星空女人频道: 2014-01-12

2014年1月18日星期六

Tiny swimming bio-bots boldly go where no bot has swum before

A team of engineers has developed a class of tiny bio-hybrid machines that swim like sperm, the first synthetic structures that can traverse the viscous fluids of biological environments on their own. Led by Taher Saif, the University of Illinois Gutgsell Professor of mechanical science and engineering, the team published its work in the journal Nature Communications.

"Micro-organisms have a whole world that we only glimpse through the microscope," Saif said. "This is the first time that an engineered system has reached this underworld."

The bio-bots are modeled after single-celled creatures with long tails called flagella -- for example, sperm. The researchers begin by creating the body of the bio-bot from a flexible polymer. Then they culture heart cells near the junction of the head and the tail. The cells self-align and synchronize to beat together, sending a wave down the tail that propels the bio-bot forward.

This self-organization is a remarkable emergent phenomenon, Saif said, and how the cells communicate with each other on the flexible polymer tail is yet to be fully understood. But the cells must beat together, in the right direction, for the tail to move.

"It's the minimal amount of engineering -- just a head and a wire," Saif said. "Then the cells come in, interact with the structure, and make it functional."

See an animation of the bio-bots in motion and a video of a free-swimming bot.

The team also built two-tailed bots, which they found can swim even faster. Multiple tails also opens up the possibility of navigation. The researchers envision future bots that could sense chemicals or light and navigate toward a target for medical or environmental applications.

"The long-term vision is simple," said Saif, who is also part of the Beckman Institute for Advanced Science and Technology at the U. of I. "Could we make elementary structures and seed them with stem cells that would differentiate into smart structures to deliver drugs, perform minimally invasive surgery or target cancer?"

The swimming bio-bot project is part of a larger National Science Foundation-supported Science and Technology Center on Emergent Behaviors in Integrated Cellular Systems, which also produced the walking bio-bots developed at Illinois in 2012.

"The most intriguing aspect of this work is that it demonstrates the capability to use computational modeling in conjunction with biological design to optimize performance, or design entirely different types of swimming bio-bots," said center director Roger Kamm, a professor of biological and mechanical engineering at the Massachusetts Institute of Technology. "This opens the field up to a tremendous diversity of possibilities. Truly an exciting advance."

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Highly efficient broadband terahertz radiation from metamaterials

Terahertz electromagnetic waves occupy a middle ground between electronics waves, like microwave and radio waves, and photonics waves, such as infrared and UV waves. Potentially, THz waves may accelerate telecom technologies and break new ground in understanding the fundamental properties of photonics. Challenges related to efficiently generating and detecting THz waves has primarily limited their use.

Traditional methods seek to either compress oscillating waves from the electronic range or stretch waves from the optical range. But when compressing waves, the THz frequency becomes too high to be generated and detected by conventional electronic devices. So, this approach normally requires either a large-scale electron accelerator facility or highly electrically-biased photoconductive antennas that produce only a narrow range of waves.

To stretch optical waves, most techniques include mixing two laser frequencies inside an inorganic or organic crystal. However, the natural properties of these crystals result in low efficiency.

So, to address these challenges, the Ames Laboratory team looked outside natural materials for a possible solution. They used human-made materials called metamaterials, which exhibit optical and magnetic properties not found in nature.

Institute of Technology in Germany, created a metamaterial made up of a special type of meta-atom called split-ring resonators. Split-ring resonators, because of their u-shaped design, display a strong magnetic response to any desired frequency waves in the THz to infrared spectrum.

Ames Laboratory physicist Jigang Wang, who specializes in ultra-fast laser spectroscopy, designed the femto-second laser experiment to demonstrate THz emission from the metamaterial of a single nanometer thickness.

"The combination of ultra-short laser pulses with the unique and unusual properties of the metamaterial generates efficient and broadband THz waves from emitters of significantly reduced thickness," says Wang, who is also an associate professor of Physics and Astronomy at Iowa State University.

The team demonstrated their technique using the wavelength used by telecommunications (1.5 microns), but Wang says that the THz generation can be tailored simply by tuning the size of the meta-atoms in the metamaterial.

"In principle, we can expand this technique to cover the entire THz range," said Soukoulis, who is also a Distinguished Professor of physics and astronomy at Iowa State University.

What's more, the team's metamaterial THz emitter measured only 40 nanometers and performed as well as traditional emitters that are thousands of times thicker.

"Our approach provides a potential solution to bridge the 'THz technology gap' by solving the four key challenges in the THz emitter technology: efficiency; broadband spectrum; compact size; and tunability," said Wang.

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You've got mail: Research reveals workers' worst inbox sins

Jan. 17, 2014 — Workers obsessed with checking their emails could be damaging their own mental health and that of their colleagues, according to research at London's Kingston University.

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Occupational psychologist Dr Emma Russell believes she has identified the seven deadly email sins that can lead to 'negative repercussions' if not handled correctly.

Some of the worst habits include 'ping pong' messages back and forth and 'read receipts', which accompany every missive sent, the study, looking into which email practices stress employees out, found.

"Back in the dial-up era, when going online had a cost implication, most people checked email maybe once a day and often responded to mails as soon as they read them. Now with broadband and 3G, unlimited numbers of messages can be streamed to you via your smartphone at any time of the day or night. However many of us haven't adapted our behavior to what can seem like a constant stream of mails," Dr Emma Russell, a senior lecturer in occupational psychology at Kingston Business School, explained.

Responding to out of hours emails, for instance, may make an employee look keen but it can also mean workers find it difficult to switch off, according to the study. "This puts pressure on staff to be permanently on call and makes those they are dealing with feel the need to respond," Dr Russell explained. "Some workers became so obsessed by email that they even reported experiencing so-called 'phantom alerts' where they think their phone has vibrated or bleeped with an incoming email when in fact it has not. Others said they felt they needed to physically hold their smartphone when they were not at their desk so that they were in constant email contact."

Email ping pong, where messages are responded to immediately by both sides until a very long chain builds up, are particularly hated by many of those involved.

Dr Russell analyzed 28 email users across different companies to see which habits had positive and negative influences on their working lives.

She identified seven habits which can be positive if used in moderation but are likely to have a negative impact if not handled correctly. "This research reminds us that even though we think we are using strategies for dealing with our email at work, many of them can be detrimental to other goals and the people that we work with," Dr Russell said.

Some create a problem for the sender rather than the receiver, she said, as they can lead to them giving out the wrong impression or not remaining in control of what they are doing. For example having email alerts switched on and responding to email immediately can have positive benefits if one wants to show concern to the person who has emailed them. However, it may have negative repercussions in terms of the sender feeling that responding to emails is taking them away from other tasks and impacting on their sense of well-being.

The report was presented at the British Psychological Society's annual conference.

Seven deadly email sins:

1. Ping pong -- constant emails back and forth creating long chains

2. Emailing out of hours

3. Emailing while in company

4. Ignoring emails completely

5. Requesting read receipts

6. Responding immediately to an email alert

7. Automated replies

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Sludge as new sentinel for human health risks

Jan. 16, 2014 — Thousands of chemicals serving a variety of human needs flood into sewage treatment plants once their use life has ended. Many belong to a class of chemicals known as CECs (for chemicals of emerging concern), which may pose risks to both human and environmental health.

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Arjun Venkatesan, a recent doctorate and Rolf Halden, professor and director of the Center for Environmental Security at Arizona State University's Biodesign Institute, have carried out meticulous tracking of many of these chemicals.

In a study appearing today in the Nature Publishing Group journal Scientific Reports, both authors outline a new approach to the identification of potentially harmful, mass-produced chemicals, describing the accumulation in sludge of 123 distinct CECs.

Ten of the 11 chemicals found in greatest abundance in treated municipal sludge or biosolids were high-production volume chemicals, including flame-retardants, antimicrobials and surfactants.

The study shows a strong overlap between chemicals found in biological samples taken from the human population and those detected in municipal biosolids. These findings suggest that analysis of sludge may provide a useful surrogate for the assessment of human exposure and bioaccumulation of potentially hazardous substances.

According to Venkatesan, "presence of CECs in sewage suggests that consumers already may get exposed to these chemicals prior to their discharge into sewage, suggesting a need for human biomonitoring and risk assessment of these priority chemicals."

Prioritizing the thousands of CECs and predicting their behavior has been a daunting challenge. Evaluation is costly, tedious and time-consuming. Further, as the new study emphasizes, laboratory modeling of chemical behavior, including rates of environmental breakdown and potential for bioaccumulation often deviate significantly from real-world scenarios.

Conventional chemical screening evaluates the persistence, bioaccumulation and potential toxicity of various chemicals. The method however suffers from two shortcomings: the production rates of chemicals in current use are not incorporated into analysis and the detailed behavior of these chemicals in real-world biological systems -- including the human body -- is not assessed.

In the current study, a repository of samples from U.S. wastewater treatment plants, created and maintained by Halden at ASU's Biodesign Institute was used to conveniently identify CECs, as well as evaluate their potential for bioaccumulation and their ability to withstand degradation processes. The working hypothesis proposes that such treatment plants may act as reliable gauges for monitoring chemical prevalence and bioaccumulation potential relevant to human society and the environment.

Specifically, chemicals managing to survive primary and secondary treatment in municipal sewage systems display notable resistance to aerobic and anaerobic digestion processes and are therefore more likely to stubbornly persist in the environment upon their release.

As Halden notes, post-treatment sludge provides a sink for water-avoiding (hydrophobic) organic compounds. Such sludge is often applied to land, where the persisting hydrophobic chemicals (including polychlorinated biphenyls [PCBs], briominated flame retardants [BFRs] and various pharmaceutical and personal care products including antimicrobial agents) can accumulate in considerable quantity.

The analysis identified a total of 123 chemicals in biosolids. Of these, 17 brominated chemicals were detected in U.S. biosolids for the first time. The most abundant chemicals were surfactants, which occur commonly in detergents, emulsifiers, foaming agents and dispersants.

After surfactants, pharmaceutical and personal care products were most abundantly detected, followed by BFRs, which commonly occur in plastics, textiles, electronics, and household flame-retardants. BFRs often persist and bioaccumulate in the environment and under proper conditions are also capable of transforming into other hazardous chemicals, including brominated dioxins and furans. The study notes that the pathways by which BFRs enter wastewater treatment facilities remain speculative, requiring further investigation

The surfactant and antimicrobial chemicals identified fall into the category of high production volume (HPV) compounds, produced in annual quantities of over 450,000 kg (1 million pounds). The study notes that the abundance of some chemicals is traceable to specific societal events, for example the 2001 anthrax scare, which significantly boosted production and consumption of the antibiotic ciprofloxacin. Antibiotic accumulation in the environment is of particular concern, due to a tendency to cause heightened drug resistance in microbial pathogens.

The study reveals that 91 percent of the 11 most abundant compounds detected in biosolid samples are HPV chemicals, reinforcing the strong link between the occurrence of hydrophobic chemicals in sludge and their production volume.

Hydrophobic compounds occurring in the range of parts per trillion are generally of low environmental occurrence or experience significant biodegradability, or both. On the other hand, those chemicals occurring in parts per million quantities are of potential concern, owing to low biodegradability, high usage and the tendency to accumulate in biosolids due to their hydrophobic nature.

When results of the current study were matched against a comprehensive exposure assessment of environmental chemicals conducted by the Center for Disease Control and Prevention, it was observed that roughly 70 percent of chemicals detected in biosolids were also detected in humans.

Chemical abundance in biosolids appears to be a reliable indicator of current rates of chemical usage, resistance to biodegradation and potential for bioaccumulation. Further, by using biosolids as a pre-screening step, researchers may reduce the thousands of potentially hazardous CEC chemicals in circulation to a manageable number of priority substances most in need of further evaluation. Such a list of chemicals could then be scrutinized with respect to their absorption, distribution, metabolism and excretion as well as their potential harmfulness to humans and ecosystems. "With over 85,000 chemicals in daily use in the U.S., it is a daunting task to pinpoint those that need more monitoring, regulation or replacement with safer alternatives," Halden says. "It turns out that we can use existing infrastructure, our wastewater treatment plants, to take the chemical pulse of the nation, determine chemical inventories, and zero in on risky chemicals prone to harm people, prosperity and the planet."

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Big-headed fossil flies track major ecological revolution

According to their research, published recently by The Canadian Entomologist, these fossils show their early evolution parallels an ecological revolution, one that formed the character of our modern natural communities.

The three new species of fossil big-headed flies are members of the living family Pipunculidae. One fossil, Metanephrocerus belgardeae, is well-enough preserved to name as a new species. It is named in honor of its finder, Azure Rain Belgarde, a student at the Paschal Sherman Indian School, who uncovered it on a field trip to the fossil deposits at Republic, Washington state.

The other two unnamed, more enigmatic species are described from less complete fossils uncovered at Quilchena in southern British Columbia.

"Big-headed flies are a group of bizarre insects whose round heads are almost entirely covered by their bulging compound eyes, which they use to hunt for mainly leafhoppers and planthoppers, renowned common garden insect pests," says Archibald.

"The newly discovered species were preserved in Eocene epoch fossil beds that are 49 million to 52 million years old, which is about 12 million to 15 million years after the extinction of the dinosaurs. This great extinction event also disrupted forests in which the dinosaurs had lived, with mostly low diversity and greatly disrupted food webs for millions of years."

By the time of these flies in the Eocene, however, forests had diversified again, but this time with many new kinds of flowering plants that are familiar to us today, such as birches, maples, and many others.

Along with these new, rich forests came an expanding diversity of pollinators and herbivorous insects, and with them, diversification of their insect predators, including these big-headed flies.

"With these new discoveries, we see that the early history of these oddly shaped insect predators provides a part of the puzzle revealing the broad ecological-evolutionary revolution of expanding predator-prey relationships and increasing biodiversity during the formation of new ecosystems," says Archibald.

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Not just clean but spotless -- Researchers show how cells tidy up

Jan. 17, 2014 — "Bang and the dirt is gone!" There are many commercials for products that claim to make the unpopular process of cleaning up easier. But it's not only our surroundings that need to be kept clean. Even our cells need to tidy up. The responsible cellular process is called autophagy, in which the coordinated action of a set of proteins removes damaged cell material or pathogens, such as bacteria, from a cell. At the same time autophagy also helps cells to survive in times of starvation by recycling the cells' own components to produce energy, similar to recycling stations in a city.

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The central player in autophagy: Atg1

For some time researcher had known the key coordinator of autophagy -- the protein Atg1. However, how Atg1 exactly does its job remained unclear, despite the efforts of many groups worldwide. Now, the team of Claudine Kraft at the Max F. Perutz Laboratories (MFPL) of the University of Vienna showed that Atg1 modifies a set of proteins with a specific recognition sequence. In collaboration with their colleagues Gustav Ammerer at MFPL and Ben Turk at the University of Yale, they not only deciphered the recognition sequence but also determined the cellular proteins that actually contain this sequence. One, Atg9, caught the interest of the researchers in particular, as it is not only a known component of the cellular "waste bag," but also contains a stunning six of those specific recognition sequences. Daniel Papinski, first author of the study, explains: "Every cell contains specialized recycling stations. In order to dispose its waste, a cell needs to wrap it up, similar to putting garbage in a bag. This cellular trash bag can then be brought to the cellular recycling station where the waste is broken down into the re-usable parts." Atg9 is essential for this process.

How does Atg1 coordinate the packaging of cellular waste?

To test how Atg1 precisely regulates the packaging of cellular waste, the researchers altered the recognition sequences of Atg9. They found that in this case, Atg1 is unable to modify Atg9 and no autophagy, and therefore no cellular waste disposal, takes place. "This scenario is similar to that in cells that have no machinery to dispose of waste at all," says Claudine Kraft, lead author of the study. More experiments revealed that after modification by Atg1, Atg9 recruits other proteins -- an interplay ensuring that cellular waste is packaged and disposed of. Involuntarily, the researcher saved the crucial and most exciting experiment for last. The method they used was only described a few months ago and allows monitoring how cells package their waste live under the microscope. Daniel Papinski says: "When we looked at cells that contained Atg9 with an altered recognition sequence, which Atg1 cannot modify, we observed that the wrapping up of the cellular waste stopped prematurely. Therefore, the proper function of Atg1 and Atg9 is crucial at the early stages of the waste disposal process, when the garbage is put into 'bags'."

A detailed understanding of such fundamental cellular events is essential for the study of diseases that go hand in hand with these processes -- in the case of autophagy Alzheimer's disease and cancer -- and in the long run will help to better treat or even prevent these diseases.

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Early warning: Internet surveillance predicts disease outbreak

In a new study published in Lancet Infectious Diseases, internet-based surveillance has been found to detect infectious diseases such Dengue Fever and Influenza up to two weeks earlier than traditional surveillance methods.

Senior author of the paper titled Internet-based surveillance systems for monitoring emerging infectious diseases, QUT Senior Research Fellow Dr Wenbiao Hu said when investigating the occurrence of epidemics, spikes in searches for information about infectious diseases could accurately predict outbreaks of that disease.

Dr Hu, based at QUT's Institute for Health and Biomedical Innovation, said there was often a lag time of two weeks before traditional surveillance methods could detect an emerging infectious disease.

"This is because traditional surveillance relies on the patient recognizing the symptoms and seeking treatment before diagnosis, along with the time taken for health professionals to alert authorities through their health networks," Dr Hu said.

"In contrast, digital surveillance can provide real-time detection of epidemics."

Dr Hu said the study found by using digital surveillance through search engine algorithms such as Google Trends and Google Insights, detecting the 2005-06 avian influenza outbreak "Bird Flu" would have been possible between one and two weeks earlier than official surveillance reports.

"In another example, a digital data collection network was found to be able to detect the SARS outbreak more than two months before the first publications by the World Health Organization (WHO)," he said.

"Early detection means early warning and that can help reduce or contain an epidemic, as well alert public health authorities to ensure risk management strategies such as the provision of adequate medication are implemented."

Dr Hu said the study found social media and micoblogs including Twitter and Facebook could also be effective in detecting disease outbreaks.

"There is the potential for digital technology to revolutionize emerging infectious disease surveillance," he said.

"While this study has looked at the effectiveness of digital surveillance systems retrospectively, Australia is well-placed to take the lead in developing a real-time infectious disease warning surveillance system.

"The next step would be to combine the approaches currently available such as social media, aggregator websites and search engines, along with other factors such as climate and temperature, and develop a real-time infectious disease predictor."

He said it was also important for future research to explore ways to apply internet-based surveillance systems on a global scale.

"The international nature of emerging infectious diseases combined with the globalization of travel and trade, have increased the interconnectedness of all countries and means detecting, monitoring and controlling these diseases is a global concern."

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Chimps can use gestures to communicate in hunt for food

Researchers at Georgia State University's Language Research Center examined how two language-trained chimpanzees communicated with a human experimenter to find food. Their results are the most compelling evidence to date that primates can use gestures to coordinate actions in pursuit of a specific goal.

The team devised a task that demanded coordination among the chimps and a human to find a piece of food that had been hidden in a large outdoor area. The human experimenter did not know where the food was hidden, and the chimpanzees used gestures such as pointing to guide the experimenter to the food.

Dr. Charles Menzel, a senior research scientist at the Language Research Center, said the design of the experiment with the "chimpanzee-as-director" created new ways to study the primate.

"It allows the chimpanzees to communicate information in the manner of their choosing, but also requires them to initiate and to persist in communication," Menzel said. "The chimpanzees used gestures to recruit the assistance of an otherwise uninformed person and to direct the person to hidden objects 10 or more meters away. Because of the openness of this paradigm, the findings illustrate the high level of intentionality chimpanzees are capable of, including their use of directional gestures. This study adds to our understanding of how well chimpanzees can remember and communicate about their environment."

The paper, "Chimpanzees Modify Intentional Gestures to Co-ordinate a Search for Hidden Food," has been published in Nature Communications. Academics at the University of Chester and University of Stirling collaborated on the research project.

Dr. Anna Roberts of the University of Chester said the findings are important.

"The use of gestures to coordinate joint activities such as finding food may have been an important building block in the evolution of language," she said.

Dr. Sarah-Jane Vick of the University of Stirling added, "Previous findings in both wild and captive chimpanzees have indicated flexibility in their gestural production, but the more complex coordination task used here demonstrates the considerable cognitive abilities that underpin chimpanzee communication."

Dr. Sam Roberts, also from the University of Chester, pointed out the analogy to childhood games.

"This flexible use of pointing, taking into account both the location of the food and the actions of the experimenter, has not been observed in chimpanzees before," Roberts said.

The project was supported by The Leakey Foundation, the Wenner-Gren Foundation, National Institutes of Health, the Economic and Social Research Council, the British Academy, the Carnegie Trust for the Universities of Scotland and the University of Stirling.

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Fighting flies: Brain cells promote fighting in male fruit flies

Jan. 17, 2014 — When one encounters a group of fruit flies invading their kitchen, it probably appears as if the whole group is vying for a sweet treat. But a closer look would likely reveal the male flies in the group are putting up more of a fight, particularly if ripe fruit or female flies are present. According to the latest studies from the fly laboratory of California Institute of Technology (Caltech) biologist David Anderson, male Drosophilae, commonly known as fruit flies, fight more than their female counterparts because they have special cells in their brains that promote fighting. These cells appear to be absent in the brains of female fruit flies.

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"The sex-specific cells that we identified exert their effects on fighting by releasing a particular type of neuropeptide, or hormone, that has also been implicated in aggression in mammals including mouse and rat," says Anderson, the Seymour Benzer Professor of Biology at Caltech, and corresponding author of the study. "In addition, there are some recent papers implicating increased levels of this hormone in people with personality disorders that lead to higher levels of aggression."

The team's findings are outlined in the January 16 version of the journal Cell.

At first glance, a fruit fly may seem nothing like a human being. But look much closer, at a genetic level, and you will find that many of the genes seen in these flies are also present -- and play similar roles -- in humans. However, while such conservation holds for genes involved in basic cellular functions and in development, whether it was also true for genes controlling complex social behaviors like aggression was far from clear.

"Our studies are the first, to our knowledge, to identify a gene that plays a conserved role in aggression all the way from flies to humans," explains Anderson, who is also a Howard Hughes Medical Institute investigator. If that is true for one such gene, it is also is likely true for others, Anderson says. "Our study validates using fruit flies as a model to discover new genes that may also control aggression in humans."

The less-complex nervous system of the fruit fly makes them easier to study than people or even mice, another genetic model organism. For this particular study, the research team created a small library consisting of different fly lines; in each line, a different set of specific neurons was genetically labeled and could be artificially activated, with each neuron type secreting a different neuropeptide. Forty such lines were tested for their ability to increase aggression when their labeled neurons were activated. The one that produced the most dramatic increase in aggression had neurons expressing a particular neuropeptide called tachykinin, or Tk.

Next, Anderson and his colleagues used a set of genetic tools to identify exactly which neurons were responsible for the effect on aggression and to see if the gene that encodes for Tk also controls aggressive behavior by acting in that cell.

"We had to winnow away the different cells to find exactly which ones were involved in aggression -- that's how we discovered that within this line, there was a male-specific set of neurons that was responsible for increased aggressive behavior," explains Kenta Asahina, a postdoctoral scholar in Anderson's lab and lead author of the study. Male-specific neurons controlling courtship behavior had previously been identified in flies, but this was the first time a male-specific neuron was found that specifically controls aggression. Having identified that neuron, the team was then able to modify its gene expression. Says Asahina, "We found that if you overproduce the gene in that cell and then stimulate the cell, you get an even stronger effect to promote aggression than if you stimulate the cell without overproducing the gene."

In fact, combining cell activation and the overproduction of the neuropeptide, which is released when the cell is activated, caused the flies to attack targets they normally would not. For example, when the researchers eliminated cues that normally promote aggression in a target fly -- such as pheromones -- the flies containing the hyperactivated "aggression" neurons attacked those targets despite the absence of the cues.

Moreover, this combined activation of the cell and the gene produced such a strong effect that the researchers were even able to get a fly to attack an inanimate object -- a fly-sized magnet -- when it was moved around in an arena.

Such behavior had never been observed previously. "A normal fly will chase the magnet, but will never attack the magnet," Asahina explains. "By over-activating these neurons, we are able to get the fly to attack an object that displays none of the normal signals that are required to elicit aggression from another fly."

"These results suggest that what these neurons are doing is promoting a state of aggressive arousal in the fly," Anderson says. "This elevated level of aggressiveness drives the fly to attack targets it would normally ignore. I wouldn't anthropomorphize the fly and say that it has increased 'anger,' but activating these neurons greatly lowers its threshold for attack."

The finding that these neurons are present in the brains of male but not female flies indicates that this sex difference in aggressive behavior is genetically based. At the same time, Asahina stresses, finding a gene that influences aggression does not mean that aggression is controlled only by genes and always genetically programmed.

"This is a very important distinction, because when people hear about a gene implicated in behavior, they automatically think it means that the behavior is genetically determined. But that is not necessarily the case," he says. "The key point here is that we can say something about how the gene acts to influence this behavior -- that is, is by functioning as a chemical messenger in cells that control this behavior in the brain. We've been able to study the problem of aggressive behavior at two levels, the cell level and the gene level, and to link those studies together by genetic experiments."

This research, Anderson says, has given his team a beachhead into the circuitry in the fly brain that controls aggression, a behavior that they will continue to try to decode.

"We have to use this point of entry to discover the larger circuit in which those cells function," Anderson says. "If aggression is like a car, and if more aggression is like a car going faster, we want to know if what we're doing when we trigger these cells is stepping on the gas or taking the foot off the brake. And we want to know where and how that's happening in the brain. That's going to take a lot of work."

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One step at a time, researchers learning how humans walk

It's never been completely clear how human beings accomplish the routine, taken-for-granted miracle we call walking, let alone running. But findings published last month in the Journal of Experimental Biology outline a specific interaction between the ankle, knee, muscles and tendons that improve the understanding of a leg moving forward in a way that maximizes motion while using minimal amounts of energy.

The research could find some of its earliest applications in improved prosthetic limbs, said researchers in the College of Engineering at Oregon State University. Later on, a more complete grasp of these principles could lead to walking or running robots that are far more agile and energy-efficient than anything that exists today.

"Human walking is extraordinarily complex and we still don't understand completely how it works," said Jonathan Hurst, an OSU professor of mechanical engineering and expert in legged locomotion in robots. There's a real efficiency to it -- walking is almost like passive falling. The robots existing today don't walk at all like humans, they lack that efficiency of motion and agility.

"When we fully learn what the human leg is doing," Hurst added, "we'll be able to build robots that work much better."

Researchers have long observed some type of high-power "push off" when the leg leaves the ground, but didn't really understand how it worked. Now they believe they do. The study concluded there are two phases to this motion. The first is an "alleviation" phase in which the trailing leg is relieved of the burden of supporting the body mass.

Then in a "launching" phase the knee buckles, allowing the rapid release of stored elastic energy in the ankle tendons, like the triggering of a catapult.

"We calculated what muscles could do and found it insufficient, by far, for generating this powerful push off," said Daniel Renjewski, a postdoctoral research associate in the Dynamic Robotics Laboratory at OSU. "So we had to look for a power-amplifying mechanism.

"The coordination of knee and ankle is critical," he said. "And contrary to what some other research has suggested, the catapult energy from the ankle is just being used to swing the leg, not add large amounts of energy to the forward motion."

Walking robots don't do this. Many of them use force to "swing" the leg forward from something resembling a hip point. It can be functional, but it's neither energy-efficient nor agile. And for more widespread use of mobile robots, energy use is crucially important, the researchers said.

"We still have a long way to go before walking robots can move with as little energy as animals use," Hurst said. "But this type of research will bring us closer to that."

The research was supported by the German Research Foundation. The Dynamic Robotics Laboratory at OSU is supported by the Human Frontier Science Program, the National Science Foundation and the Defense Advanced Research Projects Agency, and has helped create some of the leading technology in the world for robots that can walk and run.

One model can run a nine-minute mile and step off a ledge, and others are even more advanced. Robots with the ability to walk and maneuver over uneven terrain could ultimately find applications in prosthetic limbs, an exo-skeleton to assist people with muscular weakness, or use in the military, disaster response or any dangerous situation.

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