bluuebunny/crossref_metadata_2025 huggingface dataset:
Coordination “Fingerprints” of Boron Measured by EELS
Authors: Sauer H. , Brydson R. , Engel W. , Rowley P.N.
Published: June 2020

The electron energy-loss near-edge structure (ELNES) associated with a core-loss edge measured using electron energy-loss spectroscopy (EELS) provides, in favourable cases, a “fingerprint” corresponding to the specific nearest-neighbour coordination of the excited atom.

Boron atoms in boron-oxygen compounds occur in both trigonal (BO3) and tetrahedral (BO4) coordinations. The B K-ELNES of BO3 and BO4 units (Figs, le and 2b) are remarkably different and arise from the differing local symmetries which determine the final state molecular orbitals. The BK-ELNES of BO3 units exhibit a sharp π∗ peak at ca. 194 eV followed by a broader σ∗ peak some 9-10 eV higher in energy, which may possess a low energy shoulder. BO4 B K-ELNES show no π∗ peak and display solely a σ∗ peak at ca. 199 eV together with a high energy shoulder. Both these spectra may be modelled using multiple scattering calculations.

The mineral howlite contains both BO3 and BO4 units and is sensitive to electron-beaminduced damage.
Comparison of Calculated and Recorded Electron Energy-Loss Spectra of Aluminium and Carbon
Authors: Reimer L. , Oelgeklaus R.
Published: June 2020

Quantitative electron energy-loss spectroscopy (EELS) needs a correction for the limited collection aperture α and a deconvolution of recorded spectra for eliminating the influence of multiple inelastic scattering. Reversely, it is of interest to calculate the influence of multiple scattering on EELS. The distribution f(w,θ,z) of scattered electrons as a function of energy loss w, scattering angle θ and reduced specimen thickness z=t/Λ (Λ=total mean-free-path) can either be recorded by angular-resolved EELS or calculated by a convolution of a normalized single-scattering function ϕ(w,θ). For rotational symmetry in angle (amorphous or polycrystalline specimens) this can be realised by the following sequence of operations :

(1)

where the two-dimensional distribution in angle is reduced to a one-dimensional function by a projection P, T is a two-dimensional Fourier transform in angle θ and energy loss w and the exponent -1 indicates a deprojection and inverse Fourier transform, respectively.
PRSUPR: A PC Based Automation and Data Reduction Software Package for Wavelength Dispersive Electron Beam Micro-Analysis
Authors: Donovan John J. , Rivers Mark L.
Published: June 2020

Although several commercial automation packages are available for use on the micro-probe, we at Berkeley feel that they all suffer from a number of shortcomings. A few of the most important features missing are :

1.

The ability to produce quantitative results of the highest accuracy over the entire analytical range of the micro-probe using the most advanced matrix correction software available.

2.

A simple yet versatile user interface making extensive use of multiple choice menus and defaulted experimental parameters for exceptional ease of use.

3.

Full support of manual and automated modes for both standard and unknown samples for a wide variety of sample configurations and analytical methods.

4.

Hardware independence and completely configurable program for various micro-probe stage and spectrometer arrangements for use with any micro-probe hardware.

5.

Capability on a PC for BOTH real-time on-line data acquisition and analysis when connected to the micro-probe, and off-line analysis of data when not connected.

6.

Ability to run on an inexpensive and widely available computer platform without the need for graphics hardware.
Resolution Enhancement for X-RAY Spectroscopy at Low Energies
Authors: Statham Peter
Published: June 2020

For microanalysis with Si(Li) EDX systems, the procedures for background subtraction and peak overlap correction, by least-squares fitting for example, are well established. However, the use of EDX as a research tool to investigate the precise form of the x-ray spectral distribution (i.e. “spectroscopy”) is much less common. In the region from 0 to 1keV, matrix effects such as absorption in the sample are strong, x-ray line profiles are affected by chemical effects and relative line intensities often differ from the simplistic descriptions suggested by “slide rules” and “KLM” markers so this is a particularly interesting region to study. EDX is suitable for spectroscopy because the efficiency is usually more reproducible than that for a Bragg crystal spectrometer. However, the resolution is not sufficient to see many of the above effects so it is worth considering what prospects there are for enhancement.

In theory, monochromatic x-radiation of energy E eV produces a Gaussian spectral peak in an EDX energy histogram with resolution given by

where F is the “Fano factor”.
Development of Field-Emission Gun for High-Voltage Electron Microscope
Authors: Tomita T. , Katoh S. , Kitajima H. , Kokubo Y. , Ishida Y.
Published: June 2020

It is well known that the combination of a field emission gun (FEG) and a conventional transmission electron microscope (CTEM) is extremely important for nanometer area analysis in analytical electron microscopy. However, the smaller illumination angle and reduced energy spread of FEG than those of a conventional electron gun (W hair pin filament or LaB6) give a slowly damping envelop function in phase contrast transfer function (PCTF). Thus the FEG ensures application not only to analytical microscopy but also to high resolution electron microscopy to improve the information limit.

In a high voltage electron microscope (above 200 kV), high-speed vacuum pumps have to be provided below the acceleration tube to get an ultra high vacuum (UHV) around the field emission tip located at the top of the acceleration tube. However, this method is not always the best way to provide UHV because of the poor vacuum conductance caused by the electrodes inside the acceleration tube.
Techniques for Capture of Low Velocity (<200 m/s) Particles
Authors: Bearman Gregory , Bradley James
Published: June 2020

Collection of low velocity, micron-size, dust particles (~50 - 200 m/s) is an upcoming challenge for dust instruments aboard NASA’s Comet Rendezvous and Asteroid Flyby (CRAF) mission, scheduled for launch in 1995. There will be three dust analysis instruments on board, each of which will capture cometary dust intact for analysis by different techniques. Each instrument has its own restrictions on dust collection processes because of differing techniques and science goals. SEMPA, the Scanning Electron Microscope and Particle Analyzer, is one of the CRAF dust analysis instruments. The work reported here examines particle capture in light of SEMPA’s particular functional requirements. These include particle visibility for imaging and x-ray analysis, high contrast, no interfering x-ray lines, and collection without size discrimination. A number of collection techniques have been tested in our laboratory with dust from a free-expansion, gas-drag dust gun that accelerates micron-size dust to ~50 - 200 m/s, the expected relative velocity of the spacecraft and the dust at the comet.
X-ray microanalysis of cardiac myocytes isolated from K-depleted rabbits
Authors: Warley Alice , Ward Jeremy P.T.
Published: June 2020

Chronic heart disease is conmonly associated with electrolyte disturbances, including hypokalemia and K depletion. Previous work suggests that chronic K depletion results in an adaptive increase in the density of the membrane bound sodium pump. Such altered properties of the sarcolemma should be reflected in the composition of cardiac myocytes isolated from control and K depleted animals.

Adult male NZW rabbits were fed either a standard diet or a diet deficient in K. The animals were anaesthetised, the hearts removed, and myocytes were isolated by collagenase disaggregation. Cells from control animals were kept in a medium containing 4 mM extracellular K to mimic normal serum concentrations of this element. Cells from K depleted animals were maintained in solutions containing either 2 mM external K, (K concentration in serum from depleted animals) or 4mM K to mimic repletion. The cells were concentrated by centrifugation (500 g, 5 min), the supernatant removed, and drops of the pellet quench frozen in liquefied propane.
Subcellular calcium content of myocardium after ischemia and reperfusion: X-ray microanalysis
Authors: Horikawa Yoshifumi , Kaneko Noboru , Uchida Tatsuroh , Hosoda Saichi , Teraoka Kunihiko , Nakamura Sachiko
Published: June 2020

We have reported that calcium accumulation inside the mitochondria was induced by ischemia. Other authors have reported similar results. But there has been no study to clarify whether calcium accumulation in the mitochondria is reversible or irreversible. The goal of this study is to clarify whether calcium content in the mitochondria is changed by reperfusion for 60 minutes.

9 male rats (17- 20 weeks old) were used. After cervical fracture, the heart was quickly excised and the aorta was cannulated. We circulated Krebs-Henseleit solution at 37°C. Samples were divided into three groups. The control group was perfused with 95%O + 80cmH2O Krebs-Henseleit solution for 30 minutes. The ischemic group was perfused with 50%O2 + 15cmH2O solution for 30 minutes. In the reperfusion group, control solution was circulated for 60 minutes after 30 minutes ischemic perfusion. Just after perfusion, specimens were taken from the papillary muscle of the left ventricle and rapidly frozen by the metal contact method.
Quantitative imaging in high-resolution studies of calcium binding to myofilaments
Authors: Cantino Marie E. , Allen Taylor StC. , Johnson Dale E. , Gordon Albert M.
Published: June 2020

A full understanding of the role of calcium in regulating contraction requires accurate information about the amount of calcium bound to myofilaments under various conditions. One recent approach has been to use fluorescent probes which change their properties with changes in the amount of calcium bound to troponin C. However, several studies have demonstrated that cross bridge binding, as well as calcium binding, can change the fluorescence properties of the probes attached to regulatory proteins on the thin filaments in muscle (1,2). Another approach is to use45Ca to assay binding, but this method does not directly yield information about the spatial distribution of binding. Electron probe x-ray microanalysis provides an independent method for directly measuring calcium at various locations along the sarcomere (3). We have been exploring whether digital image acquisition and analysis can be used to extract meaningful data from these samples, in which the Ca concentrations of interest are just above the detection limit for the technique.
Mitochondrial matrix calcium ions regulate energy production in myocardium: A cytochemical study
Authors: Jacob W.A. , Hertsens R. , Van Bogaert A. , De Smet M.
Published: June 2020

In the past most studies of the control of energy metabolism focus on the role of the phosphorylation potential ATP/ADP.Pion the regulation of respiration. Studies using NMR techniques have demonstrated that the concentrations of these compounds for oxidation phosphorylation do not change appreciably throughout the cardiac cycle and during increases in cardiac work. Hence regulation of energy production by calcium ions, present in the mitochondrial matrix, has been the object of a number of recent studies.

Three exclusively intramitochondnal dehydrogenases are key enzymes for the regulation of oxidative metabolism. They are activated by calcium ions in the low micromolar range. Since, however, earlier estimates of the intramitochondnal calcium, based on equilibrium thermodynamic considerations, were in the millimolar range, a physiological correlation was not evident. The introduction of calcium-sensitive probes fura-2 and indo-1 made monitoring of free calcium during changing energy metabolism possible. These studies were performed on isolated mitochondria and extrapolation to the in vivo situation is more or less speculative.
Biomedical elemental analysis and imaging using synchrotron x-ray microscopy
Authors: Jones K. W. , Gordon B. M. , Schidlovsky G. , Spanne P. , Dejun Xue , Saubermann A. J.
Published: June 2020

The application of synchrotron x-ray microscopy to biomedical research is currently in progress at the Brookhaven National Synchrotron Light Source. The current status of the x-ray microscope (XRM) from a technical standpoint is reviewed. Some of the items considered are photon flux, spatial resolution, quantitation, minimum detection limits, and beam-induced specimen damage. Examples of measurements made with the XRM are then given.

The XRM has generally used continuous energy bending magnet radiation as the x-ray source. A mechanical collimator placed close to the specimen is used to define x-ray beams of 3-5/μm size. The size of the beam can be adjusted to some extent by tilting the collimator with respect to the beam direction. The photon flux is maximized by locating the XRM as close to the x-ray source as possible (9 m). Flux values of about 3 × 108 photons/(s-μm2) are obtained with a 100mA current of electrons in the storage ring.
Investigation of thin sections of biological standards by EDX, EELS, and Auger electron spectroscopy
Authors: Lehner S. , Bauer H.E. , Wurster R. , Seiler H.
Published: June 2020

In order to compare different microanalytical techniques commercially available cation exchange membrane SC-1 (Stantech Inc, Palo Alto), was loaded with biologically relevant elements as Na, Mg, K, and Ca, respectively, each to its highest possible concentration, given by the number concentration of exchangeable binding sites (4 % wt. for Ca). Washing in distilled water, dehydration through a graded series of ethanol, infiltration and embedding in Spurr’s low viscosity epoxy resin was followed by thin sectioning. The thin sections (thickness of about 50 nm) were prepared on carbon foils and mounted on electron microscopical finder grids.

The samples were analyzed with electron microprobe JXA 50A with transmitted electron device, EDX system TN 5400, and on line operating image processing system SEM-IPS, energy filtering electron microscope CEM 902 with EELS/ESI and Auger spectrometer 545 Perkin Elmer.

With EDX, a beam current of some 10-10 A and a beam diameter of about 10 nm, a minimum-detectable mass of 10-20 g Ca seems within reach.
Fluorescence effects in quantitative microprobe analysis
Authors: Reed S.J.B.
Published: June 2020

Characteristic fluorescence

The theory of characteristic fluorescence corrections was first developed by Castaing. The same approach, with an improved expression for the relative primary x-ray intensities of the exciting and excited elements, was used by Reed, who also introduced some simplifications, which may be summarized as follows (with reference to K-K fluorescence, i.e. K radiation of element ‘B’ exciting K radiation of ‘A’):

1.

The exciting radiation is assumed to be monochromatic, consisting of the Kα line only (neglecting the Kβ line).

2.

Various parameters are lumped together in a single tabulated function J(A), which is assumed to be independent of B.

3.

For calculating the absorption of the emerging fluorescent radiation, the depth distribution of the primary radiation B is represented by a simple exponential.

These approximations may no longer be justifiable given the much greater computing power now available. For example, the contribution of the Kβ line can easily be calculated separately.
Automated mineral analysis in TASK8
Authors: Chambers William F. , Chodos Arthur A. , Hagan Roland C.
Published: June 2020

TASK8 was designed as an electron microprobe control program with maximum flexibility and versatility, lending itself to a wide variety of applications. While using TASKS in the microprobe laboratory of the Los Alamos National Laboratory, we decided to incorporate the capability of using subroutines which perform specific end-member calculations for nearly any type of mineral phase that might be analyzed in the laboratory. This procedure minimizes the need for post-processing of the data to perform such calculations as element ratios or end-member or formula proportions. It also allows real time assessment of each data point.

The use of unique “mineral codes” to specify the list of elements to be measured and the type of calculation to perform on the results was first used in the microprobe laboratory at the California Institute of Technology to optimize the analysis of mineral phases. This approach was used to create a series of subroutines in TASK8 which are called by a three letter code.
Macroprobe Mode for the Study of Segregation in Steels
Authors: Gilles Auclair , Danièle Benoit
Published: June 2020

During these last 10 years, high performance correction procedures have been developed for classical EPMA, and it is nowadays possible to obtain accurate quantitative analysis even for soft X-ray radiations. It is also possible to perform EPMA by adapting this accurate quantitative procedures to unusual applications such as the measurement of the segregation on wide areas in as-cast and sheet steel products.

The main objection for analysis of segregation in steel by means of a line-scan mode is that it requires a very heavy sampling plan to make sure that the most significant points are analyzed. Moreover only local chemical information is obtained whereas mechanical properties are also dependant on the volume fraction and the spatial distribution of highly segregated zones. For these reasons we have chosen to systematically acquire X-ray calibrated mappings which give pictures similar to optical micrographs. Although mapping requires lengthy acquisition time there is a corresponding increase in the information given by image anlysis.
Determination of Stoichiometry of GaAs Component in (Gaas)Ge Epitaxially Grown Thin Films by Electron Microprobe X-Ray Analysis
Authors: Liu D. R. , Shinozaki S. S. , Baird R. J.
Published: June 2020

The epitaxially grown (GaAs)Ge thin film has been arousing much interest because it is one of metastable alloys of III-V compound semiconductors with germanium and a possible candidate in optoelectronic applications. It is important to be able to accurately determine the composition of the film, particularly whether or not the GaAs component is in stoichiometry, but x-ray energy dispersive analysis (EDS) cannot meet this need. The thickness of the film is usually about 0.5-1.5 μm. If Kα peaks are used for quantification, the accelerating voltage must be more than 10 kV in order for these peaks to be excited. Under this voltage, the generation depth of x-ray photons approaches 1 μm, as evidenced by a Monte Carlo simulation and actual x-ray intensity measurement as discussed below. If a lower voltage is used to reduce the generation depth, their L peaks have to be used. But these L peaks actually are merged as one big hump simply because the atomic numbers of these three elements are relatively small and close together, and the EDS energy resolution is limited.
Fourier Transform Vibrational Microscopy
Authors: Bergin F.J.
Published: June 2020

The continued improvement in Fourier transform instrumentation has considerably widened the range of materials and systems amenable to vibrational spectroscopic analysis. In particular these improvements have been crucial to the development of Fourier transform vibrational microscopy and, in recent years, there has been a proliferation of applications of FT-IR microscopy. Although primarily developed for analysis where high spatial resolution is required, the infrared microscope can also serve as an extremely useful and versatile sampling accessory. During the last few years we have been involved in IR microscopy on several fronts, from the analysis of eluting materials from chromatographic columns, inhomogeneous films on metallic substrates, small contaminants in lub oils, etc.. These applications have relied on the high spatial resolution of the microscope. However we have also been involved in the use of the IR microscope as a general sampling accessory focusing on its use in the analysis of bulk materials by diffuse and specular reflectance and for the analysis of thin films on non-metallic substrates.
Influence of Smoking on Asbestos Phagocytosis by Macrophages in Guinea Pigs
Authors: Gray L.D. , Brady D.E. , Holiday D.B. , Swinford G.L.
Published: June 2020

Cigarette smoking greatly enhances the risk of lung cancers of all types in persons occupationally exposed to asbestos (1). Pulmonary macrophage recruitment and subsequent phagocytosis of asbestos fibers has been shown to occur within hours of asbestos exposure in guinea pigs (2) and is the predominant and chronic phagocytic response after about 1-2 days post exposure. In an initial qualitative examination of lung tissues from smoke and asbestos exposed guinea pigs (3), a number of macrophages were observed which had engulfed large numbers of asbestos fibers. A morphometric analysis was performed to examine the effect of cigarette smoke exposure on the phagocytosis of asbestos by guinea pig pulmonary macrophages in vivo, and specifically, to determine if phagocytosis was increased in animals exposed to both smoke and asbestos.

We used three treatment groups of male, Hartley guinea pigs. Each group (n=4) received the same level of asbestos exposure (15mg Amosite 3 times, 1 dose/week) and varied levels of smoking exposure.
SIMS Microarea Depth Profiling of Microelectronic Device Structures
Authors: von Criegern Rolf , Zeininger Heinz
Published: June 2020

In recent years, considerable progress has been made in SIMS (secondary ion mass spectrometry) with respect to its ability to measure dopant depth profiles in μm2-sized areas of microelectronic devices. This progress is mainly due to the fact that for the first time two of the main requirements associated with this application are fulfilled within one instrument (the Cameca IMS 4F):

. the availability of a sub-μm ion beam of a species ensuring high secondary ion yields of the dopants (in this case: negative secondary ions emitted upon cesium bombardment)

and . a mass spectrometer system with high transmission (from sample to detector; in this case: about 27%).

The lateral resolution (smallest spot size of the cesium beam) which we obtain with our instrument is about 0.3 μm so that indeed areas as small as 1 μm2 can be defined on a sample. The detection limit for a dopant in an analytical volume of 1 μm × 1 μm × 10 nm (10 nm = sputter depth per data point in the profile) is then determined by the secondary ion yield and the instrument transmission.
Iodine as a Tracer for Intracellular Drug Localization: X-Ray Microanalysis
Authors: Gary Kirk R. , Lee Ping , Reasor Mark J.
Published: June 2020

The antiarrhythmic drug, amiodarone. is a cationic amphiphilic compound which can cause cellular lipidosis and pulmonary toxicity. It contains two atoms of iodine per molecule. We have previosly reported our results on the use of x-ray microanalysis to quantitatively measure the subcellular distribution of iodine in rat alveolar macrophages following a single adminstration of the drug. We found small amounts of iodine throughout the alveolar macrophages. The major accumulations were observed in the lipid lamellar structures, which were of lysosomal origin and appeared as amorphous bodies in freeze-dried cryosection. More recently we have examined the effects of long-term treatment of one week and nine weeks with amiodarone. Severe lipidosis in the alveolar macrophages occurred after one week treatment with amiodarone (Fig.l). Substantial changes in iodine distribution occurred in cells with increasing length of drug treatment. In addition to the high concentrations of iodine in the lamellar bodies, the iodine levels in the nuclei slowly increased with the length of treatment, and after 9 weeks of treatment, approached the high levels found in the lamellar bodies.
X-Ray Microprobe Analysis of Frozen Hydrated Cryosections for Study of Central and Peripheral Nervous System
Authors: Saubermann Albert J. , Castiglia Carolyn M. , Foster Margaret C. , Lagasse Robert S. , LoPachin Richard M.
Published: June 2020

Knowledge of elemental distribution is of great importance to understanding normal and abnormal function of the nervous system. Because elements of biological interest are easily displaced using conventional preparative methods, low temperature preparative methods are necessary to preserve elemental distribution. We have applied our methods for x-ray microprobe analysis of frozen hydrated cryosections to investigations of the central and peripheral nervous system in invertebrate and vertebrate animals. We have applied these methods to several areas of neuroscience including neuroanatomy/neurochemistry neurophysiology, neuropharmacology, neurotoxicology, and neuropathology.

X-ray microprobe analysis is not a substitute for electrophysiological measurements. Unfortunately there is often confusion between what is measured by the electron probe and between what is measured with microelectrodes. The information we obtain from x-ray microprobe analysis (XMPA) provides a measure of elemental mass fraction usually on the basis of dry mass, although using frozen hydrated techniques provides additional information by relating elemental mass to wet weight mass.
Quantitative Trace Element Analysis of Micro-Samples by SIMS
Authors: Chia V. K. F. , Bleiler R. J. , Anderson C. L. , Odom R. W.
Published: June 2020

A number of researchers have applied secondary ion mass spectrometry (SIMS) in various areas of medical research. The potential of SIMS as an analytical tool in elemental microanalysis of biological specimens lies in its sub-part per million (ppm) elemental detection sensitivities and its ability to generate two and three dimensional distributions of the intensities of mass selected secondary ions. Established techniques such as inductively coupled plasma (ICP) and electron probe microanalysis (EPMA) are also capable of sub-ppm elemental detection limits. ICP detection limits are adversely affected as the sample volume decreases below 1 milliliter. The EPMA technique can achieve ppm detection limits with volumes in the 100 picoliter range but its detection limits do not decrease as the sample volume increases. SIMS combines excellent detection sensitivities with small sample masses (picogram) which makes it a very useful complementary technique to ICP and EPMA especially for minor and trace element level analyses in small volumes of biological fluids.
Why the Bloch Wave Solution for Reflection Fails on the Au(110) Surface
Authors: MA YIQUN
Published: June 2020

The Bloch wave method has been widely used for interpreting reflection high energy electron diffraction (RHEED) patterns and the consistency between the theory and high energy electron reflection (HEER) experiments has been claimed by different authors. The recent rigorous investigation on the consistency between the Bloch wave method and the multislice approach due to Cowley and Moodie in the reflection case for Au(001) surface has also provided a clear theoretical proof for the validity of the Bloch wave method in reflection case. However, a severe deviation of the Bloch wave solution for the Au(110) surface in the reflection case from the stabilized solution of its multislicing via the multislice iteration has recently revealed by the BMCR method (Bloch wave + Multislice Combined for Reflection).

Fig.1 shows the results calculated for the Au(110) surface using the BMCR method. The incident angle is 30mRad and the absorption is included by taking the imaginary potential as 10% of the real potential in both the Bloch wave and multislice calculation.
Stability of Fluorinated Organic Compounds as Measured by Parallel-Detection EELS
Authors: Ciliax B.J. , Kirk K.L. , Leapman R.D.
Published: June 2020

The use of fluorine-labelling to localize specific organic compounds at the sub-cellular level by means of electron energy loss spectroscopy (EELS) was suggested over ten years ago. Since then, however, there have been differing reports about the susceptibility of fluorinated compounds to fluorine loss in the electron beam; damage doses appear to range over several orders of magnitude. Recent advances in EELS, i.e. the availability of parallel detectors, have generated renewed interest in this labelling technique. We therefore have undertaken a more systematic study of radiation damage in a series of aromatic and aliphatic fluorinated compounds as a function of dose and temperature.

Energy loss spectra were recorded using a VG Microscopes HB501 STEM equipped with a Gatan model 666 parallel-detection spectrometer. The vacuum at the specimen was better than 5×10−9 mbar and the specimen could be cooled from room temperature to 100 K. Samples were prepared by air drying thin layers of the compounds dissolved in appropriate solvents on to ˜10 nm carbon or aluminum evaporated films supported on 200 mesh copper grids.
point-Analysis Using the Extrapolation Method in the Analytical Electron microscope
Authors: Horita Zenji , Nishimachi Ryuzo , Sano Takeshi , Nemoto Minoru
Published: June 2020

Absorption correction is often required in quantitative x-ray microanalysis of thin specimens using the analytical electron microscope. For such correction, it is convenient to use the extrapolation method[l] because the thickness, density and mass absorption coefficient are not necessary in the method. The characteristic x-ray intensities measured for the analysis are only requirement for the absorption correction. However, to achieve extrapolation, it is imperative to obtain data points more than two at different thicknesses in the identical composition. Thus, the method encounters difficulty in analyzing a region equivalent to beam size or the specimen with uniform thickness. The purpose of this study is to modify the method so that extrapolation becomes feasible in such limited conditions. Applicability of the new form is examined by using a standard sample and then it is applied to quantification of phases in a Ni-Al-W ternary alloy.

The earlier equation for the extrapolation method was formulated based on the facts that the magnitude of x-ray absorption increases with increasing thickness and that the intensity of a characteristic x-ray exhibiting negligible absorption in the specimen is used as a measure of thickness.
The effect of small additions of Cu on precipitation in Al-Mg-Si alloys
Authors: Tamizifar M. , Cliff G. , Devenish R.W. , Lorimer G.W.
Published: June 2020

Small additions of copper, <1 wt%, have a pronounced effect on the ageing response of Al-Mg-Si alloys. The object of the present investigation was to study the effect of additions of copper up to 0.5 wt% on the ageing response of a series of Al-Mg-Si alloys and to use high resolution analytical electron microscopy to determine the composition of the age hardening precipitates.

The composition of the alloys investigated is given in Table 1. The alloys were heat treated in an argon atmosphere for 30m, water quenched and immediately aged either at 180°C for 15 h or given a duplex treatment of 180°C for 15 h followed by 350°C for 2 h2. The double-ageing treatment was similar to that carried out by Dumolt et al. Analyses of the precipitation were carried out with a HB 501 Scanning Transmission Electron Microscope. X-ray peak integrals were converted into weight fractions using the ratio technique of Cliff and Lorimer.
Detection and Quantification Problems in the Analysis of Light Elements With UTW Detectors
Authors: L’Espérance Gilles , Botton Gianluigi , Caron Mario
Published: June 2020

Recent developments in windowless (WL) or ultra-thin window (UTW) detectors, improved energy resolution, larger angles of collection (0.15-0.2 sterad), higher voltages (200-400 kV) make energy dispersive spectrometry more attractive for the analysis of low Z elements down to beryllium (Ref. 1 and Fig. 1). It lends itself to faster, more routine analysis and offers in many cases the possibility of carrying out qualitative analysis for a wider range of materials thickness. It has, however, generally been recognised to have lower sensitivities than EELS except for some elements in biological materials. Also, UTW analysis have been restricted to qualitative analyses, largely due to the large absorption even for relatively thin samples.

This paper presents results that can typically be achieved with both SEM and TEM’s, difficulties in quantifying the data and the sensitivity that can be expected.

The detectors (Link LZ-4 and Link LZ-5) on both our SEM (JEOL 840) and TEM (JEOL 2000FX) have a resolution of ≈ 134 ev at 5.9 kev and allow the detection of boron from pure B with the peak well resolved from the background and a peak/valley ration of 12.
Examination of Extra Electron Diffraction Spots Observed in Deuterium-Irradiated Silicon by Using Parallel Electron Beam Illumination
Authors: Oshima Ryuichiro , Honda Shoichiro , Tanabe Tetsuo
Published: June 2020

In order to examine the origin of extra diffraction spots and streaks observed in selected area diffraction patterns of deuterium irradiated silicon, systematic diffraction experiments have been carried out by using parallel beam illumination.

Disc specimens 3mm in diameter and 0.5mm thick were prepared from a float zone silicon single crystal(B doped, 7kΩm), and were chemically thinned in a mixed solution of nitric acid and hydrogen fluoride to make a small hole at the center for transmission electron microscopy. The pre-thinned samples were irradiated with deuterium ions at temperatures between 300-673K at 20keV to a dose of 1022ions/m2, and induced lattice defects were examined under a JEOL 200CX electron microscope operated at 160kV.

No indication of formation of amorphous was obtained in the present experiments. Figure 1 shows an example of defects induced by irradiation at 300K with a dose of 2xl021ions/m2. A large number of defect clusters are seen in the micrograph.
Structural Analysis of a Metastable Al-Ge Phase Using CBED
Authors: Exelby D.R. , Vincent R.
Published: June 2020

With standard x-ray diffraction it is often impossible to solve structures in multi-phase materials. Electron probes offer diffraction from micron-sized areas though dynamical effects will be present. Here we describe a structural analysis using electron diffraction from a metastable phase in the Al-Ge system. Preliminary analysis had provided a trial structure, that is summmarised here. This phase, found in recrystallised, amorphous equiatomic Al-Ge films, was body centred tetragonal with space group I/4mcm and a=6.26Å; c=5.0Å, which was consistent with the C16 structure. To confirm the structure a set of medium order intensities was obtained from LACBED zone axis patterns around [001]. On a zone axis we find annuli filled with a network of non-systematic HOLZ reflections from a single layer in the reciprocal lattice. Thus for thin, strain-free crystals, their intensities can approach the kinematic limit. Conditional Patterson transforms of the intensities for both hkl and hk2 reflections gave peaks corresponding to inter-string vectors in agreement with the C16 structure.
Structure Information From Electron Diffraction Intensities
Authors: Gjønnes J. , Bøe N. , Gjønnes K.
Published: June 2020

Structure information of high precision can be extracted from intentsity details in convergent beam patterns like the one reproduced in Fig 1. From low order reflections for small unit cell crystals,bonding charges, ionicities and atomic parameters can be derived, (Zuo, Spence and O’Keefe, 1988; Zuo, Spence and Høier 1989; Gjønnes, Matsuhata and Taftø, 1989) , but extension to larger unit cell ma seem difficult. The disks must then be reduced in order to avoid overlap calculations will become more complex and intensity features often less distinct Several avenues may be then explored: increased computational effort in order to handle the necessary many-parameter dynamical calculations; use of zone axis intensities at symmetry positions within the CBED disks, as in Figure 2 measurement of integrated intensity across K-line segments. In the last case measurable quantities which are well defined also from a theoretical viewpoint can be related to a two-beam like expression for the intensity profile:

With as an effective Fourier potential equated to a gap at the dispersion surface, this intensity can be integrated across the line, with kinematical and dynamical limits proportional to and at low and high thickness respctively (Blackman, 1939).
Determination of Positional Parameters by CBED
Authors: Tanaka Michiyoshi , Tsuda Kenji
Published: June 2020

Convergent-beam electron diffraction (CBED) has been successfully applied to the determination of symmetries of perfect crystals and of characteristics of crystal imperfections. CBED is now entering a stage of quantitative studies. Vincent et al. first demonstrated for AuGeAs a method to determine atomic positions with use of CBED patterns, in which the positional parameters were determined by fitting the intensities of higher-order Laue-zone (HOLZ) reflections calculated under the (quasi) kinematical approximation with the experimental intensities.

We report a simple case of the positional parameter determination for the low temperature phase of SrTiO3. This material undergoes a second order phase transformation at 110 K from the high temperature form of Pm3m to the low temperature form of I4/mcm upon the slight rotation of the oxygen octahedra or the condensation of the R25 mode (Fig. 1). The structure analysis of the phase I4/mcm means to determine the rotation angle ϕ and the isotropic Debye-Waller factor B of the oxygen ions.
Incommensurate Boundary Shifts in the AlMnSi Cubic Phase
Authors: Andersen S. , Guo Y.X. , Høier R.
Published: June 2020

The icosahedral quasicrystalline (IQ) phases of rapidly solidified materials, and especially that of the AlMnSi type, have been subjected to intensive research in recent years. These phases have been found to be closely related to periodic phases of similar composition, and orientation relationships have been found between the IQ and its decomposition products. Consequently, they are also of great importance in the study of the IQs. The most recognized periodic phase in this respect is probably the primitive α-AlMnSi phase (a = 12.68 Å). The 138 atoms in the unit cell are arranged in large atomic clusters, the socalled Mackay Icosahedra, with slightly deformed icosahedral symmetry. These clusters are believed also to be the building blocks of the quasicrystals and of some additional periodic decomposition phases, the difference between the structures being realized through a different stacking of the clusters. A thorough understanding of these periodic phases is therefore clearly important. Here we present a study of some of the defects that frequently appear in the α-phase.
Magnetic Scattering in High-Energy Electron Diffraction
Authors: Bird David , Barnard John
Published: June 2020

Over the past 25 years or so, neutron diffraction has become the standard method of probing the internal magnetic structure of crystals. More recently, however, it has been found that x-ray magnetic scattering, although weak, can be observed using bright x-ray sources. The success of x-ray techniques leads one to wonder whether magnetic scattering might also be observed using electrons, and it is this question that is addressed here. Clearly, electrons are influenced by the internal magnetic fields of specimens_this is the basis of Lorentz microscopy of ferromagnetic domains. Here we examine scattering from more exotic forms of magnetic order, such as anti-ferromagnetism. The interesting point is that antiferromagnets have magnetic Bragg spots which appear between the basic lattice spots as the magnetic order sets in. Analysis of these spots forms the basis of neutron, and now x-ray, studies of magnetic structures. The extra ingredient that electrons might offer is that imaging in such spots could reveal the local magnetic structure including domains, dynamic effects etc., in just the same way that satellite dark-field imaging has contributed to studies of structural phase transitions.
Two-photon excitation microscopy in cellular biophysics
Authors: Piston David W. , Bennett Brian D. , Summers Robert G.
Published: June 2020

Two-photon excitation microscopy (TPEM) provides attractive advantages over confocal microscopy for three-dimensionally resolved fluorescence imaging and photochemistry. Two-photon excitation arises from the simultaneous absorption of two photons in a single quantitized event whose probability is proportional to the square of the instantaneous intensity. For example, two red photons can cause the transition to an excited electronic state normally reached by absorption in the ultraviolet. In practice, two-photon excitation is made possible by the very high local instantaneous intensity provided by a combination of diffraction-limited focusing of a single laser beam in the microscope and the temporal concentration of 100 femtosecond pulses generated by a mode-locked laser. Resultant peak excitation intensities are 106 times greater than the CW intensities used in confocal microscopy, but the pulse duty cycle of 10-5 maintains the average input power on the order of 10 mW, only slightly greater than the power normally used in confocal microscopy.
Functional information from magnetic resonance imaging
Authors: Koretsky Alan P. , e Silva Afonso Costa , Lin Yi-Jen
Published: June 2020

Magnetic resonance imaging (MRI) has become established as an important imaging modality for the clinical management of disease. This is primarily due to the great tissue contrast inherent in magnetic resonance images of normal and diseased organs. Due to the wide availability of high field magnets and the ability to generate large and rapidly switched magnetic field gradients there is growing interest in applying high resolution MRI to obtain microscopic information. This symposium on MRI microscopy highlights new developments that are leading to increased resolution. The application of high resolution MRI to significant problems in developmental biology and cancer biology will illustrate the potential of these techniques.

In combination with a growing interest in obtaining high resolution MRI there is also a growing interest in obtaining functional information from MRI. The great success of MRI in clinical applications is due to the inherent contrast obtained from different tissues leading to anatomical information.
The quantitative comparison of experimental and simulated diffraction contrast images
Authors: McKernan Stuart
Published: June 2020

For many years the concept of quantitative diffraction contrast experiments might have consisted of the determination of dislocation Burgers vectors using a g.b = 0 criterion from several different 2-beam images. Since the advent of the personal computer revolution, the available computing power for performing image-processing and image-simulation calculations is enormous and ubiquitous. Several programs now exist to perform simulations of diffraction contrast images using various approximations. The most common approximations are the use of only 2-beams or a single systematic row to calculate the image contrast, or calculating the image using a column approximation. The increasing amount of literature showing comparisons of experimental and simulated images shows that it is possible to obtain very close agreement between the two images; although the choice of parameters used, and the assumptions made, in performing the calculation must be properly dealt with. The simulation of the images of defects in materials has, in many cases, therefore become a tractable problem.
Ionization delocalization and alchemi of B2-ordered alloys
Authors: Anderson I. M. , Bentley J.
Published: June 2020

Recent formulations of the ALCHEMI technique have explicitly accounted for ionization delocalization of an element i with a single linear parameter Li,- that represents the extent of localization. The x-ray emission of a spectral line characteristic of the element is assumed to be proportional to a linear combination of the thickness-averaged electron intensity at (1) the site of the atom (fraction: Li) and (2) averaged over the unit cell (fraction:1 - Li)). The parameter Li is assumed to be characteristic of the elemental shell and independent of the diffracting conditions. In consequence of these assumptions, it has been shown that ionization delocalization correction can be performed in conjunction with "statistical" ALCHEMI by correcting only the extracted correlation coefficients.

The parameter γiξ / Ii(0) is defined to be the ratio of the characteristic intensity (I) of element i at a crystal orientation (ξ) to its characteristic intensity at a reference orientation (0), which is ideally free of electron channeling effects.
Experimental measurement of Debye-Waller factors
Authors: Zuo J. M. , Holmestad R. , Tomokiyo Y. , Yase K.
Published: June 2020

Effects of atomic thermal vibration in a crystal on the diffracted intensities is described by the Debye-Waller factor (DWF). In general, DWF is a 3×3 symmetric matrix with six independent elements. For isotropic atomic vibration or atoms with cubic site symmetry, a single DWF B suffices:

here s=sinθb/λ. DWFs are among the refined parameters in structure analysis in x-ray or neutron diffraction. The accuracy of DWF in such measurements often depends on the quality of the crystal. In quantitative electron diffraction, accurate DWF is needed for 1) converting Fourier coefficients of potential to that of charge density, 2) comparison with theoretical calculations of static crystals, 3) estimation of high order structure factor and absorption coefficients.

DWF can be determined from measured amplitude of high order structure factors where the effects of bonding is minimal and DWF largest. Fig. 1 shows a plot of logrithmitic of ratios of measured MgO electron structure factors and calculated ones without temperature factor.
Strain analysis with nanometer resolution using a conventional transmission electron microsopy technique: electron diffraction contrast imaging revisited
Authors: Janssens Koenraad G F , Van der Biest Omer , Vanhellemont Jan , Maes Herman E , Hull Robert
Published: June 2020

There is a growing need for elastic strain characterization techniques with submicrometer resolution in several engineering technologies. In advanced material science and engineering the quantitative knowledge of elastic strain, e.g. at small particles or fibers in reinforced composite materials, can lead to a better understanding of the underlying physical mechanisms and thus to an optimization of material production processes. In advanced semiconductor processing and technology, the current size of micro-electronic devices requires an increasing effort in the analysis and characterization of localized strain. More than 30 years have passed since electron diffraction contrast imaging (EDCI) was used for the first time to analyse the local strain field in and around small coherent precipitates1. In later stages the same technique was used to identify straight dislocations by simulating the EDCI contrast resulting from the strain field of a dislocation and comparing it with experimental observations. Since then the technique was developed further by a small number of researchers, most of whom programmed their own dedicated algorithms to solve the problem of EDCI image simulation for the particular problem they were studying at the time.