Gel permeation chromatographic characterization of sodium hyaluronate and its fractions prepared by ultrasonic degradation

Summary High-molecular-weight sodium hyaluronate isolated from rooster combs was degraded by ultrasonication. The molecular weight of hyaluronate and its polydispersity was determined by gel-permeation chromatography. During 75-min treatment the molecular weight value decreased from 1.39×10⁶ Da to 2.25×10⁵ Da while the polydispersity of the molecular weight increased from 1.29 to 2.36. The reciprocal value of the square of the hyaluronate's molecular weight was linearly proportional to the time of ultrasonication.     

Novel polyester/SiO2 nanocomposite membranes: Synthesis,properties and morphological studies

In this paper, a new type of soluble polyester/silica (PE/SiO₂) hybrid was prepared by the ultrasonic irradiation process. The coupling agent γ-glycidyloxypropyltrimethoxysilane (GOTMS) was chosen to enhance the compatibility between the polyester (PE) and silica (SiO₂). Furthermore, the effects of the coupling agent on the morphologies and properties of the PE/SiO₂ hybrids were investigated using UV-vis and FT-IR spectroscopies and FE-SEM. The densities and solubilities of the PE/SiO₂ hybrids were also measured. The results show that the size of the silica particle was markedly reduced by the introduction of the coupling agent, which made the PE/SiO₂ hybrid films become transparent. Furthermore, thermal stability, residual solvent in the membrane film and structural ruination of membranes were analyzed by thermal gravimetric analysis (TGA). The effects of SiO₂ nanoparticles on the glass transition temperature (T_g) of the prepared nanocomposites were studied by differential scanning calorimetry (DSC). Moreover, their mechanical properties were also characterized. It can be observed that the Young's moduli (E) of the hybrid films increase linearly with the silica content. The results obtained from gas permeation experiments with a constant pressure setup showed that adding SiO₂ nanoparticles to the polymeric membrane structure increased the permeability of the membranes.     

超声辐照引发MMA微乳液聚合

研究了超声波引发甲基丙烯酸甲酯(MMA)的微乳液聚合.辐照40min时单体转化率高达90%.透射电镜观察发现,PMMA微乳液平均粒径为36.5nm,粒径分布窄,表明超声波引发是制备PMMA微乳液的有效方法.采用分光光度计对微乳液聚合过程中乳胶粒的形成和大小进行了间接表征,研究了超声功率输出、乳化剂、助乳化剂、单体和引发剂对MMA微乳液聚合的影响.     

超声辐照下聚乙烯熔体挤出流变特性的研究

研究了超声辐照作用下HDPE和LLDPE的挤出流变特性。结果表明,超声辐照可以促进聚乙烯分子链段的运动,降低熔体的挤出口模压力和表观粘度,明显提高聚乙烯熔体的流动性,使挤出物外观质量明显提高,为改善聚乙烯的加工性能及制品质量提供了新途径。     

超声筛查早期诊断婴儿发育性髋关节异常的临床管理

目的 了解鄞州区0~6月龄婴儿发育性髋关节异常（developmental dysplasia of hip,DDH）的流行病学特征,探讨DDH 的临床管理模式。方法 由鄞州区妇幼保健机构社区医师和鄞州区第二医院围生医生共同负责完成DDH 的临床初筛工作,可疑或异常者转儿科进一步检查,并予B 超筛查,对不同人群分别进行早期干预、复查、随访及骨盆正位X 线片检查,必要时转小儿骨科治疗。结果 2012 年5 月至2013 年5 月,共6 890 例0~6月龄婴儿进行髋关节B 超筛查,初筛阳性率5.73%（395/6 890）,复查阳性率0.59%（34/5729）;月龄越小筛查阳性率越高,差异有统计学意义（P＜0.05）。新生儿及1~3月龄婴儿初筛阳性率高,但复查阳性率明显降低,差异有统计学意义（P＜0.05）;4~6月龄婴儿初筛及复查阳性率差异无统计学意义（P ＞0.05）。结论 鄞州区采取的社区门诊检查- 区医院儿科复查-B 超筛查及转诊治疗的管理模式,可作为基层推进DDH 的早发现和早治疗的有效手段。     

Identification and control of nonlinear systems by a dissimilation particle swarm optimization-based Elman neural network

In this paper, we first present a learning algorithm for dynamic recurrent Elman neural networks based on a dissimilation particle swarm optimization. The proposed algorithm computes concurrently both the evolution of network structure, weights, initial inputs of the context units, and self-feedback coefficient of the modified Elman network. Thereafter, we introduce and discuss a novel control method based on the proposed algorithm. More specifically, a dynamic identifier is constructed to perform speed identification and a controller is designed to perform speed control for Ultrasonic Motors (USM). Numerical experiments show that the novel identifier and controller based on the proposed algorithm can both achieve higher convergence precision and speed than other state-of-the-art algorithms. In particular, our experiments show that the identifier can approximate the USM's nonlinear input–output mapping accurately. The effectiveness of the controller is verified using different kinds of speeds of constant, step, and sinusoidal types. Besides, a preliminary examination on a randomly perturbation also shows the robust characteristics of the two proposed models.     

Ultrasonic attenuation in polycrystals using a self-consistent approach

The self-consistent method of averaging elastic moduli to define the effective medium of a polycrystal is used to investigate the dynamic problem of wave propagation. An alternative covariance tensor describing the elastic moduli fluctuations of the polycrystal containing self-consistent elastic properties is derived and found to be significantly smaller than the covariance tensor formed through traditional Voigt averaging. Attenuation curves are generated using the self-consistent elastic moduli and covariance tensors and these results are compared with previous Voigt-averaged estimates. The second-order polycrystalline dispersion relation for the self-consistent scheme is found for cases of low and high crystallite anisotropy. The attenuation coefficients and dispersion relations derived through the self-consistent scheme are considerably different than previous estimates. Experimentally measured longitudinal attenuation coefficients support the use of the self-consistent scheme for estimation of attenuation.     

连续臂丛神经阻滞镇痛对断指再植血流动力学影响的研究

目的研究连续臂丛神经阻滞镇痛对断指再植术后再植指血流动力学的影响,探讨其缓解血管痉挛、增加血流量的可行性。方法将60例急诊行断指再植术患者按随机数字表法分为术后连续臂丛神经阻滞镇痛组（CA组）和对照组（NA组）,每组30例。观察两组患者再植指术后血管痉挛、血管栓塞和指体坏死发生例数并计算再植指成活率,记录两组术后即刻（T1）、术后24h（T2）再植指固有动脉血流动力学参数及动脉内径（AD）、远指端血氧饱和度（SpO2）和温度（Ts）变化。结果断指再植术后成活率CA组高于NA组,血管痉挛、血管栓塞和指体坏死发生率CA组均低于NA组,差异均有统计学意义（均P＜0.05）。在T2时CA组各项血流动力学参数、AD、SpO2、Ts均高于NA组,阻力指数（RI）低于NA组,差异均有统计学意义（均P＜0.05）。结论术后连续臂丛神经阻滞镇痛可以缓解再植指固有动脉痉挛,增加指体血流量,提高了断指再植的成功率。     

Sonochemical synthesis,formation mechanism,and solar cell application of tellurium nanoparticles

Tellurium inherently tends to form 1-D structures and while the 0-D Te nanostructures have better properties and applications in solar cell. In the present study, 0-D Te nanostructures including rice-like and spherical nanoparticles with the particle size of 15–40 nm were successfully synthesized via a facile sonochemical method. In the absence of ultrasonic irradiation nanorods were produced while performing the reaction under ultrasonic waves (at 200 W for 30 min) led to the formation of nanoparticles. Finally, the efficiency of various as-synthesized Te nanostructures in quantum dot-sensitized solar cells (QDSSCs) were evaluated. Using rice-like nanoparticles led to increase in J_SC, V_OC, FF and η parameters from 1.22, 0.54, 0.49 and 0.32% to 1.57, 0.64, 0.63 and 0.63%, respectively, compared with nanorods.     

基于ARM的嵌入式超声传播时间测量装置

应用超声波检测技术进行检测时,通常需对超声波在介质中的传播时间进行精准的测量,为精准测量超声波的传播时间,设计了一套基于ARM的嵌入式超声传播时间测量装置。该装置电路运行稳定,成本低廉,采用多次测量结果取算数平均值的方法以减小随机干扰,采用参比方法放置接收探头以消减电路中电子器件的延时。通过对实验结果进行分析,得出该装置可精准测量超声波在实验试块中的传播时间且满足设计要求,分辨率可达一纳秒。