Multivariate statistical methods are frequently used in nuclear magnetic resonance (NMR)-based metabonomic researches to analyze NMR spectra of biofluids. Based on the fact that the NMR spectrum of a given sample are a sum of the NMR signals from all constituting ingredients, we developed a nonnegative matrix factorization (NMF) method, capable of finding parts-based and linear representations of non-negative data, for analyzing the data acquired in NMR-based metabonomic studies. Detail comparisons were made between the NMF method and the commonly use principal component analysis (PCA) method by employing the two methods to discriminate the urine and serum spectra of type-2 diabetic patients from those of the healthy controls. It was shown that, compared to the PCA method, the NMF method is a more effective and accurate method for processing NMR spectra acquired in the metabonomic studies, partially due to its unique features such as the non-negative constraints and part-based representation. The disadvantages of the PCA method were also analyzed and discussed.

In this paper, a comprehensive simulation of the vector field imaging based on the inter-molecular multiple quantum coherences (iMQC) was performed. The results showed that this imaging technique can be applied to image heterogeneities on the scale of dozens of micrometers, with adequate suppression of the signals from homogeneous medium. It was shown that imaging of field heterogeneities can also be achieved through phase cycling even without correlation gradients. These results would be of great help in extending the applications of iMQC imaging and in further understanding the mechanism underlying iMQC imaging.

Great progresses have been made in the past decades in understanding intra- and inter-molecular multiple-quantum coherences (MQCs) and developing their applications in nuclear magnetic resonance. To develop further applications for MQCs, it is useful to understand their physical bases and ways of practical implementation. In this review, the principles of dipolar coupling are described firstly. Comprehensive descriptions of MQCs based on intra- and inter-molecular dipolar coupling are then summarized, respectively. Finally, the applications of intra- and inter-molecular MQCs in chemistry and biomedicine are presented.

Noninvasive visualization of in vivo delivery of liver specific non-ionic polymeric contrast agent in mice was studied with a 1.5 T clinical MRI scanner. Abdominal MR images were acquired immediately, 6, 12, 24, and 168 h (7 day) after injection of the contrast agents with a 3-inch diameter single-loop surface coil. Intensity non-uniformity correction and signal instability correction were performed before data analysis. The results showed that these corrections increased the data reliability and MRI was an effective method for noninvasive visualization of in vivo delivery of paramagnetically labeled polymer conjugates.

Arbitrary Waveform Generator (AWG) plays an important role in general purpose signal generators. It is widely used in physics, electronics and computer area. In this paper, a non-PC dependent AWG designed specifically for use in low-field MRI is proposed. The performance of the AWG is tested with MRI experiment. Potential problems in the current design are discussed.

A design of a gradient waveform generator with self-triggering function for magnetic resonance imaging (MRI) is proposed. In the present design, a high precision DAC (24-bit) chip having a relatively large group delay is used. With this design and the proposed self-triggering technique, the group delay of gradient waveforms can be eliminated. As a result, high precision DAC can be applied to MRI scanner.

Phase coherence between RF transmitter and receiver in digital MRI spectrometer was studied. In order to keep phase coherence between the transmitter and the receiver, we implemented a method in which the frequencies of the transmitter and the receiver were switched simultaneously during pulse sequence execution, and reset to their original values, respectively, at the end of sequence. The experimental results showed that this method is suitable for digital spectrometer and independent on the structure of transmitter and receiver.

A Fourier Transformation (FT)-based method for measuring the RF-field distribution was proposed. This method can be easily implemented to estimate the quality of RF coils and the results obtained are not related to the inhomogeneity of the samples. Compared to the commonly used fitting method, the FT method has two advantages. Firstly, it does not require setting initial values for computation. Secondly, the proposed method is capable of detecting inslice RF field inhomogeneity of a single pixel or a small domain.

A software system is developed for use in low-field medical MRI systems. In this paper, the data acquisition and processing systems in the software are introduced. The software allows scan schemes that could meet the requirements of almost all commonly-used MRI experiment. The prescan customizing method could control all kinds of scan schemes. The software is spectrometer-independent so that it can be implemented conveniently in different types of spectrometers. We implemented this software system in a Dispect spectrometer and the experimental results acquired on a 0.35 T system are presented.

A new image enhancement algorithm combining wavelet domain and image domain processing was proposed. Dual-tree complex wavelet transform (DTCWT) was used in the wavelet transform due to its good directional selectivity. To enhance the images, high frequency wavelet coefficients were firstly modified to enhance the local contrast and the details of image. The overall contrast of the image was then adjusted with non-linear transforms in the image domain. The algorithm allows automatic selection of processing parameters according to the characteristics of the raw images. Compared with results reported previously, images processed by this algorithm achieved better results both visually and statistically.

An allyl poly (ethylene oxide) (PEO) grafted multi-walled carbon nanotubes (MWNT) was synthesized. The packing structure of MWNT-PEO was studied by solid state ¹³C NMR and TEM. The NMR results showed that the ¹³C NMR signals of MWNT are observable, and that the PEO chains grafted on the MWNT are amorphous. This demonstrated that there exist n-π interactions between the n orbitals of the PEO ether oxygen and the π system of MWNT.

NRG is a specific peptide with targeting binding affinity to tumor blood vessel. In this study, tumor-targeting functional peptides were constructed by connecting NGR peptide with functional peptides. To study the interaction between the constructed peptides with human breast cancer cell, binding epitope and affinity were measured with NMR spectroscopy. The spectroscopic and relaxation data showed that these peptides can bind to human breast cancer cell with high affinity.

We applied nuclear magnetic resonance spectroscopy（NMR）to study pancreatic juice (PJ) taken from patients with chronic pancreatitis (CP) and pancreatic cancer. The aim of the study is to assign the main resonances in the ¹H NMR spectra of PJ and to discover the characteristic metabolites the changes of which can be used to differentiate CP from pancreatic cancer. 1D proton spectroscopy, 2D TOCSY and J-resolved spectra (JRES) were performed to assign the main resonances. We found a triplet at δ1.19 that only appeared in the spectra of PJ from the CP patients, but not in the spectra of PJ from the pancreatic cancer patients. The triplet was assigned to be the resonance of ethoxyl, which might be associated with the metabolism of alcohol in pancreas.

In this article, the phase transition of polymer PNIPAAM in water/methanol mixtures was studied by nuclear magnetic resonance (NMR) spectroscopy. It was found that ¹H NMR spectrum, relaxation time and diffusion coefficient of PNIPAAM changed dramatically when phase transition occurred at ~6 mol % methanol and reentrant transition occurred at ~36 mol % methanol. These results indicate that NMR spectroscopy can be used to characterize phase transition of PNIPAAM in water/methanol mixture sensitively.

Principles of synchronous phase detecting and digital servo for rubidium atomic frequency standards (RAFS) were discussed. A digital servo system for rubidium frequency standards was designed with microcontroller unit, ADC and DAC. Frequency locking of a RAFS using the servo system was realized. The resulting frequency stability reached the level of common commercial RAFS.

In this contribution, trimethylphosphine oxide (TMPO), pyridine and trimethylphosphine (TMP) were selected as NMR probe molecules to study the acid strength of several industrially used zeolites (H-Y, H-ZSM5 and H-MOR) theoretically. The relationship between chemical shifts of these probe molecules and acid strength of zeolites was revealed. In the meanwhile, the applicability of probe molecules on the characterization of Bronsted acidity was discussed. Since the ¹H, ¹⁵N and ³¹P chemical shift ranges of adsorbed D5-pyridine and TMP on the Bronsted acid sites in zeolites were relatively very smaller (i.e., δ 18.2 ~ 18.7,  δ  -191.0~-186.9, δ  -8.7~-3.5 for ¹H, ¹⁵N and ³¹P, respectively), they were only used to detect the existence of acidic protons in the zeolites. However, the ³¹P chemical shift range of adsorbed TMPO ranges from δ 62.8 to δ 90.5, and it may be expected that the adsorbed TMPO were very sensitive to measure solid acid strengths of the zeolites catalysts, compared with the ³¹P NMR of adsorbed TMPO.

Providing spectral resolution comparable to those of high resolution spectroscopy on tissue extracts, high resolution magic angle spinning (HR-MAS) NMR spectroscopy on intact tissue has been used widely in NMR-based metabonomic studies. In order to prevent enzymatic degradation and/or diffusion of metabolites, the HR-MAS NMR experiments are often performed at low temperature with a short acquisition time. Statistical total correlation spectroscopy (STOCSY) is a novel tool developed previously for NMR-based metabonomic studies. It takes advantage of the multicollinearity of the intensity variables in a set of ¹H NMR spectra to generate a pseudo-two-dimensional NMR spectrum, without needing extra acquisition time. In this paper, STOCSY was used to analyze HR-MAS ¹H spectra of rat kidney tissue. Pseudo 2D spectra were generated from a set of 1D HR-MAS NMR spectra and used to observe intramolecular correlations among the resonances. The STOCSY results are helpful in peak assignment.

Starting from the structures of Mavromoustakos´ molecular dynamics and Monte Carlo simulations, the equilibrium geometry structures and the vibrational frequencies of the SARTANS group AT1 antagonists V8, V12 and BZI8 were calculated at the B3LYP/6-31G(d) level, and the chemical shifts of the protons were calculated by B3LYP-GIAO method with the basis set of 6-311G(d, p). The computational results were found in reasonable agreement with the NMR experimental data of ROE and the ¹H spectrum. Few differences were found between the structures of Mavromoustakos´s and ours´. It is postulated that both the structures obtained are reasonable. With superimposition of the optimized structure, there is similarity in the biphenyl imidazole rings of the three molecules belonging to SARTANS group.

Bruker´s CryoProbes^TM show large improvement in terms of NMR detection sensitivity over the last few decades. This paper provides a detailed review on the technical innovation and applications of various Bruker CryoProbes^TM. The large increase of detection sensitivity of CryoProbes^TM enables experiments on samples with amounts that were considered too small just a few years ago to have reliable results. With the CryoProbes^TM, sample throughput can also be increased up to 16-fold. With the increasing variety of CryoProbe models, the applications of Cryoprobes^TM will expand further into other new fields.