In this issue:Virtual Tests
Can you reduce something as complicated as human lungs to some partial differential equations and lines of computer code? The answer, according to associate professor of mechanical engineering Greg Chini and his student William Matern '12, is maybe. And they're working on it.
Predicting how the tiny air sacs in lungs known as alveoli change in response to treatment could give doctors a better handle on the biggest health problem facing premature infants: collapsed lungs, also known as chronic lung disease. Internal surface tension keeps their lungs from inflating at birth, and while they can be treated with a substance called surfactant, a lack of understanding about the underlying mechanics limits doctors' ability to fine-tune the treatment. "If we could solve these equations, we would, for example, be able to predict how alveoli deform in response to some imposed displacement, and we would be able to predict their behavior," says Chini.
Chini's and Matern's work is an example of mathematical modeling, a tool of great power in engineering and physics that is increasingly being taken up in biological and medical science. Models are mathematical formulas that reflect various rules of nature—the inverse-square law, perhaps, or pressure-volume curves—that are supplemented with empirical data about the problem in question. This kind of work is sometimes called an "in silico" experiment, the digital equivalent of "in vitro" experiments done in petri dishes rather than on live subjects. "In silico experiments can be detailed and cheap alternatives to traditional lab experiments," Matern says. For medicine, they're especially useful: You can't, after all, apply different types of surfactant to babies' lungs and then operate to see how the alveoli reacted.
Given enough insight and effort, the result can be astonishing—modern airplanes are largely designed by mathematical modeling. Medicine is seeking similar breakthroughs. "There is a whole spectrum of mathematical models being developed, from the very detailed and specific to the general and overarching," says Chini. "This is an exciting time: coupling mathematical representations of biological systems with mechanical responses, seeking new understanding."
In medicine, there's still a long way to go before a mathematical model could, for example, dispense the right type and amount of surfactant in return for information about breathing patterns. The goal now, Chini says, is to "try to develop a conceptual understanding of the mechanisms regarding collapse and reinflation of alveoli."
Although Matern is heading to graduate school in biomedical engineering at Johns Hopkins in the fall, he's interested in continuing to pursue the research. "Will has had a really good idea that we're going to try," says Chini. "He has the ability to step back and take another tack or angle. That's something you need to be able to do as a researcher, but it's hard to teach how."
When doctoral candidate Rick Trinkner '12G published a research paper about the effects of different parenting styles on children's behavior, he should have known he would hear from two particularly interested readers. "Both of my folks have asked me what kind of parent they were," he admits.
Trinkner is the lead author of "Don't Trust Anyone Over 30," which has the sober subtitle "Parental legitimacy as a mediator between parenting style and changes in delinquent behavior." Published in the Journal of Adolescence, the study uses data from the New Hampshire Youth Survey, a seven-year longitudinal survey of middle- and high-school students in southeastern New Hampshire.
Trinkner and his coauthors (Ellen Cohn, professor of psychology; Cesar Rebellon, associate professor of sociology; and Karen Van Gundy, associate professor of sociology) examined students' answers about parental legitimacy and delinquent behavior from 2007 through 2009 to see if there were any correlations to behavior. He was particularly interested in three parenting styles known to social scientists as "authoritarian," "authoritative" and "permissive." Authoritarian parents value discipline over empathy and warmth, while authoritative value warmth over discipline. Permissive parents don't value discipline much at all.
Analysis of the survey data found that students who reported having "it's my way or the highway" authoritarian parents also reported more delinquent behavior. On the other hand, students who reported having authoritative parents—those most likely to discuss the rules with their children—reported much less delinquent behavior. This conclusion has generated some controversy.
"Some people have asked me, 'Are you saying you're supposed to let your kids run amok?'" says Trinkner. "No, the research says you can keep your standards—just let your kids express how they're feeling, talk with them about it. We all like to express our feelings, and we feel better if we're allowed to speak out, even if it doesn't change anything."
As evidence, consider that the study found no correlation between permissive parenting and delinquent behavior. Kids' behavior, it seems, is improved not by having fewer rules but by having more discussion about those rules. "It seems like there's this balance, this line that you really have to walk," he says. "A lot of times it seems to come down to talking with the child while still setting standards of behavior."
Trinkner, who is 29 with a 10-year-old stepdaughter, decided to study parental authority not to weigh in about how to parent but because he's "really always been interested in how individuals interact with authority figures and how that interaction influences their behavior." He notes that many people are a mix of parenting styles, often depending on circumstance. Everybody is authoritarian when it comes to children running across a busy road, for example. He also cautions that the small number of minorities—20 percent—in the survey means the results cannot be extrapolated to nonwhite families.
And what about that pair of really interested readers? For the most part, Trinkner's mother was authoritative, leaning toward permissive, while his father tended toward authoritarian, says Trinkner. "When I was violating curfew, I definitely wanted to go to Mom."
Considering that she spends a lot of her research time in the woods, Serita Frey has a surprising admission: "I'm not very good at identifying trees." But there's a reason. "I'm always looking down. I always want to see what's popping out of the ground."
These days, Frey, a professor of soil microbial ecology, isn't always happy with what she sees. Years of research dating back to her own undergraduate days, fueled by experiments at plots around UNH and long-term measurements at the Harvard Forest research site in Petersham, Mass., have shown her that humans are altering a vital, nearly invisible part of the ecosystem: microbes, including fungi, in the soil. Figuring out the extent of the damage is a huge and important project.
"We are very concerned about understanding what these organisms are doing in response to global change and different human activities," she says, "such as global warming, invasive species, biodiversity loss and nitrogen deposition."
Do microbes really matter? Yes, says Frey, because they operate like the microbes in the human gut—without them, there's no digestion, so to speak. "They are responsible for all of the decomposition that occurs in an ecosystem—leaf litter decay, decomposition of dead animal remains, dead wood," she says. This recycling of nutrients, making them available to new growth, is vital to the health of the trees and underbrush. And many trees, pine trees in particular, require certain types of fungus living on their roots to be able to draw the nutrients out of the soil. No fungus, no food—and eventually, no tree.
While there are many culprits responsible for this unsettling change, Frey points in particular to nitrogen produced by coal- and gas-fired power plants and auto emissions, as well as other forms of pollution. "Fossil-fuel combustion puts nitrogen into the atmosphere, and it comes down in rain or snow, effectively acting as a fertilizer," she says. "Our forests are historically very nitrogen-limited ... so these ecosystems are not adapted for high levels of nitrogen." Decomposition by fungi slows down appreciably with excess nitrogen, she says. "They decline in numbers and abundance, and their activity goes down." The phenomenon used to be called acid rain, she says, but the situation is broader than just pH levels. "New England has some of the highest levels of nitrogen deposition in U.S., and it's only expected to increase."
Pinpointing the extent of the problem and the methods to attack it are critical. Aside from the long-term forest study, she is subjecting small swaths of forest to excess nitrogen, heat and other factors over a period of years to see what happens. "There are a lot of different things going on, some positive, some negative. Some species may thrive under wetter, warmer nitrogen-rich conditions; are they the ones that are important for decomposition? We don't know." ~
blog comments powered by Disqus