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PurposeThe aim of this study was to identify the efficacy of diffusion kurtosis imaging (DKI) in tracking and monitoring the dynamic change of parotid glands (PGs), submandibular glands (SMGs), sublingual glands (SLGs), and acute xerostomia in nasopharyngeal carcinoma (NPC) patients treated with induction chemotherapy (IC) plus concurrent chemoradiotherapy (CCRT).MethodsThe prospective study recruited 42 participants treated with IC+CCRT. All patients underwent DKI scanning six times: before IC, before RT, in the middle of the RT course, immediately after RT, and 1 and 3 months post-RT. Mean diffusion coefficient (MD) and mean kurtosis (MK) of PG, SMG, SLG, saliva flow rate measured under resting (uSFR) and stimulated condition (sSFR), and xerostomia questionnaire (XQ) scores were recorded.ResultsAt each time point, sSFR was significantly higher than uSFR (p < 0.05 for all). MD of the salivary glands and XQ scores increased over time while MK, uSFR, and sSFR decreased. After IC, the significant differences were detected in MD and MK of bilateral SMG and MK of the left SLG (p < 0.05 for all), but not in MD and MK of PG, uSFR, sSFR, and XQ scores. After RT, sSFR at 1m-RT decreased significantly (p = 0.03) while no significant differences were detected in uSFR and XQ scores. Moderate-strong correlations were detected in ΔMD-PG-R%, ΔMK-PG-R%, ΔMD-PG-L%, ΔMK-PG-L%, ΔMD-SMG-R%, ΔMK-SMG-R%, ΔMD-SMG-L%, ΔMK-SMG-L%, and ΔMD-SLG-R%, with correlation coefficients (p < 0.05 for all) ranging from 0.401 to 0.714. ΔuSFR% was correlated with ΔMD-SMG% (p = 0.01, r = −0.39), ΔMD-SLG% (p < 0.001, r = −0.532), and ΔMK-SMG% (p < 0.001, r = −0.493). ΔsSFR% correlated with ΔMD-PG% (p = 0.001, r = −0.509), ΔMD-SMG% (p = 0.015, r = −0.221), and ΔMK-PG% (p < 0.001, r = 0.524). ΔXQ% was only correlated with ΔMK-PG% (p = 0.004, r = 0.433).ConclusionDKI is a promising tool for tracking and monitoring the acute damage of PG, SMG, and SLG induced by IC+CCRT in NPC patients.

Additional file 2. . The comparison of fMRI parameters between RG and NRG

Additional file 1. . MRI standard protocol

SCF N 2 may have good dielectric properties, so that it has drawn great attention from the scientists worldwide. In this paper, the rod-plate electrode model of 5mm gap with DC voltage was established, and the breakdown process of the SCF N 2 was studied under the SC condition with the fluid dynamics method according to the gas-dielectric discharge principle. The results show that the breakdown voltage increases with the increase of pressure and temperature of the SCF N 2 . However, the apparent saturation trend of the breakdown field is not observed. Under the supercritical condition T=127K and Pa=5MPa, the SCF N 2 breakdown strength can reach to 77.7% of that of SF 6 . Therefore, SCF N 2 is proved to be a promising dielectric medium for replacement SF 6 in the future.

Based on the theory of consumer behavior and consumer demand theory, for the consumer purchase behavior of green food in Harbin, theoretical model of the influence factors on the consumer purchase behavior of green food is constructed. The logistic regression analysis method is used, and the hypotheses are tested. The results show that lifestyle, purchase experience, health consciousness, income level, price, shopping convenience and reference group have a significant impact on the consumer purchase behavior of green food in Harbin. And price, health consciousness and income level are the major factors. However, because of the nutrition and climate environment, the two research variables did not pass the test of significance. Therefore, there is no significant correlation between the purchase behavior and the two factors.

The experimental observations indicate that streamers in short gap always exhibit irregularity and self-similarity, so the random fractal method can be applied to simulate this phenomenon. In this paper, a two dimensional stochastic streamer discharge process which combines the traditional streamer theory and fractal growth theory in non-uniform electric field under time domain is simulated to quantify the channel tortuosity of short SF6 gap. The box counting method is used to characterize the channel tortuosity and estimate the fractal dimensions of discharge channels. In addition, influences of both applied voltage and streamer channel conductivity of discharge channels are also analyzed.

In allusion to the deficiency of SF6 which is a widely used insulating medium in high voltage electric apparatus, it is necessary to search a alternative medium with excellent interrupting performance and harmless to the environment. Supercritical fluid (SCF) which is in the intermediate state of gas and liquid, with many unique physical and chemical properties combines the advantages of gas and liquid: high ability of mass transfer and high heat transfer. And SCF has high breakdown strength and fast dielectric recovery capability after breakdown, therefore, SCF has a high potential as an insulating medium. In this article, the molecular dynamics (MD) of supercritical nitrogen under different electric fields is researched by analyzing Radial Distribution Function (RDF) and Mean Square Displacement (MSD). The simulation results indicate that: the clusters of nitrogen molecule are reduced and the first neighbor structure of nitrogen is weakened by applying an electric field. Meanwhile, the molecular diffusion is influenced by the molecular polarization under electric field, and in the electric field of 103∼109 V/m, the nitrogen diffusion coefficient increases first and then decreases.

As an important component of the vessel's Dynamic Positioning (DP) System, thrust allocation determines the control input of each thruster device from the control law. Thrust allocation problems can be formulated as nonlinear optimization problems. A chaos Particle Swarm Optimization (PSO) algorithm combined with multi-agent scheme is proposed for the thrust allocation in this paper. The algorithm which uses multi-agent topological structure has three functions that keeps the diversity of the particle swarm population, improving particle swarm global search ability, and enhancing information diversity. Relying on chaotic local search to get rid of local optima, it can also improve the convergence precision. The numerical simulations are conducted to demonstrate the effectiveness of the proposed methods, and the results are compared with PSO algorithm.

This article explores the current situation of university students taking part time jobs as tutors in families. This is very popular in China, especially in cities and towns. After systematic investigations, the author suggests that the office of student affairs in Chinese universities should play a substantial role by providing opportunities for these students to become better tutors.