Odile Madden knows a lot about plastic. A materials scientist with the Smithsonian Museum Conservation Institute, she has spent the past eight years studying plastics […]

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Monday, Aug. 21 was an unusual day across North America. Early in the morning, families, colleagues and tourists were searching for special solar glasses with […]

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As average annual temperatures increase, mosquitoes have also been on the move—up the mountains of the Hawaiian islands. Once a refuge for native birds susceptible […]

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Structural investigations of amorphous and nanocrystalline phases forming in solution are historically challenging. Few methods are capable of in situ atomic structural analysis and rigorous control of the system. A mixed-flow reactor (MFR) is used for total X-ray scattering experiments to examine the short- and long-range structure of phases in situ with pair distribution function (PDF) analysis. The adaptable experimental setup enables data collection for a range of different system chemistries, initial supersaturations and residence times. The age of the sample during analysis is controlled by adjusting the flow rate. Faster rates allow for younger samples to be examined, but if flow is too fast not enough data are acquired to average out excess signal noise. Slower flow rates form older samples, but at very slow speeds particles settle and block flow, clogging the system. Proper background collection and subtraction is critical for data optimization. Overall, this MFR method is an ideal scheme for analyzing the in situ structures of phases that form during crystal growth in solution. As a proof of concept, high-resolution total X-ray scattering data of amorphous and crystalline calcium phosphates and amorphous calcium carbonate were collected for PDF analysis.

Under the anomalous transmission condition in the Bragg mode, X-ray interference fringes were observed between two beams with different hyperbolic trajectories in a very weakly bent plane-parallel perfect crystal with negative strain gradient. The origin of the fringes was analysed based on the dynamical theory of diffraction for a distorted crystal. In the reflected beam from the entrance surface, the interference fringes were observed between once- and twice-reflected beams from the back surface. In the transmitted beam from the back surface, the interference fringes were observed between the direct beam and once-reflected beam from the entrance surface. In the emitted beam from the lateral surface, the interference fringes were observed between the beams after different numbers of reflections in the crystal. The multiply reflected beams were formed by a combined result of long propagation length along the beam direction with large divergence of the refracted beams when the strain gradient was negative. The period of these interference fringes was sensitive to very weak strain, of the order of 10−7.

The use of strongly bent crystals in spectrometers for pulses of a hard X-ray free-electron laser is explored theoretically. Diffraction is calculated in both dynamical and kinematical theories. It is shown that diffraction can be treated kinematically when the bending radius is small compared with the critical radius given by the ratio of the Bragg-case extinction length for the actual reflection to the Darwin width of this reflection. As a result, the spectral resolution is limited by the crystal thickness, rather than the extinction length, and can become better than the resolution of a planar dynamically diffracting crystal. As an example, it is demonstrated that spectra of the 12 keV pulses can be resolved in the 440 reflection from a 20 µm-thick diamond crystal bent to a radius of 10 cm.

In this study, the atomic structure of the ternary icosahedral ZnMgTm quasicrystal (QC) is investigated by means of single-crystal X-ray diffraction. The structure is found to be a member of the Bergman QC family, frequently found in Zn–Mg–rare-earth systems. The ab initio structure solution was obtained by the use of the Superflip software. The infinite structure model was founded on the atomic decoration of two golden rhombohedra, with an edge length of 21.7 Å, constituting the Ammann–Kramer–Neri tiling. The refined structure converged well with the experimental diffraction diagram, with the crystallographic R factor equal to 9.8%. The Bergman clusters were found to be bonded by four possible linkages. Only two linkages, b and c, are detected in approximant crystals and are employed to model the icosahedral QCs in the cluster approach known for the CdYb Tsai-type QC. Additional short b and a linkages are found in this study. Short interatomic distances are not generated by those linkages due to the systematic absence of atoms and the formation of split atomic positions. The presence of four linkages allows the structure to be pictured as a complete covering by rhombic triacontahedral clusters and consequently there is no need to define the interstitial part of the structure (i.e. that outside the cluster). The 6D embedding of the solved structure is discussed for the final verification of the model.

A new approach is presented to obtain candidate structures from atomic pair distribution function (PDF) data in a highly automated way. It fetches, from web-based structural databases, all the structures meeting the experimenter's search criteria and performs structure refinements on them without human intervention. It supports both X-ray and neutron PDFs. Tests on various material systems show the effectiveness and robustness of the algorithm in finding the correct atomic crystal structure. It works on crystalline and nanocrystalline materials including complex oxide nanoparticles and nanowires, low-symmetry and locally distorted structures, and complicated doped and magnetic materials. This approach could greatly reduce the traditional structure searching work and enable the possibility of high-throughput real-time auto-analysis PDF experiments in the future.

The generalized Darwin–Hamilton equations [Wuttke (2014). Acta Cryst. A70, 429–440] describe multiple Bragg reflection from a thick, ideally imperfect crystal. These equations are simplified by making full use of energy conservation, and it is demonstrated that the conventional two-ray Darwin–Hamilton equations are obtained as a first-order approximation. Then an efficient numeric solution method is presented, based on a transfer matrix for discretized directional distribution functions and on spectral collocation in the depth coordinate. Example solutions illustrate the orientational spread of multiply reflected rays and the distortion of rocking curves, especially if the detector only covers a finite solid angle.

A mysterious nocturnal animal was leaving its tracks on the delicate mirrors of the telescopes at the Smithsonian's Whipple Observatory in Arizona. With a little ingenuity and a live trap, the mystery was solved. The visitor proved to be a ringtail cat, a member of the raccoon family.

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The Crab Nebula is one of the most studied objects in the night sky. First observed by Chinese astronomers in 1054 A.D., and possibly others, this supernova remnant and its neutron star have become favorite targets for amateur and professional astronomers alike. The Chandra X-Ray Observatory is operated for NASA by the Smithsonian Astrophysical Observatory in Cambridge, Mass.

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What does it take to care for a pride of lions? Go behind the scenes with Great Cats Curator Craig Saffoe as he works with animal keepers and veterinarians to prepare the National Zoo's frisky lion cubs for their public debut. For more about the Zoo's growing pride and to watch them on live webcams: http://nationalzoo.si.edu/Animals/GreatCats/default.cfm?cam=LC4

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The post “How Soil Savvy are You?, is featured in the exhibition “Dig It! The Secrets of Soil,” from the Smithsonian Traveling Exhibition Service appeared first on Smithsonian Insider.

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Keepers at the Smithsonian's National Zoo perform an artificial insemination procedure on a pair of Stanley Cranes. A Stanley Crane chick was successfully hatched on May 23, 2011.

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Tom Crouch, Senior curator in the National Air and Space Museum's Aeronautics Division, discusses Thaddeus Lowe and the birth of American aerial reconnaissance during the Civil War. This presentation was recorded on May 11, 2011 on the National Mall.

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The post How do paleontologists identify dinosaur teeth? Smithsonian Curator Matthew Carrano identifies Cretaceous dinosaur teeth from the Washington D.C. area. appeared first on Smithsonian Insider.

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The post Pam Wintle, senior film archivist, describes the moving image collection of the Human Studies Film Archives appeared first on Smithsonian Insider.

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Speeding Up Science from Facebook Stories on Vimeo. In January 2011, Oregon State University ichthyologist Brian Sidlauskas led a research expedition into the little-known Cuyuni […]

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The post Samuel P. Langley, Secretary of the Smithsonian, and his development of the ill-fated Aerodrome A appeared first on Smithsonian Insider.

Marine biologist Tuck Hines and a local Chesapeake crabber narrate the fall of the blue crab, and what may be the start of a recovery. […]

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Meg studies intergroup competition in white‐faced capuchin monkeys by tracking them through radio telemetry collars and observing their behaviors.

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myVolcano is a crowd-sourcing app that enables you to share your photographs and descriptions of volcanic hazards, as well as collecting samples and measurements of […]

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Get a look behind the scenes as we installed “Outside the Spacecraft: 50 Years of Extra-vehicular Activity,” a new exhibition on view at the Museum […]

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Five critically endangered Cuban crocodiles hatched at the National Zoo’s Reptile Discovery Center between July 29 and Aug. 7. The eggs were laid by Dorothy, […]

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Elastic has created some of the most intriguing title sequences in recent television history. Directed by Patrick Clair (Australian b. 1982), the opening credits for […]

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Judy Garland’s iconic ruby slippers from “The Wizard of Oz” are one of the most popular attractions at the National Museum of American History. But […]

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National Air and Space Museum Curator John Anderson describes major flight innovations made possible by the Full Scale Tunnel, built in 1931 at the National […]

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The Moon and its surface provide insight into the early history of the solar system in this video from the Smithsonian’s National Air and Space […]

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Jeopardy’s Clue Crew visits the Smithsonian’s National Zoo!

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Part 1 – Public Programs Coordinator Gloria Kenyon demonstrates crafting for the next Handi Hour program at the Renwick Gallery of the Smithsonian American Art […]

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Scientists at the Smithsonian Conservation Biology Institute (SCBI) have found that poaching is an emerging crisis for Asian elephants in Myanmar. Researchers first became aware […]

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The Weeping Goldsmith, written as a first-person narrative, follows Botanist John Kress through nine years as he surveys Myanmar’s teak forests, bamboo thickets, timber plantations, rivers and mangroves to document its incredible botanical biodiversity.

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