Lost foam casting(LFC) process is a special casting method in which polymeric foam patterns with refractory coatings are utilized as a mould component. In this work, four types of foam: expandable polyethylene(EPE), e...Lost foam casting(LFC) process is a special casting method in which polymeric foam patterns with refractory coatings are utilized as a mould component. In this work, four types of foam: expandable polyethylene(EPE), expandable polypropylene(EPP) and expandable polystyrene(EPS) foams with two different densities were employed as pattern materials. LFC and conventional green sand mould casting methods were used to cast a low carbon steel, A216 Grade WCB. Both casting processes were carried out at 1,580 °C. Chemical analysis results showed that the carbon contamination level was high and was influenced by pattern type. Metallographic investigations revealed a significant increase in the percentage of pearlite phase in all LFC samples. Densities of manufactured samples were calculated in order to evaluate porosity of the products. It was determined that the densities of the LFC samples were lower than the green sand mould cast reference sample(RS). Vickers hardness tests were also carried out and increments in hardness values with increased carbon content was observed.展开更多
A method for classifying orbits near asteroids under a polyhedral gravitational field is presented, and may serve as a valuable reference for spacecraft orbit design for asteroid exploration. The orbital dynamics near...A method for classifying orbits near asteroids under a polyhedral gravitational field is presented, and may serve as a valuable reference for spacecraft orbit design for asteroid exploration. The orbital dynamics near aster- oids are very complex. According to the variation in orbit characteristics after being affected by gravitational perturbation during the periapsis passage, orbits near an as- teroid can be classified into 9 categories： （1） surrounding- to-surrounding, （2） surrounding-to-surface, （3） surrounding- to-infinity, （4） infinity-to-infinity, （5） infinity-to-surface, （6） infinity-to-surrounding, （7） surface-to-surface, （8） surface- to-surrounding, and （9） surface-to- infinity. Assume that the orbital elements are constant near the periapsis, the gravitation potential is expanded into a harmonic series. Then, the influence of the gravitational perturbation on the orbit is studied analytically. The styles of orbits are dependent on the argument of periapsis, the periapsis radius, and the periapsis velocity. Given the argument of periapsis, the orbital energy before and after perturbation can be derived according to the periapsis radius and the periapsis velocity. Simulations have been performed for orbits in the gravitational field of 216 Kleopatra. The numerical results are well consistent with analytic predictions.展开更多
This paper describes the research of rollovers of passenger cars and proposes a ramp type test as a typical dynamic rollover test with evaluations of occupant injuries and vehicle deformation in accordance with variou...This paper describes the research of rollovers of passenger cars and proposes a ramp type test as a typical dynamic rollover test with evaluations of occupant injuries and vehicle deformation in accordance with various parametric functions. Many types of rollover tests have been conducted in the past and they have their merits and demerits. However, the ramp rollover test has a characteristic to evaluate both dummy injuries and vehicle deformations, and to perform tests under many conditions by exchanging ramp dimensions, steer timings made rotation and velocity of the vehicle.展开更多
AIM:To study the potential value and specificity of plasma miR-216a as a marker for pancreatic injury.METHODS:Two rat models were applied in this article:L-arginine-induced acute pancreatitis was used as one model to ...AIM:To study the potential value and specificity of plasma miR-216a as a marker for pancreatic injury.METHODS:Two rat models were applied in this article:L-arginine-induced acute pancreatitis was used as one model to explore the potential value of plasma miR-216a for detection of pancreatic injury;nonlethal sepsis induced in rats by single puncture cecal ligation and puncture(CLP)was used as the other model to evaluate the specificity of plasma miR-216a compared with twocommonly used markers(amylase and lipase)for acute pancreatitis.Plasmas were sampled from rats at indicated time points and total RNA was isolated.Real-Time Quantitative reverse transcriptase-polymerase chain reaction was used to quantify miR-216a in plasmas.RESULTS:In the acute pancreatitis model,among five time points at which plasmas were sampled,miR-216a concentrations were significantly elevated 24 h after arginine administration and remained significantly increased until 48 h after operation(compared with 0 h time point,P<0.01,Kruskal-Wallis Test).In the CLP model,plasma amylase and lipase,two commonly used biomarkers for acute pancreatitis,were significantly elevated 24 h after operation(compared with 0 h time point,P<0.01 and 0.05 respectively,Pairwise Bonferroni corrected ttests),while miR-216a remained undetectable among four tested time points.CONCLUSION:Our article showed for the first time that plasma miR-216a might serve as a candidate marker of pancreatic injury with novel specificity.展开更多
[目的]探究微小RNA(microRNA,miR)-216a靶向调控酪氨酸蛋白激酶2/信号转导和转录激活因子3(Janus protein tyrosine protein kinase 2/signal transducer and activator of transcription 3,JAK2/STAT3)信号通路对鼻咽癌细胞增殖、侵袭...[目的]探究微小RNA(microRNA,miR)-216a靶向调控酪氨酸蛋白激酶2/信号转导和转录激活因子3(Janus protein tyrosine protein kinase 2/signal transducer and activator of transcription 3,JAK2/STAT3)信号通路对鼻咽癌细胞增殖、侵袭、自噬及血管生成的影响。[方法]Target Scan Human预测miR-216a与JAK2的结合位点,双荧光素酶实验验证miR-216a与JAK2是否结合;免疫组化染色检测正常鼻咽黏膜组织、鼻咽癌组织标本p-JAK2、p-STAT3的表达水平,并分析p-JAK2、p-STAT3表达水平与患者临床病理参数的关系。采用LipofectamineTM3000将miR-216a模拟物双链小RNA、阴性对照双链小RNA转染至CNE-2细胞构建过表达miR-216a细胞系,细胞分为对照组、miR-NC组、miR-216a组。将抑制剂双链小RNA,抑制剂对照双链小RNA转染至CNE-2细胞构建低表达miR-216a细胞系,细胞分为对照组、抑制miR-NC组、抑制miR-216a组。采用qRT-PCR检测细胞JAK2、STAT3 mRNA表达水平;MTT法、Transwell小室、皮下种植瘤模型、小管形成实验、吖啶橙染色分别检测细胞增殖、侵袭、移植瘤生长、血管形成和自噬泡形成的能力;Western blot检测JAK2、p-JAK2、STAT3、p-STAT3、微管相关蛋白轻链3-Ⅱ(microtubule-associated protein light chain 3-Ⅱ,CL3-Ⅱ)、酵母自噬相关基因6的哺乳动物同源体(autophagy related protein ATG6,Beclin1)、血管内皮生长因子(vascular endothelial growth factor,VEGF)的表达水平。[结果]双荧光素酶实验验证了miR-216a对JAK2的靶向调控作用。鼻咽癌组织p-JAK2、p-STAT3阳性表达率(75.0%,68.3%)明显高于正常鼻咽黏膜组织(10%,13.3%)(P<0.05)。p-JAK2、p-STAT3表达越高,浸润深度越严重,越容易发生淋巴结和远处转移(P均<0.05)。细胞实验显示:与miR-NC组相比,miR-216a组细胞24、48、72、96 h吸光度值(0.32±0.03 vs 0.15±0.04、0.58±0.07 vs 0.24±0.06、0.86±0.10 vs 0.41±0.06、1.48±0.11 vs 0.75±0.07)、细胞侵袭数目(101.00±11.00 vs 22.67±5.77)、血�展开更多
文摘Lost foam casting(LFC) process is a special casting method in which polymeric foam patterns with refractory coatings are utilized as a mould component. In this work, four types of foam: expandable polyethylene(EPE), expandable polypropylene(EPP) and expandable polystyrene(EPS) foams with two different densities were employed as pattern materials. LFC and conventional green sand mould casting methods were used to cast a low carbon steel, A216 Grade WCB. Both casting processes were carried out at 1,580 °C. Chemical analysis results showed that the carbon contamination level was high and was influenced by pattern type. Metallographic investigations revealed a significant increase in the percentage of pearlite phase in all LFC samples. Densities of manufactured samples were calculated in order to evaluate porosity of the products. It was determined that the densities of the LFC samples were lower than the green sand mould cast reference sample(RS). Vickers hardness tests were also carried out and increments in hardness values with increased carbon content was observed.
文摘A method for classifying orbits near asteroids under a polyhedral gravitational field is presented, and may serve as a valuable reference for spacecraft orbit design for asteroid exploration. The orbital dynamics near aster- oids are very complex. According to the variation in orbit characteristics after being affected by gravitational perturbation during the periapsis passage, orbits near an as- teroid can be classified into 9 categories： （1） surrounding- to-surrounding, （2） surrounding-to-surface, （3） surrounding- to-infinity, （4） infinity-to-infinity, （5） infinity-to-surface, （6） infinity-to-surrounding, （7） surface-to-surface, （8） surface- to-surrounding, and （9） surface-to- infinity. Assume that the orbital elements are constant near the periapsis, the gravitation potential is expanded into a harmonic series. Then, the influence of the gravitational perturbation on the orbit is studied analytically. The styles of orbits are dependent on the argument of periapsis, the periapsis radius, and the periapsis velocity. Given the argument of periapsis, the orbital energy before and after perturbation can be derived according to the periapsis radius and the periapsis velocity. Simulations have been performed for orbits in the gravitational field of 216 Kleopatra. The numerical results are well consistent with analytic predictions.
文摘This paper describes the research of rollovers of passenger cars and proposes a ramp type test as a typical dynamic rollover test with evaluations of occupant injuries and vehicle deformation in accordance with various parametric functions. Many types of rollover tests have been conducted in the past and they have their merits and demerits. However, the ramp rollover test has a characteristic to evaluate both dummy injuries and vehicle deformations, and to perform tests under many conditions by exchanging ramp dimensions, steer timings made rotation and velocity of the vehicle.
基金Supported by National Nature Science Foundation of China,No.30971344Innovative Fund for PhD granted by the Second Military Medical University
文摘AIM:To study the potential value and specificity of plasma miR-216a as a marker for pancreatic injury.METHODS:Two rat models were applied in this article:L-arginine-induced acute pancreatitis was used as one model to explore the potential value of plasma miR-216a for detection of pancreatic injury;nonlethal sepsis induced in rats by single puncture cecal ligation and puncture(CLP)was used as the other model to evaluate the specificity of plasma miR-216a compared with twocommonly used markers(amylase and lipase)for acute pancreatitis.Plasmas were sampled from rats at indicated time points and total RNA was isolated.Real-Time Quantitative reverse transcriptase-polymerase chain reaction was used to quantify miR-216a in plasmas.RESULTS:In the acute pancreatitis model,among five time points at which plasmas were sampled,miR-216a concentrations were significantly elevated 24 h after arginine administration and remained significantly increased until 48 h after operation(compared with 0 h time point,P<0.01,Kruskal-Wallis Test).In the CLP model,plasma amylase and lipase,two commonly used biomarkers for acute pancreatitis,were significantly elevated 24 h after operation(compared with 0 h time point,P<0.01 and 0.05 respectively,Pairwise Bonferroni corrected ttests),while miR-216a remained undetectable among four tested time points.CONCLUSION:Our article showed for the first time that plasma miR-216a might serve as a candidate marker of pancreatic injury with novel specificity.
文摘[目的]探究微小RNA(microRNA,miR)-216a靶向调控酪氨酸蛋白激酶2/信号转导和转录激活因子3(Janus protein tyrosine protein kinase 2/signal transducer and activator of transcription 3,JAK2/STAT3)信号通路对鼻咽癌细胞增殖、侵袭、自噬及血管生成的影响。[方法]Target Scan Human预测miR-216a与JAK2的结合位点,双荧光素酶实验验证miR-216a与JAK2是否结合;免疫组化染色检测正常鼻咽黏膜组织、鼻咽癌组织标本p-JAK2、p-STAT3的表达水平,并分析p-JAK2、p-STAT3表达水平与患者临床病理参数的关系。采用LipofectamineTM3000将miR-216a模拟物双链小RNA、阴性对照双链小RNA转染至CNE-2细胞构建过表达miR-216a细胞系,细胞分为对照组、miR-NC组、miR-216a组。将抑制剂双链小RNA,抑制剂对照双链小RNA转染至CNE-2细胞构建低表达miR-216a细胞系,细胞分为对照组、抑制miR-NC组、抑制miR-216a组。采用qRT-PCR检测细胞JAK2、STAT3 mRNA表达水平;MTT法、Transwell小室、皮下种植瘤模型、小管形成实验、吖啶橙染色分别检测细胞增殖、侵袭、移植瘤生长、血管形成和自噬泡形成的能力;Western blot检测JAK2、p-JAK2、STAT3、p-STAT3、微管相关蛋白轻链3-Ⅱ(microtubule-associated protein light chain 3-Ⅱ,CL3-Ⅱ)、酵母自噬相关基因6的哺乳动物同源体(autophagy related protein ATG6,Beclin1)、血管内皮生长因子(vascular endothelial growth factor,VEGF)的表达水平。[结果]双荧光素酶实验验证了miR-216a对JAK2的靶向调控作用。鼻咽癌组织p-JAK2、p-STAT3阳性表达率(75.0%,68.3%)明显高于正常鼻咽黏膜组织(10%,13.3%)(P<0.05)。p-JAK2、p-STAT3表达越高,浸润深度越严重,越容易发生淋巴结和远处转移(P均<0.05)。细胞实验显示:与miR-NC组相比,miR-216a组细胞24、48、72、96 h吸光度值(0.32±0.03 vs 0.15±0.04、0.58±0.07 vs 0.24±0.06、0.86±0.10 vs 0.41±0.06、1.48±0.11 vs 0.75±0.07)、细胞侵袭数目(101.00±11.00 vs 22.67±5.77)、血�
