That process of turning sunlight directly into usable energy — called photosynthesis — may soon be a feat humans are able to mimic to harness the sun’s energy for clean, storable, efficient fuel. If so, it could open a whole new frontier of clean energy. Enough energy hits the earth in the form of sunlight in one hour to meet all human civilization’s energy needs for an entire year.

Yulia Puskhar, a biophysicist and professor of physics in Purdue’s College of Science, may have a way to harness that energy by mimicking plants.

Wind power and solar power, harnessed by photovoltaic cells, are the two major forms of clean energy available. Adding a third — synthetic photosynthesis — would dramatically change the renewable energy landscape. The ability to store the energy easily, without requiring bulky batteries, would dramatically improve humans’ ability to power society cleanly and efficiently.

Both wind turbines and photovoltaics have downside in terms of environmental effects and complicating factors. Pushkar hopes that artificial photosynthesis might be able to bypass those pitfalls.

“We and other researchers around the world are working incredibly hard to try to come up with accessible energy,” Pushkar said. “Energy that is clean and sustainable that we can create with nontoxic, easily available elements. Our artificial photosynthesis is the way forward.”

Photosynthesis is a complex dance of processes whereby plants convert the sun’s radiance and water molecules into usable energy in the form of glucose. To do this, they use a pigment, usually the famous chlorophyll, as well as proteins, enzymes and metals.

The closest process to artificial photosynthesis humans have today is photovoltaic technology, where a solar cell converts the sun’s energy into electricity. That process is famously inefficient, able to capture only about 20% of the sun’s energy. Photosynthesis, on the other hand, is radically more efficient; it is capable of storing 60% of the sun’s energy as chemical energy in associated biomolecules.

The efficiency of simple photovoltaic cells — solar panels — is limited by semiconductors’ ability to absorb light energy and by the cell’s ability to produce power. That limit is something scientists could surpass with synthetic photosynthesis.

“With artificial photosynthesis, there are not fundamental physical limitations,” Pushkar said. “You can very easily imagine a system that is 60% efficient because we already have a precedent in natural photosynthesis. And if we get very ambitious, we could even envision a system of up to 80% efficiency.

“Photosynthesis is massively efficient when it comes to splitting water, a first step of artificial photosynthesis. Photosystems II proteins in plants do this a thousand times a second. Blink, and it’s done.”

Pushkar’s group is mimicking the process by building her own artificial leaf analog that collects light and splits water molecules to generate hydrogen. Hydrogen can be used as a fuel by itself via fuel cells or be added to other fuels such as natural gas, or built into fuel cells to power everything from vehicles to houses to small electronic devices, laboratories and hospitals. Her most recent discovery, an insight into the way water molecules split during photosynthesis, was recently published in the journal Chem Catalysis: Cell Press.

Scientists in Pushkar’s lab experiment with natural photosystem II proteins and synthetic catalysts combinations in attempts to understand what works best — and why. She also puts a priority on using compounds and chemicals that are readily abundant on Earth, easily accessible and nontoxic to the planet.

Progress in artificial photosynthesis is complicated, though, by the fact that photosynthesis is so multifaceted, a fact bemoaned by biochemistry students everywhere.

“The reaction is very complex,” Pushkar said. “The chemistry of splitting water molecules is extremely intricate and difficult.”

Scientists have been working on artificial photosynthesis since the 1970s. That’s a long time, but not when you remember that photosynthesis took millions of years to evolve. Not only that, but scientists believe that, unlike flight, communication or intelligence, photosynthesis has evolved only once — about 3 billion years ago, only about 1.5 billion years into Earth’s existence.

Pushkar posits that within the next 10-15 years, enough progress will have been made that commercial artificial photosynthesis systems may begin to come online. Her research is funded by the National Science Foundation.

However, something unexpected will occur as E. coli cells end their journey through your digestive tract. Without warning, they will find themselves swimming in your toilet bowl, clinging to the last bits of nutrients attached to their bodies. How do these tiny organisms adapt to survive sudden starvation? Scientists at Washington University in St. Louis wondered.

Close examination of nutrient-deprived E. coli under the microscope — a routine process in a lab that studies bacterial cell size — revealed cells that looked different, and that these differences are related to their ability to survive.

“Their cytoplasm shrank. As it shrank, the inner membrane pulled away from the outer membrane and left a big space at one end of the cell,” said Petra Levin, professor of biology in Arts & Sciences, whose postdoctoral scientist, Corey Westfall, and undergraduate student, Jesse Kao, first made the observation.

The space to which Levin refers, between the bacteria’s inner and outer membranes, is called the periplasm. In collaboration with Kerwyn Casey Huang, professor of bioengineering and of microbiology and immunology at Stanford University, and his postdoctoral scientist, Handuo Shi, Levin found an unexpected developmental response to starvation — one that may be keeping E. coli alive until they find their next buffet.

The work is published this week in the Proceedings of the National Academy of Sciences.

The biologists showed that when E. coli cells lack nutrients, the cytoplasm becomes more dense as its volume decreases, probably because of water loss. At the same time, the periplasm increases in volume as the inner membrane pulls away from the outer membrane.

“Although we don’t know for sure yet, we think that the cell is concentrating the nutrients in the cytoplasm so that it can keep running metabolism at a high rate,” Levin said. “Perhaps this is an adaptation to E. coli‘s constantly and rapidly changing lifestyle, in which it knows that each environment is temporary.”

The shrinking is reversible, the scientists found. Once they transferred the starving bacteria into a nutrient-rich medium, the inner membrane and the cytoplasm expanded. The bacterial cells rapidly rebounded from starvation, especially when E. coli received their favorite carbon source, glucose. And, importantly, if the Tol-Pal system was intact.

The Tol-Pal system is a critical cellular machinery composed of proteins that connect the outer membrane to the inner membrane. But its function has been understudied. As the inner membrane expands, the Tol-Pal system helps to reconnect it with the outer membrane, the scientists speculate. When the Tol-Pal system was absent, the internal contents of the cells bled out.

“We speculate that Tol-Pal acts as the zipper slider, helping the inner membrane zip into the outer membrane coat during recovery,” Levin said.

What happens to the transmembrane proteins, embedded in both the inner and outer membrane, when the inner membrane pulls away from the outer membrane? Do they get ripped apart? Levin and colleagues do not know yet and hope to answer these questions in the future.

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Materials provided by Washington University in St. Louis. Original written by Marta Wegorzewska. Note: Content may be edited for style and length.

Researchers at the University of Washington have developed a deep learning method that can do just that: If given a single photo of a waterfall, the system creates a video showing that water cascading down. All that’s missing is the roar of the water and the feeling of the spray on your face.

The team’s method can animate any flowing material, including smoke and clouds. This technique produces a short video that loops seamlessly, giving the impression of endless movement. The researchers will present this approach June 22 at the Conference on Computer Vision and Pattern Recognition.

“A picture captures a moment frozen in time. But a lot of information is lost in a static image. What led to this moment, and how are things changing? Think about the last time you found yourself fixated on something really interesting — chances are, it wasn’t totally static,” said lead author Aleksander Holynski, a doctoral student in the Paul G. Allen School of Computer Science & Engineering.

“What’s special about our method is that it doesn’t require any user input or extra information,” Holynski said. “All you need is a picture. And it produces as output a high-resolution, seamlessly looping video that quite often looks like a real video.”

Developing a method that turns a single photo into a believable video has been a challenge for the field.

“It effectively requires you to predict the future,” Holynski said. “And in the real world, there are nearly infinite possibilities of what might happen next.”

The team’s system consists of two parts: First, it predicts how things were moving when a photo was taken, and then uses that information to create the animation.

To estimate motion, the team trained a neural network with thousands of videos of waterfalls, rivers, oceans and other material with fluid motion. The training process consisted of asking the network to guess the motion of a video when only given the first frame. After comparing its prediction with the actual video, the network learned to identify clues — ripples in a stream, for example — to help it predict what happened next. Then the team’s system uses that information to determine if and how each pixel should move.

The researchers tried to use a technique called “splatting” to animate the photo. This method moves each pixel according to its predicted motion. But this created a problem.

“Think about a flowing waterfall,” Holynski said. “If you just move the pixels down the waterfall, after a few frames of the video, you’ll have no pixels at the top!”

So the team created “symmetric splatting.” Essentially, the method predicts both the future and the past for an image and then combines them into one animation.

“Looking back at the waterfall example, if we move into the past, the pixels will move up the waterfall. So we will start to see a hole near the bottom,” Holynski said. “We integrate information from both of these animations so there are never any glaringly large holes in our warped images.”

Finally, the researchers wanted their animation to loop seamlessly to create a look of continuous movement. The animation network follows a few tricks to keep things clean, including transitioning different parts of the frame at different times and deciding how quickly or slowly to blend each pixel depending on its surroundings.

The team’s method works best for objects with predictable fluid motion. Currently, the technology struggles to predict how reflections should move or how water distorts the appearance of objects beneath it.

“When we see a waterfall, we know how the water should behave. The same is true for fire or smoke. These types of motions obey the same set of physical laws, and there are usually cues in the image that tell us how things should be moving,” Holynski said. “We’d love to extend our work to operate on a wider range of objects, like animating a person’s hair blowing in the wind. I’m hoping that eventually the pictures that we share with our friends and family won’t be static images. Instead, they’ll all be dynamic animations like the ones our method produces.”

Video showing method: https://www.youtube.com/watch?v=4zKliOMilGY

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Materials provided by University of Washington. Original written by Sarah McQuate. Note: Content may be edited for style and length.

“Physics models have theorized this boundary for years,” said Dan Reisenfeld, a scientist at Los Alamos National Laboratory and lead author on the paper, which was published in the Astrophysical Journal today. “But this is the first time we’ve actually been able to measure it and make a three-dimensional map of it.”

The heliosphere is a bubble created by the solar wind, a stream of mostly protons, electrons, and alpha particles that extends from the Sun into interstellar space and protects the Earth from harmful interstellar radiation.

Reisenfeld and a team of other scientists used data from NASA’s Earth-orbiting Interstellar Boundary Explorer (IBEX) satellite, which detects particles that come from the heliosheath, the boundary layer between the solar system and interstellar space. The team was able to map the edge of this zone — a region called the heliopause. Here, the solar wind, which pushes out toward interstellar space, collides with the interstellar wind, which pushes in towards the Sun.

To do this measurement, they used a technique similar to how bats use sonar. “Just as bats send out sonar pulses in every direction and use the return signal to create a mental map of their surroundings, we used the Sun’s solar wind, which goes out in all directions, to create a map of the heliosphere,” said Reisenfeld.

They did this by using IBEX satellite’s measurement of energetic neutral atoms (ENAs) that result from collisions between solar wind particles and those from the interstellar wind. The intensity of that signal depends on the intensity of the solar wind that strikes the heliosheath. When a wave hits the sheath, the ENA count goes up and IBEX can detect it.

“The solar wind ‘signal’ sent out by the Sun varies in strength, forming a unique pattern,” explained Reisenfeld. “IBEX will see that same pattern in the returning ENA signal, two to six years later, depending on ENA energy and the direction IBEX is looking through the heliosphere. This time difference is how we found the distance to the ENA-source region in a particular direction.”

They then applied this method to build the three-dimensional map, using data collected over a complete solar cycle, from 2009 through 2019.

“In doing this, we are able to see the boundary of the heliosphere in the same way a bat uses sonar to ‘see’ the walls of a cave,” he added.

The reason it takes so long for the signal to return to IBEX is because of the vast distances involved. Distances in the solar system are measured in astronomical units (AU) where 1 AU is the distance from the Earth to the Sun. Reisenfeld’s map shows that the minimum distance from the Sun to the heliopause is about 120 AU in the direction facing the interstellar wind, and in the opposite direction, it extends at least 350 AU, which is the distance limit of the sounding technique. For reference, the orbit of Neptune is about 60 AU across.

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Materials provided by DOE/Los Alamos National Laboratory. Note: Content may be edited for style and length.

Marine sediments are a massive habitat for undescribed microbes

The muddy sediments of the sea floor are a massive global habitat for these ecologically important microorganisms; after all, our oceans cover more than 70 percent of the earth’s surface. Thousands of microbial species live here, most of which are still largely unknown. “Our study identifies some of these microbial players and reveals their lifestyles. At the same time, it tells us something about what happens to the vast amounts of DNA that are constantly released into the environment but do not accumulate anywhere and, accordingly, are obviously somehow being recycled,” Kenneth Wasmund explains. Previous research has shown that microorganisms grown in the laboratory might use DNA as an energy source. “Our research has now focused on microbes that actually live and actively function in the seafloor, while using DNA as a food source,” he adds.

Deciphering bacteria that use DNA for food by functional microbiome analyses

To this end, colleagues from the University of Calgary in Canada collected samples from the seafloor in the Baffin Bay, a marginal sea of the Atlantic Ocean between Greenland and Canada. To identify and characterise DNA-foraging microbes in these samples, the research team used an array of experimental, analytical, and bioinformatic methods. “In this collaboration of all four divisions at CMESS, we made full use of the excellent research infrastructure and unleashed the full expertise for functional microbiome analyses that is present at our Centre,” says Alexander Loy, head of the research group at the University of Vienna.

In laboratory incubations, the researchers fed purified DNA that was isotopically-labelled with heavy carbon atoms (13C) to the sediment bacteria. Using stable isotope probing, including a specific isotope imaging technique, they were then able to track the heavy carbon and as a result could see which bacteria degraded the labelled DNA. In addition, the scientists reconstructed the genetic information present in the cells, i.e. the genomes, of the DNA-eating microorganisms to learn about their functional potential and distribution in the world’s oceans.

Novel DNA-eating bacteria in the seafloor

The metagenomic analysis showed that the bacteria were equipped with DNA-degrading enzymes that enable them to chop-up DNA into small pieces to help them take it up and consume it. One bacterial species stood out as it had a particularly sophisticated set of tools for degrading DNA. Their appetite for DNA, also called nucleic acid, is now borne in their name: The research team named them Izemoplasma acidinucleici.

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Materials provided by University of Vienna. Note: Content may be edited for style and length.

So far, propagation of near-field light in a single direction is achieved by specific interactions between the electric dipole and the magnetic dipole in a system, which has led to inevitable complexities in device design. Hyperbolic metamaterials (HMMs), an important class of artificial anisotropic material with hyperbolic isofrequency contours, have attracted attention due to their unique ability to control near-field light by enabling subwavelength confinement of electromagnetic waves. Large wave-vector modes in HMMs are of particular interest because those modes are easier to integrate and have a smaller loss of energy at transfer.

As reported in Advanced Photonics, researchers from Tongji University in China recently demonstrated an all-electric scheme able to flexibly control the propagation direction of near-field light. They reported anomalous unidirectional excitation of hyperbolic modes with large wave-vector at subwavelength scales. According to their research, selective near-field coupling in HMMs is enabled by discrete electric dipoles with different phases, which serve as a metasource composed of all-electric components and with a symmetry-associated inner freedom.

Their research not only addresses the need for an all-electric experimental design scheme for near-field photonics, but also contributes fundamentally valuable symmetry-based excitation principles. Using a Huygens metasource, the researchers were able to observe the unidirectional excitation of hyperbolic bulk modes in a planar HMM. They found that unidirectional excitation in free space is the same as in the vertical direction, but opposite to that in the horizontal direction. These different propagation characteristics in horizontal and vertical directions are unique to the hyperbolic modes. In addition, the researchers used spin metasources to study the directional propagation of light in a planar hyperbolic waveguide. They found that, for the clockwise-rotating spin metasource, only the guided mode propagating from right to left is excited. And for the counterclockwise-rotating source, only the guided mode propagating from left to right is excited.

Overall, the research advances the fields of optical science and information communication, as the results provide the necessary conditions for highly efficient and experimentally verified photonics routing. For emerging applications in integrated optical devices, as well as wireless power transfer, switching, and filtering, this work promises unprecedented flexible control of near-field light.

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Materials provided by SPIE–International Society for Optics and Photonics. Note: Content may be edited for style and length.