Chemists modify rules for reaction rates

By Carol Clark

Theoretical chemists at Emory University have solved an important mystery about the rates of chemical reactions and the so-called Polanyi rules.

The findings, published in the journal Science, reveal why a reaction involving methane does not conform to the known rules, a problem that has baffled physical chemists in recent years.

“We showed that a pre-reactive, long-range force can align the reaction of a chorine atom with methane, or natural gas, in a way that actually inhibits the reaction,” says Joel Bowman, a professor of theoretical chemistry at Emory and the Cherry L. Emerson Center for Computational Chemistry. “We believe that the theoretical work that we did has extended and modified the Polanyi rules.”

Bowman published the results with Gabor Czako, a post-doctoral fellow in theoretical chemistry who performed most of the complex computational and mathematical analyses that uncovered the results.

Long-range, their findings could play a role in the development of cleaner, more efficient fuels.

The reactive properties of methane are of particular interest, since it is an important fuel. Photo by Carol Clark.

Understanding the dynamics of chemical reactions is key to driving reactions efficiently, whether in a laboratory experiment or in an industrial application. In 1986, John Polanyi shared the Nobel Prize in chemistry, in part by providing general rules for how different forms of energy affect the rates of reactions.

“The Polanyi rules tell you the best way to deposit energy in a simple molecule to make a chemical reaction occur,” Bowman says. “It’s a bit like knowing in advance how to invest $1,000 to maximize the return on investment.”

Polanyi developed the framework based on studies of simple reactions of chlorine and fluorine atoms with hydrogen gas. As technology has advanced in recent years, some chemists began testing the Polanyi rules for more complicated reactions, and the rules appeared to break down. Most notably, sophisticated molecular beam experiments by Kopin Liu at the Institute of Atomic and Molecular Sciences in Taiwan showed that the reaction of halogen atoms with methane did not conform to the rules.

“Suddenly, the rules appeared to have changed, and no one could explain why,” Bowman says. “We decided to roll up our sleeves and attack the problem theoretically.”

Bowman and Czako drew from the computational power of the Emerson Center, specialized software and analytical techniques. They first created theoretical-computational simulations of the experiments done by Liu and others, and then described the results mathematically.

“Our calculations showed essentially an exact agreement with the experimental results,” Bowman says. “When theory and experiment agree you’re happy, but you still want to know why.”

Determining why the reactions did not conform to the Polanyi rules was another complicated task, involving quantum mechanics and forces that govern the reaction down to the atomic level.

“As theoreticians, we’re able to zoom in and look at the results of our calculations in a way that’s virtually impossible in an experiment,” Bowman says.

They identified a subtle interplay between the Polanyi rules and a pre-reactive long-range force of methane with chlorine. If you follow the Polanyi rules, this long-range force, or steric control, will misalign the reactants, preventing them from docking correctly and inhibiting a reaction. But if you apportion the energy in the opposite way to the rules, the misalignment is wiped out and the reaction occurs.

“This long-range force was playing a bigger role than was previously realized,” Bowman says. “It can actually trump the Polanyi rules, at least in the reactions that Liu and we looked at. The Polanyi rules are certainly not all wrong, they just appear to be too simple to apply to more complex reactions.”

The research was funded by the National Science Foundation and the U.S. Department of Energy.

The reactive properties of natural gas are of particular interest since it is an important fuel. Bowman and Czako are now applying their techniques to study the combustion of methane and oxygen, which produces carbon dioxide. “It’s important to understand the dynamics of this reaction, because it might lead to more efficient ways to produce fuel, and a reduction in the levels of pollution emitted,” Bowman says.

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'Piedmont Divide' to bridge art and science

In a previous work called "Collector," above, John Grade created tusk-like forms that were used as oyster beds in Washington's Willapa Bay.

Environmental artist John Grade comes to Atlanta as an Emory artist-in-residence Nov. 6-19 to design and build large-scale sculptural installations. His project, "Piedmont Divide" will visually and conceptually link the campus Quadrangle and Lullwater Preserve. Using materials derived from indigenous plants and trees, Grade will relate the form and construction method of the two installations to Emory’s research on West Nile virus and worldwide water sustainability.

The Emory Visual Arts Gallery will function as a working studio, available to the public as "Piedmont Divide" unfolds. Area residents are invited to participate as volunteers on the project. Grade’s residency also includes a follow-up visit in the spring to oversee the disassembly of the sculpture, as part of a larger creative arts performance. For more info, visit: visualarts.emory.edu.

The ultimate goal of the "Piedmont Divide" collaboration is to raise environmental awareness in Emory and Atlanta.

Grade’s sculptures are shaped by natural landscapes, often changing form throughout their lifespans. One example is his 2007 wooden sculpture, "Collector," which was submerged in Washington’s Willapa Bay, where it acted as an oyster bed. After the oysters were eaten by Grade and friends, the tusk-like forms were transported on the grill of Grade’s pick-up truck to a slot canyon in Little Death Hollow, Utah. There, covered with insects from the ride, it was washed clean by flooding.

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Captive chimps up for endangered status

A wild adult male chimpanzee, above, at Gombe National Park in Tanzania, where Thomas Gillespie's lab is working with the Jane Goodall Institute to understand the pathogens responsible for declining chimp populations. Mahale, a site near Gombe, is one of the confirmed places where human visitors have accidentally infected chimps with fatal respiratory pathogens. Photo by Matthew Heintz.

Currently, it is legal in the United States to keep a chimpanzee as a pet, and to dress the animal up and use it in movies, or for other entertainment purposes. A group of petitioners is seeking to ban those practices, including the Association of Zoos and Aquariums, the Jane Goodall Institute, the Pan African Sanctuary Alliance and the Wildlife Conservation Society. They have asked the U.S. Fish and Wildlife Service to extend endangered status protection to captive chimpanzees in this country.

The Fish and Wildlife Service is now reviewing the matter, and is accepting comments from experts and the general public through October 31.

Thomas Gillespie, a primate disease ecologist at Emory, is among the expert petitioners.

Gillespie, left, speaking at a recent symposium on ape health in Kyoto, Japan.

Following is a letter to the Parks and Wildlife Service from Gillespie:

I am writing in regard to the request for information concerning the status of chimpanzees, and to voice my professional opinion that all chimpanzees, captive and wild, should be correctly classified as an endangered species within the Endangered Species Act (ESA) of the United States.

I am an associate professor of global health and biodiversity conservation with faculty appointments in the Department of Environmental Studies, the Rollins School of Public Health and the program in Population Biology, Ecology and Evolution at Emory University.

Currently, wild chimpanzees are listed as endangered under the ESA, yet captive chimpanzees in the United States are only considered “threatened” and are thereby deprived of the protections afforded to endangered species. Chimpanzees are the only species that suffers such “split-listing,” since all other endangered animal species are afforded endangered status whether wild or captive-born. One unfortunate outcome of this policy loophole is that private citizens can buy and sell chimpanzees as pets or use them for entertainment purposes, activities with demonstrated negative effects on ape welfare and public perception of conservation status.

Wild chimpanzee populations are declining, and a global effort is needed to save the species from extinction. It is important to note that wild chimpanzees are more endangered today than they were in 1990 (when wild populations were listed as endangered, and all threats to chimpanzee survival needed to be addressed.) Thus, the United Stats must do everything in its power to promote chimpanzee conservation, including regulating the use of captive chimpanzees. We send a confusing message to citizens and governments of ape range-states when the United States pushes for increased protection abroad while not protecting chimpanzees domestically.

In addition to my concerns raised above, I would like to elaborate on a threat to wild chimpanzees that relates directly to captive chimpanzees not receiving the protections afforded to all other endangered species. There is now overwhelming evidence that even mildly pathogenic human respiratory pathogens are capable of causing high rates of mortality in wild chimpanzee populations. If precautions are not enforced, tourists and researchers can be responsible for introducing such pathogens to wild chimpanzee populations as we have witnessed repeatedly in recent years.

Although guidelines have been implemented at chimpanzee tourism sites to reduce the risk of transmission of such pathogens, enforcement is variable. Tourists arrive at chimpanzee tourism sites after a lifetime of experiencing countless images of chimpanzees in advertising, films and television programs portraying human-chimpanzee contact and proximity. Many tourists are disappointed when they learn that they will not be allowed to touch or hold a wild chimpanzee. Tourists often push their guides to allow them to get closer to chimpanzees or fail to move away from chimps when they approach as mandated. Guides are put in a difficult situation of wanting to enforce guidelines to protect the apes, but not wanting to risk losing a substantial tip if tourists are disappointed by their experience. This is not a hypothetical situation, this is something that I have witnessed countless times over the past 14 years while conducting research at a diversity of sites in Sub-Saharan African that host chimpanzee tourism.

Sincerely,
Thomas Gillespie

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A few things you may not know about water

"Water Study" will lead participants through a "scientific experiment" in campus creeks.

By Carol Clark

Chances are you haven’t thought much about water lately. Unless you are a rancher in drought-stricken Texas, and you just relocated your cattle out of state because nothing is left for them to eat. Or if you are a young girl in rural Kenya, facing a miles-long walk to fetch water for the family, and a return trip bearing the heavy load.

We tend to take water for granted in lush Atlanta. But it’s moving front and center at Emory this year, through a series of events that will draw from science, art, the environment and the imaginations of all those who want to dive into the experience.

You can fall in behind dancers in haz-mat suits, as they lead people through a “scientific experiment” along the creek in Baker Woodlands. The interactive performance, called “Water Study,” takes place every evening from Oct. 15 to 19. And you can join a line of people accumulating across campus at noon on Oct. 18, to pour water from vessel to vessel until the last drop vanishes.



More water-related surprises are on the way in November, and in the spring. To prime the pump, so to speak, here are a few random facts about water.

Two-thirds of the Earth’s surface is covered in water, and all of that water came from space after the planet cooled down. One theory is that the water came from meteorites. The Herschel telescope, however, recently zeroed in on the properties of a comet, and learned it has water with the same deuterium-to-hydrogen ratio as Earth’s oceans.

Texas is experiencing its most severe one-year drought ever. Drier than normal conditions are expected to continue at least for months, and possibly until 2020, according to a state climatologist. The National Weather Service reports that livestock and agriculture losses have topped $5.2 billion. During the past 11 months, more than 6,000 square miles have burned across the state, an area larger than the state of Connecticut.


Comet McNaught shoots over the Pacific Ocean off Chili. Comets are like icy time capsules that may hold clues to our solar system’s evolution, including the source of Earth’s water. Credit: European Southern Observatory.

Water use has been growing at more than twice the rate of population increase during the last century, according to the Food and Agriculture Organization. By 2025, the FAO projects that two-thirds of the world population could be under stress conditions of water scarcity.

Globally, diarrhea is the leading cause of illness and death, and 88 percent of these deaths are due to a lack of sanitation facilities and safe water for drinking and hygiene, according to the United Nations. More than one in six people worldwide don’t have access to safe water.

Environmentalist and author Janisse Ray, on the banks of the Altamaha River. Photo by Carol Clark.

Georgia’s Altamaha River flows 135 miles across the bottom third of the state. Its banks are mostly wetland wilderness, and it is one of the few almost entirely undammed rivers in the United States. Environmentalist Janisse Ray describes the river in her new book Drifting into Darien: “The Altamaha’s size and nature have led it to be called Georgia’s Little Amazon, the most powerful river east of the Mississippi. Despite this distinction, most people remain unaware of it, which prompted Reg Murphy in his National Geographic article to call it 'the river almost nobody knows.'"

Now is a great time of year to paddle the Altamaha.

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Lesson No. 1: Learn to relax

Laura Diamond writes in the Atlanta Journal-Constitution:

About 75 college students sat on yoga mats, taking deep breaths as they contoured their bodies in different positions.

Last week’s yoga class taught Emory University freshmen how to make their bodies stronger and more flexible. Students also learned how yoga could reduce their stress — a crucial lesson as they embarked on their first college midterms all while adjusting to living on their own.

This balance of physical, emotional and spiritual well-being is a cornerstone of Emory University’s new Health 100 course, a requirement for all freshmen.

Several colleges across the country have added programs and requirements in recent years to address students’ physical health and combat the obesity epidemic. But Emory officials have taken a more holistic approach and created a course based on the research they’ve conducted on predictive health, which stresses maintaining good health and preventing disease as opposed to just curing illnesses people already have.

The course abandoned the “do this, don’t do that” mentality found in most health lectures, said Michelle Lampl, director of the Emory Center for the Study of Human Health. “We are not here to admonish or preach to the students,” she said. “We are teaching them a healthier approach to life. They didn’t come here to fill their heads while destroying their bodies.”

Rather than professors lecturing to students, upperclassmen teach the class through small-group discussions. They help the freshmen come up with health goals and give advice on different aspects of college life.

Read the whole article in the AJC.

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