579 research outputs found
True ternary fission of superheavy nuclei
We found that a true ternary fission with formation of a heavy third fragment
(a new type of radioactivity) is quite possible for superheavy nuclei due to
the strong shell effects leading to a three-body clusterization with the two
doubly magic tin-like cores. The simplest way to discover this phenomenon in
the decay of excited superheavy nuclei is a detection of two tin-like clusters
with appropriate kinematics in low-energy collisions of medium mass nuclei with
actinide targets. The three-body quasi-fission process could be even more
pronounced for giant nuclear systems formed in collisions of heavy actinide
nuclei. In this case a three-body clusterization might be proved experimentally
by detection of two coincident lead-like fragments in low-energy U+U
collisions.Comment: 4 pages, 7 figure
The Reasonableness of Argumentation from Expert Opinion in Medical Discussions: Institutional Safeguards for the Quality of Shared Decision Making
The ideal of shared decision making starts from the assumption that physicians and patients are able to take a joint decision as to what is the best treatment. However, since medical consultations are to be viewed as discussions between an expert and a layman, in practice it will often be the case that the patient has to rely on the physician’s expertise. In this article we examine the extent to which the Dutch laws, guidelines and professional conventions within the medical domain positively influence the quality of the process of shared decision making, even in cases where the physician makes use of an argument from expert opinion. To this end, we will chart some of the most important institutional safeguards for the quality of medical decisions and analyze how these safeguards relate to the critical questions associated with the argument scheme of argumentation from expert opinion
Microscopic Description of Nuclear Fission Dynamics
We discuss possible avenues to study fission dynamics starting from a
time-dependent mean-field approach. Previous attempts to study fission dynamics
using the time-dependent Hartree-Fock (TDHF) theory are analyzed. We argue that
different initial conditions may be needed to describe fission dynamics
depending on the specifics of the fission phenomenon and propose various
approaches towards this goal. In particular, we provide preliminary
calculations for studying fission following a heavy-ion reaction using TDHF
with a density contraint. Regarding prompt muon-induced fission, we also
suggest a new approach for combining the time-evolution of the muonic wave
function with a microscopic treatment of fission dynamics via TDHF
An evaporation-based model of thermal neutron induced ternary fission of plutonium
Ternary fission probabilities for thermal neutron induced fission of
plutonium are analyzed within the framework of an evaporation-based model where
the complexity of time-varying potentials, associated with the neck collapse,
are included in a simplistic fashion. If the nuclear temperature at scission
and the fission-neck-collapse time are assumed to be ~1.2 MeV and ~10^-22 s,
respectively, then calculated relative probabilities of ternary-fission
light-charged-particle emission follow the trends seen in the experimental
data. The ability of this model to reproduce ternary fission probabilities
spanning seven orders of magnitude for a wide range of light-particle charges
and masses implies that ternary fission is caused by the coupling of an
evaporation-like process with the rapid re-arrangement of the nuclear fluid
following scission.Comment: 25 pages, 12 figures, accepted for publication in IJMP
Constructing a Periodic Table of Arguments
The existing classifications of arguments are unsatisfying in a number of ways. This paper proposes an alternative in the form of a Periodic Table of Arguments. The newly developed table can be used as a systematic and comprehensive point of reference for the analysis, evaluation and production of argumentative discourse as well as for various kinds of empirical and computational research in the field of argumentation theory
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Evaluating the Use of Digital Creativity Support by Journalists in Newsrooms
This paper reports the evaluation of a new digital support tool designed to increase journalist creativity and productivity in newsrooms. After outlining the tool’s principles, interactive features and architecture, the paper reports the installation and use of the tool over 2 months by 12 journalists in the newsrooms of 3 newspapers. Results from this evaluation revealed that tool use was associated with published news articles rated as more novel but not more valuable than published articles written by the same journalists without the tool. However, tool use did not increase journalist productivity. The evaluation results were used to inform future changes to the digital creativity support tool
The minimal N=4 no-scale model from generalized dimensional reduction
We consider the generalized dimensional reduction of pure ungauged N=4, D=5
supergravity, where supersymmetry is spontaneously broken to N=2 or N=0 with
identically vanishing scalar potential. We explicitly construct the resulting
gauged D=4 theory coupled to a single vector multiplet, which provides the
minimal N=4 realization of a no-scale model. We discuss its relation with the
standard classification of N=4 gaugings, extensions to non-compact twists and
to higher dimensions, the N=2 theories obtained via consistent Z_2 orbifold
projections and prospects for further generalizations.Comment: 1+28 pages, no figures, JHEP3 LaTeX, published versio
Fission studies with 140 MeV -Particles
Binary fission induced by 140 MeV -particles has been measured for
Ag, La, Ho and Au targets. The measured
quantities are the total kinetic energies, fragment masses, and fission cross
sections. The results are compared with other data and systematics. A minimum
of the fission probability in the vicinity is observed.Comment: 4 figures, 2 table
Gauged N=4 supergravities
We present the gauged N=4 (half-maximal) supergravities in four and five
spacetime dimensions coupled to an arbitrary number of vector multiplets. The
gaugings are parameterized by a set of appropriately constrained constant
tensors, which transform covariantly under the global symmetry groups SL(2) x
SO(6,n) and SO(1,1) x SO(5,n), respectively. In terms of these tensors the
universal Lagrangian and the Killing Spinor equations are given. The known
gaugings, in particular those originating from flux compactifications, are
incorporated in the formulation, but also new classes of gaugings are found.
Finally, we present the embedding chain of the five dimensional into the four
dimensional into the three dimensional gaugings, thereby showing how the
deformation parameters organize under the respectively larger duality groups.Comment: 36 pages, v2: references added, comments added, v3: published
version, references added, typos corrected, v4: sign mistakes in footnote 4
and equation (2.13) correcte
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