Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature dis...Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature distribution were discussed. The simulation results indicate that the system temperature distribution presents a roughly concentric shape, a steep temperature gradient is observed in diamond cutting tool, and the highest temperature is located in chip. Centrosymmetry parameter method was used to monitor defect structures. Dislocations and vacancies are the two principal types of defect structures. Residual defect structures impose a major change on the workpiece physical properties and machined surface quality. The defect structures in workpiece are temperature dependent. As the temperature increases, the dislocations are mainly mediated from the workpiece surface, while the others are dissociated into point defects. The relatively high cutting speed used in nanomachining results in less defect structures, beneficial to obtain highly machined surface quality.展开更多
采用mt DNA D-loop作为分子标记,对西藏的4个藏猪群体(林芝、山南、昌都和日喀则)遗传多样性进行了研究。结果表明,西藏藏猪mt DNA D-loop高变区A+T含量(62.90%)明显高于G+C含量(37.1%),富含A和T,存在碱基偏倚性。在长度为435 bp的序列...采用mt DNA D-loop作为分子标记,对西藏的4个藏猪群体(林芝、山南、昌都和日喀则)遗传多样性进行了研究。结果表明,西藏藏猪mt DNA D-loop高变区A+T含量(62.90%)明显高于G+C含量(37.1%),富含A和T,存在碱基偏倚性。在长度为435 bp的序列中,共检测到20个变异位点,界定了26个单倍型,单倍型多样度(Hd)为0.705±0.021,平均核苷酸差异数(k)为1.231,核苷酸多样度(Pi)为0.002 83。其中,Hd、k和Pi在昌都藏猪群体中最高,日喀则藏猪最低。此外,Hap1和Hap3单倍型是4个群体的共享单倍型,表明4个藏猪群体存在两个共同的母系祖先单倍型。展开更多
目的探讨不同剂量地塞米松对兔海水淹溺性肺水肿(pulm onary edem a of seaw ater drow ning,PE-SW D)的治疗作用及其机制。方法 40只家兔随机分为4组:对照组(C G)、海水淹溺组(SG)和不同剂量地塞米松治疗组(D G 1:0.2 m g/kg,D G 2:1 m...目的探讨不同剂量地塞米松对兔海水淹溺性肺水肿(pulm onary edem a of seaw ater drow ning,PE-SW D)的治疗作用及其机制。方法 40只家兔随机分为4组:对照组(C G)、海水淹溺组(SG)和不同剂量地塞米松治疗组(D G 1:0.2 m g/kg,D G 2:1 m g/kg)。SG组兔给予气管内灌注3 m L/kg海水,D G 1及D G 2组在C G组的基础上分别静注0.2 m g/kg、1 m g/kg地塞米松。于淹溺前及淹溺后30 m in,120 m in进行动脉血气分析,淹溺后120 m in采血、收集肺泡灌洗液并取肺组织,测定肺湿/干重比、肺泡灌洗液蛋白含量,以生化法测定血清一氧化氮(N O)、丙二醛(M D A)、总超氧化物歧化酶(T-SO D)含量,观察肺组织病理形态并计算肺损伤病理评分。结果与C G组比较,SG、D G 1、D G 2组在淹溺后30 m in PaO 2显著下降(P<0.01),但在淹溺后120 m in,D G 1及D G 2组较SG组PaO 2明显增高(P<0.05);在淹溺后120 m in,D G 1及D G 2组较SG组肺湿/干重比、肺泡灌洗液蛋白含量及肺损伤病理评分显著下降(P<0.05),但D G 1组与D G 2组之间比较无明显差异(P>0.05);与C G组比较,SG组血清N O 2-/N O 3-和M D A含量显著增高(P<0.01),SO D含量显著下降(P<0.01),但D G 1及D G 2组与SG组比较,N O 2-/N O 3-和M D A含量明显下降(P<0.05),SO D含量明显增高(P<0.05),但两组之间差异无显著性(P>0.05)。结论地塞米松可改善兔海水淹溺性肺水肿的缺氧、减轻肺损伤程度,但增加剂量并不能增加治疗效果,其作用机制复杂,部分与提高血清抗氧自由基水平,抑制脂质过氧化反应有关。展开更多
测定并分析了杜洛克猪、长白猪和大白猪3个引入猪种及合作藏猪共178个个体的线粒体DNA D环(mt DNA D-loop)高变区核苷酸序列,研究引入猪种对合作藏猪遗传资源的影响.结果表明:合作藏猪核苷酸多样度和平均核苷酸差异系数均低于杜洛克猪...测定并分析了杜洛克猪、长白猪和大白猪3个引入猪种及合作藏猪共178个个体的线粒体DNA D环(mt DNA D-loop)高变区核苷酸序列,研究引入猪种对合作藏猪遗传资源的影响.结果表明:合作藏猪核苷酸多样度和平均核苷酸差异系数均低于杜洛克猪和大白猪,仅高于长白猪,而其单倍型多样度高于3个引入猪种.单倍型分析结果表明:合作藏猪仅分布在亚洲单倍类,杜洛克猪和大白猪同时具有亚洲和欧洲两个单倍类,欧洲起源猪种没有入侵到合作藏猪母系.展开更多
基金Project (50925521) supported by the National Natural Science Fund for Distinguished Young Scholars of China
文摘Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature distribution were discussed. The simulation results indicate that the system temperature distribution presents a roughly concentric shape, a steep temperature gradient is observed in diamond cutting tool, and the highest temperature is located in chip. Centrosymmetry parameter method was used to monitor defect structures. Dislocations and vacancies are the two principal types of defect structures. Residual defect structures impose a major change on the workpiece physical properties and machined surface quality. The defect structures in workpiece are temperature dependent. As the temperature increases, the dislocations are mainly mediated from the workpiece surface, while the others are dissociated into point defects. The relatively high cutting speed used in nanomachining results in less defect structures, beneficial to obtain highly machined surface quality.
文摘采用mt DNA D-loop作为分子标记,对西藏的4个藏猪群体(林芝、山南、昌都和日喀则)遗传多样性进行了研究。结果表明,西藏藏猪mt DNA D-loop高变区A+T含量(62.90%)明显高于G+C含量(37.1%),富含A和T,存在碱基偏倚性。在长度为435 bp的序列中,共检测到20个变异位点,界定了26个单倍型,单倍型多样度(Hd)为0.705±0.021,平均核苷酸差异数(k)为1.231,核苷酸多样度(Pi)为0.002 83。其中,Hd、k和Pi在昌都藏猪群体中最高,日喀则藏猪最低。此外,Hap1和Hap3单倍型是4个群体的共享单倍型,表明4个藏猪群体存在两个共同的母系祖先单倍型。
文摘目的探讨不同剂量地塞米松对兔海水淹溺性肺水肿(pulm onary edem a of seaw ater drow ning,PE-SW D)的治疗作用及其机制。方法 40只家兔随机分为4组:对照组(C G)、海水淹溺组(SG)和不同剂量地塞米松治疗组(D G 1:0.2 m g/kg,D G 2:1 m g/kg)。SG组兔给予气管内灌注3 m L/kg海水,D G 1及D G 2组在C G组的基础上分别静注0.2 m g/kg、1 m g/kg地塞米松。于淹溺前及淹溺后30 m in,120 m in进行动脉血气分析,淹溺后120 m in采血、收集肺泡灌洗液并取肺组织,测定肺湿/干重比、肺泡灌洗液蛋白含量,以生化法测定血清一氧化氮(N O)、丙二醛(M D A)、总超氧化物歧化酶(T-SO D)含量,观察肺组织病理形态并计算肺损伤病理评分。结果与C G组比较,SG、D G 1、D G 2组在淹溺后30 m in PaO 2显著下降(P<0.01),但在淹溺后120 m in,D G 1及D G 2组较SG组PaO 2明显增高(P<0.05);在淹溺后120 m in,D G 1及D G 2组较SG组肺湿/干重比、肺泡灌洗液蛋白含量及肺损伤病理评分显著下降(P<0.05),但D G 1组与D G 2组之间比较无明显差异(P>0.05);与C G组比较,SG组血清N O 2-/N O 3-和M D A含量显著增高(P<0.01),SO D含量显著下降(P<0.01),但D G 1及D G 2组与SG组比较,N O 2-/N O 3-和M D A含量明显下降(P<0.05),SO D含量明显增高(P<0.05),但两组之间差异无显著性(P>0.05)。结论地塞米松可改善兔海水淹溺性肺水肿的缺氧、减轻肺损伤程度,但增加剂量并不能增加治疗效果,其作用机制复杂,部分与提高血清抗氧自由基水平,抑制脂质过氧化反应有关。
文摘测定并分析了杜洛克猪、长白猪和大白猪3个引入猪种及合作藏猪共178个个体的线粒体DNA D环(mt DNA D-loop)高变区核苷酸序列,研究引入猪种对合作藏猪遗传资源的影响.结果表明:合作藏猪核苷酸多样度和平均核苷酸差异系数均低于杜洛克猪和大白猪,仅高于长白猪,而其单倍型多样度高于3个引入猪种.单倍型分析结果表明:合作藏猪仅分布在亚洲单倍类,杜洛克猪和大白猪同时具有亚洲和欧洲两个单倍类,欧洲起源猪种没有入侵到合作藏猪母系.
