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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.

Bose-Einstein condensation in a gas of sodium atoms

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

The stability of two-dimensional (2D) layers and membranes is subject of a long standing theoretical debate. According to the so called Mermin-Wagner theorem, long wavelength fluctuations destroy the long-range order for 2D crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled. These dangerous fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes making that a two-dimensional membrane can exist but should present strong height fluctuations. The discovery of graphene, the first truly 2D crystal and the recent experimental observation of ripples in freely hanging graphene makes these issues especially important. Beside the academic interest, understanding the mechanisms of stability of graphene is crucial for understanding electronic transport in this material that is attracting so much interest for its unusual Dirac spectrum and electronic properties. Here we address the nature of these height fluctuations by means of straightforward atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon. We find that ripples spontaneously appear due to thermal fluctuations with a size distribution peaked around 70 \AA which is compatible with experimental findings (50-100 \AA) but not with the current understanding of stability of flexible membranes. This unexpected result seems to be due to the multiplicity of chemical bonding in carbon.

Intrinsic ripples in graphene

Characterizing Raman modes and gas sensing features of functionalized tetragonal graphyne quantum dots: A first principles study

The real space decimation method has been successfully applied over the years to understand the critical phenomena as well as the nature of single particle excitations in periodic, quasiperiodic, fractal, and decorated lattices in one dimension and beyond. The power of the method is specially revealed through its application in lattice models, leading to an elegant understanding of the nature of the single-particle states and the corresponding transport properties. In this review, we discuss, using a variety of decorated lattices, how the realm of this method is extended to unravel diverse electronic phases of matter, such as the Dirac systems, or lattices exhibiting flat bands and topological phase transitions.

Application of the real space decimation method in determining intricate electronic phases of matter: a review.

Two novel phases of germa-graphene: Prediction, electronic and transport applications

The optical properties of (8,0) single wall carbon nanotubes (SWCNTs) alloyed with nitrogen (N) are computed using ab initio density functional theory (DFT). Both the real as well as imaginary dielectric constant in the long wavelength limit depends essentially on the nature of electromagnetic field. It is observed that for CN3 systems, the reflectivity vanishes at 3.45, 6.95, and 8.20 eV, respectively for parallel, perpendicular polarization, and unpolarized light with incidence (1,0,0), while for C3N the vanishing reflectivity occurs only for parallel polarization at 8.05 eV. Although the magnitude of the significant peaks of loss function of CN3 systems are comparable to C3N in perpendicular and unpolarized situation, however, they are significantly one order of magnitude higher in CN3 for parallel polarization.

Debnarayan Jana

Papers

Characterizing Raman modes and gas sensing features of functionalized tetragonal graphyne quantum dots: A first principles study

Application of the real space decimation method in determining intricate electronic phases of matter: a review.

Two novel phases of germa-graphene: Prediction, electronic and transport applications

A comparative study of optical properties of c3n and cn3 systems through density functional theory (dft)

Silicene and transition metal based materials: prediction of a two-dimensional piezomagnet