bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time Course of Total Myofibrillar Calcium During the Cardiac Cycle: X-RAY Microprobe Analysis of Voltage-Clamped Guinea-Pig Ventricular Myocytes
Authors: Wendt-Gallitelli Maria Fiora , Isenberg Gerrit 
Published: June 2020

We report methodological efforts and results in measuring the changes in total myofibrillar Ca-concentration during systole and diastole. The measurements were made by means of electron microprobe analysis (EPMA) from ultrathin cryosections. We believe that EPMA is the only method that can adequately measure total [Ca] at the place of interest, in this case at the overlapping myofilaments of the A-band. In combination with cryotechniques, it it can be used to assess total [Ca] without disturbing the original in vivo Ca-gradients.EPMA was performed on isolated ventricular myocytes. The cells were studied at 36 °C and 2 mM extracellular Ca using a whole-cell voltage clamp. Together with the membrane currents, contractions were recorded as unloaded shortening. In a different population of myocytes, Ca ionized in the cytosol ([Ca2+]c) was estimated by microspectrofluometry (50 μM Indo-1, sodium-salt, applied through the patch pipette). The voltage-clamp gave the opportunity of controlling the voltage-operated Ca-influx, and in turn Ca-induced release of Ca from the sarcoplasmic reticulum (SR), and thus the amount of contraction.
High-resolution biological microanalysis in the field-emission STEM
Authors: Leapman R.D. , Andrews S.B. 
Published: June 2020

The recent availability of a cryotransfer stage, efficient electron energy loss spectrometers (EELS), and ultrathin window energy-dispersive x-ray spectrometers (EDXS) for the VG Microscopes HB501 field-emission STEM now provides this instrument with the potential for high resolution (<20 nm) biological microanalysis. In practice, limits are normally imposed by the sample itself, due to damage in the electron beam and to changes in structure and composition during freezing, sectioning, transfering and freeze-drying. We have therefore investigated what types of useful high-resolution analytical information can be obtained from rapidly frozen samples, including thin tissue cryosections and frozen isolated macromolecules and macromolecular assemblies.Frozen-hydrated samples were cryotransfered at ~-175C into the VG STEM after which a vacuum of ~3x10-9 mbar was maintained. Samples were freeze-dried by warming to ~-90C over 30 min and were then recooled to below ~-160C to minimize radiation damage and contamination during analysis. Digital annular dark-field images were obtained at low dose (~10 e/Å2) with single electron sensitivity, using a probe current of 2 to10 pA and a beam energy of 100 keV.
X-ray microanalysis of ion distributions in rye leaf cells at sub-zero temperatures
Authors: Pihakaski-Maunsbach Kaarina , Harvey Diana M.R. 
Published: June 2020

X-ray microanalysis has been used in a new application to study potassium changes induced by cold acclimation and freezing injuries in plant cells. Potassium is a key ion since it is the major free cation present in the plant cytoplasm. Most studies dealing with freezing injuries have been conducted on whole plants or pieces of tissues thawn after freezing. Rapid freezing of tissue pieces from defined temperatures, followed by freeze-substitution and analysis of ions by X-ray microanalysis from different cell organelles, allows conclusions about the temperature at which damage occurs.Seeds of winter rye (Secale cereale L. cv Voima) were germinated in vermiculite at 25 °C for 3 days (non-acclimated, NA). A portion of the seedlings were transferred after 2 days to 5 °C for 4 weeks (cold acclimated, A). Specimens for freeze substitution were taken from the growing temperatures, and from the temperatures where 50% (LT50) and 100% (LT100) of the plants were killed.
Measurement and parameterization of ϕ(ρz) curves for quantitative electron probe microanalysis
Authors: Brown J. D. 
Published: June 2020

The goal of correction methods for quantitative electron probe microanalysis is to convert k-ratios for any type of specimen, any x-ray line and all electron beam energies into accurate concentrations. Early attempts to approach this goal were hindered by sparse data on electron interactions with solids, limited knowledge of x-ray parameters such as mass absorption coefficients and limited computing power which made necessary mathematical simplifications in practical applications.In developing the early models for quantitative analysis, the argument was made that the absorption correction was insensitive to the shape of the ϕ(ρz) curve. For that reason, a number of very crude models which ranged from constant x-ray generation as a function of depth(l) to an exponential decrease from the surface(2) were used. In fact, these models worked quite well for the restricted conditions for which they were designed but of course lack accuracy when applied to more general situations.
ϕ(ρz) measurements
The measurement of the fluorescence of Si K x-rays by Au M x-rays
Authors: Small John A. , Wight Scott A. , Myklebust Robert L. , Newbury Dale E. 
Published: June 2020

The characteristic fluorescence correction is used in electron probe microanalysis to account for the x-ray intensity excited in element “a” by the x-rays from the characteristic line of another element, “b”, in the sample. Since the excited intensity is not generated by the primary electron beam, it is necessary to apply the fluorescence correction for quantitative elemental analysis. This correction can be significant particularly when element “b” is a major component of the sample and the characteristic line for element “b” is slightly higher in energy than the critical excitation energy for the excited line of element “a”.The fluorescence correction, which is used in the various analytical programs, is described in equation 1.where I'*fa/I'*pa is the ratio of the emitted “a” intensity excited by “b” x-rays to the emitted intensity excited by the primary electron beam. The various parameters in this equation are accurately known for the K x-ray lines, but only very limited information is available for the M x-ray lines.
A robust method for determining the Duane-Hunt energy limit from EDS
Authors: Myklebust Robert L. , Fiori Charles E. , Newbury Dale E. 
Published: June 2020

The electron beam energy is a parameter required for quantitative electron probe microanalysis. In fact, it occurs in all parts of the ZAF type matrix correction procedure as well as in all of the other matrix correction procedures. Recently, there has been much interest in analyzing materials using lower beam voltages. Since the correction procedures use the so called “overvoltage” term (beam energy/excitation energy), uncertainties in the beam voltage will generate larger errors than when high beam voltages are used. The user may well be faced with an instrument that does not have a very precise voltmeter to measure the beam voltage, or the reported voltage may not actually represent the potential drop from the filament to ground (specimen). The true beam energy may differ from the “measured” potential drop by several hundred volts.It is difficult and potentially exciting to measure the beam voltage with a calibrated voltmeter; however, we have a built-in method available in the energy-dispersive x-ray detector.
From the evaluation of the NIST Standard K-411 to the concept of a model standard in quantitative electron microprobe analysis
Authors: Vincent Yang S. , Wagstaff Jerry H. , McKay Gordon A. 
Published: June 2020

The National Institute of Standards and Technology (NIST, formally NBS) offers a wide spectrum of high quality standards. For microanalytical standards, mineral glasses SRM470 (K-411 and K-412) “provide a highly homogeneous material at microscopic spatial resolution”. Other advantages are their availability and stable compositions. At NASA-JSC, standard K-411 was evaluated along with other microprobe standards by the backward-ZAF-calculation method described by Yang and Gordon, in which no real analysis was performed. Instead, our CAMECA MBX electron microprobe was set up collecting standard records covering different elements of different standards. Then, data of the peak intensity of each standard record were converted to the elemental level and were plotted out for comparison (e.g., Figure 1). Three ZAF packages: CAMECA ZAF, CAMECA PAP, and DUST were used for data reductions.First, we use the NIST certified data for the K-411 composition with the oxygen concentration being calculated stoichiometrically. The results show that Si is obviously under corrected by all three ZAF packages.
Computer-Assisted Wavelength-Dispersive X-Ray Mapping
Authors: Chambers William F. , Doyle Joe H. 
Published: June 2020

Elemental x-ray maps frequently provide one of the best ways to display compositional gradients and inhomogeneities in a sample. Two problems consistently plague the effective use of elemental x-ray mapping: Proper exposure and the maintenance of x-ray focus. Solutions applicable to Cameca MBX microprobes have been previously reported. These solutions involved aligning the X-axis of the electron beam raster parallel to the insensitive axis of the analyzing crystal and synchronously scanning the spectrometer with the Y-axis of the electron beam raster to maintain x-ray focus. The ability of the Cameca to set the beam current via an external computer was also utilized.We have recently needed to duplicate these capabilities on JEOL microprobes. JEOL and MBX instruments differ in three important aspects relating to their x-ray mapping capabilities.. First, although JEOL instruments can read the beam current, they do not have the capability of setting it via an external computer.
FR-IR Molecular Microanalysis System
Authors: Reffner John A. , Wihlborg William T. 
Published: June 2020

The IRμs™ is the first fully integrated system for Fourier transform infrared (FT-IR) microscopy. FT-IR microscopy combines light microscopy for morphological examination with infrared spectroscopy for chemical identification of microscopic samples or domains. Because the IRμs system is a new tool for molecular microanalysis, its optical, mechanical and system design are described to illustrate the state of development of molecular microanalysis. Applications of infrared microspectroscopy are reviewed by Messerschmidt and Harthcock.Infrared spectral analysis of microscopic samples is not a new idea, it dates back to 1949, with the first commercial instrument being offered by Perkin-Elmer Co. Inc. in 1953. These early efforts showed promise but failed the test of practically. It was not until the advances in computer science were applied did infrared microspectroscopy emerge as a useful technique. Microscopes designed as accessories for Fourier transform infrared spectrometers have been commercially available since 1983. These accessory microscopes provide the best means for analytical spectroscopists to analyze microscopic samples, while not interfering with the FT-IR spectrometer’s normal functions.
Hexachlorobenzine Toxicity in the Monkey Ovary: I. Ultrastructure Induced by Low (0.1 Mg/Kg) Dose Exposure
Authors: Singh A. , Friesen D. , Jarrell J. , Villeneuve D. C. 
Published: June 2020

Introduction. Hexachlorobenzene (HCB), a persistent and mobile organochlorine pesticide, is known to occur in the environment. The HCB has been shown to be present in human serum and follicular fluid. An objective of the present study was to detect the cytologic effects of HCB on ovarian follicles in a primate model.Materials and Methods. Eight Cynomolgus monkeys were housed under controlled conditions at the Animal Facility of Health and Welfare, Ottawa. Animals were orally administered gelatin capsules containing HCB mixed with glucose in daily dosages of 0.0 or 0.1 mg/kg body weight for 90 days; the former was the control group. On the menstrual period following completion of dosing, the monkeys underwent an induction cycle of IVF. At necropsy, one ovary from each animal was diced into ca. 2- to 3-mm cubed specimens that were fixed by immersion in 2.5% glutaraldehyde in 0.1 M cacodylate buffer (pH 7.3); specimens were again fixed in 2% osmium tetroxide prepared in the same buffer.
Ultrastructure of Hamster and Rat Lungs After Chronic Inhalation Exposure to Cadmium Compounds
Authors: Thiedemann K.-U. , Lüthe N. , Kreft A. , Abel U. , Heinrich U. , Glaser U. 
Published: June 2020

Chronic inhalation exposure to aerosolized CdCl2 increases the incidence of lung tumors in rats. For the present study small numbers of rats and hamsters were derived from the experimental groups of a longterm inhalation study with CdCl2, CdSO4, CdO and CdS. The goal of our LM, SEM and TEM investigations was to collect detailed observations on fibrotic, hyperplastic, and preneoplastic alterations of lung tissue occurring during this experiment.Immediately after sacrifice, the lungs of the animals were fixed by intratracheal instillation of Karnovsky fixative. Tissue samples were collected from the right middle lobe of the lung. For TEM the samples were postfixed with OSO4 and routine embedded in Epon. For SEM the tissue was CPD dried, mounted on Al-stubs and sputtered with Au.Exposure to all Cd compounds caused a significant increase in tumor incidence in rats but not in hamsters. In both species a multifocal alveolar bronchiolization and a generalized thickening of the alveolar septa were observed.
Characterisation and Classification of Individual Coal Mine Dust Particles by Computer-Controlled Electron Microprobe Analysis
Authors: Dorriné W. , Van Espen P. , Adams F. , Préat B. 
Published: June 2020

Extremely dusty working conditions are a serious health risk for coal miners. Quartz and other minerals are known to cause lung diseases when inhaled over long periods of time. In this work, a study was made of the mineral content in coal mine dust. Individual particles were characterised using computer controlled electron microprobe analysis and then classified into different mineral categories using a multivariate classification procedure.Coal mine dust particles were collected from the Zolder coal mine, Belgium, using a BAT II cyclone sampling unit. Small quantities of the dust were suspended in n-hexane using an ultrasonic water bath. Approximately 100 μl of the suspension were spotted on a plexiglass stub and dried. The excess carbon was removed by ashing the samples for two hours in a low temperature asher (LTA). The samples were coated with a carbon layer of ±40 nm for microprobe analysis. An identical sample preparation procedure was used to prepare 6 mineral standards : biotite, illite, kaolinite, quartz, muscovite and ripidolite.
Methods to Study Interactions Between Inhaled Substances and Epithelium of the Respiratory Tract in Vitro
Authors: Adler Kenneth B. , Akley Nancy J. , Lee Jianngwu 
Published: June 2020

Epithelium lining the tracheobronchial tree represents the first cells with which particulates, gases, microbes, etc., come into contact upon inhalation. Thus, interactions between such inhaled substances and epithelial cells probably are integral to the pathogenesis of several occupational or environmental - related pulmonary lesions, yet such interactions have not yet been elucidated fully. Many published studies have described patterns of deposition within extra- and intrapulmonary airways and alveolar ducts, and histologic and ultrastructural changes in epithelium in vivo in response to inhalation and deposition. However, our knowledge of specific structural and functional responses of airway epithelium on a cellular level is limited, since exposures of animals in vivo or even tissues in situ do not allow for studying intracellular responses, especially subtle sublytic alterations which could be the basis for subsequent pathogenic responses.For this reason, investigators have utilized cell culture systems to examine intracellular mechanisms related to responses of respiratory epithelium to deleterious substances which may be inhaled in an occupational or environmental setting.
Bulk Specimen Preparation For X-Ray Microanalysis of Plant Cells
Authors: Ahlstrand Gilbert G. , Zeyen Richard J. 
Published: June 2020

Numerous plant pathological investigations have been published where pathologists determined elemental differences between diseased and healthy plant tissue using unfractured bulk specimens and energy dispersive x-ray microanalysis (EDX). In these studies effects of specimen preparation procedures were largely ignored (1). Our objective was to compare bulk specimen preparation procedures using healthy leaf epidermal (surface) cells of barley, Hordeum vulgare, (Fig. 1) to determine advantages and disadvantages of each procedure for reference to future pathological work using EDX. Three preparation procedures were compared: 1) Frozen-hydrated (FH) specimens to maintain soluble and insoluble elements in situ; 2) Freeze-dried (FD) specimens to maintain total soluble and insoluble elements and allow deeper beam penetration than does FH, and; 3) Formalin/acetic acid/ethanol (FAA) fixed specimens, dehydrated in ethanol, and critical point dried (CD) using CO2, for determination of elemental loss in liquid fixatives (2,3).Aluminum specimen stubs were colloidal graphite coated (leaf segments attached to graphite areas) leaving clean Al margins for calibration.
Intergranular Boron Segregation in Nickel-Based Superalloys
Authors: Koopman Mark C. , Thompson Raymond G. 
Published: June 2020

Boron has long been known for its beneficial effects on grain boundary toughness at high temperature in stress rupture and more recently at low temperature in Ni3Al. It also has a bad reputation for promoting intergranular microfissuring in the heat affected zone of welds. Although its intergranular segregation behavior is documented for the nickel aluminides, its segregation in high nickel alloys has not been well documented. The present research is directed at exploring the chemistry of intergranular surfaces in an alloy matrix similar to alloy 718 with controlled interstitial and substitutional impurities.A base composition contained typical alloy 718 levels of Ni, Cr, Fe, Mo, Nb, Al, Ti, and less than 0.001w% of S, B, C, P, Si, Zr, and Hf. Three modifications of this matrix where examined: one with .0.01 B and Hf; one with 0.01 B, C, Hf, and Zr; and one with 0.01 B, S, P, and Zr. Specimens where electrolytically charged with hydrogen to promote intergranular fracture.
Multispectral Surface Analytical Microscopy: A Third-Generation Scanning Auger Electron Microscope
Authors: Prutton M , El Gomati M M , Greenwood J C , Kennyr P G , Barkshire I R , Dee J C 
Published: June 2020

The quantitative interpretation of scanning Auger electron microscope (SAM) images has been shown to require the use of multi-spectral imaging of the surface under study. In a multi-spectral analytical microscope (MULSAM) a set of maps (bands) is acquired from the same area of a sample using scattered electrons with different kinetic energies as well as other signals from the sample such as current flowing to ground, the conventional SEM signal and characteristic x-rays. The resulting set of bands is a multi-spectral image which can be processed using models of the electron scattering in the sample and statistical transforms well known in LANDSAT imaging technology. The processed images can separate the mixed effects of topography, surface chemical inhomogeneity and bulk chemical composition fluctuations occurring in the bands of raw data.A computer controlled, UHV, energy analysing, scanning electron SEM will be described in this paper. The microscope contains facilities for collecting up to 23 256 by 256 pixel image bands from the same area of the sample.
Convergent-Beam RHEED of GaAs(110) in a STEM: Theory and Experiment
Authors: Bleloch A. L. , Howie A. , Lanzerotti M. Y. 
Published: June 2020

A number of approaches to the theory of reflection high energy electron diffraction (RHEED) have been published over the years. There have been, however, few direct comparisons with experiment. In particular, the authors are not aware of calculations of the type of convergent beam RHEED (CBRHEED) pattern with very large convergence angle presented here. (By the principle of reciprocity, parallel illumination and a large collection angle in STEM is equivalent to a large angle convergent probe in a conventional transmission electron microscope (CTEM)) Large angle CBRHEED patterns provide a convenient method for investigating the origin and sensitivity of the so called surface resonance lines. These lines are the prominent features marked on Figure 1. There have been a number of attempts to explain this phenomenon. Initial results of calculations on GaAs patterns are presented together with experimental results.The approach is an extension of that of Collela in that Bloch wave amplitudes in three dimensions are computed with suitable reflection boundary conditions.
Kinematic Approximations in TED and RHEED Analysis of Reconstructed Surfaces
Authors: Peng L. -M. , Whelan M. J. 
Published: June 2020

In recent years there has been a trend in the structure determination of reconstructed surfaces to use high energy electron diffraction techniques, and to employ a kinematic approximation in analyzing the intensities of surface superlattice reflections. Experimentally this is motivated by the great success of the determination of the dimer adatom stacking fault (DAS) structure of the Si(111) 7 × 7 reconstructed surface.While in the case of transmission electron diffraction (TED) the validity of the kinematic approximation has been examined by using multislice calculations for Si and certain incident beam directions, far less has been done in the reflection high energy electron diffraction (RHEED) case. In this paper we aim to provide a thorough Bloch wave analysis of the various diffraction processes involved, and to set criteria on the validity for the kinematic analysis of the intensities of the surface superlattice reflections.The validity of the kinematic analysis, being common to both the TED and RHEED case, relies primarily on two underlying observations, namely (l)the surface superlattice scattering in the selvedge is kinematically dominating, and (2)the superlattice diffracted beams are uncoupled from the fundamental diffracted beams within the bulk.
Investigation of Beam Energy Threshold and Atom Diffusion Effects in Ionization Damage of Organic Molecular Crystals
Authors: Howie A. , Mohd Muhid M.N. , Valdré U. 
Published: June 2020

The electron beam damage cross section σ(E) in thin aromatic molecular crystals has an appearance threshold near lkeV beam energy shown in fig. 1. By contrast no such threshold appears (fig. 2) for damage in sufficiently thin crystals of much more sensitive non-aromatic molecules. We conclude that the usually dominant valence excitation damage mechanism is suppressed by the aromatic π-electron screening, leaving the less probable carbon K-shell ionisation process as the key damage event. Alternative explanations based on critical momentum transfer to whole molecules in these weakly bonded crystals could also give a threshold effect but its position in energy would increase with the mass of the molecule which is contrary to observation.Quantitative investigation of this hypothesis is complicated by strong scattering and energy loss which can prevent the beam penetrating deeper layers in the crystal with sufficient energy to damage them. The results have therefore been simulated by Monte Carlo methods which explain well the dependence of the damage cross sections on both beam energy and crystal thickness.