|Jupiter. By NASA, ESA, and A. Simon (Goddard Space Flight Center) [Public domain], via Wikimedia Commons|
Tuesday, 27 September 2016
Astronomers using NASA's Hubble Space Telescope have imaged what may be water vapor plumes erupting off the surface of Jupiter's moon Europa. This finding bolsters other Hubble observations suggesting the icy moon erupts with high altitude water vapor plumes.
The observation increases the possibility that missions to Europa may be able to sample Europa's ocean without having to drill through miles of ice.
"Europa's ocean is considered to be one of the most promising places that could potentially harbor life in the solar system," said Geoff Yoder, acting associate administrator for NASA's Science Mission Directorate in Washington. "These plumes, if they do indeed exist, may provide another way to sample Europa's subsurface."
The plumes are estimated to rise about 125 miles (200 kilometers) before, presumably, raining material back down onto Europa's surface. Europa has a huge global ocean containing twice as much water as Earth's oceans, but it is protected by a layer of extremely cold and hard ice of unknown thickness. The plumes provide a tantalizing opportunity to gather samples originating from under the surface without having to land or drill through the ice.
The team, led by William Sparks of the Space Telescope Science Institute (STScI) in Baltimore observed these finger-like projections while viewing Europa's limb as the moon passed in front of Jupiter.
The original goal of the team's observing proposal was to determine whether Europa has a thin, extended atmosphere, or exosphere. Using the same observing method that detects atmospheres around planets orbiting other stars, the team realized if there was water vapor venting from Europa's surface, this observation would be an excellent way to see it.
"The atmosphere of an extrasolar planet blocks some of the starlight that is behind it," Sparks explained. "If there is a thin atmosphere around Europa, it has the potential to block some of the light of Jupiter, and we could see it as a silhouette. And so we were looking for absorption features around the limb of Europa as it transited the smooth face of Jupiter."
In 10 separate occurrences spanning 15 months, the team observed Europa passing in front of Jupiter. They saw what could be plumes erupting on three of these occasions.
This work provides supporting evidence for water plumes on Europa. In 2012, a team led by Lorenz Roth of the Southwest Research Institute in San Antonio, detected evidence of water vapor erupting from the frigid south polar region of Europa and reaching more than 100 miles (160 kilometers) into space. Although both teams used Hubble's Space Telescope Imaging Spectrograph instrument, each used a totally independent method to arrive at the same conclusion.
"When we calculate in a completely different way the amount of material that would be needed to create these absorption features, it's pretty similar to what Roth and his team found," Sparks said. "The estimates for the mass are similar, the estimates for the height of the plumes are similar. The latitude of two of the plume candidates we see corresponds to their earlier work."
But as of yet, the two teams have not simultaneously detected the plumes using their independent techniques. Observations thus far have suggested the plumes could be highly variable, meaning that they may sporadically erupt for some time and then die down. For example, observations by Roth's team within a week of one of the detections by Sparks' team failed to detect any plumes.
If confirmed, Europa would be the second moon in the solar system known to have water vapor plumes. In 2005, NASA's Cassini orbiter detected jets of water vapor and dust spewing off the surface of Saturn's moon Enceladus.
Scientists may use the infrared vision of NASA's James Webb Space Telescope, which is scheduled to launch in 2018, to confirm venting or plume activity on Europa. NASA also is formulating a mission to Europa with a payload that could confirm the presence of plumes and study them from close range during multiple flybys.
"Hubble's unique capabilities enabled it to capture these plumes, once again demonstrating Hubble's ability to make observations it was never designed to make," said Paul Hertz, director of the Astrophysics Division at NASA Headquarters in Washington. "This observation opens up a world of possibilities, and we look forward to future missions - such as the James Webb Space Telescope - to follow up on this exciting discovery."
The work by Sparks and his colleagues will be published in the Sept. 29 issue of The Astrophysical Journal.
The Hubble Space Telescope is a project of international cooperation between NASA and ESA (the European Space Agency.) NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. STScI, which is operated for NASA by the Association of Universities for Research in Astronomy in Washington, conducts Hubble science operations.
For more information, visit:
Tuesday, 20 September 2016
In 1892, wire glass was patented by Frank Schulman. Wire glass, as the name suggests, is simply a wire mesh inserted during the plate glass manufacturing process to create a single monolithic glass with properties useful where fire safety requirements apply.
In recent years, new materials have become available that offer both fire-ratings and safety ratings so the continued use of wired glass is being debated worldwide. The US International Building Code effectively banned wired glass in 2006.
Canada’s building codes still permit the use of wired glass but the codes are being reviewed and traditional wired glass is expected to be greatly restricted in its use. Australia has no similar review taking place.
Wired glass is still utilized in the U.S. for its fire-resistant abilities, and is well-rated to withstand both heat and hose streams. This is why wired glass exclusively is used on service elevators to prevent fire ingress to the shaft, and also why it is commonly found in institutional settings which are often well-protected and partitioned against fire. The wire prevents the glass from falling out of the frame even if it cracks under thermal stress, and is far more heat-resistant than a laminating material.
For more information visit:
Tuesday, 13 September 2016
It is the double helix, with its stable and flexible structure of genetic information, that made life on Earth possible in the first place. Now a team from the Technical University of Munich (TUM) has discovered a double helix structure in an inorganic material. The material comprising tin, iodine and phosphorus is a semiconductor with extraordinary optical and electronic properties, as well as extreme mechanical flexibility.
Flexible yet robust - this is one reason why nature codes genetic information in the form of a double helix. Scientists at TU Munich have now discovered an inorganic substance whose elements are arranged in the form of a double helix.
The substance called SnIP, comprising the elements tin (Sn), iodine (I) and phosphorus (P), is a semiconductor. However, unlike conventional inorganic semiconducting materials, it is highly flexible. The centimeter-long fibers can be arbitrarily bent without breaking.
"This property of SnIP is clearly attributable to the double helix," says Daniela Pfister, who discovered the material and works as a researcher in the work group of Tom Nilges, Professor for Synthesis and Characterization of Innovative Materials at TU Munich. "SnIP can be easily produced on a gram scale and is, unlike gallium arsenide, which has similar electronic characteristics, far less toxic."
The semiconducting properties of SnIP promise a wide range of application opportunities, from energy conversion in solar cells and thermoelectric elements to photocatalysts, sensors and optoelectronic elements. By doping with other elements, the electronic characteristics of the new material can be adapted to a wide range of applications.
Due to the arrangement of atoms in the form of a double helix, the fibers, which are up to a centimeter in length can be easily split into thinner strands. The thinnest fibers to date comprise only five double helix strands and are only a few nanometers thick. That opens the door also to nanoelectronic applications.
"Especially the combination of interesting semiconductor properties and mechanical flexibility gives us great optimism regarding possible applications," says Professor Nilges. "Compared to organic solar cells, we hope to achieve significantly higher stability from the inorganic materials. For example, SnIP remains stable up to around 500°C (930 °F)."
|A double helix. Zephyris at the English language 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|
"Similar to carbon, where we have the three-dimensional (3D) diamond, the two dimensional graphene and the one dimensional nanotubes," explains Professor Nilges, "we here have, alongside the 3D semiconducting material silicon and the 2D material phosphorene, for the first time a one dimensional material - with perspectives that are every bit as exciting as carbon nanotubes."
Just as with carbon nanotubes and polymer-based printing inks, SnIP double helices can be suspended in solvents like toluene. In this way, thin layers can be produced easily and cost-effectively. "But we are only at the very beginning of the materials development stage," says Daniela Pfister. "Every single process step still needs to be worked out."
Since the double helix strands of SnIP come in left and right-handed variants, materials that comprise only one of the two should display special optical characteristics. This makes them highly interesting for optoelectronics applications. But, so far there is no technology available for separating the two variants.
Theoretical calculations by the researchers have shown that a whole range of further elements should form these kinds of inorganic double helices. Extensive patent protection is pending. The researchers are now working intensively on finding suitable production processes for further materials.
An extensive interdisciplinary alliance is working on the characterization of the new material: Photoluminescence and conductivity measurements have been carried out at the Walter Schottky Institute of the TU Munich. Theoretical chemists from the University of Augsburg collaborated on the theoretical calculations. Researchers from the University of Kiel and the Max Planck Institute of Solid State Research in Stuttgart performed transmission electron microscope investigations. Mössbauer spectra and magnetic properties were measured at the University of Augsburg, while researchers of TU Cottbus contributed thermodynamics measurements.
For more information, visit:
Wednesday, 7 September 2016
In 1948, the first rubberised asphalt road surface in the U.S. was applied to 6,217-ft of Exchange Street in Akron, Ohio, a city that was home to a large rubber industry. The paving mixture contained 7 to 11 pounds of crumbled synthetic rubber per ton of asphalt. This full-scale use followed a test made on a small section resurfaced in 1947. Goodyear President Paul W. Litchfield proposed the paving material - and donated the rubber - to the city after he had seen its use in Holland, where it had been used since the 1930s and was claimed to be more durable, waterproof and safer in extremes of weather. However, by 1959, wear was judged to be no better than less expensive asphalt alone, and rubber additive is no longer used.
A synthetic rubber is any artificial elastomer. These are mainly polymers synthesised from petroleum by products. About 15 billion kilograms (5.3×1011 oz) of rubbers are produced annually, and of that amount two thirds are synthetic. Global revenues generated with synthetic rubbers are likely to rise to approximately US$56 billion in 2020. Synthetic rubber, like natural rubber, has uses in the automotive industry for tires, door and window profiles, hoses, belts, matting, and flooring.
|Chemical structure of cis-polyisoprene, the main constituent of natural rubber.By Smokefoot (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons|
Natural rubber, coming from latex of Hevea brasiliensis, is mainly poly-cis-isoprene containing traces of impurities like protein, dirt etc. Although it exhibits many excellent properties in terms of mechanical performance, natural rubber is often inferior to certain synthetic rubbers, especially with respect to its thermal stability and its compatibility with petroleum products.
Synthetic rubber is made by the polymerization of a variety of petroleum-based precursors called monomers. The most prevalent synthetic rubbers are styrene-butadiene rubbers (SBR) derived from the copolymerization of styrene and 1,3-butadiene. Other synthetic rubbers are prepared from isoprene (2-methyl-1,3-butadiene), chloroprene (2-chloro-1,3-butadiene), and isobutylene (methylpropene) with a small percentage of isoprene for cross-linking. These and other monomers can be mixed in various proportions to be copolymerized to produce products with a range of physical, mechanical, and chemical properties. The monomers can be produced pure and the addition of impurities or additives can be controlled by design to give optimal properties. Polymerization of pure monomers can be better controlled to give a desired proportion of cis and trans double bonds.
For more information visit:
Tuesday, 30 August 2016
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."
For more information visit:
Wednesday, 24 August 2016
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.
Tuesday, 16 August 2016
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.
For more information visit:-