993 resultados para 235
Resumo:
采用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)技术,分别对两种合成的聚芳醚酮环状低聚物和两种芳香族大环预聚体进行了分析研究,并讨论了上述聚合物中不同聚合度离子组份的分布规律,对它们的结构进行了确认.实验结果表明,MALDI-TOF-MS是分析上述聚合物直观、准确、快速的分析工具.
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根据经典热力学和动力学两方面理论 ,推导出了聚合物熔体在强静电场作用下成核率和晶核长大率的表达式 ,从理论上解释了聚合物熔体在强静电场作用下的结晶行为.
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Five new organotin compounds were synthesized and characterized, X-ray crystal structure analysis of (Z)-3-triphenylstannyl-1,1-diphenyl propenol was performed, The crystal belongs to space group P2(1)/n. The cell parameters are: a = 1.235 7(2) nm, b = 0.987 4(2) nm, c = 2.208 1(4) nm, beta = 95.23(3)degrees, V = 2.683 0(9) nm(3), Z = 4, R = 0.027 9, R-w = 0.064 5. The tin atom of the molecule exists in a distorted tetrahedron, Z isomer of double bond is obtained.
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The plastic zone size and crack opening displacement of phenolphthalein polyether ketone (PEK-C) at various conditions were investigated. Both of them increase with increasing temperature (decreasing strain rate), i.e. yield stress steadily falls. Thus, the mechanism increasing the yield stress leads to increased constraint in the crack tip and a corresponding reduction in the crack opening displacement and the plastic deformation zone. The effect of the plastic deformation on the fracture toughness is also discussed.
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The ansa-zirconocene derivative tetramethyldisiloxandiyl bis(1-indenyl) zirconium dichloride (1) has been prepared by the reaction of the dilithium salt of 1,3-bis(l-indenyl) tetramethyldisiloxane with ZrCl4 . 2THF, After catalytic hydrogenation, the corresponding tetrahydroindenyl complex (2) has been formed. Both 1 and 2 have been shown by H-1 NMR spectra to be the mixture of the cis(meso) and trans(rac) isomers, The pure trans isomers 1(l), 2(l) and cis isomer 2(c) were obtained by recrystallization, The crystal structures of 1(l) and 2(c) were determined by X-ray diffraction. Both crystals of 1(l) and 2(c) are monoclinics, belonging to space groups P2(1)/n(1(l)) and P2(1)/c(2(c)). In the unit cell of 2(c), one of the six-membered rings of the tetrahydroindenyl Ligands has two different conformations which have the same probabilities.
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1,3-二(1-茚基)四甲基二硅氧烷相继与丁基锂及ZrCl_4·2THF作用,生成硅氧硅桥联二(1-茚基)二氯化锆(Me_2SiOSiMe_2)[Ind]_2ZrCl_2(1)。对其进行催化氢化得到相应的四氢茚基化合物(Me_2SiOSiMe_2)[IndH_4]_2ZrCl_2(2)。1和2均含有顺式和反式二种异构体(1_c和1_t以及2_c和2_t),通过重结晶得到纯的单一异构体1_t、2_c和2_t,1_c和2_t的晶体结构经X射线衍射测定,二者均属单斜晶系,P2_1/n(1_t)和P2_1/c(2c)空间群,其中2_c分子的一个配体六元环在晶胞中具有两种几率完全相等的不同构象。
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A layer of palladium particles was electrodeposited on a glassy carbon electrode. The dispersed Pd particles resulted in a large decrease in overvoltage for the electrochemical oxidation of H2O2 down to +0.4 V vs. Ag/AgCl, based on which a new kind of cholesterol sensor was fabricated. Cholesterol oxidase was immobilized on the Pd-dispersed electrode by cross-linking with glutaraldehyde and a layer of poly(o-phenylenediamine) (PPD) film was electropolymerized on the enzyme layer. The sensor shows a linear response in the concentration range 0.05-4.50 mmol l-1 with a rapid response of less than 20 s. The polymer film can prevent interference from uric acid and ascorbic acid and also increases the thermal stability of the sensor. The sensor can be used for 200 assays without an obvious decrease in activity.
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X-ray photoelectron spectra of some bioinorganic complexes of La, Pr, Nd, Sm, and Gd with N-acetylvaline have-been measured. The complex formation does not give any detectable influence on the binding energy of the N 1s peak in the amino group, but has some appreciable effect on the binding energy of the C 1s peak and the O 1s peak in the carboxyl and carbonyl group of the biological ligand. The spin-orbit splitting between the 3d5/2 and 3d3/2 core level of the rare earth ion in these bioinorganic complexes also becomes slightly larger than that of the free rare earth atom due to the effect of the crystal field from the biological ligands.
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Dysprosium and ytterbium monophosphides have been prepared by the solid state reaction. The optical and electrical properties have been studied. Evidence that DyP and YbP are semiconductors has been obtained from the study of the absorption spectrum, the negative temperature coefficient of resistance and the rectifying effect. Their energy gaps are determined as 1.15 eV for DyP and 1.30 eV for YbP, electric conduction type is n-type, resistivities are about 10(-2) ohm cm and Hall mobility is 8.5-80 cm2/Vs. The p-n junction is formed on the LnP/Si.
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A novel Prussian blue chemically modified electrode (CME) was constructed and characterized for liquid chromatography electrochemical detection (LCEC) of catecholamines. Both anodic and cathodic peaks could be obtained by monitoring at constant applied potential at anodic and slightly cathodic potential ranges (0.3-0.7 and -0.2-0.1 V vs. SCE), respectively. When arranged in a series configuration, using the modified electrodes as generating and collecting detectors, extremely high effective collection efficiencies of 0.91 (for norepinephrine) and 0.58 (for dihydroxyphenylacetic acid) were achieved in dual-electrode LCEC for catecholamines; and a linear response range over 3 orders of magnitude and a detection limit of 10 pg were obtained with a downstream CME as the indicating detector.
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固体化合物(NH_4)_6Mo_7O_(24)·4H_2O和(PPh_3)_2CuCl与饱和液体NH_4HS反应获得桔红针状标题晶体。晶体空间群为P2_1/c,晶胞参数a=11.742(2),b=28.186(7),c=19.304(3),β=100.57(2)°,V=6280.4(?)~3,D_c=1.46g/cm~3,Z=4,F(000)=2816。在3≤2θ≤45°范围内收集到8414个独立衍射强度数据,其中3856个I≥1.5σ(I)强度数据参加结构计算。标题化合物分子是以{MoCu_3S_3Cl}类立方烷型簇为核心的分子,Mo—Cu的平均距离为2.716。
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The solution of non-volatile solutes can be concentrated to saturation by membrane distillation. If the solute is easy to crystalize, the membrane distillation-crystallization phenomenon will appear during the membrane distillation of saturated solutions. It is possible that crystalline products are separated from concentrated solutions by a membrane process. In this work the PVDF capillary membrane, which was improved on hydrophobicity by using LiCl instead of a water-soluble polymer as an additive, has been used for treating the waste water of taurine. The crystalline product has been obtained from the waste water by the membrane distillation-crystallization technique. The results have shown good prospects for a membrane distillation application for treatment of industrial waste water.
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标题配合物是以THF作溶剂,通过(C_5H_5)_2NdCl·ZLiCl和甲基萘钠的还原反应合成的。其晶体属单斜晶系,P 2/c空间群,晶胞参数α=9.235(2)A,b=11.695(2)A,c=20.810(3)A,β=92.88(1)°,Z=2。研究结果表明,标题配合物由相互不相联的〔Li3DME〕~+和〔(η~5-C_5H_5)_3Nd(μ-H)Nd(η~5-C_5H_5)_3〕~-离子对组成。阳离子中,Li原子与由3个DME提供的6个O原子配位,形成八面体构型,Li—O平均键长为2.116A;阴离子中,2个Nd原子不直接键合,系通过桥H联接,Nd—H=2.19A。此外,每个Nd原子各有3个C_5H_5~-与之配位,Nd—C平均键长为2.812A。
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将稀土氯化物作为Diels-Alder环加成反应的催化剂,在缓和条件下制得了几种降冰片烯衍生物。稀土氯化物不仅提高了反应速度,而且还改变了产物的构型比(endo/exo)。由试验的几种稀土氯化物的结果,可以看出催化活性有随稀土元素原子序数递增而增加的趋势。降低反应温度有利于内型产物的生成。比较了催化与非催化反应的活化能和级数。
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Clip domain serine protease (cSP), characterized by conserved clip domains, is a new serine protease family identified mainly in arthropod, and plays important roles in development and immunity. In the present study, the full-length cDNA of a cSP (designated EscSP) was cloned from Chinese mitten crab Eriocheir sinensis by expressed sequence tags (ESTs) and PCR techniques. The 1380 bp EscSP cDNA contained a 1152 bp open reading frame (ORF) encoding a putative cSP of 383 amino acids, a 5'-untranslated region (UTR) of 54 bp, and a 3'-UTR of 174 bp. Multiple sequence alignment presented twelve conserved cysteine residues and a canonical catalytic triad (His(185), Asp(235) and Ser(332)) critical for the fundamental structure and function of EscSP. Two types of cSP domains, the clip domain and tryp_spc domain, were identified in the deduced amino acids sequence of EscSP. The conservation characteristics and similarities with previously known cSPs indicated that EscSP was a member of the large cSP family. The mRNA expression of EscSP in different tissues and the temporal expression in haemocytes challenged by Listonella anguillarum were measured by real-time RT-PCR. EscSP mRNA transcripts could be detected in all examined tissues, and were higher expressed in muscle than that in hepatopancreas. gill, gonad, haemocytes and heart. The EscSP mRNA expression in haemocytes was up-regulated after L anguillarum challenge and peaked at 2 h (4.96 fold, P < 0.05) and 12 h (9.90 fold, P < 0.05). Its expression pattern was similar to prophenoloxidase (EsproPO), one of the components of crab proPO system found in our previous report. These results implied that EscSP was involved in the processes of host-pathogen interaction probably as one of the proPO system members. (C) 2009 Elsevier Ltd. All rights reserved.