Holography - Just Another Method of Image Processing?

The advantage of all different kinds of electron holography lies in the fact that in addition to the image intensity they make use of the phase in real space and in Fourier space. Therefore, they are in principle superior to conventional imaging techniques, even if these are supported by highly sophisticated methods of image processing. The technique of electron off-axis holography, under development in Tübingen for more than 20 years, now enters atomic resolution domain. After correction of aberrations, amplitudes and phases can be determined quantitatively, both in real space and Fourier space, opening up novel facilities for the analysis of structures at atomic dimensions

A holographic biprism as a perfect energy filter?

a b s t r a c t It has often been stated that a holographic biprism represents a near perfect energy filter and only elastically scattered electrons can participate in the interference fringes. This is based on the assumption that the reference wave does not contain inelastically scattered electrons. In this letter we show that this is not exactly true because of the delocalised inelastic interaction of the reference wave with the sample. We experimentally and theoretically show that inelastic scattering plays a role in the fringe formation, but it is shown that this contribution is small and can usually be neglected in practice

Subjective caregiver burden: validity of the 10-item short version of the Burden Scale for Family Caregivers BSFC-s

Background Subjective burden is a central variable describing the situation encountered by family caregivers. The 10-item short version of the Burden Scale for Family Caregivers (BSFC-short/BSFC-s) was developed to provide an economical measure of this variable. The present study examined the reliability and validity of the BSFC-s. Methods Comprehensive data from “the IDA project” were the basis of the calculations, which included 351 dyads and examined medical data on people with dementia, interview data from their family caregivers, and health insurance data. A factor analysis was performed to explore the structure of the BSFC-s; Cronbach’s alpha was used to evaluate the internal consistency of the scale. The items were analyzed to determine the item difficulty and the discriminatory power. Construct validity was tested with five hypotheses. To establish the predictive validity of the BSFC-s, predictors of institutionalization at a follow-up time of 2.5 years were analyzed (binary logistic regression). Results The BSFC-s score adhered to a one-factor structure. Cronbach's alpha for the complete scale was .92. A significant increase in the BSFC-s score was observed when dementia progressed, disturbing behavior occurred more frequently, care requirements increased, and when caregivers were diagnosed with depression. Caregiver burden was the second strongest predictor of institutionalization out of a total of four significant predictors. Conclusions All hypotheses that referred to the construct validity were supported. The BSFC-short with its ten items is a very economical instrument for assessing the caregiver’s total subjective burden in a short time frame. The BSFC-s score has predictive validity for the institutionalization of people with dementia. Therefore it is an appropriate outcome measure to evaluate caregiver interventions. The scale is available for free in 20 languages (http://www.caregiver-burden.eu webcite). This availability facilitates the comparison of international research findings

50 Years of Electron Biprism -50 Years of Exciting Electron Physics

This paper, from Hannes Lichte of the Institute of structure Physics at Dresden University, covers the electron biprism. Lichte includes formulas and diagrams to explain electron waves, scheme of electron biprism interferometry, coherence measurements, and electron holography.Â

50 Years of Electron Biprism -50 Years of Exciting Electron Physics

In 1953, Gottfried Moellenstedt invented the electron biprism, more or less by accident, with the serendipity characteristic to him: Aiming at dark-field imaging in an electron microscope, he stretched a thin tungsten wire across the objective aperture to block off the zero beam. However, instead of a dark field image, because of inadvertent charging of the wire under the beam, he found two images of the ZnO-needles serving as an object. Instead of trying the dark field imaging over and over again, he asked what the effect would be if the obtained two images were superimposed. Is coherence given? Moellenstedt, educated by Walther Kossel in diffraction of electron waves, had a vision: Together with his PhD-student Heinrich Dueker, he developed the electron biprism, consisting of a 1 micron m thin wire deliberately chargeable by means of a voltage source, as a beam splitter for coherent superposition of the electron waves passing the filament on the right and on the left. In 1955 they published the first results showing biprism interference fringes [G. Moellenstedt and H. Dueker, Naturwiss. 42, 41 (1955)], which, since then, gave access to the understanding of electron waves and their use for analysis of object structures up to atomic dimensions. Target Audience: 2-4 Year College Faculty/Administrator

Correlation and the density-matrix approach to inelastic electron holography in solid state plasmas.

Collective excitations in solid state plasmas are a good candidate to measure correlation lengths of conduction electrons. The method of choice seems to be energy filtered electron holography in the transmission electron microscope sTEMd since the interference fringes contain information on the partial coherence of those electrons. Previous experiments showed surprisingly high coherence. We calculate the density-density correlation function in the Al plasma excitation from the dynamic form factor and compare it to results based on similar arguments. For the Al plasma excitation, we find a small extension of 0.120.3 nm over which the movement of charges is correlated. Using the density-matrix formalism, the coherence length of plasmon scattered fast electrons in the TEM is calculated and found to agree with experiment. We show that the small correlation length of conduction electrons does not contradict the coherence length of .10 nm found for fast probe electrons having excited a plasmon in Al. The difference of nearly two orders of magnitude can be traced back to the long-range Coulomb interaction between probe and target electrons. Two unexpected predictions ensue from the present approach: Inelastic holography experiments should show strongly increased contrast of interference fringes in vacuo, i.e., outside the specimen, and contrast inversion of fringes in inelastic holograms of very small particles