Preparation and Characterization of Hyaluronic Acid Hydrogel Blends with Gelatin

Porous hydrogel blends composed of various weight ratios of hyaluronic acid (HA) and gelatin (Gel) were fabricated by a freeze-drying method. The 1-ethyl-3(3-dimethylaminopropyl) carbodiimide (EDC) was used as a crosslinker to improve their biostability. The effect of the component and crosslinker content on the morphology, swelling ratio (SR), and mechanical properties were investigated. The results indicated that after chemical crosslinking the hydrogel showed a smoother and denser surface with less pores and a crosssection with smaller pores than that without crosslinking. The crosssection morphologies of the HA/Gel hydrogels changed from a sheet-like appearance to a fiber-like appearance with increasing HA content. The addition of HA improved the swelling property, but reduced the compressive strength. As the crosslinker content increased, the SR decreased; however, the compressive strength of the HA/Gel hydrogels increased. All these results suggest that HA/Gel hydrogel crosslinked by EDC is a potential candidate for tissue engineering scaffolds.     

一种新的激光车辙深度测量方法研究

车辙深度测量通常使用共梁式多路激光测距传感器测量路面多个离散点,由多个测量点组成的断面信息计算车辙深度,因横向采样点间距宽,导致测量误差较大。提出了一种新的激光车辙深度测量方法,采用线激光器和三维(3D)相机组合集成测量路面3D断面,通过3D断面解算车辙深度。3D相机以一定夹角采集激光器投射在路面的线结构光图像,获取路面的3D断面数据,对断面数据通过拉依达准则进行异常值剔除,再进行旋转、平移和模型识别,最终计算路面左右轮迹和最大车辙深度。实际证明,数据重复性和相关性都达到98%以上,与传统方法相比较,该方法采样间距小、测量精度高、成本低、通用性强,具有广阔的使用推广价值。     

Fabrication and Properties of Gelatin/Chitosan Microspheres Loaded with 5-Fluorouracil

The use of microspheres as drug delivery vehicles for anticancer therapeutics has great potential to revolutionize the future of cancer therapy. The present paper describes the influence of process variables on the encapsulation and loading efficiency of 5-Fluorouracil (5-FU) in gelatin/chitosan (Gel/Cs) microspheres. The influences of preparation parameters, including the contents of the emulsifier Span-80, the cross-linking agent and 5-FU, and the stirring speed, on drug loading and encapsulation efficiency of the microspheres were investigated. The experimental results indicated that drug loading and encapsulation efficiency of microspheres increased with increasing concentration of the cross-linking agent; and then decreased when the concentration of the cross-linking agent was higher than 0.3 ml·g^?1 of Gel/Cs. Drug loading and encapsulation efficiency increased with increasing concentration of Span-80; they reached the maximum value when the concentration of the emulsifier was 0.012 g·ml^?1. The loading and encapsulation efficiency of the microspheres also increased with increasing stirring speed. In addition, drug loading and encapsulation efficiency increased with increasing concentration of 5-FU; however, the encapsulation efficiency decreased when the concentration of 5-FU was higher than 40 mg·ml^?1.     

原位退火温度对Mg_2Si薄膜结构及方块电阻的影响

采用磁控溅射法和原位退火工艺在钠钙玻璃衬底上制备Mg_2Si半导体薄膜.首先在钠钙玻璃衬底上依次溅射一定厚度的Si、Mg薄膜,冷却至室温后原位退火4h,在400~600℃退火温度下制备出一系列Mg_2Si薄膜样品.采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)对Mg_2Si薄膜样品的晶体结构和表面形貌进行表征,利用四探针测试仪测试薄膜样品的方块电阻,讨论了原位退火温度对Mg_2Si薄膜结构、表面形貌及电学性能的影响.结果表明,采用原位退火方式成功在钠钙玻璃衬底上制备出单一相的Mg_2Si薄膜,退火温度为550℃时,结晶度最好,连续性和致密性最强,方块电阻最小.这对后续Mg_2Si薄膜器件的设计与制备提供了重要的参考.     

2010年环境力学夏季讲习班简介

<正>2010年环境力学夏季讲习班于8月21日～25日在南京河海大学举办.本次讲习班由国家自然科学基金委员会数理科学部主办,河海大学承办,中国力学学会环境力学专业委员会、美国工程力学学会、江苏省力学学会、海岸灾害及防护教育     

2007年度力学科学处面上项目、青年基金和地区基金资助情况介绍

经力学专家评审组及数理科学部工作会议审议,2007年度力学科学处面上、青年、地区基金资助项目已确定(见附表1).现将有关信息公布如下:     

Controllable Preparation of Monodisperse Polystyrene Microspheres with Different Sizes by Dispersion Polymerization

Summary: Monodisperse polystyrene (PS) microspheres with different sizes were prepared by dispersion polymerization in dispersion media of ethanol/water and isopropayl alcohol/water, respectively. The effect of polarity of the dispersion medium, stabilizer and initiator concentration on the average sizes and size range were evaluated. The results show that monodisperse PS microspheres with different sizes could be prepared in dispersion media of ethanol and isopropyl alcohol/water when appropriate initiator and stabilizer concentrations were employed, and the latter is a more appropriate medium to prepare uniform PS microspheres. It was found that the microsphere sizes reduced with increasing water content in the dispersion medium. Furthermore, in isopropyl alcohol/water dispersions, the average sizes decreased with increasing stabilizer concentration.     

P和As掺杂Mn4Si7第一性原理计算

采用第一性原理计算方法,对本征Mn₄Si₇以及P和As掺杂的Mn₄Si₇的电子结构和光学性质进行计算解析。计算结果表明本征Mn₄Si₇是带隙值为0.810 eV的间接带隙半导体材料,P掺杂Mn₄Si₇的带隙值增大为0.839 eV,As掺杂Mn₄Si₇的带隙值减小为0.752 eV。掺杂使得Mn₄Si₇的能带结构和态密度向低能方向移动,同时使得介电函数的实数部分在低能区明显增大,虚数部分几乎全部区域增加且8 eV以后趋向于零。此外掺杂还增加了高能区的消光系数、吸收系数、反射系数以及光电导率,明显改善了Mn₄Si₇的光学性质。     

水平液─固流中颗粒抑制湍流的行为和条件

用激光多普勒分相测量方法，考察了水平含颗粒水流的主流区，亚毫米颗粒对水流湍流有抑制行为，湍流削弱程度与颗粒浓度、流动发展长度、水流雷诺数等因素有关．按照不出现尾涡脱落和至少能响应一部分大尺度涡的运动这两个基本条件，分析了湍流抑制与有关参量的依赖性．结果表明，流动尺度和颗粒尺寸之比，对于颗粒消耗而不增生湍流起着最主要的作用．在一定的水流雷诺数下，只要这一比值很大，亚毫米颗粒就会表现出对湍流的抑制作用     

Condition numbers and backward perturbation bound for linear matrix equations

This paper deals with the normwise perturbation theory for linear (Hermitian) matrix equations. The definition of condition number for the linear (Hermitian) matrix equations is presented. The lower and upper bounds for the condition number are derived. The estimation for the optimal backward perturbation bound for the Hermitian matrix equations is obtained. Copyright © 2010 John Wiley & Sons, Ltd.