3,863 research outputs found
The Spectral Function for Finite Nuclei in the Local Density Approximation
The spectral function for finite nuclei is computed within the framework of
the Local Density Approximation, starting from nuclear matter spectral
functions obtained with a realistic nucleon-nucleon interaction. The spectral
function is decomposed into a single-particle part and a ''correlated'' part;
the latter is treated in the local density approximation.
As an application momentum distributions, quasi-particle strengths and
overlap functions for valence hole states, and the light-cone momentum
distribution in finite nuclei are computed.Comment: 21 pages + 9 figures available upon request, RevTex, preprint
KVI-108
Neoclassical Theory of Elementary Charges with Spin of 1/2
We advance here our neoclassical theory of elementary charges by integrating
into it the concept of spin of 1/2. The developed spinorial version of our
theory has many important features identical to those of the Dirac theory such
as the gyromagnetic ratio, expressions for currents including the spin current,
and antimatter states. In our theory the concepts of charge and anticharge
relate naturally to their "spin" in its rest frame in two opposite directions.
An important difference with the Dirac theory is that both the charge and
anticharge energies are positive whereas their frequencies have opposite signs
Orbital M1 versus E2 strength in deformed nuclei: A new energy weighted sum rule
Within the unified model of Bohr and Mottelson we derive the following linear
energy weighted sum rule for low energy orbital 1 excitations in even-even
deformed nuclei S_{\rm LE}^{\rm lew} (M_1^{\rm orb}) \cong (6/5) \epsilon
(B(E2; 0^+_1 \rightarrow 2_1^+ K=0)/Z e^2^2) \mu^2_N with B(E2) the E2
strength for the transition from the ground state to the first excited state in
the ground state rotational band, the charge r.m.s. radius squared and
the binding energy per nucleon in the nuclear ground state. It is
shown that this energy weighted sum rule is in good agreement with available
experimental data. The sum rule is derived using a simple ansatz for the
intrinsic ground state wave function that predicts also high energy 1
strength at 2 carrying 50\% of the total moment of the
orbital M1 operator.Comment: REVTEX (3.0), 9 pages, RU924
Mechanisms for spin suppression and orbital enhancement in M1 transitions: Critical assessment
9 págs.; 3 figs.; 3 tabs.We discuss different nuclear structure properties that may lead to spin suppression in magnetic dipole excitations (as well as in Gamow-Teller transitions). We especially compare the triaxial and the axial asymptotic deformation limits and show that the summed B(M1) strength can be quite different in the two cases. A connection between triaxial deformation and spin suppression is established. It is known, however, that modern Hartree-Fock calculations yield axially symmetric solutions for several nuclei which were previously thought to be triaxial. We show that taking into account the effects of higher shells can lead to an enhanced orbital contribution to M1 excitations without affecting ground-state magnetic moments. © 1989 The American Physical Society.This work was supported by a NATO Collaborative
Research Grant (0702/87) and by the Department of Energy
DE-FG05-86ER40299. One of us (E.M.G.) is also
indebted to DGICYT (Spain) for partial financial support
under Contract No. PB8710311.Peer Reviewe
Impact of ConcanavalinA affinity in the intracellular fate of Protein Corona on Glucosamine Au nanoparticles
Biological fate and toxicity of nanoparticles (NPs) are connected to the interaction between NPs and the protein corona (PC) spontaneously forming around NPs in biological matrixes. PC is a dynamic entity that confers biological identity to NPs. In this work, fluorescence cross-correlation spectroscopy (FCCS) is used to study the impact of specific interactions between the NP surface and proteins on the intracellular fate of PC. The stability of the PC formed around glucosamide-functionalized Au-NPs from ConcanavalinA (ConA) or Bovine Serum Albumin (BSA) is characterized by FCCS. The NPs show higher affinity for ConA and competitive assays show that ConA easily exchanges BSA. A549 cells are exposed to glucosamide-functionalized Au-NPs with preformed ConA and BSA PCs. Intracellularly the frequency of cross-correlation for Au NPs with ConA PC remains constant to a 70% value until 24 h while for BSA it decreases to a 15% during the same period. FCCS measurements in several locations in the cell point out a different level of aggregation for the NPs with either ConA or BSA PCs. Our results show that the affinity of NPs functionalized with a ligand with affinity for a specific protein in bulk is retained intracellularly influencing NP fate and translocation
Properties of Nucleon Resonances by means of a Genetic Algorithm
We present an optimization scheme that employs a Genetic Algorithm (GA) to
determine the properties of low-lying nucleon excitations within a realistic
photo-pion production model based upon an effective Lagrangian. We show that
with this modern optimization technique it is possible to reliably assess the
parameters of the resonances and the associated error bars as well as to
identify weaknesses in the models. To illustrate the problems the optimization
process may encounter, we provide results obtained for the nucleon resonances
(1230) and (1700). The former can be easily isolated and thus
has been studied in depth, while the latter is not as well known
experimentally.Comment: 12 pages, 10 figures, 3 tables. Minor correction
Lattice dynamics and phonon softening in Ni-Mn-Al Heusler alloys
Inelastic and elastic neutron scattering have been used to study a single
crystal of the NiMnAl Heusler alloy over a broad
temperature range. The paper reports the first experimental determination of
the low-lying phonon dispersion curves for this alloy system. We find that the
frequencies of the TA modes are relatively low. This branch exhibits an
anomaly (dip) at a wave number , which softens with
decreasing temperature. Associated with this anomalous dip at , an
elastic central peak scattering is also present. We have also observed
satellites due to the magnetic ordering.Comment: 6 pages, 6 figures. Accepted for publication in the Physical Review
Ginzburg-Landau theory of the zig-zag transition in quasi-one-dimensional classical Wigner crystals
We present a mean-field description of the zig-zag phase transition of a
quasi-one-dimensional system of strongly interacting particles, with
interaction potential , that are confined by a power-law
potential (). The parameters of the resulting one-dimensional
Ginzburg-Landau theory are determined analytically for different values of
and . Close to the transition point for the zig-zag phase
transition, the scaling behavior of the order parameter is determined. For
the zig-zag transition from a single to a double chain is of second
order, while for the one chain configuration is always unstable and
for the one chain ordered state becomes unstable at a certain
critical density resulting in jumps of single particles out of the chain.Comment: 12 pages, 11 figure
Quantum interference structures in trapped ion dynamics beyond the Lamb-Dicke and rotating wave approximations
We apply wave packet methods to study an ion-trap system in the strong
excitation regime imposing neither the rotating wave nor the Lamb-Dicke
approximations. By this approach we show the existence of states with
restricted phase space evolution, as a genuine consequence of quantum
interference between wave packet fractions. A particular instance of such a
state oscillates between maximal entanglement and pure disentanglement between
the constitute subsystems. The characteristic crossover time is very rapid
making them suitable for state preparations of EPR or Schrodinger cat states.
Over longer time periods the dynamics of these states exhibits collapse-revival
patterns with well resolved fractional revivals in autocorrelation, inversion
and entanglement.Comment: 11 pages, 5 figures. Replaced with revised version. Phys. Rev. A 77,
053808 (2008
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