Hot topics

David Bradley Science Writer

Protons are seemingly elementary particles and as such one might assume that science knows all there is to know about them. But, together with the origin of its positive charge, physicists have been at a loss to add up the proton’s “spin”. Until now.

The spin of a sub-atomic particle is one of its characteristic properties along with its charge. It is a quantum property, although it can be pictured simply as a kind of rotation. As is often the case with quantum concepts, however, the analogy only stretches so far in that a proton has a spin 1/2, which means it has to “rotate” through 720 degrees, rather than 360 degrees, to get back to its initial state; like tracing one’s fingertip along a “Moebius strip”.

Protons consist of two “up” and one “down” quark linked by gluon chains. Each quark has a spin 1/2, two ups add up to 1 and then the down subtracts a half leaving the proton with a net spin 1/2. However, researchers at the European Muon Collaboration demonstrated in the 1980s that the proton’s spin is not produced by its quarks, In fact, they contribute only a quarter of the value of this quantum property.

“This result was so surprising that it was called the spin-crisis,” explains Yasuyuki Akiba, a PHENIX team member. Particle physicists were therefore confronted with a fundamental question: What else contributes to the spin of the proton?

Scientists suspected that the deficit might be paid for by the gluons that hold the quarks together.

Now, by analyzing data from a year-long experiment carried out at the Brookhaven National Laboratory’s Relativistic Heavy Ion Collider (RHIC) in 2006, the PHENIX collaboration at BNL in Upton, USA, together with scientists from the RIKEN BNL Research Center and the RIKEN Nishina Center for Accelerator-Based Science have shown that the gluons are not the main source of the proton’s spin either.

Some models predict that the missing spin comes mainly from gluons, while others suggest that the contribution from the orbital angular momentum of quarks within the proton may also be significant. The analysis suggests that the gluon contribution is about 40%. With 25% from the quarks, that leaves 35% still to be accounted for, which may be due to angular momentum or some other factor.

“Although there is still a significant uncertainty in this result, our data show that models predicting large gluon spin can now be firmly excluded,” Akiba says.

Links:

Phys Rev Lett, 2009, 103, 012003
RIKeN Experimental Group

David Bradley Science Writer

Chemists in the US have demonstrated a definitive link between the size of catalyst particles on a solid surface, their electronic properties and their ability to accelerate a chemical reaction. The study could help improve the design of yet more-efficient catalysts to reduce energy requirements for countless industrial processes and cut greenhouse gas emissions.

Ideally, catalysts are substances that speed chemical reactions without themselves being consumed in the reaction. In reality, they are never 100 percent efficient, can be degraded by repeated reaction cycles, and often become poisoned by by-products. Nevertheless, they are at the heart of thousands of chemical reactions used to make everything from pharmaceuticals to plastics.

“One of the big uncertainties in catalysis is that no one really understands what size particles of the catalyst actually make a chemical reaction happen,” says Scott Anderson of the University of Utah. “If we could understand what factors control activity in catalysts, then we could make better and less expensive catalysts.”

Catalysts are commonly made from rare metals including, gold, rhodium, palladium, and platinum, and there is typically a range of catalyst particle sizes present. In almost all cases, the size of the most active particles is unknown. In gold catalysts, which have been intensively studied recently, it has been shown that the bulk of the metal in a catalyst powder exists in the form of particles that are too big to do any catalysis, and only a small fraction of the metal is active.

“If you could make a catalyst with only the right size particles, you could save 90 percent of the cost or more,” asserts Anderson. He also points out that switching to cheaper and more common metals, such as zinc, nickel, and copper, and “tuning” their properties would also let chemists reduce costs significantly. The process of tuning such base metals would involve reducing the particle size until it reaches a catalytic optimum, which is the focus of the Utah team’s work.

Previous work showed how to alter electronic and chemical properties of a catalyst in a gas, but things are different once the particles are mounted on a metal oxide surface for real-life industrial processes.

In the new study, Anderson and his students took a step toward tuning catalysts to have desired properties. In work with Bill Kaden and William Kunkel, and Tianpin Wu, the team has demonstrated, for the first time, that the size of palladium metal catalyst “nanoparticles” deposited on a titanium dioxide surface affects not only the catalyst’s level of activity in converting carbon monoxide to carbon dioxide, but also the particles’ electronic properties.

As the size of a catalyst metal particle is reduced to the nanoscale, its properties initially remain the same as bulk metal. However, when the particles are just 10 nanometres across (containing 10,000 atoms or so) the movements of electrons in the metal become confined, so boosting their energy.

When there are fewer than about 100 atoms in catalyst particles, the size variations also result in fluctuations in the electronic structure of the catalyst atoms. Those fluctuations strongly affect the particles’ ability to act as a catalyst, Anderson says.

The study not only showed how catalytic activity varies with catalyst particle size, “but we have been able to correlate that size dependence with observed electronic differences in the catalyst particles,” Kaden adds. “People had speculated this should be happening, but no one has ever seen it.”

Links:

Science, 2009, in press
Scott L. Anderson homepage

David Bradley Science Writer

An analysis of observations from the Hinode satellite suggest that the solar wind generated by the sun is probably driven by a process involving powerful magnetic fields, according to researchers at University College London and their colleagues.

The study carried out by the UCL Mullard Space Science Laboratory, Observatoire de Paris, Konkoly Observatory in Hungary and Instituto de Astronomía y Física del Espacio in Argentina, could have implications for our understanding of our nearest star and its effects on Earth and our electronic systems including communications satellites and even devices on the ground.

Scientists have long speculated as to what gives rise to the solar wind, a constant stream of extremely high energy particles that pours out from the sun in all directions. The Extreme Ultraviolet Imaging Spectrometer (EIS), on board the Japanese-UK-US Hinode satellite has produced unprecedented data that is now enabling scientists to reveal the underlying forces that give rise to the solar wind. Data provided by the SOHO/MDI consortium, international collaboration between ESA and NASA suggest that a process referred to as “slipping reconnection” may drive the solar wind.

UCL’s Deb Baker explains: “Solar wind is an outflow of million-degree gas and magnetic field that engulfs the Earth and other planets. It fills the entire solar system and links with the magnetic fields of the Earth and other planets. Changes in the Sun’s million-mile-per-hour wind can induce disturbances within near-Earth space and our upper atmosphere and yet we still don’t know what drives these outflows.

“However, our latest study suggests that it is the release of energy stored in solar magnetic fields which provides the additional driver for the solar wind. This magnetic energy release is most efficient in the brightest regions of activity on the Sun’s surface, called active regions or sunspot groups, which are strong concentrations of magnetic field. We believe that this fundamental process happens everywhere on the Sun on virtually all scales.”

The team studied images taken in February 2007 from the EIS instrument, which show hot plasma outflows. At the edges of active regions where slipping reconnection might occur, according to computer models, the researchers explain that a slow, continuous restructuring of the magnetic field leads to the release of energy and acceleration of particles in the Sun’s hot outer atmosphere, its corona.

The locations proposed by the computer model correlated with gas moving outward at up to 160,000 kilometres per hour, a thousand times faster than a terrestrial hurricane.

Links:

Astrophys. J. 2009, 705, 926-935
Deb Baker homepage

Recently, several Intute staff members have been involved in a project to help raise awareness of sixteen major new digitisation projects, funded by the UK’s Joint Information Systems Committee (JISC). These sixteen projects span a huge range of material, which is now all freely available to scholars at UK universities. Indeed, many of the digitisation projects have made their content freely accessible to anyone via the Internet.

An index of all JISC-funded digitisation projects may be found here: http://www.jisc.ac.uk/whatwedo/programmes/digitisation/projects.aspx

Intute’s role was to bring these resources to the attention of the research community, and particularly to political and social historians, for whom the digitised content was likely to prove most beneficial. We did this via various conferences and workshops, where we also tried to get a better idea of the kind of things that academics looked for in digital collections of primary sources.

As far as design is concerned, several of the people we spoke to wished that search interfaces followed more of a standard, so that it didn’t take so much time and effort learning the different ways in which to get the best out of any given collection. It was felt that this might also make it easier to cross-search several different collections.

A mark of good design was when content was ‘pushed’ to the user to illustrate the kinds of thing that the collection contained. Some researchers indicated that they were not always aware at first of how rich and broad a collection was, and the message they wanted to get across was, “don’t make the content seem more limited than it really is”. Several researchers who attended the workshops were pleasantly surprised to locate material relevant to their study in unexpected places, which perhaps reinforces the need for digitisers not to market their resources too narrowly, and to emphasise the relevance of their content to researchers who might not be able to spot the value of the project from its title.

This observation leads to a more general one – that all too often the people who might expect to get the most out of digital collections are not aware of them and don’t know where to find out about them. Many researchers are quite busy enough conducting their research using traditional sources such as monographs and journal articles, and they don’t often look up from their work to check whether something new has become available.

A service such as Intute can help people keep up with new Web resources in their field via features such as MyIntute’s email alerts

For other humanities websites with alerting services, take a look at Intute’s catalogue

The project found that some traditional information channels, such as academic journals, often don’t give the same kind of critical attention to new electronic resources as they do to books – frequently because electronic resources require different and unfamiliar review processes. Embedding digital resources better into existing channels of academic communication would arguably benefit both the producers and intended consumers of the content.

For more resources on the peer review process for digital humanities resources, see these Intute results

The full IJDDiP (Intute/JISC Digitisation Dissemination Project) final report can be downloaded from http://www.jisc.ac.uk/media/documents/programmes/digitisation/intutefinal.pdf.

During the course of the project, Intute commissioned several notable historians to write introductions to various aspects of historical research that stand to benefit from the JISC-funded digital collections. These introductions lead the reader to many of the best online resources for research into the fields that are covered:

• British Electoral History

• Crime and Punishment in 19th-Century Britain

• History of British Healthcare

• History of British News Media

• History of Ireland and its relationship with Britain

For some good resources about the digitisation of historical resources, see these Intute records.

David Bradley Science Writer

The media was recently drenched with the idea that water had been found on the Moon, offering speculation as to our nearest neighbour offering an oasis-like site for a lunar base from which we could launch missions to Mars and beyond. The truth, if it is ever confirmed, is a little more subtle.

The Apollo missions of the 1970s had always hinted at the presence of water on the Moon, although its presence in samples brought back to earth was thought to be nothing more than contamination. In 1998, scientists announced that the Lunar Prospector spacecraft had detected 300 million tonnes of water on the moon and hinted that there may be as much as 6 billion tonnes. In July, an analysis of tiny beads of volcanic glass collected by two Apollo missions revealed water trapped inside, suggesting that the Moon’s water had not been entirely vaporized by the violent events that led to its formation. The discovery had implications for the volcanic origin of possible water reservoirs at the Moon’s poles.

However, new evidence released at the end of September based on data from India’s Chandrayaan-1 probe and the Deep Impact and Cassini missions suggests that there may well be some degree of hydration up there. Researchers in India and the US used data from NASA’s Moon Mineralogy Mapper, the M3, aboard the Chandrayyan-1 satellite, which was launched into orbit around the moon in October 2008 to reveal the presence of water on the moon. Chandrayaan’s mission ceased in August 2009.

M3 uses reflectance spectrometry to determine the content of minerals in the thin layer of upper soil on the surface of the moon. The data revealed the presence of chemical bonds between hydrogen and oxygen atoms, like those found between the oxygen atom and its attendant hydrogen atoms in H₂O.

However, the next generation of lunar astronauts are not likely to sip from moon springs or splash their silvery boots in lunar puddles because revelations of chemical bonds between hydrogen and oxygen atoms is indicative of water molecules but is even more indicative of hydroxyl ions (OH^-). It could be that good, old-fashioned H₂O forms only when the solar wind doth blow and brings with it hydrogen atoms that can combine with the hydroxyl radicals forming “H⁺OH^-” (H₂O). It may be that less than a litre of actual water is present per tonne of rock spread across the surface to a depth of a few centimetres and present as water of hydration of the minerals from which the rock is composed.

The rocks and soils that comprise the lunar surface contain about 45 percent oxygen, mostly in the form of silicate minerals. The constant deluge of hydrogen atoms from the solar wind could readily pull oxygen and hydroxyl from the soil and form water molecules on the fly, especially given the hydrogen ions are moving at one third the speed of light when they hit.

Taylor and other M3 team members believe their findings will be of particular significance as mankind continues to plan for a return to the moon. The maps created by M3 could provide mission planners with locations prime for extraction of needed water from the lunar soil.

Following the lunar announcement, Jim Bell, President of The Planetary Society, said: “The possible presence of minor amounts of hydrated material on the Moon is intriguing, though the findings still need to be confirmed by other methods and other investigators. Chandrayaan is another great example of the power and value of international collaboration in space exploration, and The Planetary Society congratulates the entire Chandrayaan, Deep Impact and Cassini teams.”

Researchers still hope to find liquid water at the bottom of the deepest, darkest lunar craters at depths that never see sunlight nor feel the solar wind. Such, hopefully, icy depths are akin to the cold places on the planet Mars where evidence of water ice has been found.

LINKS
Science, 2009, in press
Chandrayaan-1 site

David Bradley Science Writer

US researchers have found a way to monitor geological faults deep in the Earth that could help them predict an imminent earthquake more precisely than with other methods. This is the first time that scientists have been able to detect temporal changes in fault strength at seismogenic depth from the Earth’s surface.

The late Paul Silver and Taka’aki Taira of the Carnegie Institution’s Department of Terrestrial Magnetism, working with Fenglin Niu of Rice University and Robert Nadeau of the University of California, Berkeley, used highly sensitive seismometers to detect subtle changes in earthquake waves that travel through the San Andreas Fault zone near Parkfield, California, over a two-decade time span.

“Fault strength is a fundamental property of seismic zones,” explains Taira, who has moved to the Berkeley since the research was done. “Earthquakes are caused when a fault fails, either because of the build-up of stress or because of a weakening of the fault. Changes in fault strength are much harder to measure than changes in stress, especially for faults deep in the crust. Our result opens up exciting possibilities for monitoring seismic risk and understanding the causes of earthquakes.”

Seismologists have focused the San Andreas Fault near Parkfield, the “Earthquake Capital of the World,” for years. The site has a sophisticated array of borehole seismometers, the High-Resolution Seismic Network, as well as other geophysical instruments in situ. Researchers consider it a natural laboratory for seismology because of the frequent quakes that occur there.

Earlier studies have suggested that there are fluid-filled fractures within the fault zone and that these shift. When this happens, “repeating” earthquakes apparently become smaller and more frequent, which researchers say is indicative of a weakened fault. “Movement of the fluid in these fractures lubricates the fault zone and thereby weakens the fault,” says Niu.

“The total displacement of the fluids is only about 10 metres at a depth of about three kilometres, so it takes very sensitive seismometers to detect the changes, such as we have at Parkfield.” Niu further explains that it seems to be distant earthquakes that cause the fluids to shift, such as the 2004 Sumatra-Andaman Earthquake, which led to tsunamis throughout the Indian Ocean that year.

The authors speculate that such large events should produce a temporal clustering of global seismicity, a hypothesis that appears to be supported by the unusually high number of large earthquakes occurring in the three years following the 2004 earthquake. The team presents additional evidence that a similar phenomenon occurred following the 1992 Landers earthquake.

LINKS

Nature, 2009, 461, 636-640
Department of Terrestrial Magnetism at the Carnegie Institution of Washington
Northern California Earthquake Data Center (NCEDC)

David Bradley Science Writer

Nerve agents, such as Sarin, are extremely toxic organophosphates that can kill within minutes. Now, US researchers have developed a molecular sensor that works 100,000 times faster than earlier detection systems and destroys the agent as it does so.

When inhaled, compounds such as Sarin, Soman, and Tabun, which are relatively easy to make, lead to death within minutes by blocking the enzyme acetylcholinesterase (AChE) in nerve cells. Sarin was used in the Tokyo subway terrorist attack and security experts are worried that this and other nerve agents might be used again.

Now, Julius Rebek Jr and Trevor Dale at the Scripps Research Institute in La Jolla, California, USA, have developed a new class of sensor that can detect these neurotoxins very quickly and selectively destroy the neurotoxic molecules as they do so.

Previously developed neurotoxin detection methods are not particularly sensitive are difficult to use and devices are not portable. Moreover, they merely detect the nerve agents, they do nothing to address the acute problem of possible exposure in an accidental release or terrorist attack.

Rebek and Dales’ new sensor molecule consists of a fluorescent aromatic ring system equipped with an oxime group (–C=N–OH). This type of group binds extremely quickly to organophosphates. But, more than that, there is an alcohol group next to the oxime group, which leads to a split when the sensor encounters an organophosphate and results in an intramolecular ring closure, which leads to fluorescence.

This process can be readily detected by a fluorescence monitor, but the process also effectively destroys the organophosphate, rendering it harmless. The whole detection process from organophosphate first hitting the sensor molecule to ring closure and fluorescence occurs at a rate four to five orders of magnitude faster than the original detection reagent.

The team explains that the next step is to develop a simple, rapid-response, detector for organophosphates using these new reagents. A combined filter system for installation in the event of an emergency would not only monitor levels of the organophosphate neurotoxins but would neutralize them at the same time.

Links:
Angew Chem Int Edn, 2009, in press
Rebek site

David Bradley Science Writer

An international team of researchers has developed a new magnetic carbon material that not only acts as a semiconductor but is also magnetic and could help scientists develop the next generation of microelectronic devices.

The new carbon material is based on graphene, which resembles graphite, the form of carbon found in pencil “lead”, but which exists as single sheet-like layers resembling nanoscopic chicken wire fencing. Graphene was first created by scientists in Manchester five years ago and is not only 200 times stronger than steel but because its electrons are highly mobile it has unique electro-optical properties. As such, some researchers think that graphene is the natural successor to silicon and could lead to the advent of spintronic devices that exploit electron spin and charge in computer memory and data processing.

Now, researchers from the Virginia Commonwealth University, USA, Peking University in Beijing, China, the Chinese Academy of Science in Shanghai, and Tohoku University in Sedai, Japan have used computer modelling to design a chemical cousin of graphene, which they call graphone. Experiments with the new material confirm the electromagnetic properties predicted by the computer models.

The team points out that while the properties of graphene can be modified relatively easily by introducing “defects” into its structure or by saturating it with hydrogen atoms, it has not proven easy to make it magnetic.

“The new material we are predicting – graphone – makes graphene magnetic simply by controlling how much hydrogen is put on graphene,” explains VCU’s Puru Jena. “One of the important impacts of this research is that semi-hydrogenation provides us a very unique way to tailor magnetism,” adds team member Qiang Sun, “The resulting ferromagnetic graphone sheet will have unprecedented possibilities for the applications of graphene-based materials.”

The team explains that graphene undergoes a transition from its original “metallic” state to semiconductor when all the carbon valencies are fully hydrogenated, to make graphane. However, density functional theory predicted that half hydrogenation (to make graphone) would result in a ferromagnetic semiconductor with a small indirect gap. This they confirmed experimentally.

“From graphene to graphane and to graphone, the system evolves from metallic to semiconducting and from nonmagnetic to magnetic. Hydrogenation provides a novel way to tune the properties with unprecedented potentials for applications,” the team says.

Further Reading
Nano Lett, 2009, in press

David Bradley Science Writer

Methanol could become an intermediate fuel source ahead of the advent of the hydrogen economy if only there were a way to make it cheaply and easily at low energy cost. A new catalyst could now open the door to making methanol from methane more efficiently.

The so-called “hydrogen economy” is a hot topic in the environmental debate. Hydrogen could become the ultimate clean fuel if it could be produced using sustainable, energy sources. Using hydrogen to power fuel cells for vehicles and even buildings would produce only electricity and warm water as waste products with no local pollution. Unfortunately, hydrogen is not the easiest substance to store nor transport as it is highly explosive. Being a gas means it also requires compression or complex porous materials for safe storage.

Methanol, on the other hand, could be used as a possible fuel cell fuel or a substitute for petroleum ahead of hydrogen. As a liquid, it can be stored much more easily and cheaply than hydrogen and could be distributed by way of the existing network of filling stations. In one sense, methanol would probably represent an intermediate step on the way to a hydrogen economy as it still relies on finding a renewable carbon source. That aside, methanol will always have a bigger carbon footprint than hydrogen because it is a carbon compound.

Nevertheless, researchers have now developed a new solid catalyst for the direct low-temperature oxidation of methane (natural gas) to methanol, a chemical tool for which researchers have been searching for many years. Ferdi Schüth at the Max Plank Institute of Coal Research in Mülheim, Germany, and Markus Antonietti at the Max Planck Institute for Colloids and Interfaces in Potsdam-Golm, Germany, and their colleagues have developed a novel catalyst that they say could provide a “second wind” for methanol research.

The problem chemists have faced in developing oxidation catalysts for producing methanol from methane is that the bonds in methane are very strong. Moreover, preventing the oxidized methane from simply converting fully to carbon dioxide has proved difficult. A catalyst must be highly active, to keep the reaction conditions mild as well as highly selective to control the products effectively.

The platinum catalysts developed by Roy Periana’s team allowed the low-temperature oxidation of methane in concentrated sulfuric acid at around 200 Celsius to form methyl sulfate, which could then be converted to methanol. However, this approach was plagued with separation and recycling problems for the dissolved catalyst. Schüth explains that, “a solid catalyst that can be easily separated could make such a process viable on a small scale, making possible the efficient, decentralized consumption of natural gas.”

The German team has now developed just such a solid catalyst with high reactivity and selectivity using a recently discovered class of high-performance polymer as a support material for the catalytic platinum particles. Their successful preliminary tests suggest it might be developed into a commercially viable material for producing methanol from methane.

Angew Chem Int Edn, 2009, 48, 6909-6912
Max-Planck-Institut für Kohlenforschung homepage

David Bradley Science Writer

Steel “fuses” that distort when a building shakes during an earthquake to dissipate the energy could allow multi-story buildings hold themselves together during even violent earthquakes and then return to standing plumb straight afterwards. The fuses would then be replaced once the aftershocks die down.

The system has been tested in Japan, will not only help a multi-story building hold itself together during a violent earthquake, but also return it to standing up straight on its foundation afterward, true and plumb, with damage confined to a few easily replaceable parts.

Researchers at Stanford University and the University of Illinois in the US designed the system to protect buildings from irreparable structural damage even in earthquakes of magnitude 7 of higher, such as the recent event in Indonesia. The team has successfully tested the system on an enormous “shake table” in Japan.

“This new structural system has the potential to make buildings far more damage resistant and easier to repair,” explains Stanford’s Greg Deierlein, “so people could reoccupy buildings a lot faster after a major earthquake than they can now.”

The steel frames, or fuses, would be situated around the building’s core or along exterior walls and could be made part of the building’s initial design or incorporated into an existing building undergoing a seismic refit. The materials employed are commonly used in the construction industry and can be easily made using standard fabrication methods.

“The idea of this structural system is that we concentrate the damage in replaceable fuses,” Deierlein explains. The fuses are built to flex and distort, which dissipates the vibrational energy of the earthquake. “What is unique about these frames is that, unlike conventional systems, they actually rock off their foundation under large earthquakes,” Deierlein adds.

The fuses support rocking frames in steel “shoes” secured at their base and with steel tendons running down their centre. These tendons are made of high-strength steel cables twisted together, as the earth moves, they flex and then rebound to their normal length, which pulls the building back into proper vertical alignment afterwards.

Deierlein and his colleagues tested the system at the Hyogo Earthquake Engineering Research Center in Miki City, Japan. They used various configurations to find the most resilient setup.

“This is the first time we’ve put this whole system together to see how it would respond dynamically in a building as if it were subjected to an earthquake,” says Deierlein. It performs well under extreme earthquake shaking.” He adds that even simulating earthquakes above 7 left the rocking frame virtually undamaged on the test rig, which had three 100-tonne “storeys”.

Most seismically designed buildings are self-sacrificial, which means the occupants are saved, but the building must be demolished afterwards. The steel fuse system means that the building would also be saved and when the fuses blow they are simply replaced

Professor Gregory Deierlein homepage