What Are The Effects Of Thermal Conductive Materials on The Freeze-thaw Resistance Of Concrete? (Material Science / Engineering)

Byeong-Hun Woo and colleagues studied the effects of thermal conductive materials on the freeze-thaw resistance of concrete. They performed two experiments: freeze-thaw and rapid cyclic thermal attack in order to evaluate the thermal durability of concrete with thermal conductive materials. They showed that the graphite had a negative effect on the freeze-thaw and rapid cyclic thermal attack. While, the use of silicon carbide (50%) and steel fiber significantly improved thermal durability of concrete. Their study recently appeared in the Journal Materials.

Cold regions have two kinds of threatening factors for vehicle users. One is black ice and the other is pot-holes caused by the freeze–thaw cycle. Black ice makes the surface of the road slippery and causes traffic accidents. To prevent the generation of black ice, people use chemical salts such as CaCl2. However, chemical salts cause deterioration of concrete and reduce the service life of the concrete. While, the water present in the concrete mix freezes and this freezing causes deterioration such as such as cracking, scaling etc. This is called freezing and thawing. This deterioration occurs due to lack of air on the surface layer of concrete mass. Study showed that the combination of both black ice and chemical salts accelerate deterioration of concrete.

However, to overcome this problem, many studies tried to enhance the thermal conductivity of the materials. Like, some suggested the use of carbon nanofibers and carbon nanotubes, while others suggested the use of graphene as they have good thermal conductivities. But, they have certain limitations such as properties and cost.

Thus, to overcome this limitation Byeong-Hun Woo and colleagues now applied a substitution method. The reason behind using substitution method is that, the aggregates occupies more than 65% of the volume fraction. They used silicon carbide (SiC) as the substituting material and substituted it for 50% and 100% of fine aggregate in order to improve the thermal conductivity.

“Silicon carbide was chosen as the substituting material of the fine aggregate; as silicon carbide has good thermal conductivity and hardness, it is considered sufficient as a fine aggregate substitution material.”

— they said

In addition, they used graphite at 5% of volume for enhancing the thermal conductivity, and the arched-type steel fiber for compensating the reduction in mechanical properties by the graphite. Furthermore, they used steel fiber (upto 1% vol. fraction) as the thermal conductive material because the steel fiber has a high level of thermal conductivity. However, there’s a risk if we apply all these various thermal conductive materials to the concrete, why? Because it would generate thermal damage by the difference in the thermal conductivity of each material in the cold environment, e.g., via freeze–thaw. Thus, it is necessary to verify or assess the thermal durability of concrete with thermal conductive materials, in conditions such as freeze-thaw.

For this reason, Byeong-Hun Woo and colleagues performed two experiments: freeze–thaw (FT) and rapid cyclic thermal attack (RCTA). Their concrete was made for application as road paving material, therefore, the FT resistance was important. In addition, cold regions usually change the air temperature very rapidly. Therefore, it was essential to performed RCTA test for assessing the thermal durability of concrete.

RCTA test concept © Woo et al.

They found that, Arched type steel fiber improves the mechanical properties of concrete due to the anchorage effect. On the contrary, it was demonstrated that using graphite brought about a negative effect on the mechanical properties. However, graphite is a good material for improving the thermal conductivity of concrete. Therefore, the decrease in mechanical properties caused by using graphite could be compensated by using arched type steel fiber.

They also found that, SiC is able to be used as fine aggregate and has sufficient thermal conductivity. In addition, it was demonstrated through the thermal conductivity results that the steel fiber could be used as a thermal conductive material. The combination of SiC and steel fiber maximized the improvement in the thermal conductivity of concrete. Adding graphite also brought about an increase in thermal conductivity.

“Using 100% silicon carbide was considered the acceptable range, but 50% of silicon carbide was the best. Graphite decreased all the properties except for the thermal conductivity.”

Finally, it has been demonstrated from the results of the FT test and RCTA test that use of graphite is not suitable for FT and RCTA resistance. However, the arched type steel fiber showed a remarkable improvement of the FT resistance and RCTA. In addition, SiC compensated for the negative effect of graphite on the FT and RCTA.

“We suggest the content of graphite and use of other conductive materials should be carefully consider in further studies”

— they concluded.

Featured image: Used thermal conductive materials. (a) Arched-type steel fiber; (b) SiC; (c) Graphite © Woo et al.


Reference: Woo, B.-H.; Yoo, D.-H.; Kim, S.-S.; Lee, J.-B.; Ryou, J.-S.; Kim, H.-G. Effects of Thermal Conductive Materials on the Freeze-Thaw Resistance of Concrete. Materials 2021, 14, 4063. https://doi.org/10.3390/ma14154063


Note for editors of other websites: To reuse this article fully or partially kindly give credit either to our author/editor S. Aman or provide a link of our article

Ibrutinib Effective Treatment For Difficult To Treat Forms of Hairy Cell Leukemia (Medicine)

The oral targeted therapy drug ibrutinib is an effective treatment option for high-risk hairy cell leukemia, according to a new study conducted by researchers at The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCCC – James).

Hairy cell leukemia is a rare form of B-cell blood cancer that is diagnosed in 600 to 800 people annually in the United States. Researchers note that while the disease generally has a good prognosis for the majority of people affected, a small group of patients with variants of the disease do not respond well to existing U.S. Food and Drug Administration (FDA) approved therapies or cannot tolerate the side effects of established therapies.

“There is a critical unmet need for therapy options in this subset of patients to achieve long-term cancer control,” said Kerry Rogers, MD, principal investigator of the clinical trial and a hematologist/scientist at the OSUCCC – James. “Our study shows that ibrutinib (pronounced eye-broo-ti-nib) is a safe, effective and well-tolerated option for patients with relapsed or variant forms of hairy cell leukemia. It is a very important discovery for patients facing this diagnosis.”

For this phase 2 clinical trial, a multi-institutional team led by the OSUCCC – James recruited 44 patients with high-risk hairy cell leukemia to test the effectiveness of the drug ibrutinib, 15 of whom were treated in Columbus, Ohio, at the OSUCCC – James.

All study participants had either classic hairy cell leukemia and had received other treatments previously or the variant form of the disease where it is not likely that the standard therapies — the chemotherapy drugs cladribine (pronounced KLAD-rih-been) and pentostatin (pronounced PEN-toh-STA-tin) — would be effective.

Researchers reported their findings in the June 24 issue of Blood.

Ibrutinib is an oral therapy in a class of drugs known as Bruton’s tyrosine kinase (BTK) inhibitors. These drugs block specific chemical reactions in the body that are involved in cellular processes. Use of the drug for this study was considered experimental; however, ibrutinib is FDA approved for the treatment of certain cancers, including mantle cell lymphoma, chronic lymphocytic leukemia/small lymphocytic lymphoma and others.

“The underlying cellular biology of these diseases is similar, so we wanted to determine if this FDA-approved drug that is used to treat other forms of blood cancer could also serve as an effective treatment for this small segment of hairy cell leukemia patients who did not respond to traditional therapies,” said Rogers, who is an assistant professor in Ohio State’s College of Medicine.

“Even though hairy cell leukemia is a disease with a generally good prognosis, there is a small group of patients for whom current therapies are inadequate for cancer control,” Rogers added. “This is an effective, well-tolerated new treatment option for patients impacted by the highest-risk forms of hairy cell leukemia. It’s a very exciting development that could transform survivorship for this subset of patients from months and years, to years and decades.”

This study was sponsored by the Cancer Therapy Evaluation Program at the National Cancer Institute and grants from the National Cancer Institute/National Institutes of Health and conducted at the OSUCCC – James; the NCI clinical trials center, Karmanos; Mayo Clinic and MD Anderson Cancer Center. The study began in 2013 and is closed to patient accrual.

Featured image: Hairy cell leukemia slide © OSU


Reference: Kerry A. Rogers, Leslie A. Andritsos, Lai Wei, Eric M. McLaughlin, Amy S. Ruppert, Mirela Anghelina, James S. Blachly, Timothy Call, Dai Chihara, Anees Dauki, Ling Guo, S. Percy Ivy, Lacey R. James, Daniel Jones, Robert J. Kreitman, Gerard Lozanski, David M. Lucas, Apollinaire Ngankeu, Mitch Phelps, Farhad Ravandi, Charles A. Schiffer, William E. Carson, Jeffrey A. Jones, Michael R. Grever; Phase 2 study of ibrutinib in classic and variant hairy cell leukemia. Blood 2021; 137 (25): 3473–3483. doi: https://doi.org/10.1182/blood.2020009688


Provided by OSU

Researchers Discover Nucleotide Sequence Responsible For Effectively Fighting Pathologies (Biology)

HSE researchers uncover the fundamental mechanisms behind the maturation of microRNA molecules

Researchers from HSE University have discovered nucleotide sequences characteristic of microRNA isoforms (microRNAs with errors). The discovery will help predict errors in microRNA behaviour and create drugs that can detect targets (such as viruses) more effectively. The results of the study have been published in the RNA Biology journal.

MicroRNAs (miRNAs) are very small molecules that regulate all the processes in a cell, including the transformation of inherited information in RNA or proteins (gene expression). Each microRNA has its own unique set of targets–genes whose activity it can suppress. Recent studies show that even slight changes in microRNA nucleotide sequences (so-called microRNA isoforms or isomiRs) can completely rebuild numerous targets. This can drastically alter the biological function of the molecule. However, until recently, researchers did not know why some microRNAs have isoforms, while others do not.

HSE Faculty of Biology and Biotechnology researchers Anton Zhiyanov, Stepan Nersisyan, and Alexander Tonevitsky applied bioinformatics methods to find the answer to this question. The team managed to create an algorithm that characterizes the fundamental differences between microRNAs that have isoforms and those that do not.

Stepan Nersisyan, Junior Research Fellow at the HSE International Laboratory of Microphysiological Systems © Stepan Nersisyan

Their study also has important applications for the creation of artificial molecules similar to microRNAs. Dozens of research teams across the globe are currently working to solve this problem. Researchers artificially synthetize molecules that are similar to microRNAs (so-called short hairpin RNAs or shRNAs) in order to ‘knock down’ the gene they are interested in. In addition to having academic applications, this technology is also used in therapy to suppress ‘bad’ genes that cause diseases.

The authors of the study demonstrated that such artificially synthetized molecules can also have isoforms.

‘Some combinations of nucleotides (AGCU, AGUU) are most often found in microRNAs where no errors occur. Combinations such as CCAG and some of its variations can predict changes and target failure with up to 70% precision. Sequencing short hairpin RNAs from our own experiments revealed that they also have isoforms. This means that it is possible to have a situation where we invent a molecule with a specific list of targets, but in practice, isoforms appear with unintended targets of their own. Our algorithm helps predict such events at the computer analysis stage without having to carry out costly experiments,’ said Stepan Nersisyan, Junior Research Fellow at the HSE International Laboratory of Microphysiological Systems.

Featured image: The pattern discovered by the researchers. Letters that grow upwards represent error-free microRNA processing, while those growing downwards represent a processing pattern with errors. The bigger the letter, the stronger the correlation. © Nersisyan S. et al.


Reference: Anton Zhiyanov, Stepan Nersisyan & Alexander Tonevitsky (2021) Hairpin sequence and structure is associated with features of isomiR biogenesis, RNA Biology, DOI: 10.1080/15476286.2021.1952759


Provided by HSE

A Novel Method For the Rapid Repair of Peripheral Nerve Injuries (Material Science)

Bar-Ilan University researchers have developed nerve guidance conduits filled with smart gel that accelerate regeneration of torn nerve fibers

Each year, hundreds of thousands of people worldwide suffer from peripheral nerve injuries, which often leave them with long-term disabilities. The peripheral nervous system is analogous to the circulatory system; a network of vessels that reaches all parts of the body, but instead of blood flowing through vessels, electrical signals propagate information through thin fibers called axons, which are engulfed within nerve trunks. These nerve trunks are the communication network relaying information from all parts of the body to the brain, coordinating activity, and generating motor and sensory function. If one of the nerve trunks is damaged or torn – a common condition in limb injuries – a patient can experience pain, paralysis and even a life-long disability.

In such situations, surgical intervention is necessary to repair the damaged nerve. The standard treatments are direct suturing of detached nerves or, in cases where the gap formed in the nerve trunk is large, surgeons transfer an intact nerve trunk from the patient’s leg and implant it at the site of the injury, thus creating damage in another area (i.e., the leg). Today, there are methods to rejoin nerve trunks to allow the axons to regrow and restore motor and sensory function. One such method is by implanting a synthetic hollow nerve conduit aimed at bridging the gap and allowing the nerve to heal without secondary damage to the patient.

One of the main problems preventing optimal regeneration is that axons within severed nerves have difficulty regenerating and reaching their target. This may be attributed in part to misguided axons that sprout in multiple directions, decreasing probability to reach their target organs. “They need orienting cues to help them,” explains Prof. Orit Shefi, of Bar-Ilan University’s Kofkin Faculty of Engineering, Institute for Nanotechnology and Advanced Materials, and Gonda (Goldschmied) Multidisciplinary Brain Research Center. Dr. Merav Antman-Passig, a researcher in her lab, adds: “These guiding instructions need to remain in the body for an extended time, since axons grow fairly slowly.”

A technique developed by the research team of Prof. Shefi’s laboratory, led by Dr. Antman-Passig and Dr. Jonathan Giron, is used to fill a nerve conduit with gel containing a number of physical and chemical components that promote and align axon regrowth. Their technique was recently published in Advanced Functional Materials.

The researchers filled hollow nerve conduits with engineered aligned collagen gels. In the body, aligned collagen fibers help axon pathfinding, but, in the hollow nerve guides available today, the aligned collagen fibers are absent. The aligned collagen gel acts as a scaffold for axons and directs their growth. In addition, the conduits contain a substance called NGF (nerve growth factor) which, as its name implies, is essential for the growth of the nervous system. “Imagine that we implanted guiding cues in the gel, which are the aligned collagen fibers, and that these guiding cues also have a treat for the growing axons,” explains Dr. Antman-Passig “like bait neatly scattered for the growing axons.” Prof. Shefi adds: “An axon that reaches the gel follows these cues and finds the right direction more easily. In fact, the novel system combines several techniques for nerve regeneration. Axons like to grow toward these markers that can be left for them, like collagen scaffolding and NGF. The novelty of our method is in the engineering of an organized tissue-like gel that contains components that help restore the nerves, and especially in extending the duration of activity of the gel in the body. If collagen and NGF are simply added in hollow nerve conduits, just like real bait, different cells consume them and actually break them down. After a short time, the growing axons do not have these road signs. In the method we developed, we extended the time that these factors are accessible to axons during regeneration. We did this by incorporating NGF-coated magnetic particles that we arranged into the correct structure via a magnetic alignment strategy. This also creates an arrangement of the particles and collagen.”

After characterizing the gel components, the researchers implanted them in nerve conduits and examined the direction of their growth and the platform’s efficacy. The researchers measured the direction of the cell growth and found that with the help of the gel combining aligned collagen and NGF- coated particles, they were able to direct and enhance their growth. Subsequently, they examined the efficacy of the conduit in the rehabilitation of rats with peripheral nerve injury at the sciatic nerve, which prevented them from walking properly. The number of axons that penetrated the innovative gel-filled tube and successfully crossed the injured area was greater compared to the empty tube, and accordingly the restoration of nerve tissue was the highest. The researchers showed that with the implantation of the tubes and the use of the engineered collagen gel, the functional motor restoration was highest, in comparison to the use of other types of conduits and compared to conduits with gel that was not enriched.

The researchers are now exploring commercialization options and hope that will help functional recovery and accelerate nerve repair following injury.


Reference: Antman-Passig, M., Giron, J., Karni, M., Motiei, M., Schori, H., Shefi, O., Magnetic Assembly of a Multifunctional Guidance Conduit for Peripheral Nerve Repair. Adv. Funct. Mater. 2021, 31, 2010837. https://doi.org/10.1002/adfm.202010837


Provided by Bar-Ilan University

New Discoveries From The Period Of The Bar-Kochba Revolt (Archeology)

Archaeological finds recently discovered in the Wadi Rashash Basin in southeastern Samaria may refute accepted assumptions about the period of the revolt

In the summer of 2020, Dr. Dvir Raviv of the Department of Israel Studies and Archeology at Bar-Ilan University conducted an archeological survey in the Wadi Rashash Basin in southeastern Samaria. The Jewish population in the area between the Great Revolt and the Bar Kochba Revolt.

The two sites near the settlement of Wadi Rashash are Horbat Jaba’it and Horbat al-Marjim. A large mapping system (documented as early as the 1980s) was re-mapped at Horbat Jaba’it, where pottery fragments – mainly jars and cooking pots – were found for the first time, allowing its installation to be dated to the days of the Bar Kochba revolt (136-132). A dozen coins from the Second Temple period were found on the ruins – from the Hasmonean period, from the days of Agrippa I, from the days of the emperors Claudius and Nero and a coin from the second year of the Great Revolt (68-67) bearing the inscription “Herut Zion”.

coin

A large, branched hiding system was discovered in Horbat al-Marjim, in addition to a system documented in a previous survey at the site. Dozens of fragments of pottery, glass and metal vessels dating to two periods – Iron Age 2 (8th-9th centuries BCE) and the days of the Bar-Kochba revolt were found in the cavities. Rome.

On the northern cliff of the Wadi Rashash Canyon, which stretches east of the Great Waterfall, were found three natural cave complexes in which evidence of human use in ancient times was discovered. The inhabitants of these caves enjoyed both the proximity to the inhabited area and the proximity to natural water sources – Ein Rashash and Ein Duma. Wadi Rashash Cave is the most prominent of the caves surveyed and is located in the eastern part of the canyon, c. 200 m east of the waterfall. The opening of the cave is located at the bottom of a vertical and slightly stepped cliff, c. 30 m above the creek channel.

In view of the crumbling nature of the cliff rocks it is possible that in ancient times the cave was larger and in the past centuries part of its ceiling collapsed. This option is supported by a relatively large amount of pottery found at the site and may teach about a relatively large group of refugees who fled to this cave. Antiquities robbers who have visited the cave in recent years have emptied much of the cave’s contents while creating a large dirt estuary at the front. In the mounds of dirt at the bottom of the cave and in the estuary at the front, the survey team discovered many finds that were probably brought to the site by Jewish refugees at the end of the Bar-Kochba revolt, as well as two potsherds – a jar and a bowl – from the Iron Age 2.

coin

The Bar Kochba finds include pottery fragments – mainly jars and cooking pots – as well as a bronze coin from the third year of the Bar Kochba revolt (135-134 AD). The inside of the coin is decorated with a musical instrument, probably a violin, and around it is the inscription “Shimon” (Bar-Kochba’s first name); On the back is a palm tree in a wreath, surrounded by the inscription “To Herut Yerushalayim”, from which a few letters survived. The palm is a symbol of victory, and the violin, being one of the vessels of the temple,  expresses a longing for a temple that was a sword at that time.

The location of Wadi Rashash Cave, only about a kilometer and a half from Horbat Jabit and Horbat al-Marjim, sites where hiding systems from the Second Revolt were discovered, suggests that the origin of the refugees who fled to the cave in question was from these sites.

The bar-Kochba coin from Wadi Rashash indicates the presence of a Jewish population in the area until the end of the Bar-Kochba revolt, in contrast to a claim previously made in a study that the Jewish settlement north of Jerusalem was destroyed during the Great Revolt and not blown afterwards. According to Dr. Raviv, several dozen refugees probably hid in the caves of Wadi Rashash, and in all the dozens of known refuge caves throughout Eretz Yehuda and especially in the desert, thousands of refugees hid . The coin with the inscription “Shimon” is the first evidence Roman, ruled by the manager of Bar-Kochba.

Coin, cave and rebellion

Coin photography: Tal Rogovsky

Photo by Wadi Rashash (above): Yehezkel Blumstein 

Photo of the cave (below): Dvir Raviv


Provided by Bar-Ilan University

“Magic-angle” Trilayer Graphene May Be A Rare, Magnet-proof Superconductor (Physics)

New findings might help inform the design of more powerful MRI machines or robust quantum computers.

MIT physicists have observed signs of a rare type of superconductivity in a material called magic-angle twisted trilayer graphene. In a study appearing today in Nature, the researchers report that the material exhibits superconductivity at surprisingly high magnetic fields of up to 10 Tesla, which is three times higher than what the material is predicted to endure if it were a conventional superconductor.

The results strongly imply that magic-angle trilayer graphene, which was initially discovered by the same group, is a very rare type of superconductor, known as a “spin-triplet,” that is impervious to high magnetic fields. Such exotic superconductors could vastly improve technologies such as magnetic resonance imaging, which uses superconducting wires under a magnetic field to resonate with and image biological tissue. MRI machines are currently limited to magnet fields of 1 to 3 Tesla. If they could be built with spin-triplet superconductors, MRI could operate under higher magnetic fields to produce sharper, deeper images of the human body.

The new evidence of spin-triplet superconductivity in trilayer graphene could also help scientists design stronger superconductors for practical quantum computing.

“The value of this experiment is what it teaches us about fundamental superconductivity, about how materials can behave, so that with those lessons learned, we can try to design principles for other materials which would be easier to manufacture, that could perhaps give you better superconductivity,” says Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics at MIT.

His co-authors on the paper include postdoc Yuan Cao and graduate student Jeong Min Park at MIT, and Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Japan.

Strange shift

Superconducting materials are defined by their super-efficient ability to conduct electricity without losing energy. When exposed to an electric current, electrons in a superconductor couple up in “Cooper pairs” that then travel through the material without resistance, like passengers on an express train.

Jeong Min Park stands next to a dilution refrigerator apparatus, the type of apparatus that measures at very cold temperatures, just a tenth of a degree above absolute zero temperature.
Credits:Image: Courtesy of the researchers

In a vast majority of superconductors, these passenger pairs have opposite spins, with one electron spinning up, and the other down — a configuration known as a “spin-singlet.” These pairs happily speed through a superconductor, except under high magnetic fields, which can shift the energy of each electron in opposite directions, pulling the pair apart. In this way, and through mechanisms, high magnetic fields can derail superconductivity in conventional spin-singlet superconductors.  

“That’s the ultimate reason why in a large-enough magnetic field, superconductivity disappears,” Park says.

But there exists a handful of exotic superconductors that are impervious to magnetic fields, up to very large strengths. These materials superconduct through pairs of electrons with the same spin — a property known as “spin-triplet.” When exposed to high magnetic fields, the energy of both electrons in a Cooper pair shift in the same direction, in a way that they are not pulled apart but continue superconducting unperturbed, regardless of the magnetic field strength.

Jarillo-Herrero’s group was curious whether magic-angle trilayer graphene might harbor signs of this more unusual spin-triplet superconductivity. The team has produced pioneering work in the study of graphene moiré structures — layers of atom-thin carbon lattices that, when stacked at specific angles, can give rise to surprising electronic behaviors.

The researchers initially reported such curious properties in two angled sheets of graphene, which they dubbed magic-angle bilayer graphene. They soon followed up with tests of trilayer graphene, a sandwich configuration of three graphene sheets that turned out to be even stronger than its bilayer counterpart, retaining superconductivity at higher temperatures. When the researchers applied a modest magnetic field, they noticed that trilayer graphene was able to superconduct at field strengths that would destroy superconductivity in bilayer graphene.

“We thought, this is something very strange,” Jarillo-Herrero says.

A super comeback

In their new study, the physicists tested trilayer graphene’s superconductivity under increasingly higher magnetic fields. They fabricated the material by peeling away atom-thin layers of carbon from a block of graphite, stacking three layers together, and rotating the middle one by 1.56 degrees with respect to the outer layers. They attached an electrode to either end of the material to run a current through and measure any energy lost in the process. Then they turned on a large magnet in the lab, with a field which they oriented parallel to the material.

As they increased the magnetic field around trilayer graphene, they observed that superconductivity held strong up to a point before disappearing, but then curiously reappeared at higher field strengths — a comeback that is highly unusual and not known to occur in conventional spin-singlet superconductors.

“In spin-singlet superconductors, if you kill superconductivity, it never comes back — it’s gone for good,” Cao says. “Here, it reappeared again. So this definitely says this material is not spin-singlet.”

They also observed that after “re-entry,” superconductivity persisted up to 10 Tesla, the maximum field strength that the lab’s magnet could produce. This is about three times higher than what the superconductor should withstand if it were a conventional spin-singlet, according to Pauli’s limit, a theory that predicts the maximum magnetic field at which a material can retain superconductivity.

Trilayer graphene’s reappearance of superconductivity, paired with its persistence at higher magnetic fields than predicted, rules out the possibility that the material is a run-of-the-mill superconductor. Instead, it is likely a very rare type, possibly a spin-triplet, hosting Cooper pairs that speed through the material, impervious to high magnetic fields. The team plans to drill down on the material to confirm its exact spin state, which could help to inform the design of more powerful MRI machines, and also more robust quantum computers.

“Regular quantum computing is super fragile,” Jarillo-Herrero says. “You look at it and, poof, it disappears. About 20 years ago, theorists proposed a type of topological superconductivity that, if realized in any material, could [enable] a quantum computer where states responsible for computation are very robust. That would give infinite more power to do computing. The key ingredient to realize that would be spin-triplet superconductors, of a certain type. We have no idea if our type is of that type. But even if it’s not, this could make it easier to put trilayer graphene with other materials to engineer that kind of superconductivity. That could be a major breakthrough. But it’s still super early.”

This research was supported by the U.S. Department of Energy, the National Science Foundation, the Gordon and Betty Moore Foundation, the Fundacion Ramon Areces, and the CIFAR Quantum Materials Program.

Featured image: MIT physicists have observed signs of a rare type of superconductivity in a material called “magic-angle” twisted trilayer graphene.Credits:Image: Courtesy of the researchers


Reference: Cao, Y., Park, J.M., Watanabe, K. et al. Pauli-limit violation and re-entrant superconductivity in moiré graphene. Nature (2021). https://doi.org/10.1038/s41586-021-03685-y


Provided by MIT

Researchers Discover A ‘Layer Hall Effect’ in A 2D Topological Axion Antiferromagnet (Physics)

Unique quantum physics signal presence of sought-after topological Axion insulating state

Researchers have discovered a “layer” Hall effect in a solid state chip constructed of antiferromagnetic manganese bismuth telluride, a finding that signals a much sought-after topological Axion insulating state, the team reports in the current edition of the journal Nature.

Researchers have been trying to find evidence of a topological Axion insulating (TAI) state and developed some candidate materials based on theoretical calculations. The layered Hall effect represents the first clear experimental evidence of the state, a feature bound by the laws of quantum physics, according to Boston College Assistant Professor of Physics Qiong Ma, a senior researcher on the project, which included 36 scientists from universities in the U.S., Japan, China, Taiwan, Germany, and India.

Researchers believe that when it is fully understood, TAI can be used to make semiconductors with potential applications in electronic devices, Ma said. The highly unusual properties of Axions will support a new electromagnetic response called the topological magneto-electric effect, paving the way for realizing ultra-sensitive, ultrafast, and dissipationless sensors, detectors and memory devices.

At the center of this line of inquiry among physicists and materials scientists are Axions, weakly-interacting particles first postulated by theorists more than 30 years ago, Ma said. They are one of the primary candidates for Dark Matter, a mysterious form of matter thought to account for approximately 85 percent of the universe.

While the search for Axions in high-energy physics is actively ongoing, it has been recently proposed that Axions can be realized as quasi-particles in solid state materials. The prime candidate as the place to locate Axions is in a quantum TAI material, where researchers suggest Axions exist as low-energy electronic excitations, Ma said.

“We set out to search for the topological Axion insulating state in a carefully designed quantum device made of even-number-layered MnBi2Te4 – or manganese bismuth telluride,” Ma said. “Previous studies have demonstrated the insulating state, namely, very large resistance, which is, however, true for any insulator. We wanted to further demonstrate properties that are unique to Axion insulators and do not exist in regular insulators, such as diamond.”

The material forms a two-dimensional layered crystal structure, which allowed Ma and her colleagues to mechanically exfoliate atom-thick flakes using cellophane tape that can be found in most drug stores and supermarkets. Thin flake structures with even numbers of layers were proposed to be an Axion insulator.

Ma worked closely with fellow Boston College physicists Brian Zhou and Kenneth Burch. Zhou used a unique quantum technique to detect the magnetism of MnBi2Te4. Burch has a unique glovebox facility used to process the sample in an inert environment.

“We first characterized the layer number with optical methods and then performed electrical transport measurements, such as measuring the sample resistance under different conditions, including varying electric field, magnetic field and environmental temperature,” Ma said.

The researchers found the Hall effect, a well known law of physics where electrons travel at an angle from the axis under the influence of an applied magnetic field. But in this case, these electrons were traveling without such assistance, Ma said. The key was the materials’ topology, or the quantum characteristics of its electrons and the waves in which they function.

“We observed a novel property for electrons travelling across this material in its Axion insulating state: The electrons do not travel in a straight line; instead, they deflect to the transverse direction. This effect was usually only observed under a large magnetic field, known as the Hall effect,” Ma said. “But here, the deflection occurs due to inherent topology of the materials and without external magnetic field. More interestingly, the electrons deflect to opposite sides on the top and bottom layers. Therefore, we coined it as the layer Hall effect. The layer Hall effect serves as a distinct signature of the topological Axion insulating state, which will not happen in regular insulators.”

Ma, whose research on the project is supported by the U.S. Department of Energy, said the team was surprised to find that the topological Axion insulating state and the layer Hall effect can be effectively controlled by the so-called Axion field, which is the product of applying both an electric field and a magnetic field.

“This means that whether the electrons deflect to the left or to the right on the top and bottom layers can be switched by the collective application of the electrical and magnetic fields,” Ma said. “A single field is not able to switch one situation to the other.”

Harvard University Assistant Professor of Chemistry Suyang Xu, a lead author of the report, added, “We are very excited about this work because it demonstrates the first realistic platform for the topological Axion insulator state.”

Ma said the identification of the topological Axion insulating state leads to the next step of searching for signatures of the defining Axion dynamics in this system, which is known as the topological magnetoelectric effect (ME).

“The topological ME effect is a fundamentally new mechanism to convert electricity to magnetism, or vice versa, without lost energy, and has great potential to realize ultra-energy-efficient spintronic and memory devices,” said Ma.

To demonstrate such will require further optimization of the material quality, the geometry of the device, and expanded experimental capabilities, Ma said.

Featured image credit: Unsplash/CC0 Public Domain


Reference: Gao, A., Liu, YF., Hu, C. et al. Layer Hall effect in a 2D topological axion antiferromagnet. Nature (2021). https://doi.org/10.1038/s41586-021-03679-w


Provided by Boston College

Researchers Reverse Emphysema in Mice By Injecting Blood Vessel Wall Cells (Medicine)

Researchers at Weill Cornell Medicine and NewYork-Presbyterian in New York have discovered that injecting mice with pulmonary endothelial cells–the cells that line the walls of blood vessels in the lung–can reverse the symptoms of emphysema. The study, which will be published July 21 in the Journal of Experimental Medicine (JEM), may lead to new treatments for chronic obstructive pulmonary disease (COPD), an inflammatory lung disease associated with smoking that is thought to be the third leading cause of death worldwide.

Emphysema is one of the characteristic features of COPD in which the tiny air sacs, or alveoli, within the lungs are gradually destroyed, leading to breathing difficulties and, eventually, respiratory failure. The loss of alveoli is accompanied by a remodeling of the lung’s blood vessels that could indicate changes in the endothelial cells that form the blood vessel walls. Under normal circumstances, endothelial cells secrete molecules that help surrounding tissues maintain and repair themselves, but dysfunctional endothelial cells can drive various diseases, including tissue fibrosis and cancer.

“However, it is not clear whether endothelial dysfunction drives COPD pathophysiology or is simply the consequence of damaged alveolar surface area,” says Dr. Augustine M.K. Choi, the Stephen and Suzanne Weiss Dean of Weill Cornell Medicine and a co-senior author of the new JEM study.

Choi and colleagues found that various markers of healthy endothelial cells were reduced in the lungs of COPD patients, as well as in laboratory mice with an induced form of emphysema. Indeed, in the lung endothelial cells of mice with emphysema, numerous genes were associated with endothelial dysfunction, including genes that promote inflammation, cell death, and vascular remodeling.

“We took these features to denote a potentially dysfunctional state that could drive the development of emphysema,” says co-senior author Dr. Shahin Rafii, Chief of the Division of Regenerative Medicine, Director of the Ansary Stem Cell Institute, and the Arthur B. Belfer Professor in Genetic Medicine at Weill Cornell Medicine. “This could indicate that re-establishing a healthy vasculature–by either intravenous delivery of normal lung endothelial cells or reversing aberrant endothelial cell signaling–could encourage repair and regeneration of damaged lung tissue.”

Remarkably, injecting mice with healthy lung endothelial cells reduced the alveolar destruction associated with emphysema and restored lung function. Other cell types–even endothelial cells from other tissues–failed to have any beneficial effect.

Choi and colleagues then investigated the role of leucine-rich alpha-2-glycoprotein-1 (LRG1), a cell signaling protein linked to diabetic nephropathy and various forms of cancer that the researchers found to be elevated in the lung endothelial cells of patients with COPD. Removing LRG1 from endothelial cells protected mice from the tissue destruction associated with emphysema, the researchers discovered.

“Taken together, our data strongly suggest the critical role of endothelial cell function in mediating the pathogenesis of COPD/emphysema,” says co-first author Dr. Alexandra Racanelli, an Instructor in Medicine at Weill Cornell Medicine. “Targeting endothelial cell biology by administering healthy lung endothelial cells and/or inhibiting the LRG1 pathway may therefore represent strategies of immense potential for the treatment of patients with advanced COPD or emphysema.”

Dr. Shu Hisata from Jichi Medical University is a co-first author. Dr. Choi is a cofounder and equity stockholder for Proterris, which develops therapeutic uses for carbon monoxide. Dr. Choi also has a use patent on CO and a patent in COPD. Dr. Rafii is the founder of and a nonpaid consultant to Angiocrine Bioscience.

Featured image: Injection of healthy lung endothelial cells (right) reverses the destruction of lung tissue seen in mice with emphysema (left). ©2021 Hisata et al.


Reference: Shu Hisata, Alexandra C. Racanelli, Pouneh Kermani, Ryan Schreiner, Sean Houghton, Brisa Palikuqi, Balvir Kunar, Aiyuan Zhou, Keith McConn, Allyson Capili, David Redmond, Daniel J. Nolan, Michael Ginsberg, Bi-Sen Ding, Fernando J. Martinez, Joseph M. Scandura, Suzanne M. Cloonan, Shahin Rafii, Augustine M.K. Choi; Reversal of emphysema by restoration of pulmonary endothelial cells. J Exp Med 2 August 2021; 218 (8): e20200938. doi: https://doi.org/10.1084/jem.20200938


Provided by Rockefeller University

Astrophysicist Outlines Ambitious Plans For The First Gravitational Wave Observatory On The Moon (Astronomy)

Vanderbilt astrophysicist Karan Jani has led a series of studies that make the first case for a gravitational wave infrastructure on the surface of the moon. The experiment, dubbed Gravitational-Wave Lunar Observatory for Cosmology, uses the moon’s environment and geocentric orbit to analyze mergers of black holes, neuron stars and dark matter candidates within almost 70 percent of the entire observable volume of the universe, he said.

“By tapping into the natural conditions on the moon, we showed that one of the most challenging spectrum of gravitational waves can be measured better from the lunar surface, which so far seems impossible from Earth or space,” Jani said.

WHY IT MATTERS

“The moon offers an ideal backdrop for the ultimate gravitational wave observatory, since it lacks an atmosphere and noticeable seismic noise, which we must mitigate at great cost for laser interferometers on Earth,” said Avi Loeb, professor of science at Harvard University and bestselling author of books about black holes, the first stars, the search for extraterrestrial life and the future of the universe. “A lunar observatory would provide unprecedented sensitivity for discovering sources that we do not anticipate and that could inform us of new physics. GLOC could be the jewel in the crown of science on the surface of the moon.”

This work comes as NASA revives its Artemis program, which aims to send the first woman and the next man to the moon as early as 2024. Ongoing commercial work by aerospace companies, including SpaceX and BlueOrigin, also has added to the momentum behind planning for ambitious scientific infrastructure on the surface of the moon.

WHAT’S NEXT

“In the coming years, we hope to develop a pathfinder mission on the moon to test the technologies of GLOC,” Jani said. “Unlike space missions that last only a few years, the great investment benefit of GLOC is it establishes a permanent base on the moon from where we can study the universe for generations, quite literally the entirety of this century.” Currently the observatory is theoretical, with Jani and Loeb receiving a strong endorsement from the international gravitational-wave community.

Karan Jani (Vanderbilt University)

“It was a great privilege to collaborate with an innovative young thinker like Karan Jani,” Loeb said. “He may live long enough to witness the project come to fruition.”

FUNDING

The work was funded by the Stevenson Chair endowment funds at Vanderbilt University and the Black Hole Initiative at Harvard University, which is funded by grants from the John Templeton Foundation and the Gordon and Betty Moore Foundation.

GO DEEPER

The article, “Gravitational-wave Lunar Observatory for Cosmology,” was published in the Journal of Cosmology and Astroparticle Physics on June 24.

Featured image: Conceptual design of Gravitational-wave Lunar Observatory for Cosmology on the surface of the moon. (Karan Jani)


Provided by Vanderbilt University