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

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Current-driven excitation of magnetic multilayers

In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Recent observations of Type 1a supernovae indicating an accelerating universe have once more drawn attention to the possible existence, at the present epoch, of a small positive Λ-term (cosmological constant). In this paper we review both observational and theoretical aspects of a small cosmological Λ-term. We discuss the current observational situation focusing on cosmological tests of Λ including the age of the universe, high redshift supernovae, gravitational lensing, galaxy clustering and the cosmic microwave background. We also review the theoretical debate surrounding Λ: the generation of Λ in models with spontaneous symmetry breaking and through quantum vacuum polarization effects — mechanisms which are known to give rise to a large value of Λ hence leading to the "cosmological constant problem." More recent attempts to generate a small cosmological constant at the present epoch using either field theoretic techniques, or by modelling a dynamical Λ-term by scalar fields are also extensively discussed. Anthropic arguments favouring a small Λ-term are briefly reviewed. A comprehensive bibliography of recent work on Λ is provided.

http://cds.cern.ch/record/385991/files/9904398.pdf

The Case for a Positive Cosmological Λ-Term

A theory of oscillations in the exchange coupling between two transition-metal ferromagnets separated by a nonmagnetic transition-metal spacer is developed for a one-band model. A close analogy between oscillations in the exchange and de Haas--van Alphen oscillations is established and exploited to show that the period, asymptotic decay, and temperature dependence of the oscillations are determined by properties of the Fermi surface in the spacer layer. The theory describes many features of the oscillations in the exchange coupling observed recently in Co/Ru, Co/Cr, and Fe/Cr superlattices.

Oscillations of the exchange in magnetic multilayers as an analog of de Haas-van Alphen effect.

A general theory of oscillations in the exchange coupling J between two transition metal ferromagnets separated by a nonmagnetic transition metal spacer is developed. Detailed calculations of J as a function of the spacer layer thickness are made for a specific model based on a simple cubic tight-binding band structure. For a suitable choice of band filling a good account is given of the main features observed in Co/Ru, Co/Cr and Fe/Cr layered structures. An analysis of the numerical accuracy required in computing J from a total energy difference is given and this throws some light on difficulties experienced by previous workers using this approach. A general expression for J is obtained for an arbitrary band and finite temperature in the limit of large spacer thickness. A close analogy between oscillations in the exchange coupling and de Haas-van Alphen oscillations is established and the relation to RKKY theory is also discussed. It is shown that the period, asymptotic decay and temperature dependence of the oscillations in J are determined by properties of the Fermi surface of the spacer layer.

https://iopscience.iop.org/article/10.1088/0953-8984/3/26/015/pdf

Oscillations in the exchange coupling of ferromagnetic layers separated by a nonmagnetic metallic layer

An explanation of the giant magnetoresistance effect observed in some magnetic superlattices is given in terms of an equivalent network of resistors. The model leads to a simple analytic formula that relates the magnetoresistance to the spin-dependent electron mean-free paths and thickness of the magnetic and nonmagnetic layers in the superlattice. The formula is used to study the giant magnetoresistance of Co/Cu and Fe/Cr superlattices, and is also used to predict the most favorable values of parameters for a large magnetoresistance effect. >

A resistor network theory of the giant magnetoresistance in magnetic superlattices

We present theoretical studies of the influence of spin-orbit coupling on the spin-wave excitations of the Fe monolayer and bilayer on the W(110) surface. The Dzyaloshinskii-Moriya interaction is active in such films by virtue of the absence of reflection symmetry in the plane of the film. When the magnetization is in plane, this leads to a linear term in the spin-wave dispersion relation for propagation perpendicular to the magnetization, to produce a dispersion curve similar in nature to that found for electrons on semiconducting surfaces when the Rashba coupling is active. We also show spin-polarized electron-loss spectroscopy response functions that illustrate the role of spin-orbit coupling in such measurements. In addition to the modifications of the dispersion relations for spin waves, the presence of spin-orbit coupling in the W substrate leads to a substantial increase in the linewidth of the spin-wave modes. The formalism we have developed applies to a wide range of systems, and the particular system explored in the numerical calculations provides us with an illustration of phenomena which will be present in other ultrathin ferromagnet/substrate combinations.

Spin-orbit coupling and spin waves in ultrathin ferromagnets: The spin-wave Rashba effect

We present theoretical studies of the nature of the spin excitations in ultrathin free standing Fe(110) films, and such films adsorbed on a semi-infinite W(110) substrate. The calculations are carried out within the framework of an itinerant electron theory, with a realistic underlying electronic structure. The energy bands of the film and substrate are described by a nine band empirical tight binding picture, to include the relevant d bands and overlapping sp complex. Ferromagnetism in the Fe film is driven by on site Coulomb interactions between the $3d$ electrons, treated in mean field theory while a description of the spin wave excitations is generated through use of the random phase approximation. Results are reported and discussed for Fe films three, four, and five layers in thickness. A principal conclusion which emerges from these studies is that the ``frozen magnon'' or adiabatic description of spin wave excitations proves inadequate in a qualitative sense, for systems such as those studied here. The spin waves are embedded in the Stoner continuum, with the consequence they are heavily damped by decay to Stoner excitations, save for the lowest lying mode at long wavelengths. A consequence is that throughout much of the surface Brillouin zone, the spectrum of spin excitations at each wave vector consists of a broad feature which shows dispersion, with no evidence of the sequence of standing spin wave modes predicted by a theory based on the adiabatic approximation. For the five layer film, even near the center of the surface Brillouin zone, while we find a weakly damped low lying acoustic spin wave, the first standing wave is quite broad, and the second standing wave structure is so broad it cannot be viewed as a well defined excitation. At large wave vectors, we find a single broad feature in the spectral density which shows dispersion, very similar to a spin wave, rather than a sequence of standing modes. The results are very similar in character to recent SPEELS data on the Co/Cu system. The physical reasons for the breakdown of the adiabatic method are discussed.

R. B. Muniz

Papers

Oscillations of the exchange in magnetic multilayers as an analog of de Haas-van Alphen effect.

Oscillations in the exchange coupling of ferromagnetic layers separated by a nonmagnetic metallic layer

A resistor network theory of the giant magnetoresistance in magnetic superlattices

Spin-orbit coupling and spin waves in ultrathin ferromagnets: The spin-wave Rashba effect

Theory of spin excitations in Fe(110) multilayers