Second harmonic magnetoacoustic responses of magnetic nanoparticles in magnetoacoustic tomography with magnetic induction

Due to the unique magnetic, mechanical and thermal properties, magnetic nanoparticles(MNPs) have comprehensive applications as the contrast and therapeutic agents in biomedical imaging and magnetic hyperthermia. The linear and nonlinear magnetoacoustic responses determined by the magnetic properties of MNPs have attracted more and more attention in biomedical engineering. By considering the relaxation time of MNPs, we derive the formulae of second harmonic magnetoacoustic responses(2H-MARs) for a cylindrical MNP solution model based on the mechanical oscillations of MNPs in magnetoacoustic tomography with magnetic induction(MAT-MI). It is proved that only the second harmonic magnetoacoustic oscillations can be generated by MNPs under an alternating magnetic excitation. The acoustic pressure of the 2H-MAR is proportional to the square of the magnetic field intensity and exhibits a linear increase with the concentration of MNPs. Numerical simulations of the 2H-MAR are confirmed by the experimental measurements for various magnetic field intensities and solution concentrations using a laser vibrometer. The favorable results demonstrate the feasibility of the harmonic measurements without the fundamental interference of the electromagnetic excitation, and suggest a new harmonic imaging strategy of MAT-MI for MNPs with enhanced spatial resolution and improved signal-to-noise ratio in biomedical applications.     

金属Al背电极二维AZO光栅的制备和陷光特性

研究了背电极金属Al膜上二维ZnO:Al光栅的制备及其反射光谱特性.在厚度为300 nm的Al膜上溅射80 nm ZnO:Al薄膜,旋涂AZ5206光刻胶,用波长为325 nm的激光进行光刻制作光栅掩模.采用溶脱-剥离法在Al衬底上制备周期(624~1250 nm)和槽深(100~300 nm)可独立调控的ZnO:Al二维光栅.表面形貌采用原子力显微镜和扫描电镜观察,反射光谱用带积分球的分光光度计测试,双向反射分布函数用散射仪测量.结果表明,300 nm Al膜上织构二维ZnO:Al光栅背电极结构,当光栅槽深为228 nm,周期从624 nm增加到986 nm时,背电极总反射率、漫反射率以及雾度均随光栅周期增大而显著增加,而当周期从986 nm增加到1250 nm时,总反射率、漫反射率以及雾度略有增加.双向反射分布函数测试结果进一步证实了上述实验结果,即随着周期增大,漫反射峰值越大,衍射峰个数也增多.提示背反电极上槽深为228 nm、周期为986 nm的二维ZnO:Al光栅具有较好的散射效果,其中漫反射占总反射的百分比为45%.     

基于锥面衍射实现高效率双光栅光谱合成

分析了基于锥面衍射的双光栅光谱合成系统的可行性,设计了激光入射角为Littrow角附近的双多层介质膜（MLD）光栅光谱合成系统,开展了两路合成实验。当入射极角等于自准直入射角,入射方位角为6°时,光栅衍射效率近似等于光束自准直入射时的衍射效率。基于锥面衍射原理,对中心波长为1050.24 nm和1064.33 nm的两束光纤激光子束进行合成,入射极角为43.99°,测得合成效率为92.9%,较基于非锥面衍射的双光栅光谱合成系统的合成效率提高了8.8%;测得合成光斑光束质量M_x²＝1.204,M_y²＝1.467,与基于非锥面衍射的双光栅光谱合成系统输出光斑光束质量基本一致。     

K-invariants in the universal enveloping algebra of the desitter group

Let G be a non-compact connected semisimple Lie group with finite center and let G^K denote the centralizer of a maximal compact subgroup K of G inG, the universal enveloping algebra over of the Lie algebra of G. In [4] Lepowsky defines an injective anti-homo morphism P:G ^KK ^MA, where M is the centralizer in K of a Cartan subalgebraa of the symmetric pair (G,K),K andA are the universal enveloping algebras over corresponding to K anda, respectively, andK ^M is the centralizer of M inK. The subalgebra P(G ^K) ofK ^MA has considerable significance in the infinite dimensional representation theory of G. In this paper we explicitly compute P(G ^K) when G=S0_o(4,1), and show how this result leads to the determination of all irreducible representations of G and its universal covering group Spin(4,1).Partially supported by CONICET (Argentina) grants.     

Periodic solutions of semilinear partial differential equations of parabolic type

Summary In this paper we obtain necessary and sufficient conditions for the existence of solutions of a class of periodic-Dirichlet problems for parabolic- partial differential equations. The structure of the solution set and the asymptotic behaviour of the solution is also studied.Entrata in Redazione il 17 giugno 1983.     

乙基苯胺的转动光谱及分子结构

本文使用傅里叶变换微波谱仪研究了乙基苯胺类物质(邻乙基苯胺,间乙基苯胺,对乙基苯胺)的分子结构. 由于此类分子含氮原子(I¹⁴N=1),因此跃迁谱线中都呈现出核四级裂分. 通过比较实验测定得到的分子结构,可总结苯胺环上不同位置乙基的取代对氨基及分子整体结构的影响.     

碳纳米纤维负载Co3S4复合材料的合成及其在染料敏化太阳电池对电极的应用

采用水热法合成四硫化三钴（Co₃S₄）催化材料,并利用球磨和喷涂技术将其制备成对电极,结合新型无碘电解液Co²⁺/Co³⁺用于染料敏化太阳电池（dye-sensitized solar cells,简称DSCs）来研究其光电性能。测试结果显示,基于Co₃S₄对电极,DSCs的能量转化效率（power conversion efficiency,简称PCE）只有6.06%,远远低于Pt对电极（8.05%）。为了提高Co₃S₄的催化能力,采用静电纺丝技术制备碳纳米纤维（electrospun carbon nanofibers,简称ECs）,结合水热法制备出不同负载量的碳纳米纤维负载四硫化三钴（Co₃S₄/ECs）复合催化材料用于对电极,结果表明,Co₃S₄/ECs的PCE最高可达（8.22±0.08）%,优于Pt对电极。     

Algebraic study of chiral anomalies

The algebraic structure of chiral anomalies is made globally valid on non-trivial bundles by the introduction of a fixed background connection. Some of the techniques used in the study of the anomaly are improved or generalized, including a systematic way of generating towers of descent equations.This work was supported in part by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Division of High Energy Physics of the U.S. Department of Energy under contract DE-AC03-76SF00098 and in part by the National Science Foundation under research grant PHY81-18547