Magneto-transport properties of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction

Hole-doped rare-earth manganite La_0.7Ca_0.3MnO₃ and the electron-doped manganite La_0.7Ce_0.3MnO₃ both show a metal-insulator transition around 250 K associated with a ferromagnetic transition and colossal magnetoresistance. In an earlier publication we have reported the rectifying characteristic of La_0.7Ca_0.3MnO₃/SrTiO₃/La_0.7Ce_0.3MnO₃ tunnel junction at room temperature, showing that it is possible to fabricate a diode out of the polaronic insulator regime of doped manganites. Here we report the magneto-transport properties of such a tunnel junction above and below the metal-insulator transition. We show, from the large positive magnetoresistance of the tunnel junction at low temperature, that La_0.7Ce_0.3MnO₃ could be a minority spin carrier ferromagnet. The implication of this observation is discussed.     

Diliberto–Straus algorithm for the uniform approximation by a sum of two algebras

In 1951, Diliberto and Straus [5] proposed a levelling algorithm for the uniform approximation of a bivariate function, defined on a rectangle with sides parallel to the coordinate axes, by sums of univariate functions. In the current paper, we consider the problem of approximation of a continuous function defined on a compact Hausdorff space by a sum of two closed algebras containing constants. Under reasonable assumptions, we show the convergence of the Diliberto–Straus algorithm. For the approximation by sums of univariate functions, it follows that Diliberto–Straus’s original result holds for a large class of compact convex sets.     

Bestimmung von Corticosteroiden im Blut durch Doppelmarkierung und Messung von 14C und 3H in der Gasphase

Ohne ZusammenfassungAuszug aus der Dissertation Reinhard Ködding, Technische Hochschule München 1961.     

制备大直径无气泡聚苯乙烯空心微球

 高品质聚苯乙烯（PS）空心微球是惯性约束聚变（ICF）实验用多层塑料微球靶的重要芯轴,常由乳液技术制备。针对由乳液技术制备的PS微球壳壁内容易形成气泡而且大直径微球制备困难的问题,实验研究了对壳壁内存在的气泡以及消除方法和制备大直径PS微球的制备技术。     

Measurement of Titanium and Manganese K -shell Ionization Cross Sections by Electron Impact

报道了电子引起的钛、锰原子的Ｋ壳层电离截面实验值。实验中,采用了薄靶厚衬底技术,并将衬底中反射的电子对测量值的影响进行了修正。实验结果与其他文献报道的测量结果相吻合。最后,还将实验结果与Ｃａｓｎａｔｉ等人的经验公式进行了比较。     

The role of the longitudinal component of the electric field vector in two-wave mixing in photorefractive BaTiO3

It is shown that for waves incident with a polarisation in the plane of the grating the component of the electric field in the direction of propagation must be included in the calculations. Coupled differential equations for both the transverse and longitudinal components are derived for wave interaction in photorefractive BaTiO₃. Analytic solutions for the electric field of the signal wave are obtained under the assumption that the pump wave is undepleted. For the parameters considered the longitudinal component is shown to be negligible.     

Preparation,characterization, and binding profile of imprinted semi-IPN cryogel composite for aluminum

Human body is greatly exposed to aluminum due to its high abundance in the environment. This nonessential metal is a threat to the patients of chronic renal disorders, as it is easily retained in their plasma and quickly accumulates in different tissues. Thus, there is great need to remove it from the aqueous environment. In this study, Al³⁺ imprinted semiinterpenetrating polymer network (semi-IPN)-based cryogel composite was prepared and applied for the purification of environmental and drinking water samples from aluminum. Poly (2-hydroxyethyl methacrylate) (pHEMA) discs were produced via cryogenic treatment and imprinted semi-IPN was introduced to the 3-(trimethoxysilyl) propyl acrylatemodified macroporous cryogel discs. The adsorption properties and selectivity of the aluminum (III) imprinted semi-IPN cryogel composite were studied in detail. The imprinted semi-IPN cryogel composite showed good selectivity towards aluminum (III) ions with the imprinting factor (IF) of 76.4 in the presence of competing copper (II), nickle (II), and iron (III) ions. The maximum adsorption capacity of 271 μmol g^-1 was obtained for aluminum (III) at pH 7.0 within 10 min using imprinted semi-IPN cryogel composite. The good selectivity and reusability of aluminum (III)-imprinted semi-IPN cryogel composite makes this material an eligible candidate for the purification of drinking water from aluminum (III) leaving important minerals remained in the water.     

温度与应变率对钽流动应力的影响

 研究了温度在-100～400 ℃、应变率在10^-5～10³ s^-1范围内温度和应变率的变化对钽的流动应力的影响。结果表明,钽的流动应力对温度和应变率的变化相当敏感。同时还就两种本构模型对钽的温度效应与应变率效应的不同处理方法作了比较,指出Zerilli-Armstrong模型能更好地描述温度与应变率对钽流动应力的影响。     

冲击波作用下CHBr3/NaCl界面热弛豫特性研究

非透明材料冲击温度测量是通过对界面光辐射历史的观察实现的 ,因此对界面光辐射历史的研究是非透明材料冲击温度测量的基础。但由于冲击阻抗的失配导致界面上出现波的反射而引起温度的变化与界面热流动产生的温度变化交杂在一起 ,以及过程的瞬时性 ,使得对这一过程的实验研究显得非常困难。设计了一种界面波阻抗近似相同的特殊实验装置 ,用光辐射测量技术研究了在冲击压缩下CHBr3/NaCl界面的热弛豫过程。实验结果和理论分析表明CHBr3/NaCl界面的热弛豫时间在纳秒量级 ,与Grover等人的理论预估一致。