Astronomers Developed Method For Computing the Polarized Image Of A Ring Orbiting A Black Hole (Astronomy)

Synchrotron radiation from hot gas near a black hole results in a polarized image. The image polarization is determined by effects including the orientation of the magnetic field in the emitting region, relativistic motion of the gas, strong gravitational lensing by the black hole, and parallel transport in the curved spacetime. Now, Narayan and colleagues explored these effects using a simple model of an axisymmetric, equatorial accretion disk around a Schwarzschild black hole. Their study recently appeared in the Astrophysical Journal .

The Event Horizon Telescope (EHT) Collaboration has recently published the first images of a black hole. These images achieve a diffraction limited angular resolution that corresponds to approximately 5GM/c², where M is the mass of the black hole. They reveal a bright ring of emission with a twisting polarization pattern and a prominent rotationally symmetric mode.

The polarization structure in the EHT images depends on details of the emitting plasma, principally the magnetic field geometry. However, it is also affected by the strongly curved spacetime near the black hole. Over the past few decades, simulated polarimetric images of black holes have been studied as a means to understand astrophysical properties of their surrounding accretion flows and to infer the disk inclination and black hole spin through the effects of parallel transport. While they are becoming increasingly realistic, these simulations are generally difficult to use for broad parameter surveys because of their computational cost, and they often provide little insight into how to decouple astrophysical and relativistic effects.

Now, Narayan and colleagues develop a simple toy model to understand polarimetric images of black holes. This model consists of a ring of magnetized fluid orbiting a Schwarzschild black hole. Their model allows arbitrary emission radius, magnetic field geometry, equatorial fluid velocity, and observer inclination.

“We test this model using currently favored general relativistic magnetohydrodynamic simulations of M87*, using ring parameters given by the simulations.”

The model

They considered an accretion disk around a Schwarzschild black hole of mass M. They used standard geometrized units: G = c = 1. The fluid radiates from the equatorial plane within a narrow range of radii centered on a dimensionless radius R, measured in units of M (or GM/c², including the physical constants). With respect to a distant observer, the ring is tilted from a face-on orientation by an angle θo. They assumed that the tilt is towards the North, so that the line-of-nodes between the ring orbital plane and the observer’s sky plane is in the East-West direction. They take the sky angular coordinate x to be oriented towards the West (i.e., to the right), and the coordinate y towards the North (i.e., towards the top). The fluid has radial and tangential components of velocity in the plane of the ring, but no vertical velocity. In the comoving frame of the fluid, the magnetic field has radial, azimuthal and vertical components.

Figure 1. Geometry in the P-frame. This frame is aligned with the rotating gas at emission radius R and emission azimuth φ. The ˆx direction lies along the radial line from the black hole at O to the emission point P, and ˆy is the azimuthal direction. The equatorial magnetic field B~eq and fluid velocity ~β lie at angles η and χ to ˆx in the x-y plane, respectively. © Narayan et al.


Later, they computed the following primary observables: (1) the shape of the ring as viewed by the distant observer, (2) the variation of the polarized intensity around the observed ring, and (3) the orientation and pattern of the polarization vectors around the ring. And, then compared EHT polarimetric image of M87 with their ring model.


1) Of Primary Observables

Figure 2. Geometry in the geodesic frame, or G-frame. In the Schwarzschild metric, each null geodesic is confined to a plane that intersects the black hole. The G-frame, defined for photons emitted at point P and reaching a distant observer at relative angle ψ, corresponds to Cartesian axes centered on the black hole, with ˆx in the direction of P and the ˆx-ˆz plane given by the geodesic plane. © Narayan et al.

For first case they found that, the shape of ring appears to be flat because of tilt. Means, it appears elliptical in shape, with a minor axis radius equal to cos θo ≈ 1 − (1/2) sin²θo times the original ring radius. The sin θo terms describe the effect of tilt on lensing. Geodesics reaching the observer from the upper half of the ring (0 < φ < π) travel a longer distance near the black hole and suffer more deflection (this is the case shown schematically in Fig. 2), while geodesics from the lower half (π < φ < 2π) experience less deflection. This causes an upward shift of the observed ring, i.e., a net positive bias in y. The shift is of the order of sin θo in units of GM/c².

While for second case, they found that, observed polarized intensity depends on the Doppler factor δ as well as the path length lp and the angle ζ between the photon wave-vector ~k(F) in the fluid frame and the local magnetic field B~. For small tilt angles, the variation in the path length is small and not very important.

Finally, for third case, they found that, for a radial velocity (χ = π), the phase of β2 is π, i.e., the polarization vectors should be tangentially oriented. This is indeed seen in the brightest part of the ring in the Bottom Left panel in Fig. 3. Similarly, for a tangential velocity (χ = −π/2), the phase of β2 = 0 and the polarization ticks should be radial, as seen in the Top Right panel of Fig. 3. Finally, if there is no velocity but we consider strong lensing (small R), then equation (40) shows that β2 has phase = π and the polarization should be tangential, as in the Bottom Right panel.

Figure 3. Polarization patterns corresponding to models with a “vertical” magnetic field (non-zero Bz in the fluid frame). In each case, the directions of the ticks indicate the orientation of the polarization E~-vector around the ring as viewed on the sky. The lengths of the ticks are proportional to the polarized intensity. Top Left: Ring with a very large radius and no orbital velocity, so that neither velocity aberration nor lensing plays a role. Top Right: Large ring radius (i.e., no lensing), and fluid orbiting with a tangential velocity β = 0.3 in the clockwise direction (χ = – 90°). Bottom Left: Large ring radius (no lensing), and fluid flowing with velocity β = 0.3 radially inward (χ = –180°). Bottom Right: Ring with a small radius R = 6M, hence strong gravitational lensing, but with no fluid velocity, hence no aberration. © Narayan et al.

2) Of Comparison

They also compared EHT polarimetric image of M87 with their ring model and found that the fractional polarization of their model is significantly higher than that seen in EHT images of M87* (EHTC VII). This may indicate significant sub-beam depolarization, potentially from strong internal Faraday effects (EHTC VIII). If so, observations at higher frequencies, where Faraday effects are suppressed, may show significantly higher image polarizations, while observations at lower frequencies are expected to show a heavily depolarized “core.”

Figure 4. Comparison of the EHT polarimetric image of M87* on 2017 April 11 (left) with a representative ring model (right). Ticks show polarization fraction (color), magnitude (length), and position angle (direction); grayscale is identical for the two panels and shows total intensity of the EHT image of M87. Ticks are only plotted where the M87 polarization exceeds 2% of the maximum intensity. All images are shown after convolution with a circular beam of FWHM 23 µas (shown in the left panel). © Narayan et al.

Their polarized ring model provides intuition and insights about how a black hole’s accretion flow and spacetime combine to produce a polarized image. It also provides a pathway to constrain these physical properties through direct comparisons with data and images from the EHT, GRAVITY, and future X-ray polarimetry studies.

“Further studies which examine the capability of the model in matching snapshots of GRMHD simulations with similar magnetic field and flow conditions will elucidate how readily field geometries may be directly inferred from polarized images.”

— concluded authors of the study

Reference: Ramesh Narayan, Daniel C. M. Palumbo, Michael D. Johnson, Zachary Gelles, Elizabeth Himwich, Dominic O. Chang, Angelo Ricarte, Jason Dexter, Charles F. Gammie, Andrew A. Chael, The Event Horizon Telescope Collaboration: Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Anne-Kathrin Baczko, David Ball, Mislav Balokovic, John Barrett, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Wilfred Boland, Katherine L. Bouman, Geoffrey C. Bower, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Avery E. Broderick, Dominique Broguiere, Thomas Bronzwaer, Do-Young Byun, John E. Carlstrom, Chi-kwan Chan, Shami Chatterjee, Koushik Chatterjee, Ming-Tang Chen, Yongjun Chen, Paul M. Chesler, Ilje Cho, Pierre Christian, John E. Conway, James M. Cordes, Thomas M. Crawford, Geoffrey B. Crew, Alejandro Cruz-Osorio, Yuzhu Cui, Jordy Davelaar, Mariafelicia DeLaurentis, Roger Deane, Jessica Dempsey, Gregory Desvignes, Sheperd S. Doeleman, Ralph P. Eatough, Heino Falcke, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Raquel Fraga-Encinas, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Roberto Garcıa, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, Roman Gold, Jose L. Gomez, Arturo I. Gomez-Ruiz, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Michael H. Hecht, Ronald Hesper, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, Makoto Inoue, Sara Issaoun, David J. James, Buell T. Jannuzi, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jimenez-Rosales, Svetlana Jorstad, Taehyun Jung et al., “The Polarized Image of a Synchrotron Emitting Ring of Gas Orbiting a Black Hole”, Astrophysical Journal, ApJ 912(1), pp. 1-29, 2021. DOI: 10.3847/1538-4357/abf117

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Bats Are Mostly Associated With Death and Darkness, But the Bad Rap They Get is Undeserved (Culture)

They’re often referred to as creatures of the night – linked to vampires in European folklore – and were misleadingly associated with the spread of COVID-19 last year.

Because of their nocturnal lifestyles and cave-dwelling tendencies, bats are among the world’s most misunderstood animals. They often receive negative attention and Halloween associations in modern media. There’s even a condition for it – chiroptophobia, or the fear of bats.

But while these flying mammals are predominantly associated with death and darkness in the West, they’ve historically enjoyed a more diverse representation in many parts of the East, where they’ve come to be associated with a wide range of cultures, folklore, and customs that are largely positive in nature.

Countering negative perceptions

new study recently published in the Journal of Ethnobiology aims to shine the spotlight on these more positive beliefs and cultural perceptions regarding bats to hopefully counter the negative narratives surrounding them, and possibly also help design culturally-grounded conservation strategies for these tiny ecosystem warriors.

The collaborative effort was initiated by Rimba, a Malaysian non-profit research group focused on conducting conservation science, and involved researchers from Monash University Malaysia, University of Bristol, Indian Institute of Science Education and Research, Manamea Art Studio, Philippines Biodiversity Conservation Foundation, Chinese Academy of Sciences, University of Mandalay, Wildlife Conservation Society Indonesia Program, University College Sabah Foundation, and Kyoto University.

“As bat conservationists, we were thrilled to discover the wealth of positive stories and symbols related to bats, especially those in Malaysian cultures.”

The team studied 60 cultures from 24 countries across the region, analysing citations of key articles, websites, local knowledge and information from those working on bat-related research.

They discovered 119 bat cultural values, with more than 60% having only positive values, and only 10% having negative values. The findings imply that the Asia-Pacific region and its customs contain far more positive correlations with bats, which may translate into opportunities for human-bat coexistence.

For instance, among Chinese communities, bats are known to represent beneficial qualities such as health, prosperity, and long life. The pronunciation of the word “bat” in Chinese (蝠) is “fú”, which is a homonym to the Chinese word for “blessing” (福), directly associating the bat with good luck and blessings.

They’re popular motifs in artwork among Malaysian and Indonesian cultures, too, and bat-inspired patterns can be found in both batik, songket and pua kumbu. The popular Malay folk dance zapin also has steps that symbolise humility, which draws inspiration from the flying fox’s (a large fruit bat) elbow. In some parts of India, they’re even considered divine animals, with ties to the deities Muni, Kali, and Lakshmi.

Bats hanging upside down.

Positive representations of bats are similarly abundant among indigenous communities of the Asia-Pacific.

For the Ibans of Borneo, bats are considered the spiritual messengers of respected shamans, and a bat flying into one’s home is interpreted as the arrival of a shaman bringing good vibes. Among the Samoans, the flying fox is painted as a heroic saviour in mythology, having played a role in the rescue of the Tongan king’s wife.

“I’ve always been fascinated by bats as the only mammals to have ever evolved the ability to fly,” says Dr Cyren Wong Zhi Hoong of Monash University Malaysia, who was part of the project.

“I like to imagine that this was a fascination that our ancestors shared. I think that this collaborative research is a wonderful opportunity for us to remind people of how amazing bats are, and the historical role they’ve played in shaping the cultural fabric of this region.”

A bat hanging among bushes.

Cultural expressions are closely tied to the communities’ interactions with animals and their habitats. According to the research team, habitat destruction and species extinctions are likely to impact communities’ social memory and ethnobiological information delivery.

Review reflects a rich collection

The team’s literature review renders a clear indication for a rich collection of socio-cultural representations of bats across the Asia-Pacific region. They were able to help correct and supply additional information in the literature, emphasising the significance of local involvement and leadership in ethnobiological research, and the need for more locally spearheaded documentation efforts.

“As bat conservationists, we were thrilled to discover the wealth of positive stories and symbols related to bats, especially those in Malaysian cultures, as these accounts rarely penetrate mainstream media,” says the project’s lead investigator, Mary-Ruth Low, a senior conservation scientist with Rimba.

“We’re hopeful that this publication will help more Malaysians realise the positive impact that bats have had on our ancestors’ lives, and will spur further efforts to document cultural accounts and traditions related to bats in the region.”

Reference: Mary-Ruth Low, Wong Zhi Hoong, Zhiyuan Shen, Baheerathan Murugavel, Nikki Mariner, Lisa Marie Paguntalan, Krizler Tanalgo, Moe Moe Aung, . Sheherazade, Lawrence Alan Bansa, Tuanjit Sritongchuay, Jason Hideki Preble, Sheema Abdul Aziz, “Bane or Blessing? Reviewing Cultural Values of Bats across the Asia-Pacific Region”, J. of Ethnobiology, 41(1):18-34 (2021).

Provided by Monash University

Are Chemicals Shrinking Your Penis And Depleting Your Sperm? Here’s What the Evidence Really Says (Biology)

A doomsday scenario of an end to human sperm production has been back in the news recently, now with the added threat of shrinking penises.

Professor Shanna Swan, a US epidemiologist who studies environmental influences on human development, recently published a book titled Countdown.

In it, she suggests sperm counts could reach zero by 2045, largely owing to the impact of a range of environmental pollutants used in manufacturing everyday products – phthalates and bisphosphenol A (BPA) from plastics, and per- and poly-fluoroalkyl substances (PFAS) used, for example, in waterproofing. Under this scenario, she says, most couples wanting to conceive would need to rely on assisted reproductive technologies.

She’s also warned these chemicals are shrinking penis size.

Such extraordinary claims require extraordinary evidence. I would argue the evidence is not strong enough.

Correlation doesn’t equal causation

Epidemiologists find associations between disease and potential contributing factors, like lung cancer and smoking. But their work can’t identify the causes of disease – just because two things are associated doesn’t mean one is causing, or caused by, the other.

An article written by environmental activist Erin Brockovich in The Guardian in March leads by referring to “hormone-disrupting chemicals that are decimating fertility”. But causation is far from established.

It’s reasonable to expect chemicals that affect hormone function in our bodies, such as BPA and PFAS, could affect reproduction in males and females, given available evidence. But we don’t have irrefutable proof.

A man and a pregnant woman outside with their dog.
Could environmental pollutants be leading to infertility? Establishing cause and effect isn’t clear-cut. Photo: Shutterstock

Selective reporting

In 2017, Swan and several colleagues published an exhaustive review study showing an apparent drop in men’s sperm counts of 59.3% between 1973 and 2011. This research informs the arguments Swan makes in Countdown, and those we’ve seen in the media.

What’s not often mentioned is the fact the researchers only observed a decline in sperm count in groups of men from North America, Europe, Australia and New Zealand, but not in groups of men from South America, Asia or Africa.

When Swan and her colleagues combined the data from all countries, they saw a decline because the studies of “Western” men outweigh those of men elsewhere (in the number of studies and participants).

Swan and her colleagues worked hard to avoid bias when conducting their study. But selection bias (related to how study participants are chosen), publication bias (resulting from researchers’ tendency to report only observations they think will be of interest) and other limitations of the original work used as the basis for their investigation could be influencing the results of the larger study.

Many studies from different parts of the world show declining sperm counts, which is concerning, but we don’t fully understand the reasons for the apparent decline. Blaming chemicals in the environment overlooks other important factors such as chronic disease, diet, and obesity, which people can act on to improve their fertility.

The problem with extrapolation

Swan’s 2017 study boils down to a straight descending line drawn between sperm counts of groups of men studied at different times between 1973 and 2011.

Just because a straight line can be drawn through the data, this doesn’t justify extrapolation of that line beyond its earliest and latest data points. It’s unscientific to assume trends in data exist outside the range of observations.

We know sperm counts of men in the early 1940s were about 113 million sperm per millilitres of semen, not the roughly 140 million/ml you get from extrapolating backwards from Swan’s research. Concluding sperm counts will reach zero in 2045, based on extrapolating forward from the available data, is just as likely to be incorrect.

When Swan told news website Axios, “If you look at the curve on sperm count and project it forward”, she was encouraging unjustifiable and unscientific interpretation of her data – even though she acknowledged it was “risky” to extrapolate in this way. Unfortunately, this caution is too often unmentioned.

For example, Brockovich writes: “That would mean no babies. No reproduction. No more humans.” That’s hyperbole. It’s just not science.

An illustration of sperm.
Swan has extrapolated from recent data to predict sperm counts could reach zero by 2045. But this isn’t necessarily accurate. Photo: Shutterstock

Relax, your penis isn’t shrinking

Claims of shrinking penises are obvious clickbait. But only a single study, of 383 young men from the Veneto region in northeastern Italy, links men’s penis size to the types of chemicals Swan attributes to declining sperm counts.

Within Veneto there are geographic zones with varied levels of PFAS contamination. A group of 212 men who live in areas with high or intermediate PFAS exposure, and have high levels of these chemicals in their bodies, had an average penis length of 8.6cm, about 10% lower than the average of a group of 171 men from an area without exposure (9.7cm).

But a few features of this study affect the reliability of the observations, and whether we can generalise them to other populations.

  1. Men were grouped according to where they lived, not where they were born. Since genital size is determined before birth, the environment during their mothers’ pregnancies is more relevant to penis size than where the men lived at the time of the study. Some men will likely have relocated from their place of birth, but how many, and where they may have moved to and from, we don’t know.
  2. The levels of PFAS exposure for men living in the contaminated regions of Veneto are extreme, because of decades of industrial pollution. How the potential effect of such large exposures relates to smaller and more common exposures to pollutants, such as from plastic food wrap, we don’t know.
  3. The study is missing details about its subjects, and the conditions under which measurements were made. It’s usual to exclude people with conditions that might affect study outcomes, such as congenital abnormalities, but it’s not clear whether this happened in the study. Variables that influence penile measurements (such as room temperature, posture, and whether the penis is held straight or hanging) are not mentioned.

And from a semantic perspective, for penises to be “shrinking” they must be getting shorter over time, on either an individual or population basis. I cannot find any reports of men’s penises shortening as a consequence of environmental pollution. Available data doesn’t suggest a decline in penis size over the past few decades.

While environmental pollution is a pressing concern, the evidence suggests the catastrophic collapse of human reproduction and accompanying penis shrinkage is thankfully a pretty unlikely prospect.

Provided by Monash University

Why Extreme Heat Might Cancel Your Flight? (Earth Science)

In some cases, offloading passengers or the cargo isn’t enough to solve the problem. And climate change may only make the problem worse.

Every spring and summer, the headlines appear more familiar: Airlines are grounding flights because it’s simply too hot to fly. These declarations often come out of the toastiest U.S. cities, like Phoenix, which last year set a personal record of “most number of days over 110 degrees Fahrenheit.” Like humans on particularly scorching days, planes often can’t operate properly in extreme heat. In these cases, the aircraft is physically unable to take off because of the temperature.

It’s an awkward situation for airlines and their customers, who might not get why the perfect-seeming weather is stopping their trip. “You can see snow, you can see ice on the wings, you can see heavy rain or lightning, and you don’t want to get in a plane when that’s happening,” says Jennifer Griswold, an atmospheric scientist at the University of Hawai’i at Manoa. “But if it’s just sunny and really bright out and there’s not a cloud in the sky, it’s like, what’s wrong?” Meanwhile, flight operators are keenly aware of how quickly extreme heat can derail flight plans — and know that it’s going to become an even larger stumbling block in the future.

When Physics Keeps You Grounded

To understand why air temperature can make or break a functional flight, you have to know that pilots and flight engineers think of the gas-filled atmosphere instead as a fluid: Planes interact with the air similar to how we interact with water when we float. As a plane cruises down a runway, it pushes against the air. Due to one of the main rules in physics — every action comes with an equal and opposite reaction — the air pushes back. Some of that response translates into lift, the official name for the force that pushes planes into the sky.about:blank

But higher-than-expected temperatures interfere with how the air pushes back. Like with water, adding heat to air separates the molecules and forces more space between them. A hot summer day therefore means that the density of the air hovering just above the tarmac drops. More broadly, as high temperatures thin the atmosphere, oxygen molecules spread farther apart from one another. With fewer air molecules pushing back beneath the wings of the plane, the air fails to generate enough force for takeoff.

If the heat is too intense and the air too thin, the flight will stay grounded and might get a chance to take off once the sun sets and the temperatures drop. In some milder cases, there are a few options for pilots to compensate for the lower-density air and still take off on-schedule, some more theoretical than others.

For one, the plane could travel faster along the runway. But for safety reasons, the Federal Aviation Administration limits maximum takeoff speed. Plus, a quicker departure would burn more fuel, an expensive option airlines like to avoid, says Diandong Ren, an aviation researcher at Curtin University in Australia. This is also one of the least climate-friendly choices, seeing as fuel contributes to global carbon emissions (along with contrails).

Longer runways might be a solution. While engines rely on oxygen to react with fuel to generate power, lower-density oxygen is harder for the engine to consume and power generation decreases. More tarmac, meanwhile, would allow pilots to ascend more slowly and give the plane the room it needs to take off. Still, airports might balk at the expense of further construction, and in some cases, the idea runs up against the hard reality of physical limits. As it is, some airports take up all the space they possibly can.

A flight could also drop weight, since it’s easier to lift a lighter plane. This is usually the simplest, most agreed-upon solution, Ren says. But leaving packages or passengers behind can make for uncomfortable moments: Griswold was on a small aircraft in Florida where the airline chose this solution, and the last few arriving passengers were told they couldn’t board (they were not happy).about:blank

Overall, the inconvenience and the cost accumulates with every flight that cuts passengers or packages. With consistently rising temperatures, climate change has — and will continue to — ensure that planes drop weight more often, leaving global trade and travel to deal with the consequences. 

Extreme Heat: The Climate Change Guarantee

In 2015, a team of researchers analyzed how climate change will impact flights coming out of airports in four U.S. cities — Phoenix, Denver, New York City and Washington, D.C — in the coming decades. The team concluded that starting around 2050, the number of spring and summer days where it would be too hot to fly at normal weights could become up to twice as common as they are today. Predicted changes depend on individual airports. Phoenix, for example, has historically encountered only occasional days where planes had to cut 10,000 pounds to fly. In the future, the airport could start to see about 20 days a year where flights have to drop that much weight.

The researchers based their predictions on the global warming scenario that estimates a total temperature rise of around 9 degrees Fahrenheit by 2100. Though that’s one of the more extreme outcomes climate scientists have drafted, it’s still within the realm of possibility.

Regardless of how much warming may occur within coming decades, gradual climate change-induced temperature increases have already tampered with flights. The same paper found that as surface temperatures have gone up about 1.4 degrees Fahrenheit in the past century — with the bulk of that change occurring since 1980 — so too have the number of summer days where planes had to cut weight.

Other changes in the atmosphere have interfered with flight weights, too. Every few years, tropical portions of the Pacific Ocean heat up or cool down. Called El Niño when the temperatures rise and La Niña when they fall, the oceanic shifts change rainfall, humidity levels, wind patterns and temperature around the world. about:blank

When examining how El Niño and La Niña shifted conditions at 11 U.S. airports from 1979 to 2015, Griswold and her co-author found that the air density, or how tightly packed the air molecules were over the ground, was all over the place depending on location. Contingent on the geography, fluctuations in temperature and moisture can go in either direction during El Niño and La Niña. Some airports saw hotter, more humid conditions — a bad combo for flights, since higher levels of water in the air make the atmosphere less dense, too. Others got lucky with cooler, dryer weather. “The take-home from that particular work was that it’s very regional,” Griswold says. “Each airport needs to know what they would expect.”

Griswold’s research looked back at how weather has affected flights, though scientists don’t fully understand how climate change will shift weather patterns like El Niño and La Niña and what those repercussions might be for flights. And there’s still a lot to learn about how other important flight influences, like visibility conditions or wind direction and speed, hamper takeoff, Griswold says. It will also be crucial to figure out how too-low air density at one airport means other locations across the country don’t get the planes they were banking on to meet their own takeoff needs. “There’s 10 or 12 that are hubs,” Griswold says. “If they go down, it’s like a domino effect.” 

In other words, if you’re reading news about temperatures preventing takeoffs at one airport in the U.S. and hoping to get on a flight yourself that day, you might (indirectly) feel the burn yourself.

Featured image credit: Jaromir Chalabala/Shutterstock

Provided by Discover Magazine

New Strep A Human Challenge Model Paves The Way to Test Vaccines Against the Deadly Bacteria (Medicine)

Researchers have successfully developed a new Strep A human challenge model, paving the way to test vaccines against the common deadly bacteria that causes sore throats, scarlet fever and skin sores.

The collaborative research effort, led by the Murdoch Children’s Research Institute (MCRI) and published in The Lancet Microbe, found the model, which deliberately infected healthy adult volunteers with the bacteria in a controlled environment, was safe and would now be used to trial Strep A candidate vaccines.

Strep A infections affect about 750 million people and kill more than 500,000 globally every year – more than influenza, typhoid or whooping cough. Strep A can also cause severe life-threatening infections like toxic shock syndrome and flesh eating disease and post-infectious illnesses such as acute rheumatic fever, rheumatic heart disease and kidney disease.

Strep A infections disproportionately affect young children, the elderly, pregnant women and Indigenous Australians. There is currently no vaccine available to prevent Strep A and can only potentially be treated with antibiotics.

MCRI’S Dr Josh Osowicki said given Strep A only naturally infected humans, researchers were limited in what they could learn in the lab and using animal models.

“Human challenge models can be used to test vaccines, drugs and diagnostic tests, as well as driving all sorts of wonderful scientific collaborations to understand more about how diseases work and how to stop them,” he said.

“We have developed the only current Strep A controlled human infection model, ready to be used as a platform to evaluate new vaccine candidates and therapeutics.”

Dr Osowicki said the research team tested a Strep A strain they believed would cause a strep throat and was unlikely to cause acute or chronic health problems.

The study involved 25 volunteers, aged 18-40 years who stayed at Nucleus Network, a phase 1 clinical trials unit based in Melbourne for up to six days with blood tests and saliva and throat swabs collected regularly.

Dr Osowicki said 85 per cent of participants developed a convincing case of strep throat, well up on the at least 60 per cent anticipated.

“Starting at one-tenth of the dose used in old 1970s studies, we applied our special Strep A strain on the back of each participant’s throat,” he said. “To our surprise, from the very first participant at the low starting dose, our strain caused strep throat in most participants.”

The volunteers developed mild to moderate symptoms including a sore throat, sweats, fever and headache. All quickly recovered and were followed up for six months after they were sent home, according to the study.

Melbourne resident Tania O’Meara’s daughter Eden was just 11 months old when she almost lost her leg to a flesh-eating bacterial infection caused by Strep A.

“We put our daughter to bed with what seemed like a cold but the next morning she woke up with a fever and was very pale, limp and dehydrated,” she said.

“We took her to the hospital but the doctor couldn’t get the IV drip in because Eden was so dehydrated and they were forced to drill it into her leg. They also noticed that the skin on her leg looked like it was turning a different colour.”

Ms O’Meara said Eden required surgery on her right calf to remove the dead flesh.

“We were told that she could die and we braced ourselves so it was a miracle that they were able to save her leg and even her calf muscle,” she said.

Eden, now three, needed three more surgeries and has since made a full recovery.

Ms O’Meara said she was relieved that a vaccine for Step A may not be too far away.

“I don’t want any other family to experience what we went through. It is an absolute tragedy that this bacteria is cutting so many lives short,” she said.

MCRI Professor Andrew Steer said the team expected to start testing candidate Strep A vaccines developed by researchers in Australia and overseas before the end of the year.

The trials, to be conducted in Melbourne, would involve about 50 participants receiving a candidate vaccine or placebo and having the Strep A challenge strain applied on their throats.

“The global burden of Strep A is an unmet public health challenge. We hope this research will accelerate the development of a vaccine and move things forward to bigger field trials,” Professor Steer said.

“A vaccine for Strep A will save hundreds of thousands of lives every year and prevent millions of infections that send children and adults to the hospital or doctor.”


Researchers from the University of Melbourne, The Royal Children’s Hospital, Université Libre de Bruxelles in Brussels, Monash University, Griffith University, The University of Tennessee, The University of Queensland, Oxford Vaccine Group and Telethon Kids Institute also contributed to the study.

Publication: Joshua Osowicki, Kristy I. Azzopardi, Loraine Fabri, Hannah R. Frost, Tania Rivera-Hernandez, Melanie R. Neeland, Alana L. Whitcombe, Anneke Grobler, Sarah J. Gutman, Ciara Baker, Janet M.F. Wong, Jason D. Lickliter, Claire S. Waddington, Manisha Pandey, Tibor Schuster, Allen C. Cheng, Andrew J. Pollard, James S. McCarthy, Michael F. Good, James B. Dale, Michael Batzloff, Nicole J. Moreland, Mark J. Walker, Jonathan R. Carapetis, Pierre R. Smeesters and Andrew C. Steer. ‘A controlled human infection model of Streptococcus pyogenes pharyngitis: an observational, dose-finding study (CHIVAS-M75),’ The Lancet Microbe. DOI: 10.1016/S2666-5247(20)30240-8

Provided by Murdoch Children’s Research Institute

An Early Night Sleep Can Reduce A Child’s Weight Just As Much As Exercise (Biology)

Getting extra sleep can reduce a child’s weight just as well as exercise, according to a new study.

The research, published in Pediatricsshows how children can achieve equivalent physical and mental health benefits by choosing different activity trade-offs across the day.

The study, led by the Murdoch Children’s Research Institute and the University of South Australia, and supported by the National Heart Foundation of Australia, examined the optimal balance between children’s physical activity, sleep, and sedentary time across the 24-hour day to better inform tailored lifestyle choices.

On a minute-for-minute basis, moderate-to-vigorous physical exercise was shown to be 2-6 times more potent than sleep or sedentary time.

While exercise has a greater and faster impact on physical health and wellbeing, children may be able to achieve the same 7.4 per cent reduction in body mass index (BMI) by either:

  • exercising 17 more minutes (moderate-to-vigorous exercise) OR
  • sleeping an extra 52 minutes OR
  • reducing their sitting or sedentary time by an extra 56 minutes

Similarly, children may significantly improve their mental health by either:

  • exercising 35 minutes more (moderate-to-vigorous exercise), OR
  • sleeping an extra 68 minutes OR
  • reducing their sitting or sedentary time by 54 minutes

The study assessed 1179 children aged 11-12 years, from the Child Health CheckPoint Study, which was led by researchers from MCRI.

International guidelines suggest that children need 9-11 hours’ sleep, 60 minutes of physical exercise, and no more than two hours of recreational screen time per day, yet only 7 per cent of children are regularly meeting these goals.

The Heart Foundation’s Director of Physical Activity, Adjunct Professor Trevor Shilton, said the Heart Foundation was happy to support such an innovative approach to investigating children’s physical health and mental wellbeing.

“This study confirms that physical activity is the quickest and most effective way to deliver benefits for children’s physical health and mental wellbeing. But the findings also offer some flexibility for families,” he said.

“Helping young people make healthy choices and helping families create an environment that supports them in these choices can improve their quality of life in the future, as well as reducing their risk of chronic diseases, such as heart disease.”

Reference: Ng E, Wake M, Olds T, Lycett K, Edwards B, Le H, Dumuid D. Equivalence Curves for Healthy Lifestyle Choices. Pediatrics. 2021 Mar 26:e2020025395. doi: 10.1542/peds.2020-025395. Epub ahead of print. PMID: 33771915.

Provided by Murdoch Children’s Research Institute

Treating Cerebral Aneurysms with a New Filling Method (Medicine)

[POSTECH joint research team develops a new concept of cerebral aneurysm treatment using a reinforced photocrosslinked biocompatible material in the form of microfibers.]

Cerebral aneurysms are malformations caused by abnormalities on the walls of blood vessels in the brain. When these blood vessels rupture, about 30% of the sufferers die on the spot, giving these the rightful label of ‘ticking bombs in the head’. Recently, a research team at POSTECH has come up with a new treatment that can disassemble these time bombs by filling the aneurysm in blood with a new method.

In order to overcome the shortcomings of coil embolization*1, POSTECH’s joint research team (Professor Joonwon Kim and Dr. Jongkyeong Lim of the Department of Mechanical Engineering with Professor Hyung Joon Cha and Ph.D. candidate Geunho Choi of the Department of Chemical Engineering) has developed a new structurally stable, biocompatible embolization material that does not decompose in the human body. In addition, a new concept of cerebral aneurysm therapy (treatment device) capable of stably forming and controlling the material in the form of microfibers in the intravascular environment was presented. These research findings were published as the outside back cover paper of Advanced Materials on April 8, 2021.

Early detection of cerebral aneurysms is increasing due to periodic health examinations. The current treatment method uses coil embolization, which lowers the direction and pressure of internal blood flow by filling the aneurysm with a platinum coil before it ruptures. However, coil embolization surgery is a financial burden since it requires many platinum coils (KRW 600,000 (USD 550) per coil) commensurate to the aneurysm size. Moreover, due to the coil’s fine spring structure, the aneurysm may burst during surgery or the inside of the aneurysm may not be completely filled. There are also other problems in which the coil may be detached from the affected area due to recompression caused by the low filling rate after operation.

Hydrogels*2, which respond to various stimuli such as temperature, pH, and light, and exhibit soft mechanical strength, have attracted great attention as an embolic material that can fill an aneurysm at a high rate. Among them, photocrosslinkable hydrogels are considered to be most suitable for embolization thanks to their easy spatiotemporal control. But their practical usage is limited. In addition, materials being developed for aneurysm embolization currently use high concentrations of biologically inactive synthetic hydrogels that are toxic and not biocompatible. These can also cause severe swelling in the body – often leading to ruptures – and have thwarted their commercialization. In addition, conventional surgical methods could not be applied to clinical applications because it was impossible to produce and control hydrogels using light in an intravascular environment, which has a tortuous geometric structure and high absorbance.

The research team led by Professor Hyung Joon Cha of the Department of Chemical Engineering proposed an alginate-based hydrogel derived from algae that can be double-crosslinked as a new material for aneurysm embolization. This new embolic material exhibits excellent biocompatibility and uses the synergistic effect of rapid covalent crosslinking by irradiation with the harmless visible light and ionic crosslinking using calcium ions present in the blood. In addition, since no degrading enzymes exist in the human body, it does not degrade and exhibits outstanding structural stability without swelling. This can safely and effectively fill the aneurysm and successfully prevent rupture. Since it is possible to mount a contrast medium, it exhibits radiopacity so that the embolic material applied through CT or MRI can be monitored continuously for a long time.


The research team led by Professor Joonwon Kim of the Department of Mechanical Engineering developed a microfluidic device with an integrated optical fiber. This device is a new concept surgical device that can stably produce and control photocrosslinkable hydrogels in the form of microfibers in an extreme intravascular environment, which has a tortuous geometric structure and high absorbance.

Double-crosslinked alginate-based hydrogel microfibers produced and controlled in these microfluidic devices can safely and evenly fill the aneurysms. During this stage, the microfibers intertwine with each other to form a lump to block the flow of fluid from entering the aneurysm and maintain the structural shape and constant mechanical strength without dissociation even in the pulsating environment after surgery. This minimizes a resurge of the pressure inside the aneurysm or its rupture.


“This research is the first in the world to develop a new material for embolization that may be biocompatible without side effects and be stably maintained in the human body for a long time,” remarked Professor Hyung Joon Cha. “We plan to deliberate on commercialization through a technology transfer.”

Professor Joonwon Kim explained, “This research is the first in the world to develop a method that can be used to treat aneurysms by microfibrillating a photocrosslinkable hydrogel microfiber in blood vessels.” He added, “It is anticipated these materials will be effectively applicable to many vascular diseases requiring embolization.”

“The new concept of embolization method developed in this study was verified using the Advanced Dynamic Angio Model (ADAM) simulator implemented by the new deep coating technology*3 and 3D vascular replica production technology*4 using liquid embolic materials previously developed by the research team. The ADAM simulator is a system that provides a virtual environment that is very similar to the surgical environment of a real patient, and can be used for simulation of various vascular diseases,” explained Professor Kim.

This research was conducted with the support from the research-centered hospital nurturing R&D project supported by the Ministry of Health and Welfare and the Korea Health Industry Development Institute, and the Mid-career Research Program and the Nano-New Materials Core Technology Development Program funded by the Ministry of Science and ICT and the National Research Foundation of Korea.

All images credit: POSTECH

1. Embolization
Minimally invasive treatment that blocks one or more blood vessels or abnormal blood vessels. In catheter (i.e. microconduit) embolization procedures, the embolic material is inserted into the blood vessel through the catheter to prevent the inflow of blood to the site.

2. Hydrogel
A network structure in which a water-soluble polymer forms 3D crosslinks through physical or chemical bonds.

3. Adv. Mater. Interfaces 2019, 6, 1901485

4. Adv. Funct. Mater. 2020, 30, 2003395

5. Lim, J., Choi, G., Joo, K.I., Cha, H.J. and Kim, J. (2021), Hydrogel Microfibers: Embolization of Vascular Malformations via In Situ Photocrosslinking of Mechanically Reinforced Alginate Microfibers using an Optical‐Fiber‐Integrated Microfluidic Device (Adv. Mater. 14/2021). Adv. Mater., 33: 2170111.

Provided by POSTECH

Engineering Diseased Human Skin In Vitro (Biology)

Professor Dong-Woo Cho’s research team at POSTECH develops an artificial diabetic skin based on 3D cell printing.

The skin, which covers the surface of the human body, is its largest organ. It is the representative organ to show changes stemming from organ or physiological activity. It is especially common for diabetic patients to suffer from skin diseases or infections. Recently, a POSTECH research team has succeeded in creating a 3D artificial skin that enables observation of skin diseases of diabetic patients.

A research team led by Professor Dong-Woo Cho and Minjun Ahn of POSTECH’s Department of Mechanical Engineering and Professor Byoung Soo Kim of School of Biomedical Convergence Engineering at Pusan National University has successfully produced an in vitro diseased skin model that displays the pathophysiological hallmarks of type 2 diabetes based on 3D cell printing system. These research findings were recently published in Biomaterials, a world-renowned international journal in biomaterials.

Despite continuous research to produce artificial skin with 3D cell printing technology, artificial skin displaying the pathological process present in the native skin has not been reported yet.

Inspired by the interaction between the epidermis and skin cells found in real skin, the research team hypothesized that when normal keratinocytes interact with the dermal layer made of diabetic fibroblasts*1, they will differentiate into diabetic epidermis. To prove this, diabetic artificial skin with skin wounds based on 3D printing technique was fabricated using each cell.

In this diabetic artificial skin, slow re-epithelialization*2, a typical feature of diabetic skin, was observed. In addition, when the diabetic fat tissue layer containing blood vessels was added, insulin resistance, adipocyte hypertrophy, pro-inflammatory response, and vascular dysfunction, which are commonly observed in diabetes, were confirmed.

“Through 3D cell printing, we can now observe skin diseases in vitro, without actually experiencing it,” remarked the researchers. “We anticipate it to be a way to replace animal models that have been conventionally used to observe skin diseases. It is significant that its applicability as a disease model for new drug development has been proven.”

This research was conducted with the support from the Creative Research Program and the Nano-New Materials Core Technology Development Program of the National Research Foundation of Korea.

1. Fibroblast
Cells that make up an important component of fibrous connective tissue.

2. Re-epithelialization (再上皮化)
The re-proliferation of the skin surface that has been removed.

All images credit: POSTECH

Reference: Kim BS, Ahn M, Cho WW, Gao G, Jang J, Cho DW. Engineering of diseased human skin equivalent using 3D cell printing for representing pathophysiological hallmarks of type 2 diabetes in vitro. Biomaterials. 2021 May;272:120776. doi: 10.1016/j.biomaterials.2021.120776. Epub 2021 Mar 24. PMID: 33798956.

Provided by POSTECH

Novel Anti-PD-1 therapy, Dostarlimab, Approved As A New Therapeutic Avenue For Recurrent or Advanced Endometrial Cancer in Europe (Medicine)

Supported by the preliminary results* reported from the multi-center, phase I GARNET ongoing study — showing the promise of a novel immune-based therapy, dostarlimab, for the more effective treatment of patients with recurrent or advanced mismatch repair deficient (dMMR/MSI-H) endometrial cancer—this anti-PD-1 novel immunotherapy is the first to have received approval from the European Medicines Agency (EMA) for the treatment of this patient population.

This important development represents new hope for these patients, and a significant  forward step in improving clinical outcomes for these patients with a poor prognosis and formerly few treatment options available once their disease progresses on or following prior treatment with chemotherapy.

Specifically, the GARNET study was designed to respond to an unmet clinical need. Namely, to improve clinical outcomes and achieve durable responses in these patients. Commenting for our Global Communications, Ana Oaknin, Principal Investigator of VHIO’s Gynecological Malignancies Group, and Lead Investigator of the GARNET clinical trial, said: “The approval of this immune-based therapy provides a much-needed, new therapeutic avenue for patients with advanced or recurrent endometrial cancer recurrent or advanced mismatch repair deficient endometrial cancer; representing 30% of patients suffering from this tumor type.”

She continued, “Through our ongoing investigations**, we are evaluating dostarlimab as monotherapy in patients with advanced solid tumors in expansion cohorts. We hope to report similarly promising clinical activity in these additional cohorts of participants with specific types of advanced disease.”

Featured image: Ana Oaknin © VHIO

References: (1) Oaknin A, Tinker AV, Gilbert L, Samouëlian V, Mathews C, Brown J, Barretina-Ginesta MP, Moreno V, Gravina A, Abdeddaim C, Banerjee S, Guo W, Danaee H, Im E, Sabatier R. Clinical Activity and Safety of the Anti-Programmed Death 1 Monoclonal Antibody Dostarlimab for Patients With Recurrent or Advanced Mismatch Repair-Deficient Endometrial Cancer: A Nonrandomized Phase 1 Clinical Trial. JAMA Oncol. 2020 Nov 1;6(11):1766-1772. (2)  Study of TSR-042, an Anti-programmed Cell Death-1 Receptor (PD-1) Monoclonal Antibody, in Participants With Advanced Solid Tumors (GARNET).

Provided by VHIO