When Algorithms Compete, Who Wins?

Companies like Netflix and Hulu compete for subscribers to make sure their businesses thrive. But there’s another type of competition at work that receives far less attention – the competition among the machine learning algorithms used by these kinds of competitor companies.

James Zou, Stanford assistant professor of biomedical data science and an affiliated faculty member of the Stanford Institute for Human-Centered Artificial Intelligence, says that as algorithms compete for clicks and the associated user data, they become more specialized for subpopulations that gravitate to their sites. And that, he finds in a new paper with graduate student Antonio Ginart and undergraduate Eva Zhang, can have serious implications for both companies and consumers.

Perhaps consumers don’t mind if Hulu recommendations seem intended for urban teenagers or Netflix offers better choices for middle-aged rural men, but when it comes to predicting who should receive a bank loan or whose resume should reach a hiring manager, these algorithms have real-world repercussions.

“The key insight is that this happens not because the businesses are choosing to specialize for a specific age group or demographic,” Ginart says. “This happens because of the feedback dynamics of the competition.”

Inevitable Specialization

Before they started their research, Zou’s team recognized that there’s a feedback dynamic at play if companies’ machine learning algorithms are competing for users or customers and at the same time using customer data to train their model. “By winning customers, they’re getting a new set of data from those customers, and then by updating their models on this new set of data, they’re actually then changing the model and biasing it toward the new customers they’ve won over,” Ginart says.

The team wondered: How might that feedback affect the algorithms’ ability to provide quality recommendations? To get at an answer, they analyzed algorithmic competition  mathematically and simulated it using some standard datasets. In the end, they found that when machine learning algorithms compete, they eventually (and inevitably) specialize, becoming better at predicting the preferences of a subpopulation of users.

“It doesn’t matter how much data you have, you will always see these effects,” Zou says. Moreover, “The disparity gets larger and larger over time – it gets amplified because of the feedback loops.”

In addition, the team showed that beyond a certain mathematically calculable number of competitors, the quality of predictions declines for the general population. “There’s actually a sweet spot –  an optimal number of competitors that optimizes the user experience,” Ginart says. Beyond that number, each AI agent has access to data from a smaller fraction of users, reducing their ability to generate quality predictions.

The team’s mathematical theorems apply whenever an online digital platform is competing to provide users with predictions, Ginart says. Examples in the real world include companies that use machine learning to predict users’ entertainment preferences (Netflix, Hulu, Amazon) or restaurant tastes (Yelp, TripAdvisor), as well as companies that specialize in search, such as Google, Bing, and DuckDuckGo.

“If we go to Google or Bing and type in a search query, you could say that what Google is trying to do is predict what links we will consider most relevant,” Ginart says. And if Bing does a better job of making those predictions, maybe we’ll be more inclined to use that platform, which in turn alters the input into that machine learning system and changes the way it makes predictions in the future.

The theorems also apply to companies that predict users’ credit risk or even the likelihood that they will jump bail. For example, a bank may become very good at predicting the creditworthiness of a very specific cohort of people – say, people over the age of 45 or people of a specific income bracket – simply because they’ve gathered a lot of data for that cohort. “The more data they have for that cohort, the better they can service them,” Ginart says. And although these algorithms get better at making accurate predictions for one subpopulation, the average quality of service actually declines as their predictions for other groups become less and less accurate.

Imagine a bank loan algorithm that relies on data from white, middle-aged customers and therefore becomes adept at predicting which members of that population should receive loans. That company is actually missing an opportunity to accurately identify members of other groups (Latinx millennials, for example) who would also be a good credit risk. That failure, in turn, sends those customers elsewhere, reinforcing the algorithm’s data specialization, not to mention compounding structural inequality.

Seeking Solutions

In terms of next steps, the team is looking at the effect that buying datasets (rather than collecting data only from customers) might have on algorithmic competition. Zou is also interested in identifying some prescriptive solutions that his team can recommend to policymakers or individual companies. “What do we do to reduce these kinds of biases now that we have identified the problem?” he says.

“This is still very new and quite cutting-edge work,” Zou says. “I hope this paper sparks researchers to study competition between AI algorithms, as well as the social impact of that competition.”

Stanford HAI’s mission is to advance AI research, education, policy and practice to improve the human condition. Learn more.

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Scientists launch quest to develop quantum sensors for probing quantum materials

When it comes to fully understanding the hidden secrets of quantum materials, it takes one to know one, scientists say: Only tools that also operate on quantum principles can get us there.

A new Department of Energy research center will focus on developing those tools. Based at the University of Illinois at Urbana-Champaign, the Center for Quantum Sensing and Quantum Materials brings together experts from UIUC, DOE’s SLAC National Accelerator Laboratory, Stanford University and the University of Illinois-Chicago.

They’ll work on developing three cutting-edge quantum sensing devices: a scanning qubit microscope, a spectroscopy instrument that takes advantage of pairs of entangled electrons and another instrument that will probe materials with pairs of photons from SLAC’s X-ray free-electron laser, the Linac Coherent Light Source, which has recently reopened after an upgrade.

These new techniques will allow researchers to see in much greater detail why quantum materials do the weird things they do, paving the way to discovering new quantum materials and inventing even more sensitive probes of their behavior.

The work will focus on understanding the atomic-level processes behind unconventional superconductors that conduct electricity with no resistance at relatively high temperatures; topological insulators, which carry current with no loss along their edges; and strange metals, which superconduct when chilled but have strange properties at higher temperatures.

“What is exciting is that this center gives us a chance to create some really new quantum measurement techniques for studying energy-relevant quantum materials,” center Director Peter Abbamonte, a professor of physics at UIUC, said in a press release.

“We often get trapped in the cycle of using the same old measurements – not because we don’t need new kinds of information or knowledge, but because developing techniques is expensive and time consuming,” Abbamonte said. The new center, he said, will allow scientists to push the envelope of quantum measurement by tackling bigger problems.

Exotic entangled states

Quantum materials get their name from the fact that their exotic properties stem from the cooperative behavior of electrons and other phenomena that obey the rules of quantum mechanics, rather than the familiar Newtonian laws of physics that govern our everyday world. These materials could eventually have a huge impact on future energy technologies – for instance, by allowing people to transmit power with essentially no loss over long distances and making transportation much more energy efficient.

But a quantum material may contain a confounding mixture of exotic, overlapping states of matter that are hard to sort out with conventional tools.

“In the quantum world everything becomes entangled, so the boundaries of one object start to overlap with the boundaries of another,” said SLAC Professor Thomas Devereaux, one of six SLAC and Stanford researchers collaborating in the new center. “We’ll be probing this entanglement using various tools and techniques.”

Quantum sensors are nothing new. They include superconducting quantum interference devices, or SQUIDs, invented half a century ago to detect extremely small magnetic fields, and superconducting transition edge sensors, which incorporate SQUIDS to detect exquisitely small signals in astronomy, nuclear non-proliferation, materials analysis and homeland defense.

At a basic level, they operate by putting the sensor into a known quantum state and allowing it to interact with the object of interest. The interaction changes the state of the quantum system, and measuring the new state of the system reveals information about the object that could not be obtained with conventional approaches.

Qubits on a tip

In one of the technologies under development, the scanning qubit microscope, the quantum sensor would consist of one or more qubits placed on the tip of a probe and moved over the surface of a material. A qubit is a basic unit of quantum information, like the bits of ordinary computer memory that flip back and forth between zero and 1. But a qubit exists as a superposition of both zero and 1 states at once. The scanner’s qubit might consist of a single hydrogen atom, for instance, with the spin of its single electron simultaneously existing as up, down and all possible states in between.

“You can try to entangle the qubit sensor with the quantum state of the material you’re studying so you can actually sense the entanglement of quantum states within the material,” said Kathryn Moler, Stanford’s vice provost and dean of research. “If we can do that, it will be really cool.”

Other SLAC and Stanford researchers collaborating in research for the new center are Professors Zhi-Xun Shen and David Reis, Assistant Professor Ben Feldman and staff scientist Mariano Trigo.

The center is one of 10 Energy Frontier Research Centers awarded $100 million by the DOE Office of Science.

For questions or comments, contact the SLAC Office of Communications at communications@slac.stanford.edu.

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Researchers develop a new way to create a spectrum of natural-looking hair colors

We’ve long been warned of the risks of dyeing hair at home and in salons. Products used can cause allergies and skin irritation — an estimated 1% of people have an allergy to dye. Furthermore, repeated use of some dyes has been linked to cancer.

But there soon may be a solution for the growing list of salons and hair color enthusiasts searching for natural alternatives to dyes and cosmetics.

Northwestern University researchers have developed a new way to create a spectrum of natural-looking hair colors, ranging from blond to black, by using enzymes to catalyze synthetic melanin.

The research was published Oct. 30 in the journal Chemistry of Materials.

Melanin is an enigmatic and ubiquitous material often found in the form of brown or black pigment. Northwestern’s Nathan Gianneschi, the research lead and associate director for the International Institute for Nanotechnology, said every type of organism produces melanin, making it a readily available and versatile material to use in the lab.

“In humans, it’s in the back of our eye to help with vision, it’s in our skin to help with protecting skin cells from UV damage,” Gianneschi said. “But birds also use it as a spectacular color display — peacock feathers are made of melanin entirely.”

Gianneschi is the Jacob and Rosalind Cohn Professor of Chemistry in Northwestern’s Weinberg College of Arts and Sciences and a professor of materials science and engineering and biomedical engineering in the McCormick School of Engineering. Claudia Battistella, a postdoctoral fellow in Gianneschi’s lab, is the paper’s first author.

In the typical process of coloring hair, stylists use bleach to strip melanin from hair, then add ammonia and dye to open and penetrate the hair cuticles for permanent color. Work being done with melanin in other parts of the lab inspired Battistella to see how it applied to hair dye.

Battistella thought by replacing melanin instead of removing it and depositing color on the surface of hair instead of within it, she could create a more sustainable way to create lasting color. In this process, researchers dye hair by combining mushroom enzymes with an amino acid, causing a process that mimics reactions that naturally occur in the body. Preliminary studies revealed potential for the colored layer to persist through several washes.

“The dyeing process is similar from a stylist’s point of view, but these conditions are milder, so they take a little longer,” Battistella said. “Though it could be combined with a base, it’s not necessary to use one, and there is no need for chemical pigments. Because we already have melanin in our bodies, we believe we won’t have allergic reactions to it.”

 

Because we already have melanin in our bodies, we believe we won’t have allergic reactions to it.”

Claudia Battistella
Chemistry Postdoc

 

Because melanin also fades in hair due to sun exposure and aging, researchers also wondered about the sun’s impact on the dye. Along with being a milder process than traditional dye, coating hair in synthetic melanin holds potential to protect hair from sun damage that can cause whitening. Studies showed that compared to untreated hair, hair treated with melanin pigment was damaged less when exposed to ultraviolet rays.

The paper identifies four key advantages to using synthetic melanin instead of traditional dyes:

• Synthetic melanin avoids the use of ammonia as a base layer.
• The precursors to treating hair with melanin are less toxic.
• The process uses safer, more scalable chemicals.
• There is vast potential in future cosmetic translations of synthetic melanin.

Given the industry’s desire to move away from carcinogens and other toxic chemicals, Gianneschi believes his lab will be able to break through the regulatory industry. The team then hopes to find a partner willing to develop the dye on a larger scale. From Gianneschi’s perspective, the main motivation for the research isn’t just excitement over melanin’s potentially vast commercial use.

“From a biomedical perspective, there’s a huge market of people with a hair dye allergy,” Gianneschi said. “Our first thought was it would be great to have a solution to help those people.”

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Touch and taste? It’s all in the suckers

Octopuses have captured the human imagination for centuries, inspiring sagas of sea monsters from Scandinavian kraken legends to TV’s “Voyage to the Bottom of the Sea” and, most recently, Netflix’s less-threatening “My Octopus Teacher.” With their eight suction-cup covered arms, their very appearance is unique, and their ability to use those appendages to touch and taste while foraging further sets them apart.

In fact scientists have wondered for decades how those arms, or more specifically the suction cups on them, do their work, prompting a number of experiments into the biomechanics. But very few have studied what is happening on a molecular level. In a new report, Harvard researchers got a glimpse into how the nervous system in the octopus’ arms (which operate largely independently from its centralized brain) manage this feat. The work published Thursday in Cell.

The scientists identified a novel family of sensors in the first layer of cells inside the suction cups that have adapted to react and detect molecules that don’t dissolve well in water. The research suggests these sensors, called chemotactile receptors, use these molecules to help the animal figure out what it’s touching and whether that object is prey.

Video: Peter B. Kilian

“We think because the molecules do not solubilize well, they could, for instance, be found on the surface of octopuses’ prey and [whatever the animals touch],” said Nicholas Bellono, an assistant professor of molecular and cellular biology and the study’s senior author. “So, when the octopus touches a rock versus a crab, now its arm knows, ‘OK, I’m touching a crab [because] I know there’s not only touch but there’s also this sort of taste.’”

In addition, scientists found diversity in what the receptors responded to and the signals they then transmitted to the cell and nervous systems.

“We think that this is important because it could facilitate complexity in what the octopus senses and also how it can process a range of signals using its semi-autonomous arm nervous system to produce complex behaviors,” Bellono said.

The scientists believe this research can help uncover similar receptor systems in other cephalopods, the invertebrate family that also includes squids and cuttlefish. The hope is to determine how these systems work on a molecular level and answer some relatively unexplored questions about how these creatures’ capabilities evolved to suit their environment.

“Not much is known about marine chemotactile behavior and with this receptor family as a model system, we can now study which signals are important for the animal and how they can be encoded,” said Lena van Giesen, a postdoctoral fellow in the Bellono Lab and lead author of the paper. “These insights into protein evolution and signal coding go far beyond just cephalopods.”

Along with Giesen, other co-authors from the lab include Peter B. Kilian, an animal technician, and Corey A.H. Allard, a postdoctoral fellow.

“The strategies they have evolved in order to solve problems in their environment are unique to them and that inspires a great deal of interest from both scientists and non-scientists alike,” Kilian said. “People are drawn to octopuses and other cephalopods because they are wildly different from most other animals.”

The team set out to uncover how the receptors are able to sense chemicals and detect signals in what they touch, like an arm around a snail, to help them make choices.

Octopus arms are distinct and complex. About two-thirds of an octopus’s neurons are located in their arms. Because the arms operate partially independently from the brain, if one is severed it can still reach for, identify, and grasp items.

“People are drawn to octopuses and other cephalopods because they are wildly different from most other animals.”

— Peter B. Kilian

The team started by identifying which cells in the suckers actually do the detecting. After isolating and cloning the touch and chemical receptors, they inserted them in frog eggs and in human cell lines to study their function in isolation. Nothing like these receptors exists in frog or human cells, so the cells act essentially like closed vessels for the study of these receptors.

The researchers then exposed those cells to molecules such as extracts from octopus prey and others items to which these receptors are known to react. Some test subjects were water-soluble, like salts, sugars, amino acids; others do not dissolve well and are not typically considered of interest by aquatic animals. Surprisingly, only the poorly soluble molecules activated the receptors.

Researchers then went back to the octopuses in their lab to see whether they too responded to those molecules by putting those same extracts on the floors of their tanks. They found the only odorants the octopuses receptors responded to were a non-dissolving class of naturally occurring chemicals known as terpenoid molecules.

“[The octopus] was highly responsive to only the part of the floor that had the molecule infused,” Bellono said. This led the researchers to believe that the receptors they identified pick up on these types of molecules and help the octopus distinguish what it’s touching. “With the semi-autonomous nervous system, it can quickly make this decision: ‘Do I contract and grab this crab or keep searching?’”

While the study provides a molecular explanation for this aquatic touch-taste sensation in octopuses through their chemotactile receptors, the researchers suggest further study is needed, given that a great number of unknown natural compounds could also stimulate these receptors to mediate complex behaviors.

“We’re now trying to look at other natural molecules that these animals might detect,” Bellono said.

This research was supported by the New York Stem Cell Foundation, the Searle Scholars Program, the Sloan Foundation, the Klingenstein-Simons Fellowship, the National Institutes of Health, and the Swiss National Science Foundation.

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Asteroid’s Scars Tell Stories of its Past

By studying impact marks on the surface of asteroid Bennu – the target of NASA’s OSIRIS-REx mission – a team of researchers led by the University of Arizona has uncovered the asteroid’s past and revealed that despite forming hundreds of millions of years ago, Bennu wandered into Earth’s neighborhood only very recently.

The study, published in the journal Nature, provides a new benchmark for understanding the evolution of asteroids, offers insights into a poorly understood population of space debris hazardous to spacecraft, and enhances scientists’ understanding of the solar system.

The researchers used images and laser-based measurements taken during a two-year surveying phase in which the OSIRIS-REx spacecraft, about the size of a 15-passenger van, orbited Bennu and broke the record for the smallest spacecraft to orbit a small body. 

Presented at the opening day of the American Astronomical Society’s Division for Planetary Sciences meeting on Oct. 26, the paper details the first observations and measurements of impact craters on individual boulders on an airless planetary surface since the Apollo missions to the moon 50 years ago, according to the authors.

The publication comes just a few days after a major milestone for NASA’s University of Arizona-led OSIRIS-REx mission. On Oct. 20, the spacecraft successfully descended to asteroid Bennu to grab a sample from its boulder-scattered surface – a first for NASA. The sample has now been successfully stowed and will be returned to Earth for study in 2023, where it could give scientists insight into the earliest stages of the formation of our solar system.

Impact Craters on Rocks Tell a Story

Although Earth is being pelted with more than 100 tons of space debris each day, it is virtually impossible to find a rockface pitted by impacts from small objects at high velocities. Courtesy of our atmosphere, we get to enjoy any object smaller than a few meters as a shooting star rather than having to fear being struck by what essentially amounts to a bullet from outer space.

Planetary bodies lacking such a protective layer, however, bear the full brunt of a perpetual cosmic barrage, and they have the scars to show for it. High-resolution images taken by the OSIRIS-REx spacecraft during its two-year survey campaign allowed researchers to study even tiny craters, with diameters ranging from a centimeter to a meter, on Bennu’s boulders.

The team found boulders of 1 meter or larger to be scarred, on average, by anywhere from one to 60 pits – impacted by space debris ranging in size from a few millimeters to tens of centimeters.

“I was surprised to see these features on the surface of Bennu,” said the paper’s lead author, Ronald Ballouz, a postdoctoral researcher in the UArizona Lunar and Planetary Laboratory and a scientist with the OSIRIS-REx regolith development working group. “The rocks tell their history through the craters they accumulated over time. We haven’t observed anything like this since astronauts walked on the moon.”

For Ballouz, who grew up during the 1990s in post-civil war Beirut, Lebanon, the image of a rock surface pitted with small impact craters evoked childhood memories of building walls riddled with bullet holes in his war-torn home country.

“Where I grew up, the buildings have bullet holes all over, and I never thought about it,” he said. “It was just a fact of life. So, when I looked at the images from the asteroid, I was very curious, and I immediately thought these must be impact features.”

The observations made by Ballouz and his team bridge a gap between previous studies of space debris larger than a few centimeters, based on impacts on the moon, and studies of objects smaller than a few millimeters, based on observations of meteors entering Earth’s atmosphere and impacts on spacecraft.

“The objects that formed the craters on Bennu’s boulders fall within this gap that we don’t really know much about,” Ballouz said, adding that rocks in that size range are an important field of study, mainly because they represent hazards for spacecraft in orbit around Earth. “An impact from one of these millimeter to centimeter-size objects at speeds of 45,000 miles per hour can be dangerous.”

This composite image of a boulder on Bennu’s surface shows the cascading rim of one of the asteroid’s ancient craters that originated while Bennu resided in the asteroid belt. The image combines photos from OSIRIS-REx and reconstructed shape models built from the OSIRIS-REx laser altimeter instrument. The overlaid colors highlight the topography of the boulder (warmer colors are higher elevation).University of Arizona/Johns Hopkins APL/York University

Ballouz and his team developed a technique to quantify the strength of solid objects using remote observations of craters on the surfaces of boulders – a mathematical formula that allows researchers to calculate the maximum impact energy that a boulder of a given size and strength could endure before being smashed. In other words, the crater distribution found on Bennu today keeps a historical record of the frequency, size and velocity of impact events the asteroid has experienced throughout its history.

“The idea is actually pretty simple,” Ballouz said, using a building exposed to artillery fire as an analogy to boulders on an asteroid. “We ask, ‘What is the largest crater you can make on that wall before the wall disintegrates?’ Based on observations of multiple walls of the same size, but with different sized craters, you can get some idea of the strength of that wall.”

The same holds true for a boulder on an asteroid or other airless body, said Ballouz, who added that the approach could be used on any other asteroid or airless body that astronauts or spacecraft may visit in the future.

“If a boulder gets hit by something larger than an object that would leave a certain size cater, it would just disappear,” he explained. In other words, the size distribution of boulders that have persisted on Bennu serve as silent witnesses to its geologic past.

A Newcomer to Earth’s Neighborhood

Applying the technique to boulders ranging in size from pebbles to parking garages, the researchers were able to make inferences about the sizes and type of impactors to which the boulders were exposed, and for how long.

The authors conclude that the largest craters on Bennu’s boulders were created while Bennu resided in the asteroid belt, where impact speeds are lower than in the near-Earth environment, but are more frequent and often near the limit of what the boulders could withstand. Smaller craters, on the other hand, were acquired more recently, during Bennu’s time in near-Earth space, where impact speeds are higher but potentially disruptive impactors are much less common.

Based on these calculations, the authors determine that Bennu is a relative newcomer to Earth’s neighborhood. Although it is thought to have formed in the main asteroid belt more than 100 million years ago, it is estimated that it was kicked out of the asteroid belt and migrated to its current territory only 1.75 million years ago. Extending the results to other near-Earth objects, or NEOs, the researchers also suggest that these objects likely come from parent bodies that fall in the category of asteroids, which are mostly rocky with little or no ice, rather than comets, which have more ice than rock.

While theoretical models suggest that the asteroid belt is the reservoir for NEOs, no observational evidence of their provenance was available other than meteorites that fell to Earth and were collected, Ballouz said. With these data, researchers can validate their models of where NEOs come from, according to Ballouz, and get an idea of how strong and solid these objects are – crucial information for any potential missions targeting asteroids in the future for research, resource extraction or protecting Earth from impact.

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Aprotinin a new drug candidate for the treatment of COVID-19

Researchers from the University of Kent, the Goethe-University in Frankfurt am Main (Germany), and the Hannover Medical School (Germany) have identified a drug with the potential to provide a treatment for COVID-19.

The international team led by Professor Martin Michaelis, Dr Mark Wass (both School of Biosciences, University of Kent), and Professor Jindrich Cinatl (Institute of Medical Virology, Goethe-University) found that the approved protease inhibitor aprotinin displayed activity against SARS-CoV-2, the coronavirus that causes COVID-19, in concentrations that are achieved in patients. Aprotinin inhibits the entry of SARS-CoV-2 into host cells and may compensate for the loss of host cell protease inhibitors that are downregulated upon SARS-CoV-2 infection.

Aprotinin aerosols are approved in Russia for the treatment of influenza and could be readily tested for the treatment of COVID-19.

Professor Martin Michaelis said: ‘”he aprotinin aerosol has been reported to be tolerated extremely well in influenza patients. Hence, it may have a particular potential to prevent severe COVID-19 disease when applied early after diagnosis.”

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Individuals may legitimise hacking when angry with system or authority

University of Kent research has found that when individuals feel that a system or authority is unresponsive to their demands, they are more likely to legitimise hacker activity at an organisation’s expense.

Individuals are more likely to experience anger when they believe that systems or authorities have overlooked pursuing justice on their behalf or listening to their demands. In turn, the study found that if the systems or authorities in question were a victim of hacking, individuals would be more likely to legitimise the hackers’ disruptive actions as a way to manifest their own anger against the organisation.

With more organisations at risk to cyber security breaches, and more elements of individuals’ social lives taking place online, this research is timely in highlighting how hackers are perceived by individuals seeking justice.

The research, led by Maria Heering and Dr Giovanni Travaglino in the School of Psychology, was carried out with British undergraduate students and participants on academic survey crowdsourcer, Prolific Academic. The participants were presented with fictional scenarios of unfair treatment from authorities, with complaints either dismissed or pursued, before they were told that hackers had defaced the authorities’ websites. Participants were then asked to indicate how much they disagreed or agreed with the hackers’ actions. These hackers were predominantly supported by participants perceiving them as a way to ‘get back at’ the systems who do not listen to their demands.

Maria Heering said: ‘When individuals perceive a system as unjust, they are motivated to participate in political protest and collective action to promote social change. However, if they believe they will not have voice, they will legitimise groups and individuals who disrupt the system on their behalf. While this study explored individuals’ feelings of anger, there is certainly more to be explored in this research area. For example, there might be important differences between the psychological determinations of individuals’ support for humorous, relatively harmless forms of hacking, and more serious and dangerous ones.’

Their research paper ‘“If they don’t listen to us, they deserve it”: The effect of external efficacy and anger on the perceived legitimacy of hacking’ is published in Group Processes & Intergroup Relations. DOI: https://doi.org/10.1177/1368430220937777

Research

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Bridges With Limb-Inspired Architecture Could Withstand Earthquakes, Cut Repair Costs

Structural damage to ailing bridges can mean billions of dollars in repairs. New bridge designs promise more damage-resistant structures and lower restoration costs. But if these designs haven’t been implemented in the real world, predicting how they can be damaged and what repair strategies should be implemented remain unresolved.

In a study published in the Journal of Structural Engineering, Texas A&M University and the University of Colorado, Boulder researchers have conducted a comprehensive damage and repair assessment of a still-to-be-implemented bridge design using a panel of experts from academia and industry. The researchers said the expert feedback method offers a unique and robust technique for evaluating the feasibility of bridge designs that are still in early research and development phases.

“Bridges, particularly those in high-seismic regions, are vulnerable to damage and will need repairs at some point. But now the question is what kind of repairs should be used for different types and levels of damage, what will be the cost of these repairs and how long will the repairs take — these are all unknowns for new bridge designs,” said Petros Sideris, assistant professor in the Zachry Department of Civil and Environmental Engineering. “We have answered these questions for a novel bridge design using an approach that is seldomly used in structural engineering.”

Most bridges are monolithic systems made of concrete poured over forms that give the bridges their shape. These bridges are strong enough to support their own weight and other loads, such as traffic. However, Sideris said if there is an unexpected occurrence of seismic activity, these structures could crack, and remedying the damage would be exorbitantly expensive.

The hybrid sliding-rocking bridge column tested in the Center for Infrastructure Renewal’s large-scale experimental facilities./ Justin Baetge/Texas A&M Engineering

To overcome these shortcomings, Sideris and his team have developed a new design called a hybrid sliding-rocking bridge. Instead of a monolithic design, these bridges are made of columns containing limb-inspired joints and segments. Hence, in the event of an earthquake, the joints allow some of the energy from the ground motion to diffuse while the segments move slightly, sliding over one another rather than bending or cracking. Despite the overall appeal of the hybrid sliding-rocking bridge design, little is known about how the bridges will behave in real-world situations.

“To find the correct repair strategy, we need to know what the damages look like,” Sideris said. “Our bridge design is relatively new and so there is little scientific literature that we could refer to. And so, we took an unconventional approach to fill our gap in knowledge by recruiting a panel of experts in bridge damage and repair.”

For their study, Sideris and Abbie Liel, professor at the University of Colorado, Boulder, and the team recruited a panel of eight experts from industry and academia to determine the damage states in experimentally tested hybrid sliding-rocking segment designed columns. Based on their evaluations of the observed damage, the panel provided repair strategies and estimated costs for repair. The researchers then used that information to fix the broken columns, retested the columns under the same initial damage-causing conditions and compared the repaired column’s behavior to that of the original column through computational investigations.

The panel found that columns built with their design sustained less damage overall compared to bridges built with conventional designs. In fact, the columns showed very little damage even when subject to motions reminiscent of a powerful once-in-a-few-thousand-years earthquake. Furthermore, the damage could be repaired relatively quickly with grout and carbon fibers, suggesting that no special strategy was required for restoration.

“Fixing bridges is a slow process and costs a significant amount of money, which then indirectly affects the community,” Sideris said. “Novel bridge designs that may have a bigger initial cost for construction can be more beneficial in the long run because they are sturdier. The money saved can then be used for helping the community rather than repairing infrastructure.”

This work is funded by the National Science Foundation.

Other contributors include Jakub Valigura, former graduate student researcher from the University of Colorado, Boulder and Mohammad Salehi, former graduate student in the civil and environmental engineering department at Texas A&M.

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Face mask aims to deactivate virus to protect others

In the pandemic, people wear face masks to respect and protect others — not merely to protect themselves, says a team of Northwestern University researchers.

With this in mind, the researchers developed a new concept for a mask that aims to make the wearer less infectious. The central idea, which received support from the National Science Foundation through a RAPID grant, is to modify mask fabrics with anti-viral chemicals that can sanitize exhaled, escaped respiratory droplets.

By simulating inhalation, exhalation, coughs and sneezes in the laboratory, the researchers found that non-woven fabrics used in most masks work well to demonstrate the concept. A lint-free wipe with just 19% fiber density, for example, sanitized up to 82% of escaped respiratory droplets by volume. Such fabrics do not make breathing more difficult, and the on-mask chemicals did not detach during simulated inhalation experiments.

The research was published today (Oct. 29) in the journal Matter.

Importance of protecting others

“Masks are perhaps the most important component of the personal protective equipment (PPE) needed to fight a pandemic,” said Northwestern’s Jiaxing Huang, who led the study. “We quickly realized that a mask not only protects the person wearing it, but much more importantly, it protects others from being exposed to the droplets (and germs) released by the wearer.

“There seems to be quite some confusion about mask wearing, as some people don’t think they need personal protection,” Huang added. “Perhaps we should call it public health equipment (PHE) instead of PPE.”

Huang is a professor of materials science and engineering in Northwestern’s McCormick School of Engineering. Graduate student Haiyue Huang and postdoctoral fellow Hun Park, both members of Huang’s laboratory, are co-first authors of the paper.

“Where there is an outbreak of infectious respiratory disease, controlling the source is most effective in preventing viral spread,” said Haiyue Huang, a 2020 Ryan Fellowship Awardee. “After they leave the source, respiratory droplets become more diffuse and more difficult to control.”

The goal and results

Although masks can block or reroute exhaled respiratory droplets, many droplets (and their embedded viruses) still escape. From there, virus-laden droplets can infect another person directly or land on surfaces to indirectly infect others. Huang’s team aimed to chemically alter the escape droplets to make the viruses inactivate more quickly.

To accomplish this, Huang sought to design a mask fabric that: (1) Would not make breathing more difficult, (2) Can load molecular anti-viral agents such as acid and metal ions that can readily dissolve in escaped droplets, and (3) Do not contain volatile chemicals or easily detachable materials that could be inhaled by the wearer.

82%New design sanitizes up to 82% of droplets

After performing multiple experiments, Huang and his team selected two well-known antiviral chemicals: phosphoric acid and copper salt. These non-volatile chemicals were appealing because neither can be vaporized and then potentially inhaled. And both create a local chemical environment that is unfavorable for viruses.

“Virus structures are actually very delicate and ‘brittle,’” Huang said. “If any part of the virus malfunctions, then it loses the ability to infect.”

Huang’s team grew a layer of a conducting polymer polyaniline on the surface of the mask fabric fibers. The material adheres strongly to the fibers, acting as reservoirs for acid and copper salts. The researchers found that even loose fabrics with low-fiber packing densities of about 11%, such as medical gauze, still altered 28% of exhaled respiratory droplets by volume. For tighter fabrics, such as lint-free wipes (the type of fabrics typically used in the lab for cleaning), 82% of respiratory droplets were modified.

Working through shutdown

Huang’s team scrambled to assemble resources to start this new line of research, right before Northwestern entered the “essential-only” state. Several team members received “essential” designation to work throughout Illinois’ “Stay-at-Home” order.

“As an adviser, I must admit that I did not see all the technical challenges coming,” Huang said. “But I am very pleased that my team members have exhibited amazing drive and creativity to tackle those difficulties and get the work done.”

One unexpected difficulty was how to measure and quantify the degree of chemical modification of escaped droplets. “For acid-modified droplets, I thought we could do this simply by collecting them on a pH paper and seeing the color changes of the landed droplets,” Huang said. “I insisted that Haiyue and Hun should try this first, and only to realize that it wasted a few weeks of their time.”

Park noted yet another problem: “The droplets tend to spread out on pH papers, leaving barely detectable drying marks, and the pH dyes do not have enough color intensity to generate a clear contrast of the dried droplets under optical microscope. So it was very difficult to even ‘see’ the droplets, let alone determine the acid content in them.”

Then Park and Haiyue Huang realized that polyaniline — the polymer they used to coat the fabrics — is a great color indicator for acid itself as it turns from dark blue to green.

“I was laughing at myself when I found out their new idea — I should have thought about it much earlier,” Huang said. “I was even more impressed that Haiyue and Hun quickly invented a new way to make ultrasmooth and uniform polyaniline films that work perfectly as a colorimetric indictor for microscopy observation of acidic droplets.”

 

Our research has become an open knowledge, and we will love to see more people joining this effort to develop tools for strengthening public health responses.”

Jiaxing Huang
materials scientist

 

With this breakthrough, the team was able to generate hundreds of microscopy images. Next, Yihan Liu, a master’s student in Huang’s lab joined the project remotely, working from home to develop imaging analysis algorithms to quantity how much the escaped droplets are modified.

“I was stuck home in the spring and summer anyway, so I was very glad that I can make some good use of myself to help out the project,” Liu said. “My parents were pleased to learn that I was not only safe, and also doing something meaningful. I have lived up to their support of my tuition!”

Earlier this year, Huang engaged a team of clinical and biomedical researchers overseas with frontline COVID-19 experiences to discuss his hypotheses, propose research needs and even potential solutions. Together, the researchers published their ideas the journal ACS Nano.

Huang hopes the current work provides a scientific foundation for other researchers, particularly in other parts of the world, to develop their own versions of this chemical modulation strategy and test it further with viral samples or even with patients.

“Our research has become an open knowledge, and we will love to see more people joining this effort to develop tools for strengthening public health responses,” Huang said. “The work is done nearly entirely in lab during campus shutdown. We hope to show researchers in non-biological side of science and engineering and those without many resources or connections that they can also contribute their energy and talent.”

This work was mainly supported by the National Science Foundation (RAPID DMR-2026944). Huang is a member of Northwestern’s International Institute of Nanotechnology,

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Study: Republicans and Democrats hate the other side more than they love their own side

The bitter polarization between the Republican and Democratic parties in the U.S. has been on the rise since Newt Gingrich’s partisan combat against President Bill Clinton in the 1990s. But according to a new Northwestern University-led study, disdain for the opposing political party now — and for the first time on record — outweighs affection for one’s own party.

The study, titled “Political sectarianism in America,” will be published Oct. 30 by the journal Science. The authors provide a broad survey of current scientific literature to interpret the current state of politics.

The paper introduces the construct of “political sectarianism” to describe the phenomenon. Political sectarianism has the hallmarks of religious fervor, such as sin, public shaming and apostasy. But unlike traditional sectarianism, where political identity is secondary to religion, political identity is primary.

“The current state of political sectarianism produces prejudice, discrimination and cognitive distortion, undermining the ability of government to serve its core functions of representing the people and solving the nation’s problems,” said lead author Eli Finkel. “Along the way, it makes people increasingly willing to support candidates who undermine democracy and to favor violence in support of their political goals.”

Finkel is professor of social psychology with appointments in Northwestern’s Weinberg College of Arts and Sciences and the Kellogg School of Management.

To ensure that their synthesis captured the collective knowledge base, Finkel recruited coauthors from six academic disciplines: political science, psychology, sociology, economics, management and computational social science.

A systematic review of dozens of published research studies led the authors to identify three key ingredients of political sectarianism, which, when combined, form the “poisonous cocktail” seen today. They include seeing the other side as different (othering), as dislikeable (aversion) and as immoral (moralization).

Using nationally representative survey data since the 1970s, the authors calculated the difference between Americans’ warm feelings toward their fellow partisans and their cold feelings toward opposing partisans. While feelings toward fellow partisans have remained consistently warm, feelings toward opposing partisans have chilled further from tepid to frosty. Indeed, those feelings have grown so frigid that they now exceed warm feelings toward fellow partisans, turning out-party hate into the dominant feeling in American politics.

“Things have gotten much more severe in the past decade, and there is no sign we’ve hit bottom,” said co-author James Druckman, Payson S. Wild Professor of political science and Institute for Policy Research fellow at Northwestern. “As much as the parties differ from one another, partisans perceive even greater differences, believing, for example, that the other party is ideologically extreme, engaged and hostile. Correcting these types of misperceptions could partially vitiate sectarianism.”

The researchers identify the multiple causes of political sectarianism and suggest potential approaches to address and mitigate it. The three causes include:

• Identity alignment, meaning political party identities have sorted into a “mega-identity” separated along racial, religious, educational and geographic lines;
• The rise of partisan media, impacted by the termination of the FCC “fairness doctrine” in 1987, which required broadcasters to discuss controversial topics in an unbiased way; and
• Elite ideological polarization, with Republican politicians moving further right and Democratic politicians moving further left — and politicians in both parties becoming increasingly reliant on ideologically extreme donors

A proposed behavioral intervention includes correcting misperceptions of opposing partisans and encouraging people to engage in cross-party interactions.

“If the differences between Democrats and Republicans really were as extreme as Americans believe, that could help to explain the contempt,” Finkel observes. “But these differences exist more in people’s heads than in reality. There’s a whole lot of common ground, but Americans struggle to see it.”

Finkel offers that simply reminding people of what they have in common reduces out-party hate.

The researchers advise that structural fixes are also required, including tweaking social media algorithms to limit the reach of false or hyperpartisan content and incentivizing politicians to appeal to a broader proportion of Americans. Reforms around campaign finance and partisan gerrymandering are suggested as ways to reduce sectarianizing behaviors and to generate more robust competition in the marketplace of ideas.

Additional co-authors include Christopher A. Bail, Duke University; Mina Cikara, Harvard University; Peter H. Ditto, University of California-Irvine; Shanto Iyengar, Stanford University; Samara Klar, University of Arizona, Tucson; Lilliana Mason, University of Maryland; Mary C. McGrath, Northwestern University; Brendan Nyhan, Dartmouth College; David G. Rand, Massachusetts Institute of Technology; Linda J. Skitka, University of Illinois–Chicago; Joshua A. Tucker, New York University; Jay J. Van Bavel, New York University; and Cynthia S. Wang, Northwestern University.

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Most isolated massive stars are kicked out of their clusters

A pair of University of Michigan studies reveals how some massive stars—stars eight or more times the mass of our sun—become isolated in the universe: most often, their star clusters kick them out.

Massive stars typically reside in clusters. Isolated massive stars are called field massive stars. The papers published by U-M students examined most of these stars in the Small Magellanic Cloud, a dwarf galaxy near the Milky Way.

The studies, appearing in the same issue of The Astrophysical Journal, reveal how these field massive stars originate, or become so isolated. Understanding how field massive stars become isolated—whether they form in isolation or whether they become isolated by being ejected from a star cluster—will help astronomers probe the conditions in which massive stars are formed. Understanding this and cluster formation is critical for understanding how galaxies evolve.

“About a quarter of all massive stars appear to be isolated, and that’s our big question,” said recent undergraduate Johnny Dorigo Jones. “How they’re found to be isolated, and how they got there.”

Dorigo Jones shows in his paper that the vast majority of field massive stars are “runaways,” or stars ejected from clusters. Graduate student Irene Vargas-Salazar looked for field massive stars that may have formed in relative isolation by looking for evidence of tiny clusters around them. That means these relatively isolated stars could have formed in conjunction with these smaller stars. But she found very few of these faint clusters.

“Because massive stars require a lot of material to form, there are usually a lot of smaller stars around them,” Vargas-Salazar said. “My project asks specifically how many of these field massive stars could have formed in the field.”

Dorigo Jones examined how field massive stars are ejected from clusters. He looks at the two different mechanisms that produce runaways: dynamical ejection and binary supernova ejection. In the first, the massive stars are ejected from their clusters—by up to half a million miles per hour—because of unstable orbital configurations of stellar groups. In the second, a massive star is ejected when a binary pair has one star that explodes and shoots its companion out into space.

“By having the velocities and the masses of our stars, we’re able to compare the distributions of those parameters to the model predictions to determine the certain contributions from each of the ejection mechanisms,” Dorigo Jones said.

He found that dynamical ejections—ejections caused by unstable orbital configurations—were about 2 to 3 times more numerous than supernova ejections. But Dorigo Jones also found the first observational data that shows a large fraction of the field massive stars came from a combination of both dynamical and supernova ejections.

“These have been studied in the past but we have now set the first observational constraints on the numbers of these two-step runaways,” he said. “The way we reach that conclusion is we’re essentially seeing that the stars that trace the supernova ejections in our sample are a bit too numerous and too fast compared to the model predictions. You can imagine this being remedied by these stars being reaccelerated upon a supernova kick, having first been dynamically ejected.”

The researchers found that potentially up to half of the stars first thought to be from supernova ejections were first dynamically ejected.

Vargas-Salazar’s findings also support the idea that most field massive stars are runaways, but she looked at opposite conditions: she looked for field massive stars that formed in relative isolation in tiny clusters of smaller stars, where the massive target star is, called the “tip of the iceberg, or TIB clusters. She did this using two algorithms, “friends-of-friends” and “nearest neighbors,” to search for those clusters around 310 field massive stars in the Small Magellanic Cloud.

The “friends-of-friends” algorithm measures the number density of stars by counting how many stars there are at a specific distance from the target star and then doing the same for those stars in turn. The more tightly packed the stars are, the more likely it is to be a cluster. The “nearest neighbors” algorithm measures the number density of stars between the target star and its nearest 20 companions. The more compact and denser the group, the more likely they are to be clusters, Vargas-Salazar said.

Using statistical tests, Vargas-Salazar compared these observations with three random-field datasets and compared the known runaway massive stars to nonrunaways. She found that only a few of the field massive stars appeared to have TIB clusters around them, suggesting that very few actually formed in the field. The balance of the field stars must have originated as runaways.

“In the end, we showed that 5% or less of the stars had TIB clusters. Instead, our findings imply that the majority of stars in field samples could be runaways,” Vargas-Salazar said. “Our findings are actually supporting the result that Johnny found, wrapped in a neat little bow.”

Vargas-Salazar’s findings provide part of the answer to the question of how massive stars form, says Sally Oey, senior author on both of the papers and professor of astronomy at U-M.

“Johnny and Irene’s work are flip sides of the same coin,” Oey said. “Irene’s numbers are consistent with Johnny’s in that the vast majority of field massive stars are runaways, but that a few are not. This is a critical finding for understanding how massive stars and clusters form, and in what conditions.”

Both Dorigo Jones and Vargas-Salazar’s work was supported by the National Science Foundation.

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Cellular networks vulnerable to wildfires across U.S.

About one in four people in the United States lives in an area served by cellular phone towers at risk of an outage caused by wildfires, according to researchers at the University of Wisconsin–Madison.

Their study, presented today to a meeting of internet network researchers, found more than 430,000 cell network transceivers covering approximately 85 million people are in areas the U.S. Forest Service considers at moderate or high wildfire risk. The research suggests ways to make the sites more fire-hardy.

“This is a kind of roadmap for cell service providers to make assessments, allocate resources and take steps to make their infrastructure more resilient in the face of this threat,” says Paul Barford, a UW–Madison professor of computer science.

Paul Barford and Carol Barford, who directs UW–Madison’s Center for Sustainability and the Global Environment and is a co-author of the wildfire study, also collaborated on a 2018 project describing thousands of miles of fiber optic cable in the U.S. likely to be inundated by rising sea levels. Wildfire danger has a distinctly different footprint, and presented a complex set of prediction problems.

“Fires are a fact of life for many ecosystems,” says graduate student Scott Anderson, first author of the study, which was supported by the National Science Foundation and the U.S. Department of Homeland Security and presented at the ACM Internet Measurement Conference. “Assessing the risk of fire, though, is complex. It varies a lot over time based on the amount of fuel available, how dry that fuel can get as climate changes, and almost unpredictable factors like the source of ignition.”

The researchers worked with historical records of wildfires, and matched the Forest Service’s map of Wildfire Hazard Potential to a crowdsourced database of cellular network equipment locations from OpenCelliD.

Six states — California, Florida, Texas, South Carolina, Georgia and North Carolina — each have at least 5,000 transceivers in high-risk areas.

UW–Madison researchers mapped the cellular network coverage of cell phone towers in the continental U.S. at moderate (above), high and very high risk of outages cause by wildfires. Images courtesy of Scott Anderson.

High risk.

Very high risk.

“We think of the wildfire threat as being concentrated only in the western part of the United States,” Anderson says. “But we did see that there are areas that are at risk outside of the West, including the southeastern United States — especially in Florida — and even up around Philadelphia.”

The threat will only grow as climate change makes many areas more fire prone, and as more Americans make their homes near the cusp of both wilderness and civilization.

“The areas that need the most attention are those that are where urban growth has gotten very close to forests and other sources of fuel for wildfires,” Paul Barford says. “The service providers are very interested in having their infrastructure available in those areas, because that’s what their customers are asking for. But those are also places where there’s the greatest risk of damage because of fires.”

The biggest threat to cell service may not be direct fire damage to a tower.

“When we looked at fires in the fall of 2019 in California, the major reason that providers reported loss of services was due to power outages,” Anderson says. “Power lines are just as vulnerable, or maybe more vulnerable, to outage or to damage than the cell towers.”

Most cell sites depend on a single source of electricity, so first among the researchers’ recommendations for protecting cellular networks is emergency power.

“Cell towers in high-risk areas all need to have backup power, battery backup or generator backup, that can enable them to continue to operate even if fire cuts off their primary power,” Barford says.

In high-fire-risk areas, priority should be given to more open, accessible property when choosing tower sites, and more care taken to maintain a physical buffer around sites by regularly removing vegetation that could draw a fire right up to delicate equipment.

The stakes can be high. More than 80 percent of California’s 911 calls come from cellphones, and cellular networks are vital to first responders trying to contain a fire and organize in an emergency. When firefighting and rescue agencies forecast the direction a fire is expected to take, they need to quickly deliver warnings and instructions to the people in harm’s way.

“One of the ways of communicating that risk to people in these fire-prone areas — to send emergency notifications that say a fire is on the way, everyone in this area must evacuate — is through the cellular infrastructure,” Anderson says. “If those messages can’t go through because of disruptions in the cellular network, that can have life or death consequences.”

THIS RESEARCH WAS SUPPORTED BY GRANTS FROM THE NATIONAL SCIENCE FOUNDATION (CNS-1703592) AND DEPARTMENT OF HOMELAND SECURITY (AFRL FA8750- 12-2-0328).

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Trends in hurricane behavior show stronger, slower and farther-reaching storms

A new normal is taking shape as a warming planet is changing hurricane behaviors and patterns. Research over the last decade has shown alarming trends resulting in more destructive hurricanes. Global trends suggest hurricanes are getting stronger, moving more slowly over land, and deviating farther north and south of the equator.

With these changes come stronger winds, increased flooding, and risks posed to cities that historically have not been hit by these types of storms.

Also known as tropical cyclones or typhoons, hurricanes are low-pressure storm systems that form over warm ocean water and can strengthen to massive sizes, bringing with them heavy rain, intense wind and storm surges. They can even spawn tornadoes.

James Kossin PHOTO: BRYCE RICHTER

James Kossin has been studying hurricane patterns for more than 30 years as a researcher with the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information who is based at the University of Wisconsin–Madison Cooperative Institute for Meteorological Satellite Studies.

Kossin’s latest research, published in May 2020 in the Proceedings of the National Academy of Sciences, examined more than 40 years of hurricane data captured by weather satellites from 1979 to 2017. His analysis revealed an increasing trend of higher maximum sustained winds in hurricanes.

In short, hurricanes have gotten stronger.

“What we’re finding globally is about six percent per decade of change,” says Kossin. “If you have a hurricane, there is an increased chance of it being at major hurricane intensity compared to storms in past decades.”

Hurricanes begin their lifecycle as smaller tropical depressions but are not classified as a major hurricane until wind speeds exceed 111 mph. Kossin’s work suggests hurricanes globally are now about 25 percent more likely to achieve or exceed this maximum sustained wind speed threshold compared to 40 years ago.

Kossin’s hurricane intensification research adds to a growing body of work on other hurricane attributes that are affected by a warmer planet, like hurricane slowdown and migration. While high winds due to intensification pose serious risks to cities and its residents, the flooding caused by hurricanes is their deadliest impact.

Hurricane slowdown

In a related paper published in Nature in 2018, Kossin compared 68 years (1949-2016) of worldwide hurricane track and intensity data, known as best-track data, from NOAA and other agencies to identify changes in forward translation speeds — the speed at which a hurricane moves. Kossin found that, worldwide, hurricane translational speeds have slowed down by an average of 10 percent.

“Just a 10 percent slowdown in hurricane translational speed can more than double rainfall totals caused by a one-degree Celsius increase of global warming,” says Kossin.

In 2017, Hurricane Harvey spent several days over Houston, Texas, dousing the city and surrounding areas with more than 50 inches of rainfall. Similarly, in 2020, Hurricane Sally inundated states like Florida, Mississippi and Alabama when the storm stalled because it lacked a high-pressure system to push it back into the North Atlantic Ocean.

The slowing hurricanes are likely the result of high- and low-pressure systems becoming more balanced. A warming planet smooths out differences between the two pressure systems resulting in less forceful movements needed to push hurricanes along. Additionally, a warmer atmosphere holds more moisture, allowing for an already saturated storm like a hurricane to carry more water and drop it over land. Roughly, a one-degree Celsius difference in atmospheric temperatures translates to an atmosphere that can hold seven percent more moisture.

The reductions in translational speeds, however, are not the same everywhere. There are four distinct hurricane regions around the globe and each one is experiencing different rates of slowing. Over the past 68 years, the North Atlantic Region has seen a slowdown of six percent, while the Western North Pacific Region, an area that includes southeast Asia, has experienced a slowdown of 20 percent, the most significant of all of the regions. Kossin identified a reduction of 15 percent for the nearby Australian Region and the U.S. has seen a slowdown of 17 percent since 1900.

Although Hurricane Harvey’s and Florence’s behaviors are not directly attributable to climate change, Kossin says storms like these are examples of the increased risks cities face when storms slow down.

Poleward migrations

Most hurricanes form and are sustained in warm ocean waters of 80–89 degrees Fahrenheit. Those warm temperatures are typically found within an area north and south of the equator. Kossin’s research from a 2014 paper in Nature identified a trend of hurricanes traveling beyond their usual ranges — reaching farther north and south.

Referred to as poleward migration, the analysis was based on 30 years of hurricane data and looked at where the storms reached their maximum sustained winds. Over those three decades, Kossin identified a shift of 32 miles per decade in the northern hemisphere, and 38 miles per decade in the southern hemisphere. The study further breaks down specific hurricane regions like the North Atlantic and the Western North Pacific.

Satelliite image of hurricanes Katia, Irma and Jose in September 2017. UW-MADISON CIMSS

“This can have huge impacts to cities that are not used to seeing these types of storms hit their shores,” says Kossin. “Since the research came out in 2014, we continued to look at these trends and we now have a medium confidence that the polar migration in the Western North Pacific Ocean has a human fingerprint on it.”

This means that anthropogenic climate change is in part causing these hurricanes to reach beyond their typical boundaries, at least in certain regions. Further, it indicates that ocean temperature increases are not the only forces driving hurricane development. A warming planet also interferes with global wind patterns.

As a hurricane travels farther north and south from the tropics, it encounters stronger vertical wind shear, which can distort the hurricane and weaken it. However, due to climate change, wind shear at certain latitudes is thought to be diminished, enabling the poleward shift.

Continuing to assess the impact of climate change on hurricanes will be instrumental to protecting communities most affected by these devastating storms. With each new year of hurricane data, Kossin has more observations to study and map out the trends — whether it’s hurricane strength or movement over time. To date, his research results raise concerns.

“It’s becoming increasingly clear that tropical cyclone behavior is changing in very dangerous ways all across the globe as the planet warms,” says Kossin.

This work is supported by NOAA.

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Tidal Evolution

Sailing by moonlight
you wallow in the opulence
of your oceanic abode.
An illusion of permanence
concealing the current
that now bathes you
in shameful nakedness.

Plucked from the waves.
Abandoned by the sea
in shallow pools of half-life,
you struggle for air
with every passing tide
a seasoned reminder
of a present past.

Surging spray
falls with remorse
upon flaking skin;
dead to the possibilities
of this liminal existence
you flip flop
towards the palisades
of your ancestral home.

A chance explosion
frees you from
your rocky prison,
but with sea in sight
you no longer feel
its aching weight.
Tentatively you stretch
out a limb
and turn your back
to the water,
never to return.

Fish that could briefly venture onto dry land, may have gotten a boost from the tide (Image Credit: Zina Deretsky / National Science Foundation via Wikimedia Commons).

This poem is inspired by recent research, which has found that large tides may have driven the evolution of fish towards life on land.

The Devonian period is a period of geological time that occurred on Earth from 416 million to 358 million years ago. It is sometimes called the ‘Age of Fishes’ because of the immense diversification of fish that took place during this period. One such group to emerge was the bony fish, the earliest of which were the first animals to evolve lungs; but exactly what it was that triggered this evolution and subsequent adaptation to life on land, is uncertain. One theory suggests that it might have been caused by particularly large tides, which transported fish from the sea and caused them to become isolated in small pools. These challenging habitats may then have driven the evolution of lungs and, later on, the transformation of fins into front and hind legs, so that the fish could make their way to more frequently replenished pools closer to the sea.

In order to test this tidal theory, researchers have used a mathematical model of the tidal system to simulate, in detail, the tides that would have occurred on Earth during the Early Devonian period. Data on the positions of the continents, the distance of the Moon, the duration of Earth’s day, and the physical properties of seawater were fed into the model. These simulations revealed that during this period large tides occurred across the planet, with a difference of more than four metres in sea level between high and low tide being reported in the area near what is now South China. Given that fossil records indicate that it was specifically around South China that bony fish originated, this new research lends further credence to the possible role that tides may have played in the evolutionary development of life on Earth.

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