Measurement of lens aberrations by means of image displacements in beam-tilt series

Electron microscope image aberrations are determined by means of the beam tilt/image displacement method with respect to the precision required to obtain a resolution of 1 A. The method simultaneously yields all image aberrations to the fourth order and it is independent of the material used for the procedure. The experimental procedure using amorphous carbon is described and errors in measuring beam-tilt angles, magnifications and image displacements can be kept sufficiently small to achieve the required accuracy. The method is applied to determine aberration constants of a CM300 FEG/UT microscope with correction of the three-fold astigmatism. The coefficient of spherical aberration and the modulus of the three-fold astigmatism were measured to 0.60 (+/- 0.02) mm and 150 (+/- 50) nm, respectively. The beam tilt/image displacement procedure is also computer simulated using an amorphous model structure yielding the same values for the lens aberrations which are used for imaging. However, a coefficient of spherical aberration of 0.67 mm is obtained by applying the focus variation/diffractogram analysis on the same model.     

Reusing knowledge in embedded systems modelling

Model‐based design is a promising technique to improve the quality of software and the efficiency of the software development process. We are investigating how to efficiently model embedded software and its environment to verify the requirements for the system controlled by the software. The software environment consists of mechanical, electrical and other parts; modelling it involves learning how these parts work, deciding what is relevant to model and how to model it. It is not possible to fully automate these steps. There are general guidelines, but given that every modelling problem differs, much is left to the modeller's own preference, background and experience. Still, when the next generation of a system is designed, the new system will have common elements with its previous version. Therefore, lessons learned from the current model could inform future models. We propose a framework for identifying the non‐formal elements of knowledge, insights and a model itself, which can support modelling of the next system generation. We will present the application of our framework on an action research case – modelling mechanical parts of a paper‐inserting machine.     

Transformation Mechanism of the Dehydration of Diaspore

The dehydration of diaspore to corundum was investigated by means of X-ray powder diffraction at reaction temperatures (400° and 600°C) as well as by transmission electron microscopy (TEM). The TEM studies were performed at the reaction interface of partially dehydrated natural diaspore crystals. The corundum produced consisted of thin dense regions which were separated by nanometer-sized pores forming lamellae with a periodicity of 3.7 nm. At the reaction front a transition phase (D') could be detected in electron diffraction patterns. The phase D' is isotypic to diaspore, but with a larger spacing of the close-packed (100) oxygen planes ( a _D' from 0.475 to 0.480 nm). The expansion with respect to diaspore is explained by breaking of the hydrogen bonds of diaspore, considered to be the initial step of the transformation. The spacing of the lamellar pore system in corundum is explained by the misfit of the (100) planes of D' and the (0003) planes of corundum. We conclude that at well-fitting regions of the closed-packed planes at the D'/C interface, dense corundum is formed, while at misfitting regions, the formation of corundum is not favored and the pores are produced. Hence, the transformation of the solid phases takes place as a two-step process, i.e., D → D'→ C.     

Structure and Chemistry of Basal-Plane Inversion Boundaries in Antimony Oxide-Doped Zinc Oxide

The atomic structure and the chemistry of basal - plane inversion boundaries in Sb₂O₃-doped ZnO were investigated using quantitative transmission electron microscopy techniques. Electron microdiffraction and high - resolution transmission electron microscopy were used to determine the orientation of the polar c -axis on both sides of the inversion boundary and the translation state between the inverted ZnO domains. Quantitative energy - dispersive X - ray spectroscopy combined with high - resolution transmission electron microscopy allowed us to determine the exact amount and the arrangement of antimony in the boundary layer. Inversion boundaries are head - to - head oriented with a displacement vector of the oxygen sublattice of R _IB=⅓[01[Onemacr]0] – 0.102[0001]. The boundary plane consists of a highly ordered SbZn₂ monolayer in which the cations occupy the octahedral interstices of the structure. In the octahedral boundary layer, zinc and antimony atoms constitute a honeycomb superstructure with a threefold (3 m ) in - plane symmetry.     

Cryo-3D Printing of Hierarchically Porous Polyhydroxymethylene Scaffolds for Hard Tissue Regeneration

High molecular weight polyhydroxymethylene (PHM) has a repeat unit identical to that of low molecular weight sugar alcohols and exhibits carbohydrate-like properties. Herein, cryogenic extrusion-based 3D printing is combined with a phase separation in water to fabricate hierarchically porous PHM scaffolds containing interconnected macro-, micro-, and nanopores. As PHM is infusible and insoluble in common solvents, its precursor polyvinylene carbonate (PVCA) dissolved in dimethylsulfoxide (DMSO) is used to 3D print hierarchically porous PVCA scaffolds that are converted into PHM by hydrolysis without impairing the pore architectures. Similar to low-temperature deposition manufacturing, the PVCA/DMSO freezes on a build platform at −78 °C. However, instead of removing the frozen solvent by sublimation, the frozen scaffold is immersed in water to recover DMSO and to effect phase separation by precipitation. However, the computer-guided printhead pathway controls macropore formation phase separation of frozen PVCA/DMSO upon contact with water accounts for simultaneous micro- and nanopore formation. Contrary to 3D printing of PVCA/DMSO at ambient temperature, this cryo-3D printing process does not require shear thinning additives and affords significantly improved build precision with macropore sizes variable between 200 and 1500 µm. Cryo-3D-printed PHM scaffolds are biocompatible and promote osteoblast proliferation.     

Displacement field measurement of metal sub-lattice in inversion domains of indium-doped zinc oxide

The displacement field of the metal sub-lattice in homologous compounds In₂O₃(ZnO)_m is investigated by means of aberration-corrected high-resolution transmission electron microscopy. The elastic state in these compounds is characterised by plane strain where little column bending occurs due to surface relaxation. The compound contains inversion domain boundaries (IDBs) on basal and pyramidal planes of ZnO where the displacements are concentrated. The structure is imaged in <1 1¯ 0 0> of ZnO with negative spherical aberration and using bright atom contrast condition. Local atomic shifts are measured with precision of ca. 5 picometres in real space with a peak finding algorithm. The strain tensor and lattice rotations are calculated from displacements displaying dilatation, shear and rotation at pyramidal IDBs which reveal a mirror plane through the centre of each inversion domain.     

Active transportation: Do current traffic safety policies protect non-motorists?

Objective

This study investigated the impact that state traffic safety regulations have on non-motorist fatality rates.

Methods

Data obtained from the National Highway Traffic Safety Administration (NHTSA), the Federal Highway Administration (FHWA), and the National Institute on Alcohol Abuse and Alcoholism (NIAAA) were analyzed through a pooled time series cross-sectional model using fixed effects regression for all 50 states from 1999 to 2009. Two dependent variables were used in separate models measuring annual state non-motorist fatalities per million population, and the natural log of state non-motorist fatalities. Independent variables measuring traffic policies included state expenditures for highway law enforcement and safety per capita; driver cell phone use regulations; graduated driver license regulations; driver blood alcohol concentration regulations; bike helmet regulations; and seat belt regulations. Other control variables included percent of all vehicle miles driven that are urban and mean per capita alcohol consumption per year.

Results

Non-motorist traffic safety was positively impacted by state highway law enforcement and safety expenditures per capita, with a decrease in non-motorist fatalities occurring with increased spending. Per capita consumption of alcohol also influenced non-motorist fatalities, with higher non-motorist fatalities occurring with higher per capita consumption of alcohol. Other traffic safety covariates did not appear to have a significant impact on non-motorist fatality rates in the models.

Conclusion

Our research suggests that increased expenditures on state highway and traffic safety and the initiation/expansion of programs targeted at curbing both driver and non-motorist intoxication are a starting point for the implementation of traffic safety policies that reduce risks for non-motorists.     

Critical assessment of the speckle statistics in fluctuation electron microscopy and comparison to electron diffraction

The technique of fluctuation electron microscopy (FEM) is applied to thin films of amorphous germanium and of polycrystalline gold in a transmission electron microscope. Even though the method was introduced as a tool for quantitative analysis of structural fluctuations in amorphous materials, the basic principles are applicable to any disordered specimen independent of the dimension of disorder. Hence, we extended the technique of FEM to a well-known specimen, gold, whereby it was possible to reinterpret the results of the measurements on amorphous germanium. The hollow-cone dark field images, the statistical analysis of which is the basis of FEM, are examined with respect to the effects of frequency filtering, and are compared to electron diffraction. We find that the angular dependence of the normalised variance, as measured by FEM, yields information similar to the average intensity of hollow-cone dark field image series. Both plots are basically identical to a scan through a selected-area diffraction pattern convoluted by the corresponding angular resolution function. Hence, it appears questionable whether standard FEM analysis provides more information than the classical pair distribution function, which is experimentally limited to short-range order. Frequency selective analysis of the normalised variance, however, gives supplementary information on preferred inter-atomic distances related to the medium-range order of the specimen.     

Effect of sequential implanting with Synovex on steer and heifer performance

Studies were conducted using 72 (Exp. 1) and 248 (Exp. 2) steer and heifer calves from 1 to 2 mo of age through slaughter to determine whether preweaning implants affect postweaning feed conversion of cattle that are rapidly grown and(or) finished in the feedlot. In Exp. 1, treatments were three Synovex (S) implants administered 0, 70, and 140 d postweaning (NSSS) or Synovex-C (C) administered preweaning and three implants administered postweaning (CSSS). In Exp. 2, treatments were no implants (NNNN), implants administered 0, 74, and 148 d postweaning to calves that had either received no preweaning implant (NSSS), or C (CSSS), and CSSS plus trenbolone acetate (TBA) administered with the last S implant (CSSS-TBA). Synovex-S or -H implants were administered postweaning to steers and heifers, respectively. Steer and heifer calves implanted with C in the preweaning phase were 9.0 and 13.0 kg (Exp. 1) and 7.5 and 15.0 kg (Exp. 2) heavier (P < .10), respectively, at weaning than nonimplanted steer and heifer calves. In Exp. 1, preweaning implant had no affect on postweaning performance or quality grade. In Exp. 2, preweaning implants (NSSS vs CSSS) decreased (P < .10) steer postweaning gains, whereas postweaning implants (NSSS vs NNNN) increased (P < .10) DM intake; however, feed:gain ratio was not affected by implant strategy. Heifers in Exp. 2 that received implants had greater postweaning (P < .10) DM intakes and daily gains than heifers not receiving implants (NNNN); however, feed:gain ratios among treatment groups were unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)