The radiations of Selenium 75 and Antimony 124 were examined with a thin lens magnetic spectrometer at a resolution of 2.5% in momentum. Selenium 75 The gamma ray and internal conversion spectra were obtained for Se⁷⁵ which decays by K-capture to As⁷⁵. Transitions were observed at the energies 66, 98, 121, 137, 198, 265, 280, 303, and 400 kev. Accurate K/L ratios were obtained for the 98 kev. and 137 kev. transitions. A decay scheme is proposed with tentative spin and parity assignments to several energy levels. Antimony 124 The beta ray and internal conversion spectra of Sb¹²⁴ were examined. Five beta groups were observed with end-point energies 2.315, 1.58, 0.94, 0.60, and 0.35 mev. Conversion lines were observed for transitions of energies 604, 651, and 723 kev. Conversion coefficients were calculated on the basis of the decay scheme of Langer et al. All three transitions have conversion coefficients which would correspond to electric quadrupole radiation. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The angular distribution of the annihilation radiation from slow positrons in copper has been determined with a pair of scintillation counters in coincidence. A strong Cu⁶⁴ source from the Chalk River pile provided the positrons. Very small solid angle geometry was used and results of high internal consistency were obtained. The distribution has the form C(λ) = (const) e[superscript -λ/λ₀] where C(λ) is the counting rate for an angular correlation of (180-λ)⁰ between the two quanta. The mean value of λ₀= (3.60±.04)x10[superscript -3]radians. Assuming that this departure from antiparallelism is caused by the motion of the annihilating particles, their mean centre of mass momentum in copper is found to be p̅[subscript Cu] = (0 .985±.01)mc/137. This result lies within the experimental errors of the values 1.2 mc/ 137 and 1.1 mc/137 obtained by De Benedetti for gold and Du Mond for copper, respectively. It also lies within the computational error of the lower limit of 0.8 mc/137 estimated by DeBenedetti. The same equipment was used to measure (μ/ρ) for lead for hν = mc² by a new method-- that of intercepting one of the annihilation quanta in very pure lead and plotting the coincidence rate against lead thickness. An accurately exponential absorption was observed which gave the value (μ/ρ)[subscript Pb]= (0.155± .002) gm/cm². This method avoids almost completely the difficulty of discriminating against scattered radiation inherent in previous absorption measurements. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A theoretical investiation of steady radiation fronts was carried out for the experimentally realistic situation in which ionizing or dissociating radiation passes through a transparent window into an absorbing gas. It was shown that five different types of radiation fronts may occur -depending on the ratio of photon flux to absorber density. It was possible to calculate the flow in each case provided the final temperature behind the radiation front was assumed. This final temperature may be calculated if the structure and all reactions within the radiation front are taken into account. An analytic expression can be obtained if particle motion and recombination are neglected , and the radiation is assumed to be monochromatic. This ideal case corresponds closely to a weak R-type radiation front. A first order relativistic correction indicates that the width of the front decreases as the velocity of the front approaches the speed of light. In an associated experiment radiation fronts in oxygen and iodine were produced by an intense light pulse from a constricted arc. The experiment in iodine demonstrated the beginning of the formation of a radiation front during the 10 μsec light pulse. Radiation induced shock waves were observed in oxygen after the decay of the light pulse. These Mach 1.1 shocks were considered theoretically as unsteady one-dimensional flow and were treated by the method of characteristics, which was modified to include the energy input. The agreement between the theoretical and experimental results was satisfactory. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

At the commencement of any studies in radiobiology it is necessary to decide on a suitable system for investigation, either animal or plant.

The metastable radionuclide Pt-195m decays predominantly by internal conversion (IC) with a half-life of 4 days. The vacancies created in the inner atomic shells by the primary IC decay modes result in copious emission of low energy Auger electrons. The biological effects of these electrons, which have ranges of subcellular dimensions, are of interest to basic and applied radiation biophysics. Using radiolabeled platinum complexes which bind to DNA, one can examine the effect of Pt-195m Auger cascades close to the DNA. Trans-Pt-195m (trans-dichlorodiammineplatinum (II); specific activity 0.5 mCi/mg), a DNA-binding compound, has been synthesized and its effect on the survival of Chinese hamster V79 cells determined. The cellular uptake of Pt-195m reaches a plateau in 3-4 hours and varies nonlinearly with extracellular activity concentration. Following an 18 hour incubation, 75% of the cellular radioactivity is found in the cytoplasm, and 25% in the nucleus. About 42% of the activity in the nucleus is DNA-bound. The activity is eliminated from the cell, postincubation, with a 24 hour half-life. Cell survival data, when corrected for the chemical toxicity of the unlabeled trans-Pt, give a survival curve typical of densely ionizing radiation of high linear energy transfer such as alpha particles. The mean lethal cellular uptake of radioactivity is 0.032 $\pm$ 0.003 pCi/cell at 37% survival. Theoretical calculations of the Pt-195m Auger electron spectrum using Monte Carlo methods indicate about 30 Auger electrons are expected per decay. Dosimetric considerations give a value of 4.8 for the relative biological effectiveness of Pt-195m compared to 250 kVp x-rays. Theoretical Monte Carlo calculations imply that the density of chemical species produced by Auger electrons in liquid water in the immediate vicinity of a Pt-195m decay site is comparable to the density along the track of a 4 MeV alpha particle. This explains qualitatively the efficacy of Pt-195m in causing biological effects. Potential therapeutic applications of radioplatinum complexes are noted. This work is supported in part by U.S.P.H.S. Grants CA-32877 and CA-15523.

<p>In the present thesis, an experimental database is used to investigate multipath, focusing mostly on the diffuse component. The experimental conditions cover the case of CW, coherently received microwave radiation, with a sampled aperture linear array, scattered at low-grazing angles, over the sea surface. A variety of frequencies covering the entire X-band and grazing angles were employed to explore the diffuse multipath structure.</p> <p>A new technique, Thomson's multiple-window-method (MWM), proves to be the proper tool for this experimental investigation. The following characteristics of diffuse multipath, for this particular class of experimental conditions, are extracted for the first time ever: <ul> <li>Amplitude statistics (1st order statistics). </li> <li>Complete wavenumber and frequency domain power spectra (2nd order statistics). </li> <li>Bispectra (3rd order statistics). </li> <li>Coherencies and transfer functions between channels at different frequencies and grazing angles. </li> <li>An improved method for estimating angles of arrival. </li> </ul></p> <p>Theory plays supportive role only, since the general problem of electromagnetic scattering from rough surfaces still remains to be solved. The main contributions from this research regarding diffuse multipath at low grazing angles are: <ul> <li>The shape of wavenumber/frequency domain power spectra. </li> <li>Confirmation that amplitude statistics for the Lpol channel are K distributed.</li> <li>The wavenumber/frequency domain bispectra indicate a non-Gaussian structure for the diffuse multipath component. </li> </ul></p> <p>Any theory that deals with microwave scattering, over the sea surface, at low grazing angles, how to take these findings into account.</p> / Doctor of Philosophy (PhD)

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 54-60). Also available on the World Wide Web.

No description available.

No description available.

No description available.