A Quadrupole-Central-Transition 17O NMR Study of Nicotinamide: Experimental Evidence of Cross-Correlation between Second-Order Quadrupolar Interaction and Magnetic Shielding Anisotropy

2018 ◽  
Vol 122 (18) ◽  
pp. 4813-4820 ◽  
Author(s):  
Jiahui Shen ◽  
Victor Terskikh ◽  
Xiaoling Wang ◽  
Ivan Hung ◽  
Zhehong Gan ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Cross Correlation ◽  
Second Order ◽  
Magnetic Shielding ◽  
Quadrupolar Interaction ◽  
17O Nmr ◽  
Central Transition ◽  
Nmr Study

17O NMR Study of Chromium(VI) Ions in Water

1996 ◽  
Vol 118 (34) ◽  
pp. 7969-7980 ◽  
Author(s):  
Nicola E. Brasch ◽  
David A. Buckingham ◽  
A. Bram Evans ◽  
Charles R. Clark
Keyword(s):  
17O Nmr ◽  
Chromium Vi ◽  
Nmr Study

scholarly journals Parsimonious truncated Newton method for time-domain full waveform inversion based on Fourier-domain full-scattered-field approximation

Geophysics ◽  
2021 ◽  
pp. 1-147
Author(s):  
Peng Yong ◽  
Romain Brossier ◽  
Ludovic Métivier
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Cross Correlation ◽  
Waveform Inversion ◽  
Field Approximation ◽  
Second Order ◽  
Vector Product ◽  
First Order ◽  
Full Waveform ◽  
Truncated Newton

In order to exploit Hessian information in Full Waveform Inversion (FWI), the matrix-free truncated Newton method can be used. In such a method, Hessian-vector product computation is one of the major concerns due to the huge memory requirements and demanding computational cost. Using the adjoint-state method, the Hessian-vector product can be estimated by zero-lag cross-correlation of the first-order/second-order incident wavefields and the second-order/first-order adjoint wavefields. Different from the implementation in frequency-domain FWI, Hessian-vector product construction in the time domain becomes much more challenging as it is not affordable to store the entire time-dependent wavefields. The widely used wavefield recomputation strategy leads to computationally intensive tasks. We present an efficient alternative approach to computing the Hessian-vector product for time-domain FWI. In our method, discrete Fourier transform is applied to extract frequency-domain components of involved wavefields, which are used to compute wavefield cross-correlation in the frequency domain. This makes it possible to avoid reconstructing the first-order and second-order incident wavefields. In addition, a full-scattered-field approximation is proposed to efficiently simplify the second-order incident and adjoint wavefields computation, which enables us to refrain from repeatedly solving the first-order incident and adjoint equations for the second-order incident and adjoint wavefields (re)computation. With the proposed method, the computational time can be reduced by 70% and 80% in viscous media for Gauss-Newton and full-Newton Hessian-vector product construction, respectively. The effectiveness of our method is also verified in the frame of a 2D multi-parameter inversion, in which the proposed method almost reaches the same iterative convergence of the conventional time-domain implementation.

Solid-state 17O NMR Study of Small Biological Compounds

2007 ◽  
Vol 62 (11) ◽  
pp. 1422-1432 ◽  
Author(s):  
Kazuhiko Yamada ◽  
Tadashi Shimizu ◽  
Yoshida Mitsuru ◽  
Miwako Asanuma ◽  
Masataka Tansho ◽  
...  
Keyword(s):  
Solid State ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Multiple Quantum ◽  
Peptide Analysis ◽  
17O Nmr ◽  
Nmr Study ◽  
Biological Compounds ◽  
Nmr Tensors ◽  
Angle Spinning

We present a systematic experimental and theoretical investigation of the oxygen chemical shielding and electric-field-gradient tensors in polycrystalline amino acids and a peptide. Analysis of the 17O magic-angle-spinning (MAS), multiple-quantum MAS, and stationary nuclear magnetic resonance (NMR) spectra yield the magnitudes and the relative orientations between the two NMR tensors. The obtained 17O NMR parameters are sensitive to the hydrogen bond environments. We also demonstrate that solid-state 17O NMR is potentially useful for studying the secondary structures of peptides and proteins.

Closer to the polydopamine structure: new insights from a combined 13C/1H/2H solid-state NMR study on deuterated samples

2018 ◽  
Vol 9 (24) ◽  
pp. 3379-3387 ◽  
Author(s):  
Monica Cîrcu ◽  
Claudiu Filip
Keyword(s):  
Solid State ◽  
Experimental Evidence ◽  
Solid State Nmr ◽  
Water Dynamics ◽  
Π Stacking ◽  
Nmr Study

13C/1H/2H ss-NMR on deuterated samples provide strong experimental evidence for the most probable monomer connectivity, π–π stacking, and the water dynamics in polydopamine.

Effects of organic ammonium cations on the isolation of {Ti4} cyclic clusters from water: an 17O NMR study

2020 ◽  
Vol 49 (18) ◽  
pp. 5957-5964
Author(s):  
Weiming Liu ◽  
Caiyun Liu ◽  
Wenli Wu ◽  
Guanyun Zhang ◽  
Jian Zhang ◽  
...  
Keyword(s):  
Cluster Compounds ◽  
Acidic Water ◽  
17O Nmr ◽  
Nmr Study ◽  
Solution Speciation

The organic ammonium cations change the solution speciation of Ti4+ in acidic water and promote the formation of {Ti18O27}. However, the crystalline precipitates are {Ti4} cluster compounds.

Postsynaptic Dorsal Column and Cuneate Correlations in the Raccoon: A Re-evaluation by Parallel-Cascade Analysis

2002 ◽  
Vol 88 (6) ◽  
pp. 3372-3376
Author(s):  
Andrew S. French ◽  
Susan H. Dick ◽  
Douglas D. Rasmusson
Keyword(s):  
Cross Correlation ◽  
Volterra Series ◽  
Receptive Fields ◽  
Dorsal Column ◽  
Second Order ◽  
Input Signals ◽  
Cascade Analysis ◽  
Postsynaptic Dorsal Column ◽  
Positive Correlations ◽  
Cascade Method

In a previous study, we reported evidence for correlations between the firing of postsynaptic dorsal column (PSDC) neurons and cuneate neurons with overlapping receptive fields on the glabrous skin of the raccoon forepaw. The evidence was based on cross-correlation and frequency response analyses of spontaneously firing neurons. However, cross-correlation without white noise Gaussian analog inputs or Poisson distributed pulse train inputs is difficult to interpret because of the inherent convolution with the autocorrelation of the unknown input signals. While the data suggested positive correlations in the spinocuneate direction for most neuron pairs, we could not estimate the temporal characteristics of these putative connections. We have now re-analyzed these data using a parallel-cascade method to estimate the first- and second-order kernels of a Volterra series approximation to the spinocuneate system. This unbiased analysis suggests that a positive correlation occurs after about 5 ms, probably followed by a negative correlation at about 12 ms. Second-order kernels also had repeatable structure, indicating dual pathways with time separations of at least 10 ms.

Formation of mononuclear rhodium(III) sulfates: 103Rh and 17O NMR study

2009 ◽  
Vol 35 (8) ◽  
pp. 577-581 ◽  
Author(s):  
A. V. Belyaev ◽  
M. A. Fedotov ◽  
S. N. Vorob’eva
Keyword(s):  
17O Nmr ◽  
Nmr Study
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