Pyqcm: An open-source Python library for quantum cluster methods

Pyqcm is a Python/C++ library that implements a few quantum cluster methods with an exact diagonalization impurity solver. Quantum cluster methods are used in the study of strongly correlated electrons to provide an approximate solution to Hubbard-like models. The methods covered by this library are Cluster Perturbation Theory (CPT), the Variational Cluster Approach (VCA) and Cellular (or Cluster) Dynamical Mean Field Theory (CDMFT). The impurity solver (the technique used to compute the cluster's interacting Green function) is exact diagonalization from sparse matrices, using the Lanczos algorithm and variants thereof. The core library is written in C++ for performance, but the interface is in Python, for ease of use and inter-operability with the numerical Python ecosystem. The library is distributed under the GPL license.Comment: Submission to SciPost. arXiv admin note: substantial text overlap with arXiv:0806.269

Paired-cosmogenic nuclide paleoaltimetry

International audienceGoal-The reconstruction of past topographies remains challenging and only a few methods allow accurate determination of past surface elevations. We propose here a new technique for deriving paleo-elevations, in which multiple cosmogenic nuclides are measured in the same geological sample exposed at the Earth's surface. This method relies on the altitude dependence of the cosmogenic nuclides' production rates combined with the radioactive decays of nuclides with different half-lives. Theory-The position of the two cosmogenic nuclide exposure curves (26 Al/ 10 Be vs 10 Be or 10 Be/ 21 Ne vs 10 Be) depends on the altitude of exposure. If the studied surfaces have been exposed for sufficiently long durations (>500 ka), or have been affected by low erosion rates (500 ka), or low erosion rates (<1 mMa −1), the values of the pre-burial nuclides ratios indeed depend strongly on the altitude of exposure. It may be important to consider the pre-burial altitude of exposure in order to calculate accurate burial ages

Two MATLAB programs for computing paleo-elevations and burial ages from paired-cosmogenic nuclides

International audienceMethods based on cosmic-ray produced nuclides are key to improve our understanding of the Earth surface dynamic. Measuring multiple cosmogenic nuclides in the same rock sample has a great potential, but data interpretation requires rigorous and often complex mathematical treatments. In order to make progress on this topic, this paper presents two easy-to-use MATLAB © programs permitting to derive information from pairs of cosmogenic nuclides (26 Al-10 Be or 10 Be-21 Ne) measured in rock samples that have been exposed to cosmic rays in the past: "Paleoaltitude.m" and "Burial.m" Codes available here as supplementary material. "Paleoaltitude.m" computes paleoelevations from a sample whose burial age is known. This new paleoaltimetry method is presented in detail in Blard et al. [1]. The present article also develops the mathematical approach. Since the elevation of exposure may affect the accuracy of a burial age [1], the second MATLAB© script "Burial. m" is designed to compute burial ages from 26 Al-10 Be or 10 Be-21 Ne pairs, taking into account the position of a sample (elevation and latitude) during its preburial exposure history

Sex-dependent circadian alterations of both central and peripheral clock genes expression and gut–microbiota composition during activity-based anorexia in mice

International audienceAbstract Rationale Patients with anorexia nervosa (AN) often present sleep disorders and circadian hormonal dysregulation. The role of the microbiota–gut–brain axis in the regulation of feeding behavior has emerged during the last decades but its relationships with the circadian rhythm remains poorly documented. Thus, we aimed to characterize the circadian clock genes expression in peripheral and central tissues in the activity-based anorexia mouse model (ABA), as well as the dynamics of the gut–microbiota composition. Methods From day 1 to day 17, male and female C57Bl/6 mice were submitted or not to the ABA protocol (ABA and control (CT) groups), which combines a progressive limited access to food and a free access to a running wheel. At day 17, fasted CT and ABA mice were euthanized after either resting (EoR) or activity (EoA) phase ( n = 10–12 per group). Circadian clock genes expression was assessed by RT-qPCR on peripheral (liver, colon and ileum) and central (hypothalamic suprachiasmatic nucleus or SCN) tissues. Cecal bacterial taxa abundances were evaluated by qPCR. Data were compared by two-way ANOVA followed by post-tests. Results ABA mice exhibited a lower food intake, a body weight loss and an increase of diurnal physical activity that differ according with the sex. Interestingly, in the SCN, only ABA female mice exhibited altered circadian clock genes expression ( Bmal1, Per1, Per2, Cry1, Cry2 ). In the intestinal tract, modification of clock genes expression was also more marked in females compared to males. For instance, in the ileum, female mice showed alteration of Bmal1 , Clock , Per1 , Per2 , Cry1 , Cry2 and Rev-erbα mRNA levels, while only Per2 and Cry1 mRNAs were affected by ABA model in males. By contrast, in the liver, clock genes expression was more markedly affected in males compared to females in response to ABA. Finally, circadian variations of gut–bacteria abundances were observed in both male and female mice and sex-dependent alteration were observed in response to the ABA model. Conclusions This study shows that alteration of circadian clock genes expression at both peripheral and central levels occurs in response to the ABA model. In addition, our data underline that circadian variations of the gut–microbiota composition are sex-dependent