Rapid Extraction Chemistry Using a Single Column for 230Th/U Dating of Quaternary Hydrothermal Sulfides

230Th/U dating can provide high-precision age constraints on Quaternary hydrothermal sulfides. However, low content of U and Th often involves extraction chemistry for the separation and enrichment of U and Th, but these chemical processes are very complex. We developed a simplified procedure consisting of total sample dissolution and single-column extraction chemistry, which can reduce the time and improve the accuracy of the dating. Concentrated HCl-HF followed by HNO3 was added to ensure complete dissolution. A single column filled with 0.4 mL of AG 1-X8 anion resin was used, then 8 M HNO3, 8 M HCl and 0.1 M HNO3 were used to elute most of the matrix metals, Th and U. This process provided more than 95% recoveries for U and Th, and negligible blanks. Meanwhile, Pb and Bi interferences were tested and showed no effect on the U and Th isotope ratio. The 230Th/238U activity of the Geological Survey of Japan geochemical reference material JZn-1 in secular equilibrium was determined and showed a radioactive equilibrium (1.00 ± 0.01, n = 5, all errors 2σ) and an in-house standard QS-1 was consistent to 0.0078 ± 0.0001 (n = 8, ±2σ) with an average age of 705 ± 10 yrs BP (n = 8, ±2σ). The technique greatly shortens the sample preparation time and allows more concise and effective analysis of U-Th isotopes. It is ideally suited for the high-precision 230Th/U dating of Quaternary submarine hydrothermal sulfides and sulfides from other settings.

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High-precision isotopic analyses of uranium and plutonium by total sample volatilization and signal integration

International Journal of Mass Spectrometry and Ion Processes ◽

10.1016/0168-1176(91)80081-w ◽

1991 ◽

Vol 103 (2-3) ◽

pp. 93-105 ◽

Cited By ~ 84

Author(s):

E.L. Callis ◽

R.M. Abernathey

Keyword(s):

High Precision ◽

Total Sample ◽

Signal Integration ◽

Isotopic Analyses

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MC2: a two-phase algorithm for leveraged matrix completion

Information and Inference A Journal of the IMA ◽

10.1093/imaiai/iax020 ◽

2018 ◽

Vol 7 (3) ◽

pp. 581-604 ◽

Cited By ~ 1

Author(s):

Armin Eftekhari ◽

Michael B Wakin ◽

Rachel A Ward

Keyword(s):

Broad Class ◽

Matrix Completion ◽

A Priori ◽

Total Sample ◽

Second Phase ◽

Sample Complexity ◽

Two Phase ◽

The Matrix ◽

Leverage Scores ◽

Uniform Random Sampling

Abstract Leverage scores, loosely speaking, reflect the importance of the rows and columns of a matrix. Ideally, given the leverage scores of a rank-r matrix $M\in \mathbb{R}^{n\times n}$, that matrix can be reliably completed from just $O (rn\log ^{2}n )$ samples if the samples are chosen randomly from a non-uniform distribution induced by the leverage scores. In practice, however, the leverage scores are often unknown a priori. As such, the sample complexity in uniform matrix completion—using uniform random sampling—increases to $O(\eta (M)\cdot rn\log ^{2}n)$, where η(M) is the largest leverage score of M. In this paper, we propose a two-phase algorithm called MC2 for matrix completion: in the first phase, the leverage scores are estimated based on uniform random samples, and then in the second phase the matrix is resampled non-uniformly based on the estimated leverage scores and then completed. For well-conditioned matrices, the total sample complexity of MC2 is no worse than uniform matrix completion, and for certain classes of well-conditioned matrices—namely, reasonably coherent matrices whose leverage scores exhibit mild decay—MC2 requires substantially fewer samples. Numerical simulations suggest that the algorithm outperforms uniform matrix completion in a broad class of matrices and, in particular, is much less sensitive to the condition number than our theory currently requires.

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Determination of Arsenic, Chromium and Lead in titanium dioxide pigments by ICP- OES with Concomitant Metals Analyser

International Journal of Scientific Research in Science and Technology ◽

10.32628/ijsrst196664 ◽

2019 ◽

pp. 296-305

Author(s):

Beena Sunilkumar ◽

S. B. Singh

Keyword(s):

Titanium Dioxide ◽

Matrix Effects ◽

Mineral Acid ◽

Icp Oes ◽

Acid Decomposition ◽

Simple Method ◽

Sample Dissolution ◽

The Matrix ◽

Generating System

A simple method has been developed for the determination of trace toxic elements like arsenic, lead and chromium in titanium dioxide pigment samples by ICP OES attached with a Concomitant Metals Analyser. Open mineral acid decomposition was used for sample dissolution employing a mixture of nitric and hydrofluoric acids. The continuous online generation of hydrides into the plasma was achieved through a concomitant metals analyser. The recovery of arsenic, lead and chromium and the matrix effects of titanium on these elements have been studied with spiking experiments. The proposed method has been successfully applied to the determination of arsenic and other elements in titanium pigment samples. The continuous hydride generating system, Concomitant Metals Analyser (CMA) improved the sensitivity of analysis nearly five times in pigment samples. The precision of the measurements was found to be less than 10% RSD.

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An updated matrix to predict rapid radiographic progression of early rheumatoid arthritis patients: pooled analyses from several databases

Rheumatology ◽

10.1093/rheumatology/kez542 ◽

2019 ◽

Vol 59 (8) ◽

pp. 1842-1852 ◽

Cited By ~ 1

Author(s):

Antoine Vanier ◽

Josef S Smolen ◽

Cornelia F Allaart ◽

Ronald Van Vollenhoven ◽

Patrick Verschueren ◽

...

Keyword(s):

High Precision ◽

Radiographic Progression ◽

Area Under The Curve ◽

X Rays ◽

Early Ra ◽

The Matrix ◽

Moderate Sensitivity ◽

Baseline Characteristics ◽

One Year ◽

Post Hoc

Abstract Objective In early RA, some patients exhibit rapid radiographic progression (RRP) after one year, associated with poor functional prognosis. Matrices predicting this risk have been proposed, lacking precision or inadequately calibrated. We developed a matrix to predict RRP with high precision and adequate calibration. Methods Post-hoc analysis by pooling individual data from cohorts (ESPOIR and Leuven cohorts) and clinical trials (ASPIRE, BeSt and SWEFOT trials). Adult DMARD-naïve patients with active early RA for which the first therapeutic strategy after inclusion was to prescribe methotrexate or leflunomide were included. A logistic regression model to predict RRP was built. The best model was selected by 10-fold stratified cross-validation by maximizing the Area Under the Curve. Calibration and discriminatory power of the model were checked. The probabilities of RRP for each combination of levels of baseline characteristics were estimated. Results 1306 patients were pooled. 20.6% exhibited RRP. Four predictors were retained: rheumatoid factor positivity, presence of at least one RA erosion on X-rays, CRP > 30mg/l, number of swollen joints. The matrix estimates RRP probability for 36 combinations of level of baseline characteristics with a greatly enhanced precision compared with previously published matrices (95% CI: from ± 0.02 minimum to ± 0.08 maximum) and model calibration is excellent (P = 0.79). Conclusion A matrix proposing RRP probability with high precision and excellent calibration in early RA was built. Although the matrix has moderate sensitivity and specificity, it is easily usable and may help physicians and patients to make treatment decisions in daily clinical practice.

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