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61.
Ramos CI Barros CM Fernandes AM Santana-Marques MG Correia AJ Tomé JP Carrilho Mdo C Faustino MA Tomé AC Neves MG Cavaleiro JA 《Journal of mass spectrometry : JMS》2005,40(11):1439-1447
Electrospray ionisation mass spectrometry (ESI-MS), electrospray ionisation tandem mass spectrometry (ESI-MS/MS) and Ultraviolet-visible (UV-vis) spectroscopy were used to investigate the non-covalent interactions between small oligonucleotide duplexes with the GC motif and a group of cationic meso(N-methylpyridynium-4-yl)porphyrins (four free bases with one to four positive charges, and the zinc complex of the tetracationic free base).The results obtained point to outside binding of the porphyrins, with the binding strength increasing with the number of positive charges. Fragmentations involving losses from both chains were observed for the porphyrins with N-methylpyridinium-4-yl groups in opposite meso positions. 相似文献
62.
Ricci curvature and the topology of open manifolds 总被引:6,自引:0,他引:6
In this paper, we prove that an open Riemannian n-manifold with Ricci curvature and for some is diffeomorphic to a Euclidean n-space if the volume growth of geodesic balls around p is not too far from that of the balls in . We also prove that a complete n-manifold M with is diffeomorphic to if , where is the volume of unit ball in .
Received 5 May, 1997 相似文献
63.
64.
We characterize active redundancy through compensator transform and use the reverse rule of order 2 (RR2) property between compensator processes to investigate the problem of where to allocate a spare in a k-out-of-n:F system of dependent components through active redundancy. 相似文献
65.
K. Giannakopoulos N. Boukos A. Travlos T. Monteiro M.J. Soares M. Peres A. Neves M.C. Carmo 《Applied Physics A: Materials Science & Processing》2007,88(1):41-44
Isolated, self assembled ZnO nanoparticles are grown in two steps: by the electron beam evaporation of Zn on oxidised silicon
wafers, during which isolated Zn nanodots are grown, and a subsequent annealing in oxygen that results in the desired ZnO
nanodots. Low temperature PL measurements of the ZnO nanodots show that the near band edge part of the spectra is dominated
by a zero phonon line near 3.36 eV which is an overlap of two emitting lines near 3.363 eV and 3.367 eV. Characterization
by TEM and EELS shows that the nanoparticles are zinc oxide single crystals grown with their c-axis perpendicular to the substrate;
their distribution, size and crystallinity depend on the deposition parameters of zinc and the growth substrate. We discuss
the effect of these parameters on the morphology of the resulting material. Our approach demonstrates a simple method for
the growth of high purity isolated ZnO nanodots of similar sizes, distributed uniformly on a large surface.
PACS 61.46.Df; 81.05.Dz; 81.07.-b 相似文献
66.
A two-dimensional (in-plane) numerical model for surface waves propagation based on the non-linear dispersive wave approach described by Boussinesq-type equations, which provide an attractive theory for predicting the depth-averaged velocity field resulting from that wave-type propagation in shallow water, is presented. The numerical solution of the corresponding partial differential equations by finite-difference methods has been the subject of several scientific works. In the present work we propose a new approach to the problem: the spatial discretization of the system composed by the Boussinesq equations is made by a finite element method, making use of the weighted residual technique for the solution approach within each element. The model is validated by comparing numerical results with theoretical solutions and with results obtained experimentally. 相似文献
67.
R F B Serpa E F O de Jesus M J Anjos L F de Oliveira L A Marins M G T do Carmo J D Corrêa Junior M S Rocha R T Lopes A M B Martinez 《Analytical sciences》2008,24(7):839-842
Knowledge about the spatial distribution and the local concentration of trace elements in tissues is of great importance, since trace elements are involved in many biological functions of living organisms. However, there are few methods available to measure the spatial (two (three)-dimensional) elemental distribution in animal brain. X-ray microfluorescence with synchrotron radiation is a multielemental mapping technique, which was used in this work to determine the topographic of iron, zinc and copper in coronal sections of female Wistar rats of different ages. Young (14 days old) and middle-aged (20 months old) rats (n = 8) were analyzed. The measurements were carried out at the XRF beam line at the Synchrotron Light National Laboratory (Campinas, Brazil). Two-dimensional scanning was performed in order to study the tendency of elemental concentration variation. The acquisition time for each pixel was 10 s/step and the step size was 300 microm/step in both directions. It was observed that the iron distribution was more conspicuous in the cortical area, thalamus and bellow the thalamus. On the other hand, the zinc distribution was more pronounced in the hippocampus. The iron, copper and zinc levels increased with advancing age. Therefore, this study reinforces the idea that these elements are involved in the chemical mechanisms of the brain that induce some neurological diseases, since they are also present in high levels in specific areas of the brain, such as the hippocampus and the substantia nigra of patients with these disorders. 相似文献
68.
Angel A. Recio Despaigne Jeferson G. da Silva Ana Cerúlia M. do Carmo Flavio Sives Oscar E. Piro Eduardo E. Castellano Heloisa Beraldo 《Polyhedron》2009,28(17):3797-3803
In the present work 2-formylpyridine-para-chloro-phenyl hydrazone (H2FopClPh) and 2-formylpyridine-para-nitro-phenyl hydrazone (H2FopNO2Ph) were obtained, as well as their copper(II) and zinc(II) complexes [Cu(H2FopClPh)Cl2] (1), [Cu(2FopNO2Ph)Cl] (2), [Zn(H2FopClPh)Cl2] (3) and [Zn(H2FopNO2Ph)Cl2] (4). Upon re-crystallization in DMSO:acetone conversion of 2 into [Cu(2FopNO2Ph)Cl(DMSO)] (2a) and of 4 into [Zn(2FopNO2Ph)Cl(DMSO)] (4a) occurred. The crystal structures of 1, 2a, 3 and 4a were determined. 相似文献
69.
D.J. Rogers F. Hosseini Teherani A. Largeteau G. Demazeau C. Moisson D. Turover J. Nause G. Garry R. Kling T. Gruber A. Waag F. Jomard P. Galtier A. Lusson T. Monteiro M.J. Soares A. Neves M.C. Carmo M. Peres G. Lerondel C. Hubert 《Applied Physics A: Materials Science & Processing》2007,88(1):49-56
2 cm diameter hydrothermal ZnO crystals were grown and then made into substrates using both mechanical and chemical-mechanical polishing (CMP). CMP polishing showed superior results with an (0002) Ω scan full width half maximum (FWHM) of 67 arcsec and an root mean square (RMS) roughness of 2 Å. In comparison, commercial melt-grown substrates exhibited broader X-ray diffraction (XRD) linewidths with evidence of sub-surface crystal damage due to polishing, including a downward shift of c-lattice parameter. Secondary ion mass spectroscopy revealed strong Li, Fe, Co, Al and Si contamination in the hydrothermal crystals as opposed to the melt-grown substrates, for which glow discharge mass spectroscopy studies had reported high levels of Pb, Fe, Cd and Si. Low temperature photoluminescence (PL) studies indicated that the hydrothermal crystal had high defect and/or impurity concentrations compared with the melt-grown substrate. The dominant bound exciton for the melt-grown substrate was indexed to Al. ZnO films were grown using pulsed laser deposition. The melt-grown substrates gave superior results with XRD (0002) Ω and 2θ/Ω WHM of 124 and 34 arcsec, respectively. Atomic force microscope measurements indicated a low RMS roughness (1.9 nm) as confirmed by fringes in the XRD 2θ/Ω scan. It was suggested that the improvement in XRD response relative to the substrate might be due to “healing” of sub-surface polishing damage due to the elevated Ts used for the growth. Indeed the c-lattice parameter for the homoepitaxial layer on the melt-grown substrate had become that which would be expected for strain-free ZnO. Furthermore, the stability of the PL peak positions relative to bulk ZnO, confirmed that the films appear practically strain free. 相似文献
70.