Category Archives: Biological physics

Human brain compensates for age-related color vision loss

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Daily Mail: As humans age, the eye’s ability to distinguish colors diminishes. However, the effect goes almost unnoticed because of the brain’s ability to compensate for the loss. In a study published this week in the journal PLOS ONE, Sophie Wuerger of the University of Liverpool in the UK and colleagues looked at 185 people between the ages of 18 and 75, all of whom had normal color vision. They found that despite age-related yellowing of the lens of the eye, neural pathways in the brain are able to adjust so that people’s perceptions of color remain fairly constant over their lifetime.

“Squeezed light” used to monitor molecules inside living cells

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MIT Technology Review: A lot of internal cellular activity occurs at subnanometer scales. Such activity is hard to view with conventional imaging techniques because of diffraction, or the way that light shone on an object is deflected as it strikes tiny particles in the object. The amount of diffraction depends on a phenomenon called quantum noise—uncertainties concerning the light photons’ positions. A new technique developed by Michael Taylor of the University of Queensland, Australia, and his colleagues uses “squeezed light”—carefully manipulated photons that reduce the amount of quantum noise. The researchers were able to attain a resolution of 10 nm, a 14% improvement over conventional imaging. The technique has allowed them to monitor the motions and interactions of nanoparticles inside a living cell. By monitoring multiple areas throughout the cell, they were able to create a map of nanoparticle diffusion patterns. And because of the lower diffraction rate, they were also able to image the cell to the same resolution as conventional techniques but at much lower light intensity, and therefore less risk of damage to the cell.

Moth claims title for best high-frequency hearing

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BBC: The greater wax moth has been shown in a recent study to be able to detect some sounds with frequencies up to 300 kHz. In comparison, humans top out at 20 kHz and dolphins, which can communicate in ultrasound, at 160 kHz. The study was led by James Windmill of Strathclyde University in Glasgow, Scotland, who says the moths may have evolved the capability as a defensive response to predatory bats, which employ ultrasound to communicate. Ultrasound waves degrade quickly when traveling through air, so a better understanding of how moths utilize the frequencies might help Windmill ‘s team and other scientists in the development of microacoustic devices such as miniature microphones.

 

Sensor uses carbon nanotubes to test saliva for glucose

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MIT Technology Review: A new way to test people’s glucose levels should make that process less painful for people with type 2 diabetes. Current tests rely on blood samples drawn from finger pricks. Now Mitchell Lerner of the University of Pennsylvania in Philadelphia and colleagues have developed a carbon nanotube–based transistor that can detect glucose levels in a variety of body fluids, including saliva. The nanotubes are coated with molecules of pyrene-1-boronic acid, which makes then highly sensitive for glucose detection. When exposed to glucose, the nanotube transistor’s current-voltage curve changes, and that change can be measured to indicate the glucose concentration. Although the technology has been around for a while, what the research team did was find a way to make the tubes quickly and cheaply. The system is less useful for type 1 patients, who have to give themselves daily injections of insulin. Because it takes at least 30 minutes for the glucose to show up in saliva, the device cannot quickly give an accurate reading of the blood glucose levels.

Size and structure of children’s brains can affect the way they learn

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Science News: The size of the hippocampus, the brain region associated with learning and memory, can be important in how fast children learn math skills, according to a recent study published in the Proceedings of the National Academy of Sciences. For their study, Vinod Menon of Stanford University and colleagues focused on children in the third grade, because that is considered a critical age for the learning of basic arithmetic skills. They tested IQ and math and reading performance in 24 8- and 9-year-olds and took MRI scans of their brains. All the children then underwent eight weeks of one-on-one math tutoring. The researchers noticed that “the speed and accuracy of arithmetic problem solving increased with tutoring, with some children improving significantly more than others.” Although neither IQ nor measured mathematical ability appeared to predict how a child would perform, those with the largest hippocampuses showed the most improvement. The researchers hope the findings will help educators tailor math tutoring to individual children as opposed to the one-size-fits-all approach currently in use.

New standards recommended for tar sands oil pipelines

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NPR: The US Environmental Protection Agency (EPA) is recommending new standards for the proposed Keystone XL pipeline project, which would carry tar sands oil from Alberta, Canada, to the US. Because of the 2010 Enbridge spill in Michigan’s Kalamazoo River, which is still being cleaned up, the EPA has determined that a tar sands oil spill can be more harmful than a conventional oil spill and may require different methods and equipment to clean up. From that spill, the agency learned that tar sands oil tends to sink to the bottom of bodies of water and doesn’t biodegrade. Because the oil is also much stickier than either conventional crude or refined oil, it is nearly impossible to clean from surfaces such as rocks. In addition, to ease the flow of the tar sands oil through the pipeline, benzene or other petroleum-based products are added, which during a spill can be slowly released back into the environment and pose a hazard. TransCanada, the company that will build the Keystone pipeline, says it has already included 57 new safeguards. However, Stephen Hamilton of Michigan State University points out that even with safeguards in place to protect against a potential spill, the production of tar sands oil remains a huge environmental risk because of the greater amount of greenhouse gases emitted in its production compared with that of conventional oil.

Global warming will cause shifts in regional climates and ecosystems

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Nature: The rate of change in Earth’s climate zones will increase with rising global temperature, according to a study published online this week in Nature. Irina Mahlstein of the University of Colorado Boulder and colleagues are the first to analyze the pace of climate change in reference to Earth’s various climate zones. The researchers used global mean temperature and precipitation data to run several different climate-modeling scenarios. In one model, the pace of shifting climate zones nearly doubled by the end of the century and affected 20% of all land area. If that were to occur, Earth would become progressively warmer and drier. As a result, plant and animal species would have increasingly less time to adapt to the changes and might risk extinction.

Bacteria used to deliver radiation treatment to pancreatic tumors

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Science: Pancreatic cancer is exceptionally lethal—only 4% of patients survive past 5 years—partly because of its aggressive metastasizing. Now a novel way to halt its spread has been proposed. Listeria monocytogenes is a bacterium that has previously been shown to directly attack tumor cells when it is modified to carry the tumor cells’ DNA. Claudia Gravekamp of the Albert Einstein College of Medicine in New York and her colleagues combined the modified Listeria with a radioactive compound and used it to treat mice with human pancreatic cancer tumors. The radioactive bacteria treatment reduced the number of metastatic cancer cells by up to 90%, while nonirradiated bacteria eliminated 50% of the metastasized cells. In addition, the radioactive bacteria shrank the primary tumor by 64% versus just 20% for the nonradioactive treatment. And there was very little damage to healthy tissue. Although a 90% elimination of metastasized cells is impressive, the remaining 10% are more than enough to be lethal. The researchers believe that use of a radiation source with a longer half-life could be 100% effective. Certain issues need to be addressed, however, before the treatment can be used on humans, including the risk of inducing sickness by using Listeria, which is itself a dangerous bacteria even in an attenuated form, and the potential buildup of radiation in the kidneys after the bacteria die.

Video reveals mechanics of moths’ hovering ability

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BBC: Jonathan Dyhr of the University of Washington in Seattle and his colleagues used high-speed video cameras to film moths hovering. They put the moths in an environment where the walls could be tilted to make the moths feel like they were tumbling forward or backward. In response, the moths flapped their wings and pivoted their abdomens upward or downward. The change in position of the abdomen changed the airflow over the wings, which balanced the forces that keep the moth in the air. Because moths are relatively large insects, Dyhr says, they make a good model for small, winged robots. Having a clear understanding of the physical mechanics of hovering will be useful for engineers and provides answers for some basic biological questions.

Molecular structure of human bones successfully modeled

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MIT News: Bone is made from a combination of collagen—a soft, flexible biomolecule—and hydroxyapatite—a hard, brittle mineral. How the two materials combine to form something that is hard and tough yet still slightly flexible has been hard to determine because the structure can only be imaged in two dimensions—either surface images or cross-sectional slices. And computers have only recently reached the point that they can create models of the structure in reasonable timeframes. Markus Buehler of MIT and his colleagues have now taken advantage of the new generation of supercomputers to iterate through models created from 2D scans and measurements of structural stresses. The result is the first successful model of the molecular structure of human bone. The model reveals that hydroxyapatite grains are embedded in a matrix of collagen. The mineral absorbs many of the forces applied to the structure, while stretching forces are absorbed by the collagen. Having a clear picture of bone’s structure may help researchers to better understand bone diseases, such as osteoporosis, and to develop bone-like materials for biomedicine or even structural engineering.