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32 results on '"Tracy, James L."'

10. Mass Measurements of Neutron-Deficient Yb Isotopes and Nuclear Structure at the Extreme Proton-Rich Side of the N=82 Shell

Author

Beck, Sönke, primary, Kootte, Brian, additional, Dedes, Irene, additional, Dickel, Timo, additional, Kwiatkowski, A. A., additional, Lykiardopoulou, Eleni Marina, additional, Plaß, Wolfgang R., additional, Reiter, Moritz P., additional, Andreoiu, Corina, additional, Bergmann, Julian, additional, Brunner, Thomas, additional, Curien, Dominique, additional, Dilling, Jens, additional, Dudek, Jerzy, additional, Dunling, Eleanor, additional, Flowerdew, Jake, additional, Gaamouci, Abdelghafar, additional, Graham, Leigh, additional, Gwinner, Gerald, additional, Jacobs, Andrew, additional, Klawitter, Renee, additional, Lan, Yang, additional, Leistenschneider, Erich, additional, Minkov, Nikolay, additional, Monier, Victor, additional, Mukul, Ish, additional, Paul, Stefan F., additional, Scheidenberger, Christoph, additional, Thompson, Robert I., additional, Tracy, James L., additional, Vansteenkiste, Michael, additional, Wang, Hua-Lei, additional, Wieser, Michael E., additional, Will, Christian, additional, and Yang, Jie, additional

Published
2021
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17. Hemlock woolly adelgid niche models from the invasive eastern North American range with projections to native ranges and future climates.

Author

Kantola, Tuula, Tracy, James L., Lyytikäinen-Saarenmaa, Päivi, Saarenmaa, Hannu, Coulson, Robert N., Trabucco, Antonio, and Holopainen, Markus

Subjects
*COLD (Temperature), *SUBSET selection, *FEATURE selection, *CLIMATOLOGY, *EXTREME environments, POTENTIAL distribution
Abstract

The hemlock woolly adelgid (Adelges tsugae Annand - HWA) is invasive in eastern North America where it causes extensive mortality to hemlock communities. The future of these communities under projected climate change is an issue of landscape ecological interest and speculation. We employed the MaxEnt algorithm with the random subset feature selection algorithm (RSFSA) in creating HWA niche models. Final models were ensembles of 12 statistically best models with six predictors each. Out of 119 climatic, topographic, and soil variables, 42 were used in at least one final model. Soil features, followed by climate and topographic features, were most common in selected models. The three most important variables among all models were November potential evapotranspiration, slope, and percent Ochrepts soil. The potential distributions of HWA within eastern North America were projected under historical and four future climate scenarios for 2050 and 2070 under low and high CO2 emissions. The mean of the minimum values for the minimum temperature of the coldest month from the 12 MaxEnt model projections in eastern North America was -15.8°C. This value was close to -15°C, the extreme minimum temperature found for both HWA occurrence points and previously reported HWA cold temperature limits. These results indicate that HWA may be close to equilibrium distribution in eastern North America under current climate. We also reverse-casted the eastern North American MaxEnt model back onto the HWA native ranges in eastern Asia and western North America. The projections match best with native ranges in Asian islands, such as Japan, and the Cascade Mountains in western North America. Statistically significant HWA range shifts of 221-468 km northwards and 110-164 km eastwards were projected by the 12 models for 2050-2070. The 2070 high CO2 emission scenario models projects HWA suitability throughout most of the northern range of eastern hemlock. [ABSTRACT FROM AUTHOR]

Published
2019
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18. A binding energy study of the Atomic Mass Evaluation 2012 and an updated beta-decay study of neutron-rich ⁷⁴Cu

Author

Tracy, James L. and Tracy, James L.

Abstract

A study of ground state binding energy values listed in the Atomic Mass Evaluation 2012 (AME2012) using an interpretive approach, as opposed to the exploratory methods of previous models, is presented. This model is based on a postulate requiring all protons to pair with available neutrons to form bound alpha clusters as the ground state for an N = Z core upon which excess neutrons are added. For each core, the trend of the binding energy as a function of excess neutrons in the isotopic chain can be fit with a three-term quadratic function. The quadratic parameter reveals a smooth decaying exponential function. By re-envisioning the determination of mass excess, the constant-term fit parameters, representing N = Z nuclei, reveal a near-symmetry around Z = 50. The linear fit parameters exhibit trends which are linear functions of core size. A neutron drip-line prediction is compared against current models. By considering the possibility of an alpha-cluster core, a new ground-state structure grouping scheme is presented; nucleon-nucleon pairing is shown to have a greater role in level filling. This model, referred to as the Alpha-Deuteron-Neutron Model, yields promising first results when considering root-mean-square variances from the AME2012. The beta-decay of the neutron-rich isotope ⁷⁴Cu has been studied using three highpurity Germanium clover detectors at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. A high-resolution mass separator greatly improved the purity of the ⁷⁴Cu beam by removing isobaric contaminants, thus allowing decay through its isobar chain to the stable ⁷⁴Ge at the center of the LeRIBSS detector array without any decay chain member dominating. Using coincidence gating techniques, 121 gamma-rays associated with ⁷⁴Cu were isolated from the collective singles spectrum. Eighty-seven of these were placed in an expanded level scheme, and updated beta-feeding level intensities and log(ft) values are presented based on multiple newly-placed excited states up to 6.8 MeV. The progression of simulated Total Absorption gamma-ray Spectroscopy (TAGS) based on known levels and beta feeding values from previous measurements to this evaluation are presented and demonstrate the need for a TAGS measurement of this isotope to gain a more complete understanding of its decay scheme.

Published
2016

20. Host specificity of the leaf beetle, Diorhabda elongata deserticola (Coleoptera: Chrysomelidae) from Asia, a biological control agent for saltcedars (Tamarix: Tamaricaceae) in the Western United States

Author

DeLoach, C. Jack, Lewis, Phil A, Herr, John C., Carruthers, Raymond I, Tracy, James L, Johnson, Joye, DeLoach, C. Jack, Lewis, Phil A, Herr, John C., Carruthers, Raymond I, Tracy, James L, and Johnson, Joye

Abstract

Four species of saltcedars, Tamarix ramosissima Ledeb., Tamarix chinensis Lour., Tamarix parviflora DC., and T. canariensis Willd. and their hybrids, are exotic, invasive small trees from Asia that cause great damage to riparian ecosystems of the western United States. They displace native plant communities, degrade wildlife habitat (including that of many endangered species), increase soil salinity and wildfires, lower water tables, reduce water available for agriculture and municipalities, and reduce recreational use of affected areas. Phytophagous insects are abundant on saltcedar in the Old World and we selected Diorhabda elongata Brullé deserticola Chen as the top candidate biological control agent because of the great damage it causes, and its high host specificity, broad geographic range, and presumed adaptability in the United States. Literature review and our overseas surveys indicated that this insect is associated only with species of Tamarix and occasionally with Myricaria but not with Reumaria or Frankenia (all Tamaricales) in the Old World. In quarantine facilities in the United States, and overseas, we tested beetles from China and Kazakhstan on six species and three hybrids (26 accessions) of Tamarix and on 58 species of other plants, in 15 tests of different types, using 1852 adults and 3547 larvae, over 10 years. Survival from larvae to adults averaged 55–67% on the Tamarix species, 12% on Myricaria sp., and only 1.6% on the three Frankenia spp. No larvae completed their development on any of the other 54 plant species tested, where most larvae died during the first instar. Adults oviposited readily on T. ramosissima accessions, less on Tamarix aphylla (L.) Karst. (athel), and only rarely on other plants. The host range of the D. e. deserticola we tested from Kazakhstan was not different from those we tested from China. Therefore, D. e. deserticola, is sufficiently host-specific and was approved for field release in North America. This is the first

Published
2003

26. Think Tanks.

Author

Tracy, James L., primary, Dickson, Paul, additional, and Lasby, Clarence G., additional

Published
1972
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