Astronomers Discovered Two Extremely Red Main-belt Asteroids (Planetary Science)

A team of international astronomers discovered two extremely red main-belt asteroids: 203 Pompeja and 269 Justitia. These were identified from combined visible and near-infrared spectroscopic observations collected at the IRTF and SAO observatories. Their study recently appeared in Arxiv.

The majority of asteroids in the Solar System are found in the main asteroid belt (MBA). This is located between the orbits of Mars and Jupiter, with the greatest concentration of asteroids between 2.12 and 3.3 AU. Early in the history of the solar system, the gravity of newly formed Jupiter brought an end to the formation of planetary bodies in this region and caused the small bodies to collide with one another, fragmenting them into the asteroids we observe today. But, not all MBAs experienced catastrophic destruction. Some are larger than 110 km in diameter and still exists, means these objects can be regarded as the last remains of the original population of planetesimals that initially populated the inner solar system. Moreover, if such MBA’s escaped catastrophic destruction, their orbital elements have not been substantially altered which means, those orbital elements maintained their state at the end of migration state of solar system.

Now, a team of international astronomers performed their observations on the 3.0-m NASA Infra-red Telescope Facility (IRTF) on Mt. Mauna Kea, Hawaii, USA and at the 1.0- m Seoul National University Astronomical Observatory (SAO), Republic of Korea. They also recorded asteroidal spectroscopic data by two different instruments mounted on these telescope and discovered two extremely red main-belt asteroids: 203 Pompeja and 269 Justita.

The first extremely red asteroid called, “203 Pompeja” was discovered by chance in the visible to near-infrared wavelength range during spectroscopic survey. It has diameter if 111.3 km and an albedo of 0.045. It is located in the middle main-belt.

While, the second very red asteroid called “269 Justitia” had already been discovered and have a diameter of 54.4 km and an albedo of 0.080. It is also located in the middle main-belt.

Figure 1. Spectra of the very red spectral slope MBAs 203 Pompeja and 269 Justitia and other dark (low-albedo) objects in the visible and near-infrared region. Comparison of the very red asteroids with: top left panel: typical spectral types of dark asteroids from the Bus-DeMeo classification scheme, top right: typical Hildas and Jovian Trojans, bottom left: meteorites with a very red spectral slope, bottom right: dark outer Solar System objects spectrally similar to the very red asteroids © Hasegawa et al.

They also found that, these two asteroids have a redder spectral slope than any other D-type body, which are the reddest objects in the asteroid belt, and similar to RR and IR-class objects found in the outer Solar System among trans-Neptunian objects (TNO’s) and Centaurs.

In addition, their spectroscopic results suggested the presence of complex organic materials on the surface layer of these asteroids, implying that they could have formed in the vicinity of Neptune and been transplanted to the main belt region during a phase of planetary migration.

Finally, 203 Pompeia is the only very red asteroid known so far among the ∼250 bodies with diameter larger than 110 km (i.e. presumably structurally intact) found in the asteroid belt.

“These discoveries add another piece of evidence that the main asteroid belt hosts a population of bodies that were formed in the outskirt of the Solar System.”, concluded authors of the study.

To know more: Read on The Astrophysical Journal Letters the article ” Discovery of two TNO-like bodies in the asteroid belt “, by Sunao Hasegawa, Michael Marsset, Francesca E. DeMeo, Schelte J. Bus, Jooyeon Geem, Masateru Ishiguro, Myungshin Im, Daisuke Kuroda and Pierre Vernazza

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

Researchers Devise A New Way To Repair The Ruptured Wall Of the Heart From A Severe Heart Attack (Medicine)

Heart attack, medically known as myocardial infarction (MI), is a common heart condition. MI is caused by problems in blood supply to parts of the heart. In severe cases, MI could be accompanied by ruptures in the wall separating different parts of the heart, such as in the ventricular septum (a wall that separates the right ventricle that pumps deoxygenated blood to the lungs for oxygenation, from the left ventricle that pumps oxygenated blood to rest of the body). Not surprisingly, without appropriate surgical intervention, a VSR due to MI increases the chances of death.

Current surgical techniques used to close VSR due to MI have proven ineffective in several situations, which put a group of Chinese medical researchers to work. These researchers from The First Affiliated Hospital of Zhengzhou University and Capital Medical University in China specifically worked on VSR due to MI accompanied by life-threatening fluctuations in blood pressure, or hemodynamic instability (HI). The researchers successfully devised a surgical technique that improved outcomes in patients suffering from VSR and HI due to MI (VSR-HI-MI), according to a study published in Chinese Medical Journal. Further explaining the motivation of their study, Dr. Chao Liu (first author of the study) says, “We aimed to present a novel surgical repair technique that can be safely, feasibly, and effectively used in hemodynamically unstable patients with VSR in the acute phase.”

A group of Chinese medical researchers has now been successful in devising a new surgical technique, called SurCOP, to repair ruptures caused by heart attacks. © Chinese Medical Journal

The medical researchers, who aimed to save the lives of patients with VSR-HI-MI, call their novel surgical technique as SurCOP, a method combining devices called an occluder and a patch. While the occluder is used to repair the “hole” in the heart, the patch (derived from biocompatible materials) is used to close it. This is an upgraded version of the conventionally used surgical method in which only a simple patch is used. The doctors then tested the improved technique on nine consenting patients with VSR-HI-MI and compared the outcomes to 54 others. The results showed that the procedure had an impressive 100% success rate. Also, compared to a bleak 10% survival rate if managed conservatively, SurCOP achieved a promising 77.8% survival rate when a median follow-up time of 187 days were considered. Importantly, none of the patients who underwent SurCOP developed VSR after the surgery.

These are incredibly promising findings. Overall, the study highlights how well the surgical technique of SurCOP, tackles the clinical problems posed by VSR-HI-MI. Elated at the success of the study, Dr. Liu concludes, “Our experience has shown that the SurCOP technique is a safe, easy-to-manipulate, and effective method. We hope that we could receive feedback from surgeons who will attempt performing this alternative therapeutic technique and work together to improve the prognosis of patients with VSR.”

Indeed, the world can now heal a little better from complications arising from heart attacks.


Provided by Cactus Communications

Sanaria Vaccine Results Demonstrate Unprecedented Progress In Battle Against Variant Malaria Parasites (Medicine)

Finding Published in Nature Offer Potential for Use by Travelers and Prevention of Malaria in African Populations in Near Future

Researchers from Sanaria® Inc. and the National Institutes of Health (NIH) are making progress in the development of highly protective malaria vaccines.

In an article published today in Nature, Sanaria’s PfSPZ-CVac (CQ) vaccine is reported as being safe and protecting 100% of six subjects against a variant malaria parasite three months after their last dose in the company’s Phase 1 safety and efficacy trial. This is the first time complete protection against a variant malaria parasite has ever been achieved that long after vaccine administration.

The variant parasite used in the trial is a Brazilian malaria parasite genetically more variant from the African parasites in the vaccine than 700 malaria parasites from Africa. Protection was achieved at a dose that is 20% of the company’s first-generation malaria vaccine dosage.

“These results represent extremely important progress, unanticipated by most malaria experts,” said Professor Martin Grobusch, Head of the Center of Tropical Medicine and Travel Medicine, Amsterdam University Medical Centers. “Until recently, malaria vaccine developers sought to achieve high-level protection against non-variant malaria parasites, often only two to three weeks after vaccination, with immunity waning thereafter. The finding of 100% protection against variant parasites that are so divergent from the vaccine parasites at three months is unprecedented. This vaccine approach should be advanced now as a potential tool to protect travelers to Africa and further developed for the prevention of malaria in African populations.”

The Nature paper also includes results of a second study using PfSPZ-CVac (PYR), which combines Sanaria’s PfSPZ with pyrimethine (PYR), a drug used for seasonal malaria prevention in African preschoolers. This vaccine was well tolerated and protected 82% of the 17 subjects to whom it was administered from the Brazilian variant parasites or the African vaccine parasites three months after their last dose.

“We are encouraged by the significant findings reported in this seminal paper, which justify our investment in Sanaria and its systematic, scientifically sound approach to developing the highly protective, cost effective vaccines required to eliminate malaria, a scourge of humanity, particularly for the most underserved on our planet,” said Holm Keller, Co-Managing Director, the EU Malaria Fund.

“Sanaria’s vaccine development program is designed to produce safe, cost-effective vaccines that provide high-level protection against malaria parasites that cause more than 400,000 deaths annually, primarily in Africa,” said Stephen L. Hoffman, Sanaria’s CEO. “With this goal in mind, Sanaria and our partners in the International PfSPZ Consortium have pursued a step-by-step approach to maintaining safety, increasing efficacy toward 100% against variant parasites, increasing the durability of efficacy, and decreasing the required vaccine dosage. This study reports huge progress in all four areas.”

Sanaria® PfSPZ-CVac is a chemo-attenuated, live whole parasite vaccine in which an anti-malarial drug is co-administered with parasite cells (PfSPZ) to kill them before a clinical infection develops. In the trial reported in Nature, the anti-malarial was either chloroquine (CQ) or PYR and efficacy was measured by controlled human malaria infection (CHMI). In addition to exposure in natural settings in Africa, the company has relied on CHMI of vaccinated and unvaccinated adults to assess vaccine efficacy. This is a rigorous test of malaria vaccines that can be conducted with small numbers of trial participants since 100% of unvaccinated subjects develop malaria.

The clinical trial was sponsored by Sanaria Inc. and conducted by the LMIV, NIAID and NIH. The full paper in Nature can be accessed at here.

Reference: Mwakingwe-Omari, A., Healy, S.A., Lane, J. et al. Two chemoattenuated PfSPZ malaria vaccines induce sterile hepatic immunity. Nature (2021).

Provided by Sanaria

New Beetle Found in Fossil Feces Attributed to Dinosaur Ancestor (Paleontology)

The tiny beetle Triamyxa coprolithica is the first-ever insect to be described from fossil faeces. The animal the researchers have to thank for the excellent preservation was probably the dinosaur ancestor Silesaurus opolensis, which 230 million years ago ingested the small beetle in large numbers.

In a recently published study in Current Biology, vertebrate palaeontologists from Uppsala University and entomologists from National Sun Yat-sen University (Taiwan), Friedrich-Schiller-Universität Jena (Germany), and Universidad de Guadalajara (Mexico) used synchrotron microtomography to 3D-reconstruct the beetles while they were still trapped within the fossilised faecal matter. The coprolite contained abundant beetle body parts, most belonging to the same small species. A few specimens were found nearly complete, with much of the delicate legs and antennae still intact. The well-preserved state of these fossils made it possible to produce a detailed description of the new beetle genus and to compare it with more modern ones. Triamyxa coprolithica represents a previously unknown extinct lineage of the suborder Myxophaga, whose modern representatives are small and live on algae in wet environments.

The tiny beetle Triamyxa coprolithica is the first-ever insect to be described from fossil feces. © Qvarnström et al.

“We were absolutely amazed by the abundance and fantastic preservation of the beetles in the coprolite fragment. In a way, we must really thank Silesaurus, which likely was the animal that helped us accumulating them,” says Martin Qvarnström, researcher at Uppsala University and one of the co-authors of the paper.

Silesaurus opolensis – the probable producer of the coprolite – was a relatively small dinosaur ancestor with an estimated body weight of 15 kilograms that lived in Poland approximately 230 million years ago. In a previous study, the authors assigned coprolites with disarticulated beetle remains to Silesaurus based on the size and shape of the coprolites as well as several anatomical adaptations in the animal. Silesaurus possessed a beak at the tip of its jaws that could have been used to root in the litter and perhaps peck insects off the ground, somewhat like modern birds. But although Silesaurus ingested numerous individuals of Triamyxa coprolithica, the beetle was likely too small to have been the only targeted prey. Instead, Triamyxa likely shared a habitat with larger beetles, which are represented by disarticulated remains in the coprolites, and other prey, which never ended up in the coprolites in a recognisable shape.

The tiny beetle Triamyxa coprolithica is the first-ever insect to be described from fossil feces. © Qvarnström et al.

“I never thought that we would be able to find out what the Triassic precursor of the dinosaurs ate for dinner,” says Grzegorz Niedwiedzki, palaeontologist at Uppsala University and one of the co-authors of the paper.

The preservation of the beetles in the coprolite is similar to specimens from amber, which normally yield the best-preserved insect fossils. Amber, however, was mainly formed during relatively recent geological time. This study shows that coprolites may be valuable for studying early insect evolution and, at the same time, the diet of extinct vertebrates.

The synchrotron scanning was carried out at the European Synchrotron Radiation Facility (ESRF) in Grenoble.

Featured image: The animal the researchers have to thank for the excellent preservation of the beetle Triamyxa coprolithica was was probably the dinosaur ancestor Silesaurus opolensis. © Magorzata Czaja

Provided by Uppsala University

Reactive Oxygen Species (ROS): Key Components in Cancer Therapies (Medicine)

Reactive oxygen species (ROS) are highly reactive chemicals which contain oxygen radicals. Hypochlorous acid, peroxides, superoxide, singlet oxygen, alpha-oxygen and hydroxyl radicals are the major examples of ROS, which are familiar to persons from many walks of life as they are used in many domestic and industrial processes. ROS are naturally produced during a variety of biochemical reactions within the cell organelles such as the endoplasmic reticulum, mitochondria and peroxisomes. ROS are also formed as a byproduct of the normal metabolism of oxygen. The production of ROS can be induced by various factors such as heavy metals, tobacco, smoke, drugs, xenobiotics, pollutants and radiation. From various experimental studies, it is reported that ROS acts as either tumor suppressing or tumor promoting agent. The elevated level of ROS can arrest the growth of tumor through the persistent increase in cell cycle inhibition. The increased level of ROS can induce apoptosis by both intrinsic and extrinsic pathways. ROS is considered to be tumor suppressing agent as the production of ROS is due to use of most of the chemotherapeutic agents in order to activate the cell death. The cytotoxic effect of ROS provides impetus towards apoptosis but in higher levels, ROS can cause initiation of malignancy that leads to uncontrolled cell death in cancer cells. Whereas, some species of ROS can influence various activities at cellular level that include cell proliferation. This recent review, published in Anti-Cancer Agents in Medicinal Chemistry explains the significance of ROS in cancer therapy.

Scientific reports suggest that ROS may promote either cell proliferation or cell death depending on the intensity or location of the oxidative burst and the activity of the antioxidant system. The ability of ROS to stimulate cell growth or cell death mainly depends on the intensity or duration of redox signals and defense mechanisms of antioxidants. The existing anti-cancer drugs exert harmful effects on normal cells which are partially activated by ROS. These species exert reverse cellular effects by promoting either cell proliferation and tumor progression or cell death. ROS act as “double edged sword” by acting not only as disease inducers or sustainers but also act as therapeutic weapons in cancer cells. The increased level of ROS in mitochondria is found to induce cell proliferation, cell survival, cell migration, and epithelial-mesenchymal transition through mitogen-activated protein kinase (MAPK) and Ras-ERK activation.

With these intracellular effects in view, various reactive oxygen species can be applied therapeutically for the treatment of different types of cancer cells. Novel therapeutic approaches of anti-cancer drugs are based on formation ROS or modulation of antioxidant mechanisms. By being able to differentiate between normal and cancer cells through the use of molecular signals researchers can target cancer cells for destruction in vivo. In spite of the current techniques of ROS signaling in cancer biology, the dual nature of ROS is still a great challenge in cancer therapies that target to ROS. The understanding of properties of ROS as major factor in signaling pathways may offer hope in the clinic for safer and effective pharmacological anti-cancer interventions in the future.

Reference: Biswa Mohan Sahoo*, Bimal Krishna Banik, Preetismita Borah and Adya Jain, “Reactive Oxygen Species (ROS): Key components in Cancer Therapies”, Anti-Cancer Agents in Medicinal Chemistry 2021; 21() .

Provided by Bentham Science Publishers

When And Why Do Politicians Use Emotive Rhetoric in Parliamentary Speeches? (Politics)

A study involving Toni Rodon, a professor with the UPF Department of Political and Social Sciences, argues that emotive rhetoric is one of the tools that politicians use strategically to attract voters. Published in American Political Science Review, the article analyses two million parliamentary speeches delivered in the lower houses of parliament in the UK (between 2001 and 2019) and Ireland (between 2002 and 2013).

Politicians use emotional resources in their speeches in parliament depending on the type of debate and use emotive rhetoric strategically and selectively, mainly to attract voters. This is one of the main conclusions of a study published in the journal American Political Science Review (APSR) involving Toni Rodon, a professor with the UPF Department of Political and Social Sciences and member of the Research Group on Institutions and Political Actors, together with Moritz Osnabrügge (Durham University, as first author) and Sara B. Hobolt (London School of Economics and Political Science).

“Our research provides evidence that incentives to attract voters differ systematically depending on the type of debate”

In recent years, much research has been done showing that emotions are important in politics and that the use of emotive rhetoric, based on positive or negative language, is common during election campaigns. Research has also been conducted within political parties regarding the stance adopted and the dissent expressed in parliamentary debates, but when and why politicians use emotive rhetoric in their legislative speeches has been studied less, and is now elaborated on by the authors in their work.

Emotive language usually refers to a style of communication that arouses an emotional response from the listener, thus evoking positive or negative reactions that go beyond the specific meaning of the word or phrase used. So, it can be a powerful tool to convince people of the validity of a particular message, and from the point of view of electoral competition, there is evidence linking emotion-eliciting appeals with the electoral success of certain political formations.

Analysis of two million speeches in the House of Commons and in the Dáil Éireann

The analysis included in article covers two million speeches delivered in the House of Commons and in the Dáil Éireann, the lower houses of parliament of Great Britain and Ireland, respectively. Specifically, a million parliamentary speeches, i.e., all those that were delivered in the House of Commons between 2001 and 2019, and a further one million speeches delivered in the Dáil Éireann between 2002 and 2013.

The authors chose the British Parliament because it is one of the oldest in the world, an ideal institutional environment for studying these kinds of speeches. “We focused on the House of Commons because it is the more powerful of the two legislative chambers in the UK and the debates held there differ in terms of their profile and the size of the audience, which has allowed us to compare emotive rhetoric across different types of debate”, the authors assert. In a second stage, the study of the speeches delivered in the lower house of the Irish parliament has allowed confirming and generalizing their findings.

High and low profile legislative debates: two different styles of discourse

The article which, based on an analysis of how politicians use emotive rhetoric in parliament, contributes to the understanding of political competition and legislative behaviour, underlines differences with regard to incentives that legislators have according to the type of debate. “Our research provides evidence that incentives to attract voters differ systematically depending on the type of debate”, the authors suggest. Thus, in high-profile legislative debates, parliamentarians have more incentives to use emotive rhetoric to attract the attention of a wider audience, which they capture by using more emotive political content and language.

It could be said that PMQs is the debate to which citizens are most exposed, and this gives incentives for MPs to use more emotive language.

In the House of Commons, this is the case of Prime Minister’s Questions (PMQs), a debate held weekly. It is a convention during which the prime minister answers questions from MPs, especially the leader of the opposition. It is the parliamentary highlight of the week, broadcast live and covered extensively by the media.

It could be said that PMQs is the debate to which citizens are most exposed, and this gives incentives for MPs to use more emotive languageOther high-profile debates are the Queen’s Speech, which take place annually at the start of each new year of parliament (at which the Queen reads the government’s main priorities, and which also involves the prime minister and the opposition leader) or the Dáil Leaders’ Questions, which are put to the Irish prime minister.

Conversely, in low-profile legislative debates, which are not so avidly followed and generate less expectation, politicians mostly address their colleagues in parliament, and therefore emotional rhetoric is less pronounced.

A new application to measure emotive rhetoric

The study presents a new methodological application to measure emotive rhetoric, and it does so by combining the Affective Norms for English Words (ANEW) dictionary, with word-embedding techniques that enables creating a dictionary specific to the field. Thus, the new tool categorizes emotional and neutral words via ANEW and also identifies new words used in parliamentary speeches to broaden these two categories.

Word Clouds of Emotive and Neutral Words

Word Clouds of Emotive and Neutral Words

For example, some of the neutral words incorporated by the authors are “walkway”, “diameter”, “metres” and “radiators” and some of the emotional words, “appalling”, “empathy”, “horrific” and “admiration”. With regard to areas where we find a higher average level of emotive rhetoric there is “fabric of society”, “social groups” and “welfare and quality of life”, and the areas where we find a lower level of emotive rhetoric, “political system” and “economy”. “Our measurement technique more accurately captures the emotive use of language in a political environment”, the researchers assert.

The authors conclude their work with a reminder: although emotive parliamentary speeches may have positive implications, with increased public interest in the activities of their representatives and in politics in general, there is the risk of negative consequences: “Emotive rhetoric may also increase polarization and may favour politicians who prioritize emotional appeals over competent, coherent policy, and can harm the quality of deliberation and at the same time the quality of democratic representation”, they warn.

Featured image: Appearance of the House of Commons during a Questions to the Prime Minister session. PHOTO: Wikipedia

Reference work: Osnabrügge, M., Hobolt, S.B., Rodon, T. “Playing to the Gallery: Emotive Rhetoric in Parliaments” (May 2021). American Political Science Review (pp. 1-15) DOI:

Provided by UPF

Harvard-led Researchers Document Quantum Melting of Wigner Crystals (Physics)

The study marks a major step toward creating a system for studying quantum phase transitions

In 1934, physicist Eugene Wigner made a theoretical prediction based on quantum mechanics that for 87 years went unseen.

The theory suggested how a metal that normally conducts electricity could turn into a nonconducting insulator when the density of electrons is reduced. Wigner theorized that when electrons in metals are brought to ultracold temperatures, these electrons would be frozen in their tracks and form a rigid, non-electricity conducting structure — a crystal — instead of zipping around at thousands of kilometers per second and creating an electric current. Since he discovered it, the structure was coined a Wigner Crystal and was observed for the first time in 1979.

What’s remained stubbornly elusive to physicists, however, has been the melting of the crystal state into a liquid in response to quantum fluctuations. At least, it was: Now, almost 90 years later, a team of physicists co-led by Hongkun Park and Eugene Demler in the Faculty of Arts and Sciences has finally experimentally documented this transition.

The work is described in a new study published in the journal Nature and marks a big step toward creating a system for studying these kinds of transitions between states of matter at the quantum level, a long-sought-after goal in the field.

“This is right at the border of matter of changing from partially quantum material to partially classical material and has many unusual and interesting phenomena and properties,” said Eugene Demler, a senior author on the paper. “The crystal themselves have been seen, but this, sort of, pristine transition — when quantum mechanics and classical interactions are competing with each other — has not been seen. It has taken 86 years.”

Led by Park and Demler, the research team focused on observing Wigner crystals and their phase transitions in the study. In chemistry, physics, and thermodynamics, phase transitions happen when a substance changes from a solid, liquid, or gas to a different state. When quantum fluctuations near absolute zero temperature drive these transitions, they are called quantum phase transitions. These quantum transitions are thought to play an important role in many quantum systems.

In the case of a Wigner crystal, the crystal-to-liquid transition happens from a competition between the classical and quantum aspects of the electrons – the former dominating in the solid phase, in which electrons are “particle-like,” and the latter dominating in the liquid, in which electrons are “wave-like.” For a single electron, quantum mechanics tells us that the particle and wave nature are complementary.

“It is striking that, in a system of many interacting electrons, these different behaviors manifest in distinct phases of matter,” said Park. “For these reasons, the nature of the electron solid-liquid transition has drawn tremendous theoretical and experimental interest.”

The Harvard scientists report using a novel experimental technique developed by You Zhou, Jiho Sung, and Elise Brutschea — researchers from the Park Research Group and lead authors on the paper — to observe this solid to liquid transition in atomically thin semiconductor bilayers. In general, Wigner crystallization requires very low electron density, making its experimental realization a major experimental challenge. By constructing two interacting electron layers from two atomically thin semiconductors, experimentalists created a situation in which the crystallization is stabilized at higher densities.

To see the transition, the researchers used a method called exciton spectroscopy. They use light to excite an electron in the system and bind it to the electron vacancy, or hole, it leaves behind, forming hydrogen-like electron-hole pair known as an exciton. This pair interacts with the other electrons in the material and modifies its properties so they can be optically seen.

The findings from the paper were largely accidental and came as a surprise, according to the researchers. The Park group initially set out in a different direction and were puzzled when they noticed the electrons in their material displayed insulating behavior. They consulted with theorists from Demler’s lab and soon realized what they had.

The researchers plan on using their new method to continue to investigate other quantum phase transitions.

“We now have an experimental platform where all these [different quantum phase transition] predictions can now be tested,” Demler said.

Featured image: A schematic of a quantum phase transition from an electron liquid to a bilayer Wigner crystal. Each ball represents a single electron. © Ella Maru Studio in collaboration with Hongkun Park and You Zhou

Provided by Harvard University

Want New Advanced Materials? There’s A Phase Transition For That (Material Science)

Believe it or not, steel has something in common with bacterial appendages: they can both undergo a special type of physical transformation that remains puzzling. Now, researchers from Japan and China have used direct microscopic observations to provide more clarity to how this transformation occurs.

In a study recently published in Nature Communications, researchers from The University of Tokyo Institute of Industrial Science and Fudan University Department of Physics have revealed previously unknown physical details that underpin crystalline solid-to-solid phase transitions in soft materials, and possibly how researchers can more fully exploit the properties of advanced materials.

A special type of solid-to-solid phase transition, known as a martensitic transition, is an exciting frontier in medicine, technology, and other fields. The martensitic transition is enabled by a coordinated movement of atoms in a material, which changes the properties of the material without changing its chemical composition. Metal alloys and proteins can both undergo this transition. Researchers hypothesize that in easily deformable soft materials, the transition may occur differently from those observed in hard materials with stable defects. At present, this hypothesis is difficult to test, something the researchers aimed to address.

“Traditionally, it has been challenging to microscopically observe the dynamic process of martensitic transitions in soft materials on a single-particle level,” says co-senior author of the study Hajime Tanaka. “One must devise a means to do so in a way that quickly initiates the transition without harmful perturbation to the system.”

To do this, the researchers used a gentle technique known as ion exchange–in principle, the same method used to remove calcium and magnesium ions from water–to quickly change the crystal structure of polymeric microparticles. One can observe the kinetics of the resulting martensitic transitions with a microscope with single-particle resolution.

“The microscopy results were unambiguous,” explains Peng Tan, co-senior author of the study. “We observed three previously unknown mechanisms by which body-centered cubic soft colloidal crystals form from face-centered cubic ones, depending on the condition.”

The researchers examined the features of these pathways–termed thermally activated in-grain nucleation, grain-boundary-premelting-assisted nucleation, and wall-assisted growth–with particular focus on how the energy barrier to the transition is reduced in each case.

“Softness of a crystal plays a critical role in thermally activated in-grain nucleation,” explains Tanaka. “Whereas, the other two pathways may occur even in hard materials.”

These results have diverse applications. For example, some pharmaceuticals can alter their availability in the body by solid-to-solid phase transitions; therefore, understanding how to control when and where such transitions occur could provide a new means of targeted drug delivery. A greater understanding of the physical mechanisms of solid-to-solid transformations supports the development of new materials that can be tailored for applications.

The article, “Revealing thermally-activated nucleation pathways of diffusionless solid-to-solid transition,” was published in Nature Communications at DOI: 10.1038/s41467-021-24256-9

Featured image: Researchers from The University of Tokyo Institute of Industrial Science and Fudan University experimentally interrogate a phenomenon that bridges diverse fields of science and engineering © Institute of Industrial Science, the University of Tokyo

Provided by University of Tokyo

Astronomers Identified A White Dwarf So Massive That It Might Collapse (Planetary Science)

Astronomers have discovered the smallest and most massive white dwarf ever seen. The smoldering cinder, which formed when two less massive white dwarfs merged, is heavy, “packing a mass greater than that of our Sun into a body about the size of our Moon,” says Ilaria Caiazzo, the Sherman Fairchild Postdoctoral Scholar Research Associate in Theoretical Astrophysics at Caltech and lead author of the new study appearing in the July 1 issue of the journal Nature. “It may seem counterintuitive, but smaller white dwarfs happen to be more massive. This is due to the fact that white dwarfs lack the nuclear burning that keep up normal stars against their own self gravity, and their size is instead regulate­­­d by quantum mechanics.”

The discovery was made by the Zwicky Transient Facility, or ZTF, which operates at Caltech’s Palomar Observatory; two Hawaiʻi telescopes – W. M. Keck Observatory on  Maunakea, Hawaiʻi Island and University of Hawaiʻi Institute for Astronomy’s Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) on Haleakala, Maui – helped characterize the dead star, along with the 200-inch Hale Telescope at Palomar, the European Gaia space observatory, and NASA’s Neil Gehrels Swift Observatory.

White dwarfs are the collapsed remnants of stars that were once about eight times the mass of our Sun or lighter. Our Sun, for example, after it first puffs up into a red giant in about 5 billion years, will ultimately slough off its outer layers and shrink down into a compact white dwarf. About 97 percent of all stars become white dwarfs.

While our Sun is alone in space without a stellar partner, many stars orbit around each other in pairs. The stars grow old together, and if they are both less than eight solar-masses, they will both evolve into white dwarfs.

The new discovery provides an example of what can happen after this phase. The pair of white dwarfs, which spiral around each other, lose energy in the form of gravitational waves and ultimately merge. If the dead stars are massive enough, they explode in what is called a type Ia supernova. But if they are below a certain mass threshold, they combine together into a new white dwarf that is heavier than either progenitor star. This process of merging boosts the magnetic field of that star and speeds up its rotation compared to that of the progenitors.

Astronomers say that the newfound tiny white dwarf, named ZTF J1901+1458, took the latter route of evolution; its progenitors merged and produced a white dwarf 1.35 times the mass of our Sun. The white dwarf has an extreme magnetic field almost 1 billion times stronger than our Sun’s and whips around on its axis at a frenzied pace of one revolution every seven minutes (the zippiest white dwarf known, called EPIC 228939929, rotates every 5.3 minutes).

“We caught this very interesting object that wasn’t quite massive enough to explode,” says Caiazzo. “We are truly probing how massive a white dwarf can be.”

What’s more, Caiazzo and her collaborators think that the merged white dwarf may be massive enough to evolve into a neutron-rich dead star, or neutron star, which typically forms when a star much more massive than our Sun explodes in a supernova.

“This is highly speculative, but it’s possible that the white dwarf is massive enough to further collapse into a neutron star,” says Caiazzo. “It is so massive and dense that, in its core, electrons are being captured by protons in nuclei to form neutrons. Because the pressure from electrons pushes against the force of gravity, keeping the star intact, the core collapses when a large enough number of electrons are removed.”

If this neutron star formation hypothesis is correct, it may mean that a significant portion of other neutron stars take shape in this way. The newfound object’s close proximity (about 130 light-years away) and its young age (about 100 million years old or less) indicate that similar objects may occur more commonly in our galaxy.

Magnetic and Fast

The white dwarf was first spotted by Caiazzo’s colleague Kevin Burdge, a postdoctoral scholar at Caltech, after searching through all-sky images captured by ZTF. This particular white dwarf, when analyzed in combination with data from Gaia, stood out for being very massive and having a rapid rotation.

“No one has systematically been able to explore short-timescale astronomical phenomena on this kind of scale until now. The results of these efforts are stunning,” says Burdge, who, in 2019, led the team that discovered a pair of white dwarfs zipping around each other every seven minutes.

The team then analyzed the spectrum of the star using Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS), and that is when Caiazzo was struck by the signatures of a very powerful magnetic field and realized that she and her team had found something “very special,” as she says. The strength of the magnetic field together with the seven-minute rotational speed of the object indicated that it was the result of two smaller white dwarfs coalescing into one.

Data from Swift, which observes ultraviolet light, helped nail down the size and mass of the white dwarf. With a diameter of 2,670 miles, ZTF J1901+1458 secures the title for the smallest known white dwarf, edging out previous record holders, RE J0317-853 and WD 1832+089, which each have diameters of about 3,100 miles.

The white dwarf ZTF J1901+1458 is about 2,670 miles across, while the moon is 2,174 miles across. The white dwarf is depicted above the Moon in this artistic representation; in reality, the white dwarf lies 130 light-years away in the constellation of Aquila. Credit: Giuseppe Parisi

In the future, Caiazzo hopes to use ZTF to find more white dwarfs like this one, and, in general, to study the population as a whole. “There are so many questions to address, such as what is the rate of white dwarf mergers in the galaxy, and is it enough to explain the number of type Ia supernovae? How is a magnetic field generated in these powerful events, and why is there such diversity in magnetic field strengths among white dwarfs? Finding a large population of white dwarfs born from mergers will help us answer all these questions and more.”

The study, titled “A highly magnetised and rapidly rotating white dwarf as small as the Moon,” was funded by the Rose Hills Foundation, the Alfred P. Sloan Foundation, NASA, the Heising–Simons Foundation, the A. F. Morrison Fellowship of the Lick Observatory, the NSF, and the Natural Sciences and Engineering Research Council of Canada.


Provided by W.M. Keck Observatory