Three compounds of novel pyrazolo[3,4-d]pyrimidin-4-one derivatives (A~C) were synthesized through a multi-step reaction using ethyl-2-cyano-3-ethoxyacrylate and 3,4-dimethylphenylhydrazine. The structures of these compounds were identified by nuclear magnetic resonance (NMR, i.e., ¹H NMR, ¹³C NMR), and liquid chromatography-mass spectrum (LC-MS), and the ¹H NMR signals of each compound were fully assigned. The in vivo analgesic activity of synthesized compound A was preliminarily evaluated through mass spectrometry brain imaging and formalin induced pain model in mice. The imaging data and results showed that compound A could cross the blood-brain barrier and penetrate into the brain of mice, and produce a dose-dependent analgesic activity. This study provided a piece of fundamental research data on structural and in vivo activity for developing anti-pain drugs based on pyrazolo[3,4-d]pyrimidin-4-one scaffold.

In this paper, ²H nuclear magnetic resonance (NMR) was performed to study the motions of the embedded cations in the cation-doped lead bromide perovskite (MA_0.6DMA_0.4PbBr₃). By selectively deuterating dimethylamine (DMA) and methylammonium (MA) cations, we achieved selective NMR observations of the different embedded cations in the materials. The results show that at low temperatures, both the DMA and MA cations in the material have molecular motions close to the double rotation model. As the temperature increases, the motion freedom of the DMA and MA cations increases, and the motions gradually transform into fast isotropic motions. It was observed that the DMA cations have higher mobility than the MA cations in the same materials at the same temperature, indicating that there is a significant inhomogeneity in the states of cations in the material. Based on the study of the cation motions, the molecular mechanism of the phase transition of the material was discussed.

Cytochrome c (cyt c) is an important multifunctional protein. In mitochondria, it acts as a carrier for electron transporting. In cytoplasm, it may act as an apoptotic initiator to initiate the apoptotic process. Whether and how a complex cytoplasmic environment affects its conformation has not been confirmed yet. In this study, the conformational changes of wild type saccharomyces cerevisiae iso-1 cyt c in yeast cell homogenate were tracked by methyl-based nuclear magnetic resonance (NMR) technique. At least four different oxidative conformations and one reduced conformation of cyt c were identified in cell homogenate. And over time, the transitions among different conformations of cyt c were observed. The results indicate that the conformation of cyt c changes with environment, which may be closely related to resistance to oxidative stress.

Parahydrogen-induced polarization (PHIP) technique can greatly enhance the sensitivity of nuclear magnetic resonance (NMR) signals, and has been applied in the fields of magnetic resonance imaging, in situ chemical reaction monitoring, etc. In addition to improving the sensitivity of different molecules in the PHIP, it is also crucial to extend and preserve the high polarization state. To achieve this, a possible approach is to transfer the polarized state into a nuclear spin singlet state. Here, we focus on the singlet states preparation in hexene molecule that can be polarized by PHIP. By designing optimal control pulses, a five-spin system in hexene molecule was manipulated, and various quantum states were prepared respectively. Our results show that three different nuclear spin singlet states could be prepared with the group CH₂=CH- in hexene. The three different nuclear spin singlet states have longer lifetime than that of the initial state polarized by PHIP, and thus can be utilized as the intermediate states to delay the decay of the polarization state. By comparing the lifetime of the singlet state with the longitudinal relaxation time of the corresponding spin, it is deduced that converting the state of the polarized hexene to longitudinal magnetization may also be an effective way to preserve the polarizability.

Multi-channel magnetic resonance imaging methods utilize multiple receiving coils to simultaneously under-sample k-space for fast magnetic resonance imaging. Post-processing algorithms were often used to restore the missing information for under-sampled images. However, the quality of reconstructed images is far from satisfying, especially at higher acceleration factor. In this backdrop, a fast multi-channel magnetic resonance imaging method based on parallel complex asymmetric U-Net (PCAU-Net) was proposed, which extends single-channel real-valued U-shaped convolutional neural network to multi-channel complex convolutional neural network. A U-shaped network with an asymmetric structure was designed to reduce the model complexity by reducing the network size in decoding. A 1×1 convolution block was added before skip-connection for PCAU-Net to share cross-channel information. The residual connection between the input and output of the network facilitates loss backpropagation. The experimental results show that by using regular and random sampling templates, the proposed PCAU-Net method can reconstruct the complex magnetic resonance images with high quality compared with the conventional generalized auto-calibrating partially parallel acquisitions (GRAPPA) reconstruction algorithm and iterative self-consistent parallel imaging reconstruction (SPIRiT) algorithm at different acceleration factors. Moreover, compared with the parallel complex U-Net (PCU-Net) method, PCAU-Net reduces model parameters and shortens the training time.

The classification of the breast imaging-reporting and data system (BI-RADS) based on magnetic resonance imaging (MRI) refers to the classification of the degree of lesions according to the image signs of lesions, which is usually subjective. Moreover, the benign and malignant lesions of BI-RADS 3-5 are overlapping, which is prone to unnecessary invasive treatment due to high diagnostic categories in clinical diagnosis. To address these problems, this research applied radiomics for feature extraction and fusion of T₁-weighted (T1W) and dynamic contrast-enhanced (DEC) MRI. The least absolute shrinkage and selection operator (LASSO) algorithm was used to screen out the optimal feature collection of each type of MR image. Support vector machine (SVM), random forest (RF), K-nearest neighbour (KNN) and logistic regression (LR) algorithms were applied for BI-RADS 3-5 classification, based on which the benign and malignant lesions were further classified. The results showed that the classification accuracy of breast BI-RADS 3-5 by four radiomics models based on feature fusion was 81.25%, 87.50%, 78.38%, and 81.25%, respectively. Their accuracy in distinguishing the benign and malignant breast lesions was 90.91%, 93.55%, 92.73%, and 94.55%, respectively. This indicates that the combination of radiomics and machine learning correlation algorithm has a good effect on breast MRI BI-RADS classification and benign and malignant differentiation, and feature fusion can further improve the accuracy of classification prediction.

Accelerating the release of the antenna residual energy to weaken the antenna ringing signal is beneficial to shorten the echo time (TE) of low-field nuclear magnetic resonance (NMR) instruments, thus improving the measurement resolution and signal-to-noise ratio (SNR) of fast relaxation components. The antenna Q value has an opposite effect on the energy emission efficiency and discharge speed. For this reason, we first designed a new Q-switch circuit, which can greatly shorten the energy discharge time while ensuring the transmission efficiency. On this basis, an optimized pulse sequence was applied to overcome the defect that traditional phase alternated pair stacking (PAPs) cannot eliminate 90° pulse ringing, and the SNR was further improved by the method of phase cycling. Finally, the new Q-switch circuit was tested on a 2 MHz core analyzer, the Q value of the antenna was reduced to about 1/5 of the transmit period, and the antenna recovery time was reduced from 280.0 μs to 18.2 μs. Moreover, with the new Q-switch circuit and optimized pulse sequence, the T₂ signal of the fast relaxation component can be effectively obtained when TE=60 μs.

To ensure the safety and precision of surgery, the robotic system applied in magnetic resonance (MR) image-guided robot-assisted surgery should be MR-compatible. In terms of this issue, a MR compatibility analysis method for surgical robotic system based on image quality evaluation is proposed in this paper, and the image sets are extended. The image quality evaluation model is constructed by combining evaluation parameters such as signal-to-noise ratio of MR images, image change factor and MR image distortion. The model can analyze the effect of the robot component and robot motion on image quality, forming a basis for image quality evaluation. The experimental results show that the image quality evaluation method can fully analyze the MR compatibility of the robotic system component, and provide an evaluative method and theoretical basis for the MR compatibility analysis of other kinds of medical robotic systems.

In this paper, a microstrip resonator based on double split rings is used to build an electron spin resonance (ESR) measurement system. The resonator is optimized by the finite element electromagnetic simulation and the 3 dB bandwidth is 58.7 MHz. Due to the open structure of the resonator, large-size samples with high dielectric loss can be measured nondestructively. The ESR signal of 2,2-diphenyl-1-picrylhydrazyl (DPPH) powder with different quality is measured at room temperature, and the result indicated that the spin detection limit of this system can reach 9.66 \times10¹² spins/Gs Hz^1/2. It is demonstrated that the system can be used to characterize films deposited on different substrates such as silicon, glasses or ceramics regardless of its high frequency losses through the measurement of DPPH sample spin-coated on silicon and zerodur. Our system provides a convenient approach to research the defect of thin films and to characterize their performances within microwave frequency.

EasySpin is a popular software for simulating and fitting a wide range of electron paramagnetic resonance (EPR) spectra, and LabVIEW is a graphical programming language development environment. This paper introduces a graphical user interface (GUI) LV-EasySpin that is designed by using LabVIEW for EasySpin. LV-EasySpin provides an intuitive way to visually simulate and fit EPR multicomponent spectra. Through various examples, the design idea and implementation scheme of the GUI are illustrated in the paper. We hope this simple and easy-to-operate interface LV-EasySpin will reduce the difficulty for users analyzing EPR spectra.