Hot topics

David Bradley Science Writer

A more environmentally friendly way to make ethylene (a primary feedstock for the chemical industry, which also goes by the name of ethene) would use natural gas as the raw material rather than cracking crude oil. Now, a golden opportunity in the form of a two-centred gold complex has come to light.

Ethylene is one of the chemical industry’s primary feedstock materials from which a whole range of different compounds are made, among them the coolant and antifreeze compound ethylene glycol and plastics such as polyethylene. Ethylene is currently produced from oil by steam cracking. However, direct conversion of natural gas, methane, to ethylene could also be viable on an industrial scale if a suitable catalyst and reaction setup were developed. One of the big advantages of such an approach is that methane supplies are likely to provide us with raw material long after oil has dwindled.

Scientists working with Thorsten Bernhardt at the University of Ulm, Germany and Uzi Landman at the Georgia Institute of Technology, in Atlanta, Georgia, USA, explain that the problem with the conversion of methane to ethylene is one of bond strength. The bonds between carbon and hydrogen atoms in the methane molecule, are very strong and so difficult to break. To compel the carbon in methane to form bonds with other carbon atoms requires a lot of energy. Additionally, any efforts to do so, usually produce lots of side-products containing more than the requisite two carbon atoms found in ethylene.

Activating methane to allow it to form bigger molecules, such as ethylene, is a complex process. The team explains that in order to find a suitable catalyst a clearer understanding of the process at the molecular level is needed. As such Bernhardt and colleagues investigated different catalytic metal clusters, aggregates of a few metal atoms, as model systems for the process. They found that particles containing two charged gold atoms (ions) in pairs could convert methane to ethylene at low temperatures and pressures in the gas phase without forming significant quantities of side-products.

methane to ethane using a golden cat (Credit: Bernhardt et al/Wiley-VCH)

In order to understand how this process works, the team “trapped” the reaction intermediates and used computational techniques to model the energy levels of starting materials, catalyst, intermediates, and products. They found that each gold ion in the dimer binds to a single methane molecule, this severs hydrogen from the methane and the two carbon atoms can then form a single bond to each other. This is a precursor to ethylene itself which has a strong double bond between its carbon atoms. The precursor initially remains bound to one of the gold ions, while the second gold ion, suddenly finds itself able to bond to a new methane molecule. In the final step, this second methane molecule nudges away the ethylene precursor, the carbon single bond, which can then form a carbon double bond. The newly trapped methane then pairs up with yet another methane and the cycle begins again.

“Both the activation of the carbon-hydrogen bonds of the methane and the subsequent splitting off of the ethylene molecule require cooperative action of several atoms bound to the gold dimer,” Berhnardt explains. “Our insights are not only of fundamental interest, but may also be of practical use.”

LINKS

Angew Chem Int Edn 2010, 49, 980-983
http://dx.doi.org/10.1002/anie.200905643

Bernhardt
http://www.uni-ulm.de/iok/bernhardt/

David Bradley Science Writer

The European Southern Observatory’s Very Large Telescope (VLT) has helped an international team of astronomers to detect a stellar mass black hole that lies at a much greater distance from Earth than any observed before. The black hole is in the spiral galaxy NGC 300, about six million light years away in the constellation Sculptor.

The spiral galaxy NGC 300 lying in the constellation Sculptor (Credit: Galex/NASA)

Paul Crowther and Vik Dhillon, of the University of Sheffield, UK, Robin Barnard and Simon Clark of the The Open University, Milton Keynes, UK, and Stefania Carpano and Andy Pollock of ESAC, in Madrid, Spain report the black hole which has a mass of about twenty times that of the Sun in the Monthly Notices of the Royal Astronomical Society.

The stellar-mass black holes found in our Milky Way galaxy commonly weigh up to ten times the mass of the Sun. The newly discovered black hole is not only the most distant, but the second most massive stellar-mass black hole ever found. It is also entwined with a star that will soon become a black hole itself.

Lead author Crowther, explains: “This is the most distant stellar-mass black hole ever weighed, and it’s the first one we’ve seen outside our own galactic neighbourhood, the Local Group. The black hole’s curious partner is a Wolf-Rayet star, which also has a mass of about twenty times as much as the Sun. Wolf-Rayet stars are near the end of their lives and expel most of their outer layers into their surroundings before exploding as supernovae, with their cores imploding to form black holes.

An artist's impression of the newly discovered black hole and its stellar companion (Credit: ESO/L. Calçada)

In less than a million years, a blink of the eye cosmologically speaking, the Wolf-Rayet star will explode as a supernova and its remnants collapse into a black hole. Only one other system of this type has previously been seen, but other systems comprising a black hole and a companion star are not unknown to astronomy. The existence of such systems hints at an underlying galactic chemistry. Astronomers believe that a higher concentration of heavy chemical elements influences how a massive star evolves, increasing how much matter it sheds, resulting in a smaller black hole when the remnant finally collapses.

LINKS

Monthly Notices Royal Astronom Soc, 2010, in press
http://www.eso.org/public/archives/releases/sciencepapers/eso1004/eso1004.pdf

Paul Crowther
http://pacrowther.staff.shef.ac.uk/main.html

David Bradley Science Writer

An estimated 513 billion barrels of “technically recoverable” heavy oil lie in Venezuela’s Orinoco Oil Belt, a 50,000 square kilometre region in the East Venezuela Basin Province.

Worldwide consumption of petroleum was 85.4 million barrels per day in 2008. The three largest consuming countries were United States with 19.5 million barrels per day, China with 7.9 million barrels per day, and Japan with 4.8 million barrels per day. So the Venezuelan heavy oil represents a potential supply that could last a decade at the current rate of consumption.

The United States Geological Survey (USGS) has carried out the first assessment that identifies how much oil might be technically recoverable using currently technology and standard industry practices. According to USGS Energy Resources Program Coordinator Brenda Pierce, this part of the world has one of the world’s largest recoverable oil accumulations. The USGS’s report is part of its program directed at estimating the technically recoverable oil and gas resources of priority petroleum basins worldwide. This is the largest accumulation ever assessed by the USGS.

“Knowing the potential for extractable resources from this tremendous oil accumulation, and others like it, is critical to our understanding of the global petroleum potential and informing policy and decision makers,” explains Pierce. “Accumulations like this one were previously very difficult to produce, but advances in technology and new understandings in geology allow us to assess how much is now technically recoverable.”

USGS team member and a co-author of the report, Christopher Schenk explains further: “Heavy oil is a type of oil that is very thick and therefore does not flow very easily. As a result, specialized production and refining processes are needed to generate petroleum products, but it is still oil and can generate many of the same products as other types of oil.”

The estimated petroleum resources in the Orinoco Oil Belt, range from 380 to 652 billion barrels of oil (at a 95 and 5 percent chance of occurrence, respectively). Schenk says that the estimates are based on a rate of oil recovery of between 40 and 45 percent.

Credit: USGS

However, others are sceptical that these oil reserves are economically or environmentally viable. Venezuelan oil geologist Gustavo Coronel told the Associated Press that he doubted the recovery rate could be much higher than 25 percent given the nature of the crude oil. More intriguing is that the USGS announcement seems to have been timed to coincide with an international auction for drilling rights in the Orinoco Belt which took place on 28th January, with results to be announced on 10th February.

Moreover, there are no little energy and environmental costs to be considered in recovering heavy crude oil as it is not necessarily as easy to extract as conventional crude oil. Moreover, the existence of such reserves while perhaps saving us from short-term oil shortages does not address the issues of carbon emissions and potential climate change.

Links

USGS Assessment
http://pubs.usgs.gov/fs/2009/3028/

Energy Resources Program
http://energy.usgs.gov/

Auction news
http://www.reuters.com/article/idUSTRE60S5D320100129

Crude claims
http://rawstory.com/2010/01/usgs-claims-venezuela-holds-earths-largest-oil-reserves/

AP report
http://ca.news.finance.yahoo.com/s/22012010/2/biz-finance-venezuela-s-orinoco-area-holds-vast-supply-crude.html

David Bradley Science Writer

Porous solid catalysts are a mainstay of the modern chemical industry, allowing reactions that would otherwise take an age to progress to be run much, much faster. One group of such catalysts are the zeolites and particularly important among them is one known as ZSM-5, an aluminosilicate material with an MFI structure. However, despite its attractions, ZSM-5 can behave badly because its chemical building blocks do not join together perfectly. This leads to chemical starting materials on which the catalyst is to act often becoming stuck before they can get into the reactive pores and be converted into product. Now, Dutch scientist Marianne Kox has discovered the nature of the miniscule deviations that can make ZSM-5 such a troublemaker.

Catalytic ZSM-5 isn't always on its best behaviour (Credit: Nature Materials/Weckhuysen et al)

Catalysts are essential to the production of a vast array of pharmaceutical drugs, agrochemicals, fuels and countless other chemical products that are made from simple starting materials. Kox and colleague Lukasz Karwacki, together with researchers at the Max Planck Institute for Coal Research in Mülheim an der Ruhr, Germany, ExxonMobil Chemical Europe Inc, Machelen, Belgium, the Centre for Nanoporous Materials, at the University of Manchester, UK, UOP LLC, a Honeywell Company, in Des Plaines, Illinois, USA, and Nicholas Copernicus University, Torun, Poland, have used a raft of spectroscopic techniques, on the micro scale to analyse the structure of zeolite ZSM-5 and have obtained spatial and time-resolved data on the three-dimensional interior of these porous materials. The data reveal the deviations from one porous unit to the next that can lead to reduced efficiency, catalytic poisoning, and unwanted chemical by-products.

Catalytic ZSM-5 (Credit: Nature Materials/Weckhuysen et al)

Kox is working as part of the Vici project run by Bert Weckhuysen, Professor of Inorganic Chemistry and Catalysis at Utrecht University in The Netherlands. Details of the research were published in Nature Materials. The team developed a new approach that correlates confocal fluorescence microscopy with focused ion beam–electron back-scatter diffraction, transmission electron microscopy lamelling and diffraction, atomic force microscopy and X-ray photoelectron spectroscopy to study a wide range of coffin-shaped zeolite crystals of differing shapes, sizes, structures, and chemical compositions.

The powerful combination of techniques demonstrates “a unified view on the morphology-dependent MFI-type [zeolite] intergrowth structures and provides evidence for the presence and nature of internal and outer-surface barriers for molecular diffusion,” the team say. “It has been found that internal-surface barriers originate not only from a 90° mismatch in structure and pore alignment but also from small angle differences of 0.5 to 2 degrees for particular crystal morphologies. Furthermore, outer-surface barriers seem to be composed of a silicalite outer crust with a thickness varying from 10 to 200 nanometres.”

LINKS

Nature Mater, 2009, 8, 959-965
http://dx.doi.org/10.1038/nmat2530

Bert Weckhuysen

David Bradley Science Writer

Scientists in Canada have identified a toxic chlorination by-product of chlorination in tap water, dichloroquinone, using a newly developed procedure based on liquid chromatography (LC), electrospray ionization (ESI), and tandem mass spectrometry (tandem-MS). The levels of the compound may be present at a few nanograms per litre, which the researchers suggest may represent a bladder cancer risk as well as being associated with adverse reproductive effects.

Untreated water can carry several potentially lethal diseases, including typhoid, dysentery, cholera, and diarrhoea. Treatment and disinfection through chlorination usually renders water safe to drink and helps keep these illnesses at bay, at least in those parts of the world where chlorination facilities exist.

However, some scientists are concerned that the chlorination of water itself may be a risk factor for more insidious diseases. For instance, some studies have suggested that there may be a link between drinking chlorinated tap water and an increased risk of bladder cancer. Now, researchers at the University of Alberta, in Canada, have identified a chlorination by-product that may represent a risk factor, dichloroquinone.

Xing-Fang Li group

Xing-Fang Li and colleagues explain that common reactions between chlorinating agents and natural organic molecules in water are known to produce tiny quantities of chloroform and chlorinated acetic acid derivatives. The presence of these compounds in drinking water are tightly regulated but the team suspected that there are other compounds formed in disinfected tap water that are not, among them chlorinated quinones. The researchers point out that concentrations of such compounds were below detection thresholds previously but are now under suspicion.

Quinones are organic molecules containing a six-membered carbon ring to which are attached two oxygen atoms bound by double bonds on opposite sides of the ring; microbial activity can lead to the presence of these compounds in water. Earlier, independent work suggests that halogenated quinones, those containing chlorine or bromine, can react with DNA and proteins even at very low concentrations and cause damage to these critical biomolecules. The Canadian team has now successfully identified a representative of this class of compounds, 2,6-dichloro-1,4-benzoquinone, in chlorinated drinking water.

The chemistry of clean water

“The scientific understanding of drinking-water quality has advanced substantially since trihalomethanes [e.g. chloroform] were first discovered [in water] in 1974,” the team says. “Effective management of disinfection by-products health risks requires better knowledge of disinfection chemistry combined with toxicology,” the researchers add.

LINKS

Angew Chem Int Edn, 2010, in press
http://dx.doi.org/10.1002/anie.200904934

Fang group

David Bradley Science Writer

Three billion years ago, the red planet, Mars, was warm enough to sustain lakes of liquid water, according to satellite images just published in the journal Geology. Previously, astronomers had assumed that this period was simply too cold and arid for surface water.

Researchers at Imperial College London and University College London now suggest that during the Hesperian Epoch, the Martian surface around the equator was spotted with lakes, each approximately 20 kilometres across, formed from melted ice. Earlier studies had hinted at the warm and wet early history of Mars during the period 4 billion to 3.8 billion years ago, well before the Hesperian Epoch. Detailed images from NASA’s Mars Reconnaissance Orbiter, which is currently circling the planet, suggest that there were later warm and wet periods; age is determined by meteorite crater count. The evidence lies in several flat-floored depressions located above Ares Vallis, a giant gorge that runs 2000 km across the equator of Mars.

Martian lakes

According to Nicholas Warner, of IC’s Department of Earth Science and Engineering, “Most of the research on Mars has focused on its early history and the recent past. Scientists had largely overlooked the Hesperian Epoch as it was thought that Mars was then a frozen wasteland. Excitingly, our study now shows that this middle period in Mars’ history was much more dynamic than we previously thought.”

Warner and colleagues, Sanjeev Gupta, Jung-Rack Kim, Shih-Yuan Lin, and Jan-Peter Muller, claim that there may have been increased volcanic activity, meteorite impacts or shifts in Mars’ orbit during this period, which could have warmed its atmosphere enough to melt ice. This in turn would have bolstered the greenhouse effect temporarily, trapping more heat from the sun and making the planet warm enough for liquid water to exist on its surface.

Until now, the Ares Vallis depressions have remained a mystery to scientists, although they suspected that their formation was due to sublimation of ice directly to water vapour. The loss of ice would have created cavities between the soil particles, which would have caused the ground beneath to subside.

Martian channels

The researchers have now discovered small, sinuous channels that connect the depressions, which they say could only have been formed by running water, essentially making the sublimation theory redundant. The team also compared the Mars images with images of thermokarst landscapes on Earth in places such as Siberia and Alaska. Thermokarst landscapes are areas where permafrost is melting, creating lakes that are interconnected by the same type of channels the team says exist on Mars. The team says that the melting ice created lakes that may have burst their banks allowing water to carve pathways through the frozen ground from higher lakes into lower-lying lakes.

UCL’s Muller who works at the Mullard Space Science Laboratory who carried out the 3D mapping of the Martian surface, explains how modelling with sub-metre resolution allowed the team to test their hypotheses much more rigorously than ever before.

Topographic image

One thing that the scientists do not yet know is how long the warm and wet period lasted during the Hesperian epoch or how long the lakes remained liquid. Nevertheless, the study may have implications for so-called “astrobiologists” looking for evidence of life on Mars. The team say these lake beds indicate regions on the planet that may have once been suitable for some form of microbial Martian life. As such, they represent good targets for future robotic missions seeking out ancient life on Mars.

LINKS

Geology, 2010, 38, 71-74
http://dx.doi.org/10.1130/G30579.1
Video flypast

David Bradley Science Writer

After a frustrating false start, the Large Hadron Collider (LHC) finally got it up and running in its underground home at CERN on the Swiss-French border near Geneva. The scientists behind the world’s biggest scientific, announced that they had primed to energies higher than any previous particle accelerator has ever reached; beating the US Tevatron at Fermilab in Illinois by 20%.

The LHC accelerated protons from an “injection” energy of 0.45 trillion electronvolts to 1.18 TeV. An electronvolt is the energy gained by a single electron being accelerated by a 1 volt potential difference. 1.0 TeV is about 0.16 billionths of a Joule, equivalent to the kinetic energy of a flying mosquito.

The LHC is one of the most ambitious scientific projects every undertaken. Ultimately, the scientists behind it hope that it will reveal one of the most mysterious of natural phenomena – mass. The machine will smash together sub-atomic particles at high speeds. Scientists hope to find the so-called Higgs boson among the collision debris. This particle is the key ingredient in a significant theory – the Higgs-Brout-Englert-Guralnik-Hagen-Kibble mechanism – developed in the 1960s that attempts to explain mass of certain subatomic particles based on the existence of the elusive boson.

The first beams were injected into the LHC on 20th November 2009, although the team does not expect to carry out any actual science until 2010. Nevertheless on 23rd November, they had succeeded in circulating two beams of particles simultaneously and recorded collision data for the first time. The record-breaking energies were reached on 30th November.

“I was here 20 years ago when we switched on CERN’s last major particle accelerator, LEP,” enthused Accelerators and Technology Director Steve Myers. “I thought that was a great machine to operate, but this is something else. What took us days or weeks with LEP, we’re doing in hours with the LHC.”

LHC control room while ramping up the beams to high energies. (Credit: CERN)

The next step is to increase the beam intensity before delivering good quantities of collision data to the experiments before Christmas. So far, all the LHC commissioning work has been carried out with a low-intensity pilot beam. Higher intensity is needed to provide meaningful proton-proton collision rates. Safety is paramount and so the current work is looking at how stable the much higher intensity beams will be. If successful, the scientists will then calibrate the LHC until the end of the year and then begin the first particles physics experiments proper early in 2010 during which collision energies of 7 TeV will be used. Imagine seven mosquitoes colliding in the space.

LHC control room celebrations (Credit: CERN)

Links:

The Large Hadron Collider
CERN on Twitter

David Bradley Science Writer

Researchers have shown that networks of chitin filaments are an integral part of the silica shells of tiny marine creatures known as diatoms. The discovery could open the way to emulating these incredibly diverse and potentially very useful substances for materials science and engineering applications.

Some of the most bizarre and beautiful structural forms in nature exist in the world of the diatom, so named from the Greek meaning “cut through”. They represent a major group of eukaryotic algae that has existed since Jurassic times and are among the most common plant-type plankton, phytoplankton. They are mostly unicellular but form ribbon and fan-like colonies. Their most outstanding feature is that each cell is encapsulated by a unique shell of hydrated silicon dioxide, known as a frustule.

There is an almost infinite diversity of frustules but they commonly consist of two asymmetrical sides with a division down the middle, hence the name – diatom. Diatom frustules are not composed solely of hydrated silica but contain other substances, making them among the most fascinating natural hybrid materials having some quite unusual mechanical and optical properties.

However, scientists do not yet fully understand the biochemical mechanisms by which diatoms lay down silica and combine it with other substances in the biomineralization process of frustule construction.

Now, researchers at TU Dresden and the Max Planck Institute the Chemical Physics of Solids in Dresden, Germany, have identified another of the critical components of the diatom frustule. TU Dresden’s Eike Brunner and colleagues report details in the journal Angewandte Chemie, that show how they found an organic network of cross-linked chitin (poly-N-acetyl-d-glucosamine) filaments.

Brunner

Chitin is a well-known biological macromolecule comprising long molecular chains of sugar building blocks, it is a polysaccharide in other words, loosely related to cellulose and starch. Chitin is the second most abundant polysaccharide on Earth after cellulose. Insects and crustaceans combine chitin with calcium carbonate and proteins to form their exoskeletons. “Chitin plays an important role in the biomineralization of such calcium carbonate based shells and structures,” explains Brunner. He and his team have now demonstrated for the first time that the silica cell walls of the diatom Thalassiosira pseudonana also contain a chitin-based network.

SEM image of T. pseudonana before and after silica dissolution reveals chitin scaffold (Credit: Brunner et al)

In order to make this discovery, the team dissolved the silica components of diatom shells in an ammonium fluoride solution. The residue appears under the scanning electron microscope to be a delicate, net-like scaffolding. This network resembles the cell wall in form and size and consists of cross-linked fibres with an average diameter of about 25 nanometres. The team carried out a spectroscopic analysis of the fibres, which proved that they are composed mainly of chitin and several previously unknown biomolecules.

“Our results suggest that the chitin-based network structure serves as a supporting scaffold for silica deposition, while the other biomolecules actively influence it,” Brunner explains. “This mechanism is thus analogous to calcium carbonate biomineralization.”

Further work is underway to reveal the function and form of the scaffold materials as well as to investigate other species.

Links:

Angew Chem, Int Edn, 2009 in press

Eike Brunner

David Bradley Science Writer

A recent study shows just how long mercury pollutants can persist in the environment and continue to cause problems. The study demonstrates that riverbank and floodplain soils contaminated by a textile manufacturing plant in Waynesboro, Virginia more than half a century ago are the major source of mercury in fish from several Shenandoah Valley rivers.

According to US Geological Survey scientist Jack Eggleston approximately 200 kg of mercury enters the South River every year. However, in order to meet safety standards in fish for human consumption, mercury loads should not exceed about 2 kg pounds per year. Such a tolerance level would require a 99% reduction in contamination asserts hydrologist Eggleston who has authored a report highlighting this serious environmental problem.

Mercury from the textile plant washed into the South River and subsequently contaminated the South Fork Shenandoah River, the Shenandoah River, and the floodplains along the three rivers. The textile plant, operated by DuPont, discharged mercury waste into the river during the period 1929 to 1950. It is difficult to know in retrospect whether those responsible for this action gave any consideration to the long-term environmental impact.

Since 1977, the Commonwealth of Virginia has enforced a fish consumption health advisory on 200 km of river downstream of the textile plant. Safety standards set by the US Environmental Protection Agency state that 0.3 parts per million of mercury in fish are allowable. High concentrations of mercury occur in fish because mercury accumulates throughout the lifetime of an organism. Smaller fish eaten by bigger, predatory fish and so on leads to even greater accumulation up to the point at which people are eating the fish.

During the study, USGS scientists and partners from the Virginia Department of Environmental Quality (VDEQ), and the EPA collected and analysed hundreds of water and sediment samples. They then used computer models to simulate water, sediment and mercury movement in the South River watershed, which revealed how the mercury can still be entering the water 50 years after the plant stopped discharging.

“Now we know why fish continue to have elevated mercury,” says Eggleston. Knowing that contaminated soil is the issue could allow a remediation program to be instigated to extract the toxic metal from the soil.

The South River Science Team working on the project also comprised scientists from government agencies, universities, DuPont itself, and environmental groups who have met regularly over the past decade. DuPont provides financial support for the work.

South Fork Shenandoah River (Credit: Virginia.gov)

Links:

USGS mercury report

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.

Protons consist of two "up" and one "down" quark linked by gluon chains but contribute only a quarter of the total proton spin (large black arrow) (Credit: RIKEN)

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