New VISTAs in Science Education

In the summer of 2012, a colleague and I attended the four-week Virginia Initiative for Science Teaching and Achievement (VISTA) Elementary Summer Science Institute where we were trained to conduct inquiry-based science teaching in a problem-based learning setting. We then implemented our training in our own academic classrooms by developing a Problem-Based Learning unit meeting the objectives of our Virginia standards-based science curriculum and selecting a topic with tics to our local community. Toward demonstrating that students, teachers, and educational systems stand to benefit from the implementation of this methodology, this article clarifies the following aspects: 1) outlines the problem, scenario, and process of developing a Problem-Based Leaming unit; 2) explains the delivery in the classroom; 3) analyzes ongoing formative and summative assessments; 4) and, discusses the influence on students, teachers, and instruction as a whole

The Effect of Chemical Amendments Used for Phosphorus Abatement on Greenhouse Gas and Ammonia Emissions from Dairy Cattle Slurry: Synergies and Pollution Swapping

peer-reviewedLand application of cattle slurry can result in incidental and chronic phosphorus (P) loss to waterbodies, leading to eutrophication. Chemical amendment of slurry has been proposed as a management practice, allowing slurry nutrients to remain available to plants whilst mitigating P losses in runoff. The effectiveness of amendments is well understood but their impacts on other loss pathways (so-called ‘pollution swapping’ potential) and therefore the feasibility of using such amendments has not been examined to date. The aim of this laboratory scale study was to determine how the chemical amendment of slurry affects losses of NH3, CH4, N2O, and CO2. Alum, FeCl2, Polyaluminium chloride (PAC)- and biochar reduced NH3 emissions by 92, 54, 65 and 77% compared to the slurry control, while lime increased emissions by 114%. Cumulative N2O emissions of cattle slurry increased when amended with alum and FeCl2 by 202% and 154% compared to the slurry only treatment. Lime, PAC and biochar resulted in a reduction of 44, 29 and 63% in cumulative N2O loss compared to the slurry only treatment. Addition of amendments to slurry did not significantly affect soil CO2 release during the study while CH4 emissions followed a similar trend for all of the amended slurries applied, with an initial increase in losses followed by a rapid decrease for the duration of the study. All of the amendments examined reduced the initial peak in CH4 emissions compared to the slurry only treatment. There was no significant effect of slurry amendments on global warming potential (GWP) caused by slurry land application, with the exception of biochar. After considering pollution swapping in conjunction with amendment effectiveness, the amendments recommended for further field study are PAC, alum and lime. This study has also shown that biochar has potential to reduce GHG losses arising from slurry application.This research was funded by the Teagasc Walsh Fellowship Scheme and the AnimalChange Framework 7 Project (FP7-KBBE-2010-4)

Intrinsic selection biases of ground-based gravitational wave searches for high-mass BH-BH mergers

The next generation of ground-based gravitational wave detectors may detect a few mergers of comparable-mass M\simeq 100-1000 Msun ("intermediate-mass'', or IMBH) spinning black holes. Black hole spin is known to have a significant impact on the orbit, merger signal, and post-merger ringdown of any binary with non-negligible spin. In particular, the detection volume for spinning binaries depends significantly on the component black hole spins. We provide a fit to the single-detector and isotropic-network detection volume versus (total) mass and arbitrary spin for equal-mass binaries. Our analysis assumes matched filtering to all significant available waveform power (up to l=6 available for fitting, but only l<= 4 significant) estimated by an array of 64 numerical simulations with component spins as large as S_{1,2}/M^2 <= 0.8. We provide a spin-dependent estimate of our uncertainty, up to S_{1,2}/M^2 <= 1. For the initial (advanced) LIGO detector, our fits are reliable for $M\in[100,500]M_\odot$ ($M\in[100,1600]M_\odot$). In the online version of this article, we also provide fits assuming incomplete information, such as the neglect of higher-order harmonics. We briefly discuss how a strong selection bias towards aligned spins influences the interpretation of future gravitational wave detections of IMBH-IMBH mergers.Comment: 18 pages, 15 figures, accepted by PRD. v2 is version accepted for publication, including minor changes in response to referee feedback and updated citation

Dynamics of Multidimensional Secession

We explore a generalized Seceder Model with variable size selection groups and higher dimensional genotypes, uncovering its well-defined mean-field limiting behavior. Mapping to a discrete, deterministic version, we pin down the upper critical size of the multiplet selection group, characterize all relevant dynamically stable fixed points, and provide a complete analytical description of its self-similar hierarchy of multiple branch solutions.Comment: 4 pages, 4 figures, PR

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Newsletter of the Boston University School of Medicine, Student American Medical Association (SAMA

Squeezing out the last 1 nanometer of water: A detailed nanomechanical study

In this study, we present a detailed analysis of the squeeze-out dynamics of nanoconfined water confined between two hydrophilic surfaces measured by small-amplitude dynamic atomic force microscopy (AFM). Explicitly considering the instantaneous tip-surface separation during squeezeout, we confirm the existence of an adsorbed molecular water layer on mica and at least two hydration layers. We also confirm the previous observation of a sharp transition in the viscoelastic response of the nanoconfined water as the compression rate is increased beyond a critical value (previously determined to be about 0.8 nm/s). We find that below the critical value, the tip passes smoothly through the molecular layers of the film, while above the critical speed, the tip encounters "pinning" at separations where the film is able to temporarily order. Pre-ordering of the film is accompanied by increased force fluctuations, which lead to increased damping preceding a peak in the film stiffness once ordering is completed. We analyze the data using both Kelvin-Voigt and Maxwell viscoelastic models. This provides a complementary picture of the viscoelastic response of the confined water film

Optimization of double drive pulse pumping in Ne-like Ge x-ray lasers

Pumping of the Ne-like Ge x-ray laser with two 100 ps duration pulses (a prepulse and main pulse) is investigated using a fluid and atomic physics code coupled to a 3D ray tracing postprocessor code. The modeling predicts the optimum ratio of the irradiance of the two pulses for the maximum x-ray laser output resulting from the balance between the relative lower electron density gradients and wider gain region which is produced with a larger prepulse and the higher peak gain coefficients produced with a small prepulse. With a longer pulse interval between prepulse and main pulse, a relatively lower optimum pulse ratio is found. The threshold irradiance of the main driving pulse with a prepulse required to make an order of magnitude enhancement of laser output compared to irradiation without a prepulse is also found at 3-4x10(13) W/cm(2) for Ne-like Ge. (C) 1998 American Institute of Physics

The short-term effects of management changes on watertable position and nutrients in shallow groundwater in a harvested peatland forest

This work was funded by the Department of Agriculture, Fisheries and Food and the Environmental Protection Agency under the STRIVE program 2007 – 2013.peer-reviewedManagement changes such as drainage, fertilisation, afforestation and harvesting (clearfelling) of forested peatlands influence watertable (WT) position and groundwater concentrations of nutrients. This study investigated the impact of clearfelling of a peatland forest on WT and nutrient concentrations. Three areas were examined: (1) a regenerated riparian peatland buffer (RB) clearfelled four years prior to the present study (2) a recently clearfelled coniferous forest (CF) and (3) a standing, mature coniferous forest (SF), on which no harvesting took place. The WT remained consistently below 0.3 m during the pre-clearfelling period. Results showed there was an almost immediate rise in the WT after clearfelling and a rise to 0.15 m below ground level (bgl) within 10 months of clearfelling. Clearfelling of the forest increased dissolved reactive phosphorus concentrations (from an average of 28–230 μg L−1) in the shallow groundwater, likely caused by leaching from degrading brash mats.Environmental Protection AgencyDepartment of Agriculture, Food and the Marin