Clear vision despite a heavy head: Model explains the choice of simple movements

ScienceDaily (Nov. 9, 2011) — In one respect, handling a computer mouse is just like looking in the rearview mirror: well established movements help the brain to concentrate on the essentials. But just a simple gaze shift to a new target bears the possibility of an almost infinite number of combinations of eye and head movement: how fast do we move eye and head? How much does the eye rotate, how much the head?

Until now, it was unclear why the brain chooses a particular movement option from the set of all possible combinations. A team led by Dr. Stefan Glasauer (LMU Munich), project leader at the Bernstein Center Munich, has now developed a mathematical model that accurately predicts horizontal gaze movements. Besides eye and head contribution to the gaze shift it also predicts movement duration and velocity.

In contrast to most previous models, the researchers considered the movement of head and eye to the target as well as the counter-movement of the eye after the gaze has reached the target, but the head is still moving. "The longer the movement, the more perturbations add up," says Glasauer. "However, the faster the movement, the more errors arise from acceleration and large muscle forces." On the basis of this information, the Munich researchers calculated eye and head movements and determined the movement combination that caused the fewest disturbances. This movement matched that chosen by healthy volunteers not only in natural conditions but also in an experiment where subjects' head movements were altered by an experimental increase in the head's rotational inertia.

These findings could help teach robots humanoid movements and thus facilitate interaction with service robots. It may also be helpful in the construction of "smart" prostheses. These devices could offer the carrier a choice of movements that come closest to the natural human ones. For the next step, Glasauer and colleagues want to examine three-dimensional eye-head movements and aim to better understand simple movement learning.

The Bernstein Center Munich is part of the National Bernstein Network Computational Neuroscience (NNCN) in Germany. The NNCN was established by the German Federal Ministry of Education and Research with the aim of structurally interconnecting and developing German capacities in the new scientific discipline of computational neuroscience. The network is named after the German physiologist Julius Bernstein (1835-1917).

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by Ludwig-Maximilians-Universitaet Muenchen (LMU).

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Saglam M., Lehnen N., Glasauer S. Optimal control of natural eye-head movements minimizes the impact of noise.. J Neurosci., 31(45):16185%u201316193

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Simple compound with surprising antifreeze properties

ScienceDaily (Oct. 25, 2011) — A chemical compound used to stabilize particles in suspension has proved capable of controlling the growth of ice crystals. This finding was made by CNRS/Saint-Gobain researchers, in collaboration with CNRS-affiliated teams at INSA Lyon and Université Claude Bernard Lyon 1. Surprisingly, the compound in question is a simple molecule, not at all like the macromolecules previously known for their antifreeze properties. It offers many advantages, including low production costs, stability and ease of use, which should open the way to industrial applications.

Published in the online journal PLoS ONE, this work also provides new leads for the development of synthetic equivalents of antifreeze proteins, different from those currently produced.

The formation of ice crystals can have multiple, and often destructive, consequences. Cell degradation in living organisms, damage to land and roads in cold climates, ice crystals in ice creams… These are all examples of situations where it is useful to control ice growth. Many organisms and species that live in cold environments have adapted to control ice growth. Their resistance to low temperatures is based on the presence of antifreeze proteins, all of which are made up of very long organic chains with amphiphilic structures (partly hydrophilic, partly hydrophobic). How do these proteins interact with ice crystals? Researchers are trying to identify the mechanism enabling antifreeze proteins to identify these crystals, but the phenomenon is still not fully understood. In addition, since these proteins are extremely costly to extract, the preferred solution is to create synthetic equivalents inspired by natural structures. All proteins currently known for their "antifreeze" properties are macromolecules (like glycoproteins, polysaccharides, etc.).

A team led by Sylvain Deville(1), CNRS researcher at the LSFC (Laboratoire de Synthèse et Fonctionnalisation des Céramiques, Synthesis and Functionalization of Ceramics Laboratory, CNRS/Saint-Gobain), in collaboration with the Matériaux, Ingénierie et Sciences (Materials, Engineering and Sciences) laboratory (CNRS/INSA Lyon / Université Claude Bernard Lyon 1), has discovered that zirconium acetate, a chemical compound normally used to stabilize particles in suspension, can control ice crystal growth. The compound governs the morphology of the ice crystals obtained by freezing a solution in which it is combined with water. The crystals obtained when adding zirconium acetate are very homogenous, whereas those obtained without it show no particular uniformity.

These results are quite surprising, given that zirconium acetate is a "salt,"(2) a simple compound that is radically different from the macromolecules known for their antifreeze properties. It was not known as a substance capable of controlling ice crystal growth. Such control can be exerted in a number of ways: by reducing the speed of crystal growth (to slow their formation), by lowering the freezing point (to delay their formation), or by controlling their morphology, as in this case. Since this implies a direct interaction with the ice crystals, the researchers were surprised to find out that such radically different molecules as zirconium acetate and proteins could affect crystalline growth.

This compound offers significant advantages over existing equivalents, whether natural or synthetic. It is cheap to produce, stable, "simple" and easy to use, which bodes well for a wealth of future industrial applications. In addition, since it is totally different from all previously identified and/or developed substances with the same function, further research could lead to the development of other molecules with antifreeze properties.

This project relied on X-ray diffraction and imaging. These works were made possible by using the X-ray synchrotron (beam line ID19) at the ESRF in Grenoble, France. They are covered by two patents published on October 1, 2011.

Notes:

Laureate of an ERC Junior grant in 2011.In chemistry, a salt is an ionic compound made up of cations and anions, forming a neutral product with no net charge. This type of salt is much different from edible (table) salt.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by CNRS (Délégation Paris Michel-Ange), via AlphaGalileo.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Sylvain Deville, Céline Viazzi, Jérôme Leloup, Audrey Lasalle, Christian Guizard, Eric Maire, Jérôme Adrien, Laurent Gremillard. Ice Shaping Properties, Similar to That of Antifreeze Proteins, of a Zirconium Acetate Complex. PLoS ONE, 2011; 6 (10): e26474 DOI: 10.1371/journal.pone.0026474

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

How the zebra gets its stripes: A simple genetic circuit

ScienceDaily (Oct. 14, 2011) — Many living things have stripes, but the developmental processes that create these and other patterns are complex and difficult to untangle.

Now a team of scientists has designed a simple genetic circuit that creates a striped pattern that they can control by tweaking a single gene.

"The essential components can be buried in a complex physiological context," said Terence Hwa, a professor of physics at the University of California, San Diego, and one of the leaders of the study published October 14 in Science. "Natural systems make all kinds of wonderful patterns, but the problem is you never know what's really controlling it."

With genes taken from one species of bacterium and inserted into another, Hwa and colleagues from the University of Hong Kong assembled a genetic loop from two linked modules that senses how crowded a group of cells has become and responds by controlling their movements.

One of the modules secretes a chemical signal called acyl-homoserine lactone (AHL). As the bacterial colony grows, AHL floods the accumulating cells, causing them to tumble in place rather than swim. Stuck in the agar of their dish, they pile up.

Because AHL doesn't diffuse very far, a few cells escape and swim away to begin the process again.

Left to grow overnight, the cells create a target-like pattern of concentric rings of crowded and dispersed bacterial cells. By tweaking just one gene that limits how fast and far cells can swim, the researchers were able to control the number of rings the bacteria made. They can also manipulate the pattern by modifying how long AHL lasts before it degrades.

Although individual bacteria are single cells, as colonies they can act like a multicellular organism, sending and receiving signals to coordinate the growth and other functions of the colony. That means fundamental rules that govern the development of these patterns could well apply to critical steps in the development of other organisms.

To uncover these fundamental rules, Hwa and colleagues characterized the performance of their synthetic genetic circuit in two ways.

First, they precisely measured both the activity of individual genes in the circuit throughout the tumble-and-swim cycle. Then they derived a mathematical equation that describes the probability of cells flipping between swim and tumble motions.

Additional equations describe other aspects of the system, such as the dynamics of the synthesis, diffusion and deactivation of one of the cell-to-cell chemical signal AHL.

This three-pronged approach of "wet-lab" experiments, precise measurements of the results, and mathematical modeling of the system, characterize the emerging discipline of quantitative biology, Hwa said. "This is a prototype, a model of the kind of biology we want to do."

Co-authors include Jian-Dong Huang, associate professor of biochemistry at the University of Hong Kong additional researchers at Hong Kong Baptist University, the University of Marburg, and the University of Hong Kong including members of the 2008 iGEM team, which Hwa co-advised as a Distinguished Visiting Professor at UHK.

Hwa is a senior scientist with UC San Diego's Center for Theoretical Biological Physics.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of California - San Diego.

Journal Reference:

C. Liu, X. Fu, L. Liu, X. Ren, C. K. L. Chau, S. Li, L. Xiang, H. Zeng, G. Chen, L.-H. Tang, P. Lenz, X. Cui, W. Huang, T. Hwa, J.-D. Huang. Sequential Establishment of Stripe Patterns in an Expanding Cell Population. Science, 2011; 334 (6053): 238 DOI: 10.1126/science.1209042

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Making complex fluids look simple

ScienceDaily (June 1, 2011) — An international research team has successfully developed a widely applicable method for discovering the physical foundations of complex fluids for the first time. Researchers at the University of Vienna and University of Rome have developed a microscopic theory that describes the interactions between the various components of a complex polymer mixture. This approach has now been experimentally proven by physicists from Jülich, who conducted neutron scattering experiments in Grenoble.

The results have been published in the June issue of the journal Physical Review Letters.

Some important materials from technology and nature are complex fluids: polymer melts for plastics production, mixtures of water, oil and amphiphiles, which can be found in both living cells and in your washing machine, or colloidal suspensions such as blood or dispersion paints. They are quite different from simple fluids consisting of small molecules, such as water, because they are made of mixtures of particles between a nanometre and a micrometre in size, and have a large number of so-called degrees of freedom. The latter include vibrations, movements of the functional groups of molecules or joint movements of several molecules. They can appear on widely varied length, time, and energy scales. This makes experimental and theoretical studies difficult and, so far, has impeded understanding of the properties of these systems and the targeted development of new materials with improved properties.

A method developed and tested by physicists at Forschungszentrum Jülich, the Institut Laue-Langevin in Grenoble, and the Universities of Vienna and Rome now permits realistic modelling of complex fluids for the first time. "Our microscopic theory describes the interactions between the various components of a complex mixture and in turn, enables us to draw realistic conclusions about their macroscopic properties, such as their structure or their flow properties," said Prof. Christos Likos of the University of Vienna, an expert on theory and simulation.

The team from Vienna and Rome developed the theory model. Since the researchers were unable to include all the details of the real system -- a mixture of larger star-shaped polymers and smaller polymer chains -- they systematically eliminated the rapidly moving degrees of freedom and focused on the relevant slow degrees of freedom, a time-consuming and challenging task. "To do this, we use a relatively new method called coarse graining and replace each complex macromolecule with a sphere of the appropriate size. The challenge involves integrating the degrees of freedom that have been eliminated in the simplified systems as averages so that the characteristics of the substances are retained," Likos explained.

The team from Jülich used elaborate small angle neutron scattering experiments with the instrument D11 at the Institut Laue-Langevin in Grenoble to prove that the interactions between the spheres of the coarse-grained model realistically simulate the conditions in the real system. "We were faced with the proverbial challenge of visualizing the needle in a haystack," explained Dr. Jörg Stellbrink, a physicist and neutron scattering expert at the Jülich Centre for Neutron Science (JCNS). For neutrons, the individual polymers of the mixture cannot be readily distinguished. For this reason, the physicists "coloured" the components they were interested in, so that they stood out of the crowd. This is one of the Jülich team's specialities. In this way, they were able to selectively examine the structures and interactions on a microscopic length scale.

The physicists are especially proud of the excellent agreement between theoretical predictions and experimental results. The method will now open up a spectrum of possibilities for studying the physical properties of a whole range of different complex mixtures.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Helmholtz Association of German Research Centres, via EurekAlert!, a service of AAAS.

Journal Reference:

B. Lonetti, M. Camargo, J. Stellbrink, C. Likos, E. Zaccarelli, L. Willner, P. Lindner, D. Richter. Ultrasoft Colloid-Polymer Mixtures: Structure and Phase Diagram. Physical Review Letters, 2011; 106 (22) DOI: 10.1103/PhysRevLett.106.228301

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Simple method of dealing with harmful radioactive iodine discovered

ScienceDaily (May 24, 2011) — A novel way to immobilise radioactive forms of iodine using a microwave, has been discovered by an expert at the University of Sheffield. Iodine radioisotopes are produced by fission of uranium fuel in a nuclear reactor. Radioactive iodine is of concern because it is highly mobile in the environment and selective uptake by the thyroid gland can pose a significant cancer risk following long term exposure. Furthermore, iodine-129, which is a type of radioactive iodine, has an extremely long half life of 15.7 million years, so is one of the most significant long term hazards faced by the population due to its emission during the geological disposal of nuclear waste.

Professor Neil Hyatt, from the University´s Department of Materials Science and Engineering, has now found a way of locking up iodine radioisotopes in a durable, solid material suitable for ultimate disposal, like lead iodovanadinite(Pb5(VO4)3I). The research, which was published in the Journal of Nuclear Materials, demonstrates how his simple, inexpensive and rapid method can be done at atmospheric pressure.

Professor Hyatt and his team created a solid material for immobilisation of iodine with the formula Pb5(VO4)3I, by heating a mixture of lead iodide, lead oxide and vanadium oxide.

Previously, this has only been achieved using high pressure and a sealed container, because iodine is volatilised at high temperature. However, using the knowledge that vanadium is a good absorber of microwaves at 2.45 GHz -- the frequency used in domestic microwave ovens -- the team were able to heat the mixture of chemicals in a microwave oven to produce Pb5(VO4)3I in about three minutes.

The key to the method´s success is that Pb5(VO4)3I is a poor absorber of 2.45 GHz microwaves, so once this is formed, the sample cannot absorb microwaves, so the temperature does not get high enough for the iodine to volatilise.

Iodine-131 was the harmful gas emitted from the Fukushima power plant in Japan following the earthquake and tsunami last month, and was a significant contributor to the health effects from open-air atomic bomb testing in the 1950s, and was also emitted during the Chernobyl disaster. It is hoped the new research will reduce the public health impact associated with the release of radioactive iodine to the environment by providing a simple and inexpensive method of immobilisation in a solid material, which could be rapidly deployed in an accident scenario.

Professor Neil Hyatt, said: "In spent nuclear fuel, the iodine is not immobilised, so once the containment is breached it simply gets dispersed. At present, iodine-129 released by nuclear fuel reprocessing is discharged direct to the Irish Sea off the coast of Sellafield. Substantial quantities of this radioisotope were also released into the sea off the coast of Japan in the Fukushima incident. Our new method offers a way of safely and rapidly containing this radionuclide, reducing the potential long term impact on human health from discharge to the environment."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Sheffield.

Journal Reference:

M.C. Stennett, I.J. Pinnock, N.C. Hyatt. Rapid synthesis of Pb5(VO4)3I, for the immobilisation of iodine radioisotopes, by microwave dielectric heating. Journal of Nuclear Materials, 2011; DOI: 10.1016/j.jnucmat.2011.04.041

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Simple method of dealing with harmful radioactive iodine discovered

ScienceDaily (May 24, 2011) — A novel way to immobilise radioactive forms of iodine using a microwave, has been discovered by an expert at the University of Sheffield. Iodine radioisotopes are produced by fission of uranium fuel in a nuclear reactor. Radioactive iodine is of concern because it is highly mobile in the environment and selective uptake by the thyroid gland can pose a significant cancer risk following long term exposure. Furthermore, iodine-129, which is a type of radioactive iodine, has an extremely long half life of 15.7 million years, so is one of the most significant long term hazards faced by the population due to its emission during the geological disposal of nuclear waste.

Professor Neil Hyatt, from the University´s Department of Materials Science and Engineering, has now found a way of locking up iodine radioisotopes in a durable, solid material suitable for ultimate disposal, like lead iodovanadinite(Pb5(VO4)3I). The research, which was published in the Journal of Nuclear Materials, demonstrates how his simple, inexpensive and rapid method can be done at atmospheric pressure.

Professor Hyatt and his team created a solid material for immobilisation of iodine with the formula Pb5(VO4)3I, by heating a mixture of lead iodide, lead oxide and vanadium oxide.

Previously, this has only been achieved using high pressure and a sealed container, because iodine is volatilised at high temperature. However, using the knowledge that vanadium is a good absorber of microwaves at 2.45 GHz -- the frequency used in domestic microwave ovens -- the team were able to heat the mixture of chemicals in a microwave oven to produce Pb5(VO4)3I in about three minutes.

The key to the method´s success is that Pb5(VO4)3I is a poor absorber of 2.45 GHz microwaves, so once this is formed, the sample cannot absorb microwaves, so the temperature does not get high enough for the iodine to volatilise.

Iodine-131 was the harmful gas emitted from the Fukushima power plant in Japan following the earthquake and tsunami last month, and was a significant contributor to the health effects from open-air atomic bomb testing in the 1950s, and was also emitted during the Chernobyl disaster. It is hoped the new research will reduce the public health impact associated with the release of radioactive iodine to the environment by providing a simple and inexpensive method of immobilisation in a solid material, which could be rapidly deployed in an accident scenario.

Professor Neil Hyatt, said: "In spent nuclear fuel, the iodine is not immobilised, so once the containment is breached it simply gets dispersed. At present, iodine-129 released by nuclear fuel reprocessing is discharged direct to the Irish Sea off the coast of Sellafield. Substantial quantities of this radioisotope were also released into the sea off the coast of Japan in the Fukushima incident. Our new method offers a way of safely and rapidly containing this radionuclide, reducing the potential long term impact on human health from discharge to the environment."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Sheffield.

Journal Reference:

M.C. Stennett, I.J. Pinnock, N.C. Hyatt. Rapid synthesis of Pb5(VO4)3I, for the immobilisation of iodine radioisotopes, by microwave dielectric heating. Journal of Nuclear Materials, 2011; DOI: 10.1016/j.jnucmat.2011.04.041

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here