Erratum: X-Ray Optics on a Chip: Guiding X Rays in Curved Channels [Phys. Rev. Lett. 115, 203902 (2015)].

This corrects the article DOI: 10.1103/PhysRevLett.115.203902.

X-Ray Optics on a Chip: Guiding X Rays in Curved Channels.

We study the propagation of hard x rays in single curved x-ray waveguide channels and observe waveguide effects down to surprisingly small radii of curvature R≃10 mm and a large contour length s≃5 mm, deflecting beams up to 30°. At these high angles, about 2 orders of magnitude above the critical angle of total reflection θ(c), most radiation modes are lost by "leaking" into the cladding, while certain "survivor" modes persist. This may open up a new form of integrated x-ray optics "on a chip," requiring curvatures mostly well below the extreme values studied here, e.g., to split and to delay x-ray pulses.

Long-range orientation and atomic attachment of nanocrystals in 2D honeycomb superlattices.

Oriented attachment of synthetic semiconductor nanocrystals is emerging as a route for obtaining new semiconductors that can have Dirac-type electronic bands such as graphene, but also strong spin-orbit coupling. The two-dimensional (2D) assembly geometry will require both atomic coherence and long-range periodicity of the superlattices. We show how the interfacial self-assembly and oriented attachment of nanocrystals results in 2D metal chalcogenide semiconductors with a honeycomb superlattice. We present an extensive atomic and nanoscale characterization of these systems using direct imaging and wave scattering methods. The honeycomb superlattices are atomically coherent and have an octahedral symmetry that is buckled; the nanocrystals occupy two parallel planes. Considerable necking and large-scale atomic motion occurred during the attachment process.

Variable dislocation widths in colloidal crystals of soft thermosensitive spheres.

We report on detailed measurements of the core structure of Shockley partial dislocations in colloidal crystals. In crystalline arrays of micrometer sized thermosensitive particles, the interactions between the colloidal building blocks were tuned by changing the temperature. Individual dislocation cores were observed in a confocal microscope and their behavior as a function of temperature was studied. The obtained results qualitatively agree with the Peierls theory and are promising for further studies in which both Peierls stress and dislocation core width are measured simultaneously.

[Cryopreservation of ovarian tissue; now is the time for ethical considerations]. / Cryopreservatie van ovariumweefsel; ethische bezinning nu opportuun.

The development of ovarian tissue cryopreservation will expand the range of clinical applications in reproductive medicine. This emerging technology may have beneficial opportunities for patients, particularly in oncology, as well as for the process of oocyte donation. However, it will also lead to new moral problems requiring critical reflection concerning the criteria for tissue banking and future clinical applications. Because cryopreservation of ovarian tissue nowadays is the focus of experimental research, technology assessment is currently appropriate, anticipating introduction into clinical practice. Specific guidelines, developed by the medical profession in cooperation with ethicists and lawyers can contribute to prudent clinical use.