Tag Archives: longstanding

Physicists Question Long-Standing Beliefs on Dark Matter’s True Nature

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New insights challenge the long-held belief that dark matter was “cold” in the immediate aftermath of the Big Bang. A groundbreaking study from the University of Minnesota Twin Cities and the University of Paris-Saclay reveals that dark matter particles might have been extraordinarily hot and traveling at near-light speeds in the primordial universe, before cooling down during the formative epochs of galaxies and large-scale structures.

Hypothetical dark matter particles. Image credit: University of Adelaide.

For decades, physicists have categorized dark matter based on the velocity of its constituent particles. Cold dark matter is slow enough to clump under gravitational forces, contributing to the formation of galaxies and galaxy clusters.

This categorization is a cornerstone of the standard cosmological model, explaining the universe’s intricate web-like structure.

However, the recent findings indicate that dark matter may have emerged from the hot plasma of the early universe in an ultrarelativistic state—essentially moving at ultra-high speeds—before cooling adequately during the formation of cosmic structures.

This refined perspective broadens the potential behaviors of dark matter particles and expands the pool of candidate particles physicists can investigate through experiments and astronomical observations.

The study concentrates on a critical phase in the early universe known as reheating, which followed an explosive inflationary expansion.

During the reheating phase, the energy fueling the universe’s expansion transformed into a dense hot mixture of particles and radiation.

This discovery suggests that under certain conditions, dark matter produced during this period could exist at speeds approaching that of light while still aligning with the vast universe we observe today.

If validated, these findings could significantly impact ongoing dark matter detection initiatives, including particle colliders, underground detectors, and astrophysical studies.

Moreover, they pose new theoretical challenges regarding the fundamental nature of dark matter and its role in the universe’s evolution.

“Dark matter remains one of the biggest mysteries in physics,” explains Stephen Henrik, a graduate student at the University of Minnesota.

“Historically, one consistent assumption has been that dark matter must be cold at its inception in the primordial universe.”

“Our findings reveal a different narrative. In fact, dark matter may start off as red-hot, but has ample time to cool before galaxies commence formation.”

“The simplest dark matter candidate, low-mass neutrinos, was deemed incompatible decades ago because they could annihilate galaxy-sized structures instead of facilitating them,” states Keith Olive, a professor at the University of Minnesota.

“Neutrinos serve as a prime example of hot dark matter, whose structural formation relies on cold dark matter.”

“If a similar candidate arose during the hot Big Bang, it’s remarkable that it could cool sufficiently to behave as cold dark matter.”

“This new discovery allows us to explore a period in the universe’s history that is very close to the Big Bang,” adds Professor Yann Mambrini, a physicist at the University of Paris-Saclay.

The team’s research has been published in the journal Physical Review Letters.

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Stephen E. Henrik et al. 2025. Ultra-relativistic freezeout: Bridge from WIMP to FIMP. Physics Review Letters 135, 221002; doi: 10.1103/zk9k-nbpj

Source: www.sci.news

Nanotyrannus: Dinosaur Skeleton Resolves Long-Standing Debate Over ‘Small Tyrannosaurus’ Fossil

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Artist’s interpretation of the pack Nanotyrannus assailing a young tyrannosaurus

Anthony Hutchings

Fossils previously thought to belong to a juvenile tyrannosaurus rex have been identified as a fully mature carnivore of a distinct species, resolving a long-standing debate in paleontology.

This controversy originated from a skull unearthed in the Hell Creek Formation in Montana during the 1940s, which was initially identified as gorgosaurus. It was later proposed to be a juvenile tyrannosaurus. In 1988, other researchers posited that the fossil represented an adult of a smaller related species, which they designated Nanotyrannus lansensis.

Since then, a number of additional fossils classified as Nanotyrannus have been discovered, although many paleontologists contend that they are merely tyrannosaurus juveniles.

Now, researchers have examined a complete skeleton for the first time, providing compelling evidence that Nanotyrannus is indeed a separate species.

The skeleton is among a pair of specimens known as “Dueling Dinosaurs,” found by private fossil hunters in 2006, which includes a triceratops and what was initially believed to be a juvenile T. rex buried approximately 67 million years ago.

It was only in 2020, when the fossil came into the possession of the North Carolina Museum of Natural Sciences, that paleontologists could conduct a thorough analysis of it.

“Upon receiving the specimen, we recognized it was extraordinary,” remarks Lindsey Zanno from the North Carolina Museum of Natural Science. “We had no inkling it would radically alter decades of research concerning the world’s most renowned dinosaur.”

Mr. Zanno collaborated with his colleagues, including James Naples, a postdoctoral researcher at Stony Brook University in New York. She had initially supported the juvenile tyrannosaurus theory but was compelled to reevaluate her stance based on the findings.

“Nanotyrannus displays unique nerve and sinus patterns, a greater number of teeth, larger hands, and shorter tails. These traits remain consistent as the species develops from juvenile to adult,” she notes.

Lindsay Zanno with the proposed Nanotyrannuslansensis skeleton

North Carolina State University

Zanno and Napoli’s examination of the dinosaur’s limb bones confirmed that it was a fully mature specimen, approximately 20 years old, weighing around 700 kilograms and measuring about 5.5 meters in length. “This is roughly one-tenth the weight of an adult human and half the length of a tyrannosaurus,” Zanno explains.

Additionally, Zanno and Napoli reanalyzed 200 tyrannosaur fossils and concluded that another nearly complete skeleton, known as Jane from the Hell Creek Formation, is misclassified as a tyrannosaurid fossil. They propose that Jane is actually a new species within this genus, designated Nanotyrannus letaeus.

“Although we possess only one skeleton of N. Retheus, its anatomy suggests it was part of a larger species,” remarks Zanno. “The configuration of the palatal sinuses and the shape of the bone behind the eye are distinctive.”

Proposed Nanotyrannus lansensis skull features more teeth than the tyrannosaurus skull.

Matt Zeher/North Carolina Museum of Natural Science

Scott Parsons, a researcher at the South Carolina State Museum, asserts that this latest study clarifies the debate surrounding Nanotyrannus being its own genus and species.

“In my opinion, Nanotyrannus was among the most formidable dinosaur predators, and being pursued by one would be quite a terrifying experience,” Parsons remarks, noting its long legs and fearsome thumb claws.

“In essence, we can compare Nanotyrannus and tyrannosaurus to modern-day cheetahs and lions. While they shared a similar overall anatomy, they had distinct hunting strategies.”

Thomas Carr from Carthage College in Wisconsin has expressed that the new findings are “quite definitive” that the dueling dinosaur specimen represents an almost adult species, one that differs from tyrannosaurus.

Additionally, Holly Ballard from Oklahoma State University, who led the 2020 research, stated that there is “no contention” regarding the team’s conclusion that the fossil belonged to an individual nearing adult size.

However, neither Ballard nor Carr are fully convinced that the other fossil, Jane, constitutes a new species of Nanotyrannus. “Jane is still maturing and large,” emphasizes Ballard, suggesting it may be a new taxon rather than a juvenile tyrannosaurus. “We’re returning to the old debates,” Ballard laments.

“Moreover, in the Hell Creek Formation, if there are numerous small tyrannosaurs in circulation, where are the juvenile tyrannosaurus? ” Kerr questions, stating that it complicates the fossil record. “We simply haven’t uncovered enough tyrannosaurs to fully elucidate what was occurring during the growth phases of the tyrannosaurids in the Hell Creek Formation.”

Dinosaur hunting in Mongolia’s Gobi desert

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Source: www.newscientist.com

Possible solution to long-standing breastfeeding mystery discovered

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This may solve one of the mysteries of breastfeeding.

Svetlana Lepnitskaya/Getty Images

A newly discovered hormone discovered in mice may solve a long-standing mystery about how adult bones stay strong under the stress of breastfeeding, a discovery that could lead to new treatments for osteoporosis, a disease that causes bones to become weak and brittle.

For decades, it was unclear how bones maintain their strength during breastfeeding. Breastfeeding removes calcium from bones to produce nutritious breast milk. Breastfeeding also reduces levels of estrogen, a hormone essential for bone health. Temporary loss of bone mass This will resolve within 6-12 months after breastfeeding ends.

While conducting research unrelated to this conundrum, Holly Ingraham Researchers at the University of California, San Francisco have found that targeting receptors in the hypothalamus of the brain to inhibit estrogen production actually strengthens the bones of female mice.

“It's a bit of a paradox that we're eliminating estrogen signaling, which is thought to be beneficial for bone, and then creating women with extremely dense bones,” Ingraham said.

To find out why, they bred female mice that lacked estrogen receptors and had unusually strong bones, then surgically mated these animals with other female mice that had the receptors, linking their circulatory systems.

After 17 weeks, the mice that had been attached to the strong-bone mice had an average 152 percent increase in bone mass, suggesting that a bone-strengthening substance was circulating in the blood and being transferred from the mice that didn't have the receptor to the ones that did. Subsequent experiments revealed that this substance was a brain hormone called CCN3.

The researchers then measured CCN3 in the brains of female mice before and after pregnancy and found that it is only produced during lactation. Moreover, blocking the hormone caused bone loss in lactating mice, suggesting that it may be the mysterious molecule that prevents bone loss during lactation. This finding suggests that CCN3 may be used to repair bone in other situations as well.

To explore this further, the researchers placed patches containing CCN3 on four male mice that had suffered fractures. An equal number of animals received patches that did not contain the hormone. All rodents were 2 years old. 69 years in humans.

After three weeks, mice with the CCN3 patch had an average of 240% more bone mass than mice without the patch, suggesting that CCN3 may be useful in treating or preventing osteoporosis, which affects more than one million people. 12 percent Among U.S. adults age 50 and older.

But it's unclear whether these findings apply to humans, Ingraham said. She and her colleagues are developing a blood test for CCN3 that will allow them to test whether levels of the hormone increase in breastfeeding women.

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Source: www.newscientist.com

Active Matter Theory sheds new light on longstanding biological enigmas

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November 22, 2023A team of scientists has developed a new algorithm to solve theoretical equations for active materials, deepening our understanding of living materials. This research is of vital importance in biology and computational science, paving the way for new discoveries in cell morphology and the creation of artificial biological machines. Advanced open-source supercomputer algorithms predict the patterns and dynamics of living matter and enable exploration of its behavior across space and time. Biological materials are made up of individual components, such as tiny motors that convert fuel into motion. This process creates a pattern of movement, guiding the shape of the material itself through a consistent flow driven by constant energy consumption. Such permanently driven substances are called “active substances.”

How cells and tissues work can be explained by active matter theory, a scientific framework for understanding the shape, flow, and form of living matter. Active matter theory consists of many difficult mathematical equations. Scientists from Dresden’s Max Planck Institute for Molecular Cell Biology and Genetics (MPI-CBG), the Dresden Center for Systems Biology (CSBD), and the Dresden University of Technology have developed an algorithm implemented in open-source supercomputer code. For the first time, you can solve active matter theory equations in realistic scenarios. These solutions bring him a big step closer to solving his century-old mystery of how cells and tissues acquire their shape, and to designing artificial biological machines. 3D simulation of active substances in a dividing cell-like geometry. Credit: Singh et al. Physics of Fluids (2023) / MPI-CBG

Biological processes and behaviors are often highly complex. Physical theory provides a precise and quantitative framework for understanding physical theories. Active matter theory provides a framework for understanding and explaining the behavior of active substances, which are materials made up of individual components that can convert chemical fuels (“food”) into mechanical forces. The development of this theory was led by several Dresden scientists, including Frank Uricher, director of the Max Planck Institute for Complex Systems Physics, and Stefan Grill, director of MPI-CBG. These physical principles allow us to mathematically describe and predict the dynamics of active organisms. However, these equations are very complex and difficult to solve. Therefore, scientists need the power of supercomputers to understand and analyze living matter. There are various ways to predict the behavior of active materials, including by focusing on small individual particles, by studying active materials at the molecular level, and by studying active fluids on a larger scale. These studies help scientists understand how active substances behave at different scales in space and time. Scientist in the research group of Dresden University of Technology Ivo Sbalzarini Professor at the Dresden Center for Systems Biology (CSBD), research group leader at the Max Planck Institute molecular cell The Dean of the Department of Biology and Genetics (MPI-CBG) and Computer Science at the Technical University of Dresden has now developed a computer algorithm to solve the active substance equation. Their research was published in the journal fluid physics and it appeared on the cover. They present an algorithm that is capable of solving complex equations for active materials in three-dimensional and complex-shaped spaces.

“Our approach can handle a variety of shapes in three dimensions over time,” says research mathematician Abhinav Singh, one of the study’s first authors. He continued, “Even when the data points are not regularly distributed, our algorithm employs a novel numerical approach that works seamlessly for complex biologically realistic scenarios, and the theoretical equations Using our approach, we can finally understand the long-term behavior of active materials in both mobile and non-mobile scenarios in order to predict dynamic scenarios. Additionally, theory and simulation can be used to program biological materials and create engines at the nanoscale to extract useful work.” The other first author, Philipp Suhrcke, holds a master’s degree in computational modeling and simulation from the Technical University of Dresden. “Thanks to our research, scientists can predict, for example, the shape of tissues and when biological materials will become unstable or dysregulated, leading to growth and disease. This has far-reaching implications for our understanding of mechanisms.”

The scientists implemented the software using the open source library OpenFPM. This means that others can use it freely. OpenFPM was developed by his Sbalzarini group to democratize large-scale scientific and technical computing. The authors first developed a custom computer language that allows computational scientists to write code for a supercomputer by specifying mathematical formulas that let the computer do the work of writing the correct program code. As a result, you no longer have to start from scratch every time you write code, effectively reducing code development time in scientific research from months or years to days or weeks, greatly increasing productivity.

Because the study of three-dimensional active materials has significant computational demands, using OpenFPM the new code is scalable on shared and distributed memory multiprocessor parallel supercomputers. This application is designed to run on powerful supercomputers, but can also be run on regular office computers to study 2D materials. Ivo Sbalzarini, the study’s lead researcher, summarizes: All this has been integrated into a tool for understanding her three-dimensional behavior of living matter. Our code, which is open source, scalable, and able to handle complex scenarios, opens new avenues in active materials modeling. This could ultimately lead to an understanding of how cells and tissues acquire their shape, addressing fundamental questions in morphogenesis that have puzzled scientists for centuries. There is a gender. But it may also be useful for designing artificial biological machines with minimal components.

References: “Numerical solver for three-dimensional active fluid dynamics and its application to active turbulence” by Abhinav Singh, Philipp H. Suhrcke, Pietro Incardina, and Ivo F. Sbalzarini, October 30, 2023. fluid physics. DOI: 10.1063/5.0169546 This research was funded by the Federal Ministry of Education and Research (Bundesministerium f€ur Bildung und Forschung, BMBF), the Federal Center for Scalable Data Analysis and Artificial Intelligence, ScaDS.AI, and Dresden/Leipzig. The computer code supporting the results of this study is publicly available in the 3Dactive-hydynamics github repository at: https://github.com/mosaic-group/3Dactive-hydrodynamic sThe open source framework OpenFPM is available at: https://github.com/mosaic-group/openfpm_pdataRelated publications for embedded computer languages https://doi.org/10.1016/j.cpc.2019.03.007https://doi.org/10.1140/epje/s10189-021-00121-x (function (d, s, id) {var js, fjs = d.getElementsByTagName (s) [0]; if (d.getElementById (id)) return; js = d.createElement (s); js.id = id; js.src = “https://connect.facebook.net/en_US/sdk.js#xfbml=1&version=v2.6”; fjs.parentNode.insertBefore (js, fjs); } (document, ‘script’, ‘facebook-jssdk’));

Source: scitechdaily.com