lisa Kaltenegger, associate professor of astronomy and director of the Carl Sagan Institute

Astronomers generally agree that a large fraction of exoplanets – planets beyond our solar system – reside in the habitable zone of M-type stars, the most plentiful kinds of stars in the universe. M-type stars frequently flare, and when those ultraviolet flares strike their planets, biofluorescence could paint these worlds in beautiful colors. The next generation of Earth- or space-based telescopes can detect the glowing exoplanets, if they exist in the cosmos.

Ultraviolet rays can get absorbed into longer, safer wavelengths through a process called “photoprotective biofluorescence,” and that mechanism leaves a specific sign for which astronomers can search.

“Such biofluorescence could expose hidden biospheres on new worlds through their temporary glow, when a flare from a star hits the planet,” said Kaltenegger.

The astronomers used emission characteristics of common coral fluorescent pigments from Earth to create model spectra and colors for planets orbiting active M stars to mimic the strength of the signal and whether it could be detected for life.

In 2016, astronomers found a rocky exoplanet named Proxima b – a potentially habitable world orbiting the active M star Proxima Centauri, Earth’s closes star beyond the sun – that might qualify as a target. Proxima b is also one of the most optimal far-future travel destinations.

Said O’Malley-James: “These biotic kinds of exoplanets are very good targets in our search for exoplanets, and these luminescent wonders are among our best bets for finding life on exoplanets.”

Large, land-based telescopes that are being developed now for 10 to 20 years into the future may be able to spot this glow.

“It is a great target for the next generation of big telescopes, which can catch enough light from small planets to analyze it for signs of life, like the Extremely Large Telescope in Chile,” Kaltenegger said.

nipah

Deadly protein duo reveals new drug targets for viral diseases

It sounds like a plot point from a sci-fi movie: Two different and dangerous monsters merge into a hybrid that is more powerful and deadly than either counterpart.

Yet a research team led by Hector Aguilar-Carreno, associate professor in the Department of Microbiology and Immunology, has found a potentially similar scenario with a pair of viruses, in a study published July 31 in the Journal of Virology.

Their paper – featured on the journal’s cover in July – details how two highly lethal viruses (Nipah and Hendra) have greater pathogenic potential when their cell-sabotaging proteins are combined.

“Co-infections with these two viruses can occur in the same host, but we didn’t know what would happen if their proteins combined,” Aguilar-Carreno said. “We discovered that not only could they work together, they can work even better than they do separately.”

Members of the Aguilar-Carreno research team are experts on how Nipah and Hendra viruses attach to, and fuse with, their hosts’ cells. The viruses’ natural host is the fruit bat; this relationship was captured in an illustration, chosen for the journal cover, by Aguilar-Carreno’s husband, Armando Pacheco, a Cornell Institute of Biotechnology staff member.

The researchers’ focus is on the viral fusion proteins (or F proteins) and attachment proteins (G proteins). In previous studies, the team unveiled how the two proteins physically interact to enable viral infections: A G protein attaches to the cell; G then triggers F to flip up and down, triggering fusion between the cellular and viral membranes – the first moment of infection.

Aguilar-Carreno knew this “dance” between G and F was a crucial step in viral infection, but was curious to know how the dance might change if the proteins got new partners. Since both Nipah and Hendra viruses can potentially co-infect fruit bats, a protein partner switch is likely to occur in the wild.

He and his team tested out different Nipah-Hendra protein combinations in the lab, using genetic approaches in human cells. In some pairings, the two gripped each other in a tight, tango-like embrace. But one hybrid – a Hendra F and Nipah G – behaved like Lindy Hoppers, allowing the F protein to perform “aerials” that heightened fusion between the virus and the cell.

“This combination of proteins had a looser interaction,” Aguilar-Carreno said. “This looseness actually corresponded to greater fusion capability – and therefore an implied greater” ability to cause disease.

This hybrid protein power-couple has interesting implications.

“I find it fascinating – the tightness of the interaction is so crucial for these two proteins,” Aguilar-Carreno said. “If they’re too tight, they can’t coordinate correctly to get into the cell. And now that we know this, we can leverage that to stop viral-cell fusion.”

Aguilar-Carreno said this kind of therapeutic approach might be used to improve vaccine efficacy, or as an alternative to vaccines. His lab is working on vaccine approaches on animal models, as well as therapeutic approaches informed by this new discovery.

Aguilar-Carreno’s lab is also working on related research that may lead to vaccine-free therapies or improved vaccines to treat enveloped viruses, which include infectious diseases such as human immunodeficiency virus (HIV) and influenza. Enveloped viruses are wrapped in an outer coat made from a piece of the infected cell’s plasma membrane, which may protect the virus and help it infect other cells.

“Our work could lead to drugs,” Aguilar-Carreno said, “that enable inventions such as a flu vaccine with broader protection and greater efficacy.”

Journal Reference: Journal of Virology

Materials provided by Cornell University

Genomic data show how fish fare in evolutionary rapids

Genomic data show how fish fare in evolutionary rapids

Over recent decades, many commercially harvested fish have grown slower and matured earlier, which can translate into lower yields and a reduced resilience to overexploitation.

Scientists have long suspected that rapid evolutionary change in fish is caused by intense harvest pressure. Now, for the first time, scientists have unraveled genomic changes that prompt fisheries-induced evolution – changes that previously had been invisible to researchers, according to a study published in Science, Aug. 2.

“Most people think of evolution as a very slow process that unfolds over millennial time scales, but evolution can, in fact, happen very quickly,” said lead author Nina Overgaard Therkildsen, Cornell assistant professor of conservation genomics in the Department of Natural Resources.

In heavily exploited fish stocks, fishing almost always targets the largest individuals. “Slower-growing fish will be smaller and escape the nets better, thereby having a higher chance of passing their genes on to the next generations. This way, fishing can cause rapid evolutionary change in growth rates and other traits,” said Therkildsen. “We see many indications of this effect in wild fish stocks, but no one has known what the underlying genetic changes were.”

Therkildsen and her colleagues took advantage of an influential experiment published back in 2002. Six populations of Atlantic silversides, a fish that grows no bigger than 6 inches in length, had been subjected to intense harvesting in the lab. In two populations, the largest individuals were removed; in another two populations, the smallest individuals were removed; and in the final two populations, the fishing was random with respect to size.

After only four generations, these different harvest regimes had led to evolution of an almost two-fold difference in adult size between the groups. Therkildsen and her team sequenced the full genome of almost 900 of these fish to examine the DNA-level changes responsible for these striking shifts.

The team identified hundreds of different genes across the genome that changed consistently between populations selected for fast and slow growth. They also observed large linked-blocks of genes that changed in concert, dramatically shifting the frequencies of hundreds of genes all at the same time.

Surprisingly, however, these large shifts only happened in some of the populations, according to the new paper. This means that there were multiple genomic solutions for the fish in this experiment to get either larger or smaller.

“Some of these changes are easier to reverse than others, so to predict the impacts of fisheries-induced evolution, it is not enough to track growth rates alone, we need to monitor changes at the genomic level” said Therkildsen.

When the experiment was originally conducted nearly two decades ago by co-authors David Conover, professor of biology at the University of Oregon, and Stephan Munch of the National Marine Fisheries Service, the tools to study the genomic basis of the rapid fisheries-induced evolution they observed were not available. Fortunately, Conover and Munch had the foresight to store the samples in a freezer, making it possible to now return – armed with modern DNA sequencing tools – and reveal the underlying genomic shifts.

Research like this can assess human impacts, and improve humanity’s understanding of “the speed, consequences and reversibility of complex adaptations as we continue to sculpt the evolutionary trajectories of the species around us,” Therkildsen said.

The good news for the Atlantic silversides is that the fisheries selection was able to tap into the large reservoir of genetic variation that exists across the natural range of this species from Florida into Canada, said Therkildsen: “That genetic bank fueled rapid adaptation in the face of strong fishing pressure. Similar responses may occur in response to climate-induced shifts in other species with large genetic variability.”

In addition to Conover and Munch, contributors to “Contrasting Genomic Shifts Underlie Parallel Phenotypic Evolution in Response to Fishing” included former Cornell postdoctoral researcher Aryn P. Wilder, now a researcher at San Diego Zoo Institute for Conservation Research; Hannes Baumann, University of Connecticut; and Stephen R. Palumbi, Stanford University. This work was funded by the National Science Foundation.

Materials provided by the Cornell University

TESS satellite uncovers its ‘first nearby super-Earth’

TESS satellite uncovers its ‘first nearby super-Earth’

An international team of astronomers led by Cornell’s Lisa Kaltenegger has characterized the first potentially habitable world outside of our own solar system.

Located about 31 light-years away, the super-Earth planet – named GJ 357 d – was discovered in early 2019 owing to NASA’s Transiting Exoplanet Survey Satellite (TESS), a mission designed to comb the heavens for exoplanets, according to their new modeling research in the Astrophysical Journal Letters.

“This is exciting, as this is TESS’s first discovery of a nearby super-Earth that could harbor life – TESS is a small, mighty mission with a huge reach,” said Kaltenegger, associate professor of astronomy, director of Cornell’s Carl Sagan Institute and a member of the TESS science team.

The exoplanet is more massive than our own blue planet, and Kaltenegger said the discovery will provide insight into Earth’s heavyweight planetary cousins. “With a thick atmosphere, the planet GJ 357 d could maintain liquid water on its surface like Earth, and we could pick out signs of life with telescopes that will soon be online,” she said.

Astronomers from the Institute of Astrophysics of the Canary Islands and the University of La Laguna, both in Spain, announced the discovery of the GJ 357 system July 31 in the journal Astronomy & Astrophysics. They showed that the distant solar system – with a diminutive M-type dwarf sun, about one-third the size of our own sun – harbors three planets, with one of those in that system’s habitable zone: GJ 357 d.

Last February, the TESS satellite observed that the dwarf sun GJ 357 dimmed very slightly every 3.9 days, evidence of a transiting planet moving across the star’s face. That planet was GJ 357 b, a so-called “hot Earth” about 22% larger than Earth, according to the NASA Goddard Space Flight Center, which guides TESS.

Follow-up observations from the ground led to the discovery of two more exoplanetary siblings: GJ 357 c and GJ 357 d. The international team of scientists collected Earth-based telescopic data going back two decades – to reveal the newly found exoplanets’ tiny gravitational tugs on its host star, according to NASA.

Exoplanet GJ 357 c sizzles at 260 degrees Fahrenheit and has at least 3.4 times Earth’s mass. However, the system’s outermost known sibling planet – GJ 357 d, a super-Earth – could provide Earth-like conditions and orbits the dwarf star every 55.7 days at a distance about one-fifth of Earth’s distance from the sun. It is not yet known if this planet transits its sun.

Kaltenegger, doctoral candidate Jack Madden and undergraduate student Zifan Lin ’20 simulated light fingerprints, climates and remotely detectable spectra for a planet that could range from a rocky composition to a water world.

Madden explained that investigating new discoveries provides an opportunity to test theories and models. “We built the first models of what this new world could be like,” he said. “Just knowing that liquid water can exist on the surface of this planet motivates scientists to find ways of detecting signs of life.”

Lin described the work from an undergraduate perspective: “Working on a newly discovered planet is something of a dream come true. I was among the first group of people to model its spectra, and thinking about this still overwhelms me.”

In a nod to her institute’s namesake, the late Cornell professor Carl Sagan, Kaltenegger said: “If GJ 357 d were to show signs of life, it would be at the top of everyone’s travel list – and we could answer a 1,000-year-old question on whether we are alone in the cosmos.”

In addition to Kaltenegger, Madden and Lin, co-authors of “The Habitability of GJ 357d: Possible Climates and Observability,” include Sarah Rugheimer, Oxford University; Antigona Segura, National Autonomous University of Mexico (UNAM); Rafael Luque and Eric Pallé, both of the Institute of Astrophysics of the Canary Islands and the University of La Laguna; and Néstor Espinoza, Max Planck Institute for Astronomy, Germany.

Tour the GJ 357 system, located 31 light-years away in the constellation Hydra. Astronomers confirming a planet candidate identified by NASA’s Transiting Exoplanet Survey Satellite subsequently found two additional worlds orbiting the star.

Journal Reference: Astronomy & Astrophysics

Materials provided by Cornell University

New software helps plant breeders bring out their best

New software helps plant breeders bring out their best

Broccoli is in the eye of the beholder.

A head of broccoli that might appeal to one person – perhaps because of its deep green color – may leave another cold, due to an asymmetrical shape or too-large buds.

Cornell researchers participating in the Eastern Broccoli Project, which aims to produce broccoli varieties suited to grow on the East Coast, have devised a statistical method to standardize evaluations of broccoli, in order to make plant breeding decisions more consistent and efficient.

Now a Cornell group – doctoral student Zachary Stansell; Thomas Björkman, professor of horticulture at Cornell AgriTech; and Deniz Akdemir of the Cornell Statistical Consulting Unit – has released RateRvaR, a new software based on this method. RateRvaR is freely available, open source, easy to use and applicable to breeders of any vegetable, tree or flower with subjective features.

Using the software, breeders can select traits and ask multiple people to perform the same evaluation. The program will then analyze that data to determine which traits are more or less important in predicting overall quality, partly by prioritizing traits that are easier to judge objectively, such as size or color.

“The challenge for breeders, when they’re looking for wider adaptations, is that for certain crops, you plant all over the place and fly to various locations around the world to do the evaluations yourself,” Björkman said.

“But what if you had to check the plant twice a week for a month because it’s maturing at different rates? You can’t be jetting around the world; it just becomes impractical,” he said. “Breeders want to know not only how another person would score a plant, but how they would score it themselves, or how some idealized consumer would score it. This should open up the opportunity for breeders to do evaluations in multiple locations.”

The software can also identify traits that don’t seem relevant to the overall quality, so breeders can collect less data and still get accurate results.

“This approach can standardize evaluations and make them faster and more efficient, and it can also reveal individual biases in how a human might respond to a particular variety of a vegetable or plant,” Stansell said. “In the case of broccoli, we wanted to take the human subjectivity out of these evaluations, and this method allows us to see those biases and correct for them.”

Researchers in the Eastern Broccoli Project grow at least 40 varieties of broccoli a year, aiming to find varieties that will thrive in particular climates, from Florida in the winter to Maine in the summer. Their goal is not only to breed plants well-suited to local climates, but to produce high-quality broccoli consumers will buy.

But Stansell noticed he and his colleagues often had very different criteria for judging broccoli plants. He tended to choose heads that were very symmetrical, while another researcher was more interested in the head’s color.

Not only were their preferences inconsistent, it wasn’t even clear if they were truly significant in predicting the overall quality of the plant – a stubbornly subjective characterization.

“We were trying to get a firm hold on what is good-quality broccoli – you know it when you see it but it’s hard to define accurately,” Stansell said. “There are a lot of moving parts genetically that have to come together.”

With colleagues, he then created a scoring system and collected years’ worth of data on the traits they considered significant. They used this data to develop RateRvaR, which is based on relative importance analysis, a statistical technique that calculates the importance of different qualities in relation to each other.

“It showed us which traits we had an opportunity to make a lot of progress with, and which traits didn’t really matter,” Stansell said. “It also allowed us to develop priorities. For example, the shape of the head is really important, whereas maybe the size of the buds is less important, so we should focus on head shape and use our scarce time and resources to try to improve this particular aspect.”

Materials provided by Cornell University

New imaging method aids in water decontamination

New imaging method aids in water decontamination

A breakthrough imaging technique developed by Cornell researchers shows promise in decontaminating water by yielding surprising and important information about catalyst particles that can’t be obtained any other way.

Peng Chen, the Peter J.W. Debye Professor of Chemistry, has developed a method that can image nonfluorescent catalytic reactions – reactions that don’t emit light – on nanoscale particles. An existing method can image reactions that produce light, but that applies only to a small fraction of reactions, making the new technique potentially significant in fields ranging from materials engineering to nanotechnology and energy sciences.

The researchers then demonstrated the technique in observing photoelectrocatalysis – chemical reactions involving interactions with light – a key process in environmental remediation.

“The method turned out to be actually very simple – quite simple to implement and quite simple to do,” said Chen, senior author of “Super-Resolution Imaging of Nonfluorescent Reactions via Competition,” which published July 8 in Nature Chemistry. “It really extends the reaction imaging to an almost unlimited number of reactions.”

First author of the paper is Xianwen Mao, a postdoctoral researcher in Chen’s lab.

Catalytic reactions occur when a catalyst, such as a solid particle, accelerates a molecular change. Imaging these reactions at the nanoscale as they happen, which the new technique allows scientists to do, can help researchers learn the optimal size and shape for the most effective catalyst particles.

In the paper, the researchers applied the new technique to image the oxidation of hydroquinone, a micropollutant found in water, on bismuth vanadate catalyst particles, and discovered previously unknown behaviors of catalysts that helped render hydroquinone nontoxic.

“Many of these catalyzed reactions are environmentally important,” Chen said. “So you could study them to learn how to remove pollutants from an aqueous environment.”

Previously, Chen’s research group pioneered the application of single-molecule fluorescence imaging, a noninvasive, relatively inexpensive and easily implemented method that allows researchers to observe chemical reactions in real time. Because the method was limited to fluorescent reactions, however, his team worked for years on a more widely applicable method.

The technique they discovered relies on competition between fluorescent and nonfluorescent reactions. The competition suppresses the fluorescent reaction, allowing it to be measured and mapped, which in turn provides information about the nonfluorescent reaction.

The researchers named their method COMPetition Enabled Imaging Technique with Super-Resolution, or COMPEITS.

“This highly generalizable technique can be broadly applied to image various classes of nonfluorescent systems, such as unlabeled proteins, neurotransmitters and chemical warfare agents,” Peng said. “Therefore, we expect COMPEITS to be a breakthrough technology with profound impacts on many fields including energy science, cell biology, neuroscience and nanotechnology.”

Co-authors include research associate Chunming Li, former postdoctoral researcher Madhi Hesari and Ningmu Zou, Ph.D. ’17. The research was partly supported by the Army Research Office and the U.S. Department of Energy, and made use of the Cornell Center for Materials Research, which is supported by the National Science Foundation.

Journal: https://www.nature.com/articles/s41557-019-0288-8

Materials provided by Cornell University