The space radiation environment outside the protection of Earth’s magnetosphere is severe and difficult to shield against. cumulative effective dose astronauts on a typical Mars mission would likely introduce risk exceeding permissible limits for carcinogenesis without innovative strategies shielding. Damaging cardiovascular central nervous system effects are also expected in these environments...

Radio frequency (RF) interference and gradient induced eddy currents have been a major challenge in building a simultaneous PET/MRI system, a new carbon fiber composite material is found to be a good RF shield while introducing negligible gradient eddy currents. It also provides excellent structural support for the PET detector components. This material is therefore promising for the design of ...

Background: It has recently been shown that the particle size of materials used for radiation shielding can affect the magnitude of radiation attenuation. Over the past years, application of nano-structured materials in radiation shielding has attracted attention world-wide. The purpose of this study was to investigate the shielding properties of the lead-free shields containing micro and nano-...

the fullerene structures of c20cage and bowl,c20h10 and their n-doped structures as c20cage nh,c20bowl nh, c20h10nh, c20h10n and their isomers are optimized using the mpw1pw91/6-31g level of the theory. magnetic shielding tensors of 14n and 13c atoms are calculated by the same level of the theory. results show that doping an n atom on fullerenes affects differently on the chemical shielding of ...

A solid-state nuclear magnetic resonance (NMR) method for the site-resolved identification of the secondary structure of solid peptides and proteins is presented. This technique exploits the correlation between the backbone conformation and the CR chemical shift anisotropies (CSA) of proteins. The 13CR CSAs are measured under fast magic-angle-spinning using a new sequence of sixteen 180° pulses...

Effects of dislocation emission from a mode I crack and of pinning distances on the behavior of the crack and on fracture toughness in aluminum were studied by using the Molecular Statics Technique with atomic interactions described in terms of the Embedded Atom Method. It was found that aluminum is a ductile material in which the cracks generate dislocations, blunting the cracks. The blunting ...

The wide-spreading use of innovative lightweight materials like advanced composites and metal coated plastics in several fields of applications has pushed toward an increasing interest in the characterization of the shielding performances of test materials. In the paper, we revisit the conventional methods of measuring shielding effectiveness of materials, and introduce the nested reverberation...

However, in reality the shielding appears to vary somewhat with magnitude, leading to a relationship δ = k*σcalc + m, where k and m are determined by fitting the calculated shielding values for several known standards to their experimental shifts. For example, TMS has a δ=0 ppm and benzene has a δ=7.27 ppm. Using B3LYP/LACV3P**, the calculated averaged shielding for the TMS hydrogens is 31.9296...

NCRP 151 provides very detailed examples demonstrating the necessary concerns for shielding a conventional radiotherapy vault with a maze where the useful beam is parallel to the maze. However, it provides little guidance on how to properly shield a vault with the maze-wall acting as part of a compound primary barrier. We have modeled a new radiotherapy vault with this configuration and assesse...