The paper also shows how Teotihuacan’s engineers re-routed two rivers to align with points of astronomical significance, identified hundreds of previously unknown architectural features, and documented over 200 archaeological features that have been destroyed by mining and urbanization since the 1960s.

“We don’t live in the past, but we live with the legacies of past actions. In a monumental city like Teotihuacan, the consequences of those actions are still fresh on the landscape,” said first author Nawa Sugiyama, a professor of anthropology at UC Riverside.

Teotihuacan, about 25 miles northeast of modern Mexico City, was the largest city in the Americas and one of the largest anywhere in the ancient world. It existed from about 100 BCE-550 CE — about 1,000-2,000 years ago — and covered 8 square miles. At its height, it consisted of numerous pyramids, plazas, and well-designed residential and commercial neighborhoods housing a population of around 100,000. Some of the pyramids and other structures are visible above ground today, but most of the city’s remains lie buried beneath modern fields, buildings, and other activity areas.

To map the below-ground parts of Teotihuacan, Nawa Sugiyama and co-authors Saburo Sugiyama at Arizona State University; Tanya Catignani at George Mason University; Adrian S. Z. Chase at Claremont University; and Juan C. Fernandez-Diaz at Houston University used lidar, a mapping technology that measures the amount of time it takes light from a laser to bounce back from an object. Archaeologists often use lidar to discover buried features covered by dense forests or open fields but rarely deploy the technology where archaeological remains lie beneath urban areas.

“Lidar is often perceived as revolutionary tool to find ancient features hidden in plain sight, but we found the lidar map to be extremely messy and hard to interpret. Many of the features we identified were modern with ancient roots. But then we realized there is a far more interesting story behind this trend,” said Nawa Sugiyama.

Because the sheer scale of construction at Teotihuacan suggested massive modification of the ancient landscape, Sugiyama’s group thought that lidar could help elucidate the relationship between the layout of Teotihuacan and modern activities that overlay it. The researchers confirmed the lidar findings with surveys by foot and comparisons to previous mapping efforts.

They found that the builders of Teotihuacan leveled the ground down to the bedrock and, in some cases, quarried the bedrock itself to use as construction and fill material. In just one portion of the city, called the Plaza of the Columns Complex, the authors calculated that roughly 372,056 square meters of artificial ground accumulated over the course of roughly 300 years of construction that had been quarried elsewhere in the Teotihuacan Valley. In three of the main pyramid complexes, the authors estimate that 2,423,411 square meters of rock, dirt, and adobe had been used.

This major reshaping of the landscape affects the arrangement of modern construction and activities. The authors found that 65% of urban areas contained property or modern features that aligned orthogonally within 3 degrees of 15 degrees east of astronomical north — the same alignment as Teotihuacan. Rock fences were built along areas that lidar and excavation revealed to have underground ancient walls that made modern-day plowing difficult.

Teotihuacan engineers also rerouted the Rio San Juan and the San Lorenzo River, which cross the city. Rio San Juan follows the Teotihuacan orientation for 3 km as it traverses the city center while the San Lorenzo River has a very distinct orientation, 8 degrees south of astronomical east for 4.9 km. Previous research has interpreted them as major canals of symbolic and calendric significance.

The lidar map also showed that other sections of canals and rivers, many still actively used today, were altered at various points along its course, frequently coinciding with the Teotihuacan directionalities. A total of 16.9 km of the hydrological systems visible on the modern terrain had origins in the Early Classic Teotihuacan landscape.

On the lidar map, the group identified 298 features and 5,795 human-made terraces that had not been previously recorded. However, they also identified over 200 known features that have been destroyed by mining since 2015.

“We can’t fight modern urbanization. The lidar map provides a snapshot of these ancient features that are being abolished at an alarming rate that would otherwise go unnoticed. It’s one of many ways we can preserve our heritage landscape,” said Nawa Sugiyama.

The authors plan to use their lidar map to create a three-dimensional geospatial database that allows them to visualize stratigraphic and surface data, natural and artificial features, and to document the true extent of humans as geomorphic agents over long periods of time in the Teotihuacan Valley.

In a new paper, “Consequential Life Cycle Assessment and Optimization of High-Density Polyethylene Plastic Waste Chemical Recycling,” published in the Sept. 13 issue of the journal ACS Sustainable Chemistry & Engineering, Fengqi You, the Roxanne E. and Michael J. Zak Professor in Energy Systems Engineering and doctoral student Xiang Zhao detail a framework incorporating several mathematical models and methodologies that factor everything from chemical recycling equipment, processes and energy sources, to environmental effects and the market for end products.

The framework is the first comprehensive analysis of its kind that quantifies the life-cycle environmental impacts of plastic waste chemical recycling, such as climate change and human toxicity.

Billions of tons of plastic have been produced since the 1950s, yet most of it — 91%, according to one often cited study — has not been recycled. While growing landfills and contaminated natural areas are among the concerns, the failure to reduce and reuse plastic is also seen by some as a missed economic opportunity.

That’s why the emerging industry of chemical recycling is capturing the attention of the waste industry and researchers like You, who is helping to identify optimal technologies for chemical recycling and providing a roadmap for the future of the industry.

Not only does chemical recycling create a ‘circular economy,’ in which a waste product can be turned back into a natural resource, but it opens the door for plastics such as high-density polyethylene — used to produce items such as rigid bottles, toys, underground pipes, and mail package envelopes — to be recycled more commonly.

You’s framework can quantify the environmental consequences of market dynamics that typical life-cycle sustainability assessments would overlook. It’s also the first to combine superstructure optimization — a computational technique for searching over a large combinatorial space of technology pathways for minimizing cost — with life-cycle analysis, market information and economic equilibrium.

The paper highlights the benefits of consequential life-cycle optimization when compared with more traditional analytical tools. In one scenario, to maximize economic outcomes while minimizing environmental impacts, life-cycle optimization produced a more than 14% decrease in greenhouse gas emissions and a more than 60% reduction of photochemical air pollution when compared with the attributional life-cycle assessment approach typically used in environmental assessment studies.

While the analysis gives industry experts and policy makers a general pathway for advancing chemical recycling and a circular economy for plastics, a myriad of choices and variables along the technological path must be considered. For instance, if the market demand for basic chemicals like ethylene and propylene is strong enough, the framework recommends a specific type of chemical separation technology, while if butane or isobutene are desired, another type technology is optimal.

“It’s a chemical process and there are so many possibilities,” You said. “If we want to invest in chemical recycling, what technology would we use? That really depends on the composition of our waste, the variants of polyethylene plastic, and it depends on current market prices for end products like fuels and hydrocarbons.”

Environmental consequences of chemical recycling depend on variables such as supplier process of chemical feedstocks and products. For instance, the framework found that producing butene onsite as opposed to having it supplied can reduce photochemical air pollution from recycling plants by nearly 20%, while onsite use of natural gas increases more than 37% of potentially harmful ionizing radiation.

“There’s always something we can twist and adjust in the technology and process, and that’s the tricky part,” said You, who added that as new chemical recycling techniques emerge and markets change, consequential life-cycle optimization will remain a powerful tool for guiding the emerging industry.

The research was supported in part by the National Science Foundation.

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Materials provided by Cornell University. Original written by Syl Kacapyr, courtesy of the Cornell Chronicle. Note: Content may be edited for style and length.

Coral reefs are some of the most diverse ecosystems on Earth, providing critical habitat for thousands of species that sustain economies and provide for the diets and livelihoods of millions of people. In the largest and most comprehensive study of its kind, researchers from France and The University of Texas at Austin concluded that coral reef food webs are more delicate than previously thought. Researchers made the conclusion after synthesizing the stomach contents of most fish species found on six coral reef systems around the world.

The team revealed that the vast majority of reef fish species are very picky about what they eat, rather than opportunistically feeding on anything they could find. Although reefs will probably withstand the loss of several prey species, the loss of a single larger fish species may jeopardize the ecosystem.

“It’s remarkable that we see similar patterns in coral reef systems all over the world. Extinctions, particularly of larger fish species, may have significant impacts for coral reef systems,” said Jordan Casey, an assistant professor of marine science at UT Austin’s Marine Science Institute (UTMSI) and an author on the paper.

Many conditions can cause the local loss of fish species, such as climate change, commercial fishing and pollution. Such fish declines may leave an increasing number of prey uneaten, creating imbalances in the food web.

“Reefs rely on the efficient utilization of all creatures,” said Simon Brandl, also an author and an assistant professor at UTMSI. “If a fish specializes on eating a certain type of snail and that fish disappears, the snail might not be eaten and live happily ever after. This creates a dead end for the food it could provide to other coral reef creatures. Good news for the snail. Bad news for everything else living there.”

The study examined the feeding habits of more than 600 species found on six different coral reefs near Okinawa, Hawaii, the West Indies, New Caledonia, Madagascar and the Marshall Islands. Despite regional differences, the food webs had a strikingly similar structure: 67% of species were specialized feeders with strong preferences for specific prey items, despite the tremendous diversity of available food on coral reefs.

“Coral reefs are important to humans for a number of reasons,” Casey said. “They are a critical source of food for many people. They are also popular tourist destinations and economic engines for a number of countries. However, coral reefs can only provide these key ecosystem services if food webs remain intact.”

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Strigolactones also help plant roots form symbiotic relationships with microorganisms that allow the plant to absorb nutrients from the soil. These two factors have led to agricultural interest in using strigolactones to control the growth of weeds and root parasites, as well as improving nutrient uptake.

These root-extruding compounds don’t come without risks. They also stimulate germination of witchweeds and broomrapes, which can cause entire crops of grain to fail, making thorough research essential prior to commercial development. Scientists are still learning about the physiological roles played by this diverse group of hormones in plants. Until recently, manufacturing pure strigolactones for scientific study has been difficult and too costly for agricultural use.

“Our work provides a unique platform to investigate strigolactone biosynthesis and evolution, and it lays the foundation for developing strigolactone microbial bioproduction processes as alternative sourcing,” said corresponding author Yanran Li, a UC Riverside assistant professor of chemical and environmental engineering.

Together with co-corresponding author Kang Zhou at National University Singapore, Li directed a group that inserted plant genes associated with strigolactone production into ordinary baker’s yeast and nonpathogenic Escherichia coli bacteria that together produced a range of strigolactones.

Producing strigolactones from yeast turned out to be very challenging. Although engineered yeast is known to modify the strigolactone precursor, called carlactone, it could not synthesize carlactone with any of the specific genes used by the researchers.

“This project started in early 2018, yet for over 20 months there was basically no progress. The gatekeeping enzyme DWRF27 is not functional no matter how we try in yeast,” Li said. “Kang developed a microbial consortium technique to produce a Taxol precursor in 2015 and that inspired this wonderful collaboration.”

The team turned toward E. coli, which had already been shown capable of producing carlactone. The carlactone it produced, however, was unstable and could not be further modified by engineered E. coli into any strigolactones. Li’s group managed to optimize and stabilize the carlactone precursor.

To their delight, when the yeast and bacteria were cultured together in the same medium, the E. coli and yeast worked as a team: E. coli made carlactone, and the yeast transformed it into various final strigolactone products. The method also produced enough strigolactones to extract and study. Using this platform, the group identified the function of multiple strigolactone biosynthetic enzymes, showing that sweet orange and grape have the potential to synthesize orobanchol-type strigolactones.

The team also engineered microbe metabolism to boost strigolactone production threefold to 47 micrograms per liter, enough for scientific study. Though commercial production of strigolactones is still a long way off, the new method for biosynthesizing them from a yeast-bacterium consortium will help scientists learn more about this important group of plant hormones, especially the enzymes involved.

Enzymes are protein catalysts and are responsible for modification of carlactone by yeast. Because carlactone is unstable, it cannot be purchased from commercial sources. As a result, many plant scientists have difficulty studying new enzymes that may work to transform carlactone into strigolactones.

“The new yeast-bacterium co-culture provides a convenient way for scientists to complete such works because the bacterium makes carlactone in situ,” Zhou said. “With discovery of more enzymes and optimization of the microbial consortium, we can manufacture strigolactones in quantity in the future.”

Li and Zhou were joined in the research by Sheng Wu, Anqi Zhou, and Alex Valenzuela of UC Riverside; and Xiaoqiang Ma at the Singapore-MIT Alliance for Research and Technology. The paper, “Establishment of strigolactone-producing bacterium-yeast consortium,” is available here.

“Something didn’t seem right, but I didn’t know what to say at the time. I just went on to the next question of the assessment,” said Bullock, now a professor emerita at the University of Missouri Sinclair School of Nursing. “We stopped her labor and sent her home, but I will bet my last dollar I sent her back to an abusive relationship, and it sparked my interest in helping other nurses assist battered women. What we didn’t know at the time was the impact violence had on the baby.”

Bullock helped implement the Domestic Violence Enhanced Perinatal Home Visits (DOVE) program in rural Missouri, which empowered safety planning and reduced domestic violence for hundreds of abused pregnant women. After learning from home health visits that many of the abused women had up to nine different romantic partners during and following pregnancy, Bullock conducted a study to examine the impact of multiple father figures on the cognitive development of the newborn infants.

After administering neurodevelopmental tests during home visits three, six and 12 months after birth, she was surprised to find the infants of women who had only one male partner who abused them had worse cognitive outcomes compared to infants of women with multiple male partners, only some of whom were abusive.

“The findings highlight the variety of ways the multiple father figures may have been helping the mom support her baby, whether it was providing food, housing, childcare or financial benefits,” Bullock said. “For the women with only one partner who abused them, the infant’s father, the father may not have provided any physical or financial support or played an active role in the child’s life. It can be difficult for busy, single moms struggling to make ends meet to provide the toys and stimulation their infants need to reach crucial developmental milestones.”

Bullock added that infants coming from homes with domestic violence often go on to have worse academic outcomes in school due to neurodevelopmental lags and a higher risk for a variety of health issues, including gastrointestinal distress, trouble eating and sleeping, as well as stress and illness.

“When nurses are visiting homes to check in on pregnant women and their developing babies, we want them to be trained in recognizing the warning signs of potential intimate partner violence,” Bullock said. “I still think back to 1983 when I sent that lady back home into a terrible situation, and I am passionate about making sure I can help nurses today not make the same mistake I made.”

“Children exposed to intimate partner violence: Impact of multiple father figures” was recently published in Maternal Child Health Journal. Funding for the study was provided by the National Institutes of Nursing Research. The study involved collaborators from Johns Hopkins University and University of Virginia.

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