硬盘驱动器巨磁电阻(GMR)磁头:从微米到纳米

近年来电脑硬盘存储密度的飞速增长(年增长100％)已超出摩尔定律的预言．这种惊人的高速增长中，最关键的因素是自旋阀纳米多层膜结构，即巨磁电阻(GMR)读传感器磁头的应用．事实上，巨磁电阻磁头读传感器(reader sensor)已经实现由微电子器件向纳米电子器件转化，并且形成大规模产业．这一过程包含了自旋电子学、材料科学、微电子工程学、化学、微机械力学和工程学等诸学科和相关微加工技术综合性挑战极限，进入纳米科技领域实质性进步．     

复合结构丝中的电流密度分布和巨磁阻抗效应

提出了由中间为高电导率的非铁磁性金属丝外面包裹一层铁磁材料组成的复合结构丝的电流 密度分布和巨磁阻抗(GMI)效应模型，并对Cu/FeCoNi复合丝进行了数值模拟. 结果表明：在 相同的磁性材料几何尺寸和磁特性时，Cu/FeCoNi复合丝铁磁层内的电流随频率的升高比匀 质FeCoNi铁磁丝内的电流更趋于表面分布，而且开始出现趋肤效应时对应的频率明显降低. 当在比较低的频率下就可以观察到明显的MI变化时，复合结构丝中的电阻和电抗变化主要是 由趋肤效应引起，趋肤效应仍然是引起复合结构材料(包括多层薄膜结构) 关键词： 电流密度 巨磁阻抗效应 趋肤效应     

A DNA‐Programmed Liposome Fusion Cascade

Chemically engineered and functionalized nanoscale compartments are used in bottom‐up synthetic biology to construct compartmentalized chemical processes. Progressively more complex designs demand spatial and temporal control over entrapped species. Here, we address this demand with a DNA‐encoded design for the successive fusion of multiple liposome populations. Three individual stages of fusion are induced by orthogonally hybridizing sets of membrane‐anchored oligonucleotides. Each fusion event leads to efficient content mixing and transfer of the recognition unit for the subsequent stage. In contrast to fusion‐protein‐dependent eukaryotic vesicle processing, this artificial fusion cascade exploits the versatile encoding potential of DNA hybridization and is generally applicable to small and giant unilamellar vesicles. This platform could thus enable numerous applications in artificial cellular systems and liposome‐based synthetic pathways.     

Aggregate Conformation and Rheological Properties of Didodecyldimethylammonium Bromide in Aqueous Solution

Aggregation behavior of didodecyldimethylammonium bromide (DDAB) in aqueous solution was investigated using negative-staining and freeze-fracture transmission electron microscopy (TEM) methods. With the concentration increase, the vesicle size enlarged from the range of 100–200 nm to 500–3000 nm and the structure transform from unilamella to multilamella. Rheological and viscosity measurement results indicated that the system exhibited a gel-like material characteristic and shearing thinning in property, as shown that the apparent viscosity decreased gradually during the shear rate ascended from 1 × 10^?4–1 × 10⁴ s^?1. Furthermore, the relationship between aggregate conformation and solution rheological properties was discussed.     

色谱在药物-机体复杂巨系统研究中的应用进展

色谱是一门以分离分析为主,旨在追求复杂事物纯而净的分析化学的重要分支学科。其经过百余年的发展,理论与技术日臻完善,集科学、技术与艺术于一体。近年来,色谱及其与质谱、核磁共振波谱、原子发射光谱等联用技术极大推动了环境、食品、石油化工、生物医药等领域中所涉及复杂体系的研究进展。作为我国传统文化的核心代表,中医药为中国乃至世界人民的健康服务逾千年,从古至今历经上千年临床考验,疗效经久不衰。近年来,中国政府强调继承与创新,加大推进中医药的现代化与国际化。然而中药自身的多成分协同起效复杂性及其与机体时刻新陈代谢变化的复杂性往往相互作用,由此形成了药物-机体复杂巨系统。该复杂巨系统的分析研究是中医药现代化进程的关键瓶颈。色谱的优势在于复杂成分的分离与分析,此恰能为上述复杂巨系统提供技术支撑,色谱及其联用技术已成为推动中医药分子化、数字化、信息化乃至现代化的主流技术。该文综述了色谱及其联用技术在中药复杂体系、复杂生命过程及药物-机体复杂巨系统中的应用进展,介绍了笔者研究团队对中医药现代化的认识、研究思路和研究工作,最后笔者结合对于百年色谱与千年中医药文化之现代化交织的感悟,对色谱技术在此领域的前景做出了展望。     

Point‐to‐Plane Nonhomogeneous Electric‐Field‐Induced Simultaneous Formation of Giant Unilamellar Vesicles (GUVs) and Lipid Tubes

It is well‐known that homogeneous electric fields can be used to generate giant unilamellar vesicles (GUVs). Herein we report an interesting phenomenon of formation of GUVs and lipid tubes simultaneously using a nonhomogeneous electric field generated by point‐to‐plane electrodes. The underlying mechanism was analyzed using finite element analysis. The two forces play main roles, that is, the pulling force (F) to drag GUVs into lipid tubes induced by fluid flow, and the critical force (Fc) to prevent GUVs from deforming into lipid tubes induced by electric fields. In the center area underneath the needle electrode, the GUVs were found because F is less than Fc in that region, whereas in the edge area the lipid tubes were obtained because F is larger than Fc. The diffusion coefficient of lipid in the tubes was found to be 4.45 μm² s^?1 using a fluorescence recovery after photobleaching (FRAP) technique. The method demonstrated here is superior to conventional GUV or lipid tube fabrication methods, and has great potential in cell mimic or hollow material fabrication using GUVs and tubes as templates.     

Optical Properties of Amorphous Co‐Containing Alloys in the IR Region of the Spectrum and Their Magnetoresistive Characteristics

The optical properties of amorphous and nanocrystalline tapes of CoFeNiSiB alloys and the ac magnetoresistive effect in them have been investigated. It is shown that the magnetoresistive effect in these alloys increases by about a factor of two after lowtemperature treatment and subsequent laser annealing of these tapes in an external magnetic field. Correlation between the anomalous behavior of the dielectric function of these alloys in the IR region of the spectrum and their magnetoresistive characteristics after thermal annealings has been established. The interrelation between the density of localized electronic states near the Fermi level and the value of the magnetoresistive effect has been revealed. The influence of the induced magnetic anisotropy on the transverse permeability in amorphous and nanocrystalline CoFeNiSiB alloys and, consequently, also on the magnetoresistive effect has been analyzed.     

Polymersome‐forming amphiphilic glycosylated polymers: Synthesis and characterization

Copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) was used to prepare glycosylated polyethylene (PE)–poly(ethylene glycol) (PEG) amphiphilic block copolymers. The synthetic approach involves preparation of alkyne‐terminated PE‐b‐PEG followed by CuAAC reaction with different azide functionalized sugars. The alkyne‐terminated PE‐b‐PEG was prepared by etherification reaction between hydroxyl‐terminated PE‐b‐PEG (M_n ～ 875 g mol^?1) and propargyl bromide and azidoethyl glycosides were prepared by glycosylation of 2‐azidoethanol. Atmospheric pressure solids analysis probe‐mass spectrometry was used as a novel solid state characterization tool to determine the outcome of the CuAAC click reaction and end‐capping of PE‐b‐PEG by the azidoethyl glycoside group. The aqueous solution self‐assembly behavior of these amphiphilic glycosylated polymers was explored by TEM and dye solubilization studies. Carbohydrate‐bearing spherical aggregates with the ability to solubilize a hydrophobic dye were observed. The potential of these amphiphilic glycosylated polymers to self‐assemble via electro‐formation into giant carbohydrate‐bearing polymersomes was also investigated using confocal fluorescence microscopy. An initial bioactivity study of the carbohydrate‐bearing aggregates is furthermore presented. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5184–5193     

大学物理铁磁质教学中工程教育素材的融入

在大学物理课程铁磁质知识点的教学中,结合工程实践教育,使讲授的知识点能够理论联系实际,在提高教学效果的同时,使学生认识到理论知识在工程实践中的应用,进而使学生树立正确的知识价值观,提高学习兴趣,增强主动学习的意识.