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Magnetic Shielding (magnetic + shielding)
Terms modified by Magnetic Shielding Selected AbstractsA comparative study of some red- and blue-shifted linear H-bonded complexes of N2JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 2 2008Sean A. C. McDowell Abstract Bond length changes, harmonic vibrational frequency shifts, and changes in the proton magnetic shielding of HX and HKrX (X = F, Cl) on complexation with N2 to form the linear red-shifted N2 , HX and linear blue-shifted N2 , HKrX complexes were determined by ab initio computations, with and without counterpoise correction, at the SCF and MP2(full) levels of theory using a 6-311++G(2d,2p) basis set. The MP2 computations agree with predictions from a perturbation theory model involving the first and second derivatives of the interaction energy with respect to displacement of the HX and HKr bond lengths from their equilibrium values in the isolated monomers. The theoretical results agree qualitatively with the experimentally observed frequency shifts, with near quantitative agreement for N2 , HKrCl. The characteristic downfield shift of the isotropic proton magnetic resonance in the red-shifted complexes was obtained, but for the blue-shifted complexes, the proton NMR shifts to higher fields. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Structure, magnetizability, and nuclear magnetic shielding tensors of bis-heteropentalenes.JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2006Abstract The geometry of the heteropentalenes formed by two phosphole units has been determined at the DFT level. The magnetic susceptibility and the nuclear magnetic shielding at the nuclei of these systems have also been calculated using gauge-including atomic orbitals and a large Gaussian basis set to achieve near Hartree,Fock estimates. A comparative study of the various isomers, of their flattened analogs, and of the parent phosphole molecule, shows that the [3,4-c] isomer is the most aromatic system in the set considered, assuming diatropicity and degree of planarity as indicators, even if it is the less stable in terms of total molecular energy. Plots of magnetic field-induced current densities confirm diatropicity of P-containing bis-heteropentalenenes, showing, however, significant differences from the analogous systems with distinct heteroatoms. The maps give evidence of spiral flow nearby CC bonds, compatible with prevalent distortive behavior of , electrons exalted by pyramidalization at P, and competing against the , electron compression, which would favor planar structure. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 344,351, 2006 [source] Density functional computations of 99Ru chemical shifts: relativistic effects, influence of the density functional, and study of solvent effects on fac,[Ru(CO)3I3],MAGNETIC RESONANCE IN CHEMISTRY, Issue 11 2006Jochen Autschbach Abstract Solvent effects on the 99Ru NMR chemical shift of the complex fac,[Ru(CO)3I3], are investigated computationally using density functional theory. Further, benchmark calculations of the 99Ru shift for a set of ten Ru complexes have been performed in order to calibrate the computational model and to determine the importance of relativistic effects on the 99Ru nuclear magnetic shielding and on the chemical shift. A computational model for fac,[Ru(CO)3I3], that includes both explicit solvent molecules and a continuum model is shown to yield the best agreement with experiment. Relativistic corrections are shown to be of minor importance for determining 99Ru chemical shifts. On the other hand, the nature of the density functional is of importance. In agreement with literature data for ligand trends of 99Ru chemical shifts, the chemical shift range for different solvents is also best reproduced by a hybrid functional. Copyright © 2006 John Wiley & Sons, Ltd. [source] Recent Progress in Artificial Organ Research at Tohoku UniversityARTIFICIAL ORGANS, Issue 1 2003Tomoyuki Yambe Abstract: Tohoku University has developed various artificial organs over the last 30 years. Pneumatic driven ventricular assist devices with a silicone ball valve have been designed by the flow visualization method, and clinical trials have been performed in Tohoku University Hospital. On the basis of these developments, a pneumatic driven total artificial heart has been developed and an animal experimental evaluation was conducted. The development of artificial organs in Tohoku University has now progressed to the totally implantable type using the transcutaneous energy transmission system with amorphous fibers for magnetic shielding. Examples of implantable systems include a vibrating flow pump for ventricular assist device, an artificial myocardium by the use of shape memory alloy with Peltier elements, and an artificial sphincter for patients with a stoma. An automatic control system for artificial organs had been developed for the ventricular assist devices including a rotary blood pump to avoid suction and to maintain left and right heart balance. Based upon the technology of automatic control algorithm, a new diagnostic tool for evaluating autonomic nerve function has been developed as a branch of artificial organ research and this new machine has been tested in Tohoku University Hospital. Tohoku University is following a variety of approaches aimed at innovation in artificial organs and medical engineering fields. [source] Complete basis set prediction of methanol isotropic nuclear magnetic shieldings and indirect nuclear spin,spin coupling constants (SSCC) using polarization-consistent and XZP basis sets and B3LYP and BHandH density functionalsMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2009Teobald Kupka Abstract Efficient B3LYP and BHandH density functionals were used to estimate methanol's nuclear magnetic isotropic shieldings and spin,spin coupling constants in the basis set limit. Polarization-consistent pcS- n and pcJ- n (n = 0, 1, 2, 3 and 4), and segmented contracted XZP, where X = D, T, Q and 5, basis sets were used and the results fitted with simple mathematical formulas. The performance of the methods was assessed from comparison with experiment and higher level calculations. 1J(CH) and 3J(HH) values were determined from very diluted solutions in deuterochloroform and compared with theoretical predictions. The agreement between complete basis set (CBS) density functional theory (DFT) predicted isotropic shieldings and spin,spin values and experiment was good. The BHandH/pcS- n methanol shieldings obtained using structures optimized at the same level of theory are approaching the accuracy of the advanced coupled-cluster-singles-doubles-approximate triples (CCSD(T)) calculations. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||