The effects of alternative stress on the cell membrane deformability of chrysanthemum callus cells

The effects of alternative stress, which was generated through a strong sound field apparatus set up in our lab, on cultured chrysanthemum callus cells were studied. Meanwhile we measured the deformability of chrysanthemum cell membranes and studied the influence of the cytoskeleton after the treatment of colchicine using micropipette aspiration technique. Based on our experimental results, we found that the deformability of cell membrane decreased in stress condition. However, the effect disappeared after the treatment of cytochalasin. Therefore, we thought that the reason on the deformability of cells decreasing was the microfilament rearranging and consequently the cells becoming more rigid under the alternative stress.     

Thermodynamic issues associated with combined cyclic voltammetry and wafer curvature measurements in electrolytes

A thermodynamic framework has been provided for the interpretation of combined cyclic voltammetry and surface stress measurements, the latter being obtained from wafer curvature or beam deflection measurements of a solid electrode as a function of applied potential (so-called voltstressograms). Firstly, the derivation of electrocapillarity equations for solid electrodes has been critically reviewed by starting from the Gibbs adsorption equation appropriate for solid–electrolyte interfaces. This allowed us to demonstrate the critical importance of elastic surface strain in the thermodynamic boundary conditions of the partial derivatives intervening in the interpretation of voltstressograms. From these considerations, it was shown for the first time that the electrocapillarity equations for solid electrodes are not appropriate for describing the variation of surface stress with potential obtained from wafer curvature measurements, because such measurements are intrinsically incompatible with the constant strain condition implied in the electrocapillarity equations. An alternative explanation is provided for the experimentally observed proportionality between the current density, measured in cyclic voltammograms, and the first derivative of surface stress with respect to potential, obtained from voltstressograms.     

Use of blowing catalysts for integral skin polyurethane applications in a controlled molecular architectural environment: Synthesis and impact on ultimate physical properties

Polyurethane elastomers of a controlled molecular architecture were synthesized using a two‐step polymerization technique. The building blocks of the elastomeric materials included urea–urethane prepolymers end‐capped with diisocyanate groups and had an exact number of urea groups at both ends. Two‐dimensional bifurcated hydrogen‐bonding networks incorporating the urea groups were, with differential scanning calorimetric and dynamic mechanical thermal analyzer techniques, responsible for the increase in the glass‐transition temperature (T_g) of the hard block and sharp interface morphology between the pure “hard” domains and pure “soft” domains. The higher extent of the phase separation between the two phases contributed to higher elastic moduli for the hard blocks and higher tensile strength for the elastomeric samples. Higher elongation values were attributed to the liberation of the elastomeric chain ends that otherwise would have been constrained in the interface region. The higher T_g values of the hard blocks corresponded to an increase in the hardness values and a decrease in the tear‐strength values. The increase in the amount of urea groups within the hard segments, as a result of the increased amount of water and blowing catalyst, resulted in elastomeric foams with higher open‐cell content. This resulted in lower resilience values as measured using the pendulum rebound test and was attributed to the ability of the open cells to absorb and dissipate energy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2526–2536, 2002     

Modelling of the pressure-velocity correlation in turbulence diffusion

Most current computations of trubulent flows with second-moment closure adopt the diffusion models which neglect the effect of pressure-velocity correlation. In the present paper the importance of this correlation effect is elucidated the neglect of this effect accounts for some major defects in the wide application of the second-moment closures. Through the relation between and , established by Lumley, we propose here a new turbulence diffusion model which takes into consideration the pressure effect. Applications of this new model in the computation of shearless turbulence mixing layer and plane and round-jet flows show that the spreading rate of these flows can be satisfactorily captured.     

Millettia ferruginea extract attenuates cisplatin-induced alterations in kidney functioning,DNA damage,oxidative stress,and renal tissue morphology

This study aimed to investigate the beneficial role of Millettia ferruginea extract (MF) in preventing cisplatin (Cisp) induced nephrotoxicity in rats. A total of 55 metabolites were identified using LC-MS analysis. The in vivo results indicated that MF pretreatment for 4 weeks (20 mg/kg b.w.) remarkably attenuated the altered renal biomarkers by decreasing the levels of plasma creatinine, urea, and uric acid when compared to the Cisp-group. The nephroprotective capacity of MF was further strengthened by histopathological observations, where Cisp + MF treated rats showed lower number of inflammatory cells and tubular degenerative changes than the Cisp-group. The harmful effects of cisplatin on renal oxidative stress indicators (MDA, SOD, CAT, and GPx), were restored by the treatment of MF. In addition, the reduction of inflammatory markers (IL-6 and TNF-α), associated with alleviating DNA fragmentation, highlighted the preventive effect of MF in kidney tissue. Additionally, MF components presented lower binding energies when docked into the active site of TNF-α and IL-6. The present findings concluded that M. ferruginea extract exhibited nephroprotective potential, which may be attributed to its antioxidant and anti-inflammatory properties. Further work is recommended to confirm the current results, explore the involved mechanism of action, and determine the therapeutic doses and time.     

Effect of Electrode Pattern on the Column Structure and Yield Stress of Electrorheological Fluids

For electrorheological (ER) suspensions, the aggregate structures of particles were observed in electric fields by the use of transparent cells with different electrode patterns. Although the suspension is dispersed to noninteracting particles without electric fields, many aggregates are formed on the electrode surface in electric fields. Since the dipole–dipole interactions cause chain structures of particles and equilibrium conformations of chains are always aligned with electric field, the aggregates indicate the presence of columns spanning the electrode gap. The particle concentration in columns which are developed between parallel-plate electrodes is about 22 vol %. In striped electrodes, the particles construct striped aggregates along the electrodes and no particles remain in the insulating region. The particle concentration in striped aggregates is about 35 vol %. The nonuniformity of electric field is responsible for the high particle concentration. The increase in particle concentration of column lead to the high yield stress of electrified suspension. Therefore, the ER performance of suspension as an overall response can be improved by the electrode design.     

论英语词与句的节奏

指出学习英语的关键是对初学者进行语言感觉训练。提出只有掌握了英语的语音语调和节奏，才能学好英语。     

35CrMo结构钢热塑性变形流动应力模型

采用Gleeble 1500热模拟实验机对35CrMo结构钢进行实验研究，根据经典应力一位错关系和动态再结晶动力学方程分别对加工硬化一动态回复和动态再结晶两阶段建立流动应力模型，并统一表示为完整的35CrMo结构钢高温流动应力模型；根据实验结果计算拟合了模型中的各参数．采用建立的流动应力模型计算实验条件下的流动应力，计算结果与实验结果吻合较好．所建立的流动应力模型可以直接用于35CrMo结构钢热成形过程的数值模拟分析．     

爆破应力波中远区破岩作用分析

应用断裂与损伤力学理论，分析了爆破应力波远区破岩作用机理认为爆破应力波在远区的破坏效应是基于该区域内局部岩体强度和断裂韧度降低，使衰减后的弱应力波作用强度仍可能大于该点处的岩石极限强度所致。提出岩石损伤与缺陷的存在，会产生应力集中或放大效应的依据，并阐述爆破应力波作用下远区原生裂纹扩展的理论分析，给出了基于岩石损伤的裂纹扩展长度估算模型。     

特低渗储层应力敏感性及对油井产量的影响

对长6某特低渗储层进行了系统的应力敏感性实验研究.研究表明:该特低渗储层岩石的应力敏感程度在26%~80%的范围,岩石的渗透率越低,应力敏感性越强;原始条件下地下渗透率明显小于地面渗透率,它们之间有较好的线性关系;储层岩石应力敏感伤害后,储层岩石的渗透率不能立即恢复,最终渗透率恢复率在68.6%~100.0%,岩石渗透率越高,渗透率恢复值越大;当岩石的渗透率小于0.5×10-3μm2时,储层岩石的应力敏感性明显增强.模型预测表明,当地层压力降低5MPa时,该储层岩石的应力敏感性对油井产量的影响在8.6%~35.7%,渗透率越低下降幅度越大.