Archive for the ‘chemistry’ Category

Oldest evidence of cannabis smoking found in ancient Chinese cemetery

June 12th, 2019
Photo of skeleton and braziers in excavated tomb.

Enlarge / This is how the braziers were placed in the tomb alongside the deceased. (credit: Xinhua Wu)

The broken wooden braziers, unearthed from 2,500-year-old tombs in Western China, contained burned, blackened stones, and the interior of the wooden vessels also looked charred. To find out what had been burned in them, University of Chinese Academy of Sciences archaeologist Yemin Yang and his colleagues used gas chromatography/mass spectrometry to analyze small samples of the charred wood and the residue from the stones.

Their analysis turned up a chemical called cannabinol, or CBN—an unmistakable chemical signature of cannabis. Those ancient chemical traces offer an important clue in the history of human drug use and the domestic history of cannabis.

In around 500 BCE, the ancient Greek historian Herodotus described people near the Caspian Sea gathering in small, enclosed tents to breathe in the smoke from cannabis burned atop a bowlful of red-hot stones. Yang says people did something similar at Jirzankou, probably as part of funeral ceremonies. Archaeologists there also found the remains of a musical instrument called an angular harp, which played an important role in later funeral rites in Western China.

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Posted in Archeology, cannabis, chemistry, domestication, science | Comments (0)

Stronger than aluminum, a heavily altered wood cools passively

May 23rd, 2019
Image of a white plank.

Enlarge / A look at the lignin-free compressed wood. (credit: University of Maryland)

Most of our building practices aren't especially sustainable. Concrete production is a major source of carbon emissions, and steel production is very resource intensive. Once completed, heating and cooling buildings becomes a major energy sink. There are various ideas on how to handle each of these issues, like variations on concrete's chemical formula or passive cooling schemes.

But now, a large team of US researchers has found a single solution that appears to manage everything using a sustainable material that both reflects sunlight and radiates away excess heat. The miracle material? Wood. Or a form of wood that's been treated to remove one of its two main components.

With the grain

Wood is mostly a composite of two polymers. One of these, cellulose, is made by linking sugars together into long chains. That cellulose is mixed with a polymer called lignin, which is not really a single polymer. The precise chemical formula of its starting material can vary among species, and it typically contains multiple places where chemical bonds can form, turning the polymer into a chaotic but extremely robust mesh.

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Posted in chemistry, materials science, science, sustainability, wood | Comments (0)

Superconductivity reported at the temperature of a good freezer

May 22nd, 2019
Superconductivity reported at the temperature of a good freezer

Enlarge (credit: Manmohan Singh | Getty Images)

Superconductivity offers the promise of hyper-efficient electric motors, ultra powerful magnets, and the transmission of electricity without losses. The reality, however, has fallen considerably short of that promise, as superconducting materials are difficult and expensive to manufacture, requiring a constant bath of liquid nitrogen to keep them cold enough to operate. And progress at identifying new high-temperature superconductors went through an extended stall, with no new contenders for decades.

But behind that stall, researchers were getting a better understanding of the physics involved with superconductivity, and that understanding seems to be paying off. A few years back, researchers found that a high-pressure form of hydrogen sulfide would superconduct at 203K (-70°C), roughly 65K higher than any previous material. Now, following up on suggestions from computer modeling, researchers have discovered that a metal-hydrogen compound (LaH10) can superconduct all the way up to 250K. That's roughly -25°C, a temperature that can be reached by a good freezer.

Unfortunately, its superconductivity is dependent upon pressure and required compressing the sample between two diamonds. But the results do tell us that our understanding is on the right track, and there are undoubtedly additional chemicals worth examining.

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Posted in chemistry, Physics, science, superconductivity | Comments (0)

Who had the most merciful death on Game of Thrones? Science has an answer

April 13th, 2019
You know nothing, Jon Snow—like, maybe wear a hat when conditions are freezing in the North. Even if it musses up your luscious locks.

Enlarge / You know nothing, Jon Snow—like, maybe wear a hat when conditions are freezing in the North. Even if it musses up your luscious locks. (credit: HBO)

Warning: This story contained some mild spoilers from the first six seasons of Game of Thrones.

The world of Game of Thrones may be fictional, but that doesn't stop its fans from heatedly arguing about all the possible underlying science, because nerd-gassing about one's favorite science fiction is a time-honored tradition. Just how hot is dragon's breath? Is there a real-world equivalent of wildfire? What's the best and worst way to die? And how fast would Gendry have to run back to the wall to send a raven to King's Landing requesting help?

These and other scintillating topics are discussed in a forthcoming book by physicist (and uber-fan) Rebecca Thompson, Fire, Ice, and Physics: The Science of Game of Thrones. The book comes out in October from MIT Press, but as we gear up for the premiere of the final season Sunday night, Thompson graciously gave us a sneak preview into some of the burning science questions she investigated.

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Posted in Biology, books, chemistry, Game of Thrones, Gaming & Culture, HBO, Physics, science, Television | Comments (0)

Here’s the real reason why Terracotta Army weapons are so well-preserved

April 4th, 2019
View of Pit 1 of the Terracotta Army showing the hundreds of warriors once armed with bronze weapons.

Enlarge / View of Pit 1 of the Terracotta Army showing the hundreds of warriors once armed with bronze weapons. (credit: Xia Juxian)

Ever since archaeologists excavated the first figures of the famous Terracotta Army of Xi'an in the 1970s, they have marveled at the pristine condition of bronze weapons accompanying the figures. Scholars suggested that this was evidence of one of the earliest known anti-rust technologies, and over time, this hypothesis took on the veneer of fact, at least in popular accounts. But according to a new study in Nature: Scientific Reports, it's the unique chemical composition of the surrounding soil that is responsible for the exceptional preservation.

The Terracotta Army is composed of thousands of life-sized ceramic figures dating back to the late third century BCE, housed in three large pits inside the mausoleum of the first emperor of China, Qin Shihuang (259-210 BCE). Essentially a form of funerary art, these warrior figures were meant to accompany the emperor to the afterlife. They once held fully functional bronze weapons: spears, lances, swords, crossbows, and so forth. Over the decades, archaeologists have excavated tens of thousands of valuable weapon artifacts from the site, many of which were in nearly pristine condition, even though handles, scabbards, and similar organic pieces had long since rotted away.

Early tests showed traces of chromium on the bronze weapon surfaces, a metal element found in stainless steel that is resistant to tarnishing. Those traces suggested that the Qin artisans who made the weapons might have employed an early forerunner to the chromate conversion coatings invented in the 20th century, which are still used for preservation today.

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Posted in chemistry, History, science, Terracotta army | Comments (0)

There really is something unique about Tennessee whiskey, study finds.

April 2nd, 2019
White lightning distilled alcohol streams out of a still. It must be filtered through charcoal before barrel aging to be legally branded "Tennessee whiskey."

Enlarge / White lightning distilled alcohol streams out of a still. It must be filtered through charcoal before barrel aging to be legally branded "Tennessee whiskey." (credit: Luke Sharrett/Bloomberg/Getty Images)

Scientists are beginning to unlock the scientific secrets of what makes so-called "Tennessee whiskey" so distinct from other whiskeys, bourbons, and similar spirits, according to a presentation last weekend at a meeting of the American Chemical Society in Orlando, Florida. Specifically, they've identified many of the key aroma-active compounds responsible for the beverage's distinctive flavor profiles.

"We're aiming to create a methodology, a practical tool, to reproducibly measure the changes that happen to guide distillers," said lead investigator John Munafo of the University of Tennessee. "By mapping out all the different compounds, we can better understand what each one contributes, and in what concentrations, so distillers can tweak [those parameters] to get the flavor profile they want. That variety is what makes whiskey so interesting."

Munafo spent 12 years as director of flavor science and plant chemistry at Mars Incorporated, working primarily with chocolate (naturally). He's doing similar chemistry research at the University of Tennessee, frequently partnering with local agriculture and industry, like Sugarlands Distilling Company in Gatlinburg. Sugarlands makes an award-winning whiskey called Roaming Man, and it's keen on gaining a better understanding of the underlying science of its distillation process.

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Posted in alcohol, chemistry, Lincoln County Process, science, Tennessee whiskey, Whiskey | Comments (0)

New fuel cell material can run efficiently in reverse, storing energy

March 14th, 2019
Close-up of a hydrogen fuel cell.

Enlarge / Close-up of a hydrogen fuel cell. (credit: Wladimir Bulgar | Science Photo Library)

Lithium batteries can readily smooth out short-term hiccups in the supply of intermittent renewable energy. But they're not ideal for long-term storage, since they'll slowly discharge. They also aren't great for large quantities of energy—to store more, you keep having to buy more battery. Because of these issues, there has been research into a number of technologies that scale better, like flow batteries and renewable fuel production. But these pose their own challenges, both chemical and economic.

But researchers are now reporting a possible solution to some of these problems: a fuel cell that can be run efficiently in both directions, either using hydrogen or methane to produce electricity or using electricity to produce these fuels. Their measurements suggest that, after doing a complete cycle, they get out 75 percent of the electricity they put in to start with.

Limitations abound

Batteries, as we mentioned above, don't work for longer-term storage, as they will typically lose charge slowly. They're also expensive, as adding capacity means adding more batteries. Flow batteries solve some of these problems by storing the charged and discharged forms of a chemical in different tanks; larger or additional tanks are cheap, making expanded capacity relatively simple and inexpensive. But flow batteries aren't as efficient as traditional batteries, and the chemicals they use can be toxic or corrosive.

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Posted in chemistry, Energy, fuel cells, hydrogen, materials science, science | Comments (0)

A small molecule drug can block a broad range of flu viruses in mice

March 11th, 2019
A sign on the entrance to a grocery store announces that it is

Enlarge (credit: Mike Mozart / Flickr)

Our bodies are good at generating antibodies that are extremely specific, picking out a single pathogen from a dizzying mix of harmless bacteria and the proteins made by our own cells. But in some cases, that specificity is limiting. Those antibodies will generally pick out a very specific strain of the flu virus, leaving us vulnerable to other strains and the new variants that evolve each season.

Over the past few years, however, it's become apparent that the immune system sometimes gets wildly lucky by generating a single antibody that can neutralize a huge range of viruses. These "broadly neutralizing antibodies" provide a significant protection against viruses that the immune system normally struggles against, like HIV, Ebola, and the flu virus. Mass production of these antibodies might provide a useful therapy, and the hope is that we can incorporate what they tell us into the design of future vaccines for these pathogens.

But some clever researchers have figured out how to use a broadly neutralizing antibody as a tool to design a drug that can block the activity of a large range of flu viruses.

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Posted in antibodies, Biology, chemistry, drug development, Flu virus, immunoloogy, medicine, pharmacology, science | Comments (0)

Basquiat used invisible ink to make secret drawings in his paintings

February 3rd, 2019
Side-by-side images of the same neo-expressionist painting under different lights.

Enlarge / A detail from "Untitled" (1981) by Jean-Michel Basquiat, as viewed under normal light (left) and UV light (right). Note the hidden arrow between the letters "E" and "P." (credit: Longevity Art Preservation)

Jean-Michel Basquiat, the late neo-expressionist whose tragic life story inspired a 1996 film, used invisible ink to draw secret figures in at least one of his early paintings, Artnet News reported last month. The figures are easily visible under UV light, and more of the artist's work from this period may contain such hidden drawings.

Invisible ink has been around since at least the fourth century BC; it's mentioned in a treatise on secret communications by Aeneas Tacticus. It's familiar to anyone who has ever gotten their hand stamped when they entered a club so they could be readmitted later by holding it under UV light. There are many different types, but substances that glow in response to UV light include lemon juice, body fluids (hence the use of UV light in forensics), sunscreen, and some soaps and laundry detergents.

But invisible ink is rarely used by artists. One notable exception is the Chinese-born British artist Aowen Jin, whose 2015 exhibit at London's Horniman Museum featured a series of hand-drawn invisible-ink illustrations, which can only be seen under UV light, on the walls and floor of the Music Gallery Performance Space. Apparently, Basquiat sometimes used fluorescent materials, and signed one 1982 canvas, Orange Sports Figure, in invisible ink. But this is the first known instance of the artist intentionally embedding secret drawings into a painting.

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Posted in art, Basquiat, chemistry, Gaming & Culture, invisible ink, science, ultraviolet light | Comments (0)

Study: keep craft beer cool and drink in three months for best flavor

January 22nd, 2019
Regional differences in the aromatic compounds found in hop varieties can significantly affect the taste of craft beers.

Enlarge / Regional differences in the aromatic compounds found in hop varieties can significantly affect the taste of craft beers. (credit: DEA/G. Wright/Getty Images)

If you're a fan of craft beer with a strong, hoppy flavor, heed the science that says to store your beer in a cool place and drink it within three months or so, lest it lose that rich aroma. That's one of the key takeaways from a new study by German scientists published in the journal Brewing Science.

All beer contains hops, a key flavoring agent that also imparts useful antimicrobial properties with its rich aroma. (Without them, beer spoils quickly.) To make beer, brewers mash and steep grain in hot water, which converts all that starch into sugars. This is traditionally the stage where hops are added to the liquid extract (wort) and boiled to give the beer that hint of bitterness. That turns some of the resins (alpha acids) in the hops into iso-alpha acids, producing a bitter taste. Yeast is then added to trigger fermentation, turning the sugars into alcohol.

Add too many hops, however, and the beer will be so bitter as to be undrinkable. So in recent years, many craft brewers have started using dry-hopping as a way to put more hops in beer without getting excessive bitterness. It's added during or after the fermentation stage, after the wort has cooled. There is no isomerization of the alpha acids, so you get all that aromatic hoppy flavor without too much bitterness. Brewers can use as much as 20 times the usual amount of hops if they're dry-hopping. (Just beware of "hop creep," which can cause such bottled beers to explode.)

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Posted in beer, brewing, chemistry, craft beer, homebrewing, hops, science | Comments (0)