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‘Mona Lisa’ hides a surprising mix of toxic pigments, study shows

Leonardo da Vinci is renowned to this day for innovations in fields across the arts and sciences. Now, new analyses published in the Journal of the American…

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Leonardo da Vinci is renowned to this day for innovations in fields across the arts and sciences. Now, new analyses published in the Journal of the American Chemical Society show that his taste for experimentation extended even to the base layers underneath his paintings. Surprisingly, samples from both the “Mona Lisa” and the “Last Suppersuggest that he experimented with lead(II) oxide, causing a rare compound called plumbonacrite to form below his artworks.

Credit: Adapted from the Journal of the American Chemical Society, 2023, DOI: 10.1021/jacs.3c07000

Leonardo da Vinci is renowned to this day for innovations in fields across the arts and sciences. Now, new analyses published in the Journal of the American Chemical Society show that his taste for experimentation extended even to the base layers underneath his paintings. Surprisingly, samples from both the “Mona Lisa” and the “Last Suppersuggest that he experimented with lead(II) oxide, causing a rare compound called plumbonacrite to form below his artworks.

An aura of mystery has surrounded the paints and pigments in da Vinci’s studio, leading scientists to scour his writings and artwork to search for clues. Many paintings from the early 1500s, including the “Mona Lisa,” were painted on wooden panels that required a thick, “ground layer” of paint to be laid down before artwork was added. Scientists have found that while other artists typically used gesso, da Vinci experimented by laying down thick layers of lead white pigment and by infusing his oil with lead(II) oxide, an orange pigment that conferred specific drying properties to the paint above. He used a similar technique on the wall underneath the “Last Supper” — a departure from the traditional, fresco technique used at the time. To further investigate these unique layers, Victor Gonzalez and colleagues wanted to apply updated, high-resolution analytical techniques to small samples from these two paintings.

The team performed their analyses on a tiny, “microsample” previously obtained from a hidden corner of the “Mona Lisa,” as well as 17 microsamples obtained from across the surface of the “Last Supper.” Using X-ray diffraction and infrared spectroscopy techniques, they determined that the ground layers of these artworks not only contained oil and lead white, but also a much rarer lead compound: plumbonacrite (Pb5(CO3)O(OH)2). This material had not previously been detected in Italian Renaissance paintings, though it’d been found in later paintings by Rembrandt in the 1600s. Plumbonacrite is only stable under alkaline conditions, suggesting that it formed from a reaction between the oil and lead(II) oxide (PbO). Intact grains of PbO were also found in most of the samples taken from the “Last Supper.”

While painters were known to add lead oxides to pigments to help them dry, the technique has not been proved experimentally for paintings from da Vinci’s time. In fact, when the researchers searched through his writings, the only evidence they found of PbO was in reference to skin and hair remedies, even though it’s now known to be quite toxic. Though he might not have written it down, these results demonstrate that lead oxides must have had a place on the old master’s palette, and might have helped create the masterpieces we know today.

The authors acknowledge funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie actions.

The American Chemical Society (ACS) is a nonprofit organization chartered by the U.S. Congress. ACS’ mission is to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and all its people. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, eBooks and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.

To automatically receive news releases from the American Chemical Society, contact newsroom@acs.org.

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Mathematicians use AI to identify emerging COVID-19 variants

Scientists at The Universities of Manchester and Oxford have developed an AI framework that can identify and track new and concerning COVID-19 variants…

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Scientists at The Universities of Manchester and Oxford have developed an AI framework that can identify and track new and concerning COVID-19 variants and could help with other infections in the future.

Credit: source: https://phil.cdc.gov/Details.aspx?pid=23312

Scientists at The Universities of Manchester and Oxford have developed an AI framework that can identify and track new and concerning COVID-19 variants and could help with other infections in the future.

The framework combines dimension reduction techniques and a new explainable clustering algorithm called CLASSIX, developed by mathematicians at The University of Manchester. This enables the quick identification of groups of viral genomes that might present a risk in the future from huge volumes of data.

The study, presented this week in the journal PNAS, could support traditional methods of tracking viral evolution, such as phylogenetic analysis, which currently require extensive manual curation.

Roberto Cahuantzi, a researcher at The University of Manchester and first and corresponding author of the paper, said: “Since the emergence of COVID-19, we have seen multiple waves of new variants, heightened transmissibility, evasion of immune responses, and increased severity of illness.

“Scientists are now intensifying efforts to pinpoint these worrying new variants, such as alpha, delta and omicron, at the earliest stages of their emergence. If we can find a way to do this quickly and efficiently, it will enable us to be more proactive in our response, such as tailored vaccine development and may even enable us to eliminate the variants before they become established.”

Like many other RNA viruses, COVID-19 has a high mutation rate and short time between generations meaning it evolves extremely rapidly. This means identifying new strains that are likely to be problematic in the future requires considerable effort.

Currently, there are almost 16 million sequences available on the GISAID database (the Global Initiative on Sharing All Influenza Data), which provides access to genomic data of influenza viruses.

Mapping the evolution and history of all COVID-19 genomes from this data is currently done using extremely large amounts of computer and human time.

The described method allows automation of such tasks. The researchers processed 5.7 million high-coverage sequences in only one to two days on a standard modern laptop; this would not be possible for existing methods, putting identification of concerning pathogen strains in the hands of more researchers due to reduced resource needs.

Thomas House, Professor of Mathematical Sciences at The University of Manchester, said: “The unprecedented amount of genetic data generated during the pandemic demands improvements to our methods to analyse it thoroughly. The data is continuing to grow rapidly but without showing a benefit to curating this data, there is a risk that it will be removed or deleted.

“We know that human expert time is limited, so our approach should not replace the work of humans all together but work alongside them to enable the job to be done much quicker and free our experts for other vital developments.”

The proposed method works by breaking down genetic sequences of the COVID-19 virus into smaller “words” (called 3-mers) represented as numbers by counting them. Then, it groups similar sequences together based on their word patterns using machine learning techniques.

Stefan Güttel, Professor of Applied Mathematics at the University of Manchester, said: “The clustering algorithm CLASSIX we developed is much less computationally demanding than traditional methods and is fully explainable, meaning that it provides textual and visual explanations of the computed clusters.”

Roberto Cahuantzi added: “Our analysis serves as a proof of concept, demonstrating the potential use of machine learning methods as an alert tool for the early discovery of emerging major variants without relying on the need to generate phylogenies.

“Whilst phylogenetics remains the ‘gold standard’ for understanding the viral ancestry, these machine learning methods can accommodate several orders of magnitude more sequences than the current phylogenetic methods and at a low computational cost.”


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There will soon be one million seats on this popular Amtrak route

“More people are taking the train than ever before,” says Amtrak’s Executive Vice President.

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While the size of the United States makes it hard for it to compete with the inter-city train access available in places like Japan and many European countries, Amtrak trains are a very popular transportation option in certain pockets of the country — so much so that the country’s national railway company is expanding its Northeast Corridor by more than one million seats.

Related: This is what it's like to take a 19-hour train from New York to Chicago

Running from Boston all the way south to Washington, D.C., the route is one of the most popular as it passes through the most densely populated part of the country and serves as a commuter train for those who need to go between East Coast cities such as New York and Philadelphia for business.

Veronika Bondarenko captured this photo of New York’s Moynihan Train Hall. 

Veronika Bondarenko

Amtrak launches new routes, promises travelers ‘additional travel options’

Earlier this month, Amtrak announced that it was adding four additional Northeastern routes to its schedule — two more routes between New York’s Penn Station and Union Station in Washington, D.C. on the weekend, a new early-morning weekday route between New York and Philadelphia’s William H. Gray III 30th Street Station and a weekend route between Philadelphia and Boston’s South Station.

More Travel:

According to Amtrak, these additions will increase Northeast Corridor’s service by 20% on the weekdays and 10% on the weekends for a total of one million additional seats when counted by how many will ride the corridor over the year.

“More people are taking the train than ever before and we’re proud to offer our customers additional travel options when they ride with us on the Northeast Regional,” Amtrak Executive Vice President and Chief Commercial Officer Eliot Hamlisch said in a statement on the new routes. “The Northeast Regional gets you where you want to go comfortably, conveniently and sustainably as you breeze past traffic on I-95 for a more enjoyable travel experience.”

Here are some of the other Amtrak changes you can expect to see

Amtrak also said that, in the 2023 financial year, the Northeast Corridor had nearly 9.2 million riders — 8% more than it had pre-pandemic and a 29% increase from 2022. The higher demand, particularly during both off-peak hours and the time when many business travelers use to get to work, is pushing Amtrak to invest into this corridor in particular.

To reach more customers, Amtrak has also made several changes to both its routes and pricing system. In the fall of 2023, it introduced a type of new “Night Owl Fare” — if traveling during very late or very early hours, one can go between cities like New York and Philadelphia or Philadelphia and Washington. D.C. for $5 to $15.

As travel on the same routes during peak hours can reach as much as $300, this was a deliberate move to reach those who have the flexibility of time and might have otherwise preferred more affordable methods of transportation such as the bus. After seeing strong uptake, Amtrak added this type of fare to more Boston routes.

The largest distances, such as the ones between Boston and New York or New York and Washington, are available at the lowest rate for $20.

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International

The next pandemic? It’s already here for Earth’s wildlife

Bird flu is decimating species already threatened by climate change and habitat loss.

I am a conservation biologist who studies emerging infectious diseases. When people ask me what I think the next pandemic will be I often say that we are in the midst of one – it’s just afflicting a great many species more than ours.

I am referring to the highly pathogenic strain of avian influenza H5N1 (HPAI H5N1), otherwise known as bird flu, which has killed millions of birds and unknown numbers of mammals, particularly during the past three years.

This is the strain that emerged in domestic geese in China in 1997 and quickly jumped to humans in south-east Asia with a mortality rate of around 40-50%. My research group encountered the virus when it killed a mammal, an endangered Owston’s palm civet, in a captive breeding programme in Cuc Phuong National Park Vietnam in 2005.

How these animals caught bird flu was never confirmed. Their diet is mainly earthworms, so they had not been infected by eating diseased poultry like many captive tigers in the region.

This discovery prompted us to collate all confirmed reports of fatal infection with bird flu to assess just how broad a threat to wildlife this virus might pose.

This is how a newly discovered virus in Chinese poultry came to threaten so much of the world’s biodiversity.

H5N1 originated on a Chinese poultry farm in 1997. ChameleonsEye/Shutterstock

The first signs

Until December 2005, most confirmed infections had been found in a few zoos and rescue centres in Thailand and Cambodia. Our analysis in 2006 showed that nearly half (48%) of all the different groups of birds (known to taxonomists as “orders”) contained a species in which a fatal infection of bird flu had been reported. These 13 orders comprised 84% of all bird species.

We reasoned 20 years ago that the strains of H5N1 circulating were probably highly pathogenic to all bird orders. We also showed that the list of confirmed infected species included those that were globally threatened and that important habitats, such as Vietnam’s Mekong delta, lay close to reported poultry outbreaks.

Mammals known to be susceptible to bird flu during the early 2000s included primates, rodents, pigs and rabbits. Large carnivores such as Bengal tigers and clouded leopards were reported to have been killed, as well as domestic cats.

Our 2006 paper showed the ease with which this virus crossed species barriers and suggested it might one day produce a pandemic-scale threat to global biodiversity.

Unfortunately, our warnings were correct.

A roving sickness

Two decades on, bird flu is killing species from the high Arctic to mainland Antarctica.

In the past couple of years, bird flu has spread rapidly across Europe and infiltrated North and South America, killing millions of poultry and a variety of bird and mammal species. A recent paper found that 26 countries have reported at least 48 mammal species that have died from the virus since 2020, when the latest increase in reported infections started.

Not even the ocean is safe. Since 2020, 13 species of aquatic mammal have succumbed, including American sea lions, porpoises and dolphins, often dying in their thousands in South America. A wide range of scavenging and predatory mammals that live on land are now also confirmed to be susceptible, including mountain lions, lynx, brown, black and polar bears.

The UK alone has lost over 75% of its great skuas and seen a 25% decline in northern gannets. Recent declines in sandwich terns (35%) and common terns (42%) were also largely driven by the virus.

Scientists haven’t managed to completely sequence the virus in all affected species. Research and continuous surveillance could tell us how adaptable it ultimately becomes, and whether it can jump to even more species. We know it can already infect humans – one or more genetic mutations may make it more infectious.

At the crossroads

Between January 1 2003 and December 21 2023, 882 cases of human infection with the H5N1 virus were reported from 23 countries, of which 461 (52%) were fatal.

Of these fatal cases, more than half were in Vietnam, China, Cambodia and Laos. Poultry-to-human infections were first recorded in Cambodia in December 2003. Intermittent cases were reported until 2014, followed by a gap until 2023, yielding 41 deaths from 64 cases. The subtype of H5N1 virus responsible has been detected in poultry in Cambodia since 2014. In the early 2000s, the H5N1 virus circulating had a high human mortality rate, so it is worrying that we are now starting to see people dying after contact with poultry again.

It’s not just H5 subtypes of bird flu that concern humans. The H10N1 virus was originally isolated from wild birds in South Korea, but has also been reported in samples from China and Mongolia.

Recent research found that these particular virus subtypes may be able to jump to humans after they were found to be pathogenic in laboratory mice and ferrets. The first person who was confirmed to be infected with H10N5 died in China on January 27 2024, but this patient was also suffering from seasonal flu (H3N2). They had been exposed to live poultry which also tested positive for H10N5.

Species already threatened with extinction are among those which have died due to bird flu in the past three years. The first deaths from the virus in mainland Antarctica have just been confirmed in skuas, highlighting a looming threat to penguin colonies whose eggs and chicks skuas prey on. Humboldt penguins have already been killed by the virus in Chile.

A colony of king penguins.
Remote penguin colonies are already threatened by climate change. AndreAnita/Shutterstock

How can we stem this tsunami of H5N1 and other avian influenzas? Completely overhaul poultry production on a global scale. Make farms self-sufficient in rearing eggs and chicks instead of exporting them internationally. The trend towards megafarms containing over a million birds must be stopped in its tracks.

To prevent the worst outcomes for this virus, we must revisit its primary source: the incubator of intensive poultry farms.

Diana Bell does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

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