Share:Beaver ponds boost mercury levels downstream

Beaver ponds boost mercury levels downstream

Beaver dams transform landscapes, turning stretches of flowing streams into still ponds and flooding forests. Now, researchers have found the dams are transformative in more ways than one. Scientists in Sweden have shown that beaver ponds can cause levels of methylmercury—a particularly toxic form of mercury—to rise in downstream waters by as much as 3.5 times the background levels during summer months. Although mercury, a neurotoxin, occurs naturally in the environment, it is also released into the atmosphere when humans burn coal and other fossil fuels. Once it finds its way back to land or water, bacteria in the soil can convert it into its more toxic cousin, methylmercury. As the researchers reported online last month in Environmental Science & Technology, this kind of bacteria thrives in the waterlogged sediments, rich with decaying vegetation, that pile up behind beaver dams. But the increase in methylmercury appears to be temporary. Surprisingly, it doesn’t occur when beavers move back into old dams: Methylmercury levels above and below recolonized dams were nearly identical in the study. This could mean the submerged vegetation that was feeding the bacteria finally rotted away, leaving them with less food, scientists say. They add that their findings support the practice of leaving old dams in place in Europe and North America where beavers—whose numbers have plummeted over the last 150 years—are making a comeback. Next, the researchers hope to figure out how methylmercury works its way through the ecosystem and whether or not it’s accumulating in fish and other organisms.

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Share:Sensors may soon give prosthetics a lifelike sense of touch

Sensors may soon give prosthetics a lifelike sense of touch


Prosthetic limbs may work wonders for restoring lost function in some amputees, but one thing they can’t do is restore an accurate sense of touch. Now, researchers report that one day in the not too distant future, those artificial arms and legs may have a sense of touch closely resembling the real thing. Using a two-ply of flexible, thin plastic, scientists have created novel electronic sensors that send signals to the brain tissue of mice that closely mimic the nerve messages of touch sensors in human skin.

Multiple research teams have long worked on restoring touch to people with prosthetic limbs. 2 years ago, for example, a group at Case Western Reserve University in Cleveland, Ohio, reported giving people with prosthetic hands a sense of touch by wiring pressure sensors on the hands to peripheral nerves in their arms.

Yet although these advances have restored a rudimentary sense of touch, the sensors and signals are very different from those sent by mechanoreceptors, natural touch sensors in the skin. For starters, natural mechanoreceptors put out what amounts to a digital signal. When they sense pressure, they fire a stream of nerve impulses; the more pressure, the higher the frequency of pulses. But previous tactile sensors have been analogue devices, where more pressure produces a stronger electrical signal, rather than a more frequent stream of pulses. The electrical signals must then be sent to another processing chip that converts the strength of the signals to a digital stream of pulses that is only then sent on to peripheral nerves or brain tissue.

Inspired by natural mechanoreceptors, researchers led by Zhenan Bao, a chemical engineer at Stanford University in Palo Alto, California, set out to make sensors that churn out digital signals directly. Bao’s group started by refining sensors that they first made 5 years ago. In that earlier work, the group designed tiny rubber pillars containing electrically conductive carbon nanotubes, which were placed over a pair of electrodes side by side. When no pressure is applied, the rubber, which is an insulator, prevents current from flowing between the two electrodes. But when touched, the pressure squishes the pillars, pushing the conductive nanotubes together to make a continuous electrical path and allowing current to flow. When the pressure is removed, the rubber pillars bounce back to their original shape.

For their current work, Bao and her colleagues turned their pillars into inverted pyramids and tweaked their size so they were sensitive to a range of pressures, from a light touch to a firm handshake. They also changed the electrode setup and added another layer of flexible electronic devices, known as ring oscillators, which convert the electrical signals emerging from the touch sensitive pyramids to a stream of digital electrical pulses. The upshot was that—just like the signals from natural mechanoreceptors—when more pressure is applied, the oscillators turn out pulses at a higher frequency.

But Bao’s group didn’t stop there. The Stanford team also wanted to see if brain tissues could receive these signals. That’s typically done by inserting metal electrodes into the so-called somatosensory cortex of animals and watching their response. But metal electrodes can quickly damage natural brain tissue, making it impossible to study the transfer of signals over extended periods. So for their current study, Bao’s team decided to send the electronic pulses coming from the touch sensors to a light emitting diode, which converted them into a stream of pulses of blue light. Bao’s team then partnered with Stanford colleagues, led by Karl Deisseroth, to genetically engineer somatosensory cortex tissue of mice to absorb blue light and fire in response. They sacrificed some of the engineered mice and isolated a slice of the light-sensitive somatosensory cortex, which remained viable for several hours. Finally, they tested their touch sensors and monitored whether the mouse brain tissue received the signals and fired in response. In today’s Science they report that the brain neural tissue faithfully reproduced the firing patterns coming from the touch sensor. That raises hopes that such sensors may eventually help restore a natural sense of touch to amputees, Bao says.

“It’s great to see research moving in this direction, and this particular paper is impressive,” says John Rogers, a chemist and expert in flexible electronics at the University of Illinois, Urbana-Champaign. Both Rogers and Bao note, however, that giving amputees a natural-like sense of touch still has a ways to go. Doctors, for example, won’t be able to engineer human brain tissue to receive light signals. That means researchers will need to find other ways to pass electrical signals from a prostheses to the brain in a way that is stable and safe for long periods of time. Bao says she hopes to use flexible organic electronics for this task as well. Eventually, as these different threads of research are woven together, it’s likely to give people with prosthetic limbs a whole new feel for their surroundings.

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High rate of Texas bugs carrying Chagas disease

Source: The University of Texas at El Paso

Summary: A deadly parasite that causes Chagas disease is widespread in a common Texas insect, according to a new study. The finding suggests that the risk of Texans contracting the disease may be higher than previously thought.

Rosa Maldonado, associate professor of biological sciences at The University of Texas at El Paso, holds a vial filled with kissing bugs.
Credit: Photo by J.R. Hernandez / UTEP News Service

A deadly parasite that causes Chagas disease is widespread in a common Texas insect, according to a new study by University of Texas at El Paso (UTEP) researchers. The finding suggests that the risk of Texans contracting the disease may be higher than previously thought.

The parasite Trypanosoma cruzi (T. cruzi), which causes Chagas disease can be transmitted to humans by blood-sucking insects known as “assassin bugs” or “kissing bugs.” Unlike mosquitoes that transmit malaria through the bite, kissing bugs drop feces on the subject while filling up with blood. The feces, which are contaminated with the parasite, often lands in the bite wound. From there, it penetrates the bloodstream and affects the heart and gastrointestinal system.

Curious to know the prevalence of T. cruzi in west Texas insects, UTEP biologists set traps to collect the bugs at the University’s Indio Mountains Research Station. The station sits about 100 miles north of the U.S.-Mexico border in Hudspeth County, Texas.

In all, the researchers trapped 39 kissing bugs (Triatoma rubida) and tests revealed that 24 bugs– or 61 percent — were infected with T. cruzi. The findings were published in the journal Acta Tropica.

“It surprised me that so many of them were carrying the parasite,” says Rosa A. Maldonado, D.Sc., an associate professor of biological sciences at UTEP who led the study. “I was expecting to have some, but this is quite high.”

Maldonado adds that there’s a high rate of heart disease along the border and one of the causes could be Chagas disease.

Thirty percent of people infected with the parasite develop life-threatening symptoms like heart rhythm abnormalities and difficult eating or passing stool. The disease can also lead to an enlarged esophagus, colon and heart, and even, heart failure.

“Doctors usually don’t consider Chagas disease when they diagnose patients, so they need to be aware of its prevalence here,” says Maldonado. To prevent parasite transmission by the kissing bug, the biologist says it’s important to be aware of the presence of the bugs in the house and yard because pets like dogs and cats are also vulnerable.

But getting bitten by a kissing bug isn’t the only way to contract the disease. Once a human is infected, the parasite can be transmitted to others via organ transplants, blood transfusions and from a mother to a fetus. In addition, the parasite can be spread through foods and juices tainted by the contaminated bug feces.

Maldonado hopes her work brings more awareness to the often overlooked disease, which she calls an emerging infectious disease in the U.S. The biologist is currently investigating the prevalence of T. cruzi in kissing bugs, street dogs and cats found in El Paso, Texas, an urban city on the U.S.-Mexico border with more than 675,000 residents.

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The above post is reprinted from materials provided by The University of Texas at El Paso. Note: Materials may be edited for content and length.


NASA orbiter takes a parting look at Saturn’s moon Dione

NASA orbiter takes a parting look at Saturn’s moon Dione

Eleven years ago, NASA’s Cassini spacecraft entered orbit around Saturn. The spacecraft’s long journey, however, is nearing an end. Last year, NASA granted the orbiter one last extension—through 2017, when the fuel for its thrusters will run out. Now, the spacecraft has made its last flyby of Dione—the fourth largest of Saturn’s more than 60 moons—revealing its final images of the celestial body’s pockmarked surface, The New York Times reports. In October, Cassini will make its final flybys of another smaller moon, Enceladus, known for its jets of water vapor and ice.

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Computer scientists find mass extinctions can accelerate evolution

Summary: Computer scientists have found that robots evolve more quickly and efficiently after a virtual mass extinction modeled after real-life disasters such as the one that killed off the dinosaurs. Beyond implications for artificial intelligence, the research supports the idea that mass extinctions actually speed up evolution by unleashing new creativity in adaptations.

At the start of the simulation, a biped robot controlled by a computationally evolved brain stands upright on a 16 meter by 16 meter surface. The simulation proceeds until the robot falls or until 15 seconds have elapsed.
Credit: Joel Lehman

A computer science team at The University of Texas at Austin has found that robots evolve more quickly and efficiently after a virtual mass extinction modeled after real-life disasters such as the one that killed off the dinosaurs. Beyond its implications for artificial intelligence, the research supports the idea that mass extinctions actually speed up evolution by unleashing new creativity in adaptations.

Computer scientists Risto Miikkulainen and Joel Lehman co-authored the study published today in the journal PLOS One, which describes how simulations of mass extinctions promote novel features and abilities in surviving lineages.

“Focused destruction can lead to surprising outcomes,” said Miikkulainen, a professor of computer science at UT Austin. “Sometimes you have to develop something that seems objectively worse in order to develop the tools you need to get better.”

In biology, mass extinctions are known for being highly destructive, erasing a lot of genetic material from the tree of life. But some evolutionary biologists hypothesize that extinction events actually accelerate evolution by promoting those lineages that are the most evolvable, meaning ones that can quickly create useful new features and abilities.

Miikkulainen and Lehman found that, at least with robots, this is the case. For years, computer scientists have used computer algorithms inspired by evolution to train simulated robot brains, called neural networks, to improve at a task from one generation to the next. The UT Austin team’s innovation in the latest research was in examining how mass destruction could aid in computational evolution.

In computer simulations, they connected neural networks to simulated robotic legs with the goal of evolving a robot that could walk smoothly and stably. As with real evolution, random mutations were introduced through the computational evolution process. The scientists created many different niches so that a wide range of novel features and abilities would come about.

After hundreds of generations, a wide range of robotic behaviors had evolved to fill these niches, many of which were not directly useful for walking. Then the researchers randomly killed off the robots in 90 percent of the niches, mimicking a mass extinction.

After several such cycles of evolution and extinction, they discovered that the lineages that survived were the most evolvable and, therefore, had the greatest potential to produce new behaviors. Not only that, but overall, better solutions to the task of walking were evolved in simulations with mass extinctions, compared with simulations without them.

Practical applications of the research could include the development of robots that can better overcome obstacles (such as robots searching for survivors in earthquake rubble, exploring Mars or navigating a minefield) and human-like game agents.

“This is a good example of how evolution produces great things in indirect, meandering ways,” explains Lehman, a former postdoctoral researcher in Miikkulainen’s lab, now at the IT University of Copenhagen. He and a former student of Miikkulainen’s at UT Austin, Kenneth Stanley, recently published a popular science book about evolutionary meandering, “The Myth of the Objective: Why Greatness Cannot Be Planned.” “Even destruction can be leveraged for evolutionary creativity.”

This research was funded by the National Science Foundation (NSF), National Institutes of Health and UT Austin’s Freshman Research Initiative. Funding from NSF was provided through grants to BEACON, a multi-university center established to study evolution in action in natural and virtual settings. The University of Texas at Austin is a member of BEACON. Evolutionary biologists in BEACON assisted Miikkulainen and Lehman in designing the research project and interpreting the results.

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The above post is reprinted from materials provided by University of Texas at Austin. The original item was written by Marc Airhart. Note: Materials may be edited for content and length.


Astronauts grow (and eat) lettuce in space

Astronauts grow (and eat) lettuce in space

Today, astronauts aboard the International Space Station will eat lettuce they grew themselves in space for the first time ever, Ars Technica reports. The experiment is part of NASA’s Veg-01 project that is investigating how plants respond to a zero-gravity environment. The ability of astronauts to grow sustainable food will become more important as the agency moves toward longer duration space missions farther out in the solar system, they say. The red romaine lettuce, known as “outredgeous,” was sent back to Earth after a previous planting to make sure the leafy green was fit for human consumption. Bon appétit!


Publish Papers for Free in 3 Journals

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American Journal of Optics and Photonics
Journal of Investment and Management

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