纳米Y2O3/钴基合金激光熔覆层的组织

利用5 kW CO2激光器,在Ni基高温合金表面,熔覆纳米稀土氧化物(Y2O3)/钴基合金复合材料,制备了涂层.利用光学显微镜、扫描电镜及透射电镜分析了熔覆层的组织结构.结果表明: 熔覆层的主要相组成为γ-Co,ε-Co,Cr23C6和Y2O3;加入纳米Y2O3,凝固组织由细长的柱状树枝晶转变为较短的树枝晶;纳米Y2O3含量增大至1%时整个断面获得等轴晶组织;纳米Y2O3作为异质形核的核心,细化了组织;纳米Y2O3在熔覆层中分布不均匀,促进了γ-Co向ε-Co的转变;熔覆层的亚结构为堆跺层错.对熔覆层等轴组织形成机制进行了分析.     

金属—血清白蛋白的结构研究——Ⅵ.等离子点附近HSA和BSA中Cu(Ⅱ)和Ni(Ⅱ)金属中心的结构

本文用紫外光谱研究了等离子点附近HSA或BSA ¹Cu(Ⅱ)或Ni(Ⅱ)金属中心的结构。结果表明:在pH₄.0～5.3时,Cu(Ⅱ)—HSA配合物在低浓度时独具五配位的四方锥构型,高浓度时(>10^-4mol·l^-1)为四配位的四方平面构型,Cu(Ⅱ)—BSA、Ni(Ⅱ)—BSA在上述pH范围内均只存在四方平面构型。Cu(Ⅱ)、Ni(Ⅱ)结合位置与生理pH下的相同,均在白蛋白的N端三肽段上,与Asp^{1相似文献}   

Multilayer vesicles and vesicle clusters formed by the fullerene-based surfactant C60(CH3)5K

The self-assembly behavior of a fullerene-based surfactant, C60(CH3)5K, in water was studied using a combination of static and dynamic light scattering, as well as transmission electron microscopy, and compared to that of the compound C60(C6H5)5K. Both fullerene surfactant systems spontaneously assemble into large vesicles consisting of closed spherical shells formed by bilayers, with critical aggregation concentrations (CAC) lower than 10(-6) g ml(-1). At low concentrations, the aggregate sizes of C60(CH3)5K (radius R approximately 26.8 nm) and C60(C6H5)5K (R approximately 17.0 nm) were found to be substantially different from each other, showing that the change of the substituents surrounding the polar cyclopentadienide head group makes it possible to control the size of the resulting aggregates. Furthermore, the C60(CH3)5K vesicles were found to exist in two qualitatively different types of aggregation with a critical reaggregation concentration (CRC) located at 3.30 x 10(-6) g ml(-1). Above the CRC, larger aggregates were observed (R approximately 37.6 nm), showing a more complex form of supramolecular aggregation, e.g., in terms of multi-bilayer vesicles and/or of clusters of bilayer vesicles.     

Synthesis,crystal structure and magnetic property of a binuclear iron(III) citrate complex

The compound (Hql)₂[Fe₂(cit)₂(H₂O)₂]·4H₂O (1) [ql = quinoline, cit^4– = C(O^–)(CO^– ₂)(CH₂CO^– ₂)₂], prepared by reacting ferric nitrate, sodium citrate and quinoline in a molar ratio of 1:1:1 in aqueous solution, was characterized by density measurements, elementary analysis, i.r., X-ray crystallography and magnetic measurements. The X-ray crystallography results reveal that the molecule (1) consists of a binuclear iron(III) citrate anionic complex [Fe₂(cit)₂(H₂O)₂]^2– and two protonated quinolines [Hql]⁺. The anionic complex has a centro-symmetric structure, in which two Fe³⁺ ions are bridged by two ₂-alkoxo groups of the two deprotonated citrate ligands. The other coordination sites of the two slightly distorted octahedra are completed by all the carboxylate groups of the two cit^4– ligands in a monodentate mode, and two coordinated water molecules. Magnetic measurements indicate that the two Fe³⁺ ions are antiferromagnetically coupled below 200 K. A least-squares fit of variable-temperature (1.5–291 K) molar susceptibility data to a dimer model gave the coupling constant J/k = –6.35(7) K and Landé factor g = 2.052(9), where the spin-only Heisenberg–Dirac–van Vleck Hamiltonian is expressed as H = –2J S ₁ S ₂.     

Theoretical Studies on Reaction Mechanisms of HNCS with NH （ X^3∑）

The reaction mechanisms of HNCS with NH（X^3∑ ） were theoretically investigated. The minimum energy paths （MEP） of the reaction were calculated by using the density functional theory（DFT） at the B3LYP/6-311 ＋ ＋ G^＊＊ level. The equilibrium structural parameters, the harmonic vibrational frequencies, the total energies, and the zeropoint energies（ZPE） of all the species were calculated. The single-point energies along the MEP were further refined at the QCISD（T）/6-311 ＋ ＋ G^＊ ＊ level. It was found that the mechanisms of the HNCS ＋ NH（X^3∑） reaction involve two channels producing the HNC ＋ HNS and the N2H2 ＋ CS products. Channel 1 plays a dominant role and the HNC ＋ HNS are the main preduets. The reaction is exothermie.     

N,N''''-硝基苯酰基取代苯酰氨基硫脲的合成与生物活性

酰氨基硫脲类化合物不仅具有广谱抗菌性能 ,还具有极好的杀虫和植物生长调节活性 [1～ 3] ,因而引起许多国内外学者对硫脲类化合物的合成及其化学结构与生物活性关系方面的研究 [4～ 8] .为了进一步研究不同的取代基团对此类化合物生物活性的影响 ,作者用硝基苯酰基异硫氰酸酯与芳基酰肼加成制得相应的 N ,N -硝基苯酰基取代苯酰氨基硫脲 ( ) ,并初步测定了它们抑制大肠杆菌和枯草杆菌生长的生物活性 .这些化合物尚未见文献报道 .Ar— COCl KSCN Ar—CONCS a～ cAr CONHNH2 ( 1 ～ 7) Ar—CONHC( S) NHNHCOAr Ar:a.o-N…     

Preparation, Electrochemical Behavior and Electrocatalytic Activity of a Copper Hexacyanoferrate Modified Ceramic Carbon Electrode

A copper hexacyanoferrate modified ceramic carbon electrode （CuHCF/CCE） had been prepared by two-step sol-gel technique and characterized using electrochemical methods. The resulting modified electrode showed a pair of well-defined surface waves in the potential range of 0.40 to 1.0 V with the formal potential of 0.682 V （vs. SCE） in 0.050 mol·dm^-3 HOAc-NaOAc buffer containing 0.30 mol·dm^-3 KCl. The charge transfer coefficient （a） and charge transfer rate constant （ks） for the modified electrode were calculated. The electrocatalytic activity of this modified electrode to hydrazine was also investigated, and chronoamperometry was exploited to conveniently determine the diffusion coefficient （D） of hydrazine in solution and the catalytic rate constant （kcat）. Finally, hydrazine was determined with amperometry using the resulting modified electrode. The calibration plot for hydrazine determination was linear in 3.0 × 10^-6--7.5 × 10^-4 mol·dm^-3 with the detection limit of 8.0 × 10^-7 molodm^-3. This modified electrode had some advantages over the modified film electrodes constructed by the conventional methods, such as renewable surface, good long-term stability, excellent catalytic activity and short response time to hydrazine.     

Pseudolarolides O and P,Two Novel Triterpene Dilactones from Pseudolarix kaempferi

Pseudolarolides O ( 1 ) and P ( 2 ), two novel triterpenoids with a cycloartane‐type framework, were isolated from the seeds of Pseudolarix kaempferi Gord. (Pinaceae). Their structures were elucidated as (16R,23S,25R)‐16,23‐epoxy‐3,4 : 9,10‐disecocycloartan‐1(10),9(11)‐diene‐3(4),26(23)‐diolide ( 1 ), and (9S,16R,23S,25R)‐1,9 : 16,23‐diepoxy‐8,9 : 9,10‐disecocycloartan‐1(29),5(6),10(19)‐triene‐3(4),26(23)‐diolide ( 2 ), respectively, on the basis of spectroscopic techniques and X‐ray‐diffraction studies.     

Hf[N(SO2C8F17)2]4-catalyzed Friedel-Crafts acylation in a fluorous biphase system

In a fluorous biphase system, Hf[N(SO₂C₈F₁₇)₂]₄ complex (1 mol %) catalyzes Friedel-Crafts acylation of aromatic compounds such as anisole, toluene and chlorobenzene, and the corresponding aromatic ketones are obtained in satisfactory to high yields. The catalyst is selectively soluble in lower fluorous phase and can be easily recovered by simple phase separation. Furthermore, the catalyst can be reused without decrease of activity in most cases.     

Reversed stereoselectivity in iodohydroxylation of allenyl sulfides. An efficient synthesis of (Z)-3-organosulfur-2-iodo-2-propenols

[reaction: see text] It is observed that the iodohydroxylation of 1,2-allenyl sulfides with I(2) and water in aqueous acetone showed Z-selectivity, which is opposite to that of the iodohydroxylation of 1,2-allenyl sulfoxides.