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Tuesday, 30 August 2016

Ancient air pockets changing the history of Earth’s oxygen

Ancient air trapped in rock salt for 813 million years is changing the timeline of atmospheric changes and life on Earth.

Defining past atmospheric compositions is an important yet daunting task for geologists. Most methods for determining past Earth surface conditions rely on indirect proxies gleaned from ancient sedimentary rocks. Further complicating matters, sedimentary rocks are notoriously difficult to date because they contain remnants of other rocks formed at various times.

As a result, oxygenation, or the rise of oxygen in the Earth's atmosphere, has been presumed to occur about 550 million years ago near the boundary between the Precambrian and Paleozoic geologic periods.

The Earth seeen from Apollo 17. By NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans [Public domain or Public domain], via Wikimedia Commons
West Virginia University geologist Kathleen Benison is part of a research team using new direct methods to measure the Earth's oxygenation.

The team's study identifies, for the first time, exactly how much oxygen was in Earth's atmosphere 813 million years ago - 10.9 percent. This finding, they say, demonstrates that oxygenation on Earth occurred 300 million years earlier than previously concluded from indirect measurements.

"Diversity of life emerges right around this time period," Benison said. "We used to think that to have diversity of life we needed specific things, including a certain amount of oxygen. (The findings) show that not as much oxygen is required for organisms to develop."

Fluid inclusions, the microscopic bubbles of liquids and gases in rock salt, can contain trapped air. Analysis of this trapped air allows researchers to understand past surface conditions and how oxygen has changed over the course of geologic history.

The team used a quadrupole mass spectrometer to study the air pockets. Carefully crushing minute rock salt crystals released water and gases into the mass spectrometer, which then analyzed for various compounds of oxygen and other gases.

"There are a lot of different environmental conditions specific from the past that we can find occurring in modern samples," Benison said. "This tells us about the range of conditions on Earth and also has implications for Mars."

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Wednesday, 24 August 2016

On this day in science history: Mount Vesuvius erupted

In 79, the long-dormant Mount Vesuvius erupted in Italy, burying the Roman cities of Pompeii and Herculaneum in volcanic ash. An estimated 20,000 people died. When discovered, the sites became astonishing archaeological time capsules. Official excavations began on 6 Apr 1748 of behalf of the Italian king's interest in collecting antiquities.

Pompeii, with Vesuvius towering above. Qfl247 CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html), via Wikimedia Commons
Scientific knowledge of the geologic history of Vesuvius comes from core samples taken from a 2,000 m (6,600 ft) plus bore hole on the flanks of the volcano, extending into Mesozoic rock. Cores were dated by potassium–argon and argon–argon dating. The mountain started forming 25,000 years ago. Although the area has been subject to volcanic activity for at least 400,000 years, the lowest layer of eruption material from the Somma mountain lies on top of the 40,000‑year‑old Campanian Ignimbrite produced by the Campi Flegrei complex, and was the product of the Codola Plinian eruption 25,000 years ago.

It was then built up by a series of lava flows, with some smaller explosive eruptions interspersed between them. However, the style of eruption changed around 19,000 years ago to a sequence of large explosive plinian eruptions, of which the 79 AD one was the most recent. The eruptions are named after the tephra deposits produced by them, which in turn are named after the location where the deposits were first identified:

  • The Basal Pumice (Pomici di Base) eruption, 18,300 years ago, VEI 6, saw the original formation of the Somma caldera. The eruption was followed by a period of much less violent, lava producing eruptions.
  • The Green Pumice (Pomici Verdoline) eruption, 16,000 years ago, VEI 5.
  • The Mercato eruption (Pomici di Mercato) – also known as Pomici Gemelle or Pomici Ottaviano – 8000 years ago, VEI 6, followed a smaller explosive eruption around 11,000 years ago (called the Lagno Amendolare eruption).
  • The Avellino eruption (Pomici di Avellino), 3800 years ago, VEI 5, followed two smaller explosive eruptions around 5,000 years ago. The Avellino eruption vent was apparently 2 km west of the current crater, and the eruption destroyed several Bronze Age settlements of the Apennine culture. Several carbon dates on wood and bone offer a range of possible dates of about 500 years in the mid-2nd millennium BC. In May 2001, near Nola, Italian archaeologists using the technique of filling every cavity with plaster or substitute compound recovered some remarkably well-preserved forms of perishable objects, such as fence rails, a bucket and especially in the vicinity thousands of human footprints pointing into the Apennines to the north. The settlement had huts, pots, and goats. The residents had hastily abandoned the village, leaving it to be buried under pumice and ash in much the same way that Pompeii was later preserved. Pyroclastic surge deposits were distributed to the northwest of the vent, travelling as far as 15 km (9.3 mi) from it, and lie up to 3 m (9.8 ft) deep in the area now occupied by Naples.

The volcano then entered a stage of more frequent, but less violent, eruptions until the most recent Plinian eruption, which destroyed Pompeii.

The last of these may have been in 217 BC. There were earthquakes in Italy during that year and the sun was reported as being dimmed by a haze or dry fog. Plutarch wrote of the sky being on fire near Naples and Silius Italicus mentioned in his epic poem Punica that Vesuvius had thundered and produced flames worthy of Mount Etna in that year, although both authors were writing around 250 years later. Greenland ice core samples of around that period show relatively high acidity, which is assumed to have been caused by atmospheric hydrogen sulfide.

The mountain was then quiet (for 295 years, if the 217 BC date for the last previous eruption is true) and was described by Roman writers as having been covered with gardens and vineyards, except at the top which was craggy. The mountain may have had only one summit at that time, judging by a wall painting, "Bacchus and Vesuvius", found in a Pompeiian house, the House of the Centenary (Casa del Centenario).

Several surviving works written over the 200 years preceding the 79 AD eruption describe the mountain as having had a volcanic nature, although Pliny the Elder did not depict the mountain in this way in his Naturalis Historia:

  • The Greek historian Strabo (ca 63 BC–AD 24) described the mountain in Book V, Chapter 4 of his Geographica as having a predominantly flat, barren summit covered with sooty, ash-coloured rocks and suggested that it might once have had "craters of fire". He also perceptively suggested that the fertility of the surrounding slopes may be due to volcanic activity, as at Mount Etna.
  • In Book II of De architectura, the architect Vitruvius reported that fires had once existed abundantly below the mountain and that it had spouted fire onto the surrounding fields. He went on to describe Pompeiian pumice as having been burnt from another species of stone.
  • Diodorus Siculus (ca 90 BC–ca 30 BC), another Greek writer, wrote in Book IV of his Bibliotheca Historica that the Campanian plain was called fiery (Phlegrean) because of the mountain, Vesuvius, which had spouted flame like Etna and showed signs of the fire that had burnt in ancient history.
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Tuesday, 16 August 2016

What are Olympic medals made of?

So, the Olympic medals are made of gold, silver and bronze right? Wrong! Pure gold medals would cost an awful lot, so what are the medals really made from? 

The graphic below looks at the different metals used.

Graphic: Compound Interest

So, what of real gold? Let’s find out more:

Gold is a chemical element with the symbol Au (from Latin: aurum) and the atomic number 79. In its purest form, it is a bright, slightly reddish yellow, dense, soft, malleable and ductile metal. Chemically, gold is a transition metal and a group 11 element. It is one of the least reactive chemical elements, and is solid under standard conditions. The metal therefore occurs often in free elemental (native) form, as nuggets or grains, in rocks, in veins and in alluvial deposits. It occurs in a solid solution series with the native element silver (as electrum) and also naturally alloyed with copper and palladium. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides).

Gold's atomic number of 79 makes it one of the higher atomic number elements that occur naturally in the universe. It is thought to have been produced in supernova nucleosynthesis and from the collision of neutron stars and to have been present in the dust from which the Solar System formed. Because the Earth was molten when it was just formed, almost all of the gold present in the early Earth probably sank into the planetary core. Therefore, most of the gold that is present today in the Earth's crust and mantle is thought to have been delivered to Earth later, by asteroid impacts during the Late Heavy Bombardment, about 4 billion years ago.

Gold resists attack by individual acids, but aqua regia (literally "royal water", a mixture of nitric acid and hydrochloric acid) can dissolve it. The acid mixture causes the formation of a soluble tetrachloroaurate anion. It is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic objects, giving rise to the term acid test. Gold also dissolves in alkaline solutions of cyanide, which are used in mining and electroplating. Gold dissolves in mercury, forming amalgam alloys, but this is not a chemical reaction.

Gold is a precious metal used for coinage, jewellery, and other arts throughout recorded history. In the past, a gold standard was often implemented as a monetary policy within and between nations, but gold coins ceased to be minted as a circulating currency in the 1930s, and the world gold standard was abandoned for a fiat currency system after 1976. The historical value of gold was rooted in its relative rarity, easy handling and minting, easy smelting and fabrication, resistance to corrosion and other chemical reactions (nobility), and distinctive colour.

The world consumption of new gold produced is about 50% in jewellery, 40% in investments, and 10% in industry. Gold's high malleability, ductility, resistance to corrosion and most other chemical reactions, and conductivity of electricity have led to its continued use in corrosion resistant electrical connectors in all types of computerized devices (its chief industrial use). Gold is also used in infrared shielding, coloured glass production, gold leafing, and tooth restoration. Certain gold salts are still used as anti-inflammatories in medicine.

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Monday, 8 August 2016

Researchers reduce climate-warming CO2 to building blocks for fuels

Turning carbon dioxide into stored energy sounds like science fiction: researchers have long tried to find simple ways to convert this greenhouse gas into fuels and other useful chemicals. Now, a group of researchers led by Professor Ted Sargent of the University of Toronto's Faculty of Applied Science & Engineering have found a more efficient way, through the wonders of nanoengineering.

Drs. Min Liu and Yuanjie Pang, along with a team of graduate students and post-doctoral fellows in University of Toronto Engineering, have developed a technique powered by renewable energies such as solar or wind. The catalyst takes climate-warming carbon-dioxide (CO2) and converts it to carbon-monoxide (CO), a useful building block for carbon-based chemical fuels, such as methanol, ethanol and diesel.

The frozen version of CO2, small pellets of dry ice sublimating in air. By Richard Wheeler (Zephyris) at en.wikipedia (Transferred from en.wikipedia) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
"CO2 reduction is an important challenge due to inertness of the molecule," says Liu. "We were looking for the best way to both address mounting global energy needs and help the environment," adds Pang. "If we take CO2 from industrial flue emissions or from the atmosphere, and use it as a reagent for fuels, which provide long-term storage for green energy, we're killing two birds with one stone."

The team's solution is sharp: they start by fabricating extremely small gold "nanoneedles" - the tip of each needle is 10,000 times smaller than a human hair. "The nanoneedles act like lightning rods for catalyzing the reaction," says Liu.

When they applied a small electrical bias to the array of nanoneedles, they produced a high electric field at the sharp tips of the needles. This helps attract CO2, speeding up the reduction to CO, with a rate faster than any catalyst previously reported. This represents a breakthrough in selectivity and efficiency which brings CO2 reduction closer to the realm of commercial electrolysers. The team is now working on the next step: skipping the CO and producing more conventional fuels directly.

Their work is published in the journal Nature.

"The field of water-splitting for energy storage has seen rapid advances, especially in the intensity with which these reactions can be performed on a heterogeneous catalyst at low overpotential - now, analogous breakthroughs in the rate of CO2 reduction using renewable electricity are urgently needed," says Michael Graetzel, a professor of physical chemistry at École Polytechnique Fédérale de Lausanne and a world leader in this field. "The University of Toronto team's breakthrough was achieved using a new concept of field-induced reagent concentration."

"Solving global energy challenges needs solutions that cut across many fields," says Sargent. "This work not only provides a new solution to a longstanding problem of CO2 reduction, but opens possibilities for storage of alternative energies such as solar and wind."

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Tuesday, 2 August 2016

On this day in science: the first nylon toothbrush

In 1938, the first nylon-bristle toothbrush in the U.S. was described in a New York Times business report. Dr. West's Miracle-Tuft toothbrush, a new product from the Weco Products Company, was the first to use synthetic DuPont nylon bristles instead of natural hog bristles. It had four guarantees: “No bristle shedding, 100 per cent waterproofed, longer life, greater cleansing power.” Its price was to be 50 cents (with a fair-trade minimum of 47 cents). The report said an intensive national advertising campaign for the new toothbrush was to be launched in about six weeks. Competition came in May 1939, as Johnson & Johnson began advertising their new Tek toothbrush.

The predecessor of the toothbrush is the chew stick. Chew sticks were twigs with a frayed end used to brush against the teeth, while the other end was used as a toothpick. The earliest chew sticks were discovered in Babylonia in 3500 BC, an Egyptian tomb dating from 3000 BC, and mentioned in Chinese records dating from 1600 BC. The Greeks and Romans used toothpicks to clean their teeth and toothpick-like twigs have been excavated in Qin Dynasty tombs. Chew sticks remain common in Africa; the rural Southern United States - and in the Islamic world the use of chewing stick Miswak is considered a pious action, and has been prescribed to be used before every prayer five times a day. Miswak has been used by Muslims since 7th Century AD.

A selection of toothbrushes. By Jonas Bergsten, via Wikimedia Commons
The first bristle toothbrush, resembling the modern toothbrush, was found in China during the Tang Dynasty (619–907) and used hog bristle. The bristles were sourced from hogs living in Siberia and northern China because the colder temperatures provided firmer bristles. They were then attached to a handle manufactured from bamboo or bone, forming a toothbrush. In 1223, Japanese Zen master Dōgen Kigen recorded on Shōbōgenzō that he saw monks in China clean their teeth with brushes made of horse-tail hairs attached to an ox-bone handle. The bristle toothbrush spread to Europe, brought back from China to Europe by travellers. It was adopted in Europe during the 17th century. The earliest identified use of the word toothbrush in English was in the autobiography of Anthony Wood, who wrote in 1690 that he had bought a toothbrush from J. Barret. Europeans found the hog bristle toothbrushes exported from merchants in China too firm, and preferred softer bristle toothbrushes manufactured from horsehair. Mass-produced toothbrushes, made with horse or boar bristle, continued to be imported to England from China until the mid-20th century.

In Europe, William Addis of England is believed to have produced the first mass-produced toothbrush, in 1780. In 1770, he had been jailed for causing a riot; while in prison he decided that the method used to clean teeth – at the time rubbing a rag with soot and salt on the teeth – was ineffective and could be improved. To that end, he saved a small animal bone left over from the meal he had eaten the previous night, into which he drilled small holes. He then obtained some bristles from one of his guards, which he tied in tufts that he then passed through the holes in the bone, and which he finally sealed with glue. After his release, he started a business that would manufacture the toothbrushes he had built, and he soon became very rich. He died in 1808, and left the business to his eldest son, also called William, and it stayed in family ownership until 1996. Under the name Wisdom Toothbrushes the company now manufactures 70 million toothbrushes per year in the UK. 

By 1840 toothbrushes were being mass-produced in England, France, Germany, and Japan. Pig bristle was used for cheaper toothbrushes, and badger hair for the more expensive ones.

The first patent for a toothbrush was granted to H. N. Wadsworth in 1857 (US Patent No. 18,653) in the United States, but mass production in the United States only started in 1885. The rather advanced design had a bone handle with holes bored into it for the Siberian boar hair bristles. Unfortunately, animal bristle was not an ideal material as it retains bacteria and does not dry well, and the bristles often fell out. In addition to bone, sometimes handles were made of wood or ivory. In the United States, brushing teeth did not become routine until after World War II, when American soldiers had to clean their teeth daily.

During the 1900s, celluloid handles gradually replaced bone handles in toothbrushes. Natural animal bristles were also replaced by synthetic fibers, usually nylon, by DuPont in 1938. The first electric toothbrush, the Broxodent, was invented in Switzerland in 1954. As of the turn of the 21st century, nylon had come to be widely used for the bristles, and the handles were usually molded from thermoplastic materials.

Johnson & Johnson, a leading medical-supplies firm, introduced the "Reach" toothbrush in 1977. It differed from previous toothbrushes in three ways: First, it had an angled head, similar to dental instruments, to reach back teeth; second, the bristles were concentrated more closely than usual to clean each tooth of potentially carigenic (cavity-causing) materials; and third, the outer bristles were longer and softer than the inner bristles, to clean between teeth. The Reach toothbrush was the first to have a specialized design intended to increase its effectiveness. Other models, from other manufacturers, soon followed; each of these had unique design features intended to be, and promoted as being, more effective than the basic toothbrush design that had been employed for years.

In January 2003 the toothbrush was selected as the number one invention Americans could not live without according to the Lemelson-MIT Invention Index. 

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