Design concepts for the development of cooperative problem-solving systems

There are many problem-solving tasks that are too complex to fully automate given the current state of technology. Nevertheless, significant improvements in overall system performance could result from the introduction of well-designed computer aids. We have been studying the development of cognitive tools for one such problem-solving task, enroute flight path planning for commercial airlines. Our goal was two-fold. First, we were developing specific systems designs to help with this important practical problem. Second, we are using this context to explore general design concepts to guide in the development of cooperative problem-solving systems. These designs concepts are described

Quantized Friction across Ionic Liquid Thin Films

Ionic liquids, salts in the liquid state under ambient conditions, are of great interest as precision lubricants. Ionic liquids form layered structures at surfaces, yet it is not clear how this nano-structure relates to their lubrication properties. We measured the friction force between atomically smooth solid surfaces across ionic liquid films of controlled thickness in terms of the number of ion layers. Multiple friction-load regimes emerge, each corresponding to a different number of ion layers in the film. In contrast to molecular liquids, the friction coefficients differ for each layer due to their varying composition

Evolution of fungal phenotypic disparity

Organismal grade multicellularity has been achieved only in animals, plants, and fungi. All three kingdoms manifest phenotypically disparate body plans, but their evolution has only been considered in detail for animals. Here we seek to test the general relevance of hypotheses on the evolution of animal body plans by characterising the evolution of fungal phenotypic variety (disparity). The distribution of living fungal form is defined by four distinct morphotypes: flagellated, zygomycetous, sac-bearing, and club-bearing. The discontinuity between morphotypes is a consequence of the extinction of phylogenetic intermediates, indicating that a complete record of fungal disparity would present a much more homogeneous distribution of form. Fungal phenotypic variety gradually expands through time for the most part but sharply increases with the emergence of multicellular body plans. Simulations show these temporal trends to be decidedly non-random, and at least partially shaped by hierarchical contingency. Fungal phenotypic distance is decoupled from changes in gene number, genome size, and taxonomic diversity. Only differences in organismal complexity, the number of traits that constitute an organism, at the cellular and multicellular levels present a meaningful relationship with fungal disparity. Both animals and fungi exhibit a gradual increase in disparity through time, resulting in distributions of form made discontinuous by the extinction of phylogenetic intermediates. These congruences hint at a common mode of multicellular body plan evolution.Follow ReadMe files for explanation. Funding provided by: Natural Environment Research Council GW4+ Doctoral Training Programme*Crossref Funder Registry ID: Award Number: Funding provided by: Natural Environment Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000270Award Number: NE/P013678/1Funding provided by: Biotechnology and Biological Sciences Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000268Award Number: BB/T012773/1Funding provided by: Biotechnology and Biological Sciences Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000268Award Number: BB/N000919/1See linked manuscript

Metal Cooling in Simulations of Cosmic Structure Formation

The addition of metals to any gas can significantly alter its evolution by increasing the rate of radiative cooling. In star-forming environments, enhanced cooling can potentially lead to fragmentation and the formation of low-mass stars, where metal-free gas-clouds have been shown not to fragment. Adding metal cooling to numerical simulations has traditionally required a choice between speed and accuracy. We introduce a method that uses the sophisticated chemical network of the photoionization software, Cloudy, to include radiative cooling from a complete set of metals up to atomic number 30 (Zn) that can be used with large-scale three-dimensional hydrodynamic simulations. Our method is valid over an extremely large temperature range (10 K < T < 10^8 K), up to hydrogen number densities of 10^12 cm^-3. At this density, a sphere of 1 Msun has a radius of roughly 40 AU. We implement our method in the adaptive mesh refinement (AMR) hydrodynamic/N-body code, Enzo. Using cooling rates generated with this method, we study the physical conditions that led to the transition from Population III to Population II star formation. While C, O, Fe, and Si have been previously shown to make the strongest contribution to the cooling in low-metallicity gas, we find that up to 40% of the metal cooling comes from fine-structure emission by S, when solar abundance patterns are present. At metallicities, Z > 10^-4 Zsun, regions of density and temperature exist where gas is both thermally unstable and has a cooling time less than its dynamical time. We identify these doubly unstable regions as the most inducive to fragmentation. At high redshifts, the CMB inhibits efficient cooling at low temperatures and, thus, reduces the size of the doubly unstable regions, making fragmentation more difficult.Comment: 19 pages, 12 figures, significant revision, including new figure

Control via electron count of the competition between magnetism and superconductivity in cobalt and nickel doped NaFeAs

Using a combination of neutron, muon and synchrotron techniques we show how the magnetic state in NaFeAs can be tuned into superconductivity by replacing Fe by either Co or Ni. Electron count is the dominant factor, since Ni-doping has double the effect of Co-doping for the same doping level. We follow the structural, magnetic and superconducting properties as a function of doping to show how the superconducting state evolves, concluding that the addition of 0.1 electrons per Fe atom is sufficient to traverse the superconducting domain, and that magnetic order coexists with superconductivity at doping levels less than 0.025 electrons per Fe atom.Comment: 4 pages, 6 figure