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Wednesday, 7 December 2016

On this day in science history - Galileo spacecraft orbits Jupiter

In 1995, the Galileo spacecraft arrived at Jupiter and entered orbit after 6 years of travel including a flyby of Venus and two asteroids, Gaspra and Ida. The orbiter had also carried an atmospheric probe with scientific instruments, which it had released from the main spacecraft in July 1995, five months before reaching Jupiter. Galileo then spent a further 8 years examining Jupiter and its moons Io and Europa. 

Jupiter. By NASA, ESA, and A. Simon (Goddard Space Flight Center) [Public domain], via Wikimedia Commons
In 1994, the Galileo orbiter was present to watch the fragments of comet Shoemaker-Levy 9 crash into Jupiter. Its mission was concluded 21 September 2003 by sending the orbiter into Jupiter's atmosphere at a speed of nearly 50 km/sec, destroying it to avoid any chance of it contaminating local moons with bacteria from Earth.

Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, but two and a half times that of all the other planets in the Solar System combined. Jupiter is a gas giant, along with Saturn, with the other two giant planets, Uranus and Neptune, being ice giants. Jupiter was known to astronomers of ancient times. The Romans named it after their god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough for its reflected light to cast shadows, and making it on average the third-brightest object in the night sky after the Moon and Venus.

Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, though helium comprises only about a tenth of the number of molecules. It may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rapid rotation, the planet's shape is that of an oblate spheroid (it has a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. 

A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere. Jupiter has at least 67 moons, including the four large Galilean moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these, has a diameter greater than that of the planet Mercury.

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Tuesday, 29 November 2016

How sand 'holds its breath'

Researchers in Australia have made an important discovery about how sand 'holds its breath' - specifically, how diatoms survive in the ever-changing environmental conditions of a beach. The finding has major implications for the biofuels industry.

Sand. By Siim Sepp (Own work), via Wikimedia Commons
The popular Middle Park beach in Melbourne is under the international spotlight following a world-first study by Monash University chemists who have discovered how sand 'holds its breath'.

The discovery, published in Nature Geoscience, has major implications and potential uses in the biofuels industry, according to lead authors Associate Professor Perran Cook and PhD student Michael Bourke from the Water Studies Centre, School of Chemistry.

Sand is full of algae called diatoms, but this environment is mixed about continuously so these organisms might get light one minute then be buried in the sediment with no oxygen the next.

"This is a new mechanism by which this type of algae survive under these conditions," said Associate Professor Cook.

"Our work has found that they ferment, like yeast ferments sugar to alcohol.
"In this case, the products are hydrogen and 'fats', for example, oleate, which is a component of olive oil."

Sand often has high concentrations of algae, which are highly productive and an important food source for food webs in the bay.

It is important to understand how these organisms survive in the harsh environment in which they live.

In this work, scientists present the first study of the importance of anoxic micro-algal metabolism through fermentation in permeable sediments.

They combined flow-through reactor experiments with microbiological approaches to determine the dominant contributors and pathways of dissolved inorganic carbon production in permeable sediments.

They show that micro-algal dark fermentation is the dominant metabolic pathway, which is the first time this has been documented in an environmental setting.

"The finding that hydrogen is a by-product of this metabolism has important implications for the types of bacteria present in the sediment," said Associate Professor Cook.

"It is well known that bacteria in the sediment can 'eat' hydrogen, however, these hydrogen eating bacteria may be more common than we previously thought."

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Tuesday, 22 November 2016

Why Lithium-ion Batteries Catch Fire

Why have some of Samsung’s phones been catching fire? Check out the infographic below to find out.

Source: Compound Interest 

So, who invented the lithium battery? 

Lithium batteries were proposed by M Stanley Whittingham, now at Binghamton University, while working for Exxon in the 1970s. Whittingham used titanium(IV) sulfide and lithium metal as the electrodes. However, this rechargeable lithium battery could never be made practical. Titanium disulfide was a poor choice, since it has to be synthesized under completely sealed conditions. This is extremely expensive (it cost $1000 per kilo for titanium disulfide raw material in the 1970s).

When exposed to air, titanium disulfide reacts to form hydrogen sulfide compounds, which have an unpleasant odour. For this, and other reasons, Exxon discontinued development of Whittingham's lithium-titanium disulfide battery. Batteries with metallic lithium electrodes presented safety issues, as lithium is a highly reactive element; it burns in normal atmospheric conditions because of the presence of water and oxygen. As a result, research moved to develop batteries where, instead of metallic lithium, only lithium compounds are present, being capable of accepting and releasing lithium ions.

Reversible intercalation in graphite and intercalation into cathodic oxides was discovered in the 1970s by J. O. Besenhard at TU Munich. Besenhard proposed its application in lithium cells. Electrolyte decomposition and solvent co-intercalation into graphite were severe early drawbacks for battery life.

There were two main trends in the research and development of electrode materials for lithium ion rechargeable batteries. One was the approach from the field of electrochemistry centering on graphite intercalation compounds, and the other was the approach from the field of new nano-carbonaceous materials.

History described above is based on the former stand point. On the other hand, in the recent interview article concerning the first stage of scientific research activity directly related to the LIB developments, it is stated that looking at the major streams in research development, the negative-electrode of today’s lithium ion rechargeable battery has its origins in PAS (polyacenic semiconductive material) discovered by Professor Tokio Yamabe and later Shjzukuni Yata at the beginning of 1980’s. The seed of this technology, furthermore, was the discovery of conductive polymers by Professor Hideki Shirakawa and his group, and it could also be seen as having started from the polyacetylene lithium ion battery developed by MacDiarmid and Heeger et al.

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Tuesday, 15 November 2016

What molecules you leave on your phone reveal about your lifestyle

We leave behind trace chemicals, molecules and microbes on every object we touch. By sampling the molecules on cell phones, researchers at University of California San Diego School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences were able to construct lifestyle sketches for each phone's owner, including diet, preferred hygiene products, health status and locations visited. This proof-of-concept study, published November 14 by Proceedings of the National Academy of Sciences, could have a number of applications, including criminal profiling, airport screening, medication adherence monitoring, clinical trial participant stratification and environmental exposure studies.

"You can imagine a scenario where a crime scene investigator comes across a personal object - like a phone, pen or key - without fingerprints or DNA, or with prints or DNA not found in the database. They would have nothing to go on to determine who that belongs to," said senior author Pieter Dorrestein, PhD, professor in UC San Diego School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences. "So we thought - what if we take advantage of left-behind skin chemistry to tell us what kind of lifestyle this person has?"

Mobile phone evolution. By Anders (Own work) , via Wikimedia Commons

In a 2015 study, Dorrestein's team constructed 3D models to illustrate the molecules and microbes found at hundreds of locations on the bodies of two healthy adult volunteers. Despite a three-day moratorium on personal hygiene products before the samples were collected, the researchers were surprised to find that the most abundant molecular features in the skin swabs still came from hygiene and beauty products, such as sunscreen.

"All of these chemical traces on our bodies can transfer to objects," Dorrestein said. "So we realized we could probably come up with a profile of a person's lifestyle based on chemistries we can detect on objects they frequently use."

Thirty-nine healthy adult volunteers participated in Dorrestein's latest study. The team swabbed four spots on each person's cell phone - an object we tend to spend a lot of time touching - and eight spots on each person's right hand, for a total of nearly 500 samples. Then they used a technique called mass spectrometry to detect molecules from the samples. They identified as many molecules as possible by comparing them to reference structures in the GNPS database, a crowdsourced mass spectrometry knowledge repository and annotation website developed by Dorrestein and co-author Nuno Bandeira, PhD, associate professor at the Jacobs School of Engineering and Skaggs School of Pharmacy and Pharmaceutical Sciences at UC San Diego.

With this information, the researchers developed a personalized lifestyle "read-out" from each phone. Some of the medications they detected on phones included anti-inflammatory and anti-fungal skin creams, hair loss treatments, anti-depressants and eye drops. Food molecules included citrus, caffeine, herbs and spices. Sunscreen ingredients and DEET mosquito repellant were detected on phones even months after they had last been used by the phone owners, suggesting these objects can provide long-term composite lifestyle sketches.

"By analyzing the molecules they've left behind on their phones, we could tell if a person is likely female, uses high-end cosmetics, dyes her hair, drinks coffee, prefers beer over wine, likes spicy food, is being treated for depression, wears sunscreen and bug spray - and therefore likely spends a lot of time outdoors - all kinds of things," said first author Amina Bouslimani, PhD, an assistant project scientist in Dorrestein's lab. "This is the kind of information that could help an investigator narrow down the search for an object's owner."

There are limitations, Dorrestein said. First of all, these molecular read-outs provide a general profile of person's lifestyle, but they are not meant to be a one-to-one match, like a fingerprint. To develop more precise profiles and for this method to be more useful, he said more molecules are needed in the reference database, particularly for the most common foods people eat, clothing materials, carpets, wall paints and anything else people come into contact with. He'd like to see a trace molecule database on the scale of the fingerprint database, but it's a large-scale effort that no single lab will be able to do alone.

Moving forward, Dorrestein and Bouslimani have already begun extending their study with an additional 80 people and samples from other personal objects, such as wallets and keys. They also hope to soon begin gathering another layer of information from each sample - identities of the many bacteria and other microbes that cover our skin and objects. In a 2010 study, their collaborator and co-author, Rob Knight, PhD, professor in the UC San Diego School of Medicine and Jacobs School of Engineering and director of the Center for Microbiome Innovation at UC San Diego, contributed to a study in which his team found they could usually match a computer keyboard to its owner just based on the unique populations of microbes the person left on it. At that time, they could make the match with a fair amount of accuracy, though not yet precisely enough for use in an investigation.

Beyond forensics, Dorrestein and Bouslimani imagine trace molecular read-outs could also be used in medical and environmental studies. For example, perhaps one day physicians could assess how well a patient is sticking with a medication regimen by monitoring metabolites on his or her skin. Similarly, patients participating in a clinical trial could be divided into subgroups based on how they metabolize the medication under investigation, as revealed by skin metabolites - then the medication could be given only to those patients who can metabolize it appropriately. Skin molecule read-outs might also provide useful information about a person's exposure to environmental pollutants and chemical hazards, such as in a high-risk workplace or a community living near a potential pollution source.

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Tuesday, 8 November 2016

On this day in science history: the first X-rays were observed

In 1895, Wilhelm Röntgen first observed X-rays during an experiment at Würzburg University. After further investigation, on 1 Jan 1896, he notified other scientists of his discovery of this new radiation that would become known as X-rays. He sent copies of his manuscript and some of his X-ray photographs to several renowned physicists and friends, including Lord Kelvin in Glasgow and in Paris. On 5 Jan 1896, Die Presse published the news in a front-page article which described his investigations and suggested new methods of medical diagnoses might be made with this new kind of radiation.

Wilhelm Röntgen, by Nobel foundation [Public domain or Public domain], via Wikimedia Commons

So, what are the properties of X-Rays? 

X-ray photons carry enough energy to ionize atoms and disrupt molecular bonds. This makes it a type of ionizing radiation, and therefore harmful to living tissue. A very high radiation dose over a short period of time causes radiation sickness, while lower doses can give an increased risk of radiation-induced cancer. In medical imaging this increased cancer risk is generally greatly outweighed by the benefits of the examination. The ionizing capability of X-rays can be utilized in cancer treatment to kill malignant cells using radiation therapy. It is also used for material characterization using X-ray spectroscopy.

Hard X-rays can traverse relatively thick objects without being much absorbed or scattered. For this reason, X-rays are widely used to image the inside of visually opaque objects. The most often seen applications are in medical radiography and airport security scanners, but similar techniques are also important in industry (e.g. industrial radiography and industrial CT scanning) and research (e.g. small animal CT). The penetration depth varies with several orders of magnitude over the X-ray spectrum. This allows the photon energy to be adjusted for the application so as to give sufficient transmission through the object and at the same time good contrast in the image.

X-rays have much shorter wavelength than visible light, which makes it possible to probe structures much smaller than what can be seen using a normal microscope. This can be used in X-ray microscopy to acquire high resolution images, but also in X-ray crystallography to determine the positions of atoms in crystals.

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Wednesday, 2 November 2016

Fossilized dinosaur brain tissue identified for the first time

An unassuming brown pebble, found more than a decade ago by a fossil hunter in Sussex, has been confirmed as the first example of fossilised brain tissue from a dinosaur.

The fossil, most likely from a species closely related to Iguanodon, displays distinct similarities to the brains of modern-day crocodiles and birds. Meninges - the tough tissues surrounding the actual brain - as well as tiny capillaries and portions of adjacent cortical tissues have been preserved as mineralised 'ghosts'.

The results are reported in a Special Publication of the Geological Society of London, published in tribute to Professor Martin Brasier of the University of Oxford, who died in 2014. Brasier and Dr David Norman from the University of Cambridge co-ordinated the research into this particular fossil during the years prior to Brasier's untimely death in a road traffic accident.

The fossilised brain, found by fossil hunter Jamie Hiscocks near Bexhill in Sussex in 2004, is most likely from a species similar to Iguanodon: a large herbivorous dinosaur that lived during the Early Cretaceous Period, about 133 million years ago.

Triceratops skeleton. Source: Allie_Caulfield Derivative: User:MathKnight [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Finding fossilised soft tissue, especially brain tissue, is very rare, which makes understanding the evolutionary history of such tissue difficult. "The chances of preserving brain tissue are incredibly small, so the discovery of this specimen is astonishing," said co-author Dr Alex Liu of Cambridge's Department of Earth Sciences, who was one of Brasier's PhD students in Oxford at the time that studies of the fossil began.

According to the researchers, the reason this particular piece of brain tissue has been so well-preserved is that the dinosaur's brain was essentially 'pickled' in a highly acidic and low-oxygen body of water - similar to a bog or swamp - shortly after its death. This allowed the soft tissues to become mineralised before they decayed away completely, so that they could be preserved.

"What we think happened is that this particular dinosaur died in or near a body of water, and its head ended up partially buried in the sediment at the bottom," said Norman. "Since the water had little oxygen and was very acidic, the soft tissues of the brain were likely preserved and cast before the rest of its body was buried in the sediment."

Working with colleagues from the University of Western Australia, the researchers used scanning electron microscope (SEM) techniques in order to identify the tough membranes, or meninges, that surrounded the brain itself, as well as strands of collagen and blood vessels. Structures that could represent tissues from the brain cortex (its outer layer of neural tissue), interwoven with delicate capillaries, also appear to be present. The structure of the fossilised brain, and in particular that of the meninges, shows similarities with the brains of modern-day descendants of dinosaurs, namely birds and crocodiles.

In typical reptiles, the brain has the shape of a sausage, surrounded by a dense region of blood vessels and thin-walled vascular chambers (sinuses) that serve as a blood drainage system. The brain itself only takes up about half of the space within the cranial cavity.

In contrast, the tissue in the fossilised brain appears to have been pressed directly against the skull, raising the possibility that some dinosaurs had large brains which filled much more of the cranial cavity. However, the researchers caution against drawing any conclusions about the intelligence of dinosaurs from this particular fossil, and say that it is most likely that during death and burial the head of this dinosaur became overturned, so that as the brain decayed, gravity caused it to collapse and become pressed against the bony roof of the cavity.

"As we can't see the lobes of the brain itself, we can't say for sure how big this dinosaur's brain was," said Norman. "Of course, it's entirely possible that dinosaurs had bigger brains than we give them credit for, but we can't tell from this specimen alone. What's truly remarkable is that conditions were just right in order to allow preservation of the brain tissue - hopefully this is the first of many such discoveries."

"I have always believed I had something special. I noticed there was something odd about the preservation, and soft tissue preservation did go through my mind. Martin realised its potential significance right at the beginning, but it wasn't until years later that its true significance came to be realised," said paper co-author Jamie Hiscocks, the man who discovered the specimen. "In his initial email to me, Martin asked if I'd ever heard of dinosaur brain cells being preserved in the fossil record. I knew exactly what he was getting at. I was amazed to hear this coming from a world renowned expert like him."

The research was funded in part by the Natural Environment Research Council (NERC) and Christ's College, Cambridge.

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Tuesday, 25 October 2016

The Chemistry of Pumpkins

We eat them, we carve them, but do we really know what’s behind them? Here, we look at the chemistry of pumpkins.

Source: http://cen.acs.org/articles/93/i40/Periodic-Graphics-Chemistry-Pumpkins.html

Pumpkins are grown all around the world for a variety of reasons ranging from agricultural purposes (such as animal feed) to commercial and ornamental sales. Of the seven continents, only Antarctica is unable to produce pumpkins; the biggest international producers of pumpkins include the United States, Canada, Mexico, India, and China. The traditional American pumpkin used for jack-o-lanterns is the Connecticut Field variety.

As one of the most popular crops in the United States, 1.5 billion pounds (680,000,000 kilograms or 680,000 tonnes) of pumpkins are produced each year. The top pumpkin-producing states include Illinois, Indiana, Ohio, Pennsylvania, and California.

Pumpkins are a warm-weather crop that is usually planted in early July. The specific conditions necessary for growing pumpkins require that soil temperatures three inches (7.6 cm) deep are at least 60 °F (15.5 °C) and soil that holds water well. Pumpkin crops may suffer if there is a lack of water or because of cold temperatures (in this case, below 65 °F (18.3 °C); frost can be detrimental), and sandy soil with poor water retention or poorly drained soils that become waterlogged after heavy rain. Pumpkins are, however, rather hardy, and even if many leaves and portions of the vine are removed or damaged, the plant can very quickly re-grow secondary vines to replace what was removed.

Pumpkins produce both a male and female flower; honeybees play a significant role in fertilization. Pumpkins have historically been pollinated by the native squash bee Peponapis pruinosa, but this bee has declined, probably at least in part to pesticide sensitivity, and today most commercial plantings are pollinated by honeybees. One hive per acre (4,000 m² per hive) is recommended by the U.S. Department of Agriculture. If there are inadequate bees for pollination, gardeners often have to hand pollinate. Inadequately pollinated pumpkins usually start growing but abort before full development.

"Giant pumpkins" are a large squash (within the group of common squash Cucurbita maxima) that can exceed 1 ton (2,000 pounds) in weight. The variety arose from the large squash of Chile after 1500 A.D through the efforts of botanical societies and enthusiast farmers.

Such germplasm is commercially provocative, and in 1986 the United States extended protection for the giant squash. This protection was limited to small specimens of a very specific parameters, being a weight of 175 pounds, oblong shape, etc. In 2004, the restriction expired except for the requirement of indefinite use of the pseudonym "Dill's Atlantic Giant" for squash fitting the specific parameters or the seeds thereof.

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