A comparative study of the in vitro degradation of poly(l-lactic acid)/β-tricalcium phosphate scaffold in static and dynamic simulated body fluid

Porous poly(l-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) composite is a new promising scaffold for bone tissue engineering. Porous scaffolds fabricated by liquid anti-solvent precipitation principle were subjected to degradation in dynamic simulated body fluid (DSBF) and in static simulated body fluid (SSBF) at 37 °C for 24 weeks, respectively. Results indicated that a large number of apatite layer were formed on the scaffolds. The results further indicated that SBF flow decreased the degradation rate of molecular weight and compressive strength significantly. The porosity and mass changes were related to the apatite formation and SBF flow. All the results might be owed to the mutual effects of the flow of SBF and the addition of β-TCP. The degradation rate of scaffolds could be adjusted by the additional fraction of β-TCP to meet the requirements of application in vivo.     

考虑弯曲和轴向振动模态的一维梁压电阻抗模型及试验研究

同时考虑一维梁结构的弯曲和轴向振动,对其压电阻抗模型进行建模分析和试验验证。在0.02～42 kHz频段内区分并标记了一维钢梁弯曲振动模态前18阶及轴向振动模态前3阶。结果表明:在0.02～7.5kHz频段内,数值计算和试验结果中谐振峰对应频率的相对误差较大:11.7%～16.5%,其原因可能是低频时振动能量较低且波的传播受结构阻尼、边界条件及环境噪音等因素影响较为明显;在7.5～42kHz范围内,两者谐振峰位置符合良好,相对误差较小:0.11%～2.31%,表明该模型在高频段具有较好的适用性;轴向振动模态对应频率大于弯曲振动模态。本研究为结构健康监测过程中检测频段的选取及损伤信息的提取提供参考。     

L-半胱氨酸改性Fe3O4纳米粒子的水热合成及其应用

以L-半胱氨酸为表面改性剂与粒径调节剂,采用水热法制备具有良好分散稳定性的磁性Fe₃O₄纳米粒子。通过透射电镜（TEM）、扫描电镜（SEM）、X射线衍射仪（XRD）、比磁饱和强度测定仪（VSM）等对产物进行表征,研究L-半胱氨酸对磁性Fe₃O₄纳米粒子的形貌、粒径分布、晶型结构、分散稳定性等的影响,理论推导了L-半胱氨酸改性后的Fe₃O₄纳米粒子（L-Fe₃O₄纳米粒子）的生成机制,将该材料作为载体吸附金种后探讨其在催化对硝基苯酚方面的应用。结果表明：沉降22 h时,调节pH值为7.0制备的Fe₃O₄纳米粒子的沉降高度大约是L-Fe₃O₄纳米粒子的6.5倍;吸附金种后的L-Fe₃O₄纳米粒子催化效率大约是未改性Fe₃O₄纳米粒子的5倍。L-半胱氨酸有效的改善了Fe₃O₄纳米粒子与分散介质之间的相容性,保护并改善了纳米粒子的分散稳定性,在污水处理等方面有潜在的应用。     

氧-水蒸汽中Sr2GdRuO6纯相的合成及固相反应机理

采用氧 (或空气 ) 水蒸汽混合气氛下的固相反应 ,可合成无任何SrRuO3 杂相的纯相化合物Sr2 GdRuO6.当由Sr2 GdRuO6作先驱物 ,类似的固相反应体系 ,可成功合成无任何SrRuO3 杂相的纯相RuSr2 GdCu2 O8化合物 .此外 ,还讨论了有水蒸汽参与的固相反应合成Sr2 GdRuO6的反应机理 .结果表明 ,水蒸气的作用是抑制SrRuO3 的形成 ,而不是有利于把SrRuO3 杂相转化为Sr2 GdRuO6相 .     

胶原纤维固化杨梅单宁对UO22+的吸附

以胶原纤维为基质，通过交联剂将杨梅单宁固化在胶原纤维上制备吸附材料．实验结果表明，所制备的吸附材料对UO2^2 具有很强的吸附能力，当溶液中UO2^2 的浓度为7．5mmol/L、pH为5．0时，吸附容量达到1．19mmol UO2^2 /g(283．3mgU／g)．UO2^2 在固化杨梅单宁上的吸附平衡符合Freurldlich方程，升高温度，平衡吸附量增大。吸附动力学可用拟二级速度方程来描述，由动力学方程计算得到的平衡吸附量与实测的平衡吸附量基本相同，误差在4％以内．pH值对吸附过程有较大影响，适宜的pH在5-8之间。所制备的吸附材料具有优良的柱动力学特性，床层的有效利用率高；经解吸后的吸附柱其吸附性能基本不变。     

Selective adsorption of tannins onto hide collagen fibres

Vegetable tannins constitute one of the most important natural polyphenolic compounds and are widely distributed in root, bark, stalk and fruitage of plant[1]. On the basis of chemical structure, vegetable tannins are usually classified into hydrolysable tannins and condensed tannins. Hydrolysable tannins yield gallic acid or ellagic acid when hydrolyzed by acid, base or some enzymes, and tannic acid is a representative of hydrolysable tannins. Condensed tannins are the polymerized products of…     

4He闪烁裂变中子探测器的中子灵敏度

对4He闪烁裂变中子探测器的中子灵敏度进行了理论和实验研究。采用蒙特卡罗方法模拟了不同能量中子和不同厚度裂变靶产生的裂变碎片在4He中的能量沉积,计算结果表明:中子在4He气中的能量沉积曲线和裂变碎片的能量沉积曲线能够互补,从而使探测器对中子的能量响应变得更平坦;探测器的中子灵敏度为10-15 Ccm2量级。并对探测器的中子灵敏度进行了实验标定,实验结果与理论计算结果较为一致。     

Preparation and shape control of multiple-arm magnetic particles

Multiple-arm magnetic CuFe₂O₄ particles have been synthesized via a simple one-step solution-phase route at the presence of ethylene glycol (EG) ligands, which plays a key role for the shape control of the particle. At low EG content, hexa-arm CuFe₂O₄ particles with average arm diameter 50 nm and length 400 nm were obtained. Furthermore, a possible mechanism of shape evaluation process of these magnetic particles is discussed.     

Observations of High Densitly Disruption on HL-2A Tokamak

When the major disruption occurs, it can not only generate great heat loads on the first wall and divertor plates, but also leads to the large electromagnetic force because of the halo current. This large electromagnetic force is very dangerous to the invessel components of the divertor and vacuum vessel. Therefore, how to avoid the disruption is an important issue on tokamak operation. To control and mitigate the major disruptions, the mechanism and the characters of the disruption have to be well understood.