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Comment by Dr. Krishna Kumari Challa 6 hours ago

Our current measurements of the visible universe, in other words, are insufficient to confirm which side the hidden sector fell on at the beginning—hot or cold.

Nath is quick to point out that, rather than a failing of the experiment, this is an example of the mathematical models outrunning our current experimental capabilities.

It's not that the difference between a hot or cold hidden sector has no bearing on the visible universe, but that we haven't performed experiments—yet—with high enough precision. Nath mentions the Webb Telescope as one example of the next generation of tools that will be able to make such precise observations.

The ultimate goal of all this modeling work is to make better predictions about the state of the universe, how it all functions and what we'll find when we look deeper and deeper into the night sky.

As our experiments gain more accuracy, the questions baked into Nath's models—was the hidden sector hot or cold?—will find their answers, and those clarified models will help predict the solutions to ever-deeper questions.
"What's the significance of this?" Nath asks. Human beings, he says, "want to find their place in the universe." And more than that, "they want to answer the question, why is there a universe?

"And we are exploring those issues. It is the ultimate quest of human beings."

Jinzheng Li et al, Big bang initial conditions and self-interacting hidden dark matter, Physical Review D (2023). DOI: 10.1103/PhysRevD.108.115008

Part 4

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Comment by Dr. Krishna Kumari Challa 6 hours ago

One major variable is the temperature of the hidden sector during the Big Bang.

The visible sector, we can be fairly certain, started out very hot at the moment of the Big Bang. As the universe cools, Nath says, "what we see is the remnant of that period of the universe."

But by studying the evolution of the two sectors, Nath and his team could model both conditions—a hidden sector that started out hot, and another hidden sector that started out cold.

What they observed was surprising: Despite significant differences between the models, with major implications on what the universe looked like in early times, both the hot and cold models were consistent with the visible sector we can observe today.
part 3

Comment by Dr. Krishna Kumari Challa 6 hours ago

But we can't explain everything, the authors of this study contends. There are anomalies that don't seem to fit the so-called "Standard Model" of the universe.

That the visible and hidden sectors are mutually isolated is a misconception, they say, based on an assumption "that the visible and the hidden sectors evolved independently of each other." The new work wants to turn that assumption on its head.

In a paper published in Physical Review D, "Big Bang Initial Conditions and Self-Interacting Hidden Dark Matter, they want to ask what they call "the more important question: How do we know that they evolved independently?"

To test this assumption, Nath and his team "introduced some feeble interactions" between the two sectors into their models of the Big Bang. These meager interactions wouldn't be enough to affect the outcome of, say, particle accelerator experiments, "but we wanted to see what the effects would be on the visible sector as a whole," Nath says, "from the time of the Big Bang to the current time."
Even with minimal interactions between the two sectors, Nath and his team discovered that dark matter's influence on the visible matter we're made of could have a major impact on observable phenomena.

The Hubble expansion—which says, in the simplest terms, that galaxies are moving away from one another, and thus that the universe is expanding—for instance, contains a "quite serious" differential between what the Standard Model predicts and what has been observed. Nath's models partially account for this difference.

Comment by Dr. Krishna Kumari Challa 6 hours ago

New models of Big Bang show that visible universe and invisible dark matter co-evolved

Physicists have long theorized that our universe may not be limited to what we can see. By observing gravitational forces on other galaxies, they've hypothesized the existence of "dark matter," which would be invisible to conventional forms of observation.

95% of the universe is dark, is invisible to the eye. 

However, we know that the dark universe is there by its gravitational pull on stars. Other than its gravity, dark matter has never seemed to have much effect on the visible universe.

Yet the relationship between these visible and invisible domains, especially as the universe first formed, has remained an open question.

Now, physicists say that there is mounting evidence that these two supposedly distinct realms actually co-evolved.

Through a series of computer models, physicists have discovered that the visible and the hidden sectors, as they call them, likely co-evolved in the moments after the Big Bang, with profound repercussions for how the universe developed thereafter.

They say there was a time when some physicists effectively wrote off this hidden sector, as they can explain most of what happens within the visible—that is, if our models can accurately portray what we can see happening around us, why bother trying to measure something that has no discernible effect?

The question is, what's the influence of the hidden sector on the visible sector?"  "But what do we care? We can explain everything."

Part 1

Comment by Dr. Krishna Kumari Challa 7 hours ago

The researchers now plan to use their electron videography technique to study other types of membrane proteins and other classes of molecules and nanomaterials.

 John W. Smith et al, Electron videography of a lipid–protein tango, Science Advances (2024). DOI: 10.1126/sciadv.adk0217

Part 4

Comment by Dr. Krishna Kumari Challa 7 hours ago

The researchers achieved videography by combining a novel water-based transmission electron microscopy method with detailed, atom-level computational modeling. The water-based technique involves encapsulating nanometer-scale droplets in graphene so they can withstand the vacuum in which the microscope operates. Comparing the resulting video data to molecular models, which show how things should move based on the laws of physics, helps the researchers not only interpret but also validate their experimental data.
Currently, this is really the only experimental way to film this kind of motion over time. Life is in liquid, and it's in motion. Scientists 're trying to get to the finest details of that connection in an experimental way.
For the new study—the first published demonstration of the electron videography technique—the researchers examined nanoscale discs of lipid membranes and how they interacted with proteins normally found on the surface of or embedded in cell membranes.
Part 3

Comment by Dr. Krishna Kumari Challa 7 hours ago

Electron microscopy techniques image at the molecular or atomic scale, yielding detailed, nanometer-scale pictures. However, they often rely on samples that have been frozen or fixed in place, leaving scientists to try to infer how molecules move and interact—like trying to map the choreography of a dance sequence from a single frame of film.

Usually, researchers have to crystalize or freeze a protein, which poses challenges in capturing high-resolution images of flexible proteins. Alternately, some techniques use a molecular tag that they track, rather than watching the protein itself. In this study they are seeing the protein as it is, behaving how it does in a liquid environment, and seeing how lipids and proteins interact with each other.

Part 2

Comment by Dr. Krishna Kumari Challa 7 hours ago

Electron videography captures moving dance between proteins and lipids

In a first demonstration of "electron videography," researchers have captured a microscopic moving picture of the delicate dance between proteins and lipids found in cell membranes. The technique can be used to study the dynamics of other biomolecules, breaking free of constraints that have limited microscopy to still images of fixed molecules.

Scientists are now  are going beyond taking single snapshots, which gives structure but not dynamics, to continually recording the molecules in water, their native state.

They can really see how proteins change their configuration and, in this case, how the whole protein-lipid self-assembled structure fluctuates over time.

The researchers reported their technique and findings in the journal Science Advances.

Part 1

Comment by Dr. Krishna Kumari Challa 7 hours ago

The researchers also described other instances over a period of 19 months of observation when fosas appeared to stalk lemurs but were unsuccessful in bringing one down as food.

The impact of predation—combined with low reproductive rates and potentially high inbreeding of the lemur population of Betampona—could affect the survival of this species at this site, researchers said.

These most recent observations of fosa attacks are especially troubling, as the observation of predation attacks, especially by the elusive fosa, are very rare.

"It leads to questions of why the fosa are so bold to predate on lemurs in front of humans, and whether the fosa leave Betampona to hunt elsewhere and then return, or whether they are targeting the lemurs within the reserve,"the researchers say. "It is an incredible scenario in which you have a vulnerable species potentially over-predating on several critically endangered species."

G. Bonadonna et al, Response of diademed sifaka (Propithecus diadema) to fosa (Cryptoprocta ferox) predation in the Betampona Strict Nature Reserve, Madagascar, Ecology and Evolution (2024). DOI: 10.1002/ece3.11248

Part 2

Comment by Dr. Krishna Kumari Challa 7 hours ago

When one vulnerable species stalks another

What can be done when one threatened animal kills another? Scientists studying critically endangered lemurs in Madagascar confronted this difficult reality when they witnessed attacks on lemurs by another vulnerable species, a carnivore called a fosa.

This dynamic can be particularly complex when the predation occurs in an isolated or poor-quality habitat, according to research by scientists  in Madagascar.

In the new paper published in Ecology and Evolution, researchers describe how they were observing small groups of critically endangered diademed sifaka lemurs (Propithecus diadema) at Betampona Strict Nature Reserve when the predator struck.

"We were conducting our daily behavioural observations when we came across a very unusual sight—a predation attempt by a fosa, which is the biggest predator in Madagascar", the researchers depicted the story.

"What we saw was very rare," they wrote in their paper. "There are other small carnivores in Madagascar, but they are not big enough to be able to prey upon an adult diademed sifaka because they are among the biggest lemurs. There are not so many predators that could actually get them."

With slender bodies and long tails, fosas (or fossas, Crytoprocta ferox) have many cat-like features. They are great climbers and are sometimes compared to small cougars, though they are actually part of the weasel family.

The fosa is categorized as vulnerable by the International Union for Conservation of Nature and Natural Resources, and is at risk of extinction, as are almost all of its lemur prey. Fosas also eat other small animals such as birds and rodents.

But they're rarely caught in the act. Fosas are stealthy hunters. Researchers have mostly determined what fosas eat by examining bones and other evidence left behind in scat.

"We noticed that a female diademed sifaka that we were following after the first attack didn't run away very far," they said. "Instead she stayed still and remained vigilant, looking at the fosa."

 also documented the later discovery of the remains of another diademed sifaka, presumed to have been killed by a fosa because of the condition of the remains and because of the way that branches had been broken in the area. Signs indicated a struggle in the trees.

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