Turbulent Journal Bearings: Design Charts for Performance Prediction

Precise isotopic analysis of uranium in picomole and subpicomole quantities

“…The isotopic composition of the double spike is given in Table II. The absolute ratio of 233U/236U and the concentration in the mixed spike were determined by using a solution of mixed spike and the NBS U-500 standard (99.4% U308, "U/^U = 1.0003 ± 0.001) (14) to correct for fractionation. The limiting uncertainty in the 28sU/23eU ratio in the spike is the error in the NBS U-500 standard, as all ratios used for calibration were near unity.…”

The Absolute Isotopic Abundance and Atomic Weight of a Reference Sample of Silver

“…Analysis under identical conditions of Hl9 Ag samples ranging in amount from 4 ILg to 0.005 .... g indicated a possible mass-I07 isobaric intenerence a.t a level of 1 (± 1) X [10][11][12][13][14][15][16] A. This level of interference is below the direct measurement detection Hmit of the instrument but can be inferred from the slight decrease in the observed 109/107 ratio with decreasing sample size.…”

“…The method used for the detennination of atomic weights at NBS, which has been briefly described in previous publications [1][2][3][4][5][6][7][8][9][10][11][12][13][14], and may be described as calibrated mass spectrometry, combines the techniques of high precision chemical assay with high precision mass spectrometry. The mass spectrometers to be used for the isotopic abundance measurements are calibrated for bias using synthetic mixes of known isotopic composition, prepared from nearly pure separated isotopes.…”