Aurelia Butler
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Air pollution made an impression on Monet and other 19th century painters
The 19th century landscape paintings hanging in London’s Tate Britain museum looked awfully familiar to climate physicist Anna Lea Albright. Artist Joseph Mallord William Turner’s signature way of shrouding his vistas in fog and smoke reminded Albright of her own research tracking air pollution.“I started wondering if there was a connection,” says Albright, who had been visiting the museum on a day off from the Laboratory for Dynamical Meteorology in Paris. After all, Turner — a forerunner of the impressionist movement — was painting as Britain’s industrial revolution gathered steam, and a growing number of belching manufacturing plants earned London the nickname “The Big Smoke.”
Turner’s early works, such as his 1814 painting “Apullia in Search of Appullus,” were rendered in sharp details. Later works, like his celebrated 1844 painting “Rain, Steam and Speed — the Great Western Railway,” embraced a dreamier, fuzzier aesthetic.
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Perhaps, Albright thought, this burgeoning painting style wasn’t a purely artistic phenomenon. Perhaps Turner and his successors painted exactly what they saw: their environs becoming more and more obscured by smokestack haze.
To find out how much realism there is in impressionism, Albright teamed up with Harvard University climatologist Peter Huybers, who’s an expert in reconstructing pollution before instruments existed to closely track air quality. Their analysis of nearly 130 paintings by Turner, Paris-based impressionist Claude Monet and several others tells a tale of two modernizing cities.
Low contrast and whiter hues are hallmarks of the impressionist style. They are also hallmarks of air pollution, which can affect how a distant scene looks to the naked eye. Tiny airborne particles, or aerosols, can absorb or scatter light. That makes the bright parts of objects appear dimmer while also shifting the entire scene’s color toward neutral white.
The artworks that Albright and Huybers investigated, which span from the late 1700s to the early 1900s, decrease in contrast as the 19th century progresses. That trend tracks with an increase in air pollution, estimated from historical records of coal sales, Albright and Huybers report in the Feb. 7 Proceedings of the National Academy of Sciences.
“Our results indicate that [19th century] paintings capture changes in the optical environment associated with increasingly polluted atmospheres during the industrial revolution,” the researchers write.
Albright and Huybers distinguished art from aerosol by first using a mathematical model to analyze the contrast and color of 60 paintings that Turner made between 1796 and 1850 as well as 38 Monet works from 1864 to 1901. They then compared the findings to sulfur dioxide emissions over the century, estimated from the trend in the annual amount of coal sold and burned in London and Paris. When sulfur dioxide reacts with molecules in the atmosphere, aerosols form.
The early works of British painter Joseph Mallord William Turner, such as “Apullia in Search of Appullus,” left, painted in 1814, were rendered in sharp details. His later works, like “Rain, Steam and Speed — the Great Western Railway,” right, painted in 1844, embraced a dreamier aesthetic. The decrease in contrast between the paintings tracks with increasing air pollution from the industrial revolution, researchers say.From left: Apullia in Search of Appullus vide Ovid, Joseph Mallord William Turner/The Tate Collection (CC BY-NC-ND 3.0); World History Archive/Alamy Stock Photo
As sulfur dioxide emissions increased over time, the amount of contrast in both Turner’s and Monet’s paintings decreased. However, paintings of Paris that Monet made from 1864 to 1872 have much higher contrast than Turner’s last paintings of London made two decades earlier.
The difference, Albright and Huybers say, can be attributed to the much slower start of the industrial revolution in France. Paris’ air pollution level around 1870 was about what London’s was when Turner started painting in the early 1800s. It confirms that the similar progression in their painting styles can’t be chalked up to coincidence, but is guided by air pollution, the pair conclude.
The researchers also analyzed the paintings’ visibility, or the distance at which an object can be clearly seen. Before 1830, the visibility in Turner’s paintings averaged about 25 kilometers, the team found. Paintings made after 1830 had an average visibility of about 10 kilometers. Paintings made by Monet in London around 1900, such as “Charing Cross Bridge,” have a visibility of less than five kilometers. That’s similar to estimates for modern-day megacities such as Delhi and Beijing, Albright and Huybers say.
To strengthen their argument, the researchers also analyzed 18 paintings from four other London- and Paris-based impressionists. Again, as outdoor air pollution increased over time, the contrast and visibility in the paintings decreased, the team found. What’s more, the decrease seen in French paintings lagged behind the decrease seen in British ones.
Overall, air pollution can explain about 61 percent of contrast differences between the paintings, the researchers calculate. In that respect, “different painters will paint in a similar way when the environment is similar,” Albright says. “But I don’t want to overstep and say: Oh, we can explain all of impressionism.” More
New method creates material that could create the next generation of solar cells
Perovskites, a family of materials with unique electric properties, show promise for use in a variety fields, including next-generation solar cells. A Penn State-led team of scientists created a new process to fabricate large perovskite devices that is more cost- and time-effective than previously possible and that they said may accelerate future materials discovery.
“This method we developed allows us to easily create very large bulk samples within several minutes, rather than days or weeks using traditional methods,” said Luyao Zheng, a postdoctoral researcher in the Department of Materials Science at Penn State and lead author on the study. “And our materials are high quality — their properties can compete with single-crystal perovskites.”
The researchers used a sintering method called the electrical and mechanical field-assisted sintering technique (EM-FAST) to create the devices. Sintering is a commonly used process to compress fine powders into a solid mass of material using heat and pressure.
A typical process for making perovskites involves wet chemistry — the materials are liquefied in a solvent solution and then solidified into thin films. These materials have excellent properties, but the approach is expensive and inefficient for creating large perovskites and the solvents used may be toxic, the scientists said.
“Our technique is the best of both worlds,” said Bed Poudel, a researcher professor at Penn State and a co-author. “We get single-crystal-like properties, and we don’t have to worry about size limitations or any contamination or yield of toxic materials.”
Because it uses dry materials, the EM-FAST technique opens the door to include new dopants, ingredients added to tailor device properties, that are not compatible with the wet chemistry used to make thin films, potentially accelerating the discovery of new materials, the scientists said.“This opens up possibilities to design and develop new classes of materials, including better thermoelectric and solar materials, as well as X- and γ-ray detectors,” said Amin Nozariasbmarz, assistant research professor at Penn State and a co-author. “Some of the applications are things we already know, but because this is a new technique to make new halide perovskite materials with controlled properties, structures, and compositions, maybe there is room in the future for new breakthroughs to come from that.”
In addition, the new process allows for layered materials — one powder underneath another — to create designer compositions. In the future, manufactures could design specific devices and then directly print them from dry powders, the scientists said.
“We anticipate this FAST perovskite would open another dimension for high throughput material synthesis, future manufacturing directly printing devices from powder and accelerating the material discovery of new perovskite compositions,” said Kai Wang, an assistant research professor at Penn State and a co-author.
EM-FAST, also known as spark plasma sintering, involves applying electric current and pressure to powders to create new materials. The process has a 100% yield — all the raw ingredients go into the final device, as opposed to 20 to 30% in solution-based processing.
The technique produced perovskite materials at .2 inch per minute, allowing scientists to create quickly create large devices that maintained high performance in laboratory tests. The team reported their findings in the journal Nature Communications.Penn State scientists have long used EM-FAST to create thermoelectric devices. This work represents the first attempt to create perovskite materials with the technique, the scientists said.
“Because of the background we have, we were talking and thought we could change some parameters and try this with perovskites,” Nozariasbmarz said. “And it just opened a door to a new world. This paper is a link to that door — to new materials and new properties.”
Other Penn State researchers on the project were Wenjie Li and Dong Yang, assistant research professors; Ke Wang, staff scientist in the Materials Research Institute; Jungjin Yoon, Tao Ye and Yu Zhang, postdoctoral researchers; Yuchen Hou, doctoral candidate; and Shashank Priya, former associate vice president for research and director of strategic initiatives and professor of materials science and engineering.
Also contributing was Mohan Sanghadasa, U.S. Army Combat Capabilities Development Command Aviation and Missile Center.
Researchers received support from the National Science Foundation Industry-University Research Partnerships’ Center for Energy Harvesting Materials and Systems, U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy, Air Force Office of Scientific Research, and Office of Naval Research and Army Research. MoreReaching like an octopus: A biology-inspired model opens the door to soft robot control
Octopus arms coordinate nearly infinite degrees of freedom to perform complex movements such as reaching, grasping, fetching, crawling, and swimming. How these animals achieve such a wide range of activities remains a source of mystery, amazement, and inspiration. Part of the challenge comes from the intricate organization and biomechanics of the internal muscles.
This problem was tackled in a multidisciplinary project led by Prashant Mehta and Mattia Gazzola, professors of mechanical science & engineering at the University of Illinois Urbana-Champaign. As reported in Proceedings of the Royal Society A, the two researchers and their groups have developed a physiologically accurate model of octopus arm muscles. “Our model, the first of its kind, not only provides insight into the biological problem, but a framework for design and control of soft robots going forward,” Mehta said.
The impressive capabilities of octopus arms have long served as an inspiration for the design and control of soft robots. Such soft robots have the potential to perform complex tasks in unstructured environments while operating safely around humans, with applications ranging from agriculture to surgery.
Graduate student Heng-Sheng Chang, the study’s lead author, explained that soft-bodied systems like octopuses’ arms present a major modeling and control challenge. “They are driven by three major internal muscle groups — longitudinal, transverse, and oblique — that cause the arm to deform in several modes — shearing, extending, bending, and twisting,” he said. “This endows the soft muscular arms with significant freedom, unlike their rigid counterparts.”
The team’s key insight was to express the arm musculature using a stored energy function, a concept borrowed from the theory of continuum mechanics. Postdoctoral scholar and corresponding author Udit Halder explained that “The arm rests at the minimum of an energy landscape. Muscle actuations modify the stored energy function, thus shifting the equilibrium position of the arm and guiding the motion.”
Interpreting the muscles using stored energy dramatically simplifies the arm’s control design. In particular, the study outlines an energy-shaping control methodology to compute the necessary muscle activations for solving manipulation tasks such as reaching and grasping. When this approach was numerically demonstrated in the software environment Elastica, This model led to remarkably life-like motion when an octopus arm was simulated in three dimensions. Moreover, according to Halder, “Our work offers mathematical guarantees of performance that are often lacking in alternative approaches, including machine learning.”
“Our work is part of a larger ecosystem of ongoing collaborations at the University of Illinois,” Mehta said. “Upstream, there are biologists who perform experiments on octopuses. Downstream, there are roboticists who are taking these mathematical ideas and applying them to real soft robots.”
Mehta’s and Gazzola’s groups collaborated with Rhanor Gillette, Illinois Professor Emeritus of molecular and integrative physiology, to incorporate observed octopus physiology into their mathematical model for this study. Future work will discuss the biological implications of energy-based control. In addition, the researchers are collaborating with Girish Krishnan, an Illinois professor of industrial & enterprise systems engineering, to incorporate their mathematical ideas into real soft robot design and control. This will not only create a systematic way of controlling soft robots, but will also provide a deeper understanding of their working mechanisms.
This work was part of the CyberOctopus project, a multidisciplinary university research initiative in the University of Illinois’ Coordinated Science Laboratory supported by the Office of Naval Research. More
