Tusk or Bone? An Example of Ivory Substitute in the Wildlife Trade

Bone carvings (and other ivory substitutes) are common in the modern-day lucrative international ivory trade.  Souvenirs for unknowing travelers and market shoppers can be made of non-biological material (plastic "ivory" beads) or skillfully crafted natural objects made to resemble something other than their true origin.  Many of these items are received at the U. S. National Fish and Wildlife Forensics Laboratory (NFWFL) for species identification as part of law enforcement investigations.  Morphologists at the Lab often receive uniquely carved ivory items that have been imported with little or no documentation.  In recent years, analysts examined several purported ivory tusks suspected to be walrus, a protected marine mammal.  After examination, the Lab determined their origin as carved leg bones of cattle using principles and methods of zooarchaeology and ancient DNA analysis.  The naturally long and straight ungulate metapodials had been cut, carved, filled, stained, and polished to closely resemble unmodified ivory tusks.  Morphological species identification of these bones proved to be a challenge since diagnostic characters of the bones had been altered and country of origin was unknown. Genetic analysis showed that the bones originated from cattle.  While bone is commonly used as a substitute for ivory, this style of artifact was not previously documented in the wildlife trade prior to our analysis.  Archaeological ethnobiologists commonly encounter bone tools and other forms of material culture from prehistoric and historic contexts; in this case bone tools come from a modern context, thus the application of methods common in zooarchaeology are situated in wildlife forensics.  In addition, results reported here pertain to cross-cultural ivory trade and conservation science.</p

Enabling time-resolved 2D spatial-coherence measurements using the Fourier-analysis method with an integrated curved-grating beam monitor

Direct 2D spatial-coherence measurements are increasingly gaining importance at synchrotron beamlines, especially due to present and future upgrades of synchrotron facilities to diffraction-limited storage rings. We present a method to determine the 2D spatial coherence of synchrotron radiation in a direct and particularly simple way by using the Fourier-analysis method in conjunction with curved gratings. Direct photon-beam monitoring provided by a curved grating circumvents the otherwise necessary separate determination of the illuminating intensity distribution required for the Fourier-analysis method. Hence, combining these two methods allows for time-resolved spatial-coherence measurements. As a consequence, spatial-coherence degradation effects caused by beamline optics vibrations, which is one of the key issues of state-of-the-art X-ray imaging and scattering beamlines, can be identified and analyzed. © 2020 Optical Society of America

Author Correction: Non-local effect of impurity states on the exchange coupling mechanism in magnetic topological insulators

A Correction to this paper has been published: https://doi.org/10.1038/s41535-021-00314-

Time-reversal symmetry breaking type-II Weyl state in YbMnBi2YbMnBi_{2}

Spectroscopic detection of Dirac and Weyl fermions in real materials is vital for both, promising applications and fundamental bridge between high-energy and condensed-matter physics. While the presence of Dirac and noncentrosymmetric Weyl fermions is well established in many materials, the magnetic Weyl semimetals still escape direct experimental detection. In order to find a time-reversal symmetry breaking Weyl state we design two materials and present here experimental and theoretical evidence of realization of such a state in one of them, YbMnBi2. We model the time-reversal symmetry breaking observed by magnetization and magneto-optical microscopy measurements by canted antiferromagnetism and find a number of Weyl points. Using angle-resolved photoemission, we directly observe two pairs of Weyl points connected by the Fermi arcs. Our results not only provide a fundamental link between the two areas of physics, but also demonstrate the practical way to design novel materials with exotic properties

Time-reversal symmetry breaking type-II Weyl state in YbMnBi2

Spectroscopic detection of Dirac and Weyl fermions in real materials is vital for both, promising applications and fundamental bridge between high-energy and condensed-matter physics. While the presence of Dirac and noncentrosymmetric Weyl fermions is well established in many materials, the magnetic Weyl semimetals still escape direct experimental detection. In order to find a time-reversal symmetry breaking Weyl state we design two materials and present here experimental and theoretical evidence of realization of such a state in one of them, YbMnBi2. We model the time-reversal symmetry breaking observed by magnetization and magneto-optical microscopy measurements by canted antiferromagnetism and find a number of Weyl points. Using angle-resolved photoemission, we directly observe two pairs of Weyl points connected by the Fermi arcs. Our results not only provide a fundamental link between the two areas of physics, but also demonstrate the practical way to design novel materials with exotic properties