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Comment by Dr. Krishna Kumari Challa on June 1, 2024 at 10:33am

They calculated stellar populations without and with the presence of dark matter. With dark matter, more massive stars experienced a lower dark matter density, and hydrogen in their core fused more slowly and their evolution was slowed down. But stars in a higher dark matter density region were changed significantly—they maintained equilibrium through dark matter burning with less fusion or no fusion, which led to a new stellar population in an HR region above the main sequence.
The scientists' simulations show that stars can survive on dark matter as a fuel alone and because there is an extremely large amount of dark matter near the Galactic Center, these stars become immortal staying forever young, occupying a new, distinct, observable region of the HR diagram.
Their dark matter model may be able to explain more of the known mysteries. For lighter stars, scientists saw in their simulations that they become very puffy and might even lose parts of their outer layers something similar to this might be observed at the Galactic Center: the so-called G-objects, which might be star-like, but with a gas cloud around them.
There are a limited number of individual stars known to exist so close to the Galactic Center, as the region is extremely bright. Upcoming 30-meter telescopes will be able to see much better into the region, which will allow scientists to better understand the population of its stars and verify or rule out the dark main sequence.

Isabelle John et al, Dark Branches of Immortal Stars at the Galactic Center, arXiv (2024). DOI: 10.48550/arxiv.2405.12267

Part 3

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Comment by Dr. Krishna Kumari Challa on June 1, 2024 at 10:29am

Stars are nuclear ovens, generating heat burning hydrogen via nuclear fusion. The thermal radiation from this reaction, as well as thermodynamic convection of the stellar plasma, exerts an outward force on a star's constituents—mostly hydrogen and helium. That force is balanced by the inward force of self-gravity.

The Hertzsprung–Russell (HR) diagram classifies stars by plotting their luminosity against the effective temperature of their surface. Excluding white dwarfs and red giants, the "main sequence" of this diagram curves from its upper left to lower right, and most stars fall on this curve. (The sun falls near the middle, as their luminosities are plotted as their ratio with the sun's). Stars in different locations on the sequence correspond to stars of different masses and ages.

However, dark matter also exists in the galaxy. Its presence has been inferred by observations that find insufficient ordinary matter to account for the higher-than-expected rotational speeds of stars around the Galactic Center.

Dark matter's density is highest near the center and falls off with the distance from it. It's reasonable to expect it would be incorporated within stars near the center, where dark matter is densest. If so, dark matter annihilation—dark matter particles and antiparticles that collide and produce photons, electrons, etc.—would exert an additional outward pressure within a star and could even dominate over nuclear fusion.
A research team has found that incorporating dark matter power into the dynamics of the innermost stars—those within about a third of a light-year of the center (equivalent to about 8% of the distance to the sun's nearest star)—solves many of the known paradoxes.
To incorporate dark matter annihilation, the group used relatively standard star formation parameters over the evolutionary course of the Milky Way, and dark matter particles just slightly more massive than the proton. Using a stellar evolution computer model, they assumed that stars migrate on the main sequence towards the Galactic Center, then they began to inject dark matter energy into a star's composition. The star then evolved until it reached the red giant branch on the HR diagram, or until it reached an age of 10 billion years, the lifetime of the Milky Way.
Part 2

Comment by Dr. Krishna Kumari Challa on June 1, 2024 at 10:26am

Dark matter could make our galaxy's innermost stars immortal

Stars near the center of our galaxy are acting kind of weird. Dark matter may be the explanation.

A team of scientists have discovered a potential new class of stars that could exist within a light-year of the Milky Way's center that could be operating according to an unusual mechanism: dark matter annihilation. This process would produce an outward pressure on the stars other than hydrogen fusion, keeping them from gravitationally collapsing—and making them essentially immortal, their youth being refreshed constantly. The findings are published  on the arXiv preprint server.

Collectively, the dark matter–powered stars would inhabit a new region of a long-established diagram that classifies stars by their temperature and luminosity, placing them away from the so-called main sequence where the vast majority of stars exist.

Observing our Galactic Center, around which the galaxy's stars rotate, is quite difficult, as the region is extremely bright. A supermassive black hole, Sagittarius A*, sits at the center, with a mass four million times that of the sun. It is a bright source of radio waves, and was imaged in 2022. Stars near Sgr A* orbit it at speeds of several thousands of kilometers per second (compared to the sun's orbital speed of 240 km/s).
These close inner stars, called S-cluster stars, are very puzzling, with properties unlike any others in the Milky Way. Their provenance is unknown, since the environment within about three light-years of the center is considered hostile to star formation. They appear to be much younger than would be expected if they had moved inward from someplace else. Most mysterious of all, they look unusually young, with fewer older stars in the neighborhood than expected, and also unexpectedly, there seem to be many heavy stars.
Part 1

Comment by Dr. Krishna Kumari Challa on June 1, 2024 at 10:19am

This tiny fern has the largest genome of any organism on Earth

In a new study published in the journal iScience, researchers  presented a new record-holder for the largest amount of DNA stored in the nucleus of any living organism on the planet.

Coming in at more than 100 meters of unraveled DNA, the New Caledonian fork fern species Tmesipteris oblanceolata was found to contain more than 50 times more DNA than humans and has dethroned the Japanese flowering plant species Paris japonica, which has held this record since 2010.

In addition, the plant has achieved three Guinness World Records titles for Largest plant genome, Largest Genome, and Largest fern genome for the amount of DNA in the nucleus.

T. oblanceolata is a rare species of fern found on the island nation of New Caledonia, an overseas French territory situated in the Southwest Pacific, about 750 miles east of Australia, and some of the neighboring islands such as Vanuatu. The genus Tmesipteris is an understudied group of plants consisting of about 15 species, most of which occur across a range of Pacific Islands and Oceania.

Until now, scientists have only estimated the size of the genomes for two species of Tmesipteris—T. tannensis and T. obliqua—both of which were found to contain gigantic genomes, at 73.19 and 147.29 gigabase pairs (Gbp) respectively.

The analysis revealed the species T. oblanceolata to have a record-breaking genome size of 160.45 Gbp, which is about 7% larger than that of P. japonica (148.89 Gbp).

Tmesipteris is a unique and fascinating small genus of ferns, whose ancestors evolved about 350 million years ago—well before dinosaurs set foot on Earth—and it is distinguished by its mainly epiphytic habit [it grows mainly on the trunks and branches of trees] and restricted distribution in Oceania and several Pacific Islands.

 Oriane Hidalgo and Jaume Pellicer et al, A 160 Gbp fork fern genome shatters size record for eukaryotes. iScience (2024). DOI: 10.1016/j.isci.2024.109889

Comment by Dr. Krishna Kumari Challa on May 31, 2024 at 11:20am

‘Smart’ antibiotic can kill deadly bacteria while sparing the microbiome

We need our microbiome. But if we take antibiotics, they will disrupt it. 

Now scientists found that a compound called lolamicin targets a group of harmful microbes but does not disturb those that live peacefully in the gut.

Scientists have developed an antibiotic that kills pathogenic Gram-negative bacteria — even those resistant to many other drugs — without impairing the gut microbiome. So far, it has been studied only in mice, but if the compound works in humans, “it could help us dramatically".
However, there is a caveat: the compound’s usefulness “depends on whether bacteria will develop resistance to it in the long run”.
To find a way around the bacteria’s defences, the study’s authors started with compounds that don’t kill the bacteria but are known to inhibit the ‘Lol system’, a group of proteins that is exclusive to Gram-negative bacteria. Tinkering with those compounds produced one that the researchers called lolamicin, which “selectively kills pathogenic bacteria over non-pathogenic bacteria based on differences in Lol proteins between these bacteria.
Lolamicin had anti-microbial effects against more than 130 multidrug-resistant strains of bacteria growing in laboratory dishes.
Mice that developed blood stream infections after exposure to antibiotic-resistant bacteria all survived after being given lolamicin, whereas 87% of those that didn’t receive the compound died within three days.

https://www.nature.com/articles/d41586-024-01566-8?utm_source=Live+...

Comment by Dr. Krishna Kumari Challa on May 31, 2024 at 9:19am

New method advances cancer detection by counting tiny blood-circulating particles

Researcher are reporting a new method to detect cancer which could make cancer detection as simple as taking a blood test. With a 98.7% accuracy rate, the method—which combines PANORAMA imaging with fluorescent imaging—has the potential to detect cancer at the earliest stage and improve treatment efficacy.

The remarkably precise method allows researchers to peer into nanometer-sized membrane sacs, called extracellular vesicles or EVs, that can carry different types of cargos, like proteins, nucleic acids and metabolites, in the bloodstream.

The researchers  observed differences in small EV numbers and cargo in samples taken from healthy people versus people with cancer and are able to differentiate these two populations based on their analysis of the small EVs. The findings came from combining two imaging methods—their previously developed method PANORAMA and imaging of fluorescence emitted by small EVs—to visualize and count small EVs, determine their size and analyze their cargo.

For this research it was a matter of counting the number of small EVs to detect cancer.

Using a cutoff of 70 normalized small EV counts, all cancer samples from 205 patients were above this threshold except for one sample, and for healthy samples, from 106 healthy individuals, all but three were above this cutoff, giving a cancer detection sensitivity of 99.5% and specificity of 97.3%.

To further test the performance of the detection threshold of 70 normalized small EV counts in plasma, the team analyzed two independent sets of samples from stage I-IV or recurrent leiomyosarcoma/gastrointestinal stromal tumors and early-and-late-stage cholangiocarcinoma that were anonymously labeled and mixed in with healthy samples and achieved 100% accuracy.

Nareg Ohannesian et al, Plasmonic nano-aperture label-free imaging of single small extracellular vesicles for cancer detection, Communications Medicine (2024). DOI: 10.1038/s43856-024-00514-x

Comment by Dr. Krishna Kumari Challa on May 31, 2024 at 9:07am

Scientists create the thinnest lens on Earth, enabled by excitons

Lenses are used to bend and focus light. Normal lenses rely on their curved shape to achieve this effect, but physicists have made a flat lens of only three atoms thick that relies on quantum effects. This type of lens could be used in future augmented reality glasses.

Curved-glass lenses work because light is refracted (bent) when it enters the glass, and again when it exits, making things appear larger or closer than they actually are.

Using a single layer of a unique material called tungsten disulfide (WS₂ for short), researchers constructed a flat lens that is half a millimeter wide, but just 0.0000006 millimeters, or 0.6 nanometers, thick. This makes it the thinnest lens on Earth.

Rather than relying on a curved shape, the lens is made of concentric rings of WS₂ with gaps in between. This is called a "Fresnel lens" or "zone plate lens," and it focuses light using diffraction rather than refraction. The size of, and distance between the rings (compared to the wavelength of the light hitting it) determines the lens's focal length. The design used here focuses red light 1 mm from the lens.

A unique feature of this lens is that its focusing efficiency relies on quantum effects within WS2. These effects allow the material to efficiently absorb and re-emit light at specific wavelengths, giving the lens the built-in ability to work better for these wavelengths.
This quantum enhancement works as follows. First, WS2 absorbs light by sending an electron to a higher energy level. Due to the ultra-thin structure of the material, the negatively charged electron and the positively charged "hole" it leaves behind in the atomic lattice stay bound together by the electrostatic attraction between them, forming what is known as an "exciton."
These excitons quickly disappear again by the electron and hole merging together and sending out light. This re-emitted light contributes to the lens's efficiency.
The scientists detected a clear peak in lens efficiency for the specific wavelengths of light sent out by the excitons. While the effect is already observed at room temperature, the lenses are even more efficient when cooled down. This is because excitons do their work better at lower temperatures.

Ludovica Guarneri et al, Temperature-Dependent Excitonic Light Manipulation with Atomically Thin Optical Elements, Nano Letters (2024). DOI: 10.1021/acs.nanolett.4c00694

Comment by Dr. Krishna Kumari Challa on May 31, 2024 at 6:58am

How does the word 'not' affect what we understand? Scientists find negation mitigates our interpretation of phrases

When we're told "This coffee is hot" upon being served a familiar caffeinated beverage at our local diner or cafe, the message is clear. But what about when we're told "This coffee is not hot"? Does that mean we think it's cold? Or room temperature? Or just warm?

A team of scientists has now identified how our brains work to process phrases that include negation (i.e., "not"), revealing that it mitigates rather than inverts meaning—in other words, in our minds, negation merely reduces the temperature of our coffee and does not make it "cold."

We now have a firmer sense of how negation operates as we try to make sense of the phrases we process.

In identifying that negation serves as a mitigator of adjectives—bad or good, sad or happy, and cold or hot—we also have a better understanding of how the brain functions to interpret subtle changes in meaning.

In an array of communications, ranging from advertising to legal filings, negation is often used intentionally to mask a clear understanding of a phrase. In addition, large language models in AI tools have difficulty interpreting passages containing negation. The researchers say that their results show how humans process such phrases while also potentially pointing to ways to understand and improve AI functionality.

This research spotlights the complexity that goes into language comprehension, showing that this cognitive process goes above and beyond the sum of the processing of individual word meanings.

Find the full details of the experimental work here: Zuanazzi A, Ripollés P, Lin WM, Gwilliams L, King J-R, Poeppel D, Negation mitigates rather than inverts the neural representations of adjectives. PLoS Biology (2024). DOI: 10.1371/journal.pbio.3002622

Comment by Dr. Krishna Kumari Challa on May 31, 2024 at 6:51am

Reduced sulfur content in shipping fuel associated with increased maritime atmospheric warming

An 80% reduction in sulfur dioxide shipping emissions observed in early 2020 could be associated with substantial atmospheric warming over some ocean regions, according to a modeling study published in Communications Earth & Environment. The sudden decline in emissions was a result of the introduction of the International Maritime Organization's 2020 regulation (IMO 2020), which reduced the maximum sulfur content allowed in shipping fuel from 3.5% to 0.5% to help reduce air pollution.

Fuel oil used for large ships has a significantly higher percentage content of sulfur than fuels used in other vehicles. Burning this fuel produces sulfur dioxide, which reacts with water vapor in the atmosphere to produce sulfate aerosols. These aerosols cool the Earth's surface in two ways: by directly reflecting sunlight back to space; and by affecting cloud cover.

Increasing the number of aerosols increases the number of water droplets that form while reducing their size, both increasing the cloud coverage and forming brighter clouds which reflect more sunlight back to space. Marine cloud brightening is a form of geoengineering where marine clouds are deliberately seeded with aerosols to achieve this effect.

Researchers  calculated the effect of IMO 2020 on the atmospheric levels of sulfate aerosols over the ocean and how this affected cloud composition. They found substantial reductions in both the levels of atmospheric aerosols and the cloud droplet number density.

The greatest modeled aerosol reductions were in the North Atlantic, the Caribbean Sea, and the South China Sea—the regions with the busiest shipping lanes. The authors then estimated the effect of IMO 2020 on Earth's energy budget (the difference between the energy received from the sun and the energy radiated from the Earth) since 2020. They calculated that the estimated effect is equivalent to 80% of the observed increase in the heat energy retained on Earth over that period.

The authors suggest that the substantial modeled effect of IMO 2020 on Earth's energy budget demonstrates the potential effectiveness of marine cloud brightening as a strategy to temporarily cool the climate. However, they also warn that the intended reduction in sulfur dioxide emissions due to IMO 2020 potentially causing an inadvertent increase in marine atmospheric temperature is an example of a geoengineering termination shock, which could affect regional weather patterns.

Tianle Yuan, Abrupt reduction in shipping emission as an inadvertent geoengineering termination shock produces substantial radiative warming, Communications Earth & Environment (2024). DOI: 10.1038/s43247-024-01442-3. www.nature.com/articles/s43247-024-01442-3

Comment by Dr. Krishna Kumari Challa on May 31, 2024 at 6:44am

Antibiotic pollution disrupts the gut microbiome and blocks memory in aquatic snails, study finds

Antibiotics prevent snails from forming new memories by disrupting their gut microbiome—the community of beneficial bacteria found in their guts.

The new research highlights the damaging effects that human pollution could be having on aquatic wildlife.

In the study published in The ISME Journal, pond snails were given a favorite food—carrot juice—but had to quickly learn and remember that it was no longer safe to eat.

Snails in clean water did well, avoiding feeding on the carrot juice when it had been paired with a chemical they dislike. However, snails that had been exposed to high concentrations of antibiotics in the water failed to learn and form a memory, and continued to show normal feeding behavior even after training.

It's well known that a healthy gut microbiome is important to human health, and this  study is the first to show this is also the case in snails and other animals.

The researchers found the antibiotics altered the gut microbiome substantially and changed the abundance of bacteria that have been found to relate to healthy memory formation in other animals, including humans. This relationship between the bacteria found in the gut and brain function is called the microbiome-gut-brain axis. Chemicals produced by good gut bacteria when breaking down food can improve brain health and cognitive function.

Reducing the abundance of these healthy bacteria in the gut blocks the gut microbiome's otherwise beneficial effects on the brain.

Previous studies on the link between the gut microbiome and brain function have focused on terrestrial species. However, aquatic wildlife is more likely to be directly affected by antibiotic exposure in the environment.

Antibiotics are not removed effectively by waste treatment, and so they enter the freshwater environment. The antibiotic concentrations snails were exposed to in this new experiment were detected at similar levels in freshwater in the UK, Europe and globally.

Gabrielle Davidson et al, Antibiotic-altered gut microbiota explain host memory plasticity and disrupt pace-of-life trait covariation for an aquatic snail, The ISME Journal (2024). DOI: 10.1093/ismejo/wrae078

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