Radioactive displacement

Kasimir Fajans, 1887-. American physical chemist, bom in Poland. Professor at the University of Michigan. Codiscoverer with Gohring of uranium X (brevium). In 1913 he discovered, simultaneously with Soddy, the law of radioactive displacement of elements in the periodic system as the result of o- and /9-ray emission. 

They realized that the particles emitted by radioactive elements as they decay are in fact little bits of the atomic nuclei. By expelling them, the nucleus alters the number of protons it contains, and so it becomes the nucleus of a different element. Alpha decay carries off two protons and two neutrons (a helium nucleus), and so it converts one element to a slightly lighter element two columns earlier in the Periodic Table. Beta decay transforms a neutron into an electron (which is emitted) and a proton (which stays in the nucleus) - so the atomic number increases and the element moves one column further across the Periodic Table. Niels Bohr and Soddy formulated this rule, which was called the radioactive displacement law. 

Analysis of the radioactivity displaced by arvinized plasma indicated the presence of thrombin-anti thrombin III complex (- 70%) and what was presumed to be thrombin-a-2-macroglobulin complex (" 30%). The bound thrombin is thought to react first with antithrombin III to produce a bound inactivated thrombin-anti thrombin III complex, which is dislodged from heparin by a yet unknown plasma component(s), decomplexed by an unknown mechanism to react with a-2-macroglobulin. This mechanism is illustrated in Figure 1. After displacement, the increase in I-antithrombin III which had lost its affinity for heparin-Sepharose was attributed to the production of a post complex antithrombin III on decomplexation of the inactive complex. This modified antithrombin III has been described by Lam et al. ( ), Fish et al. (25) and Marciniak (26). Neither free I-thrombin nor I-antithrombin III were detected in the displaced eluent. 

Tenacious work of scientists and accumulation of experimental data made it possible to formulate the law of radioactive displacement. Though many scientists took part in this work the main contributions were made by F. Soddy and the Polish chemist K. Fajans and therefore this law is known as the Soddy-Fajans law. According to it, alpha decay gives rise to a radioelement displaced two boxes to the left from the starting position in the periodic table while beta decay displaces the product one box to the right. When it was shown that the charge of an atomic nucleus equals the number of the respective element in the periodic system the... 

This system is backed-up by a Standby Liquid Control System (SLCS) that injects sodium pentaborate into the moderator using a positive displacement pump (shown as a piston pump). Steam that originates in the core of a BWR, unlike the primary coolant in a PWR, exits the containment. The closing of the MSIVs isolates the radioactivity from the environment but when this is done, normal heat removal is not possible. The Residual Heat Removal (RHR) system... 

Radioactive events occur in the measured depth interval (8,100-8,200 ft) with no displacement of the low/high side gamma ray logs. The radioactive events must be perpendicular to the gamma detector and could be indications of vertical natural fractures in the formation. 

FIGURE 3.3 Displacement of prebound radioligand [A ] by non-radioactive concentrations of [A]. Curve for a= 1 denotes no cooperativity in binding (i.e., formation of the receptor dimer does not lead to a change in the affinity of the receptor for either [A] or [A ]). The curve a= 10 indicates a system whereby formation of the receptor dimer leads to a tenfold increase in the affinity for both [A ] and [A], In this case, it can be seen that addition on the nonradioactive ligand [A] actually leads to an increase in the amount of radioligand [A ] bound before a decrease at higher concentrations of [A], For this simulation [A ]/Kd = 0.1. 

In practice, there will be a limited number of ligands available that are chemically traceable (i.e., radioactive, fluorescent). Therefore, the bulk of radioligand experiments designed to quantify ligand affinity are done in a displacement mode whereby a ligand is used to displace or otherwise affect the binding of a traceable ligand. 

The displacement was monitored by observing the changing distribution of radioactive 128I between the inorganic (sodium) iodide and 2-iodooctane, and it was found, under these conditions, to be second order overall (first order with respect to 128Ie and to 2-iodooctane) with k2 = 3-00 + 0-25 x 10-5 (at 30°). 

Following immersion of the glass slides in a 1.0 (w/v) BSA-BSA solution to a depth of 2.1 cm for 30 min at 21°C, the slides were thoroughly rinsed in PBS by dilution/displacement. The slides were then completely immersed in PBS, where they were kept for different lengths of time, i.e., for 1, 2, 4, and 16 hrs. Thereafter, the slides were removed and air-dried and placed on X-ray film between Lanex Intensifying Screens as described above. The supernatants from these diffusion experiments were then concentrated 10 times by evaporation in order to establish their radioactive content. 

In order to dissipate the recoil energy Mossbauer was the first to use atoms in solid crystal lattices as emitters and also to cool both emitter and absorber. In this way it could be shown that the 7-ray emission from radioactive cobalt metal was absorbed by metallic iron. However, it was also found that if the iron sample were in any other chemical state, the different chemical surroundings of the iron nucleus produce a sufficient effect on the nuclear energy levels for absorption no longer to occur. To enable a search for the precisely required absorption frequency, a scan based on the Doppler effect was developed. It was noted that a velocity of 102 ms-1 produced an enormous Doppler shift and using the same equation (7) it follows that a readily attainable displacement of the source at a velocity of 1 cms-1 produces a shift of 108 Hz. This shift corresponds to about 100 line-widths and provides a reasonable scan width. 

Monodisperse microspheres imprinted with theophylline or 17 (3-estradiol were used in competitive radioimmunoassays showing the MIP s high selectivity for the template molecule. In this case the assay is based on the competition of the target molecule with its radioactively labeled analogue for a limited number of antibody binding sites [77,118]. Figure 15 demonstrates that displacing the radioactively marked theophylline from the imprinted polymer was only possible with theophylline as competitor. Structurally related molecules showed effects solely at elevated concentrations [77]. 

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