No abstract

Radiation is used different field and among others neutron is the one of the most hazardous particle as it is neutral and heavy. Its neutral characteristics make it more difficult particle to be shielded. In this study neutron shielding properties for some medical interested materials of water, fat and bone have been obtained using Phy-X/PSD software.

No abstract

TurkeyNuclear magnetic resonance and dynamic nuclear polarization experiments were performed to study suspensions of asphaltene in the fluorocarbons at a low magnetic field of 1.53 mT, at room temperature. The asphaltene was extracted from MC800 liquid asphalt, which was of Heavy Iran origin. The elemental composition and the surface morphology of the asphaltene were determined by scanning electron microscopy and energy dispersive X-ray analysis. Intermolecular spin-spin interactions occur between nuclear spins of hydrogen in the solvent medium and the free electron spins in the asphaltene micelles. The electron paramagnetic resonance spectrum of the asphaltene was obtained and the saturation experiments were applied to the samples prepared in vacuum. The main 1 H DNP parameters were listed. Chemical composition and molecular structure of the asphaltene were analyzed. Scanning electron microscope images have shown that asphaltenes are constituted of agglomerated particles and smooth surfaces. Energy dispersive X-ray analysis has shown that the most abundant element is carbon. IntroductionAsphaltenes, which are a part of petroleum, are regarded to be polar species, have larger aromatic structures and are containing alkyl chains, heteroatoms (such as O, S and N) and some metals [1]. Asphaltenes have unpaired electrons, which are observed using the electron spin resonance (ESR) experiments in crude petroleum [2].Dynamic nuclear polarization (DNP) utilizes the liquid state interaction between nuclei and unpaired electron spins to generate an increased nuclear polarization upon the saturation of ESR transitions of the radicals. The maximum DNP enhancement of the NMR signal is given by the electron-to-nuclear gyromagnetic ratios γ e /γ n . This ratio for proton spin is 660. In this study, the nuclear spins are the proton spins, which are the 1 H nuclei of the solvent medium and the electron spins belong to the free electrons on the asphaltene micelles. The unpaired electrons were delocalized on the incomplete carbon bonds of the condensed aromatic structure of the asphaltene particles [3]. By DNP method we have revealed dipolar interaction between hydrogen atoms of the solvent and unpaired electrons of colloidal asphaltene. Electron spin saturation and DNP enhancements have been obtained and DNP parameters determined in low magnetic field. Chemical composition and morphology of MC800 asphaltene were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis.

No abstract