On the Mixing Time of Geographical Threshold Graphs

We study the mixing time of random graphs in the $d$-dimensional toric unit cube $[0,1]^d$ generated by the geographical threshold graph (GTG) model, a generalization of random geometric graphs (RGG). In a GTG, nodes are distributed in a Euclidean space, and edges are assigned according to a threshold function involving the distance between nodes as well as randomly chosen node weights, drawn from some distribution. The connectivity threshold for GTGs is comparable to that of RGGs, essentially corresponding to a connectivity radius of $r=(\log n/n)^{1/d}$. However, the degree distributions at this threshold are quite different: in an RGG the degrees are essentially uniform, while RGGs have heterogeneous degrees that depend upon the weight distribution. Herein, we study the mixing times of random walks on $d$-dimensional GTGs near the connectivity threshold for $d \geq 2$. If the weight distribution function decays with $\mathbb{P}[W \geq x] = O(1/x^{d+\nu})$ for an arbitrarily small constant $\nu>0$ then the mixing time of GTG is \mixbound. This matches the known mixing bounds for the $d$-dimensional RGG

Conductive Strontium Titanate Layers Produced By Boron-ion Implantation

The ion implantation of boron has been found to be an effective method for increasing the conductivity of strontium titanate. A highly conductive layer was formed by implantations at doses of 3.6x1016 to 1.0x1017 ions/cm2, using an accelerating voltage of 100 kV, corresponding to a boron range of about 300 nm. The conductivity of the implanted layer was found to be further enhanced by about four orders of magnitude after annealing at 225 °C. The surface resistivity attained was typically 1000 Ω/square at room temperature. The resistance increased with rising temperature between 77 and 500 K. All samples were found to be n type, as determined by Hall-effect and thermoelectric measurements. The measured Hall mobility range was from 100 cm2/V sec at 77 K, decreasing to 5 cm2/V sec at 300 K. The existence of several defect energy levels can be inferred from the electrical data

Mid-infrared entangled photon generation in optimised asymmetric semiconductor quantum wells

The optimal design of asymmetric quantum well structures for generation of entangled photons in the mid-infrared range by spontaneous parametric down- conversion is considered, and the efficiency of this process is estimated. Calcu- lations show that a reasonably good degree of entanglement can be obtained, and that the optical interaction length required for optimal conversion is very short, in the few μm range

Distance Geometry for Kissing Spheres

A kissing sphere is a sphere that is tangent to a fixed reference ball. We develop in this paper a distance geometry for kissing spheres, which turns out to be a generalization of the classical Euclidean distance geometry.Comment: 11 pages, 2 picture

Thermal Effective Potential of the O(N) Linear sigma Model

The finite-temperature effective potential of the O(N) linear \sigma model is studied, with emphasis on the implications for the investigation of hot hadron dynamics. The contributions from all the ``bubble diagrams'' are fully taken into account for arbitrary N; this also allows to address some long-standing issues concerning the use of non-perturbative approaches in (finite-temperature) field theory.Comment: 8 pages, LaTe

Mini-mast CSI testbed user's guide

The Mini-Mast testbed is a 20 m generic truss highly representative of future deployable trusses for space applications. It is fully instrumented for system identification and active vibrations control experiments and is used as a ground testbed at NASA-Langley. The facility has actuators and feedback sensors linked via fiber optic cables to the Advanced Real Time Simulation (ARTS) system, where user defined control laws are incorporated into generic controls software. The object of the facility is to conduct comprehensive active vibration control experiments on a dynamically realistic large space structure. A primary goal is to understand the practical effects of simplifying theoretical assumptions. This User's Guide describes the hardware and its primary components, the dynamic characteristics of the test article, the control law implementation process, and the necessary safeguards employed to protect the test article. Suggestions for a strawman controls experiment are also included

Curriculum implementation exploratory studies: Final report

Throughout the history of schooling in New Zealand the national curriculum has been revised at fairly regular intervals. Consequently, schools are periodically faced with having to accommodate to new curriculum. In between major changes other specifically-focused changes may arise; for example, the increased recent emphasis upon numeracy and literacy

CD2AP links cortactin and capping protein at the cell periphery to facilitate formation of lamellipodia

Understanding the physiology of complex relationships between components of signaling pathways and the actin cytoskeleton is an important challenge. CD2AP is a membrane scaffold protein implicated in a variety of physiological and disease processes. The physiological function of CD2AP is unclear, but its biochemical interactions suggest that it has a role in dynamic actin assembly. Here, we report that CD2AP functions to facilitate the recruitment of actin capping protein (CP) to the Src kinase substrate, cortactin, at the cell periphery, and that this is necessary for formation of the short branched filaments that characterize lamellipodium formation and are required for cell migration. Superresolution fluorescence microscopy demonstrated that the efficient colocalization of CP and cortactin at the cell periphery required CD2AP. As both cortactin and CP function to enhance branched actin filament formation, CD2AP functions synergistically to enhance the function of both proteins. Our data demonstrate how the interplay between specialized actin regulatory molecules shapes the actin cytoskeleton

COOL-DOWN TIME ESTIMATION THROUGH NUMERICAL ANALYSIS FOR PARTIALLY INSULATED OFFSHORE PIPE-IN-PIPE FIELD JOINTS

ABSTRACT Offshore pipe-in-pipe systems require high performance thermal insulation to maintain high fluid temperature at arrival and to avoid hydrate formation during the cool-down process that follows a pipeline shut-down. At field joints, it might be difficult to achieve the design insulation performance due to installation challenges. In these cases, the insulation layer partially fills the gap between the inner and outer pipes and thus "cold spots" could potentially arise at field joints during the pipeline operation and cool-down. In this paper the impact on the thermal performance of partially insulated pipe-in-pipe field joints is evaluated through Computational Fluid Dynamics (CFD). Thermal convection is included in the fluid model for the pipe content and the air gap between the inner and outer pipes. Comparison is also made between the numerical analysis and simplified lumped-parameter models. Results from numerical simulations show that for the case considered no cold spot arises due to a lack of field joint insulation and lengthaveraged Overall Heat Transfer Coefficient (OHTC) can be used to predict the pipeline cool-down time. Numerical predictions have been compared to simulated service test results, which confirm the length-averaging effect on the OHTC. Further studies are recommended to assess potential cost savings that could be achieved for uninsulated field joints