The findings advance scientists’ understanding of the basic biology driving the annual summer blooms, which are both an unsightly nuisance and a potential public health hazard. In addition, the work identifies a mechanism to explain the rapid increase in Lake Erie bloom size and spatial extent in early summer.

“The study suggests that the initial buildup of blooms can happen at a much higher rate and over a larger spatial extent than would otherwise be possible, due to the broad presence of viable cells in sediments throughout the lake,” said study lead author Christine Kitchens, a research technician at the Cooperative Institute for Great Lakes Research (CIGLR) at U-M.

“These overwintering cells can quickly be entrained within the water column — particularly after a storm event — and start actively growing.”

The study is scheduled for publication Nov. 21 in the journal PLOS ONE. Kitchens conducted the work for her master’s thesis at the School for Environment and Sustainability. The other authors are Thomas Johengen, associate director of CIGLR, and Timothy Davis, an associate professor at Bowling Green State University.

Western Lake Erie has long been plagued by harmful algal blooms, or HABs, fueled largely by nutrients in agricultural runoff. The blooms are composed largely of Microcystis, a genus of colony-forming cyanobacteria that sometimes produce liver toxins called microcystins.

Lake Erie is a drinking water source for 11 million people. In 2014, a cyanobacteria bloom infiltrated the Toledo water intake, resulting in a two-day “do not drink” advisory for more than 400,000 people.

This year’s bloom was relatively small and fell short of scientists’ predictions. Johengen said scientists should consider incorporating the new information about overwintering Microcystis cells into the computer models used to make the annual bloom forecasts.

Previous studies of other temperate lakes around the world indicate that overwintering populations of Microcystis cells possess high survivability and can seed seasonal blooms. However, the exact contribution of cells in sediments has been less clear.

For Lake Erie, one 2009 study concluded that the Maumee and Sandusky rivers were a potential source of the Microcystis cells — known to scientists as “inocula” because they inoculate the lake — that initiate the summer cyanobacteria blooms. But other work suggests that river populations do not seed the Erie blooms.

The new U-M-led study is believed to be the first to assess both the abundance and viability of overwintering Microcystis cells from sediments in the Great Lakes.

The researchers collected sediment-core samples at 16 sites covering 145 square miles in the portion of western Lake Erie where harmful cyanobacteria blooms are most prevalent and persistent. The sampling was done over a two-year period in water depths ranging from 10 to 30 feet.

Back in the lab, genetic tests revealed both the total abundance of Microcystis cells and the fraction of those cells that were potentially toxic. Then experiments were conducted to assess the viability of overwintering Microcystis cells and to grow some of the cells in the lab.

While Microcystis cell concentrations declined significantly over the winter, the cells that survived remained viable — meaning they were capable of growing — the following spring. In addition, the growth experiments showed that potentially toxic Microcystis strains were successfully cultured at a slightly higher rate than nontoxic strains.

That result could help explain a previous observation by the National Oceanic and Atmospheric Administration’s Lake Erie monitoring program: that the percentage of potentially toxic Microcystis cells is highest during the early stages of a bloom and declines throughout the summer.

Johengen said it’s not yet known whether overwintering Microcystis cells pick up vital nutrients from the sediments and use those nutrients to fuel their early season growth spurt. If that’s happening, it could complicate efforts to curb Lake Erie blooms by reducing fertilizer runoff from croplands, he said.

“One limiting factor in the use of alginate hydrogels is that they’re very fragile — they tend to fall apart under mechanical load or in low salt solutions,” said Thomas Valentin, a Ph.D. student in Brown’s School of Engineering who led the work. “What we showed is by including graphene oxide nanosheets, we can make these structures much more robust.”

The material is also capable of becoming stiffer or softer in response to different chemical treatments, meaning it could be used to make “smart” materials that are able to react to their surroundings in real time, the research shows. In addition, alginate-GO retains alginate’s ability to repel oils, giving the new material potential as a sturdy antifouling coating.

The 3-D printing method used to make the materials is known as stereolithography. The technique uses an ultraviolet laser controlled by a computer-aided design system to trace patterns across the surface of a photoactive polymer solution. The light causes the polymers to link together, forming solid 3-D structures from the solution. The tracing process is repeated until an entire object is built layer-by-layer from the bottom up. In this case the polymer solution was made using sodium alginate mixed with sheets of graphene oxide, a carbon-based material that forms one-atom-thick nanosheets that are stronger pound-for-pound than steel.

One advantage to the technique is that the sodium alginate polymers link through ionic bonds. The bonds are strong enough to hold the material together, but they can be broken by certain chemical treatments. That gives the material the ability to respond dynamically to external stimuli. Previously, the Brown researchers showed that this “ionic crosslinking” can be used to create alginate materials that degrade on demand, rapidly dissolving when treated with a chemical that sweeps away ions from the material’s internal structure.

For this new study, the researchers wanted to see how graphene oxide might change mechanical properties of alginate structures. They showed that alginate-GO could be made twice as stiff as alginate alone, and far more resistant to failure through cracking.

“The addition of graphene oxide stabilizes the alginate hydrogel with hydrogen bonding,” said Ian Y. Wong, an assistant professor of engineering at Brown and the paper’s senior author. “We think the fracture resistance is due to cracks having to detour around the interspersed graphene sheets rather than being able to break right though homogeneous alginate.”

The extra stiffness enabled the researchers to print structures that had overhanging parts, which would have been impossible using alginate alone. Moreover, the increased stiffness didn’t prevent alginate-GO also from responding to external stimuli like alginate alone can. The researchers showed that by bathing the materials in a chemical that removes its ions, the materials swelled up and became much softer. The materials regained their stiffness when ions were restored through bathing in ionic salts. Experiments showed that the materials’ stiffness could be tuned over a factor of 500 by varying their external ionic environment.

That ability to change its stiffness could make alginate-GO useful in a variety of applications, the researchers say, including dynamic cell cultures.

“You could imagine a scenario where you can image living cells in a stiff environment and then immediately change to a softer environment to see how the same cells might respond,” Valentin said. That could be useful in studying how cancer cells or immune cells migrate through different organs throughout the body.

And because alginate-GO retains the powerful oil-repellant properties of pure alginate, the new material could make an excellent coating to keep oil and other grime from building up on surfaces. In a series of experiments, the researchers showed that a coating of alginate-GO could keep oil from fouling the surface of glass in highly saline conditions. That could make alginate-GO hydrogels useful for coatings and structures used in marine settings, the researchers say.

“These composite materials could be used as a sensor in the ocean that can keep taking readings during an oil spill, or as an antifouling coating that helps to keep ship hulls clean,” Wong said. The extra stiffness afforded by the graphene would make such materials or coatings far more durable than alginate alone.

The researchers plan to continue experimenting with the new material, looking for ways to streamline its production and continue to optimize its properties.

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Published online in the journal Nature on 21 November 2018, the work corrects assumptions that the region’s fossil-rich caves could never be related to each other. In fact, the research suggests fossils from Cradle caves date to just six specific time periods.

“Unlike previous dating work, which often focused on one cave, sometimes even just one chamber of the cave, we are providing direct ages for eight caves and a model to explain the age of all the fossils from the entire region,” says Dr Robyn Pickering.

“Now we can link together the findings from separate caves and create a better picture of evolutionary history in southern Africa.”

The Cradle of Humankind is a World Heritage Site made up of complex fossil-bearing caves. It’s the world’s richest early hominin site and home to nearly 40% of all known human ancestor fossils, including the famous Australopithecus africanus skull nicknamed Mrs Ples.

Using uranium-lead dating, researchers analysed 28 flowstone layers that were found sandwiched between fossil-rich sediment in eight caves across the Cradle. The results revealed that the fossils in these caves date to six narrow time-windows between 3.2 and 1.3 million years ago.

“The flowstones are the key,” says Pickering. “We know they can only grow in caves during wet times, when there is more rain outside the cave. By dating the flowstones, we are picking out these times of increased rainfall. We therefore know that during the times in between, when the caves were open, the climate was drier and more like what we currently experience.”

This means the early hominins living in the Cradle experienced big changes in local climate, from wetter to drier conditions, at least six times between 3 and 1 million years ago. However, only the drier times are preserved in the caves, skewing the record of early human evolution.

Up until now, the lack of dating methods for Cradle fossils made it difficult for scientists to understand the relationship between East and South Africa hominin species. Moreover, the South African record has often been considered undateable compared to East Africa where volcanic ash layers allow for high resolution dating.

Professor Andy Herries, a co-author in the study at La Trobe University in Australia, notes that “while the South African record was the first to show Africa as the origin point for humans, the complexity of the caves and difficultly dating them has meant that the South African record has remained difficult to interpret.”

“In this study we show that the flowstones in the caves can act almost like the volcanic layers of East Africa, forming in different caves at the same time, allowing us to directly relate their sequences and fossils into a regional sequence,” he says.

Dr Pickering began dating the Cradle caves back in 2005 as part of her PhD research. This new publication is the result of 13 years of work and brings together a team of 10 scientists from South Africa, Australia and the US. The results return the Cradle to the forefront and open new opportunities for scientists to answer complex questions about human history in the region.

“Robyn and her team have made a major contribution to our understanding of human evolution,” says leading palaeoanthropologist Professor Bernard Wood, of the Center for the Advanced Study of Human Paleobiology at the George Washington University in the USA, who is not an author on the study.

“This is the most important advance to be made since the fossils themselves were discovered. Dates of fossils matter a lot. The value of the southern African evidence has been increased many-fold by this exemplary study of its temporal and depositional context.”

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The work also could help astronomers more effectively study planets around stars unlike our sun, and better use the limited, expensive resources of the James Webb Space Telescope, now expected to launch in 2021.

“We are modeling unfamiliar atmospheres, not just assuming that the things we see in the solar system will look the same way around another star,” said Andrew Lincowski, UW doctoral student and lead author of a paper published Nov. 1 in Astrophysical Journal. “We conducted this research to show what these different types of atmospheres could look like.”

The team found, briefly put, that due to an extremely hot, bright early stellar phase, all seven of the star’s worlds may have evolved like Venus, with any early oceans they may have had evaporating and leaving dense, uninhabitable atmospheres. However, one planet, TRAPPIST-1 e, could be an Earthlike ocean world worth further study, as previous research also has indicated.

TRAPPIST-1, 39 light-years or about 235 trillion miles away, is about as small as a star can be and still be a star. A relatively cool “M dwarf” star — the most common type in the universe — it has about 9 percent the mass of the sun and about 12 percent its radius. TRAPPIST-1 has a radius only a little bigger than the planet Jupiter, though it is much greater in mass.

All seven of TRAPPIST-1’s planets are about the size of Earth and three of them — planets labeled e, f and g — are believed to be in its habitable zone, that swath of space around a star where a rocky planet could have liquid water on its surface, thus giving life a chance. TRAPPIST-1 d rides the inner edge of the habitable zone, while farther out, TRAPPIST-1 h, orbits just past that zone’s outer edge.

“This is a whole sequence of planets that can give us insight into the evolution of planets, in particular around a star that’s very different from ours, with different light coming off of it,” said Lincowski. “It’s just a gold mine.”

Previous papers have modeled TRAPPIST-1 worlds, Lincowski said, but he and this research team “tried to do the most rigorous physical modeling that we could in terms of radiation and chemistry — trying to get the physics and chemistry as right as possible.”

The team’s radiation and chemistry models create spectral, or wavelength, signatures for each possible atmospheric gas, enabling observers to better predict where to look for such gases in exoplanet atmospheres. Lincowski said when traces of gases are actually detected by the Webb telescope, or others, some day, “astronomers will use the observed bumps and wiggles in the spectra to infer which gases are present — and compare that to work like ours to say something about the planet’s composition, environment and perhaps its evolutionary history.”

He said people are used to thinking about the habitability of a planet around stars similar to the sun. “But M dwarf stars are very different, so you really have to think about the chemical effects on the atmosphere(s) and how that chemistry affects the climate.”

Combining terrestrial climate modeling with photochemistry models, the researchers simulated environmental states for each of TRAPPIST-1’s worlds.

Their modeling indicates that:

• TRAPPIST-1 b, the closest to the star, is a blazing world too hot even for clouds of sulfuric acid, as on Venus, to form.
• Planets c and d receive slightly more energy from their star than Venus and Earth do from the sun and could be Venus-like, with a dense, uninhabitable atmosphere.
• TRAPPIST-1 e is the most likely of the seven to host liquid water on a temperate surface, and would be an excellent choice for further study with habitability in mind.
• The outer planets f, g and h could be Venus-like or could be frozen, depending on how much water formed on the planet during its evolution.

Lincowski said that in actuality, any or all of TRAPPIST-1’s planets could be Venus-like, with any water or oceans long burned away. He explained that when water evaporates from a planet’s surface, ultraviolet light from the star breaks apart the water molecules, releasing hydrogen, which is the lightest element and can escape a planet’s gravity. This could leave behind a lot of oxygen, which could remain in the atmosphere and irreversibly remove water from the planet. Such a planet may have a thick oxygen atmosphere — but not one generated by life, and different from anything yet observed.

“This may be possible if these planets had more water initially than Earth, Venus or Mars,” he said. “If planet TRAPPIST-1 e did not lose all of its water during this phase, today it could be a water world, completely covered by a global ocean. In this case, it could have a climate similar to Earth.”

Lincowski said this research was done more with an eye on climate evolution than to judge the planets’ habitability. He plans future research focusing more directly on modeling water planets and their chances for life.

“Before we knew of this planetary system, estimates for the detectability of atmospheres for Earth-sized planets were looking much more difficult,” said co-author Jacob Lustig-Yaeger, a UW astronomy doctoral student.

The star being so small, he said, will make the signatures of gases (like carbon dioxide) in the planet’s atmospheres more pronounced in telescope data.

“Our work informs the scientific community of what we might expect to see for the TRAPPIST-1 planets with the upcoming James Webb Space Telescope.”

Lincowski’s other UW co-author is Victoria Meadows, professor of astronomy and director of the UW’s Astrobiology Program. Meadows is also principal investigator for the NASA Astrobiology Institute’s Virtual Planetary Laboratory, based at the UW. All of the authors were affiliates of that research laboratory.

“The processes that shape the evolution of a terrestrial planet are critical to whether or not it can be habitable, as well as our ability to interpret possible signs of life,” Meadows said. “This paper suggests that we may soon be able to search for potentially detectable signs of these processes on alien worlds.”

TRAPPIST-1, in the Aquarius constellation, is named after the ground-based Transiting Planets and Planetesimals Small Telescope, the facility that first found evidence of planets around it in 2015.

In a study published November 21 in PLOS ONE, three clinical trial participants with tetraplegia, each of whom was using the investigational BrainGate BCI that records neural activity directly from a small sensor placed in the motor cortex, were able to navigate through commonly used tablet programs, including email, chat, music-streaming and video-sharing apps. The participants messaged with family, friends, members of the research team and their fellow participants. They surfed the web, checked the weather and shopped online. One participant, a musician, played a snippet of Beethoven’s “Ode to Joy” on a digital piano interface.

“For years, the BrainGate collaboration has been working to develop the neuroscience and neuroengineering know-how to enable people who have lost motor abilities to control external devices just by thinking about the movement of their own arm or hand,” said Dr. Jaimie Henderson, a senior author of the paper and a Stanford University neurosurgeon. “In this study, we’ve harnessed that know-how to restore people’s ability to control the exact same everyday technologies they were using before the onset of their illnesses. It was wonderful to see the participants express themselves or just find a song they want to hear.”

The investigational BrainGate BCI includes a baby aspirin-sized implant that detects the signals associated with intended movements produced in the brain’s motor cortex. Those signals are then decoded and routed to external devices. BrainGate researchers and other groups using similar technologies have shown that the device can enable people to move robotic arms or to regain control of their own limbs, despite having lost motor abilities from illness or injury. This study from the collaboration includes scientists, engineers and physicians from Brown University’s Carney Institute for Brain Science, the Providence Veterans Affairs Medical Center (PVAMC), Massachusetts General Hospital (MGH) and Stanford University.

Two of the participants in this latest study had weakness or loss of movement of their arms and legs due to amyotrophic lateral sclerosis (ALS), a progressive disease affecting the nerves in the brain and spine that control movement. The third participant was paralyzed due to a spinal cord injury. All were enrolled in a clinical trial aimed at assessing the safety and feasibility of the investigational BrainGate system.

For this study, neural signals from the BrainGate BCI were routed to a Bluetooth interface configured to work like a wireless mouse. The virtual mouse was then paired to an unmodified Google Nexus 9 tablet. The participants were then asked to perform a set of tasks designed to see how well they were able to navigate within a variety of commonly used apps, and move from app to app. The participants browsed through music selections on a streaming service, searched for videos on YouTube, scrolled through a news aggregator and composed emails and chats.

The study showed that participants were able to make up to 22 point-and-click selections per minute while using a variety of apps. In text apps, the participants were able to type up to 30 effective characters per minute using standard email and text interfaces.

The participants reported finding the interface intuitive and fun to use, the study noted. One said, “It felt more natural than the times I remember using a mouse.” Another reported having “more control over this than what I normally use.”

The researchers were pleased to see how quickly the participants used the tablet interface to explore their hobbies and interests.

“It was great to see our participants make their way through the tasks we asked them to perform, but the most gratifying and fun part of the study was when they just did what they wanted to do — using the apps that they liked for shopping, watching videos or just chatting with friends,” said lead author Dr. Paul Nuyujukian, a bioengineer at Stanford. “One of the participants told us at the beginning of the trial that one of the things she really wanted to do was play music again. So to see her play on a digital keyboard was fantastic.”

The fact that the tablet devices were entirely unaltered and had all preloaded accessibility software turned off was an important part of the study, the researchers said.

“The assistive technologies that are available today, while they’re important and useful, are all inherently limited in terms of either the speed of use they enable, or the flexibility of the interface,” said Krishna Shenoy, a senior author of the paper and an electrical engineer and neuroscientist at Stanford University and Howard Hughes Medical Institute. “That’s largely because of the limited input signals that are available. With the richness of the input from the BCI, we were able to just buy two tablets on Amazon, turn on Bluetooth and the participants could use them with our investigational BrainGate system right out of the box.”

The researchers say that the study also has the potential to open important new lines of communication between patients with severe neurological deficits and their health care providers.

“This has great potential for restoring reliable, rapid and rich communication for somebody with locked-in syndrome who is unable to speak,” said Jose Albites Sanabria, who performed this research as a graduate student in biomedical engineering at Brown University. “That not only could provide increased interaction with their family and friends, but can provide a conduit for more thoroughly describing ongoing health issues with caregivers.”

As a neuroscientist and practicing critical care neurologist, senior author Dr. Leigh Hochberg of Brown University, Massachusetts General Hospital and the Providence VA Medical Center sees tremendous potential for the restorative capabilities of BCIs exemplified in this study.

“When I see somebody in the neuro-intensive care unit who has had an acute stroke and has lost the ability to move or communicate, I’d like to be able to say, ‘I’m very sorry this has happened, but we can restore your ability to use the technologies you were using before this happened, and you’ll be able to use them again tomorrow,'” Hochberg said. “And we are getting closer to being able to tell someone who has been diagnosed with ALS, ‘even while we continue to seek out a cure, you will never lose the ability to communicate.’ This work is a step toward those goals.”

Video: https://www.youtube.com/watch?time_continue=47&v=O6Qw3EDBPhg