It was demonstrated that high-resolution magic-angle-spinning (HR-MAS) ¹H NMR spectra of biological tissue samples with a volume as small as 150 nL, or 0.15 mg in weight, can be acquired in a few minutes at 21.1 T field strength using a commercial 1.6 mm fast-MAS probe with minor modification of the MAS rotor. The strategies of sealing the samples inside the MAS rotor to avoid fluid leakage as well as the ways to optimize signal to noise are discussed.

his paper presents the design and implementation of a radio frequency (RF) transmitter for NMR spectrometer, which is capable of fast modulation of the amplitude, phase and frequency of RF pulses. Two cascading numerically controlled oscillators (NCOs) were used in the digital IF subsystem. The first NCO was implemented in a field programmable gate array (FPGA), generating baseband modulating signal. The second one was a direct digital frequency synthesizer (DDS), which is responsible for sampling rate conversion, IF generation and modulation, and transmission of  modulated IF signal. The phase and frequency offset of a RF pulse can be set directly by the cascading NCOs, whereas the amplitude is set by the cascading NCOs and digital step attenuators. It was demonstrated that the basic electrical specifications and function of the transmitter can meet the needs of routine 1D/2D NMR experiments.

High-quality radio frequency (RF) coils are crucial for clinical magnetic resonance imaging (MRI). However, it is often difficult to achieve a uniform B₁ field and a high SNR simultaneously with traditionally-designed coils. In this article, we present an interventional transmitter-and-receiver RF coil for neurosurgery. This coil adopts a detachable structure that can be assembled and disassembled repeatedly on the neurosurgery gantry to reduce the interference from MRI to surgery. The simulation results and imaging experiments demonstrated that this coil is capable of producing a uniform RF field, a high SNR and a large imaging range simultaneously to meet the requirements of clinical neurosurgery.

This paper briefly introduces software-defined radio, as well as three types of radio frequency (RF) receiving system based on the method of softwaredefined radio: RF sampling with low-pass filtering for fully bandwidth; RF directly sampling with band-pass filtering for narrow band signal and IF sampling with band-pass filtering for broad band signal. Then basic principles of receiving MRI echo with the method of software-defined radio are explained. The actual design of RF receiving system for MRI echo with the software-defined radio was presented, including receiving system diagram, working principle, selection and analysis of design parameters, implementation of some function module, and issues that should be considered during design and implementation. Analysis and comparison of three types of RF receiving system based on software-defined radio for low field MRI spectrometer were given.

Prostaglandin E2 (PGE2) is a widely distributed substance in body, and involved in many physiological and pathological processes. It regulates signal transduction pathways through binding to EP1, EP2, EP3 and EP4 receptors. PGE2 is also. Sulprostone is an analogue of PGE2, playing its physiological functions through activation of EP1 and EP3. The metabolic foundation of PGE2 is still poorly understood. This work studied the metabonome of serum and liver in sulprostone-induced mice using nuclear magnetic resonance (NMR)-based analysis. The results showed that following 32 days of sulprostone treatment (i.e., 0.1 mg/kg, medium dose; 1 mg/kg, high dose), the animals showed significantly increased NADP⁺，NAD⁺，UDP，AMP and bile acids levels, and significantly reduced levels of glycogen, glucose, phenylalanine, tyrosine, uridine, inosine, nicotinic acid and GSSG in the liver. After three-weeks of recovery, choline elevation persisted in the high dose group. These results indicated that sulprostone caused metabolic disturbance of glucose, nucleic acid and amino acids in the liver. No sulprostoneinduced changes were observed in the serum data, probably due to hemeostasis. The results obtained provided more insights into the PGE2-EP1/3-signaling pathways in mouse, especially in the metabolic aspects.

Kunming (KM) mouse is a widely used model animal species in China. We measured the metabolites in plasma, urine, liver and other tissues from KM mice with nuclear magnetic resonance (NMR)-based metabonomic analysis. The representative ¹H NMR spectra of biofluids and tissues from KM mice were assigned with the aid of a range of two-dimensional NMR techniques, including COSY (Correlation Spectroscopy), TOCSY (Total Correlation Spectroscopy), J-Res (J-Resolved Spectroscopy), HSQC (Heteronuclear Single Quantum Coherence) and HMBC (Heteronuclear Multiple Bond Coherence). A total of 82 different metabolites, including 46 metabolites from the urine, 32 from the plasma, 43 from the liver extracts and 39 from the kidney cortex extracts, were identified. It was found that some metabolites existed in all the samples. Our results provide a foundation for future metabonomic studies using KM mice as the model animal.

The chemical fingerprints of 27 Angelica sinensis samples harvested at different growth stages were analyzed by ¹H NMR. Ferulic acid, ligustilide and angelica polysaccharide,  three of the active  constituents of Angelica sinensis, were identified, with their ¹H chemical shifts assigned. The relative peak areas of characteristic peaks were used to descript the changes of chemical contents in Angelica sinensis at different growth stages. The results showed that the levels of three constituents had little changes during the first year. More changes were observed in year two and year three. During the growth cycle of Angelica sinensis, the changes of angelica polysaccharide were greater than those of the other two constituents, which were proven to be the active ingredients involved in metabolism. It is concluded that ¹H NMR fingerprinting and principle component analysis can be used to analyze the active ingredient of Angelica sinensis at different growth periods.

Concentration of the calcium and magnesium ions in mammalian biofluids carries important information on metabolic homeostasis for nutrients and pathophysiology of some diseases. Methods are in urgent need to achieve rapid quantitative measurements of these ions in urines with little matrix effects. In this work, we report a simple ¹H NMR method for measuring urinary concentrations of these ions by using ethylenediaminetetraacetic acid (EDTA) as a probe and measuring EDTA complexes of calcium and magnesium ions. This method was applied to analyze human, rat and mouse urine samples. The results indicated that urinary concentrations of calcium and magnesium ions had a clear species dependence and inter-individual variation within the same species. The method offered a simple and rapid way for quantitative measurements of calcium and magnesium ions in biofluids in situ and provided some useful data for urinary calcium and magnesium ions for man, rats and mice.

In traditional two-dimensional (2D) NMR experiments, spectral resolution in the F₁ dimension is usually higher than that in the F₂ dimension. Therefore, in the HSQC experiments, the spectral resolution in the ¹³C dimension is lower than that in the ¹H dimension. This is the opposite in the ¹H, ¹³C-COSY experiments. In this work, a method for improving the resolution of 2D NMR spectrum was presented, in which HSQC and ¹H, ¹³C-COSY spectra were overlapped, and then the weaker points were selected, saved and displayed. The method was implemented as an AU program within the Bruker Topspin framework. It was demonstrated experimentally that the method could improve spectral resolution, at no cost of signal-to-noise ratio. The method can also be used to suppress F₁ noise.

A Symmetry-based Resonance Echo Saturation Irradiation DOuble Resonance (SRESIDOR) method is proposed for measuring ¹H-²⁷Al dipolar coupling constant in zeolite. The influence of ²⁷Al C_q value, υ₁ (²⁷Al) and the saturation pulse length of ²⁷Al channel on the ¹H/²⁷Al S-RESIDOR experiment were discussed. Numerical simulations indicate that ¹H/²⁷Al S-RESIDOR dephasing curves are insensitive to the ²⁷Al quadrupole coupling constant, and moderate RF field can fulfill the experiment requirements. The ¹H/²⁷Al S-RESIDOR experiment was performed on H-mordenite under fast spinning speed, and the measured ¹H/²⁷Al dipolar coupling constant is 874 Hz.

The CPMG sequence is the most widely used pulse sequence in NMR logging. However, the formation of stimulated echo will distort the first two echoes acquired with the CPMG sequence, affecting the signal-to-noise ratio (SNR) of logging tools and the outcome of reservoir evaluation. To improve the performance of NMR logging tools, a correction method for stimulated echo was proposed, based on theoretical studies on the how the stimulated echoes are formed and what are their effects on CPMG acquisition. Because the radio frequency (RF) field generated by a RF pulse might vary by the load, a relationship between stimulated echo correction coefficient and the RF field was established to calibrate the CPMG measurement made under different environment. With real logging data of low SNR, the correction method proposed  resulted a measurement error of 4.9%, which was a significant improvement from a 24.6% measurement error resulted from the traditional cast-out-the-first-two-echoes correction method. 

To meet the practical demands for nuclear quadrupole resonance (NQR)-based explosive detection system, a probe was designed for suppressing the ring tails. The probe included a high Q- value tune circuit, an impedance matching circuit and a circuit for ring tails suppression. Simulation results showed that the proposed probe design can suppress ring tails effectively, shorten recovery time, and improve the reliability of the detection system.

The chemical structures of 1,2-substituted ethylene derivatives were studied by NMR spectroscopy. Multiple-frequency selective excitation double pulsed field gradient spin echo 1D NOESY technique was found to be effective for structural elucidation of  1,2-substituted ethylene derivatives. High-quality NOE spectra were obtained, with elimination of selective population transfer (SPT). The usefulness of 1D NOE in the structural elucidation of  1,2-substituted ethylene derivatives was demonstrated using acetic acid 4-(2-cyclohexylcarbamoyl-2-phenyl-vinyl)-2-methoxy-phenyl ester as the example.

A novel compound with potential pharmaceutical applications, 4-(4-methoxyphenyl)-1-{[2-(4-nitrophenoxymethyl)-benzimidazol-1-yl]methyl}carbonylthiosemicarbazide (1) was synthesized. Its structure was determined by elemental analysis, IR and NMR techniques. The existence of two isomers of compound 1 were confirmed by NOESY spectroscopy. The ¹H  and ¹³C NMR signals of the isomers were assigned completely using 2D NMR techniques, and the corresponding coupling constants and the tautomeric ratios of isomers were also reported.

Two compounds were isolated from ethyl acetate extracted fraction of Drynaria fortunei. The compounds were characterized by ESI-MS, IR, ¹H NMR, ¹³C NMR and 2D NMR (¹H-¹H COSY, HSQC and HMBC) techniques. The ¹H NMR chemical shift of the compounds were assigned. Their structures were elucidated as kaempferol-3-O-β-D-6"'-acetyl-glucopyranosyl(1→4)-α-L-rhamnoside and kaempferol-3-O-β-D-glucopyranosyl(1→4)-α-L-rhamnoside.

This paper introduces the application of nuclear magnetic resonance (NMR) spectroscopy in coal analysis. Emphasis was put on how to analyze the chemical composition and structure of coal and pyrolysis products with NMR approaches, including solution/solid-state ¹H, ¹³C, ¹⁵N, ¹⁹F and ³¹P NMR spectroscopy. Because the NMR approaches require little sample preparation, and can be used to obtain both qualitative and quantitative information, they have becoming widely-used tools in coal industry.