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991.
992.
In this paper, we study the Hausdorff dimension of Cantor attractors of smooth interval maps with non-flat critical points.
We prove that the Hausdorff dimension is bounded from above by a constant less than 1 which depends only on the number and
order of the critical points. 相似文献
993.
994.
A kind of function-valued Padé-type approximant via the formal orthogonal polynomials (FPTAVOP) is introduced on the polynomial space and an algorithm is sketched by means of the formal orthogonal polynomials. This method can be applied to approximate characteristic values and the corresponding characteristic function of Fredholm integral equation of the second kind. Moreover, theoretical analyses show that FPTAVOP method is the most effective one for accelerating the convergence of a sequence of functions. In addition, a typical numerical example is presented to illustrate when the estimates of characteristic value and characteristic function by using this new method are more accurate than other methods. 相似文献
995.
The electronic structure and properties of polypyrrole (p-Pyr) based substituting by the group of pyrazine (Pyz) and their
model compounds were studied by the density functional theory (DFT) at the B3LYP level with 6-31G* basis set. The bond length,
the topological analyses and nucleus-independent chemical shifts (NICS) were analyzed and correlated with the electronic properties.
The bond length of all compounds is reduced with the increase in the degree of polymerization, and the band gap of these compounds
is decreased. The change of NICS shows that the conjugation degree in central section of the polymeric axis is stronger than
that in outer section, and the structure of central part was close to quinoid structure in polymers. The theoretical results
suggest that the band gap of p-Pyz (polymer of Pyz) (0.37 eV) is much smaller than the band gap of polypyrrole (1.84 eV).
The narrow band gap, large HOMO and LUMO bandwidths and small effective masses make p-Pyz have a remarkable elevation of the
conductivity, so it may be considered as a very good candidate for conducting material. 相似文献
996.
997.
Amphiphilic hyperbranched poly(amino ester)s with hydrophilic multi‐ethoxylated triacrylate backbone and hydrophobic long alkyl side chain were firstly synthesized via one pot Michael addition polymerization. The poly‐(amino ester) could dissolve in cold water and self‐assemble into loose micelle. Under 50–1000 ms bubble, the dynamic surface tension (DST) of the poly(amino ester) aqueous solution (0.5 wt%) still maintained in the range of 32–28 mN/m. The aqueous solutions of poly(amino ester)s with different molecular weights showed the lower critical solution temperature (LCST) in the range of 8–50°C, which could also be tuned by its pH. Capped with hydrophobic groups on the terminal units and partially neutralized with acid, the poly(amino ester)s still kept their stable dynamic surfactant behaviors, indicating promising application. 相似文献
998.
DNA-modified electrodes (VII) 总被引:1,自引:0,他引:1
Qi Lu Daiwen Pang Shen Hu Jieke Cheng Xiongwei Cai Caihui Shi Bingwei Mao Hongping Dai 《中国科学B辑(英文版)》1999,42(4):425-432
Two kinds of DNA-modified electrodes were prepared by covalent and adsorptive immobilization of DNA onto self-assembled monolayers
of 2, 2’-dithiodiethanol on gold electrodes and characterized by cyclic voltammetry, X-ray photoelectron spectroscopy and
scanning tunneling microscopy. The results suggest that the methods are satisfactory for the immobilization of DNA on electrodes.
Project supported by the National Natural Science Foundation of China (Grant Nos. 39370213; 39770220; 29773034), State Key
Laboratory for Physical Chemistry of Solid Surfaces (Xiamen University), and Natural Science Foundation of Hubei Province
(Grant NO. 96J037). 相似文献
999.
Twenty one ternary complexes of lanthanide with 3,5-di-tert-butyl-γ-resorcylic acid (L) and seven different substituted pyridine-N-oxides (L1–7), with compositions of REL3L1–72·nH2O (RE=Nd, Gd, Er; L1=4-picoline-N-oxide; L2=4-phenyl-pyridine-N-oxide; L3=pyridine-N-oxide; L4=3-picoline-N-oxide; L5=quinoline-N-oxide; L6=iso-quinoline-N-oxide; L7=4-methoxyl-pyridine-N-oxide; n=0, 1, 2, 5), were synthesized and characterized by means of elemental analysis, electrical conductivity, thermal analysis and IR spectra. The novel crystal structure of ErL3L32·(EtOH) has been determined by a single-crystal X-ray diffraction method. It shows that each erbium ion is linked to three 3,5-di-tert-butyl-γ-resorcylic acid ions through two different types of dentation modes in which only the carboxylate oxygen atoms participate. The coordination geometries of erbium ion can be described as a distorted octa-coordinated bicapped trigonal prism. 相似文献
1000.
Yao Chen Panpan Sun Tiancheng Li Yin Zou Yiyong Huang Yongcun Shen 《Tetrahedron letters》2018,59(25):2399-2402
Asymmetric Michael addition between 3-ethyl carboxylate substituted pyrazolones and 5-alkenylthiazolones catalyzed by a series of chiral bifunctional hydrogen bonding organocatalysts was investigated. Good yields (up to 96%) and excellent enantioselectivities (up to 99% ee) were achieved by using a squaramide containing piperidine group derived from (1S, 2S)-cyclohexanediamine. This strategy provides facile access to a diverse library of thiazole-pyrazolone derivatives with potential bioactivity. 相似文献