18,913 research outputs found
Rotational properties of nuclei around No investigated using a spectroscopic-quality Skyrme energy density functional
Nuclei in the mass region represent the heaviest systems where
detailed spectroscopic information is experimentally available. Although
microscopic-macroscopic and self-consistent models have achieved great success
in describing the data in this mass region, a fully satisfying precise
theoretical description is still missing.
By using fine-tuned parametrizations of the energy density functionals, the
present work aims at an improved description of the single-particle properties
and rotational bands in the nobelium region. Such locally optimized
parameterizations may have better properties when extrapolating towards the
superheavy region.
Skyrme-Hartree-Fock-Bogolyubov and Lipkin-Nogami methods were used to
calculate the quasiparticle energies and rotational bands of nuclei in the
nobelium region. Starting from the most recent Skyrme parametrization, UNEDF1,
the spin-orbit coupling constants and pairing strengths have been tuned, so as
to achieve a better agreement with the excitation spectra and odd-even mass
differences in Cf and Bk.
The quasiparticle properties of Cf and Bk were very well
reproduced. At the same time, crucial deformed neutron and proton shell gaps
open up at and , respectively. Rotational bands in Fm, No, and
Rf isotopes, where experimental data are available, were also fairly well
described. To help future improvements towards a more precise description,
small deficiencies of the approach were carefully identified.
In the mass region, larger spin-orbit strengths than those from
global adjustments lead to improved agreement with data. Puzzling effects of
particle-number restoration on the calculated moment of inertia, at odds with
the experimental behaviour, require further scrutiny.Comment: 9 pages, 10 figures; to be published in Physical Review
Gender and Job Performance: Evidence from Wall Street
We study the relation between gender and job performance among brokerage firm equity analysts. Women's representation in analyst positions drops from 16% in 1995 to 13% in 2005. We find women cover roughly 9 stocks on average compared to 10 for men. Women's earnings estimates tend to be less accurate. After controlling for forecast characteristics, the difference in accuracy is roughly equivalent to four years of experience. Despite reduced coverage and lower forecast accuracy, we find women are significantly more likely to be designated as All-Stars, which suggests they outperform at other aspects of the job such as client service.
Imprinting Light Phase on Matter Wave Gratings in Superradiance Scattering
Superradiance scattering from a Bose-Einstein condensate is studied with a
two-frequency pumping beam. We demonstrate the possibility of fully tuning the
backward mode population as a function of the locked initial relative phase
between the two frequency components of the pumping beam. This result comes
from an imprinting of this initial relative phase on two matter wave gratings,
formed by the forward mode or backward mode condensate plus the condensate at
rest, so that cooperative scattering is affected. A numerical simulation using
a semiclassical model agrees with our observations.Comment: 6 pages, 11 figure
Design of Copolymeric Materials
We devise a method for designing materials that will have some desired
structural characteristics. We apply it to multiblock copolymers that have two
different types of monomers, A and B. We show how to determine what sequence of
A's and B's should be synthesised in order to give a particular structure and
morphology. %For example in a melt of such %polymers, one may wish to engineer
a body-centered %cubic structure. Using this method in conjunction with the
theory of microphase separation developed by Leibler, we show it is possible to
efficiently search for a desired morphology. The method is quite general and
can be extended to design isolated heteropolymers, such as proteins, with
desired structural characteristics. We show that by making certain
approximations to the exact algorithm, a method recently proposed by
Shakhnovich and Gutin is obtained. The problems with this method are discussed
and we propose an improved approximate algorithm that is computationally
efficient.Comment: 15 pages latex 2.09 and psfig, 1 postscript figure
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