700 research outputs found
Elias Hicks and Thomas Shilltoe: Two Paths Diverge
Two prominent Quaker ministers, English Thomas Shillitoe and American Elias Hicks, at the end of their long lives of exhortation devoted to the mission of persuading others to follow the will of God, came together on the American continent in 1826-29. They turned out to be key players on opposite sides in the struggle which ended with the splitting of American Friends into two antagonistic groups, the Orthodox and the Hicksite.
Through a close reading of the journals of these two men, supplemented by biographies and other relevant materials, this paper analyzes similarities and differences in their views on humanity and the means of salvation, their messages and motivations, and traces cultural, environmental and personal factors that may have contributed to their divergence.
The basic question it examines is how two Quaker contemporaries, similarly schooled and practiced and totally sincere in following the leading of the Holy Spirit, could end so totally opposed
Fully Bayesian computing
A fully Bayesian computing environment calls for the possibility of defining vector and array objects that may contain both random and deterministic quantities, and syntax rules that allow treating these objects much like any variables or numeric arrays. Working within the statistical package R, we introduce a new object-oriented framework based on a new random variable data type that is implicitly represented by simulations. We seek to be able to manipulate random variables and posterior simulation objects conveniently and transparently and provide a basis for further development of methods and functions that can access these objects directly. We illustrate the use of this new programming environment with several examples of Bayesian computing, including posterior predictive checking and the manipulation of posterior simulations. This new environment is fully Bayesian in that the posterior simulations can be handled directly as random variables
A Complex Chemical Potential: Signature of Decay in a Bose-Einstein Condensate
We explore the zero-temperature statics of an atomic Bose-Einstein condensate
in which a Feshbach resonance creates a coupling to a second condensate
component of quasi-bound molecules. Using a variational procedure to find the
equation of state, the appearance of this binding is manifest in a collapsing
ground state, where only the molecular condensate is present up to some
critical density. Further, an excited state is seen to reproduce the usual
low-density atomic condensate behavior in this system, but the molecular
component is found to produce an underlying decay, quantified by the imaginary
part of the chemical potential. Most importantly, the unique decay rate
dependencies on density () and on scattering length () can be measured in experimental tests of this theory.Comment: 4 pages, 1 figur
Time-Dependent Variational Analysis of Josephson Oscillations in a Two-component Bose-Einstein Condensate
The dynamics of Josephson-like oscillations between two coupled Bose-Einstein
condensates is studied using the time-dependent variational method. We suppose
that the quantum state of the condensates is a gaussian wave-packet which can
translate and perform breathing shape oscillations. Under this hypotheses we
study the influence of these degrees of freedom on the tunneling dynamics by
comparing the full-model with one where these degrees of freedom are ``frozen''
at its equilibrium values. The result of our calculation shows that when the
traps are not displaced the two models agree, whereas when they are, the models
differ considerably, the former being now closer to its linear approximation.Comment: 10 pages, 2 figure
Social conformity affects experimental measurement of boldness in male but not female monk parakeets (\u3ci\u3eMyiopsitta monachus\u3c/i\u3e)
The standard approach for characterizing boldness rarely considers the influence of social environment on the expression of boldness in group-living animals. We studied a wild-caught, captive population of monk parakeets (Myiopsitta monachus) to investigate the impact of conspecific presence on boldness â a personality trait in monk parakeets â in a controlled environment. We quantified seven boldness metrics across three types of behavioural assay: novel object, emergence, and predator exposure tests in the presence of a companion pair of flock mates. Because of the high degree of sociality in this species, we hypothesized that the presence of companion birds would facilitate the focal individualsâ behavioural responses (i.e., increase the average boldness level). We found that behavioural response in a risky foraging context was inversely correlated between solitary and social condition in males, but not in females. Our results have implications for characterizing sex-specific differences of risk-taking behaviour in social animals
Evaluation of boldness assays and associated behavioral measures in a social parrot, monk parakeet (\u3ci\u3eMyiopsitta monachus\u3c/i\u3e)
Boldness reflects consistent individual differences in risk-taking behavior across various contexts. However, evaluating this basic assumption has largely been neglected in birds. In a captive monk parakeet population (Myiopsitta monachus; N = 33), we undertook an analysis of 7 measures across 3 commonly used boldness assays (i.e., novel object, emergence, and predator-exposure tests). Using principal component analysis, we derived 3 components (PCs). PC-2 loaded strongly with measures from emergence and predator-exposure tests; we interpreted it as the closest approximation of boldness. PC-1 and PC-3 described different aspects of feeding such as foraging activity and rate, respectively. Finally, we assessed the predictive power of each measure that loaded significantly on the boldness axis.We found that no single metric explained even %55 of the variation in PC-2, nor could more than %50 individuals at the extremes of the spectrum be predicted. Our results demonstrate the utility of an inclusive approach in personality research
Kinetic-inductance-limited reset time of superconducting nanowire photon counters
We investigate the recovery of superconducting NbN-nanowire photon counters
after detection of an optical pulse at a wavelength of 1550 nm, and present a
model that quantitatively accounts for our observations. The reset time is
found to be limited by the large kinetic inductance of these nanowires, which
forces a tradeoff between counting rate and either detection efficiency or
active area. Devices of usable size and high detection efficiency are found to
have reset times orders of magnitude longer than their intrinsic photoresponse
time.Comment: Submitted to Applied Physics Letter
Finite Temperature Many-Body Theory with the Lipkin Model
We have compared exact numerical results for the Lipkin model at finite
temperature with Hartree-Fock theory and with the results of including in
addition the ring diagrams. In the simplest version of the Lipkin model the
Hartree-Fock approach shows a ``phase transition" which is absent in the exact
results. For more realistic cases, Hartree-Fock provides a very good
approximation and a modest improvement is obtained by adding the ring diagrams.Comment: 17 pages, NUC-MINN-93/16-T (4 figures obtainable by fax from the
authors
Parallel algorithm with spectral convergence for nonlinear integro-differential equations
We discuss a numerical algorithm for solving nonlinear integro-differential
equations, and illustrate our findings for the particular case of Volterra type
equations. The algorithm combines a perturbation approach meant to render a
linearized version of the problem and a spectral method where unknown functions
are expanded in terms of Chebyshev polynomials (El-gendi's method). This
approach is shown to be suitable for the calculation of two-point Green
functions required in next to leading order studies of time-dependent quantum
field theory.Comment: 15 pages, 9 figure
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