磁性液体光透射变化的场致开关效应

通过研究磁性液体在平行于激光照射方向具有不同梯度的外磁场作用下,其光透射率随时间的变化情况,进一步研究了其在平行于光方向磁场作用下的开关效应,并从理论上定性地分析了导致这种现象的内在因素,讨论了微粒链的形成以及链在磁性液体内部的微观运动情况.     

CuFe2O4离子型磁性液体的场致光透射性质研究

研究了Massart法制备的CuFe2O4离子型磁性液体在磁场作用下,光透射率随时间的变化规律,光透射率的变化与磁性液体的体积分数、磁场大小、光路及磁场方向有关,为解释光透射率变化的原因,建立了在磁场作用下,磁性液体纳米微粒形成链,并在磁场梯度作用下微粒链向中心会聚,而并列链问的排斥力又使链发散的链振荡运动的微观模型。     

CuFe2O4离子型磁性液体的场致光透射性质研究

研究了Massart法制备的CuFe2O4离子型磁性液体在磁场作用下, 光透射率随时间的变化规律. 光透射率的变化与磁性液体的体积分数、磁场大小、光路及磁场方向有关. 为解释光透射率变化的原因, 建立了在磁场作用下, 磁性液体纳米微粒形成链, 并在磁场梯度作用下微粒链向中心会聚, 而并列链间的排斥力又使链发散的链振荡运动的微观模型.     

磁性液体的场致光透射驰豫回复性研究

用Massart法制备了Ni2O3/Fe2O3复合微粒磁性液体.测量了磁性液体在不同强度的外磁场作用下,沿磁场方向的光透射率随磁场通断而下降、上升的重复变化曲线.发现通磁场后光透射强度的下降速率与断磁场后光透射强度的回复速率随通断磁场重复次数变化,并趋于一致.从磁性液体的微结构变化探讨了导致这种现象的内在因素.     

基于化学诱导相变法的磁性液体合成及其磁光效应

使用化学诱导相变法制备的γ-Fe_2O_3磁性纳米颗粒,经油酸表面包裹可分散于煤油中合成磁性液体.在磁场作用下,圆偏振光透过磁性液体样品后,由于双折射效应和二向色性,透射光为椭圆偏振光.用圆偏振光作为探测光源,使用θ扫描技术可得到透射椭圆偏振光的相对强度角分布的T-θ曲线.从曲线可得到反映透射椭圆偏振光特征的相对透射强度的最小值T_(min)和最大值T_(max)以及椭圆的取向角Δθ.从这些透射光的参数可导出磁双折射效应Δn和磁二向色性Δκ.实验结果表明:随着磁场H增强或颗粒体积分数v增大,Δn和Δκ增加.所制备的磁性液体的磁双折射和磁二向色性来源于在磁场作用下,磁性液体中的磁性纳米颗粒由分散体系形成了场致链结构.     

γ-Fe2O3/Ni2O3复合纳米微粒基二元磁性液体的制备及场致光透射特性

介绍了由强磁γ-Fe2O3/Ni2O3复合纳米微粒和弱磁Fe5O7(OH)·4H2O纳米微粒构成的二元磁性液体的制备方法,并用X射线衍射仪、透射电子显微镜、振动样品磁强计分别对这两种微粒的晶体结构、表面形貌及其磁性进行了表征.同时测量了单元磁性液体和二元磁性液体在平行于激光照射方向且具有不同梯度外磁场作用下场致光透射强度的弛豫变化,揭示了二元磁性液体有不同于单元磁性液体的特征弛豫时间,并从微观结构上分析了产生弛豫时间差异的原因.     

COFe2O4-p-NiFe2O4二元离子型磁性液体的制备及其场致光透射驰豫

介绍了CoFe2O4-p-NiF2O4二元离子型磁性液体的制备方法,用X射线衍射仪、透射电子显微镜、振动样品磁强计分别对NiFe2O4微粒前驱体(p.NiFe2O4)和COFe2O4微粒的结构、粒径和磁性进行了测量与分析,研究了CoFe2O4-p-NiFe2O4二元离子型磁性液体在平行于激光照射方向具有不同梯度的外磁场作用下的场致透光的驰豫时间,并从微观结构上分析了产生驰豫时间差异的原因.     

COFe2O4-p-NiFe2O4二元离子型磁性液体的制备及其场致光透射驰豫

介绍了CoFe2O4-p-NiFe2O4二元离子型磁性液体的制备方法,用X射线衍射仪、透射电子显微镜、振动样品磁强计分别对NiFe2O4微粒前驱体（p-NiFe2O4）和CoFez04微粒的结构、粒径和磁性进行了测量与分析。研究了CoFe2O4-p-NiFe2O4二元离子型磁性液体在平行于激光照射方向具有不同梯度的外磁场作用下的场致透光的驰豫时间,并从微观结构上分析了产生驰豫时间差异的原因。     

基于磁场磁核分析的原油防蜡降粘机理

介绍了含蜡原油空间三维网状结构的形成机理及其研究进展,分析了磁场对石蜡磁性核的作用,研究了原油磁处理防蜡、降粘技术机理,并进行了试验验证。磁场作用下石蜡磁性核按能级规则取向排列,并绕磁场进动,改变了原油中石蜡的结晶过程,可以有效防止蜡晶形成三维网状结构,使石蜡结晶成核半径减小,结晶释放潜热增多,产生防蜡降粘的效果。     

预应力混凝土无梁屋盖的温度应力分析

预应力混凝土无梁屋盖在日照和季节温差作用下容易出现开裂现象，为了研究其裂缝成因，针对屋盖所处的工作环境，应用ABAQUS软件，建立了日照和季节温差作用下预应力混凝土无梁屋盖的有限元分析模型，计算得到其应力分布云图.计算表明：这类预应力混凝土无梁屋盖在日照作用下，裂缝主要出现在托板附近，方向平行于托板边缘，托板顶角处的裂缝方向与对应的托板对角线垂直；而在季节温差作用下，裂缝主要出现在后浇带附近，方向平行于托板边缘，且存在贯穿裂缝的可能.     

Labyrinthine pattern formation in magnetic fluids

A quasi two-dimensional drop of a magnetic fluid (ferrofluid) in a magnetic field is one example of the many systems, including amphiphilic monolayers, thin magnetic films, and type I superconductors, that form labyrinthine patterns. The formation of the ferrofluid labyrinth was examined both experimentally and theoretically. Labyrinth formation was found to be sensitively dependent on initial conditions, indicative of a space of configurations having a vast number of local energy minima. Certain geometric characteristics of the labyrinths suggest that these multiple minima have nearly equivalent energies. Kinetic effects on pattern selection were found in studies of fingering in the presence of timedependent magnetic fields. The dynamics of this pattern formation was studied within a simple model that yields shape evolutions in qualitative agreement with experiment.     

Spin selectivity in electron transmission through self-assembled monolayers of double-stranded DNA

In electron-transfer processes, spin effects normally are seen either in magnetic materials or in systems containing heavy atoms that facilitate spin-orbit coupling. We report spin-selective transmission of electrons through self-assembled monolayers of double-stranded DNA on gold. By directly measuring the spin of the transmitted electrons with a Mott polarimeter, we found spin polarizations exceeding 60% at room temperature. The spin-polarized photoelectrons were observed even when the photoelectrons were generated with unpolarized light. The observed spin selectivity at room temperature was extremely high as compared with other known spin filters. The spin filtration efficiency depended on the length of the DNA in the monolayer and its organization.     

Formation of magnetic single-domain magnetite in ocean ridge basalts with implications for sea-floor magnetism

Although magnetic data are the primary evidence for ocean floor spreading, the processes by which magnetic phases in ocean floor basalts are formed remain poorly constrained. Scanning transmission electron microscopic observations show that magnetic single-domain magnetite in sheeted dike basalts of Deep Sea Drilling Project hole 504B formed through oxidation-exsolution of ilmenite, exsolution of ulv?spinel lamellae, and recrystallization of end-member magnetite by interaction with convecting fluids. The data suggest that the sheeted dike basalts, with single-domain magnetite as an efficient and stable magnetic carrier, contribute significantly to sea-floor magnetism.     

Lizard reflectivity change and its effect on light transmission through body wall

Light transmission through the body wall of living, color-labile desert iguanas (Dipsosaurus dorsalis) was measured by spectrophotometry. In the dark phase, the body wall's absorption of ultraviolet light and visible light was approximately twice that of the body wall in the light phase. The shorter wavelengths of ultraviolet could penetrate the body wall in the light phase but not in the dark phase. The intensity and wavelengths of light which could penetrate the body wall without pigments are potentially mutagenic when judged by bacterial standards.     

Mesoscopic conductors and correlations in laser speckle patterns

Submicrometer disordered metallic systems at low temperatures display interesting conductance fluctuation effects, owing to the interference of coherent electron wave transmission through the system. This quantum interference phenomenon also gives rise to the striking experimental observation that the 1/f noise power (where f is frequency) in disordered conductors increases as the temperature is decreased, contrary to common intuition. The theoretical techniques developed for this problem can be applied to the transmission of light through a random medium, and this yields novel predictions for the correlations in the laser speckle patterns and the possibility of studying the positions and motions of scatterers in a medium which multiply scatter the probing light.     

微平面腔磁旋光相干增强特性研究

基于多光束相干叠加法研究了线偏振光经过微平面腔的磁旋光相干透射特性,分析得到微腔透射光强、腔共振条件、总磁旋光角及共振透射光强,并讨论了检测灵敏度、相对灵敏度及检测角量程等旋光角检测特性,研究表明在单程旋光角为零的极限情况下,相干磁旋光系统的相对检测灵敏度与微腔的锐度系数成正比。     

Observation of skyrmions in a multiferroic material

A magnetic skyrmion is a topologically stable particle-like object that appears as a vortex-like spin texture at the nanometer scale in a chiral-lattice magnet. Skyrmions have been observed in metallic materials, where they are controllable by electric currents. Here, we report the experimental discovery of magnetoelectric skyrmions in an insulating chiral-lattice magnet Cu(2)OSeO(3) through Lorentz transmission electron microscopy and magnetic susceptibility measurements. We find that the skyrmion can magnetically induce electric polarization. The observed magnetoelectric coupling may potentially enable the manipulation of the skyrmion by an external electric field without losses due to joule heating.     

磁处理对原油结蜡影响的机理分析

分析了磁处理对原油结蜡的影响因素,用石油胶体分散体系理论分析了原油结蜡过程,应用胶体化学中的"DLVO理论"解释了磁处理对原油结蜡的影响.分析认为,磁场通过对蜡晶分子间色散力的影响作用,致使蜡晶胶粒之间的范德华引力势能增大,从而促进了原油中蜡晶胶粒的聚结,这就是磁处理对原油凝胶结构产生影响从而降粘的基本原因.     

A light source smaller than the optical wavelength

A method has been developed for the efficient emission of light from subwavelength dimensions. It is based on packaging photons as molecular excitons, effectively reducing the volume of the light beam by 10(9) and making possible propagation through dimensions of 1 nanometer. Molecular microcrystals are grown in the tips of micropipettes that have inner diameters of 100 nanometers or less. Measurements are presented that demonstrate this improvement in transmission for pipettes of various diameters. The ultrasmall dimensions of these light sources, the wavelength range (ultraviolet to red) of their emission, their ease of production, and their expected unique abilities for high efficiency excitation-imaging of surfaces portend significant applications for this methodology.     

Vacuum-induced transparency

Photons are excellent information carriers but normally pass through each other without consequence. Engineered interactions between photons would enable applications as varied as quantum information processing and simulation of condensed matter systems. Using an ensemble of cold atoms strongly coupled to an optical cavity, we found that the transmission of light through a medium may be controlled with few photons and even by the electromagnetic vacuum field. The vacuum induces a group delay of 25 nanoseconds on the input optical pulse, corresponding to a light velocity of 1600 meters per second, and a transparency of 40% that increases to 80% when the cavity is filled with 10 photons. This strongly nonlinear effect provides prospects for advanced quantum devices such as photon number-state filters.