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排序方式: 共有192条查询结果,搜索用时 31 毫秒
101.
Tarita Biver Rodolfo Pardini Fernando Secco Maria Rosaria Tiné Marcella Venturini 《Supramolecular chemistry》2013,25(3):461-467
Abstract The kinetics and the equilibria of complex formation between Co(II) and the linear polyamine 1,25-dimethyl-1,4,7,10,13,16,19,22,25-nonaazapentacosane (Me2Octaen) have been investigated in aqueous solution under anaerobic conditions by the stopped-flow and potentiometric method. Static titrations and kinetic experiments indicate that below pH 5.6 the binding of Co(II) to the ligand gives rise to several 1:1 complexes differing for their degree of protonation, whereas above pH 5.6 binuclear complexes are formed as well. The analysis of the kinetic data reveals that the mostly reactive form of the ligand (denoted in its fully protonated form as H9L9+) is H6L6+. The species H5L5+ and H4L4+ yield only a minor contribution to the overall process of complex formation. Measurements at different ionic strengths have shown positive salt effects, as expected for reactive processes involving particles with charges of the same sign. The analysis of the results shows that Co2+ and H6L6+ react according to the internal conjugate base mechanism. 相似文献
102.
Reaction of 1,4-naphthoquinone or 2,3-dichloro-1,4-naphthoquinone with α,ω-diamino-derivatives of poly(alkylenoxides) leads to the formation of α,ω-bis(quinonyl) amines. A similar reaction with chloranil, bromanil, dichlorodicyanobenzoquinone, S-phenylbenzoquinone and 1,4-benzoquinone itself, leads to the formation of quinoid crown ethers. 相似文献
103.
In this study, the Hele-Shaw cell is used to examine the effect offluid elasticity on the flow patterns of two-dimensional
potential flow. Flows around a circular cylinder, a square cylinder and flows through abruptly converging-diverging channels
(slits) with different throat lengths are tested for water and 0.2 wt % polyacrylamide aqueous solution (PAA-solution). The
viscosity of the latter is well modeled by the power law, and the first normal stress difference in the steady shear flow
is around ten times higher than the shear stress. Although the PAA-solution is highly shear-thinning, the flows of PAA-solution
well reproduce the two-dimensional potential flow patterns that correspond to the respective flow configurations when the
flow rate is very low. The potential flow patterns ofPAA solution are disturbed in the opposite way of inertia effect observed
for water. The streamlines near the upstream stagnation point of cylinders are shifted upstream separating from the cylinder
surface when the flow rate is higher, while streamlines in the wake approach closer to the downstream stagnation point. Streamlines
offlow through the slit at flow rates higher than the potential flow region show that a pair ofvortices is formed upstream
the slit entrance, while the streamlines remain attached to the downstream wall after passing the slit. 相似文献
104.
Simanek's theory is extended by taking into account the nuclear spin excitations due to the motion of the electronic system. Damping of the magnons is found to be an extra criteria for having a finite interaction range for the nuclear spin system. The resonance excitation of Simanek's theory is due to the neglect of the second order in the hyperfine interaction. 相似文献
105.
The effects of natural weathering on mechanical properties and chemical structure of low density polyethylene have been studied. It is found that no simple correlation exists between the development of carbonyl groups and mechanical properties such as stress or strain at break or elastic modulus. It appears that there is recovery in the mechanical properties during the winter months. 相似文献
106.
D.L. Shannon W. Breunlich Ivo S̆laus J.W. Sunier G. Anzelon E. Tin W.T.H. Van Oers M.B. Epstein W. Ebenhöh 《Nuclear Physics A》1974,218(2):381-395
The differential cross section for the 2H(p, 2p)n reaction at Einc = 44.9 MeV is measured in noncoplanar geometry. The Amado model in general gives a good fit to the absolute cross section. The dependence of the cross section on the momentum of the undetected particle Q5, on the scattering angle θ34, as well as on the angle of the undetected particle is investigated. 相似文献
107.
J.W. Blunt M.P. Hartshorn M.H.G. Munro Lee Tin Soong R.W. Vannoort 《Tetrahedron letters》1981,22(22):2143-2144
Lithium aluminium hydride reduction of methoxyalkynol(1) yields cyclopropane derivatives (2) and (3), both formed by loss of a methoxy group; a reaction scheme for their formation is presented. 相似文献
108.
R. Becker Matthias Koch Sigrid Wachholz Tin Win 《Accreditation and quality assurance》2002,7(7):286-289
Due to the utilisation of 1,1,2-trichlorotrifluoroethane (CFE) as extraction solvent the IR-spectrometric determination of
total petrol hydrocarbon (TPH) in soil according to ISO/TR 11046 has been replaced by gas chromatography/flame ionisation
detection (GC/FID) after extraction with a halogen-free solvent according to ISO/DIS 16703:2001. The results obtained with
both methods by field laboratories in three proficiency testing (PT) rounds are compared. The consensus means obtained with
GC/FID are typically 10%–20% (ranging between 0% and 25%) higher than those found with IR-spectroscopy. On the contrary, coefficients
of variation (CV) are roughly double in case of GC/FID and are briefly discussed against the background of the Horwitz equation.
Received: 19 November 2001 Accepted: 17 March 2002 相似文献
109.
Sein Win 《Journal of Graph Theory》1982,6(4):489-492
Ore derived a sufficient condition for a graph to contain a Hamiltonian cycle. We obtain a sufficient condition, similar to Ore's condition, for a graph to contain a Hamiltonian cycle and a 1-factor which are edge disjoint. 相似文献
110.
On the Windy Postman Problem on eulerian graphs 总被引:1,自引:0,他引:1
Zaw Win 《Mathematical Programming》1989,44(1-3):97-112