5,583 research outputs found
Polarisation dependence of magnetic Bragg scattering in YMnO
The polarisation dependence of the intensity of elastic magnetic scattering
from \ymno\ single crystals has been measured at 25 K in magnetic fields
between 1 and 9 T. A significant polarisation dependence was observed in the
intensities of magnetic satellite reflections, propagation vector
\pv=0.5,0,0.25 measured with both the [100] and [010] axes parallel to the
common polarisation and applied field direction. The intensity asymmetries
observed in sets of orthorhombicly equivalent reflections show systematic
relationships which allow the phase relationship between different components
of their magnetic interaction vectors to be determined. They fix the
orientation relationships between the small and moments on the \mnfp\
and \mntp\ sub-lattices and lend support to the structure reported by Kim et
al. It was found that that which suggests
that there is a small modulation of the nuclear structure which has the same
wave-vector as the magnetic modulation leading to a small nuclear structure
factor for the satellite reflections. The differences observed indicate shifts in the atomic positions of order 0.005 \AA
Keck Spectroscopy of Two Young Globular Clusters in the Merger Remnant NGC 3921
Low-resolution UV-to-visual spectra of two candidate globular clusters in the
merger remnant NGC 3921 are presented. These two clusters of apparent magnitude
V = 22.2 (Mv = -12.5) lie at projected distances of ~5 kpc from the center and
move with halo-type radial velocities relative to the local galaxy background.
Their spectra show strong Balmer absorption lines indicative of main-sequence
turnoffs dominated by A-type stars. Comparisons with model-cluster spectra
computed by Bruzual & Charlot and others yield cluster ages in the range of
200-530 Myr, and metallicities about solar to within a factor of three. Given
their small half-light radii (Reff < 5 pc) and ages corresponding to ~100 core-
crossing times, these clusters are gravitationally bound and, hence, indeed
young globulars. Assuming that they had Chabrier-type initial mass functions,
their estimated current masses are 2.3(+-0.1)x10^6 Msun and 1.5(+-0.1)x10^6
Msun, respectively, or roughly half the mass of omegaCen. Since NGC 3921 itself
shows many signs of being a 0.7(+-0.3) Gyr old protoelliptical, these two young
globulars of roughly solar metallicity and their many counterparts observed
with the Hubble Space Telescope provide supporting evidence that, in the
process of forming elliptical-like remnants, major mergers of gas-rich disks
can also increase the number of metal-rich globular clusters. (Abridged)Comment: 22 pages, 6 figures, accepted for publication in AJ, July 200
Spectrum and decays of hadronic atoms
We describe the spectra and decays of pi pi and pi K atoms within a
non-relativistic effective field theory. The evaluations of the energy shifts
and widths are performed at next-to-leading order in isospin symmetry breaking.
The prediction for the lifetime of the pi K atom in its ground-state yields tau
= (3.7 \pm 0.4) * 10^{-15} sec.Comment: To appear in the proceedings of MESON 2004: 8th International
Workshop on Meson Production, Properties and Interaction, Cracow, Poland, 4-8
June 2004. 7 page
The Importance of Management Philosophy to the Success of Pay-for-Knowledge Systems: An Empirical Test
In recent years, pay-for-knowledge compensation systems have received serious attention from practitioners and organizational researchers. Some have hypothesized that the specific mechanics of pay-for-knowledge systems are critical to success while others have suggested that contextual factors determine whether or not these systems will be successful. Empirical research has not been very supportive of these hypotheses, however.
Another hypothesis is that management philosophy is important to the success of pay-for-knowledge systems. The purpose of this study is to test this hypothesis by addressing three questions: 1) Are the components that make up management philosophy related to the successes experienced by companies using pay-for-knowledge systems?, 2) When the components are used together, do they predict success reasonably well?, and 3) Can the components of the management philosophy be used together with what we already know about the specific mechanics and contextual factors to improve predictions of success?
The pay-for-knowledge literature focusing on determinants of success is reviewed, and related findings are summarized. The management philosophy literature is discussed, and the management philosophy construct is explicated.
Using a sample of 35 Personnel Directors of companies with pay-for-knowledge systems, components of the management philosophy construct are operationalized by focusing on its manifestations. Respondents\u27 perceptions of productivity, quality of output, employee attitudes and employee withdrawal behaviors are used as measures of success. The results show that manifestations of the management philosophy are often positively related to the success outcomes and that, when used together, some manifestations are reasonable predictors of the success outcomes.
The results also show that models using specific mechanics and contextual factors to predict success can be improved significantly by the addition of selected management philosophy manifestation measures.
Overall, the findings in this study suggest that the management philosophy communicated in day-to-day operations may be far more important than the philosophy communicated during the design and development of the pay-for-knowledge system. Implications of these findings for managers and directions for future research are discussed
Inter-molecular structure factors of macromolecules in solution: integral equation results
The inter-molecular structure of semidilute polymer solutions is studied
theoretically. The low density limit of a generalized Ornstein-Zernicke
integral equation approach to polymeric liquids is considered. Scaling laws for
the dilute-to-semidilute crossover of random phase (RPA) like structure are
derived for the inter-molecular structure factor on large distances when
inter-molecular excluded volume is incorporated at the microscopic level. This
leads to a non-linear equation for the excluded volume interaction parameter.
For macromolecular size-mass scaling exponents, , above a
spatial-dimension dependent value, , mean field like density scaling
is recovered, but for the density scaling becomes non-trivial in
agreement with field theoretic results and justifying phenomenological
extensions of RPA. The structure of the polymer mesh in semidilute solutions is
discussed in detail and comparisons with large scale Monte Carlo simulations
are added. Finally a new possibility to determine the correction to scaling
exponent is suggested.Comment: 11 pages, 5 figures; to be published in Phys. Rev. E (1999
The dynamical mass of the young cluster W3 in NGC 7252: Heavy-Weight globular cluster or ultra compact dwarf galaxy ?
We have determined the dynamical mass of the most luminous stellar cluster
known to date, i.e. object W3 in the merger remnant galaxy NGC 7252. The
dynamical mass is estimated from the velocity dispersion measured with the
high-resolution spectrograph UVES on VLT. Our result is the astonishingly high
velocity dispersion of sigma=45 +- 5 km/s. Combined with the large cluster size
R_eff=17.5 +-1.8 pc, this translates into a dynamical virial mass for W3 of 8
+- 2 x 10^7 Msun. This mass is in excellent agreement with the value 7.2 x 10^7
Msun we previously estimated from the cluster luminosity M_V=-16.2 by means of
stellar M/L ratios predicted by Simple Stellar Population models (with a
Salpeter IMF) and confirms the heavy-weight nature of this object. This results
points out that the NGC 7252-type of mergers are able to form stellar systems
with masses up to ~ 10^8 Msun. We find that W3, when evolved to ~ 10 Gyr, lies
far from the typical Milky Way globular clusters, but appears to be also
separated from omegaCen in the Milky Way and G1 in M31, the most massive old
stellar clusters of the Local Group, because it is too extended for a given
mass, and from dwarf elliptical galaxies because it is much more compact for
its mass. Instead the aged W3 is amazingly close to the compact objects named
ultracompact dwarf galaxies (UCDGs) found in the Fornax cluster (Hilker et al.
1999; Drinkwater et al. 2000), and to a miniature version of the compact
elliptical M32. These objects start populating a previously deserted region of
the fundamental plane.Comment: 8 pages, 3 figures, A&A in pres
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