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    14Nov, 2023
    Twisted magnets make brain-inspired computing more adaptable

    A form of brain-inspired computing that exploits the intrinsic physical properties of a material to dramatically reduce energy use is now a step closer to reality, thanks to a new study led by UCL and Imperial College London researchers.

    In the new study, published in the journal Nature Materials, an international team of researchers used chiral (twisted) magnets as their computational medium and found that, by applying an external magnetic field and changing temperature, the physical properties of these materials could be adapted to suit different machine-learning tasks.

    Such an approach, known as physical reservoir computing, has until now been limited due to its lack of reconfigurability. This is because a material’s physical properties may allow it to excel at a certain subset of computing tasks but not others.

    In the new study, published in the journal Nature Materials, an international team of researchers used chiral (twisted) magnets as their computational medium and found that, by applying an external magnetic field and changing temperature, the physical properties of these materials could be adapted to suit different machine-learning tasks.

    Dr Oscar Lee (London Centre for Nanotechnology at UCL and UCL Department of Electronic & Electrical Engineering), the lead author of the paper, said: “This work brings us a step closer to realising the full potential of physical reservoirs to create computers that not only require significantly less energy, but also adapt their computational properties to perform optimally across various tasks, just like our brains.

    “The next step is to identify materials and device architectures that are commercially viable and scalable.”

    Traditional computing consumes large amounts of electricity. This is partly because it has separate units for data storage and processing, meaning information has to be shuffled constantly between the two, wasting energy and producing heat. This is particularly a problem for machine learning, which requires vast datasets for processing. Training one large AI model can generate hundreds of tonnes of carbon dioxide.

    Physical reservoir computing is one of several neuromorphic (or brain inspired) approaches that aims to remove the need for distinct memory and processing units, facilitating more efficient ways to process data. In addition to being a more sustainable alternative to conventional computing, physical reservoir computing could be integrated into existing circuitry to provide additional capabilities that are also energy efficient.

    In the study, involving researchers in Japan and Germany, the team used a vector network analyser to determine the energy absorption of chiral magnets at different magnetic field strengths and temperatures ranging from -269 °C to room temperature.

    They found that different magnetic phases of chiral magnets excelled at different types of computing task. The skyrmion phase, where magnetised particles are swirling in a vortex-like pattern, had a potent memory capacity apt for forecasting tasks. The conical phase, meanwhile, had little memory, but its non-linearity was ideal for transformation tasks and classification — for instance, identifying if an animal is a cat or dog.

    Co-author Dr Jack Gartside, of Imperial College London, said: “Our collaborators at UCL in the group of Professor Hidekazu Kurebayashi recently identified a promising set of materials for powering unconventional computing. These materials are special as they can support an especially rich and varied range of magnetic textures. Working with the lead author Dr Oscar Lee, the Imperial College London group [led by Dr Gartside, Kilian Stenning and Professor Will Branford] designed a neuromorphic computing architecture to leverage the complex material properties to match the demands of a diverse set of challenging tasks. This gave great results, and showed how reconfiguring physical phases can directly tailor neuromorphic computing performance.”

    The work also involved researchers at the University of Tokyo and Technische Universität München and was supported by the Leverhulme Trust, Engineering and Physical Sciences Research Council (EPSRC), Imperial College London President’s Excellence Fund for Frontier Research, Royal Academy of Engineering, the Japan Science and Technology Agency, Katsu Research Encouragement Award, Asahi Glass Foundation, and the DFG (German Research Foundation).

    Resource : https://www.sciencedaily.com/releases/2023/11/231113111626.htm

    14Mar, 2023
    NASA To Measure Forest Health from Above

    In places across the U.S., tree cover is shrinking – forests are burned by wildfires on the West Coast and drowned by rising sea levels along the East. From the ground, it’s hard to assess the scale of the losses and the effects disappearing trees have on atmospheric carbon dioxide levels and climate change.

    NASA research scientist Jon Ranson is working to improve new technologies for studying trees from above, so future Earth-observing missions can more accurately assess forest health.

    “Trees do a huge service for the planet, in terms of sequestering carbon dioxide, taking it out of the atmosphere and putting it into wood,” Ranson said, “but trees are very sensitive to our changing climate. We’re trying to see the changes going on in forest ecosystems. If you detect things early enough, you might be able to do something about it.”

    When measured from aircraft and satellites, the wavelengths of light reflected by plants tell scientists about the amount of photosynthesis occurring, and therefore how much atmospheric carbon dioxide trees take up and store. The current standard for studying vegetation is called NDVI, or Normalized Differential Vegetation Index, which is the average of two broad portions of the infrared spectrum. NASA’s NDVI record goes back 40 years, providing a low-resolution but accurate picture of forest health.

    While NDVI is good at assessing vegetation quantity and vigor broadly, Ranson said, breaking down infrared and visible light into many more wavelengths, a technology called hyperspectral imaging, can provide insight on plants’ water content, chlorophyll and even changes in health. 

    “Vegetation has these broad spectral properties,” said Ian Adams, Earth Sciences Division Technologist at NASA’s Goddard Space Flight Center. “With hyperspectral imaging, you get lots of different measurements at smaller, closer together frequencies. There is a lot more information we can pull out if we can get better spectral resolution.”

    By dramatically increasing the number of frequencies available for researchers to study, Ranson’s work serves the priorities of the National Academies of Science’s most recent Earth Science decadal survey, which determines the field’s long-term priorities. The survey lists “surface topography and vegetation,” including forests, as a key area of study in need of more advanced technology.

     “Strategically for NASA, and more broadly for the remote sensing community, hyperspectral is one of the areas we see as the future,” Adams said.

    To make use of hyperspectral imaging by future orbital missions, data analysis techniques are first proven closer to the ground.

    Ranson’s team fitted a Skyfish drone (UAV) from partner institution Virginia Tech with a visible and infrared (VIS/IR) hyperspectral camera and lidar equipment. They flew the imaging equipment over forests near Blacksburg, VA, in a region called Mountain Lake. Comparing their UAV observations with actual CO2 levels recorded by sensors on a nearby National Ecological Observatory Network tower, Ranson’s team was able to refine calculations about how much carbon the forest removed from the atmosphere.

    These comparisons allowed them to further refine techniques for interpreting the hyperspectral data. For instance, Plants stressed by too much sunlight may release pigments to shield their chloroplasts, a condition his sensors can detect. If plants get too much shade, they may grow leaves with larger surface-areas, which can cause the sensor to overestimate plant productivity. Ranson wants to add short-wave infrared sensors to better distinguish reflections from leaves and other parts of plants, eliminating another possible source of error.

    The view from space: Seeing the forest for the trees

    Ranson’s goal is to study forests on a global scale from space.

    “We’re trying to get the complete picture,” Ranson said. “So that when we go to space, we know how to find the answer to the question, ‘Are our forests healthy? And if not, why not?’”

    Scientists and engineers at Goddard have been developing a mission concept called Concurrent Artificially intelligent Spectrometry and Adaptive Lidar System, or CASALS. If selected, CASALS would send a satellite with lidar and hyperspectral cameras into space. A constellation of such satellites could take the frequent measurements necessary to assess changes in forest productivity over time, using models perfected by Ranson’s UAV flights.“Forests take up as much carbon as the ocean does, yet forests cover only 9 percent of Earth’s surface,” said Ranson. “So, if something goes wrong with our forests, it’s a dramatic issue. We’ve got this great, great resource in forests, and we need to care for them so they’ll care for us.”

    Resource : https://www.nasa.gov/feature/nasa-to-measure-forest-health-from-above

    2Mar, 2023
    Is the future of computing biological?

    Human brains have a leg up on computers—so what’s the next logical step?

    Trying to make computers more like human brains isn’t a new phenomenon. However, a team of researchers from Johns Hopkins University argues that there could be many benefits in taking this concept a bit more literally by using actual neurons, though there are some hurdles to jump first before we get there.

    In a recent paper, the team laid out a roadmap of what’s needed before we can create biocomputers powered by human brain cells (not taken from human brains, though). Further, according to one of the researchers, there are some clear benefits the proposed “organoid intelligence” would have over current computers.

    “We have always tried to make our computers more brain-like,” Thomas Hartung, a researcher at Johns Hopkins University’s Environmental Health and Engineering department and one of the paper’s authors, told Ars. “At least theoretically, the brain is essentially unmatched as a computer.”

    It’s alive (kind of?)

    Organoids are small pieces of tissue grown in the lab to resemble whole organs; they contain many of an organ’s specialized cell types and some internal structures. They enable researchers to perform studies without needing to do human or animal testing. Hartung and various colleagues have been working with organoids grown from human brain cells. He started growing them back in 2012 from human skin samples that he reprogrammed into a stem cell-like state. The organoids are small, roughly the size of the point of a pen, but they contain many neurons—around 50,000—and various other structures that allow them to learn and remember.

    According to Hartung, these cells could be used to create computers with several benefits. For one, such machines would result in less energy consumption relative to conventional computers—and supercomputers in particular. Human brains learn faster and use less energy than computers do. The game-playing algorithm AlphaGo, for instance, was trained on data from 160,000 amateur games of Go. It would take an incredibly long amount of time for a human to play these games, yet humans still perform admirably at Go. Additionally, the human brain is very good at storing data—it’s estimated to be able to store 2.5 million gigabytes.

    In theory, organoid computers would also take up less space. In the future, they could have a three-dimensional structure—as opposed to just something on a Petri dish—meaning that their cell density could increase considerably, and more connections between the neurons could form. Finally, while wholly non-human computers are better at processing large amounts of data, human brains are better at making logical decisions—like being able to quickly identify an animal.

    Sukhpal Gill, an assistant professor of electronic engineering and computer science at Queen Mary University of London, similarly sees the potential of this kind of computing. He noted that energy consumption presents a big limitation for computing, AI, and machine learning. “Human brain cells, on the other hand, integrate such tasks with ease and also have exceptionally low energy requirements, needing just a relatively small volume of a nutrient-rich solution to function,” he told Ars.

    A long road ahead

    However, there’s a good deal of work ahead before these biocomputers can become a reality. One of the most pressing issues is size. The organoids would need to increase from 50,000 to closer to 10 million cells, he said. But it’s hard to sustain these cells at a size larger than half a millimeter because the oxygen and nutrients fed to them can’t reach the center easily, meaning you could have a “rotten core” on your hands. One solution might be perfusion, or channeling liquid into the organoid’s interior, Hartung said.

    Researchers also need to find new ways of communicating with the organoids to exchange information with them, much like how a computer works. Improving their memory is also vital. Right now, brain organoids can only hold short-term memory. You could, for instance, train them to play Pong, but they will forget everything the next day, Hartung said. Some of this likely has to do with the fact that the organoids lack microglial cells, he said. These are a kind of immune cell that also appear in the brain and perform synaptic pruning, or killing off superfluous synapses, allowing healthy brains to function normally.

    Then there are also ethical questions about creating and growing brain cells and about whether or not these organoids would be alive—if they could develop a kind of consciousness or experience pain. As such, Hartung notes that his team has been partnering with bioethicists to assess and ensure everything is done in a way that’s not morally terrifying.

    Resource : https://arstechnica.com/science/2023/03/is-the-future-of-computing-biological/

    5Nov, 2022
    NASA Invites Media to Discuss Space Station Science, Experiments

    NASA will host a media teleconference at 1 p.m. EST Wednesday, Nov. 9, to discuss the hardware, technology demonstrations, and science experiments headed to the International Space Station aboard SpaceX’s 26th commercial resupply mission for the agency.

    Audio of the teleconference will be streamed live online at:

    https://www.nasa.gov/live

    SpaceX is targeting Friday, Nov. 18, to launch its Dragon cargo spacecraft atop a Falcon 9 rocket from Launch Complex 39A at NASA’s Kennedy Space Center in Florida.

    One of the payloads aboard the cargo flight is the Moon Microscope kit for in-flight medical diagnosis that includes a portable handheld microscope and a small self-contained blood sample staining device. This will allow astronauts to collect and stain a blood sample, obtain images with the microscope, and transmit images to the ground, where flight surgeons will use them to diagnose illnesses and prescribe treatments.

    SpaceX’s Dragon also will deliver new science investigations, supplies, and equipment for the international crew, including the next set of International Space Station Roll Out Solar Arrays (iROSAs). It also will carry a study which will grow dwarf tomatoes as part of efforts to create a continuous fresh-food production system in space, and an experiment that tests an on-demand method to create specific quantities of key nutrients.

    Teleconference participants include:

    • Kirt Costello, NASA’s chief scientist for the International Space Station Program Research Office, who will provide an overview of the research and technology launching aboard the Dragon spacecrafts
    • Gioia Massa, NASA’s space crop production scientist and principal investigator for the Veg-05 study
    • Matt Mickle, Boeing’s developmental projects senior manager, who will discuss International Space Station Roll Out Solar Arrays (iROSA)
    • Timothy Macaulay, CIPHER vestibular health study lead, an experiment which will use the newly launching Falcon Goggles tool
    • Mayra Nelman-Gonzalez, immunologist in NASA’s Johnson Space Center’s Immunology and Virology Laboratory and co-investigator for the Moon Microscope technology demonstration
    • John A. Hogan, chief of the bioengineering branch at NASA’s Ames Research Center and principal investigator for the BioNutrients-2 experiment
    • A representative for the Extrusion study sponsored by the ISS National Laboratory

    To participate in the call, media must contact Lora Bleacher at least two hours prior to the start of the call for dial-in details at: lora.v.bleacher@nasa.gov. Media and the public can submit questions on social media using #AskNASA.

    Cargo resupply by U.S. companies significantly increases NASA’s ability to conduct more investigations aboard the orbiting laboratory. Those investigations lead to new technologies, medical treatments, and products that improve life on Earth. Other U.S. government agencies, private industry, and academic and research institutions can also conduct microgravity research through our partnership with the ISS National Laboratory.

    Humans have occupied the space station continuously since November 2000. In that time, 263 people and a variety of international and commercial spacecraft have visited the orbital outpost. It remains the springboard to NASA’s next great leap in exploration, including future missions to the Moon under Artemis and eventually Mars.

    Members of the public can attend the launch virtually and receive mission updates. To participate, members of the public can register to stay up to date on mission information, mission highlights, and interaction opportunities.

    For launch countdown coverage, NASA’s launch blog, and more information about the mission, visit:

    https://www.nasa.gov/spacex

    Resource : https://www.nasa.gov/press-release/nasa-invites-media-to-discuss-space-station-science-experiments

    28Oct, 2022
    Magnetic sensors track muscle length

    Using a simple set of magnets, MIT researchers have come up with a sophisticated way to monitor muscle movements, which they hope will make it easier for people with amputations to control their prosthetic limbs.

    In a new pair of papers, the researchers demonstrated the accuracy and safety of their magnet-based system, which can track the length of muscles during movement. The studies, performed in animals, offer hope that this strategy could be used to help people with prosthetic devices control them in a way that more closely mimics natural limb movement.

    “These recent results demonstrate that this tool can be used outside the lab to track muscle movement during natural activity, and they also suggest that the magnetic implants are stable and biocompatible and that they don’t cause discomfort,” says Cameron Taylor, an MIT research scientist and co-lead author of both papers.

    In one of the studies, the researchers showed that they could accurately measure the lengths of turkeys’ calf muscles as the birds ran, jumped, and performed other natural movements. In the other study, they showed that the small magnetic beads used for the measurements do not cause inflammation or other adverse effects when implanted in muscle.

    “I am very excited for the clinical potential of this new technology to improve the control and efficacy of bionic limbs for persons with limb-loss,” says Hugh Herr, a professor of media arts and sciences, co-director of the K. Lisa Yang Center for Bionics at MIT, and an associate member of MIT’s McGovern Institute for Brain Research.

    Herr is a senior author of both papers, which appear today in the journal Frontiers in Bioengineering and Biotechnology. Thomas Roberts, a professor of ecology, evolution, and organismal biology at Brown University, is a senior author of the measurement study.

    Tracking movement

    Currently, powered prosthetic limbs are usually controlled using an approach known as surface electromyography (EMG). Electrodes attached to the surface of the skin or surgically implanted in the residual muscle of the amputated limb measure electrical signals from a person’s muscles, which are fed into the prosthesis to help it move the way the person wearing the limb intends.

    However, that approach does not take into account any information about the muscle length or velocity, which could help to make the prosthetic movements more accurate.

    Several years ago, the MIT team began working on a novel way to perform those kinds of muscle measurements, using an approach that they call magnetomicrometry. This strategy takes advantage of the permanent magnetic fields surrounding small beads implanted in a muscle. Using a credit-card-sized, compass-like sensor attached to the outside of the body, their system can track the distances between the two magnets. When a muscle contracts, the magnets move closer together, and when it flexes, they move further apart.

    In a study published last year, the researchers showed that this system could be used to accurately measure small ankle movements when the beads were implanted in the calf muscles of turkeys. In one of the new studies, the researchers set out to see if the system could make accurate measurements during more natural movements in a nonlaboratory setting.

    To do that, they created an obstacle course of ramps for the turkeys to climb and boxes for them to jump on and off of. The researchers used their magnetic sensor to track muscle movements during these activities, and found that the system could calculate muscle lengths in less than a millisecond.

    They also compared their data to measurements taken using a more traditional approach known as fluoromicrometry, a type of X-ray technology that requires much larger equipment than magnetomicrometry. The magnetomicrometry measurements varied from those generated by fluoromicrometry by less than a millimeter, on average.

    “We’re able to provide the muscle-length tracking functionality of the room-sized X-ray equipment using a much smaller, portable package, and we’re able to collect the data continuously instead of being limited to the 10-second bursts that fluoromicrometry is limited to,” Taylor says.

    Seong Ho Yeon, an MIT graduate student, is also a co-lead author of the measurement study. Other authors include MIT Research Support Associate Ellen Clarrissimeaux and former Brown University postdoc Mary Kate O’Donnell.

    Biocompatibility

    In the second paper, the researchers focused on the biocompatibility of the implants. They found that the magnets did not generate tissue scarring, inflammation, or other harmful effects. They also showed that the implanted magnets did not alter the turkeys’ gaits, suggesting they did not produce discomfort. William Clark, a postdoc at Brown, is the co-lead author of the biocompatibility study.

    The researchers also showed that the implants remained stable for eight months, the length of the study, and did not migrate toward each other, as long as they were implanted at least 3 centimeters apart. The researchers envision that the beads, which consist of a magnetic core coated with gold and a polymer called Parylene, could remain in tissue indefinitely once implanted.

    “Magnets don’t require an external power source, and after implanting them into the muscle, they can maintain the full strength of their magnetic field throughout the lifetime of the patient,” Taylor says.

    The researchers are now planning to seek FDA approval to test the system in people with prosthetic limbs. They hope to use the sensor to control prostheses similar to the way surface EMG is used now: Measurements regarding the length of muscles will be fed into the control system of a prosthesis to help guide it to the position that the wearer intends.

    “The place where this technology fills a need is in communicating those muscle lengths and velocities to a wearable robot, so that the robot can perform in a way that works in tandem with the human,” Taylor says. “We hope that magnetomicrometry will enable a person to control a wearable robot with the same comfort level and the same ease as someone would control their own limb.”

    In addition to prosthetic limbs, those wearable robots could include robotic exoskeletons, which are worn outside the body to help people move their legs or arms more easily.

    The research was funded by the Salah Foundation, the K. Lisa Yang Center for Bionics at MIT, the MIT Media Lab Consortia, the National Institutes of Health, and the National Science Foundation.

    Resource : https://www.sciencedaily.com/releases/2022/10/221025150229.htm

    1Oct, 2021
    Quantum dots enable infrared lasing at room temperature for silicon photonics

    Lasers, devices that emit light in one direction, with photons traveling at one specific frequency and all with the same phase (coherent), govern the way we communicate today. Although lasers are known to most people as little torches emitting high purity color beams, the workhorse of lasers is actually in the infrared part of spectrum, where our eyes cannot see. The reason for this is that optical fibers are highly transparent to the infrared (1.3-1.6 um), allowing efficient optical transmission with very high data rates. Moreover, infrared lasers have minimum overlap with ambient light and are considered eye-safe, allowing their use in LIDAR (light detection and ranging) applications for 3D imaging, automotive and free-space communications. To date, infrared lasers are mainly made with Erbium-doped fibers or III-V epitaxial semiconductors, imposing certain limitations in their manufacturing and their easy integration with electronics.

    An important feature to take into account while working with lasers is the optical gain. The optical gain describes how well the light can be amplified in the system. If one could find a new optical gain material platform that can be produced with low cost in high volumes and can be integrated on a variety of substrates and form factors, this would definitely unleash a whole new realm of applications. Imagine such material that can be conformally coated along optical fibers or directly deposited atop CMOS silicon. Even better, imagine it to possess facile bandgap tunability so that the emission wavelength of the laser can be readily tuned across the infrared. Such solution could lead to inter- or intra-chip optical communications offering lower power consumption, low cost and higher data rates or enable multi-spectral 3D imaging capabilities.

    Colloidal quantum dot (CQD) technology is based on a solution processed optoelectronic material platform that has demonstrated already its potential for infrared optoelectronics with high performance CMOS compatible photodetectors and light emitting diodes (LEDs). The realization of an infrared CQD laser though had remained elusive.

    Now, in a recent paper published in Nature Photonics, ICFO researchers Guy Whitworth, Mariona Dalmases, and Nima Taghipour, led by ICREA Prof. at ICFO Gerasimos Konstantatos have reported the achievement of a colloidal quantum-dot-based infrared laser source operating at room temperature, compatible with CMOS technology and tunable to emit in the telecommunications window, an important milestone needed for classical or quantum communications.

    Previous to this finding, the team had already been working on an experiment where they were able to demonstrate stimulated emission and optical gain of quantum dots on thin films, but what they were lacking was actually inserting this setup into a cavity to achieve lasing.

    Infrared QD Lasing at room temperature

    To find the ideal cavity for the experiment, the team of researchers took a distributed feedback cavity (DFB), spincoating atop a thin layer of PbS CQDs as the optical gain medium. By concomitantly tuning the size of the dots and the geometrical characteristics of the DFB to optimize the cavity resonance with the gain spectrum of the quantum dots they managed to demonstrate lasing emission across the eye-safe optical communication infrared spectrum and at room temperature, thus, possibly finding the last piece of the jigsaw puzzle for silicon photonics.

    In addition, the researchers went a little further and engineered the surface of the dots in order to suppress electronic trap states in order to favor stimulated emission. They made use of a robust doping of the quantum dots to demonstrate lasing emission at lower pumping intensities, an achievement that opens a new path towards more practical implementations.

    As Prof. Gerasimos Konstantatos comments, “the results of this study are considered a major breakthrough in the field of CQD optoelectronics. This discovery may facilitate fully integrated silicon photonics, paving the way towards low-cost solution processed and CMOS integrated lasing sources for on-chip comm or LIDAR applications. Before, further advances are needed to optimize the material in order to demonstrate lasing under continuous wave or nanosecond excitation, which makes our next milestone.”

    Source: https://www.sciencedaily.com/releases/2021/09/210929112828.htm

    27Jul, 2021
    A stunning visualization of Alaska’s Yukon Delta shows a land in transition

    More northern parts of the Arctic are becoming greener

    In this visualization, the northern lobe of Alaska’s Yukon Delta appears as a tangle of sedge meadows (colored yellow-brown), with willow shrublands (green) lining networks of river channels flowing toward the Bering Sea. Sediment-rich waters are shown in their natural browns.

    The westward journey of the mighty Yukon River takes it from its headwaters in Canada’s British Columbia straight across Alaska. The river has many stories to tell, of generations of Indigenous people hunting on its banks and fishing in its waters, of paddle-wheeled boats and gold panning and pipelines.

    Where it meets the Bering Sea, the river fans out into an intricate delta resembling cauliflower lobes of river channels and ponds. The delta has a story to tell, too — that of an increasingly green Arctic.

    A composite image of the delta’s northern lobe, taken May 29 by the U.S. Geological Survey’s Landsat 8 satellite, shows willow shrublands lining river channels as they wind toward the sea. Farther inland, tussock grasses carpet the tundra. Grasslike sedge meadows populate low-lying wetlands, punctuated by ponds left behind by springtime floods along the riverbanks from snow and ice that have melted upstream.

    In southern Alaska, such as in the Kenai Peninsula, the Arctic has been getting noticeably greener since the 1980s, as global temperatures climb (SN: 4/11/19). Researchers observed this change using satellite measurements of red and near-infrared light reflected off the vegetation. Now, analyses of changing vegetation in the Yukon Delta and nearby Kuskokwim Delta show that more northern areas are getting greener too, researchers report June 1 in Earth Interactions.

    The increasing prevalence of tall willows, an important moose habitat, is one sign of these changes in the delta. Moose populations, too, are on the rise. But for the Yukon and other Arctic deltas — where higher floodwaters due to climate change are likely to deposit thicker sediment piles, supporting more greenery — many more changes are likely to come as the planet warms. 

    Source: https://www.sciencenews.org/article/alaska-yukon-delta-visualization-climate-change-land-transition

    9Jul, 2021
    What fractals, Fibonacci, and the golden ratio have to do with cauliflower
    Enlarge / Macro-photo of green Romanesco cauliflower showcases the vegetable’s striking fractal pattern.

    It’s long been observed that many plants produce leaves, shoots, or flowers in spiral patterns. Cauliflower provides a unique example of this phenomenon, because those spirals repeat at several different size scales—a hallmark of fractal geometry. This self-similarity is particularly notable in the Romanesco variety because of the distinctive conical shape of its florets. Now, a team of French scientists from the CNRS has identified the underlying mechanism that gives rise to this unusual pattern, according to a new paper published in Science. 

    Fractal geometry is the mathematical offspring of chaos theory; a fractal is the pattern left behind in the wave of chaotic activity. That single geometric pattern repeats thousands of times at different magnifications (self-similarity). For that reason, fractals are often likened to Russian nesting dolls. Many fractal patterns exist only in mathematical theory, but over the last few decades, scientists have found there are fractal aspects to many irregular yet patterned shapes in nature, such the branchings of rivers and trees—or the strange self-similar repeating buds that make up the Romanesco cauliflower. 

    Each bud is made up of a series of smaller buds, although the pattern doesn’t continue down to infinitely smaller size scales, so it’s only an approximate fractal. The branched tips, called meristems, make up a logarithmic spiral, and the number of spirals on the head of Romanesco cauliflower is a Fibonacci number, which in turn is related to what’s known as the “golden ratio.” 

    The person most closely associated with the Fibonacci sequence is the 13th-century mathematician Leonardo Pisano; his nickname was “filius Bonacci” (son of Bonacci), which got shortened to Fibonacci. In his 1202 treatise, Book of Calculation, Fibonacci described the numerical sequence that now bears his name: 1, 2, 3, 5, 8, 13, 21… and on into infinity. Divide each number in the sequence into the one that follows, and the answer will be something close to 1.618, an irrational number known as phi, aka the golden ratio. And there is a special “golden” logarithmic spiral that grows outward by a factor of the golden ratio for every 90 degrees of rotation, of which a “Fibonacci spiral” is a close approximation. 

    Scientists have long puzzled over possible underlying mechanisms for this unusual patterning in the arrangement of leaves on a stem (phyllotaxis) of so many plants—including pine cones, daisies, dahlias, sunflowers, and cacti—dating all the way back to Leonardo da Vinci. Swiss naturalist Charles Bonnet (who coined the term “phyllotaxis”) noted that these spirals exhibited either clockwise or counterclockwise golden ratios in 1754, while French brothers Auguste and Louis Bravais discovered in 1837 that the ratios of phyllotaxis spirals were related to the Fibonacci sequence. 

    In 1868, German botanist Wilhelm Hofmeister came up with a solid working model. He found that nascent leaves (“primordia”) will form at the least crowded part of the meristem, and as the plant grows, each successive leaf will move outward radially, at a rate proportional to the stem’s growth. The second leaf, for instance, will grow as far as possible from the first, and the third will grow at a distance farthest from both the first and the second leaves, and so on. It’s not a hardcore law of nature or some kind of weird botanical magic: that Fibonacci spiral is simply the most efficient way of packing the leaves. 

    According to the authors of this latest paper, the spiral phyllotaxis of cauliflower is unusual because those spirals are conspicuously visible at several different size scales, particularly in the Romanesco variety. They maintain that cauliflowers are basically failed flowers. The whole process depends on those branched tips, or meristems, which are made up of undifferentiated cells that divide and develop into other organs arranged in a spiral pattern. In the case of cauliflower, these cells produce buds that would normally bloom into flowers. Those buds develop into stems instead, but unlike normal stems, they are able to grow without leaves and thereby produce even more buds that turn into stems instead of flowers. 

    This triggers a chain reaction, resulting in that trademark pattern of repeating stems upon stems that ultimately forms the edible white flesh known as the “curd.” In the case of the Romanesco variety, its stems produce buds at an accelerating rate (instead of the constant rate typical of other forms of cauliflower). So its florets take on that distinctive pyramid-like shape that showcases the fractal patterns so beautifully. 

    The puzzle, per the authors, is how these gene regulatory networks that initially evolved to produce flowers were able to change so drastically. So co-author Eugenio Azpeitia and several colleagues combined in vivo experiments with 3D computational modeling of plant development to study the molecular underpinnings of how buds form in cauliflower (both edible cauliflower and the Romanesco variant). 

    Apparently, this is the result of self-selected mutations during the process of domestication, which over time drastically changed the shapes of these plants. The authors found that, while the meristems fail to form flowers, the meristems do experience a transient period where they’re in a flower-like state, and that influences later steps in development. In the case of Romanesco cauliflower, the curd adopts a more conical shape instead of a round morphology. The end result is those fractal-like forms at several different size scales. 

    “These results reveal how fractal patterns can be generated through growth and developmental networks that alter identities and meristem dynamics,” the authors concluded. “Our models now clarify the molecular and morphological changes over time by which meristems gain different identities to form the highly diverse and fascinating array of plant architectures found throughout nature and crops.” 

    Source : https://arstechnica.com/science/2021/07/what-fractals-fibonacci-and-the-golden-ratio-have-to-do-with-cauliflower/