Researchers Developed A New Method For Quickly and Efficiently Synthesizing Nanographenes (Material Science)

A group of researchers at Nagoya University, Japan, have developed a new method for quickly and efficiently synthesizing nanographenes, a type of nanocarbon with great potential as a next generation material.

Nanographenes are the part structures of graphene, which is a sheet of carbon atoms around 3 nanometers thick with particular potential for use in semiconductor development, having electron mobility several hundred times better than current generation materials. Graphene was first isolated in 2004, a discovery which received the 2010 Nobel Prize in physics, making it a very new material which is currently the subject of a great deal of research.

With magnetic and electric characteristics beyond those of graphene, nanographenes are equally of interest to scientists in the nanocarbon research field. The biggest obstacle, albeit an exciting one, faced by researchers is the sheer number of potential nanographenes. The number of potentially possible nanographene structures increases with the number of benzene rings (6 atoms of carbon in a hexagonal formation) to make them. For example, even a relatively small 10 benzene ring nanographene may have up to 16,000 variants. As each nanographene has different physical characteristics, the key to applied nanographene research is to identify the relationship between the structure and characteristics of as many nanographenes as possible.

Thus, scientists’ task is to create a nanographene library, containing data on the properties of as many nanographenes as possible. However, the current method of nanographene synthesis, known as a coupling reaction, is a multi-step process which produces one single nanographene. Thus, to create a 100-nanographene library, 100 separate coupling reactions would have to be carried out. Even this would be a significant undertaking, rendering the construction of a truly comprehensive nanographene library practically impossible.

To solve this problem, the Nagoya University research group, led by Professor Kenichiro Itami, have been working on the APEX reaction, a reaction which uses polycyclic aromatic hydrocarbons as templates to synthesize nanographenes. Polycyclic aromatic hydrocarbons have three areas of their structure – known as the K region, M region and bay region – which can be elongated in an APEX reaction, producing three nanographenes. These nanographenes can then be further elongated in a second reaction, meaning that a large number of nanographenes can be synthesized from a single polycyclic aromatic hydrocarbon template molecule.

With Professor Itami’s group having already developed the K region APEX reaction, and another group of scientists having done so for the bay region, they turned their attention to the M region. They activated the M region using the 1950 Nobel Prize winning Diels-Alder reaction, and succeeded in carrying out an elongation reaction on the activated M region, thus rendering all three possible sites on the polycyclic aromatic hydrocarbons capable of synthesizing nanographenes.

The researchers were able to produce 13 nanographenes with three APEX reactions, with most of these being previously unseen structures, thus proving both the efficiency and usefulness of this new method.

This exciting new piece of research and its potential to accelerate the creation of nanographene libraries is a step towards the development of the next generation of materials, which have the potential to revolutionize semiconductors and solar energy and improve lives all around the world.

Featured image: APEX reactions are carried out on the K, M and bay regions of the polycyclic aromatic hydrocarbon, synthesizing multiple nanographenes. These reactions can then be repeated, further increasing the number of potential nanographene structures that can be synthesized. © Issey Takahashi


Reference: Matsuoka, W., Ito, H., Sarlah, D. et al. Diversity-oriented synthesis of nanographenes enabled by dearomative annulative π-extension. Nat Commun 12, 3940 (2021). https://doi.org/10.1038/s41467-021-24261-y


Provided by Nagoya University

USTC Realizes the First on-chip Valley-dependent Quantum Interference (Physics)

Research team, led by academician GUO Guangcan from University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS), collaborating with researchers from Sun Yat-sen University and Zhejiang University, realized two-photon quantum interference in the structure of valley-dependent topological insulators based on the valley Hall effect.

The study was published in Physical Review Letters on June 11st, 2021.

Topological photonics has a practical application prospect in the research of photonic chips due to its robust energy transport prosperities. The key to topological phase transition is to generate an energy gap at certain degenerate points by breaking either the time-reversal symmetry (TRS) or inversion symmetry.

By breaking the spatial inversion symmetry of the system, the valley-dependent helical edge states travel in certain directions, which is known as Valley-Hall effect. Hexagonal lattice photonic crystals (PCs) with inequivalent sublattices can realize the valley-dependent topological insulators. More compact and sharp bending optical circuit can be realized, which contributes to device integration and robust energy.

In recent years, robust quantum state transfer in topology has been a hot research. Yet as the core of photonic quantum information, quantum interference remains to be verified in topologically protected PCs chip.

Researchers designed and fabricated harpoon-shaped beam splitters (HSBSs) in silicon photonic crystals. The orientation of the electromagnetic phase vortex inside PCs with hexagonal lattice structure depends on lattice structure with different topological Chern numbers and its band position, thereby to form two topological edges of different structures.

Based on a 120-deg-bending interfaces, they realized on-chip Hong-Ou-Mandel (HOM) interference in one HSBS with a high visibility of 95.6%. Furthermore, the generation of path-entangled state in valley-dependent quantum circuits is demonstrated by cascading two HSBSs.

The study provides a novel method for topological photonics, especially topological insulators, to be applied in more complex quantum information processing. Reviewers agreed that the research is interesting and important, and highly praised that “This is an interesting and important work. I find the results interesting, in particular, the implementation of the Hong-Ou-Mande effect in this device, which may have implications in high fidelity on-chip quantum information processing.”

Featured image: Harpoon-shaped beam splitters in photonic quantum chip © CHEN Yang et.al


Reference: Yang Chen, Xin-Tao He, Yu-Jie Cheng, Hao-Yang Qiu, Lan-Tian Feng, Ming Zhang, Dao-Xin Dai, Guang-Can Guo, Jian-Wen Dong, and Xi-Feng Ren, “Topologically Protected Valley-Dependent Quantum Photonic Circuits”, Phys. Rev. Lett. 126, 230503 – Published 11 June 2021. DOI: https://doi.org/10.1103/PhysRevLett.126.230503


Provided by USTC

A Way To Surmount Supercooling (Material Science)

Researchers study the conditions under which aqueous solutions in a supercooled state rapidly freeze, and find certain nanoparticles stimulate crystallization to clathrate hydrates, which may lead to new energy storage methods and higher purity materials

Scientists at Osaka UniversityPanasonic Corporation, and Waseda University used scanning electron microscopy (SEM) and X-ray absorption spectroscopy to determine which additives induce crystallization in supercooled aqueous solutions. This work may lead to the development of new energy storage materials based on latent heat.

If you put a bottle of water into the freezer, you will expect to pull out a solid cylinder of ice after a few hours. However, if the water has very few impurities and left undisturbed, it may not be frozen, and instead remain as a supercooled liquid. Be careful, because this state is very unstable, and the water will crystallize quickly if shaken or impurities are added – as many YouTube videos will attest. Supercooling is a phenomenon in which an aqueous solution maintains its liquid state without solidifying, even though its temperature is below the freezing point. Although many studies have been done on additives that trigger the freezing of supercooling liquids, the details of the mechanism are unknown. One potential application might be latent heat storage materials, which rely on freezing and melting to capture and later release heat, like a reusable freezer pack.

Now, a team of researchers led by Osaka University has shown that silver nanoparticles are very effective at inducing crystallization in clathrate hydrates. Clathrate hydrates physically look like ice and are composed of hydrogen-bonded water cages with guest molecules inside. “Using SEM with the freeze-fracture replica method, we captured the moment when a nascent cluster enveloped a silver nanoparticle in the aqueous solution of latent heat storage materials,” corresponding author Professor Takeshi Sugahara explains.

This occurs because the nanoparticles serve as a “seed,” or nucleation site, for tiny clusters to form. Once this gets started, the remaining solute and water molecules can quickly form additional clusters and then cluster densification leads to the crystallization. The researchers found that while silver nanoparticles tended to accelerate the formation of these clusters, other metal nanoparticles, such as palladium, gold, and iridium do not promote crystallization.

“The supercooling suppression effect obtained in the present study will contribute to achieve the practical use of clathrate hydrates as latent heat storage materials,” Professor Sugahara says. Material design guidelines for enhanced supercooling control, as described in this study, may lead to the application of latent heat storage materials in solar energy and heat recovery technologies with improved efficiency.

20210622_2_fig_1.png
(a) HAADF-STEM images of replica films prepared from samples #1, #2, #11, and #13 of tetra-n-butylammonium 3-methylpentanoate (TBA-3MP) aqueous solutions. In samples #11 and #13, silver nanoparticles 5-10 nm across were observed. In sample #13, which included both silver nanoparticles and F- anions, 10-30 nm clusters existed even at 281 K. With further decreases in temperature, the number density of the clusters increased, and then TBA-3MP semiclathrate hydrate crystallized with a small degree of supercooling. (b) SE-STEM image of a different area of the same film as “13-a” in panel a). Clusters of size 10-30 nm envelop a silver nanoparticle (black dots indicated by red arrows) (credit: T. Sugahara/Osaka University and H. Machida/Panasonic Corporation)

The article, “The moment of initial crystallization captured on functionalized nanoparticles” was published in Communications Materials at DOI: https://doi.org/10.1038/s43246-021-00171-w


Provided by Osaka University

Paleonursery Offers Rare, Detailed Glimpse at Life 518 Million Years Ago (Paleontology

Deposit contains exceptionally preserved fossils of soft-bodied, juvenile organisms from the Cambrian

All life on Earth 500 million years ago lived in the oceans, but scientists know little about how these animals and algae developed. A newly discovered fossil deposit near Kunming, China, may hold the keys to understanding how these organisms laid the foundations for life on land and at sea today, according to an international team of researchers.

The fossil deposit, called the Haiyan Lagerstätte, contains an exceptionally preserved trove of early vertebrates and other rare, soft-bodied organisms, more than 50% of which are in the larval and juvenile stages of development. Dating to the Cambrian geologic period approximately 518 million years ago and providing researchers with 2,846 specimens so far, the deposit is the oldest and most diverse found to date.

“It’s just amazing to see all these juveniles in the fossil record,” said Julien Kimmig, collections manager at the Earth and Mineral Sciences Museum & Art Gallery, Penn State. “Juvenile fossils are something we hardly see, especially from soft-bodied invertebrates.”

Xianfeng Yang, a paleobiologist at Yunnan University, China, led a team of Chinese researchers that collected the fossils at the research site. He measured and photographed the specimens and analyzed them with Kimmig. The researchers report the results of their study today (June 28) in the journal Nature Ecology and Evolution.

Maotianshania cylindrica, a priapulid worm. © Xianfeng Yang, Yunnan Key Laboratory for Palaeobiology, Yunnan University

The researchers identified 118 species, including 17 new species, in the lagerstätte — a sedimentary deposit of extraordinary fossils with exceptional preservation that sometimes includes preserved soft tissues.

The species include the ancestors of modern-day insects and crustaceans, worms, trilobites, algae, sponges and early vertebrates related to jawless fish. The researchers also found eggs and an abundance of rare juvenile fossils with appendages still intact and their internal soft tissues visible.

The specimens are so well-preserved that they are revealing body parts never before seen, said Sara Kimmig, assistant research professor in the Earth and Environmental Systems Institute and facility director of the Laboratory for Isotopes and Metals in the Environment at Penn State.

“The site preserved details like 3D eyes, features that have never really been seen before, especially in such early deposits,” she said.

Scientists can use CT scanning on these 3D features to reconstruct the animals and extract even more information from the fossils, according to the researchers.

The lagerstätte contains several event beds, or layers in the sediment where the fossils are found. Each layer represents a single burial event. All species identified in the study are present in the lowest layer, with subsequent layers containing diverse species, but not to the extent of the lowest one.

The researchers think these intervals could represent boom and bust periods in the marine community. Many species might have come to the area — at the time located in deeper waters toward the center of the Kunming Gulf — seeking protection from strong ocean currents. However, a change in oxygen levels or storm events that caused sediment to flow down a slope and bury everything in its path may have caused extinctions.

The abundance of juvenile fossils, on the other hand, suggests that the Haiyan Lagerstätte could have been a paleonursery. The species found in the lagerstätte may have chosen to reproduce there due to the protection it provided from predators.

Fossil of a juvenile arthropod, Leanchoilia illecebrosa, showing fine anatomical details of the appendages and preserving the gut tract. © Xianfeng Yang, Yunnan Key Laboratory for Palaeobiology, Yunnan University

“Could these worms and jellyfish and bugs have developed something as sophisticated as a paleonursery to raise their young? Whatever the case may be, it’s fascinating to be able to parallel this behavior to that of modern animals,” Sara Kimmig said.

Scientists will be able to use this collection to study how these ancient animals developed from the larval to the adult stage.

“We’ll see how different body parts grew over time, which is something we currently do not know for most of these groups,” Julien Kimmig said. “And these fossils will give us more information on their relationships to modern animals. We will see if how these animals develop today is similar to how they developed 500 million years ago, or if something has changed throughout time.”

The developmental information will also provide insights into the relationships between animal groups, as similar developmental patterns may indicate a link between species, he added.

“The Haiyan Lagerstätte will be a wealth of knowledge moving forward for many researchers, not only in terms of paleontology but also in paleo-environmental reconstructions,” said Sara Kimmig. She and her colleagues would like to conduct geochemical analyses on the specimens and the sediments. These analyses could help them potentially recreate the environment and climate during the time that this lagerstätte was deposited.

The fossils will also allow the researchers to study how animals behaved 500 million years ago when the world was a bit warmer than today and use it as a proxy for where the world is headed in terms of animal behavior in a warmer environment.

“In this deposit, we found the ancestors to most modern animals, both marine and terrestrial,” Julien Kimmig said. “If the Haiyan Lagerstätte is actually a paleonursery, it means that this type of animal behavior has not changed much in 518 million years.”

Additional contributors to this study include Dayou Zhai and Yu Liu, Yunnan University; and Shanchi Peng, Chinese Academy of Sciences.

The National Natural Science Foundation of China, the State Key Laboratory of Palaeobiology and Stratigraphy at the Nanjing Institute of Geology and Palaeontology, and the Key Research Program of the Institute of Geology & Geophysics, Chinese Academy of Sciences, funded this research.

Featured image: Chuandianella ovata, an extinct shrimp-like crustacean. © Xianfeng Yang, Yunnan Key Laboratory for Palaeobiology, Yunnan University


Provided by Penn State

First-ever Transient Pacemaker Harmlessly Dissolves in Body (Medicine)

Wireless, fully implantable device gives temporary pacing without requiring removal

  • Bioresorption bypasses need to extract non-biodegradable leads, eliminating additional risk to patient
  • Pacemaker is remotely powered by near-field communication protocols
  • Researchers tested the device across a series of large and small animal models
  • Heart surgeon: ‘This device will greatly improve a patient’s post-operative course’

Researchers at Northwestern and George Washington universities (GW) have developed the first-ever transient pacemaker — a wireless, battery-free, fully implantable pacing device that disappears after it’s no longer needed.

The thin, flexible, lightweight device could be used in patients who need temporary pacing after cardiac surgery or while waiting for a permanent pacemaker. All components of the pacemaker are biocompatible and naturally absorb into the body’s biofluids over the course of five to seven weeks, without needing surgical extraction.

The device wirelessly harvests energy from an external, remote antenna using near-field communication protocols — the same technology used in smartphones for electronic payments and in RFID tags. This eliminates the need for bulky batteries and rigid hardware, including wires (or leads). Not only can leads introduce infections, they also can become enveloped in scar tissue, causing further damage when removed.

The study was published today (June 28) in the journal Nature Biotechnology. The paper demonstrates the device’s efficacy across a series of large and small animal models.

“Hardware placed in or near the heart creates risks for infection and other complications,” said Northwestern’s John A. Rogers, who led the device’s development. “Our wireless, transient pacemakers overcome key disadvantages of traditional temporary devices by eliminating the need for percutaneous leads for surgical extraction procedures — thereby offering the potential for reduced costs and improved outcomes in patient care. This unusual type of device could represent the future of temporary pacing technology.”

“Sometimes patients only need pacemakers temporarily, perhaps after an open heart surgery, heart attack or drug overdose,” said Dr. Rishi Arora, a cardiologist at Northwestern Medicine who co-led the study. “After the patient’s heart is stabilized, we can remove the pacemaker. The current standard of care involves inserting a wire, which stays in place for three to seven days. These have potential to become infected or dislodged.” 

“The transient electronics platform opens an entirely new chapter in medicine and biomedical research,” said GW’s Igor Efimov, who co-led the study with Rogers and Arora. “The bioresorbable materials at the foundation of this technology make it possible to create whole host of diagnostic and therapeutic transient devices for monitoring progression of diseases and therapies, delivering electrical, pharmacological, cell therapies, gene reprogramming and more.” 

Rogers is the Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery in the McCormick School of Engineering and Feinberg School of Medicine and the director of the Querrey Simpson Institute for Bioelectronics. Arora is a professor of medicine at Feinberg and co-director of the Center for Arrhythmia Research. Efimov is the Alisann and Terry Collins Professor of Biomedical Engineering at GW.

Ditching restrictive, risky leads

Currently, to set up a temporary pacing after open heart surgery, surgeons must sew on temporary pacemaker electrodes on the heart muscle during surgery. These have leads that exit the front of a patient’s chest, connecting to an external pacing box that delivers a current to control the heart’s rhythm.

When the temporary pacemaker is no longer needed, physicians remove the pacemaker electrodes. Although uncommon, potential complications of implanted temporary pacemakers include infection, dislodgement, torn or damaged tissues, bleeding and blood clots.

Illustration of the device mounted on a heart, with annotation © Northwestern University/George Washington University

With Northwestern and GW’s transient pacemaker, surgeons and patients can sidestep this potentially risky procedure. The fully implantable device is light and thin — 250 microns thick and weighing less than half a gram. Soft and flexible, it encapsulates electrodes that softly laminate onto the heart’s surface to deliver an electrical pulse. 

“Instead of using wires that can get infected and dislodged, we can implant this leadless biocompatible pacemaker,” Arora said. “The circuitry is implanted directly on the surface of the heart, and we can activate it remotely. Over a period of weeks, this new type of pacemaker ‘dissolves’ or degrades on its own, thereby avoiding the need for physical removal of the pacemaker electrodes. This is potentially a major victory for post-operative patients.

“With further modifications, it eventually may be possible to implant such bioresorbable pacemakers through a vein in the leg or arm,” he added. “In this instance, it also may be possible to provide temporary pacing to patients who have suffered a heart attack or to patients undergoing catheter-based procedures, such as trans-catheter aortic valve replacement.”

Prioritizing patient comfort

Northwestern Medicine cardiac surgeon Dr. Duc Thinh Pham, who was not involved with the research, imagines a transient pacemaker undoubtedly would make his patients more comfortable. With current pacemakers, patients often feel discomfort for days after the leads are inserted. Then, they must limit their movements and activities in order to prevent the leads from dislodging.

“This transient pacemaker is brilliant,” said Pham, who has performed more than 2,000 cardiac surgeries throughout his career. “In addition to addressing the primary issue of occasional post-cardiac surgery patients needing temporary pacing due to blockages or arrhythmias, the device addresses the secondary issue of patient comfort, ability to move freely and rehabilitate. If successful, this device will greatly improve a patient’s post-operative course.”

Disappearing act

This is the second example of bioresorbable electronic medicine from the Rogers lab, which has been studying transient electronics for over a decade. In 2018, Rogers and colleagues demonstrated the world’s first bioresorbable electronic device — a biodegradable implant that speeds nerve regeneration. The team’s bioresorbable devices are completely harmless — similar to absorbable stitches. After fully degrading, the devices completely disappear through the body’s natural biological processes.

Illustration of the device mounted on the heart, without annotation © Northwestern University/George Washington University

“There is clearly a need for better temporary cardiac pacemakers,” said Dr. Bradley Knight, the Chester C. and Deborah M. Cooley Distinguished Professor of Cardiology at Feinberg and coauthor of the study. “When I first learned about the bioresorbable nerve stimulator, I contacted Professor Rogers to explore the possibility of using this technology to pace the heart. He had already started working with Dr. Efimov to develop a small version of a bioresorbable pacemaker as a proof of concept. We then worked with both teams to develop a larger version of a bioresorbable, leadless, cardiac pacemaker that could be effective on a human scale. It’s a great example of what we can create at Northwestern by bridging the expertise in engineering and medicine.”

Depending on the patient, a temporary pacemaker might be needed anywhere from a couple days to several weeks. By varying the composition and thickness of the materials in the device, Rogers’ team can control the precise number of days it remains functional before dissolving.

“We build these devices out of different types of safe, bioresorbable materials and in optimized architectures to ensure stable operation over a time period somewhat longer than is clinically necessary,” Rogers said. “We can tailor the devices to address a broad spectrum of relevant lifetimes. Transient technologies, in general, could someday provide therapy or treatment for a wide variety of medical conditions — serving, in a sense, as an engineering form of medicine.”

The paper, “Fully bioresorbable, leadless, battery-free cardiac pacemaker,” was supported by the Leducq Foundation (RHYTHM award), National Institutes of Health (award numbers R01-HL141470, R01-HL140061 and R01-HL125881), the American Heart Association (award number 19PRE34380781, AF SFRN), the National Science Foundation (award number 1842165) and the Ford Foundation. The paper’s co-first authors are Yeon Sik Choi, Rose Yin, Jahyun Koo and Anna Pfenniger.

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Featured image: Device on Day 0 © Northwestern University/George Washington University


Reference: Choi, Y.S., Yin, R.T., Pfenniger, A. et al. Fully implantable and bioresorbable cardiac pacemakers without leads or batteries. Nat Biotechnol (2021). https://doi.org/10.1038/s41587-021-00948-x


Provided by Northwestern University

Engineered Yeast Probiotic Developed To Treat Inflammatory Bowel Disease (Medicine)

Designed from the yeast used to make beer, ‘Y-bots’ can target inflammation, tissue scarring and disturbances in the balance of microbes living in the gut

The world of microbes living in the human gut can have far-reaching effects on human health. Multiple diseases, including inflammatory bowel disease (IBD), are tied to the balance of these microbes, suggesting that restoring the right balance could help treat disease. Many probiotics — living yeasts or bacteria — that are currently on the market have been optimized through evolution in the context of a healthy gut. However, in order to treat complex diseases such as IBD, a probiotic would need to serve many functions, including an ability to turn off inflammation, reverse damage and restore the gut microbiome. Given all of these needs, researchers from Brigham and Women’s Hospital have developed a “designer” probiotic — a thoughtfully engineered yeast that can induce multiple effects for treating IBD. Preclinical results from their work are published in Nature Medicine.

“We’ve taken yeast — the very yeast that’s used to make beer — and we’ve given it the ability to sense inflammation and secrete an anti-inflammatory molecule,” said corresponding author Francisco Quintana, PhD, an investigator in the Ann Romney Center for Neurologic Diseases at the Brigham. “We call this new platform ‘Y-bots’ (yeast robots) and see the potential here for developing therapeutics that can treat diseases of the gut tissue and more.”

Previous research from the Quintana lab has helped illuminate the connection between the gut and diseases that affect the brain, suggesting potential applications for engineering probiotics beyond IBD.

Quintana and colleagues developed their probiotic using Saccharomyces cerevisiae, a species of yeast used in winemaking, baking and brewing. Using the gene editing technology CRISPR/Cas9, the researchers introduced genetic elements that could sense inflammation and respond to it by secreting an enzyme that can degrade a key molecule involved in inflammation. The engineered yeast can secrete different levels of enzyme, depending upon how much of the inflammatory signal is present at a location in the gut. This means that the probiotic can have a highly localized response to inflammation. In mice, the engineered yeast successfully suppressed intestinal inflammation, reduced fibrosis and restored a balanced gut microbiome.

To bring this new therapeutic platform to bear on IBD and other diseases in humans, Quintana and colleagues will need to conduct safety studies. They also plan to further refine and test the engineered yeast to see if they can speed up tissue repair. Beyond IBD, the team plans to investigate the use of engineered probiotics for treating a common side effect of cancer immunotherapy, colitis.

“We want to use the tools of synthetic biology to engineer what can be found in nature,” said Quintana. “By engineering probiotics, our goal is to create more personalized, localized and highly controlled medications for treating diseases of the gut and beyond.”

This work was supported by the National Institutes of Health (grants NS102807, ES02530, ES029136, AI126880), the National MS Society (RG4111A1), International Progressive MS Alliance (PA-1604-08459) and Natural Sciences Engineering Research Council of Canada (NSERC 492911). Quintana and four co-authors filed a patent for the use of engineered yeast to treat inflammation.


Reference: Scott, B et al. “Self-Tunable Engineered Yeast Probiotics for the Treatment of Inflammatory Bowel Disease” Nature Medicine DOI: 10.1038/s41591-021-01390-x


Provided by Brigham and Women’s Hospital

New, Third Type of Supernova Observed (Cosmology)

An international team of astronomers has observed the first example of a new type of supernova. The discovery, confirming a prediction made four decades ago, could lead to new insights into the life and death of stars. The work is published June 28 in Nature Astronomy.

“One of the main questions in astronomy is to compare how stars evolve and how they die,” said Stefano Valenti, professor of physics and astronomy at the University of California, Davis, and a member of the team that discovered and described supernova 2018zd. “There are many links still missing, so this is very exciting.”

There are two known types of supernova. A core-collapse supernova occurs when a massive star, more than 10 times the mass of our sun, runs out of fuel and its core collapses into a black hole or neutron star. A thermonuclear supernova occurs when a white dwarf star — the remains of a star up to eight times the mass of the sun — explodes.

In 1980, Ken’ichi Nomoto of the University of Tokyo predicted a third type called an electron capture supernova.

What keeps most stars from collapsing under their own gravity is the energy produced in their central core. In an electron capture supernova, as the core runs out of fuel, gravity forces electrons in the core into their atomic nuclei, causing the star to collapse in on itself.

Evidence from late spectrum

Supernova 2018zd was detected in March 2018, about three hours after the explosion. Archival images from the Hubble Space Telescope and Spitzer Space Telescope showed a faint object that was likely the star before explosion. The supernova is relatively close to Earth, at a distance of about 31 million light years in galaxy NGC2146.

The team, led by Daichi Hiramatsu, graduate student at UC Santa Barbara and Las Cumbres Observatory, collected data on the supernova over the next two years. Astronomers from UC Davis, including Valenti and graduate students Azalee Bostroem and Yize Dong, contributed a spectral analysis of the supernova two years after the explosion, one of the lines of evidence demonstrating that 2018zd was an electron capture supernova.

Artist impressions of a super-asymptotic giant branch star and its core made up of oxygen, neon and magnesium. This is the end state of stars around 8-10 solar masses, whose core is pressure supported by electrons. When the core becomes dense enough, neon and magnesium start to eat up electrons, reducing the core pressure and inducing a core-collapse supernova explosion. © S. Wilkinson; Las Cumbres Observatory

“We had a really exquisite, really complete dataset following its rise and fade,” Bostroem said. That included very late data collected with the 10-meter telescope at the W.M. Keck Observatory in Hawaii, Dong added.

Theory predicts that electron capture supernovae should show an unusual stellar chemical spectrum years later.

“The Keck spectra we observed clearly confirm that SN 2018zd is our best candidate to be an electron capture supernova,” Valenti said.

The late spectrum data were not the only piece of the puzzle. The team looked through all published data on supernovae, and found that while some had a few of the indicators predicted for electron capture supernovae, only SN 2018zd had all six: an apparent progenitor star of the Super-Asymptotic Giant Branch (SAGB) type; strong pre-supernova mass loss; an unusual stellar chemical spectrum; a weak explosion; little radioactivity; and a neutron-rich core.

“We started by asking ‘what’s this weirdo?’ Then we examined every aspect of SN 2018zd and realized that all of them can be explained in the electron-capture scenario,” Hiramatsu said.

Explaining the Crab Nebula

The new discoveries also illuminate some mysteries of the most famous supernova of the past. In A.D. 1054 a supernova occurred in the Milky Way. According to Chinese records it was so bright that it could be seen in the daytime for 23 days, and at night for nearly two years. The resulting remnant — the Crab Nebula — has been studied in great detail. It was previously the best candidate for an electron capture supernova, but this was uncertain partly because the explosion happened nearly a thousand years ago. The new result increases the confidence that the event that formed the Crab Nebula was an electron capture supernova.

“I am very pleased that the electron capture supernova was finally discovered, which my colleagues and I predicted to exist and have a connection to the Crab Nebula 40 years ago. This is a wonderful case of the combination of observations and theory,” said Nomoto, who is also an author on the current paper.

The research is part of the Global Supernova Project, led by Professor Andrew Howell at UCSB and Las Cumbres Observatory. Additional co-authors are: Curtis McCully and Jamison Burke, Las Cumbres Observatory and UCSB; Jared Goldberg and Chengyuan Xu, UCSB; Schuyler Van Dyk and Gagandeep Anand, California Institute of Technology; Keiichi Maeda, Kyoto University; Takashi Moriya, National Astronomical Observatory of Japan; Nozomu Tominaga, Konan University, Kobe, Japan; Griffin Hosseinzadeh, Center for Astrophysics, Harvard & Smithsonian; Iair Arcavi, Tel Aviv University, Israel; Peter Brown, Texas A&M University; Jennifer Andrews, Christopher Bilinski, G. Grant Williams, Paul Smith, Nathan Smith and David Sand, Steward Observatory, University of Arizona; Alexei Filippenko, UC Berkeley; Melina Bersten and Gastón Folatelli, Instituto de Astrofísica de La Plata and Universidad Nacional de La Plata, Argentina; Patrick Kelly, University of Minnesota; Toshi- hide Noguchi, Noguchi Astronomical Observatory and Koichi Itagaki, Itagaki Astronomical Observatory, Japan. The work was partly supported by grants from the National Science Foundation and NASA.

Featured image: Supernova 2018zd, marked with a white circle on the outskirts of galaxy NGC2146, is the first example of a new, third type of supernova predicted 40 years ago. Composite image with data from the Hubble Space Telescope, Las Cumbres Observatory and other sources. © Joseph Depasquale, STScI


Reference: Hiramatsu, D., Howell, D.A., Van Dyk, S.D. et al. The electron-capture origin of supernova 2018zd. Nat Astron (2021). https://doi.org/10.1038/s41550-021-01384-2


Provided by University of California Davis

An Atlas of the Bumblebee Brain (Neuroscience)

A three-dimensional atlas of the bumblebee brain is now available. It will allow to even better research how nerve cells are interconnected and how they process information.

The buff-tailed bumblebee Bombus terrestris is one of the most common bumblebee species in Europe. It is not only active in nature as a pollinator – humans also use it in greenhouses and foil tunnels to get good harvests of tomatoes or strawberries.

The buff-tailed bumblebee is also used in science: “Basic research is increasingly using it as a model organism to analyse learning and memory, the visual system, flight control and navigation abilities,” says Dr. Keram Pfeiffer, Professor of neurobiology at the Biocenter of Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany.

Pfeiffer investigates the neuronal basis of spatial orientation in insects. Together with his doctoral student Lisa Rother and an international team, he is now presenting the first atlas of a buff-tailed bumblebee brain based on computed tomographic (CT) data in the journal Cell and Tissue Research.

Nadine Kraft and Emmy Noether group leader Dr. Basil el Jundi (both JMU) as well as Dr. Richard J. Gill and Dr. Dylan Smith from Imperial College in London were also involved in the work.

Data averaged from ten bumblebee brains

To create the atlas, the research team took micro-CT images of ten heads of buff-tailed bumblebees. From these, they first extracted the image data showing the brains. In each of these data stacks, 30 brain regions of the bumblebee were manually reconstructed in three dimensions. On JMU’s high-performance computing cluster Julia, a standard brain was then calculated from the ten data sets, based on their mean values.

The result can be viewed in the publicly accessible insectbraindb database: https://hdl.handle.net/20.500.12158/SIN-0000010.3

“The atlas will be used for research in which neuronal circuits are analysed. The functional principles of such circuits are often generally valid, so they also occur in humans, for example,” explains Pfeiffer.

Micro-CT offers advantages

Similar brain atlases already exist for a number of other insect species. However, none of them are based on micro-CT images, but a combination of immunostaining of synaptic regions and confocal microscopy.

Compared to micro-CT, this technique has two disadvantages: First, the resolution in the z-direction (front to back) is much lower than the lateral resolution. Secondly, a brain must be dissected for immunostaining. In the process, the outer brain regions in particular can be damaged and might shift in position.

Micro-CT allows the brain to be left in the animal. Thus, all parts remain intact and in their natural position. In addition, the resolution of micro-CT images is the same in all directions. This simplifies the later insertion of neuronal data and provides more detail when viewed from the side.

Goal: combine both methods

“We are currently also working on an atlas of the bumblebee brain using the conventional method of confocal microscopy,” says Pfeiffer. This method has the advantage – at least at the moment – that the contrast and resolution of the data are better.

In order to combine the advantages of both methods, the conventionally created atlas will be registered into the micro-CT atlas at the end. The result will be an atlas that offers both high resolution and high contrast as well as a realistic spatial position of the individual brain areas in relation to each other.

At the moment, only standard microscopic methods are available for staining individual nerve cells. The data collected with these methods can only be inserted into the standard brain with restrictions. “We therefore want to develop staining protocols that allow neuronal structures to be recorded directly with micro-CT,” announces the JMU neurobiologist.

Funding

The work described was financially supported by the German Research Foundation (DFG), Imperial College London and the Natural Environment Research Council NERC (UK). The publication as Open Access was made possible by the DEAL project of the German Rectors’ Conference.

Featured image: A buff-tailed bumblebee and a 3D model of the bumblebee brain, based on micro-CT. The blue regions symbolise the primary olfactory centres. The yellow/orange regions process visual information from the compound eyes, the turquoise coloured visual information from the ocelli. Shown in red/orange are the mushroom bodies important for learning. The insects’ inner compass, the central complex, is green. (Image: Erdhummel von Ivar Leidus / Wikimedia Commons CC BY-SA 4.0 / 3D-Modell von Lisa Rother / Universität Würzburg)


Publication

A micro-CT-based standard brain atlas of the bumblebee. Lisa Rother, Nadine Kraft, Dylan B. Smith, Basil el Jundi, Richard J. Gill, Keram Pfeiffer. Cell and Tissue Research, 28 June 2021, Open Access: https://doi.org/10.1007/s00441-021-03482-z


Provided by University of Wruzburg

Unusual Prey: Spiders Eating Snakes (Biology)

There are spiders that eat snakes. Observations of snake-eating spiders have been reported around the world. Two researchers from Basel and the US consolidated and analyzed over 300 reports of this unusual predation strategy.

Spiders are primarily insectivores, but they occasionally expand their menu by catching and eating small snakes. PD Dr. Martin Nyffeler, arachnologist at the University of Basel, and American herpetologist Professor Whitfield Gibbons of the University of Georgia, USA, got to the bottom of this phenomenon in a meta-analysis. Their findings from a study of 319 occurrences of this unusual feeding behavior recently appeared in the American Journal of Arachnology.

It turns out that spiders eat snakes on every continent except Antarctica. Eighty percent of the incidents studied were observed in the US and Australia. In Europe, on the other hand, this spider feeding behavior has been observed extremely rarely (less than 1 percent of all reported incidents) and is limited to the consumption of tiny, non-venomous snakes of the blind snake family (Typhlopidae) by small web-building spiders.

Black widows are particularly successful

Incidents of snake predation by spiders have never been reported from Switzerland. A possible explanation is that Switzerland’s native colubrids and vipers are too big and heavy even when freshly hatched for Swiss spiders to subdue them.

Juvenile Eastern garter snake, Thamnophis sirtalis, trapped in a brown widow web (Latrodectus geometricus) observed in Douglas, Georgia, USA. (Photo: Julia Safer)

The data analysis also showed that spiders from 11 different families are able to catch and eat snakes. «That so many different groups of spiders sometimes eat snakes is a completely novel finding,» Nyffeler emphasizes.

Black widows of the family Theridiidae were the successful snake hunters in about half of all observed incidents. Their potent venom contains a toxin that specifically targets vertebrate nervous systems. These spiders build webs composed of extremely tough silk, allowing them to capture larger prey animals like lizards, frogs, mice, birds and snakes.

Big catch 

Another new finding from the meta-analysis: spiders can subdue snakes from seven different families. They can outfight snakes 10 to 30 times their size.

The largest snakes caught by spiders are up to one meter in length, the smallest only about six centimeters. According to the statistical analysis done by the two researchers, the average length of captured snakes was 26 centimeters. Most of the snakes caught were very young, freshly hatched animals. That some spiders are able to subdue oversized prey is attributable to their highly potent neurotoxins and strong, tough webs.

Possible insights into the effect of spider venom

Many spider species that occasionally kill and eat snakes have venom that can also be lethal to humans. That means the venom of various spider species has a similar effect on the nervous systems of snakes and humans. For this reason, observations of vertebrate-eating spiders can also be important for neurobiology, as they allow conclusions to be drawn about the mechanisms by which spider neurotoxins affect vertebrate nervous systems.

Brown widow spider feeding on a Brahminy blindsnake in a garden house in Zaachila, Oaxaca, Mexico. (Photo: Matias Martinez)

«While the effect of black widow venom on snake nervous systems is already well researched, this kind of knowledge is largely lacking for other groups of spiders. A great deal more research is therefore needed to find out what components of venoms that specifically target vertebrate nervous systems are responsible for allowing spiders to paralyze and kill much larger snakes with a venomous bite,» says Martin Nyffeler.

The captured snakes are anything but helpless themselves: about 30 percent are venomous. In the US and South America, spiders sometimes kill highly venomous rattlesnakes and coral snakes. In Australia, brown snakes – which belong to the same family as cobras – often fall prey to redback spiders (Australian black widows). Martin Nyffeler says, «These brown snakes are among the most venomous snakes in the world and it’s really fascinating to see that they lose fights with spiders.»

Storage of energy reserves

When a spider catches a snake, it will often spend hours or days feasting on such a large prey. Spiders have an irregular feeding pattern. When a lot of food is available, they eat in excess, only to go hungry for long periods again afterward. They store excess food as energy reserves in their body and use it to tide them over longer periods of starvation.

Still, a spider often eats only a small part of a dead snake. Scavengers (ants, wasps, flies, molds) consume what remains.

Original publication

Martin Nyffeler and J. Whitfield Gibbons (2021).
Spiders (Arachnida: Araneae) feeding on snakes (Reptilia: Squamata).
Journal of Arachnology 49, (1-27), doi: 10.1636/JoA-S-20-050

Featured image: Scarlet snake entrapped and killed in a black widow web in the corner of the front porch of a house in Gulf Breeze, Florida, USA. (Photo: Trisha Haas)


Provided by University of Basel