Latest Science Highlights
Electronic Structure of Cobalt Nanocrystals Suspended in LiquidAdvances in the synthesis of crystals of nanometer dimensions, narrow size distribution, and controlled shape have generated interest because of the potential to create novel materials with tailored physical and chemical properties. New properties arise from quantum confinement effects and from the increasing fraction of surface atoms with unique bonding and geometrical configurations. At the ALS, an international team of scientists has performed an electronic structure study of colloidal nanocrystals—nanocrystals suspended in the liquid solvent in which they were grown. A range of photon-in/photon-out spectroscopies, including x-ray absorption spectroscopy (XAS), was applied. These techniques are element-selective, as they involve core atomic levels and can thus probe the local electronic structure of selected species in complex systems. |
Structure of Synaptic Connectors SolvedEstablishment of neural connections at specialized intercellular junctions called synapses is critical for proper brain function, and errors in the process are thought to be associated with autism and other disorders. Researchers from Stanford University and the University of Texas Southwestern Medical Center have reported high-resolution, three-dimensional structures of the proteins, called neuroligin-1 and neurexin-1β, that form this connection. Because mutations in the neurexin and neuroligin genes are among the multiple genetic causes of autism, understanding the molecular mechanism of these proteins in synapse development is a first step towards development of novel therapeutics directed to treat and possibly cure autism. |
The Iron Spin Transition in the Earth’s Lower MantleIt is now known that the iron present in minerals of the lower mantle of the Earth undergoes a pressure-induced transition with pairing of the spins of its 3d electrons. A team from the University of California, Berkeley, Tel Aviv University, and Lawrence Livermore National Laboratory has used x-ray diffraction at very high pressure to investigate the effects of this transition on the elastic properties of magnesiowüstite (Mg1–xFex)O, the second most abundant mineral in the Earth’s lower mantle. The new results suggest that the effect of the spin-pairing transition on magnesiowüstite can be large enough to require a partial revision of the most accepted model of the lower mantle composition. |
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