木瓜蛋白酶对MPA诱导的单核细胞分泌和黏附功能的抑制作用及分子机制初步研究

目的: 观察木瓜蛋白酶对单核细胞-血小板聚集物（MPA）诱导的单核细胞分泌和黏附功能的抑制作用,并初步探讨其分子机制。方法: 分离人外周血单核细胞和富血小板血浆（PRP）,检测20 U/L木瓜蛋白酶不同作用方式下凝血酶和花生四烯酸（AA）诱导的MPA形成及肿瘤坏死因子-α（TNF-α）水平。将实验分为0（对照）、20、80 U/L木瓜蛋白酶组,分别以ELISA、流式细胞术和显微镜检查测定木瓜蛋白酶与单核细胞共孵育后MPA诱导的单核细胞趋化蛋白-1（MCP-1）和组织因子（TF）释放、CD11b和CC趋化因子受体2（CCR2）表达水平以及单核细胞与人脐静脉内皮细胞黏附率,再以Western blot检测单核细胞Akt磷酸化（p-Akt）和环氧化酶-2（COX-2）表达水平。结果: 20 U/L木瓜蛋白酶与单核细胞和血小板共孵育时显著降低凝血酶和AA诱导的MPA形成和TNF-α 水平（P<0.01）。20 U/L木瓜蛋白酶组MCP-1和TF水平,CD11b和CCR2表达率,单核细胞与内皮细胞黏附率均显著低于对照组（P<0.01）,80 U/L组对五者的抑制率显著高于20 U/L组（P<0.01）。木瓜蛋白酶显著抑制p-AKT和COX-2表达,80 U/L组p-Akt和COX-2光密度比值显著低于20 U/L组（P<0.01）。结论:木瓜蛋白酶可通过抑制Akt磷酸化和COX-2表达途径而抑制MPA诱导单核细胞活化后的释放和黏附功能,从而可能有助于预防动脉粥样硬化。     

Using magnetic birefringence to determine the molecular arrangement of supramolecular nanostructures

Abstract

Supramolecular aggregates can be aligned in solution using a magnetic field. Because of the optical anisotropy of the molecular building blocks, the alignment results in an anisotropic refractive index of the solution parallel and perpendicular to the magnetic field. We present a model for calculating the magnetic birefringence, using solely the magnetic susceptibilities and optical polarizabilities of the molecules, for any molecular arrangement. We demonstrate that magnetic birefringence is a very sensitive tool for determining the molecular organization within supramolecular aggregates.     

Optimization of a Computer Simulation Model for Packing of Concrete Aggregates

A simulation algorithm was developed for modeling the dense packing of large assemblies of particulate materials (in the order of millions). These assemblies represent the real aggregate systems of portland cement concrete. Two variations of the algorithm are proposed: sequential packing model and particle suspension model. A developed multicell packing procedure as well as fine adjustment of the algorithm's parameters were useful to optimize the computational resources (i.e., to realize the trade-off between the memory and packing time). Some options to speed up the algorithm and to pack very large volumes of spherical entities (up to 10 million) are discussed. The described procedure resulted in a quick method for packing of large assemblies of particulate materials. The influence of model variables on the degree of packing and the corresponding distribution of particles was analyzed. Based on the simulation results, different particle size distributions of particulate materials are correlated to their packing degree. The developed algorithm generates and visualizes dense packings corresponding to concrete aggregates. These packings show a good agreement with the standard requirements and available research data. The results of the research can be applied to the optimal proportioning of concrete mixtures.     

综合利用沙钢冶金钢渣制砖技术研究

处理和回收沙钢冶金产生的钢渣,制得混凝土多孔砖生产用细集料,并与水泥、矿粉、水渣、球磨污泥等进行复配试验,确定了钢渣多孔砖的配比,并制得性能合格的混凝土多孔砖。通过压蒸试验确定其长期的尺寸稳定性,为后期钢渣制砖生产提供了可行性依据,进而实现冶金钢渣的回收利用最大化。     

粗粒料颗粒破碎模型研究

结合三轴试验资料,对粗粒料在不同围压和应力水平下颗粒破碎进行了研究,结果表明,相对颗粒破碎率与围压的关系可以用反双曲函数拟合;一定围压下,相对颗粒破碎率随应力水平的增长呈非线性的指数关系.在试验分析基础上,借鉴湿化变形理论,认为处于某一应力状态下的粗粒料的破碎分别由球应力和偏应力两部分引起,偏应力部分从应力水平的角度加以研究,建立了适合于粗粒料颗粒破碎率的计算模型.探讨了粗粒料颗粒破碎模型参数与围压以及应力水平的关系,建议了相对破碎率计算经验公式,并结合有关试验结果拟合出了粗粒料的颗粒破碎模型参数.对比分析表明,拟合结果与试验成果吻合较好,说明了该模型的合理性.     

小粒径再生粗骨料对预制混凝土力学性能影响的研究

研究5~10 mm小粒径再生粗骨料对预制混凝土抗压强度、劈裂抗拉强度和弹性模量的影响。结果表明,抗压强度随龄期延长而提高,且主要发生在前7 d,7 d抗压强度达到其28 d抗压强度的77%;劈裂抗拉强度随龄期的延长而提高,3 d劈裂抗拉强度达到其28 d强度的64%;弹性模量也随龄期的延长而提高,龄期为1、3、7和14 d时,弹性模量分别为其28 d弹性模量的32%、46%、62%和91%。通过与欧洲规范对比,基于试验结果,建议了劈裂抗拉强度和弹性模量的计算模型。研究结果更好的实现再生混凝土在小截面预制混凝土构件上的工程应用。     

Elucidation of protein aggregation in frozen cod and haddock by transmission electron microscopy/immunocytochemistry,light microscopy and atomic force microscopy

Polyclonal antibodies raised to both native cod myosin and actin as well as to aggregated proteins obtained from frozen cod stored for 11 months at ?10 °C were used to investigate disposition of muscle proteins in frozen cod and haddock fillets by transmission electron microscopy. Specimens from cod and haddock fillets, stored at ?10 °C, treated with anti‐aggregate antibody as the primary antibody, showed significantly more gold particles, especially around the protein aggregates and muscle fibres compared with fish stored at ?30 °C. Samples that were treated with anti‐myosin or anti‐actin antibody showed opposite results. Similar binding properties were observed in ELISA experiments involving the reaction of actin and myosin to both native and aggregate antibodies; thus immunological tests can be used for monitoring aggregate and texture changes in frozen stored fish. In addition, atomic force microscopy images obtained from cod muscle also indicated structural changes in frozen cod muscle proteins. The mica surface was covered with a continuous layer of muscle proteins comprising mainly small globular particles and a few large particles for the control cod sample stored at ?30 °C for 11 months. In contrast, cod fillets stored at ?10 °C showed a thin layer of proteins with small holes and an increased number of large particles denoting aggregates. Formation of ice crystals between the muscle fibres of frozen cod and haddock muscle was monitored without thawing by light microscopy at ?20 °C. The micrographs showed a greater proportion of large ice crystals and extensive protein fibre changes in fillets stored at ?10 °C compared with the control at ?30 °C. Copyright © 2004 Society of Chemical Industry     

Nutritional value and digestion rate of rhea meat proteins in association with storage and cooking processes

The nutritional value of proteins was investigated after the storage and cooking of rhea M. Gastrocnemius pars interna. Oxidation of basic and aromatic amino acids, surface hydrophobicity and aggregation state of proteins, were determined in raw and cooked meat. In addition, myofibrillar proteins were exposed in vitro to proteases of the digestive tract. Cooking markedly affected the protein surface hydrophobicity. The BBP bound content was three times greater in cooked than in fresh rhea meat. A small increment in tryptophan content after cooking was observed. Storage influenced Schiff bases formation indicating the presence of protein-aldehyde adducts after cooking. High content of Schiff bases was found after cooking of samples stored for 5 days, demonstrating a probable implication of free amino groups, most likely from lysine. Cooking decreased the myofibrillar protein susceptibility to pepsin activity. After cooking, the proteolysis rate by pancreatic enzymes increased. Our findings support the importance of protein aggregation in the nutritional value of meat proteins.     

Comparative study of PLA nanocomposites reinforced with clay and silica nanofillers and their mixtures

This study compares the effects of two different types of nanosized fillers (silica and montmorillonite) at three different weight fractions as well their mixtures on the thermomechanical properties of polylactide (PLA). The role of aggregation and interphase was investigated in terms of several experimental techniques, including scanning electron microscopy, wide‐angle X‐ray scattering (WAXS), thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis (DMA), and tensile measurements. The experimental results clearly suggest that silica and montmorillonite have different reinforcing and toughening effects on PLA, while the combination of the two different nanofillers has a detrimental effect on the tensile properties of the material. Four micromechanics models describing the Young's modulus of the nanocomposites were used to study the different matrix–nanofiller interactions. The best fit of the experimental results was obtained with a model that assumes the presence of an interphase surrounding each nanoparticle. The increase of the nanofiller content above a certain amount was not accompanied by a corresponding increase of the interphase, because the total nanofiller surface area was counterbalanced by the creation of aggregates. It is postulated that the aggregation effect acts antagonistically to the interphase effect. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A New Unified Model for Predicting Non-Newtonian Viscosity of Waxy Crudes

Abstract

Viscosity determination in the non-Newtonian regime has always been a major problem in the oil industry. This is due to its dependence on the wax precipitated shear and thermal history of the crude oil. The present shear rate dependent viscosity model was developed by applying the theory of suspension rheology. This model is characterized by its capacity to predict viscosities of crude oils with different shear and thermal history and those containing petroleum-based diluents. Once viscosities at two temperatures above the wax appearance temperature (WAT) and apparent viscosity in the non Newtonian regime are known, viscosities or apparent viscosities at any temperature above the gel point can be determined by using the model together with the concentration of precipitated wax at the specified temperature. Verification of the model by using two Nigerian crudes with different shear and thermal histories and two crudes obtained from the literature shows that the model predicts viscosities with an average absolute deviation of 4.9%.