9,778 research outputs found
AAOmega spectroscopy of 29 351 stars in fields centered on ten Galactic globular clusters
Galactic globular clusters have been pivotal in our understanding of many
astrophysical phenomena. Here we publish the extracted stellar parameters from
a recent large spectroscopic survey of ten globular clusters. A brief review of
the project is also presented. Stellar parameters have been extracted from
individual stellar spectra using both a modified version of the Radial Velocity
Experiment (RAVE) pipeline and a pipeline based on the parameter estimation
method of RAVE. We publish here all parameters extracted from both pipelines.
We calibrate the metallicity and convert this to [Fe/H] for each star and,
furthermore, we compare the velocities and velocity dispersions of the Galactic
stars in each field to the Besan\c{c}on Galaxy model. We find that the model
does not correspond well with the data, indicating that the model is probably
of little use for comparisons with pencil beam survey data such as this.Comment: 6 pages, 5 figures, 4 tables. Accepted for publication in A&A. Data
described in tables will be available on CDS (at
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/530/A31) once publishe
Survival law in a potential model
The radial equation of a simple potential model has long been known to yield
an exponential decay law in lowest order (Breit-Wigner) approximation. We
demonstrate that if the calculation is extended to fourth order the decay law
exhibits the quantum Zeno effect. This model has further been studied
numerically to characterize the extra exponential time parameter which
compliments the lifetime. We also investigate the inverse Zeno effect.Comment: 16 pages, 2 tables, 3 figures, AMS-Te
Systematics of the Quadrupole-Quadrupole Interaction and Convergence Properties
Our main concern in this work is to show how higher shell admixtures affect
the spectrum of a Q.Q interaction. We first review how, in the valence space,
the familiar SU(3) result for the energy spectrum can be obtained using a
coordinate space Q.Q interaction rather than the Elliott one which is symmetric
in r and p. We then reemphasize that the Elliott spectrum goes as L(L+1) where
L is the orbital angular momentum. While in many cases this is compatible with
the rotational formula which involves I(I+1), where I is the total angular
momentum, there are cases, e.g. odd-odd nuclei, where there is disagreement.
Finally, we consider higher shell admixtures and devise a scheme so as to
obtain results, with the Q.Q interaction, which converge as the model spaces
are increased. We consider not only ground state rotational bands but also
those that involve intruder states.Comment: 13 pages, Revtex, to appear in Annals of Physic
Precision atomic gravimeter based on Bragg diffraction
We present a precision gravimeter based on coherent Bragg diffraction of
freely falling cold atoms. Traditionally, atomic gravimeters have used
stimulated Raman transitions to separate clouds in momentum space by driving
transitions between two internal atomic states. Bragg interferometers utilize
only a single internal state, and can therefore be less susceptible to
environmental perturbations. Here we show that atoms extracted from a
magneto-optical trap using an accelerating optical lattice are a suitable
source for a Bragg atom interferometer, allowing efficient beamsplitting and
subsequent separation of momentum states for detection. Despite the inherently
multi-state nature of atom diffraction, we are able to build a Mach-Zehnder
interferometer using Bragg scattering which achieves a sensitivity to the
gravitational acceleration of with an
integration time of 1000s. The device can also be converted to a gravity
gradiometer by a simple modification of the light pulse sequence.Comment: 13 pages, 11 figure
Cluster Transformation Coefficients for Structure and Dynamics Calculations in n-Particle Systems: Atoms, Nuclei, and Quarks
The structure and dynamics of an n-particle system are described with coupled
nonlinear Heisenberg's commutator equations where the nonlinear terms are
generated by the two-body interaction that excites the reference vacuum via
particle-particle and particle-hole excitations. Nonperturbative solutions of
the system are obtained with the use of dynamic linearization approximation and
cluster transformation coefficients. The dynamic linearization approximation
converts the commutator chain into an eigenvalue problem. The cluster
coefficients factorize the matrix elements of the (n)-particles or
particle-hole systems in terms of the matrix elements of the (n-1)-systems
coupled to a particle-particle, particle-hole, and hole-hole boson. Group
properties of the particle-particle, particle-hole, and hole-hole permutation
groups simplify the calculation of these coefficients. The particle-particle
vacuum-excitations generate superconductive diagrams in the dynamics of
3-quarks systems. Applications of the model to fermionic and bosonic systems
are discussed.Comment: 13 pages, 5 figures, Wigner Proceedings for Conference Wigner
Centenial Pecs, July 8-12, 200
Testing Newtonian Gravity with AAOmega: Mass-to-Light Profiles of Four Globular Clusters
Testing Newtonian gravity in the weak-acceleration regime is vital to our
understanding of the nature of the gravitational interaction. It has recently
been claimed that the velocity dispersion profiles of several globular clusters
flatten out at large radii, reminiscent of galaxy rotation curves, even though
globular clusters are thought to contain little or no dark matter. We
investigate this claim, using AAOmega observations of four globular clusters,
namely M22, M30, M53 and M68. M30, one such cluster that has had this claim
made for its velocity dispersion, was included for comparison with previous
studies. We find no statistically significant flattening of the velocity
dispersion at large radii for any of our target clusters and therefore we infer
the observed dynamics do not require that globular clusters are dark matter
dominated, or a modification of gravity. Furthermore, by applying a simple
dynamical model we determine the radial mass-to-light profiles for each
cluster. The isothermal rotations of each cluster are also measured, with M22
exhibiting clear rotation, M68 possible rotation and M30 and M53 lacking any
rotation, within the uncertainties.Comment: 7 pages, 4 figures and two tables. Accepted by MNRA
Sutureless prepuceplasty with wound healing by second intention: An alternative surgical approach in children's phimosis treatment
Abstract Background A new technique for the treatment of children's phimosis is presented that minimizes the repairing time, the postoperative complications and maintains the physical foreskin appearance intact. Methods Eightyseven children with phimosis were treated with this new developed technique, between 2003 and 2005. Sutureless prepuceplasty creates a permanent surgical extension of the close prepuce. Stretching and retraction of phimotic foreskin reveals a tight prepuce ring that is cutting in its dorsal surface longitudinally. Rarely triple symmetric incisions in the preputial outlet are necessary. The foreskin is loose and moves absolutely free in bilateral courses. The wounds are healing by second intention. Antisepsis, steroids and Elicina cream, (which contains allantoin, collagen, elastin, glycolic acid and vitamins A, D, and E) should apply daily, for twenty to thirty days. Results The foreskin is moving in centripetal or efferent courses absolutely loosely, painlessly and bloodlessly. The mean time of follow-up was 27 months (one to four years). No complications were observed. Conclusion Sutureless prepuceplasty may present an acceptable alternative in children's phimosis reconstruction.</p
Generating entangled superpositions of macroscopically distinguishable states within a parametric oscillator
We suggest a variant of the recently proposed experiment for the generation
of a new kind of Schroedinger-cat states, using two coupled parametric
down-converter nonlinear crystals [F. De Martini, Phys. Rev. Lett. 81, 2842
(1998)]. We study the parametric oscillator case and find that an entangled
Schroedinger-cat type state of two cavities, whose mirrors are placed along the
output beams of the nonlinear crystals, can be realized under suitable
conditions.Comment: RevTeX 17 pages, 9 eps files for 7 figures. Submitted to Physical
Review
An unfolding signifier: London's Baltic Exchange in Tallinn
In the summer of 2007 an unusual cargo arrived at Muuga and Paldiski harbors outside Tallinn. It consisted of nearly 50 containers holding over 1,000 tons of building material ranging from marble columns, staircases and fireplaces, to sculpted allegorical figures, wooden paneling and old-fashioned telephone booths. They were once part of the Baltic Exchange in the City of London. Soon they will become facets of the landscape of Tallinn. The following article charts this remarkable story and deploys this fragmented monument to analyze three issues relating to the Estonian capital: the relocation of the âBronze Soldierâ, the demolition of the Sakala Culture Center, and Tallinnâs future role as European Cultural Capital in 2011
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