Interactions of Satellite Galaxies in Cosmological Dark Matter Halos

We present a statistical analysis of the interactions between satellite galaxies in cosmological dark matter halos taken from fully self-consistent high-resolution simulations of galaxy clusters. We show that the number distribution of satellite encounters has a tail that extends to as many as 3-4 encounters per orbit. On average 30% of the substructure population had at least one encounter (per orbit) with another satellite galaxy. However, this result depends on the age of the dark matter host halo with a clear trend for more interactions in younger systems. We also report a correlation between the number of encounters and the distance of the satellites to the centre of the cluster: satellite galaxies closer to the centre experience more interactions. However, this can be simply explained by the radial distribution of the substructure population and merely reflects the fact that the density of satellites is higher in those regions. In order to find substructure galaxies we applied (and present) a new technique based upon the N-body code MLAPM. This new halo finder MHF (MLAPM's-Halo-Finder) acts with exactly the same accuracy as the N-body code itself and is therefore free of any bias and spurious mismatch between simulation data and halo finding precision related to numerical effects.Comment: 6 pages, 4 figures, accepted by PASA (refereed contribution to the 5th Galactic Chemodynamics workshop, July 2003

Mapping Substructures in Dark Matter Halos

We present a detailed study of the real and integrals-of-motion space distributions of a satellite obtained from a self-consistent high-resolution simulation of a galaxy cluster and re-simulated using various analytical halo potentials. We found that the disrupted satellite appears as a coherent structure in integrals-of-motion space in all models (``live'' and analytical potential) although the distribution is significantly smeared for the live host halo. Further the primary mechanism for this smearing is the mass growth of the host, which changes both the energy and angular momentum of the satellite debris. Hence, this must be considered when searching for (stellar) streams with future observational experiments such as RAVE and GAIA.Comment: 5 pages, 6 figures, MNRAS accepted - minor editing without changing the conclusions, a high-resolution version of the paper is available from http://astronomy.swin.edu.au/~sgill/downloads/downloads.htm

Mechanism of the photovoltaic effects in 2-4 compounds Progress report, 1 Apr. - 30 Sep. 1968

Current gain mechanism in copper sulfide-cadmium sulfide diode upon photoexcitation in presence of reverse bia

LENS® and SFF: Enabling Technologies for Optimized Structures

Optimized, lightweight, high-strength structures are needed in many applications from aerospace to automotive. In pursuit of such structures, there have been proposed analytical solutions and some specialized FEA solutions for specific structures such as automobile frames. However, generalized 3D optimization methods have been unavailable for use by most designers. Moreover, in the cases where optimized structural solutions are available, they are often hollow, curving, thin wall structures that cannot be fabricated by conventional manufacturing methods. Researchers at Sandia National Laboratories and the University of Rhode Island teamed to solve these problems. The team has been pursuing two methods of optimizing models for generalized loading conditions, and also has been investigating the methods needed to fabricate these structures using Laser Engineered Net Shaping™ (LENS®) and other rapid prototyping methods. These solid freeform fabrication (SFF) methods offer the unique ability to make hollow, high aspect ratio features out of many materials. The manufacturing development required for LENS to make these complex structures has included the addition of rotational axes to Sandia’s LENS machine bringing the total to 5 controlled axes. The additional axes have required new efforts in process planning. Several of the unique structures that are only now possible through the use of SFF technology are shown as part of the discussion of this exciting new application for SFF.Mechanical Engineerin

Products of Random Matrices

We derive analytic expressions for infinite products of random 2x2 matrices. The determinant of the target matrix is log-normally distributed, whereas the remainder is a surprisingly complicated function of a parameter characterizing the norm of the matrix and a parameter characterizing its skewness. The distribution may have importance as an uncommitted prior in statistical image analysis.Comment: 9 pages, 1 figur

A quasi-monomode guided atom-laser from an all-optical Bose-Einstein condensate

We report the achievement of an optically guided and quasi-monomode atom laser, in all spin projection states ($m_F =$ -1, 0 and $+1$) of F=1 in Rubidium 87. The atom laser source is a Bose-Einstein condensate (BEC) in a crossed dipole trap, purified to any one spin projection state by a spin-distillation process applied during the evaporation to BEC. The atom laser is outcoupled by an inhomogenous magnetic field, applied along the waveguide axis. The mean excitation number in the transverse modes is $= 0.65 \pm 0.05$ for $m_F = 0$ and $= 0.8 \pm 0.3$ for the low field seeker $m_F = -1$

Hybrid Superconductor-Quantum Point Contact Devices using InSb Nanowires

Proposals for studying topological superconductivity and Majorana bound states in nanowires proximity coupled to superconductors require that transport in the nanowire is ballistic. Previous work on hybrid nanowire-superconductor systems has shown evidence for Majorana bound states, but these experiments were also marked by disorder, which disrupts ballistic transport. In this letter, we demonstrate ballistic transport in InSb nanowires interfaced directly with superconducting Al by observing quantized conductance at zero-magnetic field. Additionally, we demonstrate that the nanowire is proximity coupled to the superconducting contacts by observing Andreev reflection. These results are important steps for robustly establishing topological superconductivity in InSb nanowires

Evaluating a communication technology assessment tool (CTAT): A case of a cloud based communication tool

A primary concern of distributed adaptive development environment (DADE) is that of human communication and knowledge sharing among geographically dispersed developers. Emerging cloudbased communication technologies claim to provide a support for communication and knowledge sharing among developers in a DADE. However, the challenge is how to enable developers to self assess and select appropriate cloud-based communication technologies for their DADE. Based on our recent empirical study, we have developed the construct of a practical communication technologies assessment tool (CTAT). We argue that, CTAT construct, as a part of our large conceptual framework of context aware cloud adaptation (CACA), can be useful to assist developers in the self assessment of appropriate cloud-based communication technologies for their DADE. This paper presents the evaluation of the CTAT by using it for the assessment of the Force.com cloud-based Chatter communication tool. The main objective of this evaluation is to determine to what extent CTAT construct is relevant, valuable and sufficient to achieve its purpose. The results of this evaluation indicate that CTAT seems useful when performing vendor independent assessment of communication technologies in order to make an informed decision about the selection of a communication tool for the DADE