Interaction between the antibacterial compound,oleuropein, and model membranes

Oleuropein, a secoiridoid glycoside extracted from the olive tree, Olea europaea L., has been described as showing antibacterial properties. However, the exact mechanism of these antimicrobial properties is not yet well understood. In the present study, we have studied the interaction of oleuropein with phosphatidylglycerol (PG) as a model membrane for Staphylococcus aureus (S. aureus) (Gram-positive bacteria) and phosphatidylethanolamine and Escherichia coli (E. coli) lipid extract as a model membrane for E. coli (Gram-negative bacteria). The study has been carried out using monolayers as model membranes and using kinetics at constant area and compression isotherms with Brewster angle microscopy (BAM) observations. The results show that oleuropein interacts in higher extent with PG monolayers, which is related with its stronger antibacterial effect against Gram-positive bacteria. The effects on the membrane are probably produced at the cell surface because oleuropein did not form stable mixed monolayers with the lipids assayed at the air/water interface.     

Separation of ortho-substituted tetraphenylporphyrins by preparative HPLC

Summary A method for the separation of substituted tetraphenylporphyrins by preparative liquid chromatography is reported. The quality of the columns formed by axial compression of various stationary phases is tested.     

深水多波束测深系统脉冲压缩实时算法

线性调频信号是大时宽带宽积信号,通过脉冲压缩可提高探测距离和分辨率,已在深水多波束测深系统中得到广泛应用。针对深水多波束测深系统中脉冲压缩运算量大的问题,提出了一种基于分组的脉冲压缩实时算法。该算法对需要进行脉冲压缩的波束进行分组,每个节拍只计算一组波束,可大幅减少深水多波束测深系统脉冲压缩的运算时间,节省了处理器资源。该算法已成功应用于某深水多波束测深系统,经多次海试证明,工作稳定可靠。     

Compression testing of continuous fiber reinforced polymer composites with out-of-plane fiber waviness and circular notches

We investigated the face-stabilized Open-Hole Compression (OHC) test method for evaluating the effects of fiber waviness on the compression strength of continuous carbon fiber reinforced polymer composites. Temporal evaluations of the load-deformation response, acoustic emissions and optical microscopy are used to understand the failure modes and damage progression in the OHC specimen. The failure modes observed are structurally correlated to matrix failure and kink zone formation leading to fiber fracture. The results show how the resin pocket plays a more critical role than the layup in influencing the initiation of damage in the composite specimens.     

复合材料柔软性对倒金字塔微结构阵列传感器性能的影响

采用模压成型方法制备了2种柔软性不同的热塑性聚氨酯/短切碳纤维/碳纳米管(TPU/SCF-CNT)复合材料复制物, 其表面上具有倒金字塔微结构阵列, 内部有SCF与CNT共同构成的导电通路. 将复合材料复制物和相应的复合材料平整片封装成柔性传感器. 结果表明, 压力作用下传感器内复制物和平整片之间的接触电阻因倒金字塔底棱的形变而显著降低. 对使用柔软性较高的复合材料封装的传感器, 虽然其相对迟滞稍大, 但压力作用下倒金字塔底棱形变量较大, 且复制物和平整片内导电通路增加量较大, 因此其在0~2.5 kPa的线性区内具有较高的灵敏度(0.32 kPa^?1). 制备的2种传感器均具有快速响应特性, 且能在500 s(约1580次)的循环压缩/释放测试(峰值压力约3 kPa)中保持较稳定的电阻响应. 研究表明, 利用模压成型的表面倒金字塔结构复合材料复制物封装成的柔性压力传感器具有良好的传感性能.     

Performance of high-temperature thermosetting polyimide composites modified with thermoplastic polyimide

The preparation of polyimide (PI) resin with high heat resistance and toughness is a significant challenge. In this study, thermoplastic PI (TPI) was used to toughen thermosetting PIs, and toughened PI (TPI/PI) blends were prepared. The modified PI resin system exhibited good thermal stability, excellent heat resistance, and high toughness. The results indicated that the TPI/PI blends maintained the curing behavior and characteristics of the PI oligomer. The T_g of the cured TPI/PI blend exceeded 395 °C, and the T_5% values were in the range of 533–563 °C, suggesting excellent thermal stability and heat resistance. The maximum impact strength was increased by 46% compared with that of pure PI, indicating the excellent toughening effect of the TPI. Carbon fiber-reinforced PI composites were prepared using the toughening system as a matrix. The compression-after-impact values of the carbon fiber-reinforced PI composites were up to 190 MPa, indicating the excellent toughness of the materials.     

Visualization of shock-wave formation processes during shock reflection at obstacles with multiple steps

According to standard textbooks on compressible fluid dynamics, a shock wave is formed by an accumulation of compression waves. However, the process by which an accumulated compression wave grows into a shock wave has never been visualized. In the present paper, the authors tried to visualize this process using a model wedge with multiple steps. This model is useful for generating a series of compression waves and can simulate a compression process that occurs in a shock tube. By estimating the triple-point trajectory angle, we demonstrated visually that an accumulated compression wave grows into a shock wave. Further reflection experiments over a rough-surface wedge confirmed the tendency for the triple point trajectory angle to reach the asymptotic value _s in the end.This work was first presented at the Symposium on Shock Waves, Japan 2002     

Compression set in gas-blown condensation-cured polysiloxane elastomers

Accelerated thermal ageing studies on foamed condensation cured polysiloxane materials have been performed in support of life assessment and material replacement programmes. Two different types of filled hydrogen-blown and condensation cured polysiloxane foams were tested; commercial (RTV S5370), and an in-house formulated polysiloxane elastomer (Silfoam). Compression set properties were investigated using Thermomechanical (TMA) studies and compared against two separate longer term ageing trials carried out in air and in dry inert gas atmospheres using compression jigs. Isotherms measured from these studies were assessed using time-temperature (T/t) superposition. Acceleration factors were determined and fitted to Arrhenius kinetics. For both materials, the thermo-mechanical results were found to closely follow the longer term accelerated ageing trials. Comparison of the accelerated ageing data in dry nitrogen atmospheres against field trial results showed the accelerated ageing trends over predict, however the comparison is difficult as the field data suffer from significant component to component variability. Of the long term ageing trials reported here, those carried out in air deviate more significantly from field trials data compared to those carried out in dry nitrogen atmospheres. For field return samples, there is evidence for residual post-curing reactions influencing mechanical performance, which would accelerate compression set. Multiple quantum-NMR studies suggest that compression set is not associated with significant changes in net crosslink density, but that some degree of network rearrangement has occurred due to viscoelastic relaxation as well as bond breaking and forming processes, with possible post-curing reactions at early times.     

Developing an algorithm for compression, multiplexing and enhancement of multiple images

Image compression is one of the important fields that has useful applications in data storage and transmission. In this research a new algorithm is developed and tested for multiple-image compression and enhancement. The algorithm, in addition, is applied to multiple noisy images. Also, the effect of compression ratio on the peak signal to noise ratio (PSNR) is explored by applying different compression ratios. The developed algorithm gives good compression and noise immunity. It can be used for storage/transmission of encrypted and compressed information.     

小波系数压缩用于柴油十六烷值近红外光谱分析建模

近红外光谱分析建模中存在多变量高维数据处理问题,导致计算量大,不利于过程控制中应用.为此提出利用小波变换压缩近红外光谱数据的算法与准则,并结合柴油十六烷值定量分析研究压缩数据的建模效果.研究表明,经小波方法处理后,变量维数压缩30倍左右,光谱主要信息基本保留,而模型的预测精度和常规预处理方法分析相比有明显提高.光谱数据压缩的同时包含了噪声滤除和基线校正,简化数据处理步骤,有利于NIRS实际应用时提高建模效率.