520 research outputs found
Formal comparison of SUSY in the nuclear U(6/2) model and in quantum field theory
A nuclear physics example of the U(6/2) supersymmetry group is considered. It
is shown that this group contains a supersymmetric subgroup with a structure
similar to the SUSY model of the quantum field theory (QFT). A comparison of
two models help to clarify the relation between the supersymmetry schemes of
QFT and of nuclear physics. Using this similarity a relation between the
numbers of the bosonic and fermionic states similar to the fundamental relation
in QFT is obtained. For those supermultiplets with at least two fermions the
number of the bosonic and fermionic states are equal as in QFT.Comment: 11 pages and one eps-figure. Phys.Rev.C (1999) in pres
A standardised method for measuring in situ denitrification in shallow aquifers: numerical validation and measurements in riparian wetlands
A tracer test to examine in situ denitrification in shallow groundwater by a piezometer with a packer system used bromide as a tracer of dilution and acetylene (10%) to block the denitrification process at the nitrous oxide stage. During the test, dissolved oxygen, nitrate (NO3-), bromide (Br-), nitrous oxide (N2O) and dissolved organic carbon (DOC) were measured. To calibrate the experimental method, comparison with numerical simulations of the groundwater transfer were carried out, taking into account the environmental characteristics. The method was tested by measurements undertaken in different environmental conditions (geology, land use and hydrology) in two riparian wetlands. Denitrification rates measured by this method ranged from 5.7 10-6 g N-NO3-L-1 h-1 to 1.97 10-3 g N-NO3-L-1 h-1 The method is applicable in shallow aquifers with a permeability from 10-2 to 10-4m s-1
Nitrogen dynamics in the shallow groundwater of a riparian wetland zone of the Garonne, SW France: nitrate inputs, bacterial densities, organic matter supply and denitrification measurements
This study highlights the role of interactions between surface and sub-surface water of the riparian zone of a large river (the Garonne, SW
France). Information is given about the role of surface water in supplying Dissolved Organic Carbon (DOC ) to the riparian zone for nitrate
removal processes. The densities of bacteria (up to 3.3106 cell m L-1) in groundwater are strongly conditioned by the water moving during
flood events. Total bacterial densities in groundwater were related to surface water bacterial densities. In sediment, total bacteria are attached
mainly to fine particles (90 % in the fraction < 1 mm). Spatial variations in organic carbon and nitrate content in groundwater at the site
studied are correlated with exchanges between the groundwater and the river, from the upstream to the downstream part of the meander. Total
bacterial densities, nitrate and decressing organic carbon concentrations follow the same pattern. These results suggest that, in this kind of
riparian wetland, nitrate from alluvial groundwater influenced by agricultural practices may be denitrified by bacteria in the presence of
organic carbon from river surface water
Journey to the Center of the Cookie Ecosystem: Unraveling Actors' Roles and Relationships
Web pages have been steadily increasing in complexity over time, including code snippets from several distinct origins and organizations. While this may be a known phenomenon, its implications on the panorama of cookie tracking received little attention until now. Our study focuses on filling this gap, through the analysis of crawl results that are both large-scale and fine-grained, encompassing the whole set of events that lead to the creation and sharing of around 138 million cookies from crawling more than 6 million webpages. Our analysis lets us paint a highly detailed picture of the cookie ecosystem, discovering an intricate network of connections between players that reciprocally exchange information and include each other's content in web pages whose owners may not even be aware. We discover that, in most webpages, tracking cookies are set and shared by organizations at the end of complex chains that involve several middlemen. We also study the impact of cookie ghostwriting, i.e., a common practice where an entity creates cookies in the name of another party, or the webpage. We attribute and define a set of roles in the cookie ecosystem, related to cookie creation and sharing. We see that organizations can and do follow different patterns, including behaviors that previous studies could not uncover: for example, many cookie ghostwriters send cookies they create to themselves, which makes them able to perform cross-site tracking even for users that deleted third-party cookies in their browsers. While some organizations concentrate the flow of information on themselves, others behave as dispatchers, allowing other organizations to perform tracking on the pages that include their content
Boson-fermion mapping and dynamical supersymmetry in fermion models
We show that a dynamical supersymmetry can appear in a purely fermionic
system. This ``supersymmetry without bosons" is constructed by application of a
recently introduced boson-fermion Dyson mapping from a fermion space to a space
comprised of collective bosons and ideal fermions. In some algebraic fermion
models of nuclear structure, particular Hamiltonians may lead to collective
spectra of even and odd nuclei that can be unified using the dynamical
supersymmetry concept with Pauli correlations exactly taken into account.Comment: 20 pages. Revtex. One PostScript figure available on request from P
Critical test of multi-{\it j} supersymmetries from magnetic moment measurements
Magnetic moment measurements in odd nuclei directly probe the distribution of
fermion states and hence provide one of the most critical tests for multi-
supersymmetries in collective nuclei. Due to complexity of calculations and
lack of data, such tests have not been performed in the past. Using the
Mathematica software, we derive analytic expressions for magnetic moments in
the limit of the supersymmetry and
compare the results with recent measurements in Pt.Comment: 10 pages with 1 figur
Proton drip-line nuclei in relativistic mean-field theory
The position of the two-proton drip line has been calculated for even-even
nuclei with in the framework of the relativistic mean-field
(RMF) theory. The current model uses the NL3 effective interaction in the
mean-field Lagrangian and describes pairing correlations in the
Bardeen-Cooper-Schrieffer (BCS) formalism. The predictions of the RMF theory
are compared with those of the Hartree-Fock+BCS approach (with effective force
Skyrme SIII) and the finite-range droplet model (FRDM) and with the available
experimental information.Comment: 18 pages, RevTeX, 2 p.s figures, to appear in Phys. Rev.
Carbon Isotopes Near Drip Lines in the Relativistic Mean-Field Theory
We have investigated the ground-state properties of carbon isotopes in the
framework of the relativistic mean-field (RMF) theory. RMF calculations have
been performed with the non-linear scalar self-coupling of the meson
using an axially symmetric deformed configuration. We have also introduced the
vector self-coupling of the meson for the deformed mean-field
calculations. The results show that the RMF predictions on radii and
deformations are in good agreement with the available experimental data. It is
shown that several carbon isotopes possess a highly deformed shape akin to a
superdeformation. The single-particle structure of nuclei away from the
stability line has been discussed with a view to understand the properties near
the neutron drip line. Predictions of properties of carbon isotopes away from
the stability line are made.Comment: Revtex, 29 pages, 11 postscript figures include
Beta decay and shape isomerism in 74Kr
We study the properties of Kr, and particularly the Gamow Teller
strength distribution, using a deformed selfconsistent HF+RPA method with
Skyrme type interactions. Results are presented for two density-dependent
effective two-body interactions, including the dependence on deformation of the
HF energy that exhibits two minima at close energies and distant deformations,
one prolate and one oblate. We study the role of deformation, residual
interaction, pairing and RPA correlations on the Gamow Teller strength
distribution. Results on moments of inertia and gyromagnetic factors, as well
as on and transitions are also presented.Comment: 20 pages, RevTeX. 12 PS figures. To appear in Nucl. Phys.
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