scholarly journals A NanoSIMS 50 L Investigation into Improving the Precision and Accuracy of the 235U/238U Ratio Determination by Using the Molecular 235U16O and 238U16O Secondary Ions

Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 307 ◽  
Author(s):  
N. Zirakparvar ◽  
Cole Hexel ◽  
Andrew Miskowiec ◽  
Julie Smith ◽  
Michael Ambrogio ◽  
...  
Keyword(s):  
Reference Materials ◽  
The Other ◽  
Primary Beam ◽  
Uranium Compounds ◽  
Accuracy And Precision ◽  
Secondary Ions ◽  
Precision And Accuracy ◽  
Improved Accuracy ◽  
Secondary Ion ◽  
238U Ratio

A NanoSIMS 50 L was used to study the relationship between the 235U/238U atomic and 235U16O/238U16O molecular uranium isotope ratios determined from a variety of uranium compounds (UO2, UO2F2, UO3, UO2(NO3)2·6(H2O), and UF4) and silicates (NIST-610 glass and the Plesovice zircon reference materials, both containing µg/g uranium). Because there is typically a greater abundance of 235U16O+ and 238U16O+ molecular secondary ions than 235U+ and 238U+ atomic ions when uranium-bearing materials are sputtered with an oxygen primary ion beam, the goal was to understand whether use of 235U16O/238U16O has the potential for improved accuracy and precision when compared to the 235U/238U ratio. The UO2 and silicate reference materials showed the greatest potential for improved accuracy and precision through use of the 235U16O/238U16O ratio as compared to the 235U/238U ratio. For the UO2, which was investigated at a variety of primary beam currents, and the silicate reference materials, which were only investigated using a single primary beam current, this improvement was especially pronounced at low 235U+ count rates. In contrast, comparison of the 235U16O/238U16O ratio versus the 235U/238U ratio from the other uranium compounds clearly indicates that the 235U16O/238U16O ratio results in worse precision and accuracy. This behavior is based on the observation that the atomic (235U+ and 238U+) to molecular (235U16O+ and 238U16O+) secondary ion production rates remain internally consistent within the UO2 and silicate reference materials, whereas it is highly variable in the other uranium compounds. Efforts to understand the origin of this behavior suggest that irregular sample surface topography, and/or molecular interferences arising from the manner in which the UO2F2, UO3, UO2(NO3)2·6(H2O), and UF4 were prepared, may be a major contributing factor to the inconsistent relationship between the observed atomic and molecular secondary ion yields. Overall, the results suggest that for certain bulk compositions, use of the 235U16O/238U16O may be a viable approach to improving the precision and accuracy in situations where a relatively low 235U+ count rate is expected.

Characterization of Atmospheric Impurities in Tungsten Silicide Films by Secondary Ion Mass Spectrometry (SIMS)

1995 ◽  
Vol 402 ◽  
Author(s):  
Salman Mitha ◽  
David B. Sams
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Relative Sensitivity ◽  
Areal Density ◽  
Primary Beam ◽  
Tungsten Silicide ◽  
Secondary Ions ◽  
Signal Change ◽  
Ion Mass Spectrometry ◽  
Secondary Ion

AbstractConcentrations of atmospheric impurities in tungsten silicide films and impurity areal densities silicide / polysilicon interface can usually only be measured using Secondary Ion Mass Spectrometry (SIMS). Normally these measurements are made using a Cs+ primary beam with negative secondary ions being monitored. This mode is used to achieve the best possible detection limits. However the Relative Sensitivity Factors (RSFs) used to quantify the impurities, as well as the reference matrix signal, change dramatically in going from one matrix to the other. These changes affect the quantification of the impurities at the interface. An alternate mode of analysis would be to use the Cs+ primary beam and monitor MCs+ ions, where M is the impurity, because these ions typically have less matrix dependent RSFs. We measure carbon and oxygen in a tungsten silicide film on polysilicon using both modes of analysis. Preliminary data indicates that we have determined the absolute accuracy of interface areal density to within a factor of 2.2 for oxygen and to within a factor of 1.5 for carbon.

scholarly journals Extreme isotopologue disequilibrium in molecular SIMS species during SHRIMP geochronology

2017 ◽  
Vol 6 (2) ◽  
pp. 523-536 ◽  
Author(s):  
Charles W. Magee Jr. ◽  
Martin Danišík ◽  
Terry Mernagh
Keyword(s):  
Molecular Species ◽  
Secondary Ion Mass Spectrometry ◽  
Transmission Efficiency ◽  
Primary Beam ◽  
Element Analysis ◽  
Ideal Mixing ◽  
Accuracy And Precision ◽  
Secondary Ions ◽  
Shrimp Geochronology ◽  
Relative Differences

Abstract. The current limitation in the accuracy and precision of inter-element analysis in secondary ion mass spectrometry (SIMS) is the ability to find measurable quantities that allow relative differences in ionization and transmission efficiency of secondary ions to be normalized. In uranium–thorium–lead geochronology, the ability to make these corrections, or "calibrate" the data, results in an accuracy limit of approximately 1 %. This study looks at the ionization of uranium and thorium oxide species, which are traditionally used in U–Pb calibration, to explore the conditions under which isotopologues, or molecular species whose composition differs only in the isotopic composition of one or more atoms in the molecule, remain in or deviate from equilibrium. Isotopologue deficits of up to 0.2 (200 ‰) below ideal mixing are observed in UO2+ species during SIMS gechronological analyses using the SHRIMP IIe SIMS instrument. These are identified by bombarding natural U-bearing minerals with an 18O2− primary beam. The large anomalies are associated with repeat analyses down a single SIMS sputtering crater (Compston et al., 1984), analysis of high-uranium, radiation-damaged zircon, and analysis of baddeleyite. Analysis of zircon under routine conditions yield UO2+ isotopologue anomalies generally within a few percent of equilibrium. The conditions under which the isotopologue anomalies are observed are also conditions in which the UOx-based corrections, or calibration, for relative U vs. Pb ionization efficiencies fail. The existence of these isotopologue anomalies suggest that failure of the various UOx species to equilibrate with each other is the reason that none of them will successfully correct the U  / Pb ratio. No simple isotopologue-based correction is apparent. However, isotopologue disequilibrium appears to be a more sensitive tool for detecting high-U calibration breakdowns than Raman spectroscopy, which showed sharper peaks for  ∼  37 Ma high-uranium zircons than for reference zircons OG1 and Temora. U–Th–Sm / He ages were determined for aliquots of reference zircons OG1 (755±71 Ma) and Temora (323±43 Ma), suggesting that the broader Raman lines for the Temora reference zircons may be due to something other than accumulated radiation damage. Isotopologue abundances for UO+ and ThO+ and their energy spectra are consistent with most or all molecular species being the product of atomic recombination when the primary beam impact energy is greater than 5.7 keV. This, in addition to the large UO2+ instrumentally generated isotopologue disequilibria, suggests that any attempts to use SIMS to detect naturally occurring isotopologue deviations could be tricky.

Microchemical imaging in biomedical research

1992 ◽  
Vol 50 (2) ◽  
pp. 1118-1119
Author(s):  
P. Ingram
Keyword(s):  
Data Analysis ◽  
Electron Probe ◽  
The Other ◽  
X Ray ◽  
Cell Element ◽  
Physiological Information ◽  
Functional States ◽  
Elemental Maps ◽  
Electron Energy Loss ◽  
Secondary Ion

It is well established that unique physiological information can be obtained by rapidly freezing cells in various functional states and analyzing the cell element content and distribution by electron probe x-ray microanalysis. (The other techniques of microanalysis that are amenable to imaging, such as electron energy loss spectroscopy, secondary ion mass spectroscopy, particle induced x-ray emission etc., are not addressed in this tutorial.) However, the usual processes of data acquisition are labor intensive and lengthy, requiring that x-ray counts be collected from individually selected regions of each cell in question and that data analysis be performed subsequent to data collection. A judicious combination of quantitative elemental maps and static raster probes adds not only an additional overall perception of what is occurring during a particular biological manipulation or event, but substantially increases data productivity. Recent advances in microcomputer instrumentation and software have made readily feasible the acquisition and processing of digital quantitative x-ray maps of one to several cells.

Applications of Time-OF-Flight Secondary Ion Mass Spectrometry (TOF-SIMS)

1990 ◽  
Vol 48 (2) ◽  
pp. 308-309
Author(s):  
Bruno Schueler ◽  
Robert W. Odom
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Structural Information ◽  
Time Of Flight ◽  
Biological Tissues ◽  
Polymer Surfaces ◽  
Tof Sims ◽  
Secondary Ions ◽  
Ion Mass Spectrometry ◽  
Secondary Ion

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) provides unique capabilities for elemental and molecular compositional analysis of a wide variety of surfaces. This relatively new technique is finding increasing applications in analyses concerned with determining the chemical composition of various polymer surfaces, identifying the composition of organic and inorganic residues on surfaces and the localization of molecular or structurally significant secondary ions signals from biological tissues. TOF-SIMS analyses are typically performed under low primary ion dose (static SIMS) conditions and hence the secondary ions formed often contain significant structural information.This paper will present an overview of current TOF-SIMS instrumentation with particular emphasis on the stigmatic imaging ion microscope developed in the authors’ laboratory. This discussion will be followed by a presentation of several useful applications of the technique for the characterization of polymer surfaces and biological tissues specimens. Particular attention in these applications will focus on how the analytical problem impacts the performance requirements of the mass spectrometer and vice-versa.

What Hinders Accurate Depiction of Projective Shape?

Perception ◽  
1995 ◽  
Vol 24 (9) ◽  
pp. 995-1010 ◽  
Author(s):  
Emiel Reith ◽  
Chang Hong Liu
Keyword(s):  
Da Vinci ◽  
The Other ◽  
Frontoparallel Plane ◽  
Glass Pane ◽  
Drawing Task ◽  
Visual Projection ◽  
Vertical Glass ◽  
Perceptual Abilities ◽  
Improved Accuracy ◽  
Projective Shape

Adult subjects drew the visual projection of two models. One model was a trapezoid placed in the frontoparallel plane. The other was a tilted rectangle which displayed the same projective shape on a frontoparallel plane as the trapezoid. The drawing conditions were varied in two ways: the model remained available for inspection during the drawing task or it was masked after initial inspection; the subjects drew on paper placed flat on the table or on a vertical glass pane placed in front of the model (ie on a da Vinci window). The results were that (i) the projective shape of the frontoparallel trapezoid was reproduced accurately whereas that of the tilted rectangle was systematically distorted in the direction of its actual physical dimensions; (ii) when subjects drew on paper, the presence or absence of a view of the model made no difference to the amount of distortion; (iii) drawing on a da Vinci window improved accuracy even when the model was hidden. These findings provide information about the relative roles of object-centred knowledge, perceptual abilities, and depiction skills in drawing performance.

TC1725 - A Proposed Chalcopyrite Reference Material for LA-MC-ICP-MS Sulfur Isotope Determination

2021 ◽  
Author(s):  
Zhian Bao ◽  
Kaiyun Chen ◽  
Chunlei Zong ◽  
Honglin Yuan
Keyword(s):  
Reference Material ◽  
Reference Materials ◽  
Sulfur Isotope ◽  
Accuracy And Precision ◽  
Icp Ms ◽  
Geochemical Tracer ◽  
Isotope Determination

Sulfur isotope is an important geochemical tracer in diverse fields of geosciences. Controlling the accuracy and precision of microanalysis of sulfur isotope requires well-characterized reference materials with matrices similar to...

scholarly journals Deep spatio-temporal emotion analysis of geo-tagged tweets for predicting location based communal emotion during COVID-19 Lock-down

2021 ◽  
pp. 1-14
Author(s):  
M. Amsaprabhaa ◽  
Y. Nancy Jane ◽  
H. Khanna Nehemiah
Keyword(s):  
Latent Dirichlet Allocation ◽  
Temporal Analysis ◽  
The Other ◽  
Classification Model ◽  
Grid Search ◽  
Analysis Framework ◽  
Emotion Classification ◽  
Spatio Temporal ◽  
Improved Accuracy ◽  
State Of Art

Due to the COVID-19 pandemic, countries across the globe has enforced lockdown restrictions that influence the people’s socio-economic lifecycle. The objective of this paper is to predict the communal emotion of people from different locations during the COVID-19 lockdown. The proposed work aims in developing a deep spatio-temporal analysis framework of geo-tagged tweets to predict the emotions of different topics based on location. An optimized Latent Dirichlet Allocation (LDA) approach is presented for finding the optimal hyper-parameters using grid search. A multi-class emotion classification model is then built via a Recurrent Neural Network (RNN) to predict emotions for each topic based on locations. The proposed work is experimented with the twitter streaming API dataset. The experimental results prove that the presented LDA model-using grid search along with the RNN model for emotion classification outperforms the other state of art methods with an improved accuracy of 94.6%.

Secondary Ion Mass Spectrometry Reference Materials for Lithium in Carbonaceous Matrices

2022 ◽  
Author(s):  
Zebadiah Teichert ◽  
Maitrayee Bose ◽  
Peter Williams ◽  
Richard L. Hervig ◽  
Lynda B. Williams
Keyword(s):  
Mass Spectrometry ◽  
Reference Materials ◽  
Secondary Ion Mass Spectrometry ◽  
Ion Mass Spectrometry ◽  
Secondary Ion
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