Effect of strontium ions substitution on gene delivery related properties of calcium phosphate nanoparticles

Gene therapy has been considered a strategy for delivery of therapeutic nucleic acids to a specific site. Calcium phosphates are one gene delivery vector group of interest. However, low transfection efficiency has limited the use of calcium phosphate in gene delivery applications. Present work aims at studying the fabrication of strontium substituted calcium phosphate nanoparticles with improved gene delivery related properties. Strontium substituted calcium phosphate was prepared using a simple sol gel method. X-ray diffraction analysis, Fourier transform infrared spectroscopy, transmission electron microscopy, specific surface area analysis, zeta potential measurement and ion release evaluation were used to characterize the samples. This characterization showed strontium and carbonate co-substituted calcium phosphate which resulted in nano size particles with low crystallinity, high specific surface area, positive surface charge, and a high dissolution rate. These improved properties could increase the DNA concentration on the vector as well as the endosomal escape of the complex that leads to higher transfection efficiency of this novel gene delivery vector.     

Vickers Microhardness Studies on B<Subscript>4</Subscript>C Reinforced/Unreinforced Foamable Aluminium Composites

In this work we have investigated the effects of production processes on the structural and mechanical properties of B₄C reinforced/unreinforced foamable aluminium composite materials. All samples were produced with the powder metallurgy method. The production method included compression, extrusion and rolling processes. The Vickers microhardness test was applied to determine the mechanical properties of the samples. Vickers microhardness, elastic modulus and yield strength values of the samples were separately calculated and compared with each other. The experimental microhardness results were analysed using Meyer’s law, the proportional sample resistance model, the elastic–plastic deformation model and the Hays Kendall (HK) approach. The results determined that the HK approach was the most suitable model among the other applied microhardness models.     

Water-soluble quaternized mercaptopyridine-substituted zinc-phthalocyanines: Synthesis, photophysical, photochemical and bovine serum albumin binding properties

The synthesis and characterization of the new zinc phthalocyanine derivatives, tetra- (non-peripheral, 5) and octa-(peripheral, 6) substituted with 2-mercaptopyridine and their respective quaternized derivatives (8 and 9) are reported. Photochemical and photophysical properties of the new complexes are compared with those of the previously reported peripherally tetra-substituted complexes 7 and 10. The quaternized compounds exhibit excellent solubility in water, making them potential photosensitizers for use in photodynamic therapy (PDT) of cancer. Spectroscopic, aggregation, photophysical and photochemical properties of these complexes are also investigated and compared. Photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen and photodegradation quantum yield) properties of these phthalocyanine photosensitizers are very important for the assessment of these complexes as PDT agents. In this study, the effects of the position of the substituents and quaternization of the substituents on the photophysical and photochemical parameters of the zinc phthalocyanines are also reported. This study also showed that the water-soluble quaternized zinc phthalocyanines strongly bind to blood plasma proteins such as bovine serum albumin (BSA).     

约束混凝土的应力-应变分析模型

众所周知,混凝土的强度和延性在很大程度上取决于侧向约束水平。约束的刚度和基本性能（弹性,弹塑性等）是影响混凝土性能的重要因素。本研究中,建立了一个新的简单的约束混凝土模型来描述三向受压状态下混凝土的轴向和侧向变形特性。定义约束混凝土的轴向应力-应变关系为非线性曲线的弹性区。采用常失效能量准则定义了应力-应变关系曲线的下降区域。