526 research outputs found
fuck off, get free, love and love\u27s the only thing
A child, angry at concrete and strip malls, enjoying coffee from too many styrofoam cups
Ordered phases of potassium on Pt{111}: Experiment and theory
Using low-energy electron diffraction structural analysis and first-principles calculations based on the local-density approximation we have investigated the (â3Ăâ3)R30° K and (2Ă2) K overlayers on Pt{111}. The measured and calculated adsorption geometries agree quantitatively. In both phases the K adatoms occupy threefold symmetric hcp hollow sites, the preference for the hcp site over the fcc site being a consequence of the polarization of the surface Pt d electrons. We have not found any indication of K incorporation into the Pt{111} surface, as has been recently suggested
Detecting circumbinary planets using eclipse timing of binary stars - numerical simulations
The presence of a body in an orbit around a close eclipsing binary star
manifests itself through the light time effect influencing the observed times
of eclipses as the close binary and the circumbinary companion both move around
the common centre of mass. This fact combined with the periodicity with which
the eclipses occur can be used to detect the companion. Given a sufficient
precision of the times of eclipses, the eclipse timing can be employed to
detect substellar or even planetary mass companions.
The main goal of the paper is to investigate the potential of the photometry
based eclipse timing of binary stars as a method of detecting circumbinary
planets. In the models we assume that the companion orbits a binary star in a
circular Keplerian orbit. We analyze both the space and ground based photometry
cases. In particular, we study the usefulness of the on-going COROT and Kepler
missions in detecting circumbinary planets. We also explore the relations
binding the planet discovery space with the physical parameters of the binaries
and the geometrical parameters of their light curves. We carry out detailed
numerical simulations of the eclipse timing by employing a relatively realistic
model of the light curves of eclipsing binary stars. We study the influence of
the white and red photometric noises on the timing precision. We determine the
sensitivity of the eclipse timing technique to circumbinary planets for the
ground and space based photometric observations. We provide suggestions for the
best targets, observing strategies and instruments for the eclipse timing
method. Finally, we compare the eclipse timing as a planet detection method
with the radial velocities and astrometry.Comment: 9 pages, 15 figures, accepted for publication in MNRA
Computing Heavy Elements
Reliable calculations of the structure of heavy elements are crucial to
address fundamental science questions such as the origin of the elements in the
universe. Applications relevant for energy production, medicine, or national
security also rely on theoretical predictions of basic properties of atomic
nuclei. Heavy elements are best described within the nuclear density functional
theory (DFT) and its various extensions. While relatively mature, DFT has never
been implemented in its full power, as it relies on a very large number (~
10^9-10^12) of expensive calculations (~ day). The advent of leadership-class
computers, as well as dedicated large-scale collaborative efforts such as the
SciDAC 2 UNEDF project, have dramatically changed the field. This article gives
an overview of the various computational challenges related to the nuclear DFT,
as well as some of the recent achievements.Comment: Proceeding of the Invited Talk given at the SciDAC 2011 conference,
Jul. 10-15, 2011, Denver, C
Hydrogen bonding in infinite hydrogen fluoride and hydrogen chloride chains
Hydrogen bonding in infinite HF and HCl bent (zigzag) chains is studied using
the ab initio coupled-cluster singles and doubles (CCSD) correlation method.
The correlation contribution to the binding energy is decomposed in terms of
nonadditive many-body interactions between the monomers in the chains, the
so-called energy increments. Van der Waals constants for the two-body
dispersion interaction between distant monomers in the infinite chains are
extracted from this decomposition. They allow a partitioning of the correlation
contribution to the binding energy into short- and long-range terms. This
finding affords a significant reduction in the computational effort of ab
initio calculations for solids as only the short-range part requires a
sophisticated treatment whereas the long-range part can be summed immediately
to infinite distances.Comment: 9 pages, 4 figures, 3 tables, RevTeX4, corrected typo
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Spanish validation of the revised depression attitude questionnaire (R-daq)
Purpose: The aim of the study was to develop and validate a Spanish version of the Revised Depression Attitude Questionnaire (R-DAQ). Methods: The R-DAQ was used as a baseline for the study. It was translated and tested to ensure the instrument was appropriate for the target population. 537 Ecuadorian healthcare professionals completed the revised Spanish version of the R-DAQ (SR-DAQ). Statistical and exploratory factor analyses were performed to examine construct validity, internal consistency, readability and floor and ceiling effects. Results: Three factors were obtained: âProfessional confidence in depression careâ; âTherapeutic optimism about depressionâ; and âGeneralist perspective about depression occurrence, recognition, and managementâ. The internal consistency of the SR-DAQ was determined by means of Cronbachâs α coefficient, with values ranging between 0.61â0.8. The correlations with the English version reflected adequate validity. The model explained 39% of the variance. Subsequent analysis with a sample restricted to those who had received training in depression produced a model that explained 42% of the variance. Conclusion: The SR-DAQ meets the psychometric requirements for measuring depression attitude in a Spanish-speaking population and shows adequate internal consistency and validity
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