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Monday, 20 February 2017

On this day in science history: Sakurai's Object was discovered

In 1996, a bright “new” star was discovered in Sagittarius by Japanese amateur astronomer Yukio Sakurai. It was found not to be a usual nova, but instead was a star going through a dramatic evolutionary state, re-igniting its nuclear furnace for one final blast of energy called the “final helium flash.” It was only the second to be identified in the twentieth century. A star like the Sun ends its active life as a white dwarf star gradually cooling down into visual oblivion. Sakurai's Object had a mass a few times that of the Sun. Its collapse after fusing most of its hydrogen fuel to helium raised its temperature so much higher it began nuclear fusion of its helium remains. This was confirmed using its light spectrum to identify the elements present.

Sakurai's Object By ESO, [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons
Sakurai's Object is a highly evolved post-asymptotic giant branch star which has, following a brief period on the white dwarf cooling track, undergone a helium shell flash (also known as a very late thermal pulse). The star is thought to have a mass of around 0.6 M☉. Observations of Sakurai's Object show increasing reddening and pulsing activity, suggesting that the star is exhibiting thermal instability during its final helium-shell flash.

Prior to its reignition V4334 Sgr is thought to have been cooling towards a white dwarf with a temperature around 100,000 K and a luminosity around 100 L☉. The luminosity rapidly increased about a hundred-fold and then the temperature decreased to around 10,000 K. The star developed the appearance of an F class supergiant (F2 Ia). The apparent temperature continued to cool to below 6,000 K and the star was gradually obscured at optical wavelengths by the formation of carbon dust, similar to an R CrB star. Since then the temperature has increased to around 20,000 K.

The properties of Sakurai's Object are quite similar to that of V605 Aquilae. V605, discovered in 1919, is the only other known star observed during the high luminosity phase of a very late thermal pulse, and Sakurai's Object is modeled to increase in temperature in the next few decades to match the current state of V605.

During the second half of 1998 an optically thick dust shell obscured Sakurai's Object, causing a rapid decrease in visibility of the star, until in 1999 it disappeared from optical wavelength observations altogether. Infrared observations showed that the dust cloud around the star is primarily carbon in an amorphous form. In 2009 it was discovered that the dust shell is strongly asymmetrical, as a disc with a major axis oriented at an angle of 134°, and inclination of around 75°. The disc is thought to be growing more opaque due to the fast spectral evolution of the source towards lower temperatures.

Sakurai's Object is surrounded by a planetary nebula created following the star's red giant phase around 8300 years ago. It has been determined that the nebula has a diameter of 44 arcseconds and expansion velocity of roughly 32 km/s.

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Monday, 13 February 2017

Dwarf star 200 light years away contains life's building blocks

Many scientists believe the Earth was dry when it first formed, and that the building blocks for life on our planet - carbon, nitrogen and water - appeared only later as a result of collisions with other objects in our solar system that had those elements.

Today, a UCLA-led team of scientists reports that it has discovered the existence of a white dwarf star whose atmosphere is rich in carbon and nitrogen, as well as in oxygen and hydrogen, the components of water. The white dwarf is approximately 200 light years from Earth and is located in the constellation Boötes.

The Earth seen from Apollo 17. By NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans [Public domain or Public domain], via Wikimedia Commons

Benjamin Zuckerman, a co-author of the research and a UCLA professor of astronomy, said the study presents evidence that the planetary system associated with the white dwarf contains materials that are the basic building blocks for life. And although the study focused on this particular star - known as WD 1425+540 - the fact that its planetary system shares characteristics with our solar system strongly suggests that other planetary systems would also.

"The findings indicate that some of life's important preconditions are common in the universe," Zuckerman said.

The scientists report that a minor planet in the planetary system was orbiting around the white dwarf, and its trajectory was somehow altered, perhaps by the gravitational pull of a planet in the same system. That change caused the minor planet to travel very close to the white dwarf, where the star's strong gravitational field ripped the minor planet apart into gas and dust. Those remnants went into orbit around the white dwarf - much like the rings around Saturn, Zuckerman said - before eventually spiraling onto the star itself, bringing with them the building blocks for life.

The researchers think these events occurred relatively recently, perhaps in the past 100,000 years or so, said Edward Young, another co-author of the study and a UCLA professor of geochemistry and cosmochemistry. They estimate that approximately 30 percent of the minor planet's mass was water and other ices, and approximately 70 percent was rocky material.

The research suggests that the minor planet is the first of what are likely many such analogs to objects in our solar system's Kuiper belt. The Kuiper belt is an enormous cluster of small bodies like comets and minor planets located in the outer reaches of our solar system, beyond Neptune. Astronomers have long wondered whether other planetary systems have bodies with properties similar to those in the Kuiper belt, and the new study appears to confirm for the first time that one such body exists.

White dwarf stars are dense, burned-out remnants of normal stars. Their strong gravitational pull causes elements like carbon, oxygen and nitrogen to sink out of their atmospheres and into their interiors, where they cannot be detected by telescopes.

The research, published in the Astrophysical Journal Letters, describes how WD 1425+540 came to obtain carbon, nitrogen, oxygen and hydrogen. This is the first time a white dwarf with nitrogen has been discovered, and one of only a few known examples of white dwarfs that have been impacted by a rocky body that was rich in water ice.

"If there is water in Kuiper belt-like objects around other stars, as there now appears to be, then when rocky planets form they need not contain life's ingredients," said Siyi Xu, the study's lead author, a postdoctoral scholar at the European Southern Observatory in Germany who earned her doctorate at UCLA.

"Now we're seeing in a planetary system outside our solar system that there are minor planets where water, nitrogen and carbon are present in abundance, as in our solar system's Kuiper belt," Xu said. "If Earth obtained its water, nitrogen and carbon from the impact of such objects, then rocky planets in other planetary systems could also obtain their water, nitrogen and carbon this way."

A rocky planet that forms relatively close to its star would likely be dry, Young said.

"We would like to know whether in other planetary systems Kuiper belts exist with large quantities of water that could be added to otherwise dry planets," he said. "Our research suggests this is likely."

According to Zuckerman, the study doesn't settle the question of whether life in the universe is common.

"First you need an Earth-like world in its size, mass and at the proper distance from a star like our sun," he said, adding that astronomers still haven't found a planet that matches those criteria.

The researchers observed WD 1425+540 with the Keck Telescope in 2008 and 2014, and with the Hubble Space Telescope in 2014. They analyzed the chemical composition of its atmosphere using an instrument called a spectrometer, which breaks light into wavelengths. Spectrometers can be tuned to the wavelengths at which scientists know a given element emits and absorbs light; scientists can then determine the element's presence by whether it emits or absorbs light of certain characteristic wavelengths. In the new study, the researchers saw the elements in the white dwarf's atmosphere because they absorbed some of the background light from the white dwarf.

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Tuesday, 7 February 2017

What makes popcorn pop? The chemistry of popcorn

We’ve all scoffed it in the cinema, but have you thought about the chemistry behind it?  Take a look at the graphic below to find out more about the compounds that give popcorn its flavour and aroma, as well as what makes it pop!

Source: Compound Interest 
So that’s the science! But what about the history of popcorn? 

Corn was first domesticated in Mexico 9,000 years ago.  Archaeologists have discovered that people have known about popcorn for thousands of years. In Mexico, for example, they’ve found remnants of popcorn that dates to around 3600 BC. Many historians even believe that popcorn is the first corn that humans even knew about. Popping of the kernels was achieved manually through the 19th century, being sold on the east coast of the USA under names such as 'Pearls' or 'Nonpareil'. The term 'popped corn' first appeared in John Russell Bartlett’s 1848 Dictionary of Americanisms. Popcorn is an ingredient in Cracker Jack, and in the early years of the product, it was popped by hand. 

Popcorn's accessibility increased rapidly in the 1890s with Charles Cretors' invention of the popcorn maker. Cretors, a Chicago candy store owner, created a number of steam powered machines for roasting nuts, and applied the technology to the corn kernels. By the turn of the century, Cretors had created and deployed street carts equipped with steam powered popcorn makers.

During the Great Depression, popcorn was fairly inexpensive at 5–10 cents a bag and became popular. Thus, while other businesses failed, the popcorn business thrived and became a source of income for many struggling farmers, including the Redenbacher family, namesake of the famous popcorn brand. During World War II, sugar rations diminished candy production, and Americans compensated by eating three times as much popcorn as they had before. The snack was popular at heaters, much to the initial displeasure of many of the theatre owners, who thought it distracted from the films. Their minds eventually changed, however, and in 1938 a Midwestern theatre owner named Glen W. Dickson installed popcorn machines in the lobbies of his theatres. The venture was a financial success, and the trend soon spread.

In 1970, Orville Redenbacher's namesake brand of popcorn was launched. In 1981, General Mills received the first patent for a microwave popcorn bag, with popcorn consumption seeing a sharp increase by tens of thousands of pounds in the years following.

At least six localities (all in the Midwestern United States) claim to be the "Popcorn Capital of the World;": Ridgway, Illinois; Valparaiso, Indiana; Van Buren, Indiana; Schaller, Iowa; Marion, Ohio; and North Loup, Nebraska. According to the USDA, corn used for popcorn production is specifically planted for this purpose; most is grown in Nebraska and Indiana, with increasing area in Texas.

As the result of an elementary school project, popcorn became the official state snack food of Illinois.

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Monday, 30 January 2017

On this day in science history: the world's tallest geyser was discovered

In 1901, the world's tallest geyser was discovered by Dr Humphrey Haines on the North Island of New Zealand. He was following up reports of great clouds of steam, and found the Waimangu Geyser near Rotorua. It appeared after an enormous eruption of Mt. Tarawera in 1886. The Waimangu Geyser was the largest geyser in the world and erupted on a 36 hour cycle for four years, hurling black mud and rocks in the air. Waimangu is Maori for "black water." It stopped in 1904 when a landslide changed the local water table. Eruptions would typically reach 600 feet. Some superbursts are known to have reached 1,600 feet (10 times as high as Yellowstone's famous Old Faithful, and which would be higher than the Empire State Building.)

Geyser activity, like all hot spring activity, is caused by surface water gradually seeping down through the ground until it meets rock heated by magma. The geothermally heated water then rises back toward the surface by convection through porous and fractured rocks. Geysers differ from non-eruptive hot springs in their subterranean structure; many consist of a small vent at the surface connected to one or more narrow tubes that lead to underground reservoirs of water and pressure tight rock.

Steamboat Geyser in Yellowstone. By Brocken Inaglory (Own work) [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
As the geyser fills, the water at the top of the column cools off, but because of the narrowness of the channel, convective cooling of the water in the reservoir is impossible. The cooler water above presses down on the hotter water beneath, not unlike the lid of a pressure cooker, allowing the water in the reservoir to become superheated, i.e. to remain liquid at temperatures well above the standard-pressure boiling point.

Ultimately, the temperatures near the bottom of the geyser rise to a point where boiling begins which forces steam bubbles to rise to the top of the column. As they burst through the geyser's vent, some water overflows or splashes out, reducing the weight of the column and thus the pressure on the water below. With this release of pressure, the superheated water flashes into steam, boiling violently throughout the column. The resulting froth of expanding steam and hot water then sprays out of the geyser vent.

A key requirement that enables a geyser to erupt is a material called geyserite found in rocks nearby the geyser. Geyserite—mostly silicon dioxide (SiO2), is dissolved from the rocks and gets deposited on the walls of the geyser's plumbing system and on the surface. The deposits make the channels carrying the water up to the surface pressure-tight. This allows the pressure to be carried all the way to the top and not be leaked out into the loose gravel or soil that are normally under the geyser fields.

Eventually the water remaining in the geyser cools back to below the boiling point and the eruption ends; heated groundwater begins seeping back into the reservoir, and the whole cycle begins again. The duration of eruptions and time between successive eruptions vary greatly from geyser to geyser; Strokkur in Iceland erupts for a few seconds every few minutes, while Grand Geyser in the United States erupts for up to 10 minutes every 8–12 hours.

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Monday, 23 January 2017

Blood-repellent materials: A new approach to medical implants

Medical implants like stents, catheters and tubing introduce risk for blood clotting and infection - a perpetual problem for many patients.

Colorado State University engineers offer a potential solution: A specially grown, "superhemophobic" titanium surface that's extremely repellent to blood. The material could form the basis for surgical implants with lower risk of rejection by the body.

Titanium (mineral concentrate). Public Domain, https://commons.wikimedia.org/w/index.php?curid=323468

It's an outside-the-box innovation achieved at the intersection of two disciplines: biomedical engineering and materials science. The work, recently published in Advanced Healthcare Materials, is a collaboration between the labs of Arun Kota, assistant professor of mechanical engineering and biomedical engineering; and Ketul Popat, associate professor in the same departments.

Kota, an expert in novel, "superomniphobic" materials that repel virtually any liquid, joined forces with Popat, an innovator in tissue engineering and bio-compatible materials. Starting with sheets of titanium, commonly used for medical devices, their labs grew chemically altered surfaces that act as perfect barriers between the titanium and blood. Their teams conducted experiments showing very low levels of platelet adhesion, a biological process that leads to blood clotting and eventual rejection of a foreign material.

A material "phobic" (repellent) to blood might seem counterintuitive, the researchers say, as often biomedical scientists use materials "philic" (with affinity) to blood to make them biologically compatible. "What we are doing is the exact opposite," Kota said. "We are taking a material that blood hates to come in contact with, in order to make it compatible with blood." The key innovation is that the surface is so repellent, that blood is tricked into believing there's virtually no foreign material there at all.

The undesirable interaction of blood with foreign materials is an ongoing problem in medical research, Popat said. Over time, stents can form clots, obstructions, and lead to heart attacks or embolisms. Often patients need blood-thinning medications for the rest of their lives - and the drugs aren't foolproof.

"The reason blood clots is because it finds cells in the blood to go to and attach," Popat said. "Normally, blood flows in vessels. If we can design materials where blood barely contacts the surface, there is virtually no chance of clotting, which is a coordinated set of events. Here, we're targeting the prevention of the first set of events."

The researchers analyzed variations of titanium surfaces, including different textures and chemistries, and they compared the extent of platelet adhesion and activation. Fluorinated nanotubes offered the best protection against clotting, and they plan to conduct follow-up experiments.

Growing a surface and testing it in the lab is only the beginning, the researchers say. They want to continue examining other clotting factors, and eventually, to test real medical devices.

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Tuesday, 17 January 2017

Simple fats, amino acids to explain how life began

Life is a process that originated 3.5 billion years ago. It emerged when the basic components of the cells that we know today, in other words, inanimate chemical molecules, gradually joined, merged, assembled themselves and interacted. At a given moment they became alive, or what amounts to the same thing, they turned into autonomous systems. As the years passed they gradually evolved until achieving their current complexity and diversity. A piece of research by the UPV/EHU is working on the start of this trajectory by studying how the chemical molecules assembled themselves so that life could begin.

A section of DNA. 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
DNA, RNA, proteins, membranes, sugars, …cells are made up of all kinds of components. In biology, and in the studies dealing with the origin of life specifically, it is very common to focus on one of these molecules and put forward hypotheses on how life originated by analysing the specific mechanisms related to it. "Basically, these studies are looking for the 'molecule of life', in other words, they set out to establish which was the most important molecule in making this milestone happen," said Kepa Ruiz-Mirazo, researcher in the Biophysics Unit and of the UPV/EHU's Department of Logic and Philosophy of Science. However, bearing in mind that "life involves activity among a huge variety of molecules and components, a change of approach has been taking place in recent years and research that takes into account various molecules at the same time is gaining strength," he added.

Besides emerging in favour of this fresh approach, Ruiz-Mirazo's group, in collaboration with the University of Montpellier, through an internship of the UPV/EHU PhD student Sara Murillo-Sánchez, has been able to show that interaction exists between some molecules and others. "Our group has expertise in research into membranes that are created in prebiotic environments, in other words, in the study of the dynamics that fatty acids, the precursors of current lipids, may have had. 

The Montpellier group for its part specialises in the synthesis of the first peptides. So when the knowledge of each group is put together, and when we experimentally blended the fatty acids and the amino acids, we could see that there was a strong synergy between them."

As they were able to see, the catalysis of the reaction took place when the fatty acids formed compartments. As they are in an aqueous medium, and due to the hydrophobic nature of lipids, they tend to join with each other and form closed compartments; in other words, they take on the function of a membrane; "at that time the membranes obviously weren't biological but chemical ones," explained Ruiz-Mirazo. In their experiments they were able to see that the conditions offered by these membranes are favourable for amino acids. "The Montpellier group had the prebiotic reactions of the formation of dipeptides very well characterised, so they were able to see that this reaction took place more efficiently in the presence of fatty acids," he added.

Besides demonstrating the synergy between fatty acids and amino acids, Ruiz-Mirazo believes it is very important to have conducted the study using basic chemical components, in other words, molecular precursors. "Life emerged out of these basic molecules; therefore, to study its origin we cannot start from the complex phospholipids that are found in today's membranes. We have demonstrated the formation of the first coming together and formation of chains on the basis of molecular precursors. Or to put it another way, we have demonstrated that it is possible to achieve diversity and complexity in biology by starting from chemistry."

In his studies, in addition to the experimental work, Ruiz-Mirazo is working in another two spheres so in the end he is studying the origin of life from three pillars or perspectives: "firstly, we have the experimental field; another is based on theoretical models and computational simulations, which we use to analyse the results obtained in the experiments, and the third is a little broader, because we are studying from the philosophical viewpoint what life is, the influence that the conception held about life exerts on the experimental field, since each conception leads you to carry out a specific type of experiment," he explained. "These three methodologies mutually feed each other: an idea that may emerge in the philosophical analysis leads you to carry out a new simulation, and the results of the simulations mark out the path for designing the experiments. Or the other way round. Most likely we will never manage to find the answer to how life began, but we are working on it: all of us living beings on Earth have the same origin and we want to know how it happened."

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Tuesday, 10 January 2017

The chemistry of the environmental effects of fireworks

Who doesn’t love fireworks at New Year? Yet whilst fireworks are undoubtedly a spectacle, they can also have a negative effect on the environment. Take a look at the graphic below, to discover some of the issues that they can cause.

Source: Compound Interest
So that’s the science, but what about the history? Who first invented the firework?

The earliest documentation of fireworks dates back to 7th century China (time of the Tang Dynasty), where they were invented. The fireworks were used to accompany many festivities. It is thus a part of the culture of China and had its origin there; eventually it spread to other cultures and societies.

The art and science of firework making has developed into an independent profession. In China, pyrotechnicians were respected for their knowledge of complex techniques in mounting firework displays. Chinese people originally believed that the fireworks could expel evil spirits and bring about luck and happiness.

During the Song Dynasty (960–1279), many of the common people could purchase various kinds of fireworks from market vendors, and grand displays of fireworks were also known to be held. In 1110, a large fireworks display in a martial demonstration was held to entertain Emperor Huizong of Song (r. 1100–1125) and his court. A record from 1264 states that a rocket-propelled firework went off near the Empress Dowager Gong Sheng and startled her during a feast held in her honor by her son Emperor Lizong of Song (r. 1224–1264). 

Rocket propulsion was common in warfare, as evidenced by the Huolongjing compiled by Liu Bowen (1311–1375) and Jiao Yu (fl. c. 1350–1412). In 1240 the Arabs acquired knowledge of gunpowder and its uses from China. A Syrian named Hasan al-Rammah wrote of rockets, fireworks, and other incendiaries, using terms that suggested he derived his knowledge from Chinese sources, such as his references to fireworks as "Chinese flowers".

With the development of chinoiserie in Europe, Chinese fireworks began to gain popularity around the mid-17th century. Lev Izmailov, ambassador of Peter the Great, once reported from China: "They make such fireworks that no one in Europe has ever seen." In 1758, the Jesuit missionary Pierre Nicolas le Chéron d'Incarville, living in Beijing, wrote about the methods and composition on how to make many types of Chinese fireworks to the Paris Academy of Sciences, which revealed and published the account five years later. His writings would be translated in 1765, resulting in the popularization of fireworks and further attempts to uncover the secrets of Chinese fireworks.

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