具有介孔结构的MnSiO_3@Fe_3O_4@C纳米粒子的制备以及作为pH响应的T_1-T_2~*双模MRI造影剂的研究应用（英文）

本文通过一个简单的、温和的方案制备了平均尺寸为120 nm,介孔结构的纳米粒子MnSiO_3@Fe_3O_4@C.粒子的细胞毒性微小,可以用作T_1-T_2~*双模MRI造影剂.酸性条件下MnSiO_3@Fe_3O_4@C释放出大量的Mn~(2+)缩短T_1弛豫时间,提高成像分辨率.超顺磁性的Fe304可以增强T_2对比成像,检测病变组织.类似于肿瘤微环境/细胞器的酸性PBS(pH=5.0)中Mn~(2+)的释放率达到31.66V,约为中性条件(pH=7.4)下的7倍.释放的Mn~(2+)通过内吞作用被细胞摄取,经肾脏排出,细胞毒性实验表明,MnSiO_3@Fe_3O_4@C具有低的细胞毒性,即使高浓度的200 ppm MnSiO_3@Fe_3O_4@C对HeLa细胞的毒性也相对较小.对荷瘤小鼠静脉注射定量MnSiO_3@Fe_3O_4@C后,可以观察到一个快速增强的对比成像,给药24 h后,T_1MRI信号显著增强,达到132%,而T_2信号则明显降低至53.8%,活体MR成像证明了MnSiO_3@Fe_3O_4@C可以同时作为阳性和阴性造影剂.此外,得益于介孔MnSiO_3优秀的酸敏感性,MnSiO_3@Fe_3O_4@C可以作为一种潜在的药物载体,实现肿瘤的诊疗一体化.     

磁响应Fe_3O_4@PS胶体光子晶体的制备及性能研究

本文首先通过共沉淀法制备油酸修饰的磁性Fe_3O_4纳米粒子,并将其均匀分散于正辛烷中得到磁流体,然后利用一步细乳液聚合法合成了单分散Fe_3O_4@PS磁性微球。扫描电镜分析结果表明,Fe_3O_4的粒径在13nm左右,所形成的Fe_3O_4@PS微球的粒径在120~150nm左右;VSM测试结果显示所合成的Fe_3O_4@PS微球具有超顺磁性,其饱和磁化强度约为25emu/g;Fe_3O_4@PS微球表面携带明显的负电荷,其表面Zeta电势为-60mV。反射光谱测试结果表明,Fe_3O_4@PS分散于水中形成的胶体溶液在磁场作用下呈现出明亮的结构色,具有明显的带隙特征;随着磁场强度的变化,反射峰波长可在450~650nm进行调谐。     

颗粒度对鞍山式铁矿反射光谱特征的影响研究

岩矿反射光谱的决定因素是其成分及含量,变异因素主要为颗粒度、粗糙度、观测角度、表面形态等。为明确颗粒度与鞍山式铁矿反射光谱之间的关系,采用SVC HR-1024便携式地物光谱仪对鞍山式铁矿的两种主要铁矿石(赤铁矿、磁铁矿)进行不同颗粒度下的可见光-近红外光谱测试,分析颗粒度对赤铁矿、磁铁矿反射光谱的影响规律,并明确颗粒度的敏感波段与稳定波段,为以后的定量反演工作提供参考。结果表明,颗粒度对赤铁矿、磁铁矿反射光谱的影响规律具有显著差异。当赤铁矿试样粒径由0.03 mm增加到1 mm时,光谱反射率随颗粒度增加而逐渐减小,二者呈现显著负相关关系。但是在不同的波段处,赤铁矿反射光谱受颗粒度的影响程度不同,在350~550 nm波段,反射光谱受颗粒度影响非常微弱,为赤铁矿反射光谱对颗粒度的稳定波段;在550~950 nm波段,反射光谱受颗粒度影响较微弱;在950~1 250 nm波段,反射光谱受颗粒度影响较显著;在1 250~2 500 nm波段,反射光谱受颗粒度影响非常显著,为赤铁矿反射光谱对颗粒度的敏感波段。当赤铁矿试样粒径大于1 mm之后,赤铁矿反射光谱多重叠,受颗粒度影响显著减弱,且二者无明显相关性。当磁铁矿试样粒径由0.03 mm增加到4 mm时,磁铁矿反射光谱对颗粒度的响应非常微弱,颗粒度引起的光谱反射率变化不超过3%,且颗粒度与磁铁矿反射光谱间无相关性,二者间联系微弱。该研究揭示了颗粒度对鞍山式铁矿反射光谱的影响规律,定量分析了颗粒度对赤铁矿、磁铁矿反射光谱的影响程度,并确定了颗粒度与试样反射率符合的函数分布关系,为提高鞍山式铁矿的品位反演精度奠定了良好基础。     

金纳米流体的电场可调光学性质

利用多次还原法制备了不同粒径的金纳米颗粒,SEM和粒度分析表明其平均粒径分别为11 nm,35 nm和58 nm.进一步通过表面活性剂辅助的液相转移法制备出不同粒径的油基金纳米流体,测试了金纳米流体在电场作用下的光学性质.结果表明金纳米流体在电场作用下表现出明显的双折射现象,且随电场强度的变化双折射具有可调节性.金颗粒粒径和浓度对折射率有明显影响,在实验采用的浓度范围内,折射率随金颗粒浓度和粒径的增加而减小.最后,利用电流变液结构转变机理对金纳米流体的电致双折射进行了分析. 关键词： 纳米流体 双折射 电流变液     

吸附作用在纳米颗粒悬浮液换热强化中的试验与机理研究

本文通过测量SiO_2纳米颗粒在不同工质、不同浓度的悬浮液在不同温度下的导热系数,结合了液氮冷冻、切割并在断面上复形的技术,并利用电镜观察了纳米颗粒在液体中的分布、团聚和液体与之的亲和性。着重分析了纳米颗粒悬浮液中SiO_2纳米颗粒与液体的亲和性对悬浮液导热性能影响的机理。文中提出了SiO_2纳米颗粒的表面吸附层和在作布朗运动时出现”微对流”而使悬浮液换热强化。     

浓悬浮液中纳米SiO_2团聚体的渗透率

本文基于悬浮液中渗透性颗粒的短时扩散动力学理论,采用低相干光纤动态光散射方法,测量了相同粒径的纳米SiO_2团聚体在不同体积分数时的扩散系数,利用扩散系数随渗透率的变化关系得到纳米SiO_2团聚体的渗透率.结果表明:恒温条件下,具有一定渗透率的团聚体颗粒扩散得比硬球颗粒快.实验测量得到的团聚体渗透率与采用photoshop CS6对团聚体SEM图像进行处理计算得到的渗透率符合较好.     

红色荧光粉Na8.33 La1.67(SiO4)6 O2:Eu3+的制备及发光特性

采用高温固相法制备了Na_(8. 33)La_(1. 67)(SiO_4)_6O_2∶Eu~(3+)红色发光材料,利用X射线衍射仪测定其晶体结构,利用Hitachi F4600表征其发光光谱。在紫外光激发下,样品Na_(8. 33)La_(1. 67)(SiO_4)_6O_2∶Eu~(3+)呈多峰发射,分别对应于Eu~(3+)的~5D_0-~7F_j(j=0,1,2,3,4)能级跃迁,主峰是位于615 nm的~5D_0-~7F_2跃迁发射。研究了Eu~(3+)掺杂浓度对材料发光性质的影响,改变Eu~(3+)掺杂浓度,样品的发射强度随之改变,Na_(8. 33)La_(1. 67)(SiO_4)_6O_2∶Eu~(3+)材料的Eu~(3+)浓度为15%时,发光强度最大。讨论了浓度猝灭的机理,理论计算表明引起Eu~(3+)离子能量弥散的主要原因是离子间交换相互作用。     

Ag@Fe_3O_4@C-CdTe@SiO_2磁性荧光复合微球的制备与光学特征（英文）

先采用一步溶剂热法和水热法制备了碳包覆的Ag@Fe_3O_4核壳型磁性纳米粒子,然后通过表面氨基化改性后与巯基乙酸修饰的CdTe量子点反应,将量子点键合到磁性微球上,最后在其表面包覆上一层二氧化硅壳层,制备出具有荧光增强的Ag@Fe_3O_4@C-CdTe@SiO2磁性荧光复合材料。实验结果表明,该纳米粒子的平均粒径大约为150nm,磁饱和强度为224A/g(22.4emu/g),在室温下具有较好的磁性能。其中Ag@Fe_3O_4@C-CdTe磁性荧光纳米粒子的荧光强度大于Fe_3O_4@C-CdTe,其主要原因是内核为45nm的Ag纳米粒子具有表面等离子体共振作用,能够使其表面或附近的量子点荧光得到增强。     

应用低相干动态光散射法测量悬浮液中的颗粒粒径分布

利用低相干动态光散射法测量不同浓度悬浮液中的颗粒粒径分布。由低相干光源和迈克尔逊干涉仪,结合传统的动态光散射技术组成低相干动态光散射装置,通过检测单次背散射光的能谱分布,利用CONTIN算法得到不同浓度悬浮液中颗粒的粒径分布。结果表明,对于1%～10%体积浓度范围内的单分散悬浮液羊品测量得到的颗粒粒径精确度在4%以内。     

新型Ba3SiO5:Eu荧光粉的合成及光谱性质

以BaCO_3、SiO_2、Eu_2O_3为原料在还原气氛下采用高温固相法制备了Ba_3SiO_5∶Eu荧光粉体。实验结果表明,制备Ba_3SiO_5的最佳工艺条件是Ba/Si比为3,1 200℃保温4 h。光谱分析表明,Ba_3SiO_5∶Eu荧光粉在254,365,410 nm激发下发射主峰为566 nm(Eu~(2+)的4f~n~(-1)5d→4f~n)宽带发射,量子效率分别为70%、50%、10%,荧光寿命为百纳秒级;以566 nm为监视波长测得激发谱为主峰在250～450 nm范围内的宽带发射,主峰为360 nm,且在410 nm出现小峰; Eu离子最佳掺杂浓度为5%,由发光强度随掺杂离子浓度变化曲线,可以得出Ba_3SiO_5中Eu离子能量传递是基于电四级-电四级作用。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.