The 5 most popular scientific papers of December 2020 in the Nature Index journals

A major milestone in light-based quantum computing and the possibility of reversed ageing feature in these widely-discussed studies.

16 February 2021

Bec Crew

Yuancheng Lu/Sinclair Lab

The crushed optic nerve of a mouse regenerates as a result of a new treatment by Harvard researchers. The cluster of bright streaks (optic neurons) is the regeneration site.

December’s most talked-about natural-sciences papers feature two key COVID-19 papers investigating the virus’s ability to enter the brain, and why some patients experience more symptoms than others.

Also described in this list is the sobering scale of the human footprint on Earth – measured by how much stuff we’re using at any given moment – plus signs that it’s possible to turn back the clock on ageing, and an important step towards viable quantum computing.

Here is an Altmetric ranking of December 2020’s most popular papers in the natural sciences, published in the 82 high-quality journals tracked by the Nature Index.

1. “Global human-made mass exceeds all living biomass”


Human-made objects such as roads, houses, ships and smartphones now outweigh all living beings on Earth, according to this paper by a team from the Weizmann Institute of Science in Rehovot, Israel, led by Ron Milo, a professor of systems biology.

The study follows a 2018 analysis, also led by Milo, which estimated the mass of all life on Earth using a variety of independent sources including world forest surveys and remote sensing data. The total figure came to 1.1 teratonnes (a teratonne equals one trillion tonnes).

Plants (the majority of which are terrestrial) were found to account for 80% of Earth's total biomass. Bacteria came in second, representing around 15% of the global biomass. Other groups, in descending order, are fungi, single-celled organisms archaea and protists, animals, and viruses, which make up the remainder.

In this 2020 study, Milo and his colleagues estimated the mass of all inanimate solid objects made by humans that are still in use and found that it exceeds Earth's total biomass, as shown in the graphic below. (Waste, such as discarded plastic, was not included.)

alt Credit: Yinon M. Bar-On et. al

The paper has been covered by 362 online news outlets so far, and reached an estimated audience on Twitter of more than 10 million.

2. “Genetic mechanisms of critical illness in Covid-19”


Why some COVID-19 patients experience severe symptoms while others are asymptomatic has been a major challenge for researchers and healthcare workers.

This study, led by J. Kenneth Baillie, a consultant at the Intensive Care Unit at the Royal Infirmary of Edinburgh, UK, analyzed the DNA of more than 2,200 intensive care COVID-19 patients in UK hospitals. It identified faults in specific genes that may render some people at a higher risk of severe symptoms.

Baillie says clinical trials should focus on developing drugs that can address the effects of these gene mutations.

"This is a stunning realization of the promise of human genetics to help understand critical illness,” Baillie said. "Our results immediately highlight which drugs should be at the top of the list for clinical testing. We can only test a few drugs at a time, so making the right choices will save thousands of lives.”

The paper has been covered by more than 100 online news outlets, and has reached an audience of almost 10 million on Twitter. It’s also been cited 34 times, compared with the top-ranked paper in this list, which has been cited only 3 times to date.

3. “Reprogramming to recover youthful epigenetic information and restore vision”


For many people, a loss of visual acuity is a natural part of the ageing process, driven by diseases such as glaucoma, which causes irreversible damage to the optic nerve, or the inability of cells to respond to damage as they once did.

But the effects of ageing might not be as linear as previously thought, this paper, led by David A. Sinclair from the Paul F. Glenn Center for Biology of Aging Research at Harvard Medical School in Boston, Massachusetts, suggests.

Sinclair and his colleagues delivered three genes into the eyes of mice that were genetically engineered to age rapidly.

When operating at full capacity, these genes can force cells to revert to a developmental stem cell state, that is, to resemble precursor cells that can generate multiple mature cell types. But when the genes were switched on and off, which Sinclair and his team could do by administering or withholding a drug, they could successfully return damaged optical nerves in mice to a younger – but not totally reset – state.

While the researchers were careful to point out that the results have only been seen in mice, they say it could pave the way for new treatments for age-related conditions.

“It is a major landmark,” Juan Carlos Izpisua Belmonte, a developmental biologist at the Salk Institute for Biological Studies in La Jolla, California, who was not involved in the study, told Nature. “These results clearly show that tissue regeneration in mammals can be enhanced.”

The paper has been covered by 67 online news outlets, and reached an estimated audience on Twitter of more than 7 million. Audiences in Japan and the United States were the most highly engaged, according to Altmetric.

4. “Quantum computational advantage using photons”


Researchers have been racing to demonstrate a phenomenon known as quantum advantage, wherein systems based on quantum bits can perform computations that are far beyond the capacity of current supercomputers.

In this paper, a team led by Jian-Wei Pan and Chao-Yang Lu at the University of Science and Technology of China in Hefei claims to have made the first definitive demonstration of quantum advantage using light-based (photonic) quantum computing system.

As Phillip Ball reports for Nature, Pan and Lu’s experiment achieved within a few minutes what would take an ordinary supercomputer 2.5 billion years to complete.

“Contrary to Google’s first demonstration of a quantum advantage, performed [in 2019], their version is virtually unassailable by any classical computer,” says Ball.

In contrast to Google’s system, this system is not yet programmable, and so is still a long way from being able to perform practical applications, such as sorting through vast datasets for potential new drug candidates. The next step is to develop programmable chips that don’t compromise processing power.

The paper has been covered by almost 100 news outlets to date, and has reached an audience on Twitter of more than 6 million.

5. “The S1 protein of SARS-CoV-2 crosses the blood–brain barrier in mice”

Nature Neuroscience

A growing body of evidence has pointed to the possibility that the SARS-CoV-2 virus that causes COVID-19 can penetrate the brain. For example, neurological symptoms, such as brain fog, headaches, fatigue and loss of smell, persist in some patience long after they’ve cleared the infection, and scientists have found traces of the virus in certain areas of the brain in autopsies.

This study, led by Michelle A. Erickson from the Veterans Affairs Puget Sound Health Care System in Seattle, Washington, found that a viral protein of SARS-CoV-2, the spike 1 protein (S1), readily crosses the brain-blood barrier, a semipermeable border of specialized cells that forms a defence against blood-borne pathogens and toxins. One explanation is that it the protein might break away from the rest of the virus to make it across the threshold.

“It is possible that during infection by SARS-CoV-2, shed S1 is available to cross the brain-blood barrier, triggering responses in the brain itself, without necessarily involving crossing of intact virus particles,” Erickson and her colleagues write.

The study emphasizes the complexity of long-term symptoms that healthcare systems around the world may have to address in the coming decades. It has been mentioned by 102 news outlets to date and has reached an audience on Twitter of more than 12 million, more than any other paper in this list.


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