All posts by uncover reality team

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Ultra-Low Voltage Is Effective At Killing Bacteria (Biology)

According to a new study by Arkansas University researchers, ultra-low voltage electricity is effective at killing bacteria as it causes membranes that surround bacteria to leak.

Using E. coli bacteria, the team demonstrated that ultra-low voltage applied for 30 minutes created holes in the cell’s membrane that allowed leakage of small molecules, ions and proteins both in and out of the cell, killing the bacterium.

While the antimicrobial property of electricity has been long known, it was not completely understood how ultra-low voltages damage and ultimately kill bacteria until this new finding.

Such low voltage could, for example, be used to sterilize a doorknob or other high-touch surfaces that harbor bacteria without causing any harm to users. It could also be used to hinder biofilm formation in water purification and storage applications. Their research advances work to fight drug-resistant bacteria.


References: Venkata Rao Krishnamurthi et al. Microampere Electric Current Causes Bacterial Membrane Damage and Two-Way Leakage in a Short Period of Time, Applied and Environmental Microbiology (2020). DOI: 10.1128/AEM.01015-20 link: https://aem.asm.org/content/86/16/e01015-20

Silurian Trilobite Had Modern Type of Compound Eye (Paleontology)

Paleontologists have found, Aulacopleura koninckii, a species of trilobite that lived around 429 million years ago i.e. during Silurian period, was equipped with a fully modern type of visual system — “compound eye”— comparable to that of living bees, dragonflies and others.

Fig: Left eye of Aulacopleura koninckii. Image credit: Choenemann & Clarkson, doi: 10.1038/s41598-020-69219-0.

Trilobites are extinct marine arthropods that used to live during Paleozoic era (542-251 million years ago).

From the very beginning of their appearance they were equipped with compound eyes, which during the Cambrian explosion and later differentiated into highly diverse visual systems.

The most basic type, and still very common among diurnal insects and crustaceans, is the apposition compound eye.

It consists of up to 30,000 individual, more or less identical receptor units, so-called ommatidia, optically isolated from each other by a set of screening pigment cells.

In a new study, University of Cologne’s Dr. Brigitte Schoenemann and Dr. Euan Clarkson from the University of Edinburgh used digital microscopy to examine apposition compound eyes of a small trilobite called Aulacopleura koninckii.

This extinct species was first described in 1846 by the French-Czech paleontologist Joachim Barrande, a pioneer of trilobite research, from specimens collected at several paleontological sites near Loděnice in the Czech Republic.

Fig: The 429-million-year-old specimen of Aulacopleura koninckii investigated by Choenemann & Clarkson. Scale bar – 2.5 mm. Image credit: Choenemann & Clarkson, doi: 10.1038/s41598-020-69219-0.

The excellently-preserved specimen studied by the study authors is 1-2 mm high and has two protruding semi-oval eyes on the back of its head, one of which has broken off.

They identified a number of internal structures that are similar to those of the compound eyes of many modern insects and crustaceans, including their ommatidia (measuring 35 μm in diameter) that contain eight light-detecting cells grouped around a transparent tube called a rhabdom.

Each visual unit is topped with a thick lens and the remains of what the paleontologists suggest is a flat crystalline cone that light passed through before being focused onto the rhabdom.

The small size of its visual units indicates that Aulacopleura koninckii lived in bright, shallow waters and was probably active during the day, as smaller diameter lenses are efficient at capturing light under bright conditions.

The presence of pigment cell barriers between visual units suggests that the trilobite had mosaic vision with each visual unit contributing a small portion of the overall image, similar to the compound eyes of many modern insects and crustaceans.

The researchers also think that Aulacopleura koninckii likely was a translucent trilobite, comparable to modern shrimps and other smaller aquatic crustaceans with translucent shells, providing an excellent camouflage in water.


References: B. Choenemann & E.N.K. Clarkson. 2020. Insights into a 429-million-year-old compound eye. Sci Rep 10, 12029; doi: 10.1038/s41598-020-69219-0 ; link: https://www.nature.com/articles/s41598-020-69219-0

“Born Again” Planetary Nebulae Abell 30 Has Binary Central Star (Astronomy)

Using data from NASA’s Kepler spacecraft, eight planetary nebulae have been identified as `born-again’, a class of object typified by knotty secondary ejecta having low masses (∼10−4 M⊙) with nearly no hydrogen. They also explored a planetary nebula (PN) known as Abell 30.

Fig: Abell 30 planetary nebulae

Planetary nebulae are expanding shells of gas and dust that have been ejected from a star during the process of its evolution from main sequence star into a red giant or white dwarf. They are relatively rare, but important for astronomers studying the chemical evolution of stars and galaxies.

Of special interest are PNe exhibiting hydrogen-poor material in their central regions. In some cases, the hydrogen-poor material appears as a fan of knots with cometary tails stretched radially from the central star. Detailed investigations of PNe of this type could shed more light on the process of low-mass star evolution.

Abell 30 is the archetype of the so-called “born-again” PNe—identified by low-mass knotty secondary ejecta with nearly no hydrogen. Chemical studies of this PN have shown that it exhibits an extreme abundance discrepancy factor (ADF). One of the theories that may explain such an anomaly is that it is associated with binary star interactions.

Fig: The average K2 target pixel file of the central star of Abell 30 with the pixels included in the photometry aperture outlined in white. Credit: Jacoby et al., 2020.

However, finding companions to central stars of PNe is challenging for ground-based observatories due to Earth’s atmosphere, which limits the performance of these facilities. So a team of astronomers led by George H. Jacoby, analyzed the data from Kepler spacecraft’s prolonged mission, known as K2, in order to investigate Abell 30 and its central star.

The K2 light curve revealed a strong periodic signal at approximately 1.06 days, with a peak-to-peak-amplitude of about 1.7 percent. The astronomers noted that although such low-amplitude sinusoidal variability could be due to several physical processes, they favor the binary star scenario.

According to the authors of the paper, Abell 30 has a binary system in which the companion is being irradiated by the hot central star. However, the astronomers were not able to demonstrate a consistent radial velocity variation for the PN, which means that its photometric variability could be also due to a magnetic spot on the central star.

They added that further observations, especially high-resolution, time-resolved spectroscopy should be conducted in order to draw final conclusions on the nature of Abell 30’s central star.


References: Jacoby et al., Abell 30—A Binary Central Star Among the Born-Again Planetary Nebulae, arXiv:2008.01488 [astro-ph.SR] arxiv.org/abs/2008.01488 link:

Cooling Tail Method, Is The New Method For Accurate Determination Of The Radii Of Neutrons Stars (Astronomy)

Guys, we all know neutron stars are the smallest and densest astrophysical objects with visible surfaces in the Universe. They form after gravitational collapses of the iron nuclei of massive (with masses about ten solar masses) stars at the end of their nuclear evolution. We can observe these collapses as supernovae explosions.

The masses of neutron stars are typical for normal stars, about one and half solar masses, but their radii are extremely small in comparison with normal stars—they are between ten and fifteen kilometers. For comparison, the radius of the Sun is about 700,000 km. It means that the average matter density of neutron stars is a few times larger than the density of atomic nuclei, namely about 1 billion tons per cubic centimeter.

The neutron star matter consists mainly of close up neutrons, and the repulsive forces between neutrons prevent neutron stars from collapsing into a black hole. Theoretical quantitative description of these repulsive forces is not possible at the moment, and it is a fundamental problem of the nuclear physics and astrophysics. This problem is also known as the equation of state of the superdense cold matter problem. Astrophysical observations of neutron stars can limit the existing different theoretical models of the equation of state, because the neutron star radii depend on the repulsive forces.

One of the most suitable astrophysical objects for neutron star radii measurements are X-ray bursting neutron stars. They are components of close binary systems, so called low-mass X-ray binaries. In such systems, the secondary component, which is a normal solar-like star, losses its matter, and the neutron star accretes the matter. The matter flows from the normal star onto the surface of the neutron star. The surface gravity on a neutron star is very high, hundred billion times higher than on the Earth’s surface. As a result, the conditions for exploding thermonuclear burning arise on the bottom of the fresh accreted matter. It’s these explosions that we observe as X-ray flashes in low-mass X-ray binaries.

Durations of the most X-ray flashes are about 10 to 100 seconds. After the maximum, the X-ray brightness decays almost exponentially. An X-ray bursting neutron star emits as a black body with some temperature (about ten million degrees), and this temperature decreases together with the brightness decreasing. But the connection between the brightness and the temperature is not fixed. It depends on the physical structure of the upper layers of the emitting neutron star envelope (the atmosphere). The model atmospheres of X-ray bursting neutron stars can be computed for various masses and radii of, as well as for a given X-ray flash brightness, and some time ago the co-authors computed the extended grid of such model atmospheres.

The comparison of joint observational decreasing of the temperature and the X-ray brightness in some X-ray flashes with the model predictions allows to find the mass and radius of a neutron star. This method, which was named the cooling tail method, was suggested more than ten years ago. The authors of this method are Valery Suleimanov, Juri Poutanen, Mike Revnivtsev, and Klaus Werner, three of whom are the co-authors of this current publication. Further development of this approach and its application to the many X-ray flashes allowed them to limit the neutron star radii in the range from 11 to 13 km. All the following determinations, including an observation of the merging of two neutron stars by gravitational wave detectors, gave values inside of this range.

In the method, the researchers assumed that the neutron star is not rotating and has a spherical shape with a uniform temperature distribution over the surface. But the neutron stars in the considered binary systems can rotate rapidly with the typical period a few milliseconds.

In particular, the fastest rotating neutron star in the system 4U 1608-52 has a spin period of 0.0016 seconds. Shapes of such rapidly rotating neutron stars are far from spherical. They have larger radii at the equators than at the poles, and the surface gravity and the surface temperature are larger at the poles than at the equators. Therefore, there are systematic uncertainties in the method of the neutron star masses and radii determination. The obtained neutron star radii can be systematically overestimated due to their rapid rotation.

Recently Valery Suleimanov, Juri Poutanen, and Klaus Werner developed a fast approximate approach for computing the emergent radiations of rapidly rotating neutron stars. They extended the cooling tail method for thermonuclear flashes on the rapidly rotating neutron star surfaces. This extended method was applied to the X-ray burst on the surface of the neutron star in the system SAX 1810.8-2609, which is rotating with the period of about 2 milliseconds.

The study showed that the radius of this neutron star can be overestimated on the value in the range from one to a half kilometer depending on the inclination angle of the rotation axis to the line of sight. It means that the systematic corrections are not crucial and can be ignored in the first approximation. The plan is to apply this method to the fastest rotating neutron star in the system 4U 1608-52.


References: Valery F. Suleimanov, Juri Poutanen and Klaus Werner, ‘Observational appearance of rapidly rotating neutron stars’, A&A 639, A33 (2020) link: https://www.aanda.org/articles/aa/abs/2020/07/aa37502-20/aa37502-20.html

Physicists Created A New Superlattice Material For Better Energy Efficient Electrical Conductors (Physics)

Physicists has created a new material layered by two structures, forming a superlattice, that at a high temperature is a super-efficient insulator conducting current without dissipation and lost energy. Their finding could be the basis of research leading to new, better energy efficient electrical conductors.

The material is created and developed in a laboratory chamber. Over time atoms attach to it and the material appears to grow—similar to the way rock candy is formed. Surprisingly, it forms a novel ordered superlattice, which the researchers test for quantized electrical transport.

The research centers around the Quantum Anomalous Hall Effect (QAHE), which describes an insulator that conducts dissipationless current in discrete channels on its surfaces. Because QAHE current does not lose energy as it travels, it is similar to a superconducting current and has the potential if industrialized to improve energy-efficient technologies.

The main advance of their work is a higher temperature QAHE in a superlattice, and they showed that this superlattice is highly tunable through electron irradiation and thermal vacancy distribution, thus presenting a tunable and more robust platform for the QAHE.


References: Deng, H., Chen, Z., Wołoś, A. et al. High-temperature quantum anomalous Hall regime in a MnBi2Te4/Bi2Te3 superlattice. Nat. Phys. (2020). https://doi.org/10.1038/s41567-020-0998-2 link: https://www.nature.com/articles/s41567-020-0998-2

Researchers Observed The Fastest Ever Moving Star (Astronomy)

A team of researchers has observed the fastest moving star ever recorded. Their deep H+K-band (SINFONI) and K-band (NACO) data showed that the S-cluster star S4711 is on a highly eccentric trajectory around Sagittarius A with an orbital period of 7.6 yr and a periapse distance of 144 au to the supermassive black hole (SMBH). The star has the shortest orbital period and the smallest mean distance to the SMBH during its orbit to date. They also describe study of faint S-cluster star candidates, S4712–S4715, circling close to the black hole at the center of the Milky Way galaxy.

Fig: This artist’s impression shows part of the orbit of one of the stars very close to the supermassive black hole at the centre of the Milky Way. Analysis of data from ESO’s Very Large Telescope and other telescopes suggests that the orbits of these stars may show the subtle effects predicted by Einstein’s general theory of relativity. There are hints that the orbit of this star, called S2, is deviating slightly from the path calculated using classical physics. This close-up of the orbit of star S2 shows how the path of the star is slightly different when it passed the same part of its orbit for the second time, 15 years later, due to the effects of general relativity.

Space scientists have known for some time that there is a black hole situated near the center of the Milky Way galaxy (Sagittarius A*), and have theorized that there are stars that circle very close to it—known as “squeezars”, they are believed to orbit so closely to the black hole that they are accelerated to incredible speeds during parts of their orbits. In their work, the researchers have been studying a group of stars that exist close to the black hole, each starting with the letter “S” to indicate their closeness to Sagittarius A.

Fig: The distance of SgrA* stars at closest approach. Credit: Florian Peißker et al.

Prior research had identified a star called S2 as likely existing the closest to Sagittarius A, and at its closest to the black hole, was measured to be traveling at approximately 3% of the speed of light. Then last year, the researchers with this new effort found another star that circled more closely to the black hole and therefore traveled even faster, at approximately 6.7% the speed of light. Since that time, the team has continued studying the fast-moving stars and have found five more that appear to travel even faster: S4714, S4711, S4712, S4713 and S4715.

Fig: S4711 on its orbit around Sgr A*. Credit: arXiv:2008.04764 [astro-ph.GA]

Of these, two stand out from the others—S4714 and S4711. S4711 is a blue star with an orbit shorter than S2, suggesting it might be the closest of all the stars to the black hole. And S4714 has proven to be the speediest of them all—it has a longer orbit, but its orbit is elliptical, which means it is elongated, giving it time, perhaps, to pick up more speed as it moves closer to the black hole—up to 24,000 kilometers per second, or approximately 8% of the speed of light. The researchers suggest the stars are good squeezar candidates, particularly S4714 and S4711 and the short orbital time period of these stars in the dense cluster around the SMBH in the center of our Galaxy are perfect candidates to observe gravitational effects such as the periapse shift.


References: Florian Peißker, Andreas Eckart, Michal Zajaček, Basel Ali, and Marzieh Parsa, “S62 and S4711: Indications of a Population of Faint Fast-moving Stars inside the S2 Orbit—S4711 on a 7.6 yr Orbit around Sgr A”, The Astrophysical Journal, Volume 899, Number 1.. Link: https://iopscience.iop.org/article/10.3847/1538-4357/ab9c1c/meta doi: DOI: 10.3847/1538-4357/ab9c1c (2) Florian Peißker, Andreas Eckart, Marzieh Parsa, “S62 on a 9.9 yr Orbit around SgrA”, arXiv, Volume 889, Number 1, Published 2020 January 24
DOI: 10.3847/1538-4357/ab5afd link: https://arxiv.org/abs/2002.02341

Plants Hate Touch (Botany)

We will never stop carrying a torch for plants — they are way more amazing than most people give them credit for. They can hear oncoming attackers, and many send noxious chemicals into their leaves to fight back. Some even have a primitive sense of sight. So believe us when we say this: They don’t like it when you pet them. According to research, they have a very strong reaction to touch.

Plants hatred of cuddles is nothing new to scientists. In the early 1960s, for instance, scientist Frank Salisbury was studying how cocklebur plants grew by measuring their leaves with a ruler every day. Weirdly, he noticed that the plants he was measuring didn’t grow as much as their neighbors, and they eventually shriveled up and died. He concluded that it was simply the act of touching the plants that killed them.

A decade later, a plant physiologist named Mark Jaffe published the first work on this phenomenon — and coined the first word for it: thigmomorphogenesis (in Greek, thigmo means “touch,” morpho means “shape,” and genesis means “origin.”). Of the dozen or so plant species he used in his study, six had slowed growth after being touched daily. After a few more days of no touching, however, they resumed their regular growth rate.

In 1990, plant biochemist Dr. Janet Braam discovered that this stunted growth happened because of a genetic change. Touching a plant led to a specific handful of its genes being activated, which she named the “touch” (TCH) genes.

In December, researchers at La Trobe University in Australia took a closer look at this phenomenon to uncover exactly what was going on inside of the plant to activate these genes. For their study, the researchers used a plant called thale cress (Arabidopsis thaliana), a plant that’s known to pump its leaves with toxic mustard oil when insects attack and the same genus as the plants used in Braam’s original study. The scientists stroked the leaves of the plants with a soft paintbrush every 12 hours, then measured their biological response at varying periods of time after each stroke.

They found that within 30 minutes of being touched, 10 percent of the plant’s genome had been altered. At the site where the plants had been stroked, their mitochondria had ramped up their activation of genes known to suppress the touch response. Even more interesting, the same thing had happened at other places on the plant that hadn’t been touched, though to a lesser degree. Specifically, the mitochondria altered the genome by tweaking the plant’s immune system and hormone levels.

“This involves a huge expenditure of energy which is taken away from plant growth. If the touching is repeated, then plant growth is reduced by up to 30 percent,” said professor Jim Whelan, the lead researcher on the study and research director of the La Trobe Institute for Agriculture and Food, in a statement.

Why would this be? It makes sense for a plant to send out toxic chemicals when it feels the brush of a caterpillar since that could help convince the predator that it’s not a tasty snack. But to inhibit growth after too much touching? That seems like cutting off the nose to spite the face.

But there’s some logic there. For example, if plants grow too close together, they’ll get less light and fewer nutrients. Growing smaller could be a way to ensure that there’s enough to go around, co-author Dr. Yan Wang explained.

This new research might help farmers know exactly how far to space their plants to ensure they grow as big as possible. Knowing the genetic mechanisms at play in a plant’s touch defenses might even help scientists engineer plants that aren’t as touch sensitive. For that, though, they have to be careful, since it could be easy to knock out some other important senses in the process, like sensitivity to cold and heat and disease defense.

But as for houseplants, the message is clear: water them, give them sunlight, even play them music if you’d like to. But don’t pet them. They don’t like it when you pet them.


Antarctica Was Once Covered In Forests And We Have The Fossils To Prove it (Paleontology / Botany)

As far as vacation destinations go, Antarctica isn’t much. Most of its surface is covered by a layer of ice a mile thick, and it experiences the lowest temperatures ever recorded on Earth. But millions of years ago, it was a tropical paradise — compared to now, at least. At that point, it was covered not by ice, but by trees, and scientists are uncovering the fossil evidence of those long-dead forests today.

600 million years ago, you wouldn’t have recognized our planet. Instead of seven continents, all of the dry land existed in one supercontinent we now call Pangaea. The climate was different too, with higher temperatures and sultry humidity. Over hundreds of millions of years, the southern part of the supercontinent, called Gondwana, began to break away from the northernmost Laurasia until it sat near where Antarctica is today.

Those higher temperatures meant that plants could live, if not thrive — the continent was still on the South Pole, so vegetation had to withstand four to five months of darkness followed by four to five months where the sun never set. That meant that while modern plants take months to transition from season to season, plants on Gondwana had to transition in as little as a month if they were going to survive the rapid change in light and temperature.

Fig: Erik Gulbranson, palaeoecologist and assistant professor at University of Wisconsin-Milwaukee, studies some of the fossilized tree he brought from Antarctica

The kings of the Gondwanan forest during the Permian Period were towering trees belonging to the Glosspteris genus. They grew from 65 to 131 feet (20 to 30 meters) tall and had huge, flat leaves longer than your forearm. But around 251 million years ago, disaster struck. The Permian-Triassic mass extinction killed off as much as 95 percent of Earth’s species. Scientists still aren’t sure what caused it, but many think that greenhouse gas emissions from volcanoes raised the planet’s temperatures to hazardous levels and caused the oceans to acidify.

In reaction, the forests of Gondwana quickly fossilized. “The fungi in the wood itself were probably mineralized and turned into stone within a matter of weeks, in some cases probably while the tree was still alive,” researcher Erik Gulbranson told National Geographic. “These things happened incredibly rapidly. You could have witnessed it firsthand if you were there.”

That’s bad news for Permian forests, but great news for us. Today, we have fossilized wood fragments and even tree trunks from the forests that once covered our coldest continent. Who needs to imagine exotic environments on other planets? We had them right here all along.


The World’s First Trees Don’t Have Rings (Botany / Paleontology)

Every child knows that you can tell the age of a tree by counting its rings. For scientists studying a 374-million-year-old tree, that posed a problem — and not because it’s really easy to lose track of your count when you pass 20 million or so. The trunk of this tree didn’t have any rings at all, and that completely changes our understanding of how trees evolved.

Fig: A foreman uncovers a fossilized tree trunk, thought to be more than 350 million years old, at a quarry in upstate New york in 1920s

In May 2017, a team of researchers from Cardiff University in Wales, Nanjing Institute of Geology and Palaeontology in China, and State University of New York announced that the trunk of an ancient tree belonging to the group called cladoxlopsids — the ancestor of modern trees and ferns — looks nothing like the trees of today.

Tree rings are composed of xylem, a tissue that transports water from a tree’s roots to its tips. In most trees, xylem grows in a single cylinder just under the bark. New wood grows on top of that, and the tree gets ever bigger in a predictable yearly cycle. (Interestingly, palm trees don’t have rings. Their xylem grows in strands, which is why a cross-section of a palm tree is covered in dots instead of rings.)

Fig: Cardiff University/ Dr. Chris Berry

But this ancient tree fossil looked nothing like that. Instead of growing xylem in yearly rings or in strands distributed throughout, this tree grew narrow strands in the outer five centimeters of its trunk, connected together in a web formation. That means that instead of rings, the cross-section of the fossil is covered in what is like Dalmatian spots. Each of those spots, or strands, grew its own xylem rings, creating what was essentially tree trunks growing within a tree trunk. As those interconnected mini-trees got bigger, their connections split apart and repaired themselves to keep the tree from breaking under its own weight. The result was a huge tree with a flat base and a bulbous trunk.

“There is no other tree that I know of in the history of the Earth that has ever done anything as complicated as this,” said Cardiff University researcher Chris Berry in a press release. “The tree simultaneously ripped its skeleton apart and collapsed under its own weight while staying alive and growing upwards and outwards to become the dominant plant of its day.”

What’s unusual for evolution is the fact that these trees aren’t any less complicated than modern ones. Why would the oldest trees use such a complex growth strategy? To answer this question, the researchers will need to find more fossils just as well-preserved as this one.