Fate of the open-shell singlet ground state in the experimentally accessible acenes: a quantum Monte Carlo study

By means of the Jastrow correlated antisymmetrized geminal power (JAGP) wave function and quantum Monte Carlo (QMC) methods, we study the ground state properties of the oligoacene series, up to the nonacene. The JAGP is the accurate variational realization of the resonating-valence-bond (RVB) ansatz proposed by Pauling and Wheland to describe aromatic compounds. We show that the long-ranged RVB correlations built in the acenes' ground state are detrimental for the occurrence of open-shell diradical or polyradical instabilities, previously found by lower-level theories. We substantiate our outcome by a direct comparison with another wave function, tailored to be an open-shell singlet (OSS) for long-enough acenes. By comparing on the same footing the RVB and OSS wave functions, both optimized at a variational QMC level, and further projected by the lattice regularized diffusion Monte Carlo (LRDMC) method, we prove that the RVB wave function has always a lower variational energy and better nodes than the OSS, for all molecular species considered in this work. The entangled multi-reference RVB state acts against the electron edge localization implied by the OSS wave function, and weakens the diradical tendency for higher oligoacenes. These properties are reflected by several descriptors, including wave function parameters, bond length alternation, aromatic indices, and spin-spin correlation functions. In this context, we propose a new aromatic index estimator suitable for geminal wave functions. For the largest acenes taken into account, the long-range decay of the charge-charge correlation functions is compatible with a quasi-metallic behavior.Comment: 16 pages, 11 figure

Efficient Embedded System Development: A Workbench for an Integrated Methodology

International audienceThe scientific foundations of embedded system development associate two disciplines that have largely grown on their own: computer science and electrical engineering. This superposition of two domains with little common ground raises a number of industrial issues in team work organisation, sound progress tracking, and cooperation between these different skills and cultures. In this paper we introduce HOE², an integrated MDE method for embedded system development that is organised around a set of limited yet powerful artefacts. We describe how HOE² can address the issues faced during development of mixed HW/SW systems and present the first version of a tool dedicated to its instrumentation

Les rhizobiums d'acacia : biodiversité et taxonomie

La diversité des rhizobiums capables de noduler le genre Acacia est étudiée au niveau de deux laboratoires : le laboratoire ORSTOM/ISRA de Dakar s'intéresse plus particulièrement à la diversité des rhizobiums des acacias de zones sèches et le laboratoire ORSTOM/CIRAD de Nogent à celle des acacias de zone humid

L'acacia au Sénégal

Cette présentation propose une revue bibliographique de certains aspects de la nodulation des acacias, en particulier en ce qui concerne la diversité des rhizobiums qui leur sont associés, au regard de la taxonomie générale des rhizobiums, et développe plus en détails les derniers résultats obtenus au Sénégal dans ce domaine. (Résumé d'auteur

Phenotypic and genotypic characterization of Bradyrhizobia nodulating the leguminous tree Acacia albida

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Exploring intracranial aneurysm instability markers to improve disease modeling

Intracranial aneurysm (IA) shape is proposed to be a predicting factor of rupture. In this study, using 3D-angiographies, surgical and histological images, we ranked 11 IAs according to different characteristics (homogeneity, aspect and thickness), and correlations between the different ranking systems were investigated. We showed positive correlations between IA morphology (normalized total Gaussian curvature, GLN) and wall aspect ranking, and between GLN and histology ranking. Correlations between increased GLN, inhomogeneity of IA wall aspect and thickness were shown. This exploratory study supports the GLN in its ability to quantify IA shape and to be used as an IA wall feature predictor

Triglycerides and glycated hemoglobin for screening insulin resistance in obese patients

International audienceOBJECTIVE: Assessment of insulin resistance (IR) is essential in non-diabetic patients with obesity. Thus study aims to identify the best determinants of IR and to propose an original approach for routine assessment of IR in obesity. DESIGN AND PATIENTS: All adult with obesity defined by a body mass index >=30kg/m2, evaluated in the Nutrition Department between January 2010 and January 2015 were included in this cross-sectional study. Patients with diabetes were excluded. IR was diagnosed according to the HOMA-IR. Based on a logistic regression, we determined a composite score of IR. We then tested the variables with a principal component analysis and a hierarchical clustering analysis. RESULTS: A total of 498 patients with obesity were included. IR was associated with grade III obesity (OR=2.6[1.6-4.4], p\textless0.001), HbA1c>=5.7% (OR=2.6[1.7-4.0], p\textless0.001), hypertriglyceridemia \textgreater1.7mmol/l (OR=3.0[2.0-4.5], p\textless0.001) and age (OR=0.98[0.96-0.99], p=0.002). Exploratory visual analysis using factor map and clustering analysis revealed that lipid and carbohydrates metabolism abnormalities were correlated with insulin resistance but not with excessive fat accumulation and low-grade inflammation. CONCLUSIONS: Our results highlight the interest of simple blood tests such as HbA1c and triglyceride determination, which associated with BMI, may be widely available tools for screening IR in obese patients

\AA ngstrom depth resolution with chemical specificity at the liquid-vapor interface

The determination of depth profiles across interfaces is of primary importance in many scientific and technological areas. Photoemission spectroscopy is in principle well suited for this purpose, yet a quantitative implementation for investigations of liquid-vapor interfaces is hindered by the lack of understanding of electron-scattering processes in liquids. Previous studies have shown, however, that core-level photoelectron angular distributions (PADs) are altered by depth-dependent elastic electron scattering and can, thus, reveal information on the depth distribution of species across the interface. Here, we explore this concept further and show that the anisotropy parameter characterizing the PAD scales linearly with the average distance of atoms along the surface normal. This behavior can be accounted for in the low-collision-number regime. We also show that results for different atomic species can be compared on the same length scale. We demonstrate that atoms separated by about 1~\AA~along the surface normal can be clearly distinguished with this method, achieving excellent depth resolution.Comment: Submitted to Phys. Rev. Let

Human granzyme B regulatory B cells prevent effector CD4+CD25- T cell proliferation through a mechanism dependent from lymphotoxin alpha

IntroductionHuman Granzyme B (GZMB) regulatory B cells (Bregs) have suppressive properties on CD4+ effector T cells by a mechanism partially dependent on GZMB. Moreover, these cells may be easily induced in vitro making them interesting for cell therapy.MethodsWe characterized this population of in vitro induced GZMB+Bregs using single cell transcriptomics. To investigate their regulatory properties, Bregs or total B cells were also co-cultured with T cells and scRNAseq was used to identify receptor ligand interactions and to reveal gene expression changes in the T cells.ResultsWe find that Bregs exhibit a unique set of 149 genes differentially expressed and which are implicated in proliferation, apoptosis, metabolism, and altered antigen presentation capacity consistent with their differentiated B cells profile. Notably, Bregs induced a strong inhibition of T cell genes associated to proliferation, activation, inflammation and apoptosis compared to total B cells. We identified and validated 5 receptor/ligand interactions between Bregs and T cells. Functional analysis using specific inhibitors was used to test their suppressive properties and we identified Lymphotoxin alpha (LTA) as a new and potent Breg ligand implicated in Breg suppressive properties.DiscussionWe report for the first time for a role of LTA in GZMB+Bregs as an enhancer of GZMB expression, and involved in the suppressive properties of GZMB+Bregs in human. The exact mechanism of LTA/GZMB function in this specific subset of Bregs remains to be determined