星空女人频道: 2013-05-12

2013年5月18日星期六

Electric and magnetic characteristics of a material which could be used in spintronics: Promising doped zirconia

May 17, 2013 — Materials belonging to the family of dilute magnetic oxides (DMOs) -- an oxide-based variant of the dilute magnetic semiconductors -- are good candidates for spintronics applications. This is the object of study for Davide Sangalli of the Microelectronics and Microsystems Institute (IMM) at the National Research Council (CNR), in Agrate Brianza, Italy, and colleagues.

They recently explored the effect of iron (Fe) doping on thin films of a material called zirconia (ZrO₂ oxide). For the first time, the authors bridged the gap between the theoretical predictions and the experimental measurements of this material, in a paper about to be published in The European Physical Journal B.

Spintronics exploit an intrinsic property of the electrons found in semi-conductors called spin, akin to the electrons' degree of freedom. This determines the magnetic characteristics, known as magnetic moment, of the material under study. The challenge is to create such material with the highest possible temperature, as this will ensure that its magnetic properties can be used in room-temperature applications.

To study iron-doped zirconia, they examined its magnetic properties and its electronic structure from both a theoretical and experimental perspective. They then compared theory and experiments to find the most stable configuration of the material. Theoretical work included first-principles simulations. In parallel, their experimental work relied on many different well-established analytical techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and alternating gradient force magnetometer measurements.

Sangalli and colleagues therefore gained a better understanding of doped zirconia, which features oxygen vacancies, playing a crucial role in providing its unique electronic and magnetic characteristics. They have also predicted theoretically how the deviation from the standard structure influences this material's properties. They are currently investigating, experimentally, how the magnetism evolves with changing concentrations of iron and oxygen vacancies to confirm theoretical predictions.

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2013年5月17日星期五

Skydiving is never 'plane sailing'

May 17, 2013 — Skydivers show the same level of physical stress before every jump whether a first-timer or experienced jumper, say Northumbria researchers.

Previous laboratory studies have observed that when an individual is repeatedly exposed to a stressful situation, such as public speaking or performing mental arithmetic in front of an audience, their physiological responses -- levels of arousal and stress hormones -- decrease as they become accustomed to it. Such studies conclude that the more you are exposed to a stressor, the less you will respond to it.

Scientists at Northumbria University, led by Dr Michael Smith, set out to discover whether the same affect would occur in a real world setting.

The researchers studied 24 healthy male skydivers -- 11 novices carrying out their first solo skydive, and 13 experienced skydivers who had completed at least 30 jumps -- asking them to self-report their level of anxiety and also taking saliva samples to measure levels of the stress hormone cortisol before and after the jump.

They found that, although novice skydivers reported feeling more anxious prior to the jump than experienced skydivers, both sets of jumpers responded with the same levels of biological stress reactions to the jump.

Their study, published online this month in Physiology & Behavior, is the first to observe that skydiving increases levels of cortisol which does not reduce even with repeated exposure to jumping. The results also indicate that self-reports of anxiety in experienced skydivers did not match up with their actual biological stress reactions. Though they may not have perceived themselves as being as anxious as the novice skydivers, their bodies still showed the same stress reactions as a first time jumper.

Dr Michael Smith, Senior Lecturer in Psychology, said: "This study is significant because it reveals how people respond to stressors in the real world. Very few studies have been able to examine people's true reactions as it would be unethical to deliberately and repeatedly expose volunteers to severe stress in a laboratory situation. Therefore, the most stressful laboratory situations have tended to be exercises in public speaking or performing difficult tasks in front of an audience.

"We used skydiving as our 'real world' stressor because it is an activity that does pose a genuine risk to safety and survival. Although repeated exposure to a stressor dampens the stress response in the laboratory, our findings show that this is not the case for real life stressors which pose a threat to survival."

The findings highlight the usefulness of skydiving as a naturalistic stressor in future research.

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Agriculture in China predates domesticated rice: Discovery of ancient diet shatters conventional ideas of how agriculture emerged

Current archaeological thinking is that it was the advent of rice cultivation along the Lower Yangtze River that marked the beginning of agriculture in southern China. Poor organic preservation in the study region, as in many others, means that traditional archaeobotany techniques are not possible.

Now, thanks to a new method of analysis on ancient grinding stones, the archaeologists have uncovered evidence that agriculture could predate the advent of rice in the region.

The research was the result of a two-year collaboration between Dr Huw Barton, from the School of Archaeology and Ancient History at the University of Leicester, and Dr Xiaoyan Yang, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, in Beijing.

Funded by a Royal Society UK-China NSFC International Joint Project, and other grants held by Yang in China, the research is published in PLOS ONE.

Dr Barton, Senior Lecturer in Bioarchaeology at the University of Leicester, described the find as 'hitting the jackpot': "Our discovery is totally unexpected and very exciting.

"We have used a relatively new method known as ancient starch analysis to analyse ancient human diet. This technique can tell us things about human diet in the past that no other method can.

"From a sample of grinding stones we extracted very small quantities of adhering sediment trapped in pits and cracks on the tool surface. From this material, preserved starch granules were extracted with our Chinese colleagues in the starch laboratory in Beijing. These samples were analysed in China and also here at Leicester in the Starch and Residue Laboratory, School of Archaeology and Ancient History.

"Our research shows us that there was something much more interesting going on in the subtropical south of China 5,000 years ago than we had first thought. The survival of organic material is really dependent on the particular chemical properties of the soil, so you never know what you will get until you sample. At Xincun we really hit the jackpot. Starch was well-preserved and there was plenty of it. While some of the starch granules we found were species we might expect to find on grinding and pounding stones, ie. some seeds and tuberous plants such as freshwater chestnuts, lotus root and the fern root, the addition of starch from palms was totally unexpected and very exciting."

Several types of tropical palms store prodigious quantities of starch. This starch can be literally bashed and washed out of the trunk pith, dried as flour, and of course eaten. It is non-toxic, not particularly tasty, but it is reliable and can be processed all year round. Many communities in the tropics today, particularly in Borneo and Indonesia, but also in eastern India, still rely on flour derived from palms.

Dr Barton said: "The presence of at least two, possibly three species of starch producing palms, bananas, and various roots, raises the intriguing possibility that these plants may have been planted nearby the settlement.

"Today groups that rely on palms growing in the wild are highly mobile, moving from one palm stand to another as they exhaust the clump. Sedentary groups that utilise palms for their starch today, plant suckers nearby the village, thus maintaining continuous supply. If they were planted at Xincun, this implies that 'agriculture' did not arrive here with the arrival of domesticated rice, as archaeologists currently think, but that an indigenous system of plant cultivation may have been in place by the mid Holocene.

"The adoption of domesticated rice was slow and gradual in this region; it was not a rapid transformation as in other places. Our findings may indicate why this was the case. People may have been busy with other types of cultivation, ignoring rice, which may have been in the landscape, but as a minor plant for a long time before it too became a food staple.

"Future work will focus on grinding stones from nearby sites to see if this pattern is repeated along the coast."

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Slideshow: Google I/O puts 7 platforms on parade

SAN FRANCISCO -- Although it rolled out no major new products or initiatives at its annual Google I/O developer conference here, the company that started out as a search engine showed ambitions as big as the Worldwide Web. Google announced, released or hinted at significant upgrades in the works for what amounts to seven major platforms it nurtures--Android, Chrome, Glass, Google+, Google TV, Maps...oh, and Search.

A tour of its demos showed a few interesting side projects as well. They included its latest concept for a notebook PC, an automotive infotainment system and a portable mapping system. The overarching message from the event is this company will continue to pursue many overlapping and increasingly interconnected efforts in its quest to grab eyeballs.

The darling of this year's event was Project Glass, Google's effort to get ahead of the next big thing in the booming mobile industry. The crowd was peppered with "Explorer Program" pioneers sporting the futuristic eyewear like the latest in nerd fashion. Even the robotic blimp Google engineers crafted for the event (below) had embedded Glass cameras taking aerial pictures of the event.

Our virtual tour of the demo area on the following pages provides a few highlights of what's new in all seven new platforms including a look inside the latest Chromebook Pixel notebook.

Google engineers crafted their own blimp engine with an embedded Project Glass device.

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World's smallest liquid droplets ever made in the lab, experiment suggests

May 16, 2013 — Physicists may have created the smallest drops of liquid ever made in the lab.

That possibility has been raised by the results of a recent experiment conducted by Vanderbilt physicist Julia Velkovska and her colleagues at the Large Hadron Collider, the world's largest and most powerful particle collider located at the European Laboratory for Nuclear and Particle Physics (CERN) in Switzerland. Evidence of the minuscule droplets was extracted from the results of colliding protons with lead ions at velocities approaching the speed of light.

According to the scientists' calculations, these short-lived droplets are the size of three to five protons. To provide a sense of scale, that is about one-100,000th the size of a hydrogen atom or one-100,000,000th the size of a virus.

"With this discovery, we seem to be seeing the very origin of collective behavior," said Velkovska, professor of physics at Vanderbilt who serves as a co-convener of the heavy ion program of the CMS detector, the LHC instrument that made the unexpected discovery. "Regardless of the material that we are using, collisions have to be violent enough to produce about 50 sub-atomic particles before we begin to see collective, flow-like behavior."

These tiny droplets "flow" in a manner similar to the behavior of the quark-gluon plasma, a state of matter that is a mixture of the sub-atomic particles that makes up protons and neutrons and only exists at extreme temperatures and densities. Cosmologists propose that the entire universe once consisted of this strongly interacting elixir for fractions of a second after the Big Bang when conditions were dramatically hotter and denser than they are today. Now that the universe has spent billions of years expanding and cooling, the only way scientists can reproduce this primordial plasma is to bang atomic nuclei together with tremendous energy.

The new observations are contained in a paper submitted by the CMS collaboration to the journal Physical Review D and posted on the arXiv preprint server. In addition, Vanderbilt doctoral student Shengquan Tuo recently presented the new results at a workshop held in the European Centre for Theoretical Studies in Nuclear Physics and Related Areas in Trento, Italy.

Scientists have been trying to recreate the quark-gluon plasma since the early 2000s by colliding gold nuclei using the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. This exotic state of matter is created when nuclei collide and dump a fraction of their energy into the space between them. When enough energy is released, it causes some of the quarks and gluons in the colliding particles to melt together to form the plasma. The RHIC scientists had expected the plasma to behave like a gas, but were surprised to discover that it acts like a liquid instead.

When the LHC started up, the scientists moved to the more powerful machine where they basically duplicated the results they got at RHIC by colliding lead nuclei.

In what was supposed to be a control run to check the validity of their lead-lead results, the scientists scheduled the collider to smash protons and lead nuclei together. They didn't expect to see any evidence of the plasma. Because the protons are so much lighter than lead nuclei (they have only one-208th the mass), it was generally agreed that proton-lead collisions couldn't release enough energy to produce the rare state of matter.

"The proton-lead collisions are something like shooting a bullet through an apple while lead-lead collisions are more like smashing two apples together: A lot more energy is released in the latter," said Velkovska.

Last September, the LHC did a brief test run to make sure it was adjusted properly to handle proton-lead collisions. When the results of the run were analyzed, team members were surprised to see evidence of collective behavior in five percent of the collisions -- those that were the most violent. In these cases, it appeared that when the "bullet" passed through "apple" it released enough energy to melt some of the particles surrounding the bullet hole. They appeared to be forming liquid droplets about one tenth the size of those produced by the lead-lead or gold-gold collisions.

However, the initial analysis was limited to tracking the motion of pairs of particles. The researchers knew that this analysis could be influenced by another well-known phenomenon, the production of particle jets. So, when the scheduled proton-lead run took place in January and February, they searched the data for evidence of groups of four particles that exhibit collective motion. After analyzing several billion events, they found hundreds of cases where the collisions produced more than 300 particles flowing together.

According to Tuo, only two models were advanced to explain their observations at the workshop. Of the two, the plasma droplet model seems to fit the observations best. In fact, he reported that the new data is forcing the authors of the competing model -- color glass condensate, which attributes the particle correlations to the internal gluon structure of the protons themselves -- to incorporate hydrodynamic effects, meaning that it is also describing the phenomenon as liquid droplets.

U.S. members of the CMS collaboration are supported primarily by the U.S. Department of Energy and National Science Foundation.

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Brain makes call on which ear is used for cell phone

The study -- to appear online in JAMA Otolaryngology-Head & Neck Surgery -- shows a strong correlation between brain dominance and the ear used to listen to a cell phone. More than 70% of participants held their cell phone up to the ear on the same side as their dominant hand, the study finds.

Left-brain dominant people -- who account for about 95% of the population and have their speech and language center located on the left side of the brain -- are more likely to use their right hand for writing and other everyday tasks.

Likewise, the Henry Ford study reveals most left-brain dominant people also use the phone in their right ear, despite there being no perceived difference in their hearing in the left or right ear. And, right-brain dominant people are more likely to use their left hand to hold the phone in their left ear.

"Our findings have several implications, especially for mapping the language center of the brain," says Michael Seidman, M.D., FACS, director of the division of otologic and neurotologic surgery in the Department of Otolaryngology-Head and Neck Surgery at Henry Ford.

"By establishing a correlation between cerebral dominance and sidedness of cell phone use, it may be possible to develop a less-invasive, lower-cost option to establish the side of the brain where speech and language occurs rather than the Wada test, a procedure that injects an anesthetic into the carotid artery to put part of the brain to sleep in order to map activity."

He notes that the study also may offer additional evidence that cell phone use and tumors of the brain, head and neck may not necessarily be linked.

Since nearly 80% of people use the cell phone in their right ear, he says if there were a strong connection there would be far more people diagnosed with cancer on the right side of their brain, head and neck, the dominant side for cell phone use. It's likely, he says, that the development of tumors is more "dose-dependent" based on cell phone usage.

The study began with the simple observation that most people use their right hand to hold a cell phone to their right ear. This practice, Dr. Seidman says, is illogical since it is challenging to listen on the phone with the right ear and take notes with the right hand.

To determine if there is an association between sidedness of cell phone use and auditory or language hemispheric dominance, the Henry Ford team developed an online survey using modifications of the Edinburgh Handedness protocol, a tool used for more than 40 years to assess handedness and predict cerebral dominance.

The survey included questions about which hand was used for tasks such as writing; time spent talking on cell phone; whether the right or left ear is used to listen to phone conversations; and if respondents had been diagnosed with a brain or head and neck tumor.

It was distributed to 5,000 individuals who were either with an otology online group or a patient undergoing Wada and MRI for non-invasive localization purposes.

On average, respondents' cell phone usage was 540 minutes per month. The majority of respondents (90%) were right handed, 9% were left handed and 1% was ambidextrous.

Among those who are right handed, 68% reported that they hold the phone to their right ear, while 25% used the left ear and 7% used both right and left ears. For those who are left handed, 72% said they used their left ear for cell phone conversations, while 23% used their right ear and 5% had no preference.

The study also revealed that having a hearing difference can impact ear preference for cell phone use.

In all, the study found that there is a correlation between brain dominance and laterality of cell phone use, and there is a significantly higher probability of using the dominant hand side ear.

Studies are underway to look at tumor registry banks of patients with head, neck and brain cancer to evaluate cell phone usage. Controversy still exists around a potential association of cell phone use and tumors. Until this is fully understood, Dr. Seidman advises using hands-free modes for calls rather than holding a phone up to the side of the head.

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Invasive 'crazy ants' are displacing fire ants in areas throughout southeastern U.S.

May 16, 2013 — Invasive "crazy ants" are displacing fire ants in areas across the southeastern United States, according to researchers at The University of Texas at Austin. It's the latest in a history of ant invasions from the southern hemisphere and may prove to have dramatic effects on the ecosystem of the region.

The "ecologically dominant" crazy ants are reducing diversity and abundance across a range of ant and arthropod species -- but their spread can be limited if people are careful not to transport them inadvertently, according to Ed LeBrun, a research associate with the Texas invasive species research program at the Brackenridge Field Laboratory in the College of Natural Sciences

The study by LeBrun and his colleagues was published in Biological Invasions.

"When you talk to folks who live in the invaded areas, they tell you they want their fire ants back," said LeBrun. "Fire ants are in many ways very polite. They live in your yard. They form mounds and stay there, and they only interact with you if you step on their mound."

LeBrun said that crazy ants, by contrast, "go everywhere." They invade people's homes, nest in crawl spaces and walls, become incredibly abundant and damage electrical equipment.

The crazy ants were first discovered in the U.S. in 2002 by a pest control operator in a suburb of Houston, and have since established populations in 21 counties in Texas, 20 counties in Florida, and a few sites in southern Mississippi and southern Louisiana.

In 2012 the species was formally identified as Nylanderia fulva, which is native to northern Argentina and southern Brazil. Frequently referred to as Rasberry crazy ants, these ants recently have been given the official common name "Tawny crazy ants."

The Tawny crazy ant invasion is the most recent in a series of ant invasions from South America brought on by human movement. The Argentine ant invaded through the port of New Orleans in about 1891. In 1918 the black imported fire ant showed up in Mobile, Ala. Then in the 1930s, the red imported fire ant arrived in the U.S. and began displacing the black fire ant and the Argentine ants.

The UT researchers studied two crazy ant invasion sites on the Texas Gulf Coast and found that in those areas where the Tawny crazy ant population is densest, fire ants were eliminated. Even in regions where the crazy ant population is less dense, fire ant populations were drastically reduced. Other ant species, particularly native species, were also eliminated or diminished.

LeBrun said crazy ants are much harder to control than fire ants. They don't consume most of the poison baits that kill fire ant mounds, and they don't have the same kinds of colony boundaries that fire ants do. That means that even if they're killed in a certain area, the supercolony survives and can swarm back over the area.

"They don't sting like fire ants do, but aside from that they are much bigger pests," he said. "There are videos on YouTube of people sweeping out dustpans full of these ants from their bathroom. You have to call pest control operators every three or four months just to keep the infestation under control. It's very expensive."

LeBrun said that in northern Argentina and southern Brazil, where the ants are native, populations are likely held in check by other ant species and a variety of natural enemies. In the U.S. there is no such natural control.

Here the crazy ants can attain densities up to 100 times as great as all other ants in the area combined. In the process, they monopolize food sources and starve out other species. LeBrun said the crazy ants, which are omnivorous, may also directly attack and kill other ant and arthropod species.

The overall result is a significant reduction in abundance and biodiversity at the base of the food chain, which is likely to have implications for the ecosystem as a whole.

"Perhaps the biggest deal is the displacement of the fire ant, which is the 300 pound gorilla in Texas ecosystems these days," said LeBrun. "The whole system has changed around fire ants. Things that can't tolerate fire ants are gone. Many that can have flourished. New things have come in. Now we are going to go through and whack the fire ants and put something in its place that has a very different biology. There are going to be a lot of changes that come from that."

LeBrun said a great deal about the Tawny crazy ants remains unknown, including their potential range. So far, most of the colonies are in fairly wet environments with mild winters, near the coast, so it may be the case that they can't thrive in drier or colder climates, and that fire ants will remain dominant in those areas.

The spread of the Tawny crazy ants may also be limited, even within the more hospitable climates, by caution from humans. The reproductive members of the species don't fly. So when left to their own devices, crazy ant colonies can only advance about 200 meters a year. That means they're dependent on humans to colonize new areas.

"They are opportunistic nesters," said LeBrun. "They can take up residence in everything from a house plant, to an empty container left outside, to an RV. So they're easily transported by us. But the flip side of that is that if people living in or visiting invaded areas are careful and check for the crazy ants when moving or going on longer trips, they could have a huge impact on the spread." Nursery products also appear to be a key way these ants spread, so both buyers and sellers should be watchful for these ants.

LeBrun said that cutting down on the number of transplantation events could slow the spread by years or decades. And that extra time could give the ecosystem time to adapt and researchers time to develop better control methods.

"We can really make a difference," he said, "but we need to be careful, and we need to know more."

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World's melting glaciers making large contribution to sea rise

The new research found that all glacial regions lost mass from 2003 to 2009, with the biggest ice losses occurring in Arctic Canada, Alaska, coastal Greenland, the southern Andes and the Himalayas. The glaciers outside of the Greenland and Antarctic sheets lost an average of roughly 260 billion metric tons of ice annually during the study period, causing the oceans to rise 0.03 inches, or about 0.7 millimeters per year.

The study compared traditional ground measurements to satellite data from NASA's Ice, Cloud and Land Elevation Satellite, or ICESat, and the Gravity Recovery and Climate Experiment, or GRACE, missions to estimate ice loss for glaciers in all regions of the planet.

"For the first time, we've been able to very precisely constrain how much these glaciers as a whole are contributing to sea rise," said geography Assistant Professor Alex Gardner of Clark University in Worcester, Mass., lead study author. "These smaller ice bodies are currently losing about as much mass as the ice sheets."

A paper on the subject is being published in the May 17 issue of the journal Science.

"Because the global glacier ice mass is relatively small in comparison with the huge ice sheets covering Greenland and Antarctica, people tend to not worry about it," said CU-Boulder Professor Tad Pfeffer, a study co-author. "But it's like a little bucket with a huge hole in the bottom: it may not last for very long, just a century or two, but while there's ice in those glaciers, it's a major contributor to sea level rise," said Pfeffer, a glaciologist at CU-Boulder's Institute of Arctic and Alpine Research

ICESat, which ceased operations in 2009, measured glacier changes using laser altimetry, which bounces laser pulses off the ice surface to determine changes in the height of ice cover. The GRACE satellite system, still operational, detects variations in Earth's gravity field resulting from changes in the planet's mass distribution, including ice displacements.

GRACE does not have a fine enough resolution and ICESat does not have sufficient sampling density to study small glaciers, but mass change estimates by the two satellite systems for large glaciated regions agree well, the scientists concluded.

"Because the two satellite techniques, ICESat and GRACE, are subject to completely different types of errors, the fact that their results are in such good agreement gives us increased confidence in those results," said CU-Boulder physics Professor John Wahr, a study co-author and fellow at the university's Cooperative Institute for Research in Environmental Sciences.

Ground-based estimates of glacier mass changes include measurements along a line from a glacier's summit to its edge, which are extrapolated over a glacier's entire area. Such measurements, while fairly accurate for individual glaciers, tend to cause scientists to overestimate ice loss when extrapolated over larger regions, including individual mountain ranges, according to the team.

Current estimates predict if all the glaciers in the world were to melt, they would raise sea level by about two feet. In contrast, an entire Greenland ice sheet melt would raise sea levels by about 20 feet, while if Antarctica lost its ice cover, sea levels would rise nearly 200 feet.

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Carbon in a twirl: The science behind a self-assembled nano-carbon helix

May 16, 2013 — Nanotechnology draws on the fabrication of nanostructures. Scientists have now succeeded in growing a unique carbon structure at the nanoscale that resembles a tiny twirled moustache.

Their method might lead the way to the formation of more complex nano-networks. Researchers of the Electronic Properties of Materials Group at the Faculty of Physics (University of Vienna) and their international collaborators have published their results in the new open access journal of the Nature Publishing group, Scientific Reports.

Nanomaterials exhibit unique properties that can only unfold when the structures of the material are very small -- that is, at the nanoscale. In order to exploit these special properties such as, for example, specific quantum effects it is very important to produce predefined nanostructures in a controlled way and interpret the formation of their shape. Scientists try to understand how to initiate and control the growth of nanomaterials and are exploring different ways to design and build up nanostructures with fine control over shapes. In nature, many organic forms grow bilaterally, that is, symmetrically in two distinct directions. An international team of researchers from the University of Vienna (Austria), the University of Surrey (UK) and the IFW Dresden (Germany) have now achieved such a bilateral formation of inorganic nanomaterials in a controlled environment by implementing a new method.

How to grow a nanomoustache

The scientists pressurized a gas consisting of carbon and iron atoms at an elevated temperature until they observed two arms of carbon atoms spontaneously started growing out of an iron core. When the iron core was small enough, the two carbon arms started spiraling at their ends so that the whole nanostructure bore a striking resemblance with a twirled moustache. "The encouraging insights we gained from our experiments provide a very good starting point for the controlled production of extraordinary new materials with designed nanostructures," expects Dr. Hidetsugu Shiozawa, leading author of the scientific publication and researcher at the Faculty of Physics at the University of Vienna.

Useful imperfections

In order to find out more about the internal architecture of the nanomoustaches, the researchers cut their nanomaterial into extremely thin slices and used a special microscopy technique -- the transmission electron microscopy -- to have a closer look at the slices. When nanostructures grow, structural imperfections of the material emerge that are characteristic for the way the material was formed. In the observed herringbone pattern of the sliced nanomoustache, the distribution of the structural imperfections allowed the scientists to look back in time and extract further information about the formation of the nanomaterial. For future applications it will be fundamental to apply their knowledge to the growth of nanostructures in 2 or 3 dimensions in order to build regular patterns and networks at the nanoscale. Therefore, the scientists strive to understand even more about the mechanism behind the formation pattern of the nanomoustaches and are aiming at growing more dimensional and more complex nanostructures in future research projects.

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Who's your daddy? Infidelity and paternity in reed warblers

Herbert Hoi and colleagues of the University of Veterinary Medicine, Vienna, together with scientists from the Slovak Academy of Sciences, Bratislava, carried out experiments with reed warblers to see how a situation of potential infidelity affects later paternal investment in the chicks and whether it does in fact lead to extra-pair mating. They found that the males aggressively try to chase off competitors and to keep potentially "double-dealing" females in line. But whether or not they manage, they turn out to be caring fathers once the babies are born. The findings were published in April 2013 in the online journal PLOS ONE.

Reed warblers are socially monogamous, defend their territory, and both parents care for the offspring. Scientists of the Konrad-Lorenz-Institute of Ethology of the Vetmeduni Vienna for the first time tried to experimentally test the behaviour of reed warblers (Acrocephalus scirpaceus) after a potential act of "cheating" by the female. How does the male treat a competitor, and how does an "affair" affect care for the brood? To answer these questions they simulated an increased risk of adulterous behaviour in female reed warblers by briefly introducing a caged extra male to 31 reed warbler pairs during the female's fertile period. In addition they played back recorded songs of randomly selected warbler males from the area. The scientists then observed nest building activity and feeding of offspring, and determined chick paternity through DNA analyses.

When the going gets tough

From previous observations it was known that male territory owners will aggressively try to chase away intruders (conspecific males) as soon as they detect them. This territorial behaviour is interpreted as a paternity guard. Herbert Hoi and his colleagues observed that all males tried to attack and chase away the caged intruder. When the female appeared to show interest in the intruder, the male behaved considerably more aggressively, both to the intruder and to his female partner. Almost half of the females did not even approach the newcomer. Herbert Hoi explains, "We think that the males are more aggressive when their partners are watching because first, it only pays for the male to show off when the "babe" is watching him, and second, he certainly has more reason to fear being cuckolded or even losing his partner when the newcomer approaches his female."

A "cuckoo" in the nest

Hoi and colleagues found that many nests housed nestlings fathered outside the pair-bond. This was the case both in the experimental and in the control group. Those females that had been observed to show interest in the intruder were also later found to be more likely to have extra-pair chicks in their nest. In addition, the results suggest that larger females seem to be more promiscuous.

Cuckolded males are caring fathers

The researchers then looked at whether offspring care was affected by paternity uncertainty. The results were surprising: Males seem to readily procure food for the chicks, regardless whether they are their own or not. Females, however, cared significantly less for their young if they had been faced with the simulated intruder. Perhaps the female's potential infidelity had no effect on the male's subsequent feeding investment because he cannot distinguish his own from an extra-pair chick. On the other hand, females who perceived their males as unable to repel an intruder quickly enough and therefore as a "weakling," then invest less in the joint offspring. The only chance a male has to ensure successful paternity seems to be to quickly get rid of potential competitors.

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