Optimum Detector Arrangements in the Stem for Thick Objects

1976 ◽  
Vol 34 ◽  
pp. 548-549
Author(s):  
H. Rose ◽  
J. Fertig
Keyword(s):  
Signal To Noise Ratio ◽  
Dark Field ◽  
Imaging Method ◽  
Bright Field Image ◽  
Field Mode ◽  
Maximum Information ◽  
Subjective Impression ◽  
Specific Object ◽  
High Resolution Images ◽  
Pass Through

Radiation damage is the main obstacle in achieving high resolution images of biological objects. Therefore it is desirable to indicate that imaging method which yields maximum information about a specific object for a given number N0 of incident electrons. The amount of useful information is determined by the signal to noise ratio. Applying difference techniques the contrast in the STEM can be varied arbitrarily (l). Although the subjective impression of the image quality may be improved by such a procedure the amount of information available will not be changed. Most of the present day STEMs operate in the dark field mode using an annular detector which collects all electrons scattered out of the illumination cone. The corresponding incoherent bright field image is obtained from the electrons which pass through the hole of the dark field detector.

Conformational Transitions in Escherichia coli Ribosomal RNAs as Visualized by Dedicated STEM

1988 ◽  
Vol 46 ◽  
pp. 176-177
Author(s):  
J.S. Wall ◽  
V. Maridiyan ◽  
S. Tumminia ◽  
J. Hairifeld ◽  
M. Boublik
Keyword(s):  
Ionic Strength ◽  
Three Dimensional ◽  
Conformational Transitions ◽  
Dark Field ◽  
Dimensional Structure ◽  
Ribosomal Rnas ◽  
Field Mode ◽  
Freeze Dried ◽  
High Resolution Images ◽  
Low Ionic Strength

The high contrast in the dark-field mode of dedicated STEM, specimen deposition by the wet film technique and low radiation dose (1 e/Å2) at -160°C make it possible to obtain high resolution images of unstained freeze-dried macromolecules with minimal structural distortion. Since the image intensity is directly related to the local projected mass of the specimen it became feasible to determine the molecular mass and mass distribution within individual macromolecules and from these data to calculate the linear density (M/L) and the radii of gyration.2 This parameter (RQ), reflecting the three-dimensional structure of the macromolecular particles in solution, has been applied to monitor the conformational transitions in E. coli 16S and 23S ribosomal RNAs in solutions of various ionic strength.In spite of the differences in mass (550 kD and 1050 kD, respectively), both 16S and 23S RNA appear equally sensitive to changes in buffer conditions. In deionized water or conditions of extremely low ionic strength both appear as filamentous structures (Fig. la and 2a, respectively) possessing a major backbone with protruding branches which are more frequent and more complex in 23S RNA (Fig. 2a).

Enhancement of Contrast in the CEM and STEM Using Bumpy Specimens and Employing the “Dappled Field” Mode of Operation

1974 ◽  
Vol 32 ◽  
pp. 552-553 ◽  
Author(s):  
L. Gandolfi ◽  
J. Reiffel
Keyword(s):  
Operating Mode ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Specimen Preparation ◽  
Field Mode ◽  
Preparation Methods ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Mode Of Operation ◽  
Scanning Transmission

Calculations have been performed on the contrast obtainable, using the Scanning Transmission Electron Microscope, in the observation of thick specimens. Recent research indicates a revival of an earlier interest in the observation of thin specimens with the view of comparing the attainable contrast using both types of specimens.Potential for biological applications of scanning transmission electron microscopy has led to a proliferation of the literature concerning specimen preparation methods and the controversy over “to stain or not to stain” in combination with the use of the dark field operating mode and the same choice of technique using bright field mode of operation has not yet been resolved.

Effect of strain on ADF-STEM high-resolution images

1991 ◽  
Vol 49 ◽  
pp. 666-667
Author(s):  
M. Kelly ◽  
D.M. Bird
Keyword(s):  
High Resolution ◽  
Strong Influence ◽  
Intensity Variation ◽  
Dark Field ◽  
Atomic Resolution ◽  
Strain Fields ◽  
High Resolution Image ◽  
Annular Dark Field ◽  
High Resolution Images ◽  
Interesting Alternative

It is well known that strain fields can have a strong influence on the details of HREM images. This, for example, can cause problems in the analysis of edge-on interfaces between lattice mismatched materials. An interesting alternative to conventional HREM imaging has recently been advanced by Pennycook and co-workers where the intensity variation in the annular dark field (ADF) detector is monitored as a STEM probe is scanned across the specimen. It is believed that the observed atomic-resolution contrast is correlated with the intensity of the STEM probe at the atomic sites and the way in which this varies as the probe moves from cell to cell. As well as providing a directly interpretable high-resolution image, there are reasons for believing that ADF-STEM images may be less suseptible to strain than conventional HREM. This is because HREM images arise from the interference of several diffracted beams, each of which is governed by all the excited Bloch waves in the crystal.

Imaging of platinum-shadowed macromolecular complexes in dark field

1984 ◽  
Vol 42 ◽  
pp. 146-147
Author(s):  
D.W. Andrews ◽  
F.P. Ottensmeyer
Keyword(s):  
Thin Film ◽  
Three Dimensional ◽  
Average Diameter ◽  
Dark Field ◽  
Bright Field ◽  
Field Mode ◽  
Macromolecular Complexes ◽  
Average Mass ◽  
Topological Features ◽  
Projection Images

Shadowing with heavy metals has been used for many years to enhance the topological features of biological macromolecular complexes. The three dimensional features present in directionaly shadowed specimens often simplifies interpretation of projection images provided by other techniques. One difficulty with the method is the relatively large amount of metal used to achieve sufficient contrast in bright field images. Thick shadow films are undesirable because they decrease resolution due to an increased tendency for microcrystalline aggregates to form, because decoration artefacts become more severe and increased cap thickness makes estimation of dimensions more uncertain.The large increase in contrast provided by the dark field mode of imaging allows the use of shadow replicas with a much lower average mass thickness. To form the images in Fig. 1, latex spheres of 0.087 μ average diameter were unidirectionally shadowed with platinum carbon (Pt-C) and a thin film of carbon was indirectly evaporated on the specimen as a support.

Resolution in the Scanning Transmission Electron Microscope

1972 ◽  
Vol 30 ◽  
pp. 454-455
Author(s):  
M. G. R. Thomson
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Spherical Aberration ◽  
Signal To Noise Ratio ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The variation of contrast and signal to noise ratio with change in detector solid angle in the high resolution scanning transmission electron microscope was discussed in an earlier paper. In that paper the conclusions were that the most favourable conditions for the imaging of isolated single heavy atoms were, using the notation in figure 1, either bright field phase contrast with β0⋍0.5 α0, or dark field with an annular detector subtending an angle between ao and effectively π/2.The microscope is represented simply by the model illustrated in figure 1, and the objective lens is characterised by its coefficient of spherical aberration Cs. All the results for the Scanning Transmission Electron Microscope (STEM) may with care be applied to the Conventional Electron Microscope (CEM). The object atom is represented as detailed in reference 2, except that ϕ(θ) is taken to be the constant ϕ(0) to simplify the integration. This is reasonable for θ ≤ 0.1 θ0, where 60 is the screening angle.

Effets of surfaces on precipitate morphology in irradiated thin foils

1978 ◽  
Vol 36 (1) ◽  
pp. 654-655
Author(s):  
D.I. Potter ◽  
A. Taylor
Keyword(s):  
Ion Irradiation ◽  
Dark Field Image ◽  
Thin Foil ◽  
Dark Field ◽  
Al Alloy ◽  
Bright Field Image ◽  
Dislocation Loops ◽  
Precipitate Morphology ◽  
Thin Foils

Thermal aging of Ni-12.8 at. % A1 and Ni-12.7 at. % Si produces spatially homogeneous dispersions of cuboidal γ'-Ni3Al or Ni3Si precipitate particles arrayed in the Ni solid solution. We have used 3.5-MeV 58Ni+ ion irradiation to examine the effect of irradiation during precipitation on precipitate morphology and distribution. The nearness of free surfaces produced unusual morphologies in foils thinned prior to irradiation. These thin-foil effects will be important during in-situ investigations of precipitation in the HVEM. The thin foil results can be interpreted in terms of observations from bulk irradiations which are described first.Figure 1a is a dark field image of the γ' precipitate 5000 Å beneath the surface(∿1200 Å short of peak damage) of the Ni-Al alloy irradiated in bulk form. The inhomogeneous spatial distribution of γ' results from the presence of voids and dislocation loops which can be seen in the bright field image of the same area, Fig. 1b.

scholarly journals Multiplexed Plasmonic Nano-Labeling for Bioimaging of Cytological Stained Samples

Cancers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 3509
Author(s):  
Paule Marcoux-Valiquette ◽  
Cécile Darviot ◽  
Lu Wang ◽  
Andrée-Anne Grosset ◽  
Morteza Hasanzadeh Kafshgari ◽  
...  
Keyword(s):  
Accurate Determination ◽  
Cell Types ◽  
Fine Needle Biopsy ◽  
Dark Field ◽  
Imaging Method ◽  
New Methods ◽  
Formalin Fixed Paraffin ◽  
Dark Field Microscopy ◽  
Formalin Fixed Paraffin Embedded

Reliable cytopathological diagnosis requires new methods and approaches for the rapid and accurate determination of all cell types. This is especially important when the number of cells is limited, such as in the cytological samples of fine-needle biopsy. Immunoplasmonic-multiplexed- labeling may be one of the emerging solutions to such problems. However, to be accepted and used by the practicing pathologists, new methods must be compatible and complementary with existing cytopathology approaches where counterstaining is central to the correct interpretation of immunolabeling. In addition, the optical detection and imaging setup for immunoplasmonic-multiplexed-labeling must be implemented on the same cytopathological microscope, not interfere with standard H&E imaging, and operate as a second easy-to-use imaging method. In this article, we present multiplex imaging of four types of nanoplasmonic markers on two types of H&E-stained cytological specimens (formalin-fixed paraffin embedded and non-embedded adherent cancer cells) using a specially designed adapter for SI dark-field microscopy. The obtained results confirm the effectiveness of the proposed optical method for quantitative and multiplex identification of various plasmonic NPs, and the possibility of using immunoplasmonic-multiplexed-labeling for cytopathological diagnostics.

Head Instability Detection for Testing Process in Perpendicular Magnetic Recording System

2013 ◽  
Vol 770 ◽  
pp. 319-322 ◽  
Author(s):  
Piya Kovintavewat ◽  
Santi Koonkarnkhai ◽  
Aimamorn Suvichakorn
Keyword(s):  
Magnetic Recording ◽  
Signal To Noise Ratio ◽  
Disk Drive ◽  
Detection Algorithm ◽  
Recording System ◽  
High Signal ◽  
Signal To Noise ◽  
Perpendicular Magnetic Recording ◽  
Read Head ◽  
Pass Through

During hard disk drive (HDD) testing process, the magneto-resistive read (MR) head is analyzed and checked if the head is defective or not. Baseline popping (BLP) is one of the crucial problems caused by head instability, whose effect can distort the readback signal to the extent of causing possible sector read failure. Without BLP detection algorithm, the defective read head might pass through HDD assembling process, thus producing an unreliable HDD. This situation must be prevented so as to retain customer satisfaction. This paper proposes a simple (but efficient) BLP detection algorithm for perpendicular magnetic recording systems. Results show that the proposed algorithm outperforms the conventional one in terms of both the percentage of detection and the percentage of false alarm, when operating at high signal-to-noise ratio.

scholarly journals Erratum: “Signal-to-noise ratio in x-ray dark-field imaging using a grating interferometer” [J. Appl. Phys. 110, 053105 (2011)]

2011 ◽  
Vol 110 (10) ◽  
pp. 109902 ◽  
Author(s):  
Michael Chabior ◽  
Tilman Donath ◽  
Christian David ◽  
Manfred Schuster ◽  
Christian Schroer ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Dark Field ◽  
Signal To Noise ◽  
X Ray ◽  
Dark Field Imaging ◽  
Grating Interferometer ◽  
Noise Ratio ◽  
Field Imaging

scholarly journals Imaging in Hard X-ray Astronomy

2003 ◽  
Vol 214 ◽  
pp. 70-83 ◽  
Author(s):  
T. P. Li
Keyword(s):  
Gamma Ray ◽  
Signal To Noise Ratio ◽  
High Energy ◽  
High Signal ◽  
Wide Field ◽  
X Rays ◽  
X Ray ◽  
Energy Gamma ◽  
High Resolution Images ◽  
Energy Processes

The energy range of hard X-rays is a key waveband to the study of high energy processes in celestial objects, but still remains poorly explored. In contrast to direct imaging methods used in the low energy X-ray and high energy gamma-ray bands, currently imaging in the hard X-ray band is mainly achieved through various modulation techniques. A new inversion technique, the direct demodulation method, has been developed since early 90s. with this technique, wide field and high resolution images can be derived from scanning data of a simple collimated detector. The feasibility of this technique has been confirmed by experiment, balloon-borne observation and analyzing simulated and real astronomical data. Based the development of methodology and instrumentation, a high energy astrophysics mission – Hard X-ray Modulation Telescope (HXMT) has been proposed and selected in China for a four-year Phase-A study. The main scientific objectives are a full-sky hard X-ray (20–200 keV) imaging survey and high signal-to-noise ratio timing studies of high energy sources.

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