Development of high-vacuum equipment for EM specimen preparation

1992 ◽  
Vol 50 (2) ◽  
pp. 1082-1083
Author(s):  
Richard A. Denton
Keyword(s):  
Electron Microscopy ◽  
High Vacuum ◽  
The Other ◽  
Specimen Preparation ◽  
Vacuum Equipment ◽  
Optical Film ◽  
Diffusion Pump ◽  
Shadow Casting ◽  
Mechanical Pump ◽  
The U.S

High-vacuum techniques made electron microscopy possible. In the 1930s vacuum evaporators with glass or metal chambers, diffusion pumps and oil sealed mechanical pumps were used in Europe and the U.S. The earliest systems used mercury pumps with liquid air traps. Oil diffusion pumps were manufactured in the U.S. by D.P.I. from glass or metal. In 1940 the first RCA TEM went into production as the EMB. First shadow casting in the U.S. was by Williams and Wycoff in 1944 and in Europe by Műller in 1942. Due to war secrecy, neither knew about the other. In 1944 RCA built the first production evaporator for EM under the direction of Bob Picard. The system had an 18" dia. glass bell jar and a metal baseplate with an oil diffusion pump backed by a Cenco Hypervac 20 mechanical pump. In 1948 Optical Film Engineering designed a 12" dia. bell jar evaporator for EM. This SC-3 employed a Welch 5 cfm mechanical pump and a 3" diffusion pump. Carbon evaporation for substrates or replicas was invented by D.E. Bradley in England and published in 1954.

High Pressure Freezing has Come of Age - but is it Mature?

1999 ◽  
Vol 5 (S2) ◽  
pp. 426-427
Author(s):  
Kent McDonald
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Cell Types ◽  
Appropriate Technology ◽  
The Other ◽  
Current Status ◽  
Specimen Preparation ◽  
High Pressure Freezing ◽  
Upper Midwest ◽  
The U.S

It should be no secret by now that ultrarapid freezing is a superior method of specimen preparation for many biological EM projects, and that high pressure freezing is the most versatile of the freezing methods. While cryopreservation is not necessary for all EM studies, it is the method of choice for high resolution work and where “fixation artifacts”, such as distorted membranes, or extraction of the cytosol is a problem. It is true that the machines are expensive, and not always immediately available, but for some questions it is the appropriate technology to use. In the U.S., there are machines available for general use in the far West (Berkeley, CA), the upper Midwest (Madision, WI and Minneapolis, MN), and in the Northeast (Albany, NY). For locations of any of the other 8 machines around the country, interested users can call Technotrade, International at (603) 622-5011.Current Status of High Pressure Freezing: A decade ago, Studer et al. wrote an article entitled: “High Pressure Freezing Comes of Age” that illustrated how high pressure freezing (HPF) had become a proven technology, useful for preserving ultrastructure with unmatched fidelity in cell types that had previously been difficult to fix well for electron microscopy (EM).

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

A method to study the effect of chemical dissolution on the morphology of soil clay

Clay Minerals ◽  
1997 ◽  
Vol 32 (2) ◽  
pp. 315-318
Author(s):  
M. Hagiwara
Keyword(s):  
Electron Microscopy ◽  
Infrared Spectroscopy ◽  
Inorganic Material ◽  
Morphological Changes ◽  
The Other ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Chemical Dissolution ◽  
Soil Clays ◽  
Soil Clay

Soil clays contain a relatively large amount of disordered inorganic material. Chemical dissolution has been used for the removal of this material (Jackson, 1956; Hashimoto & Jackson, 1960; Follett et al, 1965 a,b; Wada & Greenland, 1970). On the other hand, Farmer et al. (1977) claimed that dissolution of allophane and imogolite with hot 5% Na2CO3 for periods of 2-100 h led to new phases which could be distinguished from the starting material by infrared spectroscopy. It is clear, therefore, that chemical dissolution can alter soil clays. This note suggests an electron microscopy specimen preparation technique to study the morphological changes. Collodion films containing densely arranged minute hollows are used for specimen supports.

Ultra-high-vacuum, high-resolution Transmission Electron Microscopy at 400 kV

1986 ◽  
Vol 44 ◽  
pp. 606-609
Author(s):  
F. A. Ponce ◽  
S. Suzuki ◽  
H. Kobayashi ◽  
Y. Ishibashi ◽  
Y. Ishida ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Vacuum ◽  
Milling Process ◽  
Electron Bombardment ◽  
Ultra High Vacuum ◽  
Specimen Preparation ◽  
Ion Milling ◽  
Transmission Electron ◽  
Preparation Stage ◽  
Resolution Imaging

Electron microscopy in an ultra high vacuum (UHV) environment is a very desirable capability for the study of surfaces and for near-atomic-resolution imaging. The existence of amorphous layers on the surface of the sample generally prevents the direct observation of the free surface structure and limits the degree of resolution in the transmission electron microscope (TEM). In conventional TEM, these amorphous layers are often of organic nature originating from the electron bombardment of hydrocarbons in the vicinity of the sample. They can in part also be contaminants which develop during the specimen preparation and transport stages. In the specimen preparation stage, contamination can occur due to backsputtering during the ion milling process. In addition, oxide layers develop from contact to air during transport to the TEM. In order to avoid these amorphous overlayers it is necessary: i) to improve the vacuum of the instrument, thus the need for ultra high vacuum; and ii) to be able to clean the sample and transfer it to the column of the instrument without breaking the vacuum around the sample.

scholarly journals History of High Vacuum and Critical Point Equipment used in EM Specimen Preparation

1993 ◽  
Vol 1 (7) ◽  
pp. 3-3
Author(s):  
Richard A. Denton
Keyword(s):  
United States ◽  
Electron Microscope ◽  
High Vacuum ◽  
Mean Free Path ◽  
The United States ◽  
Specimen Preparation ◽  
Vacuum Technology ◽  
Diffusion Pump ◽  
History Of ◽  
The Mean

The electron microscope was only possible with the development of high vacuum technology. Mechanical pumps were available early in this century, and Gaede in Germany developed the mercury pump called a “condensation pump” during WWI and in the 1920's. In 1928, Burch in England found that a low vapor pressure oil would work in a mercury pump and the oil diffusion pump was born. They were made by DPI in Rochester, Metropolitan Vickers in England, and Leyboid in Germany. Other oils became available and in the mid-30's, vacuum evaporators were in laboratory use in England, Germany and the United States.In the 1930's and 40's, the aim was to produce vacuum of 10-4 - 10-5 mm Hg where the mean free path was two feet or more and atoms, molecules and electrons could move this distance with little obstruction. In those days, we were all very happy to get 10-4 - 10-5 without worrying much as to what gas was left.

scholarly journals A Versatile and Affordable Plunge Freezing Instrument for Preparing Frozen Hydrated Specimens for Cryo Transmission Electron Microscopy (CryoEM)

2009 ◽  
Vol 17 (2) ◽  
pp. 14-17 ◽  
Author(s):  
Linda Melanson
Keyword(s):  
Electron Microscopy ◽  
High Vacuum ◽  
Specimen Preparation ◽  
Macromolecular Assemblies ◽  
Preservation Method ◽  
Transmission Electron ◽  
Structural Details ◽  
Soft Polymer ◽  
2D Crystals ◽  
Preparation Techniques

CryoEM is a powerful tool in the arsenal of structural biologists and soft polymer chemists. Hydrated specimens require a preservation method that will counteract the effects of the electron beam and the high vacuum environment of the electron microscope. Classical specimen preparation techniques using chemical fixatives are not able to capture the native structure of the once hydrated specimen perfectly. In contrast to classical methods for preserving specimens for electron microscopy, rapid freezing of radiation-sensitive specimens such as dispersed biological macromolecular assemblies, 2D crystals, and colloids allows the structural details of the specimen to be captured in their essentially native state to near atomic resolution.

scholarly journals History of High Vacuum and Critical Point Equipment used in EM Specimen Preparation

1993 ◽  
Vol 1 (8) ◽  
pp. 10-11
Author(s):  
Richard A. Denton
Keyword(s):  
New York ◽  
High Pressure ◽  
Critical Point ◽  
High Vacuum ◽  
Specimen Preparation ◽  
New York University ◽  
Vacuum Equipment ◽  
Critical Point Drying ◽  
History Of ◽  
Opening And Closing

An interesting sidelight of building our own 3″ diffusion pumps is that as we built ever larger vacuum equipment, larger pumps were required. Motivated by our success with the 3″ pump, we gradually built a series of larger pumps going up one size at a time to 10″ diameter.Critical point drying was invented by Tom Anderson and described in his fine paper in 1952. He was a bit ahead of his time as the widespread use of the technique was not until the arrival of the SEM in about 1970.I became involved in critical point drying when Dr. Gennaro of New York University asked if I could make him a unit.. He sent me a copy of Tom's original paper and we visited Tom's lab for a demonstration.With Tom's dryer, the chamber opening and closing involved a high pressure threaded seal. Fortunately, he had working with him a man big enough to be a NHL defensive end who manhandled a three foot wrench to seal and unseal the chamber.

scholarly journals Freezing Techniques: History, Comparisons, and Applications

2008 ◽  
Vol 16 (5) ◽  
pp. 12-17 ◽  
Author(s):  
Bill Graham ◽  
Jotham R. Austin ◽  
Andres Kaech ◽  
John E. Heuser
Keyword(s):  
Electron Microscopy ◽  
Osmium Tetroxide ◽  
Basic Problem ◽  
High Vacuum ◽  
Harsh Environment ◽  
Specimen Preparation ◽  
Biological Processes ◽  
Thin Sectioning ◽  
The Cost ◽  
Preparation Techniques

Specimen preparation techniques have evolved hand in hand with microscopy since the first microscopes. Since the introduction of the first Electron Microscope (EM) in the 1930’s, the basic problem with biological electron microscopy has been to preserve the structure of soft condensed, hydrated matter (e.g. tissues, cells, proteins, etc.) so that they can be viewed in the harsh environment of the electron microscope's high vacuum and ionizing radiation. For this, cells must be “fixed” with chemical cross-linkers, commonly glutaraldehyde, formaldehyde or some combination of both, stained with heavy metals (osmium tetroxide that provides contrast of biological components), dehydrated with an organic solvent, and infiltrated with a resin for eventual thin-sectioning. Only then can it be viewed with the EM. Such treatment with chemical fixatives and stains remains the standard approaches to arrest biological processes in cells or tissues, but at the cost of introducing clearly recognizable artifacts.

THE EFFECT OF INCIDENT ATOMIC VELOCITY ON THE STRUCTURE OF EVAPORATED SILVER FILMS

1956 ◽  
Vol 34 (8) ◽  
pp. 731-736 ◽  
Author(s):  
R. A. Aziz ◽  
G. D. Scott
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
High Vacuum ◽  
The Other ◽  
Qualitative Explanation ◽  
Nitrogen Gas ◽  
Silver Films ◽  
Resistivity Measurements

The influence of the incident atomic velocity on the structure of evaporated films has been studied for silver films in the thickness range from 50 to 500 Å. The thermal velocities of the evaporated atoms were reduced (i) by "reflection" from a teflon surface at room temperature, and (ii) by "diffusion" through nitrogen gas at 3.0 μ. Films formed by these two methods are compared with "normal" high vacuum films for the same rates of deposition, which were relatively slow (0.4 to 4 Å of thickness per second). The results of both resistivity measurements and electron microscopy show that "diffusion" films are less aggregated, i.e. more continuous, than "normal" high vacuum films. "Reflected" films have a structure intermediate between the other two. A qualitative explanation of the observed effects is given in terms of the formation of nuclei and the growth of aggregates.

Direct Observation of Heat Exchanger Deposits by Cross Sectioning

1967 ◽  
Vol 25 ◽  
pp. 364-365
Author(s):  
R. W. Anderson ◽  
D. L. Senecal
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Heat Exchanger ◽  
Direct Observation ◽  
Cross Sections ◽  
Preparation Method ◽  
Specimen Preparation ◽  
Flowing Water ◽  
Transmission Electron ◽  
Deposit Layer

A problem was presented to observe the packing densities of deposits of sub-micron corrosion product particles. The deposits were 5-100 mils thick and had formed on the inside surfaces of 3/8 inch diameter Zircaloy-2 heat exchanger tubes. The particles were iron oxides deposited from flowing water and consequently were only weakly bonded. Particular care was required during handling to preserve the original formations of the deposits. The specimen preparation method described below allowed direct observation of cross sections of the deposit layers by transmission electron microscopy.The specimens were short sections of the tubes (about 3 inches long) that were carefully cut from the systems. The insides of the tube sections were first coated with a thin layer of a fluid epoxy resin by dipping. This coating served to impregnate the deposit layer as well as to protect the layer if subsequent handling were required.

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