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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

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

The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Chemistry and properties of nanocrystals of different shapes.

Wave mechanics applied to semiconductor heterostructures

The band structure of GaAs-GaAlAs and InAs-GaSb superlattices is calculated by matching propagating or evanescent envelope functions at the boundary of consecutive layers. For GaAs-GaAlAs materials, the envelope functions are the solutions of an effective Hamiltonian in which both band edges and effective masses are position dependent. The effective-mass jumps modify the boundary conditions which are imposed to the eigenstates of the effective-mass Hamiltonian. In InAs-GaSb superlattices, the dispersion relations, although quite similar to those obtained in GaAs-GaAlAs materials, reflect the genuine symmetry mismatch of InAs (electrons) and GaSb (light-holes) levels. The evolution of the InAs-GaSb band structure with increasing periodicity is calculated and found to be in excellent agreement with previous LCAO results. The dispersion relations of heavy-hole bands are obtained.

Superlattice band structure in the envelope-function approximation

We present photoluminescence data on InAs quantum dots grown by molecular beam epitaxy on GaAs. Through the reduction of the number of emitting dots in small mesa structures, we evidence narrow lines in the spectra, each associated with a single InAs dot. Beyond the statistical analysis allowed by this technique, our results indicate short capture and relaxation times into the dots. This approach opens the route towards the detailed optical study of high quality easily fabricated single semiconductor quantum dots.

Photoluminescence of single InAs quantum dots obtained by self-organized growth on GaAs.

We report on calculations of intrasubband and intersubband phonon scattering in quantum-confined electron gases based on lattice-matched ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As/InP quantum wells. Dimensionality effects on the emission of acoustic phonons are studied comparing the scattering times of two-, one-, and zero-dimensional electron gases as a function of the lateral confinement. Optical phonon scattering in quantum wells and wires is discussed using a phenomenological broadening of the one-dimensional density of states. The energy relaxation rates of heated electron gases due to phonon emission and absorption have been calculated for lattice temperatures ${\mathit{T}}_{\mathit{l}}$ between 0.3 and 20 K. For a given heating power per electron, the electron temperature ${\mathit{T}}_{\mathit{e}}$ in a quantum wire can be greater or smaller than that in the corresponding quantum well, depending on the electron density ${\mathit{n}}_{\mathit{s}}$, while the energy relaxation in quantum dots with significant quantization energies is always slower than in the corresponding wells and wires.

Phonon scattering and energy relaxation in two-, one-, and zero-dimensional electron gases

We report on calculations of inlrasubband and intersubband phonon scattering in quantum-confined electron gases based on lattice-matched In x Ga 1-x As/InP quantum wells. Dimensionality effects on the emission of acoustic phonons are studied comparing the scattering times of two-, one-, and zero-dimensional electron gases as a function of the lateral confinement. Optical phonon scattering in quantum wells and wires is discussed using a phenomenological broadening of the one-dimensional density of states. The energy relaxation rates of heated electron gases due to phonon emission and absorption have been calculated for lattice temperatures T 1 between 0.3 and 20 K. For a given healing power per electron, the electron temperature T e in a quantum wire can be greater or smaller than that in the corresponding quantum well, depending on the electron density n s , while the energy relaxation in quantum dots with significant quantization energies is always slower than in the corresponding wells and wires.

Gérald Bastard

Papers

Wave mechanics applied to semiconductor heterostructures

Superlattice band structure in the envelope-function approximation

Photoluminescence of single InAs quantum dots obtained by self-organized growth on GaAs.

Phonon scattering and energy relaxation in two-, one-, and zero-dimensional electron gases

Phonon scattering and energy relaxation in two-, one-, and zero-dimensional electron gases