Science

proteins-let-cells-remember-how-well-their-last-division-went

Proteins let cells remember how well their last division went

biochemistry, Biology, cancer, DNA damage, mitosis, Science / /

Well, that went badly —

Scientists find a “mitotic stopwatch” that lets individual cells remember something.

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Image of a stopwatch against a blue-grey background.

When we talk about memories in biology, we tend to focus on the brain and the storage of information in neurons. But there are lots of other memories that persist within our cells. Cells remember their developmental history, whether they’ve been exposed to pathogens, and so on. And that raises a question that has been challenging to answer: How does something as fundamental as a cell hold on to information across multiple divisions?

There’s no one answer, and the details are really difficult to work out in many cases. But scientists have now worked out one memory system in detail. Cells are able to remember when their parent had a difficult time dividing—a problem that’s often associated with DNA damage and cancer. And, if the problems are substantial enough, the two cells that result from a division will stop dividing themselves.

Setting a timer

In multicellular organisms, cell division is very carefully regulated. Uncontrolled division is the hallmark of cancers. But problems with the individual segments of division—things like copying DNA, repairing any damage, making sure each daughter cell gets the right number of chromosomes—can lead to mutations. So, the cell division process includes lots of checkpoints where the cell makes sure everything has worked properly.

But if a cell makes it through all the checkpoints, it’s presumably all good, right? Not entirely, as it turns out.

Mitosis is the portion of cell division where the duplicated chromosomes get separated out to each of the daughter cells. Spending a lot of time in mitosis can mean that the chromosomes have picked up damage, which may cause problems in the future. And prior research found that some cells derived from the retina will register when mitosis takes too long, and the daughter cells will stop dividing.

The new work, done by a team of researchers in Okinawa, Japan, and San Diego, started by showing that this behavior wasn’t limited to retinal cells—it seems to be a general response to a slow mitosis. Careful timing experiments showed that the longer cells spent trying to undergo mitosis, the more likely the daughter cells would be to stop dividing. The researchers term this system a “mitotic stopwatch.”

So, how does a cell operate a stopwatch? It’s not like it can ask Siri to set a timer—it’s largely stuck working with nucleic acids and proteins.

It turns out that, like many things relayed to cell division, the answer comes down to a protein named p53. It’s a protein that’s key to many pathways that detect damage to cells and stop them from dividing if there are problems. (You may recall it from our recent coverage of the development of elephant stem cells.)

A stopwatch made of proteins

The researchers found that, while mitosis was going on, p53 started showing up in a complex with two other proteins (ubiquitin-specific protease 28 and the creatively named p53-binding protein 1). If you made mutations in one of the proteins that blocked this complex from forming, the mitotic stopwatch stopped ticking. This three-protein complex only started building up to significant levels if mitosis took longer than usual, and it remained stable once it formed so that it would get passed on to the daughter cells once cell division was completed.

So, why does this complex form only when mitosis takes longer than usual? The key turned out to be a protein called a kinase, which attaches a phosphate to other proteins. The researchers screened chemicals that inhibit specific kinases that are active during mitosis and DNA repair, and found a specific one that was needed for the mitotic stopwatch. In the absence of this kinase (PLK1, for the curious), the three-protein complex doesn’t form.

So, the researchers think that the stopwatch looks like this: during mitosis, the kinase slowly attaches a phosphate to one of the proteins, allowing it to form the three-protein complex. If mitosis gets done quickly enough, the levels of this complex don’t get very high, and it has no effect on the cell. But if mitosis goes more quickly, then the complex starts building up, and it’s stable enough that it’s still around in both daughter cells. The existence of the complex helps stabilize the p53 protein, allowing it to stop future cell divisions once it’s present at high enough levels.

Consistent with this idea, all three of the proteins in the complex are tumor suppressors, meaning that mutations in them make tumor formation more likely. The researchers confirmed that the mitotic stopwatch was frequently defective in tumor samples.

So, that’s how individual cells manage to store one of their memories—the memory of problems with cell division. The mitotic stopwatch, however, is just one of the memory storage systems, with completely separate systems handling different memories. And, at the same time this is happening, a large number of other pathways also feed into the activity of p53. So, while the mitotic stopwatch may efficiently handle one specific type of problem, it’s integrated into a lot of additional, complex systems operating in the cell.

Science, 2024. DOI: 10.1126/science.add9528  (About DOIs).

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This four-legged robot learned parkour to better navigate obstacles

ANYmal, robotics, Science / /

teaching an old robot new tricks —

Latest improvements to ANYmal make it better at navigating rubble and tricky terrain.

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ANYmal can do parkour and walk across rubble. The quadrupedal robot went back to school and has learned a lot.

Meet ANYmal, a four-legged dog-like robot designed by researchers at ETH Zürich in Switzerland, in hopes of using such robots for search-and-rescue on building sites or disaster areas, among other applications. Now ANYmal has been upgraded to perform rudimentary parkour moves, aka “free running.” Human parkour enthusiasts are known for their remarkably agile, acrobatic feats, and while ANYmal can’t match those, the robot successfully jumped across gaps, climbed up and down large obstacles, and crouched low to maneuver under an obstacle, according to a recent paper published in the journal Science Robotics.

The ETH Zürich team introduced ANYmal’s original approach to reinforcement learning back in 2019 and enhanced its proprioception (the ability to sense movement, action, and location) three years later. Just last year, the team showcased a trio of customized ANYmal robots, tested in environments as close to the harsh lunar and Martian terrain as possible. As previously reported, robots capable of walking could assist future rovers and mitigate the risk of damage from sharp edges or loss of traction in loose regolith. Every robot had a lidar sensor. but they were each specialized for particular functions and still flexible enough to cover for each other—if one glitches, the others can take over its tasks.

For instance, the Scout model’s main objective was to survey its surroundings using RGB cameras. This robot also used another imager to map regions and objects of interest using filters that let through different areas of the light spectrum. The Scientist model had the advantage of an arm featuring a MIRA (Metrohm Instant Raman Analyzer) and a MICRO (microscopic imager). The MIRA was able to identify chemicals in materials found on the surface of the demonstration area based on how they scattered light, while the MICRO on its wrist imaged them up close. The Hybrid was more of a generalist, helping out the Scout and the Scientist with measurements of scientific targets such as boulders and craters.

As advanced as ANYmal and similar-legged robots have become in recent years, significant challenges still remain before they are as nimble and agile as humans and other animals. “Before the project started, several of my researcher colleagues thought that legged robots had already reached the limits of their development potential,” said co-author Nikita Rudin, a graduate student at ETH Zurich who also does parkour. “But I had a different opinion. In fact, I was sure that a lot more could be done with the mechanics of legged robots.”

The quadrupedal robot ANYmal practices parkour in a hall at ETH Zürich.

Enlarge / The quadrupedal robot ANYmal practices parkour in a hall at ETH Zürich.

ETH Zurich / Nikita Rudin

Parkour is quite complex from a robotics standpoint, making it an ideal aspirational task for the Swiss team’s next step in ANYmal’s capabilities. Parkour can involve large obstacles, requiring the robot “to perform dynamic maneuvers at the limits of actuation while accurately controlling the motion of the base and limbs,” the authors wrote. To succeed, ANYmal must be able to sense its environment and adapt to rapid changes, selecting a feasible path and sequence of motions from its programmed skill set. And it has to do all that in real time with limited onboard computing.

The Swiss team’s overall approach combines machine learning with model-based control. They split the task into three interconnected components: a perception module that processes the data from onboard cameras and LiDAR to estimate the terrain; a locomotion module with a programmed catalog of movements to overcome specific terrains; and a navigation module that guides the locomotion module in selecting which skills to use to navigate different obstacles and terrain using intermediate commands.

Rudin, for example, used machine learning to teach ANYmal some new skills through trial and error, namely, scaling obstacles and figuring out how to climb up and jump back down from them. The robot’s camera and artificial neural network enable it to pick the best maneuvers based on its prior training. Another graduate student, Fabian Jenelten, used model-based control to teach ANYmal how to recognize and negotiate gaps in piles of rubble, augmented with machine learning so the robot could have more flexibility in applying known movement patterns to unexpected situations.

ANYmal on a civil defense training ground.

Enlarge / ANYmal on a civil defense training ground.

ETH Zurich / Fabian Jenelten

Among the tasks ANYmal was able to perform was jumping from one box to a neighboring box up to 1 meter away. This required the robot to approach the gap sideways, place its feet as close as possible to the edge, and then use three legs to jump while extending the fourth to land on the other box. It could then transfer two diagonal legs before bringing the final leg across the gap. This meant ANYmal could recover from any missteps and slippage by transferring its weight between the non-leaping legs.

ANYmal also was able to climb down from a 1-meter-high box to reach a target on the ground, as well as climbing up the box. It can also crouch down to reach a target on the other side of a narrow passage, lowering its base and adapting its gait accordingly. The team also tested ANYmal’s walking abilities, in which the robot successfully traversed stairs, slopes, random small obstacles and so forth.

ANYmal still has its limitations when it comes to navigating real-world environments, whether it be a parkour course or the debris of a collapsed building. For instance, the authors note that they have yet to test the scalability of their approach to more diverse and unstructured scenarios that incorporate a wider variety of obstacles; the robot was only tested in a few select scenarios. “It remains to be seen how well these different modules can generalize to completely new scenarios,” they wrote. The approach is also time-consuming since it requires eight neural networks that must be tuned separately, and some of the networks are interdependent, so changing one means changing and retraining the others as well.

Still, ANYmal “can now evolve in complex scenes where it must climb and jump on large obstacles while selecting a nontrivial path toward its target location,” the authors wrote. Thus, “by aiming to match the agility of free runners, we can better understand the limitations of each component in the pipeline from perception to actuation, circumvent those limits, and generally increase the capabilities of our robots.”

Science Robotics, 2024. DOI: 10.1126/scirobotics.adi7566  (About DOIs).

Listing image by ETH Zurich / Nikita Rudin

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astronomers-have-solved-the-mystery-of-why-this-black-hole-has-the-hiccups

Astronomers have solved the mystery of why this black hole has the hiccups

astronomy, astrophysics, black holes, Physics, Science / /

David vs. Goliath —

Blame it on a smaller orbiting black hole repeatedly punching through the accretion disk.

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graphic of hiccuping black hole

Enlarge / Scientists have found a large black hole that “hiccups,” giving off plumes of gas.

Jose-Luis Olivares, MIT

In December 2020, astronomers spotted an unusual burst of light in a galaxy roughly 848 million light-years away—a region with a supermassive black hole at the center that had been largely quiet until then. The energy of the burst mysteriously dipped about every 8.5 days before the black hole settled back down, akin to having a case of celestial hiccups.

Now scientists think they’ve figured out the reason for this unusual behavior. The supermassive black hole is orbited by a smaller black hole that periodically punches through the larger object’s accretion disk during its travels, releasing a plume of gas. This suggests that black hole accretion disks might not be as uniform as astronomers thought, according to a new paper published in the journal Science Advances.

Co-author Dheeraj “DJ” Pasham of MIT’s Kavli Institute for Astrophysics and Space research noticed the community alert that went out after the All Sky Automated Survey for SuperNovae (ASAS-SN) detected the flare, dubbed ASASSN-20qc. He was intrigued and still had some allotted time on the X-ray telescope, called NICER (the Neutron star Interior Composition Explorer) on board the International Space Station. He directed the telescope to the galaxy of interest and gathered about four months of data, after which the flare faded.

Pasham noticed a strange pattern as he analyzed that four months’ worth of data. The bursts of energy dipped every 8.5 days in the X-ray regime, much like a star’s brightness can briefly dim whenever an orbiting planet crosses in front. Pasham was puzzled as to what kind of object could cause a similar effect in an entire galaxy. That’s when he stumbled across a theoretical paper by Czech physicists suggesting that it was possible for a supermassive black hole at the center of a galaxy to have an orbiting smaller black hole; they predicted that, under the right circumstances, this could produce just such a periodic effect as Pasham had observed in his X-ray data.

Computer simulation of an intermediate-mass black hole orbiting a supermassive black hole and driving periodic gas plumes that can explain the observations.

Computer simulation of an intermediate-mass black hole orbiting a supermassive black hole and driving periodic gas plumes that can explain the observations.

Petra Sukova, Astronomical Institute of the CAS

“I was super excited about this theory and immediately emailed to say, ‘I think we’re observing exactly what your theory predicted,” Pasham said. They joined forces to run simulations incorporating the data from NICER, and the results supported the theory. The black hole at the galaxy’s center is estimated to have a mass of 50 million suns. Since there was no burst before December 2020, the team thinks there was, at most, just a faint accretion disk around that black hole and a smaller orbiting black hole of between 100 to 10,000 solar masses that eluded detection because of that.

So what changed? Pasham et al. suggest that a nearby star got caught in the gravitational pull of the supermassive black hole in December 2020 and was ripped to shreds, known as a tidal disruption event (TDE). As previously reported, in a TDE, part of the shredded star’s original mass is ejected violently outward. This, in turn, can form an accretion disk around the black hole that emits powerful X-rays and visible light. The jets are one way astronomers can indirectly infer the presence of a black hole. Those outflow emissions typically occur soon after the TDE.

That seems to be what happened in the current system to cause the sudden flare in the primary supermassive black hole. Now it had a much brighter accretion disk, so when its smaller black hole partner passed through the disk, larger than usual gas plumes were emitted. As luck would have it, that plume just happened to be pointed in the direction of an observing telescope.

Astronomers have known about so-called “David and Goliath” binary black hole systems for a while, but “this is a different beast,” said Pasham. “It doesn’t fit anything that we know about these systems. We’re seeing evidence of objects going in and through the disk, at different angles, which challenges the traditional picture of a simple gaseous disk around black holes. We think there is a huge population of these systems out there.”

Science Advances, 2024. DOI: 10.1126/sciadv.adj8898  (About DOIs).

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china-has-a-big-problem-with-super-gonorrhea,-study-finds

China has a big problem with super gonorrhea, study finds

antibiotic, antibiotic resistance, bacterial infection, CDC, ceftriaxone, china, drug resistance, gonorrhea, health, Science, sexually transmitted infection, sti / /

Alarming —

Drug-resistant gonorrhea is a growing problem—one that doesn’t heed borders.

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A billboard from the AIDS Healthcare Foundation is seen on Sunset Boulevard in Hollywood, California, on May 29, 2018, warning of a drug-resistant gonorrhea.

Enlarge / A billboard from the AIDS Healthcare Foundation is seen on Sunset Boulevard in Hollywood, California, on May 29, 2018, warning of a drug-resistant gonorrhea.

Health officials have long warned that gonorrhea is becoming more and more resistant to all the antibiotic drugs we have to fight it. Last year, the US reached a grim landmark: For the first time, two unrelated people in Massachusetts were found to have gonorrhea infections with complete or reduced susceptibility to every drug in our arsenal, including the frontline drug ceftriaxone. Luckily, they were still able to be cured with high-dose injections of ceftriaxone. But, as the US Centers for Disease Control and Prevention bluntly notes: “Little now stands between us and untreatable gonorrhea.”

If public health alarm bells could somehow hit a higher pitch, a study published Thursday from researchers in China would certainly accomplish it. The study surveyed gonorrhea bacterial isolates—Neisseria gonorrhoeae—from around the country and found that the prevalence of ceftriaxone-resistant isolates nearly tripled between 2017 and 2021. Ceftriaxone-resistant strains made up roughly 8 percent of the nearly 3,000 bacterial isolates collected from gonorrhea infections in 2022. That’s up from just under 3 percent in 2017. The study appears in the CDC’s Morbidity and Mortality Weekly Report.

While those single-digit percentages may seem low, compared to other countries they’re extremely high. In the US, for instance, the prevalence of ceftriaxone-resistant strains never went above 0.2 percent between 2017 and 2021, according to the CDC. In Canada, ceftriaxone-resistance was stable at 0.6 percent between 2017 and 2021. The United Kingdom had a prevalence of 0.21 percent in 2022.

Ceftriaxone is currently the first-line treatment for gonorrhea because Neisseria gonorrhoeae has spent the past several decades building up resistance to pretty much everything else. As the CDC notes, in the 1980s, the drugs of choice for gonorrhea infections were penicillin and tetracycline. But the bacteria developed resistance. By the 1990s, the CDC was forced to switch to a class of antibiotics called fluoroquinolones, including ciprofloxacin (Cipro). But fluoroquinolone-resistance developed, too, and resistance to Cipro is now widespread. In the early 2000s, the CDC began having to tweak the recommendations as resistance spread to new places and populations.

Resistance rising

By 2007, the agency switched to cephalosporins, including cefixime. In 2010, the CDC updated the treatment again, recommending that doctors combine cephalosporins with one of two other types of antibiotics—azithromycin or doxycycline—to try to thwart the development of resistance. But, it also was no use. Two years later, in 2012, the CDC updated recommendations when cefixime resistance developed. In 2020, azithromycin was also abandoned. The cephalosporin ceftriaxone is the last drug standing in the US to treat gonorrhea infections.

Resistance of gonococcal isolates to ciprofloxacin, penicillin, tetracycline, azithromycin, cefixime, ceftriaxone, and spectinomycin—13 Gonococcal Resistance Surveillance Program sentinel sites, China, 2022.

Enlarge / Resistance of gonococcal isolates to ciprofloxacin, penicillin, tetracycline, azithromycin, cefixime, ceftriaxone, and spectinomycin—13 Gonococcal Resistance Surveillance Program sentinel sites, China, 2022.

In China, the swift spread of ceftriaxone-resistance isolates is alarming. The data stems from 2,804 isolates, representing 2.9 percent of all cases reported in China during 2022. Those figures come from 13 of the country’s 19 provinces. While the overall prevalence of ceftriaxone-resistance isolates was 8.1 percent among the 2,804 isolates, five of those 13 provinces had prevalence rates above 10 percent. Three provinces had prevalence rates above 25 percent. In all, 18 isolates were resistant to all the antibiotics tested except for a bygone antibiotic called spectinomycin, which is discontinued in the US and elsewhere.

The study has limitations. For one, the reported number of gonorrhea cases are very likely an undercount of actual cases. Beyond gaps in reporting, many people with gonorrhea have no symptoms and, as such, don’t seek treatment. Additionally, the isolates the researchers did have represented less than 3 percent of reported cases, so it’s possible the prevalence rates don’t represent the isolates of the entire country. Also, the researchers didn’t have detailed case data that might help identify specific risk factors for resistance development, such as the antibiotic treatments patients had. The authors did note that antibiotics are only given by prescription in China.

“These findings underscore the urgent need for a comprehensive approach to address antibiotic-resistant N. gonorrhoeae in China, including identifying factors contributing to this high resistance rate, especially in provinces where the percentage of gonococcal isolates resistant to ceftriaxone is >10 percent,” the authors write.

But they also note that this is not just an alarming finding for China but also a “pressing public health concern” for the entire world. “These resistant clones have spread internationally, and collaborative cross-border efforts will be essential to monitoring and mitigating its further spread,” they write.

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the-delta-iv-heavy,-a-rocket-whose-time-has-come-and-gone,-will-fly-once-more

The Delta IV Heavy, a rocket whose time has come and gone, will fly once more

cape canaveral, delta iv heavy, delta rocket, launch, National Reconnaissance Office, nrol-70, Science, Space, united launch alliance / /
United Launch Alliance's final Delta IV Heavy rocket, seen here in December when ground crews rolled it to the launch pad at Cape Canaveral Space Force Station, Florida.

Enlarge / United Launch Alliance’s final Delta IV Heavy rocket, seen here in December when ground crews rolled it to the launch pad at Cape Canaveral Space Force Station, Florida.

This is the rocket that literally lights itself on fire before it heads to space. It’s the world’s largest rocket entirely fueled by liquid hydrogen, a propellant that is vexing to handle but rewarding in its efficiency.

The Delta IV Heavy was America’s most powerful launch vehicle for nearly a decade and has been a cornerstone for the US military’s space program for more than 20 years. It is also the world’s most expensive commercially produced rocket, a fact driven not just by its outsized capability but also its complexity.

Now, United Launch Alliance’s last Delta IV Heavy rocket is set to lift off Thursday from Cape Canaveral Space Force Station, Florida, with a classified payload for the National Reconnaissance Office, the US government’s spy satellite agency.

“This is such an amazing piece of technology, 23 stories tall, a half-million gallons of propellant and a quarter-million pounds of thrust, and the most metal of all rockets, setting itself on fire before it goes to space,” said Tory Bruno, ULA’s president and CEO. “Retiring it is (key to) the future, moving to Vulcan, a less expensive higher-performance rocket. But it’s still sad.”

45th and final Delta IV

Weather permitting, the Delta IV Heavy will light up its three hydrogen-fueled RS-68A engines at 1: 40 pm EDT (17: 40 UTC) Thursday, the opening of a four-hour launch window. The three RS-68s will fire up in a staggered sequence, a permutation designed to minimize the hydrogen fireball that ignites around the base of the rocket during engine startup.

The Delta IV Heavy will certainly have a legacy of launching national security missions, along with NASA’s Orion spacecraft on an orbital test flight in 2014 and NASA’s Parker Solar Probe in 2018 on a mission to fly through the Sun’s outer atmosphere.

But the fireball will leave an indelible mark in the memories of anyone who saw a Delta IV Heavy launch. It all comes down to the choice of super-cold liquid hydrogen as the fuel. The three RS-68 engines burn hydrogen along with liquid oxygen as the oxidizer.

“We like those propellants because they’re very, very high performance,” Bruno said. “In order to prepare the RS-68 engines to get that very cold cryogenic propellant flowing through them, before they’re ignited, we start flowing that propellant.

“Hydrogen is lighter than air, so after it flows through the engine and into the flame trench, it then rises. When the engines are finally full and ready to go and we start spinning up the pumps, then we actually drop the main load (of propellant), we ignite it, and that flame carries on up that … plume of hydrogen, which is clinging to the side of the booster and rising up.”

The Delta IV rocket cores are covered in orange foam insulation. One of the reasons for this is to protect the rocket from the fireball, leading to a “very dramatic effect of a self-immolating booster” that has the appearance of a “toasted marshmallow” as it heads to space.

A few seconds after the engines start, 12 hold-down bolts will blow to release the triple-core rocket from its restraints. More than 2 million pounds of thrust will power the Delta IV Heavy off the launch pad toward the east from Cape Canaveral. The RS-68 on the center core will throttle down to conserve liquid hydrogen and liquid hydrogen propellant, while the rocket’s two side boosters will burn through their propellants in less than four minutes.

Once the Delta IV lets go of its side boosters and falls into the Atlantic Ocean, the center core throttles up and burns for another minute and a half. A few moments later, the first stage booster jettisons, and the upper stage’s RL10 engine ignites for the first of three burns needed to propel the rocket’s classified cargo into an orbit thousands of miles above Earth.

There’s just a 30 percent chance of favorable weather for liftoff Thursday. High winds and cumulus clouds are the primary concerns. The weather forecast improves for a backup launch opportunity Friday afternoon.

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quantum-computing-progress:-higher-temps,-better-error-correction

Quantum computing progress: Higher temps, better error correction

Amazon, Computer science, ibm, Physics, quantum computing, quantum mechanics, Science / /
conceptual graphic of symbols representing quantum states floating above a stylized computer chip.

There’s a strong consensus that tackling most useful problems with a quantum computer will require that the computer be capable of error correction. There is absolutely no consensus, however, about what technology will allow us to get there. A large number of companies, including major players like Microsoft, Intel, Amazon, and IBM, have all committed to different technologies to get there, while a collection of startups are exploring an even wider range of potential solutions.

We probably won’t have a clearer picture of what’s likely to work for a few years. But there’s going to be lots of interesting research and development work between now and then, some of which may ultimately represent key milestones in the development of quantum computing. To give you a sense of that work, we’re going to look at three papers that were published within the last couple of weeks, each of which tackles a different aspect of quantum computing technology.

Hot stuff

Error correction will require connecting multiple hardware qubits to act as a single unit termed a logical qubit. This spreads a single bit of quantum information across multiple hardware qubits, making it more robust. Additional qubits are used to monitor the behavior of the ones holding the data and perform corrections as needed. Some error correction schemes require over a hundred hardware qubits for each logical qubit, meaning we’d need tens of thousands of hardware qubits before we could do anything practical.

A number of companies have looked at that problem and decided we already know how to create hardware on that scale—just look at any silicon chip. So, if we could etch useful qubits through the same processes we use to make current processors, then scaling wouldn’t be an issue. Typically, this has meant fabricating quantum dots on the surface of silicon chips and using these to store single electrons that can hold a qubit in their spin. The rest of the chip holds more traditional circuitry that performs the initiation, control, and readout of the qubit.

This creates a notable problem. Like many other qubit technologies, quantum dots need to be kept below one Kelvin in order to keep the environment from interfering with the qubit. And, as anyone who’s ever owned an x86-based laptop knows, all the other circuitry on the silicon generates heat. So, there’s the very real prospect that trying to control the qubits will raise the temperature to the point that the qubits can’t hold onto their state.

That might not be the problem that we thought, according to some work published in Wednesday’s Nature. A large international team that includes people from the startup Diraq have shown that a silicon quantum dot processor can work well at the relatively toasty temperature of 1 Kelvin, up from the usual milliKelvin that these processors normally operate at.

The work was done on a two-qubit prototype made with materials that were specifically chosen to improve noise tolerance; the experimental procedure was also optimized to limit errors. The team then performed normal operations starting at 0.1 K, and gradually ramped up the temperatures to 1.5 K, checking performance as they did so. They found that a major source of errors, state preparation and measurement (SPAM), didn’t change dramatically in this temperature range: “SPAM around 1 K is comparable to that at millikelvin temperatures and remains workable at least until 1.4 K.”

The error rates they did see depended on the state they were preparing. One particular state (both spin-up) had a fidelity of over 99 percent, while the rest were less constrained, at somewhere above 95 percent. States had a lifetime of over a millisecond, which qualifies as long-lived int he quantum world.

All of which is pretty good, and suggests that the chips can tolerate reasonable operating temperatures, meaning on-chip control circuitry can be used without causing problems. The error rates of the hardware qubits are still well above those that would be needed for error correction to work. However, the researchers suggest that they’ve identified error processes that can potentially be compensated for. They expect that the ability to do industrial-scale manufacturing will ultimately lead to working hardware.

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Puerto Rico declares public health emergency as dengue cases rise

Aedes aegypti, dengue, health, Infectious disease, mosquitoes, Puerto Rico, Science, viral infection / /

emergency —

Cases so far are up 140 percent compared to this point last year.

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Female Aedes aegypti mosquito as she was in the process of obtaining a

Female Aedes aegypti mosquito as she was in the process of obtaining a “blood meal.”

Puerto Rico has declared a public health emergency amid an ongoing outbreak of dengue infections, a mosquito-spread viral infection that can cause fever, aches, rash, vomiting, and, in about 5 percent of cases, a severe disease marked by internal bleeding and shock.

The US territory has tallied 549 cases since the start of the year, representing a 140 percent increase compared with cases tallied at this point last year, according to the territory’s health department. The Associated Press reported that more than 340 of the 549 cases have been hospitalized.

In 2023, the island nation of more than 3.2 million people had over 1,000 cases of dengue throughout the year.

But this year’s cases are rising rapidly, leading health officials to warn residents to be vigilant and take prevention measures. That includes wearing insect repellent and draining or treating any standing water where mosquitoes can breed. The mosquitoes that transmit dengue—Aedes aegypti—seem to prefer breeding in artificial containers, such as flower pots, buckets, water drums, vases, plastic containers of any kind, the inner rings of discarded automobile tires, and trash in general. They can breed in tiny amounts of water, such as in bottle caps.

Puerto Rico’s outbreak of dengue is part of a larger regional trend, the island’s health department noted. Last year, the Americas saw the highest number of dengue cases ever recorded, totaling 4,565,911, according to the Pan American Health Organization (PAHO), a division of the World Health Organization. So far this year, the region has reported 3,578,414 cases, including 1,039 deaths. The bulk of the cases are in Brazil, which has reported over 2.9 million cases so far. Paraguay has reported over 191,000 cases, and Argentina has reported over 134,000 cases.

In a December 2023 risk assessment, the PAHO deemed the risk to human health from dengue to be “high” in the region. The report noted that the effects of climate change are driving higher rainfall, higher temperatures, and more humidity, allowing A. aegypti to expand into new areas and increase breeding. A. aegypti are already found in much of South America, Central America, and the southeastern US.

This post was updated to include additional case tallies. 

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event-horizon-telescope-captures-stunning-new-image-of-milky-way’s-black-hole

Event Horizon Telescope captures stunning new image of Milky Way’s black hole

astronomy, astrophysics, black holes, Event Horizon Telescope, Physics, Science / /
A new image from the Event Horizon Telescope has revealed powerful magnetic fields spiraling from the edge of a supermassive black hole at the center of the Milky Way, Sagittarius A*.

Enlarge / A new image from the Event Horizon Telescope has revealed powerful magnetic fields spiraling from the edge of a supermassive black hole at the center of the Milky Way, Sagittarius A*.

EHT Collaboration

Physicists have been confident since the1980s that there is a supermassive black hole at the center of the Milky Way galaxy, similar to those thought to be at the center of most spiral and elliptical galaxies. It’s since been dubbed Sagittarius A* (pronounced A-star), or SgrAfor short. The Event Horizon Telescope (EHT) captured the first image of SgrAtwo years ago. Now the collaboration has revealed a new polarized image (above) showcasing the black hole’s swirling magnetic fields. The technical details appear in two new papers published in The Astrophysical Journal Letters. The new image is strikingly similar to another EHT image of a larger supermassive black hole, M87*, so this might be something that all such black holes share.

The only way to “see” a black hole is to image the shadow created by light as it bends in response to the object’s powerful gravitational field. As Ars Science Editor John Timmer reported in 2019, the EHT isn’t a telescope in the traditional sense. Instead, it’s a collection of telescopes scattered around the globe. The EHT is created by interferometry, which uses light in the microwave regime of the electromagnetic spectrum captured at different locations. These recorded images are combined and processed to build an image with a resolution similar to that of a telescope the size of the most distant locations. Interferometry has been used at facilities like ALMA (the Atacama Large Millimeter/submillimeter Array) in northern Chile, where telescopes can be spread across 16 km of desert.

In theory, there’s no upper limit on the size of the array, but to determine which photons originated simultaneously at the source, you need very precise location and timing information on each of the sites. And you still have to gather sufficient photons to see anything at all. So atomic clocks were installed at many of the locations, and exact GPS measurements were built up over time. For the EHT, the large collecting area of ALMA—combined with choosing a wavelength in which supermassive black holes are very bright—ensured sufficient photons.

In 2019, the EHT announced the first direct image taken of a black hole at the center of an elliptical galaxy, Messier 87, located in the constellation of Virgo some 55 million light-years away. This image would have been impossible a mere generation ago, and it was made possible by technological breakthroughs, innovative new algorithms, and (of course) connecting several of the world’s best radio observatories. The image confirmed that the object at the center of M87is indeed a black hole.

In 2021, the EHT collaboration released a new image of M87showing what the black hole looks like in polarized light—a signature of the magnetic fields at the object’s edge—which yielded fresh insight into how black holes gobble up matter and emit powerful jets from their cores. A few months later, the EHT was back with images of the “dark heart” of a radio galaxy known as Centaurus A, enabling the collaboration to pinpoint the location of the supermassive black hole at the galaxy’s center.

SgrAis much smaller but also much closer than M87*. That made it a bit more challenging to capture an equally sharp image because SgrAchanges on time scales of minutes and hours compared to days and weeks for M87*. Physicist Matt Strassler previously compared the feat to “taking a one-second exposure of a tree on a windy day. Things get blurred out, and it can be difficult to determine the true shape of what was captured in the image.”

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Cows in Texas and Kansas test positive for highly pathogenic bird flu

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viral spread —

The risk to the public is low, and the milk supply is safe.

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Image of cows

Wild migratory birds likely spread a deadly strain of bird flu to dairy cows in Texas and Kansas, state and federal officials announced this week.

It is believed to be the first time the virus, a highly pathogenic avian influenza (HPAI), has been found in cows in the US. Last week, officials in Minnesota confirmed finding an HPAI case in a young goat, marking the first time the virus has been found in a domestic ruminant in the US.

According to the Associated Press, officials with the Texas Animal Health Commission confirmed the flu virus is the Type A H5N1 strain, which has been ravaging bird populations around the globe for several years. The explosive, ongoing spread of the virus has led to many spillover events into mammals, making epidemiologists anxious that the virus could adapt to spread widely in humans.

For now, the risk to the public is low. According to a release from the US Department of Agriculture (USDA), genetic testing by the National Veterinary Services Laboratories indicated that H5N1 strain that spread to the cows doesn’t appear to contain any mutations that would make it more transmissible to humans. Though the flu strain was found in some milk samples from the infected cows, the USDA emphasized that all the milk from affected animals is being diverted and destroyed. Dairy farms are required to send only milk from healthy animals to be processed for human consumption. Still, even if some flu-contaminated milk was processed for human consumption, the standard pasteurization process inactivates viruses, including influenza, as well as bacteria.

So far, officials believe the virus is primarily affecting older cows. The virus was detected in milk from sick cows on two farms in Kansas and one in Texas, as well as in a throat swab from a cow on a second Texas farm. The USDA noted that farmers have found dead birds on their properties, indicating exposure to infected birds. Sick cows have also been reported in New Mexico. Symptoms of the bird flu in cows appear to include decreased milk production and low appetite.

But so far, the USDA believes the spread of H5N1 will not significantly affect milk production or the herds. Milk loss has been limited; only about 10 percent of affected herds have shown signs of the infection, and there has been “little to no associated mortality.” The USDA suggested it will remain vigilant, calling the infections a “rapidly evolving situation.”

While federal and state officials continue to track the virus, Texas officials aim to assure consumers. “There is no threat to the public and there will be no supply shortages,” Texas Agriculture Commissioner Sid Miller said in a statement. “No contaminated milk is known to have entered the food chain; it has all been dumped. In the rare event that some affected milk enters the food chain, the pasteurization process will kill the virus.”

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Taylor Swift fans dancing and jumping created last year’s “Swift quakes”

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Good vibrations —

“Shake It Off” produced tremors equivalent to a local magnitude earthquake of 0.851.

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Taylor Swift on the Eras Tour in 2023

Enlarge / Taylor Swift during her Eras Tour. Crowd motions likely caused mini “Swift quakes” recorded by seismic monitoring stations.

When mega pop star Taylor Swift gave a series of concerts last August at the SoFi Stadium in Los Angeles, regional seismic network stations recorded unique harmonic vibrations known as “concert tremor.” A similar “Swift quake” had occurred the month before in Seattle, prompting scientists from the California Institute of Technology and UCLA to take a closer look at seismic data collected during Swift’s LA concert.

The researchers concluded that the vibrations were largely generated by crowd motion as “Swifties” jumped and danced enthusiastically to the music and described their findings in a new paper published in the journal Seismological Research Letters. The authors contend that gaining a better understanding of atypical seismic signals like those generated by the Swift concert could improve the analysis of seismic signals in the future, as well as bolster emerging applications like using signals from train noise for seismic interferometry.

Concert tremor consists of low-frequency signals of extended duration with harmonic frequency peaks between 1 and 10 Hz, similar to the signals generated by volcanoes or trains. There has been considerable debate about the source of these low-frequency concert tremor signals: Are they produced by the synchronized movement of the crowd, or by the sound systems or instruments coupled to the stage? Several prior studies of stadium concerts have argued for the former hypothesis, while a 2015 study found that a chanting crowd at a football game produced similar harmonic seismic tremors. However, a 2008 study concluded that such signals generated during an outdoor electronic dance music festival came from the sound system vibrating to the musical beat.

The Caltech/UCLA team didn’t just rely on the data from the regional network stations. The scientists placed additional motion sensors throughout the stadium prior to the concert, enabling them to characterize all the seismic signals produced during the concert. The signals had such unique characteristics that it was relatively easy to identify them with a spectrogram. In fact, the authors were able to identify 43 of the 45 songs Swift performed based on the distinctive signal of each song.

They also calculated how much radiated energy was produced by each song. “Shake It Off” produced the most radiated energy, equivalent to a local magnitude earthquake of 0.851. “Keep in mind this energy was released over a few minutes compared to a second for an earthquake of that size,” said co-author Gabrielle Tepp of Caltech.

Tepp is a volcanologist and musician in her own right. That combination came in handy when it was time to conduct a lab-based experiment to test the team’s source hypothesis using a portable public announcement speaker system. They played Swift’s “Love Story” and Tepp gamely danced and jumped with the beat during the last chorus while sensors recorded the seismic vibrations. “Even though I was not great at staying in the same place—I ended up jumping around in a small circle, like at a concert—I was surprised at how clear the signal came out,” said Tepp. They also tested a steady beat as Tepp played her bass guitar in order to isolate the signal from a single instrument.

The resulting fundamental harmonic during the jumping was consistent with the song’s beat rate. However, the bass beats didn’t produce a harmonic signal, which was surprising since those beats were better synchronized with the actual musical beats than Tepp’s jumping motions. This might be due to the rounder shape of the bass beat signals compared to sharper spiking signals in response to the jumping.

Map showing the concert venue and nearby seismic stations (circles) that recorded signals from the Swift concerts (blue).

Enlarge / Map showing the concert venue and nearby seismic stations (circles) that recorded signals from the Swift concerts (blue).

Gabrielle Tepp et al., 2024

The authors noted that their experiment did not involve a stage or stadium-grade sound system, “so we cannot completely rule out loudspeakers as a vibrational energy source,” they wrote. Nonetheless, “Overall the evidence suggests that crowd movement is the primary source of the low-frequency signals, with the speaker system or instruments potentially contributing via stage of building vibrations.” The fact that the same kind of low-frequency seismic signals were not detected during pre-concert sound checks seems to support that conclusion, although there were higher frequency signals during sound checks.

The team also studied the structural response of the stadium and conducted a similar analysis of seismic readings from three other concerts at SoFi Stadium that summer: country music’s Morgan Waller, Beyoncé, and Metallica, as well as picking up clear signals at one monitoring station for the three opening acts: Pantera, DJ Khaled, and Five Finger Death Punch, respectively. The results were markedly similar to the seismic data gathered from the Taylor Swift concerts, although none of the signals matched the strongest of those detected during the Swift concerts.

The researchers were surprised to find that the seismic signals from the Metallica concert were the weakest among all the concerts and markedly different from the others, “slanted and kind of weird looking,” per Tepp. They found several comments in music forums from fans complaining about poor sound quality at the Metallica concert. “If fans had a hard time discerning the song or beat, it may explain the more variable signals because it would have influenced their movements,” the authors wrote.

It’s also possible that heavy metal live performances are less tightly choreographed than Beyoncé or Swift performances, or that heavy metal fans don’t move with the music in quite the same way. “Metal fans like to headbang a lot, so they’re not necessarily bouncing,” said Tepp. “It might just be that the ways in which they move don’t create as strong of a signal.”

Seismological Research Letters, 2024. DOI: 10.1785/0220230385  (About DOIs).

Taylor Swift fans dancing and jumping created last year’s “Swift quakes” Read More »

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SCOTUS mifepristone case: Justices focus on anti-abortion groups’ legal standing

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Demonstrators participate in an abortion-rights rally outside the Supreme Court as the justices of the court hear oral arguments in the case of the <em>US Food and Drug Administration v. Alliance for Hippocratic Medicine</em> on March 26, 2024 in Washington, DC.” src=”https://cdn.arstechnica.net/wp-content/uploads/2024/03/GettyImages-2115237711-800×533.jpeg”></img><figcaption> <p><a data-height=Enlarge / Demonstrators participate in an abortion-rights rally outside the Supreme Court as the justices of the court hear oral arguments in the case of the US Food and Drug Administration v. Alliance for Hippocratic Medicine on March 26, 2024 in Washington, DC.

The US Supreme Court on Tuesday heard arguments in a case seeking to limit access to the abortion and miscarriage drug mifepristone, with a majority of justices expressing skepticism that the anti-abortion groups that brought the case have the legal standing to do so.

The case threatens to dramatically alter access to a drug that has been safely used for decades and, according to the Guttmacher Institute, was used in 63 percent of abortions documented in the health care system in 2023. But, it also has sweeping implications for the Food and Drug Administration’s authority over drugs, marking the first time that courts have second-guessed the agency’s expert scientific analysis and moved to restrict access to an FDA-approved drug.

As such, the case has rattled health experts, reproductive health care advocates, the FDA, and the pharmaceutical industry alike. But, based on the line of questioning in today’s oral arguments, they have reason to breathe a sigh of relief.

Standing

The case was initially filed in 2022 by a group of anti-abortion organizations led by the Alliance for Hippocratic Medicine. They collectively claimed that the FDA’s approval of mifepristone in 2000 was unlawful, as were FDA actions in 2016 and 2021 that eased access to the drug, allowing for it to be prescribed via telemedicine and dispensed through the mail. The anti-abortion groups justified bringing the lawsuit by claiming that the doctors in their ranks are harmed by the FDA’s actions because they are forced to treat girls and women seeking emergency medical care after taking mifepristone and experiencing complications.

The FDA and numerous medical organizations have emphatically noted that mifepristone is extremely safe and the complications the lawsuit references are exceedingly rare. Serious side effects occur in less than 1 percent of patients, and major adverse events, including infection, blood loss, or hospitalization, occur in less than 0.3 percent, according to the American College of Obstetricians and Gynecologists. Deaths are almost non-existent.

Still, a conservative federal judge in Texas sided with the anti-abortion groups last year, revoking the FDA’s 2000 approval. A conservative panel of judges for the Court of Appeals for the 5th Circuit in New Orleans then partially overturned the ruling, undoing the lower court’s ruling on the 2000 approval, allowing the FDA’s approval to stand, but still finding the FDA’s 2016 and 2021 actions unlawful. The ruling was frozen until the Supreme Court weighed in.

Today, many of the Supreme Court Justices went back to the very beginning: the claimed scenario that the plaintiff doctors have been or will imminently be harmed by the FDA’s actions. At the outset of the hearings, Solicitor General Elizabeth Prelogar argued that the plaintiffs had not been harmed, and, even if they were, they already had federal protections and recourse. Any doctor who consciously objects to caring for a patient who has had an abortion already has federal protections that prevent them from being forced to provide that care, Prelogar argued. As such, hospitals have legal obligations and have set up contingency and staffing plans to prevent violating those doctors’ federal conscious objection protections.

SCOTUS mifepristone case: Justices focus on anti-abortion groups’ legal standing Read More »

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Bridge collapses put transportation agencies’ emergency plans to the test

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The Dali container vessel after striking the Francis Scott Key Bridge that collapsed into the Patapsco River in Baltimore on March 26. The commuter bridge collapsed after being struck by a container ship, causing vehicles to plunge into the water and halting shipping traffic at one of the most important ports on the US East Coast.

Enlarge / The Dali container vessel after striking the Francis Scott Key Bridge that collapsed into the Patapsco River in Baltimore on March 26. The commuter bridge collapsed after being struck by a container ship, causing vehicles to plunge into the water and halting shipping traffic at one of the most important ports on the US East Coast.

A container ship rammed into the Francis Scott Key Bridge in Baltimore around 1: 30 am on March 26, 2024, causing a portion of the bridge to collapse into Baltimore Harbor. Officials called the event a mass casualty and were searching for people in the waters of the busy port.

This event occurred less than a year after a portion of Interstate 95 collapsed in north Philadelphia during a truck fire. That disaster was initially expected to snarl traffic for months, but a temporary six-lane roadway was constructed in 12 days to serve motorists while a permanent overpass was rebuilt.

US cities often face similar challenges when routine wear and tear, natural disasters, or major accidents damage roads and bridges. Transportation engineer Lee D. Han explains how planners, transit agencies, and city governments anticipate and manage these disruptions.

How do agencies plan for disruptions like this?

Planning is a central mission for state and metropolitan transportation agencies.

Traditional long-term planning focuses on anticipating and preparing for growing and shifting transportation demand patterns. These changes are driven by regional and national economic and population trends.

Shorter-term planning is about ensuring mobility and safety during service disruptions. These disruption events can include construction, major scheduled events like music festivals, traffic incidents such as crashes and hazardous material spills, emergency evacuations, and events like the bridge collapse in Baltimore.

Agencies have limited resources, so they typically set priorities based on how likely a given scenario is, its potential adverse effects, and the countermeasures that officials have available.

For bridges, the Federal Highway Administration sets standards and requires states to carry out periodic inspections. In addition, agencies develop a detouring plan for each bridge in case of a structural failure or service disruption. In Baltimore, Key Bridge traffic will be routed through two tunnels that pass under the harbor, but trucks carrying hazardous materials will have to take longer detours.

Major bridges, such as those at Mississippi River crossings, are crucial to the nation’s economy and security. They require significant planning, commitment, and coordination between multiple agencies. There usually are multiple contingency plans in place to deal with immediate traffic control, incident response, and field operations during longer-term bridge repair or reconstruction projects.

What are some major challenges of rerouting traffic?

Bridges are potential choke points in highway networks. When a bridge fails, traffic immediately stops and begins to flow elsewhere, even without a formal detouring plan. Transportation agencies need to build or find excess capacity before a bridge fails so that the disrupted traffic has alternative routes.

This is usually manageable in major urban areas that have many parallel routes and bridges and built-in redundancy in their road networks. But for rural areas, failure of a major bridge can mean extra hours or even days of travel.

When traffic has to be rerouted off an interstate highway, it can cause safety and access problems. If large trucks are diverted to local streets that were not designed for such vehicles, they may get stuck on railroad tracks or in spaces too small for them to turn around. Heavy trucks can damage roads and bridges with low weight limits, and tall trucks may be too large to fit through low-clearance underpasses.

Successful rerouting requires a lot of coordination between agencies and jurisdictions. They may have to adjust road signal timing to deal with extra cars and changed traffic patterns. Local drivers may need to be directed away from these alternative routes to prevent major congestion.

It’s also important to communicate with navigation apps like Google Maps and Waze, which every driver has access to. Route choices that speed up individual trips may cause serious congestion if everyone decides to take the same alternate route and it doesn’t have enough capacity to handle the extra traffic.

Bridge collapses put transportation agencies’ emergency plans to the test Read More »