2,203 research outputs found
Butterfly Hysteresis and Slow Relaxation of the Magnetization in (Et4N)3Fe2F9: Manifestations of a Single-Molecule Magnet
(Et4N)3Fe2F9 exhibits a butterfly--shaped hysteresis below 5 K when the
magnetic field is parallel to the threefold axis, in accordance with a very
slow magnetization relaxation in the timescale of minutes. This is attributed
to an energy barrier Delta=2.40 K resulting from the S=5 dimer ground state of
[Fe2F9]^{3-} and a negative axial anisotropy. The relaxation partly occurs via
thermally assisted quantum tunneling. These features of a single-molecule
magnet are observable at temperatures comparable to the barrier height, due to
an extremely inefficient energy exchange between the spin system and the
phonons. The butterfly shape of the hysteresis arises from a phonon avalanche
effect.Comment: 18 pages, 5 eps figures, latex (elsart
On the combined effects of surface tension force calculation and interface advection on spurious currents within Volume of Fluid and Level Set frameworks
This paper deals with the comparison of Eulerian methods to take into account the capillary contribution in the vicinity of a fluid–fluid interface. Eulerian methods are well- known to produce additional vorticity close to the interface that leads to non-physical spurious currents. Numerical equilibrium between pressure gradient and capillary force for the static bubble test case within a VOF framework has been reached in [35] with the height-function technique [14,35]. However, once the bubble is translated in a uniform flow, spurious currents are maintained by slight errors induced by translation schemes. In this work, two main points are investigated: the ability of Volume of Fluid and Level Set methods to accurately calculate the curvature, and the magnitude of spurious currents due to errors in the calculation of the curvature after advection in both translating and rotating flows. The spurious currents source term is expressed from the vorticity equation and used to discuss and compare the methods. Simulations of gas–liquid Taylor flow at low capillary number show that the flow structure and the bubble velocity can be significantly affected by spurious currents
Generative Roles: Assessing Sustained Involvement in Generativity
Abstract Generative roles refer to observable, behavioral community positions that embody aspects of teaching and nurturing that are central to the concept of generativity. Two studies are presented that describe generative roles in a community sample and provide psychometric data for a short index of generative roles. The first study also provides reliability and validity data from a second informant. The second study examines generative roles at different stages of adolescence and adulthood. Participants were asked 8 yes/no questions about a variety of community roles. The validity of the GRI was supported by significant correlations with the Loyola Generativity Scale, a widely used measure of generative concern (r=.33), and measures of related constructs. The correlations were similar across age categories. The Generative Roles Index has good psychometric qualities and complements existing measures of generativity by providing behavioral, observable data on roles
Quantum tunneling in a three dimensional network of exchange coupled single-molecule magnets
A Mn4 single-molecule magnet (SMM) is used to show that quantum tunneling of
magnetization (QTM) is not suppressed by moderate three dimensional exchange
coupling between molecules. Instead, it leads to an exchange bias of the
quantum resonances which allows precise measurements of the effective exchange
coupling that is mainly due to weak intermolecular hydrogen bounds. The
magnetization versus applied field was recorded on single crystals of [Mn4]2
using an array of micro-SQUIDs. The step fine structure was studied via minor
hysteresis loops.Comment: 4 pages, 4 figure
Phase structure of SU(3) gauge theory with two flavors of symmetric-representation fermions
We have performed numerical simulations of SU(3) gauge theory coupled to Nf=2
flavors of symmetric representation fermions. The fermions are discretized with
the tadpole-improved clover action. Our simulations are done on lattices of
length L=6, 8, and 12. In all simulation volumes we observe a crossover from a
strongly coupled confined phase to a weak coupling deconfined phase.
Degeneracies in screening masses, plus the behavior of the pseudoscalar decay
constant, indicate that the deconfined phase is also a phase in which chiral
symmetry is restored. The movement of the confinement transition as the volume
is changed is consistent with avoidance of the basin of attraction of an
infrared fixed point of the massless theory.Comment: 12 pages, 11 figure
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