9,789 research outputs found
Geminal wavefunctions with Jastrow correlation: a first application to atoms
We introduce a simple generalization of the well known geminal wavefunction
already applied in Quantum Chemistry to atoms and small molecules. The main
feature of the proposed wavefunction is the presence of the antisymmetric
geminal part together with a Jastrow factor. Both the geminal and the Jastrow
play a crucial role in determining the remarkable accuracy of the many-body
state: the former permits the correct treatment of the nondynamic correlation
effects, the latter allows the wavefunction to fulfill the cusp conditions and
makes the geminal expansion rapidly converging to the lowest possible
variational energies. This ansatz is expected to provide a substantial part of
the correlation energy for general complex atomic and molecular systems. The
antisymmetric geminal term can be written as a single determinant even in the
polarized cases. In general, therefore, the computational effort to sample this
correlated wavefunction is not very demanding. We applied this Jastrow-geminal
approach to atoms up to Z=15, always getting good variational energies, by
particularly improving those with a strong multiconfigurational nature. Our
wavefunction is very useful for Monte Carlo techniques, such as Fixed node.
Indeed, the nodal surface obtained within this approach can be substantially
improved through the geminal expansion.Comment: 14 pages, 2 figures, submitted to J. Chem. Phy
An Undergraduate Collaborative Team Model to Engage Nursing Students in Research
Purpose: Student-faculty collaboration on research is an effective model to engage undergraduate students in the research process outside of the traditional curriculum. Using this model, a student-faculty team developed a longitudinal study about college students’ alcohol use behaviors and implemented an intervention to influence the culture of drinking on campus.
Methods: A longitudinal design was used to assess drinking behaviors and evaluate the effect of a mass media campaign with social norm messages and alcohol education. Undergraduate students on a faith-based, Midwestern campus completed baseline (N = 1,095) and post-intervention (N = 1,011) electronic surveys.
Results: In addition to helping students learn about and develop enthusiasm for research, this project had an impact on the drinking culture on campus. Findings showed 88% of students observed media campaign messages with 82% viewing the printed posters, 47% viewing the outdoor displays, and 25% viewing messages on social media. There was a significant change in binge drinking from the pre- (72%) to post-intervention (40%) surveys.
Conclusions: Collaborative undergraduate research teams are an effective model to help students learn how to carry out research and develop interest and enthusiasm for the process. The outcomes of the project demonstrated interventions were effective at influencing the drinking culture on campus. The development of a research program outside the required curriculum can be a successful strategy to engage students in all phases of the research process, increase enthusiasm for research, and enhance health care outcomes in various settings
The Mean Drift: Tailoring the Mean Field Theory of Markov Processes for Real-World Applications
The statement of the mean field approximation theorem in the mean field
theory of Markov processes particularly targets the behaviour of population
processes with an unbounded number of agents. However, in most real-world
engineering applications one faces the problem of analysing middle-sized
systems in which the number of agents is bounded. In this paper we build on
previous work in this area and introduce the mean drift. We present the concept
of population processes and the conditions under which the approximation
theorems apply, and then show how the mean drift is derived through a
systematic application of the propagation of chaos. We then use the mean drift
to construct a new set of ordinary differential equations which address the
analysis of population processes with an arbitrary size
A Tight Upper Limit on Oscillations in the Ap star Epsilon Ursae Majoris from WIRE Photometry
Observations of Epsilon UMa obtained with the star tracker on the Wide Field
Infrared Explorer (WIRE) satellite during a month in mid-2000 are analyzed.
This is one of the most precise photometry of an Ap star. The amplitude
spectrum is used to set an upper limit of 75 parts per million for the
amplitude of stellar pulsations in this star unless it accidentally oscillates
with a single mode at the satellite orbit, its harmonics or their one day
aliases. This is the tightest limit put on the amplitude of oscillations in an
Ap star. As the rotation period of Epsilon UMa is relatively short (5.1 d), it
cannot be argued that the observations were made at a wrong rotational phase.
Our results thus support the idea that some Ap stars do not pulsate at all.Comment: 4 pages, 4 figures, 2 style files, accepted for publication in ApJ
Explant Analysis of Total Disc Replacement
Explant analysis of human disc prostheses allow early evaluation of the host response to the prosthesis and the response of the prosthesis from the host. Furthermore, early predictions of failure and wear can be obtained. Thus far, about 2-3% of disc prostheses have been removed. Observed wear patterns are similar to that of appendicular prostheses including abrasions/scratching, burnishing, surface deformation, fatigue, and embedded debris. Chemically the polymeric components have shown little degradation in short-term implantation. In metal on metal prostheses the histologic responses consist of large numbers of metallic particles with occasional macrophages and giant cells. Only rare cases of significant inflammatory response from polymeric debris have been seen
MOST observations of the roAp stars HD 9289, HD 99563, and HD 134214
We report on the analysis of high-precision space-based photometry of the
roAp (rapidly oscillating Ap) stars HD 9289, HD 99563, and HD134214. All three
stars were observed by the MOST satellite for more than 25 days, allowing
unprecedented views of their pulsation. We find previously unknown candidate
frequencies in all three stars. We establish the rotation period of HD 9289
(8.5 d) for the first time and show that the star is pulsating in two modes
that show different mode geometries. We present a detailed analysis of HD
99563's mode multiplet and find a new candidate frequency which appears
independent of the previously known mode. Finally, we report on 11 detected
pulsation frequencies in HD 134214, 9 of which were never before detected in
photometry, and 3 of which are completely new detections. Thanks to the
unprecedentedly small frequency uncertainties, the p-mode spectrum of HD 134214
can be seen to have a well-defined large frequency spacing similar to the
well-studied roAp star HD 24712 (HR 1217).Comment: 11 pages, 12 figures, accepted for publication in A&
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