Hanny’s Voorwerp Is A Puzzling Space Object Discovered By A Dutch School teacher (Astronomy)

Many people dream of making the next big discovery to change the way humans think about the universe. For most of history, that dream has been off limits to all but research scientists. In recent decades, however, citizen science has given regular people a chance to make those big discoveries. That’s how one of the strangest space objects ever witnessed was discovered by a 24-year-old schoolteacher from the Netherlands.

Hanny’s Voorwerp Is The Green Cloud Near The Bottom, With Its Sister Galaxy IC 2497 Right above. ©WIYN/William keel/Anna Manning

But, why we are covering this? Because the fact that a regular citizen can make a huge scientific discovery is a testament to the power of citizen science. It makes us wonder…. could we make the next big space discovery?

Discoverer Hanny van Arkel told the story of the bizarre object’s discovery on her website. As a citizen volunteer for Galaxy Zoo—a citizen-science organization she discovered through her fandom of Queen-guitarist-turned-phD Brian May—van Arkel spent her free summer months in 2007 classifying galaxies from Hubble images. She had only been volunteering a week when she classified an anti-clockwise spiral galaxy…and stopped. There was more to the image than just the galaxy. “I noticed it had a nice neighbour, although I wasn’t sure it was a galaxy, so maybe ‘the smudge under it’ is a better way of explaining what I saw,” van Arkel writes. “I read on the site about irregular galaxies and this ‘smudge’ made me think of one of those, although it was much bluer and it had a remarkable form.”

She submitted the image to the Galaxy Zoo forums to see if anyone knew what the “smudge” was. No one did, but that didn’t stop them from puzzling over it. One member, who knew van Arkel was Dutch, looked up the Dutch word for “object” and posted “Hanny, here’s your Voorwerp.” “Hanny’s Voorwerp” was given a name.

Hanny Van Arkel, Discoverer Of Hanny’s Voorwerp

WHAT EXACTLY IS IT?

In January 2008, the astronomers in charge of Galaxy Zoo began investigating Hanny’s Voorwerp. What they discovered was the interaction between a region of star formation and cloud of gas flowing out from the spiral galaxy van Arkel originally classified. At the core of that galaxy is a quasar, whose black-hole-powered radiation blast sent a powerful beam of light at Hanny’s Voorwerp and turned its gas cloud an eerie green color. According to NASA, “Radio studies have revealed that Hanny’s Voorwerp is not just an island gas cloud floating in space. The glowing blob is part of a long, twisting rope of gas, or tidal tail, about 300,000 light-years long that wraps around the galaxy. The only optically visible part of the rope is Hanny’s Voorwerp. The illuminated object is so huge that it stretches from 44,000 light-years to 136,000 light-years from the galaxy’s core.” That all may mean that this galaxy collided with another galaxy around a billion years ago, thereby teaching astronomers something new about how galaxies merge.

Hanny van Arkel discovered something new about the universe. While this may have been nearly impossible for a 20-something schoolteacher in decades past, the internet has proven to be an egalitarian place where anyone can achieve amazing things, as long as they keep on trying.

What Is Heat Death Paradox? (Astronomy)

Formulated in 1862 by Lord Kelvin, Hermann von Helmholtz and William John Macquorn Rankine, the heat death paradox, also known as Clausius’s paradox and thermodynamic paradox, is a reductio ad absurdum argument that uses thermodynamics to show the impossibility of an infinitely old universe.

Assuming that the universe is eternal, a question arises: How is it that thermodynamic equilibrium has not already been achieved?

This paradox is based upon the classical model of the universe in which the universe is eternal. Clausius’s paradox is a paradox of paradigm. It was necessary to amend the fundamental ideas about the universe, which brought about the change of the paradigm. The paradox was solved when the paradigm was changed.

The paradox was based upon the rigid mechanical point of view of the Second principle of thermodynamics postulated by Rudolf Clausius according to which heat can only be transferred from a warmer to a colder object. If the universe was eternal, as claimed in the classical stationary model of the universe, it should already be cold.

Any hot object transfers heat to its cooler surroundings, until everything is at the same temperature. For two objects at the same temperature as much heat flows from one body as flows from the other, and the net effect is no change. If the universe were infinitely old, there must have been enough time for the stars to cool and warm their surroundings. Everywhere should therefore be at the same temperature and there should either be no stars, or everything should be as hot as stars.

Since there are stars and the universe is not in thermal equilibrium it cannot be infinitely old.

The paradox does not arise in Big Bang or Steady State cosmology. In Big Bang cosmology, the current age of the universe is not old enough to have reached equilibrium; while in a Steady State system, sufficient hydrogen is replenished or regenerated continuously to allow for a constant average density and preventing stars from running down.

References: Cucic (2009). “Paradoxes of Thermodynamics and Statistical Physics”, pp.1-15, arXiv:0912.1756

Blocking Vibrations That Remove Heat Could Boost Efficiency Of Next-Gen Solar Cells (Chemistry)

Led by the Department of Energy’s Oak Ridge National Laboratory and the University of Tennessee, Knoxville, a study of a solar-energy material with a bright future revealed a way to slow phonons, the waves that transport heat. The discovery could improve novel hot-carrier solar cells, which convert sunlight to electricity more efficiently than conventional solar cells by harnessing photogenerated charge carriers before they lose energy to heat.

Substituting deuterium for hydrogen makes methylammonium heavier and slows its swaying so it can interact with vibrations that remove heat, keeping charge carriers hot longer. ©Jill Hemman/ORNL, U.S. Dept. of Energy

“We showed that the thermal transport and charge-carrier cooling time can be manipulated by changing the mass of hydrogen atoms in a photovoltaic material,” said ORNL’s Michael Manley. “This route for extending the lifetime of charge carriers bares new strategies for achieving record solar-to-electric conversion efficiency in novel hot-carrier solar cells.”

UT’s Mahshid Ahmadi noted, “Tuning the organic-molecule dynamics can enable control of phonons important to thermal conductivity in organometallic perovskites.” These semiconducting materials are promising for photovoltaic applications.

Manley and Ahmadi designed and managed the study, published in Science Advances. Experts in materials synthesis, neutron scattering, laser spectroscopy and condensed matter theory discovered a way to inhibit wasteful charge cooling by swapping a lighter isotope for a heavier one in an organometallic perovskite.

When sunlight strikes a solar cell, photons create charge carriers — electrons and holes — in an absorber material. Hot-carrier solar cells quickly convert the energy of the charge carriers to electricity before it is lost as waste heat. Preventing heat loss is a grand challenge for these solar cells, which have the potential to be twice as efficient as conventional solar cells.

The conversion efficiency of conventional perovskite solar cells has improved from 3% in 2009 to more than 25% in 2020. A well-designed hot-carrier device could achieve a theoretical conversion efficiency approaching 66%.

The researchers studied methylammonium lead iodide, a perovskite absorber material. In its lattice, collective excitations of atoms create vibrations. Vibrations moving in sync with each other are acoustic phonons, whereas those moving out of sync are optical phonons.

“Typically, charge carriers first lose their heat to optical phonons, which propagate slower than acoustic phonons,” explained ORNL co-author Raphael Hermann. “Later, optical phonons interact with acoustic phonons that carry away this energy.”

However, in a region called the “hot phonon bottleneck,” exotic physics prevent electrons from losing their energy to collective vibrations that transport heat. To enhance this effect in a photovoltaic perovskite, the researchers used inertia, the tendency of an object to keep doing what it’s doing, be that resting or moving.

“We basically slowed down how fast the molecules can sway, similar to slowing a spinning ice skater by putting weights in her hands,” Hermann said.

To do that in an orderly atomic lattice, Ahmadi and ORNL’s Kunlun Hong led the synthesis of crystals of methylammonium lead iodide at the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility at ORNL. They substituted a lighter isotope of hydrogen, normally occurring protium, which has no neutrons, with a heavier one, deuterium, which has one neutron, in the perovskite’s central organic molecule, methylammonium, or MA. Isotopes are chemically identical atoms that differ only in mass owing to the difference in neutron number.

Next, Manley and Hermann together with ORNL’s Songxue Chi conducted triple-axis neutron scattering experiments at the High Flux Isotope Reactor, a DOE Office of Science User Facility at ORNL, to map the phonon dispersion in protonated and deuterated crystals. Because they saw a disagreement between their measurements and published data from inelastic X-ray measurements, they made additional measurements at the Spallation Neutron Source, another DOE Office of Science User Facility at ORNL. There, Luke Daemen of ORNL used the VISION vibrational spectrometer to reveal all possible vibrational energies. The combined results indicated that longitudinal acoustic modes with short wavelengths propagate more slowly in the deuterated sample, suggesting thermal conductivity may be reduced.

Hsin Wang of ORNL performed thermal diffusivity measurements to investigate how heat moved in the crystals. “Those measurements told us that deuteration decreased the already-low thermal conductivity by 50%,” Manley said. “We realized then that maybe this finding affects things that builders of solar devices care about — specifically, keeping charge carriers hot.”

The study provided unprecedented understanding of the effect of atomic mass increase on heat transfer.

“A lot of vibrations, like stretching modes for the hydrogen atoms, have such high frequencies that they don’t normally interact with the lower-energy vibrations of the crystal,” Daemen said. The lower-energy modes include swaying of molecules.

The swaying frequency of the organic molecule MA is a little higher than the frequency of the collective vibrations. However, when a deuterium atom substitutes for a lighter hydrogen isotope, its greater mass slows the swaying of MA. It sways at a frequency closer to that of the collective vibrations, and the two start to interact and then strongly couple. The synced phonons slow, becoming less effective at removing heat.

Hermann compared the influence of frequency to a boy’s different actions when his father pushes him on a swing. “The protonated case is like the boy moving his legs too fast to be in sync with the dad pushing. He’s not going to go higher. But if he starts moving his legs at about the same frequency as the swinging, that’s like the deuterated case. The kid has slowed down his legs just enough so that he’s starting to get in sync with the pushed swing, adding momentum. He is able to swing higher because the two motions are coupled.”

The ORNL measurements revealed an effect that far exceeded what was expected from changing the mass of the hydrogen: Deuteration slowed heat transport so much that the charge-carrier cooling time doubled.

To confirm this finding, ORNL co-author Chengyun Hua used pump-probe laser experiments to measure the electrons’ energy dissipation in the deuterated and protonated perovskites over tiny timescales, quadrillionths of a second.

“These measurements confirmed that the giant changes in phonons and thermal conductivity that the heavy isotope induced translate into a slower relaxation time for photo-excited electrons,” Hua said. “This is an important factor in improving photovoltaic properties.”

University of California, Berkeley, co-authors Yao Cai and Mark Asta, who is also with DOE’s Lawrence Berkeley National Laboratory, performed theory-based calculations to provide insight into complexities of phonon behavior.

The discovery made in the ORNL-UT-led study may provide a bright spot for future manufacturers of hot-carrier solar cells.

“Phonons look like a pretty effective knob to turn, and we know how to turn the knob,” Manley said. “When you want to improve the materials, you can add a molecule, methylammonium or something else. The finding can inform developers’ decisions about how they grow their crystals.”

Added Ahmadi, “This knowledge can be used to guide materials design for applications beyond photovoltaics, such as optical sensors and communication devices.”

References: M. E. Manley, K. Hong, P. Yin3, S. Chi, Y. Cai, “Giant isotope effect on phonon dispersion and thermal conductivity in methylammonium lead iodide”, Science Advances, 2020, Vol. 6, no. 31, eaaz1842 DOI: 10.1126/sciadv.aaz1842

Provided by Oak Ridge National Laboratory

OS Researchers Reported Compact, Low-Cost System Which Provides Fast 3D Hyperspectral Imaging (Science And Technology)

Researchers reported a new compact low-cost hyperspectral projector system that provides both depth information and hyperspectral images. The new system could be useful for autonomous driving systems, machine vision in industrial robotics, agricultural monitoring of crops, smartphone facial recognition and monitoring material surfaces for wear and corrosion.

Image shows the 3D reconstruction of a scene that contained a small red and green ramp alongside red and green candies of different sizes. Although the green color on the ramp and the green coating of the candy look quite the same to the human eye and a RGB camera, the system was able to clearly distinguish the two materials from the reconstructed spectra as well as measure the correct heights for all the objects. ©Yibo Xu, Rice University

“Our work enables fast 3D hyperspectral imaging in an efficient and low-cost manner,” said lead author Yibo Xu, who earned her Ph.D. from Rice University. “This could one day allow the sensors used for facial recognition on smartphones to be used as hyperspectral 3D scanners, which would improve color accuracy and increase the security of face classification.”

Hyperspectral imagers detect dozens to hundreds of colors, or wavelengths, instead of the three detected by normal cameras. Combining this with 3D imaging is useful for perceiving and understanding real-world scenes and objects. Previous hyperspectral 3D imaging systems have required a complicated, high-cost hardware design and came with a long acquisition and reconstruction time.

Researchers have developed a new compact low-cost hyperspectral projector system that provides both depth information and hyperspectral images using a monochrome camera as the sensor. They used the new system to analyze a scene that contained a small red and green ramp alongside red and green candies of different sizes. Although the green color on the ramp and the green coating of the candy look quite the same to the human eye and a RGB camera, the system was able to clearly distinguish the two materials from the reconstructed spectra as well as measure the correct heights for all the objects. ©Yibu Xu, Rice University

In The Optical Society (OSA) journal Optics Express, the researchers detail their new simple design for a hyperspectral stripe projector and demonstrate that it allows the use of a monochrome camera to simultaneously capture depth information and also distinguish colors that appear visually similar.

“The combination of 3D spatial and spectrally specific material information is quite powerful,” said research team member Kevin F. Kelly, Ph.D. “It can be used for analyzing cultural heritage objects and pieces of art, monitoring plants and agriculture for signs of nutrient deficiencies or disease, aiding industrial robot systems in sorting and assembly, and expanding current autonomous driving systems to better identify the roadway, other vehicles and potential hazards.”

Optimizing for speed and simplicity

Most hyperspectral 3D imaging systems measure the spectral content of a scene using a hyperspectral camera. In the new work, the researchers redesigned the hardware and developed new software to allow the use of a monochrome camera to capture 4D information (3D spatial and spectral information) from a scene at once.

A traditional digital projector uses a color wheel with just a handful of colors and is not suitable for encoding the spectral information. The researchers used a different approach that creates hyperspectral stripe patterns that can each be programmed to have an arbitrary spectrum. This allows simultaneous 3D spatial and spectral encoding while only requiring a monochrome camera to capture the images.

The projector creates stripes by using a diffraction grating to split white light from a lamp into its different color components. Each color can then be subdivided into finer wavelengths and focused onto an array of tiny, programmable mirrors called digital micromirror devices (DMD). The unique optical layout that guides light through the system makes it simple, efficient and compact. The researchers also developed new algorithms to reconstruct the collected images into a hyperspectral, 3D visualization of the scene.

“Other systems typically require two or more gratings and multiple DMDs or light modulators,” said Xu. “This not only makes them larger and more expensive but also means a brighter light source is needed. Our system achieves its compact form factor by requiring only a single DMD and a single diffraction grating.”

Capturing 3D color detail

The researchers used their new system to analyze a scene that contained a small red and green ramp alongside red and green candies of different sizes. Although the green color on the ramp and the green coating of the candy look quite the same to the human eye and an RGB camera, the system was able to clearly distinguish the two materials from the reconstructed spectra as well as measure the correct heights for all the objects.

“By having an easy way to perform controlled hyperspectral depth imaging, researchers will be able to more easily identify the chemical compounds that make up objects of interest,” said Kelly. “This could also be useful for a variety of applications from medical diagnostics to monitoring fresh produce for damage and contamination during sorting and delivery.”

The researchers are already working on the next-generation design, which will have a more refined optical system and improved reconstruction algorithms. They are also building variations that will operate beyond the visible into infrared portions of the electromagnetic spectrum.

References: Y. Xu, A. Giljum, K. F. Kelly, A Hyperspectral projector for simultaneous 3D spatial and hyperspectral imaging via structured illumination, Opt. Express, 28, 20, 29740-29755 (2020). DOI: https://doi.org/10.1364/OE.402812.

Provided by Optical Society

VFF Algorithm Could Unleash The Power Of Quantum Computers (Quantum Mechanics)

Fast-forwarding quantum calculations skips past the time limits imposed by decoherence, which plagues today’s machines.

A new algorithm that fast forwards simulations could bring greater use ability to current and near-term quantum computers, opening the way for applications to run past strict time limits that hamper many quantum calculations.

“Quantum computers have a limited time to perform calculations before their useful quantum nature, which we call coherence, breaks down,” said Andrew Sornborger of the Computer, Computational, and Statistical Sciences division at Los Alamos National Laboratory, and senior author on a paper announcing the research. “With a new algorithm we have developed and tested, we will be able to fast forward quantum simulations to solve problems that were previously out of reach.”

Computers built of quantum components, known as qubits, can potentially solve extremely difficult problems that exceed the capabilities of even the most powerful modern supercomputers. Applications include faster analysis of large data sets, drug development, and unraveling the mysteries of superconductivity, to name a few of the possibilities that could lead to major technological and scientific breakthroughs in the near future.

Recent experiments have demonstrated the potential for quantum computers to solve problems in seconds that would take the best conventional computer millennia to complete. The challenge remains, however, to ensure a quantum computer can run meaningful simulations before quantum coherence breaks down.

“We use machine learning to create a quantum circuit that can approximate a large number of quantum simulation operations all at once,” said Sornborger. “The result is a quantum simulator that replaces a sequence of calculations with a single, rapid operation that can complete before quantum coherence breaks down.”

The Variational Fast Forwarding (VFF) algorithm that the Los Alamos researchers developed is a hybrid combining aspects of classical and quantum computing. Although well-established theorems exclude the potential of general fast forwarding with absolute fidelity for arbitrary quantum simulations, the researchers get around the problem by tolerating small calculation errors for intermediate times in order to provide useful, if slightly imperfect, predictions.

In principle, the approach allows scientists to quantum-mechanically simulate a system for as long as they like. Practically speaking, the errors that build up as simulation times increase limits potential calculations. Still, the algorithm allows simulations far beyond the time scales that quantum computers can achieve without the VFF algorithm.

One quirk of the process is that it takes twice as many qubits to fast forward a calculation than would make up the quantum computer being fast forwarded. In the newly published paper, for example, the research group confirmed their approach by implementing a VFF algorithm on a two qubit computer to fast forward the calculations that would be performed in a one qubit quantum simulation.

In future work, the Los Alamos researchers plan to explore the limits of the VFF algorithm by increasing the number of qubits they fast forward, and checking the extent to which they can fast forward systems. The research was published September 18, 2020 in the journal npj Quantum Information.

References: Cîrstoiu, C., Holmes, Z., Iosue, J. et al. Variational fast forwarding for quantum simulation beyond the coherence time. npj Quantum Inf 6, 82 (2020). https://doi.org/10.1038/s41534-020-00302-0 link: https://www.nature.com/articles/s41534-020-00302-0

Provided by DOE/Los Alamos National Laboratory

These Three Trio Won Nobel Medicine Prize For Hepatitis C Discovery (Medicine)

The Nobel Prize in Physiology or Medicine 2020 was awarded jointly to Harvey J. Alter, Michael Houghton and Charles M. Rice “for the discovery of Hepatitis C virus.”

Harvey J. Alter

The three were honoured for their “decisive contribution to the fight against blood-borne hepatitis, a major global health problem that causes cirrhosis and liver cancer in people around the world.

Michael Houghton

The World Health Organization estimates there are around 70 million Hepatitis C infections globally, causing around 400,000 deaths each year. It is characterized by poor appetite, vomiting, fatigue and jaundice.

Charles M. Rice

Thanks to the trio’s discoveries, highly sensitive blood tests for the virus are now available and these have “essentially eliminated post-transfusion hepatitis in many parts of the world, greatly improving global health”, the Nobel committee said.

Their discoveries allowed the rapid development of antiviral drugs directed at Hepatitis C. For more.. Refer videos given below:

References: MLA style: Prize announcement. NobelPrize.org. Nobel Media AB 2020. Mon. 5 Oct 2020. <https://www.nobelprize.org/prizes/medicine/2020/prize-announcement/

Fly Larvae Extract Will Replace Antibiotics In Fighting Plant Pathogens (Biology / Biotechnology)

Biotechnologists from MIPT have developed a method for extracting the active constituents from the fat of black soldier fly larvae. These compounds possess unique antimicrobial properties and can destroy bacteria that cause farm crop diseases and are resistant to antibiotics. The study was published in Microorganisms.

MIPT doctoral student Heakal Mohamed holding a Petri dish used in the experiment. ©Natalia Arefieva/MIPT Press Office

Bacteria cause an essential subset of the diseases affecting farm crops. The standard way of combating them is with antibiotics, but their yearslong overuse has led to microbes developing resistance. Besides that, antibiotics do not always target harmful bacteria only. They may also kill the microbes that are beneficial to plants.

In a search for an alternative way of protecting plants from pathogenic bacteria, researchers from MIPT turned to flies of the species Hermetia illucens, commonly known as black soldier flies. The team’s hypothesis was that the constituents of the fly larvae fat could be an antimicrobial agent.

Black soldier flies originate from South America but are also found in the wild across the globe. The larvae of H. illucens are mass-produced in insect factories to feed livestock and fish. It is mainly due to larvae having an unpretentious diet and accumulating much protein and fat under a chitinous cover. The animals are fed with either larva without prior processing or in the form of a protein extract produced in multiple ways.

In their study, MIPT biotechnologists used the larvae fat obtained by mechanical squeezing under a press. To extract its biologically active constituents, the team tested 20 different organic solvents attempting to find the one best suited for the purpose. Eventually, MIPT PhD student Heakal Mohamed and the project’s principal investigator Elena Marusich selected a solving agent composed of water, methanol, and hydrochloric acid. It enabled the extraction of more than 4% of the active fatty acids contained in the larvae fat. Methanol facilitates the dissolving of fatty acids in water, and acidification stabilizes the resulting mixture. The technique proved 50 times more effective than all previously available methods.

“We found a way to mix the solvents in the right proportions for extracting the chemical compounds of interest,” said Elena Marusich, deputy head of the Laboratory of Innovative Drugs and Agricultural Biotechnology at MIPT. “The resulting extract — called AWME — has antimicrobial properties. We have shown it to be more effective than antibiotics, so it could virtually replace antibiotics in agriculture for fighting phytopathogenic bacteria.”

The researchers tested the antibacterial effect of their extract on five strains of pathogenic bacteria affecting plants. Experiments included growing bacteria on the surface of agar-containing Petri dishes. The researchers placed disks of filtering paper soaked in AWME of a specific concentration onto the growing bacterial lawn. The experiments revealed that harmful bacteria died in the presence of the fly fat extract.

The extract is stable enough to withstand prolonged storage in a refrigerator without losing its antimicrobial properties.

“A widespread use of our extract in agriculture will require additional experiments with other common plant pathogens, as well as research into the mechanisms underlying the extract’s antibacterial activity. We want to express our immense gratitude to Gennady Ivanov, a true enthusiast and pioneer of H. illucens larva cultivation in Russia, way off from the fly’s native South America. Gennady is the CEO of Biolaboratorium LLC, a resident of the Skolkovo Innovation Center, and the NordTechsad LLC, which received the 2019 Golden Autumn Award for the production of animal feed. His work and generosity made our research possible,” said Sergey Leonov, who heads the Laboratory for the Development of Innovative Drugs and Agricultural Biotechnology at MIPT.

References: Marusich, E.; Mohamed, H.; Afanasev, Y.; Leonov, S. Fatty Acids from Hermetia illucens Larvae Fat Inhibit the Proliferation and Growth of Actual Phytopathogens. Microorganisms 2020, 8(9), 1423. Doi: https://doi.org/10.3390/microorganisms8091423 link: https://www.mdpi.com/2076-2607/8/9/1423

Provided by Moscow Institute Of Physics And Technology

Scientists Demonstrated How Skyrmions Can Be Written Into A Ferromagnetic Material Faster Than Previously Thought (Physics)

A team of scientists led by the Max Born Institute (MBI), Berlin, Germany, and the Massachusetts Institute of Technology (MIT), Cambridge, USA, has demonstrated how tiny magnetization patterns known as skyrmions can be written into a ferromagnetic material faster than previously thought possible. The researchers have clarified how the topology of the magnetic system changes in this process. As reported in the journal Nature Materials, the findings are relevant for topological phase transitions in general, and may inspire new routes how to use magnetic skyrmions in information technology.

The x-ray scattering signal from a thin magnetic film increases after it was hit by a laser pulse, monitoring the formation of skyrmions. After 300 picoseconds the topological transformation is finished and skyrmions were created. The x-ray microscopy images show the magnetic patterns in the thin film before (left) and after (right) the laser pulse hit the film. The skyrmions are identified with the black dots and have a size of 70 nanometers on average. ©MBI

Magnetic skyrmions are tiny swirls in the magnetization of thin magnetic films, where the direction of magnetization points in different directions as shown schematically in the first Figure. It turns out that the particular magnetization pattern can be characterized according to its so-called topology – a mathematical concept to describe the shape or geometry of a body, a set or – as in this case – a physical field (see infobox on topology). Importantly, the topology of skyrmions is different from the simple uniform state where the magnetization points in the same direction everywhere. To change between the two spin patterns, also the topology of the system must be changed. This contributes substantially to the stability of the skyrmions but also makes their fast creation very difficult.

A laser pulse transforms a uniform magnetization (magnetization down everywhere) to a skyrmion swirl where the magnetization in the center points up. This transformation changes the so-called topology of the system. ©MBI

In their work, which employs imaging of nanometer-sized skyrmions with x-rays and electrons, the researchers were first able to show that a single laser pulse of sufficient intensity allows to create skyrmions with a particular topology – that is, the magnetization pattern swirls in a particular fashion only.

The topology is a mathematical concept to describe and distinguish the shape or geometry of, e.g., bodies. In physics, this concept is also applied to vector fields such as the magnetization pattern in a thin film. Two bodies have the same topology if they can be transformed into each other only by so-called continuous transformations such as stretching, compressing, bending, and twisting. However, cutting and gluing are not allowed in this context. This leads to the result that a mug and doughnut share the same topology. Just imagine a mug made of modeling clay: When skillfully deforming the clay, it is possible to form the doughnut without cutting or gluing the clay at any point in the process. However, it is impossible to model a doughnut out of aspoon in this way. At some point you will have to cut the doughnut hole or glue two ends of a roll to end up with a doughnut. So spoon and doughnut can be distinguished by their different topology. In physics, it is often assumed that a certain energy barrier has to be overcome in order to change the topology of a system. ©MBI

Next, they set out to understand how such a change of topology is mediated by the laser pulse by investigating how this transition from a uniform pattern to skyrmions proceeds in time. Towards that end, they performed x-ray scattering experiments at the x-ray free-electron laser European XFEL in Hamburg, Germany, where the deflection of the x-ray beam by the skyrmions is detected. Hitting the ferromagnetic thin film in its uniform state first with an optical laser pulse followed by an x-ray laser pulse, they could map out how size and spacing of the skyrmions evolve over time. The first surprising result was that the topological change was finished after 300 picoseconds, which is significantly faster than observed for skyrmions in any other ferromagnetic system before. Comparing the experimental data with theoretical simulations, the team could infer how the topological transition comes about. The laser pulse promotes the system in a high-temperature state where the magnetization breaks up in small independently fluctuating regions, rapidly changing their magnetization direction. In this topological fluctuation state, the energy barrier for the nucleation of skyrmions is very much reduced, and they appear and disappear continuously. As the system cools down after laser excitation, some of the small skyrmion nuclei freeze out and subsequently grow to form the larger skyrmions, which have been observed in the initial imaging experiments.

Given that skyrmions can have a size in the range of ten nanometers and yet be very stable at room temperature, these findings may have interesting implications for future concepts of magnetic data processing and storage. Already today, the formation of “ordinary” bits on a magnetic hard drive is limited by the ability to switch very small yet stable bits with a magnetic field. Local heating by a laser is announced to be the next technology step in providing higher storage density, and the topological switching of skyrmions via laser pulses may add a new twist to that.

References: Büttner, F., Pfau, B., Böttcher, M. et al. Observation of fluctuation-mediated picosecond nucleation of a topological phase. Nat. Mater. (2020). https://doi.org/10.1038/s41563-020-00807-1 link: https://www.nature.com/articles/s41563-020-00807-1

Provided by Forschungverbund Berlin

Researchers Identify Process For Regenerating Neurons In The Eye And Brain (Neuroscience)

The death of neurons, whether in the brain or the eye, can result in a number of human neurodegenerative disorders, from blindness to Parkinson’s disease. Current treatments for these disorders can only slow the progression of the illness, because once a neuron dies, it cannot be replaced.

David Hyde in his lab. ©Matt Cashore/University of Notre Dame.

Now, a team of researchers from the University of Notre Dame, Johns Hopkins University, Ohio State University and the University of Florida has identified networks of genes that regulate the process responsible for determining whether neurons will regenerate in certain animals, such as zebrafish.

“This study is proof of principle, showing that it is possible to regenerate retinal neurons. We now believe the process for regenerating neurons in the brain will be similar,” said David Hyde, professor in the Department of Biological Sciences at Notre Dame and co-author on the study.

For the study, published in Science, the researchers mapped the genes of animals that have the ability to regenerate retinal neurons. For example, when the retina of a zebrafish is damaged, cells called the Müller glia go through a process known as reprogramming. During reprogramming, the Müller glia cells will change their gene expression to become like progenitor cells, or cells that are used during early development of an organism. Therefore, these now progenitor-like cells can become any cell necessary to fix the damaged retina.

Like zebrafish, people also have Müller glia cells. However, when the human retina is damaged, the Müller glia cells respond with gliosis, a process that does not allow them to reprogram.

“After determining the varying animal processes for retina damage recovery, we had to decipher if the process for reprogramming and gliosis were similar. Would the Müller glia follow the same path in regenerating and non-regenerating animals or would the paths be completely different?” said Hyde, who also serves as the Kenna Director of the Zebrafish Research Center at Notre Dame. “This was really important, because if we want to be able to use Müller glia cells to regenerate retinal neurons in people, we need to understand if it would be a matter of redirecting the current Müller glia path or if it would require an entirely different process.”

The research team found that the regeneration process only requires the organism to “turn back on” its early development processes. Additionally, researchers were able to show that during zebrafish regeneration, Müller glia also go through gliosis, meaning that organisms that are able to regenerate retinal neurons do follow a similar path to animals that cannot. While the network of genes in zebrafish was able to move Müller glia cells from gliosis into the reprogrammed state, the network of genes in a mouse model blocked the Müller glia from reprogramming.

From there, researchers were able to modify zebrafish Müller glia cells into a similar state that blocked reprogramming while also having a mouse model regenerate some retinal neurons.

Next, the researchers will aim to identify the number of gene regulatory networks responsible for neuronal regeneration and exactly which genes within the network are responsible for regulating regeneration.

References: Thanh Hoang, Jie Wang, Patrick Boyd, “Gene regulatory networks controlling vertebrate retinal regeneration”, Science 01 Oct 2020:
eabb8598 DOI: 10.1126/science.abb8598 link: https://science.sciencemag.org/content/early/2020/09/30/science.abb8598/

Provided by University Of Notre Dam