The sources of error in the calculation of nuclear-magnetic-resonance shielding constants determined by density-functional theory are examined. Highly accurate Kohn-Sham wave functions are obtained from coupled-cluster electron density functions and used to define accurate-but current independent-density-functional shielding constants. These new reference values, in tandem with high-accuracy co...

background: designing and shielding of an appropriate radiography room has been one of the major concerns of radiation scientists since the first decade after the invention of x-rays. recently, report no.147 of national council on radiation protection and measurements (ncrp) has been published. in this study the researchers have investigated the effect of new report recommendation on primary an...

The long-held “shielding cone” model of the through-space NMR shielding effect of a carbon-carbon double bond predicts only the effect of the magnetic anisotropy of the double bond; it ignores other important contributors to the overall shielding. GIAO-SCF and GIAO-MP2 calculations have been performed on a simple model system, methane moved sequentially above ethene or 2-methylpropene. These ca...

The effect of material type, yarn count, pick density, type of mordant and layers of fabrics on the electromagnetic shielding properties of textile materials has been studied. The shielding effectiveness of the fabric is measured by estimating the insertion loss incurred to the signal when the sample is placed in the path of the signal at the frequency range 100 MHz-3 GHz inside the coaxial tra...

Employing Dynamic Discrete Dislocation Plasticity (D3P), an elastodynamic analysis of the shielding of a stationary crack tip by dislocations is studied. Dislocations are generated via FrankRead sources, and make a negligible contribution to the shielding of the crack tip, whereas dislocations generated at the crack tip via homogeneous nucleation dominate the shielding. Their effect is found to...

hartree-fock (hf) and density functional theory (dft) methods employed to study the effect of conformational change on the 13c chemical shifts of 6-mono axial and equatorial substituted and 6,7-di axial-axial, equatorial-equatorial and axial-equatorial substitutedderivatives of 5,6,7,8-tetrahydrodibenzo[a,c]cyclo-octene. the geometry of the conformers have been optimized in the gas phase employ...

the interaction of dppa which is an important component in cellular membrane with molecules of water asmedia, cause some changes in geometry of dppa .in this study we focused our attention on comparing thismolecule with related hydrated complexes employing different basis sets at hartree-fock levels of theory. thetheoretical nmr shielding tensor of some imported atoms were also reported.

G. Fehrenbacher, F. Gutermuth, T. Radon GSI Darmstadt, Germany An important aspect to be considered when designing the GSI future project will be the radiation protection of both the staff and the environment. One of the prerequisites for a permission for the operation of a high-energy accelerator is a careful planning of the necessary radiation shielding equipment. In order to give recommendat...

Shielding effects of a nanocage can be determined by the field felt by an encapsulated noble gas (NG) atom. Using the polarizability distributions about NG endohedral fullerenes (NGEFs), a new scheme based on the local polarizability of the NG is introduced to detect the shielding effects of fullerenes, using density functional theory calculations and Hirshfeld population analysis. For large ca...

The requirements for shielding a treatment vault with a Varian Clinac 2100 medical linear accelerator operated both with and without the flattening filter were assessed. Basic shielding parameters, such as primary beam tenth-value layers (TVLs), patient scatter fractions, and wall scatter fractions, were calculated using Monte Carlo simulations of 6, 10 and 18 MV beams. Relative integral target...