Elemental analysis of whole blood using proton-induced X-ray emmission.
A technique for the analysis of trace elements in whole blood was developed using proton-induced x-ray emission. Samples of 0.1 ml whole blood from humans and mice were dried, weighed, and then ashed in a plasma asher. Targets were prepared by placing drops made from the ash and a 100-ppM Pd solution onto Formvar backings. The samples were irradiated with 2.25-MeV protons, and the x-rays analyzed in a nondispersive x-ray detector. The elements Fe, Cu, Zn, Se, and Rb were detected with a precision of 7, 18, 7, 50, and 19%, respectively, in human whole blood. The precision of the technique was determined by statistical analyses of two different sets of 27 samples. The system was found to be linear for variations in elemental concentration. The accuracy for deterrmination of Zn was found to be within 10% by comparison to atomic absorption spectrometry.
X-ray emission analysis of human plasma by proton excitation of thick samples in air.
Thick plasma samples have been irradiated in air by 2.3 MeV protons for trace elemental analysis by proton-induced X-ray emission spectroscopy. Accurate calibration curves were obtained for Fe, Zn and Sr and detection limits in dry plasma were estimated to be 0.08 PPM for Fe, 0.065 PPM for Zn and 0.12 PPM for Sr. Low temperature ashing of these samples improved the detection limits by a factor of 3 but reduced the precision and resulted in loss of bromine from the plasma. Mass absorption coefficients for low energy X-rays in dry plasma were measured and X-ray attenuation in the sample was found to prevent the detection of trace elements with Z less than 26. The method was used to determine Sr in plasma from a patient with bone disease, the Sr being a non-radioactive bone-seeking tracer element. The results, which were in the 3--13 PPM range, were in good general agreement with the analysis of the same samples by flame photometry.
The Three Faces of Defeasibility in the Law
In this paper we will analyse the issue of defeasibility in the law, taking into account research carried out in philosophy, artificial intelligence and legal theory. We will adopt a very general idea of legal defeasibility, in which we will include all different ways in which certain legal conclusions may need to be abandoned, though no mistake was made in deriving them. We will argue that defeasibility in the law involves three different aspects, which we will call inference-based defeasibility, process-based defeasibility, and theory-based defeasibility. Only the integration of these three perspectives allows us to provide a satisfactory account of the role of defeasibility in legal reasoning.