Nature: X-ray crystallography works by firing x rays at identically arranged molecules in a crystal and measuring the resulting diffraction pattern. Getting the molecules to crystallize, however, can be difficult, and with some molecules it is impossible. Now, Makoto Fujita and Yasuhide Inokuma of the University of Tokyo and their colleagues have created metal-organic “scaffolds” that can hold molecules in a crystalline-like structure. When they tested their scaffolds using several molecules whose structures are already known via x-ray crystallography, they achieved identical results. They were also able to successfully image the molecule miyakosyne A, a chemical produced by sea sponges that is too sinewy to crystallize. The new technique will likely be very useful for imaging chemicals generally found in very small quantities. Next, Fujita and Inokuma say that they plan to create a structure that can hold bigger molecules, such as proteins.
Category Archives: Crystallography
Noctilucent clouds may have meteoric origins
Space.com: Based on data from the Solar Occultation for Ice Experiment, NASA researchers have determined that 3% of each ice crystal in noctilucent clouds consists of dust from meteors. Noctilucent clouds, which are bluish clouds that can be seen just after twilight, form at an altitude of around 80 km. Their origin has been a mystery since the clouds were first discovered in 1885. James Russell, the lead researcher, believes that this new evidence is the answer. Because meteors burn as they pass through the atmosphere, they leave behind dust, which combines with water vapor to form ice crystals only 20 to 70 nm across. Those crystals are much smaller than the crystals formed lower in the atmosphere that create cirrus clouds. And the small size also explains noctilucent clouds’ bluish color, because the smaller crystals scatter the shorter, blue wavelengths. The researchers are still interested in determining why noctilucent clouds’ zone of visibility is spreading from higher latitudes toward the equator, though they believe it may have to do with increased methane levels in the atmosphere.
World’s first room-temperature, high-energy maser
Nature: Passing microwaves through a laser-excited crystal of organic molecules amplifies the microwave signal coherently. The result is a microwave laser—a maser—that is almost 100 million times as powerful as any previously created on Earth. Despite being both theorized and built before lasers, masers were limited in their applications by their low power and by the necessity of super-cold temperatures. Inspired by a decade-old Japanese paper, Mark Oxborrow of the UK National Physical Laboratory in Teddington and his colleagues created the maser using pentacene that they borrowed from another lab and an old medical laser they found on eBay.
Supervolcanoes have short life spans, study finds
BBC: The largest volcanoes on Earth may actually form and erupt relatively quickly, possibly in as little as a few hundred years, according to researchers who published their results yesterday in PLoS One. Guilherme Gualda of Vanderbilt University and colleagues examined quartz crystals in the Bishop Tuff deposit, in California’s Long Valley, site of an ancient supervolcano. The crystals were formed in the underground magma pool, which started off as nearly pure liquid rock. Because crystal formation stops when the volcano erupts, scientists can use the crystals to estimate how long the magma pool existed. The eruption of a supervolcano can be devastating—hundreds of times larger than any eruption that has occurred in human history. Thus, to better predict eruptions, geologists seek to better understand how supervolcanoes’ magma pools develop.
Avalanche experts help make better ice cream
BBC: To improve the quality of the Nestlé company’s ice cream, its food scientists teamed up with avalanche experts at the Institute for Snow and Avalanche Research in Switzerland to study ice crystal formation. Because the temperature does not remain constant in home freezers, ice cream continuously melts and then refreezes, which causes ice crystals to form, merge, and grow. The crystals affect the ice cream’s structure and, hence, its taste. As discussed in a paper published in the journal Soft Matter, x-ray tomography was used to create time-lapse studies of the evolution of ice cream’s microstructure. According to the researchers, their study of the life cycle of ice crystals in ice cream not only will help make a tastier dessert but also could provide “new insights into the coarsening mechanisms of multiphase materials and could contribute to a better understanding of complex materials.”
Mathematicians model snowflakes using physical laws
Scientific American: A group of researchers in Germany has succeeded in using computer modeling to simulate the faceted pattern of snowflake formation. Using basic conservation laws and thermodynamics, Harald Garcke of the University of Regensburg and colleagues were able to model the way the crystal surface changes over time. They also managed to model, simultaneously, the two main types of snowflake growth: dendritic growth, in which the flakes form treelike branches, and faceted growth, dominated by flat plates, such as hexagons and triangles. Among the unexpected aspects of snowflake formation, the group found that the speed at which the snowflakes’ tips grow is directly proportional to the amount of water vapor in the air and that molecular bonds on the crystal surface have a larger effect on crystal growth than previously expected. The researchers’ approach can be applied to a variety of other systems, such as red blood cells, soap bubbles, and polycrystalline materials.
Carbon atoms set free by UV light
Nature: A team of physicists in Australia has found that sunlight can cause diamond to lose atoms. Diamonds are usually etched by laser in a process called ablation, whereby atoms are burned from the surface, leaving behind a rough, damaged area more like that of graphite, writes James Mitchell Crow for Nature. Rich Mildren and his team at Macquarie University in Sydney have shown that by cutting the laser’s pulse power, a process called desorption takes over, with excited carbon atoms popping off the surface to leave smoothly etched diamond. However, the rate of loss is very slow—even a typical mercury UV lamp in a lab would take about 10 billion years to remove a microgram of diamond. How the desorption process works is still to be determined, but Mildren has published several theories in Optical Materials Express. The discovery could prove a boon for researchers working to tap diamond’s exceptional optical and electronic properties.