New Design for a Differentially Pumped Hydration Chamber for a Siemens IA

1971 ◽  
Vol 29 ◽  
pp. 44-45
Author(s):  
R. C. Moretz ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Electron Microscopy ◽  
Water Vapor ◽  
Electron Diffraction ◽  
Water Vapor Pressure ◽  
Biological Materials ◽  
Thin Membrane ◽  
Reliable System ◽  
System A ◽  
Water Films ◽  
Aperture Opening

Electron microscopy and diffraction of biological materials in the hydrated state requires the construction of a chamber in which the water vapor pressure can be maintained at saturation for a given specimen temperature, while minimally affecting the normal vacuum of the remainder of the microscope column. Initial studies with chambers closed by thin membrane windows showed that at the film thicknesses required for electron diffraction at 100 KV the window failure rate was too high to give a reliable system. A single stage, differentially pumped specimen hydration chamber was constructed, consisting of two apertures (70-100μ), which eliminated the necessity of thin membrane windows. This system was used to obtain electron diffraction and electron microscopy of water droplets and thin water films. However, a period of dehydration occurred during initial pumping of the microscope column. Although rehydration occurred within five minutes, biological materials were irreversibly damaged. Another limitation of this system was that the specimen grid was clamped between the apertures, thus limiting the yield of view to the aperture opening.

What Improvement in Electron Microscopy and Electron Diffraction Results from Using Wet Biological Materials?

1975 ◽  
Vol 33 ◽  
pp. 296-297
Author(s):  
Donald F. Parsons
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Vapor Pressure ◽  
Biological Materials ◽  
Living Cells ◽  
Protein Crystals ◽  
Sensitive Test ◽  
Pressure Drops ◽  
Environmental Chambers ◽  
Diffraction Patterns

It is now possible to work with wet materials by using environmental chambers. Biologists would like to evaluate the advantages of this development. The unknowns are: (a) the difficulty of constructing the equipment and it's commercial availability, (b) the problems in preparing wet specimens and viewing them, (c) the resolution and contrast available (d) the difficulties peculiar to wet specimens and (e) the advantages of wet over frozen specimens. Finally, there remains the question - can living cells be examined? This talk will attempt to answer these questions. Routine wet electron microscopy has followed the introduction of differentially pumped chambers in place of film sealed chambers. Electron diffraction patterns of wet protein crystals (Fig. 1) provide a sensitive test of the performance of hydration chambers. If the vapor pressure drops more than 10% below saturation the pattern disappears due to the disorganization of drying.

Complex Superstructures Resulting from Compositional Modulation and Octahedral Tilt Twinning in AA′BB′O6 Doubly Cation Ordered Perovskites

2013 ◽  
Vol 2013 (CICMT) ◽  
pp. 000006-000013
Author(s):  
Graham King ◽  
Susana Garcia-Martin ◽  
Esteban Urones-Garrote ◽  
Gwilherm Nenert ◽  
Patrick M. Woodward
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Neutron Powder Diffraction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Compositional Modulation ◽  
System A ◽  
Transmission Electron

The ordering of cations within the perovskite structure can have a profound effect on the physical properties. A number of AA′BB′O6 perovskite phases which have both a rock salt ordering of the B/B′ cations and a layered ordering of the A/A′ cations have recently been prepared and studied. In some of these compositions complex nanoscale superstructure formation has been observed. These superstructures are the result of compositional modulations involving the occupancies of the A and A′ cations and are accompanied by a twinning of the octahedral tilt system. A wide variety of patterns are observed, such as 1-dimensional stripes or 2-dimensional chessboards which can have periodicities which are either commensurate or incommensurate with the underlying subcell. These superstructures cannot be easily detected by powder X-ray diffraction but have been observed using a combination of high resolution transmission electron microscopy, electron diffraction, and neutron powder diffraction. The factors which determine the dimensionality and periodicity of the superstructures are discussed and compared with the closely related Li based perovskite systems.

Electron Microscopy of Frozen, Hydrated Biological Specimens

1975 ◽  
Vol 33 ◽  
pp. 300-301
Author(s):  
Kenneth A. Taylor
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Liquid Nitrogen ◽  
Electron Irradiation ◽  
Biological Material ◽  
Biological Materials ◽  
Composite Support ◽  
Resolution Electron ◽  
Diffraction Patterns

Recently, a method has been developed in this laboratory for maintaining the hydration of biological materials by using frozen specimens. With this technique specimens are prepared using folding grids on which are mounted composite support films of carbon and SiO. The technique essentially embeds the biological material in a thin aqueous film between the two supporting films. The sandwiched specimens are then frozen directly in liquid nitrogen. While it was thought at first that freezing directly in liquid nitrogen might cause disordering of periodic or crystalline biological specimens, this has been shown not to be the case. High resolution electron diffraction patterns have been obtained from frozen unstained catalase crystals.The microscopy of frozen specimens depends on their resistance to damage by electron irradiation. The critical exposure for fading of the electron diffraction intensities from frozen unstained catalase crystals has been measured.

Studies of Oxide Formation on Copper Thin Films by Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 316-317
Author(s):  
G. G. Hembree ◽  
M. A. Otooni ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Crystal Surface ◽  
Crystal Defects ◽  
Diffraction Reflection ◽  
Reaction Products ◽  
Intermediate Energies ◽  
Crystal Films ◽  
Reflection Electron Microscopy

The formation of oxide structures on single crystal films of metals has been investigated using the REMEDIE system (for Reflection Electron Microscopy and Electron Diffraction at Intermediate Energies) (1). Using this instrument scanning images can be obtained with a 5 to 15keV incident electron beam by collecting either secondary or diffracted electrons from the crystal surface (2). It is particularly suited to studies of the present sort where the surface reactions are strongly related to surface morphology and crystal defects and the growth of reaction products is inhomogeneous and not adequately described in terms of a single parameter. Observation of the samples has also been made by reflection electron diffraction, reflection electron microscopy and replication techniques in a JEM-100B electron microscope.A thin single crystal film of copper, epitaxially grown on NaCl of (100) orientation, was repositioned on a large copper single crystal of (111) orientation.

Dynamical Scattering in Crystalline Biological Specimens. I. Criteria of Validity for Scattering Approximations

1975 ◽  
Vol 33 ◽  
pp. 192-193
Author(s):  
Robert M. Glaeser ◽  
Bing K. Jap
Keyword(s):  
Biological Sciences ◽  
Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Born Approximation ◽  
Materials Science ◽  
Image Data ◽  
Dynamical Effect ◽  
Crystallographic Structure ◽  
Electron Microscope Image

The dynamical scattering effect, which can be described as the failure of the first Born approximation, is perhaps the most important factor that has prevented the widespread use of electron diffraction intensities for crystallographic structure determination. It would seem to be quite certain that dynamical effects will also interfere with structure analysis based upon electron microscope image data, whenever the dynamical effect seriously perturbs the diffracted wave. While it is normally taken for granted that the dynamical effect must be taken into consideration in materials science applications of electron microscopy, very little attention has been given to this problem in the biological sciences.

Enhanced information from biological materials through technological improvements in cryo-electron microscopy

1992 ◽  
Vol 50 (1) ◽  
pp. 788-789
Author(s):  
Marc J.C. de Jong ◽  
Wim M. Busing ◽  
Max T. Otten
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Biological Materials ◽  
Electron Crystallography ◽  
Cryo Electron Microscopy ◽  
Transmission Electron ◽  
The Many ◽  
Technological Improvements ◽  
Beam Damage

Biological materials damage rapidly in the electron beam, limiting the amount of information that can be obtained in the transmission electron microscope. The discovery that observation at cryo temperatures strongly reduces beam damage (in addition to making it unnecessaiy to use chemical fixatives, dehydration agents and stains, which introduce artefacts) has given an important step forward to preserving the ‘live’ situation and makes it possible to study the relation between function, chemical composition and morphology.Among the many cryo-applications, the most challenging is perhaps the determination of the atomic structure. Henderson and co-workers were able to determine the structure of the purple membrane by electron crystallography, providing an understanding of the membrane's working as a proton pump. As far as understood at present, the main stumbling block in achieving high resolution appears to be a random movement of atoms or molecules in the specimen within a fraction of a second after exposure to the electron beam, which destroys the highest-resolution detail sought.

Application of ruthenium red/osmium tetroxide to bacteria, plant and animal tissue

1986 ◽  
Vol 44 ◽  
pp. 54-55
Author(s):  
R. L. Grayson ◽  
N. A. Rechcigl
Keyword(s):  
Electron Microscopy ◽  
Electron Density ◽  
Osmium Tetroxide ◽  
Biological Materials ◽  
Ruthenium Red ◽  
Animal Tissue

Ruthenium red (RR), an inorganic dye was found to be useful in electron microscopy where it can combine with osmium tetroxide (OsO4) to form a complex with attraction toward anionic substances. Although Martinez-Palomo et al. (1969) were one of the first investigators to use RR together with OsO4, our computor search has shown few applications of this combination in the intervening years. The purpose of this paper is to report the results of our investigations utilizing the RR/OsO4 combination to add electron density to various biological materials. The possible mechanisms by which this may come about has been well reviewed by previous investigators (1,3a,3b,4).

Characterization of submicrometer fluid Inclusions in minerals by Analytical/Transmission Electron Microscopy and electron diffraction

1990 ◽  
Vol 48 (4) ◽  
pp. 424-424
Author(s):  
George Guthrie ◽  
David Veblen
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Light Microscopy ◽  
Fluid Inclusions ◽  
Energy Dispersive Spectrometer ◽  
Analytical Transmission Electron Microscopy ◽  
Transmission Electron

The nature of a geologic fluid can often be inferred from fluid-filled cavities (generally <100 μm in size) that are trapped during the growth of a mineral. A variety of techniques enables the fluids and daughter crystals (any solid precipitated from the trapped fluid) to be identified from cavities greater than a few micrometers. Many minerals, however, contain fluid inclusions smaller than a micrometer. Though inclusions this small are difficult or impossible to study by conventional techniques, they are ideally suited for study by analytical/ transmission electron microscopy (A/TEM) and electron diffraction. We have used this technique to study fluid inclusions and daughter crystals in diamond and feldspar.Inclusion-rich samples of diamond and feldspar were ion-thinned to electron transparency and examined with a Philips 420T electron microscope (120 keV) equipped with an EDAX beryllium-windowed energy dispersive spectrometer. Thin edges of the sample were perforated in areas that appeared in light microscopy to be populated densely with inclusions. In a few cases, the perforations were bound polygonal sides to which crystals (structurally and compositionally different from the host mineral) were attached (Figure 1).

Computers and diffraction analysis

1989 ◽  
Vol 47 ◽  
pp. 44-45
Author(s):  
J. A. Eades
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Diffraction Analysis ◽  
Electron Diffraction Analysis ◽  
Image Simulation ◽  
Correct Interpretation ◽  
High Profile ◽  
High Resolution Images ◽  
Image Simulations

For well over two decades computers have played an important role in electron microscopy; they now pervade the whole field - as indeed they do in so many other aspects of our lives. The initial use of computers was mainly for large (as it seemed then) off-line calculations for image simulations; for example, of dislocation images.Image simulation has continued to be one of the most notable uses of computers particularly since it is essential to the correct interpretation of high resolution images. In microanalysis, too, the computer has had a rather high profile. In this case because it has been a necessary part of the equipment delivered by manufacturers. By contrast the use of computers for electron diffraction analysis has been slow to prominence. This is not to say that there has been no activity, quite the contrary; however it has not had such a great impact on the field.

Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

1989 ◽  
Vol 47 ◽  
pp. 462-463
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

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