RESUMO
Moiré patterns in scanning transmission electron microscopy (STEM) images of epitaxial perovskite oxides are used to assess strain and defect densities over fields of view extending over several hundred nanometers. The patterns arise from the geometric overlap of the rastered STEM electron beam and the samples' crystal periodicities and we explore the emergence and application of these moiré fringes for rapid strain analysis. Using the epitaxial functional oxide perovskites BiFeO3 and Pr1-x Ca x MnO3, we discuss the impact of large degrees of strain on the quantification of STEM moiré patterns, identify defects in the fringe patterns and quantify strain and lattice rotation. Such a wide-area analysis of crystallographic strain and defects is crucial for developing structure-function relations of functional oxides and we find the STEM moiré technique to be an attractive means of structural assessment that can be readily applied to low dose studies of damage sensitive crystalline materials.
RESUMO
We present results from an aberration corrected scanning transmission electron microscope which has been customised for high resolution quantitative Lorentz microscopy with the sample located in a magnetic field free or low field environment. We discuss the innovations in microscope instrumentation and additional hardware that underpin the imaging improvements in resolution and detection with a focus on developments in differential phase contrast microscopy. Examples from materials possessing nanometre scale variations in magnetisation illustrate the potential for aberration corrected Lorentz imaging as a tool to further our understanding of magnetism on this lengthscale.
RESUMO
We describe a technique using a focused ion beam instrument to fabricate high quality plan-view specimens for transmission electron microscopy studies. The technique is simple, site-specific and is capable of fabricating multiple large, >100 µm(2) electron transparent windows within epitaxially grown thin films. A film of La0.67Sr0.33MnO3 is used to demonstrate the technique and its structural and functional properties are surveyed by high resolution imaging, electron spectroscopy, atomic force microscopy and Lorentz electron microscopy. The window is demonstrated to have good thickness uniformity and a low defect density that does not impair the film's Curie temperature. The technique will enable the study of in-plane structural and functional properties of a variety of epitaxial thin film systems.
RESUMO
We prospectively looked at the diagnostic accuracy of clinical examination of the knee in patients with arthroscopically documented knee injuries. The study included 156 patients with 156 knee injuries (72 acute and 84 chronic) who were seen during 1 year at Martin Army Hospital at Fort Benning Georgia. All patients were given a primary diagnosis based on their history, physical examination, and routine radiographs. Fifty-seven patients were also given one or more secondary diagnoses. Magnetic resonance imaging scans and arthrograms were not used in the evaluation of these patients. The primary diagnosis was correct in 83% of the knees. Of 57 secondary diagnoses given, 54% were correct and 31% were incomplete. An incorrect diagnosis was made in 14% of knees for both primary and secondary diagnoses. There were four patients with no identifiable lesion other than synovitis. With the increasing cost of medical care, the need for expensive diagnostic studies such as magnetic resonance imaging needs to be evaluated. The cost of a magnetic resonance image scan ranges between $600 to $1200 depending on the institution. The use of magnetic resonance imaging as a routine diagnostic aid in the clinical examination of the knee is unnecessary. Arthroscopic surgery of the knee should be based on the patient's history, physical examination, and radiographs.
