Impact testing of structural biological materials

Structural biological materials must be highly impact resistant, as appendages such as antlers and horns must sustain repeated, seasonal impact loads. Determining the impact damage progression along with the impact strength is very important for understanding how nature has optimized the structure and properties of biological materials in order to guide the design of superior bio-inspired synthetic materials. A drop weight test tower based on standards for testing fiber-reinforced polymer matrix composites was designed and fabricated to accommodate the small size of biological materials. The materials tested were divided into two groups: non-mineralized and mineralized. The former demonstrated the highest impact strength and showed strong dependence on water content, while the latter were relatively brittle and demonstrated no dependence on water content. Delamination was the most common damage mode observed for all biological materials tested.     

Influence of electron donor, oxygen, and redox potential on bacterial perchlorate degradation

Experiments were conducted to assess the influence of electron donor, redox potential, and dissolved oxygen on bacterial perchlorate degradation. Microcosms containing a diverse, perchlorate-acclimated, bacterial culture fed lactate at a 1:1 electron donor-to-perchlorate ratio (electron-equivalent basis) degraded perchlorate more slowly (k = 0.038 mg ClO4-/mg VSS h) and to a lesser extent than microcosms fed lactate at 2:1 and 4:1 ratios (k = 0.045 mg ClO4-/mg VSS h). The optimal COD/ClO4- ratio to consume all perchlorate and all electron donor was approximately 1.2 mg COD/mg ClO4-. In experiments where the redox potential was held constant, the extent of perchlorate degradation increased with decreasing redox potential, and 100% removal was only achieved at the lowest redox potential examined (-220 mV); however, perchlorate degradation (32% of added perchlorate) was observed as high as +180 mV. Additions of oxygen to actively degrading treatments did not adversely effect perchlorate degradation. It appears, therefore, that addition of excess electron donor is sufficient to negate potential inhibitory effects of molecular oxygen. If the redox conditions are more oxidized, however, the rate and extent of perchlorate degradation will be significantly decreased. This is the first report of perchlorate degradation under oxidized conditions using an environmentally relevant, diverse, bacterial enrichment culture, and this is also the first report of perchlorate reduction occurring at appreciable dissolved oxygen concentrations in a batch system.     

Fatty acids and polar lipid content of cheese and mould‐contaminated cheese

Unintended infestation of food with viable mould irreversibly leads to spoilage of food. However, little data existed on the fatty acid composition and polar lipid content of mould grown on cheese and the potential influence of these parameters in mould‐infested cheese. In this study, we thus focused on the fatty acids composition and polar lipid content of cheese, mould isolated from mould‐infested cheese, as well as inoculation of cheese with cultures of isolated moulds. For this purpose, we stored three cheese samples (gouda, brown cheese, and parmesan) over extended periods in order to force mould infestation from air. The moulds grown on gouda and brown cheese were identified as Penicillium brevicompactum and Penicillium roqueforti, respectively, while a mixed culture was obtained from parmesan. From these contaminated samples, mould spores were isolated and cultivated. Finally, the (pure) cheeses were inoculated with mould spores. Three subsamples, (1) cheeses, (2) moulds isolated from cheese, and (3) cheeses infested with the isolated moulds were studied with regards to their fatty acid distribution in the neutral and the polar lipids. The different amounts of polar lipids of cheese (0.39–2%), moulds (11–30.7%), and mould‐infested cheese (1.5–5%) allowed calculating the mould content of the mould‐infested cheeses.     

Learning in embodied activity framework: a sociocultural framework for embodied cognition

International Journal of Computer-Supported Collaborative Learning - This paper proposes the Learning in Embodied Activity Framework (LEAF) which aims to synthesize across individual and...     

Prototype abstraction by monkeys (Macaca mulatta).

The authors analyze the shape categorization of rhesus monkeys (Macaca mulatta) and the role of prototype- and exemplar-based comparison processes in monkeys' category learning. Prototype and exemplar theories make contrasting predictions regarding performance on the Posner-Homa dot-distortion categorization task. Prototype theory--which presumes that participants refer to-be-categorized items to a representation near the category's center (the prototype)--predicts steep typicality gradients and large prototype-enhancement effects. Exemplar theory--which presumes that participants refer to-be-categorized items to memorized training exemplars-predicts flat typicality gradients and small prototype-enhancement effects. Across many categorization tasks that, for the first time, assayed monkeys' dot-distortion categorization, monkeys showed steep typicality gradients and large prototype-enhancement effects. These results suggest that monkeys--like humans--refer to-be-categorized items to a prototype-like representation near the category's center rather than to a set of memorized training exemplars. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Identification of invasive vegetation using hyperspectral remote sensing in the California Delta ecosystem

Estuaries are among the most invaded ecosystems on the planet. Such invasions have led in part, to the formation of a massive $1 billion restoration effort in California's Sacramento–San Joaquin River Delta. However, invasions of weeds into riparian, floodplain, and aquatic habitats threaten the success of restoration efforts within the watershed and jeopardize economic activities. The doctrine of early detection and rapid response to invasions has been adopted by land and water resource managers, and remote sensing is the logical tool of choice for identification and detection. However meteorological, physical, and biological heterogeneity in this large system present unique challenges to successfully detecting invasive weeds. We present three hyperspectral case studies which illustrate the challenges, and potential solutions, to mapping invasive weeds in wetland systems: 1) Perennial pepperweed was mapped over one portion of the Delta using a logistic regression model to predict weed occurrence. 2) Water hyacinth and 3) submerged aquatic vegetation (SAV), primarily composed of Brazilian waterweed, were mapped over the entire Delta using a binary decision tree that incorporated spectral mixture analysis (SMA), spectral angle mapping (SAM), band indexes, and continuum removal products. Perennial pepperweed detection was moderately successful; phenological stage influenced detection rates. Water hyacinth was mapped with modest accuracies, and SAV was mapped with high accuracies. Perennial pepperweed and water hyacinth both exhibited significant spectral variation related to plant phenology. Such variation must be accounted for in order to optimally map these species, and this was done for the water hyacinth case study. Submerged aquatic vegetation was not mapped to the species level due to complex non-linear mixing problems between the water column and its constituents, which was beyond the scope of the current study. We discuss our study in the context of providing guidelines for future remote sensing studies of aquatic systems.     

Tantalum-tungsten oxide thermite composites prepared by sol-gel synthesis and spark plasma sintering

Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition-tested and the results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High-Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The sol-gel derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta-WO₃) energetic composite was consolidated to a density of 9.17 g cm⁻³ or 93% relative density. In addition, those samples were consolidated without significant pre-reaction of the constituents, thus retaining their stored chemical energy.     

Accelerometer-Based Activity Recognition in Construction

Recognizing the activities of workers helps to measure and control safety, productivity, and quality in construction sites. Automated activity recognition can enhance the efficiency of the measurement system. The present study investigates accelerometer-based activity classification for automating the work-sampling process. A methodology is developed for evaluating classifiers for recognizing activities based on the features generated from accelerometer data segments. An experimental study is carried out in instructed and uninstructed modes for classifying masonry activities by using accelerometers attached to the waist of the mason. Three types of classifiers were evaluated, and multilayer perceptron, a neural network classifier, gave the best results. A 50% overlap for data segments enhanced classifier performance. The study showed that the utilization of best features instead of all features did not affect the classification accuracy significantly but reduced the run time considerably. An accuracy of 80% was obtained with accelerometers attached at both sides of the waist in an uninstructed environment. The results from preliminary studies have shown the potential of the proposed method for automating the activity recognition in construction sites.