Tag Archives: Zhen Yang

Turning marine waste into medical applications

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This 2025 Research Story on the Natural Sciences and Engineering Research Council of Canada website describes work from McGill University to turn marine waste into a bioadhesive, Note: A link has been removed,

An interdisciplinary team of researchers at McGill University has developed an ultra-strong, environmentally friendly medical glue, or bioadhesive, made from marine waste. The discovery has promising applications for wound care, surgeries, drug delivery, wearable devices and medical implants.

“A glue that can close wounds or make something strongly adhere to the skin is critical for many medical interventions,” says Audrey Moores, a chemistry professor at McGill.

A July 31, 2025 McGill University news release, which originated the research story, has more detail to offer, Note: Links have been removed,

“Many existing bioadhesive products are based on toxic compounds, while overall, there is a need to explore new materials that demonstrate both high adhesion and strong fatigue resistance, or the ability to hold even if pulled apart repeatedly,” Moores said.  
 
Moore [sic] and main co-author Jianyu Li, Associate Professor, Department of Mechanical Engineering and Canada Research Chair in Tissue Repair and Regeneration reported their findings in “Nanowhisker glues for fatigue-resistant bioadhesion and interfacial functionalization,” published in Nature Communications.  

Naturally sourced nanowhiskers give the glue its strength 

The new bioadhesive is composed of chitosan, a chemically modified form of chitin, the natural building block found in the exoskeletons of shellfish and certain fungi. 

The researchers modified the chitosan to have a nanowhisker shape – a feature that proved to be essential to the bioadhesive’s effectiveness – using a mechanochemical process pioneered by co-authors Moores and Edmond Lam in previous studies.   

 “We chemically manipulate this material to turn it into nanochitosan, which has a range of different properties we can finetune. Using this nanomaterial, we can make nanoglue,” Moores said. 

Ultrasound turns whiskers into interlocking structures 

To apply the nanoglue, researchers use a unique ultrasound technology developed by the Li group to penetrate the skin.  When exposed to sound waves, the nanowhiskers not only adhere firmly to skin but also interlock into a rigid, resilient scaffolding that drastically enhances the glue’s strength and durability. 

“Imagine you have a Band-Aid on your hand. It’s difficult to get it to stay, because your hand moves a lot,” Moores explained.  

“To get it to stick, you need the skin to be permeable to the glue. We used microneedles or ultrasound for that. 

 “We were surprised to see that ultrasound was critical to making a strong glue. While our initial strategy was to get the nanoglue to stick to the skin, we also discovered ultrasounds helped build a complex, interconnected network of our nanostructures. These nanowhisker glues are simply better than the current glues out there.”  

They say the nanostructure has promising applications beyond health care, in many engineering contexts. 

Allergy-safe, and potentially vegan 

The bioadhesive is also fully biocompatible, even for people with seafood allergies. 

“People who are allergic to shellfish are not allergic to chitin, but the proteins. We can remove these in the manufacturing process and avoid allergic reactions.  
 
“We could also theoretically make a vegan version from fungi,” Moores added. 

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This research was funded by the Natural Sciences and Engineering Research Council of Canada, the National Research Council Ocean program, the Canada Foundation for Innovation and the National Institutes of Health of the United States, the Canada Research Chairs Program, the Fonds de Recherche du Québec Nature et Technologies (FRQNT) – Centre for Green Chemistry and Catalysis and McGill University.

For those who like to listen to their science news, the Canadian Broadcasting Corporation (CBC) has an 8 mins. 8 secs. radio segment where researcher Audrey Moores is interviewed by Angelica Montgomery. on Quebec AM.

Here’s a link to and a citation for the paper,

Nanowhisker glues for fatigue-resistant bioadhesion and interfacial functionalization by Shuaibing Jiang, Tony Jin, Tianqin Ning, Zhen Yang, Zhenwei Ma, Ran Huo, Yixun Cheng, Davis Kurdyla, Edmond Lam, Rong Long, Audrey Moores & Jianyu Li. Nature Communications volume 16, Article number: 6826 (2025) DOI: https://doi.org/10.1038/s41467-025-62019-y Published: 24 July 2025

This paper is open access.

Safer, greener way to make hydrogels? Try ultrasound

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A May 9, 2025 news item on ScienceDaily announces research from McGill University (Montréal, Québec) and Polytechnique Montréal,

Researchers at McGill University, in collaboration with Polytechnique Montréal, pioneered a new way to create hydrogels using ultrasound, eliminating the need for toxic chemical initiators. This breakthrough offers a faster, cleaner and more sustainable approach to hydrogel fabrication, and produces hydrogels that are stronger, more flexible and highly resistant to freezing and dehydration. The new method also promises to facilitate advances in tissue engineering, bioadhesives and 3D bioprinting

Hydrogels are gels composed of polymers that can absorb and retain large amounts of water. They are widely used in wound dressings, drug delivery, tissue engineering, soft robotics, soft contact lenses and more.

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A May 8, 2025 McGill University news release (also on EurekAlert but published on May 9, 2025), which originated the news item, provides more details about the work,

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Gel formation within minutes

Traditional hydrogel manufacturing relies on chemical initiators, some of which can be harmful, particularly in medical applications. Initiators are the chemicals used to trigger chemical chain reactions. The McGill research team, led by Mechanical Engineering Professor Jianyu Li, has developed an alternative method using ultrasound. When applied to a liquid precursor, sound waves create microscopic bubbles that collapse with immense energy, triggering gel formation within minutes. 

“The problem we aimed to solve was the reliance on toxic chemical initiators,” said Li. “Our method eliminates these substances, making the process safer for the body and better for the environment.” 

This ultrasound-driven technique is dubbed “sonogel.”

“Typical hydrogel synthesis can take hours or even overnight under UV light,” said Li. “With ultrasound, it happens in just five minutes.” 

Revolutionizing biomedical applications

One of the most exciting possibilities for this technology is in non-invasive medical treatments. Because ultrasound waves can penetrate deep into tissues, this method could enable in-body hydrogel formation without surgery.  

“Imagine injecting a liquid precursor and using ultrasound to solidify it precisely where needed,” said Li. “This could be a game-changer for treating tissue damage and regenerative medicine. Further refinement, we can unlock new possibilities for safer, greener material production.” 

The technique also opens the door to ultrasound-based 3D bioprinting. Instead of relying on light or heat, researchers could use sound waves to precisely “print” hydrogel structures.  

“By leveraging high-intensity focused ultrasound, we can shape and build hydrogels with remarkable precision,” said Jean Provost, one of co-authors of the study and assistant professor of engineering physics at Polytechnique Montréal.  

Here’s a link to and a citation for the paper,

Ultrasound Cavitation Enables Rapid, Initiator-Free Fabrication of Tough Anti-Freezing Hydrogels by Yixun Cheng, Stephen Lee, Yihang Xiao, Shou Ohmura, Louis-Jacques Bourdages, Justin Puma, Zixin He, Zhen Yang, Jeremy Brown, Jean Provost, Jianyu Li. Advanced Science Volume 12, Issue 22 June 12, 2025 2416844 DOI: https://doi.org/10.1002/advs.202416844 First published online: 17 April 2025

This paper is open access.

Memristors could help AIs overcome ‘catastrophic forgetting’

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A March 20,205 news item on SciencDaily describes a ‘novel’ memristor,

They consume extremely little power and behave similarly to brain cells: so-called memristors. Researchers from Jülich [Forschungszentrum Juelich; Germany], led by Ilia Valov, have now introduced novel memristive components in Nature Communications that offer significant advantages over previous versions: they are more robust, function across a wider voltage range, and can operate in both analog and digital modes. These properties could help address the problem of “catastrophic forgetting,” where artificial neural networks abruptly forget previously learned information.

The problem of “catastrophic forgetting” occurs when deep neural networks are trained for a new task. This is because a new optimization simply overwrites a previous one. The brain does not have this problem because it can apparently adjust the degree of synaptic change; experts are now also talking about a so-called “metaplasticity”. They suspect that it is only through these different degrees of plasticity that our brain can permanently learn new tasks without forgetting old content. The new memristor accomplishes something similar.

“Its unique properties allow the use of different switching modes to control the modulation of the memristor in such a way that stored information is not lost,” says Ilia Valov from the Peter Grünberg Institute (PGI-7) at Forschungszentrum Jülich.

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A March 20, 2025 Forschungszentrum Juelich press release (also on EurekAlert), which originated the news item, provides context for the work along with more technical details,

Ideal candidates for neuro-inspired devices

Modern computer chips are evolving rapidly. Their development could receive a further boost from memristors—a term derived from memory and resistor. These components are essentially resistors with memory: their electrical resistance changes depending on the applied voltage, and unlike conventional switching elements, their resistance value remains even after the voltage is turned off. This is because memristors can undergo structural changes—for example, due to atoms depositing on the electrodes.

“Memristive elements are considered ideal candidates for learning-capable, neuro-inspired computer components modeled on the brain,” says Ilia Valov.

Despite considerable progress and efforts, the commercialization of the components is progressing slower than expected. This is due in particular to an often high failure rate in production and a short lifespan of the products. In addition, they are sensitive to heat generation or mechanical influences, which can lead to frequent malfunctions during operation. “Basic research is therefore essential to better control nanoscale processes,” says Valov, who has been working in this field of memristors for many years. ”We need new materials and switching mechanisms to reduce the complexity of the systems and increase the range of functionalities.”

It is precisely in this regard that the chemist and materials scientist, together with German and Chinese colleagues, has now been able to report an important success: “We have discovered a fundamentally new electrochemical memristive mechanism that is chemically and electrically more stable,” explains Valov. The development has now been presented in the journal Nature Communications.

A New Mechanism for Memristors

“So far, two main mechanisms have been identified for the functioning of so-called bipolar memristors: ECM and VCM,” explains Valov. ECM stands for ‘Electrochemical Metallization’ and VCM for ‘Valence Change Mechanism’.

  • ECM memristors form a metallic filament between the two electrodes—a tiny “conductive bridge” that alters electrical resistance and dissolves again when the voltage is reversed. The critical parameter here is the energy barrier (resistance) of the electrochemical reaction. This design allows for low switching voltages and fast switching times, but the generated states are variable and relatively short-lived.
     
  • VCM memristors, on the other hand, do not change resistance through the movement of metal ions but rather through the movement of oxygen ions at the interface between the electrode and electrolyte—by modifying the so-called Schottky barrier. This process is comparatively stable but requires high switching voltages.

Each type of memristor has its own advantages and disadvantages. “We therefore considered designing a memristor that combines the benefits of both types,” explains Ilia Valov. Among experts, this was previously thought to be impossible. “Our new memristor is based on a completely different principle: it utilizes a filament made of metal oxides rather than a purely metallic one like ECM,” Valov explains. This filament is formed by the movement of oxygen and tantalum ions and is highly stable—it never fully dissolves. “You can think of it as a filament that always exists to some extent and is only chemically modified,” says Valov.

The novel switching mechanism is therefore very robust. The scientists also refer to it as a filament conductivity modification mechanism (FCM). Components based on this mechanism have several advantages: they are chemically and electrically more stable, more resistant to high temperatures, have a wider voltage window and require lower voltages to produce. As a result, fewer components burn out during the manufacturing process, the reject rate is lower and their lifespan is longer.

Perspective solution for “catastrophic forgetting”

On top of that, the different oxidation states allow the memristor to be operated in a binary and/or analog mode. While binary signals are digital and can only output two states, analog signals are continuous and can take on any intermediate value. This combination of analog and digital behavior is particularly interesting for neuromorphic chips because it can help to overcome the problem of “catastrophic forgetting”: deep neural networks delete what they have learned when they are trained for a new task. This is because a new optimization simply overwrites a previous one.

The brain does not have this problem because it can apparently adjust the degree of synaptic change; experts are now also talking about a so-called “metaplasticity”. They suspect that it is only through these different degrees of plasticity that our brain can permanently learn new tasks without forgetting old content. The new ohmic memristor accomplishes something similar. “Its unique properties allow the use of different switching modes to control the modulation of the memristor in such a way that stored information is not lost,” says Valov.

The researchers have already implemented the new memristive component in a model of an artificial neural network in a simulation. In several image data sets, the system achieved a high level of accuracy in pattern recognition. In the future, the team wants to look for other materials for memristors that might work even better and more stably than the version presented here. “Our results will further advance the development of electronics for ‘computation-in-memory’ applications,” Valov is certain.

Here’s a link to and a citation for the paper,

Electrochemical ohmic memristors for continual learning by Shaochuan Chen, Zhen Yang, Heinrich Hartmann, Astrid Besmehn, Yuchao Yang & Ilia Valov. Nature Communications volume 16, Article number: 2348 (2025) DOI: https://doi.org/10.1038/s41467-025-57543-w Published: 08 March 2025

This paper is open access.

European medieval monks, Japanese scribes, and Middle Eastern chroniclers all contributed to volcanology

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Volcanoes are not often a topic on this blog, which is focused on emerging science and technology. However, stories featuring scientific information from unexpected sources has long been a fascination of mine and this April 5, 2023 news item on ScienceDaily shines a light on an unusual cast of medieval scientific observers spanning the globe,

By observing the night sky, medieval monks unwittingly recorded some of history’s largest volcanic eruptions. An international team of researchers, led by the University of Geneva (UNIGE), drew on readings of 12th and 13th century European and Middle Eastern chronicles, along with ice core and tree ring data, to accurately date some of the biggest volcanic eruptions the world has ever seen. Their results, reported in the journal Nature, uncover new information about one of the most volcanically active periods in Earth’s history, which some think helped to trigger the Little Ice Age, a long interval of cooling that saw the advance of European glaciers.

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llumination from the late 14th or early 15th century, which portrays two individuals observing a lunar eclipse. It features the words «La lune avant est eclipsee», «The moon is eclipsed» in english. © Source gallica.bnf.fr / BnF Courtesy: Université de Genève

An April 5, 2023 Université de Genève (UNIGE) press release (also on EurekAlert), which originated the news item, includes observations from Japanese scribes along with those from medieval European monks and Middle Eastern scholars,

It took the researchers almost five years to examine hundreds of annals and chronicles from across Europe and the Middle East, in search of references to total lunar eclipses and their colouration. Total lunar eclipses occur when the moon passes into the Earth’s shadow. Typically, the moon remains visible as a reddish orb because it is still bathed in sunlight bent round the Earth by its atmosphere. But after a very large volcanic eruption, there can be so much dust in the stratosphere – the middle part of the atmosphere starting roughly where commercial aircraft fly – that the eclipsed moon almost disappears.

Medieval chroniclers recorded and described all kinds of historical events, including the deeds of kings and popes, important battles, and natural disasters and famines. Just as noteworthy were the celestial phenomena that might foretell such calamities. Mindful of the Book of Revelation, a vision of the end times that speaks of a blood-red moon, the monks were especially careful to take note of the moon’s coloration. Of the 64 total lunar eclipses that occurred in Europe between 1100 and 1300, the chroniclers had faithfully documented 51. In five of these cases, they also reported that the moon was exceptionally dark.

The contribution of Japanese scribes 

Asked what made him connect the monks’ records of the brightness and colour of the eclipsed moon with volcanic gloom, the lead author of the work, Sébastien Guillet, senior research associate at the Institute for environmental sciences at the UNIGE,  said: “I was listening to Pink Floyd’s Dark Side of the Moon album when I realised that the darkest lunar eclipses all occurred within a year or so of major volcanic eruptions. Since we know the exact days of the eclipses, it opened the possibility of using the sightings to narrow down when the eruptions must have happened.”

The researchers found that scribes in Japan took equal note of lunar eclipses. One of the best known, Fujiwara no Teika, wrote of an unprecedented dark eclipse observed on 2 December 1229: ‘the old folk had never seen it like this time, with the location of the disk of the Moon not visible, just as if it had disappeared during the eclipse… It was truly something to fear.’ The stratospheric dust from large volcanic eruptions was not only responsible for the vanishing moon. It also cooled summer temperatures by limiting the sunlight reaching the Earth’s surface. This in turn could bring ruin to agricultural crops.

Cross-checking text and data 

“We know from previous work that strong tropical eruptions can induce global cooling on the order of roughly 1°C over a few years,” said Markus Stoffel, full professor at the Institute for environmental sciences at the UNIGE and last author of the study, a specialist in converting measurements of tree rings into climate data, who co-designed the study. “They can also lead to rainfall anomalies with droughts in one place and floods in another.”

Despite these effects, people at the time could not have imagined that the poor harvests or the unusual lunar eclipses had anything to do with volcanoes – the eruptions themselves were all but one undocumented. “We only knew about these eruptions because they left traces in the ice of Antarctica and Greenland,” said co-author Clive Oppenheimer, professor at the Department of Geography at the University of Cambridge. “By putting together the information from ice cores and the descriptions from medieval texts we can now make better estimates of when and where some of the biggest eruptions of this period occurred.”

Climate and society affected 

To make the most of this integration, Sébastien Guillet worked with climate modellers to compute the most likely timing of the eruptions. “Knowing the season when the volcanoes erupted is essential, as it influences the spread of the volcanic dust and the cooling and other climate anomalies associated with these eruptions,” he said.

As well as helping to narrow down the timing and intensity of these events, what makes the findings significant is that the interval from 1100 to 1300 is known from ice core evidence to be one of the most volcanically active periods in history. Of the 15 eruptions considered in the new study, one in the mid-13th century rivals the famous 1815 eruption of Tambora that brought on ‘the year without a summer’ of 1816. The collective effect of the medieval eruptions on Earth’s climate may have led to the Little Ice Age, when winter ice fairs were held on the frozen rivers of Europe. “Improving our knowledge of these otherwise mysterious eruptions, is crucial to understanding whether and how past volcanism affected not only climate but also society during the Middle Ages,” concludes the researcher.

Here’s a link to and a citation for the paper,

Lunar eclipses illuminate timing and climate impact of medieval volcanism by Sébastien Guillet, Christophe Corona, Clive Oppenheimer, Franck Lavigne, Myriam Khodri, Francis Ludlow, Michael Sigl, Matthew Toohey, Paul S. Atkins, Zhen Yang, Tomoko Muranaka, Nobuko Horikawa & Markus Stoffel. Nature volume 616, pages 90–95 (2023) Issue Date: 06 April 2023 DOI: https://doi.org/10.1038/s41586-023-05751-z Published online: 05 April 2023

This paper is open access.

Making longer lasting bandages with sound and bubbles

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This research into longer lasting bandages described in an August 12, 2022 news item on phys.org comes from McGill University (Montréal, Canada)

Researchers have discovered that they can control the stickiness of adhesive bandages using ultrasound waves and bubbles. This breakthrough could lead to new advances in medical adhesives, especially in cases where adhesives are difficult to apply such as on wet skin.

“Bandages, glues, and stickers are common bioadhesives that are used at home or in clinics. However, they don’t usually adhere well on wet skin. It’s also challenging to control where they are applied and the strength and duration of the formed adhesion,” says McGill University Professor Jianyu Li, who led the research team of engineers, physicists, chemists, and clinicians.

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Caption: Adhesive hydrogel applied on skin under ultrasound probe. Credit: Ran Huo and Jianyu Li

An August 12, 2022 McGill University news release (also on EurekAlert), which originated the news item, delves further into the work,

“We were surprised to find that by simply playing around with ultrasonic intensity, we can control very precisely the stickiness of adhesive bandages on many tissues,” says lead author Zhenwei Ma, a former student of Professor Li and now a Killam Postdoctoral Fellow at the University of British Columbia.

Ultrasound induced bubbles control stickiness

In collaboration with physicists Professor Outi Supponen and Claire Bourquard from the Institute of Fluid Dynamics at ETH Zurich, the team experimented with ultrasound induced microbubbles to make adhesives stickier. “The ultrasound induces many microbubbles, which transiently push the adhesives into the skin for stronger bioadhesion,” says Professor Supponen. “We can even use theoretical modeling to estimate exactly where the adhesion will happen.”

Their study, published in the journal Science, shows that the adhesives are compatible with living tissue in rats. The adhesives can also potentially be used to deliver drugs through the skin. “This paradigm-shifting technology will have great implications in many branches of medicine,” says University of British Columbia Professor Zu-hua Gao. “We’re very excited to translate this technology for applications in clinics for tissue repair, cancer therapy, and precision medicine.”

“By merging mechanics, materials and biomedical engineering, we envision the broad impact of our bioadhesive technology in wearable devices, wound management, and regenerative medicine,” says Professor Li, who is also a Canada Research Chair in Biomaterials and Musculoskeletal Health.

Here’s a link to and a citation for the paper,

Controlled tough bioadhesion mediated by ultrasound by Zhenwei Ma, Claire Bourquard, Qiman Gao, Shuaibing Jiang, Tristan De Iure-Grimmel, Ran Huo, Xuan Li, Zixin He, Zhen Yang, Galen Yang, Yixiang Wang, Edmond Lam, Zu-hua Gao, Outi Supponen and Jianyu Li. Science 11 Aug 2022 Vol 377, Issue 6607 pp. 751-755 DOI: 10.1126/science.abn8699

This paper is behind a paywall.

I haven’t seen this before but it seems that one of the journal’s editors decided to add a standalone paragraph to hype some of the other papers about adhesives in the issue,

A sound way to make it stick

Tissue adhesives play a role in temporary or permanent tissue repair, wound management, and the attachment of wearable electronics. However, it can be challenging to tailor the adhesive strength to ensure reversibility when desired and to maintain permeability. Ma et al. designed hydrogels made of polyacrylamide or poly(N-isopropylacrylamide) combined with alginate that are primed using a solution containing nanoparticles of chitosan, gelatin, or cellulose nanocrystals (see the Perspective by Es Sayed and Kamperman). The application of ultrasound causes cavitation that pushes the primer molecules into the tissue. The mechanical interlocking of the anchors eventually results in strong adhesion between hydrogel and tissue without the need for chemical bonding. Tests on porcine or rat skin showed enhanced adhesion energy and interfacial fatigue resistance with on-demand detachment. —MSL

I like the wordplay and am guessing that MSL is:

Marc S. Lavine
Senior Editor
Education: BASc, University of Toronto; PhD, University of Cambridge
Areas of responsibility: Reviews; materials science, biomaterials, engineering

Extracting biomolecules from live cells with carbon nanotubes

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Being able to extract biomolecules from living cells means nondestruction of the rest of the cell and the ability to observe the consequences of the extraction. From a July 18, 2014 news item on Azonano,

University of Houston researchers have devised a new method for extracting molecules from live cells without disrupting cell development, work that could provide new avenues for the diagnosis of cancer and other diseases.

The researchers used magnetized carbon nanotubes to extract biomolecules from live cells, allowing them to retrieve molecular information without killing the individual cells. A description of the work appears this week in the Proceedings of the National Academy of Sciences.

A July 16, 2014 University of Houston news release by Jeannie Kever, which originated the news item, provides more detail,

Most current methods of identifying intracellular information result in the death of the individual cells, making it impossible to continue to gain information and assess change over time, said Zhifeng Ren, M.D. Anderson Chair professor of physics and principal investigator at the Center for Superconductivity at UH and lead author of the paper. The work was a collaboration between Ren’s lab and that of Paul Chu, T.L.L. Temple Chair of Science and founding director of the Texas Center for Superconductivity.

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Chu, a co-author of the paper, said the new technique will allow researchers to draw fundamental information from a single cell.The researchers said the steps outlined in the paper offer proof of concept. Ren said the next step “will be more study of the biological and chemical processes of the cell, more analysis.”

The initial results hold promise for biomedicine, he said.  “This shows how nanoscience and nanoengineering can help the medical field.”

Cai said the new method will be helpful for cancer drug screening and carcinogenesis study, as well as for studies that allow researchers to obtain information from single cells, replacing previous sampling methods that average out cellular diversity and obscure the specificity of the biomarker profiles.

In the paper, the researchers explain their rationale for the work – most methods for extracting molecular information result in cell death, and those that do spare the cell carry special challenges, including limited efficiency.

This method is relatively straightforward, requiring the use of magnetized carbon nanotubes as the transporter and a polycarbonate filter as a collector, they report. Cells from a human embryonic kidney cancer cell line were used for the experiment.

The work builds on a 2005 paper published by Ren’s group in Nature Methods, which established that magnetized carbon nanotubes can deliver molecular payloads into cells. The current research takes that one step further to move molecules out of cells by magnetically driving them through the cell walls.

The carbon nanotubes were grown with a plasma-enhanced chemical vapor deposition system, with magnetic nickel particles enclosed at the tips. A layer of nickel was also deposited along the surface of individual nanotubes in order to make the nanotubes capable of penetrating a cell wall guided by a magnet.

Here’s a link to and a citation for the paper,

Molecular extraction in single live cells by sneaking in and out magnetic nanomaterials by Zhen Yang, Liangzi Deng, Yucheng Lan, Xiaoliu Zhang, Zhonghong Gao, Ching-Wu Chu, Dong Cai, and Zhifeng Ren. PNAS 2014 ; published ahead of print July 16, 2014, doi:10.1073/pnas.1411802111

This paper is behind a paywall.