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861.
叶彦谦 《福州大学学报(自然科学版)》2002,30(4):403-408
借N2 =[12 ,2 2 ,3 2 ,… ]中之数的一种特殊形式的表达式以及N2 中的部分和表推导出N中之数用N2中之数的和来表达的可能性 ,并提出合理的猜想 .对N3 =[13 ,2 3 ,3 3 ,… ]与N4=[14 ,2 4,3 4 ,… ]也得到一部分类似的结果 相似文献
862.
A novel organic disulfide, N, N′-dithiobis(3-nitroaniline)(1) was prepared by the reaction of 3-nitroaniline with sulfur monochloride
in chloroform. Compound 1 was reduced by zinc powder to give N, N′-dithiobis(1,3-phenylenediamine) (2). Poly N, N′-dithiobis
(1,3-phenylenediamine) (3) was prepared by electrochemical polymerization of compound 2 and its basic electrochemical behavior
is discussed.
Foundation item: Supported by the National Natural Science Foundation of China (29833090)
Biography: Li Zao-ying (1949-), female, Professor, research direction: synthesis and properties of organic cathode materials
of rechargeable lithium batteries. 相似文献
863.
Carbon isotopic records in paleosols over the Pliocene in Northern China: Implication on vegetation development and Tibetan uplift 总被引:2,自引:0,他引:2
Carbon isotopic composition of pedogenic carbonate can be used to estimate the proportion of C4 and C3 plants. Here we present carbon isotopic data of carbonate in a red earth section at Xifeng, central Loess Plateau. Results
show that C4 vegetation increased in ∼4.4 Ma B.P., stabilized between 4.0 and 3.0 Ma B.P. The character and timing of C4 expansion on the Loess Plateau are similar, but different with other localities, e.g. Pakistan and Africa, implying that
regional climate changes were main factors driving the expansion of C4 plants. This event is comparable in timing with increased aridity evidenced by Xifeng grain size and North Pacific eolian
dust records. Therefore we argue that the Pliocene expansion of C4 plants in northern China might have been caused by the increased aridity, which in turn might be related to rapid uplift
of the Tibetan Plateau. 相似文献
864.
Recent studies demonstrate that the V3 loop of HIV-1 gp120 plays an important role in the attachment of HIV-1 to the target cells. Several amino acids in this domain are involved in the interaction of gp120 with the co-receptors. The V3 loop elicits one of the earliest antiviral antibody responses in HIV-1 infection and has been identified as the principal neutralizing determinant (PND). A subset of antibodies to V3 loop show a broad range of neutralizing activity. Unfortunately, this loop undergoes broad mutation and is one of the hypervariable regions. Mutations of some amino acids in this PND could affect syncytium formation, virus infectivity and neutralization. Knowing the structural characteristics and biological functions of the V3 region could help us to understand mechanism of HIV infection and to develop new strategy against HIV-1. In this review, the structural characteristics, variation and biological functions of the V3 loop as well as immunological responses to the V3 loop are discussed. 相似文献
865.
新型偶氮染料中间体2-氨基-5-氨甲基-1-萘磺酸合成条件的研究 总被引:1,自引:0,他引:1
2-氨基 - 5 -氨甲基 - 1-萘磺酸 (氨甲基吐丝酸 )是一种新型活性偶氮染料中间体 ,文献报道大多采用首先把 2 -氨基 - 1-萘磺酸的氨基乙酰化保护 ,然后氨甲基化及水解反应的合成方法 ,其不仅合成步骤长 ,而且需要在高压反应釜中进行。这样的制备条件在实验室操作以及进一步中试及工业化的生产中存在很大局限性。针对这种情况 ,本研究工作对反应条件进行系统的研究后 ,改用直接将 2 -氨基 - 1-萘磺酸氨甲基化合成 2 -氨基 - 5 -氨甲基 - 1-萘磺酸 (氨甲基吐丝酸 )的方法 ,去掉了氨基乙酰化反应 ,使反应步骤简化 ;去掉了高压操作 ,使整个反应过程容易操作。改进的合成方法反应条件温和 ,整体收率稳定 ,维持在 87.2 % ,获得了较好结果。 相似文献
866.
《厦门大学学报(自然科学版)》2002,(Z1)
The numerical control (NC) precision bending process of thin-walled tube is on e of advanced plastic forming processes with high efficiency, forming precision, strength/weight ratio and low cost, thus it is playing more and more important role in manufacturing parts in aerospace and automobile industries. However, the determination of parameters crucial to make sure tube parts qualified is heavil y experience-based and involves repeated trial-and-errors in practice, which makes the production efficiency... 相似文献
867.
We recorded slow vacuolar (SV-type) channel currents of Radish vacuoles successfully for the first time by using the whole-vacuolar patch-clamp recording mode. SVtrye currents would increase and threshold potentials of activation would shift towards more negative values with the increase of concentrations of cytosolic Ca2+. When 2.5 mmol/L LaCl3 and 4 mmol/L EGTA were added to bath solutions,SV-type currents were suppressed remarkably. Then adding LaCl3 with different concentrations to pipette solutions, we found that LaCl3 with higher concentrations (> 4 × 10-7 mol/L)had a strong inhibitory effect on SV-type currents, while LaCl3 with lower concentrations (≤4 × 10-7 mol/L) promoted channel currents. This promoting effect provides an important basis at channel level for researching further the effects of rare earth on physiological activities of plants and the production-increase effects of rare earth fertilizers on crops.`` 相似文献
868.
3-D QSAR study on a set of nitroaromatic compounds 总被引:1,自引:0,他引:1
The 3-D relationships between the structures of 25 nitroaromatic compounds and their toxicities have been investigated using the comparative molecular field analysis (CoMFA) method, and a 3-D QSAR model with considerable prediction ability is obtained. In comparison with traditional 2-D techniques, CoMFA helps to give a better interpretation of toxic mechanism of tested compounds. 相似文献
869.
Azo dyes have been used in many industries (textile mill, printing and dyeing mill, paper and pulp mill) and have caused great environmental pollution due to complicated constitution and high chemical stability. The construction of azo dyes can be destroyed by ozonization, but not thoroughly when the ozone dosage is controlled to a certain extent and the operating cost is higher. Ozonization decomposed ability with ultrasonic enhancement on azo dyes has been demonstrated in the study. The conclusion derived from this investigation may be summarized as follows: (1) The decoloration rate of arsenazoⅠsolutions during sonozone treatment is more rapid than the rate obtained with ozone alone because the complicated constitution has been destroyed by the O free radical from ozone decomposition. (2) The destructing pathway of arsenazoⅠby ozone with ultrasound is identical with that of by ozone alone: the breakdown of —N== N— bonds, the conversion of benzene ring to carboxylic acid, and —HSO3 bonds to H2SO4. So, pH value of the arsenazo Ⅰ solution continuously drops down to 3.2. 相似文献
870.
Study of transmembrane La3+ movement in rat ventricular myocytes by the patch-clamp technique 总被引:1,自引:0,他引:1
We have studied transmembrane La3+ movement in rat ventricular myocytes for the first time by using the whole-cell patch-clamp recording mode. La3+ (0.01-5.0 mmol/L) could not bring out inward currents through the L-type calcium channel in rat ventricular myocytes, while it could enter the cells by the same way carried by 1μmol/L ionomycin. When the outward Na+ concentration gradient is formed, La3+ can enter the cells via Na-Ca exchange, and the exchange currentsincrease with the increase of external La3+ concentrations. But compared with Na-Ca exchange currents in the same concentration, the former is only 14%-38% of the latter. The patch-clamp experiment indicates that La3+ normally can not enter ventricular myocytes through L-type calcium channel, but it can enter the cells via Na-Ca exchange. 相似文献