Tuesday, February 22, 2011

'Tall order' sunlight-to-hydrogen system works, neutron analysis confirms

 Researchers at the Department of Energy's Oak Ridge National Laboratory have developed a biohybrid photoconversion system -- based on the interaction of photosynthetic plant proteins with synthetic polymers -- that can convert visible light into hydrogen fuel.

Photosynthesis, the natural process carried out by plants, algae and some bacterial species, converts sunlight energy into chemical energy and sustains much of the life on earth. Researchers have long sought inspiration from photosynthesis to develop new materials to harness the sun's energy for electricity and fuel production.

In a step toward synthetic solar conversion systems, the ORNL researchers have demonstrated and confirmed with small-angle neutron scattering analysis that light harvesting complex II (LHC-II) proteins can self-assemble with polymers into a synthetic membrane structure and produce hydrogen.

The researchers envision energy-producing photoconversion systems similar to photovoltaic cells that generate hydrogen fuel, comparable to the way plants and other photosynthetic organisms convert light to energy.

"Making a, self-repairing synthetic photoconversion system is a pretty tall order. The ability to control structure and order in these materials for self-repair is of interest because, as the system degrades, it loses its effectiveness," ORNL researcher Hugh O'Neill, of the lab's Center for Structural Molecular Biology, said.

"This is the first example of a protein altering the phase behavior of a synthetic polymer that we have found in the literature. This finding could be exploited for the introduction of self-repair mechanisms in future solar conversion systems," he said.

Small angle neutron scattering analysis performed at ORNL's High Flux Isotope Reactor (HFIR) showed that the LHC-II, when introduced into a liquid environment that contained polymers, interacted with polymers to form lamellar sheets similar to those found in natural photosynthetic membranes.

The ability of LHC-II to force the assembly of structural polymers into an ordered, layered state -- instead of languishing in an ineffectual mush -- could make possible the development of biohybrid photoconversion systems. These systems would consist of high surface area, light-collecting panes that use the proteins combined with a catalyst such as platinum to convert the sunlight into hydrogen, which could be used for fuel.

The research builds on previous ORNL investigations into the energy-conversion capabilities of platinized photosystem I complexes -- and how synthetic systems based on plant biochemistry can become part of the solution to the global energy challenge.

"We're building on the photosynthesis research to explore the development of self-assembly in biohybrid systems. The neutron studies give us direct evidence that this is occurring," O'Neill said.

The researchers confirmed the proteins' structural behavior through analysis with HFIR's Bio-SANS, a small-angle neutron scattering instrument specifically designed for analysis of biomolecular materials.

"Cold source" neutrons, in which energy is removed by passing them through cryogenically chilled hydrogen, are ideal for studying the molecular structures of biological tissue and polymers.

The LHC-II protein for the experiment was derived from a simple source: spinach procured from a local produce section, then processed to separate the LHC-II proteins from other cellular components. Eventually, the protein could be synthetically produced and optimized to respond to light.

O'Neill said the primary role of the LHC-II protein is as a solar collector, absorbing sunlight and transferring it to the photosynthetic reaction centers, maximizing their output. "However, this study shows that LHC-II can also carry out electron transfer reactions, a role not known to occur in vivo," he said.

The research team, which came from various laboratory organizations including its Chemical Sciences Division, Neutron Scattering Sciences Division, the Center for Structural Molecular Biology and the Center for Nanophase Materials Sciences, consisted of O'Neill, William T. Heller, and Kunlun Hong, all of ORNL; Dimitry Smolensky of the University of Tennessee; and Mateus Cardoso, a former postdoctoral researcher at ORNL now of the Laboratio Nacional de Luz Sincrotron in Brazil.

"That's one of the nice things about working at a national laboratory. Expertise is available from a variety of organizations," O'Neill said.

The work, published in the journal Energy & Environmental Science, was supported with Laboratory-Directed Research and Development funding. HFIR is supported by the DOE Office of Science.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Oak Ridge National Laboratory.

Journal Reference:

Mateus B. Cardoso, Dmitriy Smolensky, William T. Heller, Kunlun Hong, Hugh O'Neill. Supramolecular assembly of biohybrid photoconversion systems. Energy & Environmental Science, 2011; 4 (1): 181 DOI: 10.1039/C0EE00369G

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New method for unraveling molecular structures

Chemists at the Karlsruhe Institute of Technology (KIT) and the Technische Universitaet Muenchen (TUM) introduced a new method for identifying chemical compounds. The approach they used is an improvement on nuclear magnetic resonance (NMR) measurements -- for decades one of the most successful methods for determining the chemical structure of organic molecules.

The results now published in the scientific journal Angewandte Chemie show a sophisticated approach to structural data when classical methods of analysis fail.

The team of Professor Burkhard Luy from KIT and Junior Professor Stefan F. Kirsch from the TUM has now shown for the first time that certain NMR parameters, the so-called residual dipolar couplings (RDCs), can make a significant contribution towards determining the constitution of chemical compounds when traditional methods fail. To do this they embedded molecules of the compound in a gel which slightly constricts their mobility. By stretching the gel, the molecules can be aligned along a preferred orientation. While residual dipolar couplings average out in solution, they become measurable in such partially aligned samples and provide valuable structural information that can be used to build a model of the molecule.

To test this new approach to chemical structure determination the scientists examined a molecule whose atomic composition was known, but not the precise connectivities of the individual atoms in the molecule. The molecule was obtained using a unique reaction, so there were no precedents for its structure. Classical methods of analysis failed because of the compactness of the molecule. In this particular case it was only possible to determine the structure by means of residual dipolar couplings, so that the newly acquired knowledge could be used to draw conclusions about the formation of the molecule -- something that in the past could only be speculated about.

"This type of analysis will not be suitable for all structures in the future," said scientists Luy and Kirsch. "There will still be molecules whose structures will defy all attempts at unraveling, in spite of tremendous efforts and cutting-edge technologies. But this new method provides us with one further tool to help us unravel the structural mysteries of nature."

This research was funded through the German Research Foundation DFG (Heisenberg Program, Research Group FOR 934) and the Chemical Industry Fund. The scientists conducted their measurements on equipment from the Bavarian NMR Center.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Karlsruhe Institute of Technology.

Journal Reference:

Grit Kummerlöwe, Benedikt Crone; Manuel Kretschmer, Stefan F. Kirsch and Burkhard Luy. Residual Dipolar Couplings as a Powerful Tool for Constitutional Analysis: The Unexpected Formation of Tricyclic Compounds. Angewandte Chemie International Edition, 2011; DOI: 10.1002/anie.2010007305

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Successful operation of carbon nanotube-based integrated circuits manufactured on plastic substrates

As part of NEDO's Industrial Technology Research Grant Japan-Finland collaborative project, Professors Yutaka Ohno from Nagoya University in Japan and Esko I. Kauppinen from Aalto University in Finland along with their colleagues have developed a simple and fast process to manufacture high-quality carbon nanotube-based thin film transistors (TFT) on a plastic substrate.

They used this technology to manufacture the world's first sequential logic circuits using carbon nanotubes. The technology could lead to the development of high-speed, roll-to-roll manufacturing processes to manufacture low-cost flexible devices such as electronic paper in the future.

The results were published on Feb. 6, 2011 in the online edition of the journal Nature Nanotechnology.


Lightweight and flexible devices such as mobile phones and electronic paper are gaining attention for their roles in achieving a smarter ubiquitous information society. For flexible electronics, as a substitute for conventional solid silicon substrates, there is a demand for integrated circuits to be manufactured on a plastic substrate with high speed and low cost .

Thus far, flexible thin-film transistors (TFT) have been produced using a variety of semiconductor materials such as silicon and zinc-oxide, which require vacuum deposition, high-temperature curing, and complex transfer processes. In recent years, organic semiconductors have been rapidly developing, however such semiconductors still have low-mobility and there are problems with their chemical stability. Recently, carbon nanotube thin films have been attracting attention due to their chemical stability and high-mobility. However, although simple solution processes have been developed to produce TFTs, such TFTs have not been yet fulfilled capability expectations thus far, due to the deterioration of the conduction properties of carbon nanotube thin films through the dispersion process in the solution.


(1) Easy and fast thin film deposition: Gas phase filtration and transfer processes

In conventional solution processes, soot-like carbon nanotube material is first dispersed in liquid via sonication to purify the materials and to separate the tubes from each other. In such processes, it is difficult to form homogeneous carbon nanotube films. In addition, technology has not yet been developed to completely remove the dispersant. In contrast, using our innovative technology, we continuously grow nanotubes in an atmospheric pressure chemical-vapor deposition process. The nanotubes are then collected on the filter and subsequently transferred onto a polymer substrate using simple gas-phase filtration and transfer processes to achieve clean, uniform carbon nanotube films. It takes only a few seconds to deposit the carbon nanotubes. This process may be adaptable to high-speed roll-to-roll manufacturing systems in the near future.

(2) Carbon nanotube TFTs with high-mobility of 35 cm2/Vs and an on/off ratio of 6´106

In conventional solution-based carbon nanotube TFT manufacturing processes, nanotubes are dispersed using powerful ultrasound which cuts the nanotubes and reduces their length. Due to high contact resistance between these short nanotubes and the residual impurities caused by the dispersion process, the resulting TFT mobility was approximately 1 cm2/Vs. Due to the doping effect caused by residual impurities from the dispersion, the on/off ratio was only between about 104~105. When carbon nanotube thin films are manufactured using the above gas-phase filtration and transfer processes, the tubes in the film are as clean and long as those that are grown in the synthesis processes. Accordingly, TFTs with a high mobility of 35 cm2/Vs were achieved. In addition, due to precision control of the nanotube density, an on/off ratio of 6x106 was simultaneously achieved. The TFT performance we have achieved is significantly higher than the performance of organic semiconductor TFTs and carbon nanotube TFTs reported so far, and equal to the performance of low-temperature polycrystalline silicon as well as zinc oxide TFTs, which are manufactured using high-temperature processes and vacuum-based processes.

(3) Successful operation of integrated circuits on transparent and flexible plastic substrates

The gas-phase filtration and transfer processes can be applied to manufacture devices on any substrate material. This time, we integrated the high-performance carbon nanotube TFTs on plastic substrates, and achieved successful operations of ring oscillators and flip-flops. High-speed operations have been achieved with a delay time of 12 microseconds per logic gate. The flip-flops that have been manufactured through these processes are the world's first carbon nanotube-based synchronous sequential logic circuits.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Aalto University, via AlphaGalileo.

Journal Reference:

Dong-ming Sun, Marina Y. Timmermans, Ying Tian, Albert G. Nasibulin, Esko I. Kauppinen, Shigeru Kishimoto, Takashi Mizutani, Yutaka Ohno. Flexible high-performance carbon nanotube integrated circuits. Nature Nanotechnology, 2011; DOI: 10.1038/nnano.2011.1

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

Sleeping Trojan horse to aid imaging of diseased cells

A unique strategy developed by researchers at Cardiff University is opening up new possibilities for improving medical imaging.

Medical imaging often requires getting unnatural materials such as metal ions into cells, a process which is a major challenge across a range of biomedical disciplines. One technique currently used is called the 'Trojan Horse' in which the drug or imaging agent is attached to something naturally taken up by cells.

The Cardiff team, made of researchers from the Schools of Chemistry and Biosciences, has taken the technique one step further with the development of a 'sleeping Trojan horse'. The first example of its kind, this is delivery system resolves some of the current difficulties involved in transporting metal ions into cells.

It is not itself taken up by cells so does not interfere with natural functions until it is 'woken' by the addition of the metal ions. This minimises the unwanted uptake and need for time-consuming purification associated with the common 'Trojan Horse' technique.

The research was led by Dr Mike Coogan, Senior Lecturer in Synthetic Chemistry, along with the paper's first author, Flora Thorp-Greenwood.

Dr Coogan said: "The sleeping Trojan horse process happens rapidly, and the vessel is capable of carrying metals which have positron-emitting isotopes, so it has potential for use in bimodal fluorescence and PET imaging. Combined agents for these types of imaging are known but rare, so this is a significant development in the field.

"There is also additional potential for use in radiotherapy as the metal-bearing form not only enters cells but also localises in the nucleolus. In principle, the concept could also be used to improve delivery of a huge range of drugs and imaging agents into cells or the body."

The study appears in the advanced article section of Chemical Communications, published by the Royal Society of Chemistry.

Story Source:

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

Journal Reference:

Flora L. Thorp-Greenwood, Vanesa Fernández-Moreira, Coralie O. Millet, Catrin F. Williams, Joanne Cable, Jonathan B. Court, Anthony J. Hayes, David Lloyd, Michael P. Coogan. A ‘Sleeping Trojan Horse’ which transports metal ions into cells, localises in nucleoli, and has potential for bimodal fluorescence/PET imaging. Chemical Communications, 2011; DOI: 10.1039/C1CC10141B

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.

Single molecule controlled at room temperature: Tiny magnetic switch discovered

 A Kiel research group headed by the chemist, Professor Rainer Herges, has succeeded for the first time in directly controlling the magnetic state of a single molecule at room temperature. The paper was recently published in the journal Science. The switchable molecule, which is the result of a sub-project of the Collaborative Research Centre 677 "Function by Switching," could be used both in the construction of tiny electromagnetic storage units and in the medical imaging.

The scientists at the Kiel University developed a molecular machine constructed in a similar way to a record player. The molecule consists of a nickel ion surrounded by a pigment ring (porphyrin), and a nitrogen atom which hovers above the ring like the tone arm on a record player. "When we irradiate this molecule with blue-green light, the nitrogen atom is placed exactly vertically to the nickel ion like a needle," Rainer Herges explains. "This causes the nickel ion to become magnetic, because the pairing of two electrons is cancelled out," says the chemistry professor. The counter effect is blue-violet light: The nitrogen atom is raised, the electrons form a pair and the nickel ion is no longer magnetic. "We can repeat this switching of the magnetic state over 10,000 times by varied irradiation with the two different wavelengths of light, without wearing out the molecular machine or encountering side reactions," Herges enthuses.

The switch which has been discovered, with its diameter of only 1.2 nanometres, could be used as a tiny magnetic reservoir in molecular electronics. Most of all, hard disk manufacturers may be interested in this, as a higher storage capacity can be achieved by reducing the size of the magnetic particles on the surface of the disks. Professor Herges also believes the use of the magnetic switch in the medical field is feasible: "The record player molecule can be used intravenously as a contrast agent in MRT (magnetic resonance tomography) in order to search for tumours or constricted blood vessels. Initial tests in the University Medical Center Schleswig-Holstein's neuroradiology department were successful."

As the signal-to-noise ratio is improved by the switching process, a smaller amount of the contrast agent is required than for the magnetic salts currently being used. In addition, according to Herges, the molecular machine could also serve as a basis for developing new contrast agents to depict such features as temperature, pH value or even certain biochemical markers in the body in a three-dimensional form. Rainer Herges lists the possible fields of application: "Using contrast agents such as these, it could be possible to localise centres of inflammation, detect tumours and visualise many metabolic processes."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Christian-Albrechts-Universitaet zu Kiel, via AlphaGalileo.

Journal Reference:

S. Venkataramani, U. Jana, M. Dommaschk, F. D. Sonnichsen, F. Tuczek, R. Herges. Magnetic Bistability of Molecules in Homogeneous Solution at Room Temperature. Science, 2011; 331 (6016): 445 DOI: 10.1126/science.1201180

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

Van-der-Waals force up close: Physicists take new look at the atom

Measuring the attractive forces between atoms and surfaces with unprecedented precision, University of Arizona physicists have produced data that could refine our understanding of the structure of atoms and improve nanotechnology.

The discovery has been published in the journal Physical Review Letters.

Van der Waals forces are fundamental for chemistry, biology and physics. However, they are among the weakest known chemical interactions, so they are notoriously hard to study. This force is so weak that it is hard to notice in everyday life. But delve into the world of micro-machines and nano-robots, and you will feel the force -- everywhere.

"If you make your components small enough, eventually this van-der-Waals potential starts to become the dominant interaction," said Vincent Lonij, a graduate student in the UA department of physics who led the research as part of his doctoral thesis.

"If you make tiny, tiny gears for a nano-robot, for example, those gears just stick together and grind to a halt. We want to better understand how this force works."

To study the van-der-Waals force, Lonij and his co-workers Will Holmgren, Cathy Klauss and associate professor of physics Alex Cronin designed a sophisticated experimental setup that can measure the interactions between single atoms and a surface. The physicists take advantage of quantum mechanics, which states that atoms can be studied and described both as particles and as waves.

"We shoot a beam of atoms through a grating, sort of like a micro-scale picket fence," Lonij explained. "As the atoms pass through the grating, they interact with the surface of the grating bars, and we can measure that interaction."

As the atoms pass through the slits in the grating, the van-der-Waals force attracts them to the bars separating the slits. Depending on how strong the interaction, it changes the atom's trajectory, just like a beam of light is bent when it passes through water or a prism.

A wave passing through the middle of the slit does so relatively unencumbered. On the other hand, if an atom wave passes close by the slit's edges, it interacts with the surface and skips a bit ahead, "out of phase," as physicists say.

"After the atoms pass through the grating, we detect how much the waves are out of phase, which tells us how strong the van-der-Waals potential was when the atoms interacted with the surface."

Mysterious as it seems, without the van-der-Waals force, life would be impossible. For example, it helps the proteins that make up our bodies to fold into the complex structures that enable them to go about their highly specialized jobs.

Unlike magnetic attraction, which affects only metals or matter carrying an electric current, van-der-Waals forces make anything stick to anything, provided the two are extremely close to each other. Because the force is so weak, its action doesn't range beyond the scale of atoms -- which is precisely the reason why there is no evidence of such a force in our everyday world and why we leave it to physicists such as Lonij to unravel its secrets.

Initially, he was driven simply by curiosity, Lonij said. When he started his project, he didn't know it would lead to a new way of measuring the forces between atoms and surfaces that may change the way physicists think about atoms.

And with a smile, he added, "I thought it would be fitting to study this force, since I am from the Netherlands; Mr. van der Waals was Dutch, too."

In addition to proving that core electrons contribute to the van-der-Waals potential, Lonij and his group made another important discovery.

Physicists around the world who are studying the structure of the atom are striving for benchmarks that enable them to test their theories about how atoms work and interact. "Our measurements of atom-surface potentials can serve as such benchmarks," Lonij explained. "We can now test atomic theory in a new way."

Studying how atoms interact is difficult because they are not simply tiny balls. Instead, they are what physicists call many-body systems. "An atom consists of a whole bunch of other particles, electrons, neutrons, protons, and so forth," Lonij said.

Even though the atom as a whole holds no net electric charge, the different charged particles moving around in its interior are what create the van-der-Waals force in the first place.

"What happens is that the electrons, which hold all the negative charge, and the protons, which hold all the positive charge, are not always in the same places. So you can have tiny little differences in charge that are fluctuating very fast. If you put a charge close to a surface, you induce an image charge. In a highly simplified way, you could say the atom is attracted to its own reflection."

To physicists, who prefer things neat and clean and tractable with razor-sharp mathematics, such a system, made up from many smaller particles zooming around each other, is difficult to pin down. To add to the complication, most surfaces are not clean. As Lonij puts it, "Comparing such a dirty system to theory is a big challenge, but we figured out a way to do it anyway."

"A big criticism of this type of work always was, 'well, you're measuring this atom-surface potential, but you don't know what the surface looks like so you don't know what you're really measuring.'"

To eliminate this problem, Lonij's team used different types of atoms and looked at how each interacted with the same surface.

"Our technique gives you the ratio of potentials directly without ever knowing the potential for either of the two atoms," he said. "When I started five years ago, the uncertainty in these types of measurements was 20 percent. We brought it down to two percent."

The most significant discovery was that an atom's inner electrons, orbiting the nucleus at a closer range than the atom's outer electrons, influence the way the atom interacts with the surface.

"We show that these core electrons contribute to the atom-surface potential," Lonij said, "which was only known in theory until now. This is the first experimental demonstration that core electrons affect atom-surface potentials."

"But what is perhaps more important," he added, "is that you can also turn it around. We now know that the core electrons affect atom-surface potentials. We also know that these core electrons are hard to calculate in atomic theory. So we can use measurements of atom-surface potentials to make the theory better: The theory of the atom."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Arizona, via EurekAlert!, a service of AAAS.

Journal Reference:

Vincent Lonij, Catherine Klauss, William Holmgren, Alexander Cronin. Atom Diffraction Reveals the Impact of Atomic Core Electrons on Atom-Surface Potentials. Physical Review Letters, 2010; 105 (23) DOI: 10.1103/PhysRevLett.105.233202

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

Study of volcanoes in the outer solar system produces unexpected bonus for nanotechnology

 Mysterious expanding ice crystals in the moons of Saturn and Neptune may be of interest to future developers of microelectronics. Neutron scattering has discovered that methanol crystals that may be found in outer solar system 'ice lavas' have unusual expansion properties. The unexpected finding by a British planetary geologist using neutrons at the Institut Laue-Langevin and the ISIS neutron source will interest developers of 'nano-switches' -- single atom thick valves used in 'micro-electronics' at the nano scale.

Neutron scattering has discovered that methanol crystals that may be found in outer solar system 'ice lavas' have unusual expansion properties. The unexpected finding by a British planetary geologist using neutrons at the Institut Laue-Langevin and the ISIS neutron source will interest developers of 'nano-switches' -- single atom thick valves used in 'micro-electronics' at the nano scale.

Dr Dominic Fortes, UCL (University College London) made the discovery whilst investigating the internal structure of icy moons, such as Neptune's Triton, to explain the icy eruptions seen by passing space-craft. By studying the behaviour of methanol monohydrate, a known constituent of outer solar system ice, under conditions like those within the moons' interiors Fortes hoped to understand its role in volcanism.

Fortes measured structural changes in methanol crystals over a range of temperatures and pressures. He found that when heated at room pressure they would expand enormously in one direction whilst shrinking in the other two dimensions. However when heated under an even pressure they expanded in two directions, whilst compressing in the third. This unexpected expansion (elongating and thinning) under uniform pressure is known as negative linear compressibility (NLC).

Whilst these results form the next step towards understanding outer solar system volcanic activity, Fortes' discovery is of significant interest for material scientists developing nanotechnology. The predictable expansion of NLC materials in a particular direction under pressure makes them a good candidate for nano-switches where their shape-shifting properties can be used like a microscopic, pressure-controlled valve directing the flow of electricity.

NLC materials are extremely rare with only around 15 known examples. What causes this property is still relatively unknown. Scientists hope better understanding of the phenomenon can bring forward potential technological application.

"Currently the use of NLC materials in technologies such as nano-switches is purely theoretical and limited by our lack of understanding of the underlying physics," says Prof. Reinhard Neder chairman of the ILL crystallographic committee who approved Dr Fortes beam-time at the world's flagship centre for neutron science. "However, the simple structure of methanol monohydrate gives us a good chance to understand the source of this property and how to look for it in other more commercially viable materials."

"It was certainly unexpected," explains Dr Fortes. "As a planetary geologist my focus is understanding the mechanisms behind volcanic eruptions in the outer solar system. If my results open doors for more applied science back on Earth, that's a bonus."

Professor Richard Wagner, Director at the Institut Laue Langevin added "This research is a good example of how even basic academic studies can have completely unpredictable benefits in other areas of science and technology. It's because of discoveries like this that the ILL strives to maintain our delivery of world leading neutron science in both 'fundamental' and 'applied' fields."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Institut Laue-Langevin (ILL), via AlphaGalileo.

Journal Reference:

A. Dominic Fortes, Emmanuelle Suard, and Kevin S. Knight. Negative Linear Compressibility and Massive Anisotropic Thermal Expansion in Methanol Monohydrate. Science, vol 331. February 2011 p742 %u2013 746 DOI: 10.1126/science.1198640

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