Monthly Archives: 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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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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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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