Lp空间Kantorovich-Vertesi算子逼近的Jackson型估计

考虑了Kantorovich-Vertesi有理插值型算子L^*n,s（f,X,x）对L^p[-1,1]（1≤p≤∞）空间函数逼近的Jackson型估计。并获得了如下逼近阶：‖L^*n,s(f,X,x)-f(x)‖L^p[-1,1]≤Cp,sw(f,1/n 2)L^p[-1,1] （s＞2）。     

中低变质程度煤显微组分结构的13 C-NMR研究

利用13C-NMR核磁共振技术对中低变质程度煤显微组分（镜质组和惰质组）的分子结构进行了研究,计算了5种煤9个显微组分的13C-NMR结构参数,获得了样品的结构特征及变化规律。结果表明,惰质组结构中芳构化程度要高于镜质组;脂碳数量则少于镜质组,芳环上的烷烃侧链也没有镜质组长;随着煤变质程度的提高,煤分子中芳构化程度不断提高,但惰质组的芳香度随变质程度变化的规律明显不如镜质组;在中低变质阶段,对煤化进程起主导作用的的是芳构化作用而不是环缩合作用,但在惰质组中脂碳断裂形成芳环的现象不明显。惰质组中含氧官能团的总量要低于同等变质程度的镜质组。     

Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.     

Charge-transfer spectra of structurally characterized mixed-valence thiolate-bridged Cu(I)/Cu(II) cluster complexes

A series of Cu(II) and Cu(I)/Cu(II) complexes containing the cis-N(amine)(2)S(thiolate)(2) copper complex rac-2 has been synthesized to provide a basis for understanding the charge-transfer spectra of mixed-valence thiolate-bridged Cu(I)/Cu(II) complexes. In combination with Cu(Me(2)-13-N(4)ane), rac-2 yields a monobridged dinuclear homovalent adduct, rac-5, while reaction with CuCl yields the mixed-valance pentanuclear complex rac-6. In the presence of Cu(II)(acac)(2), chiral R,R-1 reacts to form a mixed-valence pentanuclear cation R,R-7. rac-6 exhibits a relatively short Cu(I). Cu(II) contact [2.8231(9) A] and associated structural features that suggest the presence of a weak Cu(I).Cu(II) interaction in a valence-trapped system. Additional structural features in rac-6 and R,R-7 include singly and doubly bridging thiolates, three- and four-coordinated Cu(I) ions, and varying Cu(I) ligand sets. These features extend the types and complexities of electronic absorptions significantly. Spectra of rac-6 and R,R-7 exhibit multiple overlapping absorptions over the entire visible and ultraviolet spectral regions studied, consonant with these observations. Trends resulting from variations in structure type and oxidation state permit a first approach toward developing a detailed assignment of the individual ligand Rydberg, LF, LMCT, MLCT, and possible MMCT absorptions in these complexes.     

Structural and spectroscopic features of mono- and binuclear nickel(II) complexes with tetradentate N(amine)2S(thiolate)2 ligation

Three complexes containing Ni(II)N(amine)2S(thiolate)2 units have been prepared and characterized. Both (R,R)-N,N'-bis(1-carboxy-2-mercaptoethyl)-1,2-diaminoethane [(R,R)-1] and N,N'-bis(2-methyl-2-mercaptoprop-1-yl)-1,3-diamino-2,2-dimethylpropane (4) act as tetradentate S-N-N-S ligands to form complexes Ni((R,R)-1) and Ni4 with nearly planar cis-NiN2S2 units. The N-Ni-N and S-Ni-S angles differ significantly in the two complexes yet are very nearly supplementary. The 1,3-disubstituted cyclohexane species rac-N,N'-bis(2-mercapto-2-methylprop-1-yl)-1,3-cyclohexanediamine (6) behaves as a bis(bidentate-N,S) ligand to form an unexpectedly intense-blue dinickel complex (1S,3R,1'S,3'R)-7, which contains two trans-NiN2S2 units bridged by 1,3-disubstituted cyclohexane groups. The coordination geometry in (1S,3R,1'S,3'R)-7 is distorted 15 degrees toward tetrahedral, most likely as a result of steric crowding, suggested by several short contacts between the NiS2 units and both the cyclohexyl and gem-dimethyl groups of the N,S-chelate rings. The complexes exhibit rich UV-vis spectra, whose deconvoluted bands are now fully assigned, from low to high energy, as ligand field (LF), pi(S) --> Ni(II) ligand-to-metal charge transfer (LMCT), sigma(S) --> Ni(II) LMCT, sigma(N) --> Ni(II) LMCT, localized S, and S,N Rydberg transitions. The unusually intense LF absorptions shown by (1S,3R,1'S,3'R)-7 are thought to result from relaxation of the Laporte restriction arising from the 15 degrees tetrahedral twist.     

Copper(II) and nickel(II) complexes of binucleating macrocyclic bis(disulfide)tetramine ligands

Novel macrocyclic bis(disulfide)tetramine ligands and several Cu(II) and Ni(II) complexes of them with additional ligands have been synthesized by the oxidative coupling of linear tetradentate N2S2 tetramines with iodine. Facile demetalation of the Ni(II) oxidation products affords the free 20-membered macrocycles meso-9 and rac-9 and the 22-membered macrocycle 16, all of which are potentially octadentate N4S4 ligands. X-ray structure analyses reveal distinctly different conformations for the two isomers of 9; meso-9 shows a stepped conformation in profile with the disulfide groups corresponding to the rise of the step, whereas rac-9 exhibits a V conformation with the disulfide groups near the vertex of the V. No metal complexes of rac-9 have been isolated. Crystallographic studies of three Cu(II) complexes reveal that depending upon the size of the macrocyclic ligand and the nature of the additional ligands (I-, NCO-, and CH3CN), the Cu(II) coordination geometry shows considerable variation (plasticity), with substantial changes in the Cu(II)-disulfide bonding. Thus, a diiodide salt contains six-coordinate Cu(II) to which all four bridging disulfide sulfur atoms form strong equatorial bonds. In contrast, isocyanato complexes of the 20- and 22-membered macrocycles exhibit trigonal-bipyramidal Cu(II) and distorted cis-octahedral Cu(II) geometries, respectively, having only one and no short equatorially bound sulfur atoms. The coordination geometry of the latter complex can also be described as four-coordinate seesaw with two semicoordinated S(disulfide) ligands. Disulfide-->Cu(II) ligand-to-metal charge transfer absorptions of both isocyanato-containing Cu(II) species appear too weak to observe, probably because of poor overlap of the sulfur orbitals with the Cu(II) d-vacancy. The dual disulfide-bridged Ni(II) units of the crystallographically characterized octahedral Ni(II) complex of meso-9 with axial iodide and acetonitrile ligands promote substantial antiferromagnetic coupling (J = -13.0(2) cm-1).     

Nonlinear Instability of the Two-Dimensional Striation Model About Smooth Steady States

The two-dimensional striation model consists of a nonlinear system of PDE's which arises in the modeling of the ionospheric plasma. The local-in-time existence of strong solutions is first proved using Banach's fixed point theorem. Then, under physically relevant assumptions, the system is shown to be nonlinearly unstable as soon as it is linearly unstable. Moreover, the instability occurs before the possible blow-up time of the solution. The proof relies on an earlier work of Hwang and Guo (2003 Hwang , H. J. , Guo , Y. ( 2003 ). On the dynamical Rayleigh–Taylor instability . Arch. of Rat. Mech. Anal. 167 : 235 – 253 .[Crossref], [Web of Science ®] , [Google Scholar]). The first step of the proof is to investigate under which conditions the linearized system is unstable and to prove that its spectrum is bounded, by means of a variational formulation. The second one consists in constructing a family of solutions depending on the parameter δ measuring the smallness of the perturbation to the steady-state. Thanks to the boundedness of the linearized spectrum, this family of solutions is shown to be unstable by means of a power series expansion in δ.