نتایج جستجو برای: proton shift
تعداد نتایج: 201000 فیلتر نتایج به سال:
The Lippmann-Schwinger equation for positronium-proton elastic scattering lacks a first-order term because the center of mass and center of charge are coincident. A consequence of this is that the high-energy behavior of the phase shift is governed by the second-Born approximation. Asymptotic analysis indicates that the high-energy form of the phase shift is dL;O(1/k ), where k is the incident ...
Cross-Polarisation-magic-angle-spinning (CPMAS) with high-power proton decoupling [Schaefer, 1976] has been widely applied to obtain high resolution NMR spectra of dilute spin1/2 in solids. This method averages out all anisotropic NMR interactions which transform as second-rank tensors, such as chemical shift anisotropical interactions. However, the principal elements of chemical shift anisotro...
The hydroxyl proton chemical shifts 6 ( H O ) of supercooled methanol (7"min= 149 K) and water have been determined (7"min= 183 K), and the pressure dependence of these shifts was measured up to 200 MPa. In both compounds the downfield shift of <5 ( H O ) continues down to the lowest temperatures reached. This result disagrees with the two state models for the hydrogen bond formation in both li...
Organic solutions of poly-γ-(benzyl-L-glutamate) (PBLG) generate a sufficient differential ordering effect (DOE) to discriminate enantiomers using proton decoupled carbon-13 NMR in natural abundance. Discrimination between enantiomers is observed through the carbon-13 chemical shift anisotropy (CSA) differences. This method is successfully applied to a large number of chiral molecules including...
Carbohydrate-protein recognition has been studied by electronic structure calculations of complexes of fucose and glucose with toluene, p-hydroxytoluene and 3-methylindole, the latter aromatic molecules being analogues of phenylalanine, tyrosine and tryptophan, respectively. We use mainly a density functional theory model with empirical corrections for the dispersion interactions (DFT-D), this ...
The sixth-order electron-loop vacuum-polarization contribution to the 2P1/2 − 2S1/2 Lamb shift of the muonic hydrogen (μ−p+ bound state) has been evaluated numerically. Our result is 0.005295 (1) meV. This eliminates the largest uncertainty in the theoretical calculation. Combined with the proposed precision measurement of the Lamb shift it will lead to a very precise determination of the proto...
Sc3CH@C80 is synthesized and characterized by (1)H, (13)C, and (45)Sc NMR. A large negative chemical shift of the proton, -11.73 ppm in the Ih and -8.79 ppm in the D5h C80 cage isomers, is found. (13)C satellites in the (1)H NMR spectrum enabled indirect determination of the (13)C chemical shift for the central carbon at 173 ± 1 ppm. Intensity of the satellites allowed determination of the (13)...
The sixth-order electron-loop vacuum-polarization contribution to the 2P1/2 − 2S1/2 Lamb shift of the muonic hydrogen (μ−p+ bound state) has been evaluated numerically. Our result is 0.005295 (1) meV. This eliminates the largest uncertainty in the theoretical calculation. Combined with the proposed precision measurement of the Lamb shift it will lead to a very precise determination of the proto...
Excitation functions A(N)(p(p),Theta(c.m.)) of the analyzing power in pp--> elastic scattering have been measured with a polarized atomic hydrogen target for projectile momenta p(p) between 1000 and 3300 MeV/ c. The experiment was performed for scattering angles 30 degrees </=Theta(c.m.)</=90 degrees using the recirculating beam of the proton storage ring COSY during acceleration. The resulting...
The accepted mechanism of Fe-containing superoxide dismutase (Fe-SOD) activity and inhibition by anions implies the existence of a group with a pK of 8.6-9.0 in the active site of reduced Fe-SOD [Bull, C. & Fee, J. A. (1985) J. Am. Chem. Soc. 107, 3295-3304]. We have performed pH titrations of reduced Fe-SOD by NMR spectroscopy and observe a pK of 8.5 at 30 degrees C which is the only pK affect...
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