Mean and Extreme Radio Properties of Quasars and the Origin of Radio Emission

We investigate the evolution of both the radio-loud fraction (RLF) and (using stacking analysis) the mean radio-loudness of quasars. We consider how these values evolve as a function of redshift and luminosity, black hole (BH) mass and accretion rate, and parameters related to the dominance of a wind in the broad emission line region. We match the FIRST source catalog to samples of luminous quasars (both spectroscopic and photometric), primarily from the Sloan Digital Sky Survey. After accounting for catastrophic errors in BH mass estimates at high-redshift, we find that both the RLF and the mean radio luminosity increase for increasing BH mass and decreasing accretion rate. Similarly both the RLF and mean radio loudness increase for quasars which are argued to have weaker radiation line driven wind components of the broad emission line region. In agreement with past work, we find that the RLF increases with increasing luminosity and decreasing redshift while the mean radio-loudness evolves in the exact opposite manner. This difference in behavior between the mean radio-loudness and the RLF in L-z may indicate selection effects that bias our understanding of the evolution of the RLF; deeper surveys in the optical and radio are needed to resolve this discrepancy. Finally, we argue that radio-loud (RL) and radio-quiet (RQ) quasars may be parallel sequences but where only RQ quasars at one extreme of the distribution are likely to become RL, possibly through slight differences in spin and/or merger history.Comment: 55 pages, 28 figures, accepted to A

Are There Opportunities to Increase Social Security Progressivity Despite Underfunding?

Reviews the payroll tax, Social Security's benefit formula, and outcomes by race, gender, and earnings level, and explores why low-income and minority groups do not receive greater returns on contributions. Simulates the effects of progressive reforms

Using alterative whole-farm modelling approaches to assess farm enterprise selection, risk and welfare

Using an expected mean-variance model the changes in farm enterprise levels and indirect utility were examined under conditions of risk aversion, budget constraints and gross margin variance. An extension of the comparative statics of the expected mean-variance model was adopted by introducing a budget constraint into the constrained optimisation problem. A 10-year expected mean-variance whole-farm model was solved for a farm in the wheat-sheep zone of Australia to provide an empirical example. Results were obtained using no planning horizon (the static model) and then with a five-year rolling planning horizon (the dynamic model). In addition, enterprise levels were constrained to match levels observed on the farm so as to compare incomes between the constrained and unconstrained models. For a cash constrained, risk averse, farmer it was found that they are likely to have larger expenditures than less risk averse operators in order to obtain the same indirect utility. Enterprise levels differed between the dynamic and static models, and a dynamic model was used to help explain inter-temporal decision-making. Risk aversion reduced the set of possible welfare improving production activities available to a farmer.Whole-farm modelling, enterprise selection, risk., Farm Management, Q12, C61,

Arecibo Observatory support of the US international cometary Explorer mission encounter at comet Giacobini-Zinner

The Arecibo Observatory in Puerto Rico participated in the support of the U.S. International Cometary Explorer (ICE) mission when the ICE spacecraft passed through the tail of comet Giacobini-Zinner on September 11, 1985. The Arecibo Observatory is a research facility of the National Astronomy and Ionosphere Center (NAIC) operated by Cornell University under contract to the National Science Foundation (NSF). Coverage of the encounter involved the use of the observatory's 305-m (1000-ft) radio reflector antenna and RF and data system equipment fabricated or modified specifically for support of the ICE mission. The successful implementation, testing, and operation of this temporary receive, record, and data relay capability resulted from a cooperative effort by personnel at the Arecibo Observatory, the Goddard Space Flight Center, and the Jet Propulsion Laboratory

Development of an Advanced Force Field for Water using Variational Energy Decomposition Analysis

Given the piecewise approach to modeling intermolecular interactions for force fields, they can be difficult to parameterize since they are fit to data like total energies that only indirectly connect to their separable functional forms. Furthermore, by neglecting certain types of molecular interactions such as charge penetration and charge transfer, most classical force fields must rely on, but do not always demonstrate, how cancellation of errors occurs among the remaining molecular interactions accounted for such as exchange repulsion, electrostatics, and polarization. In this work we present the first generation of the (many-body) MB-UCB force field that explicitly accounts for the decomposed molecular interactions commensurate with a variational energy decomposition analysis, including charge transfer, with force field design choices that reduce the computational expense of the MB-UCB potential while remaining accurate. We optimize parameters using only single water molecule and water cluster data up through pentamers, with no fitting to condensed phase data, and we demonstrate that high accuracy is maintained when the force field is subsequently validated against conformational energies of larger water cluster data sets, radial distribution functions of the liquid phase, and the temperature dependence of thermodynamic and transport water properties. We conclude that MB-UCB is comparable in performance to MB-Pol, but is less expensive and more transferable by eliminating the need to represent short-ranged interactions through large parameter fits to high order polynomials

A preliminary assessment of age at death determination using the nuclear weapons testing 14C activity of dentine and enamel

Calibration (using CALIBomb) of radiocarbon measurements made on the enamel of human teeth from people born during the nuclear era typically produce 2 possible age ranges that potentially reflect the period of tooth formation. These ranges correspond to periods before and after the 1963 atmospheric 14C maximum. Further measurements made on the collagen component of the combined dentine and cementum from the roots of the same teeth enable the appropriate age range to be selected. Using this range and the formation times for individual teeth, we estimated the year of birth of the individuals and compared these to the known dates of birth. The results were relatively accurate and confirmed those of a previous study by another research group. The present study demonstrates that it is possible to produce a good estimate of the year of birth from a single tooth

A marine reservoir effect ΔR value for Kitandach, in Prince Rupert Harbour, British Columbia, Canada

Prince Rupert Harbour (PRH), on the north Pacific Coast of British Columbia, contains at least 157 shell middens, of which 66 are known villages, in an area of approximately 180 km. These sites span the last 9500 yr and in some cases are immense, exceeding 20,000 m surface area and several meters in depth. Recent archaeological research in PRH has become increasingly reliant on radiocarbon dates from marine shell for developing chronologies. However, this is problematic as the local marine reservoir effect (MRE) remains poorly understood in the region. To account for the MRE and to better date the Harbour’s sites, we propose a ΔR of 273 ± 38 for the PRH area, based on our work at the site of Kitandach (GbTo-34), a massive shell midden-village centrally located within the Harbour. We followed the multiple paired sample approach for samples from speci fic contexts and ensured contemporaneity within the groups of marine and terrestrial materials by statistically assessing for outliers using the χ2 test. Taking together, the results for this and previous studies, it appears the MRE was fairly constant over the past 5000 yr

Gas-Surface Dynamics and Profile Evolution during Etching of Silicon

Scattering of energetic F atoms on a fluorinated Si surface is studied by molecular beam methods. The energy transfer closely follows hard-sphere collision kinematics. Energy and angular distributions of unreacted F atoms suggest significant multiple-bounce scattering in addition to single-bounce scattering and trapping desorption. An empirical model of the atom-surface interaction dynamics is used in a Monte Carlo simulation of topography evolution during neutral beam etching of Si. Model predictions of profile phenomena are validated by experiments

High multipole transitions in NIXS: valence and hybridization in 4f systems

Momentum-transfer (q) dependent non-resonant inelastic x-ray scattering measurements were made at the N4,5 edges for several rare earth compounds. With increasing q, giant dipole resonances diminish, to be replaced by strong multiplet lines at lower energy transfer. These multiplets result from two different orders of multipole scattering and are distinct for systems with simple 4f^0 and 4f^1 initial states. A many-body theoretical treatment of the multiplets agrees well with the experimental data on ionic La and Ce phosphate reference compounds. Comparing measurements on CeO2 and CeRh3 to the theory and the phosphates indicates sensitivity to hybridization as observed by a broadening of 4f^0-related multiplet features. We expect such strong, nondipole features to be generic for NIXS from f-electron systems