231 research outputs found
Fourier transform pure nuclear quadrupole resonance by pulsed field cycling
We report the observation of Fourier transform pure NQR by pulsed field cycling. For deuterium, well resolved spectra are obtained with high sensitivity showing the low frequency nu0 lines and allowing assignments of quadrupole couplings and asymmetry parameters to inequivalent deuterons. The technique is ideally applicable to nuclei with low quadrupolar frequencies (e.g., 2D, 7Li, 11B, 27Al, 23Na, 14N) and makes possible high resolution structure determination in polycrystalline or disordered materials
Optical detection of NMR J-spectra at zero magnetic field
Scalar couplings of the form J I_1 \cdot I_2 between nuclei impart valuable
information about molecular structure to nuclear magnetic-resonance spectra.
Here we demonstrate direct detection of J-spectra due to both heteronuclear and
homonuclear J-coupling in a zero-field environment where the Zeeman interaction
is completely absent. We show that characteristic functional groups exhibit
distinct spectra with straightforward interpretation for chemical
identification. Detection is performed with a microfabricated optical atomic
magnetometer, providing high sensitivity to samples of microliter volumes. We
obtain 0.1 Hz linewidths and measure scalar-coupling parameters with 4-mHz
statistical uncertainty. We anticipate that the technique described here will
provide a new modality for high-precision "J spectroscopy" using small samples
on microchip devices for multiplexed screening, assaying, and sample
identification in chemistry and biomedicine.Comment: 15 pages, 4 Figure
Plasticity in Major Ampullate Silk Production in Relation to Spider Phylogeny and Ecology
Spider major ampullate silk is a high-performance biomaterial that has received much attention. However, most studies ignore plasticity in silk properties. A better understanding of silk plasticity could clarify the relative importance of chemical composition versus processing of silk dope for silk properties. It could also provide insight into how control of silk properties relates to spider ecology and silk uses
Study on the synergy between intra-urban resident’s migration and job change in Beijing
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