Various Conditions Of Irradiation Research Articles

Nuclear Magnetic Double-Resonance Spectrum of a Strongly Coupled Two-Spin System

The density-matrix theory of double resonance is applied for a detailed analysis of the frequency-sweep nuclear magnetic double-resonance spectra of the strongly coupled two-proton system in 2-bromo-5-chlorothiophene under various conditions of irradiation. These spectra show significant relaxation and coherence effects. The results of the theory are very sensitive to the relaxation mechanisms assumed for the system, indicating the possibility of deriving significant information about the relaxation of the system by this method. Comparison of the observed and theoretical double-resonance spectra shows that the proton relaxation in this molecule is due, in large measure, to external interactions with a high degree of correlation between the interactions with the two protons. An approximation proposed by Bloch for simplifying the calculations is found to be applicable even when the irradiation frequency is close to some single-resonance transition frequencies.

Maximum permissible fluxes of intermediate energy neutrons and their measurements

The maximum and mean doses of neutrons absorbed by human tissue are calculated from data given in the literature over the range from thermal energies to 1 MeV. The results are averaged for the typical 1 E spectrum and for various conditions of irradiation. The maximum permissible dose of intermediate neutrons is 680 n/cm 2/sec. The application of known methods of neutron detection to the dosimetry of intermediate neutrons is considered and it is shown that, with certain reservations, shielded thermal neutron detectors are suitable for this purpose.

The relative biological efficiency of 4 MeV and 300 kV radiations. VI. The 50 per cent lethal dose for the chick embryo.

During the last 50 years the chick embryo has been used extensively to study radiation effects. The LD50 has been estimated many times under various conditions of irradiation. When the conditions are carefully standardised the estimate may be reproduced very precisely and when used in this way the hen's egg is a biological dosemeter of unusual accuracy.