background: gonad shielding has been recommended during pelvic x-rays since the 1950s. the popular method of gonad shielding is placement a lead shield in the midline of the pelvis. the aim of this study was to evaluate the prevalence and utility of gonad shielding in pediatrics undergoing pelvic x-rays.materials and methodsfollowing study approval, we retrospectively retrieved data from the di...

results the results showed that the epoxy plates 6 and 2 mm thick had the highest and the lowest averages of shielding effectiveness at 4.48 db and 1.90 db, respectively. however, increasing the thickness was useful up to 4 mm. in addition, in a similar attenuation pattern, x-band frequency was divided into lower, middle, and upper sections. the lower section had the highest shielding effective...

Nuclear magnetic resonance (NMR) data for graphenes are mainly lacking in the literature. We provide quantitative first-principles quantum-chemical calculations of NMR chemical shifts and shielding anisotropies as well as spin-spin couplings and anisotropies for increasingly large, hexagon-like fragments of graphene, hydrogenated graphene (graphane) and fluorinated graphene (fluorographene). Du...

We report a multinuclear solid-state ( (23)Na, (39)K, (87)Rb, (133)Cs) NMR study of tetraphenylborate salts, M[BPh 4] (M = Na, K, Rb, Cs). These compounds are isostructural in the solid state with the alkali metal ion surrounded by four phenyl groups resulting in strong cation-pi interactions. From analyses of solid-state NMR spectra obtained under stationary and magic-angle spinning (MAS) cond...

chelating is the chemical process by which a mineral (iron, cobalt, copper, zinc, and manganese) is combined with a mixture of amino acids and peptides. the resulting substances are known as chelates. another descriptive term, proteinates, refers to the amino acid bond. these chelated minerals are thought to be more digestible than nonchelated forms. in other words, chelation makes the minerals...

A methodology for optimizing the geometry and calculating the NMR shielding constants is calibrated for octahedral complexes of Pt(IV) and Ir(III) with modified nucleic acid bases. The performance of seven different functionals (BLYP, B3LYP, BHLYP, BP86, TPSS, PBE, and PBE0) in optimizing the geometry of transition-metal complexes is evaluated using supramolecular clusters derived from X-ray da...

Contributions to the gas-to-liquid chemical shifts of water arising from the electric field gradient of the surrounding molecules have been calculated as a function of the temperature. Since the theoretical model is based on perturbation theory, this part of the chemical shift may be calculated from quadrupole shielding polarizabilities and statistical mechanical ensemble averages of external e...

Phospholipids in whole cells of wild type Escherichia coli K12 are not degraded by exogenous phospholipases, whereas those of isolated outer membranes are completely degraded. It is concluded that the resistance of phospholipids in whole cells is due to shielding by one or more other outer membrane components. The nature of the shielding component(s) was investigated by testing the sensitivity ...

The 13C-Nuclear Magnetic Resonance spectra of xanthine, 1,3-dimethyl-xanthine (theophylline), 3,7-dimethyl xanthine (theobromine) and 1,3,7-trimethylxanthine (caffeine) were obtained and the lines assigned. Protonationand N-Methylation parameters are derived by comparison of the 13C-chemical shifts of the protonated cations with those of the neutral molecules and also with those of the xanthine...

The health of physiological tissue is governed by the continuous conversion of mechanical stimulus (stress) to bio-chemical response, a concept known as mechanical homeostasis. If this regulatory imperative becomes flawed, it may be detrimental, and consequently invoke or encourage the progression of various musculoskeletal disorders. This notion is corroborated by the quantification of altered...