ELECTRICAL STIMULATION ‘TUNES’ VISUAL ATTENTION


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“Existing theories of visual attention propose that working memory representations, also known as short-term memory, typically control how attention is focused on targets in our visual field,” Geoffrey Woodman, assistant professor of psychology at Vanderbilt University and co-author of the study along with Ph.D. candidate Robert M.G. Reinhart, said. “These new findings provide evidence that long-term memory representations can also underlie our ability to rapidly configure attention to focus on certain objects, and that long-term memory performance can be sharply accelerated using electrical stimulation.”

Researchers have long known that attention could be tuned, like a radio dial, to hone in on specific features, but how and where in the brain this tuning occurs has remained an open question.

By passing very weak electrical current through the brains of healthy volunteers using a process called transcranial direct-current stimulation, researchers were able to cause the volunteers to much more quickly find target objects embedded in arrays of distracting objects. The study showed that after 20 minutes of passing safe levels of weak electrical current through electrodes placed on the head, the volunteers were able to more effectively focus attention on the searched-for targets, with dramatic increases in speed.

To determine the source of the attentional improvements, the researchers examined the recordings of the volunteers’ brain activity for the neurophysiological signatures of visual working memory and long-term memory. They found that the rapid improvement in attention was most closely related to increased activity in long-term, rather than working, memory. Their findings further indicate that long-term memory more immediately integrates information that is used to control attention than was previously thought, offering new insights into the relationship between working and long-term memory in controlling attention.

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Silicon Supercapacitor Powers Phones for Weeks on Single Charge.


Charge

Material scientists at Vanderbilt University have developed a supercapacitor made out of silicon. Previously thought to be kind of a crazy idea, the silicon capacitor can be built into a chip — which could give cellphones weeks of life from one charge, or solar cells that produce energy with or without the sun. Pretty sweet deal.Published in Scientific Reports, the first-ever silicon supercap stores energy by gathering ions on the surface of the porous material. Different from batteries, which work on chemical reactions, the silicon supercaps can be charged in minutes and last way longer. Silicon had been considered unsuitable for supercaps because of the way it reacts with the electrolytes that make the energy-storing ions.

“If you ask experts about making a supercapacitor out of silicon, they will tell you it is a crazy idea,” said assistant professor Cary Pint, who headed the development team at Vanderbilt. “But we’ve found an easy way to do it.”

Pint’s team coated the silicon in carbon — well, technically a few nanometers of graphene — and it stabilized the surface of the silicon, making it perfect for storing energy.

“All the things that define us in a modern environment require electricity,” said Pint. “The more that we can integrate power storage into existing materials and devices, the more compact and efficient they will become.”

Geekosystem is a Mashable publishing partner that aims to unite all the tribes of geekdom under one common banner. This article is reprinted with the publisher’s permission.

New device stores electricity on silicon chips.


Solar cells that produce electricity 24/7, not just when the sun is shining. Mobile phones with built-in power cells that recharge in seconds and work for weeks between charges.

These are just two of the possibilities raised by a novel supercapacitor design invented by material scientists at Vanderbilt University that is described in a paper published in the Oct. 22 issue of the journal Scientific Reports.

It is the first supercapacitor that is made out of silicon so it can be built into a silicon chip along with the microelectronic circuitry that it powers. In fact, it should be possible to construct these power cells out of the excess silicon that exists in the current generation of solar cells, sensors, mobile phones and a variety of other electromechanical devices, providing a considerable cost savings.

“If you ask experts about making a supercapacitor out of silicon, they will tell you it is a crazy idea,” said Cary Pint, the assistant professor of mechanical engineering who headed the development. “But we’ve found an easy way to do it.”

Instead of storing energy in chemical reactions the way batteries do, “supercaps” store electricity by assembling ions on the of a porous material. As a result, they tend to charge and discharge in minutes, instead of hours, and operate for a few million cycles, instead of a few thousand cycles like batteries.

These properties have allowed commercial , which are made out of activated carbon, to capture a few niche markets, such as storing energy captured by regenerative braking systems on buses and electric vehicles and to provide the bursts of power required to adjust of the blades of giant wind turbines to changing wind conditions. Supercapacitors still lag behind the electrical energy storage capability of lithium-ion batteries, so they are too bulky to power most consumer devices. However, they have been catching up rapidly.

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Research to improve the energy density of supercapacitors has focused on carbon-based nanomaterials like graphene and nanotubes. Because these devices store electrical charge on the surface of their electrodes, the way to increase their energy density is to increase the electrodes’ surface area, which means making surfaces filled with nanoscale ridges and pores.

“The big challenge for this approach is assembling the materials,” said Pint. “Constructing high-performance, functional devices out of nanoscale building blocks with any level of control has proven to be quite challenging, and when it is achieved it is difficult to repeat.”

So Pint and his research team – graduate students Landon Oakes, Andrew Westover and post-doctoral fellow Shahana Chatterjee – decided to take a radically different approach: using porous silicon, a material with a controllable and well-defined nanostructure made by electrochemically etching the surface of a silicon wafer.

This allowed them to create surfaces with optimal nanostructures for supercapacitor electrodes, but it left them with a major problem. Silicon is generally considered unsuitable for use in supercapacitors because it reacts readily with some of chemicals in the electrolytes that provide the ions that store the electrical charge.

With experience in growing carbon nanostructures, Pint’s group decided to try to coat the porous with carbon. “We had no idea what would happen,” said Pint. “Typically, researchers grow graphene from silicon-carbide materials at temperatures in excess of 1400 degrees Celsius. But at lower temperatures – 600 to 700 degrees Celsius – we certainly didn’t expect graphene-like material growth.”

When the researchers pulled the porous silicon out of the furnace, they found that it had turned from orange to purple or black. When they inspected it under a powerful scanning electron microscope they found that it looked nearly identical to the original material but it was coated by a layer of graphene a few nanometers thick.

When the researchers tested the coated material they found that it had chemically stabilized the silicon surface. When they used it to make supercapacitors, they found that the graphene coating improved energy densities by over two orders of magnitude compared to those made from uncoated and significantly better than commercial supercapacitors.

The graphene layer acts as an atomically thin protective coating. Pint and his group argue that this approach isn’t limited to graphene. “The ability to engineer surfaces with atomically thin layers of materials combined with the control achieved in designing porous materials opens opportunities for a number of different applications beyond energy storage,” he said.

“Despite the excellent device performance we achieved, our goal wasn’t to create devices with record performance,” said Pint. “It was to develop a road map for integrated energy storage. Silicon is an ideal material to focus on because it is the basis of so much of our modern technology and applications. In addition, most of the silicon in existing devices remains unused since it is very expensive and wasteful to produce thin wafers.”

Pint’s group is currently using this approach to develop that can be formed in the excess materials or on the unused back sides of and sensors. The supercapacitors would store excess the electricity that the generate at midday and release it when the demand peaks in the afternoon.

When the researchers tested the coated material they found that it had chemically stabilized the silicon surface. When they used it to make supercapacitors, they found that the graphene coating improved energy densities by over two orders of magnitude compared to those made from uncoated and significantly better than commercial supercapacitors.

The graphene layer acts as an atomically thin protective coating. Pint and his group argue that this approach isn’t limited to graphene. “The ability to engineer surfaces with atomically thin layers of materials combined with the control achieved in designing porous materials opens opportunities for a number of different applications beyond energy storage,” he said.

“Despite the excellent device performance we achieved, our goal wasn’t to create devices with record performance,” said Pint. “It was to develop a road map for integrated energy storage. Silicon is an ideal material to focus on because it is the basis of so much of our modern technology and applications. In addition, most of the silicon in existing devices remains unused since it is very expensive and wasteful to produce thin wafers.”

Pint’s group is currently using this approach to develop that can be formed in the excess materials or on the unused back sides of and sensors. The supercapacitors would store excess the electricity that the generate at midday and release it when the demand peaks in the afternoon.

When the researchers tested the coated material they found that it had chemically stabilized the silicon surface. When they used it to make supercapacitors, they found that the graphene coating improved energy densities by over two orders of magnitude compared to those made from uncoated and significantly better than commercial supercapacitors.

The graphene layer acts as an atomically thin protective coating. Pint and his group argue that this approach isn’t limited to graphene. “The ability to engineer surfaces with atomically thin layers of materials combined with the control achieved in designing porous materials opens opportunities for a number of different applications beyond energy storage,” he said.

“Despite the excellent device performance we achieved, our goal wasn’t to create devices with record performance,” said Pint. “It was to develop a road map for integrated energy storage. Silicon is an ideal material to focus on because it is the basis of so much of our modern technology and applications. In addition, most of the silicon in existing devices remains unused since it is very expensive and wasteful to produce thin wafers.”

Pint’s group is currently using this approach to develop that can be formed in the excess materials or on the unused back sides of and sensors. The supercapacitors would store excess the electricity that the generate at midday and release it when the demand peaks in the afternoon.

“All the things that define us in a modern environment require electricity,” said Pint. “The more that we can integrate power storage into existing and devices, the more compact and efficient they will become.”

A Malaria Vaccine Works, With Limits.


A new type of malaria vaccine gave 100 percent protection against infection to a small number of volunteers in recent tests — but under conditions that would be nearly impossible to reproduce in the countries where most malaria victims live.

The vaccine, made by Sanaria, a Maryland company, protected six volunteers who each got five doses over 20 weeks, according to a studypublished last week in Science.

But the vaccine is expensive to make and difficult to administer, and it is not yet clear how long the protection lasts.

“This is a scientific advance rather than a practical one,” said Dr. William Schaffner, the head of preventive medicine at Vanderbilt University’s medical school. “But any vaccine that provides even a glimmer of hope opens a door, so we have to pursue it.”

Sanaria’s vaccine is made by irradiating mosquitoes that have fed on malaria-infected blood and removing their salivary glands by hand. The radiation-weakened parasites in the saliva are then purified.

In earlier trials, the vaccine failed when injected into the skin, so this time researchers from the Army, Navy and National Institutes of Health gave it by IV. Six volunteers who got five intravenous doses did not get malaria when bitten by infected mosquitoes. Six of nine volunteers who got four doses were protected.

Because the vaccine is made in small batches by hand, it is impractical for poor countries, where malaria sickens more than 200 million people a year and kills about 660,000, most of them infants and pregnant women.

Giving multiple IV doses of any vaccine is also impractical because it requires sterile conditions, trained medical personnel and follow-up. IVs are particularly hard to administer to children. “They’ve been known to squirm,” Dr. Schaffner noted.

The initial target markets for the vaccine are the military and wealthy travelers.  

Source: http://www.nytimes.com

Stars’ twinkle reveals their character.


In 1806, English poet Jane Taylor famously lamented that a little star’s twinkle left her wondering what it was.

Fast-forward 207 years and a new analysis of starlight collected by NASA’s Kepler space telescope shows patterns in the flicker that are directly tied to the amount of boiling taking place on a star’s surface, a key indicator of its size, mass and evolutionary state.

That information, in turn, reveals volumes about any orbiting planets, including those fortuitously positioned from their parent stars for liquid surface water, apparently a key ingredient for life.

“Everything you know about planets is tied to what you know about the host star,” says Fabienne Bastien, an astronomy graduate student at Vanderbilt University.

“We don’t observe the planets directly. We observe the stars and the influence that the planets have on their stars. So in order to make any conclusions about the size of the planet or the mass of the planet as it’s pulling on the star when it’s moving, you need to know the size and the mass of the star very well.”

“That directly impacts whether or not you can claim that you have an Earth-like planet,” she says.

Bastien, who is working on a doctoral dissertation, was analysing archived Kepler data for a totally different reason when she and colleagues chanced upon strange patterns in the data that they didn’t understand.

“It was a complete surprise,” says Bastien.

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Boiling surfaces

It turns out the pattern provides a quick and relatively reliable way to determine a star’s evolutionary state.

Stars like the Sun, which is about 4.6 billion years old, eventually will evolve into red giants as they run out of fuel for nuclear fusion. The new study shows the surfaces of younger dwarf stars boiling more vigorously than older giants.

“What we are looking at here is the gravitational acceleration in the stellar outer layers, what we often call the atmosphere,” says astronomer Joergen Christensen-Dalsgaard, with Aarhus University in Denmark.

“The typical methods used have uncertainties up to 150 per cent. That very imprecise method is the easiest to do, and especially if you’re dealing with 150,000 stars and you need to characterise them all, that’s what you go to because it takes the least amount of resources. Our technique lets us beat that down to 25 per cent, which is very, very good for this field,” added Bastien.

Kepler, which collected data from about 120,000 target stars between May 2009 and May 2013, was designed to search for Earth-like planets in stars’ habitable zones,

For Bastien’s study, which appears in this week’s edition of Nature, astronomers analysed a few thousand stars in the Kepler data archive.

“If you have a large enough sample, then you start to pick out patterns in the way stars of different evolutionary states behave,” she says.

While the study is based on eight-hour flicker patterns in the visible light coming from target stars, scientists translated the data into corresponding audio wavelengths, a poignant conceptualisation that no doubt would have intrigued, and delighted, poet Taylor.

Source: http://www.abc.net.au

Abdominal Pain in Childhood Linked to Anxiety, Depression in Young Adulthood.


Children with medically unexplained “functional abdominal pain” face increased risks for anxiety and depression in adolescence and young adulthood, according to a Pediatrics study.

Researchers prospectively followed some 330 children with functional abdominal pain and 150 age-matched controls without pain into adolescence and young adulthood (mean age at follow-up, 20 years). They found that children who’d had abdominal pain at baseline were significantly more likely than controls to meet criteria for lifetime anxiety disorders (51% vs. 20%) and current anxiety disorders (30% vs. 12%) at follow-up. In most cases, anxiety preceded the onset of abdominal pain. In some cases, anxiety persisted after pain had resolved.

The pain group was also more likely than the control group to meet criteria for lifetime depression at follow-up (40% vs. 16%); depression usually began after abdominal pain.

“These data underscore the importance of a biopsychosocial approach to [functional abdominal pain] that includes screening for anxiety and depression,” the researchers conclude.

Source: Pediatrics

Gut Microbes Can Split a Species.


Here’s how to create a new species. Put animals—say finches—from the same species on separate islands and let them do their thing for many, many generations. Over time, each group will adapt to its new environment, and the genomes of the two populations will become so different that if you reintroduce the animals to the same habitat, they can no longer breed successfully. Voilà, one species has become two. But a new study suggests that DNA isn’t the only thing that separates species: Some populations diverge because of the microbes in their guts.

 

The paper is “important and potentially groundbreaking,” says John Werren, a biologist at the University of Rochester in New York. “Scientists have studied speciation … for many years, and this opens up a whole new aspect to it.”

The new work involves three different species of parasitic jewel wasps, tiny insects that drill into the pupas of flies and lay their eggs, letting the offspring feed on the host. Two of the species, Nasonia giraulti and N. longicornis, are closely related, whereas the third species, N. vitripennis, diverged from the other two about 1 million years ago. When N. giraultiand N. longicornis mate in the lab, most of their offspring survive, but when either mates with N. vitripennis, almost all male larvae in the second generation die.

Seth Bordenstein and Robert Brucker, biologists at Vanderbilt University in Nashville, wondered if the reason for this mortality went beyond incompatible DNA. They knew that the gut microbes in N. vitripennis differed from those in the other two species, and they suspected that these microbes could play a role in the offspring deaths. Indeed, when they raised all three species of Nasonia without gut microbes—by rearing them on sterile food—almost all the second generation offspring of matings between N. vitripennis and N. giraulti wasps survived. Andwhen the scientists reintroduced bacteria into the germ-free wasps, most of their second-generation offspring died, the duo report online today in Science.

Werren says that the work introduces a whole new way to look at what sets species apart. Instead of just thinking about genes of the parents not meshing in hybrids, he says, biologists could now think about how the parents’ genes are incompatible with the offspring’s microorganisms. Some parental genes could enable the immune system to keep certain gut bacteria in check, for instance, and without them the gut microbes might sicken the animal and kill it.

Bordenstein goes one step further. The genes of microbes harbored by an organism are just as important for evolution as the genes in its own cells, he says, calling both together a “hologenome.” Werren disagrees. Microbes in the gut interact with the bigger organism, just like other organisms in nature interact, for instance predator and prey, Werren says. “They are not co-evolving as a single unit, so why would we call them a single genome?”

Axel Meyer, an evolutionary biologist at the University of Konstanz in Germany, is skeptical about whether gut microbes have a big effect on speciation. The paper is “exciting,” he says, “but there might be huge biological differences between species in how the microbiome [the community of microbes in an organism] is established.” As a result, he says, it is an open question whether there will be many more examples of gut microbes separating species. Werren thinks there will be. “No pun intended,” he says, “but my gut tells me that this is going to be common.”

Source: sciencemag.org

Science in the Courtroom.


Scientific evidence concerning the biological causes of bad behavior is becoming increasingly common in the courtroom. Forensic psychiatrists at Vanderbilt University have genetically screened defendants charged with first-degree murder for a gene associated with antisocial personality disorder, for example. And when it came time to sentence convicted murderer Brian Dugan, neuroscientists performed neuroimaging on Dugan’s brain in order to claim he has a defective, psychopathic brain.

What would you do if you were faced with such a decision? Imagine you’re a juror tasked with the job of recommending a sentence for a criminal found guilty of aggravated battery. The criminal, Jonathan Donahue, went into a Burger King restaurant with the hope of robbing it, then beat the manager so severely that he sustained brain damage. After he was arrested, Donahue seemed to revel in his crime, even going so far as to have a king’s crown tattooed on his back.

At the sentencing hearing, a psychiatrist provides expert testimony saying that Donahue is a diagnosed psychopath. She explains that psychopathy is a clinical diagnosis defined by impulsivity, lack of empathy, and lack of remorse. The judge tells you that the standard sentence for cases of aggravated battery is about 9 years.

First Question: With this information, how many years in prison will you recommend for Donahue?

There’s one more expert witness. This one is a neurobiologist, and he tells you that Donahue has a particular gene that contributes to atypical brain development. Specifically, the part of Donahue’s brain that controls his violence-inhibition mechanism is damaged. In normal humans, the violence-inhibition mechanism automatically creates anxiety when they recognize that other humans are in pain or distress. Psychopaths, like Donahue, lack a normal violence-inhibition mechanism.

Second Question: In light of this additional neurobiological evidence, how many years in prison will you recommend for Donahue?

How did you answer the Second Question relative to the First Question? If you increased Donahue’s sentence, you probably did so because you interpreted the neurobiological evidence as suggesting his biological constitution makes him a continued threat to society. On the other hand, if you decreased Donahue’s sentence, you probably did so because you interpreted the neurobiological evidence as suggesting his biological constitution makes him less responsible for his actions. Or, you could have dismissed the neurobiological evidence entirely and recommended the exact same sentence.

This is the double-edged sword of the science of criminal behavior. The exact same evidence could either increase or decrease punishment, depending on how that evidence is interpreted.

With scientific evidence about the causes of criminal behavior becoming more and more common in the court room, the legal system faces a pressing question: Which way will the double-edged sword cut? In Dugan’s murder case, a jury ultimately sentenced Dugan to death, but according to his attorney the scientific evidence switched a slam dunk case against Dugan into a much more complicated decision for the jurors. To investigate this question in a systematic way, my colleagues and I performed a national experiment involving US state trial court judges. We presented the judges with Donahue’s case and asked them to sentence him. The results of this experiment were published last month in Science. The judges told us that on average they sentenced convicts guilty of aggravated battery to about 9 years in prison. The judges who received only expert testimony concerning Donahue’s diagnosis of psychopathy sentenced him on average to almost 14 years in prison. But the judges who received the expert testimony concerning Donahue’s diagnosis of psychopathy as well as the evidence concerning the neurobiological causes of his psychopathy sentenced him on average to about 13 years in prison. Compared to just the diagnosis of psychopathy, that is, the neurobiological evidence reduced Donahue’s sentence by roughly a year (a statistically significant difference).

So, our study suggests which way the double-edged sword might cut—towards slightly shorter sentences. But there is another pressing question, one at the intersection of science, philosophy, and the law: Which way should the double-edged sword cut?

The presence of scientific evidence about the causes of criminal behavior is only likely to increase in the courtroom. As a result, scientists and non-scientists alike need to discuss this issue and decide how biological knowledge should influence the legal system.

To get the conversation going, in the Comments section below, list your answers to the First and Second Questions and explain your justification for the increase, decrease, or lack of any change in the prison sentence that you recommended for Donahue.

James Tabery is a professor of philosophy at the University of Utah.

Source: http://www.the-scientist.com