Scholarship & CreativityBirch trees to edge out aspens in warming world
In the coming decades birches will likely drive out many aspens in northern forests as mounting levels of carbon dioxide force the trees to compete more fiercely for soil nutrients, a University researcher and his colleagues have concluded.
Carbon dioxide, emitted when fossil fuels are burned, is a heat-trapping gas blamed for global warming. But rising carbon dioxide levels also have a fertilizing effect on trees and other plants, making them grow faster than they normally would.
At a 38-acre experimental forest in northeastern Wisconsin, U-M microbial ecologist Donald Zak and his colleagues have been pumping extra carbon dioxide into the tree canopies since 1997 to simulate atmospheric conditions expected in the latter half of this century. The forest contains several thousand trembling aspen, paper birch and sugar maple trees.
Mixed aspen-and-birch stands bathed in extra carbon dioxide grow about 45 percent faster than their untreated neighbors. To sustain that speedy growth, the experimental trees had to find a way to extract more of the essential nutrient nitrogen from the soil.
It appears that the extra carbon dioxide (CO2) helps the trees do just that, by allowing them to grow more roots and "forage" more successfully for nitrogen, says Zak, a professor at the School of Natural Resources and Environment and the Department of Ecology and Evolutionary Biology.
The birch trees seem better at nitrogen foraging than aspens, says Zak, one of the lead scientists at the federally funded experiment in Rhinelander, Wis. In mixed stands of aspen and birch subjected to elevated carbon dioxide levels, birch trees increased recent nitrogen acquisition by 68 percent, compared to a 19-percent increase among the aspens.
"The implication from that experiment is that it could alter the abundance of birch and aspen in places like Michigan by favoring birch," Zak says.
The results were published online Aug. 6 in the journal Global Change Biology.
Frog plus frying pan equals better antibiotic
What do you get when you cross a frog with a frying pan? Possibly a solution to the problem of drug-resistant bugs, University research suggests.
By creating Teflon versions of natural antibiotics found in frog skin, a research team led by biological chemist E. Neil Marsh has made the potential drugs better at thwarting bacterial defenses, an improvement that could enhance their effectiveness. Marsh discussed the work Aug. 20 at the 234th national meeting of the American Chemical Society in Boston.
Marsh and collaborators work with compounds called antimicrobial peptides (AMPs), which are produced by virtually all animals, from insects to frogs to humans. AMPs are the immune system's early line of defense, battling microbes at the first places they try to penetrate: skin, mucous membranes and other surfaces. They're copiously produced in injured or infected frog skin, for instance, and the linings of the human respiratory and gastrointestinal tracts also crank out the short proteins in response to invading pathogens. In addition to fighting bacteria, AMPs attack viruses, fungi and even cancer cells, so drugs designed to mimic them could have widespread medical applications.
Marsh had the idea of replacing sticky portions of the peptides with nonstick analogs. His inspiration came from the kitchen as much as the chemistry lab: nonstick cookware is coated with fluorinated polymers, plastic-like compounds composed of chains of carbon atoms completely surrounded by fluorine atoms. The fluorine not only makes Teflon slippery, it also makes the coating inert to almost every known chemical.
When Marsh and co-workers swapped sticky parts of their AMP molecule with nonstick, fluorinated versions, the molecules became much more resistant to proteases.
Next, the researchers plan experiments to learn whether Teflon AMPs are also less toxic than their stickier equivalents. If they are, and if further studies continue to point to their promise, eventually producing large enough quantities of fluorinated AMPs for clinical trials should be quite feasible, Marsh says.
Marsh's collaborators on this project include Ayyalusamy Ramamoorthy, associate professor of chemistry, graduate students Lindsey Gottler and Hyang-Yeol Lee, and Charles Shelburne, an assistant research scientist in the School of Dentistry. The researchers have funding from the American Heart Association and the National Science Foundation.
Small molecule spurs genes to action
Most of us think of disease as the failure of an organ or the breach of some critical fortress in the body's defense system. But for many ailments, including cancer and diabetes, disease begins with an even more fundamental error: the failure of genes to turn on and off when they should.
Hoping to understand and eventually help correct such errors, U-M researcher Anna Mapp and coworkers are developing molecules that mimic natural regulators of gene expression. In their latest work, published online Aug. 11 in the Journal of the American Chemical Society, Mapp's group shows that a small molecule they developed is able to turn on genes in living cells.
Molecules that can prompt genes to be active are called transcriptional activators because they influence transcription the first step in the process through which instructions coded in genes are used to produce proteins. Both natural transcriptional activators and their artificial counterparts typically have two essential parts: a DNA-binding domain that homes in on the specific gene to be regulated, and an activation domain that attaches itself to the cell's machinery and spurs the gene into action.
For Mapp's group, the next step toward that goal is attaching their artificial activation domains to different DNA-binding domains and assessing their function in animal cells. Once they're able to target specific genes, they plan to test their molecules in animal models of diseases such as medulloblastoma, a type of malignant brain tumor that mainly affects children.
"In medulloblastoma, genes that should be turned on, stay turned off," says Mapp, an associate professor of chemistry. "It's been shown in animal models that if you can turn those genes back on, you selectively kill the cancer cells."
Mapp's coauthors on the JACS paper are graduate students Steven Rowe, Ryan Casey, Brian Brennan and Sara Buhrlage. Mapp received funding from the American Cancer Society, the National Science Foundation, the Alfred P. Sloan Foundation, Amgen and GSK. Buhrlage was supported by the Chemistry Biology Interface Training Program.
Neutron stars warp space-time, U-M astronomers observe
Einstein's predicted distortion of space-time occurs around neutron stars, University astronomers and others have observed. Using European and Japanese/NASA X-ray observatory satellites, teams of researchers have pioneered a groundbreaking technique for determining the properties of these ultradense objects.
Neutron stars contain the densest observable matter in the universe. They cram more than a sun's worth of material into a city-sized sphere, meaning a few cups of neutron-star stuff would outweigh Mount Everest. Astronomers use these collapsed stars as natural laboratories to study how tightly matter can be crammed under the most extreme pressures nature can offer.
Researchers who study neutron stars are seeking answers to fundamental physics questions. Their centers could hold exotic particles or states of matter that are impossible to create in a lab.
The first step in addressing these mysteries is to accurately and precisely measure the diameters and masses of neutron stars. A U-M study is one of two that recently have done just that.
Like neutron stars themselves, the region around these stars also is extreme. The motions of gas in this environment are described by Einstein's general theory of relativity. Scientists now are exploiting general relativity to study neutron stars.
Research Fellow Edward Cackett and Assistant Professor Jon Miller are lead authors of a paper that has been submitted to Astrophysical Journal Letters. Independent work reported by Sudip Bhattacharyya and Tod Strohmayer of NASA's Goddard Space Flight Center bolsters the results reported by Cackett and Miller, and together the findings signal that an accessible new method for probing neutron stars has been found.
NASA describes the findings as "a big step forward."
Knowing a neutron star's size and mass allows physicists to describe the "stiffness," or "equation of state," of matter packed inside these incredibly dense objects. Besides using these iron lines to test Einstein's general theory of relativity, astronomers can probe conditions in the inner part of a neutron star's accretion disk.
"Now that we've seen this relativistic iron line around three neutron stars, we have established a new technique," Miller said. "It's very difficult to measure the mass and diameter of a neutron star, so we need several techniques to work together to achieve that goal."
Plain soap as effective as antibacterial without the risk
Antibacterial soap shows no benefit over plain soap and, in fact, may render some common antibiotics less effective, says a University public health professor.
In the first known comprehensive analysis of whether antibacterial soaps work better than plain soaps, Allison Aiello of the School of Public Health and her team found that washing hands with an antibacterial soap was no more effective in preventing infectious illness than plain soap. Moreover, antibacterial soaps at formulations sold to the public do not remove any more bacteria from the hands during washing than plain soaps.
Because of the way the main active ingredient triclosan in many antibacterial soaps reacts in the cells, it may cause some bacteria to become resistant to commonly used drugs such as amoxicillin, the researchers say.
"What we are saying is that these e-coli could survive in the concentrations that we use in our (consumer formulated) antibacterial soaps," Aiello said. "What it means for consumers is that we need to be aware of what's in the products. The soaps containing triclosan used in the community setting are no more effective than plain soap at preventing infectious illness symptoms, as well as reducing bacteria on the hands."
The study "Consumer Antibacterial Soaps: Effective or Just Risky?" appears in the August edition of Clinical Infectious Diseases. The analysis concludes that government regulators should evaluate antibacterial product claims and advertising, and further studies are encouraged.
Hedge fund manager's alma mater matters
Hedge fund investors seeking superior performance are well-advised to select younger, well-educated fund managers who are highly devoted to their jobs, says a University business professor.
The personal, educational and professional characteristics of fund managers greatly impact hedge fund returns, according to a new study by Haitao Li, assistant professor of finance at the Ross School of Business, and colleagues Xiaoyan Zhang of Cornell University and Rui Zhao of Columbia University.
"The performance of a hedge fund depends crucially on both the investment strategies it follows and the talent of its managers in implementing such strategies," Li says. "Just like any entrepreneurial activity, some hedge fund managers are better than others at making investment decisions."
Li and colleagues collected information on the characteristics of the lead manager of about 1,000 funds from 1994 to 2003. The six traits they examined include: the manager's age, years of work experience, the length of tenure at a specific hedge fund, the composite SAT score for the manager's undergraduate university, whether he or she has a CPA or CFA, and whether the manager earned an MBA. Broadly speaking, the SAT, CPA/CFA and MBA characteristics represent intelligence and education. The age, work time and tenure represent working experience and career concern.
Based on their dataset of manager characteristics and various risk-adjustment models, the researchers found that manager education and career concern have a strong impact on different aspects of hedge fund performance, such as fund risk-taking behaviors, raw and risk-adjusted returns and fund flows. Managers from higher-SAT universities tend to take fewer risks and have higher raw and risk-adjusted returns, while younger managers also tend to have higher returns and more inflows, but take more risks.
These results, they say, are consistent with their assumption that more highly educated managers are better at performing their jobs and thus can achieve higher returns at lower risk exposure. The findings also support their contention that younger managers have stronger incentives to work hard at their jobs and to establish their careers. Consequently, they are more willing to take risks and tend to perform better than older, more established fund managers, who take significantly fewer risks.
Wealth gap is increasing, U-M study shows
The rich really are getting richer and the poor are getting poorer, a new University study shows.
The study the most recent available analysis of long-term wealth trends among U.S. households is based on data from the Panel Study of Income Dynamics, conducted by the Institute for Social Research (ISR) since 1968.
Over the last 20 years, the net worth of the top two percentile of American families nearly doubled, from $1,071,000 in 1984 to $2,100,500 in 2005. But the poorest quarter of American families lost ground over the same period, with their 2005 net worth below that of 1984, measured in constant 2005 dollars.
The poorest 10 percent of families actually had a negative net worth more liabilities than assets. The poorest 5 percent of American households had a negative net worth of a little more than $1,000 in 1984, compared to nearly $9,000 in 2005.
"These findings show that the wealth gap is increasing steadily," says Frank Stafford, a senior research scientist at ISR and director of the Panel Study of Income Dynamics, which is funded primarily by the National Science Foundation and the National Institute on Aging.
Stafford and ISR economist Elena Gouskova conducted the analysis of a nationally representative sample of approximately 8,000 families.
From 2003-05, the average net worth of American families increased 12 percent, Stafford and Gouskova found. In constant 2005 dollars, overall average net worth, including home equity, rose from $275,600 to $309,600.
But during that period, the average net worth of black households fell slightly, from $59,900 to $59,500. And the median net worth of households headed by high school dropouts and by younger people, from ages 20-39, also declined.
Overall, the rate of non-collateralized, short-term debt unpaid credit card balances, student loans, and medical or legal bills rose 2 percent during the period. But black families experienced a strong 7 percent increase in the likelihood of having such debt, bringing the proportion carrying such debt to 49.7 percent. In comparison, slightly more than half of all white families (51.8 percent) had this kind of debt. The average amount of short-term debt black families carried was $12,900; for white families, the average amount of debt was $16,800.
"That's a lot of credit card debt to be carrying," Stafford says.
How Air Force women are handling the stress
About 20 percent of Air Force women deployed during the Iraq war report that they are experiencing at least one major symptom of post-traumatic stress disorder (PTSD), according to a University survey of 1,114 servicewomen.
The researchers also assessed the prevalence of family-work conflicts among the military women surveyed, and analyzed the impact of these conflicts on mental health and job functioning.
"We were surprised to find that work-family conflict is an independent and significant predictor of PTSD, above and beyond combat exposure," says Penny Pierce, a colonel in the Air Force Reserve Program, who presented preliminary findings from the survey at the annual meeting of the American Psychological Association. "This finding is important because there are things we can do to help minimize work-family stress and the toll it is taking on women in the military."
Conducted by the Institute for Social Research (ISR) and funded by a grant from the U.S. Department of Defense through the TriService Nursing Research Program, the survey is part of an ongoing study headed by Pierce, an associate professor in the School of Nursing and a faculty associate at ISR, and Research Professor Amiram Vinokur, ISR.
"Since the Gulf War, the role of women in combat has been a subject of heated debate," Pierce says. "This study is the latest attempt to assess the impact of deployment-related stressors, including family separation, on military women, who now comprise 13 percent of our nation's armed forces."
Nearly half of the women surveyed said their home lives rarely or never interfered with their work or made it difficult for them to accomplish daily tasks and spend the time they would like to on career-related activities.
But the researchers found that women who experienced higher levels of family-work conflict were more likely to have symptoms of depression and anxiety, and also were less likely to feel they could cope with daily demands and responsibilities.
A related study of Air Force men that is now underway will establish the levels of wartime stress and of family-work conflict men are experiencing, Pierce notes, as well as its relation to their mental health and ability to perform their jobs.