Semi-classical scattering in two dimensions

The semi-classical limit of quantum-mechanical scattering in two dimensions (2D) is developed. We derive the Wentzel-Kramers-Brillouin and Eikonal results for 2D scattering. No backward or forward glory scattering is present in 2D. Other phenomena, such as rainbow or orbiting do show up.Comment: 6 page

The Apollo spacecraft: A chronology. Volume 2: 8 November 1962 - 30 September 1964

A chronology of the Apollo spacecraft development and production program is presented. The subjects discussed are: (1) defining contractural relations, (2) developing hardware distinctions, and (3) developing software ground rules. Illustrations, drawings, and photographs are used extensively to supplement the technical writing. Descriptions of life support systems, communication equipment, propulsion systems, control devices, and spacecraft components are provided

High rate continuous synthesis of nanocrystalline materials in a colliding vapor stream of microdroplets

Progress in nanotechnology is driving the need of large scale synthesis of functional nanomaterials. The lack of a workforce trained on process control and scale-up of nanomaterials manufacturing, the gap between laboratories and economically practical nanofabrication and the funding strain on the survivability of startup companies all contribute to the difficulties in scaling up nanotechnologies and their commercialization [1,2]. We report here a high rate continuous synthesis of functional inorganic nanomaterials using colliding vapor stream of reagents microdroplets

Exchange effects on electron scattering through a quantum dot embedded in a two-dimensional semiconductor structure

We have developed a theoretical method to study scattering processes of an incident electron through an N-electron quantum dot (QD) embedded in a two-dimensional (2D) semiconductor. The generalized Lippmann-Schwinger equations including the electron-electron exchange interaction in this system are solved for the continuum electron by using the method of continued fractions (MCF) combined with 2D partial-wave expansion technique. The method is applied to a one-electron QD case. Cross-sections are obtained for both the singlet and triplet couplings between the incident electron and the QD electron during the scattering. The total elastic cross-sections as well as the spin-flip scattering cross-sections resulting from the exchange potential are presented. Furthermore, inelastic scattering processes are also studied using a multichannel formalism of the MCF.Comment: 11 pages, 4 figure

High rate continuous synthesis of nanocrystalline materials in a colliding vapor stream of microdroplets

Progress in nanotechnology is driving the need of large scale synthesis of functional nanomaterials. The lack of a workforce trained on process control and scale-up of nanomaterials manufacturing, the gap between laboratories and economically practical nanofabrication and the funding strain on the survivability of startup companies all contribute to the difficulties in scaling up nanotechnologies and their commercialization [1,2]. We report here a high rate continuous synthesis of functional inorganic nanomaterials using colliding vapor stream of reagents microdroplets

A proposal of a UCN experiment to check an earthquake waves model

Elastic waves with transverse polarization inside incidence plane can create longitudinal surface wave (LSW) after reflection from a free surface. At a critical incidence angle this LSW accumulates energy density, which can be orders of magnitude higher than energy density of the incident transverse wave. A specially arranged vessel for storage of ultracold neutrons (UCN) can be used to verify this effect.Comment: 8 pages 3 figures added a paragraph on vibrations along surface at critical angl

Two-dimensional shear modulus of a Langmuir foam

We deform a two-dimensional (2D) foam, created in a Langmuir monolayer, by applying a mechanical perturbation, and simultaneously image it by Brewster angle microscopy. We determine the foam stress tensor (through a determination of the 2D gas-liquid line tension, 2.35 $\pm$ 0.4 pJ$\cdot$m$^{-1}$) and the statistical strain tensor, by analyzing the images of the deformed structure. We deduce the 2D shear modulus of the foam, $\mu= 38 \pm 3 \mathrm{nN}\cdot \mathrm{m}^{-1}$. The foam effective rigidity is predicted to be $35 \pm 3 \mathrm {nN}\cdot \mathrm {m}^{- 1}$, which agrees with the value $37.5 \pm 0.8 \mathrm {nN}\cdot \mathrm {m}^{-1}$ obtained in an independent mechanical measurement.Comment: submitted May 12, 2003 ; resubmitted Sept 9, 200

Quantum conductance problems and the Jacobi ensemble

In one dimensional transport problems the scattering matrix $S$ is decomposed into a block structure corresponding to reflection and transmission matrices at the two ends. For $S$ a random unitary matrix, the singular value probability distribution function of these blocks is calculated. The same is done when $S$ is constrained to be symmetric, or to be self dual quaternion real, or when $S$ has real elements, or has real quaternion elements. Three methods are used: metric forms; a variant of the Ingham-Seigel matrix integral; and a theorem specifying the Jacobi random matrix ensemble in terms of Wishart distributed matrices.Comment: 10 page

Nonperturbative interaction effects in the thermodynamics of disordered wires

We study nonperturbative interaction corrections to the thermodynamic quantities of multichannel disordered wires in the presence of the Coulomb interactions. Within the replica nonlinear $\sigma$-model (NL$\sigma$M) formalism, they arise from nonperturbative soliton saddle points of the NL$\sigma$M action. The problem is reduced to evaluating the partition function of a replicated classical one dimensional Coulomb gas. The state of the latter depends on two parameters: the number of transverse channels in the wire, N_{ch}, and the dimensionless conductance, G(L_T), of a wire segment of length equal to the thermal diffusion length, L_T. At relatively high temperatures, $G(L_T) \gtrsim \ln N_{ch}$, the gas is dimerized, i.e. consists of bound neutral pairs. At lower temperatures, $\ln N_{ch} \gtrsim G(L_T) \gtrsim 1$, the pairs overlap and form a Coulomb plasma. The crossover between the two regimes occurs at a parametrically large conductance $G(L_T) \sim \ln N_{ch}$, and may be studied independently from the perturbative effects. Specializing to the high temperature regime, we obtain the leading nonperturbative correction to the wire heat capacity. Its ratio to the heat capacity for noninteracting electrons, C_0, is $\delta C/C_0\sim N_{ch}G^2(L_T)e^{-2G(L_T)}$.Comment: 18 page