The smell of earth after rain is called Petrichor, and it is caused by Geosmin.
Geosmin is an organic compound with the formula C12H22O. It’s produced by several classes of microbes, including cyanobacteria (blue-green algae) and actinobacteria (especially Streptomyces), and released when these microbes die. The human nose is extremely sensitive to geosmin and is able to detect it at concentrations as low as 5 parts per trillion.
“In the Drosophila brain, neural stem cells called neuroblasts undergo repeated rounds of asymmetric cell division. One of the resulting daughter cells continues to divide in a stem cell-like manner while the other cell terminally divides into two differentiating neurons. During each neuroblast division, the cell fate determinants Numb, Prospero and Brat segregate into the smaller, basal daughter cell where they prevent self-renewal and induce differentiation. This happens, because the protein kinase aPKC localizes to the opposite, apical side and removes the determinants by phosphorylating their membrane localization domains. At the same time, aPKC associates with microtubule binding proteins to ensure that the mitotic spindle is set up in an apical-basal orientation. As a result, only the basal daughter cell inherits the determinants.”
Harvard research now shows that Nodal and Lefty — two proteins linked to the regulation of asymmetry in vertebrates and the development of precursor cells for internal organs — fit the model described by Turing six decades ago.
“In Gazzaniga’s video, the boy is asked: who is your favourite girlfriend, with the word girlfriend flashed only to the right hemisphere. As predicted, the boy can’t respond verbally. He shrugs and shakes his head, indicating that he doesn’t see any word, as had been the case with W.J.. But then he giggles. It’s one of those tell-tale teen giggles — a soundtrack to a blush. His right hemisphere has seen the message, but the verbal left-hemisphere remains unaware. Then, using his left hand, the boy slowly selects three Scrabble tiles from the assortment in front of him. He lines them up to spell L-I-Z: the name, we can safely assume, of the cute girl in his class. “That told us that he was capable of language comprehension in the right hemisphere,” Gazzaniga later told me. “He was one of the first confirmation cases that you could get bilateral language — he could answer queries using language from either side.””
A drop of sugar syrup falls into a pool of methylated spirits, producing a Worthington jet and several ejected droplets. Although surface tension holds the jet in a smooth shape, the refractive index of the spirits reveals the turbulent mixing within the jet. (Photo credit: Rebecca Ing)
“This ‘quantum corral’ in the form of crossed ellipses was used by Don Eigler and his research team to demonstrate the ability to send two channels of information through one another by exploiting the quantum properties that are a consequence of the small size of the corral.” (IBM Corporation) neato.
“Xenon has been so good to me … those luscious 5d orbitals …” - Dr. Donald Eigler
Hilarious. What a great evening of science and friends.