Dose efficient annular bright field contrast with the ISTEM method: A proof of principle demonstration.

The ISTEM mode for TEM has been demonstrated to have several advantages in regard to resolution and precision. While previous works primarily focussed on the advantages due to the reduced spatial coherence, the actual image contrast, i.e. how bright or dark certain atom columns are imaged, has mostly been of secondary concern. The present work sets out to achieve the contrast of annular bright field STEM in ISTEM, producing the high contrast of light elements, for which this method is popular. It is shown from theoretical considerations that using an annular condenser aperture this aim can be realised. The optimal size of this aperture is found by simulative studies. It is then manufactured from platinum foil and installed in an image-aberration corrected microscope. ABF-like ISTEM images of strontium titanate in [100] projection are acquired. The pure oxygen columns are clearly resolved with significant contrast. The image pattern is indeed identical to what is achieved by ABF STEM. A close look at the image formation also shows that the dose needed for a given signal-to-noise ratio is at least a quarter smaller for ABF-like ISTEM compared to ABF STEM, assuming detectors of similar detective quantum efficiency.

Accuracy and precision of position determination in ISTEM imaging of BaTiO3.

In this paper we study the effect of lens aberrations (spherical aberration and astigmatism), beam tilt, contamination and shot noise on the accuracy and precision of position determination in imaging scanning transmission electron microscopy (ISTEM) on the example of BaTiO3. ISTEM images are simulated as a function of sample thickness and defocus starting from a nearly perfect microscope setting. A defocus range was identified, in which atom column positions were reliably visible and could be decently measured. By averaging over this defocus and thickness range a figure of merit was defined and used to study the influence of above mentioned disturbing effects as a function of their strength. It turned out that column positions might become inaccurate, but distances are measured accurately. These were used to obtain recommendations for the experimental setup to measure the atomic arrangement that induces ferroelectric switching of BaTiO3.

Precise measurement of the electron beam current in a TEM.

Modern quantitative TEM methods such as the ζ-factor technique require precise knowledge of the electron beam current. To this end, a macroscopic Faraday cup was designed and constructed. It can replace the viewing screen in the projection chamber of a TEM and guarantees highly accurate measurement of the electron beam with precision only limited by the used amperemeter. The easy to install, affordable device is shown to be highly apt for precision measurement of currents >5pA. The Faraday cup results are used for an assessment and a comparison of various other beam current measurement methods. It is found that the built-in screen amperemeter of the used TEM is quite inaccurate and that measurements using the screen in general tend to underestimate the current. If present, the drift tube of a spectrometer can also be used as a Faraday cup, but certain described peculiarities have to be taken into account. Direct ultrafast electron detection cameras allow precise measurement at very small currents. For the electron counting technique, which exploits single electron detection capabilities of STEM detectors, a systematic current underestimation was observed and investigated. This results in a reformulated routine for the method and with these improvements it is demonstrated to be capable of accurate high-precision measurements for currents <5pA.

Minimizing cross-cultural maladaptation: How minority status facilitates change in international acculturation.

Culturally savvy organizations recognize that selecting and developing people who can be effective in a global workforce is important in today's business environment. Nevertheless, many companies struggle to identify and develop talent who are happy and successful working and living outside their home country. We examine 1 factor that may foster success in a host country-minority status in 1's home country-as a predictor of change in acculturation over time. Specifically, we draw on the conservation of resources model to suggest that international students who have been a member of more minority groups in their home country have unique experiences working with dissimilar others that offer advantages when acculturating to new cultures and novel situations. Then, change in host country acculturation is explored as a mechanism to explain how minority status in the home country relates to intentions to leave the host country and psychological well-being 6 months after entry. Two moderators (cultural intelligence, perceived diversity climate of the host institution) of these relationships are also examined. Results revealed that the relationship between minority status in the home country and change in host country acculturation was positive and stronger for those with higher cultural intelligence. Further, the relationship between change in host country acculturation and psychological well-being was positive when perceived diversity climate of the host institution was high, but was not significant when perceived diversity climate was low. (PsycINFO Database Record

Measurement of atomic electric fields and charge densities from average momentum transfers using scanning transmission electron microscopy.

This study sheds light on the prerequisites, possibilities, limitations and interpretation of high-resolution differential phase contrast (DPC) imaging in scanning transmission electron microscopy (STEM). We draw particular attention to the well-established DPC technique based on segmented annular detectors and its relation to recent developments based on pixelated detectors. These employ the expectation value of the momentum transfer as a reliable measure of the angular deflection of the STEM beam induced by an electric field in the specimen. The influence of scattering and propagation of electrons within the specimen is initially discussed separately and then treated in terms of a two-state channeling theory. A detailed simulation study of GaN is presented as a function of specimen thickness and bonding. It is found that bonding effects are rather detectable implicitly, e.g., by characteristics of the momentum flux in areas between the atoms than by directly mapping electric fields and charge densities. For strontium titanate, experimental charge densities are compared with simulations and discussed with respect to experimental artifacts such as scan noise. Finally, we consider practical issues such as figures of merit for spatial and momentum resolution, minimum electron dose, and the mapping of larger-scale, built-in electric fields by virtue of data averaged over a crystal unit cell. We find that the latter is possible for crystals with an inversion center. Concerning the optimal detector design, this study indicates that a sampling of 5mrad per pixel is sufficient in typical applications, corresponding to approximately 10×10 available pixels.

Does the economy affect functional restoration outcomes for patients with chronic disabling occupational musculoskeletal disorders?

PURPOSE: To determine how the economy affects psychosocial and socioeconomic treatment outcomes in a cohort of chronic disabling occupational musculoskeletal disorder (CDOMD) patients who completed a functional restoration program (FRP). METHODS: A cohort of 969 CDOMD patients with active workers' compensation claims completed an FRP (a medically-supervised, quantitatively-directed exercise progression program, with multi-modal disability management). A good economy (GE) group (n = 532) was released to work during a low unemployment period (2005-2007), and a poor economy (PE) group (n = 437) was released during a higher unemployment period (2008-2010). Patients were evaluated upon admission for demographic and psychosocial variables, and were reassessed at discharge. Socioeconomic outcomes, including work return and work retention 1 year post-discharge, were collected. RESULTS: Some significant differences in psychosocial self-report data were found, but most of the effect sizes were small, so caution should be made when interpreting the data. Compared to the PE group, the GE group reported more depressive symptoms and disability at admission, but demonstrated a larger decrease in depressive symptoms and disability and increase in self-reported quality of life at discharge. The PE group had lower rates of work return and retention 1-year after discharge, even after controlling for other factors such as length of disability and admission work status. CONCLUSIONS: CDOMD patients who completed an FRP in a PE year were less likely to return to, or retain, work 1-year after discharge, demonstrating that a PE can be an additional barrier to post-discharge work outcomes. A difference in State unemployment rates of <3% (7 vs. 5%) had a disproportionate effect on patients' failure to return to (19 vs. 6%) or retain (28 vs. 15%) work.