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971.
目的建立高效液相色谱法测定宁神补心片中丹参的丹参酮ⅡA含量.方法利用Lichrospher5-C18色谱柱,流动相甲醇-水为73∶27,检测波长为270 nm,流速1.6 mL/min,柱温为30℃.结果进样量在0.208~1.664 μg范围内呈现良好的线性关系,回归方程为Y=2.735×107X 8.870×105,r=0.9996,平均回收率为98.54%,RSD=1.33%(n=5).结论该方法快速简便,准确可靠,灵敏度高,可用于宁神补心片的质量控制.  相似文献   
972.
This paper aims to investigate the fatigue cracking evolution of cold recycled asphalt mixtures with asphalt emulsion (CRME) under different curing times. The fatigue cracking model of CRME based on damage mechanics and fracture mechanics was analyzed according to the fatigue loading curve. Firstly, the fatigue cracking evolution of CRME was studied through an SCB strength test and SCB fatigue test. Then, the fatigue damage mechanics were used to establish a nonlinear fatigue cracking model, and the damage degree of CRME at the initial cracking point was determined. The Paris formula was used to characterize the law of fatigue crack propagation. Finally, the microstructure of CRME was observed by scanning electron microscopy (SEM) with the backscattering method. The results indicate that the initial cracking point appears at around 60% of the fatigue life according to the SCB fatigue test by means of image analysis. The damage variable was obtained through the cracking model, and the value of the damage variable was determined as 0.06–0.17 at the initial cracking point. In addition, the Paris formula showed that the crack growth of CRME can be reflected by the stress intensity factor and correlative parameters. Moreover, cement hydration products were mixed with the asphalt membrane to form a denser spatial structure during the curing process, which may provide higher fatigue performance of CRME. This research may provide a theoretical reference for studying the fatigue cracking behavior of CRME.  相似文献   
973.
To investigate the dynamic compressive properties of concrete after high temperature and rapid cooling, an experimental study was carried out by considering five temperatures and four strain rates. The coupling effect of high temperature and strain rate on concrete damage morphology and mechanical parameters was comparatively analyzed. The main conclusions are as follows: the compressive damage morphology of concrete is affected by strain rate development trends of significant variability under different temperature conditions. As the strain rate increases, the compressive stress and elastic modulus of concrete are gradually increased. As the temperature increases, the increase in compressive stress is gradually reduced by the strain rate. For the temperatures of 20 °C and 800 °C, the increase in compressive stress by the strain rate is 38.69% and 7.78%, respectively. Meanwhile, SEM and CT scanning technology were applied to examine the mechanism of the effect of high temperature and strain rate on the mechanical properties of concrete from the microscopic perspective, and the corresponding constitutive model was proposed.  相似文献   
974.
The durability of reinforced concrete (RC) beams strengthened with carbon fiber-reinforced polymer (CFRP) is a worldwide concern in structural engineering. As an important part of the strengthened beam, the performance of the CFRP–concrete interface under hygrothermal environments is a delicate problem. In this paper, the fatigue behavior of CFRP-strengthened RC beams is analyzed by a theoretical model. In the model, CFRP–concrete interface degradation under hygrothermal environments is involved. Since interface debonding and rebar fracture induced by intermediate cracking are two typical failure modes, the damage models of rebar and the CFRP–concrete interface are established. Based on the theoretical model, the failure mode of CFRP-strengthened RC beams can be predicted, and fatigue life can be determined. The results showed that IC debonding is more likely to occur under hygrothermal environments. The accurate prediction of failure modes is essential for fatigue life prediction.  相似文献   
975.
Soft tissue sealing around zirconia (ZrO2) abutment is critical for the long-term stability of dental implants. The goal of the study is to develop a strong basal lamina (BL)-mediated epithelial attachment to ZrO2 via a novel physicochemical immobilization method. An electrophoretic fusion (EPF) method was applied to fuse a phosphonic acid (PA) linker to ZrO2 discs. Bindings of the PA linker and the following protease activated receptor 4 (PAR4) were verified by Fourier-transform infrared spectroscopy (FITR). Then, ZrO2 discs were doped in platelet-rich plasma (PRP). Platelet-derived growth factor (PDGF) was measured to assess platelet activation. PRP-doped discs were subsequently co-cultured with human gingival epithelial cells (OBA9) to evaluate establishment of basal lamina-mediated epithelial attachment. The EPF method achieved robust immobilization of the PA linker and PAR4 onto the ZrO2 surface. The resultant PAR4-coupled ZrO2 successfully induced platelet aggregation and activation. Furthermore, a BL-mediated epithelial attachment was established. The results are significant for clinical application to minimize the risk of developing peri-implant diseases.  相似文献   
976.
Based on the theory of magnetoacoustic coupled dynamics, the purpose of this paper is to evaluate the dynamic stress concentration near an elliptical opening in exponential-gradient piezomagnetic materials under the action of antiplane shear waves. By the wave function expansion, the solutions for the acoustic wave fields and magnetic fields can be obtained. Stress analysis is performed by the complex function method and the conformal mapping method, which are used to solve the boundary conditions problem, and is used to express the dynamic stress concentration coefficient (DSCC) theoretically. As cases, numerical results of DSCCs are plotted and discussed with different incident wave numbers and material parameters by numerical simulation. Compared with circular openings, elliptical openings are widely used in material processing techniques and are more difficult to solve. Numerical results show that the dynamic stress concentration coefficient at the elliptical opening is strongly dependent on various parameters, which indicates that the elliptical opening is more likely to cause crack and damage to exponential-gradient piezomagnetic materials.  相似文献   
977.
The polymer water-lubricated bearing is widely used in marine transmission systems, and the tribological properties can be improved by addition of inorganic nano-fillers. The aim of this study is to investigate the effect of SCFs and temperature on the water-lubricating properties of high-density polyethylene (HDPE) composites. HDPE composites reinforced by varying content of short carbon fibers (SCFs) were fabricated via twin-screw extrusion and injection molding techniques to study the hardness and surface wettability of those composites. The tribological properties under water-lubricated conditions were investigated through a pin-on-disk reciprocating tribometer under different temperatures. The results showed that the increase in hardness of HDPE composites reached maximum to 42.9% after adding 25 wt % SCFs. The contact angle also increased with the increase in SCFs content and reached a maximum of 95.2° as the amount of SCFs increased to 20 wt %. The incorporation of SCFs increased the wear resistance and lubricating property of HDPE composites at different temperatures. The HDPE composite containing 20 wt % SCFs showed the lowest friction coefficient of 0.076 at 40 °C, and the wear track depth reached a maximum of 36.3 mm at 60 °C. Based on the surface wetting property and wear analysis, potential effect mechanisms of fillers and temperature were discussed. The knowledge from this study is useful for designing the anti-wear water-lubricated polymer bearing.  相似文献   
978.
In this paper, eight variables of cement, blast furnace slag, fly ash, water, superplasticizer, coarse aggregate, fine aggregate and flow are used as network input and slump is used as network output to construct a back-propagation (BP) neural network. On this basis, the learning rate, momentum factor, number of hidden nodes and number of iterations are used as hyperparameters to construct 2-layer and 3-layer neural networks respectively. Finally, the response surface method (RSM) is used to optimize the parameters of the network model obtained previously. The results show that the network model with parameters obtained by the response surface method (RSM) has a better coefficient of determination for the test set than the model before optimization, and the optimized model has higher prediction accuracy. At the same time, the model is used to evaluate the influencing factors of each variable on slump. The results show that flow, water, coarse aggregate and fine aggregate are the four main influencing factors, and the maximum influencing factor of flow is 0.875. This also provides a new idea for quickly and effectively adjusting the parameters of the neural network model to improve the prediction accuracy of concrete slump.  相似文献   
979.
BackgroundTo assess the temporal changes in the characteristics of ischemic stroke drug clinical trials conducted in mainland China in 2005–2021.MethodsA statistical analysis of registered clinical trials on ischemic stroke was performed using the platform of the Center for Drug Evaluation of China National Medical Products Administration, the Chinese Clinical Trial Registry, and ClinicalTrials.gov websites.ResultsFrom January 1, 2005 to August 1, 2021, a total of 384 registered drug clinical trials on ischemic stroke were identified in mainland China. Over time, the number of trials gradually increased each year, with a significant growth in 2014, from 16 in 2013 to 42 in 2014. Phase IV trials (31.8%) accounted for the majority, followed by phase II (16.4%), phase I (10.9%), and phase III (8.6%). In terms of sponsorship, the proportion of investigator‐initiated trials (IITs) (60.7%) was higher than industry‐sponsored trials (ISTs) (39.3%). Additionally, trials involving traditional Chinese medicines (TCMs) (36.2%) accounted for the largest proportion, followed by trials involving antithrombotic therapy (19.5%) and cerebral protection agents (16.7%). Furthermore, over the past 17 years, the number of leading drug clinical trial units for ischemic stroke in mainland China has continuously increased. The leading principal units from Beijing, Shanghai, Guangdong, Jiangsu, and Liaoning accounted for the majority of the trials (67.4%).ConclusionIn the past 17 years, great progress has been made in the research and development (R&D) of drugs and clinical trials for ischemic stroke in mainland China. The most extensive progress was observed in TCMs, antithrombotic therapy, and cerebral protection agents. More clinical trials are needed to confirm whether the newly developed drugs can improve the clinical efficacy of ischemic stroke. Simultaneously, more pharmaceutical R&D efforts of innovative drugs are warranted.  相似文献   
980.
Rationale:Angle closure glaucoma (ACG) is one of the most emergent types of glaucoma in clinical practice. Laser peripheral iridotomy (LPI) could minimize pupillary block and prevent ACG from an acute attack. However, recurrent increase in intraocular pressure (IOP) may still occur despite successful LPI. The aim of this study is to highlight the importance of postLPI pilocarpine use and larger LPI size as well as to share some experiences of cataract surgery in patients with ACG.Patient concerns:A 63-year-old female was referred to our hospital for headache, and poor control of IOP in the right eye for 3 hours.Diagnoses:The patient was diagnosed ACG in the right eye. Recurrence of ACG in the right eye and new-onset and recurrent ACG in the left eye were noted during follow-up, despite successful LPI. The diagnosis was confirmed through slit lamp and gonioscope examination.Interventions:The LPI size was enlarged and pilocarpine use was maintained at 2% (1 drop 4 times a day) in both the eyes. Finally, cataract surgery was performed in both the eyes.Outcomes:No recurrence of ACG was noted during postLPI pilocarpine use in both the eyes. The postoperative IOP was stable for >6 months after cataract surgery without any surgical intervention or antiglaucoma medication use. No discomfort or major complication was observed.Conclusion:This report highlights the importance of postLPI pilocarpine use and larger LPI size in patients with refractory ACG.  相似文献   
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