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排序方式: 共有282条查询结果,搜索用时 15 毫秒
81.
《Journal of Coordination Chemistry》2012,65(15):2520-2531
A new binuclear zinc(II) complex bridged by μ-oxalate, and end-capped with 2,2′-bipyridine (bpy), [Zn2(ox)(bpy)4](ClO4)2 · H2O, has been synthesized and characterized by elemental analyses, molar conductance, IR, and electronic spectra and single-crystal X-ray diffraction. The single-crystal X-ray analysis reveals that the [Zn2(ox)(bpy)4]2+ cation has two zinc(II) centers bridged by a planar bis(bidentate) oxalate group with Zn···Zn distance of 5.482(3) Å; each zinc(II) is in a distorted octahedral environment. The crystal structure is stabilized by non-classical C–H···O hydrogen bonds and π–π stacking interactions to form a 3-D supramolecular structure. The interaction of the complex with calf-thymus DNA (CT-DNA) was explored by using electronic and fluorescence spectra and viscosity measurements. The results reveal that the complex intercalates with CT-DNA with intrinsic binding constant of 4.1 × 104 M?1. 相似文献
82.
Pritha Talukder Shyamapada ShitAshok Sasmal Stuart R. BattenBoujemaa Moubaraki Keith S. MurraySamiran Mitra 《Polyhedron》2011,30(11):1767-1773
A novel hexanuclear complex [{(CuL)2Cu}2(μ-dca)2](ClO4)2·2L′(1) (where H2L = (OH)C6H4C(CH3)N(CH2)3NC(CH3)C6H4(OH) or N,N′-bis(2-hydroxyacetophenone) propylenediimine and dca = N(CN)2− and L′ = 2-hydroxyacetophenone) has been synthesized and characterized by elemental analysis, UV-Vis, FT-IR spectroscopic and electrochemical methods. Single crystal X-ray structural characterization reveals a centrosymmetric nature of the complex unit, where the metal centers adopt distorted square-planar and distorted octahedral geometries. Structural analysis also reveals μ2-phenoxo bridges between terminal and the central copper(II) centers of the asymmetric [(CuL)2Cu(dca)] unit, the latter being interconnected to its symmetry related counterpart by double μ1,5-dca bridges, leading to the hexanuclear complex ion [{(CuL)2Cu}2(μ-dca)2]2+. Low temperature susceptibility measurements of 1 revealed the presence of strong antiferromagnetic coupling (2J = −407 cm−1) between the copper(II) centers. 相似文献
83.
Ali Akbar Asgharinezhad Homeira EbrahimzadehFatemeh Mirbabaei Narges MollazadehNafiseh Shekari 《Analytica chimica acta》2014
In this study, diverse types of Fe3O4 nanocomposites modified by polyaniline, polypyrrole, and aniline–pyrrole copolymer were synthesized through chemical oxidative polymerization process for dispersive-μ-solid phase extraction (D-μ-SPE) in the presence of various dopants. The results showed that the nanocomposite modified by polyaniline with p-toluene sulfonic acid as a dopant demonstrated higher extraction efficiency for lorazepam (LRZ) and nitrazepam (NRZ). Also the synthesized magnetic sorbents were characterized. The nanocomposite sorbent in combination with high performance liquid chromatography–UV detection was applied for the extraction, preconcentration and determination of lorazepam and nitrazepam in urine and plasma samples. Different parameters influencing the extraction efficiency including: sample pH, amount of sorbent, sorption time, elution solvent and its volume, salt content, and elution time were optimized. The obtained optimal conditions were: sample pH, 6; amount of sorbent, 5 mg; sorption time, 5.0 min; elution solvent and its volume, 0.5 mM cethyltrimethyl ammonium bromide in acetonitrile, 150 μL; elution time, 2.0 min and without addition of NaCl. The calibration curves were linear in the concentration range of 1–2000 μg L−1. The limits of detection (LODs) were achieved in the range of 0.5–1.8 μg L−1 for NRZ and 0.2–2.0 μg L−1 for LRZ, respectively. The percent of extraction recoveries and relative standard deviations (n = 5) were in the range of 84.0–99.0, 6.1–7.8 for NRZ and 90.0–99.0, 4.1–7.0 for LRZ, respectively. Ultimately, the applicability of the method was successfully confirmed by the extraction and determination of NRZ and LRZ in human urine and plasma samples. 相似文献
84.
The reaction of diaminotetrachloro-cyclotriphosphazene with tetrachloride of μ-imino-diphosphoric acid leads to the formation of the salt-like compound [P3N3HCl4(NH2)2]+[N(POCl2)2]− which identity was unambiguously established by means of X-ray structure analysis. The structure is composed of [P3N3HCl4(NH2)2]+ cations and [N(POCl2)2]− anions joined by a system of H-bonds. As in other phosphazenium salts, the protonation of the ring N atom leads to significant changes in the endocyclic P N bond lengths. 相似文献
85.
A 2-μm composite Tm:YAG laser pumped with a narrow-band laser diode was presented. The temperature distribution and thermal lens in the Tm:YAG were numerically simulated by a finite element method and the results were used to design the special cavity, in order to achieve a high efficiency and stable output. With a 25-W incident pump power, we obtained a maximum output power of 11 W at 2018.5 nm, corresponding to a slope efficiency of 51.3% and an optical-to-optical efficiency of 44.5%, respectively. The beam quality was measured to be M_x~2= 1.8 and M_y~2= 1.6. 相似文献
86.
建立了同时测定川贝枇杷糖浆中6种有效成分(桔梗皂苷D、贝母辛、齐墩果酸、西贝素、贝母甲素和贝母乙素)含量的微流蒸发光散射检测器(μELSD)与加压毛细管电色谱(pCEC)联用检测方法。搭建pCEC-μELSD联用平台,采用C18毛细管色谱柱(EP-150-15-3-C18),流动相为乙腈(A)-10mmol?L-1甲酸-三乙胺水溶液(pH11.0)(B),梯度洗脱,柱流速为1.02μL?min-1,施加电压为+10kV,雾化载气流速为0.4L?min-1,蒸发温度为40℃。川贝枇杷糖浆中6种有效成分可在10min内得到分离检测,6种有效成分的线性范围可达4个数量级,检出限均在pg水平,加标回收率为97.9%~103.0%。所建立的pCEC-μELSD联用方法精密度、重复性和稳定性良好,且简便、快速、可靠,可用于川贝枇杷糖浆中6种有效成分的含量测定。 相似文献
87.
通过优化定距射击样本采集条件,考察了六四手枪在不同距离(0,2,5,10,15,20,25,30,35,40,45,50,60,80,100,120,140,170,200,300,500,1000cm)垂直射击PU布块靶体时相关元素(氯、钾、硫、锑、锡、钡、铅、汞、砷、铁、铜、锌、钛、钙、铑)的区域扫描图,建立了微束X射线荧光光谱(μ-XRF)面扫描技术分析射击样本的方法,并建立了六四手枪射击残留物特征元素分布图形随射击距离而变化的数据模型,同时对所得数据进行了归一化处理。本方法可协助推断射击距离,为涉枪案件的侦查与诉讼提供科学证据。 相似文献
88.
Utz Kramar Markus Harting Karen Rickers Doris Stüben 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007
Synchrotron radiation, collimated to a μm scale was used for the determination of trace elements in micro-tektites and spherule material for the first time. The experimental set-up of the SXRF microprobe at beamline L at HASYLAB at DESY offers a suitable method for performing non-destructive in situ multi-element analysis focusing on spatial trace element distributions and mineral phases of the melted ejecta material from the Cretaceous/Tertiary boundary. The spatial distribution of trace elements was determined in melt inclusions as well as in phase transitions in selected parts of chlorite–smectite spherules and tektite glass material by using a beam with a diameter of 15 μm collimated with a glass capillary for line- and area scans as well as for single point measurements for elements with Z between 19 and 92. The analyzed spherules show alteration features but also zonation and carbonate inclusions, originating from the Chicxulub impact event. These initial results demonstrate the potential of μ-SXRF analysis for the discrimination of alteration and primary signals of the spherules and re-construction of their genetic evolution. It could be shown that the spherules represent a complex mixture of different materials from the subsurface at the Chicxulub impact site. 相似文献
89.
We report a compact and efficient LD end-pumped linearly polarized Nd:YAP laser operating at 1.34 μm. The laser system with different crystal lengths, output couplers and cavity types were compared. Based on optimizing of the pump system and laser cavity, 6.2 W laser radiation at 1341.4 nm with c-axis polarized was achieved, corresponding to an optical conversion efficiency of about 24.8% with respect to the incident pump power. The laser threshold was only about 1.3 W and the optical slope efficiency was up to 27.2%. 相似文献
90.
半群中的(λ,μ)-模糊理想 总被引:1,自引:1,他引:1
在半群中给出了(λ,μ)-模糊子半群和各种(λ,μ)-模糊理想的概念,讨讹了它们的一些性质,并给出了各种(λ,μ)-模糊理想的充分必要条件. 相似文献