There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.

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The electronic properties of graphene

J. Appl. Cryst.の発刊に際して

We review the dynamical mean-field theory of strongly correlated electron systems which is based on a mapping of lattice models onto quantum impurity models subject to a self-consistency condition. This mapping is exact for models of correlated electrons in the limit of large lattice coordination (or infinite spatial dimensions). It extends the standard mean-field construction from classical statistical mechanics to quantum problems. We discuss the physical ideas underlying this theory and its mathematical derivation. Various analytic and numerical techniques that have been developed recently in order to analyze and solve the dynamical mean-field equations are reviewed and compared to each other. The method can be used for the determination of phase diagrams (by comparing the stability of various types of long-range order), and the calculation of thermodynamic properties, one-particle Green's functions, and response functions. We review in detail the recent progress in understanding the Hubbard model and the Mott metal-insulator transition within this approach, including some comparison to experiments on three-dimensional transition-metal oxides. We present an overview of the rapidly developing field of applications of this method to other systems. The present limitations of the approach, and possible extensions of the formalism are finally discussed. Computer programs for the numerical implementation of this method are also provided with this article.

Dynamical mean-field theory of strongly correlated fermion systems and the limit of infinite dimensions

The upper critical field H/sub c/2(T) of the A15 compound Nb/sub 100-x/Pt/sub x/(19 1 Me V) were studied. A stoichiometric sample that had been rapidly quenched from the liquid (splat-cooled) was also investigated. For the unirradiated samples, T/sub c/ exhibits a maximum of 10.4 K at the stoichiometric composition, while both H/sub c/2(0) and dH/sub c/2(T)/dT/sub T/ = T/sub c/ attain their maximum values on the Pt-rich side of stoichiometry. The irradiated samples show a decrease of H/sub c/2(0) with increasing neutron fluence. The results are discussed in terms of antisite disorder and a strong correlation is obtained between decreasing H/sub c/2(0) and increasing disorder of the Nb atomic sites.

The effect of composition and neutron irradiation on the upper critical field of Nb3Pt

Alternating-current electrical resistance measurements between 17 Hz and 100 kHz were made on high purity Fe, Co, and Ni wires in the vicinity of their Curie temperatures (Tc). The electrical resistance was independent of frequency for temperatures (T) aboveTc. As the temperature was lowered, however, there was an abrupt jump in the electrical resistance atTc followed by a gradual decrease toward its dc value. The magnitude of the electrical resistance jump atTc increased as the square root of the frequency. The enhancement of the electrical resistance forT≦Tc is produced by an abrupt decrease of the skin depth atTc which, in turn, is due to the sudden increase in the initial magnetic permeability atTc. Measurements of the ac electrical resistance in the vicinity of the Curie temperature of certain ferromagnetic metals can be utilized to 1) accurately determine the Curie temperature using frequencies as low as 17 Hz, and 2) quantitatively determine the initial magnetic permeability as a function of temperature and heat treatment.

Low-frequency electrical resistance of iron, cobalt, and nickel in the vicinity of their Curie temperatures

Low temperature properties of CeIr3B2 and Ulr3B2

Transport as well as magnetic relaxation properties of the mixed state were studied on strongly underdoped Y{sub 1-x}Pr{sub x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} crystals We observed two correlated phenomena--a coupling transition and a transition to quantum creep The distribution of transport current below the coupling transition is highly nonuniform, which facilitates quantum creep We speculate that in the mixed state below the coupling transition, where dissipation is non-Ohmic, the current distribution may be unstable with respect to self-channeling, resulting in the formation of very thin current-carrying layers (c) 2000 The American Physical Society

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M. B. Maple

Papers

The effect of composition and neutron irradiation on the upper critical field of Nb3Pt

Low-frequency electrical resistance of iron, cobalt, and nickel in the vicinity of their Curie temperatures

Low temperature properties of CeIr3B2 and Ulr3B2

Dynamics of flux creep in underdoped single crystals of Y 1-x Pr x Ba 2 Cu 3 O 7-δ

Origin of critical temperature universal scaling relations in type-II superconductors