On smart optimization of blazed soft X-ray gratings

The first attempts to calculate the diffraction efficiencies of gratings in the soft X-ray range were made on a scalar model. The results were simple analytical equations, that always severely overestimated the performance of real objects. In this respect, computer programs were found to be more successful, which rigorously consider all diffracted and refracted waves. Consequently soft X-ray gratings are presently optimized using these tools, which requires rather extensive calculations for any instrument optimization as general trends are not immediately obvious. Here it will be shown that the results of the rigorous calculations for gratings with blaze or sawtooth profile can be approximated rather well with a simple analytical equation. This equation contains three multiplicative factors, which deal independently with the effect of the reflectivity, the blaze angle and the groove density. This opens the possibility to initially ignore the effects of the blaze angle and thus to start an optimization in a very general way. Such optimization can be based on isoreflectivity curves and it can then provide `blaze maximum efficiency maps', i.e. simple images. In these latter images, one can identify directly the optimum parameters for a grating, i.e. the groove density providing best efficiency for a requested spectral resolving power. Only successively will the blaze angle have to be fixed. Its choice is then not the result of an extensive optimization process but of a simple calculation applied for the photon energy at which maximum efficiency performance is requested. The maps presented here are used for the optimization of a medium-resolving-power soft X-ray monochromator, which can scan the photon energy range 300–2000 eV.

Design of an Underactuated Compliant Gripper for Surgery Using Nitinol

This paper presents the development of an underactuated compliant gripper using a biocompatible superelastic alloy, namely, nitinol. This gripper has two fingers with five phalanges each and can be used as the end-effector of an endoscopic instrument. Optimization procedures are required to obtain the geometry of the transmission mechanism because of its underactuated nature and its underlying complexity. A driving mechanism further incorporated in the gripper to distribute actuation to both fingers and accomplish the grasping of asymmetrical objects without requiring supplementary inputs is also discussed. Finally, the results of numerical simulations with different materials and different grasped objects are presented and discussed.

Determination of Chlorobiphenyls in Cleaned-Up Seal Blubber and Marine Sediment Extracts: Interlaboratory Study

An interlaboratory study on the determination of individual chlorobiphenyl congeners (CBs) in cleaned-up seal blubber and marine sediment extracts was organized by the International Council for Exploration of the Sea, the Intergovernmental Oceanographic Commission, and the Oslo and Paris Commissions, as the second part of a stepwise-designed interlaboratory study on the determination of CBs in marine media. Fifty-eight laboratories from 16 countries participated in this exercise, which involved the determination of 10 CBs in a standard solution, a cleaned-up seal blubber extract, and a cleaned-up marine sediment extract. Suggestions were given for instrument optimization. Standard errors of 1.16–1.17 for the standard solution, 1.20–1.33 for the seal blubber extract, and 1.31–1.56 for the sediment extract were obtained for CBs 52,101,118,138,153, and 180 by all laboratories with the exception of the laboratories giving consistently outlying results. The results for CBs 28,31,105, and 156 showed larger standard deviations. The 2 major difficulties for participants in this exercise were correct preparation of a calibration solution and chromatographic separation. The results of the sediment analysis showed a complete lack of agreement. It is recommended that, prior to the organization of the third part of this study, participants should install gas chromatographic columns with minimum lengths of 50 m and maximum internal diameters of 0.25 mm and should prepare calibration solutions from solids of known purity.