Contrast and Resolution in Alfresco Microscopy and Thick Specimens

1972 ◽  
Vol 30 ◽  
pp. 570-571
Author(s):  
J. R. Sellar ◽  
J. M. Cowley
Keyword(s):  
Solid Material ◽  
Cell Design ◽  
Current Interest ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Transmission Electron ◽  
Environmental Cell ◽  
Scanning Transmission ◽  
Conventional Transmission Electron Microscope ◽  
Transmission Microscope

Current interest in high voltage electron microscopy, especially in the scanning mode, has prompted the development of a method for determining the contrast and resolution of images of specimens in controlled-atmosphere stages or open to the air, hydrated biological specimens being a good example. Such a method would be of use in the prediction of microscope performance and in the subsequent optimization of environmental cell design for given circumstances of accelerating voltage, cell gas pressure and constitution, and desired resolution.Fig. 1 depicts the alfresco cell of a focussed scanning transmission microscope with a layer of gas L (and possibly a thin window W) between the objective O and specimen T. Using the principle of reciprocity, it may be considered optically equivalent to a conventional transmission electron microscope, if the beams were reversed. The layer of gas or solid material after the specimen in the STEM or before the specimen in TEM has no great effect on resolution or contrast and so is ignored here.

A Comparison of Scanning and Fixed Beam High Voltage Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 6-7
Author(s):  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Scanning Transmission Electron Microscope ◽  
Recording Time ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
High Voltage Supply ◽  
Fixed Beam

Since the theoretical advantage of high voltage microscopy in terms of improved resolution has not yet been achieved, the justification for the building of high voltage microscopes has been mainly the possibility of studying thicker specimens plus the observation of some radiation damage and some relativistic n-beam dynamical diffraction effects. For most of these purposes the scanning mode of transmission electron microscopy has clear advantages.As in the case of the fixed beam instrument (FBI), the limitation on resolution of the scanning transmission electron microscope (STEM) for ideal thin specimens is determined largely by instabilities of the high voltage supply and lens currents and by mechanical instabilities. In this respect the STEM suffers from the disadvantage that the point-by-point recording of the image involves a greater recording time and hence greater sensitivity to long term instabilities.

An Environmental Wet Cell For High Voltage Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 18-19
Author(s):  
N.J. Tighe ◽  
H.M. Flower ◽  
P.R. Swann
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Image Quality ◽  
Inelastic Scattering ◽  
High Voltage ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Environmental Cell ◽  
Water Saturated ◽  
High Temperature Gas

A differentially pumped environmental cell has been developed for use in the AEI EM7 million volt microscope. In the initial version the column of gas traversed by the beam was 5.5mm. This permited inclusion of a tilting hot stage in the cell for investigating high temperature gas-specimen reactions. In order to examine specimens in the wet state it was found that a pressure of approximately 400 torr of water saturated helium was needed around the specimen to prevent dehydration. Inelastic scattering by the water resulted in a sharp loss of image quality. Therefore a modified cell with an ‘airgap’ of only 1.5mm has been constructed. The shorter electron path through the gas permits examination of specimens at the necessary pressure of moist helium; the specimen can still be tilted about the side entry rod axis by ±7°C to obtain stereopairs.

Ultrastructural characteristics of sporidia of Ustilago

1989 ◽  
Vol 47 ◽  
pp. 786-787
Author(s):  
Patricia N. Hackney
Keyword(s):  
Electron Microscope ◽  
Type System ◽  
Tube Formation ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
University Of Wisconsin ◽  
Transmission Electron ◽  
Ustilago Hordei ◽  
Silene Alba ◽  
The University

Ustilago hordei and Ustilago violacea are yeast-like basidiomycete pathogens ofHordeum vulgare and Silene alba respectively. The mating type system in both species of Ustilago is bipolar, with alleles, A,a, (U.hordei) and a1, a2 (U.violacea) at a single locus. Haploid sporidia maintain the asexual phase by budding, while the sexual phase is initiated by conjugation tube formation between the mating types during budding and conjugation.For observation of budding, sporidia were prepared by culturing the four types on YEG (yeast extract glucose) broth for 24 hours. After centrifugation at 5000g cells were either left unmated or mated in a1/a2,A/a combinations. The sporidia were then mixed 1:1 with 4% agar and the resulting 1mm cubes fixed in 8% gluteraldehyde and post fixed in osmium tetroxide. After dehydration and embedding cubes were thin sectioned with a LKB ultratome and photographed in a Zeiss 9s transmission electron microscope or in an AE1 electron microscope of MK11 1MEV at the High Voltage Electron Microscopy Center of the University of Wisconsin-Madison.

Development of High Accuracy Automatic Magnification Calibration Function for Scanning Transmission Electron Microscope

2005 ◽  
Author(s):  
Hiromi Inada ◽  
D. Terauchi ◽  
A. Takane ◽  
S. Aizawa ◽  
H. Tanaka ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Semiconductor Device ◽  
Gate Oxide ◽  
Scanning Transmission Electron Microscope ◽  
High Accuracy ◽  
Silicon Single Crystal ◽  
Calibration Function ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Transmission Microscope

Abstract In the field of semiconductor development and failure analysis, metrology of layers such as gate oxide layer is one of the important analysis due to determine semiconductor itself characteristics. The number of requirements of metrology is increasing by using both scanning and transmission electron microscopy. High accurate metrology depends on accuracy of magnification of electron microscope. We developed accurate magnification calibration for scanning transmission microscope. This method is carried out by using micro scale specimen and silicon single crystal lattice fringe images. We achieved absolute magnification error of less than 2% for all magnification. This microscope provides high accuracy metrology for semiconductor device. We describe an automatic magnification calibration function for the high magnification range required to accurately measure features from a few to tens of nm in size.

scholarly journals Ionic Nanocomplexes of Hyaluronic Acid and Polyarginine to Form Solid Materials: A Green Methodology to Obtain Sponges with Biomedical Potential

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 944
Author(s):  
María Gabriela Villamizar-Sarmiento ◽  
Ignacio Moreno-Villoslada ◽  
Samuel Martínez ◽  
Annesi Giacaman ◽  
Victor Miranda ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
High Capacity ◽  
Solid Material ◽  
Fibroblast Cell ◽  
High Porosity ◽  
Design Development ◽  
Solid Materials ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Scanning Transmission

We report on the design, development, characterization, and a preliminary cellular evaluation of a novel solid material. This material is composed of low-molecular-weight hyaluronic acid (LMWHA) and polyarginine (PArg), which generate aqueous ionic nanocomplexes (INC) that are then freeze-dried to create the final product. Different ratios of LMWHA/PArg were selected to elaborate INC, the size and zeta potential of which ranged from 100 to 200 nm and +25 to −43 mV, respectively. Turbidimetry and nanoparticle concentration analyses demonstrated the high capacity of the INC to interact with increasing concentrations of LMWHA, improving the yield of production of the nanostructures. Interestingly, once the selected formulations of INC were freeze-dried, only those comprising a larger excess of LMWHA could form reproducible sponge formulations, as seen with the naked eye. This optical behavior was consistent with the scanning transmission electron microscopy (STEM) images, which showed a tendency of the particles to agglomerate when an excess of LMWHA was present. Mechanical characterization evidenced low stiffness in the materials, attributed to the low density and high porosity. A preliminary cellular evaluation in a fibroblast cell line (RMF-EG) evidenced the concentration range where swollen formulations did not affect cell proliferation (93–464 µM) at 24, 48, or 72 h. Considering that the reproducible sponge formulations were elaborated following inexpensive and non-contaminant methods and comprised bioactive components, we postulate them with potential for biomedical purposes. Additionally, this systematic study provides important information to design reproducible porous solid materials using ionic nanocomplexes.

scholarly journals Some Current and Future Trends of High Voltage Transmission Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 2-3
Author(s):  
Gareth Thomas
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Materials Science ◽  
Future Trends ◽  
Light Elements ◽  
Special Effects ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Transmission Electron ◽  
Resolution Level

The Optimum Voltages for Electron Microscopy – The advantages of high voltage electron microscopy are now well established, and many applications, such as use of environmental cells both in metallurgy and biology, are now possible. However recent experiments at Toulouse indicate that except for light elements, there is no appreciable gain in transmission for a given resolution level as the energy is increased above 1 MeV (see Fig. 1). These results are not as optimistic as theory might indicate. Special effects such as critical voltages above 1 MeV are of interest, but knock-on radiation damage imposes limitations on many applications. Thus it would appear that 1 MeV is a reasonable upper limit for most applications in materials science.

Observations on Developing Blood Vessels in Rat Spinal Cord—A High Voltage Electron Microscopy Study

1974 ◽  
Vol 32 ◽  
pp. 66-67
Author(s):  
Richard S. Hannah
Keyword(s):  
Electron Microscopy ◽  
Spinal Cord ◽  
High Voltage ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
High Voltage Electron Microscopy ◽  
Thin Sections ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Transmission Electron

The formation of junctional complexes between endothelial cell processes was examined in rat spinal cords, from age birth to six weeks. Segments of spinal cord were removed from the region of the cervical enlargement and fixed. For comparative purposes, animals from each time group were subdivided into groups, fixed by either immersion or perfusion with an aldehyde combination in sodium cacodylate buffer and embedded in Araldite. Thin sections were examined by conventional transmission electron microscopy. Thick sections (0.5μ - 1.0μ) were stained with uranyl magnesium acetate for four hours at 60°C and lead citrate for 30 mins. and examined in the AEI Mark II High Voltage Electron Microscope.

An observation of fresh biological samples by high voltage electron microscopy

1978 ◽  
Vol 36 (2) ◽  
pp. 16-17
Author(s):  
Paulo H. Hashimoto ◽  
Takahiro Gotow ◽  
Hiroshi Takagi ◽  
Masao Komatsu ◽  
Hiroshi Fujita
Keyword(s):  
Cross Section ◽  
Biological Samples ◽  
Silicon Oxide ◽  
Platelet Rich Plasma ◽  
Electric Heater ◽  
Video Tape ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Environmental Cell ◽  
Acceleration Voltage

An environmental cell for a 3 MV-class electron microscope has been developed, and applied mostly to metallurgical subjects. We have modified it slightly, and applied it to some fresh biological samples.A cross section of the environmental cell and the capsule meshes is schematically drawn in Fig. 1. The two 400 x 100 mesh grids with respective supporting collodion films were coated with evaporated silicon oxide, and attached together with the 400 mesh bars of one at right angles to the 400 mesh bars of the other. In some cases the lower grid was additionally coated with evaporated gold. The grids together with holders A, B, and C were cooled by electric heater controled conduction from a liquid nitrogen container. A platelet-rich plasma of the r a t, and a suspension of Proteus mirabilis were used as fresh biological samples. They were introduced into the environmental cell by a gentle sucking through the pipe (Fig. 1) followed by a continuous ventilation of the atmospheric air. Then the cell was cooled to about -35°C, and the electron beam was emitted with an acceleration voltage of 2 MV. The intensity of the beam was kept as low as possible, and the image could be detected only on a TV screen. The results were recorded on a video tape.

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