Astronomers confirm star wreck as source of extreme cosmic particles

 Astronomers have long sought the launch sites for some of the highest-energy protons in our galaxy. Now a study using 12 years of data from NASA's Fermi Gamma-ray Space Telescope confirms that one supernova remnant is just such a place.

Fermi has shown that the shock waves of exploded stars boost particles to speeds comparable to that of light. Called cosmic rays, these particles mostly take the form of protons, but can include atomic nuclei and electrons. Because they all carry an electric charge, their paths become scrambled as they whisk through our galaxy's magnetic field. Since we can no longer tell which direction they originated from, this masks their birthplace. But when these particles collide with interstellar gas near the supernova remnant, they produce a tell-tale glow in gamma rays -- the highest-energy light there is.

"Theorists think the highest-energy cosmic ray protons in the Milky Way reach a million billion electron volts, or PeV energies," said Ke Fang, an assistant professor of physics at the University of Wisconsin, Madison. "The precise nature of their sources, which we call PeVatrons, has been difficult to pin down."

Trapped by chaotic magnetic fields, the particles repeatedly cross the supernova's shock wave, gaining speed and energy with each passage. Eventually, the remnant can no longer hold them, and they zip off into interstellar space.

Boosted to some 10 times the energy mustered by the world's most powerful particle accelerator, the Large Hadron Collider, PeV protons are on the cusp of escaping our galaxy altogether.

Astronomers have identified a few suspected PeVatrons, including one at the center of our galaxy. Naturally, supernova remnants top the list of candidates. Yet out of about 300 known remnants, only a few have been found to emit gamma rays with sufficiently high energies.

One particular star wreck has commanded a lot of attention from gamma-ray astronomers. Called G106.3+2.7, it's a comet-shaped cloud located about 2,600 light-years away in the constellation Cepheus. A bright pulsar caps the northern end of the supernova remnant, and astronomers think both objects formed in the same explosion.

Fermi's Large Area Telescope, its primary instrument, detected billion-electron-volt (GeV) gamma rays from within the remnant's extended tail. (For comparison, visible light's energy measures between about 2 and 3 electron volts.) The Very Energetic Radiation Imaging Telescope Array System (VERITAS) at the Fred Lawrence Whipple Observatory in southern Arizona recorded even higher-energy gamma rays from the same region. And both the High-Altitude Water Cherenkov Gamma-Ray Observatory in Mexico and the Tibet AS-Gamma Experiment in China have detected photons with energies of 100 trillion electron volts (TeV) from the area probed by Fermi and VERITAS.

"This object has been a source of considerable interest for a while now, but to crown it as a PeVatron, we have to prove it's accelerating protons," explained co-author Henrike Fleischhack at the Catholic University of America in Washington and NASA's Goddard Space Flight Center in Greenbelt, Maryland. "The catch is that electrons accelerated to a few hundred TeV can produce the same emission. Now, with the help of 12 years of Fermi data, we think we've made the case that G106.3+2.7 is indeed a PeVatron."

Bioengineered cornea can restore sight to the blind and visually impaired

Human Eye

Researchers and entrepreneurs have developed an implant made of collagen protein from pig's skin, which resembles the human cornea. In a pilot study, the implant restored vision to 20 people with diseased corneas, most of whom were blind prior to receiving the implant. The study jointly led by researchers at Linköping University (LiU) and LinkoCare Life Sciences AB has been published in Nature Biotechnology. The promising results bring hope to those suffering from corneal blindness and low vision by providing a bioengineered implant as an alternative to the transplantation of donated human corneas, which are scarce in countries where the need for them is greatest.

"The results show that it is possible to develop a biomaterial that meets all the criteria for being used as human implants, which can be mass-produced and stored up to two years and thereby reach even more people with vision problems. This gets us around the problem of shortage of donated corneal tissue and access to other treatments for eye diseases," says Neil Lagali, professor at the Department of Biomedical and Clinical Sciences at LiU, one of the researchers behind the study.

An estimated 12.7 million people around the world are blind due to their corneas, which is the outermost transparent layer of the eye, being damaged or diseased. Their only way of regaining vision is to receive a transplanted cornea from a human donor. But just one in 70 patients receives a cornea transplant. Furthermore, most of those who need cornea transplants live in low and middle-income countries in which access to treatments is very limited.

"Safety and effectiveness of the bioengineered implants have been the core of our work, says Mehrdad Rafat, the researcher and entrepreneur behind the design and development of the implants. He is an adjunct associate professor (senior lecturer) at LiU's Department of Biomedical Engineering and founder and CEO of the company LinkoCare Life Sciences AB, which manufactures the bioengineered corneas used in the study.

"We've made significant efforts to ensure that our invention will be widely available and affordable by all and not just by the wealthy. That's why this technology can be used in all parts of the world," he says.

The cornea consists mainly of the protein collagen. To create an alternative to human cornea, the researchers used collagen molecules derived from pig skin that were highly purified and produced under strict conditions for human use. The pig skin used is a byproduct of the food industry, making it easy to access and economically advantageous. In the process of constructing the implant, the researchers stabilized the loose collagen molecules forming a robust and transparent material that could withstand handling and implantation in the eye. While donated corneas must be used within two weeks, the bioengineered corneas can be stored for up to two years before use.

The researchers have also developed a new, minimally invasive method for treating the disease keratoconus, in which the cornea becomes so thin that it can lead to blindness. Today, a keratoconus patient's cornea at advanced stage is surgically removed and replaced by a donated cornea, which is sewn into place using surgical sutures. This kind of surgery is invasive and only done at larger university hospitals.

"A less invasive method could be used in more hospitals, thereby helping more people. With our method, the surgeon doesn't need to remove the patient's own tissue. Instead, a small incision is made, through which the implant is inserted into the existing cornea," says Neil Lagali, who has led the research group that has developed this surgical method.

No stitches are needed with this new surgical method. The incision in the cornea can be made with high precision thanks to an advanced laser, but also, when needed, by hand with simple surgical instruments. The method was first tested on pigs and turned out to be simpler and potentially safer than a conventional cornea transplant.

The surgical method and the implants were used by surgeons in Iran and India, two countries where many people suffer from corneal blindness and low vision, but where there is a significant lack of donated corneas and treatment options. Twenty people who were either blind or on the verge of losing sight due to advanced keratoconus participated in the pilot clinical study and received the biomaterial implant. The operations were free from complications; the tissue healed fast; and an eight-week treatment with immunosuppressive eye drops was enough to prevent rejection of the implant. With conventional cornea transplants, medicine must be taken for several years. The patients were followed for two years, and no complications were noted during that time.

The primary purpose of the pilot clinical study was to investigate whether the implant was safe to use. However, the researchers were surprised by what happened with the implant. The cornea's thickness and curvature were restored to normal. At the group level, the participants' sight improved as much as it would have after a cornea transplant with donated tissue. Before the operation, 14 of the 20 participants were blind. After two years, none of them was blind any more. Three of the Indian participants who had been blind prior to the study had perfect (20/20) vision after the operation.

A larger clinical study followed by market approval by regulatory authorities is needed before the implant can be used in healthcare. The researchers also want to study whether the technology can be used to treat more eye diseases, and whether the implant can be adapted to the individual for even greater efficacy.

Technology restores cell, organ function in pigs after death

 

Heart, concept illustration

Within minutes of the final heartbeat, a cascade of biochemical events triggered by a lack of blood flow, oxygen, and nutrients begins to destroy a body's cells and organs. But a team of Yale scientists has found that massive and permanent cellular failure doesn't have to happen so quickly.

Using a new technology they developed that delivers a specially designed cell-protective fluid to organs and tissues, the researchers restored blood circulation and other cellular functions in pigs a full hour after their deaths, they report in the Aug. 3 edition of the journal Nature.

The findings may help extend the health of human organs during surgery and expand availability of donor organs, the authors said.

"All cells do not die immediately, there is a more protracted series of events," said David Andrijevic, associate research scientist in neuroscience at Yale School of Medicine and co-lead author of the study. "It is a process in which you can intervene, stop, and restore some cellular function."

The research builds upon an earlier Yale-led project that restored circulation and certain cellular functions in the brain of a dead pig with technology dubbed BrainEx. Published in 2019, that study and the new one were led by the lab of Yale's Nenad Sestan, the Harvey and Kate Cushing Professor of Neuroscience and professor of comparative medicine, genetics, and psychiatry.

"If we were able to restore certain cellular functions in the dead brain, an organ known to be most susceptible to ischemia [inadequate blood supply], we hypothesized that something similar could also be achieved in other vital transplantable organs," Sestan said.

In the new study -- which involved senior author Sestan and colleagues Andrijevic, Zvonimir Vrselja, Taras Lysyy, and Shupei Zhang, all from Yale -- the researchers applied a modified version of BrainEx called OrganEx to the whole pig. The technology consists of a perfusion device similar to heart-lung machines -- which do the work of the heart and lungs during surgery -- and an experimental fluid containing compounds that can promote cellular health and suppress inflammation throughout the pig's body. Cardiac arrest was induced in anesthetized pigs, which were treated with OrganEx an hour after death.

Six hours after treatment with OrganEx, the scientists found that certain key cellular functions were active in many areas of the pigs' bodies -- including in the heart, liver, and kidneys -- and that some organ function had been restored. For instance, they found evidence of electrical activity in the heart, which retained the ability to contract.

"We were also able to restore circulation throughout the body, which amazed us," Sestan said.

Normally when the heart stops beating, organs begin to swell, collapsing blood vessels and blocking circulation, he said. Yet circulation was restored and organs in the deceased pigs that received OrganEx treatment appeared functional at the level of cells and tissue.

"Under the microscope, it was difficult to tell the difference between a healthy organ and one which had been treated with OrganEx technology after death," Vrselja said.

As in the 2019 experiment, the researchers also found that cellular activity in some areas of the brain had been restored, though no organized electrical activity that would indicate consciousness was detected during any part of the experiment.

The team was especially surprised to observe involuntary and spontaneous muscular movements in the head and neck areas when they evaluated the treated animals, which remained anesthetized through the entire six-hour experiment. These movements indicate the preservation of some motor functions, Sestan said.

The researchers stressed that additional studies are necessary to understand the apparently restored motor functions in the animals, and that rigorous ethical review from other scientists and bioethicists is required.

The experimental protocols for the latest study were approved by Yale's Institutional Animal Care and Use Committee and guided by an external advisory and ethics committee.

The OrganEx technology could eventually have several potential applications, the authors said. For instance, it could extend the life of organs in human patients and expand the availability of donor organs for transplant. It might also be able to help treat organs or tissue damaged by ischemia during heart attacks or strokes.

"There are numerous potential applications of this exciting new technology," said Stephen Latham, director of the Yale Interdisciplinary Center for Bioethics. "However, we need to maintain careful oversight of all future studies, particularly any that include perfusion of the brain."

Evidence that giant meteorite impacts created the continents

 

Giant impact on Earth, illustration

New Curtin research has provided the strongest evidence yet that Earth's continents were formed by giant meteorite impacts that were particularly prevalent during the first billion years or so of our planet's four-and-a-half-billion year history.

Dr Tim Johnson, from Curtin's School of Earth and Planetary Sciences, said the idea that the continents originally formed at sites of giant meteorite impacts had been around for decades, but until now there was little solid evidence to support the theory.

"By examining tiny crystals of the mineral zircon in rocks from the Pilbara Craton in Western Australia, which represents Earth's best-preserved remnant of ancient crust, we found evidence of these giant meteorite impacts," Dr Johnson said.

"Studying the composition of oxygen isotopes in these zircon crystals revealed a 'top-down' process starting with the melting of rocks near the surface and progressing deeper, consistent with the geological effect of giant meteorite impacts.

"Our research provides the first solid evidence that the processes that ultimately formed the continents began with giant meteorite impacts, similar to those responsible for the extinction of the dinosaurs, but which occurred billions of years earlier."

Dr Johnson said understanding the formation and ongoing evolution of the Earth's continents was crucial given that these landmasses host the majority of Earth's biomass, all humans and almost all of the planet's important mineral deposits.

"Not least, the continents host critical metals such as lithium, tin and nickel, commodities that are essential to the emerging green technologies needed to fulfil our obligation to mitigate climate change," Dr Johnson said.

"These mineral deposits are the end result of a process known as crustal differentiation, which began with the formation of the earliest landmasses, of which the Pilbara Craton is just one of many.

"Data related to other areas of ancient continental crust on Earth appears to show patterns similar to those recognised in Western Australia. We would like to test our findings on these ancient rocks to see if, as we suspect, our model is more widely applicable."

Plesiosaur fossils found in the Sahara suggest they weren't just marine animals

Plesiosaur illustration

Fossils of small plesiosaurs, long-necked marine reptiles from the age of dinosaurs, have been found in a 100-million year old river system that is now Morocco's Sahara Desert. This discovery suggests some species of plesiosaur, traditionally thought to be sea creatures, may have lived in freshwater.

Plesiosaurs, first found in 1823 by fossil hunter Mary Anning, were prehistoric reptiles with small heads, long necks, and four long flippers. They inspired reconstructions of the Loch Ness Monster, but unlike the monster of Lake Loch Ness, plesiosaurs were marine animals -- or were widely thought to be.

Now, scientists from the University of Bath and University of Portsmouth in the UK, and Université Hassan II in Morocco, have reported small plesiosaurs from a Cretaceous-aged river in Africa.

The fossils include bones and teeth from three-metre long adults and an arm bone from a 1.5 metre long baby. They hint that these creatures routinely lived and fed in freshwater, alongside frogs, crocodiles, turtles, fish, and the huge aquatic dinosaur Spinosaurus.

These fossils suggest the plesiosaurs were adapted to tolerate freshwater, possibly even spending their lives there, like today's river dolphins.

The new paper was headed by University of Bath Student Georgina Bunker, along with Nick Longrich from the University of Bath's Milner Centre for Evolution, David Martill and Roy Smith from the University of Portsmouth, and Samir Zouhri from the Universite Hassan II.

The fossils include vertebrae from the neck, back, and tail, shed teeth, and an arm bone from a young juvenile.

"It's scrappy stuff, but isolated bones actually tell us a lot about ancient ecosystems and animals in them. They're so much more common than skeletons, they give you more information to work with" said Dr. Nick Longrich, corresponding author on the paper.

"The bones and teeth were found scattered and in different localities, not as a skeleton. So each bone and each tooth is a different animal. We have over a dozen animals in this collection."

Whilst bones provide information on where animals died, the teeth are interesting because they were lost while the animal was alive -- so they show where the animals lived.

What's more, the teeth show heavy wear, like those fish-eating dinosaur Spinosaurus found in the same beds.

The scientists say that implies the plesiosaurs were eating the same food- chipping their teeth on the armored fish that lived in the river. This hints they spent a lot of time in the river, rather than being occasional visitors.

While marine animals like whales and dolphins wander up rivers, either to feed or because they're lost, the number of plesiosaur fossils in the river suggest that's unlikely.

A more likely possibility is that the plesiosaurs were able to tolerate fresh and salt water, like some whales, such as the beluga whale.

It's even possible that the plesiosaurs were permanent residents of the river, like modern river dolphins. The plesiosaurs' small size would have let them hunt in shallow rivers, and the fossils show an incredibly rich fish fauna.

Dr Longrich said: "We don't really know why the plesiosaurs are in freshwater.

"It's a bit controversial, but who's to say that because we paleontologists have always called them 'marine reptiles', they had to live in the sea? Lots of marine lineages invaded freshwater."

Freshwater dolphins evolved at least four times -- in the Ganges River, the Yangtze River, and twice in the Amazon. A species of freshwater seal inhabits Lake Baikal, in Siberia, so it's possible plesiosaurs adapted to freshwater as well.

The plesiosaurs belong to the family Leptocleididae- a family of small plesiosaurs often found in brackish or freshwater elsewhere in England, Africa, and Australia. And other plesiosaurs, including the long-necked elasmosaurs, turn up in brackish or fresh waters in North America and China.

Plesiosaurs were a diverse and adaptable group, and were around for more than 100 million years. Based on what they've found in Africa -- and what other scientists have found elsewhere -- the authors suggest they might have repeatedly invaded freshwater to different degrees.

"We don't really know, honestly. That's how paleontology works. People ask, how can paleontologists know anything for certain about the lives of animals that went extinct millions of years ago? The reality is, we can't always. All we can do is make educated guesses based on the information we have. We'll find more fossils. Maybe they'll confirm those guesses. Maybe not."

"It's been really interesting to see the direction this project has gone in," said lead author Georgina Bunker. The study initially began as an undergraduate project involving a single bone, but over time, more plesiosaur fossils started turning up, slowly providing a clearer picture of the animal.

The new discovery also expands the diversity of Morocco's Cretaceous. Said Dr. Samir Zouhri, "This is another sensational discovery that adds to the many discoveries we have made in the Kem Kem over the past fifteen years of work in this region of Morocco. Kem Kem was truly an incredible biodiversity hotspot in the Cretaceous."

"What amazes me" said coauthor Dave Martill, "is that the ancient Moroccan river contained so many carnivores all living alongside each other. This was no place to go for a swim."

But what does this all mean for the plausibility of something like a Loch Ness Monster? On one level, it's plausible. Plesiosaurs weren't confined to the seas, they did inhabit freshwater. But the fossil record also suggests that after almost a hundred and fifty million years, the last plesiosaurs finally died out at the same time as the dinosaurs, 66 million years ago.

Story Source: Science Daily