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Scientists find supernovae showered Earth with radioactive debris

Gorkha Post

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An international team of scientists has discovered evidence of a series of massive supernova explosions near our solar system, which showered the Earth with radioactive debris.

The scientists found radioactive iron-60 in sediment and crust samples taken from the Pacific, Atlantic and Indian Oceans.

The iron-60 was concentrated in a period between 3.2 and 1.7 million years ago, which is relatively recent in astronomical terms, said research leader Dr Anton Wallner from The Australian National University (ANU).

“We were very surprised that there was debris clearly spread across 1.5 million years,” said Dr Wallner, a nuclear physicist in the ANU Research School of Physics and Engineering. “It suggests there were a series of supernovae, one after another.

The team from Australia, the University of Vienna in Austria, Hebrew University in Israel, Shimizu Corporation and University of Tokyo, Nihon University and University of Tsukuba in Japan, Senckenberg Collections of Natural History Dresden and Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany, also found evidence of iron-60 from an older supernova around eight million years ago, coinciding with global faunal changes in the late Miocene.

A supernova is a massive explosion of a star as it runs out of fuel and collapses.

The scientists believe the supernovae in this case were less than 300 light years away, close enough to be visible during the day and comparable to the brightness of the Moon.

Although Earth would have been exposed to an increased cosmic ray bombardment, the radiation would have been too weak to cause direct biological damage or trigger mass extinctions.

The supernova explosions create many heavy elements and radioactive isotopes which are strewn into the cosmic neighbourhood.

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Researchers successfully grow human cells in sheep embryos

Raghu Kshitiz

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Researchers successfully grow human cells in sheep embryos. Represenatational image

KATHMANDU — In an incredible development that could possibly go a long way in medical practices, scientists in California are working on a way to reduce organ transplants and rejections: Growing embryos in sheep and pigs containing human patients’ cells.

In a transplant breakthrough, scientists at the University of California said they have achieved sheep embryos in which around one in every 10,000 cells was human, according to UPI report.

The researchers presented preliminary findings Saturday at the American Association for the Advancement of Science’s annual meeting in Austin, Texas.

The new finding paves way for genetically tailoring the organs to be compatible with the immune system of the patient receiving them, thus removing the possibility of rejection, the report said.

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The hybrid embryos contain both human and sheep cells and were created in an early step toward growing human organs in farm animals before transplanting them into patients.

Last year, the same researchers introduced human stem cells into early pig embryos, producing embryos with about one in every 100,000 cells being human.

The experiment began with Hiro Nakauchi, from the University of Tokyo, who grew a mouse with a rat pancreas and a rat with a mouse pancreas.

When cells from the rat-grown mouse pancreas were transplanted into a diabetic mouse, they made enough insulin to cure the condition without being rejected.

Mice and rats are different types of rodents with the former having thin slightly hairy tails, while rats have thicker hairless scaly tails.

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“The next step was to move into large animals,” Nakauchi said. Since this was prohibited in Japan, he moved to the Stanford University in the US.

Nakauchi’s rodent work has demonstrated that you can “grow organs in a different species and cure a disease without [suppressing the immune system],” added co-researcher Pablo Ross, Professor at from the University of California, Davis.

“We are working together to translate the technology into humans, to solve the terrible shortage of organs for transplantation. In the US, 20 people die every day because they cannot get the organs they need,” Ross explained.

With Agency Inputs

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