One of the stranger features of our Universe is the existence of what you might call "dual-core stars." Many stars exist as part of a multistar system, and in some cases, their orbits are extremely close. Couple that with the fact that stars can expand as they age, and you get a situation in which the outer edges of one star may engulf a second. Friction can then draw the stars' orbits closer, resulting in the core of both stars orbiting within a large, shared envelope of plasma.

Things can get more complicated still when you consider that the stars won't necessarily have life cycles that line up well—one of them could easily explode before the other, leaving behind a black hole or a neutron star. That can lead to some bizarre situations, like a star that replaces its core with a neutron star.

Now, researchers say they have probably found a more violent alternative to that merger. In this case, the neutron star didn't settle neatly into the core of its companion star. Instead, the companion star lost its outer layers to space and then saw its core disrupted in a way that caused it to explode.

Something new

The object in question, technically named VT J121001+495647, was identified by a team that compared two different surveys of the sky done at radio frequencies. The researchers looked for objects that were present when a survey was done between 2017 and 2018 and weren't present when the same area of sky was covered in a 1994–2005 survey. The brightest of these objects was VT J121001+495647.

A check of a hydrogen emission line from the object indicated that it was very broad instead of forming a sharp peak. This tells us that VT J121001+495647 has multiple components. Some are moving toward us, so the light they produce is blue-shifted, broadening the peak in that direction. Others are moving away from us and are thus broadening the peak in the red direction. The simplest explanation for this activity is that VT J121001+495647 is the debris of an exploded star, expanding out in all directions.

More accurately, we're seeing that debris slamming into material that was ejected from the star earlier, prior to its explosion. But the researchers calculate that the total amount of mass ejected earlier has to be at least the same as the mass of the Sun—a large amount of material, too large to be accounted for by a solar-wind-like process. So the material must have been ejected relatively recently for the supernova debris to be slamming into it already.

Complicating matters further, the team searched the archives for unusual events at the same location and came up with one: an X-ray burst picked up by an instrument on the International Space Station. The event was unusual in comparison to other X-ray bursts in that it was very luminous but brief, and it didn't extend to higher-energy wavelengths. The burst dates to three years prior to the imaging of VT J121001+495647, so it could have been from the supernova itself. But the duration and energy of the burst didn't match what we typically see from forming neutron stars or black holes.

Making sense of it all

Putting all the data together, we have evidence that the star ejected a lot of material a few years before it exploded, and the timing of this eruption may be linked to an X-ray burst. There are several ways to explain this phenomenon, but most don't seem to match up with the data especially well. For example, instabilities in the fusion reactions at the core of the star can cause an eruption, but they're only large enough to spit out a Sun's worth of material in the last few years before the explosion. And if that happened, the material would still be closer to where the star was than it actually is.

Interactions with a companion star could potentially produce a shell of material of the right density and distance. But the chances of them occurring so close to the star's explosion are extremely small.

So the researchers propose an alternative: The ejection of material did come through interactions with a companion object, and the interactions are what triggered the supernova.

The theoretical ideas behind that idea were explained in a series of papers released in the middle of the last decade. If the companion star has already exploded, it would then be in the form of a neutron star or black hole. If that body ended up inside the envelope of the normal star, it would form an accretion disk and jets, which would blast out a lot of the material in the outer layers of the star, forming the more distant material creating the radio signal.

If the compact companion object ends up close enough to the star's core, however, it could disrupt the core via tidal interactions. That's a problem because the orderly fusion of elements in the core provides the energy needed to keep gravity from collapsing the star. Mess with the core and the whole thing can come crashing down, producing a supernova. During this process, the infalling companion could have briefly formed an accretion disk and jets, which would then account for the X-ray burst found in the archives.

The star must have been massive enough to explode at some point anyway, but the disruption hastened the process.

There are a couple of other oddball objects we've seen in the past that could have been created by a similar mechanism. Unfortunately, we don't have the same wealth of data on them that we have for VT J121001+495647, so the timing of events can't be nailed down precisely. But with a good model of what to look for, don't be surprised if we're now able to identify others.

Science, 2021. DOI: 10.1126/science.abg6037  (About DOIs).

China appears to be accelerating its plans to land on the Moon by 2030 and would use a modified version of an existing rocket to do so.

The chief designer of the Long March family of rockets, Long Lehao, said China could use two modified Long March 5 rockets to accomplish a lunar landing in less than a decade, according to the Hong Kong-based online news site, HK01. He spoke earlier this week at the 35th National Youth Science and Technology Innovation Competition in China. The full video can be found here.

During Lehao's speech, he said one of these large rockets would launch a lunar lander into orbit around the Moon, and the second would send the crew to meet it. The crew would then transfer to the lander, go down to the Moon's surface, and spend about six hours walking on its surface. Then part of the lunar lander would ascend back to meet the spacecraft and return to Earth.

Lehao's talk does not carry the official imprimatur of Chinese space policy—at least not yet. But he remains an influential figure in Chinese space policy, said Andrew Jones, a journalist who tracks China's space program. "It's a good indication of China working towards that plan to some degree," he told Ars. "There will apparently be an announcement on this rocket at the Zhuhai Airshow in late September or early October."

The Chinese Moon plan would require several technology developments. The Long March 5 rocket, which has a capacity similar to that of a Delta IV Heavy rocket, would be upgraded to become the "Long March 5-DY." Lehao has previously described these upgrades, which would improve performance for lunar missions. China would also need a lunar lander and a next-generation spacecraft capable of deep space missions.

Nevertheless, the use of an existing rocket that has already launched seven times would simplify the mission for China. Although the country's aerospace engineers are in the early stages of developing a super-heavy lift rocket named Long March 9, it probably won't be ready for test flights before 2030. By modifying an existing rocket, China could get to the Moon faster.

This only adds further fuel to the idea that NASA and China are in something of a race to the Moon. The United States has created the "Artemis Program" for a lunar return. While this program has a nominal date of a 2024 human landing, that seems infeasible due to the lack of a finished lunar lander, space suits, and other technical problems. The year 2026 seems like the earliest possible date for a lunar landing, and of course that could slip further to the right.

Both countries are also seeking to bring international partners along. The United States has already added a dozen signatories to the "Artemis Accords," including Australia, Italy, Japan, South Korea, and the United Kingdom. China has reached a deal with Russia to build a lunar research station and is also courting European partners.

Former NASA Administrator Mike Griffin, who served under the George W. Bush administration, has long warned US policymakers that China could accelerate its Moon plans and beat NASA by using an existing heavy lift rocket.

Speaking at a 2018 Users Advisory Group meeting of the National Space Council, Griffin said, "They never seem to be in a rush. They seem to be playing the long game. So I’m not saying they will be on the Moon in six to eight years, but if they wanted to be they could. And for them to be back on the Moon when the United States can’t get back on the Moon is a travesty."

Now, China be in a rush.

We've tended to treat the RNA-based vaccines from Moderna and Pfizer/BioNTech as functionally equivalent. They take an identical approach to producing immunity and have a very similar set of ingredients. Clinical trial data suggested they had very similar efficacy—both in the area of 95 percent.

So it was a bit of a surprise to have a paper released yesterday indicating that the two produce an antibody response that's easy to distinguish, with Moderna inducing antibody levels that were more than double those seen among people who received the Pfizer/BioNTech shot. While it's important not to infer too much from a single study, this one was large enough that the results are likely to be reliable. If so, the results serve as a caution that we might not want to base too many of our expectations on relatively crude measures of antibody levels.

The new study

The work itself was remarkably simple. A Belgian medical center was vaccinating its staff and asked for volunteers willing to give blood samples. Samples were taken both prior to vaccination and six to 10 weeks after, with the levels of antibody specific to the SARS-CoV-2 spike protein tested at both points. About 700 participants received the Moderna vaccine, while roughly 950 took the one from Pfizer/BioNTech.

With the data in hand, the researchers simply compared the levels of antispike antibodies in the different groups. One thing this revealed is that those who had been infected prior to the vaccination developed a much higher response than the other participants, with over five times the amount of antibodies following vaccination.

But the notable surprise was that the Moderna vaccine generated a stronger response than the Pfizer/BioNTech version. In terms of units of antibody per millilitres of blood sample, the difference was 3,836 to 1,444, with confidence intervals that didn't come close to overlapping. In other words, it's a statistically significant difference in a sufficiently large sample that it's unlikely to be by chance.

That said, there are a couple of caveats. One is that, while the medical center was likely able to store and administer the vaccines appropriately, they were at the end of a complicated production and distribution network, and there is a chance that something happened to one of the vaccines before it made it to the clinic. A simple replication would sort this out quickly.

What to make of it?

The other important caveat is that the researchers behind the study simply measured the total levels of antibody that stuck to the spike protein. Only a subset of these will be what are termed neutralizing antibodies, which stick to spike in a way that interferes with the protein's ability to interact with cells and insert the virus's genome. Measuring neutralizing antibodies is much more difficult, so most studies do what this one has.

But it's technically possible that, despite the differences in total antibodies, both vaccines generated similar levels of neutralizing antibodies—something else an additional study could sort out. This would be consistent with the vaccines' generally similar levels of protection, as protection seems to correlate with neutralizing antibody levels.

While we wait for data to help sort this out, it's worth considering whether we might be placing a little too much emphasis on antibody levels in our decision-making. Right now, arguments about the need for boosters are based in part on the fact that antibody levels drop over time, even though that's a normal consequences of the shift away from a response to an active infection and toward a functional immune memory of that infection. And the efficacy of a booster is being based in part on the fact that it restores high levels of antibody—even though that's exactly what should happen when the immune memory cells are activated by re-exposure to the spike protein.

These results should be approached with caution, since we don't fully understand how these changes in antibody level correlate with protection.

JAMA, 2021. DOI: 10.1001/jama.2021.15125  (About DOIs).

Wind power doesn't make up the largest part of the United States' energy mix, but it grew over the last year, according to the Wind Technologies Market Report. The renewable energy source grew to more than 8 percent of the country's electricity supply—reaching 10 percent in a growing number of states—and saw a whopping $25 billion in investments in what will translate to 16.8 gigawatts of capacity, according to the report.

Released by the US Department of Energy, the sizeable report draws on a variety of data sources, including government data from the Energy Information Administration, trade data from the US International Trade Commission, and hourly pricing data from the various system operators. “The report itself covers the entire gamut of the US wind industry,” Mark Bolinger, a research scientist at Lawrence Berkeley National Laboratory and one of the authors of the report, told Ars.

Bigger is sometimes better

According to the report, the performance of wind power operations in the US has improved a great deal. We can measure this metric based on capacity factor, a ratio of the amount of energy a turbine actually produces compared to the amount it could have produced if it ran at its peak constantly. For recently constructed wind power projects, the average capacity factor has now cleared 40 percent. The biggest gains in this area, however, are seen in the US's “wind belt,” a region stretching from the Dakotas to Texas that receives a large amount of wind.

In large part, this increase is due to longer blades, which allow the turbines to generate more power as they're spun around by the wind. According to the report, in 2010, there were no turbines in the US that had rotors at or above 115 meters in diameter. However, last year, 91 percent of new turbines had rotors of this size or larger. The report also notes that this size is likely to increase.

The towers these rotors are attached to are also getting taller, sometimes along with the increase in blade size. According to Bolinger, this move isn't quite as widespread, but “it is starting to creep up now.”

In the past, there's been a “soft cap” of 500 feet on the total height of the turbines—from the base of the tower to the tip of the blades—because that triggers greater permitting requirements from the Federal Aviation Administration, he said. But with the size of the rotors increasing recently, the size of the towers themselves also needs to increase to avoid having the blades swing too low to the ground. Developers have gotten more comfortable going over 500 feet, he said, adding that some turbines are reaching 700 feet tall. Even besides the practical reason behind them, taller towers also help the turbines generate more energy.

“In general, the winds tend to be stronger at higher altitudes, so this is something that will increase the capacity factor,” he said.

The “wind belt” still sees the vast majority of wind development in the US. However, this trend of larger turbines with larger rotors allows wind operators to function quite well in areas that have lower average wind speeds. “That does open up other parts of the country to economical wind development,” he said.

There are larger up-front costs to build these larger turbines, but at a dollar-per-watt basis, they end up cheaper. They may be more expensive, but they produce more energy, Bolinger said.

Blowin’ in the wind

All of this is making wind power cheaper. In 2009, the national average price of wind power purchase agreements reached a peak of $70 per megawatt-hour. Now, in the “wind belt,” it is around $20 per megawatt-hour and averages around $30 per megawatt-hour in the country's eastern and western regions. “These are at, or near, all-time lows,” Bolinger said, although they include the impact of renewable energy tax breaks.

Wind also gets indirect subsidies, since it requires power lines to get to people. Wind operations tend to be located far away from major population centers. Bolinger said that, to improve the effectiveness of wind power, there should be better incentives to build these lines and more planning involved in building them.

“You need that critical transmission link to move the power from the wind farm to the urban centers where the power can be consumed,” he said.

Wind's growth has come in part due to tax breaks and the willingness to pay the costs of expanding the transmission grids. But it also provides benefits that aren't priced in, either. By displacing fossil fuels, wind power can reduce the emissions of various compounds such as carbon dioxide, nitrogen oxides, and sulfur dioxide, among others. Human health and the climate benefit from these reductions. The report estimates that the national average economic benefits for these reductions came to $76 per megawatt-hour generated by wind last year. According to Bolinger, this year's report is the first that includes a segment about the health and environmental benefits of the renewable energy source.

The mantis shrimp boasts one of the most powerful, ultrafast punches in nature—it's on par with the force generated by a .22 caliber bullet. This makes the creature an attractive object of study for scientists eager to learn more about the relevant biomechanics. Among other uses, it could lead to small robots capable of equally fast, powerful movements. Now a team of Harvard University researchers have come up with a new biomechanical model for the mantis shrimp's mighty appendage, and they built a tiny robot to mimic that movement, according to a recent paper published in the Proceedings of the National Academy of Sciences (PNAS).

“We are fascinated by so many remarkable behaviors we see in nature, in particular when these behaviors meet or exceed what can be achieved by human-made devices,” said senior author Robert Wood, a roboticist at Harvard University's John A. Paulson School of Engineering and Applied Sciences (SEAS). “The speed and force of mantis shrimp strikes, for example, are a consequence of a complex underlying mechanism. By constructing a robotic model of a mantis shrimp striking appendage, we are able to study these mechanisms in unprecedented detail.”

Wood's research group made headlines several years ago when they constructed RoboBee, a tiny robot capable of partially untethered flight. The ultimate goal of that initiative is to build a swarm of tiny interconnected robots capable of sustained untethered flight—a significant technological challenge, given the insect-sized scale, which changes the various forces at play. In 2019, Wood's group announced their achievement of the lightest insect-scale robot so far to have achieved sustained, untethered flight—an improved version called the RoboBee X-Wing. (Kenny Breuer, writing in Nature, described it as a "a tour de force of system design and engineering.")

Now, Wood's group has turned its attention to the biomechanics of the mantis shrimp's knock-out punch. As we've reported previously, mantis shrimp come in many different varieties; there are some 450 known species. But they can generally be grouped into two types: those that stab their prey with spear-like appendages ("spearers") and those that smash their prey ("smashers") with large, rounded, and hammer-like claws ("raptorial appendages"). Those strikes are so fast (as much as 23 meters per second, or 51mph) and powerful, they often produce cavitation bubbles in the water, creating a shock wave that can serve as a follow-up strike, stunning and sometimes killing the prey. Sometimes a strike can even produce sonoluminescence, whereby the cavitation bubbles produce a brief flash of light as they collapse.

According to a 2018 study, the secret to that powerful punch seems to arise not from bulky muscles but from the spring-loaded anatomical structure of the shrimp's arms, akin to a bow and arrow or a mouse trap. The shrimp's muscles pull on a saddle-shaped structure in the arm, causing it to bend and store potential energy, which is released with the swinging of the club-like claw. It's essentially a latch-like mechanism (technically, Latch-mediated spring actuation, or LaMSA), with small structures in the muscle tendons called sclerites serving as the latch. 

That much is well understood, and there are several other small organisms capable of producing ultra-fast moves through a similar latching mechanism: frogs' legs and chameleons' tongues, for instance, as well as the mandibles of trap jaw ants and exploding plant seeds. But biologists who have been studying these mechanisms for years have noticed something unusual in the mantis shrimp—a one-millisecond delay between when the unlatching and the snapping action occurs.

“When you look at the striking process on an ultra-high-speed camera, there is a time delay between when the sclerites release and the appendage fires,” said co-first author Nak-seung (Patrick) Hyun, a postdoctoral fellow at SEAS. “It is as if a mouse triggered a mouse trap but instead of it snapping right away, there was a noticeable delay before it snapped. There is obviously another mechanism holding the appendage in place, but no one has been able to analytically understand how the other mechanism works.”

Mantis shrimp lack special muscles to produce such fast accelerations, so biologists have suggested that the sclerites are only responsible for the initial unlatching, while the geometry of arm structure serves as a secondary latch that controls the movement of the arm. "The idea is that the linkage design itself is such that you're able to actually store energy and release it with just one input motion," co-first author Emma Steinhardt told Ars. "It's this geometric latch that is releasing all the stored energy." Steinhardt, Hyun, and their fellow co-authors set out to experimentally test this hypothesis.

For their robot version of the mantis shrimp appendage, they relied on the unique manufacturing process inspired by pop-up books (pop-up book MEMS) that Wood's group used to build RoboBee. It involves cutting designs from flat sheets, layering them and bonding the layers with glue, and then folding them into the desired shapes. A miniaturized kind of "artificial muscle" can be made with piezoelectric actuators, while thin plastic hinges make excellent joints for rotational motion. Then they conducted numerous experiments in both air and water with two different loading conditions.

They were able to identify four distinct striking phases and confirmed that, indeed, it's the geometry of the mechanism that produces the rapid acceleration after the initial unlatching by the sclerites. The little robot mechanism's performance wasn't quite mantis shrimp-level, but the appendage still reached 26 meters per second in air, the equivalent of a car going from 0 to 58 mph in just four milliseconds. While that's not quite as good as the actual animal, it's still impressive.

The medium might matter: a study last year found that the mantis shrimp punches at half the speed in air, suggesting that the mantis shrimp can precisely control its striking behavior, depending on the surrounding medium. According to Hyun, their experiments showed a so-called "added mass effect" in the water-based experiments. "In fluid mechanics, when you move really quickly, you're actually pushing a heavier mass," he told Ars. That effect was low in the RoboBee experiments, since it functions in air, but it's a critical variable when modeling the mantis shrimp strike in water.

The short delay between unlatching and the snap "is likely a crucial feature enabling repeated and extreme use without the wear and tear of contact latching mechanisms," the authors wrote.  Going forward, they hope to extend their strategy of combining physical and analytical modeling to learn more about other species, such as the underlying mechanisms of trap jaw ants or leaping frogs.

“This study exemplifies how interdisciplinary collaborations can yield discoveries for multiple fields,” said co-author Sheila Patek, a biologist at Duke University. “The process of building a physical model and developing the mathematical model led us to revisit our understanding of mantis shrimp strike mechanics and, more broadly, to discover how organisms and synthetic systems can use geometry to control extreme energy flow during ultra-fast, repeated-use, movements.”

DOI: PNAS, 2021. 10.1073/pnas.2026833118  (About DOIs).

Archaeologists working in Pompeii recently unearthed the tomb and partially mummified remains of a man who died a few decades before the eruption. The man, Marcus Venerius Secundio, according to his epitaph, had once been enslaved, but by the end of his life he’d obtained enough wealth and status to sponsor four days of theater performances in Pompeii.

Rags to riches in Imperial Rome

Archaeologists rediscovered Marcus Venerius Secundio’s tomb in the ancient cemetery, or necropolis, of Porta Sarno in the eastern part of Pompeii, where tourists aren’t allowed. His tomb was large and imposing, with a colorfully painted facade depicting green plants on a blue background; traces of the paint still cling to the stone even after 2,000 years. It was also sealed so well that its occupant’s remains had partially mummified, preserving some soft tissue and a few tufts of white hair, along with some scraps of fabric.

Because Pompeii is both amazingly well-preserved and extensively studied, archaeologists were able to match the name inscribed over the tomb’s entrance to a name on wax tablets in the house of a banker named Lucius Caecilius Jucundus, across the city from the necropolis. The banker’s tablets recorded Marcus as a “public slave” who worked as a custodian in the Temple of Venus, which once stood at the western end of town (that’s almost certainly where the second part of his name, Venerius, comes from). But at some point he became a libertus, or freedman, and began to build a new life for himself.

Slavery in Rome wasn’t always a permanent state, and many liberti went on to build relatively prosperous lives for themselves. Evidence of their history persists all over Pompeii. And the libertus Marcus evidently did quite well for himself indeed; the epitaph carved into the stone over his tomb boasts that he once sponsored four full days of theatrical performances for the people of Pompeii, given in both Greek and Latin.

That seems like an odd thing to brag about on your tombstone, but for affluent Romans, sponsoring public entertainment like plays or gladiatorial matches provided a way of showing off while also cementing one’s popularity and fame. It was philanthropy as both advertisement and power move, a la Carnegie and Rockefeller. By bragging about the plays he’d sponsored, Marcus was asserting that he’d been a mover and shaker in his day.

“Greek and Latin ludi for the duration of four days”

In recording his proudest accomplishment, Marcus also offered a glimpse of the broader cultural life of Pompeii. Greek was the most common language in the eastern Mediterranean in the early centuries CE, and plays and other performances were a huge part of the social scene in cities like Pompeii. But archaeologists haven’t found any other evidence that plays were performed in Greek in this cosmopolitan but solidly Roman city.

“That performances in Greek were organized is evidence of the lively and open cultural climate which characterized ancient Pompeii,” said archaeologist Gabriel Zuchtriegel, director of the Pompeii Archaeological Park.

Plenty of other archaeological and historical evidence paints the buried city as a diverse place, full of people and cultures from around the Roman world. Zuchtriegel described evidence of Greek theater in town as “another tessera of a large mosaic” that was Pompeii’s cultural life.

Hurricane Ida roared into the southern US state of Louisiana on Sunday at 11:55 am local time (16:55 UTC) with sustained winds of 150 mph. The storm's distinct eye moved into the state's southernmost seaport, Port Fourchon, setting about destroying buildings and scattering boats moored nearby.

But Ida did not stop there. Instead of weakening as it marched northward toward the larger cities of New Orleans and Baton Rouge, Ida appeared to maintain its organization with a distinct eye and even small vortices rotating around the center of the storm.

Ida brought many forms of devastation to Louisiana. Its storm surge swamped coastal areas and pushed water levels to flooding levels in Lake Pontchartrain near New Orleans. Heavy rains flooded low-lying areas of the state.

But probably the most damaging aspect of the storm for most Louisianans came from the storm's winds—knocking trees into thousands of homes and knocking out power to more than 1 million customers. This affected about half the state's population and nearly all of the urban Baton Rouge and New Orleans areas and may cripple initial recovery efforts.

This is because Ida's winds kept howling. More than two hours after landfall, at 2 pm CT, Ida's winds were estimated to have fallen just 5 mph, to 145 mph. At 4 pm the storm's maximum winds were still a staggering 130 mph. At 10 pm, more than 10 hours after landfall, Ida still packed the punch of a Category 2 hurricane, with estimated winds of 105 mph.

This slow weakening is in stark contrast to a typical hurricane. Based upon a simple model for a landfalling hurricane, a storm like Ida would have been expected to drop from 150 to 100 mph after four hours, and to 70 mph after 10 hours. So why did Ida maintain its devastating intensity for so long?

Some of this is due to geography. The Louisiana coastland is largely made up of swampy, marshy land barely above sea level. Anyone who has ever driven Interstate 10 across Louisiana knows this. The lengthy Atchafalaya Basin Bridge between Lafayette and Baton Rouge traverses above seemingly endless swampy ground, and this region lies about 50 miles inland from the coast. As Ida approached Louisiana, its storm surge pushed warm water from the Gulf of Mexico inland. This allowed the storm to continue traversing "over water" even as it moved dozens of miles into the state.

Ida's slow weakening was also fueled by the "brown ocean effect," in which latent heat from very wet soils can mimic the moisture-rich environment of the ocean. The Southern Louisiana marshes are fertile environments for this kind of latent heating. Because of its relatively slow movement, less than 10 mph to the north, Ida spent several hours over the more moist environment.

Ida finally succumbed to drier ground overnight and has weakened into a tropical storm by Monday morning. It should rapidly weaken further as it travels over Mississippi today. Enough of a low pressure system may still remain by late Thursday, however, to allow the remnants of Ida to become an extratropical storm after it emerges into the Atlantic Ocean and rips off to the northeast. Good riddance.

All living things on Earth use a version of the same genetic code. Every cell makes proteins using the same 20 amino acids. Ribosomes, the protein-making machinery within cells, read the genetic code from a messenger RNA molecule to determine which amino acid to put next into the particular protein they are building.

This code is universal, which is why the ribosomes in our cells can read a piece of viral messenger RNA and make a functional viral protein from it. There are plenty of other amino acids, though. While life does not generally use them, scientists have been incorporating these into proteins. Now, researchers have figured out a way to greatly expand the genetic code, allowing widespread incorporation of these non-biological amino acids. They accomplish this by running a second set of everything—proteins and RNAs—needed to translate the genetic code.

A system apart

Non-canonical amino acids can serve a number of functions. They can act as labels so a researcher’s particular protein of interest can more easily be tracked within cells. They can help to regulate a protein’s function, allowing researchers to activate and inactivate it at a specific time and place of their choosing and then observe the downstream effects. If enough of these non-canonical amino acids are strung together, the resulting proteins would constitute an entirely new class of biopolymers that might carry out functions that traditional proteins cannot—for research, therapeutic, or other purposes.

Putting non-canonical amino acids into proteins requires tinkering with the genetic code, which has no way of specifying for their use. One option is to edit the cell’s genetic code, leaving most of it intact. An alternative uses modified versions of all the components of the genetic code: orthogonal mRNAs, orthogonal ribosomes, and orthogonal enzymes that are responsible for reading the mRNAs and building the proteins within the ribosomes. Orthogonal here means that this machinery will run alongside the normal ribosomal protein-making machinery in a cell but will not interfere with it. It will read and translate only its own orthogonal mRNAs, not the normal cellular ones.

These orthogonal components would be extraneous, so not essential to the cell’s functioning. They can therefore be engineered and regulated differently and tweaked in any way scientists can dream up. They can be used to make new polymers and shed light on the mechanisms involved in normal cellular protein production. That’s something that we can’t do with the normal cellular components, since that would kill the cell.

Optimizing orthogonality

Jason Chin, head of the Centre for Chemical & Synthetic Biology (CCSB) in Cambridge, UK, has made all of these orthogonal components. But they are not very efficient. In a paper published this week in Nature Chemistry, he describes how he fixed that: by using computational algorithms to automatically design and optimize which orthogonal mRNAs are best translated by orthogonal ribosomes. Not only did he dramatically improve protein yields, the changes ensured that orthogonal ribosomes worked efficiently even when normal ribosomes were present.

“Our understanding of the factors that determine protein yield for natural translation are incomplete... only half the variance in observed protein yield can be explained by known parameters,” laments the introduction to the work. Nevertheless, his lab knew that the initiation step, when the ribosome grabs the messenger RNA, is a key step. They also knew that the structure of the mRNA is important. So they started mutating their orthogonal mRNA to change those two aspects and selected for those mutants that bound orthogonal ribosomes well but normal ribosomes less well. After hundreds of rounds of mutations, they had optimized three different orthogonal mRNAs, encoding three different proteins. One of them contained four non-canonical amino acids.

The lab then applied the same approach to optimize orthogonal enzymes, and they generated a 33-fold increase in protein yield; the orthogonal system now made just as much protein as the normal cellular system did. The cells used in this work were E. coli, but Dr. Chin has used an orthogonal system to make non-canonical proteins in yeast, mammalian cells, worms, and fruit flies.

“We anticipate that the opportunities arising from approaches to incorporate multiple distinct non-canonical amino acids will increase as the number of distinct non-canonical amino acids that can be incorporated increases,” he and his co-workers write. These algorithms they developed to design efficiently translated orthogonal mRNAs should certainly help them move toward that goal.

Nature Chemistry, 2021. DOI:  10.1038/s41557-021-00764-5

For decades, the Pacific Northwest National Laboratory (PNNL) has been home to an unusual artifact from World War II: a small cube of solid uranium metal, measuring about two inches on each side and weighing just under 2.5 kilograms. Lab lore holds that the cube was confiscated from Nazi Germany's failed nuclear reactor experiments in the 1940s, but that has never been experimentally verified.

PNNL scientists are developing new nuclear forensic techniques that should help them confirm the the pedigree of this cube—and others like it—once and for all. Those methods could also eventually be used to track illicit trafficking of nuclear material. PNNL's Jon Schwantes and graduate student Brittany Robertson presented some of their initial findings this week at the fall meeting of the American Chemical Society (a hybrid virtual/in-person event).

University of Maryland physicist Timothy Koeth is among the outsider collaborators in this ongoing research. He has spent over seven years tracking down these rare artifacts of Nazi Germany's nuclear research program, after receiving one as a gift. As of 2019, he and a UMD colleague, Miriam Herbert, had tracked down 10 cubes in the US: one at the Smithsonian, another at Harvard University, a handful in private collections—and of course, the PNNL cube.

What makes these cubes so special is their historical significance. As we reported previously:

Underpinning the Manhattan Project in the US was the fear that German scientists under Adolf Hitler's Nazi regime would beat the Allies to a nuclear bomb. The Germans had a two-year head-start, but according to Koeth, "fierce competition over finite resources, bitter interpersonal rivalries, and ineffectual scientific management" resulted in significant delays in their progress toward achieving a sustained nuclear reaction. German nuclear scientists were separated into three isolated groups based in Berlin (B), Gottow (G), and Leipzig (L).

 

Renowned physicist Werner Heisenberg headed up the Berlin group, and as the Allied forces advanced in the winter of 1944, Heisenberg moved his team to a cave under a castle in a small town called Haigerloch—now the site of the Atomkeller Museum. That's where the group built the B-VIII reactor. It resembled an "ominous chandelier," per Koeth, because it was composed of 664 uranium cubes strung together with aircraft cable and then submerged in a tank of heavy water shielded by graphite to prevent radiation exposure.

 

As the German scientists were racing against time, Manhattan Project lead Lieutenant General Leslie Groves kicked off a covert mission dubbed "Alsos," with the express purpose of gathering information and materials related to Germany's scientific research. When the Allied forces closed in at last, Heisenberg took apart the B-VIII experiment and buried the uranium cubes in a field, ferreting away key documentation in a latrine. (Pity Samuel Goudsmit, the poor physicist who had to dig those out.) Heisenberg himself escaped by bicycle, carrying a few cubes in a backpack.

As Heisenberg himself acknowledged, the German scientists' final experiment failed because the amount of uranium in the cubes was insufficient to trigger a sustained nuclear reaction. But Heisenberg was confident that "a slight increase in its size would have been sufficient to start off the process of energy production." A model described in a 2009 paper bears that out, showing that the group would only have needed 50 percent more uranium cubes to get the design to work. If it had, our world might look very different today.

The Alsos team purportedly brought the cubes confiscated from Berlin to the United States for use in the uranium processing facility at Oak Ridge. However, Koeth learned that, by April 1945, the US didn't need additional feedstock material. And there is no official record of any cubes entering the country, so most of them have never been accounted for. Ditto for the 400 or so uranium cubes that had been in use by the Gottow group, led by Kurt Diebner.

According to PNNL lore, their cube was stored at DOE headquarters until 1989. That's when it was brought to the laboratory as a radiation training tool for RadCAD, a set of hands-on courses on the detection and interception of illicit trafficking in radioactive materials.

The PNNL cube, like its brethren, is made of solid natural uranium metal. The cubes are only slightly radioactive and don't pose a health concern. Because uranium is so dense, it essentially shields itself. Any measured radiation comes from the surface. Nonetheless, the PNNL cube is kept in a double-plexiglass container to prevent exposure to radiation during handling and contamination of the cube from oxidization, according to Robertson.

The PNNL scientists were pretty confident they had a "Heisenberg cube"; among other evidence, the cube is notched, the better to hang on the cables used in the German reactor efforts. But that evidence is largely anecdotal, per Robertson and Schwantes. The cube was analyzed back in 2002 via high-resolution gamma spectroscopy to get an estimate of its age, but those results were inconclusive. "That's typically not sensitive enough to provide an accurate age for the cube," said Schwantes.

Several years ago, as the PNNL cube was being repackaged, Schwantes and a colleague shaved a few small samples off the metal for analysis. They hoped to confirm once and for all that it is one of the Heisenberg cubes—or possibly a "Diebner cube." Robertson's work—part of her doctoral thesis research—is to study those samples using her own modified analytic techniques, in conjunction with PNNL's standard nuclear forensic methods.

For instance, radiochronometry is a popular method with geologists. It's commonly used to determine the age of a uranium-rich material by measuring the byproducts of the uranium's decay, namely the radioactive isotope thorium-230 and protactinium. Robertson's modified approach involves simultaneously separating the thorium and protactinium in the hope that the materials' relative concentrations will give some indication of when the cube was made. In addition, analyzing the rare-earth-element impurities could help PNNL scientists determine where the original uranium was mined.

“Kind of a long shot”

So far, initial findings have confirmed that at least one of the three cubes being tested at PNNL is natural uranium. There are also preliminary results from Robertson's analysis of the coatings the Germans applied to the cubes to keep oxidation in check. Cyanide-based coatings were used by the Berlin group, while Diebner's Gottow group used styrene-based coatings. If one could accurately measure the relevant signatures, it would enable the team to tell whether a given cube came from the Berlin or Gottow group.

"As far as we know, no one else has performed this measurement," said Robertson. "And I have to be honest, I thought it was kind of a long shot. I didn't think an organic would last sitting next to uranium metal for this many decades and still be detectable."

That long shot paid off. Koeth's cube was among those tested, revealing a styrene coating—a bit of a surprise, given that Koeth's historic sleuthing tracked the cube to the Berlin group. However, it turns out that Diebner sent some of his group's cubes to Heisenberg in Berlin when the latter sought more fuel for his reactor. So Koeth's cube may possibly have been used by both groups.

The cane toad may be the poster animal for invasive species. Native to South America, it has been introduced to many other ecosystems in the hope it would chow down on agricultural pests. Instead, the toad has become a pest itself, most notably in Australia. Free from the predators and parasites in its native range, the toad's poison glands have turned out to be a hazard for most species that try to eat it where it has been introduced.

But that doesn't mean that it's completely free of the risk of predation. Australian cane toad tadpoles have been observed feeding on their fellow cane toad offspring. This cannibalism seems to be an evolutionary response to the lack of competing species in its invasive range, causing cane toads to turn on their remaining competition: each other. And the toad has already turned to an additional evolutionary response to try to limit the danger of cannibalism.

Only competing with themselves

From an evolutionary perspective, cannibalism can make sense as a way to limit the competition posed by other members of your species. But the research team at the University of Sydney that has tracked the cane toad's cannibalism suggests that the species' successful invasion of Australia has accentuated this evolutionary pressure—something that may also occur with other invasive predators. One of the marks of an invasive species is its abundance in its new range, at which point competition for limited resources becomes more likely. Cannibalism not only limits this competition but provides nutritional resources as well.

With the Australian population reaching about 10 times the density of the population in the cane toad's native range, there's plenty of opportunity for inter-toad competition. And that competition has been documented at early stages in the toad's development. Recently hatched toads spend several days developing into tadpoles and, during this time, often get eaten by older, more mature tadpoles. In a heavily populated body of water, clutches of eggs laid after mature tadpoles are present may be completely wiped out before they can live past the hatchling stage.

Tadpoles eating tadpoles can occur in South America. But it happens much more often in Australia. So the researchers decided to see if cannibalism was producing biological differences between the native and invasive populations.

To do so, they obtained toads from both native and invasive populations and tracked the behavior of the offspring. To start, the researchers simply placed fertilized eggs in a container with a single tadpole. This showed that the Australian cane toads had become aggressive cannibals, as eggs placed in with them were over 2.5 times more likely to be cannibalized before producing a tadpole.

While many changes can produce this sort of difference, the researchers demonstrated that the Australian tadpoles were more likely to seek out recently hatched cane toads. When given a choice of moving into empty containers and one containing cane toad hatchlings, the invasive Australian toads were nearly 30 times more likely to go into the container with hatchlings.

By the time the hatchlings reach the tadpole stage and are too large to eat, their fellow tadpoles lose interest. There's some indication that the earlier attraction is based on toxins put into the fertilized egg by the mother.

The best defense

High levels of predation tend to produce evolutionary responses to limit vulnerability, and cannibalism is no different. The researchers found that Australian toads were simply spending less of their developmental time in the vulnerable hatchling stage in order to avoid some of the impact of cannibalism.

This occurred via two different mechanisms. One of these was specifically dependent upon the presence of tadpoles. In other words, when the threat was present, development accelerated. But a separate acceleration was present regardless of whether tadpoles were present. While South American cane toads spent a total of about five days at the hatchling stage, Australian populations only spent three days. So the pressure of cannibalism had cut hatchling development time by nearly half.

If you can develop this quickly anyway, why aren't all cane toads rushing through the hatchling stage? The researchers found that growth and development of Australian tadpoles was slower than it was in South American populations. Thus, rushing through the hatchling stage exacts a cost that's paid off by slower growth and development later.

These sorts of changes driven by predator/prey interactions have been observed in a variety of species. But it's not clear if anyone has documented them so clearly when predator and prey are the same species. And the researchers involved here make a pretty compelling case that the distinct environment inhabited by an invasive species helps foster this sort of interaction. Unfortunately for Australia, the competitive cannibalism means that, while cane toads are the losers, they're also the winners.

PNAS, 2021. DOI: 10.1073/pnas.2100765118  (About DOIs).

Ants are prodigious diggers, constructing elaborate nests with multiple layers connected by an intricate network of tunnels, sometimes reaching depths of 25 feet. Now, a team of scientists from Caltech has used X-ray imaging to capture the process of how ants construct their tunnels. The scientists found that the ants have evolved to intuitively sense which grain particles they can remove while maintaining the stability of the structure, much like removing individual blocks in a game of Jenga. The team described their work in a new paper published in the Proceedings of the National Academy of Sciences.

Scientists interested in collective behavior have been studying ants for decades. That's because, as a group, ants act like a form of granular media. A few ants spaced well apart behave like individual ants. But pack enough of them closely together and they act more like a single unit, exhibiting both solid and liquid properties. You can pour fire ants from a teapot, for instance, or the ants can link together to build towers or floating rafts. Ants may be tiny critters with tiny brains, but these social insects are capable of collectively organizing themselves into a highly efficient community to ensure that the colony survives.

Several years ago, behavioral biologist Guy Theraulaz of the Institute for Advanced Study in Toulouse, France, and several colleagues combined laboratory experiments with Argentine ants and computer modeling to identify three simple rules governing the ants' tunneling behavior. To wit: (1) the ants picked up grains at a constant rate (about 2 grains every minute); (2) the ants preferentially dropped their grains near other grains to form pillars; and (3) ants typically chose grains marked with a chemical pheromone after being handled by other ants. Theraulaz et al. built a computer simulation based on those three rules and found that after a week, their virtual ants built a structure that closely resembled real ant nests. They concluded that those rules emerge from local interactions between individual ants, with no need for central coordination.

More recently, a 2020 paper found that the social dynamics of how division of labor emerges in an ant colony is similar to how political polarization develops in human social networks. Ants also excel at regulating their own traffic flow. A 2018 study by Daniel Goldman's group at Georgia Tech investigated how fire ants optimize their tunnel-digging efforts without causing traffic jams. As we reported at the time, the group concluded that when an ant encounters a tunnel in which other ants are already working, it retreats to find another tunnel. And only a small fraction of the colony is digging at any given time: 30 percent of them do 70 percent of the work. 

David Hu's biolocomotion group at Georgia Tech has also studied fire ants. In 2019, he and his colleagues reported that fire ants can actively sense changes in forces acting upon their floating raft. The ants recognize different conditions of fluid flow and can adapt their behavior accordingly to preserve the raft's stability. A paddle moving through river water will create a series of swirling vortices (known as vortex shedding), causing the ant rafts to spin. These vortices can also exert extra forces on the raft, sufficient to break it apart. The changes in both centrifugal and shearing forces acting on the raft are quite small—maybe 2 percent to 3 percent the force of normal gravity. Yet somehow, the ants can sense these small shifts with their bodies.

This latest paper focuses on western harvester ants (Pogonomyrmex occidentalis), selected because of their prolific digging ability with soil grains at the millimeter scale. Co-author José Andrade, a mechanical engineer at Caltech, was inspired to explore tunneling ants after seeing examples of anthill art. The pieces are created by pouring some kind of molten metal, plaster, or cement into an ant mound, which flows through all the tunnels and eventually hardens. Then the surrounding soil is removed to reveal the final intricate structure. Andrade was so impressed that he started to wonder if ants actually "knew" how to dig those structures.

Andrade partnered with Caltech biological engineer Joe Parker for the project; Parker's research focuses on the ecological relationships of ants with other species. "We didn't interview any ants to ask if they know what they're doing, but we did start with the hypothesis that they dig in a deliberate way," said Andrade. "We hypothesized that maybe ants were playing Jenga."

In other words, the researchers suspected that the ants poked around in the soil hunting for loose grains to remove, in much the same way people look for loose blocks to remove from a Jenga tower, leaving the critical load-bearing pieces in place. Those blocks are part of what's known as a "force chain" that serves to jam the blocks (or granular soil particles, in the case of an anthill) together to create a stable structure.

For their experiments, Andrade and his colleagues mixed 500 ml of Quikrete soil with 20 ml of water and placed the mixture in several small cups of soil. The size of the cups was selected for how easily they could be placed inside a CT scanner. Through trial and error—starting with one ant and gradually increasing the number—the researchers determined the number of ants needed to achieve the optimal excavation rate: 15.

The team took four-minute, half-resolution scans every 10 minutes while the ants were tunneling to monitor their progress. From the resulting 3D images, they created a "digital avatar" for every particle in the sample, capturing each grain's shape, position, and orientation—all of which can significantly influence the distribution of forces in the soil samples. The researchers were also able to figure out the order in which each grain was removed by the ants by comparing images taken at different instances in time.

The ants were not always cooperative when it came to diligently digging their tunnels. "They're sort of capricious," Andrade said. "They dig whenever they want to. We would put these ants in a container, and some would start digging right away, and they would make this amazing progress. But others—it would be hours and they wouldn't dig at all. And some would dig for a while and then would stop and take a break."

Andrade and Parker noticed a few emerging patterns in their analysis. For instance, the ants usually dug along the inside edges of the cups—an efficient strategy, since the sides of the cups could serve as part of the tunneling structure, saving the ants a bit of effort. The ants also favored straight lines for their tunnels, a tactic that optimizes efficiency. And the ants tended to dig their tunnels as steeply as possible. The steepest possible limit in a granular medium like soil is called the "angle of repose"; exceed that angle, and the structure will collapse. Somehow, the ants can sense that critical threshold, making sure their tunnels never exceed the angle of repose.

As for the underlying physics, the team discovered that as the ants removed grains of soil to dig their tunnels, the force chains acting upon the structure rearranged themselves from a randomized distribution to form a kind of liner around the outside of a tunnel. This redistribution of forces strengthens the tunnel's existing walls and relieves pressure exerted by grains at the tunnel's end, making it easier for the ants to remove those grains to extend the tunnel even further.

"It's been a mystery in both engineering and in ant ecology how ants build these structures that persist for decades," said Parker. "It turns out that by removing grains in this pattern that we observed, the ants benefit from these circumferential force chains as they dig down." The ants tap the individual grains to assess the mechanical forces being exerted upon them.

Parker thinks of it as a kind of behavioral algorithm. "That algorithm does not exist within a single ant," he said. "It's this emergent colony behavior of all these workers acting like a superorganism. How that behavioral program is spread across the tiny brains of all these ants is a wonder of the natural world we have no explanation for."

DOI: PNAS, 2021. 10.1073/pnas.2102267118  (About DOIs).

The Food and Drug Administration has granted full approval of the Pfizer/BioNTech COVID-19 vaccine, which will now be marketed as Comirnaty (koe-mir’-na-tee), the agency announced Monday.

The vaccine's full approval—or Biologics License Application (BLA)—applies for use of a two-dose regimen, given three weeks apart, in people ages 16 years and older. It is the first BLA to be issued for a vaccine against COVID-19. The vaccine will still be available under an Emergency Use Authorization (EUA) for adolescents ages 12 to 15 and for use as a third booster dose in certain people with compromised immune systems.

The name Comirnaty—already in use elsewhere, including Europe—is a mash-up of "COVID-19 immunity" and "mRNA" that is meant to evoke the word "community."

“The FDA’s approval of this vaccine is a milestone as we continue to battle the COVID-19 pandemic," acting FDA Commissioner Janet Woodcock said in a statement. "While this and other vaccines have met the FDA’s rigorous, scientific standards for emergency use authorization, as the first FDA-approved COVID-19 vaccine, the public can be very confident that this vaccine meets the high standards for safety, effectiveness, and manufacturing quality the FDA requires of an approved product. While millions of people have already safely received COVID-19 vaccines, we recognize that for some, the FDA approval of a vaccine may now instill additional confidence to get vaccinated. Today’s milestone puts us one step closer to altering the course of this pandemic in the US.”

In the US, over 200 million doses of Comirnaty have been administered since it initially earned an EUA on December 11, 2020. The BLA document submitted by Pfizer and BioNTech this May "builds on the extensive data and information previously submitted that supported the EUA, such as preclinical and clinical data and information, as well as details of the manufacturing process, vaccine testing results to ensure vaccine quality, and inspections of the sites where the vaccine is made," the FDA said. The agency also noted that it conducts its own data analyses to determine safety and efficacy.

In a tweet, Pfizer CEO Albert Bourla said the company and BioNTech were celebrating the approval. "It is our hope that this news will instill even further public confidence in our vaccine and the science that made it possible," Bourla added.

Safety review

Amid another devastating and entirely preventable wave of the deadly pandemic, the full approval is expected to spur more vaccination mandates by universities, healthcare systems, and other employers. Though the federal Equal Employment Opportunity Commission determined in May that employers can indeed mandate COVID-19 vaccination under the EUA given reasonable accommodations, some have suggested a full approval could give employers more confidence in issuing mandates.

Still, mandates or not, the approval alone may sway some vaccine holdouts. Previous polling by the Kaiser Family Foundation found that 31 percent of unvaccinated people would be more likely to get their shots if a vaccine earned full approval.

In the announcement Monday, the FDA also took the time to try to ease concerns and dispel myths about the vaccine. The agency noted that the mRNA vaccine works by providing to human cells a genetic code for a snippet of the pandemic coronavirus SARS-CoV-2. From there, the cells translate the code into a protein that can essentially be used as target practice by the immune system. "The result of a person receiving this vaccine is that their immune system will ultimately react defensively to the virus that causes COVID-19," the FDA noted. "The mRNA in Comirnaty is only present in the body for a short time and is not incorporated into—nor does it alter—an individual’s genetic material."

Peter Marks, director of FDA’s Center for Biologics Evaluation and Research, also emphasized how rigorously the agency looked over the plethora of safety data accumulated so far. “Our scientific and medical experts conducted an incredibly thorough and thoughtful evaluation of this vaccine," he said. "We evaluated scientific data and information included in hundreds of thousands of pages, conducted our own analyses of Comirnaty’s safety and effectiveness, and performed a detailed assessment of the manufacturing processes, including inspections of the manufacturing facilities. We have not lost sight that the COVID-19 public health crisis continues in the US and that the public is counting on safe and effective vaccines. The public and medical community can be confident that although we approved this vaccine expeditiously, it was fully in keeping with our existing high standards for vaccines in the US."

Pfizer and BioNTech submitted the BLA document in May of this year, and the FDA granted it a priority review in July. The FDA is also reviewing a BLA submission for Moderna's similar mRNA-based COVID-19 vaccine, and full approval could come in the coming weeks.

This post has been updated.

After several days of uncertainty and wild swings in forecast models, confidence is increasing in a large tropical system making landfall in the northeastern United States this weekend. In addition to causing surges along the coastline, Henri could bring gusty winds and widespread heavy rainfall from late Saturday through Monday to a region from New Jersey to Maine.

The latest forecast from the National Hurricane Center, issued at 11 am ET on Friday, shows Henri holding at sustained winds of 65 mph, just below hurricane strength. However, the wind shear hampering Henri's organization should relax some later today, and as the storm passes over the Gulf Stream, forecasters anticipate Henri will become a Category 1 or 2 hurricane. It may weaken some before landfall, however, as it passes over the cooler waters off the coast of New England.

Over the next 48 hours, the storm should now move more or less due north and will likely make landfall somewhere along Long Island, Connecticut, or Rhode Island on Sunday.

The tweet below, from meteorologist Tomer Burg, shows how a "super-ensemble" forecast incorporating a range of outputs from the premier US and European forecast models has shifted from significant uncertainty on Wednesday evening to a tighter clustering as of Friday morning. This clustering of ensemble model forecasts is one reason confidence is now higher in the track for Henri.

Regardless of its precise landfall location or intensity, Henri will bring substantial impacts to the United States this weekend. These threats include coastal flooding, wind damage, and, perhaps most concerning, inland flooding.

Flooding is likely for two reasons. First, much of New England has already experienced a wet July, and the region recently received rainfall from the remains of Tropical Storm Fred. Soil moisture across parts of New York and the New England states is at the 90th percentile level or higher. Second, Henri is forecast to move relatively slowly as it approaches Long Island and the New England coasts this weekend, probably 10 mph or less, prolonging the period of heavier rainfall.

An average of 2 to 6 inches of rain from Henri, with higher isolated totals falling on already soggy ground, could lead to road and stream flooding. The situation will also increase the potential for trees with shallow roots in softer ground to blow down in stronger wind gusts.

Henri is the eighth named storm of the 2021 Atlantic season and continues what has been a fairly busy season. Only two other years since there have been reliable satellite observations, which date back to 1966, have had eight or more named storms formed by the middle of August. These were the incredibly active years of 2005 and 2020.

Fortunately, the next week looks reasonably quiet in the tropics for late August. Although a storm may form in the Central Atlantic, it is highly likely to recurve northward before threatening any land. The next area of interest close to land may come in the western Gulf of Mexico about 10 days from now.