October 15, 2013, Volume 60, No. 9
Parents’ TV Viewing Habits Influence Kids’ Screen Time
The amount of time that children and teens spend watching television may have more to do with their parents’ TV habits than with family media rules or the location of TVs within the home, according to a study in the August 2013 issue of Pediatrics, “The Relationship Between Parents’ and Children’s Television Viewing.” As part of the Annenberg Media Environment Study, the researchers—Annenburg Public Policy Center’s Dr. Amy Bleakley, Dr. Amy Jordan and Dr. Michael Hennessy—interviewed 1,550 parents with children 17 years old or younger. They asked about the amount of time parents spent watching TV, DVDs or movies and shows on their computers, as well as the number of TVs in the home, which rooms the TVs were in, and how many rooms had computers with Internet access. They also asked about their children’s screen time as well as family rules about the amount of time spent on TV.
On average, parents spent four hours per day watching television, and those who watched more also had children who watched more. Parents’ time restrictions for their children around TV viewing only resulted in reduced screen time for the children in the 6- to 11-year-old age group. Many parents gave permission for their adolescent children to complete a survey about their TV viewing as part of the study, and these adolescents reported their daily average amount of screen time was nearly an hour more than their parents had estimated. The researchers found that parents’ TV viewing time had a stronger connection to children’s viewing time than did other factors such as rules about time limits, whether the children had a TV in the bedroom and co-viewing. Each hour of parental TV time resulted in almost an additional half hour of viewing time for their children. The authors conclude that this information is useful for education efforts about screen time and reinforces the American Academy of Pediatrics recommendation that “parents should be good media role models.”
New Method for Harvesting Energy from Light
Researchers from the University of Pennsylvania have demonstrated a new mechanism for extracting energy from light, a finding that could improve technologies for generating electricity from solar energy and lead to more efficient optoelectronic devices used in communications. The study was published in the journal ACS Nano.
Dr. Dawn Bonnell, Vice Provost for Research and Trustee Professor of Materials Science and Engineering in the School of Engineering & Applied Science, led the work, along with David Conklin, a doctoral student. The study involved a collaboration among additional Penn researchers, through the Nano/Bio Interface Center, as well as a partnership with the lab of Dr. Michael J. Therien of Duke University.
The new work centers on plasmonic nanostructures, specifically, materials fabricated from gold particles and light-sensitive molecules of porphyin, of precise sizes and arranged in specific patterns. Plasmons, or a collective oscillation of electrons, can be excited in these systems by optical radiation and induce an electrical current that can move in a pattern determined by the size and layout of the gold particles, as well as the electrical properties of the surrounding environment.
Because these materials can enhance the scatte ring of light, they have the potential to be used to advantage in a range of technological applications, such as increasing absorption in solar cells.
In 2010, Dr. Bonnell and colleagues published a paper in ACS Nano reporting the fabrication of a plasmonic nanostructure, which induced and projected an electrical current across molecules. In some cases they designed the material, an array of gold nanoparticles, using a technique Dr. Bonnell’s group invented, known as ferroelectric nanolithography.
The discovery was potentially powerful, but the scientists couldn’t prove that the improved transduction of optical radiation to an electrical current was due to the “hot electrons” produced by the excited plasmons. Other possibilities included that the porphyin molecule itself was excited or that the electric field could focus the incoming light.
“We hypothesized that, when plasmons are excited to a high energy state, we should be able to harvest the electrons out of the material,” Dr. Bonnell said. “If we could do that, we could use them for molecular electronics device applications, such as circuit components or solar energy extraction.”
To examine the mechanism of the plasmon-induced current, the researchers systematically varied the different components of the plasmonic nanostructure, changing the size of the gold nanoparticles, the size of the porphyin molecules and the spacing of those components. They designed specific structures that ruled out the other possibilities so that the only contribution to enhanced photocurrent could be from the hot electrons harvested from the plasmons.
“In our measurements, compared to conventional photoexcitation, we saw increases of three to 10 times in the efficiency of our process,” Dr. Bonnell said. “And we didn’t even optimize the system. In principle you can envision huge increases in efficiency.”
Devices incorporating this process of harvesting plasmon-induced hot electrons could be customized for different applications by changing the size and spacing of nanoparticles, which would alter the wavelength of light to which the plasmon responds.
“You could imagine having a paint on your laptop that acted like a solar cell to power it using only sunlight,” Dr. Bonnell said. “These materials could also improve communications devices, becoming part of efficient molecular circuits.”
Major Cities, Often the Safest Places in the US
Overturning a commonly-held belief that cities are inherently more dangerous than suburban and rural communities, researchers from the Perelman School of Medicine and The Children’s Hospital of Philadelphia (CHOP) have found that risk of death from injuries is lowest on average in urban counties compared to suburban and rural counties across the US. The study, which appears in the Annals of Emergency Medicine, found that for the entire population, as well as for most age subgroups, the top three causes of death were motor vehicle collisions, firearms and poisoning. When all types of fatal injuries are considered together, risk of injury-related death was approximately 20 percent lower in urban areas than in the most rural areas of the country.
“Perceptions have long existed that cities were innately more dangerous than areas outside of cities, but our study shows this is not the case,” said lead study author, Dr. Sage R. Myers, assistant professor of pediatrics, Perelman School of Medicine and attending physician, department of emergency medicine at CHOP. “These findings may lead people who are considering leaving cities for non-urban areas due to safety concerns to re-examine their motivations for moving. And we hope the findings could also lead us to re-evaluate our rural health care system and more appropriately equip it to both prevent and treat the health threats that actually exist.”
The study examined county-level data on all injury deaths across the US from 1999-2006 (because of their unusual nature, deaths from the 9-11 terrorist attacks were excluded).
Findings from the study support prior work showing that overall homicide rates are lower in rural areas than urban areas. This was found to be true in all age groups, except the oldest adults (over 65 years old). Suicide rates, on the other hand, showed an increase with rurality, but the increased rate of suicide death in rural areas only reached statistical significance for the two youngest age groups: 0-14 years and 15-19 years.
However, the magnitude of homicide- and suicide-related deaths, even in urban areas, is far outweighed by the magnitude of unintentional-injury deaths—such as those from car crashes and falls—in nonurban areas, especially in rural nonurban areas. Specifically, the rate of unintentional-injury death is over 15 times that of homicide for the entire population and the risk of unintentional-injury death is 40 percent higher in the nation’s most rural counties compared to the most urban.
The research team found that the bulk of unintentional injury deaths result from motor vehicle crashes, with motor vehicle injury-related deaths occurring at a rate that is more than 1.4 times higher than the next leading mechanism of injury death. In rural areas, this difference is even more pronounced, where motor vehicle injury-related death rates are twice that of the next leading injury mechanism. Across the rural-urban continuum, the risk of motor vehicle-related injury death is two times more likely in rural areas as compared to the most urban.
“We think our work serves as a reminder that injury is an important health issue for Americans, wherever they live. Our findings can inform both targeted prevention efforts and strategic efforts to improve trauma care in the US. This work provides a real opportunity to build systems of medical care that are positioned to best care for the populations that depend upon them for life and limb saving treatment in their time of need,” said senior study author Dr. Brendan G. Carr, assistant professor of emergency medicine and biostatistics and epidemiology.
The researchers note that next steps in this line of research should focus on creating local injury priority scores—a relatively simple and objective tool that uses data available in trauma center registries to rank injury causes according to both frequency and severity—and considering innovative ways to continue to develop the US emergency and trauma care system to assure that all Americans receive the best emergency and trauma care possible. “Trauma has been a leader in planning for care from the population perspective,” said Dr. Carr, referencing the interactive trauma system mapping tool created at Penn, “but we’ve still got work to do.”