We report the first discovery of a fast radio burst (FRB), FRB 20200125A, by the Green Bank Northern Celestial Cap (GBNCC) Pulsar Survey conducted with the Green Bank Telescope at 350 MHz. FRB ...20200125A was detected at a Galactic latitude of 58 43 with a dispersion measure of 179 pc cm3, while electron density models predict a maximum Galactic contribution of 25 pc cm3 along this line of sight. Moreover, no apparent Galactic foreground sources of ionized gas that could account for the excess DM are visible in multiwavelength surveys of this region. This argues that the source is extragalactic. The maximum redshift for the host galaxy is zmax = 0.17, corresponding to a maximum comoving distance of approximately 750 Mpc. The measured peak flux density for FRB 20200125A is 0.37 Jy, and we measure a pulse width of 3.7 ms, consistent with the distribution of FRB widths observed at higher frequencies. Based on this detection and assuming a Euclidean flux density distribution of FRBs, we calculate an all-sky rate at 350 MHz of FRBs sky−1 day−1 above a peak flux density of 0.42 Jy for an unscattered pulse having an intrinsic width of 5 ms, consistent with rates reported at higher frequencies, albeit with large uncertainties. Given the recent improvements in our single-pulse search pipeline, we also revisit the GBNCC survey sensitivity to various burst properties. Finally, we find no evidence of strong interstellar scattering in FRB 20200125A, adding to the growing evidence that some FRBs have circumburst environments where free-free absorption and scattering are not significant.
The Green Bank North Celestial Cap (GBNCC) pulsar survey will cover the entire northern sky (δ > −40°) at 350 MHz, and is one of the most uniform and sensitive all-sky pulsar surveys to date. We have ...created a pipeline to reanalyze GBNCC survey data to take a 350 MHz census of all pulsars detected by the survey, regardless of their discovery survey. Of the 1413 pulsars in the survey region, we were able to recover 670. For these we present measured signal-to-noise ratios (S/N), flux densities, pulse widths, profiles, and where appropriate, refined measurements of dispersion measures (DMs) (656 out of 670) and new or improved spectral indices (339 out of 670 total, 47 new, 292 improved). We also measure the period-pulse width relation at 350 MHz to scale as . Detection scans for several hundred sources were reanalyzed in order to inspect pulsars' single pulse behavior and 223 were found to exhibit evidence of nulling. With a detailed analysis of measured and expected S/N values and the evolving radio frequency interference environment at 350 MHz, we assess the GBNCC survey's sensitivity as a function of spin period, DM, and sky position. We find the sky-averaged limiting flux density of the survey to be 0.74 mJy. Combining this analysis with PsrPopPy pulsar population simulations, we predict 60/5 nonrecycled/MSP discoveries in the survey's remaining 21,000 pointings, and we begin to place constraints on population model parameters.
Abstract
The Green Bank North Celestial Cap survey is a 350 MHz all-sky survey for pulsars and fast radio transients using the Robert C. Byrd Green Bank Telescope. To date, the survey has discovered ...over 190 pulsars, including 33 millisecond pulsars and 24 rotating radio transients. Several exotic pulsars have been discovered in the survey, including PSR J1759+5036, a binary pulsar with a 176 ms spin period in an orbit with a period of 2.04 days, an eccentricity of 0.3, and a projected semi-major axis of 6.8 light seconds. Using seven years of timing data, we are able to measure one post–Keplerian parameter, advance of periastron, which has allowed us to constrain the total system mass to 2.62 ± 0.03
M
⊙
. This constraint, along with the spin period and orbital parameters, suggests that this is a double neutron star system, although we cannot entirely rule out a pulsar-white dwarf binary. This pulsar is only detectable in roughly 45% of observations, most likely due to scintillation. However, additional observations are required to determine whether there may be other contributing effects.
To improve exclusion systems for fruit trees, insect nets of various types were evaluated for their permeability to different beneficial and pest species, under laboratory and field conditions. Pests ...studied were the apple maggot,
Rhagoletis pomonella
(Diptera: Tephritidae) and the spotted wing drosophila,
Drosophila suzukii
(Diptera: Drosophilidae). Beneficials were
Aphidoletes aphidimyza
(Diptera: Cecidomyiidae),
Aphidius matricariae
(Hymenoptera: Braconidae) and
Aphelinus abdominalis
(Hymenoptera: Aphelinidae). Mesh nets with five different apertures (square, rectangle, triangle, rhombus and hexagon) and six different sizes (from 0.4 to 2.8 mm) were 3D-printed from strands of polylactic acid and tested in the laboratory along with two commercially available nets made of polyethylene. The physical and behavioral characteristics of the six studied species affected their ability to cross the nets. For an equal size (open area), the intrusion rate was generally greater through the square- and/or hexagonal-shaped meshes. Rectangular-shaped apertures totally excluded the apple maggot in both laboratory and field trials, provided their shortest side did not exceed 1.9 mm. For the spotted wing drosophila, a maximum of 1.0 mm was similarly required for exclusion in the laboratory. The shape factor (length/width ratio) of the apertures appeared to affect net selectivity. Field trials confirmed that more aphid predators and leafroller parasitoids colonized trees covered with larger mesh nets (2.3 × 3.4 mm), while still excluding the apple maggot. Thus, for a similar aperture size (area), an elongated rectangular-shaped mesh appears to facilitate access for beneficials, while continuing to provide effective protection against apple pests.
One of the major factors contributing to surface water contamination in agricultural areas is the use of pesticides. The Soil and Water Assessment Tool (SWAT) is a hydrologic model capable of ...simulating the fate and transport of pesticides in an agricultural watershed. The SWAT model was used in this study to estimate stream flow and atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine) losses to surface water in the Cedar Creek Watershed (CCW) within the St. Joseph River Basin in northeastern Indiana. Model calibration and validation periods consisted of five and two year periods, respectively. The National Agricultural Statistics Survey (NASS) 2001 land cover classification and the Soil Survey Geographic (SSURGO) database were used as model input data layers. Data from the St. Joseph River Watershed Initiative and the Soil and Water Conservation Districts of Allen, Dekalb, and Noble counties were used to represent agricultural practices in the watershed which included the type of crops grown, tillage practices, fertilizer, and pesticide application rates. Model results were evaluated based on efficiency coefficient values, standard statistical measures, and visual inspection of the measured and simulated hydrographs. The Nash and Sutcliffe model efficiency coefficients (E(NS)) for monthly and daily stream flow calibration and validation ranged from 0.51 to 0.66. The E(NS) values for atrazine calibration and validation ranged from 0.43 to 0.59. All E(NS) values were within the range of acceptable model performance standards. The results of this study indicate that the model is an effective tool in capturing the dynamics of stream flow and atrazine concentrations on a large-scale agricultural watershed in the midwestern USA.
This study evaluated the performance of two water quality models in accordance to specific tasks designated in the USDA Agricultural Research Service Conservation Effects Assessment Project. The Soil ...and Water Assessment Tool (SWAT) and the Annualized Agricultural Non-Point Source (AnnAGNPS) models were applied uncalibrated to the Cedar Creek watershed within the St. Joseph River watershed in northeastern Indiana to predict streamflow and atrazine losses. In order to ultimately assess the benefits of conservation practices in agricultural watersheds (which is one of the major goals of the Conservation Effects Assessment Project), proper application of the SWAT and AnnAGNPS models is essential including baseline comparisons made in an uncalibrated mode aimed at eliminating bias due to parameter optimization. Streamflow prediction results show that SWAT model performance was superior to AnnAGNPS, with SWAT model efficiency values ranging from 0.66 to 0.25 and AnnAGNPS model efficiency values ranging from 0.13 to -2.06 for monthly and annual streamflow, respectively. For uncalibrated conditions, neither model was able to adequately simulate atrazine loss concentrations. Overall results suggest that for Conservation Effects Assessment Project modeling applications at the Cedar Creek watershed scale in this study, the use of the SWAT model would be preferable to AnnAGNPS in terms of overall model performance and model support technology (e.g., model interface and documentation).
The current study measured forgetting in a time-based, naturalistic prospective memory (PM) task. In Experiment 1, younger and older participants were asked to mail a stamped postcard on a date that ...was delayed 1, 2, 5, 14, or 28 days in the future. In Experiment 2, a different sample of older participants completed the same task with similar delays to replicate results for the older sample in Experiment 1. Overall, older participants were more likely than younger participants to mail the postcard on time. In addition, delay affected on-time return rates more for the younger participants than the older participants. Younger participants' return rates illustrated the typical forgetting curve seen in numerous retrospective memory studies (i.e., rapid decline at shorter delays and slower decline for longer delays). However, older participants' return rates only declined at the longest delays. These results indicate that time-based PM performance declines with an increase in delay, but the form of the decline may differ across age groups.
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