Ab initio nonrigid X-ray nanotomography

Abstract: Reaching the full potential of X-ray nanotomography, in particular for biological samples, is limited by many factors, of which one of the most serious is radiation damage. Although sample deformation caused by radiation damage can be partly mitigated by cryogenic protection, it is still present in these conditions and, as we exemplify here using a specimen extracted from scales of the Cyphochilus beetle, it will pose a limit to the achievable imaging resolution. We demonstrate a generalized tomographic model, which optimally follows the sample morphological changes and attempts to recover the original sample structure close to the ideal, damage-free reconstruction. Whereas our demonstration was performed using ptychographic X-ray tomography, the method can be adopted for any tomographic imaging modality. Our application demonstrates improved reconstruction quality of radiation-sensitive samples, which will be of increasing relevance with the higher brightness of 4th generation synchrotron sources

Evolutionary-Optimized Photonic Network Structure in White Beetle Wing Scales.

Most studies of structural color in nature concern periodic arrays, which through the interference of light create color. The "color" white however relies on the multiple scattering of light within a randomly structured medium, which randomizes the direction and phase of incident light. Opaque white materials therefore must be much thicker than periodic structures. It is known that flying insects create "white" in extremely thin layers. This raises the question, whether evolution has optimized the wing scale morphology for white reflection at a minimum material use. This hypothesis is difficult to prove, since this requires the detailed knowledge of the scattering morphology combined with a suitable theoretical model. Here, a cryoptychographic X-ray tomography method is employed to obtain a full 3D structural dataset of the network morphology within a white beetle wing scale. By digitally manipulating this 3D representation, this study demonstrates that this morphology indeed provides the highest white retroreflection at the minimum use of material, and hence weight for the organism. Changing any of the network parameters (within the parameter space accessible by biological materials) either increases the weight, increases the thickness, or reduces reflectivity, providing clear evidence for the evolutionary optimization of this morphology.PXCT measurements were performed at the cSAXS beamline at the Swiss Light Source, Paul Scherrer Institut, Switzerland. The OMNY instrumentation was supported by the Swiss National Science Foundation SNSF (Funding scheme RQUIP, Project number 145056). This research was financially supported through the National Centre of Competence in Research Bio-Inspired Materials, the Adolphe Merkle Foundation (to B.D.W. and U.S.), a BBSRC David Phillips fellowship (BB/K014617/1), the European Research Council (ERC-2014-STG H2020 639088, to O.O. and S.V.), and the Ambizione program of the Swiss National Science Foundation SNSF (168223, to B.D.W.). The authors acknowledge support from the Winton Programme for the Physics of Sustainability

Towards personalized data-driven bundle design with QoS constraint

Singapore National Research Foundation under its International Research Centre @ Singapore Funding Initiativ

Superconducting fault current limiter (SFCL): Experiment and the simulation from finite-element method (FEM) to power/energy system software

The superconducting fault current limiter (SFCL) has been regarded as one of most popular superconducting applications. This article reviews the modern energy system with two major issues (the power stability and fault-current), and introduces corresponding approaches to mitigate these issues, including the importance of using SFCL. Then the article presents the experiment of a resistive-type SFCL used for a power electronic circuit. The experiment well matched the advanced finite-element method (FEM) SFCL model, from which the reliability of FEM SFCL model was confirmed. Afterwards, the FEM model and the power system software PSCAD were used to model a large-scale resistive-type SFCL. Under the same simulation conditions the FEM model well matched the PSCAD model. The FEM method has the advantages of offering specific electromagnetic modeling on superconducting part. The PSCAD SFCL model has much faster simulation speed and can directly cope with all ranges of power networks. This article presents a new vision and an all-in-one study to link the experiment, the numerical model, and the power/energy system software model, and their agreement can be extremely helpful for researchers and engineers to find useful evidences and reliable methods to confidently carry out successful SFCL designs for the electrical energy system

Ab initio nonrigid X-ray nanotomography

Abstract: Reaching the full potential of X-ray nanotomography, in particular for biological samples, is limited by many factors, of which one of the most serious is radiation damage. Although sample deformation caused by radiation damage can be partly mitigated by cryogenic protection, it is still present in these conditions and, as we exemplify here using a specimen extracted from scales of the Cyphochilus beetle, it will pose a limit to the achievable imaging resolution. We demonstrate a generalized tomographic model, which optimally follows the sample morphological changes and attempts to recover the original sample structure close to the ideal, damage-free reconstruction. Whereas our demonstration was performed using ptychographic X-ray tomography, the method can be adopted for any tomographic imaging modality. Our application demonstrates improved reconstruction quality of radiation-sensitive samples, which will be of increasing relevance with the higher brightness of 4th generation synchrotron sources