scholarly journals Spectrum Imaging Techniques Applied to Forensics Investigations

2005 ◽  
Vol 11 (S02) ◽  
Author(s):  
L N Brewer ◽  
P G Kotula ◽  
J A Ohlhausen ◽  
J R Michael
Keyword(s):  
Imaging Techniques ◽  
Spectrum Imaging

Energy Filtering and Spectrum Imaging of Polymers

2000 ◽  
Vol 6 (S2) ◽  
pp. 1116-1117
Author(s):  
A. Aitouchen ◽  
J. Taylor ◽  
P. Crozier ◽  
M. Libera
Keyword(s):  
Imaging Techniques ◽  
Polymeric Materials ◽  
Chemical Imaging ◽  
Polymer Particle ◽  
Initial Image ◽  
Image Region ◽  
Energy Filtering ◽  
Spectrum Imaging ◽  
Field Imaging ◽  
Tem Grid

Chemical imaging of polymeric materials is attractive, because of the inherently poor contrast typically afforded by multiphase amorphous polymers in bright-field imaging techniques. Spectrum imaging and energy-filtering approaches are being increasing applied to polymeric materials (1,2, 3).One recent example from the Stevens group using a Philips CM20 FEG TEM/STEM interfaced to an EmiSpec Vision data acquisition/control system and a Gatan 666 PEELS spectrometer is presented in figure 1. The specimen is a PVP sphere on a holey-carbon TEM grid. The specimen was cooled to approximately -125 °C in a single-tilt cryo stage. Drift correction was implemented by collecting HAADF STEM images from the sub-image region indicated by the dashed white box at periodic intervals. Based on an autocorrelation with the initial image, electronic shifts where imposed to correct for drift. A 3-D spectrum dataset was generated from the 70 x 70 pixel box around the polymer particle at an interpixel spacing of 5 nm and a pixel dwell time of 1.5 sec.

Mitochondrial Reconstructions Based on Serial Thick Sections and HVEM

1975 ◽  
Vol 33 ◽  
pp. 286-287
Author(s):  
Jerome J. Paulin
Keyword(s):  
Imaging Techniques ◽  
Three Dimensional ◽  
Posterior Pole ◽  
Dimensional Structure ◽  
Stereo Imaging ◽  
Thin Sections ◽  
Anatomical Features ◽  
The Past ◽  
Cellular Components ◽  
Mitochondrial Reticulum

Within the past decade it has become apparent that HVEM offers the biologist a means to explore the three-dimensional structure of cells and/or organelles. Stereo-imaging of thick sections (e.g. 0.25-10 μm) not only reveals anatomical features of cellular components, but also reduces errors of interpretation associated with overlap of structures seen in thick sections. Concomitant with stereo-imaging techniques conventional serial Sectioning methods developed with thin sections have been adopted to serial thick sections (≥ 0.25 μm). Three-dimensional reconstructions of the chondriome of several species of trypanosomatid flagellates have been made from tracings of mitochondrial profiles on cellulose acetate sheets. The sheets are flooded with acetone, gluing them together, and the model sawed from the composite and redrawn.The extensive mitochondrial reticulum can be seen in consecutive thick sections of (0.25 μm thick) Crithidia fasciculata (Figs. 1-2). Profiles of the mitochondrion are distinguishable from the anterior apex of the cell (small arrow, Fig. 1) to the posterior pole (small arrow, Fig. 2).

An example of spectrum imaging used for comparison of EELS quantitative analysis techniques on Al-Li

1991 ◽  
Vol 49 ◽  
pp. 726-727
Author(s):  
John A. Hunt
Keyword(s):  
Quantitative Analysis ◽  
Large Data ◽  
Difference Spectrum ◽  
Large Data Sets ◽  
Foil Thickness ◽  
Data Sets ◽  
Analysis Techniques ◽  
Spectrum Imaging ◽  
Normal Spectrum ◽  
Electron Energy Loss

Spectrum-imaging is a useful technique for comparing different processing methods on very large data sets which are identical for each method. This paper is concerned with comparing methods of electron energy-loss spectroscopy (EELS) quantitative analysis on the Al-Li system. The spectrum-image analyzed here was obtained from an Al-10at%Li foil aged to produce δ' precipitates that can span the foil thickness. Two 1024 channel EELS spectra offset in energy by 1 eV were recorded and stored at each pixel in the 80x80 spectrum-image (25 Mbytes). An energy range of 39-89eV (20 channels/eV) are represented. During processing the spectra are either subtracted to create an artifact corrected difference spectrum, or the energy offset is numerically removed and the spectra are added to create a normal spectrum. The spectrum-images are processed into 2D floating-point images using methods and software described in [1].

Application of Lattice Imaging Techniques to Amorphous Films

1975 ◽  
Vol 33 ◽  
pp. 8-9
Author(s):  
S. R. Herd ◽  
P. Chaudhari
Keyword(s):  
Nearest Neighbor ◽  
Random Network ◽  
Imaging Techniques ◽  
Network Models ◽  
Accurate Method ◽  
Direct Transmission ◽  
Lattice Imaging ◽  
Transmission Electron ◽  
Lattice Planes ◽  
Nearest Neighbor Distances

Electron diffraction and direct transmission have been used extensively to study the local atomic arrangement in amorphous solids and in particular Ge. Nearest neighbor distances had been calculated from E.D. profiles and the results have been interpreted in terms of the microcrystalline or the random network models. Direct transmission electron microscopy appears the most direct and accurate method to resolve this issue since the spacial resolution of the better instruments are of the order of 3Å. In particular the tilted beam interference method is used regularly to show fringes corresponding to 1.5 to 3Å lattice planes in crystals as resolution tests.

Studies of metaphase chromosomes in the scanning transmission x-ray microscope: Image fidelity, radiation damage and specimen preparation

1992 ◽  
Vol 50 (2) ◽  
pp. 1038-1039
Author(s):  
Shawn Williams ◽  
Xiaodong Zhang ◽  
Susan Lamm ◽  
Jack Van’t Hof
Keyword(s):  
Visible Light ◽  
Radiation Damage ◽  
Cross Section ◽  
Imaging Techniques ◽  
Dose Range ◽  
Specimen Preparation ◽  
X Rays ◽  
Metaphase Chromosomes ◽  
X Ray ◽  
Scanning Transmission

The Scanning Transmission X-ray Microscope (STXM) is well suited for investigating metaphase chromosome structure. The absorption cross-section of soft x-rays having energies between the carbon and oxygen K edges (284 - 531 eV) is 6 - 9.5 times greater for organic specimens than for water, which permits one to examine unstained, wet biological specimens with resolution superior to that attainable using visible light. The attenuation length of the x-rays is suitable for imaging micron thick specimens without sectioning. This large difference in cross-section yields good specimen contrast, so that fewer soft x-rays than electrons are required to image wet biological specimens at a given resolution. But most imaging techniques delivering better resolution than visible light produce radiation damage. Soft x-rays are known to be very effective in damaging biological specimens. The STXM is constructed to minimize specimen dose, but it is important to measure the actual damage induced as a function of dose in order to determine the dose range within which radiation damage does not compromise image quality.

An x-ray microprobe based upon a close-coupled focal-spot / glass capillary arrangement

1992 ◽  
Vol 50 (2) ◽  
pp. 1758-1759
Author(s):  
D. A. Carpenter ◽  
M. A. Taylor
Keyword(s):  
Imaging Techniques ◽  
Fluorescence Analysis ◽  
High Sensitivity ◽  
Specimen Preparation ◽  
X Rays ◽  
Glass Capillary ◽  
Close Coupling ◽  
X Ray ◽  
Point To Point ◽  
Beam Damage

The development of intense sources of x rays has led to renewed interest in the use of microbeams of x rays in x-ray fluorescence analysis. Sparks pointed out that the use of x rays as a probe offered the advantages of high sensitivity, low detection limits, low beam damage, and large penetration depths with minimal specimen preparation or perturbation. In addition, the option of air operation provided special advantages for examination of hydrated systems or for nondestructive microanalysis of large specimens.The disadvantages of synchrotron sources prompted the development of laboratory-based instrumentation with various schemes to maximize the beam flux while maintaining small point-to-point resolution. Nichols and Ryon developed a microprobe using a rotating anode source and a modified microdiffractometer. Cross and Wherry showed that by close-coupling the x-ray source, specimen, and detector, good intensities could be obtained for beam sizes between 30 and 100μm. More importantly, both groups combined specimen scanning with modern imaging techniques for rapid element mapping.

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