A novel device structure for organic light-emitting fi eld-effect transistors has been developed. The devices comprise bilayer-crystal organic semiconductors of a p-type and an n-type. The pn-junction can readily be formed by successively laminating two crystals on top of a gate insulator. This structure enables the effi cient injection and transport of electrons and holes, leading to their effective recombination. As a result, bright emissions are attained. The devices are operated by AC gate voltages. Gate-voltage phase-resolved draincurrent and emission-intensity measurements enable us to study the relationship between the emissions and carrier transport. The maximum external quantum effi ciency reaches 0.045%.

X-ray tomography is a powerful method for visualizing the three-dimensional structure of an object with a high spatial resolution. Conventional time-resolved x-ray tomography using synchrotron radiation requires fast rotation of the object, which limits the temporal resolution and hampers its application to, e.g., fluids and in vivo observation of living beings. Here, we present a multibeam x-ray optical system for high-speed 4D tomography, which can obtain projection images of a sample in a wide angular range simultaneously. It consists of about three dozen single-crystalline blades oriented with different angles to the incident beam, which each Bragg-reflect a part of the incident x-rays in the direction of the sample position. Thirty-two projection images covering an angular range of more than ± 70 ∘ were obtained without moving the sample or optical system, with an exposure time of 1 ms. The data set was successfully used for reconstructing the three-dimensional structure of two test samples. The optical system provides the basis for realizing millisecond time resolution x-ray tomography of nonrepeatable phenomena, and can be expected to be useful for other applications as well, for example, for time-resolved element-specific imaging.

Large tetragonal hen egg-white (HEW) lysozyme crystals have been grown by a salt concentration-gradient method. The grown crystals, of thicknesses greater than 1.5 mm, were observed by means of X-ray topography using white-beam synchrotron radiation. Line contrasts clearly appeared on the Laue topographs. Extinction of the line images was observed in specific reflections. These results mean that the observed lines correspond to dislocation images. From the extinction criterion it is shown that the predominant dislocations are of screw character with <110> Burgers vectors. In addition, dislocation loops with [001] Burgers vectors have been found in a tetragonal HEW lysozyme crystal including some cracks. These results are discussed in the light of dislocation elastic energy and slip systems in the crystals.

An X-ray phase tomogram was successfully obtained with an exposure time of less than 10 ms by X-ray grating interferometry, an X-ray phase imaging technique that enables high-sensitivity X-ray imaging even of materials consisting of light elements. This high-speed X-ray imaging experiment was performed at BL28B2, SPring-8, where a white X-ray beam is available, and the tomogram was reconstructed from projection images recorded at a frame rate of 100,000 fps. The setup of the experiment will make it possible to realize three-dimensional observation of unrepeatable high-speed phenomena with a time resolution of less than 10 ms.