Apr 23, 2017

Making batteries from waste glass bottles

Waste glass bottles are turned into nanosilicon anodes using a low cost chemical process.
Researchers at the University of California, Riverside's Bourns College of Engineering have used waste glass bottles and a low-cost chemical process to create nanosilicon anodes for high-performance lithium-ion batteries. The batteries will extend the range of electric vehicles and plug-in hybrid electric vehicles, and provide more power with fewer charges to personal electronics like cell phones and laptops.

Titled "Silicon Derived from Glass Bottles as Anode Materials for Lithium Ion Full Cell Batteries," an article describing the research was published in the Nature journal Scientific Reports. Cengiz Ozkan, professor of mechanical engineering, and Mihri Ozkan, professor of electrical engineering, led the project.

Even with today's recycling programs, billions of glass bottles end up in landfills every year, prompting the researchers to ask whether silicon dioxide in waste beverage bottles could provide high purity silicon nanoparticles for lithium-ion batteries.

Silicon anodes can store up to 10 times more energy than conventional graphite anodes, but expansion and shrinkage during charge and discharge make them unstable. Downsizing silicon to the nanoscale has been shown to reduce this problem, and by combining an abundant and relatively pure form of silicon dioxide and a low-cost chemical reaction, the researchers created lithium-ion half-cell batteries that store almost four times more energy than conventional graphite anodes.

To create the anodes, the team used a three-step process that involved crushing and grinding the glass bottles into a fine white power, a magnesiothermic reduction to transform the silicon dioxide into nanostructured silicon, and coating the silicon nanoparticles with carbon to improve their stability and energy storage properties.

As expected, coin cell batteries made using the glass bottle-based silicon anodes greatly outperformed traditional batteries in laboratory tests. Carbon-coated glass derived-silicon (gSi@C) electrodes demonstrated excellent electrochemical performance with a capacity of ~1420 mAh/g at C/2 rate after 400 cycles.

Changling Li, a graduate student in materials science and engineering and lead author on the paper, said one glass bottle provides enough nanosilicon for hundreds of coin cell batteries or three-five pouch cell batteries.

"We started with a waste product that was headed for the landfill and created batteries that stored more energy, charged faster, and were more stable than commercial coin cell batteries. Hence, we have very promising candidates for next-generation lithium-ion batteries," Li said.

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New quantum liquid crystals may play role in future of computers

These images show light patterns generated by a rhenium-based crystal using a laser method called optical second-harmonic rotational anisotropy. At left, the pattern comes from the atomic lattice of the crystal. At right, the crystal has become a 3-D quantum liquid crystal, showing a drastic departure from the pattern due to the atomic lattice alone.
Physicists at the Institute for Quantum Information and Matter at Caltech have discovered the first three-dimensional quantum liquid crystal -- a new state of matter that may have applications in ultrafast quantum computers of the future.

"We have detected the existence of a fundamentally new state of matter that can be regarded as a quantum analog of a liquid crystal," says Caltech assistant professor of physics David Hsieh, principal investigator on a new study describing the findings in the April 21 issue of Science. "There are numerous classes of such quantum liquid crystals that can, in principle, exist; therefore, our finding is likely the tip of an iceberg."

Liquid crystals fall somewhere in between a liquid and a solid: they are made up of molecules that flow around freely as if they were a liquid but are all oriented in the same direction, as in a solid. Liquid crystals can be found in nature, such as in biological cell membranes. Alternatively, they can be made artificially -- such as those found in the liquid crystal displays commonly used in watches, smartphones, televisions, and other items that have display screens.

In a "quantum" liquid crystal, electrons behave like the molecules in classical liquid crystals. That is, the electrons move around freely yet have a preferred direction of flow. The first-ever quantum liquid crystal was discovered in 1999 by Caltech's Jim Eisenstein, the Frank J. Roshek Professor of Physics and Applied Physics. Eisenstein's quantum liquid crystal was two-dimensional, meaning that it was confined to a single plane inside the host material -- an artificially grown gallium-arsenide-based metal. Such 2-D quantum liquid crystals have since been found in several more materials including high-temperature superconductors -- materials that conduct electricity with zero resistance at around -150 degrees Celsius, which is warmer than operating temperatures for traditional superconductors.

John Harter, a postdoctoral scholar in the Hsieh lab and lead author of the new study, explains that 2-D quantum liquid crystals behave in strange ways. "Electrons living in this flatland collectively decide to flow preferentially along the x-axis rather than the y-axis even though there's nothing to distinguish one direction from the other," he says.

Now Harter, Hsieh, and their colleagues at Oak Ridge National Laboratory and the University of Tennessee have discovered the first 3-D quantum liquid crystal. Compared to a 2-D quantum liquid crystal, the 3-D version is even more bizarre. Here, the electrons not only make a distinction between the x, y, and z axes, but they also have different magnetic properties depending on whether they flow forward or backward on a given axis.

"Running an electrical current through these materials transforms them from nonmagnets into magnets, which is highly unusual," says Hsieh. "What's more, in every direction that you can flow current, the magnetic strength and magnetic orientation changes. Physicists say that the electrons 'break the symmetry' of the lattice."

Harter actually hit upon the discovery serendipitously. He was originally interested in studying the atomic structure of a metal compound based on the element rhenium. In particular, he was trying to characterize the structure of the crystal's atomic lattice using a technique called optical second-harmonic rotational anisotropy. In these experiments, laser light is fired at a material, and light with twice the frequency is reflected back out. The pattern of emitted light contains information about the symmetry of the crystal. The patterns measured from the rhenium-based metal were very strange -- and could not be explained by the known atomic structure of the compound.

"At first, we didn't know what was going on," Harter says. The researchers then learned about the concept of 3-D quantum liquid crystals, developed by Liang Fu, a physics professor at MIT. "It explained the patterns perfectly. Everything suddenly made sense," Harter says.

The researchers say that 3-D quantum liquid crystals could play a role in a field called spintronics, in which the direction that electrons spin may be exploited to create more efficient computer chips. The discovery could also help with some of the challenges of building a quantum computer, which seeks to take advantage of the quantum nature of particles to make even faster calculations, such as those needed to decrypt codes. One of the difficulties in building such a computer is that quantum properties are extremely fragile and can easily be destroyed through interactions with their surrounding environment. A technique called topological quantum computing -- developed by Caltech's Alexei Kitaev, the Ronald and Maxine Linde Professor of Theoretical Physics and Mathematics -- can solve this problem with the help of a special kind of superconductor dubbed a topological superconductor.

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Apr 22, 2017

In young bilingual children, two languages develop simultaneously but independently

Erika Hoff, Ph.D., lead author of the study, a psychology professor in FAU’s Charles E. Schmidt College of Science, and director of the Language Development Lab.
A new study of Spanish-English bilingual children by researchers at Florida Atlantic University published in the journal Developmental Science finds that when children learn two languages from birth each language proceeds on its own independent course, at a rate that reflects the quality of the children's exposure to each language.

In addition, the study finds that Spanish skills become vulnerable as children's English skills develop, but English is not vulnerable to being taken over by Spanish. In their longitudinal data, the researchers found evidence that as the children developed stronger skills in English, their rates of Spanish growth declined. Spanish skills did not cause English growth to slow, so it's not a matter of necessary trade-offs between two languages.

"One well established fact about monolingual development is that the size of children's vocabularies and the grammatical complexity of their speech are strongly related. It turns out that this is true for each language in bilingual children," said Erika Hoff, Ph.D., lead author of the study, a psychology professor in FAU's Charles E. Schmidt College of Science, and director of the Language Development Lab. "But vocabulary and grammar in one language are not related to vocabulary or grammar in the other language."

For the study, Hoff and her collaborators David Giguere, a graduate research assistant at FAU and Jamie M. Quinn, a graduate research assistant at Florida State University, used longitudinal data on children who spoke English and Spanish as first languages and who were exposed to both languages from birth. They wanted to know if the relationship between grammar and vocabulary were specific to a language or more language general. They measured the vocabulary and level of grammatical development in these children in six-month intervals between the ages of 2 and a half to 4 years.

The researchers explored a number of possibilities during the study. They thought it might be something internal to the child that causes vocabulary and grammar to develop on the same timetable or that there might be dependencies in the process of language development itself. They also considered that children might need certain vocabulary to start learning grammar and that vocabulary provides the foundation for grammar or that grammar helps children learn vocabulary. One final possibility they explored is that it may be an external factor that drives both vocabulary development and grammatical development.

"If it's something internal that paces language development then it shouldn't matter if it's English or Spanish, everything should be related to everything," said Hoff. "On the other hand, if it's dependencies within a language of vocabulary and grammar or vice versa then the relations should be language specific and one should predict the other. That is a child's level of grammar should predict his or her future growth in vocabulary or vice versa."

Turns out, the data were consistent only with the final possibility -- that the rate of vocabulary and grammar development are a function of something external to the child and that exerts separate influences on growth in English and Spanish. Hoff and her collaborators suggest that the most cogent explanation would be in the properties of children's input or their language exposure.

"Children may hear very rich language use in Spanish and less rich use in English, for example, if their parents are more proficient in Spanish than in English," said Hoff. "If language growth were just a matter of some children being better at language learning than others, then growth in English and growth in Spanish would be more related than they are."

Detailed results of the study are described in the article, "What Explains the Correlation between Growth in Vocabulary and Grammar? New Evidence from Latent Change Score Analyses of Simultaneous Bilingual Development."

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How Venus flytrap triggers digestion

The traps' insides are lined with red glands (a) that work like a plant 'stomach' after a prey is caught. The glands secrete a digestive enzyme. This secretory mechanism was shown at the vesicle level in plants for the first time (b). The model illustration (c) shows that activated glands absorb calcium (Ca2+), thereby triggering the jasmonate signalling pathway and the secreting of hydrochloric acid (HCL) and digestive enzymes.
Venus flytrap (Dionaea muscipula) is a carnivorous plant. Catching its prey, mainly insects, with a trapping structure formed by its leaves, the plants' glands secrete an enzyme to decompose the prey and take up the nutrients released.

Although postulated since Darwin's pioneering studies, these secretory events have not been measured and analysed until now: An international team of researchers headed by Rainer Hedrich, a biophysicist from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany, present the results in the journal PNAS.

When a prey tries to escape the closed trap, it will inevitably touch the sensory hairs inside. Any mechanical contact with the hairs triggers an electrical signal that spreads across the trap in waves. From the third signal, the plant produces the hormone jasmonate; after the fifth signal, the digestive glands that line the inside of the traps like turf are activated.

Glands secrete acidic vesicles to decompose prey

What happens next in the gland cells? They increasingly produce membranous bubbles filled with liquid (secretory vesicles) and give off their content. This happens after mechanical stimulation of the sensory hairs but also when the glands come into contact with the hormone jasmonate. The entire process depends on calcium and is controlled by a number of specific proteins.

Moreover, genes are activated in the glands: "We assume that they provide for the vesicles being loaded with protons and chloride, that is hydrochloric acid," Hedrich explains and he adds: "We used ion-sensitive electrodes to measure that repeated touching of the sensory hairs triggers the influx of calcium ions into the gland. The rising calcium level in the cytoplasm causes the vesicles to fuse with the plasma membrane, similarly to the neurotransmitter secretion of neurons. The influx of calcium is followed by the efflux of protons and chloride after a time delay."

Conclusive analysis with carbon fibre electrodes

What else do the gland vesicles contain? This was analysed using carbon fibre electrodes in cooperation with Erwin Neher (Göttingen), winner of the Nobel Prize, who has a lot of experience with this technique. Together with Neher, the JMU researcher Sönke Scherzer adjusted the measurement method to the conditions prevailing inside the Venus flytrap.

The team positioned a carbon fibre electrode over the gland surface and waited with excitement what would happen. "At first, we were disappointed because we did not immediately detect signals as known from secretory cells in humans and animals," Scherzer recalls.

Should the vesicles contain hydrochloric acid in the first hours after catching the prey but no digestive enzymes yet? And no molecules yet that assure the enzymes' functioning in the acidic environment? Does the plant have to produce all this first?

That's exactly how it works: Molecular biologist Ines Fuchs found out that the plant only starts to produce the enzymes that decompose the prey after several hours. The first characteristic signals occurred after six hours and the process was in full swing 24 hours later. During this phase, the trap is completely acidic and rich in digestive enzymes.

Stabilising effect of glutathione keeps enzymes fit

Professor Heinz Rennenberg (Freiburg) also found glutathione (GSH) in the secreted enzyme. This molecule keeps the enzymes functional in the acidic environment of the Venus flytrap.

The same processes as described above take place in the same chronological order both when the sensory hairs are stimulated and when exposing the trap to the hormone jasmonate only. "A touch will very quickly trigger the jasmonate signalling pathway, but it takes time until the vesicles are produced and loaded with the proper freight which is facilitated by the hormone," Hedrich explains.

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Apr 21, 2017

Environmental 'memories' passed on for 14 generations

This is a C. elegans worm.
Led by Dr Ben Lehner, group leader at the EMBL-CRG Systems Biology Unit and ICREA and AXA Professor, together with Dr Tanya Vavouri from the Josep Carreras Leukaemia Research Institute and the Institute for Health Science Research Germans Trias i Pujol (IGTP), the researchers noticed that the impact of environmental change can be passed on in the genes for many generations while studying C. elegans worms carrying a transgene array -- a long string of repeated copies of a gene for a fluorescent protein that had been added into the worm genome using genetic engineering techniques.

If the worms were kept at 20 degrees Celsius, the array of transgenes was less active, creating only a small amount of fluorescent protein. But shifting the animals to a warmer climate of 25 degrees significantly increased the activity of the transgenes, making the animals glow brightly under ultraviolet light when viewed down a microscope.

When these worms were moved back to the cooler temperature, their transgenes were still highly active, suggesting they were somehow retaining the 'memory' of their exposure to warmth. Intriguingly, this high activity level was passed on to their offspring and onwards for 7 subsequent generations kept solely at 20 degrees, even though the original animals only experienced the higher temperature for a brief time. Keeping worms at 25 degrees for five generations led to the increased transgene activity being maintained for at least 14 generations once the animals were returned to cooler conditions.

Although this phenomenon has been seen in a range of animal species -- including fruit flies, worms and mammals including humans -- it tends to fade after a few generations. These findings, which will be published in the journal Science, represent the longest maintenance of transgenerational environmental 'memory' ever observed in animals to date.

"We discovered this phenomenon by chance, but it shows that it's certainly possible to transmit information about the environment down the generations," says Lehner. "We don't know exactly why this happens, but it might be a form of biological forward-planning," adds the first author of the study and CRG Alumnus, Adam Klosin. "Worms are very short-lived, so perhaps they are transmitting memories of past conditions to help their descendants predict what their environment might be like in the future," adds Vavouri.

Comparing the transgenes that were less active with those that had become activated by the higher temperature, Lehner and his team discovered crucial differences in a type of molecular 'tag' attached to the proteins packaging up the genes, known as histone methylation.

Transgenes in animals that had only ever been kept at 20 degrees had high levels of histone methylation, which is associated with silenced genes, while those that had been moved to 25 degrees had largely lost the methylation tags. Importantly, they still maintained this reduced histone methylation when moved back to the cooler temperature, suggesting that it is playing an important role in locking the memory into the transgenes.

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Astronomers perform largest-ever survey of high-mass binary star systems

The Milky Way.
In addition to solo stars like our Sun, the universe contains binary systems comprising two massive stars that interact with each other. In many binaries the two stars are close enough to exchange matter and may even merge, producing a single high-mass star that spins at great speed.

Until now the number of known high-mass binaries has been very small, basically confined to those identified in our galaxy, the Milky Way.

An international group of astronomers led by researchers at the University of São Paulo's Institute of Astronomy, Geophysics & Atmospheric Sciences (IAG-USP) in Brazil, have just extended the list of by identifying and characterizing 82 new high-mass binaries located in the Tarantula Nebula, also known as 30 Doradus, in the Large Magellanic Cloud. The LMC is a satellite galaxy of the Milky Way and is about 160,000 light years from Earth.

The results of the study are described in article published in the journal Astronomy & Astrophysics.

"By identifying and characterizing these 82 high-mass binaries, we have more than doubled the number of these objects, and in a completely new region with very different conditions from those found in the Milky Way," said Leonardo Andrade de Almeida, a postdoctoral fellow at IAG-USP and first author of the study.

In research supervised by Augusto Damineli Neto, a full professor at IAG and a co-author of the article, Almeida analyzed the data obtained during the VLT-FLAMES Tarantula Survey and Tarantula Massive Binary Monitoring observation campaigns performed by the European Southern Observatory (ESO) from 2011.

Using FLAMES/GIRAFFE, a spectrograph coupled to ESO's Very Large Telescope (VLT), which has four 8 m primary mirrors and operates in Chile's Atacama Desert, the observation campaigns collected spectral data for over 800 high-mass objects in the region of the Tarantula Nebula, so named because its glowing filaments resemble spider legs.

From this total of 800 observed objects, the astronomers who worked on the two surveys identified 100 candidate binaries of spectral type O (very hot and massive) in a sample of 360 stars based on parameters such as the amplitude of variations in their radial velocity (the velocity of motion away from or toward an observer).

For the last two years, Almeida has collaborated with colleagues in other countries on an analysis of these 100 candidate high-mass binaries using the FLAMES/GIRAFFE spectrograph and has managed to characterize 82 of them completely.

"This represents the largest survey and spectroscopic characterization of massive binary systems every performed," he said. "It was only possible thanks to the technological capabilities of the FLAMES/GIRAFFE spectrograph."

The scientific instrument developed by ESO can be used to obtain spectra for a number of objects simultaneously, and weaker objects can be observed because it is coupled to the VLT, which has large mirrors and captures more light, Almeida explained.

"We can collect 136 spectra in a single observation using FLAMES/GIRAFFE," he said. "Nothing similar could be done before. Our instruments could only observe individual objects and it took much longer to characterize them."

Spectroscopic analysis of the 82 binaries showed that properties such as mass ratio, orbital period (the time taken to complete one orbit) and orbital eccentricity (the amount by which the orbit deviates from a perfect circle) were highly similar to those observed in the Milky Way.

This was unexpected since the LMC embodies a phase of the universe prior to the Milky Way when the largest number of high-mass stars were formed. For this reason, its metallicity -- the proportion of its matter made up of chemical elements different from hydrogen and helium, the primordial atoms that gave rise to the first stars -- is only half that of the binaries found in the Milky Way, whose metallicity is very close to the Sun's.

"At the beginning of the universe, stars were metal-poor but chemical evolution increased their metallicity," Almeida said.

This analysis of binaries in the LMC, he added, provides the first direct constraints on the properties of massive binaries in galaxies whose stars were formed in the early universe and have the LMC's metallicity.

"The discoveries made during the study may provide better measurements for use in more realistic simulations of how high-mass stars evolved in the different phases of the universe. If so, we'll be able to obtain more precise estimates of the rate at which black holes, neutron stars and supernovae were formed in each phase, for example," he said.

High-mass stars are the most important drivers of the chemical evolution of the universe. Because they are more massive, they produce more heavy metals, evolve more rapidly, and end their lives as supernovae, ejecting all their matter into the interstellar medium. This matter is recycled to form a new population of stars.

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Genetic evidence points to nocturnal early mammals

Many modern mammals, like this wood mouse, are nocturnal, thanks to evolutionary developments such as night vision in their distant ancestors, Stanford researchers say.
Our earliest mammalian ancestors likely skulked through the dark, using their powerful night-time vision to find food and avoid reptilian predators that hunted by day. This conclusion, published by Stanford researchers April 21 in Scientific Reports, used genetic data to support existing fossil evidence suggesting that our distant relatives may have adapted to life in the dark.

The team, led by Liz Hadly, professor of biology and senior author on the paper, examined genes involved in night vision in animals throughout the evolutionary tree, looking for places where those genes became enhanced.

"This method is like using the genome as a fossil record, and with it we've shown when genes involved in night vision appear," Hadly said. "It's a very powerful way of corroborating a story that has been, up to now, only hypothesized."

Mammals versus reptiles

Mammals and reptiles share a common ancestor, with the earliest mammal-like animals appearing in the Late Triassic (about 200 million years ago). Fossil evidence suggests that early mammals had excellent hearing and sense of smell and were likely also warm-blooded. All of these features are common in their descendants, the living mammals, most of whom are nocturnal. Therefore, experts have hypothesized that early mammals were also nocturnal. This study offers direct, genetic evidence for that hypothesis.

To trace the evolution of nocturnality, the researchers studied genes that the lead author, visiting scholar Yonghua Wu, had previously found associated with night vision in certain birds, such as owls. The team members examined those night-vision genes in many mammals and reptiles, including snakes, alligators, mice, platypuses and humans. Using what they know about how those animals are related, they figured out when in their evolutionary histories, if ever, the function of these genes was enhanced.

From this, they deduced that the earliest common ancestor did not have good night vision and was instead active during the day. However, soon after the split, mammals began enhancing their night vision genes, allowing them to begin to roam at night, thus avoiding the reptiles that hunted during the day.

"Early mammals coexisted with early reptiles in the Age of the Dinosaurs and somehow escaped extinction," Wu said. "This research further supports the hypothesis that diurnal reptiles, such as lizards, snakes and their relatives, competed with mammals and may have led them to better adapt to dim light conditions."

In the millions of years that have elapsed since mammals and reptiles diverged, natural selection and evolution haven't stopped. Not all mammals are still nocturnal. Some groups of mammals have reoccupied the day, adapting in various ways to daylight activity. These animals include cheetahs, pikas, camels, elephants, and, of course, humans.

"Understanding the constant pressure to get better at seeing the world at night for over 100 million years is a beautiful way of thinking about evolution," Hadly said. "We think of it as something simple -- seeing in the light or the dark -- but these genes are being constantly refined and altered by natural selection."

Filling in our history

The methods used by these researchers could be applied to different areas of the animal evolutionary tree to learn more about the evolution of vision, including how humans made the switch to bright-light vision. This study is also an example of how little information we have about the first mammals, compared to what we know about our ancient and more compelling reptile cousins, the dinosaurs.

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Origins of Indonesian Hobbits finally revealed

This is a reconstructed skull of Homo floresiensis.
The most comprehensive study on the bones of Homo floresiensis, a species of tiny human discovered on the Indonesian island of Flores in 2003, has found that they most likely evolved from an ancestor in Africa and not from Homo erectus as has been widely believed.

The study by The Australian National University (ANU) found Homo floresiensis, dubbed "the hobbits" due to their small stature, were most likely a sister species of Homo habilis -- one of the earliest known species of human found in Africa 1.75 million years ago.

Data from the study concluded there was no evidence for the popular theory that Homo floresiensis evolved from the much larger Homo erectus, the only other early hominid known to have lived in the region with fossils discovered on the Indonesian mainland of Java.

Study leader Dr Debbie Argue of the ANU School of Archaeology & Anthropology, said the results should help put to rest a debate that has been hotly contested ever since Homo floresiensis was discovered.

"The analyses show that on the family tree, Homo floresiensis was likely a sister species of Homo habilis. It means these two shared a common ancestor," Dr Argue said.

"It's possible that Homo floresiensis evolved in Africa and migrated, or the common ancestor moved from Africa then evolved into Homo floresiensis somewhere."

Homo floresiensis is known to have lived on Flores until as recently as 54,000 years ago.

The study was the result of an Australian Research Council grant in 2010 that enabled the researchers to explore where the newly-found species fits in the human evolutionary tree.

Where previous research had focused mostly on the skull and lower jaw, this study used 133 data points ranging across the skull, jaws, teeth, arms, legs and shoulders.

Dr Argue said none of the data supported the theory that Homo floresiensis evolved from Homo erectus.

"We looked at whether Homo floresiensis could be descended from Homo erectus," she said.

"We found that if you try and link them on the family tree, you get a very unsupported result. All the tests say it doesn't fit -- it's just not a viable theory."

Dr Argue said this was supported by the fact that in many features, such as the structure of the jaw, Homo floresiensis was more primitive than Homo erectus.

"Logically, it would be hard to understand how you could have that regression -- why would the jaw of Homo erectus evolve back to the primitive condition we see in Homo floresiensis?"

Dr Argue said the analyses could also support the theory that Homo floresiensis could have branched off earlier in the timeline, more than 1.75 million years ago.

"If this was the case Homo floresiensis would have evolved before the earliest Homo habilis, which would make it very archaic indeed," she said.

Professor Mike Lee of Flinders University and the South Australian Museum, used statistical modeling to analyse the data.

Read more at Science Daily

Apr 20, 2017

Tarantulas use their lateral eyes to calculate distance

This is the arrangement of the 4 pairs of eyes on the cephalothorax of the spider Lycosa tarantula.
The tarantula species Lycosa tarantula ambushes its prey and lives in burrows around 20 cm deep topped by a structure, a kind of turret which the tarantula build from twigs, leaves and small stones, fastened with the spider's silk. From the turret, the tarantula surprises its prey and runs to pursue it, subsequently returning to the burrow from distances between 30 and 40 cm.

L. tarantula uses path integration to return to its burrow. With this mechanism, it does not follow the same path back to its burrow; instead, it moves as though it had followed the sides of a right-angle triangle, returning along the hypotenuse.

In 1999, a research team from the Autonomous University of Madrid discovered that these animals used polarised light from the sky to know their position with respect to their nest. In the new research, the scientists wanted to go beyond this, and have analysed the role of each pair of the tarantula's eyes (they have four pairs in total) in the process of distance measurement, or odometry.

"To calculate the distance it has travelled, the animal needs an odometer that registers the route, its location with respect to the finish point, which would be the burrow, and a 'compass' to track the direction of travel," according to Joaquin Ortega Escobar, lead author of a paper published in the Journal of Experimental Biology on the function of each eye in these processes.

The 'compass' would correspond to polarised light, which the median eyes use to measure the angle; direction is detected by the anterior lateral eyes. Through this research, the scientists have learned that it is principally the anterior lateral eyes (which until now had not been analysed), and to a lesser extent the posterior lateral eyes, that help tarantulas measures the distance to their nest.

Orientation with covered eyes

"These eyes look at the substrate. Seeing as they point downwards, it seems logical to think they would have a role in measuring the distance travelled. In the experiment, we covered these eyes with a water-soluble paint and observed that instead of travelling 30 cm from the nest, which is the distance we initially set, they stopped 8.5 centimetres before they reached their objective," explains the researcher.

This explains that with those eyes covered and the other six active, they have problems determining distance. "When we uncovered them, they could return to their nests perfectly. They need the lateral anterior eyes to measure the distance," he adds.

In previous work with the lateral eyes of other animals, such as desert ants (Cataglyphis fortis), the researchers observed that animals moving across a grid of black and white bands, like those used in the tarantula study, with the ventral region of their compound eyes (the part that perceives the grid) covered did not present a significant difference in the return trip to the nest compared to when the eyes were uncovered.

"The situations of these two animals are analogous. In the case of the spider, it is the anterior lateral eye that perceives the ventral field of view, while in the ant it is the ventral region of the compound eye. Spiders have simple eyes like our own, rather than compound eyes," Ortega Escobar explains.

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Why animals have evolved to favor one side of the brain

Why do people and animals naturally favor one side over the other, and what does it teach us about the brain's inner workings?
Most left-handers can rattle off a list of their eminent comrades-in-arms: Oprah Winfrey, Albert Einstein, and Barack Obama, just to name three, but they may want to add on cockatoos, "southpaw" squirrels, and some house cats. "Handed-ness" or left-right asymmetry is prevalent throughout the animal kingdom, including in pigeons and zebrafish. But why do people and animals naturally favor one side over the other, and what does it teach us about the brain's inner workings? Researchers explore these questions in a Review published April 19 in Neuron.

"Studying asymmetry can provide the most basic blueprints for how the brain is organized," says lead author Onur Güntürkün, of the Institute of Cognitive Neuroscience at Ruhr-University Bochum, in Germany. "It gives us an unprecedented window into the wiring of the early, developing brain that ultimately determines the fate of the adult brain." Because asymmetry is not limited to human brains, a number of animal models have emerged that can help unravel both the genetic and epigenetic foundations for the phenomenon of lateralization.

Güntürkün says that brain lateralization serves three purposes. The first of those is perceptual specialization: the more complex a task, the more it helps to have a specialized area for performing that task. For example, in most people, the right side of the brain focuses on recognizing faces, while the left side is responsible for identifying letters and words.

The next area is motor specialization, which brings us to the southpaw. "What you do with your hands is a miracle of biological evolution," he says. "We are the master of our hands, and by funneling this training to one hemisphere of our brains, we can become more proficient at that kind of dexterity." Natural selection likely provided an advantage that resulted in a proportion of the population -- about 10% -- favoring the opposite hand. The thing that connects the two is parallel processing, which enables us to do two things that use different parts of the brain at the same time.

Brain asymmetry is present in many vertebrates and invertebrates. "It is, in fact, an invention of nature, which evolved because many animals have the same needs for specialization that we do," says Güntürkün, who is also currently a visiting fellow at the Stellenbosch Institute for Advanced Study in South Africa. Studies have shown that birds, like chickens, use one eye to distinguish grain from pebbles on the ground while at the same time using the other eye to keep watch for predators overhead.

Research on pigeons has shown that this specialization often is a function of environmental influences. When a pigeon chick develops in the shell, its right eye turns toward the outside, leaving its left eye to face its body. When the right eye is exposed to light coming through the shell, it triggers a series of neuronal changes that allow the two eyes to ultimately have different jobs.

A zebrafish model of lateralization, meanwhile, has enabled researchers to delve into the genetic aspects of asymmetrical development. Studies of important developmental pathways, including the Nodal signaling pathway, are uncovering details about how, very early in an embryo's development, the cilia act to shuffle gene products to one side of the brain or the other. By manipulating the genes in Nodal and other pathways, researchers can study the effects of these developmental changes on zebrafish behaviors.

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