A Simple Modularity Measure for Search Spaces based on Information Theory

Within the context of Artificial Life the question about the role of modularity has turned out to be crucial, especially with regard to the problem of evolvability. In order to be able to observe the development of modular structure, appropriate modularity measures are important. We introduce a continuous measure based on information theory which can characterize the coupling among subsystems in a search problem. In order to illustrate the concepts developed, they are applied to a very simple and intuitive set of combinatorial problems similar to scenarios used in the seminal work by Simon (1969). It is shown that this measure is closely related to the classification of search problems in terms of Separability, Non-Decomposability and Modular Interdependency as introduced in (Watson and Pollack, 2005)

Alien Registration- Watson, Peter A. (Fort Fairfield, Aroostook County)

https://digitalmaine.com/alien_docs/35642/thumbnail.jp

The effect of boundary constraints on finite element modelling of the human pelvis

The use of finite element analysis (FEA) to investigate the biomechanics of anatomical systems critically relies on the specification of physiologically representative boundary conditions. The biomechanics of the pelvis has been the specific focus of a number of FEA studies previously, but it is also a key aspect in other investigations of, for example, the hip joint or new design of hip prostheses. In those studies, the pelvis has been modelled in a number of ways with a variety of boundary conditions, ranging from a model of the whole pelvic girdle including soft tissue attachments to a model of an isolated hemi-pelvis. The current study constructed a series of FEA models of the same human pelvis to investigate the sensitivity of the predicted stress distributions to the type of boundary conditions applied, in particular to represent the sacro-iliac joint and pubic symphysis. Varying the method of modelling the sacro-iliac joint did not produce significant variations in the stress distribution, however changes to the modelling of the pubic symphysis were observed to have a greater effect on the results. Over-constraint of the symphysis prevented the bending of the pelvis about the greater sciatic notch, and underestimated high stresses within the ilium. However, permitting medio-lateral translation to mimic widening of the pelvis addressed this problem. These findings underline the importance of applying the appropriate boundary conditions to FEA models, and provide guidance on suitable methods of constraining the pelvis when, for example, scan data has not captured the full pelvic girdle. The results also suggest a valid method for performing hemi-pelvic modelling of cadaveric or archaeological remains which are either damaged or incomplete

Using deep learning to correct theoretically-derived models

[no abstract

A nontrivial T1-space admitting a unique quasi-proximity

We construct a T1-space that is not hereditarily compact, although each of its open sets is the intersection of two compact open sets. The search for such a space was motivated by a problem in the theory of quasi-proximitie

Detection of Earth-like Planets Using Apodized Telescopes

The mission of NASA's Terrestrial Planet Finder (TPF) is to find Earth-like planets orbiting other stars and characterize the atmospheres of these planets using spectroscopy. Because of the enormous brightness ratio between the star and the reflected light from the planet, techniques must be found to reduce the brightness of the star. The current favorite approach to doing this is with interferometry: interfering the light from two or more separated telescopes with a $\pi$ phase shift, nulling out the starlight. While this technique can, in principle, achieve the required dynamic range, building a space interferometer that has the necessary characteristics poses immense technical difficulties. In this paper, we suggest a much simpler approach to achieving the required dynamic range. By simply adjusting the transmissive shape of a telescope aperture, the intensity in large regions around the stellar image can be reduced nearly to zero. This approach could lead to construction of a TPF using conventional technologies, requiring space optics on a much smaller scale than the current TPF approach.Comment: Accepted for publication in ApJ Letters, 9 pages, 6 figure

Picturesque Transformations: A. J. Davis in the Hudson Valley and Beyond

This thesis examines the role English landscape gardening played in shaping the career and working methods of the American architect Alexander Jackson Davis (1803â€1892) and its implications for preserving his surviving body of work in the Hudson Valley. The study is organized around a detailed study of four Davis country house projects (Blithewood, The Dr. Oliver Bronson House, Montgomery Place, and Locust Grove), each of which involve the redesign of an existing house and landscape into a radically different form; a specific mode of transformation that has a long history within English landscape gardening tradition. What emerges from this study is a very different view of A. J. Davis's professional identity than has been traditionally appreciated and a different way to "read" his watercolor drawings. In an era before the professionalization of the architectural discipline, English landscape gardening offered Davis an attractive working model to practice architecture as an artist, using his compositional skills to create artistically cohesive scenes in real landscapes blending the techniques of landscape painting and architectural design. All of this was shaped by English precedents Davis learned about through his participation in the early National Academy of Design under Samuel F. B. Morse (1791â€1872) and Davis's documented reading of English landscape gardening books. Following such influential English role models as Humphry Repton (1752â€1818), Davis designed onsite rather than drafting plans and elevations in the office, working to capture the actual conditions of light and shade, texture and color, in his designs and compositions. And like Repton, Davis was equally concerned with both "aspects" and "prospects," the way architecture formed a part of the landscape composition and framed the view outward. This thesis explores how Davis employed landscape gardening in four major country house commissions, documenting the existing conditions before he arrived on the scene and the process by which both the architectural elements in the landscape and the landscape itself was transformed over time into unified picturesque compositions. Understanding Davis in this way has major implications for preservation and interpretation of his surviving work. Landscape restoration assumes an equal position with architectural restoration. To assist current preservation work, this thesis offers a set of recommended strategies for each of the four case study sites that flow directly from the analysis and Davis's conception of landscape and architecture as inseparable parts of a single artistic whole

Generating samples of extreme winters to support climate adaptation

Recent extreme weather across the globe highlights the need to understand the potential for more extreme events in the present-day, and how such events may change with global warming. We present a methodology for more efficiently sampling extremes in future climate projections. As a proof-of-concept, we examine the UK’s most recent set of national Climate Projections (UKCP18). UKCP18 includes a 15-member perturbed parameter ensemble (PPE) of coupled global simulations, providing a range of climate projections incorporating uncertainty in both internal variability and forced response. However, this ensemble is too small to adequately sample extremes with very high return periods, which are of interest to policy-makers and adaptation planners. To better understand the statistics of these events, we use distributed computing to run three 1000-member initial-condition ensembles with the atmosphere-only HadAM4 model at 60km resolution on volunteers’ computers, taking boundary conditions from three distinct future extreme winters within the UKCP18 ensemble. We find that the magnitude of each winter extreme is captured within our ensembles, and that two of the three ensembles are conditioned towards producing extremes by the boundary conditions. Our ensembles contain several extremes that would only be expected to be sampled by a UKCP18 PPE of over 500 members, which would be prohibitively expensive with current supercomputing resource. The most extreme winters we simulate exceed those within UKCP18 by 0.85 K and 37% of the present-day average for UK winter means of daily maximum temperature and precipitation respectively. As such, our ensembles contain a rich set of multivariate, spatio-temporally and physically coherent samples of extreme winters with wide-ranging potential applications

Response of winter climate and extreme weather to projected Arctic sea-ice loss in very large-ensemble climate model simulations

Very large (~2000 members) initial-condition ensemble simulations have been performed to advance understanding of mean climate and extreme weather responses to projected Arctic sea-ice loss under 2 °C global warming above preindustrial levels. These simulations better sample internal atmospheric variability and extremes for each model compared to those from the Polar Amplification Model Intercomparison Project (PAMIP). The mean climate response is mostly consistent with that from the PAMIP multi-model ensemble, including tropospheric warming, reduced midlatitude westerlies and storm track activity, an equatorward shift of the eddy-driven jet and increased mid-to-high latitude blocking. Two resolutions of the same model exhibit significant differences in the stratospheric circulation response; however, these differences only weakly modulate the tropospheric response. The response of temperature and precipitation extremes largely follows the seasonal-mean response. Sub-sampling confirms that large ensembles (e.g. ≥400) are needed to robustly estimate the seasonal-mean large-scale circulation response, and very large ensembles (e.g. ≥1000) for regional climate and extremes

The role of iron uptake in pathogenicity and symbiosis in Photorhabdus luminescens TT01

<p>Abstract</p> <p>Background</p> <p><it>Photorhabdus </it>are Gram negative bacteria that are pathogenic to insect larvae whilst also having a mutualistic interaction with nematodes from the family <it>Heterorhabditis</it>. Iron is an essential nutrient and bacteria have different mechanisms for obtaining both the ferrous (Fe²⁺) and ferric (Fe³⁺) forms of this metal from their environments. In this study we were interested in analyzing the role of Fe³⁺and Fe²⁺iron uptake systems in the ability of <it>Photorhabdus </it>to interact with its invertebrate hosts.</p> <p>Results</p> <p>We constructed targeted deletion mutants of <it>exbD</it>, <it>feoABC </it>and <it>yfeABCD </it>in <it>P. luminescens </it>TT01. The <it>exbD </it>mutant was predicted to be crippled in its ability to obtain Fe³⁺and we show that this mutant does not grow well in iron-limited media. We also show that this mutant was avirulent to the insect but was unaffected in its symbiotic interaction with <it>Heterorhabditis</it>. Furthermore we show that a mutation in <it>feoABC </it>(encoding a predicted Fe²⁺permease) was unaffected in both virulence and symbiosis whilst the divalent cation transporter encoded by <it>yfeABCD </it>is required for virulence in the Tobacco Hornworm, <it>Manduca sexta </it>(Lepidoptera) but not in the Greater Wax Moth, <it>Galleria mellonella </it>(Lepidoptera). Moreover the Yfe transporter also appears to have a role during colonization of the IJ stage of the nematode.</p> <p>Conclusion</p> <p>In this study we show that iron uptake (via the TonB complex and the Yfe transporter) is important for the virulence of <it>P. luminescens </it>to insect larvae. Moreover this study also reveals that the Yfe transporter appears to be involved in Mn²⁺-uptake during growth in the gut lumen of the IJ nematode. Therefore, the Yfe transporter in <it>P. luminescens </it>TT01 is important during colonization of both the insect and nematode and, moreover, the metal ion transported by this pathway is host-dependent.</p