Does Singularities of the Accelerated Stephani Universe Model Affect The Light & Test Particle Motion? (Cosmology)

The Lambda-CDM model, based on Friedmann solution, is the simplest model that provides a reasonably good description of the observed universe’s accelerated expansion. However, this model don’t solve some problems, like “dark energy” and the coincidence problem. Thus, there are alternative approaches. One of the possibilities here is to consider inhomogeneous cosmological models such as the “Stephani solution”.

It allows building of the model of the universe with accelerated expansion within general relativity with no modifications or suggestions of the exotic types of matter. This is a non-static solution for expanding perfect fluid with zero shear and rotation, which contains the known Friedmann solution as a particular case. Initially, it has no symmetries, but the spatial sections of the Stephani space–time in the case of spherical symmetry have the same geometry as corresponding subspaces of the Friedmann solution. Therefore, these models have an intuitively clear interpretation. The spatial curvature in the Stephani solution depends on time that allows the attainment of the accelerated expansion of the universe.

Recently, Elena Kopteva and colleagues investigated the inhomogeneous spherically symmetric stephani universe filled with a perfect fluid with uniform energy density and non-uniform pressure, as a possible model of the acceleration of universe expansion. These models are characterized by the spatial curvature, depending on time. It has been shown that, despite possible singularities, the model can describe the current stage of the universe’s evolution.

Now, they investigated the geodesic structure of this model to verify if the singularities of the model can affect the light and test particle motion within the observable area. Their study recently appeared in the Journal Symmetry.

Figure 1. The spiralling out trajectory of the test particle in the case χ = const. © Elena Kopteva et al.

They showed that, in the case of purely radial motion, the radial velocity slightly decreases with time and radial distance, due to the universe expansion. They also showed that, both particles and photons spiral out of the center when the radial coordinate is constant.

(article continues below images)

Figure 2. The observable radial velocity in the general case of motion. The constants are chosen as follows: β = –0.111113, vr0 = 0.00005, L = 0.001, χin = 0.084, k = –1.01 (the red line), k = –1.5 (the green line) and k = –2.5 (the blue line) © Elena Kopteva et al.
Figure 3. The dependence vr(R) in the general case of motion. The constants are chosen as follows: β = –0.111113, vr0 = 0.00005, L = 0.001, χin = 0.084, k = –1.01 (the red line), k = –1.5 (the green line) and k = –2.5 (the blue line) © Elena Kopteva et al.

In addition, one interesting thing has been found in this model is that, in the case of the test particle motion with arbitrary initial velocity, the observable radial distance increases even under negative observable radial velocity, which is caused by the fact that radial distance depends on both time (T) and singularity (χ), so it can grow even when χ decreases.

“The singularities are indistinguishable for observations and do not influence the test particles and photons motion up to the current age of the universe as well as in the far enough future.”

Finally, their analysis of the geodesic structure with respect to the singularity behavior showed that the closer the exponent k to −1, the slower the solution χ(T) tends towards singularity.

Figure 4. Relative positions of the singularity (the violet line) and χ(T) (the blue line) in the general case. The dashed line indicates the current age of the universe. The constants are β = –0.111113, vr0 = 0.00005, L = 0.001, χin = 0.084, k = –2.5. © Elena Kopteva et al.

Reference: Bormotova, I.; Kopteva, E.; Stuchlík, Z. Geodesic Structure of the Accelerated Stephani Universe. Symmetry 2021, 13, 1001. https://doi.org/10.3390/sym13061001


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Underwater Seismometer Can Hear How Fast A Glacier Moves (Earth Science)

Scientists show that an ocean-bottom seismometer deployed close to the calving front of a glacier in Greenland can detect continuous seismic radiation from a glacier sliding, reminiscent of a slow earthquake.

Basal slip of marine-terminating glaciers controls how fast they discharge ice into the ocean. However, to directly observe such basal motion and determine what controls it is challenging: the calving-front environment is one of the most difficult-to-access environments and seismically noisy — especially on the glacier surface — due to heavily crevassed ice and harsh weather conditions. 

A team of scientists from Hokkaido University, led by Assistant Professor Evgeny A. Podolskiy from the Arctic Research Center, have used ocean-bottom and surface seismometers to detect previously unknown persistent coastal shaking generated by a sliding of a glacier. Their findings were published in the journal Nature Communications.

Sensors to measure glacial motion can potentially be placed on top of, within, or below the glacier; however, each approach has its own drawbacks. For example, the surface of glaciers is ‘noisy’ due to wind and tide-modulated crevassing, which can overwhelm all other signals; while the interior is quieter, it is the hardest area to access. However, all of these locations are plagued by common issues such as station drift, melt out and level loss, cold temperatures, and potential instrument destruction by iceberg calving.

In the current study, the scientists used an ocean-bottom seismometer (OBS) that was deployed near the calving front of Bowdoin Glacier (Kangerluarsuup Sermia) to listen to icequakes caused by glacial basal motion. By doing so, they insulated the sensor from the near-surface seismic noise, and also circumvented all the issues that accompany the deployment of sensors on the glacier itself and nearby. The data they collected from the OBS was correlated with data from seismic and ice-speed measurements at the ice surface.

Key advantages of deploying an ocean-bottom seismometer near the calving front of a tidewater glacier. Subglacial and ocean seismo-acoustic signals can be detected, while the impact of surface seismic sources is minimised (Evgeny A. Podolskiy, Yoshio Murai, Naoya Kanna, Shin Sugiyama. Nature Communications. June 24, 2021).

The analysis of the data revealed that there is a continuous seismic tremor generated by the glacier. In particular, the broad-band seismic signal (3.5 Hz to 14.0 Hz) detected by the OBS correlated well with the movement of the glacier. The scientists were able to identify signals that were not associated with glacial basal dynamics. Data from the OBS were necessary to establish a correlation between tremors detected by the surface stations and GPS-recorded displacement of the glacier. In the process, they demonstrated that continuous seismic data that was historically considered ‘noise’ contains signals that can be used to study glacier dynamics.

The scientists also suggested that glacier slip is similar to slow earthquakes. The characteristics of the Bowdoin-Glacier tremor remind those of tectonic tremors in Japan and Canada. Moreover, the presence of the tremor is in line with recent theoretical models and cold-laboratory experiments.

Evgeny A. Podolskiy, lead author of the study, assembling the ocean-bottom seismometer in Qaanaaq, northwest Greenland, July 2019 (Photo: I. Asaji).

The scientists have presented a novel method to collect continuous glacioseismic information about glacier motion in an extremely noisy and harsh polar environment using ocean-bottom seismology. “Future research in this area could focus on replicating and expanding upon the findings of this study at other glaciers,” says Evgeny A. Podolskiy. “The experimental support for the relationship between glacier tremors and tectonic tremors suggests that a long-term multidisciplinary approach would be beneficial in fully understanding this phenomenon.”

The ocean-bottom seismometer being deployed by the authors and colleagues, 21 July 2019, Bowdoin Fjord (Photo: I. Asaji).

Funding:

This work was supported by the Arctic Challenge for Sustainability research projects (ArCS, JPMXD1300000000; and ArCS-II, JPMXD1420318865) funded by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT); J-ARC Net; Grants-in-Aid for Scientific Research “KAKENHI” (18K18175) from the Japan Society for the Promotion of Science (JSPS);  and the Second Earthquake and Volcano Hazards Observation and Research Programme (Earthquake and Volcano Hazard Reduction Research funded by MEXT).

Featured image: The calving front of Bowdoin Glacier (Photo: Evgeny A. Podolskiy).


Original Article:

Evgeny A. Podolskiy, Yoshio Murai, Naoya Kanna, Shin Sugiyama. Ocean-bottom and surface seismometers reveal continuous glacial tremor and slipNature Communications. June 24, 2021. DOI: 10.1038/s41467-021-24142-4


Provided by Hokkaido University

Innovative Method For Producing Complex Molecules (Chemistry)

FAU team of researchers make a breakthrough in organic chemistry

A team of researchers at the Department of Chemistry and Pharmacy at FAU has successfully solved the problem of finding a straightforward, cost-effective process for producing hexaarylbenzene molecules with six different aromatic rings. These molecules are important functional materials. The results were published in the reputable journal ‘Angewandte Chemie’.

Until now, it has been possible to use certain chemical procedures to produce simple, symmetrical hexaarylbenzene (HAB) molecules, in which the hydrogen atoms of the benzene are replaced by the same atomic groups. However, only very little HAB was produced in this way.

The team of researchers led by Prof. Dr. Svetlana Tsogeva and Prof. Dr. Norbert Jux, both professors of organic chemistry, has now developed a process which even allows asymmetrical HAB with six different aromatic rings around the benzene core to be produced simply and straightforwardly. In an efficient, four-step domino reaction, the researchers produced an initial compound without the aid of – at times toxic – metals, and used this compound to synthesise large quantities of asymmetrical HAB. Controls are carried out throughout the procedure to monitor which atom groups replace the hydrogen atoms of the benzene.

These currently unresearched HAB may be of use for developing innovative liquid crystal materials or for organic electronics.

Featured image: In a straightforward, four-step domino reaction, an initial compound can now be produced without the aid of – at times toxic – metals, and used to synthesise large quantities of asymmetrical HAB. (Image: FAU/Svetlana Tsogoeva)


Reference: Grau, B..W., Dill, M., Hampel, F., Kahnt, A., Jux, N. and Tsogoeva, S..B. (2021), Four-step domino reaction enables fully controlled non-statistical synthesis of hexaarylbenzene with six different aryl groups. Angew. Chem. Int. Ed.. Accepted Author Manuscript. https://doi.org/10.1002/anie.202104437


Provided by FAU

Physicists Build A Landau-Ginzburg Theory For Higher Form Symmetries (Quantum Physics)

Physicists like symmetries. Emmy Noether taught us that symmetries result in conserved quantities. For most “ordinary” symmetries, these conserved quantities are (basically) numbers of particles.

For example, if you have a bunch of atoms in a box, the mathematical description of the box has a certain “symmetry” that enforces the dynamical statement that the number of atoms in the box can’t change, and that you can’t lose an atom!

Now, this is fine if you only care about particles. But, many interesting systems have “extended objects” — e.g. strings — which are also conserved.

“My favorite example is ordinary Maxwell electromagnetism, where magnetic field lines are strings that cannot end.”

— Nabil Iqbal, Theoretical Physicist and Associate Professor at Durham University

What is the symmetry principle enforcing the conservation of higher dimensional objects? Nowadays, we call these “higher form symmetries”, and they were explained by Davide Gaiotto and colleagues in their 2014 paper, that influenced Nabil Iqbal’s research greatly.

“The upshot is that, if you ever have extended objects that can’t break or vanish — gauge theory flux tubes, cosmic strings, magnetic field lines — you probably have one of these higher-form symmetries playing an important role.”

— told Nabil Iqbal

The idea behind higher-form symmetries is simple: just as ordinary global symmetries result in conservation laws for particles, theories that are invariant under higher-form global symmetries possess conservation laws for extended objects, such as strings or flux tubes.

“We can now try and use these new symmetries to organize our understanding. In the recent work with John, we build a Landau-Ginzburg theory for such symmetries, where we try and describe the physics close to a point where one of these symmetries is” “about” to break.”

— told Nabil Iqbal

Just as normal Landau-Ginzburg theories describe the condensation of particles, this new framework has to describe the condensation of “strings”. This is complicated but fun, and they tried to get a grasp of it using these new symmetries and principles of effective field theory.

“By the way, these are “not” gauge symmetries; gauge “symmetry” is perhaps a lousy name for something that is not really a symmetry at all. But a lot of gauge theories happen to host extended objects, and so can be nicely understood in this framework.”

If you wanna know more, just check out the video given below, Nabil Iqbal have given some online talks on it.


For more:

Nabil Iqbal, John McGreevy, “Mean string field theory: Landau-Ginzburg theory for 1-form symmetries”, Arxiv, pp. 1-47, 2021.
arXiv:2106.12610


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Matter Highway in Space Makes Galaxy Clusters Grow (Cosmology)

Study led by the University of Bonn delivers images in unprecedented detail

Six months ago, astronomers at the University of Bonn reported the discovery of an extremely long intergalactic gas filament with the X-ray telescope eROSITA. In a new study, they have now focused on an interesting structure in the filament, the northern clump. Their new observational data prove that this is a cluster of galaxies with a black hole at its center. The gas filament is therefore a galactic matter highway: The northern clump is moving along it towards two more giant galaxy clusters and will eventually merge with them. The paper will be published in the journal Astronomy & Astrophysics, along with other papers published on the occasion of the first eROSITA data release.

The universe resembles a Swiss cheese – but one with huge holes: Large areas in space are absolutely empty. In between, thousands of galaxies crowd in a comparatively small space. These clusters are connected by highways of thin matter gas, like the gossamer filaments of a spider’s web.

At least, this is what the standard model of cosmology predicts. Whether this is actually the case was hard to prove until recently. This is because the matter in the gas filaments is so diluted that it eluded the view of even the most sensitive measuring instruments: The filaments contain just ten particles per cubic meter, which is far fewer than are present in the best vacuum that humans can produce.

This is why a study led by the University of Bonn caused such a stir last winter. The researchers had discovered an intergalactic gas filament measuring at least 50 million light years in length that emanates from two giant galaxy clusters. “There is another galaxy cluster in this filament, the northern clump,” explains Prof. Dr. Thomas Reiprich of the Argelander Institute for Astronomy at the University of Bonn. “In the paper now submitted for publication, we have taken a closer look at this.”

Bow shock and matter tail

To do this, the researchers combined images from several sources: the SRG/eROSITA, XMM-Newton and Chandra satellites, as well as the EMU survey with the ASKAP radio telescope and DECam optical data. The resulting images have a richness of detail never seen before. “This allows us to identify a large galaxy at the center of the northern clump,” says Reiprich’s colleague and lead author of the study, Angie Veronica. “And at its center sits a supermassive black hole.” Two so-called matter jets emanate from it, in which the particles move away from the black hole at close to the speed of light. This produces synchrotron radiation, which can be visualized in the radio telescope images.

In addition, the northern clump contains very hot matter gas. “Because of its high temperature of 20 million degrees, it emits X-rays, which we see in the eROSITA images and have now been able to measure very precisely with the XMM-Newton satellite,” says Veronica. Overall, the combination of data sources indicates that the northern clump is likely moving at high velocity. The jets of matter emanating from the black hole point backward like the braids of a running girl; in front of the clump the gas additionally seems to form a kind of bow shock. “We also see a matter tail behind it,” Reiprich explains. “We currently interpret this observation to mean that the northern clump is losing matter as it travels. However, it could also be the case that even smaller clumps of matter in the highway are falling towards the northern clump.”

Overall, the observations confirm the view derived from theories that the gas filament is an intergalactic matter highway. The northern clump is moving along this road at high speed toward two other much larger clusters of galaxies called Abell 3391 and Abell 3395. “It falls on these piles, so to speak, and will continue to make them bigger – according to the principle: Whoever has will be given more,” explains Reiprich, who is also a member of the transdisciplinary research area “Building Blocks of Matter” at the University of Bonn. “What we’re seeing is a snapshot of this fall.”

Observations consistent with theoretical predictions

The observations are remarkably consistent with the result of the Magneticum computer simulations developed by researchers of the eROSITA consortium. They can therefore also be taken as an argument that the current assumptions about the origin and evolution of the universe are correct. This includes the thesis that a large part of matter is invisible to our measuring instruments. 85 percent of the matter in our universe is said to consist of this “dark matter”. One of its most important roles in the standard model of cosmology is as a condensation nucleus, which caused gaseous matter to condense into galaxies after the Big Bang.

Participating institutions and funding:

More than 20 scientists from Germany, Italy, the USA and Australia were involved in the study. eROSITA was developed with funding from the Max Planck Society and the German Aerospace Center (DLR). The current study was funded by the German Research Foundation (DFG).

Featured image: The northern clump – as it appears in X-rays (blue, XMM-Newton satellite), in visual light (green, DECam), and at radio wavelengths (red, ASKAP/EMU).© Veronica et al., Astronomy & Astrophysics


Publication: Angie Veronica et al: The eROSITA View of the Abell 3391/95 Field: The Northern Clump. The Largest Infalling Structure in the Longest Known Gas Filament Observed with eROSITA, XMM-Newton, Chandra. Astronomy & Astrophysics, the article will appear in the Astronomy & Astrophysics Special Issue: The Early Data Release of eROSITA and Mikhail Pavlinsky ART-XC on the SRG Mission, in advance on http://arxiv.org/abs/2106.14543


Provided by University of Bonn

Life Could Exist in the Clouds of Jupiter But Not Venus (Planetary Science)

Jupiter’s clouds have water conditions that would allow Earth-like life to exist, but this isn’t possible in Venus’ clouds, according to the groundbreaking finding of new research led by a Queen’s University Belfast scientist with participation of the University of Bonn. The study has been published in the journal Nature Astronomy.

For some decades, space exploration missions have looked for evidence of life beyond Earth where we know that large bodies of water, such as lakes or oceans, exist or have previously existed. However, the new research shows that it isn’t the quantity of water that matters for making life viable, but the effective concentration of water molecules – known as ‘water activity’.

The new study also found that research published by an independent team of scientists last year, claiming that the phosphine gas in Venus’ atmosphere indicates possible life in the sulphuric acid clouds of Venus, is not plausible.

Through this innovative research project, Dr John E. Hallsworth from the School of Biological Sciences at Queen’s and his team of international collaborators devised a method to determine the water activity of atmospheres of a planet. Using their approach to study the sulphuric acid clouds of Venus, the researchers found that the water activity was more than a hundred times below the lower limit at which life can exist on Earth.

Dr Hallsworth comments: “Our research shows that the sulphuric acid clouds in Venus have too little water for active life to exist, based on what we know of life on Earth. We have also found that the conditions of water and temperature within Jupiter’s clouds could allow microbial-type life to subsist, assuming that other requirements such as nutrients are present.”

Co-author of the report, an expert on physics and chemical biology of water, Dr Philip Ball, says: “The search for extraterrestrial life has sometimes been a bit simplistic in its attitude to water. As our work shows, it’s not enough to say that liquid water equates with habitability. We’ve got to think too about how Earth-like organisms actually use it – which shows us that we then have to ask how much of the water is actually available for those biological uses.” 

A plant scientist in extraterrestrial spheres

Dr Jürgen Burkhardt of the Institute of Crop Science and Resource Conservation (INRES), a member of the Phenorob Cluster of Excellence and the Transdisciplinary Research Area “Innovation and Technology for Sustainable Futures” at the University of Bonn, contributed to this study primarily by making calculations of water activity and sulphuric acid concentration in the cloud droplets of the Venusian atmosphere. The fact that a scientist researching plant nutrition is contributing to Life in the Venus Atmosphere is due to Dr Burkhardt’s earlier work. He had previously used the aerosol model used in the study to characterize the state of deposited hygroscopic aerosols on leaf surfaces.

Dr. Jürgen Burkhardt – from the Institute of Crop Science and Resource Conservation (INRES) at the University of Bonn.© Photo: Maximilian Meyer

“These aerosols allow microorganisms to survive under certain conditions,” Burkhardt says. A shared interest in this habitat and its very specific physicochemical conditions, such as high acid concentrations and minimal amounts of water, led to contact years ago with the study’s first author, John Hallsworth. Experimental electron microscopy studies by Hallsworth and Burkhardt on this topic had already resulted in two earlier joint publications that also addressed the question of extraterrestrial life.

Participating institutions and funding:

Co-authors of this paper include planetary scientist Christopher P. McKay (NASA Ames Research Center, CA, USA); atmosphere chemistry expert Thomas Koop (Bielefeld University, Germany); expert on physics and chemical biology of water Philip Ball (London, UK); biomolecular scientist Tiffany D. Dallas (Queen’s University Belfast); biophysics-of-lipid-membrane expert Marcus K. Dymond (University of Brighton, UK); theoretical physicist María-Paz Zorzano (Centro de Astrobiologia [CSIC-INTA], Spain); micrometeorology and aerosol expert Juergen Burkhardt (University of Bonn, Germany); expert on acid-tolerant microorganisms Olga V. Golyshina (Bangor University, UK); and atmospheric physicist and planetary scientist Javier Martín-Torres (University of Aberdeen, UK).

The research was funded by Research Councils UK (RCUK) | Biotechnology and Biological Sciences Research Council (BBSRC) and Ministry of Science and Innovation.

Featured image: Thunderclouds on Jupiter – based on images from the Juno mission’s Stellar Reference Unit camera (NASA).© NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstädt/Heidi N. Becker/Koji Kuramura


Publication: John E. Hallsworth et al.: Water activity in Venus’s uninhabitable clouds and other planetary atmospheres, Nature Astronomy, DOI: 10.1038/s41550-021-01391-3


Provided by University of Bonn

CARMENES Instrument Finds Two New Planetary Systems Formed by Earths and Super-Earths (Planetary Science)

The Institute of Astrophysics of Andalusia (IAA-CSIC) leads the detection of what, according to the data, is the most common type of planetary systems around dwarf stars, the most common in the Milky Way

The era of the detection of planets outside our Solar System, which began less than three decades ago, has so far yielded more than four thousand detected planets. Their astonishing variety has shown that the structure of our Solar System, with rocky planets in the inner regions and gaseous icy planets in the outer regions, is not as typical as previously thought, and that other configurations appear more common, such as gas giant planets very close to their stars or systems with several super-Earths around dwarf stars. In this context, a new detection of two planetary systems by the CARMENES instrument, operating at Calar Alto Observatory (CAHA, Almería), reinforces the idea that dwarf stars tend to harbour rocky planets.

The 3.5-metre telescope at Calar Alto Observatory, where the CARMENES instrument operates. © IAA CSIC

“Our current understanding of the formation of low-mass planets in orbits very close to small stars suggests that they are very abundant, with an average of at least one planet per star. Despite this abundance, we hardly have any data on the density of these planets that would allow us to deduce their composition,” says Pedro J. Amado, a researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) who heads the study.

In our Solar System, Earth, Mars, Mercury and Venus are categorised as terrestrial or rocky planets. For extrasolar planets, those between half and twice the size of Earth are considered to be terrestrial, while those up to ten times the mass of Earth are classified as super-Earths, terms that have no implications for surface conditions or habitability. In fact, while the composition of Earth-like exoplanets may be similar to that of the rocky planets in the Solar System, the composition of super-Earths may also include other combinations of gas, rock, ice or water. 

The newly detected systems are found around the red dwarf (or M-dwarf) stars G 264-012 and Gl 393. Two planets with a minimum mass of 2.5 and 3.8 times that of the Earth have been found around the former, orbiting their star every 2.3 and 8.1 days. The planet in Gl 393 has a minimum mass of 1.7 Earth masses and orbits its star every seven days. All three planets fall into the category of hot earths and super-earths, and reach temperatures that preclude the presence of liquid water on the surface.

“To understand how the different planetary systems we are observing form and evolve, we need robust statistics on the number of planets that exist, as well as information on the architecture of the systems and the density of the planets. This will allow us to explain those that do not fit the known mechanisms, such as the GJ 3512 system that we also found with CARMENES, which has a giant planet around a dwarf star, or to confirm the tendency of dwarf stars to host multiple systems,” says Pedro J. Amado (IAA-CSIC).

In this sense, this work has also made it possible to detect a new factor that seems to influence the detections, since the planet around the star Gl 393 had gone unnoticed in previous campaigns with highly efficient planet-hunting instruments. Red dwarf stars show intense activity in the form of flares that can mask the signal from potential planets, and the research team noted that the non-detection of Gl 393’s planet could be due to the fact that previous observations were carried out during a peak of activity. They concluded that planets can most easily be detected in dwarf stars with moderate activity or outside the peaks of the star’s activity cycle.

“The CARMENES work is focused on extending the available data to compose a global picture of the planetary systems. The three planets in these two systems are among the smallest in mass, and therefore in the amplitude of the radial velocity they instill in their stars, which accounts for the quality of the instrument,” concludes Pedro J. Amado (IAA-CSIC).


Reference: P. J. Amado et al. “The CARMENES search for exoplanets around M dwarfs. Two terrestrial planets orbiting G264-012 and one terrestrial planet orbiting Gl393”. Astronomy & Astrophysics, https://doi.org/10.1051/0004-6361/202140633, June 2021


Provided by IAA CSIC

Blocking Communication Key To Supporting Proper Communication in the Brain (Neuroscience)

Recall a phone number or directions just recited and your brain will be actively communicating across many regions. However, as discovered by researchers at Baylor College of Medicine, those areas that are in constant communication during this process are not necessarily relying on those interactions to coordinate coherent memory.

The findings, published in the journal Cell, showed that communication is turned off between frontal cortical regions in mouse models when one region is disrupted, all without affecting memory or behavior. Researchers say this shows that each area behaves as separate entities with its own copy of information, supporting the idea that this modular organization is critical to persistent neural activity.

“Frontal cortex neurons are persistently active when we remember specific things. It has been known for many years that this persistent activity is distributed across multiple brain regions, and it is thought that working memory relies on interactions between these regions,” said Dr. Nuo Li, assistant professor of neuroscience and a McNair Scholar at Baylor. “How these brain regions interact and properly represent memory has remained a mystery.”

Li and his colleagues were able to see that each hemisphere of the brain has a separate representation of a memory, but they are tightly coordinated on a moment-to-moment basis, resulting in highly coherent information across the hemispheres during working memory. In their study, the researchers engaged mice in simple behavior that would require them to store specific information. They were trained to delay an instructed action for a few seconds. This time delay gave researchers the chance to look at brain activity during the memory process.

“We saw many neurons simultaneously firing from both hemispheres of the cortex in a coordinated fashion. If activity went up in one region, the other region followed closely. We hypothesized that the interactions between brain hemispheres is what was responsible for this memory.”

Li and his colleagues recorded activity in each hemisphere, showing that each one made its own copy of information during the memory process. So how are the two hemispheres communicating?

Li explained that through the use of optogenetics they were able to corrupt information in a single hemisphere, affecting thousands of neurons during the memory period. What they found was unexpected.

“When we disrupted one hemisphere, the other area turned off communication, so it basically prevents the corruption from spreading and affecting activity in other regions,” Li said. “This is similar to modern networks such as electricity grids. They are connected to allow for the flow of electricity but also monitor for faults, shutting down connections when necessary so the entire electrical grid doesn’t fail.”

Through a collaboration with Dr. Shaul Druckmann and Ph.D. student Byungwoo Kang at Stanford University, theoretical analysis and network simulations of this process were created, showing that this modular organization in the brain is critical for the robustness of persistent neural activity. This robustness could be responsible for the brain being able to withstand certain injuries, protecting cognitive function from distractions.

“Understanding redundant modular organization of the brain will be important for designing neural modulation and repair strategies that are compatible with the brain’s natural processing of information,” Li said.

Others who took part in the study include the lead author Guang Chen with Baylor, Jack Lindsey with Stanford University.

Funding for this study was supported by the NIH NINDS and BRAIN Initiative grants (NS112312, NS104781, NS113110, EB02871), the Simons Collaboration on the Global Brain, and the Robert and Janice McNair Foundation. Further support was provided by the Whitehall Foundation, Alfred P. Sloan Foundation, Searle Scholars Program, Pew Scholars Program, and McKnight Foundation.


Reference: Guang Chen, Byungwoo Kang, Jack Lindsey, Shaul Druckmann, Nuo Li, Modularity and robustness of frontal cortical networks, Cell, 2021, , ISSN 0092-8674, https://doi.org/10.1016/j.cell.2021.05.026. (https://www.sciencedirect.com/science/article/pii/S0092867421006565)


Provided by BCM

Flavanols & Dihydroflavonols Inhibit The MPro Activity of SARS-CoV-2 and the Replication of HCoV-229E (Botany)

Human coronavirus 229E (HCoV-229E) is a pathogenic virus in the genus Alpha coronavirus which causes the common cold. The main protease (Mpro) is an essential enzyme required for the multiplication of SARS-CoV-2 and HCoV-229E viruses in the host cells, and thus is an appropriate candidate to screen potential medicinal compounds. Now, Dr. De-Yu Xie and colleagues investigated whether Flavonols and dihydroflavonols, two groups of plant flavonoids can effectively prevent SARS-CoV-2 infection or not. They found that the Flavanols and dihydroflavonols inhibit the main protease activity of SARS-CoV-2 and the replication of human coronaviruses 229 E. Their study recently appeared in BioRxiv.

SARS-CoV-2 is the virus that causes COVID-19, the respiratory illness responsible for the current COVID-19 pandemic. Although, there are many vaccines available in the developed countries to prevent the infection of this virus, there is an urgent need of medicine which can help us control COVID-19 effectively.

Quercetin, kaempferol, and myricetin are three flavonol molecules widely existing in plants. Likewise, dihydroquercetin, dihydrokaempferol, and dihydromyricetin are three dihydroflavonol molecules in plants. In general, flavonols and dihydroflavonols are strong antioxidants with multiple benefits to human health. While, Quercetin is a plant pigment (flavonoid), which have antiviral activity.

In their study, Dr. De-Yu Xie and colleagues hypothesized that flavonols and dihydroflavonols might inhibit the main protease activity of SARS-CoV-2 and HCoV-229E and tested this hypothesis by performing docking simulation for 3 dihydroflavonols (dihydroquercetin, dihydrokaempferol, and dihydromyricetin), 3 flavonols (Quercetin, kaempferol, and myricetin) and 2 glycosylated Quercetins. They also tested these compounds inhibition against the recombinant main protease activity of SARS-CoV-2 in vitro.

Their docking simulation results predicted that dihydrokaempferol, dihydroquercetin, dihydromyricetin, kaempferol, quercetin, myricentin, isoquercetin, and rutin could bind to at least two subsites (S1, S1′, S2, and S4) in the binding pocket and inhibit the activity of SARS-CoV-2 main protease. Their affinity scores ranged from -8.8 to -7.4.

Table 1. Affinity scores of 11 compounds binding to the main proteases of SARS-CoV-2 and HuCoV-229E © De-Yu Xie et al

Likewise, these compounds were predicted to bind and inhibit the HCoV-229E main protease activity with affinity scores ranging from -7.1 to -7.8.

Moreover, In vitro inhibition assays showed that seven available compounds i.e. dihydroquercetin, dihydromyricetin, kaempferol, quercetin, myricentin, isoquercetin, and rutin, effectively inhibited the SARS-CoV-2 main protease activity and their IC50 values ranged from 0.125 to 12.9 uM.

Finally, they tested inhibitory effects of five compounds i.e. Quercetin, isoquercetin, taxifolin, epigallocatechin gallate (EGCG) and epicatechin, on the replication of HCoV-229E in Huh-7 cells. Their resulting data indicated that all five compounds showed an inhibition against the replication of HCoV-229E in Huh-7 cells.

Based on TCID50/ml values, taxifolin started to show its inhibition at 2.5 µM and its inhibitory activity increased as its concentration was increased. Quercetin started to have inhibition at 5 µM. As its concentrations were increased, its inhibitive activities were more effective. At a concentration tested higher 10 µM, quercetin could strongly inhibit the replication of the virus. Its EC50 value was estimated to be 4.88 µM. Isoquercitrin strongly inhibited the replication starting with 2.5 µM. EGCG started to show its inhibition against the replication of the virus at 2.5 µM and its inhibition became stronger as its concentrations were increased. Moreover, epicatechin could strongly inhibit the replication starting at 20 µM.

Their findings indicated that these antioxidative flavonols and dihydroflavonols are promising candidates for curbing the two viruses.

Featured image: Ligand-receptor docking modeling showing the binding of eleven compounds to the substrate pocket of the SARS-CoV-2 main protease (Mpro). The first image shows the 3D surface view of the SARS-CoV-2 Mpro, on which the red rectangular frame indicates the substrate-binding pocket. Eleven flavonoids and ebselen bind to this pocket. Two flavan-3-ols: (+)-catechin (CA) and (-)-epicatechin (EC); three dihydroflavonol aglycones:(+)-dihydroquercetin (DHQ), (+)-dihydrokaempferol (DHK), and (+)-dihydroquercetin (DHM); three flavonols aglycones, kaempferol, quercetin, and myricetin; two glycosylated flavonols: quercetin-3-O-glycoside (isoquercitrin), and rutin. © De-Yu Xie et al.


Reference: Yue Zhu, Frank Scholle, Samantha C. Kisthardt, Deyu Xie, “Flavonols and dihydroflavonols inhibit the main protease activity of SARS-CoV-2 and the replication of human coronavirus 229E”, bioRxiv 2021.07.01.450756; doi: https://doi.org/10.1101/2021.07.01.450756


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