Phase refinement of copper perchlorophthalocyanine from a 0.23 nm-resolution electron micrograph using the Sayre equation

1994 ◽  
Vol 52 ◽  
pp. 100-101
Author(s):  
Douglas L. Dorset ◽  
Sophie Kopp ◽  
John R. Fryer ◽  
William F. Tivol ◽  
James N. Turner
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Primary Source ◽  
Direct Methods ◽  
Ccd Camera ◽  
Basis Set ◽  
X Rays ◽  
Contrast Transfer Function ◽  
Lattice Images ◽  
Integrated Intensities

The use of direct methods of phasing for electron diffraction (ED) presents opportunities which cannot be matched with x-ray diffraction. High-resolution lattice images of thin crystals obtained on the electron microscope can provide crystallographic phases after image averaging and correction for the contrast transfer function--a procedure which has no analog for x-rays. This procedure has been used for protein crystallography, where such images are often the primary source for phase information.The method has also been used in the analysis of organic molecules.A high resolution (0.23 nm) electron microscope image of epitaxially oriented copper perchlorophthalocyanine obtained at 500 kV (Fig. 1) was used to provide a basis set of 39 phases for refinement in conjunction with a set of ED amplitudes obtained at 1200 kV (Fig 2). Portions of the image were digitized with a CCD camera and a frame-grabber and analyzed using the CRISP software package. The ED pattern was scanned using a Joyce-Loebl Mk. IIIC flatbed microdensitometer to produce integrated intensities, to which no Lorenz correction was applied.

High Resolution Lattice Images of G.P.Zones and Solute Clusters in Al-Cu and Cu-Be Alloys

1982 ◽  
Vol 21 ◽  
Author(s):  
H. Yoshida ◽  
H. Hashimoto ◽  
Y. Yokota ◽  
M. Takeda
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Atomic Structures ◽  
Resolution Electron ◽  
Microscope Images ◽  
Lattice Images ◽  
Lattice Planes

ABSTRACTAtomic structures of G.P. zones and solute clusters in Al-Cu and Cu-Be alloys are studied by the atom resolution electron microscope images. The images of plate-like G.P. zones appear as dotted images with various brightnesses along (200) lattice planes. The solute clusters are also observed along (111) lattice planes.

The Use of Phase and Amplitude Information of Reconstructed Exit Waves

1997 ◽  
Vol 3 (S2) ◽  
pp. 1029-1030
Author(s):  
H.W. Zandbergen
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
High Resolution ◽  
Field Emission ◽  
Software Package ◽  
Dynamic Range ◽  
Ccd Camera ◽  
Phase Object ◽  
High Resolution Images

Exit waves can be reconstructed from through focus series of HREM images or by off-axis holography [1]. We have applied the through focus method to reconstruct exit waves, using algorithms developed by Van Dyck and Coene [2]. Electron microscopy was performed with a Philips CM30ST electron microscope with a field emission gun operated at 300 kV. The high resolution images were recorded using a Tietz software package and a 1024x1024 pixel Photometrix CCD camera having a dynamic range of 12 bits. The reconstructions were done using 15-20 images with focus increments of 5.2 nm. The resulting exit waves were corrected posteriorly for the three fold astigmatism.The exit wave is complex; consequently it contains phase and amplitude. Since in the very thin regions the specimen acts as a thin phase object, such a thin area will show little contrast, an example of which is shown in Figure 1.

Determination of the defocus value of micrographs of ice-embedded specimen without carbon support film

1993 ◽  
Vol 51 ◽  
pp. 560-561
Author(s):  
Z. Hong Zhou
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Transfer Function ◽  
Carbon Support ◽  
Objective Lens ◽  
Contrast Transfer Function ◽  
X Ray ◽  
Spatial Frequencies ◽  
High Resolution Reconstruction

It is well recognized that the contrast transfer function (CTF) of an electron microscope modulates the image contrast The effects of this CTF are to reverse the sign of the phases and to alter the amplitudes at different spatial frequencies. These changes are dependent on the defocus of the objective lens in a given microscope setting. Therefore, it is necessary to determine the defocus experimentally in order to correct the phase reversal and the amplitudes due to the CTF for attaining a high resolution reconstruction. The most straightforward way of determining the defocus value is to determine the positions of the Thon rings in the CTF by optical or computed transforms. In a crystalline specimen, the defocus value of an image can be refined against the electron diffraction amplitude. For specimen of which the x-ray structure is known, one can also use the x-ray structure factor to determine the CTF parameters.

Lattice Images of Biological and Synthetic Apatites

1974 ◽  
Vol 32 ◽  
pp. 74-75
Author(s):  
M. Spector
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Atherosclerotic Plaque ◽  
Transmission Electron Microscope ◽  
Calcium Phosphates ◽  
Transmission Electron ◽  
Lattice Images ◽  
Synthetic Hydroxyapatite ◽  
Calcified Tissues

Lattice images obtained from high resolution transmission electron microscope studies of human calcified tissues and synthetic calcium phosphates were utilized to correlate the structures of biological and synthetic apatites. Lattice spacings appearing in the Fourier images of crystallites in bone and calcified atherosclerotic plaque were comparable to the spacings seen in lattice images of synthetic hydroxyapatite crystallites.

High-Resolution Lattice Images of Superconductors Observed at 4.2 K

1990 ◽  
Vol 48 (1) ◽  
pp. 16-17
Author(s):  
Hiroyuki Yoshida ◽  
Yasuhiro Yokota ◽  
Hatsujiro Hashimoto ◽  
Masashi Iwatsuki ◽  
Yoshiyasu Harada
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Oxide Superconductors ◽  
Atomic Structures ◽  
Cryo Electron Microscopy ◽  
Resolution Observation ◽  
Lattice Images ◽  
High Resolution Images

High resolution cryo electron microscopy has been applied to the observation of microstructures of A15-type and oxide superconductors. In order to study the relation between atomic structures and superconducting properties the atomic resolution observation at cryogenic temperatures seems to be important, especially for high Tc superconductors with perovskite structure whose coherent length along c axis is closed to the lattice spacings. High resolution lattice images were obtained using a superconducting cryo electron microscope JEM-2000 SCM operated at 160 KV. The microscope enable the specimen to keep at 4.2 K without thermal drift and vibration under ultra high vacuum. The magnetic field at the specimen position is 1.4 T when the electron microscope is operated at 160 kV.Figure 1 shows a high resolution image of the electropolished thin crystal of Nb3(A10.77Ge0.23) (Tc=19 K). In the both sides of the grain boundary the (100) lattice fringes with 0.52 nm spacing of the A15 structure are clearly resolved. The high resolution images obtained for Nb3Sn superconductors gave the bright dots at the position of Nb atom chains along 001 direction as confirmed by the image contrast calculation.

Texture details in experimental lattice images from a monolamellar paraffin crystal

1986 ◽  
Vol 44 ◽  
pp. 182-183
Author(s):  
D. L. Dorset ◽  
F. Zemlin ◽  
E. Reuber ◽  
E. Beckmann ◽  
E. Zeitler
Keyword(s):  
Crystal Structure ◽  
Electron Microscope ◽  
Phase Contrast ◽  
Objective Lens ◽  
Direct Visualization ◽  
Routine Procedure ◽  
Contrast Transfer Function ◽  
Lattice Images ◽  
Similar Images ◽  
Beam Damage

The direct visualization of crystal structure at "molecular" (ca 3Å) resolution has become a routine procedure in electron microscopy in the last few years for organic materials which are resistant to electron beam damage by virtue of π-electron derealization or electrical conductivity. More recently, similar images from an aliphatic material, i.e. the paraffin n-tetratetracontane, were published based on work with an electron microscope equipped with a He-cooled superconducting objective lens. Correlation-averaged electron images at 2.5A resolution were shown to correspond well to a theoretical image based on a multislice calculation for the known crystal structure and produced at the phase contrast transfer function of the electron microscope objective lens for the defocus value used in the experiment.

CCD detectors in high-resolution biological electron microscopy

2000 ◽  
Vol 33 (1) ◽  
pp. 1-27 ◽  
Author(s):  
A. R. Faruqi ◽  
Sriram Subramaniam
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
High Resolution ◽  
Structural Information ◽  
Low Noise ◽  
Photographic Film ◽  
X Rays ◽  
Fibre Optics ◽  
Ccd Detector ◽  
Ccd Detectors

1. Introduction 11.1 The ‘band gap’ in silicon 22. Principles of CCD detector operation 32.1 Direct detection 32.2 Electron energy conversion into light 42.3 Optical coupling: lens or fibre optics? 62.4 Readout speed and comparison with film 83. Practical considerations for electron microscopic applications 93.1 Sources of noise 93.1.1 Dark current noise 93.1.2 Readout noise 93.1.3 Spurious events due to X-rays or cosmic rays 103.2 Efficiency of detection 113.3 Spatial resolution and modulation transfer function 123.4 Interface to electron microscope 143.5 Electron diffraction applications 154. Prospects for high-resolution imaging with CCD detectors 185. Alternative technologies for electronic detection 235.1 Image plates 235.2 Hybrid pixel detectors 246. References 26During the past decade charge-coupled device (CCD) detectors have increasingly become the preferred choice of medium for recording data in the electron microscope. The CCD detector itself can be likened to a new type of television camera with superior properties, which makes it an ideal detector for recording very low exposure images. The success of CCD detectors for electron microscopy, however, also relies on a number of other factors, which include its fast response, low noise electronics, the ease of interfacing them to the electron microscope, and the improvements in computing that have made possible the storage and processing of large images.CCD detectors have already begun to be routinely used in a number of important biological applications such as tomography of cellular organelles (reviewed by Baumeister, 1999), where the resolution requirements are relatively modest. However, in most high- resolution microscopic applications, especially where the goal of the microscopy is to obtain structural information at near-atomic resolution, photographic film has continued to remain the medium of choice. With the increasing interest and demand for high-throughput structure determination of important macromolecular assemblies, it is clearly important to have tools for electronic data collection that bypass the slow and tedious process of processing images recorded on photographic film.In this review, we present an analysis of the potential of CCD-based detectors to fully replace photographic film for high-resolution electron crystallographic applications.

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