Science Icebreaker Activities: An Example from Gravitational Wave Astronomy

At the beginning of a class or meeting an icebreaker activity is often used to help loosen the group and get everyone talking. Our motivation is to develop activities that serve the purpose of an icebreaker, but are designed to enhance and supplement a science-oriented agenda. The subject of this article is an icebreaker activity related to gravitational wave astronomy. We first describe the unique gravitational wave signals from three distinct sources: monochromatic binaries, merging compact objects, and extreme mass ratio encounters. These signals form the basis of the activity where participants work to match an ideal gravitational wave signal with noisy detector output for each type of source.Comment: Accepted to The Physics Teacher. Original manuscript divided into two papers at the request of the referee. For a related paper on gravitational wave observatories see physics/050920

Percolation Analysis of a Wiener Reconstruction of the IRAS 1.2 Jy Redshift Catalog

We present percolation analyses of Wiener Reconstructions of the IRAS 1.2 Jy Redshift Survey. There are ten reconstructions of galaxy density fields in real space spanning the range $\beta= 0.1$ to $1.0$, where ${\beta}={\Omega^{0.6}}/b$, $\Omega$ is the present dimensionless density and $b$ is the bias factor. Our method uses the growth of the largest cluster statistic to characterize the topology of a density field, where Gaussian randomized versions of the reconstructions are used as standards for analysis. For the reconstruction volume of radius, $R {\approx} 100 h^{-1}$ Mpc, percolation analysis reveals a slight `meatball' topology for the real space, galaxy distribution of the IRAS survey. cosmology-galaxies:clustering-methods:numericalComment: Revised version accepted for publication in The Astrophysical Journal, January 10, 1997 issue, Vol.47

Value of Private Lands Managed for Wild Northern Bobwhites in the Deep South

Successful northern bobwhite (Colinus virginiaus) management creating huntable bobwhite populations in the southeastern United States is largely practiced on private lands. These properties not only support high density bobwhite populations, they also support biodiversity including many declining or endangered species associated with frequently-burned pine savannas. The private land model has proven sustainable over centuries and has recently increased with \u3e20,000 ha of wild bobwhite lands added in Georgia, Florida, and South Carolina since 2000. The NBCI recognizes private lands are critical to restoration of bobwhites but, despite their conservation value, no studies have quantified areas under wild bobwhite management. We mapped 259 properties totaling ~ 345,614 ha with wild bobwhite management principally in Georgia, Florida, Alabama, and South Carolina, and are completing mapping in Mississippi, Virginia, and North Carolina. Our survey data found management actions were consistent across these properties including maintaining open pine canopy, reducing hardwoods in upland areas, prescribed fire on areas of appropriate sizes and distribution, year- round supplemental feeding, nest predator management, and conservative harvest rates. Adoption of these management practices are a result of long-term research demonstrating their efficacy. Density of bobwhites on a property was related to landscape composition with lower densities on more fragmented sites. Properties in core areas surrounded by other managed properties often achieved bobwhite densities of 5–8 quail/ha. Bobwhite densities on smaller isolated properties densities were ~ 2.5 quail/ha during fall. Aspects of this successful management model may be useful to other private lands as well as public management areas focused on northern bobwhite

Galactic Extinction from Colors and Counts of Field Galaxies in WFPC2 Frames: An Application to GRB 970228

We develop the ``simulated extinction method'' to measure average foreground Galactic extinction from field galaxy number-counts and colors. The method comprises simulating extinction in suitable reference fields by changing the isophotal detection limit. This procedure takes into account selection effects, in particular, the change in isophotal detection limit (and hence in isophotal magnitude completeness limit) with extinction, and the galaxy color--magnitude relation. We present a first application of the method to the HST WFPC2 images of the gamma-ray burster GRB 970228. Four different WFPC2 high-latitude fields, including the HDF, are used as reference to measure the average extinction towards the GRB in the F606W passband. From the counts, we derive an average extinction of A_V = 0.5 mag, but the dispersion of 0.4 mag between the estimates from the different reference fields is significantly larger than can be accounted by Poisson plus clustering uncertainties. Although the counts differ, the average colors of the field galaxies agree well. The extinction implied by the average color difference between the GRB field and the reference galaxies is A_V = 0.6 mag, with a dispersion in the estimated extinction from the four reference fields of only 0.1 mag. All our estimates are in good agreement with the value of 0.81\pm0.27 mag obtained by Burstein & Heiles, and with the extinction of 0.78\pm0.12 measured by Schlegel et al. from maps of dust IR emission. However, the discrepancy between the widely varying counts and the very stable colors in these high-latitude fields is worth investigating.Comment: 14 pages, 2 figures; submitted to the Astrophysical Journa

Effect of Feed Cost on the Economic Impact of PRRS

Economic impacts based on PRRS associated losses as reported in a previous study were modeled with varying grain prices. Sensitivity tables show that as grain (feed) prices rise, the economic impact of disease events increases. As corn prices rise from $2.25/bu up to$5.00/bu, there is a $92.6 million increase in the cost of PRRS to US pork producers. Every$0.50/bu increase in corn price costs the pork industry $18.52 million in PRRS associated losses. In the PRRS-affected farm, for every$0.50/bu increase, the cost per litter increases $0.886, the cost per nursery pig increases$0.072/hd and the cost per finisher pig increases $0.405/hd. With corn at$2.50 to $5.00/bu the national impact is estimated at$594.19 to $686.77 million annually, or$5.94 to $6.87/hd marketed in the US. As feed prices rise, the value of improved health care also rises. As costs rise, it is imperative to continue efforts on disease control and prevention

Building more accurate decision trees with the additive tree.

The expansion of machine learning to high-stakes application domains such as medicine, finance, and criminal justice, where making informed decisions requires clear understanding of the model, has increased the interest in interpretable machine learning. The widely used Classification and Regression Trees (CART) have played a major role in health sciences, due to their simple and intuitive explanation of predictions. Ensemble methods like gradient boosting can improve the accuracy of decision trees, but at the expense of the interpretability of the generated model. Additive models, such as those produced by gradient boosting, and full interaction models, such as CART, have been investigated largely in isolation. We show that these models exist along a spectrum, revealing previously unseen connections between these approaches. This paper introduces a rigorous formalization for the additive tree, an empirically validated learning technique for creating a single decision tree, and shows that this method can produce models equivalent to CART or gradient boosted stumps at the extremes by varying a single parameter. Although the additive tree is designed primarily to provide both the model interpretability and predictive performance needed for high-stakes applications like medicine, it also can produce decision trees represented by hybrid models between CART and boosted stumps that can outperform either of these approaches

Sensitivity curves for spaceborne gravitational wave interferometers

To determine whether particular sources of gravitational radiation will be detectable by a specific gravitational wave detector, it is necessary to know the sensitivity limits of the instrument. These instrumental sensitivities are often depicted (after averaging over source position and polarization) by graphing the minimal values of the gravitational wave amplitude detectable by the instrument versus the frequency of the gravitational wave. This paper describes in detail how to compute such a sensitivity curve given a set of specifications for a spaceborne laser interferometer gravitational wave observatory. Minor errors in the prior literature are corrected, and the first (mostly) analytic calculation of the gravitational wave transfer function is presented. Example sensitivity curve calculations are presented for the proposed LISA interferometer. We find that previous treatments of LISA have underestimated its sensitivity by a factor of $\sqrt{3}$.Comment: 27 pages + 5 figures, REVTeX, accepted for publication in Phys Rev D; Update reflects referees comments, figure 3 clarified, figure 5 corrected for LISA baselin