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The Chemistry of Seasonal Affective Disorder

The December days may be unseasonably warm this year, but the nights are as long and dark as ever. And for the millions of Americans with Seasonal Affective Disorder (SAD), it’s the darkness, not the cold, that makes winter so difficult. 

SAD affects at least five percent of Americans. As Reactions host Sophia Cai explains in this new video from the American Chemical Society, the symptoms of SAD are similar to those of garden-variety depression. It’s the timing that’s different; most people’s symptoms set in in late autumn and last through the winter. 

Scientists have yet to pinpoint the exact causes of SAD, but they do have a few ideas. Shorter days mean less sunlight. This may seem like a superficial concern—sure, sunny days make us happier—but the chemistry goes much deeper than that. Exposure to sunlight, or a lack thereof, affects the production and release of important brain chemicals, and any imbalance in these chemicals can make us feel pretty awful.

Fortunately, SAD is very treatable. Talk therapy, medication, and light therapy have all proven helpful. If you’re experiencing symptoms of SAD, give your doctor a call. Winter may be dark, but it doesn’t have to be depressing.

Header image from Reactions.

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Food
Researchers Pinpoint the Genes Behind the Durian's Foul Stench
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Durian is a popular fruit in parts of southeast Asia. It's also known for having the most putrid, off-putting odor of any item sold in the produce section. Even fans of durian know why the fruit gets a bad rap, but what exactly causes its divisive scent is less obvious. Determined to find the answer, a team of researchers funded by "a group of anonymous durian lovers" mapped the fruit's genome, as reported by the BBC.

The study, published in the journal Nature Genetics [PDF], contains data from the first-ever complete genetic mapping of a durian fruit. It confirms that durian's excess stinkiness comes from sulfur, a chemical element whose scent is often compared to that of rotten eggs.

Analysis of the fruit's chemical makeup has been done in the past, so the idea that sulfur is a major contributor to its signature smell is nothing new. What is new is the identification of the specific class of sulfur-producing genes. These genes pump out sulfur at a "turbocharged" rate, which explains why the stench is powerful enough to have durian banned in some public areas. It may seem like the smell is a defense mechanism to ward off predators, but the study authors write that it's meant to have the opposite effect. According to the paper, "it is possible that linking odor and ripening may provide an evolutionary advantage for durian in facilitating fruit dispersal." In other words, the scent attracts hungry primates that help spread the seeds of ripe durian fruits by consuming them.

The revelation opens the door to genetically modified durian that are tweaked to produce less sulfur and therefore have a milder taste and smell. But such a product would likely inspire outrage from the food's passionate fans. While the flavor profile has been compared to rotten garbage and dead animal meat, it's also been praised for its "overtones of hazelnut, apricot, caramelized banana, and egg custard" by those who appreciate its unique character.

[h/t BBC]

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science
Eye-Catching Videos Show the Beauty of Chemical Reactions
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BEAUTY OF SCIENCE, Vimeo

For those of us with only a passing high-school knowledge of chemistry, the scientific discipline can feel pretty abstract. But new online film series Envisioning Chemistry brings chemical reactions to life as works of art, visualizing chemistry in high resolution.

Created through a collaboration between the science visualization studio Beauty of Science and the Chinese Chemical Society, the series is a follow-up to Beautiful Chemistry, a 2014 project that included video of chemical reactions, animations, illustrations, and diagrams to visualize the history and practice of chemistry.

The images in Envisioning Chemistry were made using “high-resolution microscopes, infrared thermal imaging cameras, high-speed cameras, and 4K Ultra HD cameras, to reveal beauty of chemical reactions like never before,” according to the project’s website.

Envisioning Chemistry is designed as a teaching tool, so each of the films also has an associated worksheet so that teachers can use them in the classroom. There are 15 films total, and the creators hope to add more in the future.

The films explore chemistry topics like precipitation reactions, metal displacement, and electrodeposition, using elemental metals like copper, tin, lead, and zinc. “If you think you know what metals look like, well, think again!” as one video warns. By the end of the films, you may even know what words like electrodeposition mean.

Envisioning Chemistry Collection I: Beauty of Chemistry from Beauty of Science on Vimeo.

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