Positron branching

However, as shown in figure 11.16, also decays into " °Ca (jS = 89.5%). The " °K-to-" °Ar decay branch is dominated by electron capture, although a limited amount of positron emission of low energy is observed (about 0.001%). 

T. Takahashi, S. Nishimura, T. Ido, K. Ishiwata, R. Iwata, Biological evaluation of 5-methyl-branched-chain omega-[ F]-fluorofatty acid A potential myocardial imaging tracer for positron emission tomography, Nucl. Med. Biol. 23 (1996) 303-308. 

Nowadays, nuclear medicine has become an indispensible section of medical science, and the production of radionuclides and labelled compounds for application in nuclear medicine is an important branch of nuclear and radiochemistry. The development of radionuclide generators made short-lived radionuclides available at any time for medical application. New imaging devices, such as single photon emission tomography (SPET) and positron emission tomography (PET) made it possible to study local biochemical reactions and their kinetics in the living human body. 

Each mode of decay in branching may be treated separately the decay in an individual branch has a half-life based on the partial decay constant. Since only the total decay constant (the rate with which the mother nuclide, 2X in (4.50), decays) is observable directly, partial decay constants are obtained by multiplying the observed total decay constant by the fraction of parent decay corresponding to that branch. Cu decays 43 % by electron capture, 38% by negatron emission, and 19% by positron emission. The observed total decay constant is equal to 0.0541 h based on the half-life of 12.8 h. The partial constants are ... 

Notes. Half life of the isotopes are given as m minutes h hours d days and yr years. The decay modei EC for eiectron capture (3+ for positron emission (3 for beta emission iT for internai transfer. An isotope may decay by more than one modei. The 4th column lists the maximum energy of particles emitted (E ax), the branching ratio is given in brackets. The main -ray energy and intensity are listed in the 5th column. The production method (irradiation in reactor or cyclotron) is given in the 6th column. 

E. J. M. Hensen, A. M. de Jong, and R. A. van Santen have written Chapter 7, which introduces the tracer exchange positron emission profiling (TEX-PEP) as an attractive technique for in-situ investigations, for example, in a stainless steel reactor, of the adsorption and diffusive properties of hydrocarbons in zeolites under chemical steady-state conditions. Self-diffusion coefficients of hydrocarbons, labeled by proton-emitting C at finite loadings and even in the presence of another imlabeled alkane, may be extracted. The method is illustrated by adsorption and diffusion measurements of linear (n-hexane) and branched (2-methylpentane) alkanes in Fl-ZSM-5 and silicalite-1. 

Dlubek, G., Bamford, D., Rodriguez-Gonzalez, A., Bornemann, S., Stejny, J., Schade, B., Alam, M. A., and Arnold, M., Free volume, glass transition and degree of branching in metallocene-based propylene/a-olefin copolymers positron lifetime, density and DSC studies, J. Polym. Sci. B, 40, 434-453 (2002b). 

Kindi, R, and Reiter, G., Investigations on the low-temperature transitions and time effects of branched polyethylene by the positron lifetime technique, Phys. Status Solidi, A, 104, 707-713(1987). 

Reiter, G., and Kindi, P., Positron lifetime investigations on linear polyethylene compared to branched polyethylene, Phys. Status, SolidiA, 118,161-168 (1990). 

The results and developments attained in this field are indicated by the several hundred publications, including a number of reviews and monographs, which have appeared [De 53, Fe 56, Go 68a, Go 71a, Gr 64, Wa 60], and by the numerous international conferences dealing with the results achieved in this new research field [Po 67, Pr 71, Pr 75, Pr 79]. The annihilation of positrons is dealt with by researchers in numerous branches of science, such as nuclear physics, solid-state physics, chemistry and biology, and useful information has been obtained. The method has recently also been employed in the field of solution studies. 

Commonly used radionuclide Analog radionuclide Positron Radionuclide branching (T, ) [%J Emax of positron [MeV] Nuclear reaction Energy range of interest for production [MeV]... 

As traditional representations of the world involve three branches picturing the male, female and neutral features of nature, particles are classified as Fermion half-integer spin matter (electrons, protons, neutrons, muons, neutrinos,. ..) or antimatter (positrons, antiprotons,. ..) and Boson full-integer spin particles (photons, mesons, gluons,. ..). Some of these are perfectly stable (protons, electrons, neutrinos, photons,. ..) or relatively long-lived (neutrons 16.9 min, muons 2.2 x lO sec) while others are very short-lived (mesons, hyperons, x > 10 sec) or unstable (resonances, x < 10" sec), and some have not been isolated (quarks,. ..). Nuclei of common matter are made of protons and neutrons, and these latter disintegrate to a proton, an electron and a neutrino when they are isolated. Nowadays one considers a proton as being compounded... 

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