一类二维空间中广义Boussinesq水波系统解的渐近性

在二维空间中，讨论了一类Boussinesq水波系统并用初值中出现的小参数的级数形式表示了此系统的确切解，得到了此解的长时间渐近行为按指数衰减．     

沸石中组装SrAl2O4:Eu2+,Dy3+的可调发光现象

首先用溶胶-凝胶法制备符合SrAl2O4：Eu^2 ，Dy^3 化学组成的溶胶，然后通过机械研磨、水热反应和微波加热反应三种不同的组装方法和微波还原扩散法使其进入主体ZSM-5沸石的孔道中。主客体材料的荧光光谱出现显著蓝移，余辉光谱出现400nm和517nm两个发射峰，两个余辉峰的相对发射强度随组装方法和组装浓度的改变而具有可调性，呈现有规律的变化。分析其原因是由于发光材料进入沸石的纳米级孔洞引起的。     

Regularity and long time behavior of the Boltzmann equation for granular gases

This paper investigates regularity of solutions of the Boltzmann equation with dissipative collisions in a thermal bath. In the case of pseudo-Maxwellian approximation, we prove that for any initial datum f₀(ξ) in the set of probability density with zero bulk velocity and finite temperature, the unique solution of the equation satisfies f(ξ,t)∈H^∞(R³) for all t>0. Furthermore, for any t₀>0 and s?0 the Hs norm of f(ξ,t) is bounded for t?t₀. As a consequence, the exponential convergence to the unique steady state is also established under the same initial condition.     

中国股市长记忆的修正R/S分析

本文在比较各种长记忆检验方法优缺点的基础上,采用修正的R/S分析检验我国沪深两股市日收益和日绝对收益序列的长记忆性。结果表明在0.05的显著水平下,两股市的日收益序列均无长记忆,但深圳成指日收益序列的记忆长度比上证综指日收益序列的记忆长度长;以日绝对收益序列为代表的波动序列具有较强的长记忆性。     

Experiments on the oscillatory convection of low Prandtl number liquid in Czochralski configuration for crystal growth with cusp magnetic field

This paper presents results of experiments on the oscillatory convection of mercury in a Czochralski configuration with cusp magnetic field. Temperature fluctuation measurements are carried out to determine the critical Rayleigh number for the onset of time dependent natural convection. The effects of a cusp magnetic field on the supercritical natural convection coupled with rotation of crystal disk are investigated. In the presence of a rotating flow it is found that a cusp magnetic field can induce a new long wave instability and can amplify the temperature fluctuation depending on the magnitude of the relevant flow similarity parameters and the melt aspect ratios. A flow regime diagram for the amplification and damping of the temperature fluctuations is presented to provide an experimental data base for finding optimum growth conditions in the cusp magnetic field Czochralski process.     

Composites of poly(L‐lactide‐trimethylene carbonate‐glycolide) and surface modified SBA‐15 as bone repair material

This work aims to develop novel composites from a poly(L ‐lactide‐co‐trimethylene carbonate‐co‐glycolide) (PLTG) terpolymer and mesoporous silica (SBA‐15) nanofillers surface modified by post‐synthetic functionalization. SBA‐15 first reacts with a silane coupling agent, γ‐aminopropyl‐trimethoxysilane to introduce ammonium group. PLLA chains were then grafted on the surface of SBA‐15 through ammonium initiated ring‐opening polymerization of L ‐lactide. Composites were prepared via solution mixing of PLTG terpolymer and surface modified SBA‐15. The structures and properties of pure SBA‐15, γ‐aminopropyl‐trimethoxysilane modified SBA‐15 (H₂N‐SBA‐15), PLLA modified SBA‐15 (PLLA‐NH‐SBA‐15), and PLTG/PLLA‐NH‐SBA‐15 composites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, transmission electron microscopy, N₂ adsorption‐desorption, differential scanning calorimetry, contact angle measurement, and mechanical testing. The results demonstrated that PLLA chains were successfully grafted onto the surface of SBA‐15 with grafting amounts up to 16 wt.%. The PLTG/PLLA‐NH‐SBA‐15 composites exhibit good mechanical properties. The tensile strength, Young's modulus, and elongation at break of the composite containing 5 wt.% of PLLA‐NH‐SBA‐15 were 39.9 MPa, 1.3 GPa, and 273.6%, respectively, which were all higher than those of neat PLTG or of the composite containing 5 wt.% of pure SBA‐15. Cytocompatibility tests showed that the composites present very low cytotoxicity.     

Sodium alginate/magnesium oxide nanocomposite scaffolds for bone tissue engineering

A simple 2‐step method, consisting of film casting and polyvinyl alcohol leaching, is proposed to prepare magnesium oxide (MO) nanoparticle‐reinforced sodium alginate scaffolds with right properties for bone tissue engineering. The cytocompatibility of the as‐prepared scaffolds was also evaluated using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium‐bromide yellow tetrazole assay test, wherein chondrocyte cells had been considered as target cells. According to the results, the ensuing sodium alginate nanocomposites, containing 4‐wt% MO nanoparticles, demonstrated the highest physical and mechanical properties after leaching step. The Young modulus of sodium alginate/4‐wt% MO was improved about 44%, in comparison with that of the pure alginate sample. Furthermore, incorporating MO nanoparticles up to 4 wt% controlled the liquid uptake capacity of scaffolds vis‐à‐vis the resultant pure sodium alginate sample. Moreover, with increasing the nanoparticle content, the antibacterial properties of scaffolds enhanced, but their degradation rates under in vitro conditions tapered off. With the introduction of 3‐ and 4‐wt% MO, the average diameter of the bacterial zone of the scaffold samples reduced to less than 10 mm², suggesting an insensitive antimicrobial performance, compared with the pure sodium alginate and the samples with 1‐ and 2‐wt% MO content, which exhibit antimicrobial sensitivity. 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium‐bromide assay test also revealed the cultivated chondrocyte cells on the 4‐wt% MO nanoparticle‐reinforced scaffold possessed better interaction as well as appropriate cell attachment and proliferation than the pristine sodium alginate sample.     

丝素纤维/硫酸钙抗感染骨材料的制备及性能

通过控制丝素蛋白自组装过程制备了溶液状态下的丝素纳米纤维(silk fibroin nanofibers,SFFs),与硫酸钙、万古霉素(vancomycin,VCM)复合,制备了VCM/CS/SFFs抗菌骨材料。通过SEM、XRD、紫外分光光度计、万能力学试验机、抑菌圈、MTT等手段分别研究了复合材料的微观形貌与结构、药物释放、力学、抑菌及细胞相容性等性能。结果显示,与水作为固化液相比,随着SFFs溶液(0.017 5~2.1 mg·m L~(-1))的加入,复合材料凝固时间可控,降解率逐渐降低,抗水性增强,韧性提高;同时随丝素纳米纤维含量的增加骨材料抗压强度表现为先增加后减小的趋势,一周内药物释放速率降低;材料同时具有抑菌作用;MTT实验结果显示,加入丝素纳米纤维后与纯的硫酸钙相比MC3T3细胞增殖明显。     

Hemocompatible and Bioactive Heparin‐Loaded PCL‐α‐TCP Fibrous Membranes for Bone Tissue Engineering

The combination of bioactive components such as calcium phosphates and fibrous structures are encouraging niche‐mimetic keys for restoring bone defects. However, the importance of hemocompatibility of the membranes is widely ignored. Heparin‐loaded nanocomposite poly(ε‐caprolactone) (PCL)‐α‐tricalcium phosphate (α‐TCP) fibrous membranes are developed to provide bioactive and hemocompatible constructs for bone tissue engineering. Nanocomposite membranes are optimized based on bioactivity, mechanical properties, and cell interaction. Consequently, various concentrations of heparin molecules are loaded within nanocomposite fibrous membranes. In vitro heparin release profiles reveal a sustained release of heparin over the period of 14 days without an initial burst. Moreover, heparin encapsulation enhances mesenchymal stem cell (MSC) attachment and proliferation, depending on the heparin content. It is concluded that the incorporation of heparin within TCP–PCL fibrous membranes provides the most effective cellular interactions through synergistic physical and chemical cues.