Smartphone making your eyes tired? Images placed in front of the screen increase visual discomfort

ScienceDaily (July 22, 2011) — Several reports indicate that prolonged viewing of mobile devices and other stereo 3D devices leads to visual discomfort, fatigue and even headaches. According to a new Journal of Vision study, the root cause may be the demand on our eyes to focus on the screen and simultaneously adjust to the distance of the content.See Also:Health & MedicineEye CarePain ControlMatter & EnergyOpticsEngineeringComputers & MathMobile ComputingComputer ProgrammingReferenceSound effectComputer animationEye examinationHyperopia

Scientifically referred to as vergence-accommodation, this conflict and its effect on viewers of stereo 3D displays are detailed in a recent Journal of Vision article, The Zone of Comfort: Predicting Visual Discomfort with Stereo Displays.

"When watching stereo 3D displays, the eyes must focus -- that is, accommodate -- to the distance of the screen because that's where the light comes from. At the same time, the eyes must converge to the distance of the stereo content, which may be in front of or behind the screen," explains author Martin S. Banks, professor of optometry and vision science, University of California, Berkeley.

Through a series of experiments on 24 adults, the research team observed the interaction between the viewing distance and the direction of the conflict, examining whether placing the content in front of or behind the screen affects viewer discomfort. The results demonstrated that with devices like mobile phones and desktop displays that are viewed at a short distance, stereo content placed in front of the screen -- appearing closer to the viewer and into the space of viewer's room -- was less comfortable than content placed behind the screen. Conversely, when viewing at a longer distance such as a movie theater screen, stereo content placed behind the screen -- appearing as though the viewer is looking through a window scene behind the screen -- was less comfortable.

"Discomfort associated with viewing Stereo 3D is a major problem that may limit the use of technology," says Banks. "We hope that our findings will inspire more research in this area."

The team of investigators suggests future studies focus on a larger sample in order to develop population-based statistics that include children. With the explosion of stereo 3D imagery in entertainment, communication and medical technology, the authors also propose guidelines be established for the range of disparities presented on such displays and the positioning of viewers relative to the display.

"This is an area of research where basic science meets application and we hope that the science can proceed quickly enough to keep up with the increasingly widespread use of the technology," adds Banks.

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Warming climate likely to dramatically increase Yellowstone fires by mid-century

ScienceDaily (July 25, 2011) — Climate is changing fire patterns in the west in a way that could markedly change the face of Yellowstone National Park, according to new research.See Also:Plants & AnimalsEcology ResearchNatureTreesEarth & ClimateWildfiresClimateGlobal WarmingReferenceConsensus of scientists regarding global warmingEcosystemWildfireEcological succession

A study published online the week of July 25 in the Proceedings of the National Academy of Sciences shows that climate change could increase the frequency of large fires in the Greater Yellowstone Ecosystem to a point that sparks dramatic shifts in the forest vegetation, from conifer-dominated mature forests to younger stands and more open vegetation.

"Large, severe fires are normal for this ecosystem. It has burned this way about every few hundred years for thousands of years," explains study author Monica Turner, the Eugene P. Odum Professor of Ecology at the University of Wisconsin-Madison and a landscape ecologist who has worked in the Greater Yellowstone area for more than 20 years. "But if the current relationship between climate and large fires holds true, a warming climate will drive more frequent large fires in the Greater Yellowstone Ecosystem in the future."

Wildfires in this ecosystem are climate-driven and are primed by hotter, drier conditions, such as those predicted by numerous global climate models.

Already fire ecologists have noticed increased fire frequency in the west, associated with temperature increases of less than two degrees Fahrenheit and early spring snowmelt in the mountains.

For the new study, the researchers analyzed large wildfires (greater than 500 acres) and climate data in the northern Rocky Mountains from 1972 to 1999, then used these observed relationships with global climate models to project how expected climate change will impact fires during the 21st century.

"What surprised us about our results was the speed and scale of the projected changes in fire in Greater Yellowstone," says lead author Anthony Westerling, a professor of environmental engineering and geography at the University of California, Merced. "We expected fire to increase with increased temperatures, but we did not expect it to increase so much or so quickly. We were also surprised by how consistent the changes were across different climate projections."

They found that fires larger than 500 acres will likely be an annual occurrence by 2050, with fire rotation -- the time span over which the entire landscape burns -- reduced from a historic range of 100 to 300 years to less than 30 years. Interestingly, the predicted new fire regime closely resembles patterns typical of other landscapes, such as the ponderosa pine forests of the southwest.

"More frequent fires will not be catastrophic to the area -- Yellowstone will not be destroyed -- but they will undoubtedly lead to major shifts in the vegetation," says Turner. "It is critical to keep monitoring these forests and study how they respond to future fires."

For example, the iconic lodgepole pines that dominate much of the current landscape may not have time to recover between big fires, especially if hot, dry summers make it difficult for tree seedlings to germinate and grow following future fires. Some forests could shift toward fast-growing aspen and Douglas fir, or even shrubs and grassland. Such changes would also affect the region's wildlife, hydrology, carbon storage, and aesthetics.

Westerling, an expert on climate-fire interactions, cautions that the models used in the study will not work once the increase in fires creates a fundamental change in the ecosystem. As the landscape changes, the relationships between climate and fire will change as well.

"The biggest challenge for us is to understand what can happen when the ecosystem is transformed," he says. "Our projections also depend on the climate models we are using -- for example, if projections for winter snow pack or summer rainfall were to increase significantly, that would change our results."

With more frequent fires, available fuels will also dwindle and eventually become important than climate in limiting fires. At that point, existing models will break down, leaving future outcomes even more unpredictable, Turner says -- large fires could even become less severe in the future, making it an important topic for continued study.

"Our research after the immense 1988 fires revealed surprises and tremendous resilience in Yellowstone's ecosystems, and Yellowstone is likely to surprise us again in the future," Turner says. "It is an incredibly valuable natural laboratory for studying how natural ecosystems adapt to changing environmental conditions."

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Cancer-causing mineral found in U.S. road gravel: Erionite in roads may increase risk of mesothelioma

ScienceDaily (July 25, 2011) — As school buses drive down the gravel roads in Dunn County, North Dakota, they stir up more than dirt. The clouds of dust left in their wake contain such high levels of the mineral erionite that those who breathe in the air every day are at an increased risk of developing mesothelioma, a type of cancer of the membranes around the lungs, new research shows. Erionite is a natural mineral fiber that shares similar physical similarities with asbestos. When it's disturbed by human activity, fibers can become airborne and lodge themselves in people's lungs. Over time, the embedded fibers can make cells of the lung grow abnormally, leading to mesothelioma, a form of lung cancer most often associated with the related mineral asbestos.See Also:Health & MedicineMesotheliomaLung CancerDiseases and ConditionsMatter & EnergyWeapons TechnologyFossil FuelsEnergy PolicyReferenceAsbestosMesotheliomaCarcinogenIndoor air quality

Michele Carbone, M.D., Ph.D., director of the University of Hawaii Cancer Center in Honolulu, has previously linked erionite exposure in some Turkish villages to unusually high rates of mesothelioma. Recently, he and colleagues turned their attention to potential erionite exposure in the U.S., where at least 12 states have erionite-containing rock deposits. His research team -- which includes scientists from the National Institute of Environmental Health Sciences, Environmental Protection Agency, New York University, University of Chicago, University of Iowa, and University of Hacettepe -- focused their efforts on Dunn County, North Dakota, when they learned that rocks containing erionite have been used to produce gravel for the past 30 years. More than 300 miles of roads are now paved with the gravel.

The new study, reported in the July 25, 2011 issue of Proceedings of the National Academy of Sciences (PNAS) is the first to look at the potential hazards associated with erionite exposure in the U.S.

The scientists compared the erionite in North Dakota to erionite from the Turkish villages with high mesothelioma rates. They measured airborne concentrations of the mineral in various settings, studied its chemical composition, and analyzed its biological activity. When mice were injected with the erionite from Dunn County, their lungs showed signs of inflammation and abnormal cell growth, precursors to mesothelioma. Under the microscope, the fiber size of the erionite from North Dakota was similar to that of the Turkish erionite. Overall, the researchers found no chemical differences between the North Dakota erionite and samples of the cancer-causing mineral from Turkey. The airborne levels of erionite in North Dakota were comparable to levels found in Turkish villages with 6-8 percent mortality rates from mesothelioma, the researchers reported.

"Based on the similarity between the erionite from the two sources," says Carbone, "there is concern for increased risk of mesothelioma in North Dakota." The long latency period of the disease -- it can take 30 to 60 years of exposure to cause mesothelioma -- and the fact that many erionite deposits have only been mined in the past few decades suggests that the number of cases could soon be on the rise. In addition to North Dakota, California, Oregon, Arizona, Nevada and other states have erionite deposit, but the possibility of human exposure elsewhere in the U.S. has not yet been investigated.

In contrast to asbestos, which causes mesothelioma at lower rates, there are no established health benchmarks in the U.S. on safe levels of erionite exposure, because until recently, physicians thought that erionate was present only in Turkey. The new findings, however, indicate that precautionary measures should be put in place to reduce exposure to the mineral, says Carbone. In Turkey, his earlier findings led to moving villagers away from areas with high levels of erionite, into new housing built out of erionite-free materials. "Our findings provide an opportunity to implement novel preventive and detection programs in the U.S. similar to what we have been doing in Turkey," he says. Future studies could analyze erionite levels in other areas of the U.S. and develop strategies to prevent and screen for mesothelioma. The study was funded through grants from the National Cancer Institute and the 2008 AACR-Landon Innovator Award for International Collaboration in Cancer Research to Michele Carbone.

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