Versatile microporous polymer-based supports for serial macromolecular crystallography

Serial data collection has emerged as a major tool for data collection at state-of-the-art light sources, such as microfocus beamlines at synchrotrons and X-ray free-electron lasers. Challenging targets, characterized by small crystal sizes, weak diffraction and stringent dose limits, benefit most from these methods. Here, the use of a thin support made of a polymer-based membrane for performing serial data collection or screening experiments is demonstrated. It is shown that these supports are suitable for a wide range of protein crystals suspended in liquids. The supports have also proved to be applicable to challenging cases such as membrane proteins growing in the sponge phase. The sample-deposition method is simple and robust, as well as flexible and adaptable to a variety of cases. It results in an optimally thin specimen providing low background while maintaining minute amounts of mother liquor around the crystals. The 2 × 2 mm area enables the deposition of up to several microlitres of liquid. Imaging and visualization of the crystals are straightforward on the highly transparent membrane. Thanks to their affordable fabrication, these supports have the potential to become an attractive option for serial experiments at synchrotrons and free-electron lasers.

Design of a Unique Device for Residual Stresses Quantification by the Drilling Method Combining the PhotoStress and Digital Image Correlation

This paper presents a uniquely designed device combining the hole-drilling technique with two optical systems based on the PhotoStress and digital image correlation (DIC) method, where the digital image correlation system moves with the cutting tool. The authors aimed to verify whether the accuracy of the drilled hole according to ASTM E837-13a standard and the positioning accuracy of the device were sufficient to achieve accurate results. The experimental testing was performed on a thin specimen made from strain sensitive coating PS-1D, which allowed comparison of the results obtained by both methods. Although application of the PhotoStress method allows analysis of the strains at the edge of the cut hole, it requires a lot of experimenter’s practical skills to assess the results correctly. On the other hand, the DIC method allows digital processing of the measured data. However, the problem is not only to determine the data at the edge of the hole, the results also significantly depend on the smoothing levels used. The quantitative comparison of the results obtained was performed using finite element analysis.

Position Identification of Inclusions in Soft Objects by Indentation Testing

The incidence rate of breast cancer for women in Japan is increasing each year. The three main methods of screening for breast cancer are finger palpation, mammography and breast ultrasound. These methods must be improved to decrease the incidence rate. This involves the development of personal, easy-to-use devices that facilitate cancer diagnosis. This study evaluates an indentation device developed to imitate traditional finger palpation and identify the position of the tumor inside the breast. The identification procedure is based on the extended Hertzian contact theory, which was developed to evaluate the elasticity of a thin specimen. In this extended theory, the thickness effect of the specimen is represented by a thickness parameter, and the position can be identified by the analysis of the effect. The procedure is verified by using FEM for ideal inclusion model in soft object, and the accurateness of the identification is discussed for the development. In the verification, some difference in the identified position between the condition and the result of FEM is observed with the difference of the identified elasticity of the object. It was reported that the approximation of accurate elasticity could affect the accuracy of position identification. Subsequently, the identification accuracy of Young’s modulus and thickness of specimen is discussed considering the problem of inclusion. Using the proposed approach, high accuracy can be observed in the range of 5 mm to 15 mm; however, a greater level of accuracy in identification remains to be achieved in other ranges. Thus, it is concluded that identification is possible using the extended Hertzian contact theory; however, for accurate identification of cancer position in a breast, the theory requires further modification.

Modeling of thickness effect on the creep properties of Ni-based superalloys

Purpose Specimen thickness has great influences on the creep behavior of single crystal Ni-based superalloys when it is less than 3.0 mm, which is known as thickness debit effect. Experiments have detected that oxidation can influence the microstructure of the Ni-based superalloys. Here, a model is proposed to bring in both the oxidation effect and void caused damage to account for the thickness debit effect. The paper aims to discuss these issues. Design/methodology/approach The model uses the simple Norton type creep relation to describe the creep rate evolution. The damage evolution caused by void is taken to be stress controlled. The load baring area changes are calculated with the consideration of oxidation and void evolutions. Findings Simulations on specimens with different thickness from 3.0 to 0.3 mm are carried out. The results show that the present model can reproduce the decrease of the creep strength with the decreases of the specimen thickness. The damage plays a major role in the creep behavior of the thick specimen. Both the damage and the oxidation are important for the thin specimen which should be paid attention to during the calculation of the creep response of the thin-wall turbine blade. Originality/value A model is proposed to account for the thickness debit effect on the creep behavior of Ni-based superalloys. Both oxidation influence and void caused damage are introduced. The simulation results show the capability of the model to reproduce the thickness debit effect.

Fast Atomic-Scale Elemental Mapping of Crystalline Materials by STEM Energy-Dispersive X-Ray Spectroscopy Achieved with Thin Specimens

Elemental mapping at the atomic-scale by scanning transmission electron microscopy (STEM) using energy-dispersive X-ray spectroscopy (EDS) provides a powerful real-space approach to chemical characterization of crystal structures. However, applications of this powerful technique have been limited by inefficient X-ray emission and collection, which require long acquisition times. Recently, using a lattice-vector translation method, we have shown that rapid atomic-scale elemental mapping using STEM-EDS can be achieved. This method provides atomic-scale elemental maps averaged over crystal areas of ~few 10 nm2with the acquisition time of ~2 s or less. Here we report the details of this method, and, in particular, investigate the experimental conditions necessary for achieving it. It shows, that in addition to usual conditions required for atomic-scale imaging, a thin specimen is essential for the technique to be successful. Phenomenological modeling shows that the localization of X-ray signals to atomic columns is a key reason. The effect of specimen thickness on the signal delocalization is studied by multislice image simulations. The results show that the X-ray localization can be achieved by choosing a thin specimen, and the thickness of less than about 22 nm is preferred for SrTiO3in [001] projection for 200 keV electrons.

An Experimental Investigation of the Size Effects in Forming Processes of High-Purity Thin Metallic Sheets

Miniaturization of small metallic systems can lead to a softening of the mechanical behavior due to the reduction of scale. Size effects have been considerably studied recently for materials with various crystallographic structures. Under tensile conditions, thin specimen exhibit softer mechanical properties when the number of grains across thickness is lower than a critical number and this modification appears above a critical strain level. In this work, stamping tests were performed on five hundred micrometers in thickness sheets of hexagonal closed-packed cobalt. The results are compared with those obtained for face centered cubic copper and nickel. The influence of thickness over grain size ratio was studied for several proportional loadings linked to forming processes. Complex loadings were applied with 20 mm hemispherical punch and strain paths were checked with a 3D video extensometer. Hill criterion was systematically used to take into account the anisotropy of the samples. Our results revealed that the critical strain level for which the size effects appears is strongly sensitive to the stress triaxiality which, in turn, is closely dependent to the loading path.