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61.
62.
The crystat structure of {[Er_2(L—Glu)_2(H_2O)_6](ClO_4)_2·3H_2O)_2 has been studied by X-ray diffraction. The crystal is monoctinic with space group P2_1 and cell parameters a=19.987(3) , b=16.505(3) , c=11.040(2) , β=104.69(1)~o, V=3538(1) , Z=2, Dc=2.29 g. cm~(-3), μ=53.2 cm~(-1), F(000)=2384. The asymmetric unit contains two complex motecules and four centre ions. Each erbium (Ⅲ) is coordinated by five oxygen donors from four different glutamates and four oxygen donors from the aqua ligand to form a nine coordination potyhedron. The mean distances of Er—0 (carboxylate) and Er—Ow are 2.439 and 2.41 respectivety. The finat R and Rw are 0.043 and 0. 058, respectivety. 相似文献
63.
The high precision calibration of optical trap stiffness is the foundation of the weak force measurement in an optical tweezers system. And the accuracy of the trap stiffness measurement is limited by the bandwidth of the acquisition system. In this article, such an influence is analyzed and discussed. The stiffness measuring process using an acquisition system with a finite acquisition time is numerically simulated by using Monte-Carlo method. Then the simulated results are analyzed by thermal motion analysis method to deduce the trap stiffness for different trapping system and for measuring systems with different acquisition time. As a comparison the power spectrum analysis method is used to study the thermal motion of the bead and to compute the trap stiffness for the same acquisition system, from which it is concluded that the bandwidth of the acquisition system is determined by its acquisition time, not the sampling frequency. The influence of the finite acquisition time or the limited bandwidth on the trap stiffness measurement is discussed. The numerical simulation shows that the measured position, which is here the average position within the acquisition time, shifts to the trap center due to the trapping force, which gives an alternative interpretation for the deviation of the measured stiffness from the true trap stiffness. 相似文献
64.
杂环息夫碱化合物及其过渡金属配合物的合成与表征 总被引:5,自引:0,他引:5
本文合成了一种新的双齿(N,O)杂环息夫碱2-(2′-羟基)苯甲亚胺-5-(4′-硝基)偶氮苯吡啶(HL)与过渡金属的六种新配合物ML_2及M′L_3 [M=Mn(Ⅱ)、Co(Ⅱ)、Ni(Ⅱ)、Cu(Ⅱ)、Pd(Ⅱ);M′=Fe(Ⅲ)].采用元素分析、摩尔电导、红外光谱、紫外—可见光谱、磁化率以及热分析等研究了配合物的组成和性质. 相似文献
65.
采用水热法制备出Ca_9Y(PO4)7∶Ce~(3+),Tb~(3+)纳米荧光粉,通过XRD、SEM和荧光光谱等对样品进行了分析,研究在Ca_9Y(PO4)7基质中引入Ce~(3+),Tb~(3+)离子对发光性能的影响规律。研究发现因Tb~(3+)离子自身能量交叉驰豫的存在,使得单掺Tb~(3+)时,通过调节Tb~(3+)离子的浓度可以实现对发光颜色的控制。同时研究了Ce~(3+)-Tb~(3+)之间的能量传递为电多极相互作用的偶极-四极机制,Ce~(3+)-Tb~(3+)之间最大的能量传递效率为55.6%。Ca_9Y(PO4)7∶Ce~(3+),Tb~(3+)的发光颜色可以通过激活离子之间的能量传递和共发射得到可控调节。SEM分析表明荧光粉颗粒尺寸在100 nm左右,分散性好。 相似文献
66.
Zan Yao 《Journal of magnetism and magnetic materials》2009,321(3):203-206
Phase structure and magnetic properties of the as-cast and as-milled/annealed SmCo7−xMox (x=0, 0.1, 0.2, 0.3, 0.4) alloys have been systematically studied. It is found that all the as-cast series alloys are composed of the CaCu5-type and Th2Zn17-type phases. Saturation magnetization of the samples decreases with the Mo content increasing. Intrinsic coercivities (iHc) of no more than 0.06 T are observed in these as-cast samples, due to their rather coarse grain microstructures with an average grain size of 50 μm. The as-milled/annealed SmCo7−xMox powders crystallize in the disordered TbCu7-type (1:7) structure with very fine nanograins, and a minor Co3Mo phase appears in the samples with x=0.1-0.4. High iHc (?0.95 T) are achieved in these samples, with a maximum of 1.26 T located at x=0.2, which can be primarily attributed to strong pinning of the domain wall motion at the nanograin boundaries. The temperature coefficient (β) of the iHc is about −0.22%/°C in the temperature range of 25-400 °C for the as-milled/annealed samples. 相似文献
67.
Using ionic liquid as extraction solvent and 2,4-dinitrophenylhydrazine (DNPH) as derivative agent, formaldehyde in shiitake mushroom was determined by liquid-phase microextraction coupled with high-performance liquid chromatography (HPLC). Shiitake mushroom was leached with water and filtrated, then the formaldehyde in filtrate was derivatized with DNPH and extracted simultaneously into a 10 μl drop of ionic liquid suspended on the tip of the microsyringe, and finally injected into the HPLC system for determination. The proposed procedure has a detection limit of 5 μg l−1 formaldehyde in extraction solution, thus the mushroom sample filtrate could be diluted with a large ratio to eliminate the influence of sample matrix. The method has a relative standard deviation of 3.5% between days for 53.5 μg l−1 formaldehyde standards. High contents of formaldehyde (119-494 μg g−1 wet weight), which is harmful for human beings, were detected in shiitake mushroom. Therefore, strategies must be taken to prevent the accumulation and strictly control the content of formaldehyde in shiitake mushroom. 相似文献
68.
将可交联的苯乙炔结构引入到热塑性聚芳醚酮链中, 并对其交联前后的性能进行了深入研究. 相似文献
69.
A method based on cloud point extraction was developed to determine four kinds of estrogens: estriol (E3), estradiol (E2), estrone (E1), and progesterone (P) in water by high performance liquid chromatography separation and ultraviolet detection (HPLC-UV). The non-ionic surfactant Triton X-114 was chosen as extractant solvent. The parameters affecting extraction efficiency, such as concentrations of Triton X-114 and Na2SO4, equilibration temperature, equilibration time and centrifugation time were evaluated and optimized. Under the optimum conditions, preconcentration factors of 99 for E3, 73 for E2, 152 for E1 and 86 for P were obtained for 10 mL water sample. The detection of limitation was 0.23 ng mL−1 for E3, 0.32 ng mL−1 for E2, 0.25 ng mL−1 for E1 and 5.0 ng mL−1 for P. The proposed method was successfully applied to the determination of trace amount of estrogens in wastewater treatment plant (WWTP) effluent water and exposure water with 10 ng mL−1 E2 for toxicological study in our lab. For the case of WWTP effluent water samples, no estrogen was found. The accuracy of the proposed method was tested by recovery measurements of spiked samples and good recoveries of 81.2-99.5% were obtained. 相似文献
70.
本文继续文献[1~2]的研究,首先引进了生态系统的系综概念,在此基础上比较详细地讨论了生态协同学的微观方法和宏观方法.将这二者结合起来,利用生态系统输出(或可以测得)的宏观数据,建立广义金兹堡-朗道方程(GGLE),把握广义相变(群落演替)前后的信息变化,找出其微观对客观结果的作用机制,这也许是对复杂生态系统作用机制研究的一条新途径. 相似文献