The Experts below are selected from a list of 2241516 Experts worldwide ranked by ideXlab platform
Ahmed H. Zewail - One of the best experts on this subject based on the ideXlab platform.
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4D cryo-Electron Microscopy of proteins.
Journal of the American Chemical Society, 2013Co-Authors: A.w.p. Fitzpatrick, G. M. Vanacore, Ulrich J. Lorenz, Ahmed H. ZewailAbstract:Cryo-Electron Microscopy is a form of transmission Electron Microscopy that has been used to determine the 3D structure of biological specimens in the hydrated state and with high resolution. We report the development of 4D cryo-Electron Microscopy by integrating the fourth dimension, time, into this powerful technique. From time-resolved diffraction of amyloid fibrils in a thin layer of vitrified water at cryogenic temperatures, we were able to detect picometer movements of protein molecules on a nanosecond time scale. Potential future applications of 4D cryo-Electron Microscopy are numerous, and some are discussed here.
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Scanning ultrafast Electron Microscopy
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Ding-shyue Yang, Omar F. Mohammed, Ahmed H. ZewailAbstract:Progress has been made in the development of four-dimensional ultrafast Electron Microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast Electron Microscopy, the Electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast Electron Microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-Electron mode, for which the pulse contains at most one or a few Electrons, thus achieving imaging without the space-charge effect between Electrons, and still in ten(s) of seconds. For imaging, the secondary Electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered Electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-Electron Microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability.
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four dimensional Electron Microscopy
Science, 2010Co-Authors: Ahmed H. ZewailAbstract:The discovery of the Electron over a century ago and the realization of its dual character have given birth to one of the two most powerful imaging instruments: the Electron microscope. The Electron microscope's ability to resolve three-dimensional (3D) structures on the atomic scale is continuing to affect different fields, including materials science and biology. In this Review, we highlight recent developments and inventions made by introducing the fourth dimension of time in Electron Microscopy. Today, ultrafast Electron Microscopy (4D UEM) enables a resolution that is 10 orders of magnitude better than that of conventional microscopes, which are limited by the video-camera rate of recording. After presenting the central concept involved, that of single-Electron stroboscopic imaging, we discuss prototypical applications, which include the visualization of complex structures when unfolding on different length and time scales. The developed UEM variant techniques are several, and here we illucidate convergent-beam and near-field imaging, as well as tomography and scanning-pulse Microscopy. We conclude with current explorations in imaging of nanomaterials and biostructures and an outlook on possible future directions in space-time, 4D Electron Microscopy.
M. Pan - One of the best experts on this subject based on the ideXlab platform.
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High resolution Electron Microscopy of zeolites
Micron, 1996Co-Authors: M. PanAbstract:Abstract This article reviews the application of high resolution Electron Microscopy techniques to zeolite structural characterization. Examples given in this article include identification of structural intergrowth, stacking faults and framework projection net from high resolution images. Slow-scan CCD (charge-coupled device) cameras, representing the latest advance in Electron Microscopy instrumentation, are briefly introduced. Low-dose, high resolution Electron Microscopy using commercial CCD cameras is discussed. With slow-scan CCD cameras, it is shown that it is possible to directly read off the underlying zeolite structures from experimental high resolution images when suitable image processing techniques are employed. This latest advance greatly enhances the power of high resolution Electron Microscopy techniques in solving unknown zeolite structures.
Ding-shyue Yang - One of the best experts on this subject based on the ideXlab platform.
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Scanning ultrafast Electron Microscopy
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Ding-shyue Yang, Omar F. Mohammed, Ahmed H. ZewailAbstract:Progress has been made in the development of four-dimensional ultrafast Electron Microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast Electron Microscopy, the Electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast Electron Microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-Electron mode, for which the pulse contains at most one or a few Electrons, thus achieving imaging without the space-charge effect between Electrons, and still in ten(s) of seconds. For imaging, the secondary Electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered Electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-Electron Microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability.
Carsten Westphal - One of the best experts on this subject based on the ideXlab platform.
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Photoemission Electron Microscopy and scanning Electron Microscopy of Magnetospirillum magnetotacticum's magnetosome chains.
Analytical chemistry, 2014Co-Authors: C. Keutner, Alex. Von Bohlen, U. Berges, Philipp Espeter, Claus M. Schneider, Carsten WestphalAbstract:Magnetotactic bacteria are of great interdisciplinary interest, since a vast field of applications from magnetic recording media to medical nanorobots is conceivable. A key feature for a further understanding is the detailed knowledge about the magnetosome chain within the bacteria. We report on two preparation procedures suitable for UHV experiments in reflective geometry. Further, we present the results of scanning Electron Microscopy, as well as the first photoemission Electron Microscopy experiments, both accessing the magnetosomes within intact magnetotactic bacteria and compare these to scanning Electron Microscopy data from the literature. From the images, we can clearly identify individual magnetosomes within their chains.
R. Simpson - One of the best experts on this subject based on the ideXlab platform.
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Demonstration of transmission high energy Electron Microscopy
Applied Physics Letters, 2018Co-Authors: Frank E. Merrill, J. Goett, John W. Gibbs, Seth D. Imhoff, Fesseha Mariam, Christopher L. Morris, Levi P. Neukirch, John Perry, D. Poulson, R. SimpsonAbstract:High energy Electrons have been used to investigate an extension of transmission Electron Microscopy. This technique, transmission high energy Electron Microscopy (THEEM), provides two additional capabilities to Electron Microscopy. First, high energy Electrons are more penetrating than low energy Electrons, and thus, they are able to image through thicker samples. Second, the accelerating mode of a radio-frequency linear accelerator provides fast exposures, down to 1 ps, which are ideal for flash radiography, making THEEM well suited to study the evolution of fast material processes under dynamic conditions. Initial investigations with static objects and during material processing have been performed to investigate the capabilities of this technique.High energy Electrons have been used to investigate an extension of transmission Electron Microscopy. This technique, transmission high energy Electron Microscopy (THEEM), provides two additional capabilities to Electron Microscopy. First, high energy Electrons are more penetrating than low energy Electrons, and thus, they are able to image through thicker samples. Second, the accelerating mode of a radio-frequency linear accelerator provides fast exposures, down to 1 ps, which are ideal for flash radiography, making THEEM well suited to study the evolution of fast material processes under dynamic conditions. Initial investigations with static objects and during material processing have been performed to investigate the capabilities of this technique.
