Multiplets of free d- and f-metal ions: A systematic DFT study

In this work we apply in a systematic way our multi-determinantal model to calculate the fine structure of the whole atomic multiplet manifold. The key feature of this approach is the explicit treatment of near-degeneracy correlation using ad hoc configuration interaction (CI) within the active space of Kohn–Sham (KS) orbitals with open d- or f-shells. The calculation of the CI-matrices is based on a central symmetry decomposition of the energies of all single determinants (micro-states) calculated according to Density Functional Theory (DFT) for frozen KS-orbitals corresponding to the averaged configuration, eventually with fractional occupations, of the d- or f-orbitals and/or the direct calculation of the electrostatic reduced matrix elements (Racah or Slater–Condon parameters) occurring in the corresponding active space. We performed DFT calculations on all divalent and trivalent d²–d⁸ metal ions, as well as the f²–f¹² lanthanide(III) ions. We compare the results of both variants of the method with the data available in the literature. Both procedures yield multiplet energies with an accuracy of about hundred wave numbers and fine structure splitting accurate to less than a tenth of this amount

DRM et bibliothèques

Cet article traite des conséquences pour les bibliothèques (en général, et la Bibliothèque de l’EPFL en particulier) des systèmes de Digital Rights Manage- ment/DRM. Les bibliothécaires considèrent en effet que ces systèmes sont un obstacle à l’accès à l’information pour les lecteurs et posent, de plus, de graves problèmes de conservation des documents

Development of a flexible tool for the automatic comparison of bibliographic records. Application to sample collections - Développement d'un logiciel flexible pour la comparaison de notices bibliographiques et application à différentes collections

Due to the multiplication of digital bibliographic catalogues (open repositories, library and bookseller catalogues), information specialists are facing the challenge of mass-processing huge amounts of metadata for various purposes. Among the many possible applications, determining the similarity between records is an important issue. Such a similarity can be interesting from a bibliographic point of view (i.e., do the records describe the same document, the answer to which can be useful for deduplication or for collection overlap studies) as well as from a thematic point of view (suggestion of documents to the user, as well as content management within the framework of a library policy, automatic classification of documents, and so on). In order to fulfil such various needs, we propose a flexible, open-source, multiplatform software tool supporting the implementation of multiple strategies for record comparisons. In a second step, we study the relevance and performance of several algorithms applied to a selection of collections (size, origin, document types...)

MarcXimiL : near duplicates detection (and similarity analysis)

MarcXimiL is an open source tool which works on MARCXML records and calculates similarity indices between these records. After a short theoretical introduction, the tutorial will focus on how to install, parametrize and use the tool. This tool can be implemented in order to : * prevent creation of duplicates (similar records are shown during the validation process) * identify duplicates into batch files before ingest * find duplicates inside a collection * suggest to users similar records to the one found after a request * match related documents eg. preprints and articles * and so on

Infoscience, EPFL's institutional repository: facts and prospects

Green Open Access solutions require specific platforms and tools to reach their full potential and keep their promises. In order to encourage scientists from the Ecole Polytechnique de Lausanne (EPFL) to self-archive their publications, Infoscience (EPFL's institutional archive) develops innovative strategies and experiences to make this task as easy and useful as possible. Thanks to this approach, Infoscience becomes more than an easy-to-use and well-referenced dropbox, and provides added-value services as well. We motivate scientists toward Green Open Access with functionalities that not only make their fulltext-sharing experience simpler and their work more visible, but also provide them with valuable information about their own communication practices and scientific impact

ChemCalc: a building block for tomorrow’s chemical infrastructure

Web services, as an aspect of cloud computing, are becoming an important part of the general IT infrastructure, and scientific computing is no exception to this trend. We propose a simple approach to develop chemical web services, through which servers could expose the essential data manipulation functionality that students and researchers need for chemical calculations. These services return their results as JSON (JavaScript Object Notation) objects, which facilitates their use for web applications. The ChemCalc project demonstrates this approach: we present 3 web services related with mass spectrometry, namely isotopic distribution simulation, peptide fragmentation simulation and molecular formula determination. We also developed a complete web application based on these 3 web services, taking advantage of modern HTML5 and JavaScript libraries (ChemDoodle and jQuery)

Stochastic Liouville equation treatment of the electron paramagnetic resonance line shape of an S-state ion in solution

The current approaches used for the analysis of electron paramagnetic resonance spectra of Gd3+ complexes suffer from a number of drawbacks. Even the elaborate model of [Rast et al., J. Chem. Phys. 113, 8724 (2000)] where the electron spin relaxation is explained by the modulation of the zero-field splitting (ZFS), by molecular tumbling (the so called static contribution), and deformations (transient contribution), is only readily applicable within the validity range of the Redfield theory [Advances in Magnetic Resonance, edited by J.-S. Waugh (Academic, New York, 1965), Vol. 1, p. 1], that is, when the ZFS is small compared to the Zeeman energy and the rotational and vibrational modulations are fast compared to the relaxation time. Spin labels (nitroxides and transition metal complexes) have been studied for years in systems that violate these conditions. The theoretical framework commonly used in such studies is the stochastic Liouville equation (SLE). The authors shall show how the physical model of Rast et al. can be cast into the SLE formalism, paying special attention to the specific problems introduced by the [Uhlenbeck and Ornstein, Phys. Rev. 36, 823 (1930)] process used to model the transient ZFS. The resulting equations are very general and valid for arbitrary correlation times, magnetic field strength, electron spin S, or symmetry. The authors demonstrate the equivalence of the SLE approach with the Redfield approximation for two well-known Gd3+ complexes

Molecular dynamics simulations of the internal mobility of Gd3+-based MRI contrast agents: consequences for water proton relaxivity

The increasing use of contrast agents in magnetic resonance imaging (MRI) for medical diagnosis is due to the ability, called relaxivity, of these paramagnetic compounds to accelerate the relaxation of the surrounding water proton spins. A new classical force field for molecular dynamics simulations of Gd3+ polyaminocarboxylates has recently been published, which allows the study of the chelate internal mobility. We present two selected examples where such motions can affect relaxivity. Knowing the relationship between the bound water proton and oxygen mobility is important for the combined analysis of multinuclear NMR studies, and we show that they differ significantly. Next, we observe symmetry changes over time in the Gd3+ coordination polyhedron of the acyclic complexes. We propose that such rearrangements can play a role in the electron spin relaxation of Gd3+ chelates, an important result considering the uncertainty still attached to this particular factor