With the advances in NMR theories and spectrometer hardware technology, NMR is playing an increasingly important role in studying multiscale structure and dynamics of polymers. In this paper, the newest developments in solid-state ¹H and ¹³C NMR techniques and their applications in the studies of polymer structures and dynamics were reviewed. High-resolution solid-state ¹H NMR techniques, such as multiple-pulse and fast magic angle spinning (MAS), have made it possible to determine the chemical structures of polymers and to detect the intra- and inter-polymer interactions effectively. Taking advantages of through-bond (J- coupling) and through-space (dipolar coupling) interactions, two dimensional heteronuclear correlation NMR experiments now can be used to resolve the microstructures of complex polymer chains. The recoupling techniques allow dipolar interactions and chemical shift anisotropy to be observed under MAS conditions, thus enabling simultaneous detection of high-resolution ¹H or ¹³C signals and quasi-static anisotropic interactions.  The domain sizes and interphase thickness in multiphase polymers and miscibility in polymer blends can now be determined effectively using the dipolar filter techniques. In the dynamics studies, it is now possible to obtain information on local fast motions of a single bond and super-slow chain dynamics by efficient suppression of spin-diffusion among protons and recoupling of chemical shift anisotropy. In summary, the advanced solid-state NMR techniques have enabled detailed studies on polymer microstructure, phase separation and dynamic behavior at different time and length scales, and on the relationship between the microstructure and macroscopic properties of polymers.

Basic structure and work flow of pulse programmer in NMR spectrometer were introduced. The progress of pulse programmer in terms of degree of system integration, rate of data transmission and memory capacity was emphasized. The advantages and disadvantages of commercial and home-build pulse programmers were compared. A modularized pulse programmer based on USB 3.0 was proposed, which might be used in magnetic resonance imaging (MRI) scanners with multichannel transceivers.

To meet the functionality requirements and the trend of instrument miniaturization, a miniaturized NMR spectrometer console system based on fieldprogrammable gate array (FPGA) and advanced RISC machines (ARM) is proposed. This digital console has the advantages of extremely high processing speed, accurate control, short development cycle and low costs. In this paper, we introduce the functions of FPGA in the system, including data receiving, parameter configuration, pulse emission and data sampling modules. The ARM embedded module achieves the function of Ethernet communication between the console and host computer, such that the internal operation of the console will not be disturbed by the network status.

The design of a radiofrequency (RF) transmit coil for open magnetic resonance imaging (MRI) was introduced. The transmit coil is consisted of two rectangular solenoid coils with the same size which are installed on the two poles of the magnet in orthogonal directions. The two coils are positioned. A transmit coil used for 0.23 T open MRI was made. Numerical simulation of electromagnetic fields was used to optimize the distance of the turns in the coils. The homogeneity and power efficiency of the coil were measured experimentally. The deviation of the amplitude of the RF field in a sphere of 300 mm in diameter was measured to be less than 3 dB.

Fecal metabonomic NMR analysis has been found to offer important information for the complex interactions between mammalian metabolisms and their gut microbiome. In this study, we set to identify and assign saccharides signal from the NMR spectra of rat fecal samples. C18 solid-phase extraction was used to extract the saccharides from the fecal samples. The identities of the saccharides was elucidated by atomic connectivity and diffusion coefficient data obtained from 2D NMR data including ¹H-¹H COSY, ¹H-¹H TOCSY, ¹H-¹³C HSQC, ¹H-¹³C HMBC and ¹H DOSY. The saccharides identified included xylose, arabinose, galactose and arabinoxylan.

The most commonly used pulse sequence for small animal diffusion-weighted imaging on clinical MRI scanners is the single shot echo planar imaging (EPI) sequence. However, EPI is susceptible to off-resonance artifacts arising from the inhomogeneity of main field, local susceptibility gradients, and chemical shift, leading to image quality degradation. In this study, we implemented a high-resolution spinecho diffusion weighted imaging (SE-DWI) on a clinical 3 T MRI scanner. To reduce the motion artifacts, navigator echoes were acquired to correct the phase errors. The results from ischemic rat brain demonstrated that SE-DWI was feasible for imaging small animals on 3 T clinical MRI scanners.

This study investigated the metabolic change in brain of depression-like rats and the intervention effects of Yinao Jieyu recipe. Twenty rats were randomly allocated into normal group, depression group, fluoxetine group and Yinao Jieyu recipe group, with five rats in each group. The animals in the normal group were raised regularly. The animals in the other three groups were subjected to chronic unpredictable mild stress (CUMS) for 21 days. After the CUMS treatment, the animals in the depression group received saline treatment by gastrogavage for 6 weeks, and those in the fluoxetine group and Yinao Jieyu recipe group received fluoxetine and Jieyu recipe treatments, respectively, by gastrogavage for 6 weeks. In vivo ¹H MRS was performed to measure the changes of N-acetyl aspartate (NAA), choline (Cho) and creatine (Cr) levels in the left prefrontal cortex and hippocampus. Compared to the normal group, the depression group and the fluoxetine group showed significantly decreased NAA/Cr ratio in the hippocampus and frontal cortex. The Yinao Jieyu recipe group showed significantly higher NAA/Cr ratio in the hippocampus and prefrontal cortex relative to the depression group. The hippocampal Cho/Cr ratio in the depression group was found increased (P<0.05), while that in the Yinao Jieyu recipe group decreased (P<0.01), compared to the normal group. The prefrontal Cho/Cr ration in the depression group and fluoxetine group showed significant increases relative to the normal. The prefrontal Cho/Cr ratios in the Yinao Jieyu recipe group and fluoxetine group were significantly lower than that in the depression group. In conclusion, the Yinao Jieyu recipe appeared to have apparent anti-depression effects in rats subjected to CUMS.

The hyperfine splitting constant and the correlation time of 5-doxyl stearic acid in the solution of sodium alkylbenzensulfonates (ABS) were measured by electron paramagnetic resonance (ESR). The critical micelle concentration of ABS was determined and compared with the result derived from surface tension curve. It was found that the micelle microviscosity decreased and the micelle micropolarity increased with the carbon number of the short hydrophobic group at the ortho position of the sulfonic acid group.

Nuclear quadrupole resonance (NQR) is a solid-state radio frequency (RF) spectroscopic technique allowing the detection of many high explosives. However, the NQR signals are intrinsically weak, and the practical use of NQR is hindered by low signal-to-noise ratio (SNR), and artifacts arising from the thermal noise of the coil and external radio frequency interference (RFI). In this paper, we described an improved detection algorithm for detection of weak NQR signals. First, singular value decomposition using the Hankel matrix was utilized to restrain RFI and filter noise. A non-linear least squares detector based on the (multiple signal classification) MUSIC spectral estimation was applied, which not only guaranteed a high resolution in the frequency domain, but also led to significant reduction in the amount of computation. The effectiveness of this algorithm was demonstrated with the simulated and experimental results.

A chiral l-menthone hydrazone (1) reacted with nitric oxide in the presence of trace oxygen. This is a novel tandem nitration-azotization reaction, yielding α-nitro azo-compounds (2, E-1-(2-isopropyl-5-methyl-1-nitrocyclohexyl)-2-(2, 4-dinitrophenyl) diazene) in high stereo selectivity. The structure of the reaction product was characterized by DEPT, 1D NOE and 2D NMR techniques including ¹H-¹H COSY and HSQC. The ¹H and ¹³C NMR chemical shifts of the compound were assigned.

In order to establish a quality control method for Xiaoaiping Injection, one-dimensional and two-dimensional NMR techniques used to measure the important chemical constituents, including condiritul, in the injection. An NMR method for quantitative analysis of condiritul using hydroquinone as the internal standard was presented. The proton signals of condiritul at δ 5.73 and those of hydroquinone at δ 6.73 were used for quantification. Linear regression of quantitative peak area ratio (A_x/A_s, y) of condiritul-hydroquinone versus mass ratio (W_x/W_s, x) yielded a regression equation of y=0.034 1 x+0.090 6 with a correlation coefficient of 0.999 6. The precision relative standard deviation (RSD) was 1.27%, the reproducibility RSD 2.16% and the stability RSD 0.13%. The results showed that ₁H NMR can be used for quantitative measurement of condiritul in Xiaoaiping Injection.

Magnetic Resonance Imaging (MRI) is a valuable experimental method extensively used in chemical and biological research as well as medical diagnostics. It is highly sought after because of its non-invasive nature to examine deep inside the sample. Since its inception nearly 40 years ago, many imaging techniques have been developed to improve image resolution, experimental efficiency, and expand its imaging capability with low gamma nuclei. One method that shows great potential is Stray Field Imaging (STRAFI) since it utilizes the strong gradients in the fringe field of superconducting magnets. This review provides a basic introduction to stray field imaging and will cover fundamental imaging theory, the theory and methods used to execute STRAFI experiments and a brief overview of its applications in research. By providing these details we hope to show the strengths and versatility of the STRAFI experiment where conventional MRI methods may fall short.

Diabetes mellitus (DM) is a chronic metabolic disease characterized by either insulin deficiency or insulin resistance. It is known that longstanding DM causes damages to the central nervous system. The manifestations include brain atrophy and white matter lesions. Magnetic resonance imaging (MRI) and spectroscopy (MRS) are noninvasive and can provide information on the anatomical, functional and metabolic aspects of the brain. MRI and MRS have been used as diagnostic tools for many brain diseases, including diabetic encephalopathy. In this review, clinical manifestations of diabetic encephalopathy were reviewed, with emphasis on the findings detected by MRI/MRS techniques.

Autism is now widely viewed as a neurodevelopmental disorder. Structural magnetic resonance imaging (MRI) techniques, including voxelbased morphormetry and diffusion tensor imaging, have been applied to study autism. In this paper, the recent literature in this area was reviewed. It was showed that structural MRI is a powerful technique that holds great promise to understand the pathology of autism.

Gas hydrate is a clathrate compound formed from gas and water under low temperature and high pressure. So far, three types of crystal structure (i.e. I, II and H) have been found for natural gas hydrate around the world. Solid state NMR provides an important tool for structure characterization of gas hydrate and for quantitative measurement of hydration number and cage occupancy. In this paper, the principles and applications of solid state NMR techniques in studying gas hydrate were reviewed. Emphasis was given on the progresses in structural characterization of gas hydrates, identification of gas molecules and studies on structure transform, as well as the in situ monitoring of hydrate formation and dissociation. The experimental techniques and conditions for solid state NMR studies of gas hydrate were also discussed.