A novel flavone glycoside, 3′″-carbonyl-2″-β-L-quinovosyl icariside Ⅱ was isolated from a Chinese medicinal plant, Epimedium koreanum Nakai. The ¹H and ¹³C NMR chemical shifts of the compound were completely assigned using a combination of 1D(¹H, ¹³C NMR, NOE and DEPT) and 2D NMR(¹H-¹H COSY，HSQC, HMBC and NOESY) techniques and by referring to ¹H and ¹³C NMR spectra of icariside Ⅱ, 2″-rhamnosyl icariside Ⅱ and icariin. The structure of the compound was determined to be 4′-Methylether, 3-O-[3-one-β-L-quinovosyl-(1→2)-α-L-rhamnopyranoside], 5, 7-dihydroxy-2-(4-hydroxyphenyl)-8-(3-methyl-2-butenyl)-4H-1-benzopyran-4-one.

1D and 2D NMR (¹H NMR，¹³C NMR，DEPT，¹H-¹H COSY，HSQC，HMBC) methods were used to elucidate the structure of methyl 2，7，7-trimethyl-5-oxo-4-(3-methoxy -4-hydroxylphenyl)-1，4，5，6，7，8-hexahydroquinolin-3-carboxylate. The ¹H and ¹³C chemical shifts of the compound were assigned.

In this work, CeO₂-γ-Al₂O₃ mixed oxides were studied by solid-state NMR techniques to understand the interaction between CeO₂ and γ-Al₂O₃. The ²⁷Al magic angle spinning (MAS) NMR spectra of the mixed oxides showed a sharp peak at ca. 37 ppm and a highfield shoulder, in addition to the signals from tetra- and hexa-coordinated ²⁷Al sites. It was demonstrated that the sharp peak at ca. 37 ppm originates from the ²⁷Al atoms residing in the lattice of CeO₂ with an eightfold coordination, representing the interaction between CeO₂ and γ-Al₂O₃; the highfield broad shoulder peak arises from penta-coordinated Al sites originally present in γ-Al₂O₃. It was postulated that four ^_Al3+ ions have replaced the three Ce⁴⁺ ions in three CeO₂ crystal cells so that the overall charge balance of the system is maintained. Furthermore, it was shown that the concentration of Al substitution is limited, and only about 1% of the total CeO₂ can be replaced by Al³⁺.

The design and construction of a digital receiver for low-field MRI scanner based on direct RF sampling is described. The main features of this receiver include simple structure, low cost and high performance. The performance of the receiver was demonstrated experimentally.

The design of an integrated NMR spectrometer based on USB is introduced. The spectrometer, in which the control/communication unit, pulse generator, RF waveform transmitter and digital receiver are integrated onto one card, can works in two modes. In Mode I, the spectrometer communicates with a PC through USB connection, and is controlled by PC to complete all tasks including real time control of the spectrometer and data display/processing. In Mode II, the spectrometer is controlled by an integrated microprocessor and can complete all tasks without the participation of the PC. The performance of the proposed system was tested in three experiments using single-pulse, spin-echo and CPMG pulse sequences, respectively.

A synthetical algorithm for automatic phase correction of NMR spectra based on neural network (NNAPC) is proposed. Taking into account the characteristics of the NMR spectrum or the resonance peak, the proposed algorithm uses an artificial neural network to choose the most appropriate algorithm to calculate the phase angles of a given peak. Statistical analysis demonstrated that the NNAPC algorithm is more accurate and stable than the existing phase correction algorithms referenced.

Quadrature detection is widely used in modern NMR spectrometers, as it provides such advantages as avoiding peak overlapping, reducing the power requirement for the excitation radiofrequency pulse, and increasing signal-to-noise ratio of detection. However, mirror peaks may arise if the gain of the two receiver channels used in quadrature detection are not matched, or the phase difference between two channels is not exactly 90 degree. To a certain degree, the problem can be overcome by applying phase cycling during acquisition. However, manual correction is necessary when the gain difference between the two channels become large or the phase difference is far from 90 degrees. This paper proposes a simple method to correct gain and phase mismatch in quadrature detection experimentally.

This paper introduces the design and making of a surface coil for ²³Na magnetic resonance imaging. A single-loop ²³Na surface coil was made and used to acquire ²³Na density-weighted images on tubes filled with NaCl solution, boiled salted quail egg and rat brain on a Bruker Biospec 47/30 MRI scanner. This study represents the first step towards having ²³Na magnetic resonance imaging as a tool in various biomedical applications.

Multi-wall carbon nanotubes were synthesized from C₂H₂ by chemical vapor deposition (CVD) method using LaNi₅ alloy micro-particles with diameters ranging from 41 to 150 μm as catalyst. Electron spin resonance (ESR) spectra of purified carbon nanotubes were acquired at different temperatures between 100 and 290 K. The effects of the size of the catalyst particles used and addition of hydrogen gas during synthesis on the ESR characteristics (i.e., line shape, g-value and linewidth) of the produced nanotubes were investigated. It was found that the g-values of the produced nanotubes increase with their diameters: nanotubes having diameters between 10 and 20 nm (synthesized with catalyst particles having diameters between 41 to 50 μm) have an averaged g of 2.0400, while those having diameters between 70 and 120 nm (synthesized with catalyst particles having diameters between 100 to 150 μm) have an averaged g of 2.0898. It was also found that there is only one peak in the ESR spectra of carbon nanotubes with small diameters, while the nanotubes having larger diameters show two peaks, and the intensity of the additional peak increases with temperature.

As one of the most important parts of the Paul trap, the radiofrequency (RF) source has great influences on the performance of the ion trap. To improve the stability and the depth of the pseudo-potential well of the ion trap, two sets of RF sources and the corresponding detection circuits were designed and implemented in a Paul trap. With the implementation, absorbed signals of ¹⁹⁹Hg⁺ and N⁺₂ were detected from trapped ions.

Two neolignans were isolated from the bark of Hydnocarpus annamensis. Their structures were elucidated using high-resolution ESI mass spectrometry and NMR spectroscopy. The proton and carbon chemical shifts of the two compounds was assigned using 2D NMR experiments, including HSQC, HMBC, DQF-COSY and NOESY. The results of capillary electrophoresis (CE) analysis demonstrated that the two compounds are racemates.

The Atheron-Todd reaction has been used extensively for synthesis of phosphates and phosphoroamidates. In this study, we showed that daidzein can be phosphorylated by a modified Atheron-Todd procedure in which dialkyl phosphite and tetrachloromethane mixture was dropped into a mixed solution of daidzein, trithylamine and DMF. The reaction product was obtained with good yield, whose structure was determined by NMR, ESI-MS and X-ray crystallography.

Using atomic electronegativity interaction vector (AEIV) as a parameter to describe the local chemical microenvironment of carbon atoms and the γ parameter, we built a model to calculate ¹³C NMR chemical shifts in aliphatic ethers. The results obtained from 139 ¹³C NMR chemical shifts in 17 aliphatic ethers showed that the correlation coefficients R of model’s estimated value and leave-one-out (LOO) cross-validation (CV) predicted value are 0.995 7 and 0.994 2, respectively. Furthermore, the model was validated using the ¹³C NMR chemical shifts of ¹³C atoms in 5 other aliphatic ethers as testing samples, and the correlation coefficients (Q_ext) obtained was found to be 0.996 3. The results of this study showed that the parameter AEIV correlates well to the ¹³C NMR chemical shifts of aliphatic ether.

The ¹H NMR spectra of natural taxanes with different skeleton types were analyzed systematically, and the ¹H NMR spectral characteristics of natural taxane diterpenoids were summarized. The results obtained in this study may provide reference information for spectral assignment and structure elucidation of natural taxanes.