Red Crossbill Invasion of Northwestern Arkansas during 2012-2013

An irruption of Red Crossbills (Loxia curvirostra) occurred in primarily northwestern Arkansas starting in November of 2012 and lasting to the end of May of 2013. Based on recordings of call notes, most birds around Fayetteville were Type 2, the large-billed ponderosa pine crossbill, associated with a variety of conifer species. Birds recorded in Carroll County were Type 3, the small-billed western hemlock crossbill, and they were associated with small cones on shortleaf pine (Pinus echinata). One recording was obtained in Fayetteville of Type 5, the lodgepole pine crossbill, only the third recording east of the Great Plains. Crossbills at the Fayetteville Country Club were observed eating algae (Cladophora sp.) during the months of December and January, a behavior rarely reported for passerines. During March, crossbills appeared at sunflower bird feeders, which is a relatively recent phenomenon associated with low conifer seed abundance. The first two Arkansas specimens of crossbills (probably Type 3) were obtained from birds that struck windows near feeders. This is only the third recorded irruption of crossbills in Arkansas in the last 43 years, suggesting that crossbills rarely travel this far south in search of cone crops

Intergalactic Helium Absorption in Cold Dark Matter Models

Observations from the HUT and the HST have recently detected HeII absorption along the lines of sight to two high redshift quasars. We use cosmological simulations with gas dynamics to investigate HeII absorption in the cold dark matter (CDM) theory of structure formation. We consider two Omega=1 CDM models with different normalizations and one Omega_0=0.4 CDM model, all incorporating the photoionizing UV background spectrum computed by Haardt & Madau (1996). The simulated gas distribution, combined with the H&M spectral shape, accounts for the relative observed values of taubar_HI and taubar_HeII, the effective mean optical depths for HI and HeII absorption. If the background intensity is as high as H&M predict, then matching the absolute values of taubar_HI and taubar_HeII requires a baryon abundance larger (by factors between 1.5 and 3 for the various CDM models) than our assumed value of Omega_b h^2=0.0125. The simulations reproduce the evolution of taubar_heII over the observed redshift range, 2.2 < z < 3.3, if the HeII photoionization rate remains roughly constant. HeII absorption in the CDM simulations is produced by a diffuse, fluctuating, intergalactic medium, which also gives rise to the HI ly-alpha forest. Much of the HeII opacity arises in underdense regions where the HI optical depth is very low. We compute statistical properties of the HeII and HI absorption that can be used to test the CDM models and distinguish them from an alternative scenario in which the HeII absorption is caused by discrete, compact clouds. The CDM scenario predicts that a substantial amount of baryonic material resides in underdense regions at high redshift. HeII absorption is the only sensitive probe of such extremely diffuse, intergalactic gas, so it can provide a vital test of this fundamental prediction.Comment: Accepted for publication in ApJ, 36 pages, LaTeX (aaspp4), 12 figures. Changes include addition of more information on statistical uncertainties and on the adopted UV background. Also available at http://www-astronomy.mps.ohio-state.edu/~racc

Characterization of Lyman Alpha Spectra and Predictions of Structure Formation Models: A Flux Statistics Approach

In gravitational instability models, \lya absorption arises from a continuous fluctuating medium, so that spectra provide a non-linear one-dimensional ``map'' of the underlying density field. We characterise this continuous absorption using statistical measures applied to the distribution of absorbed flux. We describe two simple members of a family of statistics which we apply to simulated spectra in order to show their sensitivity as probes of cosmological parameters (H$_{0}$, $\Omega$, the initial power spectrum of matter fluctuations) and the physical state of the IGM. We make use of SPH simulation results to test the flux statistics, as well as presenting a preliminary application to Keck HIRES data.Comment: Contribution to proceedings of the 18th Texas Symposium on Relativistic Astrophysics (eds A. Olinto, J. Frieman and D. Schramm, World Scientific),Chicago, December 1996, 3 pages, LaTeX (sprocl), 2 figures. Also available at http://www-astronomy.mps.ohio-state.edu/~racc

Looking for Distributed Star Formation in L1630: A Near-infrared (J, H, K) Survey

We have carried out a simultaneous, multi-band (J, H, K) survey over an area of 1320 arcmin^2 in the L1630 region, concentrating on the region away from the dense molecular cores and with modest visual extinctions (\leq 10 mag). Previous studies found that star formation in L1630 occurs mainly in four localized clusters, which in turn are associated with the four most massive molecular cores (Lada et al. 1991; Lada 1992). The goal of this study is to look for a distributed population of pre-main-sequence stars in the outlying areas outside the known star-forming cores. More than 60% of the pre-main-sequence stars in the active star forming regions of NGC 2024 and NGC 2023 show a near-infrared excess in the color-color diagram. In the outlying areas of L1630, excluding the known star forming regions, we found that among 510 infrared sources with the near-infrared colors ((J-H) and (H-K)) determined and photometric uncertainty at K better than 0.10 mag, the fraction of the sources with a near-infrared excess is 3%--8%; the surface density of the sources with a near-infrared excess is less than half of that found in the distributed population in L1641, and 1/20 of that in the young cluster NGC 2023. This extremely low fraction and low surface density of sources with a near-infrared excess strongly indicates that recent star formation activity has been very low in the outlying region of L1630. The sources without a near-infrared excess could be either background/foreground field stars, or associated with the cloud, but formed a long time ago (more than 2 Myrs). Our results are consistent with McKee's model of photoionization-regulated star formation.Comment: 30 pages, 10 figures To appear in ApJ Oct 1997, Vol 48

Emergency escape system uses self-braking mechanism on fixed cable

Slide-wire system with a twist level slide device incorporates automatic descent and braking for the safe and rapid evacuation of personnel from tall structures. This device is used on any tall structure that might require emergency evacuation. It is also used to transfer materials and equipment

The Mah Jongg Nightmare

Sheet music contains anti-Asian racist language, stereotypes, and/or imagry.https://digitalcommons.library.umaine.edu/mmb-vp/6871/thumbnail.jp

Bayes\u27 Law, Sequential Uncertainties, and Evidence of Causation in Toxic Tort Cases

Judges are the gatekeepers of evidence. Arguably, the most difficult duty for a judicial gatekeeper is to screen the reliability of expert opinions in scientific fields such as medicine that are beyond the ken of most judges. Yet, judges have a duty to scrutinize such expert opinion evidence to determine its reliability and admissibility. In toxic tort cases, the issue of causation-whether the alleged exposures actually caused the plaintiffs injury-is nearly always the central dispute, and determining admissibility of expert causation opinion is a daunting challenge for most judges. We present a comprehensive review of the courts\u27 struggles with the screening of scientific evidence in such cases. In addition, we propose an approach to the screening of causation opinions based on probability science and logic. Central to this approach is Bayes\u27 Law, a statistical tool that courts can use to analyze the extrinsic reliability of proffered causation testimony. We explain Bayes\u27 Law and illustrate its potential application for evaluating the reliability of medical and scientific causation testimony. All evidence is probabilistic. There are uncertainties attending all testimony, not only because the honesty or objectivity of witnesses may be doubtful, but also because even honest and unbiased witnesses may be mistaken in their perceptions. Reliability of causation evidence depends on both sensitivity and specificity of the tests used to determine causation. Highly sensitive tests of causation reflect an ability to identify a high percentage of those with the agent-induced disease, whereas highly specific tests of causation reflect an ability to reject a high percentage of those who have the disease, but not induced by the agent at issue. According to Bayes\u27 Law, the reliability of causation opinion depends not only on the sensitivity and specificity of the tests employed by the causation expert, but also on the base rate of the agent-induced disease in the population. Bayes\u27 Law dictates that the lower the rate of the agent-induced disease in the population, the less reliable the opinion that the agent at issue in fact caused the plaintiffs disease given certain levels of sensitivity and specificity. The base-rate problem and its effect on reliability of causation opinions are overlooked by judges when scrutinizing the reliability of proffered causation evidence. In this Article, we encourage courts to consider a Bayes\u27 Law approach to screen out, at an early stage, those claims of injury lacking reliable evidence that an injury was more likely than not caused by exposures to toxic agents. The goal of our Article is to provide a framework that helps the gatekeeper to screen out toxic tort claims insufficiently substantiated by the underlying scientific and medical data, and allow the factfinder to decide only those toxic tort claims for which there is reliable and relevant scientific support for each link of the causal chain, from subject exposure to the injury Scientific substantiation of each causal link determines the reliability of an experts opinion that the exposure more likely than not caused the plaintiffs injury

Measuring gravitational lens time delays using low-resolution radio monitoring observations

Obtaining lensing time delay measurements requires long-term monitoring campaigns with a high enough resolution (< 1 arcsec) to separate the multiple images. In the radio, a limited number of high-resolution interferometer arrays make these observations difficult to schedule. To overcome this problem, we propose a technique for measuring gravitational time delays which relies on monitoring the total flux density with low-resolution but high-sensitivity radio telescopes to follow the variation of the brighter image. This is then used to trigger high-resolution observations in optimal numbers which then reveal the variation in the fainter image. We present simulations to assess the efficiency of this method together with a pilot project observing radio lens systems with the Westerbork Synthesis Radio Telescope (WSRT) to trigger Very Large Array (VLA) observations. This new method is promising for measuring time delays because it uses relatively small amounts of time on high-resolution telescopes. This will be important because instruments that have high sensitivity but limited resolution, together with an optimum usage of followup high-resolution observations from appropriate radio telescopes may in the future be useful for gravitational lensing time delay measurements by means of this new method.Comment: 10 pages, 7 figures, accepted by MNRA

Computational Simulations of a Mach 0.745 Transonic Truss-Braced Wing Design

A joint effort between the NASA Ames and Langley Research Centers was undertaken to analyze the Mach 0.745 variant of the Boeing Transonic Truss-Braced Wing (TTBW) Design. Two different flow solvers, LAVA and USM3D, were used to predict the TTBW flight performance. Sensitivity studies related to mesh resolution and numerical schemes were conducted to define best practices for this type of geometry and flow regime. Validation efforts compared the numerical simulation results of various modeling methods against experimental data taken from the NASA Ames 11-foot Unitary Wind Tunnel experimental data. The fidelity of the computational representation of the wind tunnel experiment, such as utilizing a porous wall boundary condition to model the ventilated test section, was varied to examine how different tunnel effects influence CFD predictions. LAVA and USM3D results both show an approximate 0.5 angle of attack shift from experimental lift curve data. This drove an investigation that revealed that the trailing edge of the experimental model was rounded in comparison to the CAD model, due to manufacturing tolerances, which had not been accounted for in the initial simulations of the experiment. Simulating the TTBW with an approximation of this rounded trailing-edge reduces error by approximately 60%. An accurate representation of the tested TTBW geometry, ideally including any wing twists and deflections experienced during the test under various loading conditions, will be necessary for proper validation of the CFD