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Tuesday, 24 November 2015

Whiffs from cyanobacteria likely responsible for Earth's oxygen

Earth's oxygen-rich atmosphere emerged in whiffs from a kind of cyanobacteria in shallow oceans around 2.5 billion years ago, according to new research from Canadian and US scientists.
The Earth by NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans.
These whiffs of oxygen likely happened in the following 100 million years, changing the levels of oxygen in Earth's atmosphere until enough accumulated to create a permanently oxygenated atmosphere around 2.4 billion years ago - a transition widely known as the Great Oxidation Event.

"The onset of Earth's surface oxygenation was likely a complex process characterized by multiple whiffs of oxygen until a tipping point was crossed," said Brian Kendall, a professor of Earth and Environmental Sciences at the University of Waterloo. "Until now, we haven't been able to tell whether oxygen concentrations 2.5 billion years ago were stable or not. These new data provide a much more conclusive answer to that question."

The findings are presented in a paper published this month in Science Advances from researchers at Waterloo, University of Alberta, Arizona State University, University of California Riverside, and Georgia Institute of Technology. The team presents new isotopic data showing that a burst of oxygen production by photosynthetic cyanobacteria temporarily increased oxygen concentrations in Earth's atmosphere.

"One of the questions we ask is: 'did the evolution of photosynthesis lead directly to an oxygen-rich atmosphere? Or did the transition to today's world happen in fits and starts?" said Professor Ariel Anbar of Arizona State University. "How and why Earth developed an oxygenated atmosphere is one of the most profound puzzles in understanding the history of our planet."

The new data supports a hypothesis proposed by Anbar and his team in 2007. In Western Australia, they found preliminary evidence of these oxygen whiffs in black shales deposited on the seafloor of an ancient ocean.

The black shales contained high concentrations of the elements molybdenum and rhenium, long before the Great Oxidation Event.

These elements are found in land-based sulphide minerals, which are particularly sensitive to the presence of atmospheric oxygen. Once these minerals react with oxygen, the molybdenum and rhenium are released into rivers and eventually end up deposited on the sea floor.

In the new paper, researchers analyzed the same black shales for the relative abundance of an additional element: osmium. Like molybdenum and rhenium, osmium is also present in continental sulfide minerals. The ratio of two osmium isotopes - 187Os to 188Os - can tell us if the source of osmium was continental sulfide minerals or underwater volcanoes in the deep ocean.

The osmium isotope evidence found in black shales correlates with higher continental weathering as a result of oxygen in the atmosphere. By comparison, slightly younger deposits with lower molybdenum and rhenium concentrations had osmium isotope evidence for less continental input, indicating the oxygen in the atmosphere had disappeared.

The paper's authors also include Professor Robert Creaser of the University of Alberta, Professor Timothy Lyons from the University of California Riverside and Professor Chris Reinhard from the Georgia Institute of Technology.

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Wednesday, 18 November 2015

Tiny protein 'compasses' found in fruit flies - and potentially humans

Tiny biological compasses made from clumps of protein may help scores of animals, and potentially even humans, to find their way around, researchers say.

Scientists discovered the minuscule magnetic field sensors in fruit flies, but found that the same protein structures appeared in retinal cells in pigeons’ eyes. They can also form in butterfly, rat, whale and human cells.

The rod-like compasses align themselves with Earth’s geomagnetic field lines, leading researchers to propose that when they move, they act on neighbouring cell structures that feed information into the nervous system to create a broader direction-sensing system.

Professor Can Xie, who led the work at Peking University, said the compass might serve as a “universal mechanism for animal magnetoreception,” referring to the ability of a range of animals from butterflies and lobsters to bats and birds, to navigate with help from Earth’s magnetic field.

Whether the compasses have any bearing on human navigation is unknown, but the Peking team is investigating the possibility. “Human sense of direction is complicated,” said Xie. “However, I believe that magnetic sense plays a key role in explaining why some people have a good sense of direction.”

The idea that animals could sense Earth’s magnetic field was once widely dismissed, but the ability is now well established, at least among some species. The greatest mystery that remains is how the sensing is done.

One type of molecular compass, proposed by the biologist Klaus Schulten, senses geomagnetic field information through the bizarre quantum behaviour of electrons that are produced when light falls on retinal proteins called cryptochromes. But Xie argues that a compass based on cryptochromes alone is not enough to navigate.

By screening the fruit fly genome, the Chinese team discovered a protein they named MagR, which forms rod-like clumps with cryptochrome proteins. This MagR-cryptochrome cluster behaves like a sophisticated magnetic sensor that in principle can sense the direction, intensity or inclination of Earth’s magnetic field.

“The nanoscale biocompass has the tendency to align itself along geomagnetic field lines and to obtain navigation cues from a geomagnetic field,” said Xie. “We propose that any disturbance in this alignment may be captured by connected cellular machinery, which would channel information to the downstream neural system, forming the animal’s magnetic sense.”

In a series of follow-up experiments, the scientists show that MagR-cryptochrome compass can form in a range of species, including monarch butterflies, pigeons, more rats, minke whales and humans. Details are reported in the journal Nature Materials.

Xie said the discovery could go beyond understanding how animals navigate, and lead to new technologies that allow scientists to control cell processes and influence animal behaviour with magnetic fields.

Simon Benjamin, who studies quantum materials at Oxford University, said that evolution seemed to have found a number of ways to sense magnetic fields. “It seems plausible that the structure discovered in this paper is key to the fruit fly’s compass, and perhaps other species as well.”

He added that the finding was exciting even if the MagR-cryptochrome cluster was not one of nature’s biocompasses, because it could be used to develop new technologies. “There is a continual drive for cheaper, smaller, more robust, or more sensitive field sensors. They’re needed to enable a vast range of applications from mining survey systems to map navigation with mobile phones.”

“It has been well documented that cryptochromes, which are crucial to the compass proposed in this new paper, may harness significant quantum effects to convert the Earth’s weak magnetic field into a signal in the animal’s brain. 

This is a tantalising possibility since the new UK quantum technology hubs are focusing about a quarter of their £150M on sensor systems. It would be remarkable if we can learn some tricks from Mother Nature in this highly-advanced field of physics,” he added.

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Wednesday, 11 November 2015

Diamonds may not be so rare as once thought

Diamonds may not be as rare as once believed, but this finding in a new Johns Hopkins University research report won't mean deep discounts at local jewellery stores.

"Diamond formation in the deep Earth, the very deep Earth, may be a more common process than we thought," said Johns Hopkins geochemist Dimitri A. Sverjensky, whose article co-written with doctoral student Fang Huang appears today in the online journal Nature Communications. The report says the results 'constitute a new quantitative theory of diamond formation,' but that does not mean it will be easier to find gem-quality diamonds and bring them to market.

"Rough diamond" by Unknown USGS employee - Original source: USGS "Minerals in Your World" website. 
For one thing, the prevalence of diamonds near the Earth's surface - where they can be mined - still depends on relatively rare volcanic magma eruptions that raise them from the depths where they form. For another, the diamonds being considered in these studies are not necessarily the stuff of engagement rings, unless the recipient is equipped with a microscope. Most are only a few microns across and are not visible to the unaided eye.

Using a chemical model, Sverjensky and Huang found that these precious stones could be born in a natural chemical reaction that is simpler than the two main processes that up to now have been understood to produce diamonds. Specifically, their model - yet to be tested with actual materials - shows that diamonds can form with an increase in acidity during interaction between water and rock.

The common understanding up to now has been that diamonds are formed in the movement of fluid by the oxidation of methane or the chemical reduction of carbon dioxide. Oxidation results in a higher oxidation state, or a gain of electrons. Reduction means a lower oxidation state, and collectively the two are known as 'redox' reactions.

"It was always hard to explain why the redox reactions took place," said Sverjensky, a professor in the Morton K. Blaustein Department of Earth and Planetary Sciences in the university's Krieger School of Arts and Sciences. The reactions require different types of fluids to be moving through the rocks encountering environments with different oxidation states.

The new research showed that water could produce diamonds as its pH falls naturally - that is, as it becomes more acidic - while moving from one type of rock to another, Sverjensky said.

The finding is one of many in about the last 25 years that expands scientists' understanding of how pervasive diamonds may be, Sverjensky said.

"The more people look, the more they're finding diamonds in different rock types now," Sverjensky said. "I think everybody would agree there's more and more environments of diamond formation being discovered."

Nobody has yet put a number on the greater abundance of diamonds, but Sverjensky said scientists are working on that with chemical models. It's impossible to physically explore the great depths at which diamonds are created: roughly 90 to 120 miles below the Earth's surface at intense pressure and at temperatures about 1,650 to 2,000 degrees Fahrenheit.

The deepest drilling exploration ever made was about 8 or 9 miles below the surface, he said.

If the study doesn't shake the diamond markets, it promises to help shed light on fluid movement in the deep Earth, which helps account for the carbon cycle on which all life on the planet depends.

"Fluids are the key link between the shallow and the deep Earth," Sverjensky said. "That's why it's important."

This research was supported by grants from the Sloan Foundation through the Deep Carbon Observatory (Reservoirs and Fluxes and Extreme Physics and Chemistry programs) and by a U.S. Energy Department grant, DE-FG-02-96ER-14616.

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Monday, 2 November 2015

On this day in history: the first synthetic rubber was announced

On 2nd November 1931, the DuPont company, of Wilmington, Delaware, announced the first synthetic rubber. It was known as DuPrene, and from 1936 as Neoprene. Many scientists were trying to make natural rubber in the 1920s and 30s. One of the Wallace Carothers team, Gerard Berchet, had left a sample of monovinylacetylene in a jar with hydrochloric acid (HCl) for about five weeks. 

Then on 17 Apr 1930, coworker Arnold M. Collins happened to look in that jar and found a rubbery white material. The HCl had reacted with the vinylacetylene, making chloroprene, which then polymerized to become polychloroprene. The new rubber was expensive, but resisted oil and gasoline, which natural rubber didn't. It was the first good synthetic rubber.

In 1935, German chemists synthesized the first of a series of synthetic rubbers known as Buna rubbers. These were copolymers, meaning the polymers were made up from two monomers in alternating sequence. Other brands included Koroseal, which Waldo Semon developed in 1935, and Sovprene, which Russian researchers created in 1940. B.F. Goodrich Company scientist Waldo Semon developed a new and cheaper version of synthetic rubber known as Ameripol in 1940.

The production of synthetic rubber in the United States expanded greatly during World War II, since the Axis powers controlled nearly all the world's limited supplies of natural rubber by mid-1942 once Japan conquered Asia. Military trucks needed rubber for tyres, and rubber was used in almost every other war machine. The U.S. government launched a major (and largely secret) effort to improve synthetic rubber production. A large team of chemists from many institutions were involved, including Calvin Souther Fuller of Bell Labs. The rubber designated GRS (Government Rubber Styrene), a copolymer of butadiene and styrene, was the basis for U.S. synthetic rubber production during World War II. By 1944, a total of 50 factories were manufacturing it, pouring out a volume of the material twice that of the world's natural rubber production before the beginning of the war. It still represents about half of total world production.

Operation Pointblank bombing targets of Nazi Germany included the Schkopau (50K tons/yr) plant and the Hüls synthetic rubber plant near Recklinghausen (30K, 17%), the Kölnische Gummifäden Fabrik tire and tube plant at Deutz on the east bank of the Rhine. The Ferrara, Italy, synthetic rubber factory (near a river bridge) was bombed August 23, 1944. Three other synthetic rubber facilities were at Ludwigshafen/Oppau (15K), Hanover/Limmer (reclamation, 20K), and Leverkusen (5K). A synthetic rubber plant at Oświęcim in Nazi-occupied Poland, was under construction on March 5, 1944.

World War Two poster about synthetic rubber tyres
Solid-fuel rockets during World War II used nitrocellulose for propellants, but it was impractical and dangerous to make such rockets very large. During the war, California Institute of Technology (Caltech) researchers came up with a new solid fuel based on asphalt mixed with an oxidizer (such as potassium or ammonium perchlorate), and aluminium powder. This new solid fuel burned more slowly and evenly than nitrocellulose, and was much less dangerous to store and use, but it tended to slowly flow out of the rocket in storage and the rockets using it had to be stockpiled nose down.

After the war, Caltech researchers began to investigate the use of synthetic rubbers to replace asphalt in their solid fuel rocket motors. By the mid-1950s, large missiles were being built using solid fuels based on synthetic rubber, mixed with ammonium perchlorate and high proportions of aluminium powder. 

Such solid fuels could be cast into large, uniform blocks that had no cracks or other defects that would cause non-uniform burning. Ultimately, all large solid-fuel military rockets and missiles would use synthetic-rubber-based solid fuels, and they would also play a significant part in the civilian space effort.

Additional refinements to the process of creating synthetic rubber continued after the war. The chemical synthesis of isoprene accelerated the reduced need for natural rubber, and the peacetime quantity of synthetic rubber exceeded the production of natural rubber by the early 1960s.

Nowadays synthetic rubber is used a great deal in printing on textiles. In this case it is called rubber paste. In most cases titanium dioxide is used with copolymerization and volatile matter in producing such synthetic rubber for textile use. Moreover, this kind of preparation can be considered to be the pigment preparation based on titanium dioxide.

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