Effect of collagen fibril formation on bioresorbability of hydroxyapatite/collagen composites

Porous hydroxyapatite/collagen (HAp/Col) composite is a promising biomaterial and a scaffold for bone tissue engineering. The effect of fibril formation of Col in the porous composite on bioresorbability and mechanical strength was investigated. The fibril formation, in mixing a self-organized HAp/Col nanocomposite and sodium phosphate buffer at a neutral condition, occurred during incubation at 37 °C, resulting in gelation of the mixture. The porous composites with and without the incubation were obtained by freeze-drying technique, in which macroscopic open pores were formed. The compressive strength of the porous composite with the incubation (34.1 ± 1.6 kPa) was significantly higher than that without the incubation (28.0 ± 3.3 kPa) due to the fibril formation of Col. The implantations of the porous composites treated with a dehydrothermal treatment in bone holes revealed that bioresorption was clearly depended on the fibril formation. The bioresorbability in vivo was almost matched to the in vitro test using enzymatic reaction of collagenase.     

多视极化SAR图象相干斑抑制的研究

本文研究多视极化合成孔径雷达(SAR)图象的相干斑抑制,提出多视极化白化滤波(MPWF)法,并进一步将它发展成具有多通道输出的全极化滤波器。本文还定量地分析了MPWF方法抑制相干斑的能力,并在理论上同全功率法、加权法和功率均衡法进行了比较。应用NASA/JPL机载L波段四视全极化SAR数据的试验结果验证了所提方法的有效性和优越性,也说明了MPWF处理能显著地提高SAR图象的分类精度。     

一种不用乘法器的增量调制DFT新结构

本文提出一种基于增量调制(DM)序列的离散傅里叶变换(DFT)结构,它不同于基于脉冲编码调制(PCM)的常规方法。提出这一想法是为了解决在常规的数字信号处理中的乘法运算问题,从而减小系统的复杂性,降低设备成本。我们将看到,本文提出的新的DFT结构取消了A/D变换器和乘法器,可望简化硬件设计、降低造价,而信噪比同样能够达到与常规的处理方法,如FFT相近的结果。计算机模拟表明,对于确定性信号,结果与常规的DFT相一致。对于带限高斯信号,只要适当地选择步长和过采样率系数,同样也能得到与常规DFT相近的结果。我们采用ROM存贮各个系数值,因此,整个运算完全是阅读和求和的过程,因而速度快,硬件结构简单,适用于语音、地震等信号的处理。本文最后给出了硬件实现方案和各个参数的选择方法,同时提供了计算机模拟结果。     

合成孔径雷达图象结构特征检测的改进算法

本义研究合成孔径雷达（ＳＡＲ）图象结构特征检测。首先讨论了 ＳＡＲ图象结构检测的原理,然后在分析Ｌｏｐｅｓ等人的算法的基础上,提出了一个改进的结构检测算法,给出改进算法的实现流程,并利用模拟和实测ＳＡＲ图象进行试验比较,充分验证了改进方法的优越性和实用性。     

Synthesis of Azulene Derivatives from 2H-Cyclohepta[b]furan-2-ones as Starting Materials: Their Reactivity and Properties

A variety of synthetic methods have been developed for azulene derivatives due to their potential applications in pharmaceuticals and organic materials. Particularly, 2H-cyclohepta[b]furan-2-one and its derivatives have been frequently used as promising precursors for the synthesis of azulenes. In this review, we describe the development of the synthesis of azulenes by the reaction of 2H-cyclohepta[b]furan-2-ones with olefins, active methylenes, enamines, and silyl enol ethers as well as their reactivity and properties.     

循环水复合缓蚀阻垢剂的试验研究

为节约用水,减少环境污染,针对不同的循环冷却水,采用阻垢正交及腐蚀试验的方法,筛选出适合四平热电厂循环冷却水的复合缓蚀阻垢剂,它具有缓蚀阻垢效果好、剂量低、使用方便等优点。此方法的试验研究,在吉林省属首次,可带来良好的社会效益与经济效益。     

Miscibility between natural rubber and tackifiers. II. Phase diagrams of the blends of natural rubber and petroleum resins

Natural rubber (NR) was blended in various ratios with 12 kinds of tackifiers that were prepared from petroleum. The blends were heated to various temperatures (20–120°C) to investigate their miscibility. The blends were visually observed for transparency or opacity at each temperature and further observed under an optical microscope for any existence of phase-separated structure. Miscibility of the blends is illustrated as phase diagrams in this article. NR/aliphatic resin systems and NR/aliphatic-aromatic copolymer systems showed phase diagrams of the lower critical solution temperature type, wherein the blends turned faintly cloudy over the binodal curves. The NR/hydrogenated petroleum resin system also showed a phase diagram of the lower critical solution temperature type. The miscible range of a blend system tends to become smaller as the molecular weight of a tackifier increases. Resins prepared by polymerization of pure aromatic monomers were completely immiscible with NR. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 221–229, 1998     

Miscibility and pressure‐sensitive adhesive performances of acrylic copolymer and hydrogenated rosin systems

Relationship between the miscibility of pressure‐sensitive adhesives (PSAs) acrylic copolymer/hydrogenated rosin systems and their performance (180° peel strength, probe tack, and holding power), which was measured over a wide range of time and temperature, were investigated. The miscible range of the blend system tended to become smaller as the molecular weight of the tackifier increased. In the case of miscible blend systems, the viscoelastic properties (such as the storage modulus and the loss modulus) shifted toward higher temperature or toward lower frequency and, at the same time, the pressure‐sensitive adhesive performance shifted toward the lower rate side as the T_g of the blend increased. In the case of acrylic copolymer/hydrogenated rosin acid systems, a somewhat unusual trend was observed in the relationship among the phase diagram, T_g, and the pressure‐sensitive adhesive performance. T_g of the blend was higher than that expected from T_gs of the pure components. This trend can be due to the presence of free carboxyl group in the tackifier resin. However, the phase diagram depended on the molecular weight of the tackifier. The pressure‐sensitive adhesive performance depended on the viscoelastic properties of the bulk phase. A few systems where a single T_g could be measured, despite the fact that two phases were observed microscopically, were found. The curve of the probe tack of this system shifted toward a lower rate side as the T_g increases. However, both the curve of the peel strength and the holding power of such system did not shift along the rate axis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 651–663, 1999     

Electrostatic switching of biopolymer layers. Insights from combined electrokinetics and reflectometric interference

Structural integrity and functional characteristics of biomacromolecules are largely defined by electrostatic forces between ionized moieties, which are often altered at interfaces. Unraveling these changes requires access to charge state and structure of surface-confined biopolymers in aqueous environments. We therefore combined electrokinetic measurements of interfacial electrical potentials with the simultaneous determination of the optical layer thickness by reflectometric interference spectroscopy. Two examples are summarized to demonstrate the resulting options: The pH-switching of grafted poly(l-glutamic acid) layers caused by dissociation-dependent helix-coil transitions was studied; potential distribution and ion mobility within the grafted polyelectrolyte were unraveled using an new theoretical model for the charging of polyelectrolyte layers. The charge-driven modulation of biopolymers at interfaces was furthermore analyzed in the adsorption of fibronectin onto polymer substrates with varied charge density; the results permit us to reach a conclusion about the relevance of electrostatic matching for orientation and anchorage of the protein. Altogether, the introduced methodology was found suitable to follow the electrosurface characteristics of biomacromolecules in situ.     

Nanoparticulation of probucol, a poorly water-soluble drug, using a novel wet-milling process to improve in vitro dissolution and in vivo oral absorption

To improve the dissolution and oral absorption properties of probucol, a novel wet-milling process using the ULTRA APEX MILL was investigated. The particle size of bulk probucol powder was 17.1 μm. However, after wet-milling with dispersing agents such as Gelucire 44/14, Gelucire 50/13, vitamin E-TPGS, and Pluronic F-108, the probucol particle sizes decreased to about 77-176 nm. Scanning electron microscopy (SEM) analysis also suggested that the probucol particles were successfully milled into the nanometer range. An in vitro dissolution study showed that the dissolution rates of all nanopowders were several folds higher than those of the corresponding mixed powders. When orally administered to rats, the AUC values of probucol nanopowders treated with Gelucire 44/14 and 50/13, and vitamin E-TPGS were about 3.06-3.54-folds greater than that of the bulk powder. Therefore, through this study, we have developed a new pharmaceutical technique to improve the dissolution rate and oral absorption of probucol using the ULTRA APEX MILL by wet-milling with various dispersing agents.