2,148,456 research outputs found
High-resolution low-dose scanning transmission electron microscopy
No full textDuring the past two decades instrumentation in scanning transmission electron microscopy (STEM) has pushed toward higher intensity electron probes to increase the signal-to-noise ratio of recorded images. While this is suitable for robust specimens, biological specimens require a much reduced electron dose for high-resolution imaging. We describe here protocols for low-dose STEM image recording with a conventional field-emission gun STEM, while maintaining the high-resolution capability of the instrument. Our findings show that a combination of reduced pixel dwell time and reduced gun current can achieve radiation doses comparable to low-dose TEM
Austrian-Hungarian joint conference on electron microscopy.
No full textAustrian-Hungarian joint conference... Austrian Society for Electron Microscopy. Group for Electron Microscopy of the Scientific Society for Measurements and Automation, Hungary Seggau-Leibnitz/Austria, 21-23 May 1987. Abstract
Biomedical and biological applications of scanning electron microscopy
No full textPodeu consultar el llibre complet a: http://hdl.handle.net/2445/32166This article summarizes the basic principles of scanning electron microscopy and the capabilities of the technique with different examples of
applications in biomedical and biological research
Accelerating data sharing and reuse in volume electron microscopy
No full textVolume electron microscopy (vEM) generates large 3D volumes of cells or tissues at nanoscale resolutions, enabling analyses of organelles in their cellular environment. Here, we provide examples of vEM in cell biology and discuss community efforts to develop standards in sample preparation and image acquisition for enhanced reproducibility and data reuse.Peer reviewe
Transfer of tilted sample information in transmission electron microscopy
Full text linkWhen a transmission electron microscope is used in imaging mode, information carried by
the sample function is transformed by the optics of the instrument during the imaging process.
A mathematical description of this physical process (the so-called imaging function)
is a requirement for an accurate analysis and the interpretation of electron microscopy
experimental data. When the sample is not imaged in tilted geometry (no defocus gradient
is present across its extent), the imaging function has a well-known and extensively
studied form : the Contrast Transfer Function (CTF) (Reimer, 1997). Several
electron microscopy techniques, however, require the sample to be tilted to fully
explore its 3-dimensional structure. Only recently a rigorous mathematical description
for the imaging process under these conditions, derived from physical
first principles, has been made available: the Tilted Contrast Imaging Function
(TCIF) (Philippsen et al., 2006).
The present work discusses in depth the nature and the characteristics of the TCIF model,
expanding it to include astigmatism. A robust and efficient software implementation is
presented, developed with the context of the IPLT software development framework
(Philippsen et al., 2007). Computer simulations of images of tilted samples are then
used to qualitatively and quantitatively analyze features of experimental images.
No computationally-feasible analytical method for the inversion of the TCIF model
is currently available, and its effects on experimental images are usually corrected using
a number of heuristic methods that involve some approximations of the imaging parameters.
Using computer simulations of tilted images, this work estimates the errors introduced
by these approximations, and suggests optimal correction strategies for electron tomography
and crystallography imaging conditions. Furthermore, this work describes possible approaches
for the determination of the imaging parameters through the analysis of the experimental images,
and for a non-analytical inversion of the effects of the TCIF model, showing preliminary
results of their implementation applied to computer simulated-images.
References:
Reimer, L. (1997). Transmission Electron Microscopy. Physics of Image Formation
and Microanalysis. Springer-Verlag GmbH, 4. A. edition.
Philippsen, A., Engel, H. and Engel, A. (2006). The contrast-imaging function
for tilted specimens. Ultramicroscopy, 107(2-3):202–12.
Philippsen, A., Schenk, A. D., Signorell, G. A., Mariani, V. and Berneche, S.et al.
(2007). Collaborative EM image processing with the IPLT image processing
library and toolbox. Journal of Structural Biology, 157(1):28–37
Transmission electron microscopy in cell biology: sample preparation techniques and image information
No full textPodeu consultar el llibre complet a: http://hdl.handle.net/2445/32166Transmission electron microscopy is a proven technique in the field of cell biology and a very useful tool in biomedical research. Innovation and improvements in equipment together with the introduction of new technology have allowed us to improve our knowledge of biological tissues, to visualize
structures better and both to identify and to locate molecules. Of all the types of
microscopy exploited to date, electron microscopy is the one with the most
advantageous resolution limit and therefore it is a very efficient technique for
deciphering the cell architecture and relating it to function. This chapter aims to
provide an overview of the most important techniques that we can apply to a
biological sample, tissue or cells, to observe it with an electron microscope, from
the most conventional to the latest generation. Processes and concepts are
defined, and the advantages and disadvantages of each technique are assessed
along with the image and information that we can obtain by using each one of
them
What can electron microscopy tell us beyond crystal structures?
No full textWZ thanks Professor Jun Yuan for a useful discussion during the revision of this article. The authors wish to thank EPSRC for financial support to the electron microscopy facility (No. EP/F019580/1) and a Platform grant (No. EP/K015540/1). Date of Acceptance: 08/01/2016Transmission electron microscopy is a powerful tool to directly image crystal structures. Not only that, it is often used to reveal crystal size and morphology, crystal orientation, crystal defects, surface structures, superstructures, etc. However, due to the 2D nature of TEM images, it is easy to make mistakes when we try to recover a 3D structure from them. Scanning electron microscopy is able to provide information on the particle size, morphology and surface topography. However, obtaining information on crystallinity of particles using SEM is difficult. In this microreview article, some practical cases of transmission and scanning electron microscopy investigations of inorganic crystals are reviewed. Commonly occurring uncertainties, imperfection and misunderstandings are discussed.Peer reviewe
Single particle electron microscopy
Full text linkElectron microscopy (EM) in combination with image analysis is a powerful technique to study protein structures at low, medium, and high resolution. Since electron micrographs of biological objects are very noisy, improvement of the signal-to-noise ratio by image processing is an integral part of EM, and this is performed by averaging large numbers of individual projections. Averaging procedures can be divided into crystallographic and non-crystallographic methods. The crystallographic averaging method, based on two-dimensional (2D) crystals of (membrane) proteins, yielded in solving atomic protein structures in the last century. More recently, single particle analysis could be extended to solve atomic structures as well. It is a suitable method for large proteins, viruses, and proteins that are difficult to crystallize. Because it is also a fast method to reveal the low-to-medium resolution structures, the impact of its application is growing rapidly. Technical aspects, results, and possibilities are presented.
Electron microscopy and other techniques
No full textThis is a third edition of the Electron Microscopy and Analysis textbook, which was published by Taylor and Francis Books UK in 2001 (ISBN 0748409688). It deals with several sophisticated techniques for magnifying images of very small objects by large amounts - especially in a physical science context. Consisting of seven chapters, presented as separate files the resource incorporates questions and answers in each chapter for ease of learning. Equally as relevant for material scientists and bioscientists, this resource is an essential textbook and laboratory manual. The chapter gives the comparison of electron microscopy with other imaging and analysis techniques.
Sample preparation for nanoanalytical electron microscopy using the FIB lift-out method and low energy ion milling
Full text linkThinning specimens to electron transparency for electron microscopy analysis can be done by conventional (2 - 4 kV) argon ion milling or focused ion beam (FIB) lift-out techniques. Both these methods tend to leave ''mottling'' visible on thin specimen areas, and this is believed to be surface damage caused by ion implantation and amorphisation. A low energy (250 - 500 V) Argon ion polish has been shown to greatly improve specimen quality for crystalline silicon samples. Here we investigate the preparation of technologically important materials for nanoanalysis using conventional and lift-out methods followed by a low energy polish in a GentleMill™ low energy ion mill. We use a low energy, low angle (6 - 8°) ion beam to remove the surface damage from previous processing steps. We assess this method for the preparation of technologically important materials, such as steel, silicon and GaAs. For these materials the ability to create specimens from specific sites, and to be able to image and analyse these specimens with the full resolution and sensitivity of the STEM, allows a significant increase of the power and flexibility of nanoanalytical electron microscopy
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