Magnetic resonance imaging (MRI) is a nonradioactive and noninvasive medical imaging technique, and it has been widely applied in the clinical diagnosis. However, using conventional proton MRI to obtain lung images is difficult, because the proton density in the lungs is about three orders of magnitude lower than that in other organs/tissues due to air cavities in the lungs. Hyperpolarized noble gases can be used as contrast agents for lung MRI. Spin-exchange optical pumping (SEOP) is a technique that can be used to enhance the nuclear spin polarizations of noble gases more than 10 000 folds, which makes noble gas lung MRI feasible. In this paper, the recent developments of hyperpolarized gases lung MRI were reviewed. Topics covered include comparison of different hyperpolarized noble gases used for lung MRI, unconventional methods for measuring quantitative parameters in hyperpolarized gas MRI, and the most updated applications of hyperpolarized gas MRI in assessing pulmonary structure and function.

Images acquired with gradient echo sequences are susceptible to artifacts induced by frequency offsets varying in spatial and temporal dimensions. This study addressed how respiration-induced local field fluctuations affect the quality of brain images acquired with a three-dimensional multi-echo gradient echo sequence. It was shown that respiration-related artifacts can be corrected by acquire a one-dimensional navigator signal before the application of phase-encoding gradient in each phase-encoding step, which later can be used to correct respiration-related phase shifts during reconstruction to yield
artifact-free images. Experimental results showed that both the respiration-related phase oscillations and image artifacts increased with echo time. It was also demonstrated that the phase fluctuations and image artifact levels in both the gradient echo images and T₂^* maps calculated from mutli-echo data reduced significantly after navigator echo phase correction.

Carbonylation of methanol with CO on Cu-H-mordenite (Cu-H-MOR) zeolites was studied by ¹³C solid-state NMR spectroscopy. By characterizing the interaction between adsorbed species and Cu²⁺ cations, we determined copper methoxy group (Cu-OCH₃) and copper acetyl group (Cu-(CO)-CH₃) as the intermediates of this reaction. The possible mechanisms of carbonylation reaction of methanol with CO on Cu-H-MOR zeolites were discussed.

The use of fluorescent additives in drilling fluid is beneficial for drilling safety, but may potentially have adverse effects on oil discovery. In this paper, the effects of addition of powdered fluorescent additives on the NMR characteristics of drilling fluids were investigated with high-resolution NMR spectroscopy. A total of fourteen types of powdered fluorescent additives were added to water and drilling fluid at different dosages and temperature (32 ℃, 90 ℃ and 150 ℃). The NMR spectra of the doped water and drilling fluid were then acquired. The results showed that some of the fluorescent additives showed no NMR signal, while the other showed peaks of hydrated additives. In the later case, the peak disappeared after adding relaxation reagent. It was concluded that commonly used powered fluorescent additives have no effects on the NMR characteristics of drilling fluids, and thus can be used without limitation in NMR surface logging.

Salmonella typhimurium is a intracellular, invasive, facultative anaerobic bacteria. With improved safety, attenuated salmonella typhimurium has been widely used in development of vaccine for preventing viruses, bacteria, and parasites infections. However, limited research has been done so far on the biological effects of attenuated salmonella typhimurium infection on animal hosts. In this work, we measured fecal metabonome of mice infected with attenuated salmonella typhimurium using NMR spectroscopy. Two sets of NMR data were acquired with the same protocols on a Bruker 500 MHz NMR spectrometer and an in-house 500 MHz NMR spectrometer developed in Wuhan Institute of Physics and Mathematics (WIPM). Multivariate data analysis methods were used to analyzed the data. It was found that infection induced increases of certain amino acids and uracil in feces, and decreases of bile acids, lactate and propionate. Such metabolic alterations indicated that infection of attenuated salmonella typhimurium may cause disturbance of gut microbiotal communities. The results obtained from the home-developed spectrometer in WIPM showed high consistency with those obtained from Bruker 500 MHz NMR spectrometer, suggesting that the WIPM spectrometer is ready for metabonomic studies.

In this paper, qualitative and quantitative NMR techniques were used to analyze samples obtained from imidacloprid production. Two-dimensional DOSY spectra demonstrated the samples contained two by-products. One-dimensional (i.e., ¹H and ¹³C NMR and DEPT) and two-dimensional (i.e., 1H-1H COSY, HSQC and HMBC) NMR techniques were used to assign the chemical shifts of the by-products, which were finally determined to be 1,1-imorpholinopropane and N-(1-propenyl) morpholine. Finally a quantitative 13C NMR method was developed to measure the contents of by-products quantitatively.

The curing process urea-formaldehyde resin without the use of hardeners was studied by time-domain nuclear magnetic resonance (TD NMR) at different temperatures. The results showed that urea-formaldehyde resin started curing at about 120 ℃ and ended around 180 ℃. The total peak area for T₂ decrease gradually with increasing temperature; and larger changes were observed when the temperature was above 140 ℃. At temperature range between 30 ℃ to 140 ℃, the peak areas decreased gradually and then increased slightly with increasing temperature at T₁ (1) = 0.014 ms; the peak areas decreased gradually with increasing temperature at T₁ (2) = 327.455 ms. The total peak area for T₁ decrease gradually with increasing temperature between 30 ℃ and 180 ℃. The urea-formaldehyde resin system weight decreased gradually with increasing temperature in the solidification process, confirming that cross-linking condensation reaction may occur, giving off formaldehyde and water.

The principles of using nuclear quadrupole resonance (NQR) to detect explosive, as well as the methods of signal processing were introduced. The main error sources of NQR signal detection were analyzed. Several methods are proposed to eliminate the errors: correlation accumulation for eliminating thermal noises; single channel adaptive algorithm for eliminate ringing; and correlation detection to hold radiofrequency interference. The experimental results showed that the signal-to-noise ratio of NQR signals can be improved effectively using correlation detection, resulting in improved accuracy of signal detection.

A small-size oven temperature controlled crystal oscillator for rubidium atomic frequency standards was designed. In the design, a Pierce oscillator circuit, a two step π type LC filter and a Complementary-Symmetery Metal-Oxicle-Semiconcluctor(COMS) inversion isolator were used. Low thermal noise transistors were employed in the circuit. The temperature of the crystal oscillator was set at the turning point of the frequency-temperature curve. The crystal oscillator was of a volume of 4 mL with a short-term frequency stability of 1.8×10^-12/s. The oscillator was of low phase noise, and its fractional frequency stability contribution to a rubidium atomic frequency standard was estimated to be in a level of 3.2×10^-13τ ^-1/2.

In this study, we calculate atomic net charge of 32 compounds using quantum chemical calculation. A generalized semiempirical relationship was used to compute the nuclear spin-spin coupling constants in these compounds. The obtained semiempirical relationship was then validated using 5 compounds as the test set. The computed results of the 32 training compounds and the 5 test compounds were all in good agreement with the experimental data. It was concluded that semiempirical relationship obtained in this study can be applied to calculate nuclear spin-spin coupling constants and that atomic net charge calculated by charge equilibration method (QEq) provides more reliable results than other parameters.

2-keto-L-gulonic acid (2-KLG) changes its molecular structure in many solvents at room temperature. A five-membered intramolecular ring structure can easily be formed by the 2,5-hemiacetal reaction after the opening of the carbonyl group in 2-KLG (-C=O) to form a O-C-O interlinkage. In this study, we showed that the ¹³C chemical shift of the carbonyl changed from δ 200 towards high field to about δ 96 after forming the intramolecular ring. Two-dimensional HMBC experiments revealed that 2-keto-L-gulonic acid formed five-membered ring 2,5-hemiacetal derivates in seven solvents, instead of
six-membered 2,6-hemiacetal derivates.

Two ginsenosides were isolated from the 80% ethanol extract of the root of Panax notoginseng, namely 6-O-(β-D-glucopyranosyl)-20-O-(β-D-xylopyranosyl)-3β，6α，12β，20(S)-tetrahydroxydammar-24-ene (compound 1) and notoginsenoside U (compound 2). Their structures were elucidated by one-imensional and two-dimensional NMR (i.e., ¹H-¹H COSY, HSQC and HMBC) experiments. The ¹³C NMR spectral data of compound 1 was compared with those reported in the previous references, and corrections were made for some previous assignments which were incorrect. The completed assignments of
compound 1 were obtained. The ¹H and ¹³C NMR signals of compound 2 in prydine-d₅ were assigned.

Phosphoramidon is a naturally occurring glycopeptide isolated from the culture of Streptomyces tanashiensis. As an inhibitor of metalloproteases, phosphoramidon has many important applications in biological and medicinal research. On the basis of one-dimensional (i.e., ¹H, ¹³C, and ³¹P) and two-dimensional (i.e., ¹H-¹H COSY, HSQC, and NOESY) NMR spectral data, the NMR signals for phosphoramidon and its β -anomer were assigned. The anomeric configurations of the two isomers were determined.

Maytenus species are shown to have antitumor activity. Friedelane triterpenoid is found to be one of most active components, especially aromatic friedelane triterpenoid with A ring or A/B rings. In this study, the chemical structures and of and ¹³C NMR characteristics of friedelane triterpenoids from Maytenus reported in the literature from 1995 to 2013 are summarized and reviewed. The findings are potentially useful for structure elucidation and assignment of the spectroscopic signals of this type of compounds.