基于扩增子测序分析益生菌牙膏中菌群多样性

通过常规方法检测益生菌牙膏中的活性菌,并采用高通量测序技术对20种市售益生菌牙膏16S rDNA的V3、V4区进行测序,扩增子测序分析不同牙膏中的菌群结构并进行α多样性分析,最后基于特异性引物,使用PCR方法检测20种牙膏中副干酪乳杆菌成分。结果表明:1)20种益生菌牙膏菌落总数均<10 CFU/g,乳酸菌总数均<10 CFU/g;2)通过扩增子测序结果分析,牙膏中还添加了干酪乳杆菌以外的乳酸菌,有18种牙膏中添加了发酵乳杆菌、嗜酸乳酸杆菌和德氏乳杆菌亚种,20种牙膏中添加了植物乳杆菌,19种牙膏中添加了罗伊氏乳杆菌。高通量测序对原核微生物的α多样性分析,表明牙膏中原核微生物丰度和菌落多样性较高;3)牙膏DNA提取物通过PCR及测序,结果表明20种牙膏均按标签标识添加了副干酪乳杆菌。

分析化学实验多元化教学模式改革与实践

创新实验教学模式是解决当前高校理工科类实验教学困境的重要途径。总结分析化学实验教学面临的难题,依托基础性、设计型和科研型实验为教学内容,建立以微视频在线课前预习、翻转课堂的课中学习和软件联用处理实验结果的新型实验教学方法。这种多元化教学模式能有效提高学生的学习主动性和创新能力。以基础性实验和研究型实验为案例,阐述多元化教学模式的具体应用,为理工科类实验教学改革提供研究依据。

Regioselective electrochemical radical cascade cyclization of internal alkynes to selenated and trifluoromethylated dihydropyran

Dihydropyran(DHP)compounds are not only found in natural products and bioactive molecules,but also serve as important precursors in organic synthesis.Nonetheless,traditional methods for the construction of such compounds are usually limited to disubstituted DHPs.To address this synthetic challenge,reported here is an efficient electrochemical strategy toward the selenated and trifluoromethylated DHP compounds.The reaction proceeded smoothly under mild electrolysis conditions.The broad substrate scope(>50 examples)and scalable synthesis demonstrated the complexity-building potential of the strategy.Initial mechanistic studies reveal that cyclization may involve a radical process.This protocol may promote the further development of diversified synthesis of multi-substituted dihydropyran.

Symptom network topological features predict the effectiveness of herbal treatment for pediatric cough

Pediatric cough is a heterogeneous condition in terms of symptoms and the underlying disease mechanisms.Symptom phenotypes hold complicated interactions between each other to form an intricate network structure.This study aims to investigate whether the network structure of pediatric cough symptoms is associated with the prognosis and outcome of patients.A total of 384 cases were derived from the electronic medical records of a highly experienced traditional Chinese medicine (TCM) physician.The data were divided into two groups according to the therapeutic effect,namely,an invalid group (group A with 40 cases of poor efficacy) and a valid group (group B with 344 cases of good efficacy).Several well-established analysis methods,namely,statistical test,correlation analysis,and complex network analysis,were used to analyze the data.This study reports that symptom networks of patients with pediatric cough are related to the effectiveness of treatment: a dense network of symptoms is associated with great difficulty in treatment.Interventions with the most different symptoms in the symptom network may have improved therapeutic effects.

Effects of different continuous fertilizer managements on soil total nitrogen stocks in China: A meta-analysis

Soil total nitrogen is critical for crop productivity and related to agricultural managements. However, the effects of different fertilizer applications on soil total nitrogen storage are not well understood. To quantify soil total nitrogen storage under different fertilizer management practices and explore the effects of climate, soil texture, experimental duration, and cropping system on soil total nitrogen storage in China, we conducted a meta-analysis of 67 fertilizer management strategies from experiments conducted over a period of at least three years. This meta-analysis included 854 observations of changes in soil total nitrogen stock(TNS) under no fertilizer application(control, CK), chemical fertilization with nitrogen, phosphorus, and potassium(CF), CF plus straw retention(CFS), and CF plus manure addition(CFM) relative to initial soil TNS. The CFM and CFS treatments increased soil TNS, and the CFM treatments increased soil C/N ratio the most. The longer the experimental duration, the greater the increase in soil TNS in the CF, CFS, and CFM treatments.Soil texture and crop type significantly affected the changes in soil TNS. The experimental duration, initial soil TNS, soil C/N ratio, and cropping system had significant linear correlations with the change in soil TNS. Temperature and precipitation were not correlated with soil TNS. Results of random forest modeling indicated that the most important factor affecting changes in soil TNS was experimental duration(positive correlation), followed by initial soil TNS(negative correlation). The CFM treatments had the largest increase in soil TNS under various conditions. We recommend promoting CFM to improve soil fertility in farmlands globally.

Effects of Ag Addition on Precipitation and Fatigue Crack Propagation Behavior of a Medium-Strength Al–Zn–Mg Alloy

Effects of trace addition of Ag on the fatigue crack propagation behavior and microstructure of a mediumstrength aged AI-Zn-Mg alloy were investigated in the present work. The results show that a combination of enhanced tensile strength and improved fatigue crack propagation resistance in Al-Zn-Mg alloys is achieved with small addition of Ag. The enhanced strength is attributed to the high density of η＇ precip- itates within the grains and narrow precipitate free zones in the vicinity of grain boundaries. The main contribution to the improvement of fatigue crack propagation resistance comes from the coarser precipitates within the grains. When subjected to two-step aging. Ag-added alloy shows larger semi-coherent matrix precipitates. These relatively coarser precipitates increase the homogeneity of deformation and therefore improve the fatigue crack propagation resistance. In addition, microstructure analysis indicates that the size and distribution of inclusions as well as the grain structures of Al-Zn-Mg alloys are independent of Ag addition.

Mechanical Design with Experimental Verification of a Lightweight Exoskeleton Chair

In this study,a human-chair model was developed as the basis for a wearable-chair design.A prototype chair,HUST-EC,based on the model was fabricated and evaluated.Employing the optimization under the golden divisional method,an optimized simulation of the operating mode with the lowest chair height was implemented.A novel multi-link support structure has been established with parameters optimized using Matlab software.The stress analysis of the solid models was conducted to ensure the adequate support from the designed chair for the user.Ten subjects participated in the evaluation experiment,who performed both static tasks and dynamic tasks.The experimental results consisted of subjective evaluation and objective evaluation.The experimental data demonstrate that(1)the HUST-EC can effectively reduce the activation level of related muscles at a variety of tasks;(2)the plantar pressure was reduced by 54%–67%;(3)the angle between the upper body and the vertical axis was reduced by 59%–77%;(4)the subjective scores for chair comfortability,portability,and stability were all higher than 7.The results further revealed that the designed chair can reduce the musculoskeletal burden and may improve work efficiency.