Probabilistic Analysis of Self-assembly

Probabilistic Analysis of Self-assembl

Directed Percolation and the Abstract Tile Assembly Model

Self-assembly is a process by which simple components build complex structures through local interactions. Directed percolation is a statistical physical model for describing competitive spreading processes on lattices. The author describes an algorithm which can transform a tile assembly system in the abstract Tile Assembly Model into a directed percolation problem, and then shows simulations of the aTAM which support this algorithm. The author also investigates two new constructs designed for Erik Winfree\u27s abstract Tile Assembly Model called the NULL tile and temperature 1.5. These constructs aid the translation between self-assembly and directed percolation and may assist self-assembly researchers in designing tilesets in the aTAM with non-deterministic local properties, but guaranteed global properties. Temperature 1.5 results indicate the brittleness of the standard temperature 2 tile assembly system, and the NULL tile is shown to assist simulations of large assembly processes while also reinforcing the need for variable temperature models to more closely simulate laboratory self-assembly

Concert recording 2017-05-04b

[Track 1]. Fanfare for the common man / Aaron Copland -- [Track 2]. Bach Buch / J.S. Bach translated by Pann -- [Track 3]. Highway musings / Ryan Key -- [Track 4]. Serenade in D minor / Antonín Dvorák

Heat Adaptation in Military Personnel : Mitigating Risk, Maximizing Performance

© Copyright © 2019 Parsons, Stacey and Woods. The study of heat adaptation in military personnel offers generalizable insights into a variety of sporting, recreational and occupational populations. Conversely, certain characteristics of military employment have few parallels in civilian life, such as the imperative to achieve mission objectives during deployed operations, the opportunity to undergo training and selection for elite units or the requirement to fulfill essential duties under prolonged thermal stress. In such settings, achieving peak individual performance can be critical to organizational success. Short-notice deployment to a hot operational or training environment, exposure to high intensity exercise and undertaking ceremonial duties during extreme weather may challenge the ability to protect personnel from excessive thermal strain, especially where heat adaptation is incomplete. Graded and progressive acclimatization can reduce morbidity substantially and impact on mortality rates, yet individual variation in adaptation has the potential to undermine empirical approaches. Incapacity under heat stress can present the military with medical, occupational and logistic challenges requiring dynamic risk stratification during initial and subsequent heat stress. Using data from large studies of military personnel observing traditional and more contemporary acclimatization practices, this review article (1) characterizes the physical challenges that military training and deployed operations present (2) considers how heat adaptation has been used to augment military performance under thermal stress and (3) identifies potential solutions to optimize the risk-performance paradigm, including those with broader relevance to other populations exposed to heat stress

Cold truths: how winter drives responses of terrestrial organisms to climate change

Winter is a key driver of individual performance, community composition, and ecological interactions in terrestrial habitats. Although climate change research tends to focus on performance in the growing season, climate change is also modifying winter conditions rapidly. Changes to winter temperatures, the variability of winter conditions, and winter snow cover can interact to induce cold injury, alter energy and water balance, advance or retard phenology, and modify community interactions. Species vary in their susceptibility to these winter drivers, hampering efforts to predict biological responses to climate change. Existing frameworks for predicting the impacts of climate change do not incorporate the complexity of organismal responses to winter. Here, we synthesise organismal responses to winter climate change, and use this synthesis to build a framework to predict exposure and sensitivity to negative impacts. This framework can be used to estimate the vulnerability of species to winter climate change. We describe the importance of relationships between winter conditions and performance during the growing season in determining fitness, and demonstrate how summer and winter processes are linked. Incorporating winter into current models will require concerted effort from theoreticians and empiricists, and the expansion of current growing-season studies to incorporate winter

Materials Performance in CO2 and Supercritical CO2

International audiencePast and current gas-cooled nuclear reactors rely on CO2-rich gases as a coolant to transfer heat from the reactor core, while future reactors may utilize a supercritical CO2 Brayton cycle for power production. The alloys used to construct these systems can experience serious corrosion issues induced by CO2 in the high temperature portions of the reactor and therefore alloy compatibility in these environments represents an important materials consideration. This article presents a summary of the extensive corrosion research that has accumulated for structural alloys in high temperature CO2 environments over a wide range of pressures relevant to past, current, and future nuclear reactors, with an emphasis on the Fe-Cr based steels that are most commonly used in these systems. The fundamental mechanisms controlling alloy degradation are presented and discussed in the context of the probable life-limiting processes to provide guidance and caution toward the informed selection of materials for future CO2 based systems