Inquiring Minds
By Virginia Stuart '75, '80G
Illustrations by Doug Panton

In this issue:

Cooking with Asphalt
Not Just Math
Mission IPM-possible

Cooking with Asphalt

From a distance, it looks as though two chefs in white coats are beating a very dark, very lumpy chocolate batter. But there's something wrong with this picture. One of the chefs is holding a blow torch to the bottom of the mixing bowl. Next they push the mixture into a large aluminum sheet-cake pan, using an industrial-size spatula, and pop it into an oven.

A closer sniff reveals that civil engineering students Kim Zienkiewicz '05 and Nicholas Pulire '05 are actually cooking up a batch of asphalt concrete using a classic New Hampshire recipe that calls for asphalt mixed with stone in 17 different sizes ranging from three-quarters of an inch in diameter to 74 microns (a dust as fine as flour).

After the mixture is aged in the oven, it is poured into a compactor, cooled and extruded into a solid cylinder, creating a striking mosaic of light gray stone set in black. Later, the students will test its density. They will also get to engage in that most popular of civil-engineering pastimes, smashing—er, strength-testing—the cylinders in a machine called the Giant Instron.

The students are working with UNH assistant professor of civil engineering Jo Sias Daniel '94, who performs asphalt research ranging from the concrete, literally, to the abstract. But even her most theoretical project could ultimately contribute to the development of more durable pavements. With a $400,000 grant from the National Science Foundation, she is working out mathematical formulas that will enable engineers to correlate tests on pavement samples in different geometrical shapes. The grant is a prestigious national Career Award for promising young researchers.

No matter how you slice it, asphalt is a complex material. It is a viscoelastic substance, which means that its behavior varies with both temperature and time. Daniel demonstrates this concept by rolling Silly Putty into a ball and bouncing it hard. The ball instantly returns to its original shape. Light pressure from her thumb applied over a longer period of seconds, however, deforms the ball to the extent that it cannot spontaneously recover. Tractor-trailer rigs weighing 40 tons each may pass over a stretch of asphalt concrete repeatedly without causing "permanent deformation," in civil-engineering terms. But when those same trucks stand in one place at a traffic light or toll booth for longer periods of time, the asphalt can not recover. Ruts form.

Asphalt concrete is also consistently inconsistent in its makeup, even when manufacturers follow the same recipe and get their materials from the same source. "Although the asphalt may be graded the same way, chemical interactions between granite and limestone aggregates can lead to completely different behavior in five years," notes Daniel.

One thing that is predictable is the vulnerability of joints between lanes on interstate highways. When a second lane of hot asphalt is laid against the now-cold edge of a previously paved lane, the two edges often fail to bind well, leaving the joint vulnerable to water intrusion and the freezing and thawing cycles that create cracks. Daniel and her students have been helping the N.H. Department of Transportation test an infrared heater that warms the cold edge just before the second lane is laid down. For the past two summers they have been testing the permeability of joints created with the heater on Interstate 93.

From the preliminary results, it looks as though preheating the cold edge to 350 degrees may prove a winning recipe for New Hampshire roads.

Not Just Math

Dinner conversation tended toward the mathematical in the household where Karen Conway grew up. She loved it when her physicist father would throw out problems to solve over supper. "Math always came easily to me," she recalls, "but I never liked just math."

Now an economist at the Whittemore School of Business and Economics, Conway works with statistics, mathematical formulas and terms like "labor supply"—abstractions that are very much rooted in everyday life. Conway sees many day-to-day household decisions through the lens of economics. Paying for prenatal care is an "investment" in the health of an unborn child, and helping a child with homework is an "investment" of time and effort in that child's education. Even her 4-year-old's decision to spend $4 on Pokémon cards instead of football stickers, she explains to her Principles of Economics class, demonstrates a kind of cost-benefit analysis.

In her research, Conway poses questions about the decisions people make. When schools invest more in the education of students, do parents choose to invest less in terms of time, effort and money? Do states compete with each other to attract retirees by eliminating so-called death taxes? Do retirees respond by moving to such states? Her answers (yes, yes and no, respectively) come from a technique called "econometrics," the use of mathematical models to look for cause-and-effect relationships between variables.

Conway also conducts research that could be useful for policymakers. Is spending on prenatal care a wise investment? Although it has widely been promoted as beneficial, some studies have cast doubt on the idea that prenatal care reduces the incidence of premature birth and low birthweight.

Conway and her collaborator, Partha Deb of Hunter College in New York City, believe they are the first economists to find a plausible explanation for this conundrum, which has been discussed in medical journals. Among the relatively small percentage of pregnancies considered "troubled" from the start, the researchers found, there was surprisingly little benefit from prenatal care. Even cessation of smoking and drinking didn't seem to help.

When these pregnancies are accounted for, however, the relationship between prenatal care and a positive outcome in terms of birthweight is clear: For every week earlier that a mother gets to the doctor in a normal pregnancy, there is an average 30-gram increase in birthweight.

Conway and Deb intend to take this research further by studying the expansion of Medicaid benefits, which, at first glance, also appears to have failed to reduce the incidence of low birthweight. Conway hopes their work may ultimately help doctors figure out better ways to tailor prenatal care to mothers in that difficult group of troubled pregnancies. For her, that would be the best possible way to make use of her mathematical abilities—"solving problems I care about."

Mission IPM-possible

In New England, virtually every unprotected apple tree is attacked by a tiny weevil called the plum curculio, which causes most of the fruit to drop off in June. Plus there are mites, scales, worms, bugs, caterpillars, moths, mildews, rusts and rots to contend with. Twenty-five years ago, growers responded to this biological onslaught by spraying, often. "We used to spray religiously every 5 to 7 days for apple scab, and if we got a big rainstorm overnight, we'd spray again the next day," recalls Chip Hardy '74, a fifth-generation apple grower in Hollis, N.H.

Enter Alan Eaton, who joined UNH Cooperative Extension in 1978. In graduate school, he had acquired a doctorate in entomology but no experience with apples and their pests. Yet he chose to accept a seemingly impossible mission: to convince apple growers and other farmers in New Hampshire to reduce their dependence on chemical sprays and try an approach now known as Integrated Pest Management (IPM).

Eaton's first task as IPM coordinator was to convince three apple growers to try the new technique on a small subplot of their orchards for one season. Since he was, in effect, asking them to risk $15,000 to $20,000 worth of crop for the sake of saving a few hundred dollars in spray, he was not surprised that many were hesitant. But Eaton did find three growers who were willing to count mites and maggots and keep track of temperature and rainfall. Spray was to be applied only when pests reached a certain threshold. Eaton, plant pathologist Bill MacHardy and several graduate students also helped the growers make use of genetics, biological controls and physical barriers. The combined approach prevents the development of resistant pests, Eaton explains, because "they aren't able to evolve in four directions simultaneously."

To their amazement, the growers saved more than 50 percent in spraying costs on the trial plots. Since then, UNH extension scientists have never lacked for growers eager to learn the latest information on pest life cycles and control methods. Growers can now base their decision to spray for apple scab not on the calendar but on the number of "degrees days" and hours of leaf wetness required for the fungus to release its spores. Eaton estimates growers are spraying 30 to 40 percent less on apple scab alone.

In a report on the IPM program's impact over the past 25 years, Eaton found that New Hampshire apple growers have saved more than $7 million in spraying costs while improving the quality of their product. (IPM has also been applied to other crops in the state, including sweet corn, blueberries, potatoes, poinsettias, bedding plants and strawberries.) Other benefits include a reduction in pesticide exposure and ground- and surface-water contamination, and an increase in the population of beneficial insects.

In fact, Eaton has introduced three parasitic insects that eat apple pests, including a wasp that attacks the European sawfly and "would rather die" than eat anything else. Once established, the wasp will continue to partially control the sawfly all on its own, says Eaton. "And from now until the next ice age," he adds, "everyone will benefit from growers' spraying less."

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