Precise measurement of the K-shell internal conversion coefficient of the 344-kev, E2 transition in Gd152

A value of 0. 0283 ± 0. 0008 was obtained for the K- shell internal conversion coefficient, aK, of the 344-kev, E2 transition in Gd152 using an electron-electron coincidence method. This value is relative to a value of 1.135 ± 0. 010 for the total internal conversion coefficient, a, of the 122-kev, E2 transition in Sm152 . a.K/a ratios of 0. 786 ± 0. 004 and 0. 589 ± 0. 003 were measured for the 344- and 122-kev transitions, respectively. The apparent 9% discrepancy with theory for aK of the 344-kev transition is not explained. The result is in excellent agreement with another measurement and also in agreement with an apparent lower trend for aK\u27s of E2 transitions in near spherical nuclei. The aK value for the 122-kev transition is in good agreement with theory. Additional measurements were performed on the 123- and 87-kev, E2 transitions in Gd154 and Dy160, respectively, and aK/a ratios of 0. 531 ± 0. 007 and 0. 341 ± 0. 011 were obtained. Construction and performance of the beta-ray spectrometers used in these coincidence measurements are described along with limitations of the experimental technique

Rotational and intrinsic levels in Tm169 and Lu175

Nuclear levels in Tm169 excited by electron capture of Yb169, and levels in Lu175 excited by both beta decay of Yb175 and electron capture of Hf175 have been studied by using the curved-crystal gamma-ray spectrometer and the ring-focusing beta-ray spectrometer, as well as a semicircular beta-ray spectrometer for low energies. From the precision energies and the multipolarity determinations, the levels in Tm169 have the following energies in kev, and spin and parity assignments: A (ground state) (½+), B 8.42 (3/2+), C 118.20 (5/2+), D 138.95 (7/2+), E 316.19 (7/2+), F 379.31 (7/2-), G 472.91 (9/2-). Levels A, B, C, and D are members of a rotational band whose characteristic constants are given. Levels E and F are interpreted as particle excitations and level G as a rotational level based on the state F. The Lu175 excited states have the following energies in kev, spins, and parities: A (ground state) (7/2+), B 113.81 (9/2+), C 251.46 (11/2+), D 343.40 (5/2+), E 396.31 (9/2-), F 432.76 (7/2+), G 504.7 (1/2+). A, B, and C form a rotational band for which the characteristic constants are given. Some features of the levels and transition probabilities are discussed and compared with the unified model. A brief survey of second-order rotational energy constants and of intrinsic excitation levels is given

SOME LIFETIME MEASUREMENTS OF ISOMERIC STATES IN THE RARE EARTH REGION WITH MAGNETIC COINCIDENCE BETA-RAY SPECTROMETERS

The half-lives of nine isomeric states in the rare earth region were measured using magnetic beta-ray spectrometers and an associated fast-slow coincidence system utilizing a time-to-pulse-height converter. The half-lives of the 8. 40-, 118- and 139-keV levels in Tm1 69 were determined to be (4. 13 ± 0. 12) nsec, (63 ± 7) psec and (289 ± 24) psec, respectively. The half-life of the 8. 40-keV level was determined using both Erl69 and Ybl69 decay. Several different methods were used to measure the 8. 40-keV level lifetime including applying various accelerating voltages to the radioactive sources. Comparisons are made with theory for the K = 1/2 rotational band in Tm169. The half-life obtained for the 8. 40-keV level in Tm169 corresponds to an energy level width of (1. 10 ± 0. 03) x l0-7 eV. If there were no broadening of the individual line profiles in the Mossbauer effect pattern, the width at half-maximum of the resolved Mossbauer lines would be (2. 20 ± 0. 06) x 10-7 eV compared to the narrowest experimental Mossbauer gross line width of 5. 04 x 10-7 eV. The half-lives of the 87- and 105-keV levels in Gd155 were also determined and were found to be (6. 27 ± 0. 35) nsec and (1. 20 ± 0. 04) nsec, respectively. Comparisons were made with the theoretical predictions of Nilsson for these two levels. The theoretical-experimental comparison would assign a spin of 5/2 to the 1 05-keV level and a spin of 3/2 to the 87-keV level if the comparison could be taken at face value. The half-lives of the 122-keV level in Sml52, 89-keV level in Gdl56, 396-keV level in Lu175 and 80-keV level in Prl44 were also determined. The half-lives of these four levels were found to be (1. 36 ± 0. 06) nsec, (2. 22 ± 0. 08) nsec, (3. 31 ± 0. 10) nsec and (143 ± 11) psec, respectively. These four half-life values agree well with values obtained by other investigators.</p

Rotational spectrum of Tm171

The gamma rays emitted from Tm171 following the Er171 beta decay have been measured with the twometer curved-crystal spectrometer and a semicircular beta-ray spectrometer, enabling a comparison of the nuclear levels and rotational parameters for the Tm171 ground-state band with the corresponding levels and parameters of Tm169. The measured gamma rays have the following energies in kev: 5.06±0.05, 12.40±0.05, 111.63±0.02, 116.69±0.03, 124.03±0.03, 210.62±0.15, 284.9±0.7, 295.97±0.15, 308.37±0.15. In comparing the rotational parameters, a slight increase in the deformation of Tm171 over that of Tm169 is noted. The relatively large change in the decoupling parameter (a=-0.8563) for Tm171 compared with that of Tm169 cannot be accounted for entirely by the small change in nuclear deformation

A z = 2.5 protocluster associated with the radio galaxy MRC 2104-242: star formation and differing mass functions in dense environments

We present results from a narrow-band survey of the field around the high-redshift radio galaxy MRC 2104−242. We have selected Hα emitters in a 7 arcmin2 field and compared the measured number density with that of a field sample at similar redshift. We find that MRC 2104−242 lies in an overdensity of galaxies that is 8.0 ± 0.8 times the average density of a blank field, suggesting it resides in a large-scale structure that may eventually collapse to form a massive cluster. We find that there is more dust obscured star formation in the protocluster galaxies than in similarly selected control field galaxies and there is tentative evidence of a higher fraction of starbursting galaxies in the denser environment. However, on average we do not find a difference between the star formation rate (SFR)–mass relations of the protocluster and field galaxies and so conclude that the SFR of these galaxies at z ∼ 2.5 is governed predominantly by galaxy mass and not the host environment. We also find that the stellar mass distribution of the protocluster galaxies is skewed towards higher masses and there is a significant lack of galaxies at M 1010.5M_) galaxies, the density of the protocluster field increases to ∼55 times the control field density

The host galaxy of the z=2.4 radio-loud AGN MRC 0406-244 as seen by HST

We present multicolour Hubble Space Telescope images of the powerful z=2.4 radio galaxy MRC 0406-244 and model its complex morphology with several components including a host galaxy, a point source, and extended nebular and continuum emission. We suggest that the main progenitor of this radio galaxy was a normal, albeit massive (M ~10^{11} solar masses), star-forming galaxy. The optical stellar disc of the host galaxy is smooth and well described by a S\'ersic profile, which argues against a recent major merger, however there is also a point-source component which may be the remnant of a minor merger. The half-light radius of the optical disc is constrained to lie in the range 3.5 to 8.2kpc, which is of similar size to coeval star forming galaxies. Biconical shells of nebular emission and UV-bright continuum extend out from the host galaxy along the radio jet axis, which is also the minor axis of the host galaxy. The origin of the continuum emission is uncertain, but it is most likely to be young stars or dust-scattered light from the AGN, and it is possible that stars are forming from this material at a rate of 200^{+1420}_{-110} solar masses per year.Comment: Accepted for publication in MNRA

Production of Secondary Organic Aerosol During Aging of Biomass Burning Smoke From Fresh Fuels and Its Relationship to VOC Precursors

After smoke from burning biomass is emitted into the atmosphere, chemical and physical processes change the composition and amount of organic aerosol present in the aged, diluted plume. During the fourth Fire Lab at Missoula Experiment, we performed smog-chamber experiments to investigate formation of secondary organic aerosol (SOA) and multiphase oxidation of primary organic aerosol (POA). We simulated atmospheric aging of diluted smoke from a variety of biomass fuels while measuring particle composition using high-resolution aerosol mass spectrometry. We quantified SOA formation using a tracer ion for low-volatility POA as a reference standard (akin to a naturally occurring internal standard). These smoke aging experiments revealed variable organic aerosol (OA) enhancements, even for smoke from similar fuels and aging mechanisms. This variable OA enhancement correlated well with measured differences in the amounts of emitted volatile organic compounds (VOCs) that could subsequently be oxidized to form SOA. For some aging experiments, we were able to predict the SOA production to within a factor of 2 using a fuel-specific VOC emission inventory that was scaled by burn-specific toluene measurements. For fires of coniferous fuels that were dominated by needle burning, volatile biogenic compounds were the dominant precursor class. For wiregrass fires, furans were the dominant SOA precursors. We used a POA tracer ion to calculate the amount of mass lost due to gas-phase oxidation and subsequent volatilization of semivolatile POA. Less than 5% of the POA mass was lost via multiphase oxidation-driven evaporation during up to 2 hr of equivalent atmospheric oxidation

A decade of monitoring Atlantic cod Gadus morhua spawning aggregations in Massachusetts Bay using passive acoustics

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Caiger, P. E., Dean, M. J., DeAngelis, A. I., Hatch, L. T., Rice, A. N., Stanley, J. A., Tholke, C., Zemeckis, D. R., & Van Parijs, S. M. A decade of monitoring Atlantic cod Gadus morhua spawning aggregations in Massachusetts Bay using passive acoustics. Marine Ecology Progress Series, 635, (2020): 89-103, doi:10.3354/meps13219.Atlantic cod Gadus morhua populations in the northeast USA have failed to recover since major declines in the 1970s and 1990s. To rebuild these stocks, managers need reliable information on spawning dynamics in order to design and implement control measures; discovering cost-effective and non-invasive monitoring techniques is also favorable. Atlantic cod form dense, site-fidelic spawning aggregations during which they vocalize, permitting acoustic detection of their presence at such times. The objective of this study was to detect spawning activity of Atlantic cod using multiple fixed-station passive acoustic recorders to sample across Massachusetts Bay during the winter spawning period. A generalized linear modeling approach was used to investigate spatio-temporal trends of cod vocalizing over 10 consecutive winter spawning seasons (2007-2016), the longest such timeline of any passive acoustic monitoring of a fish species. The vocal activity of Atlantic cod was associated with diel, lunar, and seasonal cycles, with a higher probability of occurrence at night, during the full moon, and near the end of November. Following 2009 and 2010, there was a general decline in acoustic activity. Furthermore, the northwest corner of Stellwagen Bank was identified as an important spawning location. This project demonstrated the utility of passive acoustic monitoring in determining the presence of an acoustically active fish species, and provides valuable data for informing the management of this commercially, culturally, and ecologically important species.Thanks to Eli Bonnell, Genevieve Davis, Julianne Bonell, Samara Haver, and Eric Matzen for assistance in MARU deployments, Dana Gerlach and Heather Heenehan for help in passive acoustic data analysis, and the NEFSC passive acoustics group for useful discussions. Funding for 2007−2012 passive acoustic surveys was provided by Excelerate Energy and Neptune LNG to Cornell University. Fieldwork for 2013−2015 was funded through the 2013−2014 NOAA Saltonstall-Kennedy grant program (Award No. NA14NMF4270027), and jointly funded by The Nature Conservancy, Massachusetts Division of Marine Fisheries, and the Cabot Family Charitable Foundation. Funding for 2016 SoundTrap data was provided by NOAA’s Ocean Acoustics Program (4 Sanctuaries Project)