We have developed an NMR micro-imaging system in our laboratory. It features low cost, high performance, simple and convenient operation, as well as easy maintenance. This system may be divided into two parts. The hardware part mainly includes a Selective Excitation Unit (SEU), three channels of Pulse Gradient field Unit and two micro-imaging probes with RF coil diameters of 5mm and 25mm, respectively. Whereas the software, integrating with real-time control and waveform generation, was implemented with Delphi 2.0. The operation of our system is rather simple, i.e. the users need only to set or choose waveform from the list on the form, and to write a proper pulse program on the NMR spectrometer. Since our MRI system includes SEU, PFG unit and micro imaging probeheads, we believe, it will be used in various fields of research.

¹H NMR spectroscopy has been used to assess chronic toxicological effects of rare earth. Male Wistar rats have been administrated orally with La(NO₃)₃ at doses of 0.2,2.0,10 20mg/kg body weight for six months. The analysis for ¹H NMR spectra of rats serum and rats urine after dosing rare earth was reported. The ¹H NMR variation of numerous low-Mr metabolites, including ketone bodies, lactate, glucose, urea, citrate and various amino acids, provided a sensitive measure of La³⁺-induced renal and liver damage and information on abnormal patterns of metablite excretion. The assay of some biochemical indexes in plasma supported NMR results. ¹H NMR techniques could be applied to clinical diagnosis of abnormal metabolism of the inborn disease and the investigation of the toxicological effects of other drugs.

Nitrogen-14 nuclear magnetic resonance (¹⁴N NMR) was introduced as a method of quantitative nitrogen analysis, and applied to the determination of the nitrate content in several humic acids. The result shows that the sensitivity of ¹⁴N NMR detection for small molecules containing nitrogen is relatively high. It is demonstrated that solution ¹⁴N NMR technique can be used in nitrogen analysis for the merits of its convenience without spoilage to the sample and the simultaneous determination of several nitrogen-containing species.

A computer program for the prediction of ¹³C NMR chemical shifts of saturated aldehydes and ketones is developed. The topological, geological, and electronic descriptors are generated. The variable selection by using leaps-and-bounds regression is performed. The regression coefficient R is 0.975, and the RMS of cross-validation is 1.27.

Three protopanaxodiol monodesmosides isolated from mild acid hydrolysis products of root saponins of Panax notoginseng were identified as ginsenoside-Rg5, 20(R)-ginsenoside-Rg3 and 20(S)-ginsenoside-Rg3. The complete assignments of ¹H and ¹³C NMR chemical shifts of these glycosides were obtained by means of 2D NMR techniques, such as ¹H-¹H COSY, TOCSY, ROESY, HMBC as well as HMQC. The differences of chemical shifts of 20(R)-and 20(S)-isomer were discussed.

Systematic studies were made on carbon-13 nuclear magnetic resonance (¹³C NMR) and its regularity of chemical shift sum (CSS). In this paper, a novel integer molecular graph-theoretical invariant, called M-index, was developed and found to be excellently correlated with ¹³C NMR CSS of alkanes with good results through cross validation (CV) of the leave one out (LOO) procedure:CSS=14.329^* M-21.089; n=65,R=0.991,SD=7.684,F=3648.021, U=215381.656, Q=3719.563; CV:R=0.990, R²(01)=0.981, SD(01)=8.086, F(01)=3288.113, U(01)=214982.172, Q(01)=4119.042.

According to the WBR theory and by means of the "Promoted matrix computation method", the authors computed and studied the relaxation equations of strong coupling system, especially the effect of J coupling on transverse relaxation, longitudinal relaxation and cross relaxation. Finally the authors gained the following valuable conclusions. (1) The effect of weak coupling on the computation of relaxation is very small and neglectable. (2) The strong coupling has hardly any effect on the computation of transverse relaxation. (3) The strong coupling has a certain extern effect on the computation of longitudinal relaxation and cross relaxation, especially this effect achieves maximum when the match condition ω_a-ω_b≈2πJ comes into existence and can't be neglected.

Frequency synthesizer is an important part in Nuclear Magnetic Resonance (NMR). With rapid development of micro-electronics technology, Direct Digital Synthesizer (DDS) becomes possible. Application of DDS to NMR spectroscopy has been successful, but it is generally limited to low frequency range. In order to solve the difficulty, we studied and designed a frequency synthesizer, which involves multiple DDS chips running in parallel.

The results of ²⁷Al NMR investigation of structure and composition of Citrate complex of Aluminium by computer non-linear fit of pH dependence are reported here. ²⁷Al NMR study of copolymer of HPAM and AlCit at different concentration ratios of HPAM and AlCit shows that HPAM as ligand first attack aluminum coordinated with water. It can be deduced that there are three phases in the mixed solution of copolymer of HPAM and AlCit based on the study of spin-lattice relaxation time of linked polymer at different total concentrations of mixed solution.

The molecular configuration and motion behaviour of polyethylene glycol (PEG) at Al₂O₃/water interface were investigated by using the electron spin resonance (ESR) technique, coupled with spin label technique. The adsorption isotherms of PEG on the Al₂O₃ surface were of S type and the amount of adsorption decreased with the increas of molecular weight. The adsorption of PEG on the Al₂O₃ surface was of the multipoint adsorption, where most segments of PEG were bound to the surface and a few residual segments were dangling in the solution.

¹³C NMR spectra of 7 new kinds of α-naphthaleneacetic aryl esters are reported in this paper. They will have potential application value used as plant growth regulators, antitumor medicine or chemical picking agent for fruits. The chemical shifts of all ¹³C NMR peaks have been assigned. The effects of structure on the chemical shifts were discussed.

Safety of MRI for both patients and employees is reviewed. The safety concerns and considerations of exposure to static magnetic fields, radio-frequency fields, switching magnetic field gradients, acoustic noise and image enhanced contrast agents are described. In the absence of ferromagnetic foreign bodies, there is no replicated scientific study showing a health hazard associated with static magnetic field exposure and no evidence for hazards associated with cumulative exposure to the field. In magnetic resonance, time-varying gradient magnetic fields (dB/dt) may stimulate nerves or muscles by inducing electric fields in patients. For gradient ramp duration of less than a few milliseconds, mean peripheral nerve stimulation is a safe indicator of high dB/dt. During an MR procedure, most of the transmitted RF power is transformed into heat within the patient's tissue as a result of resistive losses, and the primary bioeffects associated with the RF radiation are directly related to the thermogenic qualities of this electromagnetic field. During the operation of MR systems, various types of acoustic noise produced, and they may produce substantial hearing problems in patients. The simplest and least expensive means of preventing problems associated with acoustic noise is to encourage the routine use of earplugs. The total incidence of adverse reactions of Gadolinium-based MR imaging contrast agents ranges from approximately 2% to 4%, cautions should be taken during MRI measurement.