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排序方式: 共有498条查询结果,搜索用时 15 毫秒
31.
Kneller JM Soto RJ Surber SE Colomer JF Fonseca A Nagy JB Pietrass T 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,147(2):261-265
In a typical continuous-flow optical pumping setup, the chemical shift of xenon in the adsorbed phase depends on the gas flow rate due to warming of the sample surface by the gas stream. Calibration of the system using the (207)Pb resonance of solid lead nitrate is necessary to determine the actual sample temperature. Optimum pulse repetition rates are strongly affected by gas flow and spin-lattice relaxation rates. The interplay of flow and pulse repetition rate alters signal intensity ratios and may lead to the complete suppression of signals. 相似文献
32.
We point out that, due to the use of static nucleon propagators in Heavy-Baryon Chiral Perturbation Theory (HBχPT), the current calculations of the nucleon-nucleon potential miss certain contributions starting at two loops. These contributions
give rise to contact interactions, which are both parametrically and numerically more important than the so-called NNLO potentials.
They show a peculiar dependence on the light-quark masses, which should be taken into account when performing chiral extrapolations
of lattice data. However, they do not appear to have an impact on phenomenology since they can be absorbed into redefinitions
of unknown parameters which are usually fitted to data. 相似文献
33.
This paper addresses, theoretically and experimentally, the impact of the cross-polarization modulation (XPolM) phenomenon on the conversion efficiency of a four wave mixing (FWM) process taking place in a bulk-SOA with input signals linearly co-polarized at 0°, 45°, 90°, and −45°. Based on the experimental determination of the output polarization states of the pump and probe signals, a technique is proposed to incorporate the XPolM effect in classic models describing the FWM. It is demonstrated that classic models lacking the inclusion of the XPolM effect can reflect a significant error in the estimation of the conversion efficiency. 相似文献
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A tripodal receptor functionalized with a stilbazolium dye derivative has been designed, synthesized and has been used for the colorimetric discrimination between certain ω-amino acids in mixed DMSO-water 90:10 v/v solutions. 相似文献
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38.
Brbara L. Almeida Joanna M. Ramos Otvio Versiani Marta Sousa Claudio Alberto Tllez Soto Ana Lúcia Ramalho Mercê Antnio Slvio Mangrich Judith Felcman 《Polyhedron》2008,27(18):3662-3668
A new complex of Cu(II) of stoichiometry [Cu(PCr)(H2O)] was prepared from aqueous solution at pH 6. Its synthesis, characterization, thermogravimetric, vibrational spectroscopy, and electron paramagnetic resonance analyses were described and suggest that phosphocreatine (PCr) in solid state is acting as a tridentate ligand (the nitrogen atom of the guanidine group and the oxygen atoms of the phosphate group and the carboxylate group being the donor atoms). The fourth position is occupied by a water molecule. These results were confirmed through computational calculations (DFT/B3LYP:6-311G theoretical procedure). The tetra coordination of Cu(II) arranged in a quadratic planar geometry was found to be more stable in the DFT calculations. The calculated vibrational spectrum agrees well with the FT-IR experimental spectrum. 相似文献
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An effective action for QCD at one-loop order, which is real, manifestly Lorentz and gauge invariant and which depends on an infinite family of gauge invariants (tr(F μν F μν), tr(F μν F μν F ?σ F ?σ),...), is obtained. Moreover, anAnsatz for a vacuum configuration is made, whose corresponding vacuum energy density is lower than the one for the SavvidyAnsatz. Both the cases of pure QCD and of QCD with massless fermions are considered. 相似文献