基于几何结构的零件切片轮廓特征点提取方法

零件功能的多样性决定了其几何结构的多样性。为深入理解产品的设计意图和获得零件的精确描述,在对零件的三维数据进行预处理时,需要针对不同结构的零件,运用不同的处理方法。本文对预处理中的特征点提取方法做了一些探索。首先,根据传统分类法将零件分为规则结构零件和非规则结构零件,具体描述了其特征点性质;然后,分别采用对应的特征点提取算法对其进行处理;最后,通过实例验证了该方法的可行性。     

加氢催化热解在提取生物标志化合物中的应用

近年未加氢催化热解技术被用于提取有机大分子中共价键结合的小分子化合物。本文利用固定床反应器对干酪根进行加氢催化热解,提取干酪根中共价键结合的生物标志化合物。实验条件：反应温度520℃,氢气压力大于10MPa,氢气流量8.0～10.0 L/min,催化剂Mo负载量达到1%。结果表明,加氢产物收率明显高于索氏抽提,产物的GC-MS分析与对应的索式抽提产物特征相似,而且含有更丰富的生物标志物,显示了更多的地球化学信息。     

Diltiazem concentrations in plasma vs PR intervals on electrocardiogram in 8 men

AIM: To develop an acute tolerant model in describing relationship between diltiazem (Dil) concentrations in plasma and PR intervals on ECG in men. METHOD: Both plasma concentrations of Dil and changes of ECG were simultaneously determined after po Dil 90 mg in 8 men. RESULTS: A two-compartmental pharmacokinetic model with first-order input gave a good fitting for the plasma concentration of Dil. Corresponding pharmacokinetic parameters were estimated: t1/2 beta, 5.9 +/- 1.0 h; MRT, 15.9 +/- 1.0 h; t0, 0.38 +/- 0.07 h; tmax, 2.7 +/- 0.4 h, and Cmax, 161 +/- 60 micrograms.L-1. The good fittings for plasma concentration-effect data were obtained with tolerant model E = S x C/(1 + T/T50). The pharmacodynamic parameters were given as follows: S, 829 +/- 293 s.g-1.L; Kt0, 0.037 +/- 0.024 h-1 and T50, 10 +/- 4 micrograms.L-1. CONCLUSION: Relationship between Dil concentrations in plasma and PR interval changes in men after po 90 mg was described using an acute tolerant model.     

Specific substitutions at amino acid 256 of the sarcoplasmic/endoplasmic reticulum Ca2+ transport ATPase mediate resistance to thapsigargin in thapsigargin-resistant hamster cells

High levels of resistance to thapsigargin (TG), a specific inhibitor of intracellular Ca2+ transport ATPases (SERCAs), can be developed in culture by stepwise exposure of mammalian cells to increasing concentrations of TG. We have identified, in two independently selected TG-resistant hamster cell lines of different lineages, mutant forms of SERCA. In the TG-resistant Chinese hamster lung fibroblast cell line DC-3F/TG, a T --> C change at nucleotide 766 introduces a Phe256 --> Leu alteration within the first cytosolic loop of the SERCA. In contrast, in the TG-resistant Syrian hamster smooth muscle cell line DDT/TG 4 microM, a T --> C change at nucleotide 767 introduces a Phe256 --> Ser mutation at that position. When these specific mutations are introduced into a wild-type full-length avian SERCA1 cDNA, transfection experiments reveal that Ca2+ transport function and ATP hydrolytic activity are not altered by such mutations. However, a 4-5-fold resistance to TG inhibition of Ca2+ transport function occurs upon the introduction of either the Phe256 --> Leu or the Phe256 --> Ser mutation into wild-type SERCA1. These specific mutations also render the hydrolytic activity of the ATPase resistant to inhibition by TG. Our results not only implicate amino acid 256 in TG-SERCA interactions, but also demonstrate that specific mutations within SERCA can mediate resistance to TG.     

铸铁热分析试样的宏观组织及影响因素

探讨了铸铁热分析试样内部偶点附近的宏观组织及影响因素,试验结果表明:一般的热分析试样中大都存在严重的宏观缩松,此缩松位置正好位于热电偶结点周围,这会降低热分析仪器对铁水含Si量的测试精度,石英管和加入的T3粉对这种宏观缩松没有影响,但增加样杯的锥度,可以把宏观缩松区上移至石英管以外的区域,使得偶点附近的凝固组织均匀致密。     

基于胰高血糖素类肽1受体的2型糖尿病治疗药物研究进展

胰高血糖素类肽(GLP-1)和葡萄糖依赖性促胰岛素多肽(GIP)为肠内分泌细胞在机体摄入营养时分泌的激素,因其能促进胰岛素的分泌和维持血糖的动态平衡,又被称为肠促胰素。而机体内广泛存在的二肽基肽酶-4(DPP-4)可快速灭活GLP-1和GIP,因此抑制DPP-4的活性可增强GLP-1和GIP激素的活性水平,从而改善2型糖尿病（T2DM）患者的胰岛功能和血糖控制,越来越多基于该靶点的药物被开发出来用于治疗2型糖尿病。本文综述了近年来国内外相关文献,阐述了肠促胰岛素与T2DM之间的关系,并介绍GLP－1发挥效应的机制、以及GLP类降糖药物、DPP-4抑制剂的开发设计原理。     

Effects of Different Gluten Proteins on Starch’s Structural and Physicochemical Properties during Heating and Their Molecular Interactions

Starch–gluten interactions are affected by biopolymer type and processing. However, the differentiation mechanisms for gluten–starch interactions during heating have not been illuminated. The effects of glutens from two different wheat flours (a weak-gluten (Yangmai 22, Y22) and a medium-strong gluten (Yangmai 16, Y16)) on starch’s (S) structural and physicochemical properties during heating and their molecular interactions were investigated in this study. The results showed that gluten hindered the gelatinization and swelling of starch during heating when temperature was below 75 °C, due to competitive hydration and physical barriers of glutens, especially in Y22. Thus, over-heating caused the long-range molecular order and amylopectin branches of starch to be better preserved in the Y22-starch mixture (Y22-S) than in the Y16-starch mixture (Y16-S). Meanwhile, the starch’s degradation pattern during heating in turn influenced the polymerization of both glutens. During heating, residual amylopectin branching points restricted the aggregation and cross-linking of gluten proteins due to steric hindrance. More intense interaction between Y16 and starch during heating mitigated the steric hindrance in starch–gluten networks, which was due to more residual short-range ordered starch and hydrogen bonds involved in the formation of starch–gluten networks in Y16-S during heating.     

Deciphering the Effect of Lysine Acetylation on the Misfolding and Aggregation of Human Tau Fragment 171IPAKTPPAPK180 Using Molecular Dynamic Simulation and the Markov State Model

The formation of neurofibrillary tangles (NFT) with β-sheet-rich structure caused by abnormal aggregation of misfolded microtubule-associated protein Tau is a hallmark of tauopathies, including Alzheimer’s Disease. It has been reported that acetylation, especially K174 located in the proline-rich region, can largely promote Tau aggregation. So far, the mechanism of the abnormal acetylation of Tau that affects its misfolding and aggregation is still unclear. Therefore, revealing the effect of acetylation on Tau aggregation could help elucidate the pathogenic mechanism of tauopathies. In this study, molecular dynamics simulation combined with multiple computational analytical methods were performed to reveal the effect of K174 acetylation on the spontaneous aggregation of Tau peptide ¹⁷¹IPAKTPPAPK¹⁸⁰, and the dimerization mechanism as an early stage of the spontaneous aggregation was further specifically analyzed by Markov state model (MSM) analysis. The results showed that both the actual acetylation and the mutation mimicking the acetylated state at K174 induced the aggregation of the studied Tau fragment; however, the effect of actual acetylation on the aggregation was more pronounced. In addition, acetylated K174 plays a major contributing role in forming and stabilizing the antiparallel β-sheet dimer by forming several hydrogen bonds and side chain van der Waals interactions with residues I171, P172, A173 and T175 of the corresponding chain. In brief, this study uncovered the underlying mechanism of Tau peptide aggregation in response to the lysine K174 acetylation, which can deepen our understanding on the pathogenesis of tauopathies.     

Microencapsulation properties of protein isolates from three selected Phaseolus legumes in comparison with soy protein isolate

The spray-drying microencapsulation properties of protein isolates from three selected Phaseolus legumes (kidney, red and mung beans; KPI, RPI and MPI), at a specific concentration (6 g/100 mL) and oil/protein ratio (1:1, w/w) were compared with soy protein isolate (SPI). The oil retention efficiency (RE), redispersion and dissolution behavior, as well as microstructure of the spray-dried powders were characterized. The influence of storage at 75% relative humidity for 7 days on these characteristics was also evaluated. The results indicated that the microencapsulation properties (except RE in the KPI case) of the three protein isolates were considerably poorer than SPI, though their emulsifying ability was even superior. The microencapsulating properties of these protein isolates were largely associated with their interfacial properties, especially the interfacial protein concentration. Among the three protein isolates, the spray-dried powders with KPI exhibited highest RE but least redispersion and/or dissolution behavior. The storage resulted in a severe loss of RE and ability to be redispersed and/or dissoluted, with much higher extent observed for the KPI powder. These results suggest that appropriate modifications, especially in interfacial properties, should be conducted on these proteins to warrant their application as wall materials in spray-drying microencapsulation.