349 research outputs found

    Regulations and Ethical Considerations for Astronomy Education Research II: Resources and Worked Examples

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    This article discusses the legal and ethical requirements of human subjects research proposals in astronomy education research. We present an overview of the relevant laws, regulations, and guidelines that inform an Institutional Review Board evaluation of proposed research. We also present examples of potential research projects in astronomy education research and discuss their ethical issues

    Twisted algebra R-matrices and S-matrices for bn(1)b_n^{(1)} affine Toda solitons and their bound states

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    We construct new Uq(a2n1(2))U_q(a^{(2)}_{2n-1}) and Uq(e6(2))U_q(e^{(2)}_6) invariant RR-matrices and comment on the general construction of RR-matrices for twisted algebras. We use the former to construct SS-matrices for bn(1)b^{(1)}_n affine Toda solitons and their bound states, identifying the lowest breathers with the bn(1)b^{(1)}_n particles.Comment: Latex, 24 pages. Various misprints corrected. New section added clarifying relationship between R-matrices and S-matrice

    Balancing food and density-dependence in the spatial distribution of an interference-prone forager

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    Foraging distributions are thought to be density-dependent, because animals not only select for a high availability and quality of resources, but also avoid conspecific interference. Since these processes are confounded, their relative importance in shaping foraging distributions remains poorly understood. Here we aimed to rank the contribution of density-dependent and density-independent effects on the spatio-temporal foraging patterns of eurasian oystercatchers. In our intertidal study area, tides caused continuous variation in oystercatcher density, providing an opportunity to disentangle conspecific interference and density-independent interactions with the food landscape. Spatial distributions were quantified using high-resolution individual tracking of foraging activity and location. In a model environment that included a realistic reconstruction of both the tides and the benthic food, we tested a family of behaviour-based optimality models against these tracking data. Density-independent interactions affected spatial distributions much more strongly than conspecific interference, even in an interference-prone species like oystercatchers. Spatial distributions were governed by avoidance of bill injury costs, selection for high interference-free intake rates and a decreasing availability of benthic bivalve prey after their exposure. These density-independent interactions outweighed interference competition in terms of effect size. We suggest that the bottleneck in our mechanistic understanding of foraging distributions may be primarily the role of density-independent prey attributes unrelated to intake rates, like damage costs in the case of oystercatchers foraging on perilous prey. At a landscape scale, above the finest inter-individual distances, effects of conspecific interaction on spatial distributions may have been overemphasised

    Aggregation and aging in silica gel

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    Aggregation and aging of silica gels, prepared by controlled addition of water glass to hydrochloric acid, and the transformation of an aged gel to a crystalline phase have been studied in-situ using high-brilliance synchrotron radiation. Small angle X-ray scattering (SAXS) has proved to be very informative in readily detecting transformations in the silica gels which can be described using the concepts of mass and surface fractality. The interpretation of SAXS spectra of aged silica gels has been accompanied by computer simulations of aggregation and aging based on a model for the aging mechanism and the calculation of the corresponding structure-factor patterns. Comparison with experimental spectra of aged silica highlights the important role of particle growth on the fractal dimension. Gel transformations during the transition from an amorphous gel to the crystalline phase of silicalite have been successfully monitored, in-situ, both for heterogeneous and for homogeneous preparations, using the combination of small and wide angle X-ray scattering (SAXS-WAXS

    Bird radar validation in the field by time-referencing line-transect surveys

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    Track-while-scan bird radars are widely used in ornithological studies, but often the precise detection capabilities of these systems are unknown. Quantification of radar performance is essential to avoid observational biases, which requires practical methods for validating a radar’s detection capability in specific field settings. In this study a method to quantify the detection capability of a bird radar is presented, as well a demonstration of this method in a case study. By time-referencing line-transect surveys, visually identified birds were automatically linked to individual tracks using their transect crossing time. Detection probabilities were determined as the fraction of the total set of visual observations that could be linked to radar tracks. To avoid ambiguities in assigning radar tracks to visual observations, the observer’s accuracy in determining a bird’s transect crossing time was taken into account. The accuracy was determined by examining the effect of a time lag applied to the visual observations on the number of matches found with radar tracks. Effects of flight altitude, distance, surface substrate and species size on the detection probability by the radar were quantified in a marine intertidal study area. Detection probability varied strongly with all these factors, as well as species-specific flight behaviour. The effective detection range for single birds flying at low altitude for an X-band marine radar based system was estimated at ∼1.5 km. Within this range the fraction of individual flying birds that were detected by the radar was 0.50±0.06 with a detection bias towards higher flight altitudes, larger birds and high tide situations. Besides radar validation, which we consider essential when quantification of bird numbers is important, our method of linking radar tracks to ground-truthed field observations can facilitate species-specific studies using surveillance radars. The methodology may prove equally useful for optimising tracking algorithms

    Birds flee en mass from New Year’s Eve fireworks

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    Anthropogenic disturbances of wildlife, such as noise, human presence, hunting activity, and motor vehicles, are becoming an increasing concern in conservation biology. Fireworks are an important part of celebrations worldwide, and although humans often find fireworks spectacular, fireworks are probably perceived quite differently by wild animals. Behavioral responses to fireworks are difficult to study at night, and little is known about the negative effects fireworks may have on wildlife. Every year, thousands of tons of fireworks are lit by civilians on New Year’s Eve in the Netherlands. Using an operational weather radar, we quantified the reaction of birds to fireworks in 3 consecutive years. Thousands of birds took flight shortly after midnight, with high aerial movements lasting at least 45 min and peak densities measured at 500 m altitude. The highest densities were observed over grasslands and wetlands, including nature conservation sites, where thousands of waterfowl rest and feed. The Netherlands is the most important winter staging area for several species of waterfowl in Europe. We estimate that hundreds of thousands of birds in the Netherlands take flight due to fireworks. The spatial and temporal extent of disturbance is substantial, and potential consequences are discussed. Weather radar provides a unique opportunity to study the reaction of birds to fireworks, which has otherwise remained elusive

    Prospects of Transition Interface Sampling simulations for the theoretical study of zeolite synthesis

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    The transition interface sampling (TIS) technique allows to overcome large free energy barriers within reasonable simulation time, which is impossible for straightforward molecular dynamics. Still, the method does not impose an artificial driving force, but it surmounts the timescale problem by an importance sampling of true dynamical pathways. Recently, it was shown that the efficiency of TIS to calculate reaction rates is less sensitive to the choice of reaction coordinate than those of the standard free energy based techniques. This could be an important advantage in complex systems for which a good reaction coordinate is usually very difficult to find. We explain the principles of this method and discuss some of the promising applications related to zeolite formation.Comment: 9 pages, accepted for publication in Phys. Chem. Chem. Phys. for the special issue of the CECAM workshop: Computational aspects of building blocks, nucleation, and synthesis of porous materials Aug. 29 2006 to Aug. 31 200
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