Spectral Hardness Decay with Respect to Fluence in BATSE Gamma-Ray Bursts

We have analyzed the evolution of the spectral hardness parameter Epk as a function of fluence in gamma-ray bursts. We fit 41 pulses within 26 bursts with the trend reported by Liang & Kargatis (1996) which found that Epk decays exponentially with respect to photon fluence. We also fit these pulses with a slight modification of this trend, where Epk decays linearly with energy fluence. In both cases, we found the set of 41 pulses to be consistent with the trend. For the latter trend, which we believe to be more physical, the distribution of the decay constant is roughly log-normal, with a mean of 1.75 +/- 0.07 and a FWHM of 1.0 +/- 0.1. Regarding an earlier reported invariance in the decay constant among different pulses in a single burst, we found probabilities of 0.49 to 0.84 (depending on the test used) that such invariance would occur by coincidence, most likely due to the narrow distribution of decay constant values among pulses.Comment: 17 pages, 7 figure pages, 2 table pages, submitted to The Astrophysical Journa

Evolution of the Low-Energy Photon Spectra in Gamma-Ray Bursts

We report evidence that the asymptotic low-energy power law slope alpha (below the spectral break) of BATSE gamma-ray burst photon spectra evolves with time rather than remaining constant. We find a high degree of positive correlation exists between the time-resolved spectral break energy E_pk and alpha. In samples of 18 "hard-to-soft" and 12 "tracking" pulses, evolution of alpha was found to correlate with that of the spectral break energy E_pk at the 99.7% and 98% confidence levels respectively. We also find that in the flux rise phase of "hard-to-soft" pulses, the mean value of alpha is often positive and in some bursts the maximum value of alpha is consistent with a value > +1. BATSE burst 3B 910927, for example, has a alpha_max equal to 1.6 +/- 0.3. These findings challenge GRB spectral models in which alpha must be negative of remain constant.Comment: 12 pages (including 6 figures), accepted to Ap

NOTES: ARE LAND-USE CHANGES REFLECTED IN DIETS OF MOURNING DOVES (ZENAIDA MACROURA) IN EASTERN SOUTH DAKOTA

Food habits of the mourning dove (Zenaida macroura) have been extensively studied in the southern United States (McClure 1943, Korschgen 1958, Carpenter 1971) and consist primarily of vegetable matter throughout their range (Beckwith 1959). Diet studies in several states have indicated agricultural crops, specifically corn and wheat, were the most readily consumed plant seeds (Korshgen 1958, Carpenter 1971). Similarities observed in diets of doves were dependent on the agricultural crops available within the area. For example, in Missouri, some seasonal variability was documented suggesting doves forage based on food availability as much as by food preference (Korschgen 1958). However, in the agriculturally- dominated landscape of east central South Dakota (SD), the two most important food items for doves were green (Setaria viridis) and yellow foxtail (S. glauca; Van’t Hul and Jenks 1992). Large-scale land use changes have occurred in eastern South Dakota in the past few decades and several factors have contributed to increased grassland to cropland conversion (Wright and Wimberly 2013). Conversion of grasslands to agricultural crops has increased as demand for biofuels and commodity prices increased (Secchi and Babcock 2007, Searchinger et al. 2008, Fargione et al. 2009, Wright and Wimberly 2013). In east central South Dakota, corn and soybean plantings have increased from 2,400,000 ha in 1991 to 4,400,000 ha in 2013 (United States Department of Agriculture 2014). These significant land-use changes that have occurred in the intervening 20 years may influence mourning dove feeding habits. We compared mourning dove diet composition in Minnehaha County, South Dakota, USA, to those published 20 years earlier from a study conducted approximately 60 km north (Van’t Hul and Jenks 1992)

The electric dipole response of 76^{76}Se above 4 MeV

The dipole response of $^{76}_{34}$Se in the energy range 4 to 9 MeV has been analyzed using a $(\vec\gamma,{\gamma}')$ polarized photon scattering technique, performed at the High Intensity $\gamma$-Ray Source facility, to complement previous work performed using unpolarized photons. The results of this work offer both an enhanced sensitivity scan of the dipole response and an unambiguous determination of the parities of the observed J=1 states. The dipole response is found to be dominated by $E1$ excitations, and can reasonably be attributed to a pygmy dipole resonance. Evidence is presented to suggest that a significant amount of directly unobserved excitation strength is present in the region, due to unobserved branching transitions in the decays of resonantly excited states. The dipole response of the region is underestimated when considering only ground state decay branches. We investigate the electric dipole response theoretically, performing calculations in a 3D cartesian-basis time-dependent Skyrme-Hartree-Fock framework.Comment: 20 pages, 18 figures, to be submitted to PR

Are Land-use Changes Reflected in Diets of Mourning Doves (Zenaida macroura) in Eastern South Dakota

Food habits of the mourning dove (Zenaida macroura) have been extensively studied in the southern United States (McClure 1943, Korschgen 1958, Carpenter 1971) and consist primarily of vegetable matter throughout their range (Beckwith 1959). Diet studies in several states have indicated agricultural crops, specifically corn and wheat, were the most readily consumed plant seeds (Korshgen 1958, Carpenter 1971). Similarities observed in diets of doves were dependent on the agricultural crops available within the area. For example, in Missouri, some seasonal variability was documented suggesting doves forage based on food availability as much as by food preference (Korschgen 1958). However, in the agriculturally dominated landscape of east central South Dakota (SD), the two most important food items for doves were green (Setaria viridis) and yellow foxtail (S. glauca; Van’t Hul and Jenks 1992)

Comparisons of electron fluxes measured in the crustal fields at Mars by the MGS magnetometer/electron reflectometer instrument with a B field–dependent transport code

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95296/1/jgre1782.pd

Seniority Structure of \u3csup\u3e136\u3c/sup\u3eXe\u3csub\u3e82\u3c/sub\u3e

The level structure of the N = 82 nucleus 136Xe was studied with the inelastic neutron scattering reaction followed by γ-ray detection. A number of the spins and parities were reassigned, and many level lifetimes were determined for the first time using the Doppler-shift attenuation method. New shell-model calculations were also performed using both the full Z = 50–82 model space, and a reduced model space including only the 1d5/2 and 0g7/2 orbitals. This new information characterizing 136Xe was used to identify the seniority structure of the low-lying levels and to assign (π0g7/2)4υ=0, (π0g7/2)4υ=2, (π0g7/2)4υ=4, (π1d5/2)(π0g7/2)3υ=1, and (π1d5/2)2(π0g7/2)2υ=0 configurations to describe all observed states below 2.8 MeV

Neurology

Contains reports on eight research projects.U.S. Navy (Office of Naval Research (Nonr-1841(70))U. S. Public Health Service (MH-06175-02)U. S. Air Force (AF49(638)-1313)U. S. Public Health Service (B-3055-4)U. S. Public Health Service (B-3090-4

Studies of \u3csup\u3e54,56\u3c/sup\u3eFe Neutron Scattering Cross Sections

Elastic and inelastic neutron scattering differential cross sections and γ-ray production cross sections have been measured on 54,56Fe at several incident energies in the fast neutron region between 1.5 and 4.7 MeV. All measurements were completed at the University of Kentucky Accelerator Laboratory (UKAL) using a 7-MV Model CN Van de Graaff accelerator, along with the neutron production and neutron and γ-ray detection systems located there. The facilities at UKAL allow the investigation of both elastic and inelastic scattering with nearly mono-energetic incident neutrons. Time-of-flight techniques were used to detect the scattered neutrons for the differential cross section measurements. The measured cross sections are important for fission reactor applications and also for testing global model calculations such as those found at ENDF, since describing both the elastic and inelastic scattering is important for determining the direct and compound components of the scattering mechanism. The γ-ray production cross sections are used to determine cross sections to unresolved levels in the neutron scattering experiments. Results from our measurements and comparisons to model calculations are presented

Lifetime Measurements of Low-Spin Negative-Parity Levels in \u3csup\u3e160\u3c/sup\u3eGd

160Gd(n,n′γ) experiments were performed with accelerator-produced monoenergetic neutrons. Excitation functions at neutron energies from 1.5 to 2.8 MeV aided in the placement of γ rays in the level scheme and angular distributions at three neutron energies resulted in the determination of 28 excited-level lifetimes or limits in 160Gd, including the lifetimes of several negative-parity levels attributed to octupole vibrations