The founder of contemporary thermodynamics and physical chemistry is the American physicist Josiah Willard Gibbs. In the 1870s he derived the phase rule, which describes the maximum number of different phases a substance or mixture of substances can assume simultaneously. For pure substances, the Gibbs Phase Rule predicts a maximum of 3 phases.

Professor Remco Tuinier, of the Institute for Complex Molecular Systems: “At the time, Einstein called Gibbs’ thermodynamics the only theory he really trusted. If we take water as an example, there is one point, with a specific temperature and pressure, where water occurs as gas, liquid and ice at the same time. The so-called triple point.” Assistant professor Mark Vis, from the same research group as Tuinier, adds: “This classic Gibbs phase rule is as solid as a rock and has never been defied.”

SHAPE MATTERS According to this phase rule, the mixture studied by the researchers would also exhibit a maximum of three phases at one specific point at the same time. But Tuinier and his colleagues now show that in this mixture there is a whole series of circumstances in which four phases exist at the same time. There is even one point at which there are five coexisting phases. Two too many, according to Gibbs. At that specific one point, also called a five-phase equilibrium, a gas phase, two liquid crystal phases, and two solid phases with ‘ordinary’ crystals exist simultaneously. And that has never been seen before. “This is the first time that the famous Gibbs rule has been broken,” Vis says enthusiastically.

The crux lies in the shape of the particles in the mixture. Gibbs did not take this into consideration, but the Eindhoven scientists now show that it is precisely the specific length and diameter of the particles that play a major role. Tuinier: “In addition to the known variables of temperature and pressure, you get two additional variables: the length of the particle in relation to its diameter, and the diameter of the particle in relation to the diameter of other particles in the solution.”

RANKED RODS

In their theoretical models, the researchers worked with a mixture of two substances in a background solvent: rods and polymers. This is also called a colloidal system, in which the particles are solid and the medium is liquid. Because the particles cannot occupy exactly the same space, they interact with each other. “This is also called the excluded volume effect; it causes the rods to want to sit together. They are, as it were, pushed towards each other by the polymer chains. In this way, you get a region in the mixture that mainly contains rods, and an area that is rich in polymers,” explains Tuinier.

He continues: “The rods then sink to the bottom, because they’re usually heavier. That’s the beginning of segregation, creating phases.” The lower part, which mainly contains rods, will eventually become so crowded that the rods will interfere with each other. They then take up a preferential position, so that they are less in each other’s way.

With the rods it looks like a neat arrangement next to each other. Eventually you get five different phases, a gas phase with unaligned rods at the top (an isotropic phase), a liquid phase with rods pointing in about the same direction (nematic liquid crystal), a liquid phase with rods lying in different layers (smectic liquid crystal), and two solid phases at the bottom.

MAYONNAISE AND MONITORS

Vis: “Our research contributes to the fundamental knowledge about this kind of phase transition and helps to understand and predict more precisely when these kinds of transition occur.” And that is useful in many areas. Think of pumping complex mixtures around in industrial reactors, making complex products like colloidal mixtures such as mayonnaise and paint, or ice that forms on car windows and black ice on roads.

Even in liquid crystals in monitors, these processes play a role. “Most industries choose to work with a single-phase system, where there is no segregation. But if the exact transitions are clearly described, then the industry can actually use those different phases instead of avoiding them,” says Vis.

CHANCE

It was more or less chance that the researchers arrived at an equilibrium of more than three phases. When simulating and programming plate-shaped particles and polymers, PhD students Álvaro González García and Vincent Peters from Tuinier’s group saw a four-phase equilibrium. Tuinier: “Álvaro came to me one day and asked me what had gone wrong. Because four phases just couldn’t be right.”

Then the researchers tried out multiple shapes, such as cubes and also rods. Tuinier: “With the rods, most phases turned out to be possible, we even found a five-phase equilibrium. That could also mean that even more complicated equilibria are possible, as long as you search long enough for complex different particle shapes.”

Researchers at Rice University’s Laboratory for Nanophotonics (LANP) have long known that a nanoparticle’s shape affects how it interacts with light, and their latest study shows how shape affects a particle’s ability to use light to catalyze important chemical reactions.

In a comparative study, LANP graduate students Lin Yuan and Minhan Lou and their colleagues studied aluminum nanoparticles with identical optical properties but different shapes. The most rounded had 14 sides and 24 blunt points. Another was cube-shaped, with six sides and eight 90-degree corners. The third, which the team dubbed “octopod,” also had six sides, but each of its eight corners ended in a pointed tip.

All three varieties have the ability to capture energy from light and release it periodically in the form of super-energetic hot electrons that can speed up catalytic reactions. Yuan, a chemist in the research group of LANP director Naomi Halas, conducted experiments to see how well each of the particles performed as photocatalysts for hydrogen dissociation reaction. The tests showed octopods had a 10 times higher reaction rate than the 14-sided nanocrystals and five times higher than the nanocubes. Octopods also had a lower apparent activation energy, about 45% lower than nanocubes and 49% lower than nanocrystals.

“The experiments demonstrated that sharper corners increased efficiencies,” said Yuan, co-lead author of the study, which is published in the American Chemical Society journal ACS Nano. “For the octopods, the angle of the corners is about 60 degrees, compared to 90 degrees for the cubes and more rounded points on the nanocrystals. So the smaller the angle, the greater the increase in reaction efficiencies. But how small the angle can be is limited by chemical synthesis. These are single crystals that prefer certain structures. You cannot make infinitely more sharpness.”

Lou, a physicist and study co-lead author in the research group of LANP’s Peter Nordlander, verified the results of the catalytic experiments by developing a theoretical model of the hot electron energy transfer process between the light-activated aluminum nanoparticles and hydrogen molecules.

“We input the wavelength of light and particle shape,” Lou said. “Using these two aspects, we can accurately predict which shape will produce the best catalyst.”

The work is part of an ongoing green chemistry effort by LANP to develop commercially viable light-activated nanocatalysts that can insert energy into chemical reactions with surgical precision. LANP has previously demonstrated catalysts for ethylene and syngas production, the splitting of ammonia to produce hydrogen fuel and for breaking apart “forever chemicals.”

“This study shows that photocatalyst shape is another design element engineers can use to create photocatalysts with the higher reaction rates and lower activation barriers,” said Halas, Rice’s Stanley C. Moore Professor of Electrical and Computer Engineering, director of Rice’s Smalley-Curl Institute and a professor of chemistry, bioengineering, physics and astronomy, and materials science and nanoengineering.

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In a new paper publishing in Science, the researchers show how they are able to make use of existing seismic monitoring equipment, as well as historic seismic data, to determine how much the temperature of the earth’s oceans has changed and continues changing, even at depths that are normally out of the reach of conventional tools.

They do this by listening for the sounds from the many earthquakes that regularly occur under the ocean, says Jörn Callies, assistant professor of environmental science and engineering at Caltech and study co-author. Callies says these earthquake sounds are powerful and travel long distances through the ocean without significantly weakening, which makes them easy to monitor.

Wenbo Wu, postdoctoral scholar in geophysics and lead author of the paper, explains that when an earthquake happens under the ocean, most of its energy travels through the earth, but a portion of that energy is transmitted into the water as sound. These sound waves propagate outward from the quake’s epicenter just like seismic waves that travel through the ground, but the sound waves move at a much slower speed. As a result, ground waves will arrive at a seismic monitoring station first, followed by the sound waves, which will appear as a secondary signal of the same event. The effect is roughly similar to how you can often see the flash from lightning seconds before you hear its thunder.

“These sound waves in the ocean can be clearly recorded by seismometers at a much longer distance than thunder — from thousands of kilometers away,” Wu says. “Interestingly, they are even ‘louder’ than the vibrations traveling deep in the solid Earth, which are more widely used by seismologists.”

The speed of sound in water increases as the water’s temperature rises, so, the team realized, the length of time it takes a sound to travel a given distance in the ocean can be used to deduce the water’s temperature.

“The key is that we use repeating earthquakes — earthquakes that happen again and again in the same place,” he says. “In this example we’re looking at earthquakes that occur off Sumatra in Indonesia, and we measure when they arrive in the central Indian ocean. It takes about a half hour for them to travel that distance, with water temperature causing about one-tenth-of-a second difference. It’s a very small fractional change, but we can measure it.”

Wu adds that because they are using a seismometer that has been in the same location in the central Indian Ocean since 2004, they can look back at the data it collected each time an earthquake occurred in Sumatra, for example, and thus determine the temperature of the ocean at that same time.

“We are using small earthquakes that are too small to cause any damage or even be felt by humans at all,” Wu says. “But the seismometer can detect them from great distances , thus allowing us to monitor large-scale ocean temperature changes on a particular path in one measurement.”

Callies says the data they have analyzed confirm that the Indian Ocean has been warming, as other data collected through other methods have indicated, but that it might be warming even faster than previously estimated.

“The ocean plays a key role in the rate that the climate is changing,” he says. “The ocean is the main reservoir of energy in the climate system, and the deep ocean in particular is important to monitor. One advantage of our method is that the sound waves sample depths below 2,000 meters, where there are very few conventional measurements.”

Depending on which set of previous data they compare their results to, ocean warming appears to be as much as 69 percent greater than had been believed. However, Callies cautions against drawing any immediate conclusions, as more data need to be collected and analyzed.

Because undersea earthquakes happen all over the world, Callies says it should be possible to expand the system he and his fellow researchers developed so that it can monitor water temperatures in all of the oceans. Wu adds that because the technique makes use of existing infrastructure and equipment, it is relatively low-cost.

“We think we can do this in a lot of other regions,” Callies says. “And by doing this, we hope to contribute to the data about how our oceans are warming.”

Extensive iron and lead corrosion of the water distribution system in Flint, coupled with lead release, created “red water” complaints, rapid loss of chlorine disinfectant and an outbreak of Legionnaires Disease that killed 12 people. State and federal agencies have disbursed $450 million in aid so far. In August, the state of Michigan reached a mediated settlement in a civil suit and is expected to pay about $600 million to victims, many of whom are children.

“The Flint story is a cautionary tale of poor anticipation of risks, actions that were too little too late, reactionary and not driven by scientific data,” John R. Scully, University of Virginia Charles Henderson Chaired Professor of Materials Science and Engineering, said. Scully also serves as technical editor in chief of CORROSION Journal.

In a paper published Sept. 8 in the Proceedings of the National Academy of Sciences, Scully and Raymond J. Santucci, who earned his Ph.D. from UVA’s Department of Materials Science and Engineering in 2019, address unresolved scientific questions that can help avert future lead poisoning disasters. Lead poisoning from degrading lead pipes is a pervasive threat, and future incidents are likely.

“This requires a fresh perspective, to avoid just looking in the rearview mirror and instead focus on what lies around the curve ahead,” Scully said.

Commonly proposed strategies offer false comfort based on sparse water testing, rules of thumb, and traditional mitigation strategies rather than by rigorously challenged sound scientific principles, according to the paper’s authors.

“We need to better understand the scientific factors that govern lead release, and that starts with a better testing strategy and understanding of some fundamental truths,” Scully said.

Scully and Santucci argue that the people who manage and regulate public water systems should be using scientific data to predict the risks of lead release. Risk assessments based on scientific data should replace current reliance on water sampling, which is imprecise and often too late to prevent a disaster.

A predictive framework for lead corrosion would allow regulators and infrastructure managers to anticipate problems and manage the risk of water conditions associated with unacceptable lead release.

Santucci and Scully recommend better thermodynamic and kinetic calculations and models that can predict lead release and accumulation. The models proposed could generate risk assessments based on dynamic data such as water chemistry, reaction rates, scale formation and inhibitor corrosion mechanisms, as well as water stagnation and flow.

Citizen scientists can help meet the data-gathering challenge. “Rapid accurate testing, perhaps via mobile phone test kits, could provide more real-time data. Hand-held, mobile tech that enables citizens to monitor their own drinking water should have advanced already,” Scully said.

Santucci and Scully illustrate how chemical thermodynamics can predict the formation of thermodynamically stable lead-based compounds on lead pipe surfaces. Certain compounds form advantageous films that might act as kinetic barriers to hinder corrosion and function to sequester otherwise soluble lead.

“Stable film development depends on a certain equilibrium chemistry, with consequences for phosphate treatment,” Santucci said. “Add more phosphate and you can remove more soluble lead to form a protective lead phosphate film. Remove phosphate completely, and you then rely on hoping that other lead compounds (lead -carbonate, -sulfate, -oxide, etc.) can remove the levels of lead you need,” which is usually not the case.

In phosphate-treated water, a lead-phosphate film will form. “From our data, it is thermodynamically impossible to stay within the acceptable range of the EPA’s Lead and Copper rule without an inhibitor like phosphate. But it takes time for the scale to form. We need to explore new inhibitor chemicals and surface-altering agents that optimize the protective scale coverage on a pipe wall,” Santucci said.

The authors also suggest altogether new ideas to anticipate, monitor and prevent future lead in water crises. Artificial intelligence and machine learning could help identify relationships between water and pipe conditions and lead levels in drinking water. Santucci and Scully also propose a promising strategy of using isotope analysis to trace the sources of lead. “This strategy would enhance our understanding of how lead is released from lead pipes and other not so obvious sources, which is dearly lacking,” their paper states.

Public officials may argue that the investment in scientific research and modeling is unnecessary because lead-based pipes are being replaced, albeit at homeowners’ expense. Scully and Santucci disagree with that perspective. “Total replacement of lead service lines is a wonderful goal, but finding all sources of lead can be difficult,” Scully said.

Replacing lead in public water systems does not simply mean replacing lead pipes. Additional sources include lead-based solder used to join pipes together and commercial brass that commonly contains small amounts of lead, and lead ions that soak into the corrosion film of steel pipes over time. Partial replacement of lead pipes with other pipes such as steel or copper can actually increase lead release due to galvanic corrosion, a process where contact between two dissimilar metals causes protection of one and accelerated degradation of the other.

Santucci and Scully argue for holistic, kinetic models that incorporate the rate of lead release from all possible sources, under many real-world operating conditions.

“The root cause of the Flint water crisis can be found at the intersection of materials science, surface science, water chemistry and electrochemistry,” Scully said. “A better-informed society can prevent such disasters from happening in the future through improved risk assessment, anticipation and management of factors affecting lead release. We all have a part to play in averting future lead poisoning disasters.”

Major theories in human evolution argue that parents continuing to provide food to their offspring until they have grown up has enabled our species to have the largest brains of any species on the planet relative to our body size. Brains are expensive tissue and grow slowly leading to long childhoods. Ongoing parental care through long childhoods allow children time to learn the skills they need to survive in adulthood. Such long childhoods are rare across animals, equaled only by other great apes, like chimpanzees.

Chimpanzees may have long childhoods, but mothers rarely directly provide them with food after ages four to five years when they are weaned. Mostly mothers let their offspring forage for themselves. So then what do chimpanzee mothers provide their sons that gives them a competitive edge over orphaned sons? We do not yet know the answer but scientists do have some ideas.

“One idea is that mothers know where to find the best food and how to use tools to extract hidden and very nutritious foods, like insects, honey and nuts,” Crockford points out. “Offspring gradually learn these skills through their infant and juvenile years. We can speculate that one reason offspring continue to travel and feed close to their mothers every day until they are teenagers, is that watching their mothers helps them to learn.” Acquiring skills which enable them to eat more nutritious foods may be why great apes can afford much bigger brains relative to their body size than other primates.

“Another idea is that mothers pass on social skills,” Roman Wittig, last author on the study and director of the Ta? Chimpanzee Project, adds. “Again a bit like humans, chimpanzees live in a complex social world of alliances and competition. It might be that they learn through watching their mothers when to build alliances and when to fight.”

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A new University at Buffalo study based in Western New York is the first that simultaneously examined the preferences of community members and compared those with the community-based programs and resources available to identify the most viable strategies for addressing disparities in healthy food consumption.

Previous research has shown that only 12% and 7% of adults living at or below the poverty line meet fruit and vegetable recommendations, respectively.

“We continue to find that cost, food preferences, availability, access and limited food assistance eligibility and/or benefits are persistent barriers. Residents of underserved communities feel that increasing the affordability of fruits and vegetables through incentives, nutrition education, and increased access to healthy food options will help them to eat more fruits and vegetables,” said Christina Kasprzak, lead author on the study published in the Journal of Hunger & Environmental Nutrition.

“We also found that healthy food incentives, mobile produce markets, and nutrition education are acceptable and preferred food access strategies,” added Kasprzak, a PhD candidate in community health and health behavior in UB’s School of Public Health and Health Professions.

Researchers conducted 13 focus groups with 98 lower-income participants in urban areas of Western New York. Eight of the focus groups were conducted at local Women, Infant and Children (WIC) offices, while the remaining five were recruited by community organizations that serve lower-income families. The research team also interviewed 17 grocery store owners or managers, farmers, food distributors, and representatives from community organizations that currently or would be willing to address food access issues.

How to match needs

“Our research evaluated the capacity among local stakeholders to address the needs of lower-income communities, and made recommendations of how we can match this capacity to the preferences voiced in the focus groups with lower-income individuals,” Kasprzak said.

“By capitalizing on where there are matches between lower-income communities’ preferences and stakeholders we can ensure our efforts to expand healthy food access are viable,” Kasprzak said. “We don’t necessarily need to completely abandon the mismatches between programs and preferences, but we should heed community members’ suggestions for these programs and avoid blindly establishing programs that may not be fruitful.”

Cost, limited availability and accessibility, taste preferences and limited federal nutrition eligibility and benefits were the most frequently mentioned barriers to fruit and vegetable consumption. Study participants expressed frustration with having to decide between buying fresh produce and less healthy food options because of cost differences.

Another recurring theme among study participants was that they said they often had to travel outside their neighborhood, which required transportation, to find affordable and high-quality produce.

Researchers also reported that twice as many participants felt they lacked access to healthy food as those who said they had access.

What did participants say would help them buy and eat more fresh foods? Increasing the affordability, as well as nutrition education and recipe ideas. Some participants expressed a desire to learn healthier ways to prepare foods unique to their culture.

Include the working poor

Many participants favored increasing federal nutrition program benefits — such as Supplemental Nutrition Assistance Program (SNAP) — or expanding the eligibility requirements for these programs to include the working poor.

On the retail side, store owners and managers interviewed said they’d be willing to expand their fresh produce offerings to meet customers’ demands, while supporting efforts to improve the health of the community.

For corner stores — whose prices generally are known to be higher — owners wanted guidance on what to stock, how to price and promote those items, and where to source fruits and vegetables.

Farmers expressed a willingness to accept SNAP benefits for Community Supported Agriculture (CSA) shares, and to provide produce to urban corner stores.

Kasprzak was pleasantly surprised to learn that there is ample opportunity for local stakeholders to help lower-income communities access and eat more fruits and vegetables.

“By connecting the dots, we can potentially enhance the reach of existing programs that are preferred by these communities,” she said.

Ultimately, though, the barriers of cost of fruits and vegetables and limited eligibility and benefits for nutrition assistance programs are not wholly addressed by the food access programs discussed in the research paper, Kasprzak notes.

“For example, an incentive program makes fruits and vegetables more affordable but does not directly drive down the cost of produce. Therefore, more concerted efforts at the state or national level are needed.”

“We know that many of the programs that community members would like to see already exist, but budget and expertise to market these programs are often lacking in small organizations,” added Lucia Leone, PhD, the senior author on the paper and an assistant professor of community health and health behavior at UB. “Support from local policy makers is crucial for both getting the word out about these programs and ensuring their sustainability.”