308 research outputs found
Field Purification in the intensity-dependent Jaynes-Cummings model
We have found that, in the intensity-dependent Jaynes-Cummings model, a field
initially prepared in a statistical mixture of two coherent states,
and , evolves toward a pure state. We have also shown that an
even-coherent state turns periodically a into rotated odd-coherent state during
the evolution.Comment: 14 pages, RevTex, 3 figures, accepted for publication in Physics
Letters
Profile and reproductive roles of seminal plasma melatonin of boar ejaculates used in artificial insemination programs
Melatonin (MLT) is present in seminal plasma (SP) of mammalian species, including pigs, and it is credited with antioxidant properties. This study aims to identify the sources of variation and the role of boar SP MLT on sperm quality and functionality and in vivo fertilizing ability of liquid-stored semen doses used in AI programs. The SP MLT was measured using an ELISA kit in a total of 219 ejaculates collected from 76 boars, and reproductive records of 5,318 AI sows were recorded. Sperm quality was assessed according to motility (computer-aided sperm analysis) and viability (cytometry evaluation). Sperm functionality was assessed according to the cytometric determination of intracellular H2O2 generation, total and mitochondrial O2- production, and lipid peroxidation in liquid AI semen samples stored at 17°C over 144 h. The concentration of SP MLT differed among seasons (P < 0.01) and day length periods (P < 0.001) of the year, demonstrating that the ejaculates collected during the increasing day length period (9.80 ± 1.38 pg/mL, range: 2.75–21.94) had lower SP MLT concentrations than those collected during the decreasing day length period (16.32 ± 1.67 pg/mL, range: 5.02–35.61). The SP MLT also differed (P < 0.001) among boars, among ejaculates within boar, and among portions within the ejaculate, demonstrating that SP from the first 10 mL of sperm-rich ejaculate fraction (SRF) exhibited lower MLT concentrations than post-SRF. The SP MLT was negatively related (P < 0.001) to mitochondrial O2- production in viable sperm. The SP MLT did not differ among AI boars (n = 14) hierarchically grouped according to high and low fertility outcomes. In conclusion, SP MLT concentration in AI boars varies depending on the season of ejaculate collection and differs among boars, ejaculates within boar, and portions within ejaculate. The SP MLT may act at the mitochondrial level of sperm by reducing the generation of O2-. However, this antioxidant role of SP MLT was not reflected in sperm quality or in vivo fertility outcomes of AI semen doses
Coulomb and nuclear breakup effects in the single neutron removal reaction 197Au(17C,16C gamma)X
We analyze the recently obtained new data on the partial cross sections and
parallel momentum distributions for transitions to ground as well as excited
states of the 16C core, in the one-neutron removal reaction 197Au(17C,16C
gamma)X at the beam energy of 61 MeV/nucleon. The Coulomb and nuclear breakup
components of the one-neutron removal cross sections have been calculated
within a finite range distorted wave Born approximation theory and an eikonal
model, respectively. The nuclear contributions dominate the partial cross
sections for the core excited states. By adding the nuclear and Coulomb cross
sections together, a reasonable agreement is obtained with the data for these
states. The shapes of the experimental parallel momentum distributions of the
core states are described well by the theory.Comment: Revtex format, two figures included, to appear in Phys. Rev. C.
(Rapid communications
Uncorrelated scattering approximation for the scattering and break-up of weakly bound nuclei on heavy targets
The scattering of a weakly bound (halo) projectile nucleus by a heavy target
nucleus is investigated. A new approach, called the Uncorrelated Scattering
Approximation, is proposed. The main approximation involved is to neglect the
correlation between the fragments of the projectile in the region where the
interaction with the target is important. The formalism makes use of
hyper-spherical harmonics, Raynal-Revay coefficients and momentum-localized
wave functions to expand projectile channel wave functions in terms of products
of the channel wave function of the individual fragments. Within this approach,
the kinetic energy and angular momentum of each fragment is conserved during
the scattering process. The elastic, inelastic and break-up S-matrices are
obtained as an analytic combination involving the bound wave function of the
projectile and the product of the S-matrices of the fragments. The approach is
applied to describe the scattering of deuteron on Ni at several
energies. The results are compared with experimental data and
continuum-discretized coupled-channels calculations.Comment: 34 pages, 5 figures, accepted for publication in Nucl. Phys.
Core excitation in Coulomb breakup reactions
Within the pure Coulomb breakup mechanism, we investigate the one-neutron
removal reaction of the type A(a,b)X with Be and C
projectiles on a heavy target nucleus Pb at the beam energy of 60
MeV/nucleon. Our intention is to examine the prospective of using these
reactions to study the structure of neutron rich nuclei. Integrated partial
cross sections and momentum distributions for the ground as well as excited
bound states of core nuclei are calculated within the finite range distorted
wave Born approximation as well as within the adiabatic model of the Coulomb
breakup. Our results are compared with those obtained in the studies of the
reactions on a light target where the breakup proceeds via the pure nuclear
mechanism. We find that the transitions to excited states of the core are quite
weak in the Coulomb dominated process as compared to the pure nuclear breakup.Comment: Revtex format, five postscript figures included, to appear in Phys.
Rev.
From nonwetting to prewetting: the asymptotic behavior of 4He drops on alkali substrates
We investigate the spreading of 4He droplets on alkali surfaces at zero
temperature, within the frame of Finite Range Density Functional theory. The
equilibrium configurations of several 4He_N clusters and their asymptotic trend
with increasing particle number N, which can be traced to the wetting behavior
of the quantum fluid, are examined for nanoscopic droplets. We discuss the size
effects, inferring that the asymptotic properties of large droplets correspond
to those of the prewetting film
Elastic scattering and breakup of 17^F at 10 MeV/nucleon
Angular distributions of fluorine and oxygen produced from 170 MeV 17^F
incident on 208^Pb were measured. The elastic scattering data are in good
agreement with optical model calculations using a double-folding potential and
parameters similar to those obtained from 16^O+208^Pb. A large yield of oxygen
was observed near \theta_lab=36 deg. It is reproduced fairly well by a
calculation of the (17^F,16^O) breakup, which is dominated by one-proton
stripping reactions. The discrepancy between our previous coincidence
measurement and theoretical predictions was resolved by including core
absorption in the present calculation.Comment: 9 pages, 5 figure
Energetics and Possible Formation and Decay Mechanisms of Vortices in Helium Nanodroplets
The energy and angular momentum of both straight and curved vortex states of
a helium nanodroplet are examined as a function of droplet size. For droplets
in the size range of many experiments, it is found that during the pickup of
heavy solutes, a significant fraction of events deposit sufficient energy and
angular momentum to form a straight vortex line. Curved vortex lines exist down
to nearly zero angular momentum and energy, and thus could in principle form in
almost any collision. Further, the coalescence of smaller droplets during the
cooling by expansion could also deposit sufficient angular momentum to form
vortex lines. Despite their high energy, most vortices are predicted to be
stable at the final temperature (0.38 K) of helium nanodroplets due to lack of
decay channels that conserve both energy and angular momentum.Comment: 10 pages, 8 figures, RevTex 4, submitted to Phys. Rev.
Dynamics of liquid He-4 in confined geometries from Time-Dependent Density Functional calculations
We present numerical results obtained from Time-Dependent Density Functional
calculations of the dynamics of liquid He-4 in different environments
characterized by geometrical confinement. The time-dependent density profile
and velocity field of He-4 are obtained by means of direct numerical
integration of the non-linear Schrodinger equation associated with a
phenomenological energy functional which describes accurately both the static
and dynamic properties of bulk liquid He-4. Our implementation allows for a
general solution in 3-D (i.e. no symmetries are assumed in order to simplify
the calculations). We apply our method to study the real-time dynamics of pure
and alkali-doped clusters, of a monolayer film on a weakly attractive surface
and a nano-droplet spreading on a solid surface.Comment: q 1 tex file + 9 Ps figure
Neutrino Masses, Mixing and New Physics Effects
We introduce a parametrization of the effects of radiative corrections from
new physics on the charged lepton and neutrino mass matrices, studying how
several relevant quantities describing the pattern of neutrino masses and
mixing are affected by these corrections. We find that the ratio omega = sin
theta / tan theta_atm is remarkably stable, even when relatively large
corrections are added to the original mass matrices. It is also found that if
the lightest neutrino has a mass around 0.3 eV, the pattern of masses and
mixings is considerably more stable under perturbations than for a lighter or
heavier spectrum. We explore the consequences of perturbations on some flavor
relations given in the literature. In addition, for a quasi-degenerate neutrino
spectrum it is shown that: (i) starting from a bi-maximal mixing scenario, the
corrections to the mass matrices keep tan theta_atm very close to unity while
they can lower tan theta_sol to its measured value; (ii) beginning from a
scenario with a vanishing Dirac phase, corrections can induce a Dirac phase
large enough to yield CP violation observable in neutrino oscillations.Comment: 14 pages, 21 figures. Uses RevTeX4. Added several comments and
references. Final version to appear in PR
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