CLL谐振变换器谐振电路参数优化设计

CLL谐振变换器谐振网络电路参数的设计关系到变换器性能的好坏。基于基波近似法,并结合特征阻抗分析方法,提出一种CLL谐振变换器谐振网络电路参数优化设计方案。详细分析了CLL谐振变换器的直流增益特性、谐振网络电流有效值和谐振电容电压应力,同时采用特征阻抗分析方法给出了实现开关管软开关的限制条件。实验结果验证了所提方案的正确性。     

考虑元件综合重要度的电网安全性风险评估方法

从系统学角度出发,综合考虑系统中元件的结构属性、状态属性及社会属性,提出一种考虑元件综合重要度的电网安全性风险评估方法。综合元件结构重要度因子模型与元件状态灵敏度因子模型构建元件综合重要度模型,该模型克服了传统风险评估方法中对于不同元件的重要度无法表征的不足;综合考虑电网结构与状态,建立表征电网潮流分布均衡性与负荷损失的严重度模型,完善安全性风险评估指标体系。仿真结果表明,相较于传统方法,该方法对电网N-1故障风险排序更为合理,对N-k故障序列分级风险辨识度更高。     

自支撑拱顶厚度公式的外压安全系数分析

总结了API 650自支撑拱顶厚度的计算公式,根据受压球壳的基本公式推定,除因内压造成储罐需锚固的情况之外,在API 650适用范围内,内压工况对钢制自支撑拱顶的厚度不起控制作用,但对铝制自支撑拱顶厚度有重要影响。对比大挠度球壳厚度外压公式可知,API 650提供的自支撑拱顶厚度公式均来源于该公式,且在不同条件下取不同的外压安全系数,该系数均大于GB 150规定的外压球壳安全系数。     

PEDF Improves Cardiac Function in Rats with Acute Myocardial Infarction via Inhibiting Vascular Permeability and Cardiomyocyte Apoptosis

Pigment epithelium-derived factor (PEDF) is a pleiotropic gene with anti-inflammatory, antioxidant and anti-angiogenic properties. However, recent reports about the effects of PEDF on cardiomyocytes are controversial, and it is not known whether and how PEDF acts to inhibit hypoxic or ischemic endothelial injury in the heart. In the present study, adult Sprague-Dawley rat models of acute myocardial infarction (AMI) were surgically established. PEDF-small interfering RNA (siRNA)-lentivirus (PEDF-RNAi-LV) or PEDF-LV was delivered into the myocardium along the infarct border to knockdown or overexpress PEDF, respectively. Vascular permeability, cardiomyocyte apoptosis, myocardial infarct size and animal cardiac function were analyzed. We also evaluated PEDF’s effect on the suppression of the endothelial permeability and cardiomyocyte apoptosis under hypoxia in vitro. The results indicated that PEDF significantly suppressed the vascular permeability and inhibited hypoxia-induced endothelial permeability through PPARγ-dependent tight junction (TJ) production. PEDF protected cardiomyocytes against ischemia or hypoxia-induced cell apoptosis both in vivo and in vitro via preventing the activation of caspase-3. We also found that PEDF significantly reduced myocardial infarct size and enhanced cardiac function in rats with AMI. These data suggest that PEDF could protect cardiac function from ischemic injury, at least by means of reducing vascular permeability, cardiomyocyte apoptosis and myocardial infarct size.     

Starting to Gel: How Arabidopsis Seed Coat Epidermal Cells Produce Specialized Secondary Cell Walls

For more than a decade, the Arabidopsis seed coat epidermis (SCE) has been used as a model system to study the synthesis, secretion and modification of cell wall polysaccharides, particularly pectin. Our detailed re-evaluation of available biochemical data highlights that Arabidopsis seed mucilage is more than just pectin. Typical secondary wall polymers such as xylans and heteromannans are also present in mucilage. Despite their low abundance, these components appear to play essential roles in controlling mucilage properties, and should be further investigated. We also provide a comprehensive community resource by re-assessing the mucilage phenotypes of almost 20 mutants using the same conditions. We conduct an in-depth functional evaluation of all the SCE genes described in the literature and propose a revised model for mucilage production. Further investigation of SCE cells will improve our understanding of plant cell walls.     

Hydrostatic Pressure Influences HIF-2 Alpha Expression in Chondrocytes

Hypoxia-inducible factor (HIF)-2α is considered to play a major role in the progression of osteoarthritis. Recently, it was reported that pressure amplitude influences HIF-2α expression in murine endothelial cells. We examined whether hydrostatic pressure is involved in expression of HIF-2α in articular chondrocytes. Chondrocytes were cultured and stimulated by inflammation or hydrostatic pressure of 0, 5, 10, or 50 MPa. After stimulation, heat shock protein (HSP) 70, HIF-2α, nuclear factor kappa B (NF-κB), matrix metalloproteinase (MMP)-13, MMP-3, and vascular endothelial growth factor (VEGF) gene expression were evaluated. The levels of all gene expression were increased by inflammatory stress. When chondrocytes were exposed to a hydrostatic pressure of 5 MPa, HIF-2α, MMP-13, and MMP-3 gene expression increased significantly although those of HSP70 and NF-κB were not significantly different from the control group. In contrast, HIF-2α gene expression did not increase under a hydrostatic pressure of 50 MPa although HSP70 and NF-κB expression increased significantly compared to control. We considered that hydrostatic pressure of 5 MPa could regulate HIF-2α independent of NF-κB, because the level of HIF-2α gene expression increased significantly without upregulation of NF-κB expression at 5 MPa. Hydrostatic pressure may influence cartilage degeneration, inducing MMP-13 and MMP-3 expression through HIF-2α.     

乳癌组织中人类表皮生长因子受体2蛋白的纯化及鉴定

目的建立乳腺癌组织中人类表皮生长因子受体2(human epidermal growth factor receptor 2,HER2)蛋白的纯化方法。方法采用新鲜的乳腺癌组织制备匀浆液,经60%饱和硫酸铵盐析沉淀法进行乳腺癌组织蛋白的粗提;再通过DEAE-Sephadex A-50离子交换层析和两次Sephacryl S-200分子筛层析进一步纯化HER2蛋白;纯化蛋白进行SDS-PAGE和Western blot鉴定。结果纯化后HER2蛋白相对分子质量为185 000;HER2蛋白可与兔抗人HER2多克隆抗体发生特异性结合。结论建立的纯化方法获得了具有免疫学活性的HER2蛋白,为HER2单克隆抗体的制备奠定了基础。     

镀铬故障排除实例

通过对10个镀铬生产故障实例的分析,说明了电镀产品的形状、电极的形态、挂具的形状、零件在挂具上的分布、镀槽的大小和形状等因素对镀铬生产的影响,提出了故障原因查找和故障处理的方法。指出了镀铬生产线预防同类故障发生的技术措施和故障判别经验。     

铅在土壤-蔬菜体系中的迁移规律

采集中山市农田中的土壤及对应种植的蔬菜,测定土壤和蔬菜中铅的含量,并计算出不同蔬菜对土壤中铅的富集系数,进而分析土壤中的铅含量、蔬菜中铅含量与蔬菜铅富集系数的相关性情况,以研究铅在土壤-蔬菜体系中的迁移规律。结果表明:不同蔬菜中铅含量差异明显,铅在土壤-蔬菜体系中的迁移能力因蔬菜种类不同而不同,蔬菜中铅含量与土壤中铅含量不具显著相关性,与其富集系数具显著相关性。