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排序方式: 共有87条查询结果,搜索用时 31 毫秒
51.
A. Valletta A. Bianconi A. Perali N.L. Saini 《Zeitschrift für Physik B Condensed Matter》1997,104(4):707-713
The superconducting gap, the critical temperature and the isotope coefficient in a superlattice of metallic quantum stripes is calculated as a function of the electron number density. We show that it is possible to design a particular artificial superlattice of quantum stripes that exhibits the curves of T c and of the isotope coefficient as a function of the charge density as in cuprate superconductors. The shape of the superlattice is designed in order to tune the chemical potential near the bottom of the third subband for an electron number density of ρ ~ 5:810-2Å-2. The superconducting critical temperature shows a resonant amplification as a function of electron number density ρ with a maximum at a critical value ρ c. The isotope coefficient shows a sharp drop from a regime where α > 0:5 at ρ < ρ c to a regime where α < 0:2 at ρ ≥ ρ c. The underdoped and overdoped regime in cuprate superconductors is associated with a transition from a quasi 1D behavior for ρ > ρ c to quasi 2D behavior for ρ < ρ c with opening of a pseudogap at ρ ~ ρ c. 相似文献
52.
G. Cirri M. Bianconi F. Cordero A. Bicci M. Dobrowolny C. Bonifazi 《Il Nuovo Cimento C》1992,15(2):203-217
Summary This paper presents experimental results on the effects of increasing gas pressure on electron gun operations. The electron
gun used is the gun EGA which has been developed for the TSS-1 mission. Various gases have been used with pressures in the
range from 10−6 to a few times 10−3 mbar. The measurements, taken in a vacuum chamber, show a steady increase in the slope of theI–V characteristics of the gun when the pressure is increased, as a consequence of ionization phenomena induced by the electron
beam. Further measurements have been taken of the overall current on a target at some distance from the gun itself. An attempt
is also made at a theoretical calculation of the effects observed, based on simplified models. 相似文献
53.
Adsorbate-substrate interactions in the initial oxidation of the (100), (110), and (111) single-crystal faces of aluminum have been studied by partial photoyield spectroscopy with the final-state energy tuned to coincide with an inter-atomic Auger transition [A1 (2p) O (2s) V.B.]. This higher energy final state is shown to provide significantly better surface sensitivity than that obtained with typical constant final-state spectroscopy using low-energy, secondary electrons. Models for the initial oxidation are discussed. 相似文献
54.
A. Bianconi M. DellAriccia A. Giovannelli E. Burattini N. Cavallo P. Patteri E. Pancini C. Carlini F. Ciardelli D. Papeschi P. Pertici G. Vitulli G. Dalba P. Fornasini S. Mobilio L. Palladino 《Chemical physics letters》1982,90(4):257-260
The local structure of the metal-atom surroundings in polystyrene-ruthenium complexes (PSt-Ru) has been studied by EXAFS. EXAFS at the Ru K-edge (22,118 keV) has been measured for metallic Ru and PSt-Ru. Numerical elaboration of the data gives the Ru-C distance (d = 2.05 A) and the number of carbon atoms coordinated to the metal (coordination number 6) in PSt-Ru. 相似文献
55.
Surface resonances above the Fermi level of Aluminum have been observed using surface soft-X-ray absorption spectroscopy. These surface resonances occur at 4.3 eV above the L2.3 absorption threshold on the Aluminum (100) surface and at 12.1 eV on the Aluminum (111) surface. Excited state and surface EXAFS aspects of the spectra are discussed. 相似文献
56.
Naidek KP Bianconi F da Rocha TC Zanchet D Bonacin JA Novak MA Vaz Md Winnischofer H 《Journal of colloid and interface science》2011,358(1):39-46
We synthesized magnetic spinel ferrites from trimetallic single-source precursors. Fe(II), Co(II), and Ni(II) ferrite nanoparticles in the range of 9-25 nm were synthesized by solvothermal decomposition of trimetallic acetate complex precursors in benzyl ether in the presence of oleic acid and oleylamine, using 1,2-dodecanediol as the reducing agent. For comparison, spinel ferrite nanoparticles were synthesized by stoichiometric mixtures of metal acetate or acetylacetonate salts. The nanoparticles (NP) were characterized by TEM, DLS, powder XRD, and Raman spectroscopy; and their magnetic properties were characterized by ZFC-FC and M(H) measurements. The ferrite-NP were more homogeneous and had a narrower size distribution when trimetallic complexes were used as precursors. As a consequence, the magnetic properties of these ferrite-NP are closer to the aimed room temperature superparamagnetic behavior, than are those of other ferrites obtained by a mixture of salts. 相似文献
57.
Recently, the percolation transition has been characterized on interacting networks both in presence of interdependent interactions and in presence of antagonistic interactions. Here we characterize the phase diagram of the percolation transition in two Poisson interdependent networks with a percentage q of antagonistic nodes. We show that this system can present a bistability of the steady state solutions, and both discontinuous and continuous phase transitions. In particular, we observe a bistability of the solutions in some regions of the phase space also for a small fraction of antagonistic interactions 0<q<0.4. Moreover, we show that a fraction q>q c =2/3 of antagonistic interactions is necessary to strongly reduce the region in phase-space in which both networks are percolating. This last result suggests that interdependent networks are robust to the presence of antagonistic interactions. Our approach can be extended to multiple networks, and to complex boolean rules for regulating the percolation phase transition. 相似文献
58.
N.?L.?SainiEmail author H.?Oyanagi T.?Ito V.?Scagnoli M.?Filippi S.?Agrestini G.?Campi K.?Oka A.?Bianconi 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,36(1):75-80
We have studied doping evolution of the temperature dependent local Cu-O displacements in the La2-x
Sr
x
CuO4 superconductor by polarized Cu K-edge extended X-ray absorption fine structure (EXAFS) measurements. While temperature dependent Debye-Waller factor of the Cu-O bonds, measuring the local Cu-O displacements, shows an anomalous increase at low temperature for the underdoped single crystals, we do not find such a dependence for the case of the overdoped system. The results, which are discussed in the light of recent angle resolved photoemission measurements, provide an evidence for some important correlation between the doping dependent electron-lattice interaction, the charge inhomogeneities and the local Cu-O displacements in the copper oxide superconductors.Received: 9 July 2003, Published online: 19 November 2003PACS:
74.72.Dn La-based cuprates - 61.10.Ht X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc. - 74.81.-g Inhomogeneous superconductors and superconducting systems 相似文献
59.
Bose-Einstein condensation in complex networks. 总被引:13,自引:0,他引:13
The evolution of many complex systems, including the World Wide Web, business, and citation networks, is encoded in the dynamic web describing the interactions between the system's constituents. Despite their irreversible and nonequilibrium nature these networks follow Bose statistics and can undergo Bose-Einstein condensation. Addressing the dynamical properties of these nonequilibrium systems within the framework of equilibrium quantum gases predicts that the "first-mover-advantage," "fit-get-rich," and "winner-takes-all" phenomena observed in competitive systems are thermodynamically distinct phases of the underlying evolving networks. 相似文献
60.
M.Federson R.Bianconi L.Barbanti 《应用数学学报(英文版)》2004,20(4):623-640
We consider the multidimensional abstract linear integral equation of Volterra type x(t) (*)∫Rtα(s)x(s)ds=f(t),t∈R,(1)as the limit of discrete Stieltjes-type systems and we prove results on the existence of continuous solutions. The functions x, α and f are Bauach space-valued defined on a compact interval R of R^n Rt is a subinterval of R depending on t ∈ R and (*) f denotes either the Bochner-Lebesgue integral or the Henstock integral. The results presented here generalize those in [1] and are in the spirit of [3]. As a consequence of our approach, it is possible to study the properties of (1) by transferring the properties of the discrete systems, The Henstock integral setting enables us to consider highly oscillating functions. 相似文献