Geoffrey B. Matthews

Multivariate analysis of the impacts of the turbine fuel JP-4 in a microcosm toxicity test with implications for the evaluation of ecosystem dynamics and risk assessment

Turbine fuels are often the only aviation fuel available in most of the world. Turbine fuels consist of numerous constituents with varying water solubilities, volatilities and toxicities. This study investigates the toxicity of the water soluble fraction (WSF) of JP-4 using the Standard Aquatic Microcosm (SAM). Multivariate analysis of the complex data, including the relatively new method of nonmetric clustering, was used and compared to more traditional analyses. Particular emphasis is placed on ecosystem dynamics in multivariate space.The WSF is prepared by vigorously mixing the fuel and the SAM microcosm media in a separatory funnel. The water phase, which contains the water-soluble fraction of JP-4 is then collected. The SAM experiment was conducted using concentrations of 0.0, 1.5 and 15% WSF. The WSF is added on day 7 of the experiments by removing 450 ml from each microcosm including the controls, then adding the appropriate amount of toxicant solution and finally bringing the final volume to 3 L with microcosm media. Analysis of the WSF was performed by purge and trap gas chromatography. The organic constituents of the WSF were not recoverable from the water column within several days of the addition of the toxicant. However, the impact of the WSF on the microcosm was apparent. In the highest initial concentration treatment group an algal bloom ensued, generated by the apparent toxicity of the WSF of JP-4 to the daphnids. As the daphnid populations recovered the algal populations decreased to control values. Multivariate methods clearly demonstrated this initial impact along with an additional oscillation seperating the four treatment groups in the latter segment of the experiment. Apparent recovery may be an artifact of the projections used to describe the multivariate data. The variables that were most important in distinguishing the four groups shifted during the course of the 63 day experiment. Even this simple microcosm exhibited a variety of dynamics, with implications for biomonitoring schemes and ecological risk assessments.

A novel nonmetric multivariate approach to the evaluation of biomarkers in terrestrial field studies

This study evaluated the usefulness of using groups of biomarkers as measures of exposure and which statistical approach wouldbe most robust for analysing such data. We used both analysis of variance (ANOVA) and nonmetric cluster and associationanalysis (NCAA) to look for patterns in biomarker responses of populations of gray-tailed voles (Microtus canicaudus)in field enclosures exposed to azinphos-methyl (Guthion2S) at 0.0, 1.55 and 4.67 kg active ingredient(AI)ha-1 (four enclosures per treatment level). Biomarkers measured were hematocrit,total leukocyte counts, leukocyte differentiation, plasma lactate dehydrogenase (LDH), isocitratedehydrogenase, creatine phosphokinase (CPK) activities, and plasma creatinine and blood urea nitrogenconcentrations. Brain cholinesterase (AChE) activity was measured in a subset of animals. The ANOVAwas able to distinguish differences between treatment groups only for brain AChE. The NCAA confirmedthe ANOVA analysis that brain AChE activity differed significantly among the treatment groups. However,NCAA also identified LDH and CPK activity, and neutrophil and lymphocyte numbers as importantdiscriminants of pesticide treatment. Additionally, changes in blood cell parameters due to spatialgradients were layered over the effects due to the pesticide.

Procedural modeling of medieval castles

This research paper describes a new method in which the discovery and construction of man-made structures, specifically medieval castles, in a three dimensional environment can be intelligently constructed given only a random terrain and simple user-defined suggestions. Our method of procedural modeling makes use of convex hulls, extracted from a given terrain, to provide several construction elements that are used to complete the finished model.In developing the procedurally modeled castles, we employed hybrid multi-fractals using Perlin noise as way to generate random terrains. It was essential to implement the random/fractal terrain generation to provide sufficient means of testing several cases, as opposed to using the same terrain over and over. This provided a fast and efficient means of testing a component of the modeling method on several different terrains.The approach this modeling procedure first takes is common among the construction of man made buildings. Just as one would do when first setting up a tent, for example, the first step is to locate a suitable site. The target for such a search is a satisfactory foundation in which to build upon. Our approach was to search the generated terrain for those facets whose normals are within some tolerance of straight up. This will find those portions of the terrain that are the most horizontal and, therefore, offer the most potential for a natural foundation for the castle, and require the least movement of soil.Once the horizontal facets of the terrain have been located they are grouped together. Now the decision as to what shape the encompassing foundation will take must be made. This is done because in most cases the grouped facets will contain holes or appear to branch which does not lend itself well to a foundation. Obviously bounding squares, rectangles, circumferences, or any other user defined shape, for that matter, could do this job. In fact, many castles are indeed built in such a way that they are quite symmetric and using a user defined shape may provide a very desirable foundation. However, our method implements a more general approach that provides a unique foundation and therefore a unique castle construction each time it is presented with a terrain.Our approach to foundation shape creation is to use the points from the grouped horizontal facets and use the convex hull of these points as the boundary of the foundation. One major advantage and positive visual effect that using a convex hull foundation provides over a user defined bounding shape is that it gives the appearance of the castle being built to suit its environment with minimal modification to the terrain.To provide easy access to these candidate foundation hulls, a scoring system was created which accepts a users request for a convex hull from the set generated initially. The request defines desired attributes such as position, altitude, and area along with weights that specify the importance of the attributes. The foundation finder then scores the hulls according the the users request and returns the highest scoring hull.We discovered that the convex hulls lent themselves very nicely to the other elements of the castle. Castle walls could be built simply by using either the foundation convex hull or a similar hull by using the hulls sides to project onto the terrain where the walls should be built. In addition, concentric outer and inner walls could be built by using hulls varying in scale and by perturbing the points of the hull to provide additional randomness. The towers along the walls could simply be placed at the points along the boundary of the hulls.The convex hulls were also employed in the creation of the castle moat. Using three hulls; one for the inner shore, another to define the middle band of the moat where it is at its deepest, and one for the outer shore, the terrain can be interpolated into a v-shape to create the moat. Additional terrain interpolation was also implemented to erode raised foundations back into the generated terrain to prevent sharp cliff-like artifacts. This too used convex hull boundaries to specify the points that were to interpolated.Convex hulls were also used when expanding the size of the castles. Castles often outgrew their usefulness and would need to be expanded in order to further serve a meaningful purpose. We again put to use the request system when expanding the area of a castle by using the first foundation request that was used to obtain the first convex hull foundation. Using the same request lets us retrieve the most similar, more importantly closest, piece of foundation-worthy land. We can then create a new convex hull using an enlarged version of our initial foundation hull and the newly requested convex hull, for example, in order to create a new outer wall.

A Framework for the Assessment of Enjoyment in Video Games

We2 present an overview of current research in the measurement of enjoyment in video games. We attempt to systematize the disparate approaches found with the vocabulary and constructs of quasi-experimentation. In each area, we try to make some recommendations for improvement, and find some areas in need of further research.

Nonmetric clustering: new approaches for ecological data

Ecological studies and multispecies ecotoxicological tests are based on the examination of a variety of physical, chemical and biological data with the intent of finding patterns in their changing relationships over time. The data sets resulting from such studies are often noisy, incomplete, and difficult to envision. We have developed machine learning and visualization software to aid in the analysis, modelling, and understanding of such systems. The software is based on nonmetric conceptual clustering, which attempts to analyze the data into clusters that are strongly associated with several measured parameters. Our analysis and visualization tools not only confirmed suspected ecological patterns, but revealed aspects of the data that were unnoticed by ecologists using conventional statistical techniques.<<ETX>>