SUMMARY We quantified the flow field generated by tethered and free-swimming Euchaeta antarctica using the particle image velocimetry (PIV)technique. The streamlines around the free-swimming specimens were generally parallel to the body axis, whereas the streamlines around all of the tethered copepodids demonstrated increased curvature. Differences noted in the streamline pattern, and hence the vorticity, dissipation rate and strain rate fields, are explained by considering the forces on the free-swimming specimen compared to the tethered specimen. Viscous flow theory demonstrates that the force on the fluid due to the presence of the tether irrevocably modifies the flow field in a manner that is consistent with the measurements. Hence,analysis of the flow field and all associated calculations differ for tethered versus free-swimming conditions. Consideration of the flow field of the free-swimming predatory copepodid shows the intensity of the biologically generated flow and the extent of the mechanoreceptive signal quantified in terms of shear strain rate. The area in the dorso-ventral view surrounded by the 0.5 s-1 contour of exy, which is a likely threshold to induce an escape response, is 11 times the area of the exoskeletal form for the free-swimming case. Thus, mechanoreceptive predators will perceive a more spatially extended signal than the body size.

Swimming capacity is dependent on size (Johnson and Tarling, 2008) and organism size is directly related to the spatial extent of the hydrodynamic disturbance, which potentially provides a sensory field for prey, predators and conspecifics (Abrahamsen et al., 2010 Accepted 15 February 2011 SUMMARY Krill aggregations vary in size, krill density and uniformity depending on the species of krill. These aggregations may be structured to allow individuals to sense the hydrodynamic cues of neighboring krill or to avoid the flow fields of neighboring krill, which may increase drag forces on an individual krill. To determine the strength and location of the flow disturbance generated by krill, we used infrared particle image velocimetry measurements to analyze the flow field of free-swimming solitary specimens (Euphausia superba and Euphausia pacifica) and small, coordinated groups of three to six E. superba. Euphausia pacifica individuals possessed shorter body lengths, steeper body orientations relative to horizontal, slower swimming speeds and faster pleopod beat frequencies compared with E. superba. The downward-directed flow produced by E. pacifica has a smaller maximum velocity and smaller horizontal extent of the flow pattern compared with the flow produced by E. superba, which suggests that the flow disturbance is less persistent as a potential hydrodynamic cue for E. pacifica. Time record analysis reveals that the hydrodynamic disturbance is very weak beyond two body lengths for E. pacifica, whereas the hydrodynamic disturbance is observable above background level at four body lengths for E. superba. Because the nearest neighbor separation distance of E. superba within a school is less than two body lengths, hydrodynamic disturbances are a viable cue for intraspecies communication. The orientation of the position of the nearest neighbor is not coincident with the orientation of the flow disturbance, however, which indicates that E. superba are avoiding the region of strongest flow.

Previous assessments of the economic feasibility and large-scale productivity of microalgae biofuels have not considered the impacts of land and carbon dioxide (CO 2) availability on the scalability of microalgae-based biofuels production. To accurately assess the near-term productivity potential of large-scale microalgae biofuel in the US, a geographically realized growth model was used to simulate microalgae lipid yields based on meteorological data. The resulting lipid productivity potential of Nannochloropsis under large-scale cultivation is combined with land and CO 2 resource availability illustrating current geographically feasible production sites and corresponding productivity in the US. Baseline results show that CO 2 transport constraints will limit US microalgae based bio-oil production to 4% of the 2030 Department of Energy (DOE) alternative fuel goal. The discussion focuses on synthesis of this large-scale productivity potential results including a sensitivity analysis to land and CO 2 resource assumptions, an evaluation of previous modeling efforts and their assumptions regarding the transportation of CO 2 , the feasibility of microalgae to meet DOE 2030 alternative fuel goals, and a comparison of the productivity potential in several key regions of the US.

Current assessments of the commercial viability and productivity potential of microalgae biofuels have been forced to extrapolate small-scale research data. The resulting analyses are not representative of microalgae cultivation and processing at industrial scale. To more accurately assess the current near-term realizable, large-scale microalgae productivity potential in the USA, this paper presents a model of microalgae growth derived from industrial-scale outdoor photobioreactor growth data. This model is combined with thermal models of the photobioreactor system and 15 years of hourly historical weather data from 864 locations in the USA to more accurately assess the current productivity potential of microalgae. The resulting lipid productivity potential of Nannochloropsis is presented in the form of a map that incorporates various land availability models to illustrate the near-term feasible cultivation locations and corresponding productivity potentials for the USA. The discussion focuses on a comparison of model results with productivity potentials currently reported in literature, an assessment demonstrating the scale of Department of Energy 2030 alternative fuel goals, and a critical comparison of productivity potential in several key regions of the USA. Keywords Biofuels . GIS . Microalgae . Model . Productivity potential Abbreviations PAR Photosynthetic active radiation PFD Photon flux density GIS Geographic information system PBR Photobioreactor ORP Open raceway pond DOE Department of Energy NLCD National Land Cover Database Nomenclature c p Specific heat of water (kJ kg −1 K −1 ) E a Activation energy carboxylation Rubisco (J mol −1 ) G bottom Solar energy reaching the bottom (W m −2 ) G n Solar energy reaching node n (W m −2 ) G sur Solar energy reaching the surface (W m −2Thermal conductivity of water (W m −1 K −1 ) L n Distance between nodes (m) m n Total mass represented by node n (kg) Q i Energy stored/released by ground (W m −2 ) R Universal gas constant (J K −1 mol −1 )Electronic supplementary material The online version of this article (

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Lay Abstract Copepods are small marine invertebrates that are one of the most abundant multicellular organisms on Earth. They serve as an important link in the marine food chain between small oceanic plant life, called phytoplankton, and larger organisms such as fish. As with all organisms, they must adapt to the surrounding fluid environment. Since copepods are small, they inhabit an aquatic flow regime that provides a balance of inertial and fluid viscous forces on the organism. The flow created by copepods controls, to a large degree, the interaction with prey, predators, and other individuals of the same species. Hence, examination of the flow disturbances created during cruise and escape behaviors provides insight into the method and consequences of propulsion in this unique flow environment. The genus Euchaeta includes species that inhabit ocean waters at different latitudes extending from the subtropics to the poles. The body shapes of these species are very similar, with the primary difference being much larger body size in colder waters. Thus, Euchaeta species provide a natural experiment to study adaptation to fluid property variation between habitats. Here, variation in body size, swimming and escape speeds, or viscosity has direct consequences on the hydrodynamic disturbance created by organism motion. We expected that body size and viscosity would work in opposite directions in shaping the spatial and temporal properties of the hydrodynamic disturbances generated by these copepod species. The results reveal an intriguing interplay between body size and the fluid environment that alters planktonic interactions, including the ability to prey on food items and the ability to escape from predators, in a complex manner. The complex interaction for the genus Euchaeta partially explains species adaptations to the local environmental conditions.

The microalgae biofuels life cycle assessments (LCA) present in the literature have excluded the effects of direct land use change (DLUC) from facility construction under the assumption that DLUC effects are negligible. This study seeks to model the greenhouse gas (GHG) emissions of microalgae biofuels including DLUC by quantifying the CO equivalence of carbon released to the atmosphere through the construction of microalgae facilities. The locations and types of biomass and Soil Organic Carbon that are disturbed through microalgae cultivation facility construction are quantified using geographical models of microalgae productivity potential including consideration of land availability. The results of this study demonstrate that previous LCA of microalgae to biofuel processes have overestimated GHG benefits of microalgae-based biofuels production by failing to include the effect of DLUC. Previous estimations of microalgae biofuel production potential have correspondingly overestimated the volume of biofuels that can be produced in compliance with U.S. environmental goals.

Large class sizes are increasingly common in mechanical engineering undergraduate courses due to increased enrollments of undergraduate students with a disproportional investment to faculty numbers. Simultaneously, active learning is promoted to faculty members over traditional lectures due to published findings of improved student learning. Active learning typically involves a break in the lecture to allow for problem solving, discussion, or other activities. One common type of active learning in large classes is classroom response systems (e.g. clickers). Based on classroom experience, the use of active learning with classroom response systems in large classes, particularly in the first year, can lead to a disruptive learning environment. In this preliminary study, a 1 st year course and a 4 th year course (n=120 and 135, respectively) were surveyed in Fall of 2015 to quantify student's ratings of active learning with classroom response systems and disruption. The student's impressions of active learning (e.g., interactive clicker problem solving) were assessed using a survey at the end of the course. Students were overwhelmingly positive about the advantages of active learning (>80% responded favorably) in the both courses. However, the students in the 1 st year course had less positive feedback on active learning and higher ratings of disruption in the classroom than the students in the 4 th year course (34% rated as disruptive in 1 st year, 14% rated disruptive in the 4 th year). The class rank, where higher values represented a greater number of years past secondary school, was positively correlated with rankings of a more disruptive environment suggesting that nontraditional students may find active learning more disruptive. This preliminary study suggests that using classroom response systems (clickers) in the 1 st year curriculum with large class sizes may lead students to feel that the class was disruptive and that active learning was not as positive of an experience as active learning environments later in the curriculum.