In real soundings of the Earth’s atmosphere, it has been found that the phase and amplitude of the signal received undergo strong oscillations at altitudes above the neutral atmosphere and below the Elayer of the ionosphere. This ionospheric scintillation effect is a consequence of multipath propagation resulting from inhomogeneities in the refractivity field of the ionosphere. Ionospheric scin...

stools were determined by liquid scintillation counting. Plasma and urine alkylating activity was measured by reaction with 4-(4-nitrobenzyl)pyridine. Protein binding of cyclophosphamide and plasma alkylating metabolites were deter mined by plasma ultrafiltration. Injected Cyclophosphamide distributed rapidly into 64% of body weight, and plasma Cyclophosphamide half-life in patients without pri...

The TopCountTM Microplate Scintillation Counter quantitates radioisotopes by liquid scintillation counting in standard microplate formats. Assays that previously had to be transferred from microplates to vials or to non-standard formats for counting can now be quantitated directly in microplates. TopCount can count up to 12 samples simultaneously with performance comparable to that of discrete ...

Cosmogenic sulfur-35 in water as dissolved sulfate ((35)SO4) has successfully been used as an intrinsic hydrologic tracer in low-SO4, high-elevation basins. Its application in environmental waters containing high SO4 concentrations has been limited because only small amounts of SO4 can be analyzed using current liquid scintillation counting (LSC) techniques. We present a new analytical method f...

Liquid scintillation counting of 3H-labeled whole-blood samples is severely impaired owing to quenching by blood pigments. In this study, dry oxidation and chemical solubilization followed by decolorization were the two general methods used to eliminate color quenching. Three blood volumes were examined: 0.25, 0.50, and 1.0 mL. Dry oxidation yielded complete recoveries of 3H label with counting...

An informal bilateral comparison of (14)C liquid scintillation (LS) counting at the National Research Council of Canada (NRC) and the National Institute of Standards and Technology (NIST) has been completed. Two solutions, one containing (14)C-labeled sodium benzoate and one containing (14)C-labeled n-hexadecane, were measured at both laboratories. Despite observed LS cocktail instabilities, th...

The determination of radium and/or uranium concentrations in natural waters is useful in a wide range of environmental studies. In this work, a low-background liquid scintillation system (Wallac, Quantulus 1220) was used to determine simultaneously 226Ra and uranium (total) activities in natural water samples. Sample preparation involved filtration and 1 : 10 concentration by evaporation. Then,...

It is most important to assure 4 π−geometry in liquid scintillation counting for accurate results1. Usually this can be assured by dissolution of the sample in an appropriate cocktail. The cocktail does not only contain a solvent but also at least one scintillator and surfactants for aqueous samples because aqueous samples are completely insoluble in the pure organic solvents and scintillators....

The TopCountTM Microplate Scintillation Counter quantitates radioisotopes by liquid scintillation counting in standard microplate formats. Assays that previously had to be transferred from microplates to vials or to non-standard formats for counting can now be quantitated directly in microplates. TopCount can count up to 12 samples simultaneously with performance comparable to that of discrete ...

Kinetic isotope effects (KIEs) are a very powerful tool for investigating enzyme mechanisms. Precision of measurement is the most important factor for KIE determinations, especially for small heavy atom KIEs. Internal competition is commonly used to measure small KIEs on V/K. Several methods, including such as liquid scintillation counting, mass spectrometry, nuclear magnetic resonance spectros...