295 research outputs found
Ability of new durum wheat pure lines to meet yield stability and quality requirements in low input and organic systems
Low-input production schemes adopted in organic or conventional farms require crop varieties that combine good product quality and high yield stability under non optimal environmental conditions (Gooding et al., 1999). These traits are not yet found among the durum wheat genotypes available in France. Consequently the cultivation of this crop is hardly successful in stockless organic farms in southern France, which are characterised by very low nitrogen resources. Some hopes emerged with the identification of new durum wheat pure lines with a high grain protein content in breeding experiments conducted near Montpellier in 2001 and 2002. The aim of the present work was to confirm and elucidate the origin of the enhanced protein performance of these new lines through a field experiment with nitrogen resources ranging from very low to sub-optimal levels
The nonrelativistic limit of Dirac-Fock codes: the role of Brillouin configurations
We solve a long standing problem with relativistic calculations done with the
widely used Multi-Configuration Dirac-Fock Method (MCDF). We show, using
Relativistic Many-Body Perturbation Theory (RMBPT), how even for relatively
high-, relaxation or correlation causes the non-relativistic limit of states
of different total angular momentum but identical orbital angular momentum to
have different energies. We show that only large scale calculations that
include all single excitations, even those obeying the Brillouin's theorem have
the correct limit. We reproduce very accurately recent high-precision
measurements in F-like Ar, and turn then into precise test of QED. We obtain
the correct non-relativistic limit not only for fine structure but also for
level energies and show that RMBPT calculations are not immune to this problem.Comment: AUgust 9th, 2004 Second version Nov. 18th, 200
Dielectronic Resonance Method for Measuring Isotope Shifts
Longstanding problems in the comparison of very accurate hyperfine-shift
measurements to theory were partly overcome by precise measurements on
few-electron highly-charged ions. Still the agreement between theory and
experiment is unsatisfactory. In this paper, we present a radically new way of
precisely measuring hyperfine shifts, and demonstrate its effectiveness in the
case of the hyperfine shift of and in
. It is based on the precise detection of dielectronic
resonances that occur in electron-ion recombination at very low energy. This
allows us to determine the hyperfine constant to around 0.6 meV accuracy which
is on the order of 10%
dftatom: A robust and general Schr\"odinger and Dirac solver for atomic structure calculations
A robust and general solver for the radial Schr\"odinger, Dirac, and
Kohn--Sham equations is presented. The formulation admits general potentials
and meshes: uniform, exponential, or other defined by nodal distribution and
derivative functions. For a given mesh type, convergence can be controlled
systematically by increasing the number of grid points. Radial integrations are
carried out using a combination of asymptotic forms, Runge-Kutta, and implicit
Adams methods. Eigenfunctions are determined by a combination of bisection and
perturbation methods for robustness and speed. An outward Poisson integration
is employed to increase accuracy in the core region, allowing absolute
accuracies of Hartree to be attained for total energies of heavy
atoms such as uranium. Detailed convergence studies are presented and
computational parameters are provided to achieve accuracies commonly required
in practice. Comparisons to analytic and current-benchmark density-functional
results for atomic number = 1--92 are presented, verifying and providing a
refinement to current benchmarks. An efficient, modular Fortran 95
implementation, \ttt{dftatom}, is provided as open source, including examples,
tests, and wrappers for interface to other languages; wherein particular
emphasis is placed on the independence (no global variables), reusability, and
generality of the individual routines.Comment: Submitted to Computer Physics Communication on August 27, 2012,
revised February 1, 201
Tensorial form and matrix elements of the relativistic nuclear recoil operator
Within the lowest-order relativistic approximation () and to
first order in , the tensorial form of the relativistic corrections of
the nuclear recoil Hamiltonian is derived, opening interesting perspectives for
calculating isotope shifts in the multiconfiguration Dirac-Hartree-Fock
framework. Their calculation is illustrated for selected Li-, B- and C-like
ions. The present work underlines the fact that the relativistic corrections to
the nuclear recoil are definitively necessary for getting reliable isotope
shift values.Comment: 22 pages, no figures, submitted to J. Phys.
Neanderthal selective hunting of reindeer? The case study of Abri du Maras (south-eastern France)
Fieldwork was supported by the Regional Office of Archaeology Rhône-Alpes, the French Ministry of Culture and Communication and the Ardèche Department through several scientific programs. M.G.Chacon, F. Rivals and E. Allué research are funded by ‘CERCA Programme/Generalitat de Catalunya’. Thanks to Jean-Jacques Hublin, Annabell Reiner and Steven Steinbrenner from the Max Planck Institute (MPI-EVA) for analytical support (isotope analysis). We are grateful to the two anonymous reviewers for their constructive remarks on this manuscript. The English manuscript was edited by L. Byrne, an official translator and native English speaker.Peer reviewedPostprin
Alternative medicines for AIDS in resource-poor settings: Insights from exploratory anthropological studies in Asia and Africa
The emergence of alternative medicines for AIDS in Asia and Africa was discussed at a satellite symposium and the parallel session on alternative and traditional treatments of the AIDSImpact meeting, held in Marseille, in July 2007. These medicines are heterogeneous, both in their presentation and in their geographic and cultural origin. The sessions focused on the role of these medications in selected resource poor settings in Africa and Asia now that access to anti-retroviral therapy is increasing. The aims of the sessions were to (1) identify the actors involved in the diffusion of these alternative medicines for HIV/AIDS, (2) explore uses and forms, and the way these medicines are given legitimacy, (3) reflect on underlying processes of globalisation and cultural differentiation, and (4) define priority questions for future research in this area. This article presents the insights generated at the meeting, illustrated with some findings from the case studies (Uganda, Senegal, Benin, Burkina Faso, China and Indonesia) that were presented. These case studies reveal the wide range of actors who are involved in the marketing and supply of alternative medicines. Regulatory mechanisms are weak. The efficacy claims of alternative medicines often reinforce a biomedical paradigm for HIV/AIDS, and fit with a healthy living ideology promoted by AIDS care programs and support groups. The AIDSImpact session concluded that more interdisciplinary research is needed on the experience of people living with HIV/AIDS with these alternative medicines, and on the ways in which these products interact (or not) with anti-retroviral therapy at pharmacological as well as psychosocial levels
Magnetic state of plutonium ion in metallic Pu and its compounds
By LDA+U method with spin-orbit coupling (LDA+U+SO) the magnetic state and
electronic structure have been investigated for plutonium in \delta and \alpha
phases and for Pu compounds: PuN, PuCoGa5, PuRh2, PuSi2, PuTe, and PuSb. For
metallic plutonium in both phases in agreement with experiment a nonmagnetic
ground state was found with Pu ions in f^6 configuration with zero values of
spin, orbital, and total moments. This result is determined by a strong
spin-orbit coupling in 5f shell that gives in LDA calculation a pronounced
splitting of 5f states on f^{5/2} and f^{7/2} subbands. A Fermi level is in a
pseudogap between them, so that f^{5/2} subshell is already nearly completely
filled with six electrons before Coulomb correlation effects were taken into
account. The competition between spin-orbit coupling and exchange (Hund)
interaction (favoring magnetic ground state) in 5f shell is so delicately
balanced, that a small increase (less than 15%) of exchange interaction
parameter value from J_H=0.48eV obtained in constrain LDA calculation would
result in a magnetic ground state with nonzero spin and orbital moment values.
For Pu compounds investigated in the present work, predominantly f^6
configuration with nonzero magnetic moments was found in PuCoGa5, PuSi2, and
PuTe, while PuN, PuRh2, and PuSb have f^5 configuration with sizeable magnetic
moment values. Whereas pure jj coupling scheme was found to be valid for
metallic plutonium, intermediate coupling scheme is needed to describe 5f shell
in Pu compounds. The results of our calculations show that both spin-orbit
coupling and exchange interaction terms in the Hamiltonian must be treated in a
general matrix form for Pu and its compounds.Comment: 20 pages, LaTeX; changed discussion on reference pape
Relativistic transition wavelenghts and probabilities for spectral lines of Ne II
Transition wavelengths and probabilities for several 2p4 3p - 2p4 3s and 2p4
3d - 2p4 3p lines in fuorine-like neon ion (NeII) have been calculated within
the multiconfiguration Dirac-Fock (MCDF) method with quantum electrodynamics
(QED) corrections. The results are compared with all existing experimental and
theoretical data
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