Evolving collective behavior in an artificial ecology

Collective behavior refers to coordinated group motion, common to many animals. The dynamics of a group can be seen as a distributed model, each “animal” applying the same rule set. This study investigates the use of evolved sensory controllers to produce schooling behavior. A set of artificial creatures “live” in an artificial world with hazards and food. Each creature has a simple artificial neural network brain that controls movement in different situations. A chromosome encodes the network structure and weights, which may be combined using artificial evolution with another chromosome, if a creature should choose to mate. Prey and predators coevolve without an explicit fitness function for schooling to produce sophisticated, nondeterministic, behavior. The work highlights the role of species’ physiology in understanding behavior and the role of the environment in encouraging the development of sensory systems

Using the past to restore the future: Quantifying historical vegetation to assist in tidal freshwater wetland restoration

Wetlands have been providing humans with critical natural ecosystem services throughout our time on Earth. Nevertheless, these invaluable ecosystems have been habitually altered as a cost of human progression. Two of the most common alterations to wetlands are hydrologic, in the form of damming, and filling. Both occurred along Kimages Creek in Charles City County, VA during the 19th and 20th centuries. In 2010 the Lake Charles dam was partially removed, restoring the creek’s tidal communication with the James River and beginning tidal forested freshwater wetland restoration. Upon the recession of the body of water, numerous woody stumps were revealed

Preventing violence: Evaluating outcomes of parenting programmes

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Urinary Levoglucosan as a Biomarker for Wood Smoke: Results of Human Exposure Studies

Urinary levoglucosan was investigated as a potential biomarker for wood smoke exposure in two different controlled experimental settings. Nine subjects were exposed to smoke from a campfire in a controlled setting and four were exposed to smoke from an older model wood stove. All subjects were asked to provide urine samples before and after exposure, and to wear personal PM2.5 monitors during the exposure. Urinary levoglucosan measurements from both studies showed no consistent response to the smoke exposure. A third experiment was conducted to assess the contribution of dietary factors to urinary levoglucosan levels. Nine subjects were asked to consume caramel and provide urine samples before and after consumption. Urinary levoglucosan levels increased within 2 hours of caramel consumption and returned to pre-exposure levels within 24 hours. These studies suggest that diet is a major factor in determining urinary levoglucosan levels and recent dietary history needs to be taken into account for future work involving levoglucosan as a biomarker of wood smoke exposure

Transgranular Stress Corrosion Cracking of 304L Stainless Steel Pipe Clamps in Direct Use Geothermal Water Heating Applications

Direct use geothermal heating relies on heat extracted from naturally occurring geothermal water sources to provide heating needs for commercial and residential use. The city of Boise, Idaho maintains the largest district geothermal heating system in the United States, utilizing a source of geothermal water at 80 °C. 304 Stainless steel (UNS S30400) pipe clamps are used throughout the system as repair seals and for new service connections. Occasionally unexpected fracture of the stainless steel clamps occurs with time-in-service periods as short as 1 year. A failure analysis was conducted, including visual, microstructural, compositional, and mechanical characterization, to determine the cause and source of the degradation. Cracking of the clamps was limited to localized regions with the remainder of the clamp unaffected. Branched, brittle cracks were observed in the failure region and exhibited transgranular propagation. Based on the temperature, available moisture, stress level, and type of material used it was determined that the likely cause of failure was neutral pH, dilute chloride-induced stress corrosion cracking. Based on this failure analysis, geothermal or other buried heated water systems must consider protective measures or more SCC-resistant materials to prevent susceptible conditions from developing, compared to conventional water systems, to ensure maximum lifetime performance

Chimeric streptavidins as host proteins for artificial metalloenzymes

The streptavidin scaffold was expanded with well-structured naturally occurring motifs. These chimeric scaffolds were tested as hosts for biotinylated catalysts as artificial metalloenzymes (ArM) for asymmetric transfer hydrogenation, ring-closing metathesis and anion−π catalysis. The additional second coordination sphere elements significantly influence both the activity and the selectivity of the resulting hybrid catalysts. These findings lead to the identification of propitious chimeric streptavidins for future directed evolution efforts of artificial metalloenzymes